Вот так всё обычно и происходит...
Не болейте! :)
Показаны сообщения с ярлыком клетки. Показать все сообщения
Показаны сообщения с ярлыком клетки. Показать все сообщения
15.09.2015
10.08.2014
08.08.2014
Анимация - клетка
моя веселая попытка послать лучи добра путем демонстрации основ строения эукариотической клетки
15.01.2013
31.08.2012
Ограничение калорий - работает ли для всех видов?
Много сейчас говорят о таком интересном способе продления жизни как снижение потребляемых калорий. Показано множество успешных результатов на грызунах. Всё очень аргументировано и элегантно. Однако совсем недавно в сети появились сообщения о подобных опытах, проведённых на приматах. И там результаты оказались не столь однозначными.
Вот одно из таких сообщений:Calorie Restriction May Make Rats Live Longer, But Doesn’t Work For PrimatesСпасибо за наводку jtotheizzoe.
Remember those famous studies in worms, mice and rats that indicated that a restricted-calorie diet increased lifespan? Well, the results of a 30-year study in rhesus monkeys has just been reported, and the results make it pretty clear that it doesn’t apply to primates … likely including us.
The molecular pathways and gene circuits that are activated in our bodies as a result of long-term calorie restriction are immensely complicated. Like a tangled ball of yarn complicated. We don’t understand how they work, frankly, and there’s just no magic bullet when it comes to diet and lifespan in creatures like monkeys and humans (I’m looking at you, resveratrol). It’s certainly good for one’s long-term survival not to overeat into Honey-Boo-Boobesity, but what does current science say about calories, long life and naked apes?
Studies of humans who live past 100 point to genetics as more important than restricting calories. Which genes? Time may tell. And none of this has helped us understand how different diet compositions may affect aging.
Read more at Nature News.
18.05.2012
Чем грозит устранение бесплодия будущим эмбрионам?
Наткнулась на статью на
http://www.laboratoryequipment.com/news-Fertility-Treatment-Heightens-Risk-of-Birth-Defects-050712.aspx о том, что применение некоторых средств борьбы с бесплодием повышает риск появления дефектов развития у плода... Интересное исследование...
Fertility Treatments Heighten Risk of Birth Defects
May 7, 2012
A six week embryonic age or eight week gestational age intact Embryo, found in a Ruptured Ectopic pregnancy case. Image: Vilas Gayakwad, Wikimedia
A Univ. of Adelaide study has identified the risk of major birth defects associated with different types of assisted reproductive technology.
In the most comprehensive study of its kind in the world, researchers from the Univ.’s Robinson Institute have compared the risk of major birth defects for each of the reproductive therapies commonly available internationally, such as: IVF (in vitro fertilization), ICSI (intracytoplasmic sperm injection) and ovulation induction. They also compared the risk of birth defects after fresh and frozen embryo transfer.
The results are being published in the prestigious New England Journal of Medicine, and presented in Barcelona, Spain at the World Congress on Building Consensus in Gynecology, Infertility and Perinatology.
"While assisted reproductive technologies are associated with an increased risk of major birth defects overall, we found significant differences in risk between available treatments," says the lead author of the study, Associate Prof. Michael Davies from the Univ. of Adelaide’s Robinson Institute and School of Paediatrics and Reproductive Health.
Researchers linked a census of more than 6100 assisted reproductive technology births in South Australia to a registry of more than 300,000 births and 18,000 birth defects. They compared risks of birth defects across all infertility treatments to pregnancies in women with no record of infertility. They also compared successive pregnancies for women.
Previous studies have identified an increased risk of birth defects associated with infertility treatment, but this is the first study to compare all forms of available treatment. This is also the first study to compare pregnancies within women by the treatments received.
"The unadjusted risk of any birth defect in pregnancies involving assisted conception was 8.3 percent (513 defects), compared with 5.8 percent for pregnancies not involving assisted conception (17,546 defects)," Davies says.
"The risk of birth defects for IVF was 7.2 percent (165 birth defects); and the rate for ICSI was higher at 9.9 percent (139 defects). A history of infertility, either with or without assisted conception, was also significantly associated with birth defects. While factors associated with the causes of infertility explained the excess risk associated with IVF, the increased risk for a number of other treatments could not readily be explained by patient factors. ICSI, for instance, had a 57 percent increase in the odds of major defect, although the absolute size of the risk remained relatively small," he says.
Davies says cryopreservation (freezing) of embryos was associated with a substantially reduced risk of birth defects, particularly for ICSI. "This may be due to developmentally compromised embryos failing to survive the freeze/thaw process," he says.
Also of concern was the tripling of risk in women using clomiphene citrate to stimulate ovulation outside of a closely supervised clinical setting.
"While confined to a small group in our study, this is of particular concern as clomiphene citrate is now very widely available at low cost, and may easily be used contrary to manufacturers' very specific instructions to avoid use if pregnant, as it may cause fetal malformations. This aspect of the study will need additional confirmation from future research," Davies says.
He says the study now needs to be expanded to include more recent years of treatment, as the reproductive technologies have undergone continual innovation which may influence the associated risks of treatment.
Source: Univ. of Adelaide
Fertility Treatments Heighten Risk of Birth Defects
May 7, 2012
A six week embryonic age or eight week gestational age intact Embryo, found in a Ruptured Ectopic pregnancy case. Image: Vilas Gayakwad, Wikimedia
A Univ. of Adelaide study has identified the risk of major birth defects associated with different types of assisted reproductive technology.
In the most comprehensive study of its kind in the world, researchers from the Univ.’s Robinson Institute have compared the risk of major birth defects for each of the reproductive therapies commonly available internationally, such as: IVF (in vitro fertilization), ICSI (intracytoplasmic sperm injection) and ovulation induction. They also compared the risk of birth defects after fresh and frozen embryo transfer.
The results are being published in the prestigious New England Journal of Medicine, and presented in Barcelona, Spain at the World Congress on Building Consensus in Gynecology, Infertility and Perinatology.
"While assisted reproductive technologies are associated with an increased risk of major birth defects overall, we found significant differences in risk between available treatments," says the lead author of the study, Associate Prof. Michael Davies from the Univ. of Adelaide’s Robinson Institute and School of Paediatrics and Reproductive Health.
Researchers linked a census of more than 6100 assisted reproductive technology births in South Australia to a registry of more than 300,000 births and 18,000 birth defects. They compared risks of birth defects across all infertility treatments to pregnancies in women with no record of infertility. They also compared successive pregnancies for women.
Previous studies have identified an increased risk of birth defects associated with infertility treatment, but this is the first study to compare all forms of available treatment. This is also the first study to compare pregnancies within women by the treatments received.
"The unadjusted risk of any birth defect in pregnancies involving assisted conception was 8.3 percent (513 defects), compared with 5.8 percent for pregnancies not involving assisted conception (17,546 defects)," Davies says.
"The risk of birth defects for IVF was 7.2 percent (165 birth defects); and the rate for ICSI was higher at 9.9 percent (139 defects). A history of infertility, either with or without assisted conception, was also significantly associated with birth defects. While factors associated with the causes of infertility explained the excess risk associated with IVF, the increased risk for a number of other treatments could not readily be explained by patient factors. ICSI, for instance, had a 57 percent increase in the odds of major defect, although the absolute size of the risk remained relatively small," he says.
Davies says cryopreservation (freezing) of embryos was associated with a substantially reduced risk of birth defects, particularly for ICSI. "This may be due to developmentally compromised embryos failing to survive the freeze/thaw process," he says.
Also of concern was the tripling of risk in women using clomiphene citrate to stimulate ovulation outside of a closely supervised clinical setting.
"While confined to a small group in our study, this is of particular concern as clomiphene citrate is now very widely available at low cost, and may easily be used contrary to manufacturers' very specific instructions to avoid use if pregnant, as it may cause fetal malformations. This aspect of the study will need additional confirmation from future research," Davies says.
He says the study now needs to be expanded to include more recent years of treatment, as the reproductive technologies have undergone continual innovation which may influence the associated risks of treatment.
Source: Univ. of Adelaide
17.02.2012
Аспирантам посвящается
Бугага. А ведь в науке реально чаще всего всё именно так и происходит... К сожалению или к счастью. :)
24.12.2011
20.12.2011
Допамин в свежих научных новостях
Я очень люблю допамин. Да и как можно его не любить, если именно это чудесное вещество отвечает за нашу мотивацию, удовольствие и другие приятности? В этом блоге достаточно много постов посвящены этому нейромедиатору, поэтому сейчас я хочу поделиться ссылкой на свежайшую статью из авторитетного источника, в которой раскрываются какие-то интересные и не известные до этого, сведения о допамине.
Сообщение на http://www.eurekalert.org/pub_releases/2011-12/osum-ans120111.php гласит, что допамин может быть крайне полезен при лечении опухолей. Оказывается, этот катехоламин способен увеличить эффективность действия противораковых препаратов и радиотерапии! Допамин улучшает приток крови к опухолям и таким образом повышает концентрацию действующих веществ именно в месте потребности, так же увеличивается уровень насыщения этих участков кислородом, что так же способствует борьбе с опухолью. Такие результаты были получены на животных моделях рака груди и кишечника.
Сообщение на http://www.eurekalert.org/pub_releases/2011-12/osum-ans120111.php гласит, что допамин может быть крайне полезен при лечении опухолей. Оказывается, этот катехоламин способен увеличить эффективность действия противораковых препаратов и радиотерапии! Допамин улучшает приток крови к опухолям и таким образом повышает концентрацию действующих веществ именно в месте потребности, так же увеличивается уровень насыщения этих участков кислородом, что так же способствует борьбе с опухолью. Такие результаты были получены на животных моделях рака груди и кишечника.
04.11.2011
Паразит мозг не съест, но химию его изменит...
Сто лет не обновляла этот бложик, пардон.
Вот вам забавная новость. На английском, ага, как обычно.
Некоторые паразиты (токсоплазма, например) в мозгу могут феерически изменять выработку допамина.
Brain parasite directly alters brain chemistry
A research group from the University of Leeds has shown that infection by the brain parasite Toxoplasma gondii, found in 10-20 per cent of the UK's population, directly affects the production of dopamine, a key chemical messenger in the brain.
Their findings are the first to demonstrate that a parasite found in the brain of mammals can affect dopamine levels.
Whilst the work has been carried out with rodents, lead investigator Dr Glenn McConkey of the University's Faculty of Biological Sciences, believes that the findings could ultimately shed new light on treating human neurological disorders that are dopamine-related such as schizophrenia, attention deficit hyperactivity disorder, and Parkinson's disease.
This research may explain how these parasites, remarkably, manipulate rodents' behaviour for their own advantage. Infected mice and rats lose their innate fear of cats, increasing the chances of being caught and eaten, which enables the parasite to return to its main host to complete its life cycle.
In this study, funded by the Stanley Medical Research Institute and Dunhill Medical Trust, the research team found that the parasite causes production and release of many times the normal amount of dopamine in infected brain cells.
Dopamine is a natural chemical which relays messages in the brain controlling aspects of movement, cognition and behaviour. It helps control the brain's reward and pleasure centres and regulates emotional responses such as fear. The presence of a certain kind of dopamine receptor is also associated with sensation-seeking, whereas dopamine deficiency in humans results in Parkinson's disease.
These findings build on earlier studies in which Dr McConkey's group found that the parasite actually encodes the enzyme for producing dopamine in its genome.
"Based on these analyses, it was clear that T. gondii can orchestrate a significant increase in dopamine production in neural cells," says Dr McConkey.
"Humans are accidental hosts to T. gondii and the parasite could end up anywhere in the brain, so human symptoms of toxoplasmosis infection may depend on where parasite ends up. This may explain the observed statistical link between incidences of schizophrenia and toxoplasmosis infection."
Dr McConkey says his next experiments will investigate how the parasite enzyme triggers dopamine production and how this may change behaviour.
http://www.eurekalert.org/pub_releases/2011-11/uol-bpd110411.php
Вот вам забавная новость. На английском, ага, как обычно.
Некоторые паразиты (токсоплазма, например) в мозгу могут феерически изменять выработку допамина.
Brain parasite directly alters brain chemistry
A research group from the University of Leeds has shown that infection by the brain parasite Toxoplasma gondii, found in 10-20 per cent of the UK's population, directly affects the production of dopamine, a key chemical messenger in the brain.
Their findings are the first to demonstrate that a parasite found in the brain of mammals can affect dopamine levels.
Whilst the work has been carried out with rodents, lead investigator Dr Glenn McConkey of the University's Faculty of Biological Sciences, believes that the findings could ultimately shed new light on treating human neurological disorders that are dopamine-related such as schizophrenia, attention deficit hyperactivity disorder, and Parkinson's disease.
This research may explain how these parasites, remarkably, manipulate rodents' behaviour for their own advantage. Infected mice and rats lose their innate fear of cats, increasing the chances of being caught and eaten, which enables the parasite to return to its main host to complete its life cycle.
In this study, funded by the Stanley Medical Research Institute and Dunhill Medical Trust, the research team found that the parasite causes production and release of many times the normal amount of dopamine in infected brain cells.
Dopamine is a natural chemical which relays messages in the brain controlling aspects of movement, cognition and behaviour. It helps control the brain's reward and pleasure centres and regulates emotional responses such as fear. The presence of a certain kind of dopamine receptor is also associated with sensation-seeking, whereas dopamine deficiency in humans results in Parkinson's disease.
These findings build on earlier studies in which Dr McConkey's group found that the parasite actually encodes the enzyme for producing dopamine in its genome.
"Based on these analyses, it was clear that T. gondii can orchestrate a significant increase in dopamine production in neural cells," says Dr McConkey.
"Humans are accidental hosts to T. gondii and the parasite could end up anywhere in the brain, so human symptoms of toxoplasmosis infection may depend on where parasite ends up. This may explain the observed statistical link between incidences of schizophrenia and toxoplasmosis infection."
Dr McConkey says his next experiments will investigate how the parasite enzyme triggers dopamine production and how this may change behaviour.
http://www.eurekalert.org/pub_releases/2011-11/uol-bpd110411.php
27.05.2011
Клетки кожи могут думать?
Феерические новости - клетки кожи генерируют сигналы и очень странно себя ведут. Подробный анализ этого интереснейшего предположения предлагаю рассмотреть, спасибо Dr. Jeffrey H. Toney, который написал статью у себя в блоге http://scienceblogs.com/deanscorner/2011/05/could_skin_cells_think.php:
Figure 4: Synaptic responses of HFF-iN cells.
There seems to be a brain-centric theme emerging this week in groundbreaking science. Scientists at the Stanford University School of Medicine have reported in Nature the first example of transforming human skin cells into functional nerve cells. Could skin cells someday be able to "think"? Could they be used to create a biological computer or in regenerative medicine?
How did they do it? Excerpted, and revised for clarity, from their Abstract: {my comments in italics}
Somatic cell nuclear transfer, cell fusion, or expression of lineage-specific factors have been shown to induce cell-fate changes in a variety of cell types. We recently observed that forced expression of a combination of three transcription factors {factors that affect how genes become expressed} can efficiently convert mouse fibroblasts into functional induced neuronal (iN) cells13. Here we show that the same three factors can generate functional neurons from human pluripotent stem cells as early as 6 days after transgene activation. Importantly, the vast majority of human iN cells were able to generate action potentials and many matured to receive synaptic contacts when co-cultured with primary mouse cortical neurons. Our data demonstrate that non-neural human somatic cells, as well as pluripotent stem cells, can be converted directly into neurons by lineage-determining transcription factors. These methods may facilitate robust generation of patient-specific human neurons for in vitro disease modelling or future applications in regenerative medicine.
Their conclusions:
In this report, we have identified a combination of transcription factors that are capable of converting human fibroblasts directly into neurons. Like mouse iN cells13 and neurons derived from ES cells19, 20, 21 and iPS cells22, 23, the human iN cells seem relatively immature, as indicated by their slightly depolarized membrane potentials and the relatively low-amplitude synaptic responses. Compared to mouse iN cells, human iN cells required longer culture periods to develop synaptic activity. Future studies will be necessary to thoroughly optimize conditions for human iN cell generation and maturation, which would facilitate applications of this method for the study of human neuronal development and disease.
This is, yet another, amazing example of a creative use of biological techniques to generate something thought to be impossible in the past - transforming a common skin cell into a functioning neuron!
Figure 4: Synaptic responses of HFF-iN cells.
There seems to be a brain-centric theme emerging this week in groundbreaking science. Scientists at the Stanford University School of Medicine have reported in Nature the first example of transforming human skin cells into functional nerve cells. Could skin cells someday be able to "think"? Could they be used to create a biological computer or in regenerative medicine?
How did they do it? Excerpted, and revised for clarity, from their Abstract: {my comments in italics}
Somatic cell nuclear transfer, cell fusion, or expression of lineage-specific factors have been shown to induce cell-fate changes in a variety of cell types. We recently observed that forced expression of a combination of three transcription factors {factors that affect how genes become expressed} can efficiently convert mouse fibroblasts into functional induced neuronal (iN) cells13. Here we show that the same three factors can generate functional neurons from human pluripotent stem cells as early as 6 days after transgene activation. Importantly, the vast majority of human iN cells were able to generate action potentials and many matured to receive synaptic contacts when co-cultured with primary mouse cortical neurons. Our data demonstrate that non-neural human somatic cells, as well as pluripotent stem cells, can be converted directly into neurons by lineage-determining transcription factors. These methods may facilitate robust generation of patient-specific human neurons for in vitro disease modelling or future applications in regenerative medicine.
Their conclusions:
In this report, we have identified a combination of transcription factors that are capable of converting human fibroblasts directly into neurons. Like mouse iN cells13 and neurons derived from ES cells19, 20, 21 and iPS cells22, 23, the human iN cells seem relatively immature, as indicated by their slightly depolarized membrane potentials and the relatively low-amplitude synaptic responses. Compared to mouse iN cells, human iN cells required longer culture periods to develop synaptic activity. Future studies will be necessary to thoroughly optimize conditions for human iN cell generation and maturation, which would facilitate applications of this method for the study of human neuronal development and disease.
This is, yet another, amazing example of a creative use of biological techniques to generate something thought to be impossible in the past - transforming a common skin cell into a functioning neuron!
08.02.2011
Кое-что новенькое о культивировании стволовых клеток
Статейка о том, как взрослые стволовые клетки выращивали в специальных гидрогелях и подвергали всяческим физическим и химическим влияниям http://www.eurekalert.org/pub_releases/2010-11/uoc--bpa111610.php
О возможности культивирования плюрипотентных клеток в определённых условиях http://www.eurekalert.org/pub_releases/2010-12/uoia-ssp121510.php
О возможности культивирования плюрипотентных клеток в определённых условиях http://www.eurekalert.org/pub_releases/2010-12/uoia-ssp121510.php
10.05.2010
Эндометриальные стволовые клетки и допамин
Информация о возможных способах лечения болезни Паркинсона стволовыми клетками описан на http://www.eurekalert.org/pub_releases/2010-05/nioc-esc050610.php
Endometrial stem cells restore brain dopamine levels
Mouse study may lead to new therapies for Parkinson's Disease
Endometrial stem cells injected into the brains of mice with a laboratory-induced form of Parkinson's disease appeared to take over the functioning of brain cells eradicated by the disease.The finding raises the possibility that women with Parkinson's disease could serve as their own stem cell donors. Similarly, because endometrial stem cells are readily available and easy to collect, banks of endometrial stem cells could be stored for men and women with Parkinson's disease.
"These early results are encouraging," said Alan E. Guttmacher, M.D., acting director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the NIH Institute that funded the study. "Endometrial stem cells are widely available, easy to access and appear to take on the characteristics of nervous system tissue readily."
Parkinson's disease results from a loss of brain cells that produce the chemical messenger dopamine, which aids the transmission of brain signals that coordinate movement.
This is the first time that researchers have successfully transplanted stem cells derived from the endometrium, or the lining of the uterus, into another kind of tissue (the brain) and shown that these cells can develop into cells with the properties of that tissue.
The findings appear online in the Journal of Cellular and Molecular Medicine.
The study's authors were Erin F. Wolff, Xiao-Bing Gao, Katherine V. Yao, Zane B. Andrews, Hongling Du, John D. Elsworth and Hugh S. Taylor, all of Yale University School of Medicine.
Stem cells retain the capacity to develop into a range of cell types with specific functions. They have been derived from umbilical cord blood, bone marrow, embryonic tissue, and from other tissues with an inherent capacity to develop into specialized cells. Because of their ability to divide into new cells and to develop into a variety of cell types, stem cells are considered promising for the treatment of many diseases in which the body's own cells are damaged or depleted.
In the current study, the researchers generated stem cells using endometrial tissue obtained from nine women who did not have Parkinson's disease and verified that, in laboratory cultures, the unspecialized endometrial stem cells could be transformed into dopamine-producing nerve cells like those in the brain.
The researchers also demonstrated that, when injected directly into the brains of mice with a Parkinson's-like condition, endometrial stem cells would develop into dopamine-producing cells.
Unspecialized stem cells from the endometrial tissue were injected into mouse striatum, a structure deep in the brain that plays a vital role in coordinating balance and movement. When the researchers examined the animals' striata five weeks later, they found that the stem cells had populated the striatum and an adjacent brain region, the substantia nigra. The substantia nigra produces abnormally low levels of dopamine in human Parkinson's disease and the mouse version of the disorder. The researchers confirmed that the stem cells that had migrated to the substantia nigra became dopamine-producing nerve cells and that the animals' dopamine levels were partially restored.
The study did not examine the longer-term effects of the stem cell transplants or evaluate any changes in the ability of the mice to move. The researchers noted that additional research would need to be conducted to evaluate the safety and efficacy of the technique before it could be approved for human use.
According to the researchers, stem cells derived from endometrial tissue appear to be less likely to be rejected than are stem cells from other sources. As expected, the stem cells generated dopamine producing cells when transplanted into the brains of mice with compromised immune systems. However, the transplants also successfully gave rise to dopamine producing cells in the brains of mice with normal immune systems.
According to Dr. Taylor, because women could provide their own donor tissue, there would be no concern that their bodies would reject the implants. Moreover, because endometrial tissue is widely available, banks of stem cells could be established. The stem cells could be matched by tissue type to male recipients with Parkinson's to minimize the chances of rejection.
In addition, Dr. Taylor added that endometrial stem cells might prove to be easier to obtain and easier to use than many other types of stem cells. With each menstrual cycle, women generate new endometrial tissue every month, so the stem cells are readily available. Even after menopause, women taking estrogen supplements are capable of generating new endometrial tissue. Because doctors can gather samples of the endometrial lining in a simple office procedure, it is also easier to collect than other types of adult stem cells, such as those from bone marrow, which must be collected surgically.
"Endometrial tissue is probably the most readily available, safest, most easily attainable source of stem cells that is currently available. We hope the cells we derived are the first of many types that will be used to treat a variety of diseases," said senior author Hugh S. Taylor, M.D., of Yale University. "I think this is just the tip of the iceberg for what we will be able to do with these cells."
###
The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute's Web site at http://www.nichd.nih.gov/. The National Institutes of Health (NIH) — The Nation's Medical Research Agency — includes 27 Institutes and Centers and is a component of the U. S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical, and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.
16.04.2010
Новая система измерения параметров клеток
Читаю на http://www.biologynews.net/archives/2010/04/12/mit_new_cell_measurement_system.html
Using a sensor that weighs cells with unprecedented precision, MIT and Harvard researchers have measured the rate at which single cells accumulate mass — a feat that could shed light on how cells control their growth and why those controls fail in cancer cells.
The research team, led by Scott Manalis, MIT associate professor of biological engineering, revealed that individual cells vary greatly in their growth rates, and also found evidence that cells grow exponentially (meaning they grow faster as they become larger).
The new measurement system, reported in the April 11 edition of the journal Nature Methods, is the first technique that can measure cells' mass as they grow over a period of time, ranging from five to 30 minutes. Previous methods for measuring cell growth rates have focused on volume or length measurements, and have not yet exhibited the necessary precision for revealing single cell growth models.
How they did it: The cell-mass sensor, which Manalis first demonstrated in 2007, consists of a fluid-filled microchannel etched in a tiny silicon slab that vibrates inside a vacuum. As cells flow through the channel, one at a time, their mass slightly alters the slab's vibration frequency. The mass of the cell can be calculated from that change in frequency, with a resolution as low as a femtogram (10-15 grams).
Michel Godin, a former postdoctoral associate in Manalis' lab and co-lead author of the paper, developed a way to trap a cell within the microchannel by precisely coordinating the flow direction. That enables the researchers to repeatedly pass a single cell through the channel every second or so, measuring it each time it moves through.
The researchers studied four types of cells: two strains of bacteria (E. coli and B. subtilis), a strain of yeast and mammalian lymphoblasts (precursors to white blood cells). They showed that B. subtilis cells appear to grow exponentially, but they did not obtain conclusive evidence for E. coli. That's because there is so much variation between individual cell growth rates in E. coli, even for cells of similar mass, says Francisco Delgado, a grad student in Manalis' lab and co-lead author of the paper.
If cells do grow exponentially, it means there must be some kind of mechanism to control that growth. Otherwise, when cells divide into two slightly different-sized daughter cells, as they often do, the larger cell in each generation would always grow faster than the smaller cell, leading to inconsistent cell sizes.
"If there were no control over the process, the variation in cell size would be all over the map," says Marc Kirschner, professor of systems biology at Harvard Medical School and an author of the paper. However, biologists don't know yet how that control mechanism might work.
Next steps: In their current studies, the researchers are tagging proteins inside the cell with fluorescent molecules that reveal what stage of the cell cycle the cell is in, allowing them to correlate cell size with cell cycle position. They are also working on a way to add chemicals such as nutrients, antibiotics and cancer drugs to the fluid inside the microchannel, so they can study how those substances affect growth rates.
Source : Massachusetts Institute of Technology
25.02.2010
Отличный пост о повреждениях ДНК и стволовых клетках
Две мои любимейшие темы в одном чудесном посте. Автор - Ed Yong
All of our cells are staffed by armies of executioners. They are usually restrained but when unleashed, they can set off a fatal chain reaction that kills the cell. This suicide squad does away with billions of cells every day. It helps to balance the production of new cells with the loss of old ones, to sculpt growing tissues and to destroy potential cancer cells.
But a new study suggests that the executioners aren't always lethal. In fact, they're essential for life. Through the unorthodox method of damaging our DNA, they can actually activate important genes. This technique for switching genes on is new to science but it's apparently vital for allowing some types of stem cell to produce new types of tissue.
Stem cells are bundles of untapped potential, with the ability to produce hundreds of specialist cells across the body. This process is called differentiation. Its details vary depending on which type of cell is being produced, but scientists have recently found that some aspects are apparently common to all tissues, be they muscle, blood or bone. Surprisingly, one of these is the recruitment of executioner proteins - caspases.
Caspases cut up other proteins and in doing so, some of them produce yet more caspases. The result is a growing army of death, hacking and slashing its way through the cell. But one of these killers - caspase-3 - is a necessary part of differentiation. Get rid of it and, suddenly, stem cells can't produce their specialised daughters. Now, thanks to Brian Larsen from the Sprott Centre for Stem Cell Research, we know why.
Caspase-3 activates a protein called CAD (or caspase-activated DNase in full) by slicing apart other proteins holding it at bay. Once released, CAD lives up to its villainous acronym. It pairs up with an identical twin to create a molecule that looks and acts like a pair of scissors. The pair can cut DNA, cleaving the famous double helix in two. These sorts of cuts are normally very bad news for a cell. If they aren't repaired quickly and accurately, the consequences can include death or cancer.
But Larsen has found that stem cells deliberately break their own DNA by recruiting caspase-3 and CAD. This act of self-harm switches on important genes that are needed for differentiation; without it, the generalist cells can't specialise. This is an entirely new way of activating genes and it appears to be both important and widespread.
Larsen studied stem-like cells called myoblasts, which give rise to various types of muscle cells. As the myoblasts differentiated, Larsen watched for signs of shattered DNA using a clever test called the 'comet assay'. The technique involves puncturing a cell and placing it in an electric field. The field drives DNA through the punctured cell but only if it has already been broken into small pieces. If it has, it appears as a streak outside the cell, rather like the tail of a comet.
Sure enough, the comet test revealed that differentiating cells suffer from significant amounts of damaged DNA. Thankfully, the injuries are only temporary and the cells soon marshal their repairmen to fix the breaks.
The myoblasts need these breaks to produce muscle fibres and to create the breaks, they rely on caspase-3 and its ability to activate CAD. Larsen managed to block the development of muscle fibres by dousing myoblasts with chemicals that neutralise caspase-3. The same thing happened if he used cells with mutant versions of CAD, which couldn't be activated. In both cases, the cells failed to show any signs of broken DNA.
CAD targets a gene called p21 that's absolutely necessary for the development of muscle and plenty of other tissues. Larsen found that CAD cuts p21's 'promoter', a stretch of DNA lying next to the gene that's responsible for switching it on. Somehow, these cuts activate the gene. It's still not clear how this works, but Larsen has some ideas. The cuts could change how the surrounding DNA is packaged, exposing the p21 gene and making it easier to 'read'. Alternatively, the cuts could remove chemical 'marks' attached to the DNA that would otherwise silence it.
Damaging your own DNA may seem like a rather extreme tactic for a cell to take but it's not unheard of as a deliberate ploy. Whenever we face new infections, our body generates antibodies by breaking the DNA of special genes, stitching them back together in new combinations. That's a very controlled process, but so is the damage that leads to differentiation. It's a careful surgical strike, rather than a shock and awe campaign.
During differentiation, Larsen found that DNA breaks are actually few and far between. They appear to be carefully orchestrated so that the entire genome doesn't become a shattered mess. This precision is even more remarkable when you consider that CAD cuts DNA indiscriminately, with little care for specific sequences. Larsen thinks that CAD is constrained by the way the DNA is packaged, so that only places that are meant to be cut are exposed for slicing and dicing. Only further experiments will tell if he is right.
Reference: Larsen et al. 2010. Caspase 3/caspase-activated DNase promote cell differentiation by inducing DNA strand breaks. http://dx.doi.org/10.1073/pnas.0913089107
Статья с http://scienceblogs.com/notrocketscience/2010/02/our_cells_produce_new_tissues_by_recruiting_executioners_to.php
29.09.2008
Культуры клеток в 22х измерениях скоро станут реальностью! :)
Какая прелесть! Это ведь именно то, что нужно сейчас нашим культуральщикам! Трёхмерная культура клеток!!! Это, конечно, не 22 и даже не 11 измерений, но нет ничего невозможного... Информация с http://www.biology-blog.com/blogs/permalinks/9-2008/reversible-3-d-cell-culture-gel-invented.html
Reversible 3-D cell culture gel invented
Reversible 3-D cell culture gel invented
Singapore's Institute of Bioengineering and Nanotechnology (IBN), which celebrates its fifth anniversary this year, has invented a unique user-friendly gel that can liquefy on demand, with the potential to revolutionize three-dimensional (3D) cell culture for medical research.
As reported in Nature Nanotechnology (Y.S. Pek, A. C. A. Wan, A. Shekaran, L. Zhuo and J. Y. Ying, "A Thixotropic Nanocomposite Gel for Three-Dimensional Cell Culture"), IBN's novel gel media has the unique ability to liquefy when it is subjected to a moderate shear force and rapidly resolidifies into a gel within one minute upon removal of the force. This phenomenon of reverting between a gel and a liquid state is known as thixotropy.
IBN's thixotropic gel is synthesized from a nanocomposite of silica and polyethylene glycol (PEG) under room temperature, without special storage conditions. This novel material facilitates the safe and convenient culture of cells in 3D since cells can be easily added to the gel matrix without any chemical processes.
As per IBN Executive Director Jackie Y. Ying, Ph.D., "Cell culture is conventionally performed on a flat surface such as glass slides. It is an essential process in biological and medical research, and is widely used to process cells, synthesize biologics and develop therapys for a large variety of diseases.
"Cell culture within a 3D matrix would better mimic the actual conditions in the body as in comparison to the conventional 2D cell culture on flat surfaces. 3D cell culture also promises the development of better cell assays for drug screening," Dr. Ying added.
Another key feature of IBN's gel is the ease with which scientists can transfer the cultured cells from the matrix by pipetting the mandatory amount from the liquefied gel.
Unlike conventional cell culture, trypsin is not mandatory to detach the cultured cells from the solid media. As trypsin is an enzyme that is known to damage cells, particularly in stem cell.
cultures, the long-term quality and viability of cells cultured using IBN's thixotropic gel would improve substantially without the exposure to this enzyme.
Scientists are also able to control the gel's stiffness, thus facilitating the differentiation of stem cells into specific cell types.
"Ways to control stem cell differentiation are important as stem cells can be differentiated into various cell types. Our gel can provide a novel method of studying stem cell differentiation, as well as an effective new means of introducing biological signals to cells to investigate their effect in 3D cultures," said Shona Pek, IBN Research Officer.
Andrew Wan, Ph.D., IBN Team Leader and Principal Research Scientist, added, "Another interesting property of the gel is its ability to support the extracellular matrix (ECM) secretions of cells. Gel stiffness is modulated by ECM secretions, and can be used to study ECM production by cells responding to drug therapys or disease conditions.
"The thixotropic gel may then provide new insights for basic research and drug development," Dr. Wan added.
Posted by: Janet http://www.a-star.edu.sg/astar/index.jsp
04.09.2008
Начало всех начал :))) Стволовая клетка-мама.
Мама крови. Вот она! Наконец, эмбриональная предшественница клеток крови - чётко определена. Информация с http://www.scientificblogging.com/news_releases/discovery_mother_of_all_blood_stem_cells
Discovery - 'Mother' Of All Blood Stem Cells
Submitted by News Staff on 29 August 2008 - 1:00am. Developmental
Johns Hopkins researchers say they have discovered the earliest form of human blood stem cells and deciphered the mechanism by which these embryonic stem cells replicate and grow. They also found a surprising biological marker that pinpoints these stem cells, which serve as the progenitors for red blood cells and lymphocytes.
The research reported today used federally approved embryonic stem cell lines.
The biochemical marker, angiotensin-converting enzyme (ACE), is well known for its role in the regulation of blood pressure, blood vessel growth, and inflammation. ACE inhibitors are already widely used to treat hypertension and congestive heart failure, and the findings are, the researchers say, likely to hold promise for developing new treatments for heart diseases, anemias, leukemia and other blood cancers, and autoimmune diseases because they show for the first time that ACE plays a fundamental role in the very early growth and development of human blood cells.
"We figured out how to get the 'mother' of all blood stem cells with the right culture conditions," says Elias Zambidis, M.D., Ph.D., of the Institute of Cell Engineering at the Johns Hopkins University School of Medicine and the Division of Pediatric Oncology at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins.
"There is real hope that in the future we can grow billions of blood cells at will to treat blood-related disorders, and just as critically if not more so, we've got ACE as a 'new' old marker to guide our work," Zambidis adds.
Researchers did not expect ACE to have a role in blood stem cells, he notes, "but were very pleasantly surprised to discover it as a beacon for finding the earliest blood stem cells known, as well as new ways to find and manipulate this marker to make them grow."
The team's findings, published Aug. 26 in the online edition of the journal Blood, explain that these earliest stem cells marked by ACE, called hemangioblasts, first arise normally in the developing human fetus, when a woman is three or four weeks pregnant. Hemangioblasts can now be derived in unlimited supply experimentally from cultured human embryonic stem cells, which are the origin of all cell types in the body. These hemangioblasts go on to become either blood cells or endothelial cells, which form the inner lining of the heart, veins and arteries, and lymph vessels.
The research grew out of Zambidis' interest in understanding the complex biological processes of blood development and the transformation of embryonic stem cells into the various types of cells that make up the human body.
Hemangioblasts make the body's earliest form of blood in the fetal yolk sac, which nourishes a fertilized egg, and later in the fetal liver and bone marrow. However, because human embryonic cells disappear early in gestation, their role in the early production of blood could not, to the researchers' knowledge, be studied in humans because scientists had no way to identify these human progenitor blood stems cells to follow their development. The scientists suspected they existed in humans, however, because they have been found in mice and zebra fish.
To find the blood stem cell, Zambidis' team grew human embryonic stem cells in culture and fed them growth factors over 20 days. Each time the cell colonies expanded, the researchers sampled individual cells, searching for ones capable of making both endothelial and blood cells, the hallmark of hemangioblasts.
They plucked the newly discovered hemangioblasts from culture dishes, grew them in conditions that Zambidis and his team developed to speed replication, and tested cells for their ability to make endothelial and blood cells. Cells capable of making endothelial cells and all the elements of blood (platelets, and white and red cells) were specifically marked with ACE on their outer surface.
The researchers found not only that ACE was a marker for hemangioblasts, but turning off the enzyme also helps guide the cells' replication and maturation into either blood or endothelial cells. By treating the hemangioblasts with losartan, an ACE pathway blocking agent routinely used to treat high blood pressure, dramatically increased the rate of blood cell production.
The next step, Zambidis adds, is to test this research in animal models and show that "we can make lots and lots of blood cells from human stem cells for transfusions, regenerate new vascular trees for heart diseases, as well as create test tube factories for making transplantable blood cells that treat diseases. We are very far from treatment," Zambidis cautions, "but this is a big step."
If the new technique of mass producing progenitor blood cells is eventually proven to work in humans, it would allow patients getting bone marrow transplants to have their own stem cells creating the blood they need, significantly reducing rejection risk.
The research reported today used federally approved embryonic stem cell lines, but other related research by the team comes from nonapproved lines. The study was supported by grants from the National Institutes of Health and the Maryland Stem Cell Research Fund.
Загадка клеточного деления - разгадана!
Ну разве не радость? Прочитала на http://www.scientificblogging.com/news_releases/50_year_cell_division_mystery_solved_say_researchers
Researchers from Oregon State University say they have resolved a controversy that cellular biologists have been arguing over for nearly 50 years, with findings that may aid research on everything from birth defects and genetic diseases to the most classic "cell division" issue of them all – cancer.
The exact mechanism that controls how chromosomes in a cell replicate and then divide into two cells, a process fundamental to life, has never been completely pinned down, researchers say. You can find the basics in any high school biology textbook, but the devil is in the details.
"Researchers have been debating cell cleavage ever since the cell was discovered, with two basic models proposed around 1960 of how a contractile ring pulls together and allows a single cell to split into two," said Dahong Zhang, an OSU associate professor of zoology. "Part of the problem is that until now there was no decisive way to manipulate the cytoskeleton, such as the microtubules and filaments that are involved, and see what was happening as it occurred."
To address that, Zhang developed some new instrumentation that uses "microneedles" and state-of-the-art imaging techniques which allow direct manipulation of the cytoskeleton, while capturing the results of contractile ring formation. The system has not only solved this decades-old riddle, but "the technology is a very powerful new approach," Zhang said, that should find applications in other cell biology research issues.
It has been known for some time, scientists say, that a "contractile ring," which is composed of some of the same fibers used in muscle contraction, move into the correct position, pull and split a cell in two after its chromosomes have been separated. This is distribution of genetic materials at its most basic level, and it has to be done at exactly the right place and time. When the process breaks down, cancer and other serious medical or genetic issues can be a result.
But if you think of the cell as a sphere, what was less clear was whether the "equator" contracted or the "poles" relaxed to allow this contraction and division. Two distinct theories were formed, called polar relaxation and equatorial stimulation, to explain this aspect of cell division – and some scientists have spent much of their careers arguing for one side or the other.
Turns out, Zhang said, that both sides were correct. Nature and evolution have actually created a basic way for a cell to divide with a backup system that can work if the other approach fails.
"Accurate cell division is one of the most critical of all life functions, and there clearly is an evolutionary value to having redundancy, a system able to do it two different ways," Zhang said. "It makes perfect sense when you think about it. The findings speak plainly for themselves, and there should no longer be a question over which model is right."
By labeling cells and moving microtubules around while still being able to see them and their impact on microfilaments, OSU researchers were able to selectively inhibit one mechanism of cell division or the other. They discovered that in the same cell type, it could divide either by polar relaxation or equatorial stimulation – the two mechanisms are not mutually exclusive.
The findings, Zhang said, add significantly to the basic understanding of cell biology, and should be of special interest to cancer researchers. Cancer is essentially the loss of normal control over cell division and migration. In fact, a compound used in Zhang's laboratory to inhibit cell division while they studied it was taxol – a commonly used cancer drug.
Accurate and effective cell division, researchers say, is also key to the understanding of some genetic diseases, miscarriages, birth defects and other issues.
The studies were supported by the National Science Foundation and the American Heart Association.
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