Stem cell

“ Advances in research show that stem cell science can progress in an ethical way. Since I announced my policy in 2001, my Administration has expanded funding of research into stem cells that can be drawn from children, adults, and the blood in umbilical cords with no harm to the donor, and these stem cells are currently being used in medical treatments. Science also offers the hope that we may one day enjoy the potential benefits of embryonic stem cells without destroying human life. ”

“ This policy has allowed important research to go forward and has allowed America to continue to lead the world in embryonic stem cell research without encouraging the further destruction of living human embryos. ”

“ THE LIFE OF THE STEM-CELL OR CYTULA IS THE PRODUCT OR RESULTANT OF THE PATERNAL LIFE-MOVEMENT THAT IS CONVEYED IN THE SPERMATOZOON AND THE MATERNAL LIFE-MOVEMENT THAT IS CONTRIBUTED BY THE OVUM.
The admirable work done by recent observers has shown that the individual development, in man and the other animals, commences with the formation of a simple "stem-cell" of this character, and that this then passes, by repeated segmentation (or cleavage) , into a cluster of cells, known as "the segmentation sphere" or "segmentation cells." ”

“ The revelation that there are groups that are now creating stem cells for the sole purpose of research, is a perfect illustration of the deep complexities our society faces as a result of science and life. Even scientists who are involved in stem cell research have raised questions about what took place in Virginia. ”

“ This week I made a decision on a complex and difficult issue, the federal role in embryonic stem cell research. Based on preliminary work, scientists believe these cells, which may have the ability to replace diseased or defective human tissue, offer great promise. They could help improve the lives of those who suffer from many terrible diseases -- from juvenile diabetes to Alzheimer's, from Parkinson's to spinal cord injuries. ”

“ The actual blending of the two cells produces a third cell, which is the germ of the child, or new organism conceived. One may also say of this sexual coälescence that the stem cell is a simple hermaphrodite, it unites both sexual substances in itself. ”

“ Since stem cells could be made to ignore the body's rules to stop replicating after a certain number, they were able to reproduce forever, constantly renewing themselves. The only other cells with that immortal characteristic were cancer cells. In fact, it was as though he had given Emma a new kind of cancer—one that produced cells as healthy as those in a newborn. Today she probably could have run up those stairs.
Although his stem cell technology was going to create a new era in regenerative medicine, he had experienced his share of bumps in the road. ”

“ However, demands for blood cell formation vary across mammals and thus the size of the active stem cell compartment could vary across species.
Methodology/Principle Findings Here we investigate the allometric scaling of the hematopoietic system in a large group of mammalian species using reticulocyte counts as a marker of the active stem cell pool. Our model predicts that the total number of active stem cells, in an adult mammal, scales with body mass with the exponent 3⁄4. ”

“ Expanding Approved Stem Cell Lines in Ethically Responsible Ways
By the authority vested in me as President by the Constitution and the laws of the United States of America, and to provide leadership with respect to research on pluripotent stem cells derived by ethically responsible techniques so that the potential of pluripotent stem cells can be explored without violating human dignity or demeaning human life, it is hereby ordered as follows:
Section 1.⁠ Research on Alternative Sources of Pluripotent Stem Cells. ”

“ The Secretary of Health and Human Services (Secretary) shall conduct and support research on the isolation, derivation, production, and testing of stem cells that are capable of producing all or almost all of the cell types of the developing body and may result in improved understanding of or treatments for diseases and other adverse health conditions, but are derived without creating a human embryo for research purposes or destroying, discarding, or subjecting to harm a human embryo or fetus. ”

“ He knew that some of the buzz about stem cells involved the fantasy that someday they might be used to forestall the aging process. Responsible researchers all said that they weren't trying to extend life; they were only hoping to make a normal lifetime more livable. Rejuvenative medicine. Winston Bartlett, however, had just taken stem cell potential to its obvious conclusion ”

“ The miraculous stem cell cures in this story are essentially an extrapolation of research well underway that has been the subject of magazine covers and is possibly the most promising and, yes, problematic field of medical research. The clocks at the Dorian Institute ran faster than ordinary timepieces, and research areas and cures that currently are only speculation were made real there. But that's why it's called fiction. As with the example cited above, many stem cell miracles conjured here may be just over the horizon. ”

“ Indeed, if we assume that a cell replicates 100 times before senescence, then the lifetime of a murine stem cell is longer than the lifetime of a mouse, consistent with the view [21] that a single stem cell may be enough to maintain hematopoiesis for the entire murine lifespan. In fact, our present allometric relation predicts that, although larger mammals require larger active stem cell pools, the expected lifetime of each species-specific stem cell is always longer than the expected lifetime of the mammal. ”

“ Heart disease, Alzheimer’s, Stem Cells, Aortic Stenosis, Medical Columns, Aging, Fountain of Youth, Regenerative Medicine
"The potential [of stem cells] for saving lives . . . may be unlimited. Given the proper signal or environment, stem cells, transplanted into human tissue, can be induced to develop into brain, heart, skin, bone marrow cells—indeed any specialized cells. The scientific research community believes that the transplanted stem cells may be able to regenerate dead or dying human tissue, reversing the progress of disease." ”

“ No human blastocyst may be produced by fertilization solely for the purpose of stem cell research. (3) No stem cells may be taken from a human blastocyst more than fourteen days after cell division begins ”

“ Abstract Background Many biological processes are characterized by allometric relations of the type Y = Y 0 Mb between an observable Y and body mass M, which pervade at multiple levels of organization. In what regards the hematopoietic stem cell pool, there is experimental evidence that the size of the hematopoietic stem cell pool is conserved in mammals. ”

“ As such, detailed studies of bone marrow physiology may shed light on the mechanisms responsible for the 3⁄4 scaling relations which pervade in living systems. Finally, the reduced size of the active stem cell pool in mice, cats and humans indicates that stochastic effects may play a sizeable role in the overall dynamics of the hematopoietic system in these mammals. ”

“ They were created from embryos that have already been destroyed, and they have the ability to regenerate themselves indefinitely, creating ongoing opportunities for research. I have concluded that we should allow federal funds to be used for research on these existing stem cell lines where the life and death decision has already been made. ”

“ However, there were "immortal cells" buried within us all, so‐called stem cells that could replicate forever, unchanged. They were present at the very beginning of life and all our differing body tissue was created from them. Some still lingered on in our body, as though to be available for spare parts. If one could figure out how to transfer the characteristics of those cells to other cells, then the possibility existed that we could regenerate damaged or aging tissue in our vital organs. The trick was to figure out the mechanism whereby stem cells managed to cheat time. ”

“ Not just by opening up this new frontier of research today, but by supporting promising research of all kinds, including groundbreaking work to convert ordinary human cells into ones that resemble embryonic stem cells. ”

“ However, we've found that by isolating and inserting an active copy of the telomerase enzyme into adult stem cells, which can be found in minute quantities throughout the body, we can set their clock back to zero. We extract cells, 'immortalize' them with telomerase, and then return them to the body as a youthful infusion. ”

“ You see, the clinical trials have demonstrated that we can use the telomerase enzyme to 'immortalize' a patient's own stem cells and then rejuvenate their brain or liver or even their heart. So the next question that's hanging out there in space is obvious. What would happen if we could find a way to generalize the enzyme and disperse it throughout someone's entire body, not restricting it to just one organ? ”

“ Research involving human embryonic stem cells and human non-embryonic stem cells has the potential to lead to better understanding and treatment of many disabling diseases and conditions. Advances over the past decade in this promising scientific field have been encouraging, leading to broad agreement in the scientific community that the research should be supported by Federal funds. ”

“ It will thus be observed that the centrosomes and their achromatin fibers are a beautiful mechanism by which the heredity threads (chromosomes) are exactly divided into two equivalent halves.
There are some cells (Amœba proteus, for instance,) which divide in a much simpler manner than by mitosis; in these there is no complicated rearrangement of the chromosomes and no disappearance of the nuclear membrane, the nucleus simply becoming separated into two parts (Amitosis) .
The Human Ovum. The human ovum is a typical cell about one-fifth of a millimeter in size and spherical in shape. ”

“ If, for instance, all or most of the chromatin brought in by the spermatozoon should be carried into one of the first formed cells along with half of the chromatin of the egg-nucleus, then all the cells that descend from this cell may develop female characters, and all those from the other, male characters. ”

“ We are thus brought back to the fundamental question as to how the germ-cells arise in the organism. Is it possible that the nucleoplasm of the germ-cell, with its immensely complex molecular structure, potentially containing all the specific peculiarities of an individual, can arise from the nucleoplasm of any of the body-cells,—a substance which, as we have just seen, has lost the power of originating any new kind of cell, because of the continual simplification of its structure during development? ”

“ The seminal elements of the male are also only simple cells, and the entire mysterious process of fructification is after all nothing but the fusion or concrescence of two different cells, the one a female egg-cell, and the other a male semen-cell. In consequence of this fusion the germs of the two combined cells dissolve, and therewith the young, newly-generated individual begins his existence as a simple cytod, or a small germless ball of protoplasm. ”

“ If a gene is repressed, nothing happens; it remains inactive, presumably until something removes the repressing factor. But an active gene sets in motion a train of events that results in activation of one of the processes of life: The gene’s DNA directs the manufacture of RNA, which in turn brings about the synthesis of a specific protein to carry out a specific metabolic process. In other words, all the activities of the cell are dictated by active genes (the DNA molecules) through the mediation of RNA and are executed by proteins. ”

“ To see the nature of the danger, let us begin by considering living tissue itself—the living tissue that must withstand the radiation and that can be damaged by it.
Cells and Chromosomes
The average human adult consists of about 50 trillion cells—50 trillion microscopic, more or less self-contained, blobs of life. He begins life, however, as a single cell, the fertilized ovum.
After the fertilized ovum is formed, it divides and becomes two cells. Each daughter cell divides to produce a total of four cells, and each of those divides and so on. ”

“ It is (vide fig. 35A, g.e.) composed of two or three layers of cells, with granular nuclei, of which the outermost layer is more columnar than the remainder, and has elongated rather than rounded nuclei. Its cells, though they vary slightly in size, are all provided with a fair amount of protoplasm, and cannot be divided (as in the case of the germinal epithelium of Birds, Elasmobranchii, &c.) , into primitive ova, and normal epithelial cells. Very occasionally, however, a specially large cell, which, perhaps, deserves the appellation primitive ovum, may be seen. ”

“ By the time the chick is ready to be hatched there are millions.
Usually, however, a cell is small—just as much protoplasm as its still more minute nucleus can keep going; though here, again, one must be guarded, for there may be several nuclei instead of only one. The protoplasm on the external surface and around the nucleus is specialized into a more or less definite membrane. To this outer envelope are attached fine fibrils, which join up to a small body within the cell, called the centrosome, and by the lengthening and shortening of these its shape can be altered. ”

“ In some cases the protoplasm at the circumference is so modified as to give the appearance of a limiting membrane called the cell wall. In brief, then, a cell is a mass of nucleated protoplasm; the nucleus may have a nucleolus, and the cell may be limited by a cell wall. Every tissue of the human body is formed through the agency of protoplasmic cells, although in most cases the changes they undergo are so great that little evidence remains of their existence. ”

“ It is clear that at each successive stage the molecular structure of the nucleoplasm must be further removed from that of the germ-plasm, and that, at the same time, the cells of each successive stage must also diverge more widely among themselves in the molecular structure of their nucleoplasm. Early in development each cell must possess its own peculiar nucleoplasm, for the further course of development is peculiar to each cell. ”