Summary class Geromics 2024 HyoungJinChoi
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2024.03.06
orientation Geromics
2024.03.08
What is theory?
A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be scientific, belong to a non-scientific discipline, or no discipline at all. Depending on the context, a theory's assertions might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings.
In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with the scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction ("falsify") of it. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge,[1] in contrast to more common uses of the word "theory" that imply that something is unproven or speculative (which in formal terms is better characterized by the word hypothesis).[2] Scientific theories are distinguished from hypotheses, which are individual empirically testable conjectures, and from scientific laws, which are descriptive accounts of the way nature behaves under certain conditions.
Theories guide the enterprise of finding facts rather than of reaching goals, and are neutral concerning alternatives among values.[3]: 131 A theory can be a body of knowledge, which may or may not be associated with particular explanatory models. To theorize is to develop this body of knowledge.[4]: 46
The word theory or "in theory" is sometimes used outside of science to refer to something which the speaker did not experience or test before.[5] In science, this same concept is referred to as a hypothesis, and the word "hypothetically" is used both inside and outside of science. In its usage outside of science, the word "theory" is very often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for doing, which is opposed to theory.[6] A "classical example" of the distinction between "theoretical" and "practical" uses the discipline of medicine: medical theory involves trying to understand the causes and nature of health and sickness, while the practical side of medicine is trying to make people healthy. These two things are related but can be independent, because it is possible to research health and sickness without curing specific patients, and it is possible to cure a patient without knowing how the cure worked.[a]
full text link : https://en.wikipedia.org/wiki/Theory
2024.03.22
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Prepare class Before you attend this week's lecture, I would like to encourage you to watch the following YouTube video:
- Title: Mitochondrial Regulation of Stem Cell Aging
- Presenter: Danica Chen, PhD (University of California, Berkeley, USA)
- YouTube Link: https://www.youtube.com/watch?v=FoJWmaT1ptM
In this video, Professor Danica Chen discusses various methods to protect mitochondria and reverse stem cell aging by Sirtuins.
It's an insightful presentation that will undoubtedly enrich our understanding of the topic before our lecture.
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Mitochondrial Stress is a Driver of Stem Cell Aging
- Mitochondrial stress increases in stem cell during aging
- Mitochondrial dysfunction and aging produces similar defects in stem cells
- Stem cells do not age at the same rate; about one third od chronologically aged HSCs exhibit regeberative function similar to healthy young HSCs, coinciding with the health of mitochondria.
Stem cell
In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage.[1] They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type.
In mammals, roughly 50 to 150 cells make up the inner cell mass during the blastocyst stage of embryonic development, around days 5–14. These have stem-cell capability. In vivo, they eventually differentiate into all of the body's cell types (making them pluripotent). This process starts with the differentiation into the three germ layers – the ectoderm, mesoderm and endoderm – at the gastrulation stage. However, when they are isolated and cultured in vitro, they can be kept in the stem-cell stage and are known as embryonic stem cells (ESCs).
Adult stem cells are found in a few select locations in the body, known as niches, such as those in the bone marrow or gonads. They exist to replenish rapidly lost cell types and are multipotent or unipotent, meaning they only differentiate into a few cell types or one type of cell. In mammals, they include, among others, hematopoietic stem cells, which replenish blood and immune cells, basal cells, which maintain the skin epithelium, and mesenchymal stem cells, which maintain bone, cartilage, muscle and fat cells. Adult stem cells are a small minority of cells; they are vastly outnumbered by the progenitor cells and terminally differentiated cells that they differentiate into.[1]
Research into stem cells grew out of findings by Canadian biologists Ernest McCulloch, James Till and Andrew J. Becker at the University of Toronto and the Ontario Cancer Institute in the 1960s.[2][3] As of 2016, the only established medical therapy using stem cells is hematopoietic stem cell transplantation,[4] first performed in 1958 by French oncologist Georges Mathé. Since 1998 however, it has been possible to culture and differentiate human embryonic stem cells (in stem-cell lines). The process of isolating these cells has been controversial, because it typically results in the destruction of the embryo. Sources for isolating ESCs have been restricted in some European countries and Canada, but others such as the UK and China have promoted the research.[5] Somatic cell nuclear transfer is a cloning method that can be used to create a cloned embryo for the use of its embryonic stem cells in stem cell therapy.[6] In 2006, a Japanese team led by Shinya Yamanaka discovered a method to convert mature body cells back into stem cells. These were termed induced pluripotent stem cells (iPSCs).[7]
full txt link : https://en.wikipedia.org/wiki/Stem_cell
How does the total amount of stem cells in humans change over time?
At what age does it reach its maximum and minimum?
When fertilization occurs, one: start life, two 120 years.
When certain data points are plotted, it seems feasible to converge through statistical methods (considering the number of inflection points).
Are there any papers related to the number of stem cells at various ages in a particular sample?
> No results found in the initial search. (Only use 14 min)
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