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Reproductive-cell Cycle Theory
The reproductive-cell cycle theory posits that the hormones that regulate reproduction act in an antagonistic pleiotrophic manner to control aging via cell cycle signaling; promoting growth and development early in life in order to achieve reproduction, but later in life, in a futile attempt to maintain reproduction, become dysregulated and drive senescence. Rather than seeing aging as a loss of functionality as we get older, this theory defines aging as any change in an organism over time, as evidenced by the fact that if all chemical reactions in the body were stopped, no change, and thus no aging, would occur. Since the most important change in an organism through time is the chemical reactions that result in a single cell developing into a multicellular organism, whatever controls these chemical reactions that regulate cell growth, development, and death, is believed to control aging. The theory argues that these cellular changes are directed by reproductive hormones of the hy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hormone
A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physiology and behavior. Hormones are required for the normal development of animals, plants and fungi. Due to the broad definition of a hormone (as a signaling molecule that exerts its effects far from its site of production), numerous kinds of molecules can be classified as hormones. Among the substances that can be considered hormones, are eicosanoids (e.g. prostaglandins and thromboxanes), steroids (e.g. Estrogen, oestrogen and brassinosteroid), amino acid derivatives (e.g. epinephrine and auxin), protein or peptides (e.g. insulin and CLE peptides), and gases (e.g. ethylene and nitric oxide). Hormones are used to communicate between organ (anatomy), organs and Tissue (biology), tissues. In vertebrates, hormones are responsible for regulating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caloric Restriction
Calorie restriction (CR, also known as caloric restriction or energy restriction) is a dietary regimen that reduces the energy intake from foods and beverages without incurring malnutrition. The possible effect of calorie restriction on body weight management, longevity, and aging-associated diseases has been an active area of research. Dietary guidelines Caloric intake control, and reduction for overweight individuals, is recommended by US dietary guidelines and science-based societies. Calorie restriction is recommended for people with diabetes and prediabetes, in combination with physical exercise and a weight loss goal of 5-15% for diabetes and 7-10% for prediabetes to prevent progression to diabetes. Mild calorie restriction may be beneficial for pregnant women to reduce weight gain (without weight loss) and reduce perinatal risks for both the mother and child. For overweight or obese individuals, calorie restriction may improve health through weight loss, although a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theories Of Ageing
Ageing (or aging in American English) is the process of becoming older until death. The term refers mainly to humans, many other animals, and fungi; whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In a broader sense, ageing can refer to single cells within an organism which have ceased dividing, or to the population of a species. In humans, ageing represents the accumulation of changes in a human being over time and can encompass physical, psychological, and social changes. Reaction time, for example, may slow with age, while memories and general knowledge typically increase. Of the roughly 150,000 people who die each day across the globe, about two-thirds die from age-related causes. Current ageing theories are assigned to the damage concept, whereby the accumulation of damage (such as DNA oxidation) may cause biological systems to fail, or to the programmed ageing concept, whereby the internal processes (epige ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Reproduction
Human sexual reproduction, to produce offspring, begins with fertilization. Successful reproduction typically involves sexual intercourse between a healthy, sexually mature and fertile male and female. During sexual intercourse, sperm cells are ejaculated into the vagina through the penis, resulting in fertilization of an ovum to form a zygote. While normal cells contain 46 chromosomes (23 pairs), gamete cells contain only half that number, and it is when these two cells merge into one combined zygote cell that genetic recombination occurs. The zygote then undergoes a defined development process that is known as human ''embryogenesis'', and this starts the typical 38-week gestation period for the embryo (and eventually foetus) that is followed by childbirth. Assisted reproductive technology also exists, like IVF, some of which involve alternative methods of fertilization, which do not involve sexual intercourse; the fertilization of the ovum may be achieved by artificia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endocrinology
Endocrinology (from ''endocrine system, endocrine'' + ''wikt:-logy#Suffix, -ology'') is a branch of biology and medicine dealing with the endocrine system, its diseases, and its specific secretions known as hormones. It is also concerned with the integration of developmental events proliferation, growth, and differentiation, and the psychological or behavioral activities of metabolism, human development (biology), growth and development, tissue (biology), tissue function, sleep, digestion, Respiration (physiology), respiration, excretion, mood (psychology), mood, Stress (physiology), stress, lactation, Motor coordination, movement, reproduction, and sensory perception caused by hormones. Specializations include behavioral endocrinology and comparative endocrinology. The endocrine system consists of several glands, all in different parts of the body, that secrete hormones directly into the blood rather than into a Duct (anatomy), duct system. Therefore, endocrine glands are regarde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biogerontology
Biogerontology is the sub-field of gerontology concerned with the biological aging process, its evolutionary origins, and potential means to intervene in the process. The term "biogerontology" was coined by S. Rattan, and came in regular use with the start of the journal '' Biogerontology'' in 2000. It involves interdisciplinary research on the causes, effects, and mechanisms of biological aging. Biogerontologist Leonard Hayflick has said that the natural average lifespan for a human is around 92 years and, if humans do not invent new approaches to treat aging, they will be stuck with this lifespan. James Vaupel has predicted that life expectancy in industrialized countries will reach 100 for children born after the year 2000. Many surveyed biogerontologists have predicted life expectancies of more than three centuries for people born after the year 2100. Other scientists, more controversially, suggest the possibility of unlimited lifespans for those currently living. For examp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endocrinology Of Reproduction
Hormonal regulation occurs at every stage of development. A milieu of hormones simultaneously affects development of the fetus during embryogenesis and the mother, including human chorionic gonadotropin (hCG) and progesterone (P4). Embryogenesis Human chorionic gonadotropin (hCG), progesterone, 17β-estradiol, endorphins and gonadotropin-releasing hormone (GnRH) synthesis are rapidly upregulated by the developing embryo following fertilization of the ovum. During early embryonic development, paracrine/juxtacrine signaling of hCG induces blastulation and neurulation. An in vitro model of early human embryogenesis (human embryonic stem cells (hESCs)) has demonstrated that hCG promotes cell proliferation via the LH/hCG receptor (LHCGR). hCG signaling upregulates the expression of steroidogenic acute regulatory protein (StAR)-mediated cholesterol transport and the synthesis of progesterone in hESC. The production of progesterone at this time induces embryoid body (akin to blastu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabiosis
Parabiosis is a laboratory technique used in physiological research, derived from the Greek word meaning "living beside." The technique involves the surgical joining of two living organisms in such a way that they develop a single, shared physiological system. Through this approach, researchers can study the exchange of blood, hormones, and other substances between the two organisms, allowing for the examination of a wide range of physiological phenomena and interactions. Parabiosis has been employed in various fields of study, including stem cell research, endocrinology, aging research, and immunology. Heterochronic parabiosis involves parabiosis of animals of different ages; this allows researchers to study how circulating blood-borne factors influence aging and tissue regeneration. The method has led to insights into stem cell function, neurogenesis, regeneration (biology), and aging. In contrast, isochronic parabiosis joins two animals of the same age. Parabiotic experim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertility
Fertility in colloquial terms refers the ability to have offspring. In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to reproduce, which is termed fecundity. The fertility rate is the average number of children born during an individual's lifetime. In medicine, fertility refers to the ability to have children, and infertility refers to difficulty in reproducing naturally. In general, infertility or subfertility in humans is defined as not being able to conceive a child after one year (or longer) of unprotected sex. The antithesis of ''fertility'' is infertility, while the antithesis of ''fecundity'' is sterility. Demography In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to produce which is termed fecundity. While fertility can be measured, fecundity cannot be. Demographers measure the fertility rate in a variety of ways, which can be broa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germ Cells
A germ cell is any cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm. Unlike animals, plants do not have germ cells designated in early development. Instead, germ cells can arise from somatic cells in the adult, such as the floral meristem of flowering plants. Introduction Multicellular eukaryotes are made of two fundamental cell types: germ and somatic cells. Germ cells produce gametes and are the only cells that can undergo meiosis as well as mitosis. Somatic cells are all the other cells that form the building blocks of the body and they only divide by mitosis. The lineage of germ cells is called the germline. Germ cell specification begins during cleavage in many animals or in the epiblast during gastrulation in bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cancer
Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible Signs and symptoms of cancer, signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in defecation, bowel movements. While these symptoms may indicate cancer, they can also have other causes. List of cancer types, Over 100 types of cancers affect humans. Tobacco use is the cause of about 22% of cancer deaths. Another 10% are due to obesity, poor Diet (nutrition), diet, sedentary lifestyle, lack of physical activity or Alcohol abuse, excessive alcohol consumption. Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. infectious causes of cancer, Infection with specific viruses, bacteria and parasites is an environmental factor cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aging
Ageing (or aging in American English) is the process of becoming Old age, older until death. The term refers mainly to humans, many other animals, and fungi; whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In a broader sense, ageing can refer to single cells within an organism which have Cellular senescence, ceased dividing, or to the Population ageing, population of a species. In humans, ageing represents the accumulation of changes in a human being over time and can encompass physical, psychological, and social changes. Reaction time, for example, may slow with age, while memories and general knowledge typically increase. Of the roughly 150,000 people who die each day across the globe, about two-thirds die from age-related causes. Current Theory of aging, ageing theories are assigned to the damage concept, whereby the accumulation of damage (such as DNA oxidation) may cause biological systems to fail, or to the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
