Temperature is the only determinant of cryptorchidism not forming sperm Tokyo Denki University
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In the future, by clarifying the target in which the DNA replication apparatus of cells that become sperm is inactivated at 37 ° C, it is possible that spermatogenesis can be promoted by supplementing the molecule. Is also expected to develop into one of the future fertility treatments.
According to the research results of Professor Shigenobu Sword of Tokyo Denki University, the cause of sperm formation in "undescended testis" is temperature ... → Continue reading
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The state in which the activated substance returns to its original state, or irreversibly becomes irreversible, means that "Inactivated"(Fukatsuka) or"Deactivation"(Shikkatsu).
- To convert a reagent that cannot be used in the stored state into a usable state by applying chemical or physical changes.Molecular sheave,catalystIt is used for such things. →reagent
- To make a chemical change,Ground stateGives external energy to the reactants inTransition stateAfter going through the intermediate state, it is transformed into a product with lower energy.At this time, the energy given from the outside is "Activation energyIs called. →Activation energy
Activation in biology and medicine is a number of in vivo activations酵素It is often used to show the function of.It should be noted that other cases may represent different events (although the nuances are similar).
- Of the receptorConformationChanged,LigandTo change to a state that can be combined with. →Receptor
- feedbackBymetabolism酵素Refers to being induced. →metabolism
- lymphocytesActivation of immune function
- "Brain activation": 
- Region(Region) Activation → Regional activation
- Revitalizing local communities
- Revitalization of local industry
- Revitalization of local tourism
As an example in the name of the law
- "Activation of Diet deliberations" → 国会Deliberation
- "Activation of specific free trade areas"
- "Activation of business activities of small and medium-sized enterprises" → Jewelry business,中小企业
- "Improvement of urban area and revitalization of commerce in the central city area"[Source required]
- "Special cases when hiring private human resources to revitalize public affairs" →
- "Activation of specific industrial agglomeration" →
- "Activation of agriculture and forestry in specific rural areas" → Regional activation,Rural,Mountain village,Agriculture:,forestry
In local governments and industry, there are many organizations with the name "revitalization". "Activation center" "Activation mechanism" etc.
|[How to use footnotes]|
- ^ Progressive Japanese-English Chinese Dictionary "Activation"
- ^ Kojien "Activation"
- ^ As a method[Source required]Health food, music, reading aloud, mental arithmetic,VisualStimulation, laughter, etc.
- List of pages starting with "Activity"
- Political / economic
- natural Science
Spermatogenesis (Sperm, sperm,British: spermatogenesis) Is from male primordial germ cellsMitosisandMeiosisThroughspermIs the process of formation.Early cells in this pathwaySpermatogoniaAnd by mitosis of spermatogoniaPrimary sperm cellIs formed.The primary spermatocyte undergoes meiosis (meiosis first division) into two secondary spermatocytes.Each secondary spermatocyte undergoes meiosis and second division and divides into two spermatocytes.Sperm cells mature and differentiate into sperm.Thus, the primary spermatocytes give rise to two secondary spermatocytes, which further divide into four secondary spermatocytes, each of which becomes four spermatocytes..
Sperm is a lotSexual reproductionMale mature in organismsGameteIs.Spermatogenesis in men corresponds to oogenesis in women, and both processes are called gametogenesis.In mammals, of menTestes OfSeminiferous tubuleGradual differentiation is performed at.Optimal environment is very important for normal spermatogenesis and is essential for sexual reproduction.DNA methylationandHistoneModification is involved in the regulation of this process..SpermatogenesispubertyStarting from, the amount of sperm formed with aging decreases slightly, but continues uninterrupted until the individual dies.Male infertilitySee also item.
Spermatogenesis is the process of forming sperm, the mature gamete of males.Sperm is a female gamete with an eggFertilizationThen,Joined bodyIsFertilized eggIs formed.This is the basis of sexual reproduction. Both gametesHalf bodyAnd half the normal setChromosomehave.Fertilization results in a (diploid) fertilized egg with a normal number of chromosomes.The normal number of chromosomes varies from species to species.To maintain a normal number of progeny chromosomes, each gamete should be anotherSomatic cellsYou need to have half the number of chromosomes.If the gamete has the same number of chromosomes as the somatic cell, the number of chromosomes in the offspring will be double the normal number, and serious abnormalities may occur.In humans, abnormal chromosome numbers are congenital genetic disorders (Down syndrome,Kleinfelter syndrome), The nature of the fetusabortionOften leads to.Abnormal chromosome numbers at the stage of spermatogenesis can lead to these diseases.
Spermatogenesis takes place within several structures of the male reproductive system.The initial stage occurs in the testes and thenEpididymisMove to.In the epididymis, gametes mature and are preserved until ejaculation.This process is in the testiclesSeminiferous tubuleIt starts from.On the base side of the seminiferous tubuleStem cellsFrom there, division begins and progresses as it progresses to the innermost lumen of the tube.Maturation occurs in the epididymis.To form mature sperm, the process of spermatogenesis requires a temperature 37–1 ° C lower than 8 ° C (normal body temperature).Therefore, the temperature of the testes and scrotum is especially important...The structure of the testes and scrotum hanging from the body is important for controlling temperature.Clinically, small temperature fluctuations do not lead to sperm survival or loss of sperm count..
In humans, the entire process of spermatogenesis is 74 days Approximately 120 days from (according to tritium-labeled biopsy) It is estimated to take (by DNA clock measurement).It takes 3 months including the time to pass through the pipe.2 to 3 million sperms are formed every dayHowever, only about half or 1 million sperms become mature..
Each stage of the spermatogenesis process can be divided by cell type.As shown in the following table, it can be classified by ploidy, number of copies and number of chromosomes, amount of DNA contained in cells, type of cell division, and the like.Primary spermatocytes undergo cell division after DNA synthesis.
|Cell type||Ploidy/ Number of chromosomes in human||Number of DNA copies /Number of chromosomes in humans||The process to be done later|
|Spermatogonium spermatogonium||Diploid (2N) / 46||2C / 46||spermatocytogenesis (Cell division)|
|Primary spermatocyte||Diploid (2N) / 46||4C / 2x46||spermatidogenesis|
|Secondary spermatocytes two secondary spermatocytes||Ploidy (N) / 23||2C / 2x23||spermatidogenesis|
|Sperm cells four spermatids||Ploidy (N) / 23||C / 23||spermiogenesis spermatogenesis|
|sperm spermatozoids||Ploidy i (N) / 23||C / 23||spermiation sperm|
Spermatocyte formation is the process of male reproductive mother cell formation, resulting in the formation of haploid spermatocytes with half the normal genetic material.In spermatogenesis, diploid spermatogonia located in the base of the seminiferous tubule undergo mitosis, producing two diploid cells called primary spermatocytes.Primary spermatocytes migrate to the inside of the seminiferous tubule, replicate DNA, and then undergo meiosis to become haploid secondary spermatocytes.In meiosis, in order to increase the genetic diversity of gametes, chromosomes inherited from parents are randomly distributed, and genetic variation such as crossing homologous chromosomes occurs.
During division from spermatogonia to spermatogonia, each cell is not completely separated.Allowing cells to differentiate synchronouslyCytoplasmAre bridged and remain connected to each other.Also, not all cells produced by the division of spermatogonia become spermatocytes.To prevent spermatogonia from disappearing, spermatogonia undergo mitosis to ensure that they form their own copy..
Meiosis Binary fission Spermiogenesis
Meiosis of secondary spermatocytes The second division forms haploid spermatocytes.Secondary spermatocytes are not observed in most histological observations because this stage progresses so quickly.
During spermatogenesis, in sperm cellsCentrioleOn the basis ofMicrotubuleGrows elongated and begins to form the sperm tail.These microtubulesFlagellaTo form.The anterior part of the tail becomes thicker because mitochondria are placed around the flagella to ensure energy supply, and this part is called the middle piece.Sperm cell DNA is highly condensed and packaged. After the DNA is packaged with a particular nuclear basic protein, that protein is during sperm cell elongation.ProtamineIt is replaced with a protein called.The resulting condensationChromatin TheTranscriptionWill not be done.Golgi apparatus TheAcrosomeAnd surrounds the condensed nucleus.
after that,testosteroneMaturation occurs under the influence of the remaining unwanted cytoplasmOrganelleIs removed.Excess cytoplasm, called the residue, surrounds the testis.Sertoli cellsIs devoured by.The sperm formed are mature but not motile.It is released from the protected Sertoli cells in the lumen of the seminiferous tubules in a process called excretion.
Non-motile sperm are secreted by Sertoli cells with the help of peristaltic contractions and transported to the epididymis in the testicular fluid.In the epididymis, sperm acquire motility and become fertilized.However, the movement of the rest of the reproductive system of mature sperm is not the motility that the sperm acquire here, but the contraction of the muscles.
Role of Sertoli cells
At all stages of differentiation, sperm cells are in close contact with Sertoli cells.Sertoli cells are thought to structurally and metabolically support developing sperm cells.A single Sertoli cell extends from the basement membrane of the seminiferous tubule to the lumen.Sertoli cells support developing gametes and play many functions in spermatogenesis in the following ways:
- By building the blood-testis barrier, we maintain the environment necessary for differentiation and maturation.
- Secretes a substance that initiates meiosis.
- Secretes body fluids around the testes.
- Secretes androgen-binding protein (ABP). ABP concentrates testosterone in the vicinity of developing gametes.Testosterone is required in high concentrations for the maintenance of reproductive organs. Infertility without high concentration by ABP.
- Pituitary glandHormones that affect spermatogenesis control, especially polypeptide hormonesInhibinSecrete.
- It phagocytoses the cytoplasm that remains during spermatogenesis.
- Secretes anti-Müllerian hormone,Muller tubePrevent the formation of.
- Blood-testis barrierBy formingImmune systemProtects sperm cells from.
- It is an cell-cell adhesion moleculeICAM-1, And soluble ICAM-1 form the blood-testis barrierTight junctionIs a molecule that has an antagonistic effect on.. The ICAM-2 molecule regulates adhesion between the apical side of the barrier and sperm cells.
The spermatogenic process is very sensitive to environmental changes, especially hormones and temperature.Testosterone is locally elevated by binding by the androgen-binding protein present in the seminiferous tubules, and this concentration is required during spermatogenesis.Testosterone is adjacent to the seminiferous tubuleLeydig cellsと 呼 ば れ るStromal cellsProduced by.In humans and other animals, the epithelium is vulnerable to high temperatures and is adversely affected at temperatures above normal body temperature.Therefore, the testes are wrapped in a bag of skin called the scrotum, which hangs on the outside of the body.Optimal temperature is maintained at 2 ° C (8 ° C for humans and mice) below body temperature.Temperature is controlled by the cremaster muscle and the smooth muscle of the flesh-like scrotum, as it moves away from and approaches the body, and blood flow. Adjusted by.Anabolic steroids,metal(cadmium,lead), Nutrition deficiency (Vitamin B,E,ASuch),X-rayExposure toDioxin, Alcohol, and infections also adversely affect the rate of spermatogenesis.[Source required] Also, the male germline isOxidative stressIt is highly sensitive to DNA damage caused by this damage, which probably has a significant impact on fertilization and pregnancy..InsecticideExposure to spermatogenesis also affects spermatogenesis.
Hormonal regulation of spermatogenesis varies from species to species.The mechanism in humans is not completely understood.But the onset of spermatogenesisHypothalamusIt is known to occur during puberty due to the interaction between the pituitary gland and Leydig cells.If the pituitary gland has been removed,Follicle stimulating hormone(FSH) and testosterone can initiate spermatogenesis.. In contrast to FSHLuteinizing hormone(LH) plays a role in spermatogenesis other than inducing gonadal testosterone production.
FSH stimulates both the production of androgen-binding protein (ABP) by Sertoli cells and the formation of the blood-testis barrier. ABP is essential for concentrating testosterone to levels high enough to maintain spermatogenesis.Testosterone levels in the testes range from 5–10 times higher among healthy men, but 20–100 or 50–200 times higher than those found in blood... FSH can capture and concentrate testosterone in the testis, but once development begins, only testosterone is required to maintain spermatogenesis...However, when FSH increases, of type A spermatogoniaApoptosisIncreases sperm production by preventing.Activin acts to reduce the level of FSH.Studies from model organisms in rodents show that gonadotropins (both LH and FSH) support spermatogenic processes and promote spermatogenic cell survival by suppressing signals that promote apoptosis. Is suggested.
Sertoli cells themselves mediate part of spermatogenesis through hormone production.Sertoli cellsEstradiolAnd can produce activin.Leydig cells mainly produce testosterone and can also produce estradiol.estrogenHas been found to be essential for spermatogenesis in animals..Men with estrogen insensitivity syndrome (ERα deficiency) have been reported to have normal sperm counts but abnormally low sperm viability (infertility unknown)...Abnormally high levels of estrogen cause suppression of gonadotropin secretion and overproduction of testosterone in the testis, which may be detrimental to spermatogenesis.. Also,ProlactinSeems to be important for spermatogenesis.
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- Evolution of sexual reproduction
- Germ cells
- Male infertility
- Origin and function of meiosis
- Sertoli cells
- Sexual reproduction
- Semen analysis