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Morfologiczne zróżnicowanie plemników wśród płazów bezogonowych

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Piprek R. P.
Kosmos
|
2011
|
vol. 60
|
issue 1-2
81-87
EN
Comparison of the sperm structure in individual groups of Anurans shows that spermatozoa are very various. In all amphibian species sperm have an acrosome. An axial perforatorium located in the endonuclear channel is present in spermatozoa of basal anuran families. A conical perforatorium surrounds the front part of the nucleus. This structure has been secondarily lost in some anurans. There is a fossa in the basal end of the nucleus, in which the centriola is placed. Movement organ (tail) is usually composed of the axoneme and the axial fiber. Sperm provided with two flagella have developed independently about 7 times during the evolution of Anura. Analysis of the above considerations indicates three main trends in the evolution of Anuran sperm where can be distinguished: 1) modification of perforatorium, involving the reduction of axial perforatorium, conical perforatorium development or loss of both of these structures; 2) modification of the basal part of the nucleus by reduction of fossa, or development of a second fossa; 3) modification of the tail due to the disappearance of the axial fiber, undulating membrane or development of additional axoneme. Comparing the structure of Anuran spermatozoa it can be concluded that the comparative spermatology does not provide evidence for affinities of individual animal groups.
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Genetyczne mechanizmy determinacji płci i różnicowania gonad ssaków

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Piprek R. P.
Kosmos
|
2007
|
vol. 56
|
issue 1-2
39-48
EN
Sex determination and gonadal differentiation are crucial for reproductive success of an individual because they are directly responsible for correct development of gonads that orchestrate sex features and produce gametes. If germ cells are placed in a sex reversed gonad, their genetic sex will be opposite to gonadal sex, which will cause disturbance during spermatogenesis or oogenesis. This indicates that gonadal sex has to be compatible with genetic sex. A lack of compatibility is the direct cause of infertility in disorders such as sex reversal or hermaphroditism. It may be assumed that there is a system of protection against switching on genetic pathways involved in differentiation of the opposite sex gonad. In fact, genetic mechanisms underlying sex determination make up a network of positive and negative molecular interactions, both of which lead to structural changes and prevent sex reversal. All sex determination pathways depend on the existence of Sry, expression of which has to take place within a critical time window so that a testis can develop. Moreover a threshold of both Sry expression level and number of Sry-positive cells needs to be overcome. The key event of male sex determination is DNA bending by SRY, which causes direct or indirect upregulation of Sox9. Most likely SOX9 switches on the expression of multiple genes, driving a bipotential gonad towards differentiation into a testis. Surprisingly, proteins such as DAX1 and WNT4, originally recognized as anti-testis factors, have turned out to be necessary for testis development. Another important discovery was establishing that r-spondin 1 is an essential factor in the female pathway, the loss of which results in a complete sex reversal, which indicates that Sry is not an irreplaceable testis determining factor under some conditions.
3
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Zależne od płci różnice w budowie mózgu

100%
Piprek R. P.
Kosmos
|
2011
|
vol. 60
|
issue 3-4
323-331
PL
Anatomiczna analiza mózgu wskazuje na istnienie określonych rejonów wykazujących dymorfizm płciowy. Ośrodki te mogą być odpowiedzialne za seksualność, cechy psychiczne związane z płcią oraz orientację seksualną. Wiele takich miejsc odnaleziono w obrębie podwzgórza, które stanowi centrum kontroli czynności naszego organizmu w dużej mierze niezależne od naszej woli. Ponadto dymorfizm płciowy jest dostrzegalny w niektórych jądrach przodomózgowia takich jak BNST i ciało migdałowate oraz w móżdżku, jak również w systemie spoideł, stanowiących połączenia obu półkul.Co ciekawe, ośrodki mózgowe wykazujące dymorfizm płciowy często są połączone ze sobą włóknami nerwowymi, na przykład, SCN wysyła włókien nerwowych do POA, BNST i ciała migdałowatego centralnych. Rozwój tych części mózgu jest istotny dla wykształcenia seksualności osobnika. Wykazano wiele podobieństw w ośrodkach mózgu u homoseksualnych mężczyzn i kobiet. Ośrodki SDN-POA i SCN wydają się być związane z orientacją seksualną, podczas gdy SDN-POA oraz BNST zidentyfikacją płciową. Wskazuje to na biologiczne podłoże homoseksualizmu i transseksualizmu, które są kreowane jeszcze w okresie życia płodowego. Ponadto te same ośrodki mózgu, mogą być odpowiedzialne także za funkcje nie związane z seksualnością, na przykład SCN jest odpowiedzialny również za rytm dobowy, VMN za uczucie sytości, ciało migdałowate i hipokamp za pamięć, a móżdżek i AVPV kontrolują ruchy ciała. Badania wskazują także na dymorfizm płciowy ośrodków mózgu odpowiedzialnych za niektóre zaburzenia neuropsychiatryczne, takie jak depresja, ujawniając przyczyny związku zachorowalności z płcią.
EN
Present knowledge indicates the existence of many structures in the brain that are associated with sexuality and show sexual dimorphism. Interestingly, brain centers showing the relationship of sexuality are interconnected with the neural pathway, for example, the SCN sends nerve fibers to the POA, BNST and central amygdala. Centers showing sexual dimorphism are mainly located in the hypothalamus, which is involved in controlling our functions without our will. The hypothalamus is the seat of sexual behavior, sexual identity and orientation. The centers of the brain showing sexual dimorphism often show similarities in homosexual men and women. This confirms the Dorner's hypothesis, which assumes that homosexuals have a female hypothalamus. SDN-POA centers and SCN appear to be related to sexual orientation, whereas the SDN-POA centers and BNST to the gender identification. This implies the biological foundations of homosexuality and transsexualism. Interestingly, the same centers may be responsible also for functions not related to sexuality, such as the SCN that is also responsible for circadian rhythms, VMN for a feeling of satiety, and the amygdala and hippocampus for memory. There are three groups of brain structures exhibiting sexual dimorphism. First, it is the hypothalamus, which controls sexual behavior, secondly it is the amygdala, along with the hippocampus, involved in the process of remembering, and third is a system of commissures responsible for communication between two hemispheres.
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