|
|
Molecular basis of the sperm selection in the mammalian female reproductive tract
Šrámková, Adéla ; Krylov, Vladimír (advisor) ; Postlerová, Pavla (referee)
Internal fertilization is typical for all mammals. The male transfers sperm cells into the female reproductive tract, where usually one of them reach the oocyte and fertilize it. The female reproductive tract must be adapted to provide a suitable environment for the sperm cells to survive until fertilization. On the other hand, it must also be able to select developmentally competent sperm cells and prevent others to get into the close contact with the oocyte. Physical and molecular mutual communication of sperm cells with the female reproductive tract is ensured by sperm surface molecules and the receptors of the female epithelia lining. It appears that these interactions are required for key transformations, both on the sperm surface and in the cells of the female reproductive tract, where gene expression is affected. As a result of these changes, the most suitable sperm cell with all the required characteristics is allowed to fertilize the matured oocyte.
|
|
| |
|
| |
|
| |
|
|
Magnetic orientation in mammals
Tejmlová, Kristýna ; Němec, Pavel (advisor) ; Vácha, Martin (referee)
Earth's magnetic field can provide animal with both directional and positional information. The ability to perceive and utilize information extracted from the geomagnetic field is called magnetoreception. Magnetoreception mechanisms remain largely unknown. Three main hypotheses are currently supported by experimental evidence. The light-independent mechanisms are based either on electromagnetic induction or on biogenic magnetite. The light-dependent mechanism is based on specific chemical reaction between radical pairs. Perception of the geomagnetic field facilitates both long- and short-distance orientation of animals. Some animals exhibit the magnetic alignment, i.e., spontaneuos preference for a certain geomagnetic direction. Another manifestation of magnetoreception is magnetic compass (polarity- or inclination-based, depending on species), which enable an animal to determine the azimuth, i.e., the angle between the direction of motion and geomagnetic field vector. Magnetic map sense enable an animal to determine its position and direction to the goal destination, most likely utilizing the inclination and the intensity of the geomagnetic field as navigational cues. Magnetic orientation of mammals seems to be a widespread phenomenon. Light- independend, polarity compass has been reported in...
|
|
|
Bird and Mammal Taxidermy
Tuzová, Lucie ; Řezníček, Jan (advisor) ; Štěpán, Jiří (referee)
This thesis deals with the preparation of dermoplastic materials of birds and mammals. They are described in detail specific methods of preparation from the collection of material to its final treatment. The first section summarizes the theoretical knowledge concerning preparation of dermoplastic models and osteological material. The second part is dedicated to knowledge survey of high school and primary school students concerning recognition of birds and mammals dermoplastic models. The results are processed by descriptive statistics. Keywords: taxidermy, dermoplastic models and osteological material, skulls, teeth, birds, mammals.
|
|
|
The catalogue of the mammalian fauna of pleistocenne localities in Prague area
Havlová, Tereza ; Mazuch, Martin (advisor) ; Kadlecová, Eva (referee)
More than a hundred sites were in Prague in the past, where skeletal remains of Pleistocene mammals had been found. Most of these sites were brickyards or sand pits. These pits were in operation during the second half of the 19th century and first half of the 20th century. Many awards were found during construction works as well. Most of researchers attended only several most famous sites at the time of the findings. The catalog summarizes the basic known information about majority of Prague localities and includes a list of taxa wich were found there. Key words: Prague, locality, mammals, Pleistocene, brickyards, sand pits
|
|
| |
|
|
Semantic function of the mammalian tail in the design of anal pole of the body
Baxa, Marek ; Komárek, Stanislav (advisor) ; Kleisner, Karel (referee)
The tail in mammals is an important organ, which in contrast to most vertebrae, doesn't add to the motor function of their bodies. The use of the mamals' tail is much more varied and it can fulfill many different functions. This work includes a survey of these functions and analyzes collected data concerning 553 spieces of mammals across all families. The data includes information about the length of tail, the length of body, body mass, living environment and outer signs on the anal pole of these species. The resulting analysis concludes that the tail length is dependent both on the length of the mammal's body and its living environment. Outward signs of the tail depend on its length as well as the length of the body and the living environment. Distinctive tail ending and tail base probably fulfill a communicative function. The tail is more likely to have communication than cryptic significance.
|
|
|
Metabolism of uric acid during mammalian evolution
Mančíková, Andrea ; Krylov, Vladimír (advisor) ; Stibůrková, Blanka (referee)
Uric acid is the end product of purine metabolism of humans and some higher primates. In other mammals enzyme urate oxidase is capable to further convert uric acid to allantoin. During evolution of primates several mutations in urate oxidase gene had occured, led the enzyme to decrease its activity or to complete loss of function. What was the initial impetus for the utilization of uric acid and what biochemical traits of uric acid led to a tendency to retain a major of this metabolite production in the bloodstream? Uric acid has antioxidant capabilities and it is scavanger of free radicals. Increased levels of uric acid in blood has an effect on acute and chronic elevations of blood pressure. It is possible that hyperuricemia helped to maintain blood pressure under low-salt dietary conditions of primates during the Miocene. This mechanism probably have allowed to stabilize bipedalism our ancestors. Uric acid has an important role as a neuroprotector. As inhibitor the permeability blood-brain barrier, uric acid limits the infiltration of undesirable substances to the neurons and prevents central nervous system against the formation of inflammatory diseases. Such as neurodegenerative diseases may be caused by reduced serum uric acid levels. Uric acid protects against peroxinitrite damage tissues in the...
|
guest ::
