Tag: Plasma Membrane

Progesterone and zona glycoprotein (ZP3) can induce the AR but do not exert their effects through the same receptor, as far as the receptor-mediated ions fluxes are concerned. Despite the molecular dissimilarity of progesterone and ZP3, each of them can activate at least two different types of receptors responsible for Ca2+ channels—onereactingrapidly,andthusprobablyactivateddi-rectly by the inducer, and the other responding after some delay and probably regulated by the inducer indirectly tia a signaling cascade. The nature of the stallion sperm progesterone receptor as well as the putative Ca2+ channel involved in signaling remains to be elucidated. In human spermatozoa, the molecular mass recognized by C-262 was 50-52 kDa protein, which is different from that of the A and B isoforms of human intracellular progesterone receptor, 94 and 120 kDa, respectively. A specific membrane protein with affinity for progesterone has been isolated from rat brain that has an estimated molecular mass of 40-50 kDa. flovent inhaler

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DISCUSSION(7)

C-262- and P-BSA-conjugates have affinity only for the native, not for the denatured progesterone receptor of human and sperm samples. Therefore, we believe that identification of the progesterone receptor is not possible with Western blots of SDS-PAGE-separated sperm protein samples (although similar results were obtained on Western blots of SDS-PAGE human sperm protein samples as described by Sabeur et al. ). Another line of evidence for the presence of a progesterone receptor is the fact that for P-BSA-FITC and for C-262/RAM-FITC, 1) fluorescent labeling patterns (Fig. 1) and relative proportions of sperm cell populations with one type of labeling (Fig. 4) were identical and 2) ultrastructural localization was identical(Fig. 3). buy birth control online

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These non-viable spermatozoa remained P-BSA-FITC positive, probably due to postacrosomal cytosolic staining (see Figs. 1C and 3B). Although a slightly higher proportion of P-BSA-FITC spermatozoa was determined with the flow cytometer in comparison with the fluorescence microscopy observation, the differences were smaller than 3-6%. It should be mentioned that P-BSA-FITC-stained sperm samples were analyzed as fixed samples for the fluorescence microscopy but were not fixed for analysis with the flow cytometer. buy flovent inhaler

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DISCUSSION(5)

The damaged plasma membrane enables labeling of a cytosolic progesterone receptor at the postequatorial region of the sperm head (Figs. 1C and 3B). Only a few deteriorated cells could be detected with a combination of patchy apical labeling together with the postequatorial labeling (probably cells that deteriorated during the AR). The majority of deteriorated cells, however, showed only postacrosomal intracellular P-BSA-FITC binding sites. This could be the case because such cells have shed the apical plasma membrane (with its P-BSA-FITC binding sites) during the AR, prior to deterioration, as is depicted for one sperm cell in Figure 3B. The fact that we often observed P-BSA-FITC-positive free acrosome caps in our microscopical preparations supports this idea. An alternative explanation is that the deteriorated cells did not expose the progesterone receptor prior to deterioration. birth control yasmin

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In this scenario the sperm uncoating process of P-BSA-FITC-negative sperm cells was still not effective. An alternative explanation for the sperm cell population that remained negative for P-BSA-FITC or for C-262/RAM-FITC staining (after 5-h capacitation period; Figs. 5 and 6) is the possibility that they lack the progesterone receptor. However, this is unlikely, since after Percoll washing, most cells (> 95%) were positively stained for the progesterone receptor at the apical plasma membrane (Fig. 2B). buy cheap antibiotics

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DISCUSSION(3)

Thus, only a limited proportion of the sperm population in an ejaculate appears to show the progesterone receptor after prolonged incubation. Tesarik et al. also reported the presence of a selective sperm population demonstrating the progesterone receptor in humans. Protein synthesis is completely shut down during spermatogenesis, and vesicle-mediated protein transport to the plasma membrane has not been demonstrated in mature sperm cells. Therefore, the progesterone receptor is most likely present on spermatozoa before ejaculation but coated by extracellular material. antibiotic levaquin

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Immunogold labeling of P-BSA-FITC showed the exclusive localization of the gold particles on the apical plasma membrane of viable cells (Fig. 3A) and in the cytosol of deteriorated cells (Fig. 3B). Identical results were obtained by immunogold labeling of C-262/RAM-FITC. The presence of progesterone receptors in the apical plasma membrane of spermatozoa has previously been reported for humans. In contrast, Sabeur et al. demonstrated progesterone binding to the equatorial region on the human sperm head. Since Sabeur et al. subjected sperm cells to ethanol permeabilization prior to the immunolabeling procedure, this postequatorial staining most likely reflects intracellular labeling of progesterone receptors (as is depicted for deteriorated stallion sperm cells in Figs. 1B and 3B). antibiotics levaquin

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