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E Töpfer-Petersen

Publications and source records attributed to E Töpfer-Petersen.

At least 19 recordsLinked to original sources
PubMed2006

Enhanced binding of sperm with superior volume regulation to oviductal epithelium.

The plasma membrane is a key organelle with respect to sperm fertilizing ability. A sensitive way of testing plasma membrane functionality is to examine the sperm ability to moderate its swelling in response to hypo-osmotic stress (volume regulatory ability) using an electronic cell counter to assess cell volume changes. In this study of frozen-thawed bull sperm, we examined the relationship among sperm-oviductal epithelium binding capacity, osmotically induced swelling response, volume regulatory ability, and standard spermatologic parameters. Sperm cell volume distributions were measured under iso-osmotic conditions and after hypo-osmotic stress. The relative volume shift was calculated by comparing modal values of the cell volume distributions during transition from iso-osmotic to hypo-osmotic conditions. Significant correlations were found between volumetric parameters and sperm-oviduct binding capacity. Both the relative volume shift and regulative volume decrease correlated positively and significantly with the sperm-oviduct binding capacity. No significant correlations were found between sperm volumetric parameters and any of the standard sperm parameters with the exception of forward motility of Percoll-washed sperm. However, the use of multiple regression models improved the prediction level for binding capacity when motility parameters were combined with membrane integrity and volumetric parameters (R2 = .84). Spermatozoa of bulls with high nonreturn rates responded to hypotonicity as "perfect osmometers." Subfertile bulls had lower binding indices and deficiencies in volume recovery after hypotonic challenge, indicating that intact volume regulatory ability is a necessary prerequisite for binding to oviductal epithelium and is related to fertility. Volumetric parameters therefore could be used as tools in semen evaluation programs.

Animals↗
PubMed2006

Binding of boar spermatozoa to oviductal epithelium in vitro in relation to sperm morphology and storage time.

In vitro short-term storage of boar semen for up to 72 h before insemination negatively affects fertility, but this often remains undetected during semen quality assessment. One important sperm function is the ability to form the functional sperm reservoir in the oviduct. In the present study, we used the modified oviductal explant assay to study sperm binding to oviductal epithelium in vitro in diluted boar semen stored for 24 or 72 h. First, we determined the kinetics of in vitro sperm binding to oviductal epithelium in relation to co-incubation time of sperm and oviductal tissue pieces. Then, we studied how the binding of sperm to oviductal epithelium was affected by in vitro semen storage and by differences among individual boars. Sperm binding after different incubation times was significantly higher when semen was stored 24 h than after 72-h storage (P < 0.05), and peaked at 30-90 min of incubation. Sperm binding differed between boars (n = 44), and was negatively correlated to the percentage of sperm with cytoplasmic droplets (R = -0.51, P < 0.001). There were no significant changes in motility, acrosome integrity and propidium iodide stainability during the 72-h storage period. However, sperm-binding indices were significantly lower after 72 h in vitro storage than after 24-h storage in sperm from boars with normal semen quality (P < 0.05); in contrast, the binding capacity of sperm from boars with higher percentages of morphologically altered sperm remained at a low level. The sperm-binding capacity of sperm from four of the five boars with known subfertility was lower than the mean binding index minus one standard deviation of the boar population studied here. It is concluded that changes in the plasma membrane associated with in vitro ageing reduce the ability of stored boar sperm to bind to the oviductal epithelium. This study shows the potential of sperm-oviduct binding as a tool to assess both male fertility and changes in sperm function associated with in vitro ageing.

Acrosome↗
PubMed2006

Structural, biochemical and functional aspects of sperm-oocyte interactions in pigs.

Polyspermic fertilization is still a major issue in porcine IVF systems. New information is available to characterize the zona pellucida (ZP) at different developmental stages by scanning electron microscopy (SEM) and by confocal microscopy to show the distribution of ZP glycoproteins. SEM images indicated no differences between in vivo and in vitro matured oocytes; however a change in the surface structure between immature and matured oocytes, as well as between mature oocytes and preimplantation embryos was obvious. In addition, spermatozoa were more tightly fixed in the ZP of in vivo produced compared to the ZP of in vitro produced embryos. The ZP undergoes biochemical changes during maturation prior to fertilization. The acidity of the ZP increases during maturation as indicated by a shift of 1.3 pl units for ZPB/ZPC and 0.8 pl units for ZPA in 2D gel electrophoresis, which is based on increasing sulfation of the oligosaccharides during maturation. Mass spectrometry in combination with in-gel deglycosylation allowed the mapping of new glycosylation sites. Functionality of the ZP also depends on its maturation status. Induction of the acrosome reaction was delayed when capacitated spermatozoa were exposed to immature oocytes.

Animals↗
PubMed2005

Volume regulatory function and sperm membrane dynamics as parameters for evaluating cryoprotective efficiency of a freezing extender.

In the past years a series of functional assays has been developed to determine the structural, morphological and functional integrity of the plasma membrane and sperm acrosomal membrane. Cell volume regulation is an important physiological function crucial for the success of cryopreservation. In this study, the effects induced by freezing-thawing were judged by evaluating the functional characteristics of frozen-thawed semen samples submitted to secondary stress such as osmotic challenge or incubation under capacitating conditions, following cryopreservation. Prior to freezing, dog semen samples were diluted in the presence or absence of Equex STM Paste, which contains sodium dodecyl sulphate (SDS) as the active ingredient. Cell volume regulation and capacitation and calcium ionophore-induced membrane dynamics were assessed in freshly diluted and frozen-thawed semen samples by electronic volume measurement and flow cytometry. Cryopreservation led to a disturbance of the volume regulatory function and to a rapid decrease in the proportion of acrosome-reacted live spermaotozoa. Extender containing Equex STM Paste had a protective effect on isotonic cell volume, on regulatory function under hypertonic conditions, and on the proportion of live acrosome-reacted cells. The evaluation of the functional state of sperm submitted to secondary stress after freezing-thawing leads to a more subtle characterization of sperm function and helps improve the cryoprotective efficiency of the extender.

Acrosome↗
PubMed2005

Importance of sperm-binding assays for fertility prognosis of porcine spermatozoa.

There has been a considerable effort to establish correlations between the outcome of in vitro sperm-binding assays and the fertility achieved by individual males under conditions of commercial AI. During passage through the oviduct, a fertilizing spermatozoon has to bind to and interact with several targets. Generally, it is assumed that these interactions can be mimicked by in vitro binding assays. However, there is little evidence that assays based on zona binding, zona penetration, or IVF: (a) have been adequately validated; (b) provide data with a high degree of correlation to a boar of average fertility; (c) provide accurate predictions as to pregnancy rate and litter size from a given boar when used for commercial AI. This is due partly to the variability in measurements of pregnancy rate and litter size in a commercial setting and partly to the fact that sperm fertility is multifactorial. A recently developed in vitro test is based on the fact that spermatozoa bind in vivo to oviduct epithelium, creating a functional sperm reservoir, and that fertilization-competent spermatozoa are released in a time-dependent manner from these cells. Mating or insemination occurs usually hours before ovulation thus rendering such temporary sperm binding to the epithelial cells, a prerequisite for successful sperm-oocyte interaction. In vitro binding of porcine spermatozoa to explants derived from fresh oviduct epithelium may provide a useful test system to predict fertility, although detailed validation has not been published. The sperm-oviduct-binding assay tests for multifunctional characteristics of the plasma membrane and may be a valuable in vitro test to identify subfertile boars. We believe that boar subfertility might be indicated in vitro by reduced capacity of his spermatozoa to bind to oviductal cells and that this may provide information as to whether an adequate sperm reservoir will presumably be established in vivo from the sperm population that successfully has passed the barriers of the utero-tubal junction.

Animals↗
PubMed2005

Regulatory and necrotic volume increase in boar spermatozoa.

Spermatozoa of many species initially respond to hypotonicity as perfect osmometers. Thereafter they undergo a regulatory process resulting in a decrease in cell volume, similar to that reported for somatic cells. Regulatory volume increase (RVI), a complementary process which is assumed to occur following initial shrinkage of sperm volume after exposure to a hypertonic medium, has not yet been described in detail for spermatozoa. In this study, we investigated whether spermatozoa are able to regulate their volume after hypertonic stress and whether this ability is maintained in preserved sperm. Cell volume changes were recorded using electronic cell sizing. Sperm response to the ion channels blockers quinidine, tamoxifen, and dydeoxyforskolin, and to protein kinase/phosphatase inhibitors lavendustin, staurosporine, and vanadate was studied to investigate possible mechanisms of RVI. Annexin V staining was used in combination with propidium iodide to determine whether hypertonic stress may induce apoptosis. Overall protein tyrosine phosphorylation under hypertonic conditions was measured via flow cytometry using antiphosphotyrosine antibody. Spermatozoa exposed to hypertonic stress initially responded with an abundant subpopulation according to the perfect osmometer model and recovered their volume from this shrinkage after 20 min. RVI was inhibited by quinidine and tamoxifen, which indicates the involvement of the important cellular ions sodium and chloride in this process. Volume regulatory ability was essentially maintained during storage of liquid semen. However, the response of the sperm population was heterogeneous. A second population raised, containing spermatozoa with larger volumes, which demonstrated irregularities in the volume response with respect to osmotic challenge, ion channel blockers, and storage. Under hypertonic conditions, both protein kinase inhibitors (PKI) led to increased isotonic volumes and to elevated initial relative volumes and subsequent volume decrease. RVI was inhibited by the vanadate. Hypertonic stress did not result in an increase in early apoptotic cells, but produced a shift toward late necrotic cells. Substitution of sodium and chloride by choline and sulfate resulted in decreased isotonic volume of sperm treated with lavendustin. Tyrosine phosphorylation levels were reduced after 20 min under hypertonic conditions. It was concluded that RVI is regulated via a protein tyrosine kinase-dependent pathway, and that dephosphorylation occurs when volume regulation is required. The necrotic volume increase (NVI) is associated with the accumulation of sodium and chloride following uncontrolled opening of the channels. The ability to regulate volume after exposure to hypertonic conditions is important for sperm functionality and can have practical applications in spermatological diagnostics and cryopreservation.

Animals↗
PubMed2005

Genetic markers for stallion fertility--lessons from humans and mice.

Our knowledge on the many aspects of mammalian reproduction in general and equine reproduction in particular has greatly increased during the last 15 years. Advances in the understanding of the physiology, cell biology, and biochemistry of reproduction have facilitated genetic analyses of fertility. Currently, there are more than 200 genes known that are involved in the production of fertile sperm cells. The completion of a number of mammalian genome projects will aid in the investigation of these genes in different species. Great progress has been made in the understanding of genetic aberrations that lead to male infertility. Additionally, the first genetic mechanisms are being discovered that contribute to the quantitative variation of fertility traits in fertile male animals. As artificial insemination (AI) represents a widespread technology in horse breeding, semen quality traits may eventually become an additional selection criterion for breeding stallions. Current research activities try to identify genetic markers that correlate to these semen quality traits. Here, we will review the current state of genetic research in male fertility and offer some perspectives for future research in horses.

Animals↗
PubMed2004

Role of volume-stimulated osmolyte and anion channels in volume regulation by mammalian sperm.

The ability to maintain cellular volume is an important general physiological function. Swelling induced by hypotonic stress results in the opening of channels, through which ions exit with accompanying water loss (regulatory volume decrease, RVD). RVD has been shown to occur in mammalian sperm, primarily through the opening of quinine-sensitive potassium channels. However, as yet, direct evidence for the participation of anion channels in sperm RVD has been lacking. The chloride channel type ClC-3 is believed to be involved in RVD in other cell types. Using electronic cell sizing for cell volume measurement, the following results were obtained. (i) The anion channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), tamoxifen and 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) increased hypotonic swelling in concentration-dependent fashion, whereas verapamil (P-glycoprotein inhibitor) had little effect. The most potent, NPPB and DIDS, blocked RVD without affecting cell membrane integrity at effective concentrations. (ii) When gramicidin was included to dissipate Na+/K+ gradients, major secondary swelling was observed under hypotonic conditions. This secondary swelling could be reduced by NPPB, and suppressed completely by replacing chloride in the medium with sulphate, an ion which does not pass through chloride channels. It was deduced that the initial hypotonic swelling activated an anion channel through which chloride ions could then enter freely down a concentration gradient, owing to the lack of a counter-gradient of potassium. (iii) Taurine, an osmolyte often involved in RVD, does not appear to play a role in sperm RVD because lengthy preincubation with taurine did not alter sperm RVD response. Our observations provide direct evidence that a chloride channel (possibly ClC-3) is involved in the process of volume regulation in mammalian sperm.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2004

Role of potassium channels, the sodium-potassium pump and the cytoskeleton in the control of dog sperm volume.

Response to osmotic shock is an important aspect of mammalian sperm physiology. In this study we recorded volume changes of dog spermatozoa at 39, 33, and 25 degrees C under isotonic conditions and following hypotonic shock. Cell volume measurements were performed electronically in saline solutions of 300 and 150 mOsmol kg(-1), and Percoll-washed preparations were compared with unwashed samples. The involvement of potassium channels in volume control was tested by treatment with quinine, while the involvement of the plasma membrane Na(+)-K+ pump was tested by treatment with ouabain. The role of the cytoskeleton was investigated by treatment with colchicine and cytochalasin D. The number of cell populations observed varied with temperature and tonicity. In both types of sperm preparations, between two and three populations were present under isotonic conditions at 25 degrees C whereas at 39 and 33 degrees C only one population was detected. Hypotonic stress at the higher temperatures caused the single population to swell, whereas at 25 degrees C it resulted in a population of cells whose modal volume was similar to that of the middle isotonic sub-population. Both quinine and the cytoskeletal inhibitors markedly increased swelling both under hypotonic conditions at 39 degrees C and under isotonic conditions at 25 degrees C. However, little or no effect of ouabain was observed. We conclude that in dog spermatozoa swelling in response to hypotonic conditions is minimised through the activity of potassium channels and the presence of an intact cytoskeletal network. Under isotonic conditions at 25 degrees C, a considerable proportion of the sperm population is already swollen; this swelling varies between individual males and appears to be due to lowered cytoskeletal and potassium channel activity.

Animals↗
PubMed2004

Kinetics of protein tyrosine phosphorylation in sperm selected by binding to homologous and heterologous oviductal explants: how specific is the regulation by the oviduct?

Essential steps of the capacitation process take place in the oviductal isthmus. A crucial step in the process of capacitation is the phosphorylation of membrane proteins. The aims of this work were (1) to study the effect of dog sperm binding to oviductal epithelium on tyrosine phosphorylation and (2) to investigate the specificity of regulation of molecular changes by the oviduct of different species by comparing the numbers of canine sperm bound to heterologous (porcine) and homologous epithelium, and the kinetics of tyrosine phosphorylation. Semen was collected from four healthy dogs and washed through a Percoll gradient. Explants, small pieces of epithelium, were cut from porcine and estrous bitch oviducts. During 6 h of coincubation in Tyrode medium, the numbers of bound sperm were counted by microvideographic observation, and the state of tyrosine phosphorylation was determined immunocytochemically after 3, 30, 90, 180 and 360 min. Canine sperm bound in similar numbers to homologous and heterologous explants. Increasing tyrosine phosphorylation of tail proteins and subsequent phosphorylation of sperm head proteins were observed. Binding occurred mainly in sperm with non-phosphorylated heads (approximately 2% phosphorylated), while higher proportions of head-phosphorylated cells were found in unbound populations (approximately 40-60%;P<0.05). The head phosphorylation progressed significantly during incubation in unbound spermatozoa (P<0.05), while it was suppressed in bound suspensions. The rate of tyrosine phosphorylation of sperm tail proteins was higher in cells bound to explants than in unbound cells or in those incubated in control medium. There were no significant differences with respect to the kinetics of tyrosine phosphorylation between the two coincubation systems. These observations support the hypothesis that spermatozoa with non-phosphorylated heads preferentially attach to epithelial cells. Tyrosine phosphorylation of sperm head proteins and capacitation are delayed in spermatozoa in close contact with oviductal epithelium. This mechanism appears to be species-independent, as sperm bound similarly to pig and dog oviduct explants, and similar phosphorylation kinetics were observed in both types of tissue.

Animals↗
PubMed2004

Requirement for an intact cytoskeleton for volume regulation in boar spermatozoa.

Osmotically induced cell swelling triggers a chain of events leading to a net loss of major cell ions and water, resulting in cell volume recovery, a process known as regulatory volume decrease (RVD). In many cell types, there is an evidence that the cytoskeleton may play a role in the initial sensing and transduction of the signal of volume change. In this study, we tested the hypothesis that an intact microfilament and microtubule network is required for volume response and RVD in boar sperm before and after capacitation treatment and whether addition of cytochalasin D and colchicine to the capacitation medium would affect volumetric behaviour. Capacitation is a series of cellular and molecular alterations that enable the spermatozoon to fertilize an oocyte. Cell volume measurements of washed sperm suspensions were performed electronically in Hepes-buffered saline solutions of 300 and 180 mosmol/kg. After exposure to hypoosmotic conditions, boar sperm showed initial swelling (up to 150% of initial volume within 5 min), which was subsequently partially reversed (to about 120-130% after 20 min). Treatment with cytochalasin D led to reduced initial swelling (1 micromol/l) and loss of RVD in washed sperm (1-10 micromol/l) and at the beginning of incubation under capacitating conditions (5 micromol/l). Short treatment with 500 micromol/l colchicine affected the volume regulatory ability in sperm under capacitating conditions but not in washed sperm. No significant differences in cell volume response were observed after subsequent addition of cytochalasin D and colchicine to the suspensions of sperm incubated for 3 h under capacitating conditions. However, the incubation under capacitating conditions in the presence of cytochalasin D led to improved volume regulation at the end of the incubation period (23%). The microfilament network appears to be important for volume regulation in washed boar spermatozoa while intact microtubules do not seem to be necessary for osmotically induced RVD. The changes in cytoskeleton microfilament organization during capacitation, possibly affecting the osmotically induced volume response, appear to occur at the later stages of capacitation, whereas changes in microtubules, related to volume regulatory ability, may be programmed within the first stages of capacitation.

Actin Cytoskeleton↗
PubMed2003

Regulation of capacitation of canine spermatozoa during co-culture with heterologous oviductal epithelial cells.

Progress of essential steps of the capacitation is coordinated in the oviductal isthmus, where sperm are stored in close contact with the epithelium. A crucial capacitational event is the phosphorylation of sperm membrane proteins. Regulation of the tyrosine phosphorylation by the oviduct has not been examined in dog sperm yet. The aim of this work was to study the effect of dog sperm binding to porcine oviductal epithelium on capacitation-induced cellular and molecular changes. Epithelial cells were stripped from the oviducts of post-puberal sows and cultured for 5-7 days at 39 degrees C and 5% CO2 on Biomatrix-covered Chamber slides. Sperm washed through Percoll was co-incubated with the oviductal epithelium cell cultures in a bicarbonate Tyrode's medium. During co-incubation, sperm membrane changes, the state of tyrosine phosphorylation and motility were determined after 3, 30, 90, 180, 240 and 360 min. Significant increases in the percentage of capacitated and dead cells were observed in unbound sperm, while bound sperm remained uncapacitated, live and motile. An increasing tyrosine phosphorylation of tail proteins in bound, unbound and control sperm suspensions and a subsequent phosphorylation of head proteins in unbound and control sperm suspensions were observed. A significant difference regarding head phosphorylation (p < 0.05) was found between sperm bound to oviductal epithelium and unbound sperm. Binding occurred mainly in sperm with non- phosphorylated heads, while higher proportions of phosphorylated cells were found in unbound populations. The head phosphorylation progressed significantly during incubation in unbound spermatozoa (p < 0.05); however, it was suppressed in population of sperm attached to oviductal epithelium. Significant correlations between motility parameters related to hyperactivation and tail phosphorylation were found in unbound sperm. These observations support the hypothesis that spermatozoa with non-phosphorylated heads preferentially attach to epithelial cells. It can be concluded that tyrosine phosphorylation of head membrane proteins and capacitation are delayed in canine spermatozoa being in closed contact with oviductal epithelium.

Animals↗
PubMed2003

Seeking mathematical strategies in sperm function analysis: between scylla and charybdis?

During the last decades, essential progresses in reproductive biotechnology were achieved, implying development of special spermatological techniques. The major problem was to set up simple, rapid, precise and adequate evaluation methods. The key aspect to be considered in all assays of sperm fertilizing function is capacitation. As not all spermatozoa respond to fertilizing conditions in a similar manner, it seems to be logical to assess samples via their response to these specific conditions. For the spermatological practice, the sensitivity of methodology for assessment and analysis of data with respect to differences in individual response, in heterogeneity of the population, and proper temporal characterization of the response is crucial for the improvement of evaluation procedures. Currently, most used statistical analytical tools in spermatology do not always fulfil these essential sensitivity requirements. We structured our paper concerning different fields of mathematical science (distribution analysis, fractal geometry, functional approximation and differentiation) related to the modern insights in sperm function analysis. The spectrum of methods we are going to review in this paper is restricted to basic ideas to illustrate how the accuracy and sensitivity of sperm evaluation assays may be improved by applying adequate elementary tools of the mathematical analysis.

Animals↗
PubMed2003

Preferential expression of cystein-rich secretory protein-3 (CRISP-3) in chronic pancreatitis.

BACKGROUND: Chronic pancreatitis (CP) is a progressive inflammatory process resulting in exocrine and endocrine pancreatic insufficiency in advanced stages. Cysteine-rich secretory protein (CRISP-3) has been identified as a defense-associated molecule with predominant expression in the salivary gland, pancreas and prostate. AIMS: In this study, we investigated CRISP-3 expression in normal pancreatic tissues, chronic pancreatitis tissues, pancreatic cancer tissues and pancreatic cancer cell lines, as well as in other gastrointestinal organs. MATERIALS AND METHODS: 15 normal pancreatic tissues, 14 chronic pancreatitis tissues and 14 pancreatic cancer tissues as well as three pancreatic cancer cell lines were analyzed. Moreover, hepatocellular carcinoma and esophageal, stomach and colon cancers were also analyzed together with the corresponding normal controls. RESULTS: CRISP-3 was expressed at moderate to high levels in chronic pancreatitis tissues and at moderate levels in pancreatic cancer tissues but at low levels in normal pancreatic tissues, and was absent in three pancreatic cancer cell lines. CRISP-3 expression was below the level of detection in all cancerous gastrointestinal tissues and in all normal tissues except 2 of 16 colon tissue samples. CRISP-3 mRNA signals and immunoreactivity were strongly present in the cytoplasm of degenerating acinar cells and in small proliferating ductal cells in CP tissues and CP-like lesions in pancreatic cancer tissues. In contrast, CRISP-3 expression was weak to absent in the cytoplasm of cancer cells as well as in acinar cells and ductal cells in pancreatic cancer tissues and normal pancreatic tissues. CONCLUSION: These results reveal that the distribution of CRISP-3 in gastrointestinal tissues is predominantly in the pancreas. High levels of CRISP-3 in acinar cells dedifferentiating into small proliferating ductal cells in CP and CP-like lesions in pancreatic cancer suggests a role of this molecule in the pathophysiology of CP.

Adolescent↗
PubMed2003

Fate of lactadherin P47 during post-testicular maturation and capacitation of boar spermatozoa.

Polyclonal avian antibody was used partially to characterize the pig sperm lactadherin P47. P47 is a mosaic protein, composed of two epidermal growth factor (EGF)-like domains and two C1/C2 domains. P47 is homologous to the bovine mammary gland protein MGP 53/57 and mouse milk fat globule protein. Expression of P47 along the male genital tract and its localization on spermatozoa during post-testicular maturation and capacitation were studied. P47 was detected in the testis and in all parts of the epididymis by immunohistochemistry and by western blots of tissue extracts. By indirect immunocytochemistry, P47 was localized at the apical ridge of the sperm head in testicular, epididymal and ejaculated spermatozoa. The fluorescence intensity progressed during sperm transit from caput to cauda epididymis, probably caused by the ongoing expression and subsequent accumulation of P47 on the sperm surface. During the time course of capacitation, P47 appears to be unmasked by the release of coating proteins and appears to migrate from the apical ridge onto the entire acrosomal region, showing an intensive fluorescence pattern after 3 h capacitation in vitro. The kinetics of signal changes during in vitro capacitation were different in epididymal and ejaculated spermatozoa, indicating accelerated capacitational plasma membrane destabilization in epididymal spermatozoa.

Animals↗
PubMed2001

Influence of the bovine seminal plasma protein PDC-109 on the physical state of membranes.

PDC-109 is the main component of bovine seminal plasma and has been suggested to play an important role in the genesis of bovine sperm cells. Here, the effect of binding of PDC-109 to membranes on the structure and physical properties of the lipid phase was investigated. For that, ESR measurements were undertaken on model membranes (lipid vesicles) and on biological membranes (epididymal spermatozoa) by employing various spin-labeled phospholipids. We found that PDC-109 alters the membrane structure of lipid vesicles as well as of bovine epididymal spermatozoa in that the mobility of spin-labeled phospholipids was reduced in the presence of the protein. This immobilizing effect of the protein was not restricted to analogues of phosphatidylcholine but was also detected with spin-labeled phosphatidylethanolamine. However, the extent of immobilization was lower for phosphatidylethanolamine compared with phosphatidylcholine, supporting the lipid headgroup specificity of the protein. Besides phospholipid headgroups, the physical state of membrane lipids is also important for the interaction of PDC-109 with membranes, in that, e.g., the immobilizing effect of the protein on labeled lipids was larger in membranes above the phase transition temperature compared with the effect below this temperature. The results are of relevance for understanding the physiological role of PDC-109 in the genesis of sperm cells.

Animals↗
PubMed2001

Functional morphology of the zona pellucida.

The zona pellucida (ZP) is an extracellular matrix surrounding the oocyte and the early embryo that exerts several important functions during fertilization and early embryonic development. The ZP of most mammalian species is composed of three major glycoproteins that show considerable heterogeneity due to extensive post-translational modifications. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of the ZP reveals three to four glycoproteins which have been nominated ZPI. ZP2, ZP3 and ZP4. As cloning and characterization of the ZP genes of a variety of mammalian species including domestic animals show a high homology, three classes of ZP genes, ZPA, ZPB and ZPC can be discerned. The corresponding proteins were named ZPA, ZPB and ZPC. Whereas in the mouse ZPB is the primary sperm receptor. the situation is more complicated in other species. For instance, in the pig ZPA has been shown to possess receptor activity. Interaction between gametes during fertilization is at least in part regulated by carbohydrate moieties of the ZP and carbohydrate-binding proteins of the sperm surface. In domestic animals zona proteins are expressed in both the oocyte and granulosa cells in a stage-specific pattern and may play a role in granulosa cell differentiation. The role of ZP glycoproteins in immunocontraception is briefly discussed.

Animals↗