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C Kirchhoff

Publications and source records attributed to C Kirchhoff.

At least 37 records · Page 2Linked to original sources
PubMed2000

Maturational changes of the CD52-like epididymal glycoprotein on cynomolgus monkey sperm and their apparent reversal in capacitation conditions.

A major epididymal secretory protein in men has a colinear cDNA sequence with lymphocyte CD52, a sialylated glycoprotein. Immunostaining and flow cytometric detection of cynomolgus monkey sperm CD52 during epididymal maturation showed increases from 20 to 85% stained sperm from the caput to the corpus with staining intensities doubled. Freshly prepared cauda sperm showed only 10% staining while they markedly increased in percentage and intensity of staining upon incubation at 37 degrees C under capacitating conditions, but not at 4 degrees C. Western blotting of proteins from fresh cauda sperm revealed no less antigen than corpus sperm. Staining of ejaculated sperm exhibited similar increases during incubation. Further washing with a high salt medium before staining to remove any electrostatically-bound molecules masking the antigen showed no effect. Incubation-induced increases in antigen binding were accelerated by the addition of neuraminidase (0.25 and 0.5 U/ml), but not affected by the sialyl residue-rich fetuin (5 mg/ml) competing for any endogenous neuraminidase. There were no concomitant decreases in the staining of sialic acid residues during capacitation-incubation. These findings suggest a cryptic antigen epitope site as a consequence of sperm maturation and subsequent re-exposure under capacitation conditions, but not due to the removal of sialic acid residues by endogenous neuraminidase. Involvement of endogenous proteases was also ruled out, as incubation in the presence of protease inhibitors did not hinder the increases but resulted in a dose-dependent enhancement in staining, suggesting some protease-sensitive unmasking process. In conclusion, the monkey epididymal secreted CD52 on sperm underwent changes in antigenic characteristics during sperm maturation which were reversed under capacitation conditions.

Alemtuzumab↗
PubMed1999

Male-specific modification of human CD52.

CD52 is an unusually short, bipolar glycopeptide bearing a highly charged N-linked carbohydrate moiety and a glycosylphosphatidylinositol membrane anchor. It is exclusively expressed on lymphocytes and in the male genital tract where it is shed into the seminal plasma and inserts into the sperm membrane. The sperm surface molecule has potential significance as a target for antibodies that inhibit sperm function and gamete interaction. Western blot analyses suggested cell type-specific modifications of the antigen. It was purified from seminal plasma and a detailed structural analysis performed. The majority of anchor structures in male genital tract CD52 showed 2-inositol palmitoylation, rendering molecules insensitive toward phospholipase C, and a sn-1-alkyl-2-lyso-glycerol structure in place of the diacylated anchor described by Treumann et al. (Treumann, A., Lifely, M. R., Schneider, P., and Ferguson, M. A. (1995) J. Biol. Chem. 270, 6088-6099). N-Glycans of the male genital tract product were based on bi-, tri-, and tetraantennary structures of highly charged (up to -7), terminally sialylated complex-type sugars. A substantial proportion carried varying numbers of lactosamine repeats of which nearly 30% were branched. Different from lymphocytes, 10-15% of all N-glycans of the male genital tract antigen also contained peripheral fucose. These data confirm that male genital tract CD52 is distinct from the lymphocyte form by both N-linked glycans and COOH-terminal attached lipid anchor.

Antigens, CD↗
PubMed1999

Gene expression in the epididymis.

The epididymis is a tubular organ exhibiting vectorial functions of sperm concentration, maturation, transport, and storage. The molecular basis for these functions is poorly understood. However, it has become increasingly clear that regional differences along the length of the duct play a role in epididymal physiology and that region-specific gene expression is involved in the formation of these differences. Although not an overtly segmented organ, the epididymis consists of a series of highly coiled "zones," separated by connective tissue septulae and distinct by cell morphology and their pattern of gene expression. Thus, it constitutes an interesting mammalian model to study how pattern formation is achieved by differential gene activity. A large number of epididymis-expressed genes have been cloned and analyzed at the molecular level, most of them have been characterized by a distinct temporal and spatial expression pattern within the organ. Only recently have theories been developed about how and when during ontogenesis this pattern formation takes place and what its significance might be. This review summarizes the current knowledge on regionalized gene expression in the epididymis and presents hypotheses concerning its ontogenetic origin and regulation in the adult.

Animals↗
PubMed1999

Differential expression of novel abundant and highly regionalized mRNAs of the canine epididymis.

Three novel gene products have been cloned by differential screening of a dog epididymis cDNA library as part of a global appraisal of specific gene expression in the epididymis. The predicted proteins were provisionally named CE8-CE10 (for canine epididymal gene products 8-10). Northern blot analyses and in situ transcript hybridization confirmed that the cDNAs were all derived from tissue-specific, moderately to highly abundant mRNAs of the epididymal epithelium, showing a distinct regionalized expression pattern within the epididymal duct. Their sequences predict (i) a novel 19 kDa member of the Ly-6-domain protein superfamily (CE8), (ii) an approximately 30 kDa protein with multiple membrane-spanning regions (CE9), and (iii) a novel approximately 13 kDa single whey acidic protein domain protein (CE10). Closely related, cross-hybridizing gene products were abundant in the epididymis of stallions and bulls, but not in rodents or men. Changes in mRNA frequency were observed that specifically correlated with a cryptorchid situation and with the age of the dogs. Gene products restricted to the caput epididymidis were affected by both conditions, while those with a wider regional distribution were not.

Aging↗
PubMed1998

Reduced systemic availability of an antiarrhythmic drug, bidisomide, with meal co-administration: relationship with region-dependent intestinal absorption.

PURPOSE: The aim of this research was to determine the mechanism by which a co-administered meal decreases the oral absorption of bidisomide and does not influence the oral absorption of the chemically-related antiarrhythmic agent, disopyramide. METHODS: Bidisomide plasma levels, following oral administration and intravenous infusion in the fasted state and with various meal treatments, were determined in human subjects. A dialysis technique was employed to examine the potential for drug binding to meal homogenates. Plasma levels, following drug administration through duodenal and jejunal intestinal access ports and following various meal treatments with oral drug co-administration, were compared for bidisomide and disopyramide in a canine model. RESULTS: Bidisomide plasma AUC was significantly reduced following oral drug co-administration with breakfast compared to fasted-state controls in human subjects and in dogs independent of the composition of the solid cooked breakfast. While intravenous bidisomide infusion in human subjects showed a statistically significant reduction in AUC 15 minutes after oral administration of a high fat breakfast as compared to drug infusion in the fasted state, the reduction (-13%) was substantially smaller than the reduction (from -43% to -63%) observed with oral bidisomide meal co-administration. The percentages of bidisomide and disopyramide lost by binding to homogenates of cooked breakfast were 25.0 +/- 5.7% and 23.7 +/- 7.7%, respectively, as determined by dialysis at 4 hours. In dogs, the extent of absorption of disopyramide was comparable from oral, duodenal and mid-jejunal administration while the extent of bidisomide absorption from mid-jejunal administration was significantly lower than for oral or duodenal administration. Non-viscous liquid meals decreased Cmax but not AUC, while viscous homogenized solid meals decreased both Cmax and AUC for bidisomide with oral drug-meal co-administration. Oral non-caloric hydroxypropyl methylcellulose meals decreased bidisomide to the same extent as homogenized solid meals but did not lower disopyramide AUC. CONCLUSIONS: The significant reduction in bidisomide plasma levels observed with meal co-administration in human subjects was predominantly mediated through a reduction in drug absorption and was independent of solid meal composition. The difference in meal effect on the absorption of the two drugs in humans did not appear to be a function of drug binding to cooked meal components over typical human upper gastrointestinal residence times. In dogs, the high-viscosity medium generated by oral co-administration of a solid meal reduced the upper intestinal absorption of bidisomide and disopyramide. Bidisomide AUC was decreased since it was well absorbed in the upper but not lower small intestine. Disopyramide AUC was not significantly affected since it was well absorbed from both regions. A similar mechanism may play a role in drug plasma level reductions following oral co-administration with solid meals for drugs showing similar regionally-dependent absorption profiles.

Animals↗
PubMed1998

Epididymal secretion of CD52 as measured in human seminal plasma by a fluorescence immunoassay.

A major secretory protein of the human epididymis that is taken up by maturing spermatozoa is homologous to the leukocyte antigen CD52. The epididymis was shown to be the sole source of CD52 in seminal fluid, since CD52 could be detected in seminal plasma from sperm-containing ejaculates and not in ejaculates of vasectomized patients by Western blot analysis. The glycoprotein is not expressed in the testes. A fluorescence immunobinding assay was developed to quantify the amount of epididymal secretion of CD52 in the seminal plasma of various groups of fertile and infertile patients. Donor spermatozoa bearing CD52 were used as binding site tracers for free anti-CD52 antibody remaining after it had adsorbed CD52 from the seminal plasma to be assayed. The level of subsequent antibody binding to spermatozoa was measured by flow cytometry and the extent of binding inhibition was compared to a reference pool of seminal plasma to provide relative amounts of CD52 in test seminal plasma. There were no correlations between seminal plasma CD52 concentration and any semen parameter tested, including sperm concentration, percentage motility, normal sperm morphology or the concentration of seminal neutral alpha-glucosidase, fructose and zinc. There was a slight tendency towards an inverse relationship with the amount of CD52 on spermatozoa, but this was not significant. No differences were found among groups of patients classified by their semen parameters or fertility status. These findings indicate that the epididymal specific supply of CD52 is not a limiting factor for CD52 uptake onto spermatozoa.

Adult↗
PubMed1998

Dog epididymis-specific mRNA encoding secretory glutathione peroxidase-like protein.

A differential library screening procedure was used to clone a novel abundant and tissue-specific cDNA from the dog epididymis. It was tentatively named CE7 for dog epididymal gene product 7. By sequence similarity to homologous counterparts expressed in mice, rats, pigs, and macaque monkeys, it appears that the 1.5 kb dog epididymal mRNA encodes the secretory glutathione peroxidase-like protein, GPX5. This protein is very similar to the family of glutathione peroxidase enzymes, but does not contain selenocysteine. Northern blot and in situ hybridization analyses revealed that the mRNA encoding CE7/GPX5, like its species homologues, was restricted to the epididymis and transcribed by the epithelial cells in the proximal parts of the organ. While the CE7 cDNA probe cross-hybridized to epididymal mRNAs in most species included in this study, it failed to identify a human GPX5 counterpart. Northern blot analyses of epididymal RNA extracts from hemi-cryptorchid dogs suggested that testicular secretions, including androgen hormones, temperature effects, or both, were involved in the region-dependent modulation of mRNA encoding CE7 in the dog epididymis. The effect was most obvious in the caput region of the abdominal organ where the mRNA encoding CE7 was almost completely downregulated.

Amino Acid Sequence↗
PubMed1998

Molecular characterization of epididymal proteins.

By using various methods, ranging from conventional protein separation and purification to monoclonal antibody and cDNA cloning strategies, a considerable body of information has been obtained on mammalian epididymal proteins. Molecular characterization of proteins specifically produced in the human epididymis has been achieved by cDNA cloning, followed by raising antibodies against synthetic peptide epitopes. The predicted proteins have been localized in the human epididymal epithelium, within the lumen of the epididymal duct and vas deferens, and also on the surface of ejaculated spermatozoa. Sperm association has been reported for at least four human epididymal proteins, ARP, HE2, HE4, and HE5/CD52. However, as is largely the case in other species, a link to a specific function for any luminal component of the human epididymis, including the cloned secretory glycoproteins, to either sperm maturation or storage has not yet been demonstrated convincingly. Indirect evidence for a function for epididymal proteins comes from their relatively high frequency and tissue-specific expression as well as from their distinct spatial expression patterns along the human epididymal duct. However, it remains to be established (for example, by using the proteins and their antibodies in functional tests) whether, besides being essential markers of sperm maturation, they are also functionally important.

Animals↗
PubMed1998

The dog as a model system to study epididymal gene expression.

Advances in understanding the role of the epididymis in human sperm maturation and fertility are dependent upon the availability of appropriate model systems in which to examine regulatory mechanisms and functions in a controllable fashion. Of a number of mammalian species studied by us and others, we suggest that the dog epididymis offers an excellent compromise in terms of the similarity of the specific genes expressed to those in the human, their mode of regulation, and the availability of tissues suitable for cell culture studies. We have developed a set of important tools in the form of epididymis-specific canine cDNA clones and cell culture methods, with which to examine the functioning of the epididymal epithelial cells in vitro, as well as the expression of specific genes in vivo, under normal and pathological conditions (e.g. cryptorchidism). Using this model system, we have elaborated the regional patterns of gene expression in vivo for several of the major secretory protein genes of the canine epididymis, and we have examined the importance of androgens and temperature on gene expression in vitro.

Animals↗
PubMed1997

Interaction of the human epididymal protein CD52 (HE5) with epididymal spermatozoa from men and cynomolgus monkeys.

A monoclonal antibody (CAMPATH-1 G) against the human lymphocyte surface protein CD52, which is similar to the epididymal secretion HE5, was used to ascertain the presence of this protein on maturing primate spermatozoa by flow cytometry. The percentage of human viable spermatozoa stained specifically with this antibody increased from sperm in spermatocoeles (0.5%), to the efferent ducts (3.8%), corpus (47.2%), and cauda (85.7%) epididymidis. Positive cells revealed staining mainly over the whole tail and postacrosomal region of the sperm head. Spermatozoa (approximately 10%) from both the efferent ducts and corpus epididymidis took up additional antigen when incubated with human distal cauda epididymidal plasma as a source of CD52, and 12-22% of human testicular sperm (from spermatocoeles) took up CD52 from human seminal plasma. In the cynomolgus monkey, nonspecific binding of control IgG was greater than that in human males and net CD52 staining was measurable only on approximately 30% of corpus sperm where it was mainly on the principal piece. Neither caput nor cauda sperm took up human CD52 upon incubation with human seminal plasma, but an additional 27% of corpus sperm expressed CD52. Such uptake of CD52 was drastically reduced, or did not occur, when seminal plasma had been fractionated by filtration through 0.1 microns filters (filtrate II) or 300,000 Da cutoff filters (filtrate III), respectively. Western blots revealed that CD52 contents were much reduced in filtrate II and nondetectable in filtrate III of seminal plasma. Similar reduction of CD52 in the filtrate of cauda epididymidal plasma indicates the association of this epididymal secretion with large molecular factors and suggests their involvement as carriers in the in vivo transfer of the secretion onto the epididymal sperm surface. The in vitro uptake of CD52 by some but not all immature sperm and the detection by Western blotting of much less CD52 in the corpus than the cauda luminal plasma suggest that the acquisition of this epididymal secretion by spermatozoa depends on their maturation status as well as the availability of the protein in the epididymal lumen.

Animals↗
PubMed1997

Regionalized expression of CD52 in rat epididymis is related to mRNA poly(A) tail length.

The regional pattern of CD52 expression in the rat epididymis was followed by Northern analyses and carbohydrate-labelling of glycoconjugates on Western blots. CD52 mRNA showed a novel aspect of regionalization, namely region-dependent length differences in its poly(A) tail. 'Short' CD52 mRNA molecules were present in all parts of this organ and also in the seminal vesicles. Additionally, the cauda epididymidis contained mRNA molecules with an extended poly(A) tail. Their appearance coincided with the occurrence of the principal M(r) approximately 26 kDa glycopeptide in the cauda region, representing the CD52 product. CD52 expression seemed to be regulated or modulated synergistically by androgens, temperature, and (an) unknown testicular factor(s), depending on the poly(A) tail length of its mRNA. Androgens alone exerted an effect only on molecules with 'short' poly(A) tails. They were down-regulated in castrated animals, and restored to normal levels upon testosterone supplementation. However, 'long' CD52 mRNA molecules were not affected. Only if combined with the exposure of the epididymis to the elevated temperature of the abdomen, castration of animals resulted in a complete loss of the CD52 mRNA, including the 'long' cauda species. Loss of 'long' CD52 mRNA molecules was also observed when the abdominal location was combined with efferent duct ligation. This combination of treatments, however, did not affect 'short' CD52 mRNA levels. Loss of the 'long' CD52 mRNA molecules by any treatment coincided with a loss of the principal M(r) approximately 26 kDa glycopeptide from caudal protein extracts.

Animals↗
PubMed1997

The molecular biology of the sperm surface. Post-testicular membrane remodelling.

The membrane of testicular spermatozoa undergoes extensive changes in the epididymis, including rearrangement, modification and loss of pre-existing components, addition of new glycoproteins from epididymal secretions, and exchange of lipid constituents. As a result, the membrane of cauda epididymidal spermatozoa has a different composition and different properties, which collectively contribute to male fertility. Special significance has been attributed to sperm surface structures that only appear post-testicularly in the epididymis, the so-called "maturation antigens". Therefore, human post-testicular proteins have been cloned by substractive screening of epididymal cDNA libraries, employing testis as the primary negative control. To date, there is scanty information on their function and mechanism of deposition on the sperm surface. However, the major maturation antigen CD52 seems to bind firmly to the sperm membrane via its GPI anchor. Its synthesis is carefully regulated by the cells of the epididymal epithelium, with temperature and androgens acting synergistically on CD52 mRNA levels.

Animals↗
PubMed1997

Cloning of a human epididymis-specific mRNA, HE6, encoding a novel member of the seven transmembrane-domain receptor superfamily.

A novel gene product, HE6, showing homology to the seven transmembrane-domain (Tm7) receptor superfamily, has been cloned by differential screening from a human epididymal cDNA library. The cDNA clone represented an abundant approximately 5-kb mRNA, comprising 0.01% of the cDNA library. Northern blot analysis including various human tissues revealed an epididymis-specific expression. In situ transcript hybridization localized the mRNA within the epithelial cells lining the epididymal duct. Southern blot analysis, employing a fragment encoding part of the amino-terminal extracellular domain as a probe, identified an autosomal single-copy gene in the human genome. Homologous cDNA products showing 90% sequence identity were observed in the epididymides of all mammalian species investigated. A cloning and sequencing strategy, combining approximately 3.7-kb cDNA fragments obtained by conventional cDNA library construction with overlapping 5' rapid amplification of cDNA ends (RACE) fragments, yielded total sequence information of 4.7 kb for the human mRNA. This sequence comprises a long open reading frame of 3.1 kb. A homology search for related sequences revealed highest similarity (25% amino acid identity) with the secretin/vasoactive intestinal peptide (VIP) superfamily of G-protein-coupled receptors. The predicted extracellular amino-terminal extension, however, was much longer than in the other members, and showed similarity to highly glycosylated mucin-like cell-surface molecules.

Amino Acid Sequence↗
PubMed1996

Characterization of a human glycoprotein with a potential role in sperm-egg fusion: cDNA cloning, immunohistochemical localization, and chromosomal assignment of the gene (AEGL1).

Acidic epididymal glycoprotein (AEG), thus far identified only in rodents, is one of the sperm surface proteins involved in the fusion of the sperm and egg plasma membranes. In the present study, we describe the isolation and characterization of cDNA encoding a human glycoprotein related to AEG. Although this protein, designated ARP (AEG-related protein), is not the ortholog of rodent AEG, it resembles AEG in that it is an epididymal secretory glycoprotein that binds to the postacrosomal region of the sperm head. The fact that no AEG mRNA can be detected in the human epididymis suggests that ARP might be the functional counterpart of rodent AEG. The gene encoding ARP (AEGL1) was mapped by fluorescence in situ hybridization to 6p21.1-p21.2. This result indicates that AEGL1 and the mouse gene for AEG are located in the chromosomal segments with conserved syntenies.

Acrosome↗
PubMed1996

[Radiologic evaluation of acetabular defects on acetabular loosening of hip alloarthroplasty].

In 18 human pelvis specimens we produced different acetabular defects according to Paprosky. Standardized X-rays of these specimens were taken, and these X-rays were evaluated by six orthopaedic surgeons with different levels of surgical experience. A total of 350 evaluation sheets were analyzed. The X-rays of the acetabular rim were correctly interpreted in only 66% of cases. The interpretation of plates showing bone loss was even worse. A medial wall defect was correctly assessed in just 49% of cases, giving a correlation (r) or 0.60 between the real defect and the radiological estimation. While massive defects were recognized in most cases, moderate defects were correctly estimated in about 50%. Moderate defects included migration of the cup, which was overlooked in between 46% and 69% of cases. Similar results were achieved in the judgement of bone loss. Only in 25% was direct classification according to Paprosky successful; it was better in small defects and worse in massive defects, with 16%. The interobserver correlation was only 0.54. In general, in most cases the defects were underestimated. This study raises the question of whether classification systems can provide the information needed for clinical useful therapeutic algorithms. The fact that the real bone loss is generally underestimated must receive due considerations when operations are being planned.

Acetabulum↗
PubMed1996

CD52 is the 'major maturation-associated' sperm membrane antigen.

The 'major maturation-associated' sperm membrane antigen is the most prominent glycopeptide which appears on the surface of rat spermatozoa during post-testicular sperm maturation. The name describes the fact that its occurrence coincides with the spermatozoa acquiring their major physiological properties of maturation in the distal epididymis. It is shown in this study that this phenomenon is not restricted to the rat. Rather, by immunohistochemical staining, in-situ transcript hybridization and molecular analyses of genomic DNA fragments it is evident that homologous counterparts exist in other mammalian species, including the human. The human homologue is an abundant epididymal gene product that has previously been identified as lymphocyte surface antigen CD52. Thus, following the human standard nomenclature, it seems more appropriate to refer to these molecules as CD52 homologues. Localization of the mRNA for these glycosylphosphatidyl inositol (GPI)-anchored glycopeptides within the epididymal epithelium, and not within the testis, suggests that they may be transferred from epididymal to sperm cell with their GPI-anchor intact.

Alemtuzumab↗
PubMed1996

Cell-to-cell transfer of glycosylphosphatidylinositol-anchored membrane proteins during sperm maturation.

In spermatozoa, as in other eukaryotic cells, integral membrane proteins may be anchored by a hydrophobic protein domain, or by a glycosylphosphatidylinositol (GPI) lipid anchor. Contrary to the current understanding of sperm membrane biogenesis, recent evidence shows that some of the GPI-anchored proteins are not synthesized by the spermatozoa themselves, but by cells of the male genital tract. They are transported to the fluid secretions, possibly associated with membrane vesicles, and then incorporate into the sperm membrane. This novel mechanism, by which proteins can move from the membrane of one cell to that of another in vivo, may account for a significant proportion of the surface changes occurring during sperm maturation. The function of these GPI-anchored molecules is largely unknown. However, they are remarkably abundant, and the phenomenon of cell-to-cell transfer seems to be well conserved across mammalian species. All of the post-testicularly acquired GPI-anchored proteins identified thus far have also been found on cells of the immune system (CD62, CD55, CD59, CD73), and we speculate that they may have a role in protecting spermatozoa from immune attack in the male and female reproductive tracts.

Amino Acid Sequence↗