Behaviour of a sperm surface transmembrane glycoprotein basigin during epididymal maturation and its role in fertilization in mice

Basigin (bsg) is a transmembrane glycoprotein belonging to an immunoglobulin superfamily and is localized on the surface of the sperm tail. The behaviour of bsg during epididymal maturation and its role in fertilization were examined using an anti-bsg antibody. Spermatozoa from caput, corpus and cauda epididymides were immunostained by indirect immunofluorescence (IIF). Immunostaining revealed that bsg is localized on the principal piece of caput spermatozoa and the molecule was found on the middle piece during transit in the corpus and cauda epididymides. Concomitantly, the molecular mass of bsg was reduced from 37 kDa (testis) to 26 kDa (cauda epididymidis). IVF experiments were designed to assess the effect of anti-bsg antibody on the fertilization events. Anti-bsg antibody significantly inhibited primary binding to the cumulus-invested oocytes with intact zonae pellucidae in a dose-dependent manner. Consequently, the fertilization rate of cumulus-invested oocytes with intact zonae pellucidae was also inhibited. The bsg molecule was also detected on the head of live capacitated spermatozoa by IIF under IVF conditions. These findings indicate that testicular bsg is a glycosylated protein that undergoes molecular processing and deglycosylation during its transit in the epididymis. The bsg molecule that was detected on the sperm head after capacitation may facilitate the primary binding or might be involved in distinct events required for primary binding of spermatozoa to the zona pellucida during capacitation and sperm-cumulus interaction.

Partial characterization of an intra-acrosomal protein, human acrin1 (MN7)

Acrin1 (MN7), a 90-kd glycoprotein, is localized in the sperm acrosome of several rodents. The purpose of this study was to determine the molecular size and subcellular localization of acrin1 (MN7) in human sperm, and its organization in spermatids during spermiogenesis. Immunocytochemical and biochemical analyses revealed that acrin1 (MN7) is localized in the anterior acrosome and its molecular size is 90 kd, the same as in rodents. Based on molecular size, acrin1 (MN7) is likely to be a novel human acrosomal protein. During spermiogenesis, acrin1 (MN7) is initially localized in the head-cap portion of spermatids from the cap phase to the end of the acrosomal phase, and then relocates from the posterior to the anterior region of the acrosome in the maturation phase in spermatids. Such a morphological organization mechanism is also basically the same as that in rodents. Thus, acrin1 (MN7) is a common acrosomal protein of 90 kd in rodents and humans.

Transport and rearrangement of the intra-acrosomal protein acrin1 (MN7) during spermiogenesis in the guinea pig testis

We have recently shown that a 90-kDa glycoprotein, acrin1 (MN7), is exclusively localized in the dorsal region of the acrosomal apical segment of mature guinea pig sperm, and that its location changes during epididymal maturation. The present study examined the process of transport and organization of this protein in the acrosome during spermatogenesis in the guinea pig testis. Immunoperoxidase electron microscopy showed stage-specific localization of acrin1 within the developing acrosome, as follows: acrin1 first appeared in the proacrosomic vesicles of the early Golgi phase spermatids, and it was then localized in the electron-lucent matrix region of the acrosomic vesicles of the late Golgi phase spermatids. During the cap phase, acrin1 was abundant in the electron-lucent matrix of the acrosomal apical segment and in the head-cap region (principal segment). acrin1 became more restricted to the peripheral region of the electron-lucent matrix of acrosome phase spermatids and it was localized in the electron-lucent dorsal matrix region of maturation phase spermatids. In the final step of spermiogenesis, acrin1 disappeared from the equatorial and principal segments, and it was finally confined to the dorsal matrix region of the acrosomal apical segment. In addition, Western blot analysis showed that acrin1 of testes and epididymal sperm was of the identical size, indicating that acrin1 is not proteolytically modified during epididymal sperm maturation. These results indicate that acrosome morphogenesis is closely associated with the rearrangement of acrosomal proteins.

The expression and cellular localization of the sperm flagellar protein MC31/CE9 in the rat testis: possible posttranscriptional regulation during rat spermiogenesis

We isolated the MC31 cDNA clone coding the antigen specifically recognized by the monoclonal antibody mMC31, and found that MC31 was identical to rat CE9. Therefore, this molecule is called MC31/CE9. MC31/CE9, a member of the immunoglobulin superfamily molecules, was localized on the rat sperm flagellar plasma membrane. We analyzed the expression and cellular localization of MC31/CE9 mRNA and protein in the adult rat testis by use of Northern hybridization, in situ hybridization, and immunohistochemical analyses. In the course of spermatogenesis, MC31/CE9 mRNA first appeared in type B spermatogonia. The mRNA signal intensity increased progressively to pachytene spermatocytes and remained constantly at a considerable level throughout the subsequent phases of spermatocytes and round spermatids, and then decreased gradually from step-11 spermatids to disappear in step-15 spermatids. On the other hand, MC31/CE9 protein expression showed a bimodal pattern. Immunohistochemical analysis for the MC31/CE9 protein revealed its most intense immunoreactivity on the flagella of step-8 to step-19 elongated spermatids. The cytoplasmic immunoreactivity of the MC31/CE9 protein also appeared in preleptotene to early pachytene spermatocytes and elongated spermatids, with particularly intense immunoreactivity in the Golgi complexes of zygotene and early pachytene spermatocytes (stage XIII to III) as well as step-8 to step-13 spermatids. Between these two phases, the MC31/CE9 protein proved undetectable in the cytoplasm of any spermatogenic cells. Sertoli cells and Leydig cells were devoid of MC31/CE9 mRNA and its protein. Therefore, the production of MC31/CE9 is thought to be posttranscriptionally regulated during spermiogenesis.

Low dose almitrine bismesylate improves pulmonary gas exchange during canine one-lung hypoxia

The effects of low dose almitrine bismesylate on pulmonary gas exchange, venous admixture, and pulmonary perfusion were examined in a canine one-lung hypoxic model. The left lung was ventilated with 10.4% oxygen, 89.3% nitrogen, and 0.3% halothane, while the right lung was ventilated with 99.7% oxygen and 0.3% halothane. Group 1 (n = 8) was given no other drug for 60 min. In group 2 (n = 10), consecutive almitrine doses of 0.5, 1, and 2 micrograms/kg.min were administered iv for 20 min/dose. Blood gas and central hemodynamic values remained unchanged in group 1. In group 2, significant increases in PaO2 and significant decreases in venous admixture, dependent on the dose administered, were observed. Mean PaO2 increased from 222 +/- 78 (SD) to 292 +/- 75 torr, and mean venous admixture decreased from 22 +/- 7% to 18 +/- 6% at 2 micrograms/kg.min. Both the decrease in mean left pulmonary blood flow and the increase in mean right pulmonary blood flow were slight, although the cardiac output was unchanged. These results indicate that iv infusion of 2 micrograms/kg.min of almitrine weakly enhances pulmonary vasoconstriction in a hypoxic area and improves pulmonary gas exchange in a moderately hypoxic condition.