Development of the seminiferious tubules and rete testis during the prenatal period of human ontogenesis

The sources of origin and the peculiarities of formation of the seminal ducts and rete testis during the prenatal period of ontogenesis in man were studied. It has been established that the seminal duct sand the ducts of the rete testis form from the cellular cords of the coelomic epithelium and the primordial germ cells which appear simultaneously in the septum of the testis and the primordial germ cells which appear simultaneously in the septum of the testis and central part of its parenchyma in the embryos, 13.0--17.0 mm long. By plastic and graphic reconstruction, as well as by methods of subtle preparation under binocular microscope MBC-I control it was revealed that the seminal ducts anastomosed between themselves both within the limits of one and the adjacent lobules. The ducts of the rete testis do not form anastomoses, but superimpose over one another, creating an impression of a rete. Approaching the tunica albuginea they merge, continuing into the cuctuli efferentes testis.     

Structural analysis of clusterin and its subunits in ram rete testis fluid

Clusterin is a protein present in the rete testis fluid of the ram that elicits aggregation of erythrocytes and Sertoli cells in vitro. In view of its possible biologic function in relation to cell-cell interaction in the testis, we isolated this protein from ram rete testis fluid using sequential high-performance liquid chromatography columns and performed a detailed physicochemical characterization. This protein consists of two molecular variants designated form I and form II clusterin. Each form of clusterin consists of two subunits with an apparent molecular weight of 40,000. It is of note that the two subunits have no homology in their N-terminal amino acid sequences. However, the N-terminal amino acid pairs of the two subunits derived for the two forms of clusterin are identical. Using o-phthalaldehyde to block the Lys residue at the fourth amino acid pair from the N-terminus which leaves the Pro residue free for subsequent Edman degradation, we have deduced the N-terminal sequence of each of the two subunits for form I clusterin. Comparison of the NH2-terminal sequences of the two subunits of clusterin with the release 10.0 of the protein sequence data base of the Protein Identification Resource indicated no homology between either of the subunits of clusterin and any of the known proteins in the data base. A highly specific radioimmunoassay developed for clusterin was used to measure its concentrations in the fluids of the rete testis and cauda epididymis. Since a significant amount of immunoreactive clusterin was found in serum, the protein was partially purified from this source by immunoaffinity chromatography. Immunoreactive serum clusterin was smaller than the testicular clusterin (Mr 37,000 vs 40,000), but both proteins share common epitopes as demonstrated by radioimmunoassay and immunoblots. However, serum clusterin does not possess the biologic activity of the testicular clusterin in that it does not elicit cell aggregation in vitro. It is of note that deglycosylation of testicular clusterin can also eliminate this in vitro biologic activity, suggesting that the serum clusterin might be a deglycosylated form of the testicular protein and the carbohydrate core plays an important role in determining the cell aggregation activity. Studies on the distribution of this protein in the reproductive compartment indicate that it is highly concentrated in the rete testis and the cauda epididymal fluids. This suggests that this protein might have some important functions in the reproductive tract.     

Synergetic effect of pimozide and thyrotropin releasing hormone on prolactin and thyrotropin release during the drying off of ewes

The effect of pimozide and/or TRH was investigated on plasma prolactin, thyrotropin, T₄ and T₃ and udder distension in 38 ewes during drying off by feed restriction. The effect of daily injections of 2 mg pimozide (s.c.), combined or not with TRH stimulation (200 μg, i.v.) on three different days of the drying off period was examined. Blood samples were taken twice daily in each group for 9 days, while blood sampling on the days of TRH injection was also performed at 0, 15, 30 min, and 1, 2 and 4 h post-injection. Plasma was assayed for PRL, TSH, T₄ and T₃ levels. Udder distension and mastitis incidence were recorded at the end of the drying off period. TRH and pimozide both resulted in elevated plasma PRL levels and acted in a synergetic way. Udder distension and the incidence of mastitis was only influenced by pimozide. The TSH as well as the T₃ response to TRH was increased in ewes under a continuous influence of pimozide and T₃ peaks following TRH injection occurred earlier than T₄ peaks. The higher effect of pimozide upon TRH stimulated PRL and TSH release at day 8 compared to days 0 and 3 indicates a progressive involvement of dopamine on the inhibition of PRL and the sensitivity of the thyrotrophs to TRH during drying off.     

Immunolocalization of clusterin in the ram testis, rete testis, and excurrent ducts

Clusterin, a glycoprotein that elicits cell aggregation, has previously been isolated from ram rete testis fluid, and has been partially characterized. In experiments reported, we have used monoclonal antibodies against clusterin in combination with indirect immunofluorescence microscopy to investigate the distribution of clusterin in the adult ram testis, rete testis, and excurrent ducts. Tissue blocks (5 mm3) were fixed in periodate/lysine/paraformaldehyde containing 0.1% glutaraldehyde and, after embedding, 5-microM sections were prepared for immunolocalization. In the testis, 2 basic patterns were observed: 1) strong to moderate staining for clusterin in the adluminal region with little staining in the basal region of the seminiferous epithelium and germinal cells; and 2) moderate staining throughout the seminiferous epithelium between germinal cells. In the rete testis, strong clusterin staining was localized intracellularly in the rete epithelial cells, most often associated with the luminal surface. In the epididymis, intracellular clusterin was localized in some principal cells of the caput epididymidis. The luminal surfaces and spermatozoa within the lumen were strongly positive. In the vas deferens, clusterin staining was associated with the luminal surface only. The presence of clusterin was clearly detected in unwashed isolated epididymal spermatozoa, but not in spermatozoa washed with phosphate-buffered saline containing 0.05% Tween 20.     

Development of the thoracic duct in the prenatal period of human ontogeny

In 40 series of histological sections performed in human embryos and prefetuses from 4 up to 20 weeks of development, as well as in 20 corpses of fetuses and stillborns, it has been stated that the anlage of the thoracic duct appear in 6-7-week-old fetuses as lymphatic clefts surrounded with mesenchymal cells that are situated near large veins in the areas of the most active morphogenesis. Connecting with each other, the clefts form the jugular and retroperitoneal lymph sacs and a well branching network of canals. From the latter, on the 7th-8th week of development a plexus of lymph vessels appear, and later on (on the 8th-9th week)--bilaterally situating trunks of the thoracic duct. Further development of the thoracic duct is connected with the lymph nodes formation, their germs appear on the 9th-10th week along the course of the left trunk, as well as along the ductal branches and anastomoses. The formation of the lymph nodes results in reduction of some trunks and plexuses of the thoracic duct. Owing to this, its form in 14-15-week-old prefetuses resembles the one in newborns. Disturbances in the formation processes of the lymph nodes along the course of the reducing ductal areas, as well as their formation along the course of its main trunk can result in various structural variants of the thoracic duct in children and grown-up persons. Histogenesis of the thoracic duct wall and formation of the lymph nodes are not completed by birth.     

Development of the neural apparatus of the human pancreas in prenatal ontogeny

In human embryos, prefetuses and fetuses from 6 to 40 weeks of development 82 preparations of the pancreas have been studied; 39 series of slices of the human embryos have been impregnated after Bielschowsky-Boeke. For the first time the nerves grow into the pancreas anlage in embryos of 16 mm long (6 weeks). The main sources supplying the pancreas with the nerves in the period studied are nervus vagus, celiac, hepatic, splenic, right adrenal, superior mesenteric and intermesenteric plexuses. Three stages in formation of the innervational apparatus of the pancreas are distinguished during the intrauterine development. The first stage is characterized by beginning of the nerve growing into the pancreas anlage. For the second stage an increased development of the intraorganic innervational apparatus and appearance of the all main sources of the organ's innervation are specific. The third stage is characterized with an increased differentiation of receptor zones in various parts of the pancreas. The development of the pancreatic innervational apparatus by the time of birth is not completed.     

Development of the ductule system of the epididymis in the prenatal period of human ontogeny

In 285 human embryos, prefetuses, fetuses and newborns by means of a complex of morphological methods, development of the epididymal canalicular system has been studied. The anlage of the epididymal canalicular system is stated to appear in embryos 13.0-17.0 mm long (the 6th week of development) and is presented as an accumulation of epithelial cells and primary germ cells between reducing glomeruli and mesonephric canaliculi. The canalization process of the cellular accumulations and their transformation into real canaliculi takes place during the first half of the prefetal period (the 8th week of development). Further growth and development of the epididymal canaliculi takes place in the craniocaudal direction and by the end of the prefetal period (the 12th week) the canaliculi of the head are already formed, they have a twisted course; within the limits of the body and tail they are yet poorly differentiated and their course is nearly straight. During the fetal period of ontogenesis, further differentiation of the epididymal parts occurs and structure of their canaliculi becomes more complex. They acquire a twisted course in all the parts of the organ; by the end of the fetal period the form and structure of the epididymal canaliculi resemble those of the definitive organ.     

Effects of levonorgestrel and STS 557 on testis in rodents

In immature male Wistar rats levonorgestrel and STS 557 (17 alpha-cyanomethyl-17 beta-hydroxyestra-4,9(10)-diene-3-one) reduced testicular growth, testicular DNA contents and plane of tubular cross-section in a dose dependent manner. In this respect, STS was less active than levonorgestrel. In immature castrated male rats the LH-suppressing effect of STS 557 was about 15 times lower than that of levonorgestrel. The results suggested that peripheral inhibitory effect of the two progestins was coupled with central LH suppression. On the other hand, in mating tests with male hybrid mice STS 557 possessed high fertility inhibiting activities in comparison to levonorgestrel and chlormadinone acetate. Limited dissociation has been shown between fertility inhibition and mating rate. All changes were reversible. Findings are discussed in view of development of male contraceptives.     

Synapses of the human brain in early prenatal ontogeny

Synaptogenesis in presumptive cerebral cortex was studied in 7-8 week human embryos by electron microscopy. The first synapses in the regions studied appeared in 7-week embryos. These synapses were detected only in the marginal zone of the developing human cerebral cortex, where they were localized on the somas and processes of the young Cajal-Retzius' neurons. A functional role of early embryonic synaptogenesis in the developing human cerebral cortex is suggested.