L. Plöen

Synaptonemal complex analysis of the B-chromosomes in spermatocytes of the silver fox (Vulpes fulvus Desm.)

The mitotic and meiotic chromosomes of four male silver foxes (Vulpes fulvus Desm.) having, due to inter- and intraindividual variation, 1–4 B-chromosomes in addition to the standard karyotype, were investigated with special attention given to pachytene chromosome behaviour as revealed by electron and light microscopy. When occurring as univalents the B-chromosomes demonstrated a progressively folding back behavior ending in intrachromosomal pairing. When two B-chromosomes occurred in the same cell they paired normally as a bivalent with one central and two lateral elements. However, occasionally also two univalents were seen. In the presence of three B-chromosomes, a trivalent occurred in most cells, but sometimes two normally paired chromosomes and one folded univalent were seen in late pachytene. The chromosomes comprising the trivalent were never completely paired, however. Due to competitive pairing and low frequency of chiasmata the trivalents most often dissolved into one bivalent and one univalent and only a few trivalents remained at diakinesis-metaphase I. On the basis of pairing behavior and morphology it is assumed that the B-chromosomes of the silver fox are homologous. Although pairing was never observed, there was a tendency of association at pachytene between B-chromosome configurations and the sex bivalent in those individuals that had univalents and trivalents.

The nature of the 1;29 translocation in cattle as revealed by synaptonemal complex analysis using electron microscopy

Synaptonemal complex analyses were carried out by electron microscopy on surface-spread spermatocytes of one normal bull and two bulls that were heterozygous for the so-called 1;29 translocation. The autosomal bivalents of the normal karyotype, which could be arranged by size in a series, demonstrated kinetochores at the terminally located attachment plaques. One autosomal bivalent was clearly larger than the rest and apparently consisted of the long arm of the 1;29 translocation. The 1;29 translocation was the longest autosome in the set and had a kinetochore in a subtelocentric position. Some of the autosome pairs had nucleolus organizer regions in telomeric regions. The X and Y chromosomes, which were not paired at zygotene, demonstrated association in a very short segment at early pachytene; in no cells could a synaptonemal complex be seen between the X and Y. Very often the sex chromosomes were dissociated. At zygotene, a few, usually large, bivalents were unpaired proximally. This always also involved the proximal parts of the arms of the 1;29 translocation and their normal homologs. At early pachytene, the 1;29 trivalent, although to a less extensive degree, was also unpaired in the pericentric region. Configurations in which one chromosome, either 1 or 29, was completely paired with its corresponding arm in the 1;29 translocation chromosome also occurred. When unpaired proximally, the size of chromosome 1 agreed fairly well with the size of its corresponding arm, but the size of chromosome 29 was considerably larger than the corresponding arm of the 1;29 translocation chromosome. During late zygotene and early pachytene, the percent difference between chromosome 29 and its corresponding arm decreased, and at mid and late pachytene there had been a complete synaptic adjustment. The size difference and pairing behavior indicated that a deletion of the kinetochore and the most proximal segment of chromosome 29 had preceded the fusion with chromosome 1 into the 1;29 translocation. The unique structural appearance of the 1;29 translocation chromosome compared to that of other centric fusion translocations in cattle lends support to the theory of a monophyletic origin of the 1;29 translocation. The importance of the pairing behavior observed in governing recombination and chromosome disjunction is briefly discussed.

Effects of repeated intravenous infusions of the plasticizer di-(2-ethylhexyl) phthalate in young male rats.

The effects of six iv infusions of an emulsion containing the plasticizer di(2-ethylhexyl) phthalate (DEHP) on the liver and testes were investigated in 40-day-old rats. Groups of five to six animals received the emulsion every other day in doses of 0, 5, 50 or 500 mg DEHP/kg body weight. Liver effects were studied by histological examination and by measuring bromsulfophthalein clearance, peroxisomal proliferation and certain enzymes in serum. Testicular effects were evaluated by light and electron microscopy. To investigate the possibility of an age-related effect on the testis, five 25-day-old rats were given six infusions of 500 mg DEHP/kg.Compared with control animals, the high-dose group showed a 36% increase in relative liver weight and a 41% increase in the number of peroxisomes. In Epon-embedded testicular material from animals given the highest dose, which is about 100 times the highest estimated human exposure, some altered Sertoli cells and some degenerated primary spermatocytes were observed.No age-related effect on the testis similar to that found following oral administration of DEHP was observed in this study.

Spermiogenesis and the spermatozoa of the European common shrew (Sorex araneus L.).

The ultrastructure of spermiogenesis and of epididymal spermatozoa of a primitive eutherian mammal, the common shrew (Sorex araneus L.), has been studied. It was found that spermiogenesis is similar to that of scrotal mammals. The spermatozoa are large (head: 5.5 μm, nucleus: 4 μm) and show some characteristic features, e.g., a well-developed “apical body” and an exceptionally long (27 μm) middle piece with a cross-sectional area like a superellipse. Both the coarse fibers and the bundles of satellite fibrils are prominent in the proximal part of the middle piece. Thermoregulation in lower mammals is discussed and it is concluded that abdominal, and thus also testicular, temperature in the shrew is about the same as that inside the scrotum of the more advanced mammalian orders.

Differentiation of the Rat Testis Between 20 and 120 Days of Age

The differentiation of the seminiferous epithelium was studied in 20-120-day-old Sprague-Dawley rats. Body weights and the weights of the testes, seminal vesicles, and kidneys were determined. The best way of defining the development of the testis was to denote the most differentiated germ cell present. Spermatogenesis is complete at 56 days of age, but the testis continues to grow up to 108 days of age. The development of certain parameters has been calculated, and it is very important to define the age of the animals in experimental studies and to include sufficient numbers of controls.

Carbonic anhydrase—a marker for particles shed from the epithelium to the lymphoid follicles of the ileal Peyer's patch in goat kids and lambs

Carbonic anhydrase (CA) was found to be a marker for 50 nanometer membrane‐bounded particles shed from the lateral cell border of follicle‐associated epithelial cells (FAE) in the ileal Peyers patch (PP) of pre‐ and post‐natal lambs and goat kids. The CA‐positive particles seemed to filter into the underlying lymphoid tissue where they formed part of the matrix embedding the cells of the follicle centre.

Synaptonemal complex analysis of a reciprocal translocation, rcp(20;24) (q17;q25), in a subfertile bull

A reciprocal translocation was identified in a subfertile artificial insemination bull. Somatic chromosome investigation of G-banded metaphases demonstrated a 60,XY,rcp(20;24)(q17;q25) karyotype for the carrier. Synaptonemal complex analysis of the translocation by electron microscopy revealed an irregular pairing behavior of the chromosome axes involved, which resulted in a variety of configurations at pachytene. Not only was the expected quadrivalent configuration present, but also a trivalent plus univalent and two heteromorphic bivalents. Most common was an incompletely or completely paired quadrivalent configuration, which was non-homologously paired. XY association with the multivalent was seen only rarely. Histological analysis of testicular tissue showed meiotic arrest in some tubules. However, the semen picture was normal.

Testicular lesions of coprine and benzcoprine.

The effect on the testis of the disulfiram-like compounds benzcoprine (N-[1-ethoxycyclopropyl] benzamide) and coprine (N5-[1-hydroxycyclopropyl]-L-glutamine) was studied in rats and dogs. Severe degeneration of the seminiferous epithelium was induced in rats by subacute oral administration of each compound. 60 days after termination of treatment with benzcoprine most seminiferous tubules contained only occasional spermatogonia and the testicular weight was markedly decreased. The blood-testis barrier was unaffected in the benzcoprine-treated rats as judged by a lanthanum tracer technique. In dogs, oral administration of benzcoprine for 1 month caused impaired spermatogenesis, degeneration of germ cells and a decrease in the testicular weight. The results indicate that both compounds act directly on the germ cells. The effect is similar to that of alkylating compounds. Other effects of benzcoprine and coprine (bone marrow depression, lymphocytopenia, positive Ames test in organisms sensitive to base-pair substitution) are well-known properties of alkylating agents. In conclusion benzcoprine and coprine were found to cause severe changes in the testis in rats and dogs, probably due to a direct effect on the germ cells.

Synaptonemal complex analysis of an autosomal trisomy in the horse.

Synaptonemal complex analysis by electron microscopy of a trisomy 28 in a male horse demonstrated a trivalent or a bivalent plus a univalent in primary spermatocytes. Two of the chromosomes making up the trivalent were, most often, completely paired with each other and only partially paired or associated with the third one. Half of the spermatocytes analysed demonstrated heterologous pairing or association between the free axis of the trivalent and the sex bivalent. The pairings remained, to a large extent, into diakinesis-metaphase I. In most pachytene cells one autosomal bivalent showed proximal asynapsis and paired often, heterologously, with the trivalent or the sex bivalent. The horse demonstrated azoospermy, which was due, at least in part, to degeneration at both the spermatocyte and spermatid levels.

Fine structural features of Sertoli cells

The Sertoli cell may be defined as, ‘a somatic cell associated individually and simultaneously with several generations of germ cells’ (30). In 1865, Sertoli (37) described these cells as ‘celluli ramificato’ and since 1888 (6) they have borne his name. Attempts have been made to introduce other names — sustentacular cells or sustenocytes, supporting cells, nurse cells — but the name Sertoli cells is generally accepted today.