Composition and role of the synaptonemal complex.

The role of the synaptonemal complex (SC) in synapsis during meiotic prophase is examined in spermatocytes and oocytes of mice heterozygous for rearrangements, using light and electron microscopy of whole mount spreads. The duration of cytologically-characterized substages provides a morphological time axis for synaptic events. At zygotene, synapsis is restricted to homologous regions.

Hormonal control of fracture healing in a dog with chorea.

An experimental fracture in a dog with chorea was found to heal faster, and with a larger callus, than normal. Serum levels of parathormone (PTH), calcitonin (CT) and vitamin D metabolities were determined during callus formation. Serum concentrations of vitamin D metabolites were lower from the beginning while serum CT levels were higher compared to normal dogs.

The regulation of delta-opiate receptor density on 108CC15 neuroblastoma X glioma hybrid cells.

The effect of exogenous substances on the expression of opiate receptors on 108CC15 neuroblastoma X glioma hybrid cells has been studied. Cell differentiation by culture in the presence of N6-O2-dibutyryl adenosine 3',5'-cyclic monophosphate induced a three fold increase in opiate receptor density. When the cells were grown in the presence of 10(-5) M morphine hydrochloride for up to 23 days, opiate receptor densities were reduced by only 30% when compared with matched controls.

Health status of workers with past exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin in the manufacture of 2,4,5-trichlorophenoxyacetic acid: comparison of findings with and without chloracne.

Chloracne was found in 52% of 226 workers in a 1979 cross-sectional survey at a plant where 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) had been manufactured from 1948 to 1969. Mean duration of residual chloracne was 26 years, and in 29 subjects, it had been present for 30 years. A significant increased prevalence of abnormal gamma-glutamyl transpeptidase (GGT) and higher mean GGT were found in those with chloracne, compared to those without.

Pachytene chromosomes in male and female mice heterozygous for the Is(7;1)40H insertion.

Pairing of pachytene chromosomes was studied in oocytes and spermatocytes of mice heterozygous for the male-sterile Is(7;1)40H insertion using light and electron microscopy for synaptonemal complex analysis in surface-spread, silver-stained preparations. The data comprised four males and four female embryos. The insertion/deletion configurations appeared as either two bivalents or one quadrivalent in both sexes, but the proportion of bivalents was higher in oocytes.

Down regulation of opiate receptors on 108CC15 hybrid cells is inhibited by receptor occupancy.

This study reports on the molecular mechanism of delta-opiate receptor down regulation on 108CC15 neuroblastoma X glioma hybrid cells. The down regulation induced by culture in the presence of 10(-5) M 2-D-Ala, 5-D-Leu-enkephalin (DADLE) can be prevented by continued exposure to ligand concentrations greater than 4 nM, the Kd of the binding site. Below this concentration, down regulation is a rapid and irreversible process.

Synaptonemal complex analysis of mouse chromosomal rearrangements. IV. Synapsis and synaptic adjustment in two paracentric inversions.

Two paracentric inversions in the mouse, In (1) 1 Rk and In (2) 5 Rk, have been studied in surface microspreads of spermatocytes from heterozygotes. At zytogene, synaptic initiation occurs independently in three regions: within the inversion, and without, on either side. Synaptonemal complex (SC) formation is restricted to homologous regions, resulting in inversion loops in all early pachytene spermatocytes.

Fine structure and behaviour of a pericentric inversion in the sand rat, Psammomys obesus.

In pachytene spermatocytes of the sand rat, Psammomys obesus, a long autosomal bivalent was observed, which was asynaptic for a large interstitial segment of its length in early pachytene. This bivalent also exhibited unaligned kinetochores. In late pachytene spermatocytes all autosomal bivalents were fully synapsed, but one of the shortest bivalents now possessed unaligned kinetochores.

Synaptonemal complex analysis of mouse chromosomal rearrangements. III. Cytogenetic observations on two paracentric inversions.

Synaptonemal complex (SC) analysis by electron microscopy of spermatocytes in surface microspreads was carried out in mice heterozygous for two paracentric inversions: either In(1) 1 RK or In(2)5Rk. characteristic SC inversion loops are formed at synapsis in bivalents carrying the rearrangements. Although all loops were observed to be eliminated by late pachytene through synaptic adjustment, every spermatocyte at early pachytene contained a fully synapsed loop.

A pericentric inversion in the mouse.

A pericentric inversion induced in a Robertsonian chromosome was recovered and analyzed in a male heterozygous for the rearrangement. Identification was made from chromosome banding and confirmed by synaptonemal complex(SC) analyses. From the former, the chromosome was identified as Rb4Bnr.

Synaptosomal complex analysis of mouse chromosomal rearrangements. II. Synaptic adjustment in a tandem duplication.

Surface spread spermatocytes of mice heterozygous for a tandem duplication show nuclei in late zygotene-early pachytene in which the heteromorphic synaptonemal complex (SC) contains a lateral element that is buckled out into a unpaired loop as a consequence of the added length of the duplication (estimated in another study to be 21.7%, with breakpoints at 0.50 and 0.

Synaptonemal complex analysis of mouse chromosomal rearrangements. I. Cytogenetic observations on a tandem duplication.

Electron microscopy of surface-spread spermatocytes from mice heterozygous for a tandem duplication shows the heteromorphic synaptonemal complex (SC) to comprise two lateral elements of unequal length, the longer of which is buckled out in a characteristic loop, representing the unsynapsed portion of the duplication. The loop is a regular feature of late zygotene-early pachytene nuclei; it is longest at these early stages, but, through equalization of the two axes as a consequence of synaptic adjustment, it is replaced by a normal appearing SC at late pachytene. Because equalization, as indicated by a decrease in the percent difference between axes, may begin shortly after completion of synapsis, estimates of duplication segment length are restricted to a sample selected for least adjustment.

Health status of cable splicers with low-level exposure to lead: results of a clinical survey.

The results of a cross-sectional clinical field survey of 90 telephone cable splicers are presented. Despite the rare occurrence of clinically overt lead poisoning among cable splicers, the observed prevalence of symptoms was 29% for lead-associated central nervous system symptoms and 21% for gastrointestinal symptoms. These two groups of symptoms were directly related to zinc protoporphyrin (ZPP) levels but no relationship was found between them and blood lead concentrations.

End association and segregation of the achiasmatic X and Y chromosomes of the sand rat, Psammomys obesus.

In Psammomys obesus there is no pairing between the X and Y chromosomes and no chiasma formation (Solari and Ashley, 1977). It is demonstrated that ends of the axial elements of the X and Y chromosomes come together during pachytene, and regularly form at least one end-to-end junction. This achiasmatic physical connection between the ends of the X and Y persists until anaphase I, thus assuring the normal distribution of the sex chromosomes observed by light microscopy.

Synaptonemal complex karyotyping in spermatocytes of the Chinese hamster (Cricetulus griseus). IV. Light and electron microscopy of synapsis and nucleolar development by silver staining.

Synaptonemal complexes (SCs), X and Y axes, and various nucleolar structures stain preferentially with silver in surface microspread preparations and are analyzable by both light and electron microscopy. Central elements, kinetochore region material and nuclear annuli which stain with ethanolic phosphotungstic acid are seldom visible after silver staining. SCs can be characterized by length measurements equally well in light and electron micrographs, from which stages of pachytene can also be determined by differentiation of the axes of the XY pair.