Histochemical studies on the amphibian opercularis muscle (Amphibia)

Summary Histochemical studies of the opercularis muscle of the bullfrog (Rana catesbeiana) and the tiger salamander (Ambystoma tigrinum) provide evidence that the opercularis muscle of anurans is a specialized, tonic portion of the levator scapulae superior muscle. Staining results for myosin adenosine triphosphatase (ATPase) and succinate dehydrogenase (SDH), combined with measurements of muscle fiber diameters, demonstrate that the opercularis/levator scapulae superior muscle mass of both the tiger salamander and bullfrog consists of an anterior tonic portion, a middle fast oxidative-glycolytic (FOG) twitch portion, and a posterior fast-glycolytic (FG) twitch portion. In R. catesbeiana the tonic fibers represent 57.3% of the fiber total and (because they have relatively narrow diameters) about 29% of the cross-sectional area of the muscle mass, and form that part of the muscle (=opercularis muscle) that inserts on the operculum. In Ambystoma the tonic fibers represent only 8.8% of the fiber total and represent about 4% of the cross-sectional area. In the tiger salamander, the entire levator scapulae superior muscle inserts on the operculum and therefore represents the opercularis muscle. The bullfrog differs from the tiger salamander, therefore, in that the anterior tonic part of the opercularis/levator scapulae superior complex is greatly enlarged and the insertion on the operculum is limited to these tonic fibers. No evidence of a columellar muscle was found in R. catesbeiana. Previous reports of one in this species and in other anurans may be based on the tripartite nature of the opercularis/levator scapulae superior muscle mass. The middle FOG portion of the muscle may have been considered a muscle distinct from the anterior tonic portion (=opercularis muscle) and the posterior FG portion.     

Pericentric inversion of chromosome 19 in three families

Summary Pericentric inversion of chromosome 19 has been found in several members of three unrelated families from a restricted geographical region. In one of the families, an additional pericentric inversion of chromosome 9 was observed. Reproductive problems, multiple abortions in two families and a neonatal death in the third, were present. A review of previously described cases is included, and the genetic risk connected with this type of rearrangement is also discussed.     

Isolation of Thy-1 caps and analysis of their phospholipid composition in mouse T-lymphoma cells

In this study we have used a density perturbation method to isolate anti-Thy-1 antibody-induced Thy-1 caps from mouse T-lymphoma cells in the absence of detergents, and then compared the phospholipid composit on of these capped membranes with that of uncapped membranes. Initial phospholipid analysis by two-dimensional thin layer chromatography (2-D TLC) reveals a significant increase in the amount of ³²P-labeled phosphatidylcholine in the Thy-1 capped membrane. In contrast, no significant changes are observed in the labeling of phosphatidylserine, phosphatidylethanolamine, or the sphingomyelins. Therefore, it is suggested that phosphatidylcholine may be involved in the organization and/or regulation of Thy-1 antigen redistribution. The composition of phosphoinositide in uncapped and capped membranes was analysed separately using one-dimensional thin layer chromatography (1-D TLC) to resolve phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP), and phosphatidylinositol 4, 5-bisphosphate (PIP₂) from all other phospholipids. This analysis reveals a significant reduction in levels of PIP and PIP₂, but not PI, in Thy-1 caps. Through the use of ion exchange column chromatography, we have found an increased production of all three species of inositol phosphates during anti-Thy-1 antibody-induced capping. Inositol 1, 4, 5 -triphosphate (IP₃) shows the most significant increase, compared to the much smaller increases in inositol 4, 5-bisphosphate (IP₂) and inositol monophosphate (IP). These results suggest that the binding of anti-Thy-1 antibody to Thy-1 antigen activates phospholipase C which, in turn, initiates polyphosphoinositide turnover and IP₃ production. It is proposed that these observed effects are the result of early signal transducing events which are prerequisite steps in Thy-1 receptor cap formation.     

Identification of three novel missense PKU mutations among Chinese.

Three novel missense mutations have been identified in the phenylalanine hydroxylase (PAH) genes of Chinese individuals afflicted with various degrees of phenylketonuria (PKU). A T-to-C transition was observed in exon 5 of the gene, resulting in the substitution of Phe161 by Ser161. Two substitutions, G-to-T and T-to-G, were observed in exon 7, resulting in the substitution of Gly247 by Val247 and Leu255 by Val255, respectively. Expression analysis demonstrated that these mutant proteins produced between 0 and 15% of normal PAH enzyme activity. Population screening of a Chinese sample population indicates that these mutations are quite rare, together accounting for only about 4% of all PKU alleles among the Chinese. The P161S and G247V mutations were each present on a single PAH RFLP haplotype 4 chromosome in patients form Northern China, while the L255V mutation was present on chromosomes of both haplotypes 18 and 21 in patients from Southern China. These results suggest that the remaining 30% of uncharacterized PKU alleles in the Chinese population may bear a large number of relatively rare PAH mutations.     

Signal transduction and regulation of neurotrophins.

Our understanding of the molecular nature of neurotrophic interactions has been greatly enhanced by the recent isolation and characterization of several new neurotrophic factors and their receptors. Neurotrophic factors have been found to be regulated by neuronal activity in the central nervous system, and may be involved in activity-dependent processes throughout development and maturity.     

Evaluation of nucleolar organizer region-associated proteins in endometrial pathology.

In the current study the argyrophil staining technique for NOR proteins (Ag-NORs) has been performed on cases of different endometrial lesions, trying to find an aid in differentiating atypical hyperplasia from well differentiated carcinoma in biopsy specimens. We conclude that the Ag-NOR count, even though in endometrial carcinoma is significantly exceeding that of atypical hyperplastic endometrium, could be a misleading discriminator, because of a wide overlap of values in individual cases.     

T3 reverses the changes in met-enkephalin and beta-endorphin contents in the anterior lobe, but not the neuro-intermediate lobe of the pituitary of rats rendered hypothyroid by PTU-treatment

The changes in met-enkephalin and beta-endorphin contents in the pituitary in PTU-induced hypothyroidism were studied in the rat. After 2 weeks of PTU-treatment, both IR-met-enkephalin and IR-beta-endorphin contents in the pituitary were significantly reduced. Gel filtration chromatography followed by radioimmunoassay showed that the immunoactivities in the peaks of precursors, met-enkephalin, beta-lipotropin and beta-endorphin were all lower in the pituitaries from the PTU-treated rats. In another experiment, some of the PTU-treated rats were injected daily with 500 micrograms T3/kg b.w. In the hypothyroid rats, IR-met-enkephalin and IR-beta-endorphin contents were decreased in both the anterior and neurointermediate lobes. Only the changes in the anterior lobe were reversed by T3 treatment. In conclusion, while the effects on the anterior lobe are probably due to a deficiency in thyroid hormones, the mechanism for the decrease of opioid peptide contents in the neurointermediate lobe is still unclear.