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.     

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.     

Periodic acid-induced blastogenesis of lymphocytes is independent of phosphoinositide turnover

The blastogenic transformation of lymphocytes by periodic acid was investigated to determine if blastogenesis induced by this mitogen was preceded by phosphoinositide turnover as previously shown for the lectins. Although periodate oxidation stimulated nucleic acid synthesis and interleukin-2 production, no changes in phosphoinositide turnover could be detected when compared to control lymphocyte cultures. These data indicate that increased phosphoinositide turnover is not an absolute prerequisite for lymphocyte proliferation.     

Occurrence and distribution of halophilic vibrios in subtropical coastal waters of Hong Kong.

The summer occurrence and distribution of halophilic vibrios in the subtropical coastal waters of Hong Kong were investigated. The density of vibrios in six sample sites ranged from 90 to 6,700 per ml, which made up 0.41 to 40% of the total bacterial populations of these sample sites. The sucrose-positive vibrios were found to be much more common (88% of total vibrios) than the sucrose-negative ones. A total of 48 strains belonging to six Vibrio species were fully characterized. Among these, Vibrio alginolyticus was the most frequently isolated, followed by V. parahaemolyticus, V. harveyi, V. vulnificus, V. campbellii, and V. fluvialis. The finding that eight of the nine strains of V. harveyi showed a positive Kanagawa reaction warrants further study.     

High frequency DNA rearrangements associated with mouse centromeric satellite DNA

A DNA transformed mouse cell line, generated by the microinjection of a pBR322 plasmid containing the herpes thymidine kinase (tk) gene, was observed to exhibit a high frequency of DNA rearrangement at the site of exogenous DNA integration. The instability in this cell line does not appear to be mediated by the tk inserts or the immediately adjacent mouse DNA, but instead may be a consequence of the larger host environment at the chromosomal site of tk insertion. Results obtained from restriction analysis, in situ chromosome hybridizations, and cesium chloride density-gradient fractionations indicate that the tk inserts are organized as a single cluster of direct and inverted repeats embedded within pericentromeric satellite DNA. To determine the molecular identity of the flanking host sequences, one of the mouse-tk junction fragments was cloned, and subsequent restriction and sequence analyses revealed that this DNA fragment consists almost entirely of classical mouse satellite DNA. On the basis of these observations, we suggest that the instability in this cell line may reflect the endogenous instability or fluidity of satellite DNA.