Ouabain binding in rectal gland of Squalus acanthias

In an attempt to examine the mechanisms of activation of (Na, K)-ATPase when epithelial transport is stimulated, the binding of ouabain to rectal gland tissue was measured before and after stimulation with dibutyryl cAMP and theophylline. Stimulation significantly altered the characteristics of ouabain binding to slices of Squalus acanthias rectal gland and to isolated rectal gland cells, accelerating the rate of binding and increasing the amount of ouabain bound at equilibrium when low concentrations of ouabain (10(-9) to 10(-7) M) were present in the medium. Scatchard plots of ouabain binding were nonlinear, suggesting at least two classes of binding sites, one of higher and one of lower affinity. Stimulation with cAMP and theophylline appeared to increase the affinity of the high-affinity site. Ouabain binding was increased by cAMP and theophylline even in the presence of furosemide (10(-4) M) or bumetanide (10(-5) M), and when Li+ was substituted for Na+, or NO3- for Cl- -maneuvers known to inhibit rectal gland secretion. The changes in ouabain binding induced by cAMP and theophylline do not appear, therefore, to be secondary to secretory activity but may reflect a change in the configuration, environment or location of existing enzyme so as to enhance its activity. Stimulation of ouabain binding cannot be demonstrated in whole homogenates of rectal gland, indicating that intact cells are necessary for the cyclic AMP-induced increase in ouabain binding to become manifest.

Type III glycogenosis presenting as liver disease in adults with atypical histological features

Two cases of type III glycogen storage disease are reported in adults; the occurrence of cirrhosis in one case illustrates the potential development of chronic liver disease in this condition. The other was the oldest patient with this condition found in a review of published reports. Electron microscopy of peripheral blood leucocytes to demonstrate excess glycogen was found to be a quick and useful aid to diagnosis. Histology of these adult cases showed a distribution of hepatocyte vacuolation which has not been previously recorded.

Tapetoretinal degeneration in the cerebro-hepato-renal (Zellweger's) syndrome

Electrophysiological and histopathological study of a baby suffering from Zellweger's syndrome and presenting progressive retinal dysfunction showed this to be related to degenerative changes in the photoreceptor cells and pigment epithelium and to defective myelination of the optic nerve. Disturbances of bile acid and lysine metabolism were also demonstrated, lending support to the concept that Zellweger's syndrome is attributable to a widespread inadequacy of intracellular oxidative function.

HLA antigen expression on urothelial cells: detection by antibody-dependent cell-mediated cytotoxicity

Antibody-dependent cell-mediated cytotoxicity (ADCC) was used to detect HLA-A, -B and -C antigens on in vitro-cultured urothelial cells of normal or malignant derivation. Alloantisera induced specific lysis of 51Cr-labelled targets by effector lymphoid cells from non-immune donors. HLA antisera were routinely titred to dilutions greater than or equal to 10(-3) on urothelial cells in primary or long-term culture. The HLA phenotype was compared for lymphoid cells and urothelial cells from eight individuals. HLA antigens detected by complement mediated lymphocytotoxicity were also detected on urothelial cells. No deletions or gains in HLA antigens were found on normal or malignant urothelial cultures as compared with donor lymphocyte HLA typings. The results show that the established urothelial cells lines J82, TCCSuP and SCaBER have retained their donor HLA phenotype. The established cell lines T24 and RT4 derived from transitional cell carcinomas and HCV-29 from urothelium were found to have distinctive HLA profiles although donor lymphocytes were not available for comparison. The serological crossreactions seen in complement mediated lymphocytotoxicity were clearly observed in ADCC. In particular, HLA-Cw5 was found to crossreact with HLA-Cw8. HLA-Cw5 was detected on 6/8 cultures of transitional cell carcinomas and this was confirmed by absorption analysis.

Intracellular accumulation of a fluorescent derivative of paromomycin in human fibroblasts

Human fetal lung fibroblasts grown in the presence of dansyl-paromomycin (DNS-Pm), a fluorescent derivative of the aminoglycoside antibiotic, paromomycin, probably accumulate DNS-Pm in the lysosomes. The intracellular concentration of DNS-Pm is proportional to the extracellular concentration and to the length of time cells are exposed to the compound. The accumulation of DNS-Pm by human fibroblasts continued to increase for several days, reaching a saturation after 7 days. The kinetic data are consistent with the establishment of a steady state in the cell between fluid-phase pinocytosis and exocytosis of DNS-Pm. About 80% of the intracellular DNS-Pm ws released in 24 hr when fresh medium without the analogue was added. The residual 20% remained within the cells, suggesting that it may be irreversibly bound to the lysosomes, endoplasmic reticulum, or ribosomes. The uptake of paromomycin by cells in culture may be a useful means to study error propagation during growth and lifespan of cells in vitro.

HLA-A, B and C antigens in South Indian families with leprosy

Seventy-two families, selected for having at least two children affected with leprosy, were HLA typed for 57 A, B and C locus antigens recognized by the WHO Nomenclature Committee. In addition, 20 possible new "splits" were investigated. The distribution of A, B and C locus antigens in affected and unaffected family members was similar, irrespective of the type of leprosy in the family. Gene frequencies (derived by direct gene counting from 253 haplotypes), haplotype frequencies and delta values were calculated. There is evidence for heterogeneity of B5, B15, B17, Bw16 and Bw35 and for the existence of at least one A locus and one B locus antigen not previously detected. The value of the HLA system for detecting expaternal children in a highly inbred population and the effect of inbreeding on the HLA system is discussed.

Purification and characterization of a Saccharomyces cerevisiae exoribonuclease which yields 5'-mononucleotides by a 5' leads to 3' mode of hydrolysis

An exoribonuclease producing 5'-mononucleotides has been purified from ribosomes of Saccharomyces cerevisiae. The enzyme has a broad pH optimum around 8.0, requires divalent cation, and is stimulated by monovalent cation with the cation and degree of stimulation being dependent on the substrate used. With either poly(A) or rRNA as substrate, the enzyme has a processive mode of hydrolysis. The oligonucleotides, (pA)3-5, are hydrolyzed by the enzyme, and the hydrolysis is dependent on a 5'-phosphate end group. Phosphorylation of the 3' end has little effect on the rate of hydrolysis. With [3H]poly(A) or [3H]rRNA, labeled differentially at the 5' termini, a more rapid release of 5'-terminal label can be shown, providing evidence that the enzyme hydrolyzes in a 5' leads to 3' direction. Further evidence for a 5' leads to 3' mode of hydrolysis is provided by a study of the products of the hydrolysis of [3H](pA)5 labeled at the 5' termini with 32P. No 32P label is found in (pA)2 which accumulates as an intermediate.

Accuracy of in vitro protein synthesis: translation of polyuridylic acid by cell-free extracts of human fibroblasts

Errors in translation have been measured in cell-free protein synthesising extracts derived from cultured MRC-5 human diploid fibroblasts of limited lifespan. Using polyuridylic acid as messenger, the error frequency for the misincorporation of leucine was 1-2%. It was found that varying the concentration of leucine increased the error frequency for leucine misincorporation. No difference could be detected in the accuracy of translation with increasing cell age, from passage 25 to 55. The aminoglycoside antibiotic, paromomycin, was shown to have a profound effect on the leucine misincorporation, increasing the error frequency of this amino acid twenty-to fortyfold. However, there was no difference in the paromomycin-induced errors wtih increasing cell age. Another effect of this antibiotic is that it inhibits the incorporation of the cognate amino acid phenylalanine. It was found that passage 55 cell extracts were less inhibited by paromomycin than similar extracts made from lower passage cells (passages 25 and 40). When the accuracy of translation of cell extracts made from human transformed cells (HeLa) and untransformed cells (MRC-5) was compared, no detectable difference could be found. Paromomycin increased the leucine errors in extracts made from HeLa cells to a similar degree to that observed for MRC-5 fibroblasts.

Simultaneous measurement of regional blood flow and glucose extraction in rat brain

A method has been described which allows the measurement of cerebral blood flow (CBF) and solute transport across cerebral capillary wall in the same regional sample of rat brain. An inert diffusible indicator (iodoantipyrine) was used to measure a blood flow, in mixed gray and white matter, or approx. 1.0 ml/min/g. Using 3H2O as a reference molecule, the flux of [14C]D-glucose into brain was determined at blood glucose concentration levels between 0.1 and 60 mM. In all discrete areas of brain sampled, a consistent Vmax of 1.92 micromol/min/g and a Km of 8.35 mM was found. Glucose extraction by brain was inversely related to CBF, while a direct relationship was noted for glucose clearance.

Fidelity of histone synthesis in cultured human fibroblasts

The results in the literature to support Orgel's general error hypothesis of ageing only provide indirect evidence that errors in protein synthesis increase during senescence. This study attempts to provide direct evidence of errors in protein synthesis by measuring the misincorporation of 35S-methionine into histone H1 obtained from young and old fibroblasts (MRC-5). The conclusions that can be drawn from this study are: (a) the error level for the misincorporation of methionine into histone H1 is less than 7 methionines/10(5) amino acids and 2-3 methionines/10(4) amino acids in young and old cells respectively; (b) a methionine containing fraction associated with H1 is obtained after the final purification. The amount of this fraction increases with the age of the cell culture as does the number of methionine residues; (c) there is a variation in the complexity of H1 polypeptide chains, the complexity increasing with the age of cultured cells.