Deletion 2q31.3→2q33.3: gene dosage effect of ribulose 5-phosphate 3-epimerase

In a new case of interstitial del(2q), measurements of ribulose 5-phosphate 3-epimerase activity suggested that the locus for this enzyme might be localized to the subregion 2q32q33.3.     

Induction of chromosome aberrations by Sr β-particles in cultured human lymphocytes

Human blood was irradiated with β-particles from an external source of ⁹⁰Sr. The source was a rolled piece of silver foil, active dimensions: 100 × 12.5 mm, incorporating 3.7 × 10⁸ Bq (10 mCi) of ⁹⁰Sr/⁹⁰Y. After culturing for 48 h, the dicentric yield in the lymphocytes at the first metaphase was measured as a function of the dose in the blood. The aberration yield fitted the linear-quadratic function well, which is consistent with the single-track and two-track model for aberration formation at low LET radiation. The curve for ⁹⁰Sr β-rays was compared with a curve for ⁶⁰Co γ-rays. The main difference between the coefficients was in the values. With respect to ⁶⁰Co γ-rays, the RBE calculated from the dose-effect relationships for dicentric production was 2.8 at the dose of 0.14 Gy; it decreased with increasing doses. The distribution of dicentrics was consistent with the Poisson distribution but showed a tendency to over-dispersion in the region of higher doses. A reason for these discrepancies is discussed.     

Evidence for an ascorbate shuttle for the transfer of reducing equivalents across chromaffin granule membranes

Adrenal chromaffin granules must shuttle reducing equivalents from the cytosol inward to reduce ascorbic acid oxidized during norepinephrine biosynthesis by intragranular dopamine-beta-hydroxylase. A transmembrane electron shuttle between the external (cytosolic) and intragranular ascorbate pools was demonstrated in vitro in intact bovine chromaffin granules undergoing tyramine- or dopamine-stimulated dopamine-beta-hydroxylase turnover. Incubation of intact chromaffin granules with tyramine results in a time-dependent decrease in reduced intragranular ascorbate and production of octopamine. The rate of ascorbate oxidation is a function of the extragranular concentrations of tyramine over the range 50 microM to 2 mM and is 95% inhibited by addition of the dopamine-beta-hydroxylase inhibitor disulfiram. The stoichiometry of octopamine synthesized/ascorbate oxidized closely approximates unity. The presence of extragranular dopamine also induces oxidation of intragranular ascorbate which is inhibited by blocking dopamine transport with reserpine. On the other hand, incubation with octopamine, which is also transported by the granules, causes no net decrease in reduced intragranular ascorbate. The presence of 400 microM extragranular ascorbate abolishes the observed tyramine-induced intragranular ascorbate oxidation. The addition of ascorbate extragranularly 30 min after addition of tyramine reverses the oxidation of intragranular ascorbate. The measurement of [14C]ascorbate distribution ratios in granule pellets and supernatants indicates that there is no transmembrane transport of ascorbate. Extravesicular NADH had no significant effect on matrix ascorbate levels during beta-hydroxylation. These data provide new in vitro evidence that chromaffin granules shuttle reducing equivalents inwardly from an extra- to an intravesicular ascorbate pool and that cytosolic ascorbate is the source of the intragranular reducing equivalents required during norepinephrine biosynthesis.     

Computer-assisted mathematical analysis of sigmoid biological events

A program in BASIC is described which allows accurate quantificationof some numerical parameters that can be objectively correlatedto biological indexes in sigmoid biological events. Attentionwas focused on the polymerization process of actin (a muscleprotein with a mol. wt of 42 000 daltons) studied as the variationin the OD₃₆₀ index with time. The experimental points, if plotted,can be well approximated by a rational function of the typeOD₃₆₀ = f(t), which passes through the origin and can be representedgraphically by a sigmoid curve. The program was very helpfulin comparing the experimental curves and in analysing significantparameters, such as maximum velocity and asymptote, that characterizethese curves and whose interpretation would otherwise be purelysubjective. Received on July 11, 1985; accepted on January 13, 1986     

Increased rate of superoxide ion generation in Fanconi anemia erythrocytes

The rate of generation of superoxide ion, the concentration of Cu, Zn superoxide dismutase and the hematological parameters were measured in red blood cells obtained from Fanconi anemia patients and from healthy individuals. No significative difference in the superoxide dismutase concentration was found, while the rate of generation of the superoxide ion doubled in Fanconi anemia patients. The steady-state concentration of the superoxide ion was calculated from these data and was found to be 2.3 times higher in Fanconi anemia erythrocytes than in controls. The possible consequences with respect to the alterations in FA are discussed.     

Internalization of metallochromic Ca2+ indicators in mammalian cells

Two new techniques for internalizing metallochromic indicators into the cytosol of mammalian cells are described. One method consists of hypertonically treating the cells in the presence of the indicator, followed by a hypoosmotic treatment. The second method consists of incubating the cells at high density in a concentrated indicator solution in physiological saline. Using either method, arsenazo III or antipyrylazo III was internalized into Ehrlich Ascites tumor (EAT) cells at concentrations yielding measurable differential absorbance changes which correspond to changes in the intracellular Ca2+ concentration. In the case of antipyrylazo III, the amount of indicator internalized ranged between 140 and 350 microM, and was dependent on the metabolic state of the cell during loading. Control and loaded cells possessed virtually identical ATP/ADP ratios, as measured by high performance liquid chromatography (HPLC) in cell extracts. Antipyrylazo III was also internalized by rat hepatocytes without detectable cell damage. Treatment of metabolically active EAT cells with the calcium ionophore A23187 results in only a slight increase in the intracellular free Ca2+ concentration, [Ca2+]i, whereas treatment with the calcium ionophore ionomycin induces a substantial but transient increase in the [Ca2+]i. In contrast, metabolically inhibited EAT cells show a large rise in the [Ca2+]i upon addition of A23187. Thus, these techniques offer another way of measuring intracellular free Ca2+ changes in mammalian cells and may prove useful, especially where concentrations of free cytosolic Ca2+ larger than 1 microM are expected.     

Rhodotorula nothofagi sp. nov., isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

An unusual Rhodotorula isolated from decayed wood of Nothofagus obliqua (Mirb.) Blume is described and illustrated. This species differs from all accepted Rhodotorula species (1–7, 10) to warrant its establishment as a new species, Rhodotorula nothofagi sp. nov.Postgraduate student from the Instituto de Ecología y de Evolución, Universidad Austral de Chile, Valdivia.     

The determination of the separate Ca pump protein and phospholipid profile structures within reconstituted sarcoplasmic reticulum membranes via X-ray and neutron diffraction

We have previously compared the electron density profiles for several highly-functional reconstituted sarcoplasmic reticulum membranes with that for the isolated sarcoplasmic reticulum membrane (Herbette, L., Scarpa, A., Blasie, J.K., Wang, C.T., Saito, A. and Fleischer, S. (1981) Biophys. J. 36, 47–72). In this paper, we compare the separate calcium pump protein profile within these reconstituted sarcoplasmic reticulum membranes, as derived by X-ray and neutron diffraction methods, with that within isolated sarcoplasmic reticulum membranes. In addition, the time-average perturbation of the lipid bilayer by the incorporated calcium pump protein within these reconstituted sarcoplasmic reticulum membranes has been determined in some detail.     

Increased GH responsiveness to dopamine receptor stimulation in alcohol addicts during the late withdrawal syndrome

In humans the release of growth hormone (GH) elicited by dopamine (DA) and DA agonists may represent a reliable model to assess change in sensitivity of DA receptors. We now report that in chronic alcoholics, 4–7 days after the suspension of alcohol consumption, the increase of GH response to DA infusion was higher than that seen in non alcoholic volunteers. The specificity of this GH response to DA administration was demonstrated by the use of domperidone, a novel peripheral antagonist of DA receptors. These results suggest the development of hyper-responsiveness of DA receptors involved in the control of GH secretion in chronic alcoholics during the later phases of the “withdrawal syndrome”.