The effect of sodium on depolarization-induced calcium uptake and acetylcholine release by synaptosomes

The influence of external sodium concentration on potassium (depolarizing agent)-stimulated calcium uptake and Ca⁺-dependent acetylcholine release by rat cerebral cortex synaptosomes has been studied. It was found that increased sodium concentration decreases both the Ca²⁺ uptake and the acetylcholine release, whereas a low external sodium concentration is stimulatory.     

Selenium status of patients with Balkan endemic nephropathy

The selenium (Se) contents in common cereals in endemic and nonendemic areas in Serbia are very low. Plasma Se levels of both patients and healthy subjects, were also low, reflecting low Se intakes. Patients with Balkan endemic nephropathy (BEN) had significantly lower (p<0.05) plasma Se levels than healthy individuals, both from regions close to endemic areas, and from Belgrade. Mean plasma Se of BEN patients was slightly but insignificantly higher in samples taken immediately after dialysis than in those taken before, suggesting that very little of the Se present in plasma is dialyzable. Plasma SeGSH-Px activities before and after hemodialysis in both BEN and Nonendemic chronic renal failure (NCRF) patients were not significantly different, but BEN patients had lower enzyme activities than those with NCRF and healthy controls. In BEN patients, a significant correlation between plasma Se and SeGSH-Px activity was found. NCFR patients were with diagnoses: TBC of kidneys, chronic glomerulonephritis, chronic pyelonephritis, and polycystic kidneys.     

Cell growth and water relations of the halophyte,Atriplex nummularia L., in response to NaCl

Summary Growth reduction or cessation is an initial response of Atriplex nummularia L. cells to NaCl. However, A. nummularia L. cells that are adapted to 342 and 428 mM NaCl are capable of sustained growth in the presence of salt. Cells that are adapted to NaCl exhibit a reduced rate of division compared to unadapted cells. Unlike salt adapted cells of the glycophyte Nicotiana tabacum L., A. nummularia L. cells do not exhibit reduced rate of cell expansion after adaptation. However, the cell expansion rate of unadapted A. nummularia L. cells is considerably slower than that of unadapted glycophyte cells and this normally low rate of cell expansion may contribute to the enhanced capacity of the halophyte to tolerate salt. Turgor of NaCl adapted cells was equivalent to unadapted cells indicating that the cells of the halophyte do not respond to salt by osmotic over adjustment as reported for the glycophyte tobacco (Binzel et al. 1985, Plant Physiol. 79:118–125).     

Conformation and structure of 2-amino-8-(β-d-ribofuranosyl)imidazo [1,2-a]-s-triazin-4-one (5-aza-7-deaza guanosine), a potent antiviral nucleoside

The crystal and molecular structure of one imidazo[1,2-a]-s-triazine nucleoside and its antiviral activity are described. The crystal structure of 2-amino-8-(β-d-ribofuranosyl)imidazo-[1,2-a]-s-triazin-4-one monohydrate (C₁₀H₁₃N₅O₅·H₂O) was solved by X-ray counter data. The compound crystallizes in the monoclinic space group P2₁ with cell dimensions a = 7.353 (1), b = 6.465 (1), c = 13.701 (1) Å, β = 104.64 (1)°. The structure was solved by direct methods and refined by full matrix least-squares technique to a final value of the conventional R-factor of 0.049 using 1998 observed intensities. The orientation of the base relative to the sugar ring defined in terms of rotation about the C(1′)-N(8) glycosyl bond is anti (47.8°). The ribose moiety exhibits C(2′)-endo, ²E conformation. The conformation around C(4′)-C(5′) is gauche^?. Molecular packing is dominated by hydrogen bonds. Base stacking occurs long the b axis. 5-Aza-7-deazaguanosine has shown a marked antiviral activity in vitro against herpes simplex virus despite the fact that N(3) is effective as the hydrogen acceptor only.     

Permeabilization of yeast for in situ determination of α-glucosidase

A quantitative in situ assay of yeast α-glucosidase involving permeabilization of the cells by freezing and thawing is described. The assay was applied to different strains in different physiological states and was shown to give results comparable to those obtained with total cell homogenates. The primary advantage of the in situ assay was the possibility of analyzing a large number of samples from the same culture during a growth curve using a very reduced cell mass.     

13/14 translocation in a man with reproductive failure

Summary An inherited (maternal origin) 13/14 translocation with the nucleolus organizer regions eliminated and one centromere was found in an oligospermic man whose wife had had two spontaneous abortions. Meiotic studies revealed all stages of spermatogenesis with a trivalent configuration in diakinesis. Possible reasons for his subfertility and his mother's normal fertility are discussed.     

The effect of temperature and crowding on midgut amylolytic activity in Tenebrio molitor adults

The effect of two constant temperatures (23°C and 28°C), mixed group (5 + 5), and isolation on the midgut amylolytic activity during adult development of Tenebrio molitor has been investigated in vitro. Higher temperatures (28°C) and mixed groups stimulate the rate of midgut amylolytic activity. After attaining the maximal level, the amylolytic activity shows fluctuations. The possible role of hormones and primer pheromones in the control of the midgut amylolytic activity in T. molitor adults is discussed.     

A combined scanning and transmission electron microscopic study and electron probe microanalysis of human pineal acervuli

Summary Untreated, decalcified and trypsinized acervuli from human pineal bodies were studied with the scanning and transmission electron microscope as well as by electron probe microanalysis. The mulberry-like acervuli are composed of a various number of spherical lobes (135–800 m) between which clustered groups of globuli (4–14 urn in diameter) are observed. The acervular lobes are very probably formed by an aggregation of these globuli. Small round particles 125–500 Å in diameter are observed on the surface of the pineal concretions. These are not influenced by either decalcification or trypsin treatment. The acervular mineral corresponds morphologically to hydroxyapatite. The electron probe microanalysis reveals the existence of calcium and phosphorus as main components of the acervuli. Small quantities of magnesium and strontium were also detected.Dedicated to Professor Berta Scharrer on the occasion of her 70th birthdayWith the technical assistance of Mr. P.A. MilliquetThe author wishes to thank Mr. Bauer and Mr. Fryder (Nestec SA, La Tour de Peilz) for the use of the Cambridge Stereoscan electron microscope and Dr. T. Jalanti (C.M.E., Lausanne) for his help with the use of the X-ray microanalyser     

Properties of spinach chloroplast fructose-1,6-diphosphatase

Photosynthetic fructose-1,6-diphosphatase (FDPase) fractions I and II, earlier purified from spinach leaves, show a similar amino acid composition, with the exception of a higher glutamic acid content in the latter. In both fractions glutamic and aspartic acids are the main amino acids. pH activity profiles of fractions I and II are similar, with optima at 8·65–8·70, both showing a high specificity for fructose- 1,6-diphosphate. These two fractions are Mg²⁺-dependent for activity, with an Optimum Mg²⁺ concentration of 10 mM in standard conditions, which shifts to 5 mM when the MG²⁺/EDTA ratio is increased to 10; Mn²⁺ and Co²⁺ are slightly active. EDTA enhances FDPase activity slightly, with an optimum at 0·4–0·8 mM. Cysteine has no activating effect, and acts as an inhibitor above 10 mM. Both I and II have an optimum substrate concentration of 4 mM, and the substrate inhibits at concns above this value. Kinetic velocity curves are sigmoidal, with the concave zone located in the range of physiological substrate concns. (Hill coefficient 1·75 for both). This suggests a strong regulatory role of fructose-1,6-diphosphate. K_m values are 1·4 × 10⁻³ M (fraction I) and 1·1 × 10⁻³ M (fraction II). The highest activity rate occurs at 60°, in accordance with the high thermostability of both fractions; the activation energies are 14·3 kcal/mol (fraction I) and 13·0 kcal/mol (fraction II).