Urinary zinc and its relationships with microalbuminuria in type I diabetics

We investigated whether zincuria is associated with microalbuminuria in type I (insulin-dependent) diabetics (IDDM). In 169 IDDM, 215 overnight urine samples were collected for simultaneous assay of zinc and albumin. In 76 samples with excessive microalbuminuria (>15 mg/L), zincuria was higher than in the 139 other samples (0.83±0.06 vs 0.58±0.03 mg/Lp<0.001), though zincuria and microalbuminuria were not significantly correlated. An exercise provocation test was performed in 78 IDDM. Although microalbuminuria increased, zincuria did not change during the test. Another group of 83 IDDM underwent urinary zinc determination over a period of 1 h of recumbency. The 48 patients who had a zincuria higher than the mean+2 SD of control values had higher microalbuminuria at rest (48±16 μg/min vs 12±2p<0.01) and after exercise (111±33 vs 42±14p<0.02) than the remaining 35 subjects. Both subgroups did not differ for zinc intake and zincemia. Thus, incipient nephropathy as detected by the measurement of microalbuminuria is associated with a highly significant increase in zinc excretion, which is not proportional to albumin leakage, nor is it amplified during exercise. Hyperzincuria is not explained by an increase in zinc intake and does not result in hypozincemia.     

Operation Everest II: metabolic and hormonal responses to incremental exercise to exhaustion.

The reasons for the reduced exercise capacities observed at high altitudes are not completely known. Substrate availability or accumulations of lactate and ammonium could have significant roles. As part of Operation Everest II, peak oxygen uptakes were determined in five normal male volunteers with use of progressively increasing cycling work loads at ambient barometric pressures of 760, 380, and 282 Torr. Decrements from sea level (SL) to 380 and 282 Torr occurred in peak power output (19 and 47%), time to exhaustion (19 and 48%), and oxygen uptake (41 and 61%), respectively. Arterial saturations after exhaustive exercise were decreased to 63% at 380 Torr and 39% at 282 Torr. At 380 and 282 Torr, postexercise plasma concentrations of glucose and free fatty acids were not increased, whereas plasma glycerol concentrations were decreased relative to SL (145 +/- 24 microM at 380 Torr and 77 +/- 10 microM at 282 Torr vs. 213 +/- 24 microM at SL). Preexercise plasma insulin concentrations were elevated at both 380 and 282 Torr (87 +/- 16 pM at 380 Torr and 85 +/- 18 pM at 282 Torr vs. 41 +/- 30 pM at SL). In general, postexercise concentrations of plasma catecholamines were decreased at altitude compared with SL. Preexercise lactate and ammonium concentrations were not different at any simulated altitude. From these data neither substrate availability nor metabolic product accumulation limited exercise capacity at extreme simulated altitude.     

Analysis of nuclear sugar-binding components in undifferentiated and in vitro differentiated human promyelocytic leukemia cells (HL60)

The nuclear sugar-binding components (i.e., lectinlike molecules) were analyzed using isolated and membrane-depleted nuclei after incubation in the presence of fluorescein-labeled neoglycoproteins. This analysis was performed before and during the in vitro differentiation of HL60 cells into monocytes by PMA treatment and into granulocytes by DMSO treatment. The nucleoli of undifferentiated and differentiated HL60 cells were not labeled, unlike the nucleoli of other mammalian cells studied so far. This peculiarity allowed us to quantitatively analyze by flow cytometry the changes in the lectin activity associated with the extranucleolar territories enriched in ribonucleoprotein complexes. The neoglycoprotein binding was found to be significantly lower in differentiated than in undifferentiated cells. The decrease in neoglycoprotein binding was observed within the first 24 h of DMSO or PMA treatment, just before the arrest of DNA synthesis. Taking into account that the granulocytic differentiation required 72 h of chemical treatment, the extra-nucleolar lectins might be involved in modulation of the DNA synthesis rather than in phenotypic differentiation. These data are discussed in an attempt to reconcile the association of lectins with RNP complexes and their possible involvement in modulation of HL60 cell proliferation.     

Zooplankton impacts on chlorophyll and transparency in Onondaga Lake,New York,USA

The transparency of polluted, hypereutrophic Onondaga Lake, New York, USA has improved substantially in the late 1980's as a result of reductions in phytoplankton biomass, in the absence of significant reductions in external phosphorus loading. Much of this improvement has been due to the occurrence of clearing events, e.g. sudden and dramatic increases in transparency. Field measurements, laboratory experiments, and modelling analyses were utilized to identify processes regulating phytoplankton standing crop during the spring to fall interval of 1987. Changes in the zooplankton community documented over the past decade support the conclusion that increased zooplankton grazing has contributed to improvements in transparency. Herbivores now represent a greater fraction of the zooplankton population and more efficient cladocerans are present in greater numbers. Biomanipulation practices, e.g. reestablishment of piscivorous species, designed to reduce the abundance of planktivorous fish species in Onondaga Lake, may serve to reduce pressure on the grazing community and thus result in further improvements in transparency.     

Adenylate cyclase of human articular chondrocytes. Responsiveness to prostaglandins and other hormones.

Adenylate cyclase [ATP pyrophosphate lyase (cyclizing), EC 4.6.1.1] was shown to be present in cultured human articular chondrocytes. Optimal conditions of incubation time, protein and substrate concentrations and pH were determined in whole cell lysates. Maximal activity occurred at pH 8.5 with no decrease in activity up to pH 10.0. Adenylate cyclase activity of particulate membrane preparations was enhanced by the addition of crude cytosol preparations. The prostaglandins E1, E2, F1 alpha, F2 alpha, D2, B1, B2, A1 and A2, as well as adrenaline and isoprenaline, stimulated adenylate cyclase derived from either adult or foetal chondrocytes. No significant stimulation was observed in the presence of human calcitonin or glucagon. Bovine parathyroid hormone always significantly stimulated the adenylate cyclase derived from foetal chondrocytes, but not from adult chondrocytes. Preincubation of the chondrocytes in culture with indomethacin and with or without supernatant medium from cultured mononuclear cells increased the responsiveness of the adenylate cyclase to prostaglandin E1.     

Analysis in vivo of translational mutants of the rIIB cistron of bacteriophage T4

We have mapped the mutants isolated by Nelson et al. (1981) that reduce the amount of rIIB protein synthesized during bacteriophage T4 infection of Escherichia coli B and characterized their rIIB expression in vivo. These mutants fall into four distinct groups in terms of mapping and phenotype. We have located the probable site of each mutation on the DNA sequence. We have also analyzed a number of other mutations near the initiating AUG of rIIB with respect to their rIIB expression. In some of these mutants, ribosomal recognition of the wild-type initiating AUG is precluded and so initiation occurs at a different AUG, which, in some instances, we have identified.     

Ultrastructural changes in the endoplasmic reticulum during dormancy release of apple embryos (Pyrus malus L.)

Apple embryos were treated by cold (0°C) within the fruits, to break their dormancy; the controls were treated at 12°C or at 20°C. Ultrastructural features of meristematic cells in the embryonic axis were compared for each treatment. The organization of the cells of dormant embryos was described: Endoplasmic reticulum consisted in some short rough cisternae; lipid droplets regularly arranged near the plasmalemma constituted a kind of shell; mitochondria had a few cristae; and dictyosomes were rarely observed. All these features are typical of dry seeds. After cold treatments, the only evolution observed was in the endoplasmic reticulum, where highly organized stacks appeared progressively as a function of time at 0°C. An intermediate temperature (12°C) induced similar formations in the reticulum but they were rarely observed and their degree of organization was lower than that obtained at 0°C. At 20°C, endoplasmic reticulum resembled that of the dormant embryo cells. The relation between the appearance of these structures in the reticulum and the disappearance of dormancy induced by cold is discussed.Abbreviations ER endoplasmic reticulum - RER rough endoplasmic reticulum     

An X-ray determination of the molecular interactions in hemoglobin C: a disease characterized by intraerythrocytic crystals.

The X-ray structure of cyanomet human hemoglobin C has been solved and refined, R ～27%. The molecular packing can be represented in two dimensions by two sets of parallel strands, one set in the $\text{b}$ direction and the other in the $\text{c}$ direction. Taken together the two sets of strands interconnect the molecules into square nets or layers where each molecule contacts its four nearest neighbors. Molecules in one layer are displaced in $\text{a}$ and $\text{b}$ so that they fit into the “holes” of the square arrays of the adjacent layers (normal to $\text{a}$) resulting in a pseudo body-centered cubic packing. This packing can account for the hemoglobin crystallization in and fragility of the erythrocytes. The aberrant β6A3 Lys residue is in a position to influence the crystal formation.     

Homology between ricin and Ricinus communie agglutinin: Amino terminal sequence analysis and protein synthesis inhibition studies

The existence of three forms of ricin and two forms of the Ricinus communis agglutinin (RCA) was established using cation exchange chromatography, isoelectric focusing, and polyacrylamide gel electrophoresis. The preparation of the RCA we obtained was 60–75 times more potent than ricin in the agglutination of erythrocytes, but was about 4% as effective as an inhibitor of cell-free protein synthesis. When reduced with 2-mercaptoethanol, the RCA was activated 3000-fold as an inhibitor of cell-free protein synthesis, whereas ricin was activated about 600-fold by the same treatment. A mixture of the RCA A chains was about one-fifth as effective as the ricin A chain in the inhibition of cell-free protein synthesis. The purified polypeptide subunits of the castor bean lectins were subjected to automated Edman degradation. The sequence for 17 of the first 19 residues of the agglutinin A chain was determined. The first seven residues of the ricin A chain were determined and they are identical with those of the RCA A chain. Nineteen turns of Edman degradation on the RCA B chain resulted in the identification of 18 amino acids. The sequence determined for the first 17 residues of the ricin B chain was identical with that of the RCA B chain. It is likely that the identity of the ricin/RCA A and B chain sequences extends further along the polypeptide chains than the sequences we have determined. The similar structural and catalytic potentials of the RCA and ricin suggest that they bear a precursor-product relationship.