Adverse effects of tempol on hidrosaline balance in rats with acute sodium overload

We studied the effects of tempol, an oxygen radical scavenger, on hydrosaline balance in rats with acute sodium overload. Male rats with free access to water were injected with isotonic (control group) or hypertonic saline solution (0.80 mol/l NaCl) either alone (Na group) or with tempol (Na-T group). Hydrosaline balance was determined during a 90 min experimental period. Protein expressions of aquaporin 1 (AQP1), aquaporin 2 (AQP2), angiotensin II (Ang II) and endothelial nitric oxide synthase (eNOS) were measured in renal tissue. Water intake, creatinine clearance, diuresis and natriuresis increased in the Na group. Under conditions of sodium overload, tempol increased plasma sodium and protein levels and increased diuresis, natriuresis and sodium excretion. Tempol also decreased water intake without affecting creatinine clearance. AQP1 and eNOS were increased and Ang II decreased in the renal cortex of the Na group, whereas AQP2 was increased in the renal medulla. Nonglycosylated AQP1 and eNOS were increased further in the renal cortex of the Na-T group, whereas AQP2 was decreased in the renal medulla and was localized mainly in the cell membrane. Moreover, p47-phox immunostaining was increased in the hypothalamus of Na group, and this increase was prevented by tempol. Our findings suggest that tempol causes hypernatremia after acute sodium overload by inhibiting the thirst mechanism and facilitating diuresis, despite increasing renal eNOS expression and natriuresis.     

The development of the pattern of innervation in chicken hindlimb muscles: evidence for specification of nerve-muscle connections

The pattern of innervation in 13 chicken hindlimb muscles was studied at various stages of development in order to examine the mechanisms which regulate its formation. The pattern of innervation was visualized by examining the distribution of fiber types within each muscle. It was found that the fiber type which a myotube acquired was influenced by both its time of formation and its position within a muscle. The earliest generation of myotubes (primary) had a marked tendency to become type I fibers, whereas, in contrast, the later generation of myotubes (secondary) tended to differentiate into type II fibers. There were regions of muscle, however, in which primary myotubes differentiated into type II fibers and other regions in which secondary myotubes acquired type I characteristics. During the development of some muscles the pattern of fiber types changed as a result of either a selective loss of type I fibers or, in other cases, a rearrangement of some of the initial neuromuscular contacts. These observations are consistent with the pattern of innervation of a muscle being established as a result of differential projection patterns of fast and slow motoneurons and the existence of some type of chemoaffinity where particular myotubes are preferentially innervated by particular motoneurons.     

Characterization of a beta-lactamase produced by Pseudomonas paucimobilis.

A novel beta-lactamase enzyme produced by a strain of Pseudomonas paucimobilis is described. The enzyme differs from other recorded beta-lactamases from Gram-negative aerobic bacteria. It was constitutive, and had the characteristics of a penicillinase. One single band of beta-lactamase activity at pI 4.6 was seen on iso-electric focusing. The enzyme had a molecular mass of 30 kDa. The beta-lactamase was strongly inhibited by tazobactam, sulbactam and clavulanic acid but not by the thiol residue inhibitors p-chloromercuribenzoate and p-chloromercuriphenylsulphonic acid, or by metallo-enzyme inhibitors. Plasmid DNA was not demonstrable, suggesting that the enzyme was chromosomally encoded.     

E and F alpha series prostaglandins in developing muscles

Prostaglandins are known to affect myoblast proliferation and fusion in vitro and are putative regulators of in vivo myogenesis. The levels of E and F alpha series prostaglandins in the thigh muscles of chicken embryos were measured by radioimmunoassays and correlated with indicators of muscle development. Just prior to the onset of secondary myogenesis, the amounts of PGE1, PGE2 and PGF1 alpha plus PGF2 alpha per mg of protein were high. In temporal association with myotube formation, the amount of PGE1 and PGE2 per mg of protein decreased. PGF alpha levels also fell, but at a slower rate than observed with the E series prostaglandins. The decreases in the amounts of prostaglandins per mg protein appeared to be due to a decline in the total amount of prostaglandin within each muscle. These observations are consistent with prostaglandins being one of the factors that controls in vivo muscle formation.     

Synthesis and resistance to enzymic hydrolysis of stereochemically-defined phosphonate and thiophosphate analogues of P1,P4-bis(5''-adenosyl) tetraphosphate.

Novel analogues of P1,P4-bis(5'-adenosyl) tetraphosphate, Ap4A (1), have been prepared with sulphur substituents at P1 and P4 and either oxygen or methylene bridges at the P2,P3-position. Separation of three isomers of the ApspCH2ppsA species has been achieved by a combination of mplc and hplc and the Rp,Rp, Rp,Sp, and Sp,Sp diastereoisomers identified on the basis of selective enzymatic hydrolysis using snake venom phosphodiesterase. Each of these three isomers is a strong competitive inhibitor of the specific Ap4Aase from Artemia and is highly resistant to the asymmetric cleavage normally catalysed by this enzyme.     

The interaction of dietary fatty acid and cholesterol on catecholamine-stimulated adenylate cyclase activity in the rat heart

Diets supplemented with high levels of saturated or unsaturated fatty acids supplied by addition of sheep kidney fat or sunflower seed oil, respectively, were fed to rats with or without dietary cholesterol. The effects of these diets on cardiac membrane lipid composition, catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor activity associated with cardiac membranes, were determined. The fatty acid-supplemented diets, either with or without cholesterol, resulted in alterations in the proportion of the (n-6) to (n-3) series of unsaturated fatty acids, with the sunflower seed oil increasing and the sheep kidney fat decreasing this ratio, but did not by themselves significantly alter the ratio of saturated to unsaturated fatty acids. However, cholesterol supplementation resulted in a decrease in the proportion of saturated and polyunsaturated fatty acids and a dramatic increase in oleic acid in cardiac membrane phospholipids irrespective of the nature of the dietary fatty acid supplement. The cholesterol/phospholipid ratio of cardiac membrane lipids was also markedly increased with dietary cholesterol supplementation. Although relatively unaffected by the nature of the dietary fatty acid supplement, catecholamine-stimulated adenylate cyclase activity was significantly increased with dietary cholesterol supplementation and was positively correlated with the value of the membrane cholesterol/phospholipid ratio. Although the dissociation constant for the beta-adrenergic receptor, determined by [125I](-)-iodocyanopindolol binding, was unaffected by the nature of the dietary lipid supplement, the number of beta-adrenergic receptors was dramatically reduced by dietary cholesterol and negatively correlated with the value of the membrane cholesterol/phospholipid ratio. These results indicate that the activity of the membrane-associated beta-adrenergic/adenylate cyclase system of the heart can be influenced by dietary lipids particularly those altering the membrane cholesterol/phospholipid ratio and presumably membrane physico-chemical properties. In the face of these dietary-induced changes, a degree of homeostasis was apparent both with regard to membrane fatty acid composition in response to an altered membrane cholesterol/phospholipid ratio, and to down regulation of the beta-adrenergic receptor in response to enhanced catecholamine-stimulated adenylate cyclase activity.     

Mitochondria and cells produce reactive oxygen species in virtual anaerobiosis: relevance to ceramide-induced apoptosis

Observations of apoptosis in virtual anaerobiosis have raised doubts on the significance of reactive oxygen species in the cascade of events of programmed cell death. This work presents evidence that cells and mitochondrial preparations produce similar levels of hydrogen peroxide under either aerobic or virtually anaerobic conditions. These levels are relevant to the increased production of radicals induced by a ceramide analog that promotes apoptosis. This ceramide acts at center o of mitochondrial complex III.     

Proton nuclear magnetic resonance methyl and methylene linewidths from plasma decrease during postprandial lipemia

Narrow proton nuclear magnetic resonance (1H-NMR) linewidths from plasma have been associated with the presence of malignancy (Fossel et al., New Engl. J. Med. (1986) 315, 1369-1376). In that study, subjects and controls were not fasted. In the present study, 1H-NMR methyl and methylene linewidths were measured in plasma from normolipemic individuals without cancer both during fasting and every 90 min after eating a fat meal. Plasma lipoprotein levels were measured in order to relate results to postprandial lipemia. Methyl, methylene, and average 1H-NMR linewidths were strongly positively correlated with high-density lipoprotein levels and inversely correlated with triacylglycerol-rich lipoprotein levels in both the fasting and postprandial states. Linewidths decreased postprandially, reaching a nadir at the peak of plasma triacylglycerol levels. This study demonstrated that postprandial lipemia can lead to narrowing of plasma methyl and methylene resonances comparable to that reported for subjects with cancer.