Vasoconstrictor responses in thromboxane receptor knockout mice: tubuloglomerular feedback and ureteral obstruction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66280/1/j.1365-201x.2000.00641.x.pd

Filtration pressure response to infusion of atrial natriuretic peptides

The present experiments were undertaken to assess the effect of an atrial extract (ANF) and of the synthetic atriopeptin II (APII) on filtration pressure of rat kidneys. Continuous recordings of stop flow pressure (SFP) were made to obtain an index of the change of glomerular capillary pressure produced by atrial peptides and its time course. Short-term infusion of ANF or APII increased SFP from 40.6±0.99 to 50.7±1.42 mm Hg (p<0.001) and from 44.0±1.28 to 52.7±1.75 mm Hg (p<0.001) respectively. The maximum response was achieved promptly. Return of SFP to control was slow: 20 minutes after termination of the infusion SFP was still elevated by 4.9±1.27 mm Hg (p<0.01). Tubule and stellate vessel pressures increased less than 2mm Hg, changes that were not significant. Arterial pressure fell 6 mm Hg (p<0.05). When arterial pressure was reduced by an aortic clamp to 85–90 mmHg prior to administration of APII the response of SFP was markedly blunted (from a mean increase of 9.0±1.07 mm Hg to 4.5±0.53 mm Hg). The increase of SFP probably reflects an increase of glomerular capillary pressure. The finding suggests that atrial peptides increase glomerular filtration rate at least in part by increasing filtration pressure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47453/1/424_2004_Article_BF00586690.pd

Regulation of renin gene expression in kidneys of eNOS- and nNOS-deficient mice

Our study aimed to assess the roles of nitric oxide derived from endothelium NO-synthase (eNOS) and macula densa neuronal NO-synthase (nNOS) in the regulation of renal renin expression. For this purpose renin mRNA levels and renin content were determined in kidneys of wild-type (wt), nNOS-deficient (nNOS–/–), and eNOS-deficient (eNOS–/–) mice, in which the renin system was suppressed by feeding a high-salt diet (NaCl 4%), or was stimulated by feeding a low-salt (NaCl 0.02%) diet together with the converting-enzyme inhibitor ramipril (10 mg kg –1 day –1 ). In all mouse strains, renin mRNA levels were inversely related to the rate of sodium intake. In eNOS–/– mice renin mRNA levels and renal renin content were 50% lower than in wt mice at each level of salt intake, whilst in nNOS–/– mice renin expression was not different from wt controls. Administration of the general NO-synthase inhibitor nitro- l -arginine methyl ester ( l -NAME, 50 mg kg –1 day –1 ) to mice kept on the low-salt/ramipril regimen caused a decrease of renal renin mRNA levels in wt and nNOS–/– mice, but not in eNOS–/– mice. These observations suggest that neither eNOS nor nNOS is essential for up- or downregulation of renin expression. eNOS-derived NO appears to enhance renin expression, whereas nNOS-derived NO does not.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42244/1/424-439-5-567_s004249900214.pd

Instrumental and sensory approaches for the characterization of compounds responsible for wine aroma

More than 800 aromatic compounds have been identified in wine, some of them at the ng/l level. Wine, therefore, constitutes a very complex matrix, from which it is difficult to isolate a specific aroma character. Gas chromatography–olfactometry (GC–O) applied to wine extracts is used to characterize odor-active zones that are often treated in a hierarchical way by Aroma Extract Dilution Analysis (AEDA). The aromatic impact of the volatiles is evaluated, generally by determining perception thresholds. This methodology has provided convincing results concerning wine flavors, but it does have its limitations. Forinstance , data on b-damascenone have demonstrated that these methods could reach their limits for this volatile, in particular, because of the non-quantitative representation of aroma extracts of wines, and because of the difficulty to accurately determine the perception threshold in wines for a compound already present. For b-damascenone, we have shown that its very low detection threshold with GC–O, its wide range, and its dependence on the composition of the medium resulted in overestimating its direct impact on the aroma of wine. Another way to facilitate the characterization of aromatic compounds was, therefore, investigated. High-Performance Liquid Chromatography (HPLC) methods were developed for the analysis of wine extracts. From an aromatic extract, 25 fractions with various flavors were thus obtained, and reverse-phase methodology was used for the selection and characterization of red- and black-fruit aromas in red wines

ATPase activity in macula densa cells of the rabbit kidney

Na-K- and Mg-activated ATPase activities were determined in maculae densae and glomeruli dissected from both superficial and juxtamedullary nephrons of normal rabbits, using an ultramicro method including a cycling reaction. Activities were expressed as P i generated per macula densa or per glomerulus and normalized for tissue volume. Results indicate that the mean volume of superficial and juxtamedullary macula densa samples was not statistically different, while glomeruli from deep nephrons had sample volumes that were 29% larger than those from superficial nephrons ( P <0.001). Correcting for volume both superficial and juxtamedullary macula densa samples had an Na-K-ATPase activity of 0.37±0.21 fmol · h −1 · (μm 3 ) −1 . Mg-ATPase activity in both pools was also similar [0.41±0.07 and 0.52±0.1 fmol · h −1 · (μm 3 ) −1 ]. Na-K-ATPase activity in macula densa cells is estimated to be about 1/40th the activity of surrounding cortical thick ascending limb cells. Total glomerular ATPase per unit volume was significantly higher in glomeruli from superficial than from deep nephrons [0.41±0.04 vs. 0.28±0.04 fmol · h −1 · (μm 3 ) −1 P <0.05]. There was no statistically significant activity of Na-K-ATPase in either superficial or deep glomeruli. These results suggest that in contrast to previous reports, the macula densa contains Na-K-ATPase, but at a low level relative to surrounding tubular cells. Further, in normal rabbits, this activity is invariant in superficial and juxtamedullary samples.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47454/1/424_2004_Article_BF00580725.pd