The role of renal nerves and prostaglandins in control of renal hemodynamics and plasma renin activity during hypotensive hemorrhage in the dog.

The effects of hypotensive hemorrhage (HH) on renal hemodynamics and plasma renin activity (PRA) during prostaglandin (PG) synthesis inhibition were examined in three groups of dogs. In each group of animals arterial blood pressure was lowered by a 30% decrement. In the first group of eight control animals, HH was not associated with a significant change in glomerular filtration rate (GFR, 42-36 ml/min, NS); renal blood flow (RBF) declined significantly, from 234 to 171 ml/min, P < 0.05. In the second group of eight animals, pretreated with RO 20-5720 (RO, 2 mg/kg), a competitive inhibitor of PG synthesis, HH was associated with a significant fall in GFR (43-17 ml/min, P < 0.001) and RBF (195-89 ml/min, P < 0.001). In the third group of eight animals, pretreatment with indomethacin (IN, 10 mg/kg), a chemically dissimilar PG inhibitor, HH was also associated with a significant fall in GFR (38-8 ml/min, P < 0.001) and RBF (150-30 ml/min, P < 0.001). Renal denervation attenuated this renal ischemic effect of HH in the presence of PG inhibition. In the RO group, GFR (34 vs. 17 ml/min, P < 0.005) and RBF (145 vs. 89 ml/min, P < 0.025) were significantly greater in denervated vs. innervated kidneys during HH. Similarly, in animals treated with IN, a significantly higher GFR (28 vs. 8 ml/min, P < 0.005) and RBF (101 vs. 30 ml/min, P < 0.005) occurred in denervated as compared to innervated kidneys during HH. With HH, the increase in PRA in the control group (3.34-11.68 ng/ml per h, P < 0.005) was no different than that observed in the RO group (4.96-18.9 ng/ml per h, P < 0.001) or IN group (4.71-17.8 ng/ml per h, P < 0.001). In summary, the present results indicate that renal PG significantly attenuate the effect of HH to decrease GFR and RBF. Furthermore, renal denervation exerts a protective effect against the enhanced renal ischemic effects which occur in the presence of PG inhibition during HH. Finally, PG inhibition does not alter the effect of HH to cause an increase in PRA.

Precise and accurate determination of high concentrations of sulphur by isotope-dilution thermal-ionization mass-spectrometry.

An isotope-dilution thermal-ionization mass-spectrometric procedure has been developed for the accurate and precise determination of sulphur in steels and organic-based materials. The sample and isotopically enriched sulphur spike are dissolved in a sealed tube to prevent loss of sulphur and the sulphur isotopes are measured as AsS(+) ions, with silica gel as an emitter. This technique has been applied to the determination of sulphur in 13 NBS Standard Reference Materials ranging in concentration from 0.03 to 5% S. The relative uncertainty for a single determination is typically 0.5% (95% confidence interval) and arises primarily from the uncertainty in the spike calibration and from sample inhomogeneity.

Validation of the sulphur concentration of selected iron-base NBS standard reference materials by isotope-dilution spark-source mass-spectrometry.

An isotope-dilution spark-source mass-spectrometric procedure has been developed for the accurate determination of sulphur in iron-base alloys. Dissolution in a sealed tube is used to prevent volatilization losses and to effect isotope equilibration. Application of this technique to the re-analysis of existing NBS Standard Reference Materials yields results that are generally in good agreement with the certified values.

Absolute Isotopic Abundance Ratios and Atomic Weight of a Reference Sample of Nickel.

Absolute values have been obtained for the isotopic abundance ratios of a reference sample of nickel (Standard Reference Material 986), using thermal ionization mass spectrometry. Samples of known isotopic composition, prepared from nearly isotopically pure separated nickel isotopes, were used to calibrate the mass spectrometers. The resulting absolute isotopic ratios are: 58Ni/60Ni=2.596061±0.000728, 61Ni/60Ni=0.043469±0.000015,62Ni/60Ni=0.138600±0.000045, and 64Ni/60Ni=0.035295±0.000024, which yield atom percents of 58Ni=68.076886 ±0.005919, 60Ni = 26.223146±0.005144,61Ni=1.139894±0.000433, 62Ni =3.634528±0.001142, and 64Ni =0.925546±0.000599. The atomic weight calculated from this isotopic composition is 58.693353 ±0.000147. The indicated uncertainties are overall limits of error based on two standard deviations of the mean and allowances for the effects of known sources of possible systematic error.

Absolute Isotopic Abundance Ratios and Atomic Weight of a Reference Sample of Strontium.

Absolute values have been obtained for the isotopic abundance ratios of a reference sample of strontium using solid sample thermal ionization mass speelrometry. Samples of independently known isotopic composition prepared from chemically pure and nearly isotopically pure separated strontium isotopes were used to calibrate the mass speelrometry. The resulting absolute 88Sr/86Sr, 87Sr/86Sr, and 84Sr/86Sr ratios are 8.3786 ± 0.0033, 0.71034 ± 0.00026, and 0.05655 ± 0.00014 respectively which yields atom percents of: 88Sr = 82.5845 ± 0.0066, 87Sr = 7.0015 ± 0.0026, 86Sr = 9.8566 ± 0.0034. and 81Sr = 0.5574 ± 0.0015. The atomie weight calculated from these abundances is 87.61681 ± 0.00012. The indicated uncertainties are overall limits of error based on 95 percent confidence limits for the mean and allowances for the effects of possible systematic error.

Recalculation of the Faraday Constant Due to A New Value for the Atomic Weight of Silver.

A report of the Faraday constant as determined at NBS via silver coulometry and atomic weight measurements is presented. The uncertainty of the reported result represents a five-fold improvement over measurements made at NBS 20 years ago. The result should contribute to an analysis of the self-consistency of several other fundamental constants measurements. Experimental details have been reported in other publications which are cited in the text.

Absolute Isotopic Abundance Ratios and the Atomic Weight of a Reference Sample of Potassium.

Solid sample, thermal ionization, mass spectrometry has been used to obtain absolute values for the isotopic abundance ratios of a reference sample of potassium. Standards of known isotopic composition, prepared by gravimetrically mixing nearly isotopically and chemically pure separated isotopes of, 39K and 41K, were used for calibration. The absolute isotopic abundance ratios are : 39K/41K = 13.8566 ± 0.0063 and 40K/41K = 0.0017343 ± 0.0000061 which yield atom percent compositions of 39K=93.2581 ± 0.0029. 40K = 0.01167 ± 0.00004, and 41K = 6.7302 ± 0.0029. The calculated atomic weight for potassium is 39.098304 ± 0.000058. The indicated uncertainties are overall limits of error which are the sum of the uncertainty components for ratio determinations and the components covering the effects of known sources of possible systematic error.