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N Alexander

Publications and source records attributed to N Alexander.

At least 109 records · Page 6Linked to original sources
PubMed1980

Indices of sympathetic activity in the sinoaortic-denervated hypertensive rat.

Blood pressure and circulating levels of norepinephrine (NE), epinephrine (Epi), and dopamine-beta-hydroxylase (DBH) were measured sequentially in sinoaortic-denervated (SAD) Wistar rats and in sham-operated (SO) rats. Systolic tail pressure, plasma NE and E, and plasma DBH all increased significantly within 2 days in SAD rats. In separate studies of rats with indwelling arterial catheters, arterial pressure and plasma NE and DBH were increased in SAD rats in home cages; restraint caused similar increases of pressure and catecholamines in both groups. Systolic pressure remained increased up to 4 mo and plasma DBH for 10 wk in SAD rats; plasma NE and E, however, declined by 3 wk and thereafter remained close to values of SO rats. Additionally, DBH was increased in heart, mesenteric blood vessels and adrenal glands of SAD rats up to 6 wk; tissue monoamine oxidase activity was also increased up to 4 mo. These findings suggest that activation of the sympathetic nervous system initiates and probably sustains hypertension in SAD rats up to 6 wk after operation; thereafter some other mechanism(s) sustains the hypertension.

Animals↗
PubMed1980

Increased plasma normetanephrine in spontaneously hypertensive rats.

Plasma catecholamine and total plasma normetanephrine concentrations were determined in 11 spontaneously hypertensive rats (SHR) and in 11 age and sex matched Wistar Kyoto control rats (WKy). Plasma norepinephrine concentration, obtained from tail vein blood of restrained rats, was 356 +/- 67 pg/ml in SHR and 297 +/- 61 in WKy (NS), whereas epinephrine was 1079 +/- 117 in SHR and 695 +/- 107 in WKy (p < 0.05). Total plasma normetanephrine concentration was 1825 +/- 472 pg/ml in SHR and 535 +/- 109 in WKy (p < 0.02). Since normetanephrine is mainly an extraneuronal metabolite of norepinephrine, its plasma concentration could reflect the amount of the neurotransmitter which reaches effector cell sites suggesting enhanced sympathetic function accounts for blood pressure elevation in SHR. A simple and specific radioenzymatic assay for measurement of total plasma normetanephrine in rat was described.

Animals↗
PubMed1979

Plasma volumes and hematocrits in rats with chronic sinoaortic denervation hypertension.

Plasma volume changes were assessed in female Wistar rats with neurogenic hypertension induced by sinoaortic denervation, SAD. Tail veins of conscious, restrained rats were used for injection of Evans blue dye and for sampling into microhematocrit tubes. Only at 3 days did total plasma volume of SAD rats show a modest reduction of about 16% (P less than 0.05 vs. sham-operated plus unoperated controls). At 3, 6, and 13 wk, SAD mean body weight, plasma volume, and sodium concentration were similar to sham values. SAD hematocrits, however, like arterial pressures, were elevated at all postoperative times studied. In anesthetized SAD and sham rats, red blood cell (51Cr method) and plasma volumes were the same and so were hematocrits. The latter was unlike the finding in unanesthetized groups. Hematocrits from the same SAD rats were lower after induction of anesthesia than before (P less than 0.025). Thus, elevated hematocrits apparently resulted from the release of sequestered red blood cells into the circulation by unanesthetized SAD rats. In conclusion, plasma volume is within the normal range in SAD rats except for the first few postoperative days. Factors affecting volume regulation at that time are discussed.

Animals↗
PubMed1979

Plasma and lymph dopamine-beta-hydroxylase and norepinephrine during carotid occlusion.

Dopamine-beta-hydroxylase (DBH) and norepinephrine (NE) levels in superior mesenteric venous (SMV) and arterial blood and in intestinal lymph were determined sequentially before and during carotid artery occlusion (CAO) in anesthetized rabbits. During the first 15 min of CAO, SMV plasma NE increased 77% but SMV plasma DBH increased only 11%. During the second 15 min of CAO, SMV NE declined to 36% above control but SMV DBH rose further and peaked to 29% above control after CAO was released; arterial DBH and NE showed small insignificant changes. Lymph DBH and NE increased simultaneously throughout the period of CAO. Increases in mean arterial pressure during CAO correlated with superior mesenteric venous NE (r = 0.58, P less than 0.01). In additional experiments, hepatic vein plasma NE was 74% lower than portal vein NE. Thus, during acute sympathetic activation, DBH and NE increase in mesenteric venous plasma and intestinal lymph but the peak response of plasma DBH lags behind that of NE. The degree of NE change in the general circulation is minimized due to hepatic clearance of NE.

Animals↗
PubMed1967

Fluorescence decay times: proteins, coenzymes, and other compounds in water.

The fluorescence decay time (tau) was 2 to 5 nanoseconds for proteins and 4 to 5 nanoseconds for flavin, pyridine nucleotide, and vitamin B(6)coenzymes; tau varied widely in 48 compounds measured in water. Altholugh reported values of tau for a few of the soluttions studied were in excellenlt agreement. previously "calculated" lifetimes, in severall instances, are apparently erroneous. Nonexponential decay was detectable with our "nanosecond-flash" apparatus, a modification of the first commercially aavilable unit for determination of tau.

Chemical Phenomena↗