Degradation of cell constituents during starvation of Salmonella enteritidis.

Salmonella enteritidis starved in Fernbach flasks used acid-alcohol-soluble material and RNA as endogenous reserves during starvation. Organisms starved in a fermentor system consumed acid-alcohol-soluble material, RNA and protein to maintain viability. Half-life survival times were 132 h and 118 h for the Fernbach and fermentor-starved cells, respectively. The acid-alcohol-soluble fraction of the cell consisted mainly of peptides or protein. This fraction accounted for most of the loss of label from 14C-labelled cells during the first 5 days of starvation and presumably contains the primary endogenous reserve. Although the residue fraction of fermentor-starved cells provided 35% of the total loss of 14C from the cells by the 5th day, a small net increase in 14C activity of the residue fraction of Fernbach-starved cells was observed. Differences observed appeared to be due to the method of starvation.

Capoten-induced juxtaglomerular hyperplasia in rabbits.

The effects of the converting enzyme (CE) inhibitor, captopril, on blood pressure, plasma aldosterone, plasma renin activity (PRA), and kidney morphology were studied. Captopril, at a near maximum daily recommended human dose of approximately 5.0 mg/kg, was administered to rabbits over a period of six months. Mean arterial pressure, CE activity, and aldosterone levels were significantly reduced; PRA and renal renin activity were increased. Microscopic examination of the kidney showed marked hyperplasia of the juxtaglomerular apparatus in all of the treated animals.

Renin as a risk factor for atherogenesis. Part 2. Effects of hypercholesterolemia and hyporeninemia in the rabbit.

Four groups of New Zealand rabbits were used to study the effect of suppressed plasma renin activity (PRA) on atherogenesis. Control groups were fed normal rabbit chow (Group I) or normal chow supplemented with 0.25% cholesterol--0.75% corn oil (Group III). Group II animals were fed normal chow and received periodic injections of 11-desoxycorticosterone (DOC)pivalate and 0.5% saline to drink, while Group IV animals were treated similarly except that they were also fed the atherogenic diet. Blood pressure and blood chemistry measurements were performed monthly over a 7-month period. The blood pressure was unaffected by either the diet or the DOC-saline treatment, however, the PRA was greatly reduced in the animals receiving DOC-saline (Groups II and IV). Similarly, plasma aldosterone was significantly (P less than 0.05) reduced in the DOC-saline-treated animals. No atheromata were observed in the animals consuming the regular diet, regardless of DOC-saline treatment. All of the animals fed the atherogenic diet showed extensive aortic atheromata. However, there was no difference in the lesion index between the animals with normal PRA levels (Group III) and those with suppressed PRA levels (Group IV). Likewise, microscopic evaluation of the aorta, coronary arteries, and renal arteries failed to show a consistent difference in the vascular involvement between animals of Groups III and IV. We therefore conclude that the suppression of PRA does not have a protective effect on atherogenesis in the cholesterol-fed normotensive rabbit.

Renin as a risk factor for atherogenesis. Effects of hypercholesterolemia and two-kidney--one-clip hypertension in the rabbit.

Four groups of New Zealand rabbits were used to study the effect of plasma renin activity (PRA) on atherogenesis. Control groups were fed normal rabbit chow (Group I) or chow supplemented with 0.25% cholesterol and 0.75% corn oil (Group II). The two-kidney--one-clip (2K-1C) hypertensive model was produced in 2 additional groups; Group III (normal diet) and Group IV (atherogenic diet). The latter 2 groups were subgrouped according to PRA levels. Each group was examined over a 7-month period. Group II became hyperlipidemic and developed extensive lipoidal vascular lesions. Mean arterial pressure remained normal throughout the experimental period; PRA fell below normal. Group III and Group IV rabbits developed sustained hypertension irrespective of circulating PRA. The atheromas of Group III were predominantly microscopic and fibromuscular; the extent of aortic and coronary artery involvement was independent of renin response. The most extensive and complicated atheromas were seen in the 2K-1C rabbits consuming the atherogenic diet (Group IV). The lesions were mostly lipoidal, although some were fibromuscular. These results demonstrated that cardiovascular lesions and atherogenesis were exacerbated in the 2K-1C rabbits on a high cholesterol diet; however, PRA was excluded as the cause.

Is renin a risk factor?

1. These results show that elevated blood pressure and a hyperlipidemic diet exacerbate atherogenesis in the two kidney, one-clip hypertensive rabbit. Elevated PRA activity was not essential for the hypertension and did not exacerbate atherogenesis. 2. In addition, the experimentally induced, low renin state following DOC-saline did not result in a protective effect on cardiovascular lesions in rabbits fed an atherogenic diet when compared to normal renin controls. 3. Thus, in these experiments neither an increase in plasma renin accelerated atherogenesis, nor did a decrease in PRA slow the rate of production of atherosclerosis in the rabbit. 4. These observations lend no support to the thesis that renin is an independent risk factor when it is generated within the body in response to these stimuli. Indeed, it suggests that in this setting other factors, not PRA, are responsible for both hypertension in the two-kidney, one-clip rabbit and the arterial damage which occurs in this hypercholesterolemic model.

Evidence against acetone-soluble renin inhibitors in normal human plasma.

The presence of acetone-soluble renin inhibitors in normal plasma has been proposed to explain the variation of plasma reactivity (PRR) in samples from normotensive and hypertensive subjects. In our experience, acetone extraction decreased PRR in relation to unextracted control values, an observation which is not consistent with the circulating lipid-renin inhibitor hypothesis. Exposure to acetone at -40 degrees C for 1 minute invariably denatured some endogenous angiotensinogen. The PRR in extracted and unextracted plasma was positively correlated with the concentration of available angiotensinogen, r = 0.955 (p < 0.05), and r = 0.964 (p < 0.01), respectively, but the addition of exogenous substrate did not uniformly increase PRR in acetone-treated plasma above control values. These data argue against the use of acetone extraction to demonstrate the existence of circulating lipid-renin inhibitors. Acetone removed 14% to 25% of the normal plasma lipids and although the extract contained most of the major lipid classes, neutral lipids were the most abundant (73% by weight). The presence of acetone-soluble phospholipids appeared to increase angiotensin I formation in the partially purified renin-angiotensinogen system, but phospholipids interfered with the radioimmunoassay and resulted in an overestimation of angiotensin I. Plasma neutral lipids decreased in vitro renin activity by 13% (p < 0.025) but this degree of inhibition suggests that lipid-renin interactions may have minimal in vivo physiological significance. In contrast to previous reports, we found the correlation between PRR and endogenous angiotensinogen in normotensive and hypertensive plasmas to be statistically significant (r = 0.643, p < 0.01). Inactivated human angiotensinogen was also shown to be an inhibitor of renin in vitro. This effect could have possibly influenced PRR values that were determined by others in the presence of inactivated angiotensinogen.

Starvation survival of Salmonella enteritidis.

Washed cells of Salmonella enteritidis harvested from a defined medium during logarithmic growth were subjected to starvation in pH 7 phosphate buffer at 37 C. Viability was measured by slide cultures and plate counts. The survival of cell suspensions equivalent to 1 to 10 mg (dry wt)/ml was influenced by cryptic growth. The rate of cryptic growth, assessed by plate counts, increased with cell density and could not be alleviated by starvation with dialysis. Dialysis of the starving culture did retard the onset of cryptic growth but did not eliminate it, indicating that the major substrates for regrowth were relatively large cellular components. In phosphate buffer, 6.7 homologous heat-killed cells allowed for the doubling of one S. enteritidis cell. Cryptic growth was not observed when cells were starved on the surface of membrane filters or in suspensions equivalent to 20 mug (dry wt)/ml (105 cells/ml). Similar half-life survival times were calculated for both these populations, but the shape of their survival curves differed significantly. These differences were attributed to stress factors encountered during cell preparation and during starvation. The half-life survival time of S. enteritidis starved at 20 mug (dry wt)/ml was 140 h in phosphate buffer, 82 h in 3,6-endomethylene-1,2,3,-6-tetrahydrophthalic acid buffer, and 77 h in tris(hydroxymethyl)aminomethane buffer.