ISSN:0004-945X    

DOI:10.1038/icb.1970.37

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryAngiotensin II was infused into the adrenal arterial blood supply or intravenously in sheep which were either sodium replete, that is in normal sodium balance or sodium loaded, or sodium depleted by loss of parotid saliva. Aldosterone secretian was always increased in the sodium replete condition when the rate of infusion exceeded 0.1 μg./hr. intra‐arterially or 10 μg./hr. intravenously. The aldosterone response was greatly reduced when the animals were sodium loaded or sodium depleted. When sodium balance was positive, the increase of aldosterone secretion was inversely proportional to the plasma sodium concentration but it was not significantly related to the plasma potassium concentration. The inverse relation to plasma sodium did not continue into sodium depletion. When sodium balance was negative and plasma sodium concentration tended to be reduced, angiotensin infusion did not usually cause further increase of aldosterone secretion. Nephrectomy of sodium depleted animals caused aldosterone secretion to fall to basal in 8–12 hr. and restored the adrenal response to infused angiotensin II or sheep renin.Secretion rates of cortisol and corticosterone were not increased significantly by infusion of angiotensin II into the adrenal arterial blood supply. Glucocorticoid secretion was usually increased during intravenous infusion, the effect on cortisol secrection being more consistent. Systemic infusion of angiotensin II at rates which cause lartic increases of blood pressure may also cause increased release of adrenocorticotrophic hormone.It is concluded that the adrenal action of angiotensin II is primarily and predominantly on aldosterone secretion and the magnitude of this action is influenced by ambient sodium concentration and other humoral or intra‐adrenal factors operating in sodium depletion.

ISSN:0004-945X    

DOI:10.1038/icb.1970.27

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryAzathioprine, 6‐mercaptopurine and 6‐thioguanine inhibited synthesis of protein by human peripheral lymphocytesin vitro.Maximum inhibition occurred at concentration of about 60 μg./ml., whereas the blood concentrations do not exceed 2 μg./ml. Azathioprine was generally as inhibitory as 6‐mercaptopurine, or more inhibitory, at half the molar concentration. Azathioprine caused an accelerated rate of death from 12 to 24 hrs.in vitronot seen in cells incubated with 6‐mertaptopurine and 6‐thioguanine. These data correlate with greater effectiveness of azathioprine in suppressing immune responses in animals.The effect of plasma on the inhibition caused by thiopurines was variable. The degree of inhibition was generally of the same order in the presence of phytohaemagglutinin. Azathioprine suppressed phytohaemagglutinin‐stimulated lymphocytes more than 6‐mercaptopurine.2‐Hydroxy‐6‐mercaptopurine, 6‐mercaptopurine ribonucleoside, 6‐thiouric acid and 5‐mercapto‐1‐methyl‐4‐nitroimidazole (ammonium salt) caused little or no inhibition of protein synthesis by human lymphocytes. 6‐Mercaptopurine ribonucleoside and 6‐mercaptopurine ribonucleotide caused inhibition of protein synthesis by lymphocytes.The pronounced inhibition of protein synthesis by the thiopurines contransted with smaller and less constant inhibition of incorporation of radioactive precursors into ribonucleic acid.

ISSN:0004-945X    

DOI:10.1038/icb.1970.28

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryMice infected neonatally by the oronasal route with an avian reovirus (Fahey‐Crawley virus) developed pathological changes in the liver similar to those caused by murine infections with mammalian reoviruses. Further changes occurred in the central nervous system, and in the lungs, where there was severe suppurative bronchopneumonia apparently caused by secondary bacterial invasion with endogenously derivedPasteurella pneumotropica.

ISSN:0004-945X    

DOI:10.1038/icb.1970.29

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryDepending on the level of dietary cobalt, as many as nine ionophoretically distinct cobamides and cobinamides were detected in sheep rumen contents.5,6‐Dimethylbenzimidazolyl cobamide and 2‐methyladenyl cobamide together constituted more than 80% of the vitamin B12‐activity of extracts of rumen contents. The proportion of the vitamin B12‐activity due to 5,6‐dimethylbenzimidazolyl cobamide was increased from 35% to 63% by decreases in the cobalt intake from 0·34 p.p.m. to 0·04 p.p.m. but that due to 2‐methyladenyl cobamide (44%) was unaltered. Thus, a greater proportion of the “vitamin B12” synthesised in the rumen of sheep fed cobalt‐deficient rations was in a form that could be utilised by the host animal. Guanyl cobamide was occasionally present in significant concentrations at higher cobalt intakes, but the other analogues usually represented less than 3% of the total vitamin B12‐activity.Evidence was obtained that factors other than cobalt can affect both the concentrations and proportions of cobamides and cobinamides in rumen contents.The vitamin B12‐activity of extracts of sheep jugular blood plasma was almost entirely due to 5,6‐Dimethylbenzimidazolyl cobamide. 2‐Methyladenyl cobamide was present at cobalt intakes of 0·10 p.p.m. or more, but represented less than 1·5% of the total vitamin B12‐activity.

ISSN:0004-945X    

DOI:10.1038/icb.1970.30

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryAnin vitrosystem was used to investigate the factors affecting the metabolism of cobamides and cobinamides in sheep rumen micro‐organisms.Cobalt was the primary limiting factor for the synthesis of cobamides and cobinamides in the rumen contents of sheep fed cobalt dificient rations. The vitamin B12‐activity of rumen contents from such sheep increased within two hours of cobalt addition. This rise in vitamin B12‐activity was due to an increased synthesis of 2‐methyladenyl cobamide and 5,6‐dimethylbenzimidazolyl cobamides. Other cobamides and cobinamides appeared after five hours.The addition of nitrogen bases did not affect the total rate of synthesis of cobamides in sheep rumen contents. However, in the presence of adequate cobalt the addition of certain nitrogen bases stimulated the synthesis of the corresponding cobamide at the expense of other cobamides.Rumen micro‐organisms did not synthesis significant amounts of cobamides from exogenous cobinamides. When cobinamide was added to rumen contents it was apparently converted to compounds which do not have vitamin B12‐ activity forE. coli 113–3.

ISSN:0004-945X    

DOI:10.1038/icb.1970.31

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryWeanling rats fed a semi‐purified dirt containing 25 per cent casein and 67·8 per cent sucrose developed considerable deposits of calcium phosphate in their kidneys. Rats given ammonium chloride supplements in the diet excreted more hydrogen ions as ammonium and develope significantly less nuphrocalcinosis; the greater the quantity of ammonium chloride ingested. the less severe was the nephrocalcinosis, but even rats feil 5·7 per cent NH4Cl developed some mineral deposits. However, feeding ammonium chloride did not appear to dissolve deposits already formed. Mineral deposition was only reduced whilst the diet contained ammonium chloride; when the acidifying diet was replaced, mineral deposition progressed rapidly. Rats given supplements of sodium bicarbonate in the diet excreted alkaline urine containing significantly less hydrogen ion as ammonium than that of rats fed the original diet and accumulated significantly more mineral in their kidneys.

ISSN:0004-945X    

DOI:10.1038/icb.1970.32

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryNephrocalcinosis in weanling rats resulting from the feeding of a semi‐purified diet was found to be reduced by the addition of casein, gluten, amino acids (methionine, cystine and glutamic acid), or ammonium sulphate to the diet. The altered incidence of nephrocalcinosis did not appear to be related to the casein: salt mixture ratio, to changes in the serum calcium and phosphorus concentrations, or to changes in the volume of urine excreted. It is postulated that the protein supplements had an acidifying action due to oxidation of S‐amino acids which led to an increased urinary excretion of hydrogen ions and sulphate, and that the acidification of the tubular fluid increased the solubility of calcium phosphate so that less mineral deposition took place.

ISSN:0004-945X    

DOI:10.1038/icb.1970.33

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummaryThe bioassay of insect moulting hormones is facilitated by use of the Australian brown blowfly,Calliphora stygia, instead ofC. vicina, the species commonly employed. The late larval development ofC. stygiais more readily synchronized than that ofC. vicina, and the necessary treatment is described. WithC. stygia, the yield of test‐abdomens for use in the bioassay is 60–80% when larvae are kept at an elevated oxygen tension after ligation. The best yield of test‐abdomens obtained withC. vicinais approximately 40%, whether the larvae are kept in air or in oxygen.Dose‐response data for crustecdysone administered to test‐abdomens ofC. stygiaandC. vicinaare presented. Sensitivity of tbe bioassay depends in part on the Volume of test solution injected. The useful dose‐range for the moulting hormones bioassay inC. stygiacorresponds to approximately 10–75 ng. crustecdysone/abdomen. InC. vicinathe useful range is the equivalent of approximately 5–50 ng. crustecdysone/abdomen.

ISSN:0004-945X    

DOI:10.1038/icb.1970.34

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY

摘要:

SummarySerum obtained seven days after immunization of Swiss mice with sheep erythrocytes in Freund's adjuvant contains a factor, with fastα1‐globulin mobility, detectable by its ability to induce the attachment of sheep erythrocytes to normal mouse macophages. The receptor on macrophages is trypsin‐sensitive. The factor has a large degree of, though not complete, immunological specificity. It appears to be unrelated to conventional immunoglobulins. non‐agglutinating and non‐complement‐fixing. Subsidiary evidence consistent with the existence of an α‐globulin “antibody” and a consideration of its possible immunological significance are presented.

ISSN:0004-945X    

DOI:10.1038/icb.1970.35

出版商:Nature Publishing Group    

年代:1970

数据来源: WILEY