摘要:

SummaryThe activities of human plasma bradykininases (kininase I and II) have been investigated because of their importance as reactants in the kallikrein‐kinin system. The use of [14C] bradykinin as substrate allows radiometric analysis of the enzyme‐substrate reaction mixture. This is possible because separation of bradykinin from its hydrolysis products is achieved by chromatography over CM Sephadex C‐25. Use of this technique has allowed localization of bradykininase activities in plasma protein chromatograms and the separation and partial purification of kininase I and kininase II. Kininase I can be identified because it hydrofyses hippuryl‐L‐lysine, whereas kininase II converts angiotensin I to angiotensin II. The measurement of hydrolysis is simple and quantitative and has been used to demonstrate normal Michaelis‐Menten kinetics for both enzymes. The Michaelis‐Menten constants for the enzymes have been found to be 4·1 × 10‐7M (kininase I) and 0·94 × 10‐7M (kininase II).

ISSN:0004-945X    

DOI:10.1038/icb.1974.58

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryA study has been made of the levels of glucose‐6‐phosphate dehydrogenase and glutathione reductase activity and the rates of regeneration of reduced glutathione (GSH) in red blood cells from various mammalian species, including man and the kangaroo. The most significant finding was the demonstration of a direct relationship between the enzyme activity and the GSH regeneration rate in the red blood cells of ruminants as against an inverse relationship observed in human red blood cells. The experimental results suggest that the GSH regeneration test should be used with caution in studies aimed to evaluate the overall activity of the hexose monophosphate pathway of the red blood cells of man and animals.

ISSN:0004-945X    

DOI:10.1038/icb.1974.59

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryExtraction ofLeptospira interrogans(serotype,bifexa)with 0·2% trypsin yielded three precipitating antigens (‘axial filament’; antigen ‘d’; antigen ‘e’) as detected by immunodiffusion against rabbit antileptospiral serum.In contrast to ‘axial filament’ antigen, antigens ‘d’ and ‘e’ could be detected only in stationary phase leptospires. Protein antigen ‘d’ was purified and gave rise to monoprecipitin sera in rabbits. Monoprecipitin sera against both antigen ‘d’ and ‘e’ were also produced by immunizing rabbits with specific immune, precipitates in agar.Rabbit anti‐‘d’ and anti‐’ e’ immunoglobulins were initially of the 19S type but subsequently became solely 7S.

ISSN:0004-945X    

DOI:10.1038/icb.1974.60

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryNeither monoprecipitin rabbit antiserum against precipitating antigen ‘d’ nor ‘e’ ofLeptospira interrogans(serotypebiflexa)would agglutinate whole leptospires, even at very low antiserum dilution.By means of antibody fluorescent labelling and anti‐globulin cross‐linking techniques, antigen ‘d’ and ‘e’ were shown to be subsurface in cellular location.

ISSN:0004-945X    

DOI:10.1038/icb.1974.61

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryFour different antisera to different serotypes ofLeptospira interrogans(Pyrogeneszanoni, BallumcastelloniCastellan 3, AutumnalisrachmatiRachmat, AutumnalisdjasimanDjasiman) were fractionated by DEAE‐cellulose column chromatography and sucrose density gradient centrifugation to separate the γM and γG components reacting as precipitins in gels with axial filament preparations.Cross‐reactions of whole antiserum and of immunoglobulin fractions showed that the order of increasing specificity was whole serum and γM, slow γG and fast γG.

ISSN:0004-945X    

DOI:10.1038/icb.1974.62

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryThis paper records a seven year follow‐up epidemiological investigation in the surviving offspring of a flock of ewes which had experienced an outbreak of overt congenital toxoplasmosis. The following observations were made:Fifty‐one percent of the offspring of dye test (D.T.) positive ewes developed antibodies toToxoplasma.The duration and level of this antibody response varied considerably: in some sheep it was persistent and in others it fluctuated between negativity and positivity, and in one year there was a general and pronounced rise in D.T. titres.Fourteen percent of the offspring of dams with a D.T. titre of 1:64 became sero‐positive, whereas 90% of the offspring of ewes with D.T. titres of 1:1,024 or greater became sero‐positive.No congenital transmission ofToxoplasmaoccurred when the D.T. positive offspring were mated.All offspring born from D.T. negative ewes and running in contact with D.T. positive sheep remained sero‐negative over a 6 year period.Latent congenitalToxoplasmainfection persisted in 93% of D.T. positive offspring for up to 7 years.

ISSN:0004-945X    

DOI:10.1038/icb.1974.63

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryPrevious studies have shown that non‐sensitised lymphocyte preparations can kill antibody‐coated allogeneic lymphoma cells. During these studies on antibody‐induced lymphocyte‐mediated cytotoxicity it was observed that lymphocyte preparations from most normal humans tested were highly cytotoxic even tonon‐antibody‐coatedlymphoma cells of a particular cell line (EB2) but not to a second lymphoma cell line (CLA4), or to allogeneic normal lymphocytes. In contrast, if the target cells were coated with antibody, normal lymphocyte preparations killed EB2cells, CLA4cells and allogeneic lymphocytes, with equal facility.This non‐antibody‐dependent “spontaneous” cytotoxicity towards EB2cells occurred even at low lymphocyte:EB2ratios (<10:1) and was not mediated by lymphotoxin. “Spontaneous” anti‐EB2lymphocytotoxicity was increased rather than blocked in the presence of specific anti‐EB2serum.The possible relationship between “spontaneous” cytolysis of EB2cells and sensitization to EB virus is discussed.

ISSN:0004-945X    

DOI:10.1038/icb.1974.64

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryDecreases in micro‐haematocrit for blood from intact sheep with increases in centrifugation time at constant rev/min were observed. These decreases were analysed into two‐exponential components. Parameters for the exponential function were not related to the red cell concentration of the sample.Micro‐haematocrit of blood from splenectomized sheep decreased with increased centrifugation time in the manner of a single exponential, that was of similar magnitude to the slower exponential function found for blood from intact sheep.Delay in measuring micro‐haematocrit after the collection of a blood sample resulted in a variable, though small, decrease in micro‐haematocrit.Variations in heparin concentration between 10 and 40 i.u./ml blood, and in the mains voltage supplying the haematocrit centrifuge in the range 220 to 260 V, caused no significant effects on the value of micro‐haematocrit.The accuracy in measurement of micro‐haematocrit was similar over a wide range of red cell concentrations.These studies showed that 8 min centrifugation at 10,000 g of blood collected into dried heparin (20 i.u./ml blood) was optimal for measuring the micro‐haematocrit of sheep blood. Lengths of blood column varying between 2 and 5 cm had no significant effect with this centrifugation time.

ISSN:0004-945X    

DOI:10.1038/icb.1974.65

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryThe effects of mental arithmetic on heart rate, arterial blood pressure, hand blood flow and resistance to hand blood flow have been tested. Heart rate and mean arterial blood pressure always increased. In cool conditions, when resting hand blood flow was less than 4·9 ml/100 ml/min, mental arithmetic caused no change in resistance to hand blood flow. Under warm conditions, when resting hand blood flow was greater than 4·9 ml/100 ml/min, mental arithmetic caused a sustained rise in resistance to blood flow in the hand.

ISSN:0004-945X    

DOI:10.1038/icb.1974.66

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY

摘要:

SummaryAlthough studies on the clearance of endogenously circulating amino acids had been published for several mammalian and non‐mammalian vertebrate species, few data were available for the rat. Since micropuncture studies on the renal handling of amino acids are most conveniently performed on this species, endogenous clearance studies have now been undertaken using automated, ion‐exchange chromatographic techniques for amino acid analysis. Endogenous plasma amino acid concentrations were remarkably similar to those in man but renal clearances of most amino acids were considerably smaller, indicating highly efficient reabsorptive mechanisms; the urinary excretion patterns, also, were very similar to those of man, although a striking exception was observed in the case of taurine, which was cleared in the rat at rates approaching 40% of the glomerular filtration rate. It was concluded that the renal handling of amino acids, with the exception of taurine, was very similar in rat and man, so that conclusions drawn from micropuncture experiments in rats would seem likely to hold also for man.

ISSN:0004-945X    

DOI:10.1038/icb.1974.67

出版商:Nature Publishing Group    

年代:1974

数据来源: WILEY