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Biomedical subjects

G Schmidt

Publications and source records attributed to G Schmidt.

At least 631 records · Page 35Linked to original sources
PubMed1975

A space-saving media table.

A space-saving media table designed to facilitate pouring large quantities of plated media in a small area is described.

Culture Media↗
PubMed1975

Potency of influenza vaccines: mouse protection experiments in correlation to field studies in man.

The seroconversion rates have been studied following vaccination of human volunteers with two commercial influenza vaccines. Vaccine A did not give a significant increase of hemagglutination-inhibition titers. Vaccine B, on the other hand, raised the titers 2- to 8- fold, depending on the pretiters of the individuals. The potency of the same vaccines has been tested using mouse protection experiments: vaccine B gave significantly better protection rates, as measured by survival as well as by reduction of lung lesions. These results give additional evidence that the use of mouse protection experiments for the evaluation of different influenza vaccines is meaningful.

Aerosols↗
PubMed1975

Effects of vasodilating agents on the microcirculation in marginal parts of the skeletal muscle.

The present investigation was performed to gain information on the changes in the microcirculation of the skeletal muscle during the application of vasodilating agents. The flow velocity in various microvessels was measured cinematographically in isolated and non-isolated muscles of the hindlimb in cats and rats. During the intra-arterial infusion of acetylcholine (1 mug/kg times min), bradykinin (2 mug/kg times min) and isoprenaline (1 mug/kg times min) a decrease in the flow velocity up to a complete stasis was found in most of the microvessels in the marginal parts of the muscles examined. These reactions set in when the femoral flow increased and disappeared when the femoral blood flow returned to the baseline level. The experiments demonstrate that the increase in total blood flow induced by the intra-arterial infusion of vasodilating agents may be associated with a reduced perfusion of certain parts of the striated muscles.

Animals↗
PubMed1975

[Separation of reb blood cells in the isopyknic dextran and albumin density gradient].

The separation of red blood cells according to their maturity and age was compared in the isopyknic dextran and albumin density gradients, and the quality of separation was appraised by selected criteria (density distribution curves, accumulation of reticulocytes, activity of G-6-PD). The achieved quality of separation, as measured by the quotient of G-6-PD activity in the cells of lower density/G-6-PD activity in cells of higher density is of equal value in the two media. In the dextran gradient, separation of old cells seems to be accomplished more readily, while albumin affords better separation of young erythrocytes. The reticulocytes are in both media 4-5 mg/ml lighter than the total cell population. When shifting pH from 7.4 to 6.8 both in erythrocytes and reticulocytes the density decreases by 3-6 mg/ml irrespective of the type and pretreatment of the separation medium.

Albumins↗
PubMed1975

Formation and composition of the C3 activating enzyme complex of the properdin system. Sequential assembly of its components on solid-phase trypsin-agarose.

An active C3 cleaving enzyme is generated when properdin factor B (glycine-rich beta-glycoprotein, GBG) is activated (GBG is cleaved) by factor D in the presence of C3b and Mg++. Factor D can be replaced by trypsin in this reaction but even then C3b and Mg++ are required. In the absence of C3b and/or Mg++ trypsin does not generate C3 cleaving activity from GBG although it cleaves GBG and releases its GGG fragment (B) under these conditions as well. Addition of C3b to GGG immediately after its release does not yield a C3 cleaving enzyme. These findings indicate that C3b, GBG and Mg++ interact, and that only in association with C3b can GBG be cleaved in a way that its enzyme activity, residing in a C3b, GGG complex, is expressed. The complex is labile (half-life at 20 degrees C: 9 minutes); Mg++ does not affect its stability nor is it essential for the activity. It was possible to sequentially fix on agarose the essential components of the C3 cleaving enzyme and thus to elucidate the single steps and the order of its formation. C3 was activated and the resulting C3b fragment fixed on agarose by incubating C3 with trypsin covalently bound to the agarose. The agarose-C3b intermediate was capable of binding GBG provided Mg++ was present. GBG could then be cleaved by factor D or trypsin added in solution; the solid-phase-fixed complex obtained had C3 cleaving activity, in the presence as well as absence of Mg++. Omission of any of these steps or components, or changes in the sequence did not give rise to an active enzyme. Mixtures of C3b, GBG and Mg++ have weak C3 cleaving activity by themselves. C3 cleavage in such incubation mixtures proceeds slowly for hours and is not accompanied by cleavage of GBG. There is thus complete analogy between the CVF-dependent and C3b-dependent C3 cleaving systems. C3b and CVF act in the same way, they form a reversible, weakly active C3 cleaving complex with GBG and Mg++, the activity of which is markedly enhanced but becomes subject to decay when GBG is cleaved by trypsin-like enzymes while bound to CVF or C3b.

Animals↗
PubMed1975

A purine nucleoside hydrolase from Trypanosoma gambiense, purification and properties.

A purine nucleoside hydrolase from Trypanosoma gambiense was purified 160-fold. Preferred substrates of the reaction were adenosine, inosine and guanosine with a maximum of activity at pH 5.4. Competitive inhibitors of the adenosine hydrolysis were dimethylallyl adenosine, 6-methylmercaptopurine riboside, tubercidin, formycin B, 6-mercaptopurine riboside and deoxyadenosine. A metabolic scheme of adenosine nomophosphate salvage synthesis is discussed.

Adenine Phosphoribosyltransferase↗
PubMed1975

Cleavage of the third complement component (C3) and generation of the spasmogenic peptide, C3a, in human serum via the properdin pathway: demonstration of inhibitory as well as enhancing effects of epsilon-amino-caproic acid.

Human and guinea pig serum loses hemolytic activity of the third complement component (C3) during incubation at 37 degrees C. The loss is due to specific C3 cleavage involving the properdin system. This is concluded from the finding that C3 inactivation is prevented by EDTA, by elimination of properdin factor B, and unimpaired in C4 deficient guinea pig serum. In the presence of 1 M epsilon-amino-caproic acid (EACA) spontaneous C3 cleavage is considerably enhanced and accompanied by the appearance of biologically active C3a. Lower concentrations of EACA inhibit rather than enhance C3 cleavage in serum. The inhibitory effect of EACA is due to interference with the interaction of the properdin factors and their action on C3 as demonstrated in various systems: the assembly of an active C3-cleaving complex on zymosan, its regeneration after decay by factor D and factor B (GBG), cleavage of GBG by C3b and factor D in systems of purified components, and cleavage of C3 by preformed properdin complexes. Reactions involving the cobra venom factor were likewise depressed. In all these systems EACA was inhibitory even at 1M concentration. No single step in the development or action of an active properdin system was found to be enhanced by 1 M EACA. The enhancing effect of high concentrations of EACA on C3 cleavage in serum may be explained by its observed inhibition of C3b inactivator (C3bINA). This factor controls the properdin system by destroying C3b. In serum the inhibitory effect of 1 M EACA on C3bINA appears to allow escape of the properdin system from its control and thus to increase its net activity toward C3 despite inhibition of the enzymic reactions proper. At lower concentrations the effect of EACA on C3bINA is apparently less significant; therefore, at low concentrations of EACA, its inhibitory effects on C3 cleavage by the properdin system in serum prediominate.

Aminocaproates↗