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Biomedical subjects

K H Schmidt

Publications and source records attributed to K H Schmidt.

At least 19 recordsLinked to original sources
PubMed1992

Separation of T-cell-stimulating activity from streptococcal M protein.

The superantigenic properties of M protein type 5 of Streptococcus pyogenes have been implicated as an important pathogenicity factor in streptococcal autoimmune diseases. Here we show that after a single purification step by affinity chromatography on immobilized albumin or fibrinogen, M protein has no mitogenic activity for T cells. We demonstrate that the superantigenicity of M proteins of type 5 and type 1 is due to contamination with the highly potent pyrogenic exotoxins of S. pyogenes in the range of 0.1 to 0.01%. These results raise a general caveat for work with these extremely active T-cell mitogens, because the mitogenicity of other streptococcal or staphylococcal proteins could be due to similar minute contamination with potent superantigens that are undetectable by any biochemical method but extremely effective in stimulating sensitive T cells.

Antigens, Bacterial↗
PubMed1992

Comparative studies on binding of vitronectin and fibronectin to groups A and C streptococci.

Binding of 125I-labelled fibronectin and vitronectin to streptococci of group A (S. pyogenes), group B (S. agalactiae) and group C (S. dysgalactiae and S. zooepidemicus) isolated from various human infections and bovine mastitis, and S. uberis bovine isolates, was studied. Binding of vitronectin and fibronectin was common among both human groups A and C, and bovine group C streptococci. S. agalactiae strains of human and bovine origin as well as S. uberis bovine isolates bound low levels of both proteins. The binding of radiolabelled fibronectin and vitronectin to selected groups A and C streptococcal strains was specific, time-dependent and occurred with both live and heat-killed (80 degrees C for 15 min) cells. Binding declined rapidly after treatment of cells with trypsin or proteinase K, while pepsin digestion at pH 5.5 affected vitronectin but not fibronectin binding.

Culture Media↗
PubMed1991

Protein A-streptokinase fusion protein for immunodetection of specific IgG antibodies.

The streptococcal streptokinase gene truncated at its 5' end was fused to regions of the staphylococcal protein A gene encoding the Fc-binding domains A and B. The resultant fusion gene, when expressed in the Escherichia coli lacPO system or under the speA expression/secretion signals in S. sanguis, specified a bifunctional hybrid protein, SPA-SKC, capable of Fc binding and plasminogen activation. When used in immunoassays designed to titrate antisera raised against bovine chymosin, human serum albumin and fibrinogen, the assay using SPA-SKC compared well with that using a commercial SPA-enzyme conjugate. The simple preparative method together with its efficacy and ease of use, make SPA-SKC a potentially valuable detector reagent in quantitative immunology.

Antibodies, Anti-Idiotypic↗
PubMed1991

Isotachophoretic determination of 2-5A phosphodiesterase.

Together with 2-5A synthetase and ribonuclease L, 2-5A phosphodiesterase belongs to the 2-5A system, which plays an important role in the action of interferon. Analytical capillary isotachophoresis was used for the determination of 2-5A phosphodiesterase activity. Enzyme assay was optimized using snake venom phosphodiesterase as a source of 2-5A phosphodiesterase activity. The 2-5A trimer core was used as a substrate. Enzyme activity was determined in time- and concentration-dependent reactions. In addition, 2-5A phosphodiesterase activity was determined in lysates of mononuclear blood cells.

Adenine Nucleotides↗
PubMed1991

[Intraocular availability of liposome encapsulated monoclonal antibodies in the rabbit model. Results of a pilot study].

The results of local application of monoclonal antibodies (mAb) in rabbit eyes are presented. To improve intraocular access of the high-molecular-weight protein it was entrapped in large (0.2 microns) unilamellar, negatively charged liposomes. Concentrations of the free or encapsulated drug were measured by ELISA in different eye compartments following repetitive drop administration or single subconjunctival injection. Although mAb became measurable in specimens of conjunctiva and cornea, it was not detectable (less than 0.5 ng/ml) in aqueous humor, lens or the vitreous body. In contrast, concentrations of the liposome-encapsulated drug were measurable as little as 30 min after topical application in the aqueous humor.

Animals↗
PubMed1990

A secreted receptor related to M1 protein of Streptococcus pyogenes binds to fibrinogen, IgG, and albumin.

An extracellular protein (eMP) of Streptococcus pyogenes M type 1 was isolated by affinity chromatography on albumin- and IgG-Sepharose. The protein was found to bind to the human plasma proteins, fibrinogen, IgG, and albumin. Analysis of eMP by Western blotting demonstrated a major band with a molecular weight of 49 kD which was responsible for binding of the three plasma proteins. The purified protein was found to bind selectively to human and primate polyclonal IgG, human and mouse albumin, as well as human fibrinogen which has been the only fibrinogen tested. Serological investigations revealed a close relation of eMP to streptococcal M1 protein. It showed a reaction of identity with cell-extracted M1 protein in immunodiffusion. Moreover, the 49 kD peptide responsible for binding, was recognized with an antiserum directed against the 20 amino acids comprising synthetic peptide (42VAL-61GLU) of the N-terminal part of the M1 protein sequence. The affinity of M protein to plasma proteins other than fibrinogen opens new approaches to its purification by affinity chromatography.

Animals↗
PubMed1990

Viscosity measurements of suspensions of hemoglobin-containing liposomes of varying lipid composition.

The viscosity of suspensions of hemoglobin-containing liposomes (Hb liposomes) and of liposomes without Hb was determined as a function of the shear rate. Liposomes of varying lipid composition were prepared by detergent dialysis. All liposome suspensions showed non-Newtonian viscous behavior, as did erythrocyte suspensions. The viscosity of suspensions of Hb liposomes with a bilayer consisting of egg yolk lecithin and phosphatidylserine was almost identical to erythrocyte suspension viscosity. When cholesterol was included in the lipid component of the Hb liposomes, the dependence of viscosity on the shear rate decreased (flattening of the curve), but overall suspension viscosity became higher than that of erythrocyte suspensions. Evidence is provided for the lipid concentration at which liposomes can be applied intravenously.

Blood Substitutes↗
PubMed1990

Ectopic bone induction by partially purified bone extract alone or attached to biomaterials.

Formation of new bone is suggested to be caused by interaction of a set of chemical factors with mesenchymal target cells. A specific assembly of factors, i.e. chemotaxis-, adhesion-, proliferation- and differentiation-factors, as well as macromolecular structure components, essential for formation of large amounts of ectopic bone was termed "osteopoetin" (OP). In the present study a partially purified osteopoetin containing bovine bone extract (OCBE) was used to induce ectopic bone formation. In order to reduce the amount of OCBE necessary for bone induction, OCBE was seeded onto different commercially available collagens or poly-L-lactic acids (PL). Solid collagens in a sponge-like form were used for the first time to function as an attachment system for an osteoinductive substance. The test substances were implanted into abdominal muscle pouches of male Wistar rats. After 21 days the implants were harvested and evaluated histologically. OCBE resulted in the formation of large ossicles containing hematopoietic bone marrow. The minimal amount of OCBE to elicit ectopic bone formation can be reduced by a factor of 10 when attached to quickly resorbable collagens, but not when attached to slowly resorbable PL. These results suggest that collagens are suitable OCBE attachment systems and useful for clinical application.

Animals↗
PubMed1989

Non-leaky vesiculation of large unilamellar vesicles (LUV) induced by plasma high density lipoproteins (HDL): detection by HPLC.

Interaction of large unilamellar phosphatidylcholine vesicles (LUV, 75nm) and plasma high density lipoproteins (HDL) resulted in a non-leaky vesiculation of LUV. This vesiculation was detected by a HPLC-system consisting of a combination of three TSK-gel columns (6000PW, 5000PW, 3000SW). With increasing incubation time liposomal [14C]PC, entrapped [3H]inulin, and apoprotein of HDL origin decreased. The decrease was accompanied by a formation of new particles, consisting of liposomal PC and apoprotein. These particles also enclosed [3H]inulin, reflecting a hydrophilic inner space. The formation of the particles reached a maximum after one day of incubation. Retention time was 21 minutes for LUV, 28 minutes for the new particles, and 36 minutes for HDL. In vesicles with membranes consisting of phosphatidylcholine and 30% cholesterol no interactions were observed.

Carbon Radioisotopes↗
PubMed1989

Preparation of hemoglobin-containing liposomes using octyl glucoside and octyltetraoxyethylene.

Hemoglobin (Hb) was encapsulated in phosphatidylcholine vesicles by removal of the detergent n-octyl beta-D-glucoside (OG) or n-octyltetraoxyethylene (C8E4) out of mixed detergent-lipid micelles in Hb solution. Three types of apparatus were used for dialysis. Dialysis buffer flow rates, the surface area of the dialysis membranes, and detergent-lipid interactions determined the rate of dialysis, which influenced liposome size and lamellarity. Slow dialysis led to the formation of multilamellar liposomes, at increased dialysis rates Hb liposomes became smaller and unilamellar. Hb was enclosed at highest concentrations in larger liposomes, which included the negatively charged lipid phosphatidylserine or phosphatidic acid as a membrane component. Co-encapsulation of the allosteric factor inositol hexaphosphate led to oxygen dissociation curve values almost identical to those of whole blood. The oxygen-release capacity of Hb liposome suspensions in the physiological partial pressure range was comparable to whole blood. Storage of Hb liposomes for 2 months leaves oxygen-carrying characteristics virtually unchanged, with met-Hb levels increasing to only 11% of total Hb. Preparation of Hb liposomes by dialysis of octyl glucoside or C8E4 is a mild and efficient method for encapsulation of Hb. Since these Hb liposomes can be produced in scale-up batch sizes, they are a candidate for use as an oxygen-carrying blood surrogate.

Blood Substitutes↗
PubMed1989

A comparison of coronary risk factors in groups of trained and untrained adolescents.

Fifty-five experimental (29 male, 25 female) and 38 control (20 male, 18 female) adolescent subjects participated in this study to investigate the differences in coronary heart disease (CHD) risk factors in groups of trained and untrained adolescents. As expected the trained group (both sexes) had higher maximal aerobic power (VO2max) and lower systolic blood pressure at rest. The level of total cholesterol was the same in both groups, but the levels of high-density lipoprotein and its lipoprotein subfractions apolipoprotein (Apo-A) and Apo-A1 were higher, and low-density lipoprotein, Apo-B and triglycerides were significantly lower in the experimental group. The value of risk factors from the family history was the same in both groups, but the behavioural and physical risk factors such as smoking and percentage of body fat were lower in the trained group. It would appear that the group of adolescents, trained for several years in athletics and swimming, had a more beneficial lipoprotein profile and a lower level of behavioural and physical risk factors than the control group. For methodological reasons it remains an open question whether these profile differences are the consequences of self-selection procedures or the effects of training.

Adolescent↗
PubMed1989

[Studies on the effect of mistletoe extract on the chemotactic activity and on chemiluminescence of polymorphonuclear leukocytes in vitro].

In the present study, the chemotactic activity of human polymorphonuclear granulocytes was measured using the tripeptide N-F-Met-Leu-Phe and different concentrations of extracts of Viscum album as chemotactic stimuli. It turned out that the extracts have the capability of stimulating chemotaxis up to 30% of the formylated tripeptide. Incubation of isolated granulocytes for 20 minutes in medium alone prior to assessment of chemotaxis results in a 20% loss of chemotactic activity as compared to the freshly isolated cells. Incubation in a medium containing the mistletoe extract does not result in partial deactivation of chemotaxis. This protective effect of the plant extract can be interpreted on the basis of an interaction with the oxidative metabolism of the granulocytes causing partial self-deactivation of chemotaxis. Interference of the extract of Viscum album with the oxidative metabolism of phagocytes is shown in experiments with luminol enhanced chemiluminescence stimulated by opsonized zymosan. The data show a dose-dependent decline of photon emission in the presence of the extracts. The in vitro data measured in the present study provide additional evidence of an immunomodulatory effect of extracts of Viscum album from which in vivo therapeutic effects can be expected.

Amino Acid Sequence↗
PubMed1989

[Quantitative volumetric determinations on MR tomograms in communicating hydrocephalus].

For patients with communicating hydrocephalus the implantation of a cardioventricular shunt is mostly an approved therapy. However, indications are frequently problematic and therefore a shunt operation will not be always successful. The proof of periventricular oedemas in addition to clinical signs seems to be a criterion for an indication for implantation and for the selection of a special valve. With the aid of a newly developed computer programme volume estimation of the ventricular system and the periventricular oedemas has been effected for six patients on T2-weighted MR-tomograms (1.5 tesla). Quotients of the different volumes are correlated with cerebrospinal fluid (CSF) pressure obtained during shunt implantation or lumbar measurement. Distinct indications have been found for a correlation between the volume of the periventricular oedemas and the pressure measurements.

Brain Edema↗
PubMed1989

Subjective health status of day and shift-working policemen.

To assess the subjective health status of day- and shift-working police officers, a questionnaire-based study was carried out. All the day-workers had previous shift experience. To control the age factor the total population of 2659 shift-working and 1303 day-working police officers was divided into four ten-year age classes. Factor analysis revealed that all the symptoms included in the questionnaire could be grouped into six factors. The prevalence rates of complaints showed that four of these factors (autonomous symptoms, musculo-skeletal symptoms, disturbance of appetite and indigestion, respiratory infections) were influenced by the main effects of age and shift work. Across all age classes the age-related changes in prevalence rates were strengthened by shift-work. In the other two factors (nervous symptoms, gastro-intestinal symptoms) an additional interaction effect could be observed. While the prevalence rates of the day-workers increased with age, those of the shift-workers decreased in the oldest age class. This drop of prevalence rates may be attributed to the influence of selection processes.

Adult↗
PubMed1989

Complete secretion of activable bovine prochymosin by genetically engineered L forms of Proteus mirabilis.

To circumvent problems encountered in the synthesis of active chymosin in a number of bacteria and fungi, a recombinant DNA L-form expression system that directed the complete secretion of fully activable prochymosin into the extracellular culture medium was developed. The expression plasmid constructions involved the in-frame fusion of prochymosin cDNA minus codons 1 to 4 to streptococcal pyrogenic exotoxin type A gene (speA') sequences, including the speA promoter, ribosomal binding site, and signal sequence and five codons of mature SpeA. Secretion of fusion prochymosin enzymatically and immunologically indistinguishable from bovine prochymosin was achieved after transformation of two stable protoplast type L-form strains derived from Proteus mirabilis. The secreted proenzyme was converted by autocatalytic processing to chymosin showing milk-clotting activity. In controlled laboratory fermentation processes, a maximum specific rate of activable prochymosin synthesis of 0.57 x 10(-3)/h was determined from the time courses of biomass dry weight and product formation. Yields as high as 40 +/- 10 micrograms/ml were obtained in the cell-free culture fluid of strain L99 carrying a naturally altered expression plasmid of increased segregational stability. The expression-secretion system described may be generally useful for production of recombinant mammalian proteins synthesized intracellularly as aberrantly folded insoluble aggregates.

Animals↗