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Biomedical subjects

K H Schmidt

Publications and source records attributed to K H Schmidt.

At least 55 records · Page 3Linked to original sources
PubMed1994

Ocular absorption of cyclosporine A from liposomes incorporated into collagen shields.

We investigated the ability of liposomes to deliver the immunosuppressive agent cyclosporine A (CsA) to the cornea, anterior sclera, aqueous humor, and vitreous in rabbit eyes. One drop (10 microliters) of liposome-encapsulated CsA (CsA-LIP) or olive oil drops containing an equivalent concentration of CsA (CsA-DR) were administered at 15-minute intervals within the first hour and then one hourly over a 6-hour period. In addition, collagen shields soaked for 30 minutes in the liposome preparation (CsA-LIP-CS) were tested in vitro and in vivo as a new drug delivery approach. CsA levels were measured by fluorescence-immunoassay after 1, 3, or 6 hours of drug administration. CsA levels in this study were highest in cornea and anterior sclera. In animals receiving either CsA-DR or CsA-LIP, CsA levels generally increased from 1 to 6 hours. In animals receiving a single application of CsA-CS-LIP, CsA levels peaked at 3 hours and declined at 6 hours in cornea and sclera. CsA-LIP and CsA-CS-LIP delivered significantly higher levels of CsA to the cornea and sclera at 1 and 3 hours than CsA-DR. In aqueous and vitreous humor, CsA levels increased from 1 to 6 hours in animals receiving either CsA-DR or CsA-LIP. On the other hand, animals receiving a single application of CsA-CS-LIP had lower levels of CsA at 6 hours than at the earlier time points. Animals receiving CsA-LIP or CsA-CS-LIP had significantly higher levels of CsA in aqueous and vitreous humor at 1, 3, and 6 hours than animals receiving CsA-DR.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1993

Isotachophoresis of nucleic acid constituents.

Determination methods for purine and pyrimidine bases, nucleosides, nucleotides and related compounds using analytical capillary isotachophoresis are reviewed. First, the isotachophoretic characterization of these compounds, as well as methods for sample preparation prior to analysis, and the different ways of detecting unknown substances in complex biological systems are described. Then applications of isotachophoretic analysis in medical diagnosis and biomedical research are reviewed. In particular, the analysis of purines, pyrimidines, nucleosides and related compounds in blood and serum for the diagnosis and treatment of inherited diseases and cancer is described. Selected applications of nucleotide analysis in biomedical research using different tissue extracts are also reviewed, and some examples of nucleotide-dependent enzymic reactions, which were performed by means of analytical isotachophoresis, are presented.

Animals↗
PubMed1993

Determination of ascorbic acid by isotachophoresis with regard to its potential in neuroblastoma therapy.

Analytical capillary isotachophoresis was used to determine ascorbic acid (AA) in different matrices (cell-free system, neuroblastoma cell extracts and urine). The system for purging bone marrow of neuroblastoma cells, including 6-hydroxydopamine (6-OHDA) and AA, was analysed with regard to the interaction of AA with 6-OHDA and its autoxidation product, hydrogen peroxide. Furthermore, analyses concerning the uptake of AA into neuroblastoma cells as well as its excretion in urine after uptake of large amounts were carried out.

Ascorbic Acid↗
PubMed1993

Prolongation of corneal allograft survival with liposome-encapsulated cyclosporine in the rat eye.

PURPOSE: To study the effects of different formulations of topical cyclosporine (Cyclosporin A [CsA]) on corneal allograft rejection in a rat model. METHODS: Female Lewis rats received penetrating keratoplasties from female Wistar-Furth donors. A total of 78 allogeneic grafts were performed. An additional 15 syngeneic grafts (Lewis) were used as technical controls. Two CsA preparations with equivalent drug concentrations (2.1 mg/ml) were applied as drops: CsA encapsulated in large unilamellar liposomes (CsA-LIP) and CsA dissolved in olive oil (CsA-DR). Allogeneic grafts were randomly assigned to receive CsA-LIP or CsA-DR beginning on the day of surgery five times daily for 10 days. Animals without any treatment or receiving empty liposomes (EM-LIP) were used as treatment controls. Grafts were graded three times weekly and a rejection index was generated based on graft clarity, neovascularization, and vessel size. RESULTS: All syngeneic grafts remained clear over the observation period of 60 days. Rejected allogeneic grafts without any treatment and those receiving EM-LIP or CsA-DR showed a mean survival time (+/- standard deviation) of 14 +/- 4, 14 +/- 5, and 14 +/- 4 days, respectively. There was no significant difference in mean survival time between the grafts without any treatment and those in CsA-DR or EM-LIP treatment groups. The mean survival time of rejected grafts in animals receiving CsA-LIP was prolonged to 20 +/- 4 days. There was a significant difference in the mean survival time between the CsA-LIP treatment group and groups receiving CsA-DR, EM-LIP, or no treatment (P < or = 0.05). The Kaplan-Meier survival curve of the CsA-LIP treatment group was significantly different from the other experimental groups. The graft survival rate in the CsA-LIP group was 77%, whereas the rate was 37% in the non-treated group, 45% in the CsA-DR group, and 36% in the EM-LIP group. CONCLUSION: Encapsulation of CsA in liposomes might be a promising formulation for use in the prevention of corneal graft rejection.

Animals↗
PubMed1993

Studies on binding of glycosaminoglycans to Streptococcus pyogenes by using 125I-heparan sulphate as a probe.

Binding of 125I-heparan sulphate to the cell surface of Streptococcus pyogenes is mediated by proteins, that could be released from the streptococcal cell wall by using alkaline buffer. SDS-electrophoresis revealed two bands with molecular weights of 63 and 58 kDa. Binding of the 125I-labelled heparan sulphate probe to streptococci seems to be due to charge interactions, as the same probe was displaced by unlabelled heparan sulphate, other negatively charged molecules such as heparin, dextran sulphate, dermatan sulphate or by high ionic strength. The interaction was also strongly influenced by pH. The binding constant at pH 7.2 was estimated to be 9.8 x 10(6) mol/l, suggesting a moderate affinity. The presence of collagen of different types enhanced binding of 125I-labelled heparan sulphate to streptococci, whereas fibronectin and vitronectin had an inhibitory effect. The cooperation between heparan sulphate and collagen could be important for the adhesion of streptococci to connective tissue.

Bacterial Outer Membrane Proteins↗
PubMed1993

Multiple binding of type 3 streptococcal M protein to human fibrinogen, albumin and fibronectin.

M proteins are major virulence factors of group A streptococci which enable the bacteria to resist phagocytic attack. Their binding capacity for different plasma proteins seems to be one reason for the antiphagocytic activity of M protein. In the present study we demonstrate that M3 protein, isolated from the streptococcal culture supernatant of strain 4/55, and the recombinant form (rM3), purified from an E. coli lysate after cloning in phage lambda-EMBL3, show a multiple binding to fibrinogen, albumin and fibronectin in Western blot and dot binding assays. Binding of M3 protein to the multifunctional extracellular matrix and plasma protein fibronectin may not only influence phagocytosis but may also contribute to the adherence of these bacteria to endothelial and epithelial cells.

Amino Acid Sequence↗
PubMed1993

Susceptibility of chicken embryos to group A streptococci: correlation with fibrinogen binding.

One problem in investigating group A streptococcal infections and virulence is the lack of appropriate in vivo models. In this study we introduce the chicken embryo model for determining virulence of Streptococcus pyogenes. We found that M protein positive strains, if administered intravenously, were highly virulent for 12-day-old chicken embryos. The LD50 of the strains tested could be correlated directly with the amount of cell wall exposed M protein, which has been determined by the capacity of streptococci to bind fibrinogen and by the ability of streptococci to survive in fresh normal human blood. The number of colony forming units (cfu) of M+ strains necessary to kill 50% of embryonated eggs was significantly lower (< 10(2) cfu) than for M-variants (> 10(4) cfu). Albumin and/or IgG binding streptococcal cells, which can also take place in proteins of the M protein family which do not bind to fibrinogen, did not show that clear correlation to the virulence in chicken embryos that did fibrinogen binding. Application of anti-streptococcal M protein antisera from chicken and rabbit reduced the lethality of the chicken embryos. In contrast, no correlation was found between lethality of chicken embryos and the in vitro production of erythrogenic toxins by the administered strains. Thus the results indicate that the presence of M-protein with its fibrinogen binding activity on the streptococcal cell surface is necessary for virulence of group A streptococci in the chicken embryo model.

Animals↗
PubMed1993

[Postoperative management with pulsed high frequency electromagnetic energy. A clinical study of 38 patients with rhinoseptoplasty].

The effect of high frequent electromagnetic radiation pulse (PHEE) on the resorption of postoperative hematomas was investigated in 38 patients who underwent rhinoseptoplasty. 18 patients were treated twice a day using a diapulse equipment, whereas the patients in the control group did not get radiation. In the radiated patients, measurements of the infraorbital hematoma showed accelerated resorption-contrary to the course of the supraorbital hematoma. Diapulse radiation also prevented the enlargement of hematomas that usually proceeds until the third postoperative day. Results of undiminished resorption in the upper eyelid may be caused by inadequate penetration of PHEE or a methodical mistake in the analysis. Additionally, patients treated with PHEE needed a shorter course of postoperative antiphlogistic treatment when compared to the control group. The treatment might further be improved by preoperative use of PHEE or additional radiation of the liver, spleen, and adrenal gland. The results of our investigation showed the improvement of wound healing by using PHEE.

Electromagnetic Fields↗
PubMed1992

Effects of a new bone-inducing biomaterial on mesenchymal cells in vitro.

A purified bone-inducing protein complex (BIC), isolated from bovine bone and causing de novo bone formation in vivo, induces defined effects on rat mesenchymal cells in vitro. Spindle-like mesenchymal cells growing in monolayers change to polygonal cells, forming a multilayered growth pattern. The mesenchymal cells acquire alkaline phosphatase activity. Upon culture with BIC, the typical collagen Type III deposition of these mesenchymal cells is remarkably reduced whereas the collagen Type I expression remains unaffected. All these in vitro effects are consistent with the strong bone-forming capacity of BIC in vivo. A combination of two cytokines, transforming growth factor beta 1 (TGF beta 1) and epidermal growth factor (EGF), shows a similar activity to BIC. Neutralizing anti-TGF beta antibodies interfere with all in vitro effects of BIC. The neutralization of BIC and the inductive capacity of the combination of TGF beta 1 plus EGF point to the substantial role of TGF beta or TGF beta-like molecules in BIC; whether the active polypeptides are identical to TGF beta or somewhat structurally homologous to TGF beta remains to be elucidated.

Animals↗
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↗