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Biomedical subjects

C Klessen

Publications and source records attributed to C Klessen.

At least 37 records · Page 2Linked to original sources
PubMed1992

Acetylene, a mammalian metabolite of 1,1,1-trichloroethane.

1,1,1-Trichloroethane (TCE) is a widely used industrial solvent of low acute toxicity. It is slowly oxidized to trichloroethanol and trichloroacetic acid by cytochrome P-450-dependent mono-oxygenases. Increased inhalative uptake by rats under hypoxia and spin-trapping experiments indicate that TCE is also reductively metabolized to a radical intermediate. Acetylene is formed as a metabolite, suggesting transfer of an additional electron to form the corresponding carbene. Hypoxia and induction of mixed-function mono-oxygenases accelerate the formation of acetylene. Experiments performed in vitro with rat liver microsomal fractions yield analogous results.

Acetylene↗
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

Destruction of tumour parenchyma in basal cell carcinoma by tumour-associated neutral proteases: a histochemical study.

Proteolytic activity was demonstrated histochemically in frozen sections of basal cell carcinomas (BCCs). After incubation of tissue sections in 0.1 M phosphate buffer with 0.25 M NaCl the tumour epithelium was almost completely destroyed. The basal and squamous cell layers of the epidermis disintegrated to varying degrees, particularly where they were directly in contact with tumour epithelium. Serine and metalloprotease inhibitors diminished this tissue destruction. Iodoacetate enhanced tumour destruction, urea and potassium thiocyanate even more so. The high proteolytic activity of BCC demonstrated in this study may be an important factor in the proliferative, invasive and destructive behaviour of this tumour.

Basal Cell Carcinoma↗
PubMed1991

[Temperature-controlled bipolar electrocoagulation].

The safety of electrocoagulation for laparoscopic surgery has been greatly improved by the introduction of the bipolar coagulation technique. But complications caused by coagulation, especially by the overheated forceps, are still reported. In order to reduce those complications, a temperature controlled bicoagulation system was developed. This system allows coagulation with lower temperatures which can be kept constant during the coagulation process. In experiments with human fallopian tubes obtained by adnexectomy and rabbit uterine horns it is shown that those lower temperatures are sufficient for homogeneous coagulation. On line monitoring of the temperature during coagulation provides the surgeon with the possibility of directly controlling the actual temperature at the tip of the forceps. The temperature curves can easily be stored in order to be able to demonstrate the particular coagulation process even after years.

Animals↗
PubMed1989

Lectin binding sites in normal and phenobarbitale/halothane treated rat liver. A histochemical study.

The content of carbohydrate residues of both normal and phenobarbitale-halothane-hypoxia exposed rat liver has been examined by means of lectin histochemistry. Eight biotinylated lectins specific to galactose, N-acetyl-galactosamine, N-acetyl-glucosamine, fucose and mannose were applied to paraffin sections of rat liver at light microscopic level. The most distinct binding was observed at the structures of the "perisinusoidal functional unit": Kupffer cells are bound by S-WGA, SBA and PNA. Bile canaliculi display binding sites for RCA I and WGA. Cytoplasm of hepatocytes appears lectin-negative, except for PSA. The enhanced reaction of S-WGA, PNA and SBA after the preincubation of the sections with neuraminidase indicates the occurrence of sialic acid in Kupffer cells. The phenobarbitale-halothane-hypoxia exposed rat liver shows centrolobular degeneration of hepatocytes with a diminished amount of hepatocyte and Kupffer cells as well. The lectin binding pattern of sinusoidal walls, membranes of hepatocytes and bile canaliculi remains the same compared to that of normal rat liver. This finding suggests that at least the carbohydrate content of membranes in the liver resists severe destruction under phenobarbitale-halothane-hypoxia. It is assumed that there exists a connection between intact carbohydrate residues and the regeneration of liver parenchyma.

Animals↗
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↗
PubMed1988

Expression of the human interferon-alpha 1 gene under transcriptional and translational control of the speA gene.

The human gene for mature interferon-alpha 1 (IFN-alpha 1) was inserted in a new transcription-translation fusion vector system based on the expression and secretion signals of the gene for type A streptococcal pyrogenic exotoxin, speA. As deduced from the known nucleotide sequences of the component elements, the encoded IFN-alpha 1 was a fusion protein carrying an N-terminal extension of 17 amino acids. When inserted in appropriate vectors capable of replication in Escherichia coli, Bacillus subtilis and Streptococcus sanguis, this expression configuration directed the synthesis of antiviral activity in all 3 organisms, as judged by the cythopathic effect inhibition assay of Vesicular Stomatitis Virus. In E. coli JM101, IFN activity was found mainly in the cytoplasmic protein fraction whereas in the gram-positive hosts, it was completely secreted into the culture medium.

Amino Acid Sequence↗
PubMed1988

Survey of the pSM10 family of streptococcal cloning vectors.

A survey of the pSM10 family of streptococcal plasmid cloning vectors is provided. These vectors are derived from a macrolide-lincosamide-streptogramin B resistance plasmid and include general cloning vectors, shuttle vectors, helper plasmids, expression vectors, gene fusion vectors and plasmids. Besides describing their general properties, this paper also provides their genetic and physical maps.

Cloning, Molecular↗
PubMed1988

Tripartite streptokinase gene fusion vectors for gram-positive and gram-negative procaryotes.

A specific 1,596 bp HincII fragment ('skc) from the chromosome of Streptococcus equisimilis contains an active streptokinase (SK) gene (skc) lacking, in addition to the expression signals, codons 1 through 39 of wild-type skc but retaining the remainder of the skc coding sequence together with the transcription terminator. Using this fragment as an indicator gene, we constructed two types of vectors which in appropriate hosts resulted in the synthesis of SK fusion proteins after insertional activation of 'skc. The first type are open reading frame (ORF) vectors in which 'skc was inserted into pUC18 out of frame with respect to lacZ', thus conferring an SK-negative phenotype. Any DNA fragments representing ORFs inserted between the lacZ' expression signals and 'skc such that the skc reading frame was restored resulted in the production of tripartite proteins which exhibited SK activity. The second type of vector, which functioned in both gram-positive and gram-negative bacteria, used the streptococcal speA expression and secretion signals in front of the ORF to activate 'skc insertionally. Using a large fragment from the chymosin gene as the target sequence, the usefulness of these vectors for studying foreign gene expression in streptococci as well as Escherichia coli was demonstrated.

Amino Acid Sequence↗
PubMed1987

Tetrachloromethane metabolism in vivo under normoxia and hypoxia. Biochemical and histopathological effects relative to alkane exhalation.

About 250 mumol/kg tetrachloromethane is metabolized by male Sprague-Dawley rats receiving a dose of 500 mumol/kg by inhalation. Determination of enzyme activities and histopathological assessment show that various parameters reflecting cellular injury do not differ for the same amount of tetrachloromethane metabolized under different oxygen partial pressures. On the other hand, the amounts of ethane and pentane exhaled under hypoxic conditions are greater than under normoxia. The previously reported differences in the toxicity of tetrachloromethane upon exposure under normoxia or hypoxia seem to be mainly due to the different amounts of tetrachloromethane metabolized under both conditions.

Alkanes↗
PubMed1987

Lectinhistochemical demonstration of galactose- and N-acetyl-D-galactosamine residues in cells of the rat anterior pituitary.

Lectins are a useful tool for identification of differently glycosylated hypophyseal hormones, prohormones and glycoconjugates without hormone function. Beta-D-galactose and beta-N-acetyl-D-galactosamine (GalNAc) containing glycoconjugates were identified by light microscopy with biotinylated lectins in immunocytochemically localized cells of the anterior pituitary of the rat. Galactose, histochemically detectable by the peanut lectin (PNA), was found at penultimate position of the carbohydrate chain after removal of sialic acid. Galactose containing cells correspond to gonadotrophs and thyrotrophs located mainly in medioanterior regions of the pituitary. The lectins from the soybean (SBA) and horse gram (DBA) both specific for GalNAc residues, are bound to round and also polygonal cells corresponding again to gonadotrophs and thyrotrophs.

Acetylgalactosamine↗
PubMed1987

Galactose and fucose binding sites in anterior pituitary cells of the rat. Detection by means of biotinylated lectins.

The oligosaccharide chains of adenohypophyseal glycoprotein hormones fulfill important functions concerning their stability and biological activity. Galactose, histochemically detectable by the Peanut lectin (PNA), could be found after removal of sialic acid in cells situated mainly in the medioanterior region of the pituitary. The Ulex europaeus I lectin (UEA I) reacted with fucose containing sites predominantly in the Golgi-apparatus of nearly all cells. After incubation with neuraminidase, however, fucose may be detected also in the cytoplasm of cells of the medioanterior region. The biological significances of the results is discussed.

Animals↗
PubMed1986

Expression of the streptokinase gene from Streptococcus equisimilis in Bacillus subtilis.

The previously cloned and sequenced streptokinase gene (skc) from Streptococcus equisimilis H46A was inserted into plasmid vectors capable of replication in Bacillus subtilis. The skc gene was expressed by use of its own transcription and translation signals which appeared to meet the stringent requirements of B. subtilis for efficient foreign gene expression. The secreted streptokinase activity began to decline toward the end of the exponential growth phase suggesting that B. subtilis exoproteases hydrolyzed and inactivated the foreign protein.

Bacillus subtilis↗
PubMed1984

Alcianblue/PAS or PAS/alcianblue? Remarks on a classical technic used in carbohydrate histochemistry.

The combined alcian blue (AB)/PAS technic is widely used for the detection and characterization of mucosubstances in tissue sections. Mostly the sequence AB/PAS is used, occasionally also the reserved sequence PAS/AB. The present study shows clearly that the sequence of the combined technic, i.e. AB/PAS or PAS/AB is substantially influencing the results. So it could be demonstrated that by using the combination PAS/AB originally PAS-positive and AB-negative reacting mucosubstances become AB-positive. This could be caused by periodic acid oxidation followed by addition of hydrogen sulfite to aldehyde group thus providing secondary basophilic resp. AB positive material.

Adenocarcinoma↗
PubMed1984

[Thrombogenicity of a new prothrombin complex concentrate].

A prothrombin complex concentrate produced according to a new procedure was tested for potential thrombogenicity in vitro and in vivo. The results obtained by in vitro methods (NAPTT, TGt50, determination of the hydrolytic index) were not in the critical range of thrombogenicity. An effective dose of 175 U/kg for thrombus formation assessed in the stasis model of Wessler suggested comparatively low thrombogenicity. In the non stasis model no changes in the haemostaseological variables indicative of consumption reaction were observed after infusion of 125 U/kg for 30 min in rabbits. In the organs investigated (heart, liver, kidneys, adrenals) no thrombin were detected morphologically.

Animals↗
PubMed1982

Pharmacological studies on the antithrombotic action of hirudin in experimental animals.

The pharmacodynamics and pharmacokinetics of hirudin were studied in dogs, rabbits and rats. Hirudin proved to be a well tolerated substance with low toxicity. After intravenous injection it was eliminated with a half time of 50 to 60 min. It was nearly completely excreted through the kidneys in biologically active form. The efficacy of hirudin in preventing venous thrombosis, vascular shunt occlusion and disseminated intravascular coagulation in rats was demonstrated.

Animals↗