Biomedical subjects
Publications and source records attributed to H Schmidt.
Thylakoid membranes isolated from the cyanobacterium Synechocystis sp. strain PCC6803 were capable of desaturating the acyl groups in monogalactosyl diacylglycerol. This desaturation reaction required the reduced form of ferredoxin.
We compared a collection of sorbitol-fermenting (SF) Escherichia coli O157:H- strains with SF E. coli O157:H45 and non-SF E. coli O157:H7 and E. coli O157:H- strains by pulsed-field gel electrophoresis. The SF E. coli O157:H- strains had identical or closely related XbaI patterns that differed markedly from those for the other E. coli O157 strains. Plasmid content and the presence of Shiga-like toxin-converting phages were determined for the SF E. coli O157:H- strains, indicating that these strains harbor a single 90-kb plasmid. They are lysogenized by toxin-converting phages and harbor the eae gene. Nonmotile E. coli O157 strains were observed to adhere more efficiently to HEp-2 cells than the motile strains. From their phenotypic and genotypic features, the SF E. coli O157:H- strains may well represent a new clone with non-SF E. coli O157:H7 pathogenic characteristics.
A total of 50 oxacillin-resistant Staphylococcus aureus (ORSA) strains that were clumping factor negative (CFN) and protein A negative by latex agglutination were collected from patients in six different hospitals at different locations in Germany during 1991 and 1992. Antibiograms, bacteriophage typing, and plasmid analysis were performed. The antibiograms showed that, besides oxacillin, all CFN ORSA strains were resistant to gentamicin, clindamycin, erythromycin, ciprofloxacin, and fosfomycin. All these isolates were nontypeable with an international set of phages, and an additional experimental phage set indicated that the strains were phage type 16, 192. Moreover, all isolates possessed a single plasmid of 30 kb, and restriction analysis of those plasmids revealed identical patterns. For genotyping, these 50 isolates were also analyzed by pulsed-field gel electrophoresis (PFGE) and polymerase chain reaction (PCR) of the coagulase and protein A genes and then by restriction enzyme digestion and analysis of restriction fragment length polymorphisms (RFLPs). With 49 strains, electrophoresis of SmaI-digested chromosomal DNA revealed identical PFGE patterns regarding the number and size of the DNA fragments, which could be differentiated from those of clumping factor-positive ORSA strains. Typing for the coagulase gene by PCR revealed PCR products of identical sizes. The AluI restriction digestion patterns of the PCR products were identical. PCR with primers derived from the region of that part of the protein A gene that encodes the immunoglobulin G-binding domains showed a PCR product that was about 170 bp smaller than that of the protein A gene from strains that were positive in the protein A latex agglutination test. Since it is precisely this size that is required in order to encode one immunoglobulin G-binding region, we assume that this is not present in the CFN ORSA strains. The phenotypical and genotypical features identify these very unusual CFN ORSA stains as being of clonal origin.
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Familial dysautonomia (Riley-Day syndrome) is a rare genetic disorder that is transmitted via an autosomal recessive gene. The disease, typically involving Jewish children, affects the central nervous system and can be characterised by pathological deficits in peripheral autonomic and sensory neurones. The signs, which begin in early childhood, include poor perception of pain and temperature, poor co-ordination of muscles, emotional crises with hypertension and profound sweating, postural hypotension, and excessive vagal reflexes. We present the case of a 1.5-year-old child who underwent general anaesthesia for gastrostomy and fundoplication because of chronic aspiration. The technique consisted of balanced anaesthesia with invasive monitoring: intra-arterial line, central venous catheter, pulse oximetry, capnography, and monitoring of urinary output, temperature, and metabolic changes. Pulmonary problems included a dramatic decrease in SaO2 during intubation, massive bronchial secretions, and a high fluid requirement. The haemodynamic parameters remained stable. In the postoperative period, pulmonary problems included severe pneumonia with variable pulmonary shunting and requiring an inspired oxygen fraction of between 0.5 and 1.0, accompanied by bronchoconstriction, atelectasis, and profuse bronchial secretions. Controlled ventilation had to be maintained for 4 days. The cardiovascular system was unstable with intermittent episodes of bradycardia, tachycardia, and hypo- or hypertension. The patient also showed signs of autonomic crises, which were treated with diazepam. Although patients with autonomic dysfunction are at high risk in the perioperative period, they can be managed safely when therapeutic efforts are optimised.
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The clinical syndrome sepsis has been redefined recently, and the SIRS (systemic inflammatory response syndrome) concept has been developed. In the initial phase of sepsis, different mediator systems are activated finally resulting in a generalized endothelial inflammatory reaction. This reaction may lead to a vicious circle with subsequent multiple organ failure. Standard therapeutic regimen include the surgical removal of the source of sepsis, antimicrobial therapy, optimizing oxygenation, volume resuscitation, and treatment with catecholamines. Recently, new treatment modalities have become available. Replacement of antithrombin III, continuous venovenous hemofiltration, application of high doses of immunoglobulins and of low doses of hydrocortisone have been used. A monoclonal antibody against endotoxin (Centoxin) was taken from the German market in January 1993. Experimental aspects of treatment include the administration of C1 esterase inhibitor, pharmacological inhibition of nitric oxide (NO), plasmapheresis, the application of non-steroidal anti-inflammatory agents and of high-dose naloxone as well as manipulation of cytokines.
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The switching gene swi10+ has a function in mating-type switching as well as in the repair of radiation damages. We have cloned the genomic swi10+ gene by functional complementation of the switching defect of the swi10-154 mutant. The swi10+ gene is not essential for viability. The DNA sequence revealed an open reading frame of 759 nucleotides interrupted by three introns of 127, 52 and 60 bp, respectively. The positions of intron I as well as of intron III of swi10 are evolutionary conserved in comparison to the introns III and IV of the human ERCC1 gene. The analysis of cDNA clones isolated by PCR amplification confirmed the structure of the swi10 gene. The putative Swi10 protein has homologies to the human and mouse ERCC1 protein, to Rad10 of Saccharomyces cerevisiae and to parts of UvrA and UvrC of E. coli. All these proteins are essential components for excision repair of damaged DNA. The Swi10 protein contains a putative DNA binding domain previously found in other proteins. Northern blot experiments and the analyses of cDNA clones indicate that intron I of the swi10 gene is not efficiently spliced.
The glucagon-dependent activation of the phosphoenolpyruvate carboxykinase (PCK) gene is modulated by oxygen. It was proposed that heme proteins might function as O2 sensors; their actions are impaired after replacement of the central Fe2+ ion by Co2+ and inhibition of heme synthesis by succinylacetone (SA). Therefore, the effects of CoCl2 and SA, alone and in combination, on the glucagon-dependent induction of PCK activity and PCK mRNA were investigated at different physiological oxygen tensions in primary rat hepatocyte cultures. The cells were exposed to 50 microM CoCl2 and/or 2 mM SA from 4-24 h. After addition of fresh media without CoCl2 or SA, PCK was induced with 1 nM glucagon. PCK activity and PCK mRNA were elevated to 100% at 16% O2 and to about 65% at 8% O2. CoCl2 reduced these increases to about 45% at 16% O2 and to about 35% at 8% O2. SA lowered the inductions to about 50% and 40% each at 16% and 8% O2. CoCl2 plus SA diminished the elevations to about 5% at both oxygen tensions. In the presence of CoCl2 and/or SA, ornithine decarboxylase induction by insulin was not impaired; lactate dehydrogenase did not leak from the cells, which in electron microscopical inspections had normal cell structures. These findings support the hypothesis that a heme protein is involved in the activation of the PCK gene and that it acts as an O2 sensor.
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Forty-seven patients submitted to an ERCP were submitted, in one and the same session, to radiological examination with both conventional and digital luminescence radiography (DLR). Within the framework of this orientational study, DLR provided at least the same amount of information as the conventional examination, but was also associated with diagnostic advantages in particular in the region of the intrahepatic bile ducts and in the representation of a cholelithiasis.
A balance of ATP-consuming processes in human erythroleukemia (K 562) cells by use of the decreased 14CO2 formation from [1-14C]-glutamate following inhibition of energy-requiring processes is presented. This method was tested on Ehrlich mouse ascites tumour cells and was used in suspensions of K 562 cells with a low cell content. More than 90 percent of the ATP produced by oxidative phosphorylation could be accounted for in K 562 cells. Protein synthesis consumed about 35 percent, Na+/K(+)-ATPase about 20 percent and transcription processes 5-10 percent of the total ATP. The share of the Ca(2+)-dependent reactions was notably high at 25 percent in comparison with Ehrlich mouse ascites tumour cells, reticulocytes or hepatocytes. ATP consumption by DNA synthesis was assessed at 5-10 percent. Only less than 10 percent of the consumption of ATP produced oxidatively remained for other cellular reactions. The degree of coupling of K 562 cells was high in comparison with that of other eukaryotic cell types.
Slow muscle fibers were dissected from cruralis muscles of Rana esculenta and Rana pipiens. Isometric contractures were evoked by application of K(+)-rich Ringer's containing Ca2+, Ni2+, Co2+, Mn2+ or Mg2+. High (7.2 mmol/liter) external Ca2+ concentration raised, 0 Ca2+ lowered the K+ threshold. Replacing Ca2+ by Ni2+ or Co2+ had an effect similar to that of high Ca2+ Ringer's. In Mg2+ Ringer's the K+ concentration-response curve was flattened. These effects were observed already after short exposure times in both species of slow fibers. When Ca2+ was removed for long periods of time the slow fibers of R. esculenta lost their contractile response to application of high K+ concentrations much more quickly than those of R. pipiens, while the response to caffeine (20 mmol/liter) was maintained. Upon read-mission of Ca2+ contractile ability was quickly restored in the slow fibers of both R. esculenta and R. pipiens, but the effects of Ni2+ (or Co2+, Mn2+ and Mg2+) were much larger in R. esculenta than in R. pipiens slow fibers. It is concluded that divalent cations have two different sites of action in slow muscle fibers. K+ threshold seems to be affected through binding to sites at the membrane surface; these sites bind Ni2+ and Co2+ more firmly than Ca2+. The second site is presumably the voltage sensor in the transverse tubular membrane, which controls force production, and where Ca2+ is the most effective species of the divalent cations examined.