Search PubMed⌕ Search

Biomedical subjects

H Schmidt

Publications and source records attributed to H Schmidt.

At least 469 records · Page 26Linked to original sources
PubMed1995

Testing the porphyrinogenicity of propofol in a primed rat model.

We evaluated the porphyrinogenicity of propofol in a rat model. After a pilot study had been conducted to determine an optimal dose, 48 fasting male Sprague-Dawley rats were allocated randomly to six groups. The animals in groups 1-3 received saline i.p. In groups 4-6, the animals were given allylisopropylacetamide (AIA). Twelve hours later, animals in groups 1 and 4 received saline, groups 2 and 5 were given propofol 150 mg kg-1 i.p., followed by 75 mg kg-1 3 h later, and groups 3 and 6 received phenobarbitone 50 mg kg-1 i.p. and 25 mg kg-1 i.p. The animals were anaesthetized and killed 3 h after the second drug bolus and we measured the concentration of cytochrome P450, total porphyrin content and the activity of delta-aminolaevulinic acid synthase (ALAS) in the liver. Urinary delta-aminolaevulinic acid (ALA) and porphobilinogen (PBG) concentrations were measured. Analysis of variance and the t test with Bonferroni's correction were used to compare data. The hepatic cytochrome P450 concentration in the non-primed groups varied from 28.1 to 31.1 nmol g-1; administration of AIA decreased this to 20.1-20.9 nmol g-1. Total hepatic porphyrins were between 0.78 and 1.22 nmol g-1 in the non-primed groups and between 2.71 and 3.54 nmol g-1 in the AIA-primed groups. Hepatic ALAS activity was 29.2 and 35.5 nmol h-1 g-1 in groups 1 and 2. In the primed saline group, ALAS activity was measured at 134.5 nmol h-1 g-1.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Aminolevulinate Synthetase↗
PubMed1995

Propofol-induced alterations in the microcirculation of hamster striated muscle.

To investigate the effects of propofol on small vessels, we have measured changes in diameter and blood flow in microcirculatory venules and arterioles. Studies were carried out in the dorsal skinfold chamber of hamsters by intravital fluorescence microscopy. A bolus injection of propofol 25 mg kg-1 dilated small and collecting venules by a mean value of 18% and arterioles by 13%. Blood flow in venules increased by up to 69%. Intralipid dilated arterioles and post-capillary venules by 26% and 30%, respectively. After 4 h of continuous infusion (0.2-0.8 mg kg-1), only blood flow in post-capillary venules increased (66% propofol and 92% Intralipid). Post-capillary and collecting venules dilated in both groups. Therefore, propofol and Intralipid induced venodilatation and enhanced blood flow after bolus administration. After 4 h, despite dilatation in both groups, only post-capillary venules showed enhanced blood flow. These observations suggest redistribution of blood flow after prolonged administration of propofol.

Anesthetics, Intravenous↗
PubMed1995

Ketamine attenuates endotoxin-induced leukocyte adherence in rat mesenteric venules.

OBJECTIVES: To determine the influence of ketamine on endotoxin-induced leukocyte adherence and venular microhemodynamics. DESIGN: Randomized, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Thirty male Wistar rats. INTERVENTIONS: The rats were pretreated with ketamine (10 mg/kg iv) or 0.9% saline, and both groups were given endotoxin (Escherichia coli lipopolysaccharide; 5 mg/kg iv). The control group received two doses of 0.9% saline. MEASUREMENTS AND MAIN RESULTS: The rates of leukocyte adherence and changes in microhemodynamics were monitored in rat mesenteric venules, using in vivo video microscopy. The number of adherent leukocytes was determined on-line in 10-min intervals from 60 mins before until 2 hrs after endotoxin administration. Venular diameters, red blood cell velocity, volumetric blood flow, and the venular wall shear rate were monitored before and at 10, 30, and 60 mins after endotoxin exposure. A 6.3-fold increase in the number of adherent leukocytes was observed 10 mins after administration of endotoxin when compared with control animals (5.87 +/- 0.69 vs. 0.93 +/- 0.21 adherent cells/100 microns; p < .001). This increase remained unchanged for 120 mins. In ketamine-pretreated rats, a 2.6-fold increase in leukocyte adherence occurred during the first 20 mins after endotoxin exposure (2.40 +/- 0.46 vs. 0.93 +/- 0.21 adherent cells/100 microns; p < .01). However, no difference in the number of adherent leukocytes between ketamine-pretreated and control animals was found after this 20-min period. In animals of the control group, no increase in leukocyte adherence occurred during the entire observation time. Diameters of mesenteric venules did not change after endotoxin exposure in any of the groups. Red blood cell velocity and venular blood flow in the endotoxin-treated groups decreased 10 mins after the injection of endotoxin when compared with controls, but these values did not show any difference when they were compared between ketamine and saline-pretreated animals. Similarly, venular wall shear rate in the endotoxin-treated groups decreased 10 and 30 mins after injection of endotoxin. However, no significant difference occurred between ketamine and saline-pretreated animals. CONCLUSIONS: Pretreatment with ketamine attenuates endotoxin-induced leukocyte adherence by a shear rate-independent mechanism, suggesting reduced expression of adhesion molecules. These results indicate that ketamine exerts an anti-inflammatory effect, which might be beneficial in septic patients.

Animals↗
PubMed1995

Genotyping of Shiga-like toxin genes in non-O157 Escherichia coli strains associated with haemolytic uraemic syndrome.

The pheno- and genotypes of Shiga-like toxins (SLTs) in non-O157 Escherichia coli strains from patients with haemolytic uraemic syndrome were determined. The clinical isolates investigated were from Italy and Germany and belonged to serotypes O22:H8, O26:H-, O26:H11, O91:H-, O111:H- and O128:H-; one isolate was non-typable. SLT genotypes were analysed by complete nucleotide sequence analysis of the B-subunit genes. The results showed that 14 strains possessed slt-I alone, two contained slt-II alone and five isolates harboured both slt-I and slt-II genes. In only two strains were slt-II-related genes found, together with either slt-I or slt-II. These findings indicate that variants of SLT-II are rarely found in non-O157 E. coli isolates from patients with haemolytic uraemic syndrome. Polymerase chain reaction (PCR) with Taq cycle sequencing was found to be a suitable method for classification of slt genotypes.

Bacterial Toxins↗
PubMed1995

Lignocaine metabolite formation: an indicator for liver dysfunction and predictor of survival in surgical intensive care patients.

Formation of the lignocaine metabolite monoethyl-glycine-xylidide (MEGX) by hepatic cytochrome P450 enzymes is a new method for evaluating liver function. The purpose of this study was to compare MEGX formation with other liver function parameters in surgical intensive care unit patients. The study include 29 critically ill patients who had been admitted to the unit for more than 3 days with a median APACHE III score-predicted mortality > 30%. On day 4, lignocaine was given intravenously at a dose of 1 mg.kg-1 over 2 min and MEGX formation was measured 15 min later. Eighty-nine percent of the patients had MEGX values below 90 micrograms.l-1 indicating impaired liver function. Eleven patients died, 18 patients survived. The group of patients with fatal outcome had significantly lower MEGX values (median: 23 micrograms.l-1) than the group of survivors (median: 53 micrograms.l-1, p < 0.01). Bilirubin values were elevated in the non-survivor group (median: 2.8 mg.dl-1) compared to the survivors (median: 0.9 mg.dl-1, p < 0.05). There was no significant difference between two groups in the other liver function tests. We conclude from our results that the MEGX test can be considered an indicator for hepatic dysfunction and predictor of survival in critically ill patients.

Aged↗
PubMed1995

Antigen-independent reactivation of anti-E, years after allogeneic bone marrow transplantation: a case report.

Nine years after allogenic bone marrow transplantation a strong anti-E was observed in a patient transplanted with bone marrow from his HLA-identical brother. This IgG anti-E, with a titre of 4000, was detected together with autoantibodies to red blood cells and platelets and was not induced by transfusion with E+ cells. The hypothesis is proposed that the anti-E represents either antigen-independent desuppression of the donor immune system sensitized at the time of bone marrow transplantation by E antigens in the recipient, or antigen-independent memory B-cell activation by Epstein-Barr virus infection.

Autoantibodies↗
PubMed1995

Molecular characterization of the lincomycin-production gene cluster of Streptomyces lincolnensis 78-11.

The lincomycin (LM)-production gene cluster of the overproducing strain Streptomyces lincolnensis 78-11 was cloned, analysed by hybridization, as well as by DNA sequencing, and compared with the respective genome segments of other lincomycin producers. The lmb/lmr gene cluster is composed of 27 open reading frames with putative biosynthetic or regulatory functions (lmb genes) and three resistance (lmr) genes, two of which, lmrA and lmrC, flank the cluster. A very similar overall organization of the lmb/lmr cluster seems to be conserved in four other LM producers, although the clusters are embedded in non-homologous genomic surroundings. In the wild-type strain (S. lincolnensis NRRL2936), the lmb/lmr-cluster apparently is present only in single copy. However, in the industrial strain S. lincolnensis 78-11 the non-adjacent gene clusters for the production of LM and melanin (melC) both are duplicated on a large (0.45-0.5 Mb) fragment, accompanied by deletion events. This indicates that enhanced gene dosage is one of the factors for the overproduction of LM and demonstrates that large-scale genome rearrangements can be a result of classical strain improvement by mutagenesis. Only a minority of the putative Lmb proteins belong to known protein families. These include members of the gamma-glutamyl transferases (LmbA), amino acid acylases (LmbC), aromatic amino acid aminotransferases (LmbF), imidazoleglycerolphosphate dehydratases (LmbK), dTDP-glucose synthases (LmbO), dTDP-glucose 4,6-dehydratases (LmbM) and (NDP-) ketohexose (or ketocyclitol) aminotransferases (LmbS). In contrast to earlier proposals on the biosynthetic pathway of the C-8 sugar moiety (methylthiolincosaminide), this branch of the LM pathway actually seems to be based on nucleotide-activated sugars as precursors.

ATP-Binding Cassette Transporters↗
PubMed1995

Gastric tonometry: effect of sucralfate on calculated intramural pH.

Tonometric measurement of gastric intramural pH (pHi) is a noninvasive method to assess adequacy of splanchnic perfusion. Calculation of pHi may be influenced by various factors. This prospective study was designed to determine if stress ulcer prophylaxis with sucralfate interferes with pHi measurement. Twenty-five adult patients admitted to the intensive care unit (ICU) after open heart surgery were studied. Nasogastric tonometers were placed. Patients received sucralfate 1 g via the nasogastric tube 8 hours after termination of surgery, thereafter every 6 hrs. Gastric luminal pH and intramural pH were determined immediately prior and 1 hour after the first sucralfate administration. Gastric intramural pH was calculated from the arterial HCO3- concentration and the tonometrically determined intraluminal PCO2 value using the Henderson-Hasselbalch equation. Intraluminal PCO2(ss) was measured to 6.86 +/- 0.75 kPa prior to sucralfate administration as compared to 6.96 +/- 0.68 kPa 1 hour after 1 g sucralfate (P = 0.92). Intramural pH, as calculated by tonometry, was 7.31 +/- 0.05 vs 7.31 +/- 0.05, and was thus not influenced by sucralfate administration (P = 0.97). Mean gastric intraluminal juice pH was 4.2 +/- 1.3 compared to 4.2 +/- 1.2 (P = 0.59). These data suggest that sucralfate does not interfere with tonometrically determined intraluminal PCO2 measurement and calculation of gastric intramural pH.

Aged↗
PubMed1995

Autotransfusion after open heart surgery: the oxygen delivery capacity of shed mediastinal blood is maintained.

Autotransfusion of mediastinal shed blood after open heart surgery has become a common and accepted procedure in reducing the need for homologous transfusion during the last 15 years. The objectives of the present study were to investigate the oxygen delivery capacity of autotransfused shed mediastinal blood, compared to patient-blood, during cardiopulmonary bypass and in the postoperative period. Ten consecutive patients undergoing elective cardiac surgery were studied. Mediastinal shed blood was collected in the cardiotomy reservoir and retransfused during the first 18 postoperative hours. The oxygen delivery capacity of the blood to the tissues was calculated by use of the oxygen status algorithm (OSA 2.0) programme and measurement of the 2,3-diphosphoglycerate (2,3-DPG) concentration. Autotransfusion volume ranged from 450-1530 ml per patient (median 824 ml). Shed blood had a mean haemoglobin level of 8.8 g/dl and 7.4 g/dl at 1 h and 6 h of autotransfusion, respectively. There were no significant changes of 2,3-DPG concentration in the patient-blood during cardiopulmonary bypass or after autotransfusion compared to preoperative values. P50 for oxygen (3.6 and 3.6 kPa) and 2,3-DPG concentrations (5.3 and 5.1 mikromol/ml erythrocyte) in shed mediastinal blood (1h and 6h postoperatively) were not significantly different compared to patient-blood. The results demonstrate that the oxygen delivery capacity of shed mediastinal blood is maintained and that the oxygen affinity of patient-blood is not influenced by autotransfusion.

2,3-Diphosphoglycerate↗
PubMed1995

Autotransfusion after open heart surgery: quality of shed mediastinal blood compared to banked blood.

The need to conserve a patient's own blood and avoid homologous transfusion is now well recognized. Therefore, techniques designed to reduce requirements for homologous blood transfusions have been developed. One of the methods is autotransfusion of shed mediastinal blood after open-heart surgery. The objectives of the present study were to investigate osmotic fragility and oxygen transport capacity of shed mediastinal blood compared to patient blood and stored packed red blood cells (SAGM). Shed mediastinal blood from ten consecutive patients undergoing elective cardiac surgery (coronary bypass grafting) was studied and compared to patient blood, 10 units of 3 weeks old and 10 units of 5 weeks old stored packed red blood cells (SAGM). Oxygen transport capacity was investigated by calculation of p50 for oxygen by use of the oxygen status algorithm (OSA 2.0) programme and measurement of 2,3-diphosphoglycerate (2,3-DPG) concentrations. The osmotic fragility was determined using increasing concentrations of saline. 2,3-DPG concentrations in shed mediastinal blood (5.3 mikromol/ml erythrocyte) were within the range measured in patient blood, but significantly higher than SAGM blood (P < 0.001). P50 for oxygen (3.5 kPa) in shed mediastinal blood was not significantly different compared to patient blood, but significantly higher (P < 0.01) compared with stored SAGM blood. The osmotic fragility in shed mediastinal blood was not significantly different compared to patient blood, but significantly lower (P < 0.001) than the osmotic fragility in stored SAGM blood. This suggests that red cells saved from shed mediastinal blood have better oxygen transport capacity and may have longer survival compared to stored blood.

Aged↗
PubMed1995

Molecular analysis of the plasmid-encoded hemolysin of Escherichia coli O157:H7 strain EDL 933.

In this study, we determined the nucleotide sequence of the 5.4-kb SalI restriction fragment of the recombinant plasmid pEO40-1, cloned from the large plasmid of enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain EDL 933. This revealed two open reading frames which shared approximately 60% homology to the hlyC and hlyA genes of the E. coli alpha-hemolysin (alpha-hly) operon. We termed these genes EHEC-hlyA and EHEC-hlyC to distinguish them from the alpha-hly genes. Preliminary sequence analysis indicated that another open reading frame homolog to the hlyB gene is located close to the 3' end of EHEC-hlyA. The predicted molecular masses of the EHEC-hlyA and EHEC-hlyC gene products were 107 and 19.9 kDa, respectively. The EHEC hemolysin protein (EHEC-Hly) was not secreted into the culture supernatant by the strain EDL 933. However, hemolytic activity was found in the broth culture supernatant after transforming EDL 933 with the recombinant plasmid pRSC6 carrying the hlyB and hlyD genes from the E. coli alpha-hemolysin operon. The EHEC hemolysin was precipitated and used as an antigen for immunoblot analysis. This demonstrated that 19 of 20 reconvalescent-phase serum samples from patients with hemolytic uremic syndrome reacted specifically with the antigen; conversely, only 1 of 20 control serum samples demonstrated reactivity. To investigate the prevalence of EHEC hemolysin genes in diarrheagenic E. coli, a PCR was developed to specifically detect EHEC-hlyA. All Shiga-like toxin-producing O157 strains and 12 of 25 Shiga-like toxin-producing non-O157 strains were PCR positive; strains of other categories of diarrheagenic E. coli were PCR negative. All PCR-positive strains hybridized with the CVD 419 probe. We found the CVD 419 probe to be identical to the 3.4-kb HindIII fragment of plasmid pEO40 carrying most of the EHEC-hlyA gene and a part of the putative EHEC-hlyB gene. In this study, the newly discovered EHEC hemolysin was shown to be responsible for the enterohemolytic phenotype and demonstrated to be related but not identical to alpha-hemolysin. The EHEC hemolysin appears to have clinical importance because it occurs in all O157 strains tested and is reactive to sera of patients with hemolytic uremic syndrome.

Acyltransferases↗
PubMed1995

Identification of Actinobacillus actinomycetemcomitans in subgingival plaque by PCR.

The purpose of this study was to assess the sensitivity and specificity of the PCR in detecting Actinobacillus actinomycetemcomitans. The PCR's detection capability was compared with those of three other methods: culture-enhanced PCR (CE-PCR), colony hybridization (CH), and conventional culture with presumptive biochemical identification. A 285-bp stretch of the leukotoxin gene lktA of A. actinomycetemcomitans was amplified by PCR with primers TT-15 and TT-16. For CH, the PCR product was labeled with digoxigenin and used as a hybridization probe. Nucleotide sequence analysis of the PCR product of A. actinomycetemcomitans 1D4 and 1664 and three clinical isolates revealed complete homology among the tested strains, with only one base substitution (at position 1344) in comparison with the published sequence. With artificially infected subgingival plaque, the detection limit of PCR for A. actinomycetemcomitans was 10(3) CFU/ml of plaque suspension. Culturing subgingival plaque on tryptic soy-serum-bacitracin-vancomycin agar prior to PCR (CE-PCR) improved the limit of detection to 10(2) CFU/ml. Analysis of subgingival plaque samples from 35 patients with periodontal disease and 10 periodontally healthy subjects revealed that CE-PCR and CH had the highest overall rate of A. actinomycetemcomitans detection (both 58%), followed by PCR and culture (both 42%). With CH as the "gold standard", the sensitivities of CE-PCR, PCR, and culture were 88, 65, and 58%, respectively; the specificities were 84, 89, and 79%, respectively. The CE-PCR provided acceptable positive and negative predictive values (> or = 70%) when the prevalence of A. actinomycetemcomitans varied between 30 and 70%. PCR alone provided comparable predictive values over a narrower range of prevalence rates (30 to 50%), while culture did not afford acceptable predictive values at any prevalence rate. PCR and CE-PCR were found to be superior to culture with presumptive biochemical identification and should be the preferred methods for the detection of A. actinomycetemcomitans in subgingival plaque.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

Development of PCR for screening of enteroaggregative Escherichia coli.

In this study, we determined the sequence of the EcoRI-PstI fragment of the plasmid pCVD432, also termed the enteroaggregative Escherichia coli (EAggEC) probe. A primer pair complementary to this probe was designed for PCR amplification of a 630-bp region. Comparison of the analysis of the EAggEC probe sequence with those in database libraries revealed no significant similarity to any known bacterial gene. Pure cultures of E. coli cells, as well as mixed cultures from stool specimens, were investigated with the PCR assay, the EAggEC probe test, and the adherence test. Of 50 E. coli strains which demonstrated aggregative adherence to HEp-2 cells, 43 (86%) were positive with the EAggEC PCR. All 43 of these strains reacted with the EAggEC probe. Six EAggEC strains gave negative results by both molecular techniques. In contrast, only 4 of 418 (0.96%) strains representing other categories of diarrheagenic E. coli demonstrated a positive PCR result. The PCR was also successful in screening for the presence of EAggEC in enriched cultures grown from stool specimens. Compared with cell culture assays and colony hybridization, our findings revealed that the PCR assay was more rapid, simple, and highly sensitive and can therefore be recommended as a screening method for EAggEC in the clinical laboratory.

Adolescent↗
PubMed1995

Long-term shedding and clonal turnover of enterohemorrhagic Escherichia coli O157 in diarrheal diseases.

To investigate the length of time that Shiga-like toxin-producing Escherichia coli O157 is excreted after the onset of diarrhea, 456 serial stool specimens were obtained from 53 children. E. coli O157 cells were identified by the use of DNA probes followed by agglutination with a specific antiserum. Specimens were collected until three consecutive stool samples (collected within 9 days) were negative for E. coli O157. The median durations of shedding were 13 days (range, 2 to 62 days) in patients with diarrhea or hemorrhagic colitis and 21 days (range, 5 to 124 days) in patients that developed hemolytic uremic syndrome. In 36 (68%) of the patients, only the first culture was O157 positive, and the three cultures that followed were negative. In 7 (13%) of the patients, E. coli O157 cells were shed for more than 32 days after the onset of diarrhea; these long-term shedders were clinically asymptomatic by the end of this period. In 12 patients, one or two serial O157-negative cultures, obtained up to 8 days after a positive culture, were followed by another positive culture. Comparison of the first and last E. coli O157 isolates by pulsed-field gel electrophoresis revealed that in three of the seven long-term shedders, pulsed-field gel electrophoresis types varied. In two cases, a Shiga-like toxin gene was apparently lost during infection. The observation of long-term shedding accompanied by genotypic turnover has epidemiological and diagnostic implications.

Bacterial Toxins↗
PubMed1995

The diagnostic value of urinary pyridinium cross-links of collagen, serum total alkaline phosphatase, and urinary calcium excretion in neoplastic bone disease.

Bone metastases strongly affect skeletal metabolism by both their growth and their paracrine activities. However, so far no specific laboratory marker has been found to signal the spread of neoplastic disease to bone. We performed a cross-sectional study of 153 cancer patients and an equal number of healthy controls matched for sex and age, in which we determined serum levels of calcium and total alkaline phosphatase (TAP) as well as the fasting urinary excretion of calcium (uCa) and of the collagen cross-links pyridinoline (uPYD) and deoxypyridinoline (uDPD). The aim of the study was to analyze the diagnostic validity of the biochemical parameters measured with regard to neoplastic bone involvement. In the cancer group, 98 patients had overt bone metastases, as judged from radiographic and radioisotopic bone imaging. The remaining 55 patients were also in an advanced stage of disease, but there was no evidence of malignant bone involvement. In comparison to healthy controls, patients both with and without metastatic bone disease had significantly higher levels of TAP, uPYD, and uDPD (P < 0.0001). Only in cancer patients with bone metastases was the median serum calcium level higher than in the healthy controls (P < 0.02). uCa was the same in cancer patients and the control group. Within the collective of cancer patients, individuals with skeletal metastases had higher levels of serum calcium (P < 0.05), TAP (P < 0.01), and uPYD and uDPD (both P < 0.0001), than patients without evidence of malignant bone disease. uCa did not differ between the 2 groups of cancer patients. The cancer patients were then stratified into 4 subgroups according to the serum calcium level (< or = 2.6 mmol/L >) and the absence or evidence of bone metastases. This stratification revealed that in patients with bone metastases, uPYD and uDPD levels were similar in normocalcemic and hypercalcemic subjects, whereas in hypercalcemic patients, uCa levels significantly exceeded those in normocalcemic patients. When the efficacy of TAP, uCa, uPYD, and uDPD in discriminating between patients with and without bone metastases was evaluated by use of receiver-operating characteristic curves and stepwise multivariate regression analysis, uPYD was found to have the highest diagnostic validity. Using 50 mumol PYD/mol creatinine (i.e. the upper limit of normal range) as the cut-off level, the sensitivity of uPYD was 88.7%, whereas the specificity was only 41.8% (odds ratio, 5.598; 95% confidence interval, 2.547-12.306).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗