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C Heilmann

Publications and source records attributed to C Heilmann.

At least 55 records · Page 3Linked to original sources
PubMed1997

Results of dosimetric measurements in space missions.

Detector packages consisting of thermoluminescence detectors (TLDs), nuclear emulsions and plastic nuclear track detectors were exposed in different locations inside spacecraft. The detector systems, which supplement each other in their registration characteristics, allow the recording of biologically relevant portions of the radiation field independently. Results are presented and compared with calculations. Dose equivalents for the astronauts have been calculated based on the measurements; they lie between 190 microSv d-1 and 860 microSv d-1.

Astronauts↗
PubMed1997

Effects of sodium channel block with mexiletine to reverse action potential prolongation in in vitro models of the long term QT syndrome.

INTRODUCTION: Recent clinical studies have reported a greater effectiveness of sodium channel block with mexiletine to abbreviate the QT interval in patients with the chromosome 3 variant (SCN5A, LQT3) of the long QT syndrome (LQTS) than those with the chromosome 7 form of the disease (HERG, LQT2), suggesting the possibility of gene-specific therapy for the two distinct forms of the congenital LQTS. Experimental studies using the arterially perfused left ventricular wedge preparation have confirmed these clinical observations on the QT interval but have gone on to further demonstrate a potent effect of mexiletine to reduce dispersion of repolarization and prevent torsades de pointes (TdP) in both LQT2 and LQT3 models. A differential action of sodium channel block on the three ventricular cell types is thought to mediate these actions of mexiletine. This study provides a test of this hypothesis by examining the effects of mexiletine in isolated canine ventricular epicardial, endocardial, and M region tissues under conditions that mimic the SCN5A and HERG gene defects. METHODS AND RESULTS: We used standard microelectrode techniques to record transmembrane activity from endocardial, epicardial, mid-myocardial, and transmural strips isolated from the canine left ventricle. d-Sotalol, an IKr blocker, was used to mimic the HERG defect (LQT2), and ATX-II, which increases late Na channel current, was used to mimic the SCN5A defect (LQT3). d-Sotalol (100 microM) preferentially prolonged the action potential of the mid-myocardial M cell (APD90 increased from 340 +/- 65 to 623 +/- 203 msec) as did ATX-II (10 to 20 nM; APD90 increased from 325 +/- 51 to 580 +/- 178 msec; basic cycle length = 2000 msec), thus causing a marked increase in transmural dispersion of repolarization (TDR). Mexiletine (2 to 20 microM) dose-dependently reversed the ATX-II-induced prolongation of APD90 in all three cell types. Mexiletine also reversed the d-sotalol-induced prolongation of the M cell action potential duration (APD), but had little effect on the action potential of epicardium and endocardium. Due to its preferential effect to abbreviate the action potential of M cells, mexiletine reduced the dispersion of repolarization in both models. Low concentrations of mexiletine (5 to 10 microM) totally suppressed early afterdepolarization (EAD) and EAD-induced triggered activity in both models. CONCLUSIONS: Our results indicate that the actions of mexiletine are both cell and model specific, but that sodium channel block with mexiletine is effective in reducing transmural differences in APD and in abolishing triggered activity induced by d-sotalol and ATX-II. The data suggest that mexiletine's actions to reduce TDR and prevent the induction of spontaneous and programmed stimulation-induced TdP in these models are due to a preferential effect of the drug to abbreviate the APD of the M cell and to suppress the development of EADs. The data provide further support for the hypothesis that block of the late sodium current may be of value in the treatment of LQT2 as well as LQT3 and perhaps other congenital and acquired (drug-induced) forms of LQTS.

Action Potentials↗
PubMed1997

Detection of the intercellular adhesion gene cluster (ica) and phase variation in Staphylococcus epidermidis blood culture strains and mucosal isolates.

Staphylococcus epidermidis is a common cause of catheter-associated infections and septicemia in immunocompromised patients. To answer the question whether S. epidermidis skin isolates differ from isolates causing septicemic diseases, 51 strains obtained from blood cultures, 1 strain from shunt-associated meningitis, and 36 saprophytic isolates were characterized. The study demonstrates that most of the blood culture strains formed a multilayered biofilm on plastic material, whereas skin and mucosal isolates did not. Moreover, biofilm-producing strains were found to generate large bacterial autoaggregates in liquid culture. Autoaggregation and biofilm formation on polymer surfaces was associated with the presence of a DNA sequence encoding an intercellular adhesion gene cluster (ica) that mediates the production of a polysaccharide intercellular adhesin. The presence of the intercellular adhesion genes in blood culture isolates was also found to be correlated with the exhibition of black colonies on Congo red agar, whereas the adhesin-negative strains formed red colonies. Upon subcultivation on Congo red agar, the black colony forms of the blood culture strains exhibited red colony variants which were biofilm and autoaggregation negative and occurred at a frequency of 10(-5). The DNA analysis of these S. epidermidis variants by pulsed-field gel electrophoresis and Southern hybridization with an ica-specific gene probe revealed no detectable difference between the black and red colony types. Moreover, after repeated passage, the phenotype of the parent strain could be restored. Therefore, these colony forms were regarded as phase variants. This phenotypic change was observed exclusively in adhesin-positive clinical isolates and not in adhesin-negative saprophytic strains of S. epidermidis.

Bacteremia↗
PubMed1997

A site-directed Staphylococcus aureus hemB mutant is a small-colony variant which persists intracellularly.

Although small-colony variants (SCVs) of Staphylococcus aureus have been recognized for many years, this phenotype has only recently been related to persistent and recurrent infections. Clinical S. aureus SCVs are frequently auxotrophic for menadione or hemin, two compounds involved in the biosynthesis of the electron transport chain elements menaquinone and cytochromes, respectively. While this observation as well as other biochemical characteristics of SCVs suggests a link between electron-transport-defective strains and persistent infections, the strains examined thus far have been genetically undefined SCVs. Therefore, we generated a stable mutant in electron transport by interrupting one of the hemin biosynthetic genes, hemB, in S. aureus by inserting an ermB cassette into hemB. We isolated a hemB mutant, due to homologous recombination, by growth at a nonpermissive temperature and selection for erythromycin resistance. This mutant showed typical characteristics of clinical SCVs, such as slow growth, decreased pigment formation, low coagulase activity, reduced hemolytic activity, and resistance to aminoglycosides. Additionally, the mutant was able to persist within cultured endothelial cells due to decreased alpha-toxin production. Northern and Western blot analyses showed that expression of alpha-toxin and that of protein A were markedly reduced, at both the mRNA and the protein level. The SCV phenotype of the hemB mutant was reversed by growth with hemin or by complementation with intact hemB. Hence, a defect in the electron transport system allows S. aureus SCVs to resist aminoglycosides and persist intracellularly.

Aminoglycosides↗
PubMed1996

The progeny of a single virgin B cell predominates the human recall B cell response to the capsular polysaccharide of Haemophilus influenzae type b.

Restricted V region diversity is a key feature of Abs to many haptens and simple polysaccharides. Two possible mechanisms exist: 1) selection of many clonally unrelated B cells using very similar or identical VDJ and VJ rearrangements; and 2) selection of a heavily expanded progeny of few virgin B cells. How many virgin B cells eventually give rise to the total Ab response to a simple Ag is a fundamental immunologic question. In this report, we address this question in human adults by analyzing the rearranged VkappaJkappa genes of B cells responding to a single dose of the capsular polysaccharide of Haemophilus influenzae type b coupled to tetanus toxoid. We combined affinity purification of circulating vaccine-induced Ab-secreting cells with PCR amplification of cDNA followed by cloning and sequencing. Forty-eight and 42 kappa VJ gene transcripts were analyzed from two adults, respectively. Both individuals used extremely restricted repertoires with >90% of the cells using a single Vkappa gene rearranged to a single Jkappa gene. Despite the fact that the Ab responses engaged high numbers of Ab-secreting cells, analysis of the many shared, somatically acquired mutations showed that the majority of the cells originated from a common virgin B cell. Kinetic considerations implied that an extremely selected population of hypermutated memory B cells must have existed in these individuals before the first systemic immunization with the Ag. A possible role for the mucosal immune system in the priming and selection of these cells is proposed.

Adult↗
PubMed1996

Partial characterization of a new nucleotide binding glycoprotein of hepatocyte plasma membrane.

Hepatocyte plasma membranes contain a glycosylated 230-kDa Ca(2+) -dependent, Mg(2+)-stimulated ATPase (pgp230), which consists of two subunits, one of 120 kDa and the other of 110 kDa. pgp230 can be enriched by the use of affinity chromatography on Concanavalin A-Sepharose, wheat germ lectin-Sepharose, and 5'-AMP-Sepharose. It has a high-affinity Ca2+ binding site. In the presence of Ca2+, it forms a phosphorylated intermediate by autocatalytic transfer of the terminal phosphate residue from ATP. Maximal Ca(2+)-dependent autophosphorylation is observed at pH 5-6. Photoaffinity labeling using 8-azido-[alpha-32P]ATP or [y-32P]ATP confirms the presence of ATP binding sites. Incubation with [alpha-32P]ATP leads to a rapid but transient labeling of pgp230. Various nucleotides, nucleotide receptor agonists, or antagonists inhibit Ca(2+)-dependent phosphorylation by [y-32P]ATP. The concentrations of half-maximal inhibition range from 10(-7) M to 10(-3) M. The rank order of inhibitory potency is: ATP > alpha,beta-methylene-ATP > CTP = TTP > y-4-amino-phenyl-ATP = 2-methyl-thio-ATP > UTP = GTP > GDP = ADP = beta,y-methylene-ATP = beta, y-methylene-TTP = beta,y-methylene-GTP = adenosine-5'-O-2-thiodiphosphate = CMP = AMP > adenosine > cytidine > guanosine = suramin > Reactive blue 2 > iso-butyl-methyl-xanthine > thymidine > uridine. These data suggest a nucleotide binding capacity of this new hepatocyte membrane glycoprotein. Further investigations should be carried out to reveal its biological function.

Adenosine Triphosphate↗
PubMed1996

Dosimetry on the Spacelab missions IML1 and IML2, and D2 and on MIR.

Detector packages consisting of plastic nuclear track detectors, nuclear emulsions, and thermoluminescence detectors were exposed inside BIORACK during the Spacelab missions IML1 and IML2, in different sections of the MIR space station, and inside the Spacelab module at rack front panels or stowage lockers and in the Spacelab tunnel during D2. In addition, during D2, each Payload Specialist (PS) has worn three permanent detector packages; one at the neck; one at the waist; and one at the ankle. Total dose measurements, particle fluence rate and LET spectra, number of nuclear disintegrations and neutron dose from this exposure are given in this report. The results are compared to theoretical calculations and to previous missions results. The dose equivalent (total radiation exposure) received by the PSs were calculated from the measurements and range from 190 to 770 microSv d-1. Finally, a cursory investigation of results from a particle telescope from two silicon detectors, first used in the last BIORACK mission on STS76, is reported.

Atlantic Ocean↗
PubMed1996

Antibody response to Haemophilus influenzae type b capsular polysaccharide conjugated to tetanus toxoid in preterm infants.

OBJECTIVE: To evaluate the antibody response to a Haemophilus influenzae type b capsular polysaccharide (HibCP) tetanus toxoid (TT) conjugate vaccine (HibCP-TT) in preterm infants. SUBJECTS: Thirty-five healthy preterm infants with gestational ages (GA) from 27 to 36 weeks and birth weights from 920 to 2550 g. Controls were 37 term infants. METHODS: All infants were immunized with HibCP-TT at 2, 4 and 12 months of age. Antibodies to HibCP and TT were determined at each immunization and 1 month after the second and third. RESULTS: After two doses of HibCP-TT the preterm infants with GAs < or = 30 weeks (n = 8; mean GA, 29.5 weeks) had a significantly lower HibCP antibody response than the preterm infants with GAs > 30 weeks (n = 23; mean GA, 34.2 weeks) (P = 0.004), who for their part had a response not significantly different from that of the term infants. After the third dose there were no significant differences among the groups. The response to the TT part of the vaccine showed the same pattern. CONCLUSION: Although the most immature infants may show an inadequate antibody response to the initial immunizations, many preterm infants can benefit from vaccination with HibCP-TT when starting immunization at the same chronologic age as term infants.

Antibodies, Bacterial↗
PubMed1996

Molecular basis of intercellular adhesion in the biofilm-forming Staphylococcus epidermidis.

The Staphylococcus epidermidis genes icaABC are involved in the synthesis of the polysaccharide intercellular adhesin (PIA), which is located mainly on the cell surface, as shown by immunofluorescence studies with PIA-specific antiserum. PIA was shown to be a linear beta-1,6-linked glucosaminoglycan composed of at least 130 2-deoxy-2-amino-D-glucopyranosyl residues of which 80-85% are N-acetylated, the rest being non-N-acetylated and positively charged. A transposon insertion in the icaABC gene cluster (ica, intercellular adhesion) led to the loss of several traits, such as the ability to form a biofilm on a polystyrene surface, cell aggregation, and PIA production. The mutant could be complemented by transformation with the icaABC-carrying plasmid pCN27. Transfer of pCN27 into the heterologous host Staphylococcus carnosus led to the formation of large cell aggregates, the formation of a biofilm on a glass surface, and PIA expression. The nucleotide sequence of icaABC suggests that the three genes are organized in an operon and that they are co-transcribed from the mapped icaA promoter. IcaA contains four potential transmembrane helices, indicative of a membrane location. The deduced IcaA sequence shows similarity to those of polysaccharide-polymerizing enzymes, the most pronounced being with a Rhizobium meliloti N-acetylglucosaminyltransferase involved in lipo-chitin biosynthesis (22.5% overall identity and 37.4% overall similarity). This similarity suggests that IcaA has N-acetylglucosaminyltransferase activity in the formation of the beta-1, 6-linked N-acetyl-D-glucosaminyl polymer. IcaB is secreted into the medium and contains a typical signal peptide. IcaC is hydrophobic and contains six predicted transmembrane helices distributed over its entire length, typical for an integral membrane protein. Neither IcaB nor IcaC shares similarity with known proteins, and their function is unknown. Inactivation of icaA, icaB, or icaC in pCN27 led to the complete loss of the intercellular adhesion phenotype in S. carnosus, suggesting that all three genes are involved in intercellular adhesion, PIA expression, and translocation.

Bacterial Adhesion↗
PubMed1996

Characterization of Tn917 insertion mutants of Staphylococcus epidermidis affected in biofilm formation.

Biofilm formation is thought to result from the concerted action of primary attachment to a specific surface and accumulation in multilayered cell clusters. Here we describe the isolation and characterization of transposon (Tn917) mutants of Staphylococcus epidermidis O-47 which were biofilm negative in the polystyrene microtiter plate assay. Among 5,000 Tn917 insertion mutants, 4 biofilm-negative mutants were isolated. Each mutant carried one copy of Tn917. The mutants were divided into two phenotypic classes: class A (mut1 and mut1a) and class B (mut2 and mut2a). Mutants of phenotypic class A lacked four cell surface proteins, were less hydrophobic, and were affected in primary attachment to polystyrene, but were still able to form multilayered cell clusters. They were able to form a biofilm on a glass surface, a trait that was even more pronounced than in the wild-type stain O-47. Loss of several surface proteins might have led to the reduced surface hydrophilic structures, thus favoring primary attachment to a glass surface and leading to subsequent biofilm formation. Mutants of phenotype class B were able to attach to polystyrene but were unable to form multilayered cell clusters, had unchanged cell surface proteins and hydrophobicity, and were unable to form a biofilm on a glass surface, mut1 and mut2 could be complemented by wild-type DNA fragments containing the Tn917 insertion sites of mut1 and mut2, respectively. The complemented biofilm-positive clone mut1 (pRC20) produced a 60-kDa protein which is postulated to function as the adhesin for binding to plastic. The traits of binding to polystyrene and the ability to form multilayered cell clusters are phenotypically and genetically distinct.

Animals↗
PubMed1996

Outcome for patients with leukemia, multiple myeloma and lymphoma who relapse after high dose therapy and autologous stem cell support.

Relapses after autologous transplantation are a serious clinical problem in patients with haematological diseases. The decision making for handling of such patients is difficult and the aim of this retrospective analysis of posttransplant relapses was 1) to obtain information of practical importance for the management of future relapses and 2) to evaluate the basis for clinical phase I-II trials of salvage therapy combined with biological modifiers. Included in the study were 283 patients with acute leukemia, multiple myeloma and malignant lymphoma who relapsed after autologous transplantations during a five year period from 1989 to 1994. Chemo- and radiotherapy was given to 229 patients after relapse or due to progressive disease and the response evaluated after 90 days. Fifty four patients (24%) obtained a complete remission and 44 patients (19%) partial responses. The overall median survival from relapse was 5 months. In the group given salvage treatment the median survival was 7 months and in the 54 patients who obtained remission the median survival was 15 months. So far 6 of 14 patients in continuous complete remission have a remission time after relapse longer than the time in remission after transplantation. Survival after relapse depended upon the time from transplantation to relapse, primary disease and if salvage therapy was given. In conclusion posttransplant relapses can be treated but the strategy has to be evaluated in future clinical trials.

Adolescent↗
PubMed1996

Treatment of relapse after allogeneic BMT with donor leukocyte infusions in 16 patients.

Sixteen patients with relapse after allogeneic BMT were treated with donor leukocyte infusions (DLI) from the original donor. The diagnoses at relapse were: CML in chronic phase (CP) (two patients), CML in accelerated phase (AP) (four patients), AML (four patients), MDS (one patient), ALL (four patients) and relapse of Hodgkin's disease (one patient). The patients received a mean of 5.2 x 10(8) leukocytes/kg with a range of 1.4-12.3 x 10(8) leukocytes/kg. Six patients obtained complete remission (CR), one with CML in CP, three with CML in AP, one MDS and one ALL. Partial remission (PR) was seen in three patients, one patient with CML in AP, one with AML and one with Hodgkin's disease. Seven patients had no response (NR) to the infusions, including one patient with CML in CP transplanted with a syngeneic donor. Four patients developed marrow hypoplasia after DLI (three CR and one PR) and two patients (ALL with CR and MDS with CR) were hypoplastic at relapse and marrow hypoplasia continued after DLI. GVHD occurred without GVL, but GVL only occurred in one patient with absence of GVHD. Eleven patients died of leukemia, six patients are alive. Three patients with CML are in CR 12, 12 and 32 months after DLI and one patient with ALL is in CR 15 months after DLI.

Adolescent↗
PubMed1995

Identification of the Zn2+ binding region in calreticulin.

Calreticulin binds Zn2+ with the relatively high affinity/low capacity. To determine the location of the Zn2+ binding site in calreticulin different domains of the protein were expressed in E. coli, using the glutathione S-transferase fusion protein system, and their Zn(2+)-dependent interaction with Zn(2+)-IDA-agarose were determined. Three distinct domains were used in this study: the N + P-domain (the first 290 residues); the N-domain (residues 1-182) and the proline-rich P-domain (residues 180-273). The N + P-domain bound to the Zn(2+)-IDA-agarose and were eluted with an increasing concentration of imidazole. The N-domain also bound 65Zn2+ as measured by the overlay method. The P-domain did not interact with the Zn(2+)-IDA-agarose and it did not bind any detectable amount of Zn2+. Chemical modification of calreticulin with diethyl pyrocarbonate indicated that five out of seven histidines were protected in the presence of Zn2+ but they were modified by diethyl pyrocarbonate in the absence of Zn2+ suggesting that these residues may be involved in Zn2+ binding to calreticulin. We conclude that Zn2+ binding sites in calreticulin are localized to the N-domain of the protein, region that is not involved in Ca2+ binding to calreticulin.

Binding Sites↗
PubMed1995

Alterations of sarcoplasmic reticulum proteins in failing human dilated cardiomyopathy.

BACKGROUND: Previous studies provide considerable evidence that excitation-contraction coupling may be disturbed at the level of the sarcoplasmic reticulum (SR) in the failing human heart. Disturbed SR function may result from altered expression of calcium-handling proteins. METHODS AND RESULTS: Levels of SR proteins involved in calcium release (ryanodine receptor), calcium binding (calsequestrin, calreticulin), and calcium uptake (calcium ATPase, phospholamban) were measured by Western blot analysis in nonfailing human myocardium (n = 7) and in end-stage failing myocardium due to dilated cardiomyopathy (n = 14). The levels of the ryanodine receptor, calsequestrin, and calreticulin were not significantly different in nonfailing and failing human myocardium. Phospholamban protein levels (pentameric form) normalized per total protein were decreased by 18% in the failing myocardium (P < .05). However, phospholamban protein levels were not significantly different in failing and nonfailing myocardium when normalization was performed per calsequestrin. Protein levels of SR calcium ATPase, normalized per total protein or per calsequestrin, were decreased by 41% (P < .001) or 33% (P < .05), respectively, in the failing myocardium. Furthermore, SR calcium ATPase was decreased relative to ryanodine receptor by 37% (P < .05) and relative to phospholamban by 28% (P < .05). CONCLUSIONS: Levels of SR proteins involved in calcium binding and release are unchanged in failing dilated cardiomyopathy. In contrast, protein levels of calcium ATPase involved in SR calcium uptake are reduced in the failing myocardium. Moreover, SR calcium ATPase is decreased relative to its inhibitory protein, phospholamban.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1995

[Vaccine against Haemophilus influenzae type b--antibody response and adverse effects].

In 1992 it was decided to implement vaccination against Haemophilus influenzae type b (Hib) in the Norwegian vaccination programme. The chosen vaccine consists of Hib-polysaccharide conjugated to tetanus toxoid. To suit the Norwegian vaccination schedule, Hib-vaccine was given together with vaccine against diphtheria, tetanus and pertussis (DTP) at three, five and ten months of age. Since all earlier studies with the Hib-vaccine have used other time schedules, a pilot study was conducted to test antibody response and side effects when using the Norwegian schedule. 44 infants were vaccinated with Hib-vaccine and DTP at three, five and ten months of age. Blood samples showed that 95% had protective antibody titer against Hib after two doses, 100% after three. The response to the other antigens was adequate. There were only minor side effects. After introduction of the Hib-vaccine the incidence of invasive Hib-infection in children below three years of age has decreased considerably.

Antibodies, Viral↗
PubMed1995

Zn2+ binding to cardiac calsequestrin.

Zn2+ binding to canine cardiac calsequestrin was investigated using the Zn2+ specific fluorescence dye salicylcarbohydrazone (SACH), 65Zn2+ overlay and Zn(2+)-IDA chromatography. Cardiac calsequestrin binds approximately 200 moles of Zn2+/mole of protein with the Kd = 300 microM. Zn2+ binding to calsequestrin was further confirmed by 65Zn2+ overlay and Zn(2+)-dependent aggregation of the protein. However, calsequestrin did not bind to a Zn(2+)-IDA-agarose column, indicating that histidine residues may not be involved in Zn2+ binding to the protein. Circular dichroism revealed only minor Zn(2+)-dependent conformational changes in calsequestrin. We conclude that calsequestrin is a Ca(2+)- and Zn(2+)-binding protein and that Zn2+ may modulate the structure and function of the protein.

Animals↗