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Biomedical subjects

M Schreiber

Publications and source records attributed to M Schreiber.

At least 19 recordsLinked to original sources
PubMed1992

Localisation of hypoxanthine phosphoribosyl transferase in the malaria parasite Plasmodium falciparum.

The enzyme hypoxanthine phosphoribosyl transferase of the human malaria parasite Plasmodium falciparum has been located in parasites and parasite-infected erythrocytes by antibody probing. The probe was a polyclonal rabbit antiserum made against the parasite enzyme made in Escherichia coli. The enzyme is associated with membrane-bound compartments in merozoites and asexual blood parasites. In particular, indirect immunofluorescence studies reveal the enzyme localized in vesicle-like structures within the cytoplasm of the infected erythrocyte. This is the first time a P. falciparum protein of defined metabolic function has been tracked to a site outside the parasite cytosol. Studies on the targeting of the enzyme using a cell-free system suggests that the protein reaches its destination via a route different from the normal secretory pathway.

Amino Acid Sequence↗
PubMed1992

Sensitive and specific serodiagnosis of invasive amebiasis by using a recombinant surface protein of pathogenic Entamoeba histolytica.

A recombinantly expressed protein, recEh-P1, representing part of an immunodominant surface antigen of pathogenic Entamoeba histolytica, was used for serodiagnosis of invasive amebiasis. Expression was performed under the control of a T7-RNA promoter by using a modified procaryotic expression vector, designated pHisT7. This vector allowed high-yield expression of recEh-P1 fused to a stretch of sequence containing eight histidine residues, which facilitated purification by metal chelate affinity chromatography on Ni2+ columns under highly denatured conditions. Purified recEh-P1 was found to be water soluble after prolonged dialysis and was used as the antigen for the detection of antiamebic serum antibodies by immunoblotting and enzyme-linked immunosorbent assay. In both tests all sera of patients with invasive amebiasis reacted to recEh-P1 whereas none of those collected from healthy controls, including individuals with noninvasive amebiasis, or from patients suffering from bacterial or protozoan infections unrelated to E. histolytica did so.

Amino Acid Sequence↗
PubMed1992

Intermolecular cleavage of hepatitis A virus (HAV) precursor protein P1-P2 by recombinant HAV proteinase 3C.

Active proteinase 3C of hepatitis A virus (HAV) was expressed in bacteria either as a mature enzyme or as a protein fused to the entire polymerase 3D or to a part of it, and their identities were shown by immunoblot analysis. Intermolecular cleavage activity was demonstrated by incubating in vitro-translated and radiolabeled HAV precursor protein P1-P2 with extracts of bacteria transformed with plasmids containing recombinant HAV 3C. Identification of cleavage products P1, VP1, and VPO-VP3 by immunoprecipitation clearly demonstrates that HAV 3C can cleave between P1 and P2 as well as within P1 and thus shows an activity profile similar to that of cardiovirus 3C.

Capsid↗
PubMed1992

Concentrations in serum of IgG, IgM and IgA and their age-dependence in beagle dogs as determined by a newly developed enzyme-linked-immuno-sorbent-assay (ELISA).

The concentrations of immunoglobulins IgG, IgM and IgA and their age dependence were determined in the serum of normal, untreated beagle dogs by a newly developed sandwich enzyme-linked-immuno-sorbent-assay (ELISA). A clear age-dependent increase between approximately 0.8 and 1.6 years of age was observed for the immunoglobulin IgA, whereas IgG and IgM showed only a slight tendency to an age-dependent increase. For immunotoxicological characterization of various compounds especially in long term studies, this IgA age-dependence has to be considered in the planning and interpretation of studies with beagle dogs.

Age Factors↗
PubMed1992

Protective effects of diltiazem and the prostazycline analogue iloprost in human renal transplantation.

To test the hypothesis that calcium antagonists decrease the incidence and severity of delayed graft function, we conducted three separate, prospective, randomized trials. In these trials, we investigated the effects of diltiazem and those of the prostacycline analogue iloprost. In the first study, 22 control patients and 20 diltiazem patients received grafts perfused with either vehicle or diltiazem 20 mg/L in the Euro-Collins solution. Subsequently, the diltiazem subjects were given the drug as a bolus of 0.28 mg/kg, followed by a continuous infusion of 0.002 mg/min/kg for the following 2 days. Thereafter, diltiazem 60 mg was given to the treated subjects orally for up to 4 years. In the second study, 11 control subjects and 10 diltiazem subjects received the same postoperative regimen, but all grafts were harvested without addition of diltiazem to the perfusion solution. In the third protocol, four groups were studied as follows: 19 control subjects who received no specific treatment, 16 subjects who received diltiazem, 16 subjects who were given iloprost, and 14 subjects who received both iliprost and diltiazem. The donor kidney of treated patients was perfused with either diltiazem, iloprost, or both drugs. Primary graft function occurred more commonly in the groups receiving diltiazem. Further, in the first study the number of hemodialyses per patient was reduced in those patients with delayed graft function. Fewer rejection episodes occurred in patients receiving diltiazem. Plasma levels of soluble interleukin-2 receptors decreased significantly during diltiazem treatment. Moreover, renal biopsies showed less severe signs of cyclosporin-A (CyA) nephrotoxicity in diltiazem-treated patients compared to controls, even though these patients also exhibited higher CyA trough levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1992

Protective effect of ascorbic acid in high altitude hypoxia in the rat.

Control (physiological saline treated) and ascorbic acid (AA) treated (1 mg.g-1 b.w. one hour before exposure) 18-day-old rats were exposed for 1 hour to high altitude in a hypobaric chamber and the mean lethal altitudes were calculated. AA displayed a protective effect, so that in two identical experiments the mean lethal altitude was 10,900 and 10,150 m in controls, while it was 11,500 and 11,450 m in AA treated animals.

Altitude Sickness↗
PubMed1992

Protective effects of calcium antagonists in human renal transplantation.

To test the hypothesis that calcium antagonists decrease the incidence and severity of delayed graft function, we conducted three separate, prospective, randomized trials. In these trials, we investigated the effects of diltiazem and those of the prostacyclin analogue iloprost. In the first study, 22 control patients and 20 diltiazem patients received grafts perfused with either vehicle or diltiazem 20 mg/liter in the Euro-Collins solution. Subsequently, the diltiazem subjects were given the drug as a bolus of 0.28 mg/kg, followed by a continuous infusion of 0.002 mg/min/kg for the following two days. Thereafter, diltiazem 60 mg was given to the treated subjects orally for up to four years. In the second study, 11 control subjects and 10 diltiazem subjects received the same postoperative regimen, but all grafts were harvested without addition of diltiazem to the perfusion solution. In the third protocol, four groups were studied as follows: 19 control subjects who received no specific treatment, 16 subjects who received diltiazem, 16 subjects who were given iloprost, and 14 subjects who received both iloprost and diltiazem. The donor kidney of treated patients was perfused with either diltiazem, iloprost, or both drugs. Primary graft function occurred more commonly in the groups receiving diltiazem. Further, in the first study the number of hemodialyses per patient was reduced in those patients with delayed graft function. Fewer rejection episodes occurred in patients receiving diltiazem. Plasma levels of soluble interleukin-2 receptors decreased significantly during diltiazem treatment. Moreover, renal biopsies showed less severe signs of Cyclosporin A (CsA) nephrotoxicity in diltiazem-treated patients compared to controls, even though these patients also exhibited higher CsA trough levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1992

Detection of Bartonella bacilliformis in cultures, blood, and formalin preserved skin biopsies by use of the polymerase chain reaction.

A polymerase chain reaction (PCR) is described for the detection of Bartonella bacilliformis, the etiologic agent of bartonellosis, which cannot be identified biochemically. Amplification of a genomic 231 bp Bartonella DNA sequence permitted specific identification of 12 Bartonella isolates from Peruvian bartonellosis patients as well as detection of Bartonella DNA in blood samples and formaldehyde preserved skin biopsies. Specificity of amplification products was confirmed by restriction fragment analysis. No positive results were obtained with Brucella abortus, phylogenetically closely related to B. bacilliformis, and several other bacterial, fungal, and protozoal species. PCR appears as a promising technique for specific identification of B. bacilliformis in cultures and in clinical materials with further applications in taxonomic studies and in the investigation of Bartonella-like isolates obtained outside South America.

Bacteremia↗
PubMed1992

[A study of the parameters of the delivered tidal volume. Ventilation on a lung model using the CICERO anesthetic ventilator].

In many anaesthesia ventilators in common use, the tidal volume delivered is different from the tidal volume preset on the respirator. Tidal volume delivered by mechanical ventilation during anaesthesia may be influenced by fresh gas flow (FGF), the respiratory rate (RR) or the inspiratory: expiratory ratio (I:E). This may cause inadequate hypo- or hyperventilation in small children, especially in newborns and neonates. Using small tidal volumes from 20 to 100 ml preset on the respirator, we investigated in a lung model the tidal volumes delivered by the anaesthesia ventilator CICERO (Dräger, FRG) with variations of FGF, RR and I:E. MATERIAL AND METHODS. The anaesthesia ventilator CICERO (software version 4.16) was equipped with the low-compliance tubes of the "Ulmer Kinder-Set" (Rüsch Co.) and the regular CO2 canister (1500 ml) of the machine. The circuit was connected to a lung model consisting of a glass clyinder filled with copper wool with a compliance of 3.3 ml/mbar. To create a pressure-volume correlation of the entire system, i.e. the lung model, the anaesthesia circuit and the ventilator, calibrated glass syringes were used and the pressure increase in the test lung was measured. This pressure-volume correlation was linear. The pressure increase in the lung model caused by the tidal volume during ventilation therefore reflected the actual tidal volume delivered. The study was performed with small tidal volumes from 20 to 100 ml that could be adjusted exactly on the ventilator. Delivered tidal volumes were studied by varying the FGF from 1 to 6 l/min and the RR from 20 to 60/min (with I:E = 1:1.5) and by varying the RR from 20 to 60/min and the I:E from 2:1 to 1:3 (with FGF = 21/min). RESULTS. By varying FGF, RR and I:E no changes in delivered tidal volumes were noted. In all settings of the ventilator studied, the delivered tidal volume was similar to the desired tidal volume preset on the ventilator. The highest deviation from the delivered tidal volume to the tidal volume preset was 17.5% with a tidal volume of 20 ml. In preset tidal volumes 30-100 ml this deviation was lower than 10%. An intermittent "auto-PEEP" up to 5 mbar was noted during high respiratory rates (50 and 60/min) combined with an I:E at 2:1 and 1:1 or with a FGF at 4 or 6 l/min. The compliance of the ventilator equipped with the circuit was 4.2 ml/mbar. CONCLUSION. The findings in this study prove that with tidal volumes ranging from 20 to 100 ml the actual tidal volume delivered by the anaesthesia ventilator CICERO is equivalent to the tidal volume set on the machine regardless of the variation of FGF, RR and I:E. These findings are mainly based on two circumstances. Firstly, fresh gas flow is fed into a reservoir and not added to the volume delivered by the bellow during inspiration as in many other respirators. Secondly, the CICERO works with a compliance correction function integrated into the machine. Computed compressible volume from the circuit and the ventilator is added to the tidal volume preset on the ventilator; therefore, the volume delivered by the bellow consists of the volume set on the ventilator plus the compressible volume. With these characteristics the anaesthesia ventilator CICERO meets important requirements for a ventilator in paediatric anaesthesia. However, for final assessment further clinical studies are required.

Anesthesiology↗
PubMed1991

Yolk polypeptide gene expression in cultured Drosophila cells.

The transfer of chimaeric plasmids to Drosophila melanogaster cell lines has been examined as a system for investigation of the hormonal regulation of the genes coding for D. melanogaster yolk polypeptide 1 (YP1) and Locusta migratoria vitellogenin B (VgB). Constructs containing promoters and putative 5'-regulatory sequences from these genes, ligated to bacterial chloramphenicol acetyltransferase (CAT) coding DNA, were transfected into Drosophila Kc (Kc-H) and S3 cells, and transient expression of CAT was assayed. Activity was expressed both from the homologous promoter of pYP1CAT and from the heterologous locust promoter of pVgCAT at comparable levels. In S3 cells, with calcium phosphate-mediated transfer of pYP1CAT there was a twofold induction of CAT activity after the addition of 10(-6) M ecdysterone, but no hormonal stimulation was noted when the polycation polybrene was used to achieve transfection. For Kc cells, calcium phosphate was ineffective for transfection, and after transfection with polybrene neither pYP1CAT nor pVgCAT was induced by the juvenile hormone (JH) analog methoprene. It is concluded that S3 cells may be useful for investigating the molecular basis of gene regulation by ecdysteroids, but conditions suitable for the analysis of JH action have not yet been established.

Animals↗
PubMed1991

Myxoma virus expresses a secreted protein with homology to the tumor necrosis factor receptor gene family that contributes to viral virulence.

Poxviruses are known to contain a large number of open reading frames, particularly near the termini of the viral genome, that are not required for growth in tissue culture. However, many of these gene products are believed to play important roles in determining the virulence of the virus by modulating the host immune response to the infection. Recently it has been shown that Shope fibroma virus encodes, within the terminal inverted repeats, a protein (T2) related to the cellular tumor necrosis factor receptor (TNFR) and which specifically binds both TNF alpha and TNF beta. We have sequenced the terminal regions of two other Leporipoxviruses (myxoma virus and malignant rabbit fibroma virus) that are extremely invasive and capable of inducing extensive immunosuppression in rabbits and demonstrate that they also encode a closely related T2 homolog with all the structural motifs predicted for a secreted TNF binding protein. To investigate the biological role of the T2 protein, we have inactivated the myxoma virus T2 gene within each copy of the viral TIR by the insertion of a dominant selectable marker (Escherichia coli guanosine phosphoribosyltransferase) and selection of the recombinant virus in the presence of mycophenolic acid. The success of the inactivation of both copies of T2 was confirmed by the loss a broad protein band (52-56 kDa) of the predicted size for T2 from the profile of proteins secreted from mutant virus-infected BGMK cells at early times after infection. Although the T2-minus recombinant myxoma virus grew normally in tissue culture, upon infection of susceptible rabbits the viral disease was observed to be significantly attenuated. The majority of infected rabbits were able to mount an effective immune response to the infection and completely recovered. These survivor rabbits became immune to subsequent challenge with wild type myxoma virus. We conclude that the T2 viral protein is an important secreted virulence factor and that it in all likelihood functions by compromising the antiviral effects of TNF. We propose the term "viroceptor" to describe viral-encoded homologs of cellular lymphokine receptors whose function is to intercept the activity of the cognate lymphokine in order to short circuit the host immune response to the viral infection.

Amino Acid Sequence↗
PubMed1991

The target DNA sequence for resolution of poxvirus replicative intermediates is an active late promoter.

The linear double-stranded genomes of poxviruses such as Shope fibroma virus (SFV) replicate autonomously within the cytoplasm of infected cells, and it is believed that all of the replication functions are virally encoded. During DNA replication the incompletely base-paired terminal hairpin loops of the viral genome transiently exist in the form of inverted repeat replicative intermediates. These inverted repeat structures form the target for telomere resolution events that include sequence-specific cleavage and directed strand exchange to form the hairpin termini of progeny virus genomes. The terminal sequence domain which forms the telomere resolution target (TRT) shares considerable sequence similarity with viral late promoters. In this study we demonstrate that the TRT of SFV is capable of functioning as a strong viral promoter late in infection. A spectrum of TRT mutations affects telomere resolution and late transcription in a strictly concordant fashion, suggesting that the two activities may be inextricably linked. Further support for this concept comes from the demonstration that a late SFV promoter sequence designated cryptic TRT, which differs substantially from the native TRT in terms of sequence, can support telomere resolution when placed in the correct spatial context. The proposed model for telomere resolution invokes directed unwinding of the TRT double helix by a transcription initiation complex and processing of the resulting secondary structure by viral late-gene products.

Animals↗
PubMed1991

[Patient-controlled analgesia versus epidural analgesia using bupivacaine or morphine following major abdominal surgery. No difference in postoperative morbidity].

In 1987, Yeager et al. reported that intraoperative epidural anesthesia with local anesthetics and postoperative epidural analgesia with opiates diminished postoperative morbidity. In our first clinical trial on this topic, the better postoperative analgesia with epidural bupivacaine-fentanyl failed to improve the outcome after major abdominal operations over that obtained with parenteral piritramide. This randomized controlled investigation was designed to assess whether intraoperative epidural anesthesia with bupivacaine plus light general anesthesia and postoperative epidural analgesia with morphine would diminish the overall rate of postoperative complications after major abdominal operations compared with general anesthesia (without epidural) followed by patient controlled analgesia with morphine, and with intraoperative epidural anesthesia with bupivacaine and light general anesthesia followed by postoperative bupivacaine-morphine analgesia. METHODS. A total of 292 patients undergoing infrarenal aortic bypass operation, gastric resection, gastrectomy, duodenum-preserving pancreatic resection, Whipple's operation or cystectomy and neobladder formation were randomly divided into three groups: 1. PCA group (patient controlled analgesia, n = 107): patients were operated on under general anesthesia (midazolam, fentanyl, N2O/O2, if necessary with addition of halothane, enflurane or isoflurane; muscle relaxation with pancuronium bromide). Postoperative management consisted in patient-controlled analgesia with morphine (Prominject), bolus 2 mg, lock-out 5 min (recovery room, intensive care unit) or 15 min (surgical ward). 2. EBM group (epidural bupivacaine+morphine, n = 95): operation under light general anesthesia (midazolam, low-dose fentanyl, N2O/O2, pancuronium bromide). In addition, a mixture of bupivacaine (0.25%) and morphine (60 micrograms/ml) was infused (approximately 0.1 ml/kg.h) via an epidural catheter during and after the operation (approximately 72 h). 3. EM group (epidural morphine, n = 90): operation under the same kind of general-epidural anesthesia as in the EBM group. Postoperatively, epidural injection of morphine (0.05 mg/kg in 10 ml of saline) on request up to the 3rd postoperative day. Quality of analgesia (at rest and when patients coughed vigorously), strength of cough, and rate-pressure product were recorded at 8:00 h, 12:00 noon, 16:00 h and 20:00 h on the 1st, 2nd and 3rd postoperative days. Incidence and intensity of all postoperative complications (cardiovascular, pulmonary, renal and other organ failure, reoperations, major infection, sepsis, thromboembolism, metabolic and mental disturbances) were assessed from the day of operation until discharge or death (n = 10), respectively. RESULTS AND DISCUSSION. In the PCA and EM groups analgesia was equal but of slightly inferior quality compared with the EBM group. The ability to cough was best in the EBM group and significantly worse in the PCA and EM groups, with no difference between the last two. (ABSTRACT TRUNCATED AT 400 WORDS)

Abdomen↗
PubMed1991

[Indications for sonography and follow-up studies. Initial results of a prospective study].

Ultrasonic examinations of the abdomen may result in expensive secondary imaging examinations. This prospective study was conducted in collaboration with the Zentralinstitut Köln. The first aim of our study was to compare the results of abdominal sonography in three different patient groups: The first group was comprised of patients referred for a medical check-up, the second group of patients referred because of upper abdominal pain and the third group of patients with generalized atherosclerosis. The second aim was to correlate sonographic findings (classified in three degrees of severity), with subsequently induced diagnostic procedures in the three groups. 2719 patients were enrolled, 2393 (88%) in group 1, 286 (11%) in group 2 and 40 (1%) in group 3. A total of 1792 abnormal findings were diagnosed. 65.6% of the findings in group 1, 65.7% in group 2 and 88% in group 3 were abnormal. Up to now, the findings led to a nearly equal number of subsequent diagnostic procedures in groups 1 and 2. The preliminary results show that abdominal sonography may be as effective in patients for a check-up as in patients referred because of a well-defined indication. Patients with defined abdominal symptoms show more abnormal sonographic findings than patients on a check-up. Higher costs resulting from subsequent examinations deserve critical assessment in the individual patient.

Abdomen↗
PubMed1990

Parasite antigens expressed in Escherichia coli. A refined approach for epidemiological analysis.

A simple method is described to generate carrier-free recombinant antigens following their expression in Escherichia coli. A plasmid, called pMSgt11, has been constructed such that the cleavage site for the protease factor Xa separates the recombinant antigen from an enzymatically active beta-galactosidase. Thus, rapid purification of the active beta-galactosidase recombinant protein, followed by digestion with factor Xa, releases the antigen of interest. The pMSgt11 plasmid is compatible with the phage expression vector, lambda gt11 and the feasibility of applying this system has been demonstrated using malarial recombinant antigens. Inserts from lambda gt11 recombinant Plasmodium falciparum clones have been recloned into the EcoRI site of pMSgt11 and the expressed soluble fusion proteins have been purified from crude extracts using a one step affinity chromatography. After protease digestion, the fusion protein cleavage products were analysed by immunoblot with a panel of different human immune sera. We were able to successfully demonstrate specific antibody titers to the parasite-derived carrier-free antigen, without interference from anti-Escherichia coli-specific antibodies. The general application of this approach to epidemiological analysis is discussed.

Animals↗
PubMed1990

[Loeffler syndrome in a child treated with aspirin].

A 5-year-old girl was treated with acetyl-salicylic acid (Aspirin) for 3 months because rheumatic disease was suspected. She developed hemoptysis which was later followed by the clinical and roentgenological findings of Loeffler's syndrome.

Aspirin↗
PubMed1990

Bb65, a major immunoreactive protein of Bartonella bacilliformis.

A 65 kDa protein (Bb65) has been identified as one of the major specific antigens of Bartonella bacilliformis, the causative agent of bartonellosis which is a bacterial infectious disease of inhabitants of the Andes. The gene encoding this antigen (7B2) was isolated from an expression library made directly from randomly generated fragments of B. bacilliformis genomic DNA using Bartonella antibodies raised in rabbits and sera of bartonellosis patients. The Bartonella 7B2 gene was expressed in Escherichia coli and the recombinant Bb65 protein was purified by column chromatography. Using polyclonal antibodies raised in rabbits, the antigen was shown to be present in all of 13 B. bacilliformis isolates from different Peruvian regions. Immune electron microscopy demonstrated the probable cytoplasmatic localization of Bb65. When applied to enzyme immunoassays, Bb65 sensitively and specifically bound to IgG antibody of sera of bartonellosis patients, convalescents, and immunes from various Peruvian regions. IgM antibody was not recognized by Bb65, neither was IgG antibody circulating during the first 2 weeks of illness. The amino-terminal amino acid sequence of Bb65 was 53% homologous to the 65 kDa heat shock protein of Mycobacterium tuberculosis.

Amino Acid Sequence↗