Biomedical subjects

S G Spitzer

Publications and source records attributed to S G Spitzer.

At least 19 recordsLinked to original sources

PubMed2003

Influence of radiographic contrast media on myocardial tissue oxygen tension: NaCl-controlled, randomised, comparative study of iohexol versus iopromide in an animal model.

It was tested whether a bolus injection of 10 ml radiographic contrast medium (iopromide vs. iohexol), compared to a 10 ml NaCl bolus and administered into the left anterior descending artery (LAD) of farm pigs, influenced the tissue pO2 in the territory of this artery. The radiographic contrast media and the NaCl bolus were given in randomised order. The mean pO2 LAD fell from initially 40.3+/-10.9 mmHg to a minimal value of 22.5+/-8.9 mmHg 241+/-44 sec after injecting the iopromide bolus, with this result representing a mean decrease of 44.2% (p=0.0003). The initial pO2 (baseline) was reached again after approximately 10 minutes. The mean pO2 LAD fell from the initial value of 34.5+/-14.6 mmHg to a minimal value of 29.4+/-13.9 mmHg 171.7+/-11.9 sec after injection of the iohexol bolus, with this result representing a mean decrease of 14.8% (p=0.0003). The baseline pO2 was reached again after approx. 5 minutes. The drop in the pO2 after iopromide administration was significantly larger than that after iohexol (p=0.0001), and also the time after which the baseline pO2 is reached again was considerably shorter for iohexol (p=0.001). The two radiographic contrast media did not influence the tissue pO2 in either the territory of the right coronary artery or in skeletal muscle. Injection of a NaCl bolus into the LAD influenced neither the tissue pO2 of the territory of the LAD nor that of the RCA or of the skeletal muscle. The tissue temperature, heart rate and the systolic and diastolic blood pressure were not affected during the three injections. Injection of radiographic contrast media into a coronary artery can lead to a distinct, local microcirculatory impairment in the myocardial territory supplied by this artery. In this case, the extent of the microcirculation impairment seems to depend not only on the viscosity of the contrast media but rather also on its chemotoxicity.

Animals↗

PubMed2002

Influence of two non-ionic radiographic contrast media with different osmolalities on coagulation in invasive cardiology. A prospective, randomised comparative study.

PURPOSE: To investigate the influence of two non-ionic radiographic contrast media with different osmolality on thrombocytic function and the plasmatic coagulation system. MATERIAL AND METHODS: The study was carried out as a randomised, prospective, comparative study with two contrast media in a heart catheter laboratory. RESULTS: Activating influences on platelet aggregation, procoagulatory or profibrinolytic functions or injury to the endothelium could be ruled out. Apparently, also differences in substance properties, such as the media's ionic character or osmolality had no demonstrable influence on the interaction with haemostatis and blood vessels. An adjuvant, antithrombotic therapy was carried out, which consisted of platelet aggregation inhibitors and heparins. CONCLUSION: Our findings agree with the results of recent clinical trials, which demonstrated no relevant disadvantage of non-ionic contrast media as regards thrombotic complications.

Angioplasty, Balloon, Coronary↗

PubMed1999

Treatment of atrial fibrillation in open heart surgery--the potential role of microwave energy.

Treatment of atrial fibrillation by creating linear lesions in patients undergoing heart surgery (mitral valve replacement or coronary bypass grafting) receives increasing interest. Conventional rhythm surgery require tremendous operative effort and increases the risks of perioperative complications. For that reason various alternative methods for creating linear lesion are under investigation. This paper discusses several techniques for creation of transmural lesions in open heart surgery, e.g. ultra sound ablation, high current DC shocks, laser ablation, cryoablation, radio frequency ablation, cooled radio frequency ablation, and microwave ablation.

Atrial Fibrillation↗

PubMed1999

Intraoperative microwave ablation for curative treatment of atrial fibrillation in open heart surgery--the MICRO-STAF and MICRO-PASS pilot trial. MICROwave Application in Surgical treatment of Atrial Fibrillation. MICROwave Application for the Treatment of Atrial Fibrillation in Bypass-Surgery.

Concomitant microwave ablation for curative treatment of atrial fibrillation (AF) was performed in 18 patients with history of chronic atrial fibrillation and indication for open heart surgery, 11 patients with mitral valve replacement and 7 patients with coronary artery bypass grafting. There were no perioperative complications. During the postoperative period most of the patients had intermittent AF, they received low dose Sotalol therapy and electric cardioversions. Up to now seven patients have reached follow-up day 90. One patient has persistent AF. Two patients had typical atrial flutter that was electrically converted to sinus rhythm (SR), isthmus ablation is planned. The other four patients have SR, one patient without cardioversions. These four patients show recovered atrial function with observed A-wave for transmitral flow. Under visual guidance the continuous atrial lesion lines could be induced effectively and safely by the intraoperative device Lynx.

Aged↗

PubMed1999

Pacing and ICD therapy in Germany (West and East) before and after reunification in 1989.

In 1989 the two German countries, FRG and GDR, were reunited after 50 years of political separation. During this time, these countries underwent independent, and in parts quite different, developments. While the reunification has had less effect on the overall situation in the Western part of the country, the Eastern part has experienced considerable changes, including the health service. In the field of pacing and ICD therapy, this study finds that 8 years after the reunification, the German federal states of both parts of the country have converged in the field of pacing and ICD therapy.

Arrhythmias, Cardiac↗

PubMed1997

A prothrombin gene mutation is significantly associated with venous thrombosis.

This case-control study examined the prevalence of a prothrombin gene mutation in the 3'-untranslated region (UTR) first reported by Poort et al in Dutch subjects with a history of venous thrombosis and in matched control subjects without a history of thrombosis. We tested the hypothesis that the presence of the 3'UTR prothrombin mutation would convey a higher risk of venous or arterial thrombosis and therefore would be found in a higher-than-normal percentage of subjects with a history of thrombosis. Our study included 100 subjects: 50 with a history of thrombosis (21 with venous thrombosis and 29 with arterial thrombosis, who had been recruited from an anticoagulation clinic) and 50 control subjects without a history of thrombosis. DNA from these subjects was analyzed by polymerase chain reaction and agarose gel electrophoresis. We found a statistically significant increase in the prevalence of the 3'UTR mutation in subjects with a history of venous thrombosis compared with subjects without thrombosis. The prevalence of the 3'UTR prothrombin mutation was 19% (4/21;3 heterozygous and 1 homozygous) in subjects with a history of venous thrombosis, 0% (0/29) in subjects with a history of arterial thrombosis, and 2% (1/50) in control subjects (P < .0245, by Fisher's exact test for comparison of subjects with versus those without a history of venous thrombosis). The G-->A mutation at nucleotide 20,210 in the 3'UTR was confirmed by direct DNA sequencing. The similar increased prevalence of the 3'UTR mutation in subjects with venous thrombosis in our population and in the Dutch population studied by Poort et al suggests that this mutation is an important risk factor for venous thrombosis in the general white population.

Adult↗

PubMed1995

Structure of the ubiquitin-encoding genes of Cryptococcus neoformans.

Cryptococcus neoformans (Cn) contains two ubiquitin (UBI)-encoding genes located on separate chromosomes. The UBI1 gene consists of UBI fused to a 53-amino-acid (aa) tail and is 95% identical to the Saccharomyces cerevisiae (Sc) UBI1 which codes for an UBI-CEP52 ribosomal protein fusion. UBI4 is a polyubiquitin gene that contains five UBI repeats. The UBI4 aa sequences differ from Sc UBI by a single aa. UBI1 contains two introns in the UBI-encoding portion and two introns in the tail. Single introns are present in three of the repeats in UB14 and are located at the same positions as those in UBII. There was also an average of 15% nt differences among UBI repeats. The results provide evidence of extensive recombination and/or conversion events between repeated genes in Cn.

Amino Acid Sequence↗

PubMed1995

Genetic relatedness of Cryptococcus neoformans clinical isolates grouped with the repetitive DNA probe CNRE-1.

Cryptococcus neoformans isolates from eight patients with cryptococcal infection were previously assigned into three groups on the basis of repetitive DNA probe (CNRE-1) restriction fragment length polymorphisms. These groups accounted for a disproportionate number of recent clinical isolates in New York City. To further examine the genetic relatedness of isolates within and across CNRE-1 groups, the DNA sequence of the 779-base URA5 gene from each strain was amplified and sequenced. The number of nucleotide differences occurred in the third codon position or in introns. Pairwise comparisons revealed average nucleotide differences within a CNRE-1 group of 4.8 +/- 2.6 (n = 8) and between CNRE-1 groups of 21.9 +/- 7.0 (n =20) (P <0.001) Analysis of URA5 sequences defined three groups that were congruent with those defined by CNRE-1 restriction fragment length polymorphisms. PCR amplification of an rDNA intergenic spacer revealed conservation of the intergenic spacer length within groups. Electrophoretic karyotyping did not distinguish between two isolates in each of two CNRE-1 groups. DNA from all isolates studied hybridized to an alpha mating type-specific probe. We interpret these results as suggesting a clonal population structure for some pathogenic isolates of C. neoformans in New York City.

Base Sequence↗

PubMed1994

Characterization of the CNRE-1 family of repetitive DNA elements in Cryptococcus neoformans.

The pathogenic yeast Cryptococcus neoformans contains 10-20 dispersed repetitive elements that hybridize to clone CNRE-1.0. Screening of a genomic library with probes derived from CNRE-1.0 identified five phages with restriction maps that overlapped CNRE-1.0 and three additional phages that belonged to two distinct groups. Sequencing of internal 3.5-kb SstI fragments from two CNRE-1-like elements revealed 95% homology, as well as a conserved open reading frame. A PCR-RFLP assay was developed that can distinguish different subfamilies of CNRE-1-like elements.

Base Sequence↗

PubMed1994

Efficacy and quality in clinical trials. Requirements to the investigator site. European Economic Community.

Guidelines and recommendations to conduct clinical trials have been defined for Europe since 1st July 1991 to ensure high quality standards. Thus, cost and speed of clinical trials are becoming more and more important in clinical research. The article tries to summarize specific requirements to the investigator site considering the aspects of quality and data evaluation. Furtheron a model is proposed to optimize realization of clinical trials in hospital institutions. Realization of "Good Clinical practice" (GCP) at the sponsor and the investigator site will improve the quality of clinical trials for the sake of the patients and finally leads to the acceptance of European clinical trials abroad.

Clinical Trials as Topic↗

PubMed1993

Persistence of initial infection in recurrent Cryptococcus neoformans meningitis.

Patients with cryptococcal meningitis tend to have recurrences of infection. Although the original strain of Cryptococcus neoformans is assumed to persist in recurrent infections, this assumption has not been tested. Southern blot hybridisation with two genomic DNA probes and pulsed-field electrophoresis of intact chromosomes were used to investigate the genetic relation between initial and relapse isolates of C neoformans from patients with recurrent cryptococcal meningitis. Eleven isolates were obtained from four patients (three with AIDS, one with leukaemia). Isolates from each patient could be distinguished from those of the other patients; however, each patient's initial and recurrence isolates were clonally related. Our results provide strong evidence that clinical recurrences of cryptococcal meningitis result from persistence of the original infecting strain.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Use of a dispersed repetitive DNA element to distinguish clinical isolates of Cryptococcus neoformans.

We isolated a recombinant phage from a Cryptococcus neoformans genomic library that contains a member of a dispersed family of repetitive DNA elements. This clone, CNRE-1, hybridized to at least seven chromosomes in C. neoformans on the basis of pulsed-field gel analysis. Hybridization of CNRE-1 to restriction digests of genomic DNA confirmed that there are multiple copies of this element and that restriction fragment length polymorphisms are present in strains from different serotypes of C. neoformans. The utility of this probe as an epidemiologic marker was determined by testing cryptococcal isolates from a single hospital. Five isolates from four patients were closely related to a serotype A reference strain, whereas five other isolates from four additional patients exhibited distinct patterns. In two patients, the isolates obtained during recurrent cryptococcal infections were identical to the original isolates.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Single nucleotide primer extension to detect genetic diseases: experimental application to hemophilia B (factor IX) and cystic fibrosis genes.

In this report, we describe an approach to detect the presence of abnormal alleles in those genetic diseases in which frequency of occurrence of the same mutation is high (e.g., cystic fibrosis and sickle cell disease), and in others in which multiple mutations cause the disease and the sequence variation in an affected member of a given family is known (e.g., hemophilia B). Initially, from each subject, the DNA fragment containing the putative mutation site is amplified by the polymerase chain reaction. For each fragment two reaction mixtures are then prepared. Each contains the amplified fragment, a primer (18-mer or longer) whose sequence is identical to the coding sequence of the normal gene immediately flanking the 5' end of the mutation site, and either an alpha-32P-labeled nucleotide corresponding to the normal coding sequence at the mutation site or an alpha-32P-labeled nucleotide corresponding to the mutant sequence. Single nucleotide primer extensions are then carried out and analyzed by denaturing polyacrylamide gel electrophoresis and autoradiography. As predicted by the Watson-Crick base-pair rule, in the wild type only the normal base, in an affected member only the mutant base, and in carriers both the normal and the mutant base are incorporated into the primer. Thus, an essential feature of the present methodology is that the base immediately 3' to the template-bound primer is one of those altered in the mutant, since in this way an extension of the primer by a single base will give an extended molecule characteristic of either the mutant or the wild type. The method is rapid and should be useful in carrier detection and prenatal diagnosis of every genetic disease with a known sequence variation.

Alleles↗

PubMed1990

Factor IXHollywood: substitution of Pro55 by Ala in the first epidermal growth factor-like domain.

Factor IX is a multidomain protein essential for hemostasis. We describe a mutation in a patient affecting the first epidermal growth factor (EGF)-like domain of the protein. All exons and the promoter region of the gene were amplified by the polymerase chain reaction method, and sequenced. Only a single mutation (C----G), that predicts the substitution of Pro55 by Ala in the first EGF domain was found in the patient's gene. This mutation leads to new restriction sites for four enzymes. One new site (Nsi) was tested in the amplified exon IV fragment and was shown to provide a rapid and reliable marker for carrier detection and prenatal diagnosis in the affected family. The factor IX protein, termed factor IXHollywood (IXHW), was isolated to homogeneity from the patient's plasma. As compared with normal factor IX (IXN), IXHW contained the same amount of gamma-carboxy glutamic acid but twice the amount of beta-OH aspartic acid. Both IXHW and IXN contained no detectable free -SH groups. Further, IXHW could be readily cleaved to yield a factor IXa-like molecule by factor Xla/Ca2+. However, IXaHW (compared with IXaN) activated factor X approximately twofold slower in the presence of Ca2+ and phospholipid (PL), and 8- to 12-fold slower in the presence of Ca2+, PL, and factor VIIIa. Additionally, IXaHW had only approximately 10% of the activity of IXaN in an aPTT assay. In agreement with the nuclear magnetic resonance-derived structure of EGF, the Chou-Fasman algorithm strongly predicted a beta turn involving residues Asn-Pro55-Cys-Leu in IXN. Replacement of Pro55 by Ala gave a fourfold decrease in the beta turn probability for this peptide, suggesting a change(s) in the secondary structure in the EGF domain of IXHW. Since this domain of IXN is thought to have one high-affinity Ca2+ binding site and may be involved in PL and/or factor VIIIa binding, the localized secondary structural changes in IXHW could lead to distortion of the binding site(s) for the cofactor(s) and, thus, a dysfunctional molecule.

Alanine↗

PubMed1990

Experimental and theoretical evidence supporting the role of Gly363 in blood coagulation factor IXa (Gly193 in chymotrypsin) for proper activation of the proenzyme.

Factor IX is the zymogen of the serine protease factor IXa involved in blood coagulation. In addition to a catalytic domain homologous to the chymotrypsin family, it has Ca2+, phospholipid, and factor VIIIa binding regions needed for full biologic activity. We isolated a nonfunctional factor IX protein designated factor IXEagle Rock (IXER) from a patient with hemophilia B. The variant protein is indistinguishable from normal factor IX (IXN) in its migration on sodium dodecyl sulfate-gel electrophoresis, isoelectric point in urea, carbohydrate content and distribution, number of gamma-carboxyglutamic acid residues, and beta-OH aspartic acid content, and in its binding to an anti-IXN monoclonal antibody which has been shown previously to inhibit the interaction of factor VIIIa with factor IXaN. Further, IXER is cleaved to yield a factor IXa-like molecule by factor XIa/Ca2+ at a rate similar to that observed for IXN. However, in contrast to IXaN, IXaER does not bind to antithrombin-III (specific inhibitor of IXaN) and does not catalyze the activation of factor X (substrate) to factor Xa. To identify the mutation in IXER, all eight exons of IXN and IXER gene were amplified by the polymerase chain reaction technique and cloned. A single point mutation (G----T) which results in the replacement of Val for Gly363 in the catalytic domain of IXER was identified. Gly363 in factor IXa corresponds to the universally conserved Gly193 in the active site sequence of the chymotrypsin serine protease family. X-ray crystallographic data in the literature demonstrate a critical role of this Gly in stabilizing the active conformation of chymotrypsin/trypsin in two major ways: 1) in the formation of the substrate binding site; and 2) in the development of the oxyanion hole. Our computer structural data support a concept that the Gly363----Val change prevents the development of the active site conformation in factor IXa such that the substrate binding site and the oxyanion hole are not formed in the mutated enzyme.

Computer Graphics↗

PubMed1990

Replacement of isoleucine-397 by threonine in the clotting proteinase factor IXa (Los Angeles and Long Beach variants) affects macromolecular catalysis but not L-tosylarginine methyl ester hydrolysis. Lack of correlation between the ox brain prothrombin time and the mutation site in the variant proteins.

Previously, from the plasma of unrelated haemophilia-B patients, we isolated two non-functional Factor IX variants, namely Los Angeles (IXLA) and Long Beach (IXLB). Both variants could be cleaved to yield Factor IXa-like molecules, but were defective in catalysing the cleavage of Factor X (macromolecular substrate) and in binding to antithrombin III (macromolecular inhibitor). In the present study we have identified the mutation of IXLA by amplifying the exons (including flanking regions) as well as the 5' end of the gene by polymerase-chain-reaction (PCR) method and sequencing the amplified DNA by the dideoxy chain-termination method. Comparison of the normal IX and IXLA sequences revealed only one base substitution (T----C) in exon VIII of IXLA, with a predicted replacement of Ile-397 to Thr in the mature protein. This mutation is the same as found recently for IXLB. The observation that IXLB and IXLA have the same mutation is an unexpected finding, since, on the basis of their ox brain prothrombin time (PT, a test that measures the ability of the variant Factor IX molecules to inhibit the activation of Factor X by Factor VIIa-tissue factor complex), these variants have been classified into two different groups and were thought to be genetically different. Our observation thus suggests that the ox brain PT does not reflect the locus of mutation in the coding region of the variant molecules. However, our analysis suggests that the ox brain PT is related to Factor IX antigen concentration in the patient's plasma. Importantly, although the mutation in IXLA or IXLB protein is in the catalytic domain, purified IXaLA and IXaLB hydrolyse L-tosylarginine methyl ester at rates very similar to that of normal IXa. These data, in conjunction with our recent data on Factor IXBm Lake Elsinore (Ala-390----Val mutant), strengthen a conclusion that the peptide region containing residues 390-397 of normal Factor IXa plays an essential role in macromolecular substrate catalysis and inhibitor binding. However, the two mutations noted thus far in this region do not distort S1 binding site in the Factor IXa enzyme.

Animals↗

PubMed1990

Cultured normal human hepatocytes do not synthesize lipoprotein-associated coagulation inhibitor: evidence that endothelium is the principal site of its synthesis.

Human plasma contains a factor Xa-dependent inhibitor of tissue factor/factor VIIa complex termed lipoprotein-associated coagulation inhibitor (LACI). The present study examines the site(s) of LACI synthesis. In this study, cultured hepatocytes isolated from normal human liver were found to be essentially negative in LACI mRNA as revealed by Northern blot analysis using a full-length LACI cDNA as probe. The conditioned media from these cultures were also essentially negative for LACI activity. Similarly, poly(A)+ RNA obtained from normal human liver did not contain detectable LACI mRNA. In contrast, cultured human umbilical vein endothelial cells and human lung tissue (rich in endothelium) both contained abundant amounts of LACI mRNA. Moreover, erythrocyte lysates and culture media from normal monocytes, lymphocytes, or neutrophils did not contain measurable LACI activity; these cells were also negative for LACI mRNA. Platelets, however, contained LACI activity. The likely source of platelet LACI is the megakaryocyte cell since a megakaryocyte cell line (MEG-01) was found to contain LACI mRNA and to secrete small amounts of LACI activity. Additionally, human vascular smooth muscle cells and lung fibroblasts were also found to synthesize only small amounts of LACI. From these observations, we conclude that normal liver does not synthesize LACI and that endothelium is the principal source of plasma LACI. The undegraded LACI synthesized by endothelial cells had a molecular weight of approximately 41,000.

Base Sequence↗

PubMed1988

Molecular defect in factor IXBm Lake Elsinore. Substitution of Ala390 by Val in the catalytic domain.

Earlier studies with factor IXBm Lake Elsinore (IXBmLE), a nonfunctional variant of factor IX, suggested that the defect in this protein may reside in the catalytic domain of the molecule (Usharani, P., Warn-Cramer, B. J., Kasper, C. K., and Bajaj, S. P. (1985) J. Clin. Invest. 75, 76-83). In this report, genomic DNA fragments from normal IX and IXBmLE alleles were cloned into phage lambda EMBL3 and the recombinant phage identified using normal IX cDNA and synthetic oligonucleotides. Exons VI, VII, and VIII of normal IX and IXBmLE gene were also amplified using a newly developed primer-directed polymerase chain reaction method. All eight exons and flanking regions of the normal IX and IXBmLE gene were sequenced by the dideoxy chain termination method. Comparison of the normal IX and IXBmLE sequences revealed a single base substitution (C----T) in the exon VIII of the BmLE variant, which results in the replacement of Ala390 by Val in the variant molecule. Although this mutation is in the catalytic domain of the molecule, purified factor IXaBmLE is indistinguishable from normal IXa in its activity toward a small synthetic substrate, L-tosylarginine methyl ester. These data, coupled with the previous data, identify a region (around residue 390) in the normal factor IXa which appears to play a major role in the extended macromolecular substrate binding site.

Alanine↗