Biomedical subjects

H Probst

Publications and source records attributed to H Probst.

At least 37 records · Page 2Linked to original sources

PubMed1995

[Ventricular bigeminy with fixed with fixed coupling at rest and during exercise as the cause of recurrent dizziness and syncope--successful anti-arrhythmic therapy by high frequency current catheter ablation of a right ventricular arrhythmogenic focus. A case report].

In a 52-year-old patient with beginning dilatative cardiomyopathy dizziness and syncopes could be observed due to a ventricular bigeminy at rest and under exercise conditions. The patient also showed a marked reduction of exercise capacity and was handicapped in his profession as electrician and unable to work for more than 10 months. Antiarrhythmic drug therapy including the subsequent use of all available antiarrhythmic agents failed in suppressing this arrhythmia. In an electrophysiological study the arrhythmogenic focus could be localized in the right ventricular outflow tract. Application of radiofrequency current resulted in instantaneous termination of the extrasystoly; this result could be documented in repeat Holter monitorings over 12 weeks to present. This case report shows that radiofrequency catheter ablation can in special cases be applied for therapy of extrasystolic phenomena when clinical symptoms necessitate treatment and antiarrhythmic drug therapy fails.

Cardiac Complexes, Premature↗

PubMed1995

Cardiogenic shock in acute myocardial infarction. Improving survival rates by primary coronary angioplasty.

This study reports on 16 patients suffering from cardiogenic shock in the setting of acute myocardial infarction (11 men, five women; average age: 52.5 +/- 14 years) treated by means of primary coronary angioplasty: These 16 patients were part of a total population of 261 patients suffering from acute myocardial infarction at the time of admittance to the Wuppertal Heart Center, who were consecutively treated during the period from 1/90 to 6/94 by primary coronary angioplasty without having received any prior thrombolytic therapy. For all patients, primary re-opening of the vessel infarcted was successful. The period of time between onset of pain until re-opening of the vessel averaged 176 +/- 49 min. Eleven patients suffered from multi-vessel coronary artery disease. Prior to re-opening, systolic blood pressures averaged 66 +/- 10 mm Hg; average biplan left ventricular ejection fraction, 40 +/- 12%; left ventricular end-diastolic pressures (LVEDP), 26 +/- 7 mm Hg. In 63% of the cases evaluated, it proved possible to document collaterals to the infarcted vessel. Thirteen patients survived acute coronary occlusion. Two patients died due to protracted myocardial pumping failure, despite re-opened arteries that effectively re-established coronary flows. Showing symptoms of re-occlusion, one patient developed electromechanical decoupling. Thirteen patients were discharged from the hospital for normal life or subsequent treatment. Overall, this corresponds to an in-hospital survival rate of 81%. During follow-up examinations performed over 14 +/- 8 months (range 3 to 30 months), all of the patients are alive. Mean left ventricular ejection fraction increased to 56% +/- 17%; mean left ventricular end-diastolic pressure dropped to 14 mm Hg +/- 5 mm Hg. In the infarct-related artery there was no recurrence of stenoses exceeding 50%. By now, one of the patients has received elective aorto-coronary bypass grafting; for another one, multi-vessel PTCA of non-infarcted arteries is being employed; 77% of the patients state that they are satisfied with the quality of their lives. These results demonstrate that rapid revascularization using coronary angioplasty in cardiogenic shock following acute myocardial infarction substantially improves the prognosis for survival and favorably influences long-term outcome. Thus, primary PTCA is the method of choice for treating cardiogenic shock; any patient-and particularly those resistant to lyse therapy-should immediately receive this treatment.

Adult↗

PubMed1995

Primary mechanical recanalization of occluded coronary arteries without prior thrombolytic therapy in patients with acute myocardial infarction. A single-center study reporting acute results and complications.

This study reports on 261 consecutive patients admitted to the Wuppertal Heart Center with acute myocardial infarction (186 men, 75 women; average age: 58.2 +/- 11.6 years) and then treated by primary coronary artery angioplasty. Sixteen patients with cardiogenic shock were included, as well as 42 patients aged > or = 70 years, 51 patients with contraindications for thrombolysis, and 13 patients with prior coronary bypass surgery. All patients were treated between 12/89 to 6/94 and had not received prior thrombolytic therapy. The period of time between onset of pain and revascularization of the infarct-related vessel averaged 224 +/- 205 min. Half of the patients had multi-vessel disease, and about 31% had had a prior myocardial infarction. 100 patients suffered from an anterior wall infarction, 109 patients from an inferior wall infarction, 50 patients from a posterolateral infarction, and in two cases the infarct localization could not be determined from the ECG. Mean biplane left ventricular ejection fraction averaged 56 +/- 13%, left ventricular end-diastolic pressure 20 +/- 7 mm Hg. In about 50% of the patients collaterals to the infarct-related coronary artery could be documented. With the first contrast injection into the infarct-related vessel TIMI flow 0/I was demonstrated in 94.9%, TIMI flow II in 5.7% and TIMI flow III in 0.4%. Reopening of the infarct-related coronary artery with establishment of TIMI-flow III was primarily successful in 91.9%. Average time for coronary angiography and angioplasty in the cathlab was 69 +/- 28 min. In 29 patients an autoperfusion balloon catheter was used to treat manifest or threatening reocclusion. Thirty-day-mortality in the total study group was 3.4%. In patients aged > or = 70 years mortality raised to 14.3%; in patients in cardiogenic shock mortality increased to 18.7%, in patients with inferior wall infarction up to 5.5%, and in cases with multi-vessel disease up to 5.0%. The in-hospital and 30-day course were complicated by major peripheral bleeding in seven patients (2.7%) requiring blood transfusions and surgical femoral vascular repair, and in another two patients with a false aneurysm which was treated by surgical means. No hemorrhagic stroke occurred, but three ischemic strokes with complete restitutio ad integrum within the 30-day-observation period were registered. As major cardiac complication early re-occlusion of the initially reopened infarct-related coronary artery was diagnosed in 10 patients; 11 patients developed a re-infarction within the first 30-days, in three cases leading to a fatal outcome.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1994

Drug-induced changes in the expression of MDR-associated genes: investigations on cultured cell lines and chemotherapeutically treated leukemias.

The induced expression of multiple drug resistance (MDR)-associated genes as a direct response of tumor cells to antineoplastic drugs could be an important factor influencing the success of cancer chemotherapy. We investigated the effects of such compounds on mdr1/P-glycoprotein (P-gp) gene expression and drug sensitivities in the T-lymphoblastoid human cell line CCRF-CEM and MDR sublines. Thereby, we observed that actinomycin D or adriamycin administered at sublethal concentrations induced increases of mdr1 mRNA levels and resistance within 72 h. Furthermore, on leukemia cell samples collected before and after chemotherapy we checked by a complementary DNA polymerase chain reaction (cDNA-PCR) approach for similar alterations in the relative expression levels of the MDR-associated genes (a) mdr1/P-gp (b) mrp (MDR related protein), and (c) the topoisomerase II isoforms alpha and beta. We found a concomitant increase in mdr1 and mrp gene expression combined with a decreased expression of topoisomerase II alpha in the course of the second relapse of an acute lymphoblastic leukemia (ALL). This points to the emergence of at least three different MDR mechanisms in this type of leukemia unresponsive to chemotherapy. A chronic myeloid leukemia (CML) in blast crisis, however, showed combined increases in mdr1 (about 20-fold) and mrp (about four fold) gene expression after intense but unsuccessful chemotherapy over a 6-month period. Our results indicate the occurrence of induced resistance in vitro and in vivo and suggest a contribution of the newly identified ATP-binding cassette (ABC) transporter MRP in MDR.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Synchronous replication of SV 40 DNA in virus infected TC 7 cells induced by transient hypoxia.

We transiently exposed SV 40 infected TC 7 cell cultures to a reduced O2 tension (4-8 h, about 200 ppm relative to 10(5) Pa total pressure). Under the hypoxic conditions, 'working' viral replication forks were greatly retarded or stopped, and initiation of daughter strand synthesis in further SV 40 DNA molecules was suppressed. Reoxygenation released an immediate burst of SV 40 replication which mainly consisted of a synchronous viral replication round. This synchronous in vivo replication began at the known origin of replication and proceeded at normal rates to the known termination region. Viral replicons seemed to accumulate under hypoxia in a state fully prepared to begin replication immediately after recovery of a normal pO2. The shut-down and sudden reactivation of DNA synthesis under hypoxia and reoxygenation, respectively, were not accompanied by changes of the phosphorylation state of large T antigen. The described synchronization procedure can be applied to optionally large SV 40 infected cell cultures.

Animals↗

PubMed1993

Staurosporine suppresses replicon initiation in mammalian cells.

Replication in cellular replicons of mouse Ehrlich ascites, human CCRF-CEM and hamster BHK-21 cells was analyzed, after exposition of the cells to staurosporine, by measuring the overall DNA synthesis rate, by alkaline sedimentation analysis of length distributions of growing daughter strand DNA and by DNA fibre autoradiography. The results consistently indicated that micromolar concentrations of staurosporine caused, in all three cell lines, a fast suppression of replicon initiation which was reversible if the drug treatment did not exceed about 2 h. The inhibition of initiation was accompanied by a slight reduction of rates of propagation of replication forks. The data are interpreted in terms of the existence of a so far unknown factor which seems to be involved relatively directly in the initiation process of cellular replicons and has to be activated, like the large T antigen of SV 40 for the replication initiation in the viral genome, by a specific phosphorylation event. Unlike several other protein phosphorylations of cellular regulation, the kinase concerned here seems to be inhibited only by relatively high staurosporine concentrations.

Alkaloids↗

PubMed1993

Mdr1/P-glycoprotein expression in natural killer (NK) cells enriched from peripheral or umbilical cord blood.

The sensitivity to antineoplastic agents of subpopulations of haematopoietic cells during cancer chemotherapy is an open question. The performance of natural killer (NK) cells, possibly assisting the elimination of tumour cells under drug treatment might be of particular interest. We examined the expression of the transmembrane multidrug transporter mdr1/P-glycoprotein in NK-cells (CD56+) enriched from the peripheral blood or the umbilical cord blood from healthy donors by indirect immunocytofluorescence using the monoclonal P-glycoprotein antibody C219 and a polymerase chain reaction (PCR) approach with amplimers specific for the human mdr1 cDNA. As the antibody C219 apparently cross-reacts with the human mdr3 gene product whose functions are as yet unclear we also checked expression of this gene by PCR using mdr3 specific amplimers. Distinct, but rather inhomogeneous mdr1/P-glycoprotein expression was found in NK-cells enriched from the peripheral blood. NK-cells enriched from the umbilical cord blood showed quite strong mdr1 expression levels throughout, exceeding the values found in the moderately multidrug-resistant cell line CCRF VCR 100 which is permanently cultivated in the presence of 100 ng/ml vincristine. Mdr1/P-glycoprotein expression was mirrored by lowered sensitivities of the cultivated NK-cells towards actinomycin D or adriamycin. The drug sensitivity could be modulated by treatment of the cells with the immunosuppressive drug cyclosporin A. Expression of the mdr3 gene was low or absent in all NK-cell samples examined so far.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Eukaryotic initiation factor 5A is a cellular target of the human immunodeficiency virus type 1 Rev activation domain mediating trans-activation.

Expression of human immunodeficiency virus type 1 (HIV-1) structural proteins requires the presence of the viral trans-activator protein Rev. Rev is localized in the nucleus and binds specifically to the Rev response element (RRE) sequence in viral RNA. Furthermore, the interaction of the Rev activation domain with a cellular cofactor is essential for Rev function in vivo. Using cross-linking experiments and Biospecific Interaction Analysis (BIA) we identify eukaryotic initiation factor 5A (eIF-5A) as a cellular factor binding specifically to the HIV-1 Rev activation domain. Indirect immunofluorescence studies demonstrate that a significant fraction of eIF-5A localizes to the nucleus. We also provide evidence that Rev transactivation is functionally mediated by eIF-5A in Xenopus oocytes. Furthermore, we are able to block Rev function in mammalian cells by antisense inhibition of eIF-5A gene expression. Thus, regulation of HIV-1 gene expression by Rev involves the targeting of RRE-containing RNA to components of the cellular translation initiation complex.

Amino Acid Sequence↗

PubMed1993

Left ventricular malposition of a transvenous cardioverter defibrillator lead: a case report.

A case of left ventricular endocardial malposition of a transvenous implantable cardioverter defibrillator (ICD) lead through a patent foramen ovale is presented. Diagnostic modalities include lateral chest radiography, echocardiography, and electrocardiographic analysis during lead placement. The operative therapy consists of open lead replacement. Measures to avoid lead misplacement are suggested.

Defibrillators, Implantable↗

PubMed1993

Selective and synchronous activation of early-S-phase replicons of Ehrlich ascites cells.

Twelve-hour exposure of G1 Ehrlich ascites cells to controlled hypoxia (200 ppm of O2 at 1 bar) suppressed replicon initiation. Synchronous cycling, beginning with a normal S phase, was released by reoxygenation immediately. The addition of cycloheximide at reoxygenation largely resuppressed, after a short initial burst, succeeding replicon initiations. Alkaline sedimentation analysis of growing daughter strand DNA, DNA fiber autoradiography, and analysis of the newly formed DNA demonstrated that normal chain growth and DNA maturation (replicon termination) in the initially activated replicons continued in the presence of cycloheximide. After 2 to 3 h, a low level of cycloheximide-insensitive background replication emerged out of the then-ebbing single surge of activity of the initially released replicons.

Animals↗

PubMed1992

Reversible shutdown of replicon initiation by transient hypoxia in Ehrlich ascites cells. Dependence of initiation on short-lived protein.

The O2-dependent regulation of replication in Ehrlich ascites cells, characterized by a reversible shutdown of replicon initiation during hypoxia, was scrutinized with respect to the involvement of gene expression. Synchronous and asynchronous cells were subjected to transient hypoxia and examined for expression of selected 'late' growth-regulated mRNA and for the influence of inhibitors of transcription and translation on DNA replication. Irrespective of whether replicon initiation was suppressed by hypoxia or retriggered by reoxygenation, the levels of thymidine kinase mRNA and of proliferating cell-nuclear antigen/cyclin mRNA were as high as in untreated replicating cells. The level of histone H3.1 mRNA followed, with a distinct delay, the replicative activity of the cells governed by the imposed changes of pO2. The response of replication to inhibition of transcription and translation was virtually the same as to hypoxia, i.e. a selective suppression of replicon initiation. It was demonstrated that replicon initiation depends on one or several short-lived protein(s) (lifetime about 5 min) which is (are) formed under hypoxic conditions as well. The lifetime of the corresponding RNA message(s) is in the range of several hours. It is suggested that the expression of genes conditioning resting cells for DNA replication remains unaffected by hypoxia or by restoring the normal pO2. Hypoxic cell appear to rest in a state fully prepared for entering DNA replication, but a yet unknown event essential for replicon initiation is blocked. This event depends on a critical oxygen tension as well as on short-lived protein(s).

Animals↗

PubMed1992

Cycloheximide inhibits cellular, but not SV40, DNA replication.

We have prepared extracts from cycloheximide-treated cells for the study of simian-virus-40 (SV40)-DNA replication in vitro. When supplemented with the viral initiator protein (large T antigen), these extracts fully supported SV40-DNA replication. We also determined that SV40-DNA replication in vivo is much more resistant to cycloheximide than cellular DNA replication. SV40 encodes its own initiator protein, T antigen, which also functions as a DNA helicase, but depends on cellular functions for all additional replication reactions. Therefore, it appears to be quite likely that cycloheximide affects cellular DNA replication by blocking the synthesis of (a) cellular function(s) that is(are) performed by T antigen in SV40-DNA replication. Indeed, DNA fiber autoradiography and alkaline sucrose gradient centrifugation of pulse-labeled cellular DNA showed that cycloheximide treatment almost completely suppressed replicon initiation and reduced the rate of replication fork movement to about one third of the control.

Antigens, Polyomavirus Transforming↗

PubMed1990

mdr1/P-glycoprotein gene segments analyzed from various human leukemic cell lines exhibiting different multidrug resistance profiles.

Three high-level multidrug-resistant sublines of the human T-lymphoblastoid cell line CCRF-CEM were selected independently with either actinomycin D, vincristine or adriamycin. They exhibited distinct quantitative differences of cross-resistance profiles, and showed amplification and marked expression of the mdrl/P-glycoprotein gene. DNA and RNA were prepared from the cell lines, and additionally from three cell samples of patients suffering from acute lymphatic leukemia. Applying the polymerase chain reaction (PCR) for amplification, we cloned and sequenced from these sources segments of the mdrl/P-glycoprotein gene around the codon 185 which codes for an amino acid residue possibly influencing the drug binding function of the P-glycoprotein. Altogether, only 2 single nucleotide differences in an intron were found in 2 out of 40 recombinants each harboring a 209 bp genomic or a 269 bp cDNA fragment of the mdrl/P-glycoprotein gene. Our result does not support the idea of clustered point mutations in this segment of the P-glycoprotein gene as a cause of different multidrug resistance profiles. We additionally examined another segment of the P-glycoprotein gene in its second half, essentially delivering the same negative result, though.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1990

Differential regulation of HLA class I genes by interferon.

Allele-specific differences in the regulation of HLA class I genes by type I interferon (IFN) were observed after transfection of eight HLA-B, -A, or -C genes into mouse L cells. HLA-B7 and -Bw64 gene expression was significantly more inducible by type I IFN than the genes coding for HLA-B27, HLA-B51, HLA-B38, HLA-B39, HLA-Cw3, and HLA-A2 antigens. Modification of the 5' end of HLA-B7 and HLA-B27 genes revealed the presence of enhancer sequences responding to IFN treatment in the 5' untranslated region of HLA-B7, but not of HLA-B27 and suggested further, independently acting enhancer elements downstream of the transcription initiation site. Comparison of 5' enhancer region sequences in correlation with type I IFN inducibility of the different HLA class I alleles indicated that the exchange of only two nucleotides in the interferon response sequence (IRS) or enhancer A region of HLA-B7 or -Bw64 could account for nonregulated promoters in all other HLA-A, -B, or -C alleles analyzed. Thus, type I IFN stimulation of HLA class I genes in mouse L cells appears to predominantly operate in most alleles by a mechanism targeted to enhancer sequences downstream of the gene's transcription initiation site.

Alleles↗

PubMed1989

Oxygen dependent regulation of mammalian ribonucleotide reductase in vivo and possible significance for replicon initiation.

The intracellular concentration of the M2 specific free tyrosyl radical of ribonucleotide reductase in cultured Ehrlich ascites cells was estimated by EPR spectroscopy during imposition and after reversal of hypoxia. Under the same conditions, the intracellular intensity of CDP reduction was estimated indirectly by measuring the incorporation of radioactivity into DNA from labeled ribo- and deoxyribo-cytidine, respectively. The radical concentration distinctly decreased under hypoxia and reincreased upon reaeration. At the same time, the CDP reduction was greatly diminished and reactivated, respectively. These observations are interpreted in the sense of an O2 dependent regulation of the intracellular activity of ribonucleotide reductase. The O2 dependent deactivation and reactivation of the enzyme was temporally related to a specific suppression or a burst-like release of replicon initiations, respectively. Addition of 100 microM dCtd to hypoxic cells could substitute for reoxygenation with respect to triggering replicon initiations. A possible implication of the intracellular ribonucleotide reductase activity and the size of the dCTP pool in replicon initiation is discussed.

Binding Sites↗

PubMed1989

Computer-controlled discontinuous rotating gel electrophoresis for separation of very large DNA molecules.

The newly designed equipment for alternating field gel electrophoresis which permits the separation of very large DNA molecules and the simultaneous analysis of up to 35 samples is described. The field alternation is effected by intermittently rotating the submerged agarose gel by optitional angles. The time intervals between changes of position are controlled by a computer program driving a simple switching device which was designed to suit any technique using periodic switching or inversion of the electrical field. Because the electrophoresis unit provides an absolutely homogeneous electrical field, no distortion of migration lanes occurs and the resolution is very good. Moreover, by using a switching time interval gradient an almost perfect linear relationship between migration distances and molecule sizes in the range of about 100-1250 kilobase pairs is observed. In two-dimensional separations, different switching time programs for the first and second dimension allow maximum resolution of selected size ranges. Field inversion gel electrophoresis is possible as well. The performance of the method is demonstrated by comparing the chromosome sizes of different yeast strains.

Bacteriophage lambda↗

PubMed1989

No significant overreplication occurs in Ehrlich ascites cells during and after reversal of hypoxia.

Labeling with bromodeoxyuridine and analysis by isopycnic banding for emergence of DNA-helices density-labeled in both strands (HH-DNA) were used to examine whether transient controlled hypoxia induces significant overreplication in the DNA of cultured Ehrlich ascites cells within a single cell cycle. Diverse situations of the hypoxic period (4-8 h) within the BrdUrd labeling time (8-16 h) were tested. If transversal of more than one complete cell cycle by very fast cycling individual cells was avoided by using short BrdUrd labeling periods or by addition of colcemid, HH-DNA was never detected. This indicates that hypoxia does not induce significant overreplication under the conditions chosen and, in particular, that the burst of replicon initiations occurring after reoxygenation of hypoxic cells principally is not due to overreplication.

Animals↗

PubMed1989

Resistance to methotrexate and multidrug resistance in childhood malignancies.

Resistance to drugs, either primary or acquired, is a main problem in cancer chemotherapy. The paper summarizes our results in regard to resistance to methotrexate and multiple drug resistance in human cell lines of pediatric malignancies and in children with resistant cancer. In cell lines as well as in children we could demonstrate amplification of the gene coding for dihydrofolate reductase as a cause for resistance to MTX. Procedures to overcome drug resistance such as treatment with high dose MTX and leucovorin rescue are discussed. The increased expression of the mdrl gene coding for the P-glycoprotein is related to multidrug resistance. This could be shown in cell lines and in children. The expression decreased when the drug, used for induction of resistance, was omitted for a few weeks from the cell culture medium. Readdition of the drug caused a rapid increase of expression. For the first time data in children are presented which demonstrate the amplification of the gene coding for dihydrofolate reductase or increased expression of the mdrl gene as cause of drug resistance. The clinical implications of these findings are discussed.

Adolescent↗