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Biomedical subjects

A Gruber

Publications and source records attributed to A Gruber.

At least 127 records · Page 7Linked to original sources
PubMed1996

Levels of mdr1 and mrp mRNA in leukaemic cell populations from patients with acute myelocytic leukaemia are heterogenous and inversely correlated to cellular daunorubicin accumulation.

Multidrug resistance gene (mdrl) expression is associated with a poor prognosis in acute myelocytic leukaemia (AML). Whether expression of the recently described multidrug resistance-associated gene (mrp) has any prognostic importance in AML is still unclear. The aim of the present study was to investigate the functional role of the mdr1 and mrp mRNA levels in peripheral leukaemic cell populations from patients with AML. Peripheral leukaemic cells from 10 patients with AML were incubated with daunorubicin (DNR). Cellular DNR content was analysed with a fluorescence-activated cell sorter (FACS). From each cell population the 20-25% cells with the lowest and highest DNR content were sorted out, and mdr1 and mrp RNA were quantified in these subpopulations with competitive polymerase chain reaction. The ratio between the mean DNR content in the cell populations with high and low DNR content varied between 1.9 and 6.6. the cell fraction with low DNR content had higher (3.8-40 times)mdr1 mRNA levels in 10/10 patients and higher (1.4-26 times) mrp mRNA levels in 8/10, as compared to the cell fraction with high DNR accumulation. In conclusion, mdr1 and mrp mRNA expressions are heterogenous in leukaemic cell populations from patients with AML. The mdr1 expression, and to some extent mrp expression, is inversely correlated to DNR accumulation in vitro.

Adult↗
PubMed1996

Sustained-release morphine for epidural analgesia in rats.

BACKGROUND: Epidural opioid analgesia often requires either continuous infusion or repeated injections, which are inconvenient for patients, increase risk of infection, and consume expensive physician and nursing time. In addition, potential respiratory depression is a major safety concern. The authors studied whether a single dose of epidurally administered, sustained-release morphine could prolong analgesia and reduce toxic effects in rats. METHODS: Sustained-release morphine (DTC401) was prepared by encapsulating morphine sulfate in DepoFoam (Dep. Tech, San Diego, CA), a lipid-based, sustained-release drug delivery system. A standard hot-plate test for analgesia, pulse oximetry for hemoglobin oxygen saturation, corneal-reflex loss, and incidence of catalepsy were used to assess efficacy and toxicities. Cerebrospinal fluid and serum pharmacokinetic studies were performed after a single epidural dose, using a commercially available radioimmunoassay kit. RESULTS: Single epidural doses of DTC401 resulted in equivalent onset time to peak analgesia but significantly prolonged analgesia compared with morphine sulfate. Hemoglobin oxygen saturation was decreased minimally, and the incidences of catalepsy and corneal-reflex loss were minimal, even at large doses of DTC401. In contrast, the larger doses of morphine sulfate significantly decreased hemoglobin oxygen saturation, and caused catalepsy and loss of the corneal-reflex. The Cmax for DTC401 was 32% in cerebrospinal fluid and 6% in serum, relative to morphine sulfate. The terminal half-life for DTC401 was increased 32 fold in the cerebrospinal fluid compared with morphine sulfate. CONCLUSIONS: A single epidural dose of DTC401, compared with morphine sulfate, prolonged duration of analgesia, with minimal supraspinal toxic effects, in rats.

Analgesia, Epidural↗
PubMed1996

Polydnavirus DNA of the braconid wasp Chelonus inanitus is integrated in the wasp's genome and excised only in later pupal and adult stages of the female.

Many endoparasitic wasps inject, along with the egg, polydnavirus into their insect hosts, the virus being a prerequisite for successful parasitoid development. The genome of polydnaviruses consists of multiple circular dsDNA molecules of variable size. We show for a 12 kbp segment of the braconid Chelonus inanitus (CiV12) that it is integrated into the wasp genome. This is the first direct demonstration of integration for a bracovirus. PCR data indicated that the integrated form of CiV12 was present in all male and female stages investigated while the excised circular virus DNA only appeared in females after a specific stage in pupal-adult development. The data also indicated that after excision of virus DNA the genomic DNA was rejoined. This has not yet been reported for any polydnavirus. Sequence analyses in the junction regions revealed the presence of an imperfect consensus sequence of 15 nucleotides in CiV12, in each terminus of the integrated virus DNA and in the rejoined genomic DNA. Within these repeats two sequence types (ATA, TAC) were observed in the various virus clones and in the clones encompassing the rejoined genomic DNA; they corresponded to the sequence type in the right and left junction, respectively. To explain this, we propose a model of virus DNA replication in which the genomic DNA is folded to juxtapose the direct repeat of the left with that of the right junction; recombination at specific sites would then yield the two types of virus and rejoined genomic DNA.

Animals↗
PubMed1996

Impairments of the protein C system and fibrinolysis in infection-associated stroke.

BACKGROUND AND PURPOSE: Infection/inflammation appears to be an important predisposing risk factor for brain infarction, but little is known regarding underlying molecular mechanisms. We examined the hypothesis that patients with brain infarction preceded by infection/inflammation within 1 week could be identified by a distinctive procoagulant laboratory profile characterized by abnormalities in the protein C system and endogenous fibrinolysis. METHODS: We performed a case-control study examining the relationship between preceding systemic infectious/inflammatory syndromes and selected immunohematologic variables in 36 patients with acute brain infarction and 81 control subjects (community control subjects [n = 47] and hospitalized nonstroke neurological patient controls [n = 34]). RESULTS: The stroke group had a lower mean level of the circulating antithrombotic enzyme activated protein C (APC) (4.33 +/- 0.34% [log-transformed percentage of control value, mean +/- SD]) than community control subjects (4.51 +/- 0.27%, P < .02) or hospitalized neurological patient controls (4.57 +/- 0.31%, P < .005). The lowest circulating APC levels were found in the stroke group with antecedent infection/inflammation within 1 week preceding index brain infarction (4.23 +/- 0.4%, n = 12). Within the stroke group, circulating APC levels were inversely related to IgG isotype anticardiolipin antibody titers (r = -.55, P < .001). Only the stroke group with infection/inflammation within 1 week had elevated plasma C4b binding protein compared with control subjects (141 +/- 61% versus 112 +/- 44%, P < .05). Stroke patients with antecedent infection/inflammation had a distinctively lower ratio of active tissue plasminogen activator to plasminogen activator inhibitor (0.11 +/- 0.04, n = 9) than other stroke patients (0.19 +/- 0.06, n = 9, P < .01) and control subjects (0.22 +/- 0.16, n = 17, P < .02). CONCLUSIONS: Impairments in the protein C pathway and endogenous fibrinolysis may contribute to the increased risk for brain infarction after recent (< or = 1 week) infection/inflammation. A decrease in the circulating anticoagulant APC may be related to elevated antiphospholipid antibody titers.

Antibodies, Anticardiolipin↗
PubMed1996

Activated protein C resistance in ischemic stroke not due to factor V arginine506-->glutamine mutation.

BACKGROUND AND PURPOSE: Resistance to activated protein C (APC), a natural plasma anticoagulant, is the most common identifiable risk factor for venous thromboembolic disease. One point mutation in coagulation factor V that renders it APC-resistant is found in >90% of APC-resistant venous thrombosis patients. To determine the prevalence of APC resistance and of this factor V mutation in stroke, we screened a group of ischemic stroke patients. METHODS: Hispanic ischemic stroke patients were screened using two different activated partial thromboplastin time-based assays. One assay using neat patient plasma determined APC resistance, and the other assay using patient plasma diluted into factor V-deficient plasma determined APC-resistant factor V, including the Arg506-->Gln mutation. Results were compared with those in 31 Hispanic control subjects of similar ages. RESULTS: Six of 63 (9.5%) stroke patients had APC resistance compared with none of 31 (0%) control subjects. No patient or control subject had APC-resistant factor V, ie, the factor V Arg506-->Gln mutation. CONCLUSIONS: In Hispanic patients with ischemic stroke, the incidence (approximately 10%) of APC resistance is not caused by the factor V Arg506-->Gln mutation. APC resistance not caused by this factor V mutation may be a risk factor for ischemic stroke in this population.

Arginine↗
PubMed1996

Factors influencing the response to interferon therapy in chronic hepatitis C. Studies on viral genotype and induction of 2',5'-oligoadenylate synthetase in the liver and peripheral blood cells.

BACKGROUND: The mechanism behind the antiviral action of interferon (IFN) therapy in chronic hepatitis C virus (HCV) infection is not well understood, and, furthermore, few factors have been shown to be good predictors of a favourable response to IFN treatment in chronic HCV infection. METHODS: Freshly explanted liver cells and peripheral blood mononuclear cells (PBMC) from 80 patients with chronic HCV infection were used to study the capacity of IFN to induce the enzyme 2',5'-oligoadenylate synthetase (2'5'-AS) in vitro. The HCV genotype was determined in 53 patients. The induction of 2'5'-AS was correlated to the results of IFN-alpha treatment in 36 patients. RESULTS: Normalization of transaminases during IFN treatment was significantly associated with 2'5'-AS levels in liver cells cultured in the absence of IFN. A similar tendency, although not statistically significant, was found for IFN-induced levels of 2'5'-AS in liver cells. No such associations were found when PBMC were analysed. Six patients showed a sustained biochemical response. These six did not deviate significantly from the remaining patients with regard to base-line or IFN-induced levels of 2'5'-AS in liver cells or PBMC. Eradication of HCV RNA during IFN treatment did not correlate with 2'5'-AS levels in liver cells. Comparison of HCV genotype and clinical response showed that patients with genotype 3a had the most favourable outcome. No association was found between liver histology and treatment outcome. CONCLUSION: These data imply that direct effects of IFN on liver cells are of importance for the response to IFN treatment.

2',5'-Oligoadenylate Synthetase↗
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

Acute lymphoblastic leukemias from relapse engraft more rapidly in SCID mice.

It is generally believed that relapse of acute leukemia heralds progression of the disease into a more aggressive stage. The biological behavior of leukemic cells collected from four patients with adult acute lymphoblastic leukemia (ALL) prior to treatment and at relapse was studied after engraftment into 28 unconditioned mice with severe combined immunodeficiency (SCID). Leukemic cells engrafted in all but one mouse, with major differences observed in the growth and aggressiveness of the leukemias. Recipient mice of cells derived from all patients at relapse died more rapidly in overt leukemia than those which were injected with cells obtained prior to induction treatment (P=0.0002). SCID mice that received cells from one patient at the time of diagnosis also died in terminal leukemia. Other SCID mice however, that received cells from the remaining three patients prior to treatment developed occult leukemia that was detectable in the blood or bone marrow with the use of polymerase chain reaction (PCR) or flow cytometry only. Leukemic cells recovered from mice with terminal leukemia exhibited a larger proliferating fraction than cells originally injected (P=0.004). Our results demonstrate, that during the evolution from initial presentation to relapse, ALL cells may acquire biological properties which render them more aggressive in SCID mice.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Supression of telomerase activity in HL60 cells after treatment with differentiating agents.

The human promyelocytic leukemic HL60 cells are immortal and as such express high levels of telomerase activity. All-trans retinoic acid (ATRA) and 1 alpha, 25 dihydroxyvitamin D3 (VD3) induce differentiation of HL60 cells into CD11b+ mature granulocytes and monocytes, respectively. We studied telomerase activity after differentiation of HL60 cells. A marked inhibition of the enzyme activity was observed in the differentiated CD11b+ cells after 72-120 h treatment with either differentiating agent. In contrast, the VD3-treated CD11b- HL60 cells, which failed to undergo differentiation and human erythroleukemic cell line K562, exposed to ATRA retained high levels of telomerase activity. This finding suggests, that telomerase activity is repressed as a differentiation-associated event in HL60 cells. Our results provide the first evidence that immortal leukemic cells, like normal human cells, have a telomerase repressing mechanism which can be activated by differentiation and thus lead to the suppression of telomerase activity. This in vitro model may be useful for studies of the mechanisms controlling telomerase activity and in the search for physiological telomerase modulators.

Calcitriol↗
PubMed1996

Repermeation of partially embolized cerebral arteriovenous malformations: a clinical, radiologic, and histologic study.

PURPOSE: To describe the pattern and time course of embolization-related tissue lesions and repermeation of the intranidal cast after endovascular embolization of cerebral arteriovenous malformations (AVMs) with N-butyl cyanoacrylate (NBCA). METHODS: We retrospectively reviewed the records of 26 patients who were treated by endovascular embolization with NBCA and subsequent surgical extirpation to look for embolization-related tissue lesions and repermeation of the cast. A residual flow through the malformation was identified on preoperative angiograms in every case. RESULTS: Pattern and time course of embolization-related tissue lesions were typical. Until 3 months after embolization, repermeation of embolized structures did not occur. In contrast, repermeation was found in every patient who had surgery later than 3 months after the first embolization (n = 13; 50%). In these cases, histologic examination of the resected nidus disclosed capillary structures inside the lumen of embolized vessels. Capillaries were traced immunohistochemically with antibodies against membrane-bound factor VIII. No parameter other than the interval between the first embolization and surgery was found to relate to the repermeation of the cast. CONCLUSION: Intranidal recapillarization can occur later than 3 months after the first embolization with NBCA if total and solid casting of the nidus was not accomplished.

Adolescent↗
PubMed1995

Autoimmunity in Chagas disease cardiopathy: biological relevance of a cardiac myosin-specific epitope crossreactive to an immunodominant Trypanosoma cruzi antigen.

Heart tissue destruction in chronic Chagas disease cardiopathy (CCC) may be caused by autoimmune recognition of heart tissue by a mononuclear cell infiltrate decades after Trypanosoma cruzi infection. Indirect evidence suggests that there is antigenic crossreactivity between T. cruzi and heart tissue. As there is evidence for immune recognition of cardiac myosin in CCC, we searched for a putative myosin-crossreactive T. cruzi antigen. T. cruzi lysate immunoblots were probed with anti-cardiac myosin heavy chain IgG antibodies (AMA) affinity-purified from CCC or asymptomatic Chagas disease patient-seropositive sera. A 140/116-kDa doublet was predominantly recognized by AMA from CCC sera. Further, recombinant T. cruzi protein B13--whose native protein is also a 140- and 116-kDa double band--was identified by crossreactive AMA. Among 28 sera tested in a dot-blot assay, AMA from 100% of CCC sera but only 14% of the asymptomatic Chagas disease sera recognized B13 protein (P = 2.3 x 10(-6)). Sequence homology to B13 protein was found at positions 8-13 and 1442-1447 of human cardiac myosin heavy chain. Competitive ELISA assays that used the correspondent myosin synthetic peptides to inhibit serum antibody binding to B13 protein identified the heart-specific AAALDK (1442-1447) sequence of human cardiac myosin heavy chain and the homologous AAAGDK B13 sequence as the respective crossreactive epitopes. The recognition of a heart-specific T. cruzi crossreactive epitope, in strong association with the presence of chronic heart lesions, suggests the involvement of crossreactivity between cardiac myosin and B13 in the pathogenesis of CCC.

Amino Acid Sequence↗
PubMed1995

Rebound increase in thrombin generation and activity after cessation of intravenous heparin in patients with acute coronary syndromes.

BACKGROUND: The abrupt cessation of heparin and other thrombin inhibitors when used to treat acute coronary syndromes has been accompanied by a clustering of thrombotic events. It is unknown whether these events are the result of inadequate antithrombin therapy or whether they represent a rebound increase in thrombin activity. This study was designed to determine whether there is a true rebound, as defined by an increase followed by a subsequent decrease, in thrombin activity after discontinuation of intravenous heparin therapy. METHODS AND RESULTS: Thirty-five patients with recent acute myocardial infarction or unstable angina who had received at least 48 hours of intravenous heparin were studied. Patients underwent ST-segment monitoring, and blood samples for determination of thrombin generation and activity were drawn at 0, 3, 6, 10, and 24 hours after heparin discontinuation. Median aPTT was 65 seconds before heparin discontinuation. Median fibrinopeptide A increased from 9.5 to 16.9 ng/mL at 3 hours (P < .0004) and returned to 10.5 by 24 hours. Prothrombin fragment 1.2 likewise transiently increased, from 0.34 to 0.51 nmol/L at 6 hours (P < .0002). Modified antithrombin III decreased over time (P < .002), and activated protein C increased from 2.3 to 4.5 ng/mL at 3 hours (P < .001). Although there were no clinical thrombotic events in the first 24 hours, 4 patients had evidence of ischemia by ST-segment monitoring at a median of 12 hours after heparin discontinuation. The degree of increase in fibrinopeptide A and prothrombin fragment 1.2 was not found to be associated with baseline diagnosis, duration of heparin therapy, baseline level of antithrombin III, or activated protein C. CONCLUSIONS: This study demonstrates a transient rebound increase in thrombin activity as well as in activated protein C upon abrupt discontinuation of intravenous heparin. Clinicians should be vigilant for associated thrombotic events. Further investigation of the significance, mechanism, and possible prevention of this rebound phenomenon is needed.

Aged↗
PubMed1995

Frequent patient-to-patient transmission of hepatitis C virus in a haematology ward.

Blood transfusion is a well-documented route of transmission of hepatitis C virus (HCV). However, a persisting high frequency of HCV infections was recorded in our haematology ward even after screening of blood donors had been introduced. We investigated the viral strains in 37 patients with haematological malignant diseases who had developed hepatitis C when treated in the ward during 1990-93. 17 of the patients acquired hepatitis C despite being transfused only with blood components screened by second-generation anti-HCV tests. The viral strains were characterised by PCR genotyping and nucleotide sequencing of the hypervariable region of the E2 gene. Five clusters of closely related or identical viruses were found involving 2, 3, 4, 6, and 15 patients, respectively. Blood components could be ruled out as the common source of infection because no donor had given blood to all patients sharing a specific strain, and even donors whose blood had been given to several patients were negative for HCV RNA. All patients in each cluster had been treated in the ward during overlapping periods. These findings suggest that despite strict hygienic control, HCV transmission occurred between patients treated in the same hospital setting, as has previously been reported in a smaller group of haemodialysis patients.

Adult↗
PubMed1995

Increased cation transport in mdr1-gene-expressing K562 cells.

Cation-transport properties were compared in a human leukemic cell line (K562) and its vincristine-selected, mdr1-gene-expressing sublines (K562/Vcr30 and K562/Vcr150) by the capacity of the cells to accumulate the potassium analogue thallium (201Tl). Determination of the time course of thallium accumulation in the absence and presence of ouabain, an inhibitor of sodium-potassium adenosine triphosphatase (ATPase), showed that the initial (at 20 min) rate of ouabain-resistant uptake was about 70% higher in the K562/Vcr30 cells than in the parental line. The maximal rate (Vmax) of ouabain-resistant uptake was 78 mmol/h for K562 cells and 115 mmol/h for K562/Vcr30 cells, and the Michaelis constant (Km) was 0.37 and 0.18 mmol, respectively. Bumetanide (50 microM), a specific inhibitor of ouabain-resistant Na-K-Cl cotransport, inhibited the elevated 201Tl uptake in K562/Vcr150 cells but had no effect on cellular vincristine accumulation. Incubation with different multidrug resistance (MDR)-reversing agents (verapamil as well as cyclosporin A and its analogue PSC833) had no significant effect on 201Tl uptake. Membrane depolarization by an elevation of the potassium concentration in the incubation medium did not affect vincristine accumulation in any cell line, which indicated that the changed drug-transport properties in mdr1-gene-expressing cells were not due to membrane hyperpolarization. It was concluded that P-glycoprotein-positive cells have a more efficient ouabain-resistant cation-transport mechanism than to cells without P-glycoprotein. A functional relationship between this phenomenon and MDR was not identified.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

GDC-system embolization for brain aneurysms - location and follow-up.

GDC (Guglielmi detachable coil)-embolization for the treatment of brain aneurysms was first published by Guglielmi in 1991 and has become an integral part of the treatment strategy for cerebral aneurysms in many places around the world. Low morbidity and mortality rates are set against the limited possibilities of aneurysm neck occlusion, especially in large necked aneurysms. Depending on the architecture and on the kind of coil distribution, recanalization of the neck is more or less frequent. Nevertheless, rebleeding rates are low. In our series of 211 brain aneurysms from March 1992 to June 1994, 74 (35%) patients underwent GDC-embolization. 4 patients received combined treatment (GDC-embolization and subsequent surgery). Follow-up angiography was performed on 41 patients (55%) at periods of 6, 12, and 24 months (mean follow-up 8 months). To demonstrate the results in a graphic display, the aneurysms were grouped according to location and size. The analysis of the follow-up results shows the highest occlusion stability in aneurysms of the basilar tip, followed by aneurysms of the PICA origin, the basilar trunk and the PCA. Less stability was obtained in aneurysms of the PCom followed by MCA, Acom and aneurysms of the internal carotid (C1, ophthalmic). Aneurysms of the posterior circulation show generally better results than those located in the anterior circulation. This makes (in combination with the increased surgical difficulties of aneurysms in the posterior fossa) the GDC-treatment especially useful for posterior circulation aneurysms.

Cerebral Angiography↗
PubMed1995

Endosaccular occlusion of basilar artery bifurcation aneurysms using electrically detachable coils.

Thirteen patients with basilar artery bifurcation aneurysms, treated by electrothrombosis using electrically detachable coils, are presented. Nine of them presented after hemorrhage, two with mass effect, and two were found coincidentally with other ruptured aneurysms. Selection for endovascular therapy was based on the following criteria: 1) poor clinical condition (Hunt and Hess III-V); 2) high surgical risk; 3) age and poor medical condition; 4) morphological features (small necked aneurysms). With endovascular Guglielmi detachable coils aneurysm occlusion ranging from 70-100% was achieved in all cases. All five small necked and two large broad necked aneurysms were totally occluded. Two large aneurysms had a 95% occlusion and two other large aneurysms were 90% occluded. In another patient with a large broad based aneurysm only an 80% occlusion was achieved, because of tortuosity of the vertebrobasilar system. Our last patient, who presented as grade V clinically, was partially treated with a 70% aneurysmal occlusion. The clinical results were excellent in 10 and good in 2. The only poor outcome was seen in the grade V patient. There was no morbidity or mortality related to therapy. The only complication was an asymptomatic dissecting aneurysm at the origin of the vertebral artery. Angiographic follow up time ranged from 6 to 20 months with a mean of 9 months. Four patients were treated too recently to have their angiographic follow up at 6 months. Two patients were lost to follow up. Clinical follow up ranged from 1 to 17 months with a mean of 8.9 months. The analysis of our cases clearly shows that aneurysms, which were densely packed with coils, especially if small necked, were less likely to be reperfused and showed a longlasting stable result. Large broad based aneurysms were more likely to be reopened by blood flow after the first procedure, especially if loosely filled with coils, and needed up to 3 interventions to achieve a satisfying result, whereas later in the series a high percentage rate of occlusion was seen after the first procedure. We consider now also a less than 100% occlusion acceptable, because most of the aneurysms will rupture at the dome, which was occluded in all our cases. We conclude, that this new endovascular method is a viable alternative in the treatment of posterior circulation aneurysms with a high surgical risk, in old patients and those in poor clinical and medical condition.

Adult↗