Search PubMed⌕ Search

Biomedical subjects

G E Rivard

Publications and source records attributed to G E Rivard.

At least 19 recordsLinked to original sources
PubMed1992

A trial of desmopressin to reduce blood loss in patients undergoing spinal fusion for idiopathic scoliosis.

Desmopressin (DDAVP) has been reported to reduce bleeding in patients undergoing spinal fusion. To evaluate its efficacy in normal patients, 30 healthy young patients (ASA physical status I or II) undergoing spinal fusion for idiopathic scoliosis were randomly allocated to receive either 100 mL of physiologic saline solution (placebo group) or DDAVP (10 micrograms/m2 of body surface area) (DDAVP group) in a prospective, double-blind trial. Intraoperative blood loss was measured by weighing sponges and suction drainage and postoperative bleeding by wound drainage. The amount of blood loss expressed as a percent of the estimated blood volume was similar in both groups during the intraoperative period (67.0% +/- 28.8% [mean +/- SD] placebo group vs 57.4% +/- 26.5% DDAVP group), the postoperative period up to 24 h (32.5% +/- 6.4% placebo group vs 31.1% +/- 10.6% DDAVP group), and both periods (94.3% +/- 29.4% placebo group vs 88.2% +/- 30.7% DDAVP group). With the dose used in our study, we conclude that DDAVP does not reduce surgical bleeding in patients undergoing spinal fusion for idiopathic scoliosis.

Adolescent↗
PubMed1991

Lupus anticoagulants, anticardiolipin antibodies, and fetal loss. A case-control study.

BACKGROUND: Lupus anticoagulants and anticardiolipin antibodies are antiphospholipid antibodies that have been associated with fetal loss, but they have not been shown unequivocally to be a risk factor for this event. METHODS: To estimate the risk of fetal loss in association with these antibodies, we conducted a hospital-based case-control study of 331 women with spontaneous abortion or fetal death (case patients) and 993 controls. The subjects were included in the study only if they reported that they had had no previous spontaneous fetal loss. Each control was a pregnant woman who, in the same period of pregnancy as a case patient, had not had a fetal loss. Lupus anticoagulants were identified in blood samples through a series of coagulation tests, and IgG anticardiolipins by an enzyme-linked immunosorbent assay. Each subject was interviewed in person to obtain information on potential confounding variables, such as sociodemographic characteristics and medical conditions. RESULTS: Lupus anticoagulants were found in blood from 17 case patients (5.1 percent) and 38 controls (3.8 percent). The crude odds ratio for the association between lupus anticoagulants and fetal loss was 1.36 (95 percent confidence interval, 0.75 to 2.43); the odds ratio adjusted for confounders was 1.42 (95 percent confidence interval, 0.72 to 2.80). An IgG anticardiolipin level of 5 units or more was found in 4 case patients (1.2 percent) and 15 controls (1.5 percent). The crude and adjusted odds ratios for fetal loss were 0.80 (95 percent confidence interval, 0.26 to 2.41) and 1.28 (95 percent confidence interval, 0.38 to 4.21), respectively. CONCLUSIONS: There is not apparent justification for considering lupus anticoagulants or IgG anticardiolipins to be risk factors for fetal loss among women who present with spontaneous abortion or fetal death and have had no previous spontaneous fetal loss.

Abortion, Spontaneous↗
PubMed1991

Isolation of 6-mercaptopurine in human plasma by aluminum ion complexation for high-performance liquid chromatographic analysis.

A sample preparation technique and a high-performance liquid chromatographic method for 6-mercaptopurine (6-MP) that is simple, sensitive and without interference from its metabolites is described. 6-Thioguanine (6-TG) is added as an internal standard to the plasma sample, which is then treated with an aqueous solution of aluminum perchlorate to denature the plasma proteins and form complexes with 6-TG, 6-MP and its major metabolite, 6-thiouric acid (6-TUA). These complexes coprecipitate with proteins on centrifugation. 6-MP and its analogues are then extracted from the precipitate with perchloric acid containing sodium hydrosulfite and the extract is chromatographed on an Ultrasphere ODS column eluted with 0.1 M phosphoric acid and 0.001 M dithiothreitol in deionized water. The eluate is monitored at 340 nm. No interfering peak was encountered in over 300 clinical plasma samples. 6-TUA was separated from 6-MP and was found to be present in much higher concentration than 6-MP itself throughout the sampling time (6 h) following oral administration of the drug.

Aluminum↗
PubMed1991

Differential staphylococcal protein A-induced enhancement of natural killer cell activity of lymphocytes from HIV-seropositive individuals.

A decrease in Natural Killer (NK) cell activity is a common feature of the immune dysfunction found in patients with HIV-induced acquired immune deficiency syndrome (AIDS). We and others have shown earlier that staphylococcal protein A (SpA) preparations enhance NK cell activity against tumor targets. The present study was aimed at exploring whether the decreased NK activity of lymphocytes from HIV seropositive subjects could be modulated or restored in vitro by SpA. Two types of HIV-seropositive subjects were studied: hemophiliac and non-hemophiliac; matched controls were chosen among hospital staff and HIV-seronegative hemophiliac volunteers. In vitro proliferation and interleukin-2(IL-2)/interferon gamma (IFN gamma) release in response to mitogens were also studied. NK cell responses of peripheral blood lymphocytes (PBL) of HIV-seropositives were lower than those of seronegatives. However, exposure of PBL from HIV-seropositive individuals to SpA boosted their NK cell responses against NK-resistant target cells of tumor origin. The decrease in NK activity could not be attributed to the low number of NK cells, since no significant difference in NK cell number was observed between HIV-seropositive individuals and controls. Mitogen-induced blastogenic responses were present in all four groups, as was the mitogen-induced IFN gamma release. We conclude that impaired NK activity and its boosting against NK-resistant targets after SpA induction is an important characteristic of lymphocytes of HIV-seropositive individuals regardless of the disease state and that this NK defect may not be irreversible.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Recurring mutations at CpG dinucleotides in the region of the von Willebrand factor gene encoding the glycoprotein Ib binding domain, in patients with type IIB von Willebrand's disease.

The mutant von Willebrand factor (vWf) molecule in type IIB von Willebrand's disease (vWd) has an increased binding affinity for the platelet receptor glycoprotein Ib (GpIb). In previous studies we have confirmed genetic linkage of this phenotype to the vWf gene and in this report we document three recurring missense mutations in the region of the gene that encodes the GpIb binding domain. Two families with type IIB vWd were found to have an arginine to tryptophan substitution at residue 543, three families had a valine to methionine substitution at residue 553, and one kindred had an arginine to glutamine change at amino acid 578. None of these sequence changes were found in 200 normal vWf genes and within each of the six families the mutations were only found in affected subjects. This is strong circumstantial evidence in support of these substitutions representing the disease causing mutations in these families. All three of these substitutions have occurred at CpG dinucleotide sequences, and their polymorphic associations indicate that they represent recurring new mutations. Missense mutations at these sites may represent the underlying genetic pathology in a large number of type IIB vWd families.

Alleles↗
PubMed1990

Epstein-Barr virus polymorphic B-cell lymphoma associated with leukemia and with congenital immunodeficiencies.

Polymorphic B-cell lymphoma seen in four patients with congenital immunodeficiencies and in two patients with leukemia receiving chemotherapy was associated with the Epstein-Barr virus (EBV). The tumors had characteristic histologic features: they were polymorphic consisting of a mixture of lymphoblasts and differentiated cells including plasma cells, and areas of hemorrhagic necrosis were prominent. The tumors were either polyclonal, monoclonal, or multiclonal. Patients with congenital immunodeficiencies who developed these tumors died despite radiotherapy, corticosteroids plus acyclovir, or a combination of intravenous (IV) immunoglobulins and alpha 2 interferon. Patients with leukemia recovered when immunosuppressive drugs were discontinued and leukemia has not recurred over a period of 2 and 4 years, respectively, in the two patients.

Antineoplastic Agents↗
PubMed1989

High-performance liquid chromatographic determination of mitoxantrone in plasma utilizing non-bonded silica gel for solid-phase isolation to reduce adsorptive losses on glass during sample preparation.

Mitoxantrone, a highly active antineoplastic agent, was found to bind strongly to non-bonded silica gel and glassware. When a Hamilton syringe was used to load and inject a mitoxantrone solution (0.4 microgram/ml in water) on to a high-performance liquid chromatographic (HPLC) system, about 95% of the loaded compound was found to bind to the glass surface of the syringe barrel and could not be removed by rinsing with water. It could, however, be removed slowly with an acidic solution and thus a small peak of mitoxantrone was present on the chromatogram whenever a blank acidic solution was injected with the syringe. The bound mitoxantrone could be removed effectively from the syringe surface with a solution of tetramethylammonium chloride, citric acid, methanol and water (elution solvent). This binding introduces a large error in assay results and might be one of the major factors responsible for contradictory pharmacokinetic data that have been reported. A new plasma preparation scheme and an HPLC method for mitoxantrone were developed to address this binding problem. Mitoxantrone was extracted directly from plasma samples with a plastic mini-column packed with non-bonded silica gel and eluted with the above elution solvent. The eluent was analysed by HPLC on an ODS column with an absorbance detector at 658 nm. The mobile phase was 0.1 M triethylamine phosphate (pH 3.0) in water-tetrahydrofuran-methanol (69:1:30) containing 0.02 M tetramethylammonium chloride. Methylene blue was added as an internal standard. Preliminary results showed that mitoxantrone levels in human plasma followed a triphasic decay curve after an intravenous bolus injection. The terminal elimination half-lives measured in three patients (mean t1/2 gamma = 25 min) were all shorter than the published values which ranged from 56 min to 9 days.

Chemical Phenomena↗
PubMed1989

Milk could decrease the bioavailability of 6-mercaptopurine.

The bioavailability of 6-mercaptopurine (6-MP) administered orally for maintenance therapy of children with acute lymphoblastic leukemia is highly variable. Xanthine oxidase (XO) can transform 6-MP into 6-thioxanthine (6-TX) and 6-thiouric acid (6-TUA), which have no therapeutic value. XO is found in high concentration in cow's milk. Incubation at 37 degrees C for 30 min with commercial preparations of pasteurized cow's milk results in transformation of 30% of a clinically relevant concentration of 6-MP into 6-TUA. Milk boiled for 5 min has no effect on the 6-MP. Addition of gastric juice at ratios likely to be seen in children has negligible inhibitory effect on the 6-MP destroying activity of milk. Conversely, folic acid and allopurinol markedly inhibit this effect at clinically relevant concentrations. These observations may help to optimize modalities of administration of 6-MP.

Animals↗
PubMed1988

Relative sensitivity of different tests in the detection of low titer lupus anticoagulants.

Lupus anticoagulants (LA) and anticardiolipin antibodies have been strongly associated with recurrent abortion and fetal death. Because steroids have been reported to improve the fetal outcome of LA associated pregnancies, presumably by decreasing the levels of LA, it becomes desirable to have a simple and reliable test to monitor the levels of the putative antibody. To this effect, we assessed the capacity of the following coagulation tests to detect the presence of LA in serial dilutions of patient plasma with pooled normal plasma: kaolin clotting time (KCT), tissue thromboplastin inhibition test (TTIT), dilute Russell Viper venom time (DRVVT) and activated partial thromboplastin time with standard and high concentrations of phospholipids (SC and HCAPTT). All samples were also evaluated for the presence of anticardiolipin antibodies with an ELISA. The KCT was able to detect LA at a much greater dilution in normal plasma than any of the other clotting assays. The ELISA was comparable to KCT in its ability to detect high dilutions of LA.

Blood Coagulation Factors↗
PubMed1985

Maintenance chemotherapy for childhood acute lymphoblastic leukaemia: better in the evening.

The course of 118 children with acute lymphoblastic leukaemia who had achieved complete remission with a standard induction protocol and had also received meningeal prophylaxis with intrathecal methotrexate (MTX) and cranial irradiation was reviewed. Maintenance chemotherapy consisted of daily 6-mercaptopurine (6-MP), weekly MTX, and monthly vincristine and prednisone. 82 children took 6-MP and MTX in the morning and 36 in the evening. Disease-free survival as determined by Kaplan-Meier analysis was better for children on evening chemotherapy. Regression analysis (Cox proportional hazards model, with evening vs morning schedule as exposure variable, and age at diagnosis, leucocytosis at diagnosis, and sex as covariates) showed that, for those surviving free of disease for longer than 78 weeks, the risk of relapsing was 4.6 times greater for the morning schedule than for the evening one.

Adolescent↗
PubMed1979

Platelet hyporesponsiveness to epinephrine in carriers of Bartter's syndrome.

Platelet aggregation was investigated in the parents of 4 patients with Bartter's syndrome. Aggregation induced by ADP and ristocetin was normal. However, there was some depression of aggregation induced by collagen. All obligatory heterozygotes showed depressed aggregation in response to epinephrine.

Adenosine Diphosphate↗