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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↗
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↗
PubMed1979

A circulating inhibitor of platelet aggregation in Bartter's syndrome.

Aggregation studies were performed on platelets from five patients with Bartter's syndrome. Epinephrine failed to induce aggregation in all five patients. Adenosine 5'-diphosphate (ADP) produced a single reversible phase of aggregation, and there was depressed sensitivity to collagen. Response to ristocetin was normal. There was a dose-related inhibition of ADP-induced platelet aggregation when plasma from the patients was addeded to normal platelet-rich plasma. This inhibition was diminished or absent when patients were receiving aspirin. Washed platelets from two patients who were no longer undergoing aspirin therapy, showed a normal response to epinephrine in normal platelet-poor plasma. Bleeding time was reduced from 23 minutes to 12 minutes in one patient while on aspirin therapy. These studies suggest that a circulating inhibitor of platelet aggregation, probably of prostaglandin origin, is present in the plasma of patients with Bartter's syndrome.

Adenosine Diphosphate↗
PubMed1979

Possible C1q bypass loop activation in the haemolytic uraemic syndrome.

Ultrastructural and immunofluorescent microscopic studies were performed on renal tissue obtained from nine patients during the acute and convalescent phase of the haemolytic uraemic syndrome (HUS). All had glomerular deposits of IgM in the absence of circulating immune complexes. This was associated with deposition of C1q during the acute phase, and properdin and C3 during the convalescent phase. C4 was consistently absent. Since such a pattern of complement deposition does not fulfil criteria either for alternate or classical pathway activation, the possibility of C1q bypass loop activation by IgM is suggested.

Child↗
PubMed1979

Synergistic action of 5-aza-2'-deoxycytidine and 3-deazauridine on L1210 leukemic cells and EMT6 tumor cells.

The biochemical and biological effects of the combination of 5-aza-2'-deoxycytidine (5-aza-dCyd) and 3-deazauridine (3-DU) on L1210 leukemic cells and EMT6 tumor cells were investigated. The cytotoxic action of 5-aza-dCyd and 3-DU on both L1210 and EMT6 cells in vitro was synergistic when these agents were used in combination. The combination of 5-aza-dCyd and 3-DU produced a greater inhibition of in vitro growth of L1210 and EMT6 cells than did either agent alone. The in vivo antineoplastic activity of this combination was synergistic with respect to the increased survival time of BALB/c x DBA/2 F1 mice with L1210 leukemia. 3-DU, an agent that reduces the intracellular pool size of cytosine nucleotides, stimulated the incorporation of [3H]-5-aza-dCyd into DNA of both L1210 and EMT6 cells, suggesting that the synergistic action of this combination is related to the increased incorporation of 5-aza-dCyd in the presence of 3-DU.

3-Deazauridine↗
PubMed1978

Septicemia in children with leukemia.

A review of the hospital records of 164 children with leukemia diagnosed between January 1969 and December 1975 disclosed 51 episodes of septicemia in 43 patients; 57 infectious agents were isolated. Gram-positive bacteria were isolated as frequently as gram-negative bacteria, each type accounting for 45.6% of all the agents isolated. Only 2 of the 24 episodes of exclusively gram-positive septicemia were fatal, whereas 9 of the 23 episodes of exclusively gram-negative septicemia were fatal. The mean duration of neutropenia was 5.6 days in patients with gram-positive septicemia and 19.5 days in patients with gram-negative septicemia, a significant difference (P less than 0.01). Gram-positive septicemia was diagnosed after a mean of 5.9 days of hospitalization and gram-negative septicemia after a mean of 29.0 days, also a significant difference (P less than 0.001). In this exclusively pediatric population of leukemic patients gram-positive agents have to be considered as potential pathogens, and initial antibiotic therapy must be selected with this fact in mind.

Adolescent↗