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Biomedical subjects

B J Cohen

Publications and source records attributed to B J Cohen.

At least 91 records · Page 5Linked to original sources
PubMed1990

Blood donor screening for parvovirus B19.

A programme of blood donor screening for parvovirus B19 was conducted from January to May 1990. The main aim of the study was to identify a B19 positive donation that could be used as a source of viral antigen for diagnostic serology. Out of 24,000 donors tested one was positive for B19 antigen by counter current immunoelectrophoresis and over 100 ml of undiluted B19 containing material was obtained. However, much of the positive donation was incorporated in a plasma pool of 28 donations. An acid dissociation technique was used to recover B19 antigen from immune complexes formed in the plasma pool.

Antigens, Viral↗
PubMed1990

Severe anemia due to B19 parvovirus infection in children with acute leukemia in remission.

Two children developed severe anemia with reticulocytopenia while on maintenance chemotherapy for acute lymphoblastic leukemia. Bone marrow examination revealed marked erythroid hypoplasia and giant megaloblasts without evidence of relapse. One patient had evidence of B19 Parvoviremia at the time of severe anemia but failed to produce anti B19 antibodies. Despite the failure to mount an antibody response, the patient had no recurrence of viremia or anemia during the two years of follow-up after the infection. The other patient had no evidence of viremia or elevated anti-B19 antibodies at the time of anemia. However, when his serum was tested 16 months after the episode of anemia, he had elevated IgG and IgM antibodies against B19 parvovirus. The patient did not experience recurrent viremia or anemia over a two year period. Thus, patients with leukemia are at risk to develop severe anemia when infected with B19 parvovirus.

Anemia↗
PubMed1990

Transmission of human parvovirus B19 by coagulation factor concentrates.

The prevalence of antibody to human parvovirus B19 was determined in 86 children with congenital bleeding disorders. Forty-seven of 53 boys (89%) receiving non-heat-treated factor VIII or prothrombin complex concentrates were anti-B19 IgG positive compared with 38% of their age-matched controls and 48% of children treated with cryoprecipitate. Acute B19 virus infection occurred in 2 boys 3-4 weeks after they had received the same batch of commercial factor VIII concentrate. Of 11 susceptible children who had only received heat-treated National Health Service factor VIII concentrate (8Y), 1 acquired anti-B19 IgG. This suggests that 8Y heat-treated concentrate has a much reduced risk of transmitting B19 virus and, by implication, other less heat-stable viruses such as human immunodeficiency virus.

Adolescent↗
PubMed1990

Alanine stimulation of passive potassium efflux in hepatocytes is independent of Na(+)-K+ pump activity.

We have studied the effects of alanine on electrolyte content and ion transport in rat hepatocytes in primary culture. Application of 10 mM alanine is followed by 1) an increase in the rate of sodium entry; 2) an increase in intracellular sodium content; 3) an increase in ouabain-inhibitable rubidium uptake, a measure of Na(+)-K+ pump rate; 4) an increase in unidirectional potassium efflux, whether or not the Na(+)-K+ pump was inhibited; and 5) an increase in the initial rate of potassium loss after Na(+)-K+ pump inhibition. This increase occurred even when alanine was presented in Ringer made hypertonic by the addition of sucrose. Application of hypotonic solution led to a significant net loss of potassium, but no net loss of potassium was observed after alanine application. Thus alanine stimulates the Na(+)-K+ pump by increasing intracellular sodium secondary to an increase in the rate of sodium entry. Passive potassium efflux is stimulated by a mechanism that is independent of the stimulation of the Na(+)-K+ pump. The stimulated potassium efflux does not appear to be a response to cell swelling.

Alanine↗
PubMed1989

An amplified ELISA for the detection of parvovirus B19 IgM using monoclonal antibody to FITC.

A new M-antibody capture ELISA for the detection of specific IgM against parvovirus B19 is described. The test uses a monoclonal anti-fluorescein isothiocyanate (FITC) antibody conjugated to horseradish peroxidase to amplify the positive reactions. Serum samples (N = 823) submitted for B19 IgM assay were tested in parallel in the new ELISA and the standard B19 M-antibody capture radioimmunoassay (MACRIA) test. By both tests B19 IgM was detected in 38 (4.6%) samples, and not detected in 771 (94%) samples. One sample was positive in the ELISA test but negative in the RIA and of the 13 sera giving 'equivocal' results in the MACRIA, 6 were positive and 7 negative. If the RIA equivocal results were excluded, the ELISA showed 100% (38/38) sensitivity and 99.9% (771/772) specificity compared to the MACRIA test. The B19 IgM ELISA is a sensitive and specific test with better discrimination between anti B19 IgM positive and negative specimens than MACRIA.

Animals↗
PubMed1989

Dot blot hybridization assay of B19 virus DNA in clinical specimens.

A nonradioactive dot blot hybridization assay for human parvovirus B19 DNA was set up by using a biotin-labeled DNA probe and streptavidin-alkaline phosphatase conjugate. The assay was used to examine 4,895 specimens referred for B19 virus diagnosis during 1987. Of 48 specimens that gave positive reactions for B19 DNA, 41 were confirmed virus positive by electron microscopy (n = 36), radioimmunoassay (n = 26), or counterimmunoelectrophoresis (n = 20). In 7 samples which were not confirmed and in 11 samples giving weak reactions for B19 DNA, there was serological or epidemiological evidence of recent B19 infection. A further 70 specimens gave weak, apparently false-positive reactions. By electron microscopy, 13 of 16 were contaminated by bacteria, and plasmid DNA was demonstrated in one specimen. Of 55 specimens tested, 52 reacted with streptavidin-alkaline phosphatase conjugate alone. These were probable sources of nonspecificity in an otherwise practical and economic screening method for B19 virus.

Adult↗
PubMed1989

Immune response to B19 parvovirus and an antibody defect in persistent viral infection.

B19 parvovirus has been shown to persist in some immunocompromised patients, and treatment with specific antibodies can lead to decreased quantities of circulating virus and hematologic improvement. A defective immune response to B19 parvovirus in these patients was shown by comparison of results using a capture RIA and immunoblotting. In normal individuals, examination of paired sera showed that the dominant humoral immune response during early convalescence was to the virus major capsid protein (58 kD) and during late convalescence to the minor capsid species (83 kD). In patients with persistent parvovirus infection, variable titers against intact particles were detected by RIA, but the sera from these patients had minimal or no IgG to capsid proteins determined by Western analysis. Competition experiments suggested that this discrepancy was not explicable on the basis of immune complex formation alone and that these patients may have a qualitative abnormality in antibody binding to virus. In neutralization experiments, in which erythroid colony formation in vitro was used as an assay of parvovirus activity, sera from patients with poor reactivity on immunoblotting were also inadequate in inhibiting viral infectivity. A cellular response to purified B19 parvovirus could not be demonstrated using proliferation assays and PBMC from individuals with serologic evidence of exposure to virus. These results suggest that production of neutralizing antibody to capsid protein plays a major role in limiting parvovirus infection in man.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Dementia of depression among patients with neurological disorders and functional depression.

Cognitive performance on the Mini-Mental State Examination (MMSE) was assessed in depressed patients (diagnosis of major depression) with cerebrovascular lesions, with Parkinson's disease, or with functional depression (no known brain lesions). Controls for patients with brain lesions or Parkinson's disease were nondepressed patients with the same conditions. Controls for functionally depressed patients were age-matched normal individuals. Depressed patients had significantly lower total MMSE scores than their nondepressed counterparts, but depression did not have an effect on cognitive performance across the three disease groups. The only significant difference between depressed and nondepressed patients shared by all three groups was poorer performance by depressed patients on the delayed-recall task. The findings suggest that major depression may lead to a specific pattern of cognitive deficits independent of coexisting brain pathology.

Brain Damage, Chronic↗
PubMed1989

Clinical manifestations of human parvovirus B19 in adults.

Human parvovirus B19 has been associated with various clinical effects in a number of uncontrolled reports. To define the usual manifestations of B19 infection in adults and the factors that influence them we present a clinicoepidemiological study of an outbreak of B19 infection centered on a junior school. Four hundred fifty-three of 475 adults in this community were interviewed and blood was obtained for serological diagnosis. Fifty-four cases of recent infection were identified and were HLA typed. Fourteen of the cases were asymptomatic; 32 had an influenzalike illness; 23 a rash; and 26 an acute-onset polyarthropathy that was more common in women and lasted for up to 7 months. HLA-A, -B, and -C antigen frequencies were similar to a local control population and showed no association with symptoms except that HLA-DR1 was absent in those with persistent arthropathy.

Adolescent↗
PubMed1989

(Na,K)-pump: cellular role and regulation in nonexcitable cells.

The (Na,K)-pump develops and maintains ionic gradients that are of fundamental importance for proper function of most animal cells. These gradients are utilized in the form of ionic leak pathways by a number of special and general cell processes (e.g., nerve conduction, nutrient transport, pH regulation). As the sodium gradient in particular energizes many vital cell processes, alterations in cell activity will often be manifest as changes in sodium entry. The (Na,K)-pump rate varies accordingly, in order to maintain balance between Na entry and exit thereby maintaining the potential energy of the cell. Acute changes in sodium influx are balanced by increases in activity of existing pump units, with only a small change in intracellular sodium concentration. This is possible because intracellular is normally poised on the steep limb of the concentration versus activity curve for the (Na,K)-pump, at a point well below maximal activity, allowing large increases in (Na,K)-pump rate with only small changes in sodium concentration. If the increase in sodium influx is prolonged, it appears that the cell responds by synthesizing new pumps, allowing intracellular sodium concentration to return to its original values. Though increases in (Na,K)-pump activity must be accompanied by increases in potassium leak rates, in the experiments we have presented, there does not appear to be direct functional coupling between (Na,K)-pump and the K leak pathways. In these situations the matching of active influx and passive efflux of K short-term appears to occur by mechanisms not directly related to (Na,K)-pump activation.

Animals↗