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Biomedical subjects

M Stuart

Publications and source records attributed to M Stuart.

At least 55 records · Page 3Linked to original sources
PubMed1990

Infection with human immunodeficiency virus type 1 (HIV-1) among recipients of antibody-positive blood donations.

OBJECTIVE: To assess the incidence of human immunodeficiency virus type 1(HIV-1) transmission by antibody (anti-HIV-1)-positive blood components, and to determine the immunologic and clinical course in HIV-1-infected recipients. DESIGN AND SUBJECTS: We retrospectively tested approximately 200,000 donor blood component specimens stored in late 1984 and 1985 for anti-HIV-1, and we contacted recipients of positive specimens to determine their serologic status. They were compared with both recipients of HIV-1-negative transfusions and healthy (untransfused) controls. Subjects were seen at 3- to 6-month intervals for up to 4 years for clinical and immunologic evaluations. MEASUREMENTS AND MAIN RESULTS: Of 133 recipients, 9 had other possible exposures. Excluding these cases, 111 of 124 (89.5%) were anti-HIV-1-positive (95% CI, 84.1% to 94.5%). The recipient's sex, age, underlying condition, and type of component did not influence infection rates. The cumulative risk for developing the acquired immunodeficiency syndrome (AIDS) within 38 months after transfusion was 13% (CI, 7.5% to 21.6%). At 36 +/- 3 months after the index transfusion, seropositive recipients had lower counts of CD2+CDw26+, CD4+, CD4+CD29+, and CD4+CD45RA+subsets and more CD8+I2+ lymphocytes than did recipients of anti-HIV-1-negative transfusions. The CD4+ and CD2+CDw26+subsets changed the most rapidly. The absolute CD8+ count remained normal. CONCLUSIONS: Transfusion of anti-HIV-1-positive blood infected 90% of recipients. The rate of progression to AIDS within the first 38 months after infection was similar to that reported for homosexual men and hemophiliacs. Although most lymphocyte subset counts changed over time, CD8+ counts were constant.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Screening of selected male blood donors for p24 antigen of human immunodeficiency virus type 1. The Transfusion Safety Study Group.

BACKGROUND: The p24 antigen of human immunodeficiency virus type 1 (HIV-1) is sometimes detected before antibody (anti-HIV-1) is detectable in the serum of recently infected persons. This has led to the consideration of p24-antigen testing for routine screening of blood donors. METHODS: To estimate how many HIV-infected seronegative donors would be identified if p24-antigen screening was introduced, we tested selected donations from a repository of 200,000 serum samples from voluntary donors that was established in late 1984 and early 1985. The 8597 serum samples selected for p24-antigen screening were chosen because their donors had demographic characteristics known to be associated with a high prevalence of seropositivity. RESULTS: The prevalence of anti-HIV-1 antibodies in the 1984-1985 serum samples selected for p24-antigen screening was 1.54 percent--more than 100 times the 0.012 percent prevalence in present-day donations in the United States. The antigen was detected in 15 of 132 serum samples (11.4 percent) from donors who had already been confirmed as seropositive. No instance of confirmed positivity for p24 antigen was found among the 8465 seronegative serum samples. CONCLUSIONS: These data indicate that the yield of screening for p24 antigen in volunteer donors to identify HIV-1 carriers would be negligible. We therefore recommend against routine screening with currently available p24-antigen assays.

Blood Donors↗
PubMed1990

Processing strategies in a phoneme deletion task.

The present study explores the factors underlying competence in a difficult consonant deletion task, using a sample of nine-year-old children whose development had been followed from the age of four. In particular it examines the factors governing use of phonological and orthographic strategies in the deletion task, and the relations between strategy use, current reading and spelling ability, and earlier phonological awareness skills. Processes in consonant deletion are then mapped on to current dual-route models of reading and spelling.

Awareness↗
PubMed1990

Factors influencing word recognition in pre-reading children.

Current theories of reading development (e.g. Frith, 1985) propose an initial logographic phase in which printed word recognition is based on salient visual features of the print. An alternative proposition (Stuart & Coltheart, 1988) is that phonologically skilled beginning readers might be able to set up word recognition units from their phonological analyses of spoken words, and their knowledge of correspondences between sounds and letters. Neither view is supported by the present study. It is shown in a series of experiments that phonological knowledge is indeed helpful even to pre-reading children asked to discriminate printed targets from distractors in an auditory-visual matching task. However, this effect occurs for non-words as well as words and pseudohomophones, suggesting the operation of a non-lexical rule-based system rather than the establishment of word recognition units.

Child, Preschool↗
PubMed1990

Ambulatory practice variation in Maryland: implications for Medicaid cost management.

Simulation modeling with data from the Maryland Medicaid Management Information System has provided an opportunity to examine policy options and assess their likely impact on savings before program decisions were made. Analysis of a large sample of the Maryland Aid to Families with Dependent Children (AFDC) Medicaid subpopulation confirms that a significant difference in utilization and cost to Medicaid exists between usual sources of care for AFDC clients even after controlling for patient demographics and case-mix differences. Findings indicate that savings from reduced use of hospital outpatient departments may offset increases of as much as 40-50 percent in physician fees under certain assumptions.

Adolescent↗
PubMed1989

Cells of origin of histaminergic afferents to the cat median eminence.

The exact origin of histaminergic neuronal perikarya sending axons to the median eminence and posterior pituitary was investigated in the cat by using two colour double-immunostaining methods: unconjugated wheat germ agglutinin or cholera toxin as retrograde tracers combined with histamine (HA) immunohistochemistry. HA immunohistochemistry revealed the presence of HA-immunoreactive terminal-like fibers both in the external layer of the median eminence and neural lobe of the pituitary. The double-labeling studies further demonstrated the histaminergic innervation of the median eminence and neural lobe by a few HA-immunoreactive neuronal perikarya located in the posterior hypothalamus.

Animals↗
PubMed1989

Epidemiologic background of blood donors with antibody to human T-cell lymphotropic virus. Transfusion Safety Study Group.

We interviewed 51 blood donors in four major US metropolitan areas subsequently found to have had antibodies to human T-cell lymphotropic virus (anti-HTLV) in late 1984-early 1985. Sixteen donors (31%) reported that they or a sexual contact had a history of blood transfusion. Twelve donors (24%) reported that they or a sexual contact used intravenous drugs. Ten donors (20%) were blacks born in the southeastern US. Four of the male donors (15%) reported homosexual contact. The most common characteristic was an association with Japan or the Caribbean basin (61%). These results show a broader variation of epidemiologic backgrounds than anticipated.

Adult↗
PubMed1989

Zinc deficiency and eating disorders.

Decreased food intake, a cyclic pattern of eating, and weight loss are major manifestations of zinc deficiency. In this study, zinc status was evaluated in 62 patients with bulimia and 24 patients with anorexia nervosa. Forty percent of patients with bulimia and 54% of those with anorexia nervosa had biochemical evidence of zinc deficiency. The authors suggest that for a variety of reasons, such as lower dietary intake of zinc, impaired zinc absorption, vomiting, diarrhea, and binging on low-zinc foods, patients with eating disorders may develop zinc deficiency. This acquired zinc deficiency could then add to the chronicity of altered eating behavior in those patients.

Adolescent↗
PubMed1988

Tolerance of Pseudomonas aeruginosa to killing by ciprofloxacin, gentamicin and imipenem in vitro and in vivo.

In the rat croton oil pouch model, treatment with ciprofloxacin, gentamicin or imipenem caused a sharp reduction in the numbers of Pseudomonas aeruginosa when applied 24 h after infection but treatment had little or no effect when delayed until 48 h after infection. Surviving bacteria from treated animals were fully susceptible on subculture in vitro. Between 24 h and 48 h after infection there was an increase in the concentration of magnesium and a decrease in the concentration of oxygen but no significant change in the pH of the pouch fluid. In-vitro, the MBC of gentamicin was increased four-fold by the addition of magnesium ions and eight-fold under anaerobic conditions whereas these variables had no significant effect upon the MBC of ciprofloxacin and imipenem. However, cells of P. aeruginosa incubated in batch culture for 4, 24 and 48 h became progressively more tolerant to killing by all three drugs. We conclude that the tolerance of P. aeruginosa in vivo was only partly explained by biochemical changes at the site of infection. The stationary growth phase was associated with progressive tolerance to killing by ciprofloxacin, gentamicin and imipenem both in vivo and in vitro.

Animals↗
PubMed1987

The platelet cyclooxygenase metabolite 12-L-hydroxy-5, 8, 10-hepta-decatrienoic acid (HHT) may modulate primary hemostasis by stimulating prostacyclin production.

Although HHT accounts for approximately one third of the arachidonic acid (AA) metabolites produced by stimulated platelets, no well defined function has been attributed to this product. We report that HHT stimulates prostacyclin production by endothelial cells, and have identified the mechanism for this effect. In human umbilical venous endothelial cells, HHT (0.5 and 1 microM) stimulated prostacyclin (RIA for 6KPGF1 alpha) by 32 +/- 22% (1SD) and 42 +/- 38% (P less than 0.05 and less than 0.01). Similar changes were observed when the effect of HHT on exogenous [1-14C] AA metabolism in fetal bovine aortic endothelial cells (FBAECs) was studied. Kinetic analyses revealed that HHT affected vascular cyclooxygenase. HHT (1 microM) increased Vmax in test microsomes (706 +/- 21 pmol/mg/min, mean +/- 1SE) when compared to controls (529 +/- 20; P less than 0.02). No concomitant effect on Km was observed. A further effect of HHT on AA release from endothelial cell membrane phospholipids was noted. Prelabeling experiments revealed that HHT (1 microM) increased the ionophore stimulated release of AA from FBAECs (20952 +/- 555 cpm/well control mean +/- 1SE vs 25848 +/- 557 for paired HHT treated cells; P less than 0.05). The effect of HHT on platelet AA metabolism was next studied. Preincubation of washed platelets with HHT (1 microM) did not enhance thrombin or arachidonic acid induced platelet TXB2 formation. In platelets prelabelled with [1-14C]AA, HHT (1 microM) had no effect on AA release post thrombin stimulation. Conversion to cyclooxygenase metabolites was also not enhanced. HHT stimulates vascular prostacyclin without a concomitant effect on platelet AA metabolism. HHT may thus be an important local modulator of platelet plug formation.

Animals↗
PubMed1987

Effect of amniotic fluid on platelet thromboxane production.

We have studied the effect of amniotic fluid on thromboxane A2 (TXA2) production as an initial step in an evaluation of the role of this metabolite as the mediator of the pulmonary hypertension that accompanies perinatal aspiration. Term amniotic fluid enhanced platelet thromboxane B2 (TXB2) production in the presence of the aggregating agents thrombin and arachidonic acid, activity being confined to the lipid fraction. Compared with a baseline production of 1.4 +/- 0.45 pmol TXB2/10(6) platelets in response to thrombin (1 U/ml), unfractionated amniotic fluid or its lipid fraction enhanced TXB2 production to 2.87 +/- 0.53 and 2.81 +/- 0.62 pmol, respectively (P less than 0.01). Values for the aqueous extract were no different from buffer control values (1.14 +/- 0.5). No enhancement of platelet TXB2 production was observed in amniotic fluid obtained at 15 to 17 weeks. Similar activity was observed with either adult or neonatal platelets. This thromboxane enhancing property of amniotic fluid appears to be distinct from its thrombin generating property. Following perinatal aspiration, in situ production of thrombin and proaggregatory TXA2 could recruit more platelets, enhance local TXA2 production, and be responsible for the platelet thrombi that have been documented at autopsy in the pulmonary microcirculation in infants with perinatal aspiration syndrome.

Amniotic Fluid↗
PubMed1987

Dose response of experimental Pseudomonas endophthalmitis to ciprofloxacin, gentamicin, and imipenem: evidence for resistance to "late" treatment of infections.

Single intravitreal doses of ciprofloxacin, gentamicin, or imipenem were administered to rabbits with pseudomonas endophthalmitis for determination of the maximally effective dose. Treatment was given 24 hr ("early") or 48 hr ("late") after infection. With early treatment the dose-response relationship between the drug concentration and the diminution in bacterial counts in the vitreous humor was linear with all three drugs. By contrast, with late treatment the same vitreal concentrations had no significant effect on bacterial counts. The failure of late treatment was not due to an increased rate of clearance of drugs from the eyes and could not be reproduced with a similar bacterial inoculum in vitro. Bacteria cultured from treated eyes were fully sensitive when plated directly onto drug-containing agar. The poor bactericidal effect of late treatment may in part be related to transient phenotypic alterations in the bacteria in response to changes in the environment of infection such as hypoxia, low pH, and exhaustion of critical bacterial nutrients.

Animals↗