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Biomedical subjects

P Challis

Publications and source records attributed to P Challis.

7 recordsLinked to original sources
PubMed1990

Recombinant-based competitive anti-HIV assay: solution of some operating problems.

Using the Wellcozyme anti-HIV recombinant assay at 47 degrees, a strongly reactive result with an anti-HIV positive serum sample could not be reproduced when the corresponding plasma sample was used. Dilution in anti-HIV negative serum or kaolin treatment of the plasma specimen produced the clear reactivity seen with the serum sample, and a reduction in incubator temperature was also found to reduce this 'plasma effect'. Problems were also encountered initially when haemolysed serum or plasma with non-standard concentrations of anticoagulant were tested. These phenomena were not apparent when the same manufacturer's test based on cell-derived antigen was used, indicating that the introduction of new technology may cause unforeseen problems although these can usually be overcome.

AIDS Serodiagnosis↗
PubMed1989

Gelatin particle agglutination assay for HIV antibodies: a rapid, economical modification with increased sensitivity.

Modification of a commercial gelatin particle agglutination assay for anti-HIV reduces the test time to 30 min, increases the sensitivity sevenfold without any prozoning, and maintains specificity while cutting the cost of the test by 90%. The modification involves a tenfold dilution of the gelatin particles, which are added to a dilution of test serum in a 'V' well standard microplate. After incubation, plates are centrifuged briefly and allowed to stand at an inclination of 70 degrees until positive and negative reactions are clearly distinguishable within approximately 15 min.

Agglutination Tests↗
PubMed1988

Improved diabetes control reduces skeletal muscle capillary basement membrane width in insulin-dependent diabetes mellitus.

We studied the relationship between the control of blood glucose and the width of skeletal muscle capillary basement membrane in 54 insulin-dependent diabetic patients. After initial measurement of levels of glycosylated hemoglobin and the width of skeletal muscle capillary basement membrane, the patients were divided into two groups: an intensive treatment group of 30 patients who were treated with continuous subcutaneous insulin infusion and a control group of 24 patients who continued to receive conventional treatment, usually two daily injections of insulin. Both groups have been followed prospectively for periods of time up to 4 years. Within 1 year the intensive treatment group had a significant decrease in glycosylated hemoglobin levels as compared to baseline values reflecting improved control of blood glucose. This level of glycosylated hemoglobin was stable over the remainder of the follow-up period. This group also had a significant reduction in the width of skeletal muscle capillary basement membrane within 1 year and it persisted for the 4 years of observation. The control group of patients had no significant change in their level of glycosylated hemoglobin and the width of the skeletal muscle capillary basement membrane tended to increase with time. It this result in skeletal muscle capillaries applies to those of retinal and renal tissue, meticulous diabetic control for a prolonged period of time may be beneficial in preventing the progression of the microvascular complications of diabetes mellitus.

Adult↗
PubMed1985

Effect of tolrestat on red blood cell sorbitol levels in patients with diabetes.

The effect of the aldose reductase inhibitor, tolrestat, on red blood cell (RBC) sorbitol levels was studied in 23 patients with diabetes after oral dosing with tolrestat, 25 or 100 mg b.i.d. The mean (+/- SE) RBC sorbitol levels (measured 12 hours after the preceding dose) after 3, 7, and 13 days of dosing decreased after both dose levels. After 25 mg tolrestat the RBC sorbitol levels fell from 25.1 +/- 4.0 to 20.0 +/- 5.7 nmol/gm hemoglobin (21%) and after 100 mg tolrestat the level fell from 26.7 +/- 3.7 to 11.4 +/- 1.7 nmol/gm hemoglobin (57%; P less than 0.001). This latter RBC sorbitol concentration is similar to levels in individuals without diabetes. At both dosage levels the maximum decrease in RBC sorbitol levels occurred after only 3 days of dosing. Tolrestat had no effect on plasma glucose or hemoglobin A1 concentrations. The overall mean plasma unbound drug concentration measured 12 hours after 100 mg tolrestat (11.7 +/- 3.0 ng/ml; 3.3 X 10(-8) mol/L) was similar to the median inhibitory level (3 X 10(-8) mol/L) of tolrestat for sorbitol accumulation in human RBCs incubated in a high-glucose medium. Our results demonstrate the systemic bioavailability of tolrestat and its aldose reductase inhibitory activity in erythrocytes of patients with diabetes.

Administration, Oral↗
PubMedDate not supplied

Personality traits as predictors of good diabetic control.

To identify personality characteristics that might contribute to overall good control of type I diabetes mellitus, we used a biological correlate of control, glycosylated hemoglobin A1c values, as a means of selecting patients. Patients with evidence of good control (HbA1c less than 7.5%) were compared with patients with evidence of poor control (HbA1c greater than 10.4%). All patients were administered the Personality Research Form E. Need for achievement and a socially desirable response style were associated with good glycemic control. This finding is placed in the context of the complexity of health care behaviors required for adequate self-management.

Adult↗