Flow cytometry analysis of platelet antibodies

We have devised assays to detect both circulating alloantibodies to platelets (indirect assay) and platelet-association IgG and IgM (direct assay) using a flow cytometric technique. A variety of patients with immune thrombocytopenia were studied. Employment of a confocal lens in the flow cytometer increased the discrimination power of the instrument. Patients with autoimmune thrombocytopenia (idiopathic thrombocytic purpura [ITP], systemic lupus erythematosus (SLE), lymphoma, leukemia, and drug-induced thrombocytopenia showed a significant increase in platelet-associated antibody. Circulating antibodies to platelets (alloantibodies) were demonstrated in cases of platelet refractoriness and neonatal isoimmune purpura. Day-today precision of the assays ranged from 3% to 6% (coefficient of variation). No interference was shown in the presence of hemoglobin (5 g/L), triglycerides (10 g/L), or polyclonal and monoclonal immunoglobulinemia (50 g/L: IgG, IgA, IgM). The sensitivity of the direct assay was 500 attograms of IgG or IgM platelet.     

Precision of dual-photon absorptiometry

Summary Precision of dual-photon absorptiometry (DPA) measurements was determined in a lumbar spine phantom and in humans. Approximately half of the measurements were made before and half after a¹⁵³gadolinium source change. The phantom was measured with different amounts of acrylic, which simulates human soft tissue, in order to evaluate the influence of body thickness on bone mineral density (BMD). Results of scans analyzed with two software versions from Lunar Radiation Corp., the widely used 08B and a prototype 08C, are compared. DPA with a cold source significantly overestimated BMD in the phantom in the presence of large amounts (more than 25 cm) of soft tissue equivalent with version 08B but not with the newer version 08C. Similiarly, in nine subjects, there was a significant decrease in spine BMD after a source change when scans were analyzed with version 08B (mean difference 0.026 g/cm²,P=0.002) but not with 08C (0.01 g/cm²,P=0.234). No systematic effect of source change on femoral BMD measurements was observed. The SD of the mean difference of two measurements of the nine subjects was 0.019 g/cm² (1.6% of the mean value) for the spine with software version 08B and 0.024 g/cm² (2.0%) with version 08C, 0.03 g/cm² (3.3%) for the femur neck, 0.03 g/cm² (4.0%) for the greater trochanter, and 0.04 g/cm² (4.9%) for Ward's triangle region of the proximal femur. The spine phanton was scanned on two other commercial bone densitometers in order to assess inter-instrument variation. Phantom measurements of L2-4 BMD made on two Lunar Radiation Corp model DP3 scanners which differed by 2% were 10 and 12% higher than those with a Norland Corp. model 2600 scanner.     

A cluster of bacterial genes for anaerobic benzene ring biodegradation

A reductive benzoate pathway is the central conduit for the anaerobic biodegradation of aromatic pollutants and lignin monomers. Benzene ring reduction requires a large input of energy and this metabolic capability has, so far, been reported only in bacteria. To determine the molecular basis for this environmentally important process, we cloned and analyzed genes required for the anaerobic degradation of benzoate and related compounds from the phototrophic bacterium, Rhodopseudomonas palustris. A cluster of 24 genes was identified that includes twelve genes likely to be involved in anaerobic benzoate degradation and additional genes that convert the related compounds 4-hydroxybenzoate and cyclohexanecarboxylate to benzoyl-CoA. Genes encoding benzoyl-CoA reductase, a novel enzyme able to overcome the resonance stability of the aromatic ring, were identified by directed mutagenesis. The gene encoding the ring-cleavage enzyme, 2-ketocyclohexanecarboxyl-CoA hydrolase, was identified by assaying the enzymatic activity of the protein expressed in Escherichia coli. Physiological data and DNA sequence analyses indicate that the benzoate pathway consists of unusual enzymes for ring reduction and cleavage interposed among enzymes homologous to those catalyzing fatty acid degradation. The cloned genes should be useful as probes to identify benzoate degradation genes from other metabolically distinct groups of anaerobic bacteria, such as denitrifying bacteria and sulfate-reducing bacteria.     

Credentialed Persons, Credentialed Knowledge

The vast experimental literature on human error agrees with history of medicine, folklore, and superstition In discrediting knowledge claims based solely on anecdotal impressions. Since clinical experience consists of anecdotal impressions by practitioners, tt Is unavoidably a mixture of truths, half-truths, and falsehoods. The scientific method is the only known way to distinguish these, and it is both unscholariy and unethical for psychologists who deal with other persons' health, careers, money, freedom, and even life itself to pretend that clinical experience suffices and that quantitative research on diagnostic and therapeutic procedures is not needed. Disputes about philosophy of science (e.g., logical positivism) are irrelevant to this issue, which is simply one of distinguishing knowledge claims that bring reliable credentials and others that do not.     

Carbohydrate metabolism in children receiving growth hormone for 5 years

Carbohydrate metabolism was evaluated by fasting and postprandial glucose, insulin, and hemoglobin (Hb)A_1c levels in children with chronic renal insufficiency and various other growth disorders treated with growth hormone. Mean fasting and postprandial glucose remained unchanged throughout the 5-year study period in all four study groups. Median fasting insulin levels rose from lownormal levels into the normal range after 5 years of growth hormone. Average fasting insulin level after 5 years was 10 mU/l. Median postprandial insulin values also rose, yet remained within the normal range at the 5-year mark. Mean Hb A_1c levels remained within low to middle end of the normal range in the patients with growth hormone deficiency, Turner syndrome, and idiopathic short stature. Mean Hb A_1c levels at the 5 years were slightly elevated to 6.3% for the patients with chronic renal insufficiency.     

Drinking and driving among rural youth

Data concerning rural youth drinking and driving practices werecollected from 622 junior and senior high school students innorthwest Ohio, utilizing an ex post facto cross-sectional survey-researchdesign. The results suggested that 69% of the sample had usedalcohol at least once. With regard to quantity of alcohol use,about 27% reported drinking four or more drinks at a sitting.Approximately 19% of the sample had driven under the influenceof alcohol and 35% had ridden in a car with an intoxicated school-agedriver; 35% had refused a ride from a friend who was intoxicated,while 43% had tried to stop a drunk friend from driving. Nosignificant differences were found between males and femalesregarding drinking and driving but grade level was a significantmoderating factor. As grade level increased, the frequency ofeach alcohol-related behavior increased substantially (P <0.01). This paper presents prevalence data concerning drinkingand driving among rural youth as well as recommendations forcommunity health education program development.