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Biomedical subjects

B A Harris

Publications and source records attributed to B A Harris.

90 records · Page 5Linked to original sources
PubMed1977

Purification and crystallization of NADP+-specific isocitrate dehydrogenase from Escherichia coli using polyethylene glycol.

A simple and rapid method is presented for purifying the NADP+-dependent isocitrate dehydrogenase (threo-DS-isocitrate:NADP+ oxidoreductase (decarboxylating), from Escherichia coli, which relies on fractionation of the enzyme with polyethylene glycol. The shortened preparation results in a 32% relative recovery of purified enzyme at a specific activity of 127 micronmol/min per mg of protein. The Km values for threo-DS-isocitrate, NADP+, NAD+, Mg2+ and Mn2+ are 6.4, 36, 3000, 19.7 and 2.0 micronM, respectively. The stability of the enzyme as a function of dilution and temperature are also reported. Recrystallization of the purified enzyme under different conditions readily produces a variety of single crystals. Crystals grown from ammonium sulfate solutions belong to monoclinic space group C2 with a = 125 A, b = 111 A, c = 83.5 A and beta = 108degrees 45'. Density measurements of these crystals indicate there are two 80 000-dalton dimers per asymmetric unit.

Crystallization↗
PubMed1977

Penicillin V therapy for streptococcal pharyngitis: comparison of dosage schedules.

Two dosage regimens of penicillin V were compared in 327 patients with mild to moderately severe streptococcal pharyngitis. Patients fulfilling study criteria were randomly assigned to a b.i.d. or a t.i.d. dosage schedule. Those in the b.i.d. group were given 500 mg twice daily; those in the t.i.d. group were given 250 mg three times daily. Duration of therapy was ten days for both groups. Cure was based on prompt symptomatic improvement, subsidence of clinical signs, and negative throat cultures for group A beta-hemolytic streptococci. Both dosage schedules yielded similar cure rates, indicating that with penicillin V, a b.i.d. regimen is as effective as a t.i.d. regimen in treating streptococcal pharyngitis.

Acute Disease↗
PubMed1977

Analysis of methotrexate in human plasma by high-pressure liquid chromatography with fluorescence detection.

Methotrexate in human plasma at a concentration as low as 0.01 microgram/ml can be assayed with the use of high-pressure-liquid chromatography and a fluorescence detection system. Methotrexate is oxidized stoichiometrically to 2,4-diaminopteridine-6-carboxylic acid, a fluorescent product that is separable from other fluorescent materials in plasma with the use of an octadecylsilane (reversed phase) column. The detector response is linear over the range of 0.01 to 10 microgram/ml. Neither folic acid nor citrovorum factor interferes with the analysis. N-((4-([2,4-Dihydroxy-6-pteridyl)methyl]-amino)benzoyl))glutamic acid may be used as an internal standard, since it can be extracted from plasma and oxidized like methotrexate. The procedure is rapid (about 30 min) and should be a useful method for monitoring methotrexate plasma concentrations.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Hip fracture: a prospective study of hospital course, complications, and costs.

A prospective study of 79 patients with recent hip fracture revealed prior functional impairments with community mobility (49%), using a bathtub (40%), walking outdoors (26%), and stair-climbing (18%). Eighty-six per cent of patients (mean age 77.9 years) were admitted from home, with 95% surviving to discharge but only 28% returning directly home following surgical repair. In-hospital complications included confusion (49%), urinary tract infection (33%), and heart rhythm disturbance (26%). Mean length of stay was 21.7 days and mean hospital charges were $11,052. The outliers (15%) averaged 60.6 days in length of stay and $28,190 in charges. Stepwise multivariate regression revealed that lengths of stay varied significantly with prefracture functional status, presence of intertrochanteric fractures, and in-hospital complications, but not with patient age. Examination of these findings in relation to prospective reimbursement led to the conclusion that hip fracture patients are particularly vulnerable in the era of new hospital strategies to avoid high-cost patients and curtail hospital costs.

Activities of Daily Living↗
PubMedDate not supplied

Rotational motion of the knee.

This study deals with the quantitation of axial rotation at the knee. Passive rotation of the knee was measured at various degrees of flexion on 17 subjects with normal knees and 19 patients with unilateral anterolateral rotatory instability. Normal subjects were found to have bilateral symmetric rotational knee motion at each angle of flexion tested. When the knee is in a position of flexion between 30 and 90 degrees, there are approximately 45 degrees external and 25 degrees internal rotation. Rotatory motion decreases with further extension and, at 5 degrees of flexion, the knee has 23 degrees external and 10 degrees internal rotation. The knee with a torn anterior cruciate ligament and anterolateral rotatory instability was found to have an arc of rotation similar to the contralateral knee and to the control knees between 30 and 90 degrees flexion. At 15 degrees of flexion, a slightly greater arc of rotation was measured compared to normal knees. At 5 degrees of flexion, a significantly greater range of external (to 41 degrees) as well as internal (to 14 degrees) rotation was measured.

Adolescent↗
PubMedDate not supplied

Expression of human M2 muscarinic receptors in Sf9 cells: characterisation and reconstitution with G-proteins.

The gene for the human m2 muscarinic receptor was expressed in Sf9 cells using the baculovirus expression system. As assessed by [3H]NMS binding, Sf9 cells expressed receptor at levels of 3.3 pmoles/mg protein. The receptor was identified on western blots using an anti-muscarinic receptor antibody and was shown to have the pharmacological characteristics of an m2 muscarinic receptor. Membranes from Sf9 cells were examined to identify endogenous G-proteins by immuno-blotting and by ADP-ribosylation, indicating the presence of Gq, and a pertussis-toxin substrate which was not recognised by antibodies raised against the alpha-subunits of Gi1, Gi2, Gi3 or Go. Gsalpha was not detected, neither were there any cholera toxin substrates in Sf9 membranes. Sf9 membranes expressing m2 receptors did not show carbachol-stimulated GTPgammaS binding to endogenous G-proteins; however, when membranes were reconstituted with a mixture of purified Gi and Go, a maximum 8-fold stimulation of GTPgammaS binding was observed in response to carbachol that could be reduced by atropine. These data show that the human muscarinic m2 receptor expressed in Sf9 cells is functional.

Animals↗