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Biomedical subjects

D White

Publications and source records attributed to D White.

At least 271 records · Page 15Linked to original sources
PubMed1987

Adolescent self-reports of social activity: assessment of stability and relations to social adjustment.

Adolescents' self-reports of peer social activity were examined with regard to short-term stability and in relation to social adjustment. Two separate periods of data collection are reported; year 1 with 74 grade nine students and year 2 with 76 grade nine students. On both occasions, four administrations of a self-report questionnaire were undertaken. As well, in year 2, social adjustment ratings, indices of perceived competence and self-efficacy, and IQ were collected. The analyses of the measure's consistency indicated acceptable stability of the self reports across two weeks and high internal consistency. These findings indicate the potential utility of this methodology for studying peer activity. Zero-order and multiple correlation analyses between social activity, self-evaluations and social adjustment were computed. The analyses suggest that peer social activity is correlated with social self-esteem, enhanced social self-efficacy and teacher's ratings of social engagement. Social isolation appeared to be an independent dimension and was related to lowered self-esteem and teacher ratings of social withdrawal. Overall, the results of the study add to our understanding of the components of social adjustment in adolescence.

Adolescent↗
PubMed1987

Metal chelates as urographic contrast agents for magnetic resonance imaging. A comparative study.

Paramagnetic metal chelates including Fe-EDTA, Fe-CDTA, Fe-DTPA, and Gd-DTPA were compared as intravenous urographic contrast agents for magnetic resonance (MR) imaging in rats. Each compound, administered intravenously at three different doses (0.05, 0.1, and 0.2 mmol./kg.), was rapidly excreted through the kidneys yielding renal signal enhancement between 5 min. and 50 min. after injection. Gd-DTPA was most effective vor the enhancement of the renal parenchyma and pelvis. Lesser enhancement was achieved by administration of Fe-CDTA followed by Fe-EDTA and Fe-DTPA. Enhancement of skeletal muscle and liver parenchyma could not be achieved with any of the compounds included in this study. We conclude that the iron chelates mentioned above are less effective as urographic agents for MR imaging than Gd-DTPA.

Animals↗
PubMed1987

Effect of cutaneous nerve stimulation on voluntary and stretch reflex electromyographic activity in wrist flexors in humans.

1. Changes in electromyographic (e.m.g.) activity in the wrist flexors of normal human subjects were studied in response to electrical stimulation of digital nerves and to sudden extension perturbations at the wrist produced by a torque motor. 2. With the subjects maintaining a steady voluntary contraction, stimulation of the digital nerves produced a series of excitatory and inhibitory changes in the tonic e.m.g. activity from the wrist flexors. The most prominent and consistent response was a period of e.m.g. inhibition beginning 39 ms after the stimulus and lasting for approximately 36 ms. 3. The stretch reflex evoked by extension perturbations of the wrist consisted of an early response (M1) with an onset latency of approximately 30 ms, and a late response (M2) with an onset latency of approximately 60 ms. 4. The electrical stimuli and the mechanical perturbations were then delivered together, varying the interval between them so that the period of inhibition resulting from the electrical stimuli occurred at the same time as the M1 or M2 components of the stretch reflex, or during the later voluntary response. 5. The amount of e.m.g. inhibition during the M2 component was significantly greater than that during M1 (P less than 0.02). This result is compatible with the view that M1 and M2 are mediated by separate neural pathways.

Adult↗
PubMed1987

Cyclandelate. An inhibitor of cholesterol esterification.

In an in vitro study the action of cyclandelate on cholesterol metabolism was investigated. The addition of cyclandelate (100 mumol/L) inhibited the incorporation of acetate into sterol but not into fatty acid in human fibroblasts incubated with the drug for 3 hours. Further exposure of fibroblasts to cyclandelate for 17 hours resulted in a similar inhibition in the uptake and hydrolysis of LDL. Moreover, in the presence of cyclandelate (100 mumol/L), cholesterol esterification was inhibited by 90% in fibroblasts cultured with LDL and in human monocyte derived macrophages cultured with acetyl-LDL. It is likely that the inhibition by cyclandelate of cholesterol esterification in whole cells is due to a direct inhibition of the hepatic microsomal enzyme acyl coenzyme A: cholesterol acyl transferase (ACAT), since addition of the drug in a concentration of 100 mumol/L inhibited by 74% the activity of ACAT derived from rat liver. Furthermore, the intact drug molecule was required for maximal inhibition of microsomal ACAT.

Animals↗
PubMed1987

Weekly cyclophosphamide and alternate-day prednisone: an effective secondary therapy in multiple myeloma.

Intravenous or oral cyclophosphamide, 150-250 mg/m2 (500 mg maximum), once per week with alternate-day oral prednisone, 100 mg, was given to 57 myeloma patients resistant to melphalan and prednisone (MP). Seven responses in 28 primary MP-resistant patients and ten responses in 29 secondary MP-resistant patients were observed. Previous response to MP was not a significant factor in predicting response to weekly cyclophosphamide and alternate-day prednisone. The results suggest that the regimen of weekly cyclophosphamide and alternate-day prednisone may be as effective as more aggressive regimens in the treatment of patients with myeloma who have failed MP therapy. However, a randomized trial would be required to determine the relative contributions of cyclophosphamide and prednisone to the effectiveness of this regimen.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

Types and frequency of lesions of the caruncle.

We reviewed 57 consecutive biopsies of lesions of the caruncle seen in the Wills Eye Hospital Pathology Department from 1977 through 1985. The types and relative frequency of excised caruncular lesions were recorded and correlation of pathologic diagnosis with preoperative clinical diagnosis, age, and sex was made. Squamous papillomas accounted for 18 (32%) and nevi for 14 (24%) of all caruncular masses. Pyogenic granulomas accounted for five (9%), epithelial inclusion cysts for four (7%), chronic inflammation for four (7%), and oncocytomas for two (4%) of all caruncular masses. Of the 57 cases only three (5%) were malignant tumors.

Adenoma↗
PubMed1986

Isolation and characterization of dynein ATPase from bull spermatozoa.

Dialysis of demembranated bull spermatozoa against a low-salt buffer resulted in the solubilization of the outer dynein arms and 15-25% of the total ATPase activity. Low-salt extracts contained three high-Mr peptides with Mr values above 300,000. The ATPase activity was associated with two particles sedimenting at 19 S and 12 S. The heavier particle contained two major high-Mr peptides with Mr values above 300,000, one major and one minor intermediate peptides with Mr values of 91,000 and 140,000 respectively and lower-Mr peptides. The 12 S particle contained one high-Mr peptide positioned between the two heavy peptides of the 19 S particle. Even though the peptide compositions of these two particles were different, the enzymic properties of their ATPases were similar. Both particles hydrolysed in the following preference order: ATP greater than CTP greater than UTP greater than ITP greater than GTP. ATPase activities were not affected by ouabain and oligomycin but were inhibited by vanadate, erythro-9-[3-(2-hydroxynonyl)]adenine and EDTA. Enzyme activities were dependent on the presence of a bivalent cation with the following preference order: Mn2+ greater than Mg2+ greater than Ca2+ greater than Ni2+. Optimal activity was observed between pH 6.5 and 9.5. The Km for ATP ranged from 40 to 50 microM for both 19 S and 12 S ATPases. These results suggest that the 12 S and 19 S particles are dyneins from outer dynein arms.

Adenosine Triphosphatases↗