Biomedical subjects
J L Joyce
Publications and source records attributed to J L Joyce.
Inhalation anesthetics. Comparing nitrous oxide, isoflurane, halothane, enflurane.
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Increased insulin-like growth factor I binding to red blood cells of normal prepubertal children.
Young children are growing at a time when circulating levels of IGF-I measured by RIA are generally less than or equal to values in nongrowing adults. 125I-Thr59-IGF-I binding to receptors on conveniently available red blood cells was studied in 33 normal adults (nine males, 24 females) and 13 normal prepubertal children aged 3-10 y (10 boys, three girls; all Tanner stage 1). Red blood cell specific binding of 125I-Thr59-IGF-I was determined by displacement of labeled Thr59-IGF-I by unlabeled Thr59-IGF-I or insulin in a dose-dependent manner. Mean (+/- SEM) 125I-Thr59-IGF-I specific binding was significantly higher (p = 0.01) in prepubertal children than in adults (13.9 +/- 0.7% versus 11.6 +/- 0.5%/3 x 10(9) cells/mL). Specific binding did not differ between adult males and females. There was no significant correlation between specific binding and reticulocyte count. Scatchard analysis demonstrated a linear plot. Increased binding to red blood cells in the prepubertal children appeared to be due to an increase in receptor affinity (Ka = 4.97 +/- 0.42 x 10(8) M-1 versus 3.70 +/- 0.41 x 10(8) M-1; children versus adults; p = 0.03). Mean receptor concentrations were not different in children and adults (64.4 +/- 8.5 versus 58.0 +/- 5.6 binding sites/cell). There was a significant positive correlation between 125I-Thr59-IGF-I specific binding and affinity (p = 0.007, r = 0.39). We speculate that the greater specific binding of labeled Thr59-IGF-I to red blood cells in prepubertal children may provide a mechanism for enhanced cellular responsiveness to relatively low levels of circulating IGF-I.
Comparison of anaerobic susceptibility results obtained by different methods.
Susceptibility tests using 7 antimicrobial agents (carbenicillin, chloramphenicol, clindamycin, penicillin, cephalothin, metronidazole, and tetracycline) were run against 35 anaerobes including Bacteroides fragilis (17), other gram-negative bacilli (7), clostridia (5), peptococci (4), and eubacteria (2). Results in triplicate obtained by the microbroth dilution method and the aerobic modification of the broth disk method were compared with those obtained with an agar dilution method using Wilkins-Chalgren agar. Media used in the microbroth dilution method included Wilkins-Chalgren broth, brain heart infusion broth, brucella broth, tryptic soy broth, thioglycolate broth, and Schaedler's broth. A result differing by more than one dilution from the Wilkins-Chalgren agar result was considered a discrepancy, and when there was a change in susceptibility status this was termed a significant discrepancy. The microbroth dilution method using Wilkins-Chalgren broth and thioglycolate broth produced the fewest total discrepancies (22 and 24, respectively), and Wilkins-Chalgren broth, thioglycolate, and Schaedler's broth had the fewest significant discrepancies (6, 5, and 5, respectively). With the broth disk method, there were 15 significant discrepancies, although half of these were with tetracycline, which was the antimicrobial agent associated with the highest number of significant discrepancies (33), considering all of the test methods and media.