Biomedical subjects
Publications and source records attributed to A Mak.
This article examined the relationship between impulsiveness and attitudes toward institutional authority among Australian secondary school students. Reliable questionnaire measures of these constructs were completed by 48 boys and 57 girls, about 14 years of age. Correlations between impulsiveness and attitude to authority differed between the sexes, with a significant negative correlation of -.43 being obtained for boys only.
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The objective of this study was to investigate the effects of mechanical fatigue in the form of cyclic shear strain on articular cartilage. Three millimeter diameter full-thickness plugs were cored from the lateral aspect of bovine tibial plateaus. Sinusoidal shear strains of +/- 5, +/- 10, and +/- 15% were applied to the specimens at 100 Hz for 3 h (a total of 108 x 10(4) cycles). The mechanical shear properties of the tissue (loss and storage moduli) were determined as a function of the number of applied strain cycles. A rapid, irreversible decrease of approximately 35% of initial modulus was found to occur in both loss and storage modulus during application of the first 90,000 cycles. Further decay in the moduli was found to occur from 90 x 10(3) to 108 x 10(4) cycles, but was of considerably smaller magnitude than the initial decrease. The moduli remained relatively constant beyond application of 108 x 10(4) cycles. No consistent change in proteoglycan content was found to be associated with the fatigue process when comparing tested specimens with fresh, untested tissue, and with experimental controls. In addition, no structural defects in the mechanically altered tissue were revealed by scanning electron microscopy.
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1. Extensor digitorum communis (EDC) muscles from the chick synthesized and degraded proteins at linear rates, and maintained high levels of ATP, creatine phosphate and glycogen, for 9 hr of incubation. 2. The apparent viability of the EDC preparation was improved by the provision of a continuous supply of oxygen, glucose, insulin and amino acids at the levels found in chick plasma, and incubation at 33.5 degrees C. 3. Incubated muscles were in net negative protein balance; however, under optimal conditions, this represented only 0.03% of total protein/hr. Rates of protein synthesis in the EDC preparation were 65% of those determined in vivo, comparing favourably with values obtained by other workers in mammalian muscle. 4. Rates of protein synthesis responded to insulin, amino acids, and to the nutritional status of the bird, as had been observed in prior studies with mammalian muscle. By contrast to mammalian muscle protein degradation was relatively insensitive to these modifiers.
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Sixty-one supracondylar fractures above prosthetic knee replacements in 58 patients were reviewed with a mean follow-up time of 3.7 years (range, 9 months to ten years). The mean interim between arthroplasty and fracture was 2.9 years (range, intraoperative to ten years). Twenty-seven cases demonstrated notching of the anterior femoral cortex. Seventeen patients suffered from a severe neurologic disorder. Group A consisted of 30 patients with 31 fractures treated by open reduction and internal fixation or revision arthroplasty. Follow-up study revealed 25 unions, three malunions, one nonunion, and two above-knee amputations for deep sepsis. Four of 31 patients had increased pain levels or change in ambulatory status postoperatively. Group B consisted of 30 fractures in 28 patients treated by casting alone or traction followed by cast bracing. Follow-up examination showed 17 unions, seven malunions, and six nonunions. Fifteen of the 30 patients had increased pain levels or change in ambulatory status after treatment. Casting produced significant decreases in motion in both groups. The results indicate that this fracture is associated with anterior notching of the femoral cortex and preexisting neurologic disorders. Patients with a supracondylar fracture following prosthetic knee arthroplasty are best managed by secure internal fixation and early motion.
Previous work showed that the simple eukaryote Saccharomyces cerevisiae contains a group of RNAs with the general structural properties predicted for small nuclear RNAs (snRNAs), including possession of the characteristic trimethylguanosine 5'-terminal cap. It was also demonstrated that, unlike their metazoan counterparts, the yeast snRNAs are present in low abundance (200-500 molecules per haploid cell). We have now used antibody directed against the 5' cap to investigate the total set size of snRNAs in this organism. We present evidence that the number of distinct yeast snRNAs is on the order of several dozen, that the length of the capped RNAs can exceed 1000 nucleotides, and that the relative abundance of a subset of these RNAs is 1/5th to 1/20th that of the class of snRNAs described previously. These findings suggest that the six highly abundant species of snRNAs (U1-U6) typically reported in metazoans may represent a serious underestimation of the total diversity of snRNAs in eukaryotes.
Tropomyosin, extracted from the leg muscle of frogs that had been injected with [32P]orthophosphate, was fractionated into two components, alpha and beta, on a CM-cellulose column. Radioactivity was associated only with the alpha component. A single phosphorylation site was located at serine-283 (pentultimate at the COOH-terminal end) of the frog alpha tropomyosin. The same phosphorylated peptide was recovered in low yields from both rabbit skeletal alpha and cardiac tropomyosin. The presence of covalently bound phosphate in alpha tropomyosin and its absence in the beta component of rabbit skeletal muscle was suggested by 31P NMR spectroscopy. The amino acid sequences around the phosphorylation sites of frog and rabbit tropomyosin are identical. Because this sequence is not similar to any other known phosphorylation site in proteins, this indicates the existence of either specific kinase or phosphatase that can distinguish between alpha and beta tropomyosins. In a model proposed for the head-to-tail overlap of alpha tropomyosin molecules, one O-phosphoserine-283 residue could form a salt linkage with lysine-6 on one side of the overlap region and another with lysine-12 on the other side. This would predict a difference in the stability of polymers of phosphorylated and nonphosphorylated alphaalpha and alphabeta dimers of tropomyosin.
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