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Biomedical subjects

T M Cook

Publications and source records attributed to T M Cook.

At least 109 records · Page 6Linked to original sources
PubMed1988

Comparison of maximal isometric hip abductor muscle torques between hip sides.

A posturally induced "stretch weakness" of the right hip abductor muscles has been reported in many healthy right-handed persons in the literature. The purpose of this study was to test for differences in the maximal isometric hip abduction torque produced between hip sides across multiple hip abduction angles. The torques were measured on 40 healthy right-handed individuals using a specialized torque-testing table at hip abduction angles of -10, 0, 10, 20, 30, and 40 degrees. Statistical analysis of the results did not demonstrate a specific "weakness" of the right hip abductor muscles at the hip angle used to clinically test them. The results, however, did demonstrate statistically significant differences in the torque-hip angle slopes across hip sides. We hypothesized that these slope differences may result from muscle adaptation to lengths imposed by standing posture. We discuss how manual muscle testing procedures may bias the likelihood of encountering stretch weakness in muscles that are habitually maintained at near-maximal elongation.

Adult↗
PubMed1986

Intrahippocampal injection of kainic acid produces significant pyramidal cell loss in neonatal rats.

Previous reports have indicated that pyramidal cells in the developing rat hippocampal formation are not destroyed by intraventricular or intraperitoneal administration of kainic acid. We examined the neurotoxic properties of kainic acid and ibotenic acid following intrahippocampal injection in neonatal rats and found significant pyramidal cell death following injection of 1.0 microgram kainic acid in 6, 7 and 9-day-old pups. At doses 2.5 or five times this amount, significant pyramidal cell loss was obtained in 5-day-old rats as well. The susceptibility of pyramidal neurons to kainic acid increased as a function of age. The developing hippocampus was considerably more vulnerable to ibotenic acid compared with kainic acid, in contrast to the order of potency reported in adult rats. The increased sensitivity of CA3 pyramidal cells parallels the development of the mossy fiber innervation to the dendrites of these cells supporting the twofold mechanism suggested by Coyle for kainic acid neurotoxicity; that is, a direct cytotoxic action via postsynaptic receptors as well as increased sensitivity due to the presence of excitatory inputs.

Animals↗
PubMed1985

Extensive target cell loss during development results in mossy fibers in the regio superior (CA1) of the rat hippocampal formation.

The axons of dentate granule cells (mossy fibers) have been reported to appear in the regio superior (CA1) of the rat hippocampal formation following destruction of the pyramidal cells in the regio inferior (CA3). We undertook the present experiments to confirm this finding and to determine the requirements for this dramatic neuronal rearrangement. We found that extensive (greater than 80%) loss of CA3 cells, as well as the presence of surviving CA1 neurons within a narrow period of development (postnatal days 3-5) is necessary, however apparently not sufficient, for the appearance of CA1 mossy fibers. That the absence of normal target cells during a restricted period of mossy fiber development will lead to their association with novel targets suggests that much of the specificity of this developing connection depends on the presence of normal targets during a critical period.

Animals↗
PubMed1985

Effect of load and carrying position on the electromyographic activity of the gluteus medius muscle during walking.

Physical therapists often teach people with hip osteoarthritis ways to decrease gluteus medius muscle activity of the stance limb during gait. The rationale for decreasing this muscle activity is that hip muscle contraction needed for frontal plane hip stabilization is responsible for a large component of the hip joint compressive forces during stance. The magnitude and carrying position of external loads during walking are both variables that influence requirements of gluteus medius muscle force. Therefore, the purpose of this study was to determine through EMG, the relative amounts of gluteus medius muscle electrical activity produced during the stance phase of gait when subjects used varying combinations of load size (10 and 20% of body weight) and carrying position of the hands (contralateral or ipsilateral to a given hip, or anterior or posterior to the chest). We studied 24 healthy subjects and used their EMG activity during the stance phase of gait as an indication of the relative amount of myogenic hip compression force. Results indicated statistical differences in EMG according to carrying condition with the contralateral position (with loads of 10 and 20% of body weight) producing the highest levels of EMG. We discuss the kinesiologic reasons for results and the prevention of hip osteoarthritis in occupational settings.

Adult↗
PubMed1984

Electromyography in biomechanics.

The purpose of this paper is to discuss the use of EMG as related to biomechanical function and dysfunction. The uses and limitations of this technique are described and instrumentation features and methods of data collection and interpretation are presented. We also discuss factors that influence the relationship of EMG to biomechanical measurements and cite as examples studies that have used EMG. Emphasis is placed on improving the ability of the physical therapist to use and interpret EMG data in kinesiology and biomechanics.

Biomechanical Phenomena↗
PubMed1983

An electromyographic analysis of quadriceps femoris muscle setting and straight leg raising.

Physical therapists routinely advise patients to perform quadriceps femoris muscle setting or straight leg raising or both following knee surgery or trauma from knee injury. Little information exists, however, about the intensity of effort required from knee and hip musculature during the exercises. This study was designed to compare the level of electromyographic activity during maximally resisted straight leg raises with the level during quadriceps femoris muscle setting exercises for the vastus medialis, rectus femoris, gluteus medius, and biceps femoris muscles. Forty healthy young adult men and women performed randomly ordered trials of each exercise in the supine position. Electromyographic activity was recorded from surface electrodes and normalized to values derived from maximal isometric trials. Statistical analysis demonstrated significantly greater (p less than .0001) vastus medialis, biceps femoris, and gluteus medius muscle activity during quadriceps femoris muscle setting. The rectus femoris muscle was significantly more active (p less than .0001) during the straight leg raise. The study demonstrated remarkably different muscle activation levels between the exercises studied and clearly indicates that selection of the exercises needs to be based on the therapeutic objectives.

Adult↗
PubMed1982

Surgical reconstruction for calcaneonavicular coalition. Evaluation of function and gait.

The function of nineteen patients was evaluated at three to fourteen years after reconstructive surgery for calcaneonavicular coalition. Measurements of subtalar motion, single-limb functional tests, and gait analyses were carried out to determine how function in these patients differed from normal. Better function correlated well with better postoperative subtalar motion. Patients with a unilateral coalition who had good subtalar motion after resection showed symmetrical gait patterns during tests of function of the subtalar joint under conditions of stress.

Adolescent↗
PubMed1975

Bacterial metabolism of arylsulfonates: role of meta cleavage in benzene sulfonate oxidation by Pseudomonas testosteroni.

Pseudomonas testosteroni H-8 oxidizes certain lower alkylbenzene sulfonates at rates inversely related to the length of the alkyl group. Appreciable Q(O)2 values were observed for benzene sulfonate (BS), toluene sulfonate (TS), and ethylbenzene sulfonate (EBS), but not for propylbenzene sulfonate (PS) and higher homologues. Catechol oxidation was catalyzed by a constitutive catechol-2,3-oxygenase (EC 1.99.2.a). Yellow meta cleavage products accumulated when BS-grown cells were exposed to catechol, 4-methylcatechol, 3-methylcatechol, EBS and PS, but not BS or TS. Traces of a yellow metabolite (probably 2-hydroxymuconic semialdehyde) were detectable during growth on BS. PS completely inhibited growth on BS, but not on L-leucine or nutrient broth. Also, PS antagonized respiration on BS and catechol, but not glutamate, the extent of inhibition being directly related to PS concentration. Formation of a meta cleavage product from PS, and inhibition of catechol oxidation by PS, suggested that the actual inhibitor may not be PS itself, but a metabolite.

Arylsulfonates↗
PubMed1975

Hycanthone and its congeners as bacterial mutagens.

Hycanthone methanesulfonate (HCT) was shown to induce "forward" and "reverse" mutations in Salmonella typhimurium and Escherichia coli. Mutational effects of HCT on S. tyhhimurium TA1532 were concentration and time dependent. A comparison of mutagenic potency for TA1532 was made between HCT and the frame-shift mutagens quinacrine and ICR-191. An investigation of structure-activity relationships revealed the substituent in the 4-position of ring A to be critical for mutagenicity. Activity was found when this group was a hydroxymethyl (i.e., HCT) or an aldehyde (Win 25,315), but the analogues having a carboxyl group (Win 25,850) or methyl group (lucanthone) in this positionwere inactive. Removal of a single ethyl group from the side chain did not affect mutagenic activity inasmuch as the potency of desethyl HCT (Win 27,262) equaled that of HCT on a molar basis. A marginal activity was found with a sample of HCT sulfoxide (win 27,266), but this sample was found to contain traces of HCT. The HCT analogue with a terminal N-oxide in the side chain (Win 29,329) was inactive at the concentration tested.

Bacteria↗
PubMed1971

Bacterial metabolism of arylsulfonates. I. Benzene sulfonate as growth substrate for Pseudomonas testosteroni H-8.

Pseudomonas testosteroni H-8 utilizes as sole carbon source benzene sulfonate (BS), p-toluene sulfonate (pTS), and ethylbenzene sulfonate (EBS) but not higher homologs. Growth on BS was rapid (generation time, 3 hr) and efficient (Y = 57), and resulted in accumulation of sulfate. As the culture is acid-sensitive, the medium must be heavily buffered to permit extensive growth. The BS oxidase system is inducible. Cells grown on BS, but not glutamate, oxidized BS, pTS, or EBS without lag (QO(2) = 50 to 100). Oxygen uptake on BS is temperature-dependent and sensitive to cyanide. Complete oxidation of 1 mumole of BS consumed approximately 5.7 mumoles of oxygen.

Barium↗
PubMed1971

Bactericidal action of 2-hydroxy-3-(cyclohexylpropyl)-1,4-naphthoquinone on Bacillus megaterium.

The antimalarial drug, 2-hydroxy-3-(cyclohexylpropyl)-1,4-naphthoquinone (NQ), at concentrations of approximately 10(-5)m (3 mug/ml), was bactericidal for the gram-positive bacterium, Bacillus megaterium. Only a few other gram-positive bacteria were sensitive to this drug. All growth inhibitory concentrations of NQ were also bactericidal for B. megaterium, and even resting suspensions of cells were killed. The incorporation of radioactive-labeled leucine, thymidine, uracil, and diaminopimelic acid into protein, deoxyribonucleic acid, ribonucleic acid, and the cell wall polymer was arrested immediately and completely upon addition of NQ to cultures in exponential growth. NQ produced a delayed effect on aerobic respiration and no change in the rate of oxygen consumption was observed at a time when all major biosyntheses had failed. (3)H-NQ was demonstrated to bind strongly and preferentially to the bacterial cell membrane. This simultaneous shutdown of all major categories of in vivo macromolecular syntheses points to an effect of NQ upon membrane-centered energy supplying reactions or transport of essential nutrients, or both.

Anti-Bacterial Agents↗