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Biomedical subjects

M E Houston

Publications and source records attributed to M E Houston.

80 records · Page 5Linked to original sources
PubMed1978

Skeletal muscle characteristics and carbohydrate metabolism after glucose loading in hypokalaemic periodic paralysis.

A prolonged glucose load was administered to four patients with hypokalaemic periodic paralysis and four healthy control sujbects. Muscle ATP and CP concentrations as well as lactate dehydrogenase, hexokinase and phosphorylase activities were similar in those two groups, but succinate dehydrogenase was approximately 50% higher in the control muscles. Muscles fibre composition was almost identical in the two groups, whereas patients had a higher degree of capillarization. Complete muscle weakness was produced in all patients, accompanied by hypokalaemia. Glucose loading resulted in elevated insulin levels and a minor rise in blood glucose level was seen in the patients compared to the control subjects. Glucose loading decreased hexokinase activity in controls, but increased this in the patients. At similar times, muscle and blood lactate levels and blood pyruvate values were generally higher in the patients over the course of the experiment. Initial glycogen concentrations were higher in patients, but glucose loading did not result in greatly increased glycogen values. These data suggest that patients with hypokalaemic periodic paralysis have an enhanced metabolism of carbohydrates and that insulin seems to be an important factor leading to the onset of muscle weakness.

Adenosine Triphosphate↗
PubMed1977

The response of endurance-adapted adults to intense anaerobic training.

The effects of a 6 week program of intense, intermittent hill running was investigated in 5 endurance-trained men (34-37) years. Venous lactate responses averaged 10.7 mM X 1(-1) during training. Biopsies were obtained from the vastus lateralis before and after training for determinations of histochemical classification, phosphagen concentrations (ATP and CP) and activities of total LDH and selected LDH isozymes. Indices of aerobic and anaerobic capacity were also measured. Significant improvements (P less than 0.01) were noted in training distance and loads employed in leg presses, also part of the training: the treadmill test for anaerobic capacity improved by 16.7% and the terminal blood lactate level increased 14%(P less than 0.05). No changes occurred in VO2 max, body fat per cent or anaerobic power. Muscle ATP concentration increased by 14.8% (P less than 0.01) whereas the tissue level of CP remained unchanged. Total LDH activity and the LDH isozymes (LDH-1, LDH-5 and LDH-2, 3, 4) were not altered by training. No changes in fibre distribution were observed. That adaptations to the anaerobic training did occur is evident, but the cellular locus remains to be elucidated further.

Adenosine Triphosphate↗
PubMed1975

Effect of a season of ice hockey on energy capacities and associated functions.

Two elite junior ice hockey teams with players ranging in age between 16 and 20 years were measured on an extensive battery of laboratory tests at the beginning and end of a season in order to determine adaptive changes in the energy supply systems and associated functions. Pre- to post-season changes in maximal aerobic power showed a significant increase of 3% (p less than .05) only when expressed in 1/min (4.30 vs 4.43). Additionally, when measurements were made on selected determinants of oxygen transport, no change was found in ventilation as reflected in VC (5.60 vs 5.52 /min), FEV1.0 (4.37 vs 4.44 l/min), MBC (185.1 vs 186.4 l/min) and maximum exercise VE (128.0 vs 128.1 l/min, STPD) or in the cardiovascular system as reflected in hematocrit (45.3 vs 44.4%), hemoglobin (16.4 vs 16.2 g%) and maximum exercise HR (192 vs 191 beats/min). On the other hand, indicates of change in the anaerobic energy supply systems were found. Maximal anaerobic capacity improved by 16.3% (p less than 0.05) when measured in terms of run time (64.3 vs 74.8 secs) and maximal anaerobic power by 4.7% (p less than 0.05) when expressed in m/sec (1.69 vs 1.77). Although comparable percentage increases were noted when peak lactate concentration and power (kgm/sec) were used as criterion measures for these tests respectively, statistical significance was not found. When the results were analyzed by position essentially the same changes were found.

Adaptation, Physiological↗
PubMedDate not supplied

Lactam bridge stabilization of alpha-helical peptides: ring size, orientation and positional effects.

A series of 14 residue amphipathic alpha-helical peptides, in which the sidechains of glutamic acid and lysine have been covalently joined, was synthesized in order to determine the effect of spacing, position and orientation of these lactam bridges. It was found that although an (i, i+3) spacing would position the lactam bridge on the same face of the helix, these lactams with 18-member rings were actually helix-destabilizing regardless of position or location. On the other hand, (i, i+4) lactams with 21-member rings were helix-stabilizing but this was dependent on orientation. Glutamic acid-lysine lactams increased the helical content of the peptide when compared with their linear homologue in benign conditions (50 mM KH2PO4, 100 mM KCl, pH 7). Two Glu-Lys (i, i+4) lactams located at the N- and C-termini gave rise to a peptide with greater than 99% helical content in benign conditions. Peptides with Lys-Glu oriented lactams were random structures in benign conditions but in the presence of 50% TFE could be induced into a helical conformation. The stability of the single-stranded alpha-helices, as measured by thermal denaturations in 25% TFE indicated that Glu-Lys oriented lactam bridges stabilized the helical conformation relative to the linear unbridged peptide. One Glu-Lys lactam in the middle of the peptide was more effective at stabilizing helical structure than two Glu-Lys lactams positioned one at each end of the molecule. The lactams with the Lys-Glu orientation were destabilizing relative to the unbridged peptide. This study demonstrates that correct orientation and position of a lactam bridge is critical in order to design peptides with high helical content in aqueous media.

Amino Acid Sequence↗
PubMedDate not supplied

Human vastus lateralis and gastrocnemius muscles. A comparative histochemical and biochemical analysis.

Two muscles involved in locomotion the vastus lateralis and the gastrocnemius, were compared on a variety of histochemical an biochemical properties. Ten active males, age 20 - 24 years, served as subjects. Fibre type distributions, type I, type IIA and type IIB, as determined from samples extracted by muscle biopsy were similar in both muscles. In addition, no significant difference (p greater than 0.05) was found between fibre types in each muscle for fibre size, relative area, capillaries per fibre and the ratio of capillaries per fibre area. The activities of a number of enzymes representative of energy supplying pathways - the citric acid cycle (succinate dehydrogenase, SHD; beta-hydroxyacyl CoA dehydrogenase, HADH), glycogenolysis (total phosphorylase, PHOSP), glycolysis (phosphofructokinase, PFK) - were of similar magnitude between the two muscles. The only exception noted was for the activity of a glycolytic enzyme, lactate dehydrogenase, LDH, where a 16% higher value was observed in the vastus lateralis. The close degree of homogeneity displayed between these two muscles may be of significance in providing for a functional synchrony to occur in locomotor activities of varying intensity.

3-Hydroxyacyl CoA Dehydrogenases↗