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Biomedical subjects

G M Hughes

Publications and source records attributed to G M Hughes.

At least 19 recordsLinked to original sources
PubMed1996

The relationship of sustained exercise training and bone mineral density in aging male runners.

Fifty-six men aged 42-73 years (50.2 +/- 10.0 years), who were competitive distance runners 20-25 years previously, were examined for bone mineral density (BMD) to determine the relationship between sustained distance running and BMD. Subjects were classified as being highly trained (HT, n = 17), moderately trained (MT, n = 29) or untrained (UT, n = 10) according to their training in recent years. Subjects in each group were of similar age (HT 46.5 +/- 2.01, MT 53.0 +/- 1.51, UT 46.7 +/- 2.44 years) and lean body mass. Total body weight (kg) and percentage fat, however, were significantly greater (P < 0.05) in the UT group than in either the MT or HT groups (UT 80.6 +/- 2.44 kg, 22.0 +/- 1.16%; MT 74.9 +/- 1.51 kg, 17.5 +/- 0.61%; HT 70.5 +/- 1.71 kg, 13.5 +/- 0.59%). Lumbar vertebrae and hip region BMD (g.cm-2) was determined via dual energy X-ray absorptiometry (DEXA). No differences in BMD were found among the three groups in either the lumbar (HT 1.00 +/- 0.02, MT 1.02 +/- 0.03, UT 1.07 +/- 0.04 g.cm-2) or the hip regions (HT 0.99 +/- 0.03, MT 0.98 +/- 0.02, UT 1.06 +/- 0.04 g.cm-2). Furthermore, none of the groups had BMD that was significantly different from age-matched normative values taken from a reference database. A moderate correlation was found between body weight and BMD when combining all subjects (r = 0.38 for lumbar and r = 0.41 for hip). These results indicate that middle-aged to older males who have sustained exercise training in the form of running do not have significantly different lumbar vertebrae or hip region BMD compared to individuals who run less or not at all.

Absorptiometry, Photon↗
PubMed1994

The influence of red cell size relative to pore size on filtration through nuclepore filters.

A simple model relating pore passage time (PPT) to the degree of strain of the membrane of a red cell of diameter DC on passing through a pore (diameter Dp) has been developed. The model was tested for a range of mammalian and fish species for which some data was available for more than one pore size. The strain (epsilon) is estimated as (Dc-Dp)/Dc. For small epsilon, less than approximately 0.45, PPT was small but rose rapidly for higher values. The analysis provides a simple basis for choosing appropriate pore sizes, and consequently strain, for comparing mechanical properties of erythrocytes of different species.

Animals↗
PubMed1993

Routine oxygen consumption in different sizes of a tilapia, Oreochromis niloticus (Trewavas) using the closed chamber respiratory method.

Routine oxygen consumption (Vo2) measurements on 54 specimens (0.055-190.4 g) of a tilapia, Oreochromis niloticus (Trewavas) were carried out using two different types of closed respirometers: a modified cuvette for fish weighing 0.055-0.91 g and ordinary closed chamber respirometer for fish weighing more than 1 g. Vo2 values over the weight range studied had a scaling value of 0.743 which relates closely to the values for the gill respiratory surface area and morphometric oxygen diffusing capacity of O. niloticus in a previous study /13/. This shows that a close relationship exists between changes in structural parameters involved in oxygen uptake and the routine metabolism of O. niloticus with development. The values for routine Vo2 of 1.38 and 7.65 ml/h for 10 g and 100 g fish, respectively (calculated from the regression equation) show that O. niloticus is a moderately active fish.

Animals↗
PubMed1993

Effects of low environmental pH in the presence of aluminum on filtration properties of the blood of atlantic salmon (Salmo salar L.).

The time for filtration of whole blood samples through 8 microns pores of polycarbonate membranes provides an index of the deformability of fish red blood cells. Comparison of these and other haematological measurements on salmon before and after exposure to pH 5.0 and 20 microM aluminium for 2 hours shows changes which are indicative of hypoxia. The increase in deformability of the red cells will assist transfer of oxygen from the gills to the tissue cells and hence compensate environmental hazards of low pH and aluminium.

Aluminum↗
PubMed1993

Swimming performance of rainbow trout following exposure and recovery from the pyrethroid S-deltamethrin.

Oxygen consumption and swimming performance of rainbow trout exposed to sublethal concentrations (10-50 microliters/20 L) of pyrethroid (S-deltamethrin) pesticide was studied in a Brett-type respirometer during recovery. Results showed wide variations reflecting the varied responses of different individual fish to the test regime. In most cases values of oxygen consumption for the controls were higher at each swimming speed and this became significantly reduced following treatment with pesticide. Oxygen consumption soon after the treatment gave the highest values but these fish were unable to sustain swimming speeds as high as the controls or following recovery. The comparisons of swimming performance before and after treatments with deltamethrin have shown a significant effect on locomotory ability of rainbow trout which at the end of strong exposure (e.g. 50 min of 40 microliters/20 L) are almost incapable of swimming.

Animals↗
PubMed1989

Research collaboration.

The complexity and cost of cardiovascular medical care dictate research to deliver high quality and cost-conscious cardiovascular care. This goal is aided by modeling medical decision making. To be useful, the modeling must be based on real data so that the results can serve as a guide to actual practice. It is suggested that a registry of randomized clinical trials and larger data bases in cardiovascular disease and health care delivery be established. The registry would be a resource for those desiring to model decision making. The registry would contain key words allowing retrieval by modelers accessing the registry and would contain contact information for consideration of possible collaborative work. The initiation of such a registry should contain plans for its evaluation to determine whether the registry itself is a cost-effective tool to encourage the needed research.

Clinical Trials as Topic↗
PubMed1988

Relationships between swimming speed, oxygen consumption, plasma catecholamines and heart performance in rainbow trout (S. gairdneri R.).

Rainbow trout swimming at controlled speeds in a tunnel respirometer have been used to measure oxygen consumption and plasma catecholamine levels, and systolic pressure/frequency relationships. Catecholamine (CA) levels evaluated in trout plasma at low swimming speed [0.5 bodylengths/second (bl/s)] were: adrenaline (A) 1.77 +/- 0.22 nM; noradrenaline (NA) 3.94 +/- 0.83 nM; dopamine (DA) 2.40 +/- 0.36 nM. No significant increase was observed during moderate exercise (1.5 bl/s): A 1.60 +/- 0.20 nM; NA 5.76 +/- 1.07 nM; DA 2.31 +/- 0.80 nM, or stronger exercise (2.0 and 2.5 bl/s-1): A 2.10 +/- 0.21 nM; NA 5.90 +/- 0.90 nM; DA 2.21 +/- 0.40 nM. A correlation was found between heart rate at these swimming speeds, and its position on the systolic pressure frequency curve of isolated hearts, which suggests that the heart functions at maximum systolic pressure at low (0.5 bl/s-1) swimming speeds and that this pressure decreases during exercise as cardiac frequency rises.

Animals↗
PubMed1986

Comparison of the osmotic fragility of red blood cells in samples from anaesthetised and unanaesthetised trout and eel and the effect of varying oxygen levels.

The osmotic fragility of trout and eel red blood cells has been tested in fresh blood samples and following equilibration at low PO2 (7.5-25 mmHg). Percentage haemolysis curves obtained were similar to those in other vertebrates. Blood sampled shortly after cannulation (OP) shows higher % haemolysis at a given saline concentration than in samples taken 24 h after recovery from anaesthesia. Following exposure to low PO2's greater haemolysis is present and is reduced by raising the oxygen level.

Aminobenzoates↗
PubMed1985

Effects of temperature and transfer from seawater to freshwater on blood microrheology in Pacific salmon.

Blood of Pacific salmon was studied with particular interest in red blood cell (RBC) deformability in relation to migration. Blood samples were taken via cardiac puncture or chronic cannula placed in the dorsal aorta and heparinized. As an index of RBC deformability the mean passage time of single RBCs through micropores of 8 micron in diameter and 10 micron in length was determined under a pressure difference of 10 cmH2O. Despite about 100 mOsmol/l difference in plasma osmolality, there was no marked difference in RBC passage time between fish in seawater and those well acclimatized to freshwater. However, it seemed probable that a transient decrease in RBC passage time, i.e., an increase in RBC deformability, occurred immediately following transfer from seawater to freshwater. Plasma osmolality decreased to about 300 mOsmol/l within 1 hr after the transfer and showed no fluctuations thereafter. The temperature dependence of RBC deformability was much smaller in comparison with those previously observed in yellowtail and carp; salmon RBCs were still highly deformable even at 5 degrees C, a possible temperature of cold river water.

Animals↗
PubMed1985

Recovery of cardiac and ventilatory frequencies after sub-acute pesticide (ABOL-X) treatment in rainbow trout, Salmo gairdneri Richardson.

Short term, sublethal changes in coughing rate, cardiac and ventilatory frequencies in hatchery-reared rainbow trout (27-34 cm) exposed to menazon and gamma BHC containing pesticide were monitored at 15 +/- 1 degree C during recovery period to investigate the effects of this chemical on fish respiratory and cardiovascular systems. Laboratory conditions simulated a rapid environmental pollution often occurring in running waters. The coughing response was particularly sensitive to water pollutants. Average rate of ventilation was lower in treated fish than in control specimens and decreased parallel with the time of recovery. Average heart rate was higher in treated trout as compared to the controls. These changes were characteristic for hypoxic conditions and provide useful sublethal physiological indications for a rapid environmental stress. Percentage coupling and phase angle of ECGs within the ventilatory cycle were also studied during recovery when significant differences were observed between treated and untreated groups of fish.

Animals↗
PubMed1984

Scaling of respiratory areas in relation to oxygen consumption of vertebrates.

Resting oxygen consumption is generally related to the 0.75 power of the body mass. More recent studies on the morphometry of the lungs and gills of vertebrates indicate that the respiratory surfaces increase in area more closely to M1.0. A possible explanation is that the gas exchange surface is more to be related to the maximum oxygen uptake capacity, rather than to the resting condition. However, recent studies, especially in African mammals, suggest that Vo2max scales to a power similar to that for resting oxygen consumption and hence cannot be directly related to the respiratory surfaces. In fishes the situation seems to be different as Vo2max appears to increase more rapidly than standard Vo2. Consequently, the ratio between these two is greater in larger specimens and hence they have a greater scope for activity. A possible interpretation of this apparent difference may be related to differences in ventilation, as the tidal ventilation of lungs can lead to a reduction in the difference in oxygen pressure across the exchange surface, whereas in fish gills with increasing size and increasing water velocity there would be a reduction in the resistance to gas transfer. However, it is important to appreciate that such generalizations probably do not hold in all cases and the position of intermediate groups of vertebrates needs to be more closely assessed.

Animals↗
PubMed1983

Effect of acclimation temperature on oxygen transport in the blood of the carp, Cyprinus carpio.

The temperature dependence of the O2 equilibrium in whole blood was measured in carp acclimated for more than 3 weeks at 10 degrees C or 20 degrees C water temperature. O2 combining curves were obtained for the same samples at 10 degrees C or 20 degrees C using blood from the 10 degrees C or 20 degrees C acclimated fish (group A) or only at the acclimation temperature (group B). Whereas in group B the P50 was about the same at both temperatures, in group A P50 was higher at 20 degrees C than at 10 degrees C, yielding an apparent heat of oxygenation delta H = -9.9 kcal/mol at pH = 8.0. The CO2 Bohr effect in group A was delta log P50/delta pH = -0.93 at 20 degrees C and -1.17 at 10 degrees C, whereas in group B no temperature effect was seen (-0.98 and -0.97). The acclimation temperature had no effect on the electrophoretic Hb pattern. As expected, the in vivo pH changed inversely with temperature from 8.06 at 10 degrees C to 7.73 at 20 degrees C, enhancing the temperature-induced shift in P50. Acclimation reverses partly the changes in O2 affinity, thereby improving the uptake of oxygen in the gills.

Acclimatization↗
PubMed1983

Effect of acclimation temperature on intraerythrocytic acid-base balance and nucleoside triphosphates in the carp, Cyprinus carpio.

In carp acclimated to 20 degrees C or 10 degrees C intraerythrocytic pH (pHi) and plasma pH (pHe) were determined in vitro after equilibration with CO2 in either O2 or N2. ATP and GTP were determined with an enzymatic assay described in detail. The relationship between pHi, pHe and oxygen saturation was not affected by the acclimation temperature and was (pHi-6.10) = (0.853-0.159 X S) X (pHe-6.21) There was a slight but significant decrease in ATP at 20 degrees C. Apparent buffer values were affected by oxygenation and temperature. It is concluded from the recalculated CO2 Bohr factor and from the temperature effect on the buffer value that carp hemoglobin forms carbamate which decreases at a higher temperature. These changes in ATP and carbamate can partly account for the increase in whole blood oxygen affinity in carp acclimated at a high temperature.

Acid-Base Equilibrium↗