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Biomedical subjects

D G Penney

Publications and source records attributed to D G Penney.

At least 73 records · Page 4Linked to original sources
PubMed1977

Hematologic responses to carbon monoxide and altitude: a comparative study.

Groups of 40- and 90-day-old rats were exposed to 500 ppm CO (HbCO=31-43%) and simulated altitude (15,000 ft). Resulting hematologic changes were monitored after 1 day, 1 wk, 3-4 wk, and 9-11 wk of exposure. The two treatments resulted in similar changes in hemoglobin (Hb) and hematocrit ratio (Hct) in the young rats, while in the older group there were several small, but significant differences in these parameters. Mean corpuscular hemoglobin concentration (MCHC) fell 12.4-15.1% during the 1st wk of exposure in all groups except the young altitude rats, which remained at the control value. The former groups returned to control levels by the 3rd to 4th wk of exposure. Red cell 2,3-diphosphoglycerate (2,3-DPG) increased 21.6-26.1% above control during 3-4 wk of altitude exposure, but later (9-11 wk) returned toward control levels. CO exposure resulted in a sharp decrease in 2,3-DPG after 1 day of exposure only in the young rats. 2,3-DPG level progressively decreased with age in control rats. The effects of CO and altitude although similar in several respects (i.e., Hb, Hct, MCHC) differ with regard to red cell 2,3-DPG.

Adaptation, Physiological↗
PubMed1977

The perinatal rat: body weight, hematocrit and regional changes in heart weight and lactate dehydrogenase isozyme composition and activity.

Body weight (BW), hematocrit (Hct), heart weight (HW) and cardiac lactate dehydrogenase (LDH) activity and isozyme pattern were studied in the perinatal rat. BW increased linearly, from 5 days before birth till 10 days after birth, while Hct increased from 30 to 34% within 1 day of birth. HW increased in step with BW. However, the relative contribution to total HW of right ventricle (RV), interventricular septum (S) and atria declined relative to the left ventricle free wall (LVW) beginning 2 to 3 days before birth. RV/LVW declined steadily throughout the study period. LDH specific activity in LVW, RV, S and atria increased greatly prior to birth and less so afterwards, with atria showing the lowest values throughout the study. Total LDH activity in each portion of the heart paralleled the respective regional weight changes. LDH isozyme composition (percent M subunit) declined at the time of birth in LVW, RV and S from 63 to 43%; change in atrial M subunit was smaller. The change in LDH isozyme composition could be accounted for in LVW, RV and S by increasing H subunit activity alone. In atria, both M and H subunit activity increased.

Animals↗
PubMed1976

Chronic carbon monoxide poisoning: effects on performance of the isolated right ventricle.

Rats were exposed continuously for 21-35 days to 500 ppm carbon monoxide (37.4-39.2% HbCO). Aerobic resting force (RF)-active isometric twitch force (AF) curves of isolated right ventricle preparations were constructed at 27 degrees C. CO and control groups are nearly identical when expressed as percent of maximal AF over the range of RF used. There are no significant differences in AF either at the peak of the curve or at RF = 1 g. During 15 min of anoxia AF declines at both RF's used. Increased anoxic tolerance is apparent in all CO preparations when anoxic AF is plotted as percent of preanoxic AF. The effect is most marked at RF = 1 g, where time to one-half preanoxic AF is 12.6 +/- 0.9 vs.9.3 +/- 0.8 min for CO-exposed and controls, respectively. However, no significant differences in "absolute" AF are seen between the groups at either level of RF at any minute during anoxia. Aerobic recovery of CO preparations is markedly enhanced at 1 g RF. Anoxic tolerance and aerobic recovery differences, however, are smaller at the peak of the RF-AF curve. Effects on time to peak AF and maximal rate of rise of AF are not marked at either level of RF in CO preparations.

Aerobiosis↗
PubMed1976

Lactate dehydrogenase changes following several cardiac hypertrophic stresses.

The effects of four different cardiac hypertrophic stresses on cardiac lactate dehydrogenase (LDH) isozyme composition and activity were examined. Altitude-induced right ventricular hypertrophy was accompanied by an increase of 10% in the M subunit of LDH in right ventricle, left ventricle, and atria. Left ventricular hypertrophy induced by aortic stenosis also produced isozyme changes in the ventricles, but of only half the magnitude. Biventricular hypertrophy, induced by running or swimming, was accompanied by 4-5% increases in M LDH in the ventricles only. We conclude that changes in LDH activity are directly related to changes in the M subunit in all three portions of the heart. No changes in H subunit were noted under any of the stresses. It appears that the magnitude of changes in cardiac LDH isozyme composition are only marginally related to extent of hypertrophy.

Altitude↗
PubMed1975

Effects of physical training on several glycolytic enzymes in rat heart.

In response to a program of daily swimming for 16 weeks, the activities of pyruvate kinase and lactate dehydrogenase increased significantly in the hearts of young male rats. The isozyme composition in M of cardial lactate dehydrogenase increased from 28.5 to 32.7% in the trained animals. Phosphofructokinase activity and glycogen content were unchanged. The hearts of the exercising animals were 28% heavier than those of sedentary paired weight controls.

Animals↗
PubMed1975

Serum and organ creatine phosphokinase alterations in exercise.

Rats that swam for 3 h showed a 6-fold increase in serum creatine phosphokinase (SCPK) activity which declined to control values within 7 h after swimming. Of the excess SCPK, 77% was BB isoenzyme; the remainder was mainly MM with traces of MB. Kidney, liver, brain and lung contain mainly BB (50-80%) and only a trace of MB (0-7%). Heart CPK was composed of little BB (8%) and more MB (28%) and MM (64%). Skeletal muscle CPK was almost entirely MM. CPK activity is highest in skeletal muscle, intermediate in heart and brain and lowest in kidney, liver and lung. It is suggested that skeletal muscle and heart are not involved in CPK release in swimming, and kidney, liver and brain may be sites of release.

Animals↗
PubMed1970

Anaerobic rat heart. Effects of glucose and tricarboxylic acid-cycle metabolites on metabolism and physiological performance.

1. The ability of tricarboxylic acid-cycle metabolites to influence the physiological performance of the perfused anaerobic rat heart was investigated. Energy expenditure/h [(beats/min)x60xsystolic pressure/g of protein] for various anoxic conditions compared with oxygenated control hearts were: 5mm-glucose, 4.5%; 20mm- or 40mm-glucose, 10%; 20mm-glucose plus fumerate+malate+glutamate, 29%; 20mm-glucose plus oxaloacetate and alpha-oxoglutarate, 31%. 2. The energy expenditure/lactate production ratio was increased by the tricarboxylic acid-cycle metabolites, indicating that alterations in anaerobic physiological performance did not result from changes in glycolysis. 3. Analysis of tissue constituents provided further indication of an enhanced energy status for fumarate+malate+glutamate- and oxaloacetate+alpha-oxoglutarate-perfused hearts; tissue concentrations of both glycogen and ATP were higher than in the 20mm-glucose-perfused groups. 4. A marked increase in the accumulation of succinate in tissues perfused with oxaloacetate+alpha-oxoglutarate or fumarate+malate+glutamate provided further evidence that these metabolites were stimulating mitochondrial energy production under anoxia. 5. These studies indicate that mitochondrial ATP production can be stimulated in an isolated mammalian tissue perfused under anaerobiosis with a resulting enhancement of cell function.

Adenosine Triphosphate↗