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Biomedical subjects

G H Parker

Publications and source records attributed to G H Parker.

At least 19 recordsLinked to original sources
PubMed2004

Tissue metal levels in Muskrat (Ondatra zibethica) collected near the Sudbury (Ontario) ore-smelters; prospects for biomonitoring marsh pollution.

An examination of tissue metal levels in Sudbury-area muskrat (Ondatra zibethica) revealed that animals collected in the vicinity of the local ore-smelters contained elevated burdens of Cd and Ni in their liver and kidneys. Respective tissue concentrations averaged 2-fold and 3- to 6-fold higher than background values and are believed to reflect accumulations resulting from food chain contamination in regional marshes, including that reportedly characterizing Typha latifolia stands-their primary food source-and adherent sediments which may be consumed inadvertently while feeding. No evidence of site-influence or enhanced tissue metal levels was seen for Cu, Pb or Zn. While Cd : Ni accumulations were positively correlated in both the liver (r=0.78) and the kidneys (r=0.65), between-tissue comparisons indicated that hepatic : renal burdens were significantly correlated (r=0.75) only in the case of Ni. With the exception of 30-35% lower hepatic Zn levels in females relative to males within the Sudbury population, tissue metal levels did not vary according to sex or age class at either site. Our findings substantiate the potential of muskrat to serve as useful bioindicators/monitors of metal pollution in semi-aquatic environments.

Animals↗
PubMed2001

Metal levels in body tissues, forage and fecal pellets of elk (Cervus elaphus) living near the ore smelters at Sudbury, Ontario.

Ontario's only free-ranging elk herd located at Burwash-French River has been subjected to the influence of historic copper-nickel-iron (Cu-Ni-Fe) ore smelting operations within the Sudbury area. Metal levels in selected body tissues, preferred forage items and fecal pellets were determined, and their potential effects on health and reproductive viability assessed. Significant age effects were apparent in 13 out of 31 tissue metal values obtained, with most age-related differences attributable to elevated concentrations in fetal tissues. Cu and zinc (Zn) levels were four to six times higher in livers and one and a half to two times higher in the bones of fetuses as compared to post-natal animals. Enhanced pre-natal tissue burdens were also noted for cobalt (Co), Ni and lead (Pb) in muscles. However, mean cadmium (Cd) levels in kidney, liver and muscle tissues, as well as hepatic Fe concentrations, showed significant increases with age. Although Cd levels in the kidneys of older elk were still well below the reported threshold for irreversible organ damage, and not considered to be health-threatening, detailed histological study of the cortical tissues for subtle pathotoxicological effects may be warranted. Unlike renal and hepatic tissues, Cd concentrations in skeletal muscle were minimal and within levels considered acceptable for human consumption. Forage species collected in the elk range generally showed higher (two to eight times) Ni and Fe levels than the corresponding plants from a non-contaminated reference site. The highest Ni and Fe burdens were carried by eastern white cedar, a preferred winter food item for elk. No consistent site-related trends were demonstrated by Cu, Zn, Co, Pb, chromium (Cr) and Cd forage levels. Mean metal concentrations in fecal pellets generally exceeded the mean composite forage levels by a factor of 3, except for Ni, which was five times more concentrated in feces. Significantly elevated Ni and Fe levels in preferred browse species and fecal pellets of the Sudbury-area elk could be of concern and warrant further investigation.

Age Factors↗
PubMed1996

Effect of enhanced geomagnetic activity on hypothermia and mortality in rats.

The hypothesis was investigated that variability in the severity of limbic seizure-induced hypothermia in rats was affected by ambient geomagnetic activity. Data were obtained in support of this hypothesis. The depth of the hypothermia was significantly (P < 0.001) reduced if the ambient geomagnetic activity exceeded 35 nT to 40 nT. Mortality during the subsequent 5 days was increased when the geomagnetic activity was > 20 nT. The magnitude of the effect was comparable to the difference between exposure to light or to darkness during the 20 h after the induction of limbic seizures.

Animals↗
PubMed1994

Prevention of sudden cardiac death by the atypical neuroleptic acepromazine following status epilepticus in rats.

Normal male rats in which status epilepticus has been induced by injecting 30 mg/kg of pilocarpine after a single systemic administration of lithium (sufficient to produce blood levels of 0.2 mEq/L) invariably die within 24 hr. Real-time monitoring indicated sudden cardiac death; it was preceded by progressive intensification of arrhythmia. A single systemic injection (25 mg/kg) of the atypical phenothiazine acepromazine prevented the mortality and virtually eliminated the cardiac instability.

Acepromazine↗
PubMed1993

Age and proximity to local ore-smelters as determinants of tissue metal levels in beaver (Castor canadensis) of the sudbury (Ontario) area.

An examination of tissue metal levels in Sudbury-area beaver (Castor canadensis) revealed that animals in the vicinity of the local ore-smelters contained elevated burdens of Ni and Pb in the liver and kidneys. Tissue concentrations averaged 1.5- to 2.5-fold higher than background values and are believed to reflect accumulations resulting through food chain contamination. Tissue levels of Cu, Cd and Zn did not vary in relation to distance from source. Tissue Cd levels were uniformly elevated throughout the four populations examined and are believed to reflect an enhanced level of food chain transfer occurring on the poorly buffered, acid-sensitive soils of the area. Burden: body weight correlations indicated that tissue concentrations of Cd increased whereas Cu levels decreased as a function of animal age. Most striking among these age-related trends was the disproportionate uptake of Cd by renal tissues, resulting in 10-fold higher burdens than those present within the liver.

Journal Article↗
PubMed1983

Mast cell numbers in incisional wounds in rat skin as a function of distance, time and treatment.

The dynamic changes in skin mast cell (MC) numbers around incised wounds were studied, using experimental designs amenable to multiple analyses of variance. Sixty-four Wistar albino rats were shaved in the interscapular region, wounded or not wounded, and then killed 2 or 10 days later. During this period, the rats were exposed continually to a cold (2 degrees C) or control (20 degrees C) climate and treated daily over the shaved region with either tap water or a weak sulphuric acid (pH 3.5) solution. The MCs within five adjacent fields of the wound or the control reference and within the superficial and deep halves of the skin were counted (at x 400). The greatest decrease in MC numbers occurred within about 700 microns of the wound. Whereas the paucity of MCs within the wound region was evident at 2 days, near-normal levels were achieved by day 10. Cold exposure produced little effect, but MCs responded differently to the water and acid treatments as a function of distance and skin depth.

Abdomen↗
PubMed1982

Lead in the water supply alters swimming-maze behavior in adult mice.

After about two weeks of exposure to either 20 ppm or approximately 2000 ppm of lead in the drinking water or tap water only and under an ad libitum or restricted food regime, albino male and female mice (N = 48) were tested for three consecutive days (3 blocks of 3 trials per day) in a swimming maze. Body weights were not altered by lead treatments significantly. The mice treated with the lead displayed longer escape latencies and more errors than the controls on tap water. Statistically significant interactions of lead treatment by test day by test block were also apparent.

Animals↗
PubMed1982

Interactions of 2-ppm lead in the water supply with food deprivation upon maze-swimming behavior of mice.

Mice that had been given either tap water or 2 ppm lead in their drinking water and either severely food deprived (3 days before testing) or allowed food ad libitum demonstrated significant interactions of lead treatment by day by food condition and lead by block. Although not statistically significant, the food deprived-lead treated mice displayed more errors and longer latencies than the ad libitum-water controls. The food deprived-water controls and ad libitum-lead-treated mice displayed intermediate values. The importance of using multivariate statistical techniques that can evaluate dynamic repeated behavioral measurements is emphasized.

Animals↗
PubMed1978

Changes in muscle, liver, and plasma free fatty acid levels in the pigeon on acute exposure to cold.

Adult pigeons were subjected to acute cold exposure (-25 degrees C; 30 min). Fully-plumed birds, showed a pronounced increase in the level of FFA in the blood, but not in the liver or muscle. Partially-defeathered (dorsum and pectoral regions) birds, likewise, showed a marked increase in plasma FFA level but failed to indicate any change in FFA levels in the liver or the muscle. It is concluded that even if the mobilized FFA may have supported calorigenic processes in the normothermic cold-exposed pigeon, lipid reserves are unlikely to have served as a significant source of energy for thermogenic functions in the hypothermic (defeathered) bird.

Animals↗
PubMed1976

Effects of intense exercise on intracellular glycogen and fat in pigeon pectoralis.

The pigeon pectoralis muscle was electrically stimulated in vivo at a high intensity of 25 V and the intracellular glycogen and fat reserves of the muscle examined histochemically to determine the pattern of substrate utilization in the component broad white and narrow red fibre types during the intense flight-simulated exercise. 4 h of continuous stimulation resulted in the depletion of intracellular glycogen from both fibre types and a simultaneous reduction in the intracellular fat stores of the red fibres. While glycogen provides the only source of energy for the white fibres, glycogen as well as fat serves as fuel for the red fibres. It is postulated that, though fat is the major fuel for the red fibres, their glycogen reserves are utilized to ensure a steady supply of oxaloacetate essential in the oxidation of fatty acids via the Krebs cycle, and that fatty acid catabolism helps to maintain gluconeogenesis.

Animals↗
PubMed1976

Changes in blood glucose, blood and muscle lactate,and plasma lactic dehydrogenase levels in the pigeon on acute exposure to cold.

Adult pigeons were subjected to acute cold exposure (-25 degrees C; 30 min) after which the levels of blood glucose, blood and muscle lactate and plasma lactic dehydrogenase were measured. Partially defeathered (dorsum and pectoral regions) birds, following exposure to cold, showed marked reduction in blood glucose and blood and muscle (pectoralis) lactate. Fully plumed birds, in contrast, showed no significant reduction in body temperature or blood glucose and only moderately reduced lactate levels indicating the effectiveness of the insulative feather coat in maintaining thermal and metabolic homeostasis. The partially-defeathered pigeons exposed to cold showed a two-to-three-fold increase in plasma lactic dehydrogenase activity, which may reflect a molecular adaptation in their calorigenic response to cold.

Animals↗
PubMed1975

Effects of short and long term exercise on intracellular glycogen and fat in pigeon pectoralis.

In an attempt to determine the functional role of the component broad white and narrow red fibre types during activity, the pectroalis muscle of the adult pigeon (Columba livia) was electrically stimulated in situ after anaesthetizing the birds with sodium pentobarbital. For examination of the effect of short term exercise, the pectoral muscle of one side was stimulated through the innervating brachial plexus, using an electronic stimulator for 1 hr, and a biopsy sample was taken from the stimulated muscle. The stimulation was resumed for 17 hr more with additional doses of anaesthesia, and a muscle sample was taken after the decapitation of the birds in the long term experiment. Muscle samples from non-stimulated pigeons under identical conditions served as control. Fixed and frozen sections were made from the samples and were stained with Periodic Acid-Schiff's reagent for the demonstration of glycogen, while additional frozen muscle sections were stained with Fettrot 7B according to Pearse, A.G.E. (1960) for the demonstration of neutral lipids in the specimen. Thus histochemical examinations were made to study effects of short and long term exercises on energy stores in skeletal muscles. Short-term stimulation resulted in a selective depletion of intracellular glycogen stores from white fibre populations whereas prolonged long term stimulation resulted in the resynthesis of glycogen within these fibres and a concomitant reduction in the intracellular fat and glycogen reserves in most red fibres. It is postulated that during flight the white fibres indulge only in brief bursts of intense phasic activity such as in quick take-off, rapid accelerations or sudden manoeuvres and utilize glycogen as fuel whereas the red fibres perform sustained activity as in cruising flight and metabolize chiefly fat.

Animals↗