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Biomedical subjects

D E Clark

Publications and source records attributed to D E Clark.

At least 127 records · Page 7Linked to original sources
PubMed1984

The effects of oral cadmium exposure on passive avoidance performance in the adult rat.

Step-down passive avoidance acquisition and 24 h retention performance were examined in adult rats given daily doses of either 0, 1, or 5 mg/kg cadmium (Cd) (as CdCl2) via the diet. Results indicated that subjects exposed to the 5 mg/kg Cd diet were less likely to step off a safe platform onto an electrified grid floor than controls. The 1 mg/kg subjects did not differ from controls on this acquisition task. None of the groups showed differential performances on a retention test administered 24 h after acquisition training. These results are discussed in terms of recent claims that Cd exposure enhances emotional reactivity in animals.

Administration, Oral↗
PubMed1984

Effect of the pneumatic antishock garment on intramuscular pressure.

Recent case reports implicate pneumatic antishock garment (PASG) usage in subsequent development of compartment syndromes. The anterior tibial compartment pressures of eight healthy volunteers were selected for study at varying PASG inflation pressures. A wick catheter method provided continual intramuscular compartment pressure (IMP) monitoring throughout the period of study. A linear correlation between PASG pressure and IMP exists, with more than 90% of the externally applied pressure being transmitted to the muscle compartment. All subjects developed IMP greater than 50 mm Hg at PASG inflation of 60 mm Hg. Externally applied pressure appears to create a condition that may stimulate or lead to a compartment syndrome. Inflation pressure should be monitored closely during PASG application, because IMP can be assumed to be at least as high as inflation pressure. The lowest effective PASG pressure should be used.

Adult↗
PubMed1984

Effects of acute trimethyltin exposure on appetitive acquisition and extinction performance in the adult rat.

Adult male rats were given one intragastric infusion of either 7 mg/kg trimethyltin chloride (dose calculated as the base of trimethyltin [TMT]) or physiological saline. Twenty-one days after dosing, subjects from each condition were divided into two equal-sized groups and trained with either partial (PRF) or continuous (CRF) reinforcement in a straight alley maze. The acquisition phase of training, lasting 40 trials (4 trials/day), was followed by 20 trials of extinction training (4 trials/day). Analyses performed on total speed revealed that TMT-treated subjects performed at lower levels during acquisition than controls regardless of schedule condition. Also, the rate of resistance to extinction was significantly reduced for treated subjects compared with that of controls regardless of the training schedules used during acquisition. A partial reinforcement extinction effect was observed for both control and TMT-treated subjects, that is, independent of dose regimen; PRF training occasioned greater persistence during extinction than did CRF training. These findings are discussed in terms of their implications for contemporary empirical and theoretical issues relating to TMT-induced hippocampal lesions.

Animals↗
PubMed1984

Conditioned taste aversion in the adult rat induced by dietary ingestion of cadmium or cobalt.

The potential aversive qualities of dietary cadmium chloride (10, 100 mg/kg) or cobalt chloride (20, 100, 200 mg/kg) were evaluated in a conditioned saccharin aversion task. Male Long-Evans hooded rats (n = 42) were trained to drink tap water and ingest 10 grams of chow during daily 60 minute access tests. During the aversion-acquisition phase, a second bottle containing 0.1% sodium saccharin was introduced and the various metal-adulterated diets (10 grams, dose calculated as mg metal base/kg body weight) offered in place of plain chow. During extinction testing, all rats were fed the plain chow. Diets adulterated with cadmium (10 or 100 mg/kg) or cobalt (100, 200 mg/kg) induced marked conditioned saccharin aversions after 2-3 days of exposure and were found to be profoundly resistant to extinction. Both cadmium (100 mg/kg) and cobalt (100, 200 mg/kg) induced a corresponding suppression of intake of adulterated food and significant weight losses. The relation of these aversive effects to the influence of cadmium and cobalt on operant responding for food reward is discussed.

Animals↗
PubMed1983

Behavioral effects of chronic lead exposure in the adult rat.

Adult rats fed daily rations of laboratory chow laced with lead acetate, were tested for operant (schedule-controlled) responding and conditioned suppression. In Experiment 1, animals receiving 10 mg/kg lead showed significantly lower operant response rates (lever pressing) than controls. Conditioned suppression performance was not different between the two groups. During retraining that followed a 42 day no-training period, lead-treated subjects showed greater percent of prior baseline responding than controls. The groups were not different on a test for stimulus control or an appetitive resistance to extinction test. In Experiment 2, separate lead-treated groups were chronically exposed to either 10 mg/kg, 5 mg/kg, or 1 mg/kg lead daily. Behavioral tests showed that while the lowest lead level (1 mg/kg) occasioned higher rates of operant lever pressing relative to controls, the highest level (10 mg/kg) again produced lower rates. On a retraining task administered after an interpolated 90 day no-training period, the two highest exposure groups were significantly above controls regarding percent of baseline responding and there was evidence that the 5 mg/kg group was significantly superior to controls in terms of absolute response rate. No differences in conditioned suppression or resistance to extinction were observed in the second experiment.

Animals↗
PubMed1983

Traumatic rupture of the pericardium.

Patients with traumatic rupture of the pericardium rarely survive to reach a hospital. Ten cases from the Maryland Institute for Emergency Medical Services Systems and 132 previously published cases are reviewed. Patients were usually men who were victims of violent thoracic trauma. The median age was 40 years. Half of the patients had left pleuropericardial tears; tears of the diaphragmatic pericardium, right pleuropericardium, and superior mediastinal pericardium were less frequent. Associated injuries of the heart or left hemidiaphragm were common. Pericardial rupture was usually discovered during surgical exploration for other indications, but physical or radiographic signs were occasionally present. Repair is indicated for most pericardial tears to prevent herniation of the heart or abdominal viscera.

Abdominal Injuries↗
PubMed1982

Conditioned suppression in the adult rat following chronic exposure to lead.

Conditioned suppression was examined for control (N = 8) and lead-treated (N = 8) adult rats. Treated animals were exposed daily to 10 mg/kg lead administered via the diet as lead acetate. 40 days of operant lever press training on a multiple schedule using food as reward was given. Lever press training continued for an additional 5 days but during this period subjects experienced superimposed 3 min tone presentations followed by electric shock (1.3 mA, 1.5 s duration) to a grid floor. Tone presentations were observed to be significantly more disruptive of operant steady state responding for treated subjects as compared to controls. This finding supports earlier claims that lead exposure enhances emotionality.

Animals↗
PubMed1981

Renal arterial injuries caused by blunt trauma.

Ten patients from the Maine Medical Center with renal arterial injuries caused by blunt trauma are presented and analyzed along with 240 other case reports from the literature. Most patients were under 30 years of age and many were children. Injuries to the left side were more frequent; bilateral injuries occurred in 22 patients. Motor vehicle accidents were responsible for the majority of cases. Arterial thrombosis was the most common finding. Associated abdominal injuries were frequent, but the kidney itself was usually spared. Physical findings, urinalysis, and exploratory laparotomy were not reliable in the detection of arterial injury, but excretory urography and angiography were very accurate. Untreated unilateral injuries usually led to renal atrophy, but most did not cause hypertension; untreated bilateral injuries usually led to chronic renal failure or death. Few attempts at revascularization were successful. Excretory urography is recommended for all patients with blunt abdominal trauma; nonfunction should be investigated by angiography. Immediate bilateral repair is indicated in all cases of bilateral renal arterial injury, but repair of a unilateral injury is indicated only if it is promptly diagnosed in a young, stable patient.

Adolescent↗
PubMed1979

Combinative effects of hexachlorobenzene and crowding on rat adrenal cell mitochondria.

The effects of social stress (crowding) on hexachlorobenzene (HCB) toxicity in male rats was evaluated by a morphometrical analysis of adrenal cortex mitochondria. The social stress was produced by transferring singly-housed rats from cages of ample size (1000 cm2 floor space) into small cages (100 cm2 floor space) each containing four rats. Differences in cage design as well as size may have contributed to the overall stress experienced by the rats. The food of the treated rats was supplemented with 250 ppm HCB. Structural changes in mitochondrial volume, surface area, or cristae area were not significant in HCB-treated or in crowded animals when compared with those of the controls. However, increases in mitochondrial volume and diameter were significant in those animals simultaneously challenged by HCB and crowding. The results strongly suggest that even a relatively mild social stress may adversely affect the ability of an animal to resist the effects of some exogenous chemicals.

Adrenal Cortex↗
PubMed1979

Testosterone metabolism by hexachlorobenzene-induced hepatic microsomal enzymes.

Hexachlorobenzene, which is a widespread contaminant of meat and meat animal by-products throughout the world, had a profound effect on the homeostatic mechanism which controls the serum testosterone concentrations in the mouse. Significant increases in the mean hepatic weight, the concentrations of hepatic microsomal protein, cytochrome P-450, cytochrome b5, and cytochrome c reductase activity occurred in the aminals given a ration containing 250 mg of hexachlorobenzene/kg for 21 days, when compared with their nontreated controls. These increases in cytochrome concentrations and enzyme activity of the hepatic microsomes are reflected by significant increases in the in vitro metabolism of [3H]testosterone and a decrease in the serum concentrations of testosterone with a concomitant decrease in the weights of the seminal vesicles and ventral prostate of the mouse.

Animals↗