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Biomedical subjects

D M Baker

Publications and source records attributed to D M Baker.

79 records · Page 5Linked to original sources
PubMedDate not supplied

Evidence for a decrease in sympathetic control of intestinal function in the aged rat.

The ability of carbachol and isoprenaline to contract and relax respectively the longitudinal layer of ileal smooth muscle has been compared in rats aged six and twenty-four months. The concentration response curve to carbachol did not vary with the age of the animal. In contrast, the ability of isoprenaline to relax longitudinal smooth muscle precontracted with carbachol was significantly (p less than 0.02) reduced in the twenty-four month age group. This reduced response was due to a decrease in the maximal relaxation induced by isoprenaline rather than by a shift to the right of its dose-response curve. These results are discussed in the context of previous histochemical and microscopical studies which have shown a marked reduction in the density of the sympathetic innervation of the rat small intestine in old age.

Adrenergic beta-Agonists↗
PubMedDate not supplied

Ethanol self-administration in rats following exposure to dietary cadmium.

Rats were maintained on an ad lib diet containing 100 ppm cadmium (Group Cadmium-Diet) or a control diet with no added cadmium (Group Control-Diet). After 55 days of exposure to their respective diets, animals were tested for fluid intake using a nonchoice procedure that presented a 15% ethanol solution in the home cage for 5 days. Subsequently, all animals were offered a 10% ethanol solution or tap water in a 3-bottle, 2-fluid choice test in the home cage. This fluid intake test was conducted for a 5 day baseline period, and then again concurrently with avoidance acquisition (14 days) and extinction (4 days) training on a free operant (Sidman) avoidance task that required animals to lever press to avoid electric footshock. After training was terminated the choice test was continued further in the home cage for a 15 day post-avoidance period. Ethanol intake was greater for animals exposed to cadmium on all tests of fluid consumption, and all animals consumed more ethanol during the periods following termination of the stressor (avoidance extinction, post-avoidance) than during the actual period of stress (avoidance acquisition). Interpretive comments focus on the effects of cadmium on stress reactivity, sensory processing, and metabolism.

Alcohol Drinking↗
PubMedDate not supplied

Altered endothelin-1 levels in acute lower limb ischemia and reperfusion.

Tourniquet-induced ischemia is often used in orthopedic and reconstructive procedures. This is associated with muscle damage and dysfunction, which limits tourniquet application time. Endothelin-1 (ET-1) is a potent vasoconstrictor, which has been implicated in ischemic conditions and ischemia-reperfusion injury. This study aimed to investigate the role of ET-1 in human skeletal muscle subjected to tourniquet-induced acute ischemia and reperfusion. Thirteen patients undergoing total knee replacement were studied. Plasma and muscle ET-1 concentrations were measured at the start of surgery, after an hour of acute ischemia, and 15 minutes following reperfusion. ET-1 receptor binding was also studied by use of autoradiography, and ET-1 mRNA expression investigated by use of real-time polymerase chain reaction (RT-PCR). Tissue ET-1 increased following the period of acute ischemia and persisted during reperfusion. ET-1 was associated with microvessels and macrophages in the muscle. No changes in circulating ET-1 levels, ET-1 mRNA expression, or ET-1 receptor binding were found. It is concluded that the ET-1 pathway is involved in acute ischemia and reperfusion and it may contribute to the muscle injury that occurs during surgical procedures.

Acute Disease↗
PubMedDate not supplied

The effects of chronic cadmium exposure on schedule controlled responding and conditioned suppression in the adult rat.

Adult rats fed daily rations of laboratory chow with added CdCl2 were tested for schedule controlled responding and conditioned suppression (conditioned emotional response-CER). Determinations of tissue Cd, levels of metallothionein, and the ratio of Cd in the tissue to the Cd-binding capacity of metallothionein also were made. Animals were exposed daily to either 5 mg/kg Cd (Group Cd-5), 1 mg/kg Cd (Group Cd-1), or no Cd (Group Control). An initial phase of training on a variable interval 2 min (VI-2) food reinforcement schedule lasting 40 sessions (1 session/day) was followed by CER training and then an interpolated period (100 days) of continued exposure but with no training. Schedule retraining was introduced for 21 sessions (1 session/day). The results showed no group differences during original schedule training. On the CER test, Group Cd-1 was found to exhibit less suppression (defined in terms of lever press rates) than controls to preaversive stimuli. Group Cd-5 showed significantly greater suppression to the primary aversive stimulus (shock) than the other two groups. Both treatment groups showed significantly lower lever press rates than controls on the schedule retraining task. These behavioral disturbances occurred commensurate with increases in non-metallothionein bound Cd in the liver, kidney, and small intestine.

Animals↗