Biomedical subjects

J Mark Davis

Publications and source records attributed to J Mark Davis.

21 records · Page 2Linked to original sources

PubMed2002

Differential release of corticotropin-releasing hormone (CRH) in the amygdala during different types of stressors.

The purpose of this study was to determine if differences exist between the effects of acute treadmill running and restraint stress on corticotropin-releasing hormone (CRH) release within the amygdala of rats. Extracellular CRH immunoreactivity (CRH-IR) was measured in microdialysate collected from the central nucleus of the amygdala (CeA) during exposure to an inactivated treadmill (TC), during 1 h treadmill running to exhaustion (RUN), and 1 h restraint (RES). Extracellular CRH-IR increased from control levels during the first 20-min period for TC, RUN, and RES, with the largest increase during RES. During the second 20-min period, only RES maintained levels higher than control values. CRH release was higher than control during the third 20-min period of RES and RUN. A second experiment consisted of four groups of either cage controls (CC), TC, RUN, or RES. Immediately following the 60-min treatment, brains were removed and trunk blood collected for analysis of tissue CRH-IR and plasma corticosterone. While amygdala tissue CRH-IR was not different in the CC, TC and RUN rats, these groups had significantly lower levels than the RES animals. Hypothalamic tissue CRH-IR was not different between the CC and TC rats, but the levels were significantly higher in the RES and RUN rats than in the two control groups. Plasma corticosterone levels were elevated only in RES and RUN rats. Results from tissue analysis indicate that increased tissue CRH-IR in the amygdala and hypothalamus can be elicited by RES, while only the hypothalamus shows an increase following RUN. Further, extracellular CRH release in the CeA is increased throughout the period of RES, when rats are placed on the treadmill, and when the animals are approaching physical exhaustion. No increase is observed during the running period between placement on the treadmill and intense exertion. Overall, the data suggest that amygdala CRH release is regulated differently during treadmill running and restraint.

Amygdala↗

PubMed2002

Carbohydrates and physical/mental performance during intermittent exercise to fatigue.

PURPOSE: This study was designed to examine the effects of carbohydrate-electrolyte ingestion on physical and mental function associated with the performance of intermittent high-intensity (IHI) exercise similar to many common competitive sporting events. METHODS: Physically active men (N = 5) and women (N = 5), experienced in competitive soccer or basketball, completed three practice sessions and two experimental trials of an IHI shuttle running protocol designed to closely stimulate the demands of an actual competitive sporting event such as basketball. The experimental trials consisted of four 15-min quarters (QTR) of intermittent shuttle running at various percentages of .VO(2max) (walking, jogging, running, sprinting and jumping), separated by a 20-min halftime rest period (HALF) and followed by a shuttle run to fatigue. Various tests of physical and mental function (shuttle run to fatigue, 20-m maximal sprint, 10-repetition maximal vertical jumping, whole body motor skill test (MS-Test), profile of mood states (POMS), and Stroop Color-Word Test) were performed throughout the experimental trial. Carbohydrate-electrolyte (CHO) or placebo (P) drinks were consumed before exercise (5 mL.kg(-1); 6% solution) and at halftime (5 mL.kg(-1); 18% solution). Smaller volumes (3 mL.kg(-1); 6% solution) were given after QTR-1, HALF, QTR-3, and QTR-4. RESULTS: CHO ingestion resulted in a 37% longer run time to fatigue and faster 20-m sprint time during QTR-4 (P < 0.05). MS-Test performance was also improved during the latter stages of exercise along with self-reported perceptions of fatigue (subscale of POMS) (P < 0.05) in CHO versus P. CONCLUSION: These results suggest a beneficial role of carbohydrate-electrolyte ingestion on physical and mental function during intermittent exercise similar to that of many competitive team sports.

Adult↗

PubMedDate not supplied

Influence of carbohydrate on immune function following 2 h cycling.

The influence of carbohydrate compared with placebo ingestion on changes in immune cell counts and functions following 2 h intensive cycling was studied in 12 trained cyclists who functioned as their own controls. The subjects performed two tests 2 weeks apart where they cycled for 2 h at approximately 64% Watts(max) while receiving 4 mL x kg(-1) x 15 min(-1) carbohydrate (6%) (Cho) or placebo (Pla) beverages. Blood samples were collected 30 min preexercise, and immediately and 1 h postexercise. The samples were assayed for plasma cortisol and epinephrine, blood leukocyte subset counts, PHA-induced lymphocyte proliferation, and natural killer cell activity (NKCA). Compared with Pla ingestion, Cho attenuated exercise-induced changes in plasma cortisol, blood neutrophil, and monocyte counts, but not in total blood lymphocyte, T cell, and NK cell counts, PHA-induced lymphocyte proliferation, and NKCA. Thus despite a strong attenuating influence of carbohydrate ingestion on exercise-induced changes in plasma cortisol and blood neutrophil and monocyte counts, other immune measures related to lymphocyte subset counts, and function were unaffected.

Adult↗