Behavior-genetic-dependent self-selection of alcohol in rats.

Investigated self-selection of alcohol in 30 male and 30 female selectively bred rats: MNR/Har/Lu (f38), MR/Har/Lu (f33), RCA/Lu (F18), RHA/Lu (F18), and RLA/Lu (F18). In Exp. I, self-selection of alcohol of 3 concentrations was tested along with caloric-equivalent glucose solutions and distilled water. Exp. II investigated the simultaneous self-selection of 5, 10, and 20% alcohol solutions. In Exp. III effects of food deprivation on the self-selection of 10% alcohol and distilled water were studied. Self-selection of alcohol was related to the phenotypes of emotional reactivity and avoidance conditionability. Females consumed significantly larger amounts of absolute alcohol than males based on corrected body weight. Validity of sex differences is discussed. (30 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exercise training restores decreased cellular immune functions in obese Zucker rats

This study investigated whether exercise training had a beneficial effect on the decreased mitogen response and improved a decreased expression of glucose transporter 1 (GLUT-1) in splenocytes from obese Zucker rats. Experimental groups were lean and sedentary and exercise-trained obese Zucker rats. Exercise training, running on a motor-driven treadmill for 5 days/wk for 40 wk, did not induce a significant decrease in body weight in obese Zucker rats. The plasma insulin concentration, showing a significant increase compared with lean Zucker rats, was unaffected by exercise training. However, the plasma triglyceride concentration in obese Zucker rats was significantly depressed by exercise training, whereas it was still higher than that in lean Zucker rats. In addition, natural killer cell activity and concanavalin A-induced mitogenesis of splenic lymphocytes of obese Zucker rats were significantly restored. In these splenic lymphocytes, glucose uptake was significantly lower compared with that in lean Zucker rats, which was also improved by exercise training. Although the expression of GLUT-1, the major glucose transporter in immune cells, was depressed in splenic lymphocytes of obese Zucker rats, exercise training induced a significant improvement. These results suggest that exercise training has a beneficial effect on the decreased cellular immune functions in obese Zucker rats, which is associated, in part, with the improvement in GLUT-1 expression.     

Oral somatosensory factors in dietary self-selection in rats.

To study the mechanisms of the control of protein intake, 38 male albino Sprague-Dawley rats were subjected to partial trigeminal deafferentation. Oral somatosensory afferents from the lower anterior portion of the oral cavity were selectively sectioned, but somatosensation of the other parts of the mouth as well as gustatory and olfactory afferents were left intact. Ss were allowed to choose from 3 diets, only one of which contained protein. Before deafferentation, Ss chose a constant portion of their daily intake in the form of protein. After deafferentation, protein intake was all but eliminated at first but was resumed later; carbohydrate intake was reduced. When total intake had recovered to nearly preoperative values, the protein/total-intake ratio remained impaired, with deficits that ranged from seemingly random selection to extreme preferences. The variability of dietary selection between days was considerably higher than before surgery. The involvement of learning processes in homeostasis is discussed. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of taste in dietary self-selection in rats.

Conducted 3 experiments with 78 male albino Harlan and Sprague-Dawley rats in which Ss were subjected to 2 degrees of gustatory deafferentation—either the chorda tympani was sectioned alone or in combination with the glossopharyngeal nerve and the pharyngeal branch of the vagus. Ss were then presented with 2 diets, only 1 of which contained protein. Findings reveal that, after surgery, deficits were observed in body weight, food and water intake, and diet selection that were proportional to the extent of deafferentation. Approximately 76% of the Ss increased protein and decreased carbohydrate intake, but all Ss continued to select a nutritionally balanced diet (Exp I). When subjected to a nutritional challenge of intragastric protein or carbohydrate supplementation, the Ss compensated for calories and nutrients by selectively adjusting oral intake (Exp II). In saccharin preference tests, the preference as well as the total consumption of the test solutions was reduced (Exp III). Results support the hypothesis that dietary selection pattern of an animal not only reflects intrinsic factors (metabolic/physiological state) but also extrinsic factors such as the pallatability and accessibility of the diet. Findings are contrasted to the effects of oral somatosensory deafferentation and are interpreted as a change in preference within the limits of metabolic requirements. The different roles/mechanisms of the 2 sensory systems in regard to dietary self-selection are discussed. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dietary self-selection in intact, ovariectomized, and estradiol-treated female rats.

Six experiments with 84 Long-Evans rats investigated the effects of estrogenic stimulation on diet selection in intact estrous-cycling Ss, ovariectomized (OVX) Ss, and OVX Ss given estradiol benzoate (EB) hormone replacement therapy. In Exp I, OVX was associated with the nearly exclusive choice of the more calorically dense of a pair of diets varying in the concentration of fat, carbohydrate (COH), and protein, an effect that was decreased by EB. In Exp II, dietary self-selection was examined in intact estrous-cycling Ss given access to an isocaloric diet triplet of fat, COH, and protein. Total caloric intake and body weight did not vary across the estrous cycle. However, fat intake increased; COH and, to a lesser extent, protein intake decreased. An opposite diet selection occurred during diestrus. In Exp III, OVX resulted in progressive increases in COH and protein intake, with a concurrent decrease in fat consumption. EB partially reversed this diet selection profile (Exp IV). Results were confirmed by diet pairs with both naturally occurring and experimentally produced estrogenic stimulation (Exps V and VI). Data are consistent with previous findings showing estrogenic reduction in COH intake with standard high-COH commercial diets. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ursodeoxycholic acid modifies gut-derived endotoxemia in neonatal rats

We developed a model for the translocation of intraluminal endotoxin in the neonatal animal and used it to examine the capacity of a nonhepatotoxic bile acid, ursodeoxycholic acid (UDCA), to modify endotoxin translocation and cytokine response. Three-d-old Sprague-Dawley rats were randomized to receive enterally either no drug, lipopolysaccharide (LPS, 1 mg/animal), or UDCA (400 micrograms/animal) alone, or UDCA followed by LPS 1 h later. One h after LPS administration, the rats were killed and plasma endotoxin and tumor necrosis factor (TNF) were measured. Control animals had low circulating endotoxin (21.2 +/- 7.6 endotoxin units) and TNF (0.06 +/- 0.02 ng/mL). Enteral administration of LPS 1 h before the rats were killed resulted in significant elevation of endotoxin (249.5 +/- 71.3, p = 0.008) and TNF (3.6 +/- 1.3, p = 0.019). UDCA alone did not alter endotoxin levels (8.7 +/- 2.1). UDCA 1 h before LPS prevented the rise in endotoxin (38.9 +/- 11.2 endotoxin units) and TNF (0.2 +/- 0.05) significantly. Chenodeoxycholic acid was studied in a similar group of experiments and prevented neither the translocation of LPS nor the development of increased TNF levels in animals receiving LPS. In conclusion, LPS can cross the intestinal barrier in the normal neonatal rat. UDCA, administered before LPS, can decrease the translocation of LPS and prevent the cytokine response as measured by TNF levels. We speculate that UDCA, administered prophylactically, might reduce morbidity in clinical conditions leading to gut-derived endotoxemia.     

Learned aversions to proteins in rats on a dietary self-selection regimen.

101 Long-Evans and 38 Wistar rats in 4 experiments were allowed continuous access to protein and carbohydrate macronutrient sources during a sequence of cyclophosphamide (20 or 40 mg/kg, ip) injections. Significant aversions developed to the protein but not the carbohydrate source in the present experiments, in which the composition of both protein and carbohydrate diets was varied. Results suggest that Ss on a dietary self-selection regimen were more likely to develop conditioned aversions to the protein source than the carbohydrate source (Exps I, II, and III). In Exp IV, the generality of these findings was examined by determining whether aversions would selectively arise to proteins but not carbohydrates when these nutrients were conditioned in a single trial with a meal-feeding paradigm. Results show that proteins were again more salient targets for aversions than carbohydrates. Overall, findings suggest that the tendency to associate proteins with drug-induced illness more readily than carbohydrates is not limited to a self-selection regimen. The possible role of taste factors and/or postingestive effects as the basis for the differential conditioning of proteins and carbohydrates is discussed. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of androgens on dietary self-selection and carcass composition in male rats.

In 3 experiments the aromatizable androgen testosterone propionate (TP, .2 mg/day) increased protein (P) and carbohydrate (C) intake and stimulated body weight gain (BWG) in gonadectomized CD-strain male rats. A higher dose (2.0 mg/day) increased P but not C intake and was less effective in stimulating BWG. Postmortem carcass analyses revealed that the elevated P intake of both TP-treated groups was associated with increased carcass P content. The decreased weight of Ss treated with the high dose of TP was due to a reduction in body fat content. The nonaromatizable androgen 5-α-dihydrotestosterone propionate (DHTP, .2 or 2.0 mg/day) also increased P, (but not C intake) and BWG, but it did not alter carcass composition. Unlike TP, the 2 doses of DHTP were equally effective, but neither dose of DHTP was as effective as the low dose of TP in stimulating P and C intake and BWG. Results suggest that (a) androgens can increase selection of dietary P whether or not they exert significant P anabolic effects; (b) DHTP is not the major metabolite responsible for the increases in P and C intake and in BWG caused by TP; and (c) the decreases in C intake and adiposity in rats treated with the high dose of TP may be mediated by aromatized (estrogenic) metabolites of the androgen. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exercise training prevents maturation-induced decrease in insulin sensitivity

We examined the effects of exercise training initiated before maturation or after maturation on insulin sensitivity and glucose transporter GLUT-4 content in membrane fractions of skeletal muscle. Female Wistar rats (4 wk of age) were divided into sedentary and exercise-trained groups. At 12 wk of age, a subset of the trained animals (Tr) was killed along with a subset of sedentary controls (Sed). One-half of the remaining sedentary animals remained sedentary (Sed-Sed) while the other half began exercise training (Sed-Tr). The remaining rats in the original trained group continued to train (Tr-Tr). Euglycemic clamp (insulin infusion rate at 6 mU.kg body wt-1. min-1) was performed at 4, 12, and 27 wk. After euglycemic clamp in all animals except the 4-wk-old, hindlimb (gastrocnemius and part of quadriceps) muscles were removed for preparation of membrane fractions. In sedentary rats, glucose infusion rate (GIR) during euglycemic clamp was decreased from 15.9 mg.kg-1.min-1 at 4 wk of age to 9.8 mg.kg-1.min-1 at 12 wk of age and 9.1 mg.kg-1.min-1 at 27 wk of age. In exercise-trained rats, the GIR was not significantly decreased by maturation (at 12 wk) and further aging (at 27 wk). Initiation of exercise after maturation restored the GIR at 27 wk of age to the same levels as these for the corresponding exercise-trained rats. GLUT-4 content in plasma and intracellular membrane fractions of hindlimb muscle obtained just after euglycemic clamp showed the same trend as the results of GIR. These results suggest that exercise training prevented the maturation-induced decrease in insulin sensitivity. Improvement of insulin sensitivity caused by exercise training was attributed, at least in part, to the increase in insulin-sensitive GLUT-4 on the plasma membrane in skeletal muscle.     

Pavlovian conditioning of immunosuppression modifies adjuvant arthritis in rats.

Dosed 36 female Wistar rats, in 3 groups, with cyclophosphamide (CY), an immunosuppressive drug, 10 days before induction of adjuvant arthritis (by injection of complete Freund's adjuvant into each S's hind paw). A saccharin/vanilla solution (SV) was presented either 2 days before CY treatment (Group NC) or immediately before (Groups C and C2). Three further SV presentations started either 30 min after antigenic stimulation (Groups C and NC) or 2 days afterward (Group C2). The groups did not differ with respect to the degree of swelling in the injected paws. In contrast, Group C showed no external signs of a proliferation of inflammation in the uninjected hind paws, whereas approximately half of the Ss in Groups NC and C2 developed small lesions. Exp II, similar to Exp I, with 48 Ss, yielded the same results. The results essentially confirm previous findings on conditioned immunosuppression and extend them to an inflammatory joint disease. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exercise training induced alterations in prepubertal children's lipid-lipoprotein profile

PURPOSE: This study examined the effect of exercise training on prepubertal children's (ET, N = 28) lipid-lipoprotein profile, relative to a maturity matched control group (CON, N = 20). METHODS: Training for ET involved stationary cycling for 30 min, 3 times.wk-1 for 12 wk, at 79.3 +/- 1.2% (mean +/- SD) peak heart rate (HR). Controls maintained their usual lifestyle pattern. Plasma concentrations of total triacylglycerol (TG), total cholesterol (TC), and high-density lipoprotein (HDL)-cholesterol (HDL-C) were determined pre- and postintervention. Low-density lipoprotein (LDL)- cholesterol (LDL-C) was subsequently estimated from these concentrations, and the ratios TC/HDL-C and LDL-C/HDL-C were also calculated. There were no pretest differences (P > 0.05) for any of these blood analytes between groups. The following, potentially, confounding variables were also measured: peak VO2, percent body fat (%BF), dietary composition, and habitual physical activity. These variables, with pretest HDL-C, were included as covariates in two-way split plot ANCOVA analyses. Dietary variables were not included as covariates as they were not related to any of the blood analytes. RESULTS: There were no differences over time or between groups for TG and TC (P > 0.05). LDL-C decreased in ET (-10.2%) but remained unchanged in CON (0.3%) over the intervention period (P < 0.05). HDL-C increased in ET (9.3%) but decreased in CON (-8.9%) (P < 0.01). A similar, but inverted, pattern of change (P < 0.01) was revealed for both ratios, TC/HDL-C (-11.6% vs 6.3%, ET and CON, respectively), and LDL-C/HDL-C (-17.2% vs 8.0%, ET and CON, respectively). The favorable alterations in the lipid-lipoprotein profile for ET were independent of alterations in peak VO2 (group x time interaction, P < 0.05), %BF (main effect time, P < 0.01), and habitual physical activity (group x time interaction, P < 0.01). CONCLUSIONS: In conclusion, the favorable alterations in the lipoprotein profile seen in this study would suggest that it is possible to influence the prepubertal lipoprotein profile independent of alterations in confounding variables such as body composition, cardiorespiratory fitness, and habitual physical activity.     

Exercise stress test training in family practice residency programs

EST is a commonly indicated procedure in primary care medicine and as such is well suited for use by family physicians. At present there are few family physicians performing this procedure in their offices. Our survey of US family practice residency directors has shown an interest well above what would be expected for the level of current practice in the community; however, there remains an ambivalence on the need to provide EST training in the curriculum.     

Exercise training in COPD patients: the basic questions

Pulmonary rehabilitation programmes aim at improving exercise capacity, activities of daily living, quality of life and perhaps survival in patients with chronic obstructive pulmonary disease (COPD). Recently, well-designed studies investigated and confirmed the efficacy of comprehensive pulmonary rehabilitation programmes, including exercise training, breathing exercises, optimal medical treatment, psychosocial support and health education. In the present overview, the contribution of exercise training in clinical practice to the demonstrated effects of pulmonary rehabilitation is discussed by means of six basic questions. These include: 1) the significance of exercise training; 2) the optimal intensity for exercise training; 3) prescribing training modalities; 4) the effects of exercise training combined with medication, nutrition or oxygen; 5) how training effects should be maintained; and 6) where the rehabilitation programme should be performed: in-patient, out-patient or homecare? First, exercise training has been proven to be an essential component of pulmonary rehabilitation. Training intensity is of key importance. High-intensity training (>70% maximal workload) is feasible even in patients with more advanced COPD. In addition, the effects on peripheral muscle function and ventilatory adaptations are superior to low-intensity training. There is, however, no consensus on the optimal training modalities. Both walking and cycling improved exercise performance. Since peripheral muscle function has been recognized as an important contributor to exercise performance, specific peripheral muscle training recently gained interest. Improved submaximal exercise performance and increased quality of life were found after muscle training. The optimal training regimen (strength or endurance) and the muscle groups to be trained, remain to be determined. Training of respiratory muscles is recommended in patients with ventilatory limitation during exercise. The additional effects of anabolic-androgenic drugs, oxygen and nutrition are not well-established in COPD patients and need further research. In order to maintain training effects, close attention of the rehabilitation team is required. The continuous training frequency necessary to maintain training effects remains to be defined. At this point in time, out-patient-based programmes show the best results and guarantee the best supervision and a multidisciplinary approach. Future research should focus on the role of homecare programmes to maintain improvements.     

Prevention of coprophagy modifies magnesium absorption in rats fed with fructo-oligosaccharides

We developed a new type of anal cup for prevention of coprophagy and determined whether the absorption of Ca and Mg and the stimulatory effects of feeding fructo-oligosaccharides (FO) on the absorption of Ca and Mg were altered by prevention of coprophagy in rats. Rats were fed on a FO-free diet or a diet containing 50 g FO/kg for 2 weeks with or without prevention of coprophagy. FO-feeding increased the apparent absorptive ratio of Ca and Mg in rats with or without prevention of coprophagy. However, in the FO-fed groups the absorptive ratio of Mg in rats with prevention of coprophagy was higher than in rats without prevention of coprophagy. The Ca content of the femur was higher in rats fed on the FO-diet than in rats fed on the FO-free diet both with and without coprophagy. In conclusion, FO-feeding increased the absorption of Ca and Mg in rats both with and without coprophagy. Moreover, prevention of coprophagy enhanced the absorption of Mg in rats fed with FO. Coprophagy has to be considered when the effects of luminal fermentation or mineral absorption are examined in rats.     

Gastric digestion modifies absorption of butterfat into lymph chylomicrons in rats

Our objective was to characterize the time course of mesenteric lymph output, lipid composition and size of lymph chylomicrons in rats given gastric infusion of lipid emulsions containing defined fractions of butterfat, palm oil or corn oil. The concentrations of cholesterol, triacylglycerol (TAG) and phospholipid in lymph obtained before lipid infusion were 1.4-2.5-fold greater in rats chronically fed palm oil or solid butterfat compared with corn oil or liquid butterfat (P = 0.02). Total lymph chylomicron TAG output (mg/24 h) stimulated by gastric lipid infusion was 21% greater with corn oil compared with all saturated fats (P = 0.02). Total lymph chylomicron cholesterol output was 1.3-8.6-fold greater than the amount infused in all groups (P = 0.03) and was independent of the amount of cholesterol infused. The size distribution as well as the mean, median and modal diameters of lymph chylomicrons isolated during peak lymphatic TAG output were not significantly different among treatments. The fatty acid and TAG profiles of lymph chylomicrons obtained from rats infused with corn or palm oil did not differ significantly from that of the emulsion infused. In contrast, gastric lipolysis of butterfat significantly modified the lipid composition of lymph chylomicrons. We observed progressive disappearance of short- and medium-chain fatty acids in gastric contents and an absence of detectable short-chain fatty acids with concurrent proportionate increases in long-chain fatty acids and large TAG molecules in lymph chylomicrons compared with butterfat emulsions. These studies demonstrate that gastric digestion is an important modifier of lipid absorption.     

Exercise testing as a rehabilitative/training tool

Exercise testing is an exceedingly useful noninvasive method for assessing cardiovascular function not only at rest but also during programmed, supervised physical exercise. Exercise testing has been intensively studied to delineate the cardiovascular response in various disorders [3-5, 15, 19, 22, 23, 26, 32]. Exercise testing as a tool for rehabilitation and for training to perform physical activity is discussed here.     

Exercise training in heart failure: inpatient and outpatient considerations

Highly reactive oxygen species that are formed during normal metabolism and under conditions of oxidative stress are able to oxidize proteins or convert lipid and carbohydrate derivatives to compounds that react with functional groups on proteins. Among other changes, these ROS-mediated reactions lead to the formation of protein carbonyl derivatives, which serves as a marker of ROS-mediated protein damage. On the basis of this marker, it is established that oxidatively damaged protein is associated with aging and some diseases. The accumulation of oxidatively damaged protein reflects the balance among a myriad of factors that govern the rates of ROS generation and the rate at which damaged protein is degraded. Peroxynitrite, which is formed under normal physiological conditions, is able to oxidize methionine residues in proteins and to nitrate tyrosine residues; however, its ability to do so is dependent on the availability of CO2, which stimulates the nitration of tyrosine residues but inhibits the oxidation of methionine residues. Nitration of tyrosine residues may contribute to peroxynitrite toxicity, as nitration precludes the phosphorylation or nucleotidylation of tyrosine residues and thereby seriously compromises one of the most important mechanisms of cellular regulation and signal transduction.     

Neural activity in SII modifies sensory evoked potentials in SI in awake rats

The function of the projection from the secondary somatosensory cortex (SII) to the primary somatosensory cortex (SI) in rats was investigated by recording sensory evoked potentials (SEP) in SI during glutamate activation and lidocaine blockade of SII. In anesthetized animals, glutamate stimulation of SII decreased SEP latency and increased SEP amplitude, whereas no changes were evident during lidocaine blockade of SII. In awake animals, a second, later component of the SEP appeared. This second component was almost completely eliminated during lidocaine blockade of SII. We conclude that the projection from SII to SI in rats slightly facilitates the SEP response in anesthetized animals and is responsible for a major portion of the late component of the SEP in awake animals.     

Exercise attenuates oral intake of amphetamine in rats

The effects of wheel running on oral intake of amphetamine were examined in six male Sprague-Dawley rats given a 0.075-mg/ml amphetamine sulfate solution as their sole source of liquid, six rats given a 0.15-mg/ml amphetamine solution, and four rats given water as their sole source of liquid. All animals were housed in Wahmann running wheels and adjoining cages, and had ad lib access to ground Purina Chow. For the first 7 days of the experiment, the doors to the running wheels were closed; the wheels were then opened for 6 days. This cycle was repeated a second time. Animals drinking the 0.15-mg/ml amphetamine solution consumed significantly less food and gained less weight than animals in the other two groups. Although there was no difference in food intake between rats drinking water and rats drinking the 0.075-mg/ml amphetamine solution, rats in the water group gained significantly more weight than rats in the 0.075-mg/ml amphetamine group. With respect to drug intake, rats consumed significantly less amphetamine when running in the wheels than when access to the wheels was prohibited. Access to running wheels did not alter water intake. These latter results suggest that drug intake can be reduced by the provision of an alternate behavior.     

Exercise limitations and training for patients with cystic fibrosis

Exercise has much to offer to cystic fibrosis patients. Overcoming the limits of decreased pulmonary function by increasing fitness has a considerable potential to improve patients' quality of life; decreased breathlessness allows greater mobility and participation with peers in social and sporting activities, improves confidence and self-esteem and creates a greater pleasure in life for the individual patient. There are also immediate therapeutic gains and potentially long-term gains with improved survival. Above all, cystic fibrosis patients enjoy and prefer exercise as a therapeutic option to most other forms of therapy.