Improved antioxidative protection in winter swimmers. (25/2436)

Adaptation to oxidative stress is an improved ability to resist the damaging effects of reactive oxygen species, resulting from pre-exposure to a lower dose. Changes in uric acid and glutathione levels during ice-bathing suggest that the intensive voluntary short-term cold exposure of winter swimming produces oxidative stress. We investigated whether the repeated oxidative stress in winter swimmers results in improved antioxidative adaptation. We obtained venous blood samples from winter swimmers and determined important components of the antioxidative defense system in the erythrocytes or blood plasma: reduced and oxidized glutathione (GSH and GSSG), and the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (Cat). The control group consisted of healthy people who had never participated in winter swimming. The baseline concentration of GSH and the activities of erythrocytic SOD and Cat, were higher in winter swimmers. We interpret this as an adaptative response to repeated oxidative stress, and postulate it as a new basic molecular mechanism of increased tolerance to environmental stress.  (+info)

Mild impairment of learning and memory in mice overexpressing the mSim2 gene located on chromosome 16: an animal model of Down's syndrome. (26/2436)

Human Sim2 is a product of one of the genes located on human chromosome 21q22 and is a homolog of Drosophila single-minded ( sim ) which is a critical player in midline development of the central nervous system of the fly. Since Sim2 mRNA is expressed in facial, skull, palate and vertebra primordia in human and rodent embryos, features that are associated with phenotypes of Down's syndrome (DS), its trisomic state is suspected to contribute to the symptoms of DS. Here we describe that mSim2 mRNA is expressed in hippocampus and amygdala of adult mice, and that while mice overexpressing mSim2 under the control of the beta-actin promoter are viable and fertile and have superficially normal skeletal, brain and heart structures, they exhibit a moderate defect in context-dependent fear conditioning and a mild defect in the Morris water maze test. Taken together, our data show that overdosage of Sim2 may be important for the pathogenesis of Down's syndrome, especially mental retardation.  (+info)

Efficacy of aquatic exercises for patients with low-back pain. (27/2436)

We have studied 35 patients (25 female and 10 male) with low-back pain who were managed with aquatic exercises after an appropriate period of treatment for their condition in the medical institution. The exercises employed consisted of strengthening exercises for the abdominal, gluteal, and leg muscles, stretching of the back, hip, hamstrings, and calf muscles, walking in water, and swimming. All the patients had been participating in the exercise program for more than 6 months. The frequency of performing exercises was once a week for 7 patients, twice a week for 19, and 3 or more times a week for the remaining patients. The method used in this study was a survey questionnaire which was composed of questions about the patient's physical and psychological condition. Those patients who had performed exercises twice or more in a week showed a more significant improvement in the physical score than those who performed exercises only once a week. More than 90% of the patients felt they had improved after 6 months of participation in the program. The improvement in physical score was independent of the initial ability in swimming. The results obtained suggested that exercises in water may be one of the most useful modes of exercise for a patient with low-back pain.  (+info)

Effects of weight loss and exercise on the distribution of lead and essential trace elements in rats with prior lead exposure. (28/2436)

We studied the effects of weight loss and non-weight-bearing exercise (swimming) on blood and organ lead and essential metal concentrations in rats with prior lead exposure. Nine-week-old female Sprague-Dawley rats (n = 37) received lead acetate in their drinking water for 2 weeks, followed by a 4-day latency period without lead exposure. Rats were then randomly assigned to one of six treatment groups: weight maintenance with ad libitum feeding, moderate weight loss with 20% food restriction, and substantial weight loss with 40% food restriction, either with or without swimming. Blood lead concentrations were measured weekly. The rats were euthanized after a 4-week period of food restriction, and the brain, liver, kidneys, quadriceps muscle, lumbar spinal column bones, and femur were harvested for analysis for lead, calcium, copper, iron, magnesium, and zinc using atomic absorption spectrophotometry. Both swimming and nonswimming rats fed restricted diets had consistently higher blood lead concentrations than the ad libitum controls. Rats in the substantial weight loss group had higher organ lead concentrations than rats in the weight maintenance group. Rats in the moderate weight loss group had intermediate values. There were no significant differences in blood and organ lead concentrations between the swimming and nonswimming groups. Organ iron concentrations increased with weight loss, but those of the other metals studied did not. Weight loss also increased hematocrits and decreased bone density of the nonswimming rats. The response of lead stores to weight loss was similar to that of iron stores because both were conserved during food restriction in contrast to decreased stores of the other metals studied. It is possible that weight loss, especially rapid weight loss, could result in lead toxicity in people with a history of prior excessive lead exposure.  (+info)

Simultaneous evaluation of spatial working memory and motivation by the allocentric place discrimination task in the water maze in rats. (29/2436)

In order to evaluate learning and memory deficits separately from and simultaneously with motivational, motor and sensory impairments in identical animals, we developed the allocentric place discrimination task test using a water maze in rats. For this assessment task, two similar, visible platforms, one was fixed and the other was floating, were simultaneously present in a pool, and the working memory of the allocentric place discrimination task was evaluated. After training, the task accuracy was high about 85% correct and animals were used repeatedly. The accuracy decreased significantly when the pool was surrounded with a black curtain. Muscarinic receptor antagonist scopolamine 0.5 mg/kg selectively impaired the accuracy. Muscle relaxant dantrolene 10 mg/kg selectively decreased swimming speed. Under low motivational condition (warm water), still time increased and swimming speed decreased, but the accuracy was not affected. Similar to warm water, opioid receptor agonist morphine 15 mg/kg increased still time and decreased swimming speed. These results suggest that the allocentric place discrimination task is useful in evaluating spatial working memory ability independently of and concurrently with also visual, motor ability and motivation in identical animals.  (+info)

Identification of neural circuits by imaging coherent electrical activity with FRET-based dyes. (30/2436)

We show that neurons that underlie rhythmic patterns of electrical output may be identified by optical imaging and frequency-domain analysis. Our contrast agent is a two-component dye system in which changes in membrane potential modulate the relative emission between a pair of fluorophores. We demonstrate our methods with the circuit responsible for fictive swimming in the isolated leech nerve cord. The output of a motor neuron provides a reference signal for the phase-sensitive detection of changes in fluorescence from individual neurons in a ganglion. We identify known and possibly novel neurons that participate in the swim rhythm and determine their phases within a cycle. A variant of this approach is used to identify the postsynaptic followers of intracellularly stimulated neurons.  (+info)

Increased expression of transferrin receptor on membrane of erythroblasts in strenuously exercised rats. (31/2436)

This study investigated the effects of strenuous exercise on transferrin (Tf)-receptor (TfR) expression and Tf-bound iron (Tf-Fe) uptake in erythroblasts of rat bone marrow. Female Sprague-Dawley rats were randomly assigned to either an exercise or sedentary group. Animals in the exercise group swam 2 h/day for 3 mo in a glass swimming basin. Both groups received the same amount of handling. At the end of 3 mo, the bone marrow erythroblasts were freshly isolated for Tf-binding assay and determination of Tf-Fe uptake in vitro. Tissue nonheme iron and hematological iron indexes were measured. The number of Tf-binding sites found in erythroblasts was approximately 674,500 +/- 132,766 and 1,270,011 +/- 235,321 molecules/cell in control and exercised rats, respectively (P < 0. 05). Total Fe and Tf uptake by the cells was also significantly increased in the exercised rats after 30 min of incubation. Rates of cellular Fe accumulation were 5.68 and 2.58 fmol. 10(6) cells(-1). min(-1) in the exercised and control rats, respectively (P < 0.05). Tf recycling time and TfR affinity were not different in exercised and control rats. Increased cellular Fe was mainly located in the stromal fraction, suggesting that most of accumulated Fe was transported to the mitochondria for heme synthesis. The findings demonstrated that the increased cellular Fe uptake in exercised rats was a consequence of the increased TfR expression rather than the changes in TfR affinity and Tf recycling time. The increase in TfR expression and cellular Fe accumulation, as well as the decreased serum Fe concentration and nonheme Fe in the liver and the spleen induced by exercise, probably represented the early signs of Fe deficiency.  (+info)

Properties of cholinergic responses in isolated parapodial muscle fibers of Aplysia. (32/2436)

The parapodial neuromuscular junction in the marine snail Aplysia brasiliana is a model synapse for the investigation of neural modulation. The parapodial muscle fibers are innervated by cholinergic motoneurons and by serotonergic modulatory cells. The physiological properties of voltage-gated currents of the muscle membranes and the effects of serotonin on these currents have been published previously. However, the pharmacological properties of the cholinergic receptors have not been investigated. Acetylcholine (ACh) applied exogenously to dissociated muscle fibers produces a response with a reversal potential of about -52 mV; the resting membrane potential of the average muscle fiber is approximately -56 mV. ACh induces variable responses (depolarizations or hyperpolarizations) in individual cells, but the transmitter never causes a depolarization adequate to produce muscle contraction. We demonstrate that the ACh response is the result of the activation of two distinct receptors. One receptor is linked to a chloride channel and induces a hyperpolarization with a reversal potential near -70 mV. This receptor is activated selectively by suberyldicholine and by nicotine and is antagonized by curare but not by hexamethonium. The second response, presumably caused by increased conductance to mixed cations, results in muscle fiber depolarization with a reversal potential near -35 mV and does induce muscle contraction. This receptor is activated by methylcarbamylcholine and selectively blocked by hexamethonium; atypically, this receptor is not activated by nicotine nor by carbachol. The depolarizing, cation-selective receptors likely are associated with identified excitatory cholinergic motoneurons the activity of which typically results in muscle contractions because the reversal potential for this ACh response is more depolarized than the activation threshold for voltage-gated calcium channels in these fibers. The hyperpolarizing, chloride-selective receptors may be associated with inhibitory motoneurons; such motoneurons have yet to be identified, but their presence is inferred because of the occurrence of spontaneous inhibitory junctional potentials recording from muscle fibers in situ. Muscle fiber responses to exogenously applied ACh reflect the relative contribution of each receptor type in each muscle fiber.  (+info)