Acute changes in serum lipids and lipoprotein subclasses in triathletes as assessed by proton nuclear magnetic resonance spectroscopy. (33/2436)

Exercise is associated with changes in lipids that may protect against coronary heart disease (CHD). In this study of 28 triathletes, we analyzed acute changes in serum lipid and lipoprotein concentrations after completion of the 1995 World Championship Hawaii Ironman Triathlon. With standard laboratory assays, we demonstrate significant decreases in total cholesterol, VLDL cholesterol, ApoB100, and Lp(a). Total HDL cholesterol increased significantly immediately after the race. With a novel proton NMR spectroscopy assay, we demonstrate that smaller diameter LDL particles, corresponding to small, dense LDL, declined by 62%. Moreover, larger HDL subclasses, whose levels are inversely associated with CHD, increased significantly by 11%. Smaller HDL subclasses, which have been directly associated with CHD in some studies, acutely decreased by 16%. Therefore, exercise not only acutely induces changes in lipoprotein concentrations among the standard species in a manner that favorably affects CHD risk, but also induces favorable changes in specific lipoprotein subclass size distribution that also may alter CHD risk independently of the total lipoprotein serum concentration.  (+info)

Effects of exercise training on responsiveness of the mesenteric arterial bed to phenylephrine and KCl in male rats. (34/2436)

1. We aimed to determine whether there are any changes in responsiveness of the mesenteric arterial beds to phenylephrine (Phe) and KCl in exercise-trained rats, and whether vascular endothelium and/or vascular smooth muscle play a role in these changes. 2. Adult male rats were subjected to a swimming schedule every day for 28-33 days. Studies were performed in vitro using Krebs perfused mesenteric arterial beds. 3. Maximum perfusion pressure responses to KCl and Phe of the mesenteric arterial beds from exercise-trained rats were significantly lower than those from sedentary controls. However, these differences disappeared after blocking the nitric oxide synthase by NG-nitro-L-arginine (L-NOARG). 4. 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulphonate (CHAPS, 3 mg ml(-1), 2 min infusion) caused a significant increase in maximum perfusion pressure responses to KCl to the same extent in both exercise-trained and sedentary control rats. CHAPS caused about a 4.5 fold leftward shift of the curve with no change in maximum response to Phe for the mesenteric arterial beds from sedentary control rats, but not for those obtained from exercise-trained rats. However, these differences were abolished in the presence of L-NOARG. 5. Indomethacin did not alter the dose-response curves to KCl or Phe in either swimming or control groups. 6. These results suggest that there was a lower vascular responsiveness to KCl and Phe in exercise-trained rats at rest. The decrease in reactivities to KCl or decrease in sensitivity to Phe after having endothelium impairment by CHAPS of the mesenteric arterial beds of exercise-trained rats were due to an increase in both spontaneous release and upregulation of phenylephrine-stimulated release of nitric oxide from both the vascular endothelium and the vascular smooth muscle cells, and may not be a consequence of an increase in vasodilator prostaglandins by the vascular bed.  (+info)

Functional integrity of NMDA-dependent LTP induction mechanisms across the lifespan of F-344 rats. (35/2436)

Previous studies have reported a lack of an age effect in the induction of long-term potentiation (LTP) at CA1 synapses, using robust (supramaximal) stimulation parameters, but an apparent age effect on the induction threshold of LTP using less robust stimulation, in the perithreshold region. These findings have led to the suggestion that old animals may experience an alteration either in the efficacy of activation of N-methyl-D-aspartate (NMDA) receptors or in the metabolic processes subsequent to NMDA receptor activation that lead to LTP expression. An alternative explanation for the apparent threshold change in old animals is that, because of the known reduction of the intracellularly recorded, compound EPSP magnitude in old rats, equivalent electrical stimulation results in a smaller effective depolarization of the postsynaptic cells and a consequently less effective activation of NMDA receptors, which are otherwise functionally normal. To distinguish between these two hypotheses, weak orthodromic stimulation was paired with intracellularly applied current pulses, thus holding constant the degree of postsynaptic depolarization. No differences in LTP induction threshold or magnitude were observed in a large sample of rats from three age groups. It is concluded that the NMDA receptor mechanisms and associated biochemical processes leading to LTP induction are not altered in aged F-344 rats. The reduced compound EPSP in old animals was reconfirmed in the present study, and a significant correlation was found in old rats between the magnitude of the EPSP at a fixed stimulus level and their performance on a spatial memory task.  (+info)

Training in the Morris water maze occludes the synergism between ACPD and arachidonic acid on glutamate release in synaptosomes prepared from rat hippocampus. (36/2436)

We report here that release of glutamate, inositol phospholipid metabolism, and protein kinase C (PKC) activity are increased in synaptosomes prepared from hippocampi of rats that had been trained in a spatial learning task. In hippocampi obtained from animals that were untrained, activation of the metabotropic glutamate receptor by the specific agonist trans-1-amino-cyclopentyl-1,3-dicarboxylate (ACPD) increased release of glutamate but only in the presence of a low concentration of arachidonic acid. A similar interaction between arachidonic acid and ACPD was observed on inositol phospholipid turnover and on PKC activity. However, the synergistic effect of arachidonic acid and ACPD on glutamate release was occluded in hippocampal synaptosomes prepared from trained rats. Occlusion of the effect on inositol phospholipid turnover and PKC activation was also observed. These data suggest that the molecular changes that underlie spatial learning may include activation of metabotropic glutamate receptors in the presence of arachidonic acid and that the interaction between arachidonic acid and ACPD triggers the presynaptic changes that accompany learning.  (+info)

Salivary IgA subclasses and infection risk in elite swimmers. (37/2436)

The concentrations of total IgA, IgA1 and IgA2 were measured in saliva collected from 25 elite swimmers in the early and late phases of a 7 month training season and compared with the number of respiratory infections during the season. The IgA1 concentrations in the early phase of the training season were significantly associated (P = 0.01) with the number of respiratory infection episodes during the training season. The lower the concentration of IgA1, the greater the number of infection episodes. Swimmers with four or more infections during the training season had significantly lower salivary IgA1 concentrations than those with less than four infection episodes (P = 0.01). The proportion of IgA1 in the saliva of the elite swimmers (80%) was higher than for normal non-exercising adults (60%). A small proportion of athletes had salivary IgA2 concentrations below the detection limit of the assay and the mean concentration of IgA2 was significantly lower than the concentrations for a normal adult population (P = 0.01). This study suggests that measurement of IgA subclasses, in particular IgA1, at the commencement of a training season may predict infection risk in elite swimmers.  (+info)

Regulation of swimming in the Culex pipiens (Diptera, Culicidae) pupa: kinematics and locomotory trajectories. (38/2436)

High-speed videography was used to investigate swimming kinematics and locomotory trajectories during escape responses in the pupa of Culex pipiens (Diptera, Culicidae). The pupa can perform straight-line motion despite undergoing backward and forward somersaults through 400 degrees at a rate of 20 s(-)(1). For linear motion to occur, the effective stroke of the abdomen must be delivered during the part of each cycle when the body is facing forwards, allowing passive rotation to carry the body round to the correct position for the start of the next half-stroke. On-off motion of the abdomen is regulated by a click mechanism based on stressed integumentary plates which buckle at strategic points in the cycle. The importance of self-inertia as a component in positional regulation was demonstrated by increasing the kinematic viscosity of the medium: this retarded rotation and resulted in somersaulting on the spot. Whereas normally the pupa invariably directs its swimming downwards, reversal of the usual light gradient produced upward paths as well. It is concluded that straight-line motion is generated automatically by the locomotory machine without any need for sensory feedback about body orientation during each cycle, but that swimming direction can be influenced by sensory cues such as light.  (+info)

Preanalytical factors (biological variation) and the measurement of serum soluble intercellular adhesion molecule-1 in humans: influence of the time of day, food intake, and physical and psychological stress. (39/2436)

BACKGROUND: Adhesion proteins such as soluble intercellular adhesion molecule-1 (sICAM-1) may be important markers for early atherosclerosis and some other diseases. To devise optimum specimen collection procedures, we investigated the effects on serum sICAM-1 of several preanalytical factors (factors that occur before a specimen is analyzed) such as the time of the day, food ingestion, and physical and psychological stress. METHODS: Three sets of experiments were conducted: (a) 30 subjects were investigated during the morning, after an overnight fast, and then after the usual breakfast and at 1200; (b) 20 subjects were studied before and after exposure to thermal stress (sauna + swimming in ice-cold water); and (c) 15 volunteers were investigated after their driving license examination and during a (stress-free) control session. Conventional methods and kits were used to determine the blood picture and serum sICAM-1. RESULTS: All of these preanalytical factors induced a significant increase ( approximately 10%) in the concentration of sICAM-1. CONCLUSION: It is advisable to consider timing, food intake, and stress when collecting specimens and analyzing data on the concentration of sICAM-1 in serum.  (+info)

Escherichia coli O157:H7 outbreak associated with an improperly chlorinated swimming pool. (40/2436)

A cluster of gastrointestinal illnesses, including one case of hemolytic-uremic syndrome and one culture-confirmed Escherichia coli O157:H7 infection, followed a trailer park pool party. We interviewed a cohort of party attendees and park residents. A primary case was defined as the first gastrointestinal illness within a household between 5 July and 20 July in which the titer of IgG antibody to E. coli O157 (if determined) was elevated. Of 51 party attendees and trailer park residents, 18 developed a gastrointestinal illness, including 10 who met the definition of a primary case. Swimming in the pool significantly increased the risk of primary illness (relative risk = 6.3; 95% confidence interval = 1.8-18.9). No other exposure was significantly associated with primary illness, after pool exposure was controlled for. The implicated pool had little to no chlorine added during the period of 4-10 July. This outbreak provides new evidence of the importance of proper pool maintenance in controlling the spread of E. coli O157:H7.  (+info)