The effects of smoking and nicotine ingestion on exercise heat tolerance.

BACKGROUND: Smoking has a thermogenic effect and is associated with low physical performance. Nevertheless, a direct, quantitative effect of acute smoking on exercise heat tolerance has not been reported. METHODS: Sixteen healthy young male volunteers, eight cigarette smokers, and eight non-smokers participated in the study. All subjects performed a maximal oxygen consumption test (VO2max) and a standardized heat tolerance test (HTT) after at least 12 h without smoking under the following conditions: no nicotine exposure, 10 min after nicotine exposure (2 mg nicotine lozenge), and 10 min after smoking two cigarettes (0.8 mg nicotine in each cigarette, smokers only). RESULTS: There was no significant effect of nicotine exposure on physiological performance and heat tolerance in the non-smokers group. In the smokers group, cigarette smoking, but not nicotine ingestion, resulted with higher heart rate (by 9±9 bpm) at the end of the HTT (p<0.05). Moreover, both smoking and nicotine ingestion increased smokers' rectal temperature at the end of the HTT (by 0.24±0.16°C and 0.21±0.26°C, respectively, p<0.05) and were associated with higher sweat rate during the HTT (by 0.08±0.07 g/h and 0.06±0.08 g/h, respectively, p<0.05). Heart rate variability (HRV) analysis also revealed a higher LF/HF (low frequency/high frequency) ratio after exposure to nicotine and smoking in the smokers group compared with no exposure (2.13±2.57 and 2.48±2.76, respectively, p<0.05), indicating a higher sympathetic tone. CONCLUSIONS: According to this preliminary study, cigarette smoking and nicotine ingestion increase the physiological strain during a HTT in smokers. Acute smoking may, therefore, increase heat intolerance and the risk to heat injuries.

Women and exertional heat illness: identification of gender specific risk factors.

OBJECTIVE: With the expanding role of women into previously closed combat military occupational specialties, women will likely be exposed more to challenging and extreme conditions. Physical work or exercise in extreme environments could increase the risk for exertional heat illness (EHI) and exertional heat stroke (EHS), the most severe type of EHI. Although men have higher rates of EHS than women, women have slightly higher rates of other EHI. Women may respond differently to exertion in the heat than men, as they typically have higher percentage of body fat (BF%) and lower aerobic power. Further, published pilot-data using the Israeli heat tolerance test (HTT) indicate that women are more likely to be classified as heat intolerant than men. The objectives of the present study were to (1) compare male and female classification patterns of heat tolerance, and (2) identify EHI risk factors that might account for the relationship between heat tolerance classification and sex. METHODS: Fifty-five male and 20 female participants were recruited from military and university communities to participate in a standardized HTT. Subjects underwent measures to calculate anthropometric variables (BF%, body surface area, and waist circumference), a maximal oxygen uptake test to assess aerobic power (VO2max), and a standardized HTT, which consisted of treadmill walking at 5 km/h at a 2% grade for 120 minutes at 40°C and 40% relative humidity. Heat intolerance was defined as attaining a maximum heart rate (HR) greater than 150 bpm or a core body temperature (Tc) more than 38.5°C. Separate hierarchical regressions were conducted using categorical (heat tolerant/intolerant) and continuous (physiological strain index, maximum HR, Tc) HTT outcomes. Risk factors were identified with and without controlling for sex. RESULTS: Women were 3.7 (95% CI, 1.21-11.24) times more likely to be heat intolerant than men (χ²=6.85, P<.01). Compared to men, women had significantly higher BF% and lower body surface area, waist circumference, and VO2max. All heat intolerant participants had lower VO2max and higher BF% than those who were classified as heat tolerant. When VO2max and BF% were entered into regression equations to predict HTT outcomes, sex became nonsignificant; VO2max predicted maximum HR and physiological strain index after controlling for sex. CONCLUSION: The present study found that differences between men and women in heat tolerance classification are largely explained by VO2max. The higher rates of heat intolerance among women likely correlate with higher EHI risk, and underscore the need to understand the physiological and thermoregulatory differences between men and women. As lower aerobic power is a major risk factor for EHI, maximizing the aerobic power of women will be critical to force health protection and readiness as they integrate into combat military occupational specialties.

Recurrent exertional rhabdomyolysis: coincidence, syndrome, or acquired myopathy?

The purposes of this report are to review and discuss the issue of recurrent exertional rhabdomyolysis (ER), the return to physical activity after ER, and the possible causes of recurrence, with special consideration to metabolic myopathies and the possibility of an acquired post-ER myopathy. We discuss the medical investigation required prior to return to physical activity after an episode of ER and suggest two possible mechanisms for recurrence of ER in the absence of a known cause: premature return to activity and an acquired post-ER muscular disorder. We also emphasize the need to create proper guidelines for return to physical activity after ER and, for further investigation, the possible mechanisms of ER recurrence in patients without a known metabolic myopathy.

Poly(methyl metacrylate) conductive fiber optic transducers as dual biosensor platforms.

Herein the development of an alternative optic-conductive fiber configuration applied for the construction of biosensing platforms. This new approach is based on applying the chemical polymerization of pyrrole onto the surface of polymethyl metacrylate (PMMA) fibers to create a polymer--a conductive surface, onto which an additional photoactive polypyrrole-benzophenone (PpyBz) film is electrochemically generated upon the fiber surface. Irradiation of the benzophenone groups embedded in the Ppy films with UV radiation (350 nm) formed active radicals that allowed the covalent attachment of the desired bioreceptors. Characterization of the amperometric biosensing matrix was accomplished by using a model Urease (Urs) through electrochemical impedance spectroscopy (EIS) and amperometry. Both techniques have shown a low charge transfer resistance (340 k Omega) and a high sensitivity (12.3 microA mM(-1)cm(-2)). Thereafter, the construction of an optical biosensing matrix based on horseradish peroxidase (HRP) production of photons was carried out. The high signal to noise (S/N) ratio (1600) indicated clearly that this approach can serve as a new platform to replace glass optical fibers based on biosensors.

Characterization of electrogenerated polypyrrole-benzophenone films coated on poly(pyrrole-methyl metacrylate) optic-conductive fibers.

A conductive surface was created for the development of a biosensing platform via chemical polymerization of pyrrole onto the surface of poly(methyl methacrylate) (PMMA) fibers, with a subsequent electrogeneration of a photoactive linker pyrrole-benzophenone (PyBz) monomer on the fiber surface. Irradiation of the benzophenone groups embedded in the polypyrrole (Ppy) films by UV (350 nm) formed active radicals, allowing covalent attachment of the desired biomaterials. Characterization and optimization of this platform were carried out, with the platform showing conductive, stable, thin, controllable, and light-transmissible film features. Various parameters such as time deposition, process temperature, and activator plus pyrrole monomer concentrations were examined in the study. The morphology and permeability of the optic-fiber PMMA fibers were investigated to examine mass transfer ability. Cyclic voltammetry and amperometry techniques were applied to characterize the electrical features of the surface and charge transfer. The platform potential was then demonstrated by the construction of both amperometric and optical biosensors.

Self HSP60 peptide serves as an immunogenic carrier for a CTL epitope against persistence of murine cytomegalovirus in the salivary gland.

Murine cytomegalovirus (MCMV) infection is associated with persistence of virus in the salivary glands, despite relatively rapid clearance of virus from the spleen. An effective immunization against MCMV should prevent such viral persistence. We previously reported that a peptide (p458) from the sequence of the 60 kDa heat shock protein (HSP60) molecule in a conjugate vaccine can provide T cell help for the induction of protecting antibody against bacterial capsular polysaccharides. We now report that the p458 peptide as a carrier peptide can also enhance the immunogenicity of a dominant CTL epitope of the MCMV pp89 antigen-89pep. We synthesized a linear combined peptide: chimeric p458-89pep. We immunized young BALB/c mice and challenged them with MCMV. We found that the p458-89pep chimeric peptide was more effective than the 89pep in inducing 89pep-specific IFN(gamma) secretion and specific CTL activity. Moreover, the p458-89pep chimeric peptide induced sustained IFN(gamma) secretion in the salivary gland specific to 89pep and only this immunization was associated with clearance of virus from the salivary gland. These results suggest that a peptide epitope of HSP60 may be advantageous as a T cell carrier peptide in the induction of specific T cell immunity against infectious agents.