O comportamento eletroquímico da cafeína (CAF) e moléculas análogas, tais como teobromina (TB), teofilina (TF) e xantina (XA), foi estudado utilizando eletrodo de carbono vítreo. Técnicas como voltametria cíclica (VC), voltametria de pulso diferencial (VPD) e onda quadrada (VOQ) e cronoamperometria foram utilizadas para elucidação do mecanismo de oxidação da CAF. Os voltamogramas cíclicos mostraram que todos os compostos estudados apresentaram um único pico irreversível de oxidação na seguinte sequência: Epa(CAF) 1,50V > Epa(TB) 1,34V > Epa(TF) 1,0 V > Epa(XA) 0,74V. Os coeficientes angulares das curvas Ep vs pH foram de 20 mV pH-1, 35 mV pH-1, 58mVpH-1 e 59mVpH-1, respectivamente. A oxidação da TF e XA ocorre envolvendo o mesmo número de elétrons (n) e prótons (H+), enquanto para a cafeína e teobromina, o número de prótons não é igual ao número de elétrons. Este último, foi calculado utilizando os valores de largura de pico à meia altura de corrente dos voltamogramas de pulso diferencial e, exceto a XA, todos os demais derivados foram oxidados em um processo envolvendo 1 elétron. Para a cafeína, o valor de n, coincidiu com aquele calculado pela equação de Randles-Ševcik para sistemas irreversíveis, usando o coeficiente de difusão, D0 = 1,46 x10-5 cm2s-1 e coeficiente de transferência de carga, α, de 0,63. No intervalo de 10 ≤ v ≤ 75mVs-1, os coeficientes angulares dos gráficos (Epa log v) para CAF, TB, TF e XA, foram de 26, 34, 21 mV e 22 mV (década de v)-1, que é o indicativo de um processo de oxidação envolvendo a formação de cátion radical. O número de elétrons determinado por cronoamperometria para a CAF e TB foi n=1 e, comopara TF e XA foram n= 2 e 3,0. Voltamogramas cíclicos e de onda quadrada obtidos em meio de DMSO usando terafluoroborato de tetrabutilamônio mostraram no segundo ciclo, o aparecimento de um par redox quase reversível com E1/2 de + 0,50 V (versus Ag/AgCl), processo atribuído à oxidação do dímero. Para avaliar efeitos de adsorção eletroquímica da CAF na superfície do eletrodo, experimentos de espectroscopia de impedância eletroquímica (EIE) e de potencial de circuito aberto (PCO) foram utilizadas para caracterizar a superfície de eletrodos de carbono vítreo polido (p-ECV), carbono vítreo previamente tratado em solução tampão BR, pH 4,0 (BR-ECV) e carbono vítreo previamente tratado em solução de CAF (CAF-ECV). Os valores de Rct para CAF-ECV foram maiores do que os valores obtidos para o p-ECV, usando solução de K3[Fe(CN)]6 como sonda eletroquímica. / The electrochemical behavior of Caffeine (CAF) and similar molecules such as theobromine (TB), theophylline (TF) and xanthine (XA) was studied using glassy carbon electrode. Techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (VOQ) and chronoamperometry were used to elucidate the CAF oxidation mechanism. Cyclic voltammetry showed that all studied compounds had a single irreversible oxidation peak in the following sequence: Epa (CAF) 1.50V> Epa (TB) 1.34V> Epa (TF) 1.0 V> Epa (XA) 0 .74V. The angular coefficients of Ep versus pH curves were 20, 35, 58 and 59mV/pH, respectively. Oxidation of TF and X occurs involving the same number of electrons (n) and protons (H+), while for caffeine and theobromine, the number of protons is not equal to the number of electrons. The last one was calculated using the peak width values at half-maximum current obtained from the differential pulse voltammograms and, all other derivatives, except for XA, were oxidized in a process involving one electron. For caffeine, the value of n, coincided with that calculated by the Randles-Sevcik equation for irreversible systems, using the diffusion coefficient D0 = 1.46 x10-5 cm2s-1 and the charge transfer coefficient, α, of 0.63. In the range of 10 ≤ v ≤ 75mVs-1, the slopes of the graphs (Epa - log v) to CAF, TB, TF and XA were 26, 34, 21 and 22 mV(v decade)-1, which is indicative of an oxidation process involving the formation of radicalar cation. The number of electrons determined by chronoamperometry for CAF and TB oxidation was n = 1, but for TF and XA were n = 2 and 3.0, respectively. Cyclic and square wave voltammograms obtained in DMSO containing terafluoroborato tetrabutylammonium shown, in the second cycle, a quasi-reversible redox couple almost E1/2 + 0.50 V (vs. Ag / AgCl), attributed to the oxidation of a caffeine dimer. To evaluate the electrochemical adsorption effect of CAF on the electrode surface, electrochemical impedance spectroscopy experiments (IEE) and open circuit potential (OCP) were used to characterize the surface of polished glassy carbon electrodes (p-ECV), glassy carbon previously treated in BR buffer, pH 4.0, (BR-ECV), and glassy carbon previously treated in CAF solution, pH 4,0, (CAF-ECV). The Rct and OCP values for CAF-ECV were larger than the values obtained for p-ECV solution using K3[Fe(CN)6] as the electrochemical probe.

This thesis argues that caffeine use offered a survival advantage to our ancestors and that moderate use continues to offer modern humans benefits. Caffeine ingestion, through the blocking of adenosine receptors, elicits broad elements of the mammalian threat response, specifically from the ‘flight or fight’ and ‘tend and befriend’ repertoires of behaviour: in effect, caffeine hijacks elements of the stress response. If the effects of caffeine had been discovered recently, rather than being available to Homo sapiens since Neolithic hunter gatherer times, it is likely that caffeine would be considered a ‘smart’ drug. More caffeine is being ingested today than ever previously recorded. Caffeine use is found across all age groups, all socio-economic strata, most ethnic groups, and is being used increasingly by the medical and pharmaceutical industries and by the armed forces. Yet despite this wide usage and a substantial body of research literature, there is at present no clear pattern or plausible model for the way caffeine achieves its effects. There is much contradiction in the literature and ambiguity as to why caffeine use should improve performance on some tasks, impair it on others and have no effect on other tasks, for some but not all of the time. The present work argues, through an examination of the specificity of caffeine’s operation, that these effects are not arbitrary but elicited by the nature of the tasks, in particular that caffeine ingestion affects those processes and behaviours which improve the probability of survival under perceived threat or stress. This is argued through the perspective of evolutionary psychology and relies theoretically on Polyvagal Theory. The argument generates testable hypotheses and empirical support for the thesis is garnered from nine experiments on card-sorting, verbal and numerical processing, local and global categorization, field dependence-independence, the Stroop task, tests of visuo-spatial ability, and from a correlational study of caffeine use and personality traits. It is concluded that moderate caffeine use in healthy adults promotes behaviours likely to be adaptive under perceived threat or stress. Limitations of both theory and empirical work and are discussed, together with potential practical applications and suggestions for further work.

No description available.

Objectives: To determine the effect of female and male cigarette smoking, caffeine and alcohol consumption, stress and indicators of dietary status on the clinical outcomes of NF treatment. Design: Prospective cohort study. Setting: PIVET Medical Centre, Perth, Western Australia. Patients: Of 351 couples who commenced IVF treatment at PIVET Medical Centre between January 1997 and August 1998, 281 females and 247 males participated in this study, generating participation rates of 80.1% and 70.4%, respectively. Main Outcome Measures: Multivariate methods of data analyses were used to control for patient and treatment variables in the examination of the effect of lifestyle factors on the following clinical outcomes: 1) number of oocytes retrieved by transvaginal oocyte aspiration (oocyte production), 2) fertilisation, measured as the number of oocytes fertilised weighted by the number of oocytes inseminated, 3) B-hCG pregnancy, 16 days post-embryo transfer, and 4) <12 week pregnancy loss following confirmation of B-hCG pregnancy. As a measure of ovarian reserve, serum basal FSH levels were also investigated as a dependent variable. Lifestyle factors included years of cigarette smoking (smoke years), tobacco, alcohol, caffeine and fruit and vegetable consumption, and stress from daily living and NF treatment. Results: Daily stress, tobacco consumption and smoke years were the female lifestyle factors shown to have a significant effect on NF treatment. Oocyte production decreased with increasing levels of daily stress (P=0.039). However, female patients with high daily stress levels experienced higher than average rates of fertilisation in vitro (P=0.0059) and pregnancy (P--0.0207). Smoke years had an adverse effect on ovarian reserve (P=0.035), which in turn, compromised oocyte production. / Female smoke years was negatively associated with rates of fertilisation (P<0.0001), and this effect was exacerbated by cigarette smoking at the time of treatment (P=0.0187). Of the male lifestyle factors, caffeine, alcohol and fruit and vegetable consumption and IVF stress affected fertilisation in vitro. Fertilisation increased with alcohol consumption (P<0.0001), and with fruit and vegetable consumption (P<0.0001). A significant interaction term between these two factors (P=0.0144) implied a threshold of benefit from the combined effect of the consumption of alcohol and fruit and vegetables. Caffeine consumption negated the beneficial effect of alcohol consumption, as shown by a significant interaction term between alcohol consumption and caffeine consumption (P=0.0007). Male stress from NF treatment had an adverse effect on rates of fertilisation in vitro (P<0.0001). Cigarette smoking by the male partner increased the likelihood of the female partner experiencing a <12 week pregnancy loss (P=0.0084). Conclusions: In meeting with its principal objective, this study has demonstrated that specific lifestyle factors impact on the clinical outcomes of IVF treatment. It confirms the findings from former studies, namely the adverse effect of female smoking on ovarian reserve, and daily stress on ovulation. Moreover, this study has identified numerous new and unexpected relationships. Of note, the positive effect of male alcohol consumption on fertilisation in vitro and the elevated risk of early pregnancy loss associated with male smoking. This study has paved the way for future research into the identification of specific mechanisms of effect, including those suggested.

Caffeine is now an unrestricted ergogenic aid for competitive athletes. Previous reviews of caffeine's effects on exercise performance have been limited to qualitative analysis. The purpose of this paper was therefore to quantitatively meta-analyze the effects of caffeine on exercise performance. We identified 90 estimates of performance effects of caffeine in 32 peer-reviewed studies. All estimates were converted to mean power in an equivalent time trial then subjected to a mixed-model meta-analysis. The fixed effects were gender, training status (elite athlete, non-elite athlete, non-athlete), dietary caffeine status (habitual consumer, non-consumer), caffeine abstention period, caffeine dose (mg/kg body mass), type of caffeine (pure or in coffee), delay between ingestion and performance test, duration of test, and presence or absence of fatiguing exercise before the test. The random effects accounted for within- and between-study variance. We found that caffeine enhanced mean power by 2.8% (90% confidence limits ± 1.1%) in male non-elite athletes who are habitual caffeine consumers abstaining from caffeine for 2 d before consuming 6 mg/kg of caffeine capsules 1 h before performing a 30-min time trial without intervening fatiguing exercise. The effects for other athletes and conditions were: females, 3.1% (± 2.7%); elite athletes, 2.9% (± 1.4%); non-athletes, 1.3% (± 1.2%); habitual non-consumers, 4.0% (± 1.4%); 7 d of abstention, 3.4% (± 2.6%); 0.3 mg/kg of caffeine, 1.6% (± 5.3%); caffeinated coffee, 1.0% (± 1.6%); 2-h delay before exercise, 2.9% (± 1.2%); 6-s exercise test, 1.6% (± 1.7%); prior fatiguing exercise, 3.0% (± 1.6%). Each of these effects of caffeine varied typically between studies by ± 1.4% (the between-study random effect; 90% confidence limits ± 0.9 to ± 3.5%). We conclude that caffeine has a greater effect on performance with athletes, with habitual non-consumers of dietary caffeine, when administered as pure caffeine, and in endurance exercise, but there is considerable uncertainty about the magnitude of the effects on individuals. More research is needed to reduce this uncertainty and to determine the performance effects of caffeine with females, following longer periods of dietary abstention, in low doses, and for brief exercise. There has also been no research on effects of caffeine on the repetitive fatiguing exercise typical of team sports.

The mechanisms underlying caffeine’s acute effects and withdrawal symptoms are not entirely understood. The purpose was to determine whether the clusters of acute effects or withdrawal symptoms are associated with genetic polymorphisms in DARPP-32 and COMT, which mediate some of caffeine’s physiological effects. Subjects (n=1135) were from the Toronto Nutrigenomics and Healthy Study. Fourteen well-described acute effects of caffeine co-exist in six groups, while fourteen well-characterized withdrawal symptoms co-exist in three groups. Neither the rs907094 C>T polymorphism in the PPP1R1B gene encoding DARPP-32, nor the COMT Val158Met affected the odds of reporting any acute effects or withdrawal symptoms cluster. Among individuals consuming ≥ 200 mg/d of caffeine, Met/Met homozygotes were more likely to report the “increased heart rate” acute effects cluster. These results suggest that ‘slow’ COMT activity, conferred by the Met allele, may explain part of the inter-individual variability in the risk for increased heart rate among heavy caffeine consumers.

The mechanisms underlying caffeine’s acute effects and withdrawal symptoms are not entirely understood. The purpose was to determine whether the clusters of acute effects or withdrawal symptoms are associated with genetic polymorphisms in DARPP-32 and COMT, which mediate some of caffeine’s physiological effects. Subjects (n=1135) were from the Toronto Nutrigenomics and Healthy Study. Fourteen well-described acute effects of caffeine co-exist in six groups, while fourteen well-characterized withdrawal symptoms co-exist in three groups. Neither the rs907094 C>T polymorphism in the PPP1R1B gene encoding DARPP-32, nor the COMT Val158Met affected the odds of reporting any acute effects or withdrawal symptoms cluster. Among individuals consuming ≥ 200 mg/d of caffeine, Met/Met homozygotes were more likely to report the “increased heart rate” acute effects cluster. These results suggest that ‘slow’ COMT activity, conferred by the Met allele, may explain part of the inter-individual variability in the risk for increased heart rate among heavy caffeine consumers.

The first harmful effect of caffeine on genetic material was discovered in 1948. The next thirty-three years have given way to public concern and even anxiety over chromosome damage caused by caffeine. More recently, the late 1960’s, concern has arisen over the synergistic characteristic of caffeine.Furosemide, also known as Lasix, is a diuretic and is the drug of choice in treating patients with renal disease. Very little research has been done on the harmful effects furosemide may have on genetic material.This study will investigate the mutagenic potential of caffeine and the mutagenic potential of furosemide. It will also investigate the synergistic effect of caffeine when given with furosemide. Both studies will to done with increasing noses of caffeine and with increasing doses of furosemide.Fifty-six 72-hour chromosome cultures will be set up using fourteen different blood specimens. Four cultures will be made peg- specimen. Specimens numbering one to four will be testing the mutagenic potential of caffeine. Specimens numbering five to eight will be testing the mutagenic potential of furosemide. And, Specimens nine to fourteen will be testing the synergistic effect of caffeine with furosemide.Damage will be assessed by the number of chromosome aberrations, either in the form of gaps or breaks, and the degree of pulverization.Ball State UniversityMuncie, IN 47306

During the past decades, the incidence of osteoporotic fractures has increased dramatically in the Western world. Consumption of coffee and intake of caffeine have in some studies been found to be associated with increased risk of osteoporotic fractures, but overall results from previous research are inconsistent. Despite weak evidence, some osteoporosis organisations recommend limiting daily coffee or caffeine intake. The primary aim of this thesis was to study the association between long-term consumption of coffee and bone mineral density (BMD), incidence of osteoporosis and fractures. A secondary aim was to study the relation between tea consumption and fracture risk. An increased risk of osteoporotic fractures in individuals who consumed ≥ 4 cups of coffee vs &lt; 1 cup coffee per day was demonstrated in a study of 31,257 Swedish middle-aged and elderly women (a part of the Swedish Mammography Cohort - SMC) when calcium intake was low (&lt; 700 mg/day). However, no higher risks of osteoporosis or fractures were observed in the full SMC with increasing coffee consumption. In the full SMC (n = 61,433) the follow-up was longer and the number of fractures was higher. Similarly, no statistically significant associations between consumption of coffee (≥ 4 cups of coffee vs &lt; 1 cup) and incidence of osteoporotic fractures were observed in the Cohort of Swedish Men (COSM), including 45,339 men. Calcium intake did not modify the results from the investigations performed in the full SMC or COSM. Nonetheless, a 2 - 4% lower BMD at measured sites was observed in men participating in the PIVUS cohort and in women from a sub-cohort of the SMC who consumed ≥ 4 cups of coffee vs &lt; 1 cup daily. Individuals with high coffee intake and rapid metabolism of caffeine had lower BMD at the femoral neck. No association between tea consumption and risk of fractures was found in the studies. In conclusion, the findings presented in this thesis demonstrate that high consumption of coffee may be associated with a modest decrease in BMD. However, there was no evidence of a substantially increased incidence of osteoporosis or fractures typically associated with osteoporosis.

Thesis (M.S.)--James Madison University, 2009. / Includes bibliographical references.