The influence of caffeine on the metabolic and catecholamine responses to mild exercise in a cold and a warm environment was studied in eight healthy males. The subjects performed 60 minutes of cycling at 50% VO2max in a cold environment (5°C and 70% relative humidity) and a warm environment (28°C and 50% relative humidity) 30 minutes after ingesting caffeine (5mg/kg body weight) or placebo (dextrose). Caffeine ingestion prior to exercise in the warm environment resulted in increased plasma epinephrine, with no effect on plasma norepinephrine. Neither lipid nor carbohydrate metabolism was altered by caffeine in the warm trial. Exercise in the cold environment (placebo) produced increased oxygen consumption and carbohydrate metabolism, decreased lipid metabolism, and no difference in plasma catecholamines compared with the warm-placebo trial. Responses to the combination of caffeine ingestion and the cold environment did not differ from cold-placebo responses in oxygen consumption or respiratory exchange ratio during the cycling bout. However, in the cold-caffeine trial plasma epinephrine was elevated. In addition, fat oxidation, serum free fatty acids, and serum glycerol were elevated in the cold-caffeine condition. Carbohydrate oxidation was depressed, while serum glucose and blood lactate were elevated in this trial. The results of this study indicate that caffeine increases plasma epinephrine; cold increases oxygen consumption and carbohydrate metabolism, while decreasing lipid metabolism; and the combination of caffeine and cold during exercise increases plasma epinephrine and lipid metabolism, but decreases carbohydrate metabolism. / Human Performance Laboratory

This study was designed to determine if highly caffeine sensitive (HS) and less caffeine sensitive (LS) individuals differ in metabolic substrate use and endurance performance following caffeine ingestion. Twenty subjects were placed into HS and LS groups based on a series of 6 isokinetic cycle ergometer rides in which perceived exertion was held constant and work output was measured. Subjects who performed significantly more work following caffeine ingestion were classified as HS while those who did not were classified as LS. Seven subjects were selected from each of these groups to perform the experimental trials. These trials were conducted 60 min after ingestion of 6 mg-kg-1 caffeine or a placebo and consisted of a 30 min ride at70% VO2max followed by a 60 min isokinetic performance ride. The HS group achieved a higher accumulated workload over the last 30 min of the ride following caffeine ingestion compared to the placebo condition. No increase in work output was observed in the LS group following caffeine ingestion. There were no significant differences between treatments in either the HS or LS group in amount of muscle glycogen utilized during the first 30 min of the ride. During the caffeine trials serum glucose was elevated at 20, 30, and 50 min, free fatty acid concentration was elevated at the zero time point, and glycerol concentration was elevated at 60 and 90 min compared to the placebo trials. However, there were no differences between the HS and LS groups in these parameters. These data suggest that the ergogenic effects of caffeine in some individuals are not due to an alteration in substrate utilization, but may be related to an alteration in neural perception of effort. / School of Physical Education

This study was designed to determine the effect of caffeine on the teratogenicity of acetazolamide in susceptible and resistant strains of inbred mice. The highly susceptible C57BL/6J and more resistant SWV strain were used. Pregnant C57BL/6J and SWV mice were treated with caffeine, low or high dose acetazolamide, or a combination of both agents during the sensitive period of development. Untreated and vehicle-treated groups served as controls. Individual fetuses were examined for gross morphological abnormalities and skeletal variations.Findings1. A highly significant (P<.001) increase in fetal malformations, especially right forelimb ectrodactyly, was evident in C57BL/6J litters exposed on day 9 of gestation to both agents when contrasted with those exposed to either agent alone. Both frequency and severity of ectrodactyly was potentiated by caffeine.2. The SWV strain was resistant to the interaction of caffeine and acetazolamide when treated on day 9 of gestation. However, a highly significant (P<.001) increase in the rate of fetal malformation was found in litters whose dams were treated with high dose acetazolamide and caffeine on day 8 of gestation. The most common malformations observed were exencephaly and umbilical hernia.3. No differences in maternal mortality, fetal weight, litter size, or embryo mortality could be attributed to treatment in either strain.4. Skeletal examination of the number of ossified cervical and caudal vertebral centra revealed a reduction in ossification among C57BL/6J litters exposed to high dose acetazolamide or acetazolamide plus caffeine. These same centers of ossification were mildly affected by treatment in the SWV strain. In both strains the first cervical vertebrae (Cl) appeared to provide the most sensitive index of teratogenic exposure.ConclusionsThis study provides evidence that a subteratogenic dose of caffeine can potentiate the teratogenic effect of acetazolamide in both C57BL/6J and SWV mice. However, strain associated, and therefore genetically based, differences in sensitivity were confirmed. Skeletal examinations provided evidence that treatment with both agents delayed fetal development in the more susceptible C57BL/6J strain, while reduction of ossification was less evident in the SWV strain. Thus, this parameter also reflects the greater resistance of the SWV strain to the interaction of acetazolamide and caffeine. Finally, these experiments support the idea that chemical interactions may, in part, be responsible for many birth defects of unknown etiology--a claim worthy of further investigation. / Department of Biology

The aim of this series of studies was to investigate the effects of oral caffeine ingestion (5 mg . kg-1) on whole-body, short-term, high-intensity exercise (ST; representing an exercise intensity of between 100% -150% V02 max), an area that has received scant attention in the past. It was found that, in common with other 'open-ended' tests, one ST assessment, the maximal accumulated oxygen deficit (MAOD), appeared to lack both validity and reliability. Although traditional reliability markers of MAOD were favourable, the 95% limits of agreement were unacceptably large. In addition, the validity of MAOD was also found to be questionable because a study of elite runners revealed that a large proportion were unable to accomplish a plateau in the V02 -exercise intensity relationship. A follow-up study developed an original bespoke 'preloaded' ST cycling protocol that combined constant-rate exercise with an 'all-out' effort. This protocol appears to have several features that make it a more appropriate assessment to use in ergogenic studies than the MAOD. The work also considered the original, and as yet, undeveloped potential, for the assessment of rating of perceived exertion (RPE) during ST. It was shown for the first time that RPE (Borg scale; 6-20) could be used reliably during constant-rate ST. Three of the ten studies demonstrated that caffeine can be ergogenic during ST, with improvements averaging 11 % (95% GI, 7.4% -14.5%) above placebo treatment. In addition, the caffeine studies contributed to a meta-analysis of the effects of caffeine on test outcome that resulted in an effect size greater than zero, with 95% confidence intervals not crossing zero. The studies have examined potential physiological and metabolic mechanisms of action that may help explain caffeine's impact on ST. These suggest that there is some evidence that caffeine both stimulates anaerobic glycolysis and reduces electrolyte disturbance during ST. Finally this work has demonstrated for the first time that the perceptual response during constant-rate ST, as measured by RPE, is blunted following caffeine ingestion. It is concluded that caffeine is ergogenic during ST, and that while the exact mechanism(s) of action remains unknown, one consistent test outcome is a reduction in RPE during constant-rate ST.

Caffeine is used for the treatment of apnea of prematurity. The objective of this study was to determine the long term neuropathological and neurobehavioral effects of caffeine on the immature rat brain. Newborn rats were injected with either caffeine, or normal saline from postnatal days 3 to 7, equivalent to the human premature infant of 28-36 weeks. Behavioral tests revealed no abnormality in caffeine treated animals compared to controls. Fluro-Jade B stain of P4 rat brains showed that caffeine caused significant neuronal cell death in some areas of the brain, compared to controls, but this alteration was transient and not present at P8. Anti-NeuN stain at P21 showed significant neuronal cell loss in CA1 and hypothalamus regions in the caffeine group, but not at P160. Anti-Neurofilament M stain at P8, P21 and P160 showed no differences between the control and caffeine groups. We conclude that use of caffeine has no significant effect on the behavioral tests measured in our newborn rat pups. While caffeine caused neuronal cell death at P4, and neuronal cell loss in CA1 and hypothalamus regions at P21, there was no long-lasting effect on neuropathological outcome. However, given these latter findings, the use of caffeine in the premature infant must still be done with caution. / Medical Sciences

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.

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF t.p. (viewed July 19, 2010). Includes bibliographical references.

Thesis (Ph.D.)--York University, 2005. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 166-200). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNR11583

The effect of FdUrd, zeocin, caffeine and their combination on the cell cycle of green algae Chlamydomonas reinhardtii and Scenedesmus quadricauda and response of these model organisms to DNA damage were studied. Both, FdUrd and zeocin, caused DNA damage that led to cell cycle arrest in these algae. In contrast, caffeine partially abolished G2 phase block imposed by zeocin. Protein levels of three crucial cell cycle regulators - CdkA, CdkB and Wee1 kinases were measured to identify mechanisms controlling reaction to DNA damage.

Objetivo: Investigar a associação entre ingestão materna de cafeína durante o período gestacional e as medidas antropométricas de crianças aos três e seis meses de vida. Métodos: Estudo observacional longitudinal, utilizando uma amostra de conveniência de duplas mãe-filho divididos em cinco grupos: gestantes diabéticas (DM), hipertensas (HAS), tabagistas (TAB), que tiveram filhos pequenos para idade gestacional (PIG) e um grupo controle (CTL). A amostra foi selecionada em três hospitais de Porto Alegre, capital do Rio Grande do Sul, no período de 2011 a 2015. Avaliou-se a ingestão materna de cafeína na gestação por Questionário de Frequência Alimentar (QFA) realizado no sétimo dia pós-parto. Os recém-nascidos foram avaliados ao nascimento, aos três e seis meses. As medidas antropométricas utilizadas foram peso, comprimento e dobras cutâneas (DC). As análises foram realizadas por regressão linear. Resultados: A amostra foi composta por 272 duplas mãe-filho: 41 DM, 26 HAS, 68 TAB, 25 PIG e 112 CTL. Não houve diferença em peso e comprimento dos filhos de consumidoras e não consumidoras de cafeína (p>0,05). As crianças do grupo DM tiveram a maior média ajustada para DC aos três meses de idade. Houve interação entre o consumo de cafeína na gestação e a soma das DC das crianças aos três meses de idade para os grupos DM e CTL (p<0,05). A diferença da média ajustada das DC e a interação delas com o consumo de cafeína não foram observadas aos seis meses. Conclusões: O consumo materno de cafeína influenciou nos valores de DC aos três meses de idade, diminuindo-as para as crianças do grupo DM e aumentando-as no grupo CTL. / Objective: To investigate the association between maternal caffeine intake during pregnancy and anthropometric measures of infant at three and six months. Methods: A longitudinal observational study using the mother-child pairs in convenience sample divided into five groups of pregnant women: diabetic (DM), hypertensive (HYP), smokers (SMO), who had small children for gestational age (SGA) and a control group (CTL). Researchers selected the sample in three public hospitals in Porto Alegre, South of Brazil, in the period from 2011 to 2015. Food Frequency Questionnaire (FFQ) evaluated the maternal caffeine intake during pregnancy on the seventh day postpartum. Anthropometric measures used were weight, length, and skinfold thickness (SK). They assessed at birth, at three and six months of child. Linear regression was used to analyze the interaction between caffeine intake and SK. Results: We investigated 272 mother-child pairs: 41 DM, 26 HYP, 68 SMO 25 SGA and 112 CTL. There were no differences in children’s anthropometric measures of mothers consuming and not consuming caffeine (P >0.05). Children of DM group had the highest adjusted average for skinfolds at 3 months. There was interaction between caffeine consumption during pregnancy and the sum of SK of children at 3 months for DM and CTL groups (P <0.05). The difference between adjusted means for SKs infant and caffeine consumption by pregnant women were not observed at six months. Conclusions: Maternal caffeine intake influenced values of SKs at 3 months of age, reducing to the children of the DM group and increasing in the CTL group.