The diffusion coefficient of caffeine through agar gels containing a hyaluronic acid–protein complex. A model system for the study of the permeability of connective tissues

A hyaluronic acid-protein complex was embedded into agar gel. This gel complex resembles in some respects the physiological situation in connective tissue, but still permits precise physicochemical measurements to be made. The diffusion coefficient of caffeine into and from such gels has been measured as a function of both agar and hyaluronate concentration. The value for the diffusion coefficient of caffeine was also measured by using a Gouy type diffusiometer. From both types of measurement the value for D (Fick) for caffeine when extrapolated to zero caffeine and agar concentrations agreed at (6.79+/-0.01)x10(-6)cm(2).s(-1) at 25 degrees C. Although agar concentration had only a small effect on caffeine diffusion, hyaluronic acid caused a large decrease in caffeine diffusion co-efficient. The presence of the hyaluronic acid-protein complex within the gel tended to oppose gel syneresis, a concentration of 1.7mg/ml abolishing the effect and higher concentrations reversing it. The possible physiological implications of these results are discussed.     

Guarana Provides Additional Stimulation over Caffeine Alone in the Planarian Model

The stimulant effect of energy drinks is primarily attributed to the caffeine they contain. Many energy drinks also contain other ingredients that might enhance the tonic effects of these caffeinated beverages. One of these additives is guarana. Guarana is a climbing plant native to the Amazon whose seeds contain approximately four times the amount of caffeine found in coffee beans. The mix of other natural chemicals contained in guarana seeds is thought to heighten the stimulant effects of guarana over caffeine alone. Yet, despite the growing use of guarana as an additive in energy drinks, and a burgeoning market for it as a nutritional supplement, the science examining guarana and how it affects other dietary ingredients is lacking. To appreciate the stimulant effects of guarana and other natural products, a straightforward model to investigate their physiological properties is needed. The planarian provides such a system. The locomotor activity and convulsive response of planarians with substance exposure has been shown to provide an excellent system to measure the effects of drug stimulation, addiction and withdrawal. To gauge the stimulant effects of guarana we studied how it altered the locomotor activity of the planarian species Dugesia tigrina. We report evidence that guarana seeds provide additional stimulation over caffeine alone, and document the changes to this stimulation in the context of both caffeine and glucose.     

Effects of caffeine on mating behavior and sperm precedence in Tribolium castaneum

Biogenic amines such as dopamine are physiologically neuroactive substances that affect behavioral and physiological traits in invertebrates, and it has long been known that these substances affect mating behavior in insects. Caffeine is a dopamine activator and thus enhances dopamine receptor activity. However, the effects of caffeine intake on insect mating behavior have been largely unexplored. Therefore, we examined the effect of caffeine on mating behavior in the red flour beetle Tribolium castaneum. Caffeine, which activates dopamine, affected the mating behavior of T. castaneum males. Males who orally ingested caffeine courted faster than males who did not, resulting in faster mounting of females and less time to a male's external aedeagus protrusion. However, the present results showed no difference in sperm precedence measured as a P2 value between males fed caffeine and males not fed caffeine. We discuss the effects of caffeine on insect mating and the possibility that caffeine consumption may cause males to mate with more females in the laboratory.     

普洱茶后发酵中咖啡碱变化研究进展(综述)

普洱茶（熟茶）的后发酵加工工艺,是形成其独特品质特征的关键工序。咖啡碱是一种甲基黄嘌呤,是茶叶中含量比较丰富的生化成分之一,也是茶叶主要呈味物质和生理活性成分,具有促进兴奋、强心、解毒、利尿、助消化等功效。咖啡碱在普洱茶后发酵过程中呈增加趋势。文章对普洱茶后发酵过程中咖啡碱变化的相关研究进行系统综述,为普洱茶咖啡碱理论研究提供科学依据。     

Physiologic effects of caffeine on cross-country runners

This study determined the physiological effects of caffeine on cross-country runners during submaximal exercise. Ten college-age subjects (5 women; 5 men) volunteered to participate in this study. After completing a VO2max test, each subject completed 2 30-minute runs at 70% VO2max on the treadmill, 1 after ingesting caffeine and the other after ingesting a placebo. A caffeine dosage of 7 mg.kg(-1) of body weight was administered. The same dosage of vitamin C was used as a placebo. The order of treatments was randomly assigned, and the trials followed a double-blind format. The physiological data were analyzed using a repeated measures analysis of variance (SPSS). Tidal volume (TV), alveolar ventilation (VA), and rating of perceived exertion (RPE) were significantly different (p < 0.05) between treatment and control groups. The results suggest that the ingestion of caffeine at 7 mg.kg(-1) of body weight prior to submaximal running might provide a modest ergogenic effect via improved respiratory efficiency and a psychological lift.     

Repair in Schizosaccharomyces pombe as measured by recovery from caffeine enhancement of radiation-induced lethality.

Inhibition of DNA repair by caffeine is manifested in Schizosaccharomyces pombe wild-type cells as an enhancement of UV- or gamma-irradiation-induced lethality. The progress of DNA repair processes involving one or more caffeine-sensitive steps may be conveniently followed by measuring the concomitant decrease of this lethal enhancement effect. By measuring, during post-irradiation incubation, the ability of cells to overcome susceptibility to repair inhibition by caffeine, we have determined the time course and requirements for repair in S. pombe. Recovery began immediately and took 150-200 min after gamma-irradiation and more than 500 min after UV-irradiation, for exposures which gave about 10% survival in the absence of caffeine. An incubation medium capable of supporting growth was required for caffeine-sensitive repair; no recovery occurred under liquid holding conditions. Survival curves after various recovery times indicated that a logarithmic phase cell population was homogeneous with respect to caffeine-sensitive repair of both UV- and gamma-ray-induced damage. Recovery from caffeine inhibition was compared for cells of different physiological states (logarithmic and stationary phase); although the importance of the physiological state was not the same for the two types of radiation, recovery was found to occur more rapidly in the more radiation-resistant state, in each case.     

Postradiation effect of caffeine on the producer of mycoheptin, Streptoverticillium mycoheptinicum]

The modifying effect of caffeine on irradiated spores of Streptoverticillium mycoheptinicum, producing mycoheptin was found. Postradiation treatment of the strain O883: spores with caffeine resulted in decreased survival of the spores proportionally to the radiation dose increase and postradiation caffeine treatment. An increase in the frequency of the morphologically changed colonies, as well as the low and highly active variants with respect to mycoheptin production was observed. The effect may be explained by the fact that caffeine possibly inhibited the reparation process in the irradiated spores of the strain tested. The method of postradiation treatment of the spores of the mycoheptin-producing organism with caffeine which provided selection of highly active variants by the antibiotic production with the use of definite doses may be considered promising in selection of actinomycetes.     

Influence of continued ingestion of matcha on emotional behaviors after social stress in mice

ABSTRACT

Matcha has high contents of theanine, caffeine, and epigallocatechin gallate (EGCG). Among these, theanine reduces psychological and physiological stress responses, although this effect is disturbed by caffeine and EGCG. It was reported that the continued ingestion of high-quality matcha, whose molar ratio of caffeine and EGCG to theanine and arginine was kept at less than two, reduces stress responses. However, most matcha on the market has an inadequate ratio. Therefore, we investigated the influence of continued ingestion of matcha with a ratio of over two, on emotional behaviors after stress. Continued ingestion of matcha was suggested to reduce the anxiety-like behaviors induced by psychological and physiological stresses.     

The effect of physiological concentrations of caffeine on the power output of maximally and submaximally stimulated mouse EDL (fast) and soleus (slow) muscle

The ergogenic effects of caffeine in human exercise have been shown to improve endurance and anaerobic exercise performance. Previous work has demonstrated that 70 μM caffeine (physiological maximum) can directly increase mouse extensor digitorum longus (EDL) muscle power output (PO) in sprintlike activity by 3%. Our study used the work loop technique on isolated mouse muscles to investigate whether the direct effect of 70 μM caffeine on PO differed between 1) maximally and submaximally activated muscle; 2) relatively fast (EDL) and relatively slow (soleus) muscles; and 3) caffeine concentrations. Caffeine treatment of 70 μM resulted in significant improvements in PO in maximally and submaximally activated EDL and soleus (P < 0.03 in all cases). For EDL, the effects of caffeine were greatest when the lowest, submaximal stimulation frequency was used (P < 0.001). Caffeine treatments of 140, 70, and 50 μM resulted in significant improvements in acute PO for both maximally activated EDL (3%) and soleus (6%) (P < 0.023 in all cases); however, there was no significant difference in effect between these concentrations (P > 0.420 in all cases). Therefore, the ergogenic effects of caffeine on PO were higher in muscles with a slower fiber type (P < 0.001). Treatment with 35 μM caffeine failed to elicit any improvement in PO in either muscle (P > 0.72 in both cases). Caffeine concentrations below the physiological maximum can directly potentiate skeletal muscle PO. This caffeine-induced increase in force could provide similar benefit across a range of exercise intensities, with greater gains likely in activities powered by slower muscle fiber type.     

Effect of taurine and potential interactions with caffeine on cardiovascular function

The major impetus behind the rise in energy drink popularity among adults is their ability to heighten mental alertness, improve physical performance and supply energy. However, accompanying the exponential growth in energy drink usage have been recent case reports and analyses from the National Poison Data System, raising questions regarding the safety of energy drinks. Most of the safety concerns have centered on the effect of energy drinks on cardiovascular and central nervous system function. Although the effects of caffeine excess have been widely studied, little information is available on potential interactions between the other active ingredients of energy drinks and caffeine. One of the active ingredients often mentioned as a candidate for interactions with caffeine is the beta-amino acid, taurine. Although taurine is considered a conditionally essential nutrient for humans and is thought to play a key role in several human diseases, clinical studies evaluating the effects of taurine are limited. However, based on this review regarding possible interactions between caffeine and taurine, we conclude that taurine should neutralize several untoward effects of caffeine excess. In agreement with this conclusion, the European Union’s Scientific Committee on Food published a report in March 2003 summarizing its investigation into potential interactions of the ingredients in energy drinks. At the cardiovascular level, they concluded that “if there are any interactions between caffeine and taurine, taurine might reduce the cardiovascular effects of caffeine.” Although these interactions remain to be further examined in humans, the physiological functions of taurine appear to be inconsistent with the adverse cardiovascular symptoms associated with excessive consumption of caffeine–taurine containing beverages.     

Caffeine treatment inhibits drug-induced calcium release from sarcoplasmic reticulum and caffeine contracture but not tetanus in frog skeletal muscle

Effects of pretreatment with caffeine on Ca2+ release induced by caffeine, thymol, quercetin, or p-chloromercuriphenylsulfonic acid (pCMPS) from the heavy fraction of sarcoplasmic reticulum (SR) were studied and compared with those effects on caffeine contracture and tetanus tension in single fibers of frog skeletal muscle. Caffeine (1-5 mM) did induce transient Ca2+ release from SR vesicles, but subsequent further addition of caffeine (10 mM, final concentration) induced little Ca2+ release. Ca2+ release induced by thymol, quercetin, or pCMPS was also inhibited by pretreatment with caffeine. In single muscle fibers, pretreatment with caffeine (1-5 mM) partially reduced the contracture induced by 10 mM caffeine. However, tetanus tension was almost maximally induced by electrical stimulus in caffeine-treated fibers. These results indicate that SR, which becomes less sensitive to caffeine, thymol, quercetin, or pCMPS by pretreatment with caffeine, can still respond to a physiological signal transmitted from transverse tubules.     

The circulating concentrations of FSH,LH and prolactin in the oestradiol-implanted ovariectomized ewe treated with caffeine

Caffeine, a trimethylxanthine alkaloid, is a psycho-active drug that effects a wide range of physiological systems, including the reproductive system. Reports of infants with intra-uterine growth retardation and lowered birth weight as a result of in utero exposure to caffeine, are increasing. The drug is also known to alter steroidogenesis but it is not certain whether this is a direct and/or indirect effect with the involvement of the central nervous system. Thus, an experiment was designed to determine the effect of acute caffeine administration on the circulating concentrations of gonadotrophins and prolactin in the ovariectomized oestradiol-implanted ewe. A single intravenous dose of caffeine (20 mg kg⁻¹ bodyweight) did not affect circulating gonadotrophin concentrations with the parameters for the pulsatile secretion of luteinizing hormone (LH) and the mean concentration of follicle stimulating hormone (FSH) being similar in both experimental and control groups. Circulating prolactin levels, on the other hand, were significantly (P < 0.01) elevated following intravenous treatment with caffeine. The effect was immediate following caffeine administration with elevated concentrations being maintained over the next 3 h before their return to pre-treatment concentrations. The response was bi-phasic with peaks of prolactin concentrations at 1 and 3 h. The results of this experiment show that acute caffeine exposure does not affect the secretion of gonadotrophins from the anterior pituitary gland. Furthermore, they show that acute administration of caffeine stimulates prolactin secretion via an action that is independent of oestradiol feedback and which we suggest, may involve the ACTH/adrenal axis.     

The metabolism of caffeine by a Pseudomonas putida strain

1) A bacterium capable of growing aerobically with caffeine (1,3,7-trimethylxanthine) as sole source of carbon and nitrogen was isolated from soil. The morphological and physiological characteristics of the bacterium were examined. The organism was identified as a strain of Pseudomonas putida and is referred to as Pseudomonas putida C1. 15 additional caffeine-degrading bacteria were isolated, and all of them were also identified as Pseudomonas putida strains. The properties of the isolates are discussed in comparison with 6 Pseudomonas putida strains of the American Type Culture Collection. 2) The degradation of caffeine by Pseudomonas putida C1 was investigated; the following 14 metabolites were identified: 3,7-dimethylxanthine (theobromine), 1,7-dimethylxanthine, 7-methylxanthine, xanthine, 3,7-dimethyluric acid, 1,7-dimethyluric acid, 7-methyluric acid, uric acid, allantoin, allantoic acid, ureidoglycolic acid, glyoxylic acid, urea, and formaldehyde. Formaldehyde has been demonstrated to be the product of oxidative N-demethylation mediated by an inducible demethylase. A pathway of caffeine degradation is proposed.     

The prevalence and practices of caffeine use as an ergogenic aid in English professional soccer

The ergogenic properties of caffeine are well established, with evidence supporting beneficial effects for physical and technical elements of performance required for successful soccer match play. Despite this, recommended caffeine practices for professional soccer have not been established. Therefore, the present study aimed to evaluate the use and behaviours surrounding caffeine use in elite English soccer clubs. Representatives of 36 clubs from the top four tiers of English professional football (40%) completed an online survey that sought to determine if, when, how and why caffeine was prescribed to players as a means of improving sports performance. Of the clubs sampled, 97% indicated that caffeine is provided to players as a means of improving performance. Caffeine is most commonly administered prior to (> 94%) and during a game (> 48%), with frequency uninfluenced by time of matches. There was a broad range and lack of consistency in the timing, dose and mode of caffeine administration, but doses were typically low. Evidence from the present study indicate a translational gap between science and practice, highlighting a need for future work to better understand how caffeine consumption can be optimised with respect to the specific demands and constraints in professional soccer.     

Immunohistochemical localization of caffeine in young Camellia sinensis (L.) O. Kuntze (tea) leaves

The anatomical localization of caffeine within young Camellia sinensis leaves was investigated using immunohistochemical methods and confocal scanning laser microscopy. Preliminary fixation experiments were conducted with young C. sinensis leaves to determine which fixation procedure retained caffeine the best as determined by high-performance liquid chromatography analysis. High pressure freezing, freeze substitution, and embedding in resin was deemed the best protocol as it retained most of the caffeine and allowed for the samples to be sectioned with ease. Immunohistochemical localization with primary anti-caffeine antibodies and conjugated secondary antibodies on leaf sections proved at the tissue level that caffeine was localized and accumulated within vascular bundles, mainly the precursor phloem. With the use of a pressure bomb, xylem sap was collected using a micro syringe. The xylem sap was analyzed by thin-layer chromatography and the presence of caffeine was determined. We hypothesize that caffeine is synthesized in the chloroplasts of photosynthetic cells and transported to vascular bundles where it acts as a chemical defense against various pathogens and predators. Complex formation of caffeine with chlorogenic acid is also discussed as this may also help explain caffeine’s localization.     

Influence of nicotine and caffeine on rat embryonic development

The influence on embryonic development of nicotine and caffeine at dose levels approximating human consumption was investigated in Sprague-Dawley rats. One group of animals received nicotine administered subcutaneously by an Alzet mini-osmotic pump from gestational day 6 through 12 (25 mg over 7 days; rate 149 micrograms/hr). Control animals received physiological saline in a similar manner. A second group received a single intravenous injection of caffeine (25 mg/kg) on gestational day 6. Control animals were treated with physiological saline. A further group received both nicotine and caffeine on gestational day 6 as described for the two previous groups. There were no significant differences among any of the groups with respect to maternal weight gain, litter size, embryolethality, fetal weight, or crown-rump length. The offspring of nicotine treated animals showed a significantly higher incidence of hydrocephaly when compared to the controls, but in the combined treatment group no malformed fetuses were observed. Light microscopic examination of maternal liver, kidney and placentas revealed changes in the hepatic sinusoids, glomeruli and intervillous spaces after nicotine and combined treatment. In addition, the decidua basalis was poorly developed compared to the controls. Chorionic villi and fetal kidney appeared normal in all groups. A coteratogenic effect is not evident from these findings.     

Pathogen resistance of transgenic tobacco plants producing caffeine

Caffeine (1,3,7-trimethylxanthine) is a typical purine alkaloid, and produced by a variety of plants such as coffee and tea. Its physiological function, however, is not completely understood, but chemical defense against pathogens and herbivores, and allelopathic effects against competing plant species have been proposed. Previously, we constructed transgenic tobacco plants, which produced caffeine up to 5 microg per gram fresh weight of leaves, and showed them to repel caterpillars of tobacco cutworms (Spodoptera litura). In the present study, we found that these transgenic plants constitutively expressed defense-related genes encoding pathogenesis-related (PR)-1a and proteinase inhibitor II under non-stressed conditions. We also found that they were highly resistant against pathogens, tobacco mosaic virus and Pseudomonas syringae. Expression of PR-1a and PR-2 was higher in transgenic plants than in wild-type plants during infection. Exogenously applied caffeine to wild-type tobacco leaves exhibited the similar resistant activity. These results suggested that caffeine stimulated endogenous defense system of host plants through directly or indirectly activating gene expression. This assumption is essentially consistent with the idea of chemical defense, in which caffeine may act as one of signaling molecules to activate defense response. It is thus conceivable that the effect of caffeine is bifunctional; direct interference with pest metabolic pathways, and activation of host defense systems.     

Caffeine in tea plants [Camellia sinensis (L) O. Kuntze]: in situ lowering by Bacillus licheniformis (Weigmann) Chester

Tea plants (Camellia sinensis) contain 5-6% caffeine that is responsible for the stimulating effect of the beverage. As the tolerance to caffeine varies among individuals, low caffeine tea would be an ideal alternative. While assessing the potential of a few selected bacteria-Bacillus licheniformis, B. subtilis and B. firmus, to multiply on nutrient medium supplemented with glucose (5%) and tea leaf extract (2%), it was observed that only B. licheniformis could proliferate on this medium. Hence, B. licheniformis was used for further studies. Tea plants were sprayed with a suspension of B. licheniformis at a dilution of 5 x 10(8) CFU/ml containing 0.1% Tween 80 as surfactant. In situ lowering of caffeine from tea leaves was evident without affecting the quality of the other tea components. Further, there was no change in the morphological and physiological characteristics as well. It is suggested that spraying of B. licheniformis may be useful in yielding decaffeinated tea with good flavour and aroma.     

Depressing Effect of Caffeine at Crayfish Neuromuscular Synapses II. Initial Search for Possible Sites of Action

Caffeine’s unexpected depression of synaptic transmission in the superficial flexor muscle system (SFM) of Procambarus clarkii was studied by looking at three known sites of action of this drug: via adenosine and ryanodine receptors and inhibition of phosphodiesterase. 1. JPs did not change in size when exposed to physiological concentrations of adenosine, suggesting that the SFM system lacks presynaptic adenosine receptors. 2. JPs slightly increased in size in the presence of a phosphodiesterase inhibitor, the opposite response to that obtained with caffeine, suggesting that caffeine is not acting via this pathway. 3. A calcium ionophore immediately enhanced synaptic transmission in the SFM system but when given in combination with caffeine the enhancement is reduced and declines over time. 4. Serotonin enhanced synaptic transmission in the SFM system, but when given in combination with caffeine this enhancement was not observed. 5. These caffeine effects are interpreted in terms of alterations to the calcium homeostatic mechanisms of the terminals.