Glucose is molecule usually studied in relation to metabolism. Except for this traditional view, it is known that under certain conditions glucose can serve as a signal molecule for the circadian system. The circadian system is entrained by relevant synchronizing cues that can be tissue-dependent. Central oscillator is synchronized mainly by light-dark cycle, while peripheral oscillators can be entrained by food intake. Glucose transport in the organism is controlled by insulin dependent and independent mechanism. Therefore, we employed streptozotocin- induced diabetes to elucidate the influence of metabolic changes on glucose transporter ( glut1, glut4 ) 24-h expression profile in peripheral oscillators in tissues, inside (frontal cortex, cerebellum) and outside (heart) the blood-b rain barrier. Diabetes was induced by streptozotocin inje ction. Seventeen days later, sampling was performed during a 24-h cycle. Gene expression was measured using real-time PCR. We observed down- regulation of glut1 and glut4 expression in the heart of diabetic rats. The expression of glut1 and glut4 in brain areas was not down-regulated, however, we ob served trend to phase advance in glut1 expression in the cerebellum. These results may indicate higher glucose levels in diabetic brain, which might influence regulation of clock gene expressi on in different manner in brain compared to periphery., D. Šoltésová ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
The aim of this study was to look for changes in the daily profile of steroid hormones after standardized food intake. Eight young women not taking contraceptives were followed from 5:30 a.m. till 9:30 p.m. before and 1 and 2 h after eating breakfast, snack, lunch, the second snack and dinner. The differences in steroid levels before and after meals were evaluated. As expected, glucose, C-peptide and ghrelin levels changed postprandially. The steroid hormones cortisol, progesterone, pregnenolone and dehydroepiandrosterone showed a decrease after main meals, whereas testosterone and dihydrotestosterone showed no significant dependence on food intake. Estrogen levels did not exhibit a significant nycthemeral rhythm, but estradiol decreased after main meals. In our study the known nycthemeral rhythm of LH, FSH, cortisol, progesterone and pregnenolone after food intake were confirmed, but significant changes after meals were also observed in the levels of cortisol, dehydroepiandrosterone, estradiol and SHBG., B. Rácz, M. Dušková, K. Vondra, M. Šrámková, M. Hill, L. Stárka., and Obsahuje bibliografii
A daily rhythm in the oscillations of pineal dopamine, norepinephrine and epinephrine content was found in male Wistar:Han rats. The acrophases of the oscillations were localized in the first half of the dark period and generally higher values were found in the dark part of the day., I. Ahlers, B. Pástorová, P. Solár, E. Ahlersová., and Obsahuje bibliografii
Studies of insect population under field conditions to establish survival rates, longevity and dispersal rates are rare in the literature. These types of studies are important and can be used to inform studies of the effects of landscape composition and configuration on levels of biodiversity. Here the Cantharidae beetle, Rhagonycha fulva is studied under field conditions to derive estimates of daily survival rates for both males and females as well as local dispersal rates. Survival was studied at two sites, one in Wales and another in England, whilst dispersal was examined only at the Welsh site. Beetles were marked using different coloured enamel paints at the mid-point of a 200 m linear transect. The beetles were almost exclusively found (and marked) on common hogweed, Heracleum sphondylium. No difference in survival was found between males and females at both of the sites. The survival rates found at the two sites also did not differ. The overall daily survival rate was 0.771 equating with a median longevity of 4.37 days. Casual observations yielded a small number of marked individuals in excess of 400 m away from the point of marking. Movement of males along the transect differed from females. Marked females were never found far from the point of marking whilst males moved further away with time. This difference in behaviour is discussed in terms of hypothesized insect dispersal behaviour following emergence as mobile adults., Laura E. Rodwell, Jennifer J. Day, Christopher W. Foster, Graham J. Holloway., and Obsahuje bibliografii
The negative effects of continuous light (CL) seen in tomato plants are often claimed to be linked to effects of offsetting the diurnal rhythm. In this study we tested whether a short-term daily temperature drop prevents the decreased photosynthetic performance seen in tomato plants grown under CL. Tomato (Lycopersicon esculentum Mill.) plantlets were grown at constant temperature of 26°C under 16-h day (16D) or 24-h day (24D) at 150 μmol m-2 s-1 PPFD. Some 24D plants were treated daily by 2 h temperature drop from 26 to 10°C (24D+DROP). Physiological disorder, such as severe leaf chlorosis, a large decrease in net photosynthetic rate, maximal quantum yield of PSII photochemistry, and the effective quantum yield of PSII photochemistry were observed in 24D, but not in 16D and 24D+DROP plants. The daily 2-h drop in temperature eliminated a negative effect of CL on photosynthesis and prevented the development of leaf chlorosis in tomato plants. This could be due to a change in carbohydrate metabolism as the short drop in temperature might allow maintenance of the diurnal rhythms., E. N. Ikkonen, T. G. Shibaeva, E. Rosenqvist, C.-O. Ottosen., and Obsahuje seznam literatury
Daily variations of primary production and dependence of net photosynthetic rate (Ejm) on Írradiance (/) in seaweeds and seagrass Thalassodendron ciliatum inhabiting 0-52 m depths off sbore of the Seychelles Islands were studied by oxygen measurements in a flow systém under conditions close to the natural ones. The obtained curves displayed one maximum coiresponding to the daily maximum I. Saturation of P-^ by 1 was not observed even with intertidal macrophyte species. All the macrophytes studied exhibited daily variations in the shape of the P-1 curves. The I saturated photosynthetic rate {P) (4), maximum photosynthetic rate {P^, and the initial slope of the P-1 curve (a) increased from moming to midday and decreased towards evening. P in the macroalgae and seagrass was inhibited considerably by more than 280 pmol m"2 s'* photon flux densities (PFD) of photosynthetically active radiation (PAR) only in the evening. Thus in tropical waters of the Seychelles Islands radiant energy is the main factor limiting production of macrophyte communities in nátuře.