The effects of irradiation at different times of the day on rat intestinal goblet cells

Quantitative changes in jejunal goblet cells were studied in control and whole body irradiated rats using PAS-Alcian blue staining of crypt sections. A circadian dependence was observed when control animals were killed at different times during the light/dark cycle. Irradiation with 3 Gy produced a 2–3-fold increase within 36 h in goblet cells relative to controls, followed by a reduction to very low levels. There was a return to pre-treatment levels later than was observed for the columnar cells. The present results on the pattern of response of goblet cells and those of brush border enzyme activity are consistent with the hypothesis that ionizing radiation can influence differentiation. In fact during the first hours after irradiation an early induction of differentiation is evident while during the early repopulation phase columnar cells prevailed relative to the goblet cells. Only at later times were normal differentiation patterns seen. Groups of animals exposed to the same dose of radiation at different times of the day showed similar general patterns of behaviour even if the group irradiated at midnight showed a more marked and longer lasting injury.     

Plasma carnitine and acetyl-carnitine levels at different times of the day

An interest in both biochemical and clinical carnitine investigation has recently developed. A more complete and extensive study is obtained if acetyl-carnitine as well as carnitine are investigated. This research, using an improved and simplified method for carnitine and acetyl-carnitine determination in the same sample (1 ml) without radioisotopic tracer use, investigates if there are the same differences in their plasma levels at different times of the day. The sample was eluted in a chromatographic column (55 X 15 mm) containing Sephadex G-25M with phosphate buffer (25 mmol/l, pH 7.4). The fraction containing acetyl and free carnitine was divided and employed separately for two assays. The carnitine assay uses an enzymatic reaction catalyzed by carnitine acetyl-transferase (CAT) and measurements are carried out spectrophotometrically. The calibration curve shows r = 0.987 and sensitivity at 5 mumol/l (reference plasma values: 38 +/- 3 mumol/l in 9 subjects). The acetyl-carnitine assay is carried out concentrating the sample by lyophilization and then measuring the enzymatic coupled reactions catalyzed by CAT, malate dehydrogenase and citrate synthase fluorimetrically. The calibration curve gives r = 0.991 and sensitivity at 1.4 mumol/l (reference plasma values: 2.8 +/- 0.3 mumol/l in 9 subjects). Both assay methods are measured at the end point. The carnitine and acetyl-carnitine measured in the plasma of 6 normal subjects at different times of the day vary respectively from 28 to 37 mumol/l and from 1.1 to 5.2 mumol/l in agreement with plasma free fatty acid (FFA) variation from 230 to 779 microEq/l.(ABSTRACT TRUNCATED AT 250 WORDS)     

Proliferative activity of the hepatocytes at different times of day during prolonged hypokinesia

The white male Wistar rats were exposed to hypokinesia during 10 days. Essential oppression of the mitotic division of hepatocytes in the rats' liver at the hypokinesia was revealed. The cellular division was exposed to the daily oscillations. The quantity of mitoses prevailed in the day and evening. In these conditions the quantity of binucleate cells increased as compared with the control. The deficit of mitoses stipulates the delay of postnatal weight of liver at the hypokinesia. Binucleate hepatocytes are the analog of the polyploid cells and their large population compensates for the increased organism's need in liver function in the experiment.     

Frequency of sister chromatid exchanges in human lymphocytes at different times of day

Analysis of the frequency of sister chromatid exchanges in the human blood taken from normal female donors was made at 9 a. m. and 9 p. m. The morning rate of exchange is shown to be less than the evening one. The influence of physiological state of the organism on the sister chromatid exchange is suggested.     

Differences in cortisol, aldosterone and testosterone responses to ACTH 1-17 administered at two different times of day

The effects of 100 micrograms, i.m. of the analog ACTH 1-17 administered at 0800 and 1800 on the secretion of cortisol, aldosterone and testosterone have been studied in normal subjects: 8 male and 8 female. The group as a whole and the males had significantly greater absolute and percent increments in plasma cortisol after administration at 1800. In the females, there was only a greater percent increment in cortisol after the evening administration. The heptadecapeptide always significantly stimulated serum aldosterone, with no difference between the two times of administration. In the females, ACTH 1-17 significantly stimulated testosterone, with a more protracted secretion after the evening administration. In the males, there was always a significant testosterone decrease after the administration of the drug, with no difference between morning and evening. In conclusion, 100 micrograms i.m. of the analog ACTH 1-17 stimulates cortisol secretion more when given during the circadian nadir of plasma cortisol, but only in men. ACTH 1-17 increases testosterone in women and decreases it in men, whereas it seems to increase aldosterone secretion in both sexes.     

Circadian rhythms of 11-hydroxycorticosteroid excretion in rats administered cortisol at different times of the day

Male Wistar rats housed under the conditions of 12L : 12D, 24 +/- 1 degree C and free access to food and water received isotonic sodium chloride solution or cortisol in doses of 2 and 4 mg/kg, respectively. Daily stress or cortisol injections in the morning or evening are the synchronizers of 11-hydroxycorticosteroid excretion rhythm. Morning stress leads to the increase of the 12-hour rhythm. On the contrary, evening stress or cortisol administration during maximal endogenous secretion of corticosteroids are associated with the elevation of circadian periodicity. Exogenic changes in the rhythmic organization of the hypothalamo-hypophyseal-adrenocortical system are followed by activation of adaptive processes involved in the normalization of the initially modified glucocorticoid rhythm.     

Inhibition of beta-lactam antibiotics at two different times in the cell cycle of Streptococcus faecium ATCC 9790.

Treatment of Streptococcus faecium ATCC 9790 with sublytic concentrations of beta-lactam antibiotics revealed two different division blocks in the cell division cycle. One block, induced by N-formimidoyl thienamycin and methicillin, occurred before the completion of chromosome replication, whereas the other, induced by cefoxitin and cephalothin, took place later in the cycle. In addition, these antibiotics gave rise to distinct morphological forms; the antibiotics acting at the earlier block point produced mainly "dumbbells," whereas those affecting the later time formed "lemons." When used in combination N-formimidoyl thienamycin and cefoxitin exerted synergistic killing on this strain. These data suggest that beta-lactam antibiotics have at least two sites of action in S. faecium.     

Effect of napping opportunity at different times of day on vigilance and shuttle run performance

ABSTRACT

The aim of the present study was to examine the effect of a nap opportunity during the daytime realized at different times of day on physical and mental performance. Eighteen physically active males (age: 20.5 ± 3.0 years, height: 175.3 ± 5.9 cm, body-mass: 70.0 ± 8.6 kg) were tested under four experimental conditions: no-nap condition, nap at 13h00, nap at 14h00 and nap at 15h00. All nap durations were of 25-min and all tests were performed at 17h00. They performed a 5-m shuttle run test, which generated measures of the highest distance (HD) and total distance (TD). The rating of perceived exertion (RPE) was recorded after each of the six sprints in the 5-m shuttle run test. Vigilance was measured using a digit cancellation test. The results showed that TD at 17h00 was 4% greater after a nap at 14h00 than in the no-nap condition (+28 m, p < .05) or after the nap at 13h00 (+29 m, p < .05). HD was 8% higher (+9 m, p < .001) after a nap at 14h00 than in the no-nap condition and 7% higher after nap at 15h00 than in the no-nap condition (+7 m, p < .05). In addition, HD was 6% higher after nap at 14h00 (+7 m, p < .01) and 5% higher after nap at 15h00 (+9 m, p < .01) than HD after a nap at 13h00. Napping at 13h00 had no effect on physical performance at 17h00. No significant differences were observed between RPE and vigilance scores in the nap and no-nap conditions. In conclusion, napping for 25 min at 14h00 and 15h00 produces meaningful improvements in responses during repeated short-term maximal exercise tests performed at 17h00. Napping at 13h00 does not. Vigilance, as measured using a digit cancellation test, and RPE scores are not influenced by any of the nap opportunities.     

A difference in the effect of rat liver extract (chalone) on the mitotic index of chick embryo liver when extracted at different times of day.

Adult and neonatal rat liver was used as a source for liver chalone. Extracts of rat liver were prepared from two groups of rats: one group was killed at 0900 and a second group was killed at 2100. The rat liver extracts were injected into the air sacs of 15-day old chick embryos and the effect on the mitotic index of the chick liver was studied. All rat liver extracts prepared from rats killed at 2100 demonstrated significantly more inhibition of the mitotic index in the chick liver than did the extracts obtained at 0900.     

Space-time characteristics of DNA synthesis in mesothelial cells of the rat after surgery at different times of the day

Differences in the DNA synthesis dynamics (according to the label index-LI) and those of mitotic activity (MA) in the mesothelium of the rat parietal peritoneum have been studied after burn performed at 9 AM, or at 9 PM. A number of peculiarities in the regeneration character are dependent on the day time of the operation. Immediately after the PM operation inhibition of both DNA synthesis and MA is manifected more distinctly and lasts longer, but then activation of the processes occurs more intensively the LI and MA values are greater than after the AM operation. Drop in the LI and MA takes place also with a greater rate after the PM operation, but their absolute values are kept higher up to the 7th day. Despite the fact that the reaction after the AM operation is comparatively weak, it is more rhythmical: against the background of general dynamics the fluctuations are more distinctly manifested, their period is nearly similar to the circadian. Increase in the proliferative activity is accompanied with a widening of the zone, where the dividing cells are situated. After the PM operation the wavy character of the process is expressed only in the pattern of the spatial organization of the regenerating mesothelium: nearly at regular intervals the area of the MA distribution becomes widen or narrow in turn. Thus, the LI and MA dynamics in the regenerating mesothelium depend on the circadian phase of the organism's state at the moment of the operation.     

Effects of melatonin and epiphysectomy on electrical activity of the rat brain at different times of the day]

The pineal hormone melatonin in a dose-effect manner (0.1, 1 and 10 mg/kg) reorganized EEG spectral characteristics of rat sensorimotor cortex and hippocampus, decreasing medium (6-12 Hz) and high frequency (12-22 Hz) waves only in the evening. On the contrary, pinealectomy increased high-frequency waves only during morning hours. It is suggested that the observed changes may accompany anxiolytic and hypnotic effects of melatonin.     

Stem cell (CFUs) proliferation inhibitor in blood of mice injected with hydroxyurea

Abstract. Analysis of the mouse haemopoietic stem cell (CFUs) kinetics after hydroxyurea administration has provided an in vivo assay suitable for detection of factors which inhibit recruitment of non-proliferating G₀-CFUs into cell cycle, or transit of CFU's through the G₁ phase. Using this assay, it has been demonstrated that plasma obtained from mice which had received hydroxyurea approximately 12–14 hr previously, possesses a factor which inhibited the triggering of CFUs into the cell cycle. The appearance of this CFUs proliferation inhibitor occurred at a time when 60–70% of the CFUs were synchronized in the S phase of the cell cycle, as a consequence of hydroxyurea action. Some basic properties of the inhibitor were investigated.     

Effect of thyroxine on the duration of the phases of the hepatocyte mitotic cycle at different times of day]

The lengths of the synthetic phase (S) and postsynthetic gap plus a half of the mitotic time (G2+1/2 M) has been investigated in hepatocytes of control and thyroxine-treated male white rats using percent labeled mitosis curves after injection of isotope at 10, 16, 22 and 4 o'clock. In the control, the minimum lengths of G2 lasted 3.0 hours without being changed during 24 hours. On the contrary, G2+1/2 M and S varied from 3.2 to 4.4 and from 8.0 to 9.5 hours, accordingly. A prolonged administration or hormone induced changes in duration of all the above phases whose alterations in thyroxine-treated group of animals showed 2.0--3.0, 2.9--3.4 and 6.4--11.3 hours, respectively. During 24 hours, there was observed a characteristic pattern of changes in the labeling index (LI) of both groups of animals. It has been established for both the groups that the increased in LI coincides with the shortening of S-phase. The data allow to conclude that some intracycle mechanisms may exist controlling the cell division and exerting their effects on the cells at the end of G1-phase and during G2-phase. Thyroxine is a regulator of cell proliferation, and its effect was found to occur due to the intracycle mechanisms of cell cycle kinetics.     

Changes in the size of the long tubular bones and body weight of rats exercised at different times of the day

The observations were performed in autumn in 100 rats at the age of 1 month. The animals were trained in a horizontal treadmill with the speed 40 m/min, beginning with 3 min/day and gradually increasing the time up to 30 min. The control animals were not trained, the test animals were trained either once a day (at 7 a. m., 3 p. m., 11 p. m.), or three times a day and the total loading was equal to a single loading. The animals were weighed daily. Elongation of the bones, increase in their mass and in the body mass were different at training during different time of the day and the effect was not similar in different bones. Certain sexual differences of the training effect were revealed.     

Enhanced triggering of stem cell proliferation after two doses of hydroxyurea

Abstract. Hydroxyurea (HU) injected into experimental mice increases the proliferation rate of the pluripotent haemopoietic stem cells (CFUs). This effect can be enhanced if hydroxyurea is administered in two doses, separated by 2 hr. The effect does not seem to be caused by more extensive bone marrow damage.     

The effects of times of day on cognitive and visuo-motor performance efficiency

Twenty-four male graduate volunteers were administered a battery of psychological tests--critical flicker fusion (CFF; alternate and simultaneous), reaction time (simple and choice), memory (forward and backward), and associative recall--to ascertain their performance capability during the different times of day. Each subject performed the tests on two occasions, once in the morning (10:00 h) and on the second occasion in the evening (15:00 h), on two successive days, following a statistically balanced design. Analysis of variance reflected superior performance on reaction time (choice) and memory (backward) in the evening and on associative recall in the morning. While no such effects were noticeable on CFF, appreciable changes in performance with the decreasing brightness level of its light sources was observed. Further work in this direction on a variety of cognitive tests and sensory functions under various times (more than two times) throughout the day is suggested.