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)     

Thermoregulatory responses to cold water at different times of day.

This study examined how time of day affects thermoregulation during cold-water immersion (CWI). It was hypothesized that the shivering and vasoconstrictor responses to CWI would differ at 0700 vs. 1500 because of lower initial core temperatures (T(core)) at 0700. Nine men were immersed (20 degrees C, 2 h) at 0700 and 1500 on 2 days. No differences (P > 0.05) between times were observed for metabolic heat production (M, 150 W. m(-2)), heat flow (250 W. m(-2)), mean skin temperature (T(sk), 21 degrees C), and the mean body temperature-change in M (DeltaM) relationship. Rectal temperature (T(re)) was higher (P < 0.05) before (Delta = 0.4 degrees C) and throughout CWI during 1500. The change in T(re) was greater (P < 0. 05) at 1500 (-1.4 degrees C) vs. 0700 (-1.2 degrees C), likely because of the higher T(re)-T(sk) gradient (0.3 degrees C) at 1500. These data indicate that shivering and vasoconstriction are not affected by time of day. These observations raise the possibility that CWI may increase the risk of hypothermia in the early morning because of a lower initial T(core).     

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.     

The effects of different milking intervals and milking times per day in jennet milk production

In their first 150 days of lactation, nine Ragusana jennets were investigated at the 'Istituto Sperimentale Zootecnico per la Sicilia' (ISZS) in Palermo, to study the effects of different milking typologies on milk production. The jennets were kept in a paddock and were fed hay ad libitum and concentrate (3.5 kg jennet/day). From post-foaling day 21, every 3 weeks individual milk amounts were recorded, and individual milk samples were collected and analyzed for the main qualitative parameters. The compared theses were: two daily milking times with 6- and 3-h intervals; and two, three and eight daily milking times with 3-h interval. The jennets were manually milked. The foals were separated from the jennets at 0800 h, and after the last milking the foals were housed with the jennets. During the day with eight milkings, the milk yield from the jennets was fed to their respective foals, through bottles. The 6-h milking interval produced more milk (+19%) per session than the 3-h interval (P 0.01). The fat content per session, with the eight-time milking frequency (P 0.001), was greater than the others. For each milking typology, the lactation stage had a similar effect on almost all the considered variables. When observing the eight-milking times, the fat content (%) increased from 1100 to 0500 h (P 0.001). The milk yield and the fat percentage produced by two-, three- and eight-milking times were positively correlated.     

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.     

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.     

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.     

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.     

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.     

Sleep quality and high intensity interval training at two different times of day: A crossover study on the influence of the chronotype in male collegiate soccer players

The influence of the chronotype on the sleep quality in male collegiate soccer players in response to acute high intensity interval training (HIIT) performed at two different times of day was evaluated. The sleep quality was poorer in the morning-type than in the evening-type players after the evening HIIT session, whereas no significant changes in the sleep quality of the two chronotypes after the morning HIIT session was observed. The results suggest that an athlete’s chronotype should be taken into account when scheduling training sessions and to promote faster recovery processes.