The ingestion of food and the recovery of body weight following fasting in the naive rat

The total food consumption of experimentally naive rats following 24, 48, 72, and 96 hr fasts was observed during the period of the recovery of body weight. The total amount of food consumed in excess of prefast food consumption was found in all groups to be equivalent to 24 hr intake and was, therefore, independent of degree of fast and body weight lost. Moreover, it was found that rats recover lost body weight following a fast even when intake is held to prefast levels. These findings suggest that the regulation of body weight may be under the control of mechanisms in addition to the control of food intake.     

A contact detection system for identifying individual animals in groups

The system described has been in use for a period of three years to study voluntary consumption of alcohol for individual monkeys. In some experiments it has been used to monitor consumption 24 hr per day over a period of two months.     

Diurnal drinking of rats with limbic system lesions maintained in an open vivarium

The diurnal patterning of drinking of rats maintained in an open colony room was measured immediately following — and four weeks after — surgery. Drinking behavior was measured in operated control rats, or animals who had received lesions of the septum, dorsal hippocampus, habenula or combined destruction of habenula and medial-dorsal hippocampus (including part of the subiculum). Two daily measurements of water intake during weeks one and four postsurgery were made just after the lights came on in the morning and 12 hr later, just before the lights went off. All animals drank most of their water during the dark hours. However, despite the strong entraining cues available in any open colony room, rats with lesions of the dorsal hippocampus in the present experiment drank more in the light than any of the other groups. Rats with septal lesions did not drink more water per 24 hr than control animals during the first postsurgical week, but did so during the fourth week postsurgery. Lesions restricted to either the dorsal hippocampus or habenula did not alter the total amount of fluid consumed, but combined lesions involving both medial-dorsal hippocampus and habenula elevated water intake above that of all other groups both immediately after surgery and four weeks later. These results suggest that further behavioral fractionation of the limbic system may be possible. The importance of environmental isolation in the examination of circadian rhythms is inferred.     

Septal lesion and experiential influences on saline and saccharin preference-aversion functions

Relatively high (unpalatable) concentrations of saline or saccharin (independent studies) presented in 24 hr choices with water were found to more markedly and persistently suppress the subsequent preference of septal-lesioned rats for lower concentrations when compared with any such shifts in preference displayed by operated-control rats. These data were used to support the notion that the septal region is involved with a comparator mechanism which affects the animal's response to various external and internal cues guiding consumption. In addition, wide individual differences in both groups were presented and discussed to emphasize that future studies should be designed to clarify those uncontrolled genetic and/or early experience variables which must serve, at least in part, to differentially bias the adult animal's consummatory choice behavior.     

Can a 15‐Hour (Overnight) Urinary Catecholamine Measure Substitute for a 24‐Hour Measure?1

This study examined whether 15‐hr and 24‐hr urinary catecholamine measures show comparable associations with other physiological measures that are expected to correlate with sympathetic nervous system activity. Participants (193 healthy adults) provided 24‐hr urine samples that were collected in a controlled environment (hotel), and divided into 9‐hr daytime and 15‐hr overnight collections. On the same day, resting blood pressure (BP) was measured, and 8 samples of salivary Cortisol were collected. Catecholamine (15‐hr and 24‐hr) measures were correlated substantially in the entire sample, and when examined separately by sex and by race. Both 15‐hr and 24‐hr epinephrine (E) correlated significantly with systolic BP and Cortisol; 15‐hr and 24‐hr norepinephrine (NE) correlated significantly with Cortisol. Correlation coefficients for 15‐hr measures were similar, but not equivalent to those for 24‐hr measures. Urinary catecholamines obtained via 15‐hr overnight collection approximated but were not equivalent to catecholamines obtained via 24‐hr collection. Overnight collection was associated with reduced power to detect significant associations of catecholamines with criterion variables, such that use of 15‐hr rather than 24‐hr sampling required a relative increase in sample size of 1.32 times for E and 1.18 times for NE to detect similar effects. Researchers should weigh the costs of additional subjects to the benefit of decreased burden when choosing between the two sampling methods.     

Direct and circadian control of sparrow behavior by light and dark

House sparrows, Passer domesticus, have perch-hopping activity (1) which was elicited by light (direct), and (2) which exhibited daily rhythms that were entrained by environmental light-dark cycles (circadian). When photoperiod was more than 14 hr, the sparrows' activity coincided with the light; when it was less than 14 hr, the birds were also active in the dark according to circadian predictions. Bimodality was dependent on photoperiod with the maximum incidence (75%) in LD16:8. Sparrows placed in LD1:11 (skeleton of 13:11) synchronized the onsets of their activity with the light beginning 8-18 hr after the time of the last L/D irrespective of when the birds experienced the first 1 hr light. Thirty-five percent of the sparrows advanced when they entrained to LD1:11 with the first pulse 8 hr after the last L/D; 76-87% of the sparrows delayed when they entrained to LD1:11 with the first pulse 2, 5 or 18 after the last L/D. Sparrows kept in exotic light-dark cycles (with periods of 10 min, 1.5 hr, 3.0 hr, 6.0 hr, 12 hr) were active in the light. Some birds displayed circadian rhythms superimposed on short period patterns. The period lengths of the circadian rhythms were shorter (22.8 hr) than in constant dark (24.2 hr). When sparrows subjected to LD1.5:1.5 or 36 hr of constant light were placed in constant dark, the phase of their activity onsets extrapolated to 15 hr after the last lights-off.     

Effects of sleep loss on waking actigraphy

STUDY OBJECTIVES: To assess the effect of sleep loss and the effect of a sedating drug on waking actigraphy DESIGN: N/A SETTING: N/A PARTICIPANTS: Seventeen healthy volunteers, aged 19-35 yrs Interventions: Four night-day treatments presented in a Latin Square Design: placebo-8 hr time-in-bed (TIB), placebo-4 hr TIB, placebo-0 hr TIB, and diphenhydramine 50 mg-8 hr TIB. MEASUREMENTS AND RESULTS: After the appropriate TIB, medication was administered at 09:00 hr, the Multiple Sleep Latency Test at 09:30, 11:30, 13:30, 15:30, and 17:30 hr, and a 45 min performance battery at 10:30, 14:30, and 16:30 hr. Each day the volunteers wore actigraphs from 0700-1800 hrs. Decreasing TIB was associated with decreased daily mean sleep latency on the MSLT with 4 and 0 hrs differing from 8 hrs and each other. Daytime activity also was reduced by the reduced prior TIB. Increased inactivity relative to the 8 hr TIB developed between the 4 hr and 0 hr TIBs, with 4 hrs differing from 0 hrs, but not 8 hrs. Diphenhydramine 50 mg reduced mean daily sleep latency and increased percent inactive time relative to placebo. On the MSLT diphenhydramine was intermediate to 4 hr and 0 hr TIB and on actigraphy it was similar to 0 hr TIB. CONCLUSIONS: The difference in the effect of diphenhydramine on these actigraphy and MSLT may reflect the different sensitivities of the measures.     

Impact of cell cycle delay on micronucleus frequency in TK6 cells

Previous studies with TK6 cells have shown that extending the recovery period after pulse treatment allows for greater micronucleus expression for some compounds. This study explores the role of cell cycle delay in micronucleus expression after pulse treatment with three model genotoxins [mitomycin C, etoposide (ETOP), vinblastine]. Cells were treated for 4 hr and allowed to recover for 36 hr with samples removed at various time points during the recovery period and analyzed for cell cycle distribution, apoptosis and micronucleus frequency. Our results show that mitomycin C causes cell cycle delay for 20 hr after pulse treatment and cell cycle perturbation is no longer evident after 36 hr of recovery. The micronucleus frequency of cells sampled at 36 hr is doubled when compared with cells sampled at 20 hr after mitomycin C removal. When cells were treated with indirect acting genotoxins (ETOP, vinblastine), cell cycle perturbation was not observed at the 20 hr time point. Micronucleus frequency after treatment with either ETOP or vinblastine did not differ between the 20 hr and the 36 hr time point. All three compounds induced similar levels of apoptosis ranging from 4.5 to 5.6% with maximum induction occurring at the 36‐hr time point. We conclude that TK6 cells exhibit extended cell cycle arrest after exposure to MMC and can go on to express micronuclei, after overcoming cell cycle arrest. Environ. Mol. Mutagen. 55:64–69, 2014. © 2013 Wiley Periodicals, Inc.     

Rhythms of barbiturate-induced sleep time in deermice entrained to non-twenty-four hour photocycles

The present experiment examined whether entrainment to twenty-four hour days is advantageous for physiological and behavioral adaptations to a pharmacological challenge. Adult, male deermice (Peromyscus maniculatus) were injected with sodium pentobarbital at 8.5, 14.5, 20.5, 2.5 and again at 8.5 hr after light onset while entrained to a 24 hr day (light/dark (LD) 14:10). Time to recover from anesthesia was recorded. Subsequently, the dark phase of the LD cycle was reduced 15–20 min every 10 days until a 23 hr photocycle was achieved, (LD 14:9; T=23 hr). Injections of sodium pentobarbital were again administered at 8.5, 14.5, 20.5 and 2.5 hr after light onset and sleep times recorded. This procedure was repeated at T=21 hr (LD 14:7) and T=18 hr (LD 14:4). A variation in sleep time was observed during entrainment to all T-cycles except T=18 hr. Sleep time after drug administration was generally longer during the light than during the dark phase of each photocycle. Recovery from anesthesia was not compromised in mice entrained to photocycles with periods of 23 or 21 hr; however, entrainment to very short days disrupted the normal pattern of response to barbiturate administration. Entrainment to a range of daylengths that deviate appreciably from 24 hr is consistent with normal physiological function.     

Therapeutic window for cycloheximide treatment after hypoxic-ischemic brain injury in neonatal rats

We have previously shown that cycloheximide significantly inhibited apoptosis, and reduced ensuing cerebral infarction in a newborn rat model of cerebral hypoxiaischemia. This study was performed to determine the therapeutic window for cycloheximide therapy. Seven day-old newborn rat pups were subjected to 100 min of 8% oxygen following a unilateral carotid artery ligation, and cycloheximide was given at 0, 6, 12 and 24 hr after hypoxia-ischemia (HI). Apoptosis or necrosis was identified by performing flow cytometry with a combination of fluorescinated annexin V and propidium iodide, and the extent of cerebral infarction was evaluated with triphenyl tetrazolium chloride (TTC) at 48 hr and 72 hr after HI, respectively. With cycloheximide treatment at 0 hr after HI, both apoptotic and necrotic cells by flow cytometry were significantly reduced, only necrotic cells were significantly reduced at 6 and 12 hr, and no protective effect was seen if administration was delayed until 24 hr after HI compared to the HI control group. Infarct volume, measured by TTC, was significantly reduced by 92% and 61% when cycloheximide was given at 0 or 6 hr after HI respectively; however, there was an insignificant trend in infarct reduction if cycloheximide was administered 12 hr after HI, and no protective effect was observed when administration was delayed until 24 hr after HI. In summary, cycloheximide was neuroprotective when given within 6 hr after HI in the developing newborn rat brain.     

Post-ingestive effects of quinine on intake of nutritive and non-nutritive substances

Intragastric intubation of 0.75 g QHCl had no effect on 4 hr food intake, but produced anorexia over a 24 hr period when paired with consumption of a novel sucrose octa acetate (SOA) treated chow. No anorexia developed when a familiar food was available. SOA adulteration alone produced a decrement in food intake that persisted for 4 hr; this effect was independent of quinine intubation. In a second experiment, intubation of 0.375 or 0.75 g QHCl, 0.3 M LiCl, or 0.6 g SOA did not alter 4 hr chow intake, but QHCl and LiCl both produced pica that lasted for 4 hr. SOA and 0.75 g QHCl produced a 24 hr hyperphagia, while LiCl and 0.375 g QHCl produced no change in 24 hr chow intake.     

Temporal regulation of the rate of vesicular stomatitis virus mRNA translation during infection of Chinese hamster ovary cells

Vesicular stomatitis virus (VSV) mRNAs on polysomes 3 hr after infection are not translated in vivo as efficiently as mRNAs 2 hr after infection. There are 14?, 12?, 11?, and 8-fold increases in the amounts of L, G, N, and M messengers, respectively, on polysomes between 2 and 3 hr after infection. However, there are only 3?, 5?, 3?, and 4-fold increases in the rates of synthesis of the respective proteins. The in vivo translational efficiences of these messengers, which is a measure of their capacity to act as template for protein synthesis, are therefore lower at 3 hr after infection than at 2 hr. Since the mRNAs isolated 3 hr after infection are as active in a wheat germ cell-free protein synthesizing system as the mRNAs isolated at 2 hr, the decreased efficiency of VSV translation in vivo at 3 hr is not due to changes in mRNA primary structure. The observed difference is more likely due to a reduced efficiency of the host cell translational system to translate VSV mRNA at 3 hr relative to 2 hr. It was found that at 2 hr after infection, the majority of VSV mRNA is not associated with polysomes, but at 3 hr, the majority of viral messages is polysome bound.     

Morphologic changes in the murine leukemia L5178Y cells treated with antibodies in the absence of complement activity

Murine leukemia L5178Y cells treated with antiserum in the absence of complement activity showed capping and endocytosis of surface receptors after 30 min and 3 hr, respectively. Electron microscopy revealed that the number of microvilli on the treated cells was decreased after 1 hr whereas mitochondrial damage, appearance of vesicles and autosome—cytosomes, and small numbers of cell ghosts with watery cytoplasm and nucleus occurred after 6 hr. At 24 hr, some cells were obviously dead or moribund while the majority showed similar changes to those that had been seen at 6 hr. In many cells polyribosomes had become disorganized, reflecting the previously reported inhibition of protein synthesis which occurred after 6 to 8 hr. By 48 hr, many more of the cells had died but the survivors appeared to be essentially normal, indicating recovery of cells from the growth inhibitory effect of antiserum.     

The white pock mutants of rabbit poxvirus: V. In vitro translation of early host range mutant mRNA

The abortive infections of pig kidney (PK) cells by both RP mu hr23 and RP mu hr31, two early (DNA minus) white pock (mu) host range (hr) mutants of rabbit poxvirus (RPV), are characterized by the in vivo inhibition of both host and viral protein synthesis by 10 hr postinfection although viral RNA synthesis continues. Further analysis reveals that large quantities of functional viral mRNA can be isolated from PK cells abortively infected with RP mu hr23 and translated in vitro throughout the 10-hr period of infection, even though these mRNAs are almost totally inactive in vivo. The in vitro translation of accumulated mRNA isolated from PK cells abortively infected by RP mu hr31 shows a quite different pattern where the maximum amount of RNA translatable in vitro is found at 6 hr postinfection with lesser amounts at 10 hr postinfection. Although early or prereplicative viral proteins are detected with each mutant both in vivo and after in vitro translation of isolated RNA, few, if any, late proteins are observed under any conditions.     

Decreased food intake of rats kept under adiurnal feeding cycles: effect of suprachiasmatic lesions

The circadian feeding rhythm and food intake under restricted feeding conditions, including adiurnal feeding cycles, were examined in rats with bilateral lesions of the suprachiasmatic nucleus (SCN). Although rats with SCN-lesions ate nearly as much food per day as those with control-lesions, their feeding pattern did not show circadian rhythmicity. When rats with control-lesions were fed for 5 hr once every 20 hr or for 7 hr once every 28 hr, they ate less than when they were fed for 6 hr once every 24 hr, probably due to some effect of desynchronization between the feeding cycle and an endogenous circadian oscillator. Decreased food intake under adiurnal feeding cycles was also observed in rats with SCN-lesions as in those with control-lesions. It is suggested that the circadian rhythm entrained by food is related to an endogenous time-keeping system that does not include the SCN.     

Apoptotic change and NOS activity in the experimental animal diffuse axonal injury model.

Although nitric oxide (NO) plays an important role in the pathophysiological process of cerebral ischemia or severe traumatic brain injury, its contribution to the pathogenesis of moderate diffuse axonal injury (mDAI) remains to be clarified. The alterations in nitric oxide synthase (NOS) activity and the histopathological response after mDAI was investigated. Forty anesthetized Sprague-Dawley adult rats were injured with a Marmarou's weight-drop device through a Plexiglas guide tube. These rats were divided into 8 groups (control, 1 hr, 2 hr, 3 hr, 6 hr, 12 hr, 24 hr, 48 hr after trauma). The temporal pattern of apoptosis in the adult rat brain after mDAI was characterized using TUNEL histochemistry. In addition, the cDNA for NOS activity was amplified using RT-PCR. The PCR products were electrophoresed on a 2% agarose gel. eNOS activity was not detected, but nNOS activity was expressed after 3 hr and continuously 48 hr after impact, which was approximately double that of the control group at 12 and 24 hr. Subsequently, there was a decrease in activity after 48 hr. The iNOS activity increased dramatically after 12 hr and was constant for a further 12 hr followed by a dramatic decrease below the level of the control group. Significant apoptotic changes occurred 12 and 24 hr. after insult. nNOS and iNOS activity were affected after moderate diffuse axonal injury in a time-dependent manner and there was a close relation between the apoptotic changes and NOS activity. Although the nNOS activity was expressed early, its activity was not stronger than iNOS, which was expressed later.     

The free-run period is not the best Zeitgeber period for the house mouse

Two light cycles were presented simultaneously to house mice. One cycle had a period of 23.7 hr, the free-run period of the activity cycle in constant darkness, and the other a period of 24.0 hr. The activity cycles of all 31 subjects synchronized temporarily with the 24.0 hr light cycle. In contrast, only 10 mice also showed temporary synchronization with the 23.7 hr light cycle and only 2 of these spent more time synchronized with the 23.7 than the 24.0 hr light cycle. The results suggest that a relaxation oscillator is not an adequate model of the mouse circadian activity cycle. The results may have practical significance for the design of human temporal environments.     

The physiological rhythms of subjects living on a day of abnormal length.

1. Fourteen subjects, singly or in groups, have been observed while living on a 21 hr day for 8 or 16 experimental 'days' and fifteen other subjects similarly on a 27 hr day. 2. Rhythmic components of body temperature and excretion of various urinary constituents were calculated. 3. On a 21 hr day, for most components and most subjects, two periods were present, one of 21 hr and one of around or somewhat over 24 hr. 4. On a 27 hr day two periods were less often present and a larger number of observed rhythms could be satisfactorily described by a single period, usually between 23 and 28 hr. 5. In subjects spending a second week on a 21 hr day the circadian component was no less prominent than during the first week. 6. When, after life on a 21 hr day, subjects were deprived of knowledge of time, there was evidence that the 21 hr component did not persist. 7. The results are interpreted as evidence of the continuing existance of an influence with a period of around 24 hr, simultaneously rhythmic influences resulting from the subjects' habits. On a 27 hr day there was sometimes evidence of entrainment, yielding an intermediate period. 8. An attempt is made to compare the relative potency of the exogenous and of the persistent circadian influences on the several variables.     

Superantigen activation and kinetics of cytokines in the Long-Evans rat.

This study was conducted to identify and quantify, over time, selected cytokine responses in Long-Evans rats that were exposed to staphylococcus enterotoxin B (SEB). The kinetics of selected cytokines [interleukin-2 (IL-2), IL-6, interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF)] and phenotype and cell cycle analysis of T lymphocytes were determined in Long-Evans rats administered a single intraperitoneal (i.p.) dose of either 50 microg or 500 microg of SEB. Rats injected with 50 microg SEB had significantly elevated levels of IL-2, IL-6 and IFN-gamma in their serum 2 hr post-injection. IL-2 serum levels were significantly elevated at 2 hr and returned to near control values by 12 hr while both IL-6 and IFN-gamma peaked at 6 hr but remained significantly increased at 24 hr post SEB exposure. A 500 microg dose of SEB did not further enhance these cytokine responses. When spleen cells were collected for culture 2 hr after rats were injected i.p. with 50 microg SEB and cocultured with SEB, TNF and IL-6 levels were significantly increased after 2 hr incubation, while IL-2 and IL-6 were significantly elevated at 6 hr. Production of all these cytokines in spleen cell cultures continued to increase over the 24 hr sampled. Peritoneal cells were collected for culture either at 1 hr or 2 hr after injection of either 50 microg or 500 microg of SEB. IL-6 was significantly increased after 1 hr in culture while TNF was significantly increased by 2 hr regardless of whether the cells were harvested 1 or 2 hr after SEB injection. The greatest response for both IL-6 and TNF occurred when cells from animals injected with 50 microg SEB were restimulated in vitro with SEB. The peak levels for IL-6 were at 12 hr post SEB exposure while TNF peaked at 6 hr. The percentage of CD4+ cells was significantly increased at 48 hr and 72 hr post SEB (50 microg) administration while the percentage of CD8+ cells remained similar to control values for the 168-hr test period. A similar pattern was observed in cell cycling where the CD4+ cells proliferated up to 2 days post SEB injection and then were significantly suppressed at day 3. The CD8+ cells were comparable to control values. These studies demonstrate that the cytokine responses in Long-Evans rats exposed to a superantigen are somewhat similar to those that occur in mice and humans, e.g. a rapid short increase in the production of IFN-gamma and TNF that was accompanied by an increase in the production of IL-2. Additional responses noted in this species, however, were a marked increase in IL-6 production, as well as an early increase in the number and cycling of CD4+ cells followed by a down-regulation of these events. These activities occurred in the absence of notable histopathological alteration of lymphoid organs. The results indicate that the Long-Evans rat is an acceptable animal model to investigate the pathogenesis of superantigen-induced disease and that IL-6 may be an active mediator of this process.     

Delayed-onset deficits in verbal encoding strategies among patients with mild traumatic brain injury

Knowledge obtained from longitudinal animal models was used to predict the course of verbal memory deficits in 19 concussed patients and 19 control patients who were given versions of the Hopkins Verbal Learning Test--Revised at 2 hr, 48 hr, and 1 week postconcussion. The physiological literature suggests that concussed patients should exhibit a decline in performance from 2 hr to 48 hr postconcussion on a measure of complex memory strategies. Consistent with this hypothesis, mixed-factor analysis of covariance revealed that concussed patients used less semantic clustering strategies than control patients at 48 hr postconcussion, whereas minimal differences were found at 2 hr postinjury. Furthermore, a chi-square analysis showed that a significant number of concussed patients experienced a decline in the number of semantic clusters they used from 2 hr to 48 hr. No differences were found between the groups at the 1-week testing session.