The sedative effect of non-alcoholic beer in healthy female nurses

Introduction

The hop (Humulus lupulus L.), a component of beer, is a sedative plant whose pharmacological activity is principally due to its bitter resins, in particular to the α-acid degradation product 2-methyl-3-buten-2-ol. The mechanism of action of hop resin consists of raising the levels of the neurotransmitter γ-aminobutyric acid (GABA), an inhibitory neurotransmitter acting in the central nervous system (CNS).

Objectives

To analyze the sedative effect of hops as a component of non-alcoholic beer on the sleep/wake rhythm in a work-stressed population.

Methods

The experiment was conducted with healthy female nurses (n = 17) working rotating and/or night shifts. Overnight sleep and chronobiological parameters were assessed by actigraphy (Actiwatch®) after moderate ingestion of non-alcoholic beer containing hops (333 ml with 0,0% alcohol) with supper for 14 days (treatment). Data were obtained in comparison with her own control group without consumption of beer during supper.

Results

Actigraphy results demonstrated improvement of night sleep quality as regards the most important parameters: Sleep Latency diminished (p≤0.05) in the Treatment group (12.01±1.19 min) when compared to the Control group (20.50±4.21 min), as also did Total Activity (p≤0.05; Treatment group = 5284.78±836.99 activity pulses vs Control = 7258.78±898.89 activity pulses). In addition, anxiety as indexed by the State-Trait Anxiety Inventory (STAI) decreased in the Treatment group (State Anxiety 18.09±3.8 vs Control 20.69±2.14).

Conclusion

The moderate consumption of non-alcoholic beer will favour night-time rest, due in particular to its hop components, in addition to its other confirmed benefits for the organism.     

Functional diversities of two activity components of circadian rhythm in genetical splitting mice (CS strain)

CS mice, an inbred strain, showed two distinctive characteristics in the circadian rhythm of locomotor activity: (1) large variation in the freerunning period, and (2) spontaneous rhythm splitting under continuous darkness. In the splitting rhythm there was a positive correlation between the freerunning period of the evening component and the activity time of the morning component. The phase-shifting effect of a 15-min light pulse was examined on the two activity components of the splitting rhythm. There were significant differences in the amount of light-induced phase response between the two components. A light pulse during the late subjective night induced a phase advance shift only in the morning component, while a light pulse during the early subjective night induced a phase delay shift only in the evening component. These results indicate functional diversities of the two activity components in the circadian locomotor rhythm of CS mice, and suggest that the circadian system in CS mice consists of two mutually coupled oscillators which have different circadian periods and different responsiveness to light. The CS mouse is a useful model to explore a genetic background of oscillator coupling in the circadian system of nocturnal rodents. Accepted: 19 November 1998     

A comparison of the activity patterns of the sand goby Pomatoschistus minutus (Pallas) from areas of different tidal range

Sand gobies ( Pomatoschistus minutus ) collected from beaches with a large tidal range (Scotland) exhibit a circatidal rhythm of activity in constant conditions in the laboratory. There is no endogenous circadian component to the rhythm. The phasing of the rhythm is such that peak activity occurs at the predicted time of ebb tide. Light-dark (LD) cycles applied in the laboratory have a marked effect on activity greatly enhancing it at night so that the original tidal rhythm becomes nocturnal. Some evidence was obtained that LD cycles can entrain a weak nocturnal circadian rhythm in fish removed from tidal conditions. Contrary to expectations, some fish from beaches with a small and unpredictable tidal range (Oslofjord, Norway) also show a weakly persistent circatidal thythm without an endogenous circadian component, but great variability was noticed between individual fish. Laboratory LD cycles did not entrain a persistent circadian rhythm in the fish from the Oslofjord.     

Measurement and prediction of the susceptibility of lager beer to spoilage by lactic acid bacteria

J.L. FERNANDEZ AND W.J SIMPSON. 1995. The ability of 14 strains of hop-resistant lactic acid bacteria ( Lactobacillus spp., Pediococcus spp.) to grow in 17 different lager beers was assessed using a biological challenge test. All beers were spoiled by at least one strain: all strains could grow in at least one beer. The sensitivity of different beers to spoilage by lactic acid bacteria varied. Spoilage potential could be described in the form of a 'Resistance to Spoilage Value' (RSV) based on the ability of the organisms to grow in each beer. Parameters which correlated to RSV included pH, beer colour and the content of free amino nitrogen, total soluble nitrogen, a range of individual amino acids, maltotriose and the undissociated forms of SO₂ and hop bitter acids. Predictive models based on the technique of partial least squares regression and constructed using values for undissociated SO₂ content, undissociated hop bitter acids content, polyphenol content, maltotriose content, free amino nitrogen content and a colour intensity component allowed RSV to be predicted.     

The Role of Wheel Running in the Coupling of Two Simultaneous Circadian Rhythms of Motor Activity in the Rat

Motor activity is among the non-photic stimuli that act on the internal clock. We have tested the role of motor activity in the circadian pattern of rats under conditions near the lower limits of entrainment, that induce circadian rhythm dissociation. Three groups of 8 rats each were used: a) rats kept individually in 25×25×15 cm cages, b) rats in 50×25×15 cm cages, and c) rats in 50×25×15 cm cages with access to a running wheel. All the rats were kept under light-dark cycles of 22 hours (T22, 11L:11D) for 50 days, after which they were transferred to constant darkness. All the rats without a running wheel showed a motor activity pattern with two statistically significant circadian rhythms in the periodogram of Sokolove and Bushell: one circadian component entrained by the LD cycle, and another free-running. The rats with access to a running wheel showed several patterns: 5 rats showed only one rhythm entrained to the LD cycle, 2 rats showed circadian rhythm dissociation, and 1 showed only a free running rhythm. We believe that the simultaneous manifestation of two circadian components reflects the functional dissociation of the oscillators population that constitutes the circadian pacemaker, of the rat. Physical exercise acts on the pacemaker reinforcing the strongest group of oscillators, which, depending on the structure of the circadian system of the rat, is usually the one entrained to the LD cycle. This study supports the hypothesis that motor activity couples the oscillators that form the circadian system of the rat.     

The Role of Wheel Running in the Coupling of Two Simultaneous Circadian Rhythms of Motor Activity in the Rat

Motor activity is among the non-photic stimuli that act on the internal clock. We have tested the role of motor activity in the circadian pattern of rats under conditions near the lower limits of entrainment, that induce circadian rhythm dissociation. Three groups of 8 rats each were used: a) rats kept individually in 25×25×15 cm cages, b) rats in 50×25×15 cm cages, and c) rats in 50×25×15 cm cages with access to a running wheel. All the rats were kept under light-dark cycles of 22 hours (T22, 11L:11D) for 50 days, after which they were transferred to constant darkness. All the rats without a running wheel showed a motor activity pattern with two statistically significant circadian rhythms in the periodogram of Sokolove and Bushell: one circadian component entrained by the LD cycle, and another free-running. The rats with access to a running wheel showed several patterns: 5 rats showed only one rhythm entrained to the LD cycle, 2 rats showed circadian rhythm dissociation, and 1 showed only a free running rhythm. We believe that the simultaneous manifestation of two circadian components reflects the functional dissociation of the oscillators population that constitutes the circadian pacemaker, of the rat. Physical exercise acts on the pacemaker reinforcing the strongest group of oscillators, which, depending on the structure of the circadian system of the rat, is usually the one entrained to the LD cycle. This study supports the hypothesis that motor activity couples the oscillators that form the circadian system of the rat.     

Tamoxifen-Induced Cre-loxP Recombination Is Prolonged in Pancreatic Islets of Adult Mice

Tamoxifen (Tm)-inducible Cre recombinases are widely used to perform gene inactivation and lineage tracing studies in mice. Although the efficiency of inducible Cre-loxP recombination can be easily evaluated with reporter strains, the precise length of time that Tm induces nuclear translocation of CreER(Tm) and subsequent recombination of a target allele is not well defined, and difficult to assess. To better understand the timeline of Tm activity in vivo, we developed a bioassay in which pancreatic islets with a Tm-inducible reporter (from Pdx1(PB)-CreER(Tm);R26R(lacZ) mice) were transplanted beneath the renal capsule of adult mice previously treated with three doses of 1 mg Tm, 8 mg Tm, or corn oil vehicle. Surprisingly, recombination in islet grafts, as assessed by expression of the β-galactosidase (β-gal) reporter, was observed days or weeks after Tm treatment, in a dose-dependent manner. Substantial recombination occurred in islet grafts long after administration of 3×8 mg Tm: in grafts transplanted 48 hours after the last Tm injection, 77.9±0.4% of β-cells were β-gal+; in β-cells placed after 1 week, 46.2±5.0% were β-gal+; after 2 weeks, 26.3±7.0% were β-gal+; and after 4 weeks, 1.9±0.9% were β-gal+. Islet grafts from mice given 3×1 mg Tm showed lower, but notable, recombination 48 hours (4.9±1.7%) and 1 week (4.5±1.9%) after Tm administration. These results show that Tm doses commonly used to induce Cre-loxP recombination may continue to label significant numbers of cells for weeks after Tm treatment, possibly confounding the interpretation of time-sensitive studies using Tm-dependent models. Therefore, investigators developing experimental approaches using Tm-inducible systems should consider both maximal recombination efficiency and the length of time that Tm-induced Cre-loxP recombination occurs.     

Analysis of the Mechanism underlying the Rhythm Reversal from Diurnal to Nocturnal in the Cricket Gryllus bimaculatus, with Special Reference to the Role of Serotonin

The cricket, Gryllus bimaculatus, shows a rhythm reversal from diurnal to nocturnal in about a week after the imaginal molt. In the present study, we investigated the role of serotonin (5-HT) in the rhythm reversal. The 5-HT content in the brain measured by HPLC equipped with an electrochemical detector gradually increased after the imaginal molt, and in fully nocturnal adults it was about 2 times of nymphal level. We then examined the effects of 5,7-dihydroxytryptamine (5,7-DHT), a selective neurotoxine to serotonergic neurons, on the locomotor rhythm. In most animals with 5,7-DHT (25 muM or 250 muM, 32.2 nl) injected into the brain, daytime activity significantly increased even after the rhythm reversal, while nighttime activity was not significantly affected, forming rather diurnal pattern. The serotonin content in the brain of animals injected with 250 muM 5,7-DHT was reduced by about 30%. On the basis of these results, possible involvement of 5-HT in the neural mechanism controlling the locomotor rhythm is discussed.     

内蒙古草原小毛足鼠的活动性、代谢特征和体温的似昼夜节律

小毛足鼠(Phodopus roborovskii)是分布在内蒙古草原沙地的一种小型哺乳动物,关于其生物学和生态学特征,尤其是生理学特征还知之甚少。似昼夜节律是动物行为学和生理生态学中备受关注的一个领域。在室内条件下通过体内埋置无线电传感器连续监测小毛足鼠的体温、用自动监测系统连续监测活动性和TSE LabMaster呼吸代谢测定系统连续测定了其代谢率的昼夜节律性。结果发现:小毛足鼠在夜间的平均体温是(37.27±0.39)℃,昼间的平均体温是(36.11±0.18)℃;在夜间的平均代谢率是(4.65±1.10)mLO2·g-1·h-1,昼间的平均代谢率是(3.09±0.42)mLO2·g-1·h-1;在夜间的平均活动率为(237±145)次/0.1h,昼间的平均活动率为(38±5)次/0.1h。小毛足鼠的代谢率、活动性和体温的峰值相位主要集中在夜间,属典型的夜行性动物。实验结果从行为学特性和生理学特征等新的角度支持了野外观察小毛足鼠是夜行性动物的推断。综合活动性、代谢率和体温三方面同步变化的特征,为小毛足鼠的似昼夜节律变化提供了新的机理性解释。研究也表明小毛足鼠是研究野生动物似昼夜节律变化机理的好模型。     

Ring the bell for Matins: circadian adaptation to split sleep by cloistered monks and nuns

Cloistered monks and nuns adhere to a 10-century-old strict schedule with a common zeitgeber of a night split by a 2- to 3-h-long Office (Matins). The authors evaluated how the circadian core body temperature rhythm and sleep adapt in cloistered monks and nuns in two monasteries. Five monks and five nuns following the split-sleep night schedule for 5 to 46 yrs without interruption and 10 controls underwent interviews, sleep scales, and physical examination and produced a week-long sleep diary and actigraphy, plus 48-h recordings of core body temperature. The circadian rhythm of temperature was described by partial Fourier time-series analysis (with 12- and 24-h harmonics). The temperature peak and trough values and clock times did not differ between groups. However, the temperature rhythm was biphasic in monks and nuns, with an early decrease at 19:39 ± 4:30 h (median ± 95% interval), plateau or rise of temperature at 22:35 ± 00:23 h (while asleep) lasting 296 ± 39 min, followed by a second decrease after the Matins Office, and a classical morning rise. Although they required alarm clocks to wake-up for Matins at midnight, the body temperature rise anticipated the nocturnal awakening by 85 ± 15 min. Compared to the controls, the monks and nuns had an earlier sleep onset (20:05 ± 00:59 h vs. 00:00 ± 00:54 h, median ± 95% confidence interval, p= .0001) and offset (06:27 ± 0:22 h, vs. 07:37 ± 0:33 h, p= .0001), as well as a shorter sleep time (6.5 ± 0.6 vs. 7.6 ± 0.7 h, p= .05). They reported difficulties with sleep latency, sleep duration, and daytime function, and more frequent hypnagogic hallucinations. In contrast to their daytime silence, they experienced conversations (and occasionally prayers) in dreams. The biphasic temperature profile in monks and nuns suggests the human clock adapts to and even anticipates nocturnal awakenings. It resembles the biphasic sleep and rhythm of healthy volunteers transferred to a short (10-h) photoperiod and provides a living glance into the sleep pattern of medieval time.     

Between-session reliability of four hop tests and the agility T-test

The purposes of this study were firstly to investigate whether learning affects were present in the administration of 4 hop tests and the Agility T-test and secondly to assess the between-session reliability of these tests. Twenty-two recreational athletes (11 women: age 22.3 ± 3.7 years, height 167.7 ± 6.2 cm, weight 59.2 ± 6.9 kg and 11 men: age 22.8 ± 3.1 years, height 179.8 ± 4 cm, weight 79.6 ± 10 kg) took part in the study. The subjects performed 6 repetitions of each hop test and 4 repetitions of the Agility T-test once a week over a period of 3 weeks. Distances were normalized to leg length and presented as a percentage value for the single, triple and crossover hop. Results showed that there were significant differences in scores between genders and that learning affects were present in all tests. Intraclass correlation coefficients ranged from 0.76 to 0.92 for the hop tests and 0.82 to 0.96 for the Agility T-test. The results indicated that the hop and Agility T-tests are reliable tests for use with subjects in a clinical or team sport environment. The error measurement statistics presented could be of help to practitioners to determine whether changes in individuals' scores in the hop and Agility T-tests are because of a true change in performance or measurement error. Of most importance was the fact that all subjects achieved at least 90% limb symmetry index on all 4 hop tests. Therefore, we recommend that a minimum limb symmetry value of 90%, rather than previously recommended 85%, should be adopted during rehabilitation and conditioning.     

Central nervous activity of elenoside.

Elenoside is a cytotoxic arylnapthalene lignan (NSC 644013-W/1) derived from Justicia hyssopifolia (Family: Acanthaceae). The neuropharmacological activity of this lignan, a beta-D-glucoside was studied. The LD50 (24 h) of elenoside in mice is 305 +/- 7 mg/kg by i.p. route. In the present study elenoside was given to rats at doses of 25 and 50 mg/kg, and its effects on locomotor activity (Varimex test), muscular relaxant activity, open-field test and with chlorpromazine, 10 mg/kg was compared. On Varimex test, spontaneous activity was reduced. Elenoside produced a reduction in the permanence time on muscular relaxant activity (traction test). On open-field test, ambulation and rearing were reduced compared with the control group and an increase in boluses of dose-dependent rate was obtained. Thus it can be concluded that elenoside has central sedative effects and possible application in anxiety conditions.     

Reduction of the sevoflurane minimum alveolar concentration induced by methadone, tramadol, butorphanol and morphine in rats

This study aimed to estimate the reduction in the minimum alveolar concentration (MAC) of sevoflurane induced by low and high doses of methadone (5 and 10 mg/kg), tramadol (25 and 50 mg/kg), butorphanol (5 and 10 mg/kg) or morphine (5 and 10 mg/kg) in the rat. A control group received normal saline. Sixty-three adult male Sprague-Dawley rats were anaesthetized with sevoflurane (n = 7 per group). Sevoflurane MAC was then determined before and after intraperitoneal administration of the opioids or saline. The duration of the sevoflurane MAC reduction and basic cardiovascular and respiratory measurements were also recorded. The baseline MAC was 2.5 (0.3) vol%. Methadone, tramadol and morphine reduced the sevoflurane MAC (low dose: 31 ± 10, 38 ± 15 and 30 ± 13% respectively; high dose: 100 ± 0, 83 ± 17 and 77 ± 25%, respectively) in a dose-dependent manner. The low and high doses of butorphanol reduced the sevoflurane MAC to a similar extent (33 ± 7 and 31 ± 4%, low and high doses, respectively). Two rats developed apnoea following administration of high-dose butorphanol and methadone. These anaesthetic-sparing effects are clinically relevant and may reduce the adverse effects associated with higher doses of inhalational anaesthetics.     

Entrainment of Circadian Wheel-Running Rhythms of the Northern Brown Bandicoot, Isoodon macrourus, by Daily Restricted Feeding Schedules

Northern brown bandicoots (Isoodon macrourus) were subjected to restricted feeding for 3 h in the middle of the light period of a 14: 10 light/dark cycle and immediately following this in constant dark. When feeding was restricted to the middle of the light period of the light/dark cycle, all bandicoots maintained a nocturnal activity rhythm. In addition to the nocturnal rhythm, a few bandicoots showed meal-anticipatory activity during the light period. In bandicoots that did not show meal-anticipatory activity, diurnal activity was sometimes evident either during or shortly after the daily meal time. The observation of meal-anticipatory activity in some bandicoots suggests that this species may have a mechanism separate from the light-entrainable mechanism that allows the daily anticipation of periodically available food sources. In the next stage of the experiment, which was in constant dark, the meal was presented at the same time of day as it had been in the previous stage. In all bandicoots, the previously light-entrained component of activity free-ran and was eventually affected by the restricted feeding schedule to some degree. Bandicoots showed weak entrainment and relative coordination, suggesting that restricted feeding is a weak zeitgeber in this species. Evidence also suggesting that two separate but coupled pacemakers control the activity rhythms of the bandicoot was that (a) bandicoots simultaneously showed free-running light-entrainable rhythms and meal-entrained anticipatory rhythms; (b) in several bandicoots, the light-entrainable rhythm was phase advanced when it free-ran through the meal time; and (c) in one bandicoot, meal-entrained anticipatory activity was forced away from the meal time when the previously light-entrained component of activity free-ran through it.     

Effects of pulsed electric fields on inactivation and metabolic activity of Lactobacillus plantarum in model beer

AIMS: Inactivation and sublethal injury of Lactobacillus plantarum at different pulsed electric field (PEF) strengths and total energy inputs were investigated to differentiate reversible and irreversible impacts on cell functionality. METHODS AND RESULTS: Lactobacillus plantarum was treated with PEF in model beer (MB) to determine critical values of field strength and energy input for cell inactivation. Below critical values, metabolic activity and membrane integrity were initially reduced without loss of viability. Above critical values, however, irreversible cell damage occurred. Presence of nisin or hop extract, during PEF treatment, resulted in an additional reduction of cell viability by 1;5 log cycles. Also, addition of the hop extract resulted in an additional two log cycles of sublethal injury. Partial reversibility of membrane damage was observed using propidium iodide (PI) uptake and staining. Inoculated MB containing hops was stored after PEF to evaluate the efficacy of such treatment for beer preservation. CONCLUSION: Cells were inactivated only above critical values of 13 kV x cm(-1) and 64 kJ x kg(-1); below these values cell damage was reversible. Storage experiments revealed that surviving cells were killed after 15 h storage in MB containing hops. SIGNIFICANCE AND IMPACT OF THE STUDY: Both reversible and irreversible cell damage due to PEF treatment was detected, depending on specific treatment conditions. The combination of PEF and hop addition is a promising nonthermal method of preservation for beer.     

Role of Plasmids in Lactobacillus brevis BSO 464 Hop Tolerance and Beer Spoilage

Specific isolates of lactic acid bacteria (LAB) can grow in the harsh beer environment, thus posing a threat to brew quality and the economic success of breweries worldwide. Plasmid-localized genes, such as horA, horC, and hitA, have been suggested to confer hop tolerance, a trait required for LAB survival in beer. The presence and expression of these genes among LAB, however, do not universally correlate with the ability to grow in beer. Genome sequencing of the virulent beer spoilage organism Lactobacillus brevis BSO 464 revealed the presence of eight plasmids, with plasmids 1, 2, and 3 containing horA, horC, and hitA, respectively. To investigate the roles that these and the other five plasmids play in L. brevis BSO 464 growth in beer, plasmid curing with novobiocin was used to derive 10 plasmid variants. Multiplex PCRs were utilized to determine the presence or absence of each plasmid, and how plasmid loss affected hop tolerance and growth in degassed (noncarbonated) beer was assessed. Loss of three of the eight plasmids was found to affect hop tolerance and growth in beer. Loss of plasmid 2 (horC and 28 other genes) had the most dramatic effect, with loss of plasmid 4 (120 genes) and plasmid 8 (47 genes) having significant, but smaller, impacts. These results support the contention that genes on mobile genetic elements are essential for bacterial growth in beer and that beer spoilage ability is not dependent solely on the three previously described hop tolerance genes or on the chromosome of a beer spoilage LAB isolate.     

Opposite effects of tryptophan intake on motor activity in ring doves (diurnal) and rats (nocturnal)

The role of l-tryptophan as precursor of serotonin and melatonin synthesis on activity-rest rhythm was studied in ring doves, Streptopelia risoria, as a representative of diurnal animals and rats, Rattus norvegicus, as a typical nocturnal one. The animals were housed in cages equipped for horizontal activity recording in a thermostatized chamber and submitted to a 12/12h light/dark photoperiod (lights on at 08:00 h). After acclimatization, the animals received vehicle (methylcellulose) and l-tryptophan (240 mg/kg) by esophagic cannula 2h before the onset of either light or dark phase. Also, oral melatonin (2.5mg/kg) was tested for comparative purposes. After nocturnal l-tryptophan administration, rats showed increased activity (149%), while the opposite occurred in ring doves (39% decrease). No significant changes were found after diurnal l-tryptophan intake in either species. Melatonin produced effects similar to those of l-tryptophan. These results suggest that the effects of l-tryptophan administration are dependent on the nocturnal/diurnal habits of the studied species and, most probably, are mediated by increased melatonin synthesis.     

An investigation of the role of kappa opiate receptor agonists in the initiation of feeding

A large body of evidence has suggested a role for the endogenous opiates and their receptors in the regulation of appetite. In this study we have examined the relative effects of ketocyclazocine (KC), cyclazocine and ethylketocyclazocine, all putative kappa opiate receptor agonists, and morphine, a putative mu receptor agonist, on food consumption. All the kappa agonists induced feeding when administered at 8 AM as did morphine. KC failed to induce feeding during the nocturnal feeding period (2000 and 0200 hours) and morphine suppressed feeding at these times. KC and morphine suppressed starvation induced feeding when food was made available immediately after injection and had no effect when food was presented 2 and 4 hours after injection. High doses of naloxone (5 mg/kg) suppressed KC induced feeding while actually enhancing high dose morphine (25 mg/kg) induced feeding. Repeated injections of KC or morphine for 5 days resulted in enhancement of the feeding response with initiation of feeding occuring earlier. Taken together with the studies showing that the endogenous kappa ligand, dynorphin, enhabces feeding the most parsimonious interpretation of these studies is that kappa agonists are endogenous initiators of feeding and that kappa receptors are maximally saturated at times of food deprivation and during spontaneous feeding. The mu (or one of the other) opiate receptors inhibit feeding due to their sedative effect and antagonism of this effect leads to enhancement of the feeding response. It is postulated that kappa opiate receptors represent an important component of the natural feeding drive.     

Seasonality of the endogenous activity rhythm in Talitrus saltator (Montagu) from a sandy beach in northeastern Tunisia

The endogenous activity of the sandhopper Talitrus saltator (Montagu) has been investigated in a population from a relatively exposed beach in northeast Tunisia. The animals were found to exhibit a nocturnal circadian rhythm of locomotor activity, with no evidence of a circatidal component. The rhythm was monitored in individual animals over the four seasons, under constant laboratory conditions and seasonal variation in free-running period; the signal-to-noise ratio and waveform of the rhythm have been investigated, as well as the incidence of rhythmic animals in the population. The variation in these rhythm parameters is considered in relation to changes in environmental conditions prevailing at the site of collection.     

中缅树鼩体温、代谢率和蒸发失水日节律

为研究中缅树鼩(Tupaia belangeri)体温、代谢率和蒸发失水的日节律变化,采用植入式体温计测定了中缅树鼩24 h的体温,以及24 h中4个时间段(05:00～07:00时、11:00～13:00时、17:00～19:00时和23:00～01:00时)热中性区(30℃)的静止代谢率(RMR)、非颤抖性产热(NST)和蒸发失水(EWL)。结果显示,中缅树鼩的体温具有日节律变化,最高值和最低值分别出现在11:00时和03:00时,各为(39.45±0.26)℃和(36.34±0.24)℃;静止代谢率、非颤抖性产热和蒸发失水在4个时间段都有显著差异,表现出显著的日节律变化,代谢率在23:00～01:00时最大,O2含量为(2.58±0.04)ml/(g.h),在11:00～13:00时最小,O2含量为(2.28±0.09)ml/(g.h);非颤抖性产热在05:00～07:00时最大,O2含量为(3.08±0.14)ml/(g.h),在11:00～13:00最小,O2含量为(2.69±0.63)ml/(g.h);蒸发失水在17:00～19:00时最大,失水量为(3.60±0.31)mg/(g.h)。结果表明,体温的日节律变化主要与环境温度的日节律变化和下午出窝取食活动性增强有关;当夜晚环境温度相对较低的时候,通过增强静止代谢率和非颤抖性产热来增加产热,而白天环境温度相对较高的时候,通过增强蒸发失水散热来调节体温。