Sleep deprivation alters the cell population kinetics in the jejunum of the male Syrian hamster (Mesocricetus auratus)

The proliferative and functional units of the jejunum were studied every 3 hr during 24 hr in groups of control and sleep-deprived hamsters. Peaks in kinetic parameters were evident during the sleep period in control hamsters; in the absence of sleep, peak values were significantly reduced. Sleep deprivation was associated with reduction of G2 to M flux and reduction of the circadian rhythm in mitotic index from 74% to 25%. The reduction in the number of cells passing through M was reflected by a drop in labelling index 9 hr later. These findings are consistent with the theory that sleep promotes restorative processes.     

Homeostatic regulation of sleep in arrhythmic Siberian hamsters

Sleep is regulated by independent yet interacting circadian and homeostatic processes. The present study used a novel approach to study sleep homeostasis in the absence of circadian influences by exposing Siberian hamsters to a simple phase delay of the photocycle to make them arrhythmic. Because these hamsters lacked any circadian organization, their sleep homeostasis could be studied in the absence of circadian interactions. Control animals retained circadian rhythmicity after the phase shift and re-entrained to the phase-shifted photocycle. These animals displayed robust daily sleep-wake rhythms with consolidated sleep during the light phase beginning about 1 h after light onset. This marked sleep-wake pattern was circadian in that it persisted in constant darkness. The distribution of sleep in the arrhythmic hamsters over 24 h was similar to that in the light phase of rhythmic animals. Therefore, daily sleep amounts were higher in arrhythmic animals compared with rhythmic ones. During 2- and 6-h sleep deprivations (SD), it was more difficult to keep arrhythmic hamsters awake than it was for rhythmic hamsters. Because the arrhythmic animals obtained more non-rapid eye movement sleep (NREMS) during the SD, they showed a diminished compensatory response in NREMS EEG slow-wave activity during recovery sleep. When amounts of sleep during the SD were taken into account, there were no differences in sleep homeostasis between experimental and control hamsters. Thus loss of circadian control did not alter the homeostatic response to SD. This supports the view that circadian and homeostatic influences on sleep regulation are independent processes.     

The Circadian Variations In the Eithelial Growth of the Hamster Cheek Pouch: Quantitative Analysis of Dna Distributions*

The pronounced diurnal rhythm in DNA distribution of the hamster check pouch epithelium both in the S fraction and in the (G₂+ M) fraction was compared with previous studies of the changes in tritiated thymidine labelling index and mitotic activity. the DNA distributions were obtained by flow cytometry after ultrasonic disaggregation of the isolated epithelium into a suspension of single nuclei. the DNA distributions were analysed with the computer program of J. Fried (1976) and by planimetry. the S fraction was higher than the autoradiographic labelling index during the whole 24 hr period. Only the computer fitted S fraction and the labelling index had the same difference between maximal and minimal values, and maxima at the same time of day. the DNA distributions showed a diurnal release of G₁ cells into S phase proceeding through (G₂+ M) phase and returning to G₁ phase within a 24 hr period.     

Fertilizing ability in vitro of golden hamster spermatozoa after acute testicular X-irradiation]

The present study is concerned with the effect of radiation to the testis on fertilizing ability in vitro using golden hamster spermatozoa. Male hamsters at 6 and 8 weeks of age were given acute testicular X-irradiation (200 kVp, 20 mA, 0.47-0.48 Gy/min). Spermatozoa were collected from the cauda epididymides at different times after irradiation and then they were suspended in fertilization medium. After preincubation for 4-5 hr, the spermatozoa were cultured with the eggs collected from mature hamsters treated with PMSG-hCG. Fertilized eggs were examined for incidence of sperm penetration and formation of pronuclei at 4-5 hr after insemination. The fertilization rate (47.7%) at the 6th week after irradiation with a dose of 2 Gy was much lower in comparison with the control value (92.6%). However, the fertilization rates at the 3rd and 9th weeks after irradiation were 97.7 and 90.6%, respectively. In these period, no difference was found between the irradiated groups and the control groups. From the changes in sperm concentration after irradiation with a dose of 2 Gy, it was found that the fertilization rate was the lowest at the 6th week. The sensitive stage to radiation during spermatogenesis with reference to the reduction of fertilizing ability after irradiation coincides with that of decrease in the sperm concentration and sperm motility. The results of fertilization rate at the 6th week after different doses of X-irradiation (0.25-6 Gy) indicated that the reduction of fertilization rate is nearly expressed as a dose-response relationship.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sleep: sequential reduction of paradoxical (REM) and elevation of slow-wave (NREM) sleep by a non-convulsive dose of insulin in rats

Administration of a single non-convulsive dose of insulin (1.0, I.U./kg., I.P.) which produced no observable gross behavioral changes in rats, reduced rapid eye movement (REM) sleep time 100% in the first 3 hrs. and 82% by the 4th hr., reaching control subject levels (saline-treated) by the 6th hr. In contrast, slow-wave sleep (NREM) time in insulin treated animals exceeded control subject levels by 49% by the end of the 2nd hr., returning to normal by the 5th hr. Although there was no difference between insulin and saline treated rats for the total 8 hr. post-injection recording period for total percentage of time awake, or slow-wave sleep time, a 44% reduction in REM sleep time was observed in insulin treated animals compared to that of a saline treated control. The significance of these findings are discussed in terms of known neurochemical changes i.e., an increase of both brain tryptophan and serotonin in rats, induced by a subconvulsive dose of exogenous insulin.     

Lipolytic and antilipolytic responses of the Siberian hamster (Phodopus sungorus sungorus) white adipocytes after weight loss induced by short photoperiod exposure

Short day photoperiod promotes thermogenesis and extensive weight loss in Siberian hamsters (Phodopus sungorus sungorus). To determine whether a change in hormone-sensitive lipolysis occurs after short-photoperiod exposure, some lipolytic responses were measured on white adipocytes isolated from animals exposed in warm conditions to short or Long daylight photoperiod. The body mass of male Siberian hamsters exposed during 11 weeks to short days (SD; light: dark, 6:18 hr) reached only 50% of those kept in long days (LD; 16: 8 hr). In SD-hamsters, adipose depot mass also represented approximately 50% of the LD group. A lower DNA content was observed in intra-abdominal fat pads of SD-hamsters. Lipolytic responses to noradrenaline, adrenaline, isoproterenol and ACTH were unchanged. However, sensitivity to the beta-3 adrenergic agonist, BRL 37344, was moderately increased. The major component of the adrenergic control of lipolysis was mediated by beta-3 adrenoceptors in both LD- and SD-Siberian hamsters. The limited antilipolytic effect of alpha-2 adrenergic agonists, PYY or insulin was rather surprising in Siberian hamsters since these inhibitory systems are efficient in hibernants and other photoperiod-sensitive rodents. Our results show that, after short photoperiod exposure, white adipose tissue mass and DNA content are reduced, especially in the epididymal fat pad, with only minor changes in the adipocyte sensitivity to lipolytic hormones.     

Diurnal Variation in Subjective and Objective Measures of Sleepiness: the Effects of Sleep Reduction and Circadian Type

In young, good sleepers the diurnal evolution of alertness was studied as a function of degree of morningness: (1) during habitual sleep routine and (2) in a 2-hr sleep reduction protocol. During habitual sleep routine, alertness was assessed using both the subjective evaluation based on Thayer's Activation Deactivation Adjective Checklist (43 subjects) and the objective measurement of sleep latency (Multiple Sleep Latency Test, MSLT). Self-alertness scored highest around midday. Later it showed a dip, then stayed on a plateau until about 2200 hr. On average, 77+ of the subjects fell asleep at the 1400 hr MSLT session while only 35.5+ did at 1000 hr and 25.8+ at 2000 hr. Morning-types (MT) and evening-types (ET) differed only during the morning: ET fell asleep more frequently at 1000 hr and 1200 hr and rated lower self-alertness on arising than did MT. Twelve subjects were given the protocol of a 2-hr sleep reduction (both in delayed bedtime and advanced rising time conditions). At 0700 hr, MT rated their alertness lower when they had only just gotten up (delayed bedtime condition) than when they had been awake for 2 hr (advanced rising time condition). In contrast, ET had the same low level of alertness at 0800 hr, independent of the time elapsed since arising. On average the advanced rising time condition affected the general pattern of alertness more than did delayed bedtime.     

Sleep and EEG spectra in the Syrian hamster (Mesocricetus auratus) under baseline conditions and following sleep deprivation

Summary Sleep was studied by continuous 24-h recordings in adult male Syrian hamsters, chronically implanted with EEG and EMG electrodes. Three vigilance states were determined using visual scoring and EEG power spectra (0.25–25 Hz) computed for 4-s episodes.The effects of two methods of total sleep deprivation (SD) were examined on vigilance states and the EEG power spectrum. The animals were subjected to 24 h SD by: (1) forced locomotion in a slowly rotating drum, (2) gentle handling whenever the hamsters attempted a sleeping posture. In addition, the hamsters were subjected to SD by handling during the first 3 h of the L period.Sleep predominated in the L period (78.2% of 12 h) and the D period (51.2%). The power spectra of the 3 vigilance states were similar during the L and D period. In NREM sleep, power density values in the low frequency range (0.25–6.0 Hz) exceeded those of REM sleep and W by a maximum factor of 8.3 and 2.8, respectively. At frequencies above 16 Hz, NREM and REM sleep power density values were significantly lower than during W. A progressive decrease in power density for low EEG frequencies (0.25–7 Hz) during NREM sleep was seen in the course of the L period. Power density values of higher frequencies (8–25 Hz) increased at the end of the L period and remained high during the first hours of the D period.The effect of prolonged SD on vigilance states and EEG spectra was similar by both methods and strikingly small compared to similar results in rats. In contrast, 3 h SD induced a large and more prolonged effect. The similarities and differences of sleep and sleep regulation are summarized for the hamster, rat and man.Abbreviations EEG electroencephalogram - LD light dark - REM rapid eye movements - NREM sleep non REM sleep - W waking - SD sleep deprivation - TST total sleep time - L light - D dark     

A comparative study of adrenal progesterone secretion during the estrous cycles of hamsters and rats

Adrenal secretory rates and peripheral plasma levels of progesterone (PROG) were determined during the estrous cycles of hamsters and 4-day cyclic rats. In both species, the PROG concentrations in peripheral plasma were never more than 6% of those observed in adrenal venous plasma. In hamsters, adrenal PROG secretory rates varied from 3.8 ± 0.8 ng/min at 0800 hr on proestrus (P) to 8.5 ± 1 ng/min at 2000 hr on estrus (E). The rates noted on P were among the lowest observed and were similar to those noted at 0800 hr the following morning. In rats, adrenal PROG secretory rates varied from 57 ± 9 ng/min at 0800 hr on E to 130 ± 18 ng/min at 2000 hr on P. A significant decline occurred between 2000 hr on P and 0800 hr the following morning. Rats secreted 3 to 8 times more PROG than did hamsters when the secretory rates are expressed as ng/min/100 mg adrenal. In hamsters, the data suggest a relative lack of influence of female reproductive hormones on adrenal PROG secretion and in turn the latter may not be involved in reproductive hormonal changes leading to ovulation. In rats, the increased adrenal PROG secretion noted on P may be due to the influence of reproductive hormones on adrenocortical function. This elevated rate may in turn influence the hypothalamo-hypophyseal-ovarian axis.     

Diurnal Variation in Subjective and Objective Measures of Sleepiness: the Effects of Sleep Reduction and Circadian Type

In young, good sleepers the diurnal evolution of alertness was studied as a function of degree of morningness: (1) during habitual sleep routine and (2) in a 2-hr sleep reduction protocol. During habitual sleep routine, alertness was assessed using both the subjective evaluation based on Thayer's Activation Deactivation Adjective Checklist (43 subjects) and the objective measurement of sleep latency (Multiple Sleep Latency Test, MSLT). Self-alertness scored highest around midday. Later it showed a dip, then stayed on a plateau until about 2200 hr. On average, 77+ of the subjects fell asleep at the 1400 hr MSLT session while only 35.5+ did at 1000 hr and 25.8+ at 2000 hr. Morning-types (MT) and evening-types (ET) differed only during the morning: ET fell asleep more frequently at 1000 hr and 1200 hr and rated lower self-alertness on arising than did MT. Twelve subjects were given the protocol of a 2-hr sleep reduction (both in delayed bedtime and advanced rising time conditions). At 0700 hr, MT rated their alertness lower when they had only just gotten up (delayed bedtime condition) than when they had been awake for 2 hr (advanced rising time condition). In contrast, ET had the same low level of alertness at 0800 hr, independent of the time elapsed since arising. On average the advanced rising time condition affected the general pattern of alertness more than did delayed bedtime.     

ALTERATION OF NEONATAL RAT PAROTID GLAND ACINAR CELL PROLIFERATION BY GUANETHIDINE-INDUCED SYMPATHECTOMY

Newborn rats were injected with guanethidine-sulfate (20 μg/g body weight) every 48 hr from 12 hr after birth until day 14 (eight injections per animal). The guanethidine treatment resulted in an 86% absolute reduction in cell number in the superior cervical ganglia of 15 day old rats. The cells which remained after guanethidine treatment showed destruction of mitochondria and an extensive decrease in endoplasmic reticulum. Chemical sympathectomy with guanethidine induced a 3.1 hr lengthening of the acinar cell generation cycle time (17.4 hr to 20.5 hr), resulting from a longer G₁ period (6.9 hr in the control group as compared to 10.5 hr in the guanethidine-treated group), as well as a decrease in the mean percentage of [³H]thymidine-labeled acinar cells (22.3 ± 0.5% to 19.3 ± 0.5%) and mean acinar cell mitotic index (2.6 ± 0.2% to 2.1 ± 0.1%). A circadian rhythm was found to exist in parotid gland acinar cell mitotic activity of 15 day old rats and the amplitude of the rhythm was reduced from 26.5% to 14.9% in guanethidine-treated rats. This study indicates that the diminution of sympathetic influence on the developing parotid gland results in a slight, but significant alteration in acinar cell proliferation.     

Flow cytometric analysis of adriamycin-perturbed mouse mammary tumors.

The effects of a single intraperitoneal injection of adriamycin (10 mg/kg) on a fast-growing C3H mouse mammary tumor (S102F) have been analyzed volumetrically, biochemically, autoradiographically and flow cytometrically. Mathematical simulation of the data was also used to aid in the interpretation of the recovery kinetics. This dose of adriamycin did not induce regression in tumor volume but did inhibit the growth rate for 4-5 days. 3H-TdR incorporation was gradually inhibited to reach a low of 20% of control at 24 and 36 hr and then recovered back to control by 96 hr after adriamycin treatment. The flow cytometric analysis also showed a marked reduction in the relative fraction of cells in the S-phase with a minimum of 23% of control at 72 hr; however, in contrast to the 3H-TdR incorporation data, the fraction of cells in the S-phase was only at 39% of control at 96 hr after the adriamycin injection. Since the 3H-TdR incorporation data disagreed with the flow cytometry data, autoradiographic analysis was also done at selected times after the adriamycin injections, and qualitatively, this analysis confirms the flow cytometry data in that the labeling index was 29% of control at 96 hr after adriamycin. The mitotic index also dropped from 8 to 1%, respectively, for controls and at 96 hr posttreatment. The degenerate index was about 1% in control tumors and no increase was observed in treated tumors. Adriamycin-induced cell-cycle delay occurs predominately in G1 and G2 but there is also an apparent minor delay in the transit across the S-phase and some apparent cytotoxicity in G2 and/or M. The long delay in volumetric growth appears to be due to the extended cell-cycle delay rather than extensive cell killing.     

Modulation of leptin sensitivity by short photoperiod acclimation in the Djungarian hamster, Phodopus sungorus

During seasonal acclimation, Djungarian hamsters spontaneously exhibit a reduction in food intake, body mass and body fat stores, which is externally cued by shortening of day length in autumn and controlled by a sliding set-point. We investigated the function of the leptin adipostatic feedback system in the photoperiodic control of seasonal acclimation. In response to mouse recombinant leptin injections for 10 days, long day photoperiod (LD) and short day photoperiod (SD)-acclimated hamsters decreased food intake and body mass. The reduction of body mass was due to the depletion of body fat, as revealed by carcass composition analysis. In SD hamsters, leptin caused a larger reduction of body fat mass than observed under LD conditions, whereas the anorectic effect was similar in both photoperiods. The serum leptin concentration was 9.3 ± 1.2 ng/ml in LD-acclimated hamsters and decreased significantly to 4.2 ± 0.8 ng/ml and 2.1 ± 0.6 ng/ml in hamsters exposed to SD for 66 days and 116 days, respectively (P < 0.001). A strong positive correlation between total body fat mass and serum leptin concentration was found (r _S=0.935, P < 0.0001, n=70). Despite the anorectic action of exogenous leptin, higher endogenous leptin levels in LD hamsters were paralleled by higher food intake in LD hamsters as compared to SD hamsters. This paradoxical finding further supports the increased leptin sensitivity in SD hamsters as judged from leptin treatment experiments. We tested the functional significance of leptin for the controlled down-regulation of food intake and body mass induced by short photoperiod. Food restriction for 10 days during the transition phase decreased body mass below the desired sliding set-point, which was recovered in control hamsters following ad libitum refeeding. Treatment with mouse recombinant leptin during ad libitum refeeding inhibited the recovery of body mass and blunted the increase of food intake observed in controls, indicating that the sliding set-point utilizes leptin as a signal for the adjustment of the appropriate body mass level. Accepted: 15 October 1999     

Replacement of media in cell culture alters oxygen toxicity: Possible role of lipid aldehydes and glutathione transferases in oxygen toxicity

Replacement of media in cell cultures during exposure to hyperoxia was found to alter oxygen toxicity. Following 100 hr of exposure to 95% or 80% O₂, the surviving fraction (SF) of Chinese hamster fibroblasts, as assayed by clonogenicity, was less than 1 × 10^?3 when the culture media was replaced only at the onset of the O₂ exposure. Media replacement every 24 hr throughout the hyperoxic exposure resulted in SFs of 1.7 × 10^?1 (95% O₂) and 1.9 × 10^?1 (80% O₂) at 95 hr. Cellular resistance to and metabolism of 4-hydroxy-2-nonenal (4HNE), a cytotoxic byproduct of lipid peroxidation, was examined in cells 24 hr following exposure to 80% O₂ for 144 hr with media replacement. These O₂-exposed cells were resistant to 4HNE, requiring 2.6 times as long in 80 μM 4HNE to reach 30% survival as compared to density-matched normoxia control. Furthermore, during 40 and 60 min of exposure to 4HNE, the O₂-preexposed cells metabolized greater quantities of 4HNE (fmole/cell) relative to control. The activity of glutathione S-transferase (GST), an enzyme believed to be involved with the detoxification of 4HNE, was significantly increased in the O₂-preexposed cells compared with controls. Catalase activity was significantly increased, but no change was found in total glutathione content, glutathione peroxidase, manganese superoxide dismutase, and copper-zinc superoxide dismutase activities at the time of 4HNE treatment in the O₂-preexposed cells relative to density-matched control. The results demonstrate that in vitro tolerance to the cytotoxic effects of hyperoxia can be achieved through media replacement during O₂ exposure. Tolerance to oxygen toxicity conferred resistance to the cytotoxic effects of 4HNE, possibly through GST-catalyzed detoxification. These results provide further support for the hypothesis that toxic aldehydic byproducts of lipid peroxidation contribute to hyperoxic injury.     

Effects of prostaglandins on peripheral progesterone and uterine diamine oxidase in the pregnant hamster

Serum progesterone and uterine levels of diamine oxidase (DAO) activity were determined during pregnancy in hamsters. Progesterone was elevated on Day 1 of pregnancy, had a transient peak on Day 5, remained relatively constant on Days 6–10, and then increased on Days 13 and 14. Uterine DAO activity could not be detected until Day 7 of pregnancy, approximately 1 $\text{1}\text{2}$ days after the initiation of implantation. DAO activity was associated with placental tissue, and more than 90% of the activity was localized in the maternal placenta. The temporal relationship between changes in serum concentrations of progesterone and uterine levels of DAO activity following PG administration also was studied. Serum progesterone was significantly depressed by 6 hr after treatment with PGs on Day 7 of pregnancy. However, uterine levels of DAO activity at 6 hr in the treated animals were not different from those in control animals. In contrast, both the serum progesterone concentrations and uterine levels of DAO activity were significantly lower at 24 hr after PG treatment. The effects of PG treatment on uterine DAO activity were completely blocked by concomitant administration of progesterone. However, concomitant administration of Provera® only blocked the effect of one PG analog that was tested (9-deoxo-9-methylene-16,16-dimethyl0-PGE₂). The data indicate that changes in uterine DAO activity following treatment with the PGs used here are primarily a consequence of a decrease in peripheral progesterone (i.e. a luteolytic effect of the PG).     

Photoperiodic variation of Leydig cell numbers in the testis of the golden hamster: a possible mechanism for their renewal during recrudescence

Golden hamster testes regress after short day exposure. The present study asks: 1) are Leydig cell numbers depleted during short days, and 2) if so, how are they replenished during recrudescence. Control hamsters were shown 14 h of light and 10 h of dark (LD 14:10) for 10 weeks (n = 12). Testicular regression was induced by LD 6:18 for 10 weeks (n = 4), and recrudescence by switching regressed hamsters to LD 14:10 for 3 and 5 weeks (n = 8 for each group). All hamsters were injected with [3H]thymidine [3 microCi/gm body wt., intraperitoneally (i.p.)] 1 h or 2 weeks before sacrifice. Leydig cell number per testis was determined by stereological analysis of sections of perfusion-fixed testes, and labeling indices were determined by autoradiography. Leydig cell numbers were reduced significantly from 18.2 X 10(6) in control to 9.0 X 10(6) in regressed testes (p less than 0.05); then increased to 14.0 X 10(6) and 17.9 X 10(6) in 3- and 5-week recrudesced hamsters. The labeling index was nondetectable (n.d.) for regressed hamsters. In control and recrudescing hamsters the labeling index was measured at two times (t1 = 1 h vs. t2 = 2 weeks post-injection): in controls, t1 = 0.22 +/- 0.15% (mean +/- SEM) vs. t2 = 0.28 +/- 0.22%; in 1 week recrudesced, n.d. vs. 1.92 +/- 0.77% (p less than 0.05); at 3 wk, n.d. vs. 4.58 +/- 1.74% (p less than 0.05); at 5 weeks, 1.92 +/- 0.61% vs. 2.25 +/- 0.59%.(ABSTRACT TRUNCATED AT 250 WORDS)     

BK(Ca) channels compensate for loss of NOS-dependent coronary artery relaxation in cardiomyopathy

Previously, we showed that development of myocardial necrotic lesions is associated with impaired endothelium-dependent coronary artery relaxation in young cardiomyopathic hamsters. Since active necrosis declines with aging, this study was designed to determine whether coronary artery endothelium-dependent relaxation to ACh is restored and to identify the mechanisms mediating this effect. Intraluminal diameter was recorded in coronary arteries (150-250 micrometer) from control (C, 297 +/- 5 days old) and cardiomyopathic (M, 296 +/- 4 days old) hamsters. Relaxation to ACh (10(-9)-3 x 10(-5) M) was similar in vessels from C and M hamsters. However, mechanisms mediating relaxation to ACh were altered. Inhibition of nitric oxide synthase (NOS) activity with N-nitro-L-arginine (1 mM) had a greater inhibitory effect in vessels from C hamsters, indicating a reduction in NOS-dependent relaxation in vessels from M hamsters. Conversely, inhibition of large Ca(2+)-dependent K(+) (BK(Ca)) channels with charybdotoxin (CTX, 0.1 microM) had a greater inhibitory effect in vessels from M hamsters. In the presence of both N-nitro-L-arginine and CTX, relaxation to ACh was abolished in both groups. CTX (0.1 micrometer) produced a 50 +/- 4 and 30 +/- 3% contraction of vessels from M and C hamsters, respectively, indicating an enhanced role for BK(Ca) channels in regulation of coronary artery tone in M hamsters. Finally, vasodilatory cyclooxygenase products contributed to ACh-induced relaxation in vessels from M, but not C, hamsters. In conclusion, NOS-dependent relaxation of coronary small arteries is reduced in the late stage of cardiomyopathy. An increase in relaxation mediated by BK(Ca) channels and vasodilatory cyclooxygenase products compensates for this effect.     

Capacitation of hamster spermatozoa with the divalent cation chelators D-penicillamine,L-histidine,and L-cysteine in a protein-free culture medium

By using a chemically defined (protein-free) culture medium that supports sperm viability but not capacitation or the acrosome reaction, we have determined that hamster spermatozoa can be chemically capacitated in vitro by the divalent cation chelators D-penicilla-mine, L-histidine, and L-cysteine in the absence of bovine serum albumin (BSA). Washed cauda epididymal spermatozoa were preincubated (1–2 × 10⁶ sperm/ml) for 3, 4, or 6 hr at 37°C in 5% CO₂ in air. The basic culture medium used for sperm preincubation and for sperm:egg coincubation was a modified Tyrode's solution (protein-free) containing 10 mM sodium lactate, 100 μM sodium pyruvate, and 1.0 mg/ml polyvinylalcohol (TLP-PVA). Sperm viability was maintained in all preincubation and coincubation media with PHE (20 μM D-penicillamine, 100 μM hypotaurine, and 1.0 μM epinephrine). The low control sperm preincubation medium consisted of TLP-PVA. In some cases the high control preincubation medium also contained 3 mg/ml BSA (TALP-PVA). The experimental preincubation medium was TLP-PVA with additional D-penicillamine (125 or 500 μM), or L-histidine (10, 100, or 1,000 μM) or L-cysteine (25, 75, or 125 μM). After preincubation, sperm were coincubated (2 × 10⁴ sperm/ml) with cumulus-free hamster eggs in TALP-PVA ± additional D-penicillamine, L-histidine, or L-cysteine for 1.5 hr, fixed, and evaluated for percent egg penetration as an index of sperm capacitation. The results demonstrate that hamster spermatozoa can be chemically capacitated in vitro with D-penicillamine (500 μM: range of mean penetration values, 53.6%–84.3%), L-histidine (100 μM: range of mean values, 24.8%–56.3%) or L-cysteine (75 μM: 51.3%) in the absence of exogenous protein.     

Short-term complexity of cardiac autonomic control during sleep: REM as a potential risk factor for cardiovascular system in aging

Introduction

Sleep is a complex phenomenon characterized by important modifications throughout life and by changes of autonomic cardiovascular control. Aging is associated with a reduction of the overall heart rate variability (HRV) and a decrease of complexity of autonomic cardiac regulation. The aim of our study was to evaluate the HRV complexity using two entropy-derived measures, Shannon Entropy (SE) and Corrected Conditional Entropy (CCE), during sleep in young and older subjects.

Methods

A polysomnographic study was performed in 12 healthy young (21.1±0.8 years) and 12 healthy older subjects (64.9±1.9 years). After the sleep scoring, heart period time series were divided into wake (W), Stage 1–2 (S1-2), Stage 3–4 (S3-4) and REM. Two complexity indexes were assessed: SE(3) measuring the complexity of a distribution of 3-beat patterns (SE(3) is higher when all the patterns are identically distributed and it is lower when some patterns are more likely) and CCE_min measuring the minimum amount of information that cannot be derived from the knowledge of previous values.

Results

Across the different sleep stages, young subjects had similar RR interval, total variance, SE(3) and CCE_min. In the older group, SE(3) and CCE_min were reduced during REM sleep compared to S1-2, S3-4 and W. Compared to young subjects, during W and sleep the older subjects showed a lower RR interval and reduced total variance as well as a significant reduction of SE(3) and CCE_min. This decrease of entropy measures was more evident during REM sleep.

Conclusion

Our study indicates that aging is characterized by a reduction of entropy indices of cardiovascular variability during wake/sleep cycle, more evident during REM sleep. We conclude that during aging REM sleep is associated with a simplification of cardiac control mechanisms that could lead to an impaired ability of the cardiovascular system to react to cardiovascular adverse events.     

Diurnal Variations of Beta-Endorphin at Rest and After Moderate Intensity Exercise

To determine the effect of time of day on circulating beta-endorphin concentrations 14 men exercised at 75% of their maximal capacity at 0600, 1200, 1800 and 2400 hr. Each trial was separated by 3-5 days and preceded by a normal sleep cycle except for the 0600 hr trials which was preceded by 6 hr sleep. Resting physiological data indicated normal diurnal variations in heart rate, core temperature and oxygen uptake, being lowest during the 0600 hr trials and highest during the 1800 hr trials. Resting plasma beta-endorphin concentrations averaged 11.9 +/- 8.4 pmol/l during the 0600 hr trials, significantly greater than the 2400 hr trials (6.4 +/- 3.6 pmol/l; P less than 0.05). No other significant differences existed at rest. Post exercise beta-endorphin concentrations were elevated and found to be inversely related to time of day with the 0600 hr trials having the highest mean (25.7 +/- 14.7) and the 2400 hr trials the lowest (14.7 +/- 8.3). These data suggest that the plasma beta-endorphin concentrations at rest and after exercise are affected by the time of day. The results also suggest that the changes in beta-endorphin associated with exercise are not major contributors to cardiorespiratory control or changes in psychological effect associated with exercise.