Effects of a five-hour exposure of arm and leg to a slightly cool thermal environment in the afternoon on the body temperature rhythm

The purpose of this study was to determine whether the different thermal conditions of the arm and leg due to wearing different types of clothing during the afternoon could modulate the circadian rhythm of body temperature and subjective sleep quality. Six healthy female volunteers were studied twice with two types of clothing, leaving the arm and leg covered or uncovered. The environmental chamber was controlled at 24 ± 0.5°C and 50 ± 5% RH during wakefulness and 28 ± 0.5°C and 50 ± 5% RH during night sleep. One type of clothing consisted of long-sleeved shirts and full-length trousers (Type L, 989 g, 0.991 clo); the other type was of half-sleeved shirts and knee-length trousers (Type H, 750 g, 0.747 clo). One testing session lasted for 16 h from 14:00 to 06:00 h the next morning. Subjects wore Type L or Type H clothing during the afternoon exposure (14:00 - 19:00), and Type L clothing during the evening (19:00 - 22:30 h) and the night sleep (22:30 - 06:00 h). Results were as follows. (1) When wearing Type H rather than Type L clothing, skin temperatures of the arm and leg were significantly lower during the time of exposure, and increased more after the evening. (2) Rectal temperature was not significantly different between the two types of clothing except during the early part of the exposure period, but it decreased during the evening by a significantly greater amount when wearing Type H clothing. (3) Subjective sleep quality was not significantly different between the two clothing types. These results suggest that afternoon exposure of the arm and leg to a slightly cool environment does not have a strong after-effect on the body temperature and subjective sleep quality.     

Reproductive phase dependent circadian variations of plasma melatonin, testosterone, thyroxine and corticosterone in Indian palm squirrel, Funambulus pennanti

To explain the complex mechanism of environmental influence along with internal hormonal (factors) milieu on daily variations in the circulating levels of melatonin, testosterone, thyroxine and corticosterone were analyzed with the help of inferential statistics (Cosinor rhythmometry) in a seasonally breeding tropical rodent, F. pennanti during the reproductively active (RAP) and inactive phases (RIP). Plasma melatonin, thyroxine and corticosterone levels exhibited a significant circadian oscillation during both the active and inactive phases of the annual reproductive cycle. Melatonin showed higher amplitude during RIP in the circulating plasma. Testosterone presented a peak level during evening hours (16:00 - 18:00 h) during RAP only. The phase of thyroxine was noted ∼09:76 h and ∼10.35 h during active and inactive phases, respectively. Corticosterone showed a peak level at ∼12.00 h during both phases of the reproductive cycle. Further, in this tropical rodent, the minimum difference in photoperiod (∼3 - 4 hours) and maximum variation in temperature (max. 18°C - min. 10°C during RIP and max. 45°C - min. 32°C during RAP) and humidity (85% during RIP and 35% during RAP) regulated the diurnal rhythm of circulating melatonin circadian rhythm by ∼1 hour phase advance during RIP. In conclusion, the studied hormonal rhythms may be part of an integrative system to coordinate reproduction and physiological processes successfully with environmental factors.     

Shifts in thermoregulatory patterns with pregnancy in the poikilothermic mammal—The naked mole-rat (Heterocephalus glaber)

1. 1. The naked mole-rat (Heterocephalus glaber) is a poikilothermic mammal. During gestation metabolic shifts that differ from both mammalian and reptilian thermoregulatory patterns occurred.

2. 2. Body temperature was directly dependent on ambient temperature. At low ambient temperatures the temperature differential (T_b − T_a) was approximately 3°C, whereas at higher ambient temperatures the temperature differential diminished.

3. 3. In early pregnancy (prior to week 3) oxygen consumption at low ambient temperatures was greater than that of non-reproductive animals. A maximal metabolic rate (3.2 ± 1.0 ml O₂ . g⁻¹ . h⁻¹) occurred at an ambient temperature of 27°C. Thereafter the endothermic pattern of metabolism with increasing ambient temperatures was evident. Oxygen consumption decreased with increasing ambient temperature to minimal rates of 1.2 ± 0.1 ml O₂ . g⁻¹ . h⁻¹ over the ambient temperature range of 31–34°C.

4. 4. Oxygen consumption in late pregnancy (1.8 ± 0.1 ml O₂ . g⁻¹ . h⁻¹) was not correlated with ambient temperature over the entire ambient temperature range measured (24–36°C).

5. 5. Differences in thermoregulation in early and late pregnancy may be attributed to different rates of heat loss as a consequence of (a) changes in surface area and body mass or (b) vascular changes. Furthermore the thermoregulatory changes in late pregnancy may indicate that maximal overall metabolic capacity had been reached, for peak resting metabolism (expressed per animal rather than per gram body mass) in early pregnancy was similar to observed metabolism in late pregnancy.

6. 6. The dissociation of metabolism from both ambient temperature and body temperature in late pregnancy could confer an energetic advantage to this arid dwelling underground inhabitant; for it may enable the breeding female to partition a greater portion of available energy into reproduction.

Effect of Ramadan on the diurnal variation in short-term high power output

This study examined the effects of Ramadan fasting on anaerobic performances and their diurnal fluctuations. In a balanced and randomized study design, 12 subjects were measured for maximal power (P_max; force-velocity test), peak power (P_peak), and mean power (P_mean) with the Wingate test at 07:00, 17:00, and 21:00 h on four different occasions: one week before Ramadan (BR), the second week of Ramadan (SWR), the fourth week of Ramadan (ER), and two weeks after Ramadan (AR). There was an interval of 28 h between any two successive tests. Oral temperature was measured before each test. Under each condition, the results showed a time-of-day effect on oral temperature. Analysis of variance revealed a significant (Ramadan×time-of-day of test) interaction effect on P_max. This variable improved significantly from morning to evening before Ramadan (1.1±0.2 W · kg^-1), during the second week of Ramadan (0.6±0.2 W · kg^-1), and two weeks after the end of Ramadan (0.9±0.2 W · kg^-1). However, daily fluctuations disappeared during the fourth week of Ramadan. For P_peak and P_mean, there was no significant Ramadan×test-time interaction. These variables improved significantly from morning to evening before Ramadan ([1±0.3 W · kg^-1] for P_peak and [1.7±1.6 W · kg^-1] for P_mean) and in the second week of Ramadan ([0.9±0.6 W · kg^-1] for P_peak and [1.7±1.5 W · kg^-1] for P_mean). However, they were not affected by time-of-day in the fourth week of Ramadan. Considering the effect of Ramadan on anaerobic performances, in comparison with before Ramadan, no significant difference was observed during Ramadan at 07:00 h. The variables were significantly lower in the second week of Ramadan and in the fourth week of Ramadan at 17:00 h and 21:00 h. P_mean was not affected during the second week of Ramadan. In conclusion, the time-of-day effect on anaerobic power variables tends to disappear during Ramadan. In comparison with the period before Ramadan, anaerobic performances were unaffected in the morning but impaired in the evening during Ramadan.     

Continuous-flow complete-mixing system for assessing the effects of environmental factors on colony-level coral metabolism

A small-scale chamber experimental system was designed to study the effects of temperature on colony-level coral metabolism. The system continuously supplies fresh seawater to the chamber, where it is mixed immediately and completely with the seawater already present. This continuous-flow complete-mixing system (CFCM system), in conjunction with theoretical equations, allows quantitative determination of chemical uptake and release rates by coral under controlled environmental conditions. We used the massive hermatypic coral Goniastrea aspera to examine variations in pH, total alkalinity, and total inorganic carbon for 16 days at 27 °C under controlled light intensities (300 and 0 µmol m^− 2 s^− 1). We confirmed the stability of the CFCM system with respect to coral photosynthetic and calcification fluxes. In addition, we obtained daily photosynthetic and calcification rates at different temperatures (27 °C, 29 °C, 31 °C, and 33 °C). When seawater temperature was raised from 31 °C to 33 °C, the gross primary production rate (P_gross) decreased 29.5%, and the calcification rate (G) decreased 85.7% within 2 days. The CFCM system allows quantitative evaluation of coral colony chemical release and uptake rates, and metabolism.     

Comparative analysis of rhythmic parameters of the body temperature in humans measured with thermistors and digital thermometers

In this paper we compare rhythmic parameters of human body temperature simultaneously measured with digital thermometers and thermistors with memory (Thermochron iButtons®). Thirteen healthy male and female volunteers (mean age of 25) measured oral and axillary temperatures with digital thermometers every hour during wakefulness for two days and every three hours for three days, totalling five consecutive days. Concomitantly, they wore badges with thermistors in the thorax and the wrist. Temporal series circadian rhythmicity was evaluated with the Cosinor technique. Acrophases average were 17:32 h±2:02 h for axillary temperature, 10:12 h±7:26 h for thoracic temperature, 17:18 h±00:50 h for oral temperature and 4:15 h±1:55 h for wrist temperature. The rhythmic parameters of the wrist are more robust than those of the thorax. The collection of data in humans, generally performed with digital thermometers, is restricted to the waking phase and depends on the discipline of the volunteers. We suggest that the use of the thermistor with memory in the wrist can be adopted as alternative methodology to studies of human body temperature rhythmicity, especially recommended for long temporal series.     

Effects of temperature, photoperiod, and light intensity on the eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae

Eclosion rhythm of the high-altitude Himalayan strain of Drosophila ananassae from Badrinath (altitude 5123 m) was temperature-dependent and at 21°C, it was entrained by cycles of 12 h light: 12 h darkness (LD 12:12) and free-ran in constant darkness, however, it was arrhythmic at 13°C or 17°C under identical experimental conditions (Khare, P. V., Barnabas, R. J., Kanojiya, M., Kulkarni, A. D., Joshi, D. S. (2002). Temperature dependent eclosion rhythmicity in the high altitude Himalayan strains of Drosophila ananassae. Chronobiol. Int. 19:1041-1052). The present studies were designed to see whether or not these strains could be entrained at 13°C, 17°C, and 21°C by two types of LD cycles in which the photoperiod at 100 lux intensity varied from 6 h to 18 h, and the light intensity of LD 14:10 cycles varied from 0.001 lux to 1000 lux. All LD cycles entrained this strain at 21°C but not at 13°C or 17°C. These results demonstrate that the entrainment of eclosion rhythm depends on the ambient temperature and not on the photoperiod or light intensity of LD cycles. Thus the temperature has taken precedence over the light in the entrainment process of eclosion rhythm of the high altitude Himalayan strain of D. ananassae. This may be the result of natural selection in response to the environmental temperature at Badrinath that resembles that of the sub-Arctic region but the photoperiod or light intensity are of the subtropical region.     

Circadian modulation of starvation-induced hypothermia in sheep and goats

Prolonged food deprivation is known to cause a fall in the core body temperature of homeotherms. In various species of small birds and mammals (body mass up to 2-3 kg), it has been shown that starvation-induced hypothermia is modulated by the circadian system, in the sense that hypothermia is observed primarily during the inactive phase of the daily activity cycle (i.e., during the night for diurnal animals and during the day for nocturnal animals), whereas relatively normal temperatures are recorded during the active phase. To investigate whether this modulation occurs also in larger animals, we investigated the effects of 4d food deprivation on the body temperature rhythm of goats and sheep (body mass 30-40 kg). In goats, the body temperature rhythm was found to have a mean level of 39.0°C with a mean daily range of excursion of 0.42°C. The daily oscillation in body temperature persisted during the first day of fasting, but the rhythm was drastically damped, if not eliminated, over the next 3 d as body temperature descended from the baseline level of 39.0 to 38.2°C. In sheep, the rhythm was found to have a mean level of 39.3°C with a mean daily range of excursion of 0.34°C. The daily oscillation in body temperature persisted through the 4 d of food deprivation, even though the mean level of body temperature gradually fell. Temperature fell more during the third and fourth nights than during the third and fourth days. Thus, circadian modulation of starvation-induced hypothermia was observed in sheep but not in goats.     

Daily rhythms of nonshivering thermogenesis in common spiny mice Acomys cahirinus under short and long photoperiods

Daily rhythms of nonshivering thermogenesis NST were studied in common spiny mice Acomys cahirinus, acclimated to different photoperiod regimes (16L:8D and 8L:16D) at a constant ambient temperature of 26°C. Noradrenaline NA (1.5 mg/kg subcutaneous) was injected at: 06:00, 12:00, 18:00 and 24:00 h (±15 min). NST was measured as the ratio between the maximal oxygen consumption (VO₂) as response to NA — VO₂NA and VO₂ measured at 26°C — VO_{2 min}. Rectal temperatures T_bNA and T_{b min} respectively were recorded at the end of VO₂ measurements. Significant variations in T_{b min}, T_bNA, and NST were revealed, under the two different photoperiod regimes. Significant differences in VO_{2 min}, NST, T_{b min} and T_bNA were also recorded within each photoperiod acclimation group. These results suggest that daily and photoperiod depended variations in the brown adipose tissue activity, presumably emerge from amount of unoccupied receptors or changes in the receptors affinity to NA.     

Determination of the thermodynamics of carbonic anhydrase acid-unfolding by titration calorimetry

The enthalpy of unfolding (Δ_uH) of carbonic anhydrase II was determined by titrating the protein with acid and measuring the heat using isothermal titration calorimetry (ITC) in the temperature range of 5 to 59 °C. By combining the ITC results with our previous findings by differential scanning calorimetry (DSC) in the temperature range of 39 to 72 °C, the Δ_uH dependence over a wide temperature range was obtained. The temperature dependence of the enthalpy displays significant curvature indicating that the heat capacity of unfolding (Δ_uC_p) is dependent on temperature. The T-derivative of Δ_uC_p was equal to 100 ± 30 J/(mol × K²), with the result that the Δ_uC_p is equal to 15.8 kJ/(mol × K) at 5 °C, 19.0 kJ/(mol × K) at 37 °C and 21.8 kJ/(mol × K) at 64 °C. The enthalpy of unfolding is zero at 17 °C. At lower temperatures, the Δ_uH becomes exothermic.

This method of determining protein unfolding thermodynamics using acid-ITC, significantly widens the accessible T-range, provides direct estimate of the thermodynamic parameters at physiological temperature, and gives further insight into the third T-derivative of the Gibbs free energy of unfolding.     

Cheek skin temperature and thermal resistance in active and inactive individuals during exposure to cold wind

1. The present study examined the effect of the thermal state of the body (as reflected by rectal temperature) on cheek skin temperature and thermal resistance in active and inactive subjects.

2. Active subjects were exposed to a 30 min conditioning period (CP) (0 °C air with a 2 m/s wind), followed immediately by a 30 min experimental period (EP) (0 °C with a 5 m/s wind). Inactive subjects were exposed to a 30 min CP (22 °C air with no wind), followed immediately by a 45 min EP (0 °C air with a 4.5 m/s wind). The CP period was used to establish a core temperature difference between the active and inactive subjects prior to the start of EP. The 0 °C exposure was replaced with a −10 °C ambient air exposure and the experiment was repeated on a separate day. Subjects were comfortably dressed for each ambient condition.

3. Cheek skin temperature was not significantly higher in active subjects when compared to inactive subjects, but thermal resistance was higher in active subjects.

4. Cheek skin temperature and thermal resistance both decreased as ambient temperature decreased from 0 to −10 °C. The lower cheek thermal resistance at −10 °C may have been due to a greater cheek blood flow as a result of cold-induced vasodilation.

Expression of clock genes in human peripheral blood mononuclear cells throughout the sleep/wake and circadian cycles

The rhythmic expression of circadian clock genes in the neurons of the suprachiasmatic nucleus (SCN) underlies the manifestation of endogenous circadian rhythmicity in behavior and physiology. Recent evidence demonstrating rhythmic clock gene expression in non-SCN tissues suggests that functional clocks exist outside the central circadian pacemaker of the brain. In this investigation, the nature of an oscillator in peripheral blood mononuclear cells (PBMCs) is evaluated by assessing clock gene expression throughout both a typical sleep/wake cycle (LD) and during a constant routine (CR). Six healthy men and women aged (mean±SEM) 23.7±1.6 yrs participated in this five-day investigation in temporal isolation. Core body temperature and plasma melatonin concentration were measured as markers of the central circadian pacemaker. The expression of HPER1, HPER2, and HBMAL1 was quantified in PBMCs sampled throughout an uninterrupted 72 h period. The core body temperature minimum and the midpoint of melatonin concentration measured during the CR occurred 2:17±0:20 and 3:24 ±0:09 h before habitual awakening, respectively, and were well aligned to the sleep/wake cycle. HPER1 and HPER2 expression in PBMCs demonstrated significant circadian rhythmicity that peaked early after wake-time and was comparable under LD and CR conditions. HBMAL1 expression was more variable, and peaked in the middle of the wake period under LD conditions and during the habitual sleep period under CR conditions. For the first time, bi-hourly sampling over three consecutive days is used to compare clock gene expression in a human peripheral oscillator under different sleep/wake conditions.     

Conceptual model of seagrass die-off in Florida Bay: Links to biogeochemical processes

Seagrasses are recognized as important plant communities in coastal estuaries and lagoons across both tropical and temperate climes; thus, large-scale seagrass die-off events worldwide are of general concern. In Florida Bay, at the southern terminus of the Florida peninsula, seagrass die-off events up to 4000 ha have been reported and smaller scale mortality events are noted annually. In the present study, we examined several hypothesized causative factors (high temperature, hypersalinity, sulfide toxicity) of seagrass (Thalassia testudinum) mortality in Florida Bay. To test sulfide effects, in situ sulfide production was stimulated by applying a labile carbon source (glucose) to sulfate reducers in the sediment at five sites across the bay (northeastern, northcentral, and southwestern basins). During the one year study, high temperature (32–36 °C) and salinity (> 50 psu) were recorded in the bay associated with a regional drought. We also experienced major seagrass die-off events at two of our southwestern bay sites. These field conditions provided an excellent opportunity to closely examine cause–effect relationships among stressors and die-off events in the field, and verify results of our previous mesocosm experiments. Even though glucose amendments stimulated porewater sulfides in bay sediments (4–8 mmol L^− 1), no significant differences in biomass, short shoot density or final growth rates were found between control and glucose plots. In addition, the highest growth rates and shoot densities were concomitant with maximum water column salinity (> 50 psu) and temperature (32–36 °C), when porewater sulfides were also in the millimolar range. Large-scale seagrass mortality events, encompassing  50% of the entire meadow at one site, occurred at southwestern bay sites when plants were down regulating (slower growth and shoot density), probably in response to shorter day length and lower temperature (30–34 to 23–26 °C) from October, 2004 to January, 2005. Sulfate reduction rates (SRR) were also 2-fold higher in the southwestern (214–488 nmol cm^− 3 d^− 1) versus northcentral and northeastern (97–240 nmol cm^− 3 d^− 1) bay sites, possibly limited by labile carbon, which we found to stimulate SRR 3-fold in northeastern and northcentral bay sites (461–708 nmol cm^− 3 d^− 1) and 4-fold at southwestern bay sites (1211–2036 nmol cm^− 3 d^− 1). Based on a synthesis of the field data reported herein, our mesocosm experiments to date, and contributions by others, we present a conceptual model of seagrass die-off in Florida Bay outlining a cascade of stressors, stimulated by P enrichment, which leads to high O₂ consumption in the system triggering a seagrass die-off event.     

Freezing resistance improvement of Lactobacillus reuteri by using cell immobilization

Lactobacillus reuteri shows certain beneficial effects to human health and is recognized as a probiotic. However, its application in frozen foods is still not popular because of its low survival during freezing and frozen storage. Cell immobilization technique could effectively exert protection effects to microbial cells in order to enhance their endurance to unfavorable environmental conditions as well as to improve their viability and cell concentration. Ca-alginate and κ-carrageenan were used to immobilize L. reuteri in this research, and the immobilized cells were exposed to different freezing temperatures, i.e. − 20 °C, − 40 °C, − 60 °C, − 80 °C, and stored at − 40 °C and − 80 °C for 12 weeks. The objectives were to study the protection effects of cell immobilization against the adverse conditions of freezing and frozen storage, and the effects of freezing temperatures to the immobilized cells. Cell immobilization was used to raise the survival of L. reuteri during freezing and frozen storage in order to develop frozen foods with the probiotic effects of L. reuteri. Results indicated that immobilized L. reuteri possessed better survival in both freezing and frozen storage. The survival of immobilized L. reuteri was higher than that of free cells, and the effects of lower freezing temperature were better than higher freezing temperature. The immobilization effects of Ca-alginate were found to be superior to κ-carrageenan. Cell immobilized L. reuteri exhibits potential to be used in frozen foods.     

Effect of fasting and repeat feeding on metabolic rate in Southern Catfish, Silurus meridionalis chen

Southern catfish juvenile (37.6-65.9 g) were fasted for two weeks and fed with cutlets of freshly killed loach species at 2% body mass per meal twice daily (06:00 and 18:00) for four days at 27.5°C. Metabolic rates were measured during the fasting and feeding periods and all metabolic rates were adjusted to a standard body mass of 1 kg using an exponent of 0.75. The aim of this study was to investigate the effect of fasting and repeat feeding on the resting metabolic rate and the feeding metabolic rate. The results demonstrated that the standardized value of the resting metabolic rate gradually decreased from 69.6 ± 2.7 (means ± S.E.) to 42.8 ± 2.3 mgO₂ h^-1 during the two weeks of fasting. The peak feeding metabolic rate and average metabolic rate of each feeding (12 h) gradually increased with repeat feeding before leveling off. The results of this study suggest that southern catfish can regulate digestive function and gradually alter the characteristics of metabolism according to the availability of a food resource.     

Characterization of orange peel pectin and effect of sugars, -ascorbic acid, ammonium persulfate, salts on viscosity of orange peel pectin solutions

The effects of temperature and concentration on the viscosity of orange peel pectin solutions were examined at five different temperatures between 20 and 60°C and five concentration levels between 2.5–20 kg/m³. The effects of temperature was described by an Arrhenius-type equation. The activation energy for viscous flow was in the range 19.53–27.16 kJ/mol, depending on the concentration. The effect of concentration was described by two types of equation, power-law and exponential. Equations were derived which describes the combined effects of temperature and concentration on the viscosity for two different models in the range of temperatures and concentrations studied. Orange peel pectin was extracted by using HCl (pH 2.5, 90°C, 90 min) ammonium oxalate (0.25%, pH 3.5, 75°C, 90 min) and EDTA (0.5%, 90°C, 90 min) extraction procedures. The best result was obtained with ammonium oxalate extraction in which the pectin content of the final product was 30.12%, although the efficiency among the procedures varied.The average molecular weight was measured by light scattering technique. Magnitudes of intrinsic viscosity and molecular weight of pectins obtained by extraction with HCl, ammonium oxalate and EDTA were 0.262, 0.281, 0.309 m³/kg and 84 500, 91 400, 102 800 kg/kgmol, respectively. The molecular weight dependence of the intrinsic viscosity of the orange peel pectin solutions was expressed by Mark–Houwink–Sakurada equation. The data were fitted to equation as η_i=2.34×10⁻⁵(M_w,ave)^0.8224 which helps to evaluate the average molecular weight of pectin solutions from orange peel with a knowledge of their intrinsic viscosity.     

A simple in-vitro 'wet-plate' method for mass production of Phytophthora nicotianae zoospores and factors influencing zoospore production

A simple in-vitro ‘wet-plate’ method for mass-producing Phytophthora nicotianae zoospores at ≥ 1.0 × 10⁶ zoospores/ml is described. Temperature critically affected zoospore production; 22 °C was optimum, while 36 °C was completely inhibitory. Zoospores being the most important propagule of P. nicotianae, temperature of recycled irrigation water may be manipulated to reduce diseases in irrigated nursery crops.     

The daily rhythms of melatonin and free fatty acids in goats under varying photoperiods and constant darkness

The purpose of the study was to explore parallel and divergent features of the daily rhythms of melatonin and plasma free fatty acids (FFA) in goats exposed to different lighting conditions. From these features, we attempted to analyze whether the endogenous melatonin rhythm plays any role in the maintenance of the FFA rhythm. Seven Finnish landrace goats were kept under artificial lighting that simulated the annual changes of photoperiod at 60°N (longest photoperiod, 18 h; shortest, 6 h). The ambient temperature and feeding regimen were kept constant. Blood samples were collected 6 times a year at 2 h intervals for 2 d, first in the prevailing light-dark (LD) conditions and then after 3 d in constant darkness (DD). In LD conditions, the melatonin levels always increased immediately after lights-off and declined around lights-on, except in winter (18 h darkness), when the low daytime levels were restored clearly before lights-on. The FFA levels also displayed a consistent rhythmicity, with low levels at night and a transient peak around lights-on. In DD conditions, the melatonin profiles were very similar to those found in the habitual LD conditions, but the rhythm tended to advance. The FFA rhythm persisted also in DD, and the morning peak tended to advance. There was an overall parallelism between the two rhythms, with one significant exception. In winter in LD conditions, the morning rise in FFA levels coincided with lights-on and not with the declining phase of melatonin, whereas in DD conditions, the FFA peak advanced several hours and coincided with the declining phase of melatonin. From this finding and comparisons of the calculated rhythm characteristics, i.e., phase-shifts, phase differences, and correlations, we conclude that the daily rhythm of FFA levels is most probably generated by an endogenous oscillator, primarily adjusted by dawn, whereas the melatonin rhythm in this species is regulated by an oscillator primarily adjusted by dusk. The results did not exclude a modulatory effect of melatonin on the daily FFA profiles, but melatonin secretion, alone, does not explain the patterns sufficiently.     

Nitrosylmyoglobin as antioxidant--kinetics and proposed mechanism for reduction of hydroperoxides

Nitrosylmyoglobin (MbFe^IINO), which is believed to have a protective role during ischemia and reperfusion injury, was oxidized by tert-butyl hydroperoxide (t-BuOOH), and by hydrogen peroxide (H₂O₂) to the nitrite anion and metmyoglobin (MbFe^III). Further characterization of the reaction of MbFe^IINO with excess of t-BuOOH was investigated with respect to reaction stoichiometry, temperature and pH dependence. It was found that the reaction between MbFe^IINO with excess of t-BuOOH followed a simple stoichiometry and had moderate pH and temperature dependence with the activation parameters ΔH^‡ = 57.4 ± 1.4 kJ mol^- 1 and ΔS^‡ = - 112.0 ± 5.1 J mol^- 1 K^- 1, which is consistent with an associative reaction mechanism. Moreover, t-BuOOH-induced oxidation of MbFe^IINO did not result in any detectable formation of the hypervalent myoglobin (Mb) species, i.e. perferrylmyoglobin, (^√MbFe^IV = O) or ferrylmyoglobin (MbFe^IV = O), and hereby differed from H₂O₂-induced oxidation of MbFe^IINO, which results in the formation of MbFe^IV = O. Based on the obtained results and on published data, different mechanisms for the reaction of the MbFe^IINO with t-BuOOH and H₂O₂ are proposed.     

Effect of ambient temperature on in vitro fertilization of Bubaline oocyte

The present study was used to examine the effect of ambient temperature on the day of slaughter of buffaloes on oocyte cleavage and subsequent embryo development following in vitro fertilization (IVF)/chemical activation (parthenogenesis). A total of 601 oocytes were collected from buffaloes, which were sacrificed when the ambient temperature was >40 or ≤40 °C and the collected oocytes were matured in vitro. During each experiment about half of the matured oocytes were used for IVF whereas the remaining oocytes were subjected to one of the three chemical activation protocols viz. (i) 7% ethanol (ET) and 6-di methyl amino purine (6-DMAP), (ii) ET and cycloheximide (CHX) and (iii) ET followed by a combined treatment of 6-DMAP and CHX. Cleaved oocytes were cultured in mSOF supplemented with BSA, essential amino acids, non-essential amino acids, ITS (insulin transferrin and selenium) and l-glutamine. Low cleavage and subsequent embryo development was observed in those oocytes which were collected from buffaloes slaughtered at ambient temperature >40 °C than at ≤40 °C. There was no significant difference in cleavage rate following different chemical activations in oocytes collected from buffaloes slaughtered on the day when the maximum ambient temperature was >40 °C or ≤40 °C. These results suggest that high ambient temperature influences competence of oocytes to cleave and develop to blastocyst stage following natural activation with sperm and/or process of fertilization and subsequent embryo development.