Improved PCR detection sensitivity of Erwinia carotovora subsp. atroseptica in potato tuber peel extract by prior enrichment on a selective medium

A simple and sensitive method was developed to replace the need for complex and laborious DNA extraction to remove inhibitory substances in potato tuber peel extract before detection of Erwinia carotovora subsp. atroseptica (Eca) by PCR. Eca was enriched by a factor of 10⁵ when peel extract was inoculated onto a selective medium, CVP, and incubated at 27°C for 24 h. Bacterial micro-colonies which developed were suspended in 500 μl of water and the bacteria diluted in water 100-fold, or 10-fold followed by washing by centrifugation, before PCR testing. The sensitivity of detection obtained with the former was ca 10¹–10² cells ml⁻¹ and with the latter ca 10¹ cells ml⁻¹, when different numbers of streptomycin-resistant Eca strain were added to peel extract from three Eca-free potato cultivars. The method was validated and the sensitivity confirmed relative to two different commonly used Eca detection methods using naturally contaminated tubers.     

Regulation of local sweating in sleep-deprived exercising humans

Thermoregulatory sweating [total body (m _sw,b), chest (m _sw,c) and thigh (m _sw,t) sweating], body temperatures [oesophageal (T _oes) and mean skin temperature (T _sk)] and heart rate were investigated in five sleep-deprived subjects (kept awake for 27 h) while exercising on a cycle (45 min at approximately 50% maximal oxygen consumption) in moderate heat (T _air andT _wall at 35° C. Them _sw,c andm _sw,t were measured under local thermal clamp (T _sk,1), set at 35.5° C. After sleep deprivation, neither the levels of body temperatures (T _oes,T _sk) nor the levels ofm _{sw, b},m _{sw, c} orm _{sw, t} differed from control at rest or during exercise steady state. During the transient phase of exercise (whenT _sk andT _sk,1 were unvarying), them _{sw, c} andm _{sw, t} changes were positively correlated with those ofT _oes. The slopes of them _{sw, c} versusT _oes, orm _{sw, t} versusT _oes relationships remained unchanged between control and sleep-loss experiments. Thus the slopes of the local sweating versusT _oes, relationships (m _{sw, c} andm _{sw, t} sweating data pooled which reached 1.05 (SEM 0.14) mg·cm^–2·min^–1°C^–1 and 1.14 (SEM 0.18) mg·cm^–2·min^–1·°C^–1 before and after sleep deprivation) respectively did not differ. However, in our experiment, sleep deprivation significantly increased theT _oes threshold for the onset of bothm _{sw, c} andm _{sw, t} (+0.3° C,P<0.001). From our investigations it would seem that the delayed core temperature for sweating onset in sleep-deprived humans, while exercising moderately in the heat, is likely to have been due to alterations occurring at the central level.     

Effects of weather on activity and sleep in brooding king penguins (Aptenodytes patagonicus)

Avian sleep is sensitive to thermal challenges. Brooding king penguins (Aptenodytes patagonicus) defending a territory are exposed to wide daily fluctuations in ambient temperature and wind conditions. We studied the daytime behavioural time budget of 89 groups of territorial adults brooding a 1- to 5-week-old chick on Crozet Island during summer 1998. Scans were performed every 10 min and each bird was categorized as either active, resting or sleeping. Three ranges of ambient temperatures (T1=5-9°C, T2=10-13°C, T3=14-19°C) and wind conditions (calm-light, moderate, strong) were distinguished. Wind conditions did not affect the behavioural time budget of king penguins during summer. Resting, which represented about half of the daytime behavioural time budget, increased by 17% when ambient temperature increased from T1 to T3, mostly at the expense of active behaviours. The percentage of time spent sleeping was low, but was reduced by 66% when ambient temperature increased over 10°C. Thus, behavioural sleep was mainly observed in a range of temperatures within which resting metabolic rate of adult king penguins is minimal, i.e. between -1 and 11°C. It is also interesting to note that the range of ambient temperatures in which sleeping was high coincides with the most common microclimatology prevailing at the colony during summer, i.e. ambient temperatures between 5 and 10°C.     

Thermoregulatory control of feeding and sleep in premature infants

Objective: The aim of the present study was to test the thermoregulatory feeding control hypothesis in sleeping, premature infants. Research Methods and Procedures: In premature infants, the energy supply from food intake is crucial for (in order of importance): organ operation, body homeothermia, and optimal growth. The Himms‐Hagen model of thermoregulatory feeding control involving activation of heat production by brown adipose tissue (BAT) was formulated on the basis of work in (awake) rats. This hypothesis has also been put forward for the human neonate, which can also use BAT to produce metabolic heat. According to the model, feeding episodes occur during a transient increase in body temperature. Feeding is initiated by a dip in blood glucose concentration after sugar uptake by activated BAT. Results: In 14 neonates (bottle‐fed on demand), food intake always took place during an increase in skin temperature (+0.19 ± 0.21 °C). Awakening occurred 18 ± 17 minutes after the minimum skin temperature level had been reached. When feeding time was imposed, feeding was not necessarily situated during an increase in skin temperature, and the sleep duration after food intake increased significantly (+43%). This could be considered as an adaptive response to the short‐term sleep deprivation and/or stress elicited by an imposed feeding rhythm. Discussion: The validity of the model supports the use of on‐demand feeding in neonatal care units, in accordance with the infant's physiological body temperature oscillations.     

Sleep apnea is induced by a high-fat diet and reversed and prevented by metformin in non-obese rats

Objective: We assessed the relationship between a high‐fat (HF) diet and central apnea during rapid eye movement and non‐rapid eye movement sleep stages by recording ventilatory parameters in 28 non‐obese rats in which insulin resistance had been induced by an HF diet. We also studied whether metformin (an anti‐hyperglycemic drug frequently used to treat insulin resistance) could reverse sleep apnea or prevent its occurrence in this experimental paradigm. Research Methods and Procedures: Rats were fed with a standard diet (10 rats), an HF diet (8 rats), or an HF diet concomitantly with metformin treatment (10 rats). Each animal was instrumented for electroencephalographic and electromyographic recording. After 3 weeks, ventilatory parameters during sleep were recorded with a body plethysmograph. All rats were treated with metformin for 1 week, after which time the ventilatory measurements were measured again. Results: Our results showed that the three groups of animals did not differ in terms of body growth over the entire experimental period. The HF diet did not modify sleep structure or minute ventilation in the different sleep stages. A great increase (+266 ± 48%) in central apnea frequency was observed in insulin‐resistant rats. This was explained by an increase in both post‐sigh (+195 ± 35%) and spontaneous apnea (+437 ± 65%) in the different sleep stages. These increases were suppressed by metformin treatment. Discussion: Insulin resistance induced by the HF diet could be the promoter of sleep apnea in non‐obese rats. Metformin is an efficient curative and preventive treatment for sleep apnea, suggesting that insulin resistance modifies the ventilatory drive independently of obesity.     

Leg skin temperature and thigh sweat output: possible central influence of local thermal inputs

To demonstrate whether or not the skin temperature of one lower limb can have an influence on the sweat rate of the contralateral leg, the two legs of five subjects were exposed inside leg-chambers to specific local thermal conditions while sweat rates were measured on both limbs. Three experiments (C I,II,III) of 3 h were carried out: each included two phases A and B. During A, the right leg was not ventilated, while the left leg was (C I) or was not (C II–III) ventilated. During B, the legs were either removed from the leg-chambers (C I) or ventilated inside the chambers at differently controlled levels of leg skin temperature (C II–III). At all times, sweat capsules on both legs measured the sweat rates of local areas of the thigh which were also temperature-controlled. Results showed that, at constant or slightly increased mean skin and core temperatures, the sweat output of one leg could be decreased at constant (C II) or higher local skin temperature (C III) probably due to a decrease in the temperature of the opposite leg. This finding is interpreted as a consequence of a central negative effect, originating from contralateral thermal inputs.     

Do sleeping king penguins influence the movement of conspecifics through a colony?

Within a breeding colony, movements of penguins to and from territories can be associated with high energetic costs and risks of injury induced by the high aggressiveness of territorial breeders. Here, we tested whether the presence of sleeping king penguins (namely non-aggressive birds) could influence the trajectory of walking conspecifics. Also, we determined how an aggressive response from the sleeping individual's neighbours could affect the trajectory adopted by a travelling bird. We observed 150 sleeping king penguins on Possession Island (Crozet Archipelago) during the breeding season and determined whether or not travelling birds walk preferentially beside sleeping individuals. Moving penguins not attacked by territorial birds directly surrounding the sleeping individual walked preferentially beside it in 80.3% of the observations. However, birds attacked by the sleeping individual's neighbours walked beside the sleeping bird in only 27.9% of the cases. Whether the sleeping individual's neighbours were directly facing the intruder or not did not affect the probability of the intruder being attacked. Hence, travelling penguins actively chose to walk beside a sleeping individual when not attacked by the latter's neighbours. This striking tropism could represent an adapted motivated behaviour, reducing energetic costs and risks of injury associated with fighting. Accepted: 21 December 1998     

Temperature and sweating responses in one-legged and two-legged exercise.

In looking at the thermoregulatory responses resulting from symmetrical or asymmetrical exercise, this paper has focused on the effect of local skin temperature (Tsk,local) on local sweat rates (msw,local) during one-legged (W1) and two-legged (W2) exercise on an ergocycle. Five subjects underwent four 3-h tests at 36 degrees C, each consisting of six 25-min exercise periods alternating with 5-min rest periods. The subjects performed W1 and W2 at 45 and 90 W, respectively, either dehydrated or rehydrated. Body temperatures and total sweat rate were measured as well as four msw,local (on chest and thighs), assessed from sweat capsules under which Tsk,local was maintained at predetermined levels (37.0 degrees C and 35.5 degrees C). The combinations of Tsk,local levels, capsule locations, exercise intensity and hydration level chosen in our protocol led to the following results. The hydration level affected rectal temperature but not total or msw,local. No specific effect of muscle activity was found; msw,local on thighs of resting and working legs were similar. The msw,local were only influenced by exercise intensity, msw,local being more elevated during the higher intensity. No significant effect of Tsk,local on msw,local was found, whatever the experimental condition and/or the location. It was concluded that local thermal effects on msw,local could have been masked by the strong central drive for sweating which has been found to exist in subjects exercising in a warm environment.     

Diurnal sleep depth changes in the king penguin (<Emphasis Type="Italic">Aptenodytes patagonicus</Emphasis>)

Avian sleep quality depends on its depth (deeper sleep being of better quality). In king penguins (Aptenodytes patagonica), sleep may be disturbed by congeners passing in the sleeper's vicinity. As king penguin activity is increased in the morning, sleep disturbances are more likely to occur during this time period. One might therefore assume that afternoon sleepers (AS) sleep more profoundly than morning sleepers (MS). To test this hypothesis, we examined the diurnal variations in sleep depth of king penguins sleeping in resting sites adjacent to the colony of 'La Baie du Marin' (Crozet Archipelago). We measured the bodily tactile arousal threshold at the upper back level. The arousal threshold in AS was twice as high as in MS. This study demonstrates for the first time that sleep depth changes according to time of day in a diurnal wild bird. We postulate that diurnal sleep depth is increased due to decreased congener movements close to the sleeping penguin.