Effects of restricted sleep with different exercise loads upon subsequent sleep

Seven male cats were adapted to different schedules of restricted sleep. The cat was permitted to go to sleep either 2, 4 or 8 hours per day with the balance to 24-h periode spent in wakefulness enforced by means of a treadmill. Two experiments were run and the same cats served in both runs. The experiments and schedules were separated by at least two weeks during which time cats were maintained under ordinary laboratory conditions. Our experiment used treadmill speed of 2.6 m/min which was easily tolerated and effective in eliminating sleep. Another experiment used treadmill speed of 4.6 m/min which produced more physical exercise. As available sleep time become progressively shorter, REM sleep increased while SWS decreased. If restriction in sleep time was associated with more physical exercise then the composition of the subsequent sleep was different : SWS increased while REM sleep decreased. The functional significance of these opposite effects are presumably different. The immediate SWS response to the prior muscular exercise is suggestive of its recovery function.     

Potassium currents regulating secretion from Brunner's glands in guinea pig duodenum

This study examined the role of outward K(+) currents in the acinar cells underlying secretion from Brunner's glands in guinea pig duodenum. Intracellular recordings were made from single acinar cells in intact acini in in vitro submucosal preparations, and videomicroscopy was employed in the same preparation to correlate these measures with secretion. Mean resting membrane potential was -74 mV and was depolarized by high external K(+) (20 mM) and the K(+) channel blockers 4-aminopyridine (4-AP), quinine, and clotrimazole. The cholinergic agonist carbachol (60-2,000 nM; EC(50) = 200 nM) caused a concentration-dependent initial hyperpolarization of the membrane and an associated decrease in input resistance. This hyperpolarization was significantly decreased by 20 mM external K(+) or membrane hyperpolarization and increased by 1 mM external K(+) or membrane depolarization. It was blocked by the K(+) channel blockers tetraethylammonium (TEA), 4-AP, quinine, and clotrimazole but not iberiotoxin. When videomicroscopy was employed to measure dilation of acinar lumen in the same preparation, carbachol-evoked dilations were altered in a parallel fashion when external K(+) was altered. The dilations were also blocked by the K(+) channel blockers TEA, 4-AP, quinine, and clotrimazole but not iberiotoxin. These findings suggest that activation of outward K(+) currents is fundamental to the initiation of secretion from these glands, consistent with the model of K(+) efflux from the basolateral membrane providing the driving force for secretion. The pharmacological profile suggests that these K(+) channels belong to the intermediate conductance group.     

Linear mitochondrial DNAs from yeasts: telomeres with large tandem repetitions

The terminal structure of the linear mitochondrial DNA (mtDNA) from the yeast Candida parapsilosis was investigated. This mtDNA, 30 kb long, has symmetrical ends forming inverted terminal repeats. These repeats are made up of a variable number of tandemly repeating units of 738 by each; the terminal nucleotide corresponds to a precise position within the last repeat unit sequence. The ends had an open structure accessible to enzymes, with a 5 single-stranded extension of about 110 nucleotides. No circular forms were detected in the DNA preparations. Two other unrelated species, Pichia philodendra and Candida salmanticensis also appear to have a linear mtDNA of similar organization. These linear DNAs (which we name Type 2 linear mtDNAs) are distinct from the previously described linear mtDNAs of yeasts whose termini are formed by a closed hairpin loop (Type 1 linear mtDNA). The terminal structure of C. parapsilosis mtDNA is reminiscent of the linear mitochondrial genomes of the ciliate Tetrahymena although, in the latter, the telomeric tandem repeat unit is considerably shorter.     

Energetic Optimisation of Foraging Honeybees: Flexible Change of Strategies in Response to Environmental Challenges

Heterothermic insects like honeybees, foraging in a variable environment, face the challenge of keeping their body temperature high to enable immediate flight and to promote fast exploitation of resources. Because of their small size they have to cope with an enormous heat loss and, therefore, high costs of thermoregulation. This calls for energetic optimisation which may be achieved by different strategies. An ‘economizing’ strategy would be to reduce energetic investment whenever possible, for example by using external heat from the sun for thermoregulation. An ‘investment-guided’ strategy, by contrast, would be to invest additional heat production or external heat gain to optimize physiological parameters like body temperature which promise increased energetic returns. Here we show how honeybees balance these strategies in response to changes of their local microclimate. In a novel approach of simultaneous measurement of respiration and body temperature foragers displayed a flexible strategy of thermoregulatory and energetic management. While foraging in shade on an artificial flower they did not save energy with increasing ambient temperature as expected but acted according to an ‘investment-guided’ strategy, keeping the energy turnover at a high level (∼56–69 mW). This increased thorax temperature and speeded up foraging as ambient temperature increased. Solar heat was invested to increase thorax temperature at low ambient temperature (‘investment-guided’ strategy) but to save energy at high temperature (‘economizing’ strategy), leading to energy savings per stay of ∼18–76% in sunshine. This flexible economic strategy minimized costs of foraging, and optimized energetic efficiency in response to broad variation of environmental conditions.     

Honeybee Colony Thermoregulation – Regulatory Mechanisms and Contribution of Individuals in Dependence on Age,Location and Thermal Stress

Honeybee larvae and pupae are extremely stenothermic, i.e. they strongly depend on accurate regulation of brood nest temperature for proper development (33–36°C). Here we study the mechanisms of social thermoregulation of honeybee colonies under changing environmental temperatures concerning the contribution of individuals to colony temperature homeostasis. Beside migration activity within the nest, the main active process is “endothermy on demand” of adults. An increase of cold stress (cooling of the colony) increases the intensity of heat production with thoracic flight muscles and the number of endothermic individuals, especially in the brood nest. As endothermy means hard work for bees, this eases much burden of nestmates which can stay ectothermic. Concerning the active reaction to cold stress by endothermy, age polyethism is reduced to only two physiologically predetermined task divisions, 0 to ∼2 days and older. Endothermic heat production is the job of bees older than about two days. They are all similarly engaged in active heat production both in intensity and frequency. Their active heat production has an important reinforcement effect on passive heat production of the many ectothermic bees and of the brood. Ectothermy is most frequent in young bees (<∼2 days) both outside and inside of brood nest cells. We suggest young bees visit warm brood nest cells not only to clean them but also to speed up flight muscle development for proper endothermy and foraging later in their life. Young bees inside brood nest cells mostly receive heat from the surrounding cell wall during cold stress, whereas older bees predominantly transfer heat from the thorax to the cell wall. Endothermic bees regulate brood comb temperature more accurately than local air temperature. They apply the heat as close to the brood as possible: workers heating cells from within have a higher probability of endothermy than those on the comb surface. The findings show that thermal homeostasis of honeybee colonies is achieved by a combination of active and passive processes. The differential individual endothermic and behavioral reactions sum up to an integrated action of the honeybee colony as a superorganism.     

New lipophilic phthalimido- and 3-phenoxybenzyl sulfonates: inhibition of antigen 85C mycolyltransferase activity and cytotoxicity

Four new sulfonates were prepared as potential inhibitors of antigen 85C, a mycolyl transferase involved in the biosynthesis of the mycobacterial cell wall being designed on the basis of the proposed catalytic mechanism and antigen 85C crystal structure. The inhibitors contained a sulfonate moiety, 3-phenoxybenzyl alcohol or N-(hydroxyethyl)phthalimide as trehalose mimetics, and an alkyl chain of different length mimicking either the mycolate (alpha-chain or the mycolic acid (beta-branch. One compound displayed promising activity in a mycolyltransferase inhibition assay (compound 2b, IC50 = 4.3 microM). The two compounds containing a phthalimide moiety (compounds 3a and 3b) showed significant and selective cytotoxicity against the breast cancer cell line MDA-MB231.     

Thermoregulation of water foraging wasps (Vespula vulgaris and Polistes dominulus)

A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T_a and solar radiation. At moderate T_a (22–28 °C) the regression lines revealed mean thorax temperatures (T_th) of 35.5–37.5 °C in Vespula, and of 28.6–33.7 °C in Polistes. At high T_a (30–39 °C) T_th was 37.2–40.6 °C in Vespula and 37.0–40.8 °C in Polistes. The thorax temperature excess (T_th–T_a) increased at moderate T_a by 1.9 °C (Vespula) and 4.4 °C (Polistes) per kW⁻¹ m⁻². At high T_a it increased by 4.0 °C per kW⁻¹ m⁻² in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T_a (22–28 °C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T_a (30–39 °C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature.     

Masticatory muscle and temporomandibular joint pain in Croatian war veterans with posttraumatic stress disorder

The aim of this study was to investigate the prevalence and intensity of masticatory muscle and temporomandibular joint (TMJ) pain in Croatian war veterans with posttraumatic stress disorder (PTSD). The examined group consisted of 100 Croatian war veterans, in whom PTSD had previously been diagnosed. Patients were compared with 92 subjects who had not taken part in the war and in whom PTSD was excluded by psychiatric examination. The clinical examination consisted of palpation of the masticatory muscles, the prominent neck musculature, and TMJ. The examination technique used and the definition of items were previously tested for reliability and validity. 93% of the subjects with PTSD had masticatory muscle tenderness compared to 45.65% of the subjects in the control group (chi2 = 51.46, p < 0.0001). The most frequent painful location in the subjects with PTSD was the left lateral pterygoid site in 88%, and in subjects of the control group the right lateral pterygoid site in 28.26% of cases. The most painful location in the PTSD group was the left lateral pterygoid site in 72%, and in the control group the left posterior digastric in 4.35% of cases. 58% of the subjects with PTSD had TMJ tenderness compared to 3.26% of subjects in the control group (chi2 = 66.23, p < 0.0001). The most frequent painful location of TMJ in both groups was the left posterior capsule; in the PTSD group 38% and in subjects in the control group 2.17% of cases. The most painful location was the left posterior capsule in 28% of subjects with PTSD, while not one subject in the control group reported severe painful sensitivity. The very high frequency and intensity of pain in subjects with PTSD confirms the effect of stress on muscle and joint sensitivity, i.e. perception of pain.     

Dopamine protects neurons against glutamate-induced excitotoxicity

Glutamate excitotoxicity is responsible for neuronal death in acute neurological disorders including stroke, trauma and neurodegenerative disease. Loss of calcium homeostasis is a key mediator of glutamate-induced cell death. The neurotransmitter dopamine (DA) is known to modulate calcium signalling, and here we show that it can do so in response to physiological concentrations of glutamate. Furthermore, DA is able to protect neurons from glutamate-induced cell death at pathological concentrations of glutamate. We demonstrate that DA has a novel role in preventing delayed calcium deregulation in cortical, hippocampal and midbrain neurons. The effect of DA in abolishing glutamate excitotoxicity can be induced by DA receptor agonists, and is abolished by DA receptor antagonists. Our data indicate that the modulation of glutamate excitotoxicity by DA is receptor-mediated. We postulate that DA has a major physiological function as a safety catch to restrict the glutamate-induced calcium signal, and thereby prevent glutamate-induced cell death in the brain.