Geoclimatology and sleep in Africa: A mini-review.

Sleeping habits and morningness-eveningness questionnaires (chronotype), and polysomnography (internal sleep organization) were proposed to healthy volunteers living under natural climates from different locations in West Africa (Niger, Côte d'Ivoire) and Central Africa (Angola, Congo). Under the Sahelian dry climate, 138 Niger medical students (130 had afternoon naps) completed 1792 sleep questionnaires during 7-day sessions in the cool-dry and hot-dry seasons. As everywhere else on Earth, daily sleep lasted 7 to 8hours. In Abidjan (hot-humid climate), 78 medical students reported shorter sleep time, because of course schedules. Also in Abidjan, 23 African sportsmen and Expatriate soldiers slept at night and in afternoon naps. They reported similar sleep amounts than Niger students. In Congo villages, during a 5-year human African trypanosomiasis (HAT) research campaign, 45 healthy volunteers expressed morning chronotypes. The 71 HAT patients shifted from the indifferent chronotype towards morningness type. Chronotyping such patients may help evaluating treatment efficacy on brain function alterations. French soldiers executing missions in Africa were typed for morningness-eveningness. Regarding malaria prophylaxis and mosquito control, morning chronotype was more compliant than evening type. Polysomnography demonstrated internal sleep organization differences in different geoclimatic zones. The Sahelian climate promoted N3 slow-wave sleep in Africans and Expatriates during both the cool-dry and hot-dry seasons, with higher amounts in the hot-dry season. Increasing heat load by physical exercise further augmented N3. Rapid-eye-movement R sleep was high compared with values from temperate and hot-humid climates. Supramaximal exercise triggered a surprising R stage increase in the hot-dry season. In Côte d'Ivoire, Caucasian and African volunteers fragmented their sleep, although internal sleep organization approached that of temperate climates. Sleep patterns were also similar in Angola high hills and on Congo River shores. Therefore, Africans and Caucasians living in Niger hot-dry Sahelian climate exhibited major differences with those exposed to hot-humid or temperate climates.

Time course of liver nitric oxide concentration in early septic shock by cecal ligation and puncture in rats.

An overwhelming nitric oxide (NO) production is a crucial step in the circulatory events as well as in the cellular alterations taking place in septic shock. However, evidences of this role arise from studies assessing the NO production on an intermittent basis precluding any clear evaluation of temporal relationship between NO production and circulatory alterations. We evaluated this relationship by using a NO specific electrode allowing a continuous measurement of NO production. Septic shock was induced by a cecal ligation and puncture (CLP) in a first group of anesthetized rats. After the same CLP, a second group received a selective iNOS inhibitor (L-NIL). Control rats were sham operated or sham operated with L-NIL administration. While NO concentration was measured every 2 min by a NO-sensitive electrode over 7h following CLP, the liver microcirculation was recorded by a laser-Doppler flowmeter. CLP induced a severe septic shock with hypotension occurring at a mean time of 240 min after CLP. At the same time, an increase in liver NO concentration was observed, whereas a decrease in microvascular liver perfusion was noted. In the septic shock group, L-NIL administration induced an increase in arterial pressure whereas the liver NO concentration returned to baseline values. In addition, shock groups experienced an increase in iNOS mRNA. These data showed a close temporal relationship between the increase in liver NO concentration and the microvascular alteration taking place in the early period of septic shock induced by CLP. The iNOS isoform is involved in this NO increase.

Microbiosensor based on glucose oxidase and hexokinase co-immobilised on platinum microelectrode for selective ATP detection.

ATP determination is of great importance since this compound is involved in a number of vital biological processes. To monitor ATP concentration levels, we have developed a microbiosensor based on cylindrical platinum microelectrode, covered with a layer of poly-m-phenylendiamine (PPD), and layer of co-immobilised glucose oxidase and hexokinase. Conditions for biosensor measurement of ATP (pH, Mg(2+) and substrates concentration) in vitro and microbiosensor characteristics such as sensitivity, selectivity, reproducibility, storage stability were studied and optimized. Under optimal conditions the microbiosensor can measure ATP concentrations down to a 2.5 microM detection limit with response time about 15 s. Interferences by electroactive compounds like biogenic amines and their metabolites, ascorbic acid, uric acid and L-cystein are rejected in general by the PPD layer. The microbiosensor developed is insensitive to ATP analogues (or substances with similar structure), such as ADP, AMP, GTP and UTP, too. It can be used for ATP analysis in vitro in the reactions consuming or producing macroergic triphosphate molecules to study kinetics of the process and in drug design concerning development of inhibitors specific to target kinases and others target enzymes.

[Depressive-like state and sleep in laboratory mice].

In order to induce the state of anhedonia, a key symptom of depression, mice were subjected to a one-month stress procedure comprised of various stressors. Anhedonic state was defined by a reduction of preference for sucrose solution over tap water. Conventional cortical and neck-muscle electrodes were implanted to control and stressed animals under chloral-hydrate anesthesia. After a two-week recovery and habituation period, mice from chronically stressed group were re-subjected to five-day stress, and the anhedonic state was verified. As not all the stressed mice displayed a decrease in sucrose preference, animals were divided in two groups: stressed-non-anhedonic and stressed-anhedonic animals. Seven-day continuous polygraphic recording was carried out in animals from both stressed groups and the control group in recording chambers under conditions of 12/12-hour light/dark schedule. The anhedonic mice demonstrated a significant advanced shift in circadian distribution of paradoxical sleep and increased amount of paradoxical sleep during the light period. In the course of the dark period, the anhedonic group showed a slight but significant decrease in total amount of slow-wave sleep as compared to the non-anhedonic and control groups. The results suggest that the changes in sleep structure documented in the model of anhedonia are similar to those described for human depression.

Decreased heat tolerance is associated with hypothalamo-pituitary-adrenocortical axis impairment.

When rats are exposed to heat, they adapt themselves to the stressor with a wide inter-individual variability. Such differences in heat tolerance may be related to particularities in the hypothalamo-pituitary-adrenocortical (HPA) axis activation. To further this hypothesis, 80 rats instrumented with a telemetric device for abdominal temperature (Tabd) measurement were separated into two groups. Sixty-eight rats were exposed during 90 min at an ambient temperature of 40 degrees C, and 12 rats to an ambient temperature of 22 degrees C. Heat-exposed rats were then divided into three groups using the a posteriori k-means clustering method according to their Tabd level at the end of heat exposure. Heat tolerant rats (Tol, n=30) exhibiting the lowest Tabd showed a slight dehydration, a moderate triglyceride mobilization, but the highest plasma adrenocorticotropic-hormone (ACTH) and corticosterone levels. Conversely, heat exhausted rats (HE, n=14) presented the highest Tabd, a higher degree of dehydration, a greater metabolic imbalance with the lowest plasma triglyceride level and the highest lactate concentration, as well as a lowest plasma corticosterone and ACTH levels. The fact that the proopiomelanocortin (POMC) mRNA content within the pituitary was low despite of a high c-fos mRNA level is also relevant. Current inflammatory processes in HE rats were underlined by lower inhibitory factor kappaBalpha (IkappaBalpha) mRNA and higher tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mRNA. In conclusion, data show that intolerance to heat exposure is associated to an HPA axis impairment, possibly related to changes occurring in the IkappaBalpha and TNF-alpha mRNA levels.

Nitric oxide and liver microcirculation during autoregulation and haemorrhagic shock in rabbit model.

BACKGROUND: Direct evidence of nitric oxide (NO) involvement in the regulation of hepatic microcirculation is not yet available under physiological conditions nor in haemorrhagic shock. METHODS: A laser Doppler flowmetry was used to measure liver perfusion index and a specific NO-sensitive electrode was inserted into liver parenchyma of anaesthetized rabbits. Hepatic autoregulation during moderate hypovolaemia {mean arterial pressure at 50 mm Hg without liver perfusion alteration; blood withdrawal 17.7 (4.2) ml [mean (SD)]} or haemorrhagic shock [mean arterial pressure at 20 mm Hg associated with liver perfusion impairment and lactic acidosis; blood withdrawal 56.0 (6.8) ml] were investigated over 60 min and were followed by a rapid infusion of the shed blood. Involvement of NO synthases was evaluated using a non-specific inhibitor, NAPNA (Nomega-nitro-L-arginine P-nitro-anilide). RESULTS: In the autoregulation group, a decrease [30.0 (4.0) mm Hg] of mean arterial pressure did not alter liver perfusion index, whereas the liver NO concentration increased and reached a plateau [125 (10)%; compared with baseline; P<0.05]. This NO concentration was reduced to zero by the administration of NO synthase inhibitor. Haemorrhagic shock led to a rapid decrease in liver perfusion index [60 (7)%; compared with baseline; P<0.05] before an immediate and continuous increase in NO concentration [250 (50)%; compared with baseline; P<0.05]. Infusion of NO inhibitor before haemorrhagic shock reduced the NO concentration to zero and hepatic perfusion by 60 (8)% (P<0.05) of the baseline. Mean arterial pressure increased simultaneously. In these animals, during haemorrhage, a continuous increase in NO concentration still occurred and liver perfusion slightly increased. In all groups but NAPNA+haemorrhagic shock, blood replacement induced recovery of baseline values. CONCLUSIONS: NO plays a physiological role in the liver microcirculation during autoregulation. Its production is enzyme-dependent. Conversely, haemorrhagic shock induces a rapid increase in hepatic NO that is at least partially enzyme-independent.

Highly selective microbiosensors for in vivo measurement of glucose, lactate and glutamate.

An alternative approach to production of amperometric microbiosensors, which combines electrochemical electrometallization and electropolymerisation of phenylene diamine film with covalent binding enzymes, is presented. In this respect, for a sensitive detection of hydrogen peroxide (HP) at +0.4V versus Ag/AgCl (detection limit of 0.5 microM, s/n=3), carbon fiber microelectrodes (30 microm in diameter and 500 microm long) were covered with ruthenium. To obtain a highly selective detection of HP, in the presence of different interfering compounds (ascorbic acid, uric acid, etc.), an additive semi-permeable polymer film was formed on the top of the ruthenium layer by electropolymerisation of m-phenylene diamine (m-PD). The enzymatic selective layers were formed by covalent cross-linking the enzymes (glucose oxidase, lactate oxidase or glutamate oxidase) with BSA by glutaraldehyde in the presence of ascorbate oxidase. An additional polymeric layer based on polyurethane and Nafion was deposited on the top of the enzymatic membrane (glucose oxidase, lactate oxidase, or glutamate oxidase) in order to extend the dynamic range of biosensors up to 4mM for glucose (R=0.997; Y[nA]=-0.22+9.68x[glucose, mM]), 1.75mM for lactate (R=0.991; Y[nA]=0.43+15.36x[lactate, mM]) and 0.25 mM for glutamate (R=0.999; Y[nA]=0.02+29.14x[glutamate, mM]). The developed microbiosensors exhibited also negligible influences from interfering compounds at their physiological concentrations. Microbiosensors remained stable during 10h in a flow injection system at 36 degrees C and pH 7.4. The microbiosensors developed are now used in vivo and, as an example, we report here the data obtained with the glucose biosensor.

Potential role of inducible nitric oxide synthase in the sleep-wake states occurrence in old rats.

Extensive evidences now suggest that an association between inducible nitric oxide synthase and oxidative stress takes place during aging. Since the part played by inducible nitric oxide synthase in the sleep impairments associated with aging still remains unexplored, we compared its involvement in old rats (20-24 months) versus adult ones (3-5 months) using polygraphic, biochemical, voltammetric and immunohistochemical techniques. The experiments were conducted either in basal condition or after a systemic injection of selected inducible nitric oxide synthase inhibitors. We found that 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (10 mg/kg, i.p.) or aminoguanidine (400 mg/kg, i.p.) was capable to suppress rapid-eye-movement sleep and induce a delayed enhancement in slow-wave sleep in old rats. These effects did not occur in adult animals. Within the frontal cortex, the laterodorsal tegmentum and dorsal raphe nuclei, the basal inducible nitric oxide synthase activity was 85-200% higher in old rats than in adult ones. In contrast, the neuronal nitric oxide synthase activity did not vary in both groups. 2-Amino-5,6-dihydro-6-methyl-4H-1,3-thiazine administration significantly reduced inducible nitric oxide synthase activity (70-80% according to the brain areas) independently of age, but significantly decreased the cortical nitric oxide release in old rats. Finally, in frontal cortex and dorsal raphe immunohistochemical analysis showed inducible nitric oxide synthase-positive cells again only in old animals. These data support the idea that nitric oxide produced by inducible nitric oxide synthase plays a role in the triggering and maintenance of rapid-eye-movement sleep during aging.

Carbon fibre-based microbiosensors for in vivo measurements of acetylcholine and choline.

This report describes technical improvements to the manufacture of a carbon fibre electrode for the stable and sensitive detection of H2O2 (detection limit at 0.5 microM). This electrode was also modified through the co-immobilisation of acetylcholinesterase (AChE) and/or choline oxidase (ChOx) in a bovine serum albumin (BSA) membrane for the development of a sensor for in vivo measurements of acetylcholine and choline. Amperometric measurements were performed using a conventional three-electrode system forming part of a flow-injection set-up at an applied potential of 800-1100 mV relative to an Ag/AgCl reference electrode. The optimised biosensor obtained was reproducible and stable, and exhibited a detection limit of 1 microM for both acetylcholine and choline. However, due to the high operating potential used, the biosensor was prone to substantial interference from other electroactive compounds, such as ascorbic acid. Therefore, in a further step, a mediated electron transfer approach was used that incorporated horseradish peroxidase into an osmium-based redox hydrogel layered onto the active surface of the electrode. Afterwards, a Nafion layer and a coating containing AChE and/or ChOx co-immobilised in a BSA membrane were successively deposited. This procedure further increased the selectivity of the biosensor, when operated in the same flow-injection system but at an applied potential of -50 mV relative to an Ag/AgCl reference electrode. The sensor exhibited good selectivity and a high sensitivity over a concentration range (0.3-100 microM) suitable for the measurement of choline and acetylcholine in vivo.

Cortical and pontine variations occurring in the voltammetric no signal throughout the sleep-wake cycle in the rat.

Voltammetric measurements of nitric oxide (NO) were performed either in the frontal cortex (Cx) or in the nucleus raphe dorsalis (nRD) of rats equipped for polygraphic recordings. In the frontal cortex, the 650 mV signal related to NO exhibited its highest height during the waking state (W) and decreased slightly during slow-wave sleep (SWS) and even more during paradoxical sleep (PS). In the nRD, opposite variations were observed, i.e. the signal tended towards an increase during SWS and raised more consistently during PS versus W. Recordings performed either in the Cx or the nRD, throughout the light (12-h) and dark (12-h) periods, exhibited opposite nycthemeral changes, i.e. the signal height was higher in the Cx and lower in the nRD during the dark period and conversely for the light one. Paracrine and synaptic mechanisms taking place within the pons and, at least partly, also reflected in the Cx need to be further investigated.

Clinical follow-up in the rat experimental model of African trypanosomiasis.

Animal models of Human African Trypanosomiasis (HAT) have been developed to understand the pathogenic mechanisms leading to the passage into the neurological phase, most of them referring to histological aspects but not clinical or behavioral data. Our study aimed at defining simple clinical and/or behavioral markers of the passage between the hemolymphatic phase and the meningo-encephalitic stage of the disease. Sprague-Dawley rats (n=24) were infected with Trypanosoma brucei brucei AnTat 1.1E. Food intake and body weight were measured daily from the day of infection until death. Hematocrit was measured twice a week. Behavioral disturbances were evaluated through an Open-field test. A sudden weight loss occurred on the twelfth day after infection, due to a significant drop of food intake starting two days before. The rats developed an anemic state shown by the hematocrit measurements. The Open-field test showed them to be less active and reactive as soon as the second week after infestation. A complementary histological study observed trypanosomes and inflammatory cells in the choroid plexus at the same period. These results are in favor of central nervous system functional disturbances. The observed weight loss is discussed as being a parameter of the entry in the meningo-encephalitic phase. The rat model reproduces neurological symptoms observed in the human disease and may prove to be useful for further neurohistological and therapeutic studies.

Nitric oxide voltammetric measurements in the rat brain after gamma irradiation.

The effects of a lethal gamma irradiation were investigated on cerebral NO-ergic system by using a voltammetric method in freely moving rats. It is reported that the cortical NO concentration increases right from the end of the radiation exposure (15 Gy) and reaches a maximal magnitude (+120%) 24 h later. A dose-effect relationship from 2 to 15 Gy for gamma-ray exposure has also been observed. The effects, obtained with either an NO synthase inhibitor nonselective for the different NO synthase isoforms or an NO synthase inhibitor selective for the constitutive isoform, suggest that the radiation-induced increase in NO is likely to be dependent on the inducible NO synthase isoform. Moreover, experiments performed under ex vivo conditions showed that the cortical mRNA level for Ca(++)-independent NO synthase, the brain NOS activity, and urinary nitrites/nitrates increased significantly 24 h after gamma-ray exposure. These results demonstrate that a supralethal whole-body irradiation alters the NO-ergic pathways. The increase in NO obtained under such conditions might constitute a good index of central nervous system radiosensitivity during the acute phase of the radiation syndrome.

[Sleeping sickness: forgotten research?]. / Maladie du sommeil: la recherche oubliée?

Has research on sleeping sickness, i.e., human African trypanosomiasis (HAT), been forgotten? To get an idea on funding, we consulted the Medline bibliographic database for the last 14 years. The number of publications on HAT was stagnant over the study period. By comparison there was a steady increase in the number of publications dealing with malaria. These findings suggest that interest in HAT research waned in favor of other endemics even though government or other funding agencies continued to finance research networks. To illustrate this situation, we present the funding and findings of our multidisciplinary working group in a wide range of domains including sleep, endocrine rhythms, identification of biological markers, research on physiopathologic mechanisms of the host-pathogen relationship, and development on new medications. Over the last 14 years, a total of 1 million Euros was spent to produce 68 publications on Medline, i.e., roughly 15000 [symbol: see text] per publication.

Changes in the sleep-wake cycle architecture and cortical nitric oxide release during ageing in the rat.

Changes in sleep-wake states and nitric oxide release were examined in aged rats versus young-adult ones. Sleep-wake recordings and nitric oxide measurements were taken from animals chronically equipped with polygraphic and voltametric electrodes. Animals were examined in baseline conditions and in response to a 24-hour paradoxical sleep deprivation. In aged rats, basal amount of paradoxical sleep is decreased during the light phase versus young-adult animals. After paradoxical sleep deprivation, a paradoxical sleep rebound occurs with an amount and intensity that are less marked in aged animals than in young-adult rats. The amplitude of the circadian distribution for wakefulness, slow-wave sleep and paradoxical sleep amounts is reduced with age. Finally, delta-slow-wave sleep and theta-paradoxical sleep power spectra are attenuated either in baseline conditions or after paradoxical sleep deprivation in aged animals. It is also reported that cortical nitric oxide release exhibits a circadian rhythm with higher amplitude in aged rats than in young-adult ones. However, after paradoxical sleep deprivation, a limited overproduction of nitric oxide is obtained compared with young-adult ones. These results, evidencing the dynamics of the nitric oxide changes occurring in relation to the sleep-wake cycle, point out the homeostatic paradoxical sleep regulation as an age-dependent process in which the nitric oxide molecule is possibly involved.

Polysomnography in transgenic hSOD1 mice as Down syndrome model.

Sleep-wake homeostasis is crucial for behavioral performances and memory in the general population and in learning disability populations among them Down syndrome patients. We investigated, in a mouse model of Down syndrome, cortical EEG and sleep-wake architecture under baseline conditions and after a 4 hr sleep deprivation (SD). Young heterozygous transgenic mice (S/+) for the human Cu/Zn superoxide dismutase (hSOD-1) were obtained on FVB/N background. Baseline records for slow wave sleep (SWS) and wake (W) parameters were the same in S/+ and control mice whereas paradoxical sleep (PS) episode number decreased and PS latency increased after light off in S/+ mice. These data correlate well the polysomnographic phenotype of young DS patients.

In vivo monitoring of evoked noradrenaline release in the rat anteroventral thalamic nucleus by continuous amperometry.

Continuous amperometry coupled with untreated carbon-fibre electrodes was used in anaesthetized rats to measure the noradrenaline release evoked in the anteroventral thalamic nucleus by electrical stimulation of the dorsal noradrenergic bundle. As expected, the variations in the oxidation current detected in the anteroventral thalamic nucleus exhibited the characteristics of the in vivo noradrenaline release. They were closely correlated with stimulation and consistent with the anatomy of the noradrenergic system involved. They were abolished by the ejection of tetrodotoxin in the vicinity of the carbon-fibre electrode, diminished by clonidine, an alpha-2 agonist, and restored by yohimbine, an alpha-2 antagonist. Furthermore, the time course of these variations was dramatically increased by desipramine, a specific noradrenaline reuptake blocker. In contrast, neither dopamine nor serotonin reuptake blockers, nor the monoamine oxidase inhibitor pargyline were able to alter them. The main advantage of the present approach is its excellent time resolution. We show here for the first time that after single pulse stimulation, noradrenaline is released and eliminated in 118 milliseconds, this time lapse corresponding to the maximal period beyond which subsequent noradrenaline releases could not add up. These observations are in good agreement with the physiological relationship previously observed between impulse flow and noradrenaline overflow.

Effect of noradrenergic denervation of medial prefrontal cortex and dentate gyrus on recovery after sleep deprivation in the rat.

The noradrenergic-locus coeruleus (LC) system has a regulatory influence on forebrain neuronal networks. We have previously shown that the amygdala is strongly implicated in the mechanism of rebound seen after a 10 h sleep deprivation (SD). In the present study, our objective was to determine whether the medial prefrontal cortex and dentate gyrus (DG) which receive an important innervation from the LC, play a role in the rebound mechanisms. We found that microinjection of the specific noradrenergic neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, into these regions had no effect on the increase in paradoxical sleep duration seen after SD, suggesting that noradrenergic (NA) innervation of the prefrontal cortex and DG are not involved in sleep rebound regulation.

Anatomical distribution of serotonin-containing neurons and axons in the central nervous system of the cat.

By using a monoclonal antibody to serotonin (5-HT), an immunohistochemical study was undertaken to provide a comprehensive description of the 5-HT-containing neurons and of the distribution of their axonal processes in the cat brain and spinal cord. The localization of cell bodies was comparable to that previously reported in studies using formaldehyde-induced fluorescence and other 5-HT antibodies, with a large proportion of labeled neurons in the raphe nuclei and a minor, yet not negligible number, in the ventral, lateral, and dorsal reticular formation. The ascending efferent non-varicose axons were best visualized in sagittal sections and mainly seen taking a rostroventral direction through the tegmentum. The varicose axons could be grossly classified into thin and large fibers, according to the size and shape of the immunoreactive varicosities, which were elongated (up to 2 microm in length and 1 microm in width) or round (2-4 microm in diameter). Varicose axonal arborizations invaded almost every region of the gray matter and avoided large myelinated bundles except in the spinal cord. Variations in the density of the plexuses of immunoreactive fibers generally followed the anatomical divisions and were also observed within nuclei, especially in laminated structures. Only the superior olivary complex could be regarded as devoid of 5-HT-containing axons. A few areas contained extremely rich fiber plexuses. These were the olfactory tubercle, nucleus accumbens, ventral mesencephalon, periventricular gray from the hypothalamus to the pons, facial nucleus, subdivisions of the inferior olive, and the intermediolateral nucleus in the spinal cord. Varicose axons formed tight pericellular arrays in the neocortex, mainly the ectosylvian gyrus, and in the lateral septum and medullar magnocellular nucleus. These data, combined with those of the literature concerning the synaptic versus non-synaptic mode of termination of the 5-HT-immunoreactive varicosities and the high number of distinct receptors, are indicative of the multiple possible actions of serotonin in the central nervous system.

Brain extracellular glucose assessed by voltammetry throughout the rat sleep-wake cycle.

In the present study, cortical extracellular levels of glucose were monitored for the first time throughout the sleep-wake states of the freely moving rat. For this purpose, polygraphic recordings (electroencephalogram of the fronto-occipital cortices and electromyogram of the neck muscles) were achieved in combination with differential normal pulse voltammetry (DNPV) using a specific glucose sensor. Data obtained reveal that the basal extracellular glucose concentration in the conscious rat is 0.59 +/- 0.3 m M while under chloral hydrate anaesthesia (0.4 g/kg, i.p.) it increases up to 180% of its basal concentration. Regarding the sleep-wake cycle, the existence of spontaneous significant variations in the mean glucose level during slow-wave sleep (SWS = +13%) and paradoxical sleep (PS = -11%) compared with the waking state (100%) is also reported. It is to be noticed that during long periods of active waking, glucose level tends towards a decrease that becomes significant after 15 min (active waking = -32%). On the contrary, during long episodes of slow-wave sleep, it tends towards an increase which becomes significant after 12 min (SWS = +28%). It is suggested that voltammetric techniques using enzymatic biosensors are useful tools allowing direct glucose measurements in the freely moving animal. On the whole, paradoxical sleep is pointed out as a state highly dependent on the availability of energy and slow-wave sleep as a period of energy saving.

Human macrophage tumor necrosis factor (TNF)-alpha production induced by Trypanosoma brucei gambiense and the role of TNF-alpha in parasite control.

Trypanosoma brucei gambiense, a causative agent of sleeping sickness, induced a dose-dependent production of tumor necrosis factor (TNF)-alpha by human macrophages in vitro. TNF-alpha was also induced in the Mono Mac 6 cell line, which indicates a direct effect of parasite components on macrophages. Parasite-soluble factors were also potent inducers of TNF-alpha. The addition of anti-TNF-alpha to cocultures of macrophages and parasites increased the number of trypanosomes and their life span, whereas irrelevant antibodies had no effect. TNF-alpha may have a direct role (i.e., direct trypanolytic activity) and/or an indirect one, such as TNF-alpha-mediated induction of cytotoxic molecules. A direct dose-dependent lytic effect of TNF-alpha on purified parasites was observed. This lytic effect was inhibited by anti-TNF-alpha. These data suggest that, as in experimental trypanosomiasis, TNF-alpha is involved in parasite growth control in human African trypanosomiasis.