Hyperoxia increases paradoxical sleep rhythm in the pontine cat

Pontine cat is an ectothermic preparation, whose central temperature can artificially be lowered from 36 degrees C to 26 degrees C; this gradual hypothermia is accompanied by a dramatic increase in paradoxical sleep (PS). Two main hypotheses might explain this result: executive systems of PS might be switched on gradually by cold-sensitive thermodetectors, whereas inhibitory monoaminergic mechanisms appear to be warm-sensitive. On the other hand, energy saving mechanisms peculiar to hypothermia might promote PS appearance. Indeed, in normal animals, PS is selectively suppressed both by hyperthermia and hypoxia. The inhibitory effect of hypoxia might explain why hypothermia, which protects the brain against hypoxic alterations, might facilitate PS. If this last hypothesis is correct, the putative increase in cerebral oxygen supply might increase PS. For this reason, we submitted eight pontine carotid-deafferented cats, kept at the same central temperature (34 +/- 0.5 degrees C: temperature clamp) to periodic hyperoxia (PaO2 = 58 +/- 7 kPa) or room air (PaO2 = 17 +/- 2 kPa) alternatively during 4- or 12-h periods. Hyperoxia induced an 85% increase in PS, mainly due to an increase in PS rhythm (PS cycle duration was 65 +/- 4 min in normoxia and 45 +/- 4 min in hyperoxia, p<0.0001). In five animals, after hyperoxia, PS cycle returned gradually back to control values in 4 to 12 h. These findings show that PS is exquisitely sensitive to conditions that impair oxidative metabolism. The role of cholinergic executive PS systems as putative metabolic-sensitive neurons remains to be established.     

Hydrodynamic blood plasma separation in microfluidic channels

The separation of red blood cells from plasma flowing in microchannels is possible by biophysical effects such as the Zweifach–Fung bifurcation law. In the present study, daughter channels are placed alongside a main channel such that cells and plasma are collected separately. The device is aimed to be a versatile but yet very simple module producing high-speed and high-efficiency plasma separation. The resulting lab-on-a-chip is manufactured using biocompatible materials. Purity efficiency is measured for mussel and human blood suspensions as different parameters, such as flow rate and geometries of the parent and daughter channels are varied. The issues of blood plasma separation at the microscale are discussed in relation to the different regimes of flow. Results are compared with those obtained by other researchers in the field of micro-separation of blood.     

Determination of NADH in the rat brain during sleep-wake states with an optic fibre sensor and time-resolved fluorescence procedures

The present paper reports a nanosecond time-resolved fluorescence derived from the cortex and the area of the periaqueductal gray including the nucleus raphe dorsalis (PAG-nRD) in unanaesthetized freely moving rats. The measurements were acquired through a single optic fibre transmitting a subnanosecond nitrogen laser pulse (337 nm, 15 Hz) and collecting the brain fluorescence occurring at 460 nm which might depend on mitochondrial NADH (reduced form of nicotinamide adenine dinucleotide). The fluorometric method was combined with polygraphic recordings, and this procedure allowed us to define, for the first time, variations of the 460 nm signal occurring throughout the sleep-wake cycle. In the PAG-nRD, the signal exhibited moderate heterogeneous variation in amplitude during slow-wave as compared to the waking state. Constant increases were observed during paradoxical sleep as compared to the waking state. For this state of sleep the magnitude of the variations depended on the optic fibre location. In the cortex and during either slow-wave sleep or paradoxical sleep, the signal presented moderate increases which were significant during paradoxical sleep. The magnitude of the redox variations observed either in the PAG-nRD or in the cortex might be ascribed to the oxidative energy balance which is related to sleep states.     

Duration modelling and evaluation for Arabic statistical parametric speech synthesis

Multimedia Tools and Applications - Sound duration is responsible for rhythm and speech rate. Furthermore, in some languages phoneme length is an important phonetic and prosodic factor. For...     

Afferent connections of the nucleus raphe dorsalis in the cat as visualized by the horseradish peroxidase technique

Using a retrograde tracer technique with protein horseradish peroxidase (HRP), attempts were made to determine afferent projections to the nucleus raphe dorsalis (NRD). As a control, the injection of the HRP was also made into one of the following structures adjacent to the NRD: (1) mesencephalic periaque ductal gray; (2) nucleus linearis intermedius; and (3) third cranial nucleus. The present results indicate that the NRD, particularly is rostral part, receives direct projections arising from: (1) locus coeruleus complex (locus coeruleus, locus coerulus alpha, and locus subcoeruleus); (2) parabrachial nuclei (nucleus parabrachialis lateralis and medialis); (3) nucleus laterodorsalis tegmenti; (4) griseum centrale pontis, particularly the caudal part of the nucleus incertus; (5) substantia nigra; (6) lateral habenular nucleus; (7) hypothalamic areas, particularly dorsal and lateral hypothalamic areas; (8) preoptic areas; (9) anarea dorso-lateral to the inferior olivary complex and medial to the lateral reticular nucleus; and (10) raphe nuclei; particularly nucleus linearis intermedius, centralis superior, pontis and magnus. The present findings thus confirm some previous reports on the afferent projections to the NRD described in the cat and rat, and further indicate the richness of afferent connections of the NRD. Some problems of the peroxidase technique have also been discussed.     

Thermal diffusion probe and instrument system for tissue blood flowmeasurements: validation in phantoms and in vivo organs

A minimally invasive probe and instrument system for real-time measurements of temperature, thermal conductivity and tissue blood flow has been designed for research and clinical use. The essence of the probe is a thermistor, located at the tip of catheters or glass and steel needles, and operating in transient self-heated mode at constant temperature increment. Thermal conductivity and tissue blood flow are determined by use of a coupled tissue-probe thermal model. The effects of temporal baseline temperature shifts are minimized by a novel, automatic, analog compensation circuit. Very short heating periods (3 s) and cooling periods (12 s) provided near-continuous measurements (4/min). Calibration experiments performed in media of known thermal conductivity exhibit a linear response with respect to thermal conductivity. In vitro experiments performed in isolated perfused dog liver preparations are presented to evaluate this instrument system. In vivo experiments performed in cat brain, dog liver, and human tumor demonstrate the ability of this instrument system to perform physiologically valid measurements (comparison inter-subjects and intra-subjects). The minimally invasive probes (0.8 mm OD) are capable of long term measurements (several months), with minimal tissue reactions (0.3 mm around the probe)     

A dopamine-synthesizing cell group demonstrated in the human basal forebrain by dual labeling immunohistochemical technique of tyrosine hydroxylase and aromatic L-amino acid decarboxylase

The human basal forebrain has been known to contain many neurons immunoreactive (ir) to tyrosine hydroxylase (TH; the first dopamine-synthesizing enzyme). We examined whether these neurons might contain aromatic L-amino acid decarboxylase (AADC; the second step dopamine-synthesizing enzyme) by dual labeling immunohistochemistry and confocal laser-scanning microscopy. Neurons dually-labeled for TH and AADC were found in the anterior olfactory nucleus, olfactory tubercle and the ventral margin of the rostral nucleus accumbens. The examination in the basal forebrain of the macaque monkey also gave substantially the same results. These neurons appear to constitute an independent dopaminergic cell group in the primate basal forebrain.     

Forebrain afferents to the rat dorsal raphe nucleus demonstrated by retrograde and anterograde tracing methods

The dorsal raphe nucleus through its extensive efferents has been implicated in a great variety of physiological and behavioural functions. However, little is know about its afferents. Therefore, to identify the systems likely to influence the activity of serotonergic neurons of the dorsal raphe nucleus, we re-examined the forebrain afferents to the dorsal raphe nucleus using cholera toxin b subunit and Phaseolus vulgaris-leucoagglutinin as retrograde or anterograde tracers. With small cholera toxin b subunit injection sites, we further determined the specific afferents to the ventral and dorsal parts of the central dorsal raphe nucleus, the rostral dorsal raphe nucleus and the lateral wings. In agreement with previous studies, we observed a large number of retrogradely-labelled cells in the lateral habenula following injections in all subdivisions of the dorsal raphe nucleus. In addition, depending on the subdivision of the dorsal raphe nucleus injected, we observed a small to large number of retrogradely-labelled cells in the orbital, cingulate, infralimbic, dorsal peduncular, and insular cortice, a moderate or substantial number in the ventral pallidum and a small to substantial number in the claustrum. In addition, we observed a substantial to large number of cells in the medial and lateral preoptic areas and the medial preoptic nucleus after cholera toxin b subunit injections in the dorsal raphe nucleus excepting for those located in the ventral part of the central dorsal raphe nucleus, after which we found a moderate number of retrogradely-labelled cells. Following cholera toxin b subunit injections in the dorsal part of the central dorsal raphe nucleus, a large number of retrogradely-labelled cells was seen in the lateral, ventral and medial parts of the bed nucleus of the stria terminalis whereas only a small to moderate number was visualized after injections in the other dorsal raphe nucleus subdivisions. In addition, respectively, a substantial and a moderate number of retrogradely-labelled cells was distributed in the zona incerta and the subincertal nucleus following all tracer injections in the dorsal raphe nucleus. A large number of retrogradely-labelled cells was also visualized in the lateral, dorsal and posterior hypothalamic areas and the perifornical nucleus after cholera toxin b subunit injections in the dorsal part of the central raphe nucleus and to a lesser extent following injections in the other subdivisions. We further observed a substantial to large number of retrogradely-labelled cells in the tuber cinereum and the medial tuberal nucleus following cholera toxin b subunit injections in the dorsal part of the central dorsal raphe nucleus or the lateral wings and a small to moderate number after injections in the two other dorsal raphe nucleus subdivisions. A moderate or substantial number of labelled cells was also seen in the ventromedial hypothalamic area and the arcuate nucleus following cholera toxin injections in the dorsal part of the central dorsal raphe nucleus and the lateral wings and an occasional or small number with injection sites located in the other subdivisions. Finally, we observed, respectively, a moderate and a substantial number of retrogradely-labelled cells in the central nucleus of the amygdala following tracer injections in the ventral or dorsal parts of the central dorsal raphe nucleus and a small number after injections in the other subnuclei. In agreement with these retrograde data, we visualized anterogradely-labelled fibres heterogeneously distributed in the dorsal raphe nucleus following Phaseolus vulgaris-leucoagglutinin injections in the lateral orbital or infralimbic cortice, the lateral preoptic area, the perifornical nucleus, the lateral or posterior hypothalamic areas, the zona incerta, the subincertal nucleus or the medial tuberal nucleus. (ABSTRACT TRUNCATED)     

Crystalluria: a clinically useful investigation in children with primary hyperoxaluria post-transplantation

Primary hyperoxaluria type I (PH I) is a congenital error of metabolism that can be manifested by an increased oxalate production, and ultimately result in kidney failure. After a combined liver/kidney transplantation, children with PH I have persistent excretion of oxalate that causes crystal formation in the urinary tract, and could result in systemic oxalosis and eventual graft failure. We speculated that crystalluria may be predictive of this nephrolithogenic tendency and thus investigated the effect of an intensive therapeutic strategy to prevent crystal formation in 13 children at our hospital. Oxalate crystal volume (OCV) measurements were performed at regular intervals for 36 months, and compared with urine supersaturation measurements. We found that crystalluria with the OCV measurement is non-invasive, easily performed, and gives feedback on the efficacy of PH I therapy within one hour. Further study is needed to determine whether this method is a better predictor of nephrocalcinosis than is supersaturation alone.     

Le traitement du signal vocal voice signal processing

The speech processing studies have advanced rapidly in recent years spurred on by great progresses in thevlsi technologies and in the digitalization of the networks. This paper offers an overview of the most attractive techniques which have focused the recent researchs and developments in speech coding, recognition and synthesis areas. For speech compression, the emphasis is put on a family of techniques named code-excited linear prediction (celp) which dominates current studies for rates in the range of 4 to 16 kbit/s. In terms of speech recognition, particular emphasis is placed on the following three elements which are essential in order to increase the robustness of the systems : telephone line adaptation, rejection of parasite noise and out-of-vocabulary words, and keyword spotting. In terms of text-to-speech synthesis, thepsola (pitch synchronous overlap and add) technique is outlined herein. This technique gives rise to a new generation of synthesis systems which produce speech with very natural timbre. The analysis of current tendencies for each area allows to suggest attractive directions for future research.