Biomedical subjects

B Seri

Publications and source records attributed to B Seri.

10 recordsLinked to original sources

PubMed2006

Composition and organization of the SCZ: a large germinal layer containing neural stem cells in the adult mammalian brain.

Two known germinal zones continue to generate new neurons and glia in the adult mammalian brain: the subventricular zone (SVZ), lining the lateral walls of the lateral ventricle, and the subgranular zone of the dentate gyrus. Here we describe a region we will refer to as the subcallosal zone (SCZ). The SCZ is a caudal extension of the SVZ that is no longer associated to an open ventricle. It lies between the hippocampus and the corpus callosum. Cells isolated from the SCZ and cultured as neurospheres behave as neural stem cells in vitro. Using electron and light microscopy, we describe the cell types present in this region and how their organization differs from that of the SVZ. Using retroviral labeling and homotypic-homochronic microtransplantation techniques, we show that the majority of cells born in the SCZ migrate into the corpus callosum to become oligodendrocytes in vivo. This study defines the organization and fate of cells born in a large germinal region of the adult forebrain.

Aging↗

PubMed2001

Astrocytes give rise to new neurons in the adult mammalian hippocampus.

Neurogenesis in the dentate gyrus of the hippocampus persists throughout life in many vertebrates, including humans. The progenitors of these new neurons reside in the subgranular layer (SGL) of the dentate gyrus. Although stem cells that can self-renew and generate new neurons and glia have been cultured from the adult mammalian hippocampus, the in vivo primary precursors for the formation of new neurons have not been identified. Here we show that SGL cells, which express glial fibrillary acidic protein and have the characteristics of astrocytes, divide and generate new neurons under normal conditions or after the chemical removal of actively dividing cells. We also describe a population of small electron-dense SGL cells, which we call type D cells and are derived from the astrocytes and probably function as a transient precursor in the formation of new neurons. These results reveal the origins of new neurons in the adult hippocampus.

Animals↗

PubMed1990

Auditory event-related potentials and reaction times during simple sensorymotor tasks in subjects with sickle cell disease and related hemoglobinopathies.

40 subjects of both sexes assigned to five groups of 8: healthy students, homozygous sicklemics, hemoglobin SC sicklemics, sickle cell Bo thalassemics, and sickle cell B+ thalassemics were subjected to 1/simple auditory stimuli; 2/paired auditory stimuli. The subjects were asked to respond quickly, by pressing a push button on detection of the simple stimulus or the unconditional stimulus of paired stimuli. A subsequent increase in reaction times and a reduction in event-related potential component amplitudes were obvious in major (SS and SC) sicklemics compared to controls and sickle cell B thalassemics. Between simple and paired auditory conditions, reaction times were more increased in sicklemics than in controls. These findings suggest that impairment of attentiveness, performance and cognitive capability in sicklemics is a function of sickle cell anemia severity.

Adolescent↗

PubMed1990

Effects of Mel B arsobal and alpha-difluoromethylornithine on the awakening electroencephalogram of humans with gambiense trypanosomiasis disease: preliminary report.

Five males and three females, at the encephalic stage of sleeping sickness, were submitted to trypanocide therapies. Three of the patients were treated with the Mel B Arsobal drug, the five others with difluoromethylornithine, using different protocols. Awakening electroencephalographic data were obtained prior to treatment and, at regular intervals, during and after treatment. Prior to treatment the awakening tracings showed important abnormalities (slow delta waves were superimposed on theta background rhythms). During treatment (except in one patient treated with Arsobal) recordings returned gradually to fast rhythms and several days after therapy, tracings returned to the normal awakening patterns. The use of the awakening electroencephalogram as a tool to test effects of curative drugs in the sleeping sickness syndrome is discussed.

Adolescent↗

PubMed1989

[Cortical reactivity during reaction time tests in sprinters].

Thirty-two male subjects divided into 4 groups (of 8--controls, witnesses, students in physical and athletic education (PAE) and sprinters--were submitted to 1) simple auditory stimuli, 2) paired auditory stimuli, and 3) simple and paired auditory stimuli. The subjects, except the control group, have been assigned the task of quickly responding by pressing a button, accordingly the detection of the simple stimulus, of the imperative stimulus when the stimuli are paired, or the simple and imperative stimuli when they are randomly matched. The results show that the amplitude of the event-related potential components and of the CNV is significantly more important in sprinters and PEA students than in other groups. The differences indicate a greater adaptative reactivity of attentional mechanisms in athletes. In all the groups, the variations in the event-related potentials and of the CNV, as well as the variations of RT between conditions 1 and 2, indicate that the effects of activation and preparation differ depending on whether or not the signal for execution of the motor response is preceded by a preparatory signal. The decrease in event-related potentials and CNV amplitude and the elongation of RT in divided attention condition suggest that when subjects have to distinguish, at the same time, simple and paired auditory stimuli, interferences are induced. The attention is disturbed performance are impaired. Sprinters are less susceptible to interferences than control persons, their performances remaining significantly better.

Adult↗

PubMed1989

Motor skill acquisition influences brain responsiveness in sprinters.

Contingent negative variation (CNV) and reaction time were examined in four groups of eight young adult men: controls, witnesses, students in physical and athletic education, and sprinters. Subjects, except the control group, were asked to detect and respond quickly by pressing a button in the following experimental conditions: 1) simple auditory stimuli, 2) paired auditory stimuli, 3) mixed simple and paired auditory stimuli.- A higher CNV voltage and lower reaction time and reaction time variability were obvious in students in physical and athletic education and sprinters, compared to controls and witnesses. In all the groups CNV amplitude declined in the third condition, reaction time and reaction time variability augmented from condition 1 to condition 3. These results show that relationships couple attentiveness and motor activation processes. The motor activation differed for simple starter and presignalled starter conditions (conditions 1 and 2). An increase of discrimination difficulty diminished the performance.

Acoustic Stimulation↗

PubMed1987

Relation between warning stimuli and contingent negative variation in man.

Seven right handed male students were submitted to standard and target paired auditory stimuli to determine the relationship between contingent negative variation (CNV) and the slow negative waves following non paired stimuli. The warning stimuli informed subjects whether or not the impending unconditional stimulus implied a motor response. Subjects were instructed to execute the motor task at less than one second after unconditional stimulus. They were informed that the standard warning stimulus would be followed by an additional stimulus which confirmed its detection. Recordings of standard warning stimulus condition showed a subsequent increase in CNV amplitude. This significant increase appeared to be related to an enhancement in the subject's expectation towards the additional stimulus. The lowered CNV voltage in target condition seemed to be linked to the instructions, which involved a motor preparation after the imperative stimuli occurrence. It is suggested that the CNV may represent not only a general anticipatory but also an orienting process related to the signal value of the warning stimulus.

Acoustic Stimulation↗

PubMed1978

[Effects of optic nerve section in baboons on the geniculate and cortical spike activity during various states of vigilance].

Eye movement potentials during wakefulness (EMPs) and so-called spike (PGO) activities were studied in 4 adult baboons before and after optic nerve (ON) section. The latter was performed either in two stages at a 23-day interval or simultaneously. During wakefulness in the intact animal, triphasic EMPs were observed in darkness with smaller amplitude and longer duration than in the light. After section of one ON, the 3 EMP components persisted, but with a smaller amplitude of the first wave. After section of the second ON morphological changes appeared: the amplitude and duration of the potentials were intermediate between those noted in darkness and light but with an intermingled sharp spike. Geniculate EMPs reappeared 11 days after simultaneous ON section, with the same evolution as previously described. During slow wave and REM sleep, intact animals presented lateral geniculate (LG) monophasic and biphasic spikes, called spikes I and II. At the cortex, they occurred either generalized or limited to one area (anterior or posterior) and were called pontogeniculocortical spikes (PGC). After section of one ON, the pattern of occurrence of phasic activities remained identical in LG. Sharp spikes (spike III) appeared; then their occurrence increased. At the end of the second month after the second section, only spikes II and III remained, spike I disappearing, while PGC amplitude diminished. When both ONs were cut simultaneously, spike III was observed from the first day and PGC activity tended to disappear partially for 11 days. Their later evolution was similar to that noted previously. However, changes were seen earlier (the highest rate of spike III occurring at day 35). In both cases, PGC spikes at the cortex increased in amplitude and frequency of occurrence.

Animals↗

PubMed1978

[Effects of optic nerve section in baboons on the EEG activity and sleep-waking cycles].

EEG rhythms recorded during the various states of alertness and sleep--waking cycles were studied in 4 baboons before and after optic nerve section. Visual deafferentation induced a general increase in amplitude of all the cortical rhythms, with general accentuation of pre-existing activities such as occipital eye movement potentials (EMPs), the fronto-rolandic rhythm and the alpha rhythm, spindles, REM ponto-geniculo-cortical (PGC) spikes; an increase in amplitude of the geniculate rhythmic activity, its frequency and occurrence was also noticed. When the blind baboons were placed in a monotonous environment, sleep--waking cycles occurred at any time of the 24 h. Total sleep time and total REM duration were not changed; however, deep sleep (stages 3 and 4) duration decreased (by around 50%) whereas stages 1 and 2 increased. The light factor thus plays a role in the sleep--waking cycle organization. However, its influence does to seem to be essential since its loss can be compensated by auditory stimulation. Finally, light possibly influences the systems involved in slow wave sleep regulation.

Alpha Rhythm↗

PubMed1977

Nonhuman primates: laboratory animals of choice for neurophysiologic studies of sleep.

A systematic study was made of several nonhuman primates to learn more about their relative usefulness for studies of sleep. Species studied included the Guinea baboon (Papio papio), Kenya or yellow baboon (P cynocephalus), olive baboon (P anubis), sacred baboon (P hamadryas), vervet monkey (Cercopithecus aethiops), rhesus monkey (Macaca mulatta), bonnet monkey (M radiata), crab-eating monkey (M fascicularis), patas monkey (Erythrocebus patas), chimpanzee (Pan troglodytes), mongoose lemur (Lemur mongoz), black lemur (Lemur macaco fulvus), and bushbaby (Galago senegalensis). Comparisons were made of electroencephalographic activity, states of vigilance, and responses to sleep-waking drugs. The results showed that there were major similarities among the genera studied as well as individual intrageneric and intraspecies differences. It was concluded that the chimpanzee, olive baboon, and rhesus monkey were the best species for comparative studies, and that the rhesus monkey was the best single model because of its well defined sleep organization and ease of handling and housing.

5-Hydroxytryptophan↗