摘要:

ACIDOSIS is a well established concomitant of tissue ischemia. Acidosis in the pH range 6.0–7.0 is seen in cerebral ischemia and within solid tumors. Extracellular acidosis of pH 6.0 and 6.4 provided essentially complete protection from & h serum deprivation induced apoptotic death of cultured primary murine neurons. We tested the effect of p53 using transformed mouse embryo fibroblasts of either p53+/+or p53−/−genotype. Both were markedly protected from serum deprivation by acidity. Hypoxia induced fibroblast injury was also reduced at pH 6.8. Lower pH resulted in a shift from apoptotic to necrotic morphology after 24h hypoxia. Acidosis reduces apoptosis of both normal and transformed cells, irrespective of p53 status.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TELENCEPHALIN (TLCN) is a cell adhesion molecule belonging to the immunoglobulin superfamily whose expression is restricted to neurons within the most highly developed brain segment, telencephalon. Immunoelectronmicroscopic study revealed that in the hippocampal CA1 region, TLCN was localized at the surface membrane of postsynaptic spines of pyramidal cell dendrites but not at that of axonal terminals. Blocking of TLCN function using anti-TLCN antibody or recombinant soluble TLCN protein caused a striking suppression of the long-term potentiation (LTP) at the Schaffer collateral–CA1 synapses. The suppression was observed even when the blocking was initiated immediately after the tetanic stimuli. These observations suggest a role for TLCN-mediated cell—cell interactions as a key step in the development of LTP.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE used an interference paradigm in order to study integration between haptic and visual information in motor control and in perceptual analysis. Subjects either reached and grasped a visually presented sphere or matched its size with their left hand while manipulating with their right hand another sphere whose size could be smaller or greater. In four experiments haptic analysis of the manipulated sphere could be either automatically incorporated with or explicitly dissociated from visual analysis. In a fifth experiment reaching-grasping and matching were executed with the right hand, whereas manipulation was executed with the left hand. Manipulation with the right hand influenced finger shaping during grasping with the left hand when the sizes of the two objects were different. Interference was observed mainly in those experiments in which haptic analysis could be automatically integrated with visual analysis. In the matching task, no effect was observed. Finally, manipulation with the left hand did not produce any interference effect on reaching-grasping and matching executed by the right hand. The results of the present study suggest that somesthetic information is integrated with visual information only in sensorimotor transformations. In addition, they support the notion that the left hemisphere together with the right hemisphere is involved in the control of left hand reaching- grasping movements.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO study neuronal activities that influence the generation of the alpha rhythm, we used positron emission tomography and simultaneous recording of the electroencephalogram (EEG) in normal volunteers and under passive conditions. A negative correlation between regional cerebral blood flow and alpha power was found in the occipital cortex, consistent with the visual modality-specific reactivity of the alpha rhythm. A positive correlation was found in the pons, midbrain, hypothalamus, amygdala, the basal prefrontal cortex, insula and the right dorsal premotor cortex. Neuronal activities of the brain stem and limbic system that are positively correlated with alpha power may provide an anatomical basis for studies of the relationship between emotional state and brain rhythm in health and disease.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE task-dependent laterality of the auditory cortices was investigated by measuring the magnetic fields elicited by three forms of a Japanese verb, which differed in terms of prosodic and phonetic cues. Significant task- dependent magnetic fields were found in both hemispheres during a prosody-related task, but only in the left during a phoneme-related task. The latency was similar to the mismatch negatively which reflects the neural activity of automatic cue decoding. These results suggest that task-dependent schemata are activated at least partially in parallel with automatic cue-decoding processes such that those in the left hemisphere process linguistic information irrespective of acoustic cues whereas those in the right hemisphere process prosodic information.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NEUROTROPHIN -3 (NT3) or TrkC null mutant mice were examined for the presence of muscle spindles. Muscles of mastication, but not limbs, contained spindles in newborn and adolescent mutants. The intramuscular distribution and morphological properties of spindles in mutant masticatory muscles were indistinguishable from those of wild-type spindles. Intrafusal fibers of NT3- or trkC-deficient spindles expressed the slow-tonic isoform of myosin heavy chains, characteristic of wild-type spindles. Sensory nerve endings were observed in spindles of mutants by electron microscopy. Thus, NT3 or trkC, which is expressed in wild-type spindles, may serve functions other than those related to spindle assembly. Presumably, proprioceptive neurons innervating jaw muscles are dependent on factors other than NT3 for survival and maintenance.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

The cleavage process of sterol regulatory element binding proteins (SREBPs) shares several characteristics with that of β-amyloid precursor protein (βAPP). We studied the secretion of amyloid β protein Aβ from mutant M19 Chinese hamster ovary (CHO) cells that are defective in the site 2 cleavage of SREBPs. The levels as well as the C-terminal properties of Aβ secreted from M19 cells were similar to those from wild-type CHO cells, demonstrating that γ-cleavage of βAPP occurs normally in M19 cells. The present data indicated that γ-secretase of βAPP and SREBP site 2 protease are distinct enzymes.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE precise role of prostaglandin-D-synthase β (trace protein), the major constituent of cerebrospinal fluid, is unclear. In the present study, a sensitive and highly specific fluoroimmunoassay was developed. The measurement of the enzyme levels in rat CSF revealed a developmental change in the CSF levels with the highest value of 6 6 ± 8μg/ml at 7 days after birth. No significant difference in the levels was seen between different times of day. Subcutaneous injections of all-transretinoic acid caused a dramatic decrease in the protein levels in a dose- and time-dependent manner. These findings may raise the possibility that prostaglandin-D-synthase in CSF is involved in retinoic acid action on the brain.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE olfactory system provides a usefulin vivomodel for studying neuronal apoptosis. The synaptic target deafferentation (olfactory bulb ablation) of the sensory epithelium induces a massive and synchronous wave of retrograde apoptosis in the large population of olfactory sensory neurons. The proto-oncogenebcl-2is involved in the regulation of cell death and is able to block apoptosis in motoneurones. We demonstrate here that olfactory neurons over-expressing the human Bcl-2 protein in transgenic mice are long-term protected from apoptotic death following ipsilateral olfactory bulbectomy. We kinetically assessed neuronal death 32 h, 50 h and 5 days following unilateral olfactory bulbectomy, in adult C57BL6 (wild-type) and transgenic mice with olfactory neurons over-expressing the Humanbcl-2gene. Using the TUNEL method and morphometric analysis of olfactory epithelium, we confirmed the occurrence of a wave of neuronal death in wild-type mice but failed to detect a significant rate of neuronal apoptosis in the olfactory epithelium of transgenic animals. Apoptotic death of olfactory neurons probably shares common pathways with apoptotic processes occuring in other neuronal types, including motoneurons.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

CULTURED rat oligodendrocytes are lysed by complement via antibody—independent activation of the classical pathway. This susceptibility to complement lysis has been demonstrated to be due to lack of CD59, a complement regulatory protein which inhibits assembly of the membrane attack complex. In this study the effects of homologous and heterologous complement were examined in a co-culture system of rat oligodendrocytes and peripheral neurones, where axonal ensheathment was observed as early as 4 days after the addition of glial progenitors to the neurones. Following exposure to complement, ensheathing oligodendrocytes were markedly less sensitive to antibody-independent but not antibody-dependent complement lysis than were cells grown without neurones. Immunocytochemical data revealed that co-cultured oligodendrocytes remained CD59 negative, but in contrast to oligodendrocytes cultured alone, were negative for C3b when incubated with C7-deficient serum. Taken together these data indicate that the decreased sensitivity of co-cultured oligodendrocytes to complement lysis is not attributed to the increased expression of CD59, but rather in a failure to activate complement. Incubation of oligodendrocytes with neurone-conditioned medium afforded significant protection (68%), against antibody—independent complement attack, suggesting that soluble neuronal factors can protect oligodendrocytes from complement-mediated lysis.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID