摘要:

THE effect of leptin on gastric emptying of glucose was studied in freely moving rats bearing intragastric fistulas. Leptin (0.39 μg and 3.9μg) injected into the fourth ventricle inhibited gastric emptying significantly, whereas s.c. administration of leptin (10μg/kg) had no effect. Leptin receptor immunoreactivity, revealed by an antiserum that recognizes all leptin receptor isoforms, was demonstrated in choline acetyltransferase (ChAT)-containing neurones of the dorsal motor nucleus of the vagus nerve (DMX). The data indicate that leptin acts centrally to suppress gastric emptying possibly via leptin receptors located on cholinergic DMX neurones.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TWO rhesus macaques were tested on a categorization task in which they had to classify previously unseen photographs flashed for only 80 ms. One monkey was trained to respond to the presence of an animal, the second to the presence of food. Although the monkeys were not quite as accurate as humans tested on the same material, they nevertheless performed this very challenging visual task remarkably well. Furthermore, their reaction times were considerably shorter than even the fastest human subject. Such data, combined with the detailed knowledge of the monkey's visual system, provide a severe challenge to current theories of visual processing. They also argue that this form of rapid visual categorization is fundamentally similar in both monkeys and humans.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

FROM undetectable basal levels, TNFα is produced in the hypothalamus of rats challenged with a systemic low profile endotoxin (LPS) at least 30 min before its release may be detected in the plasma. The cytotoxic activity of this hypothalamic TNFα correlates with its immunore-activity. Injection of BB-1101, a matrix metalloprotease inhibitor, immediately after the LPS totally inhibits the plasma LPS-induced TNFα release without affecting the hypothalamic TNFα response. Likewise, L-NAME pretreatment, a nitric oxide inhibitor which reportedly crosses the blood-brain barrier, blunts the plasma TNFα response by almost 66%, but leaves the hypothalamic TNFα response unchanged. The present study thus describes the early occurrence of hypothalamic TNFα in response to systemic LPS injection, which is not subjected to the same regulations as plasma TNFα.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SINGLE neuron activity was recorded in monkey motor cortex during the execution of pointing movements in six directions. The amount of prior information was manipulated by varying the range of precued directions. A distribution of neural population activation was constructed in the space of movement directions. This population representation of movement direction was preshaped by the precue. Peak location and width reflected the precued range of movement directions. From this preshaped form, the population representation evolved continuously in time and gradually in parameter space toward a more sharply peaked distribution centered on the parameter value specified by the response signal. A theoretical model of motor programming generated a similar temporal evolution of an activation field representing movement direction.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO investigate whether sublethal ischemia preserves neuronal function otherwise lost after stroke, anesthe-sized rabbits were subjected to clamping of abdominal aorta to cause lumbar spinal cord ischemia. An occlusion period of 12.5 min was followed 12 or 48 h later by a second occlusion for 30 min. When scored 24 h later for hindlimb function on a 0–6 scale, the rabbits that underwent tolerizing ischemia 12 h before infarction had better motor function (n= 7; 4.29 ± 0.21,p< 0.0001) than sham–operated controls (n= 7; 1.00 ± 0.27), but those infarcted at 48 h had mixed outcomes (n= 5; 2.20 ± 0.21, ns). In correlation, the proportion of neurons with histo-logical evidence of damage was lower in the tolerized rabbits (0.15 ± 0.04) than in sham-operated controls (0.74 ± 0.09,p< 0.001). We conclude that ischemic tolerance also improves neurological function of infarcted spinal cord and could be studied for clinical application.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE structure of glutamate receptor–channel (GluR) subunits has recently been shown to differ from that of other ligand-gated channels and to contain a voltage-gated channel-like pore-forming motif. The view that the structure of GluR complexes is similar to the pentameric structure of other ligand-gated channels was questioned here. Studies of the response properties of the GluR1 subunit of the AMPA subtype of GluRs, co-expressinXenopusoocytes with its L646A mutant, which differs only by a greatly reduced sensitivity to quisqualate, provide new evidence suggesting that the GluR1 homomeric receptor channel has a tetrameric structure.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ALL insect brains contain mushroom-shaped neural bodies which are implicated in associative learning. Here we show that the mushroom bodies of the locust brain have a remarkable and hitherto undescribed neural organisation consisting of six tubular structures in which bundles of axons are enclosed by cylindrical walls of nitric oxide synthase (NOS) expressing processes. A dynamic temporo-spatial simulation shows that the tubular organization allows NO to attain and maintain locally elevated concentrations within highly structured domains in the CNS. A diffusible gaseous signalling molecule such as NO can therefore selectively affect computational processes occurring in discrete parallel channels of information flow in the brain. The implications of this are discussed in relation to the role of NO in a compartmental model of the mushroom bodies and more generally in the context of the targetting of diffusible messenger molecules in the brain.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IN order to investigate the relationship between dyslexia and central auditory processing, 19 children with spelling disability and 15 controls at grades 5 and 6 were examined using a passive oddball paradigm. Mismatch negativity (MMN) was determined for tone and speech stimuli. While there were no group differences for the tone stimuli, we found a significantly attenuated MMN in the dyslexic group for the speech stimuli. This finding leads to the conclusion that dyslexics have a specific speech processing deficit at the sensory level which could be used to identify children at risk at an early age.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SENSORY information from the genitourinary tract is transmitted to perineal muscle reflex circuits in the spinal cord and to the medullary reticular formation (MRF). This is the first report of a functional descending connection between neurons in the MRF and sensory inputs of the pudendal motoneuron reflex circuitry. In anesthetized rats, microstimulation of the MRF produced a decrease in amplitude and increase in latency of pudendal motoneuron reflex discharges (PMRD) elicited by stimulation of the dorsal nerve of the penis. No effects on pelvic nerve-elicited PMRD were found. The most robust reflex depression was observed when the lateral paragigantocellular reticular nucleus was microstimulated bilaterally. Reproductive abnormalities that occur following severe spinal cord injury probably result from disruption of these descending connections.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

BECAUSE general cognitive ability (g) is among the most heritable behavioural traits, it is a reasonable target for a search for quantitative trait loci (QTLs). We used a selected-extremes design to test candidate genes for allelic association withg. Polymorphisms in four genes in the dopamine system (DRD2, DRD3, DRD4, DAT1) were genotyped for 51 highgchildren with IQ scores > 130 and for 51 averagegcontrol children. No significant allelic or genotypic differences were found between the highgand averageggroups for these markers of the dopamine system, even though the selected-extremes design provides power to detect QTL associations that involve a relative risk of about 1.5.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID