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Biomedical subjects

F R Sharp

Publications and source records attributed to F R Sharp.

At least 199 records · Page 11Linked to original sources
PubMed1982

Functional ontogeny in the central auditory pathway of the Mongolian gerbil. A 2-deoxyglucose study.

The 2-deoxyglucose (2-DG) autoradiographic technique was used to map functional activity in the central auditory system of the mongolian gerbil, throughout the period of functional onset. Uptake of 2-DG during exposure to 105 dB SPL wide band noise (WBN) was compared to silence in adults and in neonates at 12, 14, 16 and 18 days after birth (DAB). At 12 DAB, WBN exposure increased 2-DG uptake relative to silence only in the ventral cochlear nucleus. At 14 DAB, 2-DG uptake increased during WBN in the entire cochlear nuclear complex, superior olivary complex, and ventral nucleus of the lateral lemniscus. These stimulus-evoked increases in 2-DG uptake were at adult levels. However, little or no stimulus-evoked increase was seen in higher auditory nuclei at 14 DAB. By 16 DAB, 2-DG uptake also increased during WBN exposure in the dorsal nucleus of the lateral lemniscus, inferior colliculus and medial geniculate nucleus. By 18 DAB, WBN exposure produced increases in 2-DG uptake of medullary and pontine auditory nuclei which exceeded those seen in adults. At higher levels of the pathway, increases were comparable to those seen in adults. WBN-induced increases in 2-DG uptake observed in the cochlear nuclear and superior olivary complexes of neonates were comparable in all regions at all ages, even at 12 DAB. However, the 2-DG uptake increases observed at 16 and 18 DAB were appreciably greater in those regions of the inferior colliculus and medial geniculate nucleus which respond to high frequencies.

Aging↗
PubMed1982

Bilateral [14C]2-deoxyglucose uptake by motor pathways after unilateral neonatal cortex lesions in the rat.

The left sensorimotor (SM) cortex was removed in 1-day-old and 30-day-old rats. At 90 days of age [14C]2-deoxyglucose (2DG) was injected and the right motor (MI) cortex was electrically stimulated to produce predominantly left vibrissae movements. Animals were sacrificed and their brains autoradiographed. Right motor cortex (MI) stimulation activated subcortical structures bilaterally in 3 of 5 neonatally lesioned rats. Right MI stimulation activated most subcortical structures unilaterally in 30-day lesioned rats. This implies that a critical period for SM cortex injury may occur between 1 and 30 days of age. We suggest that removal of left SM cortex at 1 day of age occurs before or during the critical period and this induces right MI cortex to form bilateral subcortical connections. The bilateral 2DG uptake increases imply the bilateral connections are functional. The unilateral subcortical activation in 2 of 5 neonatally lesioned animals may have been due to differences in size of the lesion, parameters of stimulation, or perhaps due to the time of the lesion being near the critical period. We also suggest that removal of left SM cortex at 30 days of age occurs after the critical period, but that this does not affect the predominantly ipsilateral subcortical connections from MI cortex which have previously formed during normal development.

Aging↗
PubMed1982

Thiamine deficiency limits glucose utilization and glial proliferation in brain lesions of symptomatic rats.

The effects of thiamine (B1) deficiency on local CMRglu (LMCRglu) in the vestibular nuclei were studied with the 14C-2-deoxyglucose autoradiographic method in awake asymptomatic and symptomatic rats. Animals on the B1-deficient diet for 98 days developed symptoms of ataxia and opisthotonos. The results show that B1 deficiency produces: (1) bilateral vestibular nuclei lesions in symptomatic animals; (2) very low LCMRglu rates in these lesions; and (3) limitation of glial proliferation in the lesions. Giving B1 to B1-deficient symptomatic animals produced a cellular proliferation response consisting mostly of microglia in the lesioned areas of the vestibular nuclei and a high LCMRglu rate in the regions of microglial proliferation.

Animals↗
PubMed1982

Local cerebral glucose utilization in the symptomatic thiamine-deficient rat: increases in fornix and pyramidal tract.

Local cerebral glucose utilization (LCGU) was measured in asymptomatic rats on a thiamine (B1)-deficient diet for 70 days and in symptomatic rats on a B1-deficient diet for 98 days. LCGU increased in postcommissural fornix (F), pyramidal tracts (P), and inferior internal capsule (CAI) of symptomatic, compared with asymptomatic B1-deficient rats but decreased in thalamic nuclei, auditory structures, and lesioned vestibular nuclei. B1 administration to symptomatic rats improved symptoms; decreased LCGU in F. P, and CAI; increased LCGU in the lesioned vestibular nuclei; but decreased LCGU in mammillary nuclei, anteroventral nucleus of thalamus, and medial raphe. The results indicate that B1 deficiency symptoms correlate with LCGU changes in F and P and vestibular nuclei.

Animals↗
PubMed1982

[14C]2-deoxyglucose uptake in ground squirrel brain during hibernation.

Autoradiographic patterns of [14C]2-deoxyglucose uptake are described throughout the brains of hibernating and euthermic ground squirrels. Autoradiographs of the brains of hibernating animals are generally homogeneous in comparison to euthermic animals; hence, the relative 2-deoxyglucose uptake (R2DGU) of gray to white matter for the majority of the 85 neural structures examined decreases during hibernation. Two categories of structures are identified as potentially important in hibernation: (1) structures that have the highest R2DGU during hibernation (cochlear nucleus, paratrigeminal nucleus, and superior colliculus) and (2) structures that undergo the least reduction in R2DGU in the transition from euthermia to hibernation (suprachiasmatic nucleus and lateral septal nucleus). The percentage of reduction in R2DGU that a structure undergoes in the transition from euthermia to hibernation is proportional to the R2DGU of that structure during euthermia. The suprachiasmatic, paratrigeminal, and cochlear nuclei undergo less of a reduction than would be predicted from this relationship and may be particularly important during hibernation. Sensory nuclei that receive primary afferent projections are among the structures with the highest R2DGU during hibernation. These metabolically active structures may be responsible for the sensitivity of the hibernator to environmental stimuli.

Animals↗
PubMed1981

Increasing intensities of wide band noise increase [14C]2-deoxyglucose uptake in gerbil central auditory structures.

The [14C]2-deoxyglucose (2DG) technique has been used to map the effects of increasing intensities of wide band noise on 2DG uptake in mongolian gerbil brain auditory structures. Animals were injected with [14C]2DG and exposed to silence or continuous wide band noise at 25 dB, 45 dB, 65 dB, 85 dB or 105 dB SPL. Brains were removed, frozen-sectioned and autoradiographed on X-ray film. The ratio of the optical density of gray matter structures to the optical density of cerebellar peduncles in each animal was used to semiquantitate the results. The dorsal and ventral cochlear nuclei, superior olive/trapezoid body, inferior colliculus, and the dorsal and ventral nuclei of the lateral lemniscus all showed increases in 2DG uptake during exposure to wide band noise (WBN). As noise intensity increased from 0 to 105 dB SPL, 2DG uptake increased regularly to a maximum at 85 or 105 dB SPL. As WBN intensity increased, deeper layers of inferior colliculus were activated. The medial geniculate nucleus and auditory cortex showed a lesser increase in 2DG uptake during noise exposure. Non-auditory structures, including the cerebellar cortex and the medullary reticular nuclei, showed no increase in 2DG uptake during noise exposure at any intensity tested.

Animals↗
PubMed1981

Lumbosacral plexus neuritis.

We studied four patients with neurologic disorders of the lumbosacral plexus. Except for location of symptoms, the disorder confirmed to criteria established for the clinical diagnosis of brachial plexus neuritis. Acute onset of pain in one or both legs was followed by weakness, loss of stretch reflexes, and sometimes atrophy of affected muscles. The disorder affected in individual nerves or parts of the plexus. Gradual recovery occurred in all four patients.

Adult↗
PubMed1978

Autoradiographic maps of regional brain glucose consumption in resting, awake rats using (14C) 2-deoxyglucose.

The 2-deoxy-D-[14C]-glucose (2-DG) autoradiographic method for determining regional brain glucose consumption has been applied successfully by a number of workers for mapping the alterations of brain glucose consumption which occur in association with experimental alterations of brain functional activity. This paper provides a framework for the interpretation of these and further studies by presenting: (1) the pattern of regional brain glucose consumption in the normal, resting, awake rat; (2) the anatomical identities of brain structures which on autoradiographs appear only as regional variations of optical density. For this purpose, a series of 2-DG autoradiographs of coronal brain sections from an injected animal is compared with adjacent labeled Nissl sections.

Animals↗
PubMed1976

Relative cerebral glucose uptake of neuronal perikarya and neuropil determined with 2-deoxyglucose in resting and swimming rat.

An autoradiographic method using tracer amounts of [14C]-2-deoxy-D-glucose (2-DG) was used to detect areas of the brain in which glucose consumption was altered in swimming as compared to resting rats. Areas in which changes occurred in the swimming rat were widespread in gray matter, being greatest in the cerebellar vermis and least in portions of the cerebellar hemispheres and the inferior colliculi. Improved resolution was obtained with an autoradiographic method for [3H]-2-DG. The number of grains per unit area over neuronal perikarya was either slightly greater or equal to that over the immediately surrounding neuropil in both resting and swimming rats. This indicated that the glucose consumption of neuronal perikarya and the immediately surrounding neuropil per unit volume were similar. Since gray matter is composed predominantly of neuropil, the present results indicate that the bulk of the total brain gray matter glucose consumption is accounted for by neuropil in both the resting and swimming states.

Animals↗
PubMed1976

Rotation induced increases of glucose uptake in rat vestibular nuclei and vestibulocerebellum.

A new technique for the autoradiographic measurement of regional cerebral glucose consumption using tracer amounts of radioactive 2-deoxyglucose (2-DG) was employed to study the effects of vestibular inputs on local cerebral glucose metabolism. Rats rotated in the vertical plane showed localized increases of glucose utilization in the vestibular nuclei and several areas of the cerebellum: flocculus, nodulus, ventral uvula, and accessory paraflocculus. The changes in the cerebellum occurred both in the neuronal perikarya-rich granular layer and the neuropil-rich molecular layer. Differential changes resulting from rotation occurred within the granular layer of the nodulus, where at least 7 separate longitudinal zones of differing glucose consumption were seen. This type of longitudinal organization has been described previously in other areas of the vermis with other techniques.

Animals↗