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Biomedical subjects

C Kennedy

Publications and source records attributed to C Kennedy.

At least 271 records · Page 15Linked to original sources
PubMed1982

Mapping the primate visual system with [2-14C]deoxyglucose.

The [2-14C]deoxyglucose method was used to identify the cerebral areas related to vision in the rhesus monkey (Macaca mulatta). This was achieved by comparing glucose utilization in a visually stimulated with that in a visually deafferented hemisphere. The cortical areas related to vision included the entire expanse of striate, prestriate, and inferior temporal cortex as far forward as the temporal pole, the posterior part of the inferior parietal lobule, and the prearcuate and inferior prefrontal cortex. Subcortically, in addition to the dorsal lateral geniculate nucleus and superficial layers of the superior colliculus, and structures related to vision included large parts of the pulvinar, caudate, putamen, claustrum, and amygdala. These results, which are consonant with a model of visual function that postulates an occipito-temporo-prefrontal pathway for object vision and an occipito-parieto-prefrontal pathway for spatial vision, reveal the full extent of those pathways and identify their points of contact with limbic, striatal, and diencephalic structures.

Animals↗
PubMed1982

Local cerebral glucose utilization in the newborn macaque monkey.

The [14C]deoxyglucose method for quantitative determination of local cerebral glucose utilization was employed in newborn macaque monkeys. Values ranged from a high of 180 mumol/100 gm/min in the inferior colliculus to a low of 14 mumol/100 gm/min in the centrum ovale, a wider range than had been found in this laboratory for pubescent monkeys. Relatively low values in white matter overlapped with the generally higher values in gray matter. Rates for structures in the lower neuraxis were equal to or exceeded those reported for the mature animal, while those above the midbrain were generally lower. The auditory system was unique in having rates equal to, or exceeding, its mature levels in all parts of the pathway including the cortex. In the visual system, subcortical structures were at their mature levels while rates in the cortical areas were variably low; nevertheless, the striate cortex had differential rates marking the various laminae. It was possible to demonstrate the metabolic counterpart of the ocular dominance columns in two newborn animals that had had one eye occluded during the experiment. Rates for white matter were above their mature levels, with the differences being greatest in the brainstem and cerebellum. A high correlation between glucose utilization and local blood flow measured with [14C]antipyrine (r = 0.92) was found.

Animals↗
PubMed1982

Pleiotropic effect of his gene mutations on nitrogen fixation in Klebsiella pneumoniae.

Several his mutations were found to influence nitrogen fixation in Klebsiella pneumoniae: hisB, hisC, and hisD mutants had 50% of wild-type levels of nitrogenase activity when supplied with 30 mug or less histidine/ml although this concentration did not limit protein synthesis and the mutants retained a Nif plate phenotype. A hisA mutation had a similar but more dramatic effect. At low concentrations of histidine the hisA mutant strain had only 5% of the nitrogenase activity found at high histidine concentration or in a his strain, and was also Nif on low histidine agar plates. Addition of adenine restored nitrogenase activity in the hisA but not the hisB, hisC, or hisD mutants. Low levels of intracellular ATP, a consequence of hisG enzyme activity, correlated with loss of nitrogen-fixing ability in the hisA mutant which failed to sustain nif gene expression under these conditions. Synthesis of other major cell proteins was relatively unaffected indicating that nif gene expression is selectively regulated by the energy status of the organism.

Journal Article↗
PubMed1982

Influence of low oxygen concentration on derepression of nitrogenase in Klebsiella pneumoniae.

Effects of oxygen derepression of nitrogenase were studied in Klebsiella pneumoniae, using oxyleghaemoglobin to supply and monitor very low dissolved O2 concentrations in a steady-state system. Expression of the nifH gene was studied by using a nifH::lac fusion strain, which aslo carried the Nif+ plasmid pRD1 so that the production of active nitrogenase could also be monitored. When compared with anaerobic treatments, very low concentrations of dissolved O2 inhibited derepression of both nifH::lac and pRD1 nif. Fifty percent inhibition of derepression occurred at 0.1 microM-O2. The apparent Ks of the dominant terminal oxidase was 0.08 microM-O2. These results suggest that there is a close relationship between the terminal respiratory system of these bacteria and the repression of nitrogenase by O2.

Enzyme Repression↗
PubMed1982

Systemic inflammatory complications following jejuno-ileal bypass.

The clinical and laboratory features of three patients with systemic inflammatory complications following jejuno-ileal bypass surgery for morbid obesity are described. The constellation of an asymmetrical polyarthritis, tenosynovitis, sterile skin pustules, mucous membrane ulceration and retinal vasculitis resembled Behçet's syndrome. Serum complement levels were normal and circulating immune complexes not regularly detected, although hypocomplementaemia, elevations in Clq and rheumatoid factor binding materials were noted prior to clinical relapse in one patient. Antibiotic therapy proved disappointing, whereas dapsone produced a sustained remission. Bacterial overgrowth was not invariably found which together with recurrence of symptoms following bypass reversal, suggest that bacteria may only be required to initiate, not perpetuate inflammatory complications.

Arthritis↗
PubMed1981

Nitrogen fixation gene (nifL) involved in oxygen regulation of nitrogenase synthesis in K. pneumoniae.

The enzyme complex nitrogenase, which reduces N2 to NH+4, involves two redox proteins, both irreversibly damaged by O2 (ref. 1). Enzyme activity therefore requires anaerobic conditions, a source of reductant and a large amount of ATP (approximately 16 ATPs per N2). In both aerobic and facultative anaerobic N2-fixing bacteria, nitrogenase synthesis is regulated by O2 and NH+4, but in the aerobes there are also processes to protect the enzyme from O2 damage. The mechanisms of repression by O2 and NH+4 seem to be independent in the organisms so far examined. In the facultative anaerobe, Klebsiella pneumoniae, O2 was shown to repress nitrogenase synthesis in an NH+4-constitutive strain. The fusion of the Escherichia coli lacZ gene into each transcriptional unit of the nitrogen fixation (nif) gene cluster in K. pneumoniae has facilitated studies with O2, because expression from the various nif promoters results in an O2-stable product (beta-galactosidase). Notably, the nifHDK operon (the nitrogenase structural genes) was more sensitive to O2 repression than the nifLA operon (regulatory genes). The characterization of mutants, reported here, indicates the involvement of a nif-regulatory gene product in the mechanism of O2 control of nitrogenase synthesis.

Aerobiosis↗
PubMed1981

Changes in protein synthesis underlying functional plasticity in immature monkey visual system.

Local rates of cerebral protein synthesis were determined in newborn rhesus monkeys subjected to either acute or chronic monocular visual deprivation. Chronic monocular deprivation resulted in decreased rates of protein synthesis in the laminae of the lateral geniculate nuclei innervated by the deprived eye whereas rates of protein synthesis were normal in geniculate laminae innervated by the functioning eye. Acute monocular deprivation produced no differential changes in rates of protein synthesis in any of the geniculate laminae.

Animals↗
PubMed1981

The spectrum of inflammatory skin disease following jejuno-ileal bypass for morbid obesity.

From a series of 105 patients who had undergone jejuno-ileal bypass for morbid obesity, seven developed an episodic illness featuring inflammatory skin lesions, usually associated with a non-destructive polyarthritis. Tenosynovitis, myalgia and fever had also occurred. The illness abated spontaneously in four patients. The most characteristic skin lesion was an erythematous macule which developed a central vesicle or pustule. Erythema nodosum-like lesions and liquefying nodules were also seen. Early lesions were characterised by a dense accumulation of neutrophils. Changes is dermal vessels were less destructive than is usually seen in immune complex mediated vasculitis. Circulating immune complexes could be demonstrated in patients actively developing skin lesions. They were also found in some patients long after activity had ceased and in jejuno-ileal bypass subjects who had never developed inflammatory lesions. Dapsone was effective in suppressing the skin and joint symptoms when metronidazole and/or tetracycline had failed.

Antigen-Antibody Complex↗