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Biomedical subjects

N Davis

Publications and source records attributed to N Davis.

At least 91 records · Page 5Linked to original sources
PubMed1977

Arousal from sleep: the physiological and subjective effects of a 15 dB(A) reduction in aircraft flyover noise.

The present research was concerned with whether or not a 15 dB(A) reduction in overall noise level would lessen the sleep disturbing properties of jet aircraft flyover noise and, if less disturbing, whether this would be subjectively appreciated by the sleeping individual. The results indicate that a reduction of 15 dB(A) does result in less sleep disruption but only during sleep characterized by fast-wave electroencephalographic activity. During sleep characterized by slow-wave electroencephalographic activity, such a reduction in the sleep-disturbing properties of jet aircraft noise has little effect. Moreover, even when effective during fast-wave sleep, the decreased arousal produced by the lower noise levels is not subjectively appreciated by the individual in terms of his estimate of the quality of his night's sleep. Thus, reducing the overall noise level of jet aircraft flyovers by some 15 dB(A), is, at best, minimally beneficial to sleep.

Adolescent↗
PubMed1975

Large bowel cancer: a retrospective study of 635 cases.

A retrospective survey of 635 cases of large bowel cancer treated at the Princess Alexandra Hospital, Brisbane, from 1956 to 1970 is presented. The age and sex incidence, presentation and pathology are discussed, and a detailed analysis is made of treatment and operative mortality rates. The resectability rate was 72-2%; the operative mortality rate for resectable colonic lesions was 6-6%, and for resectable rectal lesions, 7-3%. There was an operative mortality rate in the presence of acute obstruction of 17-5%. This study forms the basis of a prospective survey presently being undertaken at the Princess Alexandra Hospital.

Adolescent↗
PubMed1973

Utilization of iron gallate and other organic iron complexes by bacteria from water supplies.

The degradation of four soluble organic iron compounds by bacteria isolated from surface waters and the precipitation of iron from these complexes by the isolates was studied. All eight isolates brought about the precipitation of iron when grown on ferric ammonium citrate agar. Three isolates were able to degrade ferric malonate, and three others degraded ferric malate with iron precipitation. Only three isolates, two strains of Pseudomonas and one of Moraxella, were able to degrade gallic acid when this was supplied as the sole carbon source. One strain of Pseudomonas was found to be active in degrading ferric gallate. Electron microscopy of cells of this bacterium after growth in ferric gallate as the sole carbon source yielded results indicating uniform deposition of the iron on or in the bacterial cells. Seven of the isolates could degrade the iron gallate complex if supplied with additional carbon in the form of yeast extract.

Alcaligenes↗
PubMedDate not supplied

Analysis of Na+/Ca2+ exchange activity in human brain: the effect of normal aging.

Na+/Ca2+ exchange activity and passive permeability to Ca2+ were analyzed in plasma membrane vesicles (PMV) purified from whole rat brain and three regions of human brain: frontal cortex, temporal cortex, and cerebellum. Accumulation of Ca2+ due to Na+/Ca2+ exchange activity showed a characteristic pattern of an initial rapid rise in Ca2+ content followed by a stable plateau in both rat and human brain. Total Ca2+ accumulation in rat brain PMV was on average three-fold higher than in human brain. Passive permeability to Ca2+ was measured as the rate of Ca2+ release from PMV first loaded with 45Ca by Na+/Ca2+ exchange and then exposed to 1 mM EGTA. The Ca2+ permeabilities of human and rat brain PMV were similar. Ca2+ release from rat brain PMV was faster overall and was resolved into fast and slow components while in human brain a single slow component was found. Post mortem delay up to 4 h had no effect on Na+/Ca2+ exchange Km for Ca2+, Vmax, and peak uptake and Ca2+ release rate in rat brain PMV. Human frontal cortex was shown to have a greater Na+/Ca2+ exchange activity than that found in the cerebellum. The frontal cortex, temporal cortex and cerebellum had similar Ca2+ permeabilities. Age-related effects on Na+/Ca2+ exchange activity and Ca2+ permeability were determined in 15 tissues from human frontal cortex (age at death 21 to 93 years). No significant age related effects were seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Recovery of function after brain damage: the extrinsic stimulus specificity of spared neural traces.

Previous research has demonstrated that while primary visual cortex lesions in rats will disrupt performance of a learned brightness discrimination, the neural traces associated with this discrimination are spared. Moreover, the spared neural traces may, in certain instances, influence the postoperative reinstatement of a brightness discrimination. The present research was designed to determine the generality of this postoperative influence. The results indicate that while the normal rat and the visual decorticate rat may readily transfer learning between discriminations involving different discriminative cues, a visual lesion between two discriminations prevents this transfer. These data are interpreted as indicating that the postoperative influence of a spared neural trace is dependent upon the reoccurrence of specific extrinsic stimulus cues.

Animals↗