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Biomedical subjects

R Gray

Publications and source records attributed to R Gray.

At least 379 records · Page 21Linked to original sources
PubMed1971

Vitamin D metabolism: the role of kidney tissue.

The appearance of a polar metabolite of 25-hydroxychotecalciferol has been studied in the intestinal mucosas of nephrectomized rats and rats which have been made uremic by ureter ligation. In confirmation of previous work by Fraser and Kodicek, it was found that nephrectomy prevents the appearance of this metabolite in the intestine. On the other hand, equivalent amounts of the metabolite were found in uremic rats and in sham-operated controls, showing that the production of this metabolite is independent of the uremic state of the animals. In addition, it was shown that the metabolite produced in vitro by kidney homogenates is identical to that found in vivo in the intestine.

Animals↗
PubMedDate not supplied

Avoidance of large biases and large random errors in the assessment of moderate treatment effects: the need for systematic overviews.

In order to avoid selective biases and to minimize random errors, inference about the effects of treatment on serious endpoints needs to be based not on one, or a few, of the available trial results, but on a systematic overview of the totality of the evidence from all the relevant unconfounded randomized trials. But, only where coverage of all, or nearly all, randomized patients in all relevant trials (or a reasonably unbiased sample of such trials) can be assured, is a systematic overview of trials reasonably trustworthy, for then any selective biases are likely to be small in comparison with any moderate effects of treatment. Checks for the existence of such biases can best be conducted if reasonably detailed data are available from each trial. Future trials should take into account the results of any relevant overviews in their design, and should plan to obtain sufficient numbers of events to contribute substantially to such overviews. In many cases, this implies the need for randomized trials that are much larger than is currently standard.

Clinical Trials as Topic↗
PubMedDate not supplied

A follow-up study of attentional behavior in 6-year-old children exposed prenatally to marihuana, cigarettes, and alcohol.

Attentional behavior was examined in one hundred twenty-six 72-month-old children for whom prenatal exposure to marihuana, cigarettes, and alcohol has previously been ascertained. Discriminant Function Analysis revealed a dose-response association between prenatal cigarette exposure and impulsive behavior as manifest on poorer performance on a response inhibition task and increased errors of commission on a sustained vigilance task. Performance on a series of memory tasks particularly those requiring verbal recall was also negatively associated with maternal cigarette use. Prenatal marihuana habits were associated with increased omission errors in the vigilance task, possibly reflecting a deficit in sustained attention. In addition, Discriminant Function Analysis revealed a dose-response relationship between prenatal marihuana use and a higher rating by the mothers on an impulsive/hyperactive scale. Relatively low levels of maternal alcohol consumption was related to decreased impulsive responding both in the response inhibition task and in terms of the mothers' perception of the child's behavior. The multifaceted approach of examining attentional behavior was essential to reveal the differential associations with the three prenatally used drugs. The implications of the observations and how the findings relate to and extend the existing literature is discussed.

Adult↗
PubMedDate not supplied

The effect of irradiation dose and storage time on the ESR signal in the cuticle of different components of the exoskeleton of Norway lobster (Nephrops norvegicus).

This paper examines the potential of ESR spectroscopy to determine if Norway lobsters have been irradiated. Ninety samples, each containing 3 whole Norway lobsters, were prepared, thirty were used as controls while the remaining sixty were given irradiation doses of approximately either 1 or 3 kGy. Following irradiation the samples were stored at 1 degree C for 0, 7, 14, 21 or 28 d. After each storage period the cuticle of the tail, carapace, claws and walking legs was removed, freeze-dried and ground prior to analysis using ESR spectroscopy. The control spectra were subtracted from their respective irradiated spectra thereby leaving the radiation-induced signal. Peak heights of the signals were measured. The ESR signals derived from the different components of the exoskeleton were similar in shape and varied only in their intensities. The claw samples gave the most intense signal while that from the walking legs was the weakest. There was a significant decay in the signal intensity over the storage period with the signal derived from cuticle of the claws showing the greatest diminution (44%) and that of the tail the least (17%). The signal intensities of the walking legs and carapace decreased by 22% and 30% respectively. In conclusion ESR spectroscopy is a useful technique for the qualitative detection of irradiated Norway lobster and shows considerable potential for quantification of dose received.

Animals↗
PubMedDate not supplied

Differential effects on cognitive functioning in 9- to 12-year olds prenatally exposed to cigarettes and marihuana.

Cognitive performance was examined in 131 9-12-year-old children for whom prenatal marihuana and cigarette exposure had been ascertained. The subjects, participants in an ongoing longitudinal study, were from a low-risk, predominantly middle class sample. The tasks included the WISC-III and a series of tests assessing aspects of cognition subsumed under the rubric of executive function. Consistent with results obtained at earlier ages, discriminant function analysis revealed a dose-dependent association, which remained after controlling for potential confounds (including secondhand smoke), between prenatal cigarette exposure and lower global intelligence scores with the verbal subtests of the WISC maximally discriminating among levels of in utero exposure. In contrast, prenatal marihuana exposure was not associated with global intelligence or the verbal subtests. Rather, this drug was negatively associated with the executive function tasks that require impulse control and visual analysis/hypothesis testing and with a number of WISC subtests requiring the same abilities. The interpretation of these results is discussed in terms of executive function and is related to earlier observations of this sample and to the extant prefrontal and general marihuana literature.

Adult↗
PubMedDate not supplied

Growth from birth to early adolescence in offspring prenatally exposed to cigarettes and marijuana.

Weight, height, and head circumference were examined in children from birth to early adolescence for whom prenatal exposure to marijuana and cigarettes had been ascertained. The subjects were from a low-risk, predominantly middle-class sample participating in an ongoing longitudinal study. The negative association between growth measures at birth and prenatal cigarette exposure was overcome, sooner in males than females, within the first few years, and by the age of six, the children of heavy smokers were heavier than control subjects. Pre and postnatal environmental tobacco smoke did not have a negative effect upon the growth parameters; however, the choice of bottle-feeding or shorter duration of breast-feeding by women who smoked during pregnancy appeared to play an important positive role in the catch-up observed among the infants of smokers. Prenatal exposure to marijuana was not significantly related to any growth measures at birth, although a smaller head circumference observed at all ages reached statistical significance among the early adolescents born to the heavy marijuana users.

Analysis of Variance↗