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J Metcalfe

Publications and source records attributed to J Metcalfe.

156 records · Page 9Linked to original sources
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Predicting syndromes of amnesia from a composite holographic associative recall/recognition model (CHARM).

The composite holographic associative recall/recognition model (CHARM) is used to predict the amnesia syndromes that are expected under conditions of discrete lesions to different components of the model. The components that are needed to allow recognition, recall, and rehearsal are: (1) perceptual/lexical processing and pattern identification, (2) consciousness or working memory, (3) association formation, (4) composite storage, (5) novelty monitoring and control, and (6) retrieval. Deficits in each of these components will have specific effects on memory, generating characteristic profiles of performance. Comparison of the profiles exhibited by patients to the component-based profiles predicted by the model identify the component impaired in a given patient, and connect the memory impairments to the underlying infarcted brain structures. The model, thus, relates the memory tasks to the particular memory components that allow enactment of those tasks, and shows how the dysfunction of particular components produces specific impairments.

Amnesia↗
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Improved beta cell function, with reduction in secretion of intact and 32/33 split proinsulin, after dietary intervention in subjects with type 2 diabetes mellitus.

Diet in Type 2 diabetes often reduces both hyperglycaemia and weight and both these factors may contribute to improvement in beta cell function. Sixty-nine subjects with newly diagnosed Type 2 diabetes had their glucose, insulin, intact and 32/33 split proinsulin measured at diagnosis, and after 16 (12-20) weeks of conventional diet. In the whole group following diet there was reduction in weight (p < 0.0001), Haemoglobin A1 (p < 0.0001), and fasting glucose (p < 0.0001). There was a fall in fasting intact proinsulin (p < 0.03), 32/33 split proinsulin (p < 0.0001), and the percentage of fasting proinsulin to total insulin-like molecules (p < 0.0001). Subjects were separated according to weight loss (group 1 < 0.5 kg, group 2 0.5-4 kg, group 3 > 4 kg). Only subjects in group 3 (mean weight loss 6.2 kg) had a fall in fasting insulin (p < 0.04). The fasting glucose achieved following diet was positively correlated with the initial fasting glucose (r = 0.7) and negatively correlated with the degree of insulin deficiency at diagnosis (with the initial 30 min insulin r = -0.62). The effect of diet on the final concentration of insulin, 32/33 split proinsulin and intact proinsulin was examined using multiple regression. The final insulin concentration was determined by the initial BMI and absolute weight loss, 32/33 split proinsulin concentration by the initial fasting glucose and absolute glucose fall, and intact proinsulin concentration by a combination of both weight loss and glucose reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
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On their way home.

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Aftercare↗
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Effects of brief hypoxia and hyperoxia on tissue trace element levels in the developing chick embryo.

Brief hypoxia or hyperoxia has been shown to affect growth and metabolism of chick embryos during the late stages of development. The objective of this study was to alter the availability of oxygen to chick embryos developing in ovo and to determine the effects on tissue zinc, copper, iron and manganese levels. On day 15 of incubation fertile chicken eggs were divided into three groups: 15% O2 (hypoxic), 60% O2 (hyperoxic) and 21% O2 (normoxic) and incubated under these conditions for 72 h to day 18. Hypoxia reduced embryo, heart, brain and liver wet weights, whereas hyperoxia increased embryo, heart, lung and liver wet weights compared to normoxic controls. Chorioallantoic membrane (CAM) wet weight was increased by hypoxia and reduced by hyperoxia. Livers from hyperoxic embryos contained more zinc, iron and manganese and less copper than livers from hypoxic or normoxic embryos. Tissue concentrations of zinc, copper, iron and manganese were reduced in brains from hyperoxic compared to hypoxic or normoxic embryos. Hyperoxia increased the zinc and copper concentrations in CAM, whereas hypoxia reduced zinc and iron levels. The contents of zinc and copper were increased in hyperoxic compared to normoxic or hypoxic lungs. Hearts from hyperoxic embryos had more zinc, copper and manganese than hypoxic or normoxic hearts. Hypoxic yolk sac contained more zinc and manganese than hyperoxic or normoxic yolk sac. Except for yolk sac, the trace element content of tissues from normoxic embryos increased from day 15 to day 18 of incubation in concert with tissue growth. We conclude that the availability of oxygen to the developing chick embryo affects tissue trace element levels through its effects on tissue growth, as a result of adaptation by specific tissues to different oxygen tensions, or via effects on the regulation of trace element uptake and assimilation by the tissues.

Allantois↗
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Autoshaped discrimination learning in chicks incubated under normobaric hyperoxia.

White Leghorn chicken eggs were exposed to either 60% O2 or room air (21% O2) for the first 19 days of incubation. Chicks that hatched from these eggs were then tested in discrimination learning tasks in which keypecking was autoshaped to colored lights that were paired with either access to food (Experiment 1) or heat (Experiment 2). Chronic prenatal exposure to 60% O2 reduced hatchability but did not affect mean hatching time. Although previous research has shown that hyperoxic treatment accelerates growth in chick embryos until the 18th day of incubation, experimental chicks weighed either the same (Experiment 1) or less (Experiment 2) than controls at hatching. Prenatal exposure to hyperoxia depressed rate of acquisition, but not final performance level in both discrimination tasks. The initial performance deficit appeared to reflect a temporary depression of activity or arousal, possibly due to a relatively greater hypothermia in experimental chicks. This general pattern of results was attributed to premature depletion of essential nutrients within the egg as a result of oxygen-induced growth acceleration.

Animals↗