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Biomedical subjects

J M Warren

Publications and source records attributed to J M Warren.

At least 37 records · Page 2Linked to original sources
PubMed1982

Effects of environmental enrichment on old mice.

Fifteen male C57BL/6J mice, exposed to an enriched environment from age 600 to 750 days, were compared with 15 matched controls on 4 learning problems and an activity test. The enriched mice were significantly superior on an incidental learning and a food-seeking task, but did not differ significantly from controls on a brightness discrimination task, the Lashley III maze and an activity test. The relative abundance of high and low ribonucleic acid-containing cerebrocortical cells differed significantly between groups; the enriched mice had more cells with very high levels of RNA. The mammalian brain appears to remain responsive to environmental enrichment well into advanced age.

Age Factors↗
PubMed1981

Visual discrimination defects in cats with temporal or occipital decortications.

Performance on visual discrimination problems by seven control (C) cats, eight cats with lesions in the posterior temporal (PT) cortex, and eight with destruction of the central 3 degrees-20 degrees of the retina's projection to the marginal (M) gyrus was investigated as a function of three variables: discriminanda (objects and patterns, type of pattern), learning requirement (acquisition, transfer, retention), and stimulus-response contingency (simultaneous, successive, concurrent discrimination). Group PT was impaired on 7/11 initial learning and transfer tests and on 0/3 retention tests, with pattern stimuli; it was inferior to Group C on 1/7 object discrimination tasks. No discrimination contingency was more likely than the others to reveal a significant deficit in Group PT. Group M was not impaired relative to Group C on any individual discrimination task. However, it made significantly more total errors on seven discriminations between complex patterns (embedded or masked figures) than Group C. On three discriminations between simple patterns (unmasked figures), Group M made fewer errors than Group C. This pattern of loss is qualitatively similar to, but milder than, that observed in previous cats with M lesions, very probably because the present M lesions were relatively small. The findings indicate that M and PT ablations produce differential impairments in cats, a selective difficulty in differentiating complex patterns after M lesions and a nonselective disruption of pattern discrimination learning after PT lesions.

Animals↗
PubMed1976

Florid and subclinical rickets among immigrant children in Glasgow.

200 Asian 300 African, Chinese, or Scottish children were examined for clinical, biochemical, and radiological evidence of vitamin-D deficiency. Among the Asians there were 10 with florid rickets and 15 with subclinical rickets. Among the African, Chinese, and Scottish children there were no cases of florid rickets and only 7 cases of subclinical rickets (3 African, 3 Chinese, and 1 Scottish). Loss of metaphyseal definition is considered to be the radiological pattern of minimal active rickets and metaphyseal bands to represent the healing stage. Serum 25-hydroxycholecalciferol concentrations were low in clinical and subclinical minimal active rickets although there was some overlap with the wide range found in the "normal" group. Elevated serum-alkaline-phosphatase levels alone should not be regarded as indicating vitamin-D deficiency. The continuing prevalence of rickets in Asian children and in particular among schoolchildren warrants immediate action, which is long overdue.

Africa↗
PubMed1976

Marginal and extramarginal cortical lesions and visual discrimination by cats.

Seventy-five cats learned a shape discrimination with zero, one, or two irrelevant cues. They were then subjected to sham operations (n = 34), ablation of the marginal and splenial gyri (n = 9), or lesions in the extramarginal (EM) cortex. The 32 EM cats comprised four groups, three with small (EM1, n = 9), intermediate (EM2, n = 10), and large (EM3, n = 9) decortications, and a fourth group with both EM lesions and heavy degeneration in the lateral geniculate nucleus (LGN, n = 4). The cats with marginal or extensive extramarginal lesions were severely impaired in shape and size discrimination. Two lines of evidence indicate that their behavioral defects resulted from different neural dysfunctions. (a) The errors made by marginal gyrus cases increased sharply as a function of the number of irrelevant cues present in shape discrimination training; no other group, including Group EM3, was affected by this variable. (b) Cats with extramarginal ablations and strong LGN degeneration were no more severely impaired than were subjects with comparable extramarginal damage and little or no LGN degeneration. While the nature of the two kinds of deficits remains unclear, they seem parallel to those following posterior cortical lesions in monkeys.

Animals↗
PubMed1976

The search for cerebral dominance in monkeys.

Twelve monkeys with statistically significant and consistent manual preferences on three handedness tests were subjected to unilateral ablations in the association cortex. Eight received lesions in the foveal prestriate cortex, and four lesions in the dorsolateral frontal cortex; half the subjects in each group were operated on the dominant, and half on the nondominant hemisphere for handedness. The unilateral posterior preparations were significantly inferior to the control group of four unilateral frontals and five sham operated monkeys on three series of visual pattern discrimination problems. No evidence was obtained that lesions in the nondominant hemisphere. The results of this and four other experiments indicate that there is no cerebral dominance for problem-solving in monkeys. Recent research indicates that handedness in rhesus monkeys is only superficially similar to handedness in humans; thus, monkeys appear to lack cerebral dominance for handedness as well as for cognitive behavior.

Animals↗
PubMed1976

Metabolic balances of strontium in man.

Stable strontium balances were determined in man under strictly controlled dietary conditions in control studies and during both oral and intravenous administration of stable strontium. The diet contained about 1 mg strontium per day and most of this (88%) was excreted in stool while 17.5 per cent was excreted in urine, so that the balance was very slightly negative. During the oral intake of 1536 mg strontium per day, given as the lactate, the urinary and the fecal strontium excretions increased markedly and the balance became strongly positive. During the 6-day periods of intravenous infusions of stable strontium as the gluconate, 30-40 per cent of the infused amount was excreted in the urine and 5-10 per cent in stool. A high percentage of the strontium retained during both oral and intravenous administration was excreted in 30 days after the discontinuation of the strontium administration and there was no evidence of long term retention. The administration of stable strontium, given either orally or intravenously, was associated with an increase of the urinary calcium excretion.

Administration, Oral↗