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Biomedical subjects

J M Fletcher

Publications and source records attributed to J M Fletcher.

At least 181 records · Page 10Linked to original sources
PubMed1985

Neuropsychological sequelae of childhood cancer in long-term survivors.

In order to assess the effects of various cancer treatments on neuropsychological functioning, 74 long-term survivors of childhood cancer were examined. A comprehensive battery of tests was administered to two CNS treatment groups (irradiated and nonirradiated leukemia and lymphoma patients) and a control group (solid tumor and Hodgkin disease patients receiving no CNS treatment). The CNS-irradiated group obtained lower scores than the other two groups, with significant differences in visual-motor and fine motor skills, spatial memory, and arithmetic achievement resulting in significant differences in IQ scores (VIQ, PIQ, FSIQ). The results are discussed in relation to: (1) the effects of CNS irradiation on cognitive development; (2) the specificity of these effects; and (3) the relationship of age at diagnosis to treatment effects. It is concluded that although there is a general lowering of scores after CNS irradiation, the effect is most pronounced for nonlanguage skills. Age at diagnosis was less important than the type of treatment, with CNS irradiation reducing performance regardless of when cancer was diagnosed. There were indications that children with any type of cancer diagnosed before age 5 years are more likely to have some cognitive difficulties.

Age Factors↗
PubMed1984

Neuropsychological approaches to children: towards a developmental neuropsychology.

Neuropsychologists working with children commonly infer a CNS basis for many developmental disabilities on the basis of test performance and behavioral observations. While there is nothing inherently wrong with such inferences, the fact that there exists no specific set of brain-behavior relationships validating these inferences is frequently overlooked. In this respect, CNS inferences on the basis of the child's performance can lead to four potential fallacies concerning relationships between brain and behavior. Each of these fallacies involves a failure to recognize important behavioral and biological differences between children and adults, or simply rests on faulty logic and inadequate research. In an effort to outline a truly developmental neuropsychology for children--as opposed to diverse approaches that apply adult-based techniques to children--we propose a functional organization approach. This approach separates the different types of variables underlying a developmental neuropsychology and focuses on behavioral theory and research addressing the development of children's abilities. A specific emphasis of this approach is on processes of change--one of the primary psychological characteristics separating children and adults. The use of this approach as a general research strategy for children whose disabilities are associated with demonstrable or presumed CNS aberrations may lead to a set of behavioral laws that can be systematically related to a biological substrate.

Attention Deficit Disorder with Hyperactivity↗
PubMed1984

Neuropsychologic assessment of long-term survivors of childhood leukemia.

Thirty-two long-term survivors of childhood leukemia who were followed up at the University of Texas M. D. Anderson Hospital were evaluated with a battery of 17 neuropsychologic tests. These tests were selected to assess the development of cognitive skills and functions associated with brain impairment in children. Statistically significant differences were found between the group of children given CNS irradiation and the nonirradiated group on full-scale IQ and verbal IQ scores, mathematics skills, constructional skills, and memory for spatial material. Of particular interest was the absence of differences in language-based measures of verbal memory and the presence of group differences on measures of memory for spatial material. While the sample size was small, the findings delineate specific areas likely to be affected. These results indicate the need for caution when including cranial irradiation in CNS prophylaxis. When any CNS treatment is given, it seems appropriate that provisions be made for assessment and remediation of affected skills.

Acute Disease↗
PubMed1982

Tissue and whole-body protein synthesis in immature Zucker rats and their relationship to protein deposition.

The rates of protein synthesis in skeletal muscle, intestine, liver and in the whole body of immature (18 and 25 days old) lean and obese male Zucker rats were measured. In addition, the rate of deposition of whole-body and skeletal-muscle protein over the period 16-27 days post partum was measured by comparative slaughter and analysis of the composition of the body. At 16 days post partum, lean and obese rats had similar body protein contents, but thereafter the rate of protein deposition in the body and skeletal-muscle mass was decreased in the obese rats. The decrease was particularly marked before 21 days of age, and between 23 and 27 days post partum the fractional rate of protein deposition was the same in lean and obese rats. Of the tissues that were studied, only skeletal muscle had a lower fractional rate of protein synthesis in the obese rats. At 18 days post partum, the decrease in the absolute rate of protein synthesis in skeletal muscle accounted for at least 80% of the decline in protein synthesis in the whole body. After weaning, phenotypic differences in protein synthesis was less marked than at 18 days of age, and skeletal muscle accounted for only 50% of the difference in body protein synthesis between phenotypes. The possibility that a change in the function of the adrenal cortex contributes to differences in protein metabolism between lean and obese Zucker rats is discussed.

Age Factors↗
PubMed1982

The relationship of body and placental weight to plasma levels of insulin and other hormones during development in fetal rabbits.

The relationship of body and placental weight with plasma levels of insulin, glucose, glucagon, glucocorticoids and somatomedins in fetal rabbits between 22 days of gestation and term has been investigated. At 22, 24, 26, 28 and 30 days gestation, body and placental weights were strongly correlated and were also significantly correlated with log transformed plasma insulin concentrations in individual fetuses from nulliparous does. At 30 days gestation, mean plasma insulin levels, as well as body and placental weights, were significantly elevated in fetuses from multiparous does (p less than 0.05) and in fetuses whose growth had been increased by surgical reduction in litter size on day 9 of pregnancy (p less than 0.001). Log insulin concentrations in fetuses from multiparous does and in litter-reduced fetuses were also significantly correlated with bodyweight. The correlation coefficient for log insulin and bodyweight in all individual rabbit fetuses at 30 days gestation was 0.69 (p less than 0.001, n = 116). Fetal log plasma glucagon concentrations at 26 and 28 days gestation were negatively correlated with body weight, but were not significantly related at 30 days gestation. Neither glucose nor glucocorticoid concentrations were significantly related to bodyweight in individual fetuses. Plasma somatomedin activity in litter-reduced fetuses at 30 days gestation, was significantly higher (p less than 0.02) than in normal fetuses, but was not significantly correlated with fetal body weight. The observation of strong positive correlation between insulin and bodyweight throughout the last third of gestation reinforces the belief that fetal insulin plays an important role in the regulation of both placental and fetal growth.

Animals↗
PubMed1980

Meiosis in Sxr male mice. I. Does a Y-autosome rearrangement exist in sex-reversed (Sxr) mice?

Cytological evidence for the existence of a Y-autosomal rearrangement in meiotic cells of Sxr mice has been sought. At peachytene, in silver-stained light microscope spread preparations of XY, Sxr/+ and XO, Sxr/+ spermatocytes, evidence for pairing or association between a possible Y-bearing segment of a specific autosome and a sex chromosome could not, however, be found. Such sex chromosome-autosome associations as were seen were non-specific in nature, and occurred no more often in Sxr mice than in controls.

Animals↗
PubMed1980

Trisomy 8. Report of a mosaic human male with near-normal phenotype and normal IQ, ascertained through infertility.

Trisomy 8, in mosaic or non-mosaic form is an extremely rare chromosomal condition in man. Liveborn subjects usually present with mental retardation, bone and joint anomalies and a variety of other physical anomalies. The mental retardation associated with the condition is, however, usually moderate compared to that found in other viable human autosomal trisomic conditions. The present report describes a trisomy 8 mosaic male subject with normal IQ and near-normal phenotype, ascertained through infertility. Chromosome studies on peripheral blood lymphocytes reveal a pure trisomy 8 constitution; cultured skin fibroblasts show 46,XY/47,XY+8 mosaicism. At meiosis, the extra No. 8 chromosome is missing from the germ line. The testicular histology indicates a germ cell maturation arrest in many spermatocytes and the patient is severely oligospermic. Biochemical studies to assay levels of glutathione reductase, a red cell enzyme, the gene for which resides in chromosome 8, show increased levels in the trisomy 8 patient compared with controls.

Adult↗
PubMed1979

Light microscope analysis of meiotic prophase chromosomes by silver staining.

A method is described for the silver staining of the synaptonemal complex in surface-spread mammalian spermatocytes for light microscope examination. The method is quick, reliable, of broad applicability, and provides a means of making karyotype analysis at meiotic prophase. Many hundreds of suitable cells can be examined in an average preparation in a relatively short space of time. It has so far been applied only to mammalian spermatocytes, but could be used for karyotype analysis in oocytes of mammals and also applied to gonocytes of non-mammalian species.

Animals↗
PubMed1978

Linear discriminant function analysis in neuropsychological research: some uses and abuses.

The present paper addressed the continued misinterpretation and misapplication of linear discriminant function analysis in neuropsychological research. Methodological problems concerning the influence of shrinkage and stepwise selection procedures on LDFA are virtually ignored and affect both the classification and inferential application of LDFA. Throughout the paper examples of potential abuses of LDFA were cited and data from a familiar research problem was employed to demonstrate procedures which enable more accurate interpretation of LDFA results. Linear discriminant function analysis and its multivariate equivalents are powerful and flexible tools for exploring group differences provided appropriate applications and interpretations of results are made.

Craniocerebral Trauma↗