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Biomedical subjects

R McGee

Publications and source records attributed to R McGee.

At least 127 records · Page 7Linked to original sources
PubMed1986

The relationship between specific reading retardation, general reading backwardness and behavioural problems in a large sample of Dunedin boys: a longitudinal study from five to eleven years.

Parent and teacher reports of behaviour problems were obtained at ages 5, 7, 9 and 11 years for three groups of boys: specific reading retarded (N = 18), general reading backward (N = 22), and those with no severe reading disability (N = 436). At school entry, both groups of reading disabled boys were reported as having more behaviour problems, and the level of problems increased during their early school years. The results suggest that behaviour problems pre-date reading disability, while reading failure further exacerbates the existing problem behaviour.

Aggression↗
PubMed1985

Both substance P agonists and antagonists inhibit ion conductance through nicotinic acetylcholine receptors on PC12 cells.

Substance P stimulates substance P receptors but also inhibits ion conductance through nicotinic acetylcholine receptors. Substance P analogs, classified as agonists or antagonists based on their actions on smooth muscle, were tested to determine if they also could act at nicotinic receptors on the pheochromocytoma, PC12. All of the analogs tested, [D-Pro2, D-Trp7,9]SP, [D-Arg1, D-Pro2, D-Trp7,9, Leu11]SP, [pGlu5, MePhe8, Sar9]SP-(5-11), and [D-Pro4, D-Trp7,9,10]SP-(4-11), inhibited agonist-induced uptake of 86Rb+ through the nicotinic receptors at concentrations quite similar to those required for action at substance P receptors on smooth muscle. Thus, the chemical modifications in the analogs do not substantially alter their ability to inhibit nicotinic receptors.

Animals↗
PubMed1985

Sulfation and constitutive secretion of dopamine beta-hydroxylase from rat pheochromocytoma (PC12) cells.

The biosynthesis and secretion of dopamine beta-hydroxylase were investigated by radiolabeling rat pheochromocytoma (PC12) cells in culture. Intracellular dopamine beta-hydroxylase from a crude chromaffin vesicle fraction and secreted dopamine beta-hydroxylase from culture medium were immunoprecipitated using antiserum made against purified bovine soluble dopamine beta-hydroxylase. Analysis of the immunoprecipitated enzyme on sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that: 1) the membrane-bound form of the hydroxylase from crude secretory vesicle membrane extracts contained two nonidentical subunits in approximately stoichiometric amounts (Mr = 77,000 and 73,000); 2) the soluble hydroxylase from the lysate of these secretory vesicles was composed predominantly of a single subunit (Mr = 73,000); and 3) the hydroxylase secreted into the medium under resting conditions was also composed of a single subunit (approximate Mr = 73,000). All subunits of the multiple forms of hydroxylase were glycoproteins. Under resting conditions, the rate of secretion of hydroxylase was approximately 6% of total cellular enzyme/15 min. The secreted form of the hydroxylase incorporated [35S]sulfate, whereas no significant [35S]sulfate was incorporated into the cellular forms of enzyme. We propose that in addition to the dopamine beta-hydroxylase which is found in catecholamine storage vesicles and released during stimulus-coupled exocytosis, PC12 cells also have a constitutive secretory pathway for dopamine beta-hydroxylase and that the enzyme released by this second pathway is sulfated.

Adrenal Gland Neoplasms↗
PubMed1985

The effects of exposure to exogenous fatty acids and membrane fatty acid modification on the electrical properties of NG108-15 cells.

The role of membrane lipid composition in determining the electrical properties of neuronal cells was investigated by altering the available fatty acids in the growth medium of cultured neuroblastoma X glioma hybrid cells, clone NG108-15. Growth of the cells for several days in the presence of polyunsaturated fatty acids (linoleic, linolenic, and arachidonic) caused a pronounced decrease in the Na+ action-potential rate of rise (dV/dt) and smaller decreases in the amplitude, measured by intracellular recording. Oleic acid had no effect on the action potentials generated by the cells. In contrast, a saturated fatty acid (palmitate) and a trans monounsaturated fatty acid (elaidate) caused increases in both the rate of rise and the amplitude. No changes in the resting membrane potentials or Ca2+ action potentials of fatty acid-treated cells were observed. The membrane capacitance and time constant were not altered by exposure to arachidonate, oleate, or elaidate, whereas arachidonate caused a small increase in membrane resistance. Examination of the membrane phospholipid fatty acid composition of cells grown with various fatty acids revealed no consistent alterations which could explain these results. To examine the mechanism for arachidonate-induced decreases in dV/dt, the binding of 3H-saxitoxin (known to interact with voltage-sensitive Na+) channels was measured. Membranes from cells grown with arachidonate contained fewer saxitoxin binding sites, suggesting fewer Na+ channels in these cells. We conclude that conditions which lead to major changes in the membrane fatty acid composition have no effect on the resting membrane potential, membrane capacitance, time constant, or Ca2+ action potentials in NG108-15 cells. Membrane resistance also does not appear to be very sensitive to membrane fatty acid composition. However, changes in the availability of fatty acids and/or changes in the subsequent membrane fatty acid composition lead to altered Na+ action potentials. The primary mechanism for this alteration appears to be through changes in the number of Na+ channels in the cells.

Action Potentials↗
PubMed1985

The Rutter scale for completion by teachers: factor structure and relationships with cognitive abilities and family adversity for a sample of New Zealand children.

A large sample of 7-year-old children (n = 940) was rated by teachers using the Rutter Child Scale B, a 26-item questionnaire covering a variety of behavioural problems. A factor analysis of the data revealed three main factors of interest, identified as aggressiveness, hyperactivity and anxiety-fearfulness. Measures based upon these factors had a reasonably high level of reliability and were moderately stable over a 2-year interval. An analysis of the relationship between these three behavioural measures and some cognitive measures indicated that only hyperactivity was negatively associated with cognitive ability. However, both hyperactivity and aggressiveness were related to adversity in the child's family background. The findings suggest the usefulness of distinguishing between aggressive and hyperactive dimensions of behaviour.

Achievement↗
PubMed1985

Some characteristics of 9-year-old boys with general reading backwardness or specific reading retardation.

In 1975 Rutter and Yule distinguished between 'specific reading retardation' and 'general reading backwardness'. In a sample of 952 9-year-olds from Dunedin, New Zealand, 4.2% were identified as specific reading retarded and 4.1% as having general reading backwardness. Boys from each problem group were compared with boys without reading delay. General reading backwardness was associated with a history of long-term cognitive and motor delay. Specific reading retardation was only associated with lower verbal IQ and poor speech articulation. A number of differences between the findings of Rutter and Yule and the present results were noted.

Child↗
PubMed1985

Physical development of hyperactive boys.

Anthropometric data were collected on groups of seven-year-old Dunedin (New Zealand) boys, identified as hyperactive-only, aggressive-hyperactive, aggressive-only and non-aggressive/non-hyperactive. Measures taken included stature, weight, skeletal maturity, mid-upper arm circumference, triceps and subscapular fatfolds and body-mass index. The hypothesis that hyperactive-only boys would show delayed maturation, as indicated by lower bone-age, was not confirmed. However, these boys had significantly smaller mid-upper arm circumference, triceps fatfold and body-mass index than the other groups. The results suggest that body leanness may discriminate 'pure' hyperactive boys from aggressive-hyperactive boys.

Age Determination by Skeleton↗
PubMed1985

Agonist-induced regulation of the neuronal nicotinic acetylcholine receptor of PC12 cells.

Pheochromocytoma cells, clone PC12, possess neuronal nicotinic acetylcholine (ACh) receptors which can be activated by an agonist to produce a transient transmembrane cation flux similar to that seen with neuromuscular nicotinic ACh receptors. We have observed that these neuronal nicotinic ACh receptors are subject to long term regulation by the cholinergic agonist carbamoylcholine (carbachol). Receptor function was measured by agonist-induced uptake of 86Rb+ into the cells. Chronic exposure to concentrations of carbachol that caused receptor activation induced an adaptation (down-regulation) of the receptors, seen as a decrease in the responsiveness of the cells to a subsequent exposure to carbachol. The extent of the decreased responsiveness was proportional to the concentration of carbachol between 50 microM and 10 mM and was distinct from acute receptor desensitization. The concentrations of carbachol that caused down-regulation were greater than those that caused maximum receptor activation, but were similar to those that greatly enhanced desensitization. This suggested that promotion of the desensitized state of the receptor could be the true stimulus for down-regulation. Adaptation was observed initially after several hours of exposure and maximally within about 7 days. Recovery from the down-regulated state required several days of growth in the absence of carbachol. Treatment with the antagonist mecamylamine did not cause a similar change in the responsiveness of the cells. However, concurrent exposure to carbachol and mecamylamine prevented down-regulation. Therefore, it appeared that receptor activation was necessary for regulation to occur. Comparison of the cellular responses of chronically treated and control cells to acute stimulation with carbachol supported the hypothesis that the mechanism for this down-regulation in PC12 cells was a decrease in the number of functional ACh receptors.

Adrenal Gland Neoplasms↗
PubMed1984

Flashbacks and memory phenomena. A comment on "Flashback phenomena--clinical and diagnostic dilemmas".

Alarcon, Dickinson, and Dohn (J. Nerv. Ment. Dis., 170: 217-223, 1982) recently reviewed the phenomenon of memory flashback following use of hallucinogenic drugs. They point out that while there are a considerable number of explanations concerning the flashback mechanism, little is known about the real causes. This paper examines flashback following drug ingestion in the light of other memory phenomena concerned with "cued retrieval" effects. Such phenomena may include dream recall, delayed post-traumatic stress, mood influence on memory, and drug effects on memory. Rather than view flashbacks as "pathological" in some sense, it may be better to view them as instances of normal memory processes, which may, nevertheless, be accompanied by emotional distress. Such a view relates flashbacks to a wider memory literature, and also makes them amenable to investigation using research designs derived from that literature.

Adult↗
PubMed1984

A seven year follow-up study of the cognitive development of children who experienced common perinatal problems.

The prevalence of perinatal problems in a sample of 1037 children was described. There was no significant association between perinatal problems and socio-economic status. The association between perinatal problems and cognitive development was examined by stepwise regression analyses of the more common perinatal problems on cognitive factor scores, using measures of language and intelligence taken when the children were aged 3, 5, and 7 years. Of 14 perinatal problems analysed in this manner, only two, being a twin or being small for gestational age, were found to be consistently associated with a significantly lower cognitive factor score.

Child Development↗
PubMed1984

A longitudinal study of enuresis from five to nine years.

The prevalence of primary and secondary enuresis was examined longitudinally in a large sample of New Zealand children at ages 5, 7, and 9 years. While the prevalence of primary enuresis fell over time, secondary enuresis increased in prevalence between 5 and 7 years. There were no sex differences. An examination of some of the developmental and background characteristics of the sample indicated that enuresis was not associated with neurodevelopmental delay or 'psychosocial' factors. However, there were strong, long term associations between secondary enuresis and behavioural deviance. The behavioural results suggested that behaviour problems did not arise as a consequence of enuresis, but rather preceded it.

Child↗
PubMed1984

Behaviour problems in a population of seven-year-old children: prevalence, stability and types of disorder--a research report.

A sample of 951 children in Dunedin, New Zealand was assessed at age 7 years to examine the prevalence, nature and stability of behaviour problems. The identification of children with behaviour problems was based upon reports of parents and teachers. About 30% of the sample were identified by the parent and/or teacher as having a high level of problem behaviour. The most prevalent problem reported was antisocial behaviour, which was more common among boys than girls. Over 9% of the sample were identified as having a stable behaviour problem. Such stable problems were associated with specific reading retardation, independent ratings of behaviour during psychological testing and use of professional services for help. These children, together with those identified by both parent and teacher at age 7 years, should be regarded as having a significant behaviour disorder.

Child↗
PubMed1984

Perinatal, neurological, environmental and developmental characteristics of seven-year-old children with stable behaviour problems.

From a large sample of 7-yr-olds in Dunedin, New Zealand, a group of 52 boys and 32 girls with stable behaviour problems was selected and compared with the remainder of the sample. The groups did not differ in terms of perinatal problems except for a higher prevalence of being small for gestational age in the problem group. The mothers of the problem children tended to be younger, to have lower mental ability and poorer health than the rest of the sample. The families of the problem children were rated as having poorer relationships, and there was more parental separation and solo parenting in this group. Finally, the children with stable problems showed cognitive delays at age 7 yr.

Child↗