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Biomedical subjects

R McGee

Publications and source records attributed to R McGee.

At least 109 records · Page 6Linked to original sources
PubMed1989

Neuropsychological correlates of psychopathology in an unselected cohort of young adolescents.

Members of a birth cohort were assessed for psychopathology and neuropsychological dysfunction at age 13. Ss who met DSM-III criteria for a single disorder, multiple disorders, and no disorder were compared on 5 composite neuropsychological measures. The multiple disorders group performed significantly worse than did the nondisordered group on the Verbal, Visuospatial, Verbal Memory, and Visual-Motor Integration factors. They also showed the highest rate of neuropsychological impairment. The attention-deficit disorder group performed significantly worse than did the nondisordered group on the Verbal Memory and Visual-Motor Integration factors, and the anxiety disorder group performed significantly worse than did the nondisordered group on the Visual-Motor Integration factor. Results suggest that neuropsychological dysfunction is more often associated with multiple rather than single, psychiatric disorders in adolescents. The problem of comorbidity in studies of neuropsychological function in childhood and adolescent psychopathology is highlighted.

Adolescent↗
PubMed1989

Changes in food intake and activity after quitting smoking.

Quitting smoking often results in weight gain. The causes of the gain are not known. The present study evaluated changes in calories, total sugars, sucrose, fat, protein, and nonsugar carbohydrates as well as changes in activity levels after quitting smoking. Ninety-five subjects were randomly assigned to either early (Week 2) or late (Week 6) quit dates. Subjects were assessed on weight, food intake, activity levels, and smoking levels at baseline, at Weeks 4 and 8, and at Weeks 12 and 26 postquit. The results indicated significant increases in calories, sucrose, and fats 2 weeks after the quit date. Changes for total sugars were less consistent. Activity levels did not change significantly. Early caloric increases predicted weight gain at 26 weeks for abstinent women. No relation was found for abstinent men, but interpretation of this finding is weakened by a small subsample size. Abstinent subjects gained over 9 lb by 26 weeks postquit. Despite this gain, Week 26 results showed that caloric intake for abstinent women was approximately equal to that observed at baseline, whereas that for abstinent men had dropped significantly.

Adult↗
PubMed1989

IQ and reading progress: a test of the capacity notion of IQ.

Concepts such as developmental reading disorder and dyslexia have been used to refer to children whose actual reading achievement is substantially below that predicted by performance on IQ tests. Such diagnostic concepts assume that IQ sets a limit on either the level of achievement or the rate of progress of which a child is capable. This assumption was investigated in a longitudinal study of an unselected cohort of 741 children whose reading achievement was assessed at ages 7, 9, 11, and 13 years. Findings on rates of progress and levels of achievement clearly indicate that IQ does not set a limit on reading progress, even in extreme low IQ children. Thus, the use of IQ tests to determine achievement potential in reading appears unwarranted.

Achievement↗
PubMed1989

Cognitive and social correlates of DSM-III disorders in preadolescent children.

The relationships between some cognitive and social measures and the major syndromes found in a large preadolescent sample of children from the general population are described. The measures discriminated between disorder-no disorder for most variables examined and between the broad groups of externalizing and internalizing disorders, but not between individual diagnostic categories. An important exception was that ADDH and conduct disorder occurring as single disorders could be distinguished, but the frequent comorbidity of these and other disorders complicated many between-group comparisons.

Child↗
PubMed1988

Characterization of a delayed rectifier K+ channel in NG108-15 neuroblastoma X glioma cells: gating kinetics and the effects of enrichment of membrane phospholipids with arachidonic acid.

A voltage-sensitive K+ channel with characteristics of the delayed rectifier was studied in NG108-15 cells using the cell-attached patch-clamp technique. The primary conductance of the channel was 18 pS, but occasional openings to a subconductance state were observed. The average latency to first opening of the channel was about 4 msec. Based on about 20,000 channel openings, the open time probability density function (pdf) required at least three exponentials (time constants of about 0.2, 3 and 9 msec) to achieve an adequate fit to the data. The closed time pdf required at least six exponentials to describe the data (time constants ranging from 0.093 to 440 msec). Thus, the channel exists in at least three open and six closed states. The ensemble average describing the inactivation of the channel was well fit by two exponentials with time constants of 170 msec and 4.2 sec. To examine the effect of changes in membrane lipid composition on the properties of the channel, the phospholipids of the cells were enriched with polyunsaturated fatty acids. In patches from 20:4-enriched cells the conductance, mean first latency, and open-time pdf were similar to control cells. However, the open state probability was increased from 0.25 to 0.44 and the mean closed time was decreased from 20 to 9 msec. The closed time pdf exhibited a higher proportion of closing events associated with short time constants, i.e., the probability of the channel closing into a long-lived closed state was decreased. The decay phase of the ensemble average also was changed; the proportion of the curve described by the slower time constant was almost doubled. Thus, the delayed rectifier from NG108-15 cells can exist in at least three open and six closed states, and changes in membrane lipid composition may have subtle effects on the gating kinetics of the channel.

Animals↗
PubMed1988

Effects of prolonged depolarization on the nicotinic acetylcholine receptors of PC12 cells.

To determine whether prolonged depolarization and/or changes in intracellular Ca2+ concentrations stimulate adaptive responses of neuronal nicotinic acetylcholine receptors, PC12 pheochromocytoma cells were grown in medium containing various concentrations of K+. Nicotinic receptor function was determined as carbachol-stimulated uptake of 86Rb+. Cells were exposed to 50 mM K+ for up to 4 days and then allowed to repolarize for 60 min. Under these conditions, no changes in basal or carbachol-stimulated uptake of 86Rb+ were observed. Furthermore, neither the time course of carbachol-stimulated uptake or the carbachol concentration dependence of 86Rb+ uptake was altered. Finally, concurrent depolarization did not affect the functional down-regulation produced by chronic exposure of the cells to carbachol. Thus, neuronal nicotinic acetylcholine receptors on PC12 cells do not appear to be regulated by depolarization or prolonged elevation of the intracellular Ca2+ level.

Adrenal Gland Neoplasms↗
PubMed1988

Regulation of the number of functional voltage-sensitive Ca++ channels on PC12 cells by chronic changes in membrane potential.

The properties of the various types of voltage-sensitive Ca++ channels (VSCC) are becoming increasingly well characterized, but the mechanisms which control the number and types of channels expressed by cells are virtually unknown. To study the regulation of VSCC in neuronal cells we have used PC12 pheochromocytoma cells. Binding of [3H]nitrendipine was used to determine the number of dihydropyridine-sensitive channels, and the uptake of 45Ca++ was used to determine the functional state of VSCC on the cell surface. Prolonged depolarization by elevation of extracellular K+ caused concomitant time and concentration-dependent decreases in both [3H]nitrendipine binding and depolarization-dependent uptake of 45Ca++. Changes in binding and ion flux plateaued at about a 50% decrease with 3 days of depolarization and an extracellular K+ concentration of 50 mM. Return of the cells to normal K+ caused the recovery of both [3H]nitrendipine binding and 45Ca++ uptake within 24 hr. Measurements of the intracellular free Ca++ concentration determined that it remained elevated for several hours with K+ depolarization, but returned to normal within 15 hr. Growth of the cells with a concentration of ionomycin, which caused a similar increase in intracellular free Ca++, also caused a loss of [3H]nitrendipine binding sites. Thus, it appears that the number of functional VSCC can be regulated by changes in intracellular Ca++ such as those associated with prolonged depolarization. However, because Ca++ channel number remained depressed while intracellular free Ca++ returned to normal, other mechanisms controlling channel number also must be involved.

Adrenal Gland Neoplasms↗
PubMed1987

DSM-III disorders in preadolescent children. Prevalence in a large sample from the general population.

We investigated the prevalence of DSM-III disorders in 792 children aged 11 years from the general population and found an overall prevalence of disorder of 17.6% with a sex ratio (boys-girls) of 1.7:1. The most prevalent disorders were attention deficit, oppositional, and separation anxiety disorders, and the least prevalent were depression and social phobia. Conduct disorder, overanxious disorder, and simple phobia had intermediate prevalences. Pervasive disorders, reported by more than one source, had an overall prevalence of 7.3%. Examination of background behavioral data disclosed that children identified at 11 years as having multiple disorders had a history of behavior problems since 5 years of age on parent and teacher reports. Fifty-five percent of the disorders occurred in combination with one or more other disorders, and 45% as a single disorder.

Anxiety Disorders↗
PubMed1987

A longitudinal study of children with developmental language delay at age three: later intelligence, reading and behaviour problems.

A large sample of Dunedin (New Zealand) children were assessed at age three to identify those with language delay. 2.6 per cent were defined as delayed in verbal comprehension only, 2.3 per cent as delayed in verbal expression only, and 2.3 per cent as delayed in both ('general language delay'). Most of these children, and the remainder of the sample, were assessed for intelligence, reading and behaviour problems at ages seven, nine and 11. Those in every language-delay group had significantly lower mean IQs and lower mean reading scores than the remainder of the sample. They also more often had a low IQ or a lower reading score at ages seven and nine and a lower Verbal and Full-scale IQ at 11. The groups with delayed verbal comprehension and general language delay had significantly more behaviour problems than the remainder of the sample. The group with general language delay was consistently the most disadvantaged in later intelligence, reading and behaviour. Two of the language-delay groups (comprehension and general language) had significantly higher scores on a family disadvantage index. The results of this study confirm the importance of early language delay as a predictor of lower than average intelligence and reading ability and increased behaviour problems.

Child↗
PubMed1986

Regulation of voltage-dependent Ca2+ channels of neuronal cells by chronic changes in membrane potential.

The regulation of voltage-dependent Ca2+ channels by chronic changes in membrane potential was studied by measuring the binding of [3H]nitrendipine to membranes from PC12 pheochromocytoma cells. Depolarization of the cells by elevation of extracellular K+ caused up to a 45% loss of [3H]nitrendipine binding sites within 4 days without any change in Kd. Repolarization of the cells caused a return to control binding within 1-2 days, showing that either decreases or increases in membrane potential can cause reversible changes in [3H]nitrendipine binding sites.

Animals↗
PubMed1986

Direct anesthetic-like effects of forskolin on the nicotinic acetylcholine receptors of PC12 cells.

Forskolin is thought to be a highly specific activator of adenyl cyclase. However, when applied to rat pheochromocytoma (PC12) cells at concentrations of 1 microM or higher it caused an immediate, concentration-dependent inhibition of carbachol-stimulated uptake of 86Rb+ through the nicotinic receptors, which did not appear to be related to activation of adenyl cyclase. The inhibition of receptor activation occurred instantaneously whereas cellular cAMP content did not increase for a measureable period of time. Normal receptor function was recovered rapidly upon removal of forskolin. Additional evidence that this effect of forskolin was not related to cAMP was obtained when 1,9-dideoxyforskolin (an analog of forskolin which does not activate adenyl cyclase) also caused a rapid, concentration-dependent, rapidly reversible inhibition of receptor-mediated influx of 86Rb+ into the cells. An examination of the effect of forskolin on 86Rb+ uptake at various concentrations of carbachol showed that forskolin was not acting by competing with carbachol for the receptor activation site. Given the lipophilic nature of forskolin, it probably acts like a general anesthetic to perturb the plasma membrane lipid structure and alter the function of the nicotinic acetylcholine receptors, possibly by increasing the rate of closure of open channels.

Adenylyl Cyclases↗
PubMed1986

Cognitive correlates of depressive symptoms in 11-year-old children.

Self-reports of depressive symptoms were obtained for 792 11-year-old New Zealand children using a structured interview. The aim of the present study was to test the hypothesis that depressive symptomatology in children is associated with impairment on cognitive tasks. The results did not support this hypothesis. Depression was unrelated to performance on various subscales of the WISC-R, whereas self-reported inattention was associated with poor performance. Depressive symptoms, however, were significantly related to lower self-esteem and a poorer self-perception of scholastic ability.

Aptitude↗
PubMed1986

An evaluation of the Malaise Inventory.

This paper reports some psychometric properties of the Malaise Inventory of Rutter and colleagues from a longitudinal study of a large sample of New Zealand mothers. Malaise scores were relatively stable over time and the scale showed good psychometric properties. The measure was also sensitive to potential sources of adversity in the backgrounds of the women. Some recommendations regarding a number of the questionnaire items are made.

Adult↗