Biomedical subjects

D A Edwards

Publications and source records attributed to D A Edwards.

At least 19 recordsLinked to original sources

PubMed1992

Parent educational attainment and adolescent cigarette smoking.

In a longitudinal design, this study examined psychosocial mediators of the effects of parental educational attainment on adolescent smoking acquisition and also examined whether smoking transition had different antecedents among adolescents from families of varying educational backgrounds. Parents' low educational attainment acted as a moderate to strong risk factor for the initial onset of smoking among middle school girls. Some of this effect was mediated by the higher smoking prevalence among both parents and friends of these adolescent girls, as well as by their lowered expectations for academic success. However, these variables only partially mediated the effect of parent education. There were few indications of differential antecedents of smoking acquisition among adolescents from less and more highly educated families. Implications for public health antismoking campaigns are discussed.

Achievement↗

PubMed1992

The natural history of cigarette smoking and young adult social roles.

The relation between cigarette smoking (in adolescence and adulthood) and the occupancy of conventional adult social roles was investigated in the current study. Two alternative predictions for this relation were examined--"role incompatibility" (which predicts a negative relation between adolescent smoking and adult role occupancy) and "pseudomaturity" (which predicts a positive relation between adolescent smoking and adult role occupancy). Processes of role selection and role socialization were examined using data from a longitudinal study of smoking from adolescence to young adulthood. Both pseudomaturity and role incompatibility predictions found some support in the data, and the two views could be reconciled by considering the student role as the key transition into other adult statuses. Implications for the study of social roles and substance use are discussed.

Adolescent↗

PubMed1991

Excitotoxin lesions of the zona incerta/lateral tegmentum continuum: effects on male sexual behavior in rats.

In male rats, ibotenic acid and N-methyl-D-aspartic acid were used to destroy neuronal perikarya intrinsic to an anterior-posterior continuum including the caudal zona incerta and lateral tegmentum. Some lesions virtually eliminated male sexual behavior - an effect most closely associated with damage to the lateral hypothalamus and zona incerta. Many lesioned males who copulated to ejaculation with normally active females showed little or no mating with receptive, but relatively inactive, females. Although it is possible to identify a critical region within the subthalamus whose destruction eliminates male sexual behaviour, sexually-relevant neuronal cell bodies appear to be distributed throughout the lateral hypothalamic/incertal/tegmental continuum.

Animals↗

PubMed1991

Zona incerta lesions: effects on copulation, partner-preference and other socio-sexual behaviors.

Sexually active males prefer a sexually receptive female to a non-receptive female, and partner-preference tests provide one way of studying the effect of brain damage on sexual motivation. Male rats with bilateral electrolytic lesions of the caudal zona incerta do not mate, and we studied the effects of zona incerta destruction on copulation and partner-preference. Lesioned males did not mate but were not indifferent to sexually receptive females. They continued to show a strong preference for a sexually receptive female over a non-receptive female. In addition, lesioned males showed many incomplete mounts i.e. mounts not accompanied by the pelvic thrusting necessary for intromission and ejaculation. Anogenital investigation of the receptive female was common. Taken together, these facts suggest that zona incerta destruction eliminates copulation without affecting sexual motivation, and that the failure to mate after lesioning probably reflects an inability to properly engage the locomotor responses of copulation.

Animals↗

PubMed1991

Tyrosine hydroxylase and dopamine beta-hydroxylase inductions evoked by reserpine in the superior cervical ganglion of developing eu- and hypothyroid rats.

This study was designed to determine the effect of neonatally-produced hypothyroidism on reserpine-elicited tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (D beta H) induction in the superior cervical ganglion (SCG) in rats. Some rats were rendered hypothyroid from birth by daily treatment with propylthiouracil (PTU). Some hypothyroid rats received replacement therapy with triiodothyronine (T3). Some rats received PTU for 20 days, beginning at 90 days of age. Some rats were not treated and served as controls. TH and D beta H activities were assayed at 30, 50 and 110 days of age. Basal TH activity in the SCG for rats made hypothyroid as neonates was significantly lower than for controls at all ages tested; basal D beta H activity for these rats was lower than for controls at 30 and 50 days of age, but by 110 days was not different from that for controls. Basal TH activity for rats made hypothyroid as adults was intermediate between that for controls and rats made hypothyroid from infancy. Injecting control rats with reserpine produces a robust TH induction in the SCG at each age tested, and a strong D beta H induction at 50 and 110 days of age. Reserpine-evoked TH and D beta H inductions in rats made hypothyroid as adults were not different from those seen in controls. In contrast, rats made hypothyroid from infancy showed virtually no evidence of a reserpine-provoked TH or D beta H induction at any age tested. TH and D beta H inductions for hypothyroid rats given T3 replacement were completely normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1991

Four pathways to young-adult smoking status: adolescent social-psychological antecedents in a midwestern community sample.

Evaluated the ability of social-psychological factors, measured in adolescence, to predict young-adult smoking outcomes. Results showed substantial continuity in the antecedents of adolescent and young-adult smoking but important discontinuities as well. Beliefs in the negative social consequences of smoking and beliefs about academic success and independence were important to adolescent but not to adult smoking. Conversely, beliefs in the negative health consequences of smoking were more important to adult smoking than to adolescent smoking. Results also showed an appreciable amount of smoking onset after the high school years, as well as an appreciable amount of adolescent smoking that did not persist into young adulthood. Antecedents of late-onset smoking and of nonpersistent smoking are described.

Achievement↗

PubMed1990

Computer-assisted analysis of behavior-brain damage relationships.

Experimental destruction of subcortical brain tissue by electrolytic, radio frequency, or excitotoxin lesions is commonly used in the study of the neural control of behavior. Relating variability in the locus and extent of brain damage to lesion-produced variability in behavior is essential to a complete analysis of the behavioral effects of brain damage. We describe the use of commercially available computer accessories and software for measuring the area of irregular polygons to accurately and rapidly estimate the amount of damage to any of a number of brain structures included within an area of experimental destruction. We then describe the use of statistical programs for correlation and multiple regression in calculating relationships between damage to particular structures and behavior. As an example, we show that excitotoxin (and presumably axon-sparing) lesions of lateral hypothalamic tissue adjacent to the caudal zona incerta virtually eliminate male sexual behavior in rats. The use of multiple regression analysis, in conjunction with procedures for calculating destruction to different brain regions, provides a way of correlating brain damage and behavior that has widespread application in studies of the behavioral effects of brain lesions.

Animals↗

PubMed1990

Olfactory bulb removal: effects on sexual behavior and partner-preference in male rats.

Control and bilaterally bulbectomized male rats were tested in an arena where the male could choose to spend time with (and mate with) a sexually receptive female, a nonreceptive female, or be in a neutral compartment. Control males mated with, and showed a strong preference for, sexually receptive females. Bulbectomy virtually eliminated mating. In addition, bulbectomized males showed no preference for a receptive female over a nonreceptive female, and spent their time equally between the receptive female, the nonreceptive female, and the neutral compartment. Effects of bulbectomy on preference and copulation could be consequences of a severely impaired ability to smell--the perception of odors may be essential for sexual arousal, or the absence of preference and copulation after bulbectomy might reflect a deficit in the male's ability to make odor-dependent classification of conspecifics as appropriate sexual partners. Or the behavioral effects of bulbectomy might reflect a disruption of tonic input to the forebrain that has little or nothing to do with the sensory impairment that follows bulb removal. But whatever the reason, in partner-preference tests bulbectomized males show a striking indifference to the sexual status of females, and it seems likely that the failure to mate is causally linked to this effect of surgery.

Animals↗

PubMed1990

The natural history of cigarette smoking: predicting young-adult smoking outcomes from adolescent smoking patterns.

Assessed the magnitude of risk that adolescent cigarette smoking carries for adult smoking. Using a longitudinal, prospective design, results indicate that even infrequent experimentation in adolescence significantly raises the risk for adult smoking and that regular (at least monthly) adolescent smoking raises the risk for adult smoking by a factor of 16 compared to nonsmoking adolescents. Relative risk was also increased by an early onset of smoking and by a stable, uninterrupted course from experimentation to regular smoking. Relative risk did not significantly vary by age or sex. The continuity of smoking behavior between adolescence and adulthood supports the importance of primary prevention programs directed at adolescent populations.

Adolescent↗

PubMed1990

Connections between the pontine central gray and the ventromedial hypothalamus are essential for lordosis in female rats.

Lesions and knife cuts were used to study central gray (CG) and ventromedial hypothalamic (VMH) mediation of sexual receptivity in female rats. Lesions of the midbrain-pontine CG eliminated lordosis in female rats. Bilateral sagittal knife cuts that bracketed the rostral pontine CG also eliminated lordosis, and an experiment with the retrograde tracer Fluoro-Gold confirmed the effectiveness of these cuts in severing the lateral connections linking the VMH and the CG. Finally, females with a unilateral hypothalamic cut combined with a contralateral CG transection almost never showed lordosis. Each cut, at a different level for each side of the brain, transected axons linking the VMH and the CG. The demonstration that this combination eliminated lordosis provides new evidence that the lateral connections between the VMH and the CG are essential for the display of sexual receptivity in female rats.

Afferent Pathways↗

PubMed1990

A longitudinal study of early leg postures of preterm infants.

The prone and supine resting postures of the pelvis and legs of 106 preterm infants (25 to 34 weeks gestation) were studied longitudinally between 30 and 38 weeks post-menstrual age. All the infants subsequently had normal motor development. Posture was graded in relation to three items: the angle of elevation of the pelvis and the weight-bearing surface of the knee in prone, and the angle of rotation of the leg in supine. Although no grade was found to be exclusive to a particular postmenstrual age, all three items showed a statistically significant progressive trend. Only less than 6 per cent of the infants regressed in grade during the study. Infants dependent on oxygen for more than 28 days had significantly lower grades for leg posture in both prone and supine. Posture was not significantly altered by time ex utero or by intra-uterine growth retardation. The results show that these observation items are suitable measures of the progressive development of antigravity postures of preterm infants.

Gestational Age↗

PubMed1990

Sex differences in serum luteinizing hormone and testosterone in the human neonate during the first few hours after birth.

Blood was obtained from human male and female neonates within a few minutes after birth, and at intervals thereafter for up to 21 h. Serum LH was substantially higher at birth for boys than girls. For most boys, serum LH fell precipitously during the next hour; serum LH remained low for the remainder of the period sampled in both boys and girls. In girls, serum testosterone was low at birth and remained low for at least 21 h. At birth, serum testosterone in boys was higher than for girls, increased dramatically during the first 3 h after birth, and remained elevated (2 to 3 times higher than for girls) between 3 and 12 h after birth. In newborn human males, a sudden discharge of hypophyseal LH appears to stimulate neonatal secretion of testosterone by the testes. The functional significance of this phenomenon remains to be determined.

Chorionic Gonadotropin↗

PubMed1989

The mutagenic potential of high flash aromatic naphtha.

Catalytic reforming is a refining process that converts naphthenes to aromatics by dehydrogenation to make higher octane gasoline blending components. A portion of this wide boiling range hydrocarbon stream can be separated by distillation and used for other purposes. One such application is a mixture of predominantly 9-carbon aromatic molecules (C9 aromatics, primarily isomers of ethyltoluene and trimethylbenzene), which is removed and used as a solvent--high-flash aromatic naphtha. A program was initiated to assess the toxicological properties of high-flash aromatic naphtha since there may be human exposure through inhalation or external body contact. The current study was conducted partly to assess the potential for mutagenic activity and also to assist in an assessment of carcinogenic potential. The specific tests utilized included the Salmonella/mammalian microsome mutagenicity assay, the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) forward mutation assay in CHO cells, in vitro chromosome aberration and sister chromatid exchange (SCE) assays in CHO cells, and an in vivo chromosome aberration assay in rat bone marrow.

Administration, Inhalation↗

PubMed1989

Middle latency auditory evoked responses in normal term infants: a longitudinal study.

Middle latency auditory evoked responses (MLAERs) were measured in 21 normal term infants, three to five days after birth and then at 6 weeks, 7 months and 1 year of age. A polyphasic waveform was elicited during natural sleep in all infants at each recording session by monaural click stimulation at a rate of 9 per second. A 70 dBHL stimulus was found to be optimal as the MLAER became less well defined when the stimulus intensity approached the threshold hearing level. The first 60 to 70 msec of the waveform was found to be most stable, with decreasing detectability of peaks at longer latencies. There was no change in wave latency or reproducibility of MLAERs recorded during different sleep states. Waves Po and Na showed a significant decrease in latency with increasing stimulus intensity at term and/or 6 weeks of age. This was not evident for the remainder of the waveform. Waves Po, Na, Pa, Nb, Pb and Nc exhibited significant decreases in latency with age, attaining values indistinguishable from adults by 7 months of age.

Acoustic Stimulation↗

PubMed1988

Effect of nitrogen dioxide on surface membrane fluidity and insulin receptor binding of pulmonary endothelial cells.

Nitrogen dioxide (NO2), an environmental oxidant pollutant, is known to peroxidize membrane lipids of lung cells. We evaluated the ability of NO2 to alter the surface membrane fluidity, lipid composition, and insulin receptor binding of porcine pulmonary artery endothelial cells in culture. After 3- to 24-hr exposure to 5 ppm NO2, cells were labeled with either 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), a cationic fluorescent aromatic hydrocarbon that anchors at the lipid-water interface, or fluorescamine, a fluorescent molecular probe that covalently binds with amino groups of surface phospholipids and proteins. Membrane fluidity was measured by monitoring changes in the steady-state fluorescence anisotropies (rs) for TMA-DPH and fluorescamine. Insulin specific receptor binding was monitored by measuring time-dependent binding of 125I-insulin. Following NO2 exposure, rs values for TMA-DPH and fluorescamine were increased significantly in a time-dependent fashion, with maximum increases at 24 hr (P less than 0.001). Similar increases in rs values were observed in isolated plasma membranes as well as in lipid vesicles prepared from total lipid extracts of endothelial cells or their plasma membranes. Phosphatidylethanolamine plus phosphatidylserine content in lipid extracts from 24-hr but not 3- to 12-hr NO2-exposed cells was increased significantly (P less than 0.01) compared to control cells. Specific binding of 125I-insulin to cells exposed to NO2 for 12 and 24 hr (but not 3 and 6 hr) was reduced significantly (P less than 0.05) compared to binding in control cells. Scatchard analysis of the binding data indicated that NO2 exposure caused a 5-fold reduction in insulin receptor binding sites in endothelial cells. Recovery was achieved 24 hr after NO2 exposure with, but not without, changing culture medium. These results indicate that NO2 exposure causes reversible changes in the physical state of lipids in the superficial lipid domains of the pulmonary endothelial cell plasma membrane, and these alterations may interfere with plasma membrane-dependent functions such as receptor-ligand interaction.

Amino Acids↗

PubMed1988

Spatial variation in response to odorants on the rat olfactory epithelium.

We have measured the electro-olfactogram produced by four odorants, nicotine, i-pentyl acetate, i-pentanoic acid and cineole from twelve positions on an in vitro preparation of rat olfactory tissue. Each odorant shows a different pattern of response over the twelve positions which can be explained by differences in olfactory receptor populations between regions of the rat olfactory epithelium. The result for nicotine is further evidence that there are olfactory receptors which are stimulated by nicotine when it is presented as a vapour.

Action Potentials↗

PubMed1988

Perinatal risk factors in preterm infants with moderate-to-profound hearing deficits.

The perinatal histories of 16 preterm infants with confirmed moderate-to-profound hearing loss were examined to determine the perinatal factors that might have been associated with their abnormal auditory development. Of the 11 factors that were examined, eight factors occurred significantly more frequently in hearing-impaired infants when they were compared with 226 preterm infants who were cared for in the same intensive care unit in 1984. However, when the histories of the 16 infants with hearing loss were compared with those of 16 infants with normal hearing, who were matched according to gestational age, birthweight percentile and sex, there were no differences. The prevalence of aminoglycoside therapy was high in both groups of infants, but the mean duration of therapy in the infants with a hearing deficit was significantly longer (15 days compared with eight days; P less than 0.025). These observations suggest that younger, smaller, preterm infants with a complicated perinatal course and prolonged aminoglycoside therapy are at higher risk of auditory handicap. We recommend that the early identification of preterm infants with a hearing deficit should be achieved by recording brainstem auditory-evoked responses just before discharge from the intensive care unit.

Aminoglycosides↗

PubMed1988

Testosterone levels in plasma and testes of neonatal mice.

Newborn female and male C57BL6 mice were decapitated at birth or at different times during the first 24 h after birth and testosterone was determined by radioimmunoassay in plasma and testes. In newborn females, plasma testosterone is low and does not significantly change over the first 24 h after birth. In contrast, in newborn males, plasma testosterone more than doubles during the first 2 h after birth and then falls rapidly to remain relatively low for the remainder of the 24 h period after birth. The increase in plasma testosterone is of almost certain testicular origin since it follows a decrease in testicular testosterone content. It seems likely that the increase in plasma testosterone in male mice which reaches its peak at 2 h after birth is involved in an essential way in the development of well-documented sex differences in gonadotropin secretion and behavior.

Aging↗