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Biomedical subjects

C Jackson

Publications and source records attributed to C Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1999

Short day length alone does not inhibit spermatogenesis in the seasonally breeding four-striped field mouse (Rhabdomys pumilio).

This study was an examination of the effect of photoperiod on spermatogenesis and the accessory glands of the four-striped field mouse (Rhabdomys pumilio), a seasonally breeding rodent that occurs through Southern Africa. Adult scrotal males were exposed to either short day length (10L:14D), long day length (14L:10D), or natural photoperiod in constant-environment rooms (25 degrees C, 41% humidity; food and water ad libitum) for 8 wk in late summer, when males in the wild were spermatogenically active, and in mid-winter, when they were inactive. In neither experiment did prolonged exposure to short day length or naturally decreasing day length inhibit spermatogenic activity, and we conclude that the normal cessation of spermatogenesis that occurs in most male four-striped field mice in winter is not stimulated by day length alone.

Animals↗
PubMed1999

Ocular manifestations of equine motor neuron disease.

The characteristics of the ocular manifestations of equine motor neuron disease (EMND) are described. Forty-two horses with histories, clinical signs and necropsies compatible with EMND were the subjects of this study. Ophthalmoscopic lesions that varied in severity were found in 40 of 42 horses and appeared as a distinct pigmented reticulated pattern at the tapetal-nontapetal junction or throughout the fundus, depending upon severity. The pattern colours ranged from yellow brown to black. Areas of hyperreflectivity formed mosaic patterns in the tapetal fundus. ERG B-wave amplitudes were usually at least 50% reduced and many animals showed extinguished amplitudes. None of the horses had apparent visual impairment. Histopathologically, all 42 horses had retinal pigment epithelial (RPE) congestion with ceroid-lipofuscin. Retinal degeneration was variable even within the eyes. Thin layer chromatography (TLC) analysis of the RPE and neural retina identified both green and orange emitting fluorescent compounds not found in normal horses. All unsupplemented horses had plasma vitamin E levels <1.0 microg/ml. The potential significance of this report is the pathognomonic role the ocular manifestations exhibit in helping to diagnose equine motor neuron disease.

Animals↗
PubMed1999

Underlying structure of the National Institutes of Health Stroke Scale: results of a factor analysis. NINDS tPA Stroke Trial Investigators.

BACKGROUND AND PURPOSE: No stroke scale has been validated as an outcome measure using data from a clinical trial demonstrating a positive therapeutic effect. Therefore, we proposed to use data from the National Institute of Neurological Disorders and Stroke (NINDS) tPA Stroke Trial to determine whether the National Institutes of Health Stroke Scale (NIHSS) was valid in patients treated with tissue plasminogen activator (tPA) and to explore the underlying clinimetric structure of the NIHSS. METHODS: We performed an exploratory factor analysis of NIHSS data from Part 1 (n=291) of the NINDS tPA Stroke Trial to derive a hypothesized underlying factor structure. We then performed a confirmatory factor analysis of this structure using NIHSS data from Part 2 of the same trial (n=333). We then tested whether this final factor structure could be found in tPA- and placebo-treated patients serially over time after stroke treatment. Using 3-month outcome data, we tested for an association between the NIHSS and other measures of stroke outcome. RESULTS: The exploratory analysis suggested that there were 2 factors underlying the NIHSS, representing left and right brain function, confirming the content validity of the scale. An alternative structure composed of 4 factors could be derived, with a better goodness of fit: the first 2 factors could represent left brain cortical and motor function, respectively, and the second 2 factors could represent right brain cortical and motor function, respectively. The same factor structures were then found in tPA and placebo patient groups studied serially over time, confirming the exploratory analysis. All 3-month clinical outcomes were associated with each other at subsequent time points, confirming predictive validity. CONCLUSIONS: This is the first study of the validity of a stroke scale in patients treated with effective stroke therapy. The NIHSS appeared to be valid in patients with acute stroke and for finding treatment-related differences. The scale was valid when used serially over time after stroke, up to 3 months, and showed good agreement with other measures of outcome.

Brain↗
PubMed1999

Alcohol-specific socialization, parenting behaviors and alcohol use by children.

OBJECTIVE: This panel study examined the relations between alcohol-specific socialization by parents (monitoring of alcohol use by children, allowing alcohol use by children at home, communicating against alcohol use and setting rules against alcohol use), general dimensions of parenting behavior (responsiveness and demandingness) and alcohol use by children. METHOD: A sample of 488 fifth-grade children reported their perceptions of alcohol-specific socialization by parents, parental responsiveness and parental demandingness. These variables were used to predict alcohol use when children in the panel were in seventh grade. RESULTS: Nineteen percent of seventh-grade children reported alcohol use in the past 30 days. Logistic regression analyses indicated that, after accounting for children's age, sex, single parent status, prior use of alcohol and exposure to parental modeling of alcohol use, the odds of alcohol use were significantly greater among children who perceived no parental monitoring of alcohol use, who had been allowed by parents to have a drink with alcohol at home and who perceived relatively low levels of parental demandingness. Rules against alcohol use, parental communication against alcohol use and parental responsiveness were unrelated to the study outcome. CONCLUSIONS: Parental monitoring of alcohol use by children, family norms regarding alcohol use by children at home and parental ability to set and enforce behavioral rules merit consideration as factors that should be modified by prevention programs. There is a need, however, for additional research that further examines the relations between exposure to such parenting behaviors during childhood and alcohol use during adolescence.

Alcohol Drinking↗
PubMed1999

Brain-derived neurotrophic factor improves blood glucose control and alleviates fasting hyperglycemia in C57BLKS-Lepr(db)/lepr(db) mice.

Systemic administration of brain-derived neurotrophic factor (BDNF) decreases nonfasted blood glucose in obese, non-insulin-dependent diabetic C57BLKS-Lepr(db)/lepr(db) (db/db) mice, with a concomitant decrease in body weight. By measuring percent HbA1c in BDNF-treated and pair-fed animals, we show that the effects of BDNF on nonfasted blood glucose levels are not caused by decreased food intake but reflect a significant improvement in blood glucose control. Furthermore, once established, this effect can persist for weeks after cessation of BDNF treatment. Oral glucose tolerance tests were performed to examine the effects of BDNF on blood glucose control in the fasted state and after an oral glucose challenge. BDNF treatment normalized fasting blood glucose from initially hyperglycemic levels and also showed evidence for beneficial, although less marked, effects on the ability to remove exogenous glucose from blood. One means to lower fasting blood glucose is to reduce the glucose output of peripheral tissues that normally play a part in the maintenance of fasting hyperglycemia. Because the liver is the major endogenous source of glucose in blood during fasting, and because hepatic weight and glucose output are increased in type 2 diabetes, we evaluated the effects of BDNF on liver tissue. BDNF reduced the hepatomegaly present in db/db mice, in association with reduced liver glycogen and reduced liver enzyme activity in serum, supporting the possible involvement of liver tissue in the mechanism of action for BDNF.

Animals↗
PubMed1999

A GP prescribing educational intervention involving a medication panel.

AIM: To trial an educational intervention for general practitioners promoting Quality Use of Medicines. METHOD: Twenty-three general practitioners (GPs) from the Brisbane Inner South Division participated in 12 prescribing upskilling sessions over 13 months. The educational intervention utilised an interactive small group, case based approach with panel input from a GP, pharmacist, clinical specialist, consumer with a related diagnosis, and clinical pharmacologist, focusing on areas of nominated interest. Participants also had access to a therapeutic drug management phone service. RESULTS: Twenty-one (91%) participants completed nine or more sessions and a total of 319 of a possible 324 (98.5%) format evaluations were completed on educational sessions three to eleven. Pre and post session multiple choice questions (MCQs) were used to evaluate change in prescribing knowledge for eight of the sessions. All sessions showed a statistically significant improvement post intervention in both individual participant and overall group knowledge scores (p < 0.001). Participant feedback highlighted that: 100% agreed or strongly agreed that the educational content, panel discussion and summaries were relevant to their practice; 80% agreed or strongly agreed that the sessions were helpful in the management of their patients; 85% agreed or strongly agreed that they had gained new knowledge/skills they would apply in their practice. The therapeutic drug management phone service was utilised at least once by 72% of participants. DISCUSSION: The use of an interactive, case based prescribing intervention with medication team input, positively influences GP prescribing knowledge and management intent.

Australia↗
PubMed1998

The effect of perceived control over eating on the life satisfaction of women and men: results from a community sample.

OBJECTIVE: To test whether overweight, or perception of lack of control over eating, or both, contributed to the level of life satisfaction for women and men in a random sample of community-dwelling adults. METHOD: This study examined the effects of body mass index (BMI) and perceived control over eating on life satisfaction for women and men in a community-based sample of 1,069 women and 963 men. RESULTS: For women, both lack of perceived eating control and higher BMI were associated with less life satisfaction, and lack of control over eating was the more important predictor. For men, only lack of perceived eating control was associated with less life satisfaction. Furthermore, for both women and men, the contribution of eating control to life satisfaction was unaffected by BMI, that is, the life satisfaction of heavier people was not more affected by perceived control over eating than was the life satisfaction of lighter people. DISCUSSION: These findings suggest that psychological issues related to eating and weight can affect global aspects of well-being.

Adolescent↗
PubMed1998

Molecular characterization of Warthin tumor.

OBJECTIVE: Warthin tumor of the salivary gland is composed of oncocytic epithelium with a prominent follicular lymphoid infiltrate. The purpose of this study was to characterize the clonality of this lymphoid component by means of polymerase chain reaction technology. STUDY DESIGN: DNA was isolated from paraffin-embedded tissue from 20 cases of typical Warthin tumor of the salivary gland and amplified by polymerase chain reaction to assess B- and T-cell clonality. RESULTS: No dominant clonal populations were identified in any tumor. However, minor clonal expansions of both B and T cells were detected in up to 50% of tumors (immunoglobulin H, 50%; T-cell antigen receptor beta, 10%; T-cell antigen receptor gamma, 5%). No tumors showed evidence of bcl-2 proto-oncogene translocation, whereas 95% contained detectable Epstein-Barr virus DNA. CONCLUSION: The B- and T-cell components of Warthin tumor are polyclonal with oligoclonal expansion of both T and B cells in some lesions.

Adenolymphoma↗
PubMed1998

C-type natriuretic peptide expression and pulmonary vasodilation in hypoxia-adapted rats.

Atrial and brain natriuretic peptides (ANP and BNP, respectively) are potent pulmonary vasodilators that are upregulated in hypoxia-adapted rats and may protect against hypoxic pulmonary hypertension. To test the hypothesis that C-type natriuretic peptide (CNP) also modulates pulmonary vascular responses to hypoxia, we compared the vasodilator effect of CNP with that of ANP on pulmonary arterial rings, thoracic aortic rings, and isolated perfused lungs obtained from normoxic and hypoxia-adapted rats. We also measured CNP and ANP levels in heart, lung, brain, and plasma in normoxic and hypoxia-adapted rats. Steady-state CNP mRNA levels were quantified in the same organs by relative RT-PCR. CNP was a less potent vasodilator than ANP in preconstricted thoracic aortic and pulmonary arterial rings and in isolated lungs from normoxic and hypoxia-adapted rats. Chronic hypoxia increased plasma CNP (15 +/- 2 vs. 6 +/- 1 pg/ml; P < 0.05) and decreased CNP in the right atrium (35 +/- 14 vs. 65 +/- 17 pg/mg protein; P < 0.05) and in the lung (3 +/- 1 vs. 14 +/- 3 pg/mg protein; P < 0.05) but had no effect on CNP in brain or right ventricle. Chronic hypoxia increased ANP levels fivefold in the right ventricle (49 +/- 5 vs. 11 +/- 2 pg/mg protein; P < 0.05) but had no effect on ANP in lung or brain. There was a trend toward decreased ANP levels in the right atrium (2,009 +/- 323 vs. 2,934 +/- 397 pg/mg protein; P = not significant). No differences in CNP transcript levels were observed between the two groups of rats except that the right atrial CNP mRNA levels were lower in hypoxia-adapted rats. We conclude that CNP is a less potent pulmonary vasodilator than ANP in normoxic and hypoxia-adapted rats and that hypoxia raises circulating CNP levels without increasing cardiopulmonary CNP expression. These findings suggest that CNP may be less important than ANP or BNP in protecting against hypoxic pulmonary hypertension in rats.

Animals↗
PubMed1998

The Authoritative Parenting Index: predicting health risk behaviors among children and adolescents.

Public health research demonstrates increasing interest in mobilizing parental influence to prevent health risk behaviors among children and adolescents. This research focuses on authoritative parenting, which previous studies suggest can prevent health risk behaviors among youth. To evaluate the reliability and validity of a new survey measure of authoritative parenting, data from studies of (1) substance use in a sample of 1,236 fourth- and sixth-grade students; (2) weapon carrying and interpersonal violence in a sample of 1,490 ninth- and tenth-grade students, and (3) anger, alienation, and conflict resolution in a sample of 224 seventh- and eighth-grade students were analyzed. The Authoritative Parenting Index had a factor structure consistent with a theoretical model of the construct; had acceptable reliability; showed grade, sex, and ethnic differences consistent with other studies; and identified parenting types that varied as hypothesized with multiple indicators of social competence and health risk behaviors among children and adolescents.

Adolescent↗
PubMed1998

A longitudinal study predicting patterns of cigarette smoking in late childhood.

Early initiation of cigarette smoking so strongly predicts future smoking that several investigators have advocated delaying the age of initiation as a prevention strategy. To complement retrospective studies of early initiation, this study assessed prospectively patterns of smoking behavior in a sample of 401 children who were surveyed in the fifth, sixth, and seventh grades. The principal findings were (1) modeling of smoking by parents and friends is sufficient to influence children to initiate smoking, particularly when children also have low behavioral self-control, and (2) when modeling occurs in combination with poor adjustment to school, low parental monitoring, easy access to cigarettes, and other risk attributes, early initiators are significantly more likely to continue smoking. The results suggest that delaying initiation of smoking without also modifying child attributes and socialization factors that predict early initiation and persistent smoking is unlikely to reduce the proportion of children who become habitual smokers.

Adolescent↗
PubMed1998

Prevention of visual loss. Screening in general practice.

BACKGROUND: Diseases such as primary open angle glaucoma, diabetes, strabismus and retinoblastoma have been found to have improved outcome by early investigations. Australian GPs are currently well placed to enhance their role in preventable blindness. OBJECTIVE: To identify key clinical target areas for the prevention of visual loss and discuss opportunities to address these in everyday general practice. DISCUSSION: Undertaking visual assessment in both children and adults can have benefits in reducing the incidence of preventable blindness in the community. Upskilling and having protocols to work to can enhance the GP's ability to offer this preventive service.

Adult↗
PubMed1998

Early intervention in psychosis. The critical period hypothesis.

BACKGROUND: We consider the evidence for the proposition that the early phase of psychosis (including the period of untreated psychosis) is a critical period in which (a) long-term outcome is predictable, and (b) biological, psychological and psychosocial influences are developing and show maximum plasticity. METHOD: First-episode prospective studies, predictors of outcome and the genesis of patients' key appraisals of their psychosis are reviewed. RESULTS: The data support the notion of the 'plateau effect', first coined by Tom McGlashan, which suggested that where deterioration occurs, it does so aggressively in the first 2-3 years; and that critical psychosocial influences, including family and psychological reactions to psychosis and psychiatric services, develop during this period. CONCLUSIONS: The early phase of psychosis presents important opportunities for secondary prevention. We outline a prototype of intervention appropriate to the critical period. The data challenge the widely held assumption that first-episode psychosis is a benign illness posing little risk.

Adaptation, Psychological↗
PubMed1998

Life is sweeter.

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Adaptation, Psychological↗
PubMed1998

A life of his own.

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Adaptation, Psychological↗