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Biomedical subjects

J Hendricks

Publications and source records attributed to J Hendricks.

At least 19 recordsLinked to original sources
PubMed2001

The role of the MAP-kinase superfamily in beta-amyloid toxicity.

The mitogen-activated protein kinase (MAP kinase) pathway participates in a number of reactions of the cell when responding to various external stimuli. These stimuli include growth factor binding to its receptor as well as stressful situations such as hypoxia and oxidative stress. It has been postulated that one of the mechanisms by which beta-amyloid exerts its toxic effects is to produce oxidative stress. This study therefore investigated whether the MAP-kinase pathway was activated in cells following exposure to beta-amyloid. Neuroblastoma (N2alpha) cells were used in all experiments. The cells were exposed to 50, 100, and 500 microM glutamate, and 10, 30, and 50 microM beta-amyloid, for 24 h. The methylthiazolyl tetrazolium salt (MTT) assay was performed to determine the degree of toxicity. The generation of hydrogen peroxide was detected by fluorescence microscopy using the dye dihydrochlorofluorescein diacetate (DCDHF). Extracellular-signal-regulated kinase (ERK) and p38 MAP-kinase phosphorylation, as representatives of the MAP-kinase pathway, was determined. Treating N2alpha cells with beta-amyloid resulted in a greater than 50% reduction in cell viability. These cells also showed a significantly higher presence of hydrogen peroxide. Western Blot analysis revealed that the phosphorylation of p38 MAP kinase was dose-dependently increased in cells exposed to glutamate and beta-amyloid. On the other hand, the phosphorylation of ERK was significantly reduced in these cells. These data therefore suggest that the toxic effects of beta-amyloid involve the generation of hydrogen peroxide, leading to the activation of p38 and the down-regulation of ERK.

Alzheimer Disease↗
PubMed2001

The effects of membership in church-related associations and labor unions on age differences in voluntary association affiliations.

PURPOSE: When compositional differences between age groups are controlled, the bivariate, curvilinear pattern of age differences in voluntary association memberships is replaced by one in which peak membership levels occur in late middle age and remain relatively stable thereafter. We sought to determine if this adjusted pattern persists when widespread memberships in two types of associations are removed: (1) church-related organizations, in which membership increases with age but may be confounded with church membership per se; and (2) labor unions, in which membership is also widespread but may not be "voluntary." DESIGN AND METHODS: Total memberships in 14 types of associations were examined using aggregated data from 12 national surveys conducted between 1974 and 1994. RESULTS: The familiar curvilinear relationship at the bivariate level appears, but in the multivariate analysis, membership levels rise from ages 18-24 through 55-59 and persist close to that level through ages 85 and older. IMPLICATIONS: The results reaffirm that age differences in voluntary association affiliations are due to age-based compositional differences; they also show, however, that the pattern observed with controls is neither driven by membership in church-related "associations" nor altered when membership in labor unions is excluded.

Adolescent↗
PubMed2000

Age differences in voluntary association memberships: fact or artifact.

OBJECTIVES: To determine if the curvilinear relationship between age and voluntary association memberships is due to compositional differences between age groups. METHODS: Data are drawn from 12 nationally representative surveys covering the period 1974-1994 and including items on membership in 16 types of associations. Age is categorized into 14 groups ranging from 18-24 through 85+. Patterns of age differences in number of association memberships are examined before and after controlling for several variables related both to age and to memberships. RESULTS: At the bivariate level, number of memberships increases through ages 40-44 and then declines fairly steadily. When controls for compositional differences are introduced, the curvilinear pattern of age differences is replaced by one showing an increasing number of memberships through ages 55-59, a slight decrease in the 60-64 age group, and then generally stable membership levels through the 85+ age group. DISCUSSION: The lower levels of voluntary association memberships of older persons consistently identified in bivariate analyses appear to be largely due to differences in compositional characteristics between the older and other age groups.

Adolescent↗
PubMed2000

Influence of beta-naphthoflavone on 7,12-dimethylbenz(a)anthracene metabolism, DNA adduction, and tumorigenicity in rainbow trout.

Metabolism, DNA adduction, and tumor induction by 7, 12-dimethylbenz(a)anthracene (DMBA) were examined in cultured trout liver cells and in vivo in trout. Modulating CYP1A1 activity indicated this enzyme plays a significant role in metabolizing DMBA to water-soluble compounds in isolated trout liver cells. The major DMBA metabolites identified in trout liver cells were 10-, 11-, 8,9-, and 5,6-DMBA dihydrodiols, and DMBA, 2- or 3- or 4-phenol; 7-OH-methyl-12-methyl-benz(a)anthracene and 12-OH-methyl-7-methyl-benz(a)anthracene were minor metabolites. A very small amount of DMBA-3,4-dihydrodiol was detected, and polar metabolites, which did not migrate with any DMBA metabolite standards, were observed. Incubating trout hepatocytes with DMBA-3, 4-dihydrodiol produced three prominent, nonpolar adducts indistinguishable from those in mouse embryo cells. However, DMBA-DNA adducts, formed in trout in vivo or in trout liver cells exposed to DMBA, were predominantly more polar than those formed in mouse embryo fibroblasts, and levels of DMBA-DNA adducts formed in trout liver cells were not significantly altered by modulating CYP1A1 activity. No significant repair of DMBA-DNA adducts was detected in cultured trout liver cells over a 48-h period, supporting previous studies indicating that fish are less efficient than mammals in repairing polyaromatic hydrocarbon DNA adducts. Compared to animals receiving DMBA alone, beta-naphthoflavone pretreatment in vivo did not affect hepatic CYP1A1, DMBA-DNA adducts, nor hepatic tumor response; but did significantly reduce tumor response in two other target organs. These results collectively indicate that DMBA bioactivation to DNA-binding metabolites in trout liver cells and mouse embryo cells predominantly involve different metabolic pathways to form the DNA-binding intermediates.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2000

A pre-coital pill? A preliminary in vitro study.

The use of the progestogen-only pill as a 'pre-coital contraceptive' was tested by in vitro studies of sperm-mucus interaction. The results suggest that a single tablet of levonorgestrel 30 microg, or norethisterone 350 microg, was effective in preventing sperm migration in the cervical mucus about 12 hours later. This suggests that the progestogen-only pill may be effective as a 'morning before pill'.

Cervix Mucus↗
PubMed1999

Chlorophyllin chemoprevention in trout initiated by aflatoxin B(1) bath treatment: An evaluation of reduced bioavailability vs. target organ protective mechanisms.

Chlorophyllin (CHL) is known to inhibit DNA adduction and hepatocarcinogenesis in trout when administered at doses up to 4000 ppm in the diet with aflatoxin B(1) (AFB(1)). The principal protective mechanism is believed to involve CHL:AFB(1) complex formation, which may reduce systemic carcinogen absorption. However, mechanisms operative within the target organ in situ have not been ruled out. The present study used alternative CHL and AFB(1) exposures as well as hepatic metabolism studies to distinguish these mechanisms. Duplicate lots of 150 rainbow trout each were initiated by brief water bath exposure to 0.1 ppm AFB(1), with or without 500 ppm CHL in the water. The addition of 500 ppm CHL to the water bath, under conditions where AFB(1) is calculated to be >99% sequestered as the CHL:AFB(1) complex, reduced hepatic AFB(1)-DNA adduction by 95% and reduced hepatocarcinogenesis from 20.5% to 2%, compared with exposure to AFB(1) alone. Inclusion of 500 ppm CHL in the water bath also significantly reduced total body burden and hepatic levels of AFB(1) as well as AFB(2), a structural analogue of AFB(1) unable to directly form the 8,9-epoxide proximate electrophile but equally capable of complexing with CHL. By contrast, internal target organ CHL loading by pretreatment of trout with 4000 ppm dietary CHL for 7 days prior to (and 2 days following) AFB(1) waterbath exposure had no effect on AFB(1)-DNA adduction or tumorigenicity. Dietary CHL up to 8000 ppm had no effect on hepatic CYP2K1, CYP1A, glutathione transferase, UDP-glucuronosyl transferase, or, with one exception, the relative ratios among hepatic AFB(1) metabolites in vivo. These results support the hypothesis that CHL:AFB(1) complex formation and reduced systemic AFB(1) bioavailability is a principal mechanism for CHL chemoprevention in this model and that in situ target organ inhibitory mechanisms are relatively insignificant.

Aflatoxin B1↗
PubMed1999

Creativity over the life course--a call for a relational perspective.

Research into creativity over the life course has a long history of concentrating on individual characteristics thought to be associated with shifting patterns. In large measure creativity has been explained as a consequence of intelligence, cognitive style, personality, imagery, and other endogenous factors. These human capital factors are not sufficient in themselves to explain differential creativity either by age or among diverse groups. In addition to individual-level considerations there is an array of societal and domain specific factors that must be taken into account. A number of these are discussed under the rubric of social capital. Finally a relational perspective is advocated as an interpretative framework and discussed in terms of dialectical life span approaches to the life course.

Aging↗
PubMed1998

Chemopreventive properties of chlorophylls towards aflatoxin B1: a review of the antimutagenicity and anticarcinogenicity data in rainbow trout.

The anticarcinogenic activity of chlorophyllin (CHL), a water-soluble derivative of chlorophyll, was first reported in rainbow trout. This review describes certain experiments which set the stage for long-term tumor bioassays, in trout and other species, using CHL and various food-borne carcinogens. Initial work with trout and rat liver enzymes in the Salmonella assay showed that CHL was a potent antimutagen towards heterocyclic amines, polycyclic aromatic hydrocarbons, aflatoxins and other classes of mutagen. Antimutagenic activity was further demonstrated using the corresponding direct-acting mutagens in the absence of an exogenous metabolizing system. Mutagen-inhibitor interaction (molecular complex formation) was identified in spectrophotometry studies, suggesting that CHL acts as an 'interceptor molecule'. In vivo, CHL reduced hepatic AFB1-DNA adducts and hepatocarcinogenesis when the inhibitor and carcinogen were co-administered in the diet. Finally, co-injection of inhibitor and AFB1 into trout embryos established that CHL was more effective than chlorophyll a in reducing AFB1-DNA adducts 2 weeks after injection, and liver tumors after 1 year.

Aflatoxin B1↗
PubMed1997

The pricing of nursing care.

Despite the poor performance of the general economy, the health care industry in Australia has experienced constant growth for several decades. Overall, Australia's expenditure on health is relatively high and, with an increasingly aged population, this expenditure is not likely to decrease. With the current concerns over cost-containment in the health sector it is important to assess the value of nursing care in economic terms. This paper explores the issue of valuing of nursing care within the framework of the Australian Health Care System. Questions are posed of nurses as to whether they are prepared to confront the realities of the health care arena and whether they are ready to value nursing practice in terms of economic value. As well as answering these questions, the paper argues that nursing costs are not sufficiently reimbursed under the current Australian health benefits, and that this poor estimation of the worth of health care may stem from the historical and social influences of nursing and the care provided by nurses. The paper concludes that the Australian health care system is clearly no longer static and that the public cannot afford to support the costs associated with a growing health care industry. Moreover, nursing can no longer afford not to be viewed as an entity in it's own right. A greater awareness of nursing's output will result if organisational or institutional changes are encouraged for the benefit of the Australian society, as a whole, as well as for the nursing profession.

Attitude to Health↗
PubMed1997

The relationship of sperm counts to birth rates: a population based study.

PURPOSE: We determined if a statistical relationship exists between changes in sperm counts and birth rates by comparing data from a single geographic location for a 24-year period. MATERIALS AND METHODS: We retrospectively analyzed data from 660 men who banked 1,972 semen samples before vasectomy in Minnesota from 1971 to 1994. Using general linear models, annual variations in sperm count were determined after adjusting for age, duration of abstinence and seasonal (monthly) effects. Adjusted annual mean sperm count was then correlated with regional birth rate data obtained from The National Center for Health Statistics. RESULTS: Multiple regression analysis revealed a significant linear increase in mean annual sperm count at an estimated rate of 1.03 x 10(6) sperm per ml. per year (b = 0.14, t = 5.641, p < 0.0001). There was no effect of age (t = -0.814, p = 0.4156) but there were significant effects of abstinence (b = 0.14, t = 8.808, p < 0.0001) and month of sperm banking (b = 0.025, t = 5.00, p < 0.0001) on sperm counts. Using analysis of covariance there was a significant, nonlinear (year-to-year) fluctuation in mean sperm counts (F = 8.63, p < 0.001). For the study period mean birth rates in Minnesota (live births per 1,000 population) fluctuated yearly from 13.8 in 1973 to 16.7 in 1981. There was a strong correlation between adjusted mean yearly sperm count and annual birth rates (r = 0.63, p = 0.001). CONCLUSIONS: We found a statistically significant correlation between yearly variations in mean sperm counts and birth rates. Our data suggest that variations in male reproductive function may affect population based birth rates and, therefore, may be more important than previously understood.

Adult↗
PubMed1997

Cloning, sequencing, and embryonic expression of an N-ras proto-oncogene isolated from an enriched zebrafish (Danio rerio) cDNA library.

An enriched zebrafish (Danio rerio) complementary DNA library was constructed for screening of ras-related genes, and a positive clone was isolated from one plate of 3 x 10(4) plaques. This clone, Zras-B1, carried an insert of 2592 base pairs (bp) with an open reading frame encoding a ras p21 protein of 188 amino acids. The deduced amino-terminal 86 amino acid residues and the carboxy-terminal CAAX binding motif are identical to mammalian ras. The full-length Zras-B1-encoded protein is most closely related to human N-ras (91% identity), with lesser homology to Ha-ras (84%) and Ki-ras (85%). Preliminary screening data also indicate other ras genes in zebrafish, at least one of which is also transcribed in adults. A Zras-B1-related 3.1-kb transcript was found to be abundant in embryos from zygote through gastrulation, and may be maternally derived.

Amino Acid Sequence↗
PubMed1997

Pseudodyssynergia (contraction of the external sphincter during voiding) misdiagnosed as chronic nonbacterial prostatitis and the role of biofeedback as a therapeutic option.

PURPOSE: Chronic lower urinary tract symptoms in young men are often attributed to misdiagnosed chronic nonbacterial prostatitis. We analyzed contraction of the external urinary sphincter during voiding (pseudodyssynergia) as an etiology of voiding dysfunction in men with misdiagnosed chronic prostatitis. MATERIALS AND METHODS: The video urodynamic studies of 43 men 23 to 50 years old with chronic voiding dysfunction secondary to pseudodyssynergia performed between January 1990 and June 1996 were retrospectively analyzed. Pseudodyssynergia was diagnosed based on several criteria, including electrical activity of the external sphincter during voiding in the absence of abdominal straining, and brief and intermittent closing of the membranous urethra during voiding detected by electromyography and fluoroscopy. Patients with bacterial infection or excessive leukocytes in expressed prostatic secretions were excluded from the study. RESULTS: Of the patients 39 (91%) were firstborn men. Duration of symptoms ranged from 17 to 146 months (mean 43.6). Average number of previous antibiotic days ranged from 53 to 186 (mean 67.6). In addition, empirical trials of alpha-blockers were unsuccessful. Mean American Urological Association symptom score plus or minus standard deviation was 17.5 +/- 3.7, mean maximum flow rate was 13.3 +/- 4.2 ml. per second, mean detrusor pressure at maximum flow was 46.3 +/- 13.7 cm. water and mean detrusor contraction duration was 132.8 +/- 27.7 seconds. Behavior modification and biofeedback were successful in decreasing symptoms in 35 patients (83%) at 6 months. CONCLUSIONS: These results indicate that some men who are categorized as having and empirically treated for chronic nonbacterial prostatitis are misdiagnosed and, in fact, have functional bladder outlet obstruction. Urodynamics are helpful in diagnosing and predicting success with behavior modification and biofeedback in these patients.

Adult↗
PubMed1996

Etiology of voiding dysfunction in men less than 50 years of age.

OBJECTIVES: Chronic lower urinary tract symptoms in young men are often attributed to misdiagnosed chronic nonbacterial prostatitis. The purpose of this study was to analyze etiology of chronic voiding dysfunction in men less than 50 years of age. METHODS: The videourodynamic studies of 137 men 50 years of age or less with chronic voiding dysfunction, performed between January 1990 and October 1995, were retrospectively analyzed. RESULTS: The distribution of urodynamic abnormalities included 74 (54%) patients with primary vesical neck obstruction, 33 (24%) with obstruction localized to membranous urethra (pseudodyssnergia), 23 (17%) with impaired bladder contractility, and the remaining 7 (5%) with an acontractile bladder. Detrusor instability was present in 67 men (49%). CONCLUSIONS: Voiding dysfunction among young men is common and is often misdiagnosed. Videourodynamic evaluation is very useful in establishing the correct diagnosis and ultimately in delivery of appropriate therapy.

Adult↗
PubMed1996

Education in emergency nursing: a new beginning. Part I.

The movement of nurse education to the tertiary sector is all but complete in Australia. Trends are changing as new partnerships are being forged and the focus of education is now responsive to economic and political factors. These factors have resulted in the regionalisation of health care facilities and the de-institutionalisation of health services in Queensland, Australia. Moreover, de-institutionalisation of services coupled with economic rationalism has pre-empted the offering of post-graduate clinical courses by university nursing facilities. This paper addresses the process of developing the content of new courses under the umbrella of the Graduate Diploma/Masters in Emergency Care Nursing offered at Griffith University Gold Coast, Australia. This initiative is the first in Queensland and has revisioned the education of emergency care nursing. This course includes a tapestry of knowledge enhancing, clinical and factual subjects presented by experienced clinicians teaching with academics, recognising the collaborative nature of nursing practice with academics and clinicians working jointly in course development, teaching and clinical placement. Strategies developed collaboratively addressed course content including logistics, time management, the critical selective selection of appropriate content, assessment criteria, registerability within Queensland and other states and clinical competence. Moreover, this process of developing the course utilised the Australian National Registering Authorities' Competencies and Benner's use of the Dreyfus model to guide the knowledge level of the clinician at course completion. In particular this paper will not only address the blending of theory and practice to consolidate the relationship inherent between the clinician and education, but will establish the fact that no gap exists.

Clinical Competence↗
PubMed1996

The lifeline of triage.

Most acute hospitals operate a triage system to evaluate and prioritize the care and needs of clients presenting in the Emergency department. The emergency nurse, therefore, employs a variety of cognitive processes to clinically categorize clients in relation to the most acute need. This ability to clinically assess is a combination of knowledge and intuition grounded in experience and formal education. Therefore, the optimal functioning of the Emergency department is dependent upon not only the protocols and policies of hospitals, but the skills, experience and the confidence of individual triage nurses. This paper will reconsider the role of the triage nurse by addressing a literature deficit related to triage and the triage nurse, as the front line mediator, who is in the prime position of being able to rise the professional profile of the emergency nurse by making visible the care provided by nurses in this department and, most significantly, in the triage waiting room. This care extends beyond pointing to the waiting room clock and a sign which informs clients of the purposes of the emergency care department. This paper will also discuss a range of strategies used by the authors to enhance effective triaging to ensure a quality standard in client care.

Clinical Competence↗