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Biomedical subjects

S Hayward

Publications and source records attributed to S Hayward.

84 records · Page 5Linked to original sources
PubMedDate not supplied

Toxicological consequences of feeding PCB congeners to infant rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys.

In a study designed to minimize interspecies extrapolation of toxicological data, nine rhesus (Macaca mulatta) and 15 cynomolgus (M. fascicularis) day-old infant monkeys were separated from their dams following parturition and hand-reared using a liquid non-human primate formulation. The infants were randomly divided into a control and a treated group which received a mixture of polychlorinated biphenyl (PCB) congeners analogous to those found in breast milk from Canadian women. The concentration of congeners in the dosing media resulted in each infant receiving a total of 7.5 microg PCB congeners/kg body weight/day. The congeners were added either to the liquid formulation or to corn oil and administered to the back of the monkey's mouth for 20 weeks. Monthly blood and adipose specimens were obtained during the dosing period and then periodically until the monkey was necropsied or taken off test (minimum of 66 weeks on test) for congener analysis. Parameters such as body weight, formula consumption, tooth eruption, somatic measurements, haematology and serum biochemistry were monitored throughout the study. In addition, a qualitative evaluation of the absorption and depletion of the various congeners was undertaken as was an immunological evaluation. For the monitored parameters, very few differences were found to be statistically significant. For the immunological parameters, the only statistically differences found were a reduction over time for immunoglobulins M and G antibodies to sheep red blood cells (cyno, P = 0.025; rhesus, P = 0.002) and a treatment-related reduction in the levels of the HLA-DR cell surface marker (mean percent, P = 0.016; absolute levels, P = 0.027). There were some qualitative differences regarding absorption and depletion rates for the various congeners, but it could not be definitely ascertained whether these differences were due to species differences or dosing mode. However, statistically significant differences were found for treatment (P = 0.0293) as well as for species and vehicle regarding the concentration of PCB in blood (species;--P = 0.0399; treatment--P = 0.0001) and adipose tissue (species--P = 0.0489; treatment--P = 0.0001).

Adipose Tissue↗
PubMedDate not supplied

Lack of effect of 3,3'4,4',5-pentachlorobiphenyl (PCB 126) throughout gestation and lactation on multiple fixed interval-fixed ratio and DRL performance in rats.

There is evidence that polychlorinated biphenyl (PCB) congeners have differential effects on endpoints of neurotoxicity depending on their chemical structure: specifically, that ortho-substituted congeners are neurotoxic while coplanar (dioxin-like) congeners are relatively inactive in producing neurotoxic effects. This study extends research on the effects of developmental exposure to the coplanar congener 3,3',4,4',5-pentachlorobiphenyl (PCB 126) in Long Evans rats. Dams were dosed with 0, 0.25, or 1 microg/kg/day Monday to Friday beginning 5 weeks before and continuing through gestation and lactation. The first 2-week breeding period produced 10, 7, and 13 litters in the three dose groups, respectively, used in behavioral assessment. Breeding females from the control and low-dose group that did not conceive were rebred after 76 days of dosing, producing 6 and 6 litters used in behavioral testing. One female and male from each litter were tested on a multiple fixed interval-fixed ratio schedule of reinforcement beginning at about 200 days of age, followed immediately by performance on a DRL schedule. There were no compelling indications of a treatment-related effect on either schedule. These same rats failed to exhibit PCB-induced impairment on a spatial delayed alternation task performed prior to the current experiments. This regimen of PCB exposure produced reduced weight gain between birth and weaning in Cohort 1, and decreased thyroxine levels and changes in hematology and serum biochemistry parameters in both cohorts. These data provide further evidence for absence of behavioral toxicity as a result of gestational and lactational exposure to a dioxin-like PCB congener.

Animals↗
PubMedDate not supplied

Effects of postnatal exposure of monkeys to a PCB mixture on concurrent random interval-random interval and progressive ratio performance.

Behavioral impairment as a consequence of PCB exposure beginning in utero has been reported in both humans and animals. The present study assessed the behavioral consequences of postnatal exposure to PCBs. Male monkeys (Macaca fascicularis) were dosed from birth to 20 weeks of age with 7.5 microg/kg/day of a PCB mixture representative of the PCBs typically found in human breast milk (eight monkeys) or vehicle (four monkeys). Blood PCB levels at 20 weeks of age were 0.30-0.37 ppb for control and 1.84-2.84 ppb for treated monkeys, and fat levels were 50-198 and 1694-3560 ppb for the two groups, respectively. Beginning at about 5.0 years of age, monkeys performed under concurrent schedules of reinforcement in which separate random intervals were in effect on two buttons independently. After steady-state performance was reached, the relative reinforcement ratio on the buttons was changed a total of four times, and performance both during transition and steady state was examined. There was no evidence for treatment-related differences in performance across the series of changes in schedule contingencies. The negative results failed to support the hypothesis that performance on an intermittent schedule, combined with the requirement for shifting response strategy, would prove particularly sensitive to postnatal PCB exposure. Following the concurrent schedules, monkeys were tested under a progressive ratio (PR) schedule preceded by a training procedure consisting of a within-session series of increasing fixed ratios. PCB-treated monkeys emitted more responses than controls over the first few sessions of the PR, which may be indicative of retarded acquisition of their steady-state PR performance. These results extend previous studies in these monkeys on the characterization of PCB-induced behavioral deficits.

Adipose Tissue↗
PubMedDate not supplied

Effects of exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB 126) throughout gestation and lactation on behavior (concurrent random interval-random interval and progressive ratio performance) in rats.

There is evidence that polychlorinated biphenyl (PCB) congeners have differential effects on endpoints of neurotoxicity depending on their chemical structure: specifically, that ortho-substituted congeners are neurotoxic while coplanar (dioxin-like) congeners are relatively inactive in producing neurotoxic effects. This study extends research on the effects of developmental exposure to the coplanar congener 3,3',4,4',5-pentachlorobiphenyl (PCB 126) in Long-Evans rats. Dams were dosed with 0, 0.25, or 1 microg/kg/day Monday to Friday beginning 5 weeks before and continuing through gestation and lactation. The first 2-week breeding period produced 10, 7, and 13 litters in the three dose groups, respectively, used in behavioral assessment. Breeding females from the control and low-dose group that did not conceive were rebred after 76 days of dosing, producing six and six litters used in behavioral testing. This regimen of PCB exposure produced reduced weight gain between birth and weaning in cohort 1, and decreased thyroxine levels and changes in hematology and serum biochemistry parameters in both cohorts. One female and male from each litter were tested under a series of three concurrent random interval-random interval (RI-RI) schedules of reinforcement beginning at about 400 days of age, followed immediately by assessment under a progressive ratio (PR) schedule. The concurrent RI-RI allows assessment of performance during steady state and during behavior in transition (learning). The PR schedule provides the opportunity to assess the strength of the reinforcing event independent of response rate. During the first RI-RI schedule, the high-dose group apportioned responses less accurately than controls with respect to the scheduled relative reinforcement density on the two levers. There was also some evidence for differences in performance between treated and control groups on the third RI-RI schedule of reinforcement. There was no evidence for differences in the relative strength of the reinforcing event as assessed by PR performance. These same rats failed to exhibit PCB-induced impairment on a spatial delayed alternation task or under multiple fixed interval-fixed ratio or DRL schedules of reinforcement, performed prior to the current experiments. These data extend previous findings concerning the pattern of behavioral effects as a consequence of gestational and lactational exposure to a dioxin-like PCB congener.

Animals↗
PubMedDate not supplied

Breastfeeding outcomes of women following uncomplicated birth in Hamilton-Wentworth.

OBJECTIVE: To examine infant feeding practices up to 8 weeks postpartum in Hamilton-Wentworth. METHODS: A cross-sectional survey of 227 women using a pre-discharge, self-administered questionnaire, medical record review and follow-up telephone interview. RESULTS: Breastfeeding initiation rate was 85%. By 6-8 weeks postpartum, 30% of women had stopped breastfeeding; 55% had switched to formula within the first 14 days. Infants who did not receive supplementation in hospital were 2.49 times more likely than infants who received supplementation to breastfeed for at least 6 weeks. Although 54% of mothers who initiated breastfeeding reported receiving formula gift packs, no association was found. CONCLUSIONS: The breastfeeding initiation rate appears to have increased in Hamilton-Wentworth since 1995. However, this study reinforces the need to address early cessation and infant supplementation, and raises concern about violation of the WHO/UNICEF International Code of Marketing of Breastmilk Substitutes through mailing of formula coupons.

Adult↗
PubMedDate not supplied

Effects of flutamide and hydroxy-flutamide on the growth of human benign prostatic hyperplasia cells in primary culture: a preliminary report.

Tissues from human benign prostatic hyperplasia [BPH] were collected from twelve patients undergoing routine transurethral resection of the prostate to relieve urine out-flow obstruction. Viable epithelial organoids were obtained after enzymatic digestion of the tissue. Primary cultures of epithelium were successfully maintained on collagen gel for up to 21 days. Immunocytochemical staining revealed that there was no expression of either desmin or vimentin in these cells; however, the anticytokeratin antibodies LP-34 (cytokeratins 4, 5, 6, 10, 13, 16, 17 and 18), LE-61 (cytokeratin 18) and CAM 5.2 (cytokeratins 7 and 8) all showed positive responses, indicating the epithelial nature of the cells. Cell growth was significantly increased in the presence of 3 x 10(-10) M testosterone propionate [TP] in the culture medium. The presence of the non-steroidal anti-androgens, Flutamide and Hydroxy-Flutamide [Flu-OH], in the concentration range 1.0-0.001 micrograms per ml of medium inhibited the growth in the presence of androgens in a dose-dependent manner. The anti-androgens failed to affect cell growth in the absence of TP. In view of these preliminary findings, it is postulated that the antiandrogens might be acting either by displacing the androgen from its receptor or alternately by inhibiting the activity of prostatic 5 alpha-reductase.

Aged↗
PubMedDate not supplied

A systematic overview of the effectiveness of home visiting as a delivery strategy for public health nursing interventions.

The purpose of this systematic overview was to assess the evidence for the effectiveness of public health nursing interventions when carried out by the strategy of home visiting. A search of published and unpublished literature resulted in retrieval of 108 articles; 77 articles were judged to be relevant. Validity criteria included method of allocation to the study groups, level of agreement to participate in the study, control for confounders, method of data collection (pretesting of data collection tools, blinding of data collectors to group allocation of study participants), quantitative measure of effect and percentage of participants available at follow-up. Using these criteria, 9 articles were judged to be strong, 5 moderate and 63 weak. There were no reported negative effects of home visiting in the 9 strong articles. Positive outcomes included improvement in children's mental development, mental health and physical growth; reduction in mother's anxiety, depression, and tobacco use; improvement in maternal employment, nutrition and other health habits; government cost saving; and reduced level of care required for the elderly.

Canada↗
PubMedDate not supplied

A systematic overview of adolescent suicide prevention programs.

The purpose of this systematic overview was to summarize evidence about the effectiveness of adolescent suicide prevention curricula programs. A comprehensive search of published and unpublished literature resulted in retrieval of 11 relevant studies. The findings, of this overview indicate that there is currently insufficient evidence to support curriculum-based suicide prevention programs. The evidence suggests that there may be both beneficial and harmful effects of the programs on students. In most studies, knowledge related to suicide improved as a result of the programs. However, studies found both beneficial and harmful effects on attitudes related to suicide. One study found in increase in hopelessness and maladaptive coping for males following the intervention. The literature suggests that more broadly based comprehensive school health programs should be evaluated for their effectiveness in addressing the determinants of adolescent risk behaviour.

Adaptation, Psychological↗
PubMedDate not supplied

Evaluation research in public health: barriers to the production and dissemination of outcomes data.

Health outcomes are becoming the currency of health care exchange, and a call for evidence dominates decision making at all levels. This discussion paper reviews methodological and sociopolitical barriers that impede the production and dissemination of outcome research in public health, with particular reference to nursing. Barriers to the production of high-quality research evidence include inaccessible graduate education and inadequate research funding. Also, randomized controlled trials (the ideal design for interventions studies) are uniquely difficult to implement for public health services. Practical and ethical difficulties arise in defining the intervention, implementing random allocation methods, selecting and measuring outcomes, and articulating adequate theoretical frameworks. When health care activity is defined as output, there is a tendency to exclude the ethical standing of preventive, supportive and communitarian functions. The production and interpretation of research results must remain part of a social, political and ethical debate, not a purely scientific one.

Canada↗