Biomedical subjects

Pamela A Martin

Publications and source records attributed to Pamela A Martin.

8 recordsLinked to original sources

PubMed2006

Changes in thyroid and vitamin A status in mink fed polyhalogenated-aromatic-hydrocarbon-contaminated carp from the Saginaw River, Michigan, USA.

A study was conducted to determine whether changes in thyroid and vitamin A dynamics were induced in ranch mink exposed to environmentally relevant concentrations of polyhalogenated aromatic hydrocarbons. Adult female mink were fed diets that contained 0% (control), 10%, 20%, or 30% wild carp (Cyprinus carpio) collected from the Saginaw River, Michigan, USA. Total polychlorinated biphenyls concentrations were 0.03, 0.83, 1.05, and 1.69 mg/kg feed, respectively; the 2,3,7,8-tetrachlorodibenzo-p-diozin toxic equivalents were 3.4, 27.9, 47.6, and 73.2 ng/kg, respectively. Diets were fed 3 weeks prior to breeding and throughout gestation and lactation. When the kits were weaned at 6 weeks of age, they were continued on their respective diets until 27 weeks of age. Plasma thyroid hormone concentrations, thyroid gland activity and structure, and vitamin A dynamics were assessed in young mink at 6 and 27 weeks of age. Plasma total T4 and free T4 in 6-week-old female and male kits fed the 10% carp diet were significantly higher than those of controls, while kits fed the 20% and 30% carp diet had nonsignificant decreases relative to the control mink. Plasma total T3 concentrations in 27-week-old juvenile males fed the 30% carp diet were significantly lower than those in individuals fed the 10% carp diet. No overt thyroid toxicity was apparent as thyroid weight, activity, and structure in kits and juveniles of both sexes were similar among diet groups. Plasma retinol and total ester concentrations in both kits and juveniles were reduced in mink fed the 30% carp diet relative to controls. The ratio of retinol to retinyl palmitate in livers of juveniles fed the 30% carp diet was two times higher than that in control mink. Significant reductions in kidney retinol and fatty acyl retinyl esters were observed in kits and juveniles fed the 30% carp diet relative to control values.

Animals↗

PubMed2006

Temporal and spatial trends in chlorinated hydrocarbon concentrations of mink in Canadian Lakes Erie and St. Clair.

Mink (Mustela vison) carcasses were collected from local commercial trappers from fall 1998 to spring 2003 from tributaries and marshes within 4.8 km from the shores of Lakes Erie and St. Clair, including the Wheatley Harbour and St. Clair River Areas of Concern (AOCs), as well as from inland sites (8 to 40 km from shore). Liver concentrations, on a lipid weight basis, of chlorinated hydrocarbons were measured and compared among sites and to tissue concentrations of mink from two previous collections from similar sites over the past 25 years. Mink from the western Lake Erie sites, which included the Wheatley Harbour AOC, had significantly higher concentrations of sum PCBs and PCB Aroclors than those from the St. Clair corridor or inland sites, with concentrations from the rest of Lake Erie being intermediate. Dieldrin concentrations were also significantly higher in western Lake Erie than many other sites, and those of oxychlordane and mirex also tended to be higher (0.05 < p < 0.1). There were no differences in contaminant concentrations between the St. Clair River AOC and the downstream non-AOC Lake St. Clair site, with the exception of slightly higher levels of octachlorostyrene (OCS). Concentrations of PCBs and other chlorinated hydrocarbons in mink showed a general decrease over the past two decades. In contrast, PCBs and some organochlorine pesticides tended to increase, significantly so with oxychlordane, in western Lake Erie mink over the same time period. DDE declined at all sites. Currently, mink liver PCB concentrations are within the range associated with reproductive impairment, as determined from captive mink studies, in 11.7% of all animals collected from the Lakes Erie and St. Clair basin overall, but in almost 40% of individuals from western Lake Erie.

Animals↗

PubMed2006

Effects of environmentally relevant concentrations of atrazine on gonadal development of snapping turtles (Chelydra serpentina).

The herbicide atrazine has been suspected of affecting sexual development by inducing aromatase, resulting in the increased conversion of androgens to estrogens. We used snapping turtles (Chelydra serpentina), a species in which sex is dependent on the production of estrogen through aromatase activity in a temperature-dependent manner, to investigate if environmentally relevant exposures to atrazine affected gonadal development. Eggs were incubated in soil to which atrazine was applied at a typical field application rate (3.1 L/ha), 10-fold this rate (31 L/ha), and a control rate (no atrazine) for the duration of embryonic development. The incubation temperature (25 degrees C) was selected to produce only males. Although some males with testicular oocytes and females were produced in the atrazine-treated groups (3.3-3.7%) but not in the control group, no statistical differences were found among treatments. Furthermore, snapping turtle eggs collected from natural nests in a corn field were incubated at the pivotal temperature (27.5 degrees C) at which both males and females normally would be produced, and some males had oocytes in the testes (15.4%). The presence of low numbers of males with oocytes may be a natural phenomenon, and we have limited evidence to suggest that the presence of normal males with oocytes may represent a feminizing effect of atrazine. Histological examination of the thyroid gland revealed no effect on thyroid morphology.

Animals↗

PubMed2005

Thyroid function in nestling tree swallows and eastern bluebirds exposed to non-persistent pesticides and p, p'-DDE in apple orchards of southern Ontario, Canada.

This study examined the associated effects of pesticides and persistent residues of p,p'-DDE on thyroid function in 16-day-old tree swallows (Tachycineta bicolor) and 12-day-old eastern bluebirds (Sialia sialis). Apple orchards sprayed with pesticides in current use and reference sites were chosen for study in southern Ontario, Canada, during 2000-2001. We assessed thyroid hormone concentrations (plasma and muscle thyroxine [T4], and triiodothyronine [T3]) and the response to a challenge with thyroid stimulating hormone (TSH) as well as parameters of thyroid histology. Individual nests were exposed to as many as seven individual pesticide applications and up to five pesticide mixtures. Concentrations of p,p'-DDE in eggs from both species were highest in orchard sites, and ranged from 0.05 to 5.44 mg/kg wet weight for tree swallows, and from 0.17 to 95.4 mg/kg for eastern bluebirds. In 2000, tree swallows from sprayed orchards had elevated plasma T4 concentrations, and thyroid glands with collapsed follicles, hypertrophic epithelia, and higher follicular epithelial cells relative to chicks from reference sites. Plasma T4 concentration was positively correlated with the total number of pesticide mixtures applied during egg incubation through chick rearing. In 2001, basal plasma T3 concentration in tree swallow chicks did not differ between orchard and reference sites, though there were differences among orchards; T3 was positively correlated with total number of individual sprays applied during egg incubation through chick rearing. Tree swallows challenged with TSH showed no significant difference in thyroid hormone concentration or follicular epithelial cell height between exposure groups; however, a significantly greater proportion of chicks from reference sites were found to have thyroids with focal or diffuse hypertrophic epithelia relative to orchard chicks. In 2001, bluebirds from sprayed orchards had significantly higher T3 concentrations in response to TSH challenge; this response was positively correlated with the total number of pesticides applied during egg incubation through chick rearing.

Animals↗

PubMed2004

Stress and immune responses of nestling tree swallows (Tachycineta bicolor) and eastern bluebirds (Sialia sialis) exposed to nonpersistent pesticides and p,p'-dichlorodiphenyldichloroethylene in apple orchards of southern Ontario, Canada.

To determine the relative effects of pesticides in current use and persistent residues of p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), we examined endocrine and immune responses in tree swallow (Tachycineta bicolor) and eastern bluebird (Sialia sialis) chicks from pesticide-sprayed apple orchards and reference sites in southern Ontario, Canada, during 2000 to 2001. Nests were exposed to as many as seven individual pesticide applications and up to five mixtures of pesticides during the egg-incubation and chick-rearing stage. Eggs collected from sprayed orchards contained higher p,p'-DDE concentrations than eggs from reference sites. In 16-d-old tree swallows, no significant differences were found in body mass, basal corticosterone concentration, or the corticosterone stress response following a 10-min restraint of chicks sampled from sprayed orchards and reference sites. Challenge with adrenocorticotrophic hormone (ACTH), however, produced a higher level of corticosterone secretion in tree swallow chicks from sprayed orchards relative to chicks from reference sites. Multiple regression analysis revealed no correlation between corticosterone concentrations and exposure to pesticide sprays or p,p'-DDE in tree swallow chicks. In contrast, bluebird chicks from sprayed orchards were less responsive to challenge with ACTH and a significant negative association was found between the response to ACTH challenge and p,p'-DDE concentration in eggs. The phytohemagglutinin (PHA)-induced cutaneous basophil hypersensitivity response was similar between exposure groups in both tree swallow and bluebird nestlings. Examination of immune organs revealed that tree swallow chicks from sprayed orchards had significantly greater thymic lymphocyte density and cortical/ medullary ratios and significant splenic B-cell hyperplasia relative to reference chicks. Our results indicate that modulation in the hypothalamus-pituitary-adrenal axis in songbird chicks tested are most associated with high p,p'-DDE egg concentrations. An alteration in the endocrine or immune system may compromise songbird survival immediately after fledging or during migration.

Adrenocorticotropic Hormone↗

PubMed2002

Human fibronectin and MMP-2 collagen binding domains compete for collagen binding sites and modify cellular activation of MMP-2.

The region of fibronectin (FN) surrounding the two type II modules of FN binds type I collagen. However, little is known about interactions of this collagen binding domain with other collagen types or extracellular matrix molecules. Among several expressed recombinant (r) human FN fragments from the collagen binding region of FN, only rI6-I7, which included the two type II modules and both flanking type I modules, bound any of several tested collagens. The rI6-I7 interacted specifically with both native and denatured forms of types I and III collagen as well as denatured types II, IV, V and X collagen with apparent K(d) values of 0.2-3.7 x 10(-7) M. Reduction with DTT disrupted the binding to gelatin verifying the functional requirement for intact disulfide bonds. The FN fragments showed a weak, but not physiologically important, binding to heparin, and did not bind elastin or laminin. The broad, but selective range of ligand interactions by rI6-I7 mirrored our prior observations for the collagen binding domain (rCBD) from matrix metalloproteinase-2 (MMP-2) [J. Biol. Chem. 270 (1995) 11555]. Subsequent experiments showed competition between rI6-I7 and rCBD for binding to gelatin indicating that their binding sites on this extracellular matrix molecule are identical or closely positioned. Two collagen binding domain fragments supported cell attachment by a beta1-integrin-dependent mechanism although neither protein contains an Arg-Gly-Asp recognition sequence. Furthermore, activation of MMP-2 and MMP-9 was greatly reduced for HT1080 fibrosarcoma cells cultured on either of the fibronectin fragments compared to full-length FN. These observations imply that the biological activities of FN in the extracellular matrix may involve interactions with a broad range of collagen types, and that exposure to pathologically-generated FN fragments may substantially alter cell behavior and regulation.

Binding Sites↗

PubMed2002

Vertebroplasty for osteoporotic compression fractures: current practice and evolving techniques.

Perutaneous vertebroplasty was developed in France by Deramond et al., who provided initial reports of the procedure in 1987. This minimally invasive procedure uses a large-bore bone-cutting needle to percutaneously access a vertebral body, inject bone cement, and thereby stabilize and reinforce the remaining bone structure. The procedure was used initially to treat aggressive hemangiomas, but it then was extended to the treatment of osteolytic metastases and myeloma and currently osteoporotic compression fractures refractory to medical therapy. In this article, we review the current technique and its indications along with emerging devices and areas of current research.

Aged↗

PubMedDate not supplied

Chlorinated hydrocarbon contamination in osprey eggs and nestlings from the Canadian Great Lakes basin, 1991-1995.

Populations of osprey (Pandion haliaetus) in the Great Lakes basin declined dramatically during the 1950s-1970s due largely to adverse effects of persistent chlorinated hydrocarbons, ingested in their fish prey, on eggshell thickness and adult survival. Nevertheless, these contaminants were not measured in osprey tissues during the decades of decline on the Canadian Great Lakes. Between 1991 and 1995, we monitored recovering osprey populations on the Great Lakes, including Georgian Bay and the St. Marys River area on Lake Huron and the St. Lawrence Islands National Park, as well as at two inland sites within the basin. Current OC levels, even from the most contaminated lakes, were typically lower than those associated with reproductive effects. DDE levels in fresh eggs averaged 1.2-2.9 microg/g, well below the 4.2 microg/g level associated with significant eggshell thinning and shell breakage. Nevertheless, a proportion of eggs from all study areas did exceed this level. PCB levels in eggs seldom exceeded 5 microg/g except in one lake of high breeding density in the Kawartha Lakes inland study area, where the mean sum PCB level was 7.1 microg/g and the maximum concentration measured was 26.5 microg/g. On average, mean reproductive output (0.78-2.75 young per occupied nest) of breeding populations in Great Lakes basin study areas exceeded the threshold of 0.8 young thought necessary to maintain stable populations. We concluded that, although eggs and especially nestling plasma, are useful in reflecting local contaminant levels, ospreys are relatively insensitive, at least at the population level, to health effects of current levels of chlorinated hydrocarbons on the Canadian Great Lakes.

Animals↗