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Biomedical subjects

G A Bird

Publications and source records attributed to G A Bird.

6 recordsLinked to original sources
PubMed1998

Bioaccumulation of radionuclides in fertilized Canadian Shield lake basins.

Radionuclide tracers of heavy metals (59Fe, 60Co, 65Zn, 75Se, 85Sr, 134Cs and 203Hg) representing potential contamination from nuclear power plants, industry and agriculture were added to separate basins of Lake 226, Experimental Lakes Area, northwestern Ontario. The two basins were part of a eutrophication experiment and differed in their trophic status; the north basin (L226N) was eutrophic whereas the south basin (L226S) was mesotrophic. Our objective was to determine the uptake of the radionuclides by biota and the effect of lake trophic status on their bioaccumulation. The trophic status of the lakes did not appear to have a marked effect on the accumulation of radionuclides by the biota. This may have been because of a mid-summer leakage of nutrients between the basins which enhanced primary production in L226S, because there is a time lag between primary production and the availability of the radionuclides to the fishes or because trophic status does not affect the uptake of at least some of these radionuclides. However, there was a tendency for faster uptake of the radionuclides in L226N by fish than L226S, but the differences were not significant. Concentrations in the biota generally decreased in the order: fathead minnow > pearl dace > tadpoles > slimy sculpin > leeches. Concentrations in biota generally decreased in the order. 65Zn > 203Hg > 75Se > 134Cs > 60Co > 85Sr = 59Fe. Cobalt-60 concentrations in tadpoles were greater than in the other biota. Radionuclide concentrations in the tissues of lake whitefish indicated that uptake was predominantly from food. Radionuclide concentrations were usually higher in the posterior gut, liver and kidney than in other tissues, whereas body burdens were generally high in the muscle for 75Se, 134Cs and 203Hg; kidney and gut for 60Co; and bone for 65Zn and 75Se. Mercury-203 burdens were also high in the bone and gut.

Agriculture↗
PubMed1998

Behavior of 60Co and 134Cs in a Canadian Shield lake over 5 years.

Radionuclides were added to the anoxic hypolimnion of a Canadian Shield lake to simulate the nuclear fuel waste disposal scenario where radionuclides might enter the bottom waters of a lake. The radionuclides remained in the hypolimnion until lake mixing at autumn turnover after which 60Co was rapidly lost and 134Cs was slowly lost from the water. Only 0.4% of the 60Co and 0.6% of the 134Cs remained in the water at year 5. Highest concentrations occurred in periphyton and filter feeders, Holopedium gibberum and clams (Anodonata grandis grandis). From maximum annual concentrations in clam tissues, it was estimated that the availability of 60Co for uptake had a half-time (t1/2) of 835 days in the lake, whereas that for 134Cs was 780 days. Loss rate coefficients, k, for the radionuclides from taxa ranged from 0.0008 to 0.0043 day-1 (t1/2 = 161-866 days) for 60Co and from 0.0009 to 0.005 day-1 (t1/2 = 139-770 days) for 134Cs. Cobalt-60 concentrations in forage fish were low, whereas 134Cs concentrations increased over the first year or two, then slowly declined. On the basis of k values measured for forage fish, the biological half-time of 134Cs in forage fish ranged from 428 to 630 days. Maximum 134Cs concentrations in forage fish were higher following hypolimnetic addition than epilimnetic addition. Relatively high 134Cs concentrations in periphyton at year 5 point to the importance of benthic pathways in the recycling of contaminants to higher trophic levels. The presence of 134Cs in biota 5 years after the addition, long after concentrations were no longer detectable in surface waters, is evidence of the persistence of Cs in aquatic systems. The k values (or t1/2 values) for the loss of 60Co and 134Cs from water and their uptake and loss from biota can be used to establish parameter values for assessment models. The results demonstrate that assessment models should account for the release of radionuclides from sediment and their subsequent recycling in the food chain when modeling over the long term after the end of a radionuclide release to the environment.

Animals↗
PubMed1996

Lung volume reduction surgery for emphysema.

This article summarizes the care of patients undergoing bilateral lung volume reduction surgery as a treatment for end-stage emphysema. Surgical removal of emphysematous tissue allows for a reconfiguration of the chest wall and diaphragm, improving pulmonary mechanics. This results in reduced air trapping and improved gas exchange. It is important for nurses caring for these patients to be knowledgeable in the postoperative care of thoracic surgical patients and to have an understanding of the pathophysiology of emphysema, the medical management, and, in particular, the relationship between dyspnea and anxiety. Strategies to assist with airway clearance, control pain, prevent and alleviate dyspnea, reduce and treat anxiety, and ensure nutrition need to be incorporated into the postoperative plan of nursing care.

Chest Tubes↗
PubMed1994

Immunohistochemical characterization of endometrial lymphoid cell populations in women infected with human immunodeficiency virus.

OBJECTIVE: To determine whether lymphocytic infiltration of the endometrium accompanies human immunodeficiency virus (HIV) infection. METHODS: Endometrial samples from 12 HIV-infected women and from rigorously matched controls were examined. The following markers were used: common leukocyte antigen (CD45), T lymphocytes (CD3), monocytes-macrophages (CD68), and CD4 and CD8 lymphocytes. Cell counts were performed without knowledge of HIV status. Factors considered in relation to these markers were menstrual symptoms, pelvic pain, peripheral blood CD4+ count, and time since seroconversion. RESULTS: Histology showed conventional features of chronic endometritis in only one case. In the remainder, the endometrium of HIV-infected women, compared with controls, showed an increase in CD45 cells (P < .02) and an increase in CD3 staining cells (P < .05). This appeared to be restricted to those with menstrual symptoms, and this group also had lower peripheral blood CD4 counts. There was no difference in cells of the monocyte-macrophage series (CD68). In contrast to control samples, CD4 lymphocytes were infrequent or absent in the endometrium of HIV-infected women, regardless of peripheral blood CD4 count or presence of menstrual symptoms; however, this was not universal, as one sample showed an area of dense CD4 cell infiltration. The ratio of CD4 to CD8 was reduced in HIV-seropositive samples compared with controls (P < .02). CONCLUSION: We hypothesize that chronic endometritis of a nonclassical form may be common in advancing HIV disease, possibly directed against HIV-infected cells or self-determined antigens. This could be associated with morbidity and may represent a reservoir of infection. Endometrial depletion of CD4 cells is a common, but not universal, feature and may be independent of immune compromise.

Adult↗
PubMed1985

Pleomorphic T-cell leukaemia in a Caucasian adult: clinical phenotypic and functional characteristics.

Pleomorphic T-cell leukaemia occurring in an adult Caucasian patient is described. The leukaemia cells expressed both antigenic determinants (T4 and T8) normally detected separately on either helper or suppressor cells. They functioned as helper cells and there was evidence of unbridled antibody production. It is possible that a distinctive subtype of pleomorphic T-cell leukaemia occurs in Caucasian patients.

Epitopes↗