PubMed Health⌕ Search

Biomedical subjects

S Gifford

Publications and source records attributed to S Gifford.

At least 19 recordsLinked to original sources

The Akoya pearl oyster shell as an archival monitor of lead exposure.

The Akoya pearl oyster (Pinctada imbricata) was experimentally exposed to (a) constant levels of lead (Pb) at 180 microg L(-1) for nine weeks, or (b) two short term (pulse) exposures of Pb at 180 microg L(-1) (three weeks each) with an intervening depuration period (three weeks), to assess its utility as an (i) accumulative monitor of Pb contamination and an (ii) archival monitor for discriminating constant versus pulsed Pb exposure events. P. imbricata showed similar reductions in growth (based on shell morphology and wet weight) and Pb accumulation patterns for whole tissue and shell in response to both Pb exposure regimes. Thus the whole oyster was deemed an inappropriate accumulative monitor for assessing short-term temporal variation of Pb exposure and effect. However, using secondary ion mass spectrometry, Pb was shown to accumulate in the successively deposited nacreous layers of the shell of P. imbricata, documenting the exposure history of constant versus pulsed Pb events. Patterns of Pb deposition not only reflected the frequency of Pb exposure events but also their relative durations. Thus, the shell of P. imbricata may be employed as a suitable biological archive of Pb exposure.

Animals↗

Quantification of in situ nutrient and heavy metal remediation by a small pearl oyster (Pinctada imbricata) farm at Port Stephens, Australia.

The use of pearl oysters has recently been proposed as an environmental remediation tool in coastal ecosystems. This study quantified the nitrogen, phosphorus and heavy metal content of the tissue and shell of pearl oysters harvested from a small pearl oyster farm at Port Stephens, Australia. Each tonne of pearl oyster material harvested resulted in approximately 703 g metals, 7452 g nitrogen, and 545 g phosphorus being removed from the waters of Port Stephens. Increasing current farm production of 9.8 tyr(-1) to 499 tyr(-1) would balance current nitrogen loads entering Port Stephens from a small Sewage Treatment Plant (STP) located on its southern shores. Furthermore, manipulation of harvest dates to coincide with oyster condition would likely remove substantially greater quantities of nutrients. This study demonstrates that pearl aquaculture may be used to assist in the removal of pollutants from coastal waters while producing a commercially profitable commodity.

Animals↗

Macroalgal biomonitors of trace metal contamination in acid sulfate soil aquaculture ponds.

Earthen shrimp aquaculture ponds are often impacted by acid sulfate soils (ASS), typically resulting in increased disease and mortality of cultured organisms. Production losses have been attributed to either low pH or to elevated concentrations of toxic metals, both direct products of pyrite oxidation in ASS. The standard farm management practice to minimise effects of pyrite oxidation is to maintain pH of pond waters above 5, based on the assumption that dissolved metal bioavailability is negligible at this pH. This study aimed to test the validity of this assumption, and therefore elucidate a possible role of toxic heavy metals in observed decreases in farm productivity. Metal bioaccumulation in four genera of macroalgae, Ulva sp., Enteromorpha sp., Cladophora sp. and Chaetomorpha sp., sampled from ASS-affected shrimp aquaculture ponds were measured using inductively coupled plasma-optical emission spectroscopy (ICP-OES) to assess the relative bioavailability of dissolved metals within the system. Results showed that all four genera of macroalgae accumulated appreciable quantities of Fe, Al, Zn, Cd, Cu, As and Pb. Iron and Al, the most common metals mobilised from ASS, were both accumulated in all algal genera to concentrations three orders of magnitude greater than all other metals analysed. These findings indicate that dissolved heavy metals are indeed bioavailable within the aquaculture pond system. A literature search of heavy metal bioaccumulation by these algal genera revealed concentrations recorded in this study are comparable to highly contaminated environments, such as those exposed to urban, industrial and mining pollution. The results of this study indicate that dissolved metal bioavailability in many earthen shrimp aquaculture ponds may be higher than previously thought.

Animals↗

Pearl aquaculture-profitable environmental remediation?

Bivalve molluscs are filter feeders, with pearl oysters able to filter water at rates up to 25 lh(-1)g(-1) of dry wt. tissue. Since this process leads to rapid bioaccumulation of recalcitrant pollutants such as heavy metals, organochlorine pesticides and hydrocarbons from impacted sites, it has prompted the widespread use of molluscs as biomonitors to quantify levels of marine pollution. This paper proposes pearl oyster deployment as a novel bioremediation technology for impacted sites to remove toxic contaminants, reduce nutrient loads and lower concentrations of microbial pathogens. Estimates extrapolated from the literature suggest that a modest pearl oyster farm of 100 t oyster material per year could remove 300 kg heavy metals plus 24 kg of organic contaminants via deposition into the tissue and shell. Furthermore, it was estimated that up to 19 kg of nitrogen may be removed from the coastal ecosystem per tonne of pearl oyster harvested. Pearl oysters are also likely to filter substantial amounts of sewage associated microbial pathogens from the water column. Method of cultivation and site selection are the key to minimising negative environmental impacts of bivalve cultivation. Deployment of oysters at sites with high nutrient and contaminant loadings would be advantageous, as these compounds would be removed from the ecosystem whilst generating a value-added product. Future potential may exist for harvesting bio-concentrated elements for commercial production.

Animals↗

Study of the murine allantois by allantoic explants.

The murine allantois will become the umbilical artery and vein of the chorioallantoic placenta. In previous studies, growth and differentiation of the allantois had been elucidated in whole embryos. In this study, the extent to which explanted allantoises grow and differentiate outside of the conceptus was investigated. The explant model was then used to elucidate cell and growth factor requirements in allantoic development. Early headfold-stage murine allantoises were explanted directly onto tissue culture plastic or suspended in test tubes. Explanted allantoises vascularized with distal-to-proximal polarity, they exhibited many of the same signaling factors used by the vitelline and cardiovascular systems, and they contained at least three cell types whose identity, gene expression profiles, topographical associations, and behavior resembled those of intact allantoises. DiI labeling further revealed that isolated allantoises grew and vascularized in the absence of significant cell mingling, thereby supporting a model of mesodermal differentiation in the allantois that is position- and possibly age-dependent. Manipulation of allantoic explants by varying growth media demonstrated that the allantoic endothelial cell lineage, like that of other embryonic vasculatures, is responsive to VEGF(164). Although VEGF(164) was required for both survival and proliferation of allantoic angioblasts, it was not sufficient to induce appropriate epithelialization of these cells. Rather, other VEGF isoforms and/or the outer sheath of mesothelium, whose maintenance did not appear to be dependent upon endothelium, may also play important roles. On the basis of these findings, we propose murine allantoic explants as a new tool for shedding light not only on allantoic development, but for elucidating universal mechanisms of blood vessel formation, including vascular supporting cells, either in the intact organism or in existing in vitro systems.

Allantois↗

Safe sex or safe love: competing discourses?

The way in which sex may be constructed as safe through its relationship with 'love' is the concern of this study. Interviews with 112 heterosexual women and men from discos and bars in Melbourne, Australia, catering to single adults revealed the pervasive construction of sex within the discourses of 'love' and 'romance'. The relationship of these discourses to unsafe practices is discussed and the article presents an analysis of the normative function of the sex-as-love/sex-as-desire opposition in terms of safe sex and HIV/AIDS prevention. We conclude that health messages which emphasize that 'sex is unsafe' may be counterproductive. We illustrate how women and some men construct casual sex as a strategy for obtaining the possibility of 'love'. For these women and men, 'safe sex' as 'unprotected sex' is viewed as a strategy for maximizing the possibility that the casual encounter will result in a longer term relationship. On the other hand, 'unsafe sex' as 'unprotected sex' is viewed as a strategy that is more likely to interrupt the construction of romance in the causal encounter thus risking the possibility of love as the desired outcome.

Adult↗

Vascularization in the murine allantois occurs by vasculogenesis without accompanying erythropoiesis.

The aim of this study was to determine whether the blood vessels of the murine allantois are formed by vasculogenesis or angiogenesis. Morphological analysis revealed that differentiation of allantoic mesoderm into an outer layer of mesothelium and an inner vascular network begins in the distal region of the allantois, which is most remote from other tissues, as early as the late neural plate stage (approximately 7.75 days postcoitum). Nascent blood vessels were not found in the base of the allantois until 4-somite pairs had formed in the fetus (approximately 8.25 days postcoitum), and vascular continuity with the yolk sac and fetus was not present until the 6-somite-pair stage (approximately 8.5 days postcoitum). Immunohistochemical analysis demonstrated that flk-1, a molecular marker of early endothelial cells, is expressed in significantly more distal than basal core cells in the early allantois and never in mesothelium. Furthermore, synchronous grafting of donor yolk sac containing blood islands into blood islands of headfold-stage host conceptuses provided no evidence that the yolk sac contributes endothelial cells to the allantois. Finally, when removed from conceptuses and cultured in isolation, neural plate and headfold-stage allantoises formed a conspicuous vascular network that was positive for Flk-1. Hence, the vasculature of the allantois is formed intrinsically by vasculogenesis rather than extrinsically via angiogenesis from the adjacent yolk sac or fetus. Whether allantoic vasculogenesis is associated with erythropoiesis was also investigated. Benzidine-staining in situ revealed that primitive erythroid cells were not identified in the allantois until 6-somite pairs when continuity between its vasculature and that of the yolk sac was first evident. Nevertheless, a small number of allantoises removed from conceptuses at a considerably earlier stage were found to contain erythroid precursor cells following culture in isolation. To determine whether such erythroid cells could be of allantoic origin, host allantoises were made chimeric with lacZ-expressing donor allantoises that were additionally labeled with [3H]methyl thymidine. Following culture and autoradiography, many lacZ-expressing benzidine-stained cells were observed in donor allantoises, but none contained silver grains above background. Moreover, no cells of donor allantoic origin were found in the fetus or yolk sac. Hence, vasculogenesis seems to be independent of erythropoiesis in the allantois and to involve a distal-to-proximal gradient in differentiation of allantoic mesoderm into the endothelial cell lineage. Furthermore, this gradient is established earlier than reported previously, being present at the neural plate stage.

Allantois↗

Between two wars. Psychoanalysis in Europe, 1918-1938.

In outline form, the major centers of European psychoanalysis have been described: from the first post-war meeting of the International Psychoanalytic Association in Budapest, 1918, when institutes for analytic training were proposed, to the Anschluss in March 1938, when Vienna was occupied by the Nazis and psychoanalysis on the Continent was extinguished for almost a decade. The emphasis has been on the organization and structure of institutes, chiefly Berlin, Vienna, and London, in that order. As an institutional history, both biographic details and theoretical issues have been kept to a minimum. The exceptions have been the controversies about lay analysis, Melanie Klein's developmental theories, and Ferenczi's innovations in technique. In these issues, some detail is necessary to understand how one institute differed from another within the analytic movement, although they were unified by the International Psychoanalytic Association (IPA). The history of the British analytic community, which survived World War II intact, is highly condensed, and Prague, Budapest, and Paris are briefly mentioned. A history of psychoanalysis in Russia has yet to be written, from its early flowering before and during the Bolshevik revolution (1918-1920) to its swift repression under Stalin in the later 1920s. Among the conclusions to be drawn from these data is the extent to which political events influenced the development of analysis, then in its most expansive phase. Even theory was affected by history, as in the evolution of Freud's repetition-compulsion from observations on the traumatic neuroses of war. Socioeconomic conditions influenced the propagation of analytic ideas, favorably in post-war Berlin, adversely in Vienna. Each country evolved the kind of analysis that suited it best, with a variety of institutions within the same international movement. The causes of these variations in psychoanalytic institutes are a matter for speculation. Some analytic historians have linked Freud's advocacy of lay analysis to his estrangement from the medical establishment of Vienna, or to his dread that analysis might become the "house-maid" of medicine and psychiatry, as in America. Others find the roots of Freud's attitudes toward medicine in his conflicts about becoming a doctor, his yearning for philosophic speculation, which he "sternly held in check." In contrast, psychoanalysis in the United States was always committed to medical education as a prerequisite for becoming an analyst, and, in 1926, there was a sharp break from Freud's defense of lay analysis. Hale, among others, has suggested that the American "medical fixation" was a reaction to the chaotic state of our nineteenth century medical education, with diploma mills and self-taught healers scattered over a vast continent.(ABSTRACT TRUNCATED AT 400 WORDS)

Europe↗

Health of nations: lessons from Victoria, Australia.

In its white paper The Health of the Nation the government has announced its intention to give more priority to preventive health care. Two examples from Victoria, Australia, show how coordinated legislative and voluntary sector action can have a substantial impact on public behaviour. The introduction and enforcement of strict drink-driving laws and speed limits backed up by forceful television advertisements produced a large reduction in deaths from road traffic accidents, the death rate in relation to the number of vehicles in 1991 being among the lowest in the world. Smoking has also declined in parallel with a phased ban on advertising and use of taxes from tobacco sales to replace tobacco sponsorship of sports and arts and fund health promotion.

Accidents, Traffic↗

A community approach to diabetes education in Australia--The Region 8 (Victoria) Diabetes Education and Control Program.

The Australian Region 8 (Victoria) Diabetes Education and Control Program (DECP) is a community-based program which seeks to integrate ambulatory diabetes education programs into primary health care centres. The overall goal of the DECP is to reduce the human and economic costs of diabetes in a health region which covers 25% of the population of Victoria. Several implementation models are being tested and a rigorous evaluation has been built into the program. Diabetes education activities are targeted at 3 levels--the community, persons with diabetes, and health professionals. The DECP may provide of useful model for establishing diabetes and other chronic disease education and control programs, within community settings, in other parts of Australia and other countries.

Australia↗