Biomedical subjects
Publications and source records attributed to J Burger.
In identical experimental situations we tested 22 adults with our proposed Landolt C wall-chart and the so-called TNO Landolt-C chart. Contrary to theoretical expectations, it appeared that there was only a slight difference in the measured visual acuities. Further study will show whether this is an incidental or a structural occurrence.
Most studies of heavy metals and selenium have not examined or have failed to find differences in concentrations in the tissues of birds as a function of size or sex. Heavy metal and selenium concentrations were analyzed in breast feathers of adult black skimmers Rynchops niger, a species with marked sexual size dimorphism in which males average 35% heavier than females. Females had significantly higher concentrations of lead and cadmium than males, but there were no gender differences in mercury, selenium, chromium, manganese, and copper despite the marked sexual dimorphism in body size. There were no significant correlations of bird weight or wing length and metal and selenium concentrations, and few correlations among metal and selenium concentrations in the feathers.
Colonially-nesting species of herons and egrets breed mainly in coastal areas, along rivers or near other large bodies of water. Such areas are also preferred for human development, exposing nesting birds to various pollutants. From 1989-1991, the concentrations of heavy metals and selenium were studied in the feathers of fledgling cattle egrets Bubulcus ibis, a terrestrially-feeding insectivore, from New York and Delaware in the northeastern United States, from Puerto Rico, and from Egypt. There were geographic differences in the concentrations of lead, mercury, cadmium, manganese, selenium, and chromium in the feathers of these egrets. Lead levels were 41 times higher in the feathers of cattle egrets from Cairo compared to the other sites. This difference was attributed to the continuing use of leaded gasoline and the dense automobile traffic in Cairo. However, other differences remain unexplained. Similarly, levels of chromium and manganese were also higher in Cairo than at any other sites. Cadmium levels were similar at all places except for higher levels in eastern Puerto Rico. Mercury concentrations were twelve times higher in the feathers of cattle egrets at Aswan compared to Cairo. In Puerto Rico, we also compared levels in adult cattle egrets with young and found higher concentrations of mercury and manganese, but lower concentrations of selenium in the adults. Using feathers from young cattle egrets is a potentially sensitive tool for biomonitoring for metals, especially lead, since they reflect the local area surrounding the breeding colony.
The process of human health risk assessment (HRA) was formalized in 1983 by the National Research Council to include hazard identification, dose-response analyses, exposure assessment and risk characterization. Risk assessment for ecologic endpoints is emerging as a new discipline. Although environmental impact statements have been conducted for many years, ecologists, managers and policy makers are beginning to formalize the process in terms of risk, and are adapting the HRA paradigm to ecological risk assessment (ERA). In this paper it is suggested that the temporal scales of the two processes differ, and that these differences should be incorporated in ecological risk assessment. Even when HRA techniques are applied to a single non-human species there are temporal variations including: (1) different and often variable life spans, (2) unpredictable lengths of lifestages and different metamorphic stages, and (3) indeterminate growth in some species. When these differences are considered for multispecies assemblages, the impact on the food web will result in exposures of differing magnitudes affecting different species. The challenges for ERA include developing general principles for estimating or predicting exposure to critical life stages of the dominant species in an ecosystem, and establishing the appropriate temporal scales for predicting impacts or evaluating outcomes.
Trace element levels have seldom been examined in reptiles, although some large snakes are high on the trophic level pyramid. Lead, cadmium, mercury, selenium, chromium and manganese levels were examined in skin and whole body tissue of pine snakes (Pituophis melanoleucus) from the New Jersey Pine Barrens between 1985-1990. Depending on the element, variations in levels were primarily explained by year and tissue, and not by sex or location. There were significantly higher levels of lead, mercury, and chromium in the skin compared to the whole body tissue, suggesting that the frequent shedding of skin can act as a method of toxic metal excretion by snakes. Manganese and selenium levels were significantly higher in the body compared to the skin.
The use of feathers is a non-invasive and repeatable method for biomonitoring trace element levels in birds and their ecosystems. Trace element levels were examined in different parts of growing flight feathers from young common terns (Sterna hirundo) to determine distribution of heavy metals and selenium, potential bias from using partially grown feathers, and whether additional heavy metals and selenium are excreted in feather sheaths that are sloughed before feathers are usually sampled. Lead and mercury levels were significantly higher in the distal fully formed portion of the growing feather (with no residual blood supply) compared to the proximal, growing portion of the feather with a residual blood supply, but no significant differences were evident for cadmium and selenium. These results suggest that using partially grown feathers underestimates the amount of lead and mercury in fully formed feathers and that higher levels of lead and mercury are sequestered in feathers than are present in the blood at any one time. Significantly higher concentrations of lead and cadmium, and significantly lower levels of mercury were in the sheath compared to the whole feather blade. These data suggest that birds excrete more lead and cadmium during molt than previously thought.
Bone, feathers, and liver were analyzed for lead in herring gull chicks (Larus argentatus) of two different ages. The highest levels were found in the bone, evidence of chronic exposure. No differences were found within the bones. Differences occurred between different bones, with the ribs having twice the amount of lead than any other bone. These studies indicate that type of bone affects lead levels; thus researchers should clearly state which parts of which bones are examined. It is also suggested that for humans consistent location should be used for analysis by in vivo X-ray fluorescence.
Sport or subsistence fishermen sometimes underestimate the risks from eating local fish and distrust authorities regarding potential hazards from fish. We report on lead, cadmium, selenium, and mercury levels in snook, locally called robalo (Centropomus spp.), consumed by local fishermen in Puerto Rico, who ate up to 23 fish/wk. Median levels (in ppb, dry weight) for muscle, adipose, and liver ranged from 683 to 780 for lead, 37 to 600 for cadmium, 50 to 146 for mercury, and 361 to 3986 for selenium. Lead levels were similar in all tissues, and selenium and cadmium levels were highest in the liver. Mercury was higher in muscle than in liver. Computing exposure via ingestion for the average fisherman indicated that if one were to consume robalo throughout the year one would be exposed in excess of the EPA Reference Dose (RfD) for mercury. Using a widely accepted maximum consumption of 200 g/d for fishermen yielded hazard indices (daily consumption/RfD) below 1 for all four metals, with a value approaching 1 for mercury in adults, and over 1 for 16-kg children. The possibility that in certain localities and cultures sport or subsistence fishermen may consume fish at levels substantially above 200 g/d should be investigated in performing risk assessments, particularly outside the continental United States.
Birds are useful indicators of environmental contamination because they are relatively large, conspicuous, top predators in food chains. However, concentrations of contaminants in a bird's tissues reflect the bird's exposure over wide temporal and spatial scales. Birds are most useful as monitors of exposure when these scales are known. In this paper we report concentrations of lead, cadmium, mercury, and selenium in breast feathers of common terns (Sterna hirundo) and roseate terns (S. dougallii) trapped during incubation at breeding colonies in New York and Massachusetts. Terns arrived on the breeding grounds with breast feathers grown on their wintering grounds, and regrew certain feathers that were plucked for analysis. The regrown feathers were themselves plucked, and both sets of feathers were analyzed. For roseate terns at Cedar Beach and common terns at both sites there was a significant increase in mercury levels in the feathers grown on the breeding grounds compared to those grown on the wintering ground. The differences in mercury were far greater at Bird Island than at Cedar Beach. Selenium levels at Cedar Beach were higher for the regrown feathers than the initial feathers for roseate terns, but not for common terns. Lead and cadmium levels were not significantly different at either site for either species. These results suggest that terns are exposed to significantly higher levels of mercury in the northeastern United States than they are in the wintering grounds in South America.
To determine the incidence of gastric emptying abnormalities in children with inflammatory bowel disease, we performed dual liquid/solid-emptying studies on 25 children with ulcerative colitis (UC) and on 45 with Crohn's disease (CD) over a 6-yr period. Nutritional parameters were evaluated initially and at the time of repeat study in those with abnormal emptying after a period of nutritional rehabilitation. All UC patients and 30 of 45 with CD (67%) had normal emptying of both liquid and solid components of the meal. Fifteen children with CD had delayed emptying of the solid liquid. Fourteen of these had preceding weight loss and one had no weight gain for 3 months prior to the study. Twelve complained of upper gastrointestinal symptoms (nausea, early satiety, postprandial epigastric pain, and anorexia), and five had evidence of growth retardation. The group averaged 4.8 abnormal nutritional parameters, compared with an average of 2.2 in those with CD and normal gastric emptying. Twelve of the 15 with abnormal emptying had abnormal gastric and/or duodenal biopsies: 10 were treated with sulfasalazine and prednisone, whereas five were taking only sulfasalazine. Studies repeated 6-15 months later after establishment of weight gain by caloric supplementation showed significant improvements in gastric emptying, nutritional status, and disease activity for the group, despite persistence of upper gastrointestinal disease documented in eight patients who underwent reexamination.
We report a rare disease of skin and oropharyngeal mucosa in a 28-year-old patient occurring 2 years after an allogeneic bone marrow transplantation. The dermatologic diagnosis was unambiguously epidermolysis bullosa acquisita according to the immunofluorescence and clinical presentation. Treatment with cyclosporin A and prednisone resulted in resolution. This autoimmune skin disease may be a manifestation of graft-versus-host disease, but the relationship must remain speculative.
White-footed mice Peromyscus leucopus reared in our laboratory from wild-caught parents lived at least to 5.5 years. Once past weaning, over 80% of the mice lived at least until two years. Females maintained a constant weight whereas the weight of males increased until four years and decreased thereafter. At four-years of age both sexes bred successfully with mates of the same age, but had lower success with younger mice. Some males and females reproduced at five years of age.
Early studies suggested that the risk of haemorrhagic complications become unacceptable when platelet counts drop below 20 x 10(9)/l. Because there are insufficient data to define 20 x 10(9)/l as the threshold for prophylactic platelet transfusions, the practicability of a more restrictive transfusion policy has been assessed prospectively in 102 consecutive patients being treated for acute leukaemia. Besides platelet count, the transfusion protocol took into consideration factors such as presence of bleeding, fever, coagulation disorders, and intention to do therapeutic procedures. 31 major bleeding episodes occurred on 1.9% of the study days when platelet counts were 10 x 10(9)/l or less and on 0.07% of study days when counts were 10-20 x 10(9)/l. The findings indicate that the threshold for prophylactic transfusions can safely be set at 5 x 10(9)/l in patients without fever or bleeding manifestations and at 10 x 10(9)/l in patients with such signs. For patients with coagulation disorders or anatomical lesions, or for those on heparin, the threshold should be at least 20 x 10(9)/l. Such a restrictive platelet transfusion policy, which is applicable not only to thrombocytopenia associated with acute leukaemia but also to other forms of hypoproliferative thrombocytopenia, reduces exposure of such patients to blood donors and results in substantial health-care savings.
The circumstances which can influence the determination of the static central visual acuity are enumerated. The TNO Landolt C chart can be improved. A modified Landolt C letter chart is introduced on which the optotype is presented in 8 different positions, in vertical rows of ten per visual step above visual acuity 0.3.
Levels of lead, cadmium, and mercury were examined in breast feathers of terns nesting on offshore islets near Culebra, Puerto Rico and on Michaelmas Cay and Heron Island on the Great Barrier Reef, Australia. Levels of all metals in these tropical terns were predicted to be lower than those of terns nesting in temperate regions, because the tropical species feed offshore of non-industrial areas where contamination should be less than for temperature-nesting species that feed in inshore estuaries near industrialized areas. This prediction was not supported by the evidence. In Puerto Rico, lead and cadmium levels were highest in bridled tern (Sterna anaethetus), and mercury levels were highest in sooty (S. fuscata) and roseate tern (S. dougallii). In Australia, levels of lead and mercury were higher in black noddy (A. minutus) and lower for sooty tern; and cadmium levels were highest for brown noddy (A. stolidus) and sooty tern, and lowest for black noddy. Metal levels for the tropical terns nesting in Puerto Rico and Australia generally were not lower than levels reported for temperate-nesting or mainland nesting birds (except for mercury in Australia).
Refsum's disease (Heredopathia atactica polyneuritiformis) is caused by accumulation of phytanic acid in all body tissues due to an inherited failure of alpha-oxidation of branched chain fatty acids. Plasmapheresis has been reported to be beneficial by removal of phytanic acid from the blood. We describe a patient with Refsum's disease in whom long-term plasmapheresis did not improve clinical, biochemical or electrophysiological parameters.
Risk perception studies show that individuals tend to underestimate significant risks, overestimate negligible ones, and distrust authorities. They also rely on a variety of strategies or heuristics to reach decisions regarding their risk-taking behavior. We report on a survey of fishermen and crabbers engaged in recreational and substance fishing in a Puerto Rican estuary (near Humacao), which has been declared a "Superfund site" because of suspected contamination by mercury, and at ecologically similar control sites. Nearly everyone interviewed at the Humacao site was aware of the mercury contamination, but either denied its importance, believed the contamination was restricted to a distant part of the estuary, or assumed that the estuary would be closed by the authorities if the threat was real. All site-users consumed the fish and crabs they caught. At Humacao, the average catch was 7 fish per fishermen (mostly tilapia, Tilapia mossambica, and tarpon, Megalops atlantica) and 13 crabs per crabber (all blue crabs, Callinectes sapidus). On average, the site-users returned to the lagoons about 3-4 times per month. At control sites, fewer fish were eaten. The worst case consumption of tarpon, a species which concentrated mercury at Eastern Puerto Rico, provided an exposure exceeding the EPA reference dose, whereas consumption of one tarpon per week did not entail excess exposure. Fortunately, few individuals caught tarpon exclusively. Unlike counterparts in the northeastern United States, they trusted authorities and indicated that they would have heeded warnings of mercury contamination posted where they fished.
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