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D Vinson

Publications and source records attributed to D Vinson.

12 recordsLinked to original sources
PubMed2000

Elevated mercury concentrations in soils, sediments, water, and fish of the Madeira River basin, Brazilian Amazon: a function of natural enrichments?

Previous site-specific investigations have found that mercury concentrations in water, sediments, and biota of the Brazilian Amazon are elevated above global averages, and that these concentrations are a direct result of widespread mercury amalgamation mining operations conducted by non-organized prospectors. In order to assess the regional impacts of Hg contamination from these non-organized gold mining activities, water, sediments, and fish were systematically collected in 1997 along a 900-km reach of the Madeira River. The sampling program extended from the Amazon River upstream to Porto Velho, the site of historic and ongoing mercury amalgamation mining. Mercury concentrations were found to be elevated above global averages in all sampled media. However, the geochemical data suggest that the high mercury levels are due largely to natural sources and natural biogeochemical processes, and that the impacts of anthropogenically released mercury from mine sites is relatively localized.

Animals↗
PubMed1996

Erythropoietin stimulates G-protein-coupled phospholipase D in haematopoietic target cells.

A murine haematopoietic stem-cell line, B6SUt.EP, responsive to erythropoietin (EPO), has been found to exhibit both early and late changes in diacylglycerol (DAG) and phosphatidic acid (PA) as measured by HPLC and TLC. DAG levels peaked at 5 s with a 28.1% increase compared with control levels (from 17.3 to 22.2 pmol/10(6) cells) with a later peak at 30 min (84.2% increase from 17.3 to 31.9 pmol). These changes were concentration-dependent from 0.025 to 10 units/ml EPO (5 s, EC50=0.82 unit/ml; 30 min, EC50 = 0.10 unit/ml). In addition, PA levels increased 752.3% compared with control levels (from 8.6 to 64.7 micrograms/10(6) cells) with an early peak at 20 s, as measured by both HPLC and TLC (5 s, EC(50)=0.07 unit/ml). G-protein regulation was investigated by studying the effects of the non-hydrolysable GTP analogue guanosine 5'-[gamma-thio]triphosphate (GTP[S]) on PA synthesis. The addition of GTP[S] (10 microM) in permeabilized cells increased PA content from 6.3 micrograms to 48.6 micrograms per 10(6) cells. In the presence of EPO and GTP[S], PA levels increased to 64.8 micrograms. An antagonist of G-proteins, guanosine 5'[beta-thio]diphosphate (GDP[S]), had no effect on control levels of PA (5.9 micrograms/10(6) cells) but blocked the effect of EPO on PA (30.6 micrograms/10(6) cells). Thus, EPO stimulated both lipid second messengers, DAG and PA. Our results demonstrate DAG kinetics to be biphasic, as observed with a high concentration of EPO, or monophasic, as observed with low concentrations of EPO. The PA accumulation preceding that of DAG in the slower and sustaining phase suggests that PA was not derived from DAG. This was confirmed by the stimulation of PA (without ATP) by GTP[S], effectively excluding phosphorylation of DAG by DAG kinase in the formation of PA. In addition, phospholipase D (PLD) activation was demonstrated with a maximal increase in phosphatidylethanol at 5 min, suggesting the EPO increases PA via a guanine nucleotide-binding protein coupled to PLD. The temporal relationship of the evolution of PA and DAG is further strengthened by experiments with ethanol and propranolol as inhibitors of the DAG/PA phosphohydrolase reaction and R59022 as an inhibitor of the DAG kinase reaction.

Adenosine Triphosphate↗
PubMed1994

Relationship of hyperglycemia and severity of illness to neurologic outcome in head injury patients.

Hyperglycemia upon hospital admission has been associated with poorer neurologic outcomes in patients with brain injury, but this relationship has not been well defined. To evaluate the relationship of hyperglycemia and severity of illness to neurologic outcome, the authors examined Surgical Intensive Care Unit (SICU) records for a 6 month period at a Level I trauma center. Of 276 trauma admissions, 97 patients had intracranial injuries. The peak glucose determination on the first day of admission was correlated with the Glasgow Coma Scale (GCS) score upon admission and discharge from the SICU and with severity of illness as measured by the Simplified Acute Physiology Score (SAPS). The mean admission GCS was 10.6 (+/- 0.49 S.E.M.), the mean glucose on the first SICU day was 146 (+/- 7.7 S.E.M.), and the mean peak glucose was 176 (+/- 8.2 S.E.M.). The peak glucose was inversely related to both GCS on admission and GCS at discharge (P < 0.001). However, stepwise multiple regression analysis revealed that the best single predictor of GCS at discharge was the GCS on admission. The next best predictor was the SAPS on the first SICU day. Peak glucose did not add to the power of admission GCS and SAPS to predict neurologic outcome. Peak glucose levels in brain-injured patients may simply reflect severity of illness and injury that is better represented by SAPS.

Adult↗
PubMed1986

Qualitative and quantitative distribution of plasminogen activators in organs from healthy adult mice.

Twenty organs from healthy adult mice were tested for plasminogen activator activity. All were positive although specific activities varied 200-fold. Tissues with high activity were lung, uterus, brain and kidney. Endocrine glands were moderately rich in activator activity, and lymphoid tissues were poor. Molecular mass characterization was carried out. Two enzymatic forms were observed in all twenty organs: a 70 kDa form similar to human tissue plasminogen activator and a 48 kDa form analogous to mouse urokinase.

Animals↗
PubMed1981

Differentiation of thymocytes during chicken ontogeny: occurrence of a specific DNA ligase in relationship to cell size and surface antigens.

The activities of two forms (8.2 and 6.2 S) of DNA ligase have been studied in chicken thymocytes at different stages of development (16 and 18 days of incubation, hatching and one month after birth). Thymocytes have been sorted out on the basis of size and T antigenicity (immunofluorescence) with the activated cell sorter. Three kinds of cells can be distinguished: (a) large, antigenically negative cells of 16 days of incubation, expressing only the "heavy" (8.2 S) form of enzyme. The activity of this form decreases during development and is very low after birth; (b) large, antigenically positive cells without DNA ligase activity and (c) small, antigenically positive cells, expressing the "light" (6.2 S) enzyme. This form of enzyme appears only from 18 days of incubation onwards. These results allow us to consider the 6.2 S DNA ligase activity as an additional marker (with cell reduction and T antigenicity) for thymocyte maturation.

Aging↗
PubMed1979

Evidence for a DNA ligase change related to early cleavage in axolotl egg.

A definite change in the forms of DNA ligase appears when the axolotl egg enters cleavage. Sucrose gradient and phosphocellulose chromatography show that the a 6S form of DNA ligase exists before division, i.e. in unfertilised and fertilised egg, and a 8.2S form is present at the first division. N-ethylmaleimide sensitivity and heat stability are different for the two forms. The possible significance of this early change is discussed.

Ambystoma↗
PubMedDate not supplied

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Education, Medical↗