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Biomedical subjects

A Davison

Publications and source records attributed to A Davison.

90 records · Page 5Linked to original sources
PubMed1982

Chemical and in vivo studies of the anion oxo[N,N'-ethylenebis(2-mercaptoacetimido)]Technetate(V).

Studies of the anionic coordination complex 99Tc-oxo[N,N'-ethylene-bis(2-mercaptoacetimido)]technetate(V) ([TcO(ema)]-) are described. Syntheses performed both at carrier levels (10(-5)M) and with no carrier added (less than 10(-8)M) indicate that the complex is formed virtually quantitatively from pertechnetate ion over this range. Tissue distributions in normal rats are similar at both concentrations up to one hour after administration. It has been shown--using a combination of high-pressure liquid chromatography and field-desorption mass spectrometry--that the anion is excreted unchanged into both urine and bile. The effectiveness of this N2S2 donor set in sequestering Tc-99m, and the in vivo stability of the resulting complex, suggest that modified chelates of this structural class could provide a series of useful diagnostic agents.

Animals↗
PubMed1980

A survey of reducing agents for the synthesis of tetraphenylarsonium oxotechnetiumbis(ethanedithiolate) from [99Tc] pertechnetate in aqueous solution.

We have studied the effectiveness of various reducing agents in the production of the well-characterized complex [99TcO(SCH2CH2S)2]- from pertechnetate in aqueous solution. The reductants tested included sodium dithionite, hypophosphorous acid, formamidine sulfinic acid, dithiothreitol, hydrazine, and hydroxylamine. Of these, only sodium dithionite in the pH range 11--13 was found to give quantitative yields of the required technetium complex.

Arsenicals↗
PubMed1977

A non-invasive test for receptor binding applied to nephrogenic diabetes insipidus.

Studies in animals have determined the importance of specific receptors to the action of many hormones and drugs. In man, a non-invasive external counting technique has been used and absence of receptor function has been demonstrated in a patient with nephrogenic diabetes insipidus using radioactively labelled arginine vasopressin. This is in contrast to the findings in a patient with pituitary diabetes insipidus and a normal control. These results suggest a model for the study of hormone and drug kinetics in man avoiding multiple samplings of biological fluids.

Adult↗
PubMedDate not supplied

Progestin-rhenium complexes: metal-labeled steroids with high receptor binding affinity, potential receptor-directed agents for diagnostic imaging or therapy.

In order to investigate the possibility of developing diagnostic imaging agents for steroid-positive tumors that are labeled with the readily available radionuclide technetium-99m, we prepared four conjugate systems in which a progestin is linked to a metal chelate system. Three of these are bis-amino bis-thiol (BAT or N2S2) systems and are linked through carbon-21 of progesterone or the 17 alpha- or 11 beta-position of a nortestosterone type progestin. The fourth, an amino-amido-thiol-alcohol chelate (N2OS) system, is linked at the 16 alpha,17 alpha-positions of a dihydroprogesterone. As a model for technetium-labeled complexes, all four chelate systems were converted to their oxo-rhenium complexes. Of the four possible diastereomers in the 16 alpha,17 alpha-system, only one was isolated, while of the four possible diastereomers in the other systems, a syn pair and an anti pair (linker methylene vs rhenium-oxo, relative to the N2S2 plane) were separated in the 17 alpha-substituted series, a syn pair was isolated in the 21-substituted series, and a syn pair and the two individual anti diastereomers were separated in the 11 beta-substituted series. In competitive radiometric receptor binding assays, the 21-, 17 alpha-, and 16 alpha,17 alpha-linked systems had low affinity for the progesterone receptor (less than 0.3% that of promegestone (R5020) or 2% that of progesterone). By contrast, the two anti diastereomers of the 11 beta-linked system had affinities that were 10% and 44% that of R5020 (or 64% and 283% that of progesterone) and the syn pair had an affinity 25% that of R5020 (or 161% that of progesterone). The latter finding indicates that it is possible to prepare metal-labeled steroids that retain high affinity for steroid receptors. These and related systems, when complexed with radioactive metals, may be useful in vivo as receptor-directed agents for diagnostic imaging or therapy of steroid receptor-positive tumors.

20-alpha-Dihydroprogesterone↗
PubMedDate not supplied

Vanadium as a modulator of cellular regulatory cascades and oncogene expression.

Vanadium, a trace metal in the environment and in biological systems, influences the behavior of enzymes, mimics and regulates growth factor activity, is a potential mutagenic and carcinogenic agent, and regulates gene expression. The diverse biological actions of vanadium result from its capacity to function as an oxyanion, oxycation, or prooxidant. Vanadium is found in water, rocks, and soils in low concentration and in relatively high concentrations in coal and oil deposits. Vanadium compounds at much higher concentrations than are typically ingested are being considered in the treatment of diabetes mellitus. The actions of insulin and vanadium on the insulin receptor are similar, but the mechanisms are not identical. Vanadium modulates growth-factor-mediated signal transduction pathways. Vanadium promotes cell transformation and diminishes cell adhesion. Consistent with its mitogenic action and its capacity to mimic mitogenic growth factors, vanadium stimulates expression of protooncogenes. In particular, oxygen-derived active species are involved in the expression of the jun protooncogene in the presence of vanadium. The unique cellular activity of vanadium makes it a tool of unparalleled potential for studying mechanisms of cell growth, differentiation, and metabolism.

Animals↗
PubMedDate not supplied

Renal disease associated with antineutrophil cytoplasmic antibody: 39 patients over a 5-year period.

We have reviewed 39 adult patients who presented over a 5-year period with biopsy confirmed renal disease in association with positive antineutrophil cytoplasmic antibody (18 with C-ANCA, 21 with P-ANCA). Twenty-three (59%) had primary systemic vasculitis, typically with aggressive renal histology including focal necrotising and crescentic glomerulonephritis. In the remaining patients a wide range of clinical syndromes and renal histological appearances were apparent: 30 had abnormal renal function (serum creatinine > 140 mumol/l), including 17 who were initially dialysis-dependent. Intensive immunosuppression was administered in 33 cases. When response was assessed at 3 months, renal function was stable or improved in 17 (52%), 5 of whom were able to discontinue dialysis. There was, however, an appreciable early mortality and, at latest follow-up (1-57 months), 12 patients had died and 8 were on the dialysis programme. On immunosuppression, ANCA became negative in the majority (median time 1.5 months) but recurred during clinical relapse in 11 cases. In asymptomatic patients (12 cases), the reappearance of ANCA positivity did not herald clinical relapse. The ANCA assay has increased awareness of systemic vasculitis but not removed the need for histological confirmation before instituting immunosuppression.

Adult↗