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Biomedical subjects

B A Davis

Publications and source records attributed to B A Davis.

At least 145 records · Page 8Linked to original sources
PubMed1977

Splenic blood pool: occasional hindrance of accurate interpretation of renal dynamic scintigrams.

Because of the proximity of the spleen to the left kidney, the splenic blood pool occasionally interferes with the interpretation of the renal flow images. A review of one hundred consecutive renal dynamic studies revealed some interference in 34 per cent of the studies. The distinction between splenic blood pool and the left kidney can be made on the static images, for the renal studies. If doubt persists, a colloid scan will identify the spleen. An illustrative case is presented.

Adult↗
PubMed1977

Species variation with respect to the metabolism and excretion of d-amphetamine and d,l-N-hydroxyamphetamine succinate.

The metabolism of amphetamine and N-hydroxyamphetamine was studied in the rat and mouse. Extensive reduction of N-hydroxyamphetamine to amphetamine occurred in both species. In addition, para-hydroxylation of amphetamine was a common metabolic route, although it was more predominant in the rat. No appreciable difference in the 24-h excretion of amphetamine and p-hydroxyamphetamine in either species was seen after substitution of N-hydroxyamphetamine for amphetamine.

Amphetamines↗
PubMed1976

Qualitative and quantitative mass spectrometry of some biologically important trace metals as their tetraphenylporphyrin chelates.

The use of the mass spectrometric integrated ion current technique for the quantitative analysis of some trace metals at their tetraphenylporphyrin chelates is described. The linearity of the calibration curves and the sensitivity of the technique are improved by employing deuterated tetraphenylporphyrin chelates as loading agents. Femtomole quantities of the chelates may be detected. The use of deuterated tetraphynylporphyrin chelates as internal standards overcomes the problems of losses occurring during chromatographic separation and by thermal decomposition in the mass spectrometer.

Chelating Agents↗
PubMed1975

The separation by thin-layer chromatography of trace metals as their tetraphenylporphyrin chelates.

The tetraphenylporphyrin chelates of iron, cobalt, manganese, nickel, zinc, copper, rhodium lead, cadmium and mercury were prepared and their chromatographic behaviour investigated using four different adsorbents and eleven different solvent systems. Mixtures of lead, cadmium and mercury chelates exhibited isographic behaviour in all conditions; mixtures of the other metal chelates were adequately resolved on silica (MN Polygram Sil SHR) by the solvent system light petroleum (b.p. 80-100 degrees)-toluene-acetic acid-water (66:33:85:15, v/v, upper phase). The intense colours of the chelates permit their visual detection at levels of about 10(-10) moles; using the integrated ion-current mass spectrometric procedure, as little as 10(-14) moles of metal could be detected and assessed.

Adsorption↗
PubMed1975

In vitro studies with combinations of 5-fluorocytosine and amphotericin B.

Synergistic antifungal activity of 5-fluorocytosine (5-FC) and amphotericin B was studied using an abbreviated checkerboard titration scheme. 5-FC was titrated in twofold increments (100 to 0.05 mug/ml) in the absence and presence of graded increments of amphotericin B (1.0. 0.5, 0.1, 0.05, and 0.01 mug/ml) in buffered yeast nitrogen base. A limited number of experiments were performed using expanded dual titration checkerboard schemes and growth curve studies. Forty-eight isolates of yeastlike organisms were tested; two were inhibited by the buffer system. Evidence of synergy, as indicated by a fourfold or greater reduction of the minimal inhibitory concentration of 5-FC in the presence of subinhibitory concentrations of amphotericin B, was seen with 11 of 46 isolates, or 24%, at the fungistatic level and with three isolates, or 7% at the fungicidal level. Indifferent results were obtained for 44 and 74% of the isolates, respectively, at the fungistatic and fungicidal levels. Antagonism was observed with three isolates.

Amphotericin B↗
PubMed1975

Identification and distribution of m-tyramine in the rat.

A procedure for the quantitative evaluation of m-tyramine in mammalian tissues is described. It involves isolation of the amine by ion-exchange chromatography, followed by conversion to the dansyl derivative, chromatographic separation, and quantitation by the mass spectrometric integrated ion current technique using an isotopically labelled internal standard. The concentrations of m-tyramine in some tissues of male Wistar rats were (mean plus or minus S.D., nanograms per gram): brain 0.32 plus or minus 0.03, heart 0.44 plus or minus 0.13, kidney 12.6 plus or minus 3.4, liver 0.27 plus or minus 0.04, lung 0.33 plus or minus 0.11, spleen 0.25 plus or minus 0.07, and blood 0.15 plus or minus 0.04.

Animals↗
PubMedDate not supplied

Effects of chronic oral administration of L-deprenyl in the dog.

Dogs were administered capsules containing L-deprenyl daily over 3 weeks at dose levels of 0, 0.1, 0.5, and 1.0 mg/kg. Spontaneous behavior was measured using a canine open field test, and was not significantly affected by L-deprenyl. Plasma levels of amphetamine showed a clear dose-dependent elevation 2 h and was not significantly affected by L-deprenyl. Plasma levels of amphetamine showed a clear dose-dependent elevation 2 h following treatment, but were markedly lower after 24 h, and were undetectable 5 days following the last treatment. Plasma levels of phenylethylamine were increased, but were highly variable. Animals sacrificed 1 day following the last treatment showed a dose-dependent inhibition of monoamine oxidase B in the brain, liver, and kidney, whereas monoamine oxidase A was unaffected in these tissues. L-Deprenyl also caused an increase in phenylethylamine in the striatum and hypothalamus, but not in the neocortex. Brain levels of DA, DOPAC, 3-MT, HVA, 5-HT, and 5-HIAA were unaffected. The pharmacological profile for the dog is distinct from that of other species in that long-term treatment did not produce any significant inhibition of MAO-A activity. The absence of an effect on biogenic amines or metabolites suggests that the metabolism of dopamine is mediated at least in part through pathways other than MAO-B in the normal adult dog.

Amphetamine↗