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Biomedical subjects

M A Davis

Publications and source records attributed to M A Davis.

At least 199 records · Page 11Linked to original sources
PubMed1981

Hepatic contrast agents for computed tomography: high atomic number particulate material.

We used a stepwise approach to identify, design, synthesize, and test new high atomic number particulate contrast agents that would be especially well suited for use with computed tomography (CT). Our goal was to produce extremely radiopaque compounds with highly selective biodistribution to the normal liver. In this way, dose requirements could be lessened and toxicity minimized. Suspensions of cerium, gadolinium, and dysprosium oxide particles and silver iodide colloid were tested and compared with standard agents. All four experimental agents were selectively concentrated in the reticuloendothelial systems of rats and rabbits. These compounds produced greater and longer opacification of normal livers and larger liver-to-tumor differences in rabbits with hepatic tumors than did equivalent amounts of standard, iodinated agents. Lesions as small as 5 mm were visible with CT. These experimental materials have favorable characteristics as hepatic contrast agents, but their toxicity and long term retention may limit clinical use.

Animals↗
PubMed1981

Radiopaque liposomes: a promising new contrast material for computed tomography of the spleen.

Radiopaque, positively charged liposomes were made from lecithin, cholesterol, and stearylamine and carried diatrizoic acid salts (Renografin). Following intravenous administration of radiopaque liposomes in rats and rabbits, the spleen had the highest iodine concentration and was opacified on CT images. Contrast concentrations peaked at 30 minutes and gradually declined over a period of 24 hours. At 30 minutes, spleen CT values in rats had increased by 2.9 HU for each milligram of injected iodine (4 mg I/kg); maximum values were more than 6 times those obtained with an equivalent amount of Renografin alone. Peak spleen CT numbers of over 100 HU were consistently achieved following injections of 133 mg I/kg of opaque liposomes in rats. No acute toxicity was observed. These new contrast agents seem promising for CT of the spleen.

Animals↗
PubMed1981

Preparation and characterization of two complexes of technetium with 2-mercaptocarboxylic acids.

We have synthesized the tetraphenylarsonium salts of oxotechnetium(V)bis-(2-mercaptopropionate) and oxotechnetium(V)bis-(2-mercaptohexadecanoate) containing macromolar quantities of the long-lived isotope technetium-99. The compounds were investigated by elemental analysis, paper electrophoresis, and infrared and ultraviolet-visual spectroscopy, proton nuclear magnetic resonance, and field-desorption mass spectrometry. The findings suggest that the technetium atom is coordinated by two sulfur and three oxygen atoms in a square pyramid, the two sulfur atoms and two of the oxygen atoms forming the base and the third oxygen atom the apex. The carboxyl oxygen coordinated to technetium will not be available for binding in vivo. This factor should be considered in the design of technetium 99m-labeled radiopharmaceuticals containing a mercapto group alpha to a carboxyl group.

Chemical Phenomena↗
PubMed1981

Iodinated starch particles: new contrast material for computed tomography of the liver.

An iodinated starch suspension was used as a model particulate hepatic contrast agent for computed tomography (CT). The material, synthesized from starch and triiodobenzoic acid, formed a stable concentrated suspension, containing particles smaller than 4 micrometer. Following intravenous administration of 0.16 gI/kg to rabbits, approximately 85% of the injected dose was present in the liver, resulting in a 180 to 200 Hounsfield unit (1,000 scale) increase in liver CT value. The material produced marked and sustained normal liver opacification but no hepatic tumor enhancement. Lesions as small as 2 mm in diameter were detected. The approximate LD50 of the suspension in mice was 0.9 g I/kg. There were no signs of toxicity at sublethal doses. This suspension produces greater, more sustained, and more selective liver opacification than conventional biliary and urographic contrast materials.

Animals↗
PubMed1980

Mood disorder in women professionals.

The lifetime prevalence of affective disorder in women with M.D.'s and Ph.D's was assessed by personal interview. The two groups were matched by age, race, and marital status. Thirty-nine percent of 111 white, women physicians and 30% of 103 white women Ph.D.'s were found to have primary affective disorder. There was no excess of depression in women psychiatrists or psychologists. Eleven percent of the first degree relatives of the depressed M.D.'s and 7% of similar relatives of depressed Ph.D's had affective disorder by family history compared to only 2% of the well M.D.'s and 2% of the well Ph.D's relatives. The study confirms that depression is an extremely common problem for professional women. By emphasizing its heritability, it raises the question of the self-selection for professional careers of women with affective disorder.

Adult↗
PubMed1980

Heavy metal particulate contrast materials for computed tomography of the liver.

Silver iodide colloid was used as a model of a particulate hepatic contrast agent for computed tomography (CT). Following intravenous administration to rabbits, approximately 90% of the injected dose was phagocytized by the liver's reticuloendothelial system, resulting in a four- to five-fold increase in the liver CT number. Suspensions of CeO2, Dy2O3, and Gd2O3 were prepared using stabilizers to prevent clumping. Particles of appropriate size for reticuloendothelial cell uptake were selected by centrifugation. Intravenous injections of the three suspensions increased the CT number of rabbit liver by approximately 30 Hounsfield units (HU: 1,000 scale) for each experimental contrast agent resulted in a minimum addition of 250 HU to the liver CT number. A linear relationship was found between the CT number and its contrast material concentration. This relationship was also tested in vitro by ashing samples of livers containing various amounts of contrast material. Standard curves of CT number versus contrast material concentration in the liver were plotted, which predicted the amount of liver enhancement obtained after contrast material injection. There may be a use for heavy metal-containing particulate materials as hepatic contrast agents, since they opacify the liver more selectively, to a higher degree, and for longer periods than the conventional biliary and urographic iodinated contrast materials.

Animals↗
PubMed1980

Simultaneous 99mTc-P-butyl-IDA and 131I-rose bengal scintigraphy in neonatal jaundice.

Eight neonates with jaundice were studied simultaneously with 99mTc-p-butyl-IDA and 131I-rose bengal. Due to physical decay, 99mTc-p-butyl-IDA failed to demonstrate delayed excretion through the patent extrahepatic biliary tract in 3 of 5 patients with concomitant hepatitis; 131I-rose bengal showed small-bowel activity in all 5. Neither agent demonstrated small-bowel activity in 3 neonates with extrahepatic biliary atresia. Based on this clinical trial, 131I-rose bengal remains the radiopharmaceutical of choice for distinguishing between hepatitis and biliary atresia in these patients.

Animals↗
PubMed1980

Potential column chromatography for ionic Ga-68. II: Organic ion exchangers as chromatographic supports.

A potential Ge-68 leads to Ga-68 generator system, based on the adsorption of Ge-68 from a dilute hydrofluoric acid eluent onto a commercially available organic anionexchange resin, is described. The distribution coefficients between the resin and dilute hydrofluoric acid were measured for germanium and gallium, and the breakthrough of germanium from a generator column determined. Using 0.01 N HF, the Kd values are 27 and greater than 4,000 for gallium and germanium, respectively. Gallium-68 can be quantitatively collected with 4 ml of 0.01 N HF. After neutralization, this provides a biologically safe concentration of NaF for injection. The breakthrough levels of germanium-68 remain lower than 10(-4) for up to 600 collections.

Chromatography, Ion Exchange↗
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↗
PubMed1980

[125I]iodobenzoyl derivatives of acebutolol as potential myocardial imaging agents.

Three new iodobenzoyl derivatives of acebutolol, a cardioselective beta antagonist, were synthesized and labeled with iodine-125. The biodistributions of these labeled compounds were determined in normal rats and compared with that of thallium-201. Fifteen minutes following i.v. administration, the iodine-125-labeled meta- and para-iodobenzoyl acebutolols possessed the greatest ventricular uptake and the highest ventricle-to-blood and ventricle-to-lung ratios of the new agents. The corresonding values for thallium-201 were 2.5 to 3.0 times as high. The data in this study suggest that more lipophilic derivatives of the cardioselective beta antagonists will possess increased uptake and cardioselectivity, and thereby will compare more favorably with thallium-201 as myocardial imaging agents.

Acebutolol↗
PubMed1980

A new osmium-191 leads to iridium-191m generator.

A new osmium-191 leads to iridium-191m generator suitable for first-pass radionuclide angiocardiography has been developed. This generator system allows repeated elutions of 4.96-sec iridium-191m from its 15.4-day Os- 191 parent. The Os-191 is loaded on an anion-exchange column (AGMP-1) and Ir- 191m eluted with 0.9% NaCl at pH 1. Each elution (0.6 to 1 ml) of the generator yields about 7 to 10% Ir-191m and gives 0.003-0.008% of Os-191 breakthrough. Toxicity studies of the generator eluate carried out in animals support the safety of using iridium-191m in humans. The long shelf-life of the generator (approximately equal to 2 wk) will allow medical centers to use Ir- 191m for routine clinical diagnosis. Iridium-191m obtained by this method should find additional useful applications in nuclear medicine.

Animals↗
PubMed1979

Psychiatric disorders among professional women.

A group of 111 women physicians and 103 women PhDs, selected from the general community, were studied for the presence of psychiatric illness. Fifty-one percent of the MDs and 32% of the PhDs were diagnosed as having primary affective disorder (P less than .01). Other psychiatric disorders were found in less than 10% of each group. Depression among the psychiatrists was significantly more common (73%) than among the other physicians (46%). More than 50% of all the women reported prejudice in training or employment, and depressed subjects reported prejudice more often than well subjects. The presence of children and depression were shown to disrupt a woman's professional career. The finding of a high prevalence of affective disorder among women physicians is consistent with the reported excessive suicide risk for this group.

Adult↗
PubMed1979

Synthesis and biologic distribution of mercapto derivatives of palmitic acid.

Mercapto derivatives of palmitic acid are capable of binding 99mTc. Based on the hypothesis that 99mTc-labeled palmitic acid derivatives would behave biologically like palmitic acid and thus could be used as myocardial imaging agents, three mercaptopalmitic acid derivatives have been prepared. The synthesis of 2-mercaptopalmitic acid, 2-mercapto-1,16-hexadecanedioic acid, and 16-mercaptopalmitic acid was accomplished by reaction of the corresponding bromo compound with thiourea. The 35S-labeled compounds and [16-14C]palmitic acid were evaluated in rats with a heat-inflicted myocardial infarction to study the effect of the introduction of the mercapto group. The organ distribution of 2-[35S]mercaptopalmitic acid was most similar to that of [16-14C]palmitic acid.

Animals↗
PubMed1979

Augmentation of collateral blood flow to the ischaemic myocardium by oxygen inhalation following experimental coronary artery occlusion.

Since the mechanism by which oxygen reduces infarct size is not yet completely understood, we tested the hypothesis that breathing 100% oxygen may alter regional myocardial blood flow. In 23 anaesthetised open-chest dogs with acute occlusions of the left anterior descending coronary artery or of its apical branch, regional myocardial blood flow was determined by the microsphere technique at 15 and 30 min following coronary artery occlusion. Fifteen treated dogs were ventilated with 100% oxygen beginning 17 min after occlusion (ie, after the first determination of regional myocardial blood flow) and continuing until the end of the experiment, while the other 8 dogs served as controls and were ventilated continuously with room air. In treated dogs, following the administration of 100% oxygen, transmural flow at sites remote from the distribution of the occluded vessel (nonischaemic sites) decreased from 121 +/- 5 before oxygen to 108 +/- 6 cm3 . min-1 . 100g-1 (P less than 0.05). However, in the ischaemic sites it increased from 28 +/- 3 before oxygen to 32 +/- 3 cm3 . min-1 . 100g-1 (P less than 0.05). In the control dogs transmural flow, 15 and 30 min after occlusion, was, in nonischaemic sites, 118 +/- 7 and 125 +/- 10 cm3 . min-1 . 100g-1 NS, and in the ischaemic sites 27 +/- 4 and 25 +/- 3 cm3 . min-1 . 100g-1 NS, respectively. Thus, ventilation with 100% oxygen can augment perfusion of the ischaemic myocardium and this may be, in part, the mechanism by which it reduces infarct size.

Animals↗