Biomedical subjects

M R Violante

Publications and source records attributed to M R Violante.

28 records · Page 2Linked to original sources

PubMedDate not supplied

Cerebral water content, blood flow and EEG changes after cardiac arrest in the dog.

Changes of cerebral water content, blood flow and cortical EEG following cardiac arrest (8-14 minutes) were studied in 14 mongrel dogs. With five hours of maintenance, changes in the water content both in grey and white matter were found to be insignificant. (Grey matter: control 78.68 +/- 2.62%; arrest 79.91 +/- 1.76%. White matter: control 66.66 +/- 4.10%; arrest 67.76 +/- 1.88%). Blood flow was measured using 15 micron microspheres labeled with Sr, 85 Ce141 and Yb.169 Flow in grey matter was decreased to 47% at 3 hours and 53% at 5 hours; while in white matter it was 67% at 3 hours and 75% at 5 hours from baseline. Deterioration of the cortical electrical activity was observed in all animals having an arrest of more than 8 minutes. In aminals having arrest of longer than 12 minutes there is either no return (isoelectric) or marked slowing of cortical electrical activity. From this and previous studies, it is concluded that with more than 8 minutes of cardiac arrest and up to 5 hours of maintenance there is impairment of cortical perfusion which is not associated with a significant increase in total water content. The lack of increase in total water content, however, does not mean there is no local swelling or edema such as in endothelial cells.

Animals↗

PubMedDate not supplied

Reduction in ventricular fibrillation using calcium-enriched Renografin 76.

Renografin 76 has been shown to have significant calcium-binding properties in vivo and in vitro. Two contrast media solutions were compared by selective injection into the right coronary artery of dogs. One set of injections was made with commercially available Renografin 76 (referred to as stock Renografin) and another set of injections was made with Renografin 76 to which had been added 24 mMols/liter of calcium chloride dihydrate. Ventricular fibrillation occurred significantly more often with the stock Renografin 76. The nature of the calcium binding and its effects are discussed.

Angiography↗

PubMedDate not supplied

Protein binding to iothalamate ethyl ester.

A major problem in the development of a particulate hepatolienographic agent is the prevention of particle aggregation upon contact with blood. When iothalamate ethyl ester, a particulate suspension for potential use as an hepatolienographic agent, was mixed with human or animal plasmas, it resulted in moderate to severe flocculation. In a study conducted to define the binding of plasma proteins to the iothalamate ethyl ester particles, plasma was reversibly adsorbed to various particle preparations. Fractions obtained by incubation of the particle-plasma complexes in buffers of increased ionic strength and decreased pH were subjected to polyacrylamide disc gel electrophoresis. The fraction containing the specifically bound proteins produced three distinct bands corresponding to prealbumin, albumin, and fibrinogen. Since the particles flocculated only when mixed with plasma, it is postulated that the fibrinogen-particle interaction is a major factor leading to particle agglutination.

Blood Proteins↗

PubMedDate not supplied

Comparison of hepatic VX2-carcinomas after intra-arterial, intraportal and intraparenchymal tumor cell injection. An angiographic and computed tomographic study in the rabbit.

Hepatic VX2-carcinomas were produced in 45 rabbits by injection of approximately 25 x 10(6) tumor cells into the proper hepatic artery, the superior mesenteric vein, or directly into the liver parenchyma. With the intra-arterial and intraportal approaches, survival times (12 +/- 4 and 13 +/- 5 days, respectively), radiographic and autopsy findings revealing a liver with diffuse tumor involvement were very similar. With intraparenchymal tumor cell injection, survival time was significantly longer (18 +/- 14 days) and the hepatic VX2-carcinoma always localized. The tumor appeared hypervascular on angiography and hypodense on computed tography (CT). After intravenous injection of diatrizoate, the attenuation in the tumor increased less than in the surrounding liver so the lesion became relatively less dense and more easily recognized on CT-scans. The apparent discrepancy between angiographic and contrast enhanced CT findings can be explained with the difference in blood supply of hepatic tumors and normal liver parenchyma.

Angiography↗

PubMedDate not supplied

Hepatic CT contrast enhancement: effect of dose, duration of infusion, and time elapsed following infusion.

Contrast enhancement of the liver of anesthetized, paralyzed, and artificially ventilated rabbits was measured during suspended respiration prior to, during, and after the intravenous infusion of meglumine diatrizoate at doses of 208, 416, and 624 mg I/kg. Infusion time was 30 seconds, and, at the highest dose, infusion times of 1, 2, and 4 minutes were also used. Highest contrast enhancement values were obtained at the conclusion of each infusion, with contrast enhancement increasing proportionately with increase in dose. Highest enhancement was obtained at all times studied from the most rapid infusion. Unlike cranial CT, optimum hepatic contrast enhancement in body CT requires rapid contrast medium injection with immediate CT scanning with a very fast scanner.

Animals↗

PubMedDate not supplied

Particulate contrast media for computed tomographic scanning of the liver.

A contrast agent that is selectively accumulated in the liver should greatly improve the diagnostic value of contrast enhanced CT scanning. The advantages and disadvantages of different classes of hepatographic agents are briefly reviewed. Experimental results obtained with the particulate contrast agents, iothalamate ethyl ester and iodipamide ethyl ester, are presented in more detail. Following intravenous infusion of iodipamide ethyl ester, approximately 60% of the injected dose is accumulated in the rat liver. CT scanning experiments involving iothalamate ethyl ester infusions in New Zealand White rabbits demonstrate significantly higher liver contrast enhancement at 10-30 minutes postinfusion than is observed with diatrizoate at a sixfold greater iodine dose. The selective accumulation of a particulate contrast agent in hepatic reticuloendothelial cells compared to virtually no accumulation in implanted VX2 carcinoma demonstrates the important potential value of these agents in improving detection of liver metastases.

Animals↗

PubMedDate not supplied

New media. Particulate contrast media.

Particulate contrast agents, when compared to water-soluble media, offer the advantage of allowing the administration of high doses without creating hypertonicity gradients and ionic imbalances. Since these radiopaque particles are accumulated in the reticuloendothelial system, they could be ideal hepatic CT contrast agents. We have developed a method for making particles of 2 +/- 1 microns by precipitating from an organic solvent. Preincubation of these particles in human serum albumin overcomes the very serious problem of in vivo particle aggregation and embolization. The ethyl esters of iothalamic and iodipamic acid have been injected intravenously into mice, rats, and rabbits. Radiopacification of the liver is maximal within 2-3 hours postinfusion, with radiopaque material subsequently clearing through the biliary system. Elimination from the organism seems to be complete within a few days postinfusion. Efforts to decrease the subacute toxicity of these agents are underway.

Animals↗

PubMedDate not supplied

Biodistribution of a particulate hepatolienographic CT contrast agent: a study of iodipamide ethyl ester in the rat.

Particulate contrast agents have been shown to be efficacious in computerized tomographic detection of liver tumors. This article quantitatively defines the biodistribution of the experimental particulate agent iodipamide ethyl ester in the rat as a function of time after intravenous infusion. The contrast agent is actively accumulated in the liver and spleen with high selectivity compared to iodine concentrations in the blood or other organs. The contrast material remains at high concentration in the liver for more than 2 hours and then is slowly cleared from the organism in approximately two days. The high selectivity and retention of contrast in the liver are indicative of the value of particulate agents in contrast-enhanced computerized tomography.

Animals↗

PubMedDate not supplied

Effect of intravenously administered iodipamide ethyl ester particles on rat liver morphology.

The effect of intravenously injected iodipamide ethyl ester (IDE) particles (150 mgI/kg) on the rat liver was studied by light and electron microscopy. IDE particles were phagocytized by Kupffer cells within a few minutes postinjection. After 4 hours particles began to dissolve in the Kupffer cells causing transient morphologic alterations resembling hydropic degeneration. The number of Kupffer cells seemed, however, to be unchanged and were ultrastructurally normal by 17 days postinjection. Hepatocytes contained large lipid droplets from one to four days after IDE injection. No changes were found in the hepatocytes from one week to one year after IDE injection. The fat-storing cells and endothelial cells remained ultrastructurally normal throughout the study.

Animals↗

PubMedDate not supplied

Canine model of contrast medium induced fibrillation.

The injection of radiocontrast media into coronary arteries will produce a low incidence of ventricular fibrillation. This study establishes the injection duration (or contact time) required to produce fibrillation during right coronary angiography in dogs using a 370 mg I/ml, meglumine/sodium diatrizoate formulation (Renografin 76, Squibb). The mean contact time required to induce fibrillation was 18.8 +/- 5.8 seconds for 66 injections in 47 dogs. Prolonged ischemia of greater than 170 s did not produce either fibrillation or arrhythmias, therefore fibrillation is caused by properties of the media. The contact time was not significantly influenced by test injections and was not significantly different in repeated experiments. The canine contact time model of contrast media induced ventricular fibrillation is reproducible and will facilitate the study of risk factors that increase the possibility of fibrillation.

Angiocardiography↗