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Biomedical subjects

M Sovak

Publications and source records attributed to M Sovak.

69 records · Page 4Linked to original sources
PubMedDate not supplied

Stability of nonionic water-soluble contrast media: implications for their design.

The stability of the nonionic contrast media metrizamide, P-297, iopamidol, and nonionic phenyl ether DS-1-132 was studied by exposing their aqueous solutions to 120 C. Metrizamide showed decomposition of the sugar residue, while in P-297 the sugar substituent was cleaved off the triiodoaniline moiety. Iopamidol and DS-1-132 showed no decomposition. For stability, sugar moieties should be attached either by an ether linkage or as amides, as long as the acylamino group is not on a carbon adjacent to the anomeric carbon. Polyhydroxyalkylamines are less hydrophilic but more stable than sugars.

Chemical Phenomena↗
PubMedDate not supplied

Release of serotonin from human platelets in vitro by radiographic contrast media.

Both ionic and nonionic, monomeric and dimeric contrast media were found to release serotonin from intact human platelets in vitro. The monomeric contrast media were compared at the concentration range of 25 mg I/ml. Iothalamate was the strongest and the statistically equal metrizamide iopamidol, and P-297 were the weakest releasers. Monomeric and dimeric contrast media were compared at concentration ranges of 50 and 100 mg I/ml. They ranked, in descending order of serotonin releasing potency: iodipamide, iothalamate, P-127, iopamidol, and a statistically indistinguishable group of the monoacid dimer P-286, the nonionic dimer ZK 74 435, and metrizamide. The capability of contrast media to release serotonin seems to be a composite result of their specific physical and molecular structural properties.

Adult↗
PubMedDate not supplied

Determination of lethal dose in a protozoa: screening of contrast media toxicity.

Suitability of a protozoan culture for determination of contrast media (CM) toxicity was investigated. A culture of Blepharisma americanum was exposed to varying concentrations of CM and the time elapsed until 50% cell mortality was determined. The cultures were standardized using solutions of Na iothalamate and/or Metrizamide. A standardized culture responded reproducibly between days 6 and 10 of the culture age. Comparison of concentrations of CM needed to achieve LD50 at 7 minutes ranked CM in order of decreasing toxicity as follows: oral cholecystopaques, intravenous cholecystopaques, and urographic agents; ie ionic monomers, ionic dimers, monovalent dimers, nonionic monomers, nonionic dimers. Comparison of CM toxicity determined by protozoa LD50 at 7 minutes with i.v. LD50 in mice showed a good correlation, suggesting usefulness of the protozoan assay as a complementary or screening toxicologic method.

Contrast Media↗
PubMedDate not supplied

Development and preliminary pharmacologic evaluation of a zwitterionic oral cholecystographic agent.

A new zwitterionic iodinated molecule, 2-[3-(N-ethyl-2-hydroxyethyl) amino-acetamido-2, 4, 6-triiodobenzyl]-butyric acid (RCK-136) was synthesized, and its potential as an oral cholecystopaque was tested. In rats, 15 minutes following intravenous injection, RCK-136 reached maximum biliary concentration; 84% of the dose was excreted into bile. Biliary excretion of RCK-136 elicited a strong choleresis (44 ml of bile flow per mmol compound). Intravenous LD50 in rats averaged 390 mgI/kg. ED50 in rats, intradiencephalic, averaged 1.98 mgI/kg. The average densities of cholecystograms produced in three dogs with iosumetic acid and/or RCK-136 were comparable.

Animals↗
PubMedDate not supplied

Evaluation of intrathecal contrast media by aversion conditioning in rats.

A method for quantification of aversion conditioning in rats was adapted to assess intrathecal neurotoxicity of contrast media (CM). Metrizamide, iopamidol, nonionic dimers DL-2-87 and DL-3-117, experimental iodophenyl glucose ethers DL-2-98 and DS-1-132, and Ringer's solution were injected into non-anesthetized rats drank water mixed with their preferred flavors, and subsequently were injected with 22.5 and/or 45 mgI/kg (200 and/or 400 mgI/ml concentration). From the intake of the preferred flavored water, expressed as percentage of total fluid intake consumed during a preference test and during a subsequent free choice test, a percentage avoidance/preference score was calculated as a measure of conditioning. At 12.5 mgI/Kg level, DL-2-87, which unexpectedly precipitated from solution in vivo, caused the most aversion, followed by metrizamide. The remaining compounds induced no significant aversion and were statistically indistinguishable from one another. At 45 mgI/kg dose level, all monomeric CM induced aversion of a statistically equal degree, while DL-3-117 proved nonaversive, equal to Ringer's solution.

Animals↗
PubMedDate not supplied

Brain changes on computed tomography following metrizamide myelography. Significance and therapeutic implications.

Three cases of seizures and marked behavioral changes that occurred after intrathecal metrizamide administration are reported. In each case a cranial computed tomographic scan obtained within 24 hours of the ictus showed hyperdensity of the gray matter, and created an optical illusion of diffuse white matter edema. The literature on adverse reactions and their pathogenesis and on brain parenchymal penetration of metrizamide is reviewed.

Adult↗
PubMedDate not supplied

Vasocilators in the canine mesenteric circulation. Evaluation of a potential aid in the diagnosis of gastrointestinal bleeding.

Radiodiagnostic potential of intra-arterially injected vasodialting agents was investigated by their effect on total and segmenal resistances (VR) of mesenteric vasculature, blood flow in superior mesenteric artery and its bleeding branch; heart rate and ventricular and systemic blood pressure. Dipyridamole, isoxsuprine, protricular and systemic blood pressure. Dipyridamole, isoxsuprine, prochlorperazine, lidocaine, meglumine diatrizoate and carbon dioxide were poor dilators. Phentolamine produced hypotension; glucagon and serpasil an extremely long dilation. A large and short vasodilation was produced with tolazoline and nylidrin, but both agents increased VR of the postcapillary segment and caused transient hypotension and arrhythmias, nylidrin's side effects were smaller. Oxygen produced large and long vasodilation and minimal systemic effects. It is concluded that oxygen or possibly nylidrin are suitable agents should an intermittently bleeding mesenteric artery be dilated for diagnostic purposes prior to angiography.

Animals↗
PubMedDate not supplied

Intravenous injection of ioxilan, iohexol and diatrizoate. Effects on urine profiles in the rat.

Effects of intravenous ioxilan, a new third generation non-ionic contrast medium, diatrizoate, iohexol and saline on urine profiles were compared. Albumin, glucose, sodium, phosphate, and the enzymes NAG, LDH and GGT were followed in 24 normal rats over 7 days. Diatrizoate significantly affected all profile components during the first two hours. Albuminuria was significantly greater after diatrizoate than after iohexol or ioxilan, and excretion of glucose, LDH and GGT was significantly higher than after ioxilan. Both iohexol and ioxilan increased the excretion of albumin, LDH and GGT, while iohexol also significantly increased excretion of glucose and sodium. There was a greater excretion of glucose and GGT after iohexol than after ioxilan. Saline did not induce any changes. At day 7, serum sodium, urea, creatinine, and albumin were normal for all test substances, and kidney histology revealed no difference between the groups of animals. It is thus concluded that both high osmolar ionic and low osmolar non-ionic contrast media may cause temporary glomerular and tubular dysfunction in rats. In this model, the kidney is affected most by diatrizoate, less by iohexol, and least by ioxilan.

Animals↗
PubMedDate not supplied

Iotrol, a new myelographic agent: 1. Radiography, CT, CSF clearance, and brain penetration.

Four new myelographic agents, metrizamide, iopamidol, iohexol, and iotrol, were studied in the subarachnoid space of cynomolgus monkeys. Plain films and computed tomographic scans documented the transport of each material throughout the space and into the brain. At the concentration used (300 mg I/ml), all gave good radiopacity for myelography and delineation of the cerebral subarachnoid space. All four cleared similarly from the ventricular system. Metrizamide, however, penetrated the brain in greater degree and persisted longer than the other three agents. Next in persistence was iopamidol and least, and both statistically equal, iotrol and iohexol.

Animals↗
PubMedDate not supplied

Iotrol, a new myelographic agent: 2. Comparative electroencephalographic evaluation by spectrum analysis.

Iotrol, a nonionic dimer isotonic with cerebrospinal fluid at 300 mg l/ml, was evaluated against metrizamide, iopamidol, and iohexol by electroencephalography (EEG) in nonanesthetized cynomolgus monkeys. Each of four monkeys was injected intrathecally with 0.5 ml/kg of 300 mg l/ml of each contrast medium. EEG was obtained before, 45 min, and 3 hr postinjection. EEG spikes, motor disturbances, convulsions, and behavior changes were observed. The EEG from C3 channel was also computer-analyzed. Average percentage differences between control and test energy content of the entire EEG and of the EEG spectrum subdivided into five frequency bands were calculated. With metrizamide, three animals suffered seizures, and all were lethargic and irritable. With iopamidol, two animals convulsed; all animals were lethargic. Transient apathy and motor disturbances were observed in the iohexol animals. No motor or behavior changes were produced by iotrol. Metrizamide and iopamidol increased the spectrum energy in all bands. Neither iohexol nor iotrol affected the EEG significantly. On the basis of these findings, iotrol holds promise as a clinical contrast material for the subarachnoid space.

Animals↗
PubMedDate not supplied

Investigation of a new arthrographic contrast agent: Iotrol.

A new nonionic dimer (Iotrol; Schering AG) and diatrizoate meglumine-diatrizoate sodium (Renografin-60; Squibb) were compared as arthrographic agents by injecting these substances into the knees of rabbits. Three experienced arthrographers judged the image quality produced by Iotrol to be superior to that of Renografin-60. Following animal sacrifice, histologic examination of the synovium revealed a significant difference in the inflammatory response evoked by the contrast agents: Iotrol caused less inflammation. In a second group of rabbits, methylprednisolone was subcutaneously injected 24 hours before the arthrographic studies. The methylprednisolone significantly reduced the inflammation in the Renografin-60 subgroup when compared with the nonmedicated counterparts. No significant effect was noted in a like comparison with Iotrol. In addition, the administration of methylprednisolone led to a deterioration of the radiographic images. Based upon our data, we believe Iotrol is superior to Renografin-60 as an arthrographic agent.

Animals↗