Protein and DNA synthesis demonstrated in cell-free Ehrlichia chaffeensis organisms in axenic medium.

Ehrlichia chaffeensis, a tick-transmitted rickettsial bacterium, is the causative agent of human monocytic ehrlichiosis. Biochemical characterization of this and other related Rickettsiales remains a major challenge, as they require a host cell for their replication. We investigated the use of an axenic medium for E. chaffeensis growth, assessed by protein and DNA synthesis, in the absence of a host cell. E. chaffeensis organisms harvested from in vitro cultures grown in a vertebrate cell line were fractionated into infectious dense-core cells (DC) and the non-infectious replicating form, known as reticulate cells (RC) by renografin density gradient centrifugation and incubated in the axenic medium containing amino acids, nucleotides, and different energy sources. Bacterial protein and DNA synthesis were observed in RCs in response to glucose-6-phosphate, although adenosine triphosphate, alpha-ketoglutarate or sodium acetate supported protein synthesis. The biosynthetic activity could not be detected in DCs in the axenic medium. While the data demonstrate de novo protein and DNA synthesis under axenic conditions for E. chaffeensis RCs, additional modifications are required in order to establish conditions that support bacterial replication, and transition to DCs.

Comparison of Gastrografin to barium sulfate as a gastrointestinal contrast agent in red-eared slider turtles (Trachemys scripta elegans).

Red-eared slider turtles (Trachemys scripta elegans) commonly develop intestinal obstruction. The gastrointestinal transit time in turtles tends to be longer than in other animals, making a rapid diagnosis of obstruction difficult. Fifteen red-eared sliders were given either Gastrografin or 30% w/v barium sulfate orally to compare ease of administration, transit time, and image quality. Each contrast medium was easy to administer but barium sulfate had to be administered more slowly (mean = 40s) than Gastrografin (mean = 20s) to prevent regurgitation. The mean transit and emptying time of Gastrografin was at least 9 h faster than barium sulfate at all time points except gastric transit. Both contrast media had a smooth, uniform appearance that outlined the mucosa with well-defined margins within the stomach and proximal small intestine. Dilution of Gastrografin occurred as it progressed through the intestines, resulting in decreased opacity in the distal small intestine and colon. Pre-administration packed cell volume and total serum protein levels of four turtles receiving Gastrografin were compared with levels at 24-, 96-, and 168-hours postadministration as well as to four control turtles not receiving contrast medium. Packed cell volume and total serum protein levels did not significantly differ among the Gastrografin and control group. From a clinical perspective, administration of Gastrografin allows for quicker results with only minor hematologic changes in red-eared sliders, but visualization of this contrast medium in the lower gastrointestinal tract may be insufficient for an accurate diagnosis.

Calcium binding by gadolinium-based MR contrast agents.

PURPOSE: This study was conducted to characterize the alterations in ionic sodium, potassium, and calcium by gadolinium-based MR contrast agents. MATERIALS AND METHODS: An electrolyte solution (ES) containing 1.2 mM/L calcium ions,120 mM/L sodium, and 4.0 mM/L potassium were diluted with various gadolinium compounds and alterations in ionized electrolytes were measured using an ion-specific electrometer. Gadolinium compounds including Gd-DTPA, Gd-DOTA, gadoteridol, gadodiamide, meglumine/sodium diatrizoate (76% Urografin), and isotonic saline as a control were investigated. The dilution ranged from 5% (ES/test solution = 100/5) to 100%. Alterations of ionic electrolytes were measured. Calcium-binding capacities caused by each gadolinium compound also were measured. RESULTS: The alterations of ionic sodium and potassium by gadolinium compound were similar to those of isotonic saline. A significant reduction in ionized calcium was observed with Gd-DTPA and Gd-DOTA in comparison with gadoteridol and gadodiamide. CONCLUSION: Ionic gadolinium compounds induced significant reductions of calcium ions in vitro compared with non-ionic gadolinium compounds.

[The effect of cimetidine on the renal excretion of verografin and iodamide in dogs]. / Vliianie tsimetidina na pochechnuiu ékskretsiiu verografina i iodamida u sobak.

The intravenous injection of cimetidine in a dose of 20 mg/kg enhanced verografine and iodamide excretion in chronic canine experiments. The higher verografine and iodamide excretion was due to their increased renal tubular secretion. In dogs, cimetidine unchanged the secretion of cardiotrast, a test agent for anionic transport. Possible extrarenal mechanisms of action of cimetidine on verografine and iodamide transport were also examined.

Vicarious excretion of intravenous diatrizoate (Urograffin) in renal insufficiency: report of two cases.

Two cases of hepato-biliary excretion of intravenous sodium and meglumine diatrizoate (Urograffin 76%) are presented. One of these patients showed specification of of the gallbladder and colon while in the other case only the gallbladder was specified. In both cases there was marked deterioration of renal function. A brief review of the literature on hepatobiliary excretion of intravenous sodium and meglumine diatrizoate is given.

Evaluation of hepatic density change by dynamic CT in healthy humans and in patients with chronic liver diseases.

Dynamic computed tomography using 0.4 ml/kg of 65% meglumine diatrizoate was performed to estimate pharmacokinetics of contrast media in the liver in healthy controls (N = 11), in patients with chronic viral hepatitis (N = 17), posthepatic liver cirrhosis (N = 21), and alcoholic liver cirrhosis (N = 23). The time of peak enhancement (the time interval between peak aortic and liver enhancement) was significantly different between each group. Alcoholic liver cirrhosis was the most prolonged, followed by posthepatic liver cirrhosis, chronic viral hepatitis, and finally controls. A peak enhancement time of 28 sec had a diagnostic accuracy of 97% for chronic liver diseases. A time greater than 44 sec had a diagnostic accuracy for cirrhosis of 96%. The decay time (the time from peak enhancement of the liver to the curve's center of gravity) was also significantly different between each group. Again, alcoholic liver cirrhosis was the longest, followed by posthepatic liver cirrhosis, chronic viral hepatitis, and then the controls. Dynamic computed tomography has many potential applications in studying intrahepatic physiologic events and may contain diagnostic information for chronic liver diseases.

Vicarious gastric excretion of intravenous contrast.

Radiographic identification of vicarious excretion of intravenous contrast into the stomach has not previously been cited in the literature. We report here an instance of gastric excretion of iodinated intravenous contrast following excretory urography in a severely burned patient. The physiology and possible pathways of vicarious excretion of contrast are discussed.

Electric modification of kidney function. The excretion of radiographic contrast media and adriamycin.

The body consists of systems of conductive pathways for ionic flow of current induced by metabolic or injury potentials among tissues and cells. In vivo electrophoresis in biologically closed electric circuits (BCEC) are coupled to the mechanical transports of blood and lymph. Connections also exist with conductive media such as cerebrospinal fluid, bile, and urine. Artificial induction of current was applied over the kidneys in order to study modification of kidney function. It is thought that studies of this kind will increase our understanding of kidney function from a new angle of view and possibly add new therapeutic possibilities. In anesthetized pigs, one kidney was made anodic (electropositive) and the other cathodic (electronegative). Current was applied between electrodes in each ureter. Intravascularly injected, electronegatively charged aminotrizoate and ioxaglate were excreted mainly by the anodic kidney. Nonionic iohexol was urographically excreted by both kidneys. Excretion of electropositively charged Adriamycin by the cathodic kidney was identified macroscopically and by chemical analysis. Functional effects on the kidneys can be induced electrophoretically without causing injury.

Gallbladder opacification in infants following high dose angiocardiography.

Seven infants in congestive heart failure underwent high dose angiocardiography for diagnosis of severe congenital heart disease and subsequently displayed delayed opacification of the gallbladder. Biliary excretion of sufficient volume to opacify the gallbladder occurred despite structurally normal kidneys and no evidence of renal failure. Decreased renal clearance of contrast due to generalized diminution of glomerular filtration is postulated. The high doses of contrast and slow renal clearance allowed a relatively increased rate of hepatobiliary excretion and subsequent observation of the opacified gallbladder on abdominal radiographs. This phenomenon may not be as uncommon as is generally thought but its timing and location often do not allow an opportunity to make this observation.

Absorption and excretion of dilute gastrografin during computed tomography in pseudomembranous colitis.

Since 1955, urinary tract opacification secondary to absorption of orally or rectally administered iodinated contrast material has been recognized. Previously reported cases have involved relatively large volumes of full strength contrast necessary for fluoroscopic examination of the gastrointestinal tract. Our purpose is to report a case of urinary tract opacification in a patient who received a small amount of oral contrast in a dilute solution as preparation for computed tomography examination.

Hypernickelemia following coronary arteriography, caused by nickel in the radiographic contrast medium.

Meglumine diatrizoate ("Renografin-76", a radiographic contrast medium) contains sufficient nickel to cause hypernickelemia in patients after coronary arteriography. Nickel analyses by electrothermal atomic absorption spectrophotometry showed that nine lots of "Renografin-76" (760 g of meglumine diatrizoate per L) contained 144 +/- 44 micrograms Ni per L. Serum Ni concentrations became elevated in 11 patients after coronary arteriography (Ni dose = 19 +/- 4 micrograms per patient); peak Ni concentrations (increment = 1.8 +/- 0.4 micrograms Ni per L) occurred 0.25 or 0.5 h post-injection. Serum Ni concentrations diminished at 2 and 4 h post-injection and returned to base-line values at 24 h. The half-time (T1/2) for reduction of serum Ni concentrations averaged 1.5 h. Analysis of urine specimens from two patients showed that most of the Ni dose was excreted in urine within 24 hours. After iv administration of meglumine diatrizoate to rabbits (0.5 or 1.0 micrograms Ni per kg body wt), T1/2 values for elimination of Ni from the serum volume averaged 1.2 h, compared to T1/2 values of 5.7 and 7.4 h, respectively, when Ni was administered iv in NiCl2 or albumin solutions. Since "Renografin-76" contains edetate disodium (0.4 g per L), Ni is probably present as a Ni-EDTA complex, accounting for the rapid elimination of Ni following iv administration of the contrast medium to patients and rabbits. To reduce possible hazards of allergic or cardiovascular reactions to nickel, the authors recommend that Ni concentrations in radiographic contrast media should not exceed 10 micrograms per L.

Clinical comparison of Hexabrix, iopamidol, and Urografin-60 in whole body computed tomography.

Urografin 60, iopamidol and Hexabrix were studied in patients undergoing body CT scans to examine the pharmacodynamics of these contrast agents. Immediately following rapid injection, the lower osmolality media, Hexabrix and iopamidol, gave greater aortic concentration of iodine in addition to higher concentrations in the liver and spleen. These two agents also provided significantly better renal enhancement than Urografin 60, with Hexabrix giving higher levels than iopamidol. The higher early vascular concentrations of Hexabrix and iopamidol and the relative absence of side effects due to hyperosmolality and decreased toxicity may have advantages in dynamic CT scanning.

Blood-brain barrier disruption due to cerebral arteriography: CT findings.

Computed tomography was performed in two cases of blood-brain barrier (BBB) disruption due to cerebral arteriography. The first case showed diffuse contrast enhancement in the right frontotemporal region in the distribution of the middle cerebral artery; in the second case patchy contrast enhancement in both gray and white matter of both hemispheres was demonstrated. The possible mechanism for BBB disruption in these patients is discussed.

Mechanism of renal excretion of various X-ray contrast materials in rabbits.

The excretory behavior of nine nephrotropic contrast agents with varying physicochemical properties such as charge, lipophilicity, and molecular size was investigated. Renal clearance in comparison with inulin was determined by means of the continuous infusion method. Each contrast agent was infused at three dose levels in four to six rabbits. The investigations show that tubular transportation in proportion to glomerular filtration decreases with increasing dosages of all the contrast agents. Thus, with the highest concentration in plasma all contrast agents are eliminated at more or less the glomerular filtration rate (GFR). After administration of the low dosages the following differences are found: 1) Net tubular secretion increases for the monomeric contrast agent acids with increasing lipophilicity, in the order diatrizoate congruent to iothalamate less than iodamide less than acetrizoate. 2) The clearance studies do not reveal any tubular secretion or reabsorption for a hydrophilic cationic contrast agent. 3) The nonionic contrast agents do not show net secretion. The more lipophilic they are, the more they are reabsorbed. 4) Two dimeric contrast agents also do not reveal any tubular secretion. They seem to be reabsorbed more than monomers with the same charge.

Excretion of contrast media by the immature rabbit. Comparison of Renografin and Iopamidol.

The excretion of iodinated contrast media was studied in 13 immature rabbits after the intravenous injection of 2 ml/kg (approximately 600 mg I/kg) of radio-labelled Renografin-60, a high osmolality agent (1510 mOsm/kg), or Iopamidol-300, a new agent with a much lower osmolality (616 mOsm/kg). Renografin, but not Iopamidol, induced an immediate but transient 40% fall in blood pressure, a marked diuresis that was 3.4 times greater at its maximum than for Iopamidol, and a much lower urinary iodine concentration at the time of maximum diuresis (Renografin: 90.3 +/- 9.2 microgram/ml; Iopamidol: 213 +/- 32.9 microgram/ml). No difference between the two contrast media was found for plasma iodine concentration, renal clearance from the plasma, urinary iodine excretion rate or volume of distribution. In five additional rabbit pups, formal clearance studies made using a constant IV infusion of the agents and timed collections of urine and plasma showed that Iopamidol and Renografin were cleared at the same rate by the kidneys (P greater than 0.9).

Myocardial contrast two-dimensional echocardiography: comparison of contrast disappearance rates in normal and underperfused myocardium.

A computer algorithm was developed and applied to measure brightness decay rates of myocardial contrast opacification observed with two-dimensional echocardiography (2DE). An agitated mixture of diatrizoate meglumine and saline (Renografin-saline) was injected into the left main coronary artery of 17 closed-chest dogs during the control state as well as after placement of an intracoronary plug to induce 85% stenosis in the left anterior descending coronary artery (LAD) in five dogs. In 12 dogs, injections were also performed distally to complete intracoronary balloon occlusion of the LAD. For each injection, up to 35 electrocardiographic-gated, end-diastolic 2DE frames were digitized into an image-processing computer that determined mean pixel brightness of each of 12 myocardial segments per 2DE short-axis cross-section. Time-activity curves for each segment were generated, and contrast decay half-life (t 1/2) was calculated. Mean t 1/2 for control-state injections was found to be 24.1 +/- 7.7 sec, as opposed to 293.8 +/- 164.5 sec after complete coronary occlusion (p less than .001). In the five dogs in which 85% LAD stenosis was induced, prolongation of contrast t 1/2 from 18.3 +/- 8.9 sec during control to 44.3 +/- 21.0 sec (p less than .001) after plug insertion occurred in myocardial segments subserved by the stenosed vessel. No significant change occurred in segments that were not supplied by the stenosed vessel (21.9 +/- 9.1 sec during control vs 24.9 +/- 11.6 after plug insertion into the LAD). A reproducibility study of injection-to-injection t 1/2 in the control state indicated a correlation coefficient of r = .84 and a standard error of the estimate (SEE) equal to 5.86 sec, while interobserver t 1/2 reproducibility was r = .91 and SEE = 5.21 sec. The t 1/2 measurement derived by computer analysis of myocardial contrast 2DE may serve as an index for characterization of regional myocardial blood flow and may be applicable to evaluate interventions that alter perfusion.