Paramagnetic metalloporphyrins: infarct avid contrast agents for diagnosis of acute myocardial infarction by MRI

In previous experiments in tumors we demonstrated that metalloporphyrins are particularly avid for nonviable tumor components. This study was performed to find out whether these agents can be used as MRI contrast agents for the visualization of acute myocardial infarction (MI). A total of 44 rats, 6 normal controls and 38 with occlusive MI (2-24 h old), were used. Gadolinium mesoporphyrin (Gd-MP) or manganese tetraphenylporphyrin (Mn-TPP) was intravenously injected at doses of 0.1, 0.05, and 0.01 mmol/kg. Three to 24 h after injection, axial and coronal T1-weighted (TR/TE 300/15 ms) spin-echo MR images were obtained before and after killing the animals and correlated with triphenyl tetrazolium chloride (TTC) histochemical preparations. The Gd-MP content in infarcted and noninfarcted myocardium was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES). MRI without contrast media could not discern the MI. However, 3-24 h after injection of either Gd-MP or Mn-TPP, the infarcted area was positively stained on MR images. This area matched well with the negatively TTC-stained area on the heart slices (r = 0.97). The contrast ratios between the infarcted necrotic myocardium and the noninfarcted regions varied from 150 to 300% depending on the type of agents and doses used. Neither false-positive nor false-negative findings were encountered. The metalloporphyrin concentration was more than 10 times higher in the infarcted than in the noninfarcted heart. Metalloporphyrins appear to be promising MRI contrast agents for detection and quantification of necrosis in MI. These preclinical results may open new perspectives in cardiac imaging.

Mapping and characterization of a sequential epitope on the rabies virus glycoprotein which is recognized by a neutralizing monoclonal antibody, RG719

We have established a murine hybridoma cell line RG719 which produces a rabies virus-neutralizing IgM-type monoclonal antibody (referred to as MAb RG719). Immunoblot analysis indicated that the antibody recognized a sequential epitope of G protein. Among four rabies virus strains tested, the antigenicity to MAb RG719 was absent from the Nishigahara strain, while the other three strains (HEP, ERA and CVS) reacted to the MAb. Studies with deletion mutants of the G protein indicated that the epitope was located in a middle region of the primary structure of G protein, ranging from position 242 to 300. By comparing the estimated amino acid sequence of the four strains, we found in this region two amino acids (at positions 263 and 291) which are common to three of those strains but are not shared by the Nishigahara strain. The site-directed point mutagenesis revealed that replacement of phenylalanine-263 by leucine destroyed the epitope of the HEP G protein, while the epitope was generated on the Nishigahara G protein whose leucine-263 was replaced by phenylalanine. These observations suggest that phenylalanine-263 is essential for constructing the epitope for MAb RG719. The synthetic 20-mer peptide produced by mimicking the amino acid sequence (ranging from amino acid positions 249 to 268) of the presumed epitope region was shown to bind specifically to MAb RG719 and also to raise the virus-neutralizing antibodies in rabbits. Vaccination with the HEP vaccine produced in Japan induced in humans and rabbits production of significant amounts of the antibodies which reacted with the 20-mer peptide.

Localization of metalloporphyrin-induced "specific" enhancement in experimental liver tumors: comparison of magnetic resonance imaging, microangiographic, and histologic findings

RATIONALE AND OBJECTIVES

We investigated the tumor specificity of gadolinium mesoporphyrin (Gd-MP) and manganese tetraphenylporphyrin (Mn-TPP) as magnetic resonance (MR) imaging contrast agents.

METHODS

Fifteen rats with multiple hepatocellular carcinomas and eight rats with implanted Novikoff hepatomas were given intravenous injections of either Gd-MP or Mn-TPP at 0.05 mmol/kg, which was compared with nonspecific gadopentetate dimeglumine (0.3 mmol/kg). T1-weighted spin-echo images were obtained before and up to 48 hr after injection and compared with corresponding microangiograms and histologic specimens. The relative enhancement of organs and tumors was plotted as a function of time.

RESULTS

Initially, both metalloporphyrins behaved as nonspecific agents, similar to gadopentetate dimeglumine, and enhanced the tumor by perfusion and diffusion. However, metalloporphyrins, but not gadopentetate dimeglumine, caused a delayed (> or = 3 hr) enhancement in some compartments of certain lesions. The MR imaging-microangiography-histology matching technique revealed that those compartments were actually nonviable components, including necrosis (n = 10), thrombosis (n = 7), and cystic secretion (n = 3), but not viable tumor tissue.

CONCLUSION

Metalloporphyrins did not prove to be tumor specific. However, the observed affinity for nonviable tissue has elicited other potential applications for these agents.

A comparative study of avian reovirus pathogenicity: virus spread and replication and induction of lesions

This study examined the relationship of avian reovirus spread and replication to induction of lesions and the relevant role of the S1 segment encoding a virus-neutralizing antigen. One-day-old broiler chickens were infected via footpad or orally with two virus strains (883 and 176) that differ greatly in virulence and a reassortant (R44) that has the S1 segment from 176 and the remaining genome segments from 883. Virus replication and histological lesions in various tissues (heart, liver, spleen, kidney, bursa, hock joint, and bone marrow) were measured at 2-day intervals until day 8 postinoculation. The virulent strain 176 spread to and replicated efficiently in all tissues examined and caused extensive and severe lesions, whereas the mild strain 883 was detected only in tissues near inoculation sites and caused only minimal lesions. The appearance of lesions correlated with the presence of viral replication in each tissue tested. Together, these results indicate that induction of lesions, or pathogenicity, is directly related to virus spread and replication. Reassortant R44 behaved like strain 176 in chicken embryo fibroblasts (CEFs), i.e., both replicated much faster and produced larger plaques than strain 883. In broiler chickens, however, R44 behaved like strain 883, replicating and inducing lesions to an extent that was fat lower than that of strain 176. These results suggest that the S1 segment alone is capable of determining viral replication and plaque formation in cultured CEFs but is not sufficient to determine the virus spread and replication and the pathological change in broiler chickens.

Effect of manganese dipyridoxal diphosphate on liver magnetic resonance imaging and serum bilirubin in rats with removable biliary obstruction

RATIONALE AND OBJECTIVES

It is known that manganese dipyridoxal diphosphate (Mn-DPDP) causes persisting liver enhancement in cholestatic rats, that free Mn++ plus bilirubin induces intrahepatic cholestasis, and that free Mn++ is released in vivo after Mn-DPDP injection. Hence, there is a concern about potential secondary intrahepatic cholestasis in patients who have biliary obstruction. In this study, we further investigated this issue.

METHODS

Removable total biliary obstruction (RTBO) was induced in 12 rats. Six of them (group A) received Mn-DPDP (25 mumol/kg). The others (group B) served as control animals. The data from serial magnetic resonance imaging and serum bilirubin tests were compared.

RESULTS

Without Mn-DPDP, a minimal increase of the liver intensity was observed in both groups because of cholestasis. In group A, the intensity of the liver was strongly enhanced with Mn-DPDP but normalized within 48 hr after removal of the obstruction. In both groups, total bilirubin levels increased up to 131.67 mumol/l 2 days after RTBO but rapidly decreased within 4 hr and almost normalized within 24 hr after removal of the obstruction, suggesting a lack of Mn-DPDP influence on the bilirubin level.

CONCLUSION

We found that Mn-DPDP did not cause secondary intrahepatic cholestasis. Retained Mn++ is likely eliminated after restoration of bile flow. These results indicate that Mn-DPDP can be used in patients who have obstructive jaundice as long as it is followed by successful bile drainage.

Potential role of bile duct collaterals in the recovery of the biliary obstruction: experimental study in rats using microcholangiography, histology, serology and magnetic resonance imaging

Obstructive cholestasis induced in animals at the level of the lobar and common bile ducts is known to be reversible with time. This study was conducted not only to test the hypothesis that formation of bile duct collaterals is responsible for the recovery of biliary obstruction but also to assess the potential of hepatobiliary agent-enhanced magnetic resonance imaging for visualizing cholestasis. A total of 52 rats were divided into three groups with selective biliary obstruction, total biliary obstruction and sham surgery. We studied the evolution of cholestasis by correlating microcholangiographic, histological findings with the results of liver tests and hepatobiliary agent-enhanced magnetic resonance imaging. Lobar cholestasis undetected by liver tests but seen on magnetic resonance imaging as a difference between ligated and unligated lobes, occurred in 15 out of 20 rats subjected to selective biliary obstruction within 48 hr after ligation, and recovered later on as a result of the development of bile duct collaterals. Five rats failed to show local cholestasis as a result of the existence of interlobar accessory bile channels. All 18 total biliary obstruction-treated rats were cholestatic soon after ligation, as confirmed by high serum bilirubin and alkaline phosphatase levels and as documented by poor liver enhancement on magnetic resonance imaging. Cholestasis recovered within 4 wk with normalization of liver enhancement on magnetic resonance imaging as a result of the formation of bile duct collaterals (as demonstrated by microcholangiographic and histological study). Bile duct collateral formation is responsible for the recovery from obstructive cholestasis in rats. A similar mechanism might be present in conditions of bile duct obstruction without cholestasis. Hepatobiliary agent-enhanced magnetic resonance imaging is more sensitive than blood tests in detecting local cholestasis and can be used to monitor noninvasively the evolution of biliary obstruction.

Influence of salinity on survival and infectivity of entomopathogenic: nematodes

Exposure to NaC1, KCI, and CaCl affected the entomopathogenic nematodes Heterorhabditis bacteriophora and Steinernema glaseri differently. Survival, virulence, and penetration efficiency of S. glaseri were not affected by these salts. At high concentrations, however, all three salts inhibited its ability to move through a soil column and locate and infect a susceptible host. Calcium chloride and KCl had no effect on H. bacteriophora survival, penetration efficiency, or movement through a soil column, but moderate concentrations of these salts enhanced H. bacteriophora virulence. NaCl, however, adversely affected each of these parameters at high salinities (>16 dS/m). Salt effects on S. glaseri are attributed solely to interference with nematode host-finding ability, whereas the NaCl effects on H. bacteriophora are attributed to its toxicity and possibly to interference with host-finding behavior.

Subgenomic S1 segments are packaged by avian reovirus defective interfering particles having an S1 segment deletion

Two subgenomic segments derived from the S1 genome segment (SGS1-1 and SGS1-2) were identified in avian reovirus defective interfering (DI) particle preparations having an S1 segment deletion. Both SGS1-1 and SGS1-2 were composed of double-stranded RNA (dsRNA) with an estimated size of 400 and 380 bp, respectively. Their segment of origin was identified as the S1 by hybridization analysis. The subgenomic segments were associated with the virus fraction following CsCl density gradient centrifugation, indicating that they are packaged. The subgenomic segments were also shown to be replicated. Therefore, sequence(s) required for replication and packaging are retained. The relative amounts of subgenomic segments were shown to be inversely proportional to that of the S1 segment. The presence of subgenomic segments and concurrent reduction in the relative amount of the S1 segment were found to be directly associated with the decrease in infectious titers. These results suggest that subgenomic segments are responsible for induction of interference by specifically competing with the S1 segment during replication and/or packaging. The competitive relationship between the subgenomic segments and the S1 segment implies that segment-specific sequence(s) or factor(s) are involved in the replication and/or packaging of each individual genome segment.

Prolonged positive contrast enhancement with Gd-EOB-DTPA in experimental liver tumors: potential value in tissue characterization

To evaluate the potential of the hepatobiliary magnetic resonance (MR) imaging contrast agent gadolinium EOB-DTPA (ethoxybenzyl diethylenetriaminepentaacetic acid) for the characterization of hepatic tumors, 79 primary and six implanted hepatomas in 38 rats were studied. MR imaging findings after administration of Gd-DTPA (0.3 mmol/kg) and Gd-EOB-DTPA (30 mumol/kg) were correlated with microangiographic and histologic findings. Gd-EOB-DTPA produced a strong liver enhancement, which caused prompt negative contrast enhancement (CE) in all implanted hepatomas and in 77 of 79 primary hepatomas. A positive CE that lasted up to 2 hours was found in two of 79 primary hepatomas, both of which were highly differentiated (grade I) hepatocellular carcinomas (HCCs). The rest were moderately differentiated to undifferentiated HCCs (grades II-IV). Rim enhancement, which corresponded histologically to peritumoral malignant infiltration sequestering normal hepatocytes, was seen around all implanted and some primary hepatomas. Positive tumor CE after administration of Gd-EOB-DTPA in this study is much less frequent but much more specific in comparison with the results of previous studies with manganese-DPDP (N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis[phosphate]). These findings may help further discriminate hepatic tumors.

Clinical observation of treatment of hypertension with calcium

The effect of oral calcium supplementation (1000 mg/day) on hypertension was studied in 57 borderline and mild-to-moderate hypertensive patients in a randomized, double-blind, placebo-controlled study for 14 weeks. Twenty-five patients from the above groups (11 from the calcium-treated group and 14 from the placebo group) were studied in a crossover fashion for 14 more weeks. The high calcium intake lowered systolic blood pressure by 17 mm Hg (P < .01), and diastolic blood pressure by 11 mm Hg (P < .01). Fifty percent of the calcium-treated patients showed a significant antihypertensive effect and were termed calcium responders. In the crossover study, serum sodium was lower after taking calcium than after placebo intake (P < .05). Pretreatment plasma free calcium content of the calcium-responsive patients was significantly lower (P < .05) than in the calcium nonresponsive patients, and was highly significantly increased (P < .01) after administering calcium. The result showed that oral calcium supplementation can lower blood pressure in a significant fraction of essential hypertensive subjects, and that the free calcium level in plasma may help identify calcium-responsive individuals. While the mechanism by which increased calcium intake lowers blood pressure in hypertension is still undetermined, these data support an underlying relationship between hypertension and calcium and possibly sodium metabolism.

MR imaging evaluation of liver enhancement by Gd-EOB-DTPA in selective and total bile duct obstruction in rats: correlation with serologic, microcholangiographic, and histologic findings

PURPOSE

To investigate the behavior and potential application of the hepatobiliary magnetic resonance (MR) imaging contrast agent gadolinium-ethoxybenzyl (EOB)-diethylene-triamine-pentaacetic acid (DTPA) in cholestasis.

MATERIALS AND METHODS

Rat models of selective biliary obstruction (SBO) (n = 20) and total biliary obstruction (TBO) (n = 14) were used. Serial Gd-EOB-DTPA-enhanced MR images were obtained, and the findings were correlated with serologic, microcholangiographic, and histologic findings.

RESULTS

In SBO rats, statistically significantly prolonged enhancement of ligated lobes occurred during the acute phase (P < .01) but was absent during the chronic phase owing to bile collateral vessels. In TBO rats, statistically significantly lower liver enhancement (P < .01) was observed as long as the obstruction persisted, until collateral bile ducts developed.

CONCLUSION

The distinction between obstructed and unobstructed liver on Gd-EOB-DTPA-enhanced MR images suggests a novel application for visualizing cholestasis.

Inhibitors of sterol synthesis. Tritium-labeled 26-hydroxycholesterol of high specific activity from a byproduct of the Clemmensen reduction of diosgenin

(25R)-26-Hydroxycholesterol (I) was synthesized in six steps from (22Z,25R)-cholesta-5,22-diene-3 beta,26-diol (II) in 31% overall yield. The 26-tert-butyldiphenylsilyl ether of II was converted via its 3 beta-tosylate to (22Z,25R)-6 beta-methoxy-26-(tert- butyldiphenylsilyloxy)-3 alpha,5-cyclo-5 alpha-cholest-22-ene (V). Removal of the 26-silyl group of V gave (22Z,25R)-6 beta-methoxy-3 alpha,5-cyclo-5 alpha-cholest-22-en-26-ol, which was hydrogenated over platinum oxide and then hydrolyzed to I. Catalytic reduction in the presence of deuterium or tritium gas gave [2H]-I or [3H]-I, respectively. Analysis of the [2H]-I by mass spectrometry showed that all the deuterium was located in the sterol side chain, mainly as d2, d3, and d4 species. The 2H and 13C nuclear magnetic resonance (NMR) spectra of [2H]-I indicated that most of the deuterium was located at C-22 and C-23, with lesser amounts at C-24 and minor amounts at C-20, C-21, C-25, and C-27. NMR spectra of [2H]-I and its alpha-methoxy-alpha-(trifluoromethyl)phenylacetate diester showed no detectable 20S epimer and approximately 2% of the 25S epimer. The [3H]-I was prepared analogously to [2H]-I using carrier-free tritium and showed a specific activity of 16.9 Ci/mmol. All synthetic intermediates were characterized fully by 1H and 13C NMR, and representative 1H-1H coupling constants are given for the ring A protons of i-steroids.

Effects of buffer pH and phosphate concentration on the droplet size and EYP hydrolysis of perflubron/EYP emulsions

Oil-in-water emulsions containing perflubron (perfluorooctyl bromide; PFOB) and stabilized with egg yolk phospholipid (EYP) have potential applications as contrast agents and oxygen carriers. In this study, the effects of buffer pH and total phosphate concentration on the emulsion droplet size and EYP hydrolysis were evaluated. 90% w/v perflubron emulsions with NaH2PO4-Na2HPO4 buffers of different pH (4.7-8.7) and phosphate concentrations (30 and 60 mM) were prepared with a high-pressure homogenizer. Emulsions were stored at 40 degrees C and tested at 0, 1, 2 and 3 months. The pH dropped quickly in emulsions with pH 8.7 buffer whereas acidic and neutral buffered emulsions exhibited minor pH drops. The concentration of free fatty acids (FFA) vs emulsion pH can be fitted to a parabolic curve with a minimum at about pH 6.0. The droplet growth rates in emulsions with the pH 4.7 buffer were about 2.5 times of those in emulsions with the pH 8.7 buffer. Total phosphate concentration had only a minor effect. This study emphasizes the importance of the careful selection of buffer pH and capacity to control EYP hydrolysis and possibly emulsion droplet size.

Effects of formulation, processing and storage parameters on the characteristics and stability of perflubron emulsion

In this study, the effects of formulation, processing and storage parameters on perflubron (perfluorooctyl bromide; PFOB) emulsions were investigated. Emulsions with varying concentrations of perflubron and egg yolk phospholipid (EYP) were prepared with different processing parameters and placed at different storage temperatures. Their characteristics and stability were compared. The emulsion droplet growth rate was nearly proportional to the perflubron percentage in the range of 15-110% w/v. The initial droplet size of perflubron emulsions was inversely proportional to the concentration of EYP until a certain lower limit of droplet size was reached. The initial droplet size and droplet growth rate of perflubron emulsion were strongly dependent upon the processing parameters. The logarithmic value of the droplet growth rate decreased linearly with l/T in the range of 5-40 degrees C. The formulation and processing parameters are the key variables to be optimized to achieve better emulsion characteristics and stability.

Experimental liver cancers: Mn-DPDP-enhanced rims in MR-microangiographic-histologic correlation study

During both animal and clinical studies with manganese (II) N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis(phosphate) (DPDP), enhanced rims around liver tumors on magnetic resonance (MR) images have been observed. To elucidate the origins of these rims and to assess their potential value in the differential diagnosis of liver masses, the authors studied 15 rats with induced hepatocellular carcinoma (HCC), 10 rats with implanted Novikoff hepatomas, and 11 rabbits with implanted VX2 carcinomas. A total of 69 primary and secondary liver cancers from these three animal models were studied. Mn-DPDP- and gadolinium tetraazacyclododecantetra acetic acid (DOTA)-enhanced MR images were compared. On the Mn-DPDP-enhanced images, 34 peritumoral rims of various patterns were displayed, all of which were exclusively related to the presence of highly malignant primary and secondary liver tumors. Peritumoral zones of malignant infiltration, surrounding parenchymal compression, and bile duct proliferation were seen to be the origin of these rims after comparison of MR images with the corresponding microangiograms and histologic specimens.

The uptake of manganese dipyridoxal-diphosphate by chemically induced hepatocellular carcinoma in rats. A correlation between contrast-media-enhanced magnetic resonance imaging, tumor differentiation, and vascularization

OBJECTIVES AND RATIONALE

Negative enhancement of implanted liver tumors has been achieved in preclinical studies on manganese dipyridoxal-diphosphate (Mn-DPDP), a new hepatobiliary specific contrast agent for magnetic resonance imaging (MRI). The authors investigated the effects of Mn-DPDP on primary liver cancer and its possible mechanisms.

METHODS

Magnetic resonance imaging was performed in 15 rats with chemically induced hepatocellular carcinoma (HCC) before and after Mn-DPDP injection. Both tumor-liver contrast-to-noise ratio and absolute tumor enhancement were evaluated and compared with the MRI results of a nonspecific contrast agent, gadolinium-DOTA, and correlated with corresponding microangiographic and histologic findings.

RESULTS

Mn-DPDP injection led to a persistent positive enhancement in differentiated solid HCCs (22/23) with maximal conspicuity at 24 hours. Undifferentiated HCCs were all delineated by a prompt negative enhancement (20/20) with maximal conspicuity within 30 minutes.

Characterization of avian reovirus-induced cell fusion: the role of viral structural proteins

Cell fusion induced by avian reovirus was analyzed using virus strain FC and Vero cells. One-step growth curves showed that cell fusion was directly associated with viral replication. Cell fusion occurred most efficiently at basic pH (8.0-8.5) and fusion from without could not be demonstrated. Actinomycin D, at low concentrations, increased cell fusion, and cycloheximide prevented cell fusion, indicating that viral protein(s) were responsible for the induction of cell fusion. Immunofluorescence tests indicated that viral proteins were present on the infected cell surface. Radioimmuno-precipitation identified structural proteins mu 2C and sigma 2 as predominant viral protein species present on the infected cell surface. Cell fusion was inhibited by virus-specific antisera, suggesting that mu 2C and/or sigma 2 present on the infected cell surface were involved in the induction of cell fusion. Trypsin and chymotrypsin treatment of purified viruses cleaved both mu 2C and sigma 2 proteins, but generated different cleavage products with each protein. The addition of trypsin to the culture media following infection increased cell fusion, whereas chymotrypsin treatment decreased cell fusion. The opposite effects of trypsin and chymotrypsin on the cell fusion, together with the different specificities of these two proteases in cleavage of mu 2C and sigma 2 proteins, further suggest that the cell surface-associated mu 2C and/or sigma 2 are involved in the syncytium formation.

Identification of proteins encoded by avian reoviruses and evidence for post-translational modification

Twelve avian reovirus strain 176 proteins, 10 structural (lambda 1, lambda 2, lambda 3, mu 1, mu 2/mu 2C, sigma 1, sigma 2, sigma 3, and sigma 4), and 2 nonstructural (mu NS and sigma NS) were identified and characterized by electrophoretic analysis of purified virions and infected cell lysates. Three of the identified proteins (mu 1, mu NS, and sigma 4) have not been previously described. In pulse-chase experiments, 10 of the proteins (lambda 1, lambda 2, lambda 3, mu 1, mu 2, mu NS, sigma 1, sigma 2, sigma NS, sigma 3) were shown to be primary translation products, whereas mu 2C was shown to be a post-translational cleavage product of mu 2.

Mn-DPDP enhanced MRI in experimental bile duct obstruction

To assess both the effect of Mn-DPDP as a hepatobiliary-specific contrast agent in bile duct obstruction and the relative role of liver and kidney in the elimination of this agent from the body, an animal experiment was set up. Twelve rats were used and divided into three groups. In group 1 the common bile duct was ligated, in group 2 bile duct ligation was limited to one lobe, and group 3 served as control. Magnetic resonance T1-weighted SE images were obtained before and after the injection of 25 mumol/kg of Mn-DPDP during the first 2 h and at day 1, 2, 3, 4, and, in some animals, up to 21 days. In normal rats the absolute enhancement signal-to-noise ratio (S/N) versus time plots obtained from the liver after Mn-DPDP injection returned to precontrast values within 24 h. In the group with common bile duct ligation, important liver enhancement persisted up to 21 days. In the group with selective obstruction, liver intensity normalized after 3 days. The S/N plots from spleen, renal cortex, and obstructed liver lobe showed similarities in time course. The present data indicate that Mn elimination is strongly impaired in the presence of bile duct obstruction. Renal glomerular filtration is ineffective in eliminating Mn from the body. The persisting splenic and renal cortical enhancement suggests that free Mn or some Mn-DPDP metabolite either is strongly bound to plasma proteins and acts as a blood pooling agent and/or is uptaken by the splenic or renal parenchyma.

Comparison between Gd-DTPA, Gd-EOB-DTPA, and Mn-DPDP in induced HCC in rats: a correlation study of MR imaging, microangiography, and histology

The behaviour of two liver-specific contrast MR agents, Gd-EOB-DTPA and Mn-DPDP and one nonspecific contrast agent, Gd-DTPA, was compared in a rat model of chemically induced hepatocellular carcinoma (HCC). The study included contrast enhanced MR imaging and the corresponding microangiography and histology. Analysis of the MR images showed similar degrees of maximum relative liver enhancement: 47.5 +/- 8.2% for Gd-EOB-DTPA (0.03 mmol/kg) at 5 min postinjection and 52.5 +/- 14.4% for Mn-DPDP (0.025 mmol/kg) at 15 min; both exceeded the value obtained with Gd-DTPA (34.8 +/- 13.6%, at 5 min), even at 0.3 mmol/kg. Gd-EOB-DTPA caused a similar "negative" enhancement of all types of HCC, independent of their differentiation and vascularization, i.e., lesion-to-liver contrast-to-noise ratio (CNR) of differentiated and undifferentiated HCC increased negatively from, respectively, 1.9 +/- 1.1 and -5.1 +/- 3.1 before contrast to -5.2 +/- 2.4 and -11.8 +/- 4.8 at 5 min after contrast. On Mn-DPDP enhanced images, the undifferentiated HCCs showed up negatively (CNR -5.5 +/- 4.7 before contrast to -13.7 +/- 10 at 15 min after contrast), whereas the more differentiated tumors showed up positively (CNR from 2.3 +/- 2.0 before contrast to 12.5 +/- 3.5 at 24 hr postcontrast) due to active uptake and delayed elimination of Mn-DPDP.

Strain-specific selection of genome segments in avian reovirus coinfections

To determine whether selection of genome segments in coinfections is strain-specific, chicken embryo fibroblasts were coinfected with avian reovirus strain 883 and one of three other avian reovirus strains (176, S1133 and 81-5). Viral progeny from each coinfection (883 x 176, 883 x S1133 or 883 x 81-5) was serially passaged at a low m.o.i. The electropherotypes of the coinfection progeny and those of the plaque-derived clones obtained from passages 1 and 20 were analysed. Two 883 segments (M2 and S2) were found to be selected in the 883 x 176 coinfection, three 883 segments (M2, M3 and S2) in the 883 x S1133 coinfection, and only one 883 segment (M3) in the 883 x 81-5 coinfection, i.e. different 883 genome segments were selected in the three coinfections. It was, therefore, concluded that selection of genome segments in a coinfection of a given cell line is virus strain-specific. The selection of genome segments in coinfections was shown to be due to enhanced infectivity of the reassortants that were formed in the coinfections. In addition, defective interfering particles that lack the S1 segment were identified in the 883 x 81-5 coinfection progeny following serial passage. Selection of genome segment(s) in coinfections as described herein may have potential importance on the effect and production of divalent or multivalent vaccines.

The thermostable direct hemolysin of Vibrio parahaemolyticus is a pore-forming toxin

The hemolytic mechanism of thermostable direct hemolysin (TDH), a possible virulence factor of Vibrio parahaemolyticus, was studied. We demonstrated that TDH acts as a "pore-forming toxin" in temperature-dependent and -independent steps. The first temperature-dependent step requires only about 1-2 min incubation at 37 degrees C and makes a "pore" with a functional diameter of approximately 2 nm. The pore size was deduced from the molecular diameter of the colloidal inhibitory polysaccharides. The formation of the pores on TDH-treated erythrocyte membranes was also demonstrated by electron microscopic examination. The second step, which is a temperature-independent lytic step, causes the erythrocytes to swell owing to a colloidal osmotic influx of water via the "pores" into cells, resulting in erythrocyte lysis (or rupture) owing to increased intracellular pressure.

Role of contrast agent perfusion and of diffusion in the NMR signal enhancement of liver lesions

Both perfusion and diffusion contribute to NMR signal enhancement after intravenous injection of a nonspecific contrast agent. In the present study the roles of perfusion and diffusion in the contrast enhancement of induced liver lesions in the rat and the rabbit were evaluated. This was done by comparing Gd-DOTA absolute enhancement signal-to-noise versus time plots of various lesions with the findings from microangiography and histology. Four types of enhancement could be recognized. Diffusion was the major factor in the delayed enhancement seen in lesions that had large extravascular diffusion space.

Magnetic resonance imaging, microangiography, and histology in a rat model of primary liver cancer

RATIONALE AND OBJECTIVES

N-nitrosodiethylamine is able to induce various benign and malignant liver lesions in rats with a high success rate and a low mortality rate. It provides a more appropriate model that better simulates the various lesions occurring in patients than the usual model of tumor implantations.

METHODS

Hepatic carcinogenesis was induced in 58 Wistar rats using oral N-nitrosodiethylamine. The rats subsequently were studied by liver magnetic resonance imaging (MRI), postmortem microangiography, and histologic examination.

RESULTS

Hepatic tumors developed in 57 rats. A wide variety of the tumors in the degree of vascularization, the type of vessels, the areas of intratumoral secretion and necrosis, and the tumor cell differentiation resulted from the tumor model. The authors were able to assess the contribution of the vascular, extravascular, and cellular components in the final pattern of contrast enhancement in MRI.

CONCLUSIONS

The N-nitrosoethylamine model for hepatic tumor induction is simple, and provides a more representative range of tumors for experimental evaluation.

Drop size stability assessment of fluorocarbon emulsions

The aging of fluorocarbon emulsions prepared with natural egg yolk phospholipids (EYP) has been studied and a linear variation (r2 greater than 0.95) of the mean average volume of the droplets with time has been observed. The slope of the experimental lines, called "Stability Parameter, S" can thus be taken as a representation of the rate of aging of the emulsions. Examples are given of use of parameter S to assess the effect of formulation and processing parameters on the stability of diverse fluorocarbon emulsions. S is a useful tool to compare emulsions and ascertain any factors of stabilization/destabilization.

A tissue culture model for studying ethanol toxicity on embryonic heart cells

A tissue system in which fibroblasts and myocytes from chick embryonic hearts were separately maintained was used to study the toxicity of ethanol. To reproduce the teratogenic effects of acute, high concentrations of ethanol typical of "binge" drinking, an open tissue culture system was employed. With open cultures, the cells were initially exposed to peak alcohol levels for approximately 6 hr and were exposed to decreasing concentrations of ethanol for the remainder of each 24 hr period. After the first day of ethanol exposure, there was substantial cell loss in both fibroblast and myocyte cultures. Alcohol-induced cell loss was dose-dependent. Despite decreased cell density after the first day of ethanol exposure, the surviving cells differentiated into monolayers of fibroblasts or beating cardiac muscle fibers. However, both ethanol-exposed fibroblasts and myocytes appeared atrophic, that is, smaller and shrunken. Electrophoretic analysis or these ethanol-exposed fibroblast and myocyte cultures revealed specific reduction in the cellular contents of alpha-actinin, myosin, and actin. These decreases in cytoskeletal proteins may be responsible for the morphological abnormalities noted in these cells.

Prolonged shelf stability and biocompatibility of a concentrated injectable fluorocarbon emulsion

A four-year-old 100% w/v concentrated emulsion of perfluorooctylbromide (PFOB, perflubron) stored at 5 degrees C, when submitted to the close-to-total exchange-perfusion test in conscious rats (Hct 3-5%) still resulted in 75% survival. Particle size and size distribution, viscosity, pH were still in the acceptable range.

Characterization of avian reovirus strain-specific polymorphisms

Avian reoviruses have been associated with several pathologic conditions, but correlative relationships between genotypes and specific diseases have not been demonstrated. Six avian reoviruses (883, 176, 81-5, S1133, FC, and TX) were selected for this study, and a comparative study of the pathogenic properties of the viruses in chickens, following peroral and footpad inoculation, was carried out, along with a comparison of the electrophoretic mobility of viral genomic segments and viral proteins encoded by the gene segments. The pathogenic properties of the viruses were shown to be diverse, with three distinct pathotypes being defined: Pathotype I (883) caused only a syndrome that we have termed "transient digestive system disorder" (TDSD); Pathotype II (FC, TX, and S1133) caused only "viral arthritis syndrome" (VAS), whereas Pathotype III (176 and 81-5) caused both TDSD and VAS. Likewise, the genomes of the viruses were shown to be extremely polymorphic, with a maximum of five segments co-migrating between any two strains. Considerable variation in the electrophoretic mobility of the encoded proteins also was demonstrated with pronounced variation in the molecular size of the sigma 4 protein, the purported viral attachment protein, being evident. These results show that the genomes of avian reoviruses were extremely polymorphic, preventing correlation between genotypes and pathotypes. But these studies have provided us with the genetic elements needed to characterize the gene functions involved in viral pathogenesis.

Futility of pericardiectomy for postirradiation constrictive pericarditis?

Two patients underwent pericardiectomy for postirradiation constrictive pericarditis. Both had received radiotherapy (more than 6,000 rads) for treatment of Hodgkin's disease 17 (patient 2) and 20 years (patient 1) earlier. At the time of operation, the patients were in New York Heart Association functional class III-IV or IV. Preoperative catheterization showed the following pressures for patients 1 and 2, respectively: right atrial, 30 and 14 mm Hg; right ventricular end-diastolic, 28 and 14 mm Hg; wedge, 29 and 13 mm Hg; and left ventricular end-diastolic, 27 and 14 mm Hg. Complete epicardiectomy and pericardiectomy was attempted in both patients. However, hospital mortality was 100%; patient 1 died of multiorgan failure after six days, and patient 2 died of biventricular failure after 3 months. A review of the literature revealed 44 cases of pericardiectomy for postirradiation constrictive pericarditis and a late survival rate of less than 50%. The poor results in these patients compared with patients having pericardiectomy for other reasons seem to be due mainly to the various kinds of radiation-induced damage to the heart as a whole, including untimely coronary artery disease, myocardial fibrosis, atrioventricular conduction disturbances, and valve dysfunction, with the result that complete relief by epicardiectomy and pericardiectomy may not be technically feasible.

Production of monoclonal antibodies against thermostable direct hemolysin of Vibrio parahaemolyticus and application of the antibodies for enzyme-linked immunosorbent assay

A total nine hybridoma cell lines that produced monoclonal antibodies against thermostable direct hemolysin (Vp-TDH), a possible pathogenic toxin, of Kanagawa phenomenon-positive Vibrio parahaemolyticus was isolated and characterized. These monoclonal antibodies (mAbs) were divided into a minimum of five different specificity groups, including mAbs specific to Vp-TDH and common to Vp-TDH and Vp-TRH, a Vp-TDH-related hemolysin produced by Kanagawa phenomenon-negative V. parahaemolyticus. An enzyme-linked immunosorbent assay (ELISA) using mAb-1-D, a mAb specific for Vp-TDH, was developed for specific detection of Vp-TDH. On the other hand, the ELISA using mAb-9-D, and mAb common to both Vp-TDH and Vp-TRH, could be used for detection of both Vp-TDH and Vp-TRH. Thus, by combining these two ELISAs differential detection of Vp-TDH and Vp-TRH can be performed. Hence, the two ELISAs were applied for various strains of V. parahaemolyticus and it was found that most Kanagawa phenomenon-positive and -negative clinical isolates produced Vp-TDH and Vp-TRH, respectively, but all environmental strains, that were Kanagawa phenomenon-negative, produced neither toxin.

Biological function of the rotavirus protein VP4: observations on porcine isolates from China

Rotaviruses isolated from pigs in China were grown in MA104 cells. One tissue-culture-adapted isolate consisted of two subpopulations (variants), the RNA profiles of which differed in the relative migration of RNA segment 4 only. The variants were separated by plaque purification and by recovery from limiting dilutions and remained genetically stable. The variant possessing the slower migrating RNA segment 4, called 4S, grew faster and formed large plaques after 4-6 days incubation, whereas the variant possessing the faster migrating RNA segment 4, called 4F, grew more slowly and formed only microscopic plaques after 10-14 days incubation. The protein product of the 4F RNA occurred in much lower concentration in infected cells than the product of the 4S RNA. The RNA segments 4 of the two variants were found to be closely related when tested by dot hybridization under stringent conditions. The 4S RNA is more resistant to denaturation with methyl mercuric hydroxide than is the 4F RNA. The relevance of these findings to the biological functions of rotaviruses is discussed.

Purification of a TDH-related hemolysin produced by a Kanagawa phenomenon-negative clinical isolate of Vibrio parahaemolyticus 06: K46

A hemolysin produced by a clinical isolate of Kanagawa phenomenon-negative Vibrio parahaemolyticus 06: K46 was purified by 55% ammonium sulfate fractionation and successive column chromatographies on DEAE-cellulose, hydroxyapatite, Sepharose 4B and Mono Q. The purified hemolysin was physicochemically and immunologically identical with the Vp-TRH (V. parahaemolyticus thermostable direct hemolysin related hemolysin) recently described in V. parahaemolyticus 03: K6 (Honda et al. Infect. Immun. 56: 961-965, 1988). This indicates that V. parahaemolyticus of Kanagawa-negative clinical isolates possessing not only 03: K6 but also different serotypes such as 06: K46 produce Vp-TRH. Production of Vp-TRH by most clinical isolates of Kanagawa-negative V. parahaemolyticus was also demonstrated. These results suggest the importance of Vp-TRH among clinical isolates of Kanagawa-negative V. parahaemolyticus.