Suppression by phenobarbital of ethionine-induced hepatocellular carcinoma formation and hepatic S-adenosylethionine levels.

An 18-month carcinogenicity study was conducted in male weanling F344 rats (28/group) to examine the effects of the simultaneous feeding of selected concentrations of ethionine and 0.05% phenobarbital in a normal chow diet. The effects of a 1-6-week feeding of phenobarbital and ethionine on the hepatic levels of the related metabolites S-adenosylmethionine, S-adenosylhomocysteine and S-adenosylethionine were also examined. Ethionine at 0.3% or 0.1% induced hepatocellular carcinoma (HCCa) at incidences of 90% (19/21) and 89% (24/27), respectively. Adding phenobarbital to the 0.1% ethionine diet reduced the incidence of HCCa to 36% (10/28) and reduced the number of liver tumor-associated deaths occurring prior to terminal sacrifice from 10/27 to 1/28. No hepatic tumors were observed in rats fed 0, 0.003, 0.01, or 0.03% ethionine. Phenobarbital alone or combined with 0.03% ethionine produced no hepatic tumors. Dietary ethionine at 0.1% reduced the intracellular hepatic level of S-adenosylmethionine to <50% of that seen in control rats. Phenobarbital alone had little effect on either S-adenosylmethionine or S-adenosylhomocysteine levels. The combination of phenobarbital and 0.1% ethionine led to increases in the hepatic levels of S-adenosylmethionine of 40-60% after 3 and 6 weeks of feeding, compared to those seen in rats receiving 0.1% ethionine alone. Ethionine feeding resulted in high levels of S-adenosylethionine in the livers. Combining phenobarbital with ethionine in the diet led to 30-50% reductions in hepatic S-adenosylethionine content. The results indicate that phenobarbital inhibits hepatocarcinogenesis by ethionine, that ethionine may cause HCCa via methyl group insufficiency, and that at levels of < or =0.03% ethionine did not show evidence of tumorigenicity.

Personality types of flight crew members in a hospital-based helicopter program.

PURPOSE: To determine the personality preferences of flight crew members in a hospital-based helicopter emergency medical service (HEMS) using the Myers-Briggs Type Indicator (MBTI), and to differentiate and compare these preferences between crew specialties and a historical control population. METHODS: A prospective cohort study was conducted of all active crew members (nurses, respiratory therapists and pilots) in a hospital-based flight program. Data collected included the results of the MBTI, gender, age and years of flight experience. RESULTS: Crew members were represented by 14 of 16 possible MBTI personality types, with three types predominating. For each crew specialty, extroversion preferences predominated over introversion, and perceiving characteristics predominated over judging characteristics. Differences existed by crew specialty for the sensing-intuition and thinking-feeling dimensions. CONCLUSIONS: A personality typology has been established for individual and group preferences within one hospital-based HEMS program. This data begins to develop a data base and an investigative protocol for understanding some of the human factors regarding flight programs. Future research should focus on expanding the data base and exploring specific crew interactions based on additional diagnostic and evaluative methodologies.

S-adenosylmethionine, S-adenosylhomocysteine and DNA methylation levels in the liver of rats fed methapyrilene and analogs.

The antihistamine methapyrilene (hydrochloride) and four close structural analogs, methaphenilene, methafurylene, thenyldiamine and clorothen, were given to rats at a concentration of 0.1% in drinking water for 34 weeks. Only methapyrilene produced notable histopathological changes in the liver, bile duct hyperplasia and focal cellular change. Methapyrilene produced an early and persistent elevation in the ratio of S-adenosylmethionine to S-adenosylhomocysteine, which was 2.8 times the control levels at 34 weeks; none of the other antihistamines produced so high a ratio or altered the ratio as early. Methapyrilene, but not the other antihistamines, produced a significant increase in the methylation of liver DNA at 20 and 34 weeks, as measured by the level of 5-methyldeoxycytidine. The increase in deoxycytosine methylation is so far the only detected effect of the carcinogen methapyrilene on DNA which is absent in rats treated with its non-carcinogenic analogs.

In vitro comparisons of SENCAR and BALB/c primary epidermal cells.

Grafting experiments show that the enhanced sensitivity of the SENCAR mouse to skin carcinogenesis by initiation and promotion is a property of the skin itself, suggesting the usefulness of in vitro studies to elucidate the mechanism. Such studies have indicated that cultured epidermal cells of SENCAR mice and the resistant BALB/c strain are remarkably similar in a variety of respects. DNA repair and carcinogen binding are quantitatively similar in cultured cells of SENCAR and more resistant mouse strains. Epidermal Langerhans cell (LC) number and LC-mediated functions were indistinguishable in SENCAR and BALB/c mice. Primary epidermal cells cultured in the presence of various concentrations of 12-O-tetradecanoylphorbol-13-acetate (TPA), retinoic acid, epidermal growth factor (EGF), hydrocortisone, or fluocinolone acetonide failed to reveal differences in growth between BALB/c and SENCAR cells. Cells from these animals bound comparable amounts of EGF with similar kinetics, and the modulation of this binding by TPA and retinoic acid was indistinguishable between strains. Spontaneous expression of infectious, endogenous xenotropic type C RNA virus at very low levels could be demonstrated in primary BALB/c epidermal cells and both BALB/c and SENCAR epidermal lines resistant to Ca2+-induced terminal differentiation. The number of foci of initiated cells after exposure to carcinogens in vivo or in vitro did not differ significantly between SENCAR and BALB/c, suggesting that SENCAR sensitivity is primarily to promotion. However, there are qualitative differences between SENCAR and BALB/c foci. The appearance of foci of cells resistant to terminal differentiation in untreated SENCAR cultures supports the evidence from in vivo studies for the existence of a constitutively initiated cell population in SENCAR mouse skin.

Selecting a treatment for primary varicose veins.

The treatment of varicose veins includes injection/compression sclerotherapy and surgical stripping or ligation or both. Surgery appears to be favoured when the saphenous system is involved or when the patient is 35 to 64 years old or presents with ankle edema or flare. On the other hand, sclerotherapy has been found to be more effective in patients with dilated superficial veins or incompetent perforating veins in the lower legs and to be more acceptable and less expensive than surgical treatment.

PIP: At present 3 treatment alternatives for primary varicose veins are available: surgical stripping and ligation, injection/compression sclerotherapy, and a combination of the 2. At least 4 factors contribute to the decision of whether to treat the patient: pregnancy, obesity, oral contraceptive (OC) use, and age. Since varicose veins in pregnant women may later recede, only palliative treatment is recommended before delivery. Deep vein thrombosis may develop as a result of OC use during varicose vein treatment, leading some to advise OC discontinuation. Numerous clinical trials have endeavored to examine the relative effectiveness of treatment methods currently in use. The only randomized trial to evaluate all 3 treatment options over a 3-year period found that surgical stripping was significantly more effective than a combination of ligation and sclerotherapy, and that the combination was significantly more effective than sclerotherapy alone. Surgery appears to be the recommended treatment when the saphenous system is involved; surgery is also preferred for patients 35-64 years of age and for those presenting with signs of ankle edema and flare. Sclerotherapy seems to be more effective for dilated superficial veins and incompetent perforating veins in the lower leg. In addition, sclerotherapy is the most acceptable and least expensive method for the patient. The prevalence of primary varicose veins has been estimated at 20% in Europe and North America, with a female:male ratio of 5:1.

Disparate response of encephalomyocarditis virus and MM virus to interferon in JLS-V9R cells.

JLS-V9R cells, a Balb/c mouse bone marrow cell line chronically infected with Rauscher leukemia virus, were treated with mouse interferon and inoculated with several different lytic viruses. Relatively low interferon concentrations protected the cells against Sindbis virus, vesicular stomatitis virus and MM virus. In contrast, encephalomyocarditis virus replication was inhibited by less than 1 log even with an interferon concentration of 1000 U/ml. These findings provide further evidence that interferon-induced antiviral effects are mediated through multiple mechanisms and demonstrate that even viruses which are classified within the same family (MM and encephalomyocarditis virus) can exhibit differential interferon sensitivities.

Susceptibility determinants for mouse epidermal carcinogenesis.

SENCAR mice are markedly more susceptible to two-stage skin carcinogenesis than BALB/c mice. Studies were carried out to elucidate the basis for this sensitivity. It is not related to differences in the metabolism of polycyclic aromatic hydrocarbons (DiGiovanni et al., 1980) but appears to be determined by the target tissue, since when SENCAR skin was grafted onto nude mice they developed papillomas at a high frequency after initiation and promotion, whereas after grafting of BALB/c skin, no tumours developed. DNA repair capacity was studied in SENCAR and BALB/c epidermal cells in culture. Host cell reactivation, utilizing ultra-violet light-irradiated herpes simplex virus, was similar in cells of the two strains. SENCAR cells have a greater binding capacity for epidermal growth factor than BALB/c cells; however, the increased binding in response to retinoic acid and the rapid decrease after exposure to phorbol esters are similar in the two strains. Spontaneous expression of endogenous proviral DNA sequences for xenotropic-type C RNA viruses occurs more readily in BALB/c epidermal cells than in those of SENCAR. The frequency of spontaneous differentiation-resistant foci in vitro (Kulesz-Martin et al., 1980) is greater in SENCAR than in BALB/c epidermal cells. These results suggest that susceptibility for skin carcinogenesis in SENCAR mice is determined by the target tissue itself and has no clear relation to DNA excision repair, endogenous virus complement or epidermal growth factor receptors.

Spontaneous adrenal tumors in the aged, ovariectomized NIH swiss mouse without enhanced retrovirus expression.

A high incidence of adrenal tumors was observed in aged female NIH Swiss mice which had been ovariectomized at 2 to 4 weeks of age but not in nonovariectomized controls. Although tumors weighing more than 1 g were not infrequent in the oldest (> 24 months) animals, adrenal glands did not appear macroscopically abnormal before the age of 18 months. Histologically, however, focal or diffuse abnormalities were found in essentially every gland examined from mice over 12 months of age, including glands of normal size. Since the NIH Swiss mouse has been shown to contain an endogenous xenotropic virus whose expression is under hormonal control, the adrenal tumors were examined in detail for evidence of abnormal viral expression. We were unable, by a variety of techniques, to demonstrate elevated expression of type C virus in these adrenal tumors.

Protection against 7, 12-dimethylbenz[a]anthracene-induced rat mammary carcinoma by infection with mouse xenotropic type C virus.

A single ip inoculation of female, outbred Sprague-Dawley rats with a viable mouse xenotropic type C virus significantly reduced the incidence and/or retarded the development of mammary carcinoma induced by 7, 12-dimethylbenz[a]anthracene administered orally 7 days after virus. Although infectious virus could not be isolated from organs of infected rats, high titers of circulating and tumor-associated antibodies were detected against the viral internal core protein p30, and a low-grade antibody response to intact virus or envelope glycoprotein was found. Moreover, a cell-mediated immune response, measured by lymphocyte transformation, was detected with the use of intact virus but not with p30 antigen. No immunity developed after a single inoculation of UV-inactivated virus. These data indicated that inoculation of adult individuals of heterologous species with viable xenotropic mouse type C virus resulted in the rapid disappearance of infectious virus from the recipient, followed by the development of both humoral and cellular immunity to virion constituents. These events led, by unknown mechanisms, to the effective retardation of chemical carcinogenesis when infection preceded carcinogen administration.

Evidence that detergent-reactivated interferons are not renatured.

The sedimentation rate of human leukocyte interferon (HLIF) reactivated from sodium dodecyl sulphate (SDS) solution was studied by glycerol gradient centrifugation and compared to that of native HLIF. Reactivated HLIF consistently sedimented faster than native HLIF, indicating that full recovery of antiviral activity does not require renaturation of the entire interferon molecule.

Differential sensitivity of Rauscher murine leukaemia virus (MuLV-R) to interferons in two interferon-responsive cell lines.

The effect of interferon on the replication of vesicular stomatitis virus (VSV) and type-C oncornavirus in two Balb/c mouse cell lines, JLS-V5 and JLS-V9R, infected with MuLV-R was examined. VSV replication was inhibited threefold (0-5 log10) in both cell lines by 10 to 20 units of interferon/ml. In JLS-V5 cells C-type virus yields, as measured by 3H-uridine incorporation and reverse transcriptase activity, were also reduced threefold by 10 to 20 units of interferon/ml. However, in JLS-V9R cells, C-type virus replication was refractory to interferon at concentrations up to 1 x 10(4) units/ml. Infectious C-type virus transmitted from JLS-V9R cells to Balb/3TS cells was as sensitive to interferon as virus transmitted from JLS-V5 cells, indicating that resistance of C-type virus in JLS-V9R cells is a feature of the cells rather than of the virus strain.

Influence of interferon on the synthesis of virus particles in oncornavirus carrier cell lines. IV. Relevance to the potential application of interferon in natural infectious diseases.

That interferon reduced the release of C-type oncornavirus particles by chronically infected mouse cells was shown by radiolabeling of the particles with uridine or amino acids and by determination of particle-associated reverse transcriptase. The number of released particles, as determined by direct electron microscopic enumeration, was reduced to a lesser extent. In contrast, interferon failed to affect the number of budding particles and caused a slight increase in the number of completed particles present in the microspace contiguous to the cell membranes. A working hypothesis is that, in the presence of interferon, C-type particle assembly and release are slowed but not arrested; sizable numbers of particles continue to be assembled and released. Some of these particles may be defective in one or more proteins, such as reverse transcriptase or proteins necessary for final release. These in vitro data justify speculation that, in vivo, interferon may be expected to reduce tissue damage due to antigen-antibody complex formation, but not damage due to sytolytic immune attack on cells carrying the antigens.

Effect of medium of lowered NaCl concentration on virus release and protein synthesis in cells infected with reticuloendotheliosis virus.

When cultures producing reticuloendotheliosis virus were incubated for 24 h in medium of lowered NaCl concentration, virus production was inhibited. The extent of inhibition increased as the salt concentration of the medium was decreased. The inhibition was rapidly reversed by replacement of low-salt medium with normal medium. During the first hour after the inhibited cultures were returned to normal medium, virus was released at an accelerated rate, making the total amount of virus released by inhibited and control cultures the same. After 1 h in normal medium, the rate of virus production in the previously inhibited cultures was the same as in the control cultures. Incubation of infected cells in low-salt medium resulted in a 60% decrease in the overall rate of protein synthesis. Although returning the cells to normal medium rapidly reversed the inhibition of virus production, it did not rapidly increase the rate of protein synthesis. These results suggest that host cell-directed protein synthesis is preferentially inhibited by the low-ionic-strength medium, whereas that required for virus production continues.

RNA-directed DNA polymerase activity of reticuloendotheliosis virus: characterization of the endogenous and exogenous reactions.

Reticuloendotheliosis virus (REV) contains an endogenously instructed, RNA-directed DNA polymerase activity. Both the endogenous and exogenous DNA polymerase activities exhibited up to 10-fold greater activity at the optimum concentration of manganous ion (0.025 mM for exogenous; 0.25 mM for endogenous) than at any concentration of magnesium ion. Antiserum to the DNA polymerase of an REV group virus (spleen necrosis virus) inhibited both endogenous and exogenous DNA polymerase activity of REV, whereas antiserum to the Rous sarcoma virus (Rous-associated virus-0) [RSV(RAV-0)]DNA polymerase did not. The DNA product of the endogenous reaction is associated with the high-molecular-weight RNA of REV and anneals with REV RNA but not with RNA from Rous sarcoma virus.

Alteration of the syncytium-forming property of XC cells by productive Moloney leukemia virus infection.

The effect of productive murine leukemia virus (MuLV) infection of the syncytium-forming property of XC cells was studied MuLV-Moloney-infected XC cells, designated XC(M), initially went through a period of spontaneous syncytium formation. The syncytia then disappeared, and XC(M) cells continued to propagate and produce both infectious MuLV and MuLV group-specific antigens. However, XC(M) cells became refractory to syncytium formation that was induced by Kirsten, Friend, Rauscher, and Moloney strains of murine oncornaviruses. These data suggest that XC(M) cells lost their syncytium-forming ability as a result of productive MuLV infection.