Mutational specificity of aflatoxin B1. Comparison of in vivo host-mediated assay with in vitro S9 metabolic activation

An intrasanguineous host-mediated assay was used to determinethe pattern of mutagenesis induced by the carcinogen aflatoxinBl in the lacl gene of Escherichia coli recovered from rat liver.To investigate the influence of different types of metabolicactivation, the mutation spectrum induced by AFB1 activatedin vitro by a commercially prepared S9 microsomal fraction fromAroclor 1254-treated rats was also obtained. A total of 281forward mutations affecting the N-terminal region of the laclgene were characterized by DNA sequencing analysis. AFB1 inducedsimilar type of mutations with similar site specificity whenactivated by the standard S9 fraction or by employing a rathost-mediated assay. These results indicate the ability of thein vitro S9 fraction to mimic the in vivo metabolism, suggestingthat the same active metabolite, presumably AFB1 8, 9-epoxide,is responsible for generating a similar pattern of DNA damage,as reflected in the similarity of mutational spectra. For bothactivation systems, most mutations (>90%) were base substitutionsthat occurred primarily at G: C pairs. Somewhat over one-halfof G: C targeted substitutions were GC>TA transversions,other mutations being evenly divided between G: C>AT transitionsand GC>CG trans-versions. The mutational specificity exhibitedby activated AFB1 can be explained by incorporation of differentbases opposite a single type of non-instructive lesion duringerror-prone DNA synthesis. To what extent the mutations aredue to the main adduct (AFB1-N7-Gua), its imidazole-ring-openedderivative or an apurinic site remains unknown.     

Gallium scintigraphy in Hansen's disease

Gallium 67 imaging was used in 12 patients with documented Hansen's disease undergoing treatment or not, in an attempt to determine the pattern of the disease. Diagnosis was confirmed by histopathology in all patients. The Mitsuda reaction was seen in all patients. Specific nuclear studies were performed when needed to evaluate particular organs better. Gallium 67 images show homogeneous, diffuse and moderate accumulation over the entire skin surface (except for the face) of untreated patients with multibacillary disease. The facial skin in these cases presented homogeneous, diffuse but very marked uptake of gallium. Internal organ involvement was variable. There was a very good correlation among clinical, scintigraphic, immunological and histopathological data. The pattern of the body skin (skin outlining) and facial skin (beard distribution) may be distinct for untreated patients with multibacillary leprosy.     

Seroreactivity to human papillomavirus (HPV) types 16, 18, or 31 and risk of subsequent HPV infection: results from a population-based study in Costa Rica.

Whether antibodies to human papillomavirus (HPV) capsids, elicited by natural infection, are protective is unknown. This question was addressed in a population-based cohort of 7046 women in Costa Rica by examining the association between baseline seroreactivity to HPV-16, HPV-18, or HPV-31 virus-like particles and the risk of subsequent HPV infection at a follow-up visit 5-7 years after enrollment. Seropositivity to HPV-16, HPV-18, or HPV-31 was not associated with a statistically significant decreased risk of infection with the homologous HPV type [relative risk (RR) and [95% confidence interval (CI)], 0.74 (0.45-1.2), 1.5 (0.83-2.7), and 0.94 (0.48-1.8), respectively]. Seropositivity to HPV-16 or HPV-31 was not associated with a decreased risk of infection with HPV-16 or its genetically related types [RR (95% CI), 0.82 (0.61-1.1) and 0.93 (0.68-1.2), respectively]. Seropositivity to HPV-18 was not associated with a decreased risk of infection with HPV-18 or its genetically related types (RR 1.3; 95% CI 1.0-1.8). Thus, we did not observe immunity, although a protective effect from natural infection cannot be excluded because of the limits of available assays and study designs.     

Predictors of cervical coinfection with multiple human papillomavirus types.

Women infected with multiple human papillomavirus (HPV) types seem to be at higher risk of cervical intraepithelial neoplasia, although there is controversy about whether coinfections are associated with lower or higher grades of dysplasia. There is no established risk factor profile for infection with multiple HPV types. We analyzed data from a prospective cohort of 2,075 Brazilian women to identify determinants of HPV coinfection. Cervical specimens were collected for cytology and HPV DNA detection. Data on baseline and time-dependent putative risk factors were obtained by interview. Baseline predictors of HPV coinfection included younger age, greater number of recent sexual partners, a history of condyloma but not of other sexually transmitted diseases, and younger age at first sexual intercourse. In repeated measures analyses, there was a weak positive association between the number of sexual partners in the time interval between two study visits and the risk of coinfection. Our results suggest that the risk factor profile for HPV coinfection among HPV-infected women shares several similarities with risk factors for any HPV infection.     

Tissue factor expression correlates with tumor angiogenesis and invasiveness in human hepatocellular carcinoma.

PURPOSE: Recent studies have shown that tissue factor (TF) may be involved in tumor angiogenesis and metastasis. The role of TF in hepatocellular carcinoma (HCC) was unknown. This study evaluated whether TF expression correlates with microvessel density (MVD), vascular endothelial growth factor (VEGF) expression, tumor invasiveness, and prognosis in human HCC. EXPERIMENTAL DESIGN: Tissue samples were obtained from 58 specimens of resected HCC. Immunohistochemical expression of TF was examined, and tumor MVD was evaluated using CD34 as the endothelial marker. TF and VEGF protein levels in the tumor cytosol were quantified by ELISA. Clinicopathologic and follow-up data of patients were prospectively collected. RESULTS: The immunohistochemical expression of TF in the tumors correlated significantly with tumor MVD (P = 0.002). The median cytosolic TF protein level in the tumors was 720 pg/mg total protein (range, 67-2406 pg/mg total protein). A significant positive correlation was found between TF and VEGF levels in the tumor cytosol (r = 0.475, P < 0.001). High tumor cytosolic TF level was associated with venous invasion (P = 0.004), microsatellite nodules (P = 0.024), unencapsulated tumor (P = 0.007), and advanced tumor stage (P = 0.010). A higher than median tumor cytosolic TF level was an independent predictor of poor survival (risk ratio, 1.836; 95% confidence interval 1.130-5.312, P = 0.023). CONCLUSIONS: This study shows that TF is related to tumor angiogenesis and invasiveness in HCC. Evaluation of tumor TF expression may be useful as a prognostic indicator in patients with HCC.     

Knowledge of reproduction in teenagers and young adults in Sweden.

OBJECTIVE: To investigate the knowledge of reproductive physiology and anatomy among adolescents and young adults in Sweden, and to evaluate the education obtained on these issues. METHODS: Two hundred and nine study specific questionnaires were distributed, of which 206 were answered by students in primary school, upper secondary school and at first year of university. A total knowledge score based on 21 out of the 35 questions in the questionnaire was calculated. As only 44 of the 206 respondents answered all the questions a revised score was also calculated, in which partial dropouts were interpreted as wrong answers. RESULTS: The mean of the total knowledge score was 28.7 out of 54 among the 44 respondents answering all questions, and the revised knowledge score was 24.0. The level of knowledge tended to be higher in older age groups, among women, as well as among respondents who had visited a Youth clinic. The time of ovulation was known by 21.4% of men compared to 63.4% of women. Almost 50% of the students knew one mechanism whereby oral contraceptives act to protect against pregnancy. Of the respondents, 77.2% knew of Chlamydia trachomatis but the knowledge of other STIs, like condyloma, was poorer (16.5%). Reasons for infertility were relatively well known among the respondents. Of the respondents, 57.5% stated that they had not received enough information on reproductive issues. CONCLUSIONS: The students have not achieved sufficient knowledge concerning sexual and reproductive matters that they, according to the national curriculum, should have attained by the end of the 9th grade. An improvement of the quality of the education, adapted to the students' age and pre-existing knowledge, and a review of the contents of the education is therefore needed.     

Synergistic interactions between cannabinoids and environmental stress in the activation of the central amygdala.

Anxiety and panic are the most common adverse effects of cannabis intoxication; reactions potentiated by stress. Data suggest that cannabinoid (CB1) receptor modulation of amygdalar activity contributes to these phenomena. Using Fos as a marker, we tested the hypothesis that environmental stress and CB1 cannabinoid receptor activity interact in the regulation of amygdalar activation in male mice. Both 30 min of restraint and CB1 receptor agonist treatment (Delta9-tetrahydrocannabinol (2.5 mg/kg) or CP55940 (0.3 mg/kg); by i.p. injection) produced barely detectable increases in Fos expression within the central amygdala (CeA). However, the combination of restraint and CB1 agonist administration produced robust Fos induction within the CeA, indicating a synergistic interaction between environmental stress and CB1 receptor activation. An inhibitor of endocannabinoid transport, AM404 (10 mg/kg), produced an additive interaction with restraint within the CeA. In contrast, fatty acid amide hydrolase (FAAH) inhibitor-treated mice (URB597, 1 mg/kg) and FAAH-/- mice did not exhibit any differences in amygdalar activation in response to restraint compared to control mice. In the basolateral (BLA) and medial amygdala, restraint stress produced a low level of Fos induction, which was unaffected by cannabinoid treatment. Interestingly, the CB1 receptor antagonist SR141716 dose-dependently increased Fos expression in the BLA and CeA. These data suggest the CeA is an important neural substrate subserving the interactions between cannabinoids and environmental stress, and could be relevant to understanding the context-dependent emotional and affective changes induced by marijuana intoxication and the role of endocannabinoid signaling in the modulation of amygdalar activity.     

Signaling modulation of bile salt-induced necrosis in isolated rat hepatocytes.

Hydrophobic bile salts induce either necrosis or apoptosis depending on the severity of the injury caused by them. Since bile salt-induced apoptosis is influenced by Ca2+- and protein kinase-signaling pathways, and both necrosis and apoptosis share common initiating mechanisms, we analyzed whether these signaling cascades also influence bile salt-induced necrosis in isolated rat hepatocytes. Taurochenodeoxycholate (TCDC, 0.25-1.50 mM, 2 h) reduced, in a dose-dependent manner, the percentage of viable hepatocytes, and increased the release of the cytosolic enzyme, lactate dehydrogenase (LDH) and alanine aminotransferase (ALAT), and that of the plasma membrane enzyme, alkaline phosphatase (AP). The PKC inhibitors, H7 (100 microM) and chelerythrine (2.5 microM), both prevented significantly TCDC-induced necrosis. On the contrary, the PKA activator, dibutyryl-cAMP, exacerbated TCDC-induced cell damage in a dose-dependent manner; this effect was more likely due to cAMP-mediated PKA activation, as the PKA inhibitor, KT5720 (1 microM), counteracted this effect. Instead, the intracellular Ca2+ chelator, BAPTA/AM (20 microM), was without effect. TCDC (1 mM) increased lipid peroxidation from 0.7 +/- 0.2 to 7.5 +/- 0.9 nmol of malondialdehyde per mg of protein, p < 0.001; the addition of the free radical scavenger, diphenyl-p-phenylendiamine, completely blocked this increase and prevented significantly TCDC-induced necrosis. PKC inhibition induced only a slight attenuation of TCDC-induced lipid peroxidation. Possible mechanisms accounting for the modulatory effect of signal transduction pathways on TCDC-induced necrosis, including signaling influence on TCDC transport events and TCDC-induced oxidative stress, are discussed.