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PubMed1979

Fv-2 locus controls expression of Friend spleen focus-forming virus-specific sequences in normal and infected mice.

We have recently demonstrated that normal hemopoietic cells express RNA sequences that are homologous to sequences specific for the Friend erythroleukemia virus genome [Bernstein, A., Gamble, C., Penrose, D. & Mak, T. W. (1979) Proc. Natl. Acad. Sci. USA 76, 4455-4459]. In this communication, we report that the Fv-2 locus, the major genetic determinant controlling host susceptibility to erythroleukemia induction by Friend leukemia virus, also controls the expression of endogenous sequences related to the replication-defective component of Friend leukemia virus, Friend spleen focus-forming virus (SFFV), in normal uninfected mice. Two independent congeneic pairs of mice [C57BL/6 (B6) and B6.S; B6 and B6.C(H-7(b))], differing only in a small region of the mouse genome including the Fv-2 locus, were used for this purpose. In both cases, molecular hybridization analysis indicated that the presence of SFFV-related RNA sequences in normal mice was associated with the Fv-2(s) allele: bone marrow or spleen cellular RNA from Fv-2(rr) B6 mice contained no detectable SFFV-related sequences, whereas their congeneic Fv-2(ss) pairs contained relatively high levels of these RNA sequences. The absence of these RNA sequences in Fv-2(rr) mice was not due to deletion of these sequences from the DNA of Fv-2(rr) mice. Repopulation of lethally irradiated Fv-2(rr) mice with syngeneic Fv-2(rr) bone marrow cells did not lead to any increase in the levels of these SFFV-related RNA sequences, suggesting that the expression of these sequences is still reduced or inhibited in actively cycling Fv-2(rr) hemopoietic cells. Infection with Friend leukemia virus resulted in the appearance of high levels of RNA homologous to SFFV-specific sequences in the leukemic spleens of B6.S (Fv-2(ss)) mice, whereas these cellular RNA sequences could not be detected in the spleens of Friend virus-infected B6 (Fv-2(rr)) mice. The demonstration that the same gene locus controls both the expression of exogenous SFFV-specific sequences and erythroleukemia induction by Friend leukemia virus suggests that these sequences may be necessary for erythroleukemic transformation. In addition, the finding that the Fv-2 gene locus controls the expression of endogenous SFFV-related sequences suggests that these sequences may also be involved in normal hemopoiesis.

Animals↗
PubMed2006

Close friends', parents', and older siblings' smoking: reevaluating their influence on children's smoking.

A number of longitudinal studies have explored the role of friends', parents', and older siblings' smoking in children's smoking acquisition. A reasonable implication of this previous research is that intervention efforts could be beneficially directed toward countering the potential influence of friends' and possibly older siblings' smoking but not parents' smoking. However, methodological limitations of this previous research motivated our reevaluation of the role of friends', parents', and older siblings' smoking in children's smoking. Close friends' smoking status was assessed when children were in 5th grade, whereas parents' and older siblings' smoking status was assessed when children were in 3rd grade. The outcome, children's daily smoking status, was assessed in 12th grade. The setting was 40 Washington state school districts that participated in the long-term Hutchinson Smoking Prevention Project. Participants were the 4,576 families for whom close friends', parents', and older siblings' smoking status as well as children's smoking status were available. The probability that each close friend's smoking influenced the child to smoke daily was 9% (95% CI = 6%-12%), the probability that each parent's smoking influenced the child to smoke daily was 11% (95% CI = 9%-14%), and the probability that each older sibling's smoking influenced the child to smoke daily was 7% (95% CI = 1%-13%). These results suggest that close friends', parents', and siblings' smoking were similarly important influences on children's smoking. Family-focused interventions could be a valuable future direction of prevention research.

Adolescent↗
PubMed1979

The Friend virus genome: partial characterization of a complete DNA copy.

A complementary DNA probe has been prepared from the Friend murine erythroleukaemia virus complex released by Friend cells (FV cDNAD-) and Friend cells induced to differentiate (FV cDNAD+). Molecular hybridization analysis shows that: (a) FV cDNAD+ is close to being a complete copy of the virus genome and the distribution of sequences is uniform with respect to their distribution in the Friend virus genome. (b) Hybridization of 70S RNA from the cloned helper virus to the total FVc DNAD+ probe demonstrates that a large proportion of the cDNA is specific to the transforming spleen focus forming virus. (c) Hybridization of the probe to normal and transformed cell DNA shows that there are about seven Friend virus related genes in normal DNA and almost twice this amount in transformed cell DNA. A significant minor proportion (20%) of the cDNA probe anneals only to virus related sequences in the transformed cell DNA. (d) An analysis of the kinetics of annealing of the cDNA to an excess template RNA shows that the minimum base sequence complexity of the Friend virus complex is 4 x 10(6). (e) An analysis of the cross hybridization between FV cDNAD+ and 60 to 70S RNA isolated from virus released by uninduced and induced cells shows that the genome of the induced and uninduced Friend virus is almost identical.

Animals↗
PubMed1989

Distinct segments within the enhancer region collaborate to specify the type of leukemia induced by nondefective Friend and Moloney viruses.

The nondefective Moloney and Friend murine leukemia viruses induce T-cell lymphomas and erythroleukemias, respectively, after being injected into newborn NFS mice. In previous studies, we showed that the distinct disease specificities of the two viruses could be switched by exchanging a small segment, about 200 nucleotides in length, encompassing their enhancer regions. This segment included the direct repeat sequence and an adjacent GC-rich region of about 20 nucleotides defined in studies of Moloney murine sarcoma virus enhancer-promoter function (L. A. Laimins, P. Gruss, R. Pozzatti, and G. Khoury, J. Virol. 49:183-189, 1984). The direct repeats of Friend and Moloney viruses are identical in a central core sequence of 32 nucleotides but have sequence differences on either side of this core as well as in their GC-rich segments. To determine whether disease specificity resides in part or in all of the direct repeat and GC-rich region, we constructed recombinants between Friend and Moloney viruses within this segment and tested them for their disease-inducing phenotypes. We found that disease specificity, in particular the ability of Friend virus sequence to confer erythroleukemogenicity on Moloney virus, is encoded throughout the region in at least three separable segments: the 5' and 3' halves of the direct repeat and the GC-rich segment. When just one of these segments (either both 5' halves of the direct repeat, both 3' halves, or just the GC-rich segment) from Friend virus was substituted into a Moloney virus genome, it conferred only a negligible or low incidence of erythroleukemia (less than or equal to 5% to between 10 and 15%). Any two segments together were considerably more potent (35 to 95% erythroleukemia), with the most effective pair being the two halves of the direct repeat. Individual segments and pairs of segments were considerably more potent determinants when they were matched with a genome of the same origin. Thus, although sequences outside the enhancer region are minor determinants of disease specificity when the enhancer is derived entirely from either Friend or Moloney virus, they can play a significant role when the enhancer is of mixed origin. Some recombinant enhancers conferred a long latent period of disease induction. This was particularly striking when the 5' halves of each copy of the direct repeat sequence were derived from Moloney virus and the 3' halves were derived from Friend virus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2001

Role of natural killer cells in resistance against friend retrovirus-induced leukemia.

We have previously shown that immunization with a synthetic peptide that contains a single CD4(+) T-cell epitope protects mice against immunosuppressive Friend retrovirus infection. Cells producing infectious Friend virus were rapidly eliminated from the spleens of mice that had been immunized with the single-epitope peptide. However, actual effector mechanisms induced through T-helper-cell responses after Friend virus inoculation were unknown. When cytotoxic effector cells detected in the early phase of Friend retrovirus infection were separated based on their expression of cell surface markers, those lacking CD4 and CD8 but expressing natural killer cell markers were found to constitute the majority of effector cells that lysed Friend virus-induced leukemia cells. Depletion of natural killer cells by injecting anti-asialo-ganglio-N-tetraosylceramide antibody did not affect the number of CD4(+) or CD8(+) T cells in the spleen, virus antigen-specific proliferative responses of CD4(+) T cells, or cytotoxic activity against Friend virus-induced leukemia cells exerted by CD8(+) effector cells. However, the same treatment markedly reduced the killing activity of CD4(-) CD8(-) effector cells and completely abolished the effect of peptide immunization. Although the above enhancement of natural killer cell activity in the early stage of Friend virus infection was also observed in mice given no peptide, these results have demonstrated the importance and requirement of natural killer cells in vaccine-induced resistance against the retroviral infection.

Amino Acid Sequence↗
PubMed2006

Genetic similarity shared by best friends among adolescents.

Two observations suggest a genetic similarity among close friends: (1) the observed similarity among friends in certain traits and behaviors; (2) the evidence that many of these traits and behaviors have a genetic component. This hypothesis is tested using monozygotic (MZ) twins, dizygotic (DZ) twins, full biological siblings, and their best friends from the National Longitudinal Study of Adolescent Health (Add Health). Whether the resemblance between MZ twins' friends is larger than that between friends of DZ twins and full siblings is investigated with respect to 4 individual traits or behaviors: grade point average (GPA), AHPVT (the version Peabody Picture Vocabulary Test [PPVT] designed for Add Health), aggressive behavior, and depression. Our hypothesis is supported in analyses among same-sex friends (not among different-sex friends) for GPA, aggressive behavior, and AHPVT.

Adolescent↗
PubMed2002

Sex differences in communication with close friends: testing Tannen's claims.

In 1990 Tannen reported that men have fewer close friends than women, men discuss less intimate topics with their friends than women, and men and women respond differently to close friends' problems. 168 students completed a three-page survey designed to examine Tannen's claims. Consistent with Tannen's observations, men discussed less intimate topics (politics and school or work) with their five closest friends and reportedly were less likely to comfort or listen to their friends' problems than women were. Inconsistent with Tannen's statements, these women and men did not differ in the number of close friends they reported having or in the likelihood of offering advice when presented with a friend's problem. Present self-reports corroborate other researchers who questioned Tannen's findings and concluded that sex differences in interpersonal communication are small.

Communication↗
PubMed2002

Associations between adolescent-mother and adolescent-best friend interactions.

The present study examined associations between adolescent-mother and adolescent-best friend interactions during conflict resolution tasks. Adolescents (N = 39) were videotaped while discussing unresolved problems with their mothers and then with their best friends. Mothers' behavior with adolescents and adolescents' behavior with mothers and with best friends were coded for conflict, withdrawal, communication skills, support-validation, and problem-solving. Mothers' communication and support-validation with adolescents was positively associated with adolescents' communication and support-validation with best friends, respectively. However, their behavior was not identical. Mothers were more communicative and supportive with adolescents than adolescents were with their best friends. Second, adolescents' withdrawal and support-validation with mothers was positively associated with their withdrawal and support-validation with best friends, respectively. However, they exhibited less withdrawal with their mothers than with their best friends. Possible explanations for these findings, as well as directions for future research, are discussed.

Adolescent↗
PubMed1991

[An analysis of gp 70 expressed on Friend virus-infected rat tumor cells and the mouse melanoma antigen cross-reacting with it].

In order to analyse a virus-associated antigen which is expressed on Friend virus-infected rat tumor cells and induces strong resistance to their transplantability. I made monoclonal antibodies against it by using spleen cells of the syngeneic rats in whom the Friend virus-associated tumor cells spontaneously regressed. As a result, I was able to obtain a monoclonal antibody, named TF 1, to react specifically to the infection of Friend virus and found out that TF1 antibody reacted to gp 70, a product of the envelope gene of Friend virus, on Friend virus-infected rat tumor cells. And also I found out that B16BL6 cells, which are mouse melanoma cells and are not infected with Friend virus, were positive to TF1 antibody and made it clear that the melanoma antigen which reacted to TF 1 antibody was not gp 70, but a protein of 80-85 KD. Immunizing therefore with gp 70 cross-reacting with the melanoma antigen, I was able to observe that resistance to the transplantability of B16BL6 cells was induced. The result suggests that the melanoma antigen played a role as a tumor rejection antigen. I thus consider that gp 70 is able to induce resistance to transplantability of B16BL6 cells in mice and affects spontaneous regression of Friend virus-infected tumor cells as a virus-associated antigen in rats.

Animals↗
PubMed1994

A survey of actinic keratoses among paraquat production workers and a nonexposed friend reference group.

Follow-up on two reports of an excess of keratoses among paraquat production workers was conducted to evaluate the contribution of occupational exposures to the prevalence of keratoses among workers in a paraquat production plant in Texas. A cross-sectional study design was used to compare the prevalence of keratoses among current workers to an age, race, and sex frequency-matched group of their friends who had never worked at the plant. The analysis is based on 112 workers and 232 friends. Exposure, outcome, and covariables used in the analyses were obtained from an interview questionnaire, dermatology exam, and company records. Overall, the prevalence proportion of the presence of any actinic keratoses among workers and friends was similar (0.30 and 0.28, respectively). Among high cumulative exposed workers, the prevalence of any actinic keratoses was 0.40 compared to 0.20 among low-exposed workers and 0.28 among friends. These results were further explored using a multiple logistic regression approach to adjust for known risk and possibly confounding variables. Statistically significant high risks of actinic keratoses were demonstrated for freckling before age 16 years, older age, suntanning behaviors, occupational exposure to polycyclic aromatic hydrocarbons (PAH), and Fitzpatrick skin type. There was no significant contribution of overall exposure status (worker vs. friend). Similar to the crude analysis, the odds of actinic keratoses of high-exposed workers compared to friends was 1.9 (confidence interval [CI] = 0.9-4.2) whereas the comparable odds ratio for low-exposed workers vs. friends was 0.6 (CI = 0.2-1.7). These data do not demonstrate an excess of actinic keratoses overall nor any consistent increase in the odds of keratoses with an increase in plant exposure level.

Adult↗
PubMed1999

Social reactions of Swedish and Turkish adolescents to a close friend's suicidal disclosure.

BACKGROUND: The prevalence of nonfatal suicidal behavior has been shown to be equal in Swedish and Turkish adolescents, but more Swedish than Turkish adolescents kill themselves. Social attitudes towards self-killing are liberal/permissive in Sweden compared to condemnatory/prohibiting attitudes in Turkey. Against this background, this study investigated Swedish and Turkish adolescents' reactions to a close friend's suicidal disclosure. It also compared students' beliefs about whether or not the suicidal friend needed treatment, and their perceptions of mental illness in, and prognosis for, the suicidal friend. METHOD: A questionnaire was used to assess adolescents' attitudes towards a hypothetical close friend who discloses his/her suicidal plan. RESULTS: Swedish students were more accepting of a suicidal friend, but were also more disapproving of a suicidal disclosure by a close friend, than their Turkish peers. Turkish students, on the other hand, were more emotionally involved with, and took more responsibility for, a suicidal close friend than their Swedish counterparts. CONCLUSIONS: Due to disapproving social attitudes towards suicidal disclosures in Sweden compared to Turkey, persons undergoing suicidal crises in Sweden may choose not to communicate their suicidal intent, and hence can not make use of social support systems to combat personal crises of a suicidal nature.

Adolescent↗
PubMed2006

Family and friend closeness to adolescent sexual partners in relationship to condom use.

PURPOSE: The role of closeness of sexual partners to family and friends (i.e., how well the participant's family and friends knew their primary sexual partner) to a variety of relationship and sexual behavior measures was explored. METHODS: A sample of 151 adolescent females (aged 14-17 years) was assessed. Areas assessed include family and friend closeness, relationship intimacy, length of sexual relationship, and condom use. RESULTS: Bivariate correlations indicated that the integration of the sexual partner into the family and friend networks was related to greater relationship intimacy. Lowered condom use was related to a number of measures, including increased relationship intimacy and increased family closeness. A path analysis was conducted to assess for direct and indirect effects of family closeness, friend closeness, relationship length, and relationship intimacy on condom use. Social network closeness in family and friend networks was implicated in lowered condom use through higher relationship intimacy within adolescent dyads. CONCLUSIONS: Social network theory is useful in understanding adolescent health-related behavior. In particular, the integration of adolescent sexual partners into both family and friend networks is related to the expression of adolescent sexual behavior.

Adolescent↗
PubMed2000

Men, women and friends--are there differences in relation to mental well-being?

This is a study on associations between the number of close friends and mental well-being in a nationwide sample of the Finnish general population (n = 1,603). Mental well-being was assessed by means of the 12-item General Health Questionnaire. A total of 3% of the sample had no close friends and another 3% had only one. Over half of the sample (52%) reported having five or more friends. The overall prevalence of mental distress was 15% in men and 21% in women. According to multivariate analyses the risk of mental distress was increased in men among those with no friends (odds ratio [OR]: 2.70) and among those who had one (OR: 4.32) or two to four friends (OR: 1.75), as compared with those who had more friends. In women, having only one friend (OR: 2.30), insufficient family support (OR: 1.63) and insufficient support from relatives (OR: 1.77) associated with the risk of mental distress. These results suggest that mental well-being might be promoted if mentally distressed men seeking professional help were supported in building up and maintaining social networks and mentally distressed women were supported in harmonizing their family life.

Adult↗
PubMed2006

To be and to have a critical friend in medical teaching.

BACKGROUND: In order to stimulate reflection and continuous professional development, a model of critical friends evaluating each other was introduced in medical education. OBJECTIVE: To investigate whether the critical friend concept can serve as a pragmatic model for evaluation of medical teachers and as a fruitful tool for enhancing self-knowledge and professional development among medical educators. METHODS: Three pairs of critical friends were formed, consisting of experienced medical teachers (n = 6) at the Karolinska Institutet. Each teacher was assigned to give 1 lecture and 1 seminar in his or her specific research or clinical field. The critical friend evaluated the performance in class, acting as an observer using a pre-formed protocol. The evaluation was communicated to the teacher during a 45-minute session within 48 hours after the teaching session. Each of the 6 teachers was criticised and gave criticism within the pair configurance. The outcome of the process was evaluated by an experimenter, not participating in the process, who performed a semistructured interview with each of the 6 teachers. RESULTS: Each teacher had a different way of reflecting on teaching after the project than before and made changes in his or her way of teaching. We also noted that being a critical friend may be even more effective than having one. The majority of the feedback provided was positive and valuable. CONCLUSION: To be and to have a critical friend is worth the extra workload. Therefore, the critical friend concept should be made part of regular teaching practice.

Clinical Competence↗
PubMed2005

Breastfeeding rates in US Baby-Friendly hospitals: results of a national survey.

OBJECTIVES: The objectives of this study were to analyze all available breastfeeding data from US Baby-Friendly hospitals in 2001 to determine whether breastfeeding rates at Baby-Friendly designated hospitals differed from average US national, regional, and state rates in the same year and to determine prime barriers to implementation of the Baby-Friendly Hospital Initiative. METHODS: In 2001, 32 US hospitals had Baby-Friendly designation. Using a cross-sectional design with focused interviews, this study surveyed all 29 hospitals that retained that designation in 2003. Demographic data, breastfeeding rates, and information on barriers to becoming Baby-Friendly were also collected. Simple linear regression was used to assess factors associated with breastfeeding initiation. RESULTS: Twenty-eight of 29 hospitals provided breastfeeding initiation rates: 2 from birth certificate data and 26 from the medical record. Sixteen provided in-hospital, exclusive breastfeeding rates. The mean breastfeeding initiation rate for the 28 Baby-Friendly hospitals in 2001 was 83.8%, compared with a US breastfeeding initiation rate of 69.5% in 2001. The mean rate of exclusive breastfeeding during the hospital stay (16 of 29 hospitals) was 78.4%, compared with a national mean of 46.3%. In simple linear regression analysis, breastfeeding rates were not associated with number of births per institution or with the proportion of black or low-income patients. Of the Ten Steps to Successful Breastfeeding the 3 described as most difficult to meet were Steps 6, 2, and 7. The reason cited for the problem with meeting Step 6 was the requirement that the hospital pay for infant formula. CONCLUSION: Baby-Friendly designated hospitals in the United States have elevated rates of breastfeeding initiation and exclusivity. Elevated rates persist regardless of demographic factors that are traditionally linked with low breastfeeding rates.

Breast Feeding↗
PubMed1981

An examination of characteristics related to success of friends groups in medical school rare book libraries.

Friends of the library groups traditionally have been considered effective sources of funding for libraries. Empirical evidence was sought to determine the accuracy of this belief for medical rare book libraries. Characteristics of the medical rare book library and of the friends group were examined to identify those which are correlated with successful friends groups. Correlations were found between the amount of money contributed by the friends group and the age of the friends group, the librarian's participation in forming the group, and the amount of money spent by the library on the friends group. Recommendations are made toward a goal of larger donations from friends groups of medical rare book libraries and toward more effective management of those funds.

Financial Management↗
PubMed1979

Alterations in chloride transport during differentiation of Friend virus-transformed cells.

Friend erythroleukemic cells can be induced by a variety of agents to synthesize hemoglobin and to exhibit other characteristics suggesting erythroid maturation. Upon induction of hemoglobin synthesis with dimethylsulfoxide (DMSO), the chloride flux in Friend cells gradually increases, until after five days of exposure to DMSO (when the hemoglobin content of the cells approaches that of the mature erythrocyte) the flux is three times the value in non-induced cells. A similar flux increase is observed in the presence of a different type of inducer, hypoxanthine, but no increase in flux is seen in the mutant cell line, TG-13, which does not synthesize hemoglobin after DMSO treatment. Thus, the flux increase seems to be associate d with the induction process, rather than being a direct effect of the inducing agent. After DMSO treatment, the sulphate flux decreases and the chloride/sulphate selectivity increases, aswould be expected if the cells were becoming more like red cells. On the other hand, the sensitivity of the chloride flux to the inhibitor, furosemide, and to temperature is the same in the induced as in the non-induced Friend cells, and different from that of the mature red cell. Thus, the anion transport properties of the induced Friend cell are different from those of both the non-induced Friend cell and the mature erythrocyte. Either the system in the induced cell represents an intermediate stage in the development of the mature red cell characteristics, or else the maturation of transport function in the Friend cell differs from that in normal erythrocyte precursors.

Animals↗
PubMed2005

False consensus and adolescent peer contagion: examining discrepancies between perceptions and actual reported levels of friends' deviant and health risk behaviors.

Adolescents' perceptions of their friends' behavior strongly predict adolescents' own behavior, however, these perceptions often are erroneous. This study examined correlates of discrepancies between adolescents' perceptions and friends' reports of behavior. A total of 120 11th-grade adolescents provided data regarding their engagement in deviant and health risk behaviors, as well as their perceptions of the behavior of their best friend, as identified through sociometric assessment. Data from friends' own report were used to calculate discrepancy measures of adolescents' overestimations and estimation errors (absolute value of discrepancies) of friends' behavior. Adolescents also completed a measure of friendship quality, and a sociometric assessment yielding measures of peer acceptance/rejection and aggression. Findings revealed that adolescents' peer rejection and aggression were associated with greater overestimations of friends' behavior. This effect was partially mediated by adolescents' own behavior, consistent with a false consensus effect. Low levels of positive friendship quality were significantly associated with estimation errors, but not overestimations specifically.

Adolescent↗