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PubMed1992

Drug use of friends: a comparison of reservation and non-reservation Indian youth.

There is not much drug use at school, but reservation youth are most likely, non-reservation Indian youth next most likely, and non-Indian youth least likely to have used drugs at school. Alcohol and drugs are used most frequently at weekend parties and at night with friends. Reservation youth are twice as likely as the others to have used alcohol while driving around and three times more likely to have used drugs while driving around. Drugs are used with friends. Heavy drug users are more likely to have friends who use drugs and friends who encourage drug use and are less likely to have friends who would try to stop them from using drugs.

Adolescent↗
PubMed2002

Self-esteem, construal, and comparisons with the self, friends, and peers.

Extending the better than average effect, 3 studies examined self-, friend, and peer comparisons of personal attributes. Participants rated themselves as better off than friends, who they rated as superior to generalized peers. The exception was in direct comparisons, where the self and friends were not strongly differentiated on unambiguous negative attributes. Self-esteem and construal played moderating roles, with persons with high self-esteem (HSEs) exploiting both ambiguous positive and ambiguous negative traits to favor themselves. Persons lower in self-esteem exploited ambiguous positive traits in their favor but did not exploit ambiguous negative traits. Across self-esteem level, ratings of friends versus peers were exaggerated when attributes were ambiguous. HSEs seemed to take advantage of ambiguity more consistently to present favorable self-views; people with low self-esteem used ambiguity to favor their friends but were reluctant to minimize their own faults.

Adult↗
PubMed1991

Communication in relationships and adolescent substance use: the influence of parents and friends.

This study focused on the openness of communication in teenagers' relationships with mother, father (or parental figure), and closest friend, and its correlation with teenagers' use of cigarettes, alcohol, marijuana, and other drugs. The predictive value for substance use of perceived pressure from friends, friends' substance use, and parents' substance use was also analyzed. The findings from questionnaires and interviews conducted with 37 students at an urban and a suburban/rural high school in New England are reported. The results suggest that the degree to which adolescents talk openly with their parents may influence the extent of their substance use. The presence of at least one "open" parental figure was associated with lower levels of all substance use. However, there was no evidence that openness with a close friend or perceived pressure from friends is related to substance use.

Adolescent↗
PubMed1990

Early adolescent age and gender differences in patterns of emotional self-disclosure to parents and friends.

This study explored adolescent age and gender differences in patterns of emotional self-disclosure to parents and friends. The sample consisted of 174 junior high school students between the ages of 12 and 15. Results revealed that females exhibited greater emotional self-disclosure to parents and peers than did males, and that emotional self-disclosure to friends was greatest among older adolescents. In addition, while younger adolescents preferred to disclose information about their emotional state to parents, older adolescents chose friends. Exploratory hierarchical regression analyses revealed that emotional disclosure to parents was most strongly associated with adolescent perceptions of the openness of family communication, family cohesion, and satisfaction with family relationships. Emotional disclosure to friends was associated with adolescent self-esteem in the peer context and identity development. The results are discussed in terms of the complementary socializing processes that may operate within the contexts of family and friends.

Adolescent↗
PubMed1987

Inhibition by bryostatin 1 of the phorbol ester-induced blockage of differentiation in hexamethylene bisacetamide-treated Friend erythroleukemia cells.

Phorbol esters inhibit chemically induced differentiation in Friend erythroleukemia cells. This study examines the effect of the macrocyclic lactone bryostatin 1 on phorbol ester responses in a Friend erythroleukemia cell clone, PS 7. In several biological systems, bryostatin 1 was reported to mimic phorbol ester action, including activation of protein kinase C, but in HL-60 cells it blocked phorbol ester-induced differentiation. We report here that bryostatin 1 blocks phorbol ester action in Friend cells (clone PS 7), a second differentiating system. In this system, in contrast to HL-60 cells, the phorbol esters inhibit rather than induce differentiation. Bryostatin 1 restores the differentiation response [50% effective dose, 15 +/- 3.5 nM (SEM)] as well as blocks a second phorbol ester effect, induction of cellular adherence. The inhibition of erythroid differentiation by dexamethasone, a nonphorbol compound whose action presumably is not protein kinase C mediated, is unaffected by bryostatin 1. Although bryostatin 1 inhibits [3H]phorbol 12,13-dibutyrate binding in intact Friend erythroleukemia cell clone PS 7, the mechanism for the antagonism of phorbol ester action by bryostatin 1 in Friend cells cannot be explained by simple competition at the binding site.

Acetamides↗
PubMed1984

Synthesis of S-adenosylethionine by the gamma isozyme of methionine adenosyltransferase from Friend erythroleukemic cells.

Methionine adenosyltransferase (adenosine 5'-triphosphate-L-methionine S-adenosyltransferase, EC 2.5.1.6) was found to occur only as the gamma isozyme in Friend erythroleukemic cells. Enzyme activity in a dialyzed 105,000 X g supernatant was linear for at least 30 min and dependent on the amount of protein added. The Km for methionine was 10.6 microM. In the presence of 10% dimethyl sulfoxide, the enzyme activity was slightly inhibited and dithiothreitol was not required for maximum activity. These properties identify the methionine adenosyltransferase in Friend erythroleukemic cells as the gamma isozyme. L-Ethionine served as a substrate with a Km of 30 microM, and competitively inhibited the enzyme activity with a Ki of 150 microM. Friend erythroleukemic cells grown in the presence of ethionine accumulated S-adenosylethionine, which was dose and time dependent. Therefore, the gamma isozyme of methionine adenosyltransferase from Friend erythroleukemic cells utilize L-ethionine as substrate, resulting in an accumulation of S-adenosylethionine. These studies provide a mechanism by which ethionine through S-adenosylethionine may alter the methylation of DNA in Friend erythroleukemic cells.

Animals↗
PubMed1984

Inhibition of dimethyl sulfoxide-induced differentiation of Friend erythroleukemic cells by 5'-methylthioadenosine.

5'-Methylthioadenosine is a sulfur-containing nucleoside derived from the metabolism of polyamines which is known to exert an antiproliferative effect on several cell systems in vitro, including the Friend leukemia cell system. We have investigated the role of 5'-methylthioadenosine on the dimethyl sulfoxide-induced differentiation of this system. At a concentration of 400 microM, the drug strongly inhibited (80%) the induced differentiation of Friend cells, and this effect was already observable at a concentration as low as 10 microM (36% inhibition), as evidenced by the benzidine staining procedure and by the dot-blot hybridization of globin mRNA with a human beta-globin probe. Similar results have been obtained by using 5'-S-isobutylthioadenosine, which is a synthetic structural analogue of 5'-methylthioadenosine. The block of differentiation produced by these nucleosides was not mediated by adenine (a catabolite of both molecules) and was not reverted by spermine or spermidine, the two polyamines whose synthesis is inhibited by 5'-methylthioadenosine. We report a decrease of the aminopropyltransferases activities (the enzymes responsible for 5'-methylthioadenosine biosynthesis) in dimethyl sulfoxide-treated Friend cells, which could lead to a decrease of the intracellular content of 5'-methylthioadenosine during the erythroid maturation of Friend cells. The results obtained are consistent with the hypothesis that 5'-methylthioadenosine may act as an endogenous regulator of Friend cell differentiation.

Adenosine↗
PubMed1994

Differential influence of parental smoking and friends' smoking on adolescent initiation and escalation of smoking.

Smoking-related behaviors and attitudes of significant others (especially friends and parents) are among the most consistent predictors of adolescent smoking. However, theorists remain divided on whether the behaviors of significant others influence adolescent smoking directly or indirectly, and the relative influence of parental and peer smoking on adolescents' own smoking is still a matter of debate. In addition, little research has examined the role of significant others' behavior on different stages of smoking onset. In particular, not much information is available regarding gender and ethnic differences in social influences on smoking behavior. We use structural equation modeling to address these issues. Different theoretical perspectives from cognitive-affective theories (Ajzen 1985; Ajzen and Fishbein 1980) and social learning theories (Akers et al. 1979; Bandura 1969, 1982, 1986) have been integrated into a structural model of smoking influence. The results show that friends' smoking affects adolescent initiation into smoking both directly and indirectly, whereas parental smoking influences smoking initiation only indirectly. The data also show that friends' and parents' smoking affect smoking escalation only indirectly. In general, friends' smoking has a stronger effect on adolescents' smoking behavior, particularly on initiation. Multiple group comparisons of the structural models predicting smoking initiation among males and females reveal that parental approval of smoking plays a significant mediating role for females, but not for males. Comparisons of Whites, Blacks, Hispanics, and other ethnic groups reveal that there are some significant differences in the pathways of friends' influences among the four groups.

Adolescent↗
PubMed1976

The spleen in Friend leukemia. I. Prolonged survival of leukemic mice after autoimplantation of spleen tissue.

Friend virus infection of susceptible mice led rapidly to fulminant erythroleukemia and death. Subcutaneous implantation of leukemia spleen bits into splenectomized normal animals led to their early death from Friend leukemia. In contrast, bits of leukemic spleen implanted sc into splenectomized leukemic mice prolonged the survival of these animals. Concomitant with this survival was a reversal of the virus-induced immunosuppression and an increase in the levels of circulating, neutralizing, antivirus activity. This marked difference in response to leukemic spleen implants by leukemic as compared to normal mice reflected previous contact of the former with Friend Virus. Our studies indicated that the Friend virus-infected mouse mounted a resistance to the virus infection, which under certain conditions is capable of reversing the disease process.

Animals↗
PubMed1978

Early transport changes during erythroid differentiation of Friend leukemic cells.

Early transport changes occurring during Friend erythroleukemic cell differentiation are reported. A decrease in the rate of 86Rb transport was observed beginning approximately five hours after stimulation with 1.5% dimethylsulfoxide (DMSO), a potent inducer of Friend cell differentiation. By 12 to 14 hours after DMSO addition, the transport rate had stabilized at close to 60% of control level. This decrease in the rate of 86Rb transport preceded a previously reported decrease in cell volume. Other chemical inducers of Friend cells, such as hypoxanthine and ouabain, also caused early decreases in 86Rb influx. In contrast, xanthine, which does not induce Friend cell differentiation, also did not affect 86Rb influx. The transport of two amino acid analogues, alpha-aminoisobutyric acid and 2-aminobicyclo [2,2,1]-heptane-2-carboxylic acid, which differ in their mode of uptake, was also measured following induction by DMSO. The transport rates of both compounds decreased after a 12-hour exposure to DMSO. In contrast, the uptake of 3H-colchicine, a drug which diffuses passively across the cell membrane, was not significantly affected. Studies with several variant cell lines which do not synthesize hemoglobin in response to DMSO indicate that these non-inducible cells can be divided into two classes--those that demonstrate early changes in transport very similar to the changes observed in inducible cell lines and those which exhibit only small changes in transport. Results obtained using a revertant clone have helped to distinguish between those transport changes which are associated with the induction of hemoglobin synthesis and those which are not. In addition, these early transport changes may be useful in defining the stage in the differentiation process at which a particular variant line is blocked.

Amino Acids↗
PubMed1978

The program of Friend cell erythroid differentiation: early changes in Na+/K+ ATPase function.

Treatment of Friend erythroleukemia cells with several different chemical agents causes an early decrease in the 86Rb+ influx mediated by Na+/K+ adenosine triphosphatase (ATPase). These agents, which induce Friend cells to differentiate, include dimethylsulfoxide (DMSO), ouabain, hypoxanthine, and actinomycin D. The magnitude of the early decrease in 86Rb+ influx correlates with the proportion of cells in cultures of inducible Friend cell clones which later go on to synthesize hemoglobin. Compounds which do not incude differentiation in these cells, such as xanthine, exogenous hematin, and erythropoietin, do not cause a change in 86Rb+ influx. A change in the intracellular K+ ion concentration does not occur during induction by DMSO because, although there is a decrease in K+ content per cell soon after induction, there is a parallel decrease in cell volume. These results and previous observations from this laboratory are discussed in terms of the posible involvement of the Na+/K+ ATPase in Friend cell differentiation.

Animals↗
PubMed1989

T-cells inhibit Friend murine leukemia virus infection of B-cells in vitro.

The ability of splenic T-cells to regulate Friend murine leukemia virus replication in lipopolysaccharide-activated target B-cells infected in vitro was investigated. Removal of the T-cell fraction from spleen cells resulted in an 8- to 10-fold enhancement in the number of productively infected cells in the remaining B-cell-enriched fraction, as compared with unseparated spleen cells, and the addition of increasing numbers of purified T-cells to isolated B-cells prior to infection resulted in a directly proportional reduction in the number of B-cells releasing infectious progeny virus. Separation of splenic T-cells into Lyt 2- and Lyt 2+ T-cells before addition to infected B-cell cultures resulted in inhibition of infection only with the Lyt 2- T-cells; Lyt 2+ T-cells did not inhibit infection, even at high 1:1 ratios. Similarly, separation of splenic T-cells into L3T4+ and L3T4- T-cells before addition resulted in inhibition by L3T4+ but not L3T4- T-cells. Also, cytotoxic treatment of splenic T-cells with monoclonal anti-L3T4 antibody and complement before addition to B-cell cultures destroyed the regulatory effects. Finally, depletion of macrophages from both T-cells and B-cells before infection and coculture had no effect on the ability of T-cells to regulate B-cell infection. Collectively these results demonstrate that L3T4+ T-cells can inhibit Friend murine leukemia virus replication in target B-cells. Culture of isolated splenic T-cells with Friend murine leukemia virus in vitro resulted in the induction of alpha/beta but not interferon-gamma synthesis and in some experiments interferon-containing supernatants from T-cell-virus cultures were able to mediate suppression of B-cell infection with Friend helper virus; the addition of antibody specific for interferon-alpha/beta to cultures inhibited the ability of T-cells to regulate B-cell infection.

Animals↗
PubMed1978

Isolation and properties of DMSO resistant variant clones of Friend leukemia cells.

DMSO resistant clones have been isolated from the inducible Friend leukemia cell line 5-86 both from unmutagenized cultures and following EMS mutagenesis. All the clones can grow in the presence of 1.8% DMSO and are non-inducible or poorly inducible for hemoglobin synthesis by DMSO as well as by other known inducers of Friend leukemia (FL) cells differentiation like hemin, hypoxanthine, hexamethylene bisacetamide. The clones are also defective for the expression of other properties of differentiating Friend cells like agglutinability by plant lectins and expression of the surface protein glycophorin. Some of the clones show an impaired ability to form tumors in vivo. These resistant clones might be useful for a genetic analysis of the differentiation process of Friend leukemia cells.

Animals↗
PubMed1975

Synthesis of erythrocyte-specific proteins in cultured friend leukemia cells.

We have studied synthesis of specific proteins in two permanent lines of Friend virus-induced erythroleukemia cells (Friend line 745 and Ostertag line FSD-1, both derived from DBA/2 mice). By 96 hr following treatment with 1-2% dimethyl sulfoxide (Me2SO), up to 25% of the protein being synthesized by both these cultures is hemoglobin. At that time, hemoglobin constitutes up to 10% of the cellular soluble protein. Both lines synthesize heme and globin coordinately, and alpha and beta globin chains in a nearly balanced 1:1 ratio. However, the ratio of betaMajor:betaMinor chains synthesized by these induced Friend leukemia (FL) cells is approximately 9 in the FSD-1 line and 1.3 in the Friend Clone 745 line, whereas it is 4 in normal adult DBA/2 mouse erythrocytes. Evidence for the latter conclusion was obtained by electrophoresis of FL hemoglobins on cellulose acetate membranes, and also by chromatographic separation of alpha, betaMajor, and betaMinor globins on carboxymethylcellulose in 8 M urea at 20 degrees C. Carbonic anhydrase activity per mg protein is 3 times higher in induced than in control cultures. 2,3-diphosphoglyceric acid is not found in induced FL cells. Induced and control FL cells agglutinate strongly and equally with Phaseolus vulgaris phytohemagglutinin. The developmental process in these cultured leukemia cells appears to be an aberrant erythropoiesis.

Agglutination↗
PubMed1987

Characterization of cell lines derived from enlarged spleens induced in C57BL/6 mice by the variant BSB strain of Friend erythroleukemia virus.

BSB is a variant strain of Friend virus selected for pathogenicity in C57BL/6 mice that are resistant to parental Friend virus strains by virtue of their homozygosity for the recessive Fv-2r allele (Steeves et al., 1970, Int. J. Cancer 5, 346-356). Lines and clones of erythroleukemia cells could readily be established in culture from the enlarged spleens of BSB-infected Fv-2r homozygotes. All lines expressed viral gene products and could be induced to express hemoglobin. Some lines produced infectious virus. In addition to the viral envelope-related proteins (gPr85, gp70, and gp52) detected by precipitation with goat anti-Rauscher gp70 antiserum from tumor cell lines induced by parental Friend virus strains, BSB-induced cell lines also expressed gp80, p52, and gp45 products precipitable with the same antiserum. A rat monoclonal antibody that recognizes an epitope of an amino-terminal region of gp52 (Wolff et al., 1982, J. Virol. 43, 472-481) also precipitated the gp80 and gp45 viral proteins. The data indicate that the BSB strain of Friend virus is oncogenic in Fv-2r homozygotes. Transformation is correlated with the expression of an altered SFFV env-gene product.

Animals↗
PubMed2006

Health outcomes in adolescence: associations with family, friends and school engagement.

AIM: To examine the associations between connectedness to family and friends, and school engagement, and selected health compromising and health promoting behaviours in a sample of New Zealand adolescents. METHODS: A web-based survey was designed and administered to a random sample of 652 Year 11 students aged 16 years from all Dunedin (NZ) high schools between 30th July and 31st October 2001. Connectedness to family and friends, and school engagement were assessed, together with reports of various health compromising and health promoting behaviours. Logistic regression was used to determine the extent to which these family, friends and school variables were related to health compromising and health promoting behaviours. RESULTS: School engagement was strongly related to both low levels of health compromising and high levels of health promoting behaviours. Connectedness to family was associated primarily with fewer reports of suicidal ideation and increased reports of physical activity. Connectedness to friends was associated in the main with increased reports of health compromising behaviours. CONCLUSION: This study reinforces the importance of school and family as support networks for young people. School may well play an especially important role in health promotion among young people. The mechanisms by which engagement with school operates need to be explored further.

Adolescent↗
PubMed2006

Mutation of the Lyn tyrosine kinase delays the progression of Friend virus induced erythroleukemia without affecting susceptibility.

During the initial phase of Friend virus (FV) induced erythroleukemia, the interaction between the viral envelope glycoprotein gp55, the Erythropoietin receptor (EpoR) and the naturally occurring truncated version of the Mst1r receptor tyrosine kinase, called Sf-Stk, drives the polyclonal expansion of infected progenitors in an erythropoietin independent manner. Sf-Stk provides signals that cooperate with EpoR signals to effect expansion of erythroid progenitors. The latter phase of disease is characterized by a clonal expansion of transformed leukemic cells causing an acute erythroleukemia in mice. Signaling by Sf-Stk and EpoR mediated by gp55 renders erythroid progenitors Epo independent through the activation of the EpoR downstream pathways such as PI3K, MAPK and JAK/STAT. Previous work has shown that Src family kinases also play an important role in erythropoiesis. In particular, mutation of Src and Lyn can affect erythropoiesis. In this report we analyze the role of the Lyn tyrosine kinase in the pathogenesis of Friend virus. We demonstrate that during FV infection of primary erythroblasts, Lyn is not required for expansion of viral targets. Lyn deficient bone marrow and spleen cells are able to form Epo independent FV colonies in vitro. In vivo infection of Lyn deficient animals also results in a massive splenomegaly characteristic of the virus. However, we observe differences in the pathogenesis of Friend erythroleukemia in Lyn-/- mice. Lyn-/- mice infected with the polycythemia inducing strain of FV, FVP, do not develop polycythemia suggesting that Lyn-/- infected erythroblasts have a defect in terminal differentiation. Furthermore, the expansion of transformed cells in the spleen is reduced in Lyn-/- mice. Our data show that Lyn signals are not required for susceptibility to Friend erythroleukemia, but Lyn plays a role in later events, the terminal differentiation of infected cells and the expansion of transformed cells.

Animals↗
PubMed1985

Phospholipid localization in the plasma membrane of Friend erythroleukemic cells and mouse erythrocytes.

The distribution of phospholipids over outer and inner layers of the plasma membranes of Friend erythroleukemic cells (Friend cells) and mature mouse erythrocytes has been determined. The various techniques which have been applied to establish the phospholipid localization include the following: phospholipase A2, phospholipase C, and sphingomyelinase C treatment, fluorescamine labeling of phosphatidylethanolamine, and a phosphatidylcholine transfer protein mediated exchange procedure. The data obtained with these different techniques were found to be in good agreement with each other. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol were found to be distributed symmetrically over both layers of the plasma membrane of Friend cells. In contrast, sphingomyelin was found to be enriched in the outer layer of the membrane (80-85%), and phosphatidylserine appeared to be present mainly in the inner layer (80-90%). From these results, it was calculated that the outer and inner layers accounted for 46% and 54%, respectively, of the total phospholipid complement of that membrane. Analogous studies on the plasma membrane of mature mouse erythrocytes showed that the transbilayer distribution of the total phospholipid mass appeared to be the same as in the plasma membrane of the Friend cell, namely, 46% and 54% in outer and inner layers, respectively. The outer layer of this membrane contains 57% of the phosphatidylcholine, 20% of the phosphatidylethanolamine, 85% of the sphingomyelin, and 42% of the phosphatidylinositol, and none of the phosphatidylserine was present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗