Characterization of the stability and folding of H2A.Z chromatin particles: implications for transcriptional activation.

H2A.Z and H2A.1 nucleosome core particles and oligonucleosome arrays were obtained using recombinant versions of these histones and a native histone H2B/H3/H4 complement reconstituted onto appropriate DNA templates. Analysis of the reconstituted nucleosome core particles using native polyacrylamide gel electrophoresis and DNase I footprinting showed that H2A.Z nucleosome core particles were almost structurally indistinguishable from its H2A.1 or native chicken erythrocyte counterparts. While this result is in good agreement with the recently published crystallographic structure of the H2A.Z nucleosome core particle (Suto, R. K., Clarkson, M J., Tremethick, D. J., and Luger, K. (2000) Nat. Struct. Biol. 7, 1121-1124), the ionic strength dependence of the sedimentation coefficient of these particles exhibits a substantial destabilization, which is most likely the result of the histone H2A.Z-H2B dimer binding less tightly to the nucleosome. Analytical ultracentrifuge analysis of the H2A.Z 208-12, a DNA template consisting of 12 tandem repeats of a 208-base pair sequence derived from the sea urchin Lytechinus variegatus 5 S rRNA gene, reconstituted oligonucleosome complexes in the absence of histone H1 shows that their NaCl-dependent folding ability is significantly reduced. These results support the notion that the histone H2A.Z variant may play a chromatin-destabilizing role, which may be important for transcriptional activation.

Histone variants and histone modifications: a structural perspective.

In this review, we briefly analyze the current state of knowledge on histone variants and their posttranslational modifications. We place special emphasis on the description of the structural component(s) defining and determining their functional role. The information available indicates that this histone "variability" may operate at different levels: short-range "local" or long-range "global", with different functional implications. Recent work on this topic emphasizes an earlier notion that suggests that, in many instances, the functional response to histone variability is possibly the result of a synergistic structural effect.

Eating disorders and psychiatric disorders in the first-degree relatives of obese probands with binge eating disorder and obese non-binge eating disorder controls.

OBJECTIVE: The purposes of the present study were to examine the possibility of a familial tendency for binge eating disorder (BED) among the obese, to clarify the relationship between BED and other eating disorders, and to test the relationship between BED and other psychiatric disorders. METHOD: We studied 32 female BED outpatients and 23 obese females without BED. A possible history of eating disorders was assessed using the Structured Clinical Interview for DSM-III-R-Eating Disorders section administered by telephone interview. Family history information for other psychiatric disorders was collected using the Family History Research Diagnostic Criteria RESULTS: The frequency of all eating disorders and the risk for other psychiatric disorders were not significantly different between the relatives of the two groups. These results were consistent across generation and gender. DISCUSSION: This study failed to show a familial tendency for BED, or any significant familial relationship between BED and other eating disorders, and did not support the hypothesis of coaggregation of other psychiatric disorders with BED.

BRCA1 expression restores radiation resistance in BRCA1-defective cancer cells through enhancement of transcription-coupled DNA repair.

The breast cancer predisposition genes, BRCA1 and BRCA2, are responsible for the vast majority of hereditary breast cancer. Although BRCA2 functions to help the cell repair double-stranded DNA breaks, the function of BRCA1 remains enigmatic. Here, we develop a human genetic system to study the role of BRCA1 in oxidative DNA damage. We show that human cancer cells containing mutated BRCA1 are hypersensitive to ionizing radiation. This hypersensitivity can be reversed by the expression of forms of BRCA1 that are not growth suppressing. Reversal of hypersensitivity requires the ring finger of BRCA1, its transactivation domain, and its BRCT domain. Lastly, we show that unlike BRCA2, BRCA1 does not function in the repair of double-stranded DNA breaks. Instead, it functions in transcription-coupled DNA repair (TCR). TCR ability correlated with radioresistance as cells containing BRCA1 showed both increased TCR and radioresistance, whereas cells without BRCA1 showed decreased TCR and radiosensitivity. These findings give physiologic significance to the interaction of BRCA1 with the basal transcription machinery.

Mitogen-activated protein kinase kinase 2 activation is essential for progression through the G2/M checkpoint arrest in cells exposed to ionizing radiation.

An increasing body of evidence suggests that mitogen-induced activation of the RAF/ERK signaling pathway is functionally separate from the stress-induced activation of the SEK/JNK/p38 signaling pathway. In general, stress stimuli strongly activate the p38s and the JNKs while only weakly activating ERK1 and ERK2. However, a number of independent groups have now shown that the RAF/ERK signaling pathway is strongly activated by ionizing radiation. In this work, we examine this paradox. We show that both mitogen-activated protein (MAP) kinase kinase 1 (MEK1) and MAP kinase kinase 2 (MEK2) are activated by ionizing radiation. Blockage of this activation through the use of dominant negative MEK2 increases sensitivity of the cell to ionizing radiation and decreases the ability of a cell to recover from the G2/M cell cycle checkpoint arrest. Blocking MEK2 activation does not affect double-strand DNA break repair, however. Although MEK1 is activated to a lesser extent by ionizing radiation, expression of a dominant negative MEK1 does not affect radiation sensitivity of the cell, the G2/M checkpoint of the cell, or double-strand break repair. Because ionizing radiation leads to a different cell cycle arrest (G2/M arrest) than that typically seen with other stress stimuli, and because we have shown that MEK2 can affect G2/M checkpoint kinetics, these results provide an explanation for the observation that the MEKs can be strongly activated by ionizing radiation and only weakly activated by other stressful stimuli.

Double-strand break repair deficiency and radiation sensitivity in BRCA2 mutant cancer cells.

BACKGROUND: The protein product of the BRCA2 gene mediates repair of double-strand breaks in DNA. Because a number of cancer therapies exert cytotoxic effects via the initiation of double-strand breaks, cancers comprised of cells carrying BRCA2 gene mutations may be more amenable to treatment with agents that cause such breaks. METHODS: We identified a human pancreatic adenocarcinoma cell line lacking one copy of the BRCA2 gene and containing a mutation (6174delT) in the remaining copy. In vitro and in vivo experiments were conducted with this cell line and with other carcinoma cell lines matched for similar genetic mutations, similar differentiation status, and/or similar carcinoma type to examine double-strand break repair, sensitivity to drugs that induce double-strand breaks, and radiation sensitivity. RESULTS: BRCA2-defective cells were unable to repair the double-strand DNA breaks induced by ionizing radiation. These cells were also markedly sensitive to mitoxantrone, amsacrine, and etoposide (drugs that induce double-strand breaks) (two-sided P = .002) and to ionizing radiation (two-sided P = .001). Introduction of antisense BRCA2 deoxyribonucleotides into cells possessing normal BRCA2 function led to increased sensitivity to mitoxantrone (two-sided P = .008). Tumors formed by injection of BRCA2-defective cells into nude mice were highly sensitive (>90% tumor size reduction, two-sided P = .002) to both ionizing radiation and mitoxantrone when compared with tumors exhibiting normal BRCA2 function. Histologic analysis of irradiated BRCA2-defective tumors showed a large degree of necrosis compared with that observed for control tumors possessing normal BRCA2 function. CONCLUSION: BRCA2-defective cancer cells are highly sensitive to agents that cause double-strand breaks in DNA.

Onset of binge eating and dieting in overweight women: implications for etiology, associated features and treatment.

This study investigated differences between overweight binge eating women who reported the onset of binge eating prior to or following the onset of dieting (binged first [BF], or dieted first [DF]). Of overweight binge eating subjects enrolled in a treatment study, 38.7% indicated binge eating first, and 48.1% dieting first. The mean age of onset of binge eating differed significantly between the two groups (11.8 years vs. 25.7 years). More of the BF group (82.5%) satisfied proposed binge eating disorder (BED) criteria than did the DF group (52.0%), although short of significantly. The results suggest that: (a) the leading hypothesis concerning dieting as a cause of binge eating does not apply to a substantial number of individuals who binge eat; (b) there may be an early pattern and a late pattern in the development of binge eating among overweight individuals; and (c) the early or binge first pattern may be more likely to result in BED.

Relationship of childhood sexual abuse and eating disorders.

OBJECTIVE: To review the literature that has examined the relationship between childhood sexual abuse and the eating disorders. METHOD: Each of the five authors reviewed all identified empirical studies to be certain that inclusion/exclusion criteria were met. Two teams of raters then independently reviewed each study to determine whether it supported any of a series of six hypotheses that had been tested in this literature. RESULTS: This review indicates that childhood sexual abuse is a nonspecific risk factor for bulimia nervosa, particularly when there is psychiatric comorbidity. There is some indication that childhood sexual abuse is more strongly associated with bulimic disorders than restricting anorexia, but it does not appear to be associated with severity of the disturbance. CONCLUSION: Childhood sexual abuse is a risk factor for bulimia nervosa with significant comorbidity. Further study of the nature of this relationship is warranted.

Finkel-Biskis-Reilly mouse osteosarcoma virus v-fos inhibits the cellular response to ionizing radiation in a myristoylation-dependent manner.

DNA damage is recognized as a central component of carcinogenesis. DNA-damaging agents activate a number of signal transduction pathways that lead to repair of the DNA, apoptosis, or cell cycle arrest. It is reasoned that a cell deficient in DNA repair is more likely to acquire other cancer-promoting mutations. Despite the recent interest in the link between DNA damage and carcinogenesis, retroviral oncogenes have not yet been shown to affect the DNA damage-signaling pathway. In this report, we show that Finkel-Biskis-Reilly mouse osteosarcoma virus (FBR) v-fos, the retroviral homologue of the c-fos proto-oncogene, inhibits the cellular response to ionizing radiation. Cells that express FBR v-Fos show a decreased ability to repair DNA damage caused by ionizing radiation, and these cells show decreased survival in response to ionizing radiation. In addition, FBR v-Fos inhibits DNA-dependent protein kinase, a kinase specifically activated upon exposure to ionizing radiation. These effects were specific to ionizing radiation, as no effect of FBR v-Fos on the UV light signaling pathway was seen. Last, these effects were dependent on a lipid modification required for FBR v-Fos tumorigenesis, that of myristoylation of FBR v-Fos. A non-myristoylated mutant FBR v-Fos caused none of these effects. This study suggests that a retroviral oncogene can lead to an increased genomic instability, which can ultimately increase the carcinogenic potential of a cell.

Finkel-Biskis-Reilly osteosarcoma virus v-Fos inhibits adipogenesis and both the activity and expression of CCAAT/enhancer binding protein alpha, a key regulator of adipocyte differentiation.

Finkel-Biskis-Reilly (FBR) osteosarcoma virus v-Fos causes tumors of mesenchymal origin, including osteosarcomas, rhabdomyosarcomas, chondrosarcomas, and liposarcomas. Because the cell of origin in all these tumors is a pluripotent mesenchymal cell, the variety of tumors seen in mice which express FBR v-Fos implies that FBR v-Fos inhibits multiple differentiation pathways. To study the mechanism of FBR v-Fos' inhibition of mesenchymal differentiation, we utilized an in vitro model of adipocyte differentiation. We show by both morphological and biochemical means that FBR v-Fos inhibits adipocyte differentiation in vitro. This inhibition is due to FBR v-Fos' inhibition of the growth arrest characteristic of terminal differentiation and FBR v-Fos' inhibition of the expression and activity of a key regulator of this growth arrest, C/EBPalpha. The in vitro inhibition of adipogenesis by FBR v-Fos has in vivo significance as immunostaining of FBR v-Fos-induced tumors shows no CCAAT/enhancer binding protein (EBP)-alpha expression. These data implicate C/EBPalpha as a protein involved in the generation of liposarcomas.

Antidepressants vs. psychotherapy in the treatment of bulimia nervosa.

Studies of the effectiveness of psychotherapy and pharmacotherapy in the treatment of bulimia nervosa have been accumulating over the last decade. Only recently, however, have investigations been reported comparing the two modalities directly, assessing whether one might be more effective than the other, or whether a combination of the two approaches might be superior to either alone. This paper reviews the three combined treatment studies that have been published to date and discusses their implications for clinical practice and for future research.

Willingness to apply understood ethical principles.

Recent research suggests a discrepancy between understanding vs. implementation of ethical principles. The present study investigated the relationship between decisions with regard to what "should" vs. what "would" be done in a variety of ethical conflict situations. Additionally, this research examined the influence of the degree of closeness of the respondent to the identified person-of-reference in each conflict scenario. The results strongly supported the conclusion that while professional clinicians are capable of recognizing conduct that falls below accepted ethical standards, they are less willing to follow through with required action. Restrictiveness of conflict resolution was related to both person-of-reference group and to specific ethical situation. The results are discussed in terms of attribution theory and actor-observer effects.

Resource exchange theory: a problem-solving tool.

In the creation and operation of work environments, problem solving can be more effective with some theories or models than with others. In this article, the author describes a theory that he has found to be especially useful for his management responsibilities. The Resource Exchange Theory, he says, engenders a unique view of power that is useful in managing a reward system, negotiating, managing conflict, and empowering people.

The effect of rapid maxillary expansion on nasal airway resistance.

The purpose of this study was to evaluate changes in nasal resistance to airflow in persons undergoing rapid maxillary expansion and to reevaluate the responses at a 1-year follow-up. Nasal resistance measurements, assessed in four modes (natural state, anterior nares dilation with Tygon tubing, following administration of decongestant, and nares dilation with tubing and decongestant), were taken on a group of 38 patients receiving rapid maxillary expansion and compared with a control group not receiving expansion. Thirty-three of the patients were reevaluated 9 to 12 months after expansion was completed. Eighteen subjects in the control group were also reevaluated. Oral/nasal airflow rates (percent nasality) were recorded for the control group and for some of the expansion patients. Results indicated that some subjects receiving rapid maxillary expansion had a significantly higher nasal resistance than the control group. There was a significant median reduction in nasal resistance following rapid maxillary expansion, measured in the natural state only, and this appeared to be stable up to 1 year after maximum expansion was obtained. Rapid maxillary expansion appeared to effect an expansion at the anterior nares, which contributes to nasal resistance reduction. Individual variation in nasal resistance values was considerable and hence the median response for the group was not a reliable estimate of individual response. Due to the high individual response variability, rapid maxillary expansion is not a predictable means of decreasing nasal resistance.