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PubMed1980

New approach for studying macromolecular-ligand binding. Determination of the dissociation constant for macromolecule-bound ligand by gel filtration.

A graph is presented which permits facile determination of the dissociation constant constant for a macromolecule . ligand complex from gel filtration results; it can be used without a detailed understanding of the remainder of the text. When a solution of macromolecules and radioactive ligand is subjected to gel filtrations, the amount of ligand associated with the eluted macromolecule is easily measured. This quantity is then used for obtaining the corresponding dissociation constant from the graph. Values given in the graph had been determined from an equation, which is presented in the text, by means of a program which is run on a programmable calculator (Texas Instruments SR-52). It is also demonstrated how the validity of dissociation constants so obtained can be checked independently by means of a second calculation. A modification of these procedures permits determination of the dissociation constant for those situations where there is moderate dilution of the eluted sample relative to that applied to the gel filtration column, and the graph incorporates results from such calculations. The successful application of the present approach to the determination of the dissociation constants for a tubulin . [3H]GDP complex is described. Also, the potential importance of the present approach relative to other techniques for dissociation constant determination is discussed.

Chromatography, Gel↗
PubMed1995

Nicotinic responses in acutely dissociated rat hippocampal neurons and the selective blockade of fast-desensitizing nicotinic currents by lead.

The patch-clamp technique was used to characterize the nicotinic currents in individual neurons acutely dissociated from the hippocampi of postnatal rats of different ages, and to investigate the effects of Pb2+ on these currents, both in acutely dissociated and in cultured hippocampal neurons. The effects of Pb2+ on nicotinic acetylcholine receptors (nAChR) expressed in frog muscle fibers were also investigated. Acetylcholine could activate fast- and slowly desensitizing whole-cell currents in neurons dissociated from the hippocampi of 4- to 20-day-old rats. Similar to the currents elicited in cultured hippocampal neurons, the rapidly desensitizing currents were blocked by methyllycaconitine, and were the nicotinic responses that could be elicited in most of the acutely dissociated neurons tested, whereas the slowly desensitizing currents could be evoked only in a few neurons. Although the peak amplitude of nicotinic currents recorded from acutely dissociated neurons increased with age of the neurons as it did in cultured neurons, the mean amplitude of the currents was at least an order of magnitude smaller in acutely dissociated neurons than in cultured neurons. Pb2+ could potently and specifically inhibit activation of fast-desensitizing nicotinic currents in hippocampal neurons. Pb2+ reduced the peak amplitude of fast-desensitizing currents with an IC50 of about 3 microM and an apparent Hill coefficient of 1.0, whereas only at 30 microM could Pb2+ decrease the peak amplitude of slowly desensitizing currents by about 50%. Inhibition of fast-desensitizing currents by Pb2+ was voltage independent and noncompetitive. However, Pb2+ had no effect on acetylcholine-activated single channels in frog muscle fibers. Our results indicate that the hippocampus of the developing rat expresses functional nAChRs of diverse types, and that methyllycaconitine-sensitive neuronal nAChRs, which are highly permeable to Ca2+, are much more sensitive to Pb2+ than other nAChR subtypes.

Acetylcholine↗
PubMed1994

Dissociation as a result of phosphorylation of an aggregated form of the small stress protein, hsp27.

We have found that the small stress protein, hsp27, exists in extracts of U251 MG human glioma cells in two forms: a large or aggregated form (L-hsp27, 300-400 kDa) and a small or dissociated form (S-hsp27, < 70 kDa), as indicated by centrifugation on sucrose density gradients. Dissociation of L-hsp27 to S-hsp27 was enhanced by incubation of cells with phorbol 12-myristate-13 acetate, interleukin-1 alpha, tumor necrosis factor alpha, or okadaic acid, all of which are known to enhance or mimic the effects of phosphorylation of hsp27 without stimulation of its synthesis. Exposure of cells to chemical stressors, namely, NaAsO2 and CdCl2, also enhanced the dissociation of L-hsp27. hsp27 that had been labeled with [32P]H3PO4 in U251 MG cells was detected mostly in fractions that contained S-hsp27, and the incorporation of radioactivity to S-hsp27 was enhanced under conditions that stimulated the dissociation of L-hsp27. L-hsp27 present in the (NH4)2SO4 fraction (0-50% saturation) of cell extracts were dissociated to 32P-labeled hsp27 when incubated in the presence of [gamma-32P]ATP and Mg2+. These results indicate that the molecular configuration of hsp27 in cells is determined in part by phosphorylation and dephosphorylation of this protein by protein kinase(s) and phosphatase(s) and, moreover, that the rapid dissociation of the aggregated form of hsp27 by phosphorylation might be involved in a cellular defense mechanism for protection against stress.

Arsenates↗
PubMed1976

[Gonotrophic dissociation in Culex pipiens pipiens L. (author's transl)].

Under certain conditions gonotrophic dissociation has been observed in Culex pipiens pipiens. To contribute to a better understanding of the factors which govern the appearance of this phenomenon and of its ecological importance a population in Northern Germany has been investigated. Follicular development, feeding activity and occurrence of gonotrophic dissociation were examined in females obtained from wild-caught larval stages and kept under outdoor conditions after emergence in July and August. In addition overwintering females collected in cellars in September and October were investigated after reactivation by exposure to 16 hours illumination periods and 28 degrees C. In females emerging in August the follicles were generally small, the feeding activity was very low but the rate of gonotrophic dissociation appeared to be higher than that in mosquitoes which had emerged in July. Overwintering females had small follicles and did not take a blood meal during the first days under reactivation conditions. Only after five days a development of follicles and an increase in feeding activity became apparent. Through the effect of long illumination and high temperature the state of diapause was gradually overcome and the females were fully reactivated. At the same time the rate of gonotrophic dissociation in fed females which was high in the early time of exposure to reactivation conditions became low. This suggests that gonotrophic dissociation occurs commonly in females with low feeding activity, i.e. those which are not reactivated completely. In Northern Germany the overwintering females are unfed and nulliparous and gonotrophic dissociation does not seem to play an important role for the overwintering of the mosquito in this area.

Animals↗
PubMedDate not supplied

[The effect of physical and chemical environmental factors on the growth of Pseudomonas aeruginosa dissociants].

The growth rates of the R-, S-, and M-dissociants of a hydrocarbon oxidizing strain of Pseudomonas aeruginosa were comparatively studied under variable environmental conditions (aeration, temperature, pH, UV radiation, and concentration of NaCl). The R-dissociant was found to be more tolerant to UV radiation, high aeration, and temperature. The S-dissociant, which is the most effective in degrading hydrocarbons, gains a selection advantage under acidic conditions. The M-dissociant has advantages over the other dissociants under conditions of decreased aeration, low temperature, and high concentration of NaCl. The results of this work are important for optimizing microbial growth conditions and for identification of bacteria. Probably, the biological sense of dissociation is to broaden the boundaries within which a species can survive under changeable environmental conditions.

Culture Media↗
PubMed1993

Interaction of Sec4 with GDI proteins from bovine brain, Drosophila melanogaster and Saccharomyces cerevisiae. Conservation of GDI membrane dissociation activity.

Rab GDP dissociation inhibitor (Rab GDI), will induce the dissociation of GDP-bound rab3A from synaptic membranes and will inhibit GDP dissociation from Sec4, a member of the Rab subgroup of the Ras GTPase superfamily which is required for exocytosis in Saccharomyces cerevisiae. We report that Rab GDI releases GDP-bound Sec4 from yeast membranes. dGDI, a Drosophila homologue can similarly inhibit GDP dissociation from Sec4 and release GDP-bound Sec4 from yeast membranes. An activity partially purified from yeast cytosol dissociates GDP-bound Sec4 from yeast membranes, suggesting that yeast also possess a GDI protein that functions to recycle Sec4 from its target membrane.

Animals↗
PubMedDate not supplied

Early indicators of pathological dissociation in sexually abused children.

Although reported cases of adult multiple personality disorder (MPD) are increasing, confirmation of MPD and related dissociative disorders in children remains rare. Since MPD can cause severe impairment and psychological distress, and is thought to originate in childhood, early recognition of pathological dissociation and predictors of MPD is critical. Sexual abuse in childhood has similarly been under-reported until recently, and is highly associated with the development of dissociative disorders. This paper reviews factors in the professional neglect of these syndromes as well as recent diagnostic developments in childhood dissociative disorders. The identification of subtle dissociative symptomatology in children is illustrated and two case examples are presented.

Adolescent↗
PubMedDate not supplied

Dissociative disorders in children: behavioral profiles and problems.

Transient dissociative episodes are a common and normative phenomenon during childhood that generally decrease during adolescence to relatively low levels in adults. Retrospective clinical research has firmly established a connection between childhood trauma and the development of dissociative disorders in adults. A growing number of clinicians are now identifying dissociative symptoms in abused children, and there is increasing evidence that dissociative disorders represent a significant and hitherto unrecognized form of psychopathology in traumatized children. Pathological dissociation is a complex psychobiological process that results in a failure to integrate information into the normal stream of consciousness. It produces a range of symptoms and behaviors including: (a) amnesias; (b) disturbances in sense of self; (c) trance-like states; (d) rapid shifts in mood and behavior; (e) perplexing shifts in access to knowledge, memory, and skills; (f) auditory and visual hallucinations; and (g) vivid imaginary companionship in children and adolescents. Many of these symptoms and behaviors are misdiagnosed as attention, learning or conduct problems, or even psychoses. Early identification and therapeutic intervention appear to be particularly efficacious in children in contrast to adults, although systematic studies of treatment and outcome are presently lacking.

Child↗
PubMed1998

Nuclear transport factor p10/NTF2 functions as a Ran-GDP dissociation inhibitor (Ran-GDI).

The cytosolic nuclear transport factor p10/NTF2 is required for the translocation of karyophilic molecules through nuclear pores [1] [2] [3], and the small GTPase Ran is a key regulator of protein transport between the nucleus and cytoplasm [4] [5]. It has been reported that p10/NTF2 interacts directly and specifically with Ran-GDP but not with Ran-GTP [6]. The precise role(s) of p10/NTF2 in the Ran GTP/GDP cycle are thus far unclear, however. In this study, we show that mammalian p10/NTF2 dramatically inhibits the dissociation of [3H]GDP from Ran and the binding of [35S]GTPgammaS to Ran following the dissociation of non-radioactive GDP by RCC1, the only known mammalian guanine nucleotide exchange factor for Ran (Ran-GEF) [7]. In contrast, the dissociation of [35S]GTP gamma S from Ran, which was also catalyzed by RCC1, was not affected by p10/NTF2. Furthermore, the activities of wild-type p10/NTF2 and the mutant forms M84T and D92G in an assay of nuclear protein import in a digitonin-permeabilized cell-free system correlated with their level of inhibition of the dissociation of nucleotide from Ran-GDP. These results suggest that p10/NTF2 acts as a GDP dissociation inhibitor for Ran (Ran-GDI), thereby coordinating the Ran-dependent reactions that underlie nuclear protein import.

Animals↗
PubMed1986

Development, reliability, and validity of a dissociation scale.

Dissociation is a lack of the normal integration of thoughts, feelings, and experiences into the stream of consciousness and memory. Dissociation occurs to some degree in normal individuals and is thought to be more prevalent in persons with major mental illnesses. The Dissociative Experiences Scale (DES) has been developed to offer a means of reliably measuring dissociation in normal and clinical populations. Scale items were developed using clinical data and interviews, scales involving memory loss, and consultations with experts in dissociation. Pilot testing was performed to refine the wording and format of the scale. The scale is a 28-item self-report questionnaire. Subjects were asked to make slashes on 100-mm lines to indicate where they fall on a continuum for each question. In addition, demographic information (age, sex, occupation, and level of education) was collected so that the connection between these variables and scale scores could be examined. The mean of all item scores ranges from 0 to 100 and is called the DES score. The scale was administered to between 10 and 39 subjects in each of the following populations: normal adults, late adolescent college students, and persons suffering from alcoholism, agoraphobia, phobic-anxious disorders, posttraumatic stress disorder, schizophrenia, and multiple personality disorder. Reliability testing of the scale showed that the scale had good test-retest and good split-half reliability. Item-scale score correlations were all significant, indicating good internal consistency and construct validity. A Kruskal-Wallis test and post hoc comparisons of the scores of the eight populations provided evidence of the scale's criterion-referenced validity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Dreams as a possible reflection of a dissociated self-monitoring system.

Recently, there has been a great deal of clinical and experimental interest expressed in dissociative disorders and dissociative states. Theories of mental organization and personality have been formulated as a result of this new emphasis on dissociative phenomena. Dreams may possibly be thought of as dissociative phenomena of a particular type that reflect a monitoring of and reaction to internal and external conditions within the dreamer. Experimental and/or clinical work related to hypnosis, rapid eye movement phenomena, dreams, and hemispheric specialization are discussed to support this view. Dreams are described within the context of dissociation-based theories of personality organization. Brain behavior relationships are emphasized whenever possible.

Awareness↗
PubMed1989

Multiple personality, dissociation, and C.G. Jung's complex theory.

Jung's contributions to the study of 'dissociation' are outlined here for perhaps the first time. Jung is unique in recognising that the 'dissociability of the psyche' is a fundamental process that extends along the continuum from 'normal' mental functioning to 'abnormal' states. Dissociation is recognised by Jung as a universal and necessary psychic activity for the development of personality through the differentiation of functions. However, when the cohesion of consciousness is shattered by extreme childhood traumata, as it is in the development of multiple personality, this natural differentiation of function is intensified and the dissociative splits between autonomous forces in the psyche become more extreme. This increases the autonomy of these 'splinter psyches' from ego-consciousness and reveals their archetypal core. They then develop into the phenomenon of 'alternate personalities' in multiple personality. In a comparison of the major tenets of the complex theory with recent empirical research on multiple personality, it is demonstrated that essential characteristics of Jung's 'autonomous complexes' are congruent with the phenomenology of the 'alternate personalities' or 'personality states' of this disorder. This underscores the relevance of Jung's complex theory to present understanding of multiple personality. In addition, the phenomenon of multiple personality is, in turn, important for realising the central significance of dissociation in the complex theory and provides an excellent contemporary clinical example of the archetypal ground of the psyche.

Adult↗
PubMed1994

Dissociation and child abuse histories in an eating disorder cohort in Japan.

Dissociation and childhood abuse were studied in female eating disorder outpatients in Japan. A self-report version of the Dissociative Disorders Interview Schedule (DDIS), which includes data on physical and sexual abuse, and the Dissociative Experience Scale (DES) were used. Nine of 41 subjects who completed the DDIS reported symptoms suggesting DSM-III-R multiple personality, and 6 of the 39 subjects who completed the DES scored over 30 (reflecting a high likelihood of posttraumatic stress or multiple personality). Subjects' sexual abuse history rates were considerably greater then those in the Japanese general population. Though physical abuse history was associated with high dissociation, no difference was seen between the high and low dissociators in sexual abuse histories.

Adolescent↗
PubMed1990

The Structured Clinical Interview for DSM-III-R Dissociative Disorders: preliminary report on a new diagnostic instrument.

The authors describe the Structured Clinical Interview for DSM-III-R Dissociative Disorders (SCID-D), which investigates five groups of dissociative symptoms (amnesia, depersonalization, derealization, identity confusion, and identity alteration) and systematically rates both the severity of individual symptoms and the evaluation of overall diagnosis of dissociative disorder. Preliminary findings from a study of 48 subjects with and without psychiatric diagnoses indicate good to excellent reliability and discriminant validity for the SCID-D as a diagnostic instrument for the five dissociative disorders and as a tool for the evaluation of dissociative symptoms encountered within nondissociative syndromes.

Adult↗
PubMed1998

Affective predictors of dissociation. II: Shame and guilt.

As a contribution to an understanding of the psychodynamics of dissociative disorders this study investigated proneness to shame and to guilt as predictors of dissociative tendencies. One hundred and three Australian university students completed self-report measures of dissociative tendencies, proneness to shame and to guilt, gender, and age. Proneness to shame, proneness to guilt, and age were found to contribute significantly to the prediction of dissociative tendencies. The data provide further support for the view that common affective consequences of childhood trauma may mediate between such trauma and the development of a dissociative coping style.

Adult↗
PubMed1995

Dissociation in bulimic and non-eating-disordered women.

A relationship between dissociative experiences and the eating disorders has been reported. However the nature of that link is not clearly understood. This study investigates the links between dissociation (as measured by the Dissociative Experiences Scale-DES II) and eating psychopathology in a clinical group of bulimic women and a nonclinical group of undergraduates. In the nonclinical group, specific dissociative styles were found to be linked with bulimic attitudes on the Eating Attitudes Test. In the eating-disordered group, there was an association between the scales of the DES II and frequency of bringing. This association was primarily due to the effects of the dissociative style of absorption (e.g., daydreaming). Suggestions are made for further research, and the clinical implications of the findings are discussed.

Adult↗
PubMed2006

Low predictive power of peritraumatic dissociation for PTSD symptoms in accident survivors.

To test the predictive power of peritraumatic dissociation for the development of psychopathology, the authors assessed symptoms of peritraumatic dissociation (Peritraumatic Dissociative Experiences Questionnaire; PDEQ), posttraumatic stress disorder (Clinician-Administered PTSD Scale; CAPS), anxiety and depression (Hospital Anxiety and Depression Scale; HADS) in a sample of 214 accident victims 5 days postaccident (T1). Six months later (T2), CAPS and HADS were administered again. Acute stress disorder (ASD) and PTSD symptom levels were surprisingly low. In sequential regression analyses, initial reexperiencing and hyperarousal significantly predicted PTSD symptom level (T2) over several possibly confounding variables controlled for. Peritraumatic dissociation explained less than 3% of variance. For PTSD scores, 38% overall variance explanation was obtained; the variance for HADS scores was low. Possible explanations for the low-predictive power of peritraumatic dissociation for posttraumatic psychopathology in the sample are discussed.

Accidents↗
PubMed1996

Dissociative experiences and posttraumatic stress disorder among female victims of criminal assault and rape.

This study examines the relationship between posttraumatic stress disorder (PTSD) and dissociative experiences in a sample of 158 recent female assault victims (74 rape, 84 nonsexual assault) and 46 comparison subjects who had not been assaulted within the last year. Results indicated that victims had elevated scores on Dissociative Experiences Scale (DES) as compared to the comparison subjects, but that this elevation was not as high as for other traumatized samples. The level of dissociation reported by assault victims declined significantly over the three month course of the study. DES scores were related to PTSD diagnosis and symptom severity, but only among nonsexual assault victims. In rape victims, there was no correlation between dissociation and PTSD. Recent victims with a history of childhood sexual abuse were significantly more dissociative than those who did not report such a history. These results are discussed with regard to vulnerability factors for developing PTSD subsequent to a criminal assault.

Adult↗