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1.
Artigo em Inglês | MEDLINE | ID: mdl-36600291

RESUMO

BACKGROUND: Complex Posttraumatic Stress Disorder (CPTSD) has previously been associated with earlier trauma onset, repeated interpersonal traumatization, more dissociation, and more comorbid psychopathology. However, it is still debated if the afore-mentioned risk factors are related to CPTSD diagnosis or rather indicative of a more severe form of post-traumatic distress. The aim of this study was to compare patients with a CPTSD diagnosis to those with PTSD in trauma characteristics (onset, chronicity, interpersonal nature, familiarity with perpetrator), dissociation, and psychiatric comorbidities, while accounting for symptom severity. METHODS: In total, N = 81 patients with a trauma history (n = 43 with CPTSD; n = 37 with PTSD) underwent diagnostic interviews by trained clinicians and completed measures on CPTSD symptom severity, trauma characteristics, and dissociation (Screening for Complex PTSD; Dissociative Experience Scale Taxon). RESULTS: Patients with CPTSD reported earlier onset of trauma, more trauma perpetrated by acquaintances or family members, and more comorbidities than those with PTSD, also when accounting for symptom severity. No group differences in chronicity and dissociation were found. Severity of CPTSD was associated with earlier onset, familiarity with perpetrator, more comorbid (affective) disorders, and dissociation in both diagnostic groups. CONCLUSION: Findings largely confirm earlier research, suggesting that CPTSD is associated with traumatic events that start earlier in life and are perpetrated by acquaintances. Focusing on transdiagnostic symptoms, such as dissociation, may help to detain symptom deterioration. Due to the small sample size, findings need to be interpreted with caution and further research is needed to replicate findings in larger samples. Future research should also elucidate possible working mechanisms besides dissociation, such as emotion dysregulation or negative self-image.

2.
Tijdschr Psychiatr ; 61(4): 267-275, 2019.
Artigo em Holandês | MEDLINE | ID: mdl-31017285

RESUMO

BACKGROUND: Dissociation is a prevalent symptom in borderline personality disorder (BPD), which can have detrimental effects on everyday functioning and treatment. Until now, little is known about the brain networks implicated in dissociation in BPD. Research on dissociative disorders and posttraumatic stress disorder found alterations in networks implicated in cognitive control and arousal modulation. However, it is unknown whether these alterations are also affected in BPD.
AIM: To provide an overview of the definitions, neurobiological models, and neuroimaging research on dissociation in BPD.
METHOD: Review of the literature.
RESULTS: During dissociation in BPD, there is evidence for an altered recruitment and interplay of brain regions implicated in the regulation of stress responses and emotions, attention, memory, and self-referential processing (amygdala, anterior cingulate cortex, inferior frontal gyrus, medial prefrontal cortex, superior temporal gyrus, and inferior parietal lobule).
CONCLUSION: Dissociation is associated with alterations in brain networks that regulate affect-cognitive processing in BPD. Given the substantial impact of dissociation on treatment and neural processing, dissociative symptoms should be taken into account in future research and treatment of BPD, even if they are not the primary focus.


Assuntos
Transtorno da Personalidade Borderline/psicologia , Transtornos Dissociativos , Emoções/fisiologia , Transtorno da Personalidade Borderline/terapia , Humanos , Neuroimagem
3.
GMS J Med Educ ; 33(4): Doc54, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27579354

RESUMO

The competent physical examination of patients and the safe and professional implementation of clinical procedures constitute essential components of medical practice in nearly all areas of medicine. The central objective of the projects "Heidelberg standard examination" and "Heidelberg standard procedures", which were initiated by students, was to establish uniform interdisciplinary standards for physical examination and clinical procedures, and to distribute them in coordination with all clinical disciplines at the Heidelberg University Hospital. The presented project report illuminates the background of the initiative and its methodological implementation. Moreover, it describes the multimedia documentation in the form of pocketbooks and a multimedia internet-based platform, as well as the integration into the curriculum. The project presentation aims to provide orientation and action guidelines to facilitate similar processes in other faculties.


Assuntos
Currículo , Educação de Graduação em Medicina , Exame Físico , Docentes , Humanos , Medicina
4.
Psychol Med ; 46(15): 3137-3149, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27572473

RESUMO

BACKGROUND: Impulsivity is a core feature of borderline personality disorder (BPD) and attention deficit hyperactivity disorder (ADHD). In BPD, impulsive behavior primarily occurs under acute stress; impulse control deficits under non-stress conditions may be partly related to co-morbid ADHD. We aimed to investigate whether acute experimental stress has an impact on self-reported impulsivity, response inhibition (action withholding, action cancelation) and delay discounting in BPD compared to ADHD. METHOD: Thirty female BPD patients, 28 female ADHD patients (excluding patients with co-morbid BPD and ADHD), and 30 female healthy controls (HC) completed self-reports and behavioral measures of impulsivity (IMT, assessing action withholding; GoStop, measuring action cancelation, Delay Discounting Task) under baseline conditions and after an experimental stress induction (Mannheim Multicomponent Stress Test). RESULTS: Both patient groups reported higher impulsivity than HC, ADHD reported higher trait impulsivity than BPD. On the IMT, ADHD showed significant action-withholding deficits under both conditions, while BPD performed significantly worse than HC under stress. In BPD but not ADHD and HC, action-withholding deficits (IMT) were significantly increased under stress compared to baseline, while no group/stress effects were found for action cancelation (GoStop). Delay discounting was significantly more pronounced in BPD than in HC (no stress effect was found). CONCLUSIONS: In BPD, behavioral deficits in action withholding (but not in action cancelation) appear to be influenced by acute experimental stress. Delay discounting seems to be a general feature of BPD, independent of co-morbid ADHD and acute stress, possibly underlying typical expressions of behavioral impulsivity in the disorder.


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/psicologia , Transtorno da Personalidade Borderline/psicologia , Desvalorização pelo Atraso , Inibição Psicológica , Estresse Psicológico/psicologia , Adulto , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Transtorno da Personalidade Borderline/fisiopatologia , Estudos de Casos e Controles , Feminino , Humanos , Estresse Psicológico/fisiopatologia , Adulto Jovem
5.
Neurosci Lett ; 604: 173-7, 2015 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-26219987

RESUMO

The cerebellum is known to contribute to the acquisition and retention of conditioned motor and emotional responses. Eyeblink conditioning and fear conditioning have been studied in greatest detail. Whereas a considerable number of studies have shown that the cerebellum is also involved in extinction of conditioned eyeblink responses, the likely contribution of the cerebellum to extinction of conditioned fear responses has largely been ignored. In the present study, we analyzed functional brain imaging data (fMRI) of previous work investigating extinction of conditioned fear in 32 young and healthy men, in which event-related fMRI analysis did not include the cerebellum. This dataset was analyzed using a spatial normalization method optimized for the cerebellum. During fear acquisition, an unpleasant electric shock (unconditioned stimulus; US) was paired with one of two pictures of geometrical figures (conditioned stimulus; CS+), while the other picture (CS-) was never paired with the US. During extinction, CS+ and CS- were presented without the US. During the acquisition phase, the fMRI signal related to the CS+ was significantly higher in hemispheric lobule VI in early compared to late acquisition (p<.05, permutation corrected). During the extinction phase, the fMRI signal related to the contrast CS+>CS- was significantly higher within the anterior vermis in early compared to late extinction (p<.05, permutation corrected). The present data show that the cerebellum is not only associated with the acquisition but also with the extinction of conditioned fear.


Assuntos
Vermis Cerebelar/fisiologia , Condicionamento Clássico , Extinção Psicológica , Medo , Adolescente , Adulto , Mapeamento Encefálico , Humanos , Imageamento por Ressonância Magnética , Masculino , Adulto Jovem
6.
J. clin. endocrinol. metab ; 99(11)Nov. 2014. ilus, tab
Artigo em Inglês | BIGG - guias GRADE | ID: biblio-966004

RESUMO

OBJECTIVE: The aim was to formulate clinical practice guidelines for acromegaly. PARTICIPANTS: The Task Force included a chair selected by the Endocrine Society Clinical Guidelines Subcommittee (CGS), five experts in the field, and a methodologist. The authors received no corporate funding or remuneration. This guideline is cosponsored by the European Society of Endocrinology. EVIDENCE: This evidence-based guideline was developed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to describe both the strength of recommendations and the quality of evidence. The Task Force reviewed primary evidence and commissioned two additional systematic reviews. CONSENSUS PROCESS: One group meeting, several conference calls, and e-mail communications enabled consensus. Committees and members of the Endocrine Society and the European Society of Endocrinology reviewed drafts of the guidelines. CONCLUSIONS: Using an evidence-based approach, this acromegaly guideline addresses important clinical issues regarding the evaluation and management of acromegaly, including the appropriate biochemical assessment, a therapeutic algorithm, including use of medical monotherapy or combination therapy, and management during pregnancy.(AU)


Assuntos
Humanos , Acromegalia/terapia , Avaliação em Saúde , Terapia Combinada , Medicina Baseada em Evidências
7.
Psychol Med ; 44(13): 2889-901, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25066544

RESUMO

BACKGROUND: Studies in borderline personality disorder (BPD) have consistently revealed abnormalities in fronto-limbic brain regions during emotional, somatosensory and cognitive challenges. Here we investigated changes in resting-state functional connectivity (RSFC) of three fronto-limbic core regions of specific importance to BPD. METHOD: Functional magnetic resonance imaging data were acquired in 20 unmedicated female BPD patients and 17 healthy controls (HC, matched for age, sex and education) during rest. The amygdala, and the dorsal and ventral anterior cingulate cortex (ACC) were defined as seeds to investigate RSFC patterns of a medial temporal lobe network, the salience network and default mode network. The Dissociation Experience Scale (DES), a measure of trait dissociation, was additionally used as a predictor of RSFC with these seed regions. RESULTS: Compared with HC, BPD patients showed a trend towards increased RSFC between the amygdala and the insula, orbitofrontal cortex and putamen. Compared with controls, patients furthermore exhibited diminished negative RSFC between the dorsal ACC and posterior cingulate cortex, a core region of the default mode network, and regions of the dorsomedial prefrontal cortex. Last, increased negative RSFC between the ventral ACC and medial occipital regions was observed in BPD patients. DES scores were correlated with amygdala connectivity with the dorsolateral prefrontal cortex and fusiform gyrus. CONCLUSIONS: Our findings suggest alterations in resting-state networks associated with processing of negative emotions, encoding of salient events, and self-referential processing in individuals with BPD compared with HC. These results shed more light on the role of abnormal brain connectivity in BPD.


Assuntos
Tonsila do Cerebelo/fisiopatologia , Transtorno da Personalidade Borderline/fisiopatologia , Mapeamento Encefálico/métodos , Giro do Cíngulo/fisiopatologia , Relações Interpessoais , Rede Nervosa/fisiopatologia , Adulto , Transtornos Dissociativos/fisiopatologia , Feminino , Humanos , Imageamento por Ressonância Magnética
8.
Psychol Med ; 44(15): 3329-40, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25065373

RESUMO

BACKGROUND: Previous research on impulsivity in borderline personality disorder (BPD) has revealed inconsistent findings. Impulsive behaviour is often observed during states of emotional distress and might be exaggerated by current attention deficit hyperactivity disorder (ADHD) symptoms in individuals with BPD. We aimed to investigate different components of impulsivity dependent on stress induction controlling for self-reported ADHD symptoms in BPD. METHOD. A total of 31 unmedicated women with BPD and 30 healthy women (healthy controls; HCs), matched for age, education and intelligence, completed self-reports and behavioural tasks measuring response inhibition (go/stop task) and feedback-driven decision making (Iowa Gambling Task) under resting conditions and after experimental stress induction. ADHD symptoms were included as a covariate in the analyses of behavioural impulsivity. Additionally, self-reported emotion-regulation capacities were assessed. RESULTS: BPD patients reported higher impulsive traits than HCs. During stress conditions - compared with resting conditions - self-reported impulsivity was elevated in both groups. Patients with BPD reported higher state impulsivity under both conditions and a significantly stronger stress-dependent increase in state impulsivity. On the behavioural level, BPD patients showed significantly impaired performance on the go/stop task under stress conditions, even when considering ADHD symptoms as a covariate, but not under resting conditions. No group differences on the Iowa Gambling Task were observed. Correlations between impulsivity measures and emotion-regulation capacities were observed in BPD patients. CONCLUSIONS: Findings suggest a significant impact of stress on self-perceived state impulsivity and on response disinhibition (even when considering current ADHD symptoms) in females with BPD.


Assuntos
Transtorno da Personalidade Borderline/fisiopatologia , Comportamento Impulsivo/fisiologia , Inibição Psicológica , Desempenho Psicomotor/fisiologia , Estresse Psicológico/fisiopatologia , Adolescente , Adulto , Feminino , Humanos , Pessoa de Meia-Idade , Adulto Jovem
9.
Clin Endocrinol (Oxf) ; 78(6): 914-9, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23146135

RESUMO

OBJECTIVE: We previously reported improved body composition and cardiovascular risk markers plus a small decrease in glucose tolerance with GH administration vs placebo for 6 months to abdominally obese premenopausal women. The objective of this study was to determine whether the effects of GH treatment on cardiovascular risk markers, body composition and glucose tolerance in obese women persist 6 months after GH withdrawal. DESIGN AND PATIENTS: Fifty abdominally obese premenopausal women completed a trial of rhGH vs placebo for 6 months; thirty-nine women completed a subsequent 6-month withdrawal observation period. MEASUREMENTS: IGF-I, body composition by CT, (1) H-MRS and DXA, serum cardiovascular risk markers, oral glucose tolerance test (OGTT). RESULTS: IGF-I standard deviation scores (SDS) within the GH group were -1.7 ± 0.1 (pretreatment),-0.1 ± 0.3 (after 6 months of GH) and -1.7 ± 0.1 (6 months post-GH withdrawal). Six months after GH withdrawal, total abdominal and subcutaneous adipose tissue, total fat, trunk fat, trunk/extremity fat, hsCRP, apoB, LDL, and tPA were higher than at the 6-month (GH discontinuation) timepoint (P ≤ 0.05). All body composition and cardiovascular risk markers that had improved with GH returned to baseline levels by 6 months after GH discontinuation, as did fasting and 2-h OGTT glucose levels. CONCLUSION: The effects of GH administration to abdominally obese premenopausal women have a short time-course. The beneficial effects on body composition and cardiovascular risk markers, and the side effect of altered glucose tolerance returned to pretreatment levels after GH withdrawal. There was no suppression of endogenous IGF-I levels, which returned to baseline after GH withdrawal.


Assuntos
Hormônio do Crescimento Humano/efeitos adversos , Obesidade/tratamento farmacológico , Síndrome de Abstinência a Substâncias/fisiopatologia , Adulto , Glicemia/metabolismo , Composição Corporal/efeitos dos fármacos , Doenças Cardiovasculares/induzido quimicamente , Feminino , Teste de Tolerância a Glucose , Hormônio do Crescimento Humano/administração & dosagem , Humanos , Fator de Crescimento Insulin-Like I/metabolismo , Pessoa de Meia-Idade , Pré-Menopausa , Fatores de Risco
10.
Psychol Med ; 42(10): 2181-92, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22397907

RESUMO

BACKGROUND: Emotion dysregulation, characterized by heightened emotional arousal and increased emotional sensitivity, is a core feature of borderline personality disorder (BPD). Although current theories emphasize the disruptive potential of negative emotions on cognitive functioning in BPD, behavioral and neurobiological data on this relationship are still lacking. METHOD: Using functional magnetic resonance imaging (fMRI), neural activity was investigated in 22 unmedicated BPD patients and 22 healthy participants (matched for age, education and intelligence) performing an adapted Sternberg working memory task, while being distracted by emotional (negatively arousing) and neutral pictures from the International Affective Picture System (IAPS). RESULTS: Emotional distraction was associated with significantly higher activation in the amygdala and decreased activation in the dorsolateral prefrontal cortex (DLPFC), extending findings of previous studies in healthy individuals. Patients with BPD showed significantly longer reaction times (RTs) along with significantly higher activation in the amygdala and insula during emotional distraction compared to healthy participants, suggesting that they were more distracted by emotional pictures during the working memory task. Moreover, in the group of BPD patients, a significant negative correlation was found between activation in limbic brain regions and self-reports of current dissociative states. CONCLUSIONS: Our findings suggest hyper-responsiveness to emotionally distracting pictures in BPD patients that negatively affects working memory performance. This stresses the importance of emotion dysregulation in the context of cognitive functioning. Moreover, our findings suggest that dissociative states have a dampening effect on neural reactivity during emotional challenge in BPD.


Assuntos
Sintomas Afetivos/fisiopatologia , Transtorno da Personalidade Borderline/fisiopatologia , Emoções , Memória de Curto Prazo , Adolescente , Adulto , Sintomas Afetivos/complicações , Sintomas Afetivos/psicologia , Análise de Variância , Transtorno da Personalidade Borderline/complicações , Transtorno da Personalidade Borderline/psicologia , Encéfalo/fisiopatologia , Mapeamento Encefálico/métodos , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Pessoa de Meia-Idade , Estimulação Luminosa/métodos , Tempo de Reação , Análise e Desempenho de Tarefas , Adulto Jovem
11.
J Clin Endocrinol Metab ; 94(8): 3093-7, 2009 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-19470623

RESUMO

CONTEXT: In obesity, total IGF-I is not reduced to the degree predicted by low GH levels, and free IGF-I levels are normal to high. Total and free IGF-I may not reflect IGF-I biological activity because immunoassays cannot account for the modifying effects of IGF binding proteins on interactions between IGF-I and its receptor. OBJECTIVE: The aim of the study was to investigate the biological activity of IGF-I in obesity. DESIGN AND SETTING: We conducted a cross-sectional study at a General Clinical Research Center. STUDY PARTICIPANTS: Thirty-four healthy women (11 lean, 12 overweight, and 11 obese) of comparable age (overall mean, 30.7 +/- 1.3 yr) participated in the study. INTERVENTION: There were no interventions. MAIN OUTCOME MEASURES: We measured bioactive IGF-I (as measured by a kinase receptor activation assay), IGFBP-1, and GH using 6-h pools of serum collected every 10 min for 24 h, and fasting IGF-I and IGFBP-3. RESULTS: Mean 24-h GH (R = -0.76; P < 0.0001), total IGF-I (R = -0.36; P = 0.040), and IGFBP-1 (R = -0.41; P = 0.017) levels were inversely associated with BMI, whereas bioactive IGF-I and IGFBP-3 levels were not. Mean bioactive IGF-I was similar in the groups [2.72 +/- 0.22 (lean), 3.10 +/- 0.32 (overweight), and 2.43 +/- 0.23 [corrected] (obese) microg/liter; overall P = 0.22]. Percentage bioactive IGF-I [(bioactive/total IGF-I) x 100] was higher in obese subjects than both lean and overweight subjects (P = 0.039). CONCLUSIONS: Despite low GH secretion in obesity and decreasing IGFBP-1 with increasing BMI, 24-h mean bioactive IGF-I levels are not reduced in obese women and do not correlate with BMI or IGFBP-1 levels. This argues against elevated bioactive IGF-I as the etiology of reduced GH secretion through a feedback mechanism in obesity.


Assuntos
Fator de Crescimento Insulin-Like I/análise , Obesidade/metabolismo , Adulto , Índice de Massa Corporal , Estudos Transversais , Feminino , Hormônio do Crescimento Humano/sangue , Humanos , Proteína 1 de Ligação a Fator de Crescimento Semelhante à Insulina/sangue
12.
J Clin Endocrinol Metab ; 93(10): 4033-40, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-18647804

RESUMO

CONTEXT: Obesity is characterized by reduced GH secretion, but data regarding IGF-I levels and their determinants are conflicting. OBJECTIVES: The objectives were to determine whether IGF-I levels are reduced and to investigate determinants of GH and IGF-I in healthy overweight and obese women. DESIGN: A cross-sectional study was performed. SETTING: The study was conducted at a General Clinical Research Center. STUDY PARTICIPANTS: Thirty-four healthy women without pituitary/hypothalamic disease participated, including 11 lean [body mass index (BMI) <25 kg/m(2)], 12 overweight (BMI > or =25 kg/m(2) and <30 kg/m(2)), and 11 obese (BMI > or =30 kg/m(2)) women of comparable age (overall mean age, 30.7 +/- 7.8 yr). INTERVENTION: There was no intervention. MAIN OUTCOME MEASURES: The main outcome measures were frequent sampling (every 10 min for 24 h) for GH, peak GH after GHRH-arginine stimulation, IGF-I, IGF binding protein-3, estrone, estradiol, testosterone, free testosterone, SHBG, homeostasis model assessment of insulin resistance, and abdominal fat. RESULTS: Mean 24-h GH and peak stimulated GH were lower in overweight than lean women and lowest in obese women. Mean IGF-I levels trended lower in obese, but not overweight, compared with lean women. Free testosterone was positively associated with IGF-I (R = 0.36, P = 0.04) but not with GH measures. Visceral fat was the only determinant of mean 24-h GH (R(2) = 0.66, P < 0.0001) and of peak stimulated GH (R(2) = 0.63, P < 0.0001), and mean 24-h GH accounted for 39% of the variability of IGF-I (P = 0.0002), with an additional 28% (P < 0.0001) attributable to free testosterone levels. CONCLUSIONS: Despite a linear decrease in GH secretion and peak stimulated GH levels with increasing BMI in healthy overweight and obese women, IGF-I levels were not commensurately reduced. Androgens may contribute to this relative preservation of IGF-I secretion in overweight and obese women despite reduced GH secretion.


Assuntos
Androgênios/fisiologia , Hormônio do Crescimento Humano/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Obesidade/metabolismo , Sobrepeso/metabolismo , Adulto , Androgênios/sangue , Índice de Massa Corporal , Ritmo Circadiano/fisiologia , Estudos Transversais , Feminino , Hormônios Esteroides Gonadais/sangue , Humanos , Obesidade/sangue , Sobrepeso/sangue , Globulina de Ligação a Hormônio Sexual/análise , Globulina de Ligação a Hormônio Sexual/metabolismo
13.
Phys Rev Lett ; 94(20): 208303, 2005 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-16090294

RESUMO

State-resolved measurements on clean Ni(100) and Ni(111) surfaces quantify the reactivity of CH4 excited to v = 3 of the nu4 bend vibration. A comparison with prior data reveals that 3nu4 is significantly less effective than the nu3 C-H stretch at promoting dissociative chemisorption, even though 3nu4 contains 30% more energy. These results contradict statistical theories of gas-surface reactivity, provide clear evidence for vibrational mode specificity in a gas-surface reaction, and point to a central role for C-H stretching motion along the reaction path to dissociative chemisorption.


Assuntos
Carbono/química , Metano/química , Modelos Químicos , Níquel/química , Carbono/análise , Simulação por Computador , Ligação de Hidrogênio , Metano/análise , Conformação Molecular , Níquel/análise , Vibração
14.
Science ; 304(5673): 992-5, 2004 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-15143277

RESUMO

State-resolved gas-surface reactivity measurements revealed that vibrational excitation of nu3 (the antisymmetric C-H stretch) activates methane dissociation more efficiently than does translational energy. Methane molecules in the vibrational ground state require 45 kilojoules per mole (kJ/mol) of translational energy to attain the same reactivity enhancement provided by 36 kJ/mol of nu3 excitation. This result contradicts a key assumption underlying statistical theories of gas-surface reactivity and provides direct experimental evidence of the central role that vibrational energy can play in activating gas-surface reactions.

15.
Faraday Discuss ; (117): 147-60; discussion 161-89, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11271989

RESUMO

We have measured the sticking probability of methane excited to v = 1 of the v3 antisymmetric C-H stretching vibration on a clean Ni(100) surface as a function of rotational state (J = 0, 1, 2 and 3) and have investigated the effect of Coriolis-mixing on reactivity. The data span a wide range of kinetic energies (9-49 kJ mol-1) and indicate that rotational excitation does not alter reactivity by more than a factor of two, even at low molecular speeds that allow for considerable rotation of the molecule during the interaction with the surface. In addition, rotation-induced Coriolis-splitting of the v3 mode into F+, F0 and F- states does not significantly affect the reactivity for J = 1 at 49 kJ mol-1 translational energy, even though the nuclear motions of these states differ. The lack of a pronounced rotational energy effect in methane dissociation on Ni(100) suggests that our previous results for (v = 1, v3, J = 2) are representative of all rovibrational sublevels of this vibrational mode. These experiments shed light on the relative importance of rotational hindering and dynamical steering mechanisms in the dissociative chemisorption on Ni(100) and guide future attempts to accurately model methane dissociation on nickel surfaces.

16.
Neuroreport ; 8(8): 1975-80, 1997 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-9223088

RESUMO

Although AMPA receptor subunit configuration controls the Ca2+ permeability of the ion channel, not much is known about Ca2+ signals generated by different AMPA receptor subtypes. We examined the Ca2+ signaling properties of recombinant AMPA receptors using patch clamp to determine ionic permeability properties and Ca2+ imaging to examine changes in intra-cellular Ca2+ level ([Ca2+]i). Activation of recombinant AMPA receptors robustly increased [Ca2+]i even in cells expressing heteromeric receptors containing edited GluRB, which harbored receptors with very low average Ca2+ permeability in patch clamp studies. The results suggest that whereas the GluRB subunit controls Ca2+ permeability, Ca2+ signaling mediated by AMPA receptors correlates poorly with the presence of GluRB.


Assuntos
Cálcio/metabolismo , Receptores de AMPA/metabolismo , Linhagem Celular , Permeabilidade da Membrana Celular/efeitos dos fármacos , Permeabilidade da Membrana Celular/fisiologia , Eletrofisiologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Fura-2 , Humanos , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Técnicas de Patch-Clamp , Receptores de AMPA/agonistas , Proteínas Recombinantes/metabolismo
17.
J Neurochem ; 68(1): 204-12, 1997 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-8978727

RESUMO

The human glutamic acid decarboxylase (GAD) gene was transferred into rat cerebellar granule neurons. Following adenoviral-mediated gene transfer, nearly 100% of the neurons had transgene expression that persisted for the duration of their survival in culture. GABA levels were elevated both in the growth media and in lysates of GAD-modified granule neurons. In GAD-modified neurons, extracellular GABA levels steadily increased with time, whereas intracellular GABA levels peaked 10 days after gene transfer. GAD-modified neurons released both glutamate and GABA into the surrounding media before and after potassium-induced stimulation, but only the release of glutamate was sensitive to potassium stimulation. These data suggest that glutamatergic neurons, which initially contained no detectable GABA, can be genetically modified to release GABA constitutively.


Assuntos
Cerebelo/metabolismo , Técnicas de Transferência de Genes , Glutamato Descarboxilase/genética , Neurônios/metabolismo , Neurotransmissores/metabolismo , Adenoviridae/genética , Animais , Células Cultivadas , Cerebelo/citologia , Glutamato Descarboxilase/metabolismo , Ácido Glutâmico/metabolismo , Humanos , Ratos , Ratos Sprague-Dawley , Ácido gama-Aminobutírico/metabolismo
18.
Science ; 257(5067): 223-5, 1992 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-17794753

RESUMO

Studies in heterogeneous catalysis have long speculated on or have provided indirect evidence for the role of hydrogen embedded in the catalyst bulk as a primary reactant. This report describes experiments carried out under single-collision conditions that document the distinctive reactivity of hydrogen embedded in the bulk of the metal catalyst. Specifically, the bulk H atom is shown to be the reactive species in the hydrogenation of CH(3) adsorbed on Ni(111) to form CH(4), while the H atoms bound to the surface were unreactive. These results unambiguously demonstrate the importance of bulk species to heterogeneous catalytic chemistry.

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