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M Woerner

Publications and source records attributed to M Woerner.

At least 19 recordsLinked to original sources
PubMed2001

Ultrafast dynamics of intersubband excitations in a quasi-two-dimensional hole gas.

We present the first study of ultrafast hole dynamics after resonant intersubband excitation in a quasi-two-dimensional semiconductor. p-type Si0.5Ge 0.5/Si multiple quantum wells are studied in pump-probe experiments with 150 fs midinfrared pulses. Intersubband scattering from the second heavy-hole back to the first heavy-hole subband occurs with a time constant of 250 fs, followed by intrasubband carrier heating within 1 ps. Such processes give rise to a strong reshaping of the intersubband absorption line, which is accounted for by calculations of the subband structure, optical spectra, and hole-phonon scattering rates.

Journal Article↗
PubMed2000

Ultrafast mid-infrared response of YBa(2)Cu(3)O(7-delta)

Optical spectra of high-transition-temperature superconductors in the mid-infrared display a gap of in-plane conductivity whose role for superconductivity remains unresolved. Femtosecond measurements of the mid-infrared reflectivity of YBa(2)Cu(3)O(7-delta) after nonequilibrium optical excitation are used to demonstrate the ultrafast fill-in of this gap and reveal two gap constituents: a picosecond recovery of the superconducting condensate in underdoped and optimally doped material and, in underdoped YBa(2)Cu(3)O(7-delta), an additional subpicosecond component related to pseudogap correlations. The temperature-dependent amplitudes of both contributions correlate with the antiferromagnetic 41-millielectronvolt peak in neutron scattering, supporting the coupling between charges and spin excitations.

Journal Article↗
PubMed2000

Intervention research in psychosis: issues related to clinical assessment.

This article discusses efforts to optimize clinical assessment for intervention effectiveness trials. Generalizability is a crucial issue; investigators should choose their inclusion/exclusion criteria to increase subject inclusion and should collect data on the selection process to determine the extent of selection biases. Intervention research requires assessment instruments appropriate for a variety of treatment settings. We describe the Hillside Clinical Trials version of the Scale for the Assessment of Negative Symptoms, which has inpatient and outpatient versions to accommodate the different opportunities for social interaction in these settings. Lack of uniformity in assessment instruments complicates interpretation of results across studies and impedes communication of findings. We describe the 5-Dimensional Scale to Evaluate Psychopathology in Schizophrenia (5-STEPS), a collaborative effort to develop a standard change measure for schizophrenia treatment trials. We also discuss potential future strategies, including developing briefer yet reliable and valid diagnostic procedures, making trials more acceptable in a broad range of settings through the use of open-label treatment with blinded independent assessors, bridging efficacy and effectiveness designs by studying both a narrow efficacy and a broader effectiveness population simultaneously, and updating outcome domains to reflect current treatment strategies.

Humans↗
PubMed1999

Cerebral volume asymmetries in schizophrenia and mood disorders: a quantitative magnetic resonance imaging study.

Multiple abnormalities of brain structure have been identified in schizophrenia using in vivo neuroimaging methods, but little is known about the diagnostic specificity of these abnormalities. In a prior study of first-episode schizophrenia we found that this group lacked the normal pattern of cerebral volume asymmetries. Data from that study were combined with data from groups of patients with more chronic schizophrenia, and with bipolar and unipolar mood disorders, to determine the specificity of this abnormality to diagnostic subgroups defined by syndromal status or chronicity. The total sample comprised 235 patients (67 healthy volunteers, 81 patients with mood disorders or schizoaffective disorders, and 87 with schizophrenia or schizophreniform disorders). Asymmetries of regional cerebral volumes were measured on coronal magnetic resonance images with 3.1-mm contiguous slices and nominal in-plane resolution of 1 mm x 1 mm. Asymmetries differed significantly across groups in the occipitoparietal, prefrontal, and temporal regions. These asymmetries, and a composite index of asymmetry across regions ('torque'), all showed the same diagnostic group effect, with the schizophrenia group showing the least normal asymmetry, the mood disorder group intermediate asymmetry, and the control group the most marked asymmetry. No other diagnostic subgroup or chronicity effects were apparent. The findings support a 'continuum' rather than a 'diagnostic specificity' hypothesis, and suggest that the reduction of normal hemispheric asymmetries may mark a neurodevelopmental risk factor for major mental illnesses, and that some syndromal characteristics may be correlated with the degree of deviation from the normal anatomic pattern.

Adolescent↗
PubMed1998

The prevalence of acute extrapyramidal signs and symptoms in patients treated with clozapine, risperidone, and conventional antipsychotics.

BACKGROUND: Acute extrapyramidal side effects (EPS) are a common phenomenon of treatment with conventional antipsychotics. Previous studies found that clozapine has little propensity to cause EPS, while risperidone produces some EPS, but at levels lower than those of conventional antipsychotics. METHOD: We compared the prevalence and severity of EPS in patients treated with clozapine, risperidone, or conventional antipsychotics for at least 3 months. Our main hypothesis was that there would be differences between the three treatment groups with regard to akathisia, measured with the Barnes Akathisia Scale, and extrapyramidal motor side effects (rigidity, rigidity factor, tremor, salivation), measured with the Simpson-Angus scale. Secondarily, we were interested in possible differences between the three groups with respect to the anticholinergic comedication and the subjective impression of the patients, measured with the van Putten scale. RESULTS: We studied 106 patients (41 patients treated with clozapine, 23 patients with risperidone, and 42 patients treated with conventional antipsychotics). The sample was 57.5% male and had a mean +/- SD age of 36.6 +/- 9.3 years. The mean dose of antipsychotics calculated in chlorpromazine equivalents was 425.6 +/- 197.1 mg/day in the clozapine group, 4.7 +/- 2.1 mg/day in the risperidone group, and 476.5 +/- 476.9 mg/day in the group treated with conventional antipsychotics. The point-prevalence of akathisia was 7.3% in the clozapine group, 13% in the risperidone group, and 23.8% in the group treated with conventional antipsychotics. The point-prevalence of rigidity and cogwheeling respectively was 4.9% and 2.4% in the clozapine group, 17.4% and 17.4% in the risperidone group, and 35.7% and 26.2% in the group treated with conventional antipsychotics. CONCLUSION: Our results indicate that risperidone is superior to conventional neuroleptics in that it causes fewer EPS. In comparison to clozapine, risperidone produces EPS levels that are intermediate between clozapine and conventional antipsychotic drugs.

Acute Disease↗
PubMed1996

Gender differences in neuroleptic nonresponsive clozapine-treated schizophrenics.

Gender differences in neuroleptic-refractory chronic schizophrenic disorder patients were examined to determine whether a superior or equivalent antipsychotic response in women vs. men existed similar to that of the general schizophrenic population. Sixty-nine DSM-III schizophrenic patients (47 males and 22 females) were treated with clozapine using a standardized medication regime. The gender differences in these neuroleptic-nonresponsive chronic schizophrenic disorder patients differed from those previously observed in the general schizophrenic population in that an equivalent antipsychotic treatment response in females versus males was not found. These treatment-refractory women appear to be a severely ill subgroup of female schizophrenics with distinct onset of illness, course and treatment response characteristics.

Adolescent↗
PubMed1996

Psychobiologic correlates of treatment response in schizophrenia.

In studies conducted on largely treatment naive patients in their first episode of psychosis, we have found that treatment outcome is quite good and that most patients recover or at least achieve a substantial degree of symptom remission. However, over the course of their illness and in the context of subsequent psychotic episodes, they may experience some decrease in their treatment response from illness progression. In addition, the heterogeneity of treatment outcome is associated with specific clinical (gender, primary negative symptoms of the deficit state, duration of psychosis) and biological variables (pHVA, ventricular volume). It is unclear whether these variables represent aspects of discrete subtypes of schizophrenia or dimensional measures of pathology within the broad context of a unitary disease entity.

Follow-Up Studies↗
PubMed1996

Factors influencing treatment response and outcome of first-episode schizophrenia: implications for understanding the pathophysiology of schizophrenia.

For the majority of patients, schizophrenia is a chronic recurrent disease that leads to significant residual morbidity which occurs through a process of behavioral deterioration. The factors that influence the course of schizophrenia after its onset and the ability of treatment to modify the effects of the patient's illness are not well understood. This article examines specific clinical and biological variables that are associated with treatment response and outcome. These variables, which are both trait and state dependent, include premorbid adjustment, age and mode of onset of illness, gender, duration of psychosis, schizophrenia subtype, primary negative symptoms, and extrapyramidal signs including tardive dyskinesia and plasma HVA and brain pathomorphology. In addition, the chronic effects of antipsychotic drug treatment may influence illness course both favorably and adversely as well as potentially altering the neurobiological substrates that mediate expression of the illness and treatment response. Finally, the question of whether the active phase of the illness involves a pathologic process that leads to illness progression is discussed. In light of this discussion, we can speculate that although certain aspects of the illness in terms of its severity and course may be, to an extent, predetermined, a number of factors can exert favorable and unfavorable effects on the course of the illness and its ultimate outcome. One question for the field is to develop therapeutic strategies that minimize the morbidity of the illness in a way that does not introduce iatrogenic consequences to the patient.

Adult↗
PubMed1995

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Journal Article↗
PubMed1995

Cortical changes in starfish (Asterina pectinifera) oocytes during 1-methyladenine-induced maturation and fertilisation/activation.

Maturation of the starfish oocyte cortex to produce an effective cortical granule reaction and fertilisation envelope is believed to develop in three phases: (1) pre-methyladenine (1-MA) stimulation; (2) post-1-MA stimulation, pregerminal vesicle breakdown; and (3) post-germinal vesicle breakdown. The present study was initiated to identify what each of these phases may encompass, specifically with respect to structures associated with the oocyte cortex, including cortical granules, microvilli and vitelline layer. 1-MA treatment brought about an orientation of cortical granules such that they became positioned perpendicular to the oocyte surface, and an approximately 4-fold decrease in microvillar length. A-23187 activation of immature oocytes treated with (10 min; pregerminal vesicle breakdown) or without 1-MA resulted in a reduction in cortical granule number of 21% and 41%, respectively (mature oocytes underwent a 96% reduction in cortical granules). Elevation of the fertilisation envelope in both cases was significantly retarded compared with activated mature oocytes. In activated mature oocytes, the vitelline layer elevated 20.0 +/- 5.4 mu m from the egg's surface, whereas in immature oocytes treated with just A-23187 or with 1-MA (10 min) and A-23187, it lifted 0.35 +/- 0.1 and 0.17 +/- 0.04 mu m, respectively. The fertilisation envelopes of activated (or fertilised) immature oocytes also differed morphologically from those of mature oocytes. In activated, immature oocytes, the fertilisation envelope was not uniform in its thickness and possessed thick and thin regions as well as fenestrations. Additionally, it lacked a complete electron-dense stratum that characterised the fertilisation envelopes of mature oocytes. The nascent perivitelline space of immature oocytes was also distinguished by the presence of numerous vesicles which appeared to be derived from microvilli. Differences in the morphology of cortices from activated (fertilised) and non-activated, immature and mature oocytes substantiate previous investigations demonstrating three phases of cortical maturation, and are consistent with physiological changes that occur during oocyte maturation, involving ionic conductance of the plasma membrane, establishment of slow and fast blocks to polyspermy and elevation of a fertilisation envelope.

Adenine↗
PubMed1995

Prevalence and clinical correlates of extrapyramidal signs and spontaneous dyskinesia in never-medicated schizophrenic patients.

OBJECTIVE: This study assessed the prevalence of extrapyramidal signs and spontaneous dyskinesia in neuroleptic-naive, first-episode schizophrenic patients and examined the clinical correlates. METHOD: In a prospective study of the psychobiology of schizophrenia, the authors examined 89 neuroleptic-naive patients for the presence of extrapyramidal signs by using the Simpson-Angus Rating Scale and for dyskinesia by using the Tardive Dyskinesia Rating Scale. RESULTS: Fifteen patients (16.9%) had extrapyramidal signs, but only one had spontaneous dyskinesia at baseline. Presence of extrapyramidal signs was correlated with more negative symptoms and poorer treatment outcome that was reflected in a longer time to and lower level of remission. There was no correlation of spontaneous extrapyramidal signs with age of patient, age at onset of psychotic symptoms, or baseline psychopathology. There was no difference between patients with and without spontaneous extrapyramidal signs in terms of the subsequent development of persistent tardive dyskinesia, but the patients with spontaneous extrapyramidal signs were more likely to develop parkinsonian side effects after 8 weeks of antipsychotic treatment. CONCLUSIONS: Extrapyramidal signs are present in a proportion of neuroleptic-naive, first-episode schizophrenic patients, which suggests an involvement of these signs in the schizophrenic process that probably reflects basal ganglia pathology. The presence of spontaneous extrapyramidal signs seems to have prognostic significance insofar as it is linked to a poorer outcome and longer time to remission. Spontaneous dyskinesia appears to be a relatively rare finding.

Adolescent↗
PubMed1994

Methylphenidate response, psychopathology and tardive dyskinesia as predictors of relapse in schizophrenia.

Despite the proven efficacy of acute and maintenance pharmacotherapy in schizophrenia, practical methods for identifying patients who require continuous treatment to prevent relapse have not been established. We hypothesized that a pathologic overactivity of mesolimbic and mesocortical dopamine neural systems, that mediates positive psychotic symptoms in the acute phase of the illness, persists in some outpatients who are vulnerable to relapse despite appearing clinically stable. To test and determine if putative measures of central nervous system dopamine activity predict outcome, 41 stable outpatients receiving neuroleptic maintenance treatment underwent provocative tests with methylphenidate in a randomized double-blind placebo controlled design in which behavioral, neuromotor, biochemical, and cardiovascular responses were measured. Patients were then withdrawn from medication and monitored for 52 weeks, or until relapse. The results indicate that psychotic symptoms and their activation by methylphenidate, and the presence of tardive dyskinesia are associated with each other and with a higher risk of relapse. These findings partially support our hypothesis and offer potentially useful measures for the identification of candidates for reduced dose neuroleptic maintenance treatment strategies in schizophrenia.

Adolescent↗