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P Mitchell

Publications and source records attributed to P Mitchell.

At least 415 records · Page 23Linked to original sources
PubMed1991

The assignment of the 655 nm spectral band of cytochrome oxidase.

The spectral characteristics of the '655 nm' band of cytochrome oxidase were found to be affected by ligands of the binuclear centre, including formate and chloride, and by the resting/pulsed transition. The band titrated with near n = 1 characteristics at a midpoint of about 400 mV, in contrast to haem a3, which exhibits strong redox interaction and a titration range at significantly lower potential. Thus, although the total reduced-oxidised difference spectrum of haem a3 shows a trough at about 655 nm, this characteristic is absent in the low potential region. The 655 nm feature may arise from a charge transfer band of ferric high-spin haem a3, which is modulated by the redox state of CuB, as suggested by Beinert et al. [(1976) Biochim. Biophys. Acta 423, 339-355].

Animals↗
PubMed1991

Insomnia.

Explore the source record for details and available documents.

Aged↗
PubMed1991

Foundations of vectorial metabolism and osmochemistry.

Chemical transformations, like osmotic translocations, are transport processes when looked at in detail. In chemiosmotic systems, the pathways of specific ligand conduction are spatially orientated through osmoenzymes and porters in which the actions of chemical group, electron and solute transfer occur as vectorial (or higher tensorial order) diffusion processes down gradients of total potential energy that represent real spatially-directed fields of force. Thus, it has been possible to describe classical bag-of-enzymes biochemistry as well as membrane biochemistry in terms of transport. But it would not have been possible to explain biological transport in terms of classical transformational biochemistry or chemistry. The recognition of this conceptual asymmetry in favour of transport has seemed to be upsetting to some biochemists and chemists; and they have resisted the shift towards thinking primarily in terms of the vectorial forces and co-linear displacements of ligands in place of their much less informative scalar products that correspond to the conventional scalar energies. Nevertheless, considerable progress has been made in establishing vectorial metabolism and osmochemistry as acceptable biochemical disciplines embracing transport and metabolism, and bioenergetics has been fundamentally transformed as a result.

Biological Transport, Active↗
PubMed1991

Children's early understanding of false belief.

We investigated 3-year-olds' understanding of the representational capability of the mind by examining whether they would acknowledge that they had entertained a wrong belief. As in previous studies, children very often judged that they had believed a Smarties tube contained pencils when these were revealed as the true content, even though they had stated "Smarties" before the tube had been opened. Under another condition, when the tube was first presented, children mailed a picture into a postbox of what they thought was inside (Smarties). When asked "When you posted your picture, what did you think was in here (the tube)?" the great majority of children answered correctly with "Smarties". Additionally, children nearly always stated that the posted card displayed a picture of Smarties, and that the tube really contained pencils. On the traditional task, children may give the wrong answer because they are biased to make judgments about belief states on the basis of known physical reality. The posting task made it possible for children simultaneously to focus on physical reality and acknowledge false belief.

Child Development↗
PubMed1991

Phonatory and phonetic characteristics of prelinguistic vocal development in cri du chat syndrome.

A longitudinal case study of a child with cri du chat syndrome was undertaken to provide descriptive data on early phonatory and phonetic development in comfort state vocalizations. Vocal samples collected when the child was between 8 and 26 months of age were analyzed using perceptual and acoustic methods. Results indicated that the high vocal fundamental frequently documented in cries of infants with cri du chat syndrome was also a characteristic of comfort state vocalizations of this child. An analysis of intonation patterns indicated there was a predominance of falling intonation contours and limited interutterance variation of fundamental frequency. Phonetic development was quite delayed, with major acquisitions in babbling showing marked delay relative to chronological age. Acquisition of the first spoken word had not occurred by the age of twenty-six months. Results suggest that significant cognitive and/or motor delays may have an influence on the integrity of early vocal development, which calls into question the notion that babbling development proceeds relatively independently of other developmental domains.

Child, Preschool↗
PubMed1991

Close linkage of bipolar disorder to chromosome 11 markers is excluded in two large Australian pedigrees.

The relationship between bipolar disorder and chromosome 11 markers remains uncertain. Whilst re-analysis of the Amish pedigree weakened previous evidence for close linkage (but could not exclude the possibility of genetic heterogeneity), a recent French study has found a significant association between this condition and tyrosine hydroxylase polymorphisms. We aimed to determine if bipolar disorder in two large Australian pedigrees (of Irish and English extraction respectively) was linked to these markers. Of the 84 family members available for testing, nine were diagnosed as bipolar I, one as bipolar II and six had recurrent unipolar depression. Linkage of bipolar disorder and recurrent depression to the chromosome 11p15 markers c-Harvey ras, insulin and tyrosine hydroxylase was tested using a series of genetic models with varying penetrance levels. Additionally, linkage was examined using a series of levels of definitions of affective status (ranging from bipolar I alone to all affective illnesses). Close linkage to these markers was strongly excluded using each model and definition. The findings also persisted when a wide range of rates of 'sporadic' (non-genetic) presentations of illness were incorporated in the analysis. These results are consistent with other recent studies indicating that bipolar disorder is not linked to chromosomal region 11p15.

Adolescent↗
PubMed1991

Age and depression.

The interaction of age and depression was investigated by comparing differences between elderly (greater than or equal to 60 years old) and younger consecutive in- and out-patient referrals to a tertiary referral mood disorders unit. Older patients with unipolar major depressive episode were more likely to be psychotic and agitated regardless of depressive subtype and less likely to have personality inadequacies or a family history of affective disorder. In this sample, elderly depressives' rating of diagnosis, severity, endogeneity and social impairment were similar, irrespective of age of first onset of depression, but a positive family history and personality abnormalities were less likely in late-onset depressives.

Adjustment Disorders↗
PubMed1991

Distinguishing psychotic and non-psychotic melancholia.

To examine the necessary and sufficient status of delusions and hallucinations as clinical features of psychotic (delusional) depression, we studied a consecutive sample of 137 patients meeting DSM-III, RDC and our clinical criteria for endogenous depression/melancholia, of whom 35 had delusions and/or hallucinations, and represented our putative 'psychotic depressives' (PDs). The PDs were contrasted with the remaining 'endogenous depressives' (the EDs), and an age- and sex-matched subsample of the latter, the MEDs. Univariate and multivariate analyses of clinical features established that, in addition to the presence of delusions and/or hallucinations, the PDs could be distinguished in particular by severe psychomotor disturbance, as well as by sustained and unvarying depressive content, the absence of any diurnal mood variation and by constipation. Latent class analyses suggested that overt psychotic features (such as delusions and hallucinations) were sufficient but not necessary for a subject to be assigned to the 'psychotic' latent class, and a subsequent chart review suggested that, in some PDs actual psychotic features may not be able to be elicited because of severe psychomotor change, suggesting that clinical reliance on eliciting delusions or hallucinations may result in a number of 'masked psychotic depressives' escaping valid diagnosis.

Affective Disorders, Psychotic↗
PubMed1991

Growth hormone and other hormonal responses to clonidine in melancholic and nonmelancholic depressed subjects and controls.

To study putative differences in central neurotransmitter function in depressive subtypes, growth hormone, adrenocorticotropic hormone (ACTH), cortisol, and prolactin responses to the alpha 2-noradrenergic receptor agonist clonidine (1.3 micrograms/kg i.v.) were examined in 26 subjects with major depression, 13 of whom had melancholia. The responses of 10 of these endogenous/melancholic subjects were compared with those of 10 controls who were matched to the patients on age, sex, and menopausal status. In 15 of the depressed subjects, prolactin and cortisol responses to the putative serotonergic agonist fenfluramine were also examined to test for associations between these challenges. There were no significant differences in any of the responses between melancholic and nonmelancholic depressive subgroups after controlling for age and sex. With the exception of a greater reduction in ACTH in the endogenous/melancholic subjects, there were also no significant differences in hormonal responses between these patients and controls. There was, however, a significantly greater reduction in systolic blood pressure in the control subjects. There were no significant correlations between the responses to clonidine and fenfluramine. The findings suggest that clonidine at a dosage of 1.3 micrograms/kg is neither able to differentiate reliably between depressive subtypes nor to differentiate reliably between depressed and control subjects.

Adrenocorticotropic Hormone↗
PubMed1991

Psychosocial risk factors distinguishing melancholic and nonmelancholic depression: a comparison of six systems.

We examined six systems or scales designed to distinguish melancholia from residual nonmelancholic depressive disorders in a sample of 305 patients. A count of the number of significant psychosocial risk factors showed that a clinical diagnosis was the most differentiating (19 significant risk factors), followed by the Newcastle index (13), DSM-III (10), and the CORE system (10)--the last essentially assessing psychomotor change; Research Diagnostic Criteria (RDC) (7) and an endogeneity symptom scale (2) were the least differentiating. A subsample of "composite melancholics" was derived, comprising 138 who met "melancholia" criteria for DSM-III, RDC, and CORE, and they were contrasted with residual depressives. The composite melancholics were older, had had a briefer depressive episode, and differed significantly on 12 risk factors, essentially being less likely to report deprivational experiences such as deficient parenting and dysfunctional marital relationships. We suggest that such a risk factor strategy is of potential use in refining the clinical definition of melancholia.

Adaptation, Psychological↗
PubMed1991

Psychotic depression: a review and clinical experience.

We review research literature on psychotic (delusional) depression, including demographic, illness pattern, clinical, biological marker and treatment issues. Secondly, we report a study of a consecutive sample of 137 patients meeting criteria for DSM-III melancholia, RDC definite endogenous depression and our "clinical" criteria for endogenous depression, of whom there were 35 "psychotic depressives" (PDs). The PDs were contrasted with the remaining 76 depressives (EDs) and with an age and sex-matched subset (MEDs). The PDs were distinctly older than the EDs at assessment and at initial onset of any affective disorder. Compared to the MEDs, they tended to have longer illnesses, were more likely to be hospitalised (and to have longer stays), to receive (in the past and for the current episode) combination antipsychotic/antidepressant medication and/or ECT, and to have a poorer course over the following year. They were no more likely to have a bipolar pattern, a family history of depressive disorder, schizophrenia or alcoholism, or vegetative depressive features. Developmental psychosocial stressors and antecedent life event stressors were not over-represented. Most of the PDs had delusions, one-fifth reported hallucinations and psychomotor disturbance was marked. Other differential clinical findings were sustained mood disturbance, constipation, and the absence of a diurnal variation in mood and energy.

Adult↗
PubMed1991

Duplex ultrasound assessment of extra cranial carotid artery disease: its introduction into a radiology department.

Duplex Doppler ultrasound (DDU) is a non-invasive and potentially accurate modality for assessing carotid bifurcation disease. It is however technically difficult and an appreciable learning curve has been identified. To assess the accuracy of DDU upon introduction into a radiology department with experienced sonographers and radiologists we reviewed the first twenty-five (25) cases in patients, having both DDU and carotid angiography. Sensitivity of 95% and specificity of 81% were obtained for differentiating greater or less than 50% internal carotid artery diameter stenosis, and in detection of 80% or greater stenosis sensitivity and specificity were 83% and 100% respectively. We conclude that DDU is accurate when introduced into a department already competent in ultrasonography, with results being achieved similar to those reported from more experienced centres. Our results also support the appropriateness of the applied criteria for grading of carotid stenosis.

Carotid Artery Diseases↗
PubMed1991

Depression sub-typing: unitary, binary or arbitrary?

The strongest statistical support for the binary view of depression has been provided by factor (principal components) analytic studies which delineate a bipolar factor with features interpreted as reflecting "endogenous depression" and "neurotic depression" at opposing poles. We review the seminal studies to suggest instead that the bipolar factor has generally polarised depression and anxiety, and that no such entity or symptom complex of "neurotic depression" has been isolated. Instead "neurotic depression" has been defined principally by features of anxiety and personality style. We argue that the suggested entity is, in fact, a pseudo-entity, being no more than a residual group of non-depressive features without any significant intrinsic depressive characteristics. We support our interpretation by showing comparable solutions in published studies of depressives alone, contrasted with separate analyses of anxious and depressed patients. We also report two studies in which the "neurotic depressive" pole is made to appear and disappear by the inclusion and exclusion of anxiety items. As factor analytic studies have defined the "residual" pole so variably, we argue that some features held to distinguish neurotic depression are of no utility and that such a diagnosis is meaningless. We suggest that the clinician should not proceed (after excluding endogenous depression) to conclude that the default option is necessarily an entity "neurotic depression" and that instead a heterogeneous group of options (e.g. anxiety, personality disorder) require review. If the "neurotic depressive" type of the multivariate analytic studies is a pseudo-entity, then a modified unitary view of depression may be valid.

Adult↗
PubMed1991

Propofol as an anaesthetic agent for ECT: effect on outcome and length of course.

Recent reports of reduced seizure duration with ECT under propofol anaesthesia have led to concerns that propofol may diminish the efficacy of this treatment. To investigate the effect of propofol on the response to ECT, we reviewed records of 66 patients with primary depression treated with ECT, 37 of whom had been assessed prospectively with pre- and post-ECT Hamilton and Zung depression severity ratings. Despite demonstrating that the individual seizure duration was significantly reduced with propofol compared to thiopentone we found no evidence of reduced ECT efficacy with propofol. Courses under propofol anaesthesia were on an average two treatments longer than with thiopentone. Although this difference was not statistically significant this may have been due to a type II error. These results suggest that it is premature to abandon the use of this new anaesthetic agent in ECT without controlled prospective outcome studies.

Adult↗
PubMed1991

Carbamazepine for treatment-resistant melancholia.

BACKGROUND: There have only been a few studies of the role of carbamazepine in the management of treatment-resistant depression. METHOD: The response to carbamazepine of 16 melancholic patients, who had been depressed for an extended period despite a number of standard treatments, was studied retrospectively. RESULTS: Seven patients (44%) had a moderate or marked improvement. The responders included both psychotic and nonpsychotic depressives, and patients with concurrent organic brain disease. There was, however, a high rate of complications, with 5 of these 7 responders (71%) having to discontinue carbamazepine because of adverse effects. This high rate of complications may have reflected the older age of our sample. CONCLUSION: These findings suggest the efficacy of carbamazepine in melancholic patients who have not responded to conventional treatments, but indicate that the high rate of significant side effects may limit its long-term usefulness.

Adult↗
PubMed1991

The cost of nursing excellence in critical care.

The results of the American Association of Critical-Care Nurses Demonstration Project support the contention that high quality critical care nursing can be provided to patients at a reasonable cost. In addition, the data refute the notion that elements influenced by nurses--supplies and nursing care--are the most costly portion of the total hospital charge.

Costs and Cost Analysis↗