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Biomedical subjects

P Mitchell

Publications and source records attributed to P Mitchell.

At least 397 records · Page 22Linked to original sources
PubMed1992

Identification of intermolecular RNA cross-links at the subunit interface of the Escherichia coli ribosome.

32P-Labeled 70S ribosomes and polysomes were isolated from cultures of Escherichia coli and treated with the cross-linking reagent bis(2-chloroethyl)methylamine. Intermolecular 16S-23S RNA cross-linked complexes were separated from other products of the cross-linking reactions by a two-step sucrose density gradient centrifugation procedure and subjected to oligodeoxynucleotide-directed partial nuclease digestions with RNase H. Cross-linked RNA fragments released by such directed digests were resolved by two-dimensional gel electrophoresis and analyzed using classical oligonucleotide fingerprinting techniques. Two distinct intermolecular cross-links between the 16S and 23S RNA could be localized in this manner, involving positions 1408-1411 and 1518-1520 in the 16S RNA sequence and positions 1912-1920 in the 23S RNA sequence. These data provide the first direct topographical links between the RNA of the 30S and 50S subunits in the functional ribosome and, together with previous topographical data concerning the three-dimensional folding of the rRNA, demonstrate that there is a tight cluster at the ribosomal interface both of sites implicated in ribosomal function and of posttranscriptionally modified nucleotides in the rRNA.

Base Sequence↗
PubMed1992

Comparison of clinician rated and family corroborative witness data for depressed patients.

There appear to be few published studies that have examined the levels of agreement between ratings of features of depression as assessed by clinicians and by corroborative witnesses. We therefore report a study of 141 depressed patients assessed by a clinical psychiatrist at a semi-structured interview, reviewing family and historical data as well as depressive symptoms, and rated on a series of designated mental state signs. A family member completed questionnaire data assessing the same features. Moderate agreement was obtained only for several historical items (e.g., previous depressive episode, response to ECT). Agreement was minimal or non-existent on numerous clinical symptoms and signs of depression. A number of sources of disagreement are considered, and it is suggested that discordance may have emerged principally from the contrasting domains and training experiences of the clinicians and the corroborative witnesses.

Adjustment Disorders↗
PubMed1992

Are there any differences between bipolar and unipolar melancholia?

Although it is now more than 30 years since Leohard originally proposed the distinction between bipolar and monopolar (unipolar) forms of affective disorder, there have been relatively few studies which have investigated clinical features which may differentiate the depressed phase of bipolar disorder from unipolar depression. In this study we examined the value of a new scale for rating depressive mental state signs (the 'core' score system), and a large series of symptoms and risk factors, in distinguishing between 27 age and sex-matched pairs of bipolar and unipolar patients diagnosed as melancholic on several diagnostic criteria. In general, we found a marked similarity between the groups on clinical features of the depressive episode when allowance was made for multiple tests. Bipolar patients, however, had shorter episodes of depression and were less likely to demonstrate 'slowed movements' than unipolar subjects. There were also consistent trends on other items for psychomotor retardation to be less common and agitation to be more likely in the bipolar patients. At the least, these findings suggest that the widely-held belief that bipolar depressed patients typically have psychomotor retardation is not as clear-cut as has been previously described.

Bipolar Disorder↗
PubMed1992

Exclusion of close linkage of bipolar disorder to dopamine D1 and D2 receptor gene markers.

A potential role of dopamine in bipolar disorder has been suggested by several strands of evidence, namely the ability of dopaminergic agonists to induce mania and the effects of lithium, carbamazepine and the antipsychotics on central dopamine receptors and/or turnover. We therefore aimed to determine if bipolar disorder in two large bipolar pedigrees was linked to the recently cloned dopamine D1 (DRD1) and D2 (DRD2) receptors. (These have been mapped to chromosomal regions 5q35.1 and 11q22.3-q23, respectively). Linkage of bipolar disorder and recurrent depression to DRD1 and DRD2 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 for DRD1 also persisted when a wide range of rates of 'sporadic' (non-genetic) presentations of illness were incorporated in the analysis, but the DRD2 results did not remain statistically significant at high sporadic rates. The exclusion of linkage to DRD2 is consistent with other recent reports.

Adolescent↗
PubMed1992

Children's understanding of the evidential connotation of 'know' in relation to overestimation of their own knowledge.

This study examined five- to seven-year-olds' assumptions about the experiential connotation of 'I know that's X'. In Experiment I children tried to identify which of a set of unfamiliar targets had a given name (X), and after they had chosen, we enquired either whether they knew their chosen item was (X) or whether they were sure. Six- to seven-year-olds (N = 39) judged that they were sure more often than they judged that they knew, which suggests that although they experienced confidence that they had chosen correctly, they assumed it would be inappropriate to judge 'know', because this would imply an experiential basis, which was absent. Five- to six-year-olds (N = 36) did not discriminate between the two kinds of question. In Experiment 2, children could infer which item was a named unfamiliar cartoon character by ruling out familiar distractors. Six- to seven-year-olds (N = 35) judged that they knew they had picked the right one much more often than they judged that they knew their chosen picture was (target name). Again, five- to six-year-olds (N = 44) did not discriminate between the two kinds of question. This demonstrates powerfully that the older children held an experiential connotation of 'I know that's X', since they avoided such judgments even when they knew by inference they had chosen correctly.

Child↗
PubMed1992

Cerebrospinal fluid penetration of cefpirome in patients with non-inflamed meninges.

Twenty patients (mean age 52 +/- 12 years, mean weight 75 +/- 15 kg) scheduled for elective myelogram or spinal anaesthesia were enrolled to determine the cerebrospinal fluid (CSF) penetration of a new expanded spectrum cephalosporin antibiotic, cefpirome (HR-810). A single 2 g intravenous dose of cefpirome was administered as a bolus between 1 and 8 h before lumbar puncture. Blood samples were collected at 15 pre-determined times and a single CSF sample was obtained at the time of lumbar puncture. Serum and CSF cefpirome concentrations were determined by high performance liquid chromatography. The mean maximal serum concentration of cefpirome was 264 +/- 76 mg/L. A mean steady-state volume of distribution of 20 +/- 4 L, clearance of 7.4 +/- 1.3 L/h, and half-life of 2.5 +/- 0.5 h were determined. Mean CSF concentrations were 0.50 +/- 0.11 mg/L at 1-2 h post dose (n = 4), 0.57 +/- 0.13 mg/L at 2-4 h post dose (n = 4), 0.76 +/- 0.34 mg/L at 4-6 h post dose (n = 7), and 0.83 +/- 0.29 mg/L at 6-8.3 h post dose (n = 5). Blood:brain barrier permeability to cefpirome may not be a limiting factor as CSF concentrations were rapidly attained. Further studies are required to determine the mechanism of cefpirome transport between plasma and CSF.

Adolescent↗
PubMed1992

Predicting the course of melancholic and nonmelancholic depression. A naturalistic comparison study.

We assessed improvement patterns and predictors of outcome over a 1-year period, in a sample of depressed patients receiving treatment from a specialized mood disorders unit. Patients with melancholia had a differential improvement pattern from the nonmelancholics in the first 20 weeks, but case rates and severity levels were comparable at 20 weeks and at 1 year. Only three variables (older age at first episode, less severe depression and extraversion) were predictors of improvement in both groups. Improvement was predicted by less psychomotor disturbance, absence of personality disorder, and higher social functioning in the melancholic patients. A reported absence of timidity and shyness in childhood, a briefer duration of depression, and receipt of individual psychotherapy predicted a better outcome in the nonmelancholic patients. Although significant predictors were few overall, the suggested differential relevance for most of the isolated predictors argues for outcome studies that examine melancholic and nonmelancholic depressive disorders separately.

Age Factors↗
PubMed1992

The clinical features and associations of retinal emboli.

A series of 207 patients with retinal emboli is presented with the ocular findings and systemic associations examined. Emboli were most frequently single, unilateral, crystalline and involved the left eye. Emboli were most frequently observed at the major retinal vascular temporal arcades and posterior pole arterioles, with 40% seen at a bifurcation and 10% at an arteriovenous crossing. Non-crystalline emboli were more likely to be associated with retinal pathology, such as retinal artery or vein occlusion. Carotid ultrasound was performed in 74 patients: 18% of asymptomatic subjects had internal or common carotid stenosis greater than 75%; 21% of symptomatic patients had stenosis greater than 75%. In 70%, the stenosis was worse on the side of the embolus. In symptomatic patients, significant stenosis is more likely to be unilateral.

Aged↗
PubMed1992

Propofol and ECT.

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Electroconvulsive Therapy↗
PubMed1992

Interpersonal sensitivity and the one-year outcome of a depressive episode.

Previous studies have demonstrated that abnormalities of personality can contribute to a poor prognosis following a depressive episode. In this study the relevance of a specific personality trait, interpersonal sensitivity, to poor outcome was examined. One hundred and eleven depressives completed the Interpersonal Sensitivity Measure (IPSM) twenty weeks after a baseline assessment. High scores on the IPSM were associated with a poor outcome at one year following the baseline assessment, judged according to whether they had remitted clinically or not and by the degree of change in depression severity measured using the Hamilton and Zung Depression Rating Scales. The relevance of this personality trait to the course and treatment of depression is discussed.

Adolescent↗
PubMed1992

An Australian multicentre study of moclobemide versus amitriptyline in the treatment of depression.

This paper reports the results of a multicentre study of the new monoamine oxidase inhibitor, moclobemide, in the treatment of major depression. Moclobemide is a specific monoamine oxidase-A inhibitor which does not bind irreversibly to the enzyme, unlike the currently available MAOIs. Recent studies would suggest that in subjects taking moclobemide blood pressure elevation caused by tyramine is significantly less than that induced by the irreversible MAOIs, particularly when tyramine is administered in an oral form. Forty-eight patients with major depression were randomly allocated to treatment with either moclobemide or amitriptyline for 4 weeks in a double-blind comparison. There were no statistically significant differences between the two groups on measures of efficacy. Patients taking amitriptyline reported a greater number of side-effects and more patients in the amitriptyline group dropped out because of these. There were no reports of interactions with tyramine-containing foods.

Adult↗
PubMed1992

Children's interpretation of messages from a speaker with a false belief.

In 5 investigations we examined a new procedure for assessing children's understanding that messages arise from speakers' internal representations. 3- and 4-year-olds watched the enactment of a message-desire discrepant story in which a speaker doll, who believed wrongly that bag A was in location 1 and that bag B was in location 2, gave a message referring to the bag in location 1. In a message-desire consistent control condition, the speaker had a correct belief about the bags' locations. Children frequently judged correctly in the discrepant story that the speaker (who specified location 1) wanted the bag in location 2, and judged correctly in the consistent story that the speaker wanted the bag in location 1. That is, young children attended to the speaker's internal representations, and not just the real-world referent of the message, when judging what the speaker wanted. In one of the investigations, children performed better on the message-desire discrepant task than on a false belief task. We discuss why they might find it particularly easy to take into account false belief when inferring desire on the basis of behavior.

Child, Preschool↗
PubMed1992

Coagulation profile in severe preeclampsia.

One hundred women with severe preeclampsia or chronic hypertension with superimposed preeclampsia were seen during a 2-year period. We sought to determine whether a normal platelet count assures that no other clinically significant clotting abnormalities are present, and what level of thrombocytopenia predicts a risk of abnormalities in other coagulation indices. Fifty women had platelet counts below 150,000/microL, of whom 13 had a fibrinogen level below 300 mg/dL and two had a prolonged prothrombin time (PT) or partial thromboplastin time (PTT). The admission platelet count was an excellent predictor of subsequent thrombocytopenia (r = 0.829, P less than .001). No subject had an abnormal fibrinogen level or prolonged PT or PTT in the absence of thrombocytopenia. When monitoring intrapartum coagulation indices in preeclampsia, one can safely follow only the platelet count at admission and subsequently, reserving PT and PTT and fibrinogen levels for those cases complicated by counts less than 100,000/microL.

Adult↗
PubMed1991

Waterborne outbreak of Campylobacter jejuni in Christchurch: the importance of a combined epidemiologic and microbiologic investigation.

Campylobacter is a common cause of gastroenteritis in New Zealand; however, the source of infection usually remains unknown. Reports of two cases of Campylobacter jejuni enteritis at a camp and convention centre near Christchurch were investigated. Through interviews of persons living at or attending the camp, 42 additional cases were identified. Epidemiologic and microbiologic data strongly suggested the water supply as the source of infection. The combined epidemiologic and microbiologic investigation was useful in quickly defining the magnitude and source of the outbreak, allowing for rapid implementation of control measures.

Campylobacter Infections↗