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Biomedical subjects

P Reed

Publications and source records attributed to P Reed.

At least 55 records · Page 3Linked to original sources
PubMed1994

Factors affecting rehospitalisation rates of chronic schizophrenic patients living in the community.

Eighty-eight [corrected] patients selected from a depot neuroleptic clinic in the hospital outpatients department were assessed clinically on various demographic and clinical variables with a view to determining the factors that may contribute to high rates of rehospitalisation amongst schizophrenics in remission. It was found that rehospitalisation rates during the preceding 5 years correlated with an early age of onset of illness, severity of positive and affective symptoms, current neuroleptic dose and total AIMS score, all reflecting the severity of underlying psychotic disorder and the neuroleptic treatment required to treat the psychosis. Poor compliance with neuroleptic prophylaxis was not found to be of importance in contributing to high relapse rates in this sample. It was concluded that patients who repeatedly relapse may do so because of the clinical characteristics of their illness.

Adult↗
PubMed1994

Brief-stimulus presentations on multiform tandem schedules.

Three experiments examined the influence of a brief stimulus (a light) on the behavior of food-deprived rats whose lever pressing on tandem schedules comprising components of different schedule types resulted in food presentation. In Experiment 1, either a tandem variable-ratio variable-interval or a tandem variable-interval variable-ratio schedule was used. The variable-interval requirement in the tandem variable-ratio variable-interval schedule was yoked to the time taken to complete the variable-ratio component in the tandem variable-interval variable-ratio schedule, and the length of the variable-interval component in the latter schedule was yoked to the variable-ratio component in the former schedule. If a brief stimulus occurred following completion of the first component, then behavior was differentiated in the two components; subjects responded more quickly in the variable-ratio than in the variable-interval component. If the stimulus was removed, then response rate was determined by the nature of the final component. Similar results were obtained in Experiments 2 and 3 with the use of a three-component tandem variable-ratio variable-interval variable-ratio schedule or tandem variable-interval variable-ratio variable-interval schedule. Thus, a brief stimulus that was not explicitly paired with reinforcement engendered behavior typical of the component schedule preceding its presentation.

Journal Article↗
PubMed1994

Influence of the cost of responding on human causality judgments.

In three experiments, the effect of costs associated with responding on judgments of the causal effectiveness of the response was examined. In Experiment 1, the temporal interval between outcomes was matched on a variable interval (VI) and a variable ratio (VR) schedule. When each response was made at some "cost," and outcomes represented some "gain" for the subject, the rating of causal effectiveness for responses was higher on the VR than on the VI schedule. This relationship was absent when the outcome was a triangle flash. In Experiment 2, the number of responses required per outcome on a VI and a VR schedule were matched, and responses on the VR schedule were rated as more causally effective. In Experiment 3, a VI-to-VR yoking procedure was used. With minimal response costs, judgments were similar on the VI and VR schedules, but with greater response costs, responses performed on the VR schedule were rated as more causally effective than those emitted on the VI schedule.

Adult↗
PubMed1994

Fatty acids in erythrocytes measured by isocratic HPLC.

We developed an isocratic reversed-phase HPLC method to measure arachidonic, palmitoleic, linoleic, eicosatrienoic, oleic, palmitic, and stearic acids from hydrolyzed erythrocytes. Washed erythrocytes were heated in methanol:HCl and the fatty acids extracted into hexane:amyl alcohol. After derivatization with 4-bromomethyl-7-methoxycoumarin, samples diluted in mobile phase (acetonitrile:water, 85:15 by vol) were injected onto a 250 x 4.6 mm C18 column, and the eluted fatty acids were detected fluorometrically. For all analytes, the mean within-batch CV was 8.2% (5.5-10.8%), the mean limit of detection was 7.0 mumol/L, a linear response was maintained up to 400 mumol/L, and results agreed well with those by gas chromatography. The addition of antioxidant (butylated hydroxytoluene) was essential for sample stability. We discuss hydrolysis and extraction times, derivatization temperature, critical steps in chromatography, and concentration units.

Chromatography, High Pressure Liquid↗
PubMed1993

Lip fibromas associated with retrovirus-like particles in angel fish.

Fibromas were observed on the lips of adult female and juvenile angel fish (Pterophyllum scalare) from 3 Florida farm populations. Tumor prevalence in each population was < 1%. Affected fish were clinically normal except for those with large tumors, which had weight loss caused by physical obstruction of food intake. Fibromas originated as elevated masses from the mucocutaneous junction near the midline of the upper and/or lower lips. Characteristic features included dense fibrous stroma covered by thickened, stratified squamous epithelium, numerous intraneoplastic teeth, and scattered foci of stromal inflammation. Electron microscopy revealed intracytoplasmic type-A retrovirus-like particles in stromal cells from all tumors. Attempts to transmit fibromas, using a cell-free tumor ultrafiltrate, were unsuccessful. The relationship of the intraneoplastic viral particles to the development of lip fibromas in angel fish is uncertain.

Animals↗
PubMed1993

Biochemical diagnosis of phaeochromocytoma: two instructive case reports.

The biochemical features of two patients with phaeochromocytomas illustrate the inadvisability of depending on a single group of analytes for the diagnosis. The first case presented as a surgical emergency with retroperitoneal haemorrhage. Biochemical diagnosis was difficult since total 24 hour urinary free catecholamine excretion was within normal limits in two out of three samples, and only marginally raised in the third with an atypical preponderance of adrenaline. Plasma catecholamine concentrations were also normal. But urinary excretion of the catecholamine metabolites, metadrenaline and 4-hydroxy-3-methoxy mandelic acid (HMMA), was consistently raised. In contrast, the second patient presenting with headache and labile hypertension showed normal metabolite excretion in the face of grossly increased free noradrenaline excretion and raised plasma noradrenaline concentrations. It is therefore recommend that, as well as urinary free catecholamines, one group of their main metabolites, the 3-methoxy amines (normetadrenaline and metadrenaline) or HMMA, should routinely be measured whenever a phaeochromocytoma is suspected.

Adrenal Gland Neoplasms↗
PubMed1993

Plasma norepinephrine in sensory diabetic polyneuropathy.

OBJECTIVE: To examine whether changes in circulating norepinephrine are associated with the sensory disturbances of diabetic polyneuropathy. Experimental studies have indicated that NE can excite sprouts from injured nerves, producing pain. RESEARCH DESIGN AND METHODS: We measured supine and erect plasma NE in 13 normal, nondiabetic control subjects and three groups of diabetic patients: 20 without clinical neuropathy, 20 with chronic painful neuropathy, and 15 with painless neuropathy and foot ulceration. Neuropathy was characterized by symptom and deficit scores, sensory thresholds, electrophysiology, and cardiovascular autonomic function tests. Neuropathic pain was scored by the patients on a linear analogue scale. RESULTS: In painless neuropathy, NE levels were greatly reduced (supine, 1.3 nM; erect, 2.2 nM) compared with control subjects (supine, 2.4 nM; erect, 4.0 nM; P < 0.001) and were combined with grossly abnormal autonomic reflexes. NE also was reduced in the diabetic group without neuropathy (supine, 1.7 nM; erect, 2.7 nM; P < 0.01 vs. control subjects). By contrast, in painful neuropathy NE levels (supine, 2.2 nM; erect, 3.6 nM) were similar to control subjects and significantly higher than in painless neuropathy (P < 0.01). Furthermore, NE correlated with the severity of neuropathic pain (r = 0.46, P = 0.02). To assess whether pain, acting as a stressor, could account for the observed differences in NE, we also measured the stress hormones epinephrine and cortisol. They did not differ among the diabetic groups. CONCLUSIONS: Circulating NE is higher in painful than painless diabetic neuropathy. We suggest that painful neuropathy is associated with a relatively higher number of functioning sympathetic fibers that may contribute to pain.

Adult↗
PubMed1993

An epizootic of Edwardsiella tarda in largemouth bass (Micropterus salmoides).

Edwardsiella tarda, an opportunistic bacterial pathogen, was isolated from dying largemouth bass (Micropterus salmoides) during an epizootic in a eutrophic lake system, Lochloosa Lake, Florida, USA. Approximately 1,500 adult fish died over a 6-wk period during the late summer and early fall of 1991. A mixed population of aerobic bacteria (E. tarda, Aeromonas hydrophila, and Pseudomonas sp.) was isolated from deep cutaneous ulcers and intestines of moribund bass. However, E. tarda in pure culture was the only bacterium isolated from several viscera of several fish; E. tarda may be the etiologic agent responsible for some episodes of seasonal mortality in largemouth bass.

Animals↗
PubMed1992

Driving restrictions advised by midwestern cardiologists implanting cardioverter defibrillators: present practices, criteria utilized, and compatibility with existing state laws.

Although some patients remain at risk of losing physical control or collapsing after implantation of a cardioverter defibrillator for sustained ventricular arrhythmias, little is known about restrictions advised by arrhythmia specialists to patients with implanted devices concerning physical activities such as driving. In this study, all of the 58 cardiologists implanting cardioverter defibrillators in three contiguous midwestern states were surveyed to determine present practices and the compatibility of these practices with existing state law. Of the 51 respondents (88%), 27 cardiologists (53%) advised only those implanted patients who had had arrhythmia-induced presyncope or physical collapse to cease driving. Twenty two of the remaining cardiologists (43%) advised all implanted patients to cease driving, whereas two cardiologists (4%) never advised any implanted patient to restrict driving. Permanent driving abstinence was advised by seven of the responding cardiologists (14%), while temporary driving abstinence for periods of 2-12 months (mean 6 +/- 3 months) was recommended by the remaining 42 respondents (82%) who advised against driving. The criteria utilized, driving restrictions advised, and durations advised for driving restrictions were not uniform in any of the 13 surveyed university and nonaffiliated cardiology practices with greater than or equal to 2 implanting cardiologists. Overall, 38 cardiologists (74%) advised against driving and recommended durations that equaled or exceed their state's minimum legal requirements, although only 27 of the 51 cardiologists (53%) based their practice upon knowledge of their state's driving laws. The results of this survey suggest that the majority of cardiologists who implant cardioverter defibrillators advise their patients against driving postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Automobile Driving↗
PubMed1992

Acute intermittent porphyria treated by testosterone implant.

The hereditary disorder acute intermittent porphyria is potentially fatal. Many more females present with active disease than males and some have attacks related to their menstrual cycle and pregnancy. We present a female patient who was diagnosed while pregnant at 19 years. She subsequently developed life-threatening attacks pre-menstrually at 24 years; these were associated with weight loss. Initial treatment was with high calorie feeding via a naso-gastric tube, followed by a gastrostomy. Subsequent gonadotrophin suppression with intranasal luteinizing hormone-releasing hormone analogue (buserelin) thrice daily met with limited success. We implanted 100 mg of testosterone subcutaneously in November 1989. The buserelin was discontinued in January 1990 and menses returned 3 months later. There have been no serious attacks since then. Repeat implantation was performed at 6 monthly intervals until her present pregnancy. Baseline biochemical parameters have remained high and unaltered despite treatment although the testosterone has clearly had a marked clinical benefit, without side effects.

Acute Disease↗
PubMed1992

Differences between chronic schizophrenic patients in the hospital and in the community.

Clinical differences between stable, chronic schizophrenic patients with long stays in the hospital and schizophrenic patients living in the community were investigated. Patients were matched for age, gender, and diagnosis. Hospitalized patients had more severe thought disorder and negative symptoms, and those in the community had a significantly higher incidence of depression and anxiety. The community-based patients were also receiving higher doses of neuroleptic drugs and had a higher incidence and severity of extra-pyramidal side effects. Results suggest that living in the community, despite its obvious benefits, may have its price in terms of the distressing effects of affective symptoms and neuroleptic side effects.

Activities of Daily Living↗
PubMed1992

Effect of local context of responding on human judgment of causality.

Two experiments examined the effect of various relationships between a response (pressing the space bar of a computer) and an outcome (a triangle flashing on a screen) on judgments of the causal effectiveness of the response. In Experiment 1, when responses were required to be temporarily isolated from each other prior to an outcome, ratings of the causal effectiveness of the responses were higher than in a condition in which the probability of an outcome following a response was the same but in which no temporal isolation was required. In Experiment 2, when a number of responses were required to be emitted temporally close to the outcome, ratings of the causal effectiveness of the responses were lower than in a condition in which the probability of an outcome following a response was the same but in which no temporal proximity was required. These results suggest that, in addition to the overall probability that an outcome will follow a response, the local context of responding at the time an outcome is presented is critical in influencing ratings of causal effectiveness.

Adult↗
PubMed1991

Multiple determinants of the effects of reinforcement magnitude on free-operant response rates.

Four experiments examined the effects of increasing the number of food pellets given to hungry rats for a lever-press response. On a simple variable-interval 60-s schedule, increased number of pellets depressed response rates (Experiment 1). In Experiment 2, the decrease in response rate as a function of increased reinforcement magnitude was demonstrated on a variable-interval 30-s schedule, but enhanced rates of response were obtained with the same increase in reinforcement magnitude on a variable-ratio 30 schedule. In Experiment 3, higher rates of responding were maintained by the component of a concurrent variable-interval 60-s variable-interval 60-s schedule associated with a higher reinforcement magnitude. In Experiment 4, higher rates of response were produced in the component of a multiple variable-interval 60-s variable-interval 60-s schedule associated with the higher reinforcement magnitude. It is suggested that on simple schedules greater reinforcer magnitudes shape the reinforced pattern of responding more effectively than do smaller reinforcement magnitudes. This effect is, however, overridden by another process, such a contrast, when two magnitudes are presented within a single session on two-component schedules.

Journal Article↗
PubMed1991

Simple, optimized liquid-chromatographic method for measuring total hydroxyproline in urine evaluated.

We have optimized a method for measuring total hydroxyproline (HYP) in urine by HPLC after release from urinary peptides by solid-phase hydrolysis on Dowex 50W x 8 ion-exchange resin. The HYP was derivatized with 4-chlor-7-nitrobenzo-2-oxa-1,3-diazole, and excess reagent was removed with the use of a 100-mg C18 Bond-Elut cartridge. The HYP derivative was separated isocratically at 30 degrees C on a 250 x 4.6 mm reversed-phase column containing 5-microns particles of Spherisorb S5 ODS-2, with S-carboxymethylcysteine as internal standard. Total assay time was 14 min. The standard curve for the method was linear from the detection limit for HYP, 3.6 mumol/L, to 10 mmol/L. The between-batch CV was less than 5.1% and the mean analytical recovery of HYP was 95% +/- 1.4%. Comparison with a commercially available colorimetric method showed good correlation: y = 1.158x + 19.76 mumol/L (Syx = 74, n = 120), but HPLC results were 15% higher, probably from incomplete hydrolysis with the colorimetric method. This method offers a considerable improvement in assay time, specificity, sensitivity, precision, and cost compared with the colorimetric method.

Chromatography, High Pressure Liquid↗
PubMed1990

Context extinction following conditioning with delayed reward enhances subsequent instrumental responding.

In Experiment 1, delayed reward generated low response rates relative to immediate reward delivered with the same frequency. Lister rats exposed to delayed reward subsequently responded at a higher rate in extinction if they received nonreinforced exposure to the conditioning context after instrumental training and prior to test, compared with animals that received home cage exposure. In Experiment 2, a signaled delay of reinforcement resulted in higher rates than an unsignaled delay. Nonreinforced exposure to the conditioning context elevated response rate for subjects in the unsignaled condition relative to a home cage group, but had no effect on response rates for subjects that had received the signaled delay. In Experiment 3, following an unsignaled reinforcement delay, groups receiving either no event or signaled food in the context responded faster in extinction than groups receiving no context exposure or unsignaled food.

Animals↗
PubMed1989

An immunological cross-reactant of erythropoietin in serum which may invalidate EPO radioimmunoassay.

Atypically high radioimmunoassay estimates of erythropoietin in serum samples from two out of a series of 130 normal Norwegian children have been found to be invalid. Invalidity was due to non-parallelism of radioimmunoassay (RIA) response dilution lines given by these two sera when compared with the second International Reference Preparation (IRP). In contrast, immunoreactive erythropoietin in other sera usually shows parallelism with the IRP. Fractionation by gel filtration of the sera showing non-parallelism in the RIA showed them to contain an erythropoietin cross-reactant which was eluted before both an 125I recombinant human erythropoietin marker and normal erythropoietin. In family studies, non-parallelism of RIA response dilution lines and the large molecular size erythropoietin cross-reactant was found in serum from one sibling but not in five other family members of one of the two index cases. Radioimmunoassays based on two different antisera differed in recognition of the abnormal cross-reactant of erythropoietin.

Adolescent↗