Biomedical subjects

J Stewart

Publications and source records attributed to J Stewart.

At least 217 records · Page 12Linked to original sources

PubMed1997

Identification of classic and complex t(15;17) and/or RAR alpha/PML gene fusion in APL by cytogenetic and dual color-FISH techniques.

Acute promyelocytic leukemia (APL) is a malignant condition characterized by t(15;17)(q22;q12), which fuses the PML gene on chromosome 15 to the retinoic acid receptor alpha (RAR alpha) gene on chromosome 17. In this study, t(15;17) was identified cytogenetically by using the conventional cytogenetic technique, and its molecular counterpart RAR alpha/PML fusion on chromosome 17 on interphase nuclei was further confirmed by means of dual color- (DC-) fluorescence in situ hybridization (FISH) on serial bone marrow (BM) and peripheral blood (PB) samples from APL patients at different stages of the disease. Overall, our findings indicate that interphase DC-FISH analysis can be a useful technique as an adjunct to conventional cytogenetic investigation for detecting the presence of RAR alpha/PML fusion in APL.

Adolescent↗

PubMed1996

Role of catecholamines in the frontal cortex in the modulation of basal and stress-induced autonomic output in rats.

Exposure of animals to noxious or stressful stimuli increases heart rate (HR) and blood pressure through activation of the autonomic nervous system (ANS) and elicits the release of the catecholamines noradrenaline (NA) and dopamine (DA) in the frontal cortex. Subregions of the frontal cortex, such as the medial frontal cortex (MFC) and agranular insular cortex (AIC) project directly to brainstem nuclei involved in autonomic control. It may be hypothesized that catecholamines in the frontal cortex could influence autonomic output through actions on these descending pathways. To evaluate this hypothesis, the effects of intracortical microinjections of drugs acting at NAergic and DAergic receptors were assessed on an autonomically mediated response, the increase in HR induced by tail pinch, in rats anesthetized with urethane. Intra-MFC or AIC injections of an antagonist of beta-adrenoceptors reduced the magnitude of the HR response to pinch. Injections of an agonist of beta-adrenoceptors into these regions increased basal HR but did not affect the pinch response. Injections of drugs acting at alpha-adrenoceptors were without effect. When injected alone, drugs acting at DAergic receptors did not effect basal HR or the response to pinch, but intra-AIC injections of a combination of a D2 antagonist and an agonist of beta-adrenoceptors increased the magnitude of the pinch response. These results suggest that catecholamines, especially NA, released in the frontal cortex are important modulators of the basal and stress-induced output of the ANS.

Anesthesia, General↗

PubMed1996

Isolation and characterization of the human cytochrome P450 CYP1B1 gene.

Previously, we identified a novel human cytochrome P450 cDNA that is inducible by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and represents the first member of a new subfamily designated cytochrome P4501B1 (CYP1B1; Sutter, T. R., Tang, Y. M., Hayes, C. L., Wo, Y. P., Jabs, E. W., Li, X., Yin, H., Cody, C. W., and Greenlee, W. F. (1994) J. Biol. Chem. 269, 13092-13099). Here, we report on the isolation and initial characterization of the CYP1B1 gene. The CYP1B1 gene maps to human chromosome 2 at 2p21-22 and contains three exons and two introns. The putative open reading frame starts in the second exon and is 1629 base pairs in length. Southern analysis using DNA probes directed to each of the three exons confirmed that CYP1B1 is a single copy gene. Human CYP1B1 differs from its two most closely related members of the cytochrome P450 superfamily, CYP1A1 and CYP1A2, in the number of exons (3 versus 7) and chromosome location (2 versus 15). A single transcription initiation site was identified by primer extension analysis and S1 nuclease mapping. Based on nucleotide sequence analysis, the CYP1B1 gene lacks a consensus TATA box in the promoter region and contains nine TCDD-responsive enhancer core binding motifs (5'-GCGTG-3') located within a 2.5-kilobase pair genomic fragment 5'-ward of the transcription initiation start site. Deletion analysis of chloramphenicol acetyltransferase reporter gene constructs containing 5' CYP1B1 genomic fragments indicates that a region from -1022 to -835 containing three of the nine core binding motifs contributes to the TCDD-inducible expression of CYP1B1.

Aryl Hydrocarbon Hydroxylases↗

PubMed1996

A model of the immune network with B-T cell co-operation. I--Prototypical structures and dynamics.

Hitherto, "second generation" network models of the immune system have all been restricted to B-lymphocytes and the Ig molecules they produce. These models have not so far been able to provide a convincing mechanism for the distinction between a "Central Immune System" (CIS) composed of a connected network of lymphocyte clones which couple with "self" antigens in a tolerant mode, and a "Peripheral Immune System" (PIS) composed of clones with little or no supra-clonal organization and which produce classical immune responses when interacting with "non-self" antigens. Here, we present a new network model which explicitly incorporates B-T cell co-operation. In this model, B-cell activation is dependent on T-cell help, and activated T-cells are down-regulated by engagement of their TCRs by soluble Ig. We discuss the underlying biology on which we base the system of ordinary differential equations which defines the present network model. We then illustrate some basic features of the model by examining several prototypical situations with a small number of clones. Depending on the idiotypic connectivity structure, the model exhibits two distinct modes of coupling with antigens: an "immune response" mode in which T- and B-cell clones grow exponentially; and a "tolerant" mode in which T-cell clones are controlled by inclusion of all TCRs in the repertoire of an idiotypic B-cell network. Finally, we discuss the simplifying assumptions of the present model and argue that its range of validity is indeed the region of the state-space of the system where the discrimination between the CIS and the PIS take place.

B-Lymphocytes↗

PubMed1996

A model of the immune network with B-T cell co-operation. II--The simulation of ontogenesis.

This paper is based on a new model of the immune network which explicitly incorporates B-T cell co-operation. A major feature of this model is the simplifying assumption that inhibition by anti-TCR soluble Ig is the only possible down-regulatory influence on activated T-cells. This model is capable of coupling with antigens in both an "immune response" mode and a "tolerant" mode. In the present paper, we simulate the ontogenesis of the immune system by metadynamical recruitment of T- and B-cell clones from the thymus and the bone marrow, seeking to identify the conditions under which each of these modes of antigen coupling occurs. Achieving the tolerant mode depends principally on four parameters: a high value of SB, the rate of bone-marrow production of B-cells; a relatively high efficiency of T-help through mIg-TCR recognition compared with (MHC + peptide)-TCR interaction; and a relatively high value of the product PR.NA, where PR is the average probability that an Ig recognizes another molecule and NA is the number of antigens which are present throughout ontogeny. Analysis of the conditions under which these two modes can coexist, shows that this is possible when a sufficiently numerous set of founder antigens couple in a tolerant mode, whereas isolated antigens first presented once development is completed couple in an immune response mode. The present model thus provides a possible mechanism for the distinction (hitherto purely descriptive) between a Central Immune System organized as a network and responsible for tolerance, and a Peripheral Immune System responsible for immune responses.

B-Lymphocytes↗

PubMed1996

Routine follow up of breast cancer in primary care: randomised trial.

OBJECTIVE: To assess the effect on time to diagnosis of recurrence and on quality of life of transferring primary responsibility for follow up of women with breast cancer in remission from hospital to general practice. DESIGN: Randomised controlled trial with 18 month follow up in which women received routine follow up either in hospital or in general practice. SUBJECTS AND SETTING: 296 women with breast cancer in remission receiving regular follow up care at district general hospitals in England. MAIN OUTCOME MEASURES: Time between first presentation of symptoms to confirmation of recurrence; quality of life measured by specific dimensions of the SF-36 schedule, the EORTC symptom scale, and hospital anxiety and depression scale. RESULTS: Most recurrences (18/26, 69%) presented as interval events, and almost half (7/16, 44%) of the recurrences in the hospital group presented first to general practice. The median time to hospital confirmation of recurrence was 21 days in the hospital group (range 1-376 days) and 22 days in the general practice group (range 4-64). The differences between groups in the change in SF-36 mean scores from baseline were small: -1.8 (95% confidence interval -7.2 to 3.5) for social functioning, 0.5 (-4.1 to 5.1) for mental health, and 0.6 (-3.6 to 4.8) for general health perception. The change from baseline in the mean depression score was higher in the general practice group at the mid-trial assessment (difference 0.6, 0.1 to 1.2) but there was no significant difference between groups in the anxiety score or the EORTC scales. CONCLUSION: General practice follow up of women with breast cancer in remission is not associated with increase in time to diagnosis, increase in anxiety, or deterioration in health related quality of life. Most recurrences are detected by women as interval events and present to the general practitioner, irrespective of continuing hospital follow up.

Aftercare↗

PubMed1996

Behavioral and neurochemical recovery from partial 6-hydroxydopamine lesions of the substantia nigra is blocked by daily treatment with glutamate receptor antagonists MK-801 and CPP.

To determine whether glutamate plays a role in the recovery from lesions of the substantia nigra, measures of behavioral functioning and extracellular levels of striatal dopamine (DA) were made after partial unilateral 6-OHDA lesions in adult male rats. In experiments 1 and 2, animals were treated on days 1-8 after lesioning with the noncompetitive NMDA receptor antagonist dizocilpine maleate (MK-801; 0.25 mg/kg, i.p.) or saline, and in experiment 3 with the competitive antagonist 3-[(+/-)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid (CPP; 1.0 mg/kg, i.p.) or saline. In experiment 1, behavior was assessed 3 and 8 d after lesioning before daily drug treatment; on days 9 and 10, basal extracellular DA and metabolites were measured in both striata using microdialysis. In experiments 2 and 3, behavior was assessed on days 3 and 15 and microdialysis on days 16 and 17, 8-9 d post-termination of drug treatments. On day 3, all animals turned ipsilateral to the lesion. On days 8 or 15, saline-treated animals showed no behavioral asymmetries, whereas MK-801- and CPP-treated animals turned ipsilaterally. In antagonist-treated animals, basal levels of extracellular DA were lower on the lesioned side whether measured 9-10 or 16-17 d after lesioning, whereas in saline-treated animals DA levels on the two sides did not differ. These results suggest that glutamate plays a role in the development of compensatory changes in the DA neurons that accompany behavioral recovery from partial lesions of nigrostriatal DA system.

Animals↗

PubMed1996

Prepare for more collaboration with other professionals, Manitoba FPs told.

During the recent scientific assembly of the Manitoba chapter of the College of Family Physicians (CFPC), a session was devoted to the ways health care reform has affected family medicine. Doctors listened to guest speakers from the CFPC, Manitoba Medical Association and provincial Ministry of Health, and there was a stimulating discussion about the critical issues facing FPs.

Attitude of Health Personnel↗

PubMed1996

Opioid receptors in the ventral tegmental area contribute to stress-induced analgesia in the formalin test for tonic pain.

Exposure to stress can induce analgesia in the formalin test for tonic pain. Here, we report that blockade of opioid receptors by bilateral infusions of naltrexone methylbromide (NMB) (0.1 microgram/0.5 microliter/side) in the ventral tegmental area (VTA) in the midbrain can reduce stress-induced analgesia in this test. These findings indicate that endogeneous opioids act in the VTA to mediate stress-induced analgesia in tonic pain.

Analgesia↗

PubMed1996

Randomised comparative monotherapy trial of phenobarbitone, phenytoin, carbamazepine, or sodium valproate for newly diagnosed childhood epilepsy.

BACKGROUND: The medical treatment of childhood epilepsy is largely influenced by clinical trials in adult patients. We know of only one randomised comparative trial (of two drugs) in newly diagnosed childhood epilepsy. We have undertaken a long-term, prospective, randomised, unmasked, pragmatic trial of the comparative efficacy and toxicity of four standard antiepileptic drugs used as monotherapy in children with newly diagnosed epilepsy. METHODS: Between 1981 and 1987, 167 children aged 3-16 years, who had had at least two previously untreated tonic-clonic or partial seizures, with or without secondary generalisation, were randomly allocated treatment with phenobarbitone, phenytoin, carbamazepine, or sodium valproate. The protocol was designed to conform to standard clinical practice. Efficacy was assessed by time to first seizure after the start of treatment and time to achieving 1-year remission. FINDINGS: The overall outcome with all four drugs was good. 20% of children remained free of seizures and 73% had achieved 1-year remission by 3 years of follow-up. We found no significant differences between the drugs for either measure of efficacy at 1, 2, or 3 years of follow-up. The overall frequency of unacceptable side-effects necessitating withdrawal of the randomised drug was 9%. This total included six of the first ten children assigned phenobarbitone; no further children were allocated this drug. Of the other three drugs, phenytoin (9%) was more likely to be withdrawn than carbamazepine (4%) or sodium valproate (4%). INTERPRETATION Our data will inform choice of drug and outcome with four of the standard drugs available for newly diagnosed tonic-clonic or partial seizures with or without secondary generalisation in children.

Adolescent↗

PubMed1996

A measured breath: new techniques in pulmonary imaging and diagnosis.

The development by Dr. Hans Pasterkamp and his team at the University of Manitoba, Winnipeg, of computer software for acoustic imaging of the chest originated in the need for a noninvasive, nonthreatening way to obtain information about lung function and lung disease in infants and children. Pasterkamp's team is developing a single computer program with potential applications in three areas: the measurement of lung sounds in addition to lung function, the multiple-site mapping of chest sounds to help identify the site of disease, and the assessment of upper airways, with potential use in the diagnosis of obstructive sleep apnea. Computer-assisted acoustic imaging promises to augment and enhance more traditional methods of pulmonary testing.

Acoustics↗

PubMed1996

Relapse to heroin-seeking in rats under opioid maintenance: the effects of stress, heroin priming, and withdrawal.

It is widely believed that opioid withdrawal symptoms contribute to relapse to opioid use, but relapse is highly probable in experienced users even after prolonged abstinence and during opioid maintenance therapy. We have found using an animal model of relapse, the reinstatement procedure, that the two events that reliably reinstate heroin-seeking behavior are reexposure to heroin, and brief exposure to footshock stress. Contrary to expectation, opioid antagonist-induced withdrawal does not reinstate heroin-seeking. We now report on reinstatement of heroin-seeking in rats trained to self-administer heroin and subsequently exposed to a maintenance dose of heroin via minipump and allowed to self-administer saline. With the minipump in, naloxone-induced withdrawal did not reinstate drug-seeking, a priming injection on heroin was only mildly effective, and footshock was highly effective. Twenty-four hours after removal of the minipump (spontaneous withdrawal), animals reinitiated heroin-seeking and, subsequently, both heroin and footshock reinstated heroin-seeking. In summary, brief exposure to stress reinstated heroin-seeking in both heroin-maintained and withdrawn animals. The heroin prime reliably reinstated drug-seeking only in the absence of the minipump; opioid "withdrawal," as such, did not reinstate drug-seeking behavior. Naloxone given to heroin-maintained animals induced withdrawal symptoms, caused a mild depression in the levels of dopamine and its metabolites in the nucleus accumbens septi (NAS), but did not reinstate drug-seeking. Reinstatement of heroin-seeking during spontaneous withdrawal was not accompanied by reductions in basal dopamine and its metabolites in NAS.

Animals↗

PubMed1996

Sensitization of stress-induced feeding in rats repeatedly exposed to brief restraint: the role of corticosterone.

Groups of male Wistar rats lived in cages capable of monitoring feeding and drinking continuously at 0.1-s intervals, 24 h per day. Intact animals were subjected to 20 min of restraint stress or to brief handling (Brief Pick-Up), daily or every third day, 6 h after the beginning of the 12-h light period. In both studies, food-intake increased in the first hour after restraint, peaking between 15 and 45 min. Smaller increases were seen following Brief Pick-Up. More interestingly, the amount of food eaten increased across test sessions, indicating sensitization of the response to stress. Drinking also increased following stress, occurring before feeding and diminishing after the first 15 min. In adrenalectomized animals implanted with slow-release pellets to replace basal diurnal levels of corticosterone (ADX animals), sensitization of the feeding response to restraint stress developed across test sessions, although in these animals, the acute increase in food-intake following restraint stress was attenuated. ADX animals subjected only to Brief Pick-Up showed no increases in food-intake. Daily injections of 3.0 mg/kg corticosterone given to such ADX animals were unable to mimic the effects of restraint on either food-intake or drinking, nor did they augment the effects of restraint in ADX animals. We conclude that sensitization to the effects of brief restraint stress on food-intake can occur independently of a stress-induced rise in plasma corticosterone.

Adrenalectomy↗

PubMed1996

Resetting of the circadian clock by a conditioned stimulus.

Environmental light is the dominant temporal cue for the entrainment of circadian rhythms. In mammals, light entrains circadian rhythms by daily resetting a pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Although it is widely held that phase resetting by light involves cellular elements within the SCN that are uniquely responsive to photic cues, we now report that non-photic cues that reliably precede the onset of light can, through associative learning, come to activate these elements. In rats, a neutral non-photic stimulus paired with light in pavlovian conditioning trials was capable of eliciting cellular and behavioural effects characteristic of phase-dependent resetting of the pacemaker by light, the expression of the transcription factor Fos in SCN cells, and phase shifts in free-running activity and temperature rhythms. Thus an associative learning process, pavlovian conditioning, provides a means whereby environmental cues that predict light onset can come to mimic the effect of light on the SCN pacemaker and thereby bring about entrainment of circadian rhythms.

Animals↗

PubMed1996

Limits of clinical assessment in the accurate diagnosis of Machado-Joseph disease.

BACKGROUND: Machado-Joseph disease (MJD) is a type of autosomal dominant spinocerebellar ataxia for which molecular diagnosis is available. We identified 4 families segregating the MJD mutation in which no unequivocal clinical diagnosis could be established prior to molecular testing. Ethnic background, clinical, and molecular characteristics of 19 individuals carrying the MJD mutation in these 4 families were compared with a group of 32 Portuguese families who were clinically diagnosed as having MJD and were found to carry the MJD mutation. RESULTS: Several factors seemed to have an impact in the accuracy of the clinical diagnosis, such as ethnic origin; the number of affected individuals available for examination in each family; the absence of patients showing specific clinical features, such as extrapyramidal signs; and the size of the expanded CAG repeat in the MJD gene. CONCLUSION: Since the recognition of MJD based solely on clinical grounds might sometimes be misleading, a search for the MJD mutation should be performed in patients with a clinical diagnosis of spinocerebellar degeneration.

Adult↗

PubMed1996

Enteroviral polymerase chain reaction in the investigation of aseptic meningitis.

We used a nested polymerase chain reaction (nPCR) to seek evidence for enteroviruses in clinical samples from patients with symptoms of aseptic meningitis. When compared with conventional virus isolation methods on a total of 366 samples collected during 1994-1995, an increase in positivity from 6% to 27% was shown. The results indicate that nPCR would be a valuable aid to the laboratory diagnosis of enteroviral infections as it can detect those enteroviruses that cannot be identified by current isolation methods.

Adolescent↗

PubMed1996

Initial increases in extracellular dopamine in the ventral tegmental area provide a mechanism for the development of desipramine-induced sensitization within the midbrain dopamine system.

In an attempt to understand the basis of the changes in the mesolimbic dopamine system that occur in response to chronic treatment with the antidepressant drug, desipramine HCl (DMI), we monitored changes in extracellular dopamine in ventral tegmental area (VTA) and nucleus accumbens septi (NAS) using in vivo microdialysis in freely moving animals. Early in treatment at a time before changes in the responsiveness of the dopamine system are observed, basal levels of dopamine, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were found to be increased in the VTA of rats treated with 5.0 mg/kg DMI twice daily for 6 days compared to those of saline-treated animals. After 12 days of treatment, and in a second group of animals after 18 days of treatment, basal levels of dopamine, DOPAC, HVA and 5HIAA, and levels in response to challenge with 1.5 mg/kg d-amphetamine sulphate were measured in the NAS. No differences in these measures taken in NAS were found between DMI- and saline-pretreated animals after 12 days of treatment. In DMI-treated animals tested after 18 days, the dopamine response to amphetamine was elevated compared to that of saline-treated animals. Furthermore, although there were no differences in basal levels of dopamine, basal levels of DOPAC and HVA were increased in DMI-treated animals. These findings lend support to the view that the time-dependent sensitization of dopaminergic function brought about by the tricyclic antidepressants may share processes in common with the development of sensitization to the indirect dopamine receptor agonist, amphetamine.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1996

MK-801 increases locomotor activity without elevating extracellular dopamine levels in the nucleus accumbens.

In vivo microdialysis was used in freely moving rats to determine whether the locomotor stimulant effects of dizocilpine maleate (MK-801) were related to increased dopamine (DA) release within the nucleus accumbens (N. Acc.). Each experiment began with a baseline period of at least 2 h (starting 15-20 h after insertion of concentric, removable dialysis probes), during with activity records and dialysate samples were collected every 20 min. Rats in the first experiment then were injected with MK-801 (0.125, 0.25, or 0.50 mg/kg, i.p.) or saline, and activity and extracellular levels of DA, dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured for a further 160 min post-injection. In a second experiment, rats were given 1.5 mg/kg d-amphetamine sulphate 40 min after receiving the same doses of MK-801, and testing was continued for 120 min. Rats in a third experiment were given low, autoreceptor-preferring doses of apomorphine hydrochloride (25 or 50 micrograms/kg, s.c.) or its vehicle 40 min after injection of 0.25 mg/kg MK-801 and then monitored for 120 min. MK-801 produced strong and consistent increases in locomotor activity that were augmented by amphetamine and greatly reduced by the low doses of apomorphine. MK-801 did not increase extracellular DA levels within the N. Acc. when given alone, and it failed to influence the changes in extracellular DA produced by d-amphetamine and apomorphine. MK-801 did produce consistent, dose-related increases in DOPAC and HVA that were probably not related to transmitter release. These results indicate that the increases in locomotor activity seen following MK-801 do not arise from a drug-induced increase in DA levels within the N. Acc.

3,4-Dihydroxyphenylacetic Acid↗