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Biomedical subjects

M Barnett

Publications and source records attributed to M Barnett.

At least 19 recordsLinked to original sources
PubMed2005

Studies of collisional selection rules in thioformaldehyde (H2CS) by microwave-optical double resonance.

Individual rotational levels in the A 1A2,v4=1 state of thioformaldehyde (H2CS) are excited by a cw laser and microwave transitions in the region of 8-12 GHz are measured. Some of the microwave frequencies are found to be characteristic of rotational levels other than the level being pumped. Since the microwave frequencies are characteristic of individual rotational levels in the excited state and the excited-state lifetime is approximately 170 micros, information is obtained concerning rotational selection rules during collisions. It is found that J can change by several units and Ka by 0, +/-2, +/-4, and +/-6. The latter result confirms that o-H2CS is not converted to p-H2CS by collisions. Observation of Ka doublets indicates that there are no appreciable differences between the two components.

Journal Article↗
PubMed2004

A follow up study of patients with paraneoplastic neurological disease in the United Kingdom.

OBJECTIVES: To examine the range of clinical phenotypes, tumour associations, relevant investigations, response to therapy and outcome in a large series of non-selected patients with paraneoplastic neurological disease (PND) affecting the central nervous system (CNS) in the United Kingdom. METHODS: Data were obtained on patients either through direct referral or through the British Neurological Surveillance Unit (BNSU) from February 2000 to January 2001. Physicians were asked to supply information about age and sex of patients, presenting neurological syndromes, the basis of the diagnosis of PND, any associated malignancy, and treatment. Case notes were reviewed and follow up data obtained where possible one year after notification. RESULTS: A total of 63 patients (48 females, 15 males) were identified, 48 through the BNSU and 15 through direct referral. Of these 52 were diagnosed as having definite PND, 10 probable PND, and 1 possible PND. The median age of onset of PND was 66 years (range 30-80 years) and only 7 patients (11%) were less than 50 years at presentation. In 53 patients (84%) the PND preceded the diagnosis of cancer. Paraneoplastic sensory neuronopathy, paraneoplastic encephalomyelitis, and paraneoplastic cerebellar degeneration (PCD) were the most common syndromes reported. The benefit of magnetic resonance imaging in the diagnosis of the disease was limited, while fluorodeoxyglucose positron emission tomography was shown to be useful for the detection of an occult malignancy in 10 out of 14 patients. Antineuronal antibodies were positive in 44/57 (77%) of cases. The following tumours were diagnosed: small cell lung cancer (30%), breast cancer (14%), ovarian cancer (8%), non-small cell lung cancer (8%), Hodgkin's lymphoma (6%), other (16%). With the exception of PCD associated with mesothelioma all other tumours diagnosed in these patients had been previously documented as being associated with PND. Only treatment of the tumour was found to be associated with a stable or improved neurological outcome at last follow up (Fisher's exact test = 4.7, p<0.03). Median survival time was 43 months (95% CI 28 to 57) from onset of neurological disease as calculated using the Kaplan-Meier survival analysis. CONCLUSIONS: PND has a striking female preponderance usually affecting patients in their sixth decade and above. The median survival in our study was 43 months. The majority of patients with PND are not known to have cancer at the time of diagnosis. Our study confirms the importance of diagnosing and treating the underlying tumour.

Adult↗
PubMed2004

Attitudes of 100 patients with chronic obstructive pulmonary disease to artificial ventilation and cardiopulmonary resuscitation.

UNLABELLED: One hundred clinically stable outpatients with chronic obstructive pulmonary disease were surveyed at home by respiratory nurse specialists (RNS) about their views towards cardiopulmonary resuscitation (CPR) and in hospital ventilation. Written information about COPD, CPR and ventilation was provided and consent obtained. The breathing problem-based quality-of-life questionnaire (BP-QoL) was completed. The following information was recorded: age, sex, spirometry, hospital admissions, and antidepressant and oxygen usage in the previous year. Patients were then asked to imagine a scenario in which they were admitted to hospital and their chest condition deteriorated in spite of standard treatment. 'Having reached that stage would you wish to have noninvasive ventilation (NIV), invasive ventilation (IV) or CPR?' Three months later patients were asked to complete a postal patient satisfaction questionnaire. RESULTS: Of 100 patients 41 were male and the mean age was 74.1 years. Fifty four patients had a FEV1 <40% and 37 had a FEV1 between 40 and 59% predicted. Twenty-four patients were on long-term oxygen therapy, eight had taken antidepressants and 56 had been admitted to hospital in the previous year. Forty-eight patients wanted all additional treatments to be attempted if needed and 12 wanted none. Nineteen patients said 'no' for CPR and 10 said 'no' for CPR and IV. There was no significant statistical difference between the groups answering 'yes' or 'no'. Seventy-six per cent of patient satisfaction questionnaires were returned. All patients were satisfied with the way they had been approached and the information received, and 98% of them thought that this issue should be discussed with all patients. CONCLUSION: Attitudes towards resuscitation can be discussed with COPD patients by RNS without causing distress. Attitudes to resuscitation could not be predicted from parameters of respiratory disease severity or age.

Aged↗
PubMed2001

Effect of the total motile sperm count on the efficacy and cost-effectiveness of intrauterine insemination and in vitro fertilization.

OBJECTIVE: To determine prognostic factors for achieving a pregnancy with intrauterine insemination (IUI) and IVF. To compare the effectiveness and cost-effectiveness of IUI and IVF based on semen analysis results. DESIGN: Retrospective cohort study. SETTING: Academic university hospital-based infertility center. PATIENT(S): One thousand thirty-nine infertile couples undergoing 3,479 IUI cycles. Four hundred twenty-four infertile couples undergoing 551 IVF cycles. INTERVENTION(S): IUI and IVF treatment. MAIN OUTCOME MEASURE(S): Multiple logistic regression analysis was used to assess the significance of prognostic factors including a woman's age, gravidity, duration of infertility, diagnoses, use of ovulation induction, and sperm parameters for predicting the outcomes of clinical pregnancy and live birth rate after the first cycle of IUI and IVF. The relative effectiveness and cost-effectiveness of these treatments were then determined based on sperm count results. RESULT(S): Female age, gravidity, and use of ovulation induction were all independent factors in predicting pregnancy after IUI. The average total motile sperm count in the ejaculate was also an important factor, with a threshold value of 10 million. For IVF, only female age was an important predictor for both clinical and ongoing pregnancy. When the average total motile sperm count was under 10 million, IVF with ICSI was more cost-effective than IUI in our clinic. CONCLUSION(S): An average total motile sperm count of 10 million may be a useful threshold value for decisions about treating a couple with IUI or IVF.

Adult↗
PubMed2001

Paraneoplastic brain stem encephalitis in a woman with anti-Ma2 antibody.

A woman developed brain stem encephalopathy in association with serum anti-Ma2 antibodies and left upper lobe lung mass. T2 weighted MRI of the brain showed abnormalities involving the pons, left middle and superior cerebellar peduncles, and bilateral basal ganglia. Immunohistochemical analysis for serum antineuronal antibodies was confounded by the presence of a non-neuronal specific antinuclear antibody. Immunoblot studies showed the presence of anti-Ma2 antibodies. A premortem tissue diagnosis of the lung mass could not be established despite two CT guided needle biopsies, and the patient died as a result of rapid neurological deterioration. The necropsy showed that the lung lesion was an adenocarcinoma which expressed Ma2 immunoreactive protein. Neuropathological findings included prominent perivascular inflammatory infiltrates, glial nodules, and neuronophagia involving the brain stem, basal ganglia, hippocampus and the dentate nucleus of the cerebellum. Ma2 is an autoantigen previously identified in patients with germ cell tumours of the testis and paraneoplastic brain stem and limbic encephalitis. Our patient's clinical and immunopathological findings indicate that this disorder can affect women with lung adenocarcinoma, and that the encephalitic changes predominate in those regions of the brain known to express high concentrations of Ma proteins.

Aged↗
PubMed2001

Vision loss associated with a stiff neck complicating strabismus surgery.

An exotropic 60 year old suffered a scleral-choroidal penetration and vitreous hemorrhage during and after strabismus surgery on a highly myopic eye when her anesthetic airway management was complicated by her previously asymptomatic and unrecognized rigid cervical spine which placed both the surgeon and the anesthetist in disadvantaged positions both physically and medically. Restoration of vision and binocularity ultimately required vitrectomy and intraocular lens implantation.

Blindness↗
PubMed1999

Enantioselective induction of cyclophosphamide metabolism by phenytoin.

The objective of this study was to investigate the effect of phenytoin (PHE) on cyclophosphamide (CP) disposition. CP was administered to 6 adult patients in a preparative regimen for bone marrow transplantation consisting of busulfan and CP. Three of the patients received PHE and the other 3 "control" patients received diazepam (DZP) as anti-epileptic prophylactic treatment. Plasma samples were collected at intervals up to 24 h after CP administration. The plasma concentrations of (R)- and (S)-CP and their respective N-dechloroethylated metabolites, (R)- and (S)-DCE-CP were simultaneously fitted using an enantiospecific 2-compartment pharmacokinetic (PK) model with Bayesian control estimation. DZP had no significant effect on the metabolism of CP and any of its PK parameters. PHE, however, increased significantly the formation of (S)-DCE-CP while having no effect on the formation of (R)-DCE-CP. These results suggest that different enzymes are responsible for the formation of (S)-DCE-CP from (S)-CP and (R)-DCE-CP from (R)-CP. Additionally, assuming that PHE does not affect the passive renal elimination of (R)- and (S)-CP, this analysis suggests that the clearance of both (R)- and (S)-CP to 4-hydroxy-CP (the activation pathway) is increased by PHE.

Adult↗
PubMed1999

Predictors of participant retention in two chemoprevention feasibility trials.

Retention of participants for intervention and follow-up activities is critical in cancer chemoprevention trials. Little has been published about retention patterns and predictors of retention in prevention studies. The Carotene and Retinol Efficacy Trial (CARET) provides an opportunity to study retention of volunteer participants in a large, long-term clinical trial. Two pilot studies were conducted in different populations to test the feasibility of critical strategies for the long-term study. Thirteen percent of the asbestos-exposed workers and 18% of the smokers became inactive during the pilot study. Of those remaining active, all but 2% of asbestos-exposed workers pilot study participants and 5% of smokers pilot study participants chose to participate in the full-scale efficacy trial. Five baseline predictors of inactivity for the asbestos-exposed participants emerged: being non-White, being a current smoker, having a history of high blood pressure at baseline, reporting two or more increases in symptoms during the placebo run-in, and having higher baseline levels of negative mental health measures (i.e. anxiety, depression, and fatigue). The only significant predictor of inactivity for smoker pilot participants was reporting symptoms during the placebo run-in. The most frequently reported reasons for becoming inactive during the pilot studies were general health issues and problems and symptoms that were seen as specific to the CARET vitamins. These findings suggest areas that could be tested to optimize retention in clinical trials.

Aged↗
PubMed1999

Small noncleaved, non-Burkitt's (Burkit-Like) lymphoma: cytogenetics predict outcome and reflect clinical presentation.

PURPOSE: To correlate cytogenetic abnormalities with clinical presentation and outcome in Burkitt-like, small noncleaved non-Burkitt's lymphoma (SNC-NB). PATIENTS AND METHODS: Thirty-nine patients with SNC-NB lymphoma and a clonal karyotype were evaluated between January 1989 and January 1996. All were from British Columbia, Canada, underwent uniform clinical staging, and were treated on investigational protocols by a small group of clinicians. RESULTS: Three groups of patients were identified by clonal karyotype on cytogenetic analysis: (1) those with a c-myc translocation (n = 11); (2) those with dual translocation of c-myc and bcl-2 (n = 13); and (3) those with other cytogenetic abnormalities (n = 15). The c-myc group was younger, presented with earlier stage de nova disease, and had a better clinical prognostic factor profile. The dual-translocation and other groups were older and presented in advanced stage with poorer prognostic features, and a larger proportion of the dual-translocation group patients had transformed from previously diagnosed follicular lymphoma. The median overall survival (OS) time for all patients was 5 months. The median OS time for the dual-translocation group was only 2.5 months, as compared with 7 months and 8 months for the c-myc and other group, respectively (P < .001). There were no survivors beyond 7 months among the dual-translocation group, as opposed to 32% and 25% 2-year OS rates in the c-myc and other group. CONCLUSION: SNC-NB lymphoma is a clinically and cytogenetically heterogenous disease. Dual translocation of c-myc and bcl-2 is characterized by a rapid clinical course and extremely poor outcome. This latter entity may represent the most clinically aggressive lymphoma thus far characterized and warrants intensive investigational treatment where feasible.

Adolescent↗
PubMed1997

Dietary guar gum improves insulin sensitivity in streptozotocin-induced diabetic rats.

Although dietary recommendations for diabetics stress the need for increased carbohydrate and dietary fiber, the effectiveness of dietary fiber in improving insulin sensitivity remains controversial. The aim of this study was to compare the effects of a soluble fiber (guar gum) and an insoluble fiber (wheat bran) on insulin sensitivity in streptozotocin-induced (STZ) diabetic rats. Consequently, the rats were divided into two groups and one half were rendered diabetic with streptozotocin. The STZ diabetic and nondiabetic rats were further randomized and fed a diet containing dietary fiber (7 g/100 g diet) from either guar gum or wheat bran. The hyperinsulinemic clamp technique, combined with infusion of the glucose analog, 2-deoxyglucose (2DG), was utilized to examine insulin sensitivity. Bran-fed STZ diabetic rats were significantly (P < 0.001) hyperglycemic, which was ameliorated by guar gum. Insulin-mediated glucose disposal was increased by the guar diet compared with the bran diet in both the STZ diabetic rats [17.7 +/- 2.2 vs. 11.8 +/- 2.4 mL/(kg x min), P < 0.05] and the nondiabetic rats [20.5 +/- 2.8 vs. 15.5 +/- 1.5 mL/(kg x min), P < 0.05]. The accumulation of 2DG in peripheral muscles reflected the changes in insulin sensitivity with a trend for increased 2DG uptake in the majority of analyzed tissues in rats fed the guar diet, both nondiabetic and STZ diabetic, compared with the bran-fed rats. Accompanying these alterations in insulin sensitivity, guar gum suppressed food intake in the hyperphagic diabetic rats by 20% (P < 0.001). The present results demonstrate the effectiveness of guar gum in improving insulin sensitivity in STZ diabetic rats and suggest that reduced food intake may be an important mechanism of action of guar in hyperphagic diabetic rats.

Adipose Tissue↗
PubMed1996

Computer simulation of transposable element evolution: random template and strict master models.

It has been proposed that the most extensively studied mammalian retrotransposons replicate by some form of a master template model. This conclusion has been drawn largely from DNA sequence analysis and is based on phylogenetic tree topology, the presence and ordering of shared variants, the degree of divergence between elements within a subfamily, and the shape of the distribution of pairwise differences between elements. To investigate how robust these parameters are as predictors of the model of transposition, computer simulations of the two most extreme transposition models, the Random Template Model and the Strict Master Model, were carried out. A prototype of a computer simulator for studying retrotransposition is presented. The simulator is a versatile digital workbench that maintains DNA sequence data and allows manipulation of a range of factors including reverse transcriptase and in situ mutation rates, transposition template, and transposition rate. All parameters previously used as predictors of the model of transposition were markedly different for the two extreme models when evaluated using large sample sizes of sequences from experiments simulating up to 15 million years of evolution.

Animals↗
PubMed1996

The effect of inhibiting fatty acid oxidation on basal glucose metabolism in Psammomys obesus.

We administered etomoxir (an inhibitor of fatty acid oxidation) for five days at a dose of 50 mg/kg/day to three groups of Psammomys obesus. Group A were normoglycemic and normoinsulinemic, group B were normoglycemic and hyperinsulinemic, and group C were hyperglycemic and hyperinsulinemic. When compared with group A, the hyperglycemic/hyperinsulinemic rats of group C had elevated hepatic glucose production (HPG) and elevated glucose uptake (Rg) in all tissues measured reaching statistical significance in white gastrocnemius, soleus and diaphragm. Five days of etomoxir treatment reduced the plasma glucose levels of group C. Etomoxir treatment reduced HGP and although the change was not significant, it was supported by significant reductions of Rg in several tissues including diaphragm, heart, small intestine, brain and white adipose tissue. Five days of etomoxir treatment also reduced the plasma insulin levels in group B and group C, when compared to the levels before treatment. These results demonstrate that inhibition of fatty acid oxidation significantly reduced hyperglycemia, hyperinsulinemia and Rg in some tissues in group C animals suggesting that elevated levels of fatty acid oxidation and increased glucose turnover may be associated with development of NIDDM in Psammomys obesus.

Animals↗
PubMed1996

Multi-organ dysfunction associated with high-dose carboplatin therapy prior to autologous transplantation.

The specific contribution of high-dose carboplatin to regimen-related toxicity after autologous transplantation has been difficult to determine, particularly in patients receiving cyclophosphamide or ifosfamide. We report five cases of severe multi-system failure in patients receiving high-dose carboplatin in addition to other cytotoxics prior to autologous transplantation. Two of these patients did not receive ifosfamide or cyclophosphamide as part of their chemotherapy. The clinical picture consisted of early onset acute renal failure, arrhythmias and/or myocardial hypokinesia, mental obtundation and other neurological deficits and, in two patients, an acute myopathy. In the two patients in whom serum platinum was measured, levels were very high at the time of marrow infusion. All patients had received prior cisplatin therapy but showed either normal or only modestly impaired creatinine clearance before the transplant. These observations are consistent with a specific clinical syndrome associated with carboplatin toxicity and suggest that creatinine clearance may be inadequate as an indicator of potential renal failure when high-dose carboplatin is used.

Adult↗