Search PubMed⌕ Search

Biomedical subjects

P Mason

Publications and source records attributed to P Mason.

At least 19 recordsLinked to original sources
PubMed2006

Giant dipole resonance in the hot and thermalized 132Ce nucleus: damping of collective modes at finite temperature.

The gamma decay of the giant dipole resonance (GDR) in the 132Ce compound nucleus with temperature up to approximately 4 MeV has been measured, using the reaction 64Ni + 68Zn at E(beam) = 300, 400, and 500 MeV. The gamma and charged particles measured in coincidence with recoils are consistent with a fully equilibrated compound nucleus emission. The GDR width, obtained with the statistical model analysis, is found to increase almost linearly with temperature. This increase is rather well reproduced within a model including thermal shape fluctuations and the lifetime of the compound nucleus.

Journal Article↗
PubMed2004

Perioperative lower limb venous haemodynamics in patients under general anaesthesia.

BACKGROUND: This study prospectively determined the haemodynamic changes in the lower limb venous circulation during and shortly after elective abdominal surgery, performed under general anaesthesia. METHODS: Ten females, aged 36-65 yr, ASA I or II, undergoing total abdominal hysterectomy had their peak, mean and minimum velocities, diameter, volume flow and venous pulsatility (peak-minimum/mean velocity) measured in the left popliteal vein on recumbency with duplex at: (i) baseline, (ii) 15 min after induction, (iii) during surgery, and (iv) in recovery 30 min after extubation. Anaesthesia was induced with fentanyl and propofol, paralysis with vecuronium, maintenance with isoflurane in nitrous oxide 66%, and analgesia with morphine. Results are presented as percentage difference from baseline mean value. The Friedman and Wilcoxon([corrected(*)]) tests were applied. RESULTS: Mean velocity decreased by 23.6% during surgery and by 34.6% in recovery (P<0.05(*)). Minimum velocity was decreased by 56% during surgery and by 78% in recovery (P<0.05). The volume flow decreased by 26% during surgery, and by 54.4% in recovery (P<0.001). Diameter and peak velocity changed little at surgery and recovery (P>0.2). In contrast, the pulsatility increased by 30% on induction, 83% on surgery and 109% in recovery (P<0.05). Compared with baseline, haemodynamic changes on induction were small (P>0.1(*)). CONCLUSIONS: A significant decrease in the volume flow, mean and minimum velocities was noted during and immediately after elective total abdominal hysterectomy under general anaesthesia in ASA I and II patients. Flow changes in early recovery mirrored or enhanced those noted intraoperatively. Despite venous flow attenuation, haemodynamic readjustments produced a significant and progressive enhancement of venous flow pulsatility during the course of the procedure.

Adult↗
PubMed2004

Update on statins.

Explore the source record for details and available documents.

Cardiovascular Diseases↗
PubMed2004

Update on statins.

Explore the source record for details and available documents.

Atorvastatin↗
PubMed2004

Stable Bacillus thuringiensis (Bt) toxin content in interspecific F1 and backcross populations of wild Brassica rapa after Bt gene transfer.

Stable expression of a transgene may lead to increased fitness for wild plants after acquiring the transgene via crop-weed hybridization. Here, we investigate the stability of Bt toxin content in wild Brassica rapa acquiring the Bt gene from Bt Brassica napus. The Bt toxin content in nine Bt-expressing B. napus lines was 0.80-1.70 micro g/g leaf tissue throughout the growing season. These nine lines were crossed with three accessions of wild B. rapa and the Bt gene was successfully transferred to interspecific hybrids (F1) and successive backcross generations (BC1 to BC4). The Bt toxin level in F1 and BC progenies containing the Bt gene remained at 0.90-3.10 micro g/g leaf tissue. This study indicates that the Bt gene can persist and be stably expressed in wild B. rapa.

Bacillus thuringiensis↗
PubMed2004

Accuracy of routine diagnosis of pulmonary tuberculosis in an area of high HIV prevalence.

SETTING: Gweru Provincial Hospital, Zimbabwe. OBJECTIVES: To evaluate the accuracy of the diagnosis of pulmonary tuberculosis (PTB) in routine circumstances. DESIGN: Prospective cohort study of routinely diagnosed PTB patients between September 2000 and September 2001. RESULTS: Of 300 patients started on treatment, 161 (53.7%) were positive on direct microscopy. Of the 139 sputum-negative patients, 51 (36.7%) were positive after concentration of specimens, an additional 30 (21.6%) were positive on culture only and 58 (19.3% of the total) were negative for all laboratory investigations. There was no difference in sex, human immunodeficiency virus (HIV) serostatus or treatment outcome between the culture-positive and culture-negative presumed PTB patients. Sputum-negative patients had an increased risk of dying during treatment (RR 2.39, P = 0.015). CONCLUSIONS: The laboratory findings reveal that PTB could be confirmed in more than 80% of patients put on treatment in this setting. The treatment outcomes of the remainder did not differ from those in patients with microbiologically confirmed PTB. In a high HIV-prevalent area, clinicians rightly consider the results of the sputum microscopy test as only one element in the decision making process to put a patient on TB treatment.

Adolescent↗
PubMed2003

Hybridization between transgenic Brassica napus L. and its wild relatives: Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L., and Erucastrum gallicum (Willd.) O.E. Schulz.

The frequency of gene flow from Brassica napus L. (canola) to four wild relatives, Brassica rapa L., Raphanus raphanistrum L., Sinapis arvensis L. and Erucastrum gallicum (Willd.) O.E. Schulz, was assessed in greenhouse and/or field experiments, and actual rates measured in commercial fields in Canada. Various marker systems were used to detect hybrid individuals: herbicide resistance traits (HR), green fluorescent protein marker (GFP), species-specific amplified fragment length polymorphisms (AFLPs) and ploidy level. Hybridization between B. rapa and B. napus occurred in two field experiments (frequency approximately 7%) and in wild populations in commercial fields (approximately 13.6%). The higher frequency in commercial fields was most likely due to greater distance between B. rapa plants. All F(1) hybrids were morphologically similar to B. rapa, had B. napus- and B. rapa-specific AFLP markers and were triploid (AAC, 2n=29 chromosomes). They had reduced pollen viability (about 55%) and segregated for both self-incompatible and self-compatible individuals (the latter being a B. napus trait). In contrast, gene flow between R. raphanistrum and B. napus was very rare. A single R. raphanistrum x B. napus F1 hybrid was detected in 32,821 seedlings from the HR B. napus field experiment. The hybrid was morphologically similar to R. raphanistrum except for the presence of valves, a B. napus trait, in the distorted seed pods. It had a genomic structure consistent with the fusion of an unreduced gamete of R. raphanistrum and a reduced gamete of B. napus (RrRrAC, 2n=37), both B. napus- and R. raphanistrum-specific AFLP markers, and had <1% pollen viability. No hybrids were detected in the greenhouse experiments (1,534 seedlings), the GFP field experiment (4,059 seedlings) or in commercial fields in Québec and Alberta (22,114 seedlings). No S. arvensis or E. gallicum x B. napus hybrids were detected (42,828 and 21,841 seedlings, respectively) from commercial fields in Saskatchewan. These findings suggest that the probability of gene flow from transgenic B. napus to R. raphanistrum, S. arvensis or E. gallicum is very low (<2-5 x 10(-5)). However, transgenes can disperse in the environment via wild B. rapa in eastern Canada and possibly via commercial B. rapa volunteers in western Canada.

Brassicaceae↗
PubMed2003

Some 1,2-diphenylethane derivatives as inhibitors of retinoic acid--metabolising enzymes.

In a search for novel inhibitors of RA-metabolising enzyme inhibitors as potential anti-cancer agents some 1,2-ethandiones, 2-hydroxyethanones and 1-ethylenedioxyethanones based on aryl-substituted 1,2-diphenylethane have been examined. Several of the compounds were weak inhibitors of the non-specific rat liver microsomal P450 enzymes and moderate inhibitors of the RA-induced enzymes in cultured human genital fibroblasts, where the RA-specific enzyme CYP26 is probably expressed. The 2-hydroxyethanone (13) with a 1-(4-dimethylaminophenyl) substituent was overall the most potent compound for rat liver microsomal enzyme (IC50 = 52.1 microM; ketoconazole, 2.8 microM) and the RA-induced enzyme (100 microM, 65.9% inhibition; ketoconazole, 20 microM, 75.0%). Modification of the dimethylamino group in (13) with more hydrophobic dialkylamino functions or separate modification of the 2-(2,4-dichlorophenyl) function did not improve potency.

Animals↗
PubMed2003

A comparison of direct microscopy, the concentration method and the Mycobacteria Growth Indicator Tube for the examination of sputum for acid-fast bacilli.

SETTING: In countries with high human immunodeficiency virus prevalence, laboratory diagnosis of pulmonary tuberculosis with the standard Ziehl-Neelsen (ZN) technique is characterised by low sensitivity. OBJECTIVE: To compare test characteristics of direct microscopy, the concentration method and the Mycobacteria Growth Indicator Tube (MGIT). DESIGN: Three hundred specimens from patients diagnosed with pulmonary tuberculosis were tested for the presence of mycobacteria. Specimens were stained with ZN, decontaminated by adding 4% NaOH, concentrated by centrifuging and processed in MGIT broth. The gold standard was defined as a positive MGIT culture or a positive acid-fast bacilli smear of material obtained from a negative culture after 42 days. RESULTS: A total of 44 (14.7%) specimens were contaminated. Of 256 valid specimens, 234 (91.4%) were positive according to the gold standard definition. Decontamination and concentration of the sample increased the sensitivity of direct microscopy from 67.5% to 87.1%. Specificity remained unchanged (95.5%). The overall median time to detection of MGIT culture-positive specimens was 5 days, ranging from 4 (direct smear-positive specimens) to 12 days (concentration smear-negative specimens). CONCLUSION: The concentration method substantially increases the sensitivity of direct microscopy without much extra input. The MGIT culture technique has considerable advantages, but its relatively high contamination rate and its high cost make it a less recommendable option for widespread use in routine district laboratories.

Bacteriological Techniques↗
PubMed2002

A rare case of dysphagia: hypopharyngeal amyloidosis masquerading as a post-cricoid tumour.

Amyloidoses are a group of disorders in which deposition of abnormal amounts of protein complexes (amyloid) occurs in a variety of tissues. The upper aerodigestive tract may be affected, particularly the larynx, but hypopharyngeal involvement is rarely reported. We present a unique case of amyloidosis of the post-cricoid region causing dysphagia. This case report highlights the need for otolaryngologists to consider the possibility of submucosal amyloid deposition, in the absence of mucosal lesions, in patients who present with dysphagia secondary to an obstructive lesion of the post cricoid region.

Amyloidosis↗
PubMed2001

Physiological and anatomic evidence for functional subclasses of serotonergic raphe magnus cells.

Serotonergic cells in the medullary nucleus raphe magnus (RM) and adjacent nucleus reticularis magnocellularis (NRMC) project to the spinal cord where they are likely to modulate nociceptive transmission. Previous studies have suggested that these cells are physiologically and anatomically heterogeneous. In the present investigation, we examined whether subclasses of serotonergic RM and NRMC cells can be delineated based on their response to a visceral stimulus, and whether any such subclasses are morphologically distinct. Most RM and NRMC serotonergic cells tested (81 of 116) responded to retraction of the descending aorta into a polyethylene tube (the snare stimulus) with 57% of all cells tested excited and 13% inhibited. Responses of serotonergic cells to the snare outlasted the stimulus, were not reflective of evoked cardiovascular changes, and were observed in sino-aortic deafferented rats, evidence that the snare stimulus does not influence serotonergic cell discharge through activation of baroreceptors. Because serotonergic cells responsive to the snare were also responsive to mechanical brushing within the retroperitoneum, the snare is likely to change serotonergic cell discharge by means of the activation of mechanosensitive visceral afferents. Intracellular labeling of physiologically characterized serotonergic RM and NRMC cells showed that cells that were responsive to the snare stimulus had simpler axonal collateralization patterns than cells that were unresponsive to the snare stimulus. This association between morphological and physiological properties provides additional evidence that subpopulations of serotonergic cells exist and serve varied physiological functions.

Action Potentials↗
PubMed2001

The discharge of a subset of serotonergic raphe magnus cells is influenced by baroreceptor input.

In order to determine whether serotonergic cells in the medullary raphe magnus (RM) receive baroreceptor input, cells were tested for their responses to descending aortic occlusion, aortic nerve stimulation, or systemic phenylephrine administration in the lightly anesthetized rat. Serotonergic cells were identified physiologically by a quantitative analysis of their slow and steady discharge. Greater than 40% of the serotonergic RM cells tested responded to brief occlusion of the descending aorta at the level of the coeliac arteries, a stimulus that elevated blood pressure by about 30 mmHg. Similarly, about 40% of the serotonergic RM cells responded to stimulation of the aortic nerve, a nerve that contains primarily baroreceptor afferents from the aortic arch. Greater than 70% of RM serotonergic cells responded to phenylephrine administration which elevated blood pressure by an average of 50 mmHg. Serotonergic cell responses to all methods of baroreceptor activation were small in magnitude and were largely restricted in time to the stimulus duration. The results indicate that a subset of serotonergic cells in RM are influenced by baroreceptor activity.

Animals↗
PubMed2001

Nociceptive responsiveness during slow-wave sleep and waking in the rat.

Brainstem neurons that are thought to modulate pain are reported to have state-dependent discharge rates. Yet, the effect of behavioral state upon nociceptive transmission has not been well studied. Therefore, we examined responses to noxious thermal stimulation of the rat hindpaw presented during different behavioral states. Noxious thermal stimuli were applied to rats as they spontaneously cycled through waking and sleeping states. Two different methods of heating the paw - a focused light bulb ("radiant heat") and a CO2 laser ("laser heat")-were employed. Regardless of the heating method used, rats withdrew from noxious thermal stimulation when it was applied in each behavioral state tested. When rats were tested with radiant heat, the withdrawal latency from noxious heat was shorter during slow-wave sleep than during waking. In contrast, when tested with laser heat, there was no difference in either the response latency or magnitude evoked by noxious heat across sleep/wake states. Despite the fact that rats withdrew from noxious heat (using either method of application) applied during sleep, the rats quickly returned to sleep afterwards. The latency to sleep after noxious stimulation was significantly greater during waking than during sleeping. The behavioral response to noxious thermal stimulation includes both an initial motor withdrawal which is enhanced during sleep and arousal or alerting which is suppressed during sleep. Therefore, pain evokes at least two distinct reactions that are differentially modulated across sleep/wake cycles.

Animals↗
PubMed2001

Medical repatriation via fixed-wing air ambulance: a review of patient characteristics and adverse events.

Anaesthetists are often employed as medical escorts for patients undergoing international transfer by air ambulance. There is little published data on the types of patients being transferred and on the incidence of adverse events. We performed a retrospective review of the documentation of all air ambulance transfers performed by a single company over a 2-year period followed by a prospective assessment of all high-risk patients transferred over a 1-year period. Of 483 transfers identified, 47% were defined as high-risk and 20% were of patients receiving mechanical ventilation. In the prospective group, 28% of patients required pretransfer optimisation, 7% required a major therapeutic intervention during transfer and there was a major adverse event in 12% of transfers. There were two deaths during transport. These data support the recommendation that escorting personnel should be from an appropriate speciality, have reasonable seniority and be adequately trained and supervised.

Adolescent↗
PubMed2001

The chain of survival.

Explore the source record for details and available documents.

Advanced Cardiac Life Support↗