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Biomedical subjects

D Paterson

Publications and source records attributed to D Paterson.

At least 19 recordsLinked to original sources
PubMed2006

Structure and dynamics of a nanocolloidal silica gel dispersion.

We studied the structure and the dynamics of a nanocolloidal silica gel dispersed in an organic solvent [octylcyanobiphenyl (8CB)] as a function of the silica density by x-ray intensity fluctuation spectroscopy (XIFS). The silica density of the dispersed aerosil gel samples ranged from 0.03 to 0.20 g cm-3 and the autocorrelation of the silica scattering was probed over the q range from 0.03 to 0.15 nm-1 (corresponding to length scales from 42 to 209 nm) at a constant room temperature at which 8CB is in the smectic-A phase. The gel structure has a fractal dimension in this density range of df approximately 2.15. The time autocorrelation functions of the gels show clear density-dependent and complex dynamics. The gel relaxation times are very long and become bimodal with nonergodic character for densities from 0.10 to 0.16 g cm-3. In this same density range, the fluctuation contrast (strength) is a minimum while the relaxation time becomes independent of wave vector. Together, these results indicate that there is a narrow silica density range for these gels in which the dynamics changes dramatically. This suggests a complex phase diagram for the dynamics of aerosil gels as a function of densification.

Journal Article↗
PubMed2006

Fresnel coherent diffractive imaging.

We present an x-ray coherent diffractive imaging experiment utilizing a nonplanar incident wave and demonstrate success by reconstructing a nonperiodic gold sample at 24 nm resolution. Favorable effects of the curved beam illumination are identified.

Journal Article↗
PubMed2005

Synchrotron beam coherence: a spatially resolved measurement.

We report a precise and spatially resolved measurement of the complex degree of coherence of a one-dimensional 1.5-keV beam produced by a third-generation synchrotron source. The method of phase-space tomography is used, which requires only measurements of the x-ray intensity. We find that the field is statistically stationary to within experimental error, the correlations are very well approximated by a Gaussian distribution, and the measured coherence length is in excellent agreement with expectations.

Journal Article↗
PubMed2003

Measurement of the spatial coherence function of undulator radiation using a phase mask.

A measurement of the horizontal coherence function of 7.9 keV radiation from an undulator beam line at the Advanced Photon Source is reported. X-ray diffraction from a phase-shifting mask was used, and the coherence function was measured as a function of the width of beam-conditioning slits in the beam line. The coherence distribution is found to be best described by a Lorentzian function.

Journal Article↗
PubMed2003

The angiogenic receptor KDR is widely distributed in human tissues and tumours and relocates intracellularly on phosphorylation. An immunohistochemical study.

AIMS: Angiogenesis is an important factor in tumour growth and metastasis. Vascular endothelial growth factor receptor 2 (VEGFR-2) or KDR plays a crucial role in angiogenesis. The aim of this study was to raise and characterize antibodies against phosphorylated KDR which could be used for studies on human tissues to assess KDR activation and novel inhibitors of KDR activation in clinical trials. METHODS AND RESULTS: Three monoclonal antibodies and one rabbit polyclonal antiserum were produced. The specificity of the antibodies was confirmed by ELISA. One of the mouse antibodies and the rabbit polyclonal antiserum reacted with a 200-kDa band on a Western blot of human umbilical vein endothelial cell (HUVEC) lysates, the molecular weight of KDR. Immunohistochemical staining showed that phosphorylated KDR is present in a wide variety of normal tissues including liver, colon and placenta, and is not restricted to endothelium. It was also present in a number of human tumours including breast carcinomas, colonic carcinomas and non-Hodgkin's lymphomas. The pattern of staining was membranous, cytoplasmic and nuclear. CONCLUSIONS: This study has shown that phosphorylated KDR is present in a wide variety of tumour and tissue types and is not confined to endothelium.

Animals↗
PubMed2002

Pediatric visceral leishmaniasis in Western Sicily, Italy: a retrospective analysis of 111 cases.

The clinical and epidemiological characteristics of 111 consecutive cases of visceral leishmaniasis identified from 1980 to 2000 in a Sicilian pediatric hospital were analyzed retrospectively. The mean age of the patients was 1.7 years. All children were HIV negative, but 15% were severely malnourished. Fever and splenomegaly were present in all cases and hepatomegaly in 101 (90.1%) cases. Thrombocytopenia and anemia were both observed in 78 (70.2%) cases and leukopenia in 47 (42.3%) cases. A bone marrow aspirate was obtained in all cases; Leishmania amastigotes were detected in 89 (80.2%) cases. Initial treatment consisted of meglumine antimoniate in 99 (89.2%) patients and amphotericin B in 12 (10.8%) patients. Only two children treated with meglumine antimoniate relapsed. The findings highlight the differences between the cases of visceral leishmaniasis observed in the Mediterranean basin and those observed in other regions. The use of the term "Mediterranean visceral leishmaniasis", rather than the term "kala-azar", is proposed for cases observed in the Mediterranean area.

Amphotericin B↗
PubMed2001

Vagus nerve stimulation decreases left ventricular contractility in vivo in the human and pig heart.

1. Studies of the effect of vagus nerve stimulation on ventricular myocardial function in mammals are limited, particularly in the human. 2. The present study was designed to determine the effect of direct electrical stimulation of the left vagus nerve on left ventricular contractile state in hearts paced at 10 % above the natural rate, in anaesthetised pigs and anaesthetised human subjects undergoing open chest surgery for coronary artery bypass grafting. 3. Contractility of the left ventricle was determined from a series of pressure-volume loops obtained from a combined pressure and conductance (volume) catheter placed in the left ventricle. From the measurements a regression slope of the end-systolic pressure-volume relationship was determined to give end-systolic elastance (Ees), a load-independent measure of contractility. 4. In six anaesthetised open chest pigs, stimulation of the peripheral cut end of the left cervical vagus nerve induced a significant decrease in Ees of 26 +/- 14 %. 5. In nine patients electrical stimulation of the left thoracic vagus nerve close to its cardiac branch resulted in a significant drop in Ees of 38 +/- 16 %. 6. The effects of vagal stimulation were blocked by the muscarinic antagonist glycopyrronium (5 mg kg(-1)). 7. Administration of the beta-adrenoreceptor antagonist esmolol (1 mg kg(-1)) also attenuated the effect of vagal stimulation, indicating a degree of interaction of vagal and sympathetic influences on contractility. 8. These studies show that in the human and pig heart the left vagus nerve can profoundly decrease the inotropic state of the left ventricular myocardium independent of its bradycardic effect.

Animals↗
PubMed2000

Rats exhibiting acute behavioural tolerance to nicotine have more [125I]alpha-bungarotoxin binding sites in brain than rats not exhibiting tolerance.

Adult male Sprague-Dawley rats trained to discriminate nicotine (0.4 mg/kg, s.c. vs vehicle) using a two-lever food-reinforced operant discriminative stimulus (DS) paradigm were tested as to the ability of each subject to develop acute tolerance to nicotine. Nicotine (0.8 mg/kg, s.c.) was administered to nicotine-trained rats in their home cage and each rat tested as to its ability to detect a 2nd dose of nicotine (0.4 mg/kg, s.c.) injected at 30 min intervals thereafter (90-180 min). Tolerance was determined by evaluating nicotine-correct responding during a 2 min test session. The results of this experiment indicated that 8 out of 31 rats (26%) displayed acute tolerance (desensitizers); 18 rats (58%) did not exhibit acute tolerance (non-desensitzers) and five rats (16%) fell into a middle group and were designated as neither desensitizers or non-desensitizers. The mode time for acute tolerance was 150 min, with each desensitizer rat displaying a unique temporal profile which was replicable 4-5 weeks later. Receptor autoradiographic analysis indicated no significant differences in [3H]epibatidine binding sites in the brains of desensitizers and non-desensitizers. In contrast, [125I]alpha-bungarotoxin binding was significantly higher in a number of brain regions in desensitizers. In situ hybridization analysis revealed no difference in alpha7 nAChR subunit mRNA levels between desensitizers and non-desensitizers. These observations can be interpreted to suggest that the ability to display acute tolerance to nicotine is contingent upon the ability to upregulate alpha7 nAChRs. These data may also be central to understanding the variability of tobacco use in humans, which may be contingent on the ability of the receptors binding to alpha-bungarotoxin to be responsive to nicotine-induced desensitization.

Animals↗
PubMed2000

Neuronal nicotinic receptors in the human brain.

Neuronal nicotinic acetylcholine receptors (nAChRs) are a family of ligand gated ion channels which are widely distributed in the human brain. Multiple subtypes of these receptors exist, each with individual pharmacological and functional profiles. They mediate the effects of nicotine, a widely used drug of abuse, are involved in a number of physiological and behavioural processes and are additionally implicated in a number of pathological conditions such as Alzheimer's disease, Parkinson's disease and schizophrenia. The nAChRs have a pentameric structure composed of five membrane spanning subunits, of which nine different types have thus far been identified and cloned. The multiple subunits identified provide the basis for the heterogeneity of structure and function observed in the nAChR subtypes and are responsible for the individual characteristics of each. A substantial amount of information on human nAChR structure and function has come from studies on neuroblastoma cell lines which naturally express nAChRs and from recombinant nAChRs expressed in Xenopus oocytes. In vitro brain nAChR distribution can be mapped with a number of appropriate agonist and antagonist radioligands and subunit distribution may be mapped by in situ hybridization using subunit specific mRNA probes. Receptor distribution in the living human brain can be studied with noninvasive imaging techniques such as PET and SPECT, with a significant reduction in nAChRs in the brains of Alzheimer's patients having been identified with [11C] nicotine in PET studies. Despite the significant body of knowledge now accumulated about nAChRs, much remains to be elucidated. This review will attempt to describe the current knowledge on the nAChR subtypes in the human brain, their functional roles and neuropathological involvement.

Animals↗
PubMed1999

Front-line police officers' practices, perceptions and attitudes about the enforcement of impaired driving laws in Canada.

A survey of front line police officers' practices, perceptions and attitudes regarding detection of impaired driving, processing of driving while impaired (DWI) charges, criminal court proceedings and DWI sanctions was conducted across Canada. A sample of 1545 officers of all jurisdictions across the country, representative of different types of police services (i.e. national, provincial, municipal) and types of policing (i.e. traffic, general duty) were surveyed by mail. The results, based on a 71% response rate, indicate that: an average of 7.5 charges/year are laid by officers resulting mainly from erratic driving; videotaping and mobile breath testing could improve efficiency of DWI enforcement; it takes an average of 2 h 48 min to process each DWI charge; about 2/3 of officers say plea bargaining occurs at least sometimes; the average length of DWI trial is over 4 h; less than half of officers think Crown Attorneys are adequately prepared for DWI cases; about 3/4 of officers think the accused escapes conviction on a legal technicality at least sometimes; about 30% of officers say short-term licence suspensions and other forms of discretion are used at least sometimes; DWI places fifth in priority among 15 offences, up from eighth in a 1981 survey; DWI is a priority for most police management but human resources are not adequate; and there is greater support for administrative than for Criminal Code changes. Multiple regressions indicated that the number of DWI charges laid by officers depended mainly on the officers' personal priority regarding DWI enforcement. The results suggest that many officers want to enforce DWI laws but that the numerous procedural and legal barriers that they confront often force them to exercise discretion in the laying of DWI charges.

Accidents, Traffic↗
PubMed1999

Targeting male perpetrators of intimate partner violence: Western Australia's "Freedom from Fear" campaign.

Violence against women by their partners is now recognized as a major international public health problem, in both developed and developing countries. For example, it is estimated that each year in the US, 4 million women experience a serious assault by their partner and that the victim-related economic cost of partner violence is about US$67 billion. Traditional domestic violence campaigns focus on legal threats and sanctions in an attempt to stop men from being violent. While incarcerating violent men and issuing protection orders are necessary components of domestic violence prevention interventions, they do not--and cannot--remove women's fear of the man reappearing at some future time or place, often with tragic consequences. Furthermore, many women do not want to leave the relationship, nor do they want the man incarcerated; they simply want the violence to stop. The Western Australian "Freedom From Fear" campaign is an innovative social marketing initiative that acknowledges these factors and aims to reduce the fears of women (and children) by motivating perpetrators and potential perpetrators to voluntarily attend counseling programs.

Australia↗
PubMed1997

Vertebral osteomyelitis due to Pseudallescheria boydii.

A case of primary vertebral osteomyelitis due to an opportunistic fungus, Pseudallescheria boydii, in a child with acute myeloid leukemia, is reported. To our knowledge this is the first such case in a child, and only the second reported case in the international literature of primary spinal osteomyelitis due to this organism. We discuss the problems presented by this case both in terms of diagnosis and management. We also discuss the role of surgery and systemic antifungal chemotherapy in the treatment of deep infections due to Pseudallescheria boydii.

Child, Preschool↗
PubMed1997

Bacteremia caused by a recently described novel Desulfovibrio species.

An obligately anaerobic, fastidious, slowly growing, spiral, gram-negative bacterium was isolated from the blood of a 75-year-old man with acute onset of pyrexia. The patient responded rapidly to appropriate antibiotic therapy. Extensive investigation failed to detect a focus for the infection. Phenotypically, the organism was consistent with Desulfovibrio species. Microscopic investigation revealed an organism with a vibrioid or spirillioid morphology with rapidly progressive motility by means of a single polar flagellum. Biochemically, the organism produced large amounts of H2S and contained desulfovirdin. The 16S rRNA gene sequence of the organism was found to be most similar to those of members of the genus Desulfovibrio, with identical sequence homology to the newly proposed species described by Tee et al. (W. Tee, M. Dyall-Smith, W. Woods, and D. Eisen, J. Clin. Microbiol. 34:1760-1764, 1996). This is a second unrelated isolation of this novel species from two widely different locations in Australia. The two isolates show some phenotypic differences, indicating that they are different strains of the same species.

Aged↗
PubMed1996

Secure placement of peritoneal dialysis catheters using a laparoscopic technique.

Nineteen patients underwent laparoscopic placement of a peritoneal dialysis catheter with suture fixation into the pelvis. Operating time ranged from 20 to 60 min (median, 33), and the median postoperative stay for patients admitted solely for catheter placement was 1 day. No significant morbidity was associated with this procedure, and all but one catheter functioned well over the long term. Suture fixation of laparoscopically placed peritoneal dialysis catheters is straightforward, and may achieve better catheter function.

Catheterization↗
PubMed1995

A study to validate the modified Canadian Aerobic Fitness Test.

This study evaluated the predictive ability of the modified Canadian Aerobic Fitness Test (mCAFT) on an independent sample of subjects and compared it to the original Canadian Aerobic Fitness Test (CAFT). Male and female subjects (n = 154), 15-69 yrs of age, performed the mCAFT and a maximal treadmill test. VO2max scores predicted from the mCAFT equation did not differ significantly from those measured during the treadmill test, whether the sample was analysed overall or categorized by sex, whereas the CAFT (Jetté) equation resulted in VO2max scores that were significantly lower than either the measured values or those predicted using the mCAFT. The strength of the linear relationship between predicted and measured VO2max scores is the same for both the mCAFT (r = 0.88) and CAFT (r = 0.89). However, the mCAFT results in a lower mean square error (37.0 for mCAFT vs. 63.3 for CAFT) and thus is an improvement over the CAFT prediction.

Adolescent↗