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K Mullen

Publications and source records attributed to K Mullen.

At least 19 recordsLinked to original sources
PubMed2003

The development of an efficient and rapid enzyme linked fluorescent assay method for the detection of Listeria spp. from foods.

Conventional isolation methods, including the Health Products and Food Branch (HPFB), Health Canada method used for the isolation and identification of Listeria species and Listeria monocytogenes from foods and environmental samples, can take a week or more to complete and are usually labor-intensive. This has led to the development of various rapid methods which attempt to generate results comparable to standard methods but in a reduced time-frame with less hands-on operation. Our previous work with rapid detection systems indicated that the recommended enrichment protocols failed to grow the Listeria to detectable levels in a reliable and consistent manner. In the present study, a novel enrichment protocol is described and consists of samples being pre-enriched in Palcam broth (incubated at 35 degrees C for 26 h), enriched in UVM 2 (30 degrees C for 26 h) and then plated and analysed by a rapid detection kit, with results being generated after 52 h of incubation. In total, 200 naturally contaminated samples were analysed by both the HPFB standard method and the Palcam method. The results showed that the Palcam method is comparable to the HPFB method. Further analysis involved a rapid detection system, which applies ELISA techniques and automation in an enzyme-linked fluorescent assay (ELFA) system. This system, referred to as the Vitek Immuno Diagnostic Assay System or VIDAS, can identify Listeria to the genus or species (L. monocytogenes) level. In this comparison, an additional 324 naturally contaminated samples were analysed by both the Palcam and ELFA methods. The sensitivity and specificity of the ELFA method were 98.1% and 97.0%, respectively, while the efficiency was 97.5%. False-negative and false-positive rates were 1.9% and 3.0%, respectively. These results show that the ELFA method (when using the Palcam method for pre- and secondary enrichment) was efficient and gave reliable results after 52 h of incubation, and met Health Canada's criteria for approval as a rapid method.

Fluorescent Antibody Technique↗
PubMed2002

Interchain vs. intrachain energy transfer in acceptor-capped conjugated polymers.

The energy-transfer processes taking place in conjugated polymers are investigated by means of ultrafast spectroscopy and correlated quantum-chemical calculations applied to polyindenofluorenes end-capped with a perylene derivative. Comparison between the time-integrated luminescence and transient absorption spectra measured in solution and in films allows disentangling of the contributions arising from intrachain and from interchain energy-migration phenomena. Intrachain processes dominate in solution where photoexcitation of the polyindenofluorene units induces a rather slow energy transfer to the perylene end moieties. In films, close contacts between chains favors interchain transport of the excited singlet species (from the conjugated bridge of one chain to the perylene unit of a neighboring one); this process is characterized by a 1-order-of-magnitude increase in transfer rate with respect to solution. This description is supported fully by the results of quantum-chemical calculations that go beyond the usual point-dipole model approximation and account for geometric relaxation phenomena in the excited state before energy migration. The calculations indicate a two-step mechanism for intrachain energy transfer with hopping along the conjugated chains as the rate-limiting step; the higher efficiency of the interchain transfer process is mainly due to larger electronic coupling matrix elements between closely lying chains.

Energy Transfer↗
PubMed2001

Brachial artery elastic mechanics in patients with heart failure.

Studies of arterial elasticity in patients with heart failure (HF) have produced varying results. In addition, the direct effects of smooth muscle relaxation on arterial wall mechanics in these patients have not been well characterized. Nineteen patients with New York Heart Association class II to IV HF and 17 age- and size-matched normal subjects were studied by using a recently validated technique for measuring brachial arterial wall mechanics over a wide pressure range. The left brachial artery was imaged through a water-filled blood pressure cuff by use of an ultrasound wall-tracking system at baseline and after 0.4 mg sublingual nitroglycerin (NTG). Simultaneous radial artery pressure waveforms were recorded by tonometry. Transmural pressure (TP) was reduced by increasing water pressure in the cuff. Baseline area, compliance, and pulse wave velocity versus TP curves were similar in the normal subjects and the patients with HF. The incremental elastic modulus versus TP curve tended to be lower in the patients with HF. The wall-to-lumen ratio was increased in HF (P=0.05). NTG significantly shifted the area versus TP (P<0.001) and compliance versus TP (P<0.05) curves upward and the pulse wave velocity versus TP (P<0.05) curve downward in both groups. NTG also significantly (P<0.001) shifted the stress versus strain curve to the right in both groups but did not alter the incremental elastic modulus versus TP curve. We conclude that the brachial arterial wall-to-lumen ratio is increased in HF. This finding occurs together with a trend toward reduced arterial stiffness such that overall mechanical behavior of the brachial artery is preserved. Smooth muscle relaxation with NTG produces similar improvements in brachial arterial wall mechanics in normal subjects and in patients with HF.

Administration, Sublingual↗
PubMed2001

A family study of psychiatric comorbidity in girls and boys with attention-deficit/hyperactivity disorder.

BACKGROUND: Because attention-deficit/hyperactivity disorder (ADHD) is relatively infrequent among girls, little is known about the nature and causes of psychiatric comorbidity in girls and the reason for gender differences in the prevalence of these comorbidities. METHODS: Using blinded, structured psychiatric interviews, we studied two groups of boys: 140 ADHD probands and 120 non-ADHD comparisons. These groups had 454 and 368 first-degree biological relatives, respectively. We also studied two groups of girls: 140 ADHD probands and 122 non-ADHD comparisons. These groups had 417 and 369 first-degree biological relatives, respectively. RESULTS: The co-occurrence of ADHD and comorbid psychopathology in families was the same for families ascertained through boy and girl probands. CONCLUSIONS: Our results suggest that boys and girls do not differ in the familial risk factors that mediate comorbid psychopathology and the familial aggregation of comorbid disorders in ADHD families. Although this is consistent with prior work suggesting more similarities than differences in the nature of psychiatric comorbidity in ADHD boys and girls, we cannot make strong conclusions, owing to the possibility of cohort effects.

Adolescent↗
PubMed2001

New antidiabetic medications. Clinical evidence, clinical practice and pharmacoeconomics.

BACKGROUND: Type 2 diabetes is a progressive and complex disease with underlying defects in insulin sensitivity, insulin secretion and hepatic glucose production. There is a range of antidiabetic treatment options now available to address these defects. Determination of which therapy for which patient is not always apparent from the clinical literature or the product information. OBJECTIVE: To summarise the extent and use of clinical evidence, clinical practice and pharmacoeconomics in positioning antidiabetic agents in Australian clinical practice. DISCUSSION: This paper summarises the introduction of new agents into the options for treatment of type 2 diabetes through the Pharmaceutical Benefits Scheme. Combining evidence based medicine, accepted clinical practice and decision analysis, allows the controlled introduction of new therapies in a climate of limited resources and a population with increasing therapeutic needs.

Australia↗
PubMed2000

Dynamics in physisorbed monolayers of 5-alkoxy-isophthalic acid derivatives at the liquid/solid interface investigated by scanning tunneling microscopy

Monolayers of isophthalic acid derivatives at the liquid/solid interface have been studied with scanning tunneling microscopy (STM). We have investigated the dynamics related to the phenomenon of solvent co-deposition, which was previously observed by our research group when using octan-1-ol or undecan-1-ol as solvents for 5-alkoxy-isophthalic acid derivatives. This solvent co-deposition has now been visualized in real-time (two frames per second) for the first time. Dynamics of individual molecules were investigated in mixtures of semi-fluorinated molecules with video-STM. The specific contrast arising from fluorine atoms in STM images allows us to use this functionality as a probe to analyze the data obtained for the mixtures under investigation. Upon imaging the same region of a monolayer for a period of time we observed that non-fluorinated molecules progressively substitute the fluorinated molecules. These findings illustrate the metastable equilibrium that exists at the liquid/solid interface, between the physisorbed molecules and the supernatant solution.

Journal Article↗
PubMed2000

MALDI-TOF mass spectrometry of insoluble giant polycyclic aromatic hydrocarbons by a new method of sample preparation

The insolubility of giant polycyclic aromatic hydrocarbons (PAHs) prevents their characterization by conventional analytical methods, which require a solubilization of the analyte. Laser desorption mass spectrometry may be used to analyze insoluble samples but is limited to relatively low molecular weights (approximately 2000), in the case of PAHs. To overcome this limitation, we applied MALDI-TOF mass spectrometry. Since MALDI sample preparation also requires solubility of analyte and matrix molecules, the sample preparation needed modification. The giant PAHs (>2000 Da) were investigated after using a new sample preparation, consisting of mechanically mixing analyte and matrix without any solubilization procedures. This solvent-free process allows insoluble compounds to be characterized. Furthermore, new organic molecules can be used as a matrix. Indeed, 7,7,8,8-tetracyanoquinodimethane, a new matrix with promising properties, has proven to be particularly suitable for the measurement of PAHs. Thanks to the successful characterization with MALDI-TOF mass spectrometry, the chemical design of giant PAHs, which was hindered until now for a lack of analytical methods, can now continue to develop.

Journal Article↗
PubMed2000

Synthesis and structural characterization of hexa-tert-butyl-hexa-peri-hexabenzocoronene, its radical cation salt and its tricarbonylchromium complex

The hexa-tert-butyl substituted hexa-peri-hexabenzocoronene was synthesized in an overall yield of 83% from 4-tert-butylphenylacetylene. The key step was the oxidative cyclodehydrogenation of hexa(4-tert-butylphenyl)benzene with anhydrous FeCl3 in CH2Cl2 The high solubility of hexa-tert-butyl-hexa-peri-hexabenzocoronene in common organic solvents allowed a comprehensive spectroscopic characterization of this compound in solution. Electrochemical oxidation at -30 degrees C in the presence of tetrabutylammonium hexafluoroarsenate led to the formation of a stable radical cation salt. Reaction of hexa-tert-butyl-hexa-peri-hexabenzocoronene with an excess of tricarbonyl(naphthalene)chromium in THF/dioxane afforded a mixture of mono- and bis-tricarbonylchromium complexes which could be separated by chromatography. The molecular structures of the parent compound, its radical cation salt and its mono- tricarbonylchromium complex were determined by X-ray analysis and discussed in detail. Remarkably, the crystal structures of these compounds are mainly dominated by the formation of dimers of the aromatic cores.

Journal Article↗
PubMed2000

Thermodynamic phase diagram of the quantum hall skyrmion system

We numerically study the interacting quantum Hall Skyrmion system based on the Chern-Simons action. By noticing that the action is invariant under global spin rotations in the spin space with respect to the magnetic field direction, we obtain the low-energy effective action for a many-Skyrmion system. Performing extensive molecular dynamics simulations, we establish the thermodynamic phase diagram for a many-Skyrmion system.

Journal Article↗
PubMed2000

Irish descent, religion and food consumption in the west of Scotland.

Mortality and morbidity of people of Irish descent in Britain is high, including from cardiovascular causes potentially linked with diet. The west of Scotland has long had a pattern of Irish migration, where migrants were poorer than the host population, and their different religious background gave rise to prolonged discrimination. This paper uses data collected in 1987/88 from the west of Scotland Twenty-07 study to test whether dietary differences due to poverty or to other factors have persisted among the descendents of these migrants. Being born of Catholic parents was the index of Irish descent used, these respondents consumed less of a factor represented by fruit, yoghurt and vegetables, and more of one represented by snacks and processed foods than the rest of the sample. The picture for those reporting current Catholic affiliation in adulthood was similar. Differences are largely associated with social class and mediated not by low income but by educational disadvantage. The findings suggest the continuation of a diet affected by limited opportunities for social mobility, and thus by obstacles to sustained educational advancement, among the descendants of Irish migrants even after several generations.

Adolescent↗
PubMed2000

Vascular ATP-dependent potassium channels, nitric oxide, and human forearm reactive hyperemia.

Vascular ATP-dependent potassium (K+ATP) channels open and contribute to reactive hyperemia (RH) in animals. The contribution of K+ATP channels to ischemic vasolidation during RH and interactions with endothelium-derived nitric oxide have not been well characterized in human subjects. RH blood flow responses (mL/dL) following 5 minutes of cuff occlusion were measured using strain-gauge plethysmography in 22 normal human subjects age 42 +/- 2 years. Measurements were obtained at baseline and following intra-arterial administration of the K+ATP channel closer glibenclamide, the nitric oxide synthase inhibitor L-N-monomethyl arginine (L-NMMA), or both drugs simultaneously. Glibenclamide (100 micrograms/min) did not change basal flow (2.7 +/- 0.3 to 2.7 +/- 0.3 mL/min/dL), but L-NMMA (8 mumol/min) and combined glibenclamide and L-NMMA significantly (p < 0.05) decreased basal flow (3.0 +/- 0.5 to 2.0 +/- 0.2 and 3.3 +/- 0.5 to 2.5 +/- 0.3, respectively). Glibenclamide significantly (p < 0.01) decreased RH flow (18.2 +/- 1.3 to 14.8 +/- 1.3) and excess flow (5.3 +/- 1.2 to 1.3 +/- 1.3). L-NMMA significantly (p < 0.05) decreased RH flow (21.2 +/- 1.8 to 18.9 +/- 1.9) and tended to decrease excess flow (6.1 +/- 2.2 to 3.9 +/- 2.5). Combined drug infusion significantly (p < 0.1) decreased RH flow (21.6 +/- 2.2 to 18.0 +/- 2.4) and excess flow (6.3 +/- 1.6 to 1.6 +/- 1.6), with reductions in RH and excess flow similar to those following glibenclamide infusion alone. We conclude that forearm vascular K+ATP channels are closed at baseline. They open and contribute to RH vasodilation. The addition of nitric oxide inhibition to K+ATP channel blockade does not result in additive or synergistic inhibition of RH.

Adenosine Triphosphate↗
PubMed1999

Biochemical and viral response to consensus interferon (CIFN) therapy in chronic hepatitis C patients: effect of baseline viral concentration. Consensus Interferon Study Group.

OBJECTIVE: The effect of baseline viral concentration on response was assessed as part of a multicenter phase 3 trial evaluating the safety and efficacy of CIFN therapy for chronic HCV infection. METHODS: Patients (n = 472) received either CIFN 9 microg or IFN alpha-2b 3 MU subcutaneously t.i.w. for 24 wk, followed by 24 wk of observation. RESULTS: Efficacy was assessed by the percentage of patients who achieved normal ALT values or undetectable HCV RNA values (using RT-PCR with a sensitivity of 100 copies/ml). There was a clear relationship between baseline viral concentration and either ALT or HCV RNA response; patients with lower titer HCV RNA had better response rates. End-of-treatment HCV RNA responses were better for patients with low viral concentrations treated with CIFN (51%) than for patients treated with IFN a-2b (31%) (p = 0.03). ALT responses in patients with low viral concentrations were 60% for CIFN-treated patients and 27% for IFN alpha-2b-treated patients (p < 0.01) at the end of treatment. Patients with high titer HCV RNA were more likely to have a sustained HCV RNA response after treatment with CIFN 9 microg, compared with those treated with IFN alpha-2b (7% vs 0%, p = 0.03). CONCLUSIONS: Both genotype and baseline viral concentration were independent factors that affected response to interferon.

Adult↗
PubMed1998

Effects of short-term forearm exercise training on resistance vessel endothelial function in normal subjects and patients with heart failure.

BACKGROUND: Exercise training improves endothelium-dependent vasodilation in animals. This study was designed to determine whether forearm exercise training improves endothelium-dependent vasodilation in control subjects and patients with heart failure, a disease associated with abnormal endothelium-dependent vasodilation. METHODS AND RESULTS: We used strain gauge plethysmography to assess the effects of short-term forearm exercise training on resistance vessel function in 11 control subjects and 7 patients with New York Heart Association class II and III heart failure. Subjects performed 30 minutes of handgrip exercise four times a week for 4-6 weeks. In the control subjects, exercise training increased forearm blood flow (FBF) responses to intra-arterial acetylcholine (20 microg/min) from 6.9 +/- 3.1 to 12.2 +/- 3.0 mL/min/100 mL and peak reactive hyperemic FBF responses from 38.1 +/- 5.6 to 47.4 +/- 5.6 (P < .05). Basal FBF and responses to nitroprusside, L-N-monomethyl arginine and acute forearm exercise were not significantly changed. In the patients with heart failure, chronic forearm exercise did not significantly change any of the above-measured parameters. CONCLUSION: Forearm exercise training improves endothelium-dependent vasodilation and peak hyperemic FBF in control subjects but not in patients with heart failure. These data suggest that resistance vessel abnormalities may not be as readily modifiable by exercise training in patients with heart failure compared with control subjects.

Acetylcholine↗
PubMed1996

Contribution of collagen, elastin, and smooth muscle to in vivo human brachial artery wall stress and elastic modulus.

BACKGROUND: The contributions of collagen, elastin, and smooth muscle to arterial mechanical properties in the in vivo human artery are not known. METHODS AND RESULTS: We used a recently developed intravascular ultrasound technique to measure total brachial artery wall stress and incremental elastic modulus (Einc) in seven normal human subjects at baseline and after intra-arterial norepinephrine (1.2 micrograms) and nitroglycerin (100 micrograms). Then we applied a modified Maxwell model to estimate the elastic modulus of elastin (EE); the recruitment of collagen fibers supporting wall stress; and the differential contributions of collagen, elastin, and smooth muscle to wall stress and Einc over a wide range of pressure and smooth muscle tone. With this model, EE was 3 x 10(6) dynes/cm2. Collagen fibers were recruited increasingly as transmural arterial pressure increased and reached a value of approximately 5% to 6% at 100 mm Hg under each of the conditions studied. Isobaric smooth muscle contraction resulted in a small decrease in total wall stress and no significant change in total Einc while shifting the predominant element contributing to these mechanical parameters from collagen in parallel with the smooth muscle to collagen in series with the smooth muscle. In contrast, isometric smooth muscle contraction produced large increases in total wall stress (from 0.11 x 10(6) dynes/cm2 after nitroglycerin administration to 1.35 x 10(6) dynes/cm2 after norepinephrine administration) and Einc (from 3.84 x 10(6) dynes/cm2 after nitroglycerin administration to 57.8 x 10(6) dynes/cm2 after norepinephrine administration) entirely as a result of the additional contribution of the smooth muscle and its associated series collagen. CONCLUSIONS: This study describes a technique for determining arterial elastic properties and a model that can be used to estimate a number of mechanical parameters of the human brachial artery in vivo. This technique may be useful in studies of the arterial elastic properties of arteries in patients with vascular pathology.

Adult↗
PubMed1996

Irish descent, religion, and alcohol and tobacco use.

The West of Scotland has traditionally been a focus for Irish migration. Using data from two studies carried out in this region, one quantitative, the other qualitative, this paper shows little difference in drinking and smoking between Scots of Irish descent and other Scots. It does, however, show significant differences in these behaviours according to religious affiliation in adulthood. Rather than confirming the stereotype of Irish Catholics as heavy drinkers and smokers the present paper puts forward the hypothesis that drinkers and smokers are differentially retained in membership by different religious affiliations, and argues that this accounts for differences in reputation and in health-related behaviours.

Adolescent↗