Biomedical subjects

G Kennedy

Publications and source records attributed to G Kennedy.

At least 19 recordsLinked to original sources

PubMed1999

Analogues of 4,5-bis(3,5-dichlorophenyl)-2-trifluoromethyl-1H-imidazole as potential antibacterial agents.

A preliminary exploration of analogues of 4,5-bis(3,5-dichlorophenyl)-2-trifluoromethyl-1H-imidazole, 1, as novel antibacterial agents was carried out to determine the basic features of the structure responsible for the observed biological activity. The presence of two aryl rings, the imidazole NH and either a good electron withdrawing group or an aldehyde or amino group at C-2 were required for good levels of activity against methicillin resistant Staphylococcus aureus (MRSA).

Anti-Bacterial Agents↗

PubMed1999

Environmental contamination and human exposure to manganese--contribution of methylcyclopentadienyl manganese tricarbonyl in unleaded gasoline.

The organomanganese compound MMT (methylcyclopentadienyl manganese tricarbonyl), an antiknock additive in unleaded gasoline, has been used in Canada since 1976. Indeed, Canada is the only country where MMT is almost exclusively used. In October 1995, by court decision the Environmental protection Agency (EPA) granted Ethyl's waiver for the use of MMT in the United States. Paradoxically, in 1997 the federal government of Canada adopted a law (C-29) that banned both the interprovincial trade and the importation for commercial purposes of manganese-based substances, including MMT. However, MMT is currently widely used in Canada because of substantial stockpiling, and six Canadian provinces are challenging the law in the courts. Moreover, MMT has been approved for use in Argentina, Australia, Bulgaria, Russia, and conditionally, in New Zealand. It has been suggested by some scientists that combustion of MMT may be a significant source of exposure to inorganic Mn in urban areas. The crucial question is whether Mn contamination from industrial sources combined with the additional contamination that would result from the widespread use of MMT would lead to toxic effects. Our research efforts have attempted to assess the environmental/ecosystem Mn contamination arising from the combustion of MMT in abiotic and biotic systems as well as human exposure. The experimental evidence acquired so far provides useful information on certain environmental consequences of the use of MMT as well as raising a number of questions. Our results gave evidence indicating that roadside air, soils, plants, and animals may be contaminated by Mn. As well, some specific groups of the population could have a higher level of exposure to Mn. Nevertheless, the levels of exposure remain below international guide values. Further studies and further characterization of dose-response relationships are thus needed to provide successful implementation of evidence-based risk-assessment approaches.

Canada↗

PubMed1999

Evaluation of the fluorometric protein phosphatase inhibition assay in the determination of okadaic acid in mussels.

The protein phosphatase inhibition assay for okadaic acid, the major DSP toxin, modified to use the fluorescence substrates methylumbelliferyl phosphate (MUP) and fluorescein diphosphate (FDP), was compared to the assay using p-nitrophenylphosphate (p-NPP) and the bioluminescence assay using luciferin phosphate (L-P). Under the standard assay conditions used okadaic acid inhibited the enzyme activity dose-dependently with IC50 values of 1.5 nM (MUP) and 1.2 nM (FDP). This compares to IC50 values of 0.9 and 6 nM using L-P and p-NPP respectively. CDP-star, a chemiluminescence substrate, was not hydrolysed by the enzyme. Decreasing the enzyme concentration lowered the IC50 for the colorimetric method (IC50=2 nM [p-NPP], 0.75 nM enzyme) but no shift was observed with fluorimetry. However at enzyme concentrations < 1.5 nM (standard assay) the error margin was too great for routine analysis. The method using fluorimetry allowed detection of okadaic acid concentrations to levels < or = 1 microg/100 g of mussel tissue which is well below the limit of 20 microg/100 g (mouse bioassay) set by some regulatory agencies. Determination of the toxin content in naturally contaminated mussels in three separate experiments gave coefficients of variance ranging from 16 to 29% (MUP) and from 8 to78% (p-NPP). Multicomparison studies showed that concentrations of okadaic acid in naturally contaminated mussel samples determined by fluorescence generally agreed with those obtained using ELISA and LC-MS procedures, and with the mouse bioassay. However using the mouse bioassay as the standard, values determined by the ELISA, PP-2A and LC-MS all scored false negative results compared to those for the mouse bioassay in the range 20-40 microg/100 g mussel, and at the limit of the mouse bioassay the values by the other three methods were substantially less. With few exceptions the methods scored okadaic acid with highest to lowest values in the following order: mouse bioassay > ELISA > PP-2A > LC-MS. The fluorimetric assay was both more sensitive and accurate than the colorimetric assay (the latter showed a propensity towards false positives in the region 20 microg/100 g), and the moderate increase in equipment cost appears to be outweighed by the performance of the method.

Animals↗

PubMed1999

Endothelial activation and response in patients with hand arm vibration syndrome.

BACKGROUND: Hand-arm vibration syndrome (HAVS) is a form of secondary Raynaud's phenomenon (RP) of occupational origin. In other forms of RP, blood and blood vessel wall interaction is one factor in the pathophysiology. Cytokines and cell adhesion molecules both play an important role in this interaction, and basal vascular tone and vasodilatation are regulated by nitric oxide. METHODS: Blood flow responses to acetylcholine (ACh) and sodium nitroprusside (SNP) and levels of soluble intercellular adhesion molecule-1 (sICAM-1) and the inflammatory cytokine interleukin 8 (IL-8) were measured in eight male patients with vibration white finger disease, which is part of HAVS, and in eight healthy matched male control subjects. RESULTS: sICAM-1 levels were statistically higher (P = 0.02, Mann-Whitney U-test) and IL-8 levels (P < 0.01, Mann-Whitney) were significantly lower in the patient group. The patients with HAVS had significantly reduced vascular responses to SNP (P < 0.05, ANOVA). CONCLUSIONS: In this study, we reveal differences in vascular responses to SNP that suggest there may be an impairment of the smooth muscle response to nitric oxide in patients with HAVS. The increase in sICAM-1 that occurs in patients with HAVS suggests that leucocyte adhesion is increased and that adherent neutrophils may contribute to the microvascular damage seen in this disease. The impeded flow of blood cells through the microcirculation may result in the low levels of circulating IL-8 due to the cytokine binding to erythrocytes. The possible role of NO activity in HAVS warrants further investigation.

Acetylcholine↗

PubMed1998

Myosin conformational states determined by single fluorophore polarization.

Muscle contraction is powered by the interaction of the molecular motor myosin with actin. With new techniques for single molecule manipulation and fluorescence detection, it is now possible to correlate, within the same molecule and in real time, conformational states and mechanical function of myosin. A spot-confocal microscope, capable of detecting single fluorophore polarization, was developed to measure orientational states in the smooth muscle myosin light chain domain during the process of motion generation. Fluorescently labeled turkey gizzard smooth muscle myosin was prepared by removal of endogenous regulatory light chain and re-addition of the light chain labeled at cysteine-108 with the 6-isomer of iodoacetamidotetramethylrhodamine (6-IATR). Single myosin molecule fluorescence polarization data, obtained in a motility assay, provide direct evidence that the myosin light chain domain adopts at least two orientational states during the cyclic interaction of myosin with actin, a randomly disordered state, most likely associated with myosin whereas weakly bound to actin, and an ordered state in which the light chain domain adopts a finite angular orientation whereas strongly bound after the powerstroke.

Animals↗

PubMed1998

Bioaccumulation of manganese and its toxicity in feral pigeons (Columba livia) exposed to manganese oxide dust (Mn3O4).

Manganese tetroxide (Mn3O4) is a product from the combustion of methylcyclopentadienyl manganese tricarbonyl. Exposure to high levels of manganese can lead to serious health effects especially to the central nervous and respiratory systems. Very few studies on the effects of long-term low level exposure to Mn3O4 have been reported. The present study was therefore conducted to examine the bioaccumulation and toxicity of manganese in various organs of feral pigeons (Columba livia) when exposed to low levels of Mn3O4 via inhalation and hence to find any possible relationship between these two parameters. A total of 22 pigeons was exposed to 239 micrograms/m3 of manganese for 7 h/day, 5 days/week for 5, 9, and 13 consecutive weeks. Manganese concentrations in various tissues, e.g., brain (mesencephalon), lung, liver, intestine, pancreas, kidney, muscle, bone, and whole blood, were measured by neutron activation analysis. Various biochemical parameters in blood, e.g., hematocrit, total proteins, glucose, uric acid, alanine aminotransferase, total iron, blood urea nitrogen and triglycerides, were also measured. Manganese concentrations in brain, lung, and bone were significantly higher in Mn3O4-exposed pigeons (0.59, 0.58, and 3.02 micrograms wet tissue, respectively) than in the control group (0.46, 0.19, 1.74 micrograms/g wet tissue, respectively). However, except for total proteins such exposure did not produce any changes in various biochemical parameters which were within the normal values. Thus these results have shown that, despite significant bioaccumulation of manganese in some tissues, no significant toxic effects could be seen.

Administration, Inhalation↗

PubMed1997

Detection of proviral DNA of bovine immunodeficiency virus in bovine tissues by polymerase chain reaction (PCR) and PCR in situ hybridization.

In this study, experiments were designed to investigate the distribution of bovine immunodeficiency virus (BIV) proviral DNA in the tissues and cells of infected calves by solution-phase polymerase chain reaction (SP-PCR) and PCR in situ hybridization (PCR-ISH). Total DNA samples extracted from tissues of 10 BIV-infected and 5 uninfected calves were amplified by SP-PCR with the primers directed to the BIV conserved pol gene segment. The identity of the SP-PCR product was confirmed by Southern hybridization with a BIV pol gene cDNA probe. SP-PCR results demonstrated that BIV proviral DNA was present predominantly in neural tissues and some lymphoid tissues in BIV-infected calves. It also was detected frequently in other tissues including lung, heart, esophagus, and pancreas. Further investigation on cell location of BIV proviral DNA was performed by in situ amplification of DNA on formalin-fixed tissue sections. The amplified DNA was subjected to in situ hybridization with an internal biotinylated probe and detected with streptavidin-gold followed by silver enhancement. Specific BIV proviral DNA signals were observed in neurons, microglial cells, lymphocytes, septal macrophages, smooth muscle cells, and endothelial cells. On the basis of these results, we conclude that BIV replicates in a variety of bovine tissues in vivo and has a broad cell tropism.

Animals↗

PubMed1997

The comet assay: what can it really tell us?

A range of applications of the alkaline comet assay is covered, from investigations of the physicochemical behaviour of DNA, through studies of cellular responses to DNA damage, to biomonitoring of human populations. The underlying principles of this assay are discussed, and new evidence presented which supports the concept of relaxation of supercoiled loops, rather than alkaline unwinding, as the primary reason for comet tail formation. DNA-damaging agents that do not induce strand breaks directly can be detected when cellular repair processes convert lesions to transient strand breaks; an approach is outlined here which maximises this effect and thus widens the scope of the assay. Purified repair enzymes, applied to DNA during the course of the comet assay procedure, greatly increase the sensitivity and specificity of the assay; recent developments with formamidopyrimidine glycosylase (recognising 8-OH-gua and other damaged purines) and uvrABC (for bulky lesions) are presented. The kinetics of cellular repair after low doses of oxidative damage have been followed with this modified comet assay. Finally, the successful measurement of biomarkers of oxidative damage in human populations establishes the comet assay as a valuable tool in molecular epidemiology.

Cell Nucleus↗

PubMed1997

Smooth muscle and skeletal muscle myosins produce similar unitary forces and displacements in the laser trap.

Purified smooth muscle myosin in the in vitro motility assay propels actin filaments at 1/10 the velocity, yet produces 3-4 times more force than skeletal muscle myosin. At the level of a single myosin molecule, these differences in force and actin filament velocity may be reflected in the size and duration of single motion and force-generating events, or in the kinetics of the cross-bridge cycle. Specifically, an increase in either unitary force or duty cycle may explain the enhanced force-generating capacity of smooth muscle myosin. Similarly, an increase in attached time or decrease in unitary displacement may explain the reduced actin filament velocity of smooth muscle myosin. To discriminate between these possibilities, we used a laser trap to measure unitary forces and displacements from single smooth and skeletal muscle myosin molecules. We analyzed our data using mean-variance analysis, which does not rely on scoring individual events by eye, and emphasizes periods in the data with constant properties. Both myosins demonstrated multiple but similar event populations with discrete peaks at approximately +11 and -11 nm in displacement, and 1.5 and 3.5 pN in force. Mean attached times for smooth muscle myosin were longer than for skeletal-muscle myosin. These results explain much of the difference in actin filament velocity between these myosins, and suggest that an increased duty cycle is responsible for the enhanced force-generating capacity of smooth over skeletal-muscle myosin.

Actins↗

PubMed1997

Neuropathology of bovine herpesvirus type 5 (BHV-5) meningo-encephalitis in a rabbit seizure model.

The suitability of a rabbit seizure model for studying the neuropathogenesis of bovine herpesvirus type 5 (BHV-5) encephalitis was evaluated. Intranasal administration of BHV-5 (strain TX89) together with intramuscular administration of dexamethasone produced seizures in 70% of rabbits tested and meningo-encephalitis in 100%. Infectious BHV-5 was consistently isolated from the following sites: olfactory bulb; anterior cortex, containing the frontal cortex, olfactory tract and anterior portion of the olfactory cortex; posterior cortex, containing the temporal, parietal, piriform, entorhinal and occipital cortices; amygdala; hippocampus. Less frequently, BHV-5 was isolated from the midbrain and diencephalon, the pons and medulla, the cerebellum, and the trigeminal ganglia. Rabbits similarly infected with the Cooper strain of bovine herpesvirus type 1 showed no neurological signs or meningo-encephalitis, and virus was not recovered from the brain. The brains of BHV-5-infected rabbits showed neuronal degeneration, leptomeningitis, gliosis and perivascular cuffing, predominantly in the olfactory cortex (piriform and entorhinal cortices), amygdala and hippocampus. Mild lymphocytic meningitis was seen in the olfactory bulb and focal lymphocytic infiltration was sometimes present in the medulla and cerebellum. BHV-5, specific antigens and nucleic acids were detected in the olfactory cortex, amygdala and hippocampus by immunohistochemical methods and in-situ hybridization. The results suggested that, after intranasal BHV-5 inoculation, the virus spread to the central nervous system via the olfactory and trigeminal pathways. The olfactory pathway was more susceptible than the trigeminal pathway to neuropathogenic effects.

Animals↗

PubMed1997

Fellowship training.

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Fellowships and Scholarships↗

PubMed1997

Phase I trial of tirapazamine in combination with cisplatin in a single dose every 3 weeks in patients with solid tumors.

PURPOSE AND METHODS: Tirapazamine (SR4233, WIN 59075) is a benzotriazine-di-N-oxide bioreductive agent that is selectively activated to a reactive DNA-damaging species in hypoxic tumors. Preclinical studies show that synergistic antitumor activity results from a schedule-dependent interaction between tirapazamine and several cytotoxic drug classes, including cisplatin. In a phase I combination study, tirapazamine (130 to 260 mg/m2) was administered as a 1-hour intravenous (IV) infusion beginning 3 hours before cisplatin (75 to 100 mg/m2). Thirteen patients received 41 courses of therapy. These patients had an excellent performance status and were not heavily pretreated. The predominant diagnosis was lung cancer. RESULTS: The major acute side effects were nausea and vomiting, which were controlled with an intensive antiemetic regimen. Other acute effects included diarrhea and muscle cramping, while with repeated dosing, anorexia and fatigue predominated. Full doses of each agent were well tolerated in combination, although in this previously treated population, fatigue increased markedly after three cycles of therapy. Partial responses were observed in two patients (one with non-small-cell lung cancer and one with breast cancer), and a minor response occurred in a patient with mesothelioma. Tirapazamine pharmacokinetics were linear with respect to increasing dose with a mean maximum plasma concentration (Cmax) of 5.97 +/- 2.25 microg/mL and an area under the concentration-time curve (AUC) of 811.4 +/- 311.9 microg/mL.min at 260 mg/m2. These results are consistent with other ongoing single-agent and combination studies and indicate that therapeutically relevant levels of tirapazamine are achievable in patients based on animal models. The mean cisplatin AUC was 285.6 +/- 46.4 microg/mL.min with mean Cmax values of 3.38 +/- 0.43 microg/mL at 75 mg/m2. The clearance of cisplatin was unaffected by coadministration with tirapazamine. CONCLUSION: This trial shows that in previously treated patients, full doses of cisplatin are well tolerated with increasing doses of tirapazamine up to 260 mg/m2. The observation of clinical responses in this trial supports the phase II investigation of this regimen.

Adult↗

PubMed1997

Novel mutations and a mutational hotspot in the MODY3 gene.

Maturity-onset diabetes of the young 3 (MODY3) is a type of NIDDM caused by mutations in the transcription factor hepatocyte nuclear factor-1alpha (HNF-1alpha) located on chromosome 12q. We have identified four novel HNF-1alpha missense mutations in MODY3 families. In four additional and unrelated families, we observed an identical insertion mutation that had occurred in a polycytidine tract in exon 4. Among those families, one exhibited a de novo mutation at this location. We propose that instability of this sequence represents a general mutational mechanism in MODY3. We observed no HNF-1alpha mutations among 86 unrelated late-onset diabetic patients with relative insulin deficiency. Hence mutations in this gene appear to be most strongly associated with early-onset diabetes.

Chromosomes, Human, Pair 12↗

PubMed1997

Cognitive deficits and psychopathology in elderly schizophrenic patients.

The authors investigated the syndromal and cognitive profiles of 25 DSM-III-R older schizophrenic inpatients with continuous acute psychotic symptoms and compared them with 20 younger schizophrenic patients by means of a multidimensional assessment battery. Subjects were medically well and without neurological comorbidity and were comparable in length of current hospitalization and medication regimens. There were no significant differences between the two groups on various symptom rating scores or on neurological variables. The older group's mean scores for various cognitive measures did not reach the value for senile dementia. They also scored significantly better on a memory test and on formal cognitive functions. These findings support the notion of a stable encephalopathy, rather than a dementia-like process, underlying the course of the illness. Authors discussed limitations and implications of these findings.

Adult↗

PubMed1996

Structure and mechanism of formation of a new adduct from formaldehyde and guanosine.

Reactions between formaldehyde and guanosine in the range pH 4-10 gave N2-hydroxymethylguanosine 1, bis-N2-guanosinylmethane 2 and 7-[7-(beta-D-ribofuranosyl)-purin-6(7H)- on-2-yl]-3-(beta-D-ribofuranosyl)-5,6,7,8-tetrahydro-sym-triazino[ 1,2-alpha] purin-10(3H)-one 3a. The latter is a new adduct, the formation of which occurs in neutral solution, is favoured at higher pH and can be rationalised by a sequence of condensations involving two molecules each of guanosine and formaldehyde.

DNA Adducts↗

PubMed1996

Exposure of taxi drivers and office workers to total and respirable manganese in an urban environment.

This research measured the exposure of two groups of workers to respirable and total manganese (Mn) and characterized the Mn particles emitted from an automobile tailpipe. The exposure of 20 office workers and 9 taxi drivers in Toronto to total airborne Mn and respirable Mn was measured over a 7-day period, 24 hours per day. Subjects were asked to wear two pumps (one included a size-selective cyclone that collected the respirable particles), and two battery chargers were supplied to each person so that the pump batteries could be recharged overnight while sampling continued. All filters were analyzed by neutron activation. In addition, Mn particles emitted from a car were collected directly at the exhaust. Particles were observed using secondary electron images in a scanning electron microscope (SEM), and their elemental composition was determined by energy dispersive x-ray spectrometry. The Mn concentrations obtained for the group of office workers ranged from 0.001 to 0.034 microgram/m3 for respirable Mn and from 0.002 to 0.044 microgram/m3 for total Mn. For the taxi drivers the Mn concentrations ranged from 0.007 to 0.032 microgram/m3 for respirable Mn and from 0.008 to 0.073 microgram/m3 for total Mn. There was a significant difference (p < 0.05) between the two groups for both respirable and total Mn. SEM analysis showed that the particles were mostly heterogeneous agglomerates varying from 1 to 100 microns. Even if the specific exposure to Mn from automobiles has not been directly established, these results suggest that the related increase of exposure may be limited.

Air Pollutants, Occupational↗

PubMed1996

Total radical trapping antioxidant potential (TRAP) and exercise.

The relationship between physical activity, physical fitness and total radical trapping antioxidant potential (TRAP) was examined in the Northern Ireland Health and Activity Survey. This was a cross-sectional population study (n = 1600) using a two-stage probability sample of the population. TRAP was calculated using the sum of the individual serum antioxidant concentrations (urate, protein thiols, ascorbate, alpha tocopherol and bilirubin) multiplied by their respective stoichiometric values. Physical fitness was determined by estimation of VO2max by extrapolation from submaximal oxygen uptake, and physical activity was recorded by computer-assisted interview. Mean serum TRAP concentrations were significantly higher in males (653 +/- 8.2 mumol/l, mean +/- SEM) compared to females (564 +/- 8.0 mumol/l) (p < 0.0001). Both male and female smokers had significantly lower TRAP values than non-smokers (males p < 0.0001, females p = 0.02). In females, there was a positive relationship of TRAP with age (p < 0.001) and body mass index (p < 0.001) but a negative relationship with physical fitness (p < 0.05). The known beneficial effects of exercise and activity do not appear to be directly mediated through increased antioxidant status.

Adolescent↗

PubMed1996

Chemistry of muconaldehydes of possible relevance to the toxicology of benzene.

(Z,Z)-Muconaldehyde reacted with primary amines to give N-substituted-2(2'-oxoethyl)-pyrroles, which were reduced to N-substituted-2-(2'-hydroxyethyl)-pyrroles by sodium borohydride. The pyrrole-forming reaction is exhibited by valine and its methyl ester, and is being developed with terminal valine in hemoglobin as a means of dose monitoring (Z,Z)-muconaldehyde, a putative metabolite of benzene. Reactions in aqueous solution between (Z,Z)-muconaldehyde and adenosine, deoxyadenosine, guanosine, or deoxyguanosine leading to pyrrole-containing adducts are described. The elucidation of the structures of the adducts was assisted by the study of reactions between (Z,Z)-muconaldehyde and both nucleoside derivatives and a model compound for guanosine. Reactions of (Z,Z)-muconaldehyde are complicated by its isomerization to (E,Z)- and (E-E)-muconaldehyde. The kinetics of this process have been studied in benzene, acetonitrile, and dimethylsulfoxide.

Aldehydes↗