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M McLaughlin

Publications and source records attributed to M McLaughlin.

At least 55 records · Page 3Linked to original sources
PubMed1999

Association between variants at the GABAAbeta2, GABAAalpha6 and GABAAgamma2 gene cluster and alcohol dependence in a Scottish population.

A role for the GABA/benzodiazepine receptor complex in alcohol dependence syndrome has been suggested by several lines of evidence. To elucidate the role of GABAA subunits in human alcohol dependence syndrome, we identified polymorphisms in the GABAAbeta2 and GABAAalpha6 receptor subunit genes on 5q33 and assessed their potential contribution in an association study, together with a NciI RFLP at the GABAAgamma2 receptor subunit gene. One hundred and eight alcohol-dependent subjects and 54 unrelated controls were recruited from Scotland. Two novel genetic markers were identified at the GABAAbeta2 and GABAAalpha6 receptor subunit genes and examined for association with the alcohol dependence syndrome and subgroups of subjects with Korsakoff's psychosis and without Korsakoff's psychosis, together with a NciI RFLP at the GABAAgamma2 receptor subunit gene. The chi2 tests demonstrated associations between all alcohol-dependent subjects (not stratified) and the BanI RFLP at the GABAAbeta2 receptor subunit gene (P = 0.015), and the AlwNI RFLP at the GABAAalpha6 receptor gene (P = 0.013). Significant associations were also found between the alcohol-dependent subjects with Korsakoff's psychosis and the BanI RFLP (P = 0.039) and the AlwNI RFLP (P = 0.003). Haplotype analysis also provided evidence of association when all alcohol-dependent subjects (P = 0.013) and the subjects with Korsakoff's psychosis (P = 0.007) were compared with controls. Our findings provide evidence for a role for the GABAA receptor subunit cluster on chromosome 5q33 in susceptibility to the alcohol dependence syndrome and Korsakoff's psychosis.

Adult↗
PubMed1999

Protein kinase C modulates field-evoked transmitter release from cultured rat cerebellar granule cells via a dendrotoxin-sensitive K+ channel.

The role of protein kinase C (PKC) in the control of neurotransmitter release from cultured rat cerebellar granule cells was investigated. Release of preloaded [3H]-D-aspartate which is incorporated into synaptic vesicles in this preparation was evoked by electrical field stimulation or elevated KCl. PKC activation by phorbol esters resulted in a large facilitation of field-evoked Ca(2+)-dependent [3H]-D-aspartate release and a lesser enhancement of KCl-stimulated release. Inhibition of PKC by Ro 31-8220 or staurosporine virtually abolished field-evoked release but had no effect on KCl-evoked release. Field-evoked, but not KCl-evoked, synaptic vesicle exocytosis monitored by the fluorescent vesicle probe FM2-10 was inhibited by staurosporine. PKC was not directly modulating neurite Ca2+ channels coupled to release, as Ro 31-8220 did not inhibit these channels. Activation or inhibition of PKC modulated field-evoked plasma membrane depolarization, but had no effect on KCl-evoked depolarization, consistent with a regulation of Na+ or K+ channels activated by field stimulation. No modulation of field-evoked neurite Na+ influx was seen using phorbol esters. Phorbol ester-induced facilitation of field-evoked [3H]-D-aspartate release and neurite Ca2+ entry was non-additive with that produced by the specific K+ channel antagonist dendrotoxin-1, suggesting that PKC modulates transmitter release from field-stimulated cerebellar granule cells by inhibiting a dendrotoxin-1-sensitive K+ channel.

Animals↗
PubMed1999

Differential coupling of G-protein-linked receptors to Ca2+ mobilization through inositol(1,4,5)trisphosphate or ryanodine receptors in cerebellar granule cells in primary culture.

Rat cerebellar granule cells in primary culture possess muscarinic, metabotropic glutamatergic, histaminergic and alpha-adrenergic receptors which couple to phosphoinositide-specific phospholipase C. We have determined the ability of these receptors to elevate inositol(1,4,5)trisphosphate and to release intracellular calcium, in order to establish the correlation between these two responses. In resting cerebellar granule cells, only the muscarinic agonist carbachol evoked significant increases in both inositol(1,4, 5)trisphosphate and cytoplasmic free Ca2+. Mild depolarization (20 mM KCl) enhanced inositol(1,4,5)trisphosphate elevation by carbachol and histamine, but not by noradrenaline or the metabotropic glutamate agonist 1S,3R ACPD. In contrast, Ca2+-release responses were modified differently by 20 mM KCl-depolarization: the responses to carbachol, histamine and 1S,3R ACPD, but not the responses to noradrenaline, were markedly enhanced. The contribution of ryanodine-sensitive Ca2+-release channels (ryanodine receptors) to the calcium release signal in depolarized cells was determined. Ryanodine (10 microM) inhibited most effectively the cytoplasmic Ca2+ elevation evoked by 1S,3R ACPD (> 90%), while Ca2+ release upon stimulation by carbachol and histamine was only inhibited by approximately 60% and remained larger than in the absence of KCl. Our data are consistent with a specific coupling between metabotropic glutamate receptors and ryanodine-sensitive Ca2+-release channels which may not require generation of inositol(1, 4,5)trisphosphate.

Animals↗
PubMed1999

Alzheimer's disease: correlation of the suppression of beta-amyloid peptide secretion from cultured cells with inhibition of the chymotrypsin-like activity of the proteasome.

Peptide aldehyde inhibitors of the chymotrypsin-like activity of the proteasome (CLIP) such as N-acetyl-Leu-Leu-Nle-H (or ALLN) have been shown previously to inhibit the secretion of beta-amyloid peptide (A beta) from cells. To evaluate more fully the role of the proteasome in this process, we have tested the effects on A beta formation of a much wider range of peptide-based inhibitors of CLIP than published previously. The inhibitors tested included several peptide boronates, some of which proved to be the most potent peptide-based inhibitors of beta-amyloid production reported so far. We found that the ability of the peptide aldehyde and boronate inhibitors to suppress A beta formation from cells correlated extremely well with their potency as CLIP inhibitors. Thus, we conclude that the proteasome may be involved either directly or indirectly in A beta formation.

Aldehydes↗
PubMed1999

An epidemiological review of red cell transfusions in cancer chemotherapy.

OBJECTIVE: The objective of this chart review was to determine the frequency of transfusion and prevalence of anemia (hemoglobin result < 100 g/L) in patients receiving chemotherapy. DESIGN: This study was a retrospective review of medical charts. SETTING: Patients receiving chemotherapy were included from 12 tertiary care comprehensive cancer centres across Canada. MAIN OUTCOME MEASURE: The primary study outcome measure was red blood cell transfusion rate, controlling for patient variables. RESULTS: The 616 patients included had started chemotherapy in January-June 1992. For each subject, data collection finished 4 weeks after the end of the first regimen or after a maximum follow-up period of 26 weeks. Seventy-two patients (12%; 95% confidence interval 9.5% to 14.5%) were transfused for anemia (reasons other than blood loss), and 28% (95% confidence interval 24.5% to 31.5%) of the subjects were anemic during treatment. The univariate analyses of transfusion for anemia yielded significant associations with prognostic factors. In the multivariate analyses, platinum (odds ratio [OR] = 6.69) and anthracycline (OR = 3.56) chemotherapy, baseline hemoglobin (OR = 0.96) and disease stage (OR = 1.72) were statistically significant contributors. CONCLUSION: In this patient cohort, red blood cell transfusion was infrequent (12%). However, patient groups at high risk of transfusion could be identified, with platinum-based chemotherapy being the most significant contributing factor. The information obtained from this multicentre study may prove helpful in developing supportive care guidelines for the management of chemotherapy-related anemia requiring transfusion.

Adolescent↗
PubMed1999

Protein kinase C activation potentiates the rapid secretion of the amyloid precursor protein from rat cortical synaptosomes.

In this study we have used the presynaptic-rich rat cerebrocortical synaptosomal preparation to investigate the proteolytic cleavage of the amyloid precursor protein (AbetaPP) by the alpha-secretase pathway within the betaA4 domain to generate a soluble secreted N-terminal fragment (AbetaPPs). AbetaPP was detected in crude cortical synaptosomal membranes, although at a lower density than that observed in whole-tissue homogenates. Protein kinase C (PKC) activation induced a translocation of the conventional PKC isoform beta1 and novel PKCepsilon from cytosol to membrane fractions, but there was no alteration in the proportion of AbetaPP associated with the Triton-soluble and -insoluble fractions. AbetaPPs was constitutively secreted from cortical synaptosomes, with this secretion being enhanced significantly by the direct activation of PKC with phorbol ester. The PKC-induced secretion of AbetaPPs was only partially blocked by the PKC inhibitor GF109203X (2.5 microM), whereas the phosphorylation of the myristoylated alanine-rich C kinase substrate (MARCKS) protein was significantly inhibited by GF109203X. The differential sensitivities of the MARCKS phosphorylation and AbetaPPs secretion to GF109203X may imply that different PKC isoforms are involved in these two events in the synaptosomal system. These findings strongly suggest that the alpha-secretase activity leading to the secretion of AbetaPPs can occur at the level of the presynaptic terminal.

Alzheimer Disease↗
PubMed1998

A protective effect of apolipoprotein E e2 allele on dementia in Down's syndrome.

BACKGROUND: The apolipoprotein E (ApoE) e4 allele has been associated with an increased risk for Alzheimer's disease, whereas the e2 allele has been shown to be protective. Similar effects in Down's syndrome (DS) have been postulated but not yet demonstrated. METHODS: We obtained DNA from 221 DS individuals and from 162 population controls, and 77 DS children. Older DS subjects were evaluated for dementia and compared to age-matched DS controls. RESULTS: The DS sample with dementia (n = 31) had a significantly lower frequency of the ApoE e2 allele compared to age-matched nondemented DS controls (0% vs. 8.3%, p = .0136). The older DS population had a significantly lower frequency of ApoE e4 compared to population controls (11.7% vs. 20.6%, chi-square 8.9, p = .0028). CONCLUSIONS: The lower frequency of the e2 allele in demented DS subjects compared to age-matched nondemented DS controls suggests a protective effect for ApoE e2 in the development of dementia in DS. The lower frequency of ApoE e4 in our older DS sample compared to population controls points to a detrimental effect of the e4 allele on longevity.

Adult↗
PubMed1998

Vasopressin regulated trafficking of a green fluorescent protein-aquaporin 2 chimera in LLC-PK1 cells.

Aquaporin 2 (AQP2) transfected into LLC-PK1 cells functions as a vasopressin-regulated water channel that recycles between intracellular vesicles and the plasma membrane upon vasopressin stimulation. The green fluorescent protein (GFP) of the jellyfish, Aequorea victoria, was used as an autofluorescent tag to monitor AQP2 trafficking in transfected LLC-PK1 cells. Two chimeras were constructed, one in which GFP was fused to the amino-terminus of AQP2 [GFP-AQP2(NT)] and the second in which it was fused to the carboxyl-terminus [AQP2-GFP(CT)]. The GFP-AQP2(NT) chimera trafficked in a regulated pathway from intracellular vesicles to the basolateral plasma membrane in response to vasopressin or forskolin stimulation of cells. In contrast, the AQP2-GFP(CT) chimera expressed in LLC-PK1 cells was localized constitutively on both apical and basolateral plasma membranes. The cellular location of this chimera was not modified by vasopressin or forskolin. Thus, while the GFP-AQP2(NT) chimera will be useful to study AQP2 trafficking in vitro, the abnormal, constitutive membrane localization of the AQP2-GFP(CT) chimera suggests that one or more trafficking signals exist on the carboxyl-terminus of the AQP2 protein.

Amino Acid Sequence↗
PubMed1998

The addition of GTN to capsaicin cream reduces the discomfort associated with application of capsaicin alone. A volunteer study.

In a double blind, placebo controlled trial of 40 volunteers, the burning discomfort associated with application of capsaicin cream (0.025%) was compared to placebo, GTN cream (1.33%) and to the combination of capsaicin cream (0.025%) plus GTN cream 1.33%. Median VAS for burning pain were 0 for the placebo, GTN and GTN + capsaicin groups and 3 for the capsaicin group after single application of each cream at daily intervals. This study demonstrates that after single application the addition of GTN to capsaicin significantly reduces the burning discomfort associated with application of capsaicin alone.

Capsaicin↗
PubMed1998

Impact of transrenal aortic endograft placement on endovascular graft repair of abdominal aortic aneurysms.

PURPOSE: Successful endovascular repair of an abdominal aortic aneurysm (AAA) requires the creation of a hemostatic seal between the endograft and the underlying aortic wall. A short infrarenal aortic neck may be responsible for incomplete aneurysm exclusion and procedural failure. Sixteen patients who had an endograft positioned completely below the lowest renal artery and 37 patients in whom a porous portion of an endograft attachment system was deliberately placed across the renal arteries were studied to identify if endograft positioning could impact on the occurrence of incomplete aneurysm exclusion. METHODS: Fifty-three patients underwent aortic grafting constructed from a Palmaz balloon expandable stent and an expandable polytetrafluoroethylene (ePTFE) graft implanted in an aorto-ilio-femoral, femoral-femoral configuration. Arteriography, duplex ultrasonography and spiral CT scans were performed in each patient before and after endografting to evaluate for technical success, the presence of endoleaks, and renal artery perfusion. RESULTS: There was no statistically significant difference in patient demography, AAA size, or aortic neck length or diameter between patients who had their endografts placed below or across the renal arteries. However, significantly more proximal aortic endoleaks occurred in those patients with infrarenal endografts (P < or = .05). Median serum creatinine level before and after endografting was not significantly different between the 2 patient subgroups, with the exception of 2 patients who had inadvertent coverage of a single renal orifice by the endograft. Median blood pressure and the requirement for antihypertensive therapy remained the same after transrenal aortic stent grafting. Significant renal artery compromise did not occur after appropriately positioned transrenal stents as shown by means of angiography, CT scanning, and duplex ultrasound scan. Mean follow-up time was 10.3 months (range, 3 to 18 months). Patients who had significant renal artery stenosis (> or =50%) before aortic endografting did not show progression of renal artery stenosis after trans-renal endografting. Two patients with transrenal aortic stent grafts had inadvertent coverage of 1 renal artery by the endograft because of device malpositioning, which resulted in nondialysis dependent renal insufficiency. In addition, evidence of segmental renal artery infarction (<20% of the kidney), which did not result in an apparent change in renal function, was shown by means of follow-up CT scans in 2 patients with transrenal endografts. CONCLUSION: Transrenal aortic endograft fixation using a balloon expandable device in patients with AAAs can result in a significant reduction in the risk of proximal endoleaks. Absolute attention to precise device positioning, coupled with the use of detailed imaging techniques, should reduce the risk of inadvertent renal artery occlusion from malpositioning. Long-term follow-up is essential to determine if there will be late sequelae of transrenal fixation of endografts, which could adversely effect renal perfusion.

Aged↗
PubMed1998

Coping and appraisal of daily stressors predict heart rate and blood pressure levels in young women.

An anger-provocation paradigm was used to assess the effects of coping processes and appraisal of daily stressors on stress reactivity in 33 normotensive undergraduate women. Participants performed a mental arithmetic and an interpersonal conflict task during the pre- and postmenstrual phases of their menstrual cycles. Increased use of the emotion-focused coping processes of tension reduction and positive reappraisal was correlated with lower levels of baseline heart rate, whereas distancing was associated with higher levels of systolic blood pressure reactivity during the conflict task. Perceiving daily stressors as more stressful was associated with higher baseline diastolic blood pressure levels. The authors concluded that the transactional model of stress is useful for generating hypotheses about factors that predict heart rate and blood pressure levels in women.

Adaptation, Physiological↗
PubMed1998

Basolateral distribution of caveolin-1 in the kidney. Absence from H+-atpase-coated endocytic vesicles in intercalated cells.

In kidney epithelial cells, a variety of physiological processes are dependent on the active recycling of membrane proteins between intracellular vesicles and the cell surface. Although clathrin-mediated endocytosis occurs in several renal cell types, endocytosis can also occur by non-clathrin-coated vesicles, including pinocytotic structures known as caveolae that contain a novel coat protein, caveolin. Exo- and endocytosis of a vacuolar H+-ATPase in intercalated cells also occurs via specialized "coated" vesicles that do not contain clathrin. The aim of this study was to localize caveolin in the kidney and, in addition, to determine whether it could be a component of the H+-ATPase recycling process. Using an antibody against the alpha- and beta-isoforms of caveolin-1, our immunocytochemical data show a marked heterogeneity in the cellular expression of this isoform of caveolin in kidney. In contrast, caveolin-3 was not detectable in renal epithelial cells. Caveolin-1 was abundant in endothelial cells and smooth muscle cells and was present in the parietal cells of Bowman's capsule. Distal tubule cells, connecting tubule cells, and collecting duct principal cells exhibited marked punctate basolateral staining, corresponding to the presence of caveolae detected by electron microscopy, whereas all intercalated cells were negative in both cortex and medulla. These data indicate that although caveolin-1 may participate in basolateral events in some kidney epithelial cell types, it does not appear to be involved in the regulated recycling of H+-ATPase in intercalated cells. Therefore, these cells recycle H+-ATPase by a mechanism that involves neither clathrin nor caveolin-1.

Animals↗
PubMed1997

Characterization of pigs transgenic for human decay-accelerating factor.

BACKGROUND: To prevent the central role played by complement activation in the hyperacute rejection of pig organs transplanted into primates, pigs transgenic for human decay-accelerating factor (HDAF) have recently been produced. The data presented here extend previous immunohistochemical findings by documenting the immunological characterization and the levels of expression of HDAF in these transgenic pigs. METHODS: Animals from 30 independently derived lines were included in this study. HDAF expression was characterized by immunoprecipitation and epitope mapping. Quantitative analysis was performed by radiometric assays followed by Scatchard analysis and by double-determinant radioimmunoassay. Deposition of iC3b on porcine aortic endothelial cells was determined by radioimmunoassay. DNA slot-blot analysis and densitometric scanning were used to evaluate HDAF transgene copy number. RESULTS: The integrity of HDAF expressed by these transgenic pigs could be demonstrated. HDAF was present in 72% of the organs analyzed, although considerable variation in expression occurred, both between animals and within the same pig. High levels of HDAF on porcine aortic endothelial cells resulted in iC3b deposition at levels as low as that detected on human endothelial cells. Twenty-six organs expressed levels of HDAF greater than those observed in the equivalent human tissue. HDAF expression did not correlate with the number of copies of the transgene incorporated into the porcine genome. CONCLUSIONS: Transgenic pigs, which express levels of functional HDAF even greater than those observed in humans, have successfully been produced. Pigs transgenic for human complement inhibiting molecules could represent a source of organs for future clinical xenotransplantation.

Animals↗
PubMed1997

Direct modulation of G-proteins by polyunsaturated fatty acids: a novel eicosanoid-independent regulatory mechanism in the developing lung.

Basal and fatty-acid-modulated G-protein function was studied in 1-3-day-pre-term, fetal guinea-pig, type II (fATII) pneumocyte apical membrane. Unstimulated (tonic) high-affinity GTPase activity (measured as [gamma-32P]GTP hydrolysis rate) was high and 77% pertussis toxin-insensitive. Alteration of this activity was used as a marker of G-protein regulation. Arachidonic acid (AA) showed a dose-dependent (IC50 = 48+/-8 microM) inhibition of activity at concentrations significantly below critical micellar concentrations; this effect was mimicked by other polyunsaturated fatty acids (IC50 for linoleic acid = 47 +/- 2 microM; IC50 for oleic acid = 106 +/- 11 microM). Saturated fatty acids showed no effect. The effect of AA on ouabain-insensitive ATPases in the same preparation was significantly lower, suggesting a specificity of the GTPase modulation effect. AA modulation of GTPase activity was not attenuated by blocking eicosanoid metabolism with inhibitors of 5'-lipoxygenase, cyclo-oxygenase and P-450. In order to explore further the mechanism of AA-G-protein interaction, the effect of AA on the time course and equilibrium binding of [35S]GTP[S] to apical membrane was studied. Consistent with our GTPase assay data, AA inhibited binding with an IC50 value of 71+/-1 microM; stearic acid did not mimic this effect. This is the first report of unsaturated-fatty-acid-specific modulation of lung G-protein function: since AA also up-regulates perinatal lung alveolar Na+ transport, we suggest this lipid/G-protein switch helps maintain pulmonary fluid homoeostasis around birth.

Animals↗
PubMed1996

Renal epithelial protein (Apx) is an actin cytoskeleton-regulated Na+ channel.

Apx, the amphibian protein associated with renal amiloride-sensitive Na+ channel activity and with properties consistent with the pore-forming 150-kDa subunit of an epithelial Na+ channel complex initially purified by Benos et al. (Benos, D. J., Saccomani, G., and Sariban-Sohraby, S.(1987) J. Biol. Chem. 262, 10613-10618), has previously failed to generate amiloride-sensitive Na+ currents (Staub, O., Verrey, F., Kleyman, T. R., Benos, D. J., Rossier, B. C., and Kraehenbuhl, J.-P.(1992) J. Cell Biol. 119, 1497-1506). Renal epithelial Na+ channel activity is tonically inhibited by endogenous actin filaments (Cantiello, H. F., Stow, J., Prat, A. G., and Ausiello, D. A.(1991) Am. J. Physiol. 261, C882-C888). Thus, Apx was expressed and its function examined in human melanoma cells with a defective actin-based cytoskeleton. Apx-transfection was associated with a 60-900% increase in amiloride-sensitive (Ki = 3 microM) Na+ currents. Single channel Na+ currents had a similar functional fingerprint to the vasopressin-sensitive, and actin-regulated epithelial Na+ channel of A6 cells, including a 6-7 pS single channel conductance and a perm-selectivity of Na+:K+ of 4:1. Na+ channel activity was either spontaneous, or induced by addition of actin or protein kinase A plus ATP to the bathing solution of excised inside-out patches. Therefore, Apx may be responsible for the ionic conductance involved in the vasopressin-activated Na+ reabsorption in the amphibian kidney.

Actins↗
PubMed1996

Antigen retrieval in cryostat tissue sections and cultured cells by treatment with sodium dodecyl sulfate (SDS).

A simple method for antigen retrieval in tissue sections and cell cultures is described. Because many antibodies recognize denatured proteins on western blots, but are poorly reactive by immunocytochemistry, the effect of applying sodium dodecyl sulfate (SDS) to cryostat sections of tissues and to cell cultures prior to immunostaining was examined. In many cases, a 5-min pretreatment with 1% SDS produced a dramatic increase in staining intensity by indirect immunofluorescence. Among the antibodies tested that showed a positive effect of SDS were an anti-Na/K-ATPase monoclonal antibody, an anti-AE1/2 anion exchanger polyclonal antipeptide antibody, a monoclonal anti-caveolin antibody, and an anti-rab4 monoclonal antibody. In other cases, including antibodies against gp330, aquaporin 1, and aquaporin 2, no effect of SDS was detected. The results show that SDS treatment can be used as a simple method of antigen retrieval in cryostat sections and on cultured cells. In some cases, antigens were not detectable without pretreatment with SDS.

Animals↗