Search PubMed⌕ Search

Biomedical subjects

K Clarke

Publications and source records attributed to K Clarke.

At least 37 records · Page 2Linked to original sources
PubMed2001

Recombinant canine IL-13 receptor alpha2-Fc fusion protein inhibits canine allergen-specific-IgE production in vitro by peripheral blood mononuclear cells from allergic dogs.

Human IL-13, like IL-4, is involved in the regulation of B-cell development, IgE synthesis and allergic responses. However, because IL-13 does not affect either murine Ig class switching or IgE production in vitro, the use of murine models to study the role of IL-13 in IgE-mediated diseases has been limited. In this communication, we report that recombinant protein of canine IL-13 (rcaIL-13) stimulates production of allergen-specific-IgE in vitro by peripheral blood mononuclear cells (PBMC) from flea allergen-sensitized dogs, and that this stimulation activity is specifically inhibited by recombinant protein of canine IL-13Ralpha2 and Fc fragment of canine IgG heavy chain (rcaIL-13Ralpha2-Fc). The data suggest that the regulatory effects of IL-13 on IgE production in canine PBMC are similar to those reported in humans. Thus, canine IL-13 may be a central mediator of allergic diseases in dogs, and allergic dogs may be excellent models for research on IgE-mediated diseases in humans.

Amino Acid Sequence↗
PubMed2001

Development of chronic colitis is dependent on the cytokine MIF.

The cytokine macrophage-migration inhibitory factor (MIF) is secreted by a number of cell types upon induction by lipopolysaccharide (LPS). Because colitis is dependent on interplay between the mucosal immune system and intestinal bacteria, we investigated the role of MIF in experimental colitis. MIF-deficient mice failed to develop disease, but reconstitution of MIF-deficient mice with wild-type innate immune cells restored colitis. In addition, established colitis could be treated with anti-MIF immunoglobulins. Thus, murine colitis is dependent on continuous MIF production by the innate immune system. Because we found increased plasma MIF concentrations in patients with Crohn's disease, these data suggested that MIF is a new target for intervention in Crohn's disease.

Adoptive Transfer↗
PubMed2001

Free fatty acids, but not ketone bodies, protect diabetic rat hearts during low-flow ischemia.

To determine whether the effects of fatty acids on the diabetic heart during ischemia involve altered glycolytic ATP and proton production, we measured energetics and intracellular pH (pH(i)) by using (31)P NMR spectroscopy plus [2-(3)H]glucose uptake in isolated rat hearts. Hearts from 7-wk streptozotocin diabetic and control rats, perfused with buffer containing 11 mM glucose, with or without 1.2 mM palmitate or the ketone bodies, 4 mM beta-hydroxybutyrate plus 1 mM acetoacetate, were subjected to 32 min of low-flow (0.3 ml x g wet wt(-1) x min(-1)) ischemia, followed by 32 min of reperfusion. In control rat hearts, neither palmitate nor ketone bodies altered the recovery of contractile function. Diabetic rat hearts perfused with glucose alone or with ketone bodies, had functional recoveries 50% lower than those of the control hearts, but palmitate restored recovery to control levels. In a parallel group with the functional recoveries, palmitate prevented the 54% faster loss of ATP in the diabetic, glucose-perfused rat hearts during ischemia, but had no effect on the rate of ATP depletion in control hearts. Palmitate decreased total glucose uptake in control rat hearts during low-flow ischemia, from 106 +/- 17 to 52 +/- 12 micromol/g wet wt, but did not alter the total glucose uptake in the diabetic rat hearts, which was 42 +/- 5 micromol/g wet wt. Recovery of contractile function was unrelated to pH(i) during ischemia; the glucose-perfused control and palmitate-perfused diabetic hearts had end-ischemic pH(i) values that were significantly different at 6.36 +/- 0.04 and 6.60 +/- 0.02, respectively, but had similar functional recoveries, whereas the glucose-perfused diabetic hearts had significantly lower functional recoveries, but their pH(i) was 6.49 +/- 0.04. We conclude that fatty acids, but not ketone bodies, protect the diabetic heart by decreasing ATP depletion, with neither having detrimental effects on the normal rat heart during low-flow ischemia.

Animals↗
PubMed2001

Increased uncoupling proteins and decreased efficiency in palmitate-perfused hyperthyroid rat heart.

The physiological role of mitochondrial uncoupling proteins (UCPs) in heart and skeletal muscle is unknown, as is whether mitochondrial uncoupling of oxidative phosphorylation by fatty acids occurs in vivo. In this study, we found that UCP2 and UCP3 protein content, determined using Western blotting, was increased by 32 and 48%, respectively, in hyperthyroid rat heart mitochondria. Oligomycin-insensitive respiration rate, a measure of mitochondrial uncoupling, was increased in all mitochondria in the presence of palmitate: 36% in controls and 71 and 100% with 0.8 and 0.9 mM palmitate, respectively, in hyperthyroid rat heart mitochondria. In the isolated working heart, 0.4 mM palmitate significantly lowered cardiac output by 36% and cardiac efficiency by 38% in the hyperthyroid rat heart. Thus increased mitochondrial UCPs in the hyperthyroid rat heart were associated with increased uncoupling and decreased myocardial efficiency in the presence of palmitate. In conclusion, a physiological effect of UCPs on fatty acid oxidation has been found in heart at the mitochondrial and whole organ level.

Animals↗
PubMed2000

Magnetic resonance spectroscopy evidence of abnormal cardiac energetics in Xp21 muscular dystrophy.

OBJECTIVES: Our aim was to measure the cardiac phosphocreatine to adenosine triphosphate ratio (PCr/ATP) noninvasively in patients and carriers of Xp21 muscular dystrophy and to correlate the results with left ventricular (LV) function as measured by echocardiography. BACKGROUND: Duchenne and Becker muscular dystrophy (the Xp21 dystrophies) are associated with the absence or altered expression of dystrophin in cardiac and skeletal muscles. They are frequently complicated by cardiac hypertrophy and dilated cardiomyopathy. The main role of dystrophin is believed to be structural, but it may also be involved in signaling processes. Defects in energy metabolism have been found in skeletal muscle in patients with Xp21 muscular dystrophy. We therefore hypothesized that a defect in energy metabolism may be part of the mechanism leading to the cardiomyopathy of Xp21 muscular dystrophy. METHODS: Thirteen men with Becker muscular dystrophy, 10 female carriers and 23 control subjects were studied using phosphorus-31 magnetic resonance spectroscopy and echocardiography. RESULTS: The PCr/ATP was significantly reduced in patients (1.55+/-0.37) and carriers (1.37+/-0.25) as compared with control subjects (2.44+/-0.33; p<0.0001 for both groups). The PCr/ATP did not correlate with LV ejection fraction or mass index. CONCLUSIONS: Altered expression of dystrophin leads to a reduction in the PCr/ATP. Since this reduction did not correlate with indexes of left ventricular function, this raises the possibility of a direct link between altered dystrophin expression and the development of cardiomyopathy in such patients.

Adenosine Triphosphate↗
PubMed2000

Vision and touch through the looking glass in a case of crossmodal extinction.

When observing ourselves in a mirror, we see our body and adjacent objects (e.g. a comb or razor) projecting the image of distant objects. Are these recoded by the brain as reflecting stimuli in peripersonal space? To address this, we exploited the neuropsychological phenomenon of crossmodal, visual-tactile extinction, as shown by patient BV following right-hemisphere stroke. In such crossmodal extinction, a right visual event impairs the perception of a simultaneous left tactile event. In BV, the right visual stimulus (an LED flash) induced more extinction of touch on the contralesional left hand when presented near the ipsilesional right hand, than when distant from it. This agrees with previous data in patients and monkeys showing that visual-tactile interactions are strongest within peripersonal space. Crucially, we also found that an ipsilesional flash produced more extinction when observed as the distant mirror-reflection of an LED that lay close to the ipsilesional hand, rather than as a distant LED flash projecting an equivalent visual image directly. This suggests that in BV, seeing his own hand via a mirror activates a representation of peripersonal space around that hand, not of the extrapersonal space suggested by the distant visual image in the mirror. We discuss the possible neural basis of interpreting mirror reflections.

Aged↗
PubMed2000

In vivo biodistribution of a humanized anti-Lewis Y monoclonal antibody (hu3S193) in MCF-7 xenografted BALB/c nude mice.

The biodistribution characteristics of a humanized anti-Lewis(y) antibody (hu3S193) radiolabeled to three radioisotopes, 125I, 111In, and 90Y, were examined in a BALB/c nude mouse xenograft model of breast cancer. The immunoreactivity of both 125I- and 111In-bound hu3S193 exceeded 50% and was 20% for 90Y. In vivo, labeled antibody was shown by gamma camera imaging and immunohistochemical and autoradiographic techniques to localize to Lewis(y)-expressing breast xenografts with minimal normal tissue uptake. Maximal radioisotope uptake peaked at 48 h for all three isotopes; however, the percentage of injected dose/gram and tumor retention were greater for 111In- and 90Y-bound antibody than for 125I-bound antibody. Although immunoreactivity of 111In- and 125I-labeled hu3S193 in serum was stable over a 5-day period, the amount of unlabeled 111In in serum was lower than 125I, which together with higher tumor uptake indicates better retention of 111In-labeled hu3S193 and catabolites within the tumor cells. Superior tumor uptake and retention of 111In-labeled hu3S193 and similar blood clearance compared with 125I-labeled hu3S193, suggest that radiometals are the preferred radioisotope for this antibody-antigen system. Humanized 3S193 is a promising new construct for the targeting and potential therapy of Lewis(y)-expressing tumors.

Adenocarcinoma↗
PubMed2000

Construction, production, and characterization of humanized anti-Lewis Y monoclonal antibody 3S193 for targeted immunotherapy of solid tumors.

The Lewis Y (Ley) antigen is a blood group-related antigen that is expressed in a high proportion of epithelial cancers (including breast, colon, ovary, and lung cancer) and is an attractive target for monoclonal antibody-directed therapy. The murine monoclonal 3S193 (IgG3) was generated in BALB/c mice by immunization with Ley-expressing cells of the MCF-7 breast carcinoma cell-line. The murine 3S193 showed high specificity for Ley in ELISA tests with synthetic Ley and Ley-containing glycoproteins and glycolipids and also reacted strongly in rosetting assays and cytotoxic tests with Ley-expressing cells. We generated a humanized form of the murine 3S193 antibody by linking cDNA sequences encoding the variable region of murine 3S913 with frameworks of the human KOL heavy chain and REI K chain. The genes for the humanized 3S193 monoclonal antibody IgG1 were transfected into mouse myeloma NS0 cells and cloned for the establishment of high antibody-producing colonies. Humanized 3S193 antibody was subsequently produced through in vitro culture and under good manufacturing practice conditions using hollow-fiber bioreactors. The purified humanized 3S193 (hu3S193) was subsequently characterized and validated for use in preliminary immunotherapy investigations. hu3S193 reacted specifically with Ley antigen, with similar avidity to the murine form. hu3S193 demonstrated potent immune effector function, with higher antibody-dependent cell-mediated cytotoxicity than its murine counterpart and potent complement-dependent cytotoxicity (ED50, 1.0 microg/ml). The in vivo immunotherapeutic potential of hu3S193 was assessed in a human breast xenograft model using MCF-7, Ley-positive cells. Six i.v. doses of up to 1 mg of hu3S193 were administered to animals bearing established tumors (120-130 mm3) with no significant effect on tumor growth. In contrast, in an MCF-7 xenograft preventive model, a 1-mg hu3S193 dosage schedule was able to significantly slow tumor growth compared with placebo and isotype-matched control IgG1 antibody. hu3S193 has promise for immunotherapy of Ley-positive tumors and is currently entering Phase I clinical trials.

Amino Acid Sequence↗
PubMed2000

D-beta-hydroxybutyrate protects neurons in models of Alzheimer's and Parkinson's disease.

The heroin analogue 1-methyl-4-phenylpyridinium, MPP(+), both in vitro and in vivo, produces death of dopaminergic substantia nigral cells by inhibiting the mitochondrial NADH dehydrogenase multienzyme complex, producing a syndrome indistinguishable from Parkinson's disease. Similarly, a fragment of amyloid protein, Abeta(1-42), is lethal to hippocampal cells, producing recent memory deficits characteristic of Alzheimer's disease. Here we show that addition of 4 mM d-beta-hydroxybutyrate protected cultured mesencephalic neurons from MPP(+) toxicity and hippocampal neurons from Abeta(1-42) toxicity. Our previous work in heart showed that ketone bodies, normal metabolites, can correct defects in mitochondrial energy generation. The ability of ketone bodies to protect neurons in culture suggests that defects in mitochondrial energy generation contribute to the pathophysiology of both brain diseases. These findings further suggest that ketone bodies may play a therapeutic role in these most common forms of human neurodegeneration.

1-Methyl-4-phenylpyridinium↗
PubMed2000

Prognostic significance of immunohistochemical micrometastases in node negative gastric cancer patients.

BACKGROUND AND OBJECTIVES: The purpose of this study is to examine the prognostic significance of immunohistochemical (IHC) evidence of lymph node (LN) metastases in histologic node negative gastric cancer patients. METHODS: Retrospective review from 1981 to 1998 revealed 25 patients resected for T1-4N0M0 gastric and gastroesophageal (GE) junction adenocarcinoma. All cases were reviewed and histopathologic parameters were defined for each primary tumor. All LNs underwent IHC analysis with the epithelial marker CAM 5.2. Data are reported as median (range). RESULTS: The median number of LN resected was 7 (range 1-33). The median follow-up time was 25 months (range 4-195) with an overall 5-year survival rate of 55%. For patients with IHC evidence of LN micrometastasis (n = 9), the 5-year survival rate was significantly decreased (35%) compared to a 66% 5-year survival rate for IHC negative patients (n = 16, P = 0.05). CONCLUSIONS: The presence of IHC-detected LN micrometastases correlates with worse prognosis for patients with histologic node negative gastric cancer. IHC may be a useful additional staging modality in this subset of patients.

Adult↗
PubMed2000

Metabolite and water apparent diffusion coefficients in the isolated rat heart: effects of ischemia.

A decrease in the apparent diffusion coefficient (ADC) of water is important in the detection of acute brain disorders, yet it is unknown whether changes in myocardial ADCs hold similar potential. Consequently, in this study a STEAM pulse sequence was modified in order to measure the ADCs of water and the (1)H-NMR detectable metabolites, taurine (an inert marker) and creatine, during perfusion, ischemia, and reperfusion in the isolated rat heart. At the short diffusion time of 50 ms, myocardial ADCs were (1.06 +/- 0. 07) x 10(-3) mm(2)/s for water, (0.29 +/- 0.01) x 10(-3) mm(2)/s for taurine and (0.26 +/- 0.01) x 10(-3) mm(2)/s for creatine. Heart water and taurine ADCs remained constant during ischemia, yet the total creatine ADC increased by 35% owing to the hydrolysis of PCr to creatine. The average cardiomyocyte diameter, calculated from taurine ADC values measured at diffusion times between 50 ms and 1510 ms, was 40 microm in the perfused heart and 27 microm by the end of ischemia. It is concluded that the taurine ADC measured at short diffusion times does not reveal ischemic injury in the heart, but at long diffusion times may be used to calculate changes in myocyte diameter. Magn Reson Med 44:208-214, 2000.

Analysis of Variance↗
PubMed2000

Factors affecting the severity of motor vehicle traffic crashes involving elderly drivers in Ontario.

A population-based cross-sectional study was conducted to examine factors affecting the severity of motor vehicle traffic crashes (MVTCs) involving elderly drivers in Ontario. The study population included drivers aged 65 and over involved in injury-producing MVTCs between 1988 and 1993 on Ontario public roads. Information was obtained from the Canadian Traffic Accident Information Databank (TRAID) compiled from police reports. The severity of MVTC was classified as fatal, major, minor or minimal. Comparisons between fatal-, major-, minor- and minimal-injury crashes were conducted. Percentage distributions of crashes at each level of severity involving elderly drivers were examined according to specific factors and tested using the X2 test. Multivariate unconditional logistic regression was used to calculate the estimated relative risk as odds ratios (ORs) while controlling for confounding factors. A number of factors were significantly related to the increased risk of fatal-injury in crashes compared with a reference category for each variable. These included age (OR = 1.4 for 70-79 and OR = 2.3 for 80 + ), sex (OR = 1.4 for males), failing to yield right-of-way/disobeying traffic signs (OR = 1.7), non-use of seat belts (OR = 4.0), ejection from vehicle (OR = 11.3), intersection without traffic controls (OR = 1.7), roads with higher speed limits (OR = 7.9 for 70-90 km/h; OR= 5.8 for 100 km/h), snowy weather (OR= 1.6), head-on collisions (OR=55.1), two-vehicle turning collisions (OR = 3.1 for left-turn, OR = 8.7 for right-turn), overtaking (OR = 5.6), and changing lanes (OR = 2.1). Adverse medical/physical conditions increased the risk of fatality by a factor of 5 for drivers 75-79 years of age and a factor of 3.5 for those 80 years and over. However, in the age group 65-74, medical/physical condition did not appear to be related to risk of fatality. Similar but weaker associations between these factors and risk of major- and minor-injury in crashes were also observed. To reduce the severity of crashes involving elderly drivers, strategies could target specific factors such as head-on collisions, single-vehicle collisions, and traffic controls at intersections. Driver conditions such as medical/physical conditions and driver actions such as failing to yield right-of-way/disobeying traffic signs should be examined further.

Accidents, Traffic↗
PubMed2000

Unconscious activation of visual cortex in the damaged right hemisphere of a parietal patient with extinction.

Visual extinction is a sign classically associated with right parietal damage. The patient can see a single stimulus presented in the ipsilesional or contralesional visual field, but is characteristically unaware of the same contralesional stimulus during simultaneous stimulation of both fields. The ipsilesional stimulus is said to 'extinguish' the contralesional stimulus from awareness during bilateral stimulation, perhaps due to a pathological bias in attention towards the ipsilesional side. Recent psychophysical evidence suggests that, although extinguished stimuli are not consciously seen, they may undergo residual processing and exert implicit effects on performance. However, the neural structures mediating such residual processing for extinguished stimuli remain unknown. Here we studied the neural activity evoked by an extinguished visual stimulus, using event-related functional MRI (fMRI), in a patient with circumscribed right inferior parietal damage and profound left-sided extinction. Monochrome objects (faces or houses) were presented in the left or right field, either unilaterally or bilaterally on each trial, with the patient indicating by button press whether he saw an object on the left, the right or on both sides. He usually saw only the right object on bilateral trials, yet the fMRI data showed activation of visual cortex contralateral to the extinguished left stimulus on these trials (compared with right-only stimulation), in both striate and early extrastriate areas of the right hemisphere. This activity had a similar location and time-course to that resulting from a single stimulus in the left versus right visual field. Cortical pathways involved in the normal processing of a single seen stimulus can thus still be activated by an unseen, extinguished stimulus after right parietal damage. Comparison of fMRI responses for faces versus houses revealed some category-specific activation for extinguished stimuli in right fusiform regions, but only at low statistical threshold. These results are discussed in terms of theoretical accounts for parietal extinction and, more generally, for the neural substrates of visual awareness.

Aged↗
PubMed2000

Prolonged disease-free survival after autografting for chemosensitive non-bulky low grade non-Hodgkin's Lymphoma.

The results of autografting in patients with relapsed low grade non-Hodgkin's Lymphoma (NHL) have generally been disappointing due to the failure to maintain remission and the late development of myelodysplasia. Most series have used regimens that include total body irradiation and purged stem cells. We evaluated the outcome in 32 patients with low grade NHL autografted using chemotherapy-only busulfan-based conditioning and unpurged stem cells. Seven of 10 patients with poor prognostic features at diagnosis remain alive in CR a median of 78 months (range 14-129) post-transplant. Twenty two patients with relapsed, chemosensitive, low bulk disease, most of whom did not have marrow involvement or an elevated LDH, were transplanted. Only five of the 22 have relapsed, with an 86 +/- 8% overall survival and 72 +/- 10% event free survival (EFS) after a median follow-up of 56.5 months. All but one patient has an EFS period longer, often substantially so, than their previous longest remission. No patient has developed myelodysplasia. These data suggest that in selected patients with poor prognosis or relapsed low grade NHL autografting has a favourable impact on the natural history of their disease and may result in long-term disease control.

Actuarial Analysis↗