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Biomedical subjects

J M Thomas

Publications and source records attributed to J M Thomas.

At least 73 records · Page 4Linked to original sources

Indefinite allograft survival mediated by donor bone marrow is dependent on the presence of a functional CD95 (Fas) gene in recipients.

It is well documented that donor bone marrow in combination with peri-transplant anti-thymocyte globulin (ATG) administration induces transplantation tolerance in a variety of animal models. Our previous work showed that the ability of donor marrow to induce tolerance was dependent on the presence of CD95 ligand (Fas-ligand) on the donor cells. In this study we investigate whether CD95 (Fas) on the recipient cells is required. By comparing skin allograft survival times between wild-type C57BL/6 ATG-treated recipients and C57BL/6(lpr/lpr) ATG-treated recipients (which do not have a functional CD95 gene), we show that donor bone marrow could induce indefinite transplant survival (median survival time >200 days) only in recipients with a functional CD95 gene. Thus, we conclude that the CD95 ligand-CD95 apoptotic pathway plays a major role in donor bone marrow-induced transplantation tolerance.

Animals↗

The role of synchrotron-based studies in the elucidation and design of active sites in titanium-silica epoxidation catalysts.

X-ray absorption fine structure (XAFS) measurements unambiguously establish the structure of the active centers in high-performance Ti-SiO2 epoxidation catalysts. Subtleties in structural changes in proceeding from the dispersed titanocene dichloride precursor to the anchored Ti(IV) centers are charted, in situ, by both near-edge (XANES) and extended-edge (EXAFS) measurements. The active centers are tripodally attached titanol groups: (Si-O)3-TiOH. These permit facile expansion of the coordination shell (also monitored by in situ XAFS studies) during catalysis, and thereby lead to the formulation of a plausible mechanism of epoxidation of alkenes that is consonant with recent DFT computations. Previously proposed mechanisms, based on a three-coordinated titanyl group (as well as possible five- or six-coordinated active sites), are discounted. Comparable XAFS studies of soluble catalytically active four-coordinated Ti(IV)-containing molecular entities establish that the heterogeneous Ti-SiO2 catalyst has "single-site" active centers. Equipped with such information, minute changes in hydrophobicity and local composition (e.g., replacement of one Si by a Ge) can be wrought so as to boost the performance of the catalyst. The merits of using combined in situ X-ray absorption spectroscopic and X-ray diffractometric measurements are also highlighted.

Catalysis↗

Molecular sieve catalysts for the regioselective and shape- selective oxyfunctionalization of alkanes in air.

Framework-substituted, molecular-sieve, aluminophosphate, microporous solids are the centerpieces of a new approach to the aerobic oxyfunctionalization of saturated hydrocarbons. The sieves, and the few percent of the Al(III) sites within them that are replaced by catalytically active, transition-metal ions in high oxidation states (Co(III), Mn(III), Fe(III)), are designed so as to allow free access of oxygen in to and out of the interior of these high-area solids. Certain metal-substituted, molecular sieves permit only end-on approach of linear alkanes to the active centers, thereby favoring enhanced reactivity of the terminal methyl groups. By optimizing cage dimension, with respect to that of the hydrocarbon reactant, as well as adjusting the average separation of active centers within a cage, and by choosing the sieve with the appropriate pore aperture, highly selective conversions such as n-hexane to hexanoic acid or adipic acid, and cyclohexane to cyclohexanol, cyclohexanone, or adipic acid, may be effected at low temperature, heterogeneously in air.

Aerobiosis↗

Structural elucidation of microporous and mesoporous catalysts and molecular sieves by high-resolution electron microscopy.

Twenty years ago, one of us embarked (Bursill, L. A.; Lodge, E. A.; Thomas, J. M. Zeolitic structures as revealed by high-resolution electron microscopy. Nature 1980, 286, 111-113) on the study of zeolites (renowned for their electron-beam sensitivity) by high-resolution transmission electron microscopy (HRTEM). In the ensuing years, high-resolution imaging aided by optical diffractometry has yielded details of the open framework structures of a number of new aluminosilicate and aluminophosphate molecular sieves and catalysts. The nature of intergrowth and recurrently twinned structures, as well as new types of structural imperfection in hitherto uncharacterized materials, has also been elucidated. With continued improvements in instrumental development, encompassing higher accelerating voltages, better objective lenses and vacua, computational advances, and the arrival of slow-scan CCD detectors, electron crystallographic methods and HRTEM imaging now enable the ab initio three-dimensional structures of micro- and mesoporous solids, with their occluded structure-directing organic species, to be determined. High-resolution scanning transmission electron microscopy using subnanometric probes provides supplementary structural and ultramicro analytical information and electron spectroscopic imaging (at the attogram level). In its high-angle annular dark-field mode, it is capable of locating and determining the composition of individual nanoparticle catalysts (consisting of just a few atoms) supported on porous hosts.

Journal Article↗

STEALTH matters: a novel paradigm of durable primate allograft tolerance.

We review a novel strategy for tolerance induction developed in rhesus macaques and termed STEALTH. We summarize the evolution of the STEALTH model, the results of successful trials in inducing long-term, stable transplant tolerance in rhesus kidney and diabetic islet recipients and discuss information related to the mechanism by which durable tolerance is induced. STEALTH tolerance is induced by a 3-day treatment course of CD3epsilon immunotoxin (IT) combined with a 14-day treatment with deoxyspergualin (DSG). IT causes profound depletion of sessile lymph node T cells as well as the more accessible circulating T cells. DSG, an inhibitor of HSC 70-mediated NF-kappaB nuclear translocation, arrests maturation of myeloid dendritic cells, blocks production of proinflammatory cytokines induced by IT administration, and promotes systemic production of Th2 type cytokines that persist indefinitely. Such Th2 cytokine deviation has not been reported in NHP transplant recipients. These studies provide proof of principle in a preclinical model that prevention of both acute and chronic allograft rejection, for at least 2.2-4.9 years of follow-up, can be achieved in NHP in the absence of chronic immunosuppressive drugs or other interventions. This strategy for inducing NHP tolerance is discussed in relation to current tolerance paradigms.

Animals↗

Gene transfer of the Bcl-2 gene confers cytoprotection to isolated adult porcine pancreatic islets exposed to xenoreactive antibodies and complement.

BACKGROUND: Exposing adult porcine pancreatic islets (PI) to xenoreactive natural antibodies (XNA) induces brisk inflammatory injury that involves activation of the complement system. Gene transfer of Bcl-2 has been shown to protect PI from apoptosis and necrosis in several models. In this study, we investigated the effect of Bcl-2 gene transfer on protection of PI from primate XNA and complement-mediated injury. METHODS: The PI were isolated from adult female sows. Only islet preparations that exhibited >90% viability and purity were used. Fresh rhesus monkey serum served as the XNA source. Gene transfer of Bcl-2 was achieved with an adenoviral vector (AdBcl-2) at 500 particle forming units (pfu)/cell. The Bcl-2 expression was confirmed by Western blot technique. Untransfected and transfected PI were incubated in 50% fresh complete serum (CS) or heat-inactivated (HI) rhesus serum for 24 hours. The PI viability was analyzed with acridine orange and ethidium bromide staining. Antibody and complement-mediated cytotoxicity were tested by intracellular lactate dehydrogenase (LDH) release. The PI function was assessed in vitro by static incubation studies and in vivo after intraportal transplantation in diabetic severe combined immunodeficiency (SCID) mice. RESULTS: The AdBcl-2 gene transfer resulted in Bcl-2 gene expression in >90% of PI cells. Following exposure to XNA, <15% of the untransfected cells were viable. Similar results were obtained in PI transfected with a similar recombinant adenovirus encoding the reporter gene E coli beta-galactosidase (AdLacZ), an irrelevant gene. A significant increase in LDH release was observed in control PI after exposure to CS compared with PI that overexpressed Bcl-2 (82.89% +/- 7.78% vs 34.31% +/- 5.4%, P <.005). Higher insulin release was observed in vitro in PI transfected with Bcl-2 compared with untransfected PI or islets transfected with AdLacZ (stimulation index of 0.9 +/- 0.31, 0.9 +/- 0.3 vs 2.67 +/- 0.4, respectively). Only PI treated with AdBcl-2 were able to achieve euglycemia after exposure to XNA and complement after transplantation. CONCLUSIONS: Transfer of the antiapoptotic and antinecrotic Bcl-2 gene into PI can reduce primate XNA and complement-mediated lysis. Cytoprotection of PI with Bcl-2 has potential to improve survival of PI xenotransplants.

Adenoviridae↗

Induction of osteosarcoma and acute myeloid leukaemia in CBA/H mice by the alpha-emitting nuclides, uranium-233, plutonium-239 and amercium-241.

PURPOSE: To compare tumour induction in CBA/H mice, principally osteosarcoma and acute myeloid leukaemia, resulting from exposure to the alpha-emitting nuclides, uranium-233, plutonium-239 and americium-241, and to relate differences between the three nuclides to the pattern of dose delivery within tissues. MATERIALS AND METHODS: Each nuclide was administered intraperitoneally in citrate solution to three groups of adult male CBA/H mice at levels of activity which gave estimated life-time average skeletal doses of about 0.25-0.3 Gy, 0.5-1 Gy and 1-2 Gy. Animals were carefully monitored and sacrificed as soon as they showed signs of ill health; tumours were identified by standard histopathological techniques. RESULTS: Statistical modelling by Cox regression showed that, considering all three nuclides together, there was a highly significant increase in risk of death from osteosarcoma or myeloid leukaemia with increasing dose rate. For osteosarcoma, the effect was significantly greater for 239Pu than 241Am, while separate analysis for 233U showed no significant increase with increasing dose rate. For example, the increase in relative risk of death from osteosarcoma for an increase in life-time average dose rate to bone of 1 mGyd(-1) was 4.2 (2.7-6.5) for 239Pu, 2.3 (1.4-3.4) for 241Am and 1.1 (0.4-3.1) for 233U. For myeloid leukaemia, there was no significant difference between 239Pu and 241Am in the effect of dose rate. The increase in relative risk from myeloid leukaemia for an increase in average dose rate of 1 mGyd(-1) was 1.8 (1.1-2.8) for 239Pu, 2.0 (1.4-2.9) for 241Am and 1.5 (0.8-2.7) for 233U. Significant increases in renal and hepatic carcinomas were also recorded in animals exposed to 233U and 241Am, respectively. Studies of the distribution of the nuclides within the skeleton, published separately, have shown differences in their retention in individual bones and within bone. The proportions of decays occurring near to endosteal bone surfaces and throughout bone marrow were in the order: 239Pu> 241Am>233U. CONCLUSIONS: For osteosarcoma, the relative effectiveness of the nuclides in terms of average bone dose, in the order 239Pu>241Am>233U, is consistent with the proportion of dose delivered near to endosteal surfaces. For myeloid leukaemia, the greater effectiveness of 239Pu and 241Am than 233U is consistent with their accumulation in marrow.

Americium↗

Disruptive behavior in young children: what does it mean?

OBJECTIVE: To examine how the Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood (DC 0-3) primary diagnoses, Parent-Infant Relationship Global Assessment Scale, and Child Behavior Checklist/2-3 (CBCL/2-3) externalizing and internalizing symptoms augment the DSM-III-R/IV and guide treatment. METHOD: 82 children aged 18 to 47 months, who presented with disruptive behavior to an early childhood psychiatry clinic, were diagnosed using DSM-III-R/IV, DC 0-3, and the CBCL/2-3. RESULTS: Children with DSM-III-R/IV disruptive disorders or attention-deficit/hyperactivity disorder were diagnosed with DC 0-3 regulatory disorders, disorders of affect, and traumatic stress disorder. Clinically significant externalizing and internalizing symptoms co-presented in 45.1% of the children. Of children with disorders of affect, 41.2% had relationships categorized as disordered, contrasting with 21.1% of those with traumatic stress disorder and 10.3% of those with regulatory disorders. Increasingly disordered relationships were significantly correlated with externalizing and internalizing symptoms, and children with disordered relationships were 3.6 times more likely to have clinically significant levels of internalizing symptoms. CONCLUSION: In these children with disruptive behaviors, co-presentation of externalizing and internalizing symptoms is most common. Those with increased relational risk had more externalizing and internalizing symptoms and more disorders of affect.

Affective Symptoms↗

Optimising testing for phospholipid antibodies.

AIM: To compare anticardiolipin (ACL) and anti-beta2 glycoprotein 1 (beta2gp1) enzyme linked immunosorbent assays (ELISAs) in the diagnosis of antiphospholipid syndrome (APS) and to incorporate these results into a meta-analysis of published data. METHOD: Three representative commercial ACL ELISAs and an in house beta2gp1 assay were optimised and then assessed on 124 sera from normal donors, patients with infection, or patients with APS. A Medline search was screened for papers meeting defined criteria to conduct a meta-analysis. The performance of the assays used in this study was included. RESULTS: A non-quantitative ACL assay performed at least as well as the anti-beta2gp1 assay in the diagnosis of APS. Meta-analysis confirmed that neither assay is perfect, although the anti-beta2gp1 assay had a higher specificity and lower sensitivity than the ACL assay. CONCLUSIONS: The pooled data suggest that the ACL assay is used to investigate thrombosis without overt underlying pathology and that the improved specificity of the anti-beta2gp1 assay is exploited where infection, connective tissue disease, or atheroma are present.

Antibodies, Anticardiolipin↗

Successful reversal of streptozotocin-induced diabetes with stable allogeneic islet function in a preclinical model of type 1 diabetes.

The recent focus on islet transplantation as primary therapy for type 1 diabetes has heightened interest in the reversal of type 1 diabetes in preclinical models using minimal immunosuppression. Here, we demonstrated in a preclinical rhesus model a consistent reversal of all measured glycemic patterns of streptozotocin-induced type 1 diabetes. The model used single-donor islet transplantation with induction of operational tolerance. The term "operational tolerance" is used to indicate durable survival of single-donor major histocompatibility complex (MHC)-mismatched islet allografts without maintenance immunosuppressive therapy and without rejection or loss of functional islet mass or insulin secretory reserve. In this operational tolerance model, all immunosuppression was discontinued after day 14 posttransplant, and recipients recovered with excellent health. The operational tolerance induction protocol combined peritransplant anti-CD3 immunotoxin to deplete T-cells and 15-deoxyspergualin to arrest proinflammatory cytokine production and maturation of dendritic cells. T-cell deficiency was specific but temporary, in that T-cell-dependent responses in long-term survivors recovered to normal, and there was no evidence of increased susceptibility to infection. Anti-donor mixed lymphocyte reaction responses were positive in the long-term survivors, but all showed clear evidence of systemic T-helper 2 deviation, suggesting that an immunoregulatory rather than a deletional process underlies this operational tolerance model. This study provides the first evidence that operational tolerance can protect MHC nonhuman primate islets from rejection as well as loss of functional islet mass. Such an approach has potential to optimize individual recipient recovery from diabetes as well as permitting more widespread islet transplantation with the limited supply of donor islets.

Animals↗

Distinct pharmacology of 2-hydroxycarbazole-induced Ca2+ release in the sea urchin egg.

2-hydroxycarbazole, a compound structurally related to the Ca2+-mobilizing marine toxin 9-methyl-7-bromoeudistomin, has recently been proposed to activate both type 1 and type 2 ryanodine receptors in skeletal and cardiac muscle, respectively. This study was undertaken to evaluate the activity of this compound in the sea urchin egg homogenate, a model system used to characterize intracellular Ca2+ mobilization mechanisms. 2-Hydroxycarbazole was found to potently release Ca2+ in a concentration-dependent manner via a specific mechanism displaying apparent desensitization. Use of selective inhibitors of the Ca2+-mobilizing messengers inositol 1,4,5-trisphosphate, cyclic adenosine diphosphate ribose, and nicotinic acid adenine dinucleotide phosphate, as well as desensitization of homogenates to each of these molecules, failed to inhibit the response to 2-hydroxycarbazole. However, the response to 2-hydroxycarbazole was competitively antagonized by caffeine. Investigation of the Ca2+ stores accessed by 2-hydroxycarbazole revealed Ca2+ release from a thapsigargin-insensitive pool. Finally, 2-hydroxycarbazole failed to enhance [3H]ryanodine binding, suggesting the operation of a nonryanodine receptor mechanism. These results demonstrate that 2-hydroxycarbazole is acting to modulate a Ca2+ release mechanism with distinct pharmacological properties to those previously reported in the sea urchin egg.

Adenosine Diphosphate↗

[Geriatric problems seen in general practice in patients in nursing homes].

The general practitioner meets in long stay geriatrics polypathologic and frail patients. He is confronted with many problems: Staphylococcus aureus resistant to the methylpenicilline, ulcers of pressure, pain, depression, dementia, falls, etc. He will remain vigilant with ill-treat and the disorders of the nutrition. The communication will be improved by the use of validated scales. The nomination of a doctor coordinator will have to help to promote global geriatric assessment. The demography will involve the number of old patients. Sufficient financial means will have to be released in order to allow everyone to receive care of quality.

Activities of Daily Living↗

Adp-ribosyl cyclase and cyclic ADP-ribose hydrolase act as a redox sensor. a primary role for cyclic ADP-ribose in hypoxic pulmonary vasoconstriction.

Hypoxic pulmonary vasoconstriction is unique to pulmonary arteries and serves to match lung perfusion to ventilation. However, in disease states this process can promote hypoxic pulmonary hypertension. Hypoxic pulmonary vasoconstriction is associated with increased NADH levels in pulmonary artery smooth muscle and with intracellular Ca(2+) release from ryanodine-sensitive stores. Because cyclic ADP-ribose (cADPR) regulates ryanodine receptors and is synthesized from beta-NAD(+), we investigated the regulation by beta-NADH of cADPR synthesis and metabolism and the role of cADPR in hypoxic pulmonary vasoconstriction. Significantly higher rates of cADPR synthesis occurred in smooth muscle homogenates of pulmonary arteries, compared with homogenates of systemic arteries. When the beta-NAD(+):beta-NADH ratio was reduced, the net amount of cADPR accumulated increased. This was due, at least in part, to the inhibition of cADPR hydrolase by beta-NADH. Furthermore, hypoxia induced a 10-fold increase in cADPR levels in pulmonary artery smooth muscle, and a membrane-permeant cADPR antagonist, 8-bromo-cADPR, abolished hypoxic pulmonary vasoconstriction in pulmonary artery rings. We propose that the cellular redox state may be coupled via an increase in beta-NADH levels to enhanced cADPR synthesis, activation of ryanodine receptors, and sarcoplasmic reticulum Ca(2+) release. This redox-sensing pathway may offer new therapeutic targets for hypoxic pulmonary hypertension.

ADP-ribosyl Cyclase↗

Synovial sarcoma: a clinicopathologic, staging, and prognostic assessment.

PURPOSE: Synovial sarcoma (SS) is a common soft tissue sarcoma (STS) with a propensity for young adults and notable sensitivity to chemotherapy (CT). This study provides a current clinicopathologic, staging, and prognostic assessment for SS. The problems with the current American Joint Committee for Cancer (AJCC) Staging System in relation to SS are discussed. METHODS: Review of a prospective database supplemented by retrospective data. RESULTS: One hundred fifty patients were assessed; median age was 30 years and median follow-up was 52 months. Overall actuarial 5-year survival rate was 57%. Size trend, but not a cutoff of less than 5 cm versus > or = 5 cm, was a prognostic indicator (P <.001). The current AJCC/International Union Against Cancer Staging System differentiated prognosis less well than the recently proposed Royal Marsden Hospital Staging System. Age greater than 20 years at diagnosis implied worse prognosis. A local recurrence event was associated with a worse survival (P <.001). Therapeutic CT was administered to 55 patients. Eleven of 19 patients had an objective response to a combination of ifosfamide and doxorubicin. Four cases had complete response after CT. Twenty-one patients had pulmonary metastasectomy, with an actuarial 5-year survival rate of 23%. CONCLUSION: SS tends to affect young people. In this subtype of STS, size trend is the most significant influence on stage and hence survival; however, smaller SSs have an unexpectedly poor prognosis. Adequate local control may affect survival. SS is often chemosensitive, and given its poor prognosis, multicenter trials of adjuvant therapy are warranted.

Adolescent↗

A differential requirement for CD8+ donor cells in the augmentation of allograft survival by posttransplantation administration of donor spleen cells and donor bone marrow cells.

BACKGROUND: Peritransplant treatment with antithymocyte serum (ATS) and posttransplantation administration of donor bone marrow or donor splenocytes results in extended skin allograft survival. In this study, we examined the molecular basis of the tolerance promoting effect of donor bone marrow (BMC) cells and splenocytes with emphasis on the role of CD8 expression on the donor cells. METHODS: (C57BL/6J x A/J)F1 mice were treated on days -1 and +2 with ATS relative to transplantation with C3H/HeJ skin. On day +7, they were infused with CD8+ BMC, CD8- BMC, CD8+ splenocytes, or CD8- splenocyte donor subpopulations isolated by magnetic or fluorescence-based sorting. In additional experiments, B10.D2(R107) mice were treated in the same manner with C57BL/6 skin and BMC or splenocytes from C57BL/6 mice in which the CD8alpha gene had been inactivated. RESULTS: CD8+ donor bone marrow cells induced operational tolerance (defined as graft acceptance in the absence of chronic immunosuppression) in skin graft recipients at a dose that was reduced by 250-fold relative to unfractionated bone marrow cells (1.0x10(5) cells per recipient, median survival time (MST)=41 days vs. 2.5x10(7) cells per recipient, MST=49 days, P=0.40). Similarly, donor bone marrow cells from CD8 knockout mice did not promote graft acceptance (MST=98 days vs. animals not treated with bone marrow cells, MST=70 days, P=0.16). In contrast, the extension of graft survival by donor splenocytes did not require the presence of CD8+ donor cells because splenocytes depleted of CD8+ cells extended graft survival (MST=55 days) as well as unsorted splenocytes (44 days, P=0.2), and splenocytes from CD8 knockout animals (MST=145 days) extended graft survival at least as well as unsorted splenocytes (MST=74 days, P=0.4) CONCLUSIONS: These results suggest that the prolongation of graft survival by donor bone marrow is dependent on the presence of the CD8 molecule, whereas prolongation by donor splenocytes is not. Therefore, we suggest that the prolongation of graft survival by these cell types occurs via distinct molecular mechanisms probably mediated by different cell types.

Animals↗

A dielectric analysis of liquid and glassy solid glucose/water solutions.

Dielectric relaxation data covering a temperature range from above room temperature to below the glass transition for 40% (w/w) and 75% (w/w) glucose/water solutions in the frequency range between 5 and 13 MHz are presented. These data are used to obtain correlation times for the dielectric relaxation in the viscous liquid and the glass and are compared with correlation times determined from deuterium nuclear spin relaxation times [J. Chem. Phys., 110 (1999) 3472-3483]. The two sets of results have the same temperature dependence, but differ in magnitude by a factor of 3, implying that the relaxation is a small-step rotational diffusion. Both the structural relaxation (alpha process) and the slow beta process are present. In the 40% glucose/water sample, there is a dielectric relaxation attributable to the ice that forms at low temperature. It is shown that the reciprocal of the viscosity, the correlation time derived from the dielectric relaxation, and the dc conductivity have a similar dependence on temperature.

Electric Conductivity↗

Collagen, convulxin, and thrombin stimulate aggregation-independent tyrosine phosphorylation of CD31 in platelets. Evidence for the involvement of Src family kinases.

Platelet endothelial cell adhesion molecule-1 (CD31) is a 130-kDa glycoprotein receptor present on the surface of platelets, neutrophils, monocytes, certain T-lymphocytes, and vascular endothelial cells. CD31 is involved in adhesion and signal transduction and is implicated in the regulation of a number of cellular processes. These include transendothelial migration of leukocytes, integrin regulation, and T-cell function, although its function in platelets remains unclear. In this study, we demonstrate the ability of the platelet agonists collagen, convulxin, and thrombin to induce tyrosine phosphorylation of CD31. Furthermore, we show that this event is independent of platelet aggregation and secretion and is accompanied by an increase in surface expression of CD31. A kinase capable of phosphorylating CD31 was detected in CD31 immunoprecipitates, and its activity was increased following activation of platelets. CD31 tyrosine phosphorylation was reduced or abolished by the Src family kinase inhibitor PP2, suggesting a role for these enzymes. In accordance with this, each of the Src family members expressed in platelets, namely Fyn, Lyn, Src, Yes, and Hck, was shown to co-immunoprecipitate with CD31. The involvement of Src family kinases in this process was confirmed through the study of mouse platelets deficient in Fyn.

Animals↗