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Biomedical subjects

R N Smith

Publications and source records attributed to R N Smith.

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

Heme oxygenase-1, a protective gene that prevents the rejection of transplanted organs.

Endothelial cells (EC) play a pivotal role in regulating inflammatory reactions such as those involved in the rejection of transplanted organs. This occurs through the expression of a series of pro- and anti-inflammatory genes that are associated with the activation of these cells. Presumably, the expression of pro-inflammatory genes promotes events that lead to graft rejection, while expression of anti-inflammatory (protective) genes suppresses those events and thus contributes in sustaining graft survival. Understanding how the expression of these genes is regulated and their mechanism of action are important issues for the development of new therapeutic strategies to suppress graft rejection. We have studied this phenomenon using experimental models of transplantation in rats. We discuss here data that supports the concept that grafts can express anti-inflammatory (protective) genes that mitigate inflammatory reactions leading to graft rejection. The data reviewed focus on the role of one of such genes, the stress responsive gene heme oxygenase-1, and of its byproduct carbon monoxide, which can suppress graft rejection and lead to long-term graft survival.

Animals↗
PubMed2001

Oral findings in Carpenter syndrome.

Acrocephalopolysyndactyly Type II (Carpenter Syndrome) is determined by autosomal recessive inheritance. Only some 40 cases have been described. Variable clinical signs have been described including prolonged retention of primary teeth and hypodontia. This paper describes the oral and dental findings in a family containing two affected brothers. The family pedigree is informative, as the mother has had children by three partners. The two affected individuals are full brothers. The first affected brother has delayed dental development, severe hypodontia and small tooth crown size. Mesio-distal and bucco-lingual dimensions were measured on the study models and compared with population data. The younger brother also has delayed dental development but only mild hypodontia. Their half sister has severe hypodontia but no signs of Carpenter Syndrome. This family study demonstrates two affected individuals with typical clinical features and a pedigree compatible with autosomal recessive inheritance. Small tooth crown size has been shown by standardized measurement and evidence advanced that hypodontia is not part of the syndrome but a coincidental finding which segregates independently. We have also shown that the marked delay in emergence of teeth is associated more with problems of tooth eruption, possibly related to the bony abnormalities, than to a generalized delay in dental development.

Acrocephalosyndactylia↗
PubMed2001

A study of the effect of isothiazolones on the performance and characteristics of a laboratory-scale rotating biological contactor.

AIMS: To study the effect of the isothiazolone biocide (Kathon WT) on the performance of laboratory-scale rotating biological contactors (RBCs) and their component biofilms. METHODS AND RESULTS: Biofilms were established on the RBCs and then exposed to 0.7-15 p.p.m. isothiazolones. Young, 1-week-old, biofilms were found to attain treatment efficiency equal to that of mature, 2-month-old, biofilms. Isothiazolone concentrations at 3 p.p.m. and above caused a progressive decline in treatment efficiency and 15 p.p.m. isothiazolones inhibited all microbial activity and resulted in the death of the biofilms. Bio-oxidation and the biodegradation of isothiazolones within the biofilms ontinued unhindered at concentrations which caused the total inhibition of planktonic bacteria. CONCLUSION: There was at least a 10-fold difference in susceptibility of planktonic and biofilm bacteria to isothiazolones. The chemical oxygen demand (COD) test was shown to be a reliable tool for investigating the efficiency of wastewater treatment units when the influent contains isothiazolones, while the biochemical oxygen demand (BOD) was unreliable due to the inhibition of bio-oxidation by the biocide. SIGNIFICANCE AND IMPACT OF THE STUDY: The results show that RBCs can be used to treat effluents containing isothiazolones at concentrations up to 1.5 p.p.m.

Adenosine Triphosphate↗
PubMed2000

Identification and characterization of a novel hepatic canalicular ATP diphosphohydrolase.

We have identified and characterized a novel ATP diphosphohydrolase (ATPDase) with features of E-type ATPases from porcine liver. Immunoblotting with a specific monoclonal antibody to this ectoenzyme revealed high expression in liver with lesser amounts in kidney and duodenum. This ATPDase was localized by immunohistochemistry to the bile canalicular domain of hepatocytes and to the luminal side of the renal ductular epithelium. In contrast, ATPDase/cd39 was detected in vascular endothelium and smooth muscle in these organs. We purified the putative ATPDase from liver by immunoaffinity techniques and obtained a heavily glycosylated protein with a molecular mass estimated at 75 kDa. This enzyme hydrolyzed all tri- and diphosphonucleosides but not AMP or diadenosine polyphosphates. There was an absolute requirement for divalent cations (Ca(2+) > Mg(2+)). Biochemical activity was unaffected by sodium azide or other inhibitors of ATPases. Kinetic parameters derived from purified preparations of hepatic ATPDase indicated V(max) of 8.5 units/mg of protein with apparent K(m) of 100 microM for both ATP or ADP as substrates. NH(2)-terminal amino acid sequencing revealed near 50% identity with rat liver lysosomal (Ca(2+)-Mg(2+))-ATPase. The different biochemical properties and localization of the hepatic ATPDase suggest pathophysiological functions that are distinct from the vascular ATPDase/cd39.

Adenosine↗
PubMed2000

Spontaneous chronic colitis in TCR alpha-mutant mice; an experimental model of human ulcerative colitis.

Mice with targeted disruption of the T cell receptor alpha gene (TCR alpha-/-) spontaneously develop chronic colitis. Colonic inflammation begins at 6-8 weeks of age and chronic colitis is established in about 60% of mice by 16-20 weeks of age. The disease is also associated with autoantibodies (anti-tropomyosin antibodies, anti-neutrophil cytoplasmic antibodies) and an oligoclonal immune response to luminal bacterial antigens. Although T cells, but not B cells or autoantibodies, are essential for the development of colitis, B cells and/or autoantibodies may have a regulatory role in the pathogenesis of this colitis because the colitis is more severe in B cell deficient TCR alpha-/- mice. Cytokines, specifically IL-4 and IL-1, also play an important role in the development of colitis in TCR alpha-/- mice. Enteric bacteria located in the large intestine are an important factor in the pathogenesis of this colitis because germ-free TCR alpha-/- mice do not develop colitis and appendectomy at an early age delays the onset of this colitis. The colitis in TCR alpha-/- mice resembles human ulcerative colitis and provides a useful model to study the pathogenesis of human inflammatory bowel disease.

Animals↗
PubMed1999

Human CD4+ T cells mediate rejection of porcine xenografts.

It has previously been demonstrated that xenograft rejection in rodents is dependent on CD4+ T cells. However, because of the lack of an appropriate in vivo model, little is known about the cellular basis of human T cell-mediated rejection of xenografts. In this study, we have evaluated the ability of human T cells to mediate rejection of porcine skin grafts in a novel in vivo experimental system using immunodeficient mice as recipients. Recombinase-activating gene-1-deficient mice (R-) lacking mature B and T cells were grafted with porcine skin and received human lymphocytes stimulated in vitro with irradiated porcine PBMC. Skin grafts on mice given either unseparated, activated human lymphocytes, or NK cell-depleted lymphocyte populations were rejected within 18 days after adoptive cell transfer. In contrast, skin grafts on mice given T cell-depleted human lymphocytes or saline showed no gross or histologic evidence of rejection up to 100 days after adoptive transfer. Purified CD4+ T cells were also able to mediate rejection of porcine skin grafts. These data suggest that human CD4+ T cells are sufficient to induce rejection of porcine xenografts. Thus, strategies directed toward CD4+ T cells may effectively prevent cellular rejection of porcine xenografts in humans.

Animals↗
PubMed1999

Lessons for human inflammatory bowel disease from experimental models.

Experiments carried out in new rodent models of chronic intestinal inflammation provide important clues about the pathogenesis of human inflammatory bowel disease (IBD). Genetic factors and enteric microflora are driving forces regulating mucosal immune responses, some of which are pathogenic and lead to colitis. CD4(+) T cells are the major pathogenic cells in colitis, and the type of injury depends on the nature of the cytokine imbalance. The cytokine network controlled by CD4(+) T cells dictates the outcome of the mucosal immune responses. Certain cytokines, such as transforming growth factor-beta and interleukin-10, have a suppressive role, and immunoregulatory T cells capable of secreting these cytokines may be induced at intestinal mucosal sites. Lessons learned from these experimental models are leading to new strategies for the treatment of IBD.

Journal Article↗
PubMed1999

Colitis in transgenic and knockout animals as models of human inflammatory bowel disease.

Spontaneous colitis in knockout (KO) and transgenic rodents provides experimental models to study the development of mucosal inflammation and inflammatory bowel disease (Crohn's disease and ulcerative colitis). Genetic and environmental factors, particularly the normal enteric flora, are important factors in the development of mucosal inflammation. The normal mucosal homeostasis is disrupted when there is either cytokine imbalance, abrogation of oral tolerance, alteration of epithelial barrier and function or loss of immunoregulatory cells. Some but not all immunodeficiencies, in the appropriate setting, lead to colitis. CD4+ T cells have been identified as the pathogenic T cells in colitis, which mediate inflammation by either the Th1 or the Th2 pathway. The Th1 pathway dominates most colitis models and in Crohn's disease. In contrast, the colitis in TCR alpha KO mice shares many features of ulcerative colitis including the dominance of Th2 pathway in colonic inflammation. A major benefit of these models is in the development of therapeutic strategies for the treatment of inflammatory bowel disease.

Animals↗
PubMed1999

A critical role for human CD4+ T-cells in rejection of porcine islet cell xenografts.

T-cell-mediated rejection is likely to present a significant barrier to porcine islet xenotransplantation. Little is known, however, about human anti-porcine islet rejection because no suitable model exists to study this process. To address this problem, we have developed an immunodeficient mouse model to study rejection of fetal porcine islet cell clusters (ICCs) by human lymphocytes. Transplantation of porcine ICCs into hyperglycemic recombinase activating gene-deficient (R-) mice restores normal blood glucose levels within 5 weeks. Adoptive transfer of in vitro-stimulated human peripheral blood mononuclear cells into R- mice before islet cell transplantation leads to acute cellular rejection of porcine ICCs. The first human cells observed to infiltrate rejecting grafts are CD4+ T-cells. Although CD8+ T-cells are observed within the grafts at later time points, CD4+ T-cells predominate until the graft is destroyed. Adoptive transfer of purified human CD4+ T-cells before ICC transplantation is sufficient to cause acute cellular rejection. These data demonstrate that human CD4+ T-cells play a critical role in porcine ICC xenograft rejection.

Adoptive Transfer↗
PubMed1999

Modulation of nucleoside [correction of nucleotide] triphosphate diphosphohydrolase-1 (NTPDase-1)cd39 in xenograft rejection.

BACKGROUND: There is increasing evidence showing that extracellular nucleosides [corrected] may be important mediators of vascular inflammation. Nucleoside [corrected] triphosphate diphosphohydrolase-1 (NTPDase-1, identical to CD39), the major vascular endothelial ectonucleotidase, is responsible for the hydrolysis of both extracellular ATP and ADP in the blood plasma to AMP. Studies were therefore conducted to evaluate the role of vascular NTPDase-1/cd39 in modulating platelet activation and vascular injury in cardiac xenografts. MATERIALS AND METHODS: Cardiac xenografts from both wild-type and cd39 knockout mice (C57BL/6 x 129 Svj) were transplanted into Lewis rats. Alterations in cd39 mRNA transcripts and NTPDase activity expression were evaluated in wild-type grafts in untreated rats and then following complement depletion and immunosuppression. Rejection responses were studied with both mutant and wild-type grafts in the following models: presensitization with or without complement depletion, complement depletion alone, and with chronic immunosuppression to induce long-term graft survival. RESULTS: NTPDase biochemical activity in wild-type xenografts rapidly decreased after transplantation but soon rebounded with graft survival. Elevated levels of cd39 mRNA with associated increases in NTPDase activity were observed in all long-term surviving wild-type grafts. Hyperacute xenograft rejection times were comparable in wild-type and mutant grafts but cd39-deficient grafts were subject to more rapid rejection and exhibited pronounced vascular injury in complement-depleted, presensitized rats. The cd39-deficient grafts in immunosuppressed recipients were subject to increased intravascular platelet sequestration and fibrin deposition; this resulted in focal myocardial infarction in long-term surviving mutant xenografts. CONCLUSIONS: Augmentation of NTPDase-1 activity may be an important adaptive response for graft survival. Our results suggest that NTPDase-1/cd39 influences pathways of vascular injury in cardiac xenografts.

Adenosine Triphosphatases↗
PubMed1998

Determination of lingual myoarchitecture in whole tissue by NMR imaging of anisotropic water diffusion.

The muscular anatomy of the tongue consists of a complex three-dimensional array of fibers, which together produce the variations of shape and position necessary for deglutition. To define the myoarchitecture of the intact mammalian tongue, we have utilized NMR techniques to assess the location and orientation of muscle fiber bundles through measurement of the direction-specific diffusional properties of water molecules. Whole sheep tongues were excised and imaged with a slice-selective stimulated-echo diffusion sequence in the midline sagittal plane, and three-dimensional diffusion tensors were determined for each voxel. The derived diffusion tensors were depicted graphically as octahedra whose long axes indicate local muscle fiber orientation. Two distinct groups of midline fibers were identified: 1) in-plane sagittal fibers originating in the posteroinferior region of the tongue, radiating with a fanlike projection anteriorly and superiorly and merging with vertically oriented fibers, and 2) cross-plane (transverse) fibers, oriented at right angles to the vertically aligned fibers, predominantly in the anterior and superior regions of the tongue. Regional comparison of diffusion anisotropy revealed uniform and parallel alignment (high anisotropy) in the posteroinferior region of the tongue, corresponding to the base of the genioglossus, and less uniform, orthogonally aligned fibers (low anisotropy) in the anterosuperior region of the tongue, corresponding to the core intrinsic muscles. These data indicate that lingual myoarchitecture, determined through direction-dependent mobility of water molecules, can be depicted as discrete regions of muscle fibers, whose orientation and extent of diffusion anisotropy predict local contractility.

Animals↗
PubMed1997

Suppressive role of B cells in chronic colitis of T cell receptor alpha mutant mice.

The role of antibodies (Abs) in the development of chronic colitis in T cell receptor (TCR)-alpha-/- mice was explored by creating double mutant mice (TCR-alpha-/- x immunoglobulin (Ig)mu-/-), which lack B cells. TCR-alpha-/- x Ig mu-/- mice spontaneously developed colitis at an earlier age, and the colitis was more severe than in TCR-alpha-/- mice. Colitis was induced in recombination-activating gene-1 (RAG-1-/-) mice by the transfer of mesenteric lymph node (MLN) cells from TCR-alpha-/- x Ig mu-/- mice. When purified B cells from TCR-alpha-/- mice were mixed with MLN cells before cell transfer, colitis did not develop in RAG-1-/- mice. Administration of the purified Ig from TCR-alpha-/- mice and a mixture of monoclonal autoAbs reactive with colonic epithelial cells led to attenuation of colitis in TCR-alpha-/- x Ig mu-/- mice. Apoptotic cells were increased in the colon, MLN, and spleen of TCR-alpha-/- x Ig mu-/- mice as compared to Ig mu-/- mice and TCR-alpha-/- mice. Administration of the purified Ig from TCR-alpha-/- mice into TCR-alpha-/- x Ig mu-/- mice led to decrease in the number of apoptotic cells. These findings suggest that although B cells are not required for the initiation of colitis, B cells and Igs (autoAbs) can suppress colitis, presumably by affecting the clearance of apoptotic cells.

Adoptive Transfer↗
PubMed1997

Early voiding difficulty after colposuspension.

OBJECTIVE: To determine the incidence of post-operative voiding dysfunction (POVD) after colposuspension and to identify pre-operative risk factors. PATIENTS AND METHODS: A retrospective study of 100 women having colposuspension to determine the preoperative clinical assessment (history, physical examination, symptom-specific questionnaire and visual analogue score assessment of urological symptoms), pre-operative urodynamic investigations (uroflowmetry, twin-channel subtracted cystometry and video-cystourethrography), information on post-operative catheter management and the presence and management of any POVD. RESULTS: Twenty-one women experienced significant POVD attributable to their colposuspension. This resolved within 6 months in 19, but persisted beyond 6 months in two. Women experiencing POVD were significantly older and were more likely to have previously undergone a hysterectomy. The risk of POVD was 12% for those aged < 50 years, 25% at age 50-64, and 50% for those over 65 years. The duration of post-operative catheterization was related to the presence of symptoms of voiding difficulty. CONCLUSIONS: The risk of POVD after colposuspension increases with age. In women over 65 years old, consideration should be given to an elective temporary discharge home with a suprapubic catheter in situ for 7-10 days before initiating a catheter-clamping regimen.

Adult↗
PubMed1997

Protective immunity against Clostridium difficile toxin A induced by oral immunization with a live, attenuated Vibrio cholerae vector strain.

Clostridium difficile causes pseudomembranous colitis through the action of Rho-modifying proteins, toxins A and B. Antibodies directed against C. difficile toxin A prevent or limit C. difficile-induced colitis. We engineered plasmid pETR14, containing the hlyB and hlyD genes of the Escherichia coli hemolysin operon, to express a fusion protein containing 720 amino acid residues from the nontoxic, receptor-binding, carboxy terminus of C. difficile toxin A and the secretion signal of E. coli hemolysin A. We introduced pETR14 into Vibrio cholerae and found that the toxin A-HlyA fusion protein was secreted by a number of V. cholerae strains and recognized by both monoclonal and polyclonal anti-C. difficile toxin A antibodies. We introduced pETR14 into an attenuated V. cholerae strain, O395-NT, and inoculated rabbits orally with this construct. Colonization studies disclosed that the V. cholerae vector containing pETR14 was recoverable from rabbit ilea up to 5 days after oral inoculation. Vaccination produced significant systemic anti-C. difficile toxin A immunoglobulin G and anti-V. cholerae vibriocidal antibody responses. Vaccination also produced significant protection against toxin A in an ileal loop challenge assay, as assessed by determination of both fluid secretion and histological changes. These results suggest that the hemolysin system of E. coli can be used successfully in V. cholerae vector strains to effect secretion of large heterologous antigens and that a V. cholerae vector strain secreting a nontoxic, immunogenic portion of C. difficile toxin A fused to the secretion signal of E. coli HlyA induces protective systemic and mucosal immunity against this toxin.

Administration, Oral↗
PubMed1995

Imaging myocardial fiber architecture in vivo with magnetic resonance.

Methods are presented to image the fiber architecture of the human myocardium in vitro and in vivo. NMR images are obtained of the diffusion anisotropy tensor, indicative of local myofiber orientation. Studies of cardiac necropsy specimens demonstrate classic features of ventricular myoarchitecture including the continuous endocardial to epicardial variation of fiber helix angles (angles to the ventricular circumferential direction) of approximately +1.3 to -1.3 radians. Cross-fiber anisotropy is also observed. In the beating heart, NMR diffusion data must be corrected for the effects of myocardial deformation during the cardiac cycle. This correction can be performed using an independent MRI method to map the strain-rate tensor field of the myocardium through time. Combining fiber orientation with local myocardial strain rate, local rates of myocardial fiber shortening may be computed.

Anisotropy↗
PubMed1995

A randomised comparison over 8 months of 100 micrograms and 200 micrograms twice weekly doses of transdermal oestradiol in the treatment of severe premenstrual syndrome.

OBJECTIVE: To determine the efficacy of a 100 micrograms twice weekly dose of Estraderm TTS compared with a 200 micrograms dose in the treatment of severe PMS, and to determine the overall acceptability of the treatment. To determine the serum oestradiol levels produced by the two doses of Estraderm and to discover whether the lower dose suppresses ovulation. DESIGN: Main: randomised, prospective, comparative study. Subsidiary: cross-sectional and prospective. SETTING: Premenstrual syndrome clinic in teaching hospital. SUBJECTS: Women with severe PMS confirmed by prospective daily symptom recording. INTERVENTIONS: Estraderm TTS at a dose of either 100 or 200 micrograms twice weekly continuously with either dydrogesterone 10 mg or medroxyprogesterone acetate 5 mg, from day 17 to day 26 of each cycle. MAIN OUTCOME MEASURES: Main: change in total, exponentially smoothed, average maximum score (total-ESAmax) of 10 common premenstrual syndrome symptoms derived from Trigg's trend analysis and patient satisfaction. Subsidiary: plasma oestradiol and day 21 progesterone levels. RESULTS: Main: no difference in change in total-ESAmax between Estraderm 100 micrograms and 200 micrograms groups. Greater drop-out rate and greater incidence of side effects attributed to oestrogen in higher dosage group. Satisfaction rate of 45% to 57% at eight months. Subsidiary: 1. Mean (95% CI) oestradiol level of 300 pmol/l (255 to 345) with Estraderm 100 micrograms and 573 (494 to 693) with Estraderm 200 micrograms; 2. Estraderm 100 micrograms suppresses mid-luteal progesterone from a mean (95% CI) of 35.5 (28.4 to 42.7) to 3.4 (2.4 to 4.5). CONCLUSIONS: Estraderm TTS 100 micrograms twice weekly is as effective as 200 micrograms twice weekly in reducing symptom levels in severe premenstrual syndrome but is better tolerated. Estraderm 100 micrograms suppresses ovulation and results in a mean plasma oestradiol level similar to that observed in a spontaneous cycle.

Administration, Cutaneous↗