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Biomedical subjects

S Till

Publications and source records attributed to S Till.

At least 19 recordsLinked to original sources
PubMed2002

Calcium-activated potassium channel SK1- and IK1-like immunoreactivity in injured human sensory neurones and its regulation by neurotrophic factors.

Calcium-activated potassium ion channels SK and IK (small and intermediate conductance, respectively) may be important in the pathophysiology of pain following nerve injury, as SK channels are known to impose a period of reduced excitability after each action potential by afterhyperpolarization. We studied the presence and changes of human SK1 (hSK1)- and hIK1-like immunoreactivity in control and injured human dorsal root ganglia (DRG) and peripheral nerves and their regulation by key neurotrophic factors in cultured rat sensory neurones. Using specific antibodies, hSK-1 and hIK-1-like immunoreactivity was detected in a majority of large and small/medium-sized cell bodies of human DRG. hSK1 immunoreactivity was decreased significantly in cell bodies of avulsed human DRG (n = 8, surgery delay 8 h to 12 months). There was a decrease in hIK1-like immunoreactivity predominantly in large cells acutely (<3 weeks after injury), but also in small/medium cells of chronic cases. Twenty-three injured peripheral nerves were studied (surgery delay 8 h to 12 months); in five of these, hIK1-like immunoreactivity was detected proximally but not distally to injury, whereas neurofilament staining confirmed the presence of nerve fibres in both regions. These five nerves, unlike the others, had all undergone Wallerian degeneration previously and the loss of hIK1-like immunoreactivity may therefore reflect reduced axonal transport of this ion channel across the injury site in regenerated fibres, as well as decreased expression in the cell body. In vitro studies of neonatal rat DRG neurones showed that nerve growth factor (NGF) significantly increased the percentage of hSK1-positive cells, whereas neurotrophin 3 (NT-3) and glial cell line-derived neurotrophic factor (GDNF) failed to show a significant effect. NT-3 stimulated hIK1 expression, while NGF and GDNF were ineffective. As expected, NGF increased expression of the voltage-gated sodium channel SNS1/PN3 in this system. Decreased retrograde transport of these neurotrophic factors in injured sensory neurones may thus reduce expression of these ion channels and increase excitability. Blockade of IK1-like and other potassium channels by aminopyridines (4-AP and 3,4-DAP) may also explain the paraesthesiae induced by these medications. Selective potassium channel openers are likely to represent novel therapies for pain following nerve injury.

Adult↗
PubMed2001

T cell phenotypes of the normal nasal mucosa: induction of Th2 cytokines and CCR3 expression by IL-4.

Mucosal environments such as that of the nose are points of first contact between the human organism and its environment. At these sites the immune system must be regulated to differentiate between and respond appropriately to pathogens and harmless contaminants. T cell-driven immune responses broadly fall into Th1- or Th2-type phenotypes, with increasing evidence that the recruitment of these T lymphocyte subsets is mediated by selective expression of specific chemokine receptors. We have investigated the immunology of the normal nasal mucosa. We show that nasal T cell lines from normal individuals, expanded by culture in IL-2, show reduced expression of the Th2-type cytokines IL-4 and IL-5 compared with lines derived from the blood of the same subjects. These T cells also show reduced expression of the Th2-selective chemokine receptor, CCR3, but similar levels of CCR4 compared with the blood-derived lines. This apparent suppression of Th2 cytokine and CCR3 expression by nasal T cells was reversed by addition of IL-4 to the culture medium. These data are consistent with the presence of a nasal mucosal microenvironment that suppresses Th2 responses and may represent a protective measure against atopic allergic disease in humans and a favoring of Th1 responses to infectious agents. In contrast, T cell expression of CCR1 was higher in the nose than in the blood regardless of the culture medium cytokine environment in keeping with a role for this receptor in tissue homing or lymphocyte activation.

Adult↗
PubMed2001

Increased sodium channel SNS/PN3 immunoreactivity in a causalgic finger.

The sodium channels SNS/PN3 and NaN/SNS2 are regulated by the neurotrophic factors-nerve growth factor (NGF) and glial-derived neurotrophic factor (GDNF), and may play an important role in the development of pain after nerve injury or inflammation. These key molecules have been studied in an amputated causalgic finger and control tissues by immunohistochemistry. There was a marked increase in the number and intensity of SNS/PN3-immunoreactive nerve terminals in the affected finger, while GDNF-immunoreactivity was not observed, in contrast to controls. No differences were observed for NGF, trk A, NT-3 or NaN/SNS2-immunoreactivity. While further studies are required, these findings suggest that accumulation of SNS/PN3 and/or loss of GDNF may contribute to pain in causalgia, and that selective blockers of SNS/PN3 and/or rhGDNF may provide effective novel treatments.

Aged↗
PubMed2001

The immunomodulatory drugs cyclosporin A, mycophenolate mofetil, and sirolimus (rapamycin) inhibit allergen-induced proliferation and IL-5 production by PBMCs from atopic asthmatic patients.

We have used an optimized, physiologically relevant in vitro assay system to show that in a concentration-dependent fashion the immunomodulatory drugs cyclosporin A, mycophenolate mofetil, and sirolimus (rapamycin), as well as the glucocorticoid dexamethasone, inhibit allergen-driven T-cell proliferation and IL-5 production in PBMCs from allergen-sensitized atopic asthmatic individuals at physiologic concentrations. This effect of cyclosporin A might at least partially account for its established clinical efficacy in sparing systemic glucocorticoid therapy while improving lung function in chronic, severe, glucocorticoid-dependent asthma. The data are also compatible with the hypothesis that the newer immunomodulatory drugs mycophenolate mofetil and sirolimus exert similar effects, perhaps with a more favorable benefit/risk ratio.

Asthma↗
PubMed2000

SIMKK, a mitogen-activated protein kinase (MAPK) kinase, is a specific activator of the salt stress-induced MAPK, SIMK.

In eukaryotes, mitogen-activated protein kinases (MAPKs) play key roles in the transmission of external signals, such as mitogens, hormones, and different stresses. MAPKs are activated by MAPK kinases through phosphorylation of MAPKs at both the threonine and tyrosine residues of the conserved TXY activation motif. In plants, several MAPKs are involved in signaling of hormones, stresses, cell cycle, and developmental cues. Recently, we showed that salt stress-induced MAPK (SIMK) is activated when alfalfa cells are exposed to hyperosmotic conditions. Here, we report the isolation and characterization of the alfalfa MAPK kinase SIMKK (SIMK kinase). SIMKK encodes an active protein kinase that interacts specifically with SIMK, but not with three other MAPKs, in the yeast two-hybrid system. Recombinant SIMKK specifically activates SIMK by phosphorylating both the threonine and tyrosine residues in the activation loop of SIMK. SIMKK contains a putative MAPK docking site at the N terminus that is conserved in mammalian MAPK kinases, transcription factors, and phosphatases. Removal of the MAPK docking site of SIMKK partially compromises but does not completely abolish interaction with SIMK, suggesting that other domains of SIMKK also are involved in MAPK binding. In transient expression assays, SIMKK specifically activates SIMK but not two other MAPKs. Moreover, SIMKK enhances the salt-induced activation of SIMK. These data suggest that the salt-induced activation of SIMK is mediated by the dual-specificity protein kinase SIMKK.

Amino Acid Sequence↗
PubMed1999

A MAP kinase is activated late in plant mitosis and becomes localized to the plane of cell division.

In eukaryotes, mitogen-activated protein kinases (MAPKs) are part of signaling modules that transmit diverse stimuli, such as mitogens, developmental cues, or various stresses. Here, we report a novel alfalfa MAPK, Medicago MAP kinase 3 (MMK3). Using an MMK3-specific antibody, we detected the MMK3 protein and its associated activity only in dividing cells. The MMK3 protein could be found during all stages of the cell cycle, but its protein kinase activity was transient in mitosis and correlated with the timing of phragmoplast formation. Depolymerization of microtubules by short treatments with the drug amiprophosmethyl during anaphase and telophase abolished MMK3 activity, indicating that intact microtubules are required for MMK3 activation. During anaphase, MMK3 was found to be concentrated in between the segregating chromosomes; later, it localized at the midplane of cell division in the phragmoplast. As the phragmoplast microtubules were redistributed from the center to the periphery during telophase, MMK3 still localized to the whole plane of division; thus, phragmoplast microtubules are not required to keep MMK3 at this location. Together, these data strongly support a role for MMK3 in the regulation of plant cytokinesis.

Amino Acid Sequence↗
PubMed1998

Increased expression of high affinity IgE (FcepsilonRI) receptor-alpha chain mRNA and protein-bearing eosinophils in human allergen-induced atopic asthma.

FcepsilonRI receptors play an important role in allergen-induced mediator release and antigen presentation by mast cells, basophils, and monocyte/macrophages in atopic disorders. The expression of FcepsilonRI by tissue eosinophils in atopic asthma after allergen challenge has not been established. For this reason we attempted to identify mRNA and protein product + FcepsilonRIalpha eosinophils in cytospins made from bronchoalveolar lavage (BAL) from atopic asthmatics (n = 9) and nonatopic normal subjects (n = 4) 24 h after segmental challenge with allergen or diluent. Messenger RNA for FcepsilonRIalpha was determined using in situ hybridization and FcepsilonRIalpha protein expression by immunocytochemistry using a mouse monoclonal antibody 22E7. Colocalization of FcepsilonRIalpha receptors to eosinophils was performed using chromotrope 2R. When compared with a control challenge, segmental challenge with Dermatophagoides pteronyssinus induced significant BAL eosinophilia (p = 0.007). The total number of BAL FcepsilonRIalpha mRNA and protein-positive cells also increased in asthmatics, median values 2 (0.7-7.2) and 11.5 (0.6-65.0) x 10(6) cells (p = 0.02) and 0 (0-0.3 x 10(6)) and 3.1 x 10(6) (0.45 - 162.5 x 10(6)) cells (p = 0.007), respectively, for mRNA and protein. Net increases in FcepsilonRIalpha+ cells correlated with the net increases in BAL eosinophils (r = 0.98, p = 0.0001 for mRNA and r = 0.72, p = 0.02 for protein). Colocalization studies with chromotrope 2R revealed that only 4% of FcepsilonRIalpha+ cells were eosinophils after control challenge and, in contrast, 85 to 95% of FcepsilonRIalpha+ cells were eosinophils after allergen. There were no differences in the numbers of FcepsilonRIalpha+ cells or eosinophils in normal control subjects. Our results demonstrated that local endobronchial allergen provocation in atopic asthmatics results in increased synthesis and expression of FcepsilonRIalpha predominantly on BAL eosinophils.

Adult↗
PubMed1997

IL-5 secretion by allergen-stimulated CD4+ T cells in primary culture: relationship to expression of allergic disease.

BACKGROUND: IL-5-producing allergen-specific T cells are thought to play a prominent role in the pathogenesis of allergic inflammation. We hypothesized that T cell allergen-driven IL-5 synthesis is elevated in patients with atopic disease as compared with that in atopic patients free of disease and nonatopic control subjects. OBJECTIVES: The purpose of this study was to compare IL-5 and interferon-gamma (IFN-gamma) secretion and proliferation by peripheral blood T cells from sensitized atopic patients with asthma, rhinitis, and no symptoms and from nonatopic control subjects in response to the allergen Dermatophagoides pteronyssinus (Der p) and the control recall antigen Mycobacterium tuberculosis purified protein derivative (PPD). METHODS: To measure allergen-induced IL-5 production and proliferation, we developed a short-term culture technique that required a single antigenic stimulation of freshly isolated peripheral blood mononuclear cells (PBMC). With this technique, we measured Der p- and PPD-induced IL-5 production and proliferation in PBMC from atopic patients with asthma who were allergic to Der p, atopic patients with rhinitis, atopic patients with no symptoms, and a group of nonatopic normal control subjects. In four experiments, CD4+ or CD8+ T cells were depleted from PBMC to confirm that IL-5 synthesis was T cell dependent. RESULTS: T cell IL-5 production, but not IFN-gamma production, in response to Der p was elevated in atopic patients with asthma and atopic patients with rhinitis compared with findings in atopic patients with no symptoms or nonatopic control subjects. IL-5 production was abrogated by depletion of CD4+, but not CD8+, T cells. In subjects with asthma, allergen-driven IL-5 production correlated with bronchial hyperreactivity. Allergen-induced proliferation was also higher in patients with asthma than in atopic subjects with no symptoms or nonatopic controls. T cell IL-5 and IFN-gamma production and proliferation in response to PPD were similar regardless of atopic status or disease. CONCLUSIONS: Elevated IL-5 production is a characteristic of allergen-specific peripheral blood CD4+ T cells from sensitized patients with atopic disease but not atopy per se.

Allergens↗
PubMed1997

IL-5 production by allergen-stimulated T cells following grass pollen immunotherapy for seasonal allergic rhinitis.

Grass pollen immunotherapy for the treatment of seasonal allergic rhinitis ('summer hayfever') results in improvement in symptoms, a reduction in the early and late phase responses to allergen provocation and decreased tissue eosinophilia. Immunotherapy may act by altering the pattern of cytokine production by allergen-specific T cells from a 'Th2-type' (IL-4 and IL-5) profile to a 'Th1-type' (interferon-gamma (IFN-gamma)) profile. We set out to determine whether clinical improvement following specific allergen immunotherapy is accompanied by reduced production of the pro-eosinophilic and archetypal 'Th2-type' cytokine, IL-5. Peripheral blood mononuclear cells (PBMC) were isolated from (i) 13 patients who had received 6 or 7 years' continuous conventional immunotherapy with timothy grass pollen (Phleum pratense); (ii) 14 patients who had received 3 or 4 years of conventional immunotherapy followed by 3 years of placebo treatment; (iii) 12 matched seasonal rhinitic patients who had never received immunotherapy; and (iv) 17 non-atopic normal controls. PBMC were stimulated with 20 microg/ml and 200 microg/ml P. pratense extract, or 10 microg/ml of Mycobacterium tuberculosis purified protein derivative (PPD), at 2 x 10(6) cells/ml and 5 x 10(6) cells/ml. IL-5 concentrations in culture supernatants collected after 6 days' culture were measured by ELISA. IL-5 production in response to stimulation with P. pratense extract was highly reproducible and was elevated in both of the immunotherapy treated groups and the untreated rhinitics relative to non-atopic controls (P<0.005 for each group relative to non-atopic controls, under each of the four conditions tested). However, no significant reduction was observed in IL-5 production when immunotherapy treated patients were compared with untreated rhinitic controls. Moreover, abrogation of the cutaneous late-phase responses to allergen following treatment was not associated with reduced IL-5 production by allergen-stimulated peripheral blood T cells. Reduced IL-5 production by peripheral blood T cells may not be necessary for immunotherapy to be effective. Local immunodulation of T cell responses may play a role in this form of treatment.

Adult↗
PubMed1997

IL-13 production by allergen-stimulated T cells is increased in allergic disease and associated with IL-5 but not IFN-gamma expression.

Interleukin-13 (IL-13) shares many, but not all, of the properties of the prototypic T-helper type 2 (Th2) cytokine IL-4, but its role in allergen-driven T-cell responses remains poorly defined. We hypothesized that allergen stimulation of peripheral blood T cells from patients with atopic disease compared with non-atopic controls results in elevated IL-13 synthesis in the context of a 'Th2-type' pattern. Freshly isolated peripheral blood mononuclear cells (PBMC) obtained from sensitized atopic patients with allergic disease, and non-atopic control subjects, were cultured with the allergens Phleum pratense (Timothy grass pollen) or Dermatophagoides pteronyssinus (house dust mite) and the non-allergenic recall antigen Mycobacterium tuberculosis purified protein derivative (PPD). Supernatant concentrations of IL-13, along with IL-5 and interferon-gamma (IFN-gamma) (Th2- and Th1-type cytokines, respectively) were determined by enzyme-linked immunosorbent assay (ELISA). Allergen-induced IL-13 and IL-5 production by T cells from patients with allergic disease was markedly elevated (P = 0.0075 and P = 0.0004, respectively) compared with non-atopic controls, whereas IFN-gamma production was not significantly different. In contrast to allergen, the prototypic Th1-type antigen M. tuberculosis PPD induced an excess of IFN-gamma over IL-13 and IL-5 production, and absolute concentrations of cytokines were not affected by the presence or absence of atopic disease. Addition of exogenous recombinant IFN-gamma or IL-12, cytokines known to inhibit Th2-type responses, significantly inhibited allergen-driven production of both IL-13 and IL-5, but not T-cell proliferation, whereas exogenous IL-4 did not significantly affect production of IL-13 or IL-5. We conclude that allergen-specific T cells from atopic subjects secrete elevated quantities of IL-13 compared with non-atopic controls, in the context of a Th2-type pattern of cytokine production.

Allergens↗
PubMed1995

Using a mixture model to predict the occurrence of diabetic retinopathy.

Diabetes mellitus is a common condition which has several serious complications associated with it. In this paper a mixture model, based on one previously used to predict the onset of AIDS, is used to predict the onset of one of these complications, diabetic retinopathy, the major cause of adult blindness in the U.K. This model differs from the previous AIDS model by introducing covariates into the model and using a wider choice of mixture distributions. The fit and distributional assumptions of the model are then discussed for this example. The model is fitted to the data by maximum likelihood. It is important that the training set contains balanced numbers of individuals with and without retinopathy.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Secretion of the eosinophil-active cytokines interleukin-5, granulocyte/macrophage colony-stimulating factor and interleukin-3 by bronchoalveolar lavage CD4+ and CD8+ T cell lines in atopic asthmatics, and atopic and non-atopic controls.

Specific eosinophil accumulation and activation within the asthmatic bronchial mucosa are thought to occur at least partly through the actions of cytokines, including interleukin (IL)-5, IL-3 and granulocyte/macrophage colony-stimulating factor (GM-CSF). Although mRNA encoding some of these cytokines has been demonstrated in bronchoalveolar lavage (BAL) fluid cells and bronchial biopsies from asthmatics, it has yet to be established whether these cells produce the translated products and whether expression is associated with CD4+ T helper or CD8+ cytotoxic T cells. We addressed this problem by raising polyclonal CD4+ and CD8+ T cell lines from the BAL fluid of six atopic asthmatics, five atopic non-asthmatics and seven non-atopic non-asthmatic controls. BAL fluid cells obtained at fiberoptic bronchoscopy were depleted of adherent cells, and then T lymphocytes expanded by stimulation with monoclonal anti-CD3 antibody and recombinant human IL-2. When lymphocytes had expanded to sufficient numbers, CD4+ and CD8+ cells were separated by positive selection with magnetic beads coated with anti-CD4 or anti-CD8 monoclonal antibodies and further expanded. Cytokine secretion by standardized cell numbers was measured by enzyme-linked immunosorbent assays. BAL CD4+ T cell lines from the asthmatics secreted significantly elevated quantities of both IL-5 and GM-CSF as compared with lines from the atopic and non-atopic controls (p = 0.023-0.003). In contrast, IL-3 secretion did not significantly differ between the groups. In some subjects, CD8+ T cell lines also secreted significant quantities of these cytokines and there was a trend for IL-5 secretion by these cells to be higher in asthmatics than non-atopic controls (p = 0.035). These data are consistent with the hypothesis that activated T lymphocytes from asthmatics, particularly of the CD4+ subset, are predisposed to release elevated quantities of cytokines relevant to the accumulation and activation of eosinophils.

Adult↗
PubMed1990

The effects of improved blood glucose on growth hormone and cortisol secretion in insulin-dependent diabetes mellitus.

Growth hormone and cortisol secretion were studied in 25 patients with insulin-dependent diabetes before (Study 1) and 2 weeks after improved glucoregulation (Study 2). Blood samples for serum growth hormone (GH) and blood glucose determination were collected at hourly intervals whilst blood samples for cortisol and C-peptide were collected every 6 h during the 24-h period in Study 1 and Study 2. Glycaemic control was significantly improved in Study 2 compared to that in Study 1 (8.5 vs 13.3 mmol/l; P less than 0.001). With improved control, growth hormone levels rose by 21% (5.7 vs 4.7 mU/l; P less than 0.05). Throughout both study periods growth hormone levels were higher in patients with no residual C-peptide secretion (10 CpN patients) compared with patients with residual beta-cell function (15 CpP patients) (7.1 vs 3.2 mU/l in Study 1; 8.9 vs 4.2 mU/l in Study 2; P less than 0.001). Characteristic shapes of the 24-h blood glucose profile curves during both study periods were significantly different between the CpN and CpP group. Plasma cortisol decreased in both groups with improved metabolic control (P less than 0.001) but the observed different diurnal pattern did not change. These results demonstrate the importance of residual endogenous insulin secretion in determining growth hormone secretion in insulin-dependent diabetes and have important implications for glycaemic control and risk of microvascular complications.

Adult↗
PubMed1990

Effects of improved blood glucose on insulin-induced hypoglycaemia, TRH, GnRH and exercise tests in insulin-dependent diabetes.

In order to evaluate effects of metabolic control on pituitary function in insulin-dependent diabetes exercise, hypoglycaemia (insulin tolerance test), thyrotrophin releasing hormone and gonadotrophin releasing hormone, tests were performed on 25 patients before (Study 1) and after 2 weeks of improved metabolic control (Study 2). Patients were sub-divided into C-peptide negative (CpN, 10 patients with no residual C-peptide secretion) and C-peptide positive (CpP, 15 patients with residual beta-cell function) groups for analysis of results. Exercise induced higher growth hormone responses in CpN patients independent of metabolic control (P less than 0.001). Thyrotrophin releasing hormone induced higher growth hormone responses in CpN patients; this response was threefold greater after improved control (P less than 0.005). Growth hormone and cortisol response to hypoglycaemia and thyroid stimulating hormone and prolactin secretion in response to thyrotrophin releasing hormone were unaffected by residual beta-cell function or metabolic control. Luteinizing hormone response to gonadotrophin releasing hormone in CpN patients was impaired and lower after improved control (P less than 0.002). The results indicate an association between residual pancreatic insulin secretory and hypothalamic/pituitary function, possibly reflecting central neurosecretion of insulin.

Blood Glucose↗
PubMed1990

Data management and expert systems for outpatient diabetes care--16 years experience with diabeta.

The continuing development and implementation of a computer-based diabetes register and management system are described. For 15 years the system has been used as a readily accessible source of clinical data, for letter generation, for prompting screening procedures and for clinical audit and research. Later developments include the incorporation of specialist "intelligence" for advising management of individual patients. This is intended for use by non-specialists to enable their greater participation in diabetes care. It is currently undergoing preliminary evaluation with a view to conducting clinical trials both in Hospital and in General Practice.

Data Collection↗
PubMed1984

Use of a biothesiometer to measure individual vibration thresholds and their variation in 519 non-diabetic subjects.

A series of 519 non-diabetic subjects had vibration thresholds at three points measured using a biothesiometer. Thresholds appeared to be log normally distributed and increased with age. Centile charts of this relation were derived from the data giving a range for normal thresholds. The biothesiometer provides a quick and reliable assessment of vibration thresholds, which when related to the centile charts gives an objective measure of the progress of diabetic peripheral neuropathy.

Adolescent↗
PubMedDate not supplied

Information technology and computer-based decision support in diabetic management.

This paper describes the application of computer-based techniques within an intelligent, knowledge-based framework to the management of diabetes. The objectives are to structure data collection and storage so that the relevant patient-specific data are collected and made accessible as needed, and to provide clinical decision support on either a day-by-day or longer timescale as appropriate; these objectives relating to both hospital clinic and general practice. For longer-term management, a prototype rule set (greater than 500 rules) has been developed (coded in Sigma PROLOG), validated and tested on patient data. The data collection programs (written in SCULPTOR) to feed the ruleset have been tested in the hospital clinic and compared with the resident data collection system for usability, and impact on the running of the clinic. Links between the data collection programs and the ruleset program have been written and tested. The computer system will also incorporate a module, combining knowledge-based advisory system and glucose/insulin model as patient simulator, that can be tested as a potential decision aid for adjusting insulin dosage on a daily basis.

Data Collection↗