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Biomedical subjects

K J Lindley

Publications and source records attributed to K J Lindley.

At least 37 records · Page 2Linked to original sources
PubMed2000

Sulfonylurea receptor 1 and Kir6.2 expression in the novel human insulin-secreting cell line NES2Y.

NES2Y is a proliferating human insulin-secreting cell line that we have derived from a patient with persistent hyperinsulinemic hypoglycemia of infancy. This disease is characterized by unregulated insulin release despite profound hypoglycemia. NES2Y cells, like beta-cells isolated from the patient of origin, lack functional ATP-sensitive potassium channels (KATP) and also carry a defect in the insulin gene-regulatory transcription factor PDX1. Here, we report that the NES2Y beta-cells that are transfected with the genes encoding the components of KATP channels in beta-cells, sulfonylurea receptor (SUR) 1 and Kir6.2, have operational KATP channels and show normal intracellular Ca2+ and secretory responses to glucose. However, these cells, designated NESK beta-cells, have impaired insulin gene transcription responses to glucose. NES2Y beta-cells that are transfected with either Kir6.2 or SUR1 alone do not express functional KATP channels and have impaired intracellular free Ca2+ concentration-signaling responses to depolarization-dependent beta-cell agonists. These findings document that in NES2Y beta-cells, coexpression of both subunits is critically required for fully operational KATP channels and KATP channel-dependent signaling events. This article further characterizes the properties of the novel human beta-cell line, NES2Y, and documents the usefulness of these cells in diabetes-related research.

ATP-Binding Cassette Transporters↗
PubMed1999

Engineering a glucose-responsive human insulin-secreting cell line from islets of Langerhans isolated from a patient with persistent hyperinsulinemic hypoglycemia of infancy.

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a neonatal disease characterized by dysregulation of insulin secretion accompanied by profound hypoglycemia. We have discovered that islet cells, isolated from the pancreas of a PHHI patient, proliferate in culture while maintaining a beta cell-like phenotype. The PHHI-derived cell line (NES2Y) exhibits insulin secretory characteristics typical of islet cells derived from these patients, i.e. they have no K(ATP) channel activity and as a consequence secrete insulin at constitutively high levels in the absence of glucose. In addition, they exhibit impaired expression of the homeodomain transcription factor PDX1, which is a key component of the signaling pathway linking nutrient metabolism to the regulation of insulin gene expression. To repair these defects NES2Y cells were triple-transfected with cDNAs encoding the two components of the K(ATP) channel (SUR1 and Kir6.2) and PDX1. One selected clonal cell line (NISK9) had normal K(ATP) channel activity, and as a result of changes in intracellular Ca(2+) homeostasis ([Ca(2+)](i)) secreted insulin within the physiological range of glucose concentrations. This approach to engineering PHHI-derived islet cells may be of use in gene therapy for PHHI and in cell engineering techniques for administering insulin for the treatment of diabetes mellitus.

ATP-Binding Cassette Transporters↗
PubMed1997

Therapy for persistent hyperinsulinemic hypoglycemia of infancy. Understanding the responsiveness of beta cells to diazoxide and somatostatin.

The neonatal disorder persistent hyperinsulinemic hypoglycemia of infancy (PHHI) arises as the result of mutations in the subunits that form the ATP-sensitive potassium (KATP) channel in pancreatic beta cells, leading to insulin hypersecretion. Diazoxide (a specific KATP channel agonist in normal beta cells) and somatostatin (octreotide) are the mainstay of medical treatment for the condition. To investigate the mechanism of action of these agents in PHHI beta cells that lack KATP currents, we applied patch clamp techniques to insulin-secreting cells isolated from seven patients with PHHI. Five patients showed favorable responses to medical therapy, and two were refractory. Our data reveal, in drug-responsive patients, that a novel ion channel is modulated by diazoxide and somatostatin, leading to termination of the spontaneous electrical events that underlie insulin hypersecretion. The drug-resistant patients, both of whom carried a mutation in one of the genes that encode KATP channel subunits, also lacked this novel K+ channel. There were no effects of diazoxide and somatostatin on beta cell function in vitro. These findings elucidate for the first time the mechanisms of action of diazoxide and somatostatin in infants with PHHI in whom KATP channels are absent, and provide a rationale for development of new therapeutic opportunities by K+ channel manipulation in PHHI treatment.

Blood Glucose↗
PubMed1997

Tetrahydrobiopterin regulates cyclic GMP-dependent electrogenic Cl- secretion in mouse ileum in vitro.

1. Basal electrogenic Cl- secretion, measured as the short-circuit current (Isc), was variable in ileum removed from tetrahydrobiopterin (BH4)-deficient hph-1 mice and wild-type controls in vitro, although values were not significantly different. 2. The basal nitrite release and mucosal cyclic guanosine 3',5'-monophosphate (cyclic GMP) production were similar in control and BH4-deficient ileum. 3. Mucosally added Escherichia coli heat-stable toxin (STa, 55 ng ml-1) increased the nitrite release, cyclic GMP levels and the Isc in control ileum, but its secretory actions were reduced in BH4-deficient ileum. 4. L-Arginine (1 mM) increased the nitrite release, cyclic GMP production and the Isc in control ileum, but the actions were reduced in BH4-deficient ileum. 5. Serosal carbachol (1 mM) stimulated maximum short-circuit currents of similar magnitude in both control and BH4-deficient ileum, whilst nitrite release and cyclic GMP production were minimal. 6. E. coli STa and L-arginine increased electrogenic Cl- secretion across intact mouse ileum in vitro by releasing nitric oxide and elevating mucosal cyclic GMP. The inhibition of these processes in the hph-1 mouse ileum suggests that BH4 may be a target for the modulation of electrogenic transport, and highlight the complexity of the interactions between nitric oxide and cyclic GMP in the gut.

Animals↗
PubMed1997

Non-infective colitis in infancy: evidence in favour of minor immunodeficiency in its pathogenesis.

Forty two infants below the age of 2 years presenting with chronic non-infective diarrhoea and shown to have histologically proved colitis were investigated over a five year period. Allergic colitis was the most common cause of colitis, accounting for 62% of the cases. Other colitides diagnosed included: non-specific colitis, autoimmune enterocolitis, and ulcerative colitis accounting for 10% each; severe combined immunodeficiency 7%, and Crohn's disease 3%. A positive family history and a personal history of atopy were obtained in 48% and 29% of the cases respectively. Serum immunoglobulin A, IgG2, and IgG4 were very low in over 50% of the entire cohort of infants with colitis; 66% of those with severe combined immunodeficiency, autoimmune enterocolitis, and ulcerative colitis (n = 11) had low CD3 and CD4 T lymphocytes with an accompanying increase in CD8 in two thirds of those with severe combined immunodeficiency. T lymphocytes were normal in those with allergic colitis. Thus infants with proved non-infective colitis as a group show a high prevalence of IgA, IgG2, and IgG4 deficiency. It is likely that this minor deficiency of mucosa associated immunoglobulin production has a role in the pathogenesis of the colitic process.

Autoimmune Diseases↗
PubMed1997

Characterization of ion channels in stimulus-secretion coupling in pancreatic islets.

The regulation of insulin secretion from beta-cells of the pancreatic islets of Langerhans is a highly integrated process involving several plasma membrane ion channels. The key to our understanding of the normal process is the hypothesis that glucose-induced closure of K+ channels leads to a depolarization of the cell membrane potential and the opening of voltage-gated Ca2+ channels. Support for this is provided by direct electrophysiological recordings of ion channel activity, and by recent data that have revealed how gene defects in ion channel subunits leads to the loss of regulated insulin secretion. Here, we review the general features of stimulus-response coupling in beta-cells, and how novel initiatives are providing key insights into beta-cell pathogenesis.

Adenosine Triphosphate↗
PubMed1997

Non infective colitis in infancy: evidence in favour of minor immunodeficiency in its pathogenesis.

Forty two infants below the age of two years presenting with chronic non infective diarrhoea and shown to have histologically proven colitis were investigated over a five year period at this hospital. Allergic colitis was the most common cause of colitis accounting for sixty two percent of the cases. Other colitides diagnosed included: non specific colitis, autoimmune enterocolitis and ulcerative colitis accounting for 9.5% each, severe combined immunodeficiency 7.1% and Crohn's disease 2.8%. A positive family history and a personal history of atopy was obtained in 47.6% and 28.6% of the cases. Serum immunoglobulin A, IgG2 and IgG4 were very low in over 50% of the infants with colitis. Sixty six percent of those with severe combined immunodeficiency, autoimmune enterocolitis and ulcerative colitis (n = 11) had low CD3 and CD4 T lymphocytes with an accompanying elevated CD8 in 2/3 of those with severe combined immunodeficiency. T lymphocytes were normal in those with allergic colitis. We conclude that infants with proven non infective colitis show as a group a high prevalence of IgA, IgG2 and IgG4 deficiency. It is likely that this minor deficiency of mucosal associated immunoglobulin production have a role in the pathogenesis of the colitic process.

Autoimmune Diseases↗
PubMed1996

Loss of functional KATP channels in pancreatic beta-cells causes persistent hyperinsulinemic hypoglycemia of infancy.

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a disorder of childhood associated with inappropriate hypersecretion of insulin by the pancreas. The pathogenesis of the condition has hitherto remained controversial. We show here that insulin-secreting cells from a homogeneous group of five infants with PHHI lack ATP-sensitive K+ channel (KATP) activity. As a consequence, PHHI beta-cells are spontaneously electrically active with high basal cytosolic Ca2+ concentrations due to Ca2+ influx. Our findings define the pathogenesis of this disease as a novel K+ channel disorder.

ATP-Binding Cassette Transporters↗
PubMed1996

Investigating inflammatory bowel disease--white cell scanning, radiology, and colonoscopy.

OBJECTIVE: To evaluate different methods of examination of the bowel in suspected inflammatory bowel disease. DESIGN: Prospective investigation of all children over a three year period with suspected inflammatory bowel disease. A technetium-99m-HMPAO labelled white cell scan (Tc-WCS), barium follow through examination (Ba-FT), and colonoscopy plus biopsy were undertaken. SETTING: Great Ormond Street Hospital for Children, London. SUBJECTS: 39 children (20 male and 19 female), median age 12.1 years (range 3.9-15.1 years). MAIN OUTCOME MEASURES: There was total agreement in 21/39 cases, positive in 16, and negative in five. Of 31 histologically proved cases, positive results were obtained in 28 Tc-WCSs (sensitivity 90%), 10 of 24 Ba-FTs (sensitivity 42%), and 27 colonoscopies (sensitivity 87%). CONCLUSION: The Tc-WCS is sensitive, specific, and non-invasive and should be a first line investigation. Ba-FT with a high radiation burden and relatively low sensitivity requires its role to be redefined. Colonoscopy, with endoscopic biopsy, has a high pick-up rate where facilities and expertise exist.

Adolescent↗
PubMed1996

Ionic control of beta cell function in nesidioblastosis. A possible therapeutic role for calcium channel blockade.

A preterm female infant presented with intractable hypoglycaemia within 10 minutes of delivery. Normoglycaemia could be maintained only by the intravenous infusion of glucose at a rate of 20-22 mg/kg/min. Persistent hyperinsulinaemic hypoglycaemia of infancy was diagnosed from an inappropriately raised plasma insulin concentration (33 mU/l) at the time of hypoglycaemia (blood glucose < 0.5 mmol/l). Medical treatment with glucagon, somatostatin, and diazoxide led to only a modest reduction in the intravenous glucose requirement; a 95% pancreatectomy was performed and histological 'nesidioblastosis' confirmed. In vitro electrophysiological studies using patch clamp techniques on isolated pancreatic beta cells characterised the ionic basis for insulin secretion in nesidioblastosis. The beta cells were depolarised in low ambient glucose concentrations with persistently firing action potentials; these were blocked reversibly by the calcium channel blocking agent verapamil. Persistent postoperative hyperinsulinaemic hypoglycaemia was treated with oral nifedipine. This increased median blood glucose concentrations from 3.5 to 4.8 mmol/l and increased in duration the child's tolerance to fasting from 3 to 10.5 hours. These data allude to an abnormality in the ionic control of insulin release in nesidioblastosis and offer a new logical approach to treatment which requires further evaluation.

Blood Glucose↗
PubMed1995

Effects of dietary polyunsaturated fatty acids on small intestinal secretory and absorptive function: studies in rat jejunum in vitro.

1. Recent initiatives which advocate an increase in dietary polyunsaturated fat intake have led to the study of the effects of this upon gastrointestinal function. 2. Weanling rats were for 21 weeks fed diets containing 10% fat that were either high or low in polyunsaturated fats. Jejunal function was studied in vitro in an Ussing chamber. 3. Basal intestinal short-circuit was similar in both groups. 4. A decreased EC50 for the non-neural electrogenic secretory responses to acetylcholine, bethanecol and isobutylmethylxanthine was apparent in the jejuna of rats fed a diet high in polyunsaturated fatty acids. 5. Submaximal electrogenic galactose absorption was increased in the rats fed a diet high in polyunsaturated fatty acids. 6. Changing the composition of dietary lipid resulted in a change in the fatty composition of the apical enterocyte membrane. 7. Diets high in polyunsaturated fatty acids may be both prosecretory and proabsorptive in the small intestine.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Lipid peroxidation and electrogenic ion transport in the jejunum of the vitamin E deficient rat.

Increased concentrations of reactive oxygen species in children with depleted antioxidant defences have been implicated in a cycle of malnutrition, malabsorption, and infection leading to protracted diarrhoea. A rat model of chronic vitamin E deficiency has been used to study the effects of antioxidant depletion on jejunal structure and function in vitro. Basal intestinal short circuit current (Isc), a measure of net electrogenic ion movement across the intestinal epithelium, was greater in chronically vitamin E deficient jejuna than controls, as was the electrogenic secretory response to aminophylline and Escherichia coli STa but not to bethanechol. The galactose stimulated current was also greater in vitamin E deficient jejuna. Indices of lipid peroxidation (concentrations of thiobarbituric acid reactive substances and malondialdehyde) were increased in the vitamin E deficient small bowel. Small intestinal brush border membranes from vitamin E deficient animals displayed changes in both static and dynamic components of membrane fluidity measured by steady state fluorescence polarography. The results of these studies support the hypothesis that oxidative stress in subjects with compromised antioxidant defences results in small intestinal hypersecretion, which could predispose to or perpetuate protracted diarrhoea.

Animals↗
PubMed1993

Modulation of small-intestinal secretion and absorption in chronic vitamin E deficiency: studies in rat jejunum in vitro.

1. A vicious cycle of malabsorption and malnutrition has been implicated in the pathogenesis of protracted diarrhoeal disease in infancy. Vitamin E deficiency is common in malnourished infants with protracted diarrhoea. We have studied the effects of chronic vitamin E deficiency on small-intestinal secretion and absorption in the rat. 2. Weanling rats were fed vitamin E-sufficient or -deficient diets for 21 weeks. Jejunal function was studied in vitro in an Ussing chamber after this period. 3. Steady-state isotopic flux experiments in unstimulated tissues demonstrated net Na+ and Cl- secretion in vitamin E-deficient jejuna but net Na+ and Cl- absorption in vitamin E-sufficient jejuna. 4. Basal intestinal short-circuit current was the same in both groups. 5. Cyclic nucleotide and maximal non-neuronal acetylcholine-mediated electrogenic secretion were increased in vitamin E-deficient jejuna. 6. Exogenous 5-hydroxytryptamine (serotonin) induced a smaller increment in electrogenic secretion in vitamin E-deficient jejuna. 7. Vitamin E-deficient jejuna were less responsive to exogenous noradrenaline, resulting in a smaller alpha 2-adrenergic-mediated decrease in intestinal short-circuit current. 8. Fasting for 72h produced a greater increment in intestinal short-circuit current in vitamin E-deficient jejuna. 9. Chronic vitamin E deficiency is prosecretory in the small intestine and may predispose to the perpetuation of protracted diarrhoeal diseases.

Absorption↗