RESUMEN
Adenoid hyperplasia is a common cause of nasal obstruction in the pediatric age group. Recently, the adenoids were shown to harbor Helicobacter pylori (HP) based only on the rapid urease test (RUT). We conducted this pilot study to identify the presence of HP in the adenoids histologically and assess the reliability of both the RUT and histology in detecting HP in an extragastric location, using nested (two-steps) polymerase chain reaction (nPCR). Consecutive patients undergoing adenoidectomy for obstructive adenoid hyperplasia were enrolled. Adenoid specimens were subjected to the RUT. Histological sections stained with hematoxylin and eosin, Giemsa and Warthin-Starry were examined. We then used nPCR to detect the presence of HP in the studied specimens. Twenty-five patients (3-10 years; mean of 5.5 years) were enrolled. Twenty-one (84%) adenoids were positive by the RUT. Seventeen (68%) had bacteria on histological sections; four (16%) contained HP-like organisms. However, all specimens were negative by nPCR. No patient had a history of symptoms suggestive of laryngopharyngeal reflux within 6 months of the study. In conclusion, the children enrolled in this study did not have HP in their adenoids. High false positive results can occur with the RUT when used on adenoid tissues. It is not possible to rely solely on morphology to detect HP in an extragastric location. The nPCR remains the best way to identify HP accurately, but does not imply its presence in an active role.
Asunto(s)
Tonsila Faríngea/microbiología , Infecciones por Helicobacter/microbiología , Helicobacter pylori/aislamiento & purificación , Adenoidectomía , Tonsila Faríngea/metabolismo , Tonsila Faríngea/cirugía , Niño , Preescolar , Infecciones por Helicobacter/diagnóstico , Humanos , Proyectos Piloto , Reacción en Cadena de la Polimerasa , Ureasa/farmacocinéticaRESUMEN
No intravenously injectable enzyme preparate containing urease as an alternetive to hemodialysis, hemoperfusion and CAPD systems in patients having chronic renal failure has been encountered in literature. In this study, it has been aimed to convert blood urea to alanine by using PEG-urease/PEG-AlaDH enzyme pair encapsulated within living erythrocyte. In this system, urea is decomposed into NH3 and HCO3- and the ammonia released is converted into alanine by reacting pyruvate under the catalytic action of alaninedehydrogenase. The production of pyruvate and NADH by erythrocyte required in the second stage of the reaction will make the process a feasible and ceaseless one. The success of the system will enable the renal patients with diabetes mellitus. Urease and AlaDH were covalently immobilized on activated PEG. PEG-urease/PEG-AlaDH were encapsulated in erythrocyte (1/1)(v/v) by using slow dialysis methods. The activity of enzyme system, encapsulation yield and hemogram analysis were determined for each sample.
Asunto(s)
Aminoácido Oxidorreductasas/farmacocinética , Sistemas de Liberación de Medicamentos/métodos , Eritrocitos/enzimología , Ureasa/farmacocinética , Alanina/biosíntesis , Alanina-Deshidrogenasa , Aminoácido Oxidorreductasas/sangre , Aminoácido Oxidorreductasas/metabolismo , Amoníaco/análisis , Diabetes Mellitus/terapia , Composición de Medicamentos , Sistemas de Liberación de Medicamentos/normas , Enzimas Inmovilizadas/sangre , Enzimas Inmovilizadas/metabolismo , Enzimas Inmovilizadas/farmacocinética , Pruebas Hematológicas , Humanos , Cinética , Polietilenglicoles , Ácido Pirúvico/análisis , Ureasa/sangre , Ureasa/metabolismoRESUMEN
Spherical activated carbon was employed as a new support material for the immobilization of urease. Activity and kinetic behavior of the enzyme were observed. Urease activity was decreased by 10% for the uncoated samples during the washing process whereas a 30% reduction in activity was observed for the coated samples due to the electrical discharge. Activity versus time plots generally appeared to be s-shaped curves at different initial urea levels. At high substrate concentration the kinetics no longer obeyed the Michaelis-Menten relationship due to the inhibition mechanism and diffusion for the support system.
Asunto(s)
Carbón Orgánico , Ureasa , Enzimas Inmovilizadas , Potenciometría , Ureasa/farmacocinéticaRESUMEN
The in vitro effect of urea and hydrolysis of urea by urease on mucus H+ permeability is reported here. The effective DHCl values indicate a strong pH dependence for H+ diffusion in both water and mucus layers, with no apparent trend at concentrations between 1 and 50 mM urea. However, the estimated DHCl at near-neutral and alkaline pH are 4- to 10-fold lower through mucus than through aqueous films. Moreover, the pKa values of HCO3- and NH3 (generated by urease action on urea) had a profound effect on measured DHCl. These in vitro studies suggest that a high local concentration of NH3 and HCO3- within the mucus layer, generated by the action of Helicobacter pylori urease on endogenous intragastric urea, could greatly accelerate proton flux to the surface epithelium by operation of a buffer shuttle. This results in enhanced H+ permeability, particularly at pKa values of HCO3- and NH3, and in extreme circumstances it may result in gastric ulcer formation.
Asunto(s)
Gastritis/metabolismo , Helicobacter pylori , Moco/metabolismo , Úlcera Péptica/metabolismo , Urea/metabolismo , Ureasa/farmacocinética , Animales , Difusión , Gastritis/microbiología , Infecciones por Helicobacter/complicaciones , Concentración de Iones de Hidrógeno , Hidrólisis , Técnicas In Vitro , Modelos Biológicos , Úlcera Péptica/microbiología , Permeabilidad , Porcinos , Agua/metabolismoRESUMEN
The advent of genetic engineering has resulted in a proliferation of protein pharmaceuticals available for a variety of therapeutic needs. However, the formulation and delivery of these proteins remain an intriguing challenge. Polymer-based protein drug delivery systems continue to be investigated, although many of the fabrication techniques used to incorporate proteins into the polymer matrix or device result in irreversible inactivation (denaturation) of the proteins. A well-characterized model enzyme, urease, was formulated in 33% (w/w) poloxamer 407 (Pluronic F-127) vehicle and injected intraperitoneally (ip) into rats in an attempt to achieve both preservation of biological activity and sustained release of the protein. The resulting ammonia concentration in plasma-time profiles were compared with those for rats injected with an identical dose (27.6 units of activity per 200 g of body weight) of urease dissolved in pH 7 phosphate buffer. Neither a pH 7 phosphate buffer solution nor poloxamer 407 (33%, w/w) dissolved in pH 7 phosphate buffer, when injected ip into rats, resulted in elevated ammonia levels in plasma. The time to reach a maximum ammonia level in plasma was increased approximately threefold following the injection of the urease-poloxamer 407 formulation, compared with that in control rats administered an identical dose of urease in solution. In addition, hyperammonemia was extended almost threefold in treated rats compared with control rats, without untoward effects. However, prolonged hyperammonemia in animals receiving an ip injection of the urease-poloxamer 407 formulation may have potentially resulted from the reduced clearance of ammonia and ammonium ion in the proximal tubules of the rats.(ABSTRACT TRUNCATED AT 250 WORDS)