Route and type of nutrition influence mucosal immunity to bacterial pneumonia. (41/174666)

OBJECTIVE: To develop a model of established respiratory immunity against Pseudomonas aeruginosa pneumonia and to investigate the effects of route and type of nutrition on this immunity. SUMMARY BACKGROUND DATA: Diet influences the ability of gut-associated lymphoid tissue (GALT) to maintain mucosal immunity. Complex enteral diets and chow maintain normal GALT populations against established IgA-mediated antiviral respiratory immunity. Both intravenous and intragastric total parenteral nutrition (TPN) produce GALT atrophy, but only intragastric TPN preserves established antiviral immunity. The authors hypothesized that both GALT-depleting diets (intragastric and intravenous TPN) would impair immunity against bacterial pneumonia. METHODS: P. aeruginosa was administered intratracheally to determine the mortality rate at increasing doses, and liposomes containing P. aeruginosa antigens were used to generate effective respiratory immunization. In the final experiment, mice received liposomes containing P. aeruginosa antigens to establish immunity and then were randomized to chow, complex enteral diets, intragastric TPN, or intravenous TPN. After 5 days of diet, mice received live intratracheal P. aeruginosa, and the death rate was recorded at 24 and 48 hours. RESULTS: The LD50 and LD100 were 9 x 10(7) and 12 x 10(7), respectively. Immunization reduced the mortality rate from 66% to 12%. This immunization was maintained in mice fed chow or a complex enteral diet and was lost in animals receiving intravenous TPN. Intragastric TPN partially preserved this respiratory immunity. CONCLUSIONS: Protection against bacterial pneumonia can be induced by prior antigenic immunization. This protection is lost with intravenous TPN, partially preserved with a chemically defined enteral diet, and completely preserved with chow or complex enteral diets. Both route and type of nutrition influence antibacterial respiratory tract immunity.  (+info)

Perioperative growth hormone treatment and functional outcome after major abdominal surgery: a randomized, double-blind, controlled study. (42/174666)

OBJECTIVE: To evaluate short- and long-term effects of perioperative human growth hormone (hGH) treatment on physical performance and fatigue in younger patients undergoing a major abdominal operation in a normal postoperative regimen with oral nutrition. SUMMARY BACKGROUND DATA: Muscle wasting and functional impairment follow major abdominal surgery. METHODS: Twenty-four patients with ulcerative colitis undergoing ileoanal J-pouch surgery were randomized to hGH (12 IU/day) or placebo treatment from 2 days before to 7 days after surgery. Measurements were performed 2 days before and 10, 30, and 90 days after surgery. RESULTS: The total muscle strength of four limb muscle groups was reduced by 7.6% in the hGH group and by 17.1% in the placebo group at postoperative day 10 compared with baseline values. There was also a significant difference between treatment groups in total muscle strength at day 30, and at the 90-day follow-up total muscle strength was equal to baseline values in the hGH group, but still significantly 5.9% below in the placebo group. The work capacity decreased by approximately 20% at day 10 after surgery, with no significant difference between treatment groups. Both groups were equally fatigued at day 10 after surgery, but at day 30 and 90 the hGH patients were less fatigued than the placebo patients. During the treatment period, patients receiving hGH had reduced loss of limb lean tissue mass, and 3 months after surgery the hGH patients had regained more lean tissue mass than placebo patients. CONCLUSIONS: Perioperative hGH treatment of younger patients undergoing major abdominal surgery preserved limb lean tissue mass, increased postoperative muscular strength, and reduced long-term postoperative fatigue.  (+info)

Symptomatic gastro-oesophageal reflux disease: double blind controlled study of intermittent treatment with omeprazole or ranitidine. The European Study Group. (43/174666)

OBJECTIVE: To assess intermittent treatment over 12 months in patients with symptomatic gastro-oesophageal reflux disease. DESIGN: Randomised, multicentre, double blind, controlled study. Patients with heartburn and normal endoscopy results or mild erosive changes received omeprazole 10 mg or 20 mg daily or ranitidine 150 mg twice daily for 2 weeks. Patients remaining symptomatic had omeprazole 10 mg or ranitidine dose doubled for another 2 weeks while omeprazole 20 mg was continued for 2 weeks. Patients who were symptomatic or mildly symptomatic were followed up for 12 months. Recurrences of moderate or severe heartburn during follow up were treated with the dose which was successful for initial symptom control. SETTING: Hospitals and primary care practices between 1994 and 1996. SUBJECTS: 677 patients with gastro-oesophageal reflux disease. MAIN OUTCOME MEASURES: Total time off active treatment, time to failure of intermittent treatment, and outcomes ranked from best to worst. RESULTS: 704 patients were randomised, 677 were eligible for analyses; 318 reached the end of the study with intermittent treatment without recourse to maintenance antisecretory drugs. The median number of days off active treatment during follow up was 142 for the entire study (281 for the 526 patients who reached a treatment related end point). Thus, about half the patients did not require treatment for at least 6 months, and this was similar in all three treatment groups. According to outcome, 378 (72%) patients were in the best outcome ranks (no relapse or one (or more) relapse but in remission until 12 months); 630 (93%) had three or fewer relapses in the intermittent treatment phase. Omeprazole 20 mg provided faster relief of heartburn. The results were similar in patients with erosive and non-erosive disease. CONCLUSIONS: Intermittent treatment is effective in managing symptoms of heartburn in half of patients with uncomplicated gastro-oesophageal reflux disease. It is simple and applicable in general practice, where most patients are seen.  (+info)

The optically determined size of exo/endo cycling vesicle pool correlates with the quantal content at the neuromuscular junction of Drosophila larvae. (44/174666)

According to the current theory of synaptic transmission, the amplitude of evoked synaptic potentials correlates with the number of synaptic vesicles released at the presynaptic terminals. Synaptic vesicles in presynaptic boutons constitute two distinct pools, namely, exo/endo cycling and reserve pools (). We defined the vesicles that were endocytosed and exocytosed during high K+ stimulation as the exo/endo cycling vesicle pool. To determine the role of exo/endo cycling vesicle pool in synaptic transmission, we estimated the quantal content electrophysiologically, whereas the pool size was determined optically using fluorescent dye FM1-43. We then manipulated the size of the pool with following treatments. First, to change the state of boutons of nerve terminals, motoneuronal axons were severed. With this treatment, the size of exo/endo cycling vesicle pool decreased together with the quantal content. Second, we promoted the FM1-43 uptake using cyclosporin A, which inhibits calcineurin activities and enhances endocytosis. Cyclosporin A increased the total uptake of FM1-43, but neither the size of exo/endo cycling vesicle pool nor the quantal content changed. Third, we increased the size of exo/endo cycling vesicle pool by forskolin, which enhances synaptic transmission. The forskolin treatment increased both the size of exo/endo cycling vesicle pool and the quantal content. Thus, we found that the quantal content was closely correlated with the size of exo/endo cycling vesicle pool but not necessarily with the total uptake of FM1-43 fluorescence by boutons. The results suggest that vesicles in the exo/endo cycling pool primarily participate in evoked exocytosis of vesicles.  (+info)

Molecular dynamics of the sodium channel pore vary with gating: interactions between P-segment motions and inactivation. (45/174666)

Disulfide trapping studies have revealed that the pore-lining (P) segments of voltage-dependent sodium channels undergo sizable motions on a subsecond time scale. Such motions of the pore may be necessary for selective ion translocation. Although traditionally viewed as separable properties, gating and permeation are now known to interact extensively in various classes of channels. We have investigated the interaction of pore motions and voltage-dependent gating in micro1 sodium channels engineered to contain two cysteines within the P segments. Rates of catalyzed internal disulfide formation (kSS) were measured in K1237C+W1531C mutant channels expressed in oocytes. During repetitive voltage-clamp depolarizations, increasing the pulse duration had biphasic effects on the kSS, which first increased to a maximum at 200 msec and then decreased with longer depolarizations. This result suggested that occupancy of an intermediate inactivation state (IM) facilitates pore motions. Consistent with the known antagonism between alkali metals and a component of slow inactivation, kSS varied inversely with external [Na+]o. We examined the converse relationship, namely the effect of pore flexibility on gating, by measuring recovery from inactivation in Y401C+E758C (YC/EC) channels. Under oxidative conditions, recovery from inactivation was slower than in a reduced environment in which the spontaneous YC/EC cross-link is disrupted. The most prominent effects were slowing of a component with intermediate recovery kinetics, with diminution of its relative amplitude. We conclude that occupancy of an intermediate inactivation state facilitates motions of the P segments; conversely, flexibility of the P segments alters an intermediate component of inactivation.  (+info)

Central peptidergic neurons are hyperactive during collateral sprouting and inhibition of activity suppresses sprouting. (46/174666)

Little is known regarding the effect of chronic changes in neuronal activity on the extent of collateral sprouting by identified CNS neurons. We have investigated the relationship between activity and sprouting in oxytocin (OT) and vasopressin (VP) neurons of the hypothalamic magnocellular neurosecretory system (MNS). Uninjured MNS neurons undergo a robust collateral-sprouting response that restores the axon population of the neural lobe (NL) after a lesion of the contralateral MNS (). Simultaneously, lesioned rats develop chronic urinary hyperosmolality indicative of heightened neurosecretory activity. We therefore tested the hypothesis that sprouting MNS neurons are hyperactive by measuring changes in cell and nuclear diameters, OT and VP mRNA pools, and axonal cytochrome oxidase activity (COX). Each of these measures was significantly elevated during the period of most rapid axonal growth between 1 and 4 weeks after the lesion, confirming that both OT and VP neurons are hyperactive while undergoing collateral sprouting. In a second study the hypothesis that chronic inhibition of neuronal activity would interfere with the sprouting response was tested. Chronic hyponatremia (CH) was induced 3 d before the hypothalamic lesion and sustained for 4 weeks to suppress neurosecretory activity. CH abolished the lesion-induced increases in OT and VP mRNA pools and virtually eliminated measurable COX activity in MNS terminals. Counts of the total number of axon profiles in the NL revealed that CH also prevented axonal sprouting from occurring. These results are consistent with the hypothesis that increased neuronal activity is required for denervation-induced collateral sprouting to occur in the MNS.  (+info)

Ischemic tolerance in murine cortical cell culture: critical role for NMDA receptors. (47/174666)

Murine cortical cultures containing both neurons and glia (days in vitro 13-15) were exposed to periods of oxygen-glucose deprivation (5-30 min) too brief to induce neuronal death. Cultures "preconditioned" by sublethal oxygen-glucose deprivation exhibited 30-50% less neuronal death than controls when exposed to a 45-55 min period of oxygen-glucose deprivation 24 hr later. This preconditioning-induced neuroprotection was specific in that neuronal death induced by exposure to excitotoxins or to staurosporine was not attenuated. Neuroprotection was lost if the time between the preconditioning and severe insult were decreased to 7 hr or increased to 72 hr and was blocked if the NMDA antagonist 100 microM 3-((D)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid was applied during the preconditioning insult. This was true even if the duration of preconditioning was increased as far as possible (while still remaining sublethal). A similar preconditioning effect was also produced by sublethal exposure to high K+, glutamate, or NMDA but not to kainate or trans-1-aminocyclopentane-1, 3-dicarboxylic acid.  (+info)

Ionic currents underlying spontaneous action potentials in isolated cerebellar Purkinje neurons. (48/174666)

Acutely dissociated cell bodies of mouse Purkinje neurons spontaneously fired action potentials at approximately 50 Hz (25 degrees C). To directly measure the ionic currents underlying spontaneous activity, we voltage-clamped the cells using prerecorded spontaneous action potentials (spike trains) as voltage commands and used ionic substitution and selective blockers to isolate individual currents. The largest current flowing during the interspike interval was tetrodotoxin-sensitive sodium current (approximately -50 pA between -65 and -60 mV). Although the neurons had large voltage-dependent calcium currents, the net current blocked by cobalt substitution for calcium was outward at all times during spike trains. Thus, the electrical effect of calcium current is apparently dominated by rapidly activated calcium-dependent potassium currents. Under current clamp, all cells continued firing spontaneously (though approximately 30% more slowly) after block of T-type calcium current by mibefradil, and most cells continued to fire after block of all calcium current by cobalt substitution. Although the neurons possessed hyperpolarization-activated cation current (Ih), little current flowed during spike trains, and block by 1 mM cesium had no effect on firing frequency. The outward potassium currents underlying the repolarization of the spikes were completely blocked by 1 mM TEA. These currents deactivated quickly (<1 msec) after each spike. We conclude that the spontaneous firing of Purkinje neuron cell bodies depends mainly on tetrodotoxin-sensitive sodium current flowing between spikes. The high firing rate is promoted by large potassium currents that repolarize the cell rapidly and deactivate quickly, thus preventing strong hyperpolarization and restoring a high input resistance for subsequent depolarization.  (+info)