Search

An N-balance experiment was conducted to test the hypothesis that d-Methionine (d-Met) has the same bioavailability and efficacy as l-Methionine (l-Met) when fed to weanling pigs. A Met-deficient basal diet containing 0.24% standardized ileal digestible (SID) Met was formulated. Six additional diets were formulated by adding 0.036%, 0.072%, or 0.108% d-Met or l-Met to the basal diet, and these diets, therefore, contained 77%, 87%, or 97% of the requirement for SID Met. Fifty-six barrows (10.53 ± 1.17 kg) were housed in metabolism crates and allotted to the seven diets with eight replicate pigs per diet. Feces and urine were collected quantitatively with 7-d adaptation and 5-d collection periods. Blood and tissue samples from pigs fed the basal diet and pigs fed diets containing 0.108% supplemental Met were collected on the last day. Results indicated that N retention (%) linearly increased (P < 0.01) as supplemental d-Met or l-Met increased in diets. Based on N retention (%) as a response, the linear slope-ratio regression estimated the bioavailability of d-Met relative to l-Met to be 101% (95% confidence interval: 57%-146%). The villus height and crypt depth in the jejunum were not affected by the Met level or Met source. Total antioxidant capacity or thiobarbituric acid reactive substance concentrations in plasma or tissue samples from pigs fed the control diet or diets containing 0.108% supplemental d-Met or l-Met were not different. Abundance of mRNA for some AA transporters analyzed in intestinal mucosa of pigs also did not differ. Therefore, it is concluded that d-Met and l-Met are equally bioavailable for weanling pigs.

A number of feed additives are marketed to assist in boosting the pigs' immune system, regulate gut microbiota, and reduce negative impacts of weaning and other environmental challenges. The most commonly used feed additives include acidifiers, zinc and copper, prebiotics, direct-fed microbials, yeast products, nucleotides, and plant extracts. Inclusion of pharmacological levels of zinc and copper, certain acidifiers, and several plant extracts have been reported to result in improved pig performance or improved immune function of pigs. It is also possible that use of prebiotics, direct-fed microbials, yeast, and nucleotides may have positive impacts on pig performance, but results have been less consistent and there is a need for more research in this area.

Background: Idiopathic sudden sensorineural hearing loss (ISSNHL) is a condition which is difficult to define and treat. Sensorineural hearing loss being a situation where rehabilitation therapy with hearing aids is the only treatment option, ISSNHL is an exception which can be treated medically if identified early enough. Aims and Objectives: The aim of the study was (i) to calculate the recovery of hearing and other symptoms in patients diagnosed of ISSNHL treated with medical management as per institutional protocol and (ii) to determine the association between recovery with medical management and factors such as time of presentation and comorbidities in patients with ISSNHL. Materials and Methods: In the Department of ENT, MCH, Kottayam, a protocol for the management of ISSNHL was worked out as per guidelines from standard otology textbooks. All patients with suspected ISSNHL were admitted. Hearing assessment was done using pure tone audiometry during inpatient care and on discharge of the patient. Patients were discharged after completion of the treatment and followed up for a period of at least 6 months. Results: The inference of our study is that cases who presented early in the first 24-48 h of onset of symptoms have maximum chance of recovery irrespective of associated comorbidities. Conclusion: The study highlights the fact that ISSNHL is and should be consider ed as a medical emergency. [ABSTRACT FROM AUTHOR]

Purpose: Use of the Mitrofanoff principle is a valuable adjunct to many reconstructive urological procedures in the pediatric age group requiring clean intermittent catheterization (CIC) especially if the urethra is not easily catheterizable. We present our experience with 122 children and analyze the results of this operation. Materials and Methods: 133 Mitrofanoff channels (100 appendicular, 31 ureteric and 2 Monti) were constructed in 122 children (93 boys and 29 girls) of mean age 6.3 years over the period from 1997 to 2005. The procedure was part of the reconstructive procedure in patients of neurogenic bladder (n=44), exstrophy-epispadias (n=40), posterior Urethral valve (n=30), and other diseases (n=8). Additional procedures included augmentation cystoplasty (n=90) and bladder neck procedure (n=46). Results: Mean follow-up was 2.6 years in 109 patients. Overall results were satisfactory. Major complication rates with the Mitrofanoff conduit using appendicular and ureteric channels were 7.4 % in and 25.8%, respectively, most of the ureteric channels due to non-use, there being alternate channels for catheterization. Only six (4.5%) children required re-operation for significant problems with the Mitrofanoff conduit: revision of stoma due to stenosis or kinking (n=4) and closure of stoma due to troublesome leak (n=2). Children and parents were satisfied with the results of the operation and the majority was compliant with regular CIC. All children were socially well accepted and those above 6 years of age were attending regular school. Conclusions: The Mitrofanoff procedure is a feasible and acceptable option, with a low complication rate, for use as part of complex urinary reconstruction in a developing country. Patient education, family motivation, and cost reduction are important factors for success.

Urea transporters (UTs) effect rapid flux of urea across biological membranes. In the mammalian kidney, UT activity is essential for effective urine concentration. In bacteria, UT-mediated urea uptake permits intracellular urease to degrade urea to ammonia and C[O.sub.2], a process that either buffers acid loads or provides nutrient nitrogen. We have characterized the urea transport channel protein ApUT from Actinobacillus pleuropneumoniae. Kinetic analysis of bacterial inside-out membranes enriched in ApUT showed ~28-fold increase in urea permeability (3.3 [+ or -] 0.4 x [10.sup.-4] cm/s) compared with control vesicles (0.11 [+ or -] 0.02 x [10.sup.-4] cm/s). In addition to urea, ApUT also conducts water. Urea and water transport across the channel was phloretin and mercury inhibitable, and the site of inhibition may be located on the cytoplasmic side of the protein. Glycerol and urea analogs, such as methylamine, dimethylurea, formamide, acetamide, methylurea, propanamide, and ethylamine did not permeate across ApUT. urea permeability; water permeability; bacterial vesicles; urea analogs

Recently measured water permeability through bilayers of different lipids is most strongly correlated with the area per lipid A rather than with other structural quantities such as the thickness. This paper presents a simple three-layer theory that incorporates the area dependence in a physically realistic way and also includes the thickness as a secondary modulating parameter. The theory also includes the well-known strong correlation of permeability upon the partition coefficients of general solutes in hydrocarbon environments (Overton's rule). Two mathematical treatments of the theory are given; one model uses discrete chemical kinetics and one model uses the Nernst-Planck continuum equation. The theory is fit to the recent experiments on water permeability in the accompanying paper.

Despite intense study over many years, the mechanisms by which water and small nonelectrolytes cross lipid bilayers remain unclear. While prior studies of permeability through membranes have focused on solute characteristics, such as size, polarity, and partition coefficient in hydrophobic solvent, we focus here on water permeability in seven single component bilayers composed of different lipids, five with phosphatidylcholine headgroups and different chain lengths and unsaturation, one with a phosphatidylserine headgroup, and one with a phosphatidylethanolamine headgroup. We find that water permeability correlates most strongly with the area/lipid and is poorly correlated with bilayer thickness and other previously determined structural and mechanical properties of these single component bilayers. These results suggest a new model for permeability that is developed in the accompanying theoretical paper in which the area occupied by the lipid is the major determinant and the hydrocarbon thickness is a secondary determinant. Cholesterol was also incorporated into DOPC bilayers and X-ray diffuse scattering was used to determine quantitative structure with the result that the area occupied by DOPC in the membrane decreases while bilayer thickness increases in a correlated way because lipid volume does not change. The water permeability decreases with added cholesterol and it correlates in a different way from pure lipids with area per lipid, bilayer thickness, and also with area compressibility.

Determining the mechanisms of flux through protein channels requires a combination of structural data, permeability measurement, and molecular dynamics (MD) simulations. To further clarify the mechanism of flux through aquaporin 1 (AQP1), osmotic [p.sub.f]/([cm.sup.3]/s/pore) and diffusion [p.sub.d] ([cm.sup.3]/s/Pore) permeability coefficients per pore of [H.sub.2] and [D.sub.2]O in AQP1 were calculated using MD simulations. We then compared the simulation results with experimental measurements of the osmotic AQP1 permeabilities of [H.sub.2]O and [D.sub.2]O. In this manner we evaluated the ability of MD simulations to predict actual flux results. For the MD simulations, the force field parameters of the [D.sub.2]O model were reparameterized from the TIP3P water model to reproduce the experimentally observed difference in the bulk self diffusion constants of [H.sub.2]O vs. [D.sub.2]O. Two MD systems (one for each solvent) were constructed, each containing explicit palmitoyl-oleoyl-phosphatidyl-ethanolamine (POPE) phospholipid molecules, solvent, and AQP1. It was found that the calculated value of [p.sub.j] for [D.sub.2]O is ~15% smaller than for [H.sub.2]O. Bovine AQP1 was reconstituted into palmitoyl-oleoyl-phosphatidylcholine (POPC) liposomes, and it was found that the measured macroscopic osmotic permeability coefficient [P.sub.f] (cm/s) of [D.sub.2]O is ~21% lower than for [H.sub.2]O. The combined computational and experimental results suggest that deuterium oxide permeability through AQP1 is similar to that of water. The slightly lower observed osmotic permeability of [D.sub.2]O compared to [H.sub.2]O in AQP1 is most likely due to the lower self diffusion constant of [D.sub.2]O.

Genetically encoded sensor proteins provide unique opportunities to advance the understanding of complex cellular interactions in physiologically relevant contexts; however, previously described sensors have proved to be of limited use to report cell signaling in vivo in mammals. Here, we describe an improved [Ca.sup.2+] sensor, GCaMP2, its inducible expression in the mouse heart, and its use to examine signaling in heart cells in vivo. The high brightness and stability of GCaMP2 enable the measurement of myocyte [Ca.sup.2+] transients in all regions of the beating mouse heart and prolonged pacing and mapping studies in isolated, perfused hearts. Transgene expression is efficiently temporally regulated in cardiomyocyte GCaMP2 mice, allowing recording of in vivo signals 4 weeks after transgene induction. High-resolution imaging of [Ca.sup.2+] waves in GCaMP2-expressing embryos revealed key aspects of electrical conduction in the preseptated heart. At embryonic day (e.d.) 10.5, atrial and ventricular conduction occur rapidly, consistent with the early formation of specialized conduction pathways. However, conduction is markedly slowed through the atrioventricular canal in the e.d. 10.5 heart, forming the basis for an effective atrioventricular delay before development of the AV node, as rapid ventricular activation occurs after activation of the distal AV canal tissue. Consistent with the elimination of the inner AV canal muscle layer at e.d. 13.5, atrioventricular conduction through the canal was abolished at this stage. These studies demonstrate that GCaMP2 will have broad utility in the dissection of numerous complex cellular interactions in mammals, in vivo. atrioventricular node | [Ca.sup.2+] imaging | genetic sensor | heart development | fluorescent [Ca.sup.2+] sensor

Aquaporins (AQPs) accelerate the movement of water and other solutes across biological membranes, yet the molecular mechanisms of each AQP's transport function and the diverse physiological roles played by AQP family members are still being defined. We therefore have characterized an AQP in a model organism, Drosophila melanogaster, which is amenable to genetic manipulation and developmental analysis. To study the mechanism of Drosophila Malpighian tubule (MT)-facilitated water transport, we identified seven putative AQPs in the Drosophila genome and found that one of these, previously named DRIP, has the greatest sequence similarity to those vertebrate AQPs that exhibit the highest rates of water transport. In situ mRNA analyses showed that DRIP is expressed in both embryonic and adult MTs, as well as in other tissues in which fluid transport is essential. In addition, the pattern of DRIP expression was dynamic. To define DRIP-mediated water transport, the protein was expressed in Xenopus oocytes and in yeast secretory vesicles, and we found that significantly elevated rates of water transport correlated with DRIP expression. Moreover, the activation energy required for water transport in DRIP-expressing secretory vesicles was 4.9 kcal/mol. This low value is characteristic of AQP-mediated water transport, whereas the value in control vesicles was 16.4 kcal/mol. In contrast, glycerol, urea, ammonia, and proton transport were unaffected by DRIP expression, suggesting that DRIP is a highly selective water-specific channel. This result is consistent with the homology between DRIP and mammalian water-specific AQPs. Together, these data establish Drosophila as a new model system with which to investigate AQP function. fluid homeostasis; osmosis; channel; membrane

Elasmobranchs such as the dogfish shark Squalus acanthius achieve osmotic homeostasis by maintaining urea concentrations in the 300- to 400-mM range, thus offsetting to some degree ambient marine osmolalities of 900-1,000 mosmol/kg[H.sub.2]O. These creatures also maintain salt balance without losing urea by secreting a NaCl-rich (500 mM) and urea-poor (18 mM) fluid from the rectal gland that is isotonic with the plasma. The composition of the rectal gland fluid suggests that its epithelial cells are permeable to water and not to urea. Because previous work showed that lipid bilayers that permit water flux do not block flux of urea, we reasoned that the plasma membranes of rectal gland epithelial cells must either have aquaporin water channels or must have some selective barrier to urea flux. We therefore isolated apical and basolateral membranes from shark rectal glands and determined their permeabilities to water and urea. Apical membrane fractions were markedly enriched for Na-K-2CI cotransporter, whereas basolateral membrane fractions were enriched for Na-K-ATPase. Basolateral membrane osmotic water permeability (Pf) averaged 4.3 [+ or -] 1.3 X [10.sup.-3] cm/s, whereas urea permeability averaged 4.2 [+ or -] 0.8 X [10.sup.-7] cm/s. The activation energy for water flow averaged 16.4 kcal/mol. Apical membrane Pf averaged 7.5 [+ or -] 1.6 X [10.sup.-4] cm/s, and urea permeability averaged 2.2 [+ or -] 0.4 X [10.sup.-7] cm/s, with an average activation energy for water flow of 18.6 kcal/mol. The relatively low water permeabilities and high activation energies argue strongly against water flux via aquaporins. Comparison of membrane water and urea permeabilities with those of artificial liposomes and other isolated biological membranes indicates that the basolateral membrane urea permeability is fivefold lower than would be anticipated for its water permeability. These results indicate that the rectal gland maintains a selective barrier to urea in its basolateral membranes. elasmobranchs; apical and basal membrane permeability; membrane vesicles