Interleukin-1α-induced changes in chromium-51 absorption, tissue retention, and urinary excretion in rats

The effects of interleukin-1 alpha (IL-1α) on chromium-51 absorption, tissue retention, and urinary excretion were studied in adult male Sprague-Dawley rats. Ten rats were deprived of food for 12 h, injected intraperitoneally with mouse recombinant IL-1α (1 Μg/kg of body weight in phosphate-buffered saline [PBS]) or control (0.1% bovine serum albumin [BSA] in PBS). Two hours after dosing with the IL-1α, rats were fed 50 ΜL (200 ΜCi, 0.36 Μg Cr) of⁵¹CrCl₃ by micropipet. Blood was collected from the tail at 0.25, 0.5, 1, 2, and 4 h. Six hours after dosing with⁵¹CrCl₃, rats were exsanguinated and blood and tissues were sampled. The IL-lα significantly decreased chromium-51 in blood, urine, and some tissues compared to the control. The decreased absorption, retention, and urinary excretion of chromium-51 from⁵¹CrCl₃ in this study may be due to IL-1α-mediated increases in the production of prostaglandins and/or decreased production of gastric acid.     

How does salt retention raise blood pressure?

A critical question in hypertension research is: How is long-term blood pressure controlled? Excessive NaCl ingestion or NaCl retention by the kidneys and the consequent tendency toward plasma volume expansion lead to hypertension. Nevertheless, the precise mechanisms linking salt to high blood pressure are unresolved. The discovery of endogenous ouabain, an adrenocortical hormone, provided an important clue. Ouabain, a selective Na+ pump inhibitor, has cardiotonic and vasotonic effects. Plasma endogenous ouabain levels are significantly elevated in approximately 40% of patients with essential hypertension and in animals with several forms of salt-dependent hypertension. Also, prolonged ouabain administration induces hypertension in rodents. Mice with mutant Na+ pumps or Na/Ca exchangers (NCX) and studies with a ouabain antagonist and an NCX blocker are revealing the missing molecular mechanisms. These data demonstrate that alpha2 Na+ pumps and NCX1 participate in long-term regulation of vascular tone and blood pressure. Pharmacological agents or mutations in the alpha2 Na+ pump that interfere with the action of ouabain on the pump, and reduced NCX1 expression or agents that block NCX all impede the development of salt-dependent or ouabain-induced hypertension. Conversely, nanomolar ouabain, reduced alpha2 Na+ pump expression, and smooth muscle-specific overexpression of NCX1 all induce hypertension. Furthermore, ouabain and reduced alpha2 Na+ pump expression increase myogenic tone in isolated mesenteric small arteries in vitro, thereby tying these effects directly to the elevation of blood pressure. Thus, endogenous ouabain, and vascular alpha2 Na+ pumps and NCX1, are critical links between salt and hypertension. New pharmacological agents that act on these molecular links have potential in the clinical management of hypertension.     

A comparison of the retention of pathogenic Escherichia coli?O157 by sprouts,leaves and fruits

The retention (binding to or association with the plant) of Escherichia coli by cut leaves and fruits after vigorous water washing was compared with that by sprouts. Retention by fruits and leaves was similar but differed from retention by sprouts in rate, effect of wounding and requirement for poly-β,1-6-N-acetyl-D-glucosamine. Escherichia coli was retained by cut ends of lettuce leaves within 5 min while more than 1 h was required for retention by the intact epidermis of leaves and fruits, and more than 1 day for sprouts. Retention after 5 min at the cut leaf edge was specific for E. coli and was not shown by the plant-associated bacteria Agrobacterium tumefaciens and Sinorhizobium meliloti. Escherichia coli was retained by lettuce, spinach, alfalfa, bean, tomato, Arabidopsis thaliana, cucumber, and pepper leaves and fruits faster than by sprouts. Wounding of leaves and fruits but not sprouts increased bacterial retention. Mutations in the exopolysaccharide synthesis genes yhjN and wcaD reduced the numbers of bacteria retained. PgaC mutants were retained by cut leaves and fruits but not by sprouts. There was no significant difference in the retention of an O157 and a K12 strain by fruits or leaves. However, retention by sprouts of O157 strains was significantly greater than K12 strains. These findings suggest that there are differences in the mechanisms of E coli retention among sprouts, and leaves and fruits.     

Golgi retention signals: do membranes hold the key?

The diverse forms and functions of cellular organelles are, presumably, a consequence of their particular molecular compositions. The generation and maintenance of this diversity is achieved by the targeting of newly synthesized proteins to specific locations and their subsequent retention there. Sequences that retain proteins in the endoplasmic reticulum (ER) have been identified at the C-termini of resident ER proteins, where they are readily accessible to potential receptors. By contrast, recent results have demonstrated that retention of proteins in the Golgi complex involves sequences located within transmembrane domains. This suggests the novel possibility that the membrane composition of the Golgi complex plays a role in retention of resident Golgi proteins.     

Activation, dysfunction and retention of T cells in vaccine sites after injection of incomplete Freund’s adjuvant, with or without peptide

We conducted a randomized clinical trial in 45 patients with resected AJCC stage IIB-IV melanoma to characterize cellular and molecular events at sites of immunization with incomplete Freund’s adjuvant (IFA) alone, or a melanoma vaccine in IFA. At a primary vaccine site, all patients received a multi-peptide melanoma vaccine in IFA. At a replicate vaccine site, which was biopsied, group 1 received IFA only; group 2 received vaccine in IFA. Lymphocytes isolated from replicate vaccine site microenvironments (VSME) were compared to time-matched peripheral blood mononuclear cells (PBMC) in ELISpot and flow cytometry assays. Compared to PBMC, the VSME had fewer naïve and greater proportions of effector memory CD8⁺ T cells (T_CD8). The vast majority of T_CD8 within the VSME were activated (CD69⁺), with a concentration of antigen-specific (tetramer^pos) cells in the VSME, particularly in vaccine sites with peptide (group 2). CXCR3⁺ lymphocytes were concentrated in the VSME of all patients, suggesting IFA-induced chemokine recruitment. T_CD8 expression of retention integrins αEβ7 and α1β1 was elevated in VSME, with the highest levels observed in antigen-specific cells in VSME containing peptide (group 2). T_CD8 retained in the VSME of both groups were strikingly dysfunctional, with minimal IFN-γ production in response to peptide stimulation and few tetramer^pos cells producing IFN-γ. These data suggest that vaccine-induced selective retention and dysfunction of antigen-specific T_CD8 within VSME may represent a significant mechanism underlying transient immune responses and low clinical response rates to peptide vaccines administered in IFA.     

Transport and retention of nitrogen and phosphorus in the sub-tropical Richmond River estuary, Australia – A budget approach

Nitrogen and phosphorus loads in the sub-tropicalRichmond River estuary were quantified and materialbudgets were developed over two years of contrastingfreshwater discharge. During both years >74% of thenitrogen and >84% of the phosphorus load enteredthe estuary during one month when flooding occurred inthe catchment. Due to larger flood magnitude, loadsduring the 1995/96 year were 3.3 and 2.5 times greaterthan during the 1994/95 year for nitrogen andphosphorus respectively. During floods the estuarinebasin was completely flushed of brackish water and themajority of the nutrient loads passed directly throughthe estuary. The nutrient load retained in the estuaryduring floods was inversely proportional to floodmagnitude. Annual budgets show that >97% of thenutrient load entering the estuary was from diffusecatchment sources; precipitation, urban runoff, andsewage were negligible. Less than 2.5% of thenitrogen and <5.4% of the phosphorus loads enteringthe estuary were retained in sediments. During dryseasons the estuary became a net sink for nitrogeninput from the ocean and the estuarine sedimentsremained a net source of phosphorus to the watercolumn and ocean. The process of flood scouring islikely to be the cleansing mechanism responsible formaintaining water quality both on an annual basis andover the last 50 years and may also be responsible forpotential nitrogen limitation. The sub-tropicalRichmond River estuary contrasts with the majority oftemperate systems of North America and Europe whichtypically have lower inter- and intra-annual nutrientload variability, longer and less variable flushingtimes, and greater nutrient retention.     

Assessing the Jarman–Bell Principle: Scaling of intake,digestibility, retention time and gut fill with body mass in mammalian herbivores

Differences in allometric scaling of physiological characters have the appeal to explain species diversification and niche differentiation along a body mass (BM) gradient — because they lead to different combinations of physiological properties, and thus may facilitate different adaptive strategies. An important argument in physiological ecology is built on the allometries of gut fill (assumed to scale to BM^1.0) and energy requirements/intake (assumed to scale to BM^0.75) in mammalian herbivores. From the difference in exponents, it has been postulated that the mean retention time (MRT) of digesta should scale to BM^1.0–0.75 = BM^0.25. This has been used to argue that larger animals have an advantage in digestive efficiency and hence can tolerate lower-quality diets. However, empirical data does not support the BM^0.25 scaling of MRT, and the deduction of MRT scaling implies, according to physical principles, no scaling of digestibility; basing assumptions on digestive efficiency on the thus-derived MRT scaling amounts to circular reasoning. An alternative explanation considers a higher scaling exponent for food intake than for metabolism, allowing larger animals to eat more of a lower quality food without having to increase digestive efficiency; to date, this concept has only been explored in ruminants. Here, using data for 77 species in which intake, digestibility and MRT were measured (allowing the calculation of the dry matter gut contents (DMC)), we show that the unexpected shallow scaling of MRT is common in herbivores and may result from deviations of other scaling exponents from expectations. Notably, DMC have a lower scaling exponent than 1.0, and the 95% confidence intervals of the scaling exponents for intake and DMC generally overlap. Differences in the scaling of wet gut contents and dry matter gut contents confirm a previous finding that the dry matter concentration of gut contents decreases with body mass, possibly compensating for the less favorable volume–surface ratio in the guts of larger organisms. These findings suggest that traditional explanations for herbivore niche differentiation along a BM gradient should not be based on allometries of digestive physiology. In contrast, they support the recent interpretation that larger species can tolerate lower-quality diets because their intake has a higher allometric scaling than their basal metabolism, allowing them to eat relatively more of a lower quality food without having to increase digestive efficiency.     

Role of AT₁ receptor-mediated salt retention in angiotensin II-dependent hypertension

Activation of type 1 angiotensin II (AT(1)) receptors in the kidney promotes blood pressure elevation and target organ damage, but whether renal AT(1) receptors influence the level of hypertension by stimulating sodium retention or by raising systemic vascular resistance has not been established. In the current studies, we used a kidney cross-transplantation strategy to determine whether increased sodium reabsorption by AT(1) receptors in the kidney mediates the chronic hypertensive response to angiotensin II. We found this to be true. In addition, we also identified a second, nontrivial component of blood pressure elevation induced by activation of renal AT(1) receptors that is sodium-independent. As the kidney has the capacity to limit the transmission of elevated systemic blood pressure into the renal microcirculation, prior studies struggled to clearly discriminate the relative contributions of blood pressure elevation vs. activation of AT(1) receptors to hypertensive kidney injury. In our model, we found that rapid surges in blood pressure, which may overcome the kidney's capacity to prevent perturbations in renal hemodynamics, correlate closely with kidney damage in hypertension. Moreover, maximal kidney injury in hypertension may require activation of a pool of nonrenal, systemic AT(1) receptors. These studies provide insight into precise mechanisms through which AT(1) receptor blockade influences the progression of hypertensive kidney disease.     

Is urodilatin the missing link in exercise-dependent renal sodium retention?

Schmidt, W., A. Bub, M. Meyer, T. Weiss, D. Schneider, N. Maassen, and W. G. Forssmann. Is urodilatin the missing link inexercise-dependent renal sodium retention? J. Appl.Physiol. 84(1): 123-128, 1998.The purpose of thepresent study was to investigate the behavior of plasma atrialnatriuretic peptide [ANP-(99126)] concentration([ANP]) and renal urodilatin [Uro; ANP-(95126)] excretion during and after exercise and theirpossible effects on renal Na⁺retention. Ten male subjects performed a cycle ergometer test for 60 min at 60% of maximum workload. Blood and urine samples were collectedbefore, during, and up to 24 h after exercise. During exercise, plasma[ANP] and renal Uro excretion were oppositely affected:whereas [ANP] increased from 46.5 ± 5.1 to 124.1 ± 10.6 pg/ml, urinary Uro excretion decreased from 120.8 ± 16.0 to49.5 ± 9.8 fmol/min and remained at a lower level until 1 h afterexercise. Glomerular filtration rate showed lowest values duringexercise (from 164.9 ± 15.3 to 75.8 ± 10.1 ml/min), and urineflow and the fractional excretion rate ofNa⁺(FE_Na⁺) andCl()had their nadir during the first hour after exercise. Positiverelationships were observed between Uro excretion andFE_Na⁺(P < 0.05) and, whereas a tendency toward a negative correlation was obtained between[ANP] andFE_Na⁺. It seemspossible that Uro may be, among other factors, involved in theexercise-related regulation of renalNa⁺ retention. The specific rolesUro and ANP play during exercise, however, remain to be investigated.

     

Synthesis and moisture absorption and retention activities of a carboxymethyl and a quaternary ammonium derivative of α,α-trehalose

Carboxymethyl α,α-trehalose (CMT) and a quaternary ammonium derivative of α,α-trehalose (QT) were successfully prepared, and their moisture absorption and retention activities were assessed. Results showed that both CMT and QT had better moisture absorption abilities at 43% and 81% relative humidity (RH) than α,α-trehalose. In addition, the two α,α-trehalose derivatives had better moisture retention abilities than α,α-trehalose under three humidity conditions: 81% RH, 43% RH, and under dry conditions. Therefore, carboxymethylation and quaternarization could improve the moisture absorption and retention abilities of α,α-trehalose. CMT and QT showed better moisture absorption ability and moisture retention ability than that of hyaluronan (HA), and could potentially find a use as moisture retention ingredient, for example, in cosmetics.     

Nutrient retention function of a stream wetland complex—A high-frequency monitoring approach

The ability of riverine ecosystems to retain nutrients depends on different hydrological, chemical and biological conditions including exchange processes between streams and wetlands. We investigated nutrient retention in a stream wetland complex on the time scale of daily hydrological exchange between both systems. Daily mass balances of NO₃-N, NH₄-N, TP and SRP were calculated with data obtained by two automated measurement stations in a stream reach upstream and downstream of a wetland. The pattern of hydrological exchange between stream and wetland was used to classify characteristic hydrological periods like floods, base and low flows. The nutrient retention function of the stream wetland complex varied considerably during phases of similar hydrologic conditions. Despite re-wetting measures in the wetland, an overall net export of all nutrients except for NH₄-N characterised the whole growing season. Nitrate retention occurred during summer flood (retention in the wetland, 23 kg NO₃-N d^?1, 17% of the input load) and low flow (retention in the stream, 1 kg NO₃-N d^?1, 2% of the input load). TP retention during summer could be assigned to sedimentation (0.7 kg TP d^?1, 7% during flooding in the wetland, 0.2 kg TP d^?1, 4% during low flow in the stream). SRP retention was only intermittent. We concluded that the nutrient retention of streams and wetlands can only be optimised by restoration measures that regard both systems as one functional unit in terms of nutrient retention.     

Regulation of pendrin by cAMP: possible involvement in β-adrenergic-dependent NaCl retention

The sodium-independent anion exchanger pendrin is expressed in several tissues including the kidney cortical collecting duct (CCD), where it acts as a chloride/bicarbonate exchanger and has been shown to participate in the regulation of acid-base homeostasis and blood pressure. The renal sympathetic nervous system is known to play a key role in the development of salt-induced hypertension. This study aimed to determine whether pendrin may partly mediate the effects of β adrenergic receptors (β-AR) on renal salt handling. We investigated the regulation of pendrin activity by the cAMP/protein kinase A (PKA) signaling pathway, both in vitro in opossum kidney proximal (OKP) cells stably transfected with pendrin cDNA and ex vivo in isolated microperfused CCDs stimulated by isoproterenol, a β-AR agonist. We found that stimulation of the cAMP/PKA pathway in OKP cells increased the amount of pendrin at the cell surface as well as its transport activity. These effects stemmed from increased exocytosis of pendrin and were associated with its phosphorylation. Furthermore, cAMP effects on the membrane expression and activity of pendrin were abolished by mutating the serine 49 located in the intracellular N-terminal domain of pendrin. Finally, we showed that isoproterenol increases pendrin trafficking to the apical membrane as well as the reabsorption of both Cl(-) and Na(+) in microperfused CCDs. All together, our results strongly suggest that pendrin activation by the cAMP/PKA pathway underlies isoproterenol-induced stimulation of NaCl reabsorption in the kidney collecting duct, a mechanism likely involved in the sodium-retaining effect of β-adrenergic agonists.     

Digesta retention time in the Galápagos tortoise (Chelonoidis nigra)

The retention time of food in the digestive tract of animals has important implications for digestive physiology. Retention time impacts digestive efficiency and among herbivores affects plant–animal interactions including herbivory and seed dispersal. Poorly studied yet iconic Galápagos tortoises are large-bodied generalist herbivores and ecosystem engineers which migrate seasonally. Potentially variable digesta retention times due to strong seasonal and altitudinal temperature gradients may influence tortoise seed dispersal abilities and rates of herbivory. We fed captive adult tortoises living in semi-natural conditions on Galápagos with inert particles and seeds from locally available fruits to determine whether seed size and ambient temperature influenced retention time. Median retention time varied from 6 to 28 days, with a mode of 12 days. Seed size had no effect on any of our measures of retention time, but ambient temperature was inversely correlated with retention times. Long retention time facilitates long distance seed dispersal by Galápagos tortoises, which may improve effectiveness. The effect of temperature, which may double from hot lowlands to cold highlands through the seasonal cycle, on tortoise digesta retention time will strongly influence seed dispersal efficiency and may influence patterns of food selection and migration in this species.     

Is sludge retention time a decisive factor for aerobic granulation in SBR?

This study investigated the role of sludge retention time (SRT) in aerobic granulation under negligible hydraulic selection pressure. Results showed that no successful aerobic granulation was observed at the studied SRTs in the range of 3-40 days. A comparison analysis revealed that hydraulic selection pressure in terms of the minimum settling velocity would be much more effective than SRT for enhancing heterotrophic aerobic granulation in sequencing batch reactor (SBR). It was shown that SRT would not be a decisive factor for aerobic granulation in SBR.     

pH optimum of the photosystem II H₂O oxidation reaction: effects of PsbO, the manganese-stabilizing protein, Cl- retention, and deprotonation of a component required for O₂ evolution activity

Hydroxide ion inhibits Photosystem II (PSII) activity by extracting Cl(-) from its binding site in the O(2)-evolving complex (OEC) under continuous illumination [Critchley, C., et al. (1982) Biochim. Biophys. Acta 682, 436]. The experiments reported here examine whether two subunits of PsbO, the manganese-stabilizing protein, bound to eukaryotic PSII play a role in protecting the OEC against OH(-) inhibition. The data show that the PSII binding properties of PsbO affect the pH optimum for O(2) evolution activity as well as the Cl(-) affinity of the OEC that decreases with an increasing pH. These results suggest that PsbO functions as a barrier against inhibition of the OEC by OH(-). Through facilitation of efficient retention of Cl(-) in PSII [Popelkova, H., et al. (2008) Biochemistry 47, 12593], PsbO influences the ability of Cl(-) to resist OH(-)-induced release from its site in the OEC. Preventing inhibition by OH(-) allows for normal (short) lifetimes of the S(2) and S(3) states in darkness [Roose, J. L., et al. (2011) Biochemistry 50, 5988] and for maximal steady-state activity by PSII. The data presented here indicate that activation of H(2)O oxidation occurs with a pK(a) of ～6.5, which could be a function of deprotonation of one or more amino acid residues that reside near the OEC active site on the D1 and CP43 intrinsic subunits of the PSII reaction center.     

Study of the retention properties of warfarin enantiomers on a β-cyclodextrin polymeric support

High-performance liquid chromatography was used to study the retention properties of (R)- and (S)-warfarins on a silica support coated with a β-cyclodextrin polymer. The influence of the methanol content of the acetate buffer eluent was investigated at pH 4. The measure of the variations of retention time with temperature enables one to determine the enthalpy and the entropy of adsorption. The plot of the two thermodynamic functions shows a minimum around 30% (v/v) methanol. At low methanol contents, the decrease of the hydrophobic interactions with increasing methanol content explains the decrease of the enthalpic and entropic terms. Above 40% (v/v) methanol, the decrease of the adsorption enthalpy absolute value is due to the solvation by the organic component. From the analysis of peak shape in mass-overload conditions, the column capacity toward each enantiomer was determined. A lower capacity was found toward (S)-warfarin, the more retained enantiomer. Peak shape analysis in mass-overload conditions was used to determine the adsorption isotherm. A Langmuir-type adsorption isotherm accounts well for the experimental data.