Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin

We measured the efflux of 5-hydroxytryptamine (5-HT, serotonin) from an intact secretory granule extracted from the mast cell of the beige mouse. The efflux was measured with amperometry after rupture of the granule membrane was triggered by electroporation. We determined the diffusivity of 5-HT within the secretory granule to be 2.0 x 10(-8) cm2 s(-1) when the granule is in contact with a physiological saline and found that this diffusivity depends on the valence of the cation in the external electrolyte. There is a fivefold increase in the diffusion coefficient of 5-HT determined in CsCl (150 mM, pH 7.2) at 3.7 x 10(-8) cm2 s(-1) compared to that determined in histamine dihydrochloride (Hi, 100 mM at pH 4.5) at 0.7 x 10(-8) cm2 s(-1). We found that the rate of expansion of the granule matrix observed in physiological medium correlates with the efflux of 5-HT, and that the rate of swelling of the matrix and the efflux depend on the microviscosity within the granule matrix and not the bulk viscosity of the external solution. The low diffusivity of 5-HT (approximately 500-fold less than in the bulk), the observation that the valence of the counterion affects this diffusivity, and the relationship between the volume changes of the matrix and the efflux suggest that 5-HT is released from the granule by ion exchange. We discuss the implications of this result for exocytotic release in mast cells and propose that an ion exchange mechanism could control the rate of release in other secretory systems.     

Effects of fish meal and sodium bentonite on daily gain, wool growth, carcass characteristics, and ruminal and blood characteristics of lambs fed concentrate diets

We evaluated the effects of replacing some soybean meal (SBM) protein with fish meal (FM) protein in diets adequate and slightly deficient in CP, with or without .75% sodium bentonite (NaB) on performance and ruminal and blood metabolites of individually fed Suffolk lambs. Diets were based on corn, SBM, and cottonseed hulls. In Exp. 1, five lambs were assigned to each of the three dietary treatments (11% CP with 3% FM, 13% CP with 0 or 3% FM). Lambs fed diets that contained 11% CP with 3% FM or 13% CP with 0% FM had similar DMI and ADG. Gain and feed efficiency were slightly improved (P = .18) by the 13% CP diet with 3% FM. In Exp. 2, 32 lambs were assigned to four dietary treatments (13.5% CP of DM) in a 2 x 2 factorial arrangement (0 or 3% FM, and 0 or .75% NaB on an as-fed basis). The DMI and ADG were increased (P < .05) by FM and NaB supplementation. Interactions (P < .05) revealed that NaB increased DMI, ADG, gain per feed (g/kg of DMI), and plasma urea N concentration in the absence of FM but not in the presence of FM in the diet. Neither FM nor NaB influenced (P = .25) wool growth. Total ruminal VFA were increased (P < .06) by FM and NaB. Differences in mineral content of phalanx bone, liver, and kidney were small and may be related to the mineral content of diets and the effect of NaB on mineral solubilities. Similar DMI and ADG of lambs fed FM and NaB separately and in combination suggest that their beneficial effect is not additive.     

Mode beating and spontaneous emission noise effects in avariable-waveguide model for the dynamics of gain-guided semiconductorlaser arrays

The spatio-temporal dynamics of gain-guided semiconductor laser arrays are studied by means of a generalized variable-waveguide model deduced from the semiclassical Maxwell-Bloch equations including spontaneous emission noise. Lateral confinement of the optical field is provided by the permittivity distribution associated with the spatial distribution of carriers. The laser field is then described by a set of noise-driven rate equations for the complex amplitudes of the slowly varying modal functions coupled to the carrier distribution evolution, which is sensitive to mode beating effects. The model is applied to a four-stripe gain-guided array, where the influences of spontaneous emission noise and mode beating on the final state are discussed. We show that, in this model, mode beating plays a determinant role in the dynamic behavior of the system, while spontaneous emission noise does not affect this behavior except during transient evolution     

Role of T cells and germinal center formation in the generation of immune responses to the thymus-independent carbohydrate dextran B512

Immunization with the thymus-independent (TI) Ag native dextran (DX) B512 induces germinal center (GC) formation in the spleen. However, despite this GC formation, the anti-DX response is poor, and no affinity maturation can be observed. Using cholera toxin (CT) as an adjuvant, splenic as well as humoral responses to DX are improved. In this study, we investigated immune responses against DX in mice lacking TNF receptor I and in athymic mice. The adjuvant effect of CT on these responses was also evaluated. Mice lacking the TNF receptor I allowed us to investigate the role of follicular dendritic cell networks and GC formation in the spleen for the generation of Ab responses to DX, whereas we could investigate the role of T cells in GC development to TI Ags using athymic mice. We found that the humoral immune response to TI DX B512 was not dependent upon T cells or the presence of GCs, although GC development occurred after DX immunization. However, T cells were required for this GC formation, since athymic mice could not develop GCs after immunization with DX. We also show that even if CT is able to directly activate B cells when administered as an adjuvant, the major effect may require T cell participation; this is also the case for TI Ags. In contrast, CT adjuvancy is independent of GC formation.     

Evidence for auditory temporal distinctiveness: Modality effects in order and frequency judgments.

Two new, long-lasting phenomena involving modality of stimulus presentation are documented. In one series of experiments we investigated effects of modality of presentation on order judgments. Order judgments for auditory words were more accurate than order judgments for visual words at both the beginning and the end of lists, and the auditory advantage increased with the temporal separation of the successive items. A second series of experiments investigated effects of modality on estimates of presentation frequency. Frequency estimates of repeated auditory words exceeded frequency estimates of repeated visual words. The auditory advantage increased with frequency of presentation, and this advantage was not affected by the retention interval. These various effects were taken as support for a temporal coding assumption, that auditory presentation produces a more accurate encoding of time of presentation than does visual presentation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinct mechanisms of plasma LDL lowering by dietary fiber in the guinea pig: specific effects of pectin, guar gum, and psyllium

Pectin (PE), guar gum (GG), and psyllium (PSY) lower plasma low density lipoprotein (LDL) cholesterol concentrations in guinea pigs with different orders of magnitude by inducing defined alterations in hepatic cholesterol homeostasis (Fernandez et al. 1994. Am. J. Clin. Nutr. 59: 869-879; 61: 127-134 and 1995. J. Lipid Res. 36: 1128-1138). To further explore specific mechanisms responsible for the differences in plasma and hepatic cholesterol lowering, the effects of these fibers were evaluated on cholesterol absorption, hepatic cholesterol 7 alpha-hydroxylase activity, the rate-limiting enzyme of bile acid synthesis, and in vivo LDL transport to target specific primary and secondary mechanisms accounting for the observed responses. Fibers were fed with physiological (0.04%), low cholesterol (LC), or pharmacological high cholesterol (HC) (0.25%) levels to assess whether cholesterol intake influences plasma LDL lowering mechanisms. Intake of PE, GG, or PSY with LC or HC diets lowered plasma and hepatic cholesterol concentrations (P < 0.001). PE and PSY up-regulated 7 alpha-hydroxylase activity 3-fold with LC and PE by 5-fold with HC diets. In contrast, GG intake had no effect on 7 alpha-hydroxylase activity. Cholesterol absorption was reduced 30% by PE intake while no differences were found between control and PSY groups. GG reduced cholesterol absorption only with HC diets. Intake of PE, GG, or PSY with HC diets resulted in faster plasma LDL fractional catabolic rates (FCR) (P < 0.01) with no effect on LDL apoB flux rates (FR) or pool size, suggesting that fiber reduced LDL cholesterol concentration without decreasing the number of LDL particles. In addition to reducing LDL apoB FR, PE and PSY increased LDL FCR with HC diets while GG effects were limited to lowering LDL apoB FR. These results indicate that the distinctive reductions in hepatic cholesterol induced by PE, GG, and PSY associated with plasma cholesterol lowering result from different mechanisms specific to each fiber and that the levels of dietary cholesterol contribute to the different metabolic responses.     

Multilayer piezoelectric devices based on PZT

A PZT 53/47 was obtained by a modified chemical route. Small-particle-size powders were allowed to obtain high solid content, non-aqueous slips with Newtonian behaviour. The use of both the tape-casting technique and the common multilayer ceramic fabrication process led to a high-density multilayer ceramic body without cracks or delaminations, and a homogeneous microstructure. The architecture of multilayer piezoelectrics has an important effect on the clamping of resonance modes, particularly on planar modes, by modifying the nature of the electrode and the effect of the polarization procedure. This fact is corroborated by the dielectric and piezoelectric properties measured.     

Effects of long-term storage on properties of an alginate impression material

OBJECTIVE: To determine whether angiotensinogen (AGT) and angiotensin II type 1 (AT1) receptor genes contribute to the development of arterial hypertension in members of French Caucasian families and in subjects with hypertension associated with non-insulin-dependent diabetes mellitus (NIDDM). METHODS: Sibpair linkage analyses were performed with microsatellites near the AGT and AT1 receptor genes in 179 hypertensive sibpairs from 69 NIDDM kindreds. In addition, population/association studies were performed with the M235T and T174M polymorphisms of the AGT gene, and the A1166C polymorphism of the AT1 receptor gene. RESULTS: No evidence for linkage between the AGT and AT1 receptor loci and hypertension was observed. In addition, the distributions of genotypes of AGT and AT1 receptor gene polymorphisms did not differ significantly among a group of unrelated individuals with both hypertension and NIDDM (n = 188) and three groups of unrelated control subjects with NIDDM (n = 117), hypertension (n = 75) or none of these conditions (n = 125). CONCLUSIONS: These results suggest that the AGT and AT1 receptor genes are not major genetic determinants of hypertension associated with NIDDM in this population, although we can not exclude the possibility that these loci make a minor contribution in a polygenic context.