Role of acidic stores in secretory epithelia

There is growing evidence that intracellular calcium plays a primary role in the pathophysiology of the pancreas in addition to its crucial importance in major physiological functions. Pancreatic acinar cells have a remarkably large amount of Ca²⁺ stored in both the endoplasmic reticulum (ER) and the acidic stores. The vast majority of the classical ER Ca²⁺ store is located in the basal part of the acinar cells with extensions protruding into the apical area, however, the acidic stores are exclusively located in the secretory granular area of the cells. Both types of Ca²⁺ store respond to all three intracellular Ca²⁺ messengers – inositol trisphosphate (InsP₃), cyclic-ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). The two stores interact with each other via calcium-induced calcium release; however, they can be separated using pharmacological tools. The ER relies on sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) that can be blocked by the specific inhibitor thapsigargin. The acidic store requires a low pH that can be modified by blocking vacuolar H⁺-ATPase.     

Cloning and Use of a Coral 36B4 Gene to Study the Differential Expression of Coral Genes Between Light and Dark Conditions

This paper aims to validate reference genes for gene expression studies between light and dark conditions in the scleractinian coral Stylophora pistillata for future gene expression studies of the “light-enhanced calcification” phenomenon. For this purpose, we cloned, sequenced, and characterized a candidate reference gene, the 36B4 gene from the coral S. pistillata, and validated 36B4 and β-actin as reference genes. To illustrate the future applications of these reference genes, we tested the dark and light expression of two photosynthetic genes (Rubisco and D1 protein of the photosystem II) and two genes encoding proteins involved in calcium transport for coral calcification (a calcium ATPase and a calcium channel). Results show that both photosynthetic genes are enhanced during the light when standardized against 36B4 and β-actin, whereas the two genes encoding proteins involved in calcium transport are not differentially expressed between light and dark conditions. The characterization of a coral 36B4 and the establishment of such valid reference genes will be useful for future gene expression studies between diverse conditions (aposymbiotic/symbiotic, stress/control, light/dark conditions) in scleractinian corals. Nucleotide sequence of the coral 36B4 gene cloned in this study is available in the Genbank database under the accession number EU069460.     

酸性蛋白酶在酱油酿造中的应用研究

低盐固态酿造酱油,在发酵过程中pH偏酸。采用在发酵中期添加适量的酸性蛋白酶,弥补在制曲时米曲霉所产生的酸性蛋白酶活性的不足。增强在酸性环境下对蛋白质的分解作用,提高原料蛋白质的利用率,增产酱油8.0％左右。     

SGP28, a novel matrix glycoprotein in specific granules of human neutrophils with similarity to a human testis-specific gene product and to a rodent sperm-coating glycoprotein

A novel 28 kDa glycoprotein was purified from exocytosed material from human neutrophils and its primary structure partially determined. Degenerate oligonucleotide primers were used to amplify cDNA clones from a human bone marrow cDNA library. The deduced 245 amino acid sequence of the 2124 bp full-length cDNA showed high degrees of similarity to the deduced sequences of the human gene TPX-1 and of sperm coating glycoprotein from rat and mouse. Subcellular fractionation of human neutrophils indicated that the protein is localized in specific granules. The protein was named SGP28 (specific granule protein of 28 kDa).     

Muscimol Potentiation of Acidic Amino Acid Release from Cerebellar Synaptosomes Is Chloride Dependent

In previous studies we have shown that the depolarization-induced release of preaccumulated acidic amino acids and newly synthesized glutamate from cerebellar synaptosomal preparations is potentiated by γ-aminobutyric acid (GABA) agonists through a GABAergic presynaptic mechanism. Here we report a systematic analysis of the ionic requirements of the potentiating effect of muscimol on the high K⁺-evoked release of d-[³H]aspartate. Our studies show that: Ca²⁺, Na⁺, and Mg²⁺ are not required for muscimol to exert its effect; a depolarizing concentration of K⁺ is a necessary, but not sufficient, condition to observe the presynaptic effect in question; and a minimal Cl^- concentration (50–70 mM) is also required. A possible model based on these findings is proposed.     

Purified Rat Brain Microvessels Exhibit Both Acid and Neutral Sphingomyelinase Activities

Purified rat brain microvessels have been shown to hydrolyze radiolabeled sphingomyelin by means of two different enzyme systems. Enzymatic activity was detected at pH 7.4 and was strongly stimulated by magnesium or manganese and inhibited by calcium. Activity at pH 5.1 could also be found and was not dependent on any of these cations. At neutral pH and in the presence of magnesium, the rate of sphingomyelin hydrolysis did not exhibit a linear relationship with protein concentration. In contrast, increasing the protein concentration from 0.05 to 0.5 mg/ml resulted in a constant increase of sphingomyelin hydrolysis at pH 5.1. Kinetic parameters of both neutral and acid activities have been determined and were similar in magnitude to values reported previously for neural sphingomyelinases. This work demonstrates the occurrence of a neutral sphingomyelinase activity in purified rat brain microvessels, an observation raising the question of its role at the level of the blood-brain interface.     

Schistosoma mansoni: histochemical analysis of the postacetabular gland secretion of cercariae

Contents of the funduses and ducts of the postacetabular glands of Schistosoma mansoni cercariae, the secreted deposits, and the surface film were compared by their histochemical reactions. Techniques for carbohydrate-containing substances, neutral and acid mucosubstance, proteins and amino acids, and enzymes were used. The secretion reacted differently before (within the glands) and after (in secreted deposits) emission.Before emission, the postacetabular gland contents reacted as a neutral mucosubstance containing periodate-engendered and periodate-reactive aldehydes rich in vic-glycols or their substituted amines, probably hexoses other than glucose, such as fucose or galactose. No reactions of significance were observed for acid groups or for glycogen or lipids. In this state, the secretion is termed mucigen.After emission, the secretion stained not only as mucigen, but also as acid mucosubstance, apparently sialomucin. After emission, it is termed mucin.It is probable that acid radicals were present in mucigen but were masked stearically by the presence of adjacent neutral radicals or basic proteins. The surface film reacted as both a neutral and an acid mucosubstance. Evidence suggested that the film itself was neutral and that the reaction for acid mucosubstance was from an overlay of mucin secreted from the postacetabular glands.Proteins and amino acids, especially arginine, and some tyrosine and tryptophan were indicated in mucigen and in mucin by the histochemical tests. There was no histochemical evidence of enzymes. Secretion of the postacetabular glands is concluded from histochemical reactions, as from earlier chromatographic data (Stirewalt and Evans 1960), to be a carbohydrate-protein-lipid complex.