Effect of propylgallate on a dipalmitoylphosphatidylglycerol and calcium mixture

Effect of propylgallate (PrG) on the thermotropic behavior of mixtures of dipalmitoylphosphatidylglycerol (DPPG) and Ca2+ was studied by means of differential scanning calorimetry (DSC). In the case of DPPG or DPPG/Ca (molar ratio, 15 : 1), the transition temperature (Tm) of the main transition and the subtransition decreased from 40 degrees C to 29 degrees C and from 29 degrees C to 20 degrees C, respectively, with an increase in the concentration of PrG. The addition of PrG to the DPPG/Ca mixture induced a shoulder on the high temperature side in the reheating scan. Neither PrG nor low concentrations of Ca2+ bind to the Lc phase of DPPG. When the molar ratio of DPPG to Ca was 1 : 1, the subtransition did not occur, that is, only the main transition (Tm = 90 degrees C) appeared. The Tm of the main transition was slightly affected by PrG. On the addition of PrG, another metastable endothermic transition peak (Tm = 78 degrees C) appeared. It is concluded that Ca2+ and PrG inhibit each other's binding.     

The role of calcium on protein secretion of the albumen gland in Helisoma duryi (Gastropoda)

Abstract. The albumen gland of the freshwater pulmonate snail Helisoma duryi produces and secretes the perivitelline fluid, which coats fertilized eggs and provides nutrients to the developing embryos. It is known that perivitelline fluid secretion is stimulated by dopamine through the activation of a dopamine D₁‐like receptor, which in turn stimulates cAMP production leading to the secretion of perivitelline fluid. This paper examines the glandular release of perivitelline fluid and provides evidence for the role of Ca²⁺ in the regulated secretion of perivitelline fluid based on protein secretion experiments and inositol 1,4,5‐trisphosphate assays. Dopamine‐stimulated protein secretion by the albumen gland is reduced in Ca²⁺‐free medium or in the presence of plasma membrane Ca²⁺ channel blockers, although the Ca²⁺ channel subtype involved is unclear. In addition, dopamine‐stimulated protein secretion does not directly involve phospholipase C‐generated signaling pathways and Ca²⁺ release from intracellular stores. Sarcoplasmic/endoplasmic reticulum Ca²⁺‐ATPase inhibitors had little effect on protein secretion when applied alone; however, they potentiated dopamine‐stimulated protein secretion. Dantrolene, an inhibitor of ryanodine receptors, 8‐(N,N‐diethylamino)‐octyl‐3,4,5‐trimethoxybenzoate hydrochloride, a nonspecific inhibitor of intracellular Ca²⁺ channels, and 2‐aminoethyldiphenylborate, an inhibitor of inositol 1,4,5‐trisphosphate receptors, did not suppress protein secretion, suggesting Ca²⁺ release from internal stores does not directly regulate protein secretion. Thus, the influx of Ca²⁺ from the extracellular space appears to be the major pathway mediating protein secretion by the albumen gland. The results are discussed with respect to the role of Ca²⁺ in controlling exocytosis of proteins from the albumen gland secretory cells.     

Comparative studies on the statoblasts of higher phylactolaemate bryozoans

Statoblasts of five higher phylactolaemates were compared morphologically. As a result, they were divided into two groups: Group I comprising Lophopus crystallinus, Lophopodella carteri, and Pectinatella gelatinosa, and Group II comprising Pectinatella magnifica and Cristatella mucedo. These two groups are thought to represent independent evolutionary series. In Group I and in P. magnifica, the statoblasts are curved to varying degrees after the manner of a saddle. When the dorsal and ventral valves are flattened, therefore, the contour is different between the two. In Group I, the outermost layer of a mature statoblast is hard-gelatinous and basophilic; it remains intact after the statoblast is set free. The statoblast does not float until it is dry, and the float is similar in size on both valves. In Group II, a mature statoblast is covered by a softgelatinous basophilic layer, which decays after the statoblast is released. The statoblast floats without drying, and the float is better developed on the dorsal valve than on the ventral. Moreover, in the members of Group II, large yolk granules are first formed, followed by much smaller yolk granules. When their statoblasts are treated with KOH, the shell is separated completely into two valves. These characters are common to many lower phylactolaemates. By contrast, in L. carteri and P. gelatinosa, the yolk granules are uniformly small and the capsule proper resists KOH treatment. On these points, L. crystallinus is somewhat different from these two species, suggesting its primitive nature.     

The Ha locus of wheat: identification of a polymorphic region for tracing grain hardness in crosses.

The grain softness proteins or friabilins are known to be composed of three main components: puroindoline a, puroindoline b, and GSP-1. cDNAs for GSP-1 have previously been mapped to group-5 chromosomes and their location on chromosome 5D is closely linked to the grain hardness (Ha) locus of hexaploid wheat. A genomic DNA clone containing the GSP-1 gene (wGSP1-A1) from hexaploid wheat has been identified by fluorescent in situ hybridization as having originated from the distal end of the short arm of chromosome 5A. A genomic clone containing the gene (wGSP1-D1) was also isolated from Aegilops tauschii, the donor of the D genome to bread wheat. There are no introns in the GSP-1 genes, and there is high sequence identity between wGSP1-A1 and wGSP1-D1 up to 1 kb 5' and 300 bp 3' to wGSP1-D1. However, regions further upstream and downstream of wGSP1-D1 share no significant sequence identity to corresponding sequences in wGSP1-A1. These regions therefore identified potentially valuable sequences for tracing the Ha locus through assaying polymorphic DNA sequences. The sequence from 300 to 500 bp 3' to wGSP1-D1 (wGSP1-D13) was mapped to the Ha locus in a mapping population. wGSP1-D13 was also tightly linked to genes for puroindoline a and puroindoline b which have been previously mapped to be at the Ha locus. In addition wGSP1-D13 was used to detect RFLPs between near isogenic soft and hard Falcon lines and in a random selection of soft and hard wheats.