Original Article

The pancreas taken from the frog (Rana nigromaculata) was fixed in 1% OsO_4 and sliced into ultrathin sections for electron microscopic studies. The following observations were made: 1. A great \u27number of minute granules found in the cytoplasm of a pancreatic cell were called the microsomes, which were divided into two types, the C-microsome and S-microsome. 2. Electron microsopic studies of the ergastoplasm showed that it is composed of the microsome granules and A-substance. The microsomes were seen embedded in the A-substance which was either filamentous or membranous. The membranous structure, which was called the Am-membrane, was seen to form a sac, with a cavity of varying sizes, or to form a lamella. 3. The Am-membrane has close similarity to α-cytomembrane of Sjostrand, except that the latter is rough-surfaced. It was deduced that the Am-membrane, which is smooth-surfaced, might turn into the rough-surfaced α-cytomembrane. 4. There was the Golgi apparatus in the supranuclear region of a pancreatic cell. It consisted of the Golgi membrane, Golgi vacuole and. Golgi vesicle. 5. The mitochondria of a pancreatic cell appeared like long filaments, and some of them were seen to ramify. 6. The membrane of mitochondria, i. e. the limiting membrane, consisted of the Ammembrane. The mitochondria contained a lot of A-substances, as well as the C-microsomes and S-microsomes. When the mitochondria came into being, there appeared inside them chains of granules, which appeared like strips of beads, as the outgrowths of the A-substance and the microsome granules attached to the Am-membrane. They are the so-called cristae mitochondriales. 7. The secretory granules originate in the microsomes. They came into being when the microsomes gradually thickened and grew in size as various substances became adhered to them. Some of the secretory granules were covered with a membrane and appeared like what they have called the intracisternal granule of Palade.It seemed that this was a phenomenon attendant upon the dissolution and liqutefaction of the secretory granule. 8. Comparative studies were made of the ergastoplasm of the pancreatic cells from the frogs in hibernation, the frogs artificially hungered, the frogs which were given food after a certain period of fasting, the frogs to which pilocarpine was given subcutaneously, and the very young, immature frogs. The studies revealed that the ergastoplasm of the pancreatic cells greatly varied in form with the difference in nutritive condition and with different developmental stages of the cell. The change in form and structure occured as a result of transformation of the microsomes and A-substance. The ergastoplasm, even after it has come into being, might easily be inactivated if nutrition is defective. The ergastoplasm is concerned in the secretory mechanism, which is different from the secretory phenomenon of the secretory granules. It would seem that structurally the mitochondria have no direct relation to this mechanism

Sinking particles in the photic zone: relations with biogeochemical properties in different sectors of the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC)-Brazil

35 pages, 18 figures, 2 tables.-- This is an open access article distributed under the terms of the Creative Commons licenseOver the last decades, regional climate changes, erosion, and heightened agricultural runoffs have increased nutrient and particle input in rivers, unbalancing the biogeochemical cycle of this suspended material along estuaries. In this context, particle fluxes in the euphotic zone, a very productive layer and important to maintain the food chain and estuarine preservation, require better understanding. This study aims to evaluate particle sedimentation fluxes in the photic zone of the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC), considering sectors under different salinities and trophic statuses. A cylindrical sediment trap was installed at the base of the photic layer to measure particle fluxes and photopigments. Meanwhile, water samples were taken to measure temperature, salinity, pH, dissolved oxygen, and nutrients. Valo Grande (a freshwater domain) showed high nutrient concentrations, in which high fluxes of phaeopigments and chlorophyll-b highlighted the contribution of vegetable detritus to particle sinking. In the Batatais mangrove creek, the high fluxes of organic particles (675.32 mg m-2 d-1) and chlorophyll-a (98.40 mg m-2 d-1) evinced a high contribution of microplankton to carbon sinking. During the winter of 2018, flocculation processes were evinced in the flood tide of the Cananéia Bay as an important driver of sedimentation rates, with considerable fluxes of inorganic particles (1161.20 mg m-2 d-1) and chlorophyll-a (83.27 mg m-2 d-1). In the summer of 2019, we observed a lower flux in total particles (451.24 mg m-2 d-1) in a period of haline stratification. In the Ararapira Channel, the lowest organic particle fluxes (<100 mg m-2 d-1) were associated with ultra-oligotrophic conditions, indicating a low influence of microplankton on sinking particles. These findings suggest that freshwater input, tidal variation, and trophic status are relevant controls of sinking particles in different CIELC sectorsThe authors would like to thank the financial support of CNPq (310624/2016-9-7), FAPESP (2020/16485-7 and 2018/08738 -2), and CAPES (Financing Code 001)Peer reviewe

Thermal and microchemical characterisations of CaSO4-SiO2 investment materials for casting jewellery alloys

Differential thermal analysis (DTA) and thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to study the thermal decomposition of calcium sulphate in the CaSO4 (25 wt%)-bonded silica investment which is the commonly used material for casting jewellery gold-based alloys. The thermal decomposition of CaSO4 generates sulphur dioxide, leads to gas porosity in the molten gold-based alloys and therefore, defective jewellery products. This latter reaction was studied as a function of the temperature and atmosphere (air, argon and argon-5% hydrogen). in order to simulate, as for as possible, different casting conditions used by the jewellery industry. Furthermore, special attention was given to the effect of the presence of Zn, Cu2O. CuO and Ag2O on the thermal decomposition of CaSO4. DTG-TG results confirmed that the temperature of the thermal decomposition of CaSO4 bonded with silica was lower with respect to the nearly pure CaSO4. Unfortunately, it was very close to the casting temperature of some typical gold alloys. in addition, the temperature of the decomposition was further lowered when inert and reducing atmospheres are used, as well as in the presence of ZnO, Cu2O. CuO and Ag2O. (C) 1998 Elsevier Science B.V