Effects of 3,5-Dihalogenated-4-hydroxybenzonitriles on the Activity of Mitochondria From White Potato Tubers

Effects of the herbicide 3,5-diiodo-4-hydroxybenzonitrile (ioxynil), and its dibromo and dichloro analogs, upon the respiration of mitochondria isolated from white potato tubers (Solanum tuberosum L.) were investigated. Mitochondrial-mediated oxygen uptake was monitored polarographically with a platinum oxygen electrode.     

Rule-based production planning in flexible manufacturing systems

Production planning in flexible manufacturing may require the solution of a large-scale discrete-event dynamic stochastic optimization problem, due to the complexity of the system to be optimized, and to the occurrence of discrete events (new orders and hard failures). The production planning problem is here approached for a multistage multipart-type manufacturing shop, where each work cell can share its processing time among the different types of parts. The solution of this problem is obtained by an open-loop-feedback control strategy, updated each time a new event occurs. At each event time, two coupled problems are solved: 1) a product-order scheduling problem, conditioned on estimated values of the production capacities of all component work cells; and 2) a production-capacity planning problem, conditioned on predefined sequences of the product orders to be processed. In particular, the article aims at defining a production planning procedure that integrates both analytical tools, derived from mathematical programming, and knowledge-based rules, coming from experience. The objective is to formulate a hybrid (knowledge-based/analytical) planning architecture, and to analyze its use for multicell multipart-type manufacturing systems.     

Effect of cytoplasmic acidification on the membrane potential of T-lymphocytes: Role of trace metals

Summary The effect of lowering intracellular pH on the membrane potential (E _m ) of rat thymic lymphocytes was studied using the potential-sensitive dyebis-oxonol. Cells were acid loaded by addition of the electroneutral K⁺/H⁺ exchanging ionophore nigericin. Acidification to pH 6.3 in Na⁺-free solution resulted in a biphasic change inE _m : an early transient hyperpolarization followed by a sustained depolarization. These changes were associated with a rise in cytosolic free Ca²⁺ ([Ca²⁺] _i ). The hyperpolarization was eliminated when the change in [Ca²⁺] _i was prevented using BAPTA, an intracellular Ca²⁺ chelator. Moreover, a similar hyperpolarization was elicited by elevation of [Ca²⁺] _i at physiological pH _i using ionomycin, suggesting involvement of Ca²⁺-activated K⁺ channels. In contrast, the depolarization phase could not be mimicked by raising [Ca²⁺] _i with ionomycin. However, intracellular BAPTA effectively inhibited the acidificationinduced depolarization. Inhibition was also obtained by extracellular addition of EGTA or dithiothreitol, even when the external free Ca²⁺ concentration remained unaltered. These observations suggested a possible role of contaminating trace metals. Cytosolic acidification is envisaged to induce intracellular accumulation of one or more trace metals, which induces the observed changes inE _m . Accordingly, similar changes inE _m can be induced without acidification by the addition of small amounts of Cu²⁺ to the medium. The ionic basis of theE _m changes induced by acidification and the significance of these observations are discussed.     

Fine structure of the excretory system of the deep posterior (Ebner's) salivary glands of the human tongue

Human deep posterior lingual glands (von Ebner's glands) are located beneath the circumvallate papillae. They are formed by tubuloalveolar adenomeres, intercalated ducts and excretory ducts coming together in the main excretory duct. The tubuloalveolar cells, pyramid-shaped, show large and dense secretory granules (clear cored) throughout the cytoplasm, rare basal folds and packed cisternae of rough endoplasmic reticulum (RER) at the basal pole. The columnar cells of the intercalated ducts are arranged in a monolayer. They are characterized by dense, clear-core secretory granules (mostly in the apical cytoplasm), a basal nucleus, well-developed RER and Golgi apparatus, and thin filaments distributed in supra- and perinuclear cytoplasm. Striated ducts are absent. Excretory ducts, coming together in the main duct, are lined by a bistratified epithelium. The inner layer consists of columnar cells showing bundles of tonofilaments with scarce secretory activity. The outer layer is composed of basal cells lying on the basal lamina. The main excretory duct, which opens at the bottom of the vallum, shows a stratified epithelium. The outer side is composed of 2-3 layers of malpighian cells lying on the basal lamina. The inner side consists of a single layer of cuboidal-columnar cells with dense apical granules and well-developed organelles synthesizing and condensing secretions. These cells interpolate with goblet cells, rare mitochondria-rich cells, ciliated cells and numerous small globous cells showing a clear matrix and lacking secretory granules. The cilia show a 9 + 2 microtubular structure with basal bodies provided with striated rootlets. Myoepithelial cells surround with their processes the basal portions of the secretory cells and the intercalated ducts. The conclusions concern some comparative aspects and some hypothesis on the functional role of goblet cells, ciliated cells and epithelial cells lining the different ducts, also in relation to the final secretory product.