Evidence that fasting can induce a selective loss of uncoupling protein from brown adipose tissue mitochondria of mice

The effects of fasting and refeeding on the concentration of uncoupling protein in brown adipose tissue mitochondria have been investigated in mice. Fasting mice for 48 h led to a large decrease in the total cytochrome oxidase activity of the interscapular brown fat pad. Mitochondrial GDP binding and the specific mitochondrial concentration of uncoupling protein also fell on fasting. After 24 h refeeding both GDP binding and the mitochondrial concentration of uncoupling protein were normalized, but there was no alteration in the total tissue cytochrome oxidase activity. Fasting appears to induce a selective loss of uncoupling protein from brown adipose tissue mitochondria, which is rapidly reversible on refeeding.     

True absorption and endogenous fecal excretion of manganese in relation to its dietary supply in growing rats

A conventional balance study with 48 male weanling rats was conducted to determine true absorption and endogenous fecal excretion of manganese (Mn) in relation to dietary Mn supply, following the procedures of a previously adapted isotope dilution technique. After 10 d on a diet with 1.5 ppm Mn, eight animals each were assigned to diets containing 1.5, 4.5, 11.2, 35, 65, or 100 ppm Mn on a dry-matter basis. Three days later, each rat was given an intramuscular⁵⁴Mn injection and kept on treatment for a balance period of 16 d. Apparent Mn absorption assessed for the final 8 d, averaged 8.6 μg/d without significant treatment effects, although Mn intake ranged from 18.6 to 1200 μg/d, in direct relation to dietary Mn concentrations. Mean fecal excretion of endogenous Mn for the six treatments was 0.9, 2.7, 7.4, 11.0, 16.3, and 17.7 μg/d, respectively. These values delineate the rates to which true absorption exceeded apparent rates. True absorption, as percent of Mn intake, averaged 28.7, 15.9, 11.7, 6.1, 3.4, and 2.0, respectively, as compared with mean values of 23.9, 10.9, 6.2, 3.4, 1.2, and 0.5 for percent apparent absorption. It was concluded that both true absorption and endogenous fecal excretion markedly responded to Mn nutrition and that the reduction in the efficiency of true absorption was quantitatively the most significant homeostatic response for maintaining stable Mn concentrations in body tissues.     

In vitro propagation of cassava (Manihot esculenta Crantz)

A method is presented for the rapid in vitro propagation of cassava (Manihot esculenta Crantz). Nodal explants were induced to grow as multiple-shoot cultures on a medium containing 1.0 M 6-benzylamino purine (BAP), supplemented with 0.25 M -naphthaleneacetic acid (NAA). Nodes were removed from the shoots after three weeks of growth and subcultured on fresh culture medium. An average of 7.0 nodes were produced from each explanted node after three weeks in culture. Nodal explants were transferred to a medium containing 2.5 M indole-3-butyric acid (IBA) to improve root initiation on the developing plantlets. Plant establishment was possible upon transfer to soil. In vitro propagation offers enhanced rates of multiplication over more conventional methods of propagation. In addition, in vitro propagation facilitates the storage and international exchange of cassava germplasm.     

Somatic embryogenesis and plant regeneration from immature inflorescence segments of Coix lacryma-jobi

Callus was obtained from segments of immature inflorescence of Coix lacryma-jobi cultured on N6 medium containing 1–2 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 3–5% sucrose. Plantlets were regenerated when embryogenic calluses were transferred onto MS medium with 0.5 mg/l kinetin and 0.01 mg/l naphthaleneacetic acid (NAA). Regenerated plants had the diploid chromosome number (2n=20).     

Anther and tissue culture-induced grain chalkiness and associated variants in rice

Rice, Oryza sativa, plants regenerated from anther culture with and without in vitro selection pressure were evaluated for chalky seed. Progeny evaluated included 21 spontaneously doubled haploids selfed 4 times, progeny from plants regenerated from S-aminoethylcysteine resistant callus selfed 4 times and backcrosses of both types to the parental type. All lines with in vitro histories had higher seed chalkiness than the controls both in the intensity of chalkiness and in the number of seeds expressing the character. The full range of intensity and amount of chalkiness was expressed in the progeny. The average intensity of anther/tissue culture-derived progeny was 4–5, based on a scale of 1 (translucent) to 10 (fully opaque), and the average amount of chalkiness within plants sampled was 50–75 percent. The chalky characteristic is transmitted from parent to offspring into a range of identifiable F₂ segregants. Disclaimer statement Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the USDA, and does not imply its approval to the exclusion of other products that may also be suitable.     

Introduction of a nitrogen-fixing cyanobacterium into tobacco shoot regenerates

Tobacco (Nicotiana tabacum L.) shoots associated with the nitrogen-fixing cyanobacterium Anabaena variabilis Kütz. (ATCC 29413) were regenerated in mixed cultures of tobacco callus and the cyanobacterium. The cyanobacteria were localized inside the tissues as well as on the surface of regenerated shoots, formed heterocysts, and were capable of acetylene reduction.     

Involution of the caudal musculature during metamorphosis in the ascidian,Botryllus schlosseri

Summary The caudal musculature of the free-swimming tadpole of the ascidian, B. schlosseri consists of cylindrical mononucleated cells connected in longitudinal rows flanking the axial notochord. During resorption of the larval tail, which is apparently induced by the contraction of the epidermis, muscle cells are dissociated and pushed into the body cavity where most of them are rapidly engulfed by phagocytes. In the initial stages of tail withdrawal muscle cells display surface alterations due to the disruption of intercellular junctions and disarrangement of myofibrils. Extensive degenerative changes, with shrinkage of mitochondria and disintegration of the contractile material are subsequently observed. Lysosomes and autophagic vacuoles are rarely seen and appear to play a secondary role in the degradation of the muscle cells, which occurs predominantly within the phagocytes. Myofilaments and myofibrils have never been observed within autophagic vacuoles. Clumps of muscle fragments and degenerated phagocytes undergo eventual dissolution in the blood lacunae, concomitantly with the differentiation of the young oozooid.This investigation was supported in part by a grant from the Muscular Dystrophy Associations of America and by CNR contract No. 7100396/04115542 from the Istituto di Biologia del Mare, Venice. We gratefully acknowledge the skillful assistance of Mr. G. Gallian, Mr. M. Fabbri and Mr. G. Tognon. We also thank the staff of the Stazione Idrobiologica at Chioggia for collecting the colonies.     

Die Feinstruktur des paraganglionären Gewebes im Plexus suprarenalis des Meerschweinchens

Zusammenfassung Die Feinstruktur der chromaffinen paraganglionären Zellinseln im Endoneuralraum des Plexus suprarenalis wird beschrieben.Das paraganglionäre Gewebe liegt neben Kapillaren mit teilweise fenestrierten Endothelien und spärlich verstreuten Bindegewebszellen. Es wird von zwei Zellarten aufgebaut:Typ I-Zellen (chromaffine Zellen) mit großen, locker strukturierten Kernen enthalten im Zytoplasma elektronendichte Granula (1000–1600 Å Durchmesser) mit eng anliegender Membranbegrenzung und Vesikel von 2000–4000 Å Durchmesser, deren dichter Inhalt meist exzentrisch gelegen und durch einen weiten Spalt von der Membran getrennt ist. Weiters beobachtet man ausgedehnte Golgiregionen und in ihrer Nähe uncharakteristische (Entwicklungs-) Formen der beschriebenen Granula, Mitochondrien, Ergastoplasma und freie Ribosomen. Mikrotubuli und Plasmafilamente sind regelmäßig, multivesiculated bodies gelegentlich zu finden.Typ II-Zellen (Hüllzellen) bilden eine Basalmembran aus und umgeben die chromaffinen Zellen mit dünnen Fortsätzen. Die Zellorganellen sind in der Nähe des Kernes gelegen, die Fortsätze weisen eine dichte, z. T. geordnete, fibrilläre Strukturierung auf. An der Zelloberfläche beobachtet man regionäre Zytoplasmaverdichtungen. Die Hüllzellen enthalten keine Bläschen mit elektronendichtem Inhalt.Markfreie Nerven, in Schwannsche Zellen und Hüllzellen gelagert, ziehen an die Typ I-Zellen heran und bilden an deren Oberfläche synaptische Verbindungen aus. Dabei erscheinen die chromaffinen Zellen stets als postsynaptischer Teil der Formation.Die Typ I-Zellen werden als endokrin tätige Zellen aufgefaßt, die durch Abgabe von Katecholaminen hemmend auf die Impulstransmission wirken. Die Typ II-Zellen entsprechen den Schwannschen Zellen.

---

Fine structure of paraganglionic tissue in the suprarenal plexus of the guinea pig

Summary The fine structure of chromaffin paraganglionic tissue situated in the endoneural space of the plexus surparenalis is described.The paraganglionic tissue is found near capillaries with partially fenestrated endothelial cells and rarely scattered connective tissue cells. Two cell types are observed:Type I-cells (chromaffin cells) with great, fine structured nucleus show in their cytoplasm electron dense granules (1,000–1,600 Å in diameter) with clinching membranes and vesicles of 2,000 to 4,000 Å in diameter. In the latter the normally excentric situated dense core is separated from the membrane by a wide cleft. Further large Golgi areas and near them uncharacteristic (developing) kinds of the granules, as described above, mitochondria, ergastoplasm and ribosomes occur. Microtubules and filaments are regularely, multivesiculated bodies occasionally found.Type II-cells (surrounding cells) produce a basement membrane and envelope the chromaffin cells with fine processes. The cell organells are near the nucleus. The processes show a compact, partially fibrillar structure. On the cell surface condensations of the cytoplasm are observed in some regions. The surrounding cells do not contain vesicles with an electron dense core.Myelinated nerves, wrapped by Schwann cells and surrounding cells approach to type I-cells and build synaptic junctions to their surface. In such cases constantly the chromaffin cells are seen as the postsynaptic part of the formation.The type I-cells are thought to be of endocrine function, having an inhibitory effect on impulse transmission by secreting catecholamines. The type II-cells correspond to the cells of Schwann.