Nitrate assimilatory properties of barley grown under long-term N limitation: Effects of local nitrate supply in split-root cultures

The effect of nitrate availability on characteristics of the nitrate assimilatory system was investigated in N-limited barley (Hordeum valgare L. cv. Golf), grown with the seminal root system split into initially equal-sized halves. The cultures were continuously supplied with nitrate-N at a relative addition rate (RA) of 0.09 day^?1, which resulted in relative growth rates (RG) that were ca 85% of those observed under surplus nitrate nutrition. The total N addition was divided between the subroots in ratios of 100:0, 80:20, 70:30, 60:40, and 50:50. For comparison, standard cultures were grown at RAs ranging from 0.03 to 0.18 day^?1. Initially, biomass and N partitioning to the subroots responded strongly and proportionally to the nitrate distribution ratio. After 12-14 days no further effect was observed. The V_max for net nitrate uptake and in vitro nitrate reductase (NR) activity were measured in acclimated plants, i.e., after > 14 days under a certain nitrate regime. In subroots fed from 20 to 100% of the total N addition, V_max for net nitrate uptake increased slightly, whereas NR activity was unaffected. Uptake and NR activities were insignificant in the 0%-subroot. Uneven nitrate supply to individual subroots had negligible effect on the whole-plant ability for nitrate uptake, and the relative V_max (unit N taken up per unit N in whole plant tissue and time) remained about 7-fold in excess of the demand set by growth. Balancing nitrate concentrations (the resulting external nitrate concentrations at a certain RA) generally ranged between 2 and 10 μM at growth-limiting RA, both when predicted from uptake kinetics and when actually measured. When comparing split root and standard cultures when acclimated, it appears that uptake and NR activities in roots respond more strongly to over-all nitrate availability than to nitrate availability to individual subroots.     

A Comparison of the Polypeptide Pattern Between a Brain Primary Culture and Fractions of Bulk-Isolated Glial Cells

Abstract: This paper reports on the electrophoretic protein/polypeptide pattern of a rat brain primary culture. For comparison, the polypeptide pattern of neuronal and glial enriched fractions from adult rat brain and cerebral hemispheres from newborn and adult rat have been analysed. Water-soluble and SDS-extractable polypeptide fractions appeared and/or increased in amount in the cultures until confluency. The polypeptide pattern of the cultures most resembled that of the glial cell fractions, showing some of this fraction's specificity. Removal of fetal calf serum and addition of 0.1 mM dibutyryl cyclic adenosine monophosphate (dB-cAMP) produced few changes in the electrophoretic pattern. The study thus provides evidence in favour of the astroglial nature of the brain primary culture. It also shows that the cells undergo some maturation in the culture.     

Effect of abscisic acid on CO2 exchange in Lemna gibba

The effects of abscisic acid (ABA) on photosynthesis, dark respiration, and photorespiration were studied in Lemna gibba L. plants. The initial concentration of ABA in the nutrient solution was 10⁻⁷M and in a few experiments, 10⁻⁶M. The cultures were grown in the same solution for time periods ranging from one hour to 12 days. Net photosynthesis, measured as CO₂ uptake by infrared gas analyser technique, was inhibited after four hours of ABA treatment and reached a minimum after four to seven days depending on the time of the year. After 12 days a substantial recovery of photosynthesis was observed. Dark respiration was significantly stimulated after two to seven days of ABA treatment but then returned to the control level. The transient effects of ABA on photosynthesis and dark respiration corresponded to the previously measured time course of [¹⁴C]-ABA uptake by Lemna . Photorespiration measured as oxygen inhibition of photosynthesis was not affected by ABA.     

Effect of lectins on the interactions between human peripheral blood lymphocytes and monocytes

Interactions between normal human peripheral blood T lymphocytes and monocytes were investigated by measuring the in vitro cellular adherence of these cells in the presence and in the absence of mitogens. Concanavalin A (Con A), lentil lectin (Lc), and phytohemagglutinin (PHA) in mitogenic doses increased 15 to 20 times the binding of T lymphocytes to monocytes. The lectin-induced binding was similar to that produced by neuraminidase-gal-actose-oxidase treatment. A good correlation was found between the early cellular adherence induced by these lectins and by neuraminidase-galactose-oxidase and the blastogenesis of the T lymphocytes measured after 3 days of culture by [³H]thymidine uptake. However, wheat germ agglutinin (WGA), a nonmitogenic lectin, also increased the binding of T lymphocytes to monocytes. Addition of specific carbohydrates completely inhibited the cellular interactions induced by lectins. Peanut agglutinin (PNA) induced adherence of lymphocytes only after treatment of these cells with neuraminidase. Striking differences were not found between the lectin-induced adherence observed with autologous and heterologous cells. Killing of monocytes abolished entirely the lectin-induced adherence of lymphocytes, however killed T lymphocytes were still able to interact weakly with live monocytes. Dexamethasone was found to be a potent inhibitor of mitogen-induced cellular interactions.     

Evolution des activités protéolytiques digestives chez les Jeunes Mulgilidae

Proteolytic activity in the stomach, pyloric caeca and intestine decreases with increasing size in the three fish species Mugil auratus, M. capito and M. saliens. Differences between these species are found mainly in the gastric proteolytic activity which appears to be related to diet. This activity is pronounced in M. saliens whose diet is mainly carnivorous. Comparison of regression lines relating gastric proteolytic activity to size reveals differences which distinguish M. auratus from both of the other species. Total proteolytic activity exhibits high variability depending on the types of diet.     

Die Pulvillen vonCalliphora erythrocephala (Diptera,Brachycera) als Adhäsionsorgane

Zusammenfassung Die Pulvillen vonCalliphora erythrocephala wurden licht und fluoreszenzmikroskopisch, raster- und transmissions-elektronenmikroskopisch untersucht. Das Adhäsionssekret wurde dünnschichtchromatographisch mit dem Körperoberflächen-Lipid verglichen.Die Pulvillen tragen auf der Ventralseite mehrere Tausend langer dünner Hafthaare mit sohlenartigen Endverbreiterungen. Die Kutikula des Pulvillus besteht hauptsächlich aus elastischen Kutikulatypen (Endo- und Mesokutikula) in verschiedenen, spezifischen Ausbildungsformen.Die Pulvillen enthalten ein sekretorisches Epithel ohne Ausführgänge, das Protein- und Lipideinschlüsse zeigt.Das Pulvillensekret ist eine schwerflüchtige, ölige Flüssigkeit, die nicht identisch ist mit dem Körperoberflächen-Lipid. Das Sekret wird in der homogenen Kutikala des Pulvillus gespeichert und über das Porenkanalsystem der Ventralseite nach außen geleitet.Der Zusammenhang zwischen der Struktur der Pulvillen und ihrer Rolle beim Adhäsionsvorgang wird diskutiert.

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The pulvilli ofCalliphora erythrocephala (Diptera, Brachycera) as adhesive organs

Summary The pulvilli ofCalliphora erythrocephala were examined by light microscopy, fluorescent light microscopy, SEM and TEM. The adhesive secretion was compared with the general surface lipid layer by means of thinlayerchromatography.On the ventral surface the pulvilli bare several thousand long, slender tenent hairs with solelike spatulate tips. The pulvillar cuticle is composed on the whole of elastic cuticle types (endocuticle, mesocuticle) with specific modifications of structure. The pulvilli contain a secretory epithelium without transport ducts which has lipid and proteinaceous inclusions.The pulvillar secretion is a slowly volatile oily liquid which is not identical to the general surface lipid. The secretion is stored in the homogeneous cuticle within the pulvillus and transported to the ventral surface via the pore canal system.The correlation between the structure of pulvilli and their function in the adhesion process is discussed here.

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Abkürzungen bl Basales Labyrinth - cv coated vesicle - db dense body - dlk Dichter Lamellenkörper - dw Dorsalwand - e Epithel - ef Endokutikulafasern in der Übergangszone (meso 2b) - endo 1 lamelläre Endokutikula - endo 2 homogene Endokutikula - endo 3 gelatinöse Endokutikula - ep Empodium - epi Epikutikula - exo Exokutikula - fr Fersenregion - fs Faltensaum - hh Hafthaare - hs Haarschaft - k Kutikula - kr Kralle - ku Kutikulinschicht - l Lumen - li Lipid - lr Dorsale Längsrippen - m Mitochondrium - mb Mesokutikulabalken in der Übergangszone (meso 2b) - meso 1 helle homogene Mesokutikula - meso 2a dunkle homogene Mesokutikula, kompakt - meso 2b Übergangszone, in der dunkle homogene Mesokutikulabalken mit faseriger Endokutikula verzahnt sind - mt Mikrotubulus - mvbd Dunkler multivesikulärer Körper - n Kern - pc Porenkanal - ps Proximalsklerit - pt Prätarsus - rer Rauhes endoplasmatisches Retikulum - s Schulter - sd Sehnendrüse - se Sehne - so Sohle - sr Saumregion - t Tubulus - t₅ Tarsalglied 5 - ta Tasche - td Tarsaldrüse - te Tarsalepithel - tg Taschengrund - tk Terminalkanäle - utr Unguitractor - v Heller Vesikel - va Proteinvakuole - w Wachsschicht - z Zementschicht