A Comparison of Pectinases from Ditylenchus dipsaci and Allium cepa Callus Tissue

Ground and whole Ditylenchus dipsaci maintained on onion callus contain no culturable micro-organisms when tested with five check media. Healthy onion callus does not produce pectolytic enzymes. Pectolytic enzymes are present in infected callus. These enzymes are, however, associated with resident nematodes and not host tissues. These results suggest that D. dipsaci is the actual source of the endo-polygalacturonase and endo-pectinmethyltrans-eliminase extracted from them.     

Fine structural and enzyme histochemical observations on the dorsal tail tubercle of Mertensiella caucasica (Urodela,Amphibia)

Summary Dorsal tubercle and skin of Mertensiella caucasica have been investigated with the electron microscope and enzyme histochemical methods. The epidermis of the tubercle consists of 8–9 cell layers, that of normal dorsal skin of 5–6. The tubercle is filled with large mucous glands which are surrounded by an almost complete layer of smooth muscle cells (myoepithelial cells). Their glandular cells undergo cyclical changes and are characterized by specific secretory granules, which differ from those of the relatively small mucous glands of the normal dorsal skin.In the connective tissue of the tubercle a relatively rich supply of nerve fibres has been found, which in part contain synaptic and dense core vesicles or accumulations of mitochondria. In the normal dorsal skin nerve fibres occur less frequently.The following enzymes have been demonstrated in the mucous glands of the tubercle: SDH, acid phosphatase, unspecific esterases, E 600 resistant esterase.The tubercle seems to stimulate the female cloaca chemically and mechanically.     

On catecholamine-containing cells in the rat interatrial septum

Summary The interatrial septum of the rat heart contains cells which show a strong intensive-yellow paraformaldehyde-induced fluorescence. By electron microscopy these cells are characterized by an abundance of dense-core vesicles.Cholinergio axons form axo-somatic synaptic contacts with the catecholamine-containing cells. These cells, packed with dense-core vesicles, are frequently interdigitated and interconnected by zonulae and maculae adhaerentes and occludentes. The catecholamine-containing cells are surrounded by satellite cells either individually or in groups.The catecholamine-containing cells, which bear blunt, plumpish processes, can be subdivided, on the basis of position and morphology into two types. One class of cells lies within the fibroblast capsule of the intra-atrial ganglion (van der Zypen, Hasselhorst, Merz and Fillinger, 1974). A second aggregation of catecholamine-containing cells occurs outside the ganglia in close proximity to capillaries. The capillaries exhibit pores in the area of contact with the catecholaminergic cells. The structure of these catecholamine-containing cells is described and their possible function discussed.

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Zusammenfassung Im Septum interatriale des Rattenherzens treten Zellen in Erscheinung, die nach Paraformaldehyd-Bedampfung eine intensive hellgelbliche Fluoreszenz zeigen. Diese Zellen zeichnen sich durch einen großen Reichtum an dense-core vesicles aus. Cholinerge Axone bilden axo-somatische Synapsen an den katecholaminhaltigen Zellen aus. Die mit dense-core vesicles angefüllten Zellen sind oft ineinander verzahnt und durch Zonulae adhaerentes verbunden. Einzeln oder in Gruppen werden die katecholamin-enthaltenden Zellen von Satelliten-Zellen umgeben.Die mit kurzen plumpen Fortsätzen versehenen katecholaminhaltigen Zellen lassen aufgrund ihrer Lage und eines andersartigen Baues zwei Typen erkennen. Eine Gruppe von Zellen liegt innerhalb der Fibrozytenkapsel des Ganglion intraatriale (van der Zypen, Hasselhorst, Merz und Fillinger, 1974). Eine zweite Ansammlung von Katecholamin enthaltenden Zellen findet sich außerhalb der Ganglien in engem Kontakt zu Kapillaren. Die Kapillaren weisen im Bereich des Kontaktes mit den katecholaminergen Zellen Poren auf. Die Struktur dieser Zellen wird geschildert und ihre mögliche Funktion diskutiert.

     

Substrate inactivation of enzymes in vitro and in vivo

Some enzymes are inactivated by their natural substrates during catalytic turnover, limiting the ultimate extent of reaction. These enzymes can be separated into three broad classes, depending on the mechanism of the inactivation process. The first type is enzymes which use molecular oxygen as a substrate. The second type is inactivated by hydrogen peroxide, which is present either as a substrate or a product, and are stabilized by high catalase activity. The oxidation of both types of enzymes shares common features with oxidation of other enzymes and proteins. The third type of enzyme is inactivated by non-oxidative processes, mainly reversible loss of cofactors or attached groups. Sub classes are defined within each broad classification based on kinetics and stoichiometry. Reaction-inactivation is in part a regulatory mechanism in vivo, because specific proteolytic systems give rapid turnover of such labelled enzymes. The methods for enhancing the stability of these enzymes under reaction conditions depends on the enzyme type. The kinetics of these inactivation reactions can be used to optimize bioreactor design and operation.     

Behavioral adaptations for raiding in the slave-making ant,Polyergus breviceps

We studied recruitment behavior of the slavemaking ant Polyergus breviceps,which typically raids colonies of Formica gnava.The first test series demonstrated the importance of social context, by showing that recruitment was high during raiding, but virtually absent during preraid circling and during the return trip after a slave raid. The second test series showed that Formicapupae (alone or together with adults) must be present for workers of Polyegrusto recruit nestmates. The third test series demonstrated that panic alarm by raided Formicais caused by a pheromone, and we suggest that adults of Formicamay be the source of this secretion. Finally, the fourth test series showed that formic acid is lethal to adults of Formicabut has almost no adverse effect on Polyergus.This relative immunity by Polyergusmay enable them to remain organized while entering nests of Formicaduring slave raids.     

Small marine pelagic fish and the threat of fishing; are they endangered?

Evidence of the collapse and recovery of major marine fisheries for pelagic fish species is reviewed, distinguishing the influence of fishing compared with natural (environmental) effects. In one only of the best documented cases (Icelandic spring-spawning herring) has the stock failed to reappear, after 20 years. Several others, e.g. California sardine, have persisted at 1/000th or possibly less of their peak size for some years before beginning to recover. Fishing has been the main cause of collapse in most but not all cases, due initially to the escalation of catchability as stock size decreases–a phenomenon characteristic of fisheries for pelagic species due to their shoaling habit, ease of detection and vulnerability to modern fishing methods. It is concluded that although the threat of fishing to the continuity of the species is remote, excessive depletion (although avoidable by firm and timely management) is potentially able to cause temporary disappearance of local stock and disruption of the ecosystem.     

Ocean current variability and the spawning season of Hawaiian reef fishes

Synopsis The spawning patterns of four Hawaiian reef fishes with similar reproductive habits, but different biogeographic distributions were studied from September 1980 to October 1981. Two species are Hawaiian endemics [Centropyge potteri (Pomacanthidae) and Chaetodon multicinctus (Chaetodontidae)] and the other two have pan-tropical Pacific distributions [Ctenochaetus strigosus and Zebrasoma flavescens (Acanthuridae)]. All showed increased spawning activity from January to July, the prevalent pattern among a majority of coastal marine fishes in Hawaii. Environmental correlatives to the period of peak reproduction include cycles of (a) daylight length and temperature which probably function as proximate cues and (b) seasonal variations in ocean current patterns which may ultimately affect survival of larvae and dispersal. Peak reproduction takes place during months when (1) mesoscale eddies most likely occur, and (2) the probability is greatest of drifting objects remaining near the islands.     

Control of photosynthesis in leaves as revealed by rapid gas exchange and measurements of the assimilatory force FA

The rapid transients of CO₂ gas exchange have been measured in leaves ofHelianthus annuus L. In parallel experiments the assimilatory force F_A, which is the product of the phosphorylation potential and the redox ratio NADPH/NADP, has been calculated from measured ratios of dihydroxyacetone phosphate to phosphoglycerate in the chloroplast stroma and in leaves. The following results were obtained: (i) When the light-dependent stroma alkalization was measured under steady-state conditions for photosynthesis in air containing 2000 μl · l^-1 CO₂, alkalization increased with photosynthesis as the quantum flux density (irradiance) was increased. This contrasts to the light-dependent stroma alkalisation measured in dark-adapted leaves during the dark-light transient (Laisk et al. 1989, Planta177, 350–358) which reached a maximum at a quantum flux density far below that necessary to saturate photosynthesis. This maximum was about three times higher than the maximum stroma alkalization at light- and CO₂-saturated photosynthesis. (ii) Accurate calculations of the assimilatory force F_A require a consideration of the stromal pH. However, under many conditions, changes in the stromal pH resulting from changes in photosynthetic flux can be neglected because they are small. (iii) Stromal ratios of dihydroxyacetone phosphate to phosphoglycerate are generally lower than ratios measured in leaf extracts. The value of F_A calculated from stromal metabolites was about 30% lower than F_A calculated from cellular metabolites. Still, it appears sufficient for many purposes to calculate F_A from metabolite measurements in leaf extracts. (iv) In the light, the catalytic capacity of the photosynthetic apparatus is adjusted to the level of irradiance. The response of carbon assimilation to large increases in irradiance is slow because it requires enzyme activation. Deactivation of the Calvin cycle induced by decreases in irradiance is slower than activation. (v) Changes in catalytic capacity and in the availability or level of substrates such as CO₂ alter the flux resistance of the Calvin cycle. A decrease in flux resistance explains why F_A often does not increase by much and may actually decrease when carbon flux is increased. Adjustments of flux resistances in the Calvin cycle and of photosystem-II activity in the electron-transport chain permit varying rates of photosynthesis at low levels of ATP and NADPH. As NADP remains available, the danger of over-reduction which leads to photoinactivation of electron transport is minimized. K.R. und U.H. were guests of the Estonian Academy of Sciences. Support by the Estonian Academy of Sciences, the Sonderforschungsbereich 251 of the University of Würzburg and the Fonds der Chemischen Industrie is gratefully acknowledged.     

Purification and Characterization of Sorbitol Dehydrogenase from Bovine Brain

Sorbitol dehydrogenase (EC 1.1.1.14) was isolated from bovine brain and purified 3,000-fold to apparent homogeneity, as judged by polyacrylamide gel electrophoresis. The purified enzyme had a specific activity of 36 units/mg of protein; a molecular weight of 39,000 for each of the four identical subunits and 155,000 for the intact enzyme were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel exclusion chromatography, respectively. The presence of one Zn2+ per subunit was confirmed by atom absorption spectroscopy; inactivation of the enzyme by metal-chelating agents points to the essential role that Zn2+ plays in the catalytically competent enzyme. The enzyme is also inactivated by thiol-blocking reagents; with respect to inactivation by sodium pyrophosphate, sorbitol dehydrogenase is different from closely related alcohol dehydrogenase.     

Enzyme Variation of Eimeria arizonensis from Peromyscus truei and P. boylii

ABSTRACT. Cricetid rodents, Peromyscus truei and P. boylii , were inoculated with sporulated oocysts of Eimeria arizonensis collected from wild P. truei maintained in the lab. In P. truei the prepatent period was 4–5 days, the patent period was 9–11 days, and sporulated oocysts were 21.5 × 25.0 (20–23 × 24–26) μm with sporocysts 7.7 × 12.0 (6–8 × 10–13) pm. In P. boylii the prepatent period was 6–7 days, the patent period was 8–9 days, and sporulated oocysts were 20.1 × 23.2 (18–22 × 21–24) pm with sporocysts 6.8 × 10.0 (5–8 × 9–12) pm. Sporulated oocysts from both host species were used in direct side-by-side comparison of isozyme banding patterns using protein electrophoresis. The parasite has polytypic loci for leucine aminopeptidase (LAP), lactate dehydrogenase (LDH), and 6-phosphogluconate dehydrogenase (6-PGD). In oocysts from P. truei , LAP showed one band with fast migration and LDH and 6-PGD each showed two bands, one with fast and one with slow migration. In oocysts from P. boylii , LAP and LDH each had one band with slow migration and 6-PGD had one band with moderate migration. Oocysts of E. arizonensis collected from P. boylii were used to inoculate P. truei. The prepatent and patent periods, structural measurements, and isozyrne banding patterns of the resultant oocysts were the same as those from P. truei when inoculated with oocysts from P. truei.