Evidence for Na+/H+ antiport inMethanospirillum Hungatei

The growth and methane formation ofMethanospirillum hungatei were inhibited by an inhibitor of Na⁺/H⁺ antiport amiloride. After addition of NaCl or LiCl, when the cells had a lower intracellular pH and were deenergized, they extruded protons into the external medium. The acidification of the external medium was stimulated by protonophores and inhibited by amiloride. These findings suggest the existence of an Na⁺/H⁺ antiport in the cytoplasmic membrane ofM. hungatei and its role in the energetics of methanogenic bacteria.     

Microphotometric determination of structure-bound oxidoreductase activities avoiding nothing-dehydrogenase artefacts: succinate dehydrogenase

 A tetrazolium-based microphotometric method has been devised for the determination of structure-bound dehydrogenase activities with correction for nothing-dehydrogenase artefacts. The method is based on the microphotometric recording of maximum reaction rates in a simple incubation chamber and consists of two successive measurements on the same section, the first in the absence and the second in the presence of the substrate. Following the first measurement, the substrate-free medium is quickly exchanged with the substrate-containing medium and a second measurement is taken. Subtraction of the first from the second reaction rate yields the enzyme activity corrected for nothing-dehydrogenase. Measurements of succinate dehydrogenase (SDH) in skeletal muscle fibres, liver, cardiac atrium and ventricle demonstrate the feasibility of the method. Measurements on the extensor digitorum longus muscle of rat reveal a range of up to fivefold differences in SDH activity within the fibre population of this muscle. Accepted: 11 April 1997     

Occurrence ofEnterococcus spp. in waters

We studied 630 bacterial strains isolated from surface waters and determined as enterococci on the basis of their growth on Slanetz-Bartley agar in typical colonies. The strains were tested and characterized by several key conventional tests for basic differentiation of enterococci and by commercial test kits. We identified 135 strains ofE. fœcium (21%), 115E. fœcalis (18%), 30E. mundtii (5%), 27E. hirae (4%), 22E. casseliflavus (3%), 21E. gallinarum (3%), 17E. durans-E. hirae complex (3%), 5E. durans (1%), and 1 strain ofE. avium. 150 strains were classified only asEnterococcus sp. (25%) and 107 strains (17%) isolated from Slanetz-Bartley agar were not enterococci. We found that the non-enterococcal group consisted of other Gram-positive cocci and Gram-positive and Gram-negative rods. Based on the identification we tried to find a relation between taxonomic position of isolated strains and their colony morphology on Slanetz-Bartley agar. Out of the total of 523 identified enterococci, 345 strains (66%) formed purple colonies, 136 red colonies (26%), 37 pink colonies (7%) and 5 cream colored colonies (1%). There was no correlation among the color, size or colony morphology and the taxonomic characterization of enterococcal strains.     

Ontogeny of a new Palaeogene pipid frog from southern South America and xenopodinomorph evolution

Lacustrine interbeds of a volcaniclastic succession that crops out extensively in north-western Patagonia yielded impressions of articulated, nearly complete, frogs of different ontogenetic stages including tadpoles. The stratigraphic position of the fossil bearing beds in this sequence and evaluation of palaeofloristic data against the record of climatic change in southern high latitudes support a middle Eocene – early Oligocene age for the frogs. These frogs are described as a new genus and species that resembles the late Palaeocene ' Xenopus' romeri from Brazil, and differs from the middle Eocene S. pascuali from Patagonia, in the relatively wide and short braincase and fused first two presacral vertebrae. However, unlike ' X. '  romeri , the nasals are paired and bear short, but distinct, rostral processes. A parsimony analysis based on 49 adult osteological characters demonstrates that these South American fossil pipids are closely related to xenopodines, restricted to the African continent today, although their interrelationships remain poorly resolved. Interpretation of the ontogenetic stages exemplified by the fossil specimens suggests a developmental pattern more similar to that of extant xenopodines than to the ontogeny of more distant pipoid relatives. Moreover, the similarity between these fossil larvae and those of Xenopus and Silurana strongly suggests similar habits. Many of these larval features may be considered as caenogenetic, i.e. specializations of the tadpoles as obligate, microphagous suspension feeders.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139 , 439-476.     

Determination of Microgram Quantities of Stevioside from Leaves of Stevia rebaudiana Bert. by Two-Dimensional Thin Layer Chromatography

A method is described for the determination of stevioside fromleaves of Stevia rebaudiana Bert. Separation upon non-activatedsilica gel impregnated with boric acid in a two-dimensionalchromatographic system followed by clution and colorimetricassay is reported. Recuperation from chromoplates is over 95%.The observed ratio of the optical density of glucose: steviosidematches that expected theoretically so that glucose may be employedas a standard where pure stevioside is not available. Effects of the plant growth retardant, ancymidol, on the growthand morphology of the shoot system of cucumber (Cucumis sativusL. ) were investigated. Ancymidol inhibited stem elongation,reducing both number and length of internodes. Reduction inleaf area, attributable to a reduction in both cell size andnumber, was accompanied by an increase in chlorophyll per unitarea. The retardant decreased apical dominance and delayed anthesis.Gibberellic acid fully reversed ancymidol-induced inhibitionof stem elongation, internode length and production, and leafexpansion. GA_4/7 and ancymidol gave a synergistic promotionof stem elongation by increasing elongation of younger internodesand increasing internode production. Synergistic promotion ofpetiole elongation by this combination was also observed. Ancymidol,applied 7 d previously either to the shoot or root, severelyreduced the level of gibberellin-like activity in bleeding sapcollected from decapitated plants.     

Vergleichend-anatomische Untersuchung einer interglazialen Konifere

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