Diastereoselective hydrogenations of unsymmetrically substituted aromatics

Attempts to induce enantioselectivity in the catalytic hydrogenation of unsymmetrically substituted aromatics using covalently bound, well known chiral auxiliaries are described. Marked differences in stereoselectivity and rate of hydrogenolysis are noted as a function of the auxiliary used. Enantioselectivities obtained in the resulting cyclohexyl derivatives are rather poor. © 1995 Wiley-Liss, Inc.     

Inter- and intra-species intercropping of barley cultivars and legume species,as affected by soil phosphorus availability

Aims

Intercropping can improve plant yields and soil phosphorus (P) use efficiency. This study compares inter- and intra-species intercropping, and determines whether P uptake and shoot biomass accumulation in intercrops are affected by soil P availability.

Methods

Four barley cultivars (Hordeum vulgare L.) and three legume species (Trifolium subterreneum, Ornithopus sativus and Medicago truncatula) were selected on the basis of their contrasting root exudation and morphological responses to P deficiency. Monocultures and barley-barley and barley-legume intercrops were grown for 6 weeks in a pot trial at very limiting, slightly limiting and excess available soil P. Above-ground biomass and shoot P were measured.

Results

Barley-legume intercrops had 10–70% greater P accumulation and 0–40% greater biomass than monocultures, with the greatest gains occurring at or below the sub-critical P requirement for barley. No benefit of barley-barley intercropping was observed. The plant combination had no significant effect on biomass and P uptake observed in intercropped treatments.

Conclusions

Barley-legume intercropping shows promise for sustainable production systems, especially at low soil P. Gains in biomass and P uptake come from inter- rather than intra-species intercropping, indicating that plant diversity resulted in decreased competition between plants for P.

     

Adaptive surface antigen variation in Mycoplasma bovis to the host immune response

Abstract The variability of predominant Mycoplasma bovis surface antigens in the presence of specific immune pressure was analyzed in an in vitro assay to determine if M. bovis could escape immune destruction. We have shown that serum antibodies from immunized or experimentally infected calves and monoclonal antibodies which specifically react with previously characterized or as yet undefined major M. bovis membrane surface proteins cause repression of expression or shortening of the target protein, or induce switching to expression of an antigenically distinct variant protein. We have further demonstrated that removal of the inducing antibody results in reversion to the original phenotype. These results suggest that the level of expression and the length of M. bovis surface antigens in the host is modulated by cognate antibodies. According to the surface antigenic variation systems, random selection of preexisting variants resistant to antibody-mediated inhibition or direct regulation of gene expression may be means by which this organism evades host immune defences.     

Mucopolysaccharidosis-like alterations in cardiac valves of rats treated with tilorone

The purpose of this study was to examine whether the aortic and mitral valves of rats are involved in the mucopolysaccharidosis-like disorder induced by tilorone. Rats were treated with large doses of the drug for periods of 1-21 weeks. After chronic drug treatment the leaflets of both heart valves were thickened and opaque. In all treated animals the spongiosa layer of the stroma was crowded with vacuolated cells; the fibrosa layer was altered only after prolonged treatment. Ultrastructurally, the vacuolated cells of the spongiosa could be identified as histiocytes and fibroblasts, the former being the most susceptible cell type. The fibroblasts of the fibrosa represented the least sensitive cell type. The histochemical results showed that the clear cytoplasmic vacuoles in the spongiosa cells were due to lysosomal storage of polyanionic material with staining characteristics similar to cartilage matrix. After discontinuation of drug treatment the alterations persisted for several weeks. The present study shows that heart valves are involved in the mucopolysaccharidosis-like disorder induced by tilorone. The molecular pathomechanism of the disorder and the exact identification of the storage material must await further analysis.     

Tactile localisation: the function of active antennal movements in the crayfishCherax destructor

Video recordings and single frame analysis were used to study the function of the second antennae of crayfish (Cherax destructor) as a sensory system in freely behaving animals. Walking crayfish move their antennae back and forth through horizontal angles of 100 degrees and more, relative to the body long axis. At rest, animals tend to hold their antennae at angular positions between 20 and 50 degrees. Movements of the two antennae are largely independent of each other. Before and during a turn of the body the ipsilateral antenna is moved into the direction of the turn. Solid objects are explored by repeatedly moving the antennae towards and across them. Both seeing and blinded crayfish can locate stationary objects following antennal contact. On antennal contact with a small novel object, a moving animal withdraws its antenna and attacks the object. When the antenna of a blinded crayfish is lightly touched with a brush the animal turns and attacks the point of stimulation. The direction taken and the distance covered during an attack can be correlated with: the angle at which the antenna is held at the moment of contact and the distance along the antennal flagellum at which the stimulus is applied. From behavioural evidence we conclude that crayfish use information about the angular position of their antennae and about the position of stimulated mechanoreceptors along the antennal flagellum to locate objects in their environment. We suggest ways in which an active tactile system-like the crayfish's antennae--could supply animals with information about the three-dimensional layout of their environment.     

Transformation of miniature potted rose (Rosa hybrida cv. Linda) with P SAG12 -ipt gene delays leaf senescence and enhances resistance to exogenous ethylene

Key message

The P _SAG12 -ipt gene was transferred to miniature rose, as the first woody species, resulting in increased ethylene resistance due to specific up-regulation of the ipt gene under senescence promoting conditions.

Abstract

Transgenic plants of Rosa hybrida ‘Linda’ were obtained via transformation with Agrobacterium tumefaciens strain harboring the binary vector pSG529(+) containing the P _SAG12 -ipt construct. A. tumefaciens strains AGL1, GV3850 and LBA4404 (containing P_35S-INTGUS gene) were used for transformation of embryogenic callus, but transgenic shoots were obtained only when AGL1 was applied. The highest transformation frequency was 10 % and it was achieved when half MS medium was used for the dilution of overnight culture of Agrobacterium. Southern blot confirmed integration of 1–6 copies of the nptII gene into the rose genome in the tested lines. Four transgenic lines were obtained which were morphologically true-to-type and indistinguishable from Wt shoots while they were in in vitro cultures. Adventitious root induction was more difficult in transgenic shoots compared to the Wt shoots, however, one of the transgenic lines (line 6) was rooted and subsequently analyzed phenotypically. The ipt expression levels were determined in this line after exposure to exogenous ethylene (3.5 μl l^?1) and/or darkness. Darkness resulted in twofold up-regulation of ipt expression, whereas darkness combined with ethylene caused eightfold up-regulation in line 6 compared to Wt plants. The transgenic line had significantly higher content of chlorophyll at the end of the treatment period compared to Wt plants.     

Defining species in Tulasnella by correlating morphology and nrDNA ITS-5.8S sequence data of basidiomata from a tropical Andean forest

The genus Tulasnella comprises important orchid mycobionts. Molecular phylogenetic studies on nrITS-5.8S sequences of Tulasnella species previously isolated from mycorrhizas of epiphytic orchids from a tropical Andean forest showed genomic variability among clones which was difficult to interpret as intra- or interspecific variations or to correlate with described Tulasnella species. To improve this situation, we collected basidiomata of Tulasnella in an Andean forest, studied part of the sequences of fungal ribosomal genes and correlated molecular data with the morphology of the specimens. Within five basidiomata displaying slight morphological variability, we found inter-specimen nrITS1-5.8S-ITS2 variability corresponding to proportional differences of less than 1% except for one clone with 5.1% divergence. Results indicate that the slightly variable basidiomata should be considered as one species, which is morphologically tentatively assigned to the Tulasnella pruinosa complex. However, comparison of nrITS1-5.8S-ITS2 sequences, including sequences of T. pruinosa from other origins, indicate that Tulasnella sp. is only distantly related to the T. pruinosa specimens included in the analyses. Sequences of all morphologically similar and taxonomically well-identified species are required to decide whether the basidiomata analyzed in the present study represent a new species. The new sequences are rather similar to sequences obtained previously from mycorrhizae of epiphytic orchids of the same area indicating mycorrhizal potential of this fungus.     

Caffeine Impairs Myocardial Blood Flow Response to Physical Exercise in Patients with Coronary Artery Disease as well as in Age-Matched Controls

Background

Caffeine is one of the most widely consumed pharmacologically active substances. Its acute effect on myocardial blood flow is widely unknown. Our aim was to assess the acute effect of caffeine in a dose corresponding to two cups of coffee on myocardial blood flow (MBF) in coronary artery disease (CAD).

Methodology/Principal Findings

MBF was measured with ¹⁵O-labelled H2O and Positron Emission Tomography (PET) at rest and after supine bicycle exercise in controls (n = 15, mean age 58±13 years) and in CAD patients (n = 15, mean age 61±9 years). In the latter, regional MBF was assessed in segments subtended by stenotic and remote coronary arteries. All measurements were repeated fifty minutes after oral caffeine ingestion (200 mg). Myocardial perfusion reserve (MPR) was calculated as ratio of MBF during bicycle stress divided by MBF at rest. Resting MBF was not affected by caffeine in both groups. Exercise-induced MBF response decreased significantly after caffeine in controls (2.26±0.56 vs. 2.02±0.56, P<0.005), remote (2.40±0.70 vs. 1.78±0.46, P<0.001) and in stenotic segments (1.90±0.41 vs. 1.38±0.30, P<0.001). Caffeine decreased MPR significantly by 14% in controls (P<0.05 vs. baseline). In CAD patients MPR decreased by 18% (P<0.05 vs. baseline) in remote and by 25% in stenotic segments (P<0.01 vs. baseline).

Conclusions

We conclude that caffeine impairs exercise-induced hyperaemic MBF response in patients with CAD to a greater degree than age-matched controls.