Inhibition of Trichomonas vaginalis Replication by the Microtubule Stabilizer Taxol

ABSTRACT. Taxol, a plant alkaloid stabilizer of microtubules, inhibits in vitro the replication of the human pathogenic flagellate Trichomonas vaginalis in a dose-dependent fashion. Micromolar concentrations of the drug induce massive assembly of microtubules, resistant to antimicrotubule agents, and block the mitosis of the protozoa at an early stage preceding the formation of the spindle fibers and the depolymerization of the axostylar microtubules. Some hypotheses involving the inactivation of the microtubule-organizing centers and the stabilization of axostylar microtubules are formulated to explain the mechanism of action of taxol.     

The distribution and environmental state of vegetated islands within human‐impacted European rivers

1. Vegetated islands within river corridors are pivotal landscape features and are among the first to disappear as a consequence of flow regulation and channelisation. However, how vegetated islands vary along human‐impacted rivers is poorly understood. 2. We carried out a detailed analysis of the contemporary distribution, diversity and environmental state of vegetated islands within 12 human‐impacted European rivers, using 75 Landsat 7 ETM+ satellite images (1999–2002), historical maps, DEM data and landscape metrics. We tested whether channel fragmentation, catchment land use and the environmental state of fringing floodplains determine the spatial patterns of the islands. We also analysed the historical change of islands within selected sections of the Upper Danube, Upper Rhine and Olt rivers. 3. We identified 2771 islands in the contemporary landscape, varying from 0.06 to 9828 ha. Islands covered up to 21% of the active channel area and contributed up to 32% of the total riparian ecotone length. Island density ranged from 0.06 islands per river‐km (River Sava) to 1.6 islands per river‐km (River Tagliamento). River regulation has led to a marked loss of island density: 94% in the Upper Danube, 93% in the Upper Rhine, and 69% in the Olt. The environmental state of the islands was significantly less altered by human activity than of their fringing floodplains; 93.4% of the vegetated islands exhibited a near‐natural state, while 86% of the fringing floodplains were expansively converted to agricultural and urban land uses. 4. Our results highlight the ubiquitous presence of vegetated islands, their sensitivity to river regulation and their pivotal role for the future restoration and management of river corridors.     

Biological traits of stream macroinvertebrates from a semi-arid catchment: patterns along complex environmental gradients

1. The relationships between biological traits of macroinvertebrates and environmental characteristics were investigated in streams with contrasting physical, chemical or landscape level attributes. We used an ordination technique, RLQ analysis, which links an environmental table (R) with traits table (Q) through an abundance table (L) to investigate the relationship between habitat characteristics and biological traits.
2. A major environmental axis explaining the distribution of species and their distinctive biological features was obtained. This axis included variables of anthropogenic pressure (agricultural and urban uses) and natural variability (climatic and geologic) that are strongly intercorrelated in the study area, with a clear spatial component.
3. The attributes of species from frequently disturbed systems (small size, multivoltinism, diapause, ovoviviparity, etc.) were associated with semi-arid areas whereas traits common in more stable and favourable environments (large body size, semi-voltinism, isolated eggs, etc.) were found in upland forested areas.
4. The natural climatic variation was proposed as a disturbance axis of a theoretical habitat templet (driven by the intense hydrological disturbances typical of semi-arid streams), while anthropogenic pressure (mainly intensive agriculture) and high salinity, a natural consequence of geology, was proposed as an adversity axis. Different life-histories associated with contrasting environmental features were superimposed in this habitat templet.
5. The ecological–evolutionary scenario in which stream macroinvertebrates have evolved and by which their communities are organized, is closely linked to disturbance, environmental harshness and human pressure.     

Properties of a new strain of tobacco streak virus from Clematis vitalba (Ranunculaceae)

A distinct strain of tobacco streak virus (TS V/Cle), isolated in Yugoslavia from wild Clematis vitalba showing chlorotic spots or yellow netting of the leaves and from many symptomless shrubs, is described. TSV/Cle was seed transmitted in C. vitalba (70%), and in the experimental hosts Chenopodium quinoa (80%), Nicotiana benthamiana and N. megalosiphon. It was also detected in the pollen of infected C. quinoa. Purified virus preparations mostly contained quasi-spherical particles measuring 24–26 × 28, 26–28 × 28–30 and 28–31 × 32–36 mn, and sedimented in sucrose density gradient and analytical centrifugation as three components with sedimentation coefficients of 76S, 87S and 98S. The virus contained a single polypeptide species of mol. wt of c. 25 000. Unfractionated TSV/Cle preparations contained four RNA species with mol. wts, estimated by gel electrophoresis in agarose, of 1.1 × 10⁶, 0.9 × 10⁶, 0.7 × 10⁶ and 0.3 × 10⁶. In comparative experiments, TSV/Cle differed from four reference strains of TSV (TSV/B, TSV/HF, TSV/RN, and TSV/Ro) in host range and in symptoms induced in some common hosts. In agar gel double diffusion tests it was more closely related to TSV/B and TSV/M (SDI = 5) than to TSV/HF (SDI = 7), TSV/RN (SDI = 7) or TSV/Ro (SDI = 5–8). Immunoelectrophoresis experiments clearly distinguished TSV/Cle from the reference strains. TSV/Cle strain was detected in C. vitalba plants from distant and climatically different regions in Yugoslavia.