Epidermal structures and stomatal parameters of Chinese endemic Glyptostrobus pensilis (Taxodiaceae)

Glyptostrobus pensilis K. Koch, the only living species, is endemic to southern China. Epidermal structures of G .  pensilis have been studied on leaves collected from Guangzhou, southern China, the native locality of the species, and from Hangzhou, eastern China, the cultivated locality. Leaves are linear, linear-subulate and scale-like. Epidermal cells are rectangular and elongate parallel to the mid-vein on areas lacking stomata, and short, with rounded corners, on intrastomatal areas. Stomatal bands lie parallel to the mid-vein on both surfaces of leaves. Commonly the stomata have five or six subsidiary cells. Stomatal parameters (density and index) of the same surfaces of linear leaves from Guangzhou and Hangzhou show no statistically significant differences ( P  > 0.05). Considering the stomatal parameters of the same surfaces of linear-subulate leaves between the two localities, the stomatal index of the abaxial surfaces reveals no significant differences ( P  > 0.05), while the stomatal index of the adaxial surfaces and the stomatal density of both surfaces exhibit significant differences ( P  < 0.05). Intra-individual variation in stomatal index is smaller than that in stomatal density based on the coefficient of variability of stomatal parameters of the same areas of leaves. When studying the correlation between stomatal parameters of G. pensilis and atmospheric CO₂ concentrations, the stomatal parameters of linear leaves are mostly significant, and stomatal index is more useful than stomatal density.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 153–162.     

The Effect of Temperature on the Light-Induced Pigment Movement in Fish Corneal Chromatophores

Corneal chromatophores of unusual morphology were used for studies on the influence of temperature on the intracellular pigment movement in two species of marine fish from different temperature zones: the tropical puffer, Canthigaster cinctus, and boreal whitespotted greenling, Hexagrammos stelleri. It was shown that both dispersion under bright illumination and aggregation at darkening are slower or decrease at lower temperatures when examined in the range of 12–27°C. The mean speed of the pigment translocations in the individual cell process was 0.38 μm/s at the highest temperature examined, with a range of 0.17–1.0 μm/s. Near the middle of the temperature range, the dynamic characteristics of cell pigment movement in tropical and boreal species were rather close, suggesting that there would be little divergent adaptations with respect to the mechanisms of the pigment transport. Corneal chromatophores are considered as a new promising model for cell motility studies.     

Differentiation along a gradient of environmental productivity and predictability in populations of Hordeum spontaneum Koch: multilevel selection analysis

A contextual analysis combined with path analysis was applied to detect ecotype-specific past selection in hierarchically structured populations of wild barley, Hordeum spontaneum . In our analysis a multiple regression model incorporated several individual and ecotype-level unmeasured (derived) traits obtained by factor analysis from 20 measured morphological and phenological traits. Under favourable conditions (high water and nutrients) both individual and ecotype plant size (RF1) were significant predictors of individual plant fitness, estimated by either reproductive biomass or yield. Both individual and ecotype size of reproductive structures (RF2) were significantly related to individual reproductive biomass. Individual yield, however, significantly correlated with ecotype RF2 only. Transition to reproduction (RF3) correlated with neither reproductive biomass nor yield at individual level, but correlated with two estimates of fitness at ecotype level. In all cases, selection at the individual and ecotype levels was in opposition. We interpret the observed effect of ecotype identity on individual fitness not as a current group selection, but as a constraining effect of ecotype-specific past selection. The four ecotypes went through an environmentally specific selection process in their own environments with the optimal strategy evolved. Consequently, this strategy may have a constraining effect on plant performance in other environments. Under conditions of either low water or low nutrients the ecotype level did not contribute to individual fitness. The latter may suggest that a mechanism for plant responses to stress is largely independent of plant origin, with a difference between ecotypes under stressful conditions due entirely to the difference in amount, not architecture, of plasticity. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 313–318.     

Sudden expansion of a single brown bear maternal lineage across northern continental Eurasia after the last ice age: a general demographic model for mammals?

The brown bear has proved a useful model for studying Late Quaternary mammalian phylogeography. However, information is lacking from northern continental Eurasia, which constitutes a large part of the species' current distribution. We analysed mitochondrial DNA sequences (totalling 1943 bp) from 205 bears from northeast Europe and Russia in order to characterize the maternal phylogeography of bears in this region. We also estimated the formation times of the sampled brown bear lineages and those of its extinct relative, the cave bear.
Four closely related haplogroups belonging to a single mitochondrial subclade were identified in northern continental Eurasia. Several haplotypes were found throughout the whole study area, while one haplogroup was restricted to Kamchatka. The haplotype network, estimated divergence times and various statistical tests indicated that bears in northern continental Eurasia recently underwent a sudden expansion, preceded by a severe bottleneck. This brown bear population was therefore most likely founded by a small number of bears that were restricted to a single refuge area during the last glacial maximum. This pattern has been described previously for other mammal species and as such may represent one general model for the phylogeography of Eurasian mammals. Bayesian divergence time estimates are presented for different brown and cave bear clades. Moreover, our results demonstrate the extent of substitution rate variation occurring throughout the phylogenetic tree, highlighting the need for appropriate calibration when estimating divergence times.     

Identification of Microtubule-Organizing Centers in Interphase Melanophores of Xenopus Laevis Larvae In Vivo

The morphological characteristics of microtubule-organizing centers (MTOCs) in dermal interphase melanophores of Xenopus laevis larvae in vivo at 51-53 stages of development has been studied using immuno-stained semi-thick sections by fluorescent microscopy combined with computer image analysis. Computer image analysis of melanophores with aggregated and dispersed pigment granules, stained with the antibodies against the centrosome-specific component (CTR210) and tubulin, has revealed the presence of one main focus of microtubule convergence in the cell body, which coincides with the localization of the centrosome-specific antigen. An electron microscopy of those melanophores has shown that aggregation or dispersion of melanosomes is accompanied by changes in the morphological arrangement of the MTOC/centrosome. The centrosome in melanophores with dispersed pigment exhibits a conventional organization, and their melanosomes are situated in an immediate vicinity of the centrioles. In melanophores with aggregated pigment, MTOC is characterized by a three-zonal organization: the centrosome with centrioles, the centrosphere, and an outlying radial arrangement of microtubules and their associated inclusions. The centrosome in interphase melanophores is presumed to contain a pair of centrioles or numerous centrioles. Because of an inability of detecting additional MTOCs, it has been considered that an active MTOC in interphase melanophores of X. laevis is the centrosome. We assume that remaining intact microtubules in the cytoplasmic processes of mitotic melanophores (Rubina et al., 1999) derive either from the aster or the centrosome active at the interphase.     

ALPHA-FETOPROTEIN-MEDIATED TARGETING—A NEW STRATEGY TO OVERCOME MULTIDRUG RESISTANCE OF TUMOUR CELLSIN VITRO

The possibility of overcoming the multidrug resistance of human malignant cells by using doxorubicin conjugated to alpha-fetoprotein (AFP) was studied. It was shown that this type of antitumour drugs, penetrating the cell by receptor-mediated endocytosis with AFP as a vehicle, raises the sensitivity of the tumour cells that are resistant due to the expression of the multidrug resistance genemdr1. The sensitivity of antibiotic-resistant cell lines SKVLB (a human ovarian carcinoma) and MCF-7 AdrR (a human breast carcinoma) increased by 10- and 4-fold, respectively, when AFP-conjugated doxorubicin was used. The rationale of using human AFP-antitumour drug conjugates for the development of new chemotherapeutic approaches to cancer treatment is discussed.     

Rediscovery of Paramecium nephridiatum Gelei, 1925 and its Characteristics

Paramecium nephridiatum Gelei. 1925, was rediscovered. It is a euryhaline brackish-water species that morphologically resembles Paramecium woodruffi . but with multiple contractile vacuole pores. The general morphology, morphometry. and random amplified polymorphic DNA (RAPD) fingerprint patterns are presented for a number of the stocks collected around the world.     

Trends in the ecological strategies and evolution of millipedes (Diplopoda)

Five main morphotypes (polyxenoid, glomeroid, juloid, polydesmoid, and platydesmoid) are denoted and five ecomorphotypes, i.e. life‐forms (stratobionts, troglobionts, geobionts, subcorticolous xylobionts, and epiphytobionts) are oudined in the Class Diplopoda. Their distribution and that of separate higher taxa show a number of marked ecological and geographical trends. The Diplopoda as a whole is believed to be originally a forest floor‐dwelling group, with stratobionts dominating everywhere, this life‐form having given rise to all other derivative, apparently synchronously evolved life‐forms. The poor development of the derived life‐forms points to their recent evolution, probably brought about by die great climatic changes of the last 2–3 Ma. The European fauna is characteristically dominated by the life‐form of stratobionts and in most areas by the juloid morphotype. However, the distribution of orders is strongly skewed. The habitats in Europe with richest millipede faunas seem to be temperate forests in the Atlantic zone and central mountain chains, where the Order Chordeumatida is strongly represented. This area contains several long‐term, or Ice Age, refugia. Further to the north, soudi and east, especially in open landscapes, along with an increasingly continental/Mediterranean climate, representatives of the juloid morphotype, mainly members of the Order Julida, become proportionately more common, while general species diversity falls. The ecological strategies of millipedes are rooted both in the group's phylogeny and in die Earth's history. In Europe diis history is peculiar owing to the east‐west lie of the principal mountain chains, and repeated glaciations have led to the development of a mixed, fully migratory, recent European faunal kernel, or nucleus, which is forced south and cornered in die largely mountainous western and central parts of the Continent during glaciations. Many local endemics have evolved in these areas, including a substantial proportion of cavernicolous species.