ANTHERIDIAL CHROMATIN CONDENSATION FACTOR FROM MALE SEX ORGANS OF CHARA TOMENTOSA

Incubation of roots (Melandrium noctiflorum) in crude extracts obtained from maturing male sex organs of Chara tomentosa results in supercondensation of mitotic chromosomes. The observed changes, including a number of ‘secondary effects’, confirm precisely with all those kinds of alterations which are typical of M-phase cells in antheridial filaments during their progression from the proliferative period of development towards terminal differentiation into sperm cells. Biological assays performed with proteinaceous extracts of maturing antheridia indicate that the activity is confined merely to a fraction containing low molecular (4.5kDa) peptides, termed as ACCF (antheridial chromatin condensation factor). Microchemical tests showed the acidic character of ACCF and its apparent ability to form cross-links with histones and DNA-histone complexes, mediated presumably by disulfide bridges. The characteristic punctate distribution of vesicles within the cytoplasm suggests the internalization of rhodamine-isothiocyanate labelled ACCF (ACCF-TRITC) by endocytosis, implying possible sequestering and nuclear translocation upon release from the endosomal/lysosomal compartment of the cell.     

Taphonomy of dense ophiuroid accumulations from the Middle Triassic of Poland

The taphonomy of three Middle Triassic (Muschelkalk) monospecific ophiuroid taphocoenoses, comprising Aspiduriella similis (Eck), from different regions in Poland (Holy Cross Mountains, Upper Silesia and North-Sudetic Basin) has been investigated. The majority of specimens (88.5% of a total of 428 individuals) are partially disarticulated, having only proximal and median portions of their arms preserved (Taphonomic Group 2). Pristine specimens, with only faint traces of disarticulation (Taphonomic Group 1), as well as those that preserve the disc only, or which have only proximal stumps of arms preserved (Taphonomic Group 3), are much rarer (6.5% and 5%, respectively). Moreover, most specimens (76.4%) are oral side up. Only 19.2% of specimens are preserved in life position, and a small fraction (4.4%) are preserved oblique to bedding. All ophiuroids studied occur in thin, pelitic layers devoid of any trace fossils. Associated body fossils, such as bivalves, gastropods or crinoids, are very rare. Taking into account ophiuroid taphonomy, as well as sedimentological characteristics of the thin layer (burial layer), it is clear that all assemblages were transported prior to burial. The predominance of articulated skeletons indicates that the burial event (obrution event) was not only rapid, but also single – subsequent events would have destroyed the previously buried ophiuroids. Storm-related resuspension of fine-grained material from nearshore environments which covered the ophiuroids is the most likely burial agent. The fact that in all regions the ophiuroid taphofacies studied is identical suggests that the three assemblages underwent the same burial history, and that a single event might have been responsible.     Muschelkalk , ophiuroids , Poland , taphonomy , Triassic .     

Effect of Monovalent Thallium Ions on Differentiation and Multiplication of Acanthamoeba castellanii

The vegetatively multiplying Acanthamoeba castellanii cells are transformed into cysts under unfavourable feeding conditions. The cyst formation may also be induced by treatment of the cells with DNA-synthesis inhibitors or by placing the cells into special ionic medium containing magnesium and calcium at pH 9, with aeration. During Acanthamoeba encystment the morphology of the cells changes significantly, namely a cellulose-protein cyst wall appears which is easily seen under the light and electron microscope. The process of encystment in Acanthamoeba castellanii is considered as a useful simple model of cytodifferentiation of eukaryotic cells.
This communication describes the effects of monovalent thallium ions on the differentiation and multiplication of Acanthamoeba cells growing in optimal feeding conditions. Thallium ions being potassium analogues are readily accumulated by cells. On the other hand, thallium ions, unlike potassium ions, are able to form complexes with some anions, which results in disturbances of some cellular functions.
Thallium ions, added to the growth medium of 2–3-days old Acanthamoeba culture at a concentration of 0.05–1.0 mM inhibit the population growth inducing the differentiation of cells into cysts. The increase of the thallium ion concentration up to 5 or 10 mM in the growth medium causes the very fast multiplication of Acanthamoeba cells. However, at these thallium ion concentrations no cysts can be observed.
Thus, on the basis of the experimental data it seems likely that thallium ions play some role in increasing the rate of multiplication and in switching on the differentiation process (encystment) in Acanthamoeba cells.     

Morphology of Pinus uliginosa (Pinaceae) needles from populations exposed to and isolated from the direct influence of Pinus sylvestris

Eleven needle traits of two contrasting populations of Pinus uliginosa ( P. mugo complex), one located in a Pinus sylvestris forest, the other isolated from the influence of this species, were compared to quantify the degree of hybridization. Statistically significant differences between the studied populations were found, but both of them differed by a similar degree from P. sylvestris . Surprisingly, the P. uliginosa population surrounded by the P. sylvestris forest, which was expected to consist of individuals with intermediate traits, appeared to be more closely related to P. mugo than those isolated from the direct influence of P. sylvestris . Large differences in the distances between the analysed pair of populations of P. uliginosa and P. sylvestris have not influenced the morphological traits of the species. Gene flow from P. sylvestris to P. uliginosa is possible, but is likely to be small and does not differ compared with populations of P. uliginosa . The decline observed during the last three decades in both populations of the species has not influenced their needle morphological traits.  © 2003 The Linnean Society of London , Botanical Journal of the Linnean Society , 2003, 142, 83–91.     

A NEW EARLY CARBONIFEROUS MICRO-PRODUCTID BRACHIOPOD FROM SOUTH CHINA

Abstract:  We describe Muhuarina haeretica gen. et sp. nov. from a recently discovered silicified brachiopod fauna from the Lower Carboniferous of South China. This new microproductid appears to be the oldest representative of the highly differentiated, mainly Permian, aulostegoid family Cooperinidae. The internal structure of the dorsal valve of M. haeretica is dominated by strongly developed, pronounced subperipheral ridges, which suggest support for a simple schizolophe type of lophophore. Brachial ridges, as in other productides, most probably represent an attachment area of the lophophore to the dorsal epithelium. An attempt to homologize subperipheral and brachial ridges among Cooperinidae is presented.     

PHYTOALEXIN DEFICIENT 4 affects reactive oxygen species metabolism,cell wall and wood properties in hybrid aspen (Populus tremula L. × tremuloides)

The PHYTOALEXIN DEFICIENT 4 (PAD4) gene in Arabidopsis thaliana (AtPAD4) is involved in the regulation of plant – pathogen interactions. The role of PAD4 in woody plants is not known; therefore, we characterized its function in hybrid aspen and its role in reactive oxygen species (ROS)‐dependent signalling and wood development. Three independent transgenic lines with different suppression levels of poplar PAD expression were generated. All these lines displayed deregulated ROS metabolism, which was manifested by an increased H₂O₂ level in the leaves and shoots, and higher activities of manganese superoxide dismutase (MnSOD) and catalase (CAT) in the leaves in comparison to the wild‐type plants. However, no changes in non‐photochemical quenching (NPQ) between the transgenic lines and wild type were observed in the leaves. Moreover, changes in the ROS metabolism in the pad4 transgenic lines positively correlated with wood formation. A higher rate of cell division, decreased tracheid average size and numbers, and increased cell wall thickness were observed. The results presented here suggest that the Populus tremula × tremuloides PAD gene might be involved in the regulation of cellular ROS homeostasis and in the cell division – cell death balance that is associated with wood development.     

Regulation of Melanogenesis in Melanocytes

Melanogenesis refers to the biosynthesis of melanin pigment in pigment cells called melanocytes. Melanins are mixed biopolymers formed during a series of oxidation/reduction reactions that are initiated by the enzymatic hydroxylation of L-tyrosine to L-dopa. In living cells, melanogenesis is limited to melanosomes, the membrane bounded microscopic secretory granules of melanocytes. Melanosomes may be secreted into the environment as, for example, from the squid's ink gland; or be transferred to neighboring cells, such as the keratinocytes in human skin and hair; or they may remain within the pigment cell and change only their subcellular localization, as in the rapidly color-changing dermis of lower vertebrates. Regulation of the melanocytic phenotype involves synthesis of the biosynthetically active subcellular apparatus of melanogenesis, premelanosomes and tyrosinase, and the utilization of the final product, melanized melanosomes, in the translocation and secretory processes mentioned above. Genetic information for this regulation is stored in the nuclear genome whose expression is controlled by the intra- and extracellular environment. As premelanosomes become biosynthetically active, they mature into melanosomes by fusing with vesicles derived from the trans-Golgi network and the plasmalemma, thereby internalizing and incorporating contents and membrane components from inside the cell and the cell surface. In the process, melanosomes become acidified. The thesis pursued in this review explores the importance of the melanosome as the final common pathway of regulation of melanin biosynthesis.     

Predators can induce swarming behaviour and locomotory responses in Daphnia

1. Exposure to chemical cues released by fish induced a tendency to form and maintain aggregations in two Daphnia clones originating from habitats inhabited by fish (and invertebrate predators), while Daphnia from a clone originating from a fishless habitat did not aggregate in response to fish cues.
2. Daphnia from one of the two clones responsive to fish cues, also aggregated in response to chemical cues released by invertebrate predators or to a substance released from homogenized Daphnia .
3. Chemical cues released by predators and the substance released from homogenized conspecifics induced a significant decrease in Daphnia' s swimming speed and an increased readiness to perform a somersaulting escape behaviour, especially in response to light cues.     

Lectin Analysis of Surface Saccharides in Two Trichomonas vaginalis Strains Differing in Pathogenicity*

SYNOPSIS. Surface saccharides in 2 Trichomonas vaginalis strains, the moderately pathogenic, JH34A, and the mild, JH162A, were analyzed with the aid of plant lectins. Concanavalin A (Con A), wheat germ agglutinin (WGA), soybean agglutinin (SBA), castor bean agglutinin (CBA), and lectin from the garden pea (GPA) were employed in agglutination tests and in treatment of ultrathin sections for electron microscopy according to the horseradish peroxidase-3,3′-diaminobenzidine method. With Con A and WGA, small quantitative differences were noted between the 2 strains in the results of agglutination and in the reaction-product deposits observed by electron microscopy. Distribution of the binding sites for the 2 lectins was also somewhat different in the JH34A and JH162A trichomonads. In general, the reactions with the more pathogenic strain were slightly stronger. Although the reactions with SBA and CBA lectins were weaker than those with Con A or WGA, they provided the means for qualitative differentiation between the 2 trichomonad strains. SBA alone agglutinated the JH34A strain and formed demonstrable deposits on the cell surfaces. On the other hand, only CBA reacted with JH162A flagellates. The garden pea lectin failed to bind to the surface of either strain. On the basis of results obtained with the control preparations incubated in the presence of specific inhibitors, it was concluded that both strains had α-methyl-D-mannoside and/or α-methyl-D-mannoside-like as well as N-acetyl-D-glucosamine residues on their surfaces. In addition, JH34A strain had D-lactose-containing residues while JH162A trichomonads had residues with D-galactose. Neither strain appeared to possess residues containing N-acetyl-D-galactosamine.