Food webs are of crucial importance for understanding any ecosystem. The accuracy of food web and ecosystem models rests on the reliability of the information on the feeding habits of the species involved. Water boatmen (Corixoidea) is the most diverse superfamily of water bugs (Heteroptera: Nepomorpha), frequently the most abundant group of insects in a variety of freshwater habitats worldwide. In spite of their high biomass, the importance of water boatmen in aquatic ecosystems is frequently underestimated. The diet and feeding habits of Corixoidea are unclear as published data are frequently contradictory. We summarise information on the feeding habits of this taxon, which exemplify the difficulties in evaluating published data on feeding habits in an invertebrate taxon. It is concluded that Corixoidea are, unlike other true bugs, capable of digesting solid food, but their feeding habits are still insufficiently known. The dominant feeding strategy in this taxon is zoophagy, but several species consume other foods, particularly algae and detritus. Only members of the subfamily Cymatiainae seem to be exclusively predators. In other subfamilies, the diet of different species and different sexes or populations of a single species may vary depending on the food available or is still unknown. We conclude, that a multi-method approach is needed to elucidate the feeding habits of aquatic insects and invertebrates in general., Christian W. Hädicke, Dávid Rédei, Petr Kment., and Obsahuje bibliografii
The physical conditions of a large variety of structures, such as giant HII regions, holes, shells and rings, present in the interstellar medium are reviewed. Such structures are thought to result from the energy input from OB associations in the form of ionizing radiation, strong stellar winds and supernova explosions.
The study of the effects produced by every single one of the energy sources is proposed here as the way to evaluate, understand, and relate the observed structures with a given energy input. In particular, predictions fron the study of the HII region evolution sround a stellar association are reviewed. Such an evolution , lasting 10^7 yr, accounts for the aging of the exciting stars. The resultant effects are then compared with the large (expecting and static) shells observed in our galaxy, and with alternative theoretical models.
A sequence of events, based on the observed properties and the theoretical models, is proposed here as a likely scenario for the evoluton of the environment of an OB association.
Vascular endothelium plays an essential role in the pathogenesis of vasoocclusion. The changes in the endothelial cell function can be triggered by changes in gene expression caused by interaction with cytokines and blood cells. Using cDNA arrays, we have recently reported complex patterns of gene expression after stimulation of endothelial cells with TNFα and IL-1β. Better understanding of the time course of gene expression changes, their concentration dependence and reversibility after withdrawal of the offending cytokine is essential for successful prevention and therapy of vasoocclusion. Here we present a detailed study of the concentration dependence and time course of gene expression in endothelial cells after their exposure to TNFα and IL-1β. We focus on the adhesion molecules (VCAM-1, ICAM-1, E-selectin) and cytokines (IL-6, GCP-2, MCP-1) that are likely to contribute to vasoocclusion. We report differences in the time course and intensity of their expression and in their response to TNFα and IL-1β stimulation. We demonstrate that expression of the studied genes is upregulated by low TNFα concentrations that better reflect the TNFα levels detected in the plasma of patients developing vasoocclusion. These results help to understand the changes in the endothelium and to design rational prevention and therapy of vasoocclusion.
Increased colonic Cl - secretion was supposed to be a causative factor of diarrhea in inflammatory bowel diseases. Surprisingly, hyporesponsiveness to Cl - secretagogues was later described in inflamed colon. Our aim was to evaluate changes in secretory responses to cholinergic agonist ca rbachol in distal and proximal colon during colitis development, regarding secretory activity of enteric nervous system (ENS) and prostaglandins. Increased responsiveness to carbachol was observed in both distal and proximal colon after 3 days of 2 % dextran sodium sulfate (DSS) administration. It was measured in the presence of mucosal Ba2+ to emphasize Cl - secretion. The described increase was abolished by combined inhibitory effect of tetrodotoxin (TTX) and indomethacin. Indomethacin al so significantly reduced TTX- sensitive current. On the 7 th day of colitis development responsiveness to carbachol decreased in distal colon (compared to untreated mice), but did not change in proximal colon. TTX- sensitive current did not change during colitis development, but indomethacin-sensitive current was significantly increased the 7 th day. Decreased and deformed current responses to serosal Ba 2+ were observed during colitis induct ion, but only in proximal colon. We conclude that besides inhibitory effect of DSS on distal colon responsiveness, there is an early stimulatory effect that manifests in both distal and proximal colon., M. Hock ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Brachiola algerae (Vavra et Undeen, 1970) Lowman, Takvorian et Cali, 2000, originally isolated from a mosquito, has been maintained in rabbit kidney cells at 29°C in our laboratory. This culture system has made it possible to study detailed aspects of its development, including spore activation, polar tube extrusion, and the transfer of the infective sporoplasm. Employing techniques to ultrastructurally process and observe parasite activity in situ without disturbance of the cultures has provided details of the early developmental activities of B. algerae during timed intervals ranging from 5 min to 48 h. Activated and non-activated spores could be differentiated by morphological changes including the position and arrangement of the polar filament and its internal structure. The majority of spores extruded polar tubes and associated sporoplasms within 5 min post inoculation (p.i.). The multilayered interlaced network (MIN) was present in extracellular sporoplasms and appeared morphologically similar to those observed in germination buffer. Sporoplasms, observed inside host cells were ovoid, contained diplokaryotic nuclei, vesicles reminiscent of the MIN remnants, and their plasmalemma was already electron-dense with the "blister-like" structures, typical of B. algerae. By 15 min p.i., the first indication of parasite cell commitment to division was the presence of chromatin condensation within the diplokaryotic nuclei, cytoplasmic vesicular remnants of the MIN were still present in some parasites, and early signs of appendage formation were present. At 30 min p.i., cell division was observed, appendages became more apparent, and some MIN remnants were still present. By two hours p.i., the appendages became more elaborate and branching, and often connected parasite cells to each other. In addition to multiplication of the organisms, changes in parasite morphology from small oval cells to larger elongated "more typical" parasite cells were observed from 5 h through 36 h p.i. Multiplication of proliferative organisms continued and sporogony was well underway by 48 h p.i., producing sporonts and sporoblasts, but not spores. The observation of early or new infections in cell cultures 12-48 h p.i., suggests that there may also exist a population of spores that do not immediately discharge, but remain viable for some period of time. In addition, phagocytized spores were observed with extruded polar tubes in both the host cytoplasm and the extracellular space, suggesting another means of sporoplasm survival. and Finally, extracellular discharged sporoplasms tightly abutted to the host plasmalemma, appeared to be in the process of being incorporated into the host cytoplasm by phagocytosis and/or endocytosis. These observations support the possibility of additional methods of microsporidian entry into host cells and will be discussed.
The history of the journals "Photosynthetica" and "Photosynthesis Research" is traced from its beginning. Their development is related to the history of several publishers (Dr W. Junk Publishers, Martinus Nijhoff, Kluwer Academic Publishers). This account is based on recollections and records of the authors, Ad C. Plaizier, and René Marcelle (the first Editor-in-Chief of Photosynthesis Research). and Govindjee, Z. Šesták, W. R. Peters.
Male Wistar rats adapted to an artificial light-dark regimen (12 h light: 12 h darkness) were whole-body irradiated with a dose of 14.35 Gy of gamma rays. Irradiation, sham-irradiation and decapitation 30, 60 and 120 min after the exposure were performed between 2000 h and 0100 h in the darkness. The serotonin N-acetyltransferase activity (NAT), the concentration of melatonin, dopamine, norepinephrine and epinephrine were measured in the pineal gland. The serum levels of melatonin and corticosterone were also determined. Ionizing radiation did not change the activity of the key enzyme of melatonin synthesis, NAT, but decreased the concentration of pineal melatonin. The concentration of pineal dopamine and norepinephrine decreased 30 and 120 min after exposure, while the concentration of epinephrine was elevated 30 min after irradiation, though later it was markedly decreased. The serum melatonin level was not changed, but an increase in corticosterone level was observed. In the early period after the exposure, a decrease in pineal melatonin occurred, accompanied by a decrease in pineal catecholamines. On the contrary, in the phase of developed radiation injury the signs of increased melatonin synthesis were observed on days 3 and 4 after the exposure (Kassayova et al. 1993a). The underlying mechanisms require further research.
Two hundred and forty brown trout (Salmo trutta) and 49 rainbow trout (Oncorhynchus mykiss), obtained from 21 locations in Central Scotland between October 1990 and August 1993, were examined for endoparasitic helminth infections. Crepidostomum farionis (Digenea) was the most widely distributed helminth species, followed by Eubothrium crassum (Cestoda), Diphyllobothrium dendriticum and D. ditremum (Cestoda), Neoechinorhynchus rutili (Acanthocephala), Echinorhyn-chus truttae (Acanthocephala), Eustrongylides sp. (Nematoda), Capillaria salvelini (Nematoda), Cyalhocephalus truncatus (Cestoda), Raphidascaris acus (Nematoda) and Cystidicola farionis (Nematoda), in that order. The prevalences and intensities of each helminth infection were recorded. No evidence was found to indicate that even fish with the highest worm burdens (e.g. 339 plerocercoids of Diphyllobothrium spp.) were experiencing any obvious morbidity. An analysis of pairs of associations between species of helminths revealed a significantly positive association between N. rutili and C. farionis (P < 0.01). The results are discussed in terms of patterns in helminth communities in freshwater fish.