Comparative studies of D-myoinositol 1,4,5-trisphosphate and synthetic 6-deoxy D-myoinositol 1,4,5-trisphosphate: binding and calcium release activity in rat parotid microsomes.

In this study, we report our data on the binding of D-myoinositol(1,4,5)P3 and of 6-deoxy D-myoinositol(1,4,5)P3 to a rat parotid microsomal fraction and their effect on Ca2+ release. The binding affinity and the potency of 6-deoxy Ins(1,4,5)P3 to induce Ca2+ release are about 100 times lower than those of Ins(1,4,5)P3. However, maximal concentrations of both inositol trisphosphates induce similar calcium efflux and present comparable displacement of radioligand binding. Experiments were performed to exclude that the microsomal preparations used display rapid metabolism of Ins(1,4,5)P3 or 6-deoxy Ins(1,4,5)P3 during binding and Ca2+ release. We also report that, in permeabilized rat parotid acini preparations, 6-deoxy Ins(1,4,5)P3 is about 100 times less potent than Ins(1,4,5)P3 in inducing Ca2+ release. These data indicate that removal of the hydroxyl group in position 6 of the Ins(1,4,5)P3 molecule severely reduces its binding affinity which seems, in a large part at least, responsible for the reported loss of potency in mobilizing Ca2+. Nevertheless, 6-deoxy Ins(1,4,5)P3 seems to be a full agonist for the release of Ca2+.     

Reef-bryozoans and bryozoan-microreefs: Control factor evidence from the philippines and other regions

Summary In this paper, a preliminary concept on the interplay of local, regional and global control factors of bryozoan diversity and distribution pattern is introduced. Recent bryozoans from the Philippines, New Zealand and the Gulf of Aqaba are compared to the selected fossil specimens from the Oxfordian and Santonian. Reef bryozoan skeletons are studied in order to separate local control within the substrate-water interface from regional control. The latter originate mainly from the transport function of the water column (e.g. sediment load, wave energy, vagile predators). This is true especially for erect (tree-like) and massive (multilaminar) bryozoans which are subjected to the dynamics of the water body in the littoral area. This regional control, affects simultaneously several structural and substrate zones of a reef. Early life history of vertically growing reef bryozoans reflect local control, while older zoarial structures reflect the signals of regional influence. Three types of multiserial nodular bryozoans are cited: self-overgrowing sheets (‘S-Nodule’, derived from ‘S-Sheet’), circumlaterally budding colonies (‘C-Nodules’), and fungiform bryozoans. Bryozoan growth form selection allows the separation of two types of regional controls, long range control which favours the selection of specialized sheets, and slow rate control documented in the growth form modification of sheets changing into nodules. In the domain of local control epibiontic microorganisms, microbial mats and biofilms on hard substrata represent probably the most important elements, aside from the limited substrate space. Symbiotic and/or competitive bryozoan-microorganism interrelationships result in the distinct adaptations of bryozoan growth. It is apparent that bryozoan modifications of substrate micro-topography influence the character of epibiontic microbial settlement. The peak occurrence of microbial settlement on prominent external bryozoan skeleton parts is discussed as an effect of feeding currents. In contrast, smooth and unelevated exoskeletons are less favourable for micro-epibiontic colonization. Due to the high level of order in the spatial zonation patterns of epibionts on calcifying bryozoans, the term ‘bryozoan-microreef’ is introduced. Bryozoan-microreefs are locally controlled reefs. They are e.g. characterized by higher competitive abilities than bryozoans without ‘reefdwellers’. Local control has a fast rate of change and is reflected in morphologies of individual zooids and/or single zooid generations. Regional control has a slower rate but a higher range. It is important for growth modifications of the whole zoaria. The very slow rate of global control cannot be recorded within the life span of bryozoan zoaria unless it is expressed through regional control (such as monsoons). Nevertheless, global control is paleoecologically important because it is traceable in bryozoan (paleo-)biogeography. For practical purpose, we suggest to define those control factors of bryozoans as global which affect simultaneously at least one tropical and one non-tropical bryozoan community. This reportis dedicated to the memory of our friend and research colleague Mr. Joselito G. Santiago of the University of San Carlos, Marine Biology Section. Tiago (as we fondly call him) has started within the scope of the Philippine Bryozoan Project an applied research on fish abundance and productivity around a new artificial reef model. This prototype model was conceptualized with him. His promising study remained unfinished; he died May 13, 1993, while sampling inside the reef cave off Marigondon.     

Pyrimidine de novo synthesis during the life cycle of the intraerythrocytic stage of Plasmodium falciparum

The 6 enzymes involved in de novo synthesis of pyrimidines were measured in Plasmodium falciparum isolated by saponin lysis from RBC's nonsynchronized and synchronized in vitro cultures. The total activities were found to be dependent on the stage of the P. falciparum cycle. In parasites isolated from synchronized cultures, the highest activities for all enzymes were found at about 27 hr after synchronization in the late trophozoite stage, or just before schizont formation. Merozoites and ring forms contained little de novo activity. The first enzyme of the pathway, carbamyl phosphate synthetase (CPS-II) preferentially utilized glutamine. Ammonia was a poor substrate. CPS-II was unstable in the absence of the cryoprotectants, dimethylsulfoxide and glycerol. The apparent Km for MgATP--was 3.8 +/- 0.7 mM and the enzyme in all morphological forms of P. falciparum (ring, mature trophozoites and schizonts) was inhibited by UTP. The activity of the fourth enzyme of the pathway, dihydroorotate dehydrogenase, appeared to be linked to the cell's respiratory chain; inhibitors of mammalian electron transport such as cyanide, amytal, antimycin A, thenoyltrifluoroacetone and ubiquinone analogs also inhibited the P. falciparum enzyme. The demonstration of the variation of activity of the pyrimidine enzymes correlates with the increased synthesis of nucleic acids in the late trophozoite stage. These observations provide a basis for the testing of the effectiveness of pyrimidine analogs as potential antimetabolites against various forms of the parasite.     

Interaction of the tracheal tubules of Scutigera coleoptrata (Chilopoda,Notostigmophora) with glandular structures of the pericardial septum

Notostigmophora (Scutigeromorpha) exhibit a special tracheal system compared to other Chilopoda. The unpaired spiracles are localized medially on the long tergites and open into a wide atrium from which hundreds of tracheal tubules originate and extend into the pericardial sinus. Previous investigators reported that the tracheal tubules float freely in the hemolymph. However, here we show for the first time that the tracheal tubules are anchored to a part of the pericardial septum. Another novel finding is this part of the pericardial septum is structured as an aggregated gland on the basis of its specialized epithelium being formed by hundreds of oligocellular glands. It remains unclear whether the pericardial septum has a differently structure in areas that lack a connection with tracheal tubules. The tracheal tubules come into direct contact with the canal cells of the glands that presumably secrete mucous substances covering the entire luminal cuticle of the tracheal tubules. Connections between tracheae and glands have not been observed in any other arthropods.     

¹²⁵I]SD-7015 reveals fine modalities of CB₁ cannabinoid receptor density in the prefrontal cortex during progression of Alzheimer's disease

The cannabinoid type-1 receptor (CB₁R) is one of the most abundant members of the G protein-coupled receptor family in the central nervous system. Once activated by their cognate ligands, endocannabinoids, CB₁Rs generally limit the timing of neurotransmitter release at many cortical synapses. Prior studies have indicated the involvement of CB₁R in neurodegeneration and in various neuronal insults, with an emphasis on their neuroprotective role. In the present study we used a novel selective CB₁R radioligand to investigate regional variations in CB₁R ligand binding as a factor of progressive Braak tau pathology in the frontal cortex of Alzheimer’s disease (AD) patients. The frontal cortex was chosen for this study due to the high density of CB₁Rs and their well-characterized involvement in the progression of AD. Post-mortem prefrontal cortex samples from AD patients from Braak stages I to VI and controls were subjected to CB₁R autoradiography with [¹²⁵I]SD-7015 as radioligand. Regional concentration of [¹²⁵I]SD-7015, corresponding to, and thereby representing, regional CB₁R densities, were expressed in fM/g_tissue. The results show that CB₁R density inversely correlates with Braak tau pathology with the following tendency: controls 1R radioligand [¹²⁵I]SD7015 in human brains, allowing the detection of fine modalities of receptor expression and radioligand binding during the progression of AD.     

Myosin-5, kinesin-1 and myosin-17 cooperate in secretion of fungal chitin synthase

Plant infection by pathogenic fungi requires polarized secretion of enzymes, but little is known about the delivery pathways. Here, we investigate the secretion of cell wall-forming chitin synthases (CHSs) in the corn pathogen Ustilago maydis. We show that peripheral filamentous actin (F-actin) and central microtubules (MTs) form independent tracks for CHSs delivery and both cooperate in cell morphogenesis. The enzyme Mcs1, a CHS that contains a myosin-17 motor domain, is travelling along both MTs and F-actin. This transport is independent of kinesin-3, but mediated by kinesin-1 and myosin-5. Arriving vesicles pause beneath the plasma membrane, but only ~15% of them get exocytosed and the majority is returned to the cell centre by the motor dynein. Successful exocytosis at the cell tip and, to a lesser extent at the lateral parts of the cell requires the motor domain of Mcs1, which captures and tethers the vesicles prior to secretion. Consistently, Mcs1-bound vesicles transiently bind F-actin but show no motility in vitro. Thus, kinesin-1, myosin-5 and dynein mediate bi-directional motility, whereas myosin-17 introduces a symmetry break that allows polarized secretion.     

Does Lake Balaton affected by pollution? Assessment through surface water quality monitoring by using different assessment methods

In order to maintain a good environmental status of surface waters, an assessment of water quality carried out at specific intervals to monitor the changes of water quality in function of time. Human knowledge and experience are currently focused on using assessment methods, especially the integration of multiple constraining factors and considering them in conjugation with the correct decision-making process concerning the environment. When surface water is highly exposed to human activities, either from recreational or economic activity, the degree of vulnerability is high, and the quality of surface water is highly compromised. In case of Lake Balaton, there are many activities that can disrupt water dynamics. The first goal of this study is to determine the location of the least and most polluted sites around Lake Balaton. The processing of data was carried out by using multi-criteria decision techniques and environmental impact assessment method based on physical–chemical parameters in comparison with the limiting parameters. Based on the results of those methods water quality needs to be improved in western parts of the lake by using several geoengineering treatment techniques. This work covers a novel approach to comparing methods based on sum of ranking differences, whereas many method comparison studies suffer from ambiguity or from comparisons not being quite fair. This problem can be avoided if there are differences between ideal and actual rankings.     

Baculovirus actin-rearrangement-inducing factor ARIF-1 induces the formation of dynamic invadosome clusters

The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV), a pathogen of lepidopteran insects, has a striking dependence on the host cell actin cytoskeleton. During the delayed-early stage of infection, AcMNPV was shown to induce the accumulation of actin at the cortex of infected cells. However, the dynamics and molecular mechanism of cortical actin assembly remained unknown. Here, we show that AcMNPV induces dynamic cortical clusters of dot-like actin structures that mediate degradation of the underlying extracellular matrix and therefore function similarly to clusters of invadosomes in mammalian cells. Furthermore, we find that the AcMNPV protein actin-rearrangement-inducing factor-1 (ARIF-1), which was previously shown to be necessary and sufficient for cortical actin assembly and efficient viral infection in insect hosts, is both necessary and sufficient for invadosome formation. We mapped the sequences within the C-terminal cytoplasmic region of ARIF-1 that are required for invadosome formation and identified individual tyrosine and proline residues that are required for organizing these structures. Additionally, we found that ARIF-1 and the invadosome-associated proteins cortactin and the Arp2/3 complex localize to invadosomes and Arp2/3 complex is required for their formation. These ARIF-1–induced invadosomes may be important for the function of ARIF-1 in systemic virus spread.     

The Myosin Motor Domain of Fungal Chitin Synthase V Is Dispensable for Vesicle Motility but Required for Virulence of the Maize Pathogen Ustilago maydis

Class V chitin synthases are fungal virulence factors required for plant infection. They consist of a myosin motor domain fused to a membrane-spanning chitin synthase region that participates in fungal cell wall formation. The function of the motor domain is unknown, but it might deliver the myosin chitin synthase-attached vesicles to the growth region. Here, we analyze the importance of both domains in Mcs1, the chitin synthase V of the maize smut fungus Ustilago maydis. By quantitative analysis of disease symptoms, tissue colonization, and single-cell morphogenic parameters, we demonstrate that both domains are required for fungal virulence. Fungi carrying mutations in the chitin synthase domain are rapidly recognized and killed by the plant, whereas fungi carrying a deletion of the motor domain show alterations in cell wall composition but can invade host tissue and cause a moderate plant response. We also show that Mcs1-bound vesicles exhibit long-range movement for up to 20 μm at a velocity of ~1.75 μm/s. Apical Mcs1 localization depends on F-actin and the motor domain, whereas Mcs1 motility requires microtubules and persists when the Mcs1 motor domain is deleted. Our results suggest that the myosin motor domain of ChsV supports exocytosis but not long-range delivery of transport vesicles.