Does Actin Polymerization Status Modulate CaStorage in Human Neutrophils? Release and Coalescence of CaStores by Cytochalasins

The aim of this paper was to establish whether actin polymerization modulated cytosolic Ca²⁺storage in human neutrophils. Over the concentration ranges which inhibit actin polymerization, cytochalasins A, B, and D liberated Ca²⁺from membrane-bound stores within neutrophils. Two Ca²⁺storage sites were identified in neutrophils by the accumulation of the Ca²⁺binding probe, chlortetracycline: one at the center of the cell and the other at the cell periphery. Confocal imaging demonstrated that cytochalasins released Ca²⁺from the neutrophil periphery, but not from the central Ca²⁺store. Ca²⁺store release was coupled to Ca²⁺influx, suggesting that the peripheral site may be a physiological store containing a Ca²⁺influx factor. 3,3′-Dihexyloxacarbocyanine iodide staining organelles, which correlate with Ca²⁺release sites, coalesced in neutrophils after treatment with cytochalasins. We propose that peripheral Ca²⁺storage sites are restricted from coalescence by cortical polymerized actin and that Ca²⁺store coalescence and Ca²⁺release are coupled events.     

Marmoset phylogenetics, conservation perspectives, and evolution of the mtDNA control region

Marmosets (genus Callithrix) are a diverse group of platyrrhine primates with 13-15 purported taxa, many of them considered endangered. Morphological analyses constitute most of the basis for recognition of these forms as distinct taxa. The purpose of this study was to provide a molecular view, based on mitochondrial control region sequences, of the evolutionary history of the marmosets, concomitant with a molecular phylogenetic perspective on species diversity within the group. An additional purpose was to provide the first comparative examination of a complete New World monkey control region sequence with those of other mammals. The phylogenetic analyses provide convincing support for a split between the Atlantic forest and Amazonian marmosets, with the inclusion of the pygmy marmoset (Cebuella pygmaea) at the base of the Amazonian clade. The earliest branch of the Atlantic forest group was C. aurita. In the Amazonian group, the analyses do not support the recognition of C. humeralifer and the recently described C mauesi as distinct taxa. They do, however, support a clear distinction between C. argentata and a strongly supported mixed clade of C. humeralifer and C. mauesi. In the Atlantic forest group, the phylogenetic tree suggests mixing between C. penicillata, C. kuhli, and possibly C. jacchus. Most of the sequence features characteristic of other mammal control regions were also evident in marmosets, with the exception that conserved sequence blocks (CSBs) 2 and 3 were not clearly identifiable. Tandem repeat units often associated with heteroplasmy in a variety of other mammals were not evident in the marmoset sequences.      

Tetracycline fluorescence as calcium-probe for nerve membrane with some model studies using erythrocyte ghosts

Summary The tetracycline dyes, particularly chlorotetracycline, have been employed as probes of membrane-associated calcium during the excitation process of nerve. Both squid giant axons, stained internally, and lobster nerves, stained externally, show a small increase in fluorescent light during the action potential. Increasing the calcium concentration bathing a lobster nerve leads to a larger optical signal. Adding fluoride ion to the inside of a squid axon, which might be expected to influence the internal calcium-ion concentration, also leads to a larger optical signal. Squid axons have been studied under conditions of voltage clamp and the hyperpolarizing response. Model studies were done with erythrocyte ghosts to clarify the influence of membranes and calcium on the fluores-cence of the tetracyclines. Chlorotetracycline may be monitoring calcium concentration associated with the inner surface of the nerve membrane.     

Myxozoan parasitism in waterfowl

Myxozoans are spore-forming, metazoan parasites common in cold-blooded aquatic vertebrates, especially fishes, with alternate life cycle stages developing in invertebrates. We report nine cases of infection in free-flying native and captive exotic ducks (Anseriformes: Anatidae) from locations across the United States and describe the first myxozoan in birds, Myxidium anatidum n. sp. We found developmental stages and mature spores in the bile ducts of a Pekin duck (domesticated Anas platyrhynchos). Spores are lens-shaped in sutural view, slightly sigmoidal in valvular view, with two polar capsules, and each valve cell has 14-16 longitudinal surface ridges. Spore dimensions are 23.1 microm x 10.8 microm x 11.2 microm. Phylogenetic analysis of the ssrRNA gene revealed closest affinity with Myxidium species described from chelonids (tortoises). Our novel finding broadens the definition of the Myxozoa to include birds as hosts and has implications for understanding myxozoan evolution, and mechanisms of geographical and host range extension. The number of infection records indicates this is not an incidental occurrence, and the detection of such widely dispersed cases suggests more myxozoans in birds will be encountered with increased surveillance of these hosts for pathogens.     

Some remarks on the occurrence,host-specificity and validity of <Emphasis Type="Italic">Myxobolus rotundus</Emphasis> Nemeczek, 1911 (Myxozoa: Myxosporea)

Myxobolus rotundus Nemeczek, 1911 is a common and specific parasite of the common bream Abramis brama (L.). Small, round or ellipsoidal shaped plasmodia of this species develop in the gill and exhibit strong histotropism to the secondary gill lamellae with plasmodial development in their capillary network. M. rotundus is frequently found in mixed infection with M. bramae Reuss, 1906, a parasite of the afferent arteries of gill filaments. The round spores of M. rotundus resemble several other Myxobolus spp., but can be distinguished from these by their small subunit ribosomal RNA gene sequence (GenBank accession no. EU710583), which also differs from the sequence for ‘M. rotundus’ from the skin of Chinese goldfish Carassius auratus auratus (L.), which we suggest has been misidentified. The SSU rRNA gene sequence of M. rotundus myxospores from bream corresponded to Triactinomyxon type 4 actinospores (AY495707) isolated from Tubifex tubifex (Müller) by Hallett et al. (2005), and we infer from this that these are alternate life stages.     

Disentangling the impact of AM fungi versus roots on soil structure and water transport

The relative importance of roots and AM-fungi on soil physical processes was investigated by controlling the presence of roots and AM fungi in pot experiments using a mycorrhiza-defective tomato mutant and a wild-type tomato (Solanum lycopersicum L.). Root-Zone and Bulk Soil sections were established by splitting pots into two lengthwise halves using a nylon mesh that contained roots whilst allowing the free movement of fungal hyphae. Post-incubation microbial populations and fungal biomass were measured and related to soil stability, pore structure and water repellency. Unplanted controls consistently had the least fungal biomass, fatty acids, water-stable aggregates (WSA) and water repellency. Wild-type-planted treatments had significantly more WSA than mycorrhiza-defective treatments (P?<?0.01). Fluctuations in water content induced by transpiration caused significant changes in soil pore structure, measured using high-resolution X-Ray computer tomography. Porosity and mean pore size increased in soil aggregates from planted treatments, which had larger more heterogeneous pores than those in the unplanted soils. AM fungi accentuated soil stability. However, changes were not linked to repellency and fungal biomass. The presence of plants, regardless of AM fungi, appears to have the greatest impact on increasing soil stability.     

Phagocytosis of optically-trapped particles： delivery of the pure phagocytic signal

Phagocytosis is a fundamental cell biological process exhibited by a wide variety of cell types from single cell organisms, which rely on this for feeding, to phagocytes in higher animals, which rely on specialised immune cells for combating infecting micro-organisms. In the immune system, both macrophages and neutrophils play roles as phagocytes. Neutrophils are often called ＂professional phagocytes＂ because of their remarkable capacity for phagocytosis, being able to intemalise microscopic particles （diam 0.5-3 μm） of virtually any surface material. The efficiency and speed of phagocytosis is, however, increased by coating the surface of the particles with opsonins such as antibodies or the complement component C3bi （acting on J32 integrin receptors）, and C3bi-accelerated phagocytosis by neutrophils is the first line of defence by the innate immune system in vivo, operating in advance of the slower production of antibodies. Understanding the mechanism ofphagocytosis is, therefore, clearly an important goal.     

Extracellular ATP induces spikes in cytosolic free Ca but not in NADPH oxidase activity in neutrophils

In order to establish whether non-mitochondrial oxidase activity in human neutrophils is tightly related to cytosolic Ca²⁺ concentration, we simultaneously measured Ca²⁺ oscillations induced by ATP and oxidant production in single adherent neutrophils using confocal microscopy. ATP induced fast damped Ca²⁺ spikes with a period of 15 s and slower irregular spikes with a period greater than 50 s. Spikes in Ca²⁺ occurred in the absence of Ca²⁺ influx, but the amplitude was damped by inhibition of Ca²⁺ influx. Using the oxidation of hydroethidine as a cytosolic marker of oxidant production, we show that the generation of reactive oxygen species by neutrophils adherent to glass was accelerated by ATP. The step-up in NADPH oxidase activity followed the first elevation of cytosolic Ca²⁺ but, despite subsequent spikes in Ca²⁺ concentration, no oscillations in oxidase activity could be detected. ATP induced spikes in Ca²⁺ in a very reproducible way and we propose that the Ca²⁺ signal is an on-switch for oxidase activity, but the activity is apparently not directly correlated with spiking activity in cytosolic Ca²⁺.