Compression and dilation of the membrane-cortex layer generates rapid changes in cell shape

Rapid changes in cellular morphology require a cell body that is highly flexible yet retains sufficient strength to maintain structural integrity. We present a mechanism that meets both of these requirements. We demonstrate that compression (folding) and subsequent dilation (unfolding) of the coupled plasma membrane–cortex layer generates rapid shape transformations in rounded cells. Two- and three-dimensional live-cell images showed that the cyclic process of membrane-cortex compression and dilation resulted in a traveling wave of cortical actin density. We also demonstrate that the membrane-cortex traveling wave led to amoeboid-like cell migration. The compression–dilation hypothesis offers a mechanism for large-scale cell shape transformations that is complementary to blebbing, where the plasma membrane detaches from the actin cortex and is initially unsupported when the bleb extends as a result of cytosolic pressure. Our findings provide insight into the mechanisms that drive the rapid morphological changes that occur in many physiological contexts, such as amoeboid migration and cytokinesis.     

Hypervariable Domain of Nonstructural Protein nsP3 of Venezuelan Equine Encephalitis Virus Determines Cell-Specific Mode of Virus Replication

Venezuelan equine encephalitis virus (VEEV) is one of the most pathogenic members of the Alphavirus genus in the Togaviridae family. This genus is divided into the Old World and New World alphaviruses, which demonstrate profound differences in pathogenesis, replication, and virus-host interactions. VEEV is a representative member of the New World alphaviruses. The biology of this virus is still insufficiently understood, particularly the function of its nonstructural proteins in RNA replication and modification of the intracellular environment. One of these nonstructural proteins, nsP3, contains a hypervariable domain (HVD), which demonstrates very low overall similarity between different alphaviruses, suggesting the possibility of its function in virus adaptation to different hosts and vectors. The results of our study demonstrate the following. (i) Phosphorylation of the VEEV nsP3-specific HVD does not play a critical role in virus replication in cells of vertebrate origin but is important for virus replication in mosquito cells. (ii) The VEEV HVD is not required for viral RNA replication in the highly permissive BHK-21 cell line. In fact, it can be either completely deleted or replaced by a heterologous protein sequence. These variants require only one or two additional adaptive mutations in nsP3 and/or nsP2 proteins to achieve an efficiently replicating phenotype. (iii) However, the carboxy-terminal repeat in the VEEV HVD is indispensable for VEEV replication in the cell lines other than BHK-21 and plays a critical role in formation of VEEV-specific cytoplasmic protein complexes. Natural VEEV variants retain at least one of the repeated elements in their nsP3 HVDs.     

Nicotinic acetylcholine receptors alpha4beta2 and alpha7 regulate myelo- and erythropoiesis within the bone marrow

Nicotine consumed upon smoking affects numerous physiological processes through nicotinic acetylcholine receptors, which mediate cholinergic regulation by the neuronal and endogenous acetylcholine. Consequently, nicotinic receptors are expressed in many non-excitable tissues including the blood. In spite of the documented effect of nicotine on hematopoiesis, little is known about the expression and role of nicotinic receptors in the course of blood cell differentiation. The aim of the present study was to investigate whether and how nicotinic receptors are involved in the development of myeloid and erythroid cells within the bone marrow. The presence of nicotinic receptors containing alpha4(beta2) and alpha7 subunits in the bone marrow cells of C57Bl/6 mice was shown by the binding of [125I]-alpha-bungarotoxin or [3H]-Epibatidine and by flow cytometry with subunit-specific antibodies or fluorescein-labeled alpha-cobratoxin. Both TER119+ (erythroid) and CD16+CD43med (myeloid) progenitor cells bound more alpha4-specific antibodies than their mature forms, while the binding of alpha-cobratoxin and alpha7-specific antibodies was also high in mature cells. According to morphological analysis, either the absence of alpha7-containing nicotinic receptors in knockout mice or their desensitization in mice chronically treated with nicotine decreased the number of myeloid and erythroid progenitors and junior cells. In contrast, the absence of beta2-containing receptors favored myelocyte generation and erythroid cell maturation. It is concluded that the development of both myeloid and erythroid cell lineages is regulated by endogenous cholinergic ligands and can be affected by nicotine through alpha7- and alpha4beta2-containing nicotinic receptors, which play different roles in the course of the cell maturation.     

Diversity and cold-active hydrolytic enzymes of culturable bacteria associated with Arctic sea ice,Spitzbergen

The diversity of culturable bacteria associated with sea ice from four permanently cold fjords of Spitzbergen, Arctic Ocean, was investigated. A total of 116 psychrophilic and psychrotolerant strains were isolated under aerobic conditions at 4°C. The isolates were grouped using amplified rDNA restriction analysis fingerprinting and identified by partial sequencing of 16S rRNA gene. The bacterial isolates fell in five phylogenetic groups: subclasses and of Proteobacteria, the Bacillus–Clostridium group, the order Actinomycetales, and the Cytophaga–Flexibacter–Bacteroides (CFB) phylum. Over 70% of the isolates were affiliated with the Proteobacteria subclass. Based on phylogenetic analysis (<98% sequence similarity), over 40% of Arctic isolates represent potentially novel species or genera. Most of the isolates were psychrotolerant and grew optimally between 20 and 25°C. Only a few strains were psychrophilic, with an optimal growth at 10–15°C. The majority of the bacterial strains were able to secrete a broad range of cold-active hydrolytic enzymes into the medium at a cultivation temperature of 4°C. The isolates that are able to degrade proteins (skim milk, casein), lipids (olive oil), and polysaccharides (starch, pectin) account for, respectively, 56, 31, and 21% of sea-ice and seawater strains. The temperature dependences for enzyme production during growth and enzymatic activity were determined for two selected enzymes, -amylase and -galactosidase. Interestingly, high levels of enzyme productions were measured at growth temperatures between 4 and 10°C, and almost no production was detected at higher temperatures (20–30°C). Catalytic activity was detected even below the freezing point of water (at –5°C), demonstrating the unique properties of these enzymes.     

Wild Bird Surveillance for Avian Paramyxoviruses in the Azov-Black Sea Region of Ukraine (2006 to 2011) Reveals Epidemiological Connections with Europe and Africa

Despite the existence of 10 avian paramyxovirus (APMV) serotypes, very little is known about the distribution, host species, and ecological factors affecting virus transmission. To better understand the relationship among these factors, we conducted APMV wild bird surveillance in regions of Ukraine suspected of being intercontinental (north to south and east to west) flyways. Surveillance for APMV was conducted in 6,735 wild birds representing 86 species and 8 different orders during 2006 to 2011 through different seasons. Twenty viruses were isolated and subsequently identified as APMV-1 (n = 9), APMV-4 (n = 4), APMV-6 (n = 3), and APMV-7 (n = 4). The highest isolation rate occurred during the autumn migration (0.61%), with viruses isolated from mallards, teals, dunlins, and a wigeon. The rate of isolation was lower during winter (December to March) (0.32%), with viruses isolated from ruddy shelducks, mallards, white-fronted geese, and a starling. During spring migration, nesting, and postnesting (April to August) no APMV strains were isolated out of 1,984 samples tested. Sequencing and phylogenetic analysis of four APMV-1 and two APMV-4 viruses showed that one APMV-1 virus belonging to class 1 was epidemiologically linked to viruses from China, three class II APMV-1 viruses were epidemiologically connected with viruses from Nigeria and Luxembourg, and one APMV-4 virus was related to goose viruses from Egypt. In summary, we have identified the wild bird species most likely to be infected with APMV, and our data support possible intercontinental transmission of APMVs by wild birds.     

The influence of age,sex, population group,and dentition on the mandibular angle as measured on a South African sample

The mandibular angle is measured in physical anthropological assessments of human remains to possibly assist with the determination of sex and population affinity. The purpose of this investigation was to establish how the mandibular angle changes with age and loss of teeth among the sexes in South African population groups. The angles of 653 dried adult mandibles from the Pretoria Bone Collection were measured with a mandibulometer. Males and females of both South African whites and blacks were included. To compensate for imbalances in numbers among subgroups, type IV ANOVA testing was applied. No association was found between age and angle within either of the populations, within sexes, or within dentition groups. The angle was the most obtuse in individuals without molars and with an uneven distribution of molars, and most acute in the group with an even distribution of molars on both sides. Statistically significant differences (P < 0.001) were found in the angle between the two population groups and sexes in the overall sample as well as in the subgroup with absent molar teeth (P = 0.003 for sex, males more acute angle, and P = 0.001 for population group, blacks more acute angle), although a very large overlap existed. No significant differences could be demonstrated between the sexes or populations within the subgroups with molars. We concluded that the loss of molars, especially if complete or uneven, has a considerable effect on the mandibular angle. In the assessment of human remains, the mandibular angle is not very usable in determining sex. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Gleevec,an Abl Family Inhibitor,Produces a Profound Change in Cell Shape and Migration

The issue of how contractility and adhesion are related to cell shape and migration pattern remains largely unresolved. In this paper we report that Gleevec (Imatinib), an Abl family kinase inhibitor, produces a profound change in the shape and migration of rat bladder tumor cells (NBTII) plated on collagen-coated substrates. Cells treated with Gleevec adopt a highly spread D-shape and migrate more rapidly with greater persistence. Accompanying this more spread state is an increase in integrin-mediated adhesion coupled with increases in the size and number of discrete adhesions. In addition, both total internal reflection fluorescence microscopy (TIRFM) and interference reflection microscopy (IRM) revealed a band of small punctate adhesions with rapid turnover near the cell leading margin. These changes led to an increase in global cell-substrate adhesion strength, as assessed by laminar flow experiments. Gleevec-treated cells have greater RhoA activity which, via myosin activation, led to an increase in the magnitude of total traction force applied to the substrate. These chemical and physical alterations upon Gleevec treatment produce the dramatic change in morphology and migration that is observed.     

Extrinsic Factors Driving Oligodendrocyte Lineage Cell Progression in CNS Development and Injury

Neurochemical Research - Oligodendrocytes (OLs) generate myelin membranes for the rapid propagation of electrical signals along axons in the central nervous system (CNS) and provide metabolites to...     

Differential involvement of α4β2, α7 and α9α10 nicotinic acetylcholine receptors in B lymphocyte activation in vitro

Mouse B lymphocytes express several nicotinic acetylcholine receptor (nAChR) subtypes, their exact functions being not clearly understood. Here we show that α7 nAChR was present in about 60%, while α4β2 and α9(α10) nAChRs in about 10% and 20% of mouse spleen B lymphocytes, respectively; Balb/c and C57Bl/6 mice possessed different relative amounts of these nAChR subtypes. α4β2 and α7, but not α9(α10) nAChRs, were up-regulated upon B lymphocyte activation in vitro. Flow cytometry and sandwich ELISA studies demonstrated that α7 and α9(α10) nAChRs are coupled to CD40, whereas α4β2 nAChR is coupled to IgM. B lymphocytes of both α7(-/-) and β2(-/-) mice responded to anti-CD40 stronger than those of the wild-type mice, whereas the cells of β2(-/-) mice responded to anti-IgM worse than those of the wild-type or α7(-/-) mice. Inhibition of α7 and α9(α10) nAChRs with methyllicaconitine resulted in considerable augmentation of CD40-mediated B lymphocyte proliferation in cells of all genotypes; stimulation of α4β2 nAChRs with epibatidine increased the IgM-mediated proliferation of the wild-type and α7(-/-), but not β2(-/-) cells. Inhibition of α9(α10) nAChRs with α-conotoxin PeAI exerted weak stimulating effect on CD40-mediated proliferation. This nAChR subtype was up-regulated in α7(-/-) B-cells. α7 nAChRs were found recruited to immune synapses between human T and B lymphocytes, both of which produced acetylcholine. It is concluded that α7 nAChR fulfills inhibitory CD40-related mitogenic function, α4β2 nAChR produces a stimulatory IgM-related effect, while α9α10 nAChR is a "reserve" receptor, which partly compensates the absence of α7 nAChR in α7(-/-) cells. Acetylcholine is an additional mediator to modulate activation of interacting T and B lymphocytes.