Fluorimetric multiparameter cell assay at the single cell level fabricated by optical tweezers.
(1/906)
A fluorimetric multi-parameter cell sensor at the single cell level is presented which makes it possible to observe the physiological behavior of different cell lines, different physiological parameters, and statistical data at the same time. Different cell types were immobilized at predefined positions with high accuracy using optical tweezers and adhesion promoting surface layers. The process is applicable to both adherent and non-adherent cells. Coating of the immobilization area with mussel adhesive protein was shown to be essential for the process. Intracellular proton and calcium concentrations in different cell classes were simultaneously imaged and the specific activation of T lymphocytes was demonstrated. This method should be especially useful for drug screening due to the small sample volume and high information density. (+info)
Tumor-like lesions in the mantle of the mussel Modiolus difficilis from the Sea of Japan.
(2/906)
Two inner growths in the mantle beneath the epithelium were found in 1 of 1000 mussels Modiolus difficilis from Amursky Bay, Sea of Japan, within the city precincts of Vladivostok. Both growths were about 2000 microns in maximal diameter in section and elevated slightly above the mantle surface. The mantle epithelium near the growths formed deep invaginations, and clusters of mucous cells were numerous beneath the epithelium. Histological and histochemical methods were employed. Two different kinds of growth were revealed. The off-white growth consisted of cells with thin granular or vesicular cytoplasm containing glucosaminoglycans, proteins and a small amount of neutral polysaccharides. Growth cells were pure white in color after treatment of preparations with 1% H2SO4 and differed markedly from the mantle cells. The yellow growth consisted of large granular cells with neutral polysaccharides and proteins. Although growths were composed of different kinds of cells, they seemed to be derived from subepithelial mucous cells. This was supported by histological and histochemical staining reactions of some tumor and mantle epithelial cells. Mitotic indices (MI) of growths and subepithelial mucous cells were zero, MI of ciliated mantle epithelium reached 0.07%. The lesions were areas of strongly altered mucous cells of mantle epithelium and were non-neoplastic. (+info)
Heart action of the freshwater bivalve Anodonta anatina during activity.
(3/906)
1. Heart action of Anodonta anatina (L.) was investigated by recording the electrocardiogram (ECG), heart impedance, and ventricular and pericardial cavity pressure during different aspects of the normal behaviour. The contribution of mechanical and nervous mechanisms in controlling changes in heart action is discussed. 2. Pressure recordings were generally more reliable than the other methods and it is suggested that pericardial pressure pulses indicate the stroke volume output of the ventricle. 3. During spontaneous periods of prolonged shell closure there was an initial small increase in heart activity followed by a large reduction in both heart rate and systolic pressure, indicating that total heart output was considerably reduced. When the shell reopened, heart rate increased very rapidly with an initial overshoot of the normal level; systolic pressure increased more slowly with no overshoot. 4. These major changes in heart activity appear to be associated with respiratory changes and are controlled largely by the nervous regulatory system, but some minor rhythmic variations in the amplitude of heart beat are probably caused by mechanical factors. 5. Characteristic patterns of change in heart action were recorded during burrowing. These appear to result from haemodynamic changes associated with the muscular movements of the digging cycle. Control of the heart by the nervous regulatory system is apparently of much greater importance in relation to respiratory control than in relation to the haemodynamic functioning of the fluid-muscle system in locomotion. (+info)
Dynein is required for spindle assembly in cytoplasmic extracts of Spisula solidissima oocytes.
(4/906)
Meiosis I spindle assembly is induced in lysate-extract mixtures prepared from clam (Spisula solidissima) oocytes. Unactivated lysate prepared from unactivated oocytes contain nuclei (germinal vesicles, GVs) which house condensed chromosomes. Treatment of unactivated lysate with clarified activated extract prepared from oocytes induced to complete meiosis by treatment with KCl induces GV breakdown (GVBD) and assembly of monopolar, bipolar, and multipolar aster-chromosome complexes. The process of in vitro meiosis I spindle assembly involves the assembly of microtubule asters and the association of these asters with the surfaces of the GVs, followed by GVBD and spindle assembly. Monoclonal antibody m74-1, known to react specifically with the N terminus of the intermediate chain of cytoplasmic dynein, recognizes Spisula oocyte dynein and inhibits in vitro meiosis I spindle assembly. Control antibody has no affect on spindle assembly. A similar inhibitory effect on spindle assembly was observed in the presence of orthovanadate, a known inhibitor of dynein ATPase activity. Neither m74-1 nor orthovanadate has any obvious affect on GVBD or aster formation. We propose that dynein function is required for the association of chromosomes with astral microtubules during in vitro meiosis I spindle assembly in these lysate-extract mixtures. However, we conclude that dynein function is not required for centrosome assembly and maturation or for centrosome-dependent aster formation. (+info)
Ca2+ is required for phosphorylation of clam p82/CPEB in vitro: implications for dual and independent roles of MAP and Cdc2 kinases.
(5/906)
During early development gene expression is controlled principally at the translational level. Oocytes of the surf clam Spisula solidissima contain large stockpiles of maternal mRNAs which are translationally dormant or masked until meiotic maturation. Fertilisation of the oocyte leads to rapid polysomal recruitment of the abundant cyclin and ribonucleotide reductase mRNAs at about the time they undergo cytoplasmic polyadenylation. Clam p82, a 3' UTR RNA-binding protein, and a member of the CPEB (cytoplasmic polyadenylation element binding protein) family, functions as a translational masking factor in oocytes and as a polyadenylation factor in fertilised eggs. In meiotically maturing clam oocytes, p82/CPEB is rapidly phosphorylated on multiple residues to a 92-kDa apparent size, prior to its degradation during the first cell cleavage. Here we examine the protein kinase(s) that phosphorylates clam p82/CPEB using a clam oocyte activation cell-free system that responds to elevated pH, mirroring the pH rise that accompanies fertilisation. We show that p82/CPEB phosphorylation requires Ca2+ (<100 microM) in addition to raised pH. Examination of the calcium dependency combined with the use of specific inhibitors implicates the combined and independent actions of cdc2 and MAP kinases in p82/CPEB phosphorylation. Calcium is necessary for both the activation and the maintenance of MAP kinase, whose activity is transient in vitro, as in vivo. While cdc2 kinase plays a role in the maintenance of MAP kinase activity, it is not required for the activation of MAP kinase. We propose a model of clam p82/CPEB phosphorylation in which MAP kinase initially phosphorylates clam p82/CPEB, at a minor subset of sites that does not alter its migration, and cdc2 kinase is necessary for the second wave of phosphorylation that results in the large mobility size shift of clam p82/CPEB. The possible roles of phosphorylation for the function and regulation of p82/CPEB are discussed. (+info)
Actin filament-membrane attachment: are membrane particles involved?
(6/906)
The association of actin filaments with membranes is an important feature in the motility of nonmuscle cells. We investigated the role of membrane particles in the attachment of actin filaments to membranes in those systems in which the attachment site can be identified. Freeze fractures through the end-on attachment site of the acrosomal filament bundles in Mytilus (mussel) and Limulus (horseshoe crab) sperm and the attachment site of the microvillar filament bundles in the brush border of intestinal epithelial cells were examined. There are no particles on the P face of the membrane at these sites in the sperm systems and generally none at these sites in microvilli. In microvilli, the actin filaments are also attached along their lengths to the membrane by bridges. When the isolated brush border is incubated in high concentrations of Mg++ (15 mM), the actin filaments form paracrystals and, as a result, the bridges are in register (330 A period). Under these conditions, alignment of the particles on the P face of the membrane into circumferential bands also occurs. However, these bands are generally separated by 800-900 A, indicating that all the bridges cannot be directly attached to membrane particles. Thus membrane particles are not directly involved in the attachment of actin filaments to membranes. (+info)
Interspecies transfer of female mitochondrial DNA is coupled with role-reversals and departure from neutrality in the mussel Mytilus trossulus.
(7/906)
Mussels of the genus Mytilus have distinct and highly diverged male and female mitochondrial DNA (mtDNA) genomes with separate routes of inheritance. Previous studies of European populations of Mytilus trossulus demonstrated that 33% of males are heteroplasmic for a second mtDNA genome of increased length and that hybridization with Mytilus edulis does not block mtDNA introgression, in contrast to reports for American populations. Here, we demonstrate that the female mtDNA type of M. edulis has replaced the resident female mtDNA type of European M. trossulus. This is supported by COIII sequence data indicating that the female mtDNA of European M. trossulus is very similar to that of M. edulis and that in phylogenetic trees, the mtDNAs of these two species cluster together but separately from American M. trossulus sequences, the latter not being disturbed by introgressive hybridization. We also provide evidence that the mtDNA genome of increased length found in heteroplasmic males of European M. trossulus derives from a recent partition of an introgressed M. edulis female type into the male route of transmission. Neutrality tests reveal that European populations of M. trossulus display an excess of replacement polymorphism within the female mtDNA type with respect to conspecific American populations, as well as a significant excess of rare variants, of a similar magnitude to those previously reported for the invading European M. edulis mtDNA. Results are consistent with a nearly neutral model of molecular evolution and suggest that selection acting on European M. trossulus mtDNA is largely independent of the nuclear genetic background. (+info)
Mytilus mitochondrial DNA contains a functional gene for a tRNASer(UCN) with a dihydrouridine arm-replacement loop and a pseudo-tRNASer(UCN) gene.
(8/906)
A 2500-nucleotide pair (ntp) sequence of F-type mitochondrial (mt) DNA of the Pacific Rim mussel Mytilus californianus (class Bivalvia, phylum Mollusca) that contains two complete (ND2 and ND3) and two partial (COI and COIII) protein genes and nine tRNA genes is presented. Seven of the encoded tRNAs (Ala, Arg, His, Met(AUA), Pro, Ser(UCN), and Trp) have the potential to fold into the orthodox four-armed tRNA secondary structure, while two [tRNASer(AGN) and a second tRNASer(UCN)] will fold only into tRNAs with a dihydrouridine (DHU) arm-replacement loop. Comparison of these mt-tRNA gene sequences with previously published, corresponding M. edulis F-type mtDNA indicates that similarity between the four-armed tRNASer(UCN) genes is only 63.8% compared with an average of 92.1% (range 86.2-98. 5%) for the remaining eight tRNA genes. Northern blot analysis indicated that mature tRNAs encoded by the DHU arm-replacement loop-containing tRNASer(UCN), tRNASer(AGN), tRNAMet(AUA), tRNATrp, and tRNAPro genes occur in M. californianus mitochondria, strengthening the view that all of these genes are functional. However, Northern blot and 5' RACE (rapid amplification of cDNA ends) analyses indicated that the four-armed tRNASer(UCN) gene is transcribed into a stable RNA that includes the downstream COI sequence and is not processed into a mature tRNA. On the basis of these observations the M. californianus and M. edulis four-armed tRNASer(UCN) sequences are interpreted as pseudo-tRNASer(UCN) genes. (+info)