摘要:

Summary—In the ichneumonid waspHyposoter didymator, a polydnavirus was detected in the female reproductive tract. With the aim of studying the regulation of polydnavirus replication, the location and the structure of the virus‐producing cells were determined, and the virus replication process was followed inside the ovaries of young adult females observed in light and electron microscopy. The examination of ovaries of pupa females revealed that virus replication is initiated within the calyx just prior to adult emergence. This study revealed that the calyx appears to be a specialized virogenic tissue which also has, during late pupal life, a secretory function that alters the function of virus product

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89926-6

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Using two‐dimensional polyacrylamide gels stained with Coomassie blue we have studied the protein composition of the nuclear matrix obtained from mouse erythroleukemic nuclei kept at O°C throughout the isolation procedure to prepare the high ionic strength resistant fraction (control matrix) orstabilized in vitroorin vivoby different procedures prior to subfractionation (ie 37°Cincubation of isolated nuclei; sodium tetrathionate exposure of purified nuclei; heat shock of intact cells). When the matrix obtained from 37°C incubated nuclei was compared with the control matrix, striking differences in the polypeptide pattern were seen if the protein was obtained in both cases from an equivalent number of nuclei. On the other hand, if the same amount of protein for both the samples was applied to the gels the differences were less evident. Sodium tetrathionate stabilization of isolated nuclei and heat shock of intact cells produced a matrix protein pattern that was very similar and differed from that of thein vitroheat‐exposed matrix. Using specific polyclonal antisera, we demonstrate that nucleolar proteins B23/numatrin and C23/nucleolin were very abundant in the matrix obtained from chemically‐treated nuclei orin vivoheat‐stabilized nuclei but were recovered in very small amounts (B23) or completely absent (C23) in the matrix prepared from nuclei heated to 37°Cin vitro. Differences were seen also in the recovery of nuclear lamins, and especially lamin B, that was poorly represented in the sodium tetrathionate‐stabilized matrix. The results demonstrate that in mouse erythroleukemia cells the increased recovery of nuclear matrix protein that is seen afterin vitroheating of isolated nuclei is predominantly due to an additional recovery of the same types of polypeptides that are detected also in the absence of such a treatment. The data also indicate thatin vivoheat shock of intact cells produces a nuclear matrix protein pattern that is more similar to the pattern seen after stabilization of purified nuclei with sodium tetrathionate and differs significantly from that obtained by exposing nuclei to 37°Cin vitro, unlike to that what previous report

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89927-8

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Trypanosoma brucei brucei, a protozoan parasite of wild and domestic animals in Africa, is related to the pathogenic agent of human sleeping sickness. Four H1 histone proteins were isolated from nuclei of procyclic culture forms and cleaved with proteases. Amino acid sequence analysis of purified fragments indicated the presence of variants which displayed sequence identities as compared to the C‐terminal domain of human H1. Substitutions of amino acids and posttranslational modifications of the histones in iTb bruceiH1 may influence protein conformation and histone‐histone as well as histone‐DNA interactions in the chromatin of the parasite. Digestion of soluble chromatin with immobilized trypsin at low and high ionic strengths indicated an internal localization of H1 in the condensed chromatin. The influence of histone H1 ofT b bruceion the compaction pattern of the chromatin was investigated by dissociation and reconstitution experiments. Electron microscopy revealed that trypanosome H1 was able to induce condensation of the chromatin of the parasite and of rat liver into dense tangles. After dephosphorylation of H1, 30 nm fibers were induced in rat liver chromatin, while the resulting fibers were distinctly thinner inT b brucei. It can be concluded that the absence of 30 nm fibers inT b bruceichromatin cannot be explained by the divergent variants and posttranslational phosphorylations of H1 only but rather by the influence of both, the divergent core histones, previously described, and H1 pro

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89928-X

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—The membrane skeleton, responsible for shape and mechanical properties of the red cell, was purified by the Triton extraction procedure in presence of 5 mM, 150 mM or 600 mM NaCl. The proportion of spectrin, protein 4.1 and actin present in erythrocyte skeletons does not depend on the molarity of NaCl used. In contrast ankyrin, protein band 3 and protein 4.2 are removed from skeletons as the ionic strength increased. Solubilization assays of membrane skeletons were used to study protein interactions inside the skeleton. Solubilization was performed by Tris, a non‐selective disruptive reagent, or byp‐mercuribenzene sulfonic acid (PMBS), which principally release spectrin and actin. Tris action was assessed by calculation of the percentage of solubilized proteins, which increased proportionally with Tris molarity. PMBS action was kinetically determined as the decrease in skeleton turbidity. With these two reagents, we observed a lower dissociation of skeletons prepared with high ionic strength buffer. Erythrocyte pretreatment with okadaic acid, an inhibitor of serine‐threonine phosphatases, revealed a phosphorylation‐induced skeleton gelation and a better resistance to Tris‐sol

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89929-1

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Snail muscles were extracted by a solution of EDTA and electron microscopy showed that the extract contained dispersed, depolymerized collagen fibrils and cross‐shaped laminin‐like structures. The extracts were purified by ultracentrifugation followed by two different procedures which enriched the content of laminin‐like structures. The laminin‐related molecules displayed unique properties when analyzed by biochemical, immunological and morphological methods. Electrophoretic patterns of the molecular form purified primarily by ion exchange chromatography, resembled EHS‐tumor laminin and displayed a cruciform shape when viewed by electron microscopy. Immunohistology, using antiserum obtained against the agarose gel‐purified protein, showed that this laminin was primarily located in the extracellular matrix surrounding muscle fibers. Western blots using anti‐EHS laminin antibody showed reaction of a 300 kDa subunit of this snail laminin. The protein obtained by another procedure, initially using gel filtration, followed by ion exchange chromatography, also appeared to be a laminin. It had a collapsed cruciform appearance when viewed by electron microscopy. It contained several different subunits, one of which,ca300 kDa, reacted with anti‐EHS‐laminin antibody and with anti‐snail laminin antibody. In contrast, EHS laminin did not react with the anti‐snail laminin antibody. The composite results suggest that at least two different forms of laminin are extractable from snail muscle and that they share molecular properties and immune determinants w

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89930-8

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Actively migrating nematocytes of the marine polypStauridiosarsia productaare converted into completely immotile cells as soon as they become integrated in the ectodermal tissue of the tentacles. Immunocytochemical and electron microscopical methods revealed that cytoskeletal elements composed of actin, tubulin, centrin and a still unidentified protein are interwoven within the complete cell. While the organization of the sensory pole of the nematocyte, containing the cnidocil complex, the pseudovillar system and the distal half of a microtubular basket surrounding the nematocyst, is not affected by the transition from a motile to an immotile cell, the cytoskeletal elements in the basal portion of the cell are re‐organized. Thus, the basolateral cytoplasm of migrating cells contains less organized microtubular arrays and bundles of about 10 nm‐thick filaments. In the tentacle‐integrated state, the 10‐nm filaments are concentrated within a stalk‐like foot which is stabilized by some rigid microtubular arrays derived from the microtubular basket. By elongation of the microtubular basket towards the cellular basis, the nematocyst becomes indirectly anchored at the mesoglea. As indicated by pharmacological treatments, the stiffness of the stalk depends on its microtubular c

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89931-X

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Microfilaments were localised by immunofluorescence and immunogold cytochemistry to examine their distribution in granular cells of the isolated frog skin epithelium. Strongly fluorescent bundles of actin were observed beneath the plasma membrane with little evidence for actin in the central regions. Higher resolution offered by cytochemistry revealed that bundles of actin filaments comprised a substantial portion of the cortical cytoskeleton. Quantitative analysis of the frequency of gold label revealed an extremely rich array of filaments beneath the apical membrane of granular cells, with markedly less babel along the basolateral membrane and in the central cytoplasm. Treating cells with cytochalasin B or arginine vasopressin caused an apparent disruption of the apical actin fibres, concurrent with a decrease in gold label density. Assumably these signs are indicative of depolymerization of the filaments. Although the significance of this distribution is unknown, the apical polarisation of actin is consistent with a role in regulating the Na+permeability of the apical membrane. The data are discussed in relation to possible roles of the cytoskeleton in the regulation of transepithelial sodium transport by vasopressi

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89932-1

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Zebrafish hepatocytes respond to stimulation with estradiol 17β (E2) with an extreme enlargement of the endomembrane system, especially the endoplasmic reticulum (ER), and when stimulation is stopped with a rapid degradation of enlarged endomembranes. Two pathways for degradation of ER were studied: a) the autophagy which was evaluated by stereological measurement; and b) the activity of cytosolic phospholipase B (PL‐B) measured by a titration method. After a 30‐day treatment with E2 a six‐fold increase of the surface density of ER was accompanied by an increase of both autophagy and PL‐B activity. 2 days after stopping the stimulation with E2 the ER vesiculated and its surface density decreased to the half value. Interestingly, at the same time autophagic vacuoles (AV) almost disappeared from hepatocytes, while the activity of PL‐B reached its maximum at which it persisted for a further 4 days. After 4–6 days without E2 the cistern of ER became flattened again and new AVs reappeared. The data suggest that the regulation mechanisms of endomembrane degradation by PL‐B and autophagy do not depend on each other and also that the appearance of AV is strongly related to

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89933-3

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—It has recently been shown that a chronic copper exposure induces specific degeneration of olfactory receptor cells in rainbow trout; however, the exact mechanism of action of the metal is not yet known. Using X‐ray microanalysis in transmission electron microscopy, we have studied the distribution of metal in the olfactory system of fish exposed for 15, 30 and 60 days to 20 μg/l of copper. This was done in order to determine if it was accumulated in receptor cells and transported into the centralnervous system viathe olfactory nerve. No copper accumulation was detected either in the olfactory epithelium, in the olfactory nerve or in the olfactory bulb. The heavy metal was exclusively found within melanosomes of melanophores located in the lamina propria. After 60 days of exposure, the copper content in melanosomes was about two‐fold higher than that in controls. As far as some morphological recovery took place in the olfactory organ during the metal exposure, which lets us suppose that some detoxication mechanism occurs, it could be suggested that melanophores might be somehow involved in such a mec

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89934-5

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—We designed a protocol for cell labeling with the lectin wheat germ agglutinin (WGA) linked to the fluorochrome tetramethyl‐rhodamine isothiocyanate (TRITC) for effective detection of the B16F10 melanoma and Lewis lung carcinoma (LLc) cells on pulmonary histological sections from C57BL6; mice. We have also determined a suitable concentration of WGA‐TRITC (10 μg/ml), which leads to a very intense and homogeneous labeling of the cells, as it avoids cell clumping due to the presence of the lectin WGA. In order to determine to what extent the method affects these tumor cells, we have studied some important aspects related to their metastatic behavior, taking into account three parameters: a) viability and rate of proliferation of the cells culturedin vitro; b) percentage of animals C57BL6 mice) bearing metastasis 15 days after intravenous inoculation with 105B16F10 or LLc cells; and c) pattern of distribution of tumor foci in lung. There were no significant differences in these three parameters between the WGA‐TRITC labeled‐cells compared to the cultures of non‐labeled cells in either of the cell lines (B16F10, LLc). Thus, we conclude that B16F10 and LLc tumor cells can be labeled following the protocol set‐up in our study, as it allows these cells to be neatly identified on tissue sections and it causes no important physiological changes in the cells, with regard to metastatic behavior. These points make this technique very suitable for the detection of B16F10 and LLc cells on histological sections in studying their behavior during the first stages of the meta

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)89935-7

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY