摘要:

Summary—Total mRNA extracted from the brain of a marine worm,Nereis diversicolor, werein vitrotranslated using 2 cell‐free systems: rabbit reticulocyte lysate and wheat germ extract. Among numerous products newly translated in both systems, only one class of 70 kDa polypeptides immunoprecipitated when we used a mixture of 3 well defined antibodies raised against known sequences of the human prepro‐CCK. At the cellular level, using immunocytochemistry techniques, strong and moderate immunoreactivities were seen in perikarya located in various ganglionic nuclei of the worm brain. Immunoreactive nerve fibres were visible in the neuropile but not in the infracerebral region, a neurohemal area. Immunoreactions also appeared on perikarya located in the anterior and medial groups of the ventral nerve cord. Furthermore, immunolabeled cells were observed in the midgut. Interestingly, several colocalizations of materials immunologically related to human prepro‐CCK and CCK/gastrin were observed in the brain and the ventral nerve cord both in perikarya and in nerve fibres. We propose that, inNereisa polypeptide (molecular mass 70 kDa) is the large precursor of molecules related to those of the CCK/gastrin peptide

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90054-Q

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—We have observed in hepatic periovular granulomas of C3H mice infected withSchistosoma mansoni, in the chronic phase of the disease (12–19 weeks of infection), groups of early precursors and immature eosinophil granulocytes corresponding, at the ultrastructural level, to promyelocytes and myelocytes. Mitosis also seen in eosinophil myelocytes. These eosinophil myeloid foci were observed in close contact with macrophages and epithelioid cells, and they were surrounded by an extracellular matrix, rich in collagen fibres. These morphological observations give support to the concept of a peripheral proliferation of cosinophils in chronic schistosomiasis, mediated by a factor secreted by macrophages present in granulo

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90055-R

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—In vivocold stress was found to induce characteristic changes in the protein synthesis pattern ofPleurodeles waltloocytes, as analyzed by two‐dimensional gel electrophoresis. The nature of the response varied with the duration and intensity of stress. After a short period of cold stress (12 h at 8°C), synthesis and intracellular distribution of polypeptides were dramatically disturbed. There occured: 1) a reduction in synthesis of several polypeptides, including two major polypeptides (54‐kDa and 47‐kDa); 2) changes in distribution of polypeptides in oocyte,iesome polypeptides (185‐ and 96‐kDa) were blocked in the cytoplasm, while other polypeptides (82‐, 74‐, 72‐ and 68‐kDa, actin and nucleoplasmin) continued to enter the nucleus, but were quantitatively reduced; 3) no changes in the distribution of two nuclear polypeptides (53‐ and 43‐kDa); 4) changes in the relative quantities of β‐ and γ‐actin and preferential migration of γ‐actin towards the nucleus. After a long period ofin vivocold stress (5 days at 8°C), we noted a partial recuperation of synthesis and nuclear migration (except for a 96‐kDa polypeptide), but a persistent perturbation at the level of actin. For more drastic stress conditions (4°C), such a recuperation of

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90056-S

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—Simultaneous transmission and scanning electron microscopy studies were performed on lampbrush chromosomes ofNotophthalmus viridescensandXenopus laevis. The organization of their normal and landmark loop ribonucleoprotein (RNP) matrices was compared to that ofPleurodeles waltllampbrush loops, previously described. Ultrastructural observations clearly showed that in the three species, the RNP matrix of normal and landmark loops displayed a common basic structure: an RNP fibril packed into tightly juxtaposed RNP particles of remarkably uniform size,ie30 nm. Furthermore, analysis of the spatial arrangement of these constitutive RNP fibrils allowed us to establish ultrastructural similarities between the different types of loop matrices of the three species studied. Thus, granular loops with the same organization were found to be present in the three species, whereasPleurodeleswas the only one to exhibit, in its lampbrush chromosomes, the typical globular matrices previously described. “Sequential labelling loops” ofNotophthelmuswere shown to be similar of both “convoluted dense loops” ofXenopusand “dense loops”

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90057-T

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The ultrastructure of liquid crystalline phases of DNA raises numerous problems because of the structure itself which is fluid and which nature depends on the relative amount of DNA, water and ions. Different cryofixation methods were tested and compared after freeze‐fracture of the specimen. A good ultrastructural preservation of the samples can be achieved without addition of any cryoprotectant by quick‐freezing against a copper block cooled down to liquid helium temperature. Then, molecular orientations can be followed very accurately and the local disorder around a mean direction which exists in the liquid state is kept in the frozen stru

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90058-U

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The major basic nuclear protein HCc (previously named Histone‐like) of the dinoflagellateCrypthecodinium cohniiB was immunolocalized in light and electron microscopy using an affinity‐purified polyclonal antibody. Complementary conventional and cryo‐techniques were used to study the distribution of the DNA‐binding protein in interphase cells and to follow its behaviour throughout the mitotic cycle. In non‐dividing cells, the HCc protein was found to be located on extra‐chromosomal loops and chromosomal nucleofilaments dispersed in the nucleoplasm. In mitotic cells, from prophase to early telophase, it was homogeneously distributed in the (whole) dividing chromosomes. HCc protein was also detected in two compartments of all the permanently observable nucleoli: the nucleolar organizing region and the fibrillo‐granular region. In this paper we discuss the hypothetical roles, structural and/or functional, of this DNA‐binding protein, which is specific to dinoflagellates, the only eukaryotes whose chromatin is devoid of histone

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90059-V

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The distribution of viral RNA molecules in HeLa cells infected with adenovirus type 5 (Ad5) was determined byin situhybridization at the ultrastructural level at an intermediate stage of nuclear transformation, when viral DNA synthetic activities were maximal but progeny viruses were still sparse. Transcription sites of the viral DNA were localized by short pulse, high resolution autoradiography. Nascent viral RNA was found mainly within the nuclear compartment identified at the peripheral replicative zone, which is known to be the main replicative site of Ad5 viral genomes. Viral RNA molecules also were present, but to a markedly lesser extent, within the contiguous single‐stranded (ss) DNA accumulation site, another intranuclear virus‐induced structure in which some replication of viral genomes also occurs. Two other virus‐induced nuclear structures contained viral RNA, the occasional exceptionally enlarged clusters of interchromatin granules and the compact rings, both DNA‐free structures of unknown significance but which might play a role in the process of maturation of the Ad5 primary transcripts. Viral messenger RNA molecules were localized over the large areas of the cytoplasm which contain numerous ribosomes. Our analysis of the effects of various enzymatic pretreatments of the sections of infected cells on the revelation of nascent RNA byin situhybridization is

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90060-Z

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—In mammalian cells most microtubules are enriched in tyrosinated α‐tubulin (tyr‐tubulin). Other subclasses of microtubules are present in variable amounts and some are enriched in detyrosinated α‐tubulin (glu‐tubulin). We examined the effect of cell‐cell interactions on the level of glu‐tubulin in microtubules. This was studied by quantitative immunofluorescence using antibodies against tyr‐ and glu‐tubulin. We found that in cells which have established cell‐cell contacts, the ratio of glu‐/tyr‐tubulin is higher than in isolated cells. We also examined the effect of cell‐cell interactions on the glu‐/tyr‐tubulin ratio by using the antibody blocking method of Schulze and Kirschner [42]. Microtubules containing mainly tyr‐tubulin had been blocked first by a polyclonal antibody against tyr‐tubulin and several layers of secondary antibodies. The unblocked microtubules were then labeled by a monoclonal antibody against α‐tubulin. Since the coating efficiency of microtubules by the anti‐tyr tubulin depends on the amount of tyr‐tubulin in each microtubule, this procedure allows the visualization of microtubules enriched or depleted in tyr‐tubulin in specific domains of each cell. Microtubules were more extensively blocked in subconfluent than in confluent cells and preferentially at the periphery of the cytoplasm. In cells present at the margin of an artificial wound produced in a confluent monolayer, the amount of blocked microtubules increased slowly with time (between 2 and 4 h). These results are consistent with the hypothesis that cell‐cell contacts lead to increased tubulin detyrosina

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90061-Q

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—Thein vitropolymerisation of tubulin is a remarkable example of protein self‐assembly in thet several closely related microtubule structures coexist on the polymerisation plateau. Unfixed and unstainedin vitroassembled microtubules were observed in vitreous ice by cryo‐electron microscopy. New results are reported that considerably extend previous observations [47]. In ice, microtubule images have a distinctive contrast related to the number and skew of the photofilaments. The microtubules observed have from twelve to seventeen protofilaments. Comparison with thin sections of pelleted material allows a direct identification of images from microtubules with thirteen, fourteen and fifteen protofilaments. A surface lattice accommodation mechanism, previously proposed to explain how variable numbers of protofilaments can be incorporated into the basic thirteen protofilament structure, is described in detail. Our new experimental results are shown to be in overall agreement with the theoretical predictions. Only thirteen protofilament microtubules have unskewed protofilaments, this was confirmed by observations on axoneme fragments. The results imply that the microtubule surface lattice is based on a mixed packing which combines features of the standard A and B lat

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90062-R

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The two flagella of Dinoflagellates have, up to now, been poorly described. They display different structures and different patterns of behaviour compared with other organisms. In addition, the two flagella are different from each other: the transverse flagellum is ribbon‐shaped and beats with a spiral undulation inside a furrow located around the cell body while the longitudinal flagellum has a larger diameter than simple flagella because it contains structures in addition to the axoneme and propagates essentially sinusoidal waves to push the cell.Ceratiumflagella are particularly interesting to study because they both show different types of movements and have complex structures in addition to the axoneme. We propose that the additional structures are responsible for the particular movements of Dinoflagellate flagella. The presence of food particles in vacuoles in the vicinity of the flagella pocket suggests that their flagellar apparatus may not only be a propulsive organelle but could also be involved in prey capt

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90063-S

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY