摘要:

Summary—In spite of the constant development concerning physical mapping of eukaryotic genomes, the mouse chromosome 19 remains poorly characterized. In order to improve the possibilities for studying this chromosome, we have constructed a chromosome‐specificEcoRI DNA fragment library from mouse chromosomes 19 sorted by flow cytometry. The resulting library contains about 3 × 104recombinant clones. The identified inserts range in size from about 0.2–10 kb, with a 4 kb average size and with no observable redundancy. The purity of the library has been analyzed by flow‐blot. For that purpose, chromosomes from 2 cell lines, 1 with a normal karyotype and 1 with translocated chromosome 19, were sorted on nylon filters and hybridized with 9 clones of the library. Results show that 5 clones out of the 9 clearly originate from sorted chromosomes 19 and 3 and are likely to be derived from its DNA, thus indicating that the library of chromosome 19 is of hig

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90322-T

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The ultrastructure of chick embryo tendons has been examined after quick‐freezing by liquid helium and freeze‐substitution. Several stages of collagen assemblies were observed: intracellular packing of SLS‐like aggregates surrounded by membrane containing areas with a clathrin coat; fine non cross‐striated filaments connecting the cell membrane at 1 pole of the cells and collagen fibrils; tufts of filaments directly linked to collagen fibrils. This study reveals that some stages are more constant and abundant than supposed (the intracellular SLS‐like aggregates) and that other extracellular assemblies that were hypothesized but usually badly preserved by conventional electron microscopy are clearly captured by

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90323-U

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Immunsera of mice injected with clathrin‐depleted coated vesicle membranes, purified from rat liver, revealed a preferential labeling of some perinuclear structures by immunofluorescence microscopy on NRK cells. Subsequent production of 4 monoclonal antibodies was achieved. The antigen was strictly located in the Golgi area of the cell but was not an intrinsic element of the Golgi complex. The restricted location of the structures excluded these were lysosomes which appeared more dispersed in these cells. After nocodazole treatment the material was found dispersed in the cytoplasm. This provided a means of distinguishing the antigen from clathrin‐coated structures and Golgi intrinsic elements. Immunolocalization at the electron microscope level confirmed the data obtained at the light level. Some peroxidase reaction product was rarely associated with Golgi elements, but predominantly stained small neighboring Golgi vesicles (50 nm diameter), as well as tubulo‐elongated structures and some large (500 nm) irregular‐shaped vesicles. A 32 kDa molecular weight antigen was characterized by immunopurification from NRK cells metabolically labeled with35S‐Met. This 32 kDa antigen appeared as part of a higher multimolecular membrane component of 300 kDa. A 170 kDa and a 70 kDa components were immunodetected in a semi‐purified membrane fraction from rat liver, demonstrating that the antigen was a minor but very antigenic contaminant of the coated vesicle preparation used as immunogen. In conclusion, the labeled peri‐Golgi structures may be part of the newly characterized trans‐Golgi network and/or of the reticular/vesicular endosomal, prelysosomal structure r

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90324-V

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—When trypsin‐dissociated enamel organs and dental papillae were recombined in the presence of cerulenin — an antibiotic which is a potent inhibitor of fatty acid synthesis — the newly synthesized basement membrane seemed defective in a dose‐dependent manner. The three‐dimensional relationship between the basement membrane components and the plasma membrane appears to be regulated in par

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90325-W

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Using the immunofluorescence technique we attempted to locate, in theDrosophilahost,DrosophilaC virus (DCV) target organs after injection of adult flies. Two kinds of organs were infected: those which play a role in reproductive function, including the fat body and follicular cells, and others, including thoracic muscle fibers, tracheal cells, and the digestive tract. These organs correspond to those found in previous tests. Fat body proteins of a DCV‐free host population seemed to cross‐react with antivirus C antibody. This immune response depended on the origin of the host population. It is known that, when DCV is ingested from the first larval instar, it may have beneficial effects upon host development and reproduction. As DCV has a narrow host spectrum, it is suggested that it is well adapted to its natural host. Hypotheses are proposed to explain how the host resists viral infection and may in fact benefit from such an infe

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90326-X

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Birefringence changes have been studied during the contraction—relaxation cycle of the myonemes (contractile organelles consisting of a bundle of nonactin filaments) in Acantharians (Protista, Actinopoda). Myonemes can either contract rapidly or undulate slowly between their anchorage points. In thin sections they appear as a large cross‐striated bundle with long clear zones (LZs) and thin transversal dense bands (TBs). The filaments (2–4 nm in diameter) are twisted in pairs in elementary microstrands. The spacing of the LZ depends on the extent of contraction [16]. A negative birefringence has been seenin vivoandin vitro.In vivo, retardation varied with the extent of relaxation of the myoneme (2.5 nm−4.4 nm). When the myoneme was tightened, it appeared to be homogeneously dark or bright in contrast depending on the orientation for the vibrating plane of polarized light. When it was partially relaxed and moved slowly, a series of birefringent bands, 0.8–2.8 μm thick, could be seen. They propagated at the same speed (about 2 μm·s−1) by successive trains, either forward or backward. Each of these birefringent bands may correspond to 4–13 contracted LZs. It is suggested that the negative birefringence of the myoneme is mainly caused by the orientation of the filaments forming the microstrands. Our results strongly suggest that the orientation of the myoneme filaments is altered during the movement and that the orientation of the filaments in the negative bands is caused by perpendicular orientation compared to the other parts of the myoneme. These observations support our previous hypothesis in which we postulated that the length of the myoneme varies in relation to the pitch of the eleme

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90012-3

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The ultrastructure of oocyte and sperm nuclei was studied in mouse ovarian oocytes inseminatedin vitroand cultured for 1 1/2 and 3 h in a medium containing dbcAMP or lacking the maturation inhibitor. In oocytes blocked at the germinal vesicle (GV) stage, certains maturation‐linked changes were noted. Sperm apposition and sperm‐oocyte fusion were similar to that during fertilization of ovulated oocytes. The sperm nucleus and its nuclear envelope remained intact after penetrating into the ovarian oocyte. One and a half h after removal of the drug (time 0 of maturation) the germinal vesicle (GV) and sperm nucleus remained intact. In oocytes maturing for 3 h, the nuclear envelopes of the GV and sperm nucleus had fragmented. The NE of the oocyte formed quadruple membranes while the NE of the sperm remained as flat vesicles. Oocyte chromatin condensed to form chromosomes, whereas at the same time the sperm chromatin was in the process of decondensation and was surrouded by fragments of the sperm NE. The sperm chromatin, composed of DNA complexed with protamines, consisted of thin fibrils; the individual fibrils measured 3.8 nm in diameter. Near the penetrated spermatozoa only occasional Mts were detected which were not related to the proximal centriole which was recognizable in the neck‐piece of the flagellum. Thus in mouse oocytes the introduced sperm centriole is not capable of behaving as a centrosome and organizing microtubules in the form of a

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90328-Z

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Soduim butyrate decreases the c‐mycmRNA and increases the c‐fostranscript level in HTC cells. This effect is independent of the cell‐cycle phase. Actinomycin D suppresses the effect on c‐fos. Cycloheximide increases both mRNA levels. Sodium butyrate suppresses the effect on c‐mycand potentializes the effect on c‐fosmRNAs. This suggests that sodium butyrate acts at the transcriptional level and that its effect does not result from the arrest of the cells at

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90329-2

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—We have determined the nucleotide sequence of ten 240 bp repeated sequences of the DNA intergenic spacer present in circular DNA molecules purified fromD melanogasterembryos. No significant difference was found with the sequence of the chromosomal units. This suggests that most of the circular molecules homologous to the 240 bp repeats are generated by homologous recombination between adjacent chromosomal unit

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90330-6

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90331-V

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY