摘要:

Summary—Diffusion theory played a major role in the development of biology as an exact science. The question is raised, however, as to its relevance and applicability in the molecular interactions which occur in metabolism in the living cell. This review looks at diffusion theory from its inception and subsequent introduction into biology, its shortcomings with regard not only to whole‐body physiology, but more pertinently at the intracellular level, with its failure to offer a rational basis for metabolic regulation in the internum of the cell. The conclusion is reached that although diffusion inevitably occurs within cells, its role is of little importance with regard to most metabolic activity. In comparison, perfusion of the internal surfaces of the cell by streaming of the fluid compartment of the cytoplasm seems to be themodus operandiwhich allows molecular interactions to occur at rates far beyond those that diffusion would permit, and at the same time offers a mechanism which permits sensitive control of metabolic activ

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90256-E

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—The vectorial transport of membrane and macromolecules within the cytoplasm of eukaryotic cells has been the subject of intense investigation over the last decade. In this paper we review some of the recent advances made in our understanding of vesicle transport and the secretory pathway in plant cell

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90257-F

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—The interaction between monocytes and endothelial cells plays an important role in normal vascular biology and the pathogenesis of several vascular diseases. In the present study, interactions of freshly isolated human monocytes (Mos) and cultured umbilical vein endothelial cells (ECs) were quantitatively analyzed by a time lapse microcinematographic optical video systemin vitro, with reference to Mo locomotion, adherence, and cytokine influence on these processes. The interaction between Mos and ECs was found to be a dynamic process. Without any stimulation of ECs, Mos generally possessed higher binding capacity to ECs and more active motile property than neutrophils and lymphocytes. The binding ratio of Mos to ECs varied from 0 to 8. Mos crawled over the surface of ECs or along the intercellular boundary areas of ECs by extending pseudopodia as long as 60 μm in length to traverse several ECs. Mos migrated into the subendothelium and could cause the distruption of the EC monolayer. In contrast, neutrophils or lymphocytes showed less adhesiveness to ECs and exhibited less dislocation when they moved on the ECs. Pretreatment of ECs with either human recombinant interleukin‐1β (IL‐1β) or tumor necrosis factor (TNF) (10–20 U/ml for 4–8 h) significantly increased adhesion rates of both Mos and neutrophils. Furthermore, the increased adhesion of neutrophils to stimulated ECs was accompanied by incremental increases in the rate of cellular movements. These phenomena were found to be associated with activation of EC surface adhesion molecules. In addition, by using the Boyden chamber assay, we found that IL‐1 and TNF did not produce any chemotactic activity for Mos with a concentration range of 10−3to 103U/ml. These results indicates that, in comparison with neutrophils and lymphocytes, Mos exhibited active adhesive and motive properties even on unstimulated EC surfaces, which could potentially interfere with the integrity of ECs. Upon exposure to cytokine stimulation, ECs increase the expression of adhesion molecules thereby enhancing both adhesion and locomotion of leukocytes. The distinctively higher affinity for binding to cultured ECs of blood Mos and their active motility relative to other circulating leukocytes may have great consequences in various physiological and pathological processesin vivo, includi

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90258-G

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—The culture of specialized high endothelial cells (HEC) from lymphoid organs (peripheral lymph nodes (PLN) and Peyer's patches (PP)) was undertaken in order to study and characterize the cell surface molecules which are involved in lymphocyte recognition and allow homing. Cells were stimulatedin vivoby a graftversushost (GVH) type of reaction before isolation and culture. The resulting adherent and growing cells were characterized as endothelial cells because of their typical aspect and their ability to produce angiotensin‐converting enzyme and factor VIII‐related antigen. They possess tissue‐specific endothelial addressins. MECA 79 antigen is present on cells isolated from PLN while MECA 367 antigen is detected on cells from PP. Surface receptors for glycans were studied cytochemically using neoglycoproteins and fluorescence microscopy and quantified by flow cytometry experiments which showed that the specificity of sugar receptors depends upon endothelial cell origin. Indeed, sugar receptors for α‐L‐fucosyl residues were specifically expressed by endothelial cells from PLN. These receptors were inducible upon action of activated lymphocyte‐conditioned medium. Further characterization of endothelial cells from peripheral lymph nodes indicates that they indeed mediate adhesion of lymphocytesin vitro. The role of protein‐sugar interactions in this process was assessed by inhibition experiments performed with the help of neoglycoproteins. Best inhibitory effects were obtained when endothelial cells had been preincubated with α‐L‐fucosyl‐BSA and when lymphoid cells were preincubated with β‐D‐galactosyl‐BSA. Concomitant inhibition assays indicate the participation of sugar specific receptors — endogeneous lectins — on the surface of both endothelial and lymphoid cells t

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90259-H

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—A homologous protein, recombinant trout somatotropin (rtST) and its heterologous counterpart, native bovine somatotropin (bST), were administered anally to juvenile rainbow trout (Oncorhynchus mykiss). Plasma levels of rtST, determioned by radio‐immunoassay, peaked between 15 and 60 min and remained high until 2 h after administration. Immunogold labelling was used to follow the routes of transfer of rtST and bST, and to observe potential interaction between the hormones and the cells constituting the first line of non‐specific defence,iethe macrophages infiltrated between epithelial cells, or dispersed in the subepithelial lamina propria, and eosinophilic granulocytes (EGCs) of the lamina propria, whose properties have been considered to be similar to mammalian mast cells. Macrophages were immunolabelled for the homologous and heterologous proteins. EGCs took up to the heterologous but not the homologous protein. This finding was confirmed using indirect immunofluorescence assay. EGCs could internalize foreign proteins transferred from the intestinal lumen to the lamina pr

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90260-L

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—The behavior of two mammalian cell lines was investigated in Biorack during the 1st Spacelab international microgravity laboratory flight (IML‐1) in the ESA facility Biorack. The parameters determined were cell proliferation, biosynthesis of specific cell products, consumption of glucose, glutamine and production of ammonia and lactate respectively. Murine Friend leukemia virus‐transformed cells (Friend cells) were induced to differentiate and express hemoglobin (Hg) genes upon induction with dimethylsulfoxide (DMSO). No change was observed in all metabolic parameters including the production of Hg and the number of Hg‐positive cells. Electron microscopy analysis showed no difference in morphology, mean cell volume and mitotic index between the different cell samples, Murine hybridoma cells revealed an increase (+ 30–40%) of cell proliferation rate in microgravity, whereas the metabolic parameters, production of monoclonal antibodies included, were lower in the 0gthan in the 1gcontrols. The results clearly show that not all mammalian cells undergo dramatic changes in microgravity and that the effects reported on human T lymphocytes represent a un

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90261-C

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—The dodecasatellite is a 11/12 bp tandemly repeated sequence which is overrepresented, with regard to its genomic representation, in extrachromosomal circular DNAs fromD melanogasterembryos. Here we show that a bacterial plasmid carrying a cluster of dodecasatellite is not able to replicate efficiently in cultured cells. This observation does not support the hypothesis that the over‐representati results from an autonomous replication of dodecasatellite circular DNA molecu

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90262-D

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—The fine morphology, size, and perichromatin granule frequency were analysed in brown adipocyte nuclei from hibernating, arousing, and euthermic dormice,Muscardinus avellanarius. Unusual nuclear structural constituents such as nuclear amorphous bodies, coiled body‐like constituents and bundles of nucleoplasmic filaments were described as typical of hibernating nuclei. Morphometrical findings showed significant difference in total nuclear and nucleolar size in the three physiological conditions investigated as well as decreasing frequency of perichromatin granules in nuclei of hibernating to euthermic animals. A possible involvement of these granules in the intranuclear transport or storage of pre‐mRNA is discussed in the context of other experimental evi

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90263-E

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—Cell‐free extracts from goldfish brain, ovarian follicles, testes and the cell line, ATCC CCL‐71, were analyzed for post‐translationally modified tubulins. All samples, with the exception of that from brain where the reverse was true, contained more tyrosinated than detyrosinated α‐tubulin. Additionally, extracts from brain and testes exhibited acetylated α‐tubulin whereas this isoform was not visualized on blots of cell‐free preparations from follicles and CCL‐71 cells. Assembly of brain and ovary tubulin was induced with taxol. Brain tubulin, partially purified through three cycles of assembly/disassembly was associated with a variety of putative microtubule‐associated proteins (MAPs), most of which had a high molecular mass. There were very few cold stable microtubules in brain preparations whereas, for ovary, purification of tubulin was hampered by significant losses of cold stable polymer. Comparison of brain and ovary showed there was no‐correlation between the extent of α‐tubulin detyrosination or acetylation and cold stability of microtubules. Moreover, cycled tubulin from ovary contained acetylated tubulin even though this was not observed on blots of cell‐free extracts from ovary or from follicles. Cultured goldfish cells contained extensive arrays of microtubules, many of which originated from discrete organizing centers. The results reveal the widespread distribution of posttranslationally modified tubulins in goldfish tissues, the different assembly/disassembly characteristics of tubulin from brainversusovary, and the presence of putative neural MAPs, mostly

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90264-F

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Summary—The effect of various combinations of three fixative compositions (glutaraldehyde buffered in veronal acetate, cacodylate, and piperazine‐N, N'‐bis[2‐ethanesulfonic acid]—PIPES], two fixative storage times (freshvs6 weeks), and two fixation durations (3 hvs9 days) on nucleolar fine structure and nucleolar volume in three root cell‐types of oat seedlings (Avena sativaL, cv Seger) were evaluated. All fixatives show overall good preservation of fine structure. Nucleolar components are distinct and well delineated in cells fixed in solutions buffered with either cacodylate or veronal acetate; the components are more condensed when preserved in fixative buffered with PIPES. Nucleolar volume is greatest in cells fixed in the cacodylate fixative, and smallest in those preserved in the PIPES fixative. Among the treatments tested, the PIPES fixative evidently best maintains nucleolar volume. Distracting particulate deposits are abundant on nuclei and nucleoli in cells preserved in the veronal‐acetate fixative. Contrary to common assumptions, aging of buffered fixative at room temperature for 6 weeks seems to affect neither the general quality of cellular preservation nor the pH of the fixatives, although nucleolar volume is reduced by such treatment. Long‐period fixation (9 days) results in destruction of membrane integrity (mitochondria, plastids, ER), and shrinkage of organelles from the cytoplasm. Nucleolar volume is reduced with pro

ISSN:0248-4900    

DOI:10.1016/0248-4900(93)90265-G

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY