摘要:

Mammalian variants with a defect altering the cell cycle progression have been selected, characterized to different extents and preliminary genetic analysis has been carried out. The difficulties encountered in their study are discussed below. Up to now, they have limited the genetic approach to the cell cycle.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00308.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Fetal calf serum and a serum substitute, Ultroser G, were compared for their effects on the growth curves, clonal growth and cell cycle progression of rabbit chondrocytes in primary culture and during at least three cell passages and included a screen for the maintenance of cartilage‐like differentiation i.e. the presence of type II collagen. Proliferation was also compared with another serum substitute, Nu‐Serum. Ultroser G is shown to be equivalent to fetal calf serum as far as chondrocyte proliferation is concerned, clonal growth is improved and biosynthesis of type II collagen is maintained in primary cult

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00309.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Isolated porcine thyroid cells cultured in suspension in Eagle Minimum Essential Medium supplemented with calf serum (5‐20%) reorganize to form vesicles, i.e. closed structures in which all cells have an inverted polarity as compared to that found in follicles: the apical membranes are bathed by the culture medium. Under these conditions, cells neither concentrate iodide nor respond to acute thyrotropin (TSH) stimulation. When embedded in collagen gel, these vesicles undergo polarity reversal to form follicles. We describe here the change in the orientation of cell polarity and the subsequent reappearance of specific thyroid functions. Six hr after embedding, membrane areas in contact with collagen fibers show basal characteristics. At this time, cells begin to concentrate iodide and to respond to acute TSH stimulation (iodide efflux and increased cAMP levels). Most cells form follicles 24 hr after embedding, but 48 hr are required for the transformation of all vesicles into follicles. This occurs without opening of the tight junctions. Iodide organification is detected 24 hr after embedding, when periodic acid‐Schiff positive material, identified as thyroglobulin by immunofluorescence, accumulates in the lumen. Iodide concentration and organification, as well as response to TSH stimulation reach maximal levels after 3 days in the collagen matrix. After a 5‐day culture in the collagen matrix in the absence of TSH, cell activity can be stimulated by chronic treatment with low hormone concentrations (10‐100 microU/ml). As shown with thyroid cells grown in monolayer on permeable substrates (Chambard M., et al., 1983, J. Cell Biol. 96, 1172‐1177), iodide uptake and cAMP‐mediated TSH responses are expressed when the halogen and the hormone have direct access to the basal membrane. Organification, on the contrary, requires a closed apical

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00310.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Mammary gland fragments were incubated in the presence of prolactin and arachidonic acid which stimulate casein secretion. The effects of these stimuli in the presence of agents that influence arachidonic acid metabolism were investigated. Chloroquine, a blocker of phospholipase A2 activity, decreased prolactin but not arachidonic acid stimulation of casein secretion. Phospholipase A2 markedly stimulated casein secretion. Nordihydroguaiaretic acid (NDGA), an antioxidant that inhibits lipoxygenase, blocked the stimulating effect of prolactin and arachidonic acid. Ultrastructural studies indicated that phospholipase A2‐induced stimulation of secretion was comparable to that of prolactin but that arachidonic acid‐induced stimulation did not involve the same Golgi membrane modifications. These studies suggest that prolactin and phospholipase A2 stimulate secretion by a common way, and that arachidonic acid interferes with secretion by metabolic products of the lipoxygenase path

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00311.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Control of the development and functions of avian oviduct is monitored by four classes of steroid hormones, including glucocorticoids. The effects of dexamethasone (DEX), a synthetic glucocorticoid, were studied via sequential treatments with estradiol benzoate, paying special attention to changes in estrogenic oviduct responses involving DNA synthesis and cell proliferation, ovalbumin accumulation and cell differentiation. DEX exerted an antagonistic effect upon estrogen stimulation when administered separately before or after estradiol benzoate (EB). Given before EB, DEX was more strongly antagonistic for DNA synthesis than when given simultaneously with EB. Administered after EB, DEX reversed EB‐induced cell proliferation: the DNA content declined and the oviduct regressed. In the same way, protein and ovalbumin synthesis was inhibited and delayed by first intervention of DEX, and accelerated catabolism of ovalbumin and proteins was observed when DEX followed EB. DEX, which was ineffective alone, but synergistic on ovalbumin synthesis when given concomitantly with EB, prevented or dissipated the estrogenic effects, cell proliferation and secretory process when administered in sequential treatment

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00312.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

This transmission electron microscopic study demonstrated a periodic arrangement of short cross‐filaments in all the cytoplasmic layers of the human spermatozoon. These filaments were connected with adjacent cellular components (of the same type or not) thus appearing to link the sperm structures to one another. The filaments of the peripheral cytoplasm, those of the perinuclear space and those between the cytoskeletal structures of the flagellum were 3 to 5 nm, 7 to 9 nm and 2 to 4 nm wide respectively. These cross‐links displayed a 14 to 20 nm periodicity and measured 6 to 35 nm in length, depending upon their location. They were associated with electron dense patches on the outer acrosomal membrane. Plasma membrane swelling was associated with a disruption of the cortical filaments on the inside surface of the membrane. This suggested a relation between the normal morphology of the plasmalemma and the cross‐filaments. In altered sperm heads, a particular modification of the perinuclear space was found consisting of an aggregation of the cross‐filaments into repeated bundles. Many of the morphological characteristics of these cross‐filaments could be compared to similar cytoskeletal structures as known in somatic cells. The data of this study suggest that this filamentous network may play an essential role in the maintenance of the topographical relations between the various organelles which may be especially necessary due to the kinematics of

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00313.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

LamB is one of the major cellular proteins when E. coli is grown in the presence of maltose and is localized in the outer membrane. Previous immunolabellings obtained with monoclonal antibodies showed that this protein is a transmembrane protein and led to the detection of 4 epitopes exposed on the cell surface and 2 located on the inner surface of the outer membrane (Scheckman et al., 1983). In the present study, we have used this biological model in order to see whether these two classes of epitopes could be distinguished by immunocytochemical labelling performed on thin sections of E. coli embedded in Lowicryl K4M (Carleman et al., 1982). The optimal conditions of fixation and embedding were first established for labelling with poly‐ or monoclonal antibodies detected by Protein A‐gold complexes. The analysis of gold particle distribution on each side of the outer membrane after labelling with a polyclonal serum or after its adsorption on intact bacteria allowed us to conclude that the resolution of immunolabelling on thin sections was about 20 nm. The use monoclonal antibodies met with difficulties due mostly to the nonspecific labelling of the cytoplasm. Although this nonospecific labelling was decreased by fixing bacteria with paraformaldehyde alone, only one antibody gave a correct specific labelling after high dilution (1/3000). The gold particle distribution obtained with this antibody confirmed the location on the cell surface of this epit

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00314.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The epithelial cells of the ovary follicles have been studied in the prawn Macrobrachium rosenbergii using electron microscope and horseradish peroxidase. A network of circumvoluted and anastomosed tubules, measuring about 0.15 micron in diameter, communicates with the extracellular spaces. This tubular network is a structure which extensively increases the permeability of the follicular epithelium.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00315.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A device for the precise localization (better than 0.5 micron) of an object on a grid has been developed and connected to the translation system of an electron microscope. Applied to biological thin sections, this device enables to easily find and to observe a selected microcrystal projection obtained by the grid sectioning technique. Moreover, low dose observations on ribbons of ultrathin sections can be made because the information is repeated in the successive sections of the ribbon: With the device the position of the selected object is determined at high dose in one section and low dose measurement is made on the following section.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00316.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The dynamics of the synthesis of the mouse oocyte zona pellucida was studied using light microscope autoradiography after intrabursal injection of (3H) ‐fucose. Zona accretion occurred continuously from the inside, demonstrating that the oocyte itself elaborated all the raw material of the zona. The duration of zona synthesis corresponded to that of the oocyte growth phase. Zona secretion stopped one week before ovulation and there was no renewal of its materia

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00317.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY