ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85270-1

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Mammary gland growth occurs essentially during pregnancy and induction of milk synthesis is triggered at parturition. Prolactin is mammogenicin vivobut only marginallyin vitro.Prolactin induces milk synthesisin vivoand in cultured mammary cells. Prolactin is also strictly required for the multiplication of the rat lymphoid Nb2cells. Stathmin is an ubiquitous and highly conserved phosphoprotein which seems to be involved in the intracellular mechanisms which trigger cell multiplication and differentiation. In the present study, the concentration of stathmin mRNA has been evaluated during the pregnancy‐lactation‐weaning cycle in mouse and rabbit. Stathmin mRNA appeared at its highest level during pregnancy and it was almost undetectable during lactation. Prolactin injected into mid‐pregnant rabbits induced milk synthesis and this effect was not accompanied by any modification of stathmin mRNA concentration. In cultured primary rabbit mammary cells, prolactin induced casein gene expression without any alteration of stathmin mRNA concentration. In Nb2cells, prolactin induced a progressive increase of stathmin mRNA concentration. This effect was not significant until after 4 h of prolactin action. These data suggest that stathmin is involved in mammary and Nb2cell multiplication but may not be necessary for mammary cell differen

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85271-3

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—In a previous work, we have isolated the humanH19gene and shown accumulation of transcripts in various human tumors including breast carcinomas (Douc‐Rasyet al(1993)Int J Oncol2, 753–758). Questions arose, after Northern blot results, about the preciseH19mRNA location, specially in normal breast tissues and benign or malign primary breast tumors. Then we performed molecularin situhybridization to get insight into tissue expression of theH19gene. Examined resections included one normal tissue, one fibroadenoma and 13 cancers. Results obtained with theH19probe can be summarized as follows: 1) in normal breast tissues signals were focally observed in epithelial cells, but more predominantly in the palleal tissue which is sensitive to hormones; 2) in the fibroadenoma, fibroblastic cells were extensively labeled at the stroma‐epithelium boundary, but epithelial cells were negative; and 3) in primary cancers, eight specimens exhibited signals on stromal cells, one specimen on epithelial cells and four on both epithelial and stromal cells. Data provide the following evidence: 1) usually labeled cells are clustered, either within normal or pathological tissues; 2) the labeling pattern highly differs from one tumor to another; and 3)H19probe displays very different signals from one cell to another in a given compartment of a given tissue section. In conclusion, it seems that a highH19expression matches the tumor invasion. Our results suggest that the expression of this gene is concerned by the relationships between epithelial and stromal cells, and can reflect peculiar physiological states of the cells. Furthermore, we discuss results showing an abundant expression ofH19gene in some adenocarcinomas of bad prognosis, in the context of the otherwise established tumor‐suppressor role of this gene, or the strictly controlled gene dosage, which could be overridden in these particu

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85272-5

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Many studies performed to elucidate the molecular and cellular processes involved in muscular dystrophies have led to the working hypothesis of a key role for the cytoskeleton elements linking the extracellular matrix to myofibrils. It was recently suggested that cytochalasin B treatment of mouse soleus muscle promoted cell damage mediated by a cytosolic increase in free calcium concentration. Since intracellular calcium overload may be a primary event resulting from the alteration of cytoskeletal structure, this study was intended to evaluate whether or not the integrity of the F‐actin microfilament network is necessary for calcium homeostasis. The developmental establishment of the normal cytoarchitecture was altered by treatment of myoblasts with the actin‐disrupting agents cytochalasin B and D, and the effects were compared with those in myoblasts treated with colchicine. These drugs modified the morphogenesis in that they prevented the formation of elongated myotubes by myoblast fusion, but did not prevent the maturation of contractile myogenic cells. The subcellular organisation of actin filaments visualised by confocal fluorescence microscopy was modified by colchicine and cytochalasins, but appearance of contractile apparatus and mechanical activity were not precluded. Sarcolemmal addressing of dystrophin, the subsarcolemmal protein lacking in Duchenne muscular dystrophy, was not prevented by cytochalasin. The evaluation of the basal activity of cytosolic calcium measured with indo‐1 suggested that the disruption of actin or microtubules did not prevent developing muscle cells to maintain a low basal calcium activity. We propose that the global integrity of the cytoskeleton network is not crucial for the maintenance of calcium homeostasis in muscle cells developingin vitro.These results are discussed with regard to current theories attempting to understand the functional consequences of an abnormal expression of the dystrophin‐glycoprotein complex interacting with the extracellular matrix and the cyt

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85273-7

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—We explored the possibility that an insulin gene deleted in its 5'‐flanking region is expressed in adult mouse brain. We used three independent lines of mice carrying a human insulin transgene which included the insulin gene transcription unit flanked by 168 base pairs upstream and 5.5 kb downstream. Using a reverse transcription‐polymerase chain reaction assay, human insulin mRNAs were detected in whole brain extracts. In all three lines, human insulin mRNAs were localized byin situhybridization in a single cerebral site, the medial habenula. With a monoclonal antibody specific for human C‐peptide and human proinsulin, labelling was restricted to a subset of habenular cholinergic neurons, with rare immunostained fibers. No labelling was observed in the projection fibers of the retroflexus fasciculus or in their axon terminals in the interpeduncular nucleus. Electron microscope studies suggested that the processing of the human peptide involved the endoplasmic reticulum and Golgi apparatus, but there were no secretory granules in the transgene expressing cells. These findings demonstrate that the human insulin transgene tested here includes a habenula specific promoter which could be useful for physiological and molecular studies on the h

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85274-9

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Specific antibodies were prepared againstDrosophilaDNA polymerase e and DREF, a regulatory factor for DNA replication‐related genes. Using these antibodies together with those for DNA polymerase α and proliferating cell nuclear antigen (PCNA), we examined expression patterns and sub‐cellular distributions of these proteins duringDrosophiladevelopment. DNA polymerase α, ε and PCNA proteins were maternally stored in unfertilized eggs and maintained at high levels during embryogenesis. With distinct nuclear localization, proteins were observed in embryos at interphase stages throughout the 13 nuclear division cycles, suggesting that they all participate in rapid nuclear DNA replication during these cycles. In contrast, maternal storage of a DREF protein was relatively low and its level increased throughout embryogenesis. Strong nuclear staining with the anti‐DREF antibody was not observed until the nuclear division cycle 8. Immunostaining of various larval tissues from transgenic flies carrying the PCNA gene promoter‐lacZfusion gene revealed co‐expression of DREF, PCNA andlacZ, suggesting that DREF regulates the expression of PCNA gene in these tissues. In addition, we detected a relatively high level of DREF in adult males as well as females. Since DNA polymerase α, ε and PCNA are hardly detectable in adult males, DREF very likely regulates genes other than those closely linked to DNA replicatio

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85275-0

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Among their numerous functions, gap junctions play a crucial role in proliferation, differentiation and secretion processes, although their existence and potential role in ion secretion in human pancreatic ducts have yet to be established. To investigate the morphogenesis and the role of gap junctions in human pancreatic duct cells, the Capan‐1 cell line maintained in culture or heterotransplanted into nude mice was employed as model system. Capan‐1 cells polarize during their growthin vivoandin vitroforming duct‐like structures. Furthermore in culture, after confluence, these cells form domes, which is indicative of ion exchange processes. After treatment with tannic acid and freeze‐fracture, gap junctions were observed along the basolateral membranes of Capan‐1 cells on electron microscopic examination. The presence of alkaline phosphatases on gap junctions was demonstrated cytoenzymatically. In addition, cell‐to‐cell communication was visualized by microinjection of Lucifer yellow. During differentiation of Capan‐1 cells in culture, the frequency of intercellular communications increased markedly over the period (days 11–13) when the cells form duct‐like structures. The increase in gap junctions was demonstrated by analysis of the polarized cells organized in duct‐like structures that are commonly observed in the tumors formed by heterotransplantation of Capan‐1 cells into nude mice. Furthermore, gap junctions associated with tight junctions were also observed in the cells forming such structures. The role of gap junctions in ion exchange was evaluated by counting the number of domes in cultures treated with heptanol. Heptanol (an uncoupling agent of gap junction communication) completely inhibited dome formation in a reversible way, and reduced the frequency of intercellular communications by 44%. These results suggest that the gap junctions expressed by Capan‐1 cells are involved in ion secretion by the human cancerous pancreatic duct cell line, Capan‐1. In the present study, we show that: i) the expression of gap junctions is linked to development of the spatial conformation of the cells; and ii) gap junctions may

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85276-2

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—Di‐(2‐ethylexyl)phthalate (DEHP) administered to adult lactating rats from delivery to weaning induces age‐ and organ‐specific modifications of the peroxisomal morphometric parameters (VV, NAand D) in the liver and kidney of both rats and their pups. In both tissues, peroxisomal relative volume and catalase biochemical activity show a similar pattern during the development, as well as under DEHP treatment. Morphometric results suggest that two modalities of peroxisomal proliferation exist, involving: a) increases in both number and mean diameter of the organelles; b) a purely numerical increase of the organelles, accompanied by a remarkable decrement in their mean diameter. A peroxisomal population proliferated through the latter model appears unable to return to normal conditions, following treatment withdrawal. These two proliferation systems, the first implying a swelling and the latter a fragmentation of pre‐existing peroxisomal profiles, are supposed to be tissue‐specific in the adult animal. In particular, in the liver the ‘swelling’ model appears more suitable to explain peroxisome proliferation, while in the kidney this process would follow the ‘fragmentation’ model. Immature animals might instead show in both organs intermediate features of peroxisomal pro

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85277-4

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—It has already been reported that,in vitro, intermediate filaments such as desmin and vimentin are very susceptible to proteolysis by calpains (Ca2+‐activated cysteine proteinases). On the other hand, desmin and m‐calpain are both present at the onset of myoblast fusion and throughout this phenomenon. Based on these observations, the aim of this study was to demonstrate, with cultured rat myoblasts, that the amount of desmin decreased significantly as multinucleated myotubes were formed. Using immunoblot analysis, it has been shown that the desmin concentration decreased 41% as myoblasts fuse. Moreover, under conditions which stimulate myoblast fusion, desmin concentration was reduced by 21% compared to the control culture. Under our experimental conditions, which lead to a reduced desmin level, the amount of m‐calpain was increased about three‐fold. These results suggested that m‐calpain could be involved in myoblast fusionviadesmin cleavage. This hypothesis was confirmed by the results obtained after calpeptin treatment. In the presence of this cell‐penetrating inhibitor of calpains, desmin seems not to be degraded. Taking into account the observations obtained after different hydrolysis assays and as compared to those observed on cultured cells, it seems conceivable that m‐calpain would be able to initiate desmin cleavage leading to the formation of proteolytic fragments which should be immed

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85278-6

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Summary—The dynamics of change in mitochondria‐rich (MR) cells density in the skin epithelium ofBufo viridiswas studied on skin biopsies takenin vivo, throughout experimental periods lasting up to 3 months. When the bathing solution contained Cl−, MR cells' density (Dmrc) greatly decreased. There was one exception, when the acclimation solution was KCl, Dmrcin the skin increased. The rate of decrease in Dmrcdepended on the mode of acclimation. When bath NaCl concentration was elevated slowly in small increments, the change in Dmrcwas very slow. A regression line was calculated for the rate of decrease in the density of MR cells. An equation in the form of y = 1574–10.23x (where x = days; R2= 0.626) was obtained with bath NaCl that was elevated from 30 to 200 mmol/l, in 45 days. Oxytocin (60 mU/ml) increased sodium transport, independently and without effect on Cl−conductance. Theophylline (1 mmol/l), which leads also to elevation of cellular cAMP in contrast, increased Na+transport, but elevated Cl−conductance 3–4 times as well. Cl−conductance that is activated by transepithelial potential was much lower in skin from hyperosmotic NaCl‐acclimated toads, as compared with that in skin from tap water‐acclimated animals. Our experiments confirm that MR cells are a major pathway for Cl−conductance, as suggested earlier. However, the density of these cells in the skin epithelium ofB viridisdepends not only on bath NaCl concentration, but also on the mode of acclimation of the animals. Since transport functions other than gClreside in the amphibian skin MR cells, the density of MR cells must also depend on these functions. These functions, and the mechanisms responsible for the down and up regulation of MR cells' density, rem

ISSN:0248-4900    

DOI:10.1016/0248-4900(96)85279-8

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY