Mucin secretion by the human colon cell line LS174T is regulated by bile salts

We recently reported that bile salts play a role in the regulation of mucin secretion by cultured dog gallbladder epithelial cells. In this study we have examined whether bile salts also influence mucin secretion by the human epithelial colon cell line LS174T. Solutions of bile salts were applied to monolayers of LS174T cells. Mucin secretion was quantified by measuring the secretion of [3H]GlcNAc labeled glycoproteins. Both unconjugated bile salts as well as taurine conjugated bile salts stimulated mucin secretion by the colon cells in a dose-dependent fashion. Hydrophobic bile salts were more potent stimulators than hydrophilic bile salts. Free (unconjugated) bile salts were more stimulatory compared with their taurine conjugated counterparts. Stimulation of mucin secretion by LS174T cells was found to occur at much lower bile salt concentrations than in the experiments with the dog gallbladder epithelial cells. The protein kinase C activators PMA and PDB had no stimulatory effect on mucin secretion. We conclude that mucin secretion by the human colon epithelial cell line LS174T is regulated by bile salts. We suggest that regulation of mucin secretion by bile salts might be a common mechanism, by which different epithelia protect themselves against the detergent action of bile salts, to which they are exposed throughout the gastrointestinal tract.      

MTT assay based inhibition analysis of A2780 cells proliferation using Mollugo nudicaulis Lam. extract with CXCR4 and HER2 expression

It is of interest to document the inhibition of A2780 cell proliferation using Mollugo nudicaulis Lam.(M.nudicaulis) extract by MTT assay and by monitoring the CXCR4 and HER2 expression through RT-PCR analysis. Results shown that the n-hexane extract of M.nudicaulis have anticancer activity IC₅₀ values of 32.46±0.92 µg/mL on A2780 cell lines. It is further found that the CXCR4 and HER2 mRNA and protein expression were significantly reduced in M.nudicaulis treated A2780 cell lines. Thus, the n-hexane extract of M.nudicaulis is a natural source of bioactive compounds as potential anticancer agents.     

Ecological studies on the phytoplankton of Korsfjorden, western Norway. The dynamics of a spring bloom seen in relation to hydrographical conditions and light regime

The investigation was carried out at one station in Korsfjorden,a typical deep silled fjord of western Norway. During 14 cruisesfrom 4 February to 30 June 1977 ATP, chlorophll a, phaeopigmenta, and in situ ¹⁴C-assimilation were measured in the net (>30µm), nano and ultraplankton (<5 µm). Sampleswere collected from five light depths within euphotic zone.The impact of hydrographical conditions and light regime onthe bloom dynamics was also studied. In the periods 4 February-7 March and 13 April-30 June, ultraplankton contributed >60%to the total primary production while net and nanoplankton dominatedfrom 7 March to 13 April. The diatoms Skeletonema costatum,Chaetoceros compressits and C. debilis, and Rhizosolenia hebetatavar. semispina made up the main part of the biomass on 21 March,28 March and 4 April respectively. A shade adapted diatom societywas located at the top of the nutricline in late June with S.costatum, Chaetoceros spp., and Thalassiosira spp. as the dominantspecies. The highest assimilation number of eight for the netplankton and four for the ultraplankton were found at the depthof 32% light intensity on 28 March and 24 May respectively.Linear relationships were found between chlorophyll a and ATPfor the different size fractions with regression slopes rangingfrom 4.3 to 5.8. The total primary production for the periodof investigation was calculated to 74 g C m^–2. Light regimeand water column stability were decisive factors for the outburstof the first diatom bloom in late March. Grazing on net planktondiatoms increased during late March-early April. Changes inthe longshore wind-stress component were found to be essentialfor the understanding of the bloom dynamics.     

Cell density-dependent proliferation of the murine bone marrow-derived stromal cell lines

Proliferation of three murine marrow-derived stromal cell lines, LC1, LC2, and LC3, depended on initial cell density. For LC2 and LC3, the cell density-dependence was negated by conditioned-media, indicating growth dependence on a soluble growth factor. For LC1, conditioned-media failed to stimulate proliferation, suggesting growth dependence on direct cell-cell contact.     

Choline acetyltransferase activity of spinal cord cell cultures increased by co-culture with muscle and by muscle-conditioned medium

Activity of the enzyme choline acetyltransferase (CAT), which mediates the synthesis of the neurotransmitter, acetylcholine, was increased up to 20- fold in spinal cord (SC) cells grown in culture with muscle cells for 2 wk. This increase was directly related to the duration of co-culture as well as to the cell density of both the SC and muscle involved and was not affected by the presence of the acetylcholine receptor blocking agent, α-bungarotoxin. Glutamic acid decarboxylase (GAD) activity was often markedly decreased in SC-muscle cultures while the activities of acetylcholinesterase and several other enzymes were little changed. Increased CAT activity was also observed when SC cultures were maintained in medium which had been conditioned by muscle cells or by undifferentiated cells from embryonic muscle. Muscle-conditioned medium (CM) did not affect the activities of SC cell GAD or acetylcholinesterase. Dilution or concentration of the CM directly affected its ability to increase SC CAT activity , as did the duration and timing of exposure of the SC cells to the CM. The medium could be conditioned by muscle cells in the presence or absence of serum, and remained effective after dialysis or heating to 58 degrees C. Membrane filtration data were consistent with the conclusion that the active material(s) in CM had a molecular weight in excess of 50,000 daltons. We conclude that large molecular weight material that is released by muscle cells is capable of producing a specific increase in CAT activity of SC cells.     

Stable expression of mammalian beta 1,4-galactosyltransferase extends the N-glycosylation pathway in insect cells

An established lepidopteran insect cell line (Sf9) was cotransfected with expression plasmids encoding neomycin phosphotransferase and bovine beta 1,4-galactosyltransferase. Neomycin-resistant transformants were selected, assayed for beta 1,4-galactosyltransferase activity, and the transformant with the highest level of enzymatic activity was characterized. Southern blots indicated that this transformed Sf9 cell derivative contained multiple copies of the galactosyltransferase- encoding expression plasmid integrated at a single site in its genome. One-step growth curves showed that these cells supported normal levels of baculovirus replication. Baculovirus infection of the transformed cells stimulated beta 1,4-galactosyltransferase activity almost 5-fold by 12 h postinfection. This was followed by a gradual decline in activity, but the infected cells still had about as much activity as uninfected controls as late as 48 h after infection and they were able to produce a beta 1,4-galactosylated virion glycoprotein during infection. Infection of the transformed cells with a conventional recombinant baculovirus expression vector encoding human tissue plasminogen activator also resulted in the production of a galactosylated end-product. These results demonstrate that stable transformation can be used to add a functional mammalian glycosyltransferase to lepidopteran insect cells and extend their N- glycosylation pathway. Furthermore, stably-transformed insect cells can be used as modified hosts for conventional baculovirus expression vectors to produce foreign glycoproteins with "mammalianized" glycans which more closely resemble those produced by higher eucaryotes.