Kinetic studies and unstructured models of lymphocyte metabolism in fed-batch culture

The growth of two lymphocyte cell lines, a hybridoma cell line and a human cutaneous T cell lymphoma (HuT78), was studied in fed-batch culture, and unstructured models of growth developed. A criteria was established to insure that the growth rate varied by less than a specified tolerance throughout the culture period. Glutamine and serum were growth-limiting nutrients for both cell lines with half-maximal growth rates at 0. 53 mM glutamine and 0. 55%(v/v) serum for the hybridoma cells and 0. 21 mM glutamine and 1. 5% serum for the HuT-78 cells. Over the range of glucose concentrations from 5. 5 mM to 28 mM, the specific growth rate of hybridoma cells was independent of glucose concentration, whereas glucose concentrations above 5. 5 mM inhibited HuT-78 growth. For both cell lines, the growth rate was significantly inhibited by the addition of ammonium, although the hybridoma cell line was more affected by ammonia than was the HuT-78 cell line. Growth of HuT-78 cells increased in the presence of interleukin-2. Unstructured models for the hybridoma cells were similar to other models presented in the literature. Applications of these models to adoptive immunotherapy are discussed.     

Allyl mercaptan, a major metabolite of garlic compounds, reduces cellular cholesterol synthesis and its secretion in Hep-G2 cells

The cytotoxicity, cellular cholesterol synthesis, and secretion of allyl mercaptan, a major metabolite of garlic compounds, were studied in Hep-G2 cells. The cells were grown in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum and treated with 5, 25, 50, 100, 125, 250, and 500 microg of allyl mercaptan/mL for 4, 12, and 24 hours. At concentrations up to 125 microg, no significant cytotoxic effect was noted during those incubation periods. However, at a concentration of 250 microg, cell viability decreased approximately 50% compared with the control (P < 0.05) in all three incubation times. At a concentration of 500 microg, allyl mercaptan was highly toxic, causing extensive cell death. The treatment of cells with 5, 10, 25, 50, or 100 microg (noncytotoxic concentration) of allyl mercaptan resulted in a marked inhibition of (3)H-acetate incorporation into cholesterol. At concentrations between 5 and 100 microg, the cholesterol synthesis was inhibited 20 to 80% in cells and the cholesterol secretion into the medium decreased 20 to 50% compared with the control (P < 0.05). The concentration of allyl mercaptan required to suppress cholesterol synthesis by 50% was approximately 25 microg/mL. Allyl mercaptan treatment of cells incubated with 1 mM of oleic acid also resulted in a significant decrease in the cholesterol synthesis compared with the cells incubated with oleic acid alone (19.5 +/- 1.2 x 10(3) dpm/mg protein/4 h vs. 30.0 +/- 2.6 x 10(3) dpm/mg protein/4 h; P < 0.05). The present study demonstrates that allyl mercaptan is effective in inhibiting cholesterol synthesis at concentrations as low as 5 microg, and its inhibition is concentration dependent.     

Proliferative and morphological changes induced by vanadium compounds on Swiss 3T3 fibroblasts

Vanadium compounds are shown to have a mitogenic effect on fibroblast cells. The effects of vanadate, vanadyl and pervanadate on the proliferation and morphological changes of Swiss 3T3 cells in culture are compared. Vanadium derivatives induced cell proliferation in a biphasic manner, with a toxic-like effect at doses over 50mM, after 24h of incubation. Vanadyl and vanadate were equally potent at 2.5–10mM. At 50mM vanadate inhibited cell proliferation, whereas slight inhibition was observed at 100mM of vanadyl. At 10mM pervanadate was as potent as vanadate and vanadyl in stimulating fibroblast proliferation, but no effect was observed at lower concentrations. A pronounced cytotoxic-like effect was induced by pervanadate at 50mM. All of these effects were accompanied by morphological changes: transformation of fibroblast shape from polygonal to fusiform; retraction with cytoplasm condensation; and loss of lamellar processes. The magnitude of these transformations correlates with the potency of vanadium derivatives to induce a cytotoxic-like effect: pervanadate>vanadate>vanadyl. These data suggest that the oxidation state and coordination geometry of vanadium determine the degree of the cytotoxicity.     

氯化锂对KT-1/A3细胞增殖和凋亡的影响

目的：研究氯化锂(LiCl)在体外对KT—1／A3白血病细胞增殖及凋亡的影响。方法：采用液体培养实验,MTT实验,集落培养实验为指标观察LiCl对KT—1／A3细胞增殖的影响,采用DNA片段凝胶电泳及流式细胞检测为指标检测细胞凋亡。结果：①不同浓度的LiCl(5mM—25mM)对KT—1／A3细胞具有抑制增殖的作用,这种增殖抑制作用呈剂量依赖关系。②在LiCl(20mM)作用72h的DNA凝胶电泳谱可见DNA Ladder及流式细胞仪检测可见凋亡特有的AP峰,提示LiCl可诱导KT—1／A3细胞凋亡。绪论：LiCl能抑制KT—1／A3白血病细胞增殖和诱导凋亡。     

Cytotoxicity and genotoxicity evaluation of antidote oxime HI-6 tested on eight cell lines of human and rodent origin

Oxime HI-6 is an efficient reactivator of the acetylcholinesterase inhibited by organophosphorous nerve agents. In this study we have estimated cytotoxicity of HI-6 by the colony forming assay and genotoxicity by the comet assay on human and rodent cell lines. IC50 of HI-6 assessed by the colony forming capacity was 3.59 mM for HeLa cells and 5.18 mM for a mouse cell line L929. Small difference in cytotoxicity was found among other cell lines tested: IC50 was 1.61 mM for human A549 cells, 1.14 mM for UROtse line, 1.96 mM and 1.71 mM for Chinese hamster cells AA8 and UV-20, respectively. The A549 cell viability measured with the MTT test was 5 times decreased comparing 2 and 24 hours of HI-6 oxime treatment. The 5 mM HI-6 concentration reduced the viability within 2 hours to 95% only, however, it induced a significant number of DNA breaks in mouse cells L929, and also in human UROtse and HepG2 cells. 1-β-D-arabinofuranosylcytosine (10(-4) M) and hydroxyurea (10(-2) M), supplemented to the cultivation medium, did not cause any significant accumulation of DNA breaks during treatment, which indicated that the nucleotide excision repair was not acting on the induced DNA damage.     

Effect of halothane on lung carcinoma cells A 549

The halogenated hydrocarbons, such as halothane, are widely used as anesthetics in clinical practice; however their application is often accompanied with metabolic, cardiovascular and respiratory complications. One of the possible factors for this negative outcome might be the severe toxicity of these agents. In this paper, we investigate in vitro effects of halothane on human lung carcinoma A 549 cells, namely on their cytotoxicity, adhesive properties and metabolic activity. The cytotoxicity response of lung carcinoma A 549 cells to halothane was determined by lactate dehydrogenase (LDH) assay (for cytotoxicity), by detachment assay after adhesion to type IV collagen (for cell adhesive properties) and by surface tension measurements of culture medium (for cell metabolic activity). Regarding the cytotoxicity, the determined maximal non-toxic concentration of halothane on A 549 cells, given here as volume percentages (vol.%) was 0.7 vol.% expressed as aqueous concentration in the culture medium. Direct measurement of the actual halothane concentration in the culture medium showed that 0.7 vol.% corresponds to 1.05 mM and 5.25 aqueous-phase minimum alveolar concentration (MAC). Concentrations equal or higher than 1.4 vol.% (2.1 mM; 10.5 MAC) of halothane provoked complete detachment (cell death), or reduction of initial adhesion to collagen IV in half of the cell population. Surfactant production of A 549 cells, registered up to 48 h after halothane treatment, was inhibited by halothane concentrations as low as 0.6 vol.% (0.9 mM; 4.5 MAC). Our results demonstrate that sub toxic halothane concentrations of 0.6 vol.% inhibits surfactant production; concentrations in the range 0.8-1.4 vol.% induce membrane damages and concentrations equal and higher than 1.4 vol.%--cell death of approximately 50% of the cells.     

Carcinoma autoantigens T and Tn and their cleavage products interact with Gal/GalNAc-specific receptors on rat Kupffer cells and hepatocytes

We studied interactions of isolated Thomsen-Friedenreich (T)- and Tn-specific glycoproteins with the Gal/GalNAc-specific receptors on rat Kupffer cells and compared them to those with rat hepatocytes. Immunoreactive T and Tn are specific pancarcinoma epitopes. Electron microscopy of gold-labelled T and Tn antigens revealed their specific binding to Kupffer cells, followed by their uptake via the coated pit/vesicle pathway of receptor-mediated endocytosis. Preincubation of Kupffer cells with GalNAc and GalNAc-BSA, but not GlcNAc or GlcNAc-BSA specifically inhibited binding of the T and Tn glycoproteins. Desialylated, isologous erythrocytes (T RBC) are known to bind to the Gal/GalNAc receptors of rat Kupffer cells and hepatocytes. This attachment was specifically inhibited by T and Tn in a concentration-dependent manner: 50% T RBC-Kupffer cell contacts were inhibited at 8.5.10(-6) mM T and 8.5.10(-5) mM Tn antigen concentrations, respectively. The corresponding figures for hepatocytes were 6.10(-6) mM T and 1.2.10(-6) mM Tn antigen. Amino-terminal cleavage products of the T glycoprotein, possessing clusters terminating in non-reducing Gal/GalNAc, inhibited T RBC binding to Kupffer cells and hepatocytes usually at 10(-2) to 10(-5) mM concentrations, whereas GalNAc, galactose and galactose glycosides inhibited at millimolar concentrations. Galactose-unrelated carbohydrates were inactive at concentrations greater than or equal to 50 mM.     

Opposed effects of lithium on the MEK-ERK pathway in neural cells: inhibition in astrocytes and stimulation in neurons by GSK3 independent mechanisms

Lithium is widely used in the treatment of bipolar disorder, but despite its proven therapeutic efficacy, the molecular mechanisms of action are not fully understood. The present study was undertaken to explore lithium effects of the MEK/ERK cascade of protein kinases in astrocytes and neurons. In asynchronously proliferating rat cortical astrocytes, lithium decreased time- and dose-dependently the phosphorylation of MEK and ERK, with 1 mM concentrations achieving 60 and 50% inhibition of ERK and MEK, respectively, after a 7-day exposure. Lithium also inhibited [3H]thymidine incorporation into DNA and induced a G2/M cell cycle arrest. In serum-deprived, quiescent astrocytes, pre-exposure to lithium resulted in the inhibition of cell cycle re-entry as stimulated by the mitogen endothelin-1: under this experimental setting, lithium did not affect the rapid, peak phosphorylation of MEK taking place after 3-5 min, but was effective in inhibiting the long-term, sustained phosphorylation of MEK. Lithium inhibition of the astrocyte MEK/ERK pathway was independent of inositol depletion. Further, compound SB216763 inhibited Tau phosphorylation at Ser396 and stabilized cytosolic beta-catenin, consistent with the inhibition of glycogen synthase kinase-3 beta (GSK-3 beta), but failed to reproduce lithium effects on MEK and ERK phosphorylation and cell cycle arrest. In cerebellar granule neurons, millimolar concentrations of lithium enhanced MEK and ERK phosphorylation in a concentration-dependent manner, again through an inositol and GSK-3 beta independent mechanism. These opposing effects in astrocytes and neurons make lithium treatment a promising strategy to favour neural repair and reduce reactive gliosis after traumatic injury.     

Long-term Exposure to Low Lithium Concentrations Stimulates Proliferation,Modifies Stress Protein Expression Pattern and Enhances Resistance to Oxidative Stress in SH-SY5Y Cells

SH-SY5Y cells, derived from a human neuroblastoma, were submitted to short- or long-term exposures to lithium carbonate concentrations ranging from 0.5 to 8 mM. Short-term exposures (4 days) to concentrations higher than 6 mM were found to reduce cell growth rate while exposure to 8 mM resulted in significant cell mortality. These ranges of concentrations induced an overexpression of (1) the HSP27 stress protein, (2) a 108 kDa protein (P108) recognized by an anti-phospho-HSP27(Ser78) antibody, and probably corresponding to a phosphorylated HSP27 tetramer, (3) a 105 kDa protein (P105), possible glycosylated or phosphorylated form of the GRP94 stress protein and (4) a phosphorylated (inactivated) form of glycogen synthase kinase (GSK3α/β) SH-SY5Y cells, when cultured in the presence of 0.5 mM lithium for 25 weeks, displayed interesting features as compared to controls: (1) higher cell growth rate, (2) increased resistance toward the inhibitory effects of high lithium concentrations on cell proliferation, (3) lower basal level of lipid peroxidation (TBARS) and improved tolerance to oxidative stress induced by high lithium concentrations, (5) reduced expression of monomeric HSP27 versus an increase of corresponding tetrameric protein (P108) and (6) overexpression of a 105 kDa protein (P105). In conclusion, our study suggests that chronic treatment (over several months) by therapeutic relevant lithium concentrations could favour neurogenesis, decrease the vulnerability of neuronal cells to oxidative stress and induce posttranslational changes of molecular chaperones.     

Regulation of cell growth by selective COX-2 inhibitors in oral carcinoma cell lines

Evidence indicates that NSAIDs that inhibit prostaglandin (PG) synthesis can reduce the incidence of colorectal cancers and that inhibition of cyclooxygenase-2 (COX-2) may be the underlying mechanism. The objective of this study was to investigate this putative mechanism by examining the effect of selective COX-2 inhibitors (Celebrex, DFU, NS-398) and COX-1 inhibitors (Aspirin) on the growth of two human oral carcinoma cell lines (OEC-M1 and KB) and one normal fibroblast cell line (NF). We found that the growth of OEC-M1 cells could be significantly inhibited by DFU concentrations above 30 microM (31%) after 4 days, and above 50 microM (35%) after 2 days in culture; by Celebrex at concentrations above 20 microM (52%) after 6 days, above 30 microM (36%) after 5 days, and above 40 microM (33%) after 4 days in culture; and by NS-398 above 1 microM (30%) after 6 days, and above 10 microM (35%) after 5 days in culture. The growth of KB cells could be significantly inhibited by DFU concentrations above 10 microM (33%) after 6 days, above 20 microM (35%) after 4 days in culture; and by Celebrex at concentrations above 10 microM (33%) after 5 days, and above 50 microM (30%) after 4 days in culture; and by NS-398 above 1 microM (45%) after 5 days, above 20 microM (36%) after 4 days in culture. The growth of NF cells could be significantly inhibited by DFU above 30 microM (45%) after 6 days, and above 40 microM (32%) after 3 days in culture, and by Celebrex at concentrations above 10 microM (42%) after 6 days, above 30 microM (31%) after 4 days, above 50 microM (32%) after 3 days in culture, and by NS-398 above 0.1 microM (35%) after 4 days, and above 1 microM (32%) after 3 days in culture. The growth-inhibitory concentration (IC50) values for DFU on OEC-M1, KB, and NF cells were about 39.1, 14.8, and 42.9 microM at 144 h, respectively, and on KB was about 45.2 microM at 120 h. The IC50 values for Celebrex on OEC-M1, KB, and NF cells were about 19.1, 8.6, and 15.8 microM at 144 h, respectively, and on KB and NF were about 27.7 and 35.3 microM, respectively, at 120 h. The IC50 values for NS-398 on OEC-M1, KB, and NF were about 18.9, 0.7 and 1 microM, respectively, at 144 h; on KB and NF values were about 10.8 and 1.4 microM, respectively, at 120 h and on KB and NF were about 26.6 and 4.1 microM, respectively, at 96 h. The results show that the growth of these cell lines is inhibited by three COX-2 selective inhibitors but not by any COX-1 selective inhibitors. These findings suggest that COX-2 may play an important role in the generation of biochemical mediators that stimulate the growth of human oral cancer and normal fibroblast cell lines.     

A novel target of lithium therapy

Phosphatases converting 3'-phosphoadenosine 5'-phosphate (PAP) into adenosine 5'-phosphate are of fundamental importance in living cells as the accumulation of PAP is toxic to several cellular systems. These enzymes are lithium-sensitive and we have characterized a human PAP phosphatase as a potential target of lithium therapy. A cDNA encoding a human enzyme was identified by data base screening, expressed in Escherichia coli and the 33 kDa protein purified to homogeneity. The enzyme exhibits high affinity for PAP (K(m)<1 microM) and is sensitive to subtherapeutic concentrations of lithium (IC(50)=0.3 mM). The human enzyme also hydrolyzes inositol-1, 4-bisphosphate with high affinity (K(m)=0.4 microM), therefore it can be considered as a dual specificity enzyme with high affinity (microM range) for both PAP and inositol-1,4-bisphosphate. Hydrolysis of inositol-1,4-bisphosphate was also inhibited by lithium (IC(50)=0.6 mM). Thus, we present experimental evidence for a novel target of lithium therapy, which could explain some of the side effects of this therapy.     

Cyanopyrazoles as analogs of purine precursors--II. Effects on macromolecular synthesis and cell cycle progression

The cytotoxic and cytokinetic effects, and in vitro inhibition of macromolecular synthesis by cyanopyrazoles were studied using Friend leukemia and Ehrlich ascites tumor cells. At concentrations in the range of 2.5 mM to 50 microM analog 3(5)-amino-4-cyano-5(3)-trichloromethylpyrazole (I) was highly cytotoxic and completely inhibited thymidine, uridine and leucine incorporation into macromolecular material. 24 hr incubation of FL cells with cytostatic concentrations of compound I (in the range of 2 to 0.5 microM) resulted in an accumulation of cells in the G2 + M phase. Analogs N-hydroxyethyl-3(5)-amino-4-cyano-5(3)-trichloromethylpyrazole (II) and 3(5)-amino-4-cyanopyrazole (III) were not cytotoxic at concentrations up to 5 mM and did not substantially inhibit precursor incorporation into macromolecules but exhibited a cytostatic activity. These compounds caused a decrease of FL cells in the G2 + M phase and an accumulation in the S phase. Analogs I and II displayed a similar in vivo inhibitory effect on thymidine incorporation into DNA in EAT cells. The results indicate that the cytotoxicity of cyanopyrazoles correlates with their ability to inhibit precursor incorporation into macromolecular material. On the other hand, the cytostatic action of compound I is not coupled to a block of nucleic acid synthesis.     

The inhibition of hexose transport by permeant and impermeant sulfhydryl agents in rat adipocytes

The importance of exofacial sulfhydryl groups for hexose transport and its regulation was studied by comparing the effects of plasma membrane-permeant maleimide (N-ethylmaleimide) to an impermeant maleimide (glutathione-maleimide I) on 3-O-methylglucose transport into isolated rat adipocytes. The impermeant nature of glutathione-maleimide was confirmed by the finding that after a 15-min incubation, concentrations as high as 10 mM had no effect on intracellular glutathione content, while 1.7 mM N-ethylmaleimide decreased intracellular glutathione by 61%. Although N-ethylmaleimide appeared to be a more potent inhibitor of transport below 5 mM and at incubation times of less than 5 min, neither agent at concentrations which did not cause significant cell breakage inhibited basal transport rates more than 60-70%. The inhibition of transport by both agents was unaffected by extensive washing, suggesting a possible covalent interaction with the carrier. Preincubation with p-chloromercuribenzenesulfonic acid protected against the transport inhibition induced by both agents. However, only the transport inhibition induced by glutathione-maleimide was prevented by preincubation with D-glucose (50 mM) and maltose (50 mM). Transport in cells pretreated with insulin was inhibited by both agents to a similar extent as basal transport. However, treatment of cells with the maleimides before insulin caused a greater degree of inhibition. Thus, the insulin-induced increase in transport was inhibited half-maximally by 1 mM glutathione-maleimide. These results show that exofacial sulfhydryl groups, perhaps on the hexose-binding site of the carrier, are important for both the function and regulation of hexose transport.     

Effect of tri-o-cresyl phosphate on cytoskeleton in human neuroblastoma SK-N-SH cell

Cytoskeletal components play an important role in maintaining cellular architecture and internal organization, with clear involvement of defining cell shape, in cell division and other cellular processes, such as neurite extension and maintenance. Alterations of cytoskeleton in human neuroblastoma SK-N-SH cells after exposure to different concentrations of tri-ocresyl phosphate (TOCP) for 12 hr were investigated. TOCP decreased the cell viability in a dose-dependent manner; the viability of SK-N-SH was reduced to approximately 50% of baseline after a 12-hour exposure to TOCP at high concentration (5 mM). Biochemical characterization by western blotting revealed that 1 and 5 mM concentrations of TOCP significantly inhibited the expression of neurofilament high molecular weight protein (NF-H), and that 5 mM TOCP inhibited expression of microtubule-associated protein 2c and tau protein, but not β-actin. Indirect immunofluorescence analysis revealed that higher concentrations of TOCP decreased the length of neuritis and changed the structure of microfilaments, which are associated with NF-H. In addition, activities of neuropathy target esterase and acetylcholinesterase were significantly reduced after exposure to 5 mM TOCP for 12 hr. Together, these results suggested that the loss of cytoskeletal components is the early event during the process of TOCP toxicity towards human neuroblastoma SK-N-SH cells.     

Crosslinked fibrous collagen for use as a dermal implant: control of the cytotoxic effects of glutaraldehyde and dimethylsuberimidate

Collagen intended for use as a dermal implant may be crosslinked to increase its strength and persistence in vivo. Sheets of rat fibrous dermal collagen were crosslinked with either glutaraldehyde or dimethylsuberimidate and the cytotoxicity to human dermal fibroblasts resulting from these treatments was measured by following the inhibition of [3H]leucine incorporation into protein. Both agents were cytotoxic at the concentrations required to effect adequate crosslinking (0.005% and 25 mM, respectively). This cytotoxicity could be limited by extensive washing and by incubation with 5 mM L-lysine, with 66 mM (0.25% w/v) sodium borohydride, or with 71.3 mM (1% w/v) dimedone. However, cytotoxicity was most efficiently controlled by treatment with a combination of 66 mM sodium borohydride and 5 mM L-lysine or 66 mM sodium borohydride and 71.3 mM dimedone. [3H]Leucine incorporation by cells exposed to crosslinked collagen treated with these combinations approached 100% of the values recorded with cells exposed to uncrosslinked collagen.     

The FRAME alternatives laboratory database. 1. In vitro basal cytotoxicity determined by the Kenacid blue total protein assay

A database of over 280 chemicals has been compiled by using a mouse 3T3-L1 fibroblast-like cell line in exponential growth, exposed to chemicals for 72 hours in a 96-well tissue culture plate format, and determining cell number via the Kenacid blue (KB) assay for total protein. Ranking the chemicals according to their basal cytotoxicity, expressed as the concentration (mM) that inhibits increase in total cellular protein over 72 hours by 50% (the ID50 value) shows a wide range of ID50 values, from 0.00003 mM to 10,096 mM. This information includes the results for MEIC chemicals 1-50, and we have now added basal cytotoxicity data for 23 of the next 25 MEIC chemicals. When the neutral red uptake (NRU) assay was performed with the same cell cultures, before the KB assay, very similar indications of basal cytotoxicity were obtained. Comparisons between the results with 3T3-L1 cells and with a human fibroblast-like cell line, BCL-D1 showed a significant difference in order of magnitude of the ID50 value for only 5 of 52 chemicals. However, there was a difference in ID50 value of more than one order of magnitude for 8 of 24 chemicals tested with an undifferentiated teratocarcinoma cell line, F9.     

Galactosyltransferase activity and cell growth: uridine diphosphate (UDP)galactose inhibition of murine leukemic L1210 cells

UDPgalactose inhibits the growth of mouse leukemic L1210 cells. In calf serum supplemented Dulbecco's medium (CS-DMEM), 1.2 mM UDPgalactose (UDPgal) inhibited cell growth by 50% (IC50), and 5 mM UDPgalactose inhibited cell growth by 92%. Other nucleotide sugars as well as galactose, glucose, and galactose-1-phosphate had little or no effect on cell growth. Uridine nucleotides, which inhibit galactosyltransferase activity, protected L1210 cells from the growth inhibitory effect of UDPgalactose when both were added simultaneously to culture media. Unlike mouse 3T12 cells, in which no inhibition of cell growth was observed with heat-inactivated calf serum (HICS)-DMEM, 5 mM UDPgalactose inhibited L1210 cell growth in HICS-DMEM to the same degree as that observed in CS-DMEM. In contrast to 3T12 cells, L1210 cells secrete significant galactosyltransferase activity into the media. Complete inhibition of 3T12 cell growth by UDPgal was observed if HICS-DMEM medium was first conditioned by L1210 cells for 48 hours. No difference in cell growth or [3H]thymidine uptake was detected after 6 hours of exposure to UDPgalactose, but both were significantly decreased at 24 and 48 hours. Flow cytometric analysis of UDPgalactose effects on L1210 cells revealed no differences in the distribution of cells in G1, S, or G2-M of the cell cycle after 6 hours of incubation, but after 16 hours of UDPgalactose treatment, L1210 cells were arrested in early S phase. These cells were completely viable and morphologically similar to control L1210 cells. Normal growth was resumed when UDPgal was removed. The data suggest that UDPgalactose inhibition of cell growth requires extracellular galactosyltransferase activity and that the effect is mediated via the cell membrane.     

Involvement of phosphoinositides,calmodulin and glyoxalase-I in cell proliferation in callus cultures of Amaranthus paniculatus

The effect of lithium and trifluoperazine (TFP) was studied on cell proliferation in callus cultures of Amaranthus paniculatus. TFP (20 μM) and lithium (40 mM) inhibited the callus growth by 50% and 80%, respectively. The inhibition by lithium was reversed by the addition of myoinositol (2.5 mM). Equimolar concentration of NaCl, as that of LiCl, had no significant effect on callus growth. The activity of calmodulin was inhibited by TFP as tested both by in vivo and in vitro experiments. The level of phosphatidylinositol (PI) in calli grown on lithium was lower than the calli grown on the medium containing inositol alone. The activity of the enzyme glyoxalase-I was inhibited by lithium and TFP. The inhibition of the enzyme activity by lithium was reversed by the addition of inositol. Possible involvement of phosphoinositide cycle, calcium and calmodulin in cell proliferation in in vitro cultures is suggested.     

Inhibition of 2-oxoglutarate metabolism by lithium in the isolated rat kidney cortex tubules

2-Oxoglutarate metabolism in the isolated rat kidney cortex tubules was inhibited by lithium at 5 mM concentration, and at pH increased from 7.1 to 7.6. The metabolism of pyruvate and acetylcarnitine to citrate and 2-oxoglutarate was enhanced by lithium and the increased pH value. The content of 2-oxoglutarate in the renal tubular cells was lowered by lithium but increased at elevated pH values. Both the intracellular pH value and bicarbonate ion concentrations in renal tubular cells were increased by lithium in the medium containing 2-oxoglutarate. The results obtained indicate that lithium disturbs renal metabolism by intracellular alkalization, with a simultaneous inhibition of the inflow of dicarboxylic substrates to the renal tubular cells.