Quantitative analysis of dose- and time-dependent promotion of four phenotypes of altered hepatic foci by 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Sprague-Dawley rats

Determining both the mechanism by which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) acts as a tumor promoter and the shape of the dose-response curve at low doses remains an important goal of risk-assessment-directed research. In this report, we extend previous mechanistic and descriptive work done on the effect of TCDD on promotion in the two-stage model of hepatocarcinogenesis, to include lower, more clinically relevant doses. After initiation [PH + 10 mg diethylnitrosamine (DEN)/kg], groups of female Sprague-Dawley rats were administered TCDD in one of four doses: 0.01, 0.1, 1.0, or 10 ng/kg/day for 1, 3, or 6 months. Early increases in liver weight (19-69%) due to hepatocyte hypertrophy were resolved after 3- or 6-months exposures to TCDD, and were not associated with the effects of TCDD on promotion. Non-focal cell proliferation in DEN-treated groups was significantly reduced after 1 or 3 months of exposure to 0.1 ng/kg/day TCDD, leading to U-shaped dose-response curves. TCDD effects on non-focal cell proliferation were not associated with effects on promotion. GSTP-positive AHF represented approximately 97% of the total AHF. Significant increases in both the volume fraction and the number of altered hepatic foci (AHF) were observed at the highest dose (10 ng/kg/day) for GSTP-positive AHF in DEN-treated groups. Increases in the number of G6Pase- and ATPase-deficient AHF/cm3 were observed at TCDD doses as low as 0.01 ng/kg/day. This is the lowest tumor-promoting dose of TCDD reported to date. This study represents an unusually complete data set for further dose-response analysis and simulation or mathematical modeling of TCDD-mediated promotion in the rat liver.

Inhibitory effect of recombinant TGF alpha-PE40 on vascular smooth muscle cell proliferation

AIM

To study inhibitory effect of recombinant transforming growth factor alpha-Pseudomonas exotoxin fusion protein (TP40) on proliferation of the cultured vascular smooth muscle cells (SMC).

METHODS

Expression of epidermal growth factor receptor (EGFR) mRNA and EGFR in cultured proliferating and quiescent SMC was analyzed with Northern blot and immunohistochemistry. Inhibitory effects of TP40 on SMC proliferation and protein synthesis were analyzed with crystal violet staining and [3H]leucine incorporation. Competition assays were performed by the addition of 100-fold excess of EGF.

RESULTS

Expression of EGFR mRNA and EGFR in rapidly proliferating SMC increased than that in quiescent SMC. When the concentration of TP40 was 10 or 100 micrograms.L-1, inhibitory effects of TP40 on rapidly proliferating SMC proliferation and protein synthesis were much higher than that on quiescent SMC (P < 0.01), and the IC50 of [3H]leucine incorporation against rapidly proliferating and quiescent SMC were 8.01 (5.05-12.69) and 121.95 (90.98-163.47) micrograms.L-1. Excess EGF completely blocked inhibitory effects of TP40.

CONCLUSION

The rapidly proliferating SMC express EGFR at a high level. TP40 selectively inhibited the proliferation of rapidly proliferating SMC. The cytotoxic effects of TP40 were specifically mediated by EGFR.

Structural features contributing to complex formation between glycogen phosphorylase and phosphorylase kinase

A polyclonal antibody was generated against a peptide corresponding to a region opposite the regulatory face of glycogen phosphorylase b (P-b), providing a probe for detecting and quantifying P-b when it is bound to its activating kinase, phosphorylase kinase (PhK). Using both direct and competition enzyme-linked immunosorbent assays (ELISAs), we have measured the extent of direct binding to PhK of various forms of phosphorylase, including different conformers induced by allosteric effectors as well as forms differing at the N-terminal site phosphorylated by PhK. Strong interactions with PhK were observed for both P-b', a truncated form lacking the site for phosphorylation, and P-a, the phosphorylated form of P-b. Further, the binding of P-b, P-b', and P-a was stimulated a similar amount by Mg(2+), or by Ca(2+) (both being activators of PhK). Our results suggest that the presence and conformation of P-b's N-terminal phosphorylation site do not fully account for the protein's affinity for PhK and that regions distinct from that site may also interact with PhK. Direct ELISAs detected the binding of P-b by a truncated form of the catalytic gamma subunit of PhK, consistent with the necessary interaction of PhK's catalytic subunit with its substrate P-b. In contrast, P-b' bound very poorly to the truncated gamma subunit, suggesting that the N-terminal phosphorylatable region of P-b may be critical in directing P-b to PhK's catalytic subunit and that the binding of P-b' by the PhK holoenzyme may involve more than just its catalytic core. The sum of our results suggests that structural features outside the catalytic domain of PhK and outside the phosphorylatable region of P-b may both be necessary for the maximal interaction of these two proteins.

Building quantitative stereology data files with scion image, a public domain image processing and analysis software

Two-dimensional data obtained from a histological cross-section of a tissue can be utilized to obtain three-dimensional information by the methods of quantitative stereology. The resulting quantitative information is useful in both experimental studies and whole-animal investigations for regulatory and safety purposes. Quantitative stereologic analysis requires considerable data collection and calculation and is thus practical only through the use of computer hardware and software. We have previously reported the development of a program, STEREO, which compiles data from carcinogenesis experiments, recording information from tissue sections for the estimation of the number of altered hepatic foci (AHF) per liver and the volume fraction of AHF in liver on a three-dimensional basis. The data file itself was built by measuring tissue and focal transections through a slide-reading process that involved the manual use of a digitizer. In order to increase the speed and efficiency of the analytical process, we have integrated the STEREO program with a public domain software, Scion Image. This software integration involves two portions: the building macros and the interface. Macros for quantitative stereology used in Scion Image were written to customize and simplify the measurement and to generate data needed for building each of the data files. An interface program, BuildFi.exe, was developed to receive data generated from Scion Image and to align sequential tissue plots from up to four serial sections stained with different markers. As a result, the user can store data on a disk in the format of the STEREO data files. By combining STEREO with Scion Image, the slide-reading process is simplified and can be performed automatically. It has proven to be more objective, time saving, and efficient than all earlier versions.

Mad-overexpression down regulates the malignant growth and p53 mediated apoptosis in human hepatocellular carcinoma BEL-7404 cells

Mad protein has been shown as an antagonist of c-Myc protein in some cell lines. The effect of Mad protein to the malignant phenotype of human hepatoma BEL-7404 cell line was investigated experimentally. An eukarryotic vector pCDNA III containing full ORF fragment of mad cDNA was transfected into targeted cells. Under G418 selection, stable Mad-overexpressed cells were cloned. Studies on the effect of Mad over-expression in cell proliferation and cell cycle revealed that cell morphology of the Mad-overexpressed BEL-7404-M1 cells was significantly different from the parent and control vector transfected cells. DNA synthesis, cell proliferation and anchorage-independent growth in soft-agar of the mad-transfected cells were partially inhibited in comparison to control cells. Flow Cytometry analysis indicated that mad over-expression might block more transfectant cells at G0/G1 phase, resulting in the retardation of cell proliferation. RT-PCR detected a marked inhibition of the expression of cdc25A, an important regulator gene of G0/G1 to S phase in cell cycle. It was also found that Mad protein overexpression could greatly suppress p53-mediated apoptosis in BEL-7404-M1 cells in the absence of serume. Thus, Mad proteins may function as a negative regulator antagonizing c-Myc activity in the control of cell growth and apoptosis in human hepatocellular carcinoma BEL-7404 cells.

Imbalanced expression of functionally different WT1 isoforms may contribute to sporadic unilateral Wilms' tumor

Functional loss of the product of the Wilm's tumor suppressor gene (wt1) has been identified in subsets of familial Wilms' tumors. Previously, four alternative splice products of WT1 were recognized and each was found to regulate transcription of effector genes differently, suggesting that disruption of the normal ratio of these spliced products will disrupt the normal expression patterns of WT1 effector genes and perhaps lead to Wilms' tumor. In support of these suggestions, we found that four of seven cases of sporadic unilateral Wilms' tumor had striking differences in the ratios of the spliced products of WT1 compared with each other and normal kidney. These data indicate that in addition to structural mutations, alterations in the relative amounts of the mature WT1 isoforms may also be important in the etiology of sporadic Wilms' tumor.

A point mutation within exon 5 of the WT1 gene of a sporadic unilateral Wilms' tumor alters gene function

The Wilms' tumor suppressor gene, wt1, encodes a zinc-finger transcription factor, WT1, that represses transcription of a number of growth-promoting genes and inhibits cell growth. The transcripts of wt1 undergo two alternative splicing events, giving rise to four isoforms of mRNA in constant ratios. The first alternative splice introduces an extra exon 5, which encodes 17 amino acid residues inserted between the transcription regulatory domain and the DNA binding domain of WT1. Previously, we demonstrated that the 17-amino acid domain functioned as a transcription repressor when it was fused with the DNA binding domain of WT1. We have now identified a point mutation within exon 5 of wt1 in a sporadic unilateral Wilms' tumor patient. The mutation changes the last of the 17 amino acids from asparagine to serine. The protein isoform of WT1 carrying this mutation exhibited a 2-3-fold lower transcription-repressing activity than wild-type WT1 in transient cotransfection assays. The mutation also decreased growth-inhibiting activity of WT1 in two osteosarcoma cell lines, U2OS and Saos-2. By diminishing transcription-repressing and growth-inhibiting activities of WT1, this naturally occurring mutation within exon 5 of wt1 may disturb the normal function of the protein and lead to the uncontrolled cell growth characteristic of Wilms' tumor.

Translational inefficiency of acid beta-glucosidase mRNA in transgenic mammalian cells

The cDNA for acid beta-glucosidase, the Gaucher disease enzyme, was overexpressed in a variety of mammalian cells and in Sf9 insect cells. Whether overexpressed from the MFG-GC retrovirus or the tetracycline transactivator system, there was a large discrepancy between the amounts of mRNA (>750-fold) and acid beta-glucosidase protein (approximately 6- to 14-fold) produced in mammalian cells. This was not observed in Sf9 insect cells. Quantitative evaluation of translation of this mRNA in intact mammalian cells indicated a 55- to 135-fold inefficiency in cell lines compared to normal human skin fibroblasts. In vitro translation efficiency with acid beta-glucosidase mRNAs from overexpressing mammalian or insect cells was similar to that from normal human fibroblasts. A cytoplasmic, heat labile protein was suggested as inhibitory to in vitro translation of these RNAs. North-Western blots and cytoplasmic depletion experiments showed this to be an 80-kDa cytoplasmic mRNA-binding protein that recognized acid beta-glucosidase coding sequences. The cytoplasmic protein was not detected in insect cells. These results implicate acid beta-glucosidase coding sequences and a heat labile cytoplasmic protein in modulating the translation of overexpressed mRNA in transgenic cell lines.

STEREO: a program on a PC-Windows 95 platform for recording and evaluating quantitative stereologic investigations of multistage hepatocarcinogenesis in rodents

The most common organ site of neoplasms induced by carcinogenic chemicals in the rodent bioassay is the liver. The development of cancer in rodent liver is a multistage process involving sequentially the stages of initiation, promotion, and progression. During the stages of promotion and progression, numerous lesions termed altered hepatic foci (AHF) develop. STEREO was developed for the purpose of efficient and accurate quantitation of AHF and related lesions in experimental and test rodents. The system utilized is equipped with a microcomputer (IBM-compatible PC running Windows 95) and a Summagraphics MICROGRID or SummaSketch tablet digitizer. The program records information from digitization of single or serial sections obtained randomly from rat liver tissue. With this information and the methods of quantitative stereology, both the number and volume percentage fraction of AHF in liver are calculated in three dimensions. The recorded data files can be printed graphically or in the format of tabular numerical data. The results of stereologic calculations are stored on floppy disks and can be sorted into different categories and analyzed or displayed with the use of statistics and graphic functions built into the overall program. Results may also be exported into Microsoft Excel for use at a later time. Any IBM-compatible PC capable of utilizing Windows 95 and MS Office can be used with STEREO, which offers inexpensive, easily operated software to obtain three-dimensional information from sections of two dimensions for the identification and relative potency of initiators, promoters, and progressors, and for the establishment of information potentially useful in developing estimations of risk for human cancer.

[Study on the mechanism of basic fibroblast growth factor (bFGF) release induced by phorbol ester PMA]

Basic fibroblast growth factor (bFGF) is a strong mitogenic factor and inducer of angiogenesis. It may play an important role in the growth of solid tumors. Whereas bFGF is known to act extracellularly, the protein lacks a transient signal peptide. No defined mechanism for bFGF secretion has been characterized besides release from dead or injured cells. To explore molecular mechanism that modulates bFGF release, we treated CNE-2 cells with PMA for two days and found that the treatment increased bFGF gene expression in the cytoplasm and bFGF release significantly after 48 hours. This result suggests that protein kinase C is very likely to be involved in the bFGF release regulation. Our results have also shown that PKC-alpha activated by PMA in CNE-2 cells can phosphorylate bFGF (18 KDa) in CNE-2 cells. The result suggests that PKC-alpha translocation and activation can phosphorylate bFGF in CNE-2 cells and increase bFGF release.

Specific chromosomal changes in albumin simian virus 40 T antigen transgenic rat liver neoplasms

Hepatocytes isolated from 3-month-old female rats bearing the albumin promoter/enhancer SV40 T antigen construct as a transgene demonstrated a 20% aneuploidy rate and a significant duplication of chromosome 1. Other chromosome changes were observed but were not statistically significant. At this time in the development of hepatic lesions, only a relatively small number of microscopic altered hepatic foci could be noted. By contrast, hepatocytes isolated from the age-matched nontransgenic controls demonstrated only 1% aneuploidy. One hundred % of the metaphase spreads isolated from hepatocellular neoplasms in transgenic rats were aneuploid. Although there were many random changes, 70% of the neoplastic cells demonstrated an amplification of all or portions of chromosome 1q. Only 2% of the neoplastic cells had both a trisomy and a duplication. The smallest region of chromosome 1 that was duplicated was that between bands q3.7 and q4.3. A loss of chromosome 3 was detected in 50% of the neoplasms, as well as a loss of chromosome 6 in 72% of the neoplastic cells. The carcinomas with the highest proliferation rate had also lost at least one copy of chromosome 15 in 70% of the cells. The loss of chromosomes 3, 6, and 15 indicates that these regions may harbor one or more tumor suppressor genes. The amplification of a specific region of chromosome 1 is thus the first karyotypic alteration that can be identified in hepatocytes from livers from which hepatic neoplasms will arise. This indicates that expression or repression of one or more genes in this region may confer a growth advantage to preneoplastic hepatocytes, facilitating their transit to the neoplastic state in the stage of progression. Changes in chromosomes 3, 6, and 15 that occur subsequent to duplication of the q3.7-q4.3 region of chromosome 1 are changes possibly reflecting alteration of tumor suppressor genes with further enhancement of neoplastic growth.

Karyotypic changes in a multistage model of chemical hepatocarcinogenesis in the rat

Karyotypic analysis of the stages of rat hepatocarcinogenesis has been facilitated by the development of an initiation-promotion-progression (IPP) protocol that permits separation and characterization of morphologically normal and altered hepatocytes in each of these three stages. The expression of the membrane antigen gamma-glutamyl transpeptidase (GGT) during the promotion and progression stages of rat hepatocarcinogenesis permits the isolation, culture, analysis, and comparison of hepatocytes in the two stages, which express this marker of carcinogenesis. Female rats were administered 10 mg diethylnitrosamine/kg at 5 days of age. One group of initiated rats was maintained on dietary phenobarbital admixed into a laboratory chow diet at 0.05% for 9 months after weaning (promotion protocol). This initiation-promotion (IP) group was compared with one subjected to the complete IPP protocol. The IPP group was initiated with diethylnitrosamine, maintained on phenobarbital for 6 months after weaning, and then subjected to a 70% partial hepatectomy and administered 100 mg ethylnitrosourea/kg 24 h later. These rats on the IPP protocol were then maintained on phenobarbital for an additional 3 months prior to sacrifice. At sacrifice, single hepatocyte suspensions were obtained and separated into populations of cells expressing or not expressing GGT. These hepatocyte populations were cultured separately and subjected to standard cytogenetic analysis. At least five animals per treatment and 100 metaphase spreads of good morphology per animal were examined. Although GGT- cells from the IP protocol were 80% tetraploid and 20% diploid, the GGT+ hepatocytes were greater than 90% diploid. The GGT+ cells from this protocol had a low rate of random aneuploidy (4.0 +/- 1.3%) compared with corresponding cells from the IPP protocol, but a higher level of background aneuploidy compared with GGT- cells from the IP protocol. The GGT+ hepatocytes from animals on the IPP protocol had a 35% incidence of aneuploidy. In addition, the GGT+ population had a 28 +/- 5% incidence of chromosomal breakage and a 17 +/- 5% incidence of chromosomal rearrangements. The primary nonrandom chromosomal changes observed in cells from the IPP protocol included duplication of all or part (1q37-43) of chromosome 1 and the loss of chromosomes 3p and/or 6q. These studies indicate that rat hepatocytes in the stage of promotion are euploid, whereas those in the stage of progression exhibit considerable genetic instability. The presence of multiple copies of chromosome 1 or a duplication of a region of this chromosome indicates that alteration of gene dosage for one or more of the genes present in this region is critical to the neoplastic conversion of rat hepatocytes, whereas the loss of all of 3p and the last light band of 6q may indicate the presence of tumor suppressor genes. Thus, the IP and IPP protocols coupled with the ability to isolate GGT+ and GGT- hepatocytes permit the differential cytogenetic characterization of the stages of promotion and progression in rat hepatocarcinogenesis.

Divalent cations but not other activators enhance phosphorylase kinase's affinity for glycogen phosphorylase

To better understand the physical interaction between glycogen phosphorylase-b (P-b) and its only known kinase, phosphorylase kinase (PbK) and the relationship of this interaction to the activation of PbK, direct binding studies are necessary. By utilizing an enzyme-linked immunosorbent assay, a method was developed for measuring the binding of PbK to immobilized P-b under a variety of experimental conditions. A monoclonal antibody specific for the alpha subunit of PbK that had no effect on the phosphorylation of P-b by PbK or on the interaction of PbK with known effectors was used to detect PbK bound to plated P-b. Hyperbolic binding curves were obtained regardless of whether the concentration of Pbk or P-b was varied, and the assay detected changes in relative affinity caused by certain effectors of the kinase. The allosteric effector ADP, alkaline pH, and phosphorylation by cAMP-dependent protein kinase, all activators of PbK, did not cause significant changes in its relative affinity for P-b; however, Ca2+ and Mg2+ ions, which also stimulate PbK, increased its affinity for P-b, with Mg2+ being more effective. Mn2+, which inhibits the P-b conversion activity of PbK, was found to be the most potent enhancer of its affinity for P-b, although divalent cations may enhance binding. Inclusion of ATP analogs in the binding assay with Ca2+ and Mg2+ to stimulate catalytic assay conditions did not further affect the apparent affinity for P-b, which is consistent with the previously reported rapid equilibrium random bi-bi kinetic mechanism for P-b conversion.

Turnover and distribution of intravenously administered mannose-terminated human acid beta-glucosidase in murine and human tissues

Gaucher disease type 1, the most prevalent lysosomal storage disease, is caused by the defective activity of the lysosomal enzyme, acid beta-glucosidase, or glucocerebrosidase. Infusion of purified acid beta-glucosidase containing alpha-mannosyl-terminated oligosaccharides (alglucerase) is efficacious in reversing hematologic, hepatic, splenic, and bony disease manifestations. The murine tissue distribution and turnover of bolus injections of alglucerase was evaluated by enzymatic activity, quantitative cross-reacting immunologic material analyses, and immunofluorescence studies. Enzyme activity measurements detected distribution to liver, spleen, thymus, kidney, and bone marrow mononuclear cells, but not to lungs and brain. In kidney and thymus, the enzyme was transiently present. In liver and spleen, enzyme activity peaked at about 20 min postinjection followed by a biphasic decrease with t1/2 approximately 40-60 min and approximately 12-14 h. In bone marrow maximal enzyme activity was at 40-60 min with a disappearance t1/2 approximately 60 min. Quantitative cross-reacting immunologic material studies of liver and spleen showed delivery of enzyme with decreased catalytic rate constants whose degradation included denaturation and proteolytic components. By immunofluorescence the human enzyme was distributed primarily to reticuloendothelial cells of the liver and spleen. In autopsy material from a Gaucher disease type 2 patient treated with enzyme, immunohistochemical and activity studies showed distributions similar to those in mice. These studies indicate a complex delivery and intracellular degradation of acid beta-glucosidase with lower intrinsic activity than the administered therapeutic agent.

[The effects of histamine H2 receptor agonist, antagonist and antineoplastic agent on the in vitro growth of PB CFU-GM from normal individuals and HL-60 leukemia cells]

Colony forming unit of granulocytes and macrophages from peripheral blood (PB CFU-GM) represents stem and/or progenitor cells from human blood. In this paper, the effects of histamine H2 receptor agonist 4-methylhistamine (4-MH) and its antagonist ranitidine (Ranit) on the growth of PB CFU-GM cultured in methylcellulose system were studied and their differential effects on normal PB CFU-GM and leukemic HL-60 cells were compared with the effect of the antineoplastic agent cytosine arabinoside (Ara-C). It was found that the histamine H2 receptor agonist 4-MH stimulated the growth of PB CFU-GM when 4-MH was added at the concentrations from 10(-9) mol.L-1 to 10(-6) mol.L-1 among which the dose 10(-8) mol.L-1 exerted most potent stimulating effect (the PB CFU-GM colony numbers was 137.68% +/- 8.20% vs the control, P < 0.01). In contrast, the antagonist Ranit showed inhibitory effect on the growth of PB CFU-GM when at the concentrations 10(-9)-10(-5) mol.L-1 cultured for 14 d in the same methylcellulose system. The inhibition rate was 23.73% +/- 1.16% (10(-9) mol.L-1) and 41.42% +/- 6.75% (10(-6) mol.L-1), respectively. Although both Ranit and Ara-C could inhibit the growth of PB CFU-GM in vitro, Ranit exerted much greater inhibition on HL-60 leukemic cells than on normal PB CFU-GM at the dose of 10(-6) mol.L-1 (100% inhibition for HL-60 and < 50% inhibition for PB CFU-GM). However, the inhibition rate of Ara-C for both HL-60 and PB CFU-GM was 100% at the intensive chemotherapeutic dose of 10(-5) mol.L-1. It would appear that the histamine H2 receptor agonist 4-MH possesses stimulating effect on the growth of PB CFU-GM similar to its effect on CFU-GM from bone marrow as documented before. It is suggested that the histamine H2 receptor antagonist Ranit has, to some extent, potential in the treatment of myeloid leukemia, especially when combined with antineoplastic agent Ara-C at suboptimal doses.

Effect of cellular type on expression of acid beta-glucosidase: implications for gene therapy in Gaucher disease

The effects of cellular type on the expressed activity of acid beta-glucosidase were evaluated using retroviral constructs containing the human cDNA. MFG retroviral ecotropic and amphotropic vectors containing the human acid beta-glucosidase cDNA were produced and used to infect different murine cell lines (fibroblast, neuronal and monocytic) and human cells (HL60 and cord blood CD34+), respectively. The expression of human acid beta-glucosidase was evaluated by enzyme activity assays, quantitative Western blots and immunofluorescence. All cells permanently integrated viruses and expression of enzyme protein was achieved in all cell lines, but cellular transduction efficiency differed even between different neuronal cell lines (eg N18S > PC12). In most cell lines acid beta-glucosidase activity was increased between two- and three-fold with concomitant signal increases by Western blot and immunofluorescence N18S cells had poor transduction efficiency, but high cellular expression in transduced cells. In NIH3T3 and MC3T3-E1 cells acid beta-glucosidase protein was expressed in 2-, 7- and 14-day cultures after infection and at least to passage four. The expressed acid beta-glucosidase in NIH3T3 cells was at two to three times normal activity levels, and was processed similarly to the human fibroblast enzyme. Inactive human acid beta-glucosidase was expressed in MC3T3-E1 preosteoblastic cells and this was maintained during differentiation to osteoblasts. These results indicate that gene transfer results in cell lines may not be generally extrapolated to all cells in tissues or to differentiated progeny.

[An EGFR antisense oligodeoxynucleotides and its phosphorothioate analogue inhibit the growth of human hepatocarcinoma BEL-7404 cells]

We have previously reported that the malignant phenotype of human liver carcinoma cell line BEL-7404 was reversed by antisense EGFR RNA. The aim of this paper is to explore the effects of an oligomer targeted to mRNA for EGFR and growth of BEL-7404 cells. A 21-mer oligodeoxynucleotides (ODNs) complementary to the 5' initiation region of mRNA for EGFR was synthesized and added to medium. The results showed that the growth of BEL-7404 cells was inhibited by ODNs at concentration of 3.2 mumol/L. Inhibition of DNA synthesis of BEL-7404 cells was dose-dependent and reached to 62.1% at 3.2 mumol/L as measured by 3H-thymidine incorporation test. The inhibition of EGFR gene transcription of the cells was up to 10.5% and 14.3% respectively after incubation with ODNs by 5 and 24 hours as measured by densitometric scanning of dot (RNA) blots of EGFR. The EGFR protein (P 170) expression was also found to be blocked by 4 days' antisense oligomer treatment up to 37.4% as measured by densitometric scanning of specific band of Western blot. The oligonucleotide phosphorothioate (S-ODNs) complementary to the same region of the gene was also synthesized and its growth inhibition effects on BEL-7404 cells were compared with those of unmodified oligomers. ODNs attained their highest effect within 30 hours. The proliferation inhibition rate of the cells didn't increase when cells were cultured in serum free medium. In contrast, the S-ODNs induced inhibition reached comparable level after 96 hours treatment as measured by 3H-thymidine uptake and the effect lasted longer, 1 mumol/L S-ODNs showed a little effect on BEL-7404 cells' proliferation. We concluded that the antisense oligomers directed to mRNA for EG-FR could inhibit the BEL-7404 cells growth by blocking the EGFR gene expression in some degree and the phosphorothioate analogues were more stable than the unmodified ODNs in vitro.

Purification of deformin, an extracellular protein synthesized by Bartonella bacilliformis which causes deformation of erythrocyte membranes

A factor capable of deforming erythrocyte membranes, found in the culture supernatants of Bartonella bacilliformis, was purified 1840-fold using hydrophobic, ion exchange and gel exclusion chromatography. The final fractions contained a single detectable polypeptide species, referred to as deformin, having a molecular weight of 67000 by SDS-PAGE and a native molecular weight of 130,000 by gel exclusion chromatography or velocity sedimentation in a glycerol gradient. Erythrocytes treated with deformin acquire trenches, indentations, and invaginations which could be reversed by vanadate, dilauroylphosphatidylcholine (DLPC), or by raising the internal Ca2+ concentrations with the inophore A23187. Internal vacuoles also form. Erythrocytes treated with trypsin or neuraminidase are much more sensitive to deformin than untreated erythrocytes; erythrocytes treated with phospholipase D are less sensitive to deformin. This protein may play a role in causing the severe anemia which can result as a consequence of infection by B. bacilliformis.

Structure of polymerizable lipid bilayers VII: lateral organization of diacetylenic phosphatidylcholines with short proximal acyl chains

As an extension of recent results (Rhodes, Xu and Bittman (1992) Biochim. Biophys. Acta 1128, 93; Hui, Xu and Bittman (1992) Langmuir 8, 2724) with a C18 diacetylenic phosphatidylcholine, bilayers of 1,2-bis(pentacosa-4,6-diynoyl)-sn-glycero-3-phosphocholine (C25) were investigated using X-ray diffraction on multibilayers and electron diffraction on Langmuir-Blodgett deposited bilayers. Monolayers of this lipid form solid (gel phase) domains at pi > 14 mN/m. Electron diffraction data indicated that the chain spacing in these domains is 4.25 A and that the chains are tilted at angle of approximately 35 degrees relative to the bilayer plane. Wide angle data from X-ray diffraction experiments indicated a similar spacing and chain tilt. Small angle data showed that the lamellar repeat was 70 A at high humidity and < or = 60 A at low humidity. The bilayer electron density profiles indicated a bilayer structure with no interdigitation. High angle reflections indicate that the principal acyl chain repeat is preserved as a function of hydration but some rearrangement occurs for other reflections. The approximately 10 A reflection corresponding to the headgroup spacing previously observed with C18-diacetylenic phosphatidylcholine bilayers was not observed. The results are interpreted in terms of a packing model and possible limitations or constraints to the polymerization process.

Modulation of bradykinin-induced intracellular Ca2+ oscillations in v-Ki-ras-transformed fibroblasts

Modulation of bradykinin (BK)-induced intracellular Ca2+ oscillations was investigated with single cell Ca2+ analysis in v-Ki-ras-transformed NIH3T3 fibroblasts. The Ca2+ oscillations were inhibited by the addition of a specific antagonist for subtype 2 of BK receptors (B2 receptor), not the antagonist for B1 receptor. Decrease of the extracellular Ca2+ concentration suppressed the [Ca2+]i oscillations and application of thapsigargin dissipated the [Ca2+]i oscillations. These findings suggest that the continuous activation of B2 receptor leading to the fluctuations of both Ca2+ influx which refills the internal Ca2+ stores, and Ca2+ mobilization from the internal stores, is essential to the occurrence of the [Ca2+]i oscillations in these cells.

[The clinical use of MOM nutrient powder in pregnant women]

Fifty women with normal pregnancy were given MOM nutrient powder (30 g/day) from 16 weeks of gestation to the beginning of labor and another 40 cases of normal pregnancy were given iron, folic acid, calcium, vitA+D at the same time were observed and compared for the nutritional status at 16, 28, 37 weeks of gestation, the serum total protein, albumin, fasting blood sugar, cholesterol, triglyceride serum iron calcium, folic acid vitA and blood glutathione reductase activation coefficient (GRAC), Hb, hematocrit were measured in the two groups. The results showed that all the above mentioned measurements were in normal range, and there was no statistically significant difference between the 2 groups. The maternal body weight at various stages of gestation; maternal weight gain; neonatal birth weight, and the production of breast milk showed also no significant difference between the 2 groups. We conclude that the action supplementation of various nutrients by drug can be replaced by food MOM nutrient powder for the pregnant women.

[Breast-feeding in reducing regular insulin requirement in postpartum for insulin dependent diabetes mellitus and gestational diabetes mellitus]

From Jan. 1987-Jun. 1993, 37 cases of insulin dependent diabetes mellitus (IDDM) pregnant women and 10 gestational diabetes mellitus (GDM) mothers requiring regular insulin (RI) treatment during pregnancy were recruited. A comparative study of the daily RI requirement was carried out in women breast-feeding (BF) or not (non-BF) at different periods: before pregnancy, during gestation, postpartum and at present. Results showed no difference of RI requirement between BF and non-BF groups before pregnancy, during gestation and currently, but a significant decrease of RI requirement (P < 0.05) among BF mothers in postpartum period. Of the 10 GDM cases, 3 of them who did not breast feed their babies required further RI for 4-7 days in the postpartum period, whereas 7 BF mothers did not need any RI after delivery with blood glucose levels remaining within normal range. Based on the above analysis one may conclude that BF can reduce the RI requirement of IDDM and GDM mothers in the postpartum period. It is thought that more energy is needed in the process of producing milk, and serum glucose is the main substance for lactose synthesis, thus blood glucose level of BF mother is decreased, and so is the RI requirement. Therefore, mothers with diabetes mellitus are encouraged to breast feed their babies.

Characterization of the Mg(2+)-ATPase activity of the human erythrocyte membrane

The Mg(2+)-dependent ATPase activity of human erythrocyte ghosts undergoes biphasic activation in the presence of ATP (K0.5 approximately 20 microM and 400 microM). Inhibition by vanadate is also biphasic with the most sensitive component (IC50 approximately 100 microM) responsible for the remaining activity. La3+ inhibits approximately 70% of activity (IC50 approximately 25 microM) while Cd2+ can fully inhibit activity (IC50 approximately 60 microM). Partially purified activity was obtained by extracting ghosts with Triton X-100, followed by chromatography over Sepharose CL-2B. Triton distorts the curves for inhibition by vanadate and the activation by ATP. The partially purified activity is inhibited by Ca2+ (IC50 approximately 0.4 mM). These results, together with data from other studies, suggest that the total Mg(2+)-ATPase activity in the membrane represents at least two separate enzymes. Only the activity which is highly sensitive to vanadate appears to be involved in erythrocyte shape change.

The model calmodulin-binding peptide melittin inhibits phosphorylase kinase by interacting with its catalytic center

The inhibition by melittin, a model calmodulin-binding peptide, of phosphorylase kinase, which contains an intrinsic calmodulin subunit, has been characterized in detail. The inhibition was competitive with respect to phosphorylase b for both the phosphorylase kinase holoenzyme and its isolated catalytic gamma-subunit (minus calmodulin), and the ratios of the Km for phosphorylase to the Ki for melittin were similar for both forms of the kinase. These findings indicate that inhibition of the phosphorylase kinase holoenzyme by melittin is caused predominantly by its interaction with the catalytic subunit of the enzyme, and not with the endogenous calmodulin subunit. Further proof that melittin interacts directly with the catalytic site was obtained when it was observed that melittin was also a substrate for phosphorylase kinase, with a Km that was less than that for phosphorylase b, although the kcat/Km specificity constant was only 1/200th of that for phosphorylase. The apparent tight binding of melittin to the kinase active site could not be readily rationalized by conventional comparison of sequence similarity between melittin and phosphorylase; however, considerable sequence similarity, centered around the convertible seryl residue of phosphorylase, was observed when the sequences were aligned in reversed polarity. The possible regulatory significance of the direct interaction of the catalytic site of this Ca(2+)-dependent kinase with a calmodulin-binding peptide is discussed.

[Gene cloning, expression of fusion protein TGF alpha-PE 40 and its inhibition activity on cancer cell growth]

Recombinant plasmid pYX382 and pYX3825 were constructed by fusing the cDNA encoding transforming growth factor type alpha (TGF alpha) to Pseudomonas exotoxin gene (PE) in which the cell recognition domain was deleted. The chimeric proteins produced by host E. Coli cells BL21 transformed by plasmid pYX382 and pYX3825 are termed TGF alpha-PE 40 which reacts with antibody against TGF alpha or antibody against PE in immunoblotting to show a 46 kd protein band reflecting the fusion of 56 kD TGF alpha peptide and 40 kD truncated Pseudomonas exotoxin molecule. An additional signal sequence OmpA was inserted into upstream region of TGF alpha cDNA in plasmid pYX3825 resulting in the partly secreting of expression product into medium and periplasm of the cells. TGF alpha-PE 40 was purified from medium by MONO Q ion exchange column and TSK 250 gel filtration column attached to Pharmacia EPLC system. The TGF alpha-PE 40 molecules showed a very strong activities inhibiting the protein synthesis and killing the cancer cells overexpressing EGF receptor on the cell surface.