Growth arrest-specific gene 6 (Gas6)/adhesion related kinase (Ark) signaling promotes gonadotropin-releasing hormone neuronal survival via extracellular signal-regulated kinase (ERK) and Akt

We identified Ark, the mouse homolog of the receptor tyrosine kinase Axl (Ufo, Tyro7), in a screen for novel factors involved in GnRH neuronal migration by using differential-display PCR on cell lines derived at two windows during GnRH neuronal development. Ark is expressed in Gn10 GnRH cells, developed from a tumor in the olfactory area when GnRH neurons are migrating, but not in GT1-7 cells, derived from a tumor in the forebrain when GnRH neurons are postmigratory. Since Ark (Ax1) signaling protects from programmed cell death in fibroblasts, we hypothesized that it may play an antiapoptotic role in GnRH neurons. Gn10 (Ark positive) GnRH cells were more resistant to serum withdrawal-induced apoptosis than GT1-7 (Ark negative) cells, and this effect was augmented with the addition of Gas6, the Ark (Ax1) ligand. Gas6/Ark stimulated the extracellular signal-regulated kinase, ERK, and the serine-threonine kinase, Akt, a downstream component of the phosphoinositide 3-kinase (PI3-K) pathway. To determine whether ERK or Akt activation is required for the antiapoptotic effects of Gas6/Ark in GnRH neurons, cells were serum starved in the absence or presence of Gas6, with or without inhibitors of ERK and PI3-K signaling cascades. Gas6 rescued Gn10 cells from apoptosis, and this effect was blocked by coincubation of the cells with the mitogen-activated protein/ERK kinase (MEK) inhibitor, PD98059, or wortmannin (but not rapamycin). These data support an important role for Gas6/Ark signaling via the ERK and PI3-K (via Akt) pathways in the protection of GnRH neurons from programmed cell death across neuronal migration.

Syndecan-1 expression suppresses the level of myeloma matrix metalloproteinase-9

ARH-77 human myeloma cells invade into type I collagen gels but become non-invasive when engineered to express syndecan-1, a heparan sulphate proteoglycan that promotes cell adhesion to collagen. To determine if syndecan-1 expression influences the activity of proteases that may facilitate invasion, we analysed media harvested from syndecan-1 expressing and non-expressing cells. High levels of a 92 kD gelatinase accumulated in serum-free growth medium of both parental and control-transfected ARH-77, but much less 92 kD gelatinase accumulated in the medium of ARH-77 transfectants expressing syndecan-1. The gelatinase was identified as matrix metalloproteinase (MMP)-9 because its activity was immunoprecipitated with a MMP-9-specific monoclonal antibody. Gelatinase activity and Western blot analyses revealed 2-3-fold less MMP-9 in medium from syndecan-1 transfected cells than in medium from parental cells. Decreased MMP-9 was not due to increased association of MMP-9 with cells expressing syndecan-1. An inverse correlation between the syndecan 1 level and the level of MMP-9 accumulation in the media was observed using a panel of ARH-77 transfectants expressing syndecan-1. Investigation of six unrelated human myeloma cell lines confirmed that high gelatinase levels were recovered from conditioned media of those that did not express syndecan-1 (ARH-77, Mer and Col) and one line that expressed a low level of syndecan-1 (RPMI-8226), but low gelatinase levels were recovered from media of lines that expressed high levels of syndecan-1 (ARK and clone 2+). Therefore syndecan-1 may play a dual role in inhibiting the metastasis of tumour cells by promoting cell adhesion to the extracellular matrix and suppressing the proteolytic activity needed for invasion.

Evidence that endoplasmic reticulum (ER)-associated degradation of cystic fibrosis transmembrane conductance regulator is linked to retrograde translocation from the ER membrane

The ubiquitin-proteasome pathway has been implicated in the degradation of newly synthesized, misfolded and unassembled proteins in the endoplasmic reticulum (ER). Using a cell-free reticulocyte lysate system we have examined the relationship between biosynthesis and ER-associated degradation of the cystic fibrosis transmembrane conductance regulator (CFTR), a polytopic protein with 12 predicted transmembrane segments. Our results provide direct evidence that full-length, glycosylated and membrane-integrated CFTR is a substrate for degradation and that degradation involves polyubiquitination and cytosolic proteolytic activity. CFTR ubiquitination was both temperature- and ATP-dependent. Degradation was significantly inhibited by EDTA, apyrase, and the proteasome inhibitors hemin and MG132. Degradation was inhibited to a lesser extent by clasto-lactacystin beta-lactone, ALLN, and Nalpha-tosyl-L-phenylalanine chloromethyl ketone and was relatively unaffected by lactacystin and N-tosyl lysyl chloromethyl ketone. In the presence of hemin, polyubiquitinated CFTR remained tightly associated with ER microsomes. However, membrane-bound ubiquitinated CFTR could be subsequently degraded into trichloroacetic acid-soluble fragments upon incubation in hemin-free, ATP-containing lysate. Thus ER-associated degradation of CFTR occurs via a membrane-bound, rather than cytosolic, intermediate and likely involves recruitment of degradation machinery to the ER membrane. Our data suggest a model in which the degradation of polytopic proteins such as CFTR is coupled to retrograde translocation and removal of the polypeptide from the lipid bilayer.

[Study on the separation of Co2+ from Cu2+, Cd2+, Mn2+, Zn2+ and Fe3+ by extraction chromatography]

In this paper, extraction chromatography by which Co2+ can be separated from Cu2+, Cd2+, Mn2+, Zn2+, Fe3+ is developed. The chromatographic column was 17 mm i.d. x 520 mm, containing polymers synthesized by styrene, divinylbenzene and P204 (volume fraction was 40%), with particle size of 100-200 mesh. The effects of transformation of P204 from the H(+)-form to the Na(+)-form by NaAc solution, the eluent acidity, and eluent composition were investigated. The results indicated that this extraction chromatographic method is good to separate Co2+ from Cu2+, Cd2+, Mn2+, Zn2+ and Fe3+, and the condition of separation is simple and convenient. When the P204 is transformed from the H(+)-form to the Na(+)-form by pH 4.0 NaAc (0.5 mol/L), and the column is eluted with pH 2.5 ClCHCOOH-ClCHCOONa (0.1 mol/L), the separation can be completed effectively.

Impact of pregnancy-induced hypertension on fetal growth

OBJECTIVE

The purpose of this study was to evaluate the effect of different types of pregnancy-induced hypertension on fetal growth.

STUDY DESIGN

A retrospective cohort study was conducted on the basis of 16,936 births from January 1, 1989, through December 31, 1990, by means of data from a population-based perinatal database in Suzhou, China. Pregnancy-induced hypertension was classified as gestational hypertension, preeclampsia, or severe preeclampsia-eclampsia. Univariate and multivariate regression analyses were performed to examine the effect of the various types of pregnancy-induced hypertension on gestational age, preterm birth, birth weight, low birth weight, and intrauterine growth restriction.

RESULTS

Gestation was 0.6 week shorter in women with severe preeclampsia than in normotensive women (P <.01). However, the risk of preterm birth was not increased with any classification of pregnancy-induced hypertension (for severe preeclampsia: adjusted odds ratio 1.75; 95% confidence interval, 0.88-3.47). After adjustment for duration of gestation and other confounders, preeclampsia and severe preeclampsia increased the risk of intrauterine growth restriction and low birth weight. The adjusted odds ratios of low birth weight were 2.65 (1.73-4.39) for preeclampsia and 2.53 (1.19-4.93) for severe preeclampsia. However, the risk of low birth weight was not increased significantly for gestational hypertension (adjusted odds ratio 1.56 [1.00-2.41]).

CONCLUSION

Preeclampsia increases the risk of intrauterine growth restriction and low birth weight.

[A study of interferon alpha-2b as an accessory drug after glaucoma filtration surgery]

OBJECTIVE

To elucidate the inhibitory action of interferon alpha-2b (IFN alpha-2b) on the cicatrization under conjunctiva and the best way to use it after glaucoma filtration surgery.

METHODS

Immunohistochemical PAP method and image biological system 2000 (IBAS 2000) were utilized to quantitatively analyze the inhibitory effect of IFN alpha-2b on the expression of epidermal growth factor receptor (EGFR) of cultured calf fibroblasts; the effects of IFN alpha-2b on collagen contents in suture-caused cicatrization under conjunctiva and changes of aqueous humor protein after trabeculectomy performed on rabbits have also been observed.

RESULTS

IFN alpha-2b reduced the expression of EGFR of cultured bovine fibroblasts at a dose-dependent manner. The relationship between the EGFR and the dosage of IFN alpha-2b is Y = 2953.8 - 554.5 lgx (r = -0.98, P < 0.01). With 4.67 x 10(-5) micromol/L IFN alpha-2b not only reduced about 50% of the collagen in suture-caused cicatrization, but also significantly decreased the protein concentration of aqueous humour 3 and 72 hours after trabeculectomy.

CONCLUSION

It is promising that IFN alpha-2b can be used after glaucoma filtration surgery to reduce excessive cicatrization with many advantages compared with antimetabolites.

Mutations in hepatitis B DNA polymerase associated with resistance to lamivudine do not confer resistance to adefovir in vitro

To determine whether adefovir is active against lamivudine-resistant hepatitis B virus (HBV), the inhibition constants of adefovir diphosphate and lamivudine triphosphate for wild-type and mutant human HBV DNA polymerases, which contain amino acid substitutions associated with lamivudine resistance, were compared. Recombinant wild-type and mutant human HBV DNA polymerases were expressed and substantially purified using a baculovirus expression system and immunoaffinity chromatography. HBV DNA polymerase mutants M552I, M552V, and L528M/M552V showed resistance to lamivudine triphosphate with inhibition constants (Ki) increased by 8.0-fold, 19.6-fold, and 25.2-fold compared with that of wild-type HBV DNA polymerase. However, these mutants remained sensitive to adefovir diphosphate with the inhibition constants increasing by 1.3-fold and 2.2-fold or decreasing by 0.79-fold. The L528M single mutation, identified in patients with increasing HBV DNA levels during therapy with famciclovir, also remained sensitive to adefovir diphosphate with the inhibition constant increased by only 2.3-fold.

Hodgkin disease: use of Tl-201 to monitor mediastinal involvement after treatment

PURPOSE

To compare thallium-201 scintigraphy with gallium-67 scintigraphy in the detection of residual or recurrent mediastinal Hodgkin disease after treatment.

MATERIALS AND METHODS

The authors performed planar Ga-67 and Tl-201 scintigraphy in 39 patients aged 7-18 years (27 with mediastinal primary disease) after primary treatment. These scans and those in a control group of 14 patients with newly diagnosed known mediastinal Hodgkin disease were evaluated independently by two radiologists for abnormal mediastinal activity. Results were compared with chest computed tomographic (CT) findings and with the clinical criteria of disease status. Interobserver agreement and consensus agreement on gallium and thallium scan findings were evaluated with the kappa statistic, and the specificity of the two imaging methods was analyzed.

RESULTS

All study patients were judged to be free of mediastinal disease with CT and the clinical criteria. Interobserver agreement on findings in the treated and control patients was stronger with gallium scintigraphy (kappa +/- SD = 0.956 +/- 0.044) than with thallium scintigraphy (kappa = 0.638 +/- 0.110). Specificity of ratings based on thallium (85% +/- 6) and gallium (90% +/- 5) scintigraphic findings of mediastinal disease did not differ significantly (P = .48). Specificity improved when the results of the two examinations were combined (97% +/- 2).

CONCLUSION

Thallium scintigraphy can help to predict the absence of mediastinal Hodgkin disease after treatment.

Dual UV-absorbing background electrolytes for simultaneous separation and detection of small cations and anions by capillary zone electrophoresis

The simultaneous separation and detection of small cations and anions by capillary zone electrophoresis (CZE) with indirect ultraviolet (UV) detection was successfully demonstrated in a background electrolyte (BGE) containing two UV-absorbing components. Benzylamine, imidazole, benzenesulfonic acid, sulfosalicylic acid, and pyromellitic acid were tested as the components of the BGE. The success of the simultaneous separation of the cations and anions is dependent upon the proper selection of the electrolyte components and control of the migration of the ions towards the detector. High pH is beneficial to the detection of anionic analytes but not to the separation of cationic analytes because of large electroosmotic flow produced under this condition. The upper pH limit of the working pH range is confined by the pKa value of the cationic component of the BGE. The influence of pH and total electrolyte concentration on the electroosmatic flow (EOF) counteracted each other. This counteraction effect imposes an upper limit on the change of total electrolyte concentration at certain pH. It was found that the EOF should be larger by at least 10 x 10(-5) cm2V(-1)s(-1) than the electrophoretic mobilities of the anions so that the anions could be detected on the cathodic side within reasonable times and with good peak shapes. In the imidazole-sulfosalicylic acid BGE, the detection limits (signal to noise, S/N = 3) for the cations and anions ranged from 100 to 900 ppb. In the benzylamine-pyromellitic acid BGE, K+, Na+, Li+, CH3 COO-, HPO4(2-), F-, ClO3-, ClO4-, NO3-, NO2-, Cl- and SO4(2-) were separated within twelve minutes. The strategies for selection of the electrolyte components of the binary BGE were also discussed.

Identification of novel factors that regulate GnRH gene expression and neuronal migration

We used differential display PCR on two GnRH producing cell lines to identify genes involved in GnRH gene expression and neuronal migration. RNA from Gn10 cells (derived from a tumor in the olfactory area when GnRH neurons are migrating and make low levels of GnRH) and from GT1-7 cells (derived from a tumor in forebrain when GnRH neurons are postmigratory and make high levels of GnRH) was reverse transcribed into cDNA. The cDNA was amplified using three anchored primers and eight random primers from each cell line and products from duplicate reactions electrophoresed in parallel in a denaturing acrylamide gel. Differentially expressed cDNAs were excised, reamplified and used as probes in Northern analysis of total RNA from each cell line to confirm differentially expressed RNA. The cDNAs were sequenced and compared to the Genbank database. Four of five clones isolated from GT1-7 GnRH neurons are novel, while four of five clones isolated from Gn10 cells have homology to known DNA sequences. One clone, Gn8-01 encodes adhesion related kinase (Ark), a molecule that has an N-terminal domain characteristic of cell adhesion molecules and whose kinase domain may play a role in protection from apoptosis. Together these data support the usefulness of the technique to identify novel genes that play a role in the control of GnRH expression and neuronal migration.

Clinical trial designs based on sequential conditional probability ratio tests and reverse stochastic curtailing

We propose a group sequential method based on the sequential conditional probability ratio test and show that it has the conservatism desired in practice. We also propose calculating the discordant probability, that is, the probability that the sequential test concludes differently from a fixed-sample test at the planned end of the trial, recognizing that this probability could be substantial, even if the sequential test has the same size and power as the fixed-sample size test at the planned end of the study. In addition, we show that the proposed method can be used as a stochastic curtailing tool. Thus, the method accommodates unplanned interim analyses as well as those deemed necessary based on data trends, virtually without inflating the type I error, but it is less conservative than the usual stochastic curtailing. The method is implemented through an interactive computer program.

Co- and posttranslational translocation mechanisms direct cystic fibrosis transmembrane conductance regulator N terminus transmembrane assembly

Transmembrane topology of most eukaryotic polytopic proteins is established cotranslationally at the endoplasmic reticulum membrane through the action of alternating signal and stop transfer sequences. Here we demonstrate that the cystic fibrosis transmembrane conductance regulator (CFTR) achieves its N terminus topology through a variation of this mechanism that involves both co- and posttranslational translocation events. Using a series of defined chimeric and truncated proteins expressed in a reticulocyte lysate system, we have identified two topogenic determinants encoded within the first (TM1) and second (TM2) membrane-spanning segments of CFTR. Each sequence independently (i) directed endoplasmic reticulum targeting, (ii) translocated appropriate flanking residues, and (iii) achieved its proper membrane-spanning orientation. Signal sequence activity of TM1, however, was inefficient due to the presence of two charged residues, Glu92 and Lys95, located within its hydrophobic core. As a result, TM1 was able to direct correct topology for less than half of nascent CFTR chains. In contrast to TM1, TM2 signal sequence activity was both efficient and specific. Even in the absence of a functional TM1 signal sequence, TM2 was able to direct CFTR N terminus topology through a ribosome-dependent posttranslational mechanism. Mutating charged residues Glu92 and Lys95 to alanine improved TM1 signal sequence activity as well as the ability of TM1 to independently direct CFTR N terminus topology. Thus, a single functional signal sequence in either the first or second TM segment was sufficient for directing proper CFTR topology. These results identify two distinct and redundant translocation pathways for CFTR N terminus transmembrane assembly and support a model in which TM2 functions to ensure correct topology of CFTR chains that fail to translocate via TM1. This novel arrangement of topogenic information provides an alternative to conventional cotranslational pathways of polytopic protein biogenesis.

Short-term clinical study on a new aqueous humor drainage implant for refractory glaucoma

OBJECTIVE

To investigate the therapeutic effect of a new aqueous humor drainage (HAD) implant made in China for the treatment of refractory glaucoma.

METHODS

The implant was designed by ourselves and manufactured by Beijing Rubber Products Design and Research Institute. From July, 1993 to September, 1995, we observed 40 patients (41 eyes) with refractory glaucoma treated by implantation surgery, including 16 eyes with neovascular glaucoma (NVG) and 25 eyes with non-neovascular glaucoma (NNVG).

RESULTS

The mean period of postoperative follow-up was 9.2 (range, from 3-27) months, the intraocular pressure (IOP) was lowered from preoperative 7.20 +/- 1.51 kPa to postoperative 2.40 +/- 1.33 kPa in NVG group and from preoperative 6.27 +/- 1.07 kPa to postoperative 2.00 +/- 2.93 kPa in NNVG group. The success rate was 81% in NVG group and 84% in NNVG group. The common postoperative complications were flat anterior chamber, hyphema and choroidal detachment.

CONCLUSIONS

Our newly designed aqueous humor drainage implant is an economical implant in China and one of the alternative and effective methods for the treatment of refractory glaucoma. It can be widely used in clinics.

In vitro characterization of the anti-human cytomegalovirus activity of PMEA (Adefovir)

PMEA [9-[2-(phosphonomethoxy)ethyl]adenine; adefovir] has shown anti-cytomegalovirus activity in animal models and in preliminary human trials. PMEA diphosphate (PMEApp), the active antiviral metabolite of PMEA, is a potent inhibitor of human cytomegalovirus (HCMV) DNA polymerase. PMEA is efficiently taken up and phosphorylated to PMEApp in numerous human cell lines. In vitro replication of wild type and drug resistant HCMV clinical isolates is effectively inhibited by PMEA. PMEA in combination with other anti-HCMV agents shows additive inhibition of HCMV replication.

HER2/Neu and the Ets transcription activator PEA3 are coordinately upregulated in human breast cancer

HER2/Neu is overexpressed in 25-30% of all human breast cancers as a result of both gene amplification and enhanced transcription. Transcriptional upregulation of HER2/neu leads to a 6-8-fold increased abundance of its mRNA per gene copy and likely results from the elevated activity of transcription factors acting on the HER2/neu promoter. Here we report that transcripts of PEA3, an ETS transcription factor implicated in oncogenesis, were increased in 93% of HER2/Neu-overexpressing human breast tumor samples. Analyses to uncover the molecular basis for elevated PEA3 transcripts in HER2/Neu-positive breast tumors revealed that the HER2/Neu receptor tyrosine kinase initiated an intracellular signaling cascade resulting in increased PEA3 transcriptional activity; transcriptionally-activated PEA3 stimulated HER2/neu and PEA3 gene transcription by binding to sites in the promoters of these genes. PEA3 also activates transcription of genes encoding matrix-degrading proteinases, enzymes required for tumor cell migration and invasion. These findings implicate PEA3 in the initiation and progression of HER2/Neu positive breast cancer, and suggest that PEA3 and signaling proteins affecting its regulation are appropriate therapeutic targets.

Structural cues involved in endoplasmic reticulum degradation of G85E and G91R mutant cystic fibrosis transmembrane conductance regulator

Abnormal folding of mutant cystic fibrosis transmembrane conductance regulator (CFTR) and subsequent degradation in the endoplasmic reticulum is the basis for most cases of cystic fibrosis. Structural differences between wild-type (WT) and mutant proteins, however, remain unknown. Here we examine the intracellular trafficking, degradation, and transmembrane topology of two mutant CFTR proteins, G85E and G91R, each of which contains an additional charged residue within the first putative transmembrane helix (TM1). In microinjected Xenopus laevis oocytes, these mutations markedly disrupted CFTR plasma membrane chloride channel activity. G85E and G91R mutants (but not a conservative mutant, G91A) failed to acquire complex N-linked carbohydrates, and were rapidly degraded before reaching the Golgi complex thus exhibiting a trafficking phenotype similar to DeltaF508 CFTR. Topologic analysis revealed that neither G85E nor G91R mutations disrupted CFTR NH2 terminus transmembrane topology. Instead, WT as well as mutant TM1 spanned the membrane in the predicted C-trans (type II) orientation, and residues 85E and 91R were localized within or adjacent to the plane of the lipid bilayer. To understand how these charged residues might provide structural cues for ER degradation, we examined the stability of WT, G85E, and G91R CFTR proteins truncated at codons 188, 393, 589, or 836 (after TM2, TM6, the first nucleotide binding domain, or the R domain, respectively). These results indicated that G85E and G91R mutations affected CFTR folding, not by gross disruption of transmembrane assembly, but rather through insertion of a charged residue within the plane of the bilayer, which in turn influenced higher order tertiary structure.

Inhibition of growth of Dictyostelium discoideum amoebae by bisphosphonate drugs is dependent on cellular uptake

PURPOSE

The aim of the study was to determine whether bisphosphonates are internalised by Dictyostelium amoebae and whether cellular uptake is required for their growth-inhibitory effects. Bisphosphonates inhibit growth of amoebae of the slime mould Dictyostelium discoideum, by mechanisms that appear to be similar to those that cause inhibition of osteoclastic bone resorption.

METHODS

Cell-free extracts prepared from amoebae that had been incubated with bisphosphonates were analysed by 31P-n.m.r, spectroscopy or ion-exchange f.p.l.c., to identify the presence of bisphosphonates or bisphosphonate metabolites respectively. The growth-inhibitory effect of bisphosphonates towards Dictyostelium amoebae was also examined under conditions in which pinocytosis was inhibited.

RESULTS

All of the bisphosphonates studied were internalised by Dictyostelium amoebae, probably by fluid-phase pinocytosis, and could be detected in cell-free extracts. Amoebae that were prevented from internalising bisphosphonates by pinocytosis were markedly resistant to the growth-inhibitory effects of these compounds. In addition, bisphosphonates encapsulated within liposomes were more potent growth inhibitors of Dictyostelium owing to enhanced intracellular delivery of bisphosphonates.

CONCLUSIONS

All bisphosphonates inhibit Dictyostelium growth by intracellular mechanisms following internalisation of bisphosphonates by fluid-phase pinocytosis. It is therefore likely that bisphosphonates also affect osteoclasts by interacting with intracellular, rather than extracellular, processes.

ESX: a structurally unique Ets overexpressed early during human breast tumorigenesis

The >30 known members of the Ets multigene family of transcriptional regulators are increasingly being recognized for their involvement in early embryonic development and late tissue maturation, directing stage-specific and tissue-restricted programs of target gene expression. Identifiable primarily by their 85 amino acid ETS DNA-binding domain and dispersed across all metazoan lineages into distinct subfamilies, Ets genes also produce malignancies in humans and other vertebrates when overexpressed or rearranged into chimeras retaining the ETS domain, suggesting that their oncogenic potential is determined by the program of target genes they regulate. Searching for Ets factors that regulate expression of the HER2/neu (c-erbB2) oncogene in human breast cancer, we identified a new epithelium-restricted Ets encoding an ETS domain homologous to the Drosophila E74/human Elf-1 subfamily, an amino-terminal region (A-region or Pointed domain) homologous to the distantly related Ets-1 subfamily, and a serine-rich box homologous to the transactivating domain of the lymphocyte-restricted High Mobility Group (HMG) protein, SOX4. Recombinant protein encoded by ESX (for epithelial-restricted with serine box) exhibits Ets-like DNA binding specificity in electrophoretic mobility shift assays and, in transient transfection assays, transactivates Ets-responsive promoter elements including that found in the HER2/neu oncogene. ESX is located at chromosome 1q32 in a region known to be amplified in 50% of early breast cancers, is heregulin-inducible and overexpressed in HER2/neu activated breast cancer cells. Tissue hybridization suggests that ESX becomes overexpressed at an early stage of human breast cancer development known as ductal carcinoma in situ (DCIS).

Effect of incorporation of cidofovir into DNA by human cytomegalovirus DNA polymerase on DNA elongation

Cidofovir (CDV) (HPMPC) has potent in vitro and in vivo activity against human cytomegalovirus (HCMV), CDV diphosphate (CDVpp), the putative antiviral metabolite of CDV, is an inhibitor and an alternate substrate of HCMV DNA polymerase. CDV is incorporated with the correct complementation to dGMP in the template, and the incorporated CDV at the primer end is not excised by the 3'-to-5' exonuclease activity of HCMV DNA polymerase. The incorporation of a CDV molecule causes a decrease in the rate of DNA elongation for the addition of the second natural nucleotide from the singly incorporated CDV molecule. The reduction in the rate of DNA (36-mer) synthesis from an 18-mer by one incorporated CDV is 31% that of the control. However, the fidelity of HCMV DNA polymerase is maintained for the addition of the nucleotides following a single incorporated CDV molecule. The rate of DNA synthesis by HCMV DNA polymerase is drastically decreased after the incorporation of two consecutive CDV molecules; the incorporation of a third consecutive CDV molecule is not detectable. Incorporation of two CDV molecules separated by either one or two deoxynucleoside monophosphates (dAMP, dGMP, or dTMP) also drastically decreases the rate of DNA chain elongation by HCMV DNA polymerase. The rate of DNA synthesis decreases by 90% when a template which contains one internally incorporated CDV molecule is used. The inhibition by CDVpp of DNA synthesis by HCMV DNA polymerase and the inability of HCMV DNA polymerase to excise incorporated CDV from DNA may account for the potent and long-lasting anti-CMV activity of CDV.

[A short-term clinical study on a new aqueous humor drainage implant for refractory glaucoma]

OBJECTIVE

To investigate the therapeutic effect of a new aqueous humor drainage implant made in China for treatment of refractory glaucoma.

METHODS

The implant was designed by ourselves and manufactured by Beijing Rubber Products Design & Research Institute. From July 1993 to September 1995, we observed 40 cases (41 eyes) with refractory glaucoma treated with the implantation surgery, including neovascular glaucoma (NVG) 16 eyes, non-neovascular glaucoma (NNVG) 25 eyes.

RESULTS

The mean period of postoperative follow-up was 9.2 (range 3-27 months) months, the IOP was lowered from preoperative 7.20 +/- 1.51 kPa to postoperative 2.40 +/- 1.33 kPa in NVG group and from preoperative 6.27 +/- 1.07 kPa to postoperative 2.00 +/- 2.93 kPa in NNVG group. The success rate was 81% in NVG group and 84% in NNVG group. The common postoperative complications were flat anterior chamber, hyphema, choroidal detachment and so on.

CONCLUSIONS

Our newly designed aqueous humordrainage implant provides an economic implant in China. The method of implantation is simple, is one of the effective methods for treatment of refractory glaucoma and can be widely used in clinics.

Detection of chlamydia trachomatis by polymerase chain reaction assay in nonbacterial prostatitis

OBJECTIVE

To evaluate the sensitivity and specificity of polymerase chain reaction (PCR) technique in comparison with diethylaminoethyl-dextran (DEAE-dextran)-treated HeLa cell culture method for detection of chlamydia trachomatis in nonbacterial prostatitis.

METHODS

Thirty patients had symptoms of prostatitis for at least three months. None of them had evidence of urethritis on urethral Gram stain or recurrent bacteria. Routine localization of bacteria was negative. White blood cell count in expressed prostatic secretion (EPS) was more than 10 per high-power field (10/HPF). None of these patients had received antibiotics during the six weeks before the study, although all had received multiple courses of antibiotics for treatment of prostatitis syndrome. The EPS specimens from these patients were placed in 0.5-ml Eppendorf tubes and stored at -70 degrees C until they were processed for PCR and DEAE-dextran-treated HeLa cell culture.

RESULTS

Six specimens were positive for C. trachomatis by both PCR and culture, and 21 were negative by both tests. There were three specimens with discrepant results, including two that were positive by PCR and negative by culture, and one that was positive by culture and negative by PCR. Comparing PCR technique with culture method, the sensitivity, specificity, positive predictive value and negative predictive value of the former were 85.7%, 91.3%, 75.0% and 95.5% respectively.

CONCLUSIONS

PCR analysis of EPS is a highly sensitive and specific noninvasive technique for detection of chlamydia trachomatis. It provides a unique opportunity for early identification of or rapid screening for chlamydia trachomatis infection in patients with nonbacterial prostatitis. The reliability of PCR assay offers clinicians a clear indication for the initiation of treatment of chlamydia trachomatis infection.

Establishment of doxorubicin-resistant human bladder cancer cell line (BUI-87/ADMR) and its mechanism of multidrug resistance

OBJECTIVE

To establish a doxorubicin-resistant human bladder cancer cell line, BIU-87/ADMR, and to study its biological characteristics and mechanism of drug resistance.

METHODS

A human bladder cancer cell line resistant to doxorubicin, BIU-87/ADMR, has been established in vitro by exposing BIU-87 parent cells to progressively increasing concentrations of the drug over a period of 8 months. The cell line has been characterized in terms of growth kinetics, morphology, cross-resistance to other anticancerous agents, pharmacokinetics of daunorubicin and expression of P-glycoprotein (P-gp) which is closely related to the MDR phenotype.

RESULTS

The BIU-87/ADMR cell line was 6.3 times more resistant to doxorubicin than the parent BIU-87. It exhibited cross-resistance to doxorubicin derivatives (epirubicin, daunorubicin), vincristine and etoposide, but not to cisplatin and mitomycin C. Compared to the parent cells, the resistant cells have a slower growth rate and lower confluent density. Unlike the parent BIU-87, about 75% of the BIU-87/ADMR cells showed a positive reaction with monoclonal antibody against P-gp, JSB-1. Intracellular drug accumulation studies with fluorescence spectrometry indicated that the resistance exhibited by the BIU-87/ ADMR line was mainly caused by an increased active efflux.

CONCLUSIONS

The results suggest that MDR is an important phenomenon in bladder cancer and that more than one pathway of MDR may be present in human bladder cancer cell lines. BIU-87/ADMR may be a useful model for the development of new chemotherapeutic strategies in overcoming drug-resistance in the treatment of bladder cancer.

Repression of gonadotropin-releasing hormone promoter activity by the POU homeodomain transcription factor SCIP/Oct-6/Tst-1: a regulatory mechanism of phenotype expression?

POU domain transcription factors are required for neuropeptide expression in selected subsets of hypothalamic neuroendocrine neurons. We now report that expression of the gonadotropin-releasing hormone (GnRH) gene, which controls sexual development, is regulated by the POU protein SCIP/Oct-6/Tst-1. Reverse transcriptase PCR cloning and RNase protection assays demonstrated the presence of SCIP/Oct-6/Tst-1 mRNA in the GnRH-producing neuronal cell line GT1-7. The physiological relevance of this regulatory activity was suggested by the detection of SCIP/Oct-6/Tst-1 mRNA in a subset of GnRH neurons in the hypothalamus of prepubertal female rats. Coexpression of SCIP/Oct-6/Tst-1 in neuronal cells inhibited rat GnRH (rGnRH) promoter activity via three regions of the proximal rGnRH promoter containing SCIP/Oct-6/Tst-1 binding sites. DNase I footprinting, gel shift assays, and DNA and protein mutagenesis studies indicated that both direct DNA binding and protein-protein interactions are required for SCIP/Oct-6/Tst-1 modulation of GnRH gene expression. Activation of SCIP/Oct-6/Tst-1 expression in terminally differentiated GnRH neurons may be a factor determining the ratio of phenotypically "inactive" versus "active" GnRH neurons during postnatal life.

[The study and primary application of multimedia teaching and learning system for diseases of temporomandibular joint]

A multimedia computer-assistant teaching and learning system for diseases of temporomandibular joint was reported in this paper. It was designed and implemented in Windows (Chinese) on PC 486. It was emphasized that interactive teaching and learning was an available, funny method and student was the focus of teaching and learning in this system. A satisfied result was obtained by utilizing of this multimedia teaching and learning system for primary application.

Continuous and group sequential conditional probability ratio tests for phase II clinical trials

We present continuous and group sequential designs for phase II clinical trials based on the sequential conditional probability ratio test (SCPRT). The SCPRT is derived from a conditional likelihood ratio, where the conditioning is on what the corresponding (reference) fixed sample size test (RFSST) would achieve. In other words, we obtain the sequential design by controlling the maximum probability that the SCPRT does not agree with the RFSST. We shall discuss the difference between SCPRT and stochastic curtailment which also uses the concept of conditional distribution. We show that the power function of the SCPRT is virtually the same as that of the RFSST and its average sample numbers (ASNs) are close to those of Wald's sequential probability ratio test (SPRT), whereas its maximum sample size is no greater than that of the RFSST. Thus the SCPRT has all the desirable properties, such as allowing the use of the RFSST at the last analysis, of the Fleming procedure for phase II trials. The SCPRT, however, preserves the power function of the RFSST better and gives us the option for continuous monitoring. Our recommendation, therefore, is to use a group SCPRT boundary (for interim analyses performed as scheduled) embedded in a continuous SCPRT boundary (for unplanned interim analyses and analyses at times based on data trends). We provide as well a bias-adjusted estimator of the success rate after sequential stopping. We illustrate the method with several examples. The method applies to any single-arm clinical trial with binary endpoints, such as the classic paired design.

Structure of the distal human gonadotropin releasing hormone (hGnrh) gene promoter and functional analysis in Gt1-7 neuronal cells

To assess potential species-specific expression of gonadotropin releasing hormone (GnRH), the distal human (h) GnRH promoter was cloned, characterized and tested in gene transfer studies. The nucleotide sequence of approximately 3.8 kb of 5'-flanking region was determined. Homology to the rat (r) GnRH sequence was observed in the proximal promoter region between -551 h (-424 r) and the transcriptional start site and within multiple distal promoter regions. In contrast, there was little similarity in the sequences between -1131/-551 h and -1031/-424 r. A deletion panel of 5'-flanking hGnRH promoter constructs was made and tested in transient transfection assays in GnRH-producing mouse GT1-7 neuronal cells. The largest hGnRH promoter construct (-3832/+5 h) exhibited high levels of reporter activity, similar to that observed with the largest rGnRH construct (-3026/+116 r). However, in contrast to the rat gene, deletion of distal promoter sequences of the hGnRH promoter to -1971, -1131 or -551 did not result in a decrease in luciferase reporter activity. Further truncation to -350 resulted in a 3-fold decrease in luciferase activity. There was no preferential use of the putative upstream hGnRH start site in neuronal cells. DNase I protection assays showed unique protection patterns with nuclear extracts from GT1-7 and Gn10 neuronal cells and the hGnRH and rGnRH promoter fragments. These data suggest the presence of different cis-acting elements and transacting factors that mediate species-specific neuronal GnRH expression.

Kinetic analysis of the interaction of cidofovir diphosphate with human cytomegalovirus DNA polymerase

Cidofovir [CDV,(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine, HPMPC] is an acyclic cytosine nucleoside phosphonate analog with potent in vitro and in vivo activity against a broad spectrum of herpesviruses. CDV diphosphate (CDVpp), the putative antiviral metabolite of CDV, is a competitive inhibitor of dCTP and an alternate substrate for human cytomegalovirus (HCMV) DNA polymerase. HCMV DNA polymerase used a synthetic DNA primer-template with a Km value of 90 +/- 8 nM and incorporated dCTP approximately 42 times more efficiently than CDVpp. HCMV DNA polymerase also utilized a synthetic DNA primer containing a single molecule of CDV at the 3'-terminus. The Km value for this DNA primer-template was 165 +/- 42 nM and incorporation of dCTP was approximately 17 times more efficient than that of CDVpp. The slower rate of incorporation of CDVpp was due mostly to the higher Km value of CDVpp toward the enzyme-primer-template complexes. These data demonstrate that incorporation of a single CDV into DNA by HCMV DNA polymerase does not lead to chain termination.

The effects of radiofrequency catheter ablation on the metabolic enzymes and Ca(++)-ATPase of myocytes

Using histochemical technique, the effects of radiofrequency catheter ablation (RFCA) on the activities of LDH, SDH, CCO, and Ca++-ATPase of guinea-pig ventricular myocytes were examined. The histological changes were observed for comparison. Radiofrequency energy (500 kHz) delivered was 20 W x 10 s. The results were as follows: RFCA resulted in significant impairments in all the four kinds of enzymes but without statistical differences in the areas involved in this energy level. No statistically significant difference was found between the ranges of enzymatic damages and areas of pathological lesions. These findings showed a consistency in areas of the histological and histochemical lesions resulted from RFCA.

Assembly-defective OmpC mutants of Escherichia coli K-12

Novel ompC(Dex) alleles were utilized to isolate mutants defective in OmpC biogenesis. These ompC(Dex) alleles also conferred sensitivity to sodium dodecyl sulfate (SDS), which permitted the isolation of SDS-resistant and OmpC-specific phage-resistant mutants that remained Dex+. Many mutants acquired resistance against these lethal agents by lowering the OmpC level present in the outer membrane. In the majority of these mutants, a defect in the assembly (metastable to stable trimer formation) was responsible for lowering OmpC levels. The assembly defects in various mutant OmpC proteins were caused by single-amino-acid substitutions involving the G-39, G-42, G-223, G-224, Q-240, G-251, and G-282 residues of the mature protein. This assembly defect was correctable by an assembly suppressor allele, asmA3. In addition, we investigated one novel OmpC mutant in which an assembly defect was caused by a disulfide bond formation between two nonnative cysteine residues. The assembly defect was fully corrected in a genetic background in which the cell's ability to form disulfide bonds was compromised. The assembly defect of the two-cysteine OmpC protein was also mended by asmA3, whose suppressive effect was not achieved by preventing disulfide bond formation in the mutant OmpC protein.

[Significance of diagnosis and prognosis for breast carcinoma with examination of Ag-NORs]

The argyrophilic nucleolar organizer regions (Ag-NORs) was measured in the tissue sample aspirated with fine needle for 17 cases of breast benign lesion and 46 cases of breast cancer, by analysis of their micro-image with light microscope and computed. The results indicated that the amount of Ag-NORs in the nuclei of breast cancer was increased while the percentage of average areas occupied by Ag-NORs was decreased. It was significant statistically in comparing with benign lesion (P < 0.05). In addition, the amount of Ag-NORs in the nuclei of breast cancer with and that without metastasis was not different markedly (P > 0.05). However the percentage of average areas occupied by Ag-NORs was different statistically (P < 0.05). The conclusion of Ag-NORs is of benefit to distinguish from benign and malignant tumours of breast as well as significant for evaluating the prognosis for breast cancer.

IUD use and the risk of ectopic pregnancy: a meta-analysis of case-control studies

Because of inconsistent findings among case-control studies on the relationship between IUD use and the risk of ectopic pregnancy, a meta-analysis of published literature was conducted. From 1977 through 1994, 19 publications regarding 16 studies of ectopic pregnancy and IUD use were found by MEDLINE and manual search. The odds ratio (ORs) of ectopic pregnancy with current and past IUD use in each study were pooled. A quality score system was developed to assess each study. Funnel plot was used to assess potential publication biases. For current IUD use, when cases were compared to pregnant controls, there was an increased risk of ectopic pregnancy (pooled OR: 10.63, 95% confidence interval (CI): 7.66-14.74); when cases were compared to non-pregnant controls, there was no risk of ectopic pregnancy (pooled OR: 1.06, 95% CI: 0.91-1.24). Past IUD use could mildly increase the risk of ectopic pregnancy (pooled OR: 1.40, 95% CI: 1.23-1.59). Selecting pregnant or non-pregnant women as controls, however, did not affect the OR estimates of past IUD use. Current IUD use does not increase the risk of the ectopic pregnancy. However, a pregnancy with an IUD in situ is more often an ectopic one than a pregnancy with no IUD. Past IUD use could mildly elevate the risk of ectopic pregnancy.

Ten-year experience with abdominal aortic aneurysm repair in octogenarians: early results and late outcome

PURPOSE

This study was undertaken to determine the mortality and morbidity rates associated with abdominal aortic aneurysm (AAA) repair in octogenarians and to identify factors that may influence survival in this age group.

METHODS

One hundred fourteen patients (mean age 83 years) were admitted consecutively with 106 infrarenal and eight juxtarenal AAAs from 1984 through 1993. Ninety-four AAAs were asymptomatic, whereas 20 patients with symptoms had 11 intact and nine ruptured AAAs. The mean AAA diameter was 6.7 cm. Repair consisted of aortic bifurcation grafts in 77 patients (67%), tube grafts in 35 (31%), and extraanatomic procedures in 2 (2%). A total of 29 patients (25%) had undergone previous coronary artery bypass (24 patients) or transluminal coronary angioplasty (five patients) either incidentally or as a preliminary procedure before resection of their AAAs.

RESULTS

The 30-day mortality rate for the entire series was 14%, but it declined from 23% (11/48) during the first 5 years to 8% (5/66) during the second 5 years of the study period (p = 0.028). Fatal complications occurred in nine (9.6%) of the 94 patients with asymptomatic AAAs and in seven (35%) of the 20 patients who had symptomatic AAAs (p = 0.008). Considering only patients with asymptomatic AAAs, the early mortality rate in the second 5 years (4%) improved significantly (p = 0.038) in comparison to that (17%) for the first 5 years of the study period. The cumulative 5-year survival rate of 48% for 97 available operative survivors was not quite so good as that (59%) for the normal male population of the United States at the age of 80 years (p < 0.0001). Nevertheless, the 5-year survival rate was 80% for 27 operative survivors who received previous myocardial revascularization compared with 38% for 70 others who did not (p = 0.0077). Multiple Cox-regression analysis identified the perioperative homologous blood requirement (p = 0.03) and a history of previous myocardial revascularization (p = 0.03) as significant independent factors influencing late survival.

CONCLUSIONS

Repair of AAAs in properly selected octogenarians is safe and durable. When otherwise indicated, it should not be withheld on the basis of advanced age alone. Prior treatment of severe coronary artery disease is associated with enhanced late survival, but patient selection probably is an important consideration in this respect.

Structure-activity relationships of new heterocycle-containing bisphosphonates as inhibitors of bone resorption and as inhibitors of growth of Dictyostelium discoideum amoebae

The mechanisms by which bisphosphonate drugs inhibit osteoclast-mediated bone resorption are unclear. Effects of bisphosphonates on cellular enzymes, metabolic pathways, and osteoclast morphology have previously been described and could culminate in a generalized cytotoxic effect or a decreased capacity of osteoclasts to resorb bone. Recent studies of the structure-activity relationship for the bisphosphonate side chain indicate, however, that at least the newer generations of nitrogen-containing bisphosphonates probably act by binding to a specific target at a site that is complementary in structure to the bisphosphonate side chain. We have previously proposed that such a target for bisphosphonates is also present in amoebae of the cellular slime mold Dictyostelium discoideum, because growth of this microorganism is inhibited by a wide range of bisphosphonates in a manner that closely reflects the antiresorptive potencies of the bisphosphonates in vivo. We have added support for this view by examining the potency towards Dictyostelium of bisphosphonates in which slight changes in the structure of the side chain or conformational restrictions to the side chain have marked effects on antiresorptive potency. The changes in the side chain that affected the in vivo antiresorptive potency of the bisphosphonates consistently affected in a similar manner the potency of the bisphosphonates as inhibitors of the growth of Dictyostelium amoebae. These observations confirm that bisphosphonate drugs have a molecular target that is common to both Dictyostelium amoebae and osteoclasts.

Binding of an ETS-related protein within the DNase I hypersensitive site of the HER2/neu promoter in human breast cancer cells

Promoter elements accounting for HER2 (c-erbB-2/neu) overexpression were searched for in several human breast cancer cell lines (MDA-453, BT-474, ZR-75-1, MCF-7) known to express constitutively a 30-fold range in HER2 transcripts per gene copy. HER2 overexpressing cells showed a single prominent DNase I hypersensitive site near a conserved and hitherto unrecognized ets response element (GAGGAA), located 38 bases down-stream from the CAAT box and directly 5' of the TATA box in the human HER2 promoter. Transient transfection of HER2 promoter constructs (0.125, 0.5, and 2.0 kilobase pairs (kb)) demonstrated that the most proximal promoter region (0.125 kb) was capable of conferring up to 30-fold enhanced activity in HER2-overexpressing cell lines relative to low HER2-expressing control lines. Site-directed mutagenesis of the ets response element (GAGGAA-->GAGAGA) caused a > or = 60% reduction in promoter activity affecting at least 0.5 kb of upstream HER2 regulatory sequence. Gel-shift assays with nuclear extracts and oligonucleotide sequences spanning the 0.125-kb promoter region detected an ETS-immunoreactive complex, present most abundantly in cells overexpressing HER2, whose high-affinity binding depended on the GAGGAA response element. Methylation interference confirmed the ETS-specific pattern of protein binding by this complex to guanine bases in the ets response element. UV cross-linking and immunoprecipitation implicate a approximately 60-kDa ETS protein, and candidate ETS genes expressed in these breast cancer cells include GABP alpha, elk-1, elf-1, and PEA3.

Inhibitory effects of bisphosphonates on growth of amoebae of the cellular slime mold Dictyostelium discoideum

Bisphosphonates are inhibitors of bone resorption and are used increasingly as therapeutic agents for treating clinical disorders of skeletal metabolism. Their mode of action is still not fully understood. The demonstration that methylenebisphosphonate, a simple methylene analog of pyrophosphate, inhibits the axenic growth of amoebae of the slime mold Dictyostelium discoideum and is incorporated into adenine nucleotides suggested that this organism might be useful in elucidating the cellular effects of bisphosphonates. We examined 24 bisphosphonates, including all those of clinical interest as inhibitors of osteoclast-mediated bone resorption in vivo, for their effects on D. discoideum. All the geminal bisphosphonates inhibited growth of Dictyostelium, although the effectiveness of individual compounds varied widely. When the bisphosphonates were ranked there was a remarkable similarity between the order of potency as inhibitors of growth of Dictyostelium and the order of potency as inhibitors of bone resorption. Thus, bisphosphonates with more complex side-chain structures, especially those containing a nitrogen group, were more potent than simple substituted bisphosphonates, some inhibiting Dictyostelium growth even at concentrations below 10 microM. It therefore appears that the mechanism by which bisphosphonates prevent Dictyostelium growth could be similar to the mechanism by which these compounds affect the activity of osteoclasts. Because the mechanisms of action of bisphosphonates on osteoclasts remains unclear, Dictyostelium may provide an additional model for studying the biochemical mode of action of bisphosphonates. Furthermore, these studies suggest that Dictyostelium may also be a convenient organism for rapid evaluation of potentially active bisphosphonates.

[Immune function of guifudihuang pills (GFDH) and their oral liquid preparation]

Experimental observation was made on the effect of GFDH pills and their oral liquid preparation on thymus and spleen weight, formation of the antibody haemolysis plaque and phagocytic function of the macrophages of peritoneal cavity. The result revealed that both GFDH pills and their oral liquid preparation were found helpful to the enhancement of immunological function. The oral liquid preparation also increased markedly the plasma level of testosterone in immature rats.

[Mitochondrial DNA polymorphism of cattle (Bos taurus) and mithun (Bos frontalis) in Yunnan Province]

An analysis of cleavage patterns of mtDNA by restriction endonuclease was performed for fifteen Yunnan native cattle, two Kunming black and white cow, and one mithun (Bos frontalis). Two types of mtDNA molecule were detected in Yunnan native cattle: five individuals showed the type of yellow cattle (Bos taurus), the other ten showed that of zebu cattle (Bos indicus), suggesting their European and zebu origins. The mtDNA in Kunming black and white cow also consists of two restriction types. The mithun mtDNA showed the type of zebu cattle, indicating the close relationship between the origins of mithun and zebu cattle.

Purinergic agonist induction of metallothionein

Metallothionein (MT) protein is readily induced in vivo in rat liver by adenosine and adenosine agonists (2-chloroadenosine, 5-(N-ethyl) carboxamido adenosine, and 5-chloro-5-deoxyadenosine). These presumably operate via AMP/adenosine receptors of the P1 (A2) type, which use the cAMP pathway. ATP was ineffective as an inducer for MT. 2-Chloroadenosine was the most effective inducer (7.27-fold at 11 hr). This induction was blockable by the adenosine antagonists, caffeine and theophylline. MT protein induction by 2-chloroadenosine in primary cultured rat hepatocytes was modest (1.55-fold), but this was also blocked by theophylline. MT mRNA induction was assessed using dot blot and Northern gel assays. Large inductions by 2-chloroadenosine (5.1- to 41-fold) were seen, and these were detectable as early as 2 hr in vivo. Two rat hepatoma cell lines (EC3 and 2M) were studied in vitro. Modest inductions of MT mRNA were seen: 2.10-fold for EC3 and 4.12-fold for 2M. Our studies implicate the potential role of the purinergic system in the modulation of transcription of MT genes in rat liver. The sources of adenosine in vivo that might cause induction of MT mRNA and protein are not well defined, but adenosine may be important as a signal in stress response situations involving tissue damage, such as ischemia, hypoxia, and hemorrhagic shock.

Phorbol ester induction of rat hepatic metallothionein in vivo and in vitro

1. The induction of metallothionein (MT) protein by TPA (O-tetradecanoyl phorbol acetate), a protein kinase C activator, was demonstrated in vivo in rat liver and in vitro in rat hepatocytes in primary culture. In vivo half maximal induction at 25 hr was seen at 26 nmol TPA/kg body wt. Five- to seven-fold inductions were seen in vivo. De novo protein synthesis was required for this induction as demonstrated by cycloheximide inhibition of [35S]cysteine incorporation into MT protein. 2. TPA induction of MT protein in primary cultures of rat hepatocytes reached levels of 2.6-4.1-fold, as assessed by [35S]cysteine incorporation, 1.34-2.20-fold, as assessed by 109Cd binding in a metal displacement/HPLC assay, and 2.5-5-fold, as assessed by 109Cd binding in a metal displacement/Sephadex G-75 Superfine assay. 3. The induction of MT mRNA by TPA was demonstrated in vivo in rat liver and in vitro in 2 rat hepatoma cell lines, EC3 and 2M. MT mRNA was quantitated using dot blot and Northern gel assays. In vivo TPA induced hepatic MT mRNA 2.36-5.88-fold (dot blot) and 7.4-22-fold (Northern gels). In vitro TPA induced MT mRNA 1.71-15.26-fold in EC3 cells and 2.23-8.43-fold in 2M cells. MT mRNA was 0.54 kb, and alpha-tubulin mRNA was 1.62 kb in size on Northern gels. 4. TPA induction of MT protein and mRNA in vivo and in vitro is rapid and persistent and occurs at low concentrations. The 2 rat hepatoma cell lines provide a useful system in which to study MT induction in vitro without confounding secondary effects which can occur in vivo.

Induction of zinc metallothionein by calcium ionophore in vivo and in vitro

The calcium ionophore, A23187, can induce rat hepatic metallothionein (MT) when administered in vivo (5.8-fold, 5.0 microM, 11 h) and rat hepatocyte MT when administered in vitro (10.70-fold, 1.0 microM, 24 h). Several rat hepatoma cell lines (2M, 4.55-fold; JM2, 12.29-fold; EC3, 14.12-fold; HTC, 7.99-fold) and a normal rat liver cell line (Clone 9, 39.67-fold) were tested for their inducibility of MT mRNA by Cd2+ (10 microM, 8 h). Quantitatively, JM2 and 2M made the most MT mRNA, while HTC made the least. A23187 (0.1-7.0 microM) was studied as an inducer of MT mRNA in these cell lines (except for HTC) and in HeLa. A variety of responses and tolerances were seen with inductions ranging up to 32.11-fold. Quantitatively, the best responding cell lines were EC3 and 2M. A combination induction experiment, using TPA, a protein kinase C activator, and A23187 in EC3 cells revealed an additive effect of the two inducers on MT mRNA levels: TPA (10 nM), 11.71-fold; A23187 (3.0 microM), 6.71-fold; and TPA + A23187, 20.00-fold. These studies have implicated perturbations in cytosolic calcium ion concentrations, caused by the ionophore A23187, as being involved in the complicated signaling systems which can lead to induction of MT mRNA and protein.