Maize VP1 complements Arabidopsis abi3 and confers a novel ABA/auxin interaction in roots

The maize Vp1 gene and abi3 gene of Arabidopsis are believed to be orthologs based on similarities of the mutant phenotypes and amino acid sequence conservation. Here we show that expression of VP1 driven by the 35S promoter can partially complement abi3-6, a deletion mutant allele of abi3. The visible phenotype of seed produced from VP1 expression in the abi3 mutant background is nearly indistinguishable from wild type. VP1 fully restores abscisic acid (ABA) sensitivity of abi3 during seed germination and suppresses the early flowering phenotype of abi3. The temporal regulation of C1-beta-glucuronidase (GUS) and chlorophyll a/b binding protein (cab3)-GUS reporter genes in developing seeds of 35S-VP1 lines were similar to wild type. On the other hand, two qualitative differences are observed between the 35S-VP1 line and wild type. The levels of CRC and C1-GUS expression are markedly lower in the seeds of 35S-VP1 lines than in wild type suggesting incomplete complementation of gene activation functions. Similar to ectopic expression of ABI3 (Parcy et al., 1994), ectopic expression of VP1 in vegetative tissue enhances ABA inhibition of root growth. In addition, 35S-VP1 confers strong ABA inducible expression of the normally seed-specific cruciferin C (CRC) gene in leaves. In contrast, ectopic ABA induction of C1-GUS is restricted to a localized region of the root elongation zone. The ABA-dependent C1-GUS expression expanded to a broader area in the root tissues treated with exogenous application of auxin. Interestingly, auxin-induced lateral root formation is completely suppressed by ABA in 35S-VP1 plants but not in wild type. These results indicate VP1 mediates a novel interaction between ABA and auxin signaling that results in developmental arrest and altered patterns of gene expression.

Efficient evolutionary algorithm for the thin-film synthesis of inhomogeneous optical coatings

We propose an efficient evolutionary approach for the thin-film synthesis of inhomogeneous optical coatings. The proposed approach consists of global and local strategies by integration of decreasing-based mutations and self-adaptive mutations by means of family competition and adaptive rules. Numerical results indicate that the proposed approach performs robustly and is competitive with other approaches. Our approach, although somewhat slower, is flexible and can easily be adopted to other application domains. Our approach is also able to generate homogeneous solutions with two materials available.

Modulation of cell growth by the hepatitis C virus nonstructural protein NS5A

Hepatitis C virus nonstructural protein, NS5A, is a phosphoprotein produced from the processing of the viral polyprotein precursor. NS5A associates with several cellular proteins in mammalian cells, and the biological consequences of this interaction are currently unknown. To this end, five stable NS5A-expressing murine and human cell lines were established. Tetracycline-regulated NIH3T3 cells and rat liver epithelial cells as well as the constitutive, NS5A-expressing, human Chang liver, HeLa, and NIH3T3 cells all exhibited cell growth retardation compared with the control cells. Cell cycle analysis by flow cytometry indicated that the NS5A-expressing human epitheloid tumor cells had a reduced S phase and an increase in the G(2)/M phase, which could be explained by a p53-dependent induction of p21(Waf1/Cip1) protein and mRNA levels. NS5A interacts with Cdk1 in vivo and in vitro, and a significant portion of the p21(Waf1/Cip1) was found to be in a complex with Cdk2 in the NS5A-expressing human hepatic cell line. Cdk1 and cyclin B1 proteins were also reduced in human Chang liver cells consistent with the increase in G(2)/M phase. Our results suggest that the NS5A protein causes growth inhibition and cell cycle perturbations by targeting the Cdk1/2-cyclin complexes.

Optical coating designs using the family competition evolutionary algorithm

A robust evolutionary approach, called the Family Competition Evolutionary Algorithm (FCEA), is described for the synthesis of optical thin-film designs. Based on family competition and adaptive rules, the proposed approach consists of global and local strategies by integrating decreasing mutations and self-adaptive mutations. The method is applied to three different optical coating designs with complex spectral quantities. Numerical results indicate that the proposed approach performs very robustly and is very competitive with other approaches.

Electrokinetic flow in a planar slit covered by an ion-penetrable charged membrane

The electrokinetic flow of an electrolyte solution in a planar slit covered by an ion-penetrable charged membrane layer is analyzed theoretically. An approximate analytical expression for the spatial variation in the electrical potential is derived, and the electroosmotic velocity, the total electric current, and the streaming potential of the system under consideration are evaluated. The effects of epsilon' (relative permittivity of liquid phase/relative permittivity of membrane layer), eta' (viscosity of liquid phase/viscosity of membrane layer) and the valence of anions (coions) on the volumetric flow rate and total current are examined. We show that the effect of the valence of cations (counterions) on the volumetric flow rate is less significant than that of epsilon' and that of eta'. However, the effect of epsilon' on the total current is less significant than that of the valence of cations and that of eta'. The variation of total current as a function of ionic strength is found to have a local minimum, regardless of whether a pressure gradient is applied or not. The absolute streaming potential has a local maximum as the concentration of fixed charge varies, which was not found in previous studies.

A genetic algorithm with adaptive mutations and family competition for training neural networks

In this paper, we present a new evolutionary technique to train three general neural networks. Based on family competition principles and adaptive rules, the proposed approach integrates decreasing-based mutations and self-adaptive mutations to collaborate with each other. Different mutations act as global and local strategies respectively to balance the trade-off between solution quality and convergence speed. Our algorithm is then applied to three different task domains: Boolean functions, regular language recognition, and artificial ant problems. Experimental results indicate that the proposed algorithm is very competitive with comparable evolutionary algorithms. We also discuss the search power of our proposed approach.

A family competition evolutionary algorithm for automated docking of flexible ligands to proteins

In this paper, we study an evolutionary algorithm for flexible ligand docking. Based on family competition and adaptive rules, the proposed approach consists of global and local strategies by integrating decreasing mutations and self-adaptive mutations. To demonstrate the robustness of the proposed approach, we apply it to the problems of the first international contests on evolutionary optimization. Following the description of function optimization, our approach is applied to a dihydrofolate reductase enzyme with the anti-cancer drug methotrexate and with two analogs of the antibacterial drug trimethoprim. Our numerical results indicate that the proposed approach is robust. The docked lowest energy structures have rms derivations ranging from 0.72 A to 1.98 A with respect to the corresponding crystal structure.

Tin-protoporphyrin potentiates arsenite-induced DNA strand breaks, chromatid breaks and kinetochore-negative micronuclei in human fibroblasts

Numerous reports have shown that oxidative stress is involved in arsenite-induced genetic damage. Arsenite is also a potent inducer of heme oxygenase (HO)-1. To understand whether HO-1 could function as a cellular antioxidant and protect cells from arsenite injury, the effects of tin-protoporphyrin (SnPP), a competitive inhibitor of HO-1, on arsenite-induced genetic damage were examined in human skin fibroblasts (HFW). In the present study, we found that SnPP at 100 microM significantly potentiated arsenite-induced cytotoxicity, DNA strand breaks (assayed by alkaline single cell gel electrophoresis(SCGE)), and chromatid breaks. Although arsenite alone mainly induced kinetochore-plus micronuclei (K(+)-MN), SnPP only synergistically enhanced kinetochore-negative micronuclei (K(-)-MN). The increase in K(-)-MN by SnPP cotreatment was consistent with the increase in DNA strand breaks and chromatid breaks caused by SnPP. However, at higher arsenite doses, K(+)-MN was significantly reduced by SnPP. Pretreatment of HFW cells with hemin, an inducer of HO-1, significantly attenuated the cytotoxicity of arsenite. Therefore, the present results suggest that HO-1 induction by arsenite plays certain roles in protecting cells from arsenite-induced injury.

Prevention of acute and delayed cisplatin-induced nausea and vomiting with intravenous ondansetron plus intravenous dexamethasone

BACKGROUND

We conducted a prospective study to evaluate the anti-emetic effect of cisplatin-induced nausea and vomiting with intravenous (i.v.) ondansetron plus i.v. dexamethasone.

METHODS

One hundred forty-six chemotherapy (CT)-naive patients were enrolled in the study. They were scheduled to receive cisplatin 50 to 100 mg/m2 (mean, 53 mg/m2) on day 1 followed immediately by continuous infusion of 5-fluorouracil with or without other CT agents on the subsequent days. Three 8 mg doses of ondansetron i.v. were given at 4-hour intervals plus 20 mg dexamethasone i.v. infusions from the start of CT, followed by 5 mg dexamethasone i.v. every 12 hours, and the administration of dexamethasone was discontinued after the completion of CT.

RESULTS

The rates of complete protection from acute and delayed vomiting/nausea obtained in these patients were 97.3%/93.2% and 71.2%/60.3%, respectively. The rates of complete protection from both acute and delayed nausea were 70.5% and 58.9%, respectively. By comparison, the total control rate of vomiting was less in female patients than in male patients (p = 0.017), and the total control rate of nausea was lower in the age group less than 50 years (p = 0.045). The time from the start of CT to the onset of nausea appeared to be earlier than that for vomiting (log-rank test, p = 0.045). Adverse events tended to be minor, with constipation and hiccups as the most common.

CONCLUSION

These results indicate that i.v. ondansetron plus i.v. dexamethasone is a feasible anti-emetic therapy in an inpatient setting. I.v. ondansetron plus i.v. dexamethasone is highly effective in preventing acute cisplatin-induced nausea and vomiting.

Recombinant polyclonal antibody libraries

We describe a technology for generating recombinant polyclonal antibody libraries (PCALs) that enables the creation and perpetuation of standardized mixtures of polyclonal whole antibodies specific for a multiantigen (or polyantigen). Therefore, this technology combines the advantages of targeting multiple antigenic determinants -- high avidity, low likelihood of antigen 'escape variants', and efficient mediation of effector functions, with the advantages of using monoclonal antibodies -- unlimited supply of standardized reagents and the availability of the genetic material for desired manipulations. The technology for generating recombinant polyclonal antibody libraries begins with the creation of phage display Fab (antibody) libraries. This is followed by selection of sublibraries with desired antigen specificities, and mass transfer of the variable region gene pairs of the selected sublibraries to a mammalian expression vector for generation of libraries of polyclonal whole antibodies. We review here our experiments for selection of phage display antibody libraries against microbes and tumor cells, as well as the recent literature on the selection of phage display antibody libraries to multiantigen targets.

Control of cisplatin-induced emesis with intravenous ondansetron plus intravenous dexamethasone: a crossover study of triple 8-mg dose of ondansetron

Two hundred seventy-five patients were enrolled in one of two arms in a crossover fashion. Arm A: three 8-mg doses of ondansetron intravenous (IV) were given at 4-hour intervals plus dexamethasone 20 mg IV from the start of chemotherapy followed by dexamethasone 5 mg IV every 12 hours. Arm B: as in arm A but with three 8-mg doses of ondansetron IV were given at 24-hour intervals substituted for ondansetron IV given at 4-hour intervals. There were 237 patients in arm A and 223 patients in arm B. Complete protection from acute and delayed vomiting/nausea obtained in arm A was 94.5%/90.3% and 71.3%/57.8%, respectively; protection obtained in arm B was 92.7%/91.0% and 71.7%/60.5%, respectively. No differences were observed in control of acute emesis after the addition of dexamethasone to ondansetron, given as either a triple 8-mg dose at 4-hour intervals or a single 8-mg dose. The triple dose of ondansetron given at 24-hour intervals was also not more effective than ondansetron given at 4-hour intervals in preventing delayed emesis when dexamethasone was added. However, the former improved control of delayed nausea on day 2. Adverse events tended to be minor, with constipation and hiccup the most common.

Tuberculosis presenting with pelvic mass, peritoneal lesions, and elevation of serum CA125 mimicking malignant tumor: a case report

Tuberculosis is a curable infective disease which can mimic a malignant tumor. We report on a young woman who presented with abdominal fullness, body weight loss, and microcytic anemia. A pelvic mass and peritoneal lesions were found. The serum CA125 level was high. The initial gynecologic echo and abdominal CT scan revealed bilateral ovarian mass with peritoneal lesions, and malignancy was highly suspected. Diagnostic laparoscopy was performed, and peritoneal tuberculosis was pathologically proven. Combination anti-tuberculosis therapy was prescribed for one year. She was followed up in the outpatient clinic regularly with symptom improvement, body weigh gain, and improvement of anemia. We suggest that in cases of a pelvic mass and peritoneal lesions, with elevation of the serum CA125 level, tuberculosis should always be kept on the list of differential diagnoses. A tissue diagnosis should always be obtained before treatment, regardless of initial image study and laboratory findings.

Transactivation of the human cdc2 promoter by adenovirus E1A. E1A induces the expression and assembly of a heteromeric complex consisting of the CCAAT box binding factor, CBF/NF-Y, and a 110-kDa DNA-binding protein

Cyclin-dependent kinases (CDKs) play an important role in the eukaryotic cell cycle progression. Cdc2 (CDK1) is expressed in late G(1)/S phase and required for G(2) to M phase transition in higher eukaryotes. The oncoproteins, SV40 large T antigen and adenovirus E1A, induce a 110-kDa protein which specifically recognizes the two inverted CCAAT motifs of the cdc2 promoter in cycling cells and plays an essential role in transactivation of the human cdc2 promoter. Since these CCAAT motifs also conform to the consensus binding sites for the ubiquitous heterotrimeric transcription factor, CBF/NF-Y, the role of CBF/NF-Y in the transactivation of the cdc2 promoter was examined in this study. Our results indicate that CBF/NF-Y and the 110-kDa protein interact with the CCAAT box motif to form a heteromeric complex. However, mutagenesis of the pentanucleotide CCAAT motif or in the presence of urea greater than 2.5 M, no heteromeric complex was formed. In contrast, the 110-kDa protein could still bind the mutant CCAAT motif or with the wild type motif in the presence of 2.5 M urea. Furthermore, E1A.12S induced the gene expression of all three subunits of CBF/NF-Y. Coexpression of E1A and a dominant negative mutant NF-YA subunit significantly reduced the E1A-mediated transactivation of the cdc2 promoter in a dose-dependent manner. These results support the conclusion that E1A protein mediates optimal transactivation of the human cdc2 promoter by inducing the expression and assembly of a heteromeric complex consisting of the 110-kDa protein and the CBF/NF-Y which interacts with the two CCAAT motifs of the cdc2 promoter.

Inhibition of secretion by 1,3-Cyclohexanebis(methylamine), a dibasic compound that interferes with coatomer function

We noted previously that certain aminoglycoside antibiotics inhibit the binding of coatomer to Golgi membranes in vitro. The inhibition is mediated in part by two primary amino groups present at the 1 and 3 positions of the 2-deoxystreptamine moiety of the antibiotics. These two amines appear to mimic the epsilon-amino groups present in the two lysine residues of the KKXX motif that is known to bind coatomer. Here we report the effects of 1, 3-cyclohexanebis(methylamine) (CBM) on secretion in vivo, a compound chosen for study because it contains primary amino groups that resemble those in 2-deoxystreptamine and it should penetrate lipid bilayers more readily than antibiotics. CBM inhibited coatomer binding to Golgi membranes in vitro and in vivo and inhibited secretion by intact cells. Despite depressed binding of coatomer in vivo, the Golgi complex retained its characteristic perinuclear location in the presence of CBM and did not fuse with the endoplasmic reticulum (ER). Transport from the ER to the Golgi was also not blocked by CBM. These data suggest that a full complement of coat protein I (COPI) on membranes is not critical for maintenance of Golgi integrity or for traffic from the ER to the Golgi but is necessary for transport through the Golgi to the plasma membrane.

Transactivation of the human cdc2 promoter by adenovirus E1A in cycling cells is mediated by induction of a 110-kDa CCAAT-box-binding factor

Cyclin-dependent protein kinases (Cdks) are key regulatory proteins of the eukaryotic cell cycle. Cdc2 is expressed in late G1/S phase and functions in the G2 to M phase transition. Adenovirus E1A proteins are known to induce the expression of p34cdc2 and DNA synthesis in normal quiescent cells. In this study, mutational analysis of the human cdc2 promoter revealed that transactivation of the promoter by the E1A proteins in cycling cells is mediated through the two CCAAT box binding motifs. A 110-kDa protein (CBF/cdc2) was identified in nuclear extracts from monkey kidney (CV-1) cells stably expressing E1A as well as from adenovirus-transformed human 293 cells. Further, we show that this EIA-inducible CBF/cdc2 is related to the CBF which was shown to activate the heat shock protein 70 promoter. Analyses of the functional domain(s) of E1A required for the induction of the CBF and transactivation of the cdc2 promoter in these conditions revealed that E1A mutants which were defective in binding the pRB family of proteins or the cellular p300 protein were still active in assays measuring the induction of the CBF and transactivation of the cdc2 promoter, albeit with reduced efficiencies. But the E1A mutant which lost both functional domains was inactive in these assays. These results suggest that E1A has redundant functional domains for the induction of the 110-kDa CBF and activation of human cdc2 gene expression.

Potassium currents in freshly dissociated uterine myocytes from nonpregnant and late-pregnant rats

In freshly dissociated uterine myocytes, the outward current is carried by K+ through channels highly selective for K+. Typically, nonpregnant myocytes have rather noisy K+ currents; half of them also have a fast-inactivating transient outward current (ITO). In contrast, the current records are not noisy in late pregnant myocytes, and ITO densities are low. The whole-cell IK of nonpregnant myocytes respond strongly to changes in [Ca2+]o or changes in [Ca2+]i caused by photolysis of caged Ca2+ compounds, nitr 5 or DM-nitrophene, but that of late-pregnant myocytes respond weakly or not at all. The Ca2+ insensitivity of the latter is present before any exposure to dissociating enzymes. By holding at -80, -40, or 0 mV and digital subtractions, the whole-cell IK of each type of myocyte can be separated into one noninactivating and two inactivating components with half-inactivation at approximately -61 and -22 mV. The noninactivating components, which consist mainly of iberiotoxin-susceptible large-conductance Ca2+-activated K+ currents, are half-activated at 39 mV in nonpregnant myocytes, but at 63 mV in late-pregnant myocytes. In detached membrane patches from the latter, identified 139 pS, Ca2+-sensitive K+ channels also have a half-open probability at 68 mV, and are less sensitive to Ca2+ than similar channels in taenia coli myocytes. Ca2+-activated K+ currents, susceptible to tetraethylammonium, charybdotoxin, and iberiotoxin contribute 30-35% of the total IK in nonpregnant myocytes, but <20% in late-pregnant myocytes. Dendrotoxin-susceptible, small-conductance delayed rectifier currents are not seen in nonpregnant myocytes, but contribute approximately 20% of total IK in late-pregnant myocytes. Thus, in late-pregnancy, myometrial excitability is increased by changes in K+ currents that include a suppression of the ITO, a redistribution of IK expression from large-conductance Ca2+-activated channels to smaller-conductance delayed rectifier channels, a lowered Ca2+ sensitivity, and a positive shift of the activation of some large-conductance Ca2+-activated channels.

Deregulation of cdc2 gene expression correlates with overexpression of a 110 kDa CCAAT box binding factor in transformed cells

Eukaryotic cell cycle progression is regulated by an orderly and sequential activation of several cyclin-dependent kinases, which phosphorylate key substrates during this process. p34cdc2, the catalytic subunit of cdc2 kinase, is expressed at the late G1/S boundary and is required for the G2-->M phase transition. Transactivation of the human cdc2 promoter by the DNA tumor virus-encoded oncogenic protein SV40 large T antigen is mediated by induction of a novel 110 kDa CCAAT box binding factor (CBF/cdc2). To investigate whether induction of CBF/cdc2 is an intrinsic property of the viral oncoprotein or is a common event during transformation of normal cells, expression of CBF/cdc2 was analyzed in many human tumor cell lines and in rodent cells spontaneously transformed or stably expressing various oncogenes. Our results showed that CBF/cdc2 was overexpressed in all transformed cells examined, including human 293, MCF-7, HeLa and HepG2 cells. Moreover, expression of CBF/cdc2 was elevated in spontaneously transformed rat liver epithelial cells (C4T), but not detectable in the non-tumorigenic parental (RLE) cells. The elevated levels of CBF/cdc2 expression in C4T cells correlated well with increased cdc2 mRNA and p34cdc2 levels. CBF/cdc2 was also overexpressed in a rat liver epithelial cell line (WB) stably transfected with various oncogenes, v-myc, v-Ha-ras and mutated rat neu and v-src. Using an electrophoretic mobility shift assay, specific binding of CBF/cdc2 to the CCAAT box motifs of the human cdc2, cycA and cdc25C promoters was detected, suggesting that transcription of these cell cycle regulatory genes are coordinately activated by CBF/cdc2.

Surface characterization and biological properties study of silicone rubber membrane grafted with phospholipid as biomaterial via plasma induced graft copolymerization

Poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) was grafted onto the surface of a silicon rubber (SR) membrane (pMPC-SR) by plasma induced grafted copolymerization (PIP). Argon plasma was used to activate the SR surfaces. Determination was also made of the influences of grafted copolymerization reaction time, reaction temperature, and monomer concentration on polymerization yield. The surface properties of SR were characterized by ATR-FTIR, ESCA, and SEM. In those analyses the ATR-FTIR spectra indicated that the pMPC grafted onto the SR surface at 1720 and 3300 cm(-1). The elemental composition and different carbon bindings on the surface of the SR were examined by ESCA. An increasing P1s/C1s value g was obtained in the grafted polymerization yield with a concentration of 0.05-0.5M of MPC in the isolated ethanol solution. The surface morphologies of pMPC-SR differed more than those of control and Ar plasma treated surfaces. The difference could have been caused by the homogeneous graft polymerization of pMPC onto the SR membrane. In the biological analyses, protein adsorption on pMPC-SR surfaces was reduced. The reduced level increased with an increase in the pMPC grafted amount. The epithelial cell attachment and growth onto these samples were suppressed. The blood compatibility for a series of pMPC-SR surfaces was examined by platelet adhesion. Blood platelet morphologies in contact with the high ratio of pMPC-SR surfaces were maintained, meaning that in this case the release reaction for platelets never occurred. Consequently, the high amount of pMPC-SR surface had excellent blood compatibility, further suggesting that prevention of adhesion, activation of platelets, and adsorption of blood protein could be achieved.

Cloning of the American cockroach Cr-PII allergens: evidence for the existence of cross-reactive allergens between species

BACKGROUND

Previously, we have identified the 28 and 32 kd proteins as additional important allergens from the American cockroach (Periplaneta americana) Cr-PII allergenic fraction.

OBJECTIVE

The aim of this study was the cloning of P. americana Cr-PII allergens.

METHODS

A lambdagt22A cDNA library constructed from P. americana mRNA was packaged into Escherichia coli Y1090 (r-), and clones recognized by murine anti-Cr-PII monoclonal antibodies and human IgE antibodies were isolated, sequenced, and subcloned into pET 21 and expressed in E. coli BL21(DE3).

RESULTS

Six Cr-PII-positive clones recognized by human IgE antibodies were isolated. Two clones, C6 and C17, were sequenced, and we found encoding proteins of 228 and 274 amino acids with no cysteine or any potential N-glycosylation site, with predicted masses of 25.8 and 31.14 kd, respectively. Both molecules contain internal repeated sequences with a 94% identity between them. C6 and C17 showed 59% and 77.3% skin reactivities, respectively, on 22 cockroach-sensitive atopic patients. Both clones were found to have 28.9% to 31.8% identities to ANG12 protein, a precursor of the African malaria mosquito (Anopheles gambiae) and 82.7% to 85.1% identity to a nucleotide sequence of the German cockroach (Blattella germanica) Bla g Bd90K allergen. The anti-C6 and anti-C17 antibodies were able to recognize Cr-PII, recombinant proteins, five commercial American extracts, and two German cockroach extracts. Moreover, the binding of anti-C6 and anti-C17 antibodies to recombinant protein can be inhibited by B. germanica crude extract. Furthermore, Northern blot analyses have shown that B. germanica mRNAs could be detected by both cDNA probes.

CONCLUSION

Our findings provide the first evidence of antigenic cross-reactivity between P. americana and B. germanica allergens on molecular levels. The results will be a great aid in facilitating the epitope mapping and improving diagnostic and therapeutic reagents for both cockroach species.

Four-wave mixing between a soliton and noise in a system with large amplifier spacing

Depletion of soliton energy by four-wave mixing between a soliton and amplifier noise in a system with 100-km amplifier spacing is studied. Dispersion exponentially decreasing fiber is used as transmission fiber. Improvement of the system by the use of a sliding-frequency filter to reduce noise power and the depletion of soliton energy is shown. The system can be further improved by compensation for depleted soliton energy.

Sodium and calcium inward currents in freshly dissociated smooth myocytes of rat uterus

Freshly dissociated myocytes from nonpregnant, pregnant, and postpartum rat uteri have been studied with the tight-seal patch-clamp method. The inward current contains both INa and ICa that are vastly different from those in tissue-cultured material. INa is abolished by Na+-free medium and by 1 microM tetrodotoxin. It first appears at approximately -40 mV, reaches maximum at 0 mV, and reverses at 84 mV. It activates with a voltage-dependent tau of 0.2 ms at 20 mV, and inactivates as a single exponential with a tau of 0. 4 ms. Na+ conductance is half activated at -21.5 mV, and half inactivated at -59 mV. INa reactivates with a tau of 20 ms. ICa is abolished by Ca2+-free medium, Co2+ (5 mM), or nisoldipine (2 microM), and enhanced in 30 mM Ca2+, Ba2+, or BAY-K 8644. It first appears at approximately -30 mV and reaches maximum at +10 mV. It activates with a voltage-dependent tau of 1.5 ms at 20 mV, and inactivates in two exponential phases, with tau's of 33 and 133 ms. Ca2+ conductance is half activated at -7.4 mV, and half inactivated at -34 mV. ICa reactivates with tau's of 27 and 374 ms. INa and ICa are seen in myocytes from nonpregnant estrus uteri and throughout pregnancy, exhibiting complex changes. The ratio of densities of peak INa/ICa changes from 0.5 in the nonpregnant state to 1.6 at term. The enhanced role of INa, with faster kinetics, allows more frequent repetitive spike discharges to facilitate simultaneous excitation of the parturient uterus. In postpartum, both currents decrease markedly, with INa vanishing from most myocytes. Estrogen-enhanced genomic influences may account for the emergence of INa, and increased densities of INa and ICa as pregnancy progresses. Other influences may regulate varied channel expression at different stages of pregnancy.

Roles of outward potassium currents in the action potentials of guinea pig ureteral myocytes

Outward currents of freshly dissociated ureteral myocytes consist mainly of Ca(2+)-activated K+ current (IKCa) and a transient outward current (ITO). No delayed rectifier current was apparent. IKCa is small and nondecaying and fluctuates actively and irregularly. Blocking IKCa decreased resting membrane conductance and prolonged action potential plateaus, showing its roles in maintaining the resting potential and in repolarizing action potentials. It is also responsible for the membrane potential fluctuations on action potential plateaus. Neither 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride nor caffeine reduced the fluctuations in the outward current or in the action potentials, indicating that internal Ca2+ storage contributes little to the fluctuations. ITO has fast activation and inactivation kinetics with inactivation time constants of approximately 15 and 150 ms, respectively. Its highly negative voltage-availability relationship (V0.5 = -70.5 mV) suggests a low availability (< 5%) at normal resting potentials. It has only trivial effects on action potentials.

Constitutive expression of mature transforming growth factor beta1 in the liver accelerates hepatocarcinogenesis in transgenic mice

Transforming growth factor beta-1 (TGF-beta1) is a potent inhibitor of hepatocyte growth both in vivo and in vitro. In this study, we analyzed the effects of TGF-beta1 on both naturally occurring and diethylnitrosamine-induced hepatocarcinogenesis using single transgenic TGF-beta1 and double transgenic c-myc/TGF-beta1 mice in which the expression of both transgenes was targeted to the liver. Hepatocellular tumors developed spontaneously in 59% (10 of 17) of the TGF-beta1 mice by 16-18 months of age. Coexpression of TGF-beta1 and c-myc transgenes in the liver accelerated hepatic tumor growth in both the presence and absence of carcinogenic treatment. Moreover, diethylnitrosamine-initiated tumors in the c-myc/TGF-beta1 mice showed a high rate of malignant conversion associated with a reduced expression or lack of TGF-beta receptor type II. The results suggest that overexpression of TGF-beta1 may contribute to liver carcinogenesis and that loss of TGF-beta receptor type II transduced inhibitory growth signals and up-regulation of c-myc are critical steps in liver tumor progression.

The conserved B3 domain of VIVIPAROUS1 has a cooperative DNA binding activity

The biochemical activities that underlie the genetically defined activator and repressor functions of the VIVIPAROUS1 (VP1) protein have resisted in vitro analysis. Here, we show that a glutathione S-transferase (GST) fusion protein, including only the highly conserved B3 domain of VP1, has a highly cooperative, sequence-specific DNA binding activity. GST fusion proteins that include larger regions of the VP1 protein have very low activity, indicating that removal of the flanking protein sequences is necessary to elicit DNA binding in vitro. DNA competition and DNase I footprinting analyses show that B3 binds specifically to the Sph element involved in VP1 activation of the C1 gene, whereas binding to the G-box-type VP1-responsive element is of low affinity and is nonspecific. Footprint analysis of the C1 promoter revealed that sequences flanking the core TCCATGCAT motif of Sph also contribute to the recognition of the Sph element in its native context. The salient features of the in vitro GST-B3 DNA interaction are in good agreement with the protein and DNA sequence requirements defined by the functional analyses of VP1 and VP1-responsive elements in maize cells.

Growth requirements and neoplastic transformation of two types of normal human breast epithelial cells derived from reduction mammoplasty

A chemically defined culture medium was developed to support the growth of two distinctly different types of normal human breast epithelial cells (HBEC) derived from reduction mammoplasty. Type I cells expressed luminal epithelial cell markers and were deficient in gap junctional intercellular communication (GJIC), whereas Type II cells expressed basal epithelial cell markers and were efficient in GJIC. In this study, we examined and compared the growth factor and hormone requirements of these two types of cells and a series of cell lines that were obtained by sequential transfection with SV40 DNA (extended lifespan, nontumorigenic), treatment with 5-bromodeoxyuridine (BrdU)/black light (immortal and weakly tumorigenic), and infection of a virus carrying the neu oncogene (highly tumorigenic). Growth of Type I cells was inhibited by withdrawing epidermal growth factor (EGF), hydrocortisone (HC), or insulin (INS) from the culture media, but was enhanced by fetal bovine serum (FBS) supplementation. Growth of Type II cells was inhibited by withdrawal of EGF, HC, or INS from the media, and was inhibited by FBS supplementation. Withdrawal of human transferrin (HT) or 17 beta-estradiol (E2) from the media did not alter the growth of Type I or Type II cells. SV40 transfected Type I cell lines still required EGF, HC, or INS for optimal growth. However, the highly tumorigenic cell line did not show a growth dependence on EGF, HC, or INS but did appear to require HT and 3,3',5-triiodo-D.L. thyronine (T3) for optimal growth. In addition, FBS stimulated the growth of these cell lines. Thus, this study shows that Type I HBEC are distinctly different from Type II HBEC in growth response to FBS and that neoplastically transformed Type I cells could become growth factor and hormone independent.