Calorimetric study on coordination of tridentate imidazolyl calix[6]arene ligands to zinc ion in organic solvents

Complexation of three kinds of tris(imidazolyl)calix[6]arenes containing alternate p-substituents (Calix-tBu, R(1) = R(2) = tert-butyl; Calix-NH(2), R(1) = tert-butyl, R(2) = NH(2); Calix-NO(2), R(1) = tert-butyl, R(2) = NO(2)) with Zn(ClO(4))(2)(H(2)O)(6) in acetonitrile, methanol, and THF was investigated via isothermal titration calorimetry (ITC). For the coordination of these calixarene ligands to Zn(II) in acetonitrile, typical one-phase exothermic titration curves were obtained, indicating the formation of 1:1 ligand-Zn(II) complexes accompanied by large conformational changes of the ligands. In contrast, the complexation in methanol was endothermic and dominated by favorable entropy changes. The entropy gains were achieved by extensive desolvation from both Zn(II) and the ligands. ITC measurements suggest a 2:1 ligand-Zn(II) complex formation in THF in the presence of excess ligands (Calix-NH(2) and Calix-NO(2)). The 2:1 complexes were converted to 1:1 complexes upon further addition of Zn(ClO(4))(2)(H(2)O)(6). The results indicate the important role of a coordinating solvent (acetonitrile) for direct formation of the 1:1 complexes under the conditions of excess ligand. Complexation of a ditopic ligand (Calix-Tri) with three triazole moieties on the wider rim was also studied via ITC. The first coordination of the imidazole moieties to Zn(II) was an exothermic process. This was followed by the entropically favorable coordination of the triazole moieties to the divalent cation. We have also investigated exchange of the fourth ligand (H(2)O) of the Zn(II) complex of Calix-NH(2) with butylamine, heptylamine, acetonitrile, and acetamide in a noncompetitive solvent, THF. The ΔH(0) tended to decrease upon increasing the electron-pair-donating ability of the guest ligand, whereas it was also affected by an entropic term due to restricted rotation of the guest ligand inside the calixarene cavity.

High Frequency Loss Mechanism in Polymers Filled with Dielectric Modifiers

We analyzed the high frequency dielectric relaxation mechanism in high-k composite materials using film substrates made of low loss organic resin filled with ferroelectric ceramics and with single wall carbon nanotubes (SWNT). We performed broadband permittivity measurements of high-k film substrates at frequencies of 100 Hz to about 10 GHz. In order to analyze the effect of the dielectric thickness, dielectric constant, loss and conductive loss on the impedance characteristics, we used a High Frequency Structure Simulator to perform a full wave numerical analysis of several power planes. Small angle neutron scattering (SANS) was used to probe the dispersion of SWNTs in polymer matrices. It was found that organic-ceramic composites exhibit an intrinsic high frequency relaxation behavior that gives rise to frequency dependent dielectric loss. The highest frequency relaxation process dominates the overall loss characteristic. In the case of polymers modified with SWNTs, we observed that 2% mass fraction of p-doped semi-conducting SWNTs increases the dielectric constant by 3 orders of magnitude, in apparent violation of the mixing-rule. The hybrid material appears to have preferential coupling within the dispersed phase. The experimental data and numerical simulation indicate that these materials can play a significant role as embedded passive devices with functional characteristics superior to that of discrete components.

259 Cdk7 AND CYCLIN H, BUT NOT Mat1, ARE INVOLVED IN MEIOTIC RESUMPTION OF PORCINE IMMATURE OOCYTE

The complex kinase Cdk-activating kinase (CAK) consists of the catalytic subunit Cdk7, regulatory subunit Cyclin H, and assembly factor Mat1. The CAK is essential for maturation-promoting factor (MPF) activation by phosphorylating threonine 161 (T161) of Cdc2 in mitosis. Although it is known that meiotic resumption of oocytes is regulated by MPF activity, the role of CAK in meiosis is still unclear. In the present study, we attempted to confirm the involvement of CAK in meiotic resumption of porcine immature oocyte. Cumulus–oocyte complexes (COC) were collected from antral follicles of gilts and cultured up to 48 h in TYH medium containing 20% porcine follicular fluid, 3.2 mg/mL of BSA, and 1.0 IU mL–1 of pregnant mare serum gonadotropin. The T161 phosphorylation level of Cdc2 in cultured oocytes was analysed by Western blot analysis. The transcripts were collected from noncultured or cultured oocytes, and Cdk7, Cyclin H, and Mat1 expression were detected by RT-PCR. Overexpression of Cdc2 or inhibition of Cdk7, Cyclin H, and Mat1 during oocyte maturation was performed by microinjection of mRNA or antisense RNA into ooplasm of immature COC and verified by Western blot or semiquantitative RT-PCR. Maturation-promoting factor kinase activity was assayed by Histone H1 kinase activity assay. Statistical analyses in this study were carried out by Student’s t-test. The T161 phosphorylation of Cdc2 was found during the culture period from 18 h to 48h, which was after germinal vesicle breakdown (GVB). Overexpression of Cdc2 increased the incidence of GVB at 18 h, but overexpression of mutant Cdc2 (replaced T161 by alanine) had no influence on GVB. These results indicate that T161 phosphorylation of Cdc2 is important for meiotic resumption. Next, we attempted to confirm the CAK function during oocyte maturation. Transcripts of Cdk7, Cyclin H, and Mat1 were detectable throughout the culture period. Inhibition of Cdk7 and Cyclin H caused a decrease in T161 phosphorylation and MPF activity, and the incidence of GVB was significantly lower than in nontreated oocytes. In contrast, Mat1-inhibited oocytes resumed meiosis and developed to the metaphase II stage, and the incidence was not different between Mat1-inhibited oocytes and nontreated oocytes. These results suggest that Cdk7 and Cyclin H are working as CAK and activate Cdc2 by T161 phosphorylation, although Mat1 is dispensable during oocyte maturation.

A novel technology for on-site cupric oxide recovery from cupric chloride etchant waste

For on-site copper recovery in print circuit board factories, we propose a novel technology to obtain cupric oxide with a low content ratio of chloride from high chloride concentration waste, such as cupric chloride etchant waste. Our technology is designed to avoid formation of double salt and accumulation of cupric hydroxide. In the proposed method, etchant waste mixed with hydrogen peroxide solution is added to sodium hydroxide solution by stepwise addition. We performed lab-scale experiments on the influence of reaction pH conditions on the content ratio of chloride in recovering cupric oxide. The results show that recycled cupric oxide tends to contain a lower content ratio of chloride under higher starting temperatures and higher final pH conditions of the reaction. We also confirmed the optimized conditions; the starting temperature of the sodium hydroxide solution is higher than 70 degrees C, and the final pH of the reaction is 11.5 to 12. Based on the optimized temperature and pH conditions, we also performed a pilot trial to recover cupric oxide from real etchant waste. Then, we successfully obtained cupric oxide with a content ratio of chloride in 80 mg-Cl/kg-CuO.

Structural basis of the lactate-dependent allosteric regulation of oxygen binding in arthropod hemocyanin

Hemocyanin (Hc) is an oxygen carrier protein in which oxygen binding is regulated by allosteric effectors such as H(+) and L-lactate. Isothermal titration calorimetric measurements showed that L-lactate binds to dodecameric and heterohexameric Hc and to the CaeSS3 homohexamer but not to the CaeSS2 monomer. The binding of lactate caused no change in the optical absorption and x-ray absorption spectra of either oxy- or deoxy-Hc, suggesting that no structural rearrangement of the active site occurred. At pH 6.5, the oxygen binding rate constant k(obs) obtained by flash photolysis showed a significant increase upon addition of L-lactate, whereas L-lactate addition had little effect at pH 8.3. Lactate binding caused a concentration-dependent shift in the interhexameric distances at pH 6.5 based on small angle x-ray scattering measurements. These results show that L-lactate affects oxygen affinity at pH 6.5 by modulating the global structure of Hc without affecting its binuclear copper center (the active site). In contrast to this, the active site structure of deoxy-Hc is affected by changes in pH (Hirota, S., Kawahara, T., Beltramini, M., Di Muro, P., Magliozzo, R. S., Peisach, J., Powers, L. S., Tanaka, N., Nagao, S., and Bubacco, L. (2008) J. Biol. Chem. 283, 31941-31948). Upon addiction of lactate, the kinetic behavior of oxygen rebinding for Hc was heterogeneous under low oxygen concentrations at pH 6.5 due to changes in the T and R state populations, and the equilibrium was found to shift from the T toward the R state with addition of lactate.

Effect of oviductal epithelial cells on fertilization of pig oocytes in vitro

The incidence of polyspermy is reduced by co-culture of pig oocytes with oviductal cells. It is not known whether the effect is due to soluble factors secreted into the medium. Oviductal epithelial cell monolayers and cell-conditioned media were prepared and their effects on fertilization of pig oocytes were examined. In vitro matured pig oocytes were inseminated with ejaculated boar spermatozoa at a concentration of 1x10(5) or 1x10(6) cells/ml and co-cultured in one of 5 culture systems: an oviductal epithelial cell monolayer, a fibroblast monolayer, an oviductal epithelial cell-conditioned medium, or a fibroblast-conditioned medium, and medium alone (modified-TCM199). In all 5 systems, the majority (range 85 to 100%) of the oocytes were penetrated by sperm. When oocytes were inseminated with spermatozoa at a concentration of 1x10(5) cells/ml, the percentages of monospermic oocytes were significantly higher in the oocytes co-cultured with oviductal epithelial cells and fibroblasts than that of the oocytes cultured without these cells. In contrast, when oocytes were inseminated with spermatozoa at a concentration of 1x10(6) cells/ml, the percentages of monospermic oocytes were significantly higher in the oocytes co-cultured with epithelial cells than those cultured with the fibroblasts and in the control medium. The suppressive effect on polyspermy was observed in the oviductal epithelial cells-conditioned medium when oocytes were inseminated with spermatozoa at both concentrations of 1x10(5) and 1x10(6) cells/ml. The effect was absent in the fibroblasts-conditioned medium. Moreover, the effect of the epithelial cells was maintained during the culture period, whereas the proportion of monospermic oocytes co-cultured with fibroblasts showed a gradual decrease, reaching 0% after 16 h. These results suggest that a soluble factor(s) derived from the oviductal epithelial cells decreased the number of spermatozoa penetrating the oocytes without suppressing the high rate of fertilization.

Expression of estrogen receptor and proto-oncogene messenger ribonucleic acids in reproductive tracts of neonatally diethylstilbestrol-exposed female mice with or without post-puberal estrogen administration

Perinatal treatment of female mice with natural and synthetic estrogens including diethylstilbestrol (DES) results in estrogen-independent persistent proliferation and cornification of the vaginal epithelium. The dynamics of the induction of estrogen receptor (ER), c-jun, c-fos and c-myc mRNAs by 17 beta-estradiol (E2) was examined in the uterus and vagina of neonatally DES-exposed and -unexposed ovariectomized adult mice. In the uterus of neonatally DES-unexposed ovariectomized mice, the expression of ER mRNA increased within 1 h after E2 administration and declined by 12 h thereafter. ER mRNA in the vagina decreased within 1 h after the stimulation and recovered by 12 h thereafter. In the uterus, c-jun and c-fos mRNAs increased in concentration within 1 h after E2 administration, showing a peak 3 h after the stimulation; they decreased with time thereafter. In the vagina, the concentration of c-jun and c-fos mRNAs increased rapidly, reaching a peak within 1 h after the stimulation. However, the expression of c-myc in uterus and vagina was not changed by postpuberal E2. These results suggest that estrogen regulation of ER and proto-oncogene mRNAs in the vagina differs from those in the uterus. In the neonatally DES-exposed ovariectomized adult mice, uterine ER mRNA expression levels were significantly higher than in the unexposed ovariectomized controls; however, vaginal levels were drastically lower than in the controls. Expression of c-jun and c-fos mRNAs was greater in both the uterus (3- and 6-fold, respectively) and the vagina (18- and 4-fold) of neonatally DES-exposed mice than in controls. The ER mRNA and the increased levels of c-fos and c-jun mRNAs in both uterus and vagina of neonatally DES-exposed ovariectomized mice were not further altered by post-puberal E2 and may be related to ovary-independent persistent changes in the genital tract.

Vascular endothelial growth factor expression by hyalocytes and its regulation by glucocorticoid

AIM

Tumour necrosis factor-alpha (TNF-alpha) is one of the major inflammatory cytokines involved in the pathogenesis of various vitreoretinal diseases. The authors investigated the effect of hypoxia, TNF-alpha and dexamethasone on vascular endothelial growth factor (VEGF) expression by cultured hyalocytes.

METHODS

Hyalocytes were isolated from bovine vitreous. Hypoxic and TNF-alpha-dependent effects on cultured hyalocytes were investigated using several assays to determine VEGF protein expression, hypoxia-inducible factor (HIF)-1alpha protein levels, HIF-1alpha-DNA-binding ability and VEGF mRNA stability. The effects of dexamethasone on VEGF expression and its intracellular signalling under hypoxic or TNF-alpha stimulated conditions were also examined.

RESULTS

Hypoxic conditions and TNF-alpha stimulation induce VEGF expression in hyalocytes. These stimuli also stabilise HIF-1alpha protein and increase its DNA-binding ability. Dexamethasone significantly inhibits both HIF-1alpha protein levels and HIF-1alpha-DNA-binding activity, and also decreases the hypoxic- and TNF-alpha -dependent induction of VEGF expression in hyalocyte. However, dexamethasone has no significant effect on the stability of VEGF mRNA.

CONCLUSIONS

Hyalocytes may be involved in various vitreoretinal diseases by increasing HIF-1alpha protein stability and HIF-1alpha-DNA binding, and thus increasing VEGF production under pathological conditions. Dexamethasone seems to be capable of inhibiting hypoxic and TNF-alpha dependent VEGF production, presumably via its inhibitory effects on HIF-1alpha protein levels and its DNA-binding activity.

Stearoyl-CoA desaturase mRNA expression during bovine adipocyte differentiation in primary culture derived from Japanese Black and Holstein cattle

Stearoyl-CoA desaturase (SCD) catalyzes the synthesis of monounsaturated fatty acids (MUFAs). In cattle, the MUFAs are related to softness and flavor of meat. In order to investigate gene expression profile during bovine preadipocyte differentiation, we isolated stromal-vascular cells from perirenal adipose tissues of Japanese Black and Holstein steers. Gene expression level of adipocyte type fatty acid binding protein (FABP4), SCD, sterol regulatory element binding protein 1 (SREBP1) and CCAAT/enhancer binding protein alpha (C/EBP-alpha) were elucidated by real-time PCR assay. The levels of SCD mRNA expression were significantly increased to 10.8 and 6.3-fold in Japanese Black and Holstein, respectively, on day 1 of the culture. The difference in SCD expression between the two breeds may reflect differences in the fat development characteristics of the cattle breeds. Although transcription factors SREBP1 and C/EBP-alpha are supposed to regulate SCD expression, expression levels of the two factors were not completely consistent with that of SCD.

Thermodynamics of Hydrophobic Interactions: Entropic Recognition of a Hydrophobic Moiety by Poly(Ethylene Oxide)–Zinc Porphyrin Conjugates

The recognition of 4-alkylpyridines by water-soluble poly(ethylene oxide)-zinc porphyrin conjugates was studied with a focus on the thermodynamic parameters of binding. Microcalorimetric studies indicated that binding of the alkyl group of the guest in water is driven by the entropic term (delta DeltaH0 = DeltaH0(4-pentylpyridine) - DeltaH0(4-methylpyridine) = +1.7 kJ mol(-1), deltaT DeltaS0 = TDeltaS0(4-pentylpyridine) - TDeltaS0(4-methylpyridine) = +11.8 kJ mol(-1) at 298 K), thus showing the significance of water reorganization during host-guest interaction. The enthalpy-entropy compensation temperature of binding of 4-alkylpyridines was as low as 38 K; only below this temperature could the enthalpic term be a driving force. The binding affinity was modulated by the addition of cations and by varying the degree of polymerization of poly(ethylene oxide), which suggests that guest binding is coupled with polymer conformation.