Separation of calcium-48 isotope by crown ether chromatography using ethanol/hydrochloric acid mixed solvent.

Benzo-18-crown-6 ether resin embedded in porous silica beads was synthesized and used as the packing material for chromatographic separation of (48)Ca isotope. The aim of the present work is to develop efficient isotope enrichment process for double ß decay nuclide (48)Ca. To this end, ethanol/HCl mixed solvent was selected as the medium for the chromatographic separation. Adsorption of calcium on the resin was studied at different HCl concentrations and different ethanol mixing ratios in batch-wise experiments. A very interesting phenomenon was observed; Ca adsorption is controlled not by the overall HCl concentration of the mixed solvent, but by the initial concentration of added HCl solution. Calcium break-through chromatography experiments were conducted by using 75v/v% ethanol/25v/v% 8M HCl mixed solvent at different flow rates. The isotope separation coefficient between (48)Ca and (40)Ca was determined as 3.8×10(-3), which is larger than that of pure HCl solution system. Discussion is extended to the chromatographic HETP, height equivalent to a theoretical plate.

Calcium isotope fractionation in liquid chromatography with crown ether resin in methanol medium.

Breakthrough mode liquid chromatography was employed to investigate calcium (Ca) isotope fractionation in methanol medium. Highly porous silica beads, the inner pores of which were embedded with a benzo-18-crown-6 ether resin, were used as column packing material. Enrichment of heavier isotopes of Ca was observed in the frontal part of the respective Ca chromatograms. The values of the isotope fractionation coefficient (ϵ) were in the order of 10(-3) at 25 °C. Use of methanol as solvent has little advantage over the aqueous system as far as the values of ϵ are concerned. However, a substantial improvement was observed concerning the adsorption capacity of the crown ether resin for Ca ions. Molecular orbital calculations supported the present isotopic results in a qualitative fashion.

Isotope effects of neodymium in different ligands exchange systems studied by ion exchange displacement chromatography.

The isotope effects of neodymium in Nd-glycolate ligand exchange system were studied by using ion exchange chromatography. The separation coefficients of neodymium isotopes, ε's, were calculated from the observed isotopic ratios at the front and rear boundaries of the neodymium adsorption band. The values of separation coefficients of neodymium isotopes, ε's, for the Nd-glycolate ligand exchange system were compared with those of Nd-malate and Nd-citrate, which indicated that the isotope effects of neodymium as studied by the three ligands takes the following direction Malate > Citrate > Glycolate. This order agrees with the number of available sites for complexation of each ligand. The values of the plate height, HETP of Nd in Nd-ligand exchange systems were also calculated.

Vanadium isotopic composition of the sea squirt (Ciona savignyi).

Vanadium (V) in the sea squirt (Ciona savignyi) from Onagawa Bay, Miyagi, Japan, was isolated and purified through adsorption on a diamine resin and anion and cation exchanges after the dissolution of sea squirt samples with nitric acid and hydrogen peroxide. The (50)V/(51)V isotope ratio of V thus obtained was mass-spectrometrically determined to be from 2.51×10(-3) to 2.55×10(-3) with the average of 2.53×10(-3) by the thermal ionisation technique. This value agreed with those of vanadyl chloride and vanadyl nitrate both prepared from vanadyl sulphate (Wako Pure Chemical Industries, Ltd., Japan) and of V in coastal seawater (Shimokita Peninsula, Aomori, Japan) within experimental uncertainties (standard deviation of±0.04), which suggested that no appreciable V isotope fractionation occurs accompanying V uptake by the sea squirt from sea water.

Mass dependence of calcium isotope fractionations in crown-ether resin chromatography.

Benzo 18-crown-6-ether resin was synthesised by the phenol condensation polymerisation process in porous silica beads, of which particle diameter was ca 60micro Calcium adsorption chromatography was performed with the synthesised resin packed in a glass column. The effluent was sampled in fractions, and the isotopic abundance ratios of (42)Ca, (43)Ca, (44)Ca, and (48)Ca against (40)Ca were measured by a thermo-ionisation mass spectrometer. The enrichment of heavier calcium isotopes was observed at the front boundary of calcium adsorption chromatogram. The mass dependence of mutual separation of calcium isotopes was analysed by using the three-isotope-plots method. The slopes of three-isotope-plots indicate the relative values of mutual separation coefficients for concerned isotopic pairs. The results have shown the normal mass dependence; isotope fractionation is proportional to the reduced mass difference, (M - M')/MM', where M and M' are masses of heavy and light isotope, respectively. The mass dependence clarifies that the isotope fractionations are originated from molecular vibration. The observed separation coefficient epsilon is 3.1x10(-3) for the pair of (40)Ca and (48)Ca. Productivity of enriched (48)Ca by crown-ether-resin was discussed as the function of the separation coefficient and the height equivalent to the theoretical plate.

Chromatographic Zinc Isotope Separation by Chelating Exchange Resin.

Zinc isotope separations were studied by displacement chromatography using the chelating properties of malate, citrate and lactate exchange resin and EDTA as ligands. After each chromatographic operation, the heavier zinc isotopes were found to preferentially fractionated into the carboxylate complex solution phase. The separation coefficients (epsilon) for zinc isotope separation had the largest value and were obtained for the isotopic pairs (68)Zn/(64)Zn (7.16 x 10(-4)) and (66)Zn/(64)Zn (3.08 x 10(-4)), respectively, at 298 +/- 1 K. The separation coefficient per unit mass differences (epsilon/DeltaM) for the isotopic pair of (68)Zn/(64)Zn was found to range around 1.55 x 10(-4).

High enrichment of 15N by chromatographic chemical process.

Nitrogen isotope enrichment experiments were conducted to obtain highly enriched (15)N by ion-exchange process. (15)NH(4)Cl ((15)N=80%) as feeding materials were used to perform the chromatographic operation with two different flow rates and column diameters. Both separation coefficient (epsilon) and height equivalent to a theoretical plate (HETP) have same values in two run experiments. The value of HETP was more enlarged when high enrichment of (15)N was obtained in comparison with that of low enrichment. 99.756% (15)N and 13.63 g (15)N whose percentage was over 99.0% were successfully achieved by 25 m chromatographic migration with the flow rate and column diameter at 50 cm(3)/mL, 3.0 cm, respectively. High flow rate and large column diameter have advantages to the enrichment of (15)N by ion exchange process.

Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution.

Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure.

Preferable correlation to blastocyst development and pregnancy rates with a new embryo grading system specific for day 3 embryos.

PURPOSE: To investigate the cleavage stage embryo quality by the correlation between the morphological features and blastocyst development rate to develop a new embryo grading system. METHODS: A retrospective analysis, including 216 cycles of cleavage stage embryo transfer and 251 cycles of blastocyst transfer. The correlation with blastocyst development of the embryo cleavage stage, fragmentation and uniformity of blastomeres was evaluated. RESULTS: There were significant differences in the blastocyst development rate between > or =7 cells and < or=6 cells (68.8% vs. 30.7%), <50% fragmentation and > or =50% fragmentation (51.9% vs. 25.7%), and evenly sized blastomeres and unevenly sized blastomeres (48.7% vs. 30.1%) on day 3. The new grading system defined by these 3 parameters showed a preferable correlation to the pregnancy rate. CONCLUSIONS: The new grading system specific for day 3 embryos is useful for the selection of good quality embryos and may improve the pregnancy rate.

An anion-exchange chromatographic study on boron isotopic fractionation at 2 MPa at 293 K.

To study boron isotopic fractionation at high pressure, column chromatography operated in the breakthrough manner was performed at 2.0 MPa at 25.0 degrees C. The fractionation factor (S) between boron adsorbed onto strongly basic anion-exchange resin and boron in solution was obtained as 1.013, which was smaller than the values at 0.1 MPa (atmospheric pressure) found in literature. The pressure dependence of S was discussed based on the polymerization of boron in the solution and resin phases and on the occurrence of the pressure dependent isotope effect relating to the molar volume changes of boron species upon isotope substitution.

Cerium isotope effects in Ce(III) malate and lactate complex formation studied by long-distance displacement chromatography.

Isotope effects of cerium were observed in malate and lactate complex formations during the long-distance displacement chromatographic processes at 313 K. Heavier isotopes were found fractionated in the frontal edges of the Ce adsorption bands in both the systems, registering a preference of the heavier isotopes for the Ce(III) complexes in the solution phase over the simply hydrated Ce(III) ions in the resin phase. The fractionation coefficients epsilon for the 136Ce/140Ce, 138Ce/140Ce and 142Ce/140Ce isotopic pairs were 7.1 x 10(-6), 5.2 x 10(-6) and -2.1 x 10(-6) for the malate system, and 4.8 x 10(-6), 4.5 x 10(-6) and-2.6 x 10(-6) for the lactate system, respectively. They all show the mass-dependent law if the deviation of epsilon for the 138Ce/140Ce pair was considered merely due to the isobaric interference in Ce isotopic ratio measurements, suggesting the molecular vibration, rather than the nuclear field shift, mainly contributes to the Ce isotope effects in the complex formation systems. The absolute values of epsilon between the two systems are comparable, suggesting no instinct difference in structural properties between Ce malate and lactate complexes involved.

Chromatographic zinc isotope separation by phenol formaldehyde benzo crown resin.

New types of phenol formaldehyde resin having benzo crown as a functional group were synthesized and applied to zinc isotope chromatographic operation. Zinc adsorption and isotope separation capacities were dramatically improved by using phenol formaldehyde benzo-15-crown-5 resin. Zinc batch adsorption tests were performed by various dehydrated organic solvents. Separation coefficient, epsilon 8.1 x 10(-4) and height equivalent to a theoretical plate (HETP) 0.105 cm for the isotopic pair of 68Zn/64Zn in phenol formaldehyde benzo-15-crown-5 resin were obtained in the case of acetone as the solvent at 298+/-1K.

Observation of cerium isotope fractionation in ion-exchange chromatography of Ce(III)-malate complex.

The cerium isotope fractionation between Ce(III)-malate complex in aqueous solution and cerium ions in a cation-exchange resin was conducted by displacement chromatography. The pH and the chemical composition of the eluent were optimized for maintaining the self-sharpening band boundaries and the 21 m chromatographic migration of the Ce band underwent. Graphite slurry was coated on the tantalum filament prior to sample loading for reducing the isobaric interferences in cerium isotopic ratio determination by mass spectrometry. From the experimental results, it was found that the heavier isotope was enriched in the front boundary part of the cerium adsorption band, which meant that the heavier isotope was preferentially fractionated into the Ce3+ malate complex rather than simply hydrated Ce3+ ions. The isotope separation coefficient for the 136Ce/140Ce and 142Ce/140Ce was 5.2 x 10(-5) and -1.9 x 10(-5), respectively, at 298 K.

Separation of vanadium isotopes by ion-exchange chromatography.

Cation-exchange displacement chromatography of VO2+ was carried out for studying vanadium isotope effects in carboxylate ligand-exchange systems. The heavier isotope 51V was enriched in the carboxylate complex solution. The isotope separation coefficients epsilon(= alpha-1) for 50V/51V were 2.2 x 10(-4) and 2.4 x 10(-4) for citrate and lactate systems at 298 K, respectively. These values are much larger than those obtained in a previous study on the malate system. The existence of binuclear complexes of VO2+ may create the conditions for larger isotope fractionation. From the viewpoint of the process development of isotope separation, the heights equivalent to a theoretical plate of these processes were analyzed and found to be very small in each system due to the homogeneous, small and highly porous resin used. Citrate may be better than the other tested systems for the vanadium isotope separation.

Premenstrual disappearance of aminopeptidase A in endometrial stromal cells around endometrial spiral arteries/arterioles during the decidual change.

Aminopeptidase A (APA, BP-1) is a membrane-bound zinc metallopeptidase that converts angiotensin II (AngII) into AngIII by selectively hydrolyzing the N-terminal aspartyl residue. AngII has been proposed as a candidate for the initial vasoconstrictor of endometrial spiral arteries/arterioles in the preliminary step of menstruation. In the late secretory phase, endometrial stromal cells (ESC) around the blood vessels begin to differentiate into decidual cells, and AngII has been reported to accumulate around such vessels. However, whether there is a concurrent increase in renin or angiotensin-converting enzyme in this area has not been determined. We hypothesized that APA may be involved in the metabolism of AngII in the cycling endometrium. Western blot analysis in the present study demonstrated that a considerable amount of APA was present in the secretory phase endometrium. ESC in the secretory phase showed strong expression of APA by immunohistochemical analysis and of APA mRNA by in situ hybridization. In contrast, both APA mRNA and protein were absent in decidual cells. The enzyme activity and the biosynthesis of [(35)S]methionine-labeled APA significantly decreased during the in vitro decidualization of cultured ESC. These results suggest that the perivascular disappearance of APA is a differentiation-specific change that occurs along with the decidualization, and that the disappearance of APA might accelerate the accumulation of AngII around the vessels.

Possible activation of the renin-angiotensin system in the feto-placental unit in preeclampsia.

The purpose of this study was to elucidate the mechanisms underlying the regulation of feto-placental circulation mediated by the renin-angiotensin system under preeclamptic conditions. We measured angiotensin-converting enzyme (ACE) activity, protein expression, and mRNA expression in uncomplicated and preeclamptic placentas and examined the localization of ACE. In addition, ACE activity and mRNA expression in human umbilical venous endothelial cells (HUVECs) under hypoxic conditions were analyzed. ACE activity, protein expression, and mRNA expression in placental tissues from preeclampsia were all significantly higher than those from uncomplicated pregnancies. ACE activity in vessel fractions was extensively higher than that in trophoblast-rich or macrophage-rich fractions. Additionally, ACE activity in HUVECs was significantly higher than that in human arterial endothelial cells, and ACE mRNA was primarily localized to venous endothelial cells of stem villous in placentas. Furthermore, hypoxic condition induced both ACE activity and mRNA expression in HUVECs. These results suggested that venous endothelial cells within placental stem villous tissues and umbilicus play an important role in the regulation of the feto-placental renin-angiotensin system, and in response to hypoxic conditions the feto-placental unit seemed to induce ACE activity in the placenta; such an effect would be likely to lead to regulation of the fetal circulation.

Existence of placental leucine aminopeptidase/oxytocinase/insulin-regulated membrane aminopeptidase in human endometrial epithelial cells.

Human endometrial epithelial cells are known to express oxytocin receptors around the time of ovulation. Moreover, oxytocin (OT) and OT-induced prostaglandins appear to play a pivotal role in the switching of endometrial glands from the proliferative to the secretory phase. However, there have been few studies of oxytocinase (OTase), which is identical to placental leucine aminopeptidase (P-LAP)/insulin-regulated membrane aminopeptidase (IRAP). We confirmed the expression of P-LAP/OTase in human endometrium and also observed the changes in the expression of P-LAP/OTase throughout the menstrual cycle. P-LAP/OTase and its mRNA were localized in endometrial epithelial cells but not in stromal cells. In the follicular phase, immunoreactive P-LAP/OTase was homogeneously distributed on the plasma membrane and in cytoplasmic granules. Immunoblot analysis demonstrated that the majority of P-LAP/OTase was produced around the time of ovulation. After ovulation, the immunostaining was restricted to the glycogen-rich subnuclear vacuoles, a glandular marker of progesterone release from the corpus luteum. Thereafter, the membrane-bound P-LAP/OTase was released by apocrine secretion during the period of blastocyst implantation and became depleted toward the time of menstruation. Further understanding of the function of P-LAP/OTase in the endometrium appears likely to yield insights into the cyclic changes during the normal menstrual cycle.