Multicomponent polyanions. 57. Large-angle X-ray scattering study of aqueous molybdophenylphosphonate solutions

The radial distribution functions are calculated from large-angle X-ray scattering (LAXS) measurements for one concentrated aqueous molybdate/heptamolybdate solution and five aqueous molybdophenylphosphonate solutions (lithium chloride medium). Besides water and hydrated lithium, chloride, and molybdate ions, five species in all, having different nuclearities, are postulated to exist in the solutions, according to equilibrium studies using potentiometry and 31P NMR spectroscopy. The structures of the three polymolybdate species Mo7O24(6-), Mo8O26(4-), and (C6H5P)2Mo5O21(4-), for which the structures are determined crystallographically, are confirmed to exist also in aqueous solution. The principal structures of the remaining two complexes, (C6H5P)Mo6O21(OH2)5(2-) and (C6H5P)Mo7O25(OH2)4-, are elucidated with the use of structures of related species. Both anions have one group of four edge-sharing MoO6 octahedra and another group of two MoO6 octahedra connected by sharing corners, forming a bent unsymmetric six-membered ring, with the C6H5PO3 group placed on the crowded side of the ring. In the former, the group of two MoO6 octahedra is edge-shared, while in the latter, the group is face-shared, resulting in a ring small enough to tetrahedrally coordinate to the seventh molybdenum opposite the phenyl group.

A potentiometric and 51V NMR study of the aqueous H+/H2VO4-/H2O2/L-alpha-alanyl-L-histidine system

The speciation in the quaternary aqueous H+/H2VO4-/H2O2/L-alpha-alanyl-L-histidine (Ah) system has been determined from quantitative 51V NMR measurements and potentiometric data (glass electrode). The study was performed in 0.150 M Na(Cl) medium at 25 degrees C. Data were evaluated with the computer program LAKE, which is able to treat combined EMF and NMR data. The pKa values for Ah were determined as 8.06, 6.72 and 2.64. In the ternary H+/H2VO4-/Ah system, two complexes, (H+)p(H2VO4-)q(Ah)r, for which (p, q, r) values of (0, 1, 1) and (1, 1, 1) with log beta(0,1,1) = 2.52 +/- 0.03 and log beta(1,1,1) = 9.40 +/- 0.05 (pKa = 6.88), respectively, explain all data. The errors given are 3sigma. In the quaternary H+/H2VO4-/H2O2/Ah system, eight complexes were determined in addition to all binary and ternary complexes, four with a V/X/Ah ratio 1:1:1 and four with a ratio 1:2:1 (X = peroxo ligand). VX2Ah2- and VX2Ah- (pKa = 8.19) are the main complexes and predominate in the pH range 5 to 9. Three additional minor species have also been found but their compositions could not be determined owing to their small amounts. Equilibria are slow, significant decomposition of peroxide occurs only in acidic solutions. Data in the pH range 5 to 10 have been used for the LAKE calculations. Chemical shifts, compositions, and formation constants for the eight quaternary complexes are given, and equilibrium conditions are illustrated in distribution diagrams. Structural proposals for VX2Ah2- and VX2Ah- are made from 1H and 13C NMR measurements.

Speciation in vanadium bioinorganic systems. 6. Speciation study of aqueous peroxovanadates, including complexes with imidazole

Using a combination of potentiometry (glass electrode) and quantitative 51V NMR spectroscopy, the full speciation in the vanadate-peroxide and vanadate-peroxide-imidazole systems was determined in the pH range 1-10 (0.150 M Na(Cl) medium, 25 degrees C). Using the computer program LAKE, the pKa value of imidazole and the formation constants for 10 peroxovanadate species and also for three more species where a single imidazole moiety is also bound, have been calculated. The experimental data show a good fit to the calculated speciation model, even for the less abundant species. The species are either monomeric or dimeric in vanadium, and four resonances of the dimeric species have been unambiguously assigned via 2D 51V NMR. Diperoxovanadates are the favoured species at pH 2-10, when sufficient peroxide is present. Imidazole is found to bind strongly to them at pH 6-9. The equilibrium conditions are illustrated in distribution diagrams.

Speciation in the vanadate-alanylhistidine-peroxide system

The speciation in the quaternary aqueous H+-H2VO4(-)-H2O2-L-alpha-alanyl-L-histidine (Ah) system has been determined from quantitative 51V NMR measurements and potentiometric data (glass electrode). The study was performed in 0.150 M Na(Cl) medium at 25 degrees C. Data were evaluated with the computer program LAKE, which is able to treat combined potentiometric and NMR data. In the ternary H+-H2VO4(-)-Ah system, two complexes, (H+)p(H2VO4-)q(Ah)r, having (p, q, r) values (0, 1, 1) and (1, 1, 1) (pKa = 6.88) explain all data. In the quaternary H+-H2VO4(-)-H2O2-Ah system, seven complexes were determined in addition to all binary and ternary complexes, four with a V/X/Ah ratio 1:1:1 and three with a ratio 1:2:1 (X = peroxo ligand). VX2Ah2- and VX2Ah- (pKa = 8.26) are the main quaternary complexes and predominate in the pH range 5 to 9. Chemical shifts, compositions and formation constants for all the quaternary complexes are given, and equilibrium conditions are illustrated in distribution diagrams.

Chromosomal breakage-fusion-bridge events cause genetic intratumor heterogeneity

It has long been known that rearrangements of chromosomes through breakage-fusion-bridge (BFB) cycles may cause variability of phenotypic and genetic traits within a cell population. Because intercellular heterogeneity is often found in neoplastic tissues, we investigated the occurrence of BFB events in human solid tumors. Evidence of frequent BFB events was found in malignancies that showed unspecific chromosome aberrations, including ring chromosomes, dicentric chromosomes, and telomeric associations, as well as extensive intratumor heterogeneity in the pattern of structural changes but not in tumors with tumor-specific aberrations and low variability. Fluorescence in situ hybridization analysis demonstrated that chromosomes participating in anaphase bridge formation were involved in a significantly higher number of structural aberrations than other chromosomes. Tumors with BFB events showed a decreased elimination rate of unstable chromosome aberrations after irradiation compared with normal cells and other tumor cells. This result suggests that a combination of mitotically unstable chromosomes and an elevated tolerance to chromosomal damage leads to constant genomic reorganization in many malignancies, thereby providing a flexible genetic system for clonal evolution and progression.

The selection of female urinals: results of a multicentre evaluation

Female urinals are designed to enable women to empty their bladders while not on the toilet and are therefore potentially useful in preventing incontinence. However, there is little published information to guide product selection. Therefore, an evaluation of these products was undertaken by the Continence Products Evaluation Network (funded by the Medical Devices Agency). All 13 reusable female urinals available in the UK in March 1997 were evaluated. Each urinal was evaluated by 28-32 community-based women. Preliminarily, each subject tested all urinals by trying to place them in one or two of their preferred positions, to establish if the urinals were suitable for full testing. Each of the urinals that were selected for full testing were then used for 1 week each. During this week the subjects kept a diary to record leakage or spillage when using the urinal. At the end of the week a product evaluation form was filled in to record product performance. The results from full testing indicate that all urinals were successful for some subjects. However, some urinals were found to be successful for all four main positions (e.g. Petal Female Urinal) while others were successful mainly in one or two positions (e.g. Bridge Saddle Pan and Subaseal). Many urinals were successful in the standing/crouching and sitting on the edge (of chair or bed) positions, while comparatively few urinals were successful in the lying position. It was found that the chances of finding a suitable urinal increased with levels of independence. This means that subjects with higher levels of dependency found fewer urinals to be suitable for their needs when used without assistance. The results of this evaluation provide guidance for product selection. However, it is recommended that continence specialists keep samples of the full range of female urinals to enable women to experiment with urinals in order to find one that best suits their needs.

Novel and classical protein kinase C isoforms have different functions in proliferation, survival and differentiation of neuroblastoma cells

To elucidate the possibility of utilizing protein kinase C (PKC) isoforms as target genes in neuroblastoma therapy, 5 neuroblastoma cell lines and neuroblastoma tumor specimens were examined for PKC isoform expression pattern and the cell lines were analyzed for sensitivity to PKC inhibition. All cell lines [IMR-32, LAN-2, LAN-5, SH-SY5Y and SK-N-BE(2)] expressed alpha, betaII, delta and epsilon isoforms of PKC, while no PKCeta or theta protein was detected in any cell line. PKCgamma was found only in LAN-2 cells. PKCalpha, betaII and delta were detected in 5 neuroblastoma tumors and PKCepsilon in 4 out of 5 tumors. Exposure to the PKC inhibitors GF109203X, Gö 6976 or Gö 6983 caused a decrease whereas activation of PKC with 12-O-tetradecanoyl phorbol 13-acetate caused an increase in the number of neuroblastoma cells. The effect of Gö 6976 was due to both inhibited proliferation and to increased apoptosis. While GF109203X suppressed neurite outgrowth induced by a growth factor combination, Gö 6976 potentiated neurite outgrowth. Our data suggest a role for classical PKC isoforms in neuroblastoma growth and survival and for novel isoforms in neurite outgrowth.

Multicomponent Polyanions. 53. Structure of Tetrakis(trimethylammonium) Tetra-μ-oxo-bis(triaquahexadecaoxo(trioxophenylphosphato)hexamolybdate) Dihydrate, [NH(CH3)3]4[{(C6H5P)Mo6O21(H2O)3}2].2H2O

The title compound crystallized in the monoclinic space group P21/n (No. 14) [a = 11.211 (5), b = 12.862 (3), c = 23.05 (1) Å, β = 94.37 (3)°, V = 3314 (2) Å3, Z = 2]. The polyanion can be regarded as a dimer of a phenylphosphonatohexamolybdate, (C6H5P)Mo6O23(H2O)3, linked by four O atoms. In this monomeric unit the six molybdenum octahedra are grouped into two parts consisting of four and two edge-sharing octahedra, respectively. These two parts are connected by two corner-sharing O atoms to form a bent Mo6 ring. The phenylphosphonate group coordinates to the Mo6 ring from the narrow side as a tripodal ligand. The {(C6H5P)Mo6O21(H2O)3}2 units form layers parallel to (001) and the structure is stabilized by hydrogen bonds between water and neighboring anions. The monomeric unit has been shown to be a key structure in the process of deducing the aqueous solution structures of the (C6H5P)Mo_6^{2-} and (C6H5P)Mo_7^{4-} species found in a previous equilibrium study of the H+–MoO_4^{2-}–(C6H5P)O_3^{2-} system.

A multicentre comparative evaluation of catheter valves

Catheter valves are an alternative to leg bags for urine drainage, but no studies have yet been published which have compared the performance of different valves. This study was undertaken to evaluate the performance of the seven catheter valves available on the UK market in April 1996. The study was carried out by the Continence Products Evaluation (CPE) Network funded by the Medical Devices Agency (Department of Health). Each valve type was tested for 1 week by 19-36 cognitively unimpaired and manually dextrous subjects recruited from 11 test centres. At the end of each week, subjects completed an evaluation form (based on a three-point rating scale) to record product performance. The same catheter valves were also tested for ease of opening/closing by 33 subjects (mostly catheter users) who had some manual impairment. Performance scores varied widely between products. It was found that, to be successful, a valve needs to be easy to manipulate, leak-free, comfortable and inconspicuous. Prescribers need to be aware of the strengths and limitations of different valves for appropriate product selection.

Speciation in Vanadium Bioinorganic Systems. 2. An NMR, ESR, and Potentiometric Study of the Aqueous H(+)-Vanadate-Maltol System

A systematic study of the physiologically interesting vanadium-maltol (V-MaH) system has been performed in 0.150 M Na(Cl) at 25 degrees C, using NMR, ESR, and potentiometric techniques. Complexation occurs within a wide pH range, from around 1 up to 10.5. However, a pH-, concentration-, and time-dependent spontaneous reduction of vanadium(V) to vanadium(IV) occurs. From ESR spectra the conditions for this reduction are evaluated and discussed. From potentiometric (glass electrode) and quantitative (51)V NMR measurements, the full speciation in the H(+)-H(2)VO(4)(-)-MaH system was determined in the pH range 5-10.5. Data were evaluated with the computer program LAKE, which is able to treat combined emf and NMR data. The pK(a) value for MaH was determined to be 8.437 +/- 0.005. In the ternary system, three complexes are formed: VMa(2)(-), VMa(-), and VMa(2)(-), having log beta(0,1,2) = 7.02 +/- 0.03, log beta(0,1,1) = 2.66 +/- 0.05, and log beta(-)(1,1,1) = -7.37 +/- 0.21. The errors given are 3sigma. The VMa(2)(-) complex appears as the main species in a pH range from 4.5 to 8.5, whereas both mononuclear monoligand species are minor. Equilibrium conditions are illustrated in distribution diagrams, and the structures of the complexes formed are proposed.

Alzheimer amyloid beta-peptides exhibit ionophore-like properties in human erythrocytes

There is growing evidence that the amyloid beta-peptide (beta 1-40) is involved in the aetiology of Alzheimer's disease also implicating an altered calcium homeostasis of affected cells. Beta 1-40 has been proposed to form calcium channels in synthetic bilayer membranes [1]. We wanted to investigate in the present study whether beta 1-40 (or fragments thereof) could act as ionophores in a biological membrane like the one in human erythrocytes. Incubation of the cells for 2 h and 4 h at 37 degrees C together with 6 mumol L-1 of beta 1-40 or of fragments beta 1-28 and beta 25-35, resulted in a significantly decreased energy charge qualitatively similar to the one obtained by a known calcium ionophore (A 23187, 0.05 mumol L-1). Moreover, beta 1-40 and its two fragments induced a significant alteration of 45Ca permeability in human red blood cells of the same type as the one achieved by the calcium ionophore. The ionophoric action of beta 1-40 and its two fragments may lead to an increase of the intracellular calcium ion concentration, in turn resulting in enhanced Ca(2+)-ATPase activity and a decrease in energy charge. This may be valid also for neuronal plasma membranes and could, therefore, be a possible aetiological mechanism in Alzheimer's disease.

Competitive elution of protein A fusion proteins allows specific recovery under mild conditions

A novel system is described for mild elution of fusion proteins by competitive elution. The approach is based on displacement of immobilized fusions containing a monovalent IgG-binding staphylococcal protein A fragment (Z) from an IgG-affinity matrix by a divalent fragment fused to a serum-albumin-binding region derived from streptococcal protein G. Using real-time interaction analysis, the binding (K(aff)) to polyclonal human IgG was found to be 3.3 (+/- 0.4) x 10(8) M-1 for divalent ZZ and 2.0 (+/- 0.1) x 10(7) M-1 for monovalent Z. This more than tenfold difference in binding strength ensures a high efficiency in the elution step. The competitor protein can specifically be removed and recovered from the elution mixture by subsequent passage through a human serum albumin(HSA)-affinity column, leaving only the target fusion protein in the flow-through fraction. Here, we show that a recombinant Klenow fragment of DNA polymerase I expressed in Escherichia coli can be recovered with high yield, and retained activity, from a crude bacterial lysate by IgG-affinity chromatography using mild conditions during both binding and elution.

Direct effect of insulin on 45calcium uptake in human erythrocytes

OBJECTIVE

High blood pressure is prevalent in obesity and non-insulin dependent diabetes mellitus; both conditions, with insulin resistance and essential hypertension, have been associated with increasing intra-erythrocytic levels of calcium ions. We tested the hypothesis of whether insulin itself might be responsible for the abnormal red cell cytosolic free calcium.

DESIGN

The ionic effects of insulin were studied on the kinetics of 45calcium uptake in vitro in normal human erythrocytes.

SETTING

The study was performed in the outpatient clinic of a central hospital.

SUBJECTS

Sixteen healthy, normotensive individuals with normal body mass index were recruited for the study.

MAIN OUTCOME MEASURES

Blood from eight individuals was used for time-dependent studies of 45calcium uptake in erythrocytes and blood from another eight individuals was used for dose-dependent studies of insulin effect.

RESULTS

The rate of 45calcium influx in red blood cells has two components, a fast component (0-10 min), which measures the initial rate of 45calcium influx, and a slow component (10-60 min) probably reflecting a relatively large backflux of calcium (calcium efflux), which accordingly determines an apparent low rate of 45calcium influx between 10-60 min. The uptake was linear with time between 10-120 min regardless of insulin being present or not. Insulin at a concentration of 120 mU L-1 significantly decreased the 45calcium uptake in a time-dependent fashion between 10-120 min. The uptake was 508 (+/- 59) at 60 min in the presence of insulin vs. a control value of 529 (+/- 59) pmol mL red blood cells-1 (P < 0.001). The corresponding figures at 120 min were 742 (+/- 109) and 767 (+/- 127), respectively (P = 0.02). Inconsistent results were obtained on 45calcium uptake at 60 min by varying insulin concentrations from 40-640 mU L-1 and a dual effect of insulin on 45calcium uptake could not be excluded, one at a fairly low concentration of insulin (40-120 mU L-1) and another at a high concentration (160-640 mU L-1).

CONCLUSION

The data indicate a direct role of insulin in the transport process of calcium into normal human erythrocytes.

Reversed-phase high-performance liquid chromatographic determination of 7 alpha-hydroxy-4-cholesten-3-one in human serum

A method for the determination of 7 alpha-hydroxy-4-cholesten-3-one in human serum has been developed. The method is based upon solid-phase (C18) extraction of serum after addition of 7-beta-hydroxy-4-cholesten-3-one as internal standard. The extract is analysed by reversed-phase HPLC using acetonitrile-water as a mobile phase. The effluent is monitored at 241 nm. The overall recoveries of the method range from 96% to 105%. The coefficient of variation for the within-run precision is 3.2% (n = 20, mean = 13.0 ng/ml) and for the between-run precision 3.8% (n = 32, mean = 13.3 ng/ml). The limit of detection is 3 ng at a signal-to-noise ratio of 3:1, which corresponds to 1 ng/ml using 3 ml of serum. The median value of 7 alpha-hydroxy-4-cholesten-3-one found in blood donors (n = 27) was 8.9 ng/ml (range 2-35 ng/ml).