Critical role of both retinoid nuclear receptors and retinoid-X-receptors in mediating growth inhibition of ovarian cancer cells by all-trans retinoic acid

Retinoids have been shown to inhibit the growth of a number of human tumor cells, including several ovarian adenocarcinoma cell lines. All-trans retinoic acid (RA) is an effective growth suppressor of CA-OV3 cells but not SK-OV3 cells. Since the effects of RA are known to be mediated via the nuclear receptors (RARs and RXRs), we initially compared levels of the various RARs and RXRs in the CA-OV3 and SK-OV3 cell lines. The RA resistant SK-OV3 cells expressed reduced levels of RAR-alpha and RXR-alpha. Furthermore, induction of RAR-alpha by RA was impaired in the RA resistant SK-OV3 cells as was RARE binding and RARE-dependent transcriptional activity. These results suggested that changes in the amounts and/or activity of RARs and/or RXR-alpha could determine the growth response of ovarian tumor cells to RA. This was confirmed by modulating the levels of RARs and RXR-alpha in the SK-OV3 cells using the LacSwitch inducible expression system. Stably transfected clones of RA resistant SK-OV3 cells exhibited a significant inhibition of growth by RA treatment when RAR-alpha was induced. Overexpression of both RAR-alpha and RXR-alpha resulted in a level of growth inhibition nearly equal to that exhibited by the RA sensitive CA-OV3 cell line. Similar results were obtained when a combination of RXR-alpha and either RAR-beta or RAR-gamma was overexpressed in SK-OV3 cells. Our results show that the nuclear receptors and RXR-alpha play a critical role in mediating growth suppression by RA in ovarian cancer cells.

Simultaneous determination of maltose and glucose using a screen-printed electrode system

A screen-printed sensor system consisting of a glucose oxidase (GOD) electrode and an amyloglucosidase/glucose oxidase (A/G) electrode was constructed to determine maltose and glucose simultaneously in a mixture. Sensor construction was optimised so that it contained 20 units of GOD/40 units of amyloglucosidase and 0.2 mM 1,1'-ferrocenedimethanol. These components were deposited onto a screen-printed carbon electrode and an outer membrane was printed from 3.5% hydroxyethyl cellulose (HEC) solution. The optimum pH was 4.8. The linear range of the system was up to 40 mM glucose or 20 mmol/L maltose with coefficients of variation (CVs) ranging from 3.5% to 5.29%. The results obtained by using the enzyme electrode system agreed well with those obtained by the Fehling titration method. When stored dry, especially at 4 degrees C, the enzyme electrodes showed good stability over four months.

DNA optical sensor: a rapid method for the detection of DNA hybridization

A DNA optical sensor system is proposed based on the combination of sandwich solution hybridization, magnetic bead capture, flow injection and chemiluminescence for rapid detection of DNA hybridization. Bacterial alkaline phosphatase (phoA) gene and Hepatitis B virus (HBV) DNA were used as target DNA. A biotinylated DNA probe was used to capture the target gene onto the streptavidin-coated magnetic beads and a calf intestine alkaline phosphatase (CAP)-labelled DNA probe was used for subsequent enzymatic chemiluminescence detection. The detection cycle was less than 30 min, excluding the DNA hybridization time, which was about 100 min. Both the phoA gene and HBV DNA could be detected at picogramme or femtomole level. No response signal was obtained when target DNA did not exist in the sample. Successive sample detection could be made by removing the magnetic field and a washing step.

Reduction of both RAR and RXR levels is required to maximally alter sensitivity of CA-OV3 ovarian tumor cells to growth suppression by all-trans-retinoic acid

We wished to determine the effect of altering the levels or functional activity of retinoid receptors, in particular retinoic acid receptor-alpha (RAR-alpha) and retinoid X receptor-alpha (RXR-alpha) on the growth sensitivity of ovarian tumor cells to all-trans-retinoic acid (all-trans-RA). We found that CA-OV3 cells could be made resistant to all-trans-RA growth inhibition by overexpressing RAR-beta(R269Q), an efficient dominant negative mutant which inhibits the function of all RAR subtypes. Antisense technology was then used to prepare stable transfectants of the retinoid-sensitive ovarian carcinoma cell line CA-OV3 in which expression of RAR-alpha, RXR-alpha, or both RAR-alpha and RXR-alpha was reduced. The effect of all-trans-RA on ovarian tumor cell growth was determined by MTT assay, autoradiographic analysis of DNA synthesis, and anchorage-independent colony formation in soft agar. Our results show that cell lines expressing reduced levels of either RAR-alpha alone or RXR-alpha alone exhibited a small decrease in sensitivity to growth inhibition by all-trans-RA. However, maximum RA resistance was obtained in cell lines in which the levels of both RAR-alpha and RXR-alpha were reduced. These results demonstrate the importance of both retinoid nuclear receptors and retinoid-X receptors in general, and RAR-alpha and RXR-alpha in particular, as mediators of ovarian carcinoma cell growth inhibition by retinoids.

Analysis of the Pore Characteristics of Mixtures of Disks

This paper presents a study of the pore characteristics of the packing of disks by using three computer simulation algorithms: deposition under gravity (DG), random sequential adsorption, and Mason's algorithm. A pore is regarded as corresponding to a triangular subunit obtained from the Voronoi tessellation for monosized packing or radical tessellation for multisized packing, and its size and shape are respectively quantified in terms of equivalent circular diameter and circularity. The results indicate that both pore size and shape distributions are significantly affected by the simulation method, which are considered to be related to the packing constraints imposed in the simulation algorithms. Studies of the DG packing of binary mixtures suggest that the disk size distribution significantly affects packing density, a typical macroscopic property, and microscopic properties such as pore size and shape distributions. Attempts have been made to explain the results in terms of packing mechanisms for packing density and geometrical properties for pore characteristics. Copyright 1997 Academic Press. Copyright 1997Academic Press

Behavior of calcium and phosphate in artificial casein micelles

This study investigated the behavior of Ca and phosphate in artificial casein micelles using 45Ca and 32P by means of UF, equilibrium dialysis, and gel permeation HPLC in the presence of 6 M urea. Artificial casein micelles were prepared at a casein concentration of 2.5% with 30 to 40 mM Ca, 22 to 27 mM phosphate, and 10 mM citrate using 45Ca or 32P. About 75 and 65% of colloidal 45Ca and 32P, respectively, in artificial casein micelles that were formed in the presence of 30 mM Ca and 22 mM phosphate were exchanged after dialysis of artificial casein micelles against a simulated milk ultrafiltrate at 4 degrees C for 72 h. The percentages of 45Ca and 32P in the fraction of casein aggregates that were crosslinked by micellar Ca phosphate were 26.9 and 27.6%, which decreased to about 10% after equilibrium dialysis against a simulated milk ultrafiltrate at 4 degrees C for 72 h. The proportion of exchanged colloidal 45Ca and 32P in artificial casein micelles during dialysis for 72 h were higher at 25 degrees C than at 4 degrees C, suggesting that the exchange of Ca and phosphate between the diffusible and colloidal phases depended on temperature. The results suggest that the exchange of Ca and phosphate between diffusible and colloidal phases proceeds slowly, and a portion of the Ca and phosphate in the artificial casein micelles is difficult to exchange.

Flow-injection determination of lead by hydride generation and conductometric detection

Plumbane produced from the lead analyte in a flow-injection manifold by reaction with sodium borohydride is passed through a porous poly(tetrafluoroethylene) membrane in a gas-diffusion cell. The hydride reacts with bromine in the acceptor stream resulting in ionization which is detected by conductivity measurement. Direct mixing of the carrier with a reagent stream yields a limit of detection of approximately 1 mg/L. An improved detection limit of about 200 microg/L can be achieved by the incorporation of an auxiliary stream containing persulphate as oxidizing agent. The application of the method to the determination of lead in road dust and soil samples is demonstrated.

Effect of 9-cis-retinoic acid on growth and RXR expression in human breast cancer cells

A number of studies have demonstrated the ability of retinoic acid (RA) to inhibit the growth of estrogen receptor-positive (ER+) human breast cancer cell lines. The precise mechanism of growth inhibition is not known. However, the biological effects of RA in other model systems have been shown to be mediated via the nuclear retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). While several laboratories have examined the expression of RARs in various breast cancer cell lines, no information is available concerning the role of the RXRs and 9-cis-RA, the natural ligand of RXRs, in the response of breast cancer cells to RA. Using a representative panel of breast cancer cell lines, we determined the effect of 9-cis-RA on growth and cell cycle stage distribution, analyzed steady-state mRNA levels of RXR-alpha, -beta, and -gamma, and determined the effect of all-trans-RA and 9-cis-RA on RXR expression. Our results show that: (1) the growth of ER+/RA-sensitive breast cancer cells is inhibited by treatment with 9-cis-RA by blocking entry into S phase; (2) both ER+/RA-sensitive and ER-/RA-resistant breast cancer cell lines express RXR-alpha and RXR-beta mRNAs but not RXR-gamma; however, levels of these transcripts did not correlate with the RA response; and (3) levels of RXR-alpha and RXR-beta mRNA were not significantly altered following treatment with either all-trans-RA or 9-cis-RA. These results suggest that the mechanism responsible for the retinoid sensitivity of breast cancer cells does not involve transcriptional modulation of the RXRs by RA.

Current status of genetic research in Rett syndrome

Rett syndrome is a progressive neurological development syndrome. Evidences for a genetic transmission, but no conclusive data which entirely support the X chromosome involvement, exist. The chromosomal region 11p14-pte has been investigated with polymorphic markers and genes in the region have been sequenced. No sequence divergencies were detected.

Arginine 132 of cellular retinoic acid-binding protein (type II) is important for binding of retinoic acid

Cellular retinoic acid-binding protein type II (CRABP-II) is one of two small molecular weight, cytosolic proteins which specifically bind retinoic acid (RA). Crystallographic and site-directed mutagenesis studies of several related proteins have indicated that either one or two conserved amino acid residues, homologous to positions Arg111 and Arg132 of CRABP-II, are important for the binding of the hydrophobic ligand. In this report we have prepared site-directed mutations of these two positions of CRABP-II, Arg111 and Arg132, as well as Lys82 to determine the role of these residues in the binding of RA. Recombinant wild type and mutant CRABP-II proteins were expressed and purified, and the affinity for retinoids was determined by fluorometric titration and binding of 3H-labeled compounds. K82A displayed an identical Kd for all-trans-RA as wild type CRABP-II and the Kd for all-trans-RA of R111A was only slightly higher. On the other hand, the two Arg132 mutants, R132A and R132Q, of CRABP-II demonstrated undetectable binding of all-trans-RA. Taken together these data demonstrate that Arg132 is a critical amino acid residue for the binding of RA by CRABP-II.

Rett syndrome: the bcl-2 gene--a mediator of neurotrophic mechanisms?

Rett syndrome affects young girls. The molecular basis is mysterious. One tenable hypothesis can be that the programmed early infantile death of neuronal cells is reprogrammed. The bcl-2 gene on chromosome 22 has been shown to play a role in the apoptosis process. No sequence abnormalities were detected in the bcl-2 gene of 6 patients with Rett syndrome which could explain the pathophysiology of Rett syndrome.

Characterization of the von Willebrand factor gene (VWF) in von Willebrand disease type III patients from 24 families of Swedish and Finnish origin

Twenty-four patients with von Willebrand disease type III were screened for mutations in the von Willebrand factor (VWF) gene using the PCR technique, followed by direct sequencing. More than 250 kb of genomic DNA were sequenced, including the promoter and coding regions (52 exons) of the VWF gene from 24 patients. In addition to the previously reported mutations of a single cytosine deletion in exon 18 and the nonsense mutations in exons 28, 32, and 45, nine new mutations were detected: two nonsense mutations in exons 15 and 16, one allele with a thymidine insertion in exon 14, one allele with a cytosine insertion in exon 28, one 20-bp deletion in exon 15, one mutation in the donor splice site of exon 43, and three missense mutations in exons 28, 49, and 51. Forty-two mutant chromosomes were identified (42/48); 11 probands are homozygous for the mutations, and 8 are compound heterozygous. In addition, a new subfamily of the Alu sequence in the promoter region and 10 new polymorphisms were identified.

[Development of visual function in infants and children]

The development of P1 component of VEP was studied in 150 normal infants and children between the age of 2 weeks and 9 years. The results indicates that the VEP consists of simple positive waves within 8 weeks following birth, the latencies of P1 components shorten dramatically from 2 to 4 months, the development of the latencies of low, medium and high spatial frequencies of P1 components reaches adult levels in infants and children of 4 months, 4 years and 9 years, respectively and the VEP amplitudes of infants and children are significantly higher than those of adults. Based on the results of our research, the development of visual function can be divided into 3 phases: the first, within 4 months following birth; the second, 5 months to 4 years and the third, 5 to 9 years.

Mutations of von Willebrand factor gene in families with von Willebrand disease in the Aland Islands

Patients with von Willebrand disease in four families in the Aland Islands, including the original family that was described in 1926 by the Finnish physician von Willebrand, were screened for mutations in the Swedish "hot-spot" regions (exons 18, 28, 32, 43, and 45) of the von Willebrand factor gene. One cytosine deletion in exon 18 was detected in each of these families. Linkage analysis and genealogical studies suggest that the deletion present in these four families probably has an origin in common with the mutations in the Swedish patients. Apart from the deletion in exon 18, two close transitions (G-->A at S1263 and C-->T at P1266) in exon 28 on the same chromosome were identified in one individual who married into the original family and in his two children. The transitions could be due to a recombination between the von Willebrand factor gene and its pseudogene.

Nonsense mutations of the von Willebrand factor gene in patients with von Willebrand disease type III and type I

von Willebrand disease (vWD) is the most common inherited bleeding disorder in humans. The disease is caused by qualitative and quantitative abnormalities of the von Willebrand factor (vWF). Genomic DNA from 25 patients with vWD type III, the most severe form of the disease, was studied using PCR followed by restriction-enzyme analysis and direct sequencing of the products. Nonsense mutations (CGA----TGA) were detected in exons 28, 32, and 45 by screening of all the 11 CGA arginine codons of the vWF gene. Two patients were found to be homozygous and five heterozygous for the mutation. Both parents and some of the relatives of the homozygous patients carry the mutation. These are the first reported examples of homozygous point mutations associated with the severe form of vWD. In the three heterozygous probands, one of the parents carried the mutation and had vWD type I. Family studies including parents and family members with or without vWD type I indicated that these three heterozygous patients are likely to be compound heterozygous. Twenty-one individuals from these seven families with vWD type I were found to be heterozygous for the mutation.