Necessity of HuR/ELAVL1 for the activation-induced cytidine deaminase-dependent decrease in topoisomerase 1 in antibody diversification

Activation-induced cytidine deaminase (AID)-dependent DNA cleavage is the initial event of antibody gene-diversification processes such as class switch recombination (CSR) and somatic hypermutation (SHM). We previously reported the requirement of an AID-dependent decrease of topoisomerase 1 (Top1) for efficient DNA cleavage, but the underlying molecular mechanism has remained elusive. This study focuses on HuR/ELAVL1, a protein that binds to AU-rich elements in RNA. HuR-knockout (KO) CH12 cells derived from murine B lymphoma cells were found to have lower CSR and hypermutation efficiencies due to decreased AID-dependent DNA cleavage levels. The HuR-KO CH12 cells do not show impairment in cell cycles and Myc expression, which have been reported in HuR-reduced spleen B cells. Furthermore, drugs that scavenge reactive oxygen species (ROS) do not rescue the lower CSR in HuR-KO CH12 cells, meaning that ROS or decreased c-Myc protein amount is not the reason for the deficiencies of CSR and hypermutation in HuR-KO CH12 cells. We show that HuR binds to Top1 mRNA and that complete deletion of HuR abolishes AID-dependent repression of Top1 protein synthesis in CH12 cells. Additionally, reduction of CSR to IgG3 in HuR-KO cells is rescued by knockdown of Top1, indicating that elimination of the AID-dependent Top1 decrease is the cause of the inefficiency of DNA cleavage, CSR and hypermutation in HuR-KO cells. These results show that HuR is required for initiation of antibody diversification and acquired immunity through the regulation of AID-dependent DNA cleavage by repressing Top1 protein synthesis.

Supramolecular Solvent Extraction-Gas Chromatography-Tandem Mass Spectrometry for Detection of Benzodiazepines in Urines

Objective To establish a method using supramolecular solvent and gas chromatography-tandem mass spectrometry （GC-MS/MS） to analyze 9 benzodiazepines in urines. Methods Urine samples containing 9 benzodiazepines reference substance were subjected to liquid-liquid extractions with supramolecular solvent, which consisted of tetrahydrofuran and 1-hexanol. The solvent layer was evaporated to dryness by stream of nitrogen. The residue was reconstituted with methanol, and GC-MS/MS analysis was performed on it. The way of data collection was multiple reaction monitoring （MRM） mode; internal standard method was employed for quantification. Results In urine samples, when the range of mass concentration was 1-100 ng/mL for diazepam, midazolam, flunitrazepam and clozapine, 5-100 ng/mL for lorazepam and alprazolam, 2-100 ng/mL for nitrazepam and clonazepam, and 0.2-100 ng/mL for estazolam, respectively, good linearities were obtained, correlation coefficients were 0.999 1-0.999 9, the lower limits of the quantifications ranged from 0.2 to 5 ng/mL, the extraction recovery rates were 81.12%-99.52%. The intra-day precision ［relative standard deviation （RSD）］ and accuracy （bias） were lower than 9.86% and 9.51%, respectively; the inter-day precision （RSD） and accuracy （bias） were lower than 8.74% and 9.98%, respectively. Nine drugs in urine samples showed good stability at ambient temperature and -20 ℃ within 15 days. The mass concentrations of alprazolam in urine samples obtained from 8 volunteers who took alprazolam tablets orally within 8-72 h after ingestions ranged from 6.54 to 88.28 ng/mL. Conclusion The supramolecular solvent extraction GC-MS/MS method for analysis of 9 benzodiazepines in urines provided by this study is simple, fast, accurate and sensitive, which can provide technical support for monitoring of poisoning by benzodiazepines for clinical treatment and judicial identification.

Biallelic Missense Mutation in the ECEL1 Underlies Distal Arthrogryposis Type 5 (DA5D)

Distal arthrogryposis (DA) is a heterogeneous sub-group of arthrogryposis multiplex congenita (AMC), mostly characterized by having congenital contractures affecting hands, wrists, feet, and ankles. Distal arthrogryposis is mostly autosomal dominantly inherited, while only one sub-type DA type 5D is inherited in an autosomal recessive manner. Clinically, DA5D is described having knee extension contractures, micrognathia, distal joint contractures, clubfoot, ptosis, contractures (shoulders, elbows, and wrists), and scoliosis. Using whole exome sequencing (WES) followed by Sanger sequencing, we report on a first familial case of DA5D from Pakistani population having a novel biallelic missense mutation (c.158C>A, p.Pro53Leu) in the ECEL1 gene. Our result support that homozygous mutations in ECEL1 causes DA5D and expands the clinical and allelic spectrum of ECEL1 related contracture syndromes.

Geopolymerization with bagasse bottom ash and china clay, effect of calcination temperature and silica to alumina ratio

The object of this work is to investigate the most appropriate calcination temperature and the ratio of silica to alumina for geopolymerization reactions using bagasse bottom ash and china clay.

Coinheritance of two rare genodermatoses (Papillon-Lefèvre syndrome and oculocutaneous albinism type 1) in two families: a genetic study

The co-occurrence of two rare recessive genetic conditions in apparently unrelated individuals or families is extremely rare. Two geographically distant and apparently unrelated families were identified in which individuals were simultaneously affected by two rare recessive mendelian syndromes, Papillon-Lefevre syndrome and type 1 oculocutaneous albinism. The families were tested for mutations in the causative genes, cathepsin C (CTSC) and tyrosinase (TYR), respectively, by direct sequencing. To assess the relationship of the two families, both families were tested for polymorphisms at eight microsatellite markers spanning both CTSC and TYR loci. Independent mutations (c.318-1G-->A and c.817G-->C/p.W272C) were identified in CTSC and TYR, respectively, that were shared by the affected individuals in both families. The two affected genes lie close together on chromosome bands 11q14.2-14.3, and studies with linked genetic markers suggested that the families shared a small chromosomal segment carrying both mutations that had been transmitted intact from a remote common ancestor. The co-occurrence of the two rare diseases in multiple families depends on their shared chromosomal location, but not on any shared pathogenic mechanism.

Regulation of NCAM by growth factors in serum-free myotube cultures

Regulation of the neural cell adhesion molecule (NCAM) was examined in primary cultures of chick skeletal muscle grown in serum-free defined medium. Relative levels of NCAM (per microgram protein) increased 20-30% in myotubes grown on Matrigel, a reconstituted basement membrane preparation, compared to those grown on collagen; total NCAM levels on Matrigel were increased 40-55% due to the additional increase in total protein. A dose dependent increase in relative NCAM levels in myotubes grown on Matrigel in defined medium was observed with the addition of adsorbed horse serum, while relative NCAM levels in myotubes grown on collagen were unaffected by altering the serum concentration. Thus, extracellular matrix molecules and soluble factors exert trophic effects on myotube NCAM expression. Similar developmental changes in the expression of the different molecular size forms of NCAM occurred in myotubes grown on collagen and Matrigel: levels of 150K and 135K Mr forms decreased during development, while 125K remained prominent in older myotubes. Relative NCAM levels were specifically enhanced 11-26% by several factors: nerve growth factor, thyroxine, insulin-like growth factor II, dibutyryl cyclic AMP, veratridine (a sodium ion channel agonist), and nisoldipine (a calcium ion channel agonist). Total protein and overall myotube development in serum-free cultures were enhanced by fetuin, insulin-like growth factor II, acidic fibroblast growth factor, calcitonin gene-related peptide, dibutyryl cyclic AMP, and veratridine. Thus, changes in extracellular matrix, intracellular calcium, and sodium ions, as well as extracellular trophic factors, such as nerve growth factor, thyroxine, and insulin-like growth factor II, may regulate muscle NCAM expression during embryonic development.

Matrigel enhances myotube development in a serum-free defined medium

Previously reported serum-free defined media for muscle cell culture require supplementation with hormones, purified growth factors or attachment factors. This report describes a culture system that enhances embryonic chick, skeletal muscle cell growth and differentiation in a serum-free defined medium, without added specialized trophic factors. Myoblasts adhered more to and proliferated more rapidly on a reconstituted basement membrane substrate, Matrigel, than on rat-tail collagen. Matrigel contains several basement membrane attachment molecules which apparently obviate the need for added purified attachment factors. Matrigel also appeared to play a trophic role in subsequent development by enabling the serum-free growth of myotubes which suggests that Matrigel mediates the cellular interaction of growth or attachment factors. Collagen, on the other hand, did not support serum-free myotube growth. Supplementation of defined medium with increasing levels of horse serum enhanced total protein in myotubes grown on both substrates; protein was higher in Matrigel cultures for each medium tested. The serum-free defined medium supported complete morphological differentiation of myotubes grown on Matrigel and maintained myotube cultures up to 22 days. Fibroblast proliferation was higher in cultures on collagen in defined medium with high serum levels, but was virtually eliminated in cultures on Matrigel in serum-free defined medium. The culture system described supports the differentiation of embryonic muscle cells in a simple, serum-free defined medium, thus providing an in vitro model of developing myotubes which should be particularly useful for studies of regulation mediated by extracellular factors.

Plasminogen activator secretion by established lines of human ovarian carcinoma cells in vitro

Ten human ovarian carcinoma cell lines (A121, A121[as], Caov-3, Caov-4, NIH:OVCAR-3, OVCA 420, OVCA 429, OVCA 432, OVCA 433, and SK-OV-3) were examined for secretion of plasminogen activators (PAs) using a chromogenic PA assay and SDS-PAGE zymography. PA activity was detected in conditioned media from all 10 cell lines. PA levels secreted by the 10 individual lines in a 24-hr period spanned a large range, with the extremes being 8 and 5244 milliPloug units (mPU)/10(6) cells for SK-OV-3 and OVCA 420 cells, respectively. Secreted PAs were identified as urokinase (UK)-like or tissue plasminogen activator (tPA)-like using dual criteria of comigration with UK or tPA standards on SDS-PAGE zymography and fibrin-dependence characteristics. Using both criteria, all 10 cell types produced UK-like activity, while tPA-like activity was produced by only 5 of the lines: A121[as], Caov-3, NIH:OVCAR-3, OVCA 429, and OVCA 433. Two additional cell lines produced PA activities that were tPA-like if judged by only one of the two criteria. Thus, Caov-4 cells produced a PA which comigrated with tPA, yet displayed no fibrin-dependent characteristics. Conversely, SK-OV-3 cells produced a fibrin-dependent PA, yet a band comigrating with tPA was not seen on SDS-PAGE zymography. Two lines derived from primary and ascitic sites from the same patient (A121 and A121[as], respectively) produced PAs with markedly different characteristics. Thus, PA produced by A121 cells was 100% UK-like, while that produced by A121[as] cells was greater than 90% tPA-like. Also, the total PA activity secreted by A121 cells was four times that secreted by A121[as] cells. In addition to bands comigrating with UK or tPA, all of the cell lines except Caov-3 and NIH:OVCAR-3 displayed higher molecular weight PA activities suggestive of the SDS-stable complexes between PAs and PA inhibitors reported in other cell types. While our results indicate that PA production may be a general characteristic of ovarian carcinoma cells in culture, individual patterns of UK and tPA production appear to be complex and vary from cell line to cell line. The precise characteristics of PA production in a given cell line may therefore depend on currently unidentified characteristics of the original tumor.

Hormonal regulation of CA125 tumor marker expression in human ovarian carcinoma cells: inhibition by glucocorticoids

The CA125 tumor marker is an antigenic determinant present on a high-molecular-weight glycoprotein expressed by more than 80% of newly diagnosed nonmucinous epithelial ovarian cancers. OVCA 433 human ovarian carcinoma cells express the CA125 marker at the cell surface and release large quantities of this antigen into culture medium. Here we show that release of CA125 by OVCA 433 cells is 90 to 95% inhibited by treatment with 1 x 10(-7) M dexamethasone, as determined using a biotin-based enzyme-linked immunosorbent assay utilizing OC125 monoclonal antibodies to CA125. The relative cell surface density of CA125 is also decreased following dexamethasone treatment as determined by immunofluorescence techniques using OC125 monoclonal antibodies. Inhibition of CA125 expression is specific for glucocorticoids, such as cortisol and dexamethasone, and does not occur with estrogens, progestins, androgens, or mineralocorticoids. CA125 inhibition is also dependent on the concentration of steroid used, with half-maximal and maximal inhibition by dexamethasone occurring at about 3 x 10(-9) M and 1 x 10(-7) M, respectively. Previous work has shown that OVCA 433 cells are growth inhibited by glucocorticoids and contain 14,000 glucocorticoid receptors per cell with an affinity for dexamethasone (Kd = 6.6 x 10(-9) M) which corresponds well with the concentration required for half-maximal CA125 inhibition. This correspondence, together with the specificity of CA125 inhibition for glucocorticoids, suggests that this effect is mediated by glucocorticoid receptors and is a specific biological effect of glucocorticoids on this cell type. Our results demonstrate glucocorticoid inhibition of CA125 expression by ovarian carcinoma cells and suggest that endogenous or therapeutically administered glucocorticoids can influence CA125 production by tumors in vivo.

Glucocorticoid sensitivity of OVCA 433 human ovarian carcinoma cells: inhibition of plasminogen activators, cell growth, and morphological alterations

OVCA 433 human ovarian carcinoma cells secrete large amounts of plasminogen activator (PA), which consists of immunologically identifiable urokinase (UK) and tissue-type PA (tPA). Total extracellular PA activity is 95% inhibited by treatment of cells with 1 X 10(-7) M dexamethasone (Dex) for 3 days. This inhibition is both time and concentration dependent, with half-maximal inhibition occurring after 1.5 days with 1 X 10(-7) M Dex, or with 1 X 10(-9) M Dex for 3 days, respectively. Interestingly, the loss of UK activity precedes the loss of tPA activity, such that half-maximal inhibition of the two PA types occurs at 1 and 2 days, respectively. Dex treatment leads to approximately 50% inhibition of cell growth and pronounced morphological alterations, including marked enlargement, flattening, and multinucleation. Treatment of the cells with other classes of steroid hormones, i.e., estrogens, progestins, androgens, and mineralocorticoids, is without effect on UK and tPA activities, cell growth, or morphology. OVCA 433 cells contain about 14,000 nuclear glucocorticoid receptors (GR) per cell (measured at 37 degrees C), with an average affinity (Kd) for [3H]Dex of 6.6 X 10(-9) M. Only active glucocorticoids compete with [3H]Dex for nuclear GR binding sites. Our results demonstrate steroid-specific glucocorticoid responsiveness of ovarian carcinoma cells, a tumor cell type not usually considered hormonally responsive. Since almost 90% of ovarian carcinoma tumor biopsies contain GR (M. C. Galli, et al., Cancer (Phila.), 47: 1297-1302, 1981), it is possible that glucocorticoid sensitivity could be exploited clinically, particularly following the almost universal development of resistance to the chemotherapeutic drugs commonly used in this disease.

Occupational chronic exposure to metals. I. Chromium exposure of stainless steel welders--biological monitoring

External and internal chromate exposure of 103 stainless steel welders who were using manual metal are welding (MMA), metal inert gas welding (MIG) and both methods, were measured by ambient and biological monitoring. At the working places the maximum chromium trioxide concentrations were 80 micrograms/m3. The median values were 4 micrograms/m3 (MMA) and 10 micrograms/m3 (MIG). The median chromium concentrations in erythrocytes, plasma and urine of all welders were less than 0.60, 9.00 and 32.50 micrograms/l. For biological monitoring purposes, chromium levels in erythrocytes and simultaneously in plasma seem to be suitable parameters. According to our results, chromium levels in plasma and urine in the order of 10 and 40 micrograms/l seem to correspond to an external exposure of 100 micrograms chromium trioxide per cubic metre, the technical guiding concentration (TRK-value). Chromium concentrations in erythrocytes greater than 0.60 micrograms/l indicate an external chromate exposure greater than the TRK-value.