Regulation of WT1 by phosphorylation: inhibition of DNA binding, alteration of transcriptional activity and cellular translocation

Phosphorylation is one of the major post-translational mechanisms by which the activity of transcription factors is regulated. We have investigated the role of phosphorylation in the regulation of nucleic acid binding activity and the nuclear translocation of WT1. Two recombinant WT1 proteins containing the DNA binding domain with or without a three amino acid (KTS) insertion (WT1ZF + KTS and WT1ZF - KTS) were strongly phosphorylated by protein kinase A (PKA) and protein kinase C (PKC) in vitro. Both PKA and PKC phosphorylation inhibited the ability of WT1ZF + KTS or WT1ZF - KTS to bind to a sequence derived from the WT1 promoter region in gel mobility shift assays. The binding of WT1ZF - KTS to an EGR1 consensus binding site was also inhibited by prior PKA and PKC phosphorylation. We also demonstrate the RNA binding activity of WT1, but this was not altered by phosphorylation. PKA activation by dibutyryl cAMP in WT1-transfected cells resulted in the reversal of WT1 suppression of a reporter construct. Although WT1 protein is predominantly localized to the nucleus, this expression pattern is altered upon PKA activation, resulting in the cytoplasmic retention of WT1. Accordingly, phosphorylation may play a role in modulating the transcriptional regulatory activity of WT1 through interference with nuclear translocation, as well as by inhibition of WT1 DNA binding.

Is there implicit memory after propofol sedation?

Recent evidence indicates that implicit memory may be preserved during general anaesthesia. We tested for the presence of explicit and implicit memory in patients undergoing surgical procedures with local or regional anaesthesia and sedation with propofol. Initial i.v. boluses of propofol 0.5 mg kg-1 and fentanyl 1 microgram kg-1 were administered, followed by an infusion of propofol 50 micrograms kg-1 min-1. Administration of one or more doses of propofol 30 mg i.v. during operation was controlled either by the patient or the anaesthetist. At the start of the last skin stitch, patients were presented with a list of 15 stimulus words and the most frequently associated response. The infusion was then discontinued. After 1 h in the recovery area, all patients were tested for free recall, free association, cued recall and recognition on the list presented during surgery (critical list) and a matched list not presented (neutral list). Data of all patients without free recall (explicit memory) were analysed with repeated-measures analysis of variance. Of 36 patients, five demonstrated free recall. For the remaining 31 patients, cued recall and recognition showed no evidence of explicit memory. However, the free association tests demonstrated significant priming. The mean number of critical free associations was 6.6 (SEM 0.4) compared with 5.5 (0.4) neutral free association (P < 0.05). In the absence of explicit memory, implicit memory persists after intraoperative sedation with propofol.

Synergistic transcriptional activation of the tissue inhibitor of metalloproteinases-1 promoter via functional interaction of AP-1 and Ets-1 transcription factors

The tissue inhibitor of metalloproteinases-1 (TIMP-1) is an inhibitor of the extracellular matrix-degrading metalloproteinases. We characterized response elements that control TIMP-1 gene expression. One contains a binding site that selectively binds c-Fos and c-Jun in vitro and confers a response to multiple AP-1 family members in vivo. Adjacent to this is a binding site for Ets domain proteins. Although c-Ets-1 alone did not activate transcription from this element, it enhanced transcription synergistically with AP-1 either in the context of the natural promoter or when the sequence was linked upstream of a heterologous promoter. Furthermore, a complex of c-Jun and c-Fos interacted with c-Ets-1 in vitro. These results suggest that AP-1 tethers c-Ets-1 to the TIMP-1 promoter via protein-protein interaction to achieve Ets-dependent transcriptional regulation. Collectively, our results indicate that TIMP-1 expression is controlled by several DNA response elements that respond to variations in the level and activity of AP-1 and Ets transcriptional regulatory proteins.

A constant cathodic potential device for faradic stimulation of osteogenesis

The purpose of this study was to design, develop, and test a device that continuously maintains a constant potential at a cathode with respect to a reference electrode by automatically varying the potential between the cathode and an anode. The ability of the device to maintain a constant cathodic potential with respect to a silver/silver chloride reference electrode is demonstrated in acute testing with a variety of electrodes as well as in chronic testing conducted until battery failure. This constant cathodic potential device permits delivery of current at an optimal cathodic potential for faradic stimulation of osteogenesis which involves a net transfer of charge through biological tissue between, typically, an implanted cathode, the negative electrode where osteogenesis occurs, and either an implanted or a topical anode, the positive electrode required only to complete the electrical circuit. Unlike present devices that maintain a constant direct current between a cathode and an anode but permit potential between said electrodes to vary, this device presents the possible detrimental effects of an undesired electrochemical reaction due to an excessive cathodic potential.

Asymptomatic undetected mediastinal mass: a death during ambulatory anesthesia

T-cell lymphoma is the fastest growing non-Hodgkin's lymphoma occurring in children. Its clinical presentation is frequently abrupt, and total tumor mass can double every few days. At the same time, the number of ambulatory anesthesia procedures for children is increasing at a rapid rate. Anesthesiologists are constantly faced with decisions regarding the adequacy of available preoperative information. What information do we need, and how recent should it be? This case shows that recent diagnostic imaging studies not showing the presence of a mediastinal lymphoma can be misleading. It provides a strong warning to all anesthesiogists involved in ambulatory anesthesia.

Antisense transcripts and protein binding motifs within the Wilms tumour (WT1) locus

Transcription of the WT1 locus is restricted, both temporally and spatially, to a subset of epithelial cells in mammalian kidneys and gonads. WT1, one of the two divergent transcripts mapping to this locus encodes a zinc finger protein that is likely a transcriptional regulator. The other transcript, WIT1, encodes a product of unknown function that is subject to alternate splicing in the region immediately 5' of the WT1 gene. Analysis of the 5' end of this locus further revealed the presence of multiple transcriptional start sites for both genes, such that some of the WIT1 transcripts are encoded by the antisense strand of the first exon of WT1. The genomic region surrounding the transcriptional start sites appears to constitute part of a bi-directional promoter based on the ability of a DNA fragment derived from this region to direct expression of a chimeric CAT gene construct in transient transfection assays. Discrete sequences within the region are capable of interaction in vitro with nuclear extracts derived from a variety of rat and mouse tissues. Interestingly, recombinant WT1, representing the product of zinc finger region of the most abundant of the four alternatively spliced transcripts, is also capable of binding to sequences within this region.

The role of WT1 in Wilms tumorigenesis

Genetic alterations in tumor suppressor genes are believed to play an important role in the initiation of childhood and adult malignancies. Tumor-specific loss of heterozygosity for particular chromosomal regions has provided the starting point for the cloning of different tumor suppressor genes, including the Wilms tumor predisposing gene, WT1, at chromosome 11p13. This article reviews the pathology and genetics of Wilms tumor, the cloning of WT1, and the WT1 mutations reported thus far in 15 hereditary and nonhereditary Wilms tumors. The presence of constitutional WT1 mutations in 35 patients with the Denys-Drash syndrome (a syndrome consisting of nephropathy, intersex disorders, and Wilms tumor) is also described. To date, mutations in the WT1 gene have been found in less than 10% of Wilms tumors specimens examined and in greater than 95% of Denys-Drash patients. The possible significance of this observation with regard to both the cellular function of the WT1 protein and the involvement of alternative loci in the development of Wilms tumor is discussed.

Review of respirator performance testing in the workplace: issues and concerns

Performance capability of respirators has traditionally been evaluated by testing components of the respirator (e.g., filter efficiency), facepiece fit, total inward leakage, or some other measure of performance evaluated under laboratory conditions. In recent years, increased emphasis has been placed on development of test methods suitable for evaluating respirator performance in the workplace. The goal of such testing is to evaluate the level of protection provided by respirators in the work environment. The AIHA Respiratory Protection Committee believes that workplace testing of respirators has the potential to be an excellent tool for increasing knowledge about the effectiveness of respiratory protection. However, a number of technical issues remain to be addressed before optimal test protocols and data analysis methods can be defined. The progress made to date in workplace testing will be reviewed, and broader discussion about key elements that must be considered when developing guidelines for testing respirators in the workplace will be initiated.

Loss of heterozygosity mapping in Wilms tumor indicates the involvement of three distinct regions and a limited role for nondisjunction or mitotic recombination

Loss of heterozygosity (LOH) for polymorphic markers is a frequently occurring event in some tumors, reflecting the role of allele loss in the development of these tumors. We have determined LOH in 38 cases of Wilms tumor for the 2 known loci on chromosome arm 11p and for a newly detected locus on chromosome arm 16q. Only 7 of the 38 tumors studied showed reduction to homozygosity of 11p13 markers. In 4 of these tumors, reduced expression of WT1 and WIT1, genes located at 11p13 and implicated in Wilms tumorigenesis, was noted. However, this was also found in 2 of 7 tumors showing LOH exclusively of 11p15 markers and in 15 of the remaining 24 tumors in which there was no LOH for 11p markers. This suggests that events not involving mitotic recombination or chromosome nondisjunction are the most common mechanisms for mutations at the 11p Wilms tumor locus. We also noted that mitotic recombination involving 11p15 loci occurred in addition to reduced expression of the 11p13 locus genes in 2 tumors, suggesting a possible interaction between these 2 loci. In addition, LOH for 16q markers was observed in 6 tumors. In one case this was coincident with reduction of WT1 and WIT1 gene expression, and in 3 other cases it occurred in addition to 11p LOH. This indicates that an additional locus on 16q is likely to be involved in Wilms tumorigenesis.

Intravenous nitroglycerin for uterine inversion

Uterine inversion following vaginal delivery or during Cesarean section is rare. Cardiovascular instability resulting from blood loss is possible. This article describes the use of intravenous nitroglycerin as an alternative to the induction of general anesthesia and administration of volatile anesthetics to provide uterine relaxation.

Identification of a serum- and phorbol ester-responsive element in the murine tissue inhibitor of metalloproteinase gene

Tissue inhibitor of metalloproteinase (TIMP) is one of a family of metalloproteinase inhibitors and a major interstitial inhibitor of collagenase. Transcription of the TIMP gene is induced by such diverse agents as viruses, phorbol esters, serum, and growth factors. We have previously assigned the regulatory elements responsible for induction of transcription in response to viruses to the first intron of the murine TIMP gene. Here we have identified a promoter and an enhancer element responsive to serum and the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate. Based on a comparative sequence analysis of the murine and human genes, the enhancer element is part of a 38-base pair conserved sequence. Gel mobility shift assays indicate that this enhancer is a phorbol ester-responsive-like element that likely binds one of a family of AP-1 proteins. Interestingly, the region containing the phorbol ester-responsive-like element is also sufficient to direct a response to transforming growth factor beta 1 in the presence of serum.

Tissue, developmental, and tumor-specific expression of divergent transcripts in Wilms tumor

The Wilms tumor locus on chromosome 11p13 has been mapped to a region defined by overlapping, tumor-specific deletions. Complementary DNA clones representing transcripts of 2.5 (WIT-1) and 3.5 kb (WIT-2) mapping to this region were isolated from a kidney complementary DNA library. Expression of WIT-1 and WIT-2 was restricted to kidney and spleen. RNase protection revealed divergent transcription of WIT-1 and WIT-2, originating from a DNA region of less than 600 bp. Both transcripts were present at high concentrations in fetal kidney and at much reduced amounts in 5-year-old and adult kidneys. Eleven of 12 Wilms tumors classified as histopathologically heterogeneous exhibited absent or reduced expression of WIT-2, whereas only 4 of 14 histopathologically homogeneous tumors showed reduced expression. These data demonstrate a molecular basis for the pathogenetic heterogeneity in Wilms tumorigenesis.

Gene inactivation as a mechanism for the expression of recessive phenotypes

A series of Chinese hamster ovary cell hybrids were constructed which were heterozygous at the emtB and chr loci. These loci encode two recessive drug-resistance genes (emetine resistance and chromate resistance, respectively) located on a structurally hemizygous region on the long arm of chromosome 2. These heterozygous hybrids therefore exhibit wild-type sensitivity to both emetine and chromate. Drug-resistant variants were then selected in medium containing either emetine or chromate, and the mechanism of reexpression of the recessive drug-resistant allele was determined by karyotypic analysis of the resultant colonies. In previous studies at these loci we have determined that segregation of the recessive phenotype occurs primarily by (1) the loss of the chromosome 2 carrying the wild-type, drug-sensitive, allele, (2) deletion of the long arm of chromosome 2, or (3) loss of one chromosome 2 followed by duplication of the remaining homologue. However, a small proportion of segregants have also been detected which may have arisen by the mechanisms of de novo gene inactivation or mutation. In this report, hybrids are described which were constructed to allow selection for the retention of the chromosome carrying the wild-type allele and which therefore optimize isolation of these rare segregants. We demonstrate by karyotypic analysis, mutation frequency analysis, and microcell-mediated chromosome transfer that these rare segregants occur primarily by gene inactivation. We also demonstrate a dramatic increase in the proportion of segregants occurring by gene inactivation in two of these hybrids as compared with those previously reported, indicating that this mechanism may be an important mode of phenotype segregation in diploid cells and, therefore, in the development of cancers--such as the childhood tumors retinoblastoma and Wilms tumor--resulting from recessive alleles

Microtopography and soft tissue response

Implants placed in soft tissue evoke a foreign body reaction. Polymeric implants having smooth surfaces, such as silicone rubber implants, develop a nonadherent fibrogranulous tissue capsule which contracts over time and stiffens. Conventional porous implants, such as those made from textiles, usually have pores larger than 20 microns and they become infiltrated with inflammatory tissue. The in vivo cell reaction to polymeric surfaces having pores smaller than 10 microns has not been investigated systematically. In this study the histocompatibility of materials having mean pore diameters from 0.4 to 10 microns was assessed. A material available with several different defined pore sizes Versapor filter material) was tested in vivo to determine relation between pore size and qualitative tissue response. Silicone-coated samples were also tested to determine the dependence of the observed tissue response on the implant surface chemistry. Results showed nonadherent, contracting capsules around implants having pore diameters smaller than 0.5 microns. Implants with pores ranging from 1.4 to 1.9 microns evoked thin, tightly adherent fibrous capsules without inflammatory cells. Porosities of 3.3 microns and larger became infiltrated with inflammatory tissue. Results indicate that the observed tissue response is predominantly dependent on implant surface topography and that variation in implant material may have little effect. It is concluded that a defined surface topography of 1 to 2 microns appears to allow direct fibroblast attachment to the surface independent of its chemical or electrochemical nature. Attached fibroblasts then produce a minimal connective tissue response to the implant and prevent or diminish the presence of inflammatory cells at the implant/tissue interface.

Uric acid decomposition in the lower gastrointestinal tract

Uric acid is the end product of nitrogen metabolism in birds. Despite the very low aqueous solubility of this purine compound, few crystals of uric acid are found in the urine. Instead, uric acid is packaged into small spheres that can pass easily through the duct system of the kidney. After entering the cloaca, these spheres are moved with the urine by antiperistalsis into the rectum and digestive ceca. In the ceca, the uric acid is exposed to a large population of bacteria that can use the uric acid as a metabolic substrate. These bacteria degrade the uric acid to volatile fatty acids (VFA) and ammonia. The VFA are absorbed by the cecal tissue, and the ammonia is incorporated into the production of glutamine. The refluxing of uric acid into the ceca and its subsequent degradation by bacteria provides an effective mechanism for the reclamation of carbon and nitrogen from the urine.