Autoregulation of the human WT1 gene promoter

The human Wilms tumour suppressor gene, WT1, encodes a zinc-finger protein which can function as a transcriptional activator or suppressor. This study reports the analysis of the human WT1 gene promoter, and demonstrates that high levels of WT1 expression lead to autosuppression of the WT1 promoter. Deletion analyses of the promoter region implicate sequences 5' and 3' of the transcriptional start site as being crucial in WT1 autosuppression. Loss or alteration of this function of WT1 may be important in tumourigenesis.

Magnetic resonance abnormalities and cardiovascular disease in older adults. The Cardiovascular Health Study

BACKGROUND AND PURPOSE

Cerebral magnetic resonance imaging often detects abnormalities whose significance is unknown. The prevalence and correlates of findings such as ventricular enlargement, sulcal widening, and increased white matter signal intensity were examined in 303 men and women aged 65 to 95 years participating in a multicenter study of cardiovascular disease.

METHODS

Cerebral magnetic resonance imaging was performed and interpreted according to a standard protocol, and findings were correlated with measures of cardiovascular disease and its risk factors.

RESULTS

Measures of cerebral atrophy increased with age and were greater in men than in women (each P < .01). Ventricular enlargement and sulcal widening were associated with prior stroke, hypertension, diabetes, and white race (each P < .03). Extent of white matter hyperintensity was associated with age, prior stroke, hypertension, and use of diuretics (each P < .004). On multivariate analysis, age, male gender, white race, and prior stroke retained strong associations with increased ventricular and sulcal scores. After adjustment for age, prior stroke, and other risk factors, white matter hyperintensity was associated with atherosclerosis as measured by increased internal carotid artery thickness on ultrasound.

CONCLUSIONS

Cerebral atrophy and white matter hyperintensity are common in the elderly and are associated with age, prior stroke, and known cardiovascular risk factors. Though these findings have been suggested to represent normal aging, their wide variability and associations with cardiovascular disease argue against their inevitability with advancing age and support the need to identify modifiable risk factors for these abnormalities.

Environmental signals and neural crest cells

Cell lineage analysis in both the central and peripheral nervous system of vertebrates has revealed that many neural progenitor cells are multipotent. These observations have raised the general issue of when and how such multipotent progenitors generate their various differentiated progeny. The environment of these progenitors controls the cell lineage decisions in the neural crest. This review considers the roles of the environmental signals in the context of the development of several different neural crest-derived lineages.

Carcinomatous encephalitis (miliary metastases): lack of contrast enhancement

Carcinomatous encephalitis is a rare form of brain metastasis in which there is diffuse miliary spread of punctate tumor nodules in a perivascular distribution. In this case, these tiny tumor nodules were seen throughout the cortical and basal gangliar gray matter only on T2-weighted images. Contrast-enhanced CT and T1-weighted MR images did not demonstrate these tumor nodules.

Inactivation of the remaining allele of the WT1 gene in a Wilms' tumour from a WAGR patient

A candidate gene (WT1) has recently been described for the 11p13 tumour-suppressor gene involved in the development of Wilms' tumour. This gene encodes a zinc finger protein which can bind to a specific DNA sequence. We have found a 226 base deletion in the mRNA from a unilateral Wilms' tumour, which would cause a frameshift that completely deletes the zinc finger domain. The tumour developed in a patient suffering from the WAGR syndrome, who had a constitutional 11p13 deletion, and so the 226 base deletion represents the inactivation of the remaining WT1 allele in the tumour. This provides further direct evidence that loss of function of WT1 is an essential step in the development of Wilms' tumour.

Analysis of high PSA N-CAM expression during mammalian spinal cord and peripheral nervous system development

Using a monoclonal antibody that recognizes specifically a high polysialylated form of N-CAM (high PSA N-CAM), the temporal and spatial expression of this molecule was studied in developing spinal cord and neural crest derivatives of mouse truncal region. Temporal expression was analyzed on immunoblots of spinal cord and dorsal root ganglia (DRGs) extracts microdissected at different developmental stages. Analysis of the ratio of high PSA N-CAM to total N-CAM indicated that sialylation and desialylation are independently regulated from the expression of polypeptide chains of N-CAM. Motoneurons, dorsal root ganglia cells and commissural neurons present a homogeneous distribution of high PSA N-CAMs on both their cell bodies and their neurites. Sialylation of N-CAM can occur in neurons after their aggregation in peripheral ganglia as demonstrated for dorsal root ganglia at E12. Furthermore, peripheral ganglia express different levels of high PSA N-CAM. With in vitro models using mouse neural crest cells, we found that expression of high PSA N-CAM was restricted to cells presenting an early neuronal phenotype, suggesting a common regulation for the expression of high PSA N-CAM molecules, neurofilament proteins and sodium channels. Using perturbation experiments with endoneuraminidase, we confirmed that high PSA N-CAM molecules are involved in fasciculation and neuritic growth when neurons derived from neural crest grow on collagen substrata. However, we demonstrated that these two parameters do not appear to depend on high PSA N-CAM molecules when cells were grown on a fibronectin substratum, indicating the existence of a hierarchy among adhesion molecules.

Traumatic aneurysm of the superior cerebellar artery: case report and review of the literature

Less than 10% of the 250 reported cases of traumatic intracranial aneurysms have involved the posterior circulation. Traumatic aneurysms of the superior cerebellar artery are extremely rare, with only three cases previously reported. This is the first report of a traumatic superior cerebellar artery aneurysm in which the diagnosis was suggested by computed tomographic scan. The potential for a good outcome suggests the value of early angiography when the history and diagnostic imaging studies suggest the possibility of a traumatic aneurysm.

Molecular and cellular biology of Wilms' tumour

Wilms' tumour is an embryonal kidney tumour which exists in an hereditary and sporadic form. Apart from its obvious importance as a model for renal development and differentiation, the tumour has recently been exploited as an example of the action of tumour suppressor genes (or anti-oncogenes). The latter genes are characterised by a somatic loss of genetic information in tumour development, specifically from the short arm of human chromosome 11 in Wilms' tumour. To further study the developmental aspects of the tumour we have established in vitro cell cultures from tumour tissues, which, unlike the majority of Wilms' tumour cell lines, have been genotyped according to their chromosome 11 gene status and their antigen expression patterns, compared to the original normal kidney and tumour tissues. The cell cultures exist both as primary and secondary cultures, and their limited life span in culture has been extended by transfection of SV40 large T antigen. The mechanism of tumour suppression by the Wilms' locus has been explored by producing cell hybrids between the immortalised kidney cells, and an "indicator cell" (HeLa), whose chromosome 11 genotypes have been monitored in vivo and in vitro by restriction fragment length polymorphisms. Non-random patterns of inheritance of the mutant allele have also been investigated, both in tumour tissue and in syndromes, like the Beckwith-Wiedemann Syndrome, which pre-dispose to development of Wilms' tumour (and other embryonal tumours). It is also apparent that allele-specific methylation occurs in Wilms' tumour tissues, probably resulting in changes of gene expression patterns. Significant elevation of transcription of the N-myc oncogene was detected in the blastemal cells of the most malignant Wilms' tumours, whereas a marked decrease in the expression of HLA class I, at both RNA and protein levels was observed in the same cells. Wilm's tumour provides a clear illustration of the requirement for a combination of dominantly and recessively acting genes, in order to produce a malignant embryonal tumour.

Loss of chromosome 11p alleles in cultured cells derived from Wilms' tumours

Cell cultures have been produced from five Wilms' tumours. All cultures had a finite lifespan and a pattern of antigen expression which indicated that the cells were derived from the differentiated components of the tumours. No cells showed any of the expected characteristics of the putative Wilms' tumour stem cell. Nevertheless, in both cases where the original tumours showed a loss of heterozygosity at chromosome 11p alleles, the cultured cells also demonstrated a loss of heterozygosity. Thus these cell cultures definitely originated from Wilms' tumour tissue. The results demonstrate that cell cultures can be produced from the differentiated tissues present in Wilms' tumours and that these non-immortal cells show no 'transformed' phenotype, even though they possess the genetic changes present in the original tumour.

SV40 transfection of human kidney epithelial cells and stability of chromosome 11

Simian virus 40 (SV40) transformation has been used in a variety of mammalian cells and has been shown to extend their life span. We therefore decided to apply these results to normal kidney and tumoral cells derived from Wilms' patients. Wilms' tumour, a nephroblastoma which presents in early childhood, has been linked to deletions and rearrangements in chromosome 11. Analysis of gene structure in the 11p13 locus involved in the development of the tumour has been restricted by the very short life-span of the tumoral cells in vitro. We transfected normal kidney WT/NK, tumoral WT/T cells and human foetal kidney HFK cells with 2 SV40-derived plasmids SV3neo (pBR322-SV40-containing neomycin bacterial gene) and SVori- (pMK-origin mutated SV40). We isolated a high number of SV40-transfected cell lines. The efficiency of transfection appeared to be extremely low in WT/T cells compared with HFK and even WT/NK. The life span of the cell lines was increased in relation to their untransfected homologues. However, in all of the cell lines except 3, senescence occurred, after crisis step or not. We looked at different markers associated with SV40 transformation of mammalian cells and specifically with the presence of SV40 T antigen in the cells and its consequences: AIG, tumorigenicity, expression and insertion in genomic DNA of SV40 T antigen. Genetic studies involving karyotypic and restriction fragment length polymorphism (RFLP) analysis demonstrated that, despite a frequent pseudo-diploidy, the cell lines derived have conserved the 11p13 locus.

Expression of the N-myc oncogene in Wilms' tumour and related tissues

Tissue samples and cell cultures from Wilms' tumour matched histologically normal kidney samples and EBV transformed B cells from the same patients, were analysed to detect changes in the structure and expression of the N-myc oncogene. The levels of expression of HLA class I and hypoxanthine guanine phosphoribosyl transferase were also measured in the various RNA preparations. Related tissue samples, from sources including congenital mesoblastic nephroma, paediatric neuroblastoma and a number of foetal tissues were also tested. Northern blot analysis indicated that the levels of N-myc were higher in Wilms' tumour tissues (with no parallel increase in gene copy number) compared to all other sources of material including foetal kidney. Particularly high levels of expression were observed in a number of the Wilms' tumours, several of which produced metastases. In situ hybridization, using [35S]-labelled RNA probes, confirmed that the high levels of N-myc RNA were present in the blastemal elements in the Wilms' tumour. All the tissue cultures, and tissue samples from other sources, except foetal brain and neuroblastoma, contained uniformly low levels of N-myc RNA.

NAD and the synthesis of (ADP-ribose)n in a human cell strain (46BR) hypersensitive to the lethal effects of 3-aminobenzamide

The cell strain 46BR, derived from an immunodeficient individual, is hypersensitive to the lethal effects of DNA-damaging agents, and of 3-aminobenzamide (3AB), the latter being an inhibitor of the enzyme ADP-ribosyltransferase (ADPRT). This hypersensitivity is not found with the noninhibitory analogue, 3-aminobenzoate. The NAD content of 46BR cells is similar to that of fibroblasts from normal human donors, as is the decrease in NAD content following treatment with dimethylsulphate. Both the activity of ADP-ribosyltransferase and its inhibition by 3AB in permeabilized cells are similar in 46BR and in normal cell strains. High concentrations of 3AB interfere with purine metabolism in cultured cells. Again this effect is similar in 46BR and normal cells. Thus there is no apparent anomaly either in the activity of ADPRT or in the gross effects of 3AB in 46BR. The sensitivity to 3AB may be caused by a defect in a specific acceptor for the ADP-ribose synthesized by ADPRT, or in some as yet undiscovered action of the inhibitor.

Chromosomal aberrations induced by ethylene oxide in a human amniotic cell line in vitro

Ethylene oxide was found to be a potent inducer of chromatid-type aberrations in a human amniotic cell line. This induction was dose-dependent. At doses corresponding to about 9% survival, the number of chromatid exchanges was increased about 20 times, and the number of induced breaks increased 50 times, above that observed in the controls.

An appraisal of blood trauma and blood-prosthetic interface during left ventricular bypass in the calf and humans

Mechanical circulatory support was accomplished in 20 calves (mean, 140 days) and in 5 patients following operation for acquired heart disease (range, 1 hour to 8 days) employing a pneumatically actuated xenograft-valved assist pump interposed between the left ventricular apex and aorta. Following pump implantation in calves, hematocrit and platelets decreased transiently and returned to normal within 14 days. Plasma hemoglobin and erythrocyte mechanical fragility values were elevated for 48 hours. Platelet survival was slightly reduced, but erythrocyte survival values were similar to controls. In patients who received assist pumps, plasma hemoglobin and erythrocyte mechanical fragility were transiently elevated, but rapidly decreased to normal. Thrombocytopenia occurred only in the presence of bleeding and renal failure requiring hemodialysis. Pump flow of the left ventricular assist device was maintained above 2.0 L/min/m2 despite serious arrhythmias. Postmortem examination revealed no evidence of thromboemboli in the clinical patients although anticoagulant agents were not administered.

Advances in electrical assist devices

Marked improvements were realized in the development of electrically driven left ventricular assist systems. A volume reduction of 46%, a system weight reduction of 63%, and a factor of 2 improvement in overall efficiency (29%) were realized. The system, operating at a pressure of 120 mm Hg with a flow rate of approximately 7 L, requires only 7.5 W of input power. In addition, a unique brushless commutator was designed to replace standard brushes, thus increasing system life. A new polyurethane was synthesized for utilization in the TMS. This material has demonstrated high flex life in addition to being biocompatible. Further improvements in system weight and size, as well as efficiency, will be realized when flat plate pumps are mated to electric drivers.

Selection of materials for ventricular assist pump development and fabrication

A study was undertaken to select 2 of the most promising bladder materials from a list of 8 carefully chosen polymers. The polymers chosen for testing included a wide spectrum of urethanes, as well as a polyester resin and a millable polyolefin rubber. The following materials were studied: Adiprene LW-500, Avcothane 51, Biomer, Hexsyn, Hytrel 4055, Mobay 240313, Pellethane 2103-80 AE, and Tecoflex HR. The selection process was based on a test matrix which was divided into segmented steps, each a logical sequel from its predecessor, and each of increasing technical complexity. Hydrolytic stability, flexure endurance, fabricability, tissue compatibility, hemocompatibility and chronic tissue compatibility were evaluated, forming the basis for the acceptance/rejection criteria. As a result of this search, 2 biomaterials were identified as most suitable for use in conventionally flocked bladders; Biomer and Tecoflex HR. Both Biomer and Tecoflex HR bladders have demonstrated impressive results in circulatory analog loop endurance tests, with Tecoflex bladders surpassing 50 million flexes to date, and Biomer bladders (the longest running bladders) exceeding 150 million flexes. Tests are continuing.