Rescue of embryonic lethality in Mdm4-null mice by loss of Trp53 suggests a nonoverlapping pathway with MDM2 to regulate p53.

The p53 protein can inhibit cell cycling or induce apoptosis, and is thus a critical regulator of tumorigenesis. This protein is negatively regulated by a physical interaction with MDM2, an E3 ubiquitin ligase. This interaction is critical for cell viability; loss of Mdm2 causes cell death in vitro and in vivo in a p53-dependent manner. The recently discovered MDM2-related protein MDM4 (also known as MDMX) has some of the same properties as MDM2. MDM4 binds and inhibits p53 transcriptional activity in vitro. Unlike MDM2, however, MDM4 does not cause nuclear export or degradation of p53 (refs. 9,10). To study MDM4 function in vivo, we deleted Mdm4 in mice. Mdm4-null mice died at 7.5-8.5 dpc, owing to loss of cell proliferation and not induction of apoptosis. To assess the importance of p53 in the death of Mdm4-/- embryos, we crossed in the Trp53-null allele. The loss of Trp53 completely rescued the Mdm4-/- embryonic lethality. Thus, MDM2 and MDM4 are nonoverlapping critical regulators of p53 in vivo. These data define a new pathway of p53 regulation and raise the possibility that increased MDM4 levels and the resulting inactivation of p53 contribute to the development of human tumors.

Applicability of the dual isotopes δ15N and δ18O to identify nitrate in groundwater beneath irrigated cropland.

Identification of the nitrate sources that adversely impact groundwater quality is a necessary first step in the control of this major worldwide pollutant. The impact of nitrate leachate from urea-ammonium nitrate (UAN) (50% urea-N, 25% ammonium-N, 25% nitrate-N) fertilizer, whose use has increased dramatically in the last three decades largely because it can be applied through sprinkler irrigation systems to corn in all growth stages, is investigated. The dual isotopes δ15NNO3 and δ18ONO3 were measured in groundwater samples from 39 irrigation wells in two intensively sprinkler-irrigated, corn-growing areas of Nebraska with nitrate-contaminated (N > 10 mg/L) groundwater and documented UAN use to ascertain whether nitrified ammonia and nitrate fertilizers can be distinguished in the High Plains aquifer. The areas, which are highly vulnerable to nitrate leaching and differ only in the composition and thickness of their unsaturated zones, are uniquely suited to provide scientific evidence of the feasibility of identifying nitrate fertilizer leachate in groundwater and thereby add significantly to the small body of existing and inconclusive data. The dual isotope method (DIM) results indicate that the nitrate contamination in 38 wells is mostly nitrified ammonium fertilizer. Most importantly, nitrate fertilizer from UAN was not identified isotopically in groundwater beneath almost all fields with documented heavy UAN use. This could be a potentially valuable finding for fertilizer management or it could convey limitations on the appropriateness of the DIM for nitrate fertilizer source identification in groundwater. Slightly enriched δ15NNO3 values in a few wells coincide with the practice of wintering cattle on corn stubble, which reportedly occurred more frequently in one focus area. The absence of natural soil-N leachates and denitrification in groundwater enabled an apparently reliable identification of manure leachates in both areas.

Hdmx and Mdm2 can repress transcription activation by p53 but not by p63.

The p53 protein is involved in cell cycle arrest and apoptosis. To ensure that cells under non-stressed conditions are able to grow, p53 sets up a negative feedback loop by inducing Mdm2. Mdm2 is able to both inhibit the transcriptional regulation by p53 and to degrade it, thus maintaining p53 inactive until it is required. The Mdm2 related protein, Hdmx, has also been shown to inhibit the transcriptional activation of p53 but is unable to degrade it. A few years ago, the p53 family member, p63 was identified. Like p53, p63 is able to induce p53 target genes and it was shown to be able to cause cell cycle arrest and apoptosis. In this study we report that, despite the similarities between p53 and p63, neither Hdmx nor Mdm2 are able to interact with p63, to repress p63-induced transcription or to affect its half-life.

Vaginal wall sling: four years later.

Since December 1985, we have treated 65 patients with urinary stress incontinence due to intrinsic sphincter dysfunction with the vaginal wall sling procedure. Of the 54 patients who were available for follow-up, intrinsic sphincter dysfunction was related to multiple prior bladder neck suspension procedures in 48 patients. In the remaining 6 patients, 2 had pelvic trauma, 2 had neurogenic urethral dysfunction, 1 had urethral diverticulectomy, and 1 had pelvic radiation. The success rate of the vaginal wall sling procedure for correcting stress incontinence was 94.4 percent at a mean follow-up of 23.9 months. Postoperative complications were minimal. Although 83 percent were temporarily in urinary retention, in the absence of neurogenic bladder and augmentation cystoplasty, only 5.5 percent needed intermittent self-catheterization on a long-term basis. De novo detrusor instability developed postoperatively in 14.8 percent of the cases. In no patient did a vaginal inclusion cyst develop. The vaginal wall sling is a simple procedure with excellent success rate and minimal morbidity. We recommend it for patients with stress urinary incontinence due to intrinsic sphincter dysfunction.

Pedunculated scrotal mass: leiomyoma of scrotum.

Scrotal leiomyomas of the tunica dartos are extremely rare and usually misdiagnosed. A case of a pedunculated mass observed expectantly over thirty years demonstrates the benign oncologic natural history of this lesion despite its capability for substantial growth. Only limited local surgical management of such lesions is indicated.

Chylothorax: a rare complication of metastatic prostatic carcinoma.

Chylothorax is an uncommon condition rarely seen in urological oncology and it is an extremely rare complication of prostatic carcinoma. Such a case is described in which successful palliative management with a combination of chemotherapy and radiation therapy was used. Alert recognition of the process and aggressive therapy would appear to be the key to management.

Basic evaluation of female urinary incontinence.

Urinary incontinence is a common disorder that is frequently underreported because of its social implications. Although several types of urinary incontinence are recognized, they can be generally classified as failure of the bladder to store or failure of the urethral mechanism. A systematic approach for the evaluation of incontinence that includes history, physical examination, basic laboratory tests, and often urodynamic evaluation, offers the most comprehensive assessment of the etiology of incontinence.

Identification of WTAP, a novel Wilms' tumour 1-associating protein.

The Wilms' tumour suppressor gene WT1 is essential for the normal development of the genitourinary system. It appears to play a role in both transcriptional and post-transcriptional regulation of certain cellular genes. However, the mechanisms behind WT1 function are not clearly understood despite the identification of numerous potential target genes and the isolation of several WT1-binding proteins. This study therefore sets out to identify other WT1-associating proteins to help to unravel how WT1 interacts with the cellular machinery. We report the identification of a novel human WT1-associating protein, WTAP, which was isolated using the yeast two-hybrid system. Both in vitro and in vivo assays have shown that the interaction between WTAP and WT1 is specific and occurs endogenously in cells. The mouse homologue of WTAP was isolated and found to be >90% conserved at the nucleotide and protein levels. The human and mouse genes were mapped using fluorescence in situ hybridization to regions in chromosomes 6 (which is thought to harbour a tumour suppressor gene) and 17, respectively. The expression pattern of WTAP was investigated and shown to be ubiquitous, perhaps reflecting a housekeeping role. WTAP is a nuclear protein, which like WT1 localizes throughout the nucleoplasm as well as in speckles and partially co-localizes with splicing factors. Although the significance of this interaction is not yet known, WTAP promises to be an interesting WT1-binding partner.

Influence of trans unsaturated fats on experimental atherosclerosis in rabbits.

To test the effects of trans unsaturated fatty acids (t-FA) on atherosclerosis, lipidemia and enzyme activities, rabbits were fed a semipurified, cholesterol-free diet containing 40% sucrose, 25% casein and 14% fat for 5 months. Two experimental diets provided either 6% (high) or 3.2% (low) t-FA. The control group was fed a fat of composition similar to the two experimental diets but free of t-FA. Serum cholesterol and triglycerides were elevated in the rabbits fed 6% t-FA. Liver glycerides were also elevated in this group. The fatty acids of plasma, erythrocytes, epididymal fat, liver microsomes and liver mitochondria reflected the dietary composition. Levels of aortic atherosclerosis were identical in the three groups. There were no significant differences in activity of five hepatic enzymes: glucose-6-phosphatase (microsomal), fatty acid synthetase (cytosolic), malate dehydrogenase, beta-hydroxybutyrate dehydrogenase and monoamine oxidase (mitochondrial).

Repair of severe anterior vaginal wall prolapse (grade IV cystourethrocele).

The classical approach for the repair of severe anterior vaginal wall prolapse is the use of transvaginal colporrhaphy or, more recently, an abdominal paravaginal repair. Severe cystoceles develop from weaknesses of the levator sling and pubocervical fasciae resulting in 2 main anatomical changes: a central defect between the pubocervical fasciae, and a sliding herniation of the bladder and urethra (paravaginal defect). We developed a new transvaginal technique for the repair of large cystoceles (grade IV) extending outside of the introitus at rest, which includes repair of the central defect by anterior colporrhaphy, and repair of the paravaginal herniation of the bladder base and bladder neck by a needle suspension of these structures. We report our experience within a 5-year period in the treatment of 51 cases of severe bladder prolapse (grade IV cystoceles), 46 of which required this combined procedure regardless of preoperative stress urinary incontinence status. Five patients underwent anterior colporrhaphy as the only procedure, since they were continent and demonstrated a well supported bladder neck from a previous suspension operation. Other vaginal abnormalities should be repaired simultaneously to provide adequate pelvic floor support.

A prospective evaluation of leak point pressure, bladder compliance and clinical status in myelodysplasia patients with tethered spinal cords.

We evaluated prospectively 26 patients with myelodysplasia and a tethered spinal cord to determine whether surgical release of the tethered cord positively influenced leak point pressure, bladder compliance, upper tract status and/or clinical management. Urodynamics were performed immediately before and after the neurosurgical procedure, and at 3 and 6 months postoperatively. Mean patient age was 7.8 years (range 2 days to 34 years) and median interval from onset of symptoms to surgery was 60 days (range 2 days to 4 years). Patient presentation included a combination of orthopedic, neurological and urological symptoms. Of 26 patients 9 (35%) had new hydronephrosis, urinary tract infections or urinary incontinence. Leak point pressure and bladder compliance did not change significantly by 6 months postoperatively. Of the 4 patients who presented with hydronephrosis 1 worsened in status, 2 stabilized and 1 improved. Clinical status was unchanged in 16 patients, improved in 4 and worsened in 6. There was no significant relationship between patient age and urodynamic or clinical outcome. Among patients followed for at least 6 months radiographic and clinical improvement occurred in 25% and 15%, respectively. Urodynamic improvements were transient. Surgical release of a tethered cord improved the urological status in less than a quarter of the patients in this series.

Squamous cell carcinoma of the prostate: 2 cases of a rare malignancy and review of the literature.

Primary squamous cell carcinoma of the prostate is an extremely uncommon malignancy, accounting for less than 1% of all prostatic cancers. We report on 2 patients with primary squamous cell carcinoma of the prostate: 1 with organ-confined disease and 1 with metastatic disease. Both patients presented with urinary obstructive symptoms and carcinoma was not suspected on digital rectal examination. Serum acid phosphatase and prostate specific antigen levels were normal. From a review of the literature and our 2 cases it is apparent that squamous cell carcinoma of the prostate is biologically more aggressive than adenocarcinoma.

Mdmx stabilizes p53 and Mdm2 via two distinct mechanisms.

The p53 protein maintains genomic integrity through its ability to induce cell cycle arrest or apoptosis in response to various forms of stress. Substantial regulation of p53 activity occurs at the level of protein stability, largely determined by the activity of the Mdm2 protein. Mdm2 targets both p53 and itself for ubiquitylation and subsequent proteasomal degradation by acting as an ubiquitin ligase, a function that needs an intact Mdm2 RING finger. For efficient degradation of p53 nuclear export appears to be required. The Mdmx protein, structurally homologous to Mdm2, does not target p53 for degradation, but even stabilizes both p53 and Mdm2, an activity most likely mediated by heterodimerization of the RING fingers of Mdm2 and Mdmx. Here we show that Mdmx expression leads to accumulation of ubiquitylated, nuclear p53 but does not significantly affect the Mdm2-mediated ubiquitylation of p53. In contrast, Mdmx stabilizes Mdm2 by inhibiting its self-ubiquitylation.