Processing of ZrC–Mo Cermets for High-Temperature Applications, Part I: Chemical Interactions in the ZrC–Mo System

The chemical compatibility of ZrC and Mo was investigated in carburizing and carbon-free environments at temperatures from 1700° to 2200°C. Heating in the carburizing atmosphere resulted in the complete reaction of Mo with C, while the carbon-free atmosphere resulted in retained metallic phase with a maximum of 13.8 mol% Mo₂C formed. The presence of Mo₂C was not detected at 2100°C in the carbon-free atmosphere, confirming the existing phase equilibria in the Zr–Mo–C system. Heat treatments in the carbon-free atmosphere also showed liquid formation at 2200°C, as evident from microstructure analysis. Liquid formation was consistent with the interaction between Mo and Mo₂C. The liquid was found to comprise at least 7 vol% of the total component, based on a phase diagram for the Mo–C system. The formation of a liquid should allow for the processing of ZrC–Mo cermets by liquid-phase pressureless sintering.     

A retrospective study of changes in physical symptoms and body image after reduction mammaplasty

Reduction mammaplasty is performed typically to alleviate the painful physical symptoms of macromastia. Women who suffer from macromastia also frequently present to the plastic surgeon with heightened body image dissatisfaction and maladaptive behavioral changes in response to their breast size. Numerous investigations have demonstrated improvement in physical symptoms after breast reduction surgery. Studies have also suggested that psychological improvement occurs postoperatively; however, they have not used well-validated, standardized psychological measures. The present study is a retrospective analysis of the physical and psychological status of women who underwent reduction mammaplasty. One hundred ten patients who underwent a reduction mammaplasty between 1982 and 1996 were mailed a packet of questionnaires designed to assess current physical symptoms and body image. Sixty-one of the 110 patients (55 percent) responded. The vast majority reported substantial improvement or elimination of neck, back, shoulder, and breast pain, grooving from bra straps, poor posture, skin irritation, and social embarrassment. In addition, they reported significantly less dissatisfaction with their breasts as compared with a sample of breast reduction patients assessed preoperatively. Symptom relief and improved body image occurred independently of preoperative body weight, as we found few significant differences between obese and non-obese women concerning the resolution of physical symptoms or improvement in body image. Results provide further evidence of the efficacy of reduction mammaplasty not only for relief of physical symptoms but also for alleviation of body image dissatisfaction.     

hMLH1 promoter methylation and lack of hMLH1 expression in sporadic gastric carcinomas with high-frequency microsatellite instability

The frog intermediate lobe consists of a single endocrine cell type, the melanotrope cells, which are under the tonic inhibitory control of dopamine. Separation of dispersed pars intermedia cells in a Percoll density gradient has revealed the existence of two melanotrope cell subpopulations, referred to as high-density (HD) and low-density (LD) cells. The aim of the present study was to investigate the effects of dopamine on each of these melanotrope cell subsets. Increasing doses of dopamine, ranging from 10(-9)-10(-6) M, inhibited the release of alpha-melanocyte-stimulating hormone (alpha-MSH) in LD (but not in HD) melanotrope cells. In addition, dopamine provoked a significant reduction of the rate of acetylation of alpha-MSH in LD cells but not in HD cells. Similarly, dopamine significantly decreased the accumulation of POMC messenger RNA in LD cells, whereas it did not affect POMC gene expression in the HD melanotrope subset. On the other hand, microfluorimetric studies revealed that dopamine induced a significant reduction of KCl-stimulated cytosolic free calcium concentration in both LD and HD cells. The present study provides additional evidence for functional heterogeneity of melanotrope cells in the frog pars intermedia. Because dopamine plays a pivotal role in the regulation of alpha-MSH secretion, these data suggest the involvement of cell heterogeneity in the physiological process of background color adaptation in amphibians.     

Changes of telomere length cause reciprocal changes in the lifespan of mother cells in Saccharomyces cerevisiae

Budding yeast cells divide asymmetrically, giving rise to a mother and its daughter. Mother cells have a limited division potential, called their lifespan, which ends in proliferation-arrest and lysis. In this report we mutate telomerase in Saccharomyces cerevisiae to shorten telomeres and show that, rather than shortening lifespan, this leads to a significant extension in lifespan. This extension requires the product of the SIR3 gene, an essential component of the silencing machinery which binds to telomeres. In contrast, longer telomeres in a genotypically wild-type strain lead to a decrease in lifespan. These findings suggest that the length of telomeres dictates the lifespan by regulating the amount of the silencing machinery available to nontelomeric locations in the yeast genome.     

Differential effects of deoxycholic acid on proliferation of neoplastic and differentiated colonocytes in vitro

The secondary bile acid deoxycholic acid is believed to be a promoter of large bowel cancer, in part by inducing colonic epithelial proliferation. The effects of deoxycholic acid on [3H]thymidine incorporation by the human colon cancer cell line HT29 and two differentiated subclones were measured and compared. The subclone HT29-C1 has features of mature absorptive cells and HT29-N2 cells secrete mucus under cholinergic control. The three cell lines were treated with deoxycholic acid (DCA) at concentrations of 0, 5, 10, 50, 100, 150, and 300 microM for 3, 6, 9, 15, 24, and 48 hr. A significant increase in proliferation was noted in HT29 cells only at 6 hr with 5 and 10 microM deoxycholic acid. Neither the subclone HT29-C1, nor HT29-N2 cells exhibited significant change in [3H]thymidine incorporation with DCA at these concentrations or time points. Higher doses of deoxycholic acid above 50 microM and duration of exposure greater than 24 hr were cytotoxic to all three cell lines. The proliferative effects of DCA in HT29 cells were not paralleled by changes in protein kinase C activity or protein kinase C isoform expression. Quantitative and qualitative differences in PKC isoform expression were not noted in the three cell lines used in this study. The proliferative effects of DCA on HT29 cells appear to be independent of the PKC signal transduction pathway.     

Continued development of the Nimbus/University of Pittsburgh (UOP) axial flow left ventricular assist system

Nimbus and the University of Pittsburgh (UOP) have continued the development of a totally implanted axial flow blood pump under the National Institutes of Health (NIH) Innovative Ventricular Assist System (IVAS) program. This 62 cc device has an overall length of 84 mm and an outer diameter of 34.5 mm. The inner diameter of the blood pump is 12 mm. It is being designed to be a totally implanted permanent device. A key achievement during the past year was the completion of the Model 2 pump design. Ten of these pumps have been fabricated and are being used to conduct in vitro and in vivo experiments to evaluate the performance of different materials and hydraulic components. Efforts for optimizing the closed loop speed control have continued using mathematical modeling, computer simulations, and in vitro and in vivo testing. New hydraulic blade designs have been tested using computational fluid dynamics (CFD) and flow visualization. A second generation motor was designed with improved efficiency. To support the new motor, a new motor controller fabricated as a surface mount PC board has been completed. The program is now operating under a formal QA system.     

Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide

BACKGROUND: Nitric oxide (NO) is released by activated macrophages, neutrophils, and stimulated bronchial epithelial cells. Exhaled NO has been shown to be increased in patients with asthma and has been put forward as a marker of airways inflammation. However, we have found that exhaled NO is not raised in patients with cystic fibrosis, even during infective pulmonary exacerbation. One reason for this may be that excess airway secretions may prevent diffusion of gaseous NO into the airway lumen. We hypothesised that exhaled NO may not reflect total NO production in chronically suppurative airways and investigated nitrite as another marker of NO production. METHODS: Breath condensate nitrite concentration and exhaled NO levels were measured in 21 clinically stable patients with cystic fibrosis of mean age 26 years and mean FEV1 57% and 12 healthy normal volunteers of mean age 31 years. Breath condensate was collected with a validated method which excluded saliva and nasal air contamination and nitrite levels were measured using the Griess reaction. Exhaled NO was measured using a sensitive chemiluminescence analyser (LR2000) at an exhalation rate of 250 ml/s. Fourteen patients with cystic fibrosis had circulating plasma leucocyte levels and differential analysis performed on the day of breath collection. RESULTS: Nitrite levels were significantly higher in patients with cystic fibrosis than in normal subjects (median 1.93 microM compared with 0.33 microM). This correlated positively with circulating plasma leucocytes and neutrophils (r = 0.6). In contrast, exhaled NO values were not significantly different from the normal range (median 3.8 ppb vs 4.4 ppb). There was no correlation between breath condensate nitrite and lung function and between breath condensate nitrite and exhaled NO. CONCLUSIONS: Nitrite levels in breath condensate were raised in stable patients with cystic fibrosis in contrast to exhaled NO. This suggests that nitrite levels may be a more useful measure of NO production and possibly airways inflammation in suppurative airways and that exhaled NO may not reflect total NO production.     

The endogenous agonist quinolinic acid and the non endogenous homoquinolinic acid discriminate between NMDAR2 receptor subunits

The polysialic acid (polySia) capsule of Escherichia coli K1 is a key virulence determinant of the organism, allowing it to evade host defenses. The proteins necessary for expression of the capsule are encoded by the 17 kb kps gene cluster. This cluster contains two genes, kpsM and kpsT, that are required for polySia transport across the cytoplasmic membrane. KpsM is a hydrophobic integral inner membrane protein, while KpsT is a peripheral inner membrane protein that binds ATP. They belong to the ATP-binding cassette (ABC) superfamily of transporters. To study the role of KpsT in polySia translocation, we used PCR mutagenesis to isolate dominant negative mutations of plasmid-encoded kpsT. All mutations mapped to the same glutamic acid residue at position 150, adjacent to Walker motif B of KpsT. Wild-type (kps+) cells harboring one such allele, E150G, did not transport polySia to the cell surface but accumulated intracellular polysaccharide and produced small colonies containing cells that grew as long filaments. The E150G protein still bound ATP as shown by 8-azidoATP photolabeling assays. We combined the E150G allele with each of five mutations isolated previously in kpsT. Mutations that disrupt ATP-binding (K44E) or alter regions of the protein thought to interact with KpsM (G84D, S126F) suppressed the dominant negative phenotype while mutations in the C-terminal portion of the protein (C163Y, H181Y) did not suppress. These studies have allowed the development of a working model for the role of KpsT in polySia chain translocation.     

Risks and therapy options in dural arteriovenous fistulas between branches of the external carotid artery and the cavernous sinus. A case report and review of the literature

INTRODUCTION: Dural arteriovenous fistula of the Arteria carotis externa and the sinus cavernosus are rare vascular malformations. In the literature the prognosis and necessity of treatment is described very variable. PATIENTS AND METHODS: A 90 year old female presents in our outpatient clinic with acute exophthalmus, dilated episcleral veins, cerebral bruits and beginning orbital apex syndrome. After normal computerized axial tomography (CAT) without and with contrast medium, we were able to diagnose a dural AV-fistula by angiography. Shortly after dismission the patient had a spontaneous subarachnoidal haemorrhage with severe neurological symptoms. CONCLUSIONS: The suspect of an intracranial AV-malformation implies a detailed diagnostic search with precise localisation of the process. In any patient with intracerebral and intracranial fistula there has to be an individual check of possible and necessary treatment. It is impossible to classify dural AV-fistula as a benign disease with harmless clinical course.