bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Nitric Oxide Synthase Aggravates Cisplatin-Induced Nephrotoxicity: Effect of 2-Amino-4-Methylpyridine
Authors: Saad Sherif Y. , Najjar Tawfeeg A.O. , Daba Mohammed H. , Al-Rikabi Ammar C.
Published: April 2003

Background: Nitric oxide (NO) has been shown to play a role in maintaining normal renal function. However, the role of NO in cisplatin (CDDP)-induced nephrotoxicity is still unclear. The aim of the present work was to examine the effect of the NO synthase (NOS) inhibitor, 2-amino-4-methylpyridine, on the severity of CDDP-induced nephrotoxicity. Methods: Male Wistar rats were divided into six groups. Three control groups received plain drinking water or water containing 1.5% L-arginine. One of the two groups receiving plain water was treated with an intraperitoneal injection of 2-amino-4-methylpyridine (1 mg/kg in normal saline), and the other two control groups were injected intraperitoneally with normal saline. Another three groups were treated in the same manner and injected with CDDP (6 mg/kg, i.p.). CDDP was injected 1 h after 2-amino-4-methylpyridine treatment. Rats were sacrificed 7 days after CDDP treatment, and serum as well as kidneys were isolated and analysed. Results: CDDP-treated rats showed increases in the kidney weight as a percentage of the total body weight and serum creatinine and urea levels and decreases in serum albumin and calcium levels. Also, CDDP treatment induced reductions in the kidney total nitrate/nitrite (NOx), reduced glutathione (GSH) and glutathione peroxidase activity (GSH-Px) levels and an increase in the kidney malondialdehyde (MDA) production level. In contrast, 2-amino-4-methylpyridine treatment 1 h prior to CDDP injection induced marked exacerbation of CDDP-induced nephrotoxicity, as manifested by severe aggravation of the indices of nephrotoxicity. Also, 2-amino-4-methylpyridine plus CDDP-treated rats showed exaggeration of the reduction in the kidney total NOx content and GSH-Px activity and elevation of the kidney platinum accumulation level with normalization of the kidney MDA production level and rebound in the kidney GSH content. Histopathologically, CDDP-treated rats showed marked interstitial nephritis, tubular atrophy and tubular necrosis. However, treatment with 2-amino-4-methylpyridine 1 h prior to CDDP injection revealed marked exacerbation of CDDP-induced histopathological changes. Conclusions: The present findings suggest that NO plays a role in CDDP-induced nephrotoxicity. Administration of 2-amino-4-methylpyridine, an NOS inhibitor, exacerbates CDDP-induced nephrotoxicity.
Chronic Renal Failure Leads to Reduced Flow-Dependent Dilation in Isolated Rat Skeletal Muscle Arterioles due to Lack of NO Mediation
Authors: Bagi Zsolt , Hamar Peter , Antus Balazs , Rosivall Laszlo , Koller Akos
Published: April 2003

Background: Chronic renal failure (CRF) is frequently accompanied by systemic vascular alterations which further increase the morbidity and mortality of these patients. However, the nature and the underlying mechanisms of vascular dysfunction are not completely understood. We hypothesized that – in addition to other factors – CRF alters local vasomotor mechanisms that are intrinsic to the vascular wall. Methods: Changes in the diameter of isolated, pressurized (at 80 mm Hg) gracilis skeletal muscle arterioles (diameter approximately 150 µm) of female Wistar rats were investigated by videomicroscopy. Arteriolar responses to an increase in flow and vasoactive agents in partially nephrectomized (NX) and sham-operated (control) rats were compared. Results: In NX rats, serum creatinine and urine protein excretion were increased. Compared to controls, increases in intraluminal flow (from 0 to 40 µl/min) resulted in significantly reduced dilation in arterioles of NX rats (maximum: 32 ± 4 vs. 15 ± 4 µm, p < 0.05). Inhibition of nitric oxide (NO) synthesis with L-NAME reduced the dilation of control arterioles but did not affect responses of NX arterioles. Also, dilations in response to histamine were significantly reduced in arterioles from NX rats as compared to control rats. L-NAME significantly decreased histamine-induced dilations of control arterioles, but it did not affect responses of NX arterioles. Dilations in response to the NO donor sodium nitroprusside were also significantly decreased in NX arterioles as compared to responses of control vessels, whereas responses to adenosine and norepinephrine were not significantly different in the two groups. Conclusions: We conclude that in rat skeletal muscle arterioles, CRF induced by renal mass reduction alters the mechanosensitive and agonist-induced responses of peripheral arterioles, in part by interfering with NO-signaling mechanisms. These alterations could contribute to increased peripheral vascular resistance and further aggravate the cardiovascular complications in CRF.
Huge Arachnoid Cyst of the Posterior Fossa with Cerebellar Tentorium Dysplasia Associated with Juvenile Polyposis
Authors: Sugata Sei , Niiro Masaki , Tanioka Kouji , Yano Tsunehiro , Kuratsu Jun-ichi
Published: April 2003

We report an infant with a huge arachnoid cyst of the posterior fossa with dysplasia of the cerebellar tentorium and meningeal sinus and associated juvenile polyposis. Neuroimaging studies disclosed a huge median cystic lesion extending posterosuperiorly over the cerebellum. The cerebellar tentorium was raised to the parietal area; the vermis was normoplastic. Cystography showed no direct communication with the 4th ventricle or subarachnoid space. We discuss the differential diagnosis of median cysts of the posterior fossa and the association of juvenile polyposis.
Problems in the Diagnosis of Contact Dermatitis by Tattooing
Authors: Vilaplana J. , Chimenos J.M. , Fernández A.I. , Pereira-Veiga N. , Romaguera C.
Published: April 2003

The knowledge of the chemical composition of the most commonly used pigments is necessary for the diagnosis of some cases of contact eczemas caused by tattoos. Several techniques of chemical analysis and characterization were used to study the materials involved in a permanent tattooing process such as pigments, solvents, needles and specially in the metals contained in them. A battery of patch tests is proposed that includes some substances characterized in the analysed pigments.
LOAD CARRYING CAPACITY OF Ni PLATED MEDIA IN SPHERICAL INDENTATION: EXPERIMENTAL AND THEORETICAL RESULTS
Authors: Wänstrand O. , Schwarzer N. , Chudoba T. , Kassman-Rudolphi Å.
Published: April 2003

Spherical indentation ex periments have been performed on aluminium and steel specimens. Some of the specimens were layered with electroplated nickel and all were surface coated with thin vapour deposited WC/C. The experimental results were compared with simulations made with the commercially available Elastica software package. The aim of the study was to investigate how an intermediate load carrying layer between a soft and compliant base material and a thin brittle coating can improve the resistance to plastic deformation. This study shows that thick and dense electroplated nickel layers, which give good adhesion both to base materials (aluminium and steel) and to PVD coatings (WC/C), can be produced and used as load carrying layers. As expected, it was found that an intermediate load carrying layer of sufficient thickness and suitable mechanical properties improves the load carrying capacity of soft and compliant base materials. It was also found that with a stiff layer on a more compliant base material, an intermediate layer that was too thin would decrease the load carrying capacity as compared with the homogeneous base material case. Finally, although not including plastic deformation, the analytical elastic calculations proved to be valuable for the interpretation of the experimental results.
Boriding of Ferrous and Non-Ferrous Metals and Alloys in Fluidised Bed Reactor
Authors: Anthymidis K. G. , Stergioudis G. , Roussos D. , Zinoviadis P. , Tsipas D. N.
Published: April 2003

Heat treatment of alloys in fluidised bed reactors has been carried out for more than twenty five years. Recently this technology has been used for surface engineering applications in the deposition of hard and/or corrosion resistant layers. In the present study fluidised bed technology (FBT) has been used to deposit boride coatings on ferrous and non-ferrous metals and alloys. The coatings were examined by means of optical microscopy, X-ray diffraction, and Vickers microhardness testing. These techniques were used to characterise coating thickness and morphology, phase formation, and hardness. The as produced coatings were generally characterised by very good adherence and uniformity. On 0·5 wt-%C steel it was found that only one phase, Fe2B, was formed during the treatment. Fluidised bed boriding of various steel substrates produced boride layers similar to those obtained by the pack cementation boriding method. On pure Ti, a TiB layer was found, while on Ti-6Al-4V alloy both TiB and TiB2 phases were detected. Boriding pure Ni gave mainly a Ni3B coating, while boriding pure Co produced both Co4B and Co3B layers. The borided Ni showed improved tribological properties under dry wear conditions.
Effects of HVOF Parameters on Adhesion and Microstructure of Thermal Sprayed NiWCrBSi Coatings
Authors: Gil L. E. , Staia M. H.
Published: April 2003

This work evaluates the influence of processing parameters on the adhesion and morphology of a NiWCrBSi commercial alloy thermally sprayed using HVOF. A 33 factorial design experiment was used to establish the effects of the variables on coating quality. The equivalence fuel/oxygen ratio Fi, defined as the ratio [(F/O)working/(F/O)stoichiometric], was varied between 0·8 and 1·2, the spraying distance was varied between 380 and 570 mm, and the powder feedrate was varied between 60 and 120 g min-1. Response surface methodology was used to describe the empirical relationships among the parameters studied. The tensile bond strength was evaluated following ASTM C 633. Scanning electron microscopy, coupled with X-ray microanalysis, was employed to characterise the fractured surfaces after the test and to determine the fracture mode. The results indicated that the equivalence ratio Fi and the spraying distance were the main processing parameters which affected adhesion strength and the coating properties.
ANALYSIS OF XRD STRESS MEASUREMENT DATA OF NATURALLY GROWN OXIDE FILMS Al2O3 AND Cr2O3 BASED ON EXISTING REUSS, VOIGT, AND HILL MODELS
Authors: Sarioglu C.
Published: April 2003

The resistance of naturally grown alumina (Al2O3) and chromia (Cr2O3) scales to cracking and spalling under influence of growth and thermal stresses is a critical aspect of the environmental resistance of high temperature alloys such as Fe and Ni based alloys. The driving force for scale failure is the residual stress developed in the scale. In this study, strain and stress measurement techniques by XRD were reviewed. XRD data for Al2O3 and Cr2O3 films were analysed and discussed with respect to existing models. It was experimentally found that the Reuss model provided the best description of the measured strain data for these films. Strain and stress states of Al2O3 and Cr2O3 films were determined.
Plasma Species Analysis for Insitu Assessment of Surface Treatments
Authors: Cleugh D.
Published: April 2003

In order to gain the maximum potential from plasma technology in surface engineering, knowledge is required about the influence of particular plasma phase species on the treatment response. In this study, optical emission spectroscopy (OES) is used in situ, without disturbing the treatment environment, to monitor the active species observed in three different types of nitriding plasma: direct current (dc), active screen, and plasma immersion ion implantation (PI3). The spectral information obtained is considered in conjunction with metallurgical characterisation of nitrided steel samples, using optical microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, and microhardness testing. Active screen and dc nitriding have a similar nitriding effect in low alloy steel testpieces. OES evidence shows that both ions and neutrals are involved in the plasma reactions and a multistage theory is the model of best fit for nitrogen mass transfer in these dc powered plasma nitriding techniques. OES analysis can be used for in situ monitoring of treatment quality in PI3 nitriding.
Electrodeposition of Copper as a Route for Tantalum Drawing
Authors: Robin A. , Alves de Souza K. , Rosa J. Luiz , Silva M. Borges
Published: April 2003

Electrodeposition of thin copper layers on tantalum rods was applied for tantalum wire drawing. The influence of surface finishing, cathodic current density, and acid sulphate bath composition on the adhesion of the deposits was studied. The copper coatings were more adherent when obtained on a sandblasted surface. Chemical and electrochemical surface treatments did not affect significantly the adhesion. The statistical Taguchi method was employed for studying the influence of electrolysis parameters on adhesion, using the L9 orthogonal array with three factors at three levels each. The analysis of results showed a great influence of current density on adhesion, whereas the other factors, CuSO4 and H2SO4 concentrations, presented low and no significant effect, respectively. Tantalum rods electroplated by copper under the best conditions (sandblasted surface, 30 mA cm–2 cathodic current density, 150 g L–1 CuSO4, and 30 g L–1 H2SO4) were drawn. The superficial finishing of the tantalum wires was better than those obtained by the traditional route (insertion of tantalum rod into a copper tube and drawing).
Characterisation of Stress and Adhesion in Diamond Coatings Deposited on Ti and Cr Substrates Using CVD
Authors: Ali N. , Fan Q. H. , Gracio J. , Ahmed W.
Published: April 2003

Polycrystalline diamond thin films have been deposited onto titanium and chromium substrates using a conventional microwave plasma chemical vapour deposition (MPCVD) system. The coatings deposited were ∼1·5 μm in thickness. A modified scratch tester was employed to perform indentations on the coated substrates in order to evaluate the adhesion of the coatings to the substrates at 95 and 180 N loads. Complementary Raman spectroscopy studies were performed to investigate the film stress levels along the section across the indentation zone. Analysis of the results obtained suggests that the coating on the chromium substrate was under greater stress than the diamond coating on the titanium substrate. Both coatings remained attached to their substrates after a 95 N load indentation test. Interestingly, a 180 N load indentation was sufficient to delaminate the coating on the chromium substrate, whereas, the coating on the titanium substrate remained attached to its substrate. This may be attributed to titanium forming a stronger carbide bond than chromium, which plays the role of an adhesive, sticking the film to the substrate. A newly proposed adhesion characterisation method, which couples indentation loading with acoustic emissions, was used throughout this study to measure the coating adhesion quantitatively and reliably.
Post-Heat Microstructural Treatment Changes in Nickel Based Hvof Coating
Authors: Rodríguez M. A. , Gil L. , Staia M. H.
Published: April 2003

The effects of various heat treatments (oxyacetylene flame, argon atmosphere, vacuum) on the microstructure and hardness of thermal sprayed coatings has been studied. Commercial powder of the NiCrSiBW alloy known as Colmonoy 88 was sprayed using the HVOF (high velocity oxyfuel) process. Coatings were deposited on AISI 1020 steel substrates using a JP5000 gun. The processing parameters recommended by the powder manufacturer were employed. The results indicate that post-heat treatments conducted in both vacuum and argon atmosphere produced significant changes in the morphology and distribution of the hard phases, but no noticeable changes were observed when the coatings were post-heat treated with an oxyacetylene flame. The measured microhardness values were correlated with the microstructural changes which took place during post-heat treatment. SE/S234
Effect of Surface Characteristics and Clinical Procedures on Corrosion Behaviour of Dental Amalgams
Authors: Fathi M. H. , Mortazavi V. , Salehi M.
Published: April 2003

The aim of this study was to evaluate and compare the effects of chemical composition, amalgam alloy powder particle shape, and clinical procedures such as finishing and polishing on the corrosion behaviour of dental amalgams. Four different types of commercial amalgam alloy with various chemical compositions and particle shapes (lathe cut, spherical, spheroidal) were studied. A special mould was used, and 21 samples were prepared from each type of commercial amalgam. After triturating and condensation, the samples of each type of amalgam were divided into three groups. Each group was finished using one of three procedures, namely carving, carving and burnishing, or carving, burnishing, and polishing. Structural characterisation by SEM was used to investigate the surface morphology of amalgam samples. Electrochemical potentiodynamic tests were performed in physiological solution in order to determine and compare the corrosion behaviour of the four amalgams as an indication of biocompatibility. Statistically significant differences were found between the mean corrosion current densities in the three different groups of each type of commercial amalgam. The polished samples all possessed the lowest corrosion current density, and the carved samples showed the highest corrosion current density (lowest corrosion resistance). This trend was not affected by the chemical composition of the commercial amalgams. It is concluded that clinical operations and procedures may influence tarnishing and corrosion of dental amalgam, surface plaque accumulation, and recurrence of tooth caries. The results also show that particle shape affects the surface roughness of dental amalgam restoration, and hence corrosion behaviour.
Active screen plasma nitriding of austenitic stainless steel
Authors: Li C. X. , Georges J. , Li X. Y.
Published: April 2003

Active screen (AS) plasma nitriding is a new surface engineering technique which provides many advantages over conventional dc plasma nitriding. In this study the AS technique has been used to nitride austenitic stainless steel (AISI 316). The morphology, composition and properties of the AS plasma nitrided layers have been characterised and compared with those of the normal dc plasma nitrided layers. AS nitriding can achieve similar hardening effects for austenitic stainless steel when compared to conventional dc nitriding, and does not have the common problems associated with the dc technique such as ‘edging effect’. AS nitriding at a lower temperature of 420° C can also produce a precipitation free layer, the S phase, on a 316 stainless steel surface. The AS nitrided S phase exhibits not only high hardness and wear resistance but also very good corrosion resistance.
Crystallisation and Phase Transformation Behaviour of Electroless Nickel-Phosphorus Deposits and Their Engineering Properties
Authors: Keong K. G. , Sha W.
Published: April 2003

The crystallisation and phase transformation behaviour of electroless Ni-P deposits during thermal processing have a vital role in determining their material properties. Conflicting results have been reported for the correlation of crystallisation and phase transformation behaviour with deposit composition and thermal processing, and hence microstructure and material properties. These variations are believed to be caused by variations in factors including plating conditions, substrate composition and surface preparation, and testing and measuring techniques. The mechanism of electroless Ni-P plating is discussed briefly and the literature on the effect of crystallisation and phase transformation behaviour on the microstructure and material properties of electroless Ni-P deposits is critically reviewed. A comparison is made with other commonly used engineering deposits such as electroplated nickel and hard chromium. The advantages, limitations, and development of electroless Ni-P are outlined and the use of heat treatment to tailor properties for specific industrial applications are described. Finally, the challenges this technology faces in the future are considered.
Residual stress evolution and relaxation in carbon S phase layers on AISI 316 austenitic stainless steel
Authors: Sun Y. , Chin L. Y.
Published: April 2003

X-ray diffraction has been employed to study the residual stresses and lattice strains in the carbon S phase layers produced in AISI 316 stainless steel by low temperature plasma carburising. The results show that the carbon S phase layers are under a compressively stressed condition, to a level between 1.5 and 3.5 GPa. Analysis of the evolution of stresses revealed that, among various contributing factors including composition profile, lattice misfit and thermal effects, the build up of a carbon composition profile in the layer is mainly responsible for the development of a compressive residual stress during the carburising process. A simple model has been developed to predict the residual stress in the S phase layer. The model predicted that the compressive stress developed during carburising should be much higher than the values measured by XRD. This discovery suggests that stress relaxation has occurred during the carburising process. Further analysis revealed that the strain induced in the S phase by carbon supersaturation is mainly accommodated by plastic deformation, which leads to stress relaxation.
Phase II Study of Troxacitabine (BCH-4556) in Patients With Advanced and/or Metastatic Renal Cell Carcinoma: A Trial of the National Cancer Institute of Canada-Clinical Trials Group
Authors: Townsley C.A. , Chi K. , Ernst D.S. , Belanger K. , Tannock I. , Bjarnason G.A. , Stewart D. , Goel R. , Ruether J.D. , Siu L.L. , Jolivet J. , McIntosh L. , Seymour L. , Moore M.J.
Published: April 2003

Purpose: A multi-institution phase II study was undertaken by National Cancer Institute of Canada–Clinical Trials Group to evaluate the efficacy and toxicity of intravenous troxacitabine (Troxatyl; Shire Pharmaceuticals Plc, Laval, Quebec, Canada), in patients with renal cell carcinoma.

Patients and Methods: Between June 1999 and March 2000, 35 patients (24 male) with a mean age of 60 years who had advanced and/or metastatic disease were treated with troxacitabine given as an intravenous infusion over 30 minutes at a dose of 10 mg/m2 intravenously, once every 3 weeks.

Results: Of the 33 of 35 patients evaluable for response, there were two confirmed partial responses, 21 patients had stable disease (median duration, 4.4 months), and 10 patients had progressive disease. Eight patients remained stable for more than 6 months, of whom six remain free of progression. The most common drug-related nonhematologic toxicities observed were skin rash (77.1%), hand-foot syndrome (68.6%), alopecia (51.4%), fatigue (51.4%), and nausea (57.1%). Out of a total of 145 cycles of treatment, 98 were given without steroid premedication, whereas 47 cycles were given with steroid premedication. Without premedication, skin rash occurred in 37% of cycles compared with 26% when steroids were given prophylactically.

Conclusion: Troxacitabine given at a dose of 10 mg/m2 once every 3 weeks was well tolerated in patients with metastatic renal cell cancer, with common toxicities being a moderate to severe granulocytopenia and skin rash. Steroid premedication may reduce the frequency and severity of the skin rash. Our current study suggests that the nucleoside analog troxacitabine may have modest activity against renal cell carcinoma; however, larger studies are required to confirm this.
Cadherin-13, a Mediator of Calcium-Dependent Cell-Cell Adhesion, Is Silenced by Methylation in Chronic Myeloid Leukemia and Correlates With Pretreatment Risk Profile and Cytogenetic Response to Interferon Alfa
Authors: Roman-Gomez Jose , Castillejo Juan A. , Jimenez Antonio , Cervantes Francisco , Boque Concepcion , Hermosin Lourdes , Leon Angel , Grañena Albert , Colomer Dolors , Heiniger Anabel , Torres Antonio
Published: April 2003

Purpose: Cadherin-13 (CDH13) is a newly characterized cadherin molecule responsible for selective cell recognition and adhesion, the expression of which is decreased by methylation in a variety of human cancers, indicating that the CDH13 gene functions as a tumor suppressor gene. Although defective progenitor-stromal adhesion is a well-recognized feature of chronic myeloid leukemia (CML), the role of CDH13 abnormalities has not been evaluated in this disease.

Patients and Methods: We examined the methylation status of the CDH13 promoter in 179 chronic phase (CP)-CML patients and in 52 advanced-phase samples and correlated it with mRNA expression using methylation-specific polymerase chain reaction (PCR) and reverse transcriptase PCR.

Results: Aberrant de novo methylation of the CDH13 promoter region was observed in 99 (55%) of 179 of CP-CML patients, and 90 of the patients failed to express CDH13 mRNA (P < .0001). Advanced-stage samples (n = 52) showed concordant methylation results with their corresponding CP tumors, indicating that CDH13 methylation was not acquired during the course of the disease. Nevertheless, absence of CDH13 expression was more frequently observed among Sokal high-risk patients (P = .01) and was also independently associated with a shorter median progression-free survival time (P = .03) and poor cytogenetic response to interferon alfa treatment (P = .0001).

Conclusion: Our data indicate that the silencing of CDH13 expression by aberrant promoter methylation occurs at an early stage in CML pathogenesis and probably influences the clinical behavior of the disease.
Randomized Phase I Trial of Recombinant Human Keratinocyte Growth Factor Plus Chemotherapy: Potential Role as Mucosal Protectant
Authors: Meropol Neal J. , Somer Robert A. , Gutheil John , Pelley Robert J. , Modiano Manuel R. , Rowinsky Eric K. , Rothenberg Mace L. , Redding Spencer W. , Serdar Cuneyt M. , Yao Bin , Heard Robert , Rosen Lee S.
Published: April 2003

Purpose: To evaluate the safety of recombinant human keratinocyte growth factor (KGF) when administered with fluorouracil (FU) in patients with metastatic colorectal cancer.

Patients and Methods: Patients (N = 81) received KGF by intravenous (IV) bolus on days 1 to 3, followed by FU 425 mg/m2/d IV bolus plus leucovorin 20 mg/m2/d IV on days 4 to 8. KGF dose levels were 1, 10, 20, 40, 60, and 80 μg/kg/d. A randomized, placebo-controlled design was employed (2:1 randomization of KGF to placebo). Oral mucositis was assessed by examination on days 1, 4, 8, 15, and 28. In addition, patients provided daily assessments of oral symptoms using a self-administered questionnaire.

Results: Skin and oral events occurred in 13 of 18 patients (eight patients, grade 1; four patients, grade 2; and one patient, grade 3) treated with 60 and 80 μg/kg of KGF and three of 11 patients treated with 40 μg/kg (grade 1). These symptoms were dose limiting in three cases (ie, in two of 10 patients treated with 80 μg/kg and in one of eight patients treated with 60 μg/kg). The frequency of grade 2 to 4 mucositis was 43% in patients treated with KGF, compared with 67% in patients treated with placebo (P = .06). Patient self-assessments of oral pain and clinical assessments of mucositis showed good correlation (Kendall’s tau = 0.75).

Conclusion: KGF is generally well tolerated when administered IV at doses up to 40 μg/kg/d for 3 days before a 5-day course of FU plus leucovorin. A clinically meaningful biologic effect was also suggested in that patients treated with the epithelial growth factor KGF had a lower rate of grade 2 to 4 mucositis than did patients treated with placebo.
Estrogen Receptor β Messenger Ribonucleic Acid Expression in the Forebrain of Proestrous, Pregnant, and Lactating Female Rats
Authors: Gréco Béatrice , Lubbers Laura S. , Blaustein Jeffrey D.
Published: April 2003

Estrogen receptor (ER)β is present in hypothalamic and limbic neurons of female rat brains, but little is known about its regulation under physiological conditions. To determine whether ERβ expression varies during physiological conditions in which sex steroid hormone profiles are significantly different, we used in situ hybridization to assess ERβ mRNA expression in the periventricular preoptic area, bed nucleus of stria terminalis, paraventricular nucleus, supraoptic nucleus, and the posterodorsal medial amygdala of female rats on proestrus, on d 22 of pregnancy, or on d 10 of lactation (L10). In the periventricular preoptic area, d-22 pregnant females had fewer ERβ-mRNA-expressing cells than did females at proestrus, but the level of ERβ mRNA expression per cell in pregnant females was higher than in the two other groups. In the paraventricular nucleus, no changes in ERβ mRNA expression were observed; whereas in the supraoptic nucleus, proestrous females had fewer ERβ-mRNA-expressing cells than L10 females. In the posterodorsal medial amygdala, proestrous females had a greater number of ERβ-mRNA-expressing cells than did L10 females. These results demonstrate that ERβ mRNA expression is differentially regulated in a brain-region-specific and temporal manner under physiological conditions and suggest that ERβ may participate in the regulation of estrogen-sensitive reproductive functions in female rats.
Molecular Pathways Involved in the Antineoplastic Effects of Calcitriol on Insulinoma Cells
Authors: Galbiati Francesca , Polastri Luca , Thorens Bernard , Dupraz Philippe , Fiorina Paolo , Cavallaro Ugo , Christofori Gerhard , Davalli Alberto M.
Published: April 2003

We have previously reported that in tumorigenic pancreatic β-cells, calcitriol exerts a potent antitumorigenic effect by inducing apoptosis, cell growth inhibition, and reduction of solid β-cell tumors. Here we have studied the molecular pathways involved in the antineoplastic activity of calcitriol on mouse insulinoma βTC3 cells, mouse insulinoma βTC expressing or not expressing the oncogene p53, and βTC-tet cells overexpressing or not the antiapoptotic gene Bcl2. Our results indicate that calcitriol-induced apoptosis was dependent on the function of p53 and was associated with a biphasic increase in protein levels of transcription factor nuclear factor-κB. Calcitriol decreased cell viability by about 40% in p53-retaining βTC and in βTC3 cells; in contrast, βTC p53−/− cells were only minimally affected. Calcitriol-induced cell death was regulated by members of the Bcl-2 family of apoptosis regulatory proteins, as shown by calcitriol-induced up-regulation of proapoptotic Bax and Bak and the lack of calcitriol-induced cytotoxicity in Bcl-2-overexpressing insulinoma cells. Moreover, calcitriol-mediated arrest of βTC3 cells in the G1 phase of the cell cycle was associated with the abnormal expression of p21 and G2/M-specific cyclin B2 genes and involved the DNA damage-inducible factor GADD45. Finally, in βTC3 cells, calcitriol modulated the expression of IGF-I and IGF-II genes. In conclusion, these findings contribute to the understanding of the antitumorigenic effects of calcitriol on tumorigenic pancreatic β-cells and further support the rationale of its utilization in the treatment of patients with malignant insulinomas.
Oxyanion Adsorptions by Mono-, Di-, and Triamino-Functionalized MCM-48
Authors: Yoshitake Hideaki , Yokoi Toshiyuki , Tatsumi Takashi
Published: April 2003

MCM-48 is functionalized with mono-, di-, and triamino-silanes without destruction of the mesoporous structure in order to efficiently remove chromate and arsenate in aqueous solutions. The adsorption capacities achieved 160 and 182 mg/g-adsorbent for chromate and arsenate, respectively, when triamino-functionalized MCM-48 was applied. The diamino-functionalized MCM-48 adsorbed much larger amounts of chromate and arsenate: 119 and 122 mg/g-adsorbent, respectively, than did diamino-functionalized fumed silica: 79.3 and 90.7 mg/g-adsorbent. The superiority arose from the large surface area of functionalized MCM-48. At the adsorption saturation, no clear difference was found in oxyanion/N stoichiometries among the mono-, di-, and triamino-functionalized MCM-48. On the other hand, the distribution coefficient, Kd, depended on the kind of silane fixed on MCM-48. It exceeded 2 × 105 when the concentration of oxyanions was low. The adsorbent by triamino-silylation showed the largest Kd; it was three or ten times higher than that of the adsorbent by monoamino-silylation for arsenate and chromate adsorptions, respectively. Although the adsorption capacity of diamino-functionalized MCM-48 was reduced to be 47% at 50 °C, it still adsorbed a large amount of arsenate.
A Two-Echelon Repairable Inventory System with Stocking-Center-Dependent Depot Replenishment Lead Times
Authors: Wang Yunzeng , Cohen Morris A. , Zheng Yu-Sheng
Published: April 2003

Consider a two-echelon repairable inventory system consisting of a central depot and multiple stocking centers. The centers provide parts replacement service to customers and replenish their inventory from the depot, following a one-for-one policy. The depot fills center replenishment orders on a first-come-first-serve basis. Defectives received at the centers are passed to the depot for repair and depot inventory replenishment. For this system, existing models (e.g., the METRIC model) usually assume that the depot replenishment lead times (DRLTs) are i.i.d., which however, does not fit well into the service parts logistics system that motivated this research. Because the DRLTs consist of the sum of repair times, defective return times, and transportation times, they are different across stocking centers, which are located globally.

We study the impact of such center-dependent DRLTs on system performance. We derive probability distributions of the random delays at the depot experienced by center replenishment orders. We prove that a center with shorter DRLTs experiences shorter delays, and therefore, delivers better customer service. We show that for such systems, using the i.i.d. DRLT assumption introduces errors in estimating system performance. These errors become significant when both the demand rates and the depot planned inventory level are low.
Efficient Risk Sharing: The Last Frontier
Authors: Pratt John W.
Published: April 2003

When rational risk-averse agents must choose among and share monetary risks, it is known that efficient sharing is typically nonlinear, even with common beliefs. Wherever it is, the sharing rule may affect the choice, randomized choice may allow everyone to gain, and indeed a randomized choice between unacceptable risks may be acceptable. An important exception occurs if the agents' utility functions are all exponential, all logarithmic, or all the same power (HARA). Then choices should accord with a group utility function of the same form independent of the sharing rule, randomization never helps, and all efficient sharing rules are linear. This self-contained paper simplifies, refines, and completes earlier analyses, identifying all exceptions; they are the linear sharing rules that make the agents' utilities agree. Aside from HARA, this can only occur for precisely one linear sharing rule or, in periodic versions of HARA, countably many.
Decision Support for a Housing Mobility Program Using a Multiobjective Optimization Model
Authors: Johnson Michael P. , Hurter Arthur P.
Published: April 2003

As result of public housing reform and welfare reform, the operating environment of public housing authorities has changed significantly. Given these policy initiatives, housing mobility programs represent viable strategies for providing public housing residents with access to economically healthy, integrated neighborhoods.

In this paper we present a decision support methodology to assist the design of housing mobility programs. This methodology incorporates economic models for estimating dollar-valued impacts associated with tenant relocation, and a multiobjective optimization model for generating alternative relocation schemes associated with various objective function weights. Using data for Lake County, Illinois and Chicago, we demonstrate that nondominated allocations represent significant trade-offs between dollar-valued and non-dollar-valued policy objectives; existing distributions of subsidized housing represent suboptimal solutions to the housing relocation problem; and increases in available rental housing can result in housing dispersion schemes that have positive net economic benefits relative to the status quo.
Interactive Multiobjective Group Decision Making with Interval Parameters
Authors: Xanthopulos Zaharias , Melachrinoudis Emanuel , Solomon Marius M.
Published: April 2003

This paper proposes a new framework for the solution of interactive multiobjective group decision-making problems with interval parameters. Its novelty stems from a learning phase where decision makers (DMs) explore the structural characteristics of the specific Multiple Criteria Decision Making (MCDM) problem. This provides important and timely feedback to the DMs. Its core consists of four indices and their relationships.

The solution framework consists of three stages. In the first, each DM provides the limits of variation for each problem parameter. These are subsequently combined into a unique interval of variation. Then, the stochastic multiobjective problem is transformed into a deterministic one. In the second stage, DMs use the four MCDM characteristics to familiarize themselves with the problem before expressing their preferences for nondominated solutions. The DMs are then guided through an interactive procedure to find their best nondominated solutions. In the last stage, all best nondominated solutions provided by the DMs are combined using a twofold approach to find the best-compromise nondominated solution. This final choice represents the opinion of the group of DMs. Our results show that the learning phase is beneficial to DMs in judging the quality of solutions, leading to better informed decisions.
A Theoretical Extension of the Technology Acceptance Model: Four Longitudinal Field Studies
Authors: Venkatesh Viswanath , Davis Fred D.
Published: April 2003

The present research develops and tests a theoretical extension of the Technology Acceptance Model (TAM) that explains perceived usefulness and usage intentions in terms of social influence and cognitive instrumental processes. The extended model, referred to as TAM2, was tested using longitudinal data collected regarding four different systems at four organizations (N = 156), two involving voluntary usage and two involving mandatory usage. Model constructs were measured at three points in time at each organization: preimplementation, one month postimplementation, and three months postimplementation. The extended model was strongly supported for all four organizations at all three points of measurement, accounting for 40%–60% of the variance in usefulness perceptions and 34%–52% of the variance in usage intentions. Both social influence processes (subjective norm, voluntariness, and image) and cognitive instrumental processes (job relevance, output quality, result demonstrability, and perceived ease of use) significantly influenced user acceptance. These findings advance theory and contribute to the foundation for future research aimed at improving our understanding of user adoption behavior.
Technical Note: Mathematical Properties of the Optimal Product Line Selection Problem Using Choice-Based Conjoint Analysis
Authors: Chen Kyle D. , Hausman Warren H.
Published: April 2003

Selecting and pricing product lines is an essential activity in many businesses. In recent years, quantitative approaches for such tasks have been gaining in popularity. One often-employed method is to use data from traditional rankings/ratings-based conjoint analysis and attack the product line selection problem with enumeration or heuristics. In this note, we employ a relatively new methodology known as choice-based conjoint analysis (to model customer preferences) and investigate its mathematical properties when used to model the product line selection problem. Despite some inherent limitations resulting from its aggregated formulation, we show that this more parsimonious conjoint approach has some special mathematical properties that lead to an efficient optimal algorithm to tackle the product line/price selection problem. As a result, problems of realistic size can be solved efficiently using standard, commercially available mathematical programming codes.
Optimal Dynamic Pricing for Perishable Assets with Nonhomogeneous Demand
Authors: Zhao Wen , Zheng Yu-Sheng
Published: April 2003

We consider a dynamic pricing model for selling a given stock of a perishable product over a finite time horizon. Customers, whose reservation price distribution changes over time, arrive according to a nonhomogeneous Poisson process. We show that at any given time, the optimal price decreases with inventory. We also identify a sufficient condition under which the optimal price decreases over time for a given inventory level. This sufficient condition requires that the willingness of a customer to pay a premium for the product does not increase over time. In addition to shedding managerial insight, these structural properties enable efficient computation of the optimal policy.

Numerical studies are conducted to show the revenue impact of dynamic price policies. Price changes are set to compensate for statistical fluctuations of demand and to respond to shifts of the reservation price. For the former, our examples show that using optimal dynamic optimal policies achieves 2.4–7.3% revenue improvement over the optimal single price policy. For the latter, the revenue increase can be as high as 100%. These results explain why yield management has become so essential to fashion retailing and travel service industries.
A Continuous-Time Yield Management Model with Multiple Prices and Reversible Price Changes
Authors: Feng Youyi , Xiao Baichun
Published: April 2003

This article studies a continuous-time yield management model in which reversible price changes are allowed. We assume that perishable assets are offered at a set of discrete price levels. Demand at each level is a Poisson process. To maximize the expected revenue, management controls the price dynamically as sales evolve. We show that a subset of these prices that form a concave envelope is potentially optimal. We formulate the problem into an intensity control model and derive the optimal solution in closed form. Properties of the optimal solution and their policy implementations are discussed. Numerical examples are provided.
The Minimum Variance Hedge Ratio Under Stochastic Interest Rates
Authors: Lioui Abraham , Poncet Patrice
Published: April 2003

In an environment where interest rates are stochastic, we examine the case of a “pure” hedger endowed with a fixed position in a long term bond. In contrast to conventional wisdom according to which the difference between hedging through forward contracts and futures is immaterial, it turns out that the minimum variance hedge ratio using forwards comprises two terms instead of one only when using futures. The magnitude of the difference between the two hedge ratios may be important under some plausible assumptions. This result is due to the presence of additional interest rate risk that bears on the profit-and-loss statement associated with the forward position. This sheds some additional light on the respective features of forward and futures contracts written on interest rate-sensitive securities.
Attribute Conflict and Preference Uncertainty: The RandMAU Model
Authors: Fischer Gregory W. , Jia Jianmin , Luce Mary Frances
Published: April 2003

This paper extends the behavioral results reported in Fischer et al. (2000) by developing a model addressing preference uncertainty in multiattribute evaluation. The model is motivated by two hypotheses regarding properties of multiattribute profiles that lead to greater preference uncertainty. Our attribute conflict hypothesis predicts that greater within-alternative conflict (discrepancy among the attributes of an alternative) leads to more preference uncertainty. Our attribute extremity hypothesis predicts that greater attribute extremity (very high or low attribute values) leads to less preference uncertainty. To provide a deeper explanation of attribute conflict and extremity effects, we develop RandMAU, a family of additive (RandAUF) and multiplicative (RandMUF) random weights multiattribute utility models. In RandMAU models, preference uncertainty is represented as random variation in both the weighting parameters governing trade-offs among attributes and the curvature parameters governing single-attribute evaluations. Simulation results show that RandMUF successfully predicts both the attribute conflict and attribute extremity effects exhibited by the experimental participants in Fischer et al. (2000). It also predicts an outcome value effect on error whose form depends on the shape of single-attribute functions and on the type of multiattribute combination rule.
Revenue Management Without Forecasting or Optimization: An Adaptive Algorithm for Determining Airline Seat Protection Levels
Authors: van Ryzin Garrett , McGill Jeff
Published: April 2003

We investigate a simple adaptive approach to optimizing seat protection levels in airline revenue management systems. The approach uses only historical observations of the relative frequencies of certain seat-filling events to guide direct adjustments of the seat protection levels in accordance with the optimality conditions of Brumelle and McGill (1993). Stochastic approximation theory is used to prove the convergence of this adaptive algorithm to the optimal protection levels. In a simulation study, we compare the revenue performance of this adaptive approach to a more traditional method that combines a censored forecasting method with a common seat allocation heuristic (EMSR-b).
Imitation of Complex Strategies
Authors: Rivkin Jan W.
Published: April 2003

Researchers examining loosely coupled systems, knowledge management, and complementary practices in organizations have proposed, informally, that the complexity of a successful business strategy can deter imitation of the strategy. This paper explores this proposition rigorously. A simple model is developed that parametrizes the two aspects of strategic complexity: the number of elements in a strategy and the interactions among those elements. The model excludes conventional resource-based and game-theoretic barriers to imitation altogether. The model is used to show that complexity makes the search for an optimal strategy intractable in the technical sense of the word provided by the theory of NP-completeness. Consequently, would-be copycats must rely on search heuristics or on learning, not on algorithmic “solutions,” to match the performance of superior firms. However, complexity also undermines heuristics and learning. In the face of complexity, firms that follow simple hill-climbing heuristics are quickly snared on low “local peaks,” and firms that try to learn and mimic a high performer's entire strategy suffer large penalties from small errors. The model helps to explain why some winning strategies remain unmatched even though they are open to public scrutiny; why certain bundles of organizational practices diffuse slowly even though they lead to superior performance; and why some strategies yield superior returns even after many of their critical ingredients are adopted by competitors. The analysis also suggests roles for management science and managerial choice in a world of complex strategies.