bluuebunny/crossref_metadata_2025 huggingface dataset:
Signal processing challenges for applying software radio principles in future wireless terminals: an overview
Authors: Valkama Mikko , Pirskanen Juho , Renfors Markku
Published: October 2002

The general idea of software radio is to develop highly integrated radio transceiver structures with high degree of flexibility and multimode capabilities, achieved through increased role of digital signal processing software in defining the functionalities which have traditionally been implemented with analog RF techniques. This paper explores the software radio concept from the receiver architecture and signal processing points of view, with mainly the wireless terminal application in mind. We first discuss the critical issues in alternative receiver architectures with simplified analog parts and increased configurability. We also introduce certain advanced digital signal processing techniques which could potentially relieve some of the essential problems and pave the way towards DSP‐based, highly integrated, and highly configurable terminals. Big emphasis is on efficient digital multirate signal processing methods and complex (I/Q) signal processing. Copyright © 2002 John Wiley & Sons, Ltd.
Higher order finite element methods and multigrid solvers in a benchmark problem for the 3D Navier–Stokes equations
Authors: John Volker
Published: October 2002

This paper presents a numerical study of the 3D flow around a cylinder which was defined as a benchmark problem for the steady state Navier–Stokes equations within the DFG high‐priority research program flow simulation with high‐performance computers by Schafer and Turek (Vol. 52, Vieweg: Braunschweig, 1996). The first part of the study is a comparison of several finite element discretizations with respect to the accuracy of the computed benchmark parameters. It turns out that boundary fitted higher order finite element methods are in general most accurate. Our numerical study improves the hitherto existing reference values for the benchmark parameters considerably. The second part of the study deals with efficient and robust solvers for the discrete saddle point problems. All considered solvers are based on coupled multigrid methods. The flexible GMRES method with a multiple discretization multigrid method proves to be the best solver. Copyright © 2002 John Wiley & Sons, Ltd.
Adsorption of dyes and humic acid from water using chitosan‐encapsulated activated carbon
Authors: Wu Feng‐Chin , Tseng Ru‐Ling , Juang Ruey‐Shin
Published: October 2002

The adsorption isotherms and rates of two dyes and humic acid from aqueous solutions onto chitosan‐encapsulated activated carbon (CEAC) beads were measured at 30 °C. Such beads were prepared by mixing different weight percents of cuttlefish‐based chitosan (100%, 80%, 67%, and 55%) and rice‐based activated carbons. It was shown that the isotherms of dyes and humic acid were well fitted by the Freundlich equation. The adsorption capacity and rate could be enhanced when activated carbon was encapsulated with chitosan. Four simplified kinetic models including the pseudo‐first‐order equation, pseudo‐second‐order equation, intraparticle diffusion model, and the Elovich equation were tested to follow the adsorption processes. The adsorption of dyes was best described by the Elovich equation, but that of humic acid was best described by the intraparticle diffusion model. The kinetic parameters of each best‐fit model were calculated and are discussed in this paper.

© 2002 Society of Chemical Industry
Improvements and algorithmical considerations on a recent three‐dimensional model describing stress‐induced solid phase transformations
Authors: Auricchio Ferdinando , Petrini Lorenza
Published: October 2002

During mechanical loading–unloading cycles shape‐memory alloys (SMA) are able to undergo large deformations without showing residual strains (pseudoelasticity) or recovering them through thermal cycles (shape memory effect). Motivated by stress‐induced solid phase transformations, these unique behaviours induce the SMA exploitation in innovative and commercially valuable applications, stimulating, consequently, the interest in the development of constitutive models. Also if many models are now available in the literature, effective three‐dimensional proposals are still few and limited in several aspects.

In this paper, a three‐dimensional thermomechanical model recently proposed by Souza et al. (European Journal of Mechanics–A/Solids, 1998; 17: 789–806.) is taken into consideration; such a model is of particular interest for its effectiveness and flexibility, but it also shows some limitations and missing links in the algorithmical counterparts.

This work discusses some improvements to the original model as well as the development and the implementation of a robust integration algorithm to be adopted in a numerical scheme, such as a finite‐element framework. Copyright © 2002 John Wiley & Sons, Ltd.
Role of fetal sex in amniotic fluid alphafetoprotein screening
Authors: Knippel Alexander Johannes
Published: October 2002

Objectives

Previous studies have shown that fetal gender has influence on various pregnancy complications and prenatal diagnostic biochemical markers. We have evaluated, whether elevation of amniotic fluid alphafetoprotein (AF AFP) is associated with fetal sex and whether a sex‐related difference can help to identify pregnancies with AFP‐associated malformations or fetal loss.

Material and methods

From our database we obtained 6461 singleton gestations with AF AFP measurements for the period April 1997–March 1999. Patients with AF AFP >1.9 MoM were identified, details of pregnancy outcome were obtained and compared to matched‐pair controls having AF AFP <2 MoM.

Results

In 232 of 262 patients having AF AFP levels >1.9 MoM outcome information was available. Of these fetuses, significantly more had male gender (147 male fetuses versus 85 female). Having a screen‐positive result the risk of AFP‐associated malformations was significantly higher for female fetuses (25 female fetuses (29.4%) versus 22 male fetuses (15%) with AFP‐associated malformations). Adjusting the cut‐off MoM to 2.5 for male and to 2.0 for female fetuses halves the false positive rate from 3.4 to 1.7% without affecting the detection rate of 95%.

Pregnancies with false positive AF AFP had a significantly higher risk for fetal loss compared with pregnancies having normal AF AFP (ten fetal losses from 185 versus two fetal losses from 232), but fetal gender had no significant influence.

Conclusions

Adjusting AF AFP MoM cut‐offs for fetal gender could increase performance of AF‐AFP screening. Larger studies are required to determine suitable sex‐adjusted cut‐off levels. Copyright © 2002 John Wiley & Sons, Ltd.
Between pregnancy biological variability of first trimester markers of Down syndrome and the implications for screening in subsequent pregnancies: an issue revisited
Authors: Spencer Kevin
Published: October 2002

Objectives

To assess the level of correlation of first trimester biochemical and biophysical markers of Down syndrome between different pregnancies in the same individual. To assess the impact that between pregnancy biological variability has on the likelihood that women who are at increased risk in a first pregnancy being also at increased risk in a subsequent pregnancy.

Methods

During a three period women attending the OSCAR clinic at Harold Wood Hospital have had the opportunity to have first trimester screening for Down syndrome and other aneuploidies using the maternal serum biochemical markers free β‐human chorionic gonadotrophin (hCG) and pregnancy associated plasma protein‐A (PAPP‐A) in conjunction with fetal nuchal translucency (NT) thickness and maternal age. Of the 11 1105 women undergoing such screening, the computer records were examined for women who had more than one pregnancy. The results from 1002 women with two normal singleton pregnancies were available for analysis. Marker correlations (as MoM) were established between the pregnancies and the proportion of women likely to be at increased risk in each pregnancy estimated, as was the likelihood of women being at increased risk in both pregnancies.

Results

For fetal NT there was no correlation between NT MoM in the first and second pregnancy (r = 0.0959, p > 0.10). For maternal serum free β‐hCG MoM a significant correlation was found (r = 0.3976, p < 0.001), as was also found for PAPP‐A MoM (r = 0.4371, p < 0.001).

Conclusion

The implication for such between pregnancy marker association is that women who have an increased risk of Down syndrome in one pregnancy are two or three times more likely to repeat this event in their next pregnancy. This information may be useful in counselling women when undergoing first trimester screening in a subsequent pregnancy. Copyright © 2002 John Wiley & Sons, Ltd.
Issues surrounding prenatal genetic testing for achondroplasia
Authors: Gooding Holly C. , Boehm Karina , Thompson Richard E. , Hadley Don , Francomano Clair A. , Biesecker Barbara Bowles
Published: October 2002

Objectives

Mutations in the gene encoding fibroblast growth factor receptor 3 cause achondroplasia, the most prevalent form of dwarfism. Since the discovery of the mutations and gene in 1994, commercial testing has been available for use in prenatal diagnosis. This study sought to determine the awareness of, interest in and use of prenatal genetic testing for achondroplasia.

Methods

Surveys were collected from both individuals affected with achondroplasia (n = 189) and their average statured relatives (n = 136).

Results

The majority of participants were aware of the prenatal genetic testing at the time they were surveyed, but less than 10% had actually used the testing. Affected individuals were much more interested in using the testing if they became pregnant (62%) than were their relatives (28%). The groups were remarkably similar in their interest in using the testing to identify the lethal, homozygous form of achondroplasia and in their unwillingness to consider termination of pregnancies based on a diagnosis of either achondroplasia or average stature. Affected status and perception of the condition were correlated with the importance placed on knowing the prenatal diagnoses of achondroplasia and average stature. Views on abortion were highly correlated with all aspects of interest in prenatal diagnosis for achondroplasia.

Conclusion

These results elucidate the role of selected attitudes and beliefs that contribute to reproductive decision making about achondroplasia. Furthermore, the findings provide insights into education and counseling issues for families and health care practitioners. Copyright © 2002 John Wiley & Sons, Ltd.
Beam injection methods for characterizing thin‐film solar cells
Authors: Romero Manuel J. , Al‐Jassim Mowafak M. , Dhere Ramesh G. , Hasoon Falah S. , Contreras Miguel A. , Gessert Timothy A. , Moutinho Helio R.
Published: October 2002

II–VI and I–III–VI solar cells are promising for future thin‐film photovoltaics. In this paper, the roles of electron‐beam‐induced current (EBIC) and cathodoluminescence in evaluating the influence of interfaces on those solar cells are reviewed. CdTe and Cu(In,Ga)Se2(CIGS) are the absorbers of the cells investigated. For CdTe/CdS solar cells, a detailed study has been conducted of the effects of grain boundaries and the Te/CdTe or ZnTe:Cu/CdTe interfaces for back‐contacting. For CIGS solar cells, we have investigated different buffer layer schemes, showing that these interfaces are critical in the definition of the mechanisms for carrier collection. Copyright © 2002 John Wiley & Sons, Ltd.
Structural vulnerability, reliability and risk
Authors: Blockley D I , Agarwal J , Pinto J T , Woodman N J
Published: October 2002

A system is robust if it can withstand arbitrary damage. There are many practical ways to design in robustness, but there is as yet no accepted theory of robustness. Reliability theory is a useful tool for examining the probability of failure for a pre‐defined type of loading; however low‐probability–high‐consequence events may be missed. One insight into the lack of robustness is gained by identifying how a system is vulnerable. A system that is vulnerable in any one way is not robust. Like robustness, vulnerability has been defined differently in different contexts. The purpose of this paper is not to argue for particular definitions of robustness, vulnerability or risk, but rather to review a ‘theory of structural vulnerability’ developed by the authors and to show how it can be used in practice to improve the robustness of a system. The theory is one of form and connectivity. The purpose is to identify weak links within a structure as vulnerable failure scenarios. These can then be used with the probability of actions causing them to produce a measure of structural reliability and risk.
Buckling of the steel component of a composite member caused by shrinkage and creep of the concrete component
Authors: Vrcelj Z , Bradford M A , Uy B , Wright H D
Published: October 2002

The effects of shrinkage and creep in conventional reinforced and prestressed concrete members are quite well understood, and the effects of these time‐varying characteristics of the concrete component on the deflections of composite beams and columns have received a good deal of attention in recent years. However, creep and shrinkage effects may cause a redistribution of internal actions within a composite member, which increases significantly the compression within the steel component, and that may therefore lead to considerations of the possible buckling instability of the steel component. This paper reviews the research work that been documented only quite recently, which has been undertaken on the potential for composite structures using a thin external skin with a concrete infill to buckle locally, and the possible instabilities that may arise in the negative moment region of a continuous composite beam, due to the shrinkage and creep of the concrete. This paper also puts the possibilities of these instabilities into a practical perspective, indicating where this unique type of steel buckling may need to be a design consideration in the most efficient use of steel–concrete composite construction.
Adrenal Involvement in Multiple Endocrine Neoplasia Type 1
Authors: Langer Peter , Cupisti Kenko , Bartsch Detlef K. , Nies Christoph , Goretzki Peter E. , Rothmund Matthias , Röher Hans D.
Published: October 2002

Adrenal lesions belong to the spectrum of multiple endocrine neoplasia type 1 (MEN‐1) syndrome. However, the prevalence of adrenal involvement, the characteristics, and the clinical management of adrenal lesions have not yet been clearly defined. A total of 66 patients with confirmed MEN1
germline mutations and 1 additional patient with typical manifestations in three organ systems were monitored in a regular screening program that included evaluation of the adrenals (median follow‐up 96 months;
range 12 to 300 months). Age at the diagnosis of MEN‐1 and of adrenal tumors and the clinical characteristics, genotype, treatment, and follow‐up of adrenal disease were analyzed. Adrenal lesions were identified in 18 of 67 (26.8%) MEN‐1 patients and were diagnosed 5
years later than MEN‐1. The median tumor diameter at diagnosis was 3.0
cm (range 1.2–15.0 cm), with most tumors being 3 cm or smaller. Eight patients had bilateral tumors. Ten patients had nonfunctional benign tumors, three had benign adrenal Cushing syndrome, and one patient had a pheochromocytoma. Four patients developed adrenocortical carcinomas
(ACCs), three of which were functional. Nine adrenalectomies and one subtotal adrenalectomy were performed in six patients. Three patients with ACC died owing to the tumor. Patients with mutations in exons 2 and 10 developed adrenal tumors significantly more often than patients with other mutations
(p <0.01). Adrenal tumors are a common feature of MEN‐1 but occur later in the course of the disease. The lesions are often small and nonfunctional and can therefore be managed by close surveillance; others have significant malignant potential and should be considered for surgery when they are 3 cm or larger.
Locally Applied Granulocyte‐macrophage Colony‐stimulating Factor Improves the Impaired Bowel Anastomoses in Rats with Long‐term Corticosteroid Treatment
Authors: Dinc Soykan , Alagol Haluk , Gulcelik Mehmet Ali , Ozbirecikli Bulent , Kuru Bekir , Renda Nurten , Ustun Huseyin
Published: October 2002

Inflammation is an essential component of the first phase of anastomotic wound healing, and it is suppressed by corticosteroids. The anti‐inflammatory effect of corticosteroids is largely responsible for the impairment of wound healing in bowel anastomosis. It has been reported that local application of granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) improves the healing process in dermal wounds. In the present study, we investigated the effects of locally injected GM‐CSF on anastomotic wound healing in long‐term corticosteroid treated rats. Eighty male Sprague‐Dawley rats were randomized into four groups. 1: control, 2: steroid, 3:
steroid + local GM‐CSF, 4: steroid + systemic GM‐CSF. In groups 2, 3, and 4, methylprednisolone (5 mg/kg) was injected IM daily for 14 days. After 14 days, following anesthesia and laparotomy,
colonic anastomosis was performed 3 cm away from the peritoneal reflection. In group 3, 50 mg GM‐CSF was injected into the perianastomotic area. In group 4, 50 mg GM‐CSF was applied subcutaneously. On postoperative day 3, repeat laparotomies were performed and bursting pressures, hydroxyproline levels, and histopathology examinations were studied. The mean values of bursting pressures and hydroxyproline levels in group 3, treated with steroid + local GM‐CSF, were significantly higher than that of the group 2 and group 4 values. In the histopathology examination, the mean score of group 3 was significantly higher than that of groups 2 and 4.
Our study indicates that local application of GM‐CSF significantly improves the impaired anastomotic wound healing in rats treated with long‐term corticosteroid.
Modified Technique of Percutaneous Dilational Tracheostomy in 600 Cases
Authors: Leptidis Geogios , Papanicolaou Spyros , Athanassiadi Kalliopi , Zogby Houssein , Iordanidou Olga , Katsaris Georgios
Published: October 2002

Tracheostomy is frequently required for the treatment of critically ill patients to prevent the complications with prolonged translaryngeal intubation. It may facilitate airway suctioning and improve patient comfort during the process of weaning.
The purpose of the study was to introduce a new modified technique for percutaneous dilational tracheostomy (MPDT) and assess its advantages.
From November 1997 through December 2000, a series of 600 patients (350
men, 250 women; mean age 44.5 years) underwent MPDT in our department.
The technique we used is a combination of the Seldinger and Schachner techniques with an incision of 2 to 3 cm between the cricoid cartilage and the notch. Using a small automatic retractor, the thyroid muscles were dissected with the help of a curved mosquito clamp. This gave us the opportunity to control the isthmus and offered the possibility of ligation when the thyroid was large, providing a good operative field directly on the trachea. Hence we avoided traumatizing the isthmus,
which is the main source of hemorrhage during this procedure. The mean operating time was 4.5 minutes. The morbidity rate was 0.04%. One patient developed a subcutaneous emphysema and in three cases we had to ligate the external jugular vein. The surgical incision was completely healed within 3 to 4 days after removing the tracheostoma. No tracheal stenoses were observed during the follow‐up. MPDT is a safe, applicable technique that can be performed quickly even by a nonsurgeon in the intensive care unit and emergency department, with a low risk of complications because there is a direct view of the trachea and minimal trauma.
Sternal Fractures: Retrospective Analysis of 100 Cases
Authors: Athanassiadi Kalliopi , Gerazounis Michalis , Moustardas Marios , Metaxas Efstathios
Published: October 2002

Isolated sternal fractures are seen with increasing frequency in road accidents, especially since the introduction of seatbelt legislation. The medical records of all our patients who were treated with a diagnosis of sternal fracture (SF)
over the past two decades were retrospectively reviewed to determine the incidence, morbidity, and mortality of this entity. Between 1984
and 1998, 100 consecutive patients were admitted to the Department of Surge Surgery, General Hospital of Nikea‐Piraeus, Greece, for SF. There were 72 men and 28 women ranging in age between 17 and 84 years.
Sixty‐seven patients sustained an isolated SF and the remaining 33 had a SF in combination with multiple injuries such as flail chest (n = 19), head injury (n = 18), limb fractures (n = 10), spinal fractures
(n = 4), hear contusion (n = 1),
hemo‐pneumothorax (n = 9), pneumothorax (n = 6), hemomediastinum (n = 5), and pericarditis (n = 2), among others. All patients with a radiological diagnosis were admitted for cardiac monitoring for at least 24 hours. Electrocardiogram (ECG), determinations of cardiac enzyme levels such as lactic dehydrogenase, creatine kinase, and creatine kinase‐MB, and evaluation by a cardiologist were routinely performed. An echocardiogram was performed as indicated by the cardiologist. Seven patients underwent operation, two for abdominal bleeding, two for chest wall and sternal stabilization, two for open pneumothorax, and one for massive hemothorax. Eight of our patients needed ventilatory support. Four of them died from respiratory insufficiency, myocardial infarction, and heart and lung contusion.
Although an isolated SF carries a good prognosis, careful evaluation and clinical observation are essential.
Indications and Results of Liver Transplantation in Patients with Neuroendocrine Tumors
Authors: Olausson Michael , Friman Styrbjörn , Cahlin Christian , Nilsson Ola , Jansson Svante , Wängberg Bo , Ahlman Håkan
Published: October 2002

Metastases from neuroendocrine (NE)
tumors of the gastrointestinal tract, carcinoids, and endocrine pancreatic tumors (EPTs) can be confined to the liver for long periods and may exhibit slow growth. When considering liver transplantation
(LTx) for patients with NE tumors, the expected results with conventional treatment must be weighed against the risk of LTx and immunosuppression. The following indications for LTx may be considered for patients with metastatic NE tumors limited to the liver: (1) tumors not accessible to curative surgery or major tumor reduction; (2) tumors not responding to medical or interventional treatment; and (3) tumors causing life‐threatening hormonal symptoms. We excluded patients with poorly differentiated NE carcinoma or well differentiated NE carcinoma with a high proliferation index (Ki 67 > 10%). Over 4 years
(1997–2001) we have performed transplants in nine patients (five with EPTs, four with carcinoids) with a mean ± SEM follow‐up of
22 ± 5 months (range 4–45 months). Seven patients underwent orthotopic LTx and two multivisceral LTx. Eight patients are alive, six without clinical evidence of disease. Four patients developed recurrent tumors 9 to 36 months after LTx; two were detected at an early stage and underwent resection with curative intent. One patient with multivisceral Tx died after 4 months of posttransplant lymphoproliferative disease without tumor recurrence. In selected series LTx can offer good control of hormonal symptoms, a relatively long disease‐free interval, and in individual cases potential cure.
Value of Autopsy in Nonimmune Hydrops Fetalis: Series of 51 Stillborn Fetuses
Authors: Rodríguez Maria M. , Chaves Fernando , Romaguera Rita L. , Ferrer Peter L. , de la Guardia Claudia , Bruce Jocelyn H.
Published: October 2002

Nonimmune hydrops fetalis (NIHF) is used to describe fetuses and newborns with generalized edema and cavity effusions. It is helpful to alert physicians about the presence of anemia, heart failure, and/or hypoproteinemia, but this diagnosis is frequently overlooked. We reviewed the autopsy files from 1990 to 2000, selected all cases with NIHF including clinical information (with maternal laboratory tests and ultrasound), and classified patients by etiology. Among 840 stillborn autopsies during the 11-year period, we found 51 with NIHF (6.07%). The clinical summary had mentioned hydrops in 14 patients and the etiology in another 7 by fetal ultrasonography, but without addressing the possibility of hydrops. In the remaining 30 cases neither hydrops nor an etiology was mentioned. Other pertinent diagnoses were maternal diabetes mellitus (4), congenital heart disease (3), and cystic hygroma (2). The following diagnoses were made in one instance each: cardiac tumor, twin transfusion syndrome, congenital adenomatoid malformation, syphilis, Turner syndrome, and cerebral arteriovenous malformation. Postmortem and placental examination confirmed the following etiologies: congenital infections (17); placental pathology significant enough to explain NIHF (10); cardiovascular diseases (8) (further classified as congenital heart disease [3], rhabdomyoma [1], and vascular malformations [4]); chromosomal abnormalities (6); uncontrolled maternal diabetes (4); intrathoracic lesions (2); prune-belly syndrome (2); and idiopathic NIHF (2). Only 3.9% of the cases studied had no identifiable etiology. The cause of hydrops was confirmed by autopsy in 47 fetuses (92%), which further supports the importance of performing an autopsy. Thirty-two cases (62.74%) had placental abnormalities helpful to the etiology (parvovirus, syphilis, Turner's syndrome, etc.). In 20 instances, the clinical summary had no mention of either hydrops or any of the diseases leading to it. The autopsy in conjunction with placental examination and fetal ultrasound represent the best combination to determine the etiology of NIHF among stillborn fetuses.
A model of the copper centres of nitrous oxide reductase (Pseudomonas stutzeri)
Authors: Farrar Jaqui A. , Thomson Andrew J. , Cheesman Myles R. , Dooley David M. , Zumft Walter G.
Published: October 2002

Nitrous oxide reductase (N2OR), Pseudomonas stutzeri, catalyses the 2 electron reduction of nitrous oxide to di‐nitrogen. The enzyme has 2 identical subunits (M
1 ∼ 70 000) of known amino acid sequence and contains ∼ 4 Cu ions per subunit. By measurement of the optical absorption, electron paramagnetic resonance (EPR) and low‐temperature magnetic circular dichroism (MCD) spectra of the oxidised state, a semi‐reduced form and the fully reduced state of the enzyme it is shown that the enzyme contains 2 distinct copper centres of which one is assigned to an electron‐transfer function, centre A, and the other to a catalytic site, centre Z. The latter is a binuclear copper centre with at least 1 cysteine ligand and cycles between oxidation levels Cu(II)/Cu(II) and Cu(II)/Cu(I) in the absence of substrate or inhibitors. The state Cu(II)/Cu(I) is enzymatically inactive. The MCD spectra provide evidence for a second form of centre Z, which may be enzymatically active, in the oxidised state of the enzyme. Centre A is structurally similar to that of CuA in bovine and bacterial cytochrome c oxidase and also contains copper ligated by cysteine. This centre may also be a binuclear copper complex.
Turnover of the K+ transport system in Saccharomyces cerevisiae
Authors: Benito Begoña , Riballo Enriqueta , Lagunas Rosario
Published: October 2002

The stability of the K+ transport system in Saccharomyces cerevisiae has been studied upon inhibition of protein synthesis with cycloheximide. Addition of the antibiotic gave rise to an inactivation of this transport. This activation followed first‐order kinetics and was stimulated by the presence of a fermentable substrate. A half‐life of about 4 h could be calculated in the presence of glucose. The results indicate that, similarly to sugar carriers, K+ transport system is less stable than the bulk of proteins of this organism.
Bovine lens capsule basement membrane collagen exerts a negative priming on polymorphonuclear neutrophils
Authors: Monboisse Jean-Claude , Bellon Georges , Perreau Corinne , Garnotel Roselyne , Borel Jacques-Paul
Published: October 2002

After a 30 min contact between purified bovine lens capsule basement membrane type IV collagen and polymorphonuclear neutrophils, stimulation of these cells by N‐formyl‐methionyl‐leucyl‐phenylalanine, PMA or type I collagen releases a decreased amount of superoxide ions (negative priming). The inhibitory activity is located in the NCl domain. On the other hand, after pepsin digestion, the helical part of type IV collagen determines a positive priming of neutrophils.
The role of pyridoxal phosphate in the function of EspB, a protein secreted by enteropathogenic Escherichia coli
Authors: Taylor Kathleen A. , O'Connell Colin B. , Thompson Richard , Donnenberg Michael S.
Published: October 2002

The sequence of EspB, a secreted protein required for virulence of enteropathogenic Escherichia coli (EPEC), reveals a motif common to enzymes that bind pyridoxal phosphate. Pyridoxal phosphate was not found by fluorometry in concentrated supernatants of EPEC cultures that contain EspB. Plasmids containing cloned espB, in which the lysine residue conserved in the motif was substituted with either an arginine or methionine residue, remained capable of complementing an espB deletion mutant to restore EspB function. The results of these studies do not support a role for pyridoxal phosphate in EspB function.
Differential sensitivity of rat hepatocyte CYP isoforms to self‐generated nitric oxide
Authors: Vernia Santiago , Beaune Philippe , Coloma Julio , López-Garcı́a M.Pilar
Published: October 2002

Early loss of P450 in rat hepatocyte cultures appears directly related to nitric oxide (NO) overproduction. This study investigates the influence of endogenously generated NO (or NO‐derived species) on the relative expression of cytochrome P450 (CYP) isoforms in rat hepatocytes. Our results support the view that loss of P450 holoenzyme in culture is the ultimate consequence of a NO driven process, activated during the common hepatocyte isolation procedure, that leads to an accelerated and selective degradation of specific CYP apoproteins. Under conditions in which NO and peroxynitrite formation is operative, changes in the level of specific CYP isoforms result in a significant alteration of the CYP apoprotein profile that after 24 h of culture is quite different from that found in the liver of uninduced rats. This process is reverted by the early and efficient inhibition of NO synthesis, which allows for (1) maintenance of total P450 holoenzyme content, (2) preservation of the initial constitutive CYP pattern in culture and (3) the early expression of the normal inducibility in response to model inducers.
Chloride binding by the AML1/Runx1 transcription factor studied by NMR
Authors: Wolf-Watz Magnus , Bäckström Stefan , Grundström Thomas , Sauer Uwe , Härd Torleif
Published: October 2002

It is known that the DNA binding Runt domain of the AML1/Runx1 transcription factor coordinates Cl− ions. In this paper we have determined Cl− binding affinities of AML1 by 35Cl nuclear magnetic resonance (NMR) linewidth analysis. The Runt domain binds Cl− with a dissociation constant (K
d,Cl) of 34 mM. If CBFβ is added to form a 1:1 complex, the K
d,Cl value increases to 56 mM. Homology modeling suggests that a high occupancy Cl− binding site overlaps with the DNA binding surface. NMR data show that DNA displaces this Cl− ion. Possible biological roles of Cl− binding are discussed based on these findings.
E3 ligase activity of RING finger proteins that interact with Hip‐2, a human ubiquitin‐conjugating enzyme
Authors: Lee Sun-Joo , Choi Ju-Youn , Sung Yong-Mo , Park Hyewon , Rhim Hyangshuk , Kang Seongman
Published: October 2002

To identify proteins that interact with Huntingtin‐interacting protein‐2 (Hip‐2), a ubiquitin‐conjugating enzyme, a yeast two‐hybrid screen system was used to isolate five positive clones. Sequence analyses showed that, with one exception, all Hip‐2‐interacting proteins contained the RING finger motifs. The interaction of Hip‐2 with RNF2, one of the clones, was further confirmed through in vitro and in vivo experiments. Mutations in the RING domain of RNF2 prevented the clone from binding to Hip‐2, an indication that the RING domain is the binding determinant. RNF2 showed a ubiquitin ligase (E3) activity in the presence of Hip‐2, suggesting that a subset of RING finger proteins may have roles as E3s.
The protonophore CCCP induces mitochondrial permeability transition without cytochrome c release in human osteosarcoma cells
Authors: Lim Maria L.R , Minamikawa Tetsuhiro , Nagley Phillip
Published: October 2002

Mitochondrial permeability transition (MPT) and cytochrome c redistribution from mitochondria are two events associated with apoptosis. We investigated whether an MPT event obligatorily leads to cytochrome c release in vivo. We have previously shown that treatment of human osteosarcoma cells with the protonophore m‐chlorophenylhydrazone (CCCP) for 6 h induces MPT and mitochondrial swelling without significant cell death. Here we demonstrate that release of cytochrome c does not occur and the cells remain viable even after 72 h of treatment with CCCP. Bax is not mobilized to mitochondria under these conditions. However, subsequent exposure of CCCP‐treated cells to etoposide or staurosporine for 48 h results in rapid cell death and cytochrome c release that is accompanied by Bax association with mitochondria, demonstrating competency of these mitochondria to release cytochrome c with additional triggers. Our findings suggest that MPT is not a sufficient condition, in itself, to effect cytochrome c release.
Atomic structure of a glycerol channel and implications for substrate permeation in aqua(glycero)porins
Authors: Nollert Peter , Harries William E.C , Fu Daxiong , Miercke Larry J.W , Stroud Robert M
Published: October 2002

The structure of a glycerol channel from Escherichia coli at 2.2 Å resolution serves as a basis for the understanding of selective transmembrane substrate permeation. In the course of permeation, glycerol molecules diffuse through a tripathic channel with their alkyl backbone wedged against a hydrophobic corner, such that OH groups become acceptors and donors of hydrogen bonds at the same time. The structure of the channel explains the preferential permeability for linear carbohydrates and absolute exclusion of ions and charged solutes. Its gene‐duplicated sequence has a structural counterpart in a pseudo two‐fold symmetry within the monomeric channel protein.
Overexpression of mammalian integral membrane proteins for structural studies
Authors: Tate C.G.
Published: October 2002

Recent successes in the determination of atomic resolution structures of integral membrane proteins have relied on purifying the proteins from abundant natural sources. In contrast, the majority of mammalian receptors, ion channels and transporters need to be overexpressed to obtain sufficient material for structural studies. This has often proved to be very difficult. Overexpression studies on a wide range of mammalian membrane proteins have shown that a few can be expressed functionally in bacteria, but many others require an insect or mammalian cell host for activity or high level expression. The serotonin transporter, which has been expressed in all the major hosts available, is a good example that has given insights into the problem of overexpressing mammalian membrane proteins for structural studies.
Modification of Arg‐13 of μ‐conotoxin GIIIA with piperidinyl‐Arg analogs and their relation to the inhibition of sodium channels
Authors: Nakamura Mitsuhiro , Niwa Yukari , Ishida Yukisato , Kohno Toshiyuki , Sato Kazuki , Oba Yuichi , Nakamura Hideshi
Published: October 2002

μ‐Conotoxin GIIIA, a peptide toxin isolated from the marine snail Conus geographus, preferentially blocks skeletal muscle sodium channels in vertebrates. In this study, analogs of μ‐conotoxin GIIIA in which essential Arg‐13 was replaced with arginine analogs consisting of a piperidyl framework to regulate length and direction of the side chain were synthesized. Synthesized analogs exhibited similar CD and NMR spectra to that of GIIIA, suggesting a three‐dimensional structure identical to that of the native toxin. The biological activities of piperidyl analogs were decreased or lost despite the small change in the side chain of Arg‐13. The investigated structure–activity relationships in inhibiting electrically stimulated muscle contraction suggest that the guanidinium group at amino acid position 13 interacts best when spaced with three to four carbons and placed in a vertical direction from the peptide loop. Thus, the position of the guanidinium group at Arg‐13 of GIIIA must be located in a certain range for its strong interaction with the channel protein.
Functional roles of conserved transmembrane prolines in the human VPAC1 receptor
Authors: Knudsen Sanne Møller , Tams Jeppe Wegener , Fahrenkrug Jan
Published: October 2002

The importance of three conserved transmembrane prolines of the human vasoactive intestinal polypeptide (VPAC)1 receptor was examined by single alanine substitution. P266A, P300A and P348A reduced the expression level, but maintained the binding to VIP. P266A showed decreased ability to stimulate cAMP, while P300A and P348A displayed an increased potency in cAMP production combined with a high sensitivity towards GTP compared to the wild type receptor. In addition, substitutions of two conserved leucines located in position −2 and +1 from P348 were investigated. L346A and L349A reduced the receptor expression, influenced the G protein coupling and decreased the receptor activity. These observations, which are the first on conserved transmembrane prolines within this family of receptors, indicate that these residues are important for receptor expression, G protein coupling and receptor activity.
The X‐ray structure of yeast 5‐aminolaevulinic acid dehydratase complexed with two diacid inhibitors
Authors: Erskine P.T , Coates L , Newbold R , Brindley A.A , Stauffer F , Wood S.P , Warren M.J , Cooper J.B , Shoolingin-Jordan P.M , Neier R
Published: October 2002

The structures of 5‐aminolaevulinic acid dehydratase complexed with two irreversible inhibitors (4‐oxosebacic acid and 4,7‐dioxosebacic acid) have been solved at high resolution. Both inhibitors bind by forming a Schiff base link with Lys 263 at the active site. Previous inhibitor binding studies have defined the interactions made by only one of the two substrate moieties (P‐side substrate) which bind to the enzyme during catalysis. The structures reported here provide an improved definition of the interactions made by both of the substrate molecules (A‐ and P‐side substrates). The most intriguing result is the novel finding that 4,7‐dioxosebacic acid forms a second Schiff base with the enzyme involving Lys 210. It has been known for many years that P‐side substrate forms a Schiff base (with Lys 263) but until now there has been no evidence that binding of A‐side substrate involves formation of a Schiff base with the enzyme. A catalytic mechanism involving substrate linked to the enzyme through Schiff bases at both the A‐ and P‐sites is proposed.
Apigenin decreases expression of the myofibroblast phenotype
Authors: Ricupero Dennis A , Poliks Christine F , Rishikof David C , Kuang Ping-Ping , Goldstein Ronald H
Published: October 2002

We investigated the effect of the dietary flavonoid apigenin on myofibroblast function. We report that in myofibroblasts treated with apigenin, proliferation and basal levels of α1(I) collagen and α‐smooth muscle actin mRNAs were markedly reduced. Apigenin also attenuated the transforming growth factor‐β‐stimulated increases of α1(I) collagen and α‐smooth muscle actin mRNAs. Characterization of the apigenin effects indicates that apigenin reduces both the stability of the α1(I) collagen mRNA and the rate of transcription of the α1(I) collagen gene through a cycloheximide‐sensitive pathway. Western blot analyses indicate that Akt activity is reduced in apigenin‐treated myofibroblasts.
Molecular mechanism for the crystallization of bacteriorhodopsin in lipidic cubic phases
Authors: Nollert Peter , Qiu Hong , Caffrey Martin , Rosenbusch Jurg P , Landau Ehud M
Published: October 2002

Crystals of transmembrane proteins may be grown from detergent solutions or in a matrix of membranous lipid bilayers existing in a liquid crystalline state and forming a cubic phase (in cubo). While crystallization in micellar solutions appears analogous to that for soluble proteins, crystallization in lipidic matrices is poorly understood. As this method was shown to be applicable to several membrane proteins, understanding its mechanism will facilitate a rational design of crystallization, minimizing the laborious screening of a large number of parameters. Using polarization microscopy and low‐angle X‐ray diffraction, experimental evidence is provided to support a mechanistic model for the in cubo crystallization of bacteriorhodopsin in a lipid matrix. Membrane proteins are thought to reside in curved lipid bilayers, to diffuse into patches of lower curvature and to incorporate into lattices which associate to form highly ordered three‐dimensional crystals. Critical testing of this model is necessary to generalize it to other membrane proteins.
The Candida albicans Na+/H+ antiporter exports potassium and rubidium
Authors: Kinclová Olga , Potier Serge , Sychrová Hana
Published: October 2002

The Candida albicans Cnh1p belongs to the family of Na+/H+ antiporters (TC 2.A.36) but it transports besides toxic sodium and lithium also rubidium and potassium. Upon heterologous expression in a Saccharomyces cerevisiae salt‐sensitive strain, the Cnh1p is targeted to the plasma membrane and its transport activity results in increased tolerance of cells to external alkali metal cations. The cation efflux activity of Cnh1p in S. cerevisiae depends on the gradient of protons across the plasma membrane, and a Cnh1p‐mediated K+ efflux is involved in a cell response to sudden rise of cytoplasmic pH.
Phosphatidylserine induces apoptosis in CHO cells without mitochondrial dysfunction in a manner dependent on caspases other than caspases‐1, ‐3, ‐8 and ‐9
Authors: Miyato Yasuyuki , Ibuki Yuko , Ohyama Harumi , Yamada Takeshi , Goto Rensuke
Published: October 2002

Treatment of Chinese hamster ovary K1 cells with phosphatidylserine (PS) caused typical apoptosis with distinct morphological and biochemical features in a dose‐ and time‐dependent manner. However, unlike camptothecin‐induced apoptosis, changes in mitochondrial transmembrane potential were not observed. In addition, cytochromecrelease did not occur in PS‐induced apoptosis. A pan caspase inhibitor, Z‐VAD, significantly inhibited the apoptosis, but inhibitors of caspase‐1, ‐3, ‐8 and ‐9 did not. Activities of caspase‐1, ‐3, ‐8 and ‐9 were increased by treatment of the cells with camptothecin, but not with PS. These results suggest that PS‐induced apoptosis occurs without the collapse of mitochondrial transmembrane potential and without the release of cytochromec, in a manner independent of caspase‐1, ‐3, ‐8 and ‐9.
An internal segment (residues 58–119) of the hepatitis B virus X protein is sufficient to activate MAP kinase pathways in mouse liver
Authors: Nijhara Ruchika , Jana Siddhartha S. , Goswami Shyamal K. , Kumar Vijay , Sarkar Debi P.
Published: October 2002

The human hepatitis B virus X protein (HBx) is known as a dual‐specificity transactivator stimulating the transcriptional machinery in the nucleus and signal transduction pathways in the cytoplasm. HBx‐induced activation of mitogen‐activated protein kinase (MAPK) signaling cascades is considered to play an important role in hepatitis B virus‐mediated hepatocarcinogenesis. Herein, we have identified the regions of HBx that are crucial for activating such signaling cascades in vivo. A truncated mutant incorporating regions C–E (amino acids 58–140) was as effective as the full‐length HBx in activating MAPKs and enhancing activator protein‐1 binding activity. While deletion of region C (amino acids 58–84) or D (amino acids 85–119) led to a drastic loss of function, region E (amino acids 120–140) was dispensable for the activation of signaling cascades. Overall, these findings provide the first evidence for the requirement of domain 58–119 of HBx in transmitting mitogenic signals to the nucleus in vivo.
The quenching of photosystem II fluorescence does not protect the D1 protein against light induced degradation in thylakoids
Authors: Santabarbara S. , Barbato R. , Zucchelli G. , Garlaschi F.M. , Jennings R.C.
Published: October 2002

In spinach thylakoids, the quenching of the singlet excited state in the photosystem II antenna by m‐dinitrobenzene does not change the rate of the light induced degradation of the D1 reaction centre protein and offers only limited protection against photoinhibition itself. These results are discussed in terms of the role of non‐photochemical quenching as a photoprotective strategy.
PAI‐1 inhibits urokinase‐induced chemotaxis by internalizing the urokinase receptor
Authors: Degryse Bernard , Sier Cornelis F.M , Resnati Massimo , Conese Massimo , Blasi Francesco
Published: October 2002

PAI‐1 (plasminogen activator inhibitor‐1) binds the urokinase‐type plasminogen activator (uPA) and causes its degradation via its receptor uPAR and low‐density lipoprotein receptor‐related protein (LRP). While both uPA and PAI‐1 are chemoattractants, we find that a preformed uPA–PAI‐1 complex has no chemotactic activity and that PAI‐1 inhibits uPA‐induced chemotaxis. The inhibitory effect of PAI‐1 on uPA‐dependent chemotaxis is reversed when uPAR internalization is inhibited by the 39 kDa receptor‐associated protein or by anti‐LRP antibodies. Under the same conditions, the uPA–PAI‐1 complex is turned into a chemoattractant causing cytoskeleton reorganization and extracellular‐regulated kinase/mitogen‐activated protein kinases activation. Thus, uPAR internalization by PAI‐1 regulates cell migration.
Single particle macromolecular structure determination via electron microscopy
Authors: Thuman-Commike Pamela A
Published: October 2002

Three‐dimensional structure determination of macromolecules and macromolecular complexes is an integral part of understanding biological functions. For large protein and macromolecular complexes structure determination is often performed using electron cryomicroscopy where projection images of individual macromolecular complexes are combined to produce a three‐dimensional reconstruction. Single particle methods have been devised to perform this structure determination for macromolecular complexes with little or no underlying symmetry. These computational methods generally involve an iterative process of aligning unique views of the macromolecular images followed by determination of the angular components that define those views. In this review, this structure determination process is described with the aim of clarifying a seemingly complex structural method.
Modification of the laminin α4 chain by chondroitin sulfate attachment to its N‐terminal domain
Authors: Sasaki Takako , Mann Karlheinz , Timpl Rupert
Published: October 2002

The N‐terminal domain of laminin α4 chains corresponds to a short rod‐like structure which after recombinant production was found to be modified by chondroitin sulfate. Substitution occurred mainly to a single serine in its N‐terminal ASGDG sequence. A similar yet partial modification was also demonstrated for the α4 chain present in extracts of adult mouse tissues. Antibodies to the fragment were useful to demonstrate a relatively high content of α4 in several tissues and for the immunolocalization in various blood vessels, some basement membranes and interstitial regions.