bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleotide induced conformation determines posttranslational isoprenylation of the ras related rab6 protein in insect cells
Authors: Schiedel Anke C. , Barnekow Angelika , Mayer Thomas
Published: July 2002

Small GTP binding proteins of the rab/YPT family are essential regulators of vectorial transport in the eukaryotic cell. Members of the rab/YPT1 family are found on the cytoplasmic surface of distinct intracellular membrane compartments. Membrane attachment is facilitated by a C‐terminal geranylgeranyl moiety. In this report we investigated posttranslational modification and membrane binding of the rab6 protein, a member of the rab/YPT family located on the Golgi apparatus. A set of point mutations, which simulate the GDP or GTP bound conformation, was introduced into the rab6 cDNA. The mutated cDNAs were expressed in insect cells and the ability of the protein products to undergo geranylgeranyl modification and membrane association was assessed by Triton X‐114 partition and cell fractionation. We report here that the modification of rab6 in insect cells depends on protein conformation. Only the GDP bound form, but not the GTP bound form is isoprenylated and subsequently membrane bound.
Phenotype‐dependent expression of cadherin 6B in vascular and visceral smooth muscle cells
Authors: Chimori Yoshihiro , Hayashi Ken'ichiro , Kimura Kazuhiro , Nishida Wataru , Funahashi Shin-ichi , Miyata Shoji , Shimane Miyuki , Matsuzawa Yuji , Sobue Kenji
Published: July 2002

We used mRNA subtraction of differentiated and dedifferentiated smooth muscle cells (SMCs) to reveal the molecular mechanisms underlying the phenotypic modulation of SMCs. With this approach, we found that a 10 kb mRNA encoding a homotypic cell adhesion molecule, cadherin 6B, was strongly expressed in differentiated vascular and visceral SMCs, but not in the dedifferentiated SMCs derived from them. In vivo, cadherin 6B was expressed in vascular and visceral SMCs, in addition to brain, spinal cord, retina and kidney, at a late stage of chicken embryonic development. These results suggest that cadherin 6B is a novel molecular marker for vascular and visceral SMC phenotypes and is involved in the late differentiation of SMCs.
Apoptosis in yeast – a monocellular organism exhibits altruistic behaviour
Authors: Fröhlich Kai-Uwe , Madeo Frank
Published: July 2002

Apoptosis is a highly regulated form of programmed cell death crucial for life and health in metazoan animals. Apoptosis is defined by a set of cytological alterations. The recent discovery of these markers in yeast indicates the presence of the basic mechanisms of apoptosis already in unicellular eukaryotes. Oxygen radicals regulate both mammalian and yeast apoptosis. We suggest that apoptosis originated in unicellular organisms as an altruistic response to severe oxidative damage. Later, cells developed mechanisms to purposely produce reactive oxygen species as a regulator of apoptosis. Yeast may become an important model to investigate the conserved steps of apoptosis.
Wortmannin inhibits activation of nuclear transcription factors NF‐κB and activated protein‐1 induced by lipopolysaccharide and phorbol ester
Authors: Manna Sunil K , Aggarwal Bharat B
Published: July 2002

Whether all inflammatory agents activate nuclear transcription factors NF‐κB and activated protein‐1 (AP‐1) through the same mechanism is not known. We examined the effect of the phosphatidylinositol‐3‐kinase (PI‐3K) inhibitor wortmannin on the activation of NF‐κB and AP‐1 by different inflammatory agents. Wortmannin blocked NF‐κB and AP‐1 activation by lipopolysaccharide and phorbol ester but had minimal effect on activation by hydrogen peroxide, ceramide, okadaic acid and tumor necrosis factor. Inhibition of NF‐κB correlated with abrogation of the degradation of IκBα and of NF‐κB‐dependent reporter gene transcription. Thus, the mechanism of NF‐κB and AP‐1 activation by lipopolysaccharide and phorbol ester involves PI‐3K.
Thrombin stimulation of platelets causes an increase in phosphatidylinositol 5‐phosphate revealed by mass assay
Authors: Morris James B , Hinchliffe Katherine A , Ciruela Antonio , Letcher Andrew J , Irvine Robin F
Published: July 2002

Phosphatidylinositol 5‐phosphate (PtdIns5P), a novel inositol lipid, has been shown to be the major substrate for the type II PtdInsP kinases (PIPkins) [Rameh et al. (1997) Nature 390, 192–196]. A PtdInsP fraction was prepared from cell extracts by neomycin chromatography, using a protocol devised to eliminate the interaction of acidic solvents with plasticware, since this was found to inhibit the enzyme. The PtdIns5P in this fraction was measured by incubating with [γ‐32P]ATP and recombinant PIPkin IIα, and quantifying the radiolabelled PtdInsP2 formed. This assay was used on platelets to show that during 10 min stimulation with thrombin, the mass level of PtdIns5P increases, implying the existence of an agonist‐stimulated synthetic mechanism.
Aquaporin 3 cloned from Xenopus laevis is regulated by the cystic fibrosis transmembrane conductance regulator
Authors: Schreiber Rainer , Pavenstädt Hermann , Greger Rainer , Kunzelmann Karl
Published: July 2002

The cystic fibrosis transmembrane conductance regulator (CFTR) is essential for epithelial electrolyte transport and has been shown to be a regulator of epithelial Na+, K+, and Cl− channels. CFTR also enhances osmotic water permeability when activated by cAMP. This was detected initially in Xenopus oocytes and is also present in human airway epithelial cells, however, the mechanisms remain obscure. Here, we show that CFTR activates aquaporin 3 expressed endogenously and exogenously in oocytes of Xenopus laevis. The interaction requires stimulation of wild type CFTR by cAMP and an intact first nucleotide binding domain as demonstrated for other CFTR–protein interactions.
Functional crosstalk between phospholipase D2 and signaling phospholipase A2/cyclooxygenase‐2‐mediated prostaglandin biosynthetic pathways
Authors: Ueno Noriko , Murakami Makoto , Kudo Ichiro
Published: July 2002

We performed reconstitution analyses of functional interaction between phospholipase A2 (PLA2) and phospholipase D (PLD) enzymes. Cotransfection of HEK293 cells with cytosolic (cPLA2) or type IIA secretory (sPLA2‐IIA) PLA2 and PLD2, but not PLD1, led to marked augmentation of stimulus‐induced arachidonate release. Interleukin‐1‐stimulated arachidonate release was accompanied by prostaglandin E2 production via cyclooxygenase‐2, the expression of which was augmented by PLD2. Conversely, activation of PLD2, not PLD1, was facilitated by cPLA2 or sPLA2‐IIA. Thus, our results revealed functional crosstalk between signaling PLA2s and PLD2 in the regulation of various cellular responses in which these enzymes have been implicated.
Molten Globule Intermediate of Recombinant Human Growth Hormone: Stabilization with Surfactants
Authors: Bam Narendra B. , Cleland Jeffrey L. , Randolph Theodore W.
Published: July 2002

We demonstrate that a surfactant‐stabilized molten globule intermediate exists for recombinant human growth hormone (rhGH), is very hydrophobic, and tends to form aggregates. Characterization of this intermediate included equilibrium denaturation measured by electron paramagnetic resonance (EPR) and CD spectroscopy, assessment of aggregation during refolding, and fluorescence studies of its binding to the hydrophobic probe, 1‐anilinonapthalene‐8‐sulfonate (1,8‐ANS). We have found that at 4.5 M guanidinium hydrochloride (GuHCl), a molten globule intermediate of rhGH is stabilized and results in significant aggregation upon refolding. This intermediate is populated by the addition of the nonionic surfactant, Tween. This surfactant also reduces the extent of aggregation during refolding of rhGH from 4.5 M GuHCl. Overall, our studies reveal that rhGH forms a molten globule‐like intermediate during folding and this intermediate self‐associates. This self‐association is reduced upon formation of a Tween‐rhGH complex. Tween also binds to the native protein. Thus, nonionic surfactants such as Tween may act like molecular chaperones in facilitating protein folding while not altering the native conformation.
Hormone-specific regulation of the kidney androgen-regulated gene promoter in cultured mouse renal proximal-tubule cells
Authors: SOLER Montse , TORNAVACA Olga , SOLÉ Esther , MENOYO Anna , HARDY Dianne , CATTERALL James F. , VANDEWALLE Alain , MESEGUER Anna
Published: July 2002

The kidney androgen-regulated protein (KAP) is specifically expressed and differentially regulated by androgens and tri-iodothyronine (T3) in intact mouse early (PCT) and late (PR) proximal-tubule cells. Until now, detailed characterization of the molecular elements mediating androgen-responsive gene expression in the kidney has been hampered by the lack of appropriate cultured cell systems suitable for DNA transfection studies. In the present study we have analysed the hormone-dependent transactivation of the KAP gene promoter in immortalized differentiated PCT and PR proximal-tubule cells derived from L-PK/Tag1 transgenic mice. Transient transfection studies with different KAP promoter constructs indicated that a 224bp-truncated fragment was sufficient to mediate cell-specific expression of the KAP promoter. Dihydrotestosterone (DHT) stimulated in an androgen-dependent manner the transactivation of KAP in PCT and PR cells, while mutation of a putative androgen-response element (ARE) sequence located at −39bp from the transcription initiation site abolished the transactivation induced by DHT. Furthermore, insulin-like growth factor 1 (IGF-1), but not T3, enhanced the androgen-dependent transactivation of KAP in cultured PCT cells. These results demonstrate that the short 224bp fragment of the KAP promoter is sufficient to drive the proximal-tubule androgen-specific regulated expression of KAP and reveal synergistic interactions between IGF-1 and androgens for KAP regulation in PCT cells.
Tumour metastasis suppressor, nm23-β, inhibits gelatinase A transcription by interference with transactivator Y-box protein-1 (YB-1)
Authors: CHENG Sunfa , ALFONSO-JAUME Maria Alexandra , MERTENS Peter R. , LOVETT David H.
Published: July 2002

Gelatinase A transcriptional regulation is the consequence of combinatorial interactions with key promoter and enhancer elements identified within this gene. A potent 40bp enhancer response element, RE-1, located in the near 5′ flanking regions of the rat and human gelatinase A genes drives high-level expression in glomerular mesangial cells (MCs). Southwestern-blot analysis of MC nuclear extracts revealed specific interactions of RE-1 with at least four proteins, of which three have been identified as p53, activator protein 2 and the single-stranded DNA-binding factor Y-box protein-1 (YB-1). In the present study, we report the identification of a fourth 17kDa RE-1-binding protein as the rat homologue (nm23-β) of the human nm23-H1 metastasis suppressor gene. Recombinant nm23-β protein bound only the single-stranded forms of the RE-1 sequence. Mutagenesis revealed direct interaction of nm23-β with a repeat sequence, 5′-GGGTTT-3′, shown previously to specifically interact with YB-1 [Mertens, Harendza, Pollock and Lovett (1997) J. Biol. Chem. 272, 22905—22912], and recombinant nm23-β protein competed for single-stranded YB-1 binding. Transient transfection of MC with an nm23-β expression plasmid within the context of a RE-1/simian virus 40 promoter/luciferase reporter yielded a concentration-dependent repression (80—90%) of luciferase activity in MC and Rat1 fibroblasts. A similar pattern of nm23-β repression was demonstrated within the context of the RE-1/homologous gelatinase A promoter. Co-transfection of nm23-β blocked YB-1-mediated activation of transcription and expression of gelatinase A. Nm23-β may be an important physiological regulator of gelatinase A transcription that acts by competitive interference with the single-stranded transactivator YB-1. Gelatinase A is a key mediator of tumour metastasis, suggesting that competitive suppression of transcription by nm23-β (or the human nm23-H1) may be a component of the reduced metastatic capabilities of cells expressing high levels of this protein.
Primary cell culture and morphological characterization of canine dermal papilla cells and dermal fibroblasts
Authors: Bratka‐Robia Christine B. , Mitteregger Gerda , Aichinger Amanda , Egerbacher Monika , Helmreich Magdalena , Bamberg Elmar
Published: July 2002

Abstract Skin biopsies were taken from female dogs, the primary hair follicles isolated and the dermal papilla dissected. After incubation in supplemented Amniomax complete C100 medium in 24‐well culture plates, the dermal papilla cells (DPC) grew to confluence within 3 weeks. Thereafter, they were subcultivated every 7 days. Dermal fibroblast (DFB) cultures were established by explant culture of interfollicular dermis in serum‐free medium, where they reached confluence in 10 days. They were subcultivated every 5 days. For immunohistochemistry, cells were grown on cover slips for 24 h, fixed and stained with antibodies against collagen IV and laminin. DPC showed an aggregative growth pattern and formation of pseudopapillae. Intensive staining for collagen IV and laminin could be observed until the sixth passage. DFB grew as branching, parallel lines and showed only weak staining for collagen IV and laminin.
Low‐dose misoprostol for the prevention of low‐dose aspirin‐induced gastroduodenal injury
Authors: Donnelly M. T. , Goddard A. F. , Filipowicz B. , Morant S. V. , Shield M. J. , Hawkey C. J.
Published: July 2002

Introduction:

The harmful effects of non‐steroidal anti‐inflammatory drugs (NSAIDs) on the gastric mucosa and the prophylactic effects of misoprostol are both dose‐dependent.

Aim:

To investigate whether a low‐dose of misoprostol is sufficient to prevent gastric mucosal injury caused by low‐dose aspirin.

Methods:

We conducted a double‐blind placebo controlled parallel group endoscopic study in 32 evaluable volunteers. The main outcome measure was erosive injury (ulcers and superficial erosions) in the gastric mucosa over 28 days.

Results:

Most subjects developed erosions on aspirin 300 mg daily. This was significantly reduced by misoprostol 100 μg daily. (Odds ratio 0.18, 95% CI: 0.07–0.48). There were no drug‐related or gastrointestinal adverse events in subjects receiving misoprostol.

Conclusion:

Misoprostol 100 μg daily can prevent low‐dose aspirin induced gastric mucosal injury without causing identifiable adverse effects.
Concomitant overdosing of other drugs in patients with paracetamol poisoning
Authors: Schmidt Lars E. , Dalhoff Kim
Published: July 2002

Aims  Paracetamol is frequently involved in intended self‐poisoning, and concomitant overdosing of other drugs is commonly reported. The purpose of the study was to investigate further concomitant drug overdose in patients with paracetamol poisoning and to evaluate its effects on the outcome of the paracetamol intoxication.

Methods  Six hundred and seventy‐one consecutive patients admitted with paracetamol poisoning were studied and concomitant drug intake was recorded. The relative risk of hepatic encephalopathy, death or liver transplantation, hepatic dysfunction, liver cell damage, and renal dysfunction associated with concomitant overdosing of other drugs was evaluated by multivariate analysis.

Results  Concomitant drug overdose was found in 207 patients (31%, 95% confidence interval [CI] 27, 34%). Concomitant overdosing of benzodiazepines (99 cases), opioid analgesics (38 cases), acetylsalicylic acid (33 cases), and NSAID (32 cases) predominated. Concomitant benzodiazepine overdose was an independent risk factor in the development of hepatic encephalopathy (odds ratio [OR] 1.91; CI 1.00, 3.65) and renal dysfunction (OR 1.81; CI 1.00, 3.22). Concomitant overdosing of opioid analgesics was a protective factor in the development of hepatic encephalopathy (OR 0.26; CI 0.07, 0.96). Concomitant acetylsalicylic acid overdose was a risk factor in the development of hepatic encephalopathy (OR 4.87; CI 1.52, 15.7) and death or liver transplantation (OR 6.04; CI 1.69, 21.6). A tendency towards a more favourable outcome was observed in patients with concomitant NSAID overdose.

Conclusions  Concomitant overdosing of benzodiazepines or analgesics is frequent in patients admitted with paracetamol poisoning. Concomitant benzodiazepine or acetylsalicylic acid overdose was associated with more severe toxicity, whereas concomitant overdosing of opioid analgesics was associated with less toxicity.
Treatment of coagulation inhibitors with extracorporeal immunoadsorption (Ig‐Therasorb)
Authors: Jansen M. , Schmaldienst S. , Banyai S. , Quehenberger P. , Pabinger I. , Derfler K. , Hörl W. H. , Knöbl P.
Published: July 2002

Coagulation inhibitors may occur as alloantibodies in patients with congenital factor deficiencies or as autoantibodies in patients with a previously normal coagulation. We treated 10 patients with factor VIII inhibitors (three haemophiliacs and seven patients with acquired factor VIII inhibitors) and one patient with a factor V inhibitor using extracorporeal immunoadsorption to immobilized antibodies against human immunoglobulins (Ig‐Therasorb). The initial inhibitor titre was between 18 BU/ml and 540 BU/ml. Nine patients had signs of bleeding. Eighty‐nine immunoadsorption sessions were performed in the 11 patients (8·1 ± 5·1 per patient), each processing 6980 ± 880 ml of plasma in 3·8 ± 0·5 h. The mean reduction of the inhibitor titre was 71·9 ± 19·4% per session. Serum IgG, IgA and IgM levels decreased by 68·7 ± 10·1%, 55·7 ± 12·7% and 48·6 ± 11·1% respectively. In two haemophiliac patients, an initial titre reduction prior to an immune tolerance protocol was performed. Another haemophiliac patient was treated because of acute cerebral bleeding. In six out of eight patients with acquired inhibitors, a durable elimination was achieved within a median of 18 d. Treatment was safe and well‐tolerated and seems to be a promising method in the treatment of patients with coagulation inhibitors, especially when a fast inhibitor titre reduction is necessary.
Reliability of sentinel lymph node biopsy for staging melanoma
Authors: Jansen L , Nieweg O E , Peterse J L , Hoefnagel C A , Valdés Olmos R A , Kroon B B R
Published: July 2002

Background

The aim of this study was to evaluate the reliability of sentinel lymph node biopsy for staging melanoma.

Methods

Two hundred consecutive patients with a cutaneous melanoma of at least 1·0 mm Breslow thickness, without palpable regional lymph nodes, were included from 1993 in a prospective cohort study in a single tertiary care hospital. One day after lymphoscintigraphy, sentinel node biopsy was performed, guided by a γ probe and patent blue dye. Lymph node dissection was performed only if metastasis was found in a sentinel node. Median follow-up was 32 (range 3–61) months. No patient was lost to follow-up.

Results

A sentinel node was removed in 199 of 200 patients (mean 2·2 nodes per patient). Forty-eight patients (24 per cent) had metastasis in a sentinel node. Fifteen patients developed recurrence after removal of a tumour-negative sentinel node; six relapsed in the previously mapped basin (false-negative rate 11 per cent (six of 54)). The overall survival at 3 years was 93 per cent if the sentinel node was negative and 67 per cent if it was positive. Sentinel node status and Breslow thickness were strong predictors of recurrence and survival. Minor complications were seen in 18 patients.

Conclusion

The sentinel node status was a strong prognostic factor, even with a false-negative rate of 11 per cent.
Comparing global models of terrestrial net primary productivity (NPP): overview and key results
Authors: Cramer W. , Kicklighter D. W. , Bondeau A. , Iii B. Moore , Churkina G. , Nemry B. , Ruimy A. , Schloss A. L. , Intercomparison ThE. Participants OF. ThE. Potsdam NpP. Model
Published: July 2002

Seventeen global models of terrestrial biogeochemistry were compared with respect to annual and seasonal fluxes of net primary productivity (NPP) for the land biosphere. The comparison, sponsored by IGBP‐GAIM/DIS/GCTE, used standardized input variables wherever possible and was carried out through two international workshops and over the Internet. The models differed widely in complexity and original purpose, but could be grouped in three major categories: satellite‐based models that use data from the NOAA/AVHRR sensor as their major input stream (CASA, GLO‐PEM, SDBM, SIB2 and TURC), models that simulate carbon fluxes using a prescribed vegetation structure (BIOME‐BGC, CARAIB 2.1, CENTURY 4.0, FBM 2.2, HRBM 3.0, KGBM, PLAI 0.2, SILVAN 2.2 and TEM 4.0), and models that simulate both vegetation structure and carbon fluxes (BIOME3, DOLY and HYBRID 3.0). The simulations resulted in a range of total NPP values (44.4–66.3 Pg C year–1), after removal of two outliers (which produced extreme results as artefacts due to the comparison). The broad global pattern of NPP and the relationship of annual NPP to the major climatic variables coincided in most areas. Differences could not be attributed to the fundamental modelling strategies, with the exception that nutrient constraints generally produced lower NPP. Regional and global NPP were sensitive to the simulation method for the water balance. Seasonal variation among models was high, both globally and locally, providing several indications for specific deficiencies in some models.
Genetic structure and differentiation of Plantago major reveals a pair of sympatric sister species
Authors: Morgan‐Richards M. , Wolff K.
Published: July 2002

Seeds of the widespread weed Plantago major were collected from 10 European countries, as well as Trinidad and North America. The seed collections were from populations of two taxa which are ecologically rather than geographically separated and formally recognized as the subspecies Plantago major ssp. major and P.m. ssp. intermedia (also called P.m. ssp. pleiosperma). Eight polymorphic allozyme loci and 73 random‐primed DNA fragments were scored, as well as 11 morphological characters. Complete concordance between morphological traits and genetic data provides evidence that these two taxa, although very similar, are distinct species. They are both widespread, they are broadly sympatric and capable of interbreeding. However, slight morphological and ecological differences coincide with genetic clustering of populations from widely separated locations. In addition, P. major and P. intermedia differ in their population structure: P. intermedia has greater genetic diversity among populations and less genetic variance within populations than P. major. We suggest that differences between the two species in their levels of selfing may explain the distinctive genetic structure of each species. We hypothesize a link between selfing rate and lifespan of the two taxa. P. major is characterized by lower genetic variation among populations, a higher rate of outcrossing, longer lifespan and production of fewer seeds per seed capsule. P. intermedia is more highly structured with much differentiation among populations, a higher rate of inbreeding and it often grows as an annual.
ALSPAC–The Avon Longitudinal Study of Parents and Children
Authors: Golding  , Pembrey  , Jones  , The Alspac Study Team
Published: July 2002

ALSPAC (The Avon Longitudinal Study of Parents and Children, formerly the Avon Longitudinal Study of Pregnancy and Childhood) was specifically designed to determine ways in which the individual’s genotype combines with environmental pressures to influence health and development. To date, there are comprehensive data on approximately 10 000 children and their parents, from early pregnancy until the children are aged between 8 and 9. The study aims to continue to collect detailed data on the children as they go through puberty noting, in particular, changes in anthropometry, attitudes and behaviour, fitness and other cardiovascular risk factors, bone mineralisation, allergic symptoms and mental health. The study started early during pregnancy and collected very detailed data from the mother and her partner before the child was born. This not only provided accurate data on concurrent features, especially medication, symptoms, diet and lifestyle, attitudes and behaviour, social and environmental features, but was unbiased by parental knowledge of any problems that the child might develop. From the time of the child’s birth many different aspects of the child’s environment have been monitored and a wide range of phenotypic data collected. By virtue of being based in one geographic area, linkage to medical and educational records is relatively simple, and hands‐on assessments of children and parents using local facilities has the advantage of high quality control. The comprehensiveness of the ALSPAC approach with a total population sample unselected by disease status, and the availability of parental genotypes, provides an adequate sample for statistical analysis and for avoiding spurious results. The study has an open policy in regard to collaboration within strict confidentiality rules.
The aquatic thrips Organothrips indicus Bhatti (Thysanoptera: Thripidae) in Queensland, and a new species, O. wrighti, from tropical Australia
Authors: Mound Laurence A
Published: July 2002

The genus Organothrips includes the only fully aquatic thrips, the two previously known species breeding under water in the surface mucous of several unrelated monocotyledonous plants. Organothrips indicus Bhatti is recorded in Australia for the first time, breeding on water hyacinth (Eichhornia crassipes) in a greenhouse near Brisbane. Structural variation within this population is discussed, and character states considered for distinguishing this species from the Pacific taro thrips, O. bianchii Hood. A new species, Organothrips wrighti, is described from Melville Island, Northern Territory and from Cape Tribulation, Queensland. This species has fully macropterous males and is probably not aquatic. The studies on Eichhornia also gave rise to two new distribution records; Salpingothrips aimotofus Kudo is newly recorded from Australia, and the Northern Hemisphere pest thripid Echinothrips americanus Morgan is newly recorded from Thailand.
Rigid ureteroscopy in pregnant women
Authors: Shokeir  , Mutabagani
Published: July 2002

Objective

 To report our experience with rigid ureteroscopy in pregnant women.

Patients and methods

 Ten pregnant women (mean age 25 years, sd 4.5, range 22–33) with ureteric stones were treated by ureteroscopy. The mean (sd, range) gestation time was 24 (6.5, 19–33) weeks. A standard rigid ureteroscope of 11.5 F was used in eight patients and 9.5 F in two. The procedure was carried out with no ureteric dilatation in three patients and with easy dilatation in seven. Fluoroscopy was not used before or during ureteroscopy in any case. Ultrasonography was available throughout the procedures for constant renal and obstetric monitoring.

Results

 Mid and lower ureteric stones were extracted by basket or forceps in three patients and had to be disintegrated by ultrasound in two. Upper ureteric stones were displaced to the kidney, with placement of double‐pigtail ureteric stents, in three patients who were subsequently treated after delivery. Ureteric oedema was seen in one patient and the endoscopic findings were normal in the remaining patient. There were no obstetric complications. Two patients had a urinary tract infection and one complained of stent‐induced bladder irritation.

Conclusions

 Rigid ureteroscopy is a safe and reliable method in the diagnosis and treatment of ureteric calculi during pregnancy. The procedure can be performed with ultrasonographic monitoring and without using fluoroscopy.
Interspecific Variation in RGR and the Underlying Traits among 24 Grass Species Grown in Full Daylight
Authors: Ryser P. , Wahl S.
Published: July 2002

Abstract: A growth analysis was conducted with 24 central European grass species in full daylight to test whether traits underlying interspecific variation in relative growth rate (RGR) are the same in full daylight as they are at lower light, and whether this depends on the ecological characteristics of the studied species, i.e., their requirements with respect to nutrient and light availability.

In contrast to studies with herbaceous species at lower light, net assimilation rate (NAR) contributed more than leaf area ratio (LAR) or specific leaf area (SLA) to interspecific variation in RGR. This was associated with a larger interspecific variation in NAR than found in experiments with lower light. Without the two most shade‐tolerant species, however, the contribution of LAR and its components to interspecific variation in RGR was similar or even higher than that of NAR.

Leaf dry matter content correlated negatively with RGR and was the only component of LAR contributing in a similar manner to variation in LAR and RGR. There was a positive correlation between NAR and biomass allocation to roots, which may be a result of nutrient‐limited growth. RGR correlated negatively with biomass allocation to leaves. Leaf thickness did not correlate with RGR, as the positive effect of thin leaves was counterbalanced by their lower NAR.

Low inherent RGR was associated with species from nutrient‐poor or shady habitats. Different components constrained growth for these two groups of species, those from nutrient‐poor habitats having high leaf dry matter content, while those from shady habitats had thin leaves with low NAR.
Auger electron spectroscopy for quantitative analysis
Authors: Many A. , Goldstein Y. , Weisz S. Z. , Resto O.
Published: July 2002

A simple mathematical analysis shows that unless the ratio of the instrumental resolution width to the natural Auger linewidth is less than about 0.3, the measured line intensities do not represent accurately the atomic concentrations. To overcome this difficulty, a universal curve is presented whereby the experimentally measured line intensities can be corrected so as to represent quite accurately the relative atomic concentrations in one’s sample. Unfortunately, however, the available sensitivity data required for quantification were not always measured with sufficient instrumental resolution. It is our contention that there is a need for new sensitivity measurements in which the required resolution is ensured.
Evaluation of exciton absorption peak broadening factors in InGaAsP/InP multiple quantum wells
Authors: Sugawara M. , Fujii T. , Kondo M. , Kato K. , Domen K. , Yamazaki S. , Nakajima K.
Published: July 2002

We evaluated the magnitude of broadening factors of ground-state exciton absorption peaks in In1−xGaxAsyP1−y/InP (x=0.47y) multiple quantum wells (MQW’s) with about 10 nm wells. The absorption peaks broadened with a decrease of y. Analyzing the absorption peak broadening with increasing temperature, the thermal broadening factor at 300 K was found to be about 9 meV and composition independent. Analyzing the photoluminescence linewidth at 4.2 K, it was found that composition fluctuations in the well caused an inhomogeneity of the exciton energy level of 4.4 meV for the y=1.0 MQW and 7.5 meV for the y=0.6 MQW, being the greatest contributors to inhomogeneous broadening. We conclude that the exciton absorption peak broadening with a decrease of y is primarily due to the increase of composition fluctuations.
Impurity segregation correlated with microstructure in buried oxide silicon-on-insulator structures
Authors: Puga M. Margarida , Burk Dorothea E.
Published: July 2002

During the formation of silicon-on-insulator substrates by high-dose oxygen implantation, the fixturing in the ion implanter may be sputtered onto the substrate by the oxygen beam. Large densities of heavy metal contaminants are introduced into the top silicon film and buried oxide, and remain there during epitaxial layer growth and device fabrication. These contaminants can form deep level traps by complexing with boron or oxygen, precipitate out in the gate oxide surface, remain interstitially or substitutionally in the top silicon layer, and/or decorate dislocations. A correlation is shown between the microstructure and defects, and the distribution of undesired impurities in the oxygen-implanted silicon-on-insulator substrates.
Growth of superconducting V3Si on Si by molecular beam epitaxial techniques
Authors: Croke E. T. , Hauenstein R. J. , McGill T. C.
Published: July 2002

Superconducting thin films (500–1000 Å in thickness) of A15 V3Si have been grown on (111)Si substrates through molecular beam epitaxial techniques. V and Si are codeposited in a feedback-stabilized, 3:1 flux ratio from dual e-beam evaporators onto clean, heated Si substrates in an ultrahigh vacuum chamber. For the first time, the superconducting A15 V3Si phase is metastably fabricated directly on a crystalline Si substrate without the formation of thermodynamically favored Si-rich VxSiy phases. Our films exhibit superconductivity only within a narrow range of intermediate growth temperatures (centered near 400 °C), with an optimum Tc of 12.5 K. X-ray diffraction shows the superconducting films to be polycrystalline A15 V3Si. For slightly higher growth temperatures (≊530 °C), Auger profile, x-ray, and transmission electron microscopy measurements indicate the appearance of an intermediate layer of roughly 1:1 V:Si composition. Our observations demonstrate that a growth temperature near 400 °C results in successful nucleation of the superconducting A15 phase while minimizing solid phase reaction with the substrate during V3Si growth.
p-type modulation-doped HgCdTe
Authors: Han Jeong W. , Hwang S. , Lansari Y. , Harper R. L. , Yang Z. , Giles N. C. , Cook J. W. , Schetzina J. F. , Sen S.
Published: July 2002

At North Carolina State University, we have recently employed photoassisted molecular beam epitaxy to successfully prepare p-type modulation-doped HgCdTe. The modulation-doped HgCdTe samples were grown on lattice-matched (100) CdZnTe substrates cut from boules grown at Santa Barbara Research Center. In this letter, we report details of the growth experiments and describe the structural, optical, and electrical properties that this new infrared quantum alloy of HgCdTe possesses.
Multifrequency room-temperature continuous diode and Ar* laser-pumped Er3+ laser emission between 2.66 and 2.85 μm
Authors: Auzel F. , Hubert S. , Meichenin D.
Published: July 2002

cw pumped laser emission on six different wavelengths is obtained for the first time in a LiYF4:15% Er3+ crystal at room temperature under diode laser excitation for 2.66, 2.716, 2.81 μm emissions and under argon ion laser excitation for 2.77, 2.81, 2.84, 2.85 μm emissions. Threshold of 5 mW absorbed power at 0.795 μm (diode) is obtained for the 2.81 μm wavelength. Time and power evolution of the laser emissions are presented. The type of up-conversion taking place during 2.81 μm laser emission is shown to be of the addition of photons by energy transfer (APTE) type involving a two-photon summation which depopulates the 4I11/2 rather than the 4I13/2 state as up to now believed.
Control of the Schottky barrier using an ultrathin interface metal layer
Authors: Wu X. , Schmidt M. T. , Yang E. S.
Published: July 2002

Fermi level movements at Pt/GaAs and Ti/GaAs interfaces have been investigated using a direct measurement of Schottky barrier heights in a bimetal Schottky structure. Using thin interfacial layers, the Schottky barrier was smoothly varied from the characteristic value of the thick metal to that of the interfacial metal. The variation of barrier height versus the inner metal thickness was found to exhibit an exponential behavior extending over a few monolayers coverage. This experiment indicates a new approach to the fundamental study of metal-semiconductor interfaces and could be useful in device applications.
Texture analysis of Al/SiO2 films deposited by a partially ionized beam
Authors: Knorr D. B. , Lu T.-M.
Published: July 2002

The preferred crystallographic orientation, or texture, of aluminum films deposited on oxidized silicon by evaporation and by partially ionized beam (PIB) deposition is studied. Texture is quantified by the x-ray diffraction pole figure technique. The pole figures reveal important details of the crystallite distribution not quantifiable by simply taking the 2θ scan. It is found that the films deposited by the PIB technique possess a very strong {111} fiber texture whose strength can be controlled by deposition conditions. Correlation between the strength of the texture and the electromigration lifetime is discussed.
Si/SiO2 interface structures in laser-recrystallized Si on SiO2
Authors: Ogura Atsushi , Aizaki Naoaki
Published: July 2002

Si/SiO2 interface structures in laser-recrystallized Si on SiO2 were studied with a high-resolution transmission electron microscope. The (001) Si/SiO2 interface with (001) Si substrate as a seed was excellent in flatness, flatter than that of the initial interface before recrystallization. However, the (11̄5) Si/SiO2 interface with (11̄5) Si substrate was saw-toothed with {100}T and {111}T microfacets. After twin boundary generation, the interface was changed to {110}T or {111}T and was flattened considerably. A Si/SiO2 interface reaction occurred during laser recrystallization. Since low-index Si planes are thought to have low interface energies with SiO2 at their interface, atomically flat or saw-toothed interfaces appeared as a result of this interface reaction. Moreover, twin boundaries, rather than saw-toothed interfaces, might have been generated for the reduction of the interface energy.
Tunneling in semiconductor heterostructures studied by subpicosecond four-wave mixing
Authors: Leo Karl , Shah Jagdeep , Göbel Ernst O. , Damen Theo C. , Köhler Klaus , Ganser Peter
Published: July 2002

We apply time-resolved four-wave mixing as a novel tool to study resonant tunneling of carriers in semiconductor heterostructures. The polarization decay of excitons in a quantum well is much faster when the alignment of the electron levels in adjacent wells leads to resonant tunneling and subsequent scattering of the carriers.
Lateral confinement in quantum nanostructures: Self-consistent screening potentials
Authors: Luscombe James H. , Luban Marshall
Published: July 2002

Self-consistent lateral confining potentials and carrier density functions are computed for quantum nanostructures utilizing a finite-temperature Thomas–Fermi approximation for the conduction electrons and the assumption of a uniform background of donor charges. The formation of the confining potential is the result of a nonlinear, electrostatic screening process which is determined by the Fermi level pinning properties of the lateral surfaces, the doping level, and the lateral dimensions. We find that the ability to populate nanostructures with carriers depends sensitively upon the details of the system.
Surface photovoltage spectroscopy of gap states at GaAs and InP metal interfaces
Authors: Burstein L. , Bregman J. , Shapira Yoram
Published: July 2002

Surface photovoltage spectroscopy has been used in order to investigate surface states at Al/n-GaAs (110), Au/n-GaAs (110) and Al/p-InP (110), Au/p-InP (110),(100) interfaces. Our results show formation of metal-induced surface states, which can be correlated with Fermi level pinning positions. The observed energy positions are found to be in good agreement with electrically measured Schottky barrier heights. The results obtained for these metals and the different surface types are discussed and compared to published data.
As2S3/GaAs, a new amorphous/crystalline heterojunction for the III-V semiconductors
Authors: Yablonovitch E. , Gmitter T. J. , Bagley B. G.
Published: July 2002

Much of the technology of our era is based on the SiO2/Si amorphous/crystalline heterojunction interface. Now it appears that As2S3/GaAs amorphous/crystalline heterojunctions show some technological promise. We have found that properly prepared As2S3/GaAs interfaces can have reasonably good electronic quality. The interfacial recombination velocity is ≊15 000 cm/s at flat band, which results in a ∼100-fold reduction of perimeter recombination currents in p-n junction mesas. This can be important on heterojunction transistor emitter-base perimeters, solar cell and light-emitting diode perimeters, and for reducing mirror facet recombination in semiconductor lasers.
Growth of untwinned Bi2Sr2Ca2Cu3Ox thin films by atomically layered epitaxy
Authors: Eckstein J. N. , Bozovic I. , Schlom D. G. , Harris J. S.
Published: July 2002

We report the growth of untwinned epitaxial thin films of Bi-Sr-Ca-Cu-O by atomically layered heteroepitaxy on SrTiO3 substrates. These films are c-axis oriented as-layered and do not exhibit 90° in-plane defects, i.e., a-b ‘‘twinning.’’ By misorienting the surface normal from {100} by approximately 4° towards 〈111〉, the cubic symmetry of the {100} surface is adequately broken to completely align the b axis of the superconducting film with respect to the substrate. Reflection high-energy electron diffraction patterns observed during growth and post-growth x-ray diffraction analysis indicate that the incommensurate structural modulation occurs along the same direction as the step edges.
Highly multiplexed graded-index polymer waveguide hologram for near-infrared eight-channel wavelength division demultiplexing
Authors: Chen Ray T. , Lu Huey , Robinson Daniel , Jannson Tomasz
Published: July 2002

An eight-channel single-mode wavelength division demultiplexer operating at 740, 750, 760, 770, 780, 790, 800, and 810 nm with diffraction angle varying from 16° to 44° and using a graded index (GRIN) polymer waveguide is reported for the first time. Diffraction efficiency up to 55% was measured. The wavelength spreading of the Ti:Al2O3 laser (∼4 nm, 3 dB bandwidth) causes an average crosstalk figure of −15.8 dB. The beamwidth of the diffracted signal as a function of the input beamwidth, the grating interaction length, and the diffraction angle are considered. Occurrence of the maximum value is further discussed. A waveguide lens is needed to efficiently couple the diffracted light into an output fiber whenever the diffracted beam size is beyond the core diameter of the fiber involved.
Electrostatic probe measurements for microwave plasma-assisted chemical vapor deposition of diamond
Authors: Cerio F. M. , Weimer W. A.
Published: July 2002

The electron energy and density in a diamond microwave plasma-assisted chemical vapor deposition reactor are determined using a double-electrostatic-probe technique. For a reactor feed gas composition of 2% CH4, 1% O2 in H2, electron temperatures of 6 eV and electron densities of ∼1.0×1011 cm−3 were measured. These values are consistent with optical emission spectroscopic results. The electron temperature is not strongly dependent on the amount of O2 added to the reactor feed mixture, indicating that the plasma essentially retains the energetic parameters of a hydrogen plasma.
Selective deposition of silicon by plasma-enhanced chemical vapor deposition using pulsed silane flow
Authors: Parsons G. N.
Published: July 2002

We report a new low-temperature (<300 °C) process for selective deposition of silicon using time modulated flow of silane into a hydrogen plasma. Time modulated gas flow allows the chemical processes associated with deposition and surface modification or etching to occur sequentially, and be controlled independently, giving an additional degree of freedom to the deposition process. The observed selective deposition is consistent with substrate specific nucleation, and preferential etching of the nuclei during the hydrogen plasma exposure. The application of the selective deposition process to the fabrication of thin-film transistor structures is also presented.
Photoluminescence and structure properties of GaAs/ZnSe quantum wells
Authors: Zhang S. , Kobayashi N.
Published: July 2002

By improving the quality of the GaAs well layer on a ZnSe barrier, we were able to observe the quantum size effect in photoluminescence of ZnSe/GaAs/ZnSe quantum wells. After solid phase epitaxy of 2-ML GaAs on ZnSe epilayer, migration-enhanced epitaxy (MEE) of the GaAs well layer was carried out while the growth temperature was elevated in steps. Photoluminescence from the obtained quantum wells has been appreciably improved by this method. The photoluminescence spectra show a systematic shift to higher energies as the well width is reduced, clearly demonstrating the size effect in the ZnSe-GaAs system. By comparing the experimental data with calculated emission energies, the valence-band and conduction-band discontinuities between ZnSe and GaAs in the 〈001〉 direction have been determined to be 1.27±0.02 and 0.03±0.02 eV, respectively.
4×4 nonblocking integrated acousto-optic space switch
Authors: Tsai C. S. , Le P.
Published: July 2002

A 4×4 nonblocking integrated acousto-optic space switch has been realized, for the first time, in a Y-cut LiNbO3 channel-planar-channel composite waveguide 0.1×1.0×3.0 cm3 in size. Measured performances for nonblocking switching at the optical wavelength of 0.6328 μm include a worst-case crosstalk of −15.6 dB, an average throughput of −16.0 dB, a frequency resolution (frequency increment required for switching between adjacent output ports) of 18.0 MHz, and a reconfiguration time of 0.145 μs.
Room-temperature 1.3 μm electroluminescence from strained Si1−xGex/Si quantum wells
Authors: Mi Q. , Xiao X. , Sturm J. C. , Lenchyshyn L. C. , Thewalt M. L. W.
Published: July 2002

We report the first room-temperature 1.3 μm electroluminescence from strained Si1−xGex/Si quantum wells. The electroluminescence is due to band-edge carrier recombination, and its intensity increases linearly with the forward current up to 1700 A/cm2. The internal quantum efficiency is estimated to have a lower limit of 2×10−4. As the temperature is increased from 77 to 300 K, luminescence from the silicon increases relative to that from the Si1−xGex wells. A minimum band offset is required to have effective room-temperature luminescence from the Si1−xGex quantum wells.
Metalorganic chemical vapor deposition using a single solution source for high J
c Y1Ba2Cu3O7−x superconducting films
Authors: Matsuno S. , Uchikawa F. , Utsunomiya S. , Nakabayashi S.
Published: July 2002

High Jc Y1Ba2Cu3O7−x superconducting thin and thick films were prepared onto SrTiO3 (100) substrates at 700 °C by metalorganic chemical vapor deposition (MOCVD) technique using a single solution source. A mixture of Y, Ba, and Cu β-diketonate chelates was dissolved in tetrahydrofuran as a solution source. Zero resistance transition temperature and critical current density at 77 K, 0 T for thin and thick films were 90 K and 2.73×106 A/cm2, 91 K and 3.1×105 A/cm2, respectively. X-ray diffraction measurement indicated that the thin film grew epitaxially with the c-axis orientation perpendicular to the surface of the substrate and the thick films mainly consisted of a-axis orientation.
InAsP islands at the lower interface of InGaAs/InP quantum wells grown by metalorganic chemical vapor deposition
Authors: Böhrer J. , Krost A. , Bimberg D.
Published: July 2002

The optical properties of narrow InGaAs/InP quantum wells and their dependence on the gas switching procedure during the metalorganic chemical vapor deposition growth process are studied. A transition from In1−xGaxAs monolayer to InAs1−xPx monolayer splitting is observed in the photoluminescence spectrum, if the AsH3 purging time of the InP surface is equal larger than 2 s. This transition is attributed to a P-As exchange at the lower interface (InGaAs on InP) leading to InAs1−xPx interfacial islands, which are larger than the excitonic diameter.