bluuebunny/crossref_metadata_2025 huggingface dataset:
Radar observability of near-Earth objects using EISCAT 3D
Authors: Kastinen Daniel , Tveito Torbjørn , Vierinen Juha , Granvik Mikael
Published: April 2020

Abstract. Radar observations can be used to obtain accurate orbital elements for near-Earth objects (NEOs) as a result of the very accurate range and range-rate measureables. These observations allow predicting NEO orbits further into the future, and also provide more information about the properties of the NEO population. This study evaluates the observability of NEOs with the EISCAT 3D high-power large-aperture radar, which is currently under construction. Three different populations are considered: NEOs passing by the Earth with a size distribution extrapolated from fireball statistics, catalogued NEOs detected with ground-based optical telescopes, and temporarily-captured NEOs, i.e., minimoons. Two types of observation schemes are evaluated: serendipitous discovery of unknown NEOs passing the radar beam, and post-discovery tracking of NEOs using a priori orbital elements. The results indicate that 60–1200 objects per year with diameters D > 0.01 m can be discovered. Assuming the current NEO discovery rate, approximately 20 objects per year can be tracked post-discovery near closest approach. Only a marginally smaller number of tracking opportunities are also possible for the existing EISCAT UHF system. The minimoon study, which used a theoretical population model, orbital propagation, and a model for radar scanning, indicates that approximately 7 objects per year can be discovered using 8–16 % of the total radar time. If all minimoons had known orbits, approximately 80–160 objects per year could be tracked using a priori orbital elements. The results of this study indicate that it is feasible to perform routine NEO post-discovery tracking observations using both the existing EISCAT UHF radar and the upcoming EISCAT 3D radar. Most detectable objects are within 1 LD distance of the radar. Such observations would complement the capabilities of the more powerful planetary radars that typically observe objects further away from Earth. It is also plausible that EISCAT 3D could be used as a novel type of an instrument for NEO discovery, assuming a sufficiently large amount of radar time can be used. This could be achieved, e.g., by time-sharing with ionospheric and space debris observing modes.
A new parameterization of ice heterogeneous nucleation coupled to aerosol chemistry in WRF-Chem model version 3.5.1: evaluation through the ISDAC measurements
Authors: Keita Setigui Aboubacar , Girard Eric , Raut Jean-Christophe , Leriche Maud , Blanchet Jean-Pierre , Pelon Jacques , Onishi Tatsuo , Cirisan Ana
Published: April 2020

Abstract. In the Arctic, during polar night and early spring, ice clouds are separated into two leading types: (1) TIC1 clouds characterized by large concentration of very small crystals, and TIC2 clouds characterized by low concentration of large ice crystals. Using suitable parameterization of heterogeneous ice nucleation is essential for properly representing ice cloud in meteorological and climate model and subsequently understanding their interactions with aerosols and radiation. Here, we describe a new parameterization for ice crystals formation by heterogeneous nucleation coupled to aerosols chemistry in WRF-Chem. The parameterization is implemented in the Milbrandt and Yau’s two-moment cloud microphysics scheme and we assess how the WRF-Chem model responds to the real time interaction between chemistry and the new parameterization. Well-documented reference cases provided us in situ data from the spring 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) campaign over Alaska. Our analysis reveals that the new parameterization clearly improves the representation of the IWC in polluted or unpolluted air masses and shows the poor performance of the reference parameterization in representing ice clouds with low IWC. The new parameterization is, thus able to represent TIC1 and TIC2 microphysical characteristics at the top of the clouds were heterogeneous ice nucleation is most likely occurring even knowing the bias of simulated aerosols by WRF-Chem over Arctic.
Giant dust particles at Nevado Illimani: a proxy of summertime deep convection over the Bolivian Altiplano
Authors: Lindau Filipe Gaudie Ley , Simões Jefferson Cardia , Delmonte Barbara , Ginot Patrick , Baccolo Giovanni , Paleari Chiara Ileana , Di Stefano Elena , Korotkikh Elena , Introne Douglas S. , Maggi Valter , Garzanti Eduardo , Andò Sergio
Published: April 2020

Abstract. A deeper understanding of past atmospheric circulation variability in the Central Andes is a high-priority topic in paleoclimatology, mainly because of the necessity to validate climate models used to predict future precipitation trends and to develop mitigation and/or adaptation strategies for future climate change scenarios in this region. Within this context, we here investigate an 18-years firn core drilled at the Nevado Illimani in order to interpret its mineral dust record in relation to seasonal processes, in particular atmospheric circulation and deep convection. The core was dated by annual layer counting based on seasonal oscillations of dust, calcium and stable isotopes. Geochemical and mineralogical data show that dust is regionally-sourced in winter and summer. During austral summer (wet season) an increase in the relative proportion of giant dust particles (ø > 20 µm) is observed, in association to oscillations of stable isotope records (δD, δ18O). It seems that at Nevado Illimani both the deposition of dust and the isotopic signature of precipitation are influenced by atmospheric deep convection, which is also related to the total amount of precipitation in the area. This hypothesis is corroborated by local meteorological data. The interpretation of giant particle and stable isotope records suggests that during La Niña years, summer convection activity is enhanced, in agreement with atmospheric circulation studies. Giant particles and stable isotopes, when considered together, can be therefore used as a new proxy for obtaining information about deep convective activity in the past, which is ultimately related to paleo-ENSO variability.
Effect of antimicrobial peptides and monoterpenes on control of fire blight
Authors: Akhlaghi Mahdi , Tarighi Saeed , Taheri Parissa
Published: April 2020

Aim of study: Antimicrobial peptides and monoterpenes are safe compounds that have been used for control of many plant diseases. Herein, the effects of two recombinant antibacterial peptides (AMPs) were compared with two monoterpenes for control of Erwinia amylovora directly or via induction of plant defense enzyme guaiacol peroxidase (GPOD).Area of study: The experiments were performed at the Ferdowsi University of Mashhad (Iran).Material and methods: The central composite design (CCD) method was used to study the effect of mixing the compounds and copper compound (Nordox) in controlling the pathogen. The resistance level was studied on shoots of tolerant (‘Dargazi’) and semi-susceptible (‘Spadona’) pear cultivars treated with the antibacterial compounds.Main results: Thanatin and 1,8-cineole showed the highest and lowest antibacterial effects. All treatments reduced E. amylovora pathogenicity on blossom. The CCD analysis revealed that the best reduction in colony number obtained by mixing Lfc, thanatin, thymol, 1,8-cineole and Nordox at concentrations of 32, 16, 24, 250 and 250 μg/mL. Thymol and 1,8-cineole at 500 μg/mL decreased disease severity significantly compared to that of AMPs. The level of GPOD enzyme in ‘Dargazi’ was higher than in ‘Spadona’. All treatments increased the GPOD levels in both cultivars. Furthermore, resistance level and GPOD ratio were negatively correlated.Research highlights: Antimicrobial peptides showed better effect on growth inhibition of E. amylovora than monoterpenes. Mixing of these peptides and monoterpens at special dosage enhanced their antimicrobial efficacy against E. amylovora; that could represent a new method in control of fire blight disease.
Comparison on the Use of Spinal (Stylet) Needle and Simple Needle in Ultrasound Guided Thyroid Nodule FNA; Does the Needle Affect Thyroid FNA Result?
Authors: Aziz Ahari Alireza , Mohammadi Vajari Mohammad Ali , Khatibi Moghadam Navid , Hashemi Hassan , Parvin Mahmoud , Khaleghi Mohammadreza
Published: April 2020

Background: Thyroid fine needle aspiration (FNA) is currently the most acceptable method for evaluating thyroid nodules. Non-satisfactory sample is the main limitation of FNA. It has been shown that spinal needles can reduce the number of non-diagnostic samples. Objectives: In this study, we decided to compare the results obtained using spinal (stylet) needle and simple needle in thyroid nodule FNA according to the agreement between them and with the pathology results as the gold standard. Patients and Methods: Sampling of thyroid nodules of 156 patients was performed by a simple non-stylet 23 gauge needle (A) and a spinal 22 gauge needle with stylet (B). The samples were provided to the pathologist for blind examination. All samples were obtained by an expert radiologist and the pathology examination was also performed by a pathologist expert in thyroid gland diseases. Blind analysis was done using SPSS Statistics for Windows, version 16 (SPSS Inc., Chicago, Ill., USA). Results: The results of FNA with needles A and B were reported unsatisfactory in 11.51 (18 subjects) and 3.84 (six subjects), respectively (P = 0.01). The result in 63.46% (99 subjects) of the participants, in whom FNA was obtained by needle B was introduced as a better sample by the pathologist in comparison with 36.44% (57 subjects) (P < 0.001). Cancer was diagnosed in 9.56 and 7.66 of the samples yielded by needles B and A, respectively, which was not statistically significant (P = 0.54). There was also a significant relationship between thyroid imaging reporting and data system (TI-RADS) score and FNA result. Conclusion: A significant relationship between the adequate sampling results, the qualitative examination result, TI-RADS score and the needle type indicates the importance of needle type on the results of thyroid FNA. Using spinal (stylet) needles may reduce the number of non-diagnostic samples in fine needle aspiration of thyroid nodules and therefore, can have a better effect on the results of this method.
Preceptees' Experiences of Nursing Students in the Clinical Practice with Preceptorship: “Being refined while taking a firm stand with lack”
Authors: Park Jeong Sook , Park Young Suk
Published: April 2020

Purpose: The purpose of this study was to explore preceptees' experience among nursing students in the Clinical Nursing Practice program as integral practice. Specific aims were to identify problems students face as preceptees at a clinical practice and how they interact with preceptors and others. Methods: Grounded theory methodology was utilized. Data were collected from interactive field notes and transcribed notes with individual in-depth interview from 12 senior nursing students who had experiences as a preceptee in the Clinical Nursing Practice. Results: Through constant comparative analysis, a core category emerged as "Being refined while taking a firm stand with lack." The process of "Being refined while taking a firm stand with lack" consisted of four phases: sailing phase, adaptation phase, achievement phase and wistful returning phase. Conclusion: The findings of the study indicate that there is a need for nursing students to understand the limitations and strengths to learning experiences in preceptorship. In addition, the Clinical Nursing Practice as an integral practice program is needed to improve nursing capacity and for proper adaptation to real clinical environment among graduating students.
Choosing what is left: the spatial structure of a wild herbivore population within a livestock-dominated landscape
Authors: Antún Milagros , Baldi Ricardo
Published: April 2020

Shrublands and grasslands comprise over 30% of the land surface and are among the most exploited ecosystems for livestock production. Across natural landscapes, the distribution and abundance of wild herbivores are affected by interspecific competition for foraging resources, hunting and the development of infrastructure among other factors. In Argentine Patagonia, the abundance of domestic sheep grazing on native vegetation outnumbers the widely distributed guanaco (Lama guanicoe) and sheep ranching monopolizes the most productive lands. In this work, we aimed to assess the spatial variation in the abundance of guanacos in Península Valdés, a representative landscape of Patagonia, investigating the incidence of natural and human-related factors. We conducted ground surveys during the austral autumn in 2017 totaling 383.4 km along areas with and without sheep ranching. We built density surface models to account for the variation in guanaco abundance and obtained a map of guanaco density at a resolution of 4 km2. We estimated an overall density of 11.71 guanacos.km−2for a prediction area of 3,196 km2, although the density of guanacos tripled in areas where sheep ranching was terminated (in around 20% of the surface of Península Valdés) compared to areas with sheep. Guanacos were more abundant at lower values of primary productivity and sheep stocking rates and further from inhabited ranch buildings, suggesting competition with sheep and conflict with humans. Although guanacos selected open, grass-dominated habitats across sheep-free sites, fences dividing properties and paddocks played a significant role in the spatial structure of their population in Península Valdés affecting negatively the abundance of guanacos. Our results indicate that actions to improve habitat connectivity for guanacos, favor the coexistence among guanacos and sheep ranching, and promote responsible human activities and attitudes towards wildlife are needed.
O uso do webcef para avaliação da produção oral em língua inglesa na formação inicial de professores
Authors: Salomão Ana Cristina Biondo
Published: April 2020

Estudos mostram que muitos professores de inglês no Brasil ministram aulas usando sua língua materna por falta de confiança em sua proficiência oral na língua estrangeira. Neste artigo, discutimos a visão de alunos de graduação em Letras sobre o uso do WebCEF, uma plataforma on-line voltada para a avaliação da produção oral em língua estrangeira. Ela oferece a possibilidade de se fazer o upload de um vídeo gravado com a própria produção oral do aprendiz para que ele se autoavalie ou que seja avaliado por outra pessoa por meio de critérios baseados no Quadro Europeu Comum de Referência para as Línguas. Neste artigo, apresentamos os resultados de um estudo de natureza qualitativa, no qual analisamos a perspectiva de alunos que cursaram disciplinas nas quais essa ferramenta foi usada. Por meio da análise de questionários semiestruturados, buscamos compreender suas expectativas, reações e opiniões sobre as possibilidades de auxílio providas pelo WebCEF. Acreditamos que ferramentas como essa possibilitam ao professor em formação construir sua autonomia e estratégias metacognitivas que possam auxiliá-lo no desenvolvimento de sua produção oral em língua estrangeira. Nosso estudo mostra, no entanto, que ainda é preciso trabalhar o conceito de avaliação, autoavaliação e avaliação por pares, especialmente na formação de professores, para que possamos usá-los como fonte de (re)conhecimento e (re)dimensionamento da produção oral em língua estrangeira dos alunos-professores.
Marital Distress among Police Personnel in Awka Metropolis: The Influence of Argument and Self-efficacy
Authors: Chiamaka O. Joe-Akunne, , Emeka A. Nwankwo, , Samuel U. Ezeakabekwe,
Published: April 2020

The study investigated whether argument and self-efficacy would have an influence on marital distress among police personnel. A total number of one hundred and ninety-seven (197), Nigeria police force (NPF) personnel working in Police headquarters; served as participants for the study. They were selected using non-probability sampling (convenient sampling techniques). They consist of 87(44.2%) females and 110 (58.5%) males; their age ranged from 22-51 years and their mean age was 34.94 with standard deviation of 6.96. Three instruments were used namely: Marital Stress Inventory, Argumentativeness Scale and General Self-Efficacy Scale. Two by Two Factorial design was adopted. Two Way Analysis of Variance statistics was used to analyze the data.  Two hypotheses were tested: the result indicated that hypothesis one which stated that there will be a significant difference between those with positive argument and those with negative argument on marital distress among police personnel and hypothesis two which stated that there will be a significant difference between those with positive self-efficacy and those with negative self-efficacy on marital distress among police personnel were both not accepted at p>.05. Therefore, the study recommended that counselling/marital psychologist should intensify their efforts to organize seminars/conferences on the implications of these factors (argument and self-efficacy) on marital distress among police personnel.
In vitro synthesis of M and Z forms of human α1‐antitrypsin
Authors: Errington D.M. , Bathurst I.C. , Janus E.D. , Carrell R.W.
Published: July 2002

mRNA was prepared from autopsy liver samples from a homozygote for α1‐antitrypsin deficiency (PiZZ) and from a normal (PiMM) subject. Both preparation gave equivalent synthesis of α1‐antitrypsin in a wheat germ cell‐free system. This suggests that the deficiency of plasma α1‐antitrypsin associated with the Z variant is due to a failure of processing and secretion of the protein rather than of its synthesis. It is likely that it is the resultant intracellular accumulation of the Z protein rather than a deficiency of protease inhibitor that is the primary cause of the liver pathology associated with this variant.
Mutual arrangement of histone H1 molecules in extended chromatin
Authors: Nikolaev Lev G. , Glotov Boris O. , Dashkevich Viktor K. , Barbashov Sergei F. , Severin Eugenii S.
Published: July 2002

Mutual arrangement of histone H1 molecules in chromatin extended in low salt—EDTA buffer and additionally in the presence of urea was studied by means of reversible cross‐linking combined with chymotryptic digestion. In the chromatins tested, the chymotryptic halves of H1 were cross‐linked in all possible combinations; i.e., C—C, C—N and N—N. The results imply that the mutual arrangement of H1 histones is determined by the structure of extended nucleosomal chain, rather than chromatin superstructure.
Evidence that helodermin, a newly extracted peptide from Gila monster venom, is a member of the secretin/VIP/PHI family of peptides with an original pattern of biological properties
Authors: Robberecht Patrick , Waelbroeck Magali , Dehaye Jean-Paul , Winand Jacques , Vandermeers André , Vandermeers-Piret Marie-Claire , Christophe Jean
Published: July 2002

Helodermin, a newly isolated peptide from the venom of Gila monster (Heloderma suspectum) was shown to stimulate the adenylate cyclase activity of rat pancreatic membranes as effectively as secretin and VIP. It also increased cyclic AMP levels and inhibited [125I]VIP binding in rat pancreatic acini. Finally, helodermin activated adenylate cyclase in membranes from rat heart, rat brain, and human heart, showing properties analogous yet distinct from those of secretin, VIP and PHI.
Some mitogens cause rapid increases in free calcium in fibroblasts
Authors: Morris Jonathan D.H. , Metcalfe James C. , Smith Gerry A. , Hesketh T.Robin , Taylor Michael V.
Published: July 2002

Quiescent 3T3 fibroblasts grown on microcarrier beads and loaded with the [Ca2+] indicator quin2 had a cytosolic free Ca2+ concentration ([Ca2+]i) of 154 ± 11 nM (SE; n = 32). Stimulation with the mitogens vasopressin, epidermal growth factor (EGF) or prostaglandin F2α (PGF2α) caused a very rapid increase in [Ca2+]i to a maximum of 200–500 nM after 60–90 s. [Ca2+]i declined thereafter to a level above that in quiescent cells which was maintained for at least 15 min. In contrast no immediate effects on [Ca2+]i were detected after the addition of the mitogens insulin or 12‐O‐tetradecanoylphorbol 13‐acetate (TPA). These studies indicate that early changes in [Ca2+]i may be involved in the action on fibroblasts of some, but not all, mitogens.
Characterization of a factor inducing differentiation of mouse myeloid leukemic cells purified from conditioned medium of mouse Ehrlich ascites tumor cells
Authors: Tomida Mikio , Yamamoto-Yamaguchi Yuri , Hozumi Motoo
Published: July 2002

A factor inducing differentiation of mouse myeloid leukemic cells (M1) into macrophages was purified to apparent homogeneity from 168 1 of CM of Ehrlich ascites tumor cells. The purified factor was halt‐maximally active at 2 × 10−11 M. The factor was analyzed by radioiodination, SDS‐polyacrylamide gel electrophoresis and autoradiography. Its M
r was 40000–50000. On reduction, the factor lost activity, but showed no subunit structure. Treatment of the factor with endo‐β‐N‐acetylglucosaminidase F, but not endo‐β‐N‐acetylglucosaminidase H, gave rise to a molecule of M
r 20000–28000. The activity of the factor from Ehrlich cells was completely neutralized by antiserum to the factor of M
r 50000–70000 from mouse fibroblast L929 cells.
The effect of anion channel blockers on enzymatic activity of Na+/K+‐ATPase and the electrogenic Na+/K+ pump
Authors: Teisinger J. , Zemková H. , Vyskočil F.
Published: July 2002

Disulfonic stilbenes which block the anion‐transport in red blood cells were found to inhibit the brain microsomal Na+/K+‐ATPase but not the electrogenic Na+/K+ pump in intact muscle cells. In contrast to the anion‐transport system, the Na+/K+‐ATPase is inhibited by disulfonic stilbenes, apparently from the cytoplasmic side of the membrane. The pathways for anion and active cation transport are thus different but similar groups of sulfhydryl and/or amino acid residues must play an important role in both systems.
Localization of the thermosensitive X‐prolyl dipeptidyl aminopeptidase in the vacuolar membrane of Saccharomyces cerevisiae
Authors: Bordallo Carmen , Schwencke Jaime , Rendueles Maripaz Suarez
Published: July 2002

Most of the X‐prolyl dipeptidyl aminopeptidase activity of Saccharomyces cerevisiae was found to be associated with purified vacuolar membranes (specific activity approx. 75‐times higher than in the protoplast lysate). The tonoplast‐bound enzyme is thermosensitive. Another heat‐resistant enzyme was found in the protoplast lysate. The tonoplast‐bound thermosensitive enzyme shows an apparent K
m of 0.06 mM against L‐alanyl‐L‐prolyl‐p‐nitroanilide while the heat‐resistant enzyme shows an apparent K
m of 0.4 mM against the same substrate.
Guanine nucleotides decrease the free [Ca2+] required for secretion of serotonin from permeabilized blood platelets
Authors: Haslam Richard J. , Davidson Monica M.L.
Published: July 2002

Human platelets containing granule‐bound [14C]serotonin were permeabilized, equilibrated at 0°C with ATP and with various Ca2+ buffers and guanine nucleotides, and then incubated at 25°C with or without a stimulatory agonist. Ca2+ alone induced the ATP‐dependent secretion of [14C]serotonin (50% at a pCa of 5.1) but the sensitivity of secretrion to Ca2+ was greatly enhanced by guanine nucleotides [6‐fold by 100μM GTP, 100‐fold by 100 μM guanyl‐5'‐yl imidodiphosphate and > 500‐fold by 100 μM guanosine 5'‐O‐(3‐thiotriphosphate)] or by stimulatory agonists (10‐fold by 2 units thrombin/ml and 4‐fold by 1 μM 1‐O‐octadecyl‐2‐O‐acetyl‐sn‐glyceryl‐3‐phosphorylcholine). When both GTP and a stimulatory agonist were added, they had synergistic effects on secretion. Cyclic GMP and GMP acted similarly to GTP. The effects of all these guanine nucleotides were inhibited by guanosine 5'‐O‐(2‐thiodiphosphate), whereas those of stimulatory agonists were not. Our results demonstrate the presence in platelets of guanine nucleotide‐dependent and independent mechanisms regulating the sensitivity of secretrion to Ca2+.
Possible bioactive conformations of α‐melanotropin
Authors: Nikiforovich G.V. , Rozenblit S.A. , Shenderovich M.D. , Chipens G.I.
Published: July 2002

By comparing the results of energy calculation for α‐MSH and its semirigid analogues , , and , a detailed description of two possible bioactive conformations for the ‘specific’ central site of α‐MSH6–9 is proposed representing variants of chain‐reversal structure. A possible explanation of the rise in melanotropic activity of the latter two semirigid analogues is presented.
Purification of human intrinsic factor using high‐performance ion‐exchange chromatography as the final step
Authors: Gueant Jean-Louis , Kouvonen Ilkka , Michalski Jean-Claude , Masson Catherine , Gräsbeck Ralph , Nicolas Jean-Pierre
Published: July 2002

Human intrinsic factor was purified 1430‐fold from gastric juice with a yield of 75% using two steps: labile ligand affinity chromatography and high‐performance ion‐exchange chromatography. Intrinsic factor precipitated in the presence of specific autoantibodies and 15% sodium sulfate, had an estimated M
r of 59000 in 5% SDS electrophoresis and could bind to the specific ileal receptor in vitro. Its carbohydrate composition could be related to N‐lactosaminic and O‐glycosidic chains. High‐performance ion‐exchange chromatography was a mild, rapid and efficient procedure to separate completely intrinsic factor from haptocorrin (another glycoprotein of gastric juice which binds cobalamin) and from other contaminating proteins.
Action of a cytotoxin from Pseudomonas aeruginosaon human leukemic cell lines
Authors: Sasaki Terukatsu , Lutz Frieder
Published: July 2002

Quin2 loaded human leukemic, JURKAT and K562 cells, were exposed to various doses of Pseudomonas aeruginosa cytotoxin. This cytotoxin induced an increase in quin2 fluorescence indicating an increase in the cytoplasmic free Ca2+ concentration. The rate of the fluorescence increase and the lag time before the response were dependent on the doses of the cytotoxin. Addition of MnCl2 to the cytotoxin‐treated cells induced a decrease in the quin2 fluorescence at rates dependent on the doses of the cytotoxin. The cytotoxin did not stimulate the inositol lipid turnover in JURKAT cells, which was determined by the accumulation of [3H]inositol phosphates in myo‐[2‐3H]inositol‐prelabeled cells in the presence of LiCl. These results indicate that the cytotoxin increases cell permeability to both Ca2+ and Mn2+ by direct breakdown of the permeability barrier of the plasma membrane.
Stimulation of procollagenase synthesis in human rheumatoid synovial fibroblasts by mononuclear cell factor/interleukin 1
Authors: McCroskery Peter A. , Arai Sadachika , Amento Edward P. , Krane Stephen M.
Published: July 2002

In order to define mechanisms regulating the synthesis of procollagenase in human rheumatoid synovial fibroblasts, the proteins synthesized by cultured cells were labeled with [35S]methionine. Labeled medium proteins were analyzed by SDS‐PAGE directly and after immunocomplexing with a specific antibody to human fibroblast collagenase. Labeling of both the predominant form of the enzyme (M
r~55000) as well as a minor species (M
r~61000) was increased following incubation with the monokine, mononuclear cell factor/interleukin 1. The ~61 kDa form of the procollagenase appears to be a glycosylated form of the ~ 55 kDa precursor based on binding to Con A‐Sepharose and decrease in the 61 kDa form after culture in the presence of tunicamycin. Thus, mononuclear cell factor, homologous with interleukin 1, partially purified from monocyte conditioned medium increass incorporation of [35Simethionine into several medium proteins, including those complexed by the anticollagenase antibody. In the presence of mononuclear cell factor/interleukin 1, labeling of the procollagenase was increased 12‐14‐fold over control cultures incubated with medium alone. Therefore, one of the mechanisms involved in increase of collagenase activity in the medium of cultured synovial fibroblasts in the presence of mononuclear cell factor/interleukin 1 is a stimulation of enzyme protein synthesis.
Complete amino acid sequence of a new type of lethal neurotoxin from the venom of the funnel‐web spider Atrax robustus
Authors: Sheumack D.D. , Claassens R. , Whiteley N.M. , Howden M.H.H.
Published: July 2002

Robustoxin, the lethal neurotoxin isolated from the venom of the male Sydney funnel–web spider, Atrax robustus, is of unique structural type and physiological mode of action. The primary structure of this 42–residue peptide was determined to be H2N–Cys–Ala–Lys–Lys–Arg–Asn–Trp–Cys–Gly–Lys10–Asn–Glu–Asp–Cys–Cys–Cys–Pro–Met–Lys–Cys20–Ile–Tyr–Ala–Trp–Tyr–Ala–Trp–Tyr–Asn–Gln–Gln–Gly–Ser30–Cys–Gln–Thr–Thr–Ile–Thr–Gly–Leu–Phe–Lys40–Lys–Lys–Cys–H The disposition of disulphide–bridged cysteine residues at both the amino– and carboxy–termini and as a triplet at residues 14–16 appears to have no precedent amongst neurotoxins.
Neomycin inhibits inositol phosphate formation in human platelets stimulated by thrombin but not other agonists
Authors: Siess Wolfgang , Lapetina Eduardo G.
Published: July 2002

Neomycin (0.1–1 mM) added to human platelet‐rich plasma or washed platelets prelabeled with [3H]inositol inhibits aggregation, ATP secretion (ID50 0.2 mM) and formation of [3H]inositol mono‐, bis‐ and trisphosphate (ID50 0.6–0.8 mM) in response to thrombin (0.25 ). The production of inositol phosphates in response to other platelet agonists (vasopressin, platelet activating factor, prostaglandin endoperoxide analogs and collagen) is not inhibited by neomycin, even at a concentration of 2 mM. At this concentration neomycin reduces the secretion of ATP stimulated by these agents (by up to 50%). The results indicate that neomycin has multiple effects on platelets that are unrelated to a specific inhibition of inositol phospholipid degradation by phospholipase C. Low concentrations (0.1–1 mM) of neomycin might selectively inhibit the interaction of thrombin with the platelet surface, and high concentrations (> 2 mM) might unspecifically reduce platelet secretion in response to various platelet agonists.
Effects of microtubule‐associated proteins on network formation by neurofilament‐induced polymerization of tubulin
Authors: Minami Yasufumi , Sakai Hikoichi
Published: July 2002

It has been revealed that neurofilaments stimulate polymerization of tubulin and thereby cause gelation. Addition of a very small amount of MAPs to the reaction mixture of tubulin and neurofilaments resulted in promotion of gelation. This could not be ascribed to MAP‐induced cross‐linking between microtubules and neurofilaments because further increases in the MAP concentration (still substoichiometric amount) resulted in total suppression of gelation. It is concluded that MAPs promote microtubule assembly independently of neurofilaments, and lower the concentration of tubulin available for neurofilament‐induced polymerization, then preventing network formation.
Modification of room‐temperature picosecond chlorophyll fluorescence kinetics in green algae by photosystem II trap closure
Authors: Moya I. , Hodges M. , Barbet J.-C.
Published: July 2002

Room‐temperature single‐photon timing measurements on green algae at low excitation energies indicate at least three kinetic components of chlorophyll fluorescence when the reaction centres of photosystem (PS) II are open (F
o) with lifetimes of approx. 50 ps (fast), 200 ps (middle) and 450 ps (slow). The absence, in green algae, of a long‐lifetime component (1.4 ns) is at variance with previous reports. Closing the reaction centres gave rise to a similar increase in both the middle and slow lifetimes, by a factor of between 4 and 5, to produce lifetimes of approx. 850 ps and 2 ns, respectively, when all traps were closed (F
max). The yield and lifetime of the fast component were found to be independent of PS II centre closure. The yields of the middle and slow components were both modified by reduction of the primary stable electron acceptor of PS II (Qa) with the slow‐component yield increasing by a greater degree than the middle‐component yield. It was also observed that as PS II reaction centres were closed to photochemistry the fluorescence yield and average lifetime increased proportionally. This trend and the similar increases in the middle and slow lifetimes are indicative of a well‐connected system of PS II units favouring exciton transfer between PS II centres. We suggest that the fast kinetic component arises mainly from PS I while the middle and slow components arise from different types of fluorescing unit located in the granal lamellae and associated with system of well‐connected PS II.
Semiquinone anion radicals formed by the reaction of quinones with glutathione or amino acids
Authors: Gant Timothy W. , Doherty Mary d'Arcy , Odowole Duro , Sales Keith D. , Cohen Gerald M.
Published: July 2002

Quinone
Thiol
Amino acid
ESR
Semiquinone anion radical
An algorithm for secondary structure determination in proteins based on sequence similarity
Authors: Levin Jonathan M. , Robson Barry , Garnier Jean
Published: July 2002

A secondary structure prediction algorithm is proposed on the hypothesis that short homologous sequences of amino acids have the same secondary structure tendencies. Comparisons are made with the secondary structure assignments of Kabsch and Sander from X‐ray data [(1983) Biopolymers 22, 2577‐2637] and an empirically determined similarity matrix which assigns a sequence similarity score between any two sequences of 7 residues in length. This similarity matrix differs in many respects from that of the Dayhoff substitution matrix [(1978) in: Atlas of Protein Sequence and Structure, (Dayhoff M.O. ed). vol. 5. suppl. 3, pp. 353‐358, National Biochemical Research Foundation, Washington, DC]. This homologue method had a prediction accuracy of 62.2% over 3 states for 61 proteins and 63.6% for a new set of 7 proteins not in the original data base.
Atrial natriuretic factor regulation of cyclic GMP levels and steroidogenesis in isolated fasciculata cells of rat adrenal cortex
Authors: Jaiswal Neelam , Paul Aranjiniyil K. , Jaiswal Rama Kant , Sharma Rameshwar K.
Published: July 2002

Isolated fasciculata cells of rat adrenal cortex, when incubated with atrial natriuretic factor (ANF), stimulated the levels of cyclic GMP and corticosterone production in a concentration‐dependent manner without a rise in the levels of cyclic AMP. The ANF‐dependent elevation of cyclic GMP was rapid, with a detectable increment in 30 s. ANF also stimulated the particulate guanylate cyclase. These results not only indicate the coupling of cyclic GMP and corticosterone production with ANF signal, but also demonstrate that, like the ACTH signal, cyclic AMP is not the mediator of ANF‐induced adrenocortical steroidogenesis.
Photoaffinity labelling of the TSH receptor on FRTL5, cells
Authors: Furmaniak Jadwiga , Hashim Faisal A. , Buckland Paul R. , Petersen Vaughan B. , Beever Karen , Howells Roger D. , Smith Bernard Rees
Published: July 2002

An investigation of the properties of TSH receptors on FRTL5 cells using affinity labelling with a 125 I‐labelled photoactive derivative of TSH is described. Our studies suggest that FRTL5 cells contain 2 principal types of cell surface TSH receptors. One form, probably a precursor, consists of a single polypeptide chain (M
r 120 000) with an intrachain loop of amino acids formed by a disulphide bridge. The other type of receptor consists of a water‐soluble A chain (M
r 55000) linked to an amphiphilic B chain (M
r 35000) by a disulphide bridge. The 2 chain structure is probably derived from the single chain 120 000 protein by enzymatic cleavage of peptide sequences within the loop of amino acids formed by the intrachain disulphide bridge.
Physiological variant of antithrombin‐III lacks carbohydrate sidechain at Asn 135
Authors: Brennan Stephen O. , George Peter M. , Jordan Robert E.
Published: July 2002

Both normal antithrombin‐III (AT‐IIIα) and the high heparin affinity form (AT‐IIIβ) were isolated from pooled human plasma. AT‐IIIβ had a lower negative charge and lower molecular mass than AT‐IIIα. Sialidase and endo‐F digestion indicated that the inherent difference resided in the oligosaccharide component of the molecule. CNBr fragmentation showed there was an oligosaccharide sidechain missing between residues 104 and 251, subdigestion with trypsin indicated that Asn 135 was not glycosylated in AT‐IIIβ. Chromatography of total tryptic digests on concanavalin A‐Sepharose confirmed that the high heparin affinity form of antithrombin lacked an oligosaccharide moiety at Asn 135.
Nuclear protein(s) binding to the conserved DNA hexameric sequence postulated to regulate transcription of wheat histone genes
Authors: Mikami Koji , Tabata Tetsuya , Kawata Takefumi , Nakayama Takuya , Iwabuchi Masaki
Published: July 2002

Nuclear protein(s) that specifically bind(s) to the upstream hexamer motif, ACGTCA, of wheat histone H3 and H4 genes has (have) been identified. Sequences homologous to this hexamer are found to be conserved in the upstream region of not only wheat histone genes but also other plant and animal histone genes. This suggests a possible role(s) for the hexamer and the nuclear protein(s) in the transcriptional regulation of the wheat histone genes. This hexamer is homologous to the upstream core sequence, TGACGTCA, which is highly conserved in some animal genes whose expression is regulated by cAMP.
Structural features in aminoacyl‐tRNAs required for recognition by elongation factor Tu
Authors: Faulhammer Heinz G. , Joshi Rajiv L.
Published: July 2002

In bacterial polypeptide synthesis aminoacyl‐tRNA (aa‐tRNA) bound to elongation factor Tu (EF‐Tu) and GTP is part of a crucial intermediate ribonucleoprotein complex involved in the decoding of messenger RNA. The conformation and topology as well as the affinity of the macromolecules in this ternary aa‐tRNA·EF‐Tu·GTP complex are of fundamental importance for the nature of the interaction of the complex with the ribosome. The structural elements of aa‐tRNA required for interaction with EF‐Tu and GTP and the resulting functional implications are presented here.
The mechanism of action of aspartic proteases involves ‘push‐pull’ catalysis
Authors: Polgár László
Published: July 2002

In accord with the available kinetic and X‐ray crystallographic data, it is proposed that the two catalytically competent carboxyl groups of aspartic proteases constitute a functional unit which mediates the proton from the attacking water molecule to the leaving nitrogen atom of the substrate. Protonation of this nitrogen atom has been the main issue of the previous mechanistic proposals. The first step of the present mechanism involves proton transfer from the water to the aspartic diad and concurrently another proton transfer from the diad to the carbonyl oxygen of the scissile peptide bond. These proton transfers provide the driving force for the bond formation between the substrate and water, which leads to the formation of a tetrahedral intermediate. The intermediate breaks down to products by a similar facilitation, i.e. by concerted general acid‐base catalysis, which involves simultaneous proton transfers from the intermediate to the diad and from the diad to the leaving nitrogen of the substrate. The symmetrical mechanism of the formation and decomposition of the tetrahedral adduct resembles that found in the serine protease catalysis.
The cDNA clone for strictosidine synthase from Rauvolfia serpentina DNA sequence determination and expression in Escherichia coli
Authors: Kutchan T.M. , Hampp N. , Lottspeich F. , Beyreuther K. , Zenk M.H.
Published: July 2002

The cDNA clone for strictosidine synthase, the enzyme which catalyzes the stereospecific condensation of tryptamine with secologanin to form the key intermediate in indole alkaloid biosynthesis, strictosidine, has been identified with a synthetic oligodeoxynucleotide hybridization probe in a λgt11 cDNA library of cultured cells of Rauvolfia serpentina. The DNA has been sequenced, revealing an open reading frame of 1032 base pairs encoding 344 amino acids. The sequence of 60 nucleotides in the 5′‐flanking region has been determined by primer extension analysis. The encoded protein has been expressed in E. coli DH5 as detected by immunoblotting of protein extracts with antibodies raised against the native enzyme.
Involvement of proteasomes (multicatalytic proteinase) in ATP‐dependent proteolysis in rat reticulocyte extracts
Authors: Tanaka Keiji , Ichihara Akira
Published: July 2002

The role of proteasomes, particles with latent multicatalytic proteinase, in ATP‐dependent proteolysis in rat reticulocyte extracts was examined. Removal of proteasomes from the extracts by immunoprecipitation caused almost complete inhibition of ATP‐dependent degradation of [3H]methylcasein, without affecting ATP‐independent proteolysis. Peptide fragments of [3H]casein, obtained by cyanogen bromide cleavage, were rapidly degraded in an ATP‐independent fashion and this activity was not affected by removal of the proteasomes. These results suggest that proteasomes are involved in ATP‐dependent proteolysis in the extracts and that they catalyze the initial cleavage of large proteins.
Two isoforms of protein phosphatase 1 may be produced from the same gene
Authors: Cohen Patricia T.W.
Published: July 2002

A cDNA clone encoding a second type‐1 protein phosphatase catalytic subunit (1α) was isolated from a rabbit skeletal muscle cDNA library constructed in λgt10. The deduced protein sequence (330 residues, 37.5 kDa) was 19 residues longer at its N‐terminus than protein phosphatase 1β (311 residues, 35.4 kDa). The amino acid sequences of protein phosphatases 1α and 1β were identical after residue 33 of protein phosphatase 1α. The results suggest that the different N‐terminal sequences of protein phosphatases 1α and 1β are likely to be generated by differential transcription or processing of the mRNA transcribed from a single gene. Southern blotting of rabbit DNA was consistent with this interpretation.
Biological activities of chemically synthesized N‐acetylneuraminic acid‐(α2→6) ‐monosaccharide analogs of lipid A
Authors: Shimizu Tadayori , Masuzawa Toshiyuki , Yanagihara Yasutake , Shimizu Chikako , Ikeda Kiyoshi , Achiwa Kazuo
Published: July 2002

The mitogenicity and lethal toxicity of chemically synthesized lipid A analogs, in which 2,3‐acyloxyacylglucosamine‐4‐phosphate linked to tetraacetyl‐N‐acetylneuraminic acid (compound A‐207) or to N‐acetylneuraminic acid (compound A‐307), were examined. Although the mitogenic activity of the synthetic compounds was weaker than that of bacterial LPS, doses of 10–50 μg/ml of A‐207 and 5–10 μg/ml of A‐307 were capable of increasing incorporation of [3H]thymidine into cultured spleen cells of C57BL/6 mice. Lethal toxicity of A‐207 was observed at 10 μg/mouse in C57BL/6 mice sensitized with D‐galactosamine hydrochloride. However, the attachment of tetraacetyl‐N‐acetylneuraminic acid or N‐acetylneuraminic acid does not appear to enhance the biological activity of acyloxyacylglucosamine‐4‐phosphate.
Identification of the phosphorylated β‐tubulin isotype in differentiated neuroblastoma cells
Authors: Ludueña Richard F. , Zimmermann Hans-Peter , Little Melvyn
Published: July 2002

The tubulin molecule consists of an α‐ and a β‐subunit, each of which exists in several isotypic forms. It has been previously shown that one of the isotypes of neuroblastoma β‐tubulin is phosphorylated at a serine residue in vivo [(1985) J. Cell Biol. 100, 764–774]. Here we identify the phosphorylated isotype as β2 (type III). Moreover, the large size of the phosphorylated tryptic peptide and sequence comparisons of vertebrate β‐tubulins suggest that one of the two serines in positions 444 and 446 is the phosphorylated residue. Our results raise the possibility that β2‐tubulin differs functionally from the other β‐tubulin isotypes.
Photosynthetic reaction centre of Chloroflexus aurantiacus I. Primary structure of L‐subunit
Authors: Ovchinnikov Yu.A. , Abdulaev N.G. , Zolotarev A.S. , Shmukler B.E. , Zargarov A.A. , Kutuzov M.A. , Telezhinskaya I.N. , Levina N.B.
Published: July 2002

The L‐subunit primary structure of the reaction centre from Chloroflexus aurantiacus composed of 310 amino acid residues has been determined by parallel analysis of the protein and corresponding DNA. Significant homology between this protein and L‐subunits from reaction centres of purple bacteria is observed. This implies close similarity in the tertiary structure of these proteins.
Towards an understanding of the biological function of histone acetylation
Authors: Loidl Peter
Published: July 2002

A model is presented which explains the biological function of posttranslational acetylation of core histones in chromatin. Along the lines of this model histone acetylation serves as a general mechanism to destabilize nucleosome core particles during various processes occurring in chromatin. Acetylation acts as a signal that modulates histone‐protein and histone‐DNA interactions and finally leads to the displacement of particular histones from nucleosome cores. The high specificity of the acetylation signal for different processes (DNA replication, transcription, differentiation‐specific histone replacement) is achieved by site specificity and asymmetry of acetylation in nucleosomes. The essential features of this model are in accord with the more recent results on histone acetylation.
Determination of three‐dimensional structures of proteins from interproton distance data by hybrid distance geometry‐dynamical simulated annealing calculations
Authors: Nilges Michael , Clore G.Marius , Gronenborn Angela M.
Published: July 2002

A new hybrid distance space‐real space method for determining three‐dimensional structures of proteins on the basis of interproton distance restraints is presented. It involves the following steps: (i) the approximate polypeptide fold is obtained by generating a set of substructures comprising only a small subset of atoms by projection from multi‐dimensional distance space into three‐dimensional cartesian coordinate space using a procedure known as ‘embedding’; (ii) all remaining atoms are then added by best fitting extended amino acids one residue at a time to the substructures; (iii) the resulting structures are used as the starting point for real space dynamical simulated annealing calculations. The latter involve heating the system to a high temperature followed by slow cooling in order to overcome potential barriers along the pathway towards the global minimum region. This is carried out by solving Newton's equations of motion. Unlike conventional restrained molecular dynamics, however, the non‐bonded interactions are represented by a simple van der Waals repulsion term. The method is illustrated by calculations on crambin (46 residues) and the globular domain of histone H5 (79 residues). It is shown that the hybrid method is more efficient computationally and samples a larger region of conformational space consistent with the experimental data than full metric matrix distance geometry calculations alone, particularly for large systems.
Crosslinking of elongation factor Tu to tRNAPhe by trans‐diamminedichloroplatinum (II) Characterization of two crosslinking sites on EF‐Tu
Authors: Metz-Boutigue Marie-Hélène , Reinbolt Joseph , Ebel Jean-Pierre , Ehresmann Chantal , Ehresmann Bernard
Published: July 2002

In a preceding paper [(1987) Nucleic Acids Res. 15, 5787–5801], we have used trans‐diamminedichloroplatinum (II) to induce reversible RNA‐protein crosslinks within the ternary EF‐Tu/GTP/Phe‐tRNAPhe complex and have identified two crosslinking sites on the tRNA. The aim of the present paper is to determine the crosslinking sites on EF‐Tu. Two tryptic peptides located in domain I could be identified, a major one (residues 45–74) and a minor one (residues 117–154). The use of Staphylococcus aureus V8 protease led to the isolation of two major peptides (residues 56–68 and 64–68) and one minor peptide (118–124). These results are discussed in the light of the current knowledge of the topography of the EF‐Tu/tRNA complex.