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At least 1,585 records · Page 88Linked to original sources
PubMed2001

[Ecological analysis and optimization design for agricultural landscape of coastal zone along Radial Submarine Sand Ridges in north Jiangsu].

The Radial Submarine Sand Ridges (RSSR) on the inner shelf of the Southwestern Yellow Sea is one of the largest of such system in the world. It was developed into great amount of land which is mainly used for agriculture. However, the coastal zone is facing many serious environmental and resources problems such as coastal erosion, ecological fragility and over- and abuse of coastal resources. Based on comprehensive field survey, this paper proposes optimization allocation and design of agri-landscape spatial structures targeting an integrated improvement in agricultural ecology, economy and amenity of the region as well as implementation of sustainable development strategy. As a case study, rectification approaches and conceptual optimization design for Rudong County are proposed and discussed.

Agriculture↗
PubMedDate not supplied

[Cotranslational protein folding].

The review analyzes the research concerning the folding of proteins in the course of their synthesis on ribosomes. The experimental data obtained for various proteins using various methods give grounds for concluding that a nascent protein largely acquires its spatial structure while still attached to the ribosome, and final folding into the biologically active conformation takes place as soon as the completed protein is released therefrom. Cotranslational folding is characteristic of both bacterial and eukaryotic cells, and appears to be the universal and the most evolutionarily ancient mechanism.

Animals↗
PubMedDate not supplied

[Chaperone Caf1M stabilizes hybrid proteins containing sequences of F1 antigen subunit from Yersinia pestis].

The Yersinia pestis (causative agent of plague) capsule antigen is a homopolymer of Caf1 protein. Export of the subunits is mediated by the periplasmic chaperone Caf1M. To study the mechanism of Caf1M activity, two hybrid genes including coding sequences for the Caf1 signal peptide, human granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-1 (IL-1) receptor antagonist, and mature Caf1 were constructed and expressed in Escherichia coli. We have shown that in the absence of Caf1M the majority of Caf1 moieties within the hybrid proteins undergo proteolysis in the periplasmic space, presumably by the DegP protease. The coexpression of a gene for chaperone Caf1M significantly increased the amount of full-size hybrid proteins in the periplasm, probably as a result of stabilization of the subunits spatial structure within the hybrid. This effect was not observed in JCB571 cells, which lack periplasmic disulfide isomerase DsbA, essential for Caf1M activity.

Antigens, Bacterial↗
PubMedDate not supplied

[Analysis of complex formation of daunomycin with the deoxyhexanucleotide 5'-d(TpApCpGpTpA) in an aqueous solution from NMR-spectroscopy data].

Self-association of hexadeoxynucleotide 5'-d(TpApCpGpTpA) and its complexation with antitumor antibiotic daunomycin were studied by one- and two-dimensional homonuclear 1H NMR spectroscopy and heteronuclear 1H-31P NMR spectroscopy in water-salt solution. The concentration and temperature dependences of proton chemical shifts of the hexadeoxynucleotide and the ligand were measured, and equilibrium constants and thermodynamic parameters of corresponding reactions were calculated on this basis using models for the formation of hexadeoxynucleotide duplex and its complex with the antibiotic. The spatial structure of daunomycin-d(TACGTA)2 complex in solution was calculated using X-PLOR software on the basis of 2D NOE spectral data and the limit values of proton chemical shifts of the ligand. Comparative analysis of different intermolecular interactions in sequence-specific binding of the antibiotic to the DNA fragment was carried out.

Daunorubicin↗
PubMedDate not supplied

[Sequence-determined conformational changes in the coding region of the promoter DNA on transcription complex formation].

Chemical footprinting was used to study the spatial structure of bacteriophage T7 promoter D upon formation of the transcriptionally active complex with Escherichia coli RNA polymerase. Enzyme binding was shown to induce conformational changes in sites located at positions 43 and 57, several helix turns away from the transcription start. This was the first finding of a structural deformation induced by assembly of the transcription complex. The deformation was associated with specific features of the promoter nucleotide sequence, and suggested high cooperativity in the organization of the transcription complex and substantial energy perturbations caused by the enzyme.

Bacteriophage T7↗
PubMedDate not supplied

[Isolation and partial study of an anti-hemoglobine precipitine in "Biomphalaria glabrata" (author's transl)].

A protein (PaHb) with a precipiting capacity with regard to normal and pathological human hemoglobin as well as horse and hen hemoglobin has been separated on immunoadsorbent from hemolymph of Biomphalaria glabrata. The joining of PaHb and hemoglobin takes place at the level of the polypeptidic chain. A reconnaissance of the spatial structure of the globin seems to exist. The absence of heme does not lead to a decrease in the intensity of the reaction. The coefficient of the sedimentation of PaHb is of 2.74 S and its molecular weight has been estimated at 47,000 per chromatography in thin layer. The divalent cation MgCl2 strengthens the intensity of the reaction, as for CaCl2 no change is observed, and in the presence of sodium citrate one observes a clear decrease in the reaction. The intensifying of the reaction when in presence of divalent cation MgCl2 could be the result of a stabilization or an activation of the natural structure of PaHb when in presence of Mg. PaHb shows no fonctional impairment after exposure at 65 degrees C during 45 min. The localization of PaHb in the total antigenic structure of the hemolymph is situated around the level of the 5th precipitine line. The functional role of the protein seems to carry the hemoprotein of the hemolymph.

Animals↗
PubMedDate not supplied

[Theoretical conformational analysis of methylamide N-acetyl-L-arginine].

The spatial structure of methylamide N-acetyl-L-argine was studied taking into account the non-valent and electrostati interactions, the torsion energy, and the distorsion of valency angles. Calculation of the favourable conformations of the molecule was carried out with the use of all the combinations of angles phi, psi, chi1 divided by chi4 as an intital approximation. These correspond to the low energy forms of the main chain and to the minima of the torsion potentials of the side chain. Conformational possibilities of arginine and lysine were compared. The calculated stable conformation of N-acetyl-L-arginine-methylamide are compared with the geometry of arginine residues in the proteins with known structure.

Amides↗
PubMedDate not supplied

[Some X-ray diffraction parameters of liquid-crystalline dispersions of nucleic acid-chitosan complexes ].

Liquid-crystalline dispersions of nucleic acid-chitosan complexes (NA-chitosan) possess optical and X-ray diffraction properties different from those of "classical" cholesterics. It is possible that positive charge distribution (distance between charges, chitosan conformation, etc.) in the polymeric chain of chitosan molecule combining with NA molecule is the factor that affects the spatial structure of resulting dispersions.

Chitin↗
PubMed1975

Studies of the fossil dinosaur bone in the scanning electron microscope.

A fossil dinosaur bone, 80 million years old, was subjected to investigation in the scanning microscope. The bone surfaces to be examined were prepared with appropritely modified methods used in the technique of replication in transmission electron microscopy. In the scanning microscope pictures of vascular canals were obtained. The walls of these canals were shown to be formed of collagen fibrils. Moreover, it was demonstrated that the internal surface of the canal wall is made up of bundles of collagen fibrils which run obliquely, corkscrewwise, and in the form of plexus to the long axis of tke canal; Besides, osteocytes of the dinosaur bone were isolated and pictures of their spatial structure together with characteristic points of departure of processes from the cell body were obtained.

Animals↗
PubMedDate not supplied

[Shape conservatism and shaping variability. The comparative analysis of Hydrozoa and Scyphozoa early development].

The morphogenetic pathways based on the self-organization take an important part in the early development of White Sea Cnidarians--Dynamena pumila (Hydrozoa) and Aurelia aurita (Scyphozoa). Comparative analysis of their early development revealed two patterns of embryonic spatial structure reproduced in the morphogenesis of both species in spite of the differences of morphogenetic paths. These are toroidal and bilaterally symmetrical shapes. It is possible that these shapes correspond to the equilibrium states of developing system and their stable reproduction is a result of epigenetic rather than genetic program.

Animals↗
PubMedDate not supplied

[Changes in phytoperiphyton community during seasonal succession: influence of plankton sedimentation and grazing by phytophages--Chironomid larvae].

The investigation of seasonal changes in spatial structure of phytoperiphyton during succession was conducted at the lower reaches of Akulovsky water channel from April to August 2000. At the beginning of succession from April to June dominant forms were chain-forming diatoms and filamentous green algae, sedimented from plankton. Later, at the middle of June under increasing pressure of herbivorous, they were replaced by stretched unicellular diatoms and colonial cyanobacteria. In late June-August, when herbivorous predation was the most intensive, the relative abundance of typical periphytonic forms decreased while that of settled planktonic forms increased. The effect of planktonic algae sedimentation on periphyton composition was evaluated as similarity between phytoperiphyton and phytoplankton communities measured with Chekanovski--Sorensen index. The value of this index tends to decrease with the development of periphyton while showing some relation to intensity of herbivorous pressure. Minimal values of Chekanovski--Sorensen index were under moderate herbivorous density, whereas maximal values were observed in periods of extremely high or low herbivorous density.

Animals↗
PubMedDate not supplied

[Influence of end products of plasmin-mediated hydrolysis of fibrinogen and fibrin (EF and Ef fragments) on fibrinogen cross-linking].

We studied the influence of the end products of plasmin-mediated hydrolysis of fibrinogen and nonstabilized fibrin (EF and Ef fragments) on covalent cross-linking of fibrinogen molecules catalyzed by a fibrin-stabilizing factor (factor XIIIa). The data on elastic and dynamic light scattering reveal no difference in the spatial structure of covalently linked fibrinogen molecules in the presence of the hydrolysis end products EF and Ef. In contrast to the inactive fragment EF, fragment Ef significantly accelerates the enzymatic reaction. This is also confirmed by electrophoresis of the reduced samples indicating a relatively fast accumulation of gamma-dimers and A alpha-polymers as compared to the control samples. Possible molecular mechanisms of this effect are discussed.

Animals↗
PubMed2001

[Effects of interleukin-2 on the isolated rat heart and the mechanism].

The purpose of the present study was to explore the biological effects and mechanism of interleukin-2 (IL-2) on the isolated rat heart. The results showed that hrIL-2 increased the number of premature ventricular contraction, heart rate, left ventricular developed pressure, left ventricular end-diastolic pressure and coronary flow in the isolated perfused rat heart. Heat inactivated hrIL-2 had no effect on the heart. Pretreatment with ryanodine canceled the positive effects of hrIL-2 on left ventricular developed pressure, left ventricular end-diastolic pressure and coronary flow but had no effects on arrhythmogenesis and tachycardia by hrIL-2. Pretreatment with nifedipine or low extracellular calcium abolished the arrhythmogenic effect of hrIL-2 and attenuated partially the augment of heart rate, left ventricular developed pressure, left ventricular end-diastolic pressure and coronary flow. It suggests that the cardiac activity of hrIL-2 depended on the integrity of its spatial structure and transmembrane influx Ca2+ and intracellularly stored Ca2+ were involved in the cardiac activity of hrIL-2.

Animals↗
PubMed2003

Human cortical object recognition from a visual motion flowfield.

Moving dots can evoke a percept of the spatial structure of a three-dimensional object in the absence of other visual cues. This phenomenon, called structure from motion (SFM), suggests that the motion flowfield represented in the dorsal stream can form the basis of object recognition performed in the ventral stream. SFM processing is likely to contribute to object perception whenever there is relative motion between the observer and the object viewed. Here we investigate the motion flowfield component of object recognition with functional magnetic resonance imaging. Our SFM stimuli encoded face surfaces and random three-dimensional control shapes with matched curvature properties. We used two different types of an SFM stimulus with the dots either fixed to the surface of the object or moving on it. Despite the radically different encoding of surface structure in the two types of SFM, both elicited strong surface percepts and involved the same network of cortical regions. From early visual areas, this network extends dorsally into the human motion complex and parietal regions and ventrally into object-related cortex. The SFM stimuli elicited a face-selective response in the fusiform face area. The human motion complex appears to have a central role in SFM object recognition, not merely representing the motion flowfield but also the surface structure of the motion-defined object. The motion complex and a region in the intraparietal sulcus reflected the motion state of the SFM-implicit object, responding more strongly when the implicit object was in motion than when it was stationary.

Adult↗
PubMedDate not supplied

Metaplastic breast carcinoma: pathology and clinical outcome.

Metaplastic breast carcinomas are rare neoplasms showing both carcinomatous and sarcomatous elements. In this report we describe eleven cases of metaplastic breast carcinoma focusing on pathological features and the clinical behaviour of six patients with breast carcinoma with chondroid metaplasia (MCC). We collected eleven cases from 1996 to 2001: immunohistochemical tests were performed in order to obtain data on estrogen and progesterone receptors and the production of p53 gene and HER/2 neu. Neoangiogenesis was studied counting vessels immunohistochemically-stained with CD31 antibody. Six cases showed chondroid metaplasia, three cases were spindle cell carcinoma and two were metaplastic squamous carcinoma. The majority of patients (64%) had pT2 tumors without axillary node metastases: only two cases with spindle or squamous metaplasia showed nodal involvement. Fifty percent of MCC were pT1b-c tumors: no axillary metastases were observed. Vascular invasion was observed in all squamous and spindle cell types and in 66% of MCC: estrogen and progesterone receptors were absent in 90% of the tumors. Immunohistochemical staining for HER2/neu was detected in 72% of spindle cell and squamous carcinomas and in 33% of MCC. Three cases staining highly for p53 were chondroid carcinomas: the staining was uniform both in carcinomatous and in sarcomatous tissue. The majority of metaplastic carcinomas had high angionesis. One patient with a chondroid metaplastic carcinoma was found to be a carrier of a BRCA1 mutation similar to the one responsible for sickle cell disease, possibly altering the spatial structure of the gene product. Only six patients had follow-up periods longer than 36 months: five women were alive and disease-free: one patient with pT2N1 squamous metaplastic carcinoma died of disease 14 months after diagnosis. The six women with MCC were alive and disease-free. Surgical and adjuvant treatment should follow the guidelines for the other most common breast cancers even if the need for chemotherapy is unknown due to the absence of large series randomized or observational data.

Adult↗
PubMedDate not supplied

[Brachyurins--serine collagenolytic enzymes from crabs].

The properties of brachyurins, proteolytic enzymes belonging to a new subfamily of chymotrypsin-like proteases, are considered. These enzymes, found in various species of crustacean, exhibit mixed substrate specificity and a marked collagenolytic activity. The enzymatic and physicochemical properties of brachyurins I and their primary and spatial structures are discussed in detail. A separate chapter is devoted to the preparations of collagenases from the hepatopancreas of king crab: their action on the damaged skin and use in medicine.

Amino Acid Sequence↗
PubMed2003

[Application of ordinary Kriging method in entomologic ecology].

Geostatistics is a statistic method based on regional variables and using the tool of variogram to analyze the spatial structure and the patterns of organism. In simulating the variogram within a great range, though optimal simulation cannot be obtained, the simulation method of a dialogue between human and computer can be used to optimize the parameters of the spherical models. In this paper, the method mentioned above and the weighted polynomial regression were utilized to simulate the one-step spherical model, the two-step spherical model and linear function model, and the available nearby samples were used to draw on the ordinary Kriging procedure, which provided a best linear unbiased estimate of the constraint of the unbiased estimation. The sum of square deviation between the estimating and measuring values of varying theory models were figured out, and the relative graphs were shown. It was showed that the simulation based on the two-step spherical model was the best simulation, and the one-step spherical model was better than the linear function model.

Algorithms↗
PubMedDate not supplied

[Molecular construction (superstructures) with adjustable properties based on double-stranded nucleic acids].

Formation of molecular construction that consists of double-stranded molecules of nucleic acids (or synthetic polynucleotides) located at the distance 30-50 A in the spatial structure of particles of their cholesteric liquidcrystalline dispersion and crosslinked by polymeric chelate bridges is described. The resulting superstructure, which possesses peculiar physicochemical properties, could be used as integral biosensor whose properties depend on temperature, the presence of chemical or biologically active compounds of different nature, etc.

Antibiotics, Antineoplastic↗