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At least 451 records · Page 25Linked to original sources
PubMed1988

Repetition of parasuicide: an epidemiological and clinical study.

The dramatic clinical presentation of parasuicide tends to deflect attention from the repetitive pattern of this behaviour in many patients. In an epidemiological study of annual cohorts of parasuicides for 1972, 1977, and 1982 admitted to the Regional Poisoning Treatment Centre, Edinburgh, it was found that for certain subgroups of the population 'repeaters' were actually commoner than 'first-ever' patients, and a number of risk factors were identified, of which social class was particularly important. The clinical characteristics of patients distinguished by their frequency of repetition were also described, with special attention to the stability of these differentiating features over time. It is suggested that the habitual repeater requires closer study, and that the factors which lead to initiation into a parasuicidal 'career' are not necessarily those which conduce to repetition.

Adolescent↗
PubMedDate not supplied

[Neurophysiological bases of vestibular training].

Occupation-oriented vestibular selection is based on the two principles: selection of vestibular-resistant subjects, and increase of vestibular tolerance through training. The latter implies inherited ability of the central nervous system to attenuate vestibular reactions. The review surveys experimental data concerning attenuation (habituation) of vestibular reactions as a result of prolonged or reiterative excitation of labyrinthine receptors. The review discusses peculiar features of the development, stability and transfer of habituation. It gives data on disturbed habituation as a result of an exposure to stress-effects (hypokinesia, hypoxia, hypothermia) and certain drugs. The phenomenon of vestibular habituation is interpreted in terms of Sokolov's concept of the stimulus nervous model.

Aerospace Medicine↗
PubMed1985

[Experience with long-term preservation of international-standard cultures of Actinomycetes].

The results of the study on long-term maintenance (1-12 years) of 453 reference cultures of actinomycetes are presented. The cultures were maintained with the following methods: lyophilization, soil cultures and periodical passages on agarized nutrient media. Lyophilization was most efficient for storage of the majority of the cultures: 346 strains (77.4 per cent) preserved high viability over the observation period of 11-12 years. Lyophilization appeared less favourable for the cultures with low sporulation. The efficacy of the method of soil cultures on long-term storage of the whorl actinomycetes was low: 88 per cent of Streptoverticillium lost their viability within 1-2 years. However, this method was valuable for stabilization of the taxonomic features of streptomycetes. The maintenance of the actinomycetes by regular passages on agarized media every 6 months resulted in the changing of the cultural and morphological features in a number of the strains.

Actinomycetales↗
PubMed2002

Stability of a flexible polar ionic crystal surface: metastable alumina and one-dimensional surface metallicity.

A first-principles study of kappa-Al2O3 (001) and (001-) reveals new features of ion-surface stability and electronic structure. The need to generalize Tasker's rules for surface stability of low-symmetry crystals is shown. Structurally, the presence of bulk tetrahedral Al ( Al(T)) causes giant surface relaxations, with O termination at (001). Surface-layer Al(T) are strongly unfavored. This is understood with Pauling's rules and thus generally applicable to metastable aluminas. The bulk charge asymmetry and Al-sublattice anisotropy caused by the Al(T) create a 1D metallic surface state at (001-).

Journal Article↗
PubMed1997

Perceiving musical stability: the effect of tonal structure, rhythm, and musical expertise.

The goal of this study was to investigate several factors that determine musical stability in unaccompanied tonal melodies. Following M. R. Jones's (1987) theory of dynamic attending, the author assumed that strongly accented tones act as stable melodic reference points. Three main results were observed: (a) tonal structure, rhythm, and melodic factors (i.e., pitch skips or change in melodic contour) all contributed to defining the stability experienced on the melodic tones; (b) a linear combination of 5 melodic and rhythmic features provided a good fit to the stability ratings; and (c) some of these features contributed differently, depending on the extent of musical expertise of the participants. The results are interpreted within C. L. Krumhansl's (1990) model of tonal perception and Jones's theory of dynamic attending.

Auditory Perception↗
PubMed1995

Protein design: a hierarchic approach.

The de novo design of peptides and proteins has recently emerged as an approach for investigating protein structure and function. Designed, helical peptides provide model systems for dissecting and quantifying the multiple interactions that stabilize secondary structure formation. De novo design is also useful for exploring the features that specify the stoichiometry and stability of alpha-helical coiled coils and for defining the requirements for folding into structures that resemble native, functional proteins. The design process often occurs in a series of discrete steps. Such steps reflect the hierarchy of forces required for stabilizing tertiary structures, beginning with hydrophobic forces and adding more specific interactions as required to achieve a unique, functional protein.

Amino Acid Sequence↗
PubMed2005

Characterizations and properties of hairy latex particles.

Industrial latex composed of a hydrophobic core surrounded by a charged hydrophilic layer exhibits excellent stability toward monovalent salt. That feature is classically attributed to a steric effect due to a loss of entropy during overlapping of coating materials. The so-called electrosteric stabilization is, however, not a straightforward function of the nature of the hydrophilic corona. This suspension was characterized in dilute solution by scattering and electrophoresis techniques. In contrast to spherical brushes the interface between the core and the corona is not well defined. The layer is more similar to a highly hydrated nonuniform gel with few longer strands that control the hydrodynamic properties than to a polyelectrolyte brush whose dependence on ionic strength reflects the concentration of counterions inside a well-defined structure. Thus the steric contribution to stabilization of these hairy particles appears to be insignificant in the range studied. The highly hydrated nature and the global charge of the layer are two predominant factors for the stability of the particles.

Journal Article↗
PubMed1996

Temperature and pH sensitivity of trypsins from Atlantic salmon (Salmo salar) in comparison with bovine and porcine trypsin.

Four differently charged trypsins were purified from pyloric caeca of Atlantic salmon (Salmo salar). The isoelectric points of three anionic isoforms were 4.70, 4.60, and 4.55 (anionic trypsin I, II and III, respectively). And for the first time a cationic isoform (isoelectric point above 9.3) has been isolated from a marine species. The apparent molecular weights of all four isoforms were about 25 kDa as determined by SDS-PAGE. The salmon enzymes were inhibited by serine proteinase inhibitors in general and also by specific trypsin inhibitors. Anionic trypsin I and the cationic isoform were further examined. Anionic trypsin I showed the typical cold-adaptation features, low pH and temperature stability (also lower Gibb's free energy of GdnHCl-induced unfolding) and high catalytic efficiency as compared to the mammalian trypsins. The cationic isoform did not show these features, but resembled the mammalian trypsins.

Animals↗
PubMed2000

Structural differences between mesophilic, moderately thermophilic and extremely thermophilic protein subunits: results of a comprehensive survey.

BACKGROUND: Proteins from thermophilic organisms usually show high intrinsic thermal stability but have structures that are very similar to their mesophilic homologues. From prevous studies it is difficult to draw general conclusions about the structural features underlying the increased thermal stability of thermophilic proteins. RESULTS: In order to reveal the general evolutionary strategy for changing the heat stability of proteins, a non-redundant data set was compiled comprising all high-quality structures of thermophilic proteins and their mesophilic homologues from the Protein Data Bank. The selection (quality) criteria were met by 64 mesophilic and 29 thermophilic protein subunits, representing 25 protein families. From the atomic coordinates, 13 structural parameters were calculated, compared and evaluated using statistical methods. This study is distinguished from earlier ones by the strict quality control of the structures used and the size of the data set. CONCLUSIONS: Different protein families adapt to higher temperatures by different sets of structural devices. Regarding the structural parameters, the only generally observed rule is an increase in the number of ion pairs with increasing growth temperature. Other parameters show just a trend, whereas the number of hydrogen bonds and the polarity of buried surfaces exhibit no clear-cut tendency to change with growth temperature. Proteins from extreme thermophiles are stabilized in different ways to moderately thermophilic ones. The preferences of these two groups are different with regards to the number of ion pairs, the number of cavities, the polarity of exposed surface and the secondary structural composition.

Amino Acids↗
PubMed1995

Competing interactions contributing to alpha-helical stability in aqueous solution.

The stability of a 15-residue peptide has been investigated using CD spectroscopy and molecular simulation techniques. The sequence of the peptide was designed to include key features that are known to stabilize alpha-helices, including ion pairs, helix dipole capping, peptide bond capping, and aromatic interactions. The degree of helicity has been determined experimentally by CD in three solvents (aqueous buffer, methanol, and trifluoroethanol) and at two temperatures. Simulations of the peptide in the aqueous system have been performed over 500 ps at the same two temperatures using a fully explicit solvent model. Consistent with the CD data, the degree of helicity is decreased at the higher temperature. Our analysis of the simulation results has focused on competition between different side-chain/side-chain and side-chain/main-chain interactions, which can, in principle, stabilize the helix. The unfolding in aqueous solution occurs at the amino terminus because the side-chain interactions are insufficient to stabilize both the helix dipole and the peptide hydrogen bonds. Loss of capping of the peptide backbone leads to water insertion within the first peptide hydrogen bond and hence unfolding. In contrast, the carboxy terminus of the alpha-helix is stable in both simulations because the C-terminal lysine residue stabilizes the helix dipole, but at the expense of an ion pair.

Amino Acid Sequence↗
PubMed2005

Expression and characterization of a low molecular weight recombinant human gelatin: development of a substitute for animal-derived gelatin with superior features.

Gelatin is used as a stabilizer in several vaccines. Allergic reactions to gelatins have been reported, including anaphylaxis. These gelatins are derived from animal tissues and thus represent a potential source of contaminants that cause transmissible spongiform encephalopathies. We have developed a low molecular weight human sequence gelatin that can substitute for the animal sourced materials. A cDNA fragment encoding 101 amino acids of the human proalpha1 (I) chain was amplified, cloned into plasmid pPICZalpha, integrated into Pichia pastoris strain X-33, and isolates expressing high levels of recombinant gelatin FG-5001 were identified. Purified FG-5001 was able to stabilize a live attenuated viral vaccine as effectively as porcine gelatin. This prototype recombinant gelatin was homogeneous with respect to molecular weight but consisted of several charge isoforms. These isoforms were separated by cation exchange chromatography and found to result from a combination of truncation of the C-terminal arginine and post-translational phosphorylation. Site-directed mutagenesis was used to identify the primary site of phosphorylation as serine residue 546; serine 543 was phosphorylated at a low level. A new construct was designed encoding an engineered gelatin, FG-5009, with point mutations that eliminated the charge heterogeneity. FG-5009 was not recognized by antigelatin IgE antibodies from children with confirmed gelatin allergies, establishing the low allergenic potential of this gelatin. The homogeneity of FG-5009, the ability to produce large quantities in a reproducible manner, and its low allergenic potential make this a superior substitute for the animal gelatin hydrolysates currently used to stabilize many pharmaceuticals.

Antibodies↗
PubMed1980

[Stability of the population as an expression of human rationality (author's transl)].

A prominent feature of a stable population is the stability of the age structure. The present investigation demonstrates that in the Federal Republic of Germany age distribution of youth, working population and old age pensioners remained stable during the last hundred years despite fluctations in the birth rate, death rate, and life expectancy. It can be concluded that an increasing life expectancy must lead to overpopulation which will in turn reduce the birth rate and slow down human reproduction.

Age Factors↗
PubMed1988

Protein design for non-aqueous solvents.

Improving protein stability in unnatural and suboptimal environments is a promising application of protein engineering technology. Carefully designed amino acid alterations may lead to dramatic positive effects on the stability of proteins under highly perturbing conditions, such as in non-aqueous solvents. Applications of biocatalysts and proteins with specific binding capabilities in the chemical industry have been severely limited by constraints placed on the solvent environment. With the advent of convenient methods for altering the amino acid composition and even synthesizing entirely new protein molecules, it is worthwhile to consider engineering proteins for stability in non-aqueous solvents. In order to identify the features that a protein would need for stability in organic media, we have been studying the structure and properties of the hydrophobic protein crambin. Crambin is unique in that it is soluble and stable in very high concentrations of polar organic solvents. Crambin and its water-soluble homologs offer a powerful demonstration of protein engineering for non-aqueous solvents. This paper describes the structural features that contribute to crambin's special properties. Based on these observations and consideration of how non-aqueous solvents affect the interactions important in protein folding, a set of rules for designing non-aqueous solvent-stable proteins is proposed.

Amino Acid Sequence↗
PubMed2002

A developmental conundrum: a stabilized form of beta-catenin lacking the transcriptional activation domain triggers features of hair cell fate in epidermal cells and epidermal cell fate in hair follicle cells.

Wnt signaling orchestrates morphogenetic processes in which changes in gene expression are associated with dramatic changes in cell organization within developing tissue/organs. Upon signaling, excess beta-catenin not utilized at cell-cell junctions becomes stabilized, where it can provide the transcriptional activating domain for Lef/Tcf DNA binding proteins. In skin epithelium, forced stabilization of beta-catenin in epidermis promotes hair follicle morphogenesis, whereas conditional removal of beta-catenin in hair progenitor cells specifies an epidermal fate. We now report that a single protein, a stabilized version of beta-catenin lacking the COOH-terminal transactivation domain, acts in epidermis to promote hair fates and in hair cells to promote epidermal fate. This reveals fundamental differences in ways that epidermal and hair cells naturally respond to beta-catenin signaling. In exploring the phenotype, we uncovered mechanistic insights into the complexities of Lef1/Tcf/beta-catenin signaling. Importantly, how a cell will respond to the transgene product, where it will be localized, and whether it can lead to activation of endogenous beta-catenin/Tcf/Lef complexes is specifically tailored to skin stem cells, their particular lineage and their relative stage of differentiation. Finally, by varying the level of beta-catenin signaling during a cell fate program, the skin cell appears to be pliable, switching fates multiple times.

Animals↗
PubMed2001

What have we learned about the biology of atherosclerosis? The role of inflammation.

In the past, we believed that atherosclerosis gradually and progressively led to the complete occlusion of an artery, thereby causing acute coronary events. However, we now understand that rupture of a nonstenotic, yet vulnerable atherosclerotic plaque frequently leads to an acute coronary syndrome. Rupture-prone plaques typically have a thin fibrous cap, numerous inflammatory cells, a substantial lipid core, and surprisingly few smooth muscle cells. Physical disruption of such a plaque allows circulating blood coagulation factors to meet with the highly thrombogenic material in the plaque's lipid core, thereby instigating the formation of a potentially occluding and fatal thrombus. Much evidence implicates inflammation in the thinning of the fibrous cap and the disruption of the vulnerable atherosclerotic plaque. Lipid lowering undisputedly reduces the incidence of acute coronary events. However, the hypothesis that the mechanism of event reduction involves regression of fixed stenoses has proved untenable. In 14 angiographic studies, treatment of abnormal lipid levels increased luminal diameter only modestly, in stark contrast to the resounding and consistent decrease in acute coronary events produced by lipid lowering. Therefore, we now believe that lipid-lowering treatments, such as statins, modify plaques qualitatively as much as quantitatively, reducing inflammation and stabilizing noncritically stenotic, yet vulnerable plaques. Studies in rabbits with diet-induced atherosclerosis have shown that reducing cholesterol consumption indeed decreases inflammation in atheroma and improves those features of plaques associated with stability.

Animals↗
PubMed1998

A comparative study of two isoforms of laccase secreted by the "white-rot" fungus Rigidoporus lignosus, exhibiting significant structural and functional differences.

Two isoforms of laccase were obtained as the predominant phenol-oxidases in defined medium liquid cultures of the "white-rot" fungus Rigidoporus lignosus (R. lignosus). A characterization of the two laccases was made in terms of molecular mass, isoelectric point, metal content and N-terminal sequence. Furthermore, in order to gain information on the structural features related to the metal centers, a study of their geometric arrangement and their redox ability was made. It turned out that the two isoenzymes greatly differed with regard to pH stability, catalytic and copper centers features. It is proposed that all such differences are dependent on the amino acid sequences, which cause a distortion of the copper sites, thus accounting for the redox potential values and kinetic properties.

Amino Acid Sequence↗
PubMed1992

Crystal structure of the alkaline proteinase Savinase from Bacillus lentus at 1.4 A resolution.

Savinase (EC3.4.21.14) is secreted by the alkalophilic bacterium Bacillus lentus and is a representative of that subgroup of subtilisin enzymes with maximum stability in the pH range 7 to 10 and high activity in the range 8 to 12. It is therefore of major industrial importance for use in detergents. The crystal structure of the native form of Savinase has been refined using X-ray diffraction data to 1.4 A resolution. The starting model was that of subtilisin Carlsberg. A comparison to the structures of the closely related subtilisins Carlsberg and BPN' and to the more distant thermitase and proteinase K is presented. The structure of Savinase is very similar to those of homologous Bacillus subtilisins. There are two calcium ions in the structure, equivalent to the strong and the weak calcium-binding sites in subtilisin Carlsberg and subtilisin BPN', well known for their stabilizing effect on the subtilisins. The structure of Savinase shows novel features that can be related to its stability and activity. The relatively high number of salt bridges in Savinase is likely to contribute to its high thermal stability. The non-conservative substitutions and deletions in the hydrophobic binding pocket S1 result in the most significant structural differences from the other subtilisins. The different composition of the S1 binding loop as well as the more hydrophobic character of the substrate-binding region probably contribute to the alkaline activity profile of the enzyme. The model of Savinase contains 1880 protein atoms, 159 water molecules and two calcium ions. The crystallographic R-factor [formula; see text].

Amino Acid Sequence↗