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PubMed1992

The glnA gene of the extremely thermophilic eubacterium Thermotoga maritima: cloning, primary structure, and expression in Escherichia coli.

The structural gene (glnA) encoding the glutamine synthetase (GS) of the extremely thermophilic eubacterium Thermotoga maritima has been cloned on a 6.0 kb HindIII DNA fragment. Sequencing of the region containing the glnA gene (1444 bp) showed an ORF encoding a polypeptide (439 residues) with an estimated mass of 50,088 Da, which shared significant homology with the GSI sequences of other Bacteria (Escherichia coli, Bacillus subtilis) and Archaea (Pyrococcus woesei, Sulfolobus solfataricus). The T. maritima glnA gene was expressed in E. coli, as shown by the ability to complement a glnA lesion in the glutamine-auxotrophic strain ET8051. The recombinant GS has been partially characterized with respect to the temperature dependence of enzyme activity, molecular mass and mode of regulation. The molecular mass of the Thermotoga GS (590,000 Da), estimated by gel filtration, was compatible with a dodecameric composition for the holoenzyme, as expected for a glutamine synthetase of the GSI type. Comparison of the amino acid sequence of T. maritima GS with those from thermophilic and mesophilic micro-organisms failed to detect any obvious features directly related to thermal stability.

Amino Acid Sequence↗

PubMed2005

Protein structure and evolutionary history determine sequence space topology.

Understanding the observed variability in the number of homologs of a gene is a very important unsolved problem that has broad implications for research into coevolution of structure and function, gene duplication, pseudogene formation, and possibly for emerging diseases. Here, we attempt to define and elucidate some possible causes behind the observed irregularity in sequence space. We present evidence that sequence variability and functional diversity of a gene or fold family is influenced by quantifiable characteristics of the protein structure. These characteristics reflect the structural potential for sequence plasticity, i.e., the ability to accept mutation without losing thermodynamic stability. We identify a structural feature of a protein domain-contact density-that serves as a determinant of entropy in sequence space, i.e., the ability of a protein to accept mutations without destroying the fold (also known as fold designability). We show that (log) of average gene family size exhibits statistical correlation (R(2) > 0.9.) with contact density of its three-dimensional structure. We present evidence that the size of individual gene families are influenced not only by the designability of the structure, but also by evolutionary history, e.g., the amount of time the gene family was in existence. We further show that our observed statistical correlation between gene family size and contact density of the structure is valid on many levels of evolutionary divergence, i.e., not only for closely related sequence, but also for less-related fold and superfamily levels of homology.

Amino Acid Sequence↗

PubMed1998

Anomalous wide-angle X-ray scattering apparatus on the GILDA beamline at the ESRF.

The experimental apparatus for anomalous wide-angle X-ray scattering (AWAXS) on the GILDA beamline at the ESRF is described. The main features are the high beam stability and reproducibility which allow anomalous scattering effects to be resolved also on dilute elements, the large spectral range which allows AWAXS experiments at the K edges of heavy elements, and the use of a high-efficiency detection system. The apparatus has been tested in extreme conditions by performing AWAXS experiments at the Eu K edge in Eu-doped Sr metaphosphate glasses.

Journal Article↗

PubMed2002

Microscopical characterization of nanocapsules templated on ionic crystals and biological cells toward biomedical applications.

Nanocapsules, fuzzy assemblies of polyelectrolyte, represent a comparatively new class of colloids with controlled nanostructure and tunable properties. Due to the fact that the core as well as the dissolution influences the wall texture and the properties of the hollow capsules, the use of carbonate crystals as template is most convenient. Yeast cells constitute as a core candidate as well. They are a good system for testing the protective ability of shells and the permeability of the walls with respect to the needs of biological systems, namely, feeding and stability against attacks. The main features of the nanocapsules have been studied by two-photon, confocal, and atomic force microscopy. Nanocapsules are of biomedical interest because they can be used, for example, for the controlled release and targeting of drugs as well as for the protection of enzymes, proteins, and foreign cells.

Biocompatible Materials↗

PubMed1992

Ocular compensation for self-motion. Visual mechanisms.

In monkeys, there are several reflexes that generate eye movements to compensate for the observer's own movements. Two vestibuloocular reflexes compensate selectively for rotational (RVOR) and translational (TVOR) disturbances of the head, receiving their inputs from the semicircular canals and otolith organs, respectively. Two independent visual tracking systems that deal with residual disturbances of gaze are manifest in the two components of the optokinetic response: the indirect or delayed component (OKNd) and the direct or early component (OKNe). We hypothesize that OKNd--like the RVOR--is phylogenetically old, being found in all animals with mobile eyes, and that it evolved as a backup to the RVOR to compensate for rotational disturbances of gaze. Indeed, optically induced changes in the gain of the RVOR result in parallel changes in the gain of OKNd, consistent with the idea of shared pathways as well as shared functions. In contrast, OKNe--like the TVOR--seems to have evolved much more recently in frontal-eyed animals and, we suggest, acts as a backup to the TVOR to deal primarily with translational disturbances of gaze. Frontal-eyed animals with good binocular vision must be able to keep both eyes directed at the object of regard irrespective of proximity, and in order to achieve this during translational disturbances, the output of the TVOR is modulated inversely with the viewing distance. OKNe shares this sensitivity to absolute depth, consistent with the idea that it is synergistic with the TVOR and shares some of its central pathways. There is evidence that OKNe is also sensitive to relative depth cues such as motion parallax, which we suggest helps the system to segregate the object of regard from other elements in the scene. However, there are occasions when the global optic flow cannot be resolved into a single vector useful to the oculomotor system (e.g., when the moving observer looks towards the direction of heading). We suggest that on such occasions a third independent tracking mechanism, the smooth pursuit system, is deployed to stabilize gaze on the local feature of interest. In this scheme, the pursuit system has an attentional focusing mechanism that spatially filters the visual motion inputs driving the oculomotor system. The major distinguishing features of the 3 visual tracking mechanisms are summarized in Table 1.

Animals↗

PubMed1983

Carbocyclic arabinofuranosyladenine (cyclaradine): efficacy against genital herpes in guinea pigs.

Carbocyclic arabinofuranosyladenine (cyclaradine), a novel nucleoside analog with such desired features as hydrolytic and enzymatic stability, adenosine deaminase resistance, and low systemic toxicity, inhibited the replication of herpes simplex virus types 1 and 2. The 5'-methoxyacetate prodrug form exhibited significant efficacy in the topical treatment of genital infections by herpes simplex virus type 2.

Acyclovir↗

PubMed2000

Effects of nonpolar mutations in each of the seven Bacillus subtilis mrp genes suggest complex interactions among the gene products in support of Na(+) and alkali but not cholate resistance.

The Bacillus subtilis mrp (multiple resistance and pH) operon supports Na(+) and alkali resistance via an Na(+)/H(+) antiport, as well as cholate efflux and resistance. Among the individual mutants with nonpolar mutations in each of the seven mrp genes, only the mrpF mutant exhibited cholate sensitivity and a cholate efflux defect that were complemented by expression of the deleted gene in trans. Expression of mrpF in the mrp null (VKN1) strain also restored cholate transport and increased Na(+) efflux, indicating that MrpF does not require even low levels of other mrp gene expression for its own function. In contrast to MrpF, MrpA function had earlier seemed to depend upon at least modest expression of other mrp genes, i.e., mrpA restored Na(+) resistance and efflux to strain VK6 (a polar mrpA mutant which expresses low levels of mrpB to -G) but not to the null strain VKN1. In a wild-type background, each nonpolar mutation in individual mrp genes caused profound Na(+) sensitivity at both pH 7.0 and 8.3. The mrpA and mrpD mutants were particularly sensitive to alkaline pH even without added Na(+). While transport assays in membrane vesicles from selected strains indicated that MrpA-dependent antiport can occur by a secondary, proton motive force-dependent mechanism, the requirement for multiple mrp gene products suggests that there are features of energization, function, or stabilization that differ from typical secondary membrane transporters. Northern analyses indicated regulatory relationships among mrp genes as well. All the mrp mutants, especially the mrpA, -B, -D, -E, and -G mutants, had elevated levels of mrp RNA relative to the wild type. Expression of an upstream gene, maeN, that encodes an Na(+)/malate symporter, was coordinately regulated with mrp, although it is not part of the operon.

ATP-Binding Cassette Transporters↗

PubMed2003

Stiefel-manifold learning by improved rigid-body theory applied to ICA.

In previous contributions we presented a new class of algorithms for orthonormal learning of a linear neural network with p inputs and m outputs, based on the equations describing the dynamics of a massive rigid frame in a submanifold of R(p). While exhibiting interesting features, such as intrinsic numerical stability, strongly binding to the orthonormal submanifolds, and good controllability of the learning dynamics, tested on principal/independent component analysis, the proposed algorithms were not completely satisfactory from a computational-complexity point of view. The main drawback was the need to repeatedly evaluate a matrix exponential map. With the aim to lessen the computational efforts pertaining to these algorithms, we propose here an improvement based on the closed-form Rodriguez formula for the exponential map. Such formula is available in the p = 3 and m = 3 case, which is discussed with details here. In particular, experimental results on independent component analysis (ICA), carried out with both synthetic and real-world data, help confirming the computational gain due to the proposed improvement.

Algorithms↗

PubMed2005

Screening mutant libraries of fungal laccases in the presence of organic solvents.

Reliable screening methods are being demanded by biocatalysts' engineers, especially when some features such as activity or stability are targets to improve under non-natural conditions (i.e., in the presence of organic solvents). The current work describes a protocol for the design of a fungal laccase-expressed in Saccharomyces cerevisiae-highly active in organic cosolvents. A high-throughput screening assay based on ABTS (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) oxidation was validated. The stability of the ABTS radical cation was not significantly altered in the presence of acetonitrile, ethanol, or DMSO. With a coefficient of variance below 10% and a sensitivity limit of 15 pg laccase/microL, the assay was reproducible and sensitive. The expression system of Myceliophthora thermophila laccase variant T2 in S. cerevisiae was highly dependent on the presence of Cu2+. Copper concentration was limited up to 10 microM CuSO4 where expression levels (approximately 14-18 mg/L) were acceptable without compromising the reliability of the assay. A mutant library was created by error-prone PCR with 1.1 to 3.5 mutations per kb. After only 1 generation of directed evolution, mutant 6C9 displayed about 3.5-fold higher activities than parent type in the presence of 20% acetonitrile or 30% ethanol. The method provided here should be generally useful to improve the activity of other redox enzymes in mixtures of water/cosolvents.

Acetonitriles↗

PubMed2005

Ertapenem: review of a new carbapenem.

The carbapenems are beta-lactam-type antibiotics with an exceptionally broad spectrum of activity. Ertapenem is a new carbapenem developed to address the pharmacokinetic shortcomings (short half-life) of imipenem and meropenem. Ertapenem shares similar structural features with meropenem, including its stability to dehydropeptidase-1, allowing it to be administered without a dehydropeptidase-1 inhibitor. Ertapenem, like imipenem and meropenem, demonstrates broad-spectrum antimicrobial activity against many Gram-positive and -negative aerobes and anaerobes and is resistant to nearly all beta-lactamases, including extended-spectrum beta-lactamases and AmpCs. However, it differs from both imipenem and meropenem in demonstrating limited activity against Enterococcusspp., Pseudomonasaeruginosa and other nonfermentative Gram-negative bacteria commonly associated with nosocomial infections. The extensive protein binding of ertapenem extends the half-life and allows for once-daily dosing. Prospective, multicenter, randomized, double-blind, comparative clinical studies demonstrate similar clinical efficacy of ertapenem compared with other agents. Clinical trials of complicated intra-abdominal infection, acute pelvic infection, complicated skin and soft-structure infection, community-acquired pneumonia and complicated urinary tract infections demonstrated that ertapenem has equivalent efficacy and safety compared with ceftriaxone and piperacillin/tazobactam. Ertapenem is a promising new carbapenem with excellent efficacy and safety for the treatment of a variety of community-acquired infections. It also appears to be of great value as an outpatient parenteral antimicrobial therapy.

Animals↗

PubMed1990

Placing patients in the queue for coronary revascularization: evidence for practice variations from an expert panel process.

A panel of 16 cardiologists and cardiac surgeons rated 438 case scenarios for the maximum acceptable delay prior to revascularization, using a scale with seven interventional time frames and two nodes for designating dubious or inappropriate cases. If consensus was defined as agreement by 12 or more panelists, only 1.4 percent of the case scenarios showed consensus on a single rating. Dividing the scale into three broad clinical categories (revascularize promptly, place on a waiting list, or no intervention), 11.4 percent of scenarios showed all 16 panelists agreeing on a single category, rising to 59.4 percent of scenarios if agreement by 12 panelists was accepted as a consensus. The mean difference between the panelists' highest and lowest urgency ratings yielded waiting time differences of two weeks for scenarios of very unstable angina, and more than three months for those with stable angina. However, in a regression model, individual panelist factors on average had less effect than clinical features such as severity and stability of angina, or stenosis of major coronary arteries. These findings strongly support the need for consensus criteria to ensure that triage practices are consistent and fair, and also suggest that widespread adoption of a standardized approach to revascularization priorities may be feasible.

Coronary Artery Bypass↗

PubMed1991

The design of attendant propelled wheelchairs.

The attendant operated wheelchair is propelled by applying forces to handles at the rear of the chair. There are no published data to justify the design of pushing handles on existing wheelchairs. In Dundee, studies of pushing have been conducted in order to obtain subjective preferences for location and design of handles and an understanding of biomechanical factors associated with wheelchair pushing. Preferred positions for handles have been found to be in the region of 0.75 of shoulder height, 1.14 times shoulder width although deviations of +/- 5% in these values are still rated as acceptable. The preferred positions do not correspond to minimum levels of resultant force or with lowest levels of moment in any of the upper body joints. Moments occurring at the lower back are not substantially affected by handle position. The biomechanical analysis so far has not revealed why some handle positions are more comfortable for pushing than others. Further study, involving calculation of resultant moments (rather than just sagittal plane moments) at these joints and at the lower body joints, is a next step in attempting to find the indicators of discomfort. Transferring a patient from or to a wheelchair can be a difficult operation with risks of accidents to the patient through falling and risks to the attendant of strain, particularly to the back. Current footrests on wheelchairs are a major source of the problems during transfer. A new approach to footrest design is described which solves these difficulties by using a footrest that lowers onto the floor. This has other attractive features such as providing good stability and restraint of the chair during transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMed1997

Toxoplasmosis in naturally infected deer from Brazil.

Serum samples from 107 cervids were examined for Toxoplasma gondii antibodies using indirect hemagglutination (IHA), indirect immunofluorescence (IFA), enzyme linked immunosorbent assay (ELISA) and Dot-ELISA. Samples were obtained from 66 marsh deer (Blastocerus dichotomus) in the State of São Paulo (Brazil) and from 41 pampas deer (Ozotocerus bezoarticus) in the State of Goiás (Brazil). Antibodies to T. gondii were found in 23 (22%) of the deer, with 18 and 5 positive samples, respectively, for B. dichotomus and O. bezoarticus. The highest prevalence of T. gondii antibodies were young adults (32%), following by adults (27%) and fawns (13%). Only one serum sample (8%) from a newborn fawn was positive in the serological tests. The convenience of the Dot-ELISA test is obvious when compared with other serological tests for both laboratory or field surveys, mainly due to its features of practicability and reagent stability.

Age Distribution↗

PubMed2000

[Psychopathological phenomena and personality disorders (the issue of dynamic aspects of psychopathologies)].

An analysis of the interaction between pathocharacterological and psychopathological (affective, anxious-phobic and hysterical) phenomena within "borderline psychiatry" (reactions, phases, development) gives evidence to the existence of 2 clinically heterogeneous variations of comorbid interactions. The first variation: primary psychopathological syndromes manifesting without any significant correlation with personality disorders and transform into pathocharacterological ones (neurotic, postreactive) personality development by means of "amalgamating" mechanism. The second variation: secondary (in regard to personality disorders) psychopathological phenomena forming on the basis of constitutional personality traits by means of "splitting off" mechanism and are defined as personality disorders with predisposition to manifest positive psychopathological symptomatology. Formation of isolated obsessive and dissociative disorders within the structure of "basic" pathocharacterological phenomena (variation 2) predicts a future absence of growing severity of personality disorders (i.e. a dynamics traditionally defined as the development--variation 1) and stabilization of psychopathic traits with features of compensation of the latter. The possibilities of pathological dynamics in psychopathic personality with a "splitting off" of the isolated psychopathological syndromes exhausted; for decades neither growing severity of personality disorders, nor an exacerbation of those psychopathological complexes which provided a primary base for manifestation of positive symptomatology may be observed.

Adult↗

PubMed1975

Assessment of different mathematical models for calculating and expressing the results of coagulation test procedures.

Coagulation activity, expressed as percentage of normal and as clotting time ratio, was estimated in 220 specimens from patients on long-term anticoagulant treatment by 3 different coagulation test procedures, i.e. Thrombotest, Simplastin-A and Normotest. The estimates were calculated from the same determinations. The distribution of percentage values showed a fairly pronounced deviation from normality. After logarithmic transformation, the distribution was normalized, the regression lines between Thrombotest and other tests became parallel, and that between PIVKA-insensitive systems was shifted to a 45 degree line. Logarithmic transformation also stabilized the residual variance. These features make percentage values accessible for treatment according to the standard methods of bioassay statistics. Attempts to normalize the distribution of ratio values by various transformations were unsuccessful. Formal analysis of data revealed a variation in the proportionality of ratio values with the level of estimated coagulation defect. This may restrict the usefulness of the ratio approach. Logarithmic transformation partly reduced the discrepancy.

Analysis of Variance↗

PubMedDate not supplied

Preparation of Newcastle disease virus hemagglutination-inhibition test antigen.

A method of preparing antigen for Newcastle hemagglutination-inhibition (HI) tests is described; polyethylene glycol precipitation is used for the virus concentration. The virus was inactivated with either formalin or beta-propiolactone. Glycerin was used to stabilize the hemagglutinin activity of the antigen. The stability, uninfectivity, and slow eluting features of the antigen should aid in obtaining accurate HI results without the risks inherent in the use of live virus.

Animals↗

PubMedDate not supplied

Oral health status and treatment satisfaction with mandibular implant overdentures and conventional dentures: a randomized clinical trial in a senior population.

PURPOSE: The purpose of this study was to compare elderly patients' satisfaction and oral health-related quality of life with mandibular two-implant overdentures and conventional dentures. MATERIALS AND METHODS: Sixty edentulous subjects aged 65 to 75 years were randomly assigned to two groups treated with maxillary conventional dentures and either a mandibular conventional denture (n = 30) or an overdenture supported by two implants with ball retainers (n = 30). Subjects rated their general satisfaction, as well as other features of their dentures (comfort, stability, ability to chew, speech, esthetics, and cleaning ability), prior to treatment and 2 months postdelivery. Changes in ratings on the original Oral Health Impact Profile (OHIP) and its short form (OHIP-EDENT) were also used as indicators of oral health-related quality of life. RESULTS: The primary outcome of this study, ratings of general satisfaction 2 months postdelivery, was significantly better in the group treated with mandibular two-implant overdentures (P = .001). In addition, the implant group gave significantly higher ratings on comfort, stability, and ability to chew. Furthermore, using OHIP-EDENT, subjects who received mandibular two-implant overdentures had significantly fewer oral health-related quality of life problems than did the conventional group. CONCLUSION: These short-term results suggest that mandibular two-implant overdentures combined with maxillary conventional dentures provide better function and oral health-related quality of life than conventional dentures.

Aged↗

PubMedDate not supplied

The Fixion expansion nail in the surgical treatment of diaphyseal fractures of the humerus and tibia. Our experience.

The authors present their experience in the application of a Fixion expansion intramedullary nail for the treatment of diaphyseal fractures of the humerus and tibia, in a total of 40 surgeries. The features of the nail are: stability and flexibility of the instrumentation, speed of surgery, minimal exposure to radiation. The results obtained up to now are encouraging; there are no significant problems either during or after surgery, and mean consolidation time is 3 months for fractures of the humerus, and 4 months for those of the tibia. The Fixion nail is a versatile type of instrumentation that is easy to use.

Adult↗