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At least 433 records · Page 24Linked to original sources

PubMed2004

Phase-averaged characterization of respiratory sinus arrhythmia pattern.

A method for the accurate time-domain characterization of respiratory sinus arrhythmia (RSA) pattern is presented and applied to two groups of healthy subjects to lay the baseline of RSA patterns and to underlay their features: response to standing, stability in successive recordings, and individuality of the shape of RSA pattern. RSA pattern is evaluated by selective averaging of heart rate (HR) changes from multiple respiratory cycles over the respiratory phase and represents the complete modulating function of HR by respiration. The RSA pattern is evaluated with free respiration and even in cases of severe arrhythmia. Estimation error is 6-8% in magnitude, phase resolution is 0.2 rad, and sensitivity margin for respiratory-related HR variability (HRV) components is 1%. RSA magnitude, phase lag, and expiration-to-inspiration time ratio are derived in addition to the entire pattern. In a group of 10 healthy young adults, a phase lag difference of 11.4 +/- 8.5% (mean +/- SD, P < 0.004) was observed between supine and standing postures, possibly ascribed to breathing mechanics. A second group of 15 healthy young adults at supine rest showed stability of the RSA pattern in successive recordings (several weeks apart) as well as individuality among subjects. This may suggest a nonscalar individual long-term index for cardiorespiratory coupling. The method is complementary to the existing statistical and spectral methods. It allows the complete characterization of the primary RSA components and may provide new insight into the effects of vagal activity and changes in clinical conditions.

Adult↗

PubMed2006

Minimally invasive transmuscular pedicle screw fixation of the thoracic and lumbar spine.

OBJECTIVE: This study assessed the feasibility and safety of percutaneous posterior pedicle screw fixation for instabilities of the thoracic and lumbar spine, using standard instruments designed for the open approach and fluoroscopy. METHODS: All patients who underwent percutaneous posterior pedicle screw fixation of the thoracic and lumbar spine were studied retrospectively. Charts and operative notes were analyzed for epidemiological data, underlying spinal pathological features, and indications for stabilization, stabilized segments, number of implanted pedicle screws, surgical time, and complications. Postoperative computed tomographic scans were analyzed for screw position. RESULTS: From May 2002 through May 2005, 115 internal fixators were implanted percutaneously in 104 patients. A total of 488 pedicle screws were implanted, stabilizing 1 to 5 spinal motion segments. Median surgical time was 93 minutes. On postoperative computed tomographic scans, 87% of screw positions were rated good, 10% were rated acceptable, and 3% were rated unacceptable. A total of 11 revisions were necessary, 9 for misplaced screws and 2 for loosening of anchor bolts. Only two of the patients experienced new clinical symptoms (i.e., radicular pain) because of screw misplacement. No patients experienced new neurological deficits or other surgery-related morbidity. CONCLUSION: This study shows that percutaneous internal pedicle screw fixation using standard instruments is feasible and safe for posterior stabilization of the thoracic and lumbar spine. It is a straightforward alternative for open approaches or minimally invasive ones using navigation in conjunction with customized instruments. Accuracy of screw placement is similar to that reported for other techniques.

Adolescent↗

PubMed2005

Changing views about personality disorders: Comment about the prospective studies CIC, CLPS, and MSAD.

Three large-scale prospective studies (Children in the Community Study [CIC; Cohen, Crawford, Johnson, & Kasen, this issue], Collaborative Longitudinal Personality Disorders Study [CLPS; Skodol et al., this issue], and the McLean Study of Adult Development [MSAD; Zanarini, Frankenburg, Hennen, Reich, & Silk, this issue]) are discussed with respect to the following issues: shared and complementary features of the study designs, evidence for stable and changing personality disorder features, methodological issues (reliability, stability, and invariance), the relationship between Axis I and II disorders, and dimensional versus categorical representations of personality disorders.

Humans↗

PubMed2006

Recognition of ribonuclease A by 3'-5'-pyrophosphate-linked dinucleotide inhibitors: a molecular dynamics/continuum electrostatics analysis.

The proteins of the pancreatic ribonuclease A (RNase A) family catalyze the cleavage of the RNA polymer chain. The development of RNase inhibitors is of significant interest, as some of these compounds may have a therapeutic effect in pathological conditions associated with these proteins. The most potent low molecular weight inhibitor of RNase reported to date is the compound 5'-phospho-2'-deoxyuridine-3-pyrophosphate (P-->5)-adenosine-3-phosphate (pdUppA-3'-p). The 3',5'-pyrophosphate group of this compound increases its affinity and introduces structural features which seem to be unique in pyrophosphate-containing ligands bound to RNase A, such as the adoption of a syn conformation by the adenosine base at RNase subsite B(2) and the placement of the 5'-beta-phosphate of the adenylate (instead of the alpha-phosphate) at subsite P(1) where the phosphodiester bond cleavage occurs. In this work, we study by multi-ns molecular dynamics simulations the structural properties of RNase A complexes with the ligand pdUppA-3'-p and the related weaker inhibitor dUppA, which lacks the 3' and 5' terminal phosphate groups of pdUppA-3'-p. The simulations show that the adenylate 5'-beta-phosphate binding position and the adenosine syn orientation constitute robust structural features in both complexes, stabilized by persistent interactions with specific active-site residues of subsites P(1) and B(2). The simulation structures are used in conjunction with a continuum-electrostatics (Poisson-Boltzmann) model, to evaluate the relative binding affinity of the two complexes. The computed relative affinity of pdUppA-3'-p varies between -7.9 kcal/mol and -2.8 kcal/mol for a range of protein/ligand dielectric constants (epsilon(p)) 2-20, in good agreement with the experimental value (-3.6 kcal/mol); the agreement becomes exact with epsilon(p) = 8. The success of the continuum-electrostatics model suggests that the differences in affinity of the two ligands originate mainly from electrostatic interactions. A residue decomposition of the electrostatic free energies shows that the terminal phosphate groups of pdUppA-3'-p make increased interactions with residues Lys(7) and Lys(66) of the more remote sites P(2) and P(0), and His(119) of site P(1).

Adenosine Monophosphate↗

PubMed2001

Development of response-selective agonists of human C5a anaphylatoxin: conformational, biological, and therapeutic considerations.

Numerous studies on the relationship between the structure and function of peptide agonists derived from the biologically active, C-terminal region of human C5a anaphylatoxin have been reported over the past decade. These studies have been performed with the objective of parlaying this structure-function information into the design of peptide/peptidomimetic modulators of C5a receptor (C5aR)-mediated function. In this review, we describe a rational approach for the development of conformationally biased, decapeptide agonists of C5a and described how these stabilized and specific conformational features relate to the expression of specific C5a-like activities in vitro and in vivo. The therapeutic potential of such response-selective C5a agonists is discussed and underscored by the results of one such response-selective C5a agonist that was used in vivo as an effective molecular adjuvant capable of generating antigen-specific humoral and cellular immune responses. Finally, we describe the synthesis of a new generation of highly response-selective, conformationally biased C5a agonist and discuss the in vitro and in vivo biologic results that so indicate this biologic selectivity.

Animals↗

PubMed1990

Crystal structure of low humidity tetragonal lysozyme at 2.1-A resolution. Variability in hydration shell and its structural consequences.

Tetragonal crystals of hen egg white lysozyme undergo a reversible transformation, accompanied by loss of water, when the relative humidity of the environment is reduced to about 90%. The structure of the low humidity form has been analyzed, using x-ray data collected at 88% relative humidity, in order to explore the variability in protein hydration caused by a change in the amount of water surrounding the protein molecule and the consequent conformational perturbations in the molecule. The structure has been refined by the restrained least-squares method to an R value of 0.162 for 6269 observed reflections in the 10-2.1-A resolution shell. The refined structure provides interesting examples for the variability in helical parameters, the role of interactions involving side chains and water in the stabilization of secondary structural features, and favorable specific hydration sites. The protein molecule as a whole moves slightly in the low humidity form from its position in the native crystals. The hydration shell tends to move along with the protein. Significant changes, however, occur in the hydration shell. These changes cause structural perturbations in the enzyme molecule, which are most pronounced in regions involved in substrate binding.

Animals↗

PubMed1993

Clinical features in patients with chronic muscle pain--with special reference to fibromyalgia.

Clinical characteristics were studied in patients with chronic muscle pain, divided into three groups according to the characteristics of their pain; "fibromyalgia" (n = 23), "widespread muscle pain" (n = 21), and "regional muscle pain" (n = 28). Typical fibromyalgia features were also seen in the other groups of patients, but not to the same extent. In particular, sleep disturbance, subjective swelling, cold and exercise intolerance and low self-reported physical performance were significantly related to fibromyalgia. The major components of fibromyalgia were not wholly different compared with other European and North American studies, except for sleep disturbance and subjective swelling, which was somewhat more pronounced in this study. The most used medications in fibromyalgia patients at referral were analgesics, anxiolytic drugs and female sex hormones. Medication in fibromyalgia was not excessive and seemed appropriate compared to the other patient groups. Effects of various biases and classification criteria on the results of fibromyalgia studies are discussed. The characteristic features of fibromyalgia, its stability when diagnosed and the promotion of research and patient management justify the current classification of fibromyalgia at this stage.

Adult↗

PubMed1990

Identification of monoclonal antibodies capable of differentiating antigenic varieties of eastern equine encephalitis viruses.

We have isolated and characterized 3 monoclonal antibody (Mab) reagents useful in the serological identification of varieties of eastern equine encephalitis (EEE) viruses. These antibodies were specific for the E1 glycoprotein of their homologous viruses. One Mab, 1B5C-3, reacted specifically with all North American (NA) EEE viruses isolated over a 50 year period. This antigenic stability of NA isolates was genetically confirmed by oligonucleotide fingerprinting. Evolutionary stability is a unique feature among alphaviruses. The Mab, 1C1J-4 reacted specifically with 1 South American isolate of EEE virus. A third Mab, 1B1C-4, was EEE virus complex reactive. While none of these antibodies had virus neutralizing activity, the identified reactivities could be demonstrated in the more rapid serological tests of enzyme-linked immunosorbent assay and indirect immunofluorescence.

Alphavirus↗

PubMed1977

Formation of soluble fibrinogen-fibrin complex in liquid human plasma; reflexion of coagulation process in storage.

Analysis was performed on a high-molecular fraction with fibrinogen antigenicity present in Liquid Human Plasma. This fraction, although seemed to resemble macromolecular FDP (fibrinogen degradation product) derived from stabilized fibrin, has many features not shared with the latter: 1) This fraction is sensitive to sodium dodecylsulfate (SDS) treatment. 2) Degradation products of this fraction obtained by digestion with plasmin, when eluted from a column of Sephadex G-200, exhibited a single peak of FDP-D antigenicity at the position of D-monomer. 3) In SDS polyacrylamide gel electrophoresis in the presence of dithiothreitol (DDT), no evidence for the presence of gamma-dimer was obtained. Thus, it is unlikely that the high-molecular fraction is formed through interchain cross-linking between fibrinogen molecules. The formation of the high-molecular complex was discussed in relation to coagulation process in stored plasma.

Antigens↗

PubMed2000

Circulating DNA in plasma or serum.

Small amounts of DNA circulate in both healthy and diseased human plasma/serum, and increased concentrations of DNA are present in the plasma of cancer patients. Characteristics of tumor DNA have been found in genetic material extracted from the plasma of cancer patients. These features include decreased strand stability, the presence of specific oncogene or tumor suppressor gene mutations, microsatellite alterations, Ig rearrangements and hypermethylation of several genes. The results obtained in many different cancers have opened a new research area indicating that plasma DNA might eventually be a suitable target for the development of noninvasive diagnostic, prognostic and follow-up tests for cancer. Following the discovery of tumor derived DNA in plasma or serum, cell-free fetal DNA has also been found in maternal plasma and serum. This discovery provides an easily accessible source of fetal genetic material for prenatal diagnosis.

DNA, Neoplasm↗

PubMed1992

The enzymology of archaebacterial pathways of central metabolism.

From a comparison of the pathways of central metabolism in the archaebacteria, eubacteria and eukaryotes, it is clear that the basic pathways were established before the divergence of the three kingdoms, but that the notable differences may provide important clues to their evolution. From these comparisons, enzymes found in all evolutionary groups have been chosen for detailed structural studies; given the range of extreme phenotypes found within the archaebacteria, these studies will be crucial to our understanding of the structural basis for protein stability and how such features may be engineered into a protein of choice.

Archaea↗

PubMed1975

Further observations on the characteristics of a bovine parainfluenza-3 variant.

Calves were inoculated with a bovine para-influenza-3 variant to determine its pathogenicity and the stability of its cytopathic feature and its inability to agglutinate chicken erythrocytes. The inoculated calves and one contact animal developed an immune response without significant clinical illness. The clinical response in calves was similar to that induced by the parent virus strain. The variant was shown to retain its characteristic cytopathic effect for Madin Darby bovine kidney cells and its property of hemagglutination following one passage in the natural host.

Animals↗

PubMed2006

[Full arch impression techniques utilizing addition type poly vinyl siloxane for fabrication of tooth born fixed partial dentures].

A precise impression is necessary for fabricating an accurately fitting cast restoration. For this purpose, Polyvinyl Siloxane (PVS) impression materials are extremely popular because of their combination of excellent physical properties, handling characteristics and dimensional stability. Its excellent clinical features remain unaffected if simple measures are guarded. This review presents several impression techniques using PVS and recommends the one that provides the most accurate impression, utilizing the superior qualities of the PVS. The one step impression technique where no control of wash bulk and thickness exists, is considered to be the least accurate impression method with measured discrepancies as large as 7 times the original inter preparation distance and 40 times the original cross arch dimensions. Furthermore, the direct contact between the less refined putty material and the tooth preparation, as well as the high prevalence of air bubble entrapment, seriously compromises restoration longevity. The two stage impression technique has proved to produce the most accurate and reliable impressions due to complete control of the wash bulk and thickness entailed. The ideal wash bulk thickness should range between 1 to 2.5 mm all around the abutment tooth in order to minimize distortion of its subsequent die. Using a "Putty Tray" at the first stage with a predetermined space encircling the abutments will allow the wash to flow to its ideal uniform bulk size at the second stage. A uniform bulk size will prevent differential setting contraction and uneven changes at the dimensions of the die. The easiest and most clinically applicable method to achieve the desired space around the preparations is by loading the Putty material with the temporary crowns in place, followed by their removal at the second stage and occupation of the created space by the wash. In general, less control of wash bulk will result in either insufficient or excessive wash material which will determine uneven dimensional changes in the impression. This, in turn, will produce ill fitting cast restoration.

Dental Impression Materials↗

PubMed2006

The long-term stability of portable spirometers used in a multinational study of the prevalence of chronic obstructive pulmonary disease.

BACKGROUND: We report the performance of an ultrasound-based portable spirometer (EasyOne) used in a population-based survey of the prevalence of chronic obstructive pulmonary disease, conducted in 5 Latin American cities: São Paulo, Brazil; México City, México; Montevideo, Uruguay; Santiago, Chile; and Caracas, Venezuela (the Latin American COPD Prevalence Study [PLATINO]). METHODS: During the survey period (which ranged from 3 months to 6 months in the various locations) we collected daily calibration data from the 70 EasyOne spirometers used in the 5 survey cities. The calibrations were conducted with a 3-L syringe, and the calibration data were stored in the spirometer's database. RESULTS: Ninety-seven percent of the calibration volumes were within +/- 64 mL (2.1%) of the 3-L calibration signal. Excluding data from the first city studied (São Paulo), where one calibration syringe had to be replaced, 98% of the calibration checks were within +/- 50 mL (1.7%). The measured volume was affected only minimally by the syringe's peak flow or emptying time. CONCLUSION: In these 70 EasyOne spirometers neither calibration nor linearity changed during the study. Such calibration stability is a valuable feature in spirometry surveys and in the clinical setting.

Brazil↗

PubMed1977

Role of coenzyme in aminotransferase turnover.

The role of coenzyme in determining intracellular contnet of pyridoxal enzymes was assessed by analyzing effects of pyridoxine deficiency on the rapidly degraded, readily dissociable tyrosine aminotransferase (EC 2.6.1.5) and the slowly degraded, nondissociable alanine aminotransferase (EC 2.6.1.2) of rat liver. Synthesis of the tyrosine enzyme was reduced, leading to a decreased amount of this enzyme, much of which was present as active apoenzyme. Synthesis of alanine aminotransferase was unchanged but much of this enzyme was present as an inactive apoenzyme which retained immunological reactivity. Degradation rates of both enzymes (t1/2 about 1.5 h, tyrosine aminotransferase; about 3 days, alanine aminotransferase) were not changed in pyridoxine deficiency. Hence, interaction with coenzyme is not a significant determinant in intracellular degradation of these aminotransferases. Coenzymes dissociation and intracellular stability probably reflect structural features of the proteins which determine both properties.

Alanine Transaminase↗

PubMed1991

[Application of differential derivative spectrophotometry to the determination of total chlorogenic acid in Lonicera japonica Thunb. and yinqiao jiedu pian].

The total chlorogenic acid in Lonicera japonica and yinqiao jiedu pian was determined by differential derivative spectrophotometry in this paper. Quantitative analysis of this component in eight mixtures of medicinal herbs can be done without any separation. The average recovery of total chlorogenic acid is 100.40 +/- 1.82% (CV). The method features good reproducibility, favorable stability and high sensitivity.

Chlorogenic Acid↗

PubMed1990

[Application of equal value derivative spectrophotometry to the determination of coptis alkali in wanshi niuhuang qingxin pills].

The total coptis alkaloids Wanshi Niuhang Qingxin Pills were determined by equal value derivative spectrophotometry in this paper. Quantitative analysis of six mixtures of medicinal herbs can be done easily on the extract. The average recovery of berberine.HCl is 98.55 +/- 1.90% (CV). The method features good reproducibility, favorable stability and high sensitivity.

Alkaloids↗

PubMed1989

Contribution to the developmental cycle and taxonomy of Neoglyphe sobolevi Shaldybin, 1953 (Trematoda: Omphalometridae).

In Europe, the life cycle of the trematode N. sobolevi was studied for the first time. Following developmental stages are described in detail: daughter sporocysts, cercariae, metacercariae, adults. Snails Galba corvus and Lymnaea stagnalis were found to be the first intermediate hosts in nature. Metacercariae were obtained experimentally from larvae of the mosquitoes Culex pipiens molestus, adults from the intestine of hamsters (Mesocricetus auratus) and mice (Mus musculus). This is the first finding of this species in Czechoslovakia. The stability of taxonomically important features and comparison with closely related species is discussed.

Animals↗