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Biomedical subjects

G Ouyang

Publications and source records attributed to G Ouyang.

14 recordsLinked to original sources
PubMed2000

Evidence for cleft closure in actomyosin upon ADP release.

Structural insights into the interaction of smooth muscle myosin with actin have been provided by computer-based fitting of crystal structures into three-dimensional reconstructions obtained by electron cryomicroscopy, and by mapping of structural and dynamic changes in the actomyosin complex. The actomyosin structures determined in the presence and absence of MgADP differ significantly from each other, and from all crystallographic structures of unbound myosin. Coupled to a complex movement ( approximately 34 A) of the light chain binding domain upon MgADP release, we observed a approximately 9 degrees rotation of the myosin motor domain relative to the actin filament, and a closure of the cleft that divides the actin binding region of the myosin head. Cleft closure is achieved by a movement of the upper 50 kDa region, while parts of the lower 50 kDa region are stabilized through strong interactions with actin. This model supports a mechanism in which binding of MgATP at the active site opens the cleft and disrupts the interface, thereby releasing myosin from actin.

Actins↗
PubMed1999

[Low fever of unknown reason in patients undergoing autologous stem cell transplantation after hematopoietic reconstitution: a clinical analysis of 13 cases].

OBJECTIVE: To investigate the reason of low fever in patients undergoing autologous stem cell transplantation after hematopoietic reconstitution. METHODS: The reasons for low fever in 13 patients undergoing autologous stem cell transplantation after hematopoietic reconstitution were comprehensively analyzed. RESULTS: After analysis of clinical features, laboratory tests, imaging and microbiological data, no reason was found for the low fever. There was no effect on the fever with anti-microbial therapy. However the low fever was controlled by low dose prednisone 5-10 mg/d or dexamethasone 2-4 mg. CONCLUSION: The reason for the low fever is not clear; it is probably nonspecific low fever induced by high-dose radiotherapy or high-dose chemotherapy.

Adolescent↗
PubMed1998

[Three dimensional finite element analysis on the mandibular complete overdenture supported by nature roots or implants].

OBJECTIVE: To investigate the stress distribution around the bone tissue of overdenture supported by teeth roots or implants in the process of mastication which may assist to improve the design of the dentures. METHODS: By means of CT scan, CAD and a three distribution finite element methods to study the stress distribution of the supporting tissue of overdenture supported by roots or implants when various attachment retentive apparatus and various bite forces were applied. RESULTS: No matter overdenture supported by roots or implants the stress distribution on bone tissue are difference between the bar and stud attachments, However these difference were minor compared with the difference caused by the direction of force. The stress value of cortical bone around the roots or implants with twenty degree oblique force is 2.2-3 times higher than that with vertical force. Overdenture supported by implants produced 2.5-4 times higher stress in the cortical bone around than that of overdenture supported by roots when various superstructures or various loads were applied. CONCLUSION: It must consider to reduce the stress peaks and provent bone resorption by increasing the number of implants and using the force-breaking design of implant super-strcture when the overdenture were supported with implants only.

Dental Implants↗
PubMed1998

[The three-dimensional analysis of mandibular overdenture supported by implants].

In recent decade, the treatment in which two or four implants are placed in an edentulous patient to support an overdenture has been more effective and safe, and the retention and stability of overdenture have been improved by the use of attachments fabricated on implant abutments. This study aimed to investigate the supporting tissue stress distributions of implant-overdenture with a 3-D finite element model built by CT scan and CAD technology when various attachments and loads were used respectively. The results demonstrated that the establishment of the three-dimensional finite element model with CT scan and CAD technique had saved time and effort, and it did not damage the experiment model. The tissue structure was quite distinct in imaging. In terms of the stress distribution of bone tissue in the overdenture supported by implant, there was a difference between bar attachment and stud attachment. However, such a difference was minor as compared with the difference caused by the bite force direction. The stress value of cortical bone around abutment with 20 degree oblique force was 2.2-3 times that with vertical force. Therefore, to reduce high stress peaks, attention must be paid to the direction of the bite force, as this variable is much more important than the design of superstructure.

Aged↗
PubMed1995

A minimal motor domain from chicken skeletal muscle myosin.

The myosin head (S1) consists of a wide, globular region that contains the actin- and nucleotide-binding sites and an alpha-helical, extended region that is stabilized by the presence of two classes of light chains. The essential light chain abuts the globular domain, whereas the regulatory light chain lies near the head-rod junction of myosin. Removal of the essential light chain by a mild denaturant exposes the underlying heavy chain to proteolysis by chymotrypsin. The cleaved fragment, or "motor domain" (MD), migrates as a single band on SDS-polyacrylamide gel electrophoresis, with a slightly greater mobility than S1 prepared by papain or chymotrypsin. Three-dimensional image analysis of actin filaments decorated with MD reveals a structure similar to S1, but shorter by an amount consistent with the absence of a light chain-binding domain. The actin-activated MgATPase activity of MD is similar to that of S1 in Vmax and Km. But the ability of MD to move actin filaments in a motility assay is considerably reduced relative to S1. We conclude that the globular, active site region of the myosin head is a stable, independently folded domain with intrinsic motor activity, but the coupling efficiency between ATP hydrolysis and movement declines markedly as the light chain binding region is truncated.

Actins↗
PubMed1995

[A study of the relationship between electromyographic activity of the masticatory muscles and the variations of the occlusal vertical dimension for edentulous subjects]

The study was performed in fifteen edentulous subjects with the EMG activity were recorded at the varying occlusal vertical dimension maintaining constant bite force value of 4kg.The results showed that maintaining constant bite force the amplitudes of EMG activity of the anterior temporal and masseter muscles are decreased with increasing the occlusal vertical dimension and correlation relation between them,that there is a stable region about 1.0mm for the anterior temporal muscle and about 1.5mm for the masseter muscle during the changes in electrical activity.It is represent that there is a physiological region of the occlusal vertical dimension for edentulous patient.

Journal Article↗
PubMed1994

Ultrastructure of skeletal muscle fibers studied by a plunge quick freezing method: myofilament lengths.

We have set up a system to rapidly freeze muscle fibers during contraction to investigate by electron microscopy the ultrastructure of active muscles. Glycerinated fiber bundles of rabbit psoas muscles were frozen in conditions of rigor, relaxation, isometric contraction, and active shortening. Freezing was carried out by plunging the bundles into liquid ethane. The frozen bundles were then freeze-substituted, plastic-embedded, and sectioned for electron microscopic observation. X-ray diffraction patterns of the embedded bundles and optical diffraction patterns of the micrographs resemble the x-ray diffraction patterns of unfixed muscles, showing the ability of the method to preserve the muscle ultrastructure. In the optical diffraction patterns layer lines up to 1/5.9 nm-1 were observed. Using this method we have investigated the myofilament lengths and concluded that there are no major changes in length in either the actin or the myosin filaments under any of the conditions explored.

Actin Cytoskeleton↗
PubMed1993

[A comparative study of masticatory efficiency between partial denture wearers having one remaining tooth and complete denture wears]

Masticatory efficiency is one of the important indexes of judging masticatory function after dentures restored.The aim of this study was to measure and analyze masticatory efficiency of partial dentur wearers having one tooth left and complete denture wearers,by using a method of measuring msticatory crushed granules.The results showed that the crushed granules for partial denture wearers with one remaining tooth were smaller than that for complete ones.Therefore,partial dentures with a few remaining teeth were better than complete ones on effects.

Journal Article↗
PubMed1992

Frequency analysis of electromyographic signals in mandibular elevators at maximum clench level.

Power spectral analysis of electromyogram (ENG) was used to investigate the relationship between mean power frequency (MPF) and sustained contraction time. Surface EMG activity was recorded from masseter and anterior temporal muscles on both sides for seven healthy subjects while clenching at intercuspal position in maximum potential level of these muscles. A visual sense feedback of EMG potential was used to control clenching level. According to linear regression analysis, there was a negative correlation between MPF of EMG and sustained contraction time. The results indicate that the slope of MPF versus contraction time may be used for detecting muscular fatigue in the stomatognathic system.

Adult↗
PubMed1991

Power spectral analysis of electromyographic signal of masticatory muscles at rest position and habitual clench.

Thirteen normal subjects were selected for this investigation. At the vertical dimension of rest position and habitual clench, their myoelectric activities of the masseter, anterior and posterior temporal, and digastric muscles on the left and right sides were simultaneously sampled and processed by computer, and the mean power frequency (MPF) and the mean amplitude (MA) of the myoelectric signal were calculated. At rest position, the temporal muscles were major muscles and the MPF differences of various masticatory muscles were not significant. At habitual clench, with the increase in MA, the MPF of various muscles increased. The results show that MPF may have application in describing a central tendency of myoelectrical signal frequency distribution and in evaluating recruitment of motor units. MPF and MA are the quantitative indices reflecting masticatory muscle function.

Adult↗
PubMed1991

A comparative study of mastication between complete denture wearers and dentate subjects.

A computer system was used for simultaneously collecting and processing mandibular movements and the myoelectric activities of the masticatory muscles of 15 dentate subjects and 11 complete denture wearers. The displacement, velocity, cycle of mandibular movements, and the muscular mean potentials were indices in observing mastication. A good complete denture should perform with physiologic characteristics, and restore masticatory function and oral health. The kinetic energy from the velocities of lateral and vertical directions can serve for the chewing and comminution of food, but lateral comminution may affect denture retention. The mean myoelectrical potentials of the mandibular elevator muscles of complete denture wearers tend to increase at the opening phase; however, the potentials decrease at the closing phase.

Adult↗
PubMed1990

Comparison of food particle distribution masticated by subjects wearing complete dentures and with natural teeth.

The sizes of soya particles masticated by 12 complete denture wearers and 10 subjects with natural dentition were directly measured by means of a graphic digitizer and computer, following a varied number of chewing strokes. It was found that the chewed particle size frequency distributions of the two groups tended to a state of normal logarithm distribution. Compared with the dentate subjects, the mean, 20th, 50th and 80th percentile of the particle sizes chewed by complete denture wearers were increased, whilst the distribution shapes were nearly identical. The results suggest that there are no qualitative differences in the manner in which the two groups break up food. Selection and breakage functions of complete denture wearers are decreased, and this could be related to the denture conditions and the change of oral state in such individuals.

Adult↗