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Biomedical subjects

Y L Chou

Publications and source records attributed to Y L Chou.

At least 37 records · Page 2Linked to original sources
PubMed1995

Strength of the pin-bone interface of external fixation pins in the iliac crest. A biomechanical study.

The iliac crest is a frequent insertion site for external fixation pins in treating unstable pelvic or acetabular fractures and in iliofemoral distraction for superiorly dislocated hips. The pin-bone interface is critical for the success of treatment, but studies of the iliac crest are lacking. The purpose of this study was to investigate the strength of the pin-bone interface of different pins and different insertion methods. Four types of commercial pins, Wagner pins, Orthofix cortical and cancellous screws, and AO pins, were driven into sheep iliac crests by 2 methods: the intercortical and the transcortical. Specimens were tested for pullout and bending with an Instron testing machine (Model 1343) at a extension rate of 0.02 mm/sec to failure. The results revealed that the intercortical method had a stronger pullout force than the transcortical in all types of screws (p < 0.05), probably caused by longer insertion in the bone. In the pullout tests, the Wagner pins were the strongest and the Orthofix cancellous screws were the weakest. There were no differences in bending. In the iliac crest, the intercortical method was the better way of driving pins, and the new Orthofix screws were not proven to be stronger than the Wagner pins, nor were the cancellous screws more suitable than the cortical ones.

Animals↗
PubMed1995

[Application and evaluation of multiple exposure photography and motion analysis system in gait measurement].

Accurate techniques to evaluate and quantitate gait patterns have been available in clinical applications for the last 20 years. In this study, by employing multiple exposure photography, the walking velocity, stride length, step cadence and joint angle of the lower limbs were recorded for normal young men during the gait cycle. Data were compared with results from the motion analysis system and related researches. The results showed that multiple exposure photography can also provide quantitative analysis of several important time-distance parameters in the gait cycle.

Adult↗
PubMed1994

Measurement of organ volume by single photon emission computed tomography.

The aim of this study was to develop a new algorithm for volume determination by single photon emission computed tomography (SPECT). Different algorithms were evaluated through phantom studies. The results show that the algorithm combining moment-preserving bilevel thresholding and best-fit Laplacian second derivative edge detection can provide the most accurate measurement of volume. Besides, this method can be utilized in different SPECT systems with no need for further phantom studies. In patient studies, the results of liver volume calculation have indicated that this is a useful technique in clinical medicine.

Algorithms↗
PubMed1994

Significance of acceleration period in a dynamic strength testing study.

The acceleration period that occurs during isokinetic tests may provide valuable information regarding neuromuscular readiness to produce maximal contraction. The purpose of this study was to collect the normative data of acceleration time during isokinetic knee testing, to calculate the acceleration work (Wacc), and to determine the errors (ERexp, ERwork, ERpower) due to ignoring Wacc during explosiveness, total work, and average power measurements. Seven male and 13 female subjects attended the test by using the Cybex 325 system and electronic stroboscope machine for 10 testing speeds (30-300 degrees/sec). A three-way ANOVA was used to assess gender, direction, and speed factors on acceleration time, Wacc, and errors. The results indicated that acceleration time was significantly affected by speed and direction; Wacc and ERexp by speed, direction, and gender; and ERwork and ERpower by speed and gender. The errors appeared to increase when testing the female subjects, during the knee flexion test, or when speed increased. To increase validity in clinical testing, it is important to consider the acceleration phase effect, especially in higher velocity isokinetic testing or for weaker muscle groups.

Acceleration↗
PubMed1994

Study of low-temperature thermoplastic modified custom-molded cervical orthosis for cervical spine fixation.

The purpose of this experiment is to use a low-temperature thermoplastic material (Aquaplast) to make a modified custom-molded cervical orthosis. Sixteen normal young subjects who do not have previous cervical problems are tested in this study. This modified orthosis is applied on these volunteers so that external fixation of the cervical spine can be tested. Various roentgenograms for cervical flexion and extension, as well as neutral position and lateral bending, are taken to determine the fixation property of the cervical spine. A study of rotation of the cervical spine is also carried out through goniometer measurements. This clinical study proves that this low-temperature thermoplastic cervical orthosis provides good fixation for the cervical spine, especially in flexion and rotation, but is not suitable for C1- and C2-injured patients.

Adult↗
PubMed1994

Electromyographic analysis of habituation processes of treadmill walking to floor walking.

Electromyography (EMG) is an essential tool for assessing muscle performance in human locomotion. The aim of this research is to utilize EMG for assessing the habituation processes of normal adults during treadmill walking compared to floor walking. In this research, EMG activity is presented in linear envelope (LE) form to meet physiological meanings and parameter estimation. The EMG LE is generated from the raw EMG signal through band-pass filtering, rectifying, integration, and normalization procedures. The ensemble averaging of EMG LEs is used to demonstrate the pooled data of six normal subjects. The variance ratio (VR) of the EMG LE is applied to analyze the repeatability of EMG activity and thus to quantify the habituation process of normal adults walking on a treadmill. The habituation results indicated that no pretibial group reached a steady state during 12 minutes of treadmill walking. However the majority of calf groups habituated after 2 minutes of treadmill walking. In addition, changes in EMG phasic activities could be observed for both pretibial and calf groups during treadmill walking.

Adult↗
PubMed1993

(Imidazolylphenyl)pyrrol-2-one inhibitors of cardiac cAMP phosphodiesterase.

Seven 3-alkyl-4-aryl-1,5-dihydro-2H-pyrrol-2-ones were prepared as potential inhibitors of cardiac cAMP phosphodiesterase (PDE). The design of these compounds made use of rolipram, a known inhibitor of the brain cAMP PDE isozyme, as a lead structure and was guided by a model which describes the features required for potent inhibition of the cardiac isozyme. Syntheses for the new compounds are described, together with the results of theoretical and crystallographic studies aimed toward ascertaining their three-dimensional structures. The activities of these compounds as inhibitors of the cardiac and brain cAMP PDE isozymes and their positive inotropic activity in ferret papillary muscle are also reported. Selected compounds were further examined in an in vivo hemodynamic model. One compound 1,5-dihydro-4-[4-(1H-imidazol-1- yl)phenyl]-3-methyl-2H-pyrrol-2-one, was identified as a potent and selective positive inotropic agent and inhibitor of cardiac cAMP PDE.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1991

A topographical model for the c-AMP phosphodiesterase III active site.

With this minireview, concepts about how c-AMP and various inhibitor molecules interact with the phosphodiesterases seem to have come full-circle. It will be proposed and elaborated herein that an understanding of SAR for the newest, "second generation" PDE inhibitors is best accomplished by adopting a model that supposes that these compounds are transition state inhibitors. The analysis finds an interesting parallel with early studies where it was recognized that c-AMP adopts a trigonal bipyramid transition state during hydrolysis. The dynamic interaction of ligands with the phosphodiesterase enzymes will also be made evident when simple algebraic expressions are shown to be inadequate for predicting inhibitor potencies. The latter are apparently complicated by cooperative or synergistic relationships that occur among the various binding sites within the receptor. Finally, implications that can be derived from certain topographical features of the model are discussed relative to a range of potential therapeutic indications.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1991

Synthesis and biological activity of angiotensin II analogues containing a Val-His replacement, Val psi[CH(CONH2)NH]His.

The dipeptide mimic Val psi[CH(CONH2)NH]His (4) was incorporated into angiotensin II (AII) analogues to provide an octapeptide saralasin derivative (29) as well as tetrapeptide analogue 19. Three C-terminal tetrapeptides (21, 25, and 28) were also prepared. All compounds were tested for their ability to displace 3H-AII from rabbit adrenal gland homogenate and as antagonists of AII and AI on guinea pig ileum. The octapeptide analogue 29 was 700 times less active than the parent peptide 30. All the C-terminal fragments 19, 21, 25, and 28 have no measurable AII antagonist activity. Of the four tetrapeptide fragments, only 21 showed any appreciable binding activity.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1991

[Quantification of acetabular coverage in normal adult].

Quantification of acetabular coverage is important and can be expressed by superimposition of cartilage tracings on the maximum cross-sectional area of the femoral head. A practical Autolisp program on PC AutoCAD has been developed by us to quantify the acetabular coverage through numerical expression of the images of computed tomography. Thirty adults (60 hips) with normal center-edge angle and acetabular index in plain X ray were randomly selected for serial drops. These slices were prepared with a fixed coordination and in continuous sections of 5 mm in thickness. The contours of the cartilage of each section were digitized into a PC computer and processed by AutoCAD programs to quantify and characterize the acetabular coverage of normal and dysplastic adult hips. We found that a total coverage ratio of greater than 80%, an anterior coverage ratio of greater than 75% and a posterior coverage ratio of greater than 80% can be categorized in a normal group. Polar edge distance is a good indicator for the evaluation of preoperative and postoperative coverage conditions. For standardization and evaluation of acetabular coverage, the most suitable parameters are the total coverage ratio, anterior coverage ratio, posterior coverage ratio and polar edge distance. However, medial coverage and lateral coverage ratios are indispensable in cases of dysplastic hip because variations between them are so great that acetabuloplasty may be impossible. This program can also be used to classify precisely the type of dysplastic hip.

Acetabulum↗
PubMed1991

[Evaluation of the effects of pulling angle and force on intermittent cervical traction with the Saunder's Halter].

Intermittent cervical traction with proper angle and force is an effective treatment for cervical syndrome. The goals of therapy are effective traction for the affected segments without further damage to the soft tissue. The purposes of this study were to find the traction angle and force which results in the best therapeutic effect. The effect of cervical traction was evaluated by cervical roentgenography, by examining the distance of the posterior margin of the intervertebral space. For a study of the proper angle of traction, intermittent cervical traction was applied to 20 healthy normal volunteers in a supine position with a constant traction force of 15 kgf. The traction lasted for 8 seconds followed by unloading for 4 seconds and the application was alternated after 10 minutes. The elongated gaps of the posterior vertebral margins obtained from the different neck flexion angles of 35, 30, 25, 20 and 15 degrees were compared. Traction of under 30 degrees was longest for the levels of C4- 5 and C5-6. For the C6-7 and C7-T1 levels, traction was longest under 35 degrees. For study of the minimal effective traction force, the same procedures of intermittent cervical traction were applied to another 15 healthy normal volunteers, except the neck was fixed in a flexion of 35 degrees, and the traction force was 9, 12, 15 and 18 kgf. The best results were noted with a traction force of 15 or 18 kgf. However, there were more complaints of neck discomfort after traction with a force of 18 kgf.

Adult↗
PubMed1990

Cardiotonic agents. 6. Histamine analogues as potential cardiovascular selective H2 agonists.

Twenty-six alkyl and aralkyl histamine analogues were prepared as potential cardiotonic agents. Compounds were designed to allow interaction with a putative secondary aryl binding site at the H2 receptor, the presence of which was inferred from the structure of cyprohepatadine, which is known to have H2-antagonist properties. The compounds were examined for inotropic activity in ferret papillary muscle. Potent inotropic activity was generally found in N-alkyl- and N,N-dialkylimidazole-4-ethanamines, whereas N-(amidoalkyl)imidazole-4-ethanamines and N-alkylimidazole-4-propanamines were at best weakly active. Five compounds were examined in screens designed to assess hemodynamic effects and gastric acid secretion in vivo. Two of these compounds, alpha-(3-phenyl-2-transpropenyl)-1H-imidazole-4-ethanamine and N-heptyl-1H-imidazole-4-ethanamine, showed positive inotropic activity with minimal effects on heart rate and mean arterial pressure in vivo; however, both compounds were found to stimulate gastric acid secretion. These results demonstrate that selectivity between various H2-receptor-mediated activities can be obtained with substituted histamine analogues.

Animals↗
PubMed1990

[Application and evaluation of the VICON system in gait analysis].

By employing the VICON system, segment angular displacement, velocity and acceleration of the lower limbs were achieved from an Above-Knee (A/K) Amputee using a constant friction prosthesis during the swing phase of the gait cycle. By applying computer for data analysis and inputing anthropometric data of the (A/K) Amputee, kinematic trajectory and a stick diagram of lower limbs were obtained. The data were then compared with those obtained from normal subjects. The results showed that the VICON system can provide quantitative analysis of several important parameters in the gait cycle and that it is very helpful in the evaluation and rehabilitation training of abnormal gait.

Adult↗
PubMed1989

[A case report and metallurgical analysis of broken Luque rod].

Wire breakage is frequently mentioned in Luque rod instrumentation with segmental sublaminar wiring, but breakage of the Luque rod is rare. A case report of a broken Luque rod in a patient following a scoliosis post-corrective operation is presented and a metallurgical analysis is provided to evaluate the mechanism of breakage. In the metallurgical analysis, we find many slots and dimples on the rod surface which were induced by an inappropriate bending apparatus and bending manipulation. These defects resulted in a stress concentration effect and initiated fatigue. As for the stress on the rod, this resulted from the force correcting the scoliotic deformity plus the load resulting from patient's daily activity, which increased the progression of fatigue and then induced the final breakage. So, to avoid Luque rod breakage we suggest that the bending manipulation be done appropriately, with external orthosis given to those patients with severe deformity or who are daily very active.

Adult↗
PubMed1988

Platelet deposition onto fibrin-coated surfaces under flow conditions.

Platelet deposition on fibrin-coated surfaces and release from these adherent platelets were studied in an in vitro flow system. When a mixed suspension of washed platelets and red cells flowed through a fibrin-coated glass tube, only platelets were deposited onto the fibrin-coated surfaces. The density of adhered platelets increased with flow time and decreased with distance from the tube inlet. The adhesion rate increased with increasing shear rates from 45 s-1 to 180 s-1. This adhesion process appears to fit a diffusion-limited mathematical model. Comparing with glass and other protein-coated surfaces such as collagen, fibrinogen, or albumin coated surfaces, the number of adhered platelet per unit area decreased in the following descending order: collagen, fibrin, fibrinogen, glass, albumin. On the other hand, the degree of release reaction from these platelets decreased by another order: collagen, glass, fibrinogen, fibrin. We observed little release from platelets that were in contact with a fibrin-coated surface. Our results suggest that platelets specifically adhere to fibrin-coated surface and that this interaction does not induce platelet release.

Cells, Cultured↗
PubMed1987

Cardiotonic agents. 2. (Imidazolyl)aroylimidazolones, highly potent and selective positive inotropic agents.

A series of 4-alkyl-1,3-dihydro-5-[(1H-imidazolyl)benzoyl]-2H-imidazol-2-ones 9 was synthesized and evaluated in vitro for positive inotropic and cyclic AMP phosphodiesterase inhibitory activity. A wide range of inotropic and enzyme-inhibitory potencies was observed, substitution on the imidazolyl moiety being the major determinant of activity. The 4-ethyl-5-[4-(1H-imidazol-1-yl)benzoyl] congener 9g exhibited the highest potency in vitro. Incorporation of a methyl group at the imidazolyl 2-position gave 9h, which was less potent but remarkably selective in vivo for positive inotropic effects over heart rate and hypotensive effects.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMedDate not supplied

Chemical dissolution of gallstones in Taiwan: an in vitro study.

To evaluate the potential for the chemical dissolution of gallstones, 480 stones from 214 patients were studied. The stones were obtained via surgery or endoscopically. They were classified into cholesterol-rich mixed stones, brown pigment stones and black stones. The composition of bilirubin and cholesterol was determined by Fourier transformed infrared spectroscopy. Two per cent tetrasodium ethylenediamine acetate (EDTA), dimethylsulfoxide (DMSO) or methyl-tert-butyl-ethylene (MTBE) were used to dissolve the stones. To enhance solubility, surfactant polysorbate-20 was used to mix two of the individual three solvents. Methyl-tert-butyl-ethylene was found to have the best dissolution ability (by dry weight) 94, 13.4 and 20% for mixed, brown and black stones, respectively. Dimethylsulfoxide resulted in 13, 14 and 25% dissolution and EDTA 9.5, 13 and 16.5%. In contrast, pure water dissolved 4, 6 and 10.4% of the stones, respectively. A combination of the dissolution agents did not enhance the dissolution rate. In fact, the combination of solvents unexpectedly reduced the solubility of the stones: EDTA/MTBE was 17.5, 6.7 and 16.0%; DMSO/MTBE 43.2, 21.9 and 18.0%; DMSO/EDTA 9.1, 7.0 and 9.6%. In conclusion, cholesterol-rich mixed stones were able to be dissolved using MTBE but results of contact dissolution for gallstones are still far from satisfactory.

Cholelithiasis↗