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Y L Chou

Publications and source records attributed to Y L Chou.

11 recordsLinked to original sources
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

Regeneration of plants from tobacco protoplasts and some factors affecting the plant differentiation.

Protoplasts were isolated from the cell suspension culture derived from leaf and stem calli of tobacco (Nicotiana tabacum cv. Ko Hsin No. 1) haploid pollen-plants. After 12 hr in the liquid culture medium, the protoplasts became oval-shaped, and produced a new cell wall. The first division of the newly formed cells was completed after 24 hr in culture. After 4 weeks in culture, the yellowish calli reached 1 mm in size were then transferred to an auxophyton. 18 days later, the calli became 3-4 mm in size. After the calli were transferred to a differentiation culture medium, shoots and roots soon turned up. Regeneration of whole plants was obtained thereafter. The division and differentiation of regenerated cells were affected not only by the calli originated from different organs and their, age, but also by the basic components of the differentiation culture medium and the type of cytokinin used.

Cell Differentiation↗