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Biomedical subjects

J H Gao

Publications and source records attributed to J H Gao.

17 recordsLinked to original sources
PubMed1990

[Studies on the stereochemistry and structure-activity relationship of cholinolytic compounds 3-(2-phenyl-2-cyclopentyl-2-hydroxyl-ethoxy)-quinuclidines].

Four optical isomers of the new cholinolytic compound 3-(2-phenyl-2-cyclopentyl-2-hydroxyl-ethoxy)-quinuclidine (I) have been asymmetrically synthesized by two methods. Method one: Recemic 1-phenyl-1-cyclopentylepoxyethane reacting with 3R or 3S-quinuclidinol produces a mixture of (R-1) and (R-2) or (S-1) and (S-2) respectively. The chemical yields varied from 57% to 78%. The highest % de is 22 and the major product is (R-1) or (S-1). Method two: Grignard reaction of 3R or 3S-benzoyl-methoxy-quinuclidine with cyclopentyl magnesium bromide yields a mixture of (R-1) and (R-2) or (S-1) and (S-2). The chemical yield is 80%. The highest % de is 81 and the major product is (R-2) or (S-2). Preliminary evaluation of the four new optical isomers revealed the following series of biological potencies: (R-2) greater than (I) greater than (S-1) greater than (R-1) greater than (S-2). In the coupling of the compounds with the active centers of M receptors, the absolute configurations in carbon-3 of the quinuclidinyl group and carbon-2 of the substituted ethyl group play an important role. The influence of carbon-2R is greater than that of carbon-3R on cholinolytic potency.

Animals↗
PubMed1989

[Evaluation of the clinical application of 5 kinds of free upper arm flaps].

At present, there are mainly 5 kinds of free upper arm flaps selected for clinical application: superior-lateral, middle-lateral, inferior-lateral and medial and posterior upper arm flaps. We have performed 17 transplantations using the 5 kinds of the free flaps since 1983, 16 cases with satisfied results. Among the 17 transplantations, 8 flaps were superior-lateral, 4 middle-lateral, 1 inferior-lateral, 2 medial and 2 posterior up arm flaps. The flaps were used for repairing 12 defects on hands, 4 on faces, and 1 on elbow. The maximum size of the flaps is 19 x 11 cm, the minimum 6 x 9 cm. We believe that: (1) the flaps of upper arms are suitable for the reconstruction of small defects of both hands and faces; (2) among the 5 kinds of free flaps, the superior-lateral flap has more advantages than the others; (3) the main principle of the transplantation is to know the landmarks of the vessels as well as to distinguish the muscular spaces passed by the vessels.

Adolescent↗
PubMed1989

[1H, 13C NMR and stereochemistry studies of 3S-substituted alkoxylquinuclidine by two-dimensional and NOE difference NMR techniques].

By using optically pure 3S-quinuclidinol, two diastereoisomers (3S-1) and (3S-2) of 3-(substituted) alkoxy-quinuclidine were synthesized. 1H and 13C NMR spectra of (3S-1) and (3S-2) have been completely analyzed utilizing double-quantum filtered COSY, 13C-1H COSY and NOE difference experiment. The NOE difference experiment was used to determine the absolute configuration at C-11 of the diastereomers. According to the results of NOE difference and variable concentration NMR experiments, the configuration about C-11 of (3S-1) is designated as R (1A), whereas the configuration about C-11 of (3S-2) is designated as S (1B). The result was confirmed by X-ray diffraction analysis.

Magnetic Resonance Spectroscopy↗
PubMed1988

Applied anatomy of the anterolateral femoral flap.

A study of the source of the blood supply to the anterolateral femoral flap was carried out on 42 lower limbs of adult cadavers (among them 35 cadavers with injection of red latex and 1 with india ink into the arteries and 6 vascular cast specimens), and the surface locations of the vascular pedicle were detected on 50 healthy adults. It was found that the descending branch of the lateral circumflex femoral vessel was an ideal axial vessel. There are constant perforating branches of the myocutaneous artery or cutaneous branches from the intermuscular space to the anterolateral femoral skin. The area extends about 12 x 30 cm. Within the flap, the anterior branch of the anterolateral cutaneous nerve of the high is located. This flap has been widely used for free transplantation in China since 1983 with satisfactory results.

Adult↗
PubMed1985

Experimental end-to-side anastomosis of arteries less than one millimeter in diameter and clinical applications.

Experimental end-to-side anastomoses of rabbit arteries less than 1.0 mm in diameter were performed. Technical details, angle of inset, and vessel opening discrepancy are discussed. We emphasize the value of end-to-side arterial anastomoses in increasing the patency rates of anastomoses and consequently the survival rates of composite graft transfers. Twenty-eight clinical free composite tissue transfers using end-to-side arterial anastomoses were completed with total graft survival.

Animals↗
PubMedDate not supplied

Nuclear magnetic resonance signal from flowing nuclei in rapid imaging using gradient echoes.

A theoretical description of the nuclear magnetic resonance (NMR) signal from flowing nuclei has been developed for rapid imaging sequences that use small flip angles and gradient refocused echoes. Both laminar and plug flow models have been considered and formulas derived relating mean image signal intensity to flip angle, pulse sequence repetition interval (TR), and flow velocity. It is shown that the rate of approach to steady-state conditions determines the degree of flow enhancement. Experimental measurements have been performed on a flow phantom in a whole-body NMR imaging system operating at 0.15 T using the spoiled FLASH sequence with different radiofrequency pulse flip angles and flow rates. There is excellent agreement between the experimental results and the theoretical predictions up to the onset of turbulence.

Blood Flow Velocity↗
PubMedDate not supplied

Turbulent flow effects on NMR imaging: measurement of turbulent intensity.

A general expression has been derived for the NMR signal from a fluid in steady but turbulent flow in a magnetic field gradient. The precise dependences of the spin echo amplitude on both flow and experimental parameters are described in terms of the temporal autocorrelation function for velocity fluctuations in the fluid. The correlation function width determines whether a diffusion model of turbulent eddies is valid, and for physiological flow in large vessels in NMR imaging a more appropriate measure is the turbulent intensity of velocity fluctuations. The theoretical predictions have been verified in experiments using gradient echo images of flowing water. The theory also predicts that even echo rephasing phenomena may still occur in MR imaging of turbulent flows.

Humans↗
PubMedDate not supplied

A numerical investigation of the dependence of NMR signal from pulsatile blood flow in CINE pulse sequences.

The Bloch equations have been solved using numerical techniques for a uniform fluid undergoing periodic pulsatile flow in an NMR imaging experiment. The magnetization and NMR signal have been calculated for experimental parameters appropriate for a CINE sequence (TR = 40 ms, (TE = 14 ms) applied to the study of pulsatile aortic or other arterial flows. The flow velocity profile is obtained by Fourier superposition of different harmonics and it is shown that the steady-state NMR signal has reduced high-frequency components. There is also a time delay between peak signal intensity and flow because the backflow effects that can be as much as 100 ms. The apparent pulsatility depends on the NMR sequence parameters. Some limitations of the phase contrast flow-imaging method are also discussed for nonuniform flow.

Blood Flow Velocity↗