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Biomedical subjects

Y K Liu

Publications and source records attributed to Y K Liu.

At least 55 records · Page 3Linked to original sources
PubMed1987

Bone-particle-impregnated bone cement: an in vitro study.

Bone-particle-impregnated bone cement specimens (up to 30% by weight) were characterized by various test methods. The experimental bone cement showed decreased crack propagation rates and increased Young's modulus, while the ultimate tensile strength and impact strength were decreased. The viscosity could be adjusted by adding initiators lost when substituting the PMMA powder with bone particles. The present study warranted further in vivo experiments on the possibility of tissue ingrowth for which the new bone cement was developed.

Biocompatible Materials↗
PubMed1987

Pregnancy in Henoch-Schönlein purpura.

A 22-year-old white woman with Henoch-Schönlein purpura was treated with frequent plasmapheresis for increased severity of the disease activity during pregnancy. Hypertension, azotemia, and placental dysfunction were not observed. A healthy infant was delivered by cesarean section, and evidence of vasculitis was not detected in the placenta.

Adult↗
PubMed1987

A three-dimensional nonlinear finite element model of lumbar intervertebral joint in torsion.

Torsion as a cause of failure in the lumbar intervertebral joint was studied using a three-dimensional nonlinear finite element model. The role of facets and ligaments as well as the stress distributions in the posterior elements, the disk, the ligaments, and the vertebral body were examined. For physiological range of torsion, the facets carried 10 to 40 percent of the torque. The fiber stresses in the disk were the highest at the lateral margin of the outer layer of the annulus. Therefore, torsion itself is unlikely to cause posterior or posterolateral disk prolapse.

Biomechanical Phenomena↗
PubMed1986

Mechanical properties of lumbar spinal motion segments as affected by partial disc removal.

The changes in the three-dimensional motion behavior of the lumbar motion segments, as affected by partial discectomy, are presented. The injured specimens, when subjected to flexion, extension, lateral bending, or axial torsional loads, showed significant increases in their major motions when compared with the corresponding intact specimen. No significant increases in the coupled motions were observed. These results suggest that it is better to excise as little of the nucleus as possible at surgery, since it may limit the increase in motion due to the injury.

Aged↗
PubMed1986

The material properties of bone-particle impregnated PMMA.

The elastic Young's modulus and shear modulus of bone-particle impregnated polymethylmethacrylate (PMMA) has been measured experimentally at room temperature as a function of bone particle concentration. It was found that the moduli increased with increasing bone particle content. This increase was less than the stiffness increase predicted by higher-order composite theory [1, 2] under the assumption of perfect bonding between particles and matrix. It was concluded that a bond existed but that it was not a perfect bond.

Bone and Bones↗
PubMed1985

Heparin-induced thrombocytopenia and recurrent thromboembolism in siblings.

Two brothers with heparin-induced thrombocytopenia and multiple arterial and venous thromboembolism affecting peripheral vessels are described. Heparin-dependent antiplatelet antibody was detected using platelet aggregometry in both patients. Although these observations may be coincidental, the possibility of familial occurrence of this adverse reaction to heparin cannot be excluded with certainty.

Disease Susceptibility↗
PubMed1985

Torsional fatigue of the lumbar intervertebral joints.

The effect of cyclic torsional loads on the behavior of intact lumbar intervertebral joints was investigated. A total of 24 specimens, divided in two groups, were tested. In the first group, a specimen was subjected to a specified constant cyclic torque, and the resulting change in angular displacement with time was recorded. The specimens in the second group were subjected to a specified constant angular displacement and the resultant torque recorded. The results of the constant torque tests showed that fatigue failure was primarily a function of the averaged initial angular displacement and secondarily of the applied torque. The critical threshold values appear to be an initial angular displacement of +/- 1.5 degrees. All specimens, displaying an averaged initial angular displacement of less than +/- 1.5 degrees, did not fail in fatigue, while the others did. However, the specimens with angular displacements of less than +/- 1.5 degrees had lower applied torques (11.3 and 22.6 Nm), while specimens with higher applied torques (33.9 and 45.2 Nm) all exceeded the +/- 1.5 degrees threshold and failed in fatigue. Failure locations occurred in such diverse regions as end-plates, facets, laminae, capsular ligaments, etc. All specimens exhibited a synovial fluid discharge from the apophyseal joint capsule sometime during testing. Post-test examinations of all the cartilage surfaces showed fibrillation, whether or not the intervertebral joint failed.

Adult↗
PubMed1985

Immunologic thrombocytopenia in pregnancy; use of antenatal immunoglobulin therapy: case report and review.

Steroid therapy remains the treatment of choice for immunologic thrombocytopenia in pregnancy. However, for cases refractory to steroid therapy, alternate forms of treatment must be used. This case report and review discusses a successful technique for acute, short-term correction of thrombocytopenia. In limited experience the administration of high-dose immunoglobulin appears to be effective for antepartum use in patients with immunologic thrombocytopenia. The concomitant or subsequent performance of splenectomy appears to be a valuable adjunct in long-term treatment of this condition.

Adult↗
PubMed1984

Treatment of uraemic bleeding with conjugated oestrogen.

A conjugated oestrogen preparation ('Premarin') was given to 6 uraemic patients with abnormal bleeding tendency in whom bleeding time was more than 30 min despite their being on chronic dialysis. In 4 patients the bleeding time became normal after 2 to 5 days of premarin therapy. In 1 of the 4 the prolonged bleeding time was repeatedly restored to normal (less than 7 min) after a single dose of premarin (25 mg). Bleeding time remained normal for 3 to 10 days after discontinuation of premarin. Bleeding time was significantly shortened (11 min) in the other 2 patients after 7 and 9 days of treatment. There was no consistent improvement in platelet aggregation nor increase in plasma factor-VIII-ristocetin cofactor activity during premarin therapy. 5 patients underwent surgery without abnormal bleeding. There were no side effects associated with premarin administration. Premarin treatment may be beneficial to uraemic patients with abnormal bleeding.

Adult↗
PubMed1984

Procainamide-induced thrombocytopenia.

An 81-year-old female developed marked thrombocytopenia associated with numerous megakaryocytes in the bone marrow, but without anemia or leukopenia, after taking procainamide (3 g/day) for a period of 2 months. Despite continuation of this medication, treatment with prednisone led to rapid rise in platelet count, and withdrawal of steroid was followed by prompt recurrence of thrombocytopenia. The platelet counts returned to normal after discontinuation of procainamide, and readministration of this drug was followed by reappearance of thrombocytopenia. These observations indicate that exposure to procainamide can cause isolated thrombocytopenia, probably due to immune-mediated destruction of platelets, and that treatment with prednisone may be promptly beneficial in patients with procainamide-induced severe thrombocytopenia and bleeding.

Aged↗
PubMed1984

The inertial and geometrical properties of helmets.

The center of gravity (CG) and the principal mass moments of inertia about the CG of Army aviator, American football, and bicycle helmets were experimentally determined by a variation of the classic differential weighing and torsional pendulum techniques. In the course of these experiments, an innovative method for three-dimensional (3D) digitization was found. An electronic caliper, which measured length, was used with a computer algorithm to achieve 3D digitization. The results of the above measurements show that the weight of the helmet and the distances from the CG to the orthogonal coordinate axes intercepts with the outer shell surface were highly correlated with its principal mass moments of inertia. A set of regression equations was derived on theoretical considerations and served to unify the experimentally obtained data. Our results indicate that the principal mass moments of inertia of helmets vary linearly with its mass but nonlinearly with size and shape. For a helmet, given its weight and certain geometrical distances, the regression equations estimate the principal mass moments of inertia to within 5% of its experimentally-determined values. For the helmets studied in this series, a modified linear-regression relationship between the principal mass moments of inertia and its mass was found. This result is reasonable because the mass distribution of the current generation of helmets are set primarily by the head size and secondarily by helmet size, shape, and materials.

Aviation↗
PubMed1983

An in situ study of the influence of a sclerosing solution in rabbit medial collateral ligaments and its junction strength.

A double-blind study was conducted to assess the influence of a sclerosing solution on rabbit medial collateral ligaments (MCL) in situ. It was shown that repeated injections of 5% sodium morrhuate into the MCL and its bony attachments significantly increased its bone-ligament-bone junction strength, ligament mass and thickness when compared to saline-injected controls. Morphometric analysis of electron micrographs showed a highly significant corresponding increase of the collagen fibril diameters in the experimental ligament compared against the control MCL. These composite findings suggested that the sclerosing solution had a significant influence on dense connective tissue at the insertion sites. The mechanisms for these changes are uncertain and are the basis for future investigations.

Animals↗
PubMed1983

Regional and lateral specificity of acupuncture-induced action of blood-factor effects inhibiting hindlimb flexor reflexes in the rabbit.

Intravenous transfusion of blood plasma or serum from electroacupuncturally stimulated donor rabbits that displayed unilateral analgesia of a specific region of one hindlimb as shown by the lack of flexor withdrawal responses to pin pricks, caused the development of a comparable region of analgesia in naive, recipient rabbits. The site of this analgesia was comparable to that observed in the donor animals in terms of anatomical region and in terms of laterality. These findings indicate that acupunctural analgesia is induced through highly specific nervous and chemical mechanisms and that the substances produced can distinguish specific body regions located on one side of the body from the other.

Acupuncture Therapy↗
PubMed1983

Mechanical analysis of racket and ball during impact.

Several investigators have demonstrated experimentally that ball-rebound velocity after an eccentric impact against a tennis racket remains unchanged for two extreme conditions of grip firmness, i.e., when the grip is firmly clamped and when it is allowed to stand freely on its butt. The present study utilized a simple mathematical model from classical impact theory to provide analytical support for their experimental findings. It was shown that the functional relationship between the approach and rebound velocity of the ball is dependent on five dimensionless numbers: 1) the ratio of the ball to racket mass; 2) the ratio of the radius of gyration about the racket pivot to the distance of the geometric center of the racket head to the pivot; 3) the coefficient of restitution between the ball and the racket string ensemble; 4) the ratio of the distances of the center of mass and the center of the strings to the pivot; and 5) the ratio of the grip length to the distance from the pivot to the center of the strings. Because the mass and length ratios are very small numbers for tennis, the rebound-to-approach velocity of the ball is principally a function of the coefficient of restitution, which is practically independent of the conditions of grip firmness. Using published data generated from other experiments, analytical estimates were obtained for the values of the coefficient of restitution between a tennis ball and a racket strung to typical tensions for various rebound-to-approach velocity ratios. These estimates were validated directly by an independent experiment.

Biomechanical Phenomena↗
PubMed1983

Marrow neutrophil mass in patients with nonhematological tumor.

The state of granulocytopoiesis was assessed in 15 patients with metastatic carcinoma without infection, overt protein-calorie malnutrition, splenomegaly, or prior chemotherapy. Seven patients had decreased total marrow neutrophil mass, accompanied by proportional reduction in marrow proliferative and nonproliferative neutrophil pool, without increased numbers or proliferative capacity of marrow CFC or myeloid mitotic index. Four patients had decreased MGR assessed with hydrocortisone, but only one had reduced marrow nonproliferative neutrophil pool. Neither MGR nor blood neutrophil count correlates significantly with nonproliferative neutrophil pool or the number of band and segmented neutrophils in the bone marrow. The blood neutrophil count, however, correlates significantly with total marrow neutrophil mass (r = 0.69, p less than 0.01) and proliferative neutrophil pool (r = 0.68, p less than 0.01). These findings suggest that reduced marrow neutrophil mass is common in patients with metastatic carcinoma in the absence of overt protein-calorie malnutrition and that the reduced marrow neutrophil mass is most likely due to depressed granulocytopoiesis.

Aged↗