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Biomedical subjects

Y K Xu

Publications and source records attributed to Y K Xu.

At least 19 recordsLinked to original sources
PubMed1992

Effects of discectomy on the stress distribution in the lumbar spine.

The change of the stress distribution of the lumbar spine after discectomy was analysed by the three-dimensional finite element method. It was shown that the stress level in the posterior element was higher, but that in the anterior element was lower than before disc excision. The most significant change of the stress distribution was found in the trabecular bone of the vertebral body. It is considered that in discectomy the normal disc tissue should be preserved as much as possible to maintain good function of the spine.

Biomechanical Phenomena↗
PubMed1991

Influence of flexion-extension motion of lumbar spine on lumbosacral dural sac. An experimental study.

To analyze the effects of flexion-extension motion of lumbar spine on the position and shape of lumbosacral dural sac, 10 flexion/extension lateral myelograms of cadaver specimens of normal lumbar spine were measured. The results showed that moving from flexion to extension both sagittal diameter and length of the dural sac decreased significantly, the dural sac moved caudally, and the sagittal diameter of the anterior epidural space decreased in the mid-vertebral level but increased in the intervertebral level. The dynamic changes of the dural sac and their influence factors and clinical relevance were discussed.

Adult↗
PubMed1991

Lumbar intervertebral disc prosthesis. An experimental study.

To provide a more effective treatment and improve the outcome of surgical treatment of lumbar intervertebral disc protrusion, the values of lumbar intervertebral disc prosthesis (LIDP) were investigated. LIDP was specially designed and made of silicone rubber. The properties of material mechanics were investigated by compressive test and damage test of LIDP specimens. The biocompatibilities of LIDP were observed experimentally in monkeys. The surgical applicabilities were studied by in vitro experiments of fresh human lumbar spine. The results showed that LIDP has the advantages of good biomechanical applicability, biocompatibility and surgical applicability. LIDP is able to maintain the intervertebral space, stress balance and stability of the lumbar spine. after lumbar intervertebral disc excision, the replacement of LIDP could restore the functions of the lumbar spine and improve the curative results of disc excision.

Adult↗
PubMed1990

Effect of partial discectomy on the stability of the lumbar spine. A study of kinematics.

The effect on the stability of the lumbar motion segment, as affected by partial discectomy, was investigated using three-dimensional motion measurement technique. Eight functional spinal units from fresh cadaver lumbar spines were potted and clinically relevant loads applied through a special loading frame attached rigidly to the top vertebra of the specimen. Partial discectomy was performed on the right side of the specimen. The three-dimensional motions of each lumbar motion segment, before and after partial discectomy, were recorded. The results showed that partial discectomy significantly affects the stability of lumbar spinal motion segments. The clinical relevance of this finding is discussed.

Adult↗
PubMed1990

[Diagnosis of bronchogenic carcinoma with MRI].

MRI anatomy of 15 normal chests and features of 24 patients with bronchogenic carcinoma confirmed by surgery or exfoliative cell examination of sputum were analysed. The authors preliminarily conclude that MRI is of remarkable diagnostic value in demonstrating tumor size, its location and extent, exhibiting the relationship between tumor mass and its surrounding such as greater vessel, trachea and bronchi and so forth. It is also more efficient in detecting hilar or mediastinal metastatic lymphadenopathy.

Adenocarcinoma↗
PubMed1989

Deficit of uridine diphosphate galactose in galactosaemia.

The levels of uridine diphosphate galactose (UDPGal) and uridine diphosphate glucose (UDPGlc) have been determined in liver autopsy samples, erythrocytes and cultured skin fibroblasts from galactosaemic patients and compared to non-galactosaemic controls. In patients with undetectable erythrocyte galactose-1-phosphate uridyltransferase (transferase) activity, the levels of UDPGal were substantially lower than in controls. In patients with detectable transferase activity, even though in less than 1% of normal values, both UDPGal and UDPGlc levels were in the normal range. Incubation of erythrocytes from both galactosaemic patients and normal individuals with 10 mmol/L uridine increased UDPGal and UDPGlc levels several-fold, both in the presence or absence of galactose in the incubation medium. We hypothesize that a deficit of UDPGal is responsible for the late onset clinical manifestations in galactosaemia which include ovarian failure, speech defect and neurological abnormalities. We suggest that uridine administration may be of therapeutic value in raising the intracellular concentrations of UDPGal. We conclude that the transferase reaction, however small in activity, is essential for optimal UDPGal formation.

Cells, Cultured↗
PubMed1989

Uridine nucleotide sugars in erythrocytes of patients with galactokinase deficiency.

The levels of UDPglucose and UDPgalactose (UDPGal) have been measured in erythrocytes of seven patients with galactokinase deficiency. Normal levels of UDPGal were found in all patients with galactokinase deficiency (McKusick 23020). This is in contrast with reduced values of UDPGal found in patients with classical galactosaemia who have complete absence of galactose-1-phosphate uridyl transferase activity. It was demonstrated that patients with galactokinase deficiency had an incomplete enzyme block in erythrocytes by direct enzyme assay, by 14CO2 production from [1-14C]galactose, and by the appearance of labelled intermediates, notably galactose-1-phosphate and UDPhexose.

Adolescent↗
PubMed1989

Galactose metabolism in human ovarian tissue.

Galactose metabolism was studied in human ovarian tissue obtained from 14 women controls between 21 and 72 y of age, and one 21-y-old galactosemic patient with hypergonadotrophic hypogonadism. Tissue slices were incubated with 1-14C-galactose, and labeled intermediates were analyzed by anion-exchange column chromatography. Activities of enzymes related to the galactose pathway: galactokinase, transferase, epimerase, uridine diphosphoglucose (UDPGlc) and uridine diphosphogalactose pyrophosphorylases, and UDPGlc and uridine diphosphogalactose pyrophosphatases were measured in ovarian homogenates using radioisotopic, spectrophotometric, and fluorometric techniques. Incorporation of carbon label from 1-14C-galactose into various galactose and glycolytic intermediates, as well as carbon dioxide and TCA-insoluble materials was demonstrated in samples from non-galactosemic controls. In tissue from the galactosemic individual, no labeled carbon dioxide was produced and very little incorporation into TCA-insoluble material was found. Labeled galactose-1-phosphate was elevated. In normal ovarian tissue, specific activities of galactokinase, transferase, epimerase, and UDPGlc pyrophosphorylase are much higher than those found in the red cells and in testes. UDPGlc pyrophosphorylase activity is about 50 times that of transferase, suggesting that uridine nucleotide sugars have an important role in the normal development and function of the ovary. It is hypothesized that premature ovarian failure, often observed in patients with galactosemia, is due to interference with nucleotide sugar metabolism and the synthesis of galactose containing glycoproteins and glycolipids consequent to the enzymatic defect in the major pathway of galactose metabolism.

Adult↗
PubMed1989

Gonadal function and ovarian galactose metabolism in classic galactosemia.

Evaluation of ovarian steroid secretion, histologic examination of ovarian tissue, and incubation studies with radiolabelled galactose in ovarian tissue slices were performed in a 21-year-old woman with galactosemia and incipient ovarian failure. After exogenous gonadotropin administration in an attempt to achieve fertility, there was no evidence of ovulation by ultrasound; estrogen and androgen production were deficient indicating ovarian unresponsiveness. Histologic examination of the ovary revealed that the ovarian stroma had an increase in fibrous tissue and that a few hyalinized atretic follicles were present with no intermediate or evolving Graafian follicles. After incubation with galactose-1-14C, there was absence of labelled CO2 production and only labelled galactose-1-phosphate was identified as compared to controls in which several labelled intermediates could be seen. The incorporation of galactose into the TCA-insoluble fraction was drastically reduced in the patient compared to controls, suggesting that there may be a deficiency of ovarian galactose-containing glycolipids, glycoproteins and mucopolysaccharides in the galactosemic ovary. Deficiency in the production of galactose containing compounds, or galactose-1-phosphate accumulation or both, may lead to the development of hypergonadotropic hypogonadism seen in women with galactosemia.

Adolescent↗
PubMed1989

The effect of flexion-extension motion of the lumbar spine on the capacity of the spinal canal. An experimental study.

The symptoms of lumbar spinal stenosis are often posture-dependent, and it is generally accepted that the capacity of the spinal canal is affected by flexion-extension motions of the lumbar spine. A study of spinal capacity in flexion-extension of ten cadaver specimens on the lumbar spine was done and measurements were obtained from the flexion-extension lateral myelograms. There proved to be a larger capacity of dural sac of 3.5 to 6.0 ml (4.85 +/- 0.75 ml) in flexion than in extension, and the differences were highly significant (P less than 0.001). In addition, the sagittal diameter of the dural sac and the length of the spinal canal increased from extension to flexion. Because of the effect of flexion-extension motion of the lumbar spine on the spinal capacity, we suggest that maintaining the lumbar spine in flexion is more suitable since spinal canal capacity is enlarged and symptoms may be mitigated.

Adult↗
PubMed1989

[A preliminary study on the diagnostic value of magnetic resonance imaging in old myocardial infarction].

MRI manifestations in 9 patients with old myocardial infarction (OMI) were analyzed and the results were compared with the changes seen in ECG (9 patients) and coronary angiography (6 patients). The authors found that: 1. Myocardial thinning was one of the important signs of OMI (78%); 2. Signal intensity was reduced which was remarkably lower than the adjacent normal myocardium (P less than 0.01). 3. MRI provided even more direct and accurate information for assessing the site and extent of infarction than ECG; 4. The results of LVEF calculated from MRI were closely correlated with that obtained from left ventriculography (r = 0.8245, 0.01 less than P less than 0.05). The authors preliminarily conclude that MRI is an accurate method for evaluating the site and extent of myocardial infarction, myocardial tissue characterization and left ventricular function.

Adult↗
PubMed1988

Glucose-6-phosphate dehydrogenase variants and their frequency in Guangdong, China.

Erythrocyte glucose-6-phosphate dehydrogenase (G6PD) was characterized in blood samples obtained from 97 randomly selected males with enzyme deficiency from various regions of Guangdong Province, China. Nine new variants (Gd Kaiping, Gd Boluo, Gd Huiyang, Gd Gaomin, Gd Qing-Baijiang, Gd Gaozhou, Gd Huazhou, Gd Nanhai, and Gd Guangzhou) were identified. Of the 31 variants found in this province, Gd Kaiping, Gd Taiwan-Hakka, Gd Haad Yai, Gd Haad Yai-like and Gd Huiyang occurred most frequently. The frequency of each variant was calculated. The results demonstrated that the genetic heterogeneity of G6PD deficiency was high in this area.

China↗
PubMed1988

Treatment of longitudinal injuries in avascular area of meniscus in dogs by trephination.

A study promoting the healing of longitudinal injuries in an avascular area of the meniscus in 21 male dogs is reported. One horizontal hole from the peripheral vasculature to one of the artificial longitudinal injuries to both medial menisci of the knee in each dog was made with a needlelike trephine. The knee joints were not immobilized and the samples were taken 2, 4, 8, 12, and 24 weeks, respectively, after the operation. [3H]Thymidine was injected into the joint cavity 72 h before the sample was taken. Healed lengths were measured, and pathologic examinations and autoradiography were performed. The results showed that all of the injuries treated with trephination were partly or totally healed whereas those in controls were not healed at all, suggesting that trephination may be the procedure of choice for clinic orthopedists dealing with such injuries. By the 8th week, the healed length stopped increasing, the scar tissue began to mature, and the DNA synthesis of the fibroblasts in the granulation tissue and the fibrochondrocytes in the trephined meniscus reduced. It is thought that the fibrochondrocyte of the meniscus and the fibroblast in the granulation might be capable of obtaining the thymidine directly from the synovia of knee joint for their DNA metabolism. Multiplication of the fibrochondrocyte in the injured meniscus was also found.

Animals↗
PubMed1988

Lysosomal enzyme activities among Chinese: leukocyte alpha-galactosidase and beta-galactosidase.

alpha-Galactosidase and beta-galactosidase activities have been determined in leukocyte preparations from 100 randomly selected Chinese adults. For alpha-galactosidase, two groups with low activities were identified: group I consisted of 3 females having activities below 40% of normal, and group II consisted of 5 males and 1 female with activities about 60% of normal. Family studies suggested that these low alpha-galactosidase activities are genetically determined. Only 1 individual was found to have about 50% of normal beta-galactosidase activity; presumably he is a carrier for beta-galactosidase deficiency (GM1 gangliosidosis).

Adult↗