Biomedical subjects

K S Leung

Publications and source records attributed to K S Leung.

At least 19 recordsLinked to original sources

PubMed2001

Growth plate chondrocytes inhibit neo-angiogenesis -- a possible mechanism for tumor control.

Clinically, tumors seldom grow across the articular cartilage and physeal plate. It is believed that avascular cartilage may inhibit the neo-vascularization of tumor spread. The conditioned medium of growth plate chondrocytes resisted the migration of ECV304 by approximately 41% in invasion assay. Growth plate chondrocytes were shown by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to have an insignificant effect on the viability of human endothelial cells and fibroblasts. However, the proliferation of human endothelial cells was significantly inhibited by growth plate chondrocytes. The inhibitory activity was up to 35% and specific to endothelial cells. Inhibition of blood vessel formation was also demonstrated in the chick chorioallantoic membrane (CAM) assay. These findings demonstrated that growth plate chondrocytes secrete anti-angiogenesis factor(s) which specifically inhibit both the migration and proliferation of endothelial cells.

Allantois↗

PubMed2001

Expression of basic fibroblast growth factor during distraction osteogenesis.

Distraction osteogenesis is a process of tissue regeneration under an external mechanical stimulation. In the study, the spatial and temporal expression patterns of basic fibroblast growth factor in the newly formed osseous tissue during distraction osteogenesis in goats were studied using immunohistochemistry. During the distraction period, the expression of basic fibroblast growth factor was observed in the osteoblasts on the newly formed trabecular bone and the bone formation front. The cells of osteoblastic lineage and the mesenchymal cells in the distraction callus also expressed basic fibroblast growth factor. The expression of basic fibroblast growth factor in the distraction period was stronger than that during the latency and consolidation periods. However, some osteoblasts still were expressing basic fibroblast growth factor in the consolidation periods. According to these results, basic fibroblast growth factor may have a local regulatory role during distraction osteogenesis. The tensile force may stimulate the expression of basic fibroblast growth factor in osteoblasts and other cell types.

Animals↗

PubMed2000

Mechanical characterization of regenerated osseous tissue during callotasis and its related biological phenomenon.

The mechanical characteristics of the regenerated osseous tissue and osteoblastic activities during callotasis were studied using Chinese mountain goat as the animal model. Open osteotomy of the left tibiae was done in 24 goats. Distraction started 6 days after the operation with the rate of 1 mm per day for 4 weeks. The bone regeneration was monitored with serial X-ray films. The tension generated during distraction was measured with the strain gauges mounted on the distraction apparatus. The osteoblastic activities were monitored by measuring plasma bone specific alkaline phosphatase activity. The results showed that the average lengthening was 22.9 +/- 2.8 mm in each animal. The newly formed osseous tissue becomes stiffer during the course of distraction lengthening. The continuous evolution of the tensile behaviour of the newly formed osseous tissue correlates with the plasma bone specific alkaline phosphatase activities. The radiological appearance of a physis like structure took place at 12 mm lengthening. Its appearance corresponds to the changes in the tensile behaviour as well as the biological activities of the osteoblasts and may serve as a useful radiological marker in monitoring the process of callotasis in clinical practice.

Alkaline Phosphatase↗

PubMed1999

Medical data mining using evolutionary computation.

In this paper, we introduce a system for discovering medical knowledge by learning Bayesian networks and rules. Evolutionary computation is used as the search algorithm. The Bayesian networks can provide an overall structure of the relationships among the attributes. The rules can capture detailed and interesting patterns in the database. The system is applied to real-life medical databases for limb fracture and scoliosis. The knowledge discovered provides insights to and allows better understanding of these two medical domains.

Algorithms↗

PubMed1999

Enlargement of remaining patella after partial patellectomy in rabbits.

PURPOSE: The purpose was to study the radiographic patellar tendon calcification and evaluate the histology of the healing interface between the patellar tendon and the remaining patella after partial patellectomy. METHODS: We removed the distal one-third of the patella in 24 rabbits. Specimens were harvested at 8, 12, and 24 wk postoperatively (N = 8 each). RESULTS: Histological observation demonstrated that healing interfaces between the patellar tendon and patella were structurally connected by scar tissue. The radiographic patellar tendon calcification next to the healing interface was in fact trabecular bone outgrowth histologically, resulting in an enlargement of the remaining patellar in length from 0.93+/-0.28 mm at week 8, 1.26+/-0.33 mm at week 12, to 2.5+/-1.12 mm at week 24. Metaplasia of the scar tissue observed next to the healing interface of the remaining patellar articular cartilage and the outgrowth of trabecular bone from the remaining patella with healing over time may increase the articular surface of the remaining patella after partial patellectomy. CONCLUSIONS: The remaining patella might be enlarged in length after partial patellectomy because of trabecular bone outgrowth and metaplasia with healing over time. Its theoretical advantages are an increased patellofemoral contact area and a diminished patellofemoral contact pressure following surgery.

Animals↗

PubMed1997

Osteomyelitis of the spine due to Salmonella infection--conservative treatment with quinolone: a case report.

Although osteomyelitis due to Salmonella infection is known to be associated with sickle cell anemia, various hemoglobinopathies and immune suppressive states, it may also occur in normal hosts. A 16-year-old Chinese boy without sickle cell disease or any other condition that would compromise the immune system had osteomyelitis of the lumbar spine caused by Salmonella enteritidis. The condition was treated conservatively with ciprofloxacin (quinolone group). This may be the first reported case in which a patient with spinal osteomyelitis due to Salmonella infection, who was otherwise healthy, was successfully treated nonoperatively with quinolone.

Adolescent↗

PubMed1996

Identification and characterization of various differentiative growth plate chondrocytes from porcine by countercurrent centrifugal elutriation.

Countercurrent centrifugal elutriation was used to separate growth plate chondrocytes from porcine basing on their differences in sizes and densities. Eighteen fractions of cells with different sizes and densities were obtained. The mean cellular volumes increased progressively in each of successive fractions, and that increase was associated with specific phenotypic changes, such as biochemical differences in DNA synthesis, proteoglycan synthesis, and activities of alkaline phosphatase. Three distinct chondrocyte subpopulations with their unique characteristics were identified among the elutriated fractions. The resting chondrocytes were found to be small in size and quiescent. The hypertrophic chondrocytes were found to be large in size and metabolically active both in alkaline phosphatase and in proteoglycan productions. The proliferative chondrocytes exhibited a high DNA synthesis rate, and their sizes were found to be between those of the resting and hypertrophic chondrocytes.

Alkaline Phosphatase↗

PubMed1996

The hypertrophic scar and microcirculation properties.

Blood-flow measurements of microcirculation were used as a quantitative indicator for scar assessment and healing. A laser doppler flowmeter (LDF), giving an integrated instantaneous flux value through a measured volume of skin, was used for the measurements. It has been postulated that the degree of hypertrophy after thermal injury correlates with the degree of microvascular regeneration. This study looked quantitatively at microcirculation in normal and scarred skin of different clinical grading and investigated the comparative responses to changes in local temperature stimuli. An attempt is made to define microcirculation using the parameters of Vasodilation Index (Dli) and Vasomotion Intensity (% Vsm) as respective responses to a rise in local temperature of the skin from 36 degrees C to 44 degrees C. The improvements in both Dli and % Vsm with healing of scar relate to the degree of microvascular regeneration, which in turn correlates with the clinical assessment.

Adolescent↗

PubMed1996

Mechanical properties of normal skin and hypertrophic scars.

The non-linear viscoelastic properties of skin tissue were characterized by modulus of elasticity E, which represents stiffness, and percentage extension (strain, xi) at load intensities of 20, 40 and 100 gm. The latter property is a measure of the extensibility for both normal skin and hypertrophic scar. A quasi-static extensometer applies a standard rate of extension to the skin and its mechanical properties were obtained from 15 Chinese patients with burn injuries of superficial to full skin thickness burns. Clinical evaluation of hypertrophic scar is qualitative and depends on colour, thickness and hardness or firmness. Using mechanical properties assists in the characterization by providing a quantitative indicator. Higher scar grading is synonymous with increased stiffness and decreased extensibility. Correlation with clinical assessment was achieved with these in vivo viscoelastic properties.

Adolescent↗

PubMed1996

An expert system for the detection of cervical cancer cells using knowledge-based image analyzer.

Analyzing for abnormalities of cell images in the cervix uteri provides a basis for reducing deaths and morbidity from cervical cancer through detection of potentially cancerous cells, provision of prompt advice and opportunities for follow-up and treatments. However, cytopathology is usually based on subjective interpretation of morphological features. Arbitrary criteria have to be devised for their classifications. Subjective interpretations of such criteria are likely to result in diagnostic shifts and consequently disagreement occurs between different interpreters. This article presents a novel approach to the composition of segmentation and diagnosis processes for biomedical image analysis. A prototype expert system has been developed to provide an objective and reliable tool to gynaecologists. Special image analyzing techniques are used and a set of knowledge sources is designed. The expert system employs a robust control strategy which minimizes the amount of domain-specific control knowledge. It has been proved to work effectively in the detection of cervical cancer.

Artificial Intelligence↗

PubMed1996

Geometric mismatch of the Gamma nail to the Chinese femur.

The geometric mismatch of the femoral component of the Gamma nail to the Chinese femora resulted in intraoperative complications. To provide scientific data for modification of the implant, 28 pairs of normal Chinese femora were studied with the 3-dimensional reconstruction from the computed tomography scan data. Measurements were taken from the reconstituted drawings, and the anthropometric data were applied in the modification of the implant. This study is the first report on the application of Chinese anthropometric data on the design of a trauma implant. It is hoped that a larger scale of the study will provide a more comprehensive data base for wider application to orthopaedic implant design in the future.

Aged↗

PubMed1996

Multicenter trial of modified Gamma nail in East Asia.

The mismatch of the standard Gamma nail in the Chinese femora led to the modification of its femoral shaft component based on the anthropometric study of 28 pairs of Chinese femora. A multicenter clinical trial was done in 6 countries and regions in East Asia. Three hundred forty-nine fractures were treated and studied. More than 60% of the fractures were unstable by Evans classification. The average age of the patients was 73.6 years. The male to female ratio was 2:3. The mean followup period was 11.7 months. The result of the trial showed that the intraoperative complication rate was 7.7%, and complications primarily were related to faulty operative technique. There were 7.2% postoperative complications related to the fractures that again decreased toward the later stage of the trial. Functionally, there was progressive improvement of the hip score within the followup period. The results show that the modified Gamma nail gave better results in the treatment of geriatric trochanteric fractures by minimizing reaming, thereby reducing complications related to the implants.

Activities of Daily Living↗

PubMed1996

Treatment of deformed tibial intramedullary nail: report of two cases.

Fixation of long-bone fractures using high-tensile-strength intramedullary nails is now a well-established form of treatment. A high-energy injury may deform and angulate such nails. Such incidents are rare-only two cases have previously been reported in the literature. We report the cases of two patients with deformed intramedullary tibial nails as the result of second injury to the same leg. The bent nails were removed in the conventional manner despite the straight intramedullary canal.

Adult↗

PubMed1995

No change in bone-specific alkaline phosphatase activities in cultured rat osteoblastic cells under L-ascorbate and beta-glycerophosphate-induced mineralization.

Mineralization occurred both in fetal rat calvarial cells and UMR 106 osteoblastic cells when they were cultured in medium containing L-ascorbate and beta-glycerophosphate as evidenced by von Kóssa staining as well as deposition of calcium ions and inorganic phosphate in the cells. When compared with corresponding non-mineralized cell cultures, both the mineralized cultures of calvarial cells and UMR 106 cells did not exhibit any change in intracellular bone-specific alkaline phosphatase activities which were measured by wheatgerm lectin precipitation method. Our results support the hypothesis that mineralization may not exert any direct negative feedback on matrix protein synthesis in osteoblasts during bone formation.

Alkaline Phosphatase↗

PubMed1995

Bone-specific alkaline phosphatase activities in plasma and callus during callotasis in rabbits.

Using the rabbit as an animal model, the changes of enzymatic activities of bone-specific alkaline phosphatase (ALP) in plasma and in the callus during callotasis were studied. Bone-specific ALP activities were measured by the wheatgerm agglutinin precipitation method. Distractions were performed on different groups of animals commencing on 3rd, 5th and 7th day after osteotomy. Bone-specific ALP activities in the plasma of all these groups dropped significantly on first few days compared with those values before osteotomy. However, when distraction was started, the plasma bone-specific ALP rose progressively until day 35 and resumed normal gradually until day 70. Immediate rises in enzymatic activities after distractions were observed in the 5th- and 7th-day treating groups but not in the 3rd-day treating group. The bone-specific ALP activities in the callus samples also increased until day 35 and gradually decreased. With the plasma bone-specific ALP as an indicator of the biological activities of the osteoblasts, the effect of external mechanical stimulation in a form of the tension stress on the biological tissue is well demonstrated in this study.

Alkaline Phosphatase↗

PubMed1995

Naphthalene contamination of sterilized milk drinks contained in low-density polyethylene bottles. Part 2. Effect of naphthalene vapour in air.

A survey on naphthalene vapour in air was conducted, revealing that the ambient atmosphere contained concentrations of naphthalene in the range of 0.005-0.100 mg m-3. The level of naphthalene vapour in air increased to 0.35 and 4.00 mg m-3 in places exposed to lacquer paint and naphthalene-based moth-repellent, respectively. The effect of naphthalene vapour in air on milk drinks contained in low-density polyethylene (LDPE) bottles was assessed. A mathematical model was suggested to describe the migration of naphthalene from the atmosphere into milk. The model was proved to be valid for milk drinks exposed to naphthalene-based moth-repellent during storage. Moreover, the extent of migration was found to increase with the fat content of foods, which might be ascribed to an increase in diffusion, in addition to the kinetic factor, that affects naphthalene migration.

Air↗

PubMed1994

Naphthalene contamination of sterilized milk drinks contained in low-density polyethylene bottles. Part 1.

Naphthalene contamination was observed in sterilized milk drinks contained in low-density polyethylene bottles. The determination of naphthalene in the packaging material by gas chromatography showed levels of naphthalene ranging from 0.7 to 2.0 micrograms g-1. Analysis of the milk samples at the time of purchase by gas chromatography after extraction using a Dean and Stark apparatus showed levels of naphthalene in the range 0.01-0.03 microgram ml-1. The level of contamination in milk increased with storage time at room temperature (25 degrees C) and, depending on the concentration of naphthalene in the packaging material, values of 0.08-0.27 microgram ml-1 were found at the expiry date. Migration studies were carried out using peanut oil as a food stimulant. The amount of naphthalene extracted by milk from the polyethylene at 25 degrees C over a period of 60 d was related to the amount that could be extracted using peanut oil at 66 degrees C for 30 h. A mathematical model was established to describe the observed migration of naphthalene into milk, and proved valid for calculating the level of naphthalene in milk using the optimum determined values of K and Dp.

Animals↗

PubMed1994

Reconstruction of extensor mechanism after trauma and infection by transposition of the Achilles tendon: report of technique and four cases.

High-energy injuries to the knee often involve extensive soft tissue loss as well as fractures. In certain situations, the patellar tendon may be lost due to initial injury or post-injury complications such as infection. Use of the gastrocnemius flap is a popular method of covering the defect as well as controlling infection and promoting healing by increasing local vascularity. We present a method of reconstructing the patellar tendon by extending the use of the gastrocnemius flaps using its Achilles tendon and calcaneal insertion. The distal insertion of the Achilles tendon is fixed to the tibial tuberosity with a cancellous screw, and the proximal end is sutured to the quadriceps muscles. The knee is immobilized for 1 week, after which the knee is mobilized in a hinged brace. Three of the four cases had good results, one a moderate result (the initial injury was extensive, with dislocation of the knee).

Achilles Tendon↗