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Biomedical subjects

J C Goh

Publications and source records attributed to J C Goh.

At least 37 records · Page 2Linked to original sources
PubMed1995

A cadaver study of the function of the oblique part of vastus medialis.

Six normal cadaver lower limbs were mounted on a specially designed loading apparatus. Wires were used to simulate the five muscle bellies of the quadriceps, the ratio of their tensions having been determined from that of the anatomical cross-sectional areas of the muscles. A three-camera system was used to track the patella during knee movements from flexion to extension. The patellofemoral contact area was determined by pressure-sensitive film. The limb was loaded with and without tension on the wire which simulated the oblique part of the vastus medialis (VMO). Absence of VMO tension caused the patella to displace laterally (4.2 mm) and increased the load on the lateral patellar facet throughout the range of knee motion. When the tension on the wire simulating vastus lateralis was reduced by 40% to simulate the effect of a lateral release procedure, the abnormal kinematics caused by the absent VMO returned to normal.

Biomechanical Phenomena↗
PubMed1994

Vertebral body index and bone mineral density in women with spinal fractures. 66 probands compared with controls.

The bone mineral density (BMD) was measured in 61 women with compression fractures of the spine and 66 normal pre-menopausal women. Radiographs of the lateral spine were also obtained and the vertebral body index (VBI) was measured in the region L2-L4. Women with spinal fractures had lower BMD and VBI values. Using both BMD and VBI, 3 regions of fracture risk were defined. All but 2 of the fracture patients were in the moderate- or high-risk region for fracture.

Adult↗
PubMed1994

A comparison of lumbosacral loads during static and dynamic activities.

A biomechanical model to determine the loads at the lumbosacral joint was developed. This model was used to determine the lumbosacral loads during two specific activities--a stable standing posture representing a static activity, and a normal level walk representing a dynamic activity. This study involved ten healthy and young male subjects. The results obtained indicated that the lumbosacral loads during a stable standing posture was in the range of 0.82 to 1.18 times body-weight, with a mean of 1.03 (+/- 0.11) times body-weight. In comparison, during a normal level walk the lumbosacral loads were in the range between 1.41 and 2.07 times body-weight, with a mean of 1.61 (+/- 0.24) times body-weight. The walking speed of these subjects varied between 0.96 and 1.48 ms-1, with a mean of 1.25 (+ 0.18) ms-1. Results in this study indicated that there was a significant difference (p < 0.005) between the means of the lumbosacral loads of these two specified activities. An increase of 56.3% between means of the static to the dynamic case was observed.

Abdomen↗
PubMed1993

Phenotypic and genotypic characterization of Hodgkin's disease.

Although a few studies have reported clonal cytogenetic changes in Hodgkin's disease (HD), their correlation with histologic groups is poorly defined. This is because of insufficient numbers of clonally abnormal cases ascertained in each of these studies, an inherent problem associated with the cytogenetic studies of HD. In this report we present results of pathologic, phenotypic, and genetic studies on 29 HD tumors consecutively ascertained by us and the results of a comprehensive analysis of the cytogenetic data available in the literature. In our series 75% of the tumors were positive for Epstein-Barr virus (EBV) by polymerase chain reaction (PCR) assay. A higher frequency of EBV-positive tumors showed clonal karyotypic abnormalities than the EBV-negative tumors. Unlike the case in the previous reports, none of the 24 tumors studied by PCR showed the presence of t(14;18) (q32;q21)-carrying cells. From the comprehensive analysis of the literature, we identified recurring nonrandom numerical changes, deletions, and chromosome breaks in HD. Some of these are associated either with nodular sclerosis or with mixed cellular histologies. A comparison of the pattern of these nonrandom cytogenetic changes in HD and those reported for non-Hodgkin's lymphomas (NHL) identified common deletions and breaks between them. These common genetic lesions probably play a role in disease evolution.

Adolescent↗
PubMed1993

Effect of pore sizes and cholesterol-lipid solution on the fracture toughness of pure titanium sintered compacts.

Commercial pure titanium has been widely used as an implant material because of its excellent biocompatibility and good ductility. To determine the effect of pore size on the fracture resistance of porous titanium compacts, a series of fracture toughness (KQ) tests were performed on commercial pure titanium powder compacted to 0.17 and 0.62 GPa. Pore sizes ranged from 25 to 103 microns, with porosity between 8.5 and 35%. Two sets of fracture toughness tests using disc-shaped compacts (ASTM E 399-90) were performed, the first in air at 37 degrees C and the second with compacts treated in cholesterol-lipid solution at 37 degrees C. The KQ value of compacts with a smaller mean pore size (ca. 50 microns) was approximately twice that of the compacts with a larger mean pore size (100 microns). The effect of cholesterol-lipid solution treatment was detrimental, perhaps due to preferential lipid absorption by the titanium oxide and/or the presence of chlorides. For the smaller pore size compacts, the KQ values decreased by up to 20%. For the larger pore size compacts, the effect of cholesterol-lipid solution was less significant. Morphologically, compacts with smaller pore size had a predominantly ductile fracture with significantly higher dimple density than the larger pore size compacts.

Cholesterol↗
PubMed1993

Serial phenotypic, cytogenetic and molecular genetic studies in Richter's syndrome: demonstration of lymphoma development from the chronic lymphocytic leukaemia cells.

In this report we describe a unique longitudinal study on the clinical, phenotypic, cytogenetic and molecular genetic features of malignant cells from diagnosis of chronic lymphocytic leukaemia (CLL) to the development of lymphoma and lymphomatous meningitis. CLL cells at diagnosis were CD5+, CD19+, surface IgG+, kappa+, were karyotypically abnormal and showed clonal rearrangements in the immunoglobulin heavy (IgH) and kappa light chain genes. Phenotypically leukaemic cells and lymphoma cells at RS resembled CLL at diagnosis, but showed cytogenetic evolution. Geometrically leukaemic cells and lymphoma cells retained the initial clonal rearrangements in IGH and kappa genes, but showed additional supervening clonal rearrangements in both of these genes as the disease progressed to RS. Furthermore, the c-lambda DNA showed clonal rearrangements in the leukaemic cells and lymphoma cells at RS. This complete phenotypic and genotypic analysis of tumour cells during the course of the disease demonstrates the origin of lymphoma from CLL cells through progressive cytogenetic and molecular genetic changes in CLL cells.

Blotting, Southern↗
PubMed1993

Parametric modelling of a knee joint prosthesis.

This paper presents an approach for the establishment of a parametric model of knee joint prosthesis. Four different sizes of a commercial prosthesis are used as an example in the study. A reverse engineering technique was employed to reconstruct the prosthesis on CATIA, a CAD (computer aided design) system. Parametric models were established as a result of the analysis. Using the parametric model established and the knee data obtained from a clinical study on 21 pairs of cadaveric Asian knees, the development of a prototype prosthesis that suits a patient with a very small knee joint is presented. However, it was found that modification to certain parameters may be inevitable due to the uniqueness of the Asian knee. An avenue for rapid modelling and eventually economical production of a customized knee joint prosthesis for patients is proposed and discussed.

Asian People↗
PubMed1993

Fatigue testing of energy storing prosthetic feet.

This paper describes a simple approach to the fatigue testing of prosthetic feet. A fatigue testing machine for prosthetic feet was designed as part of the programme to develop an energy storing prosthetic foot (ESPF). The fatigue tester does not simulate the loading pattern on the foot during normal walking. However, cyclic vertical loads are applied to the heel and forefoot during heel-strike and toe-off respectively, for 500,000 cycles. The maximum load applied was chosen to be 1.5 times that applied by the bodyweight of the amputee and the test frequency was chosen to be 2 Hz to shorten the test duration. Four prosthetic feet were tested: two Lambda feet (a newly developed ESPF), a Kingsley SACH foot and a Proteor SACH foot. It was found that the Lambda feet have very good fatigue properties. The Kingsley SACH foot performed better than the Proteor model, with no signs of wear at the heel. The results obtained using the simple approach was found to be comparable to the results from more complex fatigue machines which simulate the load pattern during normal walking. This suggests that simple load simulating machines, which are less costly and require less maintenance, are useful substitutes in studying the fatigue properties of prosthetic feet.

Artificial Limbs↗
PubMed1993

Hodgkin's disease and non-Hodgkin's lymphoma in an HIV positive patient.

The occurrence of HIV associated non-Hodgkin's lymphoma (NHL) is a well recognized event. HIV associated Hodgkin's disease (HD) has also been observed. A unique patient with both entities is described. The patient was a 29 year old homosexual male who developed clinical IIA nodular sclerosis HD in 1985. He was HIV + with CD4/CD8 = 0.2 and his sister had HD 20 years earlier. He received MOPP and had a complete response. In October 1988 he developed weight loss with an abdominal mass and biopsy revealed diffuse small non-cleaved NHL, with bone marrow involvement. This was his first AIDS associated illness. Probes identified clonally rearranged DNA fragments in the J region of IgH chains and clonal rearrangements in the c-myc gene were also observed but EBV sequences could not be demonstrated. He was treated with m-BACOD but died in March 1989. His course was not complicated by opportunistic infection. Possible etiologies for the HD include his HIV status or shared sibling environment. The development of the NHL may have resulted from HIV infection and/or secondary to his treatment for HD. The relationship between the two lymphomas is uncertain and factors other than HIV exposure and its immune dysfunction may have been causal.

Adult↗
PubMed1993

Molecular characterization of a variant Ph1 translocation t(9;22;11) (q34;q11;q13) in chronic myelogenous leukemia (CML) reveals the translocation of the 3'-part of BCR gene to the chromosome band 11q13.

We performed cloning and sequence analysis of translocation junctions at 11q- and 22q- (Ph1) chromosomes and the corresponding germline DNAs of a variant Ph1-positive CML with t(9;22;11)(q34;q11;q13). Southern blot analysis using probes for different regions of bcr mapped the translocation break near the 5'-side of bcr exon 4. Cloning, Southern blot analysis and restriction map analysis of both bcr fragments showed that the part of bcr 3'- to the translocation break moved to 11q13. Sequence analysis of the translocation junction on the Ph1 chromosome showed that the translocation break occurred 63 bp upstream of exon 4. Compared to the germline sequence, bcr sequence from the translocated partners showed deletion of seven basepairs at the site of translocation. A probe derived from the 5'-region of the clone isolated from the 11q- chromosome identified clonal rearrangements in the leukemic DNA. Restriction map and sequence analysis showed that this clone consisted of the 3'-half of the glutathione S-transferase Pi (GST-Pi) gene and the 3'-part of bcr. We identified two point mutations in the GST-Pi allele involved in translocation. Northern blot analysis showed that the GST-Pi gene was expressed in the leukemic cells at blast crisis but not at chronic phase; however, no fusion mRNA between GST-Pi and bcr was identified. We did not find any sequence homology between 11q13 DNA and 22q11 DNA around the translocation breakpoints; however, sequences homologous to ALU repeats were identified close to the sites of translocation breaks at 22q11 and 11q13. This study supports our hypothesis that variant Ph1 translocations may occur as primary cytogenetic changes similar to the classical Ph1 translocations.

Base Sequence↗
PubMed1993

Gait analysis study on patients with varus osteoarthrosis of the knee.

Biomechanical changes that occur after high tibial osteotomy (HTO) was investigated in 30 patients with osteoarthrosis (OA) of the knee and 11 age-matched normal subjects. Of the 37 knees with varus OA evaluated, 21 were analyzed before and after surgery (average follow-up evaluation, two years). The mean age of the patient group was 58.2 years. Clinical assessment was based on the Hospital for Special Surgery (HSS) knee scoring system. Full-length weight-bearing radiograms were taken for the measurement of the mechanical axis of the lower limb. Results from clinical assessment showed that 90% of the patients had good or excellent postoperative clinical results, as opposed to 9.5% before surgery. An overall improvement in the gait parameters was evident in the group evaluated after surgery, although control levels were not attained. Further analysis based on moments about the knee showed that 57% of the surgically treated knees with good or excellent clinical results had abnormal load distribution. This may lead to deterioration in the future, and further surgery may be required. The abnormal loading was also reflected in the ground-reaction force vector diagram. Therefore, the force vector diagram can be used as a quick screening method to detect abnormal joint loading.

Aged↗
PubMed1992

Novel restriction fragment length polymorphisms in the cellular oncogene SEA.

The human homologue of the SEA oncogene has been mapped recently to chromosome band 11q13. While studying the possible involvement of this gene in the variant translocation t(9;22;11) (q34;q11;q13) in a case of chronic myelogenous leukemia, we identified novel polymorphisms for XbaI and SacI restriction enzyme sites in the SEA gene. Frequency of the polymorphic alleles was studied in 100 samples from healthy controls, 94 samples from patients with non-Hodgkin's lymphoma, 25 samples from patients with benign lymphadenopathy, and 38 samples from patients with chronic myelogenous leukemia. XbaI digestion showed a three-allele polymorphism with two frequent alleles A (8.0 kb) and B (9.2 kb) and a rare allele (5.8 kb). After SacI digestion the probe identified two primary genotypes. Genotype I showed two hybridizable DNA fragments, one each of 6.6 and 3.5 kb. In genotype II the 3.5 kb fragment was absent, instead two smaller fragments, one each of 1.9 kb and 1.6 kb were present. The 6.6 kb fragment (allele AA) had three polymorphic sites generating 6.2 kb fragment (allele BB), 7.4 kb fragment (allele CC), and 7.8 kb fragment (allele DD). Frequencies of the two genotypes and the four alleles followed Mendelian proportions in all the samples studied. Furthermore, this study shows the importance of restriction map analysis of DNA in the vicinity of the probe of an oncogene to distinguish natural polymorphisms from the disease-related rearrangements in the gene.

DNA↗
PubMed1992

Biomechanical study on the load-bearing characteristics of the fibula and the effects of fibular resection.

The objective of this research was to investigate the load-bearing function of the fibula in relation to donor leg morbidity in patients who have had fibular resections. Biomechanical loading experiments were performed on ten anatomic specimens. Force transducers were mounted in place of resected tibial and fibular segments to allow load transmission to be measured. Load transmission through the fibula varied with ankle position. With the ankle at neutral position, the load distribution to the fibula averaged 7.12% of the total force transmitted through the tibia and fibula. Maximum loads occurred at full dorsiflexion and eversion. Resection of the proximal fibula results in a significant reduction of load through the distal fibular remnant. The values varied between 0.62% and 0.81% of the total force transmitted. When a cortex screw was introduced to anchor the distal fibula remnant to the tibia, the load distribution to the distal fibula remnant was partially restored with values ranging from 1.71% to 5.14% of the total force transmitted depending on the different ankle positions. These observations suggest that more consideration of the loading characteristics of the fibula should be taken into account in planning resection operations.

Biomechanical Phenomena↗
PubMed1992

Value of gait analysis in the assessment of surgery in cerebral palsy.

Twenty-three ambulatory children with cerebral palsy were assessed preoperatively by a detailed clinical examination and by gait analysis using a video-based gait analysis system (VICON). Surgery was then performed based on either the clinical assessment alone or a combination of clinical evaluation and gait analysis. About one year after surgery, a postoperative clinical and gait analysis assessment was performed. Sixteen children had improved and seven children had not improved after surgery. Most of the children who had not improved were found to have had operations that differed from those recommended by gait analysis. Dynamic EMG studies were found to be useful in preoperative planning but did not show any consistent improvement even in the children with good results. The combination of a careful clinical assessment and gait analysis can produce better results in surgery for children with cerebral palsy.

Adolescent↗
PubMed1991

Different patterns of chromosome and molecular breakage in classic Ph1 chronic myelogenous leukemia (CML) and variant Ph1 CML.

Variant translocations involving either chromosome 9, chromosome 22, or both with other chromosomes have been reported in about 8% of chronic myelogenous leukemia (CML) patients. In the 22 Ph+ patients studied in our laboratory, two showed variant translocations: t(9;22;11) (q34;q11;q13), and t(9;11) (q34;q11). We compared the pattern of involvement of different chromosomes (and bands) in secondary structural changes in CMLs carrying the t(9;22) (q34;q11) and in the variant translocations. Analysis showed significant differences in the pattern of involvement of different chromosomes and chromosome sites in the secondary structural changes in classic CMLs. This study, thus identifies nonrandomly involved chromosome sites that may be targeted for detailed molecular analysis to obtain an understanding of their role in disease progression. In the variant translocations chromosomes and chromosome bands were nonrandomly involved. Breakpoint cluster region (bcr) of the BCR gene was found to be rearranged in our two cases. We compared the location of molecular breaks within the bcr in classic and variant translocations. We found that translocation breaks occurred more frequently in the 5' region, and less frequently in the 3' region of bcr in variant translocations as compared with classic translocations. The significance of these findings in the etiology of CML is discussed.

Bone Marrow↗
PubMed1990

The effect of submandibular gland removal on testicular and epididymal parameters.

The effect of sialoadenectomy (submandibular gland removal) for four weeks duration was studied in five C3H mice and four sham-operated controls. This preliminary experiment using small numbers of animals indicated that sperm production parameters were lowered in sialoadenectomized animals although there were no significant differences between the sialodenectomized and sham-operated group. In a second experiment using larger numbers of animals, significant differences in testicular weights, epididymal weights, and testis weights were noted. These parameters were reduced only 10-14% from control levels. Epididymal sperm head counts were reduced 10% after sialoadenectomy but the two groups were not significantly different (P less than 0.05). No difference in testicular histology was observed. The present report contrasts to that of Tsutsumi et al. (1986) who indicate that submandibular removal with subsequent depletion of epidermal growth factor (EGF), is extremely deleterious (40-55% decreases in spermatid and sperm content) to the progress spermatogenesis.

Animals↗
PubMed1990

Donor site morbidity following resection of the fibula.

Ten adults were studied two to seven years after resection of a fibula for use as a free vascularised bone graft. Six had no symptoms in the donor leg, four had some aching, weakness or paraesthesia and three had definite weakness of the long toe flexors and extensors. All knees and ankles were clinically and radiologically stable, but the distal fibular remnant was osteoporotic in nine patients. Gait analysis of the donor leg and the contralateral normal leg showed definite differences, which could be attributed to weakness of the deep muscles caused by loss of their normal origin and to the change in load transmission through the fibula.

Adult↗