Biomedical subjects

J C Choi

Publications and source records attributed to J C Choi.

32 records · Page 2Linked to original sources

PubMed1999

Hepatic involvement in hypereosinophilia: sonographic findings.

Hypereosinophilic syndrome may cause eosinophil-related tissue damage to various organs. The purpose of this paper is to describe sonographic findings in 13 patients with hypereosinophilia in whom the liver was involved. The diagnosis in these 13 patients was based on liver biopsy in seven patients with bone marrow biopsy in six patients. Eight patients had hypereosinophilic syndrome and five patients had clonorchiasis. All 13 patients had mild to marked hepatomegaly. Seven of 13 patients showed multiple round or oval hypoechoic (n = 6) or variably echogenic (n = 1) lesions measuring 1 to 2 cm with poorly defined margins in both lobes of the liver. Four patients had one or two hypoechoic lesions 3 to 4 cm in size, with geographic pattern and poorly defined margins. Two patients showed diffuse hepatomegaly with increased parenchymal echogenicity. The number of lesions and the extent of diffuse lesions seem to be proportional to the degree of eosinophilia. Hypereosinophilia may produce multiple small focal hepatic lesions or diffuse segmental or lobar echogenic lesions simulating primary or metastatic tumor of the liver.

Adult↗

PubMed1999

Porous polyethylene channel implants: a modified porous polyethylene sheet implant designed for repairs of large and complex orbital wall fractures.

PURPOSE: To evaluate the effectiveness of a modified porous polyethylene implant in orbital fracture repair. A porous polyethylene channel implant (PPCI) has internal channels that accept mini- or microplates from conventional plating systems, facilitating fixation to bone in the reconstruction of large, complex orbital fractures. METHODS: The authors used 29 PPCIs to repair 25 orbits. Seventeen cases involved repair of an acute (less than two weeks after injury) fracture of one or more orbital walls. Eight cases represented delayed reconstruction of orbital walls for late enophthalmos or for residual defects after previous operations. RESULTS: A PPCI provides a stable platform for orbital soft tissue. Excellent results were obtained in all patients with acute orbital fractures, whereas good or excellent corrections of enophthalmos and hypoglobus were achieved in all patients who underwent late repair. There were no instances of orbital infection, implant exposure or migration, worsening diplopia, visual loss, or loss of structural support during 31 months of follow-up. CONCLUSIONS: A PPCI allows controlled placement of a porous polyethylene sheet with secure fixation to stable bone. The implant design allows it to be cantilevered from the orbital rim to serve as a stable platform when fractures are too large to support the implant in the posterior orbit. PPCIs are ideally suited for reconstruction of defects resulting from displacement of orbital walls and for repair of posterior floor fractures, medial wall fractures, and combined floor and medial wall defects.

Adult↗

PubMed1998

The role and results of bone grafting in revision total knee replacement.

Failure in total knee replacement requiring revision surgery is often accompanied by significant bone loss and soft tissue asymmetry. When embarking on these complex reconstructions, careful preoperative planning is necessary to ensure that these deficiencies will be corrected by surgical technique and implant selection. This article discusses various techniques and results of bone grafting in revision total knee arthroplasty.

Arthroplasty, Replacement, Knee↗

PubMed1998

Porous polyethylene sheet implant with a barrier surface: a rabbit study.

Soft tissue adhesion to the porous polyethylene sheet implant (PPSI) raises the concern of postoperative extraocular motility disturbance after orbital blowout fracture repairs using PPSI. A PPSI with a barrier surface (PPSI-B) has been developed to reduce adhesion between soft tissue and the implant. Six PPSI-B and six conventional PPSI were implanted under the scalps of three New Zealand white rabbits. The implants were harvested at 2-, 4-, and 20-week intervals. Clinical and histologic comparisons were made between PPSI-B and PPSI with regard to adhesion at the soft tissue-implant interface. Clinically, PPSI-B demonstrated less adhesion between soft tissue and implant compared with the conventional PPSI. Both types of implants demonstrated a complete fibrovascular ingrowth by 2 weeks. Because PPSI-B causes less adhesion at the soft tissue-implant interface, consideration should be given to the use of PPSI-B in repairs of orbital blowout fractures in which extraocular muscle is exposed to the implant surface.

Animals↗

PubMed1998

Trabeculectomy with intraoperative 5-fluorouracil.

BACKGROUND AND OBJECTIVE: To investigate the outcome and complication rates of trabeculectomy following the combined use of intraoperative, topical 5-fluorouracil (5-FU) and low-dose, postoperative subconjunctival 5-FU injections. PATIENTS AND METHODS: Forty-one eyes of 41 patients with advanced, medically uncontrolled glaucoma underwent trabeculectomy with intraoperative episcleral application of 5-FU (50 mg/ml for 5 minutes). A variable number of subconjunctival 5-FU injections were administered postoperatively at the discretion of the operating surgeon. RESULTS: Six-, 12-, and 15-month life-table success rates (5 mm Hg < or = intraocular pressure [IOP < or = 21 mm Hg) were 100%, 97%, and 83%, respectively. Mean postoperative IOP was 12.1 +/- 4.3 mm Hg. An average of 2.2 +/- 1.6 (range 0 to 7) supplemental subconjunctival 5-FU injections were administered postoperatively. Corneal epithelial erosions developed in 7 (17%) of the eyes. Five of 7 patients who underwent subsequent surgical procedures maintained successful control of IOP at an average of 11.0 +/- 4.8 (range 5 to 16) months after the secondary surgery. CONCLUSION: Trabeculectomy with intraoperative 5-FU is effective in controlling IOP while possibly minimizing the need for frequent postoperative injections and the occurrence of corneal epitheliopathy.

Adult↗

PubMed1997

Use of botulinum A toxin in patients at risk of wound complications following eyelid reconstruction.

Our purpose was to determine the efficacy of botulinum A toxin (BOTOX) in promoting wound immobilization and preventing wound dehiscence in patients at risk of wound-healing complications following eyelid reconstruction. In 11 patients at risk of postoperative wound complications, we injected BOTOX into the periocular musculature in addition to standard suture tarsorrhaphy. Each patient experienced excellent wound immobilization and wound healing. There were no complications. Adjuvant use of BOTOX, in conjunction with suture tarsorrhaphy, immobilizes the eyelids and promotes wound healing in patients at risk of wound complications following eyelid reconstruction.

Adult↗

PubMed1996

Specific sequences of fibronectin activate the protein kinase C signal transduction pathway in invasive bladder cancer.

The mechanism of human bladder cancer cell invasion is not clear, but it appears that extracellular matrix components, such as fibronectin, may be involved. To investigate the role of fibronectin in tumor cell invasion and progression, we used an in vitro invasion assay to define the motility stimulating fragment of fibronectin for invasive human bladder cancer T24 cells. Using a modified Boyden chamber assay and purified fragments of fibronectin, we demonstrated that both the 120 kDa chymotrypsin generated fragment of fibronectin (containing the cell attachment RGD motif and additional sequences towards the carboxyl-terminal heparin binding domain), as well as the trypsin generated 60 kDa fragment of fibronectin (containing the carboxyl-terminal heparin binding domain and additional sequences towards the cell attachment RGD motif), were able to stimulate the migration of invasive human bladder cancer T24 cells. Control fragments containing only the amino-terminal gelatin binding region of fibronectin did not stimulate the motility of the human bladder cancer T24 cells. To determine the molecular mechanism in which these fragments may stimulate the migration of the T24 cells, we assayed for intracellular signal transduction pathway protein kinase C (PKC). We demonstrated that both the 120 kDa and the 60 kDa fragments were able to stimulate the activation of protein kinase C. Non-motility stimulating fragments of fibronectin were not able to activate protein kinase C. We conclude that the PKC signal transduction pathway may be involved in matrix mediated motility, and suggest that the inhibition of such pathway(s) may alter the malignant phenotype of human bladder cancer.

Amino Acid Sequence↗

PubMed1995

Porous polyethylene implant for orbital wall reconstruction.

Short-term and intermediate-term results from clinical use of high-density porous polyethylene implants for reconstructive orbital surgery have been encouraging. This article presents an intermediate-term result from one institution with a comprehensive comparative analysis of other available alloplastic materials. A patient survey of 32 cases of orbital reconstruction using porous polyethylene sheet implants was performed, with a mean follow-up period of 32 months (range 15 to 67). All cases were trauma-related injuries. The result was compared with that of published reports of other alloplastic materials with specific emphasis on complication rates. Complication rate following the use of porous polyethylene sheet implants was 6%. This finding was consistent with those of other reports on porous polyethylene sheet implants. A consistent, satisfactory surgical outcome and low complication rate were observed. In the authors' review, the porous polyethylene implants compared favorably in a comparative analysis of other alloplastic materials.

Adolescent↗

PubMed1994

Bacillus Calmette-Guérin interacts with the carboxyl-terminal heparin binding domain of fibronectin: implications for BCG-mediated antitumor activity.

Intravesical bacillus Calmette-Guérin (BCG) has been shown to be an effective treatment for superficial transitional cell carcinoma of the bladder. The mechanisms by which BCG achieves this effect remain unclear. Reports have attributed an important role to fibronectin both in the initial attachment of BCG to bladder surfaces and in the limitation of tumor cell motility. In the present study, using limited protease cathepsin B degradation followed by Western blot analyses with antibodies to various domains of the fibronectin molecule, we showed that BCG appears to bind to fibronectin near the carboxyl terminal and adjacent to the heparin binding domain. Furthermore a 51-chromium release assay with human bladder cancer cell line T24 as target cells and lymphokine activated killer (LAK) cells as effector cells showed that fibronectin was needed for tumor cytotoxicity by the LAK cells. By using antibodies and peptides to various domains of the fibronectin molecule, the heparin binding domain, but not the cell binding domain, carboxyl terminal region, or the amino terminal region of the fibronectin molecule, was identified as essential to tumor cell lysis by the LAK cells. Flow cytometric analysis showed that both peripheral blood lymphocytes and the LAK cells express fibronectin receptors VLA-3, VLA-4 and VLA-5 on their surfaces. However, the numbers of receptors are not significantly different in the two cell populations. We conclude that, by binding near the carboxyl terminal region and adjacent to the heparin-binding domain of the fibronectin molecule, BCG may protect this region of the molecule from tumor proteases, and may thus allow the antitumor activity of the host immune cells to take place.

BCG Vaccine↗

PubMed1992

Neural-vascular relationships in central retina of macaque monkeys (Macaca fascicularis).

The relationship of the vasculature to the neuronal layers was studied in whole-mounts and in sections of macaque retinas. Like other central nervous structures, primate retinas have local variations in vascularity that reflect local variations in metabolism, rather than simply tissue thickness or volume. A special feature of the retina is a dense vascular plexus in the nerve fiber layer, which is unmyelinated and hence must generate a substantial metabolic demand for ion pumping. Much of the retinal vasculature is laminated and located at specific layer boundaries. Throughout the central retina, two planes of capillaries bracket the inner nuclear layer to form a sclerad capillary network. In some regions, especially near the fovea, a second, more vitread network brackets the ganglion cell layer with another pair of capillary planes. Wherever the nerve fiber layer is thick, the vitread network becomes less planar and is multilayered. When surrounded by nerve fibers, capillaries tend to orient parallel to the fibers; when adjacent to ganglion cell bodies, the capillaries are less systematically oriented. At the border between the nerve fiber layer and the ganglion cell layer, rows of ganglion cells often interdigitate with nerve fiber bundles, resulting in local perturbations of capillary orientation. The volume of the sclerad capillary network is relatively constant at different locations, but the volume of the vitread network increases dramatically where the nerve fiber layer is thick. As a result, the vascularity of the retina is greatest in the peripapillary region near the optic disk, even though the total thickness of the peripapillary retina is comparable to the retinal thickness near the foveal crest. As many as 60-70% of the photons passing through the retina in the peripapillary region will encounter one or more capillaries before reaching a photoreceptor. Median capillary diameter increases with retinal depth from 4.5-4.7 microns in the nerve fiber layer to 5.0 microns at the sclerad border of the inner nuclear layer. Capillary diameter in the nerve fiber layer also increases near the optic disk.

Animals↗

PubMed1991

Ossifying fibroma.

Our experience includes seven cases of ossifying fibroma. The condition also appears in the literature under diagnostic names such as congenital fibrous dysplasia, congenital osteitis fibrosa, congenital fibrous defect of the tibia, and osteofibrous dysplasia of the tibia and fibula. The lesions develop in childhood and are located in the diaphysis of the tibia, or fibula. Of seven patients, we performed wide excision with free vascularized fibular graft in five cases, wide resection of the distal one-third of the fibula in one case, and curettage and bone graft in one case. Two of the patients who had wide excision with free vascularized fibular graft had recurrence. One case of recurrence occurred where incomplete wide excision with free-vascularized fibular graft was performed because the lesion was too close to the distal epiphysis of the tibia. One of the patients who had curettage and bone graft also had recurrence. It was concluded that children who have an ossifying fibroma requiring surgery can safely be treated with wide excision with or without free-vascularized fibular graft.

Adolescent↗

PubMed1990

Candidate cell populations for respiratory chemosensitive fields in the human infant medulla.

The histology and location of human respiratory chemosensitive fields are not known. In contrast, the physiology of respiratory chemosensory areas in the ventral medulla of cats has been studied extensively, and their anatomy has been partially described. Using basic principles of comparative cytoarchitecture and computer-aided reconstructions of serial-sectioned medullae, we describe the histology and three-dimensional distribution of putative respiratory chemosensors in the feline and human infant medulla. We found that ventrolateral neurons of the human nucleus conterminalis are homologous to neurons identified in the feline L chemosensitive field by Trouth and others, and that ventrolaterally situated neurons in the human arcuate nucleus correspond to neurons predominating in the feline S and M fields. In addition, there are foci of thickened marginal glia along the feline ventral medullary surface that colocalize with chemosensitive fields identified by physiologic studies reported by others; we identify similar foci in the infant medulla. Thickened marginal glia are intermixed with neuronal fibers, often adjacent to neurons of the feline chemosensitive fields and their human counterparts, suggesting that they constitute a chemosensory neuropil at the medullary surface. Computer-aided reconstructions provide insight into the three-dimensional topography of putative respiratory chemosensors and their relationships to other brainstem structures in ways not obvious in single or even multiple sections. This delineation of candidate human respiratory chemosensors is a first step toward their postmortem analysis in patients with central ventilatory control disorders where finding histological abnormalities in these sites would support their role in human ventilation.

Animals↗

PubMed1982

Effects of phenylethanolamine N-methyltransferase inhibitors on rat brain catecholamine levels and body temperature.

Inhibitors of phenylethanolamine N-methyltransferase (PNMT) were found to reduce hypothalamic and brainstem epinephrine (Epi) content, as well as the body temperature of male Sprague-Dawley rats. In the drug-treated animals, the time course for reduction of body temperature was better correlated with the reduction in brainstem Epi content than with the reduction in hypothalamic Epi content. These results suggest that brainstem Epi neurons may be directly involved in the regulation of body temperature by activating the heat production center or by preventing heat loss.

Animals↗

PubMedDate not supplied

Orthopedic problems in Lesch-Nyhan syndrome.

Lesch-Nyhan syndrome is an X-linked disorder of purine metabolism. The orthopedic problems and results of treatment of nine Lesch-Nyhan patients are reviewed. Associated orthopedic problems included hip subluxation or dislocation (nine of 18 hips), fractures (three), autoamputation, infections (three), minor scoliosis, and contractures. Lesch-Nyhan patients can safely undergo orthopedic procedures and the results of surgery are satisfactory and similar to those of patients with spastic cerebral palsy. All of the seven operated-on hips maintained good reduction at 6-year mean follow-up. With adequate cast technique, fractures and hip subluxation/dislocation may be treated successfully. The treating orthopedist should be aware of the increased incidence of heterotopic ossification in this population, as well as the potential for serious complications such as hardware failure or femur fracture, if appropriate immobilization is not used.

Adolescent↗