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Biomedical subjects

C W Chung

Publications and source records attributed to C W Chung.

At least 37 records · Page 2Linked to original sources
PubMed1999

Laparoscopic splenectomy for immune thrombocytopenic purpura--long-term result of 40 laparoscopic splenectomies.

Laparoscopic surgery has recently extended its indications and it has also become an acceptable surgical approach for splenectomy. In the last five years, we have performed 40 laparoscopic splenectomies for immune thrombocytopenic purpura. Thirty-five patients were female and 5 patients were male. The mean age was 34, varying from 17 to 56. After learning to perform laparoscopic splenectomy with five ports, we are now usually using three or four ports in a right lateral kidney position. There was no case of conversion to exploratory laparotomy. The mean hospital stay was 7 days. There was no perioperative mortality; but in 2 cases we had postoperative subphrenic abscesses which were successfully managed by catheter drainage. Since undergoing laparoscopic splenectomy, 28 patients (70%) were weaned effectively from their steroid medications. Eight patients (20%) have been on small doses of steroid, and 4 patients (10%) have been on the same doses of steroid with no response. The patient group with rapidly increasing platelet count after splenectomy showed a statistically significant relation with the complete response group (p < 0.001). Laparoscopic splenectomy is a safe and reasonable operative procedure for patients with immune thrombocytopenic purpura.

Adolescent↗
PubMed1999

Development of a robotic navigation system for neurosurgery.

This paper presents a robotic navigation system for image-guided neurosurgery, which can be applied to the treatment of Parkinson's disease and biopsy of brain tumor. The system integrates a computer for real-time display of brain anatomy, a magnetic tracking device for measuring the positions and orientations of surgical instruments, and a robot manipulator for guiding surgical instruments to the preplanned positions and orientations. The computer display of brain anatomy offers a convenient tool for surgeons to diagnose brain disease and to plan safe surgical paths; while the tracking device assists the robot manipulator to automatically guide surgical instruments to the preplanned direction. The registrations among the tracking device, the image system, and the robot are completed on the base of coordination mappings of external markers. An experiment of using a skull model for simulating a robotic biopsy of brain tumor has been done to verify the performance of the navigation system. The result shows that the system can accomplish a positioning accuracy around 2 mm.

Biopsy↗
PubMed1998

Identification of a glycosaminoglycan binding surface on human interleukin-8.

The activation of leukocytes by chemokines is believed to be mediated via binding of chemokines to glycosaminoglycan chains of the extracellular matrix. The binding site on the chemokine interleukin-8 (IL-8) for the glycosaminoglycan heparin has been characterized using a systematic series of site-directed mutants of IL-8 in which the basic residues of the protein have been replaced by alanine. Mutation of K64 and R68 caused the largest decrease in affinity for a heparin Sepharose matrix, with smaller effects seen with mutations of K20, R60, and K67. Heparin-derived disaccharides that could disrupt the IL-8-heparin Sepharose interaction were identified by a competitive binding assay. Heteronuclear NMR spectroscopic titration of 15N-labeled IL-8 with a trisulfated disaccharide revealed a cluster of residues on IL-8 which were perturbed by disaccharide binding. These data identify a heparin-binding surface on IL-8 that includes the C-terminal alpha-helix and the proximal loop around residues 18-23. The heparin-binding site is spatially distinct from the residues involved in receptor binding.

Affinity Labels↗
PubMed1998

The effect of the nasopharyngeal air cavity on x-ray interface doses.

We investigated the impact of air cavities in head and neck cancer patients treated by photon beams based on clinical set-ups. The phantom for investigation was constructed with a cubic air cavity of 4 x 4 x 4 cm3 located at the centre of a 30 x 30 x 16 cm3 solid water slab. The cavity cube was used to resemble an extreme case for the nasal cavity. Apart from measuring the dose profiles and central axis percentage depth dose distribution, the dose values in 0.25 x 0.25 x 0.25 cm3 voxels at regions around the air cavity were obtained by Monte Carlo simulations. A mean dose value was taken over the voxels of interest at each depth for evaluation. Single-field results were added to study parallel opposed field effects. For 10 x 10 cm2 parallel opposed fields at 4, 6 and 8 MV, the mean dose at regions near the lateral interfaces of the cavity cube were decreased by 1 to 2% due to the lack of lateral scatter, while the mean dose near the proximal and distal interfaces was increased by 2 to 4% due to the greater transmission through air. Secondary build-up effects at points immediately beyond the air cavity cube are negligible using field sizes greater than 4 x 4 cm2. For most head and neck treatment, the field sizes are usually 6 x 6 cm2 or greater, and most cavity volumes are smaller than our chosen dimensions. Therefore, the influence of closed air cavities on photon interface doses is not significant in clinical treatment set-ups.

Air↗
PubMed1996

Selectivity and antagonism of chemokine receptors.

The chemokine superfamily can be subdivided into two groups based on their amino terminal cysteine spacing. The CXC chemokines are primarily involved in neutrophil-mediated inflammation and, so far, two human receptors have been cloned. The CC chemokines tend to be involved in chronic inflammation, and recently we have cloned a fourth leukocyte receptor for this group of ligands. Understanding what makes one receptor bind its range of agonists is important if we are to develop potent selective antagonist. We have started to investigate the molecular basis of this receptor selectivity by looking at why CC chemokines do not bind to the CXC receptors in several ways. First, we looked at the role of the three-dimensional structure of the ligand, and have solved the three dimensional structure of RANTES using nuclear magnetic resonance spectroscopy. The structure is similar to that already determined for the CC chemokine macrophage inflammatory protein-1 beta, and it has a completely different dimer interface to that of the CXC chemokine interleukin-8 (IL-8). However, the monomer structures of all the chemokines are very similar, and at physiological concentrations the proteins are likely to be monomeric. Second, by examining all the known CC and CXC chemokines, we have found a region that differs between the two subfamilies. Mutations of one of the residues in this region, Leu-25 in IL-8, to tyrosine (which is conserved at this position in CC chemokines) enables the mutant IL-8 to bind CC chemokine receptor-1 (CC-CKR-1) and introduces monocyte chemoattractant activity. Using other mutations in this region, we can show a direct interaction with the N-terminus of CC-CKR-1. Third, we have found that modification of the amino terminus of RANTES by addition of one amino acid makes it into an antagonist with nanomolar potency. Taken together, this data suggests a two-site model for receptor activation and for selectivity between CC and CXC chemokines, with an initial receptor contact provided by the main body of the chemokine, and activation provided by the amino terminal region.

Amino Acid Sequence↗
PubMed1996

Peptidergic innervation of the primate meibomian gland.

PURPOSE: To localize and characterize nerves in primate meibomian glands using immunohistochemical staining for neuropeptides and neuronal enzymes. METHODS: Upper eyelids were obtained from seven rhesus monkeys (Macaca mulatta) and one cynomolgous monkey (Macaca fascicularis). The tissues were fixed either by immersion in Zamboni's fixative or by transcardiac perfusion with paraformaldehyde and glutaraldehyde and were then postfixed. Cryostat tissue sections of the lids were stained by immunohistochemistry using rabbit antisera to neuron-specific enolase (NSE), tyrosine hydroxylase (TH), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), and substance P (SP), followed by a fluorescence visualization system. RESULTS: Used as a marker for the overall nerve distribution, NSE antibodies revealed abundant smooth and varicose nerve fibers closely apposed to the basement membranes of acini of the meibomian glands. Numerous nerve fibers near the meibomian gland acini were immunoreactive for NPY and VIP, but nerve fibers containing TH, CGRP, and SP were more sparse in the meibomian glands. Nerve fibers also were visualized in other eyelid structures, including conjunctiva, epidermis, hair follicles, and subconjunctival lymphoid follicles. CONCLUSIONS: The meibomian glands of rhesus and cynomolgous monkeys are richly innervated by diverse nerve fiber types. The immunohistochemical staining suggests a largely parasympathetic origin for this innervation, with relatively smaller contributions from sympathetic and sensory sources. These findings also suggest that meibomian gland secretion is under the control of diverse neurotransmitter-neuromodulator mechanisms.

Animals↗
PubMed1995

The three-dimensional solution structure of RANTES.

The solution structure of the chemokine RANTES (regulated on activation, normal T-cell expressed and secreted) has been determined using NMR spectroscopy. Backbone and side-chain 1H and 15N assignments have been obtained using a combination of two-dimensional homonuclear and three-dimensional heteronuclear spectra. Regular elements of secondary structure have been identified on the basis of a qualitative interpretation of NOE data, J(NH-H alpha) coupling constants, and amide exchange rates. Three-dimensional structures were calculated from a total of 2146 experimental restraints using a combination of distance geometry and simulated annealing protocols. For the 13 best structures the average backbone (N, C alpha, C) atomic rmsd from the mean coordinates for residues 5-65 is 0.64 A (+/- 0.14 A) for the dimer and 0.50 A (+/- 0.08 A) for the individual monomers. Each monomer consists of a three-stranded antiparallel beta-sheet (residues 26-30, 38-43, 48-51) in a Greek key motif with a C-terminal helix (56-65) packed across the sheet, an arrangement similar to the monomeric structure of other members of this chemokine family (IL-8, PF4, MGSA/Gro alpha, and MIP-1 beta). Overall, the RANTES dimer resembles that previously reported for MIP-1 beta.

Amino Acid Sequence↗
PubMed1995

Pulmonary artery aneurysm presenting as a lung mass.

We describe a case of pulmonary artery aneurysm in which clinical clues and conventional imaging suggested a lung tumor, and the actual nature of the lesion was discovered at the time of thoracotomy. This case shows the importance of an awareness of this condition in the formulation of a differential diagnosis for a lung mass.

Aneurysm, Infected↗
PubMed1993

Health insurance and utilization of medical care for children with special health care needs.

Based on analyses of the 1988 National Center for Health Statistics, National Health Interview Survey, Child Health Supplement, this study examines the insurance coverage and utilization of physicians, hospitals, and prescribed medicine among the 9.6 million U.S. children with special health care needs, defined as children who had one or more selected chronic conditions that caused them to experience pain, discomfort, or being upset often or all of the time in the last year, or who were limited in their major childhood activities (playing or going to school) as a result of these or other impairments or health problems. The findings confirmed that substantial variation in access to routine medical care exists among these children. Though health status is an important predictor of which children use services in general, poor, minority children who lived with their mother or someone other than their parents, or those without insurance or an identifiable regular medical provider were most likely to experience financial barriers to access or were less apt to seek care than other children with comparable needs. Access to routine medical care remains particularly problematic for these subsets of children with special health care needs.

Adolescent↗
PubMed1992

Comparison of hepatitis B virus subtyping of d/y determinants by radioimmunoprecipitation assay and the polymerase chain reaction.

Using a double polymerase chain reaction a method was devised for detecting and subtyping hepatitis B virus DNA in serum samples. Primers from the S-gene were selected from the sequence analyses of five HBV HBsAg subtypes, to amplify HBV DNA and subtype for y specific DNA. Thirty-eight samples were subtyped for d and y determinants by radioimmunoprecipitation assay (RIPA) and the polymerase chain reaction (PCR). Subtyping by PCR and RIPA was in agreement in 100% of subtype y samples and 83.3% of subtype d, giving an overall correlation of 92.1%. As a third comparison, 12 amplified samples were digested by the restriction enzyme Sau 3A, which differentiates between subtypes y and d. The digest results agreed with PCR in 83.3% of the samples. In addition, we compared our standard phenol/chloroform extraction against a rapid one step method. The phenol/chloroform stage was found to be essential for the removal of nucleases and polymerase inhibitors present in sera.

Base Sequence↗
PubMed1992

Evaluation of antioxidant treatment with superoxide dismutase in rat liver transplantation after warm ischemia.

In order to investigate the effects of the exogenously administered radical scavenger superoxide dismutase (SOD) on the orthotopic liver graft, livers from male Wistar rats were transplanted after subjection to 40 min of warm ischemia and 30 min of storage at 4 degrees C. SOD was given at the onset of ischemia and before reperfusion as a supplement (6,000 IU) to the washout solutions. 30,000 IU were infused into the recipient. SOD reduced tissue levels of thiobarbituric acid-reacting substances at the end of ischemia (737 vs. 956 nmol/g; p < 0.01) and 60 min after the onset of reperfusion (629 vs. 947 nmol/g; p < 0.001) and preserved total adenine nucleotides after reperfusion (11.69 vs. 10.40 mumol/g; p < 0.01). Survival 2 weeks after transplantation was 18% (2/11) in the SOD group versus 10% (1/10; nonsignificant) in untreated animals. It is concluded that SOD protects the ischemically altered liver from radical mediated peroxidation and preserves hepatic energy stores upon reperfusion. However, in our model no major improvement in organ viability could by achieved.

Adenine Nucleotides↗
PubMed1990

A case of Leigh's disease with initial manifestation of dystonia.

A case of Leigh's disease (subacute necrotizing encephalomyelopathy) is reported with such noteworthy features as early onset, dystonia, paraparesis the presence of low attenuation areas in both basal ganglias on computerized tomography of the brain and the presence of a high signal intensity in both basal ganglias in T2 weighted image by MR. The electron microscopic findings of muscle biopsy are suggestive of pleoconial mitochondrial myopathy.

Basal Ganglia↗
PubMed1977

Sensitization potentials of methyl, ethyl, and n-butly methacrylates and mutual cross-sensitivity in guinea pigs.

Guinea pigs could be strongly sensitized to methyl, ethyl, and n-butyl methacrylates in ethanol or olive oil by the topical route, or in saline by the intradermal route. For elicitation of skin reactons, topical challenge with the compounds in olive oil or intradermal challenge with saline as the solvent was neccessary. Topical challenge with the methacrylates in ethanol failed to elicit any allergic skin reactions because of their volatility. All sensitized animals responded strongly not only to the inducing methacrylate but also to the other methacrylates, showing that mutual cross-sensitivity had occurred. Since methyl methacrylate has been reported to be a potent sensitizer in humans, the guinea-pig model described here may be useful for screening products before marketing.

Acrylates↗
PubMed1976

Dermal carcinogenicity study by mouse-skin painting with 2,4-toluendediamine alone or in representative hair dye formulations.

The chronic toxicity of 2,4-toluenediamine (2,4-TDA) alone or in conbination with a hair dye complex (2,5-toluenediamine, p-phenylenediamine, and resorcinol) was studied in Swiss-Webster mice of both sexes by a skin-painting technique. The predominant neoplasms seen in these mice were primary pulmonary adenomas and adenocarcinomas. Skin neoplasms were seen in most groups of mice, including untreated control mice. Statistical analysis of the incidences of skin neoplasms among the various groups of mice did not show any significant differences. The 2,4-TDA alone or mixed with the hair dye complex did not produce any abnormal proliferation and maturation of the squamous epithelium of the skin. The 2,4-TDA under our experimental conditions was found to be nontoxic and noncarcinogenic to the skin of mice.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Cross-sensitivity of common aminoglycoside antibiotics.

Guinea pigs were sensitized to neomycin (A, B, or C), paromomycin, gentamicin, kanamycin, streptomycin, and dihydrostreptomycin via intradermal or foot-pad injection with an adjuvant containing killed Mycobacterium butyricum or M tuberculosis H37Ra (Ra). These antibiotics produced greater cross-sensitization with an increase in the number of immunizations and chemical structural similarities. After repeated intradermal injections (adjuvant Ra) of neomycin, guinea pigs showed cross-sensitization to paromomycin, kanamycin, and streptomycin. A single intradermal injection of one of these antibiotics produced stronger reactions to the most closely related antibiotics, with no meaningful sensitization to the least-related allergens. Streptomycin-sensitized guinea pigs seldom showed a meaningful cross-sensitization to dihydrostreptomycin or the other antibiotics (except neomycin C); however, guinea pigs sensitized to dihydrostreptomycin or the other antibiotics often showed strong cross-sensitization to streptomycin.

Aminoglycosides↗