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Biomedical subjects

J H Hong

Publications and source records attributed to J H Hong.

At least 145 records · Page 8Linked to original sources
PubMed1990

[Effect of eye shielding block position on dose to lens during radiation therapy].

The lens of the eye is very sensitive to radiation and a low dose of radiation may induce cataracts a few years after radiation therapy. In treatment of head and neck tumors, such as cancer of the ethmoid or maxillary sinus, an adequate eye shielding block is mandatory for reducing the lens dose in order to prevent cataract formation. Experiments were designed to simulate the setup of the lens during radiation therapy and it was observed that the dose to the lens was correlated with the distance between the eye shielding block and the eye surface for Co-60, 10MV and 6MV X-rays. With properly fabricated divergent blocks, the optimal shielding points were found to be 6 cm, 0.9 cm and 1.4 cm above the eye surface for Co-60, 10MV and 6MV X-rays, respectively. In a 10 x 10 cm2 field, by moving the eye shielding block on the blocking tray to the optimal shielding point near the surface, the dose to the lens can be reduced from 14% to 8% for Co-60 beams and from 17% to 7% for 10MV and 6MV X-rays. This effect is more evident in larger field sizes. We recommend that the eye shielding block be placed at the optimal shielding point to minimize the dose to the lens. If the eye shielding block cannot be placed at the optimal shielding point, a simple coin placed on the eye lid surface will also reduce the lens dose substantially when a regular eye shielding block is placed on the blocking tray (Lin's coin effect).

Cataract↗
PubMed1990

The pattern of organ donation in a large urban center.

Despite increasing referrals for organ donation in metropolitan New York, procurement has remained essentially unchanged from 1983 through 1988 at 9 to 13 per million population, falling far short of increasing demand. This is not due to delay in the diagnosis of brain death, higher discard rates, or increased medical unsuitability, although exclusion because of human immunodeficiency virus (HIV) disease, or risk thereof, has increased and now accounts for 38% of exclusions. Consent for organ donation remains consistently low among blacks (24%), has increased among Hispanics from 17% in 1984 to 47% in 1988, and remains the highest, but without improvement, among whites. Causes for the observed stagnation and potential corrective factors include poorly focused educational efforts, lack of sensitivity to the grieving family by hospital personnel, physician frustration at the increasingly prominent role of government and its regulations in the practice of medicine, and eradication of competition between local organ procurement agencies.

Humans↗
PubMed1989

DNA topoisomerase: the mechanism of resistance to DNA topoisomerase II inhibitor VP-16.

K6-1 and 50B-3 cell lines, resistant to VP-16, a DNA topoisomerase II inhibitor, were established from two different types of cells respectively: human T-cell derived acute lymphoblastic leukemia cell line RPMI8402 and mouse mammary tumor cell line FM3A. IC50 values of K6-1 and 50B-3 cells to VP-16, evaluated by the colony forming ability on methyl cellulose medium, were 11- and 84-fold higher than their sensitive parental cell lines, respectively. Membrane permeability of the drug was not responsible for the resistance in K6-1 and 50B-3 cells. Quantitative analysis of drug-induced DNA cleavage (so called cleavable complex formation) was performed using 32P end-labeled pBR322 restriction fragments. The formation of the topoisomerase II-DNA cleavable complex stimulated by VP-16 in 50B-3 cells was approximately 1/5 compared with that of FM3A wild-type cells. Dot blot analysis of RNA extracted from these cell lines showed that the levels of mRNA for DNA topoisomerase II in 50B-3 cells were markedly decreased and that catalytic activity was reduced to 1/2-1/3 compared with that of parent cells. There was a slight reduction of DNA topoisomerase II mRNA in K6-1 cells. However, DNA topoisomerase II activities were similar in wild-type and K6-1 cells. In addition, 50B-3 cells showed cross resistance to VM-26, m-AMSA and adriamycin, whereas K6-1 cells exhibited increased resistance only to VM-26. These resistant cell lines did not show collateral sensitivity to CPT-11, a DNA topoisomerase I inhibitor. Southern blot analysis of genomic DNA did not show any change in the restriction pattern of the DNA topoisomerase II gene between the parental and their resistant lines. These findings suggest that the reduced levels in DNA topoisomerase II contribute to the drug resistance of 50B-3 cells.

Animals↗
PubMed1981

Evaluation of anterior extravesical ureteroneocystostomy in kidney transplantation.

We evaluated the anterior extravesical ureteroneocystostomy technique in 184 consecutive renal transplants done in 2 consecutive calendar years. Complications included 5 cases of ureteral and 1 of pelvic necrosis, and 2 of ureteral obstruction, with a ureteral complication rate of less than 4 per cent. All cases of pelvic or ureteral necrosis except 1 were seen in cadaver donor kidneys that were imported from other centers. No bladder complications were seen. Pelvioureteral obstruction, presumably of congenital origin in the cadaver donor, was discovered in the kidney after transplantation in 2 cases and was corrected successfully by pyeloureterostomy to the native ureter. The extraordinary simplicity of this technique, coupled with improvement in the complication rate, makes it our procedure of choice.

Adult↗