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Biomedical subjects

C H Yoo

Publications and source records attributed to C H Yoo.

9 recordsLinked to original sources
PubMed1999

Long-term fate of heterotopic liver transplants in rats with portal vein inflow only.

Previous studies have suggested that hepatic arterial flow in heterotopic partial liver transplants is necessary to ensure graft survival and regenerative capacity. This report presents findings in a syngeneic rat strain (Lewis) that partial liver transplants can be successfully heterotopically transplanted in the long term with the only inflow coming from the portal vein. When the host liver undergoes a nearly complete resection at 3-4 weeks, the transplanted liver regenerates to maintain the health of the host. Moderate to massive hepatocellular necrosis occurs in the first 3 months postoperatively, with recovery by 4-5 months. Liver transplants 8-10 months postoperatively appear architecturally normal. No host liver tissues were found to be regenerating after subtotal host liver resection. We conclude that portal vein reconstruction without hepatic arterial inflow can sustain a partial liver transplant in the long term, replacing the function of the host liver.

Anastomosis, Surgical↗
PubMed1999

Update on sequential isologous rat organ transplantation: pancreaticoduodenal and kidney transplantations.

This periodic report includes intermittent results of consecutive pancreaticoduodenal (Pd) and kidney (Kt) transplants in inbred rats and results on double kidney transplants that did not follow sequential transplant protocol. Eight 24-month-old Lewis pancreas, kidney, and aorta served histological controls showing normal histological architecture with no atherosclerosis developed in the aorta. Thirty-four month old pancreas and thirty-two month old kidneys, which resided in young hosts for at least three occasions, appeared as youthful Pd and Kt grafts. They show normal histological appearance for more than the expected life span of a Lewis rat. The fact that not only pancreases but also kidneys outlived their host leads to the study of other different organs' viability as aged valuable grafts. Nevertheless, the threats by the development of atherosclerosis in graft-associated aortas resulted in slow progression of the follow-ups.

Animals↗
PubMed1999

Comparison of prognostic significance of nodal staging between old (4th edition) and new (5th edition) UICC TNM classification for gastric carcinoma. International Union Against Cancer.

The description of nodal staging for gastric cancer was changed in the new fifth edition of the International Union Against Cancer (UICC) TNM classification from the anatomic sites of metastatic lymph nodes to the number of metastatic lymph nodes, as pN1 is metastasis in 1 to 6 lymph nodes, pN2 is in 7 to 15 lymph nodes, and pN3 is in 16 or more lymph nodes. The purpose of this study was to investigate the prognostic significance of the new staging system based on the number of metastatic lymph nodes compared to the old staging system by anatomic site. From 1987 to 1994 a total of 2108 patients who underwent potentially curative resections with D2 or D3 lymph node dissection and with 15 or more lymph nodes retrieved were studied retrospectively. Lymph node metastases were found in 1018 patients (48.3%). A mean of 37.9 lymph nodes were retrieved per patient, and a mean of 7.2 lymph nodes were invaded by tumor cells. We found that the new nodal staging based on the number of metastatic lymph nodes closely correlated with the depth of cancer invasion and with the old nodal staging based on the anatomic site of the metastatic nodes, with statistical significance. The 5-year survival rates after gastrectomy decreased significantly by increasing the extent of the pN classification in both nodal staging methods. In a subgroup analysis of survivals between the old and new nodal staging, the new classification showed more homogeneous survival at the same stage than the old one. With a multivariate analysis of prognostic factors, including the old and new nodal staging, the depth of invasion and the new nodal stage were the most significant prognostic factors, followed by the old nodal stage. Our data suggested that the new nodal staging based on the number of metastatic lymph nodes is not only a reliable and objective method for nodal classification, but it is also a significant prognostic determinant for gastric cancer that can be used in practice.

Female↗
PubMed1998

An active noise control algorithm for controlling multiple sinusoids.

The filtered-x LMS algorithm and its modified versions have been successfully applied in suppressing acoustic noise such as single and multiple tones and broadband random noise. This paper presents an adaptive algorithm based on the filtered-x LMS algorithm which may be applied in attenuating tonal acoustic noise. In the proposed method, the weights of the adaptive filter and estimation of the phase shift due to the acoustic path from a loudspeaker to a microphone are computed simultaneously for optimal control. The algorithm possesses advantages over other filtered-x LMS approaches in three aspects: (1) each frequency component is processed separately using an adaptive filter with two coefficients, (2) the convergence parameter for each sinusoid can be selected independently, and (3) the computational load can be reduced by eliminating the convolution process required to obtain the filtered reference signal. Simulation results for a single-input/single-output (SISO) environment demonstrate that the proposed method is robust to the changes of the acoustic path between the actuator and the microphone and outperforms the filtered-x LMS algorithm in simplicity and convergence speed.

Acoustics↗
PubMed1997

Sequential isologous organ transplantation in inbred rats: pancreaticoduodenal transplants.

A total of 847 inbred Lewis rats of mixed sex were used in this pancreaticoduodenal (Pd) donor aging study. Pd grafts were taken from 9- to 12-month-old donors and transplanted into 3-month-old recipients (thus, the first generation Pd graft, or 1 Pd). After 9 to 12 months, the same Pd grafts were again harvested and transplanted into 3-month-old rats (thus the 2 Pd generation). This cycle was repeated to obtain the 3, 4, and 5 Pd series. Sequential transplantation was able to extend the Pd grafts' mean survival time to 32 months for fourteen 4 Pd grafts, and to 39.2 months for four 5 Pd grafts (the longest lived graft survived for 42 months). The pancreas and duodenal sections of the grafts remained normal throughout the entire study. However, the aortic sections of the grafts (which were harvested to include the superior mesenteric and celiac arteries) all exhibited moderate to massive atherosclerotic changes by the 5 Pd mean survival age of 39.2 months. Such histological changes commenced even before 21 months of Pd graft age in some animals, gradually progressing to dilation of the aorta (and subsequent narrowing of aortic tributaries), as well as formation of an eggshell-like inner membrane shielding the aortic intima, by 42 months. Such atherosclerotic changes precluded transplantations beyond the 5 Pd series.

Age Factors↗
PubMed1995

Transplantation of reproductive organs.

A historical review of the literature concerning replantation and transplantation of reproductive organs has included studies from this laboratory, using rats, over the past 25 years. From the basic observation of ischemic and traumatic injury due to the transplantation, syngeneic testicle transplants, resulting in a partner's impregnation and histological restoration of the testicles, led to human testicular transplantation. As to the ovarian transplants, granulosa-theca cell tumors may transform into malignancies if followed for a prolonged period as intrasplenic ovaries, and high doses (15 to 20 mg/kg b.w.) of azathioprine can produce such malignant tumors in a shorter period. By caval-portal shunt, ovarian hormones enter directly into the portal blood stream and no typical granulosa-theca cell tumors were produced, owing to the fact that the liver cannot degrade all the hormones secreted by both ovaries. While en-bloc vagino-utero-ovarian transplantation in the rat is possible, no impregnation has been yet achieved. Finally, it is hypothesized that those who have acquired microsurgical techniques and have a full understanding of the anatomy of the reproductive system will not only be able to perform replantation of the penis, but also will be capable of allogeneic transplantation of genital organs, whether ethically approved or not, and sooner than one may think. In such cases a penile part may be obtained at a sex-change surgery or from a cadaveric donor, similar to other vital organ transplantation practices.

Animals↗