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Biomedical subjects

Y C Li

Publications and source records attributed to Y C Li.

125 records · Page 7Linked to original sources
PubMed1990

[Synthesis and bacteriostatic activity of thiosemicarbazone and their transition metal complexes].

In this paper, 8 thiosemicarbazones and 12 transition metal complexes thereof have been synthesized and tested for bacteriostatic activity against five kinds of bacteria. The results show that hetero atom or substitution group in the o-position of the aryl ring to the carbonyl group in the aldehyde or ketone is essential to the bacteriostatic activity of the thiosemicarbazones, and different mechanisms of inhibition are followed by thiosemicarbazones and their complexes. The complexes displayed activity superior to the thiosemicarbazones.

Bacteria↗
PubMed1989

Two genes associated with liver cancer are regulated by different mechanisms in rasT24 transformed liver epithelial cells.

We compared the regulation of gamma-glutamyl transferase (gamma GT) and glutathione-S-transferase-P (GST-P) expression in rat liver epithelial cells (228 cells) and a line derived from them (C5 cells) by stable transfection with a metallothionein-activated ras fusion gene (MTrasT24). Earlier studies demonstrated that steady state RNA levels of these genes are increased after transformation of liver cells by MTrasT24 (Proc. Natl. Acad. Sci., 85, 344-348, 1988). In the present study, we found that the rate of gamma GT transcription increased approximately 20 fold after transformation by MTrasT24 while the rate of GST-P transcription increased no more than two fold. However, the stability of GST-P RNA was increased about 3 fold in these cells. Comparisons of gamma GT RNA stability were not possible since nontransformed liver cells (228) contain little or no gamma GT RNA. Thus, the accumulation of gamma GT RNA in C5 cells is heavily dependent on increased rates of transcription while the more modest increases in GST-P RNA levels result in large part from increased RNA stability. In ras transformed cells both transcriptional and post-transcriptional events contribute to the increased steady state RNA levels of cellular genes.

Animals↗
PubMed1989

[The polypeptides of mumps virus and their synthesis in infected chick embryo cells].

Strain ME of mumps grown in chick amniotic cavity and purified by differential centrifugation combined with sucrose gradient centrifugation. The structural polypeptides of purified virion were analyzed by SDS polyacrylamide gel electrophoresis. Eleven polypeptides were found. Their molecular weight were between 35K-72K dalton. In addition polymers of HN protein and F1 the large subunit of F protein were detected. Hela, Vero and CE cells were infected with ME strain of mumps virus. The CE cell reveals the most sensitive host cell. CE cell infected with mumps virus and labeled with [35S]-Met, SDS-PAGE and examined by autoradiography. It was found at least eight polypeptides were synthesis in host cells and their molecular weight were between 26.5K to 94K dalton. The time course of the synthesis of polypeptides in the cells were studies. Palse-Chase experiments demonstrated the posttranslational process of Fo----F.

Animals↗
PubMed1988

MTrasT24, a metallothionein-ras fusion gene, modulates expression in cultured rat liver cells of two genes associated with in vivo liver cancer.

We studied the effects of a zinc-inducible metallothionein-ras fusion gene (MTrasT24) in cultured rat liver epithelial (RLE) cells on expression of two genes induced during liver carcinogenesis in vivo: gamma-glutamyltransferase [(5-glutamyl)-peptide:amino acid 5-glutamyltransferase, EC 2.3.2.2] and glutathione S-transferase-P (RX:glutathione R-transferase, EC 2.5.1.18). Expression of MTrasT24 increased steady-state RNA levels of gamma-glutamyltransferase and glutathione transferase-P 6- to 100-fold and 1.6- to 6-fold, respectively; in contrast, levels of alpha-tubulin RNA fell slightly or were unchanged. RNA gel blots verified that gamma-glutamyltransferase and glutathione transferase-P RNAs were of the appropriate size, and results from immunocytochemistry on transfected cells demonstrated that RLE cells carrying MTrasT24 synthesized immunoreactive, appropriately localized gamma-glutamyltransferase and glutathione transferase-P. Zinc induction studies indicated that gamma-glutamyltransferase and glutathione transferase-P RNA levels were directly dependent on MTrasT24 RNA levels. These data suggest that expression of gamma-glutamyltransferase and glutathione transferase-P expression are part of a reorientation of cellular gene expression during carcinogenesis and that activated ras expression, like chemical carcinogens, can bring about this change.

Animals↗
PubMed1987

[Establishment of a human colonic carcinoma xenograft in nude mice and its chief biological characteristics].

A human colonic cancer specimen cut into 1-2 mm3 pieces under aseptic condition was heterotransplanted hypodermically by trocar to the inguinal region of BALB/cATcL nude mice bred in our laboratory. 53 days later, a 10 X 9 X 11 mm3 tumor was obtained. The take rate was 100% (48/48). The take rate of liquid nitrogen frozen and recovered tissue pieces was also 100% (13/13). Grossly, the tumor was rich in blood supply and well encapsulated. Within the tumor, the tissue was cream-colored. G-banded chromosome analysis revealed a human chromosome pattern with the mode 70-90. Pathologic diagnosis was signet-ring cell cancer, which was identical to the surgical specimen. No change was found after maintaining 13 passages in nude mice. It was named the human colonic carcinoma xenograft XHCn/w. It provides an ideal tumor model for in vivo or in vitro experiments.

Adenocarcinoma, Mucinous↗
PubMedDate not supplied

Effects of a medical expert system on differential diagnosis of renal masses: a prospective study.

A medical expert system, RMDS, was used to prospectively evaluate patients undergoing nephrectomy for suspected renal masses. The effects of a medical expert system on differential diagnosis of renal masses were investigated. After RMDS consultation, three chief residents and one junior attending physician changed their preoperative diagnosis and significantly increased their diagnostic accuracy. The results indicate that the medical expert system may have an useful role in preoperative diagnosis of renal masses.

Bayes Theorem↗
PubMedDate not supplied

Inhibition of N-acetyltransferase activity and DNA-2-aminofluorene adducts by glycyrrhizic acid in human colon tumour cells.

Glycyrrhizic acid (GA) was tested for inhibition of arylamine N-acetyltransferase (NAT) activity in a human colon tumour (adenocarcinoma) cell line (colo 205). Two assay systems were performed, one with cellular cytosols (9000g supernatant), the other with intact colon tumour cell cultures. The NAT activity in a human colon tumour cell line was inhibited by GA in a dose-dependent manner in both types of systems examined. The data also indicated that GA decreased the apparent values of K(m) and V(max) of NAT enzymes from human colon tumour cells in both examined systems. The DNA-2-aminofluorene adduct formation in human colon tumour cells were inhibited by GA. This report is the first to demonstrate that GA does inhibit human colon tumour cell NAT activity and DNA adduct formation.

4-Aminobenzoic Acid↗
PubMedDate not supplied

The development of a closed-loop controlled functional electrical stimulation (FES) in gait training.

A closed-loop functional electrical stimulation (FES) system is developed to provide hemiplegic patients with a real-time stimulation to their muscles to prevent the drop-foot and the quadriceps weakness from happening during gait training. The FES is controlled by position sensors (ps) and triggered by footswitches (f) with real-time feedback. As the FES receives the signals from these sensors, it adjusts and outputs an optimum set of stimulation parameters automatically. One hemiplegic patient was recruited to conduct clinical evaluation and treated by using the new closed-loop FES system. It was revealed that the mean velocity, cadence, stride length, active ankle motion range, and functional ambulation category (FAC) improved significantly from 0.12 +/- 0.07 ms-1, 40.3 +/- 18.3 steps min-1, 0.35 +/- 0.10 m, 15 degrees, level 2 to 0.42 +/- 0.23 ms-1, 68.2 +/- 19.0 steps min-1, 0.70 +/- 0.22 m, 40 degrees, level 4 respectively for the patient. A paired t-test indicated that differences in the electromyography (EMG) of the tibialis anterior and the quadriceps muscles between the patient's disabled (affected side) foot and normal (unaffected side) foot are not significant (p > 0.05) after 12 weeks of training. It is concluded that this new closed-loop FES system is capable of providing this hemiplegic patient with restoration to regular walking after appropriate gait training. Future studies, including randomized-controlled study, should be implemented to document the efficacy of this system.

Electric Stimulation Therapy↗
PubMedDate not supplied

Evaluation of a decision-support system for preoperative staging of prostate cancer.

The usefulness and effectiveness of a decision-support system for preoperative staging of prostate cancers (PCES) were evaluated. The study population consisted of 43 consecutive patients with the preoperative diagnosis of prostate cancer who underwent surgical operation. Results obtained using the PCES were compared with staging by four urology attending physicians and five urology residents. The effect of PCES consultation on the physicians' staging of prostate cancer was also evaluated. To confirm the usefulness of the clinical findings of prostate-specific antigen, prostate-specific antigen density, prostate volume, and abnormal Gleason score in the PCES, their receiver operating characteristic (ROC) curves for diagnosis of advanced prostate cancer were plotted. The values of the areas under the curves were 0.772, 0.800, 0.531, and 0.752. The stage of prostate cancer was correctly determined by the PCES for 38 of the 43 patients, yielding 88.4% preoperative diagnostic accuracy. The PCES was significantly more accurate than two of the attending physicians and all residents. PCES consultation improved the residents' staging accuracy to approximately that of the attending physicians. The effect of PCES consultation on the residents' staging was significantly (p < 0.001) greater than the effect on the physicians' staging. The PCES may be useful in the preoperative staging of prostate cancers, especially during residency. The system's accuracy in determining the stage of advanced prostate cancer may make it possible to avoid unneccesary surgical operations.

Aged↗