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Biomedical subjects

T F Liu

Publications and source records attributed to T F Liu.

At least 55 records · Page 3Linked to original sources
PubMed1989

Intracavitary radiation treatment of nasopharyngeal carcinoma by the high dose rate afterloading technique.

Sixty-four patients with nasopharyngeal carcinoma were treated by various combinations of external irradiation with intracavitary radiotherapy using the high dose rate afterloading technique. The afterloading intracavitary radiation (AIR) was given as a routine boost or for residual or recurrent disease. The external irradiation dose varied from 45 to 70 Gy, whereas the AIR dose ranged from 10-50 Gy, depending on the nature of the primary nasopharyngeal lesion. The results were quite encouraging, although the longest follow-up so far has only been just over 4 years. Of 13 such cases that received external radiotherapy plus AIR as primary treatment, 12 have survived. However, of the 9 cases who received AIR for local recurrence after external radiotherapy, only 5 survived. Of the total of 64 cases treated by AIR from June 1981 to May 1986, 54 are alive. No serious radiation sequelae have been observed. It can be concluded that AIR for nasopharyngeal carcinoma is indicated for boosting the dose to the nasopharyngeal cavity with appropriate reduction in external irradiation dose, and for residual or recurrent disease after primary external radiotherapy.

Adolescent↗
PubMed1989

DNA flow cytometric analysis of human nasopharyngeal carcinoma in nude mice.

The tissue from a patient with nasopharyngeal carcinoma has been transferred to nude mice (BALB/c), and has successfully been growing through twenty passages. The tumors in the nude mice and primary human tumor have been examined for the cellular DNA content by FCM and also conventional pathological examination, chromosome analysis, and EBV test. The tumor take rate varied markedly in different passages with a mean value of approximately 70%, and showing a tendency to increase. The tumor doubling time within 6-12 weeks after transplantation of six tumors in 18 and 20 passages were 14.8 and 9.3 days respectively. However, the tumor volume at 12 weeks varied significantly, ranging from 438 to 1998 mm3. By FCM, it has been found that the values of DNA index were about the same in both primary tumor and the tumors in nude mice. The distribution of various phase cells in cell cycle was also about the same in both. In conclusion, the application of FCM to examine the cellular DNA content of the tumor in nude mice is a rapid and sensitive method, useful in the investigation on the stability of biological characteristics of human NPC in nude mice and in further studies on the effects by various therapeutic methods.

Animals↗
PubMed1989

Radiation survival properties of cultured human gastric adenocarcinoma cells and the effect of AT-1727.

Tumor cells (SGC-7901) obtained from a human gastric adenocarcinoma have been examined with regard to their intrinsic sensitivity to gamma-irradiation and as to how this intrinsic sensitivity might be altered by growth in a synthesized agent AT-1727 (N4-morpholino-methyl-3,5-dioxopiperazynyl-1,2 ethanl). Clonogenic survival was measured via colony formation assays and fitted to single-hit-multitarget formula. Exponentially growing cells exhibited the mean of survival parameters: D0 = 0.86 + 0.04 Gy; n = 7.03 + 2.3; Dq = 1.63 + 0.23 Gy and SF2 (surviving fraction of conventional daily clinical dose of 2 Gy) = 45-50%. Split-dose survival assays and delayed plating methods were used to exploit the capacity of sublethal damage repair of this cell line studied demonstrating the reappearance of initial shoulder on the survival curve and an increased survival. Alteration of radiosensitivity of SGC cells by AT-1727 was shown when cultures were incubated in a medium with the drug for a 6 hr interval between split dose irradiation, indicating the inhibition of sublethal damage repair. The radioresistance of hypoxic SGC cells was decreased when pre-treatment with AT-1727 was given 2 hr before irradiation, and the decrease of surviving fraction was drug-dose dependent. A maximum enhanced effect was obtained when 0.15 mM of AT-1727 was used, reaching an ER of 1.24. Inhibition of sublethal damage repair and action as a hypoxic radiosensitizer were considered to be two parts of the mechanism of AT-1727 in modification of radiation effects.

Adenocarcinoma↗
PubMed1988

Fluorescence of hematoporphyrin in living cells and in solution.

The fluorescence properties of hematoporphyrin (Hp) and its derivative (HpD) were investigated in leukemia cells and in normal lymphocytes under a microscope, and the results were compared with those in solution. The spectra and the time behaviour of Hp (or HpD) fluorescence in living cells were found to be almost the same as those in Hp solution of very high concentration. This implies that Hp is much more concentrated in the cells than in the medium. It was also found that irradiation with intense light easily gives rise to a photoproduct which gives an additional peak in the fluorescence spectrum. Possible methods to increase the sensitivity of cancer detection and localization are discussed.

Fluorescence↗
PubMed1988

K+-free induced early afterdepolarization in cardiac ventricular fibers of guinea pig after cold treatment.

The genesis and elimination of early afterdepolarizations (EADs) have been investigated in guinea pig cardiac ventricular fibers after a short period of cooling (5 h, 2-4 degrees C). After rewarming them to 37 degrees C, EADs could be induced by K+-free superfusion at an appropriate driving stimulation (0.2 Hz) in all preparations. A high level plateau, which linearly increases its duration with time, appears ahead of EADs. The critical point of the plateau occurred steadily, at the level of -47 +/- 4 mV. Two types of triggered activity, all of which are the rhythmic activities in low level of membrane potential (-50 to -60 mV), appear on the plateau. There is no significant change after overdriving. Agonists of the Na-K pump (K+ and T1+) could stop the rhythmic activity immediately and turn the low level of membrane potential to high one. The results showed that high level plateau is the basis of genesis of EADs, and the activation of Na-K pump plays an important part in stopping triggered rhythms arising from EADs.

Animals↗
PubMed1987

Permeance of Novikoff hepatoma gap junctions: quantitative video analysis of dye transfer.

Fluorescent dyes are commonly used to study permeable (gap) junctions, but only rarely have quantitative values for junctional dye permeability been determined. In the present study, junctional permeance (PA, i.e., the product of the junctional permeability coefficient, P, times the junctional area, A) to Lucifer Yellow CH (LY) has been obtained for pairs of Novikoff hepatoma cells. Dye was microinjected into one cell and the subsequent transfer monitored by a SIT camera and recorded on video tape. The intensities of fluorescence in the injected and "recipient" cell were measured using a Digisector (Microworks) digitizing board and an Apple II Plus computer to analyze the video records. These changes in intensity, along with an estimate of volume of the spherical cells, were used to calculate the junctional permeance (PA) of cell pairs according to Fick's diffusion equation. Junctional permeances show considerable variation ranging from 0.08 X 10(-11) to 27.0 X 10(-11) cm3/sec. Using the mean PA and a previous estimate of the mean number of junctional channels per interface in the Novikoff cultures, a value for diffusion coefficient of LY through gap junctions is calculated to be about 1.4 X 10(-6) cm2/sec. There is a general proportionality between mean PA and cell volume for hepatoma cell pairs of a certain size range. Such a relationship between cell volume and junctional capacity suggests one source of variation of PA. Other possible sources, e.g., related to position in the cell cycle, are discussed.

Animals↗
PubMed1987

Junctions between lens cells in differentiating cultures: structure, formation, intercellular permeability, and junctional protein expression.

We previously described cultures of chick embryo lens cells which displayed a marked degree of differentiation. In this report, the junctions found between the lens fiber-like cells in the differentiated "lentoids" are characterized in several ways. Thin-section methods with electron microscopy first demonstrated that numerous, large junctions between lentoid cells accompanied the other differentiated features of these cells. Freeze-fracture techniques, including quantitative analysis, then revealed that (a) junctional particles were loosely arranged as is typical of fiber cells, (b) the population of individual junctional areas in culture was indistinguishable from that found in 10- to 12-day chick embryo lenses, and (c) apparent junction formation occurred during the development of the lens cells, with lacy arrays of particles being associated with fiber-like junctions. In addition, gap junctions with hexagonally packed particles, typical of lens epithelial cells, largely disappeared during the course of differentiation. Injection of tracer dyes into lentoid cells resulted in rapid intercellular movement of dye, consistent with functional cell-to-cell channels connecting lentoid cells. During the development of the lens cells in culture, as junction formation occurred, an increase of approximately eight-fold in MP28 protein was observed within the cells. These combined results indicate that (a) extensive lens fiber junctions and functional cell-to-cell channels are found between differentiated lentoid lentoid cells in vitro, (b) lens fiber junctions appear to form during the course of lens cell differentiation in culture, (c) a significant increase occurs in the putative junctional protein before the cultures are highly developed, (d) the increased levels of MP28 and junction formation may be required for the full expression of the differentiated state in the lens fiber cell, and (e) this culture system should prove to be valuable for additional experiments on lens junctions and for other studies requiring the development of lens fiber cells in vitro.

Animals↗
PubMed1987

[Flow cytometer (FCM) in biological characteristics of nasopharyngeal carcinoma xenografts in nude mice].

Tumor tissue from a patient with nasopharyngeal carcinoma was transplanted to nude mice (BALB/c) and had successfully been maintained through ten passages. The nude mice tumor and the primary human tumor were assayed by FCM for the DNA content in addition to conventional pathological examination, chromosome analysis and EBV assay. The tumor incidence in the different passages showed a marked change ranging from 25% to 81% with a mean value of 52% which tended to increase, however. The doubling time of six tumors in the ninth passage showed no great change 6-12 weeks after transplantation with a mean about 4.3 days. But at week 12, there was a significant difference between each tumor volume, ranging from 438 to 1,998 mm3. By FCM, it was found that the DNA index remained constant in both the primary and nude mice tumors. Among the nude mice tumors in different passages, the distribution of various phase cells in cell cycle was similar to that of the primary tumor. In conclusion, the use of FCM to assay the cellular DNA content in nude mice tumor is rapid and sensitive. It is helpful, for the nude mice tumor, in identifying stability of the biological characteristics and in studying of the mechanism of chemotherapy and radiotherapy in the future.

Animals↗
PubMed1984

Preliminary report on AT1727 as a potential radiosensitizer.

AT1727 is a derivative of ICRF 154. The purpose of this study was to evaluate its "radiosensitizer" properties. From October 1979 until the end of December 1980, 89 patients with radiation resistant cancers such as soft tissue sarcoma, squamous lung cancer (with large lesion, 6-8 cm diameter) and other cancers had been included in trial. Radiation therapy was carried out using CO60 or 8 Mev Linac. Fifty-five patients had a remarkable objective remission rate of 61.8% (55/89). Eighteen of 30 patients with soft tissue sarcomas obtained obvious remission (60%), and 26 of 38 patients with lung cancer had remission (68.4%). Patients with esophageal cancer (5/6) and nasopharyngeal cancer (5/5) also had good remission rates. The side-effects of this treatment were very mild: anorexia and vomiting were noted in 50% and no significant changes were noted in liver and kidney function tests and blood platelet count. Leucopenia was slight in all but one patient. No difference in the lung fibrosis rate was noted between the two randomized groups. From the results of this study we concluded that AT1727 had some effect as a "radiosensitizer" but much more work is needed to confirm this.

Clinical Trials as Topic↗