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Biomedical subjects

C L Tang

Publications and source records attributed to C L Tang.

46 records · Page 3Linked to original sources
PubMed1992

Circular DNA molecules imaged in air by scanning force microscopy.

Routine and reproducible imaging of DNA molecules in air with the scanning force microscope (SFM) has been accomplished. Circular molecules of plasmid DNA were deposited onto red mica and imaged under various relative humidities. In related experiments, the first images of the Escherichia coli RNA polymerase-DNA complex have also been obtained. This has been possible by (1) the use of specially modified SFM tips with a consistent radius of curvature of 10 nm or less, to minimize the amount of image distortion introduced by the finite dimensions of commercially available tips, (2) the optimization of a method to deposit and bind DNA molecules to the mica surface in a stable fashion, and (3) careful control of the sample humidity, to prevent solvation of the molecules and detachment from the surface by the scanning tip or stylus. Contact forces in the range of a few nanonewtons are routinely possible in air and in the presence of residual humidity. The spatial resolution of the images appears determined by the radius of curvature of the modified styli, which can be estimated directly from the apparent widths of the DNA molecules in the images.

Air↗
PubMed1992

Substrate preparation for reliable imaging of DNA molecules with the scanning force microscope.

A simple method of substrate preparation for imaging circular DNA molecules with the scanning force microscope (SFM) is presented. These biomolecules are adsorbed onto mica that has been soaked in magnesium acetate, sonicated and glow-discharged. The stylus-sample forces that may be endured before sample damage occurs depends on the ambient relative humidity. Images of circular DNA molecules have been obtained routinely using tips specially modified by an electron beam with a radius of curvature, Rc, of about 10 nm [D. Keller and C. Chih-Chung, Surf. Sci. 268 (1992) 333]. The resolution of these adsorbed biomolecules is determined by the Rc. At higher forces individual circular DNA molecules can be manipulated with the SFM stylus. Strategies to develop still sharper probes will be discussed.

Aluminum Silicates↗
PubMed1992

Analysis of one hundred and twenty five patients with primary liver cancer surviving more than five years.

During the period of 1958-1986, a series of 125 patients with pathologically proven hepatocellular carcinoma (HCC) surviving more than 5 years was collected in authors' institute. Thirty seven of them survived more than 10 years, the longest being 30 years. Of the entire series, 55.2% of patients was discovered by screening, 48.0% of patients was subclinical HCC, 80.0% of patients had solitary tumor, and 53.6% of patients had tumor size smaller than 5 cm. Pathological findings revealed that 90.2% of tumor was grade I and II (Edmondson grading) and 81.6% of patients associated with cirrhosis. The serum HBsAg was positive in 63% and anti-HBc in 80% of the patients who had checked the HBV markers. Of the 125 patients, 108 patients received resection, 67 patients were small HCC resection, 41 patients were non-small HCC resection, re-resection for subclinical recurrence or solitary lung metastasis was done in 26 patients with resection. Limited resection amounted to 54.6% of patients with resection. Of the 125 patients, 17 patients received palliative surgery other than resection, including hepatic artery ligation, cannulation, or their combination, etc. Eight out of the 17 patients received second stage resection due to marked shrinkage of tumor. It is concluded that early resection remained the major approach to get a long-term survivor, re-resection for subclinical recurrence is also of proved merit. Resection of huge tumor is still useful but less effective. Cyto-reduction and sequential resection is a new trend. Primary liver cancer (PLC) has long been recognized as incurable malignancy with extremely low 5-year survival rate. According to the cancer statistics in the United States, the relative 5-year survival rates for patients with PLC was 2% in 1960-1963, 3% in 1970-1973, 4% in 1974-1976, 3% in 1977-1980 and 5% in 1981-1986. Patients with PLC survived more than 5 years were rarely reported in the literature. In 1971, Curutchet collected worldwide data from 45 authors covering the period for 65 years (1905-1970), only 45 patients with PLC were found to be 5-year survivors. Thanks to the progress in tumor markers, particularly alpha fetoprotin (AFP) and new localization measurements, diagnosis and treatment are possible in subclinical stage. Based on combined strategies to the treatment of PLC including resection of small liver cancer, re-resection of subclinical recurrence after curative resection, multimodality treatment, and sequential resection after shrinkage of tumor, the 5-year survival of PLC has gradually increased.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1991

Effect of a purified somatostatin monoclonal antibody and its Fab fragments on gastrin release.

The effect of a purified somatostatin monoclonal antibody, SOMA 10, and its Fab fragments on gastrin release have been examined in the isolated perfused rat stomach. SOMA 10 was purified from ascites fluid by ammonium sulfate precipitation followed by hydroxylapatite (HAP) chromatography. This gave a preparation of greater than 90% purity, as assessed by fast affinity and size exclusion high-performance liquid chromatography (HPLC). HAP-purified SOMA 10 had a binding capacity of 760 mmol somatostatin/mol antibody, a dissociation constant of 2.2 nM, and recognized amino acid residues 5-12 of the somatostatin molecule. Fab fragments of SOMA 10 were prepared and purified by protein A affinity chromatography, and the purity assessed by HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Single passage perfusion of SOMA 10 (100 micrograms/ml) into the gastric vasculature caused a paradoxical decrease in basal gastrin release. However, recirculation of the antibody (20 micrograms/ml) caused an increase in cumulated gastrin release. Perfusion of Fab fragments of SOMA 10 (66 micrograms/ml) also increased gastrin secretion. These results support the suggestion that somatostatin exerts a tonic restraint on gastrin release and that penetration of the antibody to the site of somatostatin release is necessary for it to have an effect.

Animals↗
PubMed1990

Requirement for solutions with oncotic pressure to release ANF during blood volume expansion in conscious and anesthetized rats.

We examined the effect of a 30% blood volume expansion with either blood, isotonic saline, or isotonic saline plus albumin on the release of immunoreactive-atrial natriuretic factor (IR-ANF) in conscious and barbiturate-anesthetized rats. Immediately prior to volume expansion, resting plasma IR-ANF levels were significantly (p less than 0.05) higher in the conscious animals (61 +/- 5 pg/mL, n = 19) compared to the anesthetized animals (41 +/- 3 pg/mL, n = 19). Volume expansion with blood from donor rats significantly (p less than 0.05) elevated IR-ANF in both groups, but the increase in the conscious rats (+492 +/- 32 pg/mL, n = 6) was significantly (p less than 0.05) greater than that of the anesthetized rats (74 +/- 25 pg/mL, n = 6). Similarly, volume expansion with isotonic saline containing 38 mg/mL albumin significantly (p less than 0.05) elevated IR-ANF levels in both groups, but the increase in the conscious group (379 +/- 102 pg/mL, n = 7) was significantly (p less than 0.05) greater than that of the anesthetized group (94 +/- 32 pg/mL, n = 7). These elevations in IR-ANF levels were not significantly different between either of the conscious groups or either of the anesthetized groups. Volume expansion with isotonic saline alone did not have any significant effect upon resting IR-ANF levels in either conscious (+8 +/- 14 pg/mL, n = 6) or anesthetized (-7 +/- 6 pg/mL, n = 6) animals. From these results, it would appear that a) isotonic saline alone does not stimulate IR-ANF release when used to expand blood volume, and b) barbiturate anesthesia significantly lowers resting plasma IR-ANF levels and attenuates the release of IR-ANF in response to volume expansion.

Albumins↗
PubMed1989

Long-term survivors after resection for primary liver cancer. Clinical analysis of 19 patients surviving more than ten years.

From July 1958 to June 1978, a total of 333 cases with pathologically proven primary liver cancer (PLC) were admitted to the Zhong Shan Hospital, Shanghai Medical University, Shanghai, the people's Republic of China. Of these, 39.6% (132 of 333) were resected and 14.4% (19 of 132) survived over 10 years after resection for PLC. These 19 patients surviving over 10 years were investigated in this paper. All 19 patients underwent radical resection, including right hemihepatectomy in two cases, left hemihepatectomy in ten cases, left lateral segmentectomy in three cases, and local resection in four cases. By the end of June 1988, follow-up varied from 10 years and 1 month to 26 years and 7 months, with a mean follow-up of 15 years and 4 months. All 19 patients are still alive with free of disease. The longest survival patient had a tumor measuring 10 X 8 X 6 cm in size and underwent local resection. Upon follow-up after 26 years and 7 months, the patient was found to be still living and well. Two patients with intraperitoneal ruptured PLC have survived for 19 years and 4 months, and 16 years and 11 months, respectively, after resection of the tumors free of disease and have returned to work. Subclinical recurrence of PLC was discovered in one patient in whom reoperation with cryosurgery was carried out. The patient has been in good condition with negative alpha-fetoprotein (AFP) for 8 years and 10 months after cryosurgery. Subclinical solitary pulmonary metastasis was detected in two patients because of a secondary rise in AFP level. Reoperations were carried out and the metastatic tumors were removed. These two patients are still in good health with negative AFP 9 years and 6 months, and 10 years and 1 months, respectively, after reoperation. These results indicate that early and radical resection are the principal factors influencing long-term survival; reoperation for subclinical recurrence and solitary metastasis remains an important approach to prolong survival further; intraperitoneal rupture of PLC does not exclude the possibility of cure; new surgical techniques, such as cryosurgery and bloodless hepatectomy, have been shown to be effective in some patients.

Adult↗
PubMed1973

Reduction of alpha-oxo carboxylic acids by pigeon liver 'malic' enzyme.

1. Pigeon liver ;malic' enzyme [l-malate-NADP(+) oxidoreductase (decarboxylating); EC 1.1.1.40] was shown to catalyse the reductase reaction: [Formula: see text] l-Malate was identified as the reaction product, and was formed in stoicheiometric amount. 2. In addition to oxaloacetate and pyruvate, a number of other alpha-oxo carboxylic acids were also reduced.

Animals↗