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Biomedical subjects

H Liang

Publications and source records attributed to H Liang.

At least 235 records · Page 13Linked to original sources
PubMed1988

Optimization of electrofusion parameters for efficient production of murine hybridomas.

Several factors which affect the production of murine hybridomas by electrofusion using SP2/0 myelomas were examined. These factors included the ionic composition, specific resistance and osmotic strength of the fusion medium, proteolytic pretreatment of the cells, and field strength of the single, rectangular, 15 or 20 microseconds electric pulse. Individual experiments were observed by phase microscopy, video-recorded, and subsequently analyzed. The efficiency of hybridoma formation was measured by the number of hybrid colonies which survived HAT medium selection. In most cases, the peak efficiency occurred when the pulse field was between 3 and 4 kV/cm. Ca++ and Mg++, in 0.1 and 0.5 mM concentrations, respectively, helped to prevent large-scale SP2/0 lysis following pulse application. Reduction of the osmolarity of the fusion medium allowed for an approximate two-fold increase in the hybrid production efficiency. However, other variations, including an increase of the specific resistance of the medium to 1.7 x 10(4) omega cm, and a reduction of the pulse width to 15 microseconds, allowed significantly higher efficiencies. Dispase pretreatment of the myelomas led to additional improvements when using a 15 microseconds pulse. The data suggest that for this system, the highest efficiencies are obtained by maximizing the attractive polarization forces between cells, while adjusting the ionic composition and pulse parameters to preserve myeloma viability.

Animals↗
PubMed1988

Uptake of fluorescence-labeled dextrans by 10T 1/2 fibroblasts following permeation by rectangular and exponential-decay electric field pulses.

The uptake of fluorescence-labeled dextrans by adherent 10T 1/2 murine fibroblasts following electric field pulse application was used as a criterion for the efficiency of electropermeation. The cells in monolayers were permeated by immersing a coaxial electrode in culture dishes. The percentage of cells which exhibited fluorescence uptake following electric field pulse application was measured at independently varying pulse field strength and pulse length. Dextrans with molecular weights equal to or higher than 41,000 dalton require higher field strength or longer pulse time to penetrate the cells. There is no detectable advantage of using a rectangular pulse against using an exponential decay pulse of similar power. The uptake was proportional to the product of the pulse amplitude and duration over the experimental range of 40-950 microseconds and 0.1-14.5 kV/cm. Cell survival decreases at the upper end of this range. The result provides a direct comparison of electric parameters which so far have not been standardized with regard to cell electropermeation.

Animals↗
PubMed1986

[Cytotoxic effect of hematoporphyrin derivative (HPD) plus light irradiation in vitro].

Cytotoxic effect of HPD plus light irradiation on PTK2 and HeLa cells in vitro were studied by laser microbeam irradiation. The dynamic changes, in three different steps as observed in the cells ranged from visible damage to cell lysis, were recorded at the monocellular level. It was found that the speed of the cytotoxic process varied chiefly with the dose of light used. The cytotoxic progress of PTK2 and HeLa cells was compared and analyzed. In addition, the cytotoxic effects of three different laser wavelengths (6328A, 5145A and 4880A) plus HPD were compared. The most significant killing effect occurred at 6328A wavelength of red light.

Animals↗
PubMed1983

Induced genetic deficiency of the nucleolar organizer in rat kangaroo cells (PTK1) by ultraviolet laser microirradiation.

An ultraviolet laser microbeam was used to irradiate one of the two nucleolar organizer regions of PTK1 cells in early prophase. The directed nucleolar deficiency induced by ultraviolet laser irradiation was maintained in the daughter cells through subsequent cell generations. However, the frequent occurrence of spontaneous cell fusion in low density cells following the cloning procedure facilitated a recovery of cells to two or more nucleoli.

Animals↗
PubMed1983

Establishment of nucleolar deficient sublines of PtK2 (Potorous tridactylis) by ultraviolet laser microirradiation.

One of the two nucleoli of tetraploid PtK2 WA cells in early prophase was irradiated with an ultraviolet (UV) laser microbeam. The daughter cells that maintained the nucleolar deficiency were isolated and cloned. Five nucleolar deficient sublines of PtK2 WA were established, thus providing an experimental system to study the ribosomal gene-nucleolar organizer complex.

Animals↗
PubMed1979

A new N-nitroso compound, N-3-methylbutyl-N-1-methylacetonylnitrosamine, in corn-bread inoculated with fungi.

A new N--nitroso compound, N--1--methylacetonyl--N--3--methylbutylnitrosamine (MAMBNA) is found in corn-bread inoculated with the common fungi, such as Fusarium moniliforme, Geotrichun candidum, Aspergillus terreus or A. flavipes, encountered in food of Lin Xian County, Henan Province. The preliminary identification of this compound with TLC has been confirmed by GC-MS analysis. Furthermore, we have synthesized the MAMBNA and the chemical analysis shows that it is identical with the MAMBNA isolated from the corn-bread extract. In addition to the MAMBNA, dimethylnitrosamine, diethylnitrosamine and methylbenzylnitrosamine are formed also in the fungus-inoculated corn-bread after 8-day incubation and an addition of a small amount of sodium nitrite. The presence of precursor compounds for the formation of nitrosamine in the mouldy maize flour and their significance in respect to the etiology of esophageal cancer in high-risk areas have been discussed.

Aspergillus flavus↗
PubMed1971

Dissociation of effects on protein synthesis and ribosomes from membrane changes induced by carbon tetrachloride.

Pretreatment of rats with cycloheximide protects the liver against ribosome changes but not against alterations in the endoplasmic reticulum membrane induced by the administration of CCl(4), as observed both biochemically and ultrastructurally. Another inhibitor of protein synthesis, tenuazonic acid, has effects similar to cycloheximide. Neither compound has any apparent effect when given after the administration of CCl(4) at a time at which a major shift in ribosome distribution from polysomes to ribosome monomers or subunits has already occurred. Thus, it appears that the ribosomes are not susceptible to damage by CCl(4), or more probably an active metabolic derivative of CCl(4), when they are organized as polysomes but only when they are present as monomers or subunits. Also, unlike the situation with ethionine or puromycin, the damage to the protein synthetic system of the ribosomes induced in the liver by CCl(4) appears to be irreversible. In contrast to cycloheximide or tenuazonic acid, N,N'-diphenyl-p-phenylenediamine (DPPD) protects the liver against CCl(4)-induced changes in both ribosomes and endoplasmic reticulum. These observations suggest that the changes in the ribosome-protein synthetic system induced in the liver by treatment with CCl(4) are not the direct result of damage to the membranes of the endoplasmic reticulum but are either an indirect effect of such damage or are unrelated to it. These possibilities are discussed in terms of three proposed working hypotheses.

Animals↗