Creatine kinase, myokinase, and acetylcholinesterase activities in muscle-forming primary cultures of mouse teratocarcinoma cells

Artificial Cells Capable of Long-Lived Protein Synthesis by Using Aptamer Grafted Polymer Hydrogel

Herein we report a new type of artificial cells capable of long-term protein expression and regulation. We constructed the artificial cells by grafting anti-His-tag aptamer into the polymer backbone of the hydrogel particles, and then immobilizing the His-tagged proteinaceous factors of the transcription and translation system into the hydrogel particles. Long-term protein expression for at least 16 days was achieved by continuously flowing feeding buffer through the artificial cells. The effect of various metal ions on the protein expression in the artificial cells was investigated. Utilizing the lac operator-repressor system, we could regulate the expression level of eGFP in the artificial cells by controlling the β-D-1-thiogalatopyranoside (IPTG) concentration in the feeding buffer. The artificial cells based on the aptamer grafted hydrogel provide a useful platform for gene circuit engineering, metabolic engineering, drug delivery, and biosensors.

Modelling postmortem evolution of pH in beef M. biceps femoris under two different cooling regimes

A model based on enzyme kinetics was developed to predict differences in postmortem pH change in beef muscles as affected by cooling rate. For the calibration and validation of the model, pH and temperature measurements were conducted at different positions in M. biceps femoris following conventional carcass cooling or faster cooling of the muscle after hot boning. The glycogen conversion, and, hence, the pH fall, was observed to significantly vary with position and cooling regime but only during the initial hours of cooling. Comparison of the cooling regimes indicated that fast cooling following hot boning avoids heat shortening induced by the combined effect of high temperature and low pH.

Control of muscle and neuronal differentiation in a cultured embryonal carcinoma cell line

Pluripotent murine embryonal carcinoma cells can differentiate in culture into many tissue types similar to those normally found in early embryos and may be useful in investigating some developmental events. Central to our understanding of embryonic development are explanations of cellular determination, that is, the commitment of early embryonic cells to form divergent cell types. Of relevance is recent work with the F9 line of embryonal carcinoma cells which suggests that certain extra-embryonic cell types are specifically formed following treatment of undifferentiated cells with drugs and the manipulation of culture conditions. We report here that the P19 line of embryonic carcinoma cells may provide and analogous system in which drugs can be used to manipulate the formation of tissues which normally comprise the fetus. In the presence of dimethyl sulphoxide (DMSO) aggregates of P19 cells differentiate rapidly to form large amounts of cardiac and skeletal muscle but no neurones or glia. We have previously shown that in the presence of high concentrations of retinoic acid (greater than 5 x 10(-7) M), aggregates of these same cells develop into neuronal and glial tissues but not muscle. Thus, drugs can be used to generate two quite different spectra of embryonic tissue types from the same population of embryonal carcinoma cells.

Flow cytoenzymology of the early differentiation of mouse embryonal carcinoma cells

Dual parameter flow cytoenzymology was used to detect biochemical differentiation of embryonal carcinoma cells, the undifferentiated, multipotent stem cells of teratocarcinomas. With the use of fluorogenic substrates, two enzyme systems, alkaline phosphatase (EC 3.1.3.1.) and carboxyl esterase (EC 3.1.1.), were studied. Embryonal carcinoma cells passaged in vitro for several years retained high alkaline phosphatase activities similar to those of embryonal carcinoma cells in embryoid bodies grown in vivo. Similar to the embryonal carcinoma cells in vivo, the in vitro embryonal carcinoma cells were capable of giving rise to progeny with greatly decreased levels of alkaline phosphatase. The embryonal carcinoma cell alkaline phosphatase was inhibited by 1-p-bromotetramisole, suggesting a relationship between this enzyme and somatic, nonintestinal alkaline phosphatase isoenzymes. Determinations of esterase activities in viable teratocarcinoma cells showed that prior to any evidence of morphologic differentiation, the embryonal carcinoma cells are quite heterogeneous with regard to esterase activities.

The characterization of SV40-transformed cell lines derived from mouse teratocarcinoma: growth properties and differentiated characteristics

Mouse teratocarcinoma cells derived from embryoid bodies of 129SVsl mice were cultured in vitro to permit their differentiation. These cells were then infected with simiam virus 40 (SV40) and 31 cloned cell lines (SVTER) were derived from these cultures. All 31 SVTER cell lines contained the SV40 tumor (T) antigen and grew as permanent lines in culture. Mock-infected embryoid body cultures did not give rise to permanent cell lines. The morphology of each SVTER cell line was distinct and did not change during successive subclonings. The growth properties and tumorigenic potential of all 31 SVTER cell lines were investigated. None of these lines produced tumors in 129SVsl mice. Each cell line was tested for its ability to (1) grow in medium containing 1% serum, (2) plate on cell monolayer, and (3) form clones in methocel suspension. Only three of the SVTER cell lines were transformed with respect to all three of these criteria. Most of these cell lines were minimal transformants. The SVTER cell lines were tested for creatine phospholinase (CPK), an enzyme activity chracteristic of mouse brain and muscle tissue, and the protease, plasminogen activator (PA) which is found in embryoid bodies and several differentiated cell types. Some of the SVTER cell lines contained high levels of CPK, while others had high levels of PA and a third group of cells contained neither enzyme activity. No SVTER cell line was found with high levels of both these enzyme activities. This result suggests that mutually exclusive sets of genes are expressed in these cells as might be expected from the distinct tissue distribution of the two enzyme activities studied. These SVTER cell lines may be useful in reconstructing developmental pathways of differentiating teratomas in vitro.

Biochemical markers of the progress of differentiation in cloned teratocarcinoma cell lines

The progeny of single teratocarcinoma cells will give rise to several different cell types in vitro, and the latter were shown to be functionally differentiated by biochemical criteria. In all these studies, cloned lines of mouse teratocarcinoma cells were assayed during the course of differentiation for some biochemical products characteristic of the tissues formed. The carcinoembryonic protein, alpha-foetoprotein, was not synthesized by undifferentiated embryonal carcinoma (EC) cells, but was synthesized in increasing amounts during their differentiation to endoderm-type cells in suspension culture. alpha-Foetoprotein was shown to be a product of endoderm cells, but not all endoderm cells synthesized this protein. During the course of further differentiation when EC cells or aggregates were grown in tissue-culture dishes, other biochemical products appeared. In cultures containing predominantly nerve-type cells, there was a 30-fold increase in the specific activity of acetylcholinesterase, with concomitant appearance of the aldolase isoenzyme characteristic of mouse brain. In some cultures, a small amount of muscle-type cell formation was marked by the appearance of the MB isoenzyme of creatine phosphokinase. Generally, biochemical differentiation was immature.