Differentiation and maturation of embryonal carcinoma-derived neurons in cell culture

We have previously shown that retinoic acid-treated cultures of the P19 line of embryonal carcinoma cells differentiate into neurons, glia, and fibroblast-like cells (Jones-Villeneuve et al., 1982). We report here that the monoclonal antibody HNK-1 reacts with the neurons at a very early stage of their differentiation and is, therefore, an early marker of the neuronal lineage. Cells in differentiated P 19 cultures synthesized acetylcholine but not catecholamines, suggesting that at least some of the neurons are cholinergic. The neurons also carry high-affinity uptake sites for GABA but not for serotonin. In long-term cultures, neuronal processes differentiated into axons and dendrites, which formed synapses. This biological system should prove valuable for examining the development and maturation of cholinergic neurons, since their differentiation occurs in cell culture.

Methotrexate (MTX) concentration in tumors following low-dose MTX

Methotrexate (MTX) is a folate analog competitive with reduced folates for cellular transport and metabolism. Since the normal plasma folate concentration is only 10(-8) M, we tested the possibility that there may be a saturable uptake of MTX by proliferating tumor tissue at plasma MTX concentrations of only 10(-7) to 10(-6) M. Patients with advanced malignancies, refractory to accepted therapy, were given low-dose oral MTX (30-60 mg/m2 total dose in four to eight divided doses). Tumor tissue was biopsied 18-24 h after the last oral dose of MTX. The concentrations of MTX and its polyglutamated derivatives were measured in these samples. Forty-eight percent of the drug in the tumor samples was present as a polyglutamated derivative.

The role of aggregation in embryonal carcinoma cell differentiation

Cultures of the P19 line of embryonal carcinoma cells differentiate into various cell types including cardiac muscle when aggregated and exposed to medium containing 1% dimethylsulfoxide (DMSO). DMSO-treated aggregates became completely covered with an epithelial cell type 3 to 4 days following drug exposure. This epithelial cell was tentatively identified as primitive extraembryonic endoderm by its ultrastructural appearance and its possession of cytokeratin intermediate filaments. Muscle cells developed within the interior of DMSO-treated aggregates. They first became apparent 5 to 6 days after DMSO exposure and were characterized by the presence of striated muscle-specific myosin, immature myofibrils, and intercalated discs. We determined the proportion of cells developing into epithelium and muscle in aggregates of various sizes and showed that the proportion of epithelium was highest in small aggregates whereas muscle cells developed only in aggregates of relatively large size. The muscle was usually associated with necrotic areas which developed within the interior of large aggregates. Our results suggest that cardiac muscle differentiation in the aggregates requires both the DMSO-induced formation of an epithelial cell coat and one other condition which may be the proximity to necrotic areas.

Restricted replication of herpes simplex virus type 1 in murine embryonal carcinoma cells

Herpes simplex virus type 1 (HSV-1) has a broad host range but the KOS strain of HSV-1 did not replicate efficiently in murine embryonal carcinoma (EC) cells. The yield of infectious HSV-1 from EC cells was 100- to 1000-fold lower than that from fibroblast cell lines of mouse, monkey or human origin. The thymidine kinase (TK) gene of HSV-1 is expressed early during the infectious cycle. The levels of TK mRNA and of TK activity in infected EC cells were only two- to threefold lower than levels from infected fibroblast cells. Infected EC cells supported replication of about half as much HSV-1 DNA as did fibroblast cells. The reduced yield of infectious virus was consistent with a paucity of virions in infected EC cells examined by electron microscopy, suggesting a major block late during the HSV-1 infectious cycle. We isolated a variant strain of HSV-1, called KOSEC, which replicated as efficiently in EC cells as in mouse fibroblasts. KOSEC infected EC and fibroblast cells, synthesized more TK mRNA, more TK enzyme, and more HSV-1 DNA than did the same cells infected with the KOS stain. Both HSV-1 strains induced similar levels of synthesis of gD, an early viral glycoprotein. By co-infection of EC cells with the KOS and KOSEC virus, both the elevated virus yield and the elevated TK synthesis seen in KOSEC-infected cells appeared to be recessive. Apparently a viral mutation that affects expression of some early viral functions can also overcome the EC cell restriction to HSV-1 replication.

[Influence of cell-cell interaction upon differentiation of murine embryonal carcinoma cells]

Embryonal carcinoma (EC) cells are the pluripotent stem cells of teratocarcinoma. The aggregates of P19, a mouse EC cell line, undergo differentiation and rapidly lose its colony-forming ability in culture with retinoic acid (RA) or DMSO. Loss of plating efficiency is used to assess the rate of drug-induced differentiation. When exposed respectively to DMSO or RA, the isolated EC cell mutants (D3 and RAC65) did not differentiate but the gap junctions could be formed. In RA-treated co-aggregates of RAC65 and O1A1, each cell line gave responses independent of the presence of the other cell line. However, in DMSO-treated co-aggregates of P19 and D3, D3 cells remained undifferentiated and P19 cell differentiation was much poorer than that in the absence of D3 cells. The results suggest that cell-cell interaction be present in the early stage of DMSO-induced differentiation and absent in the early stage of RA-induced differentiation.

Phase I study of high-dose cytarabine and cisplatin in patients with advanced malignancy

Nineteen patients with advanced malignancy participated in a phase I trial of high-dose cytarabine (ara-C) and cisplatin in combination. Dose and schedule were based on laboratory data indicating synergy for concurrent use of these drugs. Cisplatin (100 mg/m2) was administered during the 2nd and 3rd hours of a 3-hour ara-C infusion. The ara-C dose was escalated in subsequent patients following a starting dose of 1 g/m2. Two brief responses were noted. The study was terminated prematurely due to protracted (several weeks) nausea, occasional vomiting, and severe lassitude.

Cell-cell interaction can influence drug-induced differentiation of murine embryonal carcinoma cells

When cultured in the presence of either retinoic acid (RA) or dimethyl sulfoxide (DMSO), aggregates of the P19 line of mouse embryonal carcinoma (EC) cells differentiate and the spectrum of cell types formed depends on the drug dose. It is shown here the EC cells rapidly lose their colony-forming ability when cultured as aggregates in the presence of DMSO. This loss of plating efficiency (PE) also occurs rapidly following RA treatment. Loss of PE has been used as a quantitative procedure for assessing the rate of drug-induced differentiation. The relationship between drug dose and loss of PE is much steeper for DMSO than for RA, suggesting that these two drugs affect different stages of the differentiation decision-making apparatus. Mutant EC cell lines (D3 and RAC65) do not differentiate in the presence of drug-inducers (DMSO and RA, respectively). Neither differentiation-deficient mutant has an altered ability to form gap junctions. When D3 and P19 cells were mixed within the same DMSO-treated aggregates, the D3 cells remained undifferentiated and the P19 cells differentiated much less efficiently than if they were cultured in the absence of the D3 cells. When RAC65 and P19 cells were mixed in RA-treated aggregates, each cell responded to the drug as though the other were absent. Thus RA behaves as a cell-autonomous inducer of differentiation, whereas DMSO-induced differentiation seems to be mediated by interactions between neighboring cells.

Commitment in a murine embryonal carcinoma cell line during differentiation induced by retinoic acid

Murine embryonal carcinoma (EC) cells are induced to differentiate when cultured in the presence of retinoic acid (RA). Whereas the EC cells have a high plating efficiency, the differentiated cells have little or no colony-forming ability under the same conditions. We have assumed that the loss of colony-forming ability following exposure of EC cells to RA corresponds to the irreversible commitment of EC cells to differentiate. We found that uncommitted EC cells persist in RA-treated aggregates of EC cells and that the proportion of EC cells stabilizes at a level inversely related to the RA concentration. Both experimental evidence and mathematical modelling results are consistent with the interpretation that there is a dynamic equilibrium achieved by a balance between the processes of EC cell proliferation and differentiation. Since different cell types are induced by different RA concentrations, our results suggest that the commitment to differentiate is not related in any simple way to the developmental program which ensues.

Averaging population density

Population density is a commonly quoted statistic. Almost no general descriptive summary of the population of an area is complete without a density listing, table or map. As each such density statistic is an average, it is worth considering what kind of average is being used. This article analyzes this and illustrates the effect of some alternative calculations using population density data for Great Britain; the findings, however, are of general validity.

DNA methylation in differentiating mouse teratocarcinoma and erythroleukemia cells

We have measured the content of 5-methylcytosine (5MC) in the genomic DNA of differentiated and undifferentiated cultures of murine embryonal carcinoma (EC) and murine erythroleukemia (MEL) cells. A large proportion of deoxycytosine residues were methylated in EC cells (4.6%) and this proportion dropped significantly (4.1%) following differentiation. The alpha-1 globin genes were heavily methylated at HpaII sites in EC cells and in differentiated derivatives of these EC cells. The MEL cells had only 3.3% of their genomic deoxycytidine methylated and no significant change occurred following differentiation. The alpha-1 globin genes of MEL cells were much less methylated than the same genes in EC cells and no change in this methylation pattern accompanied the induction of hemoglobin synthesis. In EC X MEL cell hybrids which express the alpha-1 globin genes from both parents, the EC-derived genes had become demethylated. These results are consistent with the general model that DNA hypomethylation is correlated with expression of that DNA and that gene activation is accompanied by DNA demethylation. We have also measured the 5MC content of DNA isolated from nuclease-treated EC nuclei. Unexpectedly, the DNase I sensitive chromatin contained a large proportion of 5MC. This result, along with the work of others, suggests that nuclease sensitivity may often reflect the transcriptional activity of chromatin in somatic cells, but is not indicative of the active state in pluripotent EC cells.

Second primary bronchogenic carcinomas after small cell carcinoma. Report of two cases and review of the literature

Second primary carcinomas of the lung are well described. However, their occurrence following initial diagnosis of small cell lung carcinoma is rare. The development and antemortem diagnosis of metachronous second primary bronchogenic carcinomas in two long-term (more than four years) survivors of small cell lung cancer is described. The histologic types of the second carcinomas were mucoepidermoid and bronchoalveolar. On the basis of a review of the literature, only eight similar cases have been reported; none of the second primaries was mucoepidermoid or bronchoalveolar. The question of whether second primaries after small cell lung cancer represent true metachronous carcinomas, different degrees of differentiation of the same tumor, or the emergence of a previously unrecognized synchronous tumor is discussed. The need for awareness of this complication and the necessity for life-long follow-up in long-term survivors of small cell lung cancer is emphasized.

Cell membrane signals in the mechanism of insulin action. Claude P. Brown memorial lecture

Present evidence points to the rapid formation of one or several mediators by proteolysis initiated by insulin and, possibly, other hormones. Mediators act intracellularly at a number of subcellular sites, including cytoplasm, mitochondria, endoplasmic reticulum, cell membrane, and nucleus (figure 9). These mediators control enzymes that are controlled by covalent phosphorylation. As a result, the mediators impart an overall integrated control of metabolism. Evidence strongly suggests that the mediators are peptides. They appear to be formed by limited proteolysis from cell membrane proteins or glycoproteins and act as transmembrane signals following the binding of insulin to its receptor and the activation of the insulin-receptor complex.

Determination of sex with a discriminant analysis of new pelvic bone measurements: Part I

The pelves of 100 black skeletons were measured on both sides for the following: (1) length from the superiormost aspect of the pubic symphysis to the nearest rim of the acetabulum (PS-A), (2) length from the highest point of the pubic tubercle to the nearest rim of the acetabulum (PT-A), (3) acetabular diameter (AD), (4) the vertical distance from the anterior aspect of the ischial tuberosity to the farthest rim of the acetabulum (IT-A), and (5) greatest femur head diameter. From these, three indices were derived: AD/PS-A (acetabulum/pubis index), AD/PT-A (acetabular diameter/pubic tubercle-acetabular rim index), and IT-A/PS-A (ischium-acetabulum height/pubic symphysis-acetabular rim index). The left AD/PS-A ratio and left IT-A height proved statistically to be of greatest discriminating value. Using these two variables, a discriminant function was derived which, followed by sorting with femur head diameter, accurately classified 97% of our sample. The acetabulum/pubis index alone with subsequent sorting by femur head diameter correctly assigned 96% of our sample. While this does not represent an improvement of predicatability over similar methods using the ischium/pubis index, measurements required for the acetabulum/pubis index are more easily defined and should, therefore, reduce the chance of observer error.

Recovery from day-case anaesthesia. Comparison between methohexitone, Althesin and etomidate

One hundred unpremedicated patients, undergoing short gynaecological procedures, were randomly allocated to receive one of three i.v. hypnotic agents (methohexitone, Althesin and etomidate) alone or in combination with fentanyl, to supplement 66% nitrous oxide in oxygen. Recovery was assessed by the time patients took to open the eyes, to give correct date of birth, to achieve a certain level of manipulative skill with a children's post-box toy, and to perform a paper and pencil test. Satisfactory operating conditions were not obtained using etomidate alone. Administration of methohexitone alone resulted in a more rapid initial awakening than Althesin alone (P less than 0.05) and the administration of fentanyl with methohexitone reduced the total dose given of the latter (P less than 0.01). Administration of fentanyl with Althesin or methohexitone did not significantly prolong the "post-box" recovery time. Side-effects were less common with Althesin, with or without fentanyl and etomidate with fentanyl was associated with the greatest frequency of complications.

A survey of anaesthetic misadventures

Reports of anaesthetic misadventures were regularly collected in the Anaesthetic Department of a district general hospital, to identify recurring problems. Eighty-one misadventures, none of which had serious outcome, were reported during a 6-month period, in which 8312 anaesthetics were administered. Human error was more frequently responsible than equipment failure, and failure to perform a normal check was the factor most frequently associated. Local hazard warnings were circulated when necessary to members of the Department, and the reports formed the basis of departmental discussion and teaching.

A monoclonal antibody detecting the Ly-9.2 (Lgp 100) cell-membrane alloantigen

A mouse monoclonal cell line (20-1.5) was produced by the cell fusion method and the antibody secreted by this line defined the Ly-9.2 specificity--the reciprocal specificity to that previously identified as the Lgp 100 or the T100 molecule. Although most concentrated on lymph-node cells, the antigen is also found on thymocytes, spleen and bone-marrow cells as well as liver and brain tissue. The monoclonal antibody precipitates a 100,000 molecular moiety from thymocytes. The antigenic specificities appear to be highly immunogeneic and antibodies to these specificities contaminate many antisera. These sera are noncytotoxic as is the case with the monoclonal antibody even though it is of the IgG2a subclass. As with T100 or Lgp 100, the Ly-9 locus appears to be linked to the H-25 locus.