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We have isolated 40 mutants of Escherichia coli which are nonchemotactic as judged by their failure to swarm on semisolid tryptone plates or to make bands in capillary tubes containing tryptone broth. All the mutants have normal flagella, a fact shown by their shape and reaction with antiflagella serum. All are fully motile under the microscope and all are(More)
We have re-examined some of the factors affecting the induction of heart-forming mesoderm in the axolotl. The formation of functional, rhythmically contracting myocardial tissue was used as an assay. We have found that heart-forming mesoderm is fully induced and capable of completing its developmental repertoire by the end of neurulation. As has been(More)
Explants of cranial neural crest from neurula-stage Ambystoma mexicanum embryos form cartilage nodules in 10-14 days, when cultured with pharyngeal endoderm. The time course of formation of the nodules, and their appearance, correspond closely to that observed for visceral cartilage in vivo. Endoderm from any area of the sheet surrounding the pharyngeal(More)
During exponential growth, strain AW405 of Escherichia coli K-12 did not regulate the fatty acid composition of its lipids in response either to temperature or to the addition of NaCl, KCl, or MgCl2 to the medium. Growth was severely restricted at temperatures below 21 degrees C. Differential scanning calorimetry (DSC) of the isolated lipids from a culture(More)
The fatty acid compositions of the three major phospholipids of Escherichia coli K-12; phosphatidylethanolamine, phosphatidylglycerol and cardiolipin; were determined during growth in media differing in NaCl concentration. Significant differences in fatty acid composition of the phospholipids were observed in the stationary phase cultures, but no(More)
The central, intermediate and peripheral regions of 25 breast tumors were analyzed for estrogen receptors (ER) using a combined biochemical (BC)/immunohistochemical (IHC) micromethod. To optimize the regional comparison, the percentage carcinoma per sample (PCS) was evaluated and incorporated into the quantification of the ER. Correction of the measured ER(More)
The mechanisms which regulate myocardial differentiation are poorly understood. The cardiac-lethal (c) mutant of Ambystoma mexicanum, in which the heart never begins to beat, provides a valuable model system for studying this process. Using an in vitro assay, we examine the nature of the defect in c/c embryos and find (contrary to previous reports) that the(More)