Several ice-nucleating bacterial strains, including Erwinia herbicola, Pseudomonas fluorescens, and Pseudomonas syringae isolates, were examined for their ability to shed ice nuclei into the growth medium. Only E. herbicola isolates shed cell-free ice nuclei active at -2 to -10 degrees C. These cell-free nuclei exhibited a freezing spectrum similar to that of ice nuclei found on whole cells, both above and below -5 degrees C. Partially purified cell-free nuclei were examined by density gradient centrifugation, chemical and enzymatic probes, and electron microscopy. Ice-nucleating activity in these cell-free preparations was associated with outer membrane vesicles shed by cells and was sensitive to protein-modifying reagents.

Bacterial Proteins↗

PubMed1984

Bioconversion of xylan to triglycerides by oil-rich yeasts.

A series of lipid-accumulating yeasts was examined for their potential to saccharify xylan and accumulate triglyceride. Of the genera tested, including Candida, Cryptococcus, Lipomyces, Rhodosporidium, Rhodotorula, and Trichosporon, only Cryptococcus and Trichosporon isolates saccharified xylan. All of the strains could assimilate xylose and accumuate triglyceride under nitrogen-limiting conditions. Strains of Cryptococcus albidus were found to be especially useful for a one-step saccharification of xylan coupled to triglyceride synthesis. Cryptococcus terricolus, a strain constitutive for lipid accumulation, lacked extracellular xylanase, but did assimilate xylose and xylobiose and was able to continuously convert xylan to triglyceride if the culture medium was supplemented with xylanase.

Journal Article↗

PubMed1982

Medical management of the painful shoulder.

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Adrenal Cortex Hormones↗

PubMed1978

Explant culture of human colon.

Human colonic epithelium has been cultured as explants in a chemically defined medium for periods of 1 to 20 days. The viability of the explants was shown by the preservation of the ultrastructural features of the colonic epithelial cells and by active incorporation of radioactive precursors into cellular DNA and protein. A progressive decrease in the number of goblet cells, decrease in the depth of the crypts, and a change from a columnar to a cuboidal epithelium were observed. After 20 days in culture the colonic mucosa consisted of a single layer of cuboidal epithelial cells and a few glands. The ability to maintain colonic mucosa in culture was subject to both intra- and interindividual variation. Cultured human colonic mucosa also activated a chemical procarcinogen, benzo[a]pyrene, into metabolites which bound to cellular DNA. A 100-fold interindividual variation in this binding was observed.

Benzopyrenes↗

PubMed1976

The neural crest and the origin of the insulin-producing and other gastrointestinal hormone-producing cells.

It has been proposed that the endocrine cells of the digestive tract derive from the neuroectoderm (neural crest). To test this hypothesis we removed the entire ectoderm, the precursor of the neural crest, of embryonic rats prior to the formation of the neural crest and cultured the mesoendoderm for 11 days. In every case where a pancreas developed, insulin was detected or B cells were observed. Thus, a neural crest origin for these cells is eiliminated.

Amines↗

PubMed1976

5-bromodeoxyuridine may alter the differentiative program of the embryonic pancreas.

The thymidine analog, 5-bromodeoxyuridine (BrdU), inhibits the differentiation of the acinar cells of the embryonic rat pancreas, while having little effect on the growth of the tissue. The BrdU-treated pancreas contains elevated alkaline phosphatase and carbonic anhydrase activities, and, unlike the normal pancreas, contains numerous extracellular fluid-filled vacuoles, surrounded by ductlike cells. Both alkaline phosphatase and carbonic anhydrase activities are located preferentially in the ductlike cells lining the vacuoles. The biochemical, morphological, and functional features of these epithelial cells are therefore characteristic of the normal pancreatic duct cell. Thus, in the exocrine pancreas, BrdU seems to alter the normal program of differentiation by favoring the functional duct cells while inhibiting the differentiation of acinar cells.

Adenosine Triphosphatases↗

PubMed1974