Ultrastructural Studies on Caenorhabditis briggsae

A study of the fine structure of Caenorhabditis briggsae revealed several features not previously described in free-living nematodes. These were: chambered walls of the stoma, zonula adherens in the esophagus, daedaloid folds in the inner surface of the uterus and openings in the terminal web of the intestinal epithelium. Other structures observed in these studies were similar to those described from other free-living nematodes.     

Organic Acids of Ditylenchus triformis and Turbatrix aceti

Pyruvic acid, lactic acid and several tricarboxylic acid cycle acids were extracted from Ditylenchus triformis and Turbatrix aceti and identified. Fumaric acid was predominant in both nematodes. Small amounts o f malic and α-ketoglutaric acids and intermediate quantities o f lactic, citric, succinic, and pyruvic acids occurred in D. triformis. In T. aceti citric, lactic, and α-ketoglutaric acids were less abundant than succinic, malic and pyruvic acids. Only traces of aconitic and oxalacetic acids occurred in both nematodes. All the organic acids detected accounted for only about one per cent of the dry weight of nematodes o f the two species.     

Evidence for two waves of induction of DNA enzymes in stimulated human lymphocytes

The stimulation of human lymphocytes with phytohaemoagglutinin induces the appearance or increase of several enzymes of DNA metabolism [Pedrini etal., Biochem. Biophys. Res. Comm., 47:1221(1972)]. With long times of stimulation, two phenomena are observed; an increase in the levels of DNA polymerase, of a DNase acting on single-stranded DNA, and of an endonuclease, occurring between the third and fourth day, in parallel with a wave of DNA synthesis;a second wave of increase of the same enzymes and of DNA ligase,occurring between the fifth and eight day when the DNA replication rate, as measured by thymidine-pulses, has decreased to values close to the background.     

MONOGRAPH OF THE GENUS PROTOSTELIUM

Three new species of Protostelium (Order Protostelida of the Mycetozoa) are described: P. irregularis, P. zonatura, and P. pyriformis, all with rather wide distribution and occurring on dead attached plant parts, less often in soil and humus. The latter two species differ from the first and from the other two known species, P. mycophaga Olive and Stoianovitch and P. arachisporum Olive, in the endogenous origin of the stalk. P. mycophaga var. crassipes, with vesicular stalk bases, is the third variety of that species to be described. A key to the genus is included.     

Extracellular action potentials recorded from the interior of the giant esophageal cell of Ascaris

Exploration of the cytoplasm of the giant esophageal cell of Ascaris with a recording microelectrode shows the existence of shallow spaces where the microelectrode tip becomes extracellular in spite of being in the interior of the cell. When the microelectrode penetrates into these spaces from the cytoplasm, the resting potential shifts to a different level or entirely disappears. At the same time the large intracellular spikes are replaced by small transients similar to extracellularly recorded action potentials. It is concluded that such spaces are in communication with the external solution, and separated from the cytoplasm by an electrically active membrane; i.e., able to generate action potentials. Measurement of the potential differences between the interior of the spaces and the external solution shows that although some are not polarized, many spaces have a resting potential of the same polarity as that of the cytoplasm. It is suggested that although they are of larger size these spaces may be equivalent to the tubular systems which in other muscle cells are known to be involved in the spread of excitation into the cytoplasm.     

An electron microscopical study of developing sympathetic neurons in man

Summary An electron microscopic study has been made of the sympathetic ganglia of a 15 and a 17 week old male human fetus. The fetal sympathetic neurons were densely packed in a scanty connective tissue matrix which also contained blood vessels. The fetal sympathetic neurons had a large, electron-light nucleus with one or two nucleoli, and was of a somewhat mottled appearance due to irregularly dispersed aggregates of fine and coarse granules. The perikaryon usually formed a thin envelope around the nucleus and contained, except for large pigment granules, all intracytoplasmic structures which were also found in mature sympathetic neurons. Adjacent sympathetic cells were either in immediate contact, or slightly separated by a wedge of electron-light satellite expansions, or lined by primitive axons. The satellite cells were in the early state of development. Electron-dense axons either stood side by side with, or were slightly engulfed by light Schwann cell expansions and formed distinct bundles surrounded by a common basement membrane. There was practically no trace of myelin formation or Schwann cell wrapping characteristic for unmyelinated fibers as seen in the adult.This investigation was supported (in whole) by United States Public Health Service Grant NB-01879-05, Institute for Nervous Diseases and Blindness.Grateful acknowledgment is made to Professor Dr. John Lind who madea vailable the fetal material through the Laboratory of Prenatal Growth and Development, Karolinska Institutet, Stockholm, Sweden.The authors wish to thank Docent Dr. Gunnar Bloom who provided the facilities necessary to prepare the fetal material for electron microscopical examination, in his laboratory for Cell Research, Karolinska Institutet, Stockholm, Sweden.