Continuous requirement of cAMP for pre-spore differentiation in Dictyostelium discoideum

Abstract Using a shaking culture system, we have previously shown that both cell contact and cAMP are required for pre-spore differentiation in Dictyostelium discoideum [2]. In the present study, cAMP was removed from the medium by the use of a hydrolysing enzyme after cells had formed agglomerates. This treatment left the agglomerates unchanged, but caused a rapid decrease in the activity of UDP galactose transferase, a pre-spore-specific enzyme. This result indicates that cAMP is required even after agglomerate formation to maintain pre-spore differentiation.     

Acanthaster planci infestations of reefs and coral assemblages in Japan: a retrospective analysis of control efforts

Reef-building corals have been extensively degraded by Acanthaster planci infestations which have continued to spread throughout the Ryukyu archipelago since 1969. Intensive control efforts were undertaken by fishermen and divers by hand-collecting and disposal on land with removal of about 13 million starfish at the total cost of over 600 million yen from 1970 to 1983 fiscal year. The control programs were mostly unsuccessful for saving the reefs from predation because the efforts were executed on the basis of collecting efficiency, so that significant numbers of starfish continued predation after each belated campaign. Certain coral assemblages outside the Ryukyus were infested with unusually large numbers of A. planci simultaneously with the northern part of Okinawa Island and its neighboring islands in the early seventies. A shift of infestation sites occurred in the extratropical waters in the mid-seventies when the warm current, Kuroshio, changed its path and left the coast of Honshu, the main island of Japan. The Kuroshio is considered to be transporting larval A. planci downstream from the Ryukyus where large aggregations have continued to exist at different areas all through the period.     

Properties of the strongly immobilized signal observed in spin-labeled erythrocytes

A strongly immobilized signal from fatty acid spin labels was observed in human erythrocytes treated with oxidizing agents such as glutaraldehyde, hydrogen peroxide, phenylhydrazine and copper-ortho-phenanthroline. This signal was also observed in freshly prepared ghosts treated with potassium superoxide and in old erythrocyte ghosts. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of these samples demonstrated the diffuse, nondiscrete bands of high molecular weight due to the cross-linking of membrane proteins. The temperature and pH dependences of the outer hyperfine splitting of this signal were very similar to those of bovine serum albumin. We propose that the strongly immobilized signal reflects the interaction of the lipids with the cross-linked products of membrane proteins.     

Evidence for actin involvement in cardiac Z-lines and Z-line analogues

Canine and feline cardiac Z-lines and Z-rods were examined by electron microscopy before and after digestion of muscle fibers with Ca2+-activated protease (CAF). Removal by CAF of electron-dense material which covers Z-lines and Z-rods exposed interdigitating longitudinal filaments (6-7 nm in diameter) apparently continuous with thin filaments of the respective I-bands. The newly exposed longitudinal filaments of CAF-treated Z-lines and of CAF-treated Z-rods bound heavy meromyosin and therefore are actin. The width of Z-lines and length of Z-rods are determined by the amount of overlap of actin filaments of opposite polarity. The oblique filaments in Z-lines and Z-rods are responsible for the perpendicular periodicity of Z-lines and Z-rods, and are attributed to alpha-actinin.     

A Highly Sensitive Enzyme Immunoassay for Mouse β Nerve Growth Factor

Abstract: A sensitive two-site enzyme immunoassay system for mouse β nerve growth factor (NGF) was developed, based on the sandwiching of the antigen between anti-mouse β NGF antibody IgG coated to a polystyrene tube and anti-mouse β NGF antibody Fab'-linked β- d -galactosidase (β- d -galactoside hydrolase, EC 3.2.1.23). This method has the following advantages: (a) the procedures are simple and rapid compared to bioassay or two-site radioimmunoassay; (b) antibody Fab'-β- d -galactosidase complex is more stable than ¹²⁵I-labeled antibody; (c) purified β NGF is detectable at a concentration as low as 10 pg/ml. Our enzyme immunoassay was used to examine the levels of NGF in some tissues of mice. The submaxillary gland contained a high concentration of NGF. However, other tissues, such as the heart, brain, and skeletal muscle, and serum did not contain detectable NGF. These results support recent findings by other investigators that NGF was not found in the organs/tissues other than the submaxillary gland of mice.     

Changes in the Amounts of Ribulose Bisphosphate Carboxylase Synthesized and Degraded during the Life Span of Rice Leaf (Oryza sativa L.)

In situ synthesis and degradation of ribulose bisphosphate carboxylase(RuBPCase) were studied quantitatively in the 12th leaf bladeof the rice plant during the life span of the leaf. Levels ofRuBPCase protein were determined by rocket immunoelectrophoresis.The amounts of RuBPCase synthesized and degraded were estimatedusing ¹⁵N tracer. RuBPCase was scarcely recognized in the leaf when the tip ofthe leaf had just emerged from the 1 lth leaf sheath. Then itincreased rapidly and reached its maximum content a week afterthe completion of leaf expansion. At this time RuBPCase accountedfor 56% of the soluble leaf protein N (26% of the total leafN). The total amount of RuBPCase synthesized up to this timewas about 90% of the amount synthesized throughout the leaf'slife. Degradation of RuBPCase started about the time when it reachedthe maximum content and proceeded at a faster rate during senescencethan that of the remaining soluble protein. When the leaf hadsenesced completely, it contained little measurable RuBPCasealthough the total leaf N was about 30% of the maximum level.These results clearly suggest that RuBPCase is a major N componentwhich is used as remobilized N for the growth of young tissues. Influx and efflux of N and the synthesis and degradation ofRuBPCase are discussed in relation to leaf age. (Received February 18, 1983; Accepted June 16, 1983)     

Caprolactam,a light-promoted growth inhibitor in sunflower seedlings

A neutral growth inhibitor, isolated from methanolic extracts of sunflower seedlings, was characterized by spectral data as caprolactam. Light-grown se     

Gibberellin Production in Cultured Cells of Nicotiana tabacum

Endogenous gibberellins (GAs) in several kinds of crown gallcells and cultured cells derived from normal tissue of Nicotianatabacum were systematically analyzed by gas chromatography-selectedion current monitoring (GC-SICM) after chromatographic purifications,and GA₁, GA₉, GA₁₉ and GA₂₀ were identified. Agrobacterium tumefaciens,a pathogen of crown gall, was confirmed not to produce GAs inits culture. We also investigated endogenous GAs of mother plant,tobacco, and found the same kinds of GAs as in cultured cells. ³ Present address: College of Agriculture, Chonnam NationalUniversity, Kwangju 500, Korea. (Received May 19, 1982; Accepted July 22, 1983)     

Differential staining of insect neurons with nickel and cobalt

Pairs of neurons were differentially stained by intracellular injection of the divalent cations, nickel and cobalt. Pairs of neuronal tracts could be similarly labelled following immersion of their axon bundles in the markers described. Use of nickel and a 4 : 6 mixture of cobalt and nickel according to the protocols presented here revealed the morphology of cricket neuron processes as thin as 1 μm in diameter and yielded a favourable contrast between the cells marked, as well as with respect to the background of unstained tissue.     

Measurement of turbulence intensity in the center of the canine ascending aorta with a hot-film anemometer

The blood flow velocity near the central axis of the canine ascending aorta was measured with a hot-film anemometer. The cardiac output and the heart rate were controlled at will by means of an extracorporeal circulation and by atrial pacing. The turbulent component of the blood flow velocity was calculated using an ensemble average technique. Ensemble average turbulent intensity was also calculated to show the time course of turbulence in the aorta. The ratio of the mean turbulence intensity to the time mean sectional average velocity in the aorta was constant in most animals regardless of the changes in fluid mechanical parameters. The correlation between the frequency parameter and the relative mean turbulence intensity was weakly positive. The power spectrum of the turbulence was also calculated.