Affinity labelling of endothelin receptor and characterization of solubilized endothelin-endothelin-receptor complex

Chick cardiac membranes were affinity labelled by cross-linking to membrane-bound 125I-endothelin-1 with disuccinimidyl tartarate. SDS/PAGE and autoradiographic analysis of the 125I-endothelin-1-labelled material in the presence or absence of 2-mercaptoethanol revealed one major labelled band, corresponding to a molecular mass of 53 kDa, whose appearance was dose-dependently inhibited by the addition of unlabelled endothelin-1 (1-100 nM). Subtracting the molecular mass of 125I-endothelin-1 and disuccinimidyl tartarate, the binding protein appeared to have a molecular mass of 50 kDa. To investigate further the molecular properties of endothelin receptor, the 125I-endothelin-1-endothelin-receptor complex was solubilized from chick cardiac membranes using the detergent digitonin. Sucrose gradient sedimentation of the solubilized complex indicated a sedimentation coefficient of 13 S, whereas the complex of (+)-[3H]PN200-110, a dihydropyridine derivative, and dihydropyridine-sensitive Ca2+ channels sedimented at 22 S. A monoclonal antibody raised against dihydropyridine-sensitive Ca2+ channels from the chick brain did not immunoprecipitate the 125I-endothelin-1-endothelin-receptor complex. These data suggest that endothelin receptor is clearly distinct from dihydropyridine-sensitive Ca2+ channels and endothelin has its own specific 50-kDa receptor.     

Isolation of anti-endothelin receptor monoclonal antibodies for use in receptor characterization

Monoclonal antibodies reactive with endothelin (ET) receptors have been prepared by immunization of mice with rat lung membranes. Of four clones isolated, three clones preferentially recognized 32,000-dalton ET receptor and the other has a higher affinity for the 45,000-dalton receptor. The binding of 125I-ET-1 to detergent-solubilized ET receptors which were adsorbed to the antibodies was displaced by increasing concentrations of unlabeled ET isopeptides. These results demonstrate that the four clones specific for the receptor have the potential to be a useful tool in the characterization of ET receptors.     

Productivity and mineral cycling in an oak coppice forest 2. Annual net production of the forest

Annual net production was estimated in the secondary coppice forest near Tokyo, which was dominated by a deciduous oak,Quercus serrata Thunb. Lateral growth of stems and old branches was directly estimated by examining the annual rings for 35 shoots in a clear-cut quadrat of 10m×10m. Phytomasses of current organs were also weighed in the quadrat. Preharvest losses of current organs were determined by twelve 0.5 m² litter traps for fine litter and twelve 6 m² quadrats for woody litter. Branch production was also assessed indirectly by use of the stem-branch allometry and death of branches. The results of the indirect method were in sufficient agreement with the result of the direct one. Grazing loss of leaves from the canopy was estimated directly from the loss in leaf area and indirectly from the animal faeces caught by the litter traps. Net production of the canopy trees was 149 kg a⁻¹ year⁻¹, in which leaf production was 36.9 kg. Animals grazed about 14% of the leaf area by the end of the growing season. True consumption of leaves by animals was 7.6% of leaf production or 10% of leaf mass. Production of undergrowth, mainly a dwarf bamboo,Pleioblastus chino Makino, was 28 kg a⁻¹ year⁻¹, being 15% of the total stand production. Productivity of this forest was significantly higher than that of cool-temperate deciduous broadleaf forests.     

The changes of nuclear position and distribution of circumferentially aligned cortical microtubules during the progression of cell cycle inAdiantum protonemata

The intracellular positions of the nucleus and of cortical, circumferentially aligned microtubules (CCAM) in filamentous, single-celled protonemata ofAdiantum capillus-veneris were determined throughout the cell cycle in the dark. When apical growth continued at G₁ phase, the nucleus migrated keeping a constant distance from the tip. When the apical growth stopped at late S or G₂ phase, the nucleus stopped moving forward and then slightly moved backward to the site of cytokinesis. The CCAM were found only in the dome of protonemal tip when growing under continuous red light; they increased in number after dark incubation for 12 hr and then decreased after 20th hr in the dark. The CCAM were usually observed in the region between the nucleus and the tip at 28 hr in the dark. They were located around the nuclear region at pre-prophase and prophase, but then totally disappeared at metaphase and thereafter.     

Sexual differentiation in population of prothallia inLygodium japonicum

InLygodium japonicum, the archegonium was formed when the prothallium grew to approximately 1.5 mm in width irrespective of age, photoperiod, temperature or concentration of sucrose in the medium. Surgically cut prothallia produced archegonia only when the fragments regenerated to ca. 1 mm in width. Prothallia of smaller dimensions formed antheridia rather than archegonium, but only if archegoniated prothallia of the larger size coexisted in the population. Antheridiogens and inhibitors of archegonial differentiation became detectable by bioassay in conditioned media of 14-and 16-day-old prothallia, respectively, and continued to accumulate in the medium during culture in the light at 25 C. Twelve-day-old or younger prothallia are very sensitive to exogenously applied hormonal substances, whereas by day 14 the response had diminished.     

Stimulating factor for calf thymus DNA polymerase β

A factor that stimulates purified DNA polymerase β about 2-fold was separated from DNA polymerase β activity on a DNA-cellulose column. During the early stage of purification, the factor may be associated with DNA polymerase β to form a complex that sediments at 3.9 S in sucrose gradients and behaved as a 52,000 dalton protein on a Sephadex G-100 column. The complex, which contains 40,000 and 12,500 dalton polypeptides, was insensible to the stimulator, and did not show any exonuclease activity.     

Degradative removal of heparan sulfate from the surface of an ascites hepatoma, AH 66, by heparitinase

Heparitinase [EC 4.2.2.8, heparitin sulfate lyase] was prepared from an extract of cultured cells of Flavobacterium heparinum. Purification of the enzyme was achieved by repeating the hydroxyapatite column chromatography. The enzyme was used to degrade heparan sulfate occurring on the surfaces of ascites hepatoma cells, AH 66. From the supernatant of the enzyme-treated cells, breakdown products from heparan sulfate could be detected by paper chromatography. The heparitinase was found to be more effective than trypsin in removing heparan sulfate from the cells. Furthermore, on analyzing glycosaminoglycans and glycopeptides from the enzyme-treated cells and control cells, it was concluded that heparan sulfate was exclusively present on the cell surface and accessible to the heparitinase whereas other cell surface complex carbohydrates remained intact.     

Eu-actinin, a new structural protein of the Z-line of striated muscles

A new protein component of the Z-line of striated muscles was isolated from chicken breast muscle. This protein has been designated as eu-actinin because of its close similarity in polypeptide molecular weight to actin. Eu-actinin was extracted from myosin-removed myofibrils at low ionic strength at pH 6.5 and purified by column chromatography on Sepharose 4B and DEAE-cellulose. Although the polypeptide molecular weight of eu-actinin measured by SDS-polyacrylamide gel electrophoresis is similar to that of actin, other physico-chemical properties of eu-actinin definitely differ from those of actin. The isoelectric point of eu-actinin was more acidic than that of actin. The amino acid composition of eu-actinin was found to be different from that of actin or those of other muscle structural proteins. The results of analytical gel filtration on Sepharose 4B indicated that eu-actinin forms dimers through non-covalent bonding under aqueous conditions. Eu-actinin has a low axial asymmetry under low-salt conditions, as judged from its intrinsic viscosity ([eta] = 6.4 ml/g for the dimer state) and exhibits a tendency to undergo self-association with increasing ionic strength. Interactions of eu-actinin with other muscle proteins were examined by the affinity column technique. It was shown that eu-actinin binds to actin and alpha-actinin. Eu-actinin exhibited strong seeding ability for the polymerization of actin. Antibody to eu-actinin was raised in a goat and purified by affinity chromatography. The specific antibody against eu-actinin did not form precipitine lines with actin or alpha-actinin. Immunofluorescence studies revealed that eu-actinin is localized at the Z-line of myofibrils. The FITC-conjugated antibody to eu-actinin also stained the Z-lines of rabbit skeletal muscle and chicken cardiac muscle. Therefore, it was concluded that eu-actinin is a new, ubiquitous constituent of Z-lines of striated muscles.     

Quantitative determination of partially methylated alditol acetate of amino sugar by gas chromatography-mass spectrometry

Using doubly labeled N-acetyllactosamine. Hakomori's procedures to prepare partially methylated alditol acetates and their subsequent analysis by gas chromatography-mass spectrometry were followed from a quantitative aspect. It was found that both galactose and glucosamine were nearly quantitatively converted to PMAAs. Preferential loss of PMAA of glucosamine occurred on a column for gas chromatography when the amount of the PMAA injected onto a column was less than a certain level. Above this level, PMAAs of both galactose and glucosamine were eluted from the column with equal yields. However, in mass spectrometry with monitoring of total ions, the molar response factor of PMAA of glucosamine was found to be about 25% higher than that of PMAA of galactose. Based on these findings, methylation analysis of an oligosaccharide from Taka-amylase A composed of one glucosamine and five mannose residues could be carried out quantitatively.