N-Terminal Amino Acid Sequence and Processing Site of Sweet Potato Cytochrome c Oxidase Subunit II

The N-terminal amino acid sequence of sweet potato cytochromec oxidase subunit II polypeptide was determined. Comparisonsbetween the sequence and amino acid sequences deduced from thenucleotide sequences of other higher plant subunit II genesindicate a post-translational clevage of N-terminal extensionpart. ¹Present address: Institute of Low Temperature Science, HokkaidoUniversity, Sapporo, 060 Japan. (Received June 13, 1989; Accepted September 8, 1989)     

Stress fibers in the mesenteric mesothelial cells of the large intestine of the bullfrog,Rana catesbeiana

Summary Actin-containing cytoplasmic fibers were visualized in the mesenteric mesothelial cells of the large intestine of bullfrog tadpoles by rhodamine-phalloidin staining of en face preparations of mesothelial cells. These fibers were concurrently stained by immunofluorescence using antibodies to myosin or -actinin. Electron microscopy showed the presence of bundles of microfilaments in the basal cytoplasm of the cells. Such fibers in the mesothelial cells may be comparable to the stress fibers present in cultured cells. The mesothelial cells initially formed axially oriented stress fibers when they changed from a rhombic to a slender spindle-like shape. On the other hand, stress fibers disappeared as cells transformed from elongated to polygonal shapes during the period of metamorphic climax. Expression of stress fibers in these cells appears to be related to the degree of tension loaded on the mesentery, which may be generated by mesenteric winding. These stress fibers in the mesothelial cells may serve to regulate cellular transformation. They may also help to maintain cellular integrity by strengthening the cellular attachment to subepithelial tissue against tensile stress exerted on the mesentery.     

Calcium-binding protein regucalcin increases calcium-independent proteolytic activity in rat liver cytosol

The effect of regucalcin, isolated from rat liver cytosol, on neutral proteolytic activity in the hepatic cytosol was investigated. The Ca²⁺-requiring proteinase required 5–10 µM Ca²⁺ for maximal activity in the presence of a protein substrate (globin). The proteinase activity was markedly elevated by the addition of regucalcin (0.25–2.0 µM) in the absence or presence of Ca²⁺ (5.0 µM) added. The effect of regucalcin, however, was the greater in the absence of Ca²⁺ than that in the presence. The pronounced effect of regucalcin on the proteinase activity was also seen in the presence of 1.0 mM EGTA with or without Ca²⁺ (5.0 µM). In the absence of Ca²⁺, the regucalcin-increased proteinase activity was clearly inhibited by the presence of anti-regucalcin antiserum (diluted to 240-fold), leupeptin (20 and 200 µg/ml), and heavy metals (25 µM cadmium or 25 µM zinc), although the inhibition was not complete at the concentration used. The present findings suggest that regucalcin increases proteolytic activity in rat liver cytosol, and that regucalcin may activate Ca²⁺-independent neutral cysteinyl-proteinase.     

Purification and characterization of a human kidney neutral endopeptidase that hydrolyzes succinyl trialanine-4-nitroanilide and biologically active peptides

An enzyme hydrolyzing succinyl trialanine-4-nitroanilide was extracted from human kidney homogenate and purified by means of gel filtration on Sepharose CL-4B, anion-exchange chromatography on DEAE-Sepharose CL-6B and affinity chromatography on carbobenzoxy-L-Ala-L-Ala-D-Ala-polylysine-agarose. The purified enzyme consists of a single peptide, and its molecular weight was estimated to be about 125 000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme cleaved the substrate at the bond between succinyl dialanine and alanine-4-nitroanilide and showed a Km value of 2.1 mM at the optimal pH of 8.0. The activity was increased by Ca2+ and Mg2+, but was inhibited by phosphoramidon and ethylenediaminetetraacetic acid. The enzyme cleaved the oxydized insulin B chain, angiotensinogen tetradecapeptide, angiotensin I, angiotensin II, angiotensin III, [Sar1,Ala8]-angiotensin II, bradykinin, des-Pro2-bradykinin, Leu5-enkephalin, Met 5-enkephalin, [D-Ala2,Met5]-enkephalinamide and [D-Ala2-Met5]-enkephalin, but did not cleave [D-Ala2,D-Leu5]-enkephalin. The bonds on the amino side of the hydrophobic amino acids of the peptides were cleaved by the enzyme.     

Immigration of the brown planthopper, Nilaparvata lugens, exhibiting various responses to density in relation to wing morphism

Considerable inherent variations in the relation between macropterous and brachypterous wing forms, and nymphal density were found in field populations of the brown planthopper, Nilaparvata lugens Stål (Homoptera: Delphacidae), collected from various locations in Japan. When compared under uniform laboratory rearing conditions, most of the female populations exhibited higher ratios of macropters with increasing nymphal density, but some showed extremely high proportion of brachypters and the others were highly macropterous, over broad ranges of density. These results indicate the possibility that the planthoppers in Japan, which are known not to persist in winter, are derived from different migration sources.About ten generations of successive selection for brachyptery from a population showing usual density-dependent wing morphism generated populations similar to highly brachypterous ones mentioned above. Genetic analysis of the inheritance of wing morphism revealed that brachyptery in the females was controlled by a single pair of dominant alleles. However, in the males wing forms did not segregate so clearly in the crossing experiments. This suggests that wing morphism in N. lugens in under sex-limited inheritance.

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Einwanderung von Nilaparvata lugens mit unterscheidlicher Reaktion auf Populationsdischte bei der Flügelausbildung

Zusammenfassung In Feldpopulationen von Nilaparvata lugens Stål., welche in verschiedenen Regionen Japans gesammelt wurden, bestand in der Beziehung zwischen makropteren bzw. brachypteren Flügelformen und der Larvendichte eine beträchtliche Variation. Unter einheitlichen Zuchtbedingungen im Laboratorium stieg der Makropterenanteil bei den meisten Weibchenpopulationen mit steigender Temperatur; bei einigen Populationen hingegen war entweder der Brachypterenanteil oder der Makropterenanteil extrem hoch und zwar über weite Dichtebereiche. Dies deutet auf die Möglichkeit hin, dass die Zikade in Japan, wo sie bekanntlich nicht überwintert, jeweils aus verschiedenen Quellen einwandert.Wenn eine Population mit der üblichen dichteabhängigen Flügelausbildung 10 Generationen lang auf Brachypterie selektioniert wurde, entstanden Populationen, die den erwähnten hochbrachypteren Populationen aus dem Feld glichen. Die genetische Analyse der Vererbung der Brachypterie ergab, dass bei Weibchen ein einzelnes dominantes Allel verantwortlich ist. Bei Männchen dagegen trennten sich bei Kreuzungsexperimenten die Flügelformen nicht so klar. Dies deuted auf Unterschiede zwischen den Geschlechtern bei der Vererbung der Flügelformen.

     

Further evidence that central neurotensin inhibits pituitary prolactin secretion by stimulating dopamine release from the hypothalamus

Intracerebroventricular (icv) injection of neurotensin (NT) (2 micrograms/rat) suppressed prolactin (PRL) release induced by L-5-hydroxytryptophan (1 mg/100 g body wt, iv), prostaglandin E2(1 microgram/rat, icv), and FK33-824 (10 micrograms/100 g body wt, iv), a Met5-enkephalin analog, in urethane-anesthetized or conscious rats. In contrast, NT did not suppress elevated plasma PRL levels sustained by a large dose of domperidone (10 micrograms/100 g body wt, iv), a peripheral dopamine antagonist. In in vitro experiments, NT (10(-5) M) stimulated dopamine release from perifused rat hypothalamic fragments. These results suggest that central NT inhibits PRL secretion by stimulating dopamine release from the hypothalamus into hypophysical portal blood in the rat.     

Mode of Action of Bipyramidal delta-Endotoxin of Bacillus thuringiensis subsp. kurstaki HD-1

The mode of action of the toxic fragment (P-59) derived from bipyramidal-shaped delta-endotoxin of Bacillus thuringiensis subsp. kurstaki HD-1 on the silkworm Bombyx mori was investigated. An enzyme-linked immunosorbent assay showed that there was no translocation of P-59 from the gut lumen to the hemocoel. When membrane vesicles prepared from silkworm midgut were incubated with P-59, normally smooth surface of vesicles became rough, and patch formation was observed on the surface. Vesicles treated with P-59 tended to agglutinate. The vesicle-denaturing activity of a 130,000-dalton subunit protein of bipyramidal toxin was enhanced by treatment with a gut juice protease of the silkworm. P-59 did not cause any uncoupling effect on mitochondria of the silkworm midgut. These results suggest that the attacking site of this toxin is not the mitochondrion but the cell membrane of the susceptible cell.     

Phagocytosis of different matrix components by different cell types at bone-forming sites in cultured mouse calvariae

Summary Sites of bone formation on fragments of parietal bone of fetal-mice cultured for 10 days were examined by electron microscopy after addition of either ruthenium red or ferrocyanide to the postfixation fluid. Osteoclasts, osteoblast-like cells, and macrophages were the principal active cells at these formation sites. The mononuclear cells (osteoblast-like cells and macrophages) in the osteoid tissue showed evidence of having incorporated elements of calcified tissue. Osteoblast-like cells had phagocytized collagen fibrils and calcified bone matrix. This occurred more frequently in the calcifying area. Mononuclear macrophages showed not only phagocytosis and digestion of cellular debris and bone spicules in the osteoid, but also active incorporation of calcified bone matrix that had been detached from its surroundings by its pseudopod-like projections from long cytoplasmic processes. Collagen fibrils were seldom observed within the macrophages. These observations suggest that in our culture system osteoblast-like cells and macrophages at bone formation sites have a phagocytic role in bone remodeling.This study was supported in part by a grant from the Ministry of Education. Science and Culture of Japan (No. 59771321)     

Spatial relationship among individuals of the Japanese lacertidTakydromus tachydromoides (Sauria,Lacertidae)

The home range ofTakydromus tachydromoides was studied in a grassland area from April 1977 to November 1978. The mean size of home range did not differ markedly between sexes; 136.5 m² for males and 130.8 m² for females. Home ranges of adults overlapped greatly in each sex, and the lizard was considered to be non-territorial. Individuals showed return movement to a definite area (sleeping site) within the home range, and the home range did not shift within a year or between years. Characteristics of the home range of this grassland-inhabiting lizard were discussed in relation to resource abundance and predation pressure.