Mutual interactions between optic lobe circadian pacemakers in the cricket Gryllus bimaculatus

The coupling mechanism between the bilaterally paired optic lobe circadian pacemakers in the cricket Gryllus bimaculatus was investigated by recording locomotor activity, under constant light or constant red light, after the optic nerve was unilaterally severed.

Autocrine mechanism of growth of neonatal rat hepatocytes in primary culture

Hepatocytes from neonatal rats of 0 to 3 days old grew actively in primary culture without added serum or growth factors. In these culture conditions, growth of hepatocytes decreased progressively with increase in age of the rats from which they were isolated, and hepatocytes from rats of 2 weeks old showed scarcely any growth. Actively growing hepatocytes were found to secrete a growth factor that promoted their growth and that of Swiss 3T3 cells, but not that of adult hepatocytes. This growth factor in conditioned medium of growing hepatocytes was heat- and acid-stable, but sensitive to trypsin, and had a molecular weight of over 10,000. It did not inhibit the binding of [125I]epidermal growth factor to its receptor, and its growth promoting activity was not inhibited by monoclonal antibody against insulin-like growth factor II. Therefore, it seems to be a new growth factor. These results, together with previous findings (Nakamura, T., Nagao, M., & Ichihara, A. (1987) Exp. Cell Res. 169, 1-14) demonstrated a reciprocal relation between growth and maturation of neonatal hepatocytes during development, like that of adult cells, but indicated that unlike growth of the latter, growth of neonatal cells is induced by an autocrine mechanism.     

A novel anthraquinone ring cleavage enzyme from Aspergillus terreus

An enzyme activity which catalyzes the ring cleavage of the anthraquinone questin to form benzophenone desmethylsulochrin was found in the cell-free extract of Aspergillus terreus, a (+)-geodin producer. The product was identified as desmethylsulochrin by high-resolution mass spectroscopy and chemical carrier dilution analysis. The enzyme showed an absolute requirement of NADPH and molecular oxygen. Therefore, the enzyme, named questin oxygenase, was considered to be classified as a monooxygenase. The optimum pH was around 7.5. The enzyme was very unstable and lost its activity completely after storage overnight at 4 degrees C in 0.05 M phosphate buffer, pH 7.5. The instability of the questin oxygenase was partially overcome by the addition of polyols and the non-ionic detergent Tween 80 to the buffer. By DEAE-cellulose column chromatography, two protein fractions, named DE-I and DE-II, were obtained. Neither fraction reacted with questin by itself. However, the combination of DE-I and DE-II reconstituted the questin oxygenase system to convert questin to desmethylsulochrin. This result suggested that the system is not a simple combination of oxygenase and hydrolase, but requires some additional factor(s) such as electron transfer protein.     

Cloning of mRNA sequence coding for sex-specific storage protein of Bombyx mori

A major plasma protein, referred to as SP 1, exhibits sex- and stage-specific expression during the larval development of the silkworm, Bombyx mori. We have isolated a plasmid clone bearing a part of mRNA sequence coding for SP 1 and quantitated the amount of SP 1 mRNA by means of RNA blot hybridization using the cDNA probe. The developmental change in the amount of SP 1 mRNA in the fat body closely reflected that of the hemolymph concentration of SP 1, indicating that the biosynthesis of SP 1 is regulated in a sex- and developmental stage-specific fashion at the level of mRNA.     

Theoretical analysis of a site-specific chemiluminescence reaction and its application to quantitation of lipid hydroperoxides

A system was designed for chemiluminescent measurement of lipid hydroperoxides by their site-specific reaction in sodium dodecylsulfate micelles. Ferrous ion-induced decomposition of lipid hydroperoxides in the sodium dodecylsulfate micelles resulted in strong chemiluminescence of the Cypridina luciferin analog, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-alpha]pyrazin-3-one (CLA). After addition of ferrous sulfate to the micelles containing lipid hydroperoxide and luciferin, the chemiluminescence intensity reached a maximum rapidly and then decreased. The sequence of this reaction was elucidated by theoretical analysis, which demonstrated that the maximum chemiluminescence intensity is proportional to the initial concentration of hydroperoxide. Good linear relationships were observed between the maximum counts of chemiluminescence and the amounts of hydroperoxides of linoleic acid, phosphatidylcholine, choresterol (5 alpha), cumene and tert-butyl and hydrogen peroxide. This chemiluminescence method was simple and sensitive enough to detect picomole levels of linoleic acid and phosphatidylcholine hydroperoxides.     

Development of cardiac beat rate in early chick embryos is regulated by regional cues

The mesoderm of each of the paired lateral heart-forming regions (HFRs) in the stage 5-7 chick embryo includes prospective conus (pre-C), ventricle (pre-V), and sinoatrial (pre-SA) cells, arranged in a rostrocaudal sequence (C-V-SA). With microsurgery we divided each HFR into three rostrocaudally arranged segments. After 24 hr of further incubation, each segment differentiated into a spontaneously beating vesicle of heart tissue to form a multiheart embryo. The cardiac vesicles in these embryos expressed left-right and rostrocaudal beat rate gradients: the left caudal pre-SA mesoderm produced tissue with the fastest beat rate of the six while the rostral vesicle formed from right pre-C was the slowest. In another operation, we prevented the HFRs from fusing in the midline by cutting through the anterior intestinal portal at stage 8, to produce cardia bifida (CB) embryos with an independently beating half-heart on each side. In these cases, the left half-heart of 87.2% of CB embryos beat faster than the right, confirming the left-right difference in intrinsic beat rate. To assess whether the future beat rate of each region is already determined in the st 5-7 HFR, we exchanged rectangular fragments of left pre-SA mesoderm and attached endoderm with right pre-C fragments to yield a left HFR with the sequence C-V-C and a right HFR with the sequence SA-V-SA. A CB operation was subsequently performed on these exchange embryos to prevent fusion of the lateral HFRs. Preconus mesoderm, transplanted to the pre-SA region, differentiated into tissue with a rapid beat rate, while pre-SA mesoderm relocated to the preconus region formed heart tissue with a slow spontaneous rate typical of the conus. In 73% of the exchange CB embryos, the left half-heart beat faster than the right, despite the origins of its mesoderm. The exchanged mesoderm developed a rate that was appropriate for its new location rather than the site of origin of the mesodermal fragment. In a third set of operations, we implanted a fragment of st 15 differentiated conus tissue into a site lateral to the left caudal HFR in st 5, 6, and 7 embryos, and subsequently performed CB operations on them. The implant caused the adjacent half-heart to develop with a slower beat rate than in unoperated or sham-operated controls.(ABSTRACT TRUNCATED AT 400 WORDS)     

Removal of endotoxin from water by microfiltration through a microporous polyethylene hollow-fiber membrane.

The microporous polyethylene hollow-fiber membrane has a unique microfibrile structure throughout its depth and has been found to possess the functions of filtration and adsorption of endotoxin in water. The membrane has a maximum pore diameter of approximately 0.04 micron, a diameter which is within the range of microfiltration. Approximately 10 and 20% of the endotoxin in tap water and subterranean water, respectively, was smaller than 0.025 micron. Endotoxin in these water sources was efficiently removed by the microporous polyethylene hollow-fiber membrane. Escherichia coli O113 culture broth contained 26.4% of endotoxin smaller than 0.025 micron which was also removed. Endotoxin was leaked into the filtrate only when endotoxin samples were successively passed through the membrane. These results indicate that endotoxin smaller than the pore size of the membrane was adsorbed and then leaked into the filtrate because of a reduction in binding sites. Dissociation of 3H-labeled endotoxin from the membrane was performed, resulting in the removal of endotoxin associated with the membrane by alcoholic alkali at 78% efficiency.     

Biosynthesis of riboflavin. Enzymatic formation of 6,7-dimethyl-8-ribityllumazine from pentose phosphates

The xylene ring of riboflavin originates by dismutation of the precursor, 6,7-dimethyl-8-ribityllumazine. The formation of the latter compound requires a 4-carbon unit as the precursor of carbon atoms 6 alpha, 6, 7, and 7 alpha of the pyrazine ring. The formation of riboflavin from GTP and ribose phosphate by cell extract from Candida guilliermondii has been observed by Logvinenko et al. (Logvinenko, E. M., Shavlovsky, G. M., Zakal'sky, A. E., and Zakhodylo, I. V. (1982) Biokhimiya 47, 931-936). We have studied this enzyme reaction in closer detail using carbohydrate phosphates as substrates and synthetic 5-amino-6-ribitylamino-2,4-(1H,3H)-pyrimidinedione or its 5'-phosphate as cosubstrates. Several pentose phosphates and pentulose phosphates can serve as substrate for the formation of riboflavin with similar efficiency. The reaction requires Mg2+. Various samples of ribulose phosphate labeled with 14C or 13C have been prepared and used as enzyme substrates. Radioactivity was efficiently incorporated into riboflavin from [1-14C]ribulose phosphate, [3,5-14C]ribulose phosphate, and [5-14C]ribulose phosphate, but not from [4-14C]ribulose phosphate. Label from [1-13C]ribose 5-phosphate was incorporated into C6 and C8 alpha of riboflavin. [2,3,5-13C]Ribose 5-phosphate yielded riboflavin containing two contiguously labeled segments of three carbon atoms, namely 5a, 9a, 9 and 8, 7, 7 alpha. 5-Amino-6-[1'-14C] ribitylamino-2,4 (1H,3H)-pyrimidinedione transferred radioactivity exclusively to the ribityl side chain of riboflavin in the enzymatic reaction. It follows that the 4-carbon unit used for the biosynthesis of 6,7-dimethyl-8-ribityllumazine consists of the pentose carbon atoms 1, 2, 3, and 5 in agreement with earlier in vivo studies.     

Promotion of Rooting in Azukia Cuttings by Possible Glycoproteins Extracted from Lentinus edodes Culture

Macromolecules purified from Lentinus edodes mycelia cultureenhanced adventitious root formation in Azukia epicotyl cuttings.Partial purification by sequential column chromatographies gavematerial composed of 71% polysaccharides and 29% proteins. Thesugar moiety consisted of mainly xylose, glucose and arabinose,the sum of their contents being more than 76% of the total carbohydrates.The protein moiety consisted of mainly glycine and serine, whichaccounted for more than 40% of the total amino acid residues. (Received June 9, 1984; Accepted November 12, 1984)