Evidence for leukotriene C4 transport mediated by an ATP-dependent glutathione S-conjugate carrier in rat heart and liver plasma membranes

Using rat heart sarcolemma and liver plasma membrane vesicles, it has been verified that the transport of leukotriene C4 (LTC4) across membranes is an ATP-dependent process; the apparent Km for LTC4 was 150 nM (heart sarcolemma) or 250 nM (liver plasma membrane). S-(2,4-dinitrophenyl)-glutathione (DNP-SG) inhibited LTC4 uptake into the vesicles dose-dependently (I50 = 25 microM for both heart sarcolemma and liver plasma membrane vesicles). Mutual inhibition between LTC4 and DNP-SG in uptake into the vesicles demonstrates that transport of LTC4 is mediated by an ATP-dependent glutathione S-conjugate carrier.     

Cadmium-induced stimulation of lipogenesis from glucose in rat adipocytes

Exposure of adipocytes of rats to CdCl2 caused acceleration of [3-3H]glucose incorporation into lipid maximally at 500 microM in Krebs-Ringer bicarbonate buffer, pH 7.4, containing 0.2% albumin. T.l.c. of the lipids extracted from adipocytes showed that Cd2+ increased labelling of di- and tri-[14C]acylglycerols predominantly. With increasing concentrations of glucose the apparent Km value was not affected by Cd2+, but the V value was increased, similarly to the effect of insulin. In the presence of insulin, Cd2+ (5 microM) exerted a consistent additive effect with a stimulatory effect of insulin on lipogenesis at all concentrations of insulin tested (5-50 mu units/ml). The stimulation was observed at a high concentration of glucose, suggesting that Cd2+ accelerated intracellular metabolism of glucose, mimicking insulin. However, although Zn2+ and Mn2+ stimulated the transport at a rate similar to that observed with insulin (200 mu units/ml), Cd2+ had no stimulating effect on the membrane transport of 3-O-methylglucose. The biological potency of Cd2+ and the insulin-like effects of Zn2+, both of which metals belong to the same group in the Periodic Table, are similar towards glucose metabolism, but quite different towards glucose transport.     

Growth and differentiation schedule of mouse embryos obtained from delayed matings.

We previously showed that digit formation in mouse embryos from early morning mating seemed to progress faster than those from overnight mating. In this study, to confirm this phenomenon, we examine whether the embryos from normal (0 hr from ovulation to fertilization) and delayed matings (3, 6, or 9 hr from ovulation to fertilization) respond differently to some acute teratogens when they are treated at the same time point from mating. Five mg/kg of cytosine arabinoside (Ara-C) was given to pregnant mice intraperitoneally at 246, 249, or 252 hr (day of gestation (dg) 10) after mating. The patterns of Ara-C induced digit malformations in embryos from the delayed mating groups were those of more advanced stages, when compared with normal mating groups with the same time intervals from mating to Ara-C treatment. In other words, oocytes fertilized up to 9 hr after the presumed time of ovulation could grow similarly to those of normally fertilized oocytes. This catch-up phenomenon suggests that the ovulation clock should be used for the startpoint of the time scale of the growth and differentiation of embryos rather than fertilization clock.     

Analysis of growth and rotational behavior of sporangiophores in Pilobolus crystallinus (Wiggers) Tode

The growth and rotation of the sporangiophore of Pilobolus crystallinus, which are important factors in its phototropic behavior, were analyzed throughout its development. The sporangiophore initial emerged from the trophocyst and elongated at the extreme tip without rotating. The elongation rate of the sporangiophore apex then gradually decreased and the apex expanded radially to produce the sporangium, but no rotation occurred. A transient cessation of elongation after sporangium development was followed by resumption of both elongation and radial expansion in the region beneath the sporangium developing the subsporangial vesicle. Rotation was not obvious at this stage. Radial expansion of the subsporangial vesicle continued at a decreasing rate until full size was reached. Elongation then recommenced in the newly established growth zone in the upper region of the sporangiophore just beneath the subsporangial vesicle. During this period of growth, the sporangiophore rotated in a clockwise direction as viewed from above. All growth and rotation ceased about 1 h before ejection of the sporangium into the air. Based on these results, a modified classification of the developmental stages has been proposed.This work was carried out under the Joint Research Program of the Institute of Genetic Ecology, Tohoku University, Japan (892006). The authors please to thank Kaori Koga and Hiroko Kikuchi for their helpful assistance.     

Neuromodulator octopamine attenuates extrajunctional glutamate sensitivity in insect muscle

Octopamine was found to decrease extrajunctional, but not junctional glutamate responses, in mealworm neuromuscular preparations. This action of octopamine was mimicked by forskolin, 8-(4-chlorophenylthio)-adenosine 3′:5′-cyclic monophosphate (CPT-cyclic AMP), and 8-bromoguanosine 3′:5′-cyclic monophosphate (8-bromo-cyclic GMP), but not by 1,2-oleoylacetylglycerol (OAG), a protein kinase C activator. We suggest that the octopamine-induced reduction in the glutamate sensitivity of extrajunctional membranes may enable the muscle to more closely follow its neuronal input by preventing a depolarization (and hence a conductance increase) due to the discharge of unsequestered transmitter molecules at nonsynaptic sites.     

Changes in Amino Acid Composition during Germination of Soybean

As a fundamental approach to the problem of amino acid metabolism in soybean, changes in content of twenty-three free amino acids, two acidic peptides, ammonia, ethanolamine, urea and seventeen total amino acids of cotyledon, hypocotyl and root of soybean during germination were determined with an amino acid analyzer. Glycine Max M. var. T201 (non-nodule-forming) and Glycine Max M. var. T202 (nodule-forming) were used for this experiment. The content and composition of free and total amino acids of cotyledon in both T201 and T202 differ from those of other tissues in any stage of germination. However, no significant difference between these two varieties of soybean has been recognized in patterns of free and total amino acids changes during germination.

In dry bean and initial stage of germination a relatively large unknown peak appeared and disappeared thereafter when the change in free amino acid content during germination of soybean was analyzed with amino acid analyzer. From various tests on the unknown peak, it became obvious that the peak was consisted of two peptides, γ-glutamyl-tyrosine and γ-glutamylphenylalanine, which were discovered in soybean by Thompson et al. in 1962. The content of these peptides did not change during the first 20 hours of germination, but they decreased rapidly thereafter and disappeared after 70 hours.     

Isolation and characterization of gangliosides with hybrid neolacto-ganglio-type sugar chains

We have previously reported the presence of GM2 as the major ganglioside in the roe of striped mullet, Mugil cephalus, (Li, Y.-T., Hirabayashi, Y., DeGasperi, R., Yu, R. K., Ariga, T., Koerner, T. A. W., and Li, S.-C. (1984) J. Biol. Chem. 259, 8980-8985). In addition to GM2, mullet roe also contain a series of gangliosides with thin-layer chromatographic mobilities slower than GM2. Besides enzymatic hydrolysis and NMR spectroscopy, we have employed the thin-layer chromatography overlay technique using a human monoclonal IgM antibody which recognizes the GM2 epitope to study the nature of these gangliosides. Using these methods we have isolated and characterized three novel mullet roe gangliosides with the following structures: (Formula: see text). These three gangliosides all contain neolacto-series sugar chains. However, the unique feature of gangliosides 5 and 10 is that the terminal portion of the sugar chain is of the ganglio-series while the internal portion is of the neolacto series structure. Due to the substitution of a GalNAc on the internal Gal in 9 and 10 in the inner core, these two gangliosides also contain the gangliotriaosyl structure. Thus, the sugar chains in these gangliosides are of novel type and can be considered a hybrid between the two series which can be defined as the neolacto-ganglio series.