Halothane inhibits the neurotoxin stimulated [14C]guanidinium influx through 'silent' sodium channels in rat glioma C6 cells

We have investigated the effect of pharmacological agents on [14C]guanidinium ion influx through sodium channels in C6 rat glioma and N18 mouse neuroblastoma cells. The sodium channels of the N18 cells can be activated by aconitine alone, indicating that they are voltage-dependent channels. In contrast, sodium channels in the C6 cells require the synergistic action of aconitine and scorpion toxin for activation and are therefore characterized as so-called silent channels. The general anesthetic halothane used at clinical concentrations, specifically inhibited the ion flux through the silent sodium channel of C6 rat glioma cells. The voltage-dependent channels of the N18 cells were insensitive to halothane at the concentrations tested.     

Flavonoid systematics of ten sections of Ludwigia (Onagraceae)

Data for the flavonoids of 19 species in 10 sections of Ludwigia are presented. Eight flavonoids, comprising four glycoflavones, of which vitexin and isovitexin are reported for the first time in Ludwigia, and four flavonol glycosides, based on quercetin, are present in these species. Each section treated here has either glycoflavones or flavonols; presence of only onte class is considered to be advanced in the genus as a whole, compared with the presence of both glycoflavones and flavonols in the more generalized sects Myrtocarpus Cinerascentes, and Pterocaulon, which were examined earlier. Only glycoflavones are present in sects Macrocarpon (four species), Seminuda (five species), the ditypic African sect. Africana, the monotypic African sects Brenania, Cryptosperma, and Prieurea, the monotypic east Asian sect. Nipponia, and the monotypic pantropical section Fissendocarpa. Only flavonols are present in the monotypic Old Wodd section Caryophylloidea and sect. Oligospermum, which comprises nine species widespread in the OId and New Worlds.     

Volatile anesthetics inhibit the ion flux through Ca2+-activated K+ channels of rat glioma C6 cells

Ca2+-activated K+ channels in rat glioma C6 cells were investigated using monolayers of these cells in petri dishes. The ion flux through the channels was studied with 86Rb+ after addition of a Ca2+-ionophore to the incubation medium. Both the influx and efflux of 86Rb+ through these Ca2+-activated K+ channels were inhibited by the general anesthetic halothane (at clinical concentrations). Other volatile anesthetics such as isoflurane, enflurane and methoxyflurane also inhibited the Ca2+-activated K+ channels at clinical concentrations. Inhibition of these channels by general anesthetics could have profound effects on signal transmission in the brain.     

Structural changes during activation of frog muscle studied by time-resolved X-ray diffraction

The pattern given by contracting frog muscle can be followed with high time resolution using synchrotron radiation as a high-intensity X-ray source. We have studied the behaviour of the second actin layer-line (axial spacing of approximately 179 A) at an off-meridional spacing of approximately 0.023 A-1, a region of the diagram that is sensitive to the position of tropomyosin in the thin filaments. In confirmation of earlier work, we find that there is a substantial increase in the intensity of this part of the pattern during contraction. We find that the reflection reaches half its final intensity about 17 milliseconds after the stimulus at 6 degrees C. The changes in the equatorial reflections, which arise from movement of crossbridges towards the thin filaments, occur with a delay of about 12 to 17 milliseconds relative to this change in the actin pattern. In over-stretched muscle, where thick and thin filaments no longer overlap, the changes in the actin second layer-line still take place upon stimulation with a time course and intensity similar to that observed at full overlap. This indicates that tropomyosin movement, in response to calcium binding to troponin, is the first structural step in muscular contraction, and is the prerequisite for myosin binding. A change in intensity similar to that found in contracting muscle is seen in rigor, where tropomyosin is probably locked in the active position. During relaxation the earlier stages in the decrease in intensity of the second actin layer-line take place significantly sooner after the last stimulus than tension decay. In over-stretched muscles the intensity decay is appreciably faster than in the same muscles at rest length, where attached crossbridges may interfere with the return of tropomyosin to its resting position.     

Separation of Crotalus atrox (western diamondback rattlesnake) alpha-proteinase from serine proteinase and hemorrhagic factor activities

A method for obtaining Crotalus atrox alpha-proteinase (EC 3.4.24.1) in a pure form has been developed. Fractionation of the crude venom on DEAE-Sepharose, followed by gel filtration on Bio-Gel P-150 and chromatography on CM-Sepharose, yielded an alpha-proteinase preparation which showed a single band on disc and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had an activity on casein approximately twice that previously reported. The enzyme is a nonglycosylated single-chain polypeptide with a molecular weight of 26,738 and a pI of 8.15. Proteolytic activity on casein, alpha 1-antichymotrypsin, and Cl-inhibitor was abolished by treatment of alpha-proteinase with 1 mM EDTA, but full activity was retained in the presence of 1 mM phenylmethylsulfonyl fluoride. Caseinolytic activity was increased by 33 and 55% in the presence of 10 mM Mg2+ and Ca2+, respectively. Pure alpha-proteinase is devoid of esterolytic activity on H-D-Pro-Phe-Arg-p-nitroanilide (S-2302), benzoyl-L-arginine ethyl ester, and benzoyl-L-tyrosine ethyl ester. The final preparation has no hemorrhagic factor activity.     

Exoantigens of Trypanosoma cruzi. I. Conditions for Their Detection and Immunogenic Properties in Experimental Infections1

ABSTRACT Exoantigens of Trypanosoma cruzi were produced in experimentally infected BALB/c mice. The exoantigens were detected by the counterimmunoelectrophoresis method (CIE), with antisera raised in rabbits by immunization with total homogenates of culture forms of ***T. cruzi in plasma from ***field animals obtained by centrifugation and filtration. Control experiments indicated that exoantigens are not somatic components of T. cruzi leaked during the preparative procedure. Exoantigens were detected in male and female mice, 11-90 days old, between 6 and 60 days of infection, and in all mice with patent parasitemia. After 13 days of infection, mice developed antibodies to exoantigens; by CIE up to three populations of antibodies were revealed in different groups of animals. In mice between 13 and 60 days of infection, the coexistence of exoantigens and homologous antibodies was also observed. The exoantigens are not strain specific since a cross reactivity between antigens from three strains of T. cruzi (Tulahuén, Higueras, and Alejandro) was seen. Finally, the presence of antibodies to exoantigens in humans with chronic Chagas’ disease was demonstrated.     

Mixing patterns in Amazon lakes

The diel mixing patterns of two small floodplain lakes, Lago Jacaretinga in the Amazon drainage, and Lago Cristalino in the Rio Negro system, were investigated during both the high-water and low-water states of the Amazon River hydrograph. Measurements included temperature, oxygen, ammonia, phosphate, and chlorophyll. In both lakes thermal stratification developed during the day and was eroded at night. During the low-water period when the lakes were shallow, nocturnal circulation extended to the lake bottom, whereas when the lakes were deeper (greater than about 5 m), circulation did not reach the bottom and an anoxic hypolimnion developed. During the low-water period, percent of oxygen concentrations were relatively high but always less than saturation. Low oxygen concentrations were observed during the high-water period. At all times nocturnal mixing supplied a significant amount of oxygen to the lake ecosystems. Nighttime upward mixing of recycled nitrogen and phosphorus also appeared to be important nutrient sources for algal productivity.     

Ultrastructural study of oogenesis and yolk formation in an opisthobranch mollusc, Runcina

Runcina is a hermaphroditic opisthobranch mollusc of small size. It produces large eggs, rich in yolk substances, and it is thus ideal for studying the mechanisms of vitellogenesis. The rough endoplasmic reticulum and the Golgi apparatus appear to be involved in early build up of yolk precursors. Endocytotic vesicles carrying yolk proteins, taken up from the haemolymph, dominate yolk formation at a later stage. The findings presented in this study enhance the proposition of a dual pathway of auto- and heterosynthesis in yolk formation. It is not found that the yolk bodies in Runcina acquire lysosomal enzymes in order to digest the perivitelline fluid, as has been described for some pulmonates. The importance of the role played by the follicle cells in oocyte development is discussed.     

Butyrate induced accumulation of a 2.3 kb polyadenylated H1(0) histone mRNA in HeLa cells.

Sodium butyrate was used to induce the accumulation of human H1(0) mRNA in HeLa cells. The length of this mRNA (2,300 nucleotides) was determined by Northern blot hybridization and S1 nuclease analysis using a human H1(0) gene probe. The mRNA shows long 5' and 3' non coding segments and it is polyadenylated. The signal for this step of mRNA maturation (cleavage and polyadenylation) appears to be the hexanucleotide AAUAAA in analogy to most (other than histone) mRNA species. Thus, the mode of maturation of H1(0) mRNA differs, on one hand, from that of the cell cycle dependent mRNA species, where it is based on a specific stem-and-loop structure. On the other hand, the 3' end of H1(0) mRNA varies from H5 mRNA, which is characterized by two unique dyad symmetry structures at its 3' end.