Photomovement in Dunaliella salina: Fluence rate-response curves and action spectra

We determined the action spectra of the photophobic responses as well as the phototactic response in Dunaliella salina (Volvocales) using both single cells and populations. The action spectra of the photophobic responses have maxima at 510 nm, the spectrum for phototaxis has a maximum at 450–460 nm. These action spectra are not compatible with the hypothesis that flavoproteins are the photoreceptor pigments, and we suggest that carotenoproteins or rhodopsins act as the photoreceptor pigments. We also conclude that the phototactic response in Dunaliella is an elementary response, quite independent of the step-up and step-down photophobic responses. We also determined the action spectra of the photoaccumulation response in populations of cells adapted to two different salt conditions. Both action spectra have a peak a 490 nm. The photoaccumulation response may be a complex response composed of the phototactic and photophobic responses. Blue or blue-green light does not elicit a photokinetic response in Dunaliella.Diagrams of the optical set-ups used for measuring the responses at the single-cell level and of the plans for building the phototaxometer described in this paper are available to the interested readerWe thank Mr. M. Kubota for a tremendous amount of technical assistance and Mr. R. Nagy for building the phototaxometer. We thank T. Kondo, Professor H. Imaseki and the members of the Laboratory of Biological Regulation, NIBB, for their help and support in various aspects of this research. This research was supported, in part, from grants from the Okazaki Large Spectrograph (Project Nos. 86-535, 87-518, 88-523), the Japanese Society for the Promotion of Science, and the College of Agriculture and Life Sciences at Cornell University to R. W.     

D-Amino acid production from racemic amino acids by a microbial asymmetric degradation

To obtain D-amino acid from a mixture of racemic amino acids, Proteus vulgaris, having the ability of selective degradation of L-isomer in various DL-amino acids mixtures, was used as a biocatalyst. D-Isomer crystals of valine, leucine, isoleucine, histidine and ornithine were isolated at a good yield (25~41%) from the reaction mixture after 24~72 hours.     

Phototaxis in Cryptomonas sp. under condition suppressing photosynthesis

Effects of 3-(3, 4-dichlorophenyl)-l, 1-dimethylurea (DCMU)on photosynthetic oxygen evolution, respiratory oxygen uptake,phototactic response and swimming rate in Cryptomonas sp. weredetermined and compared. Photosynthetic oxygen evolution wascompletely inhibited in the presence of 10^–5 M DCMU. Thetreatment did not significantly affect the rates of respiratoryoxygen uptake, phototaxis, and swimming, indicating that directparticipation of photosynthesis in the phototaxis of this algacan be ruled out. Wavelength dependency of photosynthetic oxygen evolution wasalso determined in the range of 560 to 700 nm. The rate of photosyntheticoxygen evolution at 680 nm was as high as that at 560 nm, butno phototactic activity was seen at 680 nm although it was maximumat 560 nm. This is consistent with the above conclusion. (Received February 16, 1976; )     

Studies on Griseolic Acid Derivatives X. Synthesis and Phosphodiesterase Inhibitory Activity of 2-Substituted Derivatives of Griseolic Acid

Abstract

Griseolic acid derivatives which were modified at the 2-and/or 6-positions were first synthesized from griseolic acid by a ring opening—reclosure reaction of the adenine ring. Among these derivatives, the 2-amino-6-deamino-6-hydroxyl (guanine) derivative showed 3.3 and 45 times stronger inhibitory activity against cAMP and cGMP PDE, respectively, than those of griseolic acid. Structure-activity relationships among these derivatives are also discussed.     

The Flavonoid Apigenin Downregulates CDK1 by Directly Targeting Ribosomal Protein S9

Flavonoids have been reported to inhibit tumor growth by causing cell cycle arrest. However, little is known about the direct targets of flavonoids in tumor growth inhibition. In the present study, we developed a novel method using magnetic FG beads to purify flavonoid-binding proteins, and identified ribosomal protein S9 (RPS9) as a binding partner of the flavonoid apigenin. Similar to treatment with apigenin, knockdown of RPS9 inhibited the growth of human colon cancer cells at the G2/M phase by downregulating cyclin-dependent kinase 1 (CDK1) expression at the promoter level. Furthermore, knockdown of RPS9 suppressed G2/M arrest caused by apigenin. These results suggest that apigenin induces G2/M arrest at least partially by directly binding and inhibiting RPS9 which enhances CDK1 expression. We therefore raise the possibility that identification of the direct targets of flavonoids may contribute to the discovery of novel molecular mechanisms governing tumor growth.     

Novel molecular identification methods for the larger black flour beetle,Cynaeus angustus (Coleoptera: Tenebrionidae)

Two new methods were developed for identifying Cynaeus angustus (LeConte) (Coleoptera: Tenebrionidae) by DNA amplification using simplex and real-time PCR targeting the cytochrome c oxidase subunit I (COI) sequence reported previously. The specificities of the PCR primers and probe were also confirmed by the two PCR methods using the 22 main stored-product insect species, including DNA samples from nine tenebrionid beetle species. The results showed that the newly developed simplex and real-time PCR-based methods have sufficient specificity for analysis. The limits of detection for C. angustus total DNA by the simplex and multiplex PCR were 320 fg and 20 pg, respectively.

     

The affinity of hemoglobin for oxygen affects ventilatory responses in mutant mice with Presbyterian hemoglobinopathy

The purpose of this study was to test whether chronically enhanced O2 delivery to tissues, without arterial hyperoxia, can change acute ventilatory responses to hypercapnia and hypoxia. The effects of decreased hemoglobin (Hb)-O2 affinity on ventilatory responses during hypercapnia (0, 5, 7, and 9% CO2 in O2) and hypoxia (10 and 15% O2 in N2) were assessed in mutant mice expressing Hb Presbyterian (mutation in the beta-globin gene, beta108 Asn --> Lys). O2 consumption during normoxia, measured via open-circuit methods, was significantly higher in the mutant mice than in wild-type mice. Respiratory measurements were conducted with a whole body, unrestrained, single-chamber plethysmograph under conscious conditions. During hypercapnia, there was no difference between the slopes of the hypercapnic ventilatory responses, whereas minute ventilation at the same levels of arterial PCO2 was lower in the Presbyterian mice than in the wild-type mice. During both hypoxic exposures, ventilatory responses were blunted in the mutant mice compared with responses in the wild-type mice. The effects of brief hyperoxia exposure (100% O2) after 10% hypoxia on ventilation were examined in anesthetized, spontaneously breathing mice with a double-chamber plethysmograph. No significant difference was found in ventilatory responses to brief hypoxia between both groups of mice, indicating possible involvement of central mechanisms in blunted ventilatory responses to hypoxia in Presbyterian mice. We conclude that chronically enhanced O2 delivery to peripheral tissues can reduce ventilation during acute hypercapnic and hypoxic exposures.