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.     

Effect of thyrotropin releasing hormone injection on blood growth hormone (GH), TSH and growth hormone releasing hormone (GHRH) concentrations in cancer patients

In order to investigate whether endogenous GHRH and somatostatin were involved in the mechanism of the paradoxical GH rise after TRH injection, changes in serum GH and plasma GHRH were examined before and after TRH injection in 12 cancer patients and changes in serum TSH and GH were similarly studied in 76 cancer patients including 31 GH-responders and 45 GH-nonresponders to TRH. TRH stimulated GH secretions without altering the circulating GHRH concentration in 4 of the 12 cancer patients. There was neither a significant correlation between the increase from the basal to maximum GH and GHRH after TRH injection in the 12 cancer patients nor a reciprocal relationship between the increase in GH and TSH after TRH injection in the 76 cancer patients. These findings suggested that the paradoxical GH rise after TRH injection in cancer patients was exerted by its direct action at the pituitary level, and not mediated through the hypothalamus.     

Reevaluation of immunoreactive gonadotropin-releasing hormone (GnRH) levels in general circulation in women: changes in levels and episodic patterns before, during and after gonadotropin surges

In order to reevaluate the earlier varying data regarding circulatory gonadotropin-releasing hormone (GnRH), we assayed extracted GnRH from the plasma frequently collected at mid-cycle in 11 women. For the analysis of episodic GnRH patterns and basal levels, blood samples were obtained at 6 h intervals for 72 h and at 15 min intervals for 2 h every 12 h throughout the experimental period. All blood samples were assayed for GnRH and selected samples for LH, FSH, estradiol and progesterone. For GnRH assay, 5 or 6 ml of blood was mixed with 60 mg of ethylenediaminetetraacetic acid, disodium salt, and 3 mg of phenylmethylsulfonyl floride immediately after blood collection. These enzyme inhibitors prevented the destruction of GnRH in the blood at room temperature for at least 4 h. Plasma GnRH was extracted through several steps including florisil absorption, acidic extraction and washing with organic solvent. Nonspecific immunoreactivity in the plasma was markedly decreased through this extraction process. Our assay values (approximate range, 0.1-2.0 pg/ml) of plasma GnRH in normal women corresponded to the low range of those obtained by others who used the alcohol extraction method. The basal levels of GnRH did not change significantly throughout 3 different periods, i.e., before, during and after the LH surges, and fluctuated between a small range of 0.11 and 1.44 pg/ml. Although the peak levels of GnRH observed in its episodic patterns did not change between the periods before and during the LH surges, they decreased significantly after the LH surge compared with those seen during the LH surges (0.93 +/- 0.07 vs 1.17 +/- 0.09 pg/ml, p less than 0.05). The present data demonstrate that immunoreactive GnRH in the extracted peripheral plasma does not change significantly in its mean, basal and peak levels during the periovulatory period except for a minor but significant decrease in the peak levels shortly after an LH surge.     

Glycine activation of PEP carboxylase from monocotyledoneous C4 plants

Phosphoenolpyruvate carboxylase from $\text{Zea}\text{mays}$ leaves was found to be activated by L-glycine and inhibited by maleic acid, but was not affected by the effectors for the bacterial enzymes. The activating effect of L-glycine was observed with all the enzymes from leaves of several monocotyledoneous C₄ plants, while the enzymes from dicotyledoneous C₄ plants and mono- and dicotyledoneous C₃ plants were not activated by L-glycine. Maleic acid inhibited the enzyme activities of all the higher plants tested.     

Comparison of cytochrome P-450 species which catalyze the hydroxylations of the aromatic ring of estradiol and estradiol 17-sulfate

For identification of microsomal cytochrome P-450 (P-450) enzymes which catalyze 2- or 4-hydroxylations of estrogens in the rat liver, estradiol (E₂) and estradiol 17-sulfate (E₂-17-S) were selected as the substrates and incubated with various kinds of purified P-450 enzymes: PB-1, PB-2, PB-4 and PB-5 obtained from phenobarbital-treated male rats (Sprague-Dawley); MC-1 and MC-5 from 3-methylcholanthrene-treated male rats; and UT-1, UT-2, UT-4 and UT-5 from untreated animals. The reactions were carried out under the P-450-reconstructed system, and the resulting products were determined by HPLC using electrochemical detection. All the enzymes tested were shown to have varying degrees of catalytic activities for 2-hydroxylation of the two substrates; UT-1 and UT-2 had the highest activity. Of the induced P-450 enzymes, PB-2 and MC-1 showed fairly high catalytic activity for 4-hydroxylation of E₂. The P-450 enzymes obtained from the untreated male rats, especially UT-4, showed the highest catalytic activity for 4-hydroxylation of the two substrates. From these results and also from kinetic experiments, the P-450 enzymes which catalyze 2- and 4-hydroxylations of estrogen were considered to be different species. A part of E₂ was converted to such metabolites as estrone and those having a hydroxyl group at positions 6β, 15 or 16, each production of which was estimated to be catalyzed by single or multiple P-450s.     

Enzyme-amplified enzyme-linked immunosorbent assay for gibberellin A4 based on the NAD-dependent redox cycle

An antiserum against gibberellin A₄ (GA₄) raised in rabbits and its partially purified antibodies were used to develop radioimmunoassay (RIA) and indirect enzyme-linked immunosorbent assays (ELISAs) for GA₄. Of three immunoassays tested, an ELISA based on the NAD-dependent redox cycle (enzyme-amplified ELISA) had highest sensitivity. Levels of methylated GA₄ detected by this most sensitive method ranged from 0.1 fmol/assay (3.5 fg/assay) to 0.1 pmol/assay (3.5 pg/assay) suggesting applicability of this method to the detection of gibberellins in purified plant extracts.     

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.