4-Hydroxybenzyl alcohol accumulates in flowers and developing fruits of carrot and inhibits seed formation

Somatic embryogenesis in carrot (Daucus carota) is autonomously inhibited by 4-hydroxybenzyl alcohol (4HBA), which is produced by embryogenic cells. Because somatic embryogenesis is used as a model of zygotic embryogenesis, we assayed for 4HBA in carrot seeds and analyzed the effect of 4HBA on seed formation to determine whether 4HBA is also produced during zygotic embryogenesis. HPLC analysis showed that 4HBA accumulated in flowers and immature and mature fruits, but not in vegetative tissues. The concentration of 4HBA was highest after flowering, when the zygote developed into the early globular-stage embryo. 4HBA accumulation then decreased with seed development. Exogenous application of 4HBA to immature carrot fruits inhibited seed formation. Many 4HBA-treated seeds did not include a mature embryo. These results indicate that the production and accumulation of 4HBA occurs during carrot seed development and that 4HBA has an inhibitory effect on carrot seed formation.     

Importance of renal mitochondria in the reduction of TEMPOL,a nitroxide radical

Spin probing methods using an electron spin resonance (ESR) spectrometer are used extensively and bring us a lot of information about in vivo redox mechanisms. However, the in vivo reducing mechanisms of exogenous nitroxide radicals, which serve as typical spin probing reagents are not clear. To clarify this, we examined the sequential kinetics of a spin probe, 4-hydroxy 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) in the in vivo organs, tissue homogenates and subcellular fractions of kidney and liver using an in vivo and X-band ESR spectrometers. As a parameter of reducing activity, we calculated the half-life of TEMPOL from the decay curve of ESR signal intensity. The half-life of TEMPOL in the whole organs and homogenates of the kidney was significantly shorter than that of the liver, this indicates that the kidney has more reducing activity against TEMPOL as compared to the liver. Subcellular fractional studies revealed that this reducing activity of the kidney mainly exists in the mitochondria. Contrarily, in addition to reduction in the mitochondria, TEMPOL in the liver was reduced by the microsome and cytosol.     

Effect of a novel vasoconstrictor endothelin-1 (1-31) on human umbilical artery

To clarify the action of a novel endothelin-1 with 31 amino acids, ET-1 (1-31), on fetal circulation, its vasoconstrictive activity on human umbilical and uterine arteries was investigated in comparison with that of a conventional ET-1 (1-21). UFER micro-easy magnus was used for determination of vasoconstriction. The contraction of umbilical artery by KCl was significantly weaker than that of the uterine artery. In ETs, constriction by KCl was set as control, and the rate of constriction of uterine and umbilical arteries was used for comparison. The constriction of human uterine artery induced by ET-1 (1-31) was also significantly weaker than that by ET-1 (1-21). On the contrary, ET-1 (1-31) was a potent constrictor on the umbilical artery equally to ET-1 (1-21). The present study is the first to demonstrate that ET-1 (1-31) has a contractile activity on human vessels. Furthermore, the regulatory mechanism on constriction of umbilical artery is different from that observed in a systemic vessel, indicating a particularly important role of ET-1 (1-31) in fetal circulation.     

Guanabenz-mediated inactivation and enhanced proteolytic degradation of neuronal nitric-oxide synthase

Guanabenz, a metabolism-based irreversible inactivator of neuronal nitric-oxide synthase (nNOS) in vitro, causes the loss of immunodetectable nNOS in vivo. This process is selective in that the slowly reversible inhibitor N(G)-nitro-L-arginine did not decrease the levels of nNOS in vivo. To better understand the mechanism for the loss of nNOS protein in vivo, we have investigated the effects of guanabenz and N(G)-nitro-L-arginine in HEK 293 cells stably transfected with the enzyme. We show here that guanabenz, but not N(G)-nitro-L-arginine, caused the inactivation and loss of nNOS protein in the HEK 293 cells. In studies with cycloheximide or in pulse-chase experiments with [(35)S]methionine, we demonstrate that the loss of nNOS was due in large part to enhanced proteolysis of the protein with the half-life decreasing by one-half from 20 to 10 h. Other metabolism-based irreversible inactivators to nNOS, N(G)-methyl-L-arginine, and N(5)-(1-iminoethyl)-L-ornithine, but not the reversible inhibitor 7-nitroindazole (7-NI), caused a similar decrease in the half-life of nNOS. Proteasomal inhibitors, lactacystin, Cbz-leucine-leucine-leucinal, and N-acetyl-leucine-leucine-norleucinal, but not the lysosomal protease inhibitor leupeptin, were found to effectively inhibit the proteolytic degradation of nNOS. Thus we have shown for the first time that the irreversible inactivators of nNOS, perhaps through covalent alteration of the enzyme, enhance the proteolytic turnover of the enzyme by a mechanism involving the proteasome.     

Dark-Induced Accumulation of mRNA for a Homolog of Translationally Controlled Tumor Protein (TCTP) in Pharbitis

A cDNA encoding a homolog of human translationally controlledtumor protein (TCTP) was isolated from cotyledons of the short-dayplant Pharbitis nil cv. Violet. The level of the correspondingmRNA increased gradually during darkness. This increase wasinhibited by end-of-day exposure to far-red light. (Received October 30, 1997; Accepted January 7, 1998)     

C-ABI3, the Carrot Homologue of the Arabidopsis ABI3, is Expressed during Both Zygotic and Somatic Embryogenesis and Functions in the Regulation of Embryo-Specific ABA-Inducible Genes

A carrot gene homologous to the ABI3 gene of Arabidopsis wasisolated from a carrot somatic embryo cDNA library and designatedC-ABI3. The sequence of C-ABI3 was very similar to those ofABI3 of Arabidopsis and VP1 of maize in certain conserved regions.The expression of C-ABI3 was detected specifically in embryogeniccells, somatic embryos and developing seeds. Thus, expressionof C-ABI3 was limited to tissues that acquired desiccation tolerancein response to endogenous or exogenous abscisic acid (ABA).Endogenous levels of ABA in seeds increased transiently andthen desiccation of seeds started. The expression of C-ABI3in developing seeds was observed prior to the increase in levelsof endogenous ABA that was followed by desiccation of seeds.In transgenic mature leaves in which C-ABI3 was ectopicallyexpressed, expression of ECP31, ECP63 and ECP40 was inducedby treatment with ABA, which indicates that the expression ofECP genes was controlled by the pathway(s) that involved C-ABI3and ABA. This suggests that C-ABI3 has the same function asVP1/ABI3 factor in carrot somatic embryos. (Received March 4, 1998; Accepted September 4, 1998)     

More than a 600-fold variation in nitrogen dioxide assimilation among 217 plant taxa

Assimilation of nitrogen dioxide in response to fumigation with ¹⁵N-labelled nitrogen dioxide was studied in 217 plant taxa. The taxa included 50 wild herbaceous plants collected from roadsides (42 genera, 15 families), 60 cultivated herbaceous plants (55 genera, 30 families) and 107 cultivated woody plants (74 genera, 45 families). Two parameters, the 'NO₂-N content', or NO₂-derived reduced nitrogen content in fumigated plant leaves (mg N g^–1 dry weight), and the 'NO₂-utilization index', or percentage of the NO₂-derived reduced nitrogen in the total reduced nitrogen, were determined. The NO₂-N content differed 657-fold between the highest ( Eucalyptus viminalis ; 6·57) and lowest ( Tillandsia ionantha and T. caput-medusae ; 0·01) values in the 217 taxa; 62-fold in a family (Theaceae) and 26-fold in a species ( Solidago altissima ). Nine species had NO₂-utilization indices greater than 10%, of which Magnolia kobus , Eucalyptus viminalis , Populus nigra , Nicotiana tabacum and Erechtites hieracifolia had NO₂-N contents > 4·9. These plants can be considered 'NO₂-philic' because in them NO₂-nitrogen has an important function(s). The Compositae and Myrtaceae had high values for both parameters, whereas the monocots and gymnosperms had low ones. These findings suggest that the metabolic pathway of NO₂-nitrogen differs among plant species. The information presented here will be useful for creating a novel vegetation technology to reduce the atmospheric concentration of nitrogen dioxide.     

The Two Nuclei in the Dikaryon of the Homobasidiomycete Coprinus cinereus Change Position after Each Conjugate Division

We constructed a common-AB diploid strain of Coprinus cinereus and mated this to a compatible haploid strain to construct a diploid-haploid dikaryon. We examined the positions of the diploid and haploid nuclei in the apical and subapical cells of the dikaryon by fluorescence microscopy and microfluorometry. In 60% of apical cells the leading nucleus (the nucleus proximal to the hyphal apex) was diploid and the second nucleus (the nucleus distal to the apex) was haploid, whereas in the remaining 40% of apical cells the order of the two nuclei was reversed. It was also observed that in 97% of hyphae examined the order of the diploid and haploid nuclei was reversed between the apical cell and the subapical cell. Based on these observations, we conclude that the two nuclei alternate in taking the leading and second positions in the apical cell at almost every conjugate division in the dikaryon. Copyright 1998 Academic Press.     

Properties of an immunoglobulin binding factor from human seminal plasma.

A soluble factor (IBF) in human seminal plasma that binds serum immunoglobulins (Ig) of various species was purified to homogeneity by ammonium sulfate precipitation, preparative isoelectrofocusing, and gel filtration chromatography. The purified IBF interacted weakly with Fc and F(ab')2 fragments and not with Fab. It interacted with anti-Leu 11b and polyclonal anti-Fc gamma RIII antibodies, but not with other anti-Fc gamma R antibodies (32.2, IV.3 and 3G8). IBF is probably a non-glycosylated protein with isoelectric point ranging from 5.1 to 5.8. The estimated Mr of the purified native IBF is 27 kD, determined by sodium dodecyl sulfate polyacrylamide electrophoresis (SDS-PAGE) under non-reducing condition. In its native form, IBF did not bind Ig or interact with anti-Fc gamma R antibodies. Following SDS-PAGE under reducing condition, IBF migrated as a single protein with an estimated Mr of 16 kD and interacted with Ig of various species and with anti-Leu 11b antibodies. When carboxymethylated, however, IBF did not bind IgG. The present results suggest that free sulfhydryl groups of IBF is required for Ig binding.     

Immunohistochemical Localization of Manserin,a Novel Neuropeptide Derived from Secretogranin II,in Rat Adrenal Gland,and its Upregulation by Physical Stress

We recently identified a novel 40-amino acid neuropeptide designated manserin from the rat brain (Yajima in NeuroReport 15: 1755–1759, 2004). Manserin is highly expressed in pituitary and hypothalamic nuclei, which suggests that it plays a role in the endocrine system. In this study, we employed immunohistochemical methods to investigate the presence of manserin in rat adrenal glands, as well as its regulation by physical stress. Immunohistochemical analysis using anti-manserin antibody showed that manserin is present in the rat adrenal medulla but not in the cortex. When the colocalization of manserin and phenylethanolamine N-methyltransferase (PNMT), an epinephrine-synthesizing enzyme, was examined, virtually all PNMT-positive cells expressed manserin. Interestingly, the immunoreactivity of manserin was significantly increased when the rats were exposed to water-immersion restraint stress. These results demonstrate for the first time that adrenal manserin, a novel neuropeptide, may have a potential physiological role under stress-inducing conditions.