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At least 631 records · Page 35Linked to original sources
PubMed2002

Suppression of phorbol ester-induced NF-kappaB activation by capsaicin in cultured human promyelocytic leukemia cells.

Capsaicin, a major pungent constituent of red pepper (Capsicum annuum L.) possesses a vast variety of pharmacologic and physiologic activities. Despite its irritant properties, the compound exerts anti-inflammatory and anti-nociceptive effects. Previous studies from this laboratory revealed that capsaicin, when topically applied onto dorsal skin of female ICR mice, strongly attenuated activation of NF-kappaB and AP-1 induced by the typical tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), which may account for its anti-tumor promoting activity in mouse skin. In the present work, we have found that capsaicin suppresses TPA-stimulated activation of NF-kappaB through inhibition of IkappaB alpha degradation and blockade of subsequent nuclear translocation of p65 in human promyelocytic leukemia HL-60 cells. Methylation of the phenolic hydroxyl group of capsaicin abolished its inhibitory effect on NF-kappaB DNA binding. Likewise, TPA-induced activation of AP-1 was mitigated by capsaicin treatment.

Animals↗
PubMed2003

A new AOX homologous gene OsIM1 from rice (Oryza sativa L.) with an alternative splicing mechanism under salt stress.

A differentially expressed OsIM1 gene was isolated from rice salt-tolerant mutant M-20 by differential display. Sequence analysis revealed that the amino-acid sequence of OsIM1 showed 66% and 62% identity with PTOX from tomato ( Capsicum annuum) and AtIM from Arabidopsis, both of which encoded chloroplast-orientated terminal oxidase. Comparison of the nucleotide sequence of the OsIM1 cDNA with its genomic sequence revealed that OsIM1 genomic DNA contained nine exons and eight introns. A pseudo-transcript ( OsIM2), which probably resulted from the abnormal splicing of the OsIM1 pre-mRNA, was also identified. Southern-blot analysis showed that there existed only one copy of the OsIM1 gene in the rice genome. RFLP analysis located it on rice chromosome 3. The Northern blot revealed that OsIM1 was up-regulated by NaCl and ABA treatment. RT-PCR analysis indicated that OsIM1 and OsIM2 co-existed in the OsIM transcript pool, and the ratio of OsIM1/ OsIM2 was differentially regulated by salt stress in the salt-sensitive variety and the salt-tolerant varieties.

Alternative Splicing↗
PubMed2003

Candidate gene analysis of anthocyanin pigmentation loci in the Solanaceae.

Crop species in the Solanaceae, which includes tomato ( Lycopersicon esculentum), potato ( Solanum tuberosum), pepper ( Capsicum spp.), and eggplant ( S. melongena), exhibit natural variation in the types, levels, and tissue-specific expression patterns of anthocyanin pigments. While the identities of the genes underpinning natural variation in anthocyanin traits in these crops are largely unknown, many structural genes and regulators of anthocyanin biosynthesis have been isolated from the solanaceous ornamental species Petunia. To identify candidate genes that may correspond to loci controlling natural variation in the four crops, 13 anthocyanin-related genes were localized on a tomato F(2) genetic map. Gene map positions were then compared to mapped mutants in tomato and through comparative genetic maps to natural variants in potato, eggplant, and pepper. Similar map positions suggest that the tomato mutants anthocyaninless, entirely anthocyaninless, and anthocyanin gainer correspond to flavonoid 3'5'-hydroxylase ( f3'5'h), anthocyanidin synthase, and the Petunia Myb domain trancriptional regulatory gene an2, respectively. Similarly potato R, required for the production of red pelargonidin-based pigments, P, required for production of purple delphinidin-based pigments, and I, required for tissue-specific expression in tuber skin, appear to correspond to dihydroflavonol 4-reductase, f3'5'h and an2, respectively. The map location of an2 also overlaps pepper A and eggplant fap10.1, lla10.1, lra10.1, sa10.1, pa10.1 and ca10.1, suggesting that a homologous regulatory locus has been subjected to parallel selection in the domestication of many solanaceous crops. To test the hypothesis that tomato anthocyaninless corresponds to f3'5'h, a portion of the gene was sequenced. A premature stop codon was observed in an anthocyaninless mutant, but not in wild-type.

Anthocyanins↗
PubMed2002

QTLs involved in the restriction of cucumber mosaic virus (CMV) long-distance movement in pepper.

Partial restriction of cucumber mosaic virus (CMV) long-distance movement originating from the Capsicum annuum inbred line 'Vania' was assessed in a doubled-haploid progeny using two screening methods: the first allowed one to assess the resistance of adult plants decapitated above the fourth leaf and inoculated on the third leaf using a common CMV strain, and the second allowed one to assess CMV resistance to long-distance movement on seedlings inoculated using an atypical CMV strain. For both resistance tests, the behavior of the F(1) hybrid between 'Vania' and the susceptible line 'H3' indicated that partial resistance is inherited as a dominant trait. Phenotypic data from the two screening methods were correlated but the one performed on seedlings was much more severe. A subset of 184 molecular markers well-distributed over the pepper genome was selected for QTL mapping using the composite interval mapping (CIM) method. A total of seven genomic regions, including one major effect and several minor effect QTLs, were shown to be associated with partial restriction of CMV long-distance movement. These results are compared with those already obtained in pepper and also in other solanaceous crops, potato and tomato.

Journal Article↗
PubMed2000

Cytotoxicity of capsaicin in monkey kidney cells: lack of antagonistic effects of capsazepine and Ruthenium red.

Capsaicin is a natural product of Capsicum peppers, excitatory effects of which have been shown to be mediated by the recently cloned vanilloid receptor 1 (VR1). Since previous studies have shown that capsaicin inhibits protein synthesis, experiments were performed to investigate whether this effect is mediated by VR1 receptor on cultured monkey kidney cells (Vero cells). The capsaicin uptake was assessed in cellular homogenate and in medium by high-performance liquid chromatography (HPLC) separation and quantification on C18 reverse-phase column and fluorescence detection. Toxic effects were assessed by incorporation of [3H]L-leucine into cellular proteins in the presence of capsazepine, the VR1 vanilloid receptor antagonist and Ruthenium red or tyrosine or calcium. Capsazepine (1 to 256 microM) did not modify the uptake rate of capsaicin for incubation times up to 24 h and did not antagonize capsaicin-induced protein synthesis inhibition. It rather inhibited protein synthesis per se from 100 to 256 microM. Ruthenium red which blocks mitochondrial calcium uptake, inhibited protein synthesis and did not antagonise or increase synergistically the effects of capsaicin. Interestingly in a medium deprived of calcium and supplemented by calcium chloride (10-50 microM) the protein synthesis inhibition induced by capsaicin is antagonised somehow. There was no prevention of capsaicin diffusion into the cells. Tyrosine, which seems to be the best preventive agent of capsaicin inhibitory effects, prevents its metabolism but not its diffusion. Capsaicin might enter cells by diffusion and interfere with protein synthesis machinery by competition with tyrosine which in turn prevents the metabolism of capsaicin. The results of the present study suggest that cell responses to capsaicin may be transduced through at least two molecular pathways, one involving VR1, since the receptor antagonist capsazepine fails to prevent the inhibitory effect of capsaicin in Vero cells of renal origin.

Animals↗
PubMed1999

Cytotoxicity and genotoxicity of capsaicin in human neuroblastoma cells SHSY-5Y.

Capsaicin, a natural product of Capsicum species, induces excitation of pain perception at nociceptive terminals. Our previous studies have shown that capsaicin inhibits protein synthesis in cultured monkey kidneys cells (Vero cells) and in primoculture of rat astrocytes. We have now investigated the effect of capsaicin on human neuroblastoma cells SHSY-5Y. The cytotoxicity has been assessed by incorporation of [(3)H]L-leucine into cellular protein in the presence of capsaicin and the genotoxicity has been evaluated using the comet assay and the fragmentation assay after incubation of neuroblastoma cells with 25-100 microM capsaicin. The concentration required to inhibit 50% of the protein synthesis (IC(50)) was found to be 60 microM after incubation with the toxin during one cellular cycle (5 days) of SHSY-5Y. The results of the comet test and DNA fragmentation assay clearly suggest that capsaicin is able to induce DNA strand breaks already with concentrations in the range of 50 microM, corresponding to 29.3 microM of capsaicin not bound to alpha-1 acid glycoprotein. Several daily topical applications of preparations containing 0.075% of capsaicin could lead to blood capsaicin concentration of this order of magnitude following transdermal passage (5% of the total quantity applied). Because DNA strand breaks or DNA lesions may affect cellular functions, lead to cell death and/or mutagenesis, our data in case of inappropriate DNA repair may have important implications for the possible health threats of capsaicin, specially in the case of misuse of capsaicin preparations in pathological situations.

Capsaicin↗
PubMed2006

Capsaicin inhibits catecholamine secretion and synthesis by blocking Na+ and Ca2+ influx through a vanilloid receptor-independent pathway in bovine adrenal medullary cells.

We report here the effects of capsaicin, a flavoring ingredient in the hot pepper Capsicum family, on catecholamine secretion and synthesis in cultured bovine adrenal medullary cells. Capsaicin inhibited catecholamine secretion (IC(50)=9.5, 11.8, and 62 microM) stimulated by carbachol, an agonist of the nicotinic acetylcholine receptor, by veratridine, an activator of voltage-dependent Na(+) channels, and by high K(+), an activator of voltage-dependent Ca(2+) channels, respectively. Capsaicin also suppressed carbachol-induced (22)Na(+) influx (IC(50)=5.0 microM) and (45)Ca(2+) influx (IC(50)=24.4 muM), veratridine-induced (22)Na(+) influx (IC(50)=2.4 microM) and (45)Ca(2+) influx (IC(50)=1.1 microM), and high K(+)-induced (45)Ca(2+) influx (IC(50)=5.8 microM). The reduction in catecholamine secretion caused by capsaicin was not overcome by increasing the concentration of carbachol. Furthermore, capsazepine (10 microM), a competitive antagonist for the transient receptor potential vanilloid 1, and ruthenium red (30 microM), a nonselective cation channel antagonist, did not block the inhibition by capsaicin of catecholamine secretion. Capsaicin also suppressed both basal and carbachol-stimulated (14)C-catecholamine synthesis (IC(50)=10.6 and 26.4 microM, respectively) from [(14)C] tyrosine but not from L: -3, 4-dihydroxyphenyl [3-(14)C] alanine ([(14)C] DOPA) as well as tyrosine hydroxylase activity (IC(50)=8.4 and 39.0 microM, respectively). The present findings suggest that capsaicin inhibits catecholamine secretion and synthesis via suppression of Na(+) and Ca(2+) influx through a vanilloid receptor-independent pathway.

Adrenal Medulla↗
PubMed2003

Sweet pepper ferredoxin-like protein ( pflp) gene as a novel selection marker for orchid transformation.

A novel method for selection of transgenic plants utilizing the sweet pepper ( Capsicum annuum L.) ferredoxin-like protein ( pflp) gene as selection marker and Erwinia carotovora as the selection agent has been developed. An expression vector containing a pflp cDNA driven by a cauliflower mosaic virus 35S promoter was successfully transformed into protocorm-like bodies of Oncidium orchid by Agrobacterium tumefaciens and particle bombardment, respectively. Erwinia carotovora was used as a selection agent to screen transformants, thereby obtaining transgenic plants without the use of an antibiotic selection agent. A total of 32 independent transgenic orchid lines were obtained, out of which 9 transgenic lines (beta-glucuronidase positive) were randomly selected and confirmed by Southern and northern blot analyses. The transgenic orchid plants showed enhanced resistance to E. carotovora, even when the entire plant was challenged with the pathogen. Our results suggest the novel use of the pflp gene as a resistance selection marker in plant genetic engineering strategies. In the future, the use of the pflp gene as a selection marker may facilitate the use of smaller gene constructs due to removal of bulky antibiotic selection and reporter genes. These constructs can then be used to incorporate additional genes of choice.

Agrobacterium tumefaciens↗
PubMed2004

Studies on water transport through the sweet cherry fruit surface: IX. Comparing permeability in water uptake and transpiration.

Water uptake and transpiration were studied through the surface of intact sweet cherry (Prunus avium L.) fruit, exocarp segments (ES) and cuticular membranes (CM) excised from the cheek of sweet cherry fruit and astomatous CM isolated from Schefflera arboricola (Hayata) Hayata, Citrus aurantium L., and Stephanotis floribunda Brongn. leaves or from Lycopersicon esculentum Mill. and Capsicum annuum L. var. annuum Fasciculatum Group fruit. ES and CM were mounted in diffusion cells. Water (deionized) uptake into intact sweet cherry fruit, through ES or CM interfacing water as a donor and a polyethyleneglycol (PEG 6000, osmotic pressure 2.83 MPa)-containing receiver was determined gravimetrically. Transpiration was quantified by monitoring weight loss of a PEG 6000-containing donor (2.83 MPa) against dry silica as a receiver. The permeability coefficients for osmotic water uptake and transpiration were calculated from the amount of water taken up or transpired per unit surface area and time, and the driving force for transport. Permeability during osmotic water uptake was markedly higher than during transpiration in intact sweet cherry fruit (40.2-fold), excised ES of sweet cherry fruit (12.5- to 53.7-fold) and isolated astomatous fruit and leaf CM of a range of species (on average 23.0-fold). Partitioning water transport into stomatal and cuticular components revealed that permeability of the sweet cherry fruit cuticle for water uptake was 11.9-fold higher and that of stomata 56.8-fold higher than the respective permeability during transpiration. Increasing water vapor activity in the receiver from 0 to 1 increased permeability during transpiration across isolated sweet cherry fruit CM about 2.1-fold. Permeability for vapor uptake from saturated water vapor into a PEG 6000 receiver solution was markedly lower than from liquid water, but of similar magnitude to the permeability during self-diffusion of (3)H(2)O in the absence of osmotica. The energy of activation for self-diffusion of water across ES or CM was higher than for osmotic water uptake and decreased with increasing stomatal density. The data indicate that viscous flow along an aqueous continuum across the sweet cherry fruit exocarp and across the astomatous CM of selected species accounted for the higher permeability during water uptake as compared to self-diffusion or transpiration.

Biological Transport↗
PubMed1999

Identification of proteins associated with plastoglobules isolated from pea (Pisum sativum L.) chloroplasts.

Plastoglobules are conspicuous lipid-containing structures in the chloroplast stroma and are thought to serve as lipid reservoirs for thylakoid membranes. Plastoglobules also contain low levels of proteins. We have purified plastoglobules from a pea chloroplast membrane fraction. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the purified plastoglobules revealed more than a dozen distinct polypeptides that we propose to term plastoglobulins. For one of the proteins, termed plastoglobulin 1 (PG1), we have obtained partial N-terminal and internal protein sequences. The amino acid sequence, deduced from cDNA, encoded a precursor protein of a calculated mass of 38,491 Da which contained a 48-residue-long N-terminal signal sequence. Pre-PG1 obtained by coupled in-vitro transcription/translation was imported into pea chloroplasts, its signal sequence was cleaved and mature PG1 was assembled into plastoglobules. Homology searches of the data bases revealed similarity of PG1 to the plastoglobule-associated protein of Capsicum annuum, the carotenoid-associated protein of Cucumis sativus and to a protein of the cyanobacterium Synechocystis sp., indicating that PG1 is a novel member of an ancient protein family. Immunoelectron microscopy using PG1 specific antibodies indicated that PG1 is present in multiple copies on the surface of plastoglobules.

Amino Acid Sequence↗
PubMed2003

Characterization and genetic diversity of potato yellow mosaic virus from the Caribbean.

The begomovirus Potato yellow mosaic virus (PYMV) is responsible of significant yield losses in tomato in Guadeloupe. Four field isolates from Guadeloupe were analyzed in term of their host range using three inoculation methods (mechanical, grafting and insect vector), sequences analysis of PCR fragments and phylogenetic analysis of an infectious clone, PYMV-[GP]. Capsicum annuum, Datura stramonium, Nicotiana benthamiana, N. tabacum 'Xanthi NC', Petunia hybrida, and Solanum tuberosum were found to be hosts. All isolates from Guadeloupe, Martinique, Puerto Rico and the Dominican Republic were closely related to PYMV-[GP]. Sequence identity between PYMV-[GP] and PYMV-Ve from Venezuela and PYMTV from Trinidad and Tobago clearly confirmed that it is a new strain of PYMV.

Caribbean Region↗
PubMed2002

O-4-Linked coniferyl and sinapyl aldehydes in lignifying cell walls are the main targets of the Wiesner (phloroglucinol-HCl) reaction.

The nature and specificity of the Wiesner test (phloroglucinol-HCl reagent) for the aromatic aldehyde fraction contained in lignins is studied. Phloroglucinol reacted in ethanol-hydrochloric acid with coniferyl aldehyde, sinapyl aldehyde, vanillin, and syringaldehyde to yield either pink pigments (in the case of hydroxycinnamyl aldehydes) or red-brown pigments (in the case of hydroxybenzaldehydes). However, coniferyl alcohol, sinapyl alcohol, and highly condensed dehydrogenation polymers derived from these cinnamyl alcohols and aldehydes did not react with phloroglucinol in ethanol-hydrochloric acid. The differences in the reactivity of phloroglucinol with hydroxycinnamyl aldehydes and their dehydrogenation polymers may be explained by the fact that, in the latter, the unsubstituted (alpha,beta-unsaturated) cinnamaldehyde functional group, which is responsible for the dye reaction, is lost due to lateral chain cross-linking reactions involving the beta carbon. Fourier transform infrared spectroscopy and thioacidolysis analyses of phloroglucinol-positive lignifying plant cell walls belonging to the plant species Zinnia elegans L., Capsicum annuumvar. annuum, Populus albaL., and Pinus halepensisL. demonstrated the presence of 4- O-linked hydroxycinnamyl aldehyde end groups and 4- O-linked 4-hydroxy-3-methoxy-benzaldehyde (vanillin) end groups in lignins. However, given the relatively low abundance of 4- O-linked vanillin in lignifying cell walls and the low extinction coefficient of its red-brown phloroglucinol adduct, it is unlikely that vanillin contributes to a great extent to the phloroglucinol-positive stain reaction. These results suggest that the phloroglucinol-HCl pink stain of lignifying xylem cell walls actually reveals the 4- O-linked hydroxycinnamyl aldehyde structures contained in lignins. Histochemical studies showed that these aldehyde structures are assembled, as in the case of coniferyl aldehyde, during the early stages of xylem cell wall lignification.

Arachidonic Acids↗
PubMed2005

Photoinactivation of photosystem II in leaves.

Photoinactivation of Photosystem II (PS II), the light-induced loss of ability to evolve oxygen, inevitably occurs under any light environment in nature, counteracted by repair. Under certain conditions, the extent of photoinactivation of PS II depends on the photon exposure (light dosage, x), rather than the irradiance or duration of illumination per se, thus obeying the law of reciprocity of irradiance and duration of illumination, namely, that equal photon exposure produces an equal effect. If the probability of photoinactivation (p) of PS II is directly proportional to an increment in photon exposure (p = kDeltax, where k is the probability per unit photon exposure), it can be deduced that the number of active PS II complexes decreases exponentially as a function of photon exposure: N = Noexp(-kx). Further, since a photon exposure is usually achieved by varying the illumination time (t) at constant irradiance (I), N = Noexp(-kI t), i.e., N decreases exponentially with time, with a rate coefficient of photoinactivation kI, where the product kI is obviously directly proportional to I. Given that N = Noexp(-kx), the quantum yield of photoinactivation of PS II can be defined as -dN/dx = kN, which varies with the number of active PS II complexes remaining. Typically, the quantum yield of photoinactivation of PS II is ca. 0.1micromol PS II per mol photons at low photon exposure when repair is inhibited. That is, when about 10(7) photons have been received by leaf tissue, one PS II complex is inactivated. Some species such as grapevine have a much lower quantum yield of photoinactivation of PS II, even at a chilling temperature. Examination of the longer-term time course of photoinactivation of PS II in capsicum leaves reveals that the decrease in N deviates from a single-exponential decay when the majority of the PS II complexes are inactivated in the absence of repair. This can be attributed to the formation of strong quenchers in severely-photoinactivated PS II complexes, able to dissipate excitation energy efficiently and to protect the remaining active neighbours against damage by light.

Chloroplasts↗
PubMed1990

Specific binding of resiniferatoxin, an ultrapotent capsaicin analog, by dorsal root ganglion membranes.

We have previously demonstrated that resiniferatoxin (RTX), an unusual phorbol-related diterpene, induces similar responses in rodents to those induced by capsaicin, the pungent constituent of hot peppers (the genus Capsicum). Strikingly, RTX was 3-4 orders of magnitude more potent than was capsaicin. We report here specific binding of [3H]RTX to particulate preparations from dorsal root ganglia (DRG), a target tissue of both RTX and capsaicin action. The Kd was 0.27 nM for DRG from the rat; the Bmax was 160 fmol/mg. The respective values for pig DRG were 2.2 nM and 730 fmol/mg. Typical phorbol esters did not inhibit [3H]RTX binding. Capsaicin inhibited binding with 10(4)-fold lower affinity than RTX, consistent with the relative in vivo potencies. The specific [3H]RTX binding appears to represent the postulated capsaicin receptor.

Animals↗
PubMed1995

Molecular cloning and functional expression in E. coli of a novel plant enzyme mediating zeta-carotene desaturation.

We have cloned a cDNA from the plant Capsicum annuum which encodes a novel enzyme mediating the dehydrogenation of zeta-carotene and neurosporene to lycopene when expressed in E. coli cells accumulating zeta-carotene or neurosporene. This enzyme is unable to dehydrogenate either phytoene or lycopene. The deduced amino acid sequence suggests that this cDNA encodes a polypeptide whose mature size is ca. 59 kDa and which is synthesized as a precursor with a NH2-terminal extension resembling transit peptides for plastid targeting. Sequence comparison reveals 33-35% similarity with previously cloned plant or cyanobacterial phytoene desaturases. In contrast, only limited sequence similarity is found with a zeta-carotene desaturase from the cyanobacterium Anabaena.

Amino Acid Sequence↗
PubMed1984

Inhibition of ascorbate autoxidation by a dialyzed, heat-denatured extract of plant tissues.

Preparations obtained from various plant sources were analyzed for their effect on the autoxidation of ascorbic acid and norepinephrine. The former reaction was followed by spectrophotometric detection of ascorbic acid at 265 nm, the latter one by measuring the formation of noradrenochrome at 480 nm. Extracts were prepared from Philodendron leaves and the edible portion and seeds of green peppers (Capsicum Annuum ). The tissues were minced, homogenized in 10 volumes of 16 mM Na-phosphate buffer pH 7.4 and centrifuged at 35, 000g for 30 min. The supernatant was dialyzed in 12,000 m.w. cut-off tubing, denatured in boiling water and centrifuged at 10, 000g for 10 min. Aliquots (5-50 ul) of the supernatant were assayed in 5 ml 16 mM Na-phosphate buffer pH 7.4 containing 100 uM ascorbate or norepinephrine. The denatured extracts had marked dose-dependent inhibitory effect on the autoxidation of ascorbic acid, with negligible influence on the formation of noradrenochrome . EDTA inhibited both reactions. The selectiveness of the extract toward the autoxidation of ascorbic acid makes it unlikely that the inhibitory effect is based on sequestering metal-ions.

Ascorbic Acid↗
PubMed1994

Resiniferatoxin and piperine: capsaicin-like stimulators of oxygen uptake in the perfused rat hindlimb.

The naturally occurring capsaicin-like molecules, resiniferatoxin (RTX, Euphorbia spp.) and piperine (Piper nigrum), each stimulated oxygen uptake (VO2) in association with increased vascular resistance in a concentration-dependent manner when infused into the perfused rat hindlimb. 5 microM glyceryl trinitrate (GTN, a nitrovasodilator) significantly blocked the oxygen and pressure responses to both RTX and piperine, indicating a close relationship between changes in VO2 and the vasoconstriction. Concentrations greater than those required for maximal VO2 resulted in an inhibition of VO2, although perfusion pressure continued to increase. Time course studies showed that both RTX and piperine at high doses resulted in a tri-phasic response. An initial phase of transient VO2 stimulation was followed by a second phase of inhibition. A third phase involving an often larger but transient stimulation of VO2 followed removal of the agents and continued after the pressure returned to basal. The actions of RTX and piperine were similar to those of other active capsaicin-like molecules tested previously in this system, including capsaicinoids (Capsicum spp.), gingerols (Zingiber officinale), and shogoals (Zingiber officinale). RTX was the most potent, and piperine the least potent of this series. Although receptor involvement has yet to be unequivocally established, the data are consistent with the presence of a functional capsaicin-like (vanilloid) receptor in the vasculature of the rat hindlimb that mediates vasoconstriction and oxygen uptake. These findings may have implications for the future development of thermogenic agents.

Alkaloids↗
PubMed1984

Accumulation and transport of (2,4-dichlorophenoxy)acetic acid in plant cuticles: I. Sorption in the cuticular membrane and its components.

Partition coefficients (K) of (2,4-dichlorophenoxy)acetic acid (2,4-D) have been determined for the system plant cuticle/aqueous buffer. Cuticles isolated enzymatically from leaves (Clivia miniata, Ficus elastica, Citrus aurantium, Hedera helix, Pyrus communis cv. Conférence and cv. Williams, Olea europaea) and fruits (Lycopersicon esculentum, Capsicum annuum, Solanum melongena, Cucumis sativus) were utilized. Only the nondissociated species of 2,4-D was sorbed by cuticles and their lipophilic components. The average partition coefficient for leaf cuticles was 316 (range, 240-470) and for fruit cuticles 476 (range, 424-579). The dependence of sorption upon 2,4-D concentration was tested using tomato fruit cuticle. The sorption isotherm was linear from 2.0 to 5.0 X 10(-4) mol m-3. With increasing 2,4-D concentrations partition coefficients decreased slightly. Extraction of soluble cuticular lipids (SCL) increased the partition coefficients and these relative increases were correlated to relative amounts of SCL. In most species the hydrolytic removal of polar cuticular components resulted in a further increase of partition coefficients. No single cuticle was found to be representative for the sorption characteristics of all plant species investigated. The amounts of cuticle present in plant communities can be estimated from the data presented in conjunction with leaf area indices.

2,4-Dichlorophenoxyacetic Acid↗