Polygalacturonase-inhibiting protein accumulates in Phaseolus vulgaris L. in response to wounding, elicitors and fungal infection

Polygalacturonase-inhibiting protein (PGIP) is a cell wall-associated protein that specifically binds to and inhibits the activity of fungal endopolygalacturonases. The Phaseolus vulgaris gene encoding PGIP has been cloned and characterized. Using a fragment of the cloned pgip gene as a probe in Northern blot experiments, it is demonstrated that the pgip mRNA accumulates in suspension-cultured bean cells following addition of elicitor-active oligogalacturonides or fungal glucan to the medium. Rabbit polyclonal antibodies specific for PGIP were generated against a synthetic peptide designed from the N-terminal region of PGIP; the antigenicity of the peptide was enhanced by coupling to KLH. Using the antibodies and the cloned pgip gene fragment as probes in Western and Northern blot experiments, respectively, it is shown that the levels of PGIP and its mRNA are increased in P. vulgaris hypocotyls in response to wounding or treatment with salicylic acid. Using gold-labeled goat-anti-rabbit secondary antibodies in EM studies, it has also been demonstrated that, in bean hypocotyls infected with Colletotrichum lindemuthianum, the level of PGIP preferentially increases in those cells immediately surrounding the infection site. The data support the hypothesis that synthesis of PGIP constitutes an active defense mechanism of plants that is elicited by signal molecules known to induce plant defense genes.

Antioxidant effects of aqueous garlic extract. 2nd communication: Inhibition of the Cu(2+)-initiated oxidation of low density lipoproteins

The aqueous extract from the garlic preparation Kwai the antioxidant effect of which has been previously detected by the authors using the method of photochemiluminescence was tested in respect of the Cu(2+)-initiated oxidation of low density lipoprotein (LDL). The formation of conjugated diene which accompanies the lipid peroxidation process was detected photometrically. In this test system too, a dose-related oxidation-inhibiting effect of the extract was established. Further experiments will be required to find out whether such effect is due to the reduction of intrinsic antioxidants or to the increase of the integral antioxidant capacity of LDL.

External pH effects on the depolarization-activated K channels in guard cell protoplasts of Vicia faba

Previous studies reveal that the pH of the apoplastic solution in the guard cell walls may vary between 7.2 and 5.1 in closed and open stomata, respectively. During these aperture and pH changes, massive K+ fluxes cross the cellular plasma membrane driving the osmotic turgor and volume changes of guard cells. Therefore, we examined the effect of extracellular pH on the depolarization-activated K channels (KD channels), which constitute the K+ efflux pathway, in the plasma membrane of Vicia faba guard cell protoplasts. We used patch clamp, both in whole cells as well as in excised outside-out membrane patches. Approximately 500 KD channels, at least, could be activated by depolarization in one protoplast (density: approximately 0.6 micron-2). Acidification from ph 8.1 to 4.4 decreased markedly the whole-cell conductance, GK, of the KD channels, shifted its voltage dependence, GK-EM, to the right on the voltage axis, slowed the rate of activation and increased the rate of deactivation, whereas the single channel conductance was not affected significantly. Based on the GK-EM shifts, the estimated average negative surface charge spacing near the KD channel is 39 A. To quantify the effects of protons on the rates of transitions between the hypothesized conformational states of the channels, we fitted the experimental macroscopic steady state conductance-voltage relationship and the voltage dependence of time constants of activation and deactivation, simultaneously, with a sequential three-state model CCO. In terms of this model, protonation affects the voltage-dependent properties via a decrease in localized, rather than homogeneous, surface charge sensed by the gating moieties. In terms of either the CO or CCO model, the protonation of a site with a pKa of 4.8 decreases the voltage-independent number of channels, N, that are available for activation by depolarization.

Effects of dietary garlic supplementation in a rat model of atherosclerosis

In the present study possible antiatherogenic effects of dietary garlic were investigated in an experimental model which consists in the deendothelialisation by ballooning of the a. carotis communis of rats. 3 experimental groups were established: group I received a standard diet; the diet of group II was supplemented with 2% cholesterol and group III received 2% cholesterol and 5% dried garlic powder. Four weeks after ballooning plasma cholesterol, the average thickness of the neointima as well as the DNA content and the expression of collagens type I, III and IV in the ballooned arterial segment were determined. Furthermore, the specific activities of the enzymes glutathione peroxidase, glutathione disulfide reductase, glutathione-S-transferase and glucose 6 phosphate dehydrogenase were measured in homogenates of liver, heart and aorta. Hypercholesterolemia induced by cholesterol-feeding (group II 92 +/- 18 mg/100 ml) was significantly reduced by garlic (group III 53 +/- 19 mg/100 ml). Only little effects of garlic were seen in inhibiting neointima after ballooning. However, significant effects were found in protecting the enzymes of the glutathione dependent peroxide detoxification system, which is strongly impaired under hypercholesterolemia. Generally a normalisation, in some cases even an improvement beyond that, of the enzyme activities occurred in the garlic treated group. This indicates that in the model of atherosclerosis used here garlic is effective in lowering plasma cholesterol and in improving peroxide detoxification, however, it has only little influence on the wound healing reaction and does not significantly inhibit the development of intimal thickenings after ballooning.

Transmammary modulation of xenobiotic metabolizing enzymes in liver of mouse pups by mace (Myristica fragrans Houtt.)

The present study examines the possible transfer of the active principle(s) of mace (aril of the plant Myristica fragrans) through the transmammary route and its ability to modulate hepatic xenobiotic metabolizing enzymes in the F1 progeny of mice. An aqueous suspension of mace at the dose levels of 0.025 or 0.1 g/animal/day was administered by oral gavage to dams from day 1 of lactation and continued daily for 14 or 21 days. Dams receiving mace treatment and their F1 pups showed significantly elevated hepatic sulfhydryl content, glutathione S-transferase and glutathione reductase activities and cytochrome b5 content. Hepatic cytochrome P450 content decreased in dams (P < 0.05) receiving the lower mace dose for 21 days and the F1 pups (P < 0.001), but increased in dams receiving the higher dose for both time periods (P < 0.001) and the lower dose for 14 days (P < 0.05). Only the 14-day-old pups of dams receiving either mace dose showed significantly elevated (P < 0.001) levels of hepatic glutathione peroxidase.

Effects of extrusion of whole horse beans on protein digestion and amino acid absorption in dairy cows

Four lactating cows fitted with ruminal, duodenal, and ileal cannulas were used to determine the effects of extrusion of whole horse beans on ruminal CP degradation and absorption of AA from the small intestine. Diets contained 15% CP, of which 46% was provided by the raw or extruded whole horse beans. Spot samples of duodenal and ileal digesta were collected during a 72-h period. The markers Cr-EDTA, YbCl3, and purines were used for liquid, particulate, and bacteria, respectively. Extruded whole horse beans increased AA flow to the duodenum and disappearance in the small intestine. Diets containing extruded whole horse beans increased availability of total essential AA in the small intestine compared with diets containing raw whole horse beans.

Apparent mineralocorticoid excess

In 1979, Ulick and New first coined the term Apparent Mineralocorticoid Excess (AME) for a syndrome of hypertension, hypokalaemia, suppressed renin-angiotensin-aldosterone axis and raised urinary ratio of 11 beta-hydroxy to 11-oxo metabolities of cortisol (suggesting a failure of conversion of cortisol to cortisone). In retrospect, the first case was described in 1974 and since then over 20 children have been reported worldwide but only one adult patient. The enzyme 11beta-hydroxysteroid dehydrogenase (11beta-OHSD) confers aldosterone specificity on intrinsically nonspecific kidney mineralocorticoid receptors by converting the active glucocorticoid cortisol to its inactive 11-oxo form (cortisone). Patients with AME have a deficiency of this enzyme which allows physiological levels of cortisol to flood mineralocorticoid receptors. Dexamethasone, by suppressing adrenal cortisol production, reverts the biochemistry but not usually the BP to normal. Liquorice inhibits 11beta-OHSD by virtue of its active ingredient glycyrrhetinic acid, resulting in an identical clinical picture. Renal 11beta-OHSD is the protagonist in AME but this enzyme is found in many other tissues including liver, placenta and vasculature, and one-third of essential hypertensives have deficient 11beta-OHSD. The placental isoform is thought to be the main barrier to maternal glucocorticoids reaching the fetus. The lowest rat placental 11beta-OHSD activity is found in the largest placentas corresponding to the smallest fetuses (presumably exposed to the highest glucocorticoid levels). This is the group which in humans are most at risk of developing hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of Nigerian traditional medicines: 1. Plants used for rheumatic (inflammatory) disorders

In continuation of our evaluation of the Nigerian traditional medicine system which forms an important part of health care delivery, we investigated some plants attributed to possess potent anti-rheumatic activity. Ten plant species representing 9 different families were screened for anti-inflammatory activity. The extracts were tested for anti-inflammatory activity against acute inflammation induced by two phlogistic agents. Acute toxicity testing and phytochemical analyses were carried out. The results revealed significant anti-inflammatory activity of all extracts tested against acute inflammation.

Ethylene regulates the expression of a cysteine proteinase gene during germination of chickpea (Cicer arietinum L.)

Synthetic oligonucleotides corresponding to conserved regions of cysteine proteinases were used as primers in the RT-PCR amplification of a fragment of cDNA corresponding to a region of a cysteine proteinase gene expressed during germination of chickpea (cac for Cicer arietinum cysteine proteinase). The identity of the PCR-amplified fragment was confirmed by sequencing and the fragment used as a probe to investigate the pattern of cac gene expression during germination and its hormonal regulation. The corresponding transcript is undetected in the seed during embryogenesis and before imbibition, being detected 24 h after imbibition. Ablation of the embryonic axis before imbibition results in a dramatic decrease in the amount of transcript detected. Expression of the cac transcript in excised cotyledons is restored in the presence of aqueous extracts from embryonic axes and also by incubating the excised cotyledons in 1 mM ethephon. Experiments with various known inhibitors of ethylene action indicate that ethylene activates the expression of cac gene in the cotyledons of chickpea during normal germination.

Assessment of the autonomy of replicative and structural functions encoded by the luteo-phase of pea enation mosaic virus

The genome of pea enation mosaic virus (PEMV) is composed of two taxonomically unrelated RNAs, interacting to create what has traditionally been considered a bipartite virus. The cohesiveness of this interaction was assessed by examining the autonomy of each RNA in viral replication, coat protein expression and systemic invasion. Using a pea protoplast system, in vitro transcripts of RNA1 were found to be capable of initiating RNA2-independent replication, including the formation of the distinctive nuclear membrane-based replication complex associated with wild-type PEMV infection. Western blotting and electron microscopic analysis demonstrated that the synthesis of the RNA1-encoded coat protein, as well as virion assembly, was also independent of RNA2-directed functions. Mechanical inoculations with transcripts of RNA1 failed to establish a systemic RNA1 infection, whereas inoculations with RNA2 were able to establish a largely asymptomatic systemic infection. Combined inoculum containing RNA1 and RNA2 transcripts were able to recreate wild-type PEMV symptomatology, demonstrating the dependence of RNA1 on RNA2 for mechanical passage. With the notable exception of the adaptation of PEMV to establish a true systemic invasion, these data further strengthen the analogy between PEMV and the helper-dependent complexes associated with members of the luteovirus group.

Evidence for a stromal GTP requirement for the integration of a chlorophyll a/b-binding polypeptide into thylakoid membranes

The integration of chlorophyll a/b-binding (LHCP) polypeptides and the translocation of the 33-kD oxygen-evolving enhancer protein (OEE33) have been previously shown to occur in chloroplast extracts containing stroma, thylakoids, ATP, and MgCl2. We have re-examined the nucleotide requirement for these two reactions using stromal extract and translation products depleted of low molecular weight compounds. LHCP integration activity was up to 10-fold higher when assayed with GTP compared with ATP, CTP, or UTP. A combination of ATP and GTP supported less LHCP integration activity than GTP alone, suggesting that GTP meets the entire nucleotide requirement. Nonhydrolyzable analogs of GTP were inhibitory, consistent with the idea that GTP hydrolysis is required for integration activity. Periodate-oxidized GTP (GTPox) also inhibited the integration reaction when present during the assay. Pretreatment of stroma with GTPox followed by GTPox removal inhibited integration activity, whereas pretreatment of thylakoids had no effect. We interpret this to mean that a GTP-binding protein involved in integration is localized in the stroma. Translocation of OEE33 was more efficient with ATP than with GTP, and the combination of both nucleotides was not additive. Our data implicate the involvement of a GTPase in LHCP integration but not in the translocation of OEE33.

Genotoxic and non-genotoxic effects of betel quid ingredients on oral mucosal fibroblasts in vitro

To understand the role of betel quid (BQ) in the pathogenesis of oral submucous fibrosis (OSF) and oral cancer, we used DNA damage, cytotoxicity, and cell proliferation assays to study the pathobiological effects of aqueous extracts of three BQ constituents [betel nut (Areca catechu, BN), inflorescence of Piper betle (IPB), and lime], one BN alkaloid (arecoline), and one BN polyphenol [(+)-catechin] on cultured oral mucosal fibroblasts. Extracts of BN and IPB induced DNA strand break formation in a dose-dependent manner. Extracts of BN and IPB, (+)-catechin, and arecoline decreased cell survival and proliferation in a dose-dependent manner. However, aqueous extract of lime (50-800 micrograms/mL) increased cell proliferation by 20-40%. These results indicate that BQ contains not only genotoxic and cytotoxic agents, but also compounds which stimulate cell proliferation. These compounds may act synergistically in the pathogenesis of OSF and oral cancer in BQ chewers. In addition, five anti-oxidants [glutathione (GSH), cysteine, mannitol, catalase, and superoxide dismutase (SOD)] were tested for their protective effects against the cytotoxicity of BQ constituents. GSH (1.95 and 2.6 mmol/L) and cysteine (4 and 8 mmol/L) prevented the arecoline-induced cytotoxicity. In contrast, mannitol, catalase, and SOD did not decrease the arecoline-induced cytotoxicity. These results indicate that thiol depletion, but not the attack of oxygen free radicals, could be the mechanism for arecoline cytotoxicity. GSH could also protect cells from the cytotoxicity of IPB extract. Increasing dietary intake of GSH-rich foods or dietary supplements of GSH may have chemopreventive potential to reduce BQ-associated oral lesions.

Genotypic and phenotypic diversity of Rhizobium isolated from chickpea (Cicer arietinum L.)

The diversity of 16 strains of chickpea-infective rhizobia from various geographical origins was analysed using genotypic and phenotypic approaches. Multilocus enzyme electrophoresis was performed, and restriction fragment length polymorphisms of the amplified 16S + IGS (intergenic spacer) rRNA gene, assimilation of 147 carbon sources, antibiotic resistance, and tolerance to NaCl and extreme pH values and temperatures were tested. These approaches had different discriminating powers. Esterase polymorphisms gave a unique pattern for each strain, allowing this method to be used for strain fingerprinting. Genetic distances between strains were estimated. The three approaches used in this study yielded consistent results. They evidenced high heterogeneity among the strains, and made it possible to classify the strains into two clusters. Isozyme patterns for superoxide dismutase were particularly interesting, since they delineated the same two groups. The phenotypic tests clearly confirmed the existence of two genetic groups on the basis of 11 phenotypic characters. Owing to the large phylogenetic distance between the two groups of strains, the taxonomic status of chickpea-infective strains is discussed.

Preliminary results on the protective effect of (-)-edunol, a pterocarpan from Brongniartia podalyrioides (Leguminosae), against Bothrops atrox venom in mice

(-)-Edunol a prenylated pterocarpan was isolated from the roots of two Mexican 'snakeweeds', Brongniartia podalyrioides and B. intermedia (Leguminosae). Edunol (3.1 mg/kg, i.p.) reduced the expected mortality of mice previously treated by the same route with the LD50 of the venom of the serpent Bothrops atrox. The molecular structure and properties of edunol are similar to those previously reported for cabenegrins A-I and A-II.

Chromosomal location of lectin genes indicates they are not the basis of Rhizobium strain specificity mutations identified in pea (Pisum sativum L.)

A lectin gene family is located on linkage group 7 in pea. The lectin genes are arranged as a cluster, with no recombination observed within the multigene family. A lectin-like cDNA clone, pEA207, and eight DNA fragments generated by random priming also were mapped in the region of the lectin genes. None of the known pea mutants altering Rhizobium leguminosarum strain specificity map to this region of the genome, and therefore their altered specificities appear not to be directly produced by mutations in the lectin genes.

Primary structure, spectroscopic and inhibitory properties of a two-chain trypsin inhibitor from the seeds of charlock (Sinapis arvensis L), a member of the napin protein family

A protein with inhibitory activity toward trypsin has been isolated from Sinapis arvensis L (charlock). It has a molecular weight of 15,500 and consists of two chains connected by disulfide bonds. The amino acid sequence was determined and showed that it belongs to the napin family of storage proteins. CD studies showed an alpha-helix content of 12% and a beta-structure of about 50%.

Histamine release induced by glucose (mannose)-specific lectins isolated from Brazilian beans. Comparison with concanavalin A

The histamine releasing properties of glucose (mannose)-specific lectins isolated from Brazilian beans was examined. The Canavalia brasiliensis, Dioclea rostrata, and Dioclea virgata lectins induced histamine release in rat peritoneal mast cells similar to concanavalin A. Less potency and efficacy was observed for Canavalia maritima, Dioclea guianensis, and Dioclea violacea while very low activities were seen for the lectins from Dioclea grandiflora, Canavalia bonariensis, and Cratylia floribunda. The histamine releasing effect was quenched by higher doses of D. virgata lectin similar to what was reported for concanavalin A. This effect was abrogated by increasing the concentration of calcium in the incubating medium. As these above proteins have sites that bind calcium, higher doses of the lectins might withdraw the calcium which is essential for the mast cell secretion.

Synthesis of dehydrogenation polymers of ferulic acid with high specificity by a purified cell-wall peroxidase from French bean (Phaseolus vulgaris L.)

A cationic (pI 8.3) wall-bound peroxidase has been purified to homogeneity from suspension-cultured cells of French bean (Phaseolus vulgaris L.). The enzyme was a glycoprotein and its M(r) was 46,000 as determined by SDS/Page and h.p.l.c. gel filtration. It was localized biochemically to microsomes and the cell wall, and the latter subcellular distribution was confirmed by immunogold techniques. The native enzyme showed absorption maxima at 403, 500 and 640 nm, with an RZ (A405/A280) of 3.3. The peroxidase oxidized guaïacol and natural phenolic acids. By desorption-chemical-ionization mass spectrometry the enzyme was found to oxidize the model compound, ferulic acid, into dehydrodiferulic acid. Kinetics studies indicated an apparent Km of 113.3 +/- 22.9 microM and a Vmax of 144 mumol.min-1.nmol-1 of protein at an H2O2 concentration of 100 microM. In comparison with a second French-bean peroxidase (FBP) and horseradish peroxidase, as a model, it acted with a 6-10-fold higher specificity in this capacity. It is a member of the peroxidase superfamily of bacterial, fungal and plant haem proteins by virtue of its highly conserved amino acid sequence within the proximal and distal haem-binding sites. This is good evidence that this particular FBP may function in constructing covalent cross-linkages in the wall during development and response to pathogens.

RFLP analysis of preferential transmission in interspecific hybrids of Phaseolus vulgaris and P. coccineus

The inheritance of RFLP markers in interspecific hybrids of Phaseolus vulgaris and P. coccineus was analyzed. Of 280 cDNA probes used, 70%-85% revealed polymorphism between species while intraspecific RFLP ranged from 8% to 37%. Segregation of 63 clearly scorable markers was examined in 177 P. vulgaris x P. coccineus F2's maintained as callus. Preferential transmission of the P. vulgaris alleles was observed for 24 of the 28 loci exhibiting non-Mendelian ratios. Although the segregation ratios at 17 loci fit gametic selection, also other factors such as nuclear-cytoplasmic or embryo-endosperm interactions may be involved. In the reciprocal F2, a relatively high frequency of maternal alleles was recovered for several loci, while the paternal allele was favored at others. The cDNA clone detecting the most extreme segregation, with no P. coccineus type detected among 165 P. vulgaris x P. coccineus F2 progeny, showed high homology to histone H2A genes. The markers were mapped to nine linkage groups. Aggregation of markers with preferential maternal transmission was observed, which could be due to selection of individual chromosomes, although false linkage detection cannot be excluded. The results obtained with RFLPs may explain the skewed distribution of phenotypic traits following interspecific hybridization.

Studies of aloe. V. Mechanism of cathartic effect. (4)

Aloe-emodin-9-anthrone(AE-anthrone), produced from barbaloin in the rat large intestine, caused not only an increase in the intestinal water content but also stimulated mucus secretion. This might play an important role in the occurrence of diarrhea. It was demonstrated that the amount of AE-anthrone produced in the rat large intestine(maximal amount: 568 micrograms/rat at 4 h after injection) was enough to cause both of these effects, which were observed following intracecal administration of barbaloin (31.1 mg/kg). These results together with our previous data, which showed a relationship between increase in the intestinal water content and the stimulation of peristalsis, confirm that AE-anthrone is the principal agent responsible for the cathartic effect of barbaloin. We also propose that the increase in water content is a more important factor than stimulation of peristalsis in the induction of diarrhea by barbaloin.

[Chimeric toxin of the A-subunit of viscumin and the B-subunit of ricin]

A chimeric toxic protein was prepared from the mistletoe lectin I A-chain and ricin B-chain by using the disulfide exchange reaction. Ricin and chimeric protein were indistinguishable in binding to immobilized asialofetuin in ELISA. The chimeric protein was more toxic for Jurkat cells than native mistletoe lectin I, but not as effective as native ricin. In the presence of NH4Cl, which enhances the toxicity of some toxins and immunotoxins, but does not influence ricin toxicity, both ricin and chimeric toxin had equal cytotoxic activity. The possibility is discussed that the ricin B-chain protects the ricin A-chain from degradation during delivery from the cell surface to the place where it is translocated into the cytosol.