Conversion of Monuron to Ethyl-N-p-chlorophenyl Carbamate by Soxhlet Extraction of Plant Tissue with Ethanol

Soxhlet extraction of plant materials with alcohol converted monuron residue to carbamate. Although this conversion will not affect the accuracy of monuron determination by the Bratton-Marshall reaction, it will undoubtedly affect the accuracy if the measurement is carried out by thin layer or paper chromatography. Diuron, fenuron, and chloroxuron, which contain 1,1-dimethyl substitution, were also converted to the corresponding carbamates, while siduron, neburon, linuron, monomethyl monuron, monomethyl diuron, and p-chlorophenyl urea were not. When monuron was refluxed with other alcohols such as methanol, isopropanol, and n-butanol, monuron was also converted to other products.

Longitudinal associations between post-traumatic stress disorder and metabolic syndrome severity

BACKGROUND

Post-traumatic stress disorder (PTSD) is associated with elevated risk for metabolic syndrome (MetS). However, the direction of this association is not yet established, as most prior studies employed cross-sectional designs. The primary goal of this study was to evaluate bidirectional associations between PTSD and MetS using a longitudinal design.

METHOD

A total of 1355 male and female veterans of the conflicts in Iraq and Afghanistan underwent PTSD diagnostic assessments and their biometric profiles pertaining to MetS were extracted from the electronic medical record at two time points (spanning ~2.5 years, n = 971 at time 2).

RESULTS

The prevalence of MetS among veterans with PTSD was just under 40% at both time points and was significantly greater than that for veterans without PTSD; the prevalence of MetS among those with PTSD was also elevated relative to age-matched population estimates. Cross-lagged panel models revealed that PTSD severity predicted subsequent increases in MetS severity (β = 0.08, p = 0.002), after controlling for initial MetS severity, but MetS did not predict later PTSD symptoms. Logistic regression results suggested that for every 10 PTSD symptoms endorsed at time 1, the odds of a subsequent MetS diagnosis increased by 56%.

CONCLUSIONS

Results highlight the substantial cardiometabolic concerns of young veterans with PTSD and raise the possibility that PTSD may predispose individuals to accelerated aging, in part, manifested clinically as MetS. This demonstrates the need to identify those with PTSD at greatest risk for MetS and to develop interventions that improve both conditions.

Anti-inflammatory effects of phenolic compounds isolated from the flowers of Nymphaea mexicana Zucc

Nymphaea mexicana Zucc. is an aquatic plant species which belongs to the family Nymphaea and is commonly known as the yellow water lily. The aim of this work was to study the in vitro antiinflammatory effects of phenolic compounds isolated from the flowers of Nymphaea mexicana Zucc. Seven phenolic compounds including vanillic acid, 4-methoxy-3,5-dihydroxybenzoic acid, (2R,3R)-3,7-dihydroxyflavanone, naringenin (4), kaempferol 3-O-(3-O-acetyl-a-L-rhamnopyranoside), kaempferol 3-O-(2-O-acetyl-a-L-rhamnopyranoside), and quercetin 3-(30 0-acetylrhamnoside) (7) were isolated from the flowers of Nymphaea mexicana Zucc. These results revealed that compound 4 has the most prominent inhibitory effect on the LPS-stimulated nitric oxide (NO), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor-alpha (TNF-a) production in RAW 264.7 macrophages. In addition, compound 4 also inhibited LPS-mediated induction of protein expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and phospho-ERK in RAW 264.7 macrophages. Thus, compound 4 from the flowers of Nymphaea mexicana Zucc. may provide a potential therapeutic approach for inflammation-associated disorders.

Cotton dust, endotoxin and cancer mortality among the Shanghai textile workers cohort: a 30-year analysis

BACKGROUND

Although occupational exposure to cotton dust and endotoxin is associated with adverse respiratory health, associations with cancer are unclear. We investigated cancer mortality in relation to cotton dust and endotoxin exposure in the Shanghai textile workers cohort.

METHODS

We followed 444 cotton textile and a reference group of 467 unexposed silk workers for 30 years (26 777 person-years). HRs for all cancers combined (with and without lung cancer) and gastrointestinal cancer were estimated in Cox regression models as functions of cotton textile work and categories of cumulative exposure (low, medium, high), after adjustment for covariates including pack-years smoked. Different lag years accounted for disease latency.

RESULTS

Risks of mortality from gastrointestinal cancers and all cancers combined, with the exclusion of lung cancer, were increased in cotton workers relative to silk workers. When stratified by category of cumulative cotton exposure, in general, risks were greatest for 20-year lagged medium exposure (all cancers HR=2.7 (95% CI 1.4 to 5.2); cancer excluding lung cancer HR=3.4 (1.7-7.0); gastrointestinal cancer HR=4.1 (1.8-9.7)). With the exclusion of lung cancer, risks of cancer were more pronounced. When stratified by category of cumulative endotoxin exposure, consistent associations were not observed for all cancers combined. However, excluding lung cancer, medium endotoxin exposure was associated with all cancers and gastrointestinal cancer in almost all lag models.

CONCLUSIONS

Cotton dust may be associated with cancer mortality, especially gastrointestinal cancer, and endotoxin may play a causative role. Findings also indirectly support a protective effect of endotoxin on lung cancer.

Geranyl flavonoid derivatives from the fresh leaves of Artocarpus communis and their anti-inflammatory activity

Breadfruit (Artocarpus communis) is a widely distributed crop in tropical and subtropical regions of the world. It is used in Southeast Asia and India to treat several inflammatory disorders. The aim of this study was to investigate the presence of anti-inflammatory flavonoids in A. communis leaves. Three new geranyl flavonoids, arcommunol C (1), arcommunol D (3), and 5'-geranyl-3,4,2',4'-tetrahydroxychalcone (5), together with four known compounds, prostratol (2), arcommunol E (4), 3'-geranyl-3,4,2',4'-tetrahydroxydihydrochalcone (6), and 3'-geranyl-3,4,2',4'-tetrahydroxychalcone (7), were isolated from the leaves of A. communis. Compound 4 was isolated for the first time from natural sources. The anti-inflammatory activity of the isolated compounds (1-7) was evaluated by determining their inhibitory activity on the production of proinflammatory mediators in lipopolysaccharide (LPS)-activated RAW 264.7 murine macrophage cells. Compounds 2, 3, and 4 suppressed the LPS-induced production of nitric oxide (NO) in RAW 264.7 cells with IC50 values of 8.13 ± 0.17, 18.45 ± 2.15, and 22.74 ± 1.74 µM, respectively. Furthermore, 2 decreased lipopolysaccharide (LPS)-mediated induction of protein expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in RAW 264.7 cells. It was also found that 2 suppressed LPS-induced phosphorylation of JNK and p38 mitogen-activated protein kinase (MAPK) signaling.

Anti-inflammatory effect of the 5,7,4'-trihydroxy-6-geranylflavanone isolated from the fruit of Artocarpus communis in S100B-induced human monocytes

The fruit of Artocarpus communis Moraceae, a traditional starch crop, is a rich source of phytochemicals, such as flavonoids and their derivatives. The aim of this study was to investigate whether 5,7,4'-trihydroxy-6-geranylflavanone (AC-GF), a geranyl flavonoid derivative isolated from the fruits of A. communis, could decrease the activation of inflammatory mediators induced by S100B (ligand of receptor for advanced glycation end products, RAGE) in THP-1 monocytes. According to the results, low levels of AC-GF (≤2.5 μM) showed a great inhibitory effect on gene expression of RAGE and down-regulated both TNF-α and IL-1β secretion and gene expression (p < 0.05). AC-GF also decreased reactive oxygen species (ROS) production in response to S100B (p < 0.05). Additionally, Western blotting revealed that AC-GF could effectively attenuate RAGE-dependent signaling, including expression of protein kinase C (PKC) and p47phox, phosphorylation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK), and particularly NF-κB activation (p < 0.05). In conclusion, this is the first report that AC-GF possesses great antioxidant and anti-inflammatory properties in vitro. This finding may contribute to increased implication and utilization of the fruit of A. communis Moraceae in functional foods.

Anticancer effects of flavonoid derivatives isolated from Millettia reticulata Benth in SK-Hep-1 human hepatocellular carcinoma cells

Millettia reticulata Benth is cultivated in Asian countries. M. reticulata Benth has multiple biological functions and is one of the oldest tonic herbs in traditional Chinese medicine. It has been elevated to one of the most commonly used herbs in modern Chinese medicine. The aims of this work were to study the in vitro anticancer activity of flavonoid derivatives isolated from the stems of M. reticulata Benth. Six flavonoid derivatives including (-)-epicatechin (1), naringenin (2), 5,7,3',5'-tetrahydroxyflavanone (3), formononetin (4), isoliquiritigenin (5), and genistein (6) were isolated from the stems of M. reticulata Benth. The structures of 1-6 were determined by spectroscopic methods. The effects of flavonoid derivatives (1-6) on the viability of human cancer cells (including HepG2, SK-Hep-1, Huh7, PLC5, COLO 205, HT-29, and SW 872 cells) were investigated. The results indicated that genistein (6) had the strongest inhibitory activity with an IC(50) value of 16.23 microM in SK-Hep-1 human hepatocellular carcinoma cells. Treatment of SK-Hep-1 cells with genistein (6) caused loss of mitochondrial membrane potential. Western blot data revealed that genistein (6) stimulated an increase in the protein expression of Fas, FasL, and p53. Additionally, treatment with genistein (6) changed the ratio of expression levels of pro- and anti-apoptotic Bcl-2 family members and subsequently induced the activation of caspase-9 and caspase-3, which was followed by cleavage of poly(ADP-ribose) polymerase (PARP). These results demonstrate that genistein (6) induces apoptosis in SK-Hep-1 cells via both Fas- and mitochondria-mediated pathways.

Circulating adhesion molecules after short-term exposure to particulate matter among welders

BACKGROUND

Studies from several countries indicate that welders experience increased risk of mortality and morbidity from ischaemic heart disease. Although the underlying mechanisms are unclear, vascular responses to particulate matter contained in welding fumes may play a role. To investigate this, we studied the acute effects of welding fume exposure on the endothelial component of vascular function, as measured by circulating adhesion molecules involved in leukocyte adhesion (sICAM-1 and sVCAM-1) and coagulation (vWF).

METHODS

A panel of 26 male welders was studied repeatedly across a 6 h work-shift on a high exposure welding day and/or a low exposure non-welding day. Personal PM(2.5) exposure was measured throughout the work-shift. Blood samples were collected in the morning (baseline) prior to the exposure period, immediately after the exposure period, and the following morning. To account for the repeated measurements, we used linear mixed models to evaluate the effects of welding (binary) and PM(2.5) (continuous) exposure on each blood marker, adjusting for baseline blood marker concentration, smoking, age and time of day.

RESULTS

Welding and PM(2.5) exposure were significantly associated with a decrease in sVCAM-1 in the afternoon and the following morning and an increase in vWF in the afternoon.

CONCLUSIONS

The data suggest that welding and short-term occupational exposure to PM(2.5) may acutely affect the endothelial component of vascular function.

Cytotoxic effects of new geranyl chalcone derivatives isolated from the leaves of Artocarpus communis in SW 872 human liposarcoma cells

Breadfruit (Artocarpus communis Moraceae) is cultivated in tropical and subtropical regions as a traditional starch crop and also has potential medicinal properties. The aim of this work was to study the in vitro anticancer activity of compounds isolated from the leaves of Artocarpus communis. Three new geranyl chalcone derivatives including isolespeol (1), 5'-geranyl-2',4',4-trihydroxychalcone (2), and 3,4,2',4'-tetrahydroxy-3'-geranyldihydrochalcone (3), together with two known compounds lespeol (4) and xanthoangelol (5), were isolated from the leaves of Artocarpus communis. The structures of 1- 5 were elucidated by spectroscopy and through comparison with data reported in the literature. The effects of geranyl chalcone derivatives (1- 5) on the viability of human cancer cells (including SW 872, HT-29, COLO 205, Hep3B, PLC5, Huh7, and HepG2 cells) were investigated. The results indicate that isolespeol (1) showed the highest inhibitory activity with an IC 50 value of 3.8 muM in SW 872 human liposarcoma cells. Treatment of SW 872 human liposarcoma cells with isolespeol (1) caused the loss of mitochondrial membrane potential (DeltaPsim). Western blotting revealed that isolespeol (1) stimulated increased protein expression of Fas, FasL, and p53. The expression ratios of pro- and antiapoptotic Bcl-2 family members were also changed by isolespeol (1) treatment to subsequently induce the activation of caspase-9 and caspase-3, which was followed by cleavage of poly (ADP-ribose) polymerase (PARP). These results demonstrate that isolespeol (1) induces apoptosis in SW 872 cells through Fas- and mitochondria-mediated pathways.

Anti-inflammatory effects of phenolic compounds isolated from the fruits of Artocarpus heterophyllus

Artocarpus heterophyllus Lam is a large evergreen tree cultivated throughout Southeast Asia for its fruits. Its leaves and roots have been used for medicinal purposes. The aim of this work was to study the in vitro anti-inflammatory effects of phenolic compounds isolated from the ethyl acetate extracts of the fruits of Artocarpus heterophyllus. Three phenolic compounds were characterized as artocarpesin [5,7,2',4'-tetrahydroxy-6-(3-methylbut-3-enyl) flavone] ( 1), norartocarpetin (5,7,2',4'-tetrahydroxyflavone) ( 2), and oxyresveratrol [ trans-2,4,3',5'-tetrahydroxystilbene] ( 3) by spectroscopic methods and through comparison with data reported in the literatures. The anti-inflammatory effects of the isolated compounds ( 1- 3) were evaluated by determining their inhibitory effects on the production of proinflammatory mediators in lipopolysaccharide (LPS)-activated RAW 264.7 murine macrophage cells. These three compounds exhibited potent anti-inflammatory activity. The results indicated that artocarpesin ( 1) suppressed the LPS-induced production of nitric oxide (NO) and prostaglandin E 2 (PGE 2) through the down-regulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) protein expressions. Thus, artocarpesin ( 1) may provide a potential therapeutic approach for inflammation-associated disorders.

Heartbeat detection using energy thresholding and template match

Heartbeat detection is very important for retrieving the vital signs of heart functions. The morphologies and inter-beat intervals of heartbeats can reveal the condition of heart contraction. In this paper, we developed a heartbeat information integration scheme to deal with the information yielded by the energy thresholding and template match methods, which are usually used to detect the heartbeats and match the QRS, respectively. The proposed method are developed in SIMULINK 2.0 and assessed by the MIT/BIH arrhythmia database. The result demonstrated excellent sensitivity of detecting QRS and ventricular premature contraction in the proposed method.

Approximate entropy analysis of electroencephalogram in vasovagal syncope on tilt table test

Thirty vasovagal attacks on sublingual nitroglycerin stressed tilting test were selected. By the method of shifting window along the continuous EEG signals the linear (spectral power and coherence) and nonlinear (approximate entropy) EEG features of the whole course in the tilt table test were demonstrated. Of all the EEG parameters approximate entropy is a more sensitive index in clarifying stages of various degree of tilting stress and in identifying the syncopal transient.

Linear and nonlinear analysis of electroencephalogram of the coma

The coma is common in intensive care units. The bedside physical examination provides a means to measuring the neurological status, but it cannot be a continuous evaluation, whereas electroencephalogram (EEG) can reflect the immediate electrical activities of the brain. In this paper, we investigate the spectral parameters, complexity and irregular measures, and spectral entropy in the coma. Compared to the normal subject, the EEG of the coma has a dominance of slow wave, low complexity, less irregularity, and low spectral entropy. This result demonstrates the possibility to use EEG analysis for the monitoring of neurological function.

Continuous and online analysis of heart rate variability

Spectral analysis of heart rate variability provides a probe to assess the function of the sympathetic and parasympathetic nervous systems. Time-frequency analysis of heart rate variability is useful for investigating autonomic nervous function in patients with syncope or non-sustained ventricular tachycardia, or in anaesthesia, etc. In this paper, we developed an algorithm for continuous and online analysis of heart rate variability. The algorithm was simulated and evaluated in MATLAB, and implemented on the digital signal processor. The electrocardiogram signals from MIT/BIH arrhythmia database and one patient with syncope demonstrate the capability of the proposed method in the continuous and online analysis of heart rate variability.

The embryo MADS domain factor AGL15 acts postembryonically. Inhibition of perianth senescence and abscission via constitutive expression

AGL15 (AGAMOUS-like 15), a member of the MADS domain family of regulatory factors, accumulates preferentially throughout the early stages of the plant life cycle. In this study, we investigated the expression pattern and possible roles of postembryonic accumulation of AGL15. Using a combination of reporter genes, RNA gel blot analysis, and immunochemistry, we found that the AGL15 protein accumulates transiently in the shoot apex in young Arabidopsis and Brassica seedlings and that promoter activity is associated with the shoot apex and the base of leaf petioles throughout the vegetative phase. During the reproductive phase, AGL15 accumulates transiently in floral buds. When AGL15 was expressed in Arabidopsis under the control of a strong constitutive promoter, we noted a striking increase in the longevity of the sepals and petals as well as delays in a selected set of age-dependent developmental processes, including the transition to flowering and fruit maturation. Although ethylene has been implicated in many of these same processes, the effects of AGL15 could be clearly distinguished from the effects of the ethylene resistant1-1 mutation, which confers dominant insensitivity to ethylene. By comparing the petal breakstrength (the force needed to remove petals) for flowers of different ages, we determined that ectopic AGL15 had a novel effect: the breakstrength of petals initially declined, as occurs in the wild type, but was then maintained at an intermediate value over a prolonged period. Abscission-associated gene expression and structural changes were also altered in the presence of ectopic AGL15.

Novel antiplatelet constituents from formosan moraceous plants

Sixteen constituents from Formosan Moraceous plants were tested for their antiplatelet activities in rabbit platelet suspension and human platelet-rich plasma. Cycloartocarpin A, cycloheterophyllin, broussochalcone A, kazinol A, broussoaurone A, and broussoflavonol F showed strong inhibition of arachidonic acid (AA)-induced platelet aggregation. Of the compounds tested, broussochalcone A exhibited the most potent inhibition of platelet aggregation induced by AA (IC50 = 6.8 microM). The antiplatelet effects of cycloheterophyllin, broussochalcone A, kazinol B, broussoaurone A, and broussoflavonol F are partially due to an inhibitory effect on cyclooxygenase.

Sugars act as signal molecules and osmotica to regulate the expression of alpha-amylase genes and metabolic activities in germinating cereal grains

The molecular mechanisms that initiate and control the metabolic activities of seed germination are largely unknown. Sugars may play important roles in regulating such metabolic activities in addition to providing an essential carbon source for the growth of young seedlings and maintaining turgor pressure for the expansion of tissues during germination. To test this hypothesis, we investigated the physiological role of sugars in the regulation of alpha-amylase gene expression and carbohydrate metabolism in embryo and endosperm of germinating rice seeds. RNA gel blot analysis revealed that in the embryo and aleurone cells, expression of four alpha-amylase genes was differentially regulated by sugars via mechanisms beyond the well-known hormonal control mechanism. In the aleurone cells, expression of these alpha-amylase genes was regulated by gibberellins produced in the embryo and by osmotically active sugars. In the embryo, expression of two alpha-amylase genes and production of gibberellins were transient, and were probably induced by depletion of sugars in the embryo upon imbibition, and suppressed by sugars influx from the endosperm as germination proceeded. The deferential expression of the four alpha-amylase genes in the embryo and aleurone cells was probably due to their markedly different sensitivities to changes in tissue sugar levels. Our study supports a model in which sugars regulate the expression of alpha-amylase genes in a tissue-specific manner: via a feedback control mechanism in the embryo and via an osmotic control mechanism in the aleurone cells. An interactive loop among sugars, gibberellins, and alpha-amylase genes in the germinating cereal grain is proposed.

Studies on the synthesis of some xanthonoid derivatives possessing antiplatelet effects

2,3- and 3,4-Dihydroxyxanthone react with ethyl 2,3-dibromopropanoate to form the new, substituted 1,4-benzodioxanes 3 and 4, respectively. The regioisomers 3a and 3b; 4a and 4b were separated by column chromatography and characterized for evaluation of the antiplatelet effects in rabbit washed platelets and human platelet-rich plasma. The ethoxycarbonyl derivatives 3a (20 microM) and 3b (20 microM) strongly inhibited the aggregation of rabbit washed platelets induced by arachidonic acid and collagen. The compound 4b showed the most potent inhibition of rabbit washed-platelet aggregation induced by arachidonic acid (IC50 = 8.3 microM). Of the compounds tested in human platelet-rich plasma, compound 4b exhibited the most potent inhibition of primary and secondary aggregation induced by adrenaline (IC50 = 8.6 microM). We conclude that the antiplatelet effects of these four ethoxycarbonyl derivatives are mainly due to an inhibitory effect on thromboxane formation and interference in the adrenaline-receptor interaction.

The effects of Penicillium roqueforti toxin on the activity of rat hepatic DNA polymerases

PR toxin, a mycotoxin from cultures of Penicillium roqueforti, inhibited the in vitro activities of rat liver DNA polymerase alpha, beta, and gamma irrespectively of the nature of template-primer used. The concentration required for 50% inhibition of DNA polymerase alpha was 5-6 X 10(-6) M, while those for DNA polymerase beta and gamma were several times higher. By using DNA polymerase beta as a model, and based on the enzyme and template-primer concentration effects and also from the kinetic analysis on PR toxin inhibition, we concluded that two action mechanisms of PR toxin inhibition on in vitro DNA synthesis are operative. Inhibition of the in vitro DNA synthesis directed by DNA template was mediated primarily through alteration of the enzyme itself, whereas in the DNA synthesis reaction directed by RNA template DNA primer, the impairment of template or primer function due to PR toxin treatment probably had occurred. The inhibition of DNA polymerase by PR toxin persisted even after exhaustive dialysis. Addition of PR toxin to an ongoing reaction also inhibited DNA synthesis. Inactivation of DNA polymerase activity of PR toxin likely involved some essential amino acid residues other than sulfhydryl groups.

Differential uptake of mercury vapor by gramineous c(3) and c(4) plants

The uptake of mercury vapor by six gramineous plant species was compared under uniform conditions using a whole-plant chamber and (203)Hg-labeled mercury at a low atmospheric concentration. Mean Hg uptake by leaves of the C(3) species oats (Avena sativa), barley (Hordeum vulgare), and wheat (Triticum aestivum) was 5 times greater than that by leaves of the C(4) species corn (Zea mays), sorghum (Sorghum bicolor), and crabgrass (Digitaria sanguinalis). Although there was a difference in resistances associated with vapor entry into the leaves, as shown by estimates of gas exchange, the differential uptake by C(3) and C(4) species was largely attributable to internal resistances to Hg vapor binding. The nature of the internal resistances and the site or sites of Hg vapor binding remain unspecified.

Studies on the sorption of elemental mercury vapor by soils

Mercury vapor sorption by soil increased curvilinearly with the increase of soil moisture content until a maximum was reached. A further increase of moisture content caused a decline in mercury sorption. The percent moisture contents which gave maximal increase of 203Hg vapor sorption in these soils coincide quite closely with their water-holding capacity values at 1/3 bar. Soil microorganisms may play a part in moist soil for the increase of elemental mercury vapor sorption and subsequent transformation to mercuric form. Mercury vapor diffused into both dry and moist soil columns and the diffusion profile can be described by an exponential function of the form, y = ae-bx, where "a" is the adsorption characteristics of the soil, "b" is the diffusivity coefficient and x is the depth of soil. The diffusivity coefficient for mercury vapor varied with the soil type and its moisture content.

In vitro binding of 14C-labeled acidic compounds to serum albumin and their tissue distribution in the rat

The acidic compounds, such as phenoxyacetic acids, substituted benzoic acids, or acetylsalicylic acid, were found to bind to bovine serum albumin (BSA). Among phenoxyacetic acids, the binding affinity to BSA was highest for 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), which was approximately 4-, 24-, and 160-fold greater than those for 2,4-dichlorophenoxyacetic acid (2,4-D), o-chlorophenoxyacetic acid (CPA), and phenoxyacetic acid (PAA), respectively. There were two bound to serum albumins of other mammalian species. The binding affinity varied among species and also depended on the chemicals. However, the order of binding affinity in the albumin of each species remained the same as observed in BSA with few exceptions. Blood/tissue ratios of 14C from rats dosed with these 14C-labeled acids were highly correlated with the logarithm of the binding affinity constantsaffinity constants.

Uptake of mercury vapor by wheat: an assimilation model

Using a whole-plant chamber and (203)Hg-labeled mercury, a quantitative study was made of the effect of environmental parameters on the uptake, by wheat (Triticum aestivum), of metallic mercury vapor, an atmospheric pollutant. Factors were examined in relation to their influence on components of the gas-assimilation model, [Formula: see text]where U(Hg) is the rate of mercury uptake per unit leaf surface, C(a)' is the ambient mercury vapor concentration, C(l)' is the mercury concentration at immobilization sites within the plant (assumed to be zero), r(l.Hg) is the total leaf resistance to mercury vapor exchange, and r(m.hg) is a residual term to account for unexplained physical and biochemical resistances to mercury vapor uptake.Essentially all mercury vapor uptake was confined to the leaves. r(l.hg) was particularly influenced by illumination (0 to 12.8 klux), but unaffected by ambient temperature (17 to 33 C) and mercury vapor concentration (0 to 40 mug m(-3)). The principal limitation to mercury vapor uptake was r(m.hg), which was linearly related to leaf temperature, but unaffected by mercury vapor concentration and illumination, except for apparent high values in darkness.Knowing C(a)' and estimating r(l.hg) and r(m.hg) from experimental data, mercury vapor uptake by wheat in light was accurately predicted for several durations of exposure using the above model.

Estimation of whole-plant resistance to gaseous exchange independent of leaf temperature measurement

For studies into the uptake of mercury vapor by wheat (Triticum aestivum), a simple theory and plant chamber were employed to estimate total leaf resistance of whole plants to water vapor exchange. The estimates were independent of leaf temperature, for which mean values were indirectly determined. The approach involved the measurement, at steady-state conditions, of the net change in water vapor flux per unit of leaf surface (Deltaq(v)) in response to a small induced change in absolute humidity (DeltaC(a)). Assuming that total leaf resistance (r(l)) was constant and that change in leaf temperature (T(l)) was negligible, total leaf resistance was calculated from the equation, [Formula: see text]While the assumptions concerning r(l) and T(l) may or may not be correct, evidence is presented which indicates that such assumptions did not significantly alter estimates of r(l) from their true values for changes in ambient relative humidity ranging from 0.011 to 0.074. Total leaf resistance of groups of whole plants estimated in this manner did not differ for ambient temperatures of 17, 25, and 33 C. Mean values of r(l) ranged from 83 sec cm(-1) in darkness to 2.4 sec cm(-1) at an illumination of 12.8 klux.

Influence of dietary selenite on the binding characteristics of rat serum proteins to mercurial compounds

The effect of dietary selenite on the binding characteristics of serum proteins was investigated with rats. In the control serum, the maximal binding of phenylmercuric acetate (PMA) and methylmercuric chloride (MMC) to rat serum protein was approx. 18 and 9 nmoles per mg protein, respectively. The binding of Hg2+ was biphasic and it did not reach a maximum at the concentrations used. Selenite treatment caused a reduction in binding capacity of serum proteins to Hg2+ and PMA, and an increase in the binding affinities. However, there were no such changes for the binding of MMC. Selenite protection from mercury toxicity, therefore, acts not only via a change in tissue distribution and a change in the formation of seleno-proteins but, also, via a change in the binding characteristics to some mercury compounds. In the case of methylmercury, a different mechanism of protection must exist as the modification of tissue distribution, its binding to subcellular and soluble proteins and the binding characteristics remained equivocal.

Role of striatal dopamine in delayed neurotoxic effects of organophosphorus compounds

Mipafox administered to rats daily for 35 days produced ataxia and a reduction in the level of dopamine in the corpus striatum. Treatment with Leptophos for the same period produced slight motor dysfunction and a small but significant reduction in the level of striatal dopamine. Fenitrothion neither produced motor dysfunction nor changed the level of striatal dopamine. The cholinesterase activity of corpus striatum was inhibited by all the compounds. The results suggest the possible involvement of striatal dopamine in the delayed neurotoxic effects of certain organophosphorus compounds.

Comparative study of uptake and cellular distribution of Hg203-labeled phenyl-mercuric acetate and mercuric acetate by pea roots

Uptake and cellular distribution of mercury(203) from dilute mercuric acetate or phenylmercuric acetate solutions by excised pea roots (Pisum sativum) have been investigated. The time course of uptake showed that the amount of mercury uptake was increased with the time of incubation, and was similar for inorganic mercury or phenylmercuric acetate. The trend of mercury(203) incorporation into cellular components from mercuric acetate and phenylmercuric acetate differed greatly as the time of incubation increased. The concentrations of mercuric acetate and phenylmercuric acetate solutions or the temperature of incubation also affected the mercury(203) uptake as well as its cellular distribution. Longer time of exposure or higher concentration resulted in a greater mercury incorporation into mitochondrial fraction from phenylmercuric acetate than from inorganic mercury. This difference in intracellular distribution may be responsible for the degree of toxicity between inorganic mercury and phenylmercuric acetate in biological systems.