Comparative effects of endrin on hepatic lipid peroxidation and DNA damage,and nitric oxide production by peritoneal macrophages from C57BL/6J and DBA/2 mice

1. Endrin is a polyhalogenated cyclic hydrocarbon which produces hepatic and neurologic toxicity. In order to further assess the mechanism of toxicity ofendrin, the dose-dependent effects of endrin on hepatic lipid peroxidation and DNA damage, and nitric oxide (NO) production by peritoneal exudate cells (primarily macrophages) were investigated in C57BL/6J and DBA/2 mice which vary at the Ah receptor genetic locus. C57BL/6J mice are dioxin-responsive, while DBA/2 mice are dioxin-insensitive.2. Mice of both strains were treated with 0, 1, 2 or 4 mg endrin kg⁻¹ as a single oral dose in corn oil, and the animals were killed 24 hr post-treatment. At doses of 1,2 and 4 mg endrin kg⁻¹ in C57BL/6J mice, hepatic mitochondrial lipid peroxidation increased 1.2-, 2.2- and 3.2-fold, respectively, and 1.8-, 2.3- and 3.5-fold with microsomes, respectively. At these same doses in DBA/2 mice, hepatic mitochondrial lipid peroxidation increased 1.3-, 2.0- and 2.6-fold, respectively, and 1.5-, 1.9- and 2.5-fold with microsomes, respectively.3. Increases of 2.3-, 2.4- and 4.9-fold were observed in hepatic DNA damage (elution constants) in C57BL/6J mice at doses of 1, 2 and 4 mg endrin kg⁻¹, respectively, while at these same three doses, increases of 1.9-, 2.1- and 2.3-fold were observed for DBA/2 mice, respectively.4. Nitric oxide production by peritoneal macrophages from C57BL/6J increased by 1.3-, 1.7- and 2.0-fold with doses of 1, 2 and 4 mg endrin kg⁻¹, respectively, while in macrophages from DBA/2 mice at these same doses, increases of 1.7-, 1.7- and 1.8-fold, respectively, were observed.5. The results indicate that the responsiveness of peritoneal macrophages with respect to both DNA damage and nitric oxide production are more dose-dependent in C57BL/6J mice as compared to DBA/2 mice, while similar results are observed with the lipid peroxidation of hepatic mitochondria and microsomes of the two mouse strains. The results suggest that the toxicity of endrin is less reliant on a mechanism which may involve the Ah receptor system as compared to dioxins as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).     

Phytotoxic doses of boron in contrasting soils depend on soil water content

Boron (B) affects plant growth in soil at B doses (mg added B kg^-1 soil) that appear in the range of natural background B concentrations. A study was set up to determine B bioavailability by testing B toxicity to plant as affected by soil properties and ageing after soil dosing. Nineteen soils (pH 4.4?C7.8) and 3 synthetic soils (sand-peat mixtures) were amended with 7 doses of H₃BO₃. Barley root elongation was determined immediately after B amendment and after 1 and 5 months ageing. Soil solution B concentrations increased linearly with added B concentrations with almost no detectable adsorption. In contrast, the ratio of aqua regia soluble B/soil solution B in unamended soils (no B added) was 10?C25 times higher than in B amended soils at similar aqua regia soluble B concentrations illustrating a much lower B availability in unamended soils. Soil solution B concentrations did not decrease by ageing. The toxic B doses or soil B concentrations that decreased barley root growth by 10% (EC10 values) varied about tenfold (respectively 3?C27 mg added B kg^-1 and 5?C52 mg B kg^-1) among soils. Corresponding thresholds in soil solution varied less than fourfold (16?C59 mg B l^-1). Soil ageing for 5 months did not significantly change EC10 and EC50 values, expressed either as total soil B or as soil solution B, unless in 1 soil. Variability in EC10 and EC50 values was explained by various soil properties (soil moisture content, background B, %clay, cation exchange capacity), but covariance of these properties with the soil moisture content suggest that B dilution is the critical factor explaining B toxicity. It is concluded that effects of B amendments do not decrease by ageing and that soil solution B or B doses corrected for soil moisture content may be used as an index for B toxicity across different soils.     

Influence of mutagenic factors on the epidermis of tomatillo,currant tomato and tomato

Epidermal features of control, 16 treated and 7 mutants ofPhysalis ixocarpa BROT. (tomatillo),Lycopersicon esculentum MILL. (tomato) andL. pimpinellifolium MILL. (currant tomato) are studied. Although the distribution, ontogenesis and mature structure of stomata in control as well as in treated and mutant plants were similar, the mutagens reduced the stomatal abnormalities which were abundant (60%) inP. ixocarpa. Maximum rectification was found after combined treatment of gamma radiation (5.16 C kg^-1 [= 20 kR]) + 1 % dimethyl sulphate. Methyl ethane sulfonate, gamma radiation and gamma radiation + DMS caused an increase in epidermal cell size irrespective of the leaf size but in DMS and diethyl sulphate treated plants, a close negative correlation between leaf size and epidermal coll size was observed. The size and frequency of stomata were also affected, the large leaf usually showed high frequency and small size stomata. The data reveal that mutagens affect the epidermal structures differently.     

Evaluation of the mutagenicity and antimutagenicity of Ziziphus joazeiro Mart. bark in the micronucleus assay

The aim of this study was to evaluate the mutagenicity (clastogenicity/aneugenicity) of a glycolic extract of Ziziphus joazeiro bark (GEZJ) by the micronucleus assay in mice bone marrow. Antimutagenic activity was also assessed using treatments associated with GEZJ and doxorubicin (DXR). Mice were evaluated 24–48 h after exposure to positive (N-nitroso-N-ethylurea, NEU - 50 mg.kg⁻¹ and DXR - 5 mg.kg⁻¹) and negative (150 mM NaCl) controls, as well as treatment with GEZJ (0.5–2 g.kg⁻¹), GEZJ (2 g.kg⁻¹) + NEU and GEZJ (2 g.kg⁻¹) + DXR. There were no significant differences in the frequencies of micronucleated polychromatic erythrocytes in mice treated with GEJZ and GEJZ + DXR compared to the negative controls, indicating that GEZJ was not mutagenic. Analysis of the polychromatic:normochromatic erythrocyte ratio revealed significant differences in the responses to doses of 0.5 g.kg⁻¹ and 1–2 g.kg⁻¹ and the positive control (NEU). These results indicated no systemic toxicity and moderate toxicity at lower and higher doses of GEZJ. The lack of mutagenicity and systemic toxicity in the antimutagenic assays, especially for treatment with GEZJ + DXR, suggested that phytochemical compounds in Z. joazeiro bark attenuated DXR-induced mutagenicity and the moderate systemic toxicity of a high dose of Z. joazeiro bark (2 g.kg⁻¹). Further studies on the genotoxicity of Z. joazeiro extracts are necessary to establish the possible health risk in humans and to determine the potential as a chemopreventive agent for therapeutic use.     

Accurate repair of ultraviolet-induced damage in Micrococcus radiodurans

The nature of the patterns of elimimation of chromosomal aberrations in both root and shoot has been studied in both the species of P. canariensis Linn (2n = 12) and P. minor Retz (2n = 28) after irradiating their dry seeds with filtered and unfiltered X-rays.Doses used are 10 kR and 30 kR filtered X-rays and 10 kR and 20 kR unfiltered X-rays.The elimination curves in both root and shoot have been fitted to the equation N₁ = N₀e^?KT for both the species. The pattern of elimination for each type of aberrations was found to be exponential in both root and shoot.     

Evaluation of Mercury Contamination in Fungi Boletus Species from Latosols,Lateritic Red Earths,and Red and Yellow Earths in the Circum-Pacific Mercuriferous Belt of Southwestern China

For the first time, highly elevated levels of mercury (Hg) have been documented for several species of the edible Fungi genus Boletus growing in latosols, lateritic red earths, and red and yellow earths from the Yunnan province of China. Analysis of Hg concentrations in the genus suggests that geogenic Hg is the dominant source of Hg in the fungi, whereas anthropogenic sources accumulate largely in the organic layer of the forest soil horizon. Among the 21 species studied from 32 locations across Yunnan and 2 places in Sichuan Province, the Hg was found at elevated level in all samples from Yunnan but not in the samples from Sichuan, which is located outside the mercuriferous belt. Particularly abundant in Hg were the caps of fruiting bodies of Boletus aereus (up to 13 mg kg^-1 dry matter), Boletus bicolor (up to 5.5 mg kg^-1 dry matter), Boletus edulis (up to 22 mg kg^-1 dry matter), Boletus luridus (up to 11 mg kg^-1 dry matter), Boletus magnificus (up to 13 mg kg^-1 dry matter), Boletus obscureumbrinus (up to 9.4 mg kg^-1 dry matter), Boletus purpureus (up to 16 mg kg^-1 dry matter), Boletus sinicus (up to 6.8 mg kg^-1 dry matter), Boletus speciosus (up to 4.9mg kg^-1 dry matter), Boletus tomentipes (up to 13 mg kg^-1 dry matter), and Boletus umbriniporus (up to 4.9 mg kg^-1 dry matter). Soil samples of the 0–10 cm topsoil layer from the widely distributed locations had mercury levels ranging between 0.034 to 3.4 mg kg^-1 dry matter. In Yunnan, both the soil parent rock and fruiting bodies of Boletus spp. were enriched in Hg, whereas the same species from Sichuan, located outside the mercuriferous belt, had low Hg concentrations, suggesting that the Hg in the Yunnan samples is mainly from geogenic sources rather than anthropogenic sources. However, the contribution of anthropogenically-derived Hg sequestered within soils of Yunnan has not been quantified, so more future research is required. Our results suggest that high rates of consumption of Boletus spp. from Yunnan can deliver relatively high doses of Hg to consumers, but that rates can differ widely because of large variability in mercury concentrations between species and locations.     

Schistosoma mansoni: vaccination of mice with cryopreserved irradiated schistosomules.

In our earlier experiments, NIH/Nmri (CV) mice developed protective immunity to a Schistosoma mansoni cercarial challenge when previously exposed percutaneously to highly ⁶⁰Co-irradiated homologous cercariae. Experiments reported here were conducted to assess the immunogenicity of unfrozen and frozen and thawed schistosomules derived from ⁶⁰Co-irradiated cercariae (irradiated schistosomules). Immunization of NIH/Nmri (CV) mice by ⁶⁰Co-irradiated unfrozen schistosomules reduced worm burdens from a subsequent percutaneous challenge with normal cercariae by 41 to 72%. Immunogenicity was not narrowly dependent on irradiation dose rates between 1 and 8 kR/min, or on the total dose of irradiation given the schistosomules between 25 and 50 kR. Comparable protective immunity developed after injection of irradiated schistosomules which had been frozen to ?196 C in liquid nitrogen and thawed. Cryopreservation appears to offer a solution to the problem of storage of attenuated, immunogenic S. mansoni schistosomules.     

Herbal supplementation diets on hematology and innate immunity in goldfish against Aeromonas hydrophila

Goldfish, Carassius auratus (47 ± 3 g, n = 300) were inoculated intramuscularly (50 μl) with Aeromonas hydrophila (1.8 × 10⁶ cells ml^?1). On the 6th day of post-infection the fishes were divided into i) control, without infection fed with normal diet (C), ii) infected fish, fed with normal diet (IU), and infected fishes treated with different doses of iii) 100 mg kg^?1, iv) 200 mg kg^?1, iv) 400 mg kg^?1 and vi) 800 mg kg^?1 mixed herbal extracts supplementation diets. Hematological and immunological parameters were determined on week 1, 2 and 4. In infected goldfish were fed diets containing 100 and 200 mg kg^?1 of mixed herbal extracts supplementation feeds, the white blood cell (WBC) levels significantly increased (P < 0.05) throughout the experimental trial compared to the control. During the experimental period, the red blood cell (RBC) and haemoglobin (Hb) level in goldfish significantly decreased (P < 0.05) when fish fed with 100 and 200 mg kg^?1 of mixed herbal extracts supplementation feeds while it was restored near control when infected fish fed with 400 or 800 mg kg^?1 of herbal extracts supplementation feeds. On the other hand, the haematocrit (Ht) values decline significantly (P < 0.05) in 100, 200 and 400 mg kg^?1 of mixed herbal supplementation feeding groups on weeks 2 and 4 when compared to control group. The mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) values almost significantly differ from the control values. The infected goldfish and treated with 100 or 200 mg kg^?1 of herbal supplementation feeds exhibited significantly decline (P < 0.05) in total protein (TP), glucose (GLU) and cholesterol (CHO) levels on week 1–4 whereas it was restored when infected fish fed with 400 or 800 mg kg^?1 of herbal supplementation feeds on week 4. In comparison to untreated control goldfish, the respiratory burst activity and phagocytic activity of blood cells was significantly enhanced in infected fish feeding with 200, 400 and 800 mg kg^?1 of herbal supplementation feeds compared to the control. On the other hand, infected fish fed with all the doses of mixed herbal supplementation feeds, the lysozyme activity was significantly enhanced throughout the experimental period. This study shows that the infected goldfish treated with 400 and 800 mg kg^?1 of herbal supplementation feeds preceding the challenge with live A. hydrophila had 30% and 25% mortality. However, 100 and 200 mg kg^?1 of herbal supplementation feeds treated groups were found the percentage mortality 50% and 45%, respectively. Our results indicate that 400 or 800 mg kg^?1 of mixed herbal supplementation feeds were restored the altered hematological parameters and triggering the innate immune system of goldfish against A. hydrophila.     

The influence of gamma radiation on the biosynthesis of indoles and gibberellins in barley the action of zinc on the restitution of growth substance level in irradiated plants

Investigations were made on the effect of exposing barley seeds to gamma-radiation (5–40 kR), alone and in combination with the application of zinc (soaking the seeds in solutions containing 5.10^?5–5.10^?1% Zn for 12 hours before sowing) on growth and on the content of tryptophan, indole auxins and gibberellin-like substances in seven-day plants. Radiation decreased both growth and the content of tryptophan (e.g. by about 53% at 30 kR), of indole auxins (by about 60% auxin in the zone of IAA on the chromatogram at 30 kR), and also the content of gibberellin-like substances (by about 67% gibberellin content in the zone of GA₃ on the chromatogram) of plants. The irradiation of standard samples of tryptophan, indolyl-acetic acid and gibberellic acid alone with many times greater doses (up to 1000 kR) did not lead to marked radiochemical degradation of these substances. It can be assumed that radiation damages the enzyme systems “synthesizing” natural growth substances in plants. The damaging effect of radiation on auxins is already displayed in the synthesis of tryptophan, which is inhibited. Zinc interacts with the damaging effect of radiation on growth. Optimum concentrations of zinc (5.10^?3% Zn) counteract the effect of radiation, up to doses of about 12 kR, on the growth in height in 7-day plants so that it is equal to the controls. Normal content of tryptophan and auxin in the position of indolecetic acid on chromatograms can only be reached by the addition of zinc when the dose of radiation was not greater than about 8 kR, which is less than the influence exerted by zinc on the restitution of growth. On the other hand, the biosynthesis of gibberellin-like substances at the position of gibberellic acid on chromatograms can be restored by zinc to their original level to doses of up to 30 kR. The increased biosynthesis of auxins and gibberellins caused by zinc in irradiated plants is explained by the activation of the remaining and non—damaged enzyme systems carrying out this biosynthesis. The activation of the biosynthesis of growth substances by zinc will also contribute to the restitution effect of zinc on the growth of plants from irradiated seeds.     

The effect of dietary inclusion of starch,sucrose and xylose on the utilization of dietary energy in sheep

A calorimetric experiment of 4 × 4 Latin square design was undertaken to study the effect of sugar-beet pulp (SBP), maize starch, sucrose and xylose on energy metabolism in sheep. The four diets comprised a diet (A) of dried grass, soya-bean meal and SBP (450, 50 and 500 g kg⁻¹ on dry matter (DM) basis) and corresponding diets in which 400 g kg⁻¹ of SBP was replaced by maize starch (B), sucrose (C) or xylose (D); all diets were offered at a level of 600 g DM day⁻¹. After the Latin square was completed, energy value of the basal diet of dried grass and soya-bean meal (900 and 100 g kg⁻¹ DM; 600 g day⁻¹) was determined in the same four sheep.Treatment differences in organic matter, gross energy, nitrogen (N) and neutral detergent fibre (NDF) digestibility were non-significant. Differences in N retention were not significant.Digestible energy (DE) contents (MJ kg⁻¹ DM) were 13.27, 13.22, 13.21 and 13.21 MJ kg⁻¹ for diets A, B, C and D, respectively. Energy loss in methane was higher (P < 0.05) for Diet A than for other diets. Metabolizable energy (ME) contents for the diets A-D were 11.25, 11.22, 11.32 and 11.40 MJ kg⁻¹ DM, respectively. Metabolizability (q) of the diets averaged 0.642 and was not significantly affected by the diet given. There was a trend for heat production to be higher in sheep given the sucrose-containing diet (C) than in those given other diets (6.34 versus 6.04 MJ day⁻¹) and as a result, energy retention was lower (0.38 versus 0.64 MJ day⁻¹), but the difference did not reach statistical difference. Efficiencies of utilization of ME for maintenance and fattening (k_mf) averaged 0.67 and were in good agreement with those predicted from equations of the Agricultural Research Council (1980) excepting the lower k_mf (0.63) for Diet C.The mean ME content of SBP calculated by difference was 13.05 MJ kg⁻¹ DM and the corresponding values for mixtures of SBP + starch, SBP + sucrose and SBP + xylose (600 and 400 g kg⁻¹ DM) were 12.98, 13.16 and 13.36 MJ kg⁻¹ DM, respectively.     

The effect of some pre-ensiling treatments on silage composition and nitrogen disappearance in the rumen

Ryegrass, harvested before ear emergence, was ensiled in triplicate in laboratory silos with and without pre-ensiling treatments. These were: 4.7 M sulphuric acid (39 and 79 g kg^?1 DM); formalin (28 and 58 g kg^?1 DM); ‘Add-F’ (22.5 M formic acid; 36 and 71 g kg^?1 DM); formalin (28 and 58 g kg^?1 DM); ‘Farmline’, a commercial additive containing acids and formalin (31 g kg^?1 DM); heat (30 and 60°C for 1 h); and Lactobacillus plantarum inoculum + glucose (4.6 g kg^?1 DM). The ensilage period was 120 days. Samples of each silage were incubated, in artificial fibre bags, in the rumens of four Hereford-cross steers fitted with permanent rumen cannulae. Total nitrogen (TN) disappearance was measured after incubation periods of 1, 2, 4, 7, 12 and 24 h.Hydrochloric acid and the heating pre-treatments had no significant effect (P > 0.05) on the pH, water-soluble carbohydrates and fermentation acid values compared with those of the control. Fermentation acid production was suppressed to an increasing extent by formalin (28 g kg^?1 DM), sulphuric acid (79 g kg^?1 DM), formic acid (36 g kg^?1 DM), formalin (58 g kg^?1 DM) and formic acid (71 g kg^?1 DM).The application of L. plantarum + glucose increased fermentation acids from 90.3 g kg^?1 DM in the control to 227 g kg^?1 DM, owing to a 10-fold increase in lactic acid content from 21.7 to 202 g kg^?1 DM.All treatments, with the exception of 30°C heating, produced silages with significantly (P < 0.001) more total nitrogen as protein than the control. This ranged from 334 g kg^?1 TN (60°C heating) to 748 g kg^?1 TN (formalin; 58 g kg^?1 DM).All treatments significantly (P < 0.05) reduced TN loss, compared with the control silage values, after a 7-h incubation period in the rumen. After 24 h, however, TN disappearance from the treated silages was not significantly different from that of the control with the exception of the two silages treated with formalin alone. With these silages, the proportion of TN disappearing was 55.0 and 40.0% for the low and high application rates, respectively, compared with a value of 74.0% for the control.     

Abscission of Phaseolus and Impatiens Explants: Effects of Ionizing Radiation upon Endogenous Growth Regulators and de Novo Enzyme Synthesis

Stem-petiole explants from the lower pulvinus of the primary leaves of Phaseolus vulgaris L. cv. Red Kidney and from Impatiens sultani Hook cv. Scarlet Baby were exposed to varying dosages of γ-radiation. With bean, irradiation of 175 to 525 kiloroentgens (kR) significantly accelerated the onset of abscission with a maximum response at 175 to 280 kR. Higher dosages (beginning at 600-700 kR) usually prevented abscission. With Impatiens, 18 to 35 kR significantly accelerated both the onset of abscission and possibly the initial abscission rate; 350 kR cut the time to 100% abscission in half and substantially accelerated the initial abscission rate. Inhibition of abscission in Impatiens was not possible with the available dose rate (35 kR/hour).     

Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland

Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg^-1) and DOC (306 mg kg^-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg^-1), and the bare mudflat was with the lowest content of DOC (270 mg kg^-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg^-1 h^-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg^-1 h^-1) and invertase (9.81mg g^-1 24h^-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg^-1 h^-1), β-glycosidase (2.87 mg kg^-1 h^-1), and invertase (8.02 mg g^-1 24h^-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands.     

柠檬香蜂草对铜的耐性及其积累特征研究

以柠檬香蜂草(Melissa officinalis)幼苗为材料,设置不同浓度Cu~(2+)胁迫(CK、200、400、800和1 000mg·kg~(-1))盆栽实验,测定胁迫0、7、14、21、28d后植物生物量、叶绿素含量、抗氧化酶活性、可溶性蛋白含量、丙二醛(MDA)含量以及植物体内Cu含量等指标,探讨柠檬香蜂草对Cu~(2+)的耐受性及其积累特征。结果表明:(1)相同处理时间下,柠檬香蜂草除MDA含量外其他所有指标均随着Cu~(2+)胁迫处理浓度的增加呈低浓度促进、高浓度抑制的变化趋势,且高浓度组(800和1 000mg·kg~(-1))与低浓度组(200和400mg·kg~(-1))之间差异显著(P0.05);MDA含量在1 000mg·kg~(-1)浓度下持续增长至第14天后开始下降。(2)柠檬香蜂草体内Cu的积累量随Cu胁迫浓度的升高呈先增加后减少的趋势,并在浓度为400mg·kg~(-1)时达到最高值(0.71mg/盆)。(3)在整个胁迫过程中,柠檬香蜂草植株的铜富集系数及其耐性系数均随Cu浓度的增加而减小,各处理浓度对Cu的耐性系数均大于0.5,富集系数均大于1。研究发现,柠檬香蜂草对Cu胁迫具有一定耐受性和富集能力,具有成为铜污染土壤修复植物的潜力。     

Human nonshivering thermogenesis

Metabolic responses, skin temperatures and changes in heart rate and blood pressure were measured in a control group and in “polar swimmers” after infusion of different doses of epinephrine, norepinephrine and isoprenaline. In controls the highest infusion dose of isoprenaline (0.1 μg min⁻¹ kg⁻¹) increased metabolic rate in normal humans by 36%, while the highest infusion doses of epinephrine and norepinephrine (0.45 μg min⁻¹ kg⁻¹) increased metabolic rate by 24%, only. In “polar swimmers” the epinephrine thermogenesis was potentiated significantly, reaching about 45% of the basal metabolic rate. The norepinephrine and isoprenaline thermogenesis were not different from that of the control group. It is concluded that in humans the epinephrine thermogenesis is probably located in muscles and in the white fat (Simonsen et al., 1992), and may be the principal mechanism of metabolic adaptation to cold. It was calculated that the increased capacity of epinephrine thermogenesis in cold exposed “polar swimmers” could theoretically shift the survival limit downwards to lower environmental temperatures by about 5°C.     

Lack of micronuclei induction by fumonisin B1 mycotoxin in BALB/c mice

The genotoxic potential of fumonisin B₁ (FB₁) in vivo in BALB/c mice (male and female) was assessed by induction of micronuclei (MN) formation in bone marrow polychromatic erythrocytes. The ratio of polychromatic erythrocytes to normochromatic erythrocytes (PCE/NCE) was also determined. Mice were injected intraperitoneally (i.p.) with FB₁ at a low dose (0.1 mg?kg^?1 body mass), middle dose (1.0 mg?kg^?1 body mass) and high dose (10 mg?kg^?1 body mass) as single and multiple doses in normal saline to test the genotoxicity. Mitomycin C, a known clastogen, was used as positive control. The frequency of MN and the PCE/NCE value in animals treated with FB₁ at low, middle, and high doses in single dose studies, and the frequency of MN in multiple dose studies, were statistically non-significant from that of the controls injected with saline only. The multiple dose studies at all doses revealed that the PCE/NCE value was found to be reduced upon exposure to FB₁ as compared to the controls. In animals injected with multiple low doses of FB₁, the PCE/NCE value was found to be 0.66 in males and 0.82 in the females; at multiple middle doses the value was 0.30 in males and 0.41 in the females and was statistically significant (p?<?0.001); however, at multiple high doses, the ratio was found to be 0.36 in both males and females. The present study confirms that FB₁ is non-genotoxic in nature while the reduced ratio of PCE/NCE suggests the cytotoxic nature of FB₁.     

Vitellogenesis and other physiological responses induced by 17-β-estradiol in males of freshwater fish Rhamdia quelen

This study investigated the effects of different doses of 17-β-estradiol (E₂) in Rhamdia quelen. Groups of males exposed to different doses of E₂ (0.1 mg kg^− 1, 1 mg kg^− 1 and 10 mg kg^− 1) were compared with non-exposed male and female fish groups. Among the considered biomarkers, no significant differences were observed for micronuclei test, reduced glutathione concentration and lipid peroxidation. All E₂-treated individuals had decreased glutathione S-transferase activity. Increased catalase and superoxide dismutase activities, increased vitellogenin expression and decreased metallothionein concentration were observed in males treated with the highest dose. Liver of all test groups showed necrotic areas, but cytoplasm vacuolization was again found only in the individuals exposed to highest dose. E₂ causes deleterious hepatic effects to R. quelen, and vitellogenin expression, catalase and superoxide dismutase activity and metallothionein concentration represent appropriate biomarkers for studying E₂ effects. Additionally, the response of some biomarkers was similar in males exposed to E₂ and unexposed females, and therefore exposure to endocrine disruptors may cause consequences for fish populations.     

Evaluation of Methyl Bromide Alternatives Efficacy against Soil-Borne Pathogens,Nematodes and Soil Microbial Community

Methyl bromide (MB) and other alternatives were evaluated for suppression of Fusarium spp., Phytophthora spp., and Meloidogyne spp. and their influence on soil microbial communities. Both Fusarium spp. and Phytophthora spp. were significantly reduced by the MB (30.74 mg kg^-1), methyl iodide (MI: 45.58 mg kg^-1), metham sodium (MS: 53.92 mg kg^-1) treatments. MS exhibited comparable effectiveness to MB in controlling Meloidogyne spp. and total nematodes, followed by MI at the tested rate. By contrast, sulfuryl fluoride (SF: 33.04 mg kg^-1) and chloroform (CF: 23.68 mg kg^-1) showed low efficacy in controlling Fusarium spp., Phytophthora spp., and Meloidogyne spp. MB, MI and MS significantly lowered the abundance of different microbial populations and microbial biomass in soil, whereas SF and CF had limited influence on them compared with the control. Diversity indices in Biolog studies decreased in response to fumigation, but no significant difference was found among treatments in PLFA studies. Principal component and cluster analyses of Biolog and PLFA data sets revealed that MB and MI treatments greatly influenced the soil microbial community functional and structural diversity compared with SF treatment. These results suggest that fumigants with high effectiveness in suppressing soil-borne disease could significantly influence soil microbial community.     

Caffeine antagonizes several central effects of diazepam

In spinal cats, caffeine (3–30 mg·kg^?1 i.v.) reduced the increase of dorsal root potentials (DRPs) caused by diazepam (0.1–1 mg·kg^?1 i.v.) without affecting the prolongation of DRPs evoked by phenobarbitone (10–20 mg·kg^?1 i.v.). Caffeine antagonized the depression by diazepam, but not that by phenobarbitone, of the ventral root-evoked Renshaw cell discharge. In unrestrained cats, 50 mg·kg^?1 caffeine i.p. abolished the elevation induced by 1 mg·kg^?1 diazepam i.p. of the threshold for eliciting a rage reaction by stimulation of the lateral hypothalamus, but was ineffective against the threshold increase caused by 20 mg·kg^?1 phenobarbitine i.p. In the horizontal wire test in mice, caffeine was more potent in reversing the depression of performance induced by diazepam that that by phenobarbitone (ED50 1.8 mg·kg^?1 and 139 mg·kg^?1 p.o., respectively). The reduction of skeletal muscle tone in mice produced by diazepam was antagonized by low doses of caffeine (ED50 0.53 mg·kg^?1 p.o.). While caffeine at low doses (0.3-3 mg·kg^?1 p.o.) abolished the anticonflict effect of diazepam in rats, high doses (ED50 160 mg·kg^?1 p.o.) were necessary to antagonize the anticonvulsant effect of diazepam on pentylene-tetrazole-induced seizures in mice. The interaction between caffeine and diazepam is not due to a competition at the benzodiazepine receptors but may involve purinergic mechanisms.