The immune response and PBMC subsets in canine visceral leishmaniasis before, and after, chemotherapy

Peripheral blood mononuclear cell subsets, in vitro lymphoproliferative response to leishmanial antigen, and Leishmania-specific serum antibody levels were examined in 11 dogs, naturally infected with L. infantum, and 9 healthy control dogs. A decrease in the percentage of CD4+ T-cells and an increase in the proportion of gammadelta T-cells and sIgG+ B-cells were observed during canine visceral leishmaniasis (CVL). These changes may be responsible for the marked humoral response and the absence of in vitro lymphoproliferation to mitogen and specific parasite antigens. This possibility was supported by the analysis of these subsets after treatment with amphotericin B. One month after therapy, a significant increase in the percentage of CD4+ T-cells and a decrease of gammadelta T-cells and sIgG+ B-cells were observed. At the same time, the lymphocyte blastogenesis assay with leishmanial antigen was positive and the levels of specific antibodies to Leishmania were significantly lower than before the treatment. Five months after therapy, lymphocyte proliferative response to LSA disappeared, antibody and lymphocyte subsets levels returned to those observed during CVL. Therapeutic failure in CVL is associated with the inability of antileishmanial drugs to completely revert the profound immunodepression induced by the infection and prevent relapse.     

Soil microbial, fungal, and nematode responses to soil fumigation and cover crops under potato production

Sodium N-methyldithiocarbamate (metam sodium) and 1,3 dichloropropene are widely used in potato production for the control of soil-borne pathogens, weeds, and plant parasitic nematodes that reduce crop yield and quality. Soil fumigation with metam sodium has been shown in microcosm studies to significantly reduce soil microbial populations and important soil processes such as C and N mineralization. However, few published data report the impact of metam sodium on microbial populations and activities in potato production systems under field conditions. Fall-planted white mustard (Brassica hirta) and sudangrass (Sorghum sudanense) cover crops may serve as an alternative to soil fumigation. The effect of metam sodium and cover crops was determined on soil microbial populations, soil-borne pathogens (Verticillium dahliae, Pythium spp., and Fusarium spp.), free-living and plant-parasitic nematodes, and C and N mineralization potentials under potato production on five soil types in the Columbia Basin of Eastern Washington. Microbial biomass C was 8–23% greater in cover crop treatments compared to those fumigated with metam sodium among the soil types tested. Replacing fumigation with cover crops did not significantly affect C or N mineralization potentials. Cumulative N mineralized over a 49-day laboratory incubation averaged 18 mg NO₃-N kg⁻¹ soil across all soil types and treatments. There was a general trend for N mineralized from fumigated treatments to be lower than cover-cropped treatments. Soil fungal populations and free-living nematode levels were significantly lowered in fumigated field trials compared to cover-cropped treatments. Fumigation among the five soil types significantly reduced Pythium spp. by 97%, Fusarium spp. by 84%, and V. dahliae by 56% compared to the mustard cover crop treatment. The percentage of bacteria and fungi surviving fumigation was greater for fine- than coarse-textured soils, suggesting physical protection of organisms within the soil matrix or a reduced penetration and distribution of the fumigants. This suggests the potential need for a higher rate of fumigant to be used in fine-textured soils to obtain comparable reductions in soil-borne pathogens.     

Uptake of soil applied cadmium,nickel and selenium by bush beans

A field study was conducted to determine the phytoavailability of Cd, Ni and Se to bush beans (Phaseolus vulgaris L. cultivar. Blue Lake) when grown in an Orangeburg loamy sand (Typic Paleudult). The study was conducted using a completely randomized block design, with three metals (Cd, Ni, Se) and three metal concentrations (control, medium, and high). Application of metals either at high or medium levels did not influence the biomass production. Cadmium was relatively immobile and tended to accumulate mostly in the roots. Nickel and Se, however, tended to be more mobile in the plant as indicated by Ni accumulating equally in roots and pods and Se accumulating mostly in the roots but significantly greater than Cd and Ni in all plant parts. Our results indicate that bush beans exposed to Se had Concentration Factors (C.F.) of up to 250 in the pods and over 800 in roots. Cadmium had a C.F. of 4 in roots and negligible in above ground plant parts, while a Ni C.F. was 2 in roots and pods but negligible in leaves. This study provides evidence that Se has more potential for accumulation in bush beans than does Cd or Ni.     

Comparative study on responses of cattle and water buffalo (<Emphasis Type="Italic">Bubalus bubalis</Emphasis>) to experimental inoculation of <Emphasis Type="Italic">Brucella abortus</Emphasis> biovar 1 by the intraconjunctival route—a preliminary report

The preliminary study was conducted to assess the virulence of a strain of Brucella abortus (1969D) and to compare the susceptibility of water buffalo and cattle calves to infection by the intraconjunctival route. Seven of each cattle and water buffalo (Bubalus bubalis) calves aged 3–6 months were inoculated intraconjunctivally with counts ranging from 1.5 × 10⁷ to 1.7 × 10¹⁰ colony forming units of B. abortus. Animals were monitored over an 8-week period for clinical manifestations and serological and hematological evidence of infection. At slaughter, eight lymph nodes from each animal were sampled for bacteriological and histopathological assessments. Lymph nodes from three water buffalo (43%) and five cattle (71%) yielded B. abortus (P = 0.048). Parotid/prescapular lymph nodes were most sensitive in detecting B. abortus. Our data suggest that B. abortus strain 1969D may be used as challenge strain, and water buffalo appeared to have a lower susceptibility to B. abortus infection than cattle.     

Interactive effects of Cd and PAHs on contaminants removal from co-contaminated soil planted with hyperaccumulator plant <Emphasis Type="Italic">Sedum alfredii</Emphasis>

Purpose  

Soil contamination by multiple organic and inorganic contaminants is common but its remediation by hyperaccumulator plants is rarely reported. The growth of a cadmium (Cd) hyperaccumulator Sedum alfredii and removal of contaminants from Cd and polycyclic aromatic hydrocarbons (PAHs) co-contaminated soil were reported in this study.     

Pig manure vermicompost (PMVC) can improve phytoremediation of Cd and PAHs co-contaminated soil by Sedum alfredii

Purpose

A major challenge to phytoremediation of co-contaminated soils is developing strategies for efficient and simultaneous removal of multiple pollutants. A pot experiment was conducted to investigate the potential for enhanced phytoextraction of cadmium (Cd) by Sedum alfredii and dissipation of polycyclic aromatic hydrocarbons (PAHs) in co-contaminated soil by application of pig manure vermicompost (PMVC).

Materials and methods

Soil contaminated by Cd (5.53?mg?kg^?1 DW) was spiked with phenanthrene, anthracene, and pyrene together (250?mg?kg^?1 DW for each PAH). A pot experiment was conducted in a greenhouse with four treatments: (1) soil without plants and PMVC (Control), (2) soil planted with S. alfredii (Plant), (3) soil amended with PMVC at 5?% (w/w) (PMVC), and (4) treatment 2?+?3 (Plant?+?PMVC). After 90?days, shoot and root biomass of plants, Cd concentrations in plant and soil, and PAH concentrations in soil were determined. Abundance of PAH degraders in soil, soil bacterial community structure and diversity, and soil enzyme activities and microbial biomass carbon were measured.

Results and discussion

Application of PMVC to co-contaminated soil increased the shoot and root dry biomass of S. alfredii by 2.27- and 3.93-fold, respectively, and simultaneously increased Cd phytoextraction without inhibiting soil microbial population and enzyme activities. The highest dissipation rate of PAHs was observed in Plant?+?PMVC treatment. However, neither S. alfredii nor PMVC enhanced PAH dissipation when applied separately. Abundance of PAH degraders in soil was not significantly related to PAH dissipation rate. Plant?+?PMVC treatment significantly influenced the bacterial community structure. Enhanced PAH dissipation in the Plant?+?PMVC treatment could be due to the improvement of plant root growth, which may result in increased root exudates, and subsequently change bacterial community structure to be favorable for PAH dissipation.

Conclusions

This study demonstrated that remediation of Cd and PAHs co-contaminated soil by S. alfredii can be enhanced by simultaneous application of PMVC. Long-term evaluation of this strategy in co-contaminated field sites is needed.     

Freezing behavior of potato (Solanum tuberosum) tubers in soil

Volunteer potatoes are a major weed problem in potato rotations in regions with mild winter soil temperatures. Freezing dynamics of potato tubers in air have been previously reported, but freezing dynamics of tubers in soil may differ due to ice nucleation sites and soil water associated with soil. Laboratory experiments conducted in hydrated and dry soil columns and field experiments were conducted to determine cold temperatures required to kill potato tubers in soil. Potato tubers in air-dried soil columns exposed to decreasing temperatures typically supercooled to ?3 to ?7 C before exhibiting a distinct exotherm, which stabilized at ?1.4 to ?1.5 C, representing the freezing point of tubers. Tubers that were supercooled and removed from the cold environment before experiencing this exotherm were able to sprout and had no visual symptoms of freezing injury, whereas tubers that experienced the exotherm were nonviable and unable to sprout. Tubers in soil columns hydrated to 7% SWC supercooled much less than tubers in dry soil and exhibited an exotherm that stabilized near ?1.9 C. Tubers exposed to temperatures near the tuber-freezing point (?1.4 to ?1.9 C) for periods of 1 min to 24 h, but not undergoing an exotherm, exhibited varying degrees of injury, which increased with time of exposure. Tubers held at ?1.0 C for 4 to 24 h were unharmed and able to sprout similar to controls. In field trials conducted from 1993 to 1999 in the Columbia Basin of Washington, tubers buried at shallow depths (5 cm) were much more likely to experience lethal cold temperatures than tubers buried deeper. In general, when minimum soil temperature at tuber depth reached ?1.5 to ?1.9 C or lower, some tuber mortality occurred and when soil temperature at tuber depth reached ?2.8 C or lower, extensive tuber death occurred. Monitoring of winter soil temperatures by depth in potato- growing regions could be used to predict severity of volunteer potato for the subsequent growing season.     

Chemical composition of throughfall and stemflow from citrus canopies 1

The main objective of this study was to examine the chemical composition of incident rainfall, throughfall, and stemflow from canopies of ‘Marsh’ grapefruit, and ‘Hamlin’ and ‘Temple’ orange trees. The concentrations of ammonium (NH₄) and nitrate (NO₃) were lower in the throughfall under the canopy or along the dripline as compared to those in the incident rainfall. This reduction is due to absorption of those nitrogen (N) forms by the tree foliage, thus, provides an evidence of contribution of (N) through wet deposition to N requirement of the trees. In contrast, concentrations of potassium (K), calcium (Ca), magnesium (Mg), and chloride (Cl) were greater in the throughfall or along the dripline compared to those in the incident rainfall. This is due to possible leaching of those elements from the foliage by the rainwater. Stemflow and throughfall also had greater pH and electrical conductivity (only in two out of three citrus varieties) as compared to the incident rainfall. Good correlation were found between concentrations of either K, Mg, or Ca, and Cl, phosphorus (P), or sulfur (S) in the incident rainfall for two storm events.     

Effects of copper rates and soil ph on growth and nutrient uptake by citrus seedlings

Abstract

Soil properties, primarily pH and organic matter, influence phytotoxicity of copper (Cu). A pot experiment was conducted to evaluate the effects of copper additions (0, 25, 50, 100, 200, and 400 mg kg^?1) to three different soils [Myakka fine sand (pH 5.7), Candler fine sand (pH 6.5), and Oldsmar fine sand (pH 8.2)] on growth, and uptake of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and copper (Cu) by Swingle Citrumelo (SC) seedlings. In unamended soils, the seedling growth was similar in the Myakka and Candler fine sands (pH 5.7 to 6.5), but was significantly greater in the Oldsmar fine sand (pH 8.2). Increasing the rate of Cu from 0 to 400 mg kg^?1 decreased the soil pH by 0.98 unit in the Candler fine sand, by 1.57 pH unit in the Myakka fine sand, and negligible effects on the pH of the Oldsmar fine sand. The growth of SC seedlings decreased significantly with an increase in Cu rates in the Myakka and Candler fine sands, but not in the Oldsmar fine sand. The Cu concentration in the leaves and roots increased substantially with an increase in the Cu rate applied to the Candler and Myakka fine sands while the effect was marginal in the Oldsmar fine sand. The above effect was more pronounced on the Cu concentration in the roots than in the leaves. Increased rate of Cu application decreased the uptake of P, Mg, Ca, and K in the roots and leaves of the seedlings grown in the Myakka and Candler fine sands but not in the Oldsmar fine sand.     

Effects of surface fire on litter decomposition and occurrence of microfungi in a Cymbopogon polyneuros dominated grassland

Abstract

Litter decomposition rate, changes in macronutrients such as nitrogen (N), phosphorus (P) and potassium (K) from different grades of litter decomposition and occurrence of soil microfungi were investigated in a Cymbopogon polyneuros-dominated tall grass ecosystem from a burned and an unburned site in southern India. The litter decomposition rate was higher at the burned site than at the unburned site. This rate was also higher when the litter was mixed with the mineral soil material than leaving the litter unaffected on the soil surface. The concentrations of N, P, and K in the litter decreased as a result of progressed litter decomposition. Occurrence of microfungi identified from the different decomposition grades of the Cymbopogon polyneuros litter was higher at the burned site compared to the unburned site. Microfungal species present at both sites showed only minor differences.