Relationship Between Leaf Nitrogen and Photosynthetic Characteristics in Brassica juncea and B. campestris

The relationship between leaf nitrogen content (N) versus photosynthetic rate (PN) and other associated parameters was examined in Brassica juncea , cv. Pusa Bold and B campestris , cv. Pusa Kalyani. Leaf N, specific leaf weight (SLW), leaf area and PN were significantly higher in B. juncea , while the chlorophyll content was significantly lower compared to Brassica campestris. A significant positive correlation was obtained between leaf N content and photosynthetic rate in both species. Similarly, SLW was also positively related with leaf N content, Brassica juncea showed higher photosynthetic nitrogen use efficiency (PNUE) than B campestris. Leaf N and PNUE were negatively associated. This was attributed to a low investment of N in photosynthesis related reactions and/or partitioning of N towards compounds functionally unrelated to photosynthesis. This attribution is further supported by the negative relationship obtained between SLW and PNUE.     

Leguminous Cover Crop Effects on Nitrogen Mineralization Rates and Kinetics in Soils

Soils were collected from an experimental site (initiated in 1991) at which leguminous crops were grown as natural soil cover in the interspaces of a 19‐year‐old coconut plantation. Atylosia scarabaeoides, Centrosema pubescens, Calopogonium mucunoides and Pueraria phaseoloides were grown in separate plots during the rainy season and ploughed into the soil towards the end of the monsoon (in December every year). Soil samples were collected from this site at the end of the 7th year and incubated in PVC columns at 35 ± 1°C and 0.01 MPa moisture content for 36 weeks. The soils were then leached at periodic intervals for up to 36 weeks and nitrogen (N) mineralization rates and kinetics were determined by the double exponential model. The N mineralization rates were highest during the first week and decreased with time in all soils. Soils amended (in situ ploughing) with cover crops leached 191 mg kg^–1 more NO₃^– + NO₂^–‐N than the unamended control. The per cent organic N mineralized (total and net) and the cumulative inorganic N mineralized (NO₃^– + NO₂^–‐N) varied with the amount (biomass) and type of cover crop incorporated into the soil. In general, soils amended with cover crops had greater N mineralization potentials and rate constants than the unamended control. The kinetic parameters N_oS and N_o(1 – S) and their respective rate constants h and k also varied with the amount and type of cover crops incorporated into the soil. The results further indicated that the lignin + polyphenol : N ratio of the cover crops is extremely important in predicting the rate of decomposition and N mineralization in soils.     

Expression of a truncated Pasteurella multocida toxin antigen in Bordetella bronchiseptica

Mild or subclinical respiratory infections caused by Bordetella bronchiseptica are widespread in pigs despite multiple control efforts. Infection with virulent B. bronchiseptica strains is a common risk factor in the establishment of toxin-producing strains of Pasteurella multocida in the nasal cavity of pigs leading to the disease, atrophic rhinitis (AR). This study was designed to explore the possibility of expressing a protective epitope of P. multocida toxin (PMT) in B. bronchiseptica to create single-component mucosal vaccine to control atrophic rhinitis in pigs. To achieve this, a P. multocida toxin fragment (PMTCE), that was non-toxic and protective against lethal challenge in mice, was cloned into a broad-host-range plasmid, PBBR1MCS2, and introduced into B. bronchiseptica by electroporation. The Pasteurella gene construct was placed under the regulatory control of a promoter region that was separately isolated from B. bronchiseptica and appears to be part of the heat shock protein gene family. B. bronchiseptica harboring the plasmid under antibiotic selection expressed the 80kDa PMTCE as determined by PAGE and Western blot with a PMT-specific monoclonal antibody. When introduced into the respiratory tracts of mice, B. bronchiseptica harboring the plasmid construct was reisolated in declining numbers for 72h post-inoculation. Antibody responses (IgM, IgA and IgG) to B. bronchiseptica were detected in serum and respiratory lavage, but PMTCE-specific antibodies were not detected. While further refinements of PMT expression in B. bronchiseptica are necessary, this study provides a basis for the development of a single-component, live-attenuated vaccine against atrophic rhinitis.     

A comprehensive study of Easter lily poisoning in cats.

This study was conducted with 3 objectives in mind: first, to identify the toxic fraction (aqueous or organic) in leaves and flowers; second, to identify diagnostic marker(s) of toxicosis in cats; and, third, to evaluate the morphologic effects of intoxication. The study was conducted in 2 phases. Phase 1 was to identify which extract, organic or aqueous, was nephrotoxic and also to determine the appropriate dose for use in the phase 2 studies. Results indicated that only the aqueous extracts of leaves and flowers were nephrotoxic and pancreotoxic. To identify the proximate toxic compound, cats in the phase 2 study were orally exposed to subfractions of the aqueous flower extract, 1 subfraction per cat. Results confirmed vomiting, depression, polyuria, polydipsia, azotemia, glucosuria, proteinuria, and isosthenuria as toxic effects of the Easter lily plant. Another significant finding in serum was elevated creatinine kinase. Significant histologic kidney changes included acute necrosis of proximal convoluted tubules and degeneration of pancreatic acinar cells. Renal ultrastructural changes included swollen mitochondria, megamitochondria, edema, and lipidosis. Subfraction IIa3 of the aqueous floral extract contained most of the toxic compound(s). These studies reproduced the clinical disease, identified the most toxic fraction of the Easter lily, and helped characterize the clinical pathology, histopathology, and ultrastructural pathology associated with the disease.     

Mosquitocidal, nematicidal, and antifungal compounds from Apium graveolens L. seeds

The methanolic extract of Apium graveolens seeds was investigated for bioactive compounds and resulted in the isolation and characterization of mosquitocidal, nematicidal, and antifungal compounds sedanolide (1), senkyunolide-N (2), and senkyunolide-J (3). Their structures were determined by 1H and 13C NMR spectral methods. Compounds 1-3 gave 100% mortality at 25, 100, and 100 microg mL(-1), respectively, on the nematode, Panagrellus redivivus. Compound 1 showed 100% mortality at 50 microg mL(-1) on nematode, Caenorhabditis elegans, and fourth-instar mosquito larvae, Aedes aegyptii. Also, it inhibited the growth of Candida albicans and Candida parapsilasis at 100 microg mL(-1). Compounds 2 and 3 were isolated for the first time from A. graveolens. This is the first report of the mosquitocidal, nematicidal, and antifungal activities of compounds 1-3.     

Pharmacokinetics and relative bioavailability of tiamulin in broiler chicken as influenced by different routes of administration

The bioavailability and pharmacokinetic disposition of tiamulin in broiler chicken were investigated after administration through the crop, drinking water, and feed at 40 mg/kg body weight. Residues of tiamulin in tissues of broiler chicken were also assessed. Plasma and tissue concentrations of tiamulin were analyzed by reverse‐phase high‐performance liquid chromatography (HPLC) method. Plasma concentration–time data were described by the non‐compartmental model for all three routes, and pharmacokinetic parameters were calculated. There were no significant differences (p > 0.05) in pharmacokinetic parameters and mean plasma concentrations of tiamulin between three routes tested (crop, water, and feed), indicating equal efficacy. Tiamulin residues in edible tissues (muscles, skin, and fat) were lower than the advocated maximum residue limit (MRL of 0.1 µg/g and that of liver was 1 µg/g) on the 3rd day. No traces were found on the 5th day after drug administration. This indicated that the withdrawal period (less than 5 days) is very short, which makes it safer. This study shows that tiamulin can be used with equal efficacy through all routes of administration in broiler chicken (crop, water, and feed).     

A comparison of conventional cloning options for annatto (Bixa orellana L.)

Summary

Annatto (Bixa orellana L.) is a tree indigenous to tropical America that has been naturalised throughout the Indian sub-continent. The plant is chiefly valued for its carotenoid pigments, annatto. Methods for the clonal propagation of hardwood and softwood cuttings, air-layering, budding, and grafting of annatto were investigated. Hardwood cuttings collected during the wet Summer months (June-July) were treated with indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), or naphthaleneacetic acid (NAA) at varying concentrations. The highest percentage rooting (63.4%), along with highest number of roots (8.33 per cutting) were achieved by hardwood cuttings after 12 h of 2.5 mM IAA treatment. Among the various auxin treatments of softwood cuttings, 5.0 mM IBA in combination with 5.0 mM NAA for 5 min resulted in a significant (P < 0.05) rooting percentage (56.7%). The responses of softwood cuttings to an auxin analogue (boric acid) and/or to thiamine hydrochloride (vitamin B) were inferior to synthetic auxins. When subjected to air-layering, hardwood branches gave 100% rooting without any application of hormone. Among the different types of budding methods attempted (patch, T, or I), patch budding produced the highest efficiency (78%) of propagation. Splice-grafting could also be used for conventional propagation of annatto, with a 50% survival rate. Annatto can therefore be cloned by adopting these methods. Propagation based on softwood cuttings facilitated moderate-scale cloning of this valuable, elite germplasm.     

Carbon dioxide assimilation in urea‐treated wheat leaves

Application of 10 mM urea to the flag leaf of wheat plants enhanced in vivo urease activity several fold. Photosynthetic rate was also increased considerably. There were significant differences in the leaf internal carbon dioxide (CO₂) concentrations between the urea‐treated and untreated leaves. The finding that carbon (¹⁴C) was detected in the ethanol extract of the leaves fed with ¹⁴C‐urea suggests that CO₂ released from urea is re‐fixed by the leaves.     

Binding of host glycosaminoglycans and milk proteins: possible role in the pathogenesis of Streptococcus uberis mastitis

The role of indirect binding of host proteins through glycosaminoglycans (GAGs) on adherence and internalization of Streptococcus uberis to bovine mammary epithelial cells was evaluated. Preincubation of S. uberis with GAGs followed by incubation with fetal bovine serum (FBS), bovine milk or milk proteins resulted in greater adherence to and internalization of S. uberis into mammary epithelial cells than observed in untreated controls. Highest values were detected, when final incubation was done with milk. Greater adherence to and internalization into mammary epithelial cells were observed when heparin sulfate (HEP) and milk were used compared with any other GAG and FBS. When individual milk proteins were used, greatest adherence and internalization were observed when S. uberis strains were pretreated with HEP followed by treatment with beta-casein. The findings of this study illustrate a pathogenic strategy of S. uberis that may occur during the very early stages of infection.