Effects of 2,4-d on nitrogen fixation and carbon dioxide evolution in a soil microcosm

Two concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) 1.7 kg ha^?1 and 3.4 kg ha^?1 were applied to oats (Avena sativa L. ‘Orbit’) grown in terrestrial microcosms in a sandy soil. Carbon dioxide evolution and non-symbiotic N₂ fixation (C₂H₂ reduction) were measured weekly. On day 70 of the study, 2,4-D was applied a second time at the same application rates and soil CO₂ evolution and N₂ fixation were measured more frequently. Soil CO₂ evolution over 24 h period was significantly decreased by 40 to 50% at both application rates of 2,4-D. This response lasted less than 7 days. Nitrogen fixation was unaffected by 2,4-D except for an unexplained decrease observed in the 1.7 kg ha^?1 treatment 35 days after 2,4-D application. This effect was not observed on the following sampling date. The second application of 2,4-D failed to produce any significant change in soil CO₂ evolution or N₂ fixation. From these studies we conclude soil microbial populations either degraded or became acclimated to 2,4-D as a result of the initial application and that 2,4-D has no significant adverse effect on N₂ fixation or soil CO₂ evolution.     

Purification and glycosylation analysis of an acidic pectin methylesterase in jelly fig (Ficus awkeotsang) achenes

An acidic pectin methylesterase (PME) is responsible for the gelation of water extract from jelly fig (Ficus awkeotasang) achenes. A new, fast and efficient, method has been developed to purify this acidic PME. The method includes preparing jelly curd by traditional hand washing, extracting proteins from the curd, and separating PME by anion-exchanger. The purified PME exists as a monomer of 38 kDa determined by gel filtration, and exerts enzymatic activity over a broad pH range, particularly in acidic environments where most known PME enzymes from various species are inactivated. Chemical staining and enzymatic cleavage suggest that the jelly fig PME is an N-linked glycoprotein. Fluorophore-assisted carbohydrate electrophoresis reveals that the polysaccharide of this glycoprotein putatively consists of 22 hexoses including 16 mannose, 4 N-acetylglucosamine, and 2 galactose residues.     

Suspected Clostridium difficile-associated hemorrhagic diarrhea in a 1-week-old elk calf

Clostridium difficile-associated diarrhea was suspected in a 1-week-old elk (Cervus elaphus) calf. The isolation of a toxigenic strain of C. difficile from a diarrheic fecal sample, along with exclusion of other enteropathogens, formed the basis of this presumptive diagnosis. Further study is indicated to evaluate the role of C. difficile in neonatal diarrhea in elk.     

Co-occurrence of autoimmune thyroid disease in a multiple sclerosis cohort

Background

Multiple sclerosis (MS), Hashimoto's disease and Graves' disease are autoimmune diseases that may share similar pathogenic mechanisms. The co-occurrence rates and demographic characteristics of Graves' disease and Hashimoto's disease (HT) in our MS population are compared with the general population.

Methods

The prevalence of thyroid disease in our MS patients was determined by chart review and survey. Previous diagnosis of thyroid disease, age at diagnosis, treatment used, and about the use of disease modifying medications used to treat their MS were asked. Chart reviews were used to estimate the population prevalence of Graves' disease and Hashimoto's disease and to estimate the demographics of patients with thyroid disease.

Results

A significant co-occurrence of Graves' disease with MS (p = 0.002), and a non-significant co-occurrence of Hashimoto's disease were noted (p = 0.097). No difference in the age of onset or gender of thyroid disease in MS patients compared to the general population was found.

Conclusion

There is a significant co-occurrence in patients with MS and Graves' disease, and a trend to co-occurrence in patients with MS and Hashimoto's disease. There are no differences in the demographics of patients with thyroid disease in our MS patients compared to the general population.

     

PCR analysis of bisulfite-modified DNA to investigate developmental variation in micropropagated potatoes (Solanum tuberosum L.)

Summary Bisulfite modification of DNA from potato leaves showing juvenile and mature leaf morphologies and from leaves of autotrophic and heterotrophic microplants showing different morphologies was carried out to deaminate cytosine residues while leaving 5-methylcytosine residues intact. RAPD analysis of the DNA was then performed using selective primers; firstly, with a 50–70% GC content and subsequently with a 50–70% AT content which contained CG or CA 3' ends. Three of the 4 primers used detected band polymorphisms in the juvenile versus mature leaves and all four primers detected band polymorphisms in the autotrophic·versus heterotrophic in vitro leaf samples. These results indicate differences in methylation in the different paired DNA samples. The hypothesised increase in band numbers in the relatively less mature samples was confirmed for both the in vivo and in vitro leaf samples; a higher number of bands was amplified from the DNA of the leaves from heterotrophic cultures compared with those from autotrophic culture when the results for all primer sets were grouped. however, this trend did not apply to the results from all the individual primers. The application of this approach to the evaluation of in vitro protocols for potato micropropagation is discussed.     

改良DBL法测定稻米中的赖氨酸含量

赖氨酸是人体和动物营养中的必需氨基酸,稻米中的赖氨酸含量很低,是稻米蛋白中的第1限制氨基酸。因此,开展赖氨酸含量的遗传研究以及培育高赖氨酸含量的水稻新品种,对于提高稻米的营养价值具有重要的意义。目前作物种子的赖氨酸含量测定主要采用比色法,如茚三酮比色法[1,2]     

Effects of artificial amendments in potting media on Orthosiphon aristatus growth and development

Artificial polyacrylamide gel (PAG) and urea-formaldehyde resin foam (UFRF) amendments are used for putative enhancement of soil physical properties, including increasing their water holding capacity (WHC). Effects were investigated of these two amendments alone and combined on growth and development of Orthosiphon aristatus (Cats’ Whiskers) grown in either composted pine bark or washed river sand, including under transient water deficit stress. UFRF and PAG were incorporated into these potting media substrates at recommended rates of 30% (v/v) and 0.1% (w/w), respectively. UFRF incorporation reduced bulk density and increased air-filled porosity of composted pine bark from 0.24 g cm⁻³ and 43.3% to 0.18 g cm⁻³ and 50.2%, respectively. UFRF also reduced bulk density of sand from 1.43 g cm⁻³ to 1.17 g cm⁻³ and increased its air-filled porosity from 18.5% to 25.3%. PAG slightly decreased bulk density of composted pine bark to 0.23 g cm⁻³ and also reduced sand bulk density to 1.32 g cm⁻³. Water content of composted pine bark and sand was increased by PAG addition from 47.6% and 27.7% to 51.0% and 34.2%, respectively. However, UFRF and/or PAG did not increase plant available water (PAW) in either composted pine bark or sand. PAW was 23.8% and 14.4%, 23.6% and 15.8%, 22.8% and 14.8%, and 25.2% and 17.8% for composted pine bark and sand controls, these two substrates amended with UFRF, these substrates amended with PAG, and these substrates with UFRF plus PAG, respectively. Neither shoot length nor number was increased by adding UFRF and/or PAG. Similarly, neither shoot fresh nor dry weight was increased by UFRF and/or PAG amendments. UFRF and, moreso, UFRF plus PAG slightly delayed the onset of wilting by 4–15 h in water deficit stressed O. aristatus compared to control and PAG alone in composted pine bark (experiment 1), but PAG did not. However, in experiment 2, UFRF and/or PAG did not delay wilting in either composted pine bark or sand. Thus, when incorporated at suppliers recommended rates, neither UFRF nor PAG conferred appreciable benefits for O. aristatus plant growth in either composted pine bark or sand potting media.