Efficient Production of Doubled Haploid Plants through Chromosome Doubling of Isolated Microspores in Brassica napus

Three methods of chromosome doubling to produce doubled haploid plants from microspore cultures of Brassica napus were compared: colchicine treatment of microspore-derived plants, microspore-derived embryos, and isolated microspores. In the whole plant treatment, 53% of the treated plants set seed, but the treatment delayed plant growth and reduced seed set. When microspore-derived embryos were treated with colchicine, the doubling frequency was 32% (compared to 15% for spontaneous doubling). Direct colchicine treatment of isolated microspores resulted in a doubling efficiency of 70 % of the whole plants. This treatment also stimulated embryogenesis in microspore culture, leading to increased plant regeneration. Thus, direct chromosome doubling of isolated microspores is efficient and more than 10 000 doubled haploid plants have been produced in this manner in the past three years in order to accelerate the plant-breeding process.     

Determination of chlorophylls in Taraxacum formosanum by high-performance liquid chromatography-diode array detection-mass spectrometry and preparation by column chromatography

Taraxacum formosanum, a well-known Chinese herb shown to be protective against hepatic cancer as well as liver and lung damage, may be attributed to the presence of abundant carotenoids and chlorophylls. However, the variety and content of chlorophylls remain uncertain. The objectives of this study were to develop an high-performance liquid chromatography-diode array detection-mass spectrometry method for determination of chlorophylls in T. formosanum and preparation by column chromatography. An HyPURITY C18 column and a gradient mobile phase of water (A), methanol (B), acetonitrile (C), and acetone (D) could resolve 10 chlorophylls and an internal standard Fast Green FCF within 30 min with a flow rate at 1 mL/min and detection at 660 nm. Both chlorophylls a and a' were present in the largest amount (1389.6 μg/g), followed by chlorophylls b and b' (561.2 μg/g), pheophytins a and a' (31.7 μg/g), hydroxychlorophyll b (26.5 μg/g), hydroxychlorophylls a and a' (9.8 μg/g), and chlorophyllides a and a' (0.35 μg/g). A glass column containing 52 g of magnesium oxide-diatomaceous earth (1:3, w/w) could elute chlorophylls with 800 mL of acetone containing 50% ethanol at a flow rate of 10 mL/min. Some new chlorophyll derivatives including chlorophyllide b, pyropheophorbide b, hydroxypheophytin a, and hydroxypheophytin a' were generated during column chromatography but accompanied by a 63% loss in total chlorophylls. Thus, the possibility of chlorophyll fraction prepared from T. formosanum as a raw material for future production of functional food needs further investigation.     

Induction by antigen of intrathymic apoptosis of CD4+CD8+TCRlo thymocytes in vivo

In order to examine the mechanisms by which clonal deletion of autoreactive T cells occurs, a peptide antigen was used to induce deletion of antigen-reactive thymocytes in vivo. Mice transgenic for a T cell receptor (TCR) that reacts to this peptide contain thymocytes that progress from the immature to the mature phenotype. Intraperitoneal administration of the peptide antigen to transgenic mice results in a rapid deletion of the immature CD4+ CD8+ TCRlo thymocytes. Apoptosis of cortical thymocytes can be seen within 20 hours of treatment. These results provide direct evidence for the in vivo role of apoptosis in the development of antigen-induced tolerance.     

A high-brightness source of narrowband, identical-photon pairs

We generated narrowband pairs of nearly identical photons at a rate of 5 x 10(4) pairs per second from a laser-cooled atomic ensemble inside an optical cavity. A two-photon interference experiment demonstrated that the photons could be made 90% indistinguishable, a key requirement for quantum information-processing protocols. Used as a conditional single-photon source, the system operated near the fundamental limits on recovery efficiency (57%), Fourier transform-limited bandwidth, and pair-generation-rate-limited suppression of two-photon events (factor of 33 below the Poisson limit). Each photon had a spectral width of 1.1 megahertz, ideal for interacting with atomic ensembles that form the basis of proposed quantum memories and logic.     

The pathology of devil facial tumor disease (DFTD) in Tasmanian Devils (Sarcophilus harrisii)

A disfiguring and debilitating neoplastic condition known as devil facial tumor disease (DFTD) has been discovered in wild Tasmanian Devils (Sarcophilus harrisii) across 51% of its natural range, with population declines of up to 80% in some areas (C. Hawkins, personal communication). Between 2001 and 2004, 91 cases were examined. The tumors presented as large, solid, soft tissue masses usually with flattened, centrally ulcerated, and exudative surfaces. They were typically multicentric, appearing first in the oral, face, or neck regions. Histologically, the tumors were composed of circumscribed to infiltrative nodular aggregates of round to spindle-shaped cells, often within a pseudocapsule and divided into lobules by delicate fibrous septae. They were locally aggressive and metastasized in 65% of cases. There was minimal cytologic differentiation among the tumor cell population under light and electron microscopic examination. The results indicate DFTD to be an undifferentiated soft tissue neoplasm.     

Characterization of Newcastle disease viruses isolated from chicken,gamefowl, pigeon and quail in Mexico

Velogenic Newcastle disease has threatened the Mexican poultry industry since 1946. Seven strains of velogenic Newcastle disease virus were isolated from poultry and other avian species in central and northern Mexico from 1998 to 2006 and subjected to phylogenetic analysis and biological characterization using standard pathogenicity tests and challenge studies. Phylogenetic analysis showed that all velogenic strains belonged to genetic group V and are clearly divided in two lineages, since phylogenetic similarities between groups are of only 93–94%. Isolates from 1998 to 2001 are closely related to the strain responsible for the 2000 year outbreak raised in La Laguna region (Torreon strain), and are phylogenetically distinct from viruses isolated between 2004 and 2006 that are genetically related to the Chimalhuacan strain isolated in 1973. All the viruses of both, the Chimalhuacan and the Torreon groups, contained a virulent fusion protein cleavage site represented by the motif “GGRRQKRF”, revealing that evolutionary changes occurred at a different site. Chicken embryo mean death time value was shorter for the Chimalhuacan-like viruses (43.9 hours), when compared with the 1998–2001 average (54.3 hours). ICPI average value was higher (1.92) for viruses isolated during 2004–2006 than that for viruses isolated before 2001 (1.74). Microscopic evaluation of bursa of Fabricius and thymus of 5w-o broiler chickens challenged with 10⁶ LD₅₀/0.2 ml showed that Chimalhuacan-like isolate caused more severe lesions at 48 hpi in bursa and 72 and 96 hpi in thymus than Torreon-like isolate. Along with the MDT, ICPI and microscopic results, our findings suggest that some distinct selective pressure on the very virulent Chimalhuacan strain isolated in early 1970’s may have led to the appearance of the still velogenic but less virulent new group (Torreon-like) in the middle of 1990’s.     

Liquid chromatographic determination of narasin in feed premixes

A liquid chromatographic (LC) method has been developed to determine narasin in feed premixes. Narasin is extracted from the premix with a methanol-water solvent, and the extracted solution is assayed by using LC. Recovery of narasin from a 12.5 g/lb premix is quantitative (100%), with a relative standard deviation of 1.44%. The results correlated well (coefficient 0.92) with a turbimetric bioassay method.     

Morphine tolerance, physical dependence, and synthesis of brain 5-hydroxytryptamine

Tolerance and physical dependence development to morphine in mice can be prevented by concomitant administration of cycloheximide. The fact that the rate of synthesis of brain 5-hydroxytryptamine (5HT) increases with tolerance to morphine suggests that the protein involved may be associated with 5HT synthesis. Inhibition of this synthesis with p-chlorophenylalanine markedly decreases tolerance and physical dependence development to morphine.