Induction of 2n pollen in tulips by arresting the meiotic process with nitrous oxide gas

Triploid tulips have agronomically desirable traits such as vigorous growth and large flower size, but only a portion of all cultivated tulips is triploid. To apply 2n pollen to polyploid breeding of tulips, the polyploidizing agent, nitrous oxide gas (N₂O), was applied to bulbs. In tulips, meiosis in anthers occurs inside the bulbs from mid- to late-October. When meiosis in anthers (excised from bulbs) reached metaphase I, we treated other bulbs of the same clones with N₂O for 24–48 h. Most of the treated plants produced pollen grains with a wide-ranging or bimodal size distribution, indicating a mixture of n, 2n and aneuploid pollen grains. The use of pollen containing a relatively high proportion of giant pollen grains tended to yield larger numbers of triploids in the progeny. The number of giant pollen grains could be increased when N₂O-treated pollen grains were suspended in 10% sucrose and then sieved through a nylon mesh. Very few polyploids were observed in some cross combinations, even those involving pollen with a relatively high proportion of giant grains. Even so, this low polyploid yield most likely is due to a triploid block, because the capsules obtained in the crosses of the diploid×N₂O-treated plants contained some abnormal seeds, which were mostly triploid. Embryo culture was useful in rescuing abnormal embryos. The present study reveals that 2n pollen can be produced at high frequency using N₂O during tulip breeding.     

Parental Contributions in a Japanese Flounder Hatchery Inferred from Mitochondrial DNA Haplotypes

We analyzed a portion of the mitochondrial genome of hatchery Japanese flounder Paralichthys olivaceus to compare the genetic characteristics between maternal parents and their offspring. The maternal parents consisted of 11 subcultured fish (broodstock taken from hatchery-raised fish) and 41 wild fish. A 1098 base pair region extending from the 3'half of the cytochrome b gene to the central domain of the control region of mtDNA was amplified by PCR and analyzed using 11 restriction endonucleases. We also analyzed the number of copies of tandem repeats in the control region from the sizes of the PCR products. Each female parent had a unique haplotype, but only 31 of them were observed among the 66 offspring examined. From these results, we estimated that about 60% of the maternal parents in the hatchery contributed to the offspring we surveyed. The distribution of the family sizes of the wild fish was Poisson, which is consistent with expectation from a randomly mating population. In contrast, the distribution of family sizes of the subcultured fish deviated from a Poisson distribution. One of the sources of the deviation was that none of the six oldest fishes contributed to offspring production, which is consistent with observation that the spawning peaks later in the spawning season for older fish in flounder hatcheries. Uneven contribution of the female flounders in the hatchery has the potential to reduce substantially the genetic diversity in the offspring. Our results suggest that the misuse of subcultured fish as broodstock is an important cause of reduced genetic diversity in hatchery-raised flounder juvenile.     

Maternal and genetic effects on individual variation during early development in Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

ABSTRACT:   To investigate the changes in maternal effects during early development in Japanese flounder Paralichthys olivaceus , four-by-four factorial mating by artificial fertilization was performed to produce 16 families. Larvae and juveniles of each family were reared under common environmental conditions until completion of metamorphosis. The magnitude of maternal effects was estimated as the differences between sire and dam variance. Maternal effects were highest at hatching, and then disappeared at 30 days after hatching. During early development, larval size at hatching was largely affected by egg size, but this effect decreased as larvae grew. Estimated mean heritability during early development was nearly constant (0.14 ± 0.06 for total length and 0.10 ± 0.05 for body depth). Therefore, it is suggested that early development in Japanese flounder is affected by both maternal effect and genetic factors.     

Production and some properties of cytotoxins produced by Campylobacter species isolated from proliferative enteropathy in swine.

Cytotoxin production by Campylobacter species isolated from proliferative enteropathy in swine was examined. Twenty-one of 29 strains of C. hyointestinalis, 10 of 27 strains of C. mucosalis and 10 of 10 strains of C. coli were cytotoxin positive. By the gel filtration chromatography of C. hyointestinalis culture filtrate, cytotoxin activities were observed in two peaks (fraction I and fraction II). Most of the cytotoxic activities lay in fraction I, which is heat-labile, trypsin-sensitive and the molecular weight was estimated at 40,000. On the other hand, fraction II cytotoxin was heat-stable, trypsin-insusceptible and molecular weight was approximately 1,000.     

Geographical variation in skull morphology of gray-bellied squirrel Callosciurus caniceps

The geographical variation of the gray-bellied squirrel (Callosciurus caniceps) was examined using osteometry of skull in Southeast Asia. From the principal component analysis (PCA), the plots of the northern localities from Nan to Kanchanaburi and those of the southern localities from Narathiwat to Kuala Lumpur in male were completely separated. In female, the plots of the locality from Uttradit to Kanchanaburi and those of the locality from Pattani to Negri Sembilan were completely separated. We called these northern localities and southern localities which are distinguished by the PCA as N group and S group. The size and shape of the skulls of these squirrels indicated the differences between N group and S group from t-test and U-test. These results may be influenced by the two transitions of the phytogeography around the southernmost locality in N group and the northernmost locality in S group in the peninsular Thailand and Malay Peninsula. Localities which are located between N and S groups were called the Middle (M) group. From the PCA among N, S groups and each locality of M group, the plots of localities such as Prachuap Khiri Khan, Chumphon, Krabi, Nakhon Si Thammarat and Trang in both sexes of M group could not be separated from those of N and S groups. We suggest that the sympatric distribution of N and S groups and the hybrid of N and S populations may be seen in these localities of M group.     

Colitis associated with Clostridium difficile in specific-pathogen-free C3H-scid mice

Soft feces and a decreased delivery rate were observed in a specific-pathogen-free (SPF) C3H-scid mouse breeding colony. Grossly, the ceca were shrunken and edematous in the affected mice. Histopathologically, severe edema in the cecal submucosa as well as infiltration of inflammatory cells in the lamina propria and submucosa of the ceca and colon were observed. No pathogenic microorganisms were detected by the routine microbiological tests. By anaerobic bacterial-examination, Clostridium (C.) difficile with toxin A was isolated from the cecal contents of the affected mice. The mice were diagnosed with C. difficile-associated colitis. This case appears to be the first report of natural infection with C. difficile in SPF mice with clinical signs.     

Studies on inter-relationship of various ions in absorption by tobacco plants IV

The foliar symptoms of magnesium deficiency occur not only by the decrease in the contents of exchangeable magnesium in soil, but the antagonistic interaction among the nutrient elements in absorption. The relationship between phosphorus and magnesium in absorption was reported previously (1). In this paper influence of potassium and calcium on the magnesium absorption of tobacco plant was investigated.     

Studies on interrelationship of various ions in absorption by tobacco plants (Part 1) relation of nitrogen forms and cation levels in culture solution

The nutrient absorption by tobacco plants is sensitve to the condition of culture media, as a close absorbing relationship is kept among various nutrient elements. Tobacco plant, comparing with other plants, contains inorganic bases in its tissue in especially large amounts as against other inorganic elements. The reciprocal proportion of various bases has a great influence upon the growth and the quality of the leaf.     

Comparison of Salmonella enterica serovar Abortusequi isolates of equine origin by pulsed-field gel electrophoresis and fluorescent amplified-fragment length polymorphism fingerprinting

Equine paratyphoid is caused by Salmonella enterica serovar Abortusequi, and manifests mainly as abortion in the mare. We compared S. Abortusequi strains isolated in Japan and other countries using pulsed-field gel electrophoresis (PFGE) and fluorescent amplified-fragment length polymorphism (FAFLP) analysis. PFGE analysis of S. Abortusequi strains gave 21-27 fragments ranging in size from 33 to 602kb. Although two PFGE profiles were observed among the 20 S. Abortusequi isolates in Japan, the restriction fragments originating from the chromosome were common between the two profiles. The similarity index of the two profiles was 90.9%, while those between Japanese and five other S. Abortusequi strains were 29.8-37.5%. On the other hand, FAFLP analysis of S. Abortusequi strains generated 64-67 amplified fragments ranging in size from 100 to 400bp. One polymorphic fragment was observed among the 20 S. Abortusequi isolates in Japan. These data indicate the close relation of this agent in Japan. S. Abortusequi strains sharing a common ancestry might have been conserved in Japan.