Incidence of Enterotoxigenic Clostridium perfringens in Healthy Humans in relation to the Enhancement of Enterotoxin Production by Heat Treatment

Enterotoxin production was greatly enhanced in two of five food poisoning strains of Clostridium perfringens subjected to heat treatment prior to incubation in Duncan and Strong sporulation medium. Heating was carried out on three successive cultures of each strain, the optimum temperature for treatment being 85 °C for one strain and 95 °C for another: on each occasion cultures were heated for 20 min. The triple heat treatment procedure was used in testing strains of Cl. perfringens isolated from faeces of healthy human subjects for production of enterotoxin. Eleven of 35 (31%) individuals were found to be carriers of enterotoxigenic strains, the isolates producing more than 0·1 μ/ml of enterotoxin. Six of the 11 enterotoxigenic strains were killed by heating at 95 °C but one isolate produced more enterotoxin following treatment at this temperature than after heating at 75 °C.     

Detection of Enterotoxin in Faeces and Anti-enterotoxin in Serum after Clostridium perfringens Food-poisoning

Two outbreaks of Clostridium perfringens food-poisoning involving the same person were investigated. In the first, typical symptoms with diarrhoea and abdominal pain were observed. In the second, there were no classical signs of food-poisoning; the victim felt some flatulence and the faeces had a pasty appearance and an unpleasant smell. Counterimmunoelectrophoresis and the reversed passive haemagglutination test were rapid and reliable assay methods for enterotoxin in faeces. In the first outbreak, 13–16 μg enterotoxin/g faeces were detected, and 3–4 μg/g in the second. The detection of enterotoxin in faeces indicates the potential use of enterotoxin tests on diarrhoeal samples for diagnosing C. perfringens food-poisoning. No enterotoxin was detected in serum during the acute stage of the illness, but the antibody titre showed a considerable rise in the first two months after the food-poisoning outbreak.     

Experimental Diarrhoea in Human Volunteers Following Oral Administration of Clostridium perfringens Enterotoxin

Peroral administration of purified enterotoxin to human volunteers provoked diarrhoea and abdominal pain, symptoms identical with those encountered in outbreaks of Clostridium perfringens food poisoning. Eight milligrams of enterotoxin caused diarrhoea in one of two volunteers. All of five subjects given 10 and 12 mg of purified enterotoxin or crude enterotoxin developed the classical symptoms of this food poisoning. Passive haemagglutination anti-enterotoxin titres in serum increased in only 5 of 9 volunteers after exposure to enterotoxin. As such levels of anti-enterotoxin can be detected in normal serum samples, titration of anti-enterotoxin may be of little use in diagnosing Cl. perfringens food poisoning. Enterotoxin was detected in all diarrhoeal faecal specimens, and the enterotoxin level varied from 0·2–16 μg/g. Detection of enterotoxin in diarrhoeal faeces may be the most reliable procedure in diagnosing outbreaks of Cl. perfringens food poisoning.     

INITIATION OF CLEAVAGE IN FISH EGGS BY INJECTION OF FLAGELLA OR MICROTUBULES OF SEA URCHIN SPERMATOZOA

Flagella and their microtubules obtained from sea urchin ( Hemicentrotus pulcherrimus ) spermatozoa were injected into unfertilized eggs of the medaka ( Oryzias latipes ) with a micropipette. Upon activation, some of the eggs began the first cleavage with three or more irregular blastomeres, and developed to the morula stage. It is suggested that sperm flagellar microstubule material is one of the cleavage initiation substances.     

Role of male‐biased dispersal in inbreeding avoidance in the grey‐sided vole (Myodes rufocanus)

Effects of male‐biased dispersal on inbreeding avoidance were investigated in a semi‐natural population of Myodes (formerly Clethrionomys) rufocanus using a large outdoor enclosure (3 ha). Parentage of 918 voles weaned from 215 litters and relatedness of mates were analysed using microsatellite loci, and dispersal distances were obtained from mark–recapture live‐trapping data. Natal and breeding male‐biased dispersal was observed. There remained, however, chances that incestuous mating could occur, because not all males dispersed from their natal site, and 51 matings occurred between relatives (relatedness r > 0). The number of weaned juveniles from inbred litters was significantly smaller than that from non‐inbred litters. Fourteen incestuous matings occurred between close relatives (r ≥ 0.25), most of which were those between non‐littermate maternal half siblings (four cases) and those between paternal half siblings (seven cases). When comparing the observed frequencies to the expected ones generated by combining every oestrous female with a male randomly chosen from her surroundings, the observed values for inbreeding of r ≥ 0.25 were significantly smaller than the expectations, while no difference was observed for inbreeding of 0 < r < 0.25. These results suggest that male‐biased dispersal is partly effective to avoid incestuous mating, but it does not provide complete separation of male and female close relatives. Additional mechanisms such as kin discrimination based on familiarity may work in inbreeding avoidance of the vole.     

Allelic and genotypic diversity in long-term asexual populations of the pea aphid, Acyrthosiphon pisum in comparison with sexual populations

Many aphid species exhibit geographical variation in the mode of reproduction that ranges from cyclical parthenogenesis with a sexual phase to obligate parthenogenesis (asexual reproduction). Theoretical studies predict that organisms reproducing asexually should maintain higher allelic diversity per locus but lower genotypic diversity than organisms reproducing sexually. To corroborate this hypothesis, we evaluated genotypic and allelic diversities in the sexual and asexual populations of the pea aphid, Acyrthosiphon pisum (Harris). Microsatellite analysis revealed that populations in central Japan are asexual, whereas populations in northern Japan are obligatorily sexual. No mixed populations were detected in our study sites. Phylogenetic analysis using microsatellite data and mitochondrial cytochrome oxidase subunit I (COI) gene sequences revealed a long history of asexuality in central Japan and negated the possibility of the recent origin of the asexual populations from the sexual populations. Asexual populations exhibited much lower genotypic diversity but higher allelic richness per locus than did sexual populations. Asexual populations consisted of a few predominant clones that were considerably differentiated from one another. Sexual populations on alfalfa, an exotic plant in Japan, were most closely related to asexual populations associated with Vicia sativa L. The alfalfa-associated sexual populations harboured one COI haplotype that was included in the haplotype clade of the asexual populations. Available evidence suggests that the sexuality of the alfalfa-associated populations has recently been restored through the northward migration and colonization of alfalfa by V. sativa- associated lineages. Therefore, our results support the theoretical predictions and provide a new perspective on the origin of sexual populations.     

Kinetin-like factors in the root exudate of rice plants

Kinetin-like substances were separated from the root exudateof rice plants. Their biological activities were estimated bya chlorophyll preservation test and a cell-division promotingactivity. Ethanolic extracts of the root exudate contained threeactive substances. The chromatographic behaviour of these substancesare similar to those of zeatin, and its nucleoside and nucleotide. (Received July 3, 1970; )     

Stimulative effect of potassium ion on starch synthetase of different plant origins

The stimulative effect of K⁺ on the activity of granule-boundstarch synthetase was uniformly observed in the enzyme preparationsobtained from the root, leaf and stem of sweet potato plants.The stimulation of K⁺ was most marked with the sweet potatoenzyme, while the broad bean enzyme was also appreciably stimulated.The K⁺-effect was very small in the enzyme from rice, barleyand taro plants. (Received October 25, 1968; )     

Ascorbate photo-oxidation by a photochemically active chromoprotein isolated from the blue-green alga Anabaena cylindrica: the effect of monochromatic illumination

Ascorbate photo-oxidation by a photochemically active chromoproteinisolated from the blue-green alga Anabaena cylindrica was studiedunder monochromatic illumination. Results indicate that die chromoprotein consists of at leasttwo pigments, both of which act as light-energy receptors forascorbate photo-oxidation. (Received May 11, 1971; )