Plasmodium berghei NK65 in the Inbred A/J Mouse: Variations in Virulence of P. berghei Demes*

SYNOPSIS. Plasmodium berghei NK65 was passed thru Anopheles stephensi to golden hamsters and mice. The percent cumulative mortality was compared after each mosquito passage in early (7–13) blood passages. The strain was found to have divided into demes (populations) retaining original virulence and demes which were less virulent. The separation of virulent and less virulent demes was traced to its origin. Both virulent and less virulent demes can be passed thru mosquitoes and hamsters. No concomitant organism has been identified.     

Description of a new species Anopheles (Cellia) kosiensis (Diptera: Culicidae) from Zululand, South Africa

ABSTRACT. The Anopheles marshallii group of mosquitoes consists of four chromosomally typed species of which three have already been described and named. The fourth chromosomal species, formally known as species E, is described here as Anopheles kosiensis from Kosi Bay, Zululand, South Africa. A photograph of the X chromosome is given. The taxonomic status of Anopheles pitchfordi , a synonym of marshallii , is discussed.     

FRESHNESS IN ORAL CARE: ATTRIBUTES AND TIME-DEPENDENCY OF A MULTIDIMENSIONAL, DYNAMIC CONCEPT

This article describes an exploration of the concept of 'oral freshness' for as far as it is important in oral care. It intends to consider the most important mouth sensations and cognitive connotations, including (but not restricted to) the well-known effect of menthol in toothpaste.
Two aspects were given attention:
(1) The attributes that together form the concept of oral freshness were investigated using a 'personal construct approach'(Kelly 1955). This method consists of unbiased, structured interviews with subjects, and ultimately yields attribute dimensions that the subjects have in common.
(2) The intensity of the freshness sensation over time was investigated using the Time-Intensity method. Subjects gave repeated freshness judgments every few seconds after the intake of a freshness-related stimulus, and continued to do so after the stimulus had left their mouth. In addition we asked for 'overall' freshness judgments directly after the TI-measurements and after 2 months.
The results confirm that 'oral freshness' is a complex concept. We identified 6 attributes, some of which were perceptual/physiological and some cognitive in nature: 'water'-ness, cool/cold-ness, taste (menthol-ness), clean-ness, smell, energy (texture and touch, e.g., bubbles). Different persons will generally give different importance weights to each of these 6 attributes.
Time-intensity measurements show that temperature, menthol-content and, to some extent, the presence of bubbles (energy) influence the momentous sensation of freshness. It appears, however, that in the way freshness is remembered after a few months, mainly cleanness and taste (menthol-ness) are important. Apparently, people tend to value (temporary) sensory input during the actual freshness experience, but tend to remember the freshness result in the longer run.     

Phylogeography of the Marsh Fritillary Euphydryas aurinia (Lepidoptera: Nymphalidae) in the UK

We sampled extant (and extinct) populations of Euphydryas aurinia to examine the phylogeography of the species in the UK. We were interested in whether the genetic structuring of populations reflects anything other than a single recent post-glacial colonization event. Four hundred base pairs of the mitochondrial Cytochrome b gene were sequenced from individuals from populations throughout the UK, as well as populations in France and Portugal and seven polymorphic allozyme loci resolved. The mean number of allozyme alleles per locus was 4 and isolation by distance was shown not to be a factor in the geographic structuring of genetic diversity either with or without the inclusion of the French data (Mantel statistic Z = 0.015 and 0.112 respectively, P >0.5). Cytochrome b nucleotide diversity (average number of nucleotide differences per site between two sequences) was low overall (0.003, n = 63) but mean cytochrome b gene diversity over all populations was 0.77. The presence of the Portuguese and French haplotype in Scottish populations indicates that the Iberian peninsula was likely to be one glacial refugium for E. aurinia populations. The pattern of mitochondrial DNA found in the UK could be interpreted in one of two ways: (1) two separate colonization events or (2) a single slow colonization event. Allele frequency distributions followed a similar geographical pattern as mitochondrial DNA haplotypes. An AMOVA assigned just 2.68% of allozyme genetic variation to the grouping tested, providing more support for the single colonization event theory.     

THE PRODUCTION OF ANTIBIOTICS IN SOIL: II. PRODUCTION OF GRISEOFULVIN BY PENICILLIUM NIGRICANS

A study has been made of the conditions affecting production of griseofulvin by Penicilliiim nigricans in two types of soil, an acid, sandy podsol from Wareham Heath and a garden soil. The characteristic morphogenetic response of many fungi to low concentrations of griseofulvin was made the basis of a highly specific bioassay.
The essential prerequisites for production of griseofulvin in either soil were sterilization and enrichment with organic matter; no griseofulvin could be detected in autoclaved soil which had not been supplemented or in normal soil even when organically enriched. Garden soil was a better medium for growth of P. nigricans and production of griseofulvin than Wareham soil although this soil could be improved in this respect by liming.
The yield of griseofulvin was decreased in soil re-infected by other soil organisms, particularly by some which were known to produce antifungal antibiotics, e.g. Penicilliunr expansum, P. frequentons and two strains of Trichoderma viride. The antagonism shown to Penicilliunz nigricuns was not entirely a matter of antibiotic activity, as some fungi believed not to produce antifungal substances had an antagonistic effect. These were mostly fungi with a characteristically rapid growth rate, e.g. Mucor rarnmannianus and one strain of Trichoderma riride. In some cases Penicillium nigricans was itself antagonistic to other fungi irrespective of their ability to produce antibiotics or of their fast-growing habit.
The results were compared with those obtained from a previous study of the soil conditions affecting the production of gliotoxin by Trichoderma viride. A higher level of nutrient was required for the production of griseofulvin, and the effect of antagonism by other soil micro-organisms was more important than in the production of gliotoxin by T. viride in the soil.     

Effects of 1-methylcyclopropene alone and in combination with polyethylene bags on the postharvest life of mango fruit

Experiments were conducted to determine how 1‐methylcyclopropene (1‐MCP) treatments influence ethylene‐stimulated ripening of harvested mango cv. Zihua fruit at 20°C. The ripening response of fungicide (prochloraz) treated fruit was characterised following various 1‐MCP treatments in sealed jars followed by storage in polyethylene bags and/or subsequent ethephon (ethylene) exposure. Exposure of fruit to increasing concentrations of 1‐MCP for 12 h resulted in the reduced softening of produce when subsequently held in air for 7 days after ethephon treatment. Application levels of between 1 and 100 μl litre^?1 1‐MCP had increasing impact, while 200 μl litre^?1 1‐MCP apparently began to approach response saturation. Exposure of fruit to 50 or 100 μl litre^?1 concentrations of 1‐MCP for periods from 1 to 24 h subsequently resulted in reduced softening of produce when held in air for 7 days after ethephon treatment. Increasing periods of exposure from 1 to 12 h had increasing impact, while exposure times greater that 12 h appeared to reach saturation. In the absence of ethephon‐stimulation, the natural ripening of mangoes held in polyethylene bags was delayed by prior exposure to 100 μl litre^?1 1‐MCP for 12 h. Extended holding of 1‐MCP treated and non‐1‐MCP treated control fruit in polyethyene bags encouraged physiological and pathological deterioration. Following exposure to 100 μl litre^?1 1‐MCP for 12 h, mango fruit held for 10 days in polyethylene bags showed a delay in the onset of ripening relative to bagged but non‐1‐MCP treated control fruit. Treatment with 1‐MCP allowed storage of mango fruit in plastic bags at 20°C for 30 days. Observations suggest that 1‐MCP treatments do not adversely influence the quality of the post‐storage ethephon‐ripened fruit. Thus, application of 1‐MCP in combination with the use of polyethylene bags can extend the postharvest life of mango fruit at ambient temperature. Treatments that extend postharvest life are important in developing countries, such as China, where the cold chain infrastructure is often lacking.     

Re-establishment of the lady's slipper orchid (Cypripedium calceolus L.) in Britain

The Sainsbury Orchid Conservation Project (SOCP), based in the Micropropagation Unit of the Royal Botanic Gardens, Kew, has worked for many years with English Nature, and the Species Recovery Programme in particular, in raising plants of the lady's slipper orchid for re-establishment. This is a collaborative venture with the involvement of a large number of organizations and individuals at national and local level.Cypripedium calceolusis one of Britain's rarest plants. Thought at one time to be extinct, its decline is due to overcollection by botanists for herbarium specimens and by gardeners and it is found now on a single, fragile, natural site. It has been wardened since 1970s because of concerns about long-term safety and is protected under Schedule 8 of the Wildlife and Countryside Act 1981. Natural pollination has not been observed and hand pollination is carried out to ensure seed set. Some seed is scattered on site resulting in a few seedlings and the remaining capsules are sent to the Sainsbury Orchid Conservation Project. In addition, some plants of native origin are held in cultivation and molecular techniques are being carried out at Kew to ascertain how these are related. The best pollination strategy to increase genetic diversity is co-ordinated by English Nature and SOCP, as is the optimum collection time post-pollination to achieve maximum germination. Seedlings are propagated in the laboratory using immature green capsules sown on a range of nutrient media. No symbiotic fungus has yet been found for this species. Germination occurs after 6 weeks in the dark and the plants chilled when roots are well developed and shoots beginning to form. Plants potted up at Kew and near the native site have produced leaves and buds and extensive planting trials have now commenced. The main objective is to increase the number of localities whereCypripediumoccurs through re-establishment. As its decline is due to overcollection rather than habitat loss, many old sites have changed very little. Observation of continental populations is important in assessing suitability of potential sites as the extant clone may not be in optimum conditions. An initial planting trial on the wild site in winter 1989/90 resulted in a 75% survival rate of seedlings planted out. However, establishing seedlings is a long process and careful monitoring is required.