Expression of tracheal differentiated functions in serum-free hormone-supplemented medium

Most dissociated airway epithelial cells in culture express few of their in vivo functions and only to a limited degree. In this report, we demonstrate that hamster tracheal epithelial (HTE) cells cultured on a collagen gel substratum in a serum-free hormone-supplemented medium differentiate to cilia-beating and mucus-secreting cell types. The medium is Ham's F-12 supplemented with insulin, epidermal growth factor, transferrin, hydrocortisone, cholera toxin, bovine hypothalamus extract, and vitamin A. Under these culture conditions, HTE cells exhibit a growth rate of 24 h/population doubling and reach confluency, at a density of 2-5 X 10(4) cells/cm2, within 2 weeks. Both the collagen gel substratum and vitamin A of this culture system are important to the growth and differentiation of HTE cells in vitro. Evidence of HTE cell differentiation has been obtained at both the ultrastructural and the histochemical levels. In addition, a variety of biochemical studies (gel filtration, ion exchange column chromatography, enzyme digestion, nitrous acid treatment, and composition analysis) indicate the production of mucin-like glycoprotein in the HTE cultures. The levels of mucin-like glycoprotein were found to closely correlate with the histochemically quantitated levels of the mucous cell type. Kinetic studies demonstrate that HTE cells rapidly lose their differentiated features during the attachment stage of primary culture but redifferentiation occurs after the cultures reach confluency. The ability of HTE cells to grow and differentiate in this serum-free culture system in the absence of other cell types should greatly facilitate the study of mucociliary functions in vitro.     

Does maternal condition or predation risk influence small mammal population dynamics?

There is strong debate over whether the intrinsic traits of individuals or the extrinsic environment exert the greater influence on small mammal population dynamics. We test the roles of maternal effects (an intrinsic factor) and predation risk (an extrinsic factor) in the population dynamics of wild strain house mice using a 2-factor enclosure experiment. Pre-release supplemental feeding with a high-fat diet created female treatment founders that were 6–10% heavier than controls, a condition that we predicted would be passed on as a maternal effect. Predation risk was enhanced using regular application of predator (red fox Vulpes vulpes ) scats. Founder populations of six females and six males released into eight, 15×15 m enclosures showed near exponential population growth over 17 weeks (maximum 3 generations). But there were no responses to either treatment in terms of survival, inherited body weights, fecundity or population size. We suggest that elevated maternal condition may have only minor and transient intergenerational effects with little long-term consequence. We also suggest that the general significance of predator scats as a cue to predation risk to alter prey behaviour may have been overestimated. Hence our results question the role of either factor in causing long-term responses that influence condition to affect population processes.     

Ecosystem function and species loss – a microcosm study

There are too many kinds of organisms to be able to study and manage each, yet the loss of a single species can sometimes unravel an ecosystem. Such `fusewire species'– critical in the same sense that an electrical fuse can cut out a whole circuit – would be a rewarding focus for research and management effort. However, this approach can only be effective if these `fusewires' represent but a small proportion of the number of species in the system.  

Aim

To demonstrate methods for measuring what proportion of the species in a system are critical to ecosystem function.  

Methods

The prevalence of fusewire species was measured in manipulative experiments on an aquatic microcosm.  

Results

No single genus deletion caused changes in key characteristics of the system.  

Main conclusions

Comparison of these results with other published studies shows that the proportion of critical fusewire species varies amongst different ecosystems. The oxidation pond microcosms were shown to contain no single species indispensable to system function. They appear to be ill-suited to a management strategy which focuses on priority eukaryote species. However, a single study provides no evidence that this result is general or even typical of other kinds of ecosystems; it is presented here as an empirical model. Other methods of investigation are available; they are less experimentally rigorous but more practical. These could provide important guidance in planning an approach to management in a particular ecosystem.     

Folylpolyglutamates in Leishmania major

The intracellular folates of the protozoan parasite Leishmania major have been examined. About 95% of the exogenous [3H]folate accumulated by the protozoan is metabolized to polyglutamate conjugates within 65 hr, and the intracellular folates are about forty-fold concentrated over the folate in the medium. The predominant metabolite of folic acid is the pentaglutamate conjugate (85%), with lessor amounts of the tetraglutamate (approximately 9%) and hexaglutamate (approximately 3%), and trace (less than 2.5%) amounts of di-, tri- and hepta-glutamate conjugates. Chromatographic properties of the products indicate that the conjugates are linked through the gamma-carboxyl groups. The folylpolyglutamate distribution in Leishmania is similar to that found in mammalian tissues.     

A gastric trichobezoar in a chimpanzee

A firm, mobile, oblong mass was discovered as an incidental finding in the stomach of a chimpanzee (Pan troglodytes) during routine surgery. It was removed and determined to be a trichobezoar.     

Genetic transformation of Medicago truncatula using Agrobacterium with genetically modified Ri and disarmed Ti plasmids

Summary Fertile transgenic plants of the annual pasture legume Medicago truncatula were obtained by Agrobacterium-mediated transformation, utilising a disarmed Ti plasmid and a binary vector containing the kanamycin resistance gene under the control of the cauliflower mosaic virus 35S promoter. Factors contributing to the result included an improved plant regeneration protocol and the use of explants from a plant identified as possessing high regeneration capability from tissue culture. Genes present on the T-DNA of the Ri plasmid had a negative effect on somatic embryogenesis. Only tissue inoculated with Agrobacterium strains containing a disarmed Ti plasmid lacking the T-DNA region or a Ri plasmid with an inactivated rol A gene regenerated transgenic plants. Fertile transgenic plants were only obtained with disarmed A. tumefaciens, and the introduced NPT II gene was transmitted to R₁ progeny.Abbreviations BAP 6-benzylaminopurine - NAA 1-naphthaleneacetic acid - NPT neomycin phosphotransferase