Characterization of Rat CD4 T Cell Clones Specific for the Major Surface Glycoprotein of Pneumocystis carinii

ABSTRACT. Pneumocystis carinii are coated by abundant heterogenous major surface glycoproteins (MSGs), which facilitate interaction with the host. We have produced MSG-specific T-cell clones from the spleens of P. carinii -exposed Lewis rats and analyzed five for antigen specificity to native MSG and a recombinant form of MSG, cell surface markers, and cytokine profiles. All five of the clones were CD4+. All of the clones proliferated specifically to both the native MSG and the recombinant MSG only in the presence of antigen presenting cells demonstrating that the response is antigen/driven rather than mitogen/driven. All five of the clones secreted IL-2 and IFN-γ, although in differing amounts, implicating a Th l response. Only one of the clones produced any detectable IL-4. This is the first report of T cell clones responsive to a specific antigen of P. carinii , MSG. We conclude that the T cell clones will be helpful in mapping protective epitopes present in MSG and in functional studies of MSG.     

Surface-feeding on cephalopods by procellariiform seabirds in the southern Benguela region, South Africa

Cephalopod beaks recovered from stomach samples taken from 14 seabird species in the southern Benguela region off Southern Africa and from one species at Sub-Antarctic Marion Island, were identified as far as possible, counted and the lower rostral lengths (LRLs) measured. Dorsal mantle lengths (DMLs) and body masses of the cephalopods eaten were estimated. The results of analyses by percentage frequency of occurrence and numerical abundance are discussed with reference to present knowledge of the distribution of cephalopods eaten by seabirds in the areas studied. Division of the cephalopod component of seabird diets into species which float, and species which sink, after death indicates that the birds forage on dead or moribund cephalopods on the surface, rather than catching live bioluminescent cephalopods at night.     

Variation in total phenols and condensed tannins in Eucalyptus: leaf phenology and insect grazing

Total phenols and condensed tannins in leaves of seven species of Eucalyptus ranged from 4–40% and 0–27% respectively of the leaf dry weight. The concentrations of these compounds were variable but usually high in young and older leaves throughout the growing season, and typically increased during winter, but no other trends with season or leafage were apparent. This pattern of seasonal variation in concentrations of total phenols and condensed tannins is different to that studied for other plant species. This difference may be related to repeated production of new leaves by Eucalyptus during the growing season, and the probability that these leaves will be attacked by herbivorous insects.     

Loss of genetic diversity in pea germplasm by the elimination of individuals infected by pea seedborne mosaic virus

Significant reduction of genetic diversity was observed in seed coat colour and electrosphoretic isozyme genotypes when infected plants were eliminated in genetically heterogeneous pea populations. Some accessions where genetic homogeneity was expected were apparently mixtures. Detection of latent infections by pea seedborne mosaic virus by the ELISA method was more effective on single-plant samples than on bulked samples of four to five plants, and from older plants rather than young seedlings. The implication of these findings in relation to a virus eradication programme in plant germplasm collections are discussed.     

Diet and habitat use of moulting Greylag Geese Anser anser on the Danish island of Saltholm

The diet and habitat use of moulting Greylag Geese Anser anser were studied at the recently established moulting site on the island of Saltholm, between Denmark and Sweden. Classification of the vegetation in the area most used by Greylag Geese during their moult showed that the geese selected low saltmarsh habitats which were richest in Common Saltmarsh- grass Puccinellia maritima and that dropping density was highly correlated with Puccinellia cover. Geese showed slowest step rates and highest peck rates in vegetation types rich in Puccinellia. Examination of faecal material confirmed that the geese fed almost exclusively on PuccineEia during the main moult period, despite its limited spatial distribution. Puccinellia maritima exhibited the highest levels of protein of any of the graminoid species present except for the belowground lower stem base of Sea Club-rush Scirpus maritimus, which offers a nongrowing food resource which is difficult to extract and consume. The results of this study suggest that the statement that the "limited data available for moulting waterfowl indicate no active selection for proteinaceous foods; i.e., birds are selecting foods in proportion to their availability" does not hold for Greylag Geese moulting on Saltholm.     

Interocular Transfer of Adaptation to Spatial Frequency during Retinal Ischaemia

PROLONGED inspection of a grating pattern of repetitive light and dark contours produces a transient reduction in the visibility of low-contrast gratings the spatial frequency and orientation of which are similar to that of the inspected grating. This after-effect, often referred to as adaptation, occurs even when one eye performs the inspection and its partner is tested. Certain properties of this after-effect, with other data, suggest that its locus is visual cortex^1–7, but the evidence is largely indirect because of the difficulty of identifying sites of action within the stages of the human visual system. One of the few techniques available for inferentially partitioning the visual system stages is retinal pressure blinding, a heroic but effective method for functionally uncoupling the retina from higher stages^8–11.