Human T cell responses to the Epstein-Barr nuclear antigen-1 (EBNA-1) as evaluated by synthetic peptides

A panel of synthetic peptides derived from Epstein-Barr virus (EBV) nuclear antigen 1 (EB-NA-1) was used to examine human T cell responses to this antigen. In six of seven normal persons with past EBV infection, T cell precursors specific for five peptides (P27, amino acid residues 83-101;P62, 148-166;E31, 353-367;E41, 368-381; and E11, 461-474) were detectable. The precursor frequencies were in the range of 1:20,000 to less than 1:100,000 peripheral blood mononuclear cells as determined by limiting dilution analyses. Only two of these peptides were predicted as alpha-helices; all peptides were glycine-rich. Four other peptides were not reactive in the seven individuals tested. T cell responses were not detectable in donors without prior EBV infection. Infectious mononucleosis patients investigated 4-6 weeks after diagnosis had likewise no detectable peptide-specific T cell precursors. Thus, it appears that T cells recognizing peptides from EBNA-1 arise and persist in people with past EBV infection.     

Oxidation of glycated proteins: age-dependent accumulation of N epsilon-(carboxymethyl)lysine in lens proteins

N epsilon-(Carboxymethyl)lysine (CML) has been identified as a product of oxidation of fructoselysine (FL) in glycated (nonenzymatically glycosylated) proteins in vitro and has also been detected in human tissues and urine [Ahmed et al. (1986) J. Biol. Chem. 261, 4889-4894]. In this study, we compare the amounts of CML and FL in normal human lens proteins, aged 0-79 years, using specific and sensitive assays based on selected ion monitoring gas chromatography-mass spectrometry. Our results indicate that the lens content of FL increases significantly between infancy and about age 5 but that there is only a slight, statistically insignificant increase in FL between age 5 and 80 (mean +/- SD = 1.4 +/- 0.4 mmol of FL/mol of Lys). In contrast, the lens content of the oxidation product, CML, increased linearly with age, ranging from trace levels at infancy up to 8 mmol of CML/mol of lysine at age 79. The ratio of CML to FL also increased linearly from 0.5 to 5 mol of CML/mol of FL between age 1 and 79, respectively. These results indicate that CML, rather than FL, is the major product of glycation detectable in adult human lens protein. The age-dependent accumulation of CML in lens protein indicates that products of both glycation and oxidation accumulate in the lens with age, while the constant rate of accumulation of CML in lens with age argues against an age-dependent decline in free radical defense mechanisms in this tissue.     

Behavioural, biochemical and histological effects of trimethyltin (TMT) induced brain damage in the rat.

To assess the nature and extent of behavioural, biochemical and histological changes induced by trimethyltin (TMT), rats were treated with a single injection of TMT over a dose range of 6, 7 and 8 mg/kg i.p. Behavioural observations were performed at a minimum of 21 days after the administration of TMT. The behavioural consequences of TMT were hyperactivity in the open-field test, increased locomotor activity and deficits in passive and active avoidance behaviour, T-maze alternation and Morris Water Maze behaviour. The behavioural changes were dose dependent and were accompanied by a degree of pathological damage to the hippocampal pyramidal cells which was particularly apparent at the highest dose. The main biochemical effects of TMT involved deficits in the serotonergic and GABA-ergic systems and a decrease in M1 and M2 binding sites in the hippocampus. These results suggest that the toxic interaction of TMT with the hippocampus and other limbic brain regions may be responsible for its effect on learning and memory.     

Differences in learning by foraging juvenile pumpkinseed and bluegill sunfish in a structured habitat

Synopsis We investigated the ability of two congeneric species of sunfish to learn to forage on a novel prey item in feeding arenas containing structured habitats. Eight bluegill sunfish and eight pumpkinseed sunfish were given the opportunity to forage on whiteworms daily for 10 days. Each day, several behavioural measures were recorded for each fish. Both species of sunfish learned to feed over the 10-day period but the bluegill sunfish learned to feed more quickly than the pumpkinseed sunfish. Pumpkinseeds, however, attained a higher level of foraging efficiency. The differences in learning and foraging efficiency were related to body morphology.     

Effects of abscisic acid on somatic embryo maturation of hybrid larch

Somatic embryos of hybrid larch (Larixleptoeuropaea) whichhad been matured for 4 weeks on maturation medium, developednormally on medium supplemented with 60 µM ABA, but abnormallyon medium with no ABA. A comparative structural and histochemicalinvestigation was carried out on these two types of mature embryos.At the light microscope level, differences between both treatmentswere visible only after 2–3 weeks of maturation. At aroundthis time, abnormal development becomes evident macroscopically:ABA-minus embryos remain rather stubby as opposed to the morecylindrically shaped ABA-plus embryos. Whereas somatic embryosmatured with ABA consist of densely cytoplasmic cells showinga high rate of cell division, ABA-minus embryos are largelymade up of expanded and highly vacuolate cells, indicating thatgrowth in the latter is mainly due to cell expansion and notdivision. After 4 weeks of maturation, ABA-minus embryos beginto elongate in the hypocotyl region, and precocious germinationwas observed frequently. Again, these morphogenetic events werelargely due to abnormal timing of cell expansion. Histochemically,storage proteins were found only in somatic embryos maturedfor 4 weeks with ABA. This observation is in line with resultsobtained by total protein analysis, yielding significantly lowertotal protein contents in ABA-minus embryos both on a freshweight and a per embryo basis after 4–5 weeks of maturation.Deposition of starch grains mainly in the cortex tissue of thehypocotyl region was observed within 2 weeks of maturation invarying amounts regardless of ABA supply. Polyphenols, in particularcatechins and proanthocyanidins, were present in all embryosfrom the very onset of development. They were localized preferentiallyin the proximal suspensor cells and the basal region of theembryo. However, accumulation of polyphenols was generally muchmore pronounced in embryos matured without ABA, indicating alack of biochemical regulatory competence in those embryos. Key words: Abscisic acid, embryonal development, somatic embryo, storage protein, polyphenols     

Dynamics of the sit-to-stand movement

The strategies of the sit-to-stand movement are investigated by describing the movement in terms of the topology of an associated phase diagram. Kinematic constraints are applied to describe movement sequences, thus reducing the dimension of the phase space. This dimensional reduction allows us to apply theorems of topological dynamics for two-dimensional systems to arrive at a classification of six possible movement strategies, distinguished by the topology of their corresponding phase portrait. Since movement is treated in terms of topological structure rather than specific trajectories, individual variations are automatically included, and the approach is by nature model independent. Pathological movement is investigated, and this method clarifies how subtle abnormalities in movement lead to difficulties in achieving a stable stance upon rising from a seated position. This article was processed by the author using the LAT_EX style file pljour2 from Springer-Verlag.     

PEAK SHIFTS AND POLYMORPHISM DURING PHASE THREE OF WRIGHT'S SHIFTING-BALANCE PROCESS

The third phase of Wright's shifting-balance theory involves the export of adaptive gene combinations from one subpopulation to another. Previous results have demonstrated that this can occur at very low migration rates, but it has been argued that this simply reflects the ability of migration to overcome selection and fix any (even deleterious) alleles. Here, previous analyses are extended by concentrating on the critical balance between forward and reverse migration rates that still allows phase III to proceed. It is shown that selective advantage, dominance, recombination rate, and the number of loci all affect the ability of a genotype to invade and become fixed in a new subpopulation, but it is unlikely that phase III will occur in the absence of differential migration unless the invading genotype consists of a few dominant loci with a large selection advantage, spreading into a few populations of lower fitness. Therefore, as was envisioned by Wright, differential migration from more to less fit populations will be necessary for phase III to occur under most circumstances.