Effects of mercury on ion and osmoregulation in the shore crab Carcinus maenas (L.)

The effects of lethal mercury concentrations on regulation of hemolymph electrolytes in the shore crab Carcinus maenas were investigated. In most experiments mercury exposure reduced hemolymph osmolality and Na+, Cl- and K+ levels to 55-90% of controls in 48 hr. Mercury exposure augmented calcium levels to 120-300% of controls. The effect of mercury on all of the electrolytes varied during the year, especially on magnesium levels which showed significant increases or decreases, or remained unaffected in different experiments.     

Inactivation of microbial glutamin-(asparagin-)ase by azaserine and 6-diazo-5-oxo-L-norleucine

The effect of substrate analogues on glutamin-(asparagin-)ase from Pseudomonas aurantiaca-548 has been studied. The enzyme was demonstrated to be highly sensitive to the the action of 6-diazo-5-oxo-L-norleucine and azaserine. L-isomers of glutamine, aspartate, glutamate and several other substrate analogues with free alpha-amino groups protected the enzyme against the inhibitory DON effect. Thus, thorough preliminary selection of appropriate inhibitors, their dosage and treatment duration is needed for the recommendation of combined enzyme-inhibitor application in anti-tumour chemotherapy.     

The RAINFOR database: monitoring forest biomass and dynamics

Problem: Data from over 100 permanent sample plots which have been studied for 10–20 years need a suitable system for storage which allows simple data manipulation and retrieval for analysis. Methods: A relational database linking tree records, taxonomic nomenclature and corresponding environmental data has been built in MS Access as part of the RAINFOR project. Conclusion: The database allows flexible and long‐term use of a large amount of data: more than 100 tree plots across Amazonia, incorporating over 80 000 records of individual trees and over 300 000 total records of tree diameter measurements from successive censuses. The database is designed to enable linkages to existing soil, floristic or plant‐trait databases. This database will be a useful tool for exploring the impact of environmental factors on forest structure and dynamics at local to continental scales, and long term changes in forest ecology. As an early example of its potential, we explore the impact of different methodological assumptions on estimates of tropical forest biomass and carbon storage.     

Fatal perinatal sarcocystosis in a lamb

A 3-wk-old lamb died because of neurological disease. The predominant microscopic lesions were in the brain and spinal cord and consisted of nonsuppurative encephalomyelitis with severe gliosis throughout the gray and white matter. Immature and mature schizonts, 15.7 x 10.6 microns (8-30 x 6-18 microns), occurred in capillaries and were structurally similar to those of Sarcocystis tenella.     

Optimized linker sequences for the expression of monomeric and dimeric bispecific single-chain diabodies.

Bispecific single-chain diabodies (scDb) consist of the variable heavy and light chain domains of two antibodies connected by three linkers. The structure of an scDb in the V(H)-V(L) orientation is V(H)A-linkerA-V(L)B-linkerM-V(H)B-linkerB-V(L)A, with linkers A and B routinely chosen to be 5-6 residues and linker M 15-20 residues. Here, we applied display of scDb on filamentous phage to analyse the composition of optimal linker sequences. The three linkers were randomized in length and sequence using degenerated triplets coding for only six hydrophilic or aliphatic amino acids (Thr, Ser, Asp, Asn, Gly, Ala). Antigen-binding clones were then isolated by one to two rounds of selection on the two different antigens recognized by the bispecific scDb. Using an scDb directed against carcinoembryonic antigen (CEA) and beta-galactosidase (Gal), we found that monomeric scDb had a preferred length of 15 or more amino acid residues for the middle linker M and of 3-6 residues for the linkers A and B. No obvious bias towards a preferred linker sequence was observed. Reduction of the middle linker below 13 residues led to the formation of dimeric scDb, which most likely results from interchain pairing between all the V(H) and V(L) domains. Dimeric scDb were also formed by fragments possessing a long linker M and linkers A and B of 0 or 1 residue. We assume that these dimeric scDb are formed by intrachain pairing of the central variable domains and interchain pairing of the flanking variable domains. Thus, the latter molecules represent a novel format of bispecific and tetravalent molecules. The described strategy allows for the isolation of both optimized and minimal linker sequences for the assembly of monomeric or dimeric single-chain diabodies.     

Structural aspects of recognition motifs contributing to autoimmune responses.

Sequence analysis of autoimmune-associated antibodies has suggested a structural relatedness between genes used to encode autoantibodies and those encoding unrelated antibodies without autoreactive specificities. Subsequently, the basis for cross-reactive idiotypes across germ-line lineages, as well as conserved interspecies cross-reactivities of autoantigens among serologically similar antibodies, may result from evolutionary duplication of particular types of recognition motifs. As a first step toward elucidating structural recognition principles underlying possible cross-reactive epitopes involved in autoimmune pathologies, structural features of selected motifs associated with native ligand binding are examined for their inherent occurrence in antibody and T-cell receptor repertoires. This analysis considers the putative recognition features representative of common motif subsets shared with loop structures in CDR2 and FR3 regions of antibodies such as charge-2x-charge-x-charge or hydrogen bond donor (acceptor)-2x-charge-x-hydrogen bond donor (acceptor) type motifs, where x is any residue that can participate in maintaining a loop conformation. Such tracts encoded in the CRD2 and FR3 regions of heavy chains of antibodies and T-cell receptors (TCRs) associated with autoimmune dysfunction, with non-autoreactive antibodies, and with native host proteins. Such evolutionarily conserved motifs may be targets for complementary interactions involving autoantibodies and receptors.