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.     

Hypophysiotrophic thyrotropin releasing hormone (TRH) synthesizing neurons. Ultrastructure, adrenergic innervation and putative transmitter action

The neuropeptide thyrotropin releasing hormone (TRH) is capable of influencing both neuronal mechanisms in the brain and the activity of the pituitary-thyroid endocrine axis. By the use of immunocytochemical techniques, first the ultrastructural features of TRH-immunoreactive (IR) perikarya and neuronal processes were studied, and then the relationship between TRH-IR neuronal elements and dopamine-beta-hydroxylase (DBH) or phenylethanolamine-N-methyltransferase (PNMT)-IR catecholaminergic axons was analyzed in the parvocellular subnuclei of the hypothalamic paraventricular nucleus (PVN). In control animals, only TRH-IR axons were detected and some of them seemed to follow the contour of immunonegative neurons. Colchicine treatment resulted in the appearance of TRH-IR material in parvocellular neurons of the PVN. At the ultrastructural level, immunolabel was associated with rough endoplasmic reticulum, free ribosomes and neurosecretory granules. Non-labelled axons formed synaptic specializations with both dendrites and perikarya of the TRH-synthesizing neurons. TRH-IR axons located in the parvocellular units of the PVN exhibited numerous intensely labelled dense-core and fewer small electron lucent vesicles. These axons were frequently observed to terminate on parvocellular neurons, forming both bouton- and en passant-type connections. The simultaneous light microscopic localization of DBH or PNMT-IR axons and TRH-synthesizing neurons demonstrated that catecholaminergic fibers established contacts with the dendrites and cell bodies of TRH-IR neurons. Ultrastructural analysis revealed the formation of asymmetric axo-somatic and axo-dendritic synaptic specializations between PNMT-immunopositive, adrenergic axons and TRH-IR neurons in the periventricular and medial parvocellular subnuclei of the PVN. These morphological data indicate that the hypophysiotrophic, thyrotropin releasing hormone synthesizing neurons of the PVN are directly influenced by the central epinephrine system and that TRH may act as a neurotransmitter or neuromodulator upon other paraventricular neurons.     

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.