The factors limiting growth and survival of brown trout, Salmo trutta m.fario L. introduced to different types of streams

Fingerlings of brown trout ( Salmo trulta m. fario L.) were introduced to sections of different types of streams situated in natural catchments and those modified by Man's activity. At stations where environmental conditions were modified by such forms of impact as pollution, flow variability and impoundment, trout did not survive 5 months. In the natural river sections mortality rates increased downstream along the river continuum and were associated with increased predation. Growth rates in the upper reaches were primarily restricted by abiotic factors—temperature and trophic status: however, they were to a large extent modified by density-dependent regulation and intraspecific competition. The influence of the abiotic/biotic regulatory process, expressed as fish metabolic performance, is discussed as a framework for the determination of the carrying capacity of the riverine ecosystem.     

Interaction between protein kinase C and regulatory ligand is enhanced by a chelatable pool of cellular zinc

At micromolar concentrations, zinc (Zn) and cadmium, but not other metals, greatly augmented binding of [3H]phorbol dibutyrate ([3H]PDBu) to protein kinase C (PKC) in cell homogenates and intact cells (in the presence of ionophore). Increased binding persisted for several hours. The heavy-metal chelating agent 1,10-phenanthroline completely reversed the increased [3H]PDBu binding in cells pretreated with 65Zn and ionophore and this was associated with a decline of about 20% in cell-associated 65Zn, suggesting that a relatively small pool of intracellular Zn acts on PKC. This may be a membrane-associated pool, since 65Zn readily bound to isolated erythrocyte inside-out membranes. Phenanthroline also partially inhibited binding of [3H]PDBu to PKC in untreated cells and extracts in a Zn-reversible manner. Therefore, cellular Zn appears to regulate the interaction of ligand with PKC. PKC bound to a Zn affinity column and was eluted by metal-chelator, confirming that Zn interacts directly with PKC.     

Evolution,pollination, and systematics of the tribeNeottieae (Orchidaceae)

The various classifications of the orchid tribeNeottieae are reviewed and a new classification is proposed that divides the tribe into three subtribes,Neottiinae, Limodorinae, andCephalantherinae, based primarily on characters of the column (gynostemium). A cladistic analysis illustrates that these three subtribes are more closely related to one another than either is to any other group in subfam.Neottioideae, although there are very few apomorphic characters for the tribe. Pollination biology is also discussed showing links between breeding systems and distribution. There is also a possible role between column and labellum morphology and the emergence of a deceptive pollination syndrome from one of reward.     

Regulation of protein kinase C by Zn(2+)-dependent interaction with actin.

Zn2+ influences diverse cellular processes by poorly understood mechanisms. Some of these effects may be mediated by the protein kinase C (PKC) family of enzymes, since an influx of Zn2+ greatly increases their binding of regulatory ligand phorbol ester and induces their translocation from cytosol to the cytoskeleton. Using a model with purified components, we now show that Zn2+ acts by forming a phospholipid-dependent complex of PKC with filamentous actin, which results in expression of new binding sites for phorbol ester and phosphorylation of actin. These results provide a basis for the observed localization of PKC at actin-membrane junctions, in-vivo.     

Histochemical localization of gamma glutamyl transpeptidase in the paranodal region of peripheral nerve

Gamma glutamyl transpeptidase (GGT), an amino acid transport enzyme, was investigated in normal and degenerated sciatic nerve of rat. The enzyme activity, which is considered to be a marker for cerebrovascular endothelium, was found to be absent in microvessels of normal and degenerated nerves. In the perineurium of normal nerve, GGT activity was faint, while in degenerated nerve, it increased. The most striking finding of this study was the observation of GGT activity at the paranode of each normal myelinated axon. It is interesting that after axotomy (8 weeks), no GGT activity was observed in the Schwann cells of degenerated nerve. Thus, Schwann cell plasmalemma contributed to GGT staining only when this cell was in contact with an axon mature enough to cause it to produce myelin. We conclude that, in peripheral nerve, transmembrane amino acid transport is apparently regional and associated with the paranodal region of myelinated nerve fibers.     

Notes on ecotone attributes and functions

We attempt to identify general properties of ecotones. Earlier attempts to do so encountered difficulties resulting from contradictory conceptions of ecotones. Thus, we begin with and center our discussion on a definition of ecotone. The definition is complex. It includes scaling, structural, and functional aspects. Based on this complex definition, we offer a brief review of what is an ecotone, what attributes it has, and how it influences other habitats of interest. We identify feedback as a possibly important but ignored function of ecotones. This discussion is presented in general terms which apply to a variety of ecological situations. We point out that results of an evaluation of ecotone attributes largely depends on the spatial and temporal scale at which ecotone is conceptualized and data are collected. We suggest that some of ecotone determinants scale naturally in a repeatable fashion among various aquatic systems. Finally, we point to the concentration of dynamic properties of ecotones as applied to land/water interface.     

Biomanipulation by ecotone management in a lowland reservoir

The comparative studies on fry of dominant fish species in the lowland Sulejow Reservoir have demonstrated the importance of an unstable ecotonal shoreline zone in whole system dynamics, which affects water quality. Ecotone zone utilization by fish determines their reproductive success and consequently pressure of fry on a zooplankton community. Density of perch, which dominates in the fry community of the Reservoir, influences the utilization of ecotonal resources by dominant cyprinid fry-roach. A reverse relationship between perch and roach fry densities has been demonstrated, which in turn, affects utilization of zooplankton by roach fry. At stations of highest perch density roach reduces feeding on zooplankton and eats more algae and insects. The knowledge of competitive relations between perch and cyprinid fry has been an important aspect of application of the biomanipulation concept in the reservoir ecosystem, to improve fish yield and water quality. Hypothetical models of energy flow through the reservoir's ecosystem with poor and well developed flooded riparian ecotonal zones are established.     

The long-term fate of neurons in allografts of ganglia in AG-B-compatible normal and immunologically tolerant rats

Neurons in Ag-B-incompatible allografts of ganglia are acutely rejected while those in Ag-B-compatible grafts are able to survive the immune reaction directed against them. The present study was undertaken to determine the long-term fate of neurons in allografts of ganglia in Ag-B-compatible rats. Isogenic strains of Ag-B-compatible adult Lewis (LE) and Fischer (FR) rats were used. The sensory nodose ganglia were reciprocally exchanged between normal LE and FR and between LE and FR animals rendered immunologically tolerant of each other's histocompatibity antigens. The findings were similar in both rat strains and revealed that although neurons and glial cells (i.e., satellite and Schwann cells) could survive for prolonged periods they were nevertheless eventually rejected by normal (nonimmunosuppressed) recipients. On the other hand, neurons and glial cells survived indefinitely in allografts in tolerant rats. Moreover, these neurons were functional because they regenerated nerve fibers into cotransplanted isografts of tongue and exerted the neurotrophic influence of inducing taste bud regeneration. The results demonstrate that, unlike kidney and heart, neurons in ganglia allografts cannot survive indefinitely without immunosuppression in Ag-B-compatible animals. Nevertheless, the permanent survival and function of neurons in Ag-B-compatible grafts can be achieved, as it is in Ag-B-incompatible ganglia grafts, by rendering the recipient immunologically tolerant.