Metabolic pattern of the heart of haemoglobin- and myoglobin-free Antarctic fish Channichthys rhinoceratus

Summary Maximum activities of energy metabolism related enzymes, myofibrillar ATPase and concentrations of carnitine, lipids and myoglobin have been assayed in heart and white muscle of the ice-fish Channichthys rhinoceratus. Results are compared with those of the redblooded Paranotothenia magellanica. Increased activities of glycolytic enzymes and extremely high lactate dehydrogenase activity have been found in icefish heart, suggesting a substantial involvement of anaerobic glycolysis under conditions of oxygen depletion. During normoxia, ATP generation is achieved via oxidative pathways of carbohydrate or fatty acid catabolism. Possible implication of the myocardium in homeostatic regulation by lactate oxidation is also discussed.     

Antigenic similarities among estuarine soft-bottom benthic taxa

Summary Antisera prepared against whole-organism extracts of benthic invertebrates from Puget Sound, Washington, and North Inlet, South Carolina, were tested for specificity with extracts from both coasts. Immunological similarities among taxa reflected conventional phylogenetic relationships both within each of these areas and also between both areas. Antisera also cross-reacted with extracts to a lesser degree at higher taxonomic levels. The existence of common antigens among phylogenetically related taxa makes feasible the use of serological methods to document trophic interactions in environments where it is difficult to obtain sufficient material to serve as immunogen for production of highly specific antisera. Deep-sea or other high diversity food webs may be investigated using serological methods that are already well-developed for use in terrestrial and shallow-water environments.Contribution No. 423 from the Belle W. Baruch Institute for Marine Biology and Coastal Research and the Marine Science Program, University of South Carolina Columbia, South Carolina 29208, USA     

Experimental evaluation of the antibiotic carrying capacity of a muscle flap into a fibrotic cavity

A study was undertaken to determine the antibiotic carrying capacity of a transferred muscle flap into a fibrotic cavity using a tissue cage model in rabbits. Blood and chamber fluid antibiotic levels were determined after intramuscular hindlimb gentamicin injection up to 56 days following muscle transfer. This study suggests that muscle flaps increase the concentration of antibiotics that can be achieved within a fibrotic cavity. The measurable peak level decreases with time, probably due to increased scarring around the muscle. This model should enable the study of many different classes of antibiotics with different protein binding and other administration schedules using multiple timed doses or a combination of agents.     

Erratum

On page 565 in Volume 7, Number 3, 1998, under Molecular fold and calcium binding site, the domain numbering was wrongly reported. The correct numbering is domain A: residues 1 to 86 and 147 to 356, and domain B: residues 87 to 146. Domain C was correctly cited and remains as reported.     

Nitrogen Metabolism in Senescing Leaves

Leaf senescence is a highly organized process and not a passive decay. Photosynthesizing mesophyll cells lose their functions in an early phase, while the epidermal layer with the stomates and the phloem remains functional throughout senescence. The subcellular compartmentation is maintained and allows the cooperation of different organelles in the remobilization of constituents. Nitrogen metabolism changes at the onset of senescence from assimilation to remobilization. Enzymes involved in nitrate reduction are lost, while some enzymes of intermediary nitrogen metabolism are maintained longer, and some catabolic enzymes reach highest activities during senescence. Chloroplasts are dismantled early, but mitochondria remain active and may fuel remobilization processes. Chloroplast proteins are degraded, and this nitrogen fraction can be translocated via the phloem from senescing leaves to sinks within the same plant. In contrast, chlorophyll is degraded, fragments produced reach the vacuole, and catabolites accumulate there. Nuclear DNA is maintained until a very late phase. The export of nitrogen from senescing plant parts is important for the economic use of this macronutrient. The regulation of senescence at the whole plant level as well as at the molecular level is only rudimentarily known, although interesting new aspects have been presented recently.