Heterogeneous binding of oxygen and carbon monoxide to dissociated molluscan hemocyanin

Functional heterogeneity in O2 or CO binding of sites of dissociated molluscan hemocyanin polypeptide chains (Helix pomatia and Octopus vulgaris) has been estimated by an analysis of accurate noncooperative binding curves. Three types of experiments were performed: pure O2 or CO binding, competitive displacement of one ligand by the other, and simultaneous removal of both gases from protein partially saturated with O2 and CO. The data were analyzed in terms of a model which has two fractions of sites with different properties for O2 and CO. The relative proportion of the different binding sites and their affinity constant values were found by the combined use of the three different procedures. All species show a marked functional heterogeneity of sites for O2 binding, while for CO binding it has been observed only in the case of H. pomatia beta-hemocyanin. Moreover, in all three molluscan hemocyanins examined, the two classes of O2-binding sites, although present in different proportions within the polypeptide chains, display similar affinity constant values. The data reported show a good consistency with results obtained using digested and isolated domains, providing confidence in the analytical procedure used. From comparison of the O2/CO affinity ratios (KO2, KCO) of each class it may be suggested that the difference in O2 affinity of two kinds of binding sites is related to a different local structure of the active sites. The results, moreover, unequivocally confirm that binding and displacement of two gaseous ligands to hemocyanin occur by a simple competitive mechanism, although the binding site is structurally complex and the two ligands are bound with different geometries.     

Slight differences between adenosine deaminases from different species an immunochemical study.

IgGs against adenosine deaminase from rat brain, rat liver, mouse duodenum and human erythrocyte were purified from rabbit antisera with yields of 82-87%. The inhibition of adenosine deaminase by the antienzyme is studied, and it is demonstrated that rat and mouse antibodies are tight-binding inhibitors. These antibodies inhibit either the rat or the mouse enzymes and do not inhibit the human erythrocytes enzyme. The human antibody does not inhibit either the human or the rat or mouse enzyme. These results indicate that some differences in antigenic behaviour near the active site must be encountered among species. Comparing the sequenced of the two products corresponding to two adenosine deaminase genes recently sequenced (human and murine) a hypothesis concerning the localization of the adenosine deaminase active site is proposed.     

Some immunochemical properties of pollen extracellular nuclease

The extracellular nuclease fromPinus silvestris pollen was isolated and characterized. Molecular sieving produced only one peak of nuclease with apparent molecular mass of about 30 kDaltons, while molecular mass of the enzyme as determined by means of sodium dodecyl sulphate-DNA gel electrophoresis was 25.7 kDaltons or less. The nuclease exhibited one electrophoretic molecular form only. Specific antiserum against this nuclease was prepared and the nuclease was shown to be immunochemically cross-reactive with extracellular nuclease from Pinus nigra pollen. No immunochemical relationships were observed between pine nuclease and the pollen extracellular nucleases from the angiosperm species,Nicotiana tabacum, Corylus avellana, Alnus incana andBetula pubescens. No cross-reactivity was detected by double diffusion between the pine nuclease and the extracellular proteins from vegetative spores ofEquisetum arvense.     

Some metabolic differences between human skin and aponeurosis fibroblasts in culutre

Two types of human fibroblast strains were studied in culture. One was derived from abdomen skin and the other from abdominal muscle aponeurosis. Tissue-specific differences were found between thése two cell strains. Skin fibroblasts had faster doubling time, smaller cell volume, and lower glucose consumption when compared to aponeurosis fibroblasts. Furthermore, extracellular amino acid variations showed some specific differences, in particular a lack of serine consumption in skin fibroblasts.     

Morphological differences between native and non-native pumpkinseed in traits associated with locomotion

Adaptive strategies in morphology can significantly influence the successful invasion and establishment of non-native species. Since its introduction, the pumpkinseed (Lepomis gibbosus), a sunfish of North American origin, has spread throughout most of Europe, including the Iberian Peninsula. We hypothesized that 12 morphological traits, functionally significant for locomotion, would differ according to geographic origin (native/non-native) and habitat type (fluvial/lacustrine). Using flow-through raceways, we simultaneously reared F₁ young-of-the-year pumpkinseed from two native and two non-native populations, produced from adults kept in a common environment. Morphometric measurements were recorded at the beginning and end of the 90-day rearing period. Median-fin size and placement differed significantly between native and non-native populations, whereas paired fin size differed between fluvial and lacustrine populations. Other functionally significant traits, such as body width, also differed between native and non-native populations. Spanish populations were considered to have acquired these adaptive external morphologies through successive generations, following the species’ range expansion through the variable environments of the Iberian Peninsula.     

Some differences between the soils ofRhizophora andAvicennia mangrove swamps in sierra leone

Summary The differences existing between a fibrous mud from aRhizophora mangrove swamp and a non-fibrous mud from a nearbyAvicennia swamp have been examined.The differences found between the muds are due largely to the kind of mangrove they support.Compared to the Avicennia swamp mud, that from the Rhizophora swamp had a higher pH value and a higher content of oxidisable sulphur, nitrogen, phosphorus, and carbon. The behaviour of the muds on incubation has helped to explain why the mud under Rhizophora is considered as being more fertile than mud under Avicennia. An apparent high rate of decomposition of the Rhizophora swamp mud as compared to that of mud under Avicennia was due to high oxygen uptake during sulphur oxidation. Rhizophora-bearing mud had a very high C/N ratio and inorganic nitrogen added to it was immobilised. It is suggested that land reclaimed from Rhizophora would respond to nitrogen fertilization. The most important difference between the muds was in their behaviour on drying. The intense acidity produced by sulphur oxidation in the fibrous mud affected all other changes, chemical and microbiological. It was found that if the moisture content of the fibrous mud remained at any point between 40 and 10 per cent for any length of time, then the mud became more acid than if continuously dried.