The endocrine cells in the gastroenteropancreatic system of the bowfin, Amia calva L.: an immunohistochemical, ultrastructural, and immunocytochemical analysis.

The gastroenteropancreatic (GEP) endocrine system of bowfin (Amia calva) was described using light and electron microscopy and immunological methods. The islet organ (endocrine pancreas) consists of diffusely scattered, mostly small islets and isolated patches of cells among and within the exocrine acini. The islets are composed of abundant, centrally located B cells immunoreactive to bovine and lamprey insulin antisera and D cells showing a widespread distribution and specificity to somatostatin antibodies. A and F cells are present at the very periphery of the islets and are immunoreactive with antisera against glucagon (and glucagon-like peptide) and several peptides of the pancreatic polypeptide (PP)-family, respectively. The peptides of the two families usually collocates within the same peripheral islet cells and are the most common immunoreactive peptides present in the extra-islet tissue. Immunocytochemistry and fine structural observations characterised the granule morphology for B and D cells and identified two cell types with granules immunoreactive to glucagon antisera. These two putative A cells had similar granules, which were distinct from either B or D cells, but one of the cells had rod-shaped cytoplasmic inclusions within cisternae of what appeared to be rough endoplasmic reticulum. The inclusions were not immunoreactive to either insulin or glucagon antisera. Only small numbers of cells in the stomach and intestine immunoreacted to antisera against somatostatin, glucagon, and PP-family peptides. The paucity of these cells was reflected in the low concentrations of these peptides in intestinal extracts. The GEP system of bowfin is not unlike that of other actinopterygian fishes, but there are some marked differences that may reflect the antiquity of this system and/or may be a consequence of the ontogeny of this system in this species.     

Modeling of orthokinetic flocculation of Saccharomyces cerevisiae.

This study examined the flocculation behavior of two Saccharomyces cerevisiae strains expressing either Flo1 (LCC1209) genotype or NewFlo (LCC125) phenotype in a laminar flow field by measurement of the fundamental flocculation parameter, the orthokinetic capture coefficient. This orthokinetic capture coefficient was measured as a function of shear rate (5.95-223 s(-1)) and temperature (5-45 degrees C). The capture coefficients of these suspensions were directly proportional to the inverse of shear rate, and exhibited an increase as the temperature was increased to 45 degrees C. The capture coefficient of pronase-treated cells was also measured over similar shear rate and temperature range. A theory, which predicts capture coefficient values due to zymolectin interactions, was simplified from that developed by Long et al. [Biophys. J. 76: (1999) 1112]. This new modified theory uses estimates of: (1) cell wall densities of zymolectins and carbohydrate ligands; (2) cell wall collision contact area; and (3) the forward rate coefficient of binding to predict theoretical capture coefficients. A second model that involves both zymolectin interactions and DLVO forces was used to describe the phenomenon of yeast flocculation at intermediate shear ranges, to explain yeast flocculation in laminar flow.     

Comparative investigations of biopolymer hydration by physicochemical and modeling techniques.

The comparative investigation of biopolymer hydration by physicochemical techniques, particularly by small-angle X-ray scattering, has shown that the values obtained differ over a wide range, depending on the nature of the polymer and the environmental conditions. In the case of simple proteins, a large number of available data allow the derivation of a realistic average value for the hydration (0.35 g of water per gram of protein). As long as the average properties of proteins are considered, the use of such a default value is sufficient. Modeling approaches may be used advantageously, in order to differentiate between different assumptions and hydration contributions, and to correctly predict hydrodynamic properties of biopolymers on the basis of their three-dimensional structure. Problems of major concern are the positioning and the properties of the water molecules on the biopolymer surface. In this context, different approaches for calculating the molecular volume and surface of biopolymers have been applied, in addition to the development of appropriate hydration algorithms.     

Frost Injury as a Possible Inciting Factor in Bud and Shoot Necroses of Fraxinus excelsior L.

Large numbers of European ash have died in Poland in all age classes during the last ten years. The characteristic symptom occurring on shoots of planted and self‐sown seedlings was bark necroses starting from the shoot apex, necrotic buds, or leaf and twig scars. The results showed that in the bud tissue of cold acclimated European ash extracellular and intracellular ice formation occurred at approximately ?9 and ?32°C, respectively. In deacclimated plants in spring water supercooling is limited by the heterogenous ice nucleation temperature and consequently the cold tolerance is ?9 to ?4°C for bud tissues and ?13 to ?9°C for shoots. Isolations of fungi were performed from dead buds and from necroses occurring on the main stem. Alternaria alternata, Fusarium lateritium and Phomopsis scobina were among the fungi occurring in both these organs at frequencies of more than 7%. Cylindrocarpon heteronemum, Diplodia mutila and Tubercularia vulgaris from necroses were only isolated in frequencies; 3.3, 1.2 and 5.4%, respectively. It seems likely that freezing injury is the inciting factor, which combined with fungal colonization manifests itself as fatal damage to European ash buds and shoots.     

The taxonomic status, distribution and conservation of the lowland anoa Bubalus depressicornis and mountain anoa Bubalus quarlesi

1. The anoas are two species of dwarf buffalo, the lowland anoa Bubalus depressicornis and mountain anoa Bubalus quarlesi that are endemic to the island of Sulawesi, Indonesia. The classification of the subgenus Anoa within Bubalus is upheld by assessment of recent genetic and morphological research. The classification of anoas into two species is still debated, but with the absence of significant opposing evidence, this position is adopted here. 2. Information about the distribution of the two species is presented that adds to but largely supports existing reports. However, it is still uncertain whether the two putative species are sympatric or parapatric in their distribution. A review of anoa distribution from historical reports and recent field data (1990s to 2002) highlights their decline throughout Sulawesi, especially in the southern and north-eastern peninsulas. The decline has been attributed to local hunting for meat and habitat loss. Most populations are rapidly becoming fragmented, suggesting that the conservation of viable populations may eventually require management of metapopulations. 3. There is an urgent requirement for conservation efforts to: (i) protect anoas from hunting; (ii) prevent habitat loss in key sites; (iii) complete genetic studies to better determine the number of anoa taxa and Management Units and assess their distribution; and (iv) determine the status of the remaining anoa populations.