Immunohistochemical demonstration of villin in the normal human pancreas and in chronic pancreatitis

Human pancreatic tissue was investigated by immunohistochemistry using a polyclonal antibody against the actin binding protein villin, which participates in the formation of actin filament bundles in the microvilli. In cells of the different parts of the pancreatic duct system as well as in the acinar cells villin immunoreactivity was located mainly at the apical cell surface. This was confirmed by the ultrastructural demonstration of microvilli on the surface of duct and acinar cells, which exhibited the typical actin bundles. In chronic pancreatitis the staining for villin in duct-like structures of degenerative pancreatic tissue was irregular or even absent. This correlated with the electron microscopic observation of duct-like structures known as tubular complexes composed of cells devoid of microvilli at the apical cell surface. At the light microscopical level degenerative structures without lumen and of unknown origin showed a strong staining for villin at their basal cell surface.     

The distribution of benthic marine algae in relation to the temperature regulation of their life histories

Mainly on the basis of the distribution patterns of 42 species of the recently revised genus Cladopkora (Chlorophyceae) in the north Atlantic Ocean, it appeared possible to distinguish 10 phytogeographic distribution groups of wide applicability. Experimentally determined critical temperatures limiting essential events in the life histories of 17 benthic algal species were used to infer possible phytogeographic boundaries; these appeared to fit closely the phytogeographic boundaries derived from field-distribution data. For a temperate species, at least six different boundaries can be postulated and should be checked in the northern hemisphere: (1) the ‘northern lethal boundary’ (corresponding to the lowest winter temperature which a species can survive); (2) the ‘northern growth boundary’ (corresponding to the lowest summer temperature which, over a period of several months, permits sufficient growth); (3) the ‘northern reproductive boundary’ (corresponding to the lowest summer temperature permitting reproduction over a period of several months); (4–6) the corresponding southern boundaries. Photoperiodic responses may influence the temperature responses. Many phytogeographic boundaries appear to be of a composite nature. For instance, the southern boundary of Laminaria digitata follows the European 10°C February isotherm (which corresponds to the highest winter temperature permitting fertility in the female gametophyte, i.e. to the ‘southern reproductive boundary’), and the American 19°C summer isotherm (corresponding to the ‘southern lethal boundary’). Thus, experimental evidence supports the validity of eight of the following 10 distribution groups (for distribution groups 2 and 6, such evidence could not be found): (1) the amphiatlantic tropical-to-warm temperate group, with a north-eastern extension (examples: Gracilaria foliifera and Centroceras clavulalum); (2) the amphiatlantic tropical-to-warm temperate group, with a north-western extension (example: Hypnea musciformis); (3) the amphiatlantic tropical-to-temperate group (example: Sphacelaria rigidula =furcigera); (4) the amphiatlantic temperate group: the Cladophora rupestris type (examples: Callithamnion hookeri, Dumontia contorta; Laminaria saccharina is transitional to type 10, I., digitata to types 5 and 10); (5) the amphiatlantic temperate group: the Cl. albida type (examples: Scytosiphon lomentaria, Petalonia fascia); (6) the tropical western Atlantic group; (7) the north-east American tropical-to-temperate group (example: Gracilaria tikvahiae); (8) the north-east American temperate group and the corresponding Japanese temperate group (examples: Campylaephora hypneoides and Sargassum muticum); (9) the warm-temperate Mediterranean-Atlantic group, and the corresponding warm-temperate Californian group (examples: Saccorhiza polyschides, Laminaria hyperborea, I., ockroleuca, Macrocystis pyrifera, Hedophyllum sessile); (10) the Arctic group (examples: Saccorhiza dermatodea and Sphacelaria arctica). Distribution groups 6, 9 and 10 have comparatively narrow temperature ranges with a span of 18 22°C between their lethal boundaries and of 5 12°C between their reproductive or growth boundaries. These narrow temperature ranges limit the species in these groups to the tropics; the temperate coasts on the eastern sides of the north Pacific and north Atlantic Oceans and in the southern hemisphere; and to the Arctic, respectively. The narrow temperature ranges of group 9 make the species in this group unfit for life on the western temperate coasts of the north Pacific and north Atlantic Oceans, where algae must cope with annual temperature fluctuations of more than 20°C. Conversely, algae in group 8 (containing the numerous Japanese endemic species) are characterized by wide temperature spans (e.g. 29°C between ‘lethal boundaries’, 12–19°C between ‘growth and/or reproductive boundaries’) and must be potentially capable of occupying wide latitudinal belts on temperate coasts along the east sides of the north Pacific and north Atlantic Oceans. Algae ‘escaped’ from Japan, such as Sargassum muticum, conform to this picture. Apparently Japanese algae do not have the capacity for long distance dispersal. The corresponding east American coasts (30–45 N) harbour very few endemic species, probably as a result of the adverse nature of these sediment coasts for benthic macroalgae and their functioning as a barrier to latitudinal displacements of the flora during glaciations. The remaining distribution groups (1,2,3,4,5,7) are characterized by wide temperature spans and wide distributions, often in both the Atlantic and Pacific Oceans and in both hemispheres. Six temperate species (in distribution groups 4, 5 and 9) with an amphiaequatorial distribution have similar winter-temperature maxima permitting reproduction and corresponding with winter isotherms of 15–17°C; their upper lethal temperatures are more dissimilar and correspond with summer isotherms of 20–30°C. Their amphiaequatorial distribution can be explained by assuming glacial temperature drops along east Pacific and east Atlantic equatorial coasts in narrow belts of intensified upwelling during the presumably intensified glacial circulation of the ocean gyres.     

OPERATION OF THE PURINE NUCLEOTIDE CYCLE IN ANIMAL TISSUES

1. The operation of the purine nucleotide cycle, consisting of the enzymes adenylate deaminase (E.C. 3.5.4.6), adenylosuccinate synthetase (E.C. 6.3.4.4) and adenylosuccinate lyase (E.C. 4.3.2.2), has been reviewed with reference to its metabolic function in animal tissues.
2. Abundant evidence, both from in vitro and in vivo studies, suggests that the purine nucleotide cycle serves to stabilize the adenylate 'energy charge' (or 'phosphorylation potential') in the cytoplasm of vertebrate cells during a temporary imbalance between ATP-consumption and ATP-production. This stabilization, however, is absent or much less efficient in tissues of invertebrates.
3. The hypothesis that AMP-deaminase is involved in the regulation of glycolysis is not supported by recent work. In a variety of cell types, including skeletal muscle and blood platelets, blocking of AMP-deaminase activity (due to a genetic defect or to pharmacological inhibition) is without effect on the glycolytic rate. Detailed kinetic and histochemical analysis of energy metabolism shows lack of correlation between AMP-deaminase activity and glycolysis in skeletal muscle during exercise.
4. The purine nucleotide cycle appears to control the level of citric acid cycle intermediates in skeletal muscle. Pharmacological inhibition of adenylosuccinate lyase or adenylosuccinate synthetase leads to a reduced availability of four-carbon 'sparker' molecules to the Krebs cycle with a concomitant impairment of aerobic energy production during muscular work.
5. The cycle appears to be a major pathway for amino acid deamination in skeletal muscle and brain of vertebrates, but not in kidney or liver.