Occurrence of the periodic acid-Schiff positive granular leucocyte (PAS-GL) in some fishes and its significance

Preparations of peripheral blood of 58 species of fish, mostly teleosts, were examined for the presence of granulocytes. Heterophils are commonly found but eosinophils are rare and metachromatic basophils never seen. Granulocytes (PAS-GL) with periodic acid-Schiff positive granules, were observed in 30 species representing marine and freshwater, and 'primitive' and 'advanced' types. It is postulated that the PAS-GL is the piscine forerunner to the heparin and histamine-containing metachromatic basophil/mast cell of higher vertebrates.     

Consequences of hormone-induced desensitization of adenylate cyclase in intact cells.

A hypothesis on the role of the hormone-induced desensitization of adenylate cyclase is proposed. It is suggested that the desensitization process could provide the cell with a highly efficient cyclic AMP system for transmitting hormone stimulus without requiring a large energy consumption. Theoretical considerations show that in fact the desensitization phenomenon allows the cyclic AMP system to present a good compromise between the efficiency and economy requirements of the cells.     

COMPARATIVE POLLINATION ECOLOGY OF PYRRHOPAPPUS GEISERI AND PYRRHOPAPPUS CAROLINIANUS

Pyrrhopappus geiseri and P. carolinianus are partially cross-compatible (20–52% akene set in artificial crosses). Four barriers to gene exchange prevent or reduce hybridization. Pyrrhopappus geiseri flowers in the early spring, whereas P. carolinianus flowers from mid-spring to summer with peak flowering in May and June. Overlap in anthesis between the two species is therefore limited. The two species typically occupy different soil-types, P. geiseri on clay soils and P. carolinianus on sands. The diurnal periods of stigmatic receptivity are distinct. Pyrrhopappus geiseri is pollen receptive in the late morning and P. carolinianus at dawn. As a result of the prior three barriers P. geiseri is pollinated by bees of the Andrena verecunda complex, primarily A. crawfordi, and P. carolinianus by Hemihalictus lustrans. Pyrrhopappus geiseri and P. carolinianus are almost completely reproductively and ecologically isolated and are not members of one hologamodeme.     

On the multiplicity of glucose analogues transport systems in rat intestine.

A study has been made to test if in intact epithelium of rat jejunum with in vivo and in vitro techniques, two transport systems for glucose and analogues, as those characterized in brush border membrane vesicles from guinea pig jejunum, are operative. The passive and mediated transport components of the D-galactose and methyl alpha-D-glucopyranoside intestinal absorption and the mutual inhibitions between both substrates at different relative concentrations have been measured. The effects of cytochalasin B and low temperature (20 degrees C) on the transport in vitro have also been observed. Cytochalasin B inhibits galactose and alpha-methylglucoside transport at 0.1 and 40 mM concentrations in similar percentage. Transport of 0.1 and 40 mM galactose is inhibited 61 and 77% respectively by low temperature (20 degrees C). The transport of galactose and alpha-methylglucoside could be explained by the assumption of just one transport system shared by both substrates, with a higher affinity for alpha-methylglucoside. Operation of two systems was not demanded by the results, due perhaps to species specificity or to the distorting action of the unstirred water layers.     

Electron microscopic morphometric analysis of human T and B peripheral blood lymphocytes

Using the system of morphometric analysis described in this paper, human peripheral blood T and B lymphocytes, labeled with specific surface markers, can be compared on different analytical levels. They show differences in their surface and the eccentricity of cells, in the relative surfaces occupied by peripheral and central condensed chromatin, in the average surface of the central chromatin clumps and in the number of perichromatin granules per nuclear surface. The morphometric analysis reveals the importance of examining the nuclear and the surface parameters in the characterization of lymphocytes, confirming that a detailed analysis of the nuclear characteristics can contribute to the identification of T and B lymphocytes by transmission electron microscopy.