The influence of a line with fast diffusion on Fisher-KPP propagation

We propose here a new model to describe biological invasions in the plane when a strong diffusion takes place on a line. We establish the main properties of the system, and also derive the asymptotic speed of spreading in the direction of the line. For low diffusion, the line has no effect, whereas, past a threshold, the line enhances global diffusion in the plane and the propagation is directed by diffusion on the line. It is shown here that the global asymptotic speed of spreading in the plane, in the direction of the line, grows as the square root of the diffusion on the line. The model is much relevant to account for the effects of fast diffusion lines such as roads on spreading of invasive species.     

A somatotypical study of the geographic variations between two Spanish populations

Morphological differences between university students from Bilbao (Basque Country) and Madrid (Spanish Meseta) have been studied. The sample sizes are 99 and 119, respectively, and the age ranges from 18 to 22 years. The main differences between the two groups under study were observed concerning the skinfold thicknesses. Body weight, stature and limb girths do not show remarkable differences. The physiques, as judged from anthropometric somatotypes, differ in the first component (endomorphy): Basques have higher values.     

Lactosylceramide-induced stimulation of liposome uptake by Kupffer cells in vivo

Incorporation of 8 mol percent lactosylceramide into small unilamellar vesicles consisting of cholesterol and sphingomyelin in an equimolar ratio and containing [³H]inulin as a marker resulted in an increase in total liver uptake and a drastic change in intrahepatic distribution of the liposomes after intravenous injection into rats. The control vesicles without glycolipid accumulated predominantly in the hepatocytes, but incorporation of the glycolipid resulted in a larger stimulation of Kupffer-cell uptake (3.2-fold) than of hepatocyte uptake (1.2-fold). Liposome preparations both with and without lactosylceramide in which part of the sphingomyelin was replaced by phosphatidylserine, resulting in a net negative charge of the vesicles, were cleared much more rapidly from the blood and taken up by the liver to higher extents. The negative charge had, however, no influence on the intrahepatic distributions. The fast hepatic uptake of the negatively charged liposomes allowed competition experiments with substrates for the galactose receptors on liver cells. Inhibition of blood clearance and liver uptake of lactosylceramide-containing liposomes by $\text{N-}\text{acetyl-}\text{d}\text{-galactosamine}$ indicated the involvement of specific recognition sites for the liposomal galactose residues. This inhibitory effect of $\text{N-}\text{acetyl-}\text{d}\text{-galactosamine}$ was shown to be mainly the result of a decreased liposome uptake by the Kupffer cells, compatible with the reported presence of a galactose specific receptor on this cell type (Kolb-Bachofen et al. (1982) Cell 29, 859–866). The difference between the results on sphingomyelin-based liposomes as described in this paper and those on phosphatidylcholine-based liposomes as published previously (Spanjer and Scherphof (1983) Biochim. Biophys. Acta 734, 40–47) are discussed.     

Purification of cAMP-specific phosphodiesterase from rat heart by affinity chromatography on immobilized rolipram

Affinity chromatography on a cAMP-specific phosphodiesterase inhibitor related to Rolipram, immobilized to AH Sepharose allowed to perform an efficient purification of the cAMP-specific phosphodiesterase isoenzyme from rat heart cytosol (102-fold purification with a 35% yield in a single step). This affinity chromatography involved a biospecific interaction since a 2 mM cAMP elution step at 30 degrees C was necessary for releasing the cAMP specific form tightly bound on the affinity gel. The cAMP eluate fraction exhibited a high specificity towards cAMP (cAMP/cGMP hydrolysis ratio 5-10), a marked sensitivity to Rolipram inhibition and could be resolved in two cAMP-specific, highly Rolipram-sensitive peaks of pI 6.7 and 4.8 by IEF on polyacrylamide gel plates. Protein stain of the IEF gel revealed a single band at pI 6.7.