The permeability of rat liver lysosomes to sugars. Evidence for carrier-mediated facilitated diffusion.

1. By the osmotic-protection method, the penetration of sugars through the rat liver lysosomal membranes was studied with a view of determining whether sugar uptake was by facilitated diffusion. 2. The following criteria for this type of transport were established: sugar specificity, the order of uptake being 2-deoxy-D-glucose less than D-glucose less than D-mannose less than D-galactose less than D-ribose less than 2-deoxy-D-ribose; stereospecificity, the uptake of L-glucose and L-ribose being 50% slower than their D-stereoisomers; inhibition by 1 MM-phlorrhizin and 1 M-cytochalastin B; competition between sugars for uptake, and a Q10 (rate difference over a 10 degrees C temperature range) for uptake of approx. 2.8. 3. It is proposed that sugar uptake into lysosomes from rat liver is by facilitated diffusion.     

Proposed follow up programme after curative resection for lower third oesophageal cancer

Cyclins are indispensable elements of the cell cycle and derangement of their function can lead to cancer formation. Recent studies have also revealed more mechanisms through which cyclins can express their oncogenic potential. This review focuses on the aberrant expression of G1/S cyclins and especially cyclin D and cyclin E; the pathways through which they lead to tumour formation and their involvement in different types of cancer. These elements indicate the mechanisms that could act as targets for cancer therapy.     

Mechanisms of spatial competition in marine soft-bottom communities

Two kinds of biogenic structures, roots of seagrasses and tubes of invertebrates, were found to reduce the mobility of a variety of burrowing species, including two polychaetes (Abarenicola pacifica Healy & Wells, A. claparedii Healy & Wells), two bivalves (Macoma nasuta Conrad, Clinocardium nuttalliiConrad), two crustaceans (Upogebia pugettensis (Dana), Callianassa californiensis Dana), a holothurian (Leptosynapta clarkii Heding), and an echinoid (Dendraster excentricus (Eschscholtz)). Comparisons of burrowing in similar sediments showed that: (a) all species had about a two-fold increase in mean time to burial in dense tube-mats of polychaetes and crustaceans; (b) hard-bodied taxa were particularly restricted by roots of Zostera marina L. and were often incapable of penetrating them; (c) roots and tubes together had the greatest impact, with mobility 3 to 37 times slower; and (d) burrowing ability increased when sediments were “pre-burrowed” for 1 day. Comparisons of burrowing rates in different sediments showed effects of physical origin (sediment compaction or sorting). Overall these physical effects were second to those of purely biogenic origin, sediment binding and cohesion by roots and tubes. Nonetheless, physical effects exceeded those of extremely high densities of tube-builders (3160 individuals ·0.01 m^?2). In all substrata the movement of larger individuals, and the larger of morphologically similar pairs of species (listed second above), were more restricted by roots and tubes than were smaller ones. The results suggest a general mechanism by which dense assemblages of tube-builders and seagrasses may restrict older and larger burrowing organisms. Because physical properties of the sediment and the abundance of other burrowers are also factors affecting mobility, it is not now possible to predict what situations will render this mechanism of interaction important to natural communities.