Nitrate-uptake restraint in Banksia spp. (Proteaceae) and Melaleuca spp. (Myrtaceae) from a severely phosphorus-impoverished environment

Plant and Soil - South-western Australia has some of the most phosphorus (P)-impoverished soils in the world. Hakea prostrata (Proteaceae) has nitrate (NO3?)-uptake restraint, associated with...     

Evidence for apical endocytosis in polarized hepatic cells: phosphoinositide 3-kinase inhibitors lead to the lysosomal accumulation of resident apical plasma membrane proteins.

The architectural complexity of the hepatocyte canalicular surface has prevented examination of apical membrane dynamics with methods used for other epithelial cells. By adopting a pharmacological approach, we have documented for the first time the internalization of membrane proteins from the hepatic apical surface. Treatment of hepatocytes or WIF-B cells with phosphoinositide 3-kinase inhibitors, wortmannin or LY294002, led to accumulation of the apical plasma membrane proteins, 5'-nucleotidase and aminopeptidase N in lysosomal vacuoles. By monitoring the trafficking of antibody-labeled molecules, we determined that the apical proteins in vacuoles came from the apical plasma membrane. Neither newly synthesized nor transcytosing apical proteins accumulated in vacuoles. In wortmannin-treated cells, transcytosing apical proteins traversed the subapical compartment (SAC), suggesting that this intermediate in the basolateral-to-apical transcytotic pathway remained functional. Ultrastructural analysis confirmed these results. However, apically internalized proteins did not travel through SAC en route to lysosomal vacuoles, indicating that SAC is not an intermediate in the apical endocytic pathway. Basolateral membrane protein distributions did not change in treated cells, uncovering another difference in endocytosis from the two domains. Similar effects were observed in polarized MDCK cells, suggesting conserved patterns of phosphoinositide 3-kinase regulation among epithelial cells. These results confirm a long-held but unproven assumption that lysosomes are the final destination of apical membrane proteins in hepatocytes. Significantly, they also confirm our hypothesis that SAC is not an apical endosome.     

The site of action of the F transfer inhibitor

Summary The mechanism of inhibition of F transfer from E. coli K12 cells containing the fin ⁺ R factor R100 was studied. For this, a series of Flac double mutants carrying both a traO ^-mutation, which prevents function of the transfer inhibitor, and a suppressible mutation in one of ten genes required for conjugational DNA transfer, were constructed. The levels of retransfer of these elements from cells carrying a wild-type Fhis element and R100 showed that of the ten transfer genes, only traJ was directly affected by the transfer inhibitor. Furthermore, in the case of R100 and therefore probably in the case of F itself, it was shown that the products of the other nine genes are absent from the cell during transfer inhibition, suggesting that the traJ product is required for their synthesis.D.F. acknowledges the support of a George Murray Scholarship from the University of Adelaide, Australia.     

Autonomic neuropathy in Fabry disease: a prospective study using the Autonomic Symptom Profile and cardiovascular autonomic function tests

Background  

Fabry patients have symptoms and signs compatible with autonomic dysfunction. These symptoms and signs are considered to be due to impairment of the peripheral nervous system, but findings indicative of autonomic neuropathy in other diseases, such as orthostatic intolerance and male sexual dysfunction, are infrequently reported in Fabry disease. The aim of our study was to investigate autonomic symptoms and cardiovascular autonomic function in a large cohort of male and female Fabry patients.