Iron acquisition and virulence in the motile aeromonads: siderophore-dependent and -independent systems

During an infection, a microbial pathogen must acquire all of its iron from the host. Aeromonas isolated producing the siderophore amonabactin obtain iron either from host Fe-transferrin (siderophore dependent) or from host heme-containing molecules (siderophore independent). Isolates producing the siderophore enterobactin do not utilize Fe-transferrin in serum and probably rely exclusively on host heme iron.     

Hypersensitivity to endotoxin hepatotoxicity in rats with inflammatory lesions

Summary The ratio of sinusoidal nonparenchymal cells to hepatocytes in rat liver was significantly increased following induction of inflammation, and decreased after subsequent exposure to endotoxin, particularly in the region around the terminal portal venules. Rats with inflammatory lesions were more sensitive to endotoxin hepatocytotoxicity than normal controls, as judged from the dose-dependent increase in activity of serum transaminases and from the extent of liver tissue injury. In addition, these animals, which were already in a state of depletion of hepatic glycogen, demonstrated marked hyperglycemia 24 h after endotoxin administration in small doses of less than 2 mg/kg.     

Calcium uptake by sarcoplasmic reticulum from nerve-intact and standard skeletal muscle grafts

A freely grafted rat soleus muscle exhibits a decrease in velocity and capacity of SR calcium uptake. This deficit is not prevented by maintaining neural connections (nerve-intact graft) during grafting. Thus the greater mechanical capability of nerve-intact grafts, relative to standard grafts, is not accompanied by any enhancement of the SR tubules.     

Use of three specific radioimmunoassays in measuring neurohypophysial hormone content and plasma concentrations of vasopressin, oxytocin and DDAVP in rats after prolonged infusion of DDAVP

Specific radioimmunoassays (RIA) were employed for measuring plasma and neurohypophysial concentrations of oxytocin (OT) and vasopressin (AVP) after administration of 1-deamino-8-D-Arg-vasopressin (DDAVP). DDAVP concentrations were measured by a newly-developed specific RIA. Through the use of minipumps, DDAVP was infused i.p. over a period of 3 days in normally hydrated rats. Despite decreased urine production and increased urine osmolality no changes could be observed in neurohypophysial and plasma hormone concentrations.     

Molecular cloning of the fibroin light chain complementary DNA and its use in the study of the expression of the light chain gene in the posterior silk gland of Bombyx mori

Fibroin light chain (L-chain) mRNA (mol. wt 4.0 X 10(5) daltons) was purified from the posterior silk gland of the silkworm, Bombyx mori (J-131 strain). Double-stranded complementary DNA was synthesized and inserted into the PstI site of pBR322 employing the oligo(dC)-oligo(dG) tailing method. Several recombinant plasmids containing the inserts of about 800 base pairs were isolated. Hybridization-translation assay demonstrated that these clones hybridized specifically with the fibroin L-chain mRNA. One of these clones (pLA23) was used as a probe to investigate relative concentrations of the fibroin L-chain gene and mRNA in the posterior silk glands at different stages of late larval development.     

Seasonality in the reproductive phenology ofFicus: Its evolution and consequences

Summary Ficus can only reproduce if they are pollinated by mutualistic wasps that breed within the figs. Pollen-loaded wasps enter the figs when the female flowers are receptive. Several weeks later, their offspring load pollen within the fig and then emerge. As individual trees typically produce crops of synchronous figs at long intervals, the shortlived wasps have to move to another, receptive, tree. The wasp population can only survive, and hence the fig population reproduce, if there are trees fruiting all over the year. When only few trees are present within a population gaps in the flowering sequence may lead to the extinction of the local pollinator population. Two models are presented. One investigates the number of trees necessary in order to sustain a local pollinator population when the tree population has a seasonal pattern of fruiting. The second model investigates how such a seasonal pattern may evolve within a fig population as a result of individual selection on the trees. It is shown that pollinator populations are fragilized under seasonal conditions. Hence, the breeding system ofFicus limits their expansion into highly seasonal habitats. Seasonal habitats may also lead to seasonal adjustment of male versus female investments and to the evolution of dioecy.