The ubiquitin C‐terminal hydrolase UCH‐L1 promotes bacterial invasion by altering the dynamics of the actin cytoskeleton

Invasion of eukaryotic target cells by pathogenic bacteria requires extensive remodelling of the membrane and actin cytoskeleton. Here we show that the remodelling process is regulated by the ubiquitin C‐terminal hydrolase UCH‐L1 that promotes the invasion of epithelial cells by Listeria monocytogenes and Salmonella enterica. Knockdown of UCH‐L1 reduced the uptake of both bacteria, while expression of the catalytically active enzyme promoted efficient internalization in the UCH‐L1‐negative HeLa cell line. The entry of L. monocytogenes involves binding to the receptor tyrosine kinase Met, which leads to receptor phosphorylation and ubiquitination. UCH‐L1 controls the early membrane‐associated events of this triggering cascade since knockdown was associated with altered phosphorylation of the c‐cbl docking site on Tyr1003, reduced ubiquitination of the receptor and altered activation of downstream ERK1/2‐ and AKT‐dependent signalling in response to the natural ligand Hepatocyte Growth Factor (HGF). The regulation of cytoskeleton dynamics was further confirmed by the induction of actin stress fibres in HeLa expressing the active enzyme but not the catalytic mutant UCH‐L1_C90S. These findings highlight a previously unrecognized involvement of the ubiquitin cycle in bacterial entry. UCH‐L1 is highly expressed in malignant cells that may therefore be particularly susceptible to invasion by bacteria‐based drug delivery systems.     

The effect of exogenous hormone treatment on spermiation and vitellogenesis in the grey mullet, Mugil cephalus L.

The effects of mammalian gonadotropins, methyltestosterone and partially purified salmon gonadotropin on spermiation and oocyte maturation were studied in adult grey mullet. Methyltestosterone was a potent spermiating agent in both prespawning and spawning trials. The most effective dose was 5 mg/100 g body weight. Human chorionic gonadotropin (HCG) was moderately effective at a dose rate of 20 IU/100 g body weight. Both hormones blocked resorption of milt in captive animals. The HCG, FSH/LH combination, Synahorin+mullet pituitary homogenate, and partially purified salmon gonadotropin were equally effective, at the doses used, in inducing oocyte maturation and preventing onset of atrophy before completion of vitellogenesis. Atrophy occurred in all experimental fish at mean oocyte diameter of 750 μ. The significance of this finding is discussed. (Oceanic Institute Contribution No. 98).     

Changes in the size of the myocardial damaged area in postischemic reperfusion

The changes in the size of the myocardial injury area during reperfusion after the coronary occlusion-induced ischemia lasting 30 minutes are phasic in nature. Until 3.5 h the injured area increases and after 23.5 h relatively diminishes. After a more prolonged ischemia such manifestations are either unmarked or absent. Ischemia lasting from 30 min to 4 hours followed by reperfusion, as compared with ischemia of the same duration without reperfusion, normally gives rise to the formation of an area of injury, which is less or occasionally equal in size. The data obtained and reported indicate that in the area of coronary occlusion there are groups of cardiomyocytes that differ as regards the resistance to ischemia.     

Influenza A Gradual and Epochal Evolution: Insights from Simple Models

The recurrence of influenza A epidemics has originally been explained by a “continuous antigenic drift” scenario. Recently, it has been shown that if genetic drift is gradual, the evolution of influenza A main antigen, the haemagglutinin, is punctuated. As a consequence, it has been suggested that influenza A dynamics at the population level should be approximated by a serial model. Here, simple models are used to test whether a serial model requires gradual antigenic drift within groups of strains with the same antigenic properties (antigenic clusters). We compare the effect of status based and history based frameworks and the influence of reduced susceptibility and infectivity assumptions on the transient dynamics of antigenic clusters. Our results reveal that the replacement of a resident antigenic cluster by a mutant cluster, as observed in data, is reproduced only by the status based model integrating the reduced infectivity assumption. This combination of assumptions is useful to overcome the otherwise extremely high model dimensionality of models incorporating many strains, but relies on a biological hypothesis not obviously satisfied. Our findings finally suggest the dynamical importance of gradual antigenic drift even in the presence of punctuated immune escape. A more regular renewal of susceptible pool than the one implemented in a serial model should be part of a minimal theory for influenza at the population level.     

An improved purification method for cytosolic malate dehydrogenase from several sources

A new purification method for cytosolic malate dehydrogenases from several sources has been developed. The procedure, employing chromatographies on 5'AMP-Sepharose, DEAE-Sephacel and Blue-Sepharose, allows for a rapid isolation of the enzyme (approximately 40 hours), in large quantities, with good yields (45-54%). The specific activity of final preparations were around 1300 I.U./mg and were judged homogeneous by polyacrylamide gradient gel and sodium dodecyl sulfate polyacrylamide gel electrophoresis, high performance size exclusion chromatography and isoelectric focusing.     

DNA Sequences from Formalin-Fixed Nematodes: Integrating Molecular and Morphological Approaches to Taxonomy

To effectively integrate DNA sequence analysis and classical nematode taxonomy, we must be able to obtain DNA sequences from formalin-fixed specimens. Microdissected sections of nematodes were removed from specimens fixed in formalin, using standard protocols and without destroying morphological features. The fixed sections provided sufficient template for multiple polymerase chain reaction-based DNA sequence analyses.