A radiation hybrid map of chicken Chromosome 4

The mapping resolution of the physical map for chicken Chromosome 4 (GGA4) was improved by a combination of radiation hybrid (RH) mapping and bacterial artificial chromosome (BAC) mapping. The ChickRH6 hybrid panel was used to construct an RH map of GGA4. Eleven microsatellites known to be located on GGA4 were included as anchors to the genetic linkage map for this chromosome. Based on the known conserved synteny between GGA4 and human Chromosomes 4 and X, sequences were identified for the orthologous chicken genes from these human chromosomes by BLAST analysis. These sequences were subsequently used for the development of STS markers to be typed on the RH panel. Using a logarithm of the odds (LOD) threshold of 5.0, nine linkage groups could be constructed which were aligned with the genetic linkage map of this chromosome. The resulting RH map consisted of the 11 microsatellite markers and 50 genes. To further increase the number of genes on the map and to provide additional anchor points for the physical BAC map of this chromosome, BAC clones were identified for 22 microsatellites and 99 genes. The combined RH and BAC mapping approach resulted in the mapping of 61 genes on GGA4 increasing the resolution of the chicken–human comparative map for this chromosome. This enhanced comparative mapping resolution enabled the identification of multiple rearrangements between GGA4 and human Chromosomes 4q and Xp.     

Myristic acid increases delta6-desaturase activity in cultured rat hepatocytes

In order to study the effects of saturated fatty acids on delta6-desaturase activity, rat hepatocytes in primary culture were incubated with lauric (C12:0), myristic (C14:0) or palmitic (C16:0) acids. After optimization, the standard in vitro conditions for the measurement of delta6-desaturase activity were as follows: 60 micromol x L(-1) alpha-linolenic acid (C18:3n-3), reaction time of 20 min and protein content of 0.4 mg. Data showed that cell treatment with 0.5 mmol x L(-1) myristic acid during 43 h specifically increased delta6-desaturase activity. This improvement, reproducible for three substrates of delta6-desaturase, i.e. oleic acid (C18:1n-9), linoleic acid (C18:2n-6) and alpha-linoleic acid (C18:3n-3) was dose-dependent in the range 0.1-0.5 mmol x L(-1) myristic acid concentration.     

Targeted gene replacement of a ferredoxin gene in Trichomonas vaginalis does not lead to metronidazole resistance

Ferredoxin, Fd, is often deficient in metronidazole-resistant strains of Trichomonas vaginalis and is thought to be necessary for drug activation. To directly test whether Fd is essential for metronidazole susceptibility, gene replacement technology has been developed for T. vaginalis. The selectable marker gene neomycin phosphotransferase (NEO) flanked by approximately 2.6 and approximately 2.0 kBp of the Fd 5' and 3' flanking regions (pKO-FD-NEO) was introduced into cells on linear DNA and selected for NEO gene expression. Stable transformants were shown to contain the NEO gene in the Fd locus and to have completely lost the Fd gene. Northern and immunoblot analyses confirm the loss of Fd mRNA and protein in pKO-FD-NEO cells. Analyses of the activity of hydrogenosomal proteins in Fd KO cells show a fourfold increase in hydrogenase activity and a 95% decrease in pyruvate/ferredoxin oxidoreductase (PFO) activity. In contrast, PFO and hydrogenase mRNA levels are unchanged. Surprisingly, Fd KO cells are not resistant to metronidazole under aerobic or anaerobic conditions. These cells are capable of producing molecular hydrogen, albeit at 50% the level of the parental strain, demonstrating that the Fd gene product eliminated in KO cells is neither necessary for hydrogen production nor metronidazole activation. Together these data indicate the presence of unidentified Fds or flavodoxins capable of drug activation or an unidentified mechanism that does not require either PFO or Fd for metronidazole activation.     

Two minimal Tat translocases in Bacillus

Activity of the Tat machinery for protein transport across the inner membrane of Escherichia coli and the chloroplast thylakoidal membrane requires the presence of three membrane proteins: TatA, TatB and TatC. Here, we show that the Tat machinery of the Gram-positive bacterium Bacillus subtilis is very different because it contains at least two minimal Tat translocases, each composed of one specific TatA and one specific TatC component. A third, TatB-like component is apparently not required. This implies that TatA proteins of B. subtilis perform the functions of both TatA and TatB of E. coli and thylakoids. Notably, the two B. subtilis translocases named TatAdCd and TatAyCy both function as individual, substrate-specific translocases for the twin-arginine preproteins PhoD and YwbN, respectively. Importantly, these minimal TatAC translocases of B. subtilis are representative for the Tat machinery of the vast majority of Gram-positive bacteria, Streptomycetes being the only known exception with TatABC translocases.     

Dynamics of nuclear pore complex organization through the cell cycle

In eukaryotic cells, all macromolecules that traffic between the nucleus and the cytoplasm cross the double nuclear membrane through nuclear pore complexes (NPCs). NPCs are elaborate gateways that allow efficient, yet selective, translocation of many different macromolecules. Their protein composition has been elucidated, but how exactly these nucleoporins come together to form the pore is largely unknown. Recent data suggest that NPCs are composed of an extremely stable scaffold on which more dynamic, exchangeable parts are assembled. These could be targets for molecular rearrangements that change nuclear pore transport properties and, ultimately, the state of the cell.     

Mechanism of lipoprotein retention by the extracellular matrix

PURPOSE OF REVIEW: Considerable evidence suggests that the subendothelial retention of atherogenic lipoproteins is a key early step in atherogenesis. In humans and experimental animals, elevated levels of plasma lipoproteins are associated with increased atherosclerosis, and lipoproteins with higher affinity for arterial proteoglycans are more atherogenic. Here we discuss the molecular mechanisms underlying lipoprotein retention in the arterial wall and how this interaction can be modulated. RECENT FINDINGS: Functional proteoglycan binding sites in lipoproteins containing apolipoprotein B have been identified and shown to have atherogenic potential in vivo. In addition to apolipoprotein B, novel bridging molecules, those that can interact with both proteoglycans and lipoproteins, have been identified that mediate the retention of atherogenic particles in the vessel wall. The interaction between lipoproteins and proteoglycans can be enhanced by the modification of lipoproteins in the circulation and in the arterial wall, by alterations in the subendothelium, and by changes in proteoglycan synthesis that result in a more atherogenic profile. The retention of atherogenic lipoproteins is a potential target for therapies to reverse atherosclerosis, and in-vitro studies have identified compounds that decrease the affinity of proteoglycans for lipoproteins. SUMMARY: Considerable progress has been made in understanding the association between lipoproteins and cardiovascular disease. This review highlights the importance of the interaction between lipoproteins and the arterial matrix.     

Biocorrosion: towards understanding interactions between biofilms and metals

The term microbially influenced corrosion, or biocorrosion, refers to the accelerated deterioration of metals owing to the presence of biofilms on their surfaces. The detailed mechanisms of biocorrosion are still poorly understood. Recent investigations into biocorrosion have focused on the influence of biomineralization processes taking place on metallic surfaces and the impact of extracellular enzymes, active within the biofilm matrix, on electrochemical reactions at the biofilm-metal interface.     

Dendritic development: lessons from Drosophila and related branches

Dendrites show remarkable diversity in morphology and function, but the mechanisms that produce the characteristic forms is poorly understood. Insect systems offer a unique opportunity to manipulate and study identified neurons in otherwise undisturbed environments. Recent studies in Drosophila show that dendritic targeting, branching patterns, territories, and metamorphic remodeling are controlled in specific ways, by intrinsic genetic programs and extrinsic cues, with important implications for function. Here, we review some recent advances in our understanding of dendritic development in insects, focusing primarily on insights that have been gained from studies of Drosophila.