The many faces of c-MYC

The proto-oncogene c-MYC is implicated in various physiological processes-cell growth, proliferation, loss of differentiation, and cell death (apoptosis). Oncogenic c-MYC implies constitutive or deregulated expression of c-MYC and is associated with many human cancers often with poor prognosis. Recently, c-MYC has been implicated in the loss and dysfunction of insulin-producing beta cells in diabetes. Intriguingly, this raises the possibility that c-Myc may be a key contributor to disease, not only by deregulating cell proliferation, which is well established, but also by virtue of its opposing role in engendering apoptosis. However, given the fact that human diseases at diagnosis are generally advanced and pathologically complex, it is generally difficult to attribute a specific pathogenic role to c-MYC, or indeed any given single factor, or to assess the potential of therapies targeting individual such factors. Regulatable transgenic mouse models have shed light on these issues, have influenced our thinking about cancer, and have provided encouragement for the future development of cancer therapies based on targeting individual oncogenes such as c-MYC. Although still in its infancy, encouraging results have been reported for several approaches using gene targeting to interfere with c-MYC expression or activity both in vitro and in vivo.     

Biochemical and Physiological Aspects of Developmental Cycle of Colchicum autumnale L.

This study was conducted to examine the individual developmental stages of Colchicum autumnale. We identified the sclerenchymatic tissue in the middle part of the protuberance. This tissue supports the function of protuberance as a kind of hollow diverticulum. On the boundary of the new corm and the shoot a meristematic layer was recognized. We assume that this abscission zone-like structure can initiate dying back of the above-ground part regularly at the end of annual life-cycle. The major part of starch is reutilized in the mother corm during the autumnal stage, supporting sprouting which takes place in the soil. Decline of starch content is paralleled by increasing of total amylolytic activity. From amylolytic enzymes -amylase, -amylase and -glucosidase have been identified. The presence of pullulanase and starch phosphorylase was not observed. From free sugars glucose, fructose and sucrose were identified in corms. The level of sucrose increased significantly during winter season.     

M142.2 (cut-6), a novel Caenorhabditis elegans matrix gene important for dauer body shape

The cuticle of the nematode Caenorhabditis elegans is a collagenous extracellular matrix which forms the exoskeleton and defines the shape of the worm. We have characterized the C. elegans gene M142.2, and we show that this is a developmentally regulated gene important for cuticle structure. Transgenic worms expressing M142.2 promoter fused to green fluorescent protein showed that M142.2 is expressed in late embryos and L2d predauers, in the hypodermal cells which synthesize the cuticle. The same temporal pattern was seen by RT-PCR using RNA purified from specific developmental stages. A recombinant fragment of M142.2 was expressed in Escherichia coli and used to raise an antiserum. Immunohistochemistry using the antiserum localized M142.2 to the periphery of the alae of L1 and dauers, forming two longitudinal ribbons over the hypodermal cells. Loss-of-function of M142.2 by RNAi resulted in a novel phenotype: dumpy dauers which lacked alae. M142.2 therefore plays a major role in the assembly of the alae and the morphology of the dauer cuticle; because of its similarity to the other cut genes of the cuticle, we have named the gene cut-6.     

Some properties of<Emphasis Type="Italic">Plesiomonas shigelloides</Emphasis> treated with aminoglycosides

The effect of aminoglycoside antibiotics (amikacin, gentamicin, netilmicin and tobramycin) at sublethal concentrations (sub-MICs) on some properties of Plesiomonas shigelloides strains was evaluated. All agents decreased the bacterial surface hydrophobicity. Amikacin (1/4 of the MIC) and netilmicin (1/4 and 1/8 of the MIC) changed the hydrophobic character of P. shigelloides surface to a hydrophilic one. Treatment of the strains with aminoglycosides decreased also motility, netilmicin being the most effective. No significant changes were found in lipolytic activity of antibiotic-treated strains. In the majority of cases aminoglycosides increased sensitivity of bacteria to hydrogen peroxide. The tested antibiotics did not induce production of short-chained N-acylhomoserine lactones signal molecules. Aminoglycosides at sub-MICs affected important activities of P. shigelloides potentially associated with their virulence in dependence on strain, antibiotic and concentration.     

Discovering lactic acid bacteria by genomics

This review summarizes a collection of lactic acid bacteria that are now undergoing genomic sequencing and analysis. Summaries are presented on twenty different species, with each overview discussing the organisms fundamental and practical significance, nvironmental habitat, and its role in fermentation, bioprocessing, or probiotics. For those projects where genome sequence data were available by March 2002, summaries include a listing of key statistics and interesting genomic features. These efforts will revolutionize our molecular view of Gram–positive bacteria, as up to 15 genomes from the low GC content lactic acid bacteria are expected to be available in the public domain by the end of 2003. Our collective view of the lactic acid bacteria will be fundamentally changed as we rediscover the relationships and capabilities of these organisms through genomics.     

Human thrombocytes are able to induce a myocardial dysfunction in the ischemic and reperfused guinea pig heart mediated by free radicals-role of the GPIIb/IIIa-blocker tirofiban

In recent studies, we could demonstrate a myocardial dysfunction induced by homologous platelets in ischemic and reperfused guinea pig hearts. Aim of the current study was to find out whether or not this is a phenomenon specific for platelets isolated from guinea pigs and to further examine the mechanisms of a possible cardiodepressive effect of human platelets. Isolated guinea pig hearts were exposed to a 30 min low-flow ischemia (1 ml/min) and reperfused. Human thrombocytes were administered as bolus (20.000 thrombocytes/microl perfusion buffer) in the 15(th) min of ischemia or in the 1(st) or 5(th) min of reperfusion in the presence of thrombin. Recovery of external heart work (REHW) and intracoronary platelet retention (RET) were quantified in percent. In additional experiments, the GPIIb/IIIa-blocker tirofiban (10 microg/ml perfusion buffer) or the radical scavenger superoxide dismutase (SOD-10 U/ml perfusion buffer) were added. Platelet application in the absence of tirofiban, either during ischemia (REHW 75.4 +/- 4%, RET 22.2 +/- 2%) or the 1st min (REHW 71.6 +/- 1%, RET 31.2 +/- 2%) or the 5th min of reperfusion (REHW 63.2 +/- 4%, RET 40.5 +/- 1%) led to a significant reduction of REHW and a significant increase of RET. The coapplication of tirofiban, on the other hand, prevented RET at all three times of platelet application (1.1 +/- 1.7%, 0% or 2.1 +/- 1.2%, respectively). An improvement of REHW, however, could only be noticed during ischemia (89 +/- 2%), whereas coapplication of tirofiban in early (72.9 +/- 3%) or in late reperfusion (74.6 +/- 2%) did not lead to a significant increase of REHW. Coapplication of SOD, on the other hand, significantly improved REHW in early (88.1 +/- 1) or late (95.9 +/- 1) reperfusion but not during ischemia (83.5 +/- 2). Corresponding to REHW, RET was changed significantly by coapplication of SOD during early (1 +/- 2%) or late (0%) reperfusion but not during ischemia (21.1 +/- 4%). We conclude that human thrombocytes are able to induce a myocardial dysfunction in ischemic and reperfused guinea pig hearts mediated by reactive oxygen species and independent of intracoronary platelet adhesion.     

A model for estimating total parasite load in falciparum malaria patients

We describe an age-structured mathematical model of the malaria parasite life cycle that uses clinical observations of peripheral parasitaemia to estimate population dynamics of sequestered parasites, which are hidden from the clinical investigator. First, the model was tested on parasite populations cultured in vitro, and was found to account for approximately 72% of the variation in that sub-population of parasites that would have been sequestered in vivo. Next, the model was applied to patients undergoing antimalarial therapy. Using individual data sets we found that although the model fitted the peripheral parasite curves very well, unique solutions for the fit could not be obtained; therefore, robust estimates of sequestered parasite dynamics remained unavailable. We conclude that even given detailed data on individual parasitaemia, estimates of sequestered numbers may be difficult to obtain. However, if data on individuals undergoing similar therapy are collected at equal time intervals, some of these problems may be overcome by estimating specific parameters over groups of patients. In this manner we estimated sequestered parasite density in a group of patients sampled at identical time points following antimalarial treatment. Using this approach we found significant relationships between changes in parasite density, age structure and temperature that were not apparent from the analysis of peripheral parasitaemia only.     

Clamp loaders and sliding clamps

A coherent view of the structure and function of DNA polymerase processivity factors (sliding clamps and clamp loaders) is emerging from recent structural studies. Crystal structures of sliding clamps from the T4 and RB69 bacteriophages, and from an archaebacterium expand the gallery of ring-shaped processivity factors and clarify how the clamp interacts with the DNA polymerase. Crystallographic and electron microscopic views of clamp loaders from bacteria, archaebacteria and eukaryotes emphasize their common architecture and have produced models of how ATPbinding might be coupled to clamp opening/loading.