Antitumour activities of levans produced by Zymomonas mobilis strains

Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.     

Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex

The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S nuclear ribosomal DNA sequence and the intervening 5.8S region were sequenced from three individuals in each of eight taxa of the Mimulus guttatus species complex. Three discrete variants, or "types," of ITS sequences were found, among which 30%-40% of sites differed, compared with 1%-2% within types. Dot plots indicate that these types were not related by conspicuous rearrangements or inversions. More than one ITS type was often found in the same taxon, and two of three ITS types span species boundaries, indicating their presence prior to speciation. These ITS sequences showed essentially no positional homology with the nearest sequenced relative, tomato. In contrast, the 5.8S region was relatively unvaried, with 8 of 162 sites varied in the sample among all eight taxa. The phylogeny inferred by the most common ITS sequence type, rooted by the two other ITS types, agreed with isozymes in showing the distinctness of M. nudatus, M. laciniatus, and M. tilingii from the other five taxa.      

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

DNA degradation in wild-type and repair-deficient strains of salmonella typhimurium exposed to ultraviolet light of photodynamic treatment.

Five mutants of Salmonella typhimurium strain LT2 trp DI (ColEI)+, initiallly detected because they released little or no colicin when tested on solid medium, proved to be sensitive to ultraviotet light (u.v.). Further testing indicated that one of the mutants was deficient in genetic recombination and was probably a recA-type mutant, while three of the others were deficient in DNA polymerase activity and appeared to be typical polA mutants. The fifth mutant was less sensitive than the others to methyl methanesulphonate, showed reduced proficiency in genetic recombination, and was of approximately normal u.v. mutability. This mutant may be a counterpart of the class known as uvrD in Escherichia coli. All five mutants degraded significantly more of their DNA following exposure to u.v. than did the wild-type strain. The recA-type mutant and the possible uvrD mutant also degraded significantly more of their DNA spontaneously than did the wild-type. Treatment with visible light and acridine orange (photodynamic treatment) cause no significant degradation of DNA in the wild-type strain, a highly significant increase in the extent of DNA degradation in a polA mutant, and a decrease in the extent of degradation in the recA-type mutant.     

Induction of base-pair substitution and prameshift mutations in wild-type and repair-deficient strains of Salmonella typhimurium by the photodynamic action of methylene blue

Induction of back mutations to prototrophy by methylene blue (MB)-sensitized photodynamic (PD) treatment has been studied in wild-type and repair-deficient strains of Salmonella typhimurium carrying either the base-pair substitution mutation hisG46 or the frameshift mutation hisD3052. We found that reversion of the hisG46 mutation was increased in a strain carrying a uvrB deletion and decreased in a strain carrying a recA-type mutation. Reversion of the hisD3052 (frameshift) mutation, on the other hand, was decreased in both uvrB deletion and recA-type strains. The former results are consistent with the hypothesis that the majority of MB-sensitized PD-induced base-pair substitution mutations arise by a mechanism similar to that currently believed to be involved in UV mutagenesis. The latter results suggest that PD-induced frameshift mutations may arise in some other way, and two possible mechanisms involving sequential action of the excision repair and recombinational repair pathways are considered.     

Ion mobility mass spectrometry for peptide analysis

The use of ion mobility mass spectrometry has grown rapidly over the last two decades. This powerful analytical platform now forms an attractive prospect for comprehensive analysis of many different molecular species, including chemically complex biological molecules. This paper describes the application of IM-MS to the study of peptides. We focus on three different ion mobility devices that are most frequently found in tandem with mass spectrometers. These are instruments using linear drift tubes (LDT), those using travelling wave ion guides (TWIGS) and those employing high field asymmetric ion mobility spectrometry (FAIMS). Each technique is described. Examples are given on the use of IM-MS for the determination of peptide structure, the study of peptides that form amyloid fibrils, and the study of complex peptide mixtures in proteomic investigations. We describe and comment on the methodologies used and the outlook for this developing analytical technique.     

Lipoprotein-associated phospholipase A2 as a target of therapy

PURPOSE OF REVIEW: Considerable discussion continues regarding the precise role that secreted lipoprotein-associated phospholipase A2 (Lp-PLA2), also called platelet-activating factor acetylhydrolase, plays in atherosclerosis. Since interest in this enzyme as a putative drug target has been based primarily upon its association with low-density lipoprotein (LDL) in human plasma, this review will focus on Lp-PLA2 and human coronary heart disease. RECENT FINDINGS: Recent reports have linked Lp-PLA2 enrichment not only to the most atherogenic of LDL particles but also to the most advanced, rupture-prone, plaques. Electronegative LDL has been shown to be highly enriched in Lp-PLA2; and in advanced atheroma, Lp-PLA2 levels are highly upregulated, colocalizing with macrophages in both the necrotic core and fibrous cap. Lp-PLA2 is well placed, whether on an oxidation susceptible LDL particle or in the highly oxidative environment of an advanced rupture-prone plaque, to hydrolyse oxidized phospholipid and generate significant quantities of the two pro-inflammatory mediators, lysophosphatidylcholine and oxidized nonesterified fatty acid. Several studies have confirmed that Lp-PLA2 is an independent risk factor for cardiovascular events (i.e. myocardial infarction and stroke). Although epidemiology studies consistently support a relationship between plasma Lp-PLA2 levels and susceptibility to coronary heart disease this is not the case for Lp-PLA2 polymorphisms. Two clinical studies have linked the Ala-379-->Val polymorphism with a reduced risk of myocardial infarction, but functional differences between the AA and VV polymorphs have yet to be demonstrated. SUMMARY: Lp-PLA2 is intimately associated with several aspects of human atherogenesis. Although various lipid-lowering therapies, such as statins, have been shown to reduce plasma levels of Lp-PLA2, none has been studied in terms of its ability to lower the large macrophage-mediated upregulation of Lp-PLA2 within advanced plaques.     

2-(Alkylthio)pyrimidin-4-ones as novel, reversible inhibitors of lipoprotein-associated phospholipase A2

Starting from two weakly active hits from high throughput screening, a novel series of 2-(alkylthio)-pyrimidin-4-ones with high potency and selectivity for lipoprotein-associated phospholipase A2 has been designed. In contrast to previously known inhibitors, these have been shown to act by a non-covalent and substrate competitive mechanism.     

Effects of long-term fixation on histological quality of undecalcified murine bones embedded in methylmethacrylate

While long-term fixation and storage of specimens is common and useful for many research projects, it is particularly important for space flight investigations where samples may not be returned to Earth for several months (International Space Station) or years (manned mission to Mars). We examined two critical challenges of space flight experimentation: the effect of long-term fixation on the quality of mouse bone preservation and the preservation of antigens and enzymes for both histochemical and immunohistochemical analyses, and how the animal/sample processing affects the preservation. We show that long-term fixation minimally affects standard histological staining, but that enzyme histochemistry and immunolabeling are greatly compromised. Further, we demonstrate that whole animal preservation is not as suitable as whole leg or stripped leg preservation for long-term fixation and all histological analyses. Overall, we recommend whole leg processing for long-term storage of bone specimens in fixative prior to embedding in plastic for histological examination.     

Potent, orally active inhibitors of lipoprotein-associated phospholipase A(2): 1-(biphenylmethylamidoalkyl)-pyrimidones.

A series of 1-(biphenylmethylamidoalkyl)-pyrimidones has been designed as nanomolar inhibitors of recombinant lipoprotein-associated phospholipase A(2) with high potency in whole human plasma. 5-(Pyrazolylmethyl) derivative 16 and 5-(methoxypyrimidinylmethyl) derivative 27 demonstrated excellent pharmacodynamic profiles which correlated well with their pharmacokinetic effects.