Combinatorial modification of natural products: synthesis and in vitro analysis of derivatives of thiazole peptide antibiotic GE2270 A: A-ring modifications

Thiazole peptide GE2270 A (1) possesses potent antimicrobial activity against many gram-positive pathogens, including methicillin resistant Staphylococcus aureus (S. aureus, MRSA; MIC(90)=0.06 microg/mL) and vancomycin resistant Enterococcus spp. (VRE; MIC(90)=0.03 microg/mL); however its poor aqueous solubility has prohibited its development for the clinical treatment of infections. An integrated combinatorial and medicinal chemistry program was employed to identify derivatives of 1 that retain activity but possess greatly enhanced aqueous solubility.     

Prevalence and Genetic Diversity of Campylobacter spp. in Environmental Water Samples from a 100-Square-Kilometer Predominantly Dairy Farming Area

Water samples were taken systematically from a 100-km² area of mainly dairy farmland in northwestern England and examined for Campylobacter spp. Pulsed-field gel electrophoresis-restriction fragment length polymorphism (PFGE-RFLP) and flaA strain typing of Campylobacter jejuni and Campylobacter coli isolates were done. Data on the water source and the adjacent environment were recorded and examined as explanatory variables. Campylobacter spp. were isolated from 40.5% (n = 119) of the water samples tested. C. jejuni was isolated from 14.3%, C. coli was isolated from 18.5%, and Campylobacter lari was isolated from 4.2% of the samples. Campylobacter hyointestinalis was not isolated from any water source. The difference in prevalence between water types (trough, running, and standing) was significant (P = 0.001). C. jejuni was the species most commonly isolated from trough-water and running-water sources, while C. coli was the most frequently isolated from standing water (P < 0.001). No association was found between the presence of Escherichia coli and that of Campylobacter spp. The final multivariable logistic regression model for Campylobacter spp. included the following variables: water source, soil type, aspect, and amount of cattle fecal material in the environment (fecal pat count). Strain typing demonstrated a diverse population of C. jejuni and the presence of a common C. coli flaA type that was widely distributed throughout the area. Most of the isolates within the common flaA type were discriminated by PFGE-RFLP. These findings suggest a possible role for environmental water in the epidemiology of Campylobacter spp. in a farming environment.     

Effects of bovine urine, plants and temperature on N2O and CO2 emissions from a sub-tropical soil

Grazing ruminants urinate and deposit N onto pastoral soils at rates up to 1,000 kg ha^?1, with most of this deposited N present as urea. In urine patches, nitrous oxide (N₂O) emissions can increase markedly. Soil derived CO₂ fluxes can also increase due to priming effects.While N₂O fluxes are affected by temperature, no studies have examined the interaction of pasture plants, urine and temperature on N₂O fluxes and the associated CO₂ fluxes. We postulated the response of N₂O emissions to bovine urine application would be affected by plants and temperature. Dairy cattle urine was collected, labelled with ¹⁵N, and applied at 590 kg N ha^?1 to a sub-tropical soil,with and without pasture plants at 11°, 19°, and 23°C. Over the experimental period (28 days), 0.2% (11°C with plants) to 2.2% (23°C with plants) of the applied N was emitted as N₂O. At 11°C, plants had no effect on cumulative N₂O-N fluxes, whereas at 23°C, the presence of plants significantly increased the flux, suggesting plant-derived C supply affected the N₂O producing microbes. In contrast, a significant urine application effect on the cumulative CO₂ flux was not affected by varying temperature from 11?C23°C or by growing plants in the soil. This study has shown that plants and their responses to temperature affect N₂O emissions from ruminant urine deposition. The results have significant implications for forecasting and understanding the effect of elevated soil temperatures on N₂O emissions and CO₂ fluxes from grazed pasture systems.     

High-irradiance responses induced by far-red light in grass seedlings of the wild type or overexpressing phytochrome A

The occurrence of phytochrome-mediated highirradiance responses (HIR), previously characterised largely in dicotyledonous plants, was investigated in Triticum aestivum L., Zea mays L., Lolium multiflorum Lam. and in both wild-type Oryza sativa L. and in transgenic plants overexpressing oat phytochrome A under the control of a 35S promoter. Coleoptile growth was promoted (maize, ryegrass) or inhibited (wild-type rice) by continuous far-red light (FRc). However, at equal fluences, hourly pulses of far-red light (FRp) were equally effective, indicating that the growth responses to FRc were not true HIR. In contrast, in maize and rice, FRc increased anthocyanin content in the coleoptile in a fluence-rate dependent manner. This response was a true HIR as FRp had reduced effects. In maize, anthocyanin levels were significantly higher under FRc than under continuous red light. In rice, overexpression of phytochrome A increased the inhibition of coleoptile growth and the levels of anthocyanin under FRc but not under FRp or under continuous red light. The effect of FRc was fluence-rate dependent. In light-grown rice, overexpression of phytochrome A reduced leaf-sheath length, impaired the response to supplementary far-red light, but did not affect the response to canopy shade-light. In grasses, typical HIR, i.e. fluence-rate dependent responses showing reciprocity failure, can be induced by FRc. Under FRc, overexpressed phytochrome A operates through this action mode in transgenic rice.Abbreviations FR far-red light - FRc continuous far-red light - FRp pulses of far-red light - HIR high-irradiance responses - LFR low-fluence responses - OPHYA transgenic rice overexpressing oat phytochrome A - Pfr far-red light-absorbing form of phytochrome - phyA phytochrome A - R red light - Rc continuous red light - VLFR very low-fluence responses - WT wildtype We thank Marcelo J. Yanovsky for his help with the photographs and Professor Rodolfo A. Sanchez for providing a reprint of the paper by P.J.A.L. de Lint. This work was supported by grants from UBA (AG041) and Fundacion Antorchas (A-13218/1-15) to J.J.C.     

Drosophila P element-enhanced transfection in mammalian cells.

We constructed a gene transfer vector containing the herpes simplex virus type 1 thymidine kinase (TK) gene flanked by Drosophila P element terminal repeats (W. R. Engels, Annu. Rev. Genet. 17:315-344). This vector was introduced into mouse LTK- cells and enhanced the frequency of stable transformation to the TK+ phenotype by approximately 50-fold relative to a similar plasmid lacking the P element terminal repeats.     

Basis of unique red cell membrane properties in hereditary ovalocytosis.

Hereditary ovalocytes from a Mauritian subject are extremely rigid, with a shear elastic modulus about three times that of normal cells, and have increased resistance to invasion by the malaria parasite Plasmodium falciparum in vitro. The genetic anomaly resides in band 3; the protein gives rise to chymotryptic fragments with reduced mobility in SDS/polyacrylamide gel electrophoresis, but this is a result of anomalous binding of SDS and not a higher molecular weight. Analysis of the band 3 gene reveals (1) a point mutation (Lys56----Glu), which also occurs in a common asymptomatic band 3 (Memphis) variant and governs the electrophoretic properties, and (2) a deletion of nine amino acid residues, including a proline residue, encompassing the interface between the membrane-associated and the N-terminal cytoplasmic domains. The interaction of the mutant band 3 with ankyrin appears unperturbed. The fraction of band 3 capable of undergoing translation diffusion in the membrane is greatly reduced in the ovalocytes. Cells containing the asymptomatic band 3 variant were normal with respect to all the properties that we have studied. Possible mechanisms by which a structural change in band 3 at the membrane interface could regulate rigidity are examined.     

Archaeological discoveries at Rutland Water

This paper summarises the results of archaeological excavations on the Rutland Water site from 1967 to date. They range from Iron Age to Medieval and include Romano-British farmsteads and two Anglo-Saxon cemeteries.     

Confirmation of the structures of the phytoalexins lathodoratin and methyl-lathodoratin by synthesis

The two chromone phytoalexins were synthesized by condensing 2,4,6-trihydroxybutyrophenone with dimethylformamide.