Responses of Nine Trifolium repens L. Populations to Ultraviolet-B Radiation: Differential Flavonol Glycoside Accumulation and Biomass Production

This study aimed to quantify and identify flavonoids involvedin the response of nine populations of white clover (Trifoliumrepens L.) to ultraviolet-B radiation (UV-B). Plants were grownfor 12 weeks in controlled environment rooms with or withoutsupplemental UV-B radiation of 13.3 kJ m^-2d^-1. Methanol–waterextractable flavonoids were quantified using high performanceliquid chromatography (HPLC). Two major peaks showed significantenhancement in the HPLC chromatogram in response to supplementalUV-B. The structures of the compounds responsible were identifiedby¹H and¹³C nuclear magnetic resonance (NMR) spectroscopy tobe the flavonols quercetin-3-O-ß- D -xylopyranosyl-(1 2)-ß- D -galactopyranoside and kaempferol-3-O-ß-D -xylopyranosyl-(1 2)-ß- D -galactopyranoside. Withsupplemental UV-B, quercetin glycoside levels increased on averageby 200% while the kaempferol glycoside response was much smaller.Significant differences in flavonol accumulation were foundamong T. repens populations, both constitutively and in responseto UV-B. Stress-adapted populations displayed particularly highflavonol levels under UV-B. There was an inverse correlationbetween plant productivity and quercetin accumulation. Furthermore,higher quercetin accumulation under UV-B was correlated withtolerance against UV-B-induced growth reduction. In conclusion,within-species comparisons in T. repens lend support to a distinctrole for ortho -dihydroxylated flavonoids in the adaptationto UV-B stress and suggest particular advantages in this UV-B-inducedbiochemical adaptation for populations characterized by lowhabitat and plant productivity. Copyright 2000 Annals of BotanyCompany Ultraviolet-B, Trifolium repens, white clover, HPLC, NMR, flavonoids, flavonols, quercetin, kaempferol, biomass, genetic variation, intraspecific     

Instructions for Authors

Instructions for Authors

Instructions for Authors     

The apbE Gene Encodes a Lipoprotein Involved in Thiamine Synthesis in Salmonella typhimurium

Thiamine pyrophosphate is an essential cofactor that is synthesized de novo in Salmonella typhimurium. The biochemical steps and gene products involved in the conversion of aminoimidazole ribotide (AIR), a purine intermediate, to the 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) moiety of thiamine have yet to be elucidated. We have isolated mutations in a new locus (Escherichia coli open reading frame designation yojK) at 49 min on the S. typhimurium chromosome. Two significant phenotypes associated with lesions in this locus (apbE) were identified. First, apbE purF double mutants require thiamine, specifically the HMP moiety. Second, in the presence of adenine, apbE single mutants require thiamine, specifically both the HMP and the thiazole moieties. Together, the phenotypes associated with apbE mutants suggest that flux through the purine pathway has a role in regulating synthesis of the thiazole moiety of thiamine and are consistent with ApbE being involved in the conversion of AIR to HMP. The product of the apbE gene was found to be a 36-kDa membrane-associated lipoprotein, making it the second membrane protein implicated in thiamine synthesis.     

Effects of 2-Deoxy-d-Glucose on Methamphetamine-Induced Dopamine and Serotonin Neurotoxicity

Abstract: The mechanisms underlying the neurotoxic actions of methamphetamine (METH) and related substituted amphetamines are unknown. Previous studies with 2-deoxyglucose (2-DG) have suggested that METH-induced neurotoxicity may involve exhaustion of intracellular energy stores. However, because 2-DG also produces hypothermic effects, and because METH's neurotoxic actions are highly susceptible to thermoregulatory influence, previous findings with 2-DG are difficult to interpret. The present studies were undertaken to further examine the influence of 2-DG's glucoprivic and thermic effects in the context of METH-induced dopamine (DA) and serotonin (5-HT) neurotoxicity. 2-DG protected against METH-induced DA neurotoxicity in both rats and mice. In both species, 2-DG, alone or in combination with METH, produced hypothermic effects. METH's toxic effects on brain 5-HT neurons were either unaffected or exacerbated by 2-DG, depending on species, brain region, and dose of METH tested. These results indicate that different mechanisms may underlie METH-induced DA and 5-HT neurotoxicity, and suggest that, as compared with 5-HT neurons, DA neurons are more susceptible to temperature influence, whereas 5-HT neurons are more vulnerable than DA neurons to metabolic compromise. Additional studies are needed to further assess the role of energy stores in the neurotoxic effects of METH and related drugs.     

The role of hypersalinity in the persistence of the Texas 'brown tide' in the Laguna Madre

A brown tide bloom of the alga Aureoumbra lagunensis was presentwithout interruption in the Laguna Madre of Texas from January1990 through October 1997. This is the longest continual phytoplanktonbloom of which we are aware. Although the factors leading tothe initiation of this bloom have been well documented, thefactors contributing to its persistence are still being investigated.Two physical characteristics of the Laguna Madre may play animportant role: the long turnover time for waters in this coastallagoon (–1 year) and the hypersaline conditions that usuallyexist (40–60 PSU) due to evaporation exceeding precipitation.In this study, we examined the effects of salinity on the growthrates of the brown tide alga and on the growth of one of itsprotozoan grazers. Historical data from before the onset ofthe brown tide provide evidence for the suppression of microzooplanktonpopulations and mesozooplankton growth caused by hypersalinity.The brown tide alga will grow in a remarkably wide range ofsalinities ranging from 10 to 90 PSU. Maximum growth rates areachieved at salinities ranging from 20 to 60 PSU. One commongrazer on the brown tide alga, the heterotrophic dinoftagellateOxyrrhis marina, was found to grow more slowly under hypersalineconditions. The normally hypersaline conditions of the LagunaMadre may, therefore, favor the brown tide alga over other phytoplanktonspecies that do not grow well under hypersaline conditions,and also suppress the growth and feeding rates of potentialgrazers.     

Recommendations for the presentation of NMR structures of proteins and nucleic acids – IUPAC-IUBMB-IUPAB Inter-Union Task Group on the Standardization of Data Bases of Protein and Nucleic Acid Structures Determined by NMR Spectroscopy

The recommendations presented here are designed to support easier communication of NMR data and NMR structures of proteins and nucleic acids through unified nomenclature and reporting standards. Much of this document pertains to the reporting of data in journal articles; however, in the interest of the future development of structural biology, it is desirable that the bulk of the reported information be stored in computer-accessible form and be freely accessible to the scientific community in standardized formats for data exchange. These recommendations stem from an IUPAC-IUBMB-IUPAB inter-union venture with the direct involvement of ICSU and CODATA. The Task Group has reviewed previous formal recommendations and has extended them in the light of more recent developments in the field of biomolecular NMR spectroscopy. Drafts of the recommendations presented here have been examined critically by more than 50 specialists in the field and have gone through two rounds of extensive modification to incorporate suggestions and criticisms.     

Refined radiation hybrid map of mouse Chromosome 17

We have made a radiation hybrid map of mouse Chromosome (Chr) 17 with 75 microsatellite markers, including those from McCarthy et al. (Genome Res 7, 1153–1161, 1997). Seventy-four of the markers are linked at LOD > 9, and all link at LOD > 5. A LOD 3 framework of 18 markers was used to construct a placement map. The order obtained is in good agreement with genetic maps, and distance estimates give an idea of how recombination rates vary across the chromosome. Recombination is remarkably low with respect to RH break frequency in the region from the centromere to the end of H2. This is similar in interspecific and intersubspecific crosses despite the inversion of a substantial part of this region in Mus spretus with respect to Mus musculus. Received: 10 April 1998 / Accepted: 18 June 1998     

Effect of flutamide on survival in patients with pancreatic cancer: results of a prospective,randomised, double blind,placebo controlled trial

Objectives: To assess whether flutamide (Drogenil), a pure androgen receptor blocking agent, improves survival in patients with pancreatic carcinoma and thus whether testosterone is a major growth factor for this tumour. Design: A prospective, randomised, double blind placebo controlled trial. Subjects: 49 patients with a clinical diagnosis of pancreatic carcinoma. Interventions: 24 patients received flutamide and 25 received placebo. Main outcome measures: Death of the patient. Results: Analysis of all patients at 6 months and 1 year showed 14 and eight patients alive, respectively, in the flutamide group compared with 10 and one in the placebo group. After exclusion of those patients in both groups who received less than 6 weeks’ treatment because of advanced disease and early death the comparable results were 14 (88%) and eight (50%) alive in the flutamide group compared with 10 (50%) and one (5%) in the placebo group. Median survival for all patients was 8 months in the flutamide group compared with 4 months in the placebo group. With the 6 week exclusions median survival was 12 months compared with 5 months, respectively. Conclusions: This study supports the concept that testosterone is a growth factor for pancreatic carcinoma and that blockade of androgen receptors offers an appropriate new approach to treatment.

Key messages

• Previous work suggests that androgens may be involved in the growth of pancreatic cancer
• This study shows that the antiandrogen flutamide doubles median survival in patients with pancreatic cancer
• The treatment is well tolerated by patients with minimal side effects, an important consideration in those with advanced malignant disease
• The concept that testosterone may be a growth factor in pancreatic adenocarcinoma is supported by this trial