Molecular Architecture of Plant Thylakoids under Physiological and Light Stress Conditions: A Study of Lipid–Light-Harvesting Complex II Model Membranes

In this study, we analyzed multibilayer lipid-protein membranes composed of the photosynthetic light-harvesting complex II (LHCII; isolated from spinach [Spinacia oleracea]) and the plant lipids monogalcatosyldiacylglycerol and digalactosyldiacylglycerol. Two types of pigment-protein complexes were analyzed: those isolated from dark-adapted leaves (LHCII) and those from leaves preilluminated with high-intensity light (LHCII-HL). The LHCII-HL complexes were found to be partially phosphorylated and contained zeaxanthin. The results of the x-ray diffraction, infrared imaging microscopy, confocal laser scanning microscopy, and transmission electron microscopy revealed that lipid-LHCII membranes assemble into planar multibilayers, in contrast with the lipid-LHCII-HL membranes, which form less ordered structures. In both systems, the protein formed supramolecular structures. In the case of LHCII-HL, these structures spanned the multibilayer membranes and were perpendicular to the membrane plane, whereas in LHCII, the structures were lamellar and within the plane of the membranes. Lamellar aggregates of LHCII-HL have been shown, by fluorescence lifetime imaging microscopy, to be particularly active in excitation energy quenching. Both types of structures were stabilized by intermolecular hydrogen bonds. We conclude that the formation of trans-layer, rivet-like structures of LHCII is an important determinant underlying the spontaneous formation and stabilization of the thylakoid grana structures, since the lamellar aggregates are well suited to dissipate excess energy upon overexcitation.     

1-Methyl-3-nitropyridine: An Efficient Oxidant of NADH in Non-enzymatic and Enzyme-mediated Processes

It is shown that NADH can be effectively oxidized by 1-methyl-3-nitropyridine in non-enzymatic and enzyme-mediated processes. Mechanistic issues of these reactions are discussed. These processes seem to contribute to the observed cytotoxicity of 1-methyl-3-nitropyridine. A key role of 1-methyl-3-nitropyridinyl radical formed in the enzyme-mediated processes is emphasized.     

TNP-470 Inhibits Oxidative Stress,Nitric Oxide Production and Nuclear Factor Kappa B Activation in a Rat Model of Hepatocellular Carcinoma

The objective of this study is to determine if treatment with the angiogenesis inhibitor TNP-470 results in impairment of oxidative stress, inhibition of nuclear factor kappa B (NF-κB) activation and decrease of nitric oxide production in an experimental model of rat hepatocarcinogenesis. Tumour was induced by diethylnitrosamine and promoted by two-thirds hepatectomy plus acetaminofluorene administration. Experiments were carried out at 28 weeks after initiating the treatment. TNP-470 was administered at 30 mg/kg, three times per week from 20 to 28 weeks. Carcinomatous tissue growing outside dysplastic nodules and a marked expression of placental glutathione S-transferase were detected in rats with induced carcinogenesis. Liver concentrations of thiobarbituric acid reactive substances, reduced glutathione (GSH) and glutathione disulfide (GSSG) were significantly higher than those of controls and there was a significant increase in the GSSG/GSH ratio. Tumour growth was accompanied by augmented expression of inducible nitric oxide synthase, activation of (NF-κB) and proteolysis of IkappaB. All these effects were absent in animals receiving TNP-470. Our results indicate that TNP-470 inhibits oxidative stress, nitric oxide production and NF-κB activation induced by experimental hepatocarcinogenesis. These changes would contribute to the beneficial effects of TNP-470 in cancer treatment.     

The association of insulin resistance with serum osteoprotegerin in obese adolescents

Some data indicate a potential relationship between insulin resistance level and the concentration of osteoprotegerin (OPG) in the body. There have been few studies concerning OPG level and its relationship with insulin resistance and body composition in young people. The aim of this study was to assess serum osteoprotegerin concentration in obese adolescents, and to evaluate its potential association with insulin resistance. Seventy-eight obese adolescents and 20 healthy volunteers aged 12–18 years were recruited in the study. Selected anthropometrical measurements and blood biochemical analyses were performed. Insulin resistance in the participants was evaluated according to the homeostasis model assessment-insulin resistance (HOMA-IR) protocol. Level of OPG was assessed in serum. Obese subjects had significantly higher HOMA-IR indices and OPG levels in serum than the control group. A significant positive correlation between OPG and insulin resistance was found. It was observed that high concentrations of osteoprotegerin are associated with insulin resistance in obese adolescents.     

Substituent — Directed Aralkylation and Alkylation Reactions of the Tricyclic Analogues of Acyclovir and Guanosine

Abstract

Aryl or tert-butyl substituent in the 6 position of 3,9-dihydro-3-[(2-hydroxyethoxy)methyl]-9-oxo-6-R-5H-imidazo[1,2-α]purine (6-R-TACV)¹ 1 partly directs aralkylation reactions into unusual positions: N-4 to give 3 and C-7 to give N-5, 7-disubstituted or N-4, 7-disubstituted derivatives. In the case of alkylation the effect is limited to aryl substituent and position N-4. Replacement of acyclic moiety of 1 with a ribosyl one like in 7 prevents N-4 substitution. Cleavage of the third ring of 3b to give 3-benzylacyclovir 10 is an example of a new short route to 3-aralkyl-9-substituted guanines.     

C-Nucleoside Analogues of Nicotinamide Mononucleotide (NMN)

Abstract

5-(β-D-Ribofuranosyl)nicotinamide (lie) and 6-(β-D-ribo-furanosyDpicolinamide (IId) and their corresponding o-isomers (III) were synthesized from ribonolactone. The C-nucleoside lie was further converted to its 5′-monophosphate Up which is isosteric to NMN Ip).     

Rook Spring Seed Dispersal in the Agricultural Landscape – Frugivory, Granivory or Accidental Transport?

Seed dispersal seems to be extremely important in agrocoenoses where suitable habitats (patches) are surrounded by an unfavourable environment (matrix). The role of the rook Corvus frugilegus, an omnivorous bird, in seed dispersal was studied in the agricultural landscape of Eastern Poland. We analyzed 739 pellets produced by regurgitation, which were collected under breeding colonies in April, May and June. Our goal was to i) assess the structure of the seed pool in pellets; ii) evaluate the temporal variation in the pellet seed pool on two different time scales; iii) compare the species composition of seeds in pellets and vegetation under the rook nests. Seeds were present in 18 % of pellets; 571 seeds were found, half of them belonging to dry-fruited species, without any obvious adaptations to endozoochory. These seeds could be an additional source of food, or they could have been accidentally swallowed during foraging for other food items. Taking into consideration the abundance of the rook population, we assessed the mean number of seeds transferred by one bird to be from 4 seeds per month in April and up to 160 seeds in June. The most important factor responsible for qualitative and quantitative structure of seed pool in pellets is the time when pellets were regurgitated. The type and availability of food determines the number and species structure of dispersed seeds. The comparison of the species structure of the seed pool in pellets and of the herb layer under the breeding colonies showed that the rook could effectively disperse seeds of weeds, meadow and ruderal species, that could germinate under the dense canopy of trees at the studied sites.     

Mutational analysis in podocin-associated hereditary nephrotic syndrome in Polish patients: founder effect in the Kashubian population

Hereditary nephrotic syndrome is caused by mutations in a number of different genes, the most common being NPHS2. The aim of the study was to identify the spectrum of NPHS2 mutations in Polish patients with the disease. A total of 141 children with steroid-resistant nephrotic syndrome (SRNS) were enrolled in the study. Mutational analysis included the entire coding sequence and intron boundaries of the NPHS2 gene. Restriction fragment length polymorphism (RFLP) and TaqMan genotyping assay were applied to detect selected NPHS2 sequence variants in 575 population-matched controls. Twenty patients (14 %) had homozygous or compound heterozygous NPHS2 mutations, the most frequent being c.1032delT found in 11 children and p.R138Q found in four patients. Carriers of the c.1032delT allele were exclusively found in the Pomeranian (Kashubian) region, suggesting a founder effect origin. The 14 % NPHS2 gene mutation detection rate is similar to that observed in other populations. The heterogeneity of mutations detected in the studied group confirms the requirement of genetic testing the entire NPHS2 coding sequence in Polish patients, with the exception of Kashubs, who should be initially screened for the c.1032delT deletion.