Polymersomes Containing Iron Sulfide (FeS) as Primordial Cell Model

According to Wächtershäuser??s ??Iron-Sulfur-World?? one major requirement for the development of life on the prebiotic Earth is compartmentalization. Vesicles spontaneously formed from amphiphilic components containing a specific set of molecules including sulfide minerals may have lead to the first autotrophic prebiotic units. The iron sulfide minerals may have been formed by geological conversions in the environment of deep-sea volcanos (black smokers), which can be observed even today. Wächtershäuser postulated the evolution of chemical pathways as fundamentals of the origin of life on earth. In contrast to the classical Miller-Urey experiment, depending on external energy sources, the ??Iron-Sulfur-World?? is based on the catalytic and energy reproducing redox system $ FeS + {H_2}S \to FeS{}_2 + {H_2} $ . The energy release out of this redox reaction (?_RG°?=??38 kJ/mol, pH 0) could be the cause for the subsequent synthesis of complex organic molecules and the precondition for the development of more complex units similar to cells known today. Here we show the possibility for precipitating iron sulfide inside vesicles composed of amphiphilic block-copolymers as a model system for a first prebiotic unit. Our findings could be an indication for a chemoautotrophic FeS based origin of life.     

Cyclic di-GMP-dependent Signaling Pathways in the Pathogenic Firmicute Listeria monocytogenes

We characterized key components and major targets of the c-di-GMP signaling pathways in the foodborne pathogen Listeria monocytogenes, identified a new c-di-GMP-inducible exopolysaccharide responsible for motility inhibition, cell aggregation, and enhanced tolerance to disinfectants and desiccation, and provided first insights into the role of c-di-GMP signaling in listerial virulence. Genome-wide genetic and biochemical analyses of c-di-GMP signaling pathways revealed that L. monocytogenes has three GGDEF domain proteins, DgcA (Lmo1911), DgcB (Lmo1912) and DgcC (Lmo2174), that possess diguanylate cyclase activity, and three EAL domain proteins, PdeB (Lmo0131), PdeC (Lmo1914) and PdeD (Lmo0111), that possess c-di-GMP phosphodiesterase activity. Deletion of all phosphodiesterase genes (ΔpdeB/C/D) or expression of a heterologous diguanylate cyclase stimulated production of a previously unknown exopolysaccharide. The synthesis of this exopolysaccharide was attributed to the pssA-E (lmo0527-0531) gene cluster. The last gene of the cluster encodes the fourth listerial GGDEF domain protein, PssE, that functions as an I-site c-di-GMP receptor essential for exopolysaccharide synthesis. The c-di-GMP-inducible exopolysaccharide causes cell aggregation in minimal medium and impairs bacterial migration in semi-solid agar, however, it does not promote biofilm formation on abiotic surfaces. The exopolysaccharide also greatly enhances bacterial tolerance to commonly used disinfectants as well as desiccation, which may contribute to survival of L. monocytogenes on contaminated food products and in food-processing facilities. The exopolysaccharide and another, as yet unknown c-di-GMP-dependent target, drastically decrease listerial invasiveness in enterocytes in vitro, and lower pathogen load in the liver and gallbladder of mice infected via an oral route, which suggests that elevated c-di-GMP levels play an overall negative role in listerial virulence.     

Cholecalciferol (vitamin D 3) improves cognitive dysfunction and reduces inflammation in a rat fatty liver model of metabolic syndrome

Aim

The aim of this study was to examine the effects of cholecalciferol on systemic inflammation and memory in the setting of fatty liver disease in rats.

Materials and methods

To induce the development of fatty liver disease, the rats were fed a 35% fructose solution over 8 weeks. Group I (n = 6) was designated as the control group and fed with standard rat chow. Group II (n = 6) was provided with, standard rat chow, and 0.3 μg/kg/day of oral cholecalciferol over a duration of 2 weeks. In addition to standard rat chow, group III (n = 6) and group IV (n = 6) were given 4 mL of the 35% fructose solution per day via oral gavage for 8 weeks. However, group IV was also given 0.3 μg/kg/day of oral cholecalciferol over 2 weeks. After the treatment period, passive avoidance tasks were performed by all groups. The liver and brain were harvested for subsequent biochemical and histopathologic analyses.

Key findings

The development of fatty liver extends the memory latency period of passively avoiding tasks after 1 trial. Moreover, there were increases in brain TNF-α and plasma MDA levels according to two-way analysis of variance. Cholecalciferol supplementation decreased the latency period of passively avoiding tasks in rats with hepatosteatosis, and also significantly reduced brain TNF-α and plasma MDA levels.

Significance

Fatty liver may contribute to the development of systemic inflammation, which affects cognition and causes deficits in memory; however, the anti-inflammatory and antioxidant properties of vitamin D may improve the cognitive function of rats with hepatosteatosis.     

Regulation of cellular immune response against autologous human melanoma. II. Mechanism of induction and specificity of suppression

The cytotoxic immune response in the peripheral blood lymphocytes (PBL) against an autologous malignant melanoma cell line, PJ-M, was found to be down-regulated in in vitro co-culture (IVC) selectively by unfractionated resident lymph node lymphocytes (derived from a lymph node infiltrated with the PJ-M melanoma cells) and T4+ as well as T8+ fractions of the resident lymph node-derived lymphocytes. In this study, the mechanism involved in, and the specificities of, cytotoxic immune response in this autologous system were examined at population and clonal levels. Resident lymph node lymphocytes were isolated from both involved and uninvolved lymph nodes from the same patient. Resident lymphocytes from both sources regulated the generation of cytotoxic immune response when both types of resident lymph node lymphocytes were further sensitized against the PJ-M cells in IVC and were expanded in interleukin 2 (IL 2). An IL 2-dependent homogeneous lymphocyte line (I-10:1) bearing the phenotype of a helper T cell (T4+) and a T4+ clone (I-10.3) of the I-10:1 line, established by limiting dilution culture, also down-regulated the generation of cytotoxic immune effector cells in the PBL in IVC against the PJ-M targets. The IL 2-dependent T4+ inducer line I-10:1 generated a functionally differentiated T8+ suppressor population(s) that, in turn, could abrogate cytotoxic response in fresh PBL in IVC against PJ-M cells. The inducer line I-10:1 and its subclone I-10.3 suppressed the generation of cytotoxic effector cells in the PBL in IVC selectively against the autologous PJ-M cells. Generation of cytotoxic allo-response in IVC was unaffected by the inducer lines. These results provide further evidence for the involvement of the regulatory network in cytotoxic immune response in an autologous human tumor system, and suggest a potential explanation for cytotoxic unresponsiveness against autologous melanoma cells.     

Effects of metals on elastase fromPseudomonas aeruginosa SES-938-1

Among the numerous virulance factors produced byPseudomonas aeruginosa, elastase is the one most often associated with pathogenesis. In this study, effects of various metal ions on elastase from a new isolate ofP. aeruginosa (Strain SES-938-1) was investigated. Crude elastase was prepared from culture supernatant via salting out by ammonium sulfate, and then desalting and concentrating the sample using a centricon microconcentrator. Activities were measured at 450 nm usingN-succinyl-l-(ala)₃-p-nitroanilide as the substrate. The metal chelating agents EDTA and EGTA inhibited thePseudomonas elastase, which shows that the enzyme is a typical metalloproteinase. At a 10-mM concentration, Mn²⁺, Ni²⁺, and Zn²⁺ strongly inhibited the elastase, whereas Mg²⁺ effect was negligable. There was a gradual decrease in the enzyme activity in accordance with an increase in the concentration of metal ions.     

The STR252 – IVS10nt546 – VNTR7 phenylalanine hydroxylase minihaplotype in five Mediterranean samples

IVS10nt546 (IVS10nt-11g→a) is the most common molecular defect of the phenylalanine hydroxylase gene causing phenylketonuria in Mediterranean populations. Previous studies have proposed various and alternative hypotheses concerning the geographical origin and pattern of diffusion of this mutation in this area. In this study, this issue was re-examined on a large sample (149) of “Mediterranean” IVS10nt546 mutant alleles analysed with multiallelic intragenic polymorphisms. The analysis of intragenic microsatellite (STR) and minisatellite (VNTR) polymorphisms shows allelic heterogeneity of the IVS10nt546 mutation. Eight STR and three VNTR alleles were found in association with the splicing defect. Of the ten detected STR–VNTR combinations (“minihaplotypes”), we identified a predominant allelic association (VNTR7 – STR252) embedded in a RFLP-haplotype 6 background, which seems to correspond to the ancestral gene originating in the Turkey–Israel area. Analysis of both absolute and relative gene frequencies of the STR252 – IVS10nt546 – VNTR7 minihaplotypes, shows statistically significant (P < 0.02) variations and may suggest gene flow from Turkey and/or Israel to Italy and Spain. The associated migratory events need not be unique in time (and people) but seem to suggest they may be traced back to the expansion of the Neolithic culture and people, thus allowing dating of the origin of this mutation to at least 5000–10 000 years ago. Alternative hypotheses are discussed to explain, in light of the available historical and pre-historical evidence, the pattern of diffusion of the IVS10nt546 mutation in the Mediterranean basin. Received: 24 March 1997 / Accepted: 9 April 1997