Pressure effects on the rates of Hg-assisted chloride release from some [CrCl(diamine)(triamine)] complexes

The rate of Hg²⁺-assisted chloride release from several mer-[CrCl(diamine)(triamine)]²⁺ complexes has been measured as a function of pressure, Hg²⁺ concentration and temperature. The calculated activation volumes are independent of [Hg²⁺] and temperature and kinetic parametes 10⁴ k_Hg (25 °c) (M⁻¹ s⁻¹), ΔH^‡ (kJ mol⁻¹), ΔS^‡ (J K⁻¹ mol⁻¹), ΔV^‡ (cc mol⁻¹) are: (en)(dpt): 6.44. 75.5, −52, −5.0; (ibn)(dpt): 5.81, 89.5, −6, −0.03; (Me₂tn)(dpt): 22.2, 84.9, −11, −0.5; (tn)(dpt): 29.1, 87, −1, +0.3; (en)(2,3-tri): 1.94, 87.0, −24, −5.7; (en)(Medpt): 0.417, 94.6, −11, −0.8; (tn)(Medpt): 9.14, 98.3, +26, +1.8.     

Selenium content of livers from sex-linked dwarf and normal broiler breeders

Plasma concentrations of cGH, T₃, and T₄ were not different between dwarf and normal broiler breeders. Normal hens had a liver selenium content of 710±35 ng/g, and dwarf hens 656 ±nine ng/g (n=8). Following injections into a wing vein of different doses (1.5, 3, 6, 12, and 24 μg/kg) of the hypothalamic hormone TRH, GH was increased after 15 min. This effect seemed to last longer in dwarf chickens. Plasma concentrations of T₃ increased significantly 1 h after TRH in normal hens, but TRH was ineffective in raising T₃ levels in dwarf animals. The selenium content of livers obtained following decapitation after 2 h was also increased in normal hens up to 902±42 ng/g using the highest dose of TRH (24 μg/kg). This seemed not to be the case for dwarf animals. A much smaller. number of hepatic cGH receptors was also found in dwarf hens, whereas the affinity of the hepatic GH receptor was not influenced by the genotype. It is concluded that the sex-linked dwarf hens are unable to increase their hepatic T₄ into T₃ conversion following a TRH challenge probably because of a deficiency in hepatic GH receptors. The lower content of selenium in dwarfs and their inability to increase its uptake after TRH seem therefore to support the hypothesis that selenium has a direct role in the activity of the 5′-deiodinase complex.     

A Random Matrix Approach to Credit Risk

We estimate generic statistical properties of a structural credit risk model by considering an ensemble of correlation matrices. This ensemble is set up by Random Matrix Theory. We demonstrate analytically that the presence of correlations severely limits the effect of diversification in a credit portfolio if the correlations are not identically zero. The existence of correlations alters the tails of the loss distribution considerably, even if their average is zero. Under the assumption of randomly fluctuating correlations, a lower bound for the estimation of the loss distribution is provided.     

Agglutination Activity of Fasciola gigantica DM9-1, a Mannose-Binding Lectin

The DM9 domain is a protein unit of 60–75 amino acids that has been first detected in the fruit fly Drosophila as a repeated motif of unknown function. Recent research on proteins carrying DM9 domains in the mosquito Anopheles gambiae and the oyster Crassostrea gigas indicated an association with the uptake of microbial organisms. Likewise, in the trematode Fasciola gigantica DM9-1 showed intracellular relocalization following microbial, heat and drug stress. In the present research, we show that FgDM9-1 is a lectin with a novel mannose-binding site that has been recently described for the protein CGL1 of Crassostrea gigas. This property allowed FgDM9-1 to agglutinate gram-positive and -negative bacteria with appropriate cell surface glycosylation patterns. Furthermore, FgDM9-1 caused hemagglutination across all ABO blood group phenotypes. It is speculated that the parenchymal located FgDM9-1 has a role in cellular processes that involve the transport of mannose-carrying molecules in the parenchymal cells of the parasite.     

Comparison between touchscreen operant chambers and water maze to detect early prefrontal dysfunction in mice

The relative lack of sensitive and clinically valid tests of rodent behavior might be one of the reasons for the limited success of the clinical translation of preclinical Alzheimer's disease (AD) research findings. There is a general interest in innovative behavioral methodology, and protocols have been proposed for touchscreen operant chambers that might be superior to existing cognitive assessment methods. We assessed and analyzed touchscreen performance in several novel ways to examine the possible occurrence of early signs of prefrontal (PFC) functional decline in the APP/PS1 mouse model of AD. Touchscreen learning performance was compared between APP/PS1-21 mice and wildtype littermates on a C57BL/6J background at 3, 6 and 12 months of age in parallel to the assessment of spatial learning, memory and cognitive flexibility in the Morris water maze (MWM). We found that older mice generally needed more training sessions to complete the touchscreen protocol than younger ones. Older mice also displayed defects in MWM working memory performance, but touchscreen protocols detected functional changes beginning at 3 months of age. Histological changes in PFC of APP/PS1 mice indeed occurred as early as 3 months. Our results suggest that touchscreen operant protocols are more sensitive to PFC dysfunction, which is of relevance to the use of these tasks and devices in preclinical AD research and experimental pharmacology.     

A New Method of Synthesis of Fluorescently Labelled Oligonucleotides and Their Application in DNA Sequencing

Abstract

A new approach to the chemical synthesis of oligonucleotides bearing reporter functional groups based on the modification of cytosine residues during the final deprotection step is reported. The application of the fluorescently labelled primer for the automated DNA sequencing is shown.     

Anti-Hiv-1 Activity of 2′,3′-Dideoxinucleoside Analogues : Structure-Activity Relationship

Abstract

Among the purine and pyrimidine 2′,3′-dideoxynucleosides, 2′,3′-didehydro-2′,3′-dideoxynucleosides, 3′-azido-2′,3′-dideoxynucleosides and 3′-fluoro-2′,3′-dideoxynucleosides, several congeners have been identified which achieve a potent and selective inhibition of HIV-1 replication in vitro.     

Low C-Reactive Protein Levels in a Traditional West-African Population Living in a Malaria Endemic Area

Background

C-reactive protein (CRP) levels are reported to be elevated in populations of African descent living in affluent environments compared to populations of European ancestry. However, the natural history of CRP levels in populations of African descent living under adverse environments remains largely unknown.

Methods

CRP levels were measured with a high sensitivity assay in 624 apparently healthy individuals who contributed blood as part of a study on innate immune responsiveness in a traditional Ghanaian population living under adverse environmental conditions in a malaria endemic area. As a comparison, we included CRP measurements from 2931 apparently healthy individuals from the Dutch population that were included in the same batch of CRP analyses. Associations between CRP and body mass index (BMI), immune responsiveness, and P. falciparum parasitaemia were investigated.

Results

In an age- and sex-adjusted model, CRP levels were 0.54 mg/L lower in the Ghanaian compared to the Dutch cohort (1.52 vs. 0.98 mg/L, p<0.001). When accounting for the substantially higher average BMI in the Dutch compared to the Ghanaians (25.6 vs. 18.4 kg/m²) the difference in CRP levels disappeared. BMI associated positively with CRP in the Dutch but not in the Ghanaians. In individuals with an acute phase response, CRP levels were higher in the Ghanaian compared to the Dutch cohort (24.6 vs. 17.3 mg/L, p = 0.04). Levels of CRP were positively related to immune responsiveness and P. falciparum parasitaemia (all p<0.001) among Ghanaians.

Conclusions

Our study demonstrates that West-Africans do not exhibit an inherently high inflammatory state. The role of genes, environment and gene-environment interaction in explaining reports of elevated CRP levels in populations of African ancestry when compared to other ethnicities living in affluent environments thus merits further investigation.     

Antimicrobial and antiviral activity-guided fractionation from Scutia buxifolia Reissek extracts

Antimicrobial and antiviral activities of the fractions from Scutia buxifolia stem bark and leaves were evaluated. Best antimicrobial results occurred with the ethyl acetate (EA) and n-butanolic (NB) fractions from the leaves against Micrococcus sp. (minimal inhibitory concentration—MIC = 62.5 μg/ml), and NB fraction from stem bark and leaves against Klebsiella pneumoniae and Enterococcus faecalis (MIC = 62.5 μg/ml). The most active fractions were selected and fractioned into silica column to perform an in vitro antibiofilm assay, which evidenced subfractions EA2 and EA3 as the more active against Candida albicans (biofilm inhibitory concentration—BIC = 582 ± 0.01 μg/ml) and Staphylococcus aureus (BIC = 360 ± 0.007 μg/ml), respectively. The NB (selectivity index—SI = 25.78) and the EA (SI = 15.97) fractions from the stem bark, and the EA (SI = 14.13) fraction from the leaves exhibited a potential antiviral activity towards Herpes Simplex Virus type 1 whereas EA2 and EA3 subfractions from leaves (SI = 12.59 and 10.06, respectively), and NB2 subfraction from stem bark (SI = 12.34) maintained this good activity. Phenolic acids and flavonoids (gallic acid, chlorogenic acid, caffeic acid, rutin, isoquercitrin, quercitrin and quercetin) were identified by HPLC and may be partially responsible for the antimicrobial and antiherpes activities observed. The results obtained in this study showed that Scutia buxifolia has antibiofilm and anti-herpetic activities and that these properties are reported for the first time for this species.     

The role of canopy gaps in the regeneration of coastal dune forest

In regenerating coastal dune forest, the canopy consists almost exclusively of a single species, Acacia karroo. When these trees die, they create large canopy gaps. If this promotes the persistence of pioneer species to the detriment of other forest species, then the end goal of a restored coastal dune forest may be unobtainable. We wished to ascertain whether tree species composition and richness differed significantly between canopy gaps and intact canopy, and across a gradient of gap sizes. In three known‐age regenerating coastal dune forest sites, we measured 146 gaps, the species responsible for gap creation, the species most likely to reach the canopy and the composition of adults, seedlings and saplings. We paired each gap with an adjacent plot of the same area that was entirely under intact canopy and sampled in the same way. Most species (15 of 23) had higher abundance in canopy gaps. The probability of self‐replacement was low for A. karroo even in the largest gaps. Despite this predominance of shade‐intolerant species, regenerating dune forest appears to be in the first phase of succession with ‘forest pioneers’ replacing the dominant canopy species. The nature of these species should lead to successful regeneration of dune forest.