Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

In vitro selection of a novel nuclease-resistant RNA phosphodiesterase

BACKGROUND: Ribonucleotide-based enzymes (ribozymes) that cleave pathological RNAs are being developed as therapeutic agents. Chemical modification of the hammerhead ribozyme has produced nuclease-resistant catalysts that cleave targeted mRNAs in cell culture and exhibit antitumor activity in animals. Unfortunately, stabilizing modifications usually reduce the catalytic rate in vitro. An alternative to rationally designed chemical modifications of existing ribozymes is to identify novel motifs through in vitro selection of nuclease-stable sequence space. This approach is desirable because the catalysts can be optimized to function under simulated physiological conditions. RESULTS: Utilizing in vitro selection, we have identified a nuclease-stable phosphodiesterase that demonstrated optimal activity at simulated physiological conditions. The initial library of 10(14) unique molecules contained 40 randomized nucleotides with all pyrimidines in a nuclease-stabilized 2'-deoxy-2'-amino format. The selection required trans-cleaving activity and base-pairing specificity towards a resin-bound RNA substrate. Initial selective pressure was permissive, with a 30 min reaction time and 25 mM Mg(2+). Stringency of selection pressure was gradually increased until final conditions of 1 mM Mg(2+) and less than 1 min reaction times were achieved. The resulting 61-mer catalyst required the 2'-amino substitutions at selected pyrimidine positions and was stable in human serum (half-life of 16 h). CONCLUSIONS: We demonstrated that it is possible to identify completely novel, nuclease-resistant ribozymes capable of trans-cleaving target RNAs at physiologically relevant Mg(2+) concentrations. The new ribozyme motif has minimal substrate requirements, allowing for a wide range of potential RNA targets.     

Transfer measurements for the Ti+Ni systems at near barrier energies

Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies. Coupled channel calculations incorporating couplings to 2⁺ and 3⁻ states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer were carried out for ^46,48Ti+⁶¹Ni systems. The present paper gives the results of these studies.     

Using FTIR spectroscopy to detect sericin on historic silk

Silks represent some of the most precious ancient and historic textile artefacts in collections worldwide.Their optimum preservation demands an appreciation of their characteristics.One important concern,especially with regard to ancient Chinese silks,is whether the fabrics have been degummed.Silks with remnant sericin gum coating the fibroin fibres would require different conservation protocol.In previous research on aged silks,the presence of sericin has been inferred from amino acid analysis of hydrolysa...     

Iron-catalyzed Doyle-Kirmse reaction of allyl sulfides with (trimethylsilyl)diazomethane

[formula: see text] Iron salts efficiently catalyze the Doyle-Kirmse reaction of allyl sulfides with (trimethylsilyl)diazomethane and ethyl diazoacetate in dichloroethane at 83 degrees C. Competitive dimerization is less of a problem with (trimethylsilyl)diazomethane than with ethyl diazoacetate. Good results are obtained using only 1.5 equiv of (trimethylsilyl)diazomethane, even without slow addition. Phosphine ligands affect the kinetics, but not the diastereoselectivity. Dppe and BINAP lead to higher yields than dppp, but no enantioselection was detected with R-(+)-BINAP.     

Ambient solar UV radiation causes mortality in larvae of three species of Rana under controlled exposure conditions

Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) (290-320 nm) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, Rana clamitans and Rana septentrionalis, were exposed to full-spectrum solar radiation and solar radiation filtered to attenuate UV-B radiation or UV-B and ultraviolet-A (UV-A) (290-380 nm) radiation to determine the effects of each wavelength range on embryo and larval survival. Ambient levels of solar radiation were found to be lethal to all three species under exposure conditions that eliminated shade and refuge. Lethality was ameliorated by filtration of UV-B radiation alone, demonstrating that ambient UV-B radiation is sufficient to cause mortality. Although several studies have qualitatively demonstrated the lethality of UV-B to early life stage amphibians this study demonstrates that the larval life stages of the three species tested are more sensitive than the embryonic stages. This suggests that previous reports that have not included the larval life stage may underestimate the risk posed to some anuran populations by increasing UV-B exposure. Furthermore, this study reports quantitative UV-B dosimetry data, collected in conjunction with the exposures, which can be used to begin the assessment of the impact of environmental changes which increase UV-B exposure of these anurans.     

Suppression of nitric oxide production in mouse macrophages by soybean flavonoids accumulated in response to nitroprusside and fungal elicitation

Background

The anti-inflammatory properties of some flavonoids have been attributed to their ability to inhibit the production of NO by activated macrophages. Soybean cotyledons accumulate certain flavonoids following elicitation with an extract of the fungal pathogen Diaporthe phaseolorum f. sp. meridionalis (Dpm). Sodium nitroprusside (SNP), a nitric oxide donor, can substitute for Dpm in inducing flavonoid production. In this study, we investigated the effect of flavonoid-containing diffusates obtained from Dpm- and SNP-elicited soybean cotyledons on NO production by lipopolysaccharide (LPS)- and LPS plus interferon-γ (IFNγ)-activated murine macrophages.

Results

Significant inhibition of NO production, measured as nitrite formation, was observed when macrophages were activated in the presence of soybean diffusates from Dpm- or SNP-elicited cotyledons. This inhibition was dependent on the duration of exposure to the elicitor. Daidzein, genistein, luteolin and apigenin, the main flavonoids present in diffusates of elicited cotyledons, suppressed the NO production by LPS + IFNγ activated macrophages in a concentration-dependent manner, with IC₅₀ values of 81.4 μM, 34.5 μM, 38.6 μM and 10.4 μM respectively. For macrophages activated with LPS alone, the IC₅₀ values were 40.0 μM, 16.6 μM, 10.4 μM and 2.8 μM, respectively. Western blot analysis showed that iNOS expression was not affected by daidzein, was reduced by genistein, and was abolished by apigenin, luteolin and Dpm- and SNP-soybean diffusates at concentrations that significantly inhibited NO production by activated macrophages.

Conclusions

These results suggest that the suppressive effect of flavonoids on iNOS expression could account for the potent inhibitory effect of Dpm- and SNP-diffusates on NO production by activated macrophages. Since the physiological concentration of flavonoids in plants is normally low, the treatment of soybean tissues with SNP may provide a simple method for substantially increasing the concentration of metabolites that are beneficial for the treatment of chronic inflammatory diseases associated with NO production.