Ovine bronchial-derived relaxing factor: changes with development and hyperoxic ventilation.

Recent studies suggest that a bronchial-derived relaxing factor (BrDRF) decreases the contractility of newborn, but not fetal, rat pulmonary arteries (PAs) by a nitric oxide (NO)-mediated mechanism. We studied the effect of an adjacent bronchus on PA contractility to norepinephrine (NE) in late-gestation fetal (n = 7), neonatal (1 day old, n = 9), ventilated neonatal (24-h ventilation from birth with 100% oxygen, n = 9), and adult sheep (n = 6) in the presence and absence of the NO synthase inhibitor N(omega)-nitro-l-arginine (l-NNA). The sheep were anesthetized and killed, and fifth-generation PA rings with and without an attached adjacent bronchus (PA+Br) were contracted in standard tissue baths with NE (10(-8)-10(-6) M). NE contractions were expressed as fraction of KCl (118 mM) contraction and as grams of contraction force. NE contractions were significantly diminished by the presence of an attached bronchus in the neonatal and ventilated neonatal and adult, but not fetal, lambs. Hyperoxic ventilation markedly increased NE contractions in PA and PA+Br. l-NNA significantly enhanced NE contractions in PA+Br in postnatal but not in fetal lambs. Pretreatment with l-NNA abolished the difference between NE contractions in PA and PA+Br in neonatal but not in hyperoxic ventilated neonatal lambs. We conclude that there is a BrDRF that is developmentally regulated and has vascular activity postnatally but not during fetal life. The effect of BrDRF is predominantly mediated by NO in air-breathing neonatal lambs but may involve a second non-NO mediator following hyperoxic ventilation. We speculate that BrDRF may have an important role in postnatal changes in pulmonary arterial reactivity.     

Role of the two component signal transduction system CpxAR in conferring cefepime and chloramphenicol resistance in Klebsiella pneumoniae NTUH-K2044

Background

Klebsiella pneumoniae is a Gram-negative, non-motile, facultative anaerobe belonging to the Enterobacteriaceae family of the γ-Proteobacteria class in the phylum Proteobacteria. Multidrug resistant K. pneumoniae have caused major therapeutic problems worldwide due to emergence of extended-spectrum β-lactamase producing strains. Two-component systems serve as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions including antibiotic stress.

Principal Findings

In the present study, we investigated the role of an uncharacterized cpxAR operon in bacterial physiology and antimicrobial resistance by generating isogenic mutant (ΔcpxAR) deficient in the CpxA/CpxR component derived from the hyper mucoidal K1 strain K. pneumoniae NTUH-K2044. The behaviour of ΔcpxAR was determined under hostile conditions, reproducing stresses encountered in the gastrointestinal environment and deletion resulted in higher sensitivity to bile, osmotic and acid stresses. The ΔcpxAR was more susceptible to β-lactams and chloramphenicol than the wild-type strain, and complementation restored the altered phenotypes. The relative change in expression of acrB, acrD, eefB efflux genes were decreased in cpxAR mutant as evidenced by qRT-PCR. Comparison of outer membrane protein profiles indicated a conspicuous difference in the knock out background. Gel shift assays demonstrated direct binding of CpxR^KP to promoter region of ompC ^KP in a concentration dependent manner.

Conclusions and Significance

The Cpx envelope stress response system is known to be activated by alterations in pH, membrane composition and misfolded proteins, and this systematic investigation reveals its direct involvement in conferring antimicrobial resistance against clinically significant antibiotics for the very first time. Overall results displayed in this report reflect the pleiotropic role of the CpxAR signaling system and diversity of the antibiotic resistome in hyper virulent K1 serotype K. pneumoniae NTUH-K2044.     

Hepatoprotective properties of Caesalpinia sappan Linn. heartwood on carbon tetrachloride induced toxicity

Aim of the study was to investigate the methanol and aqueous extracts of heartwood of C. sappan for its hepatoprotective activity against CCl4 induced toxicity in freshly isolated rat hepatocytes and animals. Freshly isolated rat hepatocytes were exposed to CCl4 (1%) along with/without various concentrations of methanolic and aqueous extract of C. sappan (1000-800 microg/ml) and the levels of selected liver enzymes were estimated. Antihepatotoxic effect of methanolic extract was observed in freshly isolated rat hepatocytes at concentrations 1000-800 microg/ml and was found to be similar to that of standard drug silymarin. Wistar strain albino rat model was used for the investigation of in vivo hepatoprotective properties of aqueous and methanolic extract of C. sappan (100 and 200 mg/kg body weight). Liver damage was induced by ip administration of CCl4 (30%) suspended in olive oil (1 ml/kg body weight). Both the tested extracts showed potent hepatoprotective activity at 200 mg/kg body weight test dose which was comparable with that of the standard silymarin used in similar test dose. The methanolic and aqueous extract was able to restore the biochemical levels to normal which were altered due to CCl4 intoxication in freshly isolated rat hepatocytes and also in animals.     

wFleaBase: the <Emphasis Type="Italic">Daphnia</Emphasis> genome database

Background  

wFleaBase is a database with the necessary infrastructure to curate, archive and share genetic, molecular and functional genomic data and protocols for an emerging model organism, the microcrustacean Daphnia. Commonly known as the water-flea, Daphnia's ecological merit is unequaled among metazoans, largely because of its sentinel role within freshwater ecosystems and over 200 years of biological investigations. By consequence, the Daphnia Genomics Consortium (DGC) has launched an interdisciplinary research program to create the resources needed to study genes that affect ecological and evolutionary success in natural environments.     

Controlled search for the producers of ionophore antibiotics among Streptomycetes

A procedure was developed for directed screening of cultures producing ionophore antibiotics among streptomycetes. The procedure is based on measuring the membrane potential generated in the presence of the Men+/nH+ = -expchanger-protonophore couple. It provided isolation of cultures producing ionophore antibiotics at the fermentation broth stage. It was possible to use the procedure in screening both electrogenic and nonelectrogenic ionophores and to rapidly differentiate them. 5 cultures producing ionophore antibiotics were detected with this procedure; 3 of them carry out nonelectrogenic transport of the cations. The cation transport in the other two cultures was electrogenic. Cation selectivity of the antibiotics produced by the cultures was determined with the procedure. An antibiotic identical to indanomycin was isolated from the culture fluid of Streptomyces chromogenes.     

Direct screening for producers of antibiotics among the Micromonospora

A test system was developed for screening organisms producing antibiotics of definite chemical groups or mechanisms of action. The system includes efficient selection of cultures belonging to a definite microbiological taxon (genus Micromonospora), investigation of their biological and taxonomic features, the use of specific selective media with high concentrations of definite antibiotics for isolating antibiotic-producing cultures from natural substrates, the use of specific methods for antibiotic chemical isolation at the initial stages of the screening and chromatographic study of the screened compounds. The system provided efficient screening of valuable antibiotics in a short period.     

High strain rate response of rabbit femur bones

Strain rate dependence of the mechanical response of hard tissues has led to a keen interest in their dynamic properties. The current study attempts to understand the high strain rate characteristics of rabbit femur bones. The testing was conducted using a split-Hopkinson pressure bar equipped with a high speed imaging system to capture the fracture patterns. The bones were also characterized under quasi-static compression to enable comparison with the high strain rate results. The quasi-static compressive moduli of the epiphyseal and diaphyseal regions were measured to be in the range of 2–3 and 5–7 GPa, respectively. Under high strain rate loading conditions the modulus is observed to increase with strain rate and attains values as high as 15 GPa for epiphyseal and 30 GPa for diaphyseal regions of the femur. The strength at high strain rate was measured to be about twice the quasi-static strength value. A large number of small cracks initiated on the specimen surface close to the incident bar. Coalescence of crack branches leading to fewer large cracks resulted in specimen fragmentation. In comparison, the quasi-static failure was due to shear cracking.