Phage restriction and the presence of small plasmids in Salmonella enteritidis

Sequence variation within the variable region of the 16S rRNA at position 440 to 480 allowed the synthesis of specific PCR primers for the identification of groups within the species Photorhabdus luminescens, symbionts of entomopathogenic nematodes of the genus Heterorhabditis. For the second PCR primer the highly conserved region at 755 to 795 was used. The P. luminescens type strain specific primer could not recognize any other P. luminescens strain. The primer TEMPERATUS based on the sequence of strain DSM12190 (isolated from North West European H. megidis strain HSH2) identified all P. luminescens associated with H. megidis from North West Europe and two isolates from closely the related nematode strains from Ireland. The primer TROPICUS based on strain DSM12191 (isolated from the nematode type strain H. indica strain LN2) identified P. luminescens of tropical origin isolated from H. indica. Symbionts of H. bacteriophora could not yet be separated into well described groups with the primers used. A comparison of sequence data resulted in the identification of additional groups. The non-symbiotic P. luminescens isolates are distinct in the variable region. The group HELIOTHIDIS contains 15 P. luminescens associated with H. bacteriophora from North East America. The MARELATUS group contains symbionts of the nematode H. marelatus from the West Coast of the US. The data together with the specific symbiotic association of P. luminescens strains with different nematode species support the division of the taxon P. luminescens into different species.     

Development of a method for creating a colony of Macaca mulatta, free of herpes B virus infection

To form the colony of monkeys, free of herpes B virus, the serological study was made with the aim of finding out the carriers of this virus. 482 rhesus macaques (Macaca mulatta) from the Adler monkey house were examined for the presence of antibodies to herpes B virus by the method of point immunoblotting with the use of Herpes virus simiae as antigen. The contamination of monkeys in different open-air cages varied from 12.5% to 92%. In different age groups, it was 27% in nonpubescent monkeys (49 out of 182 animals), 55% in adolescent monkeys (55 out of 99), 73% in pubescent monkeys (131 out of 179) and 95% in monkeys over 15 years (21 out of 22 animals). 9 groups of rhesus macaques (comprising altogether 81 animals), free of herpes B virus, were selected. The monkeys were repeatedly tested within a year; after that 10-17% of formerly seronegative monkeys were rejected and removed from the selected group. After the third testing 2.5% more of the animals were found to have seroconversion. The colony of rhesus macaques thus created exists at present. The animals are subjected to constant serological observation.     

The physiological characteristics of genetic predisposition to catalepsy in rats depending on the stage of selection

Male rats with a genetic predisposition to cataleptic reactions revealed a reduced motor activity and a diminished activation of mineralocorticoid and testosterone synthesis in response to a mild stress as compared with the Wistar rats. The reactions, however, were exactly opposite in the Wistar rats with signs of cataleptic features. The data obtained suggest that, when creating genetic animal models of human diseases, the initial stages of breeding should correspond to early stages of the disease whereas advanced stages of breeding are similar to later, chronic phases of the disease.     

Translation eukaryotic initiation factor 4G recognizes a specific structural element within the internal ribosome entry site of encephalomyocarditis virus RNA

A complex of eukaryotic initiation factors (eIFs) 4A, 4E, and 4G (collectively termed eIF4F) plays a key role in recruiting mRNAs to ribosomes during translation initiation. The site of ribosomal entry onto most mRNAs is determined by interaction of the 5'-terminal cap with eIF4E; eIFs 4A and 4G may facilitate ribosomal entry by modifying mRNA structure near the cap and by interacting with ribosome-associated factors. eIF4G recruits uncapped encephalomyocarditis virus (EMCV) mRNA to ribosomes without the involvement of eIF4E by binding directly to the approximately 450-nucleotide long EMCV internal ribosome entry site (IRES). We have used chemical and enzymatic probing to map the eIF4G binding site to a structural element within the J-K domain of the EMCV IRES that consists of an oligo(A) loop at the junction of three helices. The oligo(A) loop itself is not sufficient to form stable complexes with eIF4G since alteration of its structural context abolished its interaction with eIF4G. Addition of wild type or trans-dominant mutant forms of eIF4A to binary IRES.eIF4G complexes did not further alter the pattern of chemical/enzymatic modification of the IRES.     

Amphiphilic alpha-helices are important structural motifs in the alpha and beta peptides that constitute the bacteriocin lactococcin G--enhancement of helix formation upon alpha-beta interaction

Lactococcin G (LcnG) is an antimicrobial substance (bacteriocin) consisting of two peptides, LcnG-alpha and LcnG-beta. The structures of intact LcnG-alpha and LcnG-beta as well as various fragments of these peptides were studied by circular dichroism (CD) under several conditions. All peptides had a non-structured conformation in aqueous solutions. In the presence of trifluoroethanol, dodecylphosphocholine micelles and (negatively charged) dioleoylglycerophosphoglycerol (Ole2GroPGro) liposomes, varying amounts of alpha-helical structure were induced. Comparisons of the various fragments showed that helicity was concentrated in those parts of LcnG-alpha and LcnG-beta that would become amphiphilic if an alpha-helical structure was adopted. In the presence of zwitterionic dioleoylglycerophosphocholine (Ole2GroPCho) liposomes, the peptides were much less (if at all) structured, suggesting that the excess of positive charge on the antimicrobial peptides needs to be compensated by an excess of negative charge on the membrane. The structuring of LcnG-alpha and LcnG-beta in the presence of Ole2GroPGro liposomes was considerably enhanced when both peptides were presented simultaneously to the membranes. Consecutive addition of the two peptides to Ole2GroPGro liposomes did not give this additional structuring, indicating that the individual LcnG-alpha and LcnG-beta peptides associate with the membrane in a virtually irreversible manner that makes them inaccessible for interaction with the complementary peptide. The results suggest that upon arrival at and interaction with the target membrane, LcnG-alpha and LcnG-beta form a complex that consists of approximately 50% amphiphilic alpha-helices.     

The hepatopulmonary syndrome: radiologic findings in 10 patients

OBJECTIVE: The purpose of this study was to review the radiologic manifestations of the hepatopulmonary syndrome. MATERIALS AND METHODS: We retrospectively reviewed clinical records, chest radiographs, 99m Tc-macroaggregated albumin (MAA) perfusion lung scans, chest CT scans, and pulmonary angiograms of 10 patients with proven hepatopulmonary syndrome. RESULTS: Chest radiographs showed basilar, medium-sized (1.5-3.0 mm) nodular or reticulonodular opacities in all cases. CT was done in eight cases and showed basilar dilatation of lung vessels with a larger than normal number of visible branches. The vascular basis for these opacities was best appreciated on conventional CT scans of 10-mm sections. No individual arteriovenous malformations were seen on CT scans. High-resolution CT scans showed no evidence of interstitial fibrosis. 99mTc-MAA perfusion lung imaging, done in seven patients, showed pulmonary arteriovenous shunting in five. Contrast echocardiography confirmed intrapulmonary shunting in these five patients. Pulmonary angiography, done in four cases, showed subtle distal vascular dilatation in two and moderate dilatation with early venous filling in two but did not reveal any individual arteriovenous malformations. CONCLUSION: Chest radiographs in hepatopulmonary syndrome usually show bibasilar nodular or reticulonodular opacities. Conventional CT shows that these opacities represent dilated lung vessels. High-resolution CT is useful in excluding pulmonary fibrosis or emphysema as the cause of these opacities. 99mTc-MMA perfusion imaging or contrast echocardiography can be used to confirm intrapulmonary arteriovenous shunting.     

Paradoxical improvement of impulse conduction in cardiac tissue by partial cellular uncoupling

Generally, impulse propagation in cardiac tissue is assumed to be impaired by a reduction of intercellular electrical coupling or by the presence of structural discontinuities. Contrary to this notion, the spatially uniform reduction of electrical coupling induced successful conduction in discontinuous cardiac tissue structures exhibiting unidirectional conduction block. This seemingly paradoxical finding can be explained by a nonsymmetric effect of uncoupling on the current source and the current sink in the preparations used. It suggests that partial cellular uncoupling might prevent the initiation of cardiac arrhythmias that are dependent on the presence of unidirectional conduction block.     

The control mechanisms of the electrokinetic properties of human erythrocytes in emotional stress

A study was made of the influence of psycho-emotional strain, experienced by students when taking examinations, on the erythrocyte electrophoretic mobility (EPM). It has been shown that students under psycho-emotional strain the mean value of EPM remains the same, but changes were observed in the form of EPM distribution, while estimated by asymmetry and excession coefficients. Similar results were obtained when adrenalin was added to the blood.