Evidence for natural horizontal transfer of tetQ between bacteria that normally colonize humans and bacteria that normally colonize livestock.

Though numerous studies have shown that gene transfer occurs between distantly related bacterial genera under laboratory conditions, the frequency and breadth of horizontal transfer events in nature remain unknown. Previous evidence for natural intergeneric transfers came from studies of genes in human pathogens, bacteria that colonize the same host. We present evidence that natural transfer of a tetracycline resistance gene, tetQ, has occurred between bacterial genera that normally colonize different hosts. A DNA sequence comparative approach was taken to examine the extent of horizontal tetQ dissemination between species of Bacteroides, the predominant genus of the human colonic microflora, and between species of Bacteroides and of the distantly related genus Prevotella, a predominant genus of the microflora of the rumens and intestinal tracts of farm animals. Virtually identical tetQ sequences were found in a number of isolate pairs differing in taxonomy and geographic origin, indicating that extensive natural gene transmission has occurred. Among the exchange events indicated by the evidence was the very recent transfer of an allele of tetQ usually found in Prevotella spp. to a Bacteroides fragilis strain.     

Stereoselectivity in β-cyclodextrin complexation of 1,4-dihydropyridine derivatives

Structure–interaction relationships, stereoselectivity, and solubility enhancement in inclusion compexation of β-cyclodextrins (CDs) with some racemic and enantiomerically pure 1,4-dihydropyridine derivatives (DHPs) were investigated. 1:1 and 1:2 (mole ratio) complexes were prepared and characterized by X-ray powder diffraction, differential scanning calorimetry (DSC), MS-FAB spectrometry, ¹H-NMR spectroscopy, water and phase solubility. The solubility studies have revealed different complexation equilibria for optically pure DHP enantiomers, and corresponding racemic mixtures in water solutions. By means of ¹H-NMR chemical shift measurements, the inclusion of aromatic fragments of racemic and enantiomerically pure DHP molecules within the cavities of different CDs was elucidated. Considerable stereoselectivity in complexation interactions was observed. The results indicate the potential use of cyclodextrins as chiral selectors for enantiomeric resolution of 1,4-DHP calcium antagonists. © 1993 Wiley-Liss, Inc.     

Structural and membrane modifying porperties of suzukacillin, a peptide antibiotic related to alamethicin. Part B. Pore formation in black lipid films.

Suzukacillin, a polypeptide consisting of presumably 23 amino acids and 1 phenylalaninol, is produced by a Trichoderma viride strain No. 1037 and it can be isolated from the culture medium. It shows membrane-modifying properties similar to those of alamethicin. Discrete condustance fluctuations indicate the formation of oligomer pores of varying diameter. On the basis of voltage jump relaxation experiments evidence is given that the dimer is the nucleation state from which pore formation starts and the oligomer disappears. According to the voltage-current characteristics, voltage-dependent and voltage-independent conductances are observed. A slow process is involved, which can be interpreted as a change in the equilibrium distribution between different conformations of the suzukacillin monomer at the membrane interphase. This change results from its interaction with the lipid matrix. Differences in experimental observations between suzukacillin and alamethicin are attributed to the relatively larger alpha-helix and higher number of aliphatic side chains of the suzukacillin monomer and to a more intense interaction with the lipid membrane. This leads to a higher probability of forming dimers from monomers and to the occurrence of "inactivation".     

Structural and membrane modifying properties of suzukacillin,a peptide antibiotic related to alamethicin: Part B. Pore formation in black lipid films

Suzukacillin, a polypeptide consisting of presumably 23 amino acids and 1 phenylalaninol, is produced by a Trichoderma viride strain No. 1037 and it can be isolated from the culture medium. It shows membrane-modifying properties similar to those of alamethicin. Discrete conductance fluctuations indicate the formation of oligomer pores of varying diameter. On the basis of voltage jump relaxation experiments evidence is given that the dimer is the nucleation state from which pore formation tion starts and the oligomer disappears. According to the voltage-current characteristics, voltage-dependent and voltage-independent conductances are observed. A slow process is involved, which can be interpreted as a change in the equilibrium distribution between different conformations of the suzukacillin monomer at the membrane interphase. This change results from its interaction with the lipid matrix. Differences in experimental observations between suzukacillin and alamethicin are attributed to the relatively larger α-helix and higher number of aliphatic side chains of the suzukacillin monomer and to a more intense interaction with the lipid membrane. This leads to a higher probability of forming dimers from monomers and to the occurrence of “inactivation”.     

Iron‐regulated surface determinant B (IsdB) promotes Staphylococcus aureus adherence to and internalization by non‐phagocytic human cells

Staphylococcus aureus is a human pathogen that causes invasive and recurring infections. The ability to internalize into and persist within host cells is thought to contribute to infection. Here we report a novel role for the well‐characterized iron‐regulated surface determinant B (IsdB) protein which we have shown can promote adhesion of 293T, HeLa cells and platelets to immobilized bacteria independently of its ability to bind haemoglobin. IsdB bound to the active form of the platelet integrin α_IIbβ₃, both on platelets and when the integrin was expressed ectopically in CHO cells. IsdB also promoted bacterial invasion into human cells. This was clearly demonstrated with bacteria lacking fibronectin‐binding proteins (FnBPs), which are known to promote invasion in the presence of fibronectin. However, IsdB also contributed significantly to invasion by cells expressing FnBPs in the presence of serum. Thus IsdB appears to be able to interact with the broader family of integrins that bind ligands with the RGD motif and to act as a back up mechanism to promote interactions with mammalian cells.     

Feasibility of rapid and automated importation of 3D echocardiographic left ventricular (LV) geometry into a finite element (FEM) analysis model

Background  

Finite element method (FEM) analysis for intraoperative modeling of the left ventricle (LV) is presently not possible. Since 3D structural data of the LV is now obtainable using standard transesophageal echocardiography (TEE) devices intraoperatively, the present study describes a method to transfer this data into a commercially available FEM analysis system: ABAQUS^?.     

Uncoupling protein-2 prevents neuronal death and diminishes brain dysfunction after stroke and brain trauma

Whereas uncoupling protein 1 (UCP-1) is clearly involved in thermogenesis, the role of UCP-2 is less clear. Using hybridization, cloning techniques and cDNA array analysis to identify inducible neuroprotective genes, we found that neuronal survival correlates with increased expression of Ucp2. In mice overexpressing human UCP-2, brain damage was diminished after experimental stroke and traumatic brain injury, and neurological recovery was enhanced. In cultured cortical neurons, UCP-2 reduced cell death and inhibited caspase-3 activation induced by oxygen and glucose deprivation. Mild mitochondrial uncoupling by 2,4-dinitrophenol (DNP) reduced neuronal death, and UCP-2 activity was enhanced by palmitic acid in isolated mitochondria. Also in isolated mitochondria, UCP-2 shifted the release of reactive oxygen species from the mitochondrial matrix to the extramitochondrial space. We propose that UCP-2 is an inducible protein that is neuroprotective by activating cellular redox signaling or by inducing mild mitochondrial uncoupling that prevents the release of apoptogenic proteins.     

A new species of the genus Seticornuta Morley (Hymenoptera,Ichneumonidae, Metopiinae) from South Korea

Old World species of the genus Seticornuta Morley are reviewed. Seven species of this genus were recorded worldwide, but only one species, Seticornuta albopilosa (Cameron), was known from the Old World. Here, we report one new species, Seticornuta koreana sp. n., from South Korea, and redescribe the other known Old World species, Seticornuta albopilosa, with photographs.