Role of sulfated glycans in adherence of the microsporidian Encephalitozoon intestinalis to host cells in vitro.

Microsporidia are obligate intracellular opportunistic protists that infect a wide variety of animals, including humans, via environmentally resistant spores. Infection requires that spores be in close proximity to host cells so that the hollow polar tube can pierce the cell membrane and inject the spore contents into the cell cytoplasm. Like other eukaryotic microbes, microsporidia may use specific mechanisms for adherence in order to achieve target cell proximity and increase the likelihood of successful infection.

Periplasmic cleavage and modification of the 1-phosphate group of Helicobacter pylori lipid A.

Pathogenic bacteria modify the lipid A portion of their lipopolysaccharide to help evade the host innate immune response. Modification of the negatively charged phosphate groups of lipid A aids in resistance to cationic antimicrobial peptides targeting the bacterial cell surface. The lipid A of Helicobacter pylori contains a phosphoethanolamine (pEtN) unit directly linked to the 1-position of the disaccharide backbone.

Structure-activity relationships for three macrolide antibiotics in Haemophilus influenzae.

A prior study examining differences in the activities of erythromycin and azithromycin on cellular functions in the Gram-negative pathogen, Haemophilus influenzae, revealed a marked difference in their inhibitory activities. The study revealed that protein synthesis and 50S ribosomal subunit assembly were equal targets for inhibition by azithromycin while erythromycin was a preferential inhibitor of translation. This contrast in inhibitory activities stimulated a comparative analysis of three additional antibiotics: clarithromycin, flurithromycin and roxithromycin.

An examination of the differential sensitivity to ketolide antibiotics in ermB strains of Streptococcus pyogenes and Streptococcus pneumoniae.

Several reports in the literature have described a differential sensitivity to ketolide antibiotics in ermB strains of Streptococcus pyogenes and Streptococcus pneumoniae resistant to erythromycin. Strains of S. pyogenes and S.

Recombinant human mast-cell chymase: an improved procedure for expression in Pichia pastoris and purification of the highly active enzyme.

Human mast-cell chymase (EC 3.4.21.

Biosynthesis, transport, and modification of lipid A.

Lipopolysaccharide (LPS) is the major surface molecule of Gram-negative bacteria and consists of three distinct structural domains: O-antigen, core, and lipid A. The lipid A (endotoxin) domain of LPS is a unique, glucosamine-based phospholipid that serves as the hydrophobic anchor of LPS and is the bioactive component of the molecule that is associated with Gram-negative septic shock. The structural genes encoding the enzymes required for the biosynthesis of Escherchia coli lipid A have been identified and characterized.

Neomycin and paromomycin inhibit 30S ribosomal subunit assembly in Staphylococcus aureus.

A number of different antibiotics that prevent translation by binding to the 50S ribosomal subunit of bacterial cells have recently been shown to also prevent assembly of this subunit. Antibacterial agents affecting 30S particle activities have not been examined extensively for effects on small subunit formation. The aminoglycoside antibiotics paromomycin and neomycin bind specifically to the 30S ribosomal subunit and inhibit translation.

Primary cultures of female swine genital epithelial cells in vitro: a new approach for the study of hormonal modulation of Chlamydia infection.

Previous studies have demonstrated that female reproductive hormones influence chlamydial infection both in vivo and in vitro. Due to the reduced availability of human genital tissues for research purposes, an alternative hormone-responsive model system was sought to study chlamydial pathogenesis. Mature female swine eliminated from breeding programs were selected as the animals of choice because of the similarity of a sexually transmitted disease syndrome and sequelae in swine to a disease syndrome and sequelae found in humans, because of the near identity of a natural infectious chlamydial isolate from swine to Chlamydia trachomatis serovar D from humans, and because a pig's epithelial cell physiology and the mean length of its estrous cycle are similar to those in humans.

A 50S ribosomal subunit precursor particle is a substrate for the ErmC methyltransferase in Staphylococcus aureus cells.

Macrolide antibiotics like erythromycin can induce the synthesis of a specific 23S rRNA methyltransferase which confers resistance to cells containing the erm gene. Erythromycin inhibits both protein synthesis and the formation of 50S subunits in bacterial cells. We have tested the idea that the 50S precursor particle that accumulates in antibiotic-treated Staphylococcus aureus cells is a substrate for the methyltransferase enzyme.

Bacterial ribosomal subunit assembly is an antibiotic target.

A substantial number of antimicrobial agents target some activity of the bacterial ribosome for inhibition. Mechanistic studies and recent structural investigations of the ribosome have identified the binding sites and presumed mechanism of inhibitory activity for some compounds. A second target for many of these antibiotics has recently been examined.

Vascular Corrosion Casting: Review of Advantages and Limitations in the Application of Some Simple Quantitative Methods.

Vascular corrosion casting has been used for about 40 years to produce replicas of normal and abnormal vasculature and microvasculature of various tissues and organs that could be viewed at the ultrastructural level. In combination with scanning electron microscopy (SEM), the primary application of corrosion casting has been to describe the morphology and anatomical distribution of blood vessels in these tissues. However, such replicas should also contain quantitative information about that vasculature.

Preferential inhibition of protein synthesis by ketolide antibiotics in Haemophilus influenzae cells.

The ketolide antibiotics are semi-synthetic derivatives of erythromycin A with enhanced inhibitory activity in a wide variety of microorganisms. They have significantly lower MICs than the macrolide antibiotics for many Gram-positive organisms. Two ketolides, telithromycin and ABT-773, were tested for growth-inhibitory effects in Haemophilus influenzae.

Bacterial ribosomal subunit synthesis: a novel antibiotic target.

The continuing increase in antibiotic-resistant pathogenic bacterial has stimulated research on the development of new antimicrobial agents and the identification of new cellular targets. One such target is the sequence of assembly steps required for the formation of bacterial ribosomal subunits. A large number of different protein synthesis inhibitors which affect large subunit function also prevent the 50S particle from being formed in growing cells.

Telithromycin inhibition of protein synthesis and 50S ribosomal subunit formation in Streptococcus pneumoniae cells.

The new ketolide antibiotic telithromycin (HMR3647) has been examined for inhibitory effects in cells of Streptococcus pneumoniae. The antibiotic caused a proportional decline in cell growth rate and viability with an IC(50) of 15 ng/ml. At a concentration of 7.

The ketolide antibiotic ABT-773 is a specific inhibitor of translation and 50S ribosomal subunit formation in Streptococcus pneumoniae cells.

ABT-773 is a new 3-keto macrolide antibiotic that has been shown to be very effective against infections by Gram-positive microorganisms. This work examines its inhibitory effects in cells of Streptococcus pneumoniae. ABT-773 caused a proportional decline in cell growth rates and viability with an IC(50) of 5 ng/ml.

Inhibition of 50S ribosomal subunit assembly in Haemophilus influenzae cells by azithromycin and erythromycin.

Azithromycin is an important antibiotic for the treatment of several different Gram-positive and Gram-negative bacterial infections. Erythromycin and clarithromycin are less useful antibiotics against Gram-negative infections. This difference in inhibitory activity was explored by comparing the effects of azithromycin and erythromycin on cellular functions in Haemophilus influenzae cells.

30S ribosomal subunit assembly is a target for inhibition by aminoglycosides in Escherichia coli.

The aminoglycosides paromomycin and neomycin were examined in Escherichia coli cells for an inhibitory effect on 30S ribosomal subunit assembly. Both compounds inhibited the growth rate, viable cell number, and protein synthesis rate with similar 50% inhibitory concentrations. Each drug also showed a concentration-dependent inhibition of 30S subunit formation.

Ultrastructure and blood supply of the tegmentum vasculosum in the cochlea of the duckling.

The tegmentum vasculosum of the duckling consists of a highly folded epithelium which extends over the dorsal and lateral walls of the cochlear duct, separating the scala media from the scala vestibuli. This epithelium consists of two distinct cell types, dark cells and light cells, and is well vascularized. The surface of the epithelium is formed by a mosaic of alternating dark and light cells.

Na+,K+-ATPase activity and ultrastructural localization in the tegmentum vasculosum in the cochlea of the duckling.

The tegmentum vasculosum of the avian cochlear duct mimics the stria vascularis of the mammalian cochlear duct in both location and structure, and previous studies indicate that it may be its functional counterpart with regard to endolymph synthesis. In the present study, we report on the enzymatic activity and ultrastructural localization of the Na+,K+-ATPase in the tegmentum vasculosum of the duckling. Na+,K+-ATPase activity was determined by measuring K+-dependent, ouabain-sensitive p-nitrophenyl phosphatase (p-NPPase) activity in homogenates of dissected regions of the cochlear duct.

Linezolid is a specific inhibitor of 50S ribosomal subunit formation in Staphylococcus aureus cells.

Linezolid is an oxazolidinone compound that has been shown to have impressive antimicrobial activity against a number of Gram-positive bacteria. It inhibits an initiation step of protein synthesis, and its binding site has been shown to be on the 50S ribosomal subunit. Linezolid was tested to see whether would interfere with the formation of the 50S subunit in Staphylococcus aureus cells, since a number of other 50S-specific antibiotics have this second inhibitory function.

TAN-1057A: a translational inhibitor with a specific inhibitory effect on 50S ribosomal subunit formation.

The inhibitory activities of a novel antibiotic compound have been investigated. A synthetic version of the natural product TAN-1057A was examined for its effects on translation and ribosomal subunit formation. The antibiotic at 6 microg/ml reduced the growth rate of wild-type Staphylococcus aureus cells by 50%.

Mechanisms of oxysterol-induced apoptosis.

The rationale for the present review is that oxysterols found in oxidized LDL (oxLDL) play a role in atherogenesis. This perspective is based on studies that show that induction of apoptosis in vascular cells is an important process in atherogenesis, that apoptosis can be induced by oxLDL, and that the oxysterol component of oxLDL is responsible for its proapoptotic activity. The evidence for these concepts is reviewed, as are studies on the mechanisms by which oxysterols can induce apoptosis.