Characterization of grlA, grlB, gyrA, and gyrB mutations in 116 unrelated isolates of Staphylococcus aureus and effects of mutations on ciprofloxacin MIC

One hundred sixteen unrelated clinical isolates of Staphylococcus aureus (70 ciprofloxacin resistant and 46 ciprofloxacin susceptible) from eight countries were studied for the presence of mutations in the grlA, grlB, gyrA, and gyrB gene loci. Two mutations within grlA (located at codons 80 and 84) and two mutations within gyrA (located at codons 84 and 88) were clearly associated with ciprofloxacin resistance, although other mutations detected within the four genes studied may also contribute to decreased susceptibility.     

Effects of three prepubertal body growth rates on performance of Holstein heifers during first lactation

beta1A integrin subunits with point mutations of the cytoplasmic domain were expressed in fibroblasts derived from beta1-null stem cells. beta1A in which one or both of the tyrosines of the two NPXY motifs (Y783, Y795) were changed to phenylalanines formed active alpha5 beta1 and alpha6 beta1 integrins that mediated cell adhesion and supported assembly of fibronectin. Mutation of the proline in either motif (P781, P793) to an alanine or of a threonine in the inter-motif sequence (T788) to a proline resulted in poorly expressed, inactive beta1A. Y783,795F cells developed numerous fine focal contacts and exhibited motility on a surface. When compared with cells expressing wild-type beta1A or beta1A with the D759A activating mutation of a conserved membrane-proximal aspartate, Y783, 795F cells had impaired ability to transverse filters in chemotaxis assays. Analysis of cells expressing beta1A with single Tyr to Phe substitutions indicated that both Y783 and Y795 are important for directed migration. Actin-containing microfilaments of Y783,795F cells were shorter and more peripheral than microfilaments of cells expressing wild-type beta1A. These results indicate that change of the phenol side chains in the NPXY motifs to phenyl groups (which cannot be phosphorylated) has major effects on the organization of focal contacts and cytoskeleton and on directed cell motility.     

Assembly of alcohol oxidase in peroxisomes of the yeast Hansenula polymorpha requires the cofactor flavin adenine dinucleotide

The peroxisomal flavoprotein alcohol oxidase (AO) is an octamer (600 kDa) consisting of eight identical subunits, each of which contains one flavin adenine dinucleotide molecule as a cofactor. Studies on a riboflavin (Rf) auxotrophic mutant of the yeast Hansenula polymorpha revealed that limitation of the cofactor led to drastic effects on AO import and assembly as well as peroxisome proliferation. Compared to wild-type control cells Rf-limitation led to 1) reduced levels of AO protein, 2) reduced levels of correctly assembled and activated AO inside peroxisomes, 3) a partial inhibition of peroxisomal protein import, leading to the accumulation of precursors of matrix proteins in the cytosol, and 4) a significant increase in peroxisome number. We argue that the inhibition of import may result from the saturation of a peroxisomal molecular chaperone under conditions that normal assembly of a major matrix protein inside the target organelle is prevented.     

Effect of human and murine interferon-alpha on steroid production by rat ovarian cells

The effect of interferon on the rat ovarian cell function was investigated. Cells from the ovary of juvenile rats were used as a model to investigate the effect of IFN-alpha on the secretion of estradiol and testosterone. In addition the effect of human IFN-alpha (hIFN-alpha) on the secretion of testosterone by the rat adult testis was studied. Present results show that leukocyte hIFN-alpha decreased the human chorionic gonadotropin (hCG) stimulated secretion of estradiol and testosterone by ovarian cells, and the production of testosterone by testis cells. Basal secretion of steroids was affected later and in less proportion than the hCG-dependent production. The IFN-alpha obtained from murine leukocytes, also inhibited the response of ovarian cells to the hCG stimulus.The nature of this effect in the secretion of the steroids is dose and time-dependent. The incubation of hIFN-alpha with an specific antibody completely blocked the effect of the cytokine on ovarian cells.     

Breast cancer screening in Navarra: interpretation of a high detection rate at the first screening round and a low rate at the second round

Endothelial cells and pericytes are closely associated in brain capillaries. Together with astrocytic foot processes, they form the blood-brain barrier. Capillaries were isolated from bovine brain cortex. Pure populations of endothelial cells and pericytes were isolated and cultured in vitro. Polarized monolayers of endothelial cells preferentially secreted immunoreactive endothelin-1 (Et-1) at their abluminal (brain-facing) membrane. They did not express receptors for Et-1. Pericytes expressed BQ-123-sensitive ETA receptors for endothelins as evidenced by 125I-Et-1 binding experiments. These receptors were coupled to phospholipase C as demonstrated by intracellular calcium measurements using indo-1-loaded cells. Addition of Et-1 to pericytes induced marked changes in the cell morphology that were associated with a reorganization of F-actin and intermediate filaments. It is concluded that Et-1 is a paracrine mediator at the bovine blood-brain barrier and that capillary pericytes are target cells for endothelium-derived Et-1.     

Reactive oxygen intermediates mediate a systemic signal network in the establishment of plant immunity

Recognition of an avirulent pathogen stimulates an oxidative burst generating O2- and H2O2, and these reactive oxygen intermediates (ROIs) cue the induction of defense genes and cell death in the development of a restricted lesion. This localized hypersensitive response (HR) is accompanied by the development of systemic acquired resistance to virulent pathogens. Here we show that inoculation of Arabidopsis leaves with avirulent Pseudomonas syringae induces secondary oxidative bursts in discrete cells in distant tissues, leading to low-frequency systemic micro-HRs. The primary oxidative burst induces these systemic responses, and both the primary burst and the secondary microbursts are required for systemic immunity. Hence, ROIs mediate a reiterative signal network underlying systemic as well as local resistance responses.     

Electrical basis of peristalsis in the mammalian upper urinary tract

1. Peristalsis in the mammalian upper urinary tract (UUT) is mostly myogenic in origin, originating predominately in the proximal pelvicalyceal regions of the renal pelvis, an area that is enriched with specialized smooth muscle cells termed 'atypical' smooth muscle cells. Propagating peristaltic contractions are little affected by blockers of either autonomic nerve function or nerve impulse propagation; however, blockers of sensory nerve function or prostaglandin synthesis reduce both the frequency and the strength of the spontaneous contractions underlying peristalsis. 2. The electrical drive for these peristaltic contractions has long been considered to involve mechanisms analogous to the heart, such that 'atypical' smooth muscle cells generate spontaneous 'pacemaker' action potentials. These pacemaker potentials trigger the firing of action potentials and contraction in the muscular regions of the renal pelvis, which propagate distally to the ureter, propelling urine towards the bladder. 3. Recent intracellular microelectrode and single cell/channel patch-clamp studies have revealed that the ionic conductances underlying the action potentials recorded in the UUT are likely to involve the opening and slow closure of voltage-activated 'L-type' Ca2+ channels, offset by the time-dependent opening and closure of both voltage- and Ca(2+)-activated K+ channels. 4. In the present review we summarize the current knowledge of the ionic mechanisms underlying action potential discharge in the UUT, as well as present our view on how this electrical activity supports the initiation and conduction of UUT peristalsis.