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S Nowicki

Publications and source records attributed to S Nowicki.

At least 19 recordsLinked to original sources
PubMed2001

Ampicillin-resistant Escherichia coli in gestational pyelonephritis: increased occurrence and association with the colonization factor Dr adhesin.

The pattern of ampicillin resistance and possible association with virulence factors of 78 Escherichia coli isolates taken from 78 pregnant women with pyelonephritis were evaluated. The current incidence of ampicillin resistance among pyelonephritis isolates (46%) was significantly higher than that reported in 1985 (22%). Resistance was found more frequently during the first (60%) and third (53%) trimesters than during the second trimester (33%). Of all dra(+) E. coli isolates, 75% were ampicillin resistant, whereas dra(+) isolates of O75 serotype E. coli accounted for 87% of ampicillin-resistant strains. The significant increase of ampicillin resistance among gestational pyelonephritis E. coli and the association with the dra gene cluster encoding colonization and invasive capacity may warrant further study involving obstetric and neonate wards, with the latter being at the higher risk for potential problems.

Adhesins, Escherichia coli↗
PubMed2001

Phosphorylation of the catalytic subunit of rat renal Na+, K+-ATPase by classical PKC isoforms.

In this study we have evaluated the specificity of different PKC isozymes for the phosphorylation of the catalytic alpha1 subunit of rat renal Na+,K+-ATPase (alpha1 Na+,K+-ATPase). Using in vitro phosphotransferase assays we found that classical PKCs (cPKCs) alpha, betaI, and gamma efficiently phosphorylate alpha1 Na+,K+-ATPase. However, alpha1 Na+,K+-ATPase was a poor substrate for the novel PKCs (nPKCs) delta and epsilon. Two-dimensional phosphopeptide mapping revealed a similar pattern of phosphorylation by all cPKCs. The functional significance of this finding was evaluated by measuring Na+,K+-ATPase activity (assessed by 86Rb+ uptake) in COS-7 cells expressing the rat alpha1 Na+,K+-ATPase. 1-oleoyl-2-acetoyl-sn-glycerol (OAG), a nonselective PKC activator, inhibited Na+,K+-ATPase activity in this system. On the other hand, 12-deoxyphorbol-13-phenylacetate (DPP), which preferentially activates nPKCepsilon, did not affect 86Rb+ uptake. These results indicate a differential pattern of phosphorylation and regulation of rat renal Na+,K+-ATPase activity by PKC isoforms and suggest an important role for cPKCs in the physiological regulation of the pump.

Animals↗
PubMed2001

Expression of decay accelerating factor in endometrial adenocarcinoma is inversely related to the stage of tumor.

PROBLEM: Decay accelerating factor (DAF) is implicated in protection of cell membrane from toxicity of complement. In this study, we investigated a hypothesis that DAF is up-regulated in the endometrial adenocarcinoma, which could increase potential of malignant cells to escape destruction by complement. METHODS: DAF density was evaluated in endometrial biopsies of patients with adenocarcinoma at various stages and compared with ten endometrial biopsies from non-malignant patients at the proliferative phase. RESULTS: DAF expression in normal proliferative endometrium varied between 1 and 30%. While DAF density in patients with stage I cancer was in the range 56-98% (mean 78%), stage III values varied from 28 to 16% (mean 21%), P < 0.05. DAF density in the well-differentiated Ishikawa cell line was two-fold higher than in metastatic cell line AN3CA. CONCLUSIONS: Our findings are consistent with a hypothesis that endometrial adenocarcinoma of early stage that is exposed to complement attack may up-regulate DAF to protect malignant cells from complement lysis.

Adenocarcinoma↗
PubMed2001

Rapid receptor-clustering assay to detect uropathogenic and diarrheal Escherichia coli isolates bearing adhesins of the Dr family.

Infections caused by Escherichia coli isolates expressing adhesins of the Dr family are associated with diarrhea and urinary tract infections, and these E. coli strains recognize the complement regulatory protein decay-accelerating factor (DAF) as their receptor. Clustering of the DAF receptor at the sites of bacterial adherence to epithelial cells is proposed as an alternative to PCR assay for rapid detection of Dr-positive E. coli.

Adhesins, Escherichia coli↗
PubMed2000

Nestling growth and song repertoire size in great reed warblers: evidence for song learning as an indicator mechanism in mate choice.

Females of many songbird species show a preference for mating with males that have larger song repertoires, but the advantages associated with this preference are uncertain. We tested the hypothesis that song complexity can serve as an indicator of male quality because the development of the brain regions underlying song learning and production occurs when young birds typically face nutritional and other stresses, so that song reflects how well a male fared during post-hatch development. A key prediction of this hypothesis is that variation in nestling condition should correspond to variation in the adult song repertoires of individuals. We used data from a long-term study of the great reed warbler (Acrocephalus arundinaceus) to test this prediction, correlating two measures of nestling development with subsequent repertoire size of males. We found that the length of the innermost primary feather, a standard measure of development, significantly predicted first-year repertoire size. The relationship between repertoire size and body mass was nearly significant, in spite of the large variance inherent in this measure. These data support the idea that song may provide females with information about a male's response to developmental stress, which in turn is expected to correlate with indirect or direct benefits she might receive.

Animals↗
PubMed2000

Role of decay-accelerating factor domains and anchorage in internalization of Dr-fimbriated Escherichia coli.

Dr-fimbriated Escherichia coli capable of invading epithelial cells recognizes human decay-accelerating factor (DAF) as its cellular receptor. The role of extracellular domains and the glycosylphosphatidylinositol anchor of DAF in the process of internalization of Dr(+) E. coli was characterized in a cell-cell interaction model. Binding of Dr(+) E. coli to the short consensus repeat 3 domain of DAF expressed by Chinese hamster ovary cells was critical for internalization to occur. Deletion of short consensus repeat 3 domain or replacement of Ser(165) by Leu in this domain, or the use of a monoclonal antibody to this region abolished internalization. Replacing the glycosylphosphatidylinositol anchor of DAF with the transmembrane anchor of membrane cofactor protein or HLA-B44 resulted in abolition or reduction of internalization respectively. Cells expressing glycosylphosphatidylinositol-anchored DAF but not the transmembrane-anchored DAF internalized Dr(+) E. coli through a glycolipid pathway, since the former cells were more sensitive to inhibition by methyl-beta-cyclodextrin, a sterol-chelating agent. Electron microscopic studies revealed that the intracellular vacuoles containing the internalized Dr(+) E. coli were morphologically distinct between the anchor variants of DAF. The cells expressing glycosylphosphatidylinositol-anchored DAF contained a single bacterium in tight-fitting vacuoles, while the cells expressing transmembrane-anchored DAF contained multiple (two or three) bacteria in spacious phagosomes. This finding suggests that distinct postendocytic events operate in the cells expressing anchor variants of DAF. We provide direct evidence for the DAF-mediated internalization of Dr(+) E. coli and demonstrate the significance of the glycosylphosphatidylinositol anchor, which determines the ability and efficiency of the internalization event.

Adhesins, Escherichia coli↗
PubMed2000

Dopamine-induced translocation of protein kinase C isoforms visualized in renal epithelial cells.

Short-term regulation of sodium metabolism is dependent on the modulation of the activity of sodium transporters by first and second messengers. In understanding diseases associated with sodium retention, it is necessary to identify the coupling between these messengers. We have examined whether dopamine, an important first messenger in tubular cells, activates and translocates various protein kinase C (PKC) isoforms. We used a proximal tubular-like cell line, LLCPK-1 cells, in which dopamine was found to inhibit Na(+)-K(+)-ATPase in a PKC-dependent manner. Translocation of PKC isoforms was studied with both subcellular fractionation and confocal microscopy. Both techniques revealed a dopamine-induced translocation from cytosol to plasma membrane of PKC-alpha and -epsilon, but not of PKC-delta, -gamma, and -zeta. The process of subcellular fractionation resulted in partial translocation of PKC-epsilon. This artifact was eliminated in confocal studies. Confocal imaging permitted detection of translocation within 20 s. Translocation was abolished by a phospholipase C inhibitor and by an antagonist against the dopamine 1 subtype (D(1)) but not the 2 subtype of receptor (D(2)). In conclusion, this study visualizes in renal epithelial cells a very rapid activation of the PKC-alpha and -epsilon isoforms by the D(1) receptor subtype.

Animals↗
PubMed2000

Arachidonic acid metabolic pathways regulating activity of renal Na(+)-K(+)-ATPase are age dependent.

Locally formed arachidonic acid (AA) metabolites are important as modulators of many aspects of renal tubular function, including regulation of the activity of tubular Na(+)-K(+)-ATPase. Here we examined the ontogeny of the AA metabolic pathways regulating proximal convoluted tubular (PCT) Na(+)-K(+)-ATPase activity in infant and adult rats. Eicosatetraynoic acid, an inhibitor of all AA-metabolizing pathways, abolished this effect. AA inhibition of PCT Na(+)-K(+)-ATPase was blocked by the 12-lipoxygenase inhibitor baicalein in infant but not in adult rats and by the specific cytochrome P-450 fatty acid omega-hydroxylase inhibitor 17-octadecynoic acid in adult but not in infant rats. The lipoxygenase metabolite 12(S)-hydroxyeicosatetraenoic acid (HETE) and the cytochrome P-450 metabolite 20-HETE both inhibited PCT Na(+)-K(+)-ATPase in a protein kinase C-dependent manner, but the effect was significantly more pronounced in infant PCT. Lipoxygenase mRNA was only detected in infant cortex. Expression of renal isoforms of cytochrome P-450 mRNA was more prominent in adult cortex. In summary, the AA metabolic pathways that modulated the activity of rat renal proximal tubular Na(+)-K(+)-ATPase are age dependent.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed2000

L-Dopa uptake and dopamine production in proximal tubular cells are regulated by beta(2)-adrenergic receptors.

This study assessed the role of adrenergic receptors on the regulation of the uptake of L-dopa and the production of dopamine by renal tubular cells. Scatchard analysis showed two L-dopa uptake sites with different affinities (K(m) 0.316 vs 1.53 microM). L-Dopa uptake was decreased by the nonselective adrenergic agonists epinephrine or norepinephrine (40%), by the beta-selective agonist isoproterenol or the beta(2)-selective agonist terbutaline (60%), but not by alpha-selective agonists (all 1 microM). The effect of norepinephrine, isoproterenol, or terbutaline was unaffected by addition of the beta(1)-antagonist atenolol, abolished by ICI-118, 551, a beta(2)-antagonist (both 0.1 microM), and mimicked by the addition of dibutyryl-cAMP (1 microM). Preincubation with terbutaline decreased the number of high-affinity uptake sites (V(max) = 1.10 +/- 0.3 vs. 0.5 +/- 0.1 pmol. mg protein(-1). min(-1)) without changing their affinity. Norepinephrine or terbutaline decreased dopamine production by isolated cells, and this effect was abolished by ICI-118,551 (0.1 microM). In vivo administration of ICI-118,551 reduced the urinary excretion of L-dopa and increased the excretion of 3,4-dihydroxyphenylacetic acid without significant changes in plasma L-dopa concentrations. These results demonstrate that stimulation of beta(2)-adrenergic receptors decreases the number of high-affinity L-dopa uptake sites in isolated tubular cells resulting in a reduction of the uptake of L-dopa and the production of dopamine and provide evidence for the presence of this mechanism in the intact animal.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

Vocal tract function in birdsong production: experimental manipulation of beak movements.

Kinematic analyses have demonstrated that the extent to which a songbird's beak is open when singing correlates with the acoustic frequencies of the sounds produced, suggesting that beak movements function to modulate the acoustic properties of the vocal tract during song production. If motions of the beak are necessary for normal song production, then disrupting the ability of a bird to perform these movements should alter the acoustic properties of its song. We tested this prediction by comparing songs produced normally by white-throated sparrows and swamp sparrows with songs produced when the beak was temporarily immobilized. We also observed how temporarily loading the beak of canaries with extra mass affected vocal tract movements and song production. Disruption of vocal tract movements resulted in the predicted frequency-dependent amplitude changes in the songs of both white-throated sparrows and swamp sparrows. Canaries with mass added to their beak sang with their beak open more widely than normal and produced notes with greater harmonic content than those without weights. Both manipulations resulted in acoustic changes consistent with a model in which beak motions affect vocal tract resonances, thus supporting the hypothesis that dynamic vocal tract motions and post-production modulation of sound are necessary features of normal song production.

Acoustics↗
PubMed1999

The development of within-song type variation in song sparrows.

We investigated the development of within-song type variation in song sparrows, Melospiza melodia, with two experiments designed to determine how exposure to within-type variation influences the song-learning process and whether within-type variation itself is a learned trait. In the first experiment, we compared learning between two groups of males, one group tutored exclusively with song models presented with no variation, and the other group tutored exclusively with song models presented with a range of within-type variation that is normally produced by birds in the field. The two groups in this experiment did not differ significantly in any measure of how well they learned, suggesting that exposure to within-type variation has no measurable influence on the learning process overall. Nor did the groups differ in the expression of within-song type variation in their own adult songs, demonstrating that within-type variation is not a learned feature of song sparrow song. In the second experiment, we tutored a single group of birds with both invariant and variable models, allowing us to ask how within-type variability affects learning preferences. Young birds preferentially copied song type models presented with variation significantly more than invariant models. Taken together, these experiments provide insight into the evolution of within-song type variation in song sparrows, although the functional significance of this level of variation and learning preferences based on variation remain enigmatic. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Song types as fundamental units in vocal repertoires.

We investigated whether song types function as fundamental units of song variation in song sparrows, Melospiza melodia. As the size of a male song sparrow's repertoire increases, so does the mean similarity of his song types, as measured by the sharing of minimal units of production (MUPs). It follows that if MUP similarity is important perceptually, then small repertoires (of dissimilar song types) may be functionally equivalent to large repertoires (of similar song types). We performed two experiments to test whether MUP similarity is important perceptually to male song sparrows. Both experiments used a habituation/recovery design, in which recovery in response at a switch in stimuli is used to gauge the subject's perception of the similarity of the stimuli. The results of both experiments indicate that the level of perceived similarity between pairs of songs does not depend on their level of MUP similarity, within the range of MUP similarities found between song types. Songs with high enough MUP similarity to be judged as variants of the same song type are, however, perceived to be much more similar than are any two song types. The results are compatible with a categorical model of song type perception. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Permissiveness in the learning and development of song syntax in swamp sparrows.

Vocal learning in swamp sparrows, Melospiza georgiana, is subject to a host of sensory and motor limitations. One such limitation is that young swamp sparrows almost invariably crystallize their songs with a simple trilled syntax, irrespective of the syntax of vocal models from which they learn. A striking exception to this pattern was recently identified by Podos (1996, Animal Behaviour, 51, 1061-1070), who found that large-scale organizational changes in vocal syntax, including the production of an intermittent or 'broken' syntax, were produced when birds faced limits on vocal performance capacities during motor ontogeny. Our goal in the present study was to determine whether song models with broken syntax could serve as suitable training models for young swamp sparrows, and, if so, if broken syntax could be faithfully reproduced. We hand-reared 10 male swamp sparrows and exposed them to control, rapid and broken song models. Control song models were copied with a high degree of accuracy, as in previous studies. Rapid song models were copied with deficiencies that suggested performance limits on vocal production; such deficiencies included the production of songs with broken syntax and the production of songs in which notes were dropped out as songs progressed. Broken songs proved suitable as training models. Furthermore, copies of broken song models were crystallized either with normal or with broken syntax. These data identify an unexpected direction of permissiveness in the types of songs swamp sparrows will memorize and accurately reproduce, and also point to a possible proximate basis for syntactical changes in the evolution of sparrow songs. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Inverse relationship between severity of experimental pyelonephritis and nitric oxide production in C3H/HeJ mice.

The contribution of nitric oxide to host resistance to experimental pyelonephritis is not well understood. We examined whether the inhibition of nitric oxide synthesis alters the sensitivity of lipopolysaccharide (LPS) responder (C3H/HeN) and nonresponder (C3H/HeJ) mice to experimental Escherichia coli pyelonephritis. C3H/HeJ and C3H/HeN mice were implanted subcutaneously with minipumps containing an inhibitor of nitric oxide, NG-nitro-L-arginine methyl ester (L-NAME), or a corresponding vehicle. Ascending urinary tract infection by bladder catheterization with two strains of E. coli, an O75 strain bearing Dr fimbriae and an O75 strain bearing P fimbriae, was developed in tested animals. Twenty-four hours following bladder infection, the kidneys of C3H/HeN and C3H/HeJ mice were colonized at a similar rate. However, 5 weeks postinoculation, C3H/HeN mice cleared infection while C3H/HeJ mice showed persistent colonization. Twenty-four hours following infection, C3H/HeN mice treated with L-NAME showed no significant increase of renal tissue infection compared to the saline-treated control group. However, L-NAME-treated C3H/HeJ mice showed an approximately 100-fold increase in E. coli infection rate compared to the saline-treated controls in the Dr+ group but showed no change compared to those in the P+ group. Dissemination of Dr+ E. coli but not P+ E. coli to the liver and uterus was significantly enhanced with L-NAME treatment in C3H/HeJ mice only. Nitric oxide had no direct killing effect on E. coli in vitro. Nitrite production by various organs was found to be significantly lower in C3H/HeJ mice than in C3H/HeN mice. Alteration of nitric oxide and LPS responsiveness was significantly associated with the increased sensitivity of C3H/HeJ mice to experimental Dr+ but not to P+ E. coli pyelonephritis. These findings are consistent with the hypothesis that nitric oxide synthase activity in concert with LPS responsiveness may participate in the antibacterial defense mechanisms of the C3H mouse urinary tract. This phenomenon is strain dependent and possibly related to the invasive properties of E. coli.

Animals↗
PubMed1999

Experimental transmission of Neisseria gonorrhoeae from pregnant rat to fetus.

Sprague-Dawley rats were infected on day 20 of pregnancy by intraperitoneal inoculation with Neisseria gonorrhoeae. Disseminated gonococcal infection (DGI) and pelvic inflammatory disease (PID) strains in the presence of C1q but not in the presence of bovine serum albumin (BSA) were able to spread from the pregnant rat to the fetus and resulted in fetal mortality. Transmission of DGI and PID strains that are serum resistant (ser(r)) and sac-4 positive but not of a local infection strain that is ser(s) and sac-4 negative was facilitated by the C1q-dependent mechanism. This study provides the first experimental model that may mimic the transmission of gonococcal infection from mother to the fetus during pregnancy.

Animals↗