The lux autoinducer regulates the production of exoenzyme virulence determinants in Erwinia carotovora and Pseudomonas aeruginosa

Erwinia carotovora and Pseudomonas aeruginosa secrete exoenzymes that contribute to the pathogenesis of plant and mammalian infections respectively. E.carotovora mutants defective in synthesis of the pectinase, cellulase and protease exoenzymes were isolated and classified into two groups. Group 2 mutants were found to be defective in the production of a small freely diffusible molecule, N-3-(oxohexanoyl)-L-homoserine, lactone (HSL), and were avirulent. Addition of exogenous HSL to these group 2 mutants restores synthesis of the exoenzymes and virulence in planta. Of the exoenzymes of P.aeruginosa the metalloprotease, elastase, is an established virulence determinant. Mutants of P.aeruginosa that are defective in elastase production have been isolated and were again found to fall into two groups. Analogous to the group 2 mutants of E.carotovora, group 2 mutants of P. aeruginosa are defective in the synthesis of HSL and exogenous HSL restores elastase production. HSL has now been linked to the control of bioluminescence in Vibrio fischeri, carbapenem antibiotic production of E.carotovora and the above exoenzyme virulence determinants. This information significantly enhances our understanding of the extent and nature of pheromone mediated gene expression control in prokaryotes.

Lisinopril in the treatment of hypertension: a Canadian postmarketing surveillance study

A postmarketing surveillance study in 2273 Canadian office practices provided the largest body of clinical experience to date with the angiotensin-converting enzyme (ACE) inhibitor lisinopril in the treatment of mild to moderate essential hypertension. The principal emphasis in this uncontrolled study was safety, assessed in 10,289 patients. Patients with a diastolic blood pressure > 90 mmHg were considered for the study. Both previously untreated patients and those who were experiencing adverse effects from their current antihypertensive regimen were included. Lisinopril was begun at a dose of 10 mg/day. Subsequent dose adjustments, to a maximum of 40 mg/day, were made to achieve optimal blood pressure control (diastolic blood pressure < or = 90 mmHg or > or = 10 mmHg below baseline for > or = 4 weeks at the same dose). Therapy was continued for a minimum of 4 weeks to a maximum of 12 weeks, with patients examined every 2 weeks. The frequencies of adverse effects and laboratory abnormalities were analyzed in all treated patients. All 10,289 patients enrolled were considered in the analysis of safety. One or more adverse effects were reported for 1593 (15.5%) patients, and 802 (7.8%) withdrew from the study because of adverse effects. The most frequent adverse effects were cough (4.0%), dizziness (2.3%), headache (2.1%), asthenia (1.7%), and nausea (1.0%). The physicians' global assessment rated overall tolerability as very good or good for 77.1% of the patients. Antihypertensive effect was evaluated in 5886 patients who met the criteria for efficacy analysis. The criterion response was attained in 5141 (87.3%) patients, with 68.6% responding to 10 mg/day of lisinopril, 26.3% to 20 mg/day, and 3.2% to 40 mg/day (the other 1.9% responded at nonstandard doses). Lisinopril was safe and well-tolerated. Except for cough, class effects of ACE inhibitors were rarely encountered. The results of the efficacy analysis confirm the established efficacy of lisinopril in patients with mild to moderate essential hypertension.

Focal induction of IGF binding proteins in proximal tubules of diabetic rat kidney

Diabetes-associated kidney enlargement is associated with increased kidney insulinlike growth factor I (IGF-I) binding. IGF-I binds to the type I IGF receptor, which mediates most of its actions, and to specific binding proteins (IGFBPs), which modulate its actions. To explore the nature and extent of IGF-I binding in the kidney, in vitro autoradiography was used to map the distribution of IGF binding in control and diabetic rat kidney. Specificity studies were performed with increasing concentrations of unlabeled IGF-I, IGF-II, des(1-3)IGF-I (an IGF-I derivative that binds to receptors normally but with decreased affinity to binding proteins), and insulin. In control rats, diffuse binding was found throughout the kidney with increased density in the papilla. Binding specificity in the cortex and outer medulla was typical of the type I IGF receptor (IGF-I = des[1-3]IGF-I greater than IGF-II much greater than insulin). Binding in the outer medulla of diabetic kidney was typical of the type I IGF receptor. A marked focal increase in proximal tubular binding occurred in 13 of 22 postpubertal diabetic rats. Binding specificity of the proximal tubular binding was consistent with the predominance of an IGF binding protein (IGF-I = IGF-II greater than des[1-3]IGF-I with minimal displacement by insulin). Northern-blot analysis revealed increased IGFBP-1 and IGFBP-3 mRNA in cortical tissue from diabetic rats displaying increased proximal tubular binding but not from diabetic rats not displaying this phenomenon. As cell surface association of IGFBPs is linked to potentiation of IGF activity, a possible mechanism for potentiation of local IGF-I action may be provided.

Constant-axial-intensity nondiffracting beam

Numerical solutions of the Fresnel diffraction integral with various apodizing filter functions are used to indicate that a so-called nondiffracting beam can be produced that maintains a constant spot size and constant axial intensity over a considerable range, approximately 30 m in our example.

Diabetes-related renal growth and IGF-I accumulation in castrated rats

The effects of castration on diabetes-related renal growth and IGF-I regulation were studied. In the rat, prepubertal castration is associated with a normal or increased surge in plasma insulin-like growth factor I (IGF-I) at the time of 'puberty'. In order to determine the role of sex steroids in the development of diabetes-related kidney growth and IGF-I regulation, Sprague-Dawley rats were castrated at the age of 4 weeks and streptozotocin diabetes was induced at the age of 13 weeks. The development of renal enlargement and kidney IGF-I levels was studied over the following 7 days. Kidney weight in diabetic animals was significantly greater than in controls, and by day 7, had increased by 27% (1.20 +/- 0.03 vs 0.94 +/- 0.03 g, P less than 0.001). Kidney IGF-I content was significantly elevated in diabetic rats, peaking on day 1 (diabetic, 1159 +/- 302 ng/g vs control, 237 +/- 53 ng/g, P less than 0.001) and remaining higher than control levels throughout the 7 days of the experiment. The pattern of diabetes-related kidney growth and IGF-I regulation in castrated rats resembles that of age matched intact postpubertal controls, suggesting that sex steroids do not have a direct role in these phenomena.

Holographic reproduction of a diffraction-free beam

A high resolution Bessel function profile diffraction-free beam has been reproduced from a holographic optical element made by direct physical interference.

Insulin receptor sub-types in a human lymphoid-derived cell line (IM-9): differential regulation by insulin, dexamethasone and monensin

The cells of the human IM-9 lymphocyte-derived line contain a subpopulation of insulin binding sites which differ from classical insulin binding sites in their higher binding affinity for insulin-like growth factor II (IGF-II) and insulin-like growth factor I (IGF-I). These atypical insulin binding sites are identified on IM-9 cells by [125I]IGF-II binding. To determine whether the atypical and classical insulin receptors of IM-9 cells were subject to different modes of in vivo regulation, we treated IM-9 cells with agents known to alter the surface expression of insulin receptors--insulin, dexamethasone and monensin. We then measured insulin and IGF-II binding to the surface of the washed cells. Pretreatment of IM-9 cells with 1 microM insulin for 20 h at 37 degrees C induced a 44-48% decrease in the number of high affinity insulin binding sites, but no change in the number of IGF-II binding sites. In contrast, the surface expression of both insulin and IGF-II binding sites (classical and atypical insulin receptors) increased 1.3 to 1.7-fold after treatment with dexamethasone (200 nM) and decreased 30 to 45% after monensin (1 microM). These results suggest that atypical and classical insulin receptors are differentially susceptible to down-regulation by insulin.

Neurochemical consequences following injection of the substance P analogue, DiMe-C7, into the rat ventral tegmental area

The effect on forebrain catecholamine- and indoleamine-related neurochemical levels was investigated following stimulation of the rat ventral tegmental area with the substance P analogue, DiMe-C7. DiMe-C7 (6.0 micrograms) induced a marked hyperactivity in rats with maximal response between 15 and 30 min following the injection. Fifteen min following the DiMe-C7 injection levels of dopamine and/or its metabolites (3,4-dihydroxyphenylacetic acid, homovanillic acid) were significantly increased in the nucleus accumbens, amygdala, entorhinal cortex and striatum relative to vehicle-injected animals. Although the increase in dopamine metabolism in the nucleus accumbens is consistent with the behavioural hyperactivity, it is concluded that other forebrain nuclei may also be involved in the mediation of the hyperactivity response.

Comparison of structure, mechanical properties, and functions of lumbar spinal ligaments

The organization of collagen in the supraspinous, interspinous, and longitudinal ligaments, as well as the ligamenta flava, in lumbar spines from human cadavers has been investigated by polarized light microscopy, scanning electron microscopy, and x-ray diffraction. These experiments were performed on ligaments in situ, with their bony attachments undisturbed, and on excised ligaments at a range of applied strains. Results were related to the composition (investigated by standard histologic techniques) and gross structures (investigated by light microscopy) of the ligaments. More importantly, the results were related to the mechanical properties of the ligaments, which include stiffness, failure conditions, stress relaxation, and hysteresis. Where necessary, results were supplemented by or compared with those obtained from pig ligaments. Mechanical properties were related to postural changes by ligament strains induced in cadaveric specimens, using results from the literature. Thus, ligament structures could be related to their physiologic functions.

Autocrine regulation of human tumor cell proliferation by insulin-like growth factor II: an in-vitro model

We have shown that a pleomorphic cell line of abnormal human karyotype derived from a stomach carcinoma (LIM-1839) proliferates in serum-free medium, expresses insulin-like growth factor II (IGF-II) mRNA, and secretes IGF-II (up to 56 ng/ml in serum-free conditioned medium, as measured in a rat liver RRA. No detectable levels of IGF-I can be measured in serum-free conditioned medium by RIA. These cells also secrete IGF-binding proteins, detected by a charcoal adsorption assay. The release of IGF-II and IGF binding proteins into serum-free conditioned medium (1.7 pmol/10(6) cells.24 h and 0.8 pmol binding sites/10(6) cells.24 h for 3 days, respectively) is inhibited 80% by cycloheximide (10 micrograms/ml). The LIM-1839 cells have type I and type II IGF receptors, determined by affinity cross-linking and competition binding studies. These cells proliferated 1.6-fold over 4 days in serum-free medium, with fresh medium changes on days 0 and 2: their growth was inhibited 56% by 40 micrograms/ml Sm 1.2, a monoclonal antibody which recognizes IGF-I and IGF-II. The addition of 20 and 50 ng/ml multiplication stimulating activity (rat IGF-II) caused 1.8- and 1.7-fold increases in cell growth between days 0 and 4 compared to controls, while [Thr59]IGF-I, at 20 and 50 ng/ml, caused 1.6- and 2.0-fold increases. Insulin, at 2 and 10 micrograms/ml, had no significant effect. The stimulatory effects of endogenous and exogenous IGFs on LIM-1839 cell proliferation were inhibited by a monoclonal antibody to the type I IGF receptor, alpha IR-3. These results suggest that the LIM-1839 cells are biologically responsive to endogenously produced IGF-II, and may thereby provide an in vitro model for autocrine regulation of human tumor growth by IGF-II.

Insulin-like growth factor binding to the atypical insulin receptors of a human lymphoid-derived cell line (IM-9)

The cells of the IM-9 human lymphocyte-derived line contain a sub-population of insulin-binding sites whose immunological and hormone-binding characteristics closely resemble those of the atypical insulin-binding sites of human placenta. These binding sites, which have moderately high affinity for multiplication-stimulating activity [MSA, the rat homologue of insulin-like growth factor (IGF) II] and IGF-I, are identified on IM-9 cells by 125I-MSA binding. They account for approximately 30% of the total insulin-receptor population, and do not react with a monoclonal antibody to the type I IGF receptor (alpha IR-3). The relative concentrations of unlabelled insulin, MSA and IGF-I required to displace 50% of 125I-MSA from these binding sites (1:4.7:29 respectively) are maintained for cells, particulate membranes, Triton-solubilized membranes precipitated either by poly(ethylene glycol) or a polyclonal antibody (B-10) to the insulin receptor, and receptors purified by insulin affinity chromatography. Because the atypical insulin/MSA-binding sites outnumber the type I IGF receptors in IM-9 cells by approximately 10-fold, they also compete with the latter receptors for 125I-IGF-I binding. Thus 125I-IGF-I binding to IM-9 cells is inhibited by moderately low concentrations of insulin (relative potency ratios for insulin compared with IGF-I are approx. 1/14 to 1/4) and is partially displaced (65-80%) by alpha IR-3. When type I IGF receptors are blocked by alpha IR-3 or removed by B-10 immunoprecipitation or insulin affinity chromatography, the hormone-displacement patterns for 125I-IGF-I binding resemble those of the atypical insulin/MSA-binding sites.

Comparison of catheter surface morphologies

The surface morphologies of different generic types of Foley catheter have been investigated using scanning electron microscopy (SEM). The characteristic features of each material are illustrated and it is shown that distinct differences exist between the inner and outer surfaces of latex-based catheters; these differences are attributed to the methods of manufacture. The possible relations between morphology and performance in situ are discussed.

Insulin-like growth factors and the developing and mature rat small intestine: receptors and biological actions

To determine if insulin-like growth factor-I (IGF-I) or multiplication stimulating activity (MSA, rat IGF-II) might directly influence small intestinal epithelium, we studied the distribution of IGF binding sites during development of the rat intestine. Cell membranes from suckling rat mucosa bound 2-6 times as much 125I-IGF-I and 3-5 times as much 125I-MSA as did adult membranes. Isolated villus cells from suckling and adult rats specifically bound both IGFs. IGF-I binding tended to remain high during suckling, whereas MSA binding fell progressively from the early suckling period. Competitive displacement studies with insulin, IGF-I and MSA demonstrated the presence of type-I and type-II IGF receptors. In vitro autoradiography of 125I-IGF-I binding sites in adult and suckling rat jejunum showed highest binding in the submucosa with extensions up into the lamina propria. Immunocytochemical localization of type-II receptors showed highest density in villus epithelium and vessel walls. Administration of MSA by oral and IGF-I by oral and parenteral routes (1 microgram/day for 6 days) to suckling rats stimulated jejunal brush border enzymes, but not intestinal growth. Developmental changes in receptor density and effects on brush border enzymes suggest a specific role for IGFs in post-natal development of the rat intestine.

Morphology of mineral deposits on encrusted urinary catheters investigated by scanning electron microscopy

Struvite and hydroxyapatite were precipitated from artificial urine onto the surfaces of catheter materials by the controlled addition of urease. They were precipitated both together and separately (by omitting components of the artificial urine), and with and without the inclusion of albumin (which was intended to mimic the proteinaceous debris found in infected urine). Precipitates were identified by X-ray powder diffraction and the artificially encrusted surfaces examined by scanning electron microscopy. In the presence of protein, hydroxyapatite was precipitated as a poorly crystalline form which aggregated to form a crust. Struvite crystals could be easily identified under the scanning electron microscope by their relatively large size and characteristic appearance. Fifteen encrusted catheters from patients were also examined by scanning electron microscopy, and a further six using X-ray microanalysis. Their appearance was very similar to that of the materials encrusted in vitro. Encrustation involves the formation of hydroxyapatite and the growth of struvite crystals, intimately associated with bacteria.

Calcium environment in encrusting deposits from urinary catheters investigated by interpretation of EXAFS spectra

Extended x-ray absorption fine structure (EXAFS) spectra were recorded, above the K absorption edge of Ca, from 10 encrusted urinary (Foley) catheters obtained from 10 different patients. The presence of poorly crystalline apatite was demonstrated in all the deposits, even though this phase could not be detected in the x-ray powder diffraction patterns of most samples because of the obscuring effect of struvite, which was also present. Furthermore, the EXAFS spectra could be interpreted to yield quantitative information on the average short-range structure surrounding the Ca2+ ions in the poorly crystalline apatite.

Resistance of catheters coated with a modified hydrogel to encrustation during an in vitro test

Mid-shaft specimens were cut from latex catheters coated with a modified hydrogel, latex catheters coated with silicone elastomer, and 100% silicone catheters. These specimens were subjected to controlled in vitro encrustation conditions. During a test period of 11 weeks, there was no significant difference in the quantities of encrusting deposits formed on the three materials.

Delineation of atypical insulin receptors from classical insulin and type I insulin-like growth factor receptors in human placenta

Insulin-like growth factor (IGF)-binding sites copurifying with human placental insulin receptors during insulin-affinity chromatography consist of two immunologically distinct populations. One reacts with monoclonal antibody alpha IR-3, but not with antibodies to the insulin receptor, and represents Type I IGF receptors; the other reacts only with antibodies to the insulin receptor and is precipitated with a polyclonal receptor antibody (B-10) after labelling with 125I-multiplication-stimulating activity (MSA, rat IGF-II). The latter is a unique sub-population of atypical insulin receptors which differ from classical insulin receptors by their unusually high affinity for MSA (Ka = 2 x 10(9) M-1 compared with 5 x 10(7) M-1) and relative potencies for insulin, MSA and IGF-I (40:5:1 compared with 150:4:1). They represent 10-20% of the total insulin receptor population and account for 25-50% of the 125I-MSA binding activity in Triton-solubilized placental membranes. Although atypical and classical insulin receptors are distinct, their immunological properties are very similar, as are their binding properties in response to dithiothreitol, storage at -20 degrees C and neuraminidase digestion. We conclude that atypical insulin receptors with moderately high affinity for IGFs co-exist with classical insulin receptors and Type I IGF receptors in human placenta. They provide an explanation for the unusual IGF-II binding properties of human placental membranes and may have a specific role in placental growth and/or function.

Infection of catheterised patients: bacterial colonisation of encrusted Foley catheters shown by scanning electron microscopy

The surfaces of 32 encrusted urinary catheters were examined by scanning electron microscopy to investigate the association of bacteria with the encrusting deposits. Deposits consisted of struvite crystals surrounded by aggregates of very small crystallites of hydroxyapatite. Underneath these minerals there was a layer of closely packed bacteria. Impressions of bacteria were also observed in hydroxyapatite. Crystals were often engulfed by the bacterial layer, which thus appeared to bind the crystals to each other and to the catheter surface. This thick layer of bacteria associated with crystals may protect both the bacteria from antibiotics and the crystals from acidic bladder washout solutions intended to dissolve them. Furthermore, the existence of this sessile population explains why urease-producing bacteria are not invariably detected in the urine of patients with encrusted catheters. The observation of this bacterial layer (or "biofilm") by scanning electron microscopy provided direct evidence for infection being implicated in catheter encrustation.

Resistance of conformable indwelling urinary catheters to encrustation

Conformable and conventional indwelling urinary catheters, made of latex coated with Teflon and of the same nominal size, were encrusted in vitro. The extent of encrustation was quantified by dissolving the deposits, determining the concentrations of calcium and magnesium in the resulting solutions (by atomic adsorption spectroscopy), and calculating the surface densities of calcium and magnesium. Surface densities of both elements were significantly less on the conformable than on the conventional catheters. This result can be explained by the pulsed flow of urine through the conformable catheter tending to dislodge deposits adhering to its inner surface. A similar action is expected to occur in vivo.

Comparison of in vitro encrustation on silicone and hydrogel-coated latex catheters

Mid-shaft sections of 100% silicone (Bardex) and hydrogel-coated latex (Biocath) catheters were subjected to controlled in vitro encrustation conditions for periods of up to 18 weeks. There was no significant difference in the quantities of encrusting deposits formed on these two materials during the course of the experiment.

Effect of a hydrogel coating on the surface topography of latex-based urinary catheters: an SEM study

The hydrated surface of a hydrogel-coated latex urinary catheter has been examined using low temperature SEM, and its appearance compared with those of some other catheter surfaces. The effect of the coating is to smooth over most of the ripples and fissures of the underlying latex. On hydration the hydrogel surface becomes even smoother, with shallower furrows. The surface topography compares favourably with that of 100% silicone, which has a uniformly rippled yet smooth appearance.