Transport of chloramphenicol into sensitive strains of Escherichia coli and Pseudomonas aeruginosa

The uptake of chloramphenicol by susceptible strains of Escherichia coli and Pseudomonas aeruginosa was measured as the depletion of 14C-chloramphenicol from the supernatant of centrifuged cultures. Chloramphenicol did not bind to non-growing cells or isolated cell envelopes. Chloramphenicol was recovered from cells in an unchanged form and was intracellularly concentrated several times above external concentrations. The net accumulation of the drug was reduced by an inhibitor of electron transport, by an oxidative phosphorylation uncoupler, by an inhibitor of high energy phosphate synthesis, and by lowering the temperature to + 15°C. The initial uptake of drug was saturated at 1.98 mM chloramphenicol in the medium. A 100-fold excess of each of the unlabelled isomers: L-threo, D-threo, and L-erythro chloramphenicol in cultures of either strain effectively reduced the uptake of 14C-chloramphenicol. These results indicate that chloramphenicol enters Gram-negative bacteria by means of an energy-dependent proces

Volume expansion enhances plasma endothelin-1

We hypothesized that acute volume expansion by saline infusion triggers the release of endothelin-1. Bolus intravenous saline infusion (8 mL/min) in six groups of conscious Wistar rats and spontaneously hypertensive rats did not change mean arterial pressure or heart rate (n = 8 to 12). At 1 min after infusion, the plasma endothelin-1 level was significantly increased in Wistar rats and in spontaneously hypertensive rats by 42% and 61%, respectively (unpaired data). In 12 Wistar rats, the endothelin-1 level increased from 0.68 ± 0.13 to 1.19 ± 0.17 fmol/mL (mean ± SEM, P < .0001, paired data). Thus, acute volume load by rapid saline infusion increases plasma endothelin-1 levels. Vasoconstriction induced by endothelin-1 may counteract enhanced circumferential stretch created by volume expansion. Am J Hypertens 2003;16:1057-1061 @ 2003 American Journal of Hypertension, Lt

Loss reduction in power distribution networks.

In this thesis, a new technique for power loss reduction in the distribution networks is presented. This technique depends on applying compensating capacitors at certain nodes on the system (sensitive nodes) to compensate for the reactive current flow. These sensitive nodes are selected carefully, as they have the largest effect on the system loss reduction when they are injected with reactive power from compensating capacitors. The number of these sensitive nodes is very small compared to the number of the total system nodes. The sensitive node is selected by first identifying the branch which has the largest losses due to reactive power. Then, the node therein which has the largest reactive power is selected. The capacitor rating is determined by differentiating the system losses with respect to the load connected to that node. The compensating capacitors are placed at these optimal locations with appropriate VAR rating to achieve maximum benefits in dollar savings. This novel technique has been applied to the small size (200 MVA) distribution network of the city of Kingston, Ontario, and to the medium size (560 MVA) network of the city of Windsor, Ontario. The amortized capital and labour costs of the capacitor installation have been taken into account to calculate the net saving. Also, a method for implementing the load variations throughout the year is presented. The technique of applying compensating capacitors has been combined with a method of reconfiguration of the distribution system to reduce further the losses. The combination of the two methods has been applied to the distribution networks of the cities of Windsor and Kingston, Ontario, Canada. Significant savings have been obtained in both systems. This work provides a loss reduction algorithm that is superior to any other known technique.Dept. of Electrical and Computer Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .A22. Source: Dissertation Abstracts International, Volume: 56-01, Section: B, page: 0406. Adviser: Reuben Hackam. Thesis (Ph.D.)--University of Windsor (Canada), 1994

OR-53: Plasma immunoreactive endothelin-1 levels in hypertensive rats and human subjects

Endothelin-1 (ET-1) is an endothelium-derived potent vasoconstrictor peptide of 21 amino acids. To establish reference values in different forms and models of hypertension and in human subjects an assay for plasma ET-1 was optimized. Immunoreactive (ir-) ET-1 is extracted by acetone from 1 ml plasma and subjected to a sensitive sandwich type enzyme linked immunosorbent assay. The detection limit for plasma ET-1 (3 SD above zero readings) is 0.05 fmol/ml. Mean recoveries of the 1, 2, 5, 10 fmol of ET-1 added to 1 ml plasma (n = 5, each) were 66, 75, 85 and 92 % respectively. The within-assay coefficients of variation were 12, 5, 3, 3 and 0.5 % for plasma ET-1 concentrations of 0.84, 1.5, 2.3, 5.2 and 9.9 fmol/ml respectively. Between-assay coefficients of variation for two human control plasmas containing 1.0 fmol/ml (n = 8) and 1.2 fmol/ml ET-1 (n = 7) were 8% and 10% respectively. Assay accuracy was demonstrated by the consistent recoveries of added ET-1 and by the linearity of ir-ET-1 concentrations measured in serially diluted plasma extracts (r = 0.99). No ir-ET-1 was detected when albumin buffer was extracted instead of plasma (buffer blank). Using this method, we found increased ir-ET-1 levels in plasma of three experimental rat models of hypertension. (i) Plasma ir-ET-1 concentrations were significantly higher in stroke-prone spontaneously hypertensive rats (SP-SHR) than in normotensive Wistar rats. (ii) DOCA-salt hypertensive rats exhibited 4 times higher ir-ET-1 levels than sham operated control rats. (iii) One kidney-one clip (1K-1C) hypertensive rats showed moderately increased ir-ET-1 levels compared to sham operated controls. In contrast, the ir-ET-1 levels in plasma of SHR were half that of normotensive Wistar rats. In two kidney-one clip (2K-1C) Goldblatt hypertensive rats, the plasma ir-ET-1 concentrations were not different from sham-operated control rats. The plasma ir-ET-1 concentrations of 37 healthy human subjects were 0.85 ± 0.26 fmol/ml (mean ± SD). We conclude that the present assay reliably measures plasma immunoreactive ET-1 levels in rats and in human subjects. Normal plasma ET-1 concentrations in humans and conscious rats are in the low picomolar rang

OR 47: Renal endothelin receptor type B upregulation in rats with low or high renin hypertension

Endothelin-1 (ET-1) is a potent renal and systemic vasoactive peptide. It acts through ETA and ETB receptors. We investigated density and subtype distribution of ET-1 receptors in hearts and kidneys of normotensive and hypertensive rats. Five groups of uninephrectomized Wistar rats were put on a low salt diet for six weeks. During this period, three groups of rats drank tap water and two groups received saline. One group of each regimen received DOCA subcutaneousely (1.6 mg/day). The fifth group of rats had the left renal artery clipped to induce 1K1C hypertension. At 6 weeks, mean arterial pressure (MAP) was recorded in conscious rats via a femoral artery catheter. Binding assays using 125I-ET-1 were carried out on membrane preparations in the presence and absence of the ETA receptor antagonist FR139317. On tap water, MAP was at 121.8±3.3 mmHg and DOCA or saline did not raise this MAP. On DOCA-salt and in 1K1C rats, MAP was increased to 154.5±5.8 mmHg (p<0.001) and 218.4±10.5 (p<0.001) mmHg, respectively. ET receptor subtypes were not equally expressed in the heart and the kidney: ETA was predominantly expressed in the heart, whereas ETB was predominant in the kidney. Both hypertensive models, the DOCA-salt and the 1K1C rats showed further significant changes: i) Cardiac weight index compared to controls of 2.49±0.06 mg/g was higher (p<0.001) at 3.89±0.10 and 4.86±0.18 mg/g in DOCA-salt and 1K1C hypertension, respectively, and kidney weight index compared to controls of 4.78±0.22 mg/g was higher at 10.10±0.54 mg/g in DOCA-salt (p<0.001) but tended to be below controls in 1K1C rats. ii) In the kidneys, the density of the ETB receptor subtype was upregulated in DOCA-salt and 1K1C rats from 160±8 to 217±12 and 190±2 fmol/mg (p<0.05), respectively, and ETA tended to be downregulated. iii) Plasma renin activity was decrased in DOCA-salt rats from 17±3 to 0.17±0.01 ng/ml/h and increased in 1K1C rats on low salt diet to 30±5 ng/ml/h (p<0.001). We conclude that upregulation of the ETB receptor mediating vasodilation and downregulation of the ETA receptor mediating vasoconstriction is compatible with a mainly renal counterregulatory effect of endothelin-1 to hypertension. This counterregulation may occur in both low and high renin models of hypertension. Am J Hypertens (2004) 17, 20A-21A; doi: 10.1016/j.amjhyper.2004.03.04

EXTRACTION, ISOLATION, AND CHARACTERIZATION OF BIOACTIVE COMPOUNDS AND ESSENTIAL OIL FROM SYZYGIUM JAMBOS

Objectives: Over the past few decades, phenolic compounds become important due to it has been associated with protection against different diseasesand sensory point of vision. Hence, at the present study, there has been a growing interest to carry out structural elucidation and characterization ofthe pure isolates from Syzygium jambos.Methods: S. jambos dried powder leaves were extracted by soaking in 85% methanol solvent at room temperature 25±2°C. The antioxidative activityof the isolates was assessed according to 2,2'-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and phosphomolybdenum assays.Results: A total of 8 compounds were isolated from the n-butanol extract of S. jambos (Family Myrtaceae) plant, they were identified as quercetin-3-O-rutinoside (1), prenylbenzoic acid 4-β-D-glucoside (2), morolic acid 3-O-caffeate (3), 5,4'-dihydroxy, 7-methoxy, 6-methyl-flavone (4),3,4,5-trihydroxybenzoic acid (5), quercetin (6), isoetin-7-O-β-D-glucopyranoside (7), and (4'-hydroxy-3'-methoxyphenol-β-D-[6-O-(4â€-hydroxy-3â€,5â€-dimethoxylbenzoate)] glucopyranoside) (8). Compounds 5 and 6 showed the most radical scavengers among the tested compounds with SC50 values of5.50 and 4.30 μg/ml, respectively, compared to ascorbic acid as standard and the total antioxidant capacity (TAC) values of 605.0 and 680.59 mg ascorbicacid equivalent/g compound, respectively. In vitro antimicrobial activities of the isolated compounds were tested using disc agar plate method againstfour pathogenic microbial strains including Gram-positive, Gram-negative bacteria and yeast with inhibition zones from 9 to 19 mm. Gas chromatographymassspectrometry analysis for the essential oil provides twenty four identified components representing 92% of its total oil composition.Conclusion: The results supported that S. jambos could be attributed to sources of natural antioxidant and antimicrobial applications

Measurement of plasma endothelin-1 in experimental hypertension and in healthy subjects

Background: Endothelin-1 is an endothelium-derived potent vasoconstrictor peptide of 21 amino acids. To establish reference values in different models of hypertension and in human subjects an assay for plasma immunoreactive endothelin-1 (ET-1) was optimized. Methods: ET-1 is extracted by acetone from 1 mL of plasma and subjected to a sensitive enzyme-linked immunosorbent assay. Results: The detection limit for plasma ET-1 is 0.05 fmol/mL. Mean recoveries of the 1, 2, 5, and 10 fmol of ET-1 added to 1 mL of plasma were 66%, 75%, 85%, and 92%, respectively. Within- and between-assay coefficients of variation were ≤12% and ≤10%, respectively. Assay accuracy was demonstrated by consistent recoveries of added ET-1 over the entire physiologic range of plasma concentrations and by the linearity of ET-1 concentrations measured in serially diluted plasma extracts (r = 0.99). No ET-1 was detected when albumin buffer was extracted instead of plasma. Using this method, we found increased ET-1 levels in plasma of three experimental rat models of hypertension: stroke prone spontaneously hypertensive rats (SP-SHR), deoxycorticosterone acetate-salt hypertensive rats, and one kidney-one clip hypertensive rats. In contrast, plasma ET-1 levels of SHR were half those of normotensive Wistar rats. In two kidney-one clip hypertensive rats, plasma ET-1 concentrations were not different from those found in sham-operated control rats. Plasma ET-1 concentrations of 37 healthy men were 0.85 ± 0.26 fmol/ml (mean ± SD). Conclusions: The present assay reliably measures ET-1 levels in rat and human plasma. It allows to discriminate between different forms of hypertension with high or low circulating levels of ET-1. Am J Hypertens 2003;16: 515-521 @ 2003 American Journal of Hypertension, Lt

Caval collapse during cardiopulmonary bypass: a reproducible bench model

OBJECTIVES During open heart surgery, so-called atrial chatter, a phenomenon due to right atria and/or caval collapse, is frequently observed. Collapse of the cava axis during cardiopulmonary bypass (CPB) limits venous drainage and may result downstream in reduced pump flow on (lack of volume) and upstream in increased after-load (stagnation), which in turn may both result in reduced or even inadequate end-organ perfusion. The goal of this study was to reproduce venous collapse in the flow bench. METHODS In accordance with literature for venous anatomy, a caval tree system is designed (polyethylene, thickness 0.061 mm), which receives venous inflow from nine afferent veins. With water as medium and a preload of 4.4 mmHg, the system has an outflow of 4500 ml/min (Scenario A). After the insertion of a percutaneous venous cannula (23-Fr), the venous model is continuously served by the afferent branches in a venous test bench and venous drainage is augmented with a centrifugal pump (Scenario B). RESULTS With gravity drainage (siphon: A), spontaneously reversible atrial chatter can be generated in reproducible fashion. Slight reduction in the outflow diameter allows for generation of continuous flow. With augmentation (B), irreversible collapse of the artificial vena cava occurs in reproducible fashion at a given pump speed of 2300 ± 50 RPM and a pump inlet pressure of −112 mmHg. Furthermore, bubbles form at the cannula tip despite the fact that the entire system is immersed in water and air from the environment cannot enter the system. This phenomenon is also known as cavitation and should be avoided because of local damage of both formed blood elements and endothelium, as well embolization. CONCLUSIONS This caval model provides a realistic picture for the limitations of flow due to spontaneously reversible atrial chatter vs irreversible venous collapse for a given negative pressure during CPB. Temporary interruption of negative pressure in the venous line can allow for recovery of venous drainage. This know-how can be used not only for testing different cannula designs, but also for further optimizing perfusion strategie