Double Dilution Technique Research Articles

Stability of Epinephrine in a Normal Saline Solution.

Dilution of concentrated epinephrine prior to intravenous use during clinical emergencies can delay urgent interventions. The objective of this study was to determine whether diluted epinephrine remains stable and sterile over time in common hospital settings. Epinephrine samples were prepared by clinically relevant double dilution techniques. Samples were stored in 10-mL syringes and incubated under 1 of 4 simulated hospital environments with a mixture of lighting and temperature settings: 4°C/20°C, with or without fluorescent lighting. Samples were incubated for 0, 15, 30, 60, or 90 days. Capillary zonal electrophoresis was used to quantify the concentration of epinephrine and/or presence of any degradation products. All samples were tested for the presence of bacterial growth using blood agar cultures. Diluted epinephrine samples remained stable for up to 90 days in all 4 simulated clinical storage conditions. No bacterial colony-forming units were detected in any of the environmental samples regardless of incubation duration, light, or temperature conditions. Diluted epinephrine for anticipated clinical emergencies may remain clinically useful for up to 90 days, thus improving patient safety, access to medications, and overhead costs by reducing waste.

Week to week variability of pulmonary capillary blood volume and alveolar membrane diffusing capacity in patients with heart failure

BackgroundAlveolar-capillary membrane diffusing capacity for carbon monoxide (DMCO) and pulmonary capillary volume (Vcap) can be estimated by the multi-step Roughton and Foster (RF, original method from 1957) or the single-step NO–CO double diffusion technique (developed in the 1980s). The latter method implies inherent assumptions. We sought to determine which combination of the alveolar membrane diffusing capacity for nitric oxide (DMNO) to DMCO ratio, an specific conductance of the blood for NO (θNO) and CO (θCO) gave the lowest week-to-week variability in patients with heart failure. Methods44 heart failure patients underwent DMCO and Vcap measurements on three occasions over a ten-week period using both RF and double dilution NO-CO techniques. ResultsWhen using the double diffusing method and applying θNO = infinity, the smallest week-to-week coefficient of variation for DMCO was 10 %. Conversely, the RF method derived DMCO had a much greater week-to-week variability (2x higher coefficient of variation) than the DMCO derived via the NO-CO double dilution technique. The DMCO derived from the double diffusion technique most closely matched the DMCO from the RF method when θNO = infinity and DMCO = DLNO/2.42. The Vcap measured week-to-week was unreliable regardless of the method or constants used. ConclusionsIn heart failure patients, the week-to-week DMCO variability was lowest when using the single-step NO-CO technique. DMCO obtained from double diffusion most closely matched the RF DMCO when DMCO/2.42 and θNO = infinity. Vcap estimation was unreliable with either method.

THE RESEARCH OF ANTIMICROBIAL EFFICACY OF ANTISEPTICS DECAMETHOXIN, MIRAMISTIN AND THEIR EFFECT ON NUCLEAR DNA FRAGMENTATION AND EPITHELIAL CELL CYCLE

Introduction: Nowadays, the study of biological safety of modern cationic surface-active antiseptics with a wide antimicrobial spectrum has acquired particular importance. The aim was to study antimicrobial effectiveness of antiseptics decamethoxin, miramistin and their influence on nuclear DNA fragmentation and cellular cycle. Materials and methods: A comparative microbiological study of antimicrobial efficacy and a cytometric study of the effect of decamethoxin 0,02% and miramistin 0,01% on the cellular cycle were carried out. Antimicrobial activity of decamethoxin and miramistin was estimated by their minimal inhibitory and minimal microbicidal concentrations against opportunistic microorganisms using serial double dilution technique. Decamethoxin and miramistin cytotoxicity on anterior corneal epithelial cells, after their two-week daily instillation into the eyes of a Vistar line male rats was studied using flow cytometry. The parameters of epithelial cellular cycle, nuclear DNA fragmentation and apoptosis under the influence of antiseptics were registered. Results: High antimicrobial effect of decamethoxin and miramistin against Gram-positive, Gram-negative bacteria with the significant advantages of decamethoxin were found (р<0,001). Decamethoxin caused minimal influence on anterior corneal epithelial cells, the insignificant decrease of their proliferation index, low increase of apoptosis (0.68%), no difference of mitotic activity (p>0.05). But the use of miramistin resulted in the significant increase of nuclear DNA fragmentation, decrease of proliferative activity (р<0.05). Conclusions: Higher antimicrobial effect against a wide range of opportunistic pathogens is proved in decamethoxin 0,02% comparably to miramistin 0,01% (р<0,001). In prolonged antiseptic use of the first one there were found no cytotoxic and no pro-apoptotic effects on the epithelium (р<0,05).

Antimicrobial Activity of Synthesized 2-Methylthiobenzo[g][1,2,4]- triazolo[1,5-a]quinazoline Derivatives.

The present study was carried out to evaluate the antimicrobial activity of a synthesized 2-methylthio-benzo[g][1,2,4]triazolo[1,5- a]quinazoline series. The compounds (1-21) were tested against a variety of Gram-positive bacterial species including Bacillus subtilis (RCMB 01001 69-3), Enterococcus faecalis (RCMB 0100154-2), Staphylococcus aureus (RCMB 0100183-9), Staphylococcus epidermidis (RCMB 0100183-9) and Streptococcus pyogenes (RCMB 0100172-5). In addition, Gram-negative bacteria were also tested including Pseudomonas aeruginosa (RCMB 0100243-5), Escherichia coli (RCMB 010052-6), Proteus mirabilis (RCMB 01002 54-2), Klebsiella oxytoca (RCMB 01002 83-4) and Enterobacter cloacae (RCMB 01002 64-5). Furthermore, their activities were screened against ten types of fungi i.e. Aspergillus fumigatus (RCMB 02568), Syncephalastrum racemosum (RCMB 05922), Geotricum candidum (RCMB 05097), Candida albicans (RCMB 05036), Aspergillus niger (RCMB 02724), Cryptococcus neoformans (RCMB 05642), Candida tropicalis (RCMBA 05239), Penicillium expansum (RCMB 01924), Microsporum canis (RCMB 0834) and Trichophyton mentagrophytes (RCMB 0925). Evaluation of antimicrobial activity was performed using agar well diffusion method in comparison with ampicillin and gentamycin as antibacterial reference drugs, and amphotericin B as antifungal reference drug. The minimum inhibitory concentration (MIC) was determined using the broth double dilution technique. The MIC values of the tested compounds were reported in .g/mL in which ampicillin, gentamicin and amphotericin B were used as standard reference drugs. The obtained results revealed that compounds 3, 4, 7, 8, 9, 10, 11, 14, 17, 18, 19, 20 and 21 showed significant antimicrobial activity against six bacterial and six fungal strains. The promising compounds could be employed as useful scaffolds for building of new derivatives with more potent antimicrobial effects.

IN VITRO AND GREENHOUSE EVALUATION OF BOTANICAL EXTRACTS FOR ANTIFUNGAL ACTIVITY AGAINST PHYTHOPTHORA INFESTANS

ABSTRACT The aim of this study was to evaluate plant extracts for antifungal activities against Phythopthorainfestans (Mont.) de Bary, an important pathogen of potato which causes late blight disease. Acetone, ethyl acetate and water extracts of garlic (Allium sativum L.), Pawpaw (Carica papaya), Neem (Azadirachta indica), Mexican marigold (Tagetes minuta) and peri –winkle (Vinca rosea) were screened in vitro for their antifungal activities against Phythopthora infestans using the discagar infusion and microtitre doubledilution techniques. The same extracts were then tested for antifungal activity in vivo in the greenhouse on inoculated potato plants. The water extracts of Allium sativum and Azadirachta indica were active against Phythopthora infestans and had aminimum inhibitory concentration (MICs) of 1.65 mg/ml. MICs of Allium sativum, Azadirachtaindica and Tagetes minuta acetone extracts were 0.78, 3.13 and 6.5 mg/ml respectively against Phytophthora infestans. Allium sativum and Azadirachta indica water and acetone extracts performed well and they effectively reduced potato late blight in the greenhouse. These extracts compared well with the reductions due to application of Ridomil, a synthetic fungicide applied at 42.5g/l (active ingredient) and also with levels in the non-inoculated control. Allium sativumandAzadirachta indica were effective both in vitro and in vivo in controlling late blight have a potential to be used as fungicides against the disease. The plants are readily available and the extractionmethod is also simple and could lead to high adoption as fungicides by resource poor farmers.

English

Bean anthracnose caused by Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara is one of the most devastating seed-borne diseases of common bean (Phaseolus vulgaris L.) in Ethiopia. The aim of the present investigation was to evaluate the antifungal activities of bioagents and fungicides which can be used to control bean anthracnose. Three fungicides viz., Mancozeb, Folpan and Mancolaxyl, and three bioagents viz., Trichoderma harzianum Rifai, Trichoderma viride Pers. Fr. and Pseudomonas fluorescens Migula, were screened in vitro for their antifungal activities against common bean anthracnose, C. lindemuthianum using the dual culture and microtitre double-dilution techniques. Antagonistic effects of the three bioagents tested by the dual culture method showed highly significant (P<0.01) percentage of inhibition of the mycelia germination of C. lindemuthianum. The highest percentage of inhibition of the mycelia germination (80.39%) was obtained from T. viride, followed by 75.49% from T. harzianum and 40.2% from P. fluorescens. Similarly, highly significant (P<0.01) differences were observed in the radial growth of mycelia of C. lindemuthianum. The highest growth of mycelia (3.4 cm) was measured from the control (C. lindemuthianum), whereas the least (0.67 cm) was obtained from the dual culture containing T. viride. The in vitro assays revealed that all the antagonistic bioagents produced siderophores which were capable of inhibiting mycelia growth of the pathogen. The mancozeb fungicide was found to be fatal to C. lindemuthianum at four different concentrations poisoned on potato dextrose agar medium. Key words: Bio agents, Colletotrichum lindemuthianum, dual culture, fungicides, in vitro, Phaseolus vulgaris.

The essential oils chemical compositions and antimicrobial, antioxidant activities and toxicity of three Hyptis species

Context: Hyptis suaveolens (Linn.) Poit., Hyptis rhomboidea Mart. et Gal., and Hyptis brevipes Poit., are three species of Hyptis Jacq. (Lamiaceae). Hyptis suaveolens is used for the treatment of fever, headache, gastrointestinal bloating and rheumatism in the traditional folk medicine; Hyptis rhomboidea for hepatitis, ulcer and swollen poison; and Hyptis brevipes for asthma and malaria.Objective: To characterize chemical compositions of the oils from three Hyptis species and evaluate their potential antimicrobial, radical scavenging activities and toxicities against brine shrimp.Materials and methods: The oils were obtained by hydrodistillation, and their chemical compositions were investigated by gas chromatography-mass spectrometry (GC-MS). Minimum inhibitory concentrations (MICs) were determined using the tube double-dilution technique. The antioxidant activities were investigated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and toxicities by the brine shrimp bioassay.Results: Forty-seven, 33 and 28 constituents of oils isolated, respectively, from H. suaveolens, H. rhomboidea and H. brevipes were identified. Among the essential oils, the strongest antioxidant activity was exhibited by H. brevipes with an SC50 value of 2.019 ± 0.25 μg mL−1. The H. brevipes oil exhibited the strongest antimicrobial activity (3.125–6.25 μg mL−1) on pathogens employed in the assay. They all showed significant toxicities with median lethal concentration (LC50) values of 62.2 ± 3.07 μg mL−1, 65.9 ± 6.55 μg mL−1 and 60.8 ± 9.04 μg mL−1, respectively.Discussion and conclusions: The three Hyptis species oils possess strong antimicrobial activities and toxicities. Hyptis rhomboidea and H. brevipes showed considerable antioxidant activity compared to the positive control.

Screening of plant extracts for antifungal activities against Colletotrichum species of common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata (L.) Walp)

SUMMARYThe aim of the present investigation was to evaluate the antifungal activities of plant extracts which can be used to control bean and cowpea anthracnose. Acetone, ethyl acetate and water extracts of Ipomoea batatas, Carica papaya, Allium sativum, Syzygium cordatum, Chlorophytum comosum and Agapanthus caulescens were screened in vitro for their antifungal activities against Colletotrichum lindemuthianum and Colletotrichum dematium of common bean and cowpea using the agar disc infusion and microtitre double-dilution techniques. The same extracts were then tested for antifungal activity in vivo as seed treatments against anthracnose disease. The water extracts of Carica and Syzygium were active against C. lindemuthianum and had minimum inhibitory concentrations (MICs) of 1·56 mg/ml. Syzygium, Allium and Chlorophytum water extracts were active against C. dematium and MICs were 3·13, 6·25 and 12·5 mg/ml, respectively. The MICs of Allium, Syzygium and Agapanthus acetone extracts were 0·78, 3·13 and 6·25 mg/ml, respectively, against C. lindemuthianum and 0·78, 6·25 and 3·13 mg/ml against C. dematium. Agapanthus water extracts and all the acetone extracts tested in vivo effectively reduced the incidence and severity of bean anthracnose disease in the greenhouse. Agapanthus acetone, Allium water, and both acetone and water extracts of Carica and Syzygium performed well in vivo in reducing cowpea anthracnose disease and compared well with reductions due to the application of the synthetic fungicide fludioxonil+mefenoxam (the commercial product Celest® XL) applied at 25 gai/l and also with levels in the non-inoculated control. The Agapanthus, Carica, Syzygium and Allium extracts were active on both Colletotrichum spp. in vitro and also reduced anthracnose disease of bean and cowpea and are potential seed treatments in anthracnose disease control. The easy seed treatment process and the accessibility of plants used in the present study could lead to high adoption of the use of the plant extracts as seed treatments by resource-poor, smallholder farmers.

Interaction of drug based copper(II) complexes with Herring Sperm DNA and their biological activities

Square pyramidal Cu(II) complexes with NS donor ligand and ciprofloxacin have been synthesized and characterized using analytical and spectral techniques. The synthesized complexes have been tested for their antimicrobial activity using double dilution technique in terms of minimum inhibitory concentration (MIC) and colony forming unit (CFU). The DNA binding ability of the complexes with Sperm Herring DNA has been performed using absorption titration and viscosity measurement. The nuclease activity of complexes with plasmid DNA (pUC19) has been carried out using agarose gel electrophoresis technique. Synthesized complexes have been tested for their SOD mimic activity using NBT/NADH/PMS system. The cytotoxic properties of metal complexes have been evaluated using brine shrimp lethality bioassay.

Copper(II) complexes with norfloxacin and neutral terpyridines: Cytotoxic, antibacterial, superoxide dismutase and DNA-interaction approach

Cu(II) complexes of the type [Cu(NFL)(Ln)Cl] (Ln=substituted terpyridines, NFL=norfloxacin) were synthesised and characterized. Antibacterial activity was assayed against selective Gram(+ve) and Gram(−ve) microorganisms using the double dilution technique. The binding behavior of the complexes toward Herring Sperm (HS) DNA was determined using absorption titration and hydrodynamic measurements, whereas the cleavage efficacy of the complexes toward pUC19 DNA was determined by the gel electrophoresis technique. The brine shrimp bioassay was carried out to study the in vitro cytotoxic properties of the synthesized metal complexes. The superoxide dismutase (SOD) like activity of the complexes was measured using an NBT/NADH/PMS system and is expressed in term of the concentration of complex which terminates the formation of formazan by 50% (IC50 value). The IC50 values were observed to be in the range 0.653–1.344μM.

Synthesis, characterization, antibacterial activity, SOD mimic and interaction with DNA of drug based copper(II) complexes

Novel metal complexes of the second-generation quinolone antibacterial agent enrofloxacin with copper(II) and neutral bidentate ligands have been prepared and characterized with elemental analysis reflectance, IR and mass spectroscopy. Complexes have been screened for their in-vitro antibacterial activity against two Gram (+ve) Staphylococcus aureus, Bacillus subtilis, and three Gram (−ve) Serratia marcescens, Escherichia coli and Pseudomonas aeruginosa organisms using the double dilution technique. The binding of this complex with CT-DNA has been investigated by absorption titration, salt effect and viscosity measurements. Binding constant is ranging from 1.3 × 10 4–3.7 × 10 4. The cleavage ability of complexes has been assessed by gel electrophoresis using pUC19 DNA. The catalytic activity of the copper(II) complexes towards the superoxide anion (O 2 −) dismutation was assayed by their ability to inhibit the reduction of nitroblue tetrazolium (NBT).

Antifungal activity of the plant Dodonaea viscosa var. angustifolia on Candida albicans from HIV-infected patients

The aim of this study was to determine the minimum inhibitory concentration (MIC) and the time taken by Dodonaea viscosa var. angustifolia (PLE) a South African medicinal plant, chlorhexidine gluconate (CHX) and triclosan (TRN) to kill Candida albicans. 41 strains of Candida albicans were investigated, 20 from HIV-positive patients, 20 from HIV-negative subjects and Candida albicans ATCC 90028. The MICs of an acetone extract of PLE, CHX and TRN were measured using a microtitre double dilution technique, and the time taken to kill 99.5% of the strains was determined. The MICs of PLE, CHX and TRN were 6.25–25, 0.008–0.16 and 0.0022–0.009 mg/ml, respectively. PLE killed all the test strains within 30 s and CHX 40% of the isolates from HIV-positive patients and 20% of strains from HIV-negative subjects in 1 min. During the same time TRN killed 55% and 35% of isolates from HIV-positive and HIV-negative patients. Dodonaea viscosa var. angustifolia has antifungal properties and is more effective than commercially available mouthrinses.

Accuracy of Dilution of Morphine for Intrathecal Use

Morphine is administered intrathecally alone or in combination with other drugs to provide spinal analgesia. Dose-finding studies have recommended 100 microg be used intrathecally to optimise analgesia and minimise side-effects for caesarean section and hip replacement surgery. Dilute solutions of morphine are generally not available, mandating preparation from a 10 mg/ml ampoule. We postulated that diluting morphine would be inaccurate and imprecise, contributing to the variability in patient response often reported. Twenty consultant and trainee anaesthetists were recruited and asked to prepare 100 microg of morphine from 10 mg/ml vials and from a hypothetical prediluted 500 microg/ml solution. The resultant samples were analysed using liquid chromatography. Prepared morphine doses ranged from 25 microg to 289 microg. Dilution of morphine was less accurate (P = 0.001) and more imprecise (P = 0.001) compared with using a prediluted solution. A single-step dilution technique using 0.1 ml of a solution diluted to 1.0 mg/ml was more accurate than when a double-dilution technique was used (P = 0.047). Given that dose-finding studies suggest that analgesia and side-effects vary at the dose range found in this study, we advocate the use of prediluted solutions. If dilution is to be performed a single-step dilution technique should be used.

Inhaled Nitric Oxide Does Not Prevent Pulmonary Edema After Lung Transplantation Measured By Lung Water Content: A Randomized Clinical Study

Study objective In order to assess the effects of inhaled nitric oxide (iNO) in preventing early-onset lung edema from occurring after lung transplantation, we measured extravascular lung water (EVLW) in a group of lung transplant recipients who were at high risk for developing ischemia-reperfusion-induced lung injury. Design Prospective, randomized study. Settings Surgical ICU in a teaching hospital. Patients Thirty double-lung transplant recipients. Interventions Patients were randomized to receive or not receive 20 ppm iNO at the time of reperfusion (ie, before any occurrence of lung edema). In the NO group, iNO was then administered for a 12-h period. A double-dilution technique was used for the serial assessment of EVLW, intrathoracic blood volume, and cardiac index. Standard hemodynamic and pulmonary parameters were also recorded during the first 3 postoperative days. Measurements and results Patients who received iNO did not have a different lung water content compared to control subjects (p = 0.61 [by analysis of variance (ANOVA)]). Blood oxygenation (ie, Pao2/fraction of inspired oxygen [Fio2] ratio) did not differ between the two groups (p = 0.61 [by ANOVA]). In both groups, EVLW and Pao2/Fio2 ratio dropped significantly over time, regardless of the use of iNO (p < 0.01 [by ANOVA]). Conclusions In the population studied, prophylactic iNO that was administered at 20 ppm had no effect on pulmonary edema formation and resolution following lung transplantation. In order to assess the effects of inhaled nitric oxide (iNO) in preventing early-onset lung edema from occurring after lung transplantation, we measured extravascular lung water (EVLW) in a group of lung transplant recipients who were at high risk for developing ischemia-reperfusion-induced lung injury. Prospective, randomized study. Surgical ICU in a teaching hospital. Thirty double-lung transplant recipients. Patients were randomized to receive or not receive 20 ppm iNO at the time of reperfusion (ie, before any occurrence of lung edema). In the NO group, iNO was then administered for a 12-h period. A double-dilution technique was used for the serial assessment of EVLW, intrathoracic blood volume, and cardiac index. Standard hemodynamic and pulmonary parameters were also recorded during the first 3 postoperative days. Patients who received iNO did not have a different lung water content compared to control subjects (p = 0.61 [by analysis of variance (ANOVA)]). Blood oxygenation (ie, Pao2/fraction of inspired oxygen [Fio2] ratio) did not differ between the two groups (p = 0.61 [by ANOVA]). In both groups, EVLW and Pao2/Fio2 ratio dropped significantly over time, regardless of the use of iNO (p < 0.01 [by ANOVA]). In the population studied, prophylactic iNO that was administered at 20 ppm had no effect on pulmonary edema formation and resolution following lung transplantation.

Measurement of pulmonary edema in patients with acute respiratory distress syndrome*

We measured pulmonary edema by thermal indocyanine green-dye double-dilution technique and quantitative computed tomography (CT) in patients with acute respiratory distress syndrome and compared the two techniques. Prospective human study in a university hospital. Fourteen mechanically ventilated patients with acute respiratory distress syndrome (nine primary; nine with intubation <7 days). All patients underwent a spiral CT of the thorax. We measured pulmonary thermal volume (PTV) and its components, extravascular lung water and pulmonary blood volume, with an integrated fiberoptic monitoring system (COLD Z-021). PTV was tightly correlated with lung weight (LW) measured by CT (PTV = 0.6875 * LW(CT) + 292.77; correlation coefficient = 0.91; p < .0001; bias -11 +/- 8 %). Neither etiology of acute respiratory distress syndrome (primary vs. secondary) nor days of intubation affected the accuracy of thermal dye dilution in comparison with CT. There was no correlation between the extravascular lung water (12.3 +/- 3.4 mL/kg) and CT distribution of lung tissue compartments. Extravascular lung water and pulmonary blood volume showed good reproducibility in 32 pairs of thermal dye dilution measurements. Measurements of lung edema by thermal indocyanine green-dye double-dilution method show good correlation with those by quantitative computed tomography and good reproducibility in patients with acute respiratory distress syndrome.

Evaluation of a personal monitor employing an electrochemical sensor for assessing exposure to hydrogen peroxide in the workplace.

A commercially available direct-reading instrument designed for personal monitoring of vapor phase hydrogen peroxide (VHP) was evaluated in the laboratory and the workplace. Monitoring VHP has gained increasing importance in the pharmaceutical industry because sterilization using VHP has proven to be a good alternative to previously used sterilizing methods. The current Occupational Safety and Health Administration impinger method for VHP measurements, based on bubbling air through an acid solution with subsequent laboratory analysis, is not practical for monitoring personal exposures. By employing an electrochemical sensor, the instrument evaluated provides real-time exposure data with auxiliary functions such as displaying concentrations in parts per million, data logging, and alarms. A double-dilution technique using a syringe pump was used to generate dynamic test atmospheres ranging from 0.2 to 10 ppm in an exposure chamber. Time-weighted average concentration data from the direct-reading instrument was compared with concentration data from the impingers. The overall accuracy was less than the +/-25%, National Institute for Occupational Safety and Health criterion. No significant differences in accuracy were observed at three humidity levels (i.e., 15, 50, and 80%). The instrument was similarly evaluated in a workplace under typical conditions. The results agreed within +/-0.2 ppm. Selected performance characteristics of the instrument also were investigated, including reproducibility, response and recovery times, calibration frequency, and suitability of the calibration adapter. Results of the investigation suggest that the instrument provides a means for simple and accurate monitoring of personal exposures to VHP in workplace environments.

Evaluation of a Personal Monitor Employing an Electrochemical Sensor for Assessing Exposure to Hydrogen Peroxide in the Workplace

A commercially available direct-reading instrument designed for personal monitoring of vapor phase hydrogen peroxide (VHP) was evaluated in the laboratory and the workplace. Monitoring VHP has gained increasing importance in the pharmaceutical industry because sterilization using VHP has proven to be a good alternative to previously used sterilizing methods. The current Occupational Safety and Health Administration impinger method for VHP measurements, based on bubbling air through an acid solution with subsequent laboratory analysis, is not practical for monitoring personal exposures. By employing an electrochemical sensor, the instrument evaluated provides real-time exposure data with auxiliary functions such as displaying concentrations in parts per million, data logging, and alarms. A double-dilution technique using a syringe pump was used to generate dynamic test atmospheres ranging from 0.2 to 10 ppm in an exposure chamber. Time-weighted average concentration data from the direct-reading instrument was compared with concentration data from the impingers. The overall accuracy was less than the ±25%, National Institute for Occupational Safety and Health criterion. No significant differences in accuracy were observed at three humidity levels (i.e., 15, 50, and 80%). The instrument was similarly evaluated in a workplace under typical conditions. The results agreed within ±0.2 ppm. Selected performance characteristics of the instrument also were investigated, including reproducibility, response and recovery times, calibration frequency, and suitability of the calibration adapter. Results of the investigation suggest that the instrument provides a means for simple and accurate monitoring of personal exposures to VHP in workplace environments.

Extravascular Lung Water as an Indicator of Pulmonary Dysfunction in Acute Hemorrhagic Pancreatitis

This study quantifies lung water in acute hemorrhagic pancreatitis to determine the degree to which pulmonary dysfunction occurs subclinically, before alterations in the arterial blood gases can be measured. Pancreatitis was induced in ten dogs by injecting 0.5 ml/kg of bile into the pancreatic ducts, which had been surgically cannulated. Pulmonary and systemic blood gases and blood pressures, heart rate, extravascular lung water, and lung blood flows were studied over 5 hours while cardiac output and mean arterial pressure were maintained at control values by Ringer's lactate infusion. The percentage of water in lung tissue was determined at the time of sacrifice using gravimetric measurements. Mean arterial pressure, cardiac output, and pulmonary capillary wedge pressure, reflecting intravascular volume status, did not change through at the experiment. By contrast, major disturbances were measured in the pulmonary bed with pulmonary artery pressures rising from 15.6 +/- 1.8/8.1 +/- 1.3 mmHg to 22.0 +/- 1.2/15.6 +/- 1.7 mmHg over 5 hours (p less than 0.01). Peripheral vascular resistance rose from 3.6 +/- 0.6 units to 6.6 +/- 0.4 units (p less than 0.05), whereas bronchial blood flow to the lung fell significantly. These changes in pulmonary hemodynamics were not reflected by changes in the arterial blood gases. Arterial oxygenation was maintained during 5 hours of pancreatitis. The partial pressure of carbon dioxide and the serum pH did not change significantly. There was, however, a progressive rise in extravascular lung water measured by the double-dilution technique from 10.2 +/- 0.8 ml/kg at control to 18.1 +/- 2.8 ml/kg (p less than 0.01) at 5 hours. This was confirmed by direct gravimetric measurements, which revealed an increase in the water content of the lung from 78.1 +/- 0.3% to 86.4 +/- 2.4% over the course of the experiment. Arterial blood gases, therefore, do not necessarily reflect the pulmonary deterioration in acute pancreatitis. These data supported a mechanism of lung dysfunction independent of the circulatory compromise, which often accompanies the disease in the clinical setting.

Determination of the half-lives of transactinium isotopes by relative activity method

Relative activity method offers the potentiality of providing half-life values over a wide range in a short time for different α-emitting transactinium isotopes. The method involves the preparation of a synthetic mixture using another isotope of the same element followed by the determination of atom ratio and α-activity ratio by thermal ionization mass spectrometry and α-spectrometry, respectively. A double dilution technique is described which helps in maintaining the atom ratios as well as α-activity ratios close to unity so that these could be determined with high precision and accuracy. Results obtained on the half-lives of232U,238Pu,242Pu and243Am using double dilution technique in relative activity method are summarized. Requirements, advantages and applications of this technique for determining the half-lives of other transactinium isotopes are presented.

Half-life ofAm243

The half-life of /sup 243/Am was determined by the relative activity method. Synthetic mixtures were prepared by using solutions of /sup 241/Am and /sup 243/Am isotopes. The ..cap alpha.. activity ratios and the atom ratios in these mixtures were kept close to unity by employing the double dilution technique so that these could be measured with high precision and accuracy. The ..cap alpha.. activity ratios were determined by ..cap alpha.. spectrometry on electrodeposited sources using a silicon surface barrier detector and the atom ratios were obtained by mass spectrometry. A value of 17.010 +- 0.095 was obtained for the /sup 243/Am//sup 241/Am half-life ratio which leads to a value of 7358 +- 42 yr for the half-life of /sup 243/Am using the half-life of /sup 241/Am as 432.6 yr. The uncertainty specified on the values is a combination of the one standard deviation on the average value and the error evaluated from the estimate on the various error components.