An improved method of high-precision determination of Δ(17)O of CO2 by catalyzed exchange with O2 using hot platinum.

RATIONALE: CO2 and O2 can exchange their oxygen isotopes rapidly in the presence of hot (~670 °C) platinum and this has led to a method for determining the δ(17)O value of a CO2 sample. We have improved the method to achieve a precision of 0.008 ‰ (1-σ standard deviation) in the determination of δ(17)O values. Such high precision is essential to identify the stratospheric component in tropospheric CO2 and use it for global carbon flux studies. The crucial issue in the accurate determination of the δ(17)O value is estimation of a correction factor, which depends on the amount ratio CO2/O2. An attempt was also made to investigate the mechanism of exchange with their controlling parameters. METHODS: The oxygen isotopes of a CO2 sample gas are exchanged with those of an appropriate amount of tank O2 in the presence of hot platinum. The pre-exchange CO2 and O2 gas samples as well as the post-exchange O2 sample are analyzed by isotope ratio mass spectrometry. A mixing model was developed involving the δ(18)O value of the CO2 and δ(17)O and δ(18)O values of pre- and post-exchange O2 to obtain the δ(17)O value of the CO2 sample. A correction to the measured value was determined to obtain the actual value with high accuracy and precision. RESULTS: To obtain a precision better than 0.01 ‰ requires the amount ratio CO2/O2 to be controlled to better than ~15 %. We also find that the oxygen isotopes are nearly homogeneously distributed between the O2 and the CO2 molecules. In addition, determination of the (16) O(13)C(18)O/(16)O(12)C(16)O isotopologue ratio in the CO2 shows that the abundance of (16)O(13)C(18)O is close to that expected for random partitioning of the isotopes among the CO2 isotopologues. CONCLUSIONS: The isotopic scrambling between O2 and CO2 that occurs on hot platinum allows one to accurately determine the δ(17)O values of CO2 through isotopic analysis of O2.

Cholera outbreaks in South-East Asia.

This chapter highlights the cholera situation in South Asia and the Bay of Bengal region, the original 'homeland' of cholera. A detailed discussion of cholera outbreaks in individual countries in South-East Asia follows. The countries of the World Health Organization (WHO) SEARO (South-East Asia Region) region are discussed first, followed by discussions about the other countries in South-East Asia that do not fall within the purview of the WHO SEARO classification of the member countries of the region. Therefore, the chapter attempts to provide a comprehensive yet precise outline of the major cholera outbreaks that have occurred in the region over the years.

A new feature in the internal heavy isotope distribution in ozone.

Ozone produced by discharge or photolysis of oxygen has unusually heavy isotopic composition ((18)O/(16)O and (17)O/(16)O ratio) which does not follow normal mass fractionation rule: δ(17)O ∼ 0.52(*)δ(18)O, expressed as an anomaly Δ(17)O = δ(17)O - 0.52(*)δ(18)O. Ozone molecule being an open isosceles triangle can have the heavy isotope located either in its apex or symmetric (s) position or the base or asymmetric (as) position. Correspondingly, one can define positional isotopic enrichment, written as δ(18)O (s) or δ(18)O (as) (and similarly for δ(17)O) as well as position dependent isotope anomaly Δ(17)O (s) and Δ(17)O (as). Marcus and co-workers have proposed a semi-empirical model based in principle on the RRKM model of uni-molecular dissociation but with slight modification (departure from statistical randomness assumption for symmetrical molecules) which explains many features of ozone isotopic enrichment. This model predicts that the bulk isotope anomaly is contained wholly in the asymmetric position and the Δ(17)O (s) is zero. Consequently, Δ(17)O (as) = 1.5 (*) Δ(17)O (bulk) (named here simply as the "1.5 rule") which has been experimentally confirmed over a range of isotopic enrichment. We now show that a critical re-analysis of the earlier experimental data demonstrates a small but significant departure from this 1.5 rule at the highest and lowest levels of enrichments. This departure provides the first experimental proof that the dynamics of ozone formation differs from a statistical model constrained only by restriction of symmetry. We speculate over some possible causes for the departure.

Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence.

Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these studies (see also Paper I by Meusinger et al. ["Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry," J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable isotopes in nitrate ((15)N, (17)O, and (18)O) provide additional information concerning post-depositional processes. Here, we present results from studies of the wavelength-dependent isotope effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and isotopic composition (δ(15)N, δ(18)O, and Δ(17)O). From these measurements an average photolytic isotopic fractionation of (15)ɛ = (-15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic isotopic fractionation of (15)ɛ = (-47.9 ± 6.8)‰, in good agreement with fractionations determined by previous studies for the East Antarctic Plateau which range from -40 to -74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of (14)NO3 (-) and (15)NO3 (-) in snow at a chosen temperature. The nitrogen isotopic fractionations obtained by applying this model under the experimental temperature as well as considering the shift in width and center well reproduced the values obtained in the laboratory study. These cross sections can be used in isotopic models to reproduce the stable isotopic composition of nitrate found in Antarctic snow profiles.

Oxygen isotope exchange between O2 and CO2 over hot platinum: an innovative technique for measuring Δ17O in CO2.

The isotopic composition of carbon dioxide provides a powerful tool and has been widely used for constraining the sources and sinks of atmospheric CO2. In this work, we demonstrate a simple, rapid, and clean way for measuring the triple oxygen isotope ratio of carbon dioxide with high precision. The method depends on isotope exchange between O2 and CO2 in the presence of platinum at high temperature and allows rapid measurement of Δ(17)O of CO2. The method has been established and confirmed through several tests by using artificially made CO2 with known Δ(17)O values. The analytical precision obtained for determining Δ(17)O in CO2 is 0.045‰ (1 - σ standard deviation).

Naloxone blocks the beneficial effects of aqueous extract of Murraya koenigii (L.) Spreng leaves in models of pain.

AIM: This study investigated the antinociceptive effects of aqueous extract of Murraya koenigii (AEMK) leaves (200, 400 and 800 mg/kg, orally) on animal models of acute and persistent pain and its modulation by naloxone. MATERIALS AND METHODS: Antinociceptive effects were assessed using tail-flick, hot plate and formalin tests in mice. To differentiate between central and peripheral antinociceptive effect of AEMK, naloxone (2 mg/kg) was administered along with the 800 mg/kg dose of extract. Morphine was used as a standard drug. RESULTS: AEMK and morphine significantly increased the tail-flick latency (tfl) and paw licking/jumping latency in tail-flick and hot plate tests, respectively, in comparison to control. Also, in both the tests AEMK and morphine significantly increased the AUC0-120 min. In formalin test, AEMK (400 mg/kg and 800 mg/kg) and morphine significantly reduced licking time in both early and late phases in comparison to control. CONCLUSIONS: Thus, in all three pain models AEMK showed antinociceptive effect, which was blocked by naloxone suggesting the involvement of opioidergic central mechanism.

Measurement of the 17O-excess (Δ17O) of tropospheric ozone using a nitrite-coated filter.

RATIONALE: The (17)O-excess (Δ(17)O) of tropospheric ozone (O(3)) serves as a useful marker in studies of atmospheric oxidation pathways; however, due to the complexity and expense of currently available analytical techniques, no systematic sampling campaign has yet been undertaken and natural variations in Δ(17)O(O(3)) are therefore not well constrained. METHODS: The nitrite-coated filter method is a new technique for O(3) isotope analysis that employs the aqueous phase NO(2)(-) + O(3) → NO(3)(-) + O(2) reaction to obtain quantitative information on O(3) via the oxygen atom transfer to nitrate (NO(3)(-)). The triple-oxygen isotope analysis of the NO(3)(-) produced during this reaction, achieved in this study using the bacterial denitrifier method followed by isotope-ratio mass spectrometry (IRMS), directly yields the Δ(17)O value transferred from O(3). This isotope transfer process was investigated in a series of vacuum-line experiments, which were conducted by exposing coated filters to O(3) of various known Δ(17)O values and then determining the isotopic composition of the NO(3)(-) produced on the filter. RESULTS: The isotope transfer experiments revealed a strong linear correlation between the Δ(17)O of the O(3) produced and that of the oxygen atom transferred to NO(3)(-), with a slope of 1.55 for samples with bulk Δ(17)O(O(3)) values in the atmospheric range (20-40‰). This finding is in agreement with theoretical postulates that place the (17) O-excess on only the terminal oxygen atoms of ozone. Ambient measurements yield average Δ(17)O(O(3))(bulk) values in agreement with previous studies (22.9 ± 1.9‰). CONCLUSIONS: The nitrite-coated filter technique is a sufficiently robust, field-deployable method for the determination of the triple-oxygen isotopic composition of tropospheric O(3). Further ambient measurements will undoubtedly lead to an improved quantitative view of natural Δ(17)O(O(3)) variation and transfer in the atmosphere.

17O excess transfer during the NO2 + O3 → NO3 + O2 reaction.

The ozone molecule possesses a unique and distinctive (17)O excess (Δ(17)O), which can be transferred to some of the atmospheric molecules via oxidation. This isotopic signal can be used to trace oxidation reactions in the atmosphere. However, such an approach depends on a robust and quantitative understanding of the oxygen transfer mechanism, which is currently lacking for the gas-phase NO(2) + O(3) reaction, an important step in the nocturnal production of atmospheric nitrate. In the present study, the transfer of Δ(17)O from ozone to nitrate radical (NO(3)) during the gas-phase NO(2) + O(3) → NO(3) + O(2) reaction was investigated in a series of laboratory experiments. The isotopic composition (δ(17)O, δ(18)O) of the bulk ozone and the oxygen gas produced in the reaction was determined via isotope ratio mass spectrometry. The Δ(17)O transfer function for the NO(2) + O(3) reaction was determined to be: Δ(17)O(O(3)∗) = (1.23 ± 0.19) × Δ(17)O(O(3))(bulk) + (9.02 ± 0.99). The intramolecular oxygen isotope distribution of ozone was evaluated and results suggest that the excess enrichment resides predominantly on the terminal oxygen atoms of ozone. The results obtained in this study will be useful in the interpretation of high Δ(17)O values measured for atmospheric nitrate, thus leading to a better understanding of the natural cycling of atmospheric reactive nitrogen.

Pneumonia in South-East Asia Region: public health perspective.

Globally, pneumonia is the leading cause of death in young children and burden of disease is disproportionately high in South-East Asia Region of WHO. This review article presents the current status of pneumonia disease burden, risk factors and the ability of health infrastructure to deal with the situation. Literature survey was done for the last 20 years and data from country offices were also collected. The estimated incidence of pneumonia in under five children is 0.36 episodes per child, per year. Risk factors are malnutrition (40% in India), Indoor air pollution, non-breast feeding, chronic obstructive pulmonary disease, etc. Strengthening of health care delivery system for early detection and treatment and as well as minimization of preventable risk factors can avert a large proportion of death due to pneumonia.

The role of symmetry in the mass independent isotope effect in ozone.

Understanding the internal distribution of "anomalous" isotope enrichments has important implications for validating theoretical postulates on the origin of these enrichments in molecules such as ozone and for understanding the transfer of these enrichments to other compounds in the atmosphere via mass transfer. Here, we present an approach, using the reaction NO(2)(-) + O(3), for assessing the internal distribution of the Delta(17)O anomaly and the delta(18)O enrichment in ozone produced by electric discharge. The Delta(17)O results strongly support the symmetry mechanism for generating mass independent fractionations, and the delta(18)O results are consistent with published data. Positional Delta(17)O and delta(18)O enrichments in ozone can now be more effectively used in photochemical models that use mass balance oxygen atom transfer mechanisms to infer atmospheric oxidation chemistry.

Effectiveness of an educational feedback intervention on drug prescribing in dental practice.

BACKGROUND: Irrational use of drugs as well as inappropriate and over drug prescribing leads to unnecessary expenditures and emergence of resistant bacterial strains. Feedback intervention on drug prescribing habits and face to face educational intervention of prescription audit would be effective in rationalizing prescribing practices. OBJECTIVE: To measure the impact of educational feedback intervention on the prescribing behavior of dental surgeons. METHODS: Prospective audit of twelve hundred outpatients prescriptions in dental OPD at BPKIHS of those dental surgeon who attended the educational intervention session was collected randomly by trained persons on customized data collection sheet before and after educational intervention. RESULTS: A total 1200 prescription were collected, 300 before and 300 after intervention period at the internal of one month, three months and six months. Majority of the prescriptions (39.33%) contained four drugs but after intervention, prescriptions contained mostly one drug, 73% in first month, 78.67% in third month and 65.34% in six month. Mean number of drugs per prescription after intervention were decreased. There was increased number of generic names of drugs after intervention. Amoxicillin, Metronidazole, Chlorhexidine, Povidone iodine gargle, Nimesulide, Ibuprofen, Ibuprofen + paracetamol, and Paracetamol were most commonly prescribed by dental prescribers before and after intervention. Selection of antimicrobial was done on empirical basis which was correct because Amoxicillin concentration reaches effectively in gingival crevicular fluid and Metronidazole covered effectively against anaerobic bacteria were found in orodental infection. The uses of topical anti-infective preparation as irrigants of choice that can kill majority of micro-organisms found is root canal and dental tubules and minimize systemic use of antimicrobials. Nimesulide prescribing needs to be rationalized. CONCLUSION: Feedback educational intervention of prescription audit is effective to improve their prescribing behaviors and rationalize drug utilization pattern for the benefit of the patients.

Role of probiotic in preventing acute diarrhoea in children: a community-based, randomized, double-blind placebo-controlled field trial in an urban slum.

Acute diarrhoea remains a major public health challenge in developing countries. We examined the role of a probiotic in the prevention of acute diarrhoea to discover if there was an effect directed towards a specific aetiology. A double-blind, randomized, controlled field trial involving 3758 children aged 1-5 years was conducted in an urban slum community in Kolkata, India. Participants were given either a probiotic drink containing Lactobacillus casei strain Shirota or a nutrient drink daily for 12 weeks. They were followed up for another 12 weeks. The primary outcome of this study was the occurrence of first episodes of diarrhoea. We assessed this during 12 weeks of intake of study agent and also for 12 weeks of follow-up. There were 608 subjects with diarrhoea in the probiotic group and 674 subjects in the nutrient group during the study period of 24 weeks. The level of protective efficacy for the probiotic was 14% (95% confidence interval 4-23, P<0·01 in adjusted model). The reduced occurrence of acute diarrhoea in the probiotic group compared to nutrient group was not associated with any specific aetiology. No adverse event was observed in children of either probiotic or nutrient groups. The study suggests that daily intake of a probiotic drink can play a role in prevention of acute diarrhoea in young children in a community setting of a developing country.

Discovery of two novel laccase-like multicopper oxidases from Pleurotus citrinopileatus and their application in phenolic oligomer synthesis.

BACKGROUND: Laccases and laccase-like multicopper oxidases (LMCOs) oxidize a vast array of phenolic compounds and amines, releasing water as a byproduct. Their low substrate specificity is responsible for their tremendous biotechnological interest, since they have been used for numerous applications. However, the laccases characterized so far correspond to only a small fraction of the laccase genes identified in fungal genomes. Therefore, the knowledge regarding the biochemistry and physiological role of minor laccase-like isoforms is still limited. RESULTS: In the present work, we describe the isolation, purification and characterization of two novel LMCOs, PcLac1 and PcLac2, from Pleurotus citrinopileatus. Both LMCOs were purified with ion-exchange chromatographic methods. PcLac2 was found to oxidize a broader substrate range than PcLac1, but both LMCOs showed similar formal potentials, lower than those reported previously for laccases from white-rot fungi. Proteomic analysis of both proteins revealed their similarity with other well-characterized laccases from Pleurotus strains. Both LMCOs were applied to the oxidation of ferulic and sinapic acid, yielding oligomers with possible antioxidant activity. CONCLUSIONS: Overall, the findings of the present work can offer new insights regarding the biochemistry and variability of low-redox potential laccases of fungal origin. Low-redox potential biocatalysts could offer higher substrate selectivity than their high-redox counterparts, and thus, they could be of applied value in the field of biocatalysis.

Elimination of neglected tropical diseases in the South-East Asia Region of the World Health Organization.

The neglected tropical diseases (NTDs), which affect the very poor, pose a major public health problem in the South-East Asia Region of the World Health Organization (WHO). Although more than a dozen NTDs affect the region, over the past five years four of them in particular - leprosy, lymphatic filariasis, visceral leishmaniasis (kala-azar) and yaws - have been targeted for elimination. These four were selected for a number of reasons. First, they affect the WHO South-East Asia Region disproportionately. For example, every year around 67% of all new leprosy cases and 60% of all new cases of visceral leishmaniasis worldwide occur in countries of the region, where as many as 850 million inhabitants are at risk of contracting lymphatic filariasis. In addition, several epidemiological, technological and historical factors that are unique to the region make each of these four diseases amenable to elimination. Safe and effective tools and interventions to achieve these targets are available and concerted efforts to scale them up, singly or in an integrated manner, are likely to lead to success. The World Health Assembly and the WHO Regional Committee, through a series of resolutions, have already expressed regional and global commitments for the elimination of these diseases as public health problems. Such action is expected to have a quick and dramatic impact on poverty reduction and to contribute to the achievement of the Millennium Development Goals. This paper reviews the policy rationale for disease control in the WHO South-East Asia Region, the progress made so far, the lessons learnt along the way, and the remaining challenges and opportunities.

Non-typhoidal Salmonella rates in febrile children at sites in five Asian countries.

There is increased recognition of non-typhoidal Salmonella (NTS) as a major cause of severe febrile illness in sub-Saharan Africa. However, little is known about community-based incidence of NTS in Asia. In a multicentre, community-based prospective Salmonella surveillance study, we identified a total of six NTS cases: three in Karachi, Pakistan, one in Kolkata, India, and two in North Jakarta, Indonesia. No NTS cases were identified in Hechi, People's Republic of China, and Hue, Viet Nam. Three cases were in children under 3 years, and one case was in a child aged 10 years and one in a child aged 15 years. Only one case was an adult (29 years). The highest incidence of NTS infection was in Karachi (7.2 culture-proven NTS cases per 100,000 person years in age group of 2-15 years). However, in comparison with sub-Saharan Africa, the NTS burden in Asia appears rather limited.

Phenotypic characterisation and drug sensitivity testing of mycobacteria isolated from extra-pulmonary tuberculosis.

BACKGROUND: Tuberculosis (TB) is a major cause of morbidity and mortality globally, with most cases occurring in developing countries. The importance of extra pulmonary tuberculosis (EPTB) among all forms of tuberculosis has not yet been ascertained in developing countries. OBJECTIVE: To identify and perform phenotypic characterization of clinically important mycobacterium isolates from extra-pulmonary sites along with drug susceptibility testing. MATERIALS AND METHODS: A total of 513 specimens from patients of (EPTB) with varied presentation were studied. Speciation and characterization of isolates were done on the basis of growth and biochemical characteristics. Drug susceptibility testing for mycobacterium isolates was done by proportion method. RESULTS: Fifty four patients clinically suspected to have extra-pulmonary tuberculosis were culture positive for mycobacteria. On characterization 48 of the 54 isolates were identified as M. tuberculosis, 4 as M. bovis and 2 were M. avium/intracelulare. Drug susceptibility testing was done for the both M. tuberculosis as well as M. bovis. In single drug resistance, Streptomycin was highest followed by Isoniazid, Ethambutol and Refampicin. Multi drug resistance (MDR) was found in 6 isolates and it was observed only in group I cases. CONCLUSION: EPTB accounts for 10-15 percent of all cases of tuberculosis. Mycobacterium was present in 10.5 percent samples. 48 isolates out of 54 samples were found to be M. tuberculosis. The maximum numbers of M. tuberculosis were isolated from lymph node aspiration.

Attenuation of oxidative stress and neurotoxicity involved in the antidepressant-like effect of the MK-801(dizocilpine) in Bacillus Calmette-Guerin-induced depression in mice.

Background The emerging line of research suggests that neuro-inflammation and oxidative stress are linked to the development of depression-like behavior. The tryptophan metabolizing enzyme, indolamine 2,3-dioxygenase (IDO), serves as an important interface between chronic inflammation and depression. IDO is induced by pro-inflammatory cytokines and diverts tryptophan towards the kynurenine pathway, decreasing serotonin synthesis. Further, the metabolites of kynurenine pathway increase brain oxidative stress and also cause N-methyl-D-aspartate (NMDA) receptor-mediated exitotoxicity. The resulting oxidative damage and dysfunction in glutamatergic neurotransmission alters the network connectivity of the brain, which may be the further mechanism for emergence of depression-like symptoms. Methods A depression-like illness was induced in mice by injecting Bacillus Calmette-Guerin (BCG) suspended in isotonic saline at a dose of 107 CFU I.P. The mice were then divided into different groups and were administered MK-801 or normal saline for the next 21 days, after which a battery of behavior and biochemical tests were conducted to assess them. Results The BCG group had significantly reduced sucrose preference index and an increase in immobility time in forced swim test (FST) and Tail Suspension Test (TST) as compared to the saline group. There was also a significant increase in the brain MDA levels and a decline in the brain GSH levels. The hippocampal tissue from the BCG group had significantly more comet cells than the saline group. The NMDA receptor antagonist, MK-801, was able to reverse the BCG-induced depression-like behaviour. MK-801 also showed significant decrease in brain oxidative stress but failed to show significant protection against BCG-induced neurotoxicity observed in comet assay. Conclusions The NMDA receptor antagonist, MK-801, mitigated BCG-induced, depressive-like behavior in mice by improving the sucrose preference and decreasing the duration of immobility time in TST and FST. The overall improvement in depression-like behavior was accompanied by a reduction in brain oxidative stress and comet cells, thus suggesting the antioxidant and neuroprotective action of MK-801.

Antiangiogenic activity of zinc and zinc-sorafenib combination using the chick chorioallantoic membrane assay: A descriptive study.

AIM: Zinc, a trace element, is known for downregulating several proangiogenic growth factors and cytokines. However, its antiangiogenic activity is not adequately studied. The present study was aimed to evaluate the possible antiangiogenic activity of zinc via the chick chorioallantoic membrane (CAM) assay. Furthermore, the antiangiogenic activity of the combination therapy of zinc with various doses of sorafenib, a tyrosine kinase inhibitor, was evaluated. MATERIALS AND METHODS: A pilot study was initially conducted so as to select suitable doses of zinc and sorafenib. The antiangiogenic activity after combining zinc 2.5 µg/embryo with sorafenib 1 and 2 µg/embryo was also evaluated. The antiangiogenic activity was quantified in terms of total length of blood vessels, number of junctions, number of branching points, and mean length of the blood vessels. RESULTS: Zinc 2.5 µg/embryo showed significant (P < 0.05) antiangiogenic activity, as compared to the control group. However, its effect was not comparable to that of sorafenib 2 µg/embryo. The combination of zinc 2.5 µg/embryo with sorafenib 2 µg/embryo did not show an additive/synergistic effect. The combination of zinc 2.5 µg/embryo with sorafenib 1 µg/embryo produced an antiangiogenic activity which was comparable (P > 0.05) to that of sorafenib 2 µg/embryo. CONCLUSION: Zinc caused significant antiangiogenic activity in the CAM assay. The lack of addition/synergism in the zinc-sorafenib combination could have been due to the variability in the dose/ratio selection. Addition of zinc to sorafenib therapy could improve treatment tolerability, reduce cost of therapy, and reduce the emergence of drug resistance. Future mechanistic studies could identify the exact pharmacodynamics of zinc as an angiogenesis inhibitor.

Mass-dependent isotopic fractionation in ozone produced by electrolysis.

During the electrolysis of water in an acidified medium, ozone is produced, in association with oxygen, at the anode. This ozone is found to be depleted in heavy isotopes ((18)O and (17)O), with respect to the source water, following a strict mass-dependent rule. Our experiments also suggest that the isotopes are distributed at the apex and base positions of the bent ozone molecule in a random fashion, without obeying the zero-point energy constraint. Endowed with these characteristics, the electrolytic ozone provides a source of reference that has a known internal heavy isotope distribution for spectroscopic studies. In addition, this ozone, when subjected to photolytic decomposition, can be used as a source of atomic oxygen with mass-dependent isotope ratios that can be varied by simply changing the water composition. Such an oxygen source is important for studying isotope effects in gas-phase recombination/exchange reactions such as COO + O* --> [COOO*] --> COO* + O.

Incidence, virulence factors, and clonality among clinical strains of non-O1, non-O139 Vibrio cholerae isolates from hospitalized diarrheal patients in Kolkata, India.

The incidence of Vibrio cholerae non-O1, non-O139 strains from hospitalized patients with acute diarrhea constituted 27.4% (n = 54) of the total 197 V. cholerae strains isolated from patients in Kolkata, India, in 2003. Of 197 strains, 135 were identified as O1 serotype Ogawa and 2 were identified as O139. In the same time period, six O1 background rough strains that possessed all known virulence factors were identified. Serotype analysis of the non-O1, non-O139 strains placed 42 strains into 19 serogroups, while 12 remained O nontypeable (ONT); the existing serotyping scheme involved antisera to 206 serogroups. Detection of a good number of ONT strains suggested that additional serogroups have arisen that need to be added to the current serotyping scheme. The non-O1, non-O139 strains were nontoxigenic except for an O36 strain (SC124), which regulated expression of cholera toxin as O1 classical strains did. Additionally, strain SC124 carried alleles of tcpA and toxT that were different from those of the O1 counterpart, and these were also found in five clonally related strains belonging to different serogroups. Strains carrying tcpA exhibited higher colonization in an animal model compared to those lacking tcpA. PCR-based analyses revealed remarkable variations in the distribution of other virulence factors, including hlyA, rtxA, Vibrio seventh pandemic island I (VSP-I), VSP-II, and type III secretion system (TTSS). Most strains contained hlyA (87%) and rtxA (81.5%) and secreted cytotoxic factors when grown in vitro. Approximately one-third of the strains (31.5%) contained the TTSS gene cluster, and most of these strains were more motile and hemolytic against rabbit erythrocytes. Partial nucleotide sequence analysis of the TTSS-containing strains revealed silent nucleotide mutations within vcsN2 (type III secretion cytoplasmic ATPase), indicating functional conservation of the TTSS apparatus.