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Global distribution and health threats of microcystins (MCs) have received much more attention, but there are still significant knowledge gaps in the peak periods and driving factors of MC in different phases of freshwater ecosystems. Thus, we systematically analyzed the annual variation of different MC congeners (-LR, -RR, and -YR, where L, R, and Y respectively represent leucine, arginine, and tyrosine) in particulates, dissolved water, and sediments in three eutrophic bays of Lake Taihu, China. The results indicated that particulate MCs concentration was the highest, followed by dissolved and sediment MC, with the mean concentration of 7.58 µg/L, 1.48 µg/L, and 0.15 µg/g (DW), respectively. Except for particulate MC, the concentrations of the other two types of MC showed significant differences among the three bays. The dominant congeners of the three types of MCs were different, with the highest proportion of MC-LR being observed in sediment MCs and the lowest in particulate MCs. The peak period of the three types of MC was also different, with particulate MCs reaching their peak in July and October, dissolved MCs in May to July and October, and sediment MCs reaching their peak in September. Consistent with our hypothesis, the dynamics of different types of MCs were driven by different environmental factors. Particulate MCs were primarily related to biological parameters, followed by TP and dissolved carbon. By contrast, dissolved MCs strongly correlated with water temperature and dissolved oxygen. While sediment MCs were primarily driven by properties of sediments, followed by different forms of nitrogen in the water column. Our results suggested that particulate and dissolved MCs in northern Lake Taihu pose high health threats, especially in the peak period. Moreover, a more detailed and targeted risk management strategy should be designed to prevent the possible hazards posed by different types of MC.
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Lagos , Microcistinas , Agua , Ecosistema , Monitoreo del Ambiente , Polvo , ChinaRESUMEN
In this paper, we introduce a SEIATR compartmental model to analyze and predict the COVID-19 outbreak in the Top 5 affected countries in the world, namely the USA, India, Brazil, France, and Russia. The officially confirmed cases and death due to COVID-19 from the day of the official confirmation to June 30, 2021 are considered for each country. Primarily, we use the data to make a comparison between the cumulative cases and deaths due to COVID-19 among these five different countries. This analysis allows us to infer the key parameters associated with the dynamics of the disease for these five different countries. For example, the analysis reveals that the infection rate is much higher in the USA, Brazil, and France compared to that of India and Russia, while the recovery rate is found almost the same for these countries. Further, the death rate is measured higher in Brazil as opposed to India, where it is found much lower among the remaining countries. We then use the SEIART compartmental model to characterize the first and second waves of these countries, as well as to investigate and identify the influential model parameters and nature of the virus transmissibility in respective countries. Besides estimating the time-dependent reproduction number (Rt) for these countries, we also use the model to predict the peak size and the time occurring peak in respective countries. The analysis demonstrates that COVID-19 was observed to be much more infectious in the second wave than the first wave in all countries except France. The results also demonstrate that the epidemic took off very quickly in the USA, India, and Brazil compared to two other countries considered in this study. Furthermore, the prediction of the epidemic peak size and time produced by our model provides a very good agreement with the officially confirmed cases data for all countries expect Brazil.
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BACKGROUND: Rat developmental toxicity including embryolethality and teratogenicity (mainly ventricular septal defects [VSDs] and wavy ribs) was produced by an N-phenylimide herbicide that inhibits protoporphyrinogen oxidase (PPO) common to chlorophyll and heme biosynthesis. Major characteristics of the developmental toxicity included species difference between rats and rabbits, compound-specific difference among structurally similar herbicides, and sensitive period. Protoporphyrin accumulation in treated fetuses closely correlated with the major characteristics. Iron deposits in erythroblastic mitochondria and degeneration of erythroblasts were observed in treated rat fetuses. In this study we investigated fetal anemia and subsequent developmental effects in rats, and inhibition of PPO in rats, rabbits, and humans by the herbicides in vitro. METHODS: Fetuses were treated on gestational day (GD) 12 and removed on GDs 13 through 20. All litters were examined externally. One half of litters were examined for blood and skeletal development, and the other half for interventricular foramen closure. Effects on PPO were determined in mitochondria from embryos and adult livers. RESULTS: Fetal anemia in rats was evident on GDs 13 through 16. Subsequently, enlarged heart, delayed closure of the foramen, reduced serum protein, and retarded rib ossification were observed. In vitro PPO inhibition exhibited species- and compound-specific differences corresponding to the developmental toxicity. CONCLUSION: We propose that developmental toxicity results from PPO inhibition in primitive erythroblasts, causing transient fetal anemia followed by death. Compensatory enlargement of the fetal heart results in failure of interventricular foramen closure and VSD. Reduced serum protein leads to delayed ossification and wavy ribs.
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Anemia/embriología , Anemia/patología , Feto/anomalías , Feto/embriología , Herbicidas/toxicidad , Imidas/toxicidad , Animales , Benzoxazinas/farmacología , Proteínas Sanguíneas/metabolismo , Recuento de Eritrocitos , Femenino , Mortalidad Fetal , Feto/efectos de los fármacos , Feto/patología , Corazón/efectos de los fármacos , Corazón/embriología , Hemo/biosíntesis , Hemoglobinas/metabolismo , Herbicidas/química , Humanos , Imidas/química , Concentración 50 Inhibidora , Ftalimidas/farmacología , Embarazo , Protoporfirinógeno-Oxidasa/antagonistas & inhibidores , Protoporfirinógeno-Oxidasa/metabolismo , Conejos , Ratas Sprague-Dawley , Costillas/anomalías , Costillas/embriología , Especificidad de la EspecieRESUMEN
BACKGROUND: S-53482, 7-fluoro-6-[(3,4,5,6-tetrahydro)phthalimido]-4-(2-propynyl)-1,4-benzoxazin-3(2H)-one (flumioxazin), is an N-phenylimide herbicide and developmentally toxic to rats, but not to rabbits. The day of greatest sensitivity to S-53482 is gestational day (GD) 12 in rats. There is a compound-specific difference in developmental toxicity among structurally similar compounds including S-23121 (N-[4-chloro-2-fluoro-5-[(1-methyl-2-propynyl)oxy]phenyl]-3,4,5,6-tetrahydrophthalimide; teratogenic) and S-23031 (pentyl 2-chloro-4-fluoro-5-(3,4,5,6-tetrahydrophthalimido)phenoxyacetate (flumiclorac pentyl); nonteratogenic). The herbicidal action is due to photodynamic action of accumulating protoporphyrin IX (PPIX), resulting from the inhibition of protoporphyrinogen oxidase (PPO), an enzyme in porphyrin biosynthesis. Species difference in PPIX accumulation in embryos corresponded to those of the developmental toxicity. Our objective in this study was to further investigate a link between PPIX accumulation resulting from PPO inhibition and developmental toxicity. This article is part of a series of studies to be published serially. METHODS: To investigate compound-specific differences, each compound was orally administered to rats on GD 12. To define peak period of PPIX accumulation, single oral treatments of S-53482 were given to rats or rabbits at 19:30 on GD 10 through GD 15. PPIX was extracted from embryos 14 hr after treatment. RESULTS: Remarkable PPIX accumulation was observed when treated with S-53482 or S-23121, but not with S-23031. The greatest accumulation of PPIX was observed when treated with S-53482 at 19:30 on GD 11 or GD 12. No PPIX accumulation was found on any GDs in rabbits. CONCLUSIONS: The developmentally toxic compounds caused PPIX accumulation in embryos. The peak period of PPIX accumulation corresponded to that of developmental effects. This correlation suggests a close link between PPO inhibition and developmental abnormality.
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Desarrollo Embrionario/efectos de los fármacos , Herbicidas/toxicidad , Protoporfirinógeno-Oxidasa/antagonistas & inhibidores , Protoporfirinas/metabolismo , Protoporfirinas/farmacocinética , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2 , Transportadoras de Casetes de Unión a ATP/metabolismo , Animales , Benzoxazinas/química , Benzoxazinas/toxicidad , Femenino , Herbicidas/química , Hígado/metabolismo , Ftalimidas/química , Ftalimidas/toxicidad , Conejos , Ratas , Ratas Sprague-Dawley , Teratogénesis/efectos de los fármacosRESUMEN
Objective Todescribethemonthlyincidencedistributionofhand-foot-mouthdisease(HFMD)from2010to 2012inZhoushancityandtoanalyzetheseasonaltrendandthecausesofpeakchanges.Methods Circulardistribution method was used to identify the peak period of HFMD incidence.Watson -William test and Watson's U2 test were applied for comparing the peak periods respectively.Chi -square test was conducted to analyze and compare the distribution of HFMDpathogenindifferentyearsandBonferronimethodwasusedformultiplecomparisons.Results Therewasseasonal centralized tendency of HFMD incidence during 2010 to 2012 (P<0.01).The peak period occurred between 8th of May and 1st of September which showed a significant difference among three years (P<0.01).Specifically,the peak period in 2012 was earlier than that in 2010 and 201 1 (both P<0.01 ).Among the 356 reported cases with laboratory confirmed, there was significant difference between the distribution of HFMD pathogen by Chi -square test (P <0.01 ).The predominant strain was EV71 in 2010 and 2011 accounting for 58.46%and 64.62%respectively and other enteric viruses in 2012 accounting for 48.84%.The ratio of pathogens in 2012 was statistically different from that in 2010 and 201 1 respectively(bothP<0.01).Conclusion HFMDcasesoccurwithobviouspeakseason,regionalandgeographic differences.The major pathogens of EV71 in 2010 and 2011 were changed into other enteric viruses in 2012.