Record high levels of atmospheric ammonia over India: Spatial and temporal analyses.

Atmospheric ammonia (NH3) is an alkaline gas and a prominent constituent of the nitrogen cycle that adversely affects ecosystems at higher concentrations. It is a pollutant, which influences all three spheres such as haze formation in the atmosphere, soil acidification in the lithosphere, and eutrophication in water bodies. Atmospheric NH3 reacts with sulfur (SOx) and nitrogen (NOx) oxides to form aerosols, which eventually affect human health and climate. Here, we present the seasonal and inter-annual variability of atmospheric NH3 over India in 2008-2016 using the IASI (Infrared Atmospheric Sounding Interferometer) satellite observations. We find that Indo-Gangetic Plains (IGP) is one of the largest and rapidly growing NH3 hotspots of the world, with a growth rate of +1.2% yr-1 in summer (June-August: Kharif season), due to intense agricultural activities and presence of many fertilizer industries there. However, our analyses show insignificant decreasing trends in annual NH3 of about -0.8% yr-1 in all India, about -0.4% yr-1 in IGP, and -1.0% yr-1 in the rest of India. Ammonia is positively correlated with total fertilizer consumption (r = 0.75) and temperature (r = 0.5) since high temperature favors volatilization, and is anti-correlated with total precipitation (r = from -0.2, but -0.8 in the Rabi season: October-February) as wet deposition helps removal of atmospheric NH3. This study, henceforth, suggests the need for better fertilization practices and viable strategies to curb emissions, to alleviate the adverse health effects and negative impacts on the ecosystem in the region. On the other hand, the overall decreasing trend in atmospheric NH3 over India shows the positive actions, and commitment to the national missions and action plans to reduce atmospheric pollution and changes in climate.

Atmospheric ammonia (NH3) emanations from Lake Natron's saline mudflats.

In a recent global analysis of satellite-derived atmospheric NH3 data, a hotspot was observed in the vicinity of Lake Natron, Tanzania. The lake is in the centre of an endorheic (limited drainage) basin and has shallow, saline-alkaline waters. Its remote location and the absence of nearby large anthropogenic sources suggest that the observed NH3 is mainly of natural origin. Here we explore 10 years of IASI NH3 satellite data and other publicly available datasets over the area to characterize the natural NH3 emissions in this unique ecosystem. Temporal analysis reveals that the emissions are episodic and linked with the lake's surface area. The largest NH3 column loadings generally occur at the end of the dry season in September-November over Lake Natron's largest mudflat, that is exposed with receding water levels. The timing is different from the agricultural dominated NH3 emissions in the wider Natron area, which peak early in the year, after the first wet season. The likely source of NH3 at Lake Natron is decomposition of organic material, either from rivers and springs or produced in the lake (plankton, bird excreta). High temperatures and alkalinity are known to promote NH3 losses from soda lakes. We formulate six processes that may explain why the largest losses are observed specifically over concentrated brines and/or exposed sediments. As a by-product, we also show that hyperspectral infrared sounders such as IASI are capable of mapping different types of evaporative minerals such as trona and thermonatrite.

Using satellite-based measurements to explore spatiotemporal scales and variability of drivers of new particle formation.

New particle formation (NPF) can potentially alter regional climate by increasing aerosol particle (hereafter particle) number concentrations and ultimately cloud condensation nuclei. The large scales on which NPF is manifest indicate potential to use satellite-based (inherently spatially averaged) measurements of atmospheric conditions to diagnose the occurrence of NPF and NPF characteristics. We demonstrate the potential for using satellite-based measurements of insolation (UV), trace gas concentrations (sulfur dioxide (SO2), nitrogen dioxide (NO2), ammonia (NH3), formaldehyde (HCHO), and ozone (O3)), aerosol optical properties (aerosol optical depth (AOD) and Ångström exponent (AE)), and a proxy of biogenic volatile organic compound emissions (leaf area index (LAI) and temperature (T)) as predictors for NPF characteristics: formation rates, growth rates, survival probabilities, and ultrafine particle (UFP) concentrations at five locations across North America. NPF at all sites is most frequent in spring, exhibits a one-day autocorrelation, and is associated with low condensational sink (AOD × AE) and HCHO concentrations, and high UV. However, there are important site-to-site variations in NPF frequency and characteristics, and in which of the predictor variables (particularly gas concentrations) significantly contribute to the explanatory power of regression models built to predict those characteristics. This finding may provide a partial explanation for the reported spatial variability in skill of simple generalized nucleation schemes in reproducing observed NPF. In contrast to more simple proxies developed in prior studies (e.g., based on AOD, AE, SO2, and UV), use of additional predictors (NO2, NH3, HCHO, LAI, T, and O3) increases the explained temporal variance of UFP concentrations at all sites.

Lysosomal dysfunction causes neurodegeneration in mucolipidosis II 'knock-in' mice.

Mucolipidosis II is a neurometabolic lysosomal trafficking disorder of infancy caused by loss of mannose 6-phosphate targeting signals on lysosomal proteins, leading to lysosomal dysfunction and accumulation of non-degraded material. However, the identity of storage material and mechanisms of neurodegeneration in mucolipidosis II are unknown. We have generated 'knock-in' mice with a common mucolipidosis II patient mutation that show growth retardation, progressive brain atrophy, skeletal abnormalities, elevated lysosomal enzyme activities in serum, lysosomal storage in fibroblasts and brain and premature death, closely mimicking the mucolipidosis II disease in humans. The examination of affected mouse brains at different ages by immunohistochemistry, ultrastructural analysis, immunoblotting and mass spectrometric analyses of glycans and anionic lipids revealed that the expression and proteolytic processing of distinct lysosomal proteins such as α-l-fucosidase, ß-hexosaminidase, α-mannosidase or Niemann-Pick C2 protein are more significantly impacted by the loss of mannose 6-phosphate residues than enzymes reaching lysosomes independently of this targeting mechanism. As a consequence, fucosylated N-glycans, GM2 and GM3 gangliosides, cholesterol and bis(monoacylglycero)phosphate accumulate progressively in the brain of mucolipidosis II mice. Prominent astrogliosis and the accumulation of organelles and storage material in focally swollen axons were observed in the cerebellum and were accompanied by a loss of Purkinje cells. Moreover, an increased neuronal level of the microtubule-associated protein 1 light chain 3 and the formation of p62-positive neuronal aggregates indicate an impairment of constitutive autophagy in the mucolipidosis II brain. Our findings demonstrate the essential role of mannose 6-phosphate for selected lysosomal proteins to maintain the capability for degradation of sequestered components in lysosomes and autophagolysosomes and prevent neurodegeneration. These lysosomal proteins might be a potential target for a valid therapeutic approach for mucolipidosis II disease.

The use of contextual learning to teach biochemistry to dietetic students.

This article describes the use of contextualized and "blended" learning to teach biochemistry to dietetic students during the second year of their professional training in a 4-year undergraduate degree (Bachelor of Nutrition and Dietetics). Contextualized content was used to engage students and motivate them to learn biochemistry, which many perceived as a "hard" subject. Contextualized learning presented via problem solving exercises, case-studies, and by the use of virtual subjects in laboratory class introduced content material through real life situations highly relevant to their later clinical practice. A "blended" curriculum where content was presented in a number of different modalities (on-line, on CD, or face-to-face in small/large groups and in tutorials/lectures/laboratory class) further enhanced contextualized learning by providing a range of learning modalities catering to different student learning styles. The on-line and CD material also allowed student self-assessment of learning progress through interactive quizzes in varied assessment formats, where feedback was often immediate. Student responses to this biochemistry course have been positive with 89% finding it intellectually stimulating.

Partial characterization of matrix components interacting with cartilage proteoglycans.

The charge content of aqueous suspensions of milled cartilage samples was determined by a colloid titration technique using a particle charge detector, and the data were compared with estimates from chemical analyses. Results indicated a close correlation between charge content determined by titration and that estimated by chemical analyses for samples of nasal septa only (a nonarticular cartilage). Such correlation did not hold for articular cartilages (metacarpalphalangeal joint and patella); extraction of these tissues with 0.1 or 1.2 M NaCl markedly increased the availability of the negative groups. Protein analysis, by SDS--PAGE, of the 1.2 M extracts indicated the presence of basic proteins, some of collagenous origin, such as chondrocalcin and proline-arginine-rich protein, and some of noncollagenous proteins such as pleiotrophin and histone-H2b. These data thus suggest electrostatic interactions between these basic proteins and the negative groups of proteoglycans. Such interactions would have an important effect on the osmotic properties and in the organization of cartilage.

Dependence of salt concentration on glycosaminoglycan-lysozyme interactions in cartilage.

The cationic protein, lysozyme, has an extracellular distribution in cartilage but its precise role in this tissue has not yet been established. This study describes the dependence of salt concentration on the binding properties of lysozyme isoforms of different cationic charges, isolated from bovine cartilage, to the two major and structurally similar glycosaminoglycans of cartilage, i.e., chondroitin sulfate and hyaluronan. The binding of most cartilage lysozyme isoforms and hen egg-white lysozyme (control) to chondroitin sulfate and hyaluronan linked to agarose supports displayed optimal levels at approximately 20 and 5-10 mM salt, respectively, but decreased at both lower and higher salt concentrations indicating the electrostatic nature of the interactions. However, optimal binding of the most cationic lysozyme isoform to chondroitin sulfate occurred at 60 mM salt, with significant binding remaining at 150 mM. This isoform also showed binding to hyaluronan up to 60 mM salt, while for the other isoforms binding was observed only up to 150 and 40 mM salt for chondroitin sulfate and hyaluronan, respectively. The low salt concentrations at which these interactions occur are likely to exist in cartilage as shown from equilibrium dialysis studies performed using solutions of chondroitin sulfate (up to 10%, a concentration likely to occur in cartilage). From Scatchard analysis, the affinity of binding of all lysozymes to chondroitin sulfate was similar (Kd = 10(-6) M) and slightly lower than their binding to hyaluronan (Kd = 10(-7) M) of similar molecular mass.

Temporal changes in charge content of cultured chondrocytes from bovine cartilaginous tissues.

The effective charge content of the pericellular matrix of chondrocytes has been determined while the matrix is being synthesized by cells grown in culture for several weeks. The data were compared with estimates determined by chemical analysis. When measurements were performed after digestion of the matrix with papain, there was close agreement between results obtained from both techniques for proteoglycans synthesized by chondrocytes from nasal septum (a non-articular cartilage). By contrast, no such agreement was observed for proteoglycans synthesized by chondrocytes from articular cartilage, even after solubilization of the matrix with papain. While the charge calculated from chemical analysis showed a constant increase with time in culture, that measured by colloid titration showed a cyclical pattern, with maximal values occurring on days 7 and 24 of culture and a minimal value on day 14. This inability to detect all negative groups present in the matrix synthesized by articular chondrocytes would suggest the involvement of these groups in electrostatic interactions. Partial characterization of proteins synthesized by the pericellular matrix indicates that the decrease in charge content observed on day 14 could not be attributed to proteins of a particular molecular mass but possibly to an increase in the total amount of protein present. It is concluded that the marked difference in the availability of negative groups between chondrocytes cultured from articular and non-articular cartilages may reflect differences in the interaction of these negative groups with matrix components; these differences would lead to the distinct structural organization of these two cartilaginous tissues which possess different mechanical functions.

Purification, characterization, and biosynthesis of bovine cartilage lysozyme isoforms.

The cationic protein, lysozyme, has an extracellular distribution in cartilage; however, its biological role in this tissue still remains unclear. This study describes a simple and high yielding procedure for the purification of four novel isoforms of lysozyme from the functionally different articular (metacarpalphalangeal joint) and nonarticular (nasal septum) bovine cartilages. Chromatography of the cartilage extracts on S-Sepharose revealed the presence of four major lysozyme active peaks each of which was further purified to homogeneity by gel filtration and reversed-phase chromatography. Each peak yielded a different molecular mass when analyzed by ion spray mass spectrometry, and material isolated from either cartilage source displayed an identical molecular mass for each lysozyme preparation. N-terminal amino acid sequence and amino acid composition analyses confirmed the presence of four novel lysozyme isoforms in both bovine articular and nonarticular cartilages. The lytic activity of each lysozyme isoform toward Micrococcus lysodeikticus was dependent on both the ionic strength and pH of the buffer, where an increase in activity accompanied an increase in ionic strength. The lysozymes were shown to be synthesized by chondrocytes in vitro, which in addition to the relatively high chemical amounts of lysozyme present in cartilage, would suggest that this small cationic protein has some as yet undetermined biological role within the cartilage extracellular matrix.

Determination of the charge content at the surface of cells using a colloid titration technique.

A colloid titration technique has been used to estimate the surface charge content of three distinct cell types of differing surface charge characteristics, i.e., human red blood cells, the surface of which is studded with sialic acid residues, endothelial cells which are surrounded by a thick glycocalyx, and chondrocytes which, when grown at high cell density for several weeks, synthesize a dense pericellular matrix similar to that observed in cartilaginous tissues. Estimates of the charge content obtained for human erythrocyte ghosts and cultured endothelial cells are in good agreement with the charge determined by chemical analyses. On the other hand, the charge at the surface of chondrocytes represented only a fraction of that calculated from measurements of the glycosaminoglycan content (15% by Day 12 in culture); close correlation between charge and chemical amount could be obtained only after digestion of the cell layer with collagenase and papain indicating the possible electrostatic involvement of the negative groups of the glycosaminoglycan chains with basic proteins. Thus, the colloid titration technique may provide a simple and sensitive tool to study the interactions occurring between the extracellular matrix components while the matrix is being formed and to establish the chemical nature of the molecules contributing to the cell surface charge.

Binding properties of glycosaminoglycans to lysozyme--effect of salt and molecular weight.

The cationic protein, lysozyme, is present in cartilage but its precise role in this tissue has not yet been established. This study shows that two major and structurally similar glycosaminoglycans (GAGs) of cartilage, i.e., chondroitin sulfate (CS) and hyaluronan (HA) interact with lysozyme at salt concentrations up to 40 mM. Such a low salt concentration is likely to occur in cartilage due to exclusion of microions by the high charge density of the proteoglycans (PGs). The affinity of binding to lysozyme increases with increasing molecular weight of HA and is higher for HA (Kd = 1-2 x 10(-8) M and 0.5-1 x 10(-7) M for HA of relative molecular mass of 4 x 10(5) and 5 x 10(4), respectively) than for CS (Kd = 1 x 10(-6) M). The binding displays optimal levels at around 20 mM but decreases at both lower and higher salt concentrations. This dependence of binding on salt concentration resembles that of the enzymic activity of lysozyme for its natural substrate, murein, which is structurally similar to HA/CS. The increase in binding up to 20 mM salt is characteristic for HA/CS-lysozyme interaction as such an effect was not observed in the interaction of heparin with lysozyme or of GAGs with serum albumin. Binding of HA to lysozyme was inhibited by various polyanions but not by uncharged macromolecules, indicating the electrostatic nature of the interaction. The dependence of binding on salt concentration obtained in systems where lysozyme is linked to an agarose support and the GAG is free in solution is similar to that determined when both macromolecules are free in solution; however, the number of GAG disaccharides bound per mole lysozyme increases significantly in the latter system, indicating a marked artifactual steric hindrance effect in the former.

Recent progress in cholera vaccination.

Cholera disease remains an important cause of morbidity and mortality in the third world. The parenteral cholera vaccine actually used offers only a 50% protection during 6 months. As Vibrio cholerae and its toxin don't cross the gut wall, the aim of new vaccines is to prevent the colonization and growth of the vibrio in the jejuno-ileum and to inhibit the fixation of cholera toxin (CT) on its enterocyte membrane receptor. This can be afforded by stimulation of the gut local immune system mainly represented by secretory IgA antibodies (Abs). New vaccines should comprise both bacterial and CT antigens and must be given by the oral route to induce the production of specific secretory IgA Abs in the gut. Four different ways are actually under study to produce an oral cholera vaccine. 1. Combination of CT-B subunit and killed vibrios. 2. Live recombinant Vibrio cholerae in which the CT coding gene has been deleted. 3. Synthetic peptides reproducing some immunodominant CT-epitopes. 4. Manipulation of the idiotypic network to induce the production of Abs mimicking CT-epitopes. This paper reviews the actual developments and advantages of these four approaches.

The measurement of negative charge content in cartilage using a colloid titration technique.

A colloid titration technique has been used to determine the sulfate and carboxylate content of various glycosaminoglycans and has been validated by comparing the results with data obtained using well-established techniques. The method has been applied to the measurement of the negative charge content of cartilage slices at various depths from the articular surface and to the determination of sulfate and carboxylate contents in bovine nasal septa. Titrations of nasal septa were performed on milled cartilage, on cartilage digested with papain and on proteoglycans purified by cesium chloride gradient centrifugation of guanidinium chloride extracts. The sulfate content was similar for all three preparations (0.5 mu eq per milligram dry cartilage). However, the carboxylate content determined on milled cartilage was 40% higher than that obtained for cartilage digested with papain or for purified proteoglycans; this implies the possible contribution of carboxyl groups from structural glycoproteins present in the extracellular matrix. The carboxylate content determined on purified proteoglycans was in excellent agreement with values calculated from chemical analyses.

Oral immunization against cholera toxin with a live Yersinia enterocolitica carrier in mice.

The 70-kb pYV plasmid of Yersinia enterocolitica directs the synthesis and secretion of several virulence determinants called Yops. These proteins are produced during the invasion of the host tissues and induce a strong antibody response. The yop genes are transcribed from strong promoters activated by a common transcription activator. Recombinant Y. enterocolitica strains expressing the B subunit of the cholera toxin were constructed from a yopH-ctxB operon fusion. Integration of the gene ctxB in the pYV plasmid itself, by a double crossing over, ensured its stability in the infecting bacteria. Oral inoculation of recombinant bacteria in mice elicited serum and intestinal antibody responses and resulted in protection of the immunized mice against a cholera toxin challenge. Secretory immunoglobulin A antibodies against the cholera toxin B subunit occurred not only in the intestines but also in the respiratory tract.

Binding of hyaluronan to lysozyme at various pHs and salt concentrations.

Binding of hyaluronan (HA) to lysozyme immobilized on Sepharose-6B was investigated as a function of pH and NaCl concentration. High affinity binding (Kd = 1.0-2.0 x 10(-8) M) was observed at pH 7.5 and at 10-50 mM NaCl; the number of moles of HA bound to lysozyme was twice as high at 30 mM NaCl as at 10 mM. No specific binding was observed at and above 100 mM NaCl. Binding was suppressed in the presence of chaotropic agents such as guanidinium chloride and urea. These results suggest that binding between HA and lysozyme can occur in the extracellular matrix where an electrolyte concentration as low as 50 mM could be expected due to ionic exclusion by the highly negative charge concentration arising from the polyanions present.

Fluorescence study of a field-induced director reorientation in a liquid crystalline polyacrylate.

The electric field-induced director reorientation is investigated by fluorescence spectroscopy and turbidimetry. The dynamics of this reorientation are studied as a function of temperature, applied voltage, and frequency.

Fluorescence study of field-induced director reorientations in low mass liquid crystalline compounds.

The Frederickz transition and the dynamic scattering deformation in 4-alkyloxy-4'-cyanobiphenyl compounds are investigated by fluorescence spectroscopy and turbidimetry. The main characteristics of the Frederickz deformation, reversibility and threshold voltage, in the nematic and the smectic A phase are investigated by means of fluorescence spectroscopy. Furthermore, the dynamics of the Frederickz transition are studied as a function of temperature and applied voltage. The results obtained with both techniques are compared and correlate well.

SR 33557, a novel calcium entry blocker. I. In vitro isolated tissue studies.

The effects of SR 33557 on isolated cardiovascular preparations were compared to those of nifedipine, verapamil and diltiazem. In rat aortic strips, SR 33557, like nifedipine, verapamil and diltiazem, caused a significant and simultaneous inhibition of potassium-induced 45Ca++ influx and contractile responses (nifedipine greater than SR 33557 greater than verapamil greater than diltiazem). SR 33557 also antagonized Ca(++)-induced contractions in K(+)-depolarized aorta preparations (pA2:9.08 +/- 0.03) and is the first calcium channel antagonist, structurally not related to 1,4-dihydropyridines, to inhibit competitively contractions induced by BAY K8644. In spike-generating vascular smooth muscle (rat portal vein), contractures evoked by noradrenaline (4 microM) or KCl (100 mM) were reduced by all four antagonists, the pharmacological potency being nifedipine greater than SR 33557 greater than verapamil greater than diltiazem. Unlike SR 33557, nifedipine, verapamil and diltiazem showed a parallel enhancement of frequency of spontaneous contractions in rat portal vein in spite of a concentration-related reduction in amplitude. By using rabbit atrial preparations, spontaneous right atrial rate and electrically stimulated (120/min) basal contractions of left atria were used as indices of chronotropy and inotropy. The potency series for negative chronotropic effects was nifedipine greater than SR 33557 greater than verapamil greater than diltiazem. For negative inotropic effects the potency order was verapamil greater than nifedipine greater than SR 33557 greater than diltiazem, respectively. Thus, SR 33557 should depress heart rate to a greater extent than ventricular contractility. These results suggest that SR 33557 is a potent calcium entry blocker that (unlike verapamil and diltiazem) is particularly selective for vascular smooth muscle and devoid of any potent negative inotropic actions.

Evaluation of nonideality from gel chromatographic partition coefficients. A technique with greater versatility than equilibrium dialysis.

Frontal gel chromatography has been used to measure partition coefficients which enable a quantitative evaluation of the thermodynamic nonideality of small solutes generated by the presence of high concentrations of macromolecular solutes. Equivalence of results obtained by the present method and by equilibrium dialysis is demonstrated in a comparison of results for dextran sulfate-NaCl and dextran-sorbitol systems. Interaction coefficients obtained for dextran-sorbitol and protein-polyethylene glycol 4000 systems yields results which are in reasonable agreement with those predicted on the statistical-mechanical basis of excluded volume. Because of its greater versatility in regard to the range of systems that may be studied, the frontal gel chromatographic procedure is likely to be of particular value for the quantitative characterization of thermodynamic nonideality arising from excluded volume effects in concentrated mixtures of macromolecular solutes.

[Diagnostic studies in carbon monoxide poisoning]. / Le dépistage de l'intoxication au monoxyde de carbone.

Origin, symptomatology, seriousness and mechanism of carbon monoxide toxicity have been reviewed as are the diagnosis based on clinical or analytical data upon which the physician may rely to search out a CO intoxication. Treatments are discussed and the best therapy is proposed in case of mild or severe poisonings.