Ion interaction reagent reversed-phase high-performance liquid chromatography determination of anti-tuberculosis drugs and metabolites in biological fluids

New methods of ion interaction reagent (IIR) RP-HPLC are presented for the determination of anti-tuberculosis drugs and their metabolites, singly or in multi-component mixtures, in biological fluids. The following analytes are considered: isoniazid, ethionamide, pyrazinamide, morphazinamide, p-aminosalicylic acid, nicotinic and isonicotinic acids. Aqueous solutions of three different ion interaction reagents are alternatively or comparatively used as the mobile phases, namely: (A) 5.00 mM octylamine at pH 3.00 for o-phosphoric acid, (B) 5.00 mM octylamine at pH 8.00 for o-phosphoric acid, and (C) 5.00 mM 1,6 diaminohexane at pH 6.00 for o-phosphoric acid. The response linearity between peak area and analyte concentration is verified for all the analytes in the concentration range within the determination limits and 2.00 mg/l. Detection limits are always lower than 82 μg/l for standard solutions; in the analysis of samples of rat serum, rat plasma and human serum, the matrix effect is negligible, the detection limits are always lower than 94 μg/l and the average recovery yield is always greater than 96%.     

The effects of tin (Sn) additions on the growth of spinach plants

An increase in bioavailable tin in the environment could result in bioaccumulation thereof in agricultural crops, and therefore, have adverse health consequences on humans that eat these crops. The aims of the current study were thus to assess the uptake of Sn by spinach plants, and the subsequent effects this will have on the uptake of Na, Zn, K, Ca, and Mg as well as the growth of spinach plants. Spinach plants were grown in sand culture and received tin at concentrations of 0.02, 0.2, 2 and 20 mg/L along with a nutrient solution. The uptake of tin at detectible concentrations only occurred at the highest concentrations (2 and 20 mg/L), and it was mostly retained in the roots of the plants. Tin additions also resulted in no visual toxicity symptoms, and might be beneficial to biomass production. Further field trials are needed to ensure that these experimental results remain true under field conditions.     

Trp-999 of beta-galactosidase (Escherichia coli) is a key residue for binding,catalysis, and synthesis of allolactose,the natural lac operon inducer

Trp-999 is a key residue for the action of beta-galactosidases (Escherichia coli). Several site specific substitutions (Phe, Gly, Tyr, Leu) for Trp-999 were made. Each substitution caused greatly decreased affinities for substrates and inhibitors that bind in the "shallow" mode, while the affinities of inhibitors that bind in the "deep" mode were not decreased nearly as much. This shows that Trp-999 is important for binding in the shallow mode. The residue is also very important for binding glucose to galactosyl-beta-galactosidase (as a transgalactosidic acceptor). Substitution greatly diminished the affinity for glucose. Substitutions also changed the activation thermodynamics and, subsequently, the rates of the catalytic reactions. The enthalpies of activation of the glycolytic bond cleavage step (galactosylation, k(2)) became less favorable while the entropies of activation of that step became more favorable as a result of the substitutions. Differing magnitudes of these enthalpic and entropic effects with ONPG as compared to PNPG caused the k(2) values for ONPG to decrease but to increase for PNPG. The enthalpies of activation for the common hydrolytic step (degalactosylation, k(3)) increased while the entropies of activation for this step did not change much. As a result, k(3) became small and rate determining for each substituted enzyme. The substitutions caused the rate constant (k(4)) of the transgalactosidic acceptor reactions with glucose (for the formation of allolactose) to become much larger and of the same order of magnitude as the normally large rate constants for transgalactosidic acceptor reactions with small alcohols. This is probably because glucose can approach with less restriction in the absence of Trp-999. However, since glucose binds very poorly to the galactosyl-beta-galactosidases with substitutions for Trp-999, the proportion of lactose molecules converted to allolactose is small. Thus, Trp-999 is also important for ensuring that an appropriate proportion of lactose is converted to allolactose.     

Role of sulphur availability on cadmium-induced changes of nitrogen and sulphur metabolism in maize (Zea mays L.) leaves

The interactions between sulphur nutrition and Cd exposure were investigated in maize (Zea mays L.) plants. Plants were grown for 12 days in nutrient solution with or without sulphate. Half of the plants of each treatment were then supplied with 100 microM Cd. Leaves were collected 0, 1, 2, 3, 4 and 5 days from the beginning of Cd application and used for chemical analysis and enzyme assays. Cd exposure produced symptoms of toxicity (leaf chlorosis, growth reduction) and induced a noticeable accumulation of non-protein SH compounds. As phytochelatins are glutamate- and cysteine-rich peptides, the effect of cadmium on some enzyme activities involved in N and S metabolism of maize leaves was studied in relation to the plant sulphur supply. In vivo Cd application to S-sufficient plants resulted in a drop of all measured enzyme activities. On the other hand, S-deficient plants showed a decrease in nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2) activity, and an increase in NAD-dependent glutamate dehydrogenase (GDH; EC 1.4.1.2) and phosphoenolpyruvate carboxylase (PEPc; EC 4.1.1.31) activity as a result of the Cd treatment. Furthermore, in the same plants ATP sulphurylase (ATPs; EC 2.7.7.4) and O-acetylserine sulphydrylase (OASs; EC 4.2.99.8) showed a particular pattern as both enzymes exhibited a transient maximum value of activity after 4 days from the beginning of Cd exposure. Results provide evidence that the increase of ATPs, OASs, GDH and PEPc activities, observed exclusively in S-deficient Cd-treated plants, may be part of the defence mechanism based on the production of phytochelatins.     

Correlazione Tra Corredo Cromosomico e Dimensioni Delle Microspore Nella Tassonomia Botanica. Spettro Genetico dei Pollini

Resumé

Corrélation entre le nombre des chromosomes et les dimensions des microscopores dans la taxonomie botanique. spectre génétique pollinique.

Le concept de proportion domine dans la nature vivante. L'intéraction du noyau et du cytoplasme détermine sur le volume de ce dernier et en conséquence sur la cellule à l'état jeune, une régulation des dimensions cellulaires.

Non seulement la forme des divers pollens, mais aussi leurs dimensions (en tenant compte des fluctuation possibles), constituent des caractères qui peuvent avoir une importance taxonomique, tant par eux memes que par le fait d'etre mis en rapport avec les nombres des chromosomes.

On a déjà constaté que le numéro diploïde 24 est le plus fréquent, soit dans le règne animal que dans le régne végétal et que les numéros diploïdes compris entre 12 et 32 sont plus fréquents dans les plantes, que les autres numéros. Corrélativement l'A. a constaté que le diamètre équatorial le plus fréquent dans les pollens est celui de 23–25 microns; suivent, avec des fréquences décroissantes, les mesures 16–14–18–32–12 etc. microns.

De même, tandis que les numéros diploïdes éleves (2a = 100–200) sont très rares dans les plantes, les espéces avec des pollens à grains volumineux sont elles aussi en nombre très réduit.

Parmi les Convolvulacées, au nombre chromosomique diploïde 2n = 14 de Cuscuta europaea correspondent des microspores de 18–25 μ à 2n = 50 de Convolvulus arvensis, microspores de 50–70 μ, tandis que les Ipomées ayant un nombre élevé de chromosomes (2n = 60, 2n = 90 ca.) ont des grains de pollen d'un diamètre de 150–210 microns. Parmi les Nyctaginacées, le genre Bougainvillea (2n=20) a des pollens de petites dimensions dont le diamètre equatorial est de 30–40 microns, tandis que le genre Mirabilis (2n = 58) a des graines de pollens de grandes dimensions, de 160–226 microns de diamètre.

Bien d'autres exemples de corrélation semblables, appartenant à plusieurs genres et families de plantes, peuvent être cités, sur la base de l'examen des pollens de plus de 1000 espèces.

Si des espèces de proche parenté et semblables au point de vue de la taxonomie, diffèrent entre elles par le nombre des chromosomes respectifs, elles diffèrent aussi quant aux dimensions des pollens.

Le cardinal diamétrique equatorial des grains de pollens des espèces vraisemblablement élémentaires et de leurs variétés est souvent très proche du cardinal chromosomique diploïde des entités respectives; il est quelquefois un des ses multiples, très rarement un sous-multiple.

Tandis que la proportionalité entre les dimensions des grains de pollen et le nombre des chromosomes est fréquente dans les espèce élémentaires, elle nè se rencontre pas dans beaucoup d'autre cas, à cause de l'interférence de la polyploïdie. Dans les Cucurbitacées, aux pollens avec grains de 20 et 22 μ (Bryonia dioica, Momordica charantia) correspondent 2n = 20 et 2n = 22 respectivement; tandis que dans les espèces à gros grains de pollens (Cucurbita pepo: 170 μ; Cucumis sativus: 72–76 μ) ont a trouvé jusqu'à present: 2n = 40,42 (80) et 2n = 14,28 respectivement.

Une des manifestations de la polyploïdie, est la présence dans les pollens de macro-grains, de grains abortifs, de sillons et de pores aberrants, en somme de grains atypiques par leur forme et parfois aussi par leur coleur, présence qui, outre à indiquer l'origine hybride, peut, dans certains cas, inciter à faire des recherches sur les parents supposés et à tirer un plus grand parti de ces caractères.

Dans bien de cas il est possible de dessiner les spectre des pourcentages selon lesquels les différentes entités on concouru à la constituion de la variété ou de la cultivar.

L'A. propose d'appeler un tel diagramme: spectre génétique pollinique. [Agrave] le définir concourent aussi bien les différences morphologiques et microchimiques, que le pourcentage des grains physiologiquement inactifs (abortifs).

La biométrie est très utile dans l'interprétation des préparations microscopiques hétérogènes des allopolyploïdes.     

LAITOR - Literature Assistant for Identification of Terms co-Occurrences and Relationships

Background  

Biological knowledge is represented in scientific literature that often describes the function of genes/proteins (bioentities) in terms of their interactions (biointeractions). Such bioentities are often related to biological concepts of interest that are specific of a determined research field. Therefore, the study of the current literature about a selected topic deposited in public databases, facilitates the generation of novel hypotheses associating a set of bioentities to a common context.     

Perception of pungent odorants alone and in binary mixtures

The present investigation explores the stimulus–response(psychophysical) functions for total nasal perceived intensityfor two pungent odorants, formaldehyde and ammonia, presentedeither alone or with different backgrounds of the other irritant.Stimuli were comprised of four formaldehyde concentrations (1.0,3.5, 6.9 and 16.7 p.p.m.); four ammonia concentrations (210,776, 1172 and 1716 p.p.m.); and their 16 binary mixtures. Ammoniafunctions showed a consistent upward concavity. At low, mediumand high concentrations, the total perceived intensity of themixtures showed hypoadditivity, simple additivity and hyperadditivity,respectively. That is, the intensity of the corresponding mixtureswas significantly lower than, equal to, or greater than thesum of its components. The progressive involvement of pungency,aroused by common chemical sense stimulation, may be responsiblefor the increasing additivity observed. Simple additivity, andeven hyperadditivity, may characterize mixtures involving commonchemical stimulation.     

Interactions in caffeine-sucrose and coffee-sucrose mixtures: evidence of taste and flavor suppression

Taste–taste and flavor–taste interactions (suppression)in caffeine–sucrose and coffee–sucrose mixtureswere determined. Similar interactions for both types of mixturesshowed an extended hypoadditivity effect for overall taste orflavor intensity (percentage of suppression about 30–40%).Futhermore, mutual suppression among the components has beendetermined. Firstly, the physical intensity of the suppressivecomponent controls the amount of suppression of the other component.Thus, the suppression of bitterness and coffee flavor qualitiesincrease when sucrose levels increase, and similarly, the suppressionof sweetness increases when caffeine or coffee levels rise.Secondly, the magnitude of suppression depends upon the qualityof the suppressive component. Comparisons of the reciprocalactions were made at similar subjective intensities of the mixture'sconstituents in isolation. The results showed that, at similarperceived intensities, caffeine bitterness or coffee flavorwere suppressed by sucrose but sweetness was not affected bycaffeine or coffee.