Madhumita J. Mukhopadhyay

Manganese in cell metabolism of higher plants

Manganese, a group VII element of the periodic table, plays an important role in biological systems and exists in a variety of oxidation states. The normal level of Mn in air surrounding major industrial sites is 0.03 μg/m3, in drinking water 0.05 mg/liter and in soil between 560 and 850 ppm.Manganese is an essential trace element for higher plant systems. It is absorbed mainly as divalent Mn2+, which competes effectively with Mg2+ and strongly depresses its rate of uptake. The accumulation of Mn particularly takes place in peripheral cells of the leaf petiole, petiolule and palisade and spongy parenchyma cells.Mn is involved in photosynthesis and activation of different enzyme systems. Mn deficiency may be expressed as inhibition of cell elongation and yield decrease.Mn toxicity is one of the important growth limiting factors in acid soils. Plant tops are affected to a greater extent than root systems. The toxicity symptoms are, in general, similar to the deficiency symptoms.Toxic effects of Mn on plant growth have been attributed to several physiological and biochemical pathways, although the detailed mechanism is still not very clear. Higher O2 uptake and loss of control in Mn activated enzyme systems have been associated with Mn toxicity.Mn interferes with the uptake, transport and use of several essential elements including Ca, Fe, Cu, Al, Si, Mg, K, P and N. Excess of Mn reduces the uptake of certain elements and increases that of others.pH plays an important role in Mn uptake. Acidic pH causes a lack of substantial amount of nitrate as an alternative electron acceptor and leads to a high amount of Mn in leaves. High microbial activity, water logging and poorly structured soils cause severe Mn toxicity even in neutral soils.The molecular mechanism of Mn-tolerance is not yet clear. The level of tolerance is different in different species and seems to be controlled by more than one gene.Further information is required on the factors affecting the distribution, accumulation and membrane permeability of the metal in different plant parts and different species. Understanding of the genetic basis of Mn-tolerance is necessary to improve adaptation of crops against acid soils, water logging and other adverse soil conditions.RésuméLe manganèse, un élément du groupe VII du tableau périodique, joue un rôle important au niveau des systèmes biologiques et existe sous différents états d’oxydation. Le niveau normal du manganèse dans l’air au voisinage de parcs industriels est de 0.03 μg/m3, de 0.05 mg/litre dans l’eau potable et entre 560 et 850 ppm dans le sol.Le manganèse est un oligoélément essentiel pour les plantes supérieures. Il est surtout absorbé sous la forme bivalente Mn2+ qui entre efficacement en compétition avec l’ion Mn2+ et réduit substantiellement son taux d’absorption. L’accumulation du Mn a particulièrement lieu dans les cellules périphériques du pétiole, dans le pétiolule et les cellules du parenchyme palissadique et aérifère.Le Mn est impliqué dans la photosynthèse et active aussi différents systèmes enzymatiques. Une déficience en Mn peut inhiber l’élongation des cellules et diminuer la croissance.La toxicité du Mn est un des principaux facteurs réduisant la croissance en sol acide. Les parties aériennes des plantes sont beaucoup plus affectées que le système racinaire. Les symptômes de toxicité sont habituellement similaires à ceux d’une déficience.Les effets toxiques du Mn sur la croissance des plantes interviennent dans plusieurs sentiers physiologiques et biochimiques, quoique les mécanismes ne soient pas encore connus de façon détaillée. Une assimilation plus élevée de l’oxygène ainsi qu’un dérèglement des systèmes enzymatiques dépendant du Mn ont été associés à la toxicité due à ce métal.Le Mn perturbe l’absorption, le transport et l’utilisation de divers éléments essentiels, notamment le Ca, Fe, Cu, Al, Si, Mg, K, P et N. Un excès de Mn réduit l’apport de certains éléments et augmente celui d’autres éléments.Le pH joue un rôle important dans l’absorption du Mn. Dans le cas d’un pH acide, il n’y a pas assez de nitrate agissant comme accepteur alternatif d’électrons, de sorte qu’une grande quantité de Mn se retrouve dans les feuilles. Une grande activité microbienne, la présence d’eau stagnante et un sol insuffisamment développé augmentent considérablement la toxicité, même en sol neutre.Les mécanismes moléculaires de la tolérance au Mn demeurent obscurs. Le seuil de tolérance varie d’une espèce à l’autre et semble être sous le contrôle de plus d’un gène.Des données additionnelles sont requises concernant les facteurs influençant la distribution, l’accumulation de ce métal et la perméabilité membranaire dans diverses parties des plantes chez différentes espèces. Une meilleure connaissance des bases génétiques de la tolérance au Mn est nécessaire pour améliorer l’adaptation des plantes à l’acidité des sols, à la présence d’eau stagnante ainsi qu’à des conditions adverses des sols.

Genotoxicity of Sennosides on the Bone Marrow Cells of Mice

Preparations of a number of plants which contain hydroxyanthraquinones as active constituents are used worldwide for their laxative effect. Anthraquinone glycosides of Cassia angustifolia and C. fistula were investigated for their ability to induce a clastogenic effect on the bone marrow cells of Swiss albino mice. The endpoints screened were chromosomal aberrations and frequency of aberrant cells. Oral exposure to doses of these anthraquinones and their equivalent amount in leaf and pod extracts did not induce significant numbers of chromosomal aberrations or aberrant cells. The results indicate that anthraquinone sennoside B and rhein are weakly genotoxic.

In vivo cytogenetic studies on blends of aspartame and acesulfame-K

Aspartame and acesulfame-K, non-nutritive sweeteners, are permitted individually in diets and beverages. These sweeteners of different classes, used in combination, have been found to possess a synergistic sweetening effect. Whether they also have a synergistic genotoxic effect is unknown. Swiss Albino male mice were exposed to blends of aspartame (3.5, 35, 350mg/kg body weight) and acesulfame-K (1.5, 15 and 150mg/kg body weight) by gavage. Bone marrow cells isolated from femora were analysed for chromosome aberrations. Statistical analysis of the results show that aspartame in combination with acesulfame-K is not significantly genotoxic.

Studies on the anticlastogenic effect of turmeric and curcumin on cyclophosphamide and mitomycin C in vivo.

Turmeric and its main constituent curcumin were assessed in vivo for their anticlastogenic potential. In one experimental set, Swiss albino male mice were given turmeric (8, 12 and 16 mg/kg body weight) or curcumin (2, 4 and 8 mg/kg body weight) as a single intraperitoneal injection. In another set, the mice were given 8 mg/kg body weight of turmeric or one of three concentrations of curcumin (2, 4 and 8 mg/kg body weight) as a dietary supplement by gavage for 7 consecutive days. 30 min after the last dose the mice were administered a single acute dose of two known clastogens, cyclophosphamide (CP) (20 mg/kg body weight) or mitomycin C (MMC) (1.5 mg/kg body weight). After 18 hr, chromosome preparations were made from bone marrow cells. The endpoints studied were chromosome aberrations and damaged cells. Clastogenicity of the chemicals was compared using turmeric- or curcumin-primed and non-primed animals. As single agents turmeric and curcumin were not clastogenic even after 7 days of priming. Turmeric/curcumin could not inhibit CP- or MMC-induced clastogenicity. Although curcumin is reported to be the active chemopreventive principle in turmeric effective against a number of potential carcinogens in several experimental systems, it was virtually ineffective against the clastogenicity of CP or MMC at the doses tested.

In vitro propagation of Iphigenia indica, an alternative source of colchicine

The present study involves in vitro propagation of Iphigenia indica (Kunth.) through multiplication of whole corms and corm buds. The whole corms produced very small micro-corms, which developed plants individually whereas corm buds multiplied to produce numerous shoots at variable rates in presence of α-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP). The best response in corm and bud multiplication was obtained in Murashige and Skoogs basal medium (MS) supplemented with 2.69 μM NAA and 8.88 μM BAP. The shoots regenerated were further cultured on MS medium containing NAA and indole-3-butyric acid (IBA) for initiation of roots. MS medium with 5.38 μM NAA and 4.92 μM IBA induced highest percentage of roots (81%) within 2 weeks in culture.

In Vitro Clonal Propagation Through Bud Culture of Hemidesmus indicus (L) R Br: An Important Medicinal Herb

The present study involves in vitro propagation of Hemidesmus indicus (L) R Br through bud multiplication and subsequent plant regeneration. The buds multiplied to produce numerous shoots at variable rates in presence of a-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP) as well as NAA and kinetin. The best response in bud multiplication was obtained in Murashige and Skoog’s (MS) basal medium supplemented with 0.1 mg I-1 NAA and 2.0 mg I-1 BAP (7-8 shoots per explant) and the bud break time was only 4 days after inoculation. The multiplication rate was low when the buds were cultured in NAA and kinetin media and the shootlets regenerated were very thin, weak and elongated. The shoots regenerated were further cultured on MS and half strength MS basal media with variable levels of indole-3-butyric acid (IBA) for initiation of roots. Culture of shootlets for 34 weeks in one half strength of MS medium followed by culturing in the same medium with 1.5 mg 1-1 IBA induced highest production of roots (3-5 roots per shoot) within 2 weeks. Chromosome number stability with no detectable structural changes was observed in the regenerates. The rooted plants were successfully established in the soil with 85% survival rate.

Comparison of different plants in screening for Mn clastogenicity.

Cationic (MnSO4.H2O) and anionic (KMnO4) manganese salts in aqueous solutions enhanced the frequency of chromosomal aberrations including both chromosome- and chromatid-type breaks, gaps, translocations and spindle disturbances in different plant systems in vivo to a statistically significant level. The activity of the cationic salt was more drastic, particularly on the submerged plant studied (Vallisneria spiralis L.), on prolonged exposure, when compared with bulbs of Allium cepa L. and seeds of Pisum sativum L.

Clastogenic effect of ginger rhizome in mice.

The present study focuses on the clastogenic effect of ginger rhizome. Crude aqueous extracts of ginger were gavaged at doses of 0.5, 1, 2, 5, 10 g/kg body weight and ginger oil (0.625, 1.250 and 2.50 ml/kg body weight) was administered by intraperitoneal injection to male mice. Chromosome damage was studied in a preparation made from bone marrow cells following colchicine injection to all mice and examination of the cells after pretreatment in hypotonic solution, fixation, air drying and staining in Giemsa solution. Attention is drawn to the weakness of the clastogenic activity expressed by the ginger extract. In comparison ginger oil gave a higher frequency of chromosomal aberrations. It is suggested therefore, that the extract may contain substance(s) that suppress clastogenesis in the bone marrow cells of mice. Copyright

Genome analysis of species of Calathea utilizing chromosomal and nuclear DNA parameters

The species of Calathea of Marantaceae under Scitaminaceae are economically important as ornamental foliage plants. These are native of South America and distributed throughout the tropics. The plants are tuberous or rhizomatous and propagate mostly by vegetative means. In the present study, an attempt has been made to evaluate the genomic diversity of four different species of Calathea in relation to morphological and cytological characteristics as well as 4C nuclear DNA contents at the inter- and intra-specific levels. Differences were observed in morphological characters including petiole length, leaf area and ornamentation. These characters may serve as identifying parameters of individual species. Chromosome analysis has indicated the somatic chromosome number to range from 2n = 24 to 2n = 28 among these species. The species or varieties of Calathea having the same chromosome number differed in relation to chromosome types and number of chromosomes of individual type. The 4C nuclear DNA contents did not vary much and there was no direct correlation with the ploidy status of these species of Calathea. A variation was recorded among these species in total chromosome length. The chromosome length and volume also did not reveal any direct correlation with chromosome number, instead a consistency in difference of these two characters was noted. Differential coiling of the arm and the ratios of different protein components (histone and non-histone) in chromosome organization have been suggested to be responsible for such differences in chromosome length and volume respectively. It is suggested that cryptic structural alteration in chromosomes has played a role in speciation of this genus.

Inhibition of clastogenic effect of cyclophosphamide and mitomycin C by neem leaf-extract in mice

Azadirachta indica commonly known as ‘Neem’ is well known for its medicinal properties in the indigenous Indian system of medicine. Almost every part of the tree has some beneficial use. The anticlastogenic activity of ‘Neem’ against cyclophosphamide (CP) and mitomycin C (MMC) was studied in vivo in bone marrow cells of mice. Aqueous leaf‐extracts of A. indica were injected intraperitoneally at doses 3, 6, 12 and 24 mg/kg body weight. Simultaneously, two known clastogens CP (10 mg/kg) and MMC (1.5 mg/kg) were administered individually to animals treated with 6 and 12 mg/kg of the leaf‐extract. The end‐points screened were chromosomal aberrations and damaged (aberrant) cells. Neem leaf‐extract per se was found to be a weak clastogen; 6 and 12 mg/kg of the leaf‐extract inhibited the clastogenicity of CP and MMC. The extent of inhibition was different for the two clastogens. An ANOVA test showed that the reduction in the frequency of chromosomal aberrations was significantly less when the leaf‐extract was given in combination with CP. MMC co‐administered with the leaf‐extract showed a trend that was not statistically significant. The difference may be attributed to the degree of modulation of bioactivation of cytochrome P‐450 enzymes, or the repair of damaged DNA or a difference in detoxification of the reactive species of the two genotoxicants.