De novo in vitro shoot morphogenesis from shoot tip-induced callus cultures of Gymnema sylvestre (Retz.) R. Br. ex Sm

BACKGROUND: Gymnema sylvestre is a medicinal woody perennial vine known for its sweetening properties and antidiabetic therapeutic uses in the modern and traditional medicines. Its over-exploitation for the therapeutic uses and to meet the demand of pharmaceutical industry in raw materials supply for the production of anti-diabetic drugs has led to considerable decline in its natural population. RESULTS: An efficient system of shoot bud sprouting from nodal segment explants and indirect plant regeneration from apical meristem-induced callus cultures of G. sylvestre have been developed on Murashige and Skoog (MS) medium amended with concentrations of cytokinins. Of the three growth regulators tested, N6-benzylaminopurine (BAP) was the most efficient and 2.0 mg L-1 gave the best shoot formation efficiency. This was followed by thidiazuron (TDZ) and kinetin (Kin) but, most of the TDZ-induced micro shoots showed stunted growth. Multiple shoot formation was observed on medium amended with BAP or TDZ at higher concentrations. The produced micro shoots were rooted on half strength MS medium amended with auxins and rooted plantlets acclimatized with 87% survival of the regenerates. CONCLUSIONS: The developed regeneration system can be exploited for genetic transformation studies, particularly when aimed at producing its high yielding cell lines for the anti-diabetic phytochemicals. It also offers opportunities for exploring the expression of totipotency in the anti-diabetic perennial vine.

Larvicidal & emergence inhibitory activities of NeemAzal T/S 1.2 per cent EC against vectors of malaria, filariasis & dengue.

Background & objectives: Vector control, using agents of chemical origin, continues to be practiced in the control of vector borne diseases. However, due to some drawbacks including lack of selectivity, environmental contamination, and emergence and spread of vector resistance, development of natural products for vector control has been a priority in this area. In the present study we evaluated the larvicidal and emergence inhibitory activities of a neem based formulation Neem Azal T/S 1.2 per cent EC against the vectors of malaria, filariasis and dengue. Method: Larvicidal and emergence inhibition (EI) activity of a neem formulation, NeemAzal T/S 1.2 per cent EC, was studied in the laboratory respectively against early 4th and early 3rd instar larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti following standard procedures. Results: Among the three vector species studied, An. stephensi was highly susceptible to NeemAzal T/S as revealed by the LC50 and LC90 values (1.92 and 2.76 ppm). The formulation produced an overall mortality or inhibition of emergence of 90 per cent (EI90, when 3rd instar larvae were treated) at 0.046, 0.208 and 0.866 ppm in An. stephensi, Cx. quinquefasciatus and Ae. aegypti, respectively. The corresponding EI50 values were 0.006, 0.048 and 0.249 ppm. On treatment, NeemAzal T/S induced certain morphogenetic abnormalities, broadly characterized in five types, in larvae, pupae and adults of all the three vector species. The percentage of dead specimens of any stage showing morphogenetic abnormalities was the maximum in Cx. quinquefasciatus (14.4%; n=2113) followed by Ae. aegypti. Interpretation & conclusions: Our results indicated that because of its emergence inhibition activity, NeemAzal T/S 1.2 per cent EC could be a promising candidate for the use in integrated vector management programme and replace chemical insecticides.

The "third eye"-- a new concept of trans-differentiation of pineal gland into median eye in amphibian tadpoles of Bufo melanostictus.

Median third eye was found to develop from transplanted pineal gland of external gill stage tadpoles in the recipient 5 toe stage tadpoles of Bufo melanostictus. Pineal gland along with a bit part of brain tissue of the donor external gill stage tadpole was cut out and transplanted into a pit made between two lateral eyes of 5 toe stage recipient tadpoles. Half of the operated tadpoles were treated with vitamin A (15 IU/ml.) for 15 days. Median "third eye" was found to develop in the both untreated and vitamin A treated tadpoles. However, vitamin A increased the percentage of the development of median eyes. Morphological and histological study revealed that newly transformed median eyes were similar to that of normal functional eyes. A stalk like structure developed which connects the median eye to the brain. The median third eye could not develop when pineal gland of 5 toe stage mature tadpole was transplanted into the tadpole of the same age.

Ammonia differentially suppresses the cAMP chemotaxis of anterior-like cells and prestalk cells in Dictyostelium discoideum.

A drop assay for chemotaxis to cAMP confirms that both anterior-like cells (ALC) and prestalk cells (pst cells) respond to cAMP gradients. We present evidence that the chemotactic response of both ALC and pst cells is suppressed by ammonia, but a higher concentration of ammonia is required to suppress the response in pst cells. ALC show a chemotactic response to cAMP when moving on a substratum of prespore cells in isolated slug posteriors incubated under oxygen. ALC chemotaxis on a prespore cell substratum is suppressed by the same concentration of ammonia that suppresses ALC chemotaxis on the agar substratum in drop assays. Chemotaxis suppression is mediated by the unprotonated (NH3) species of ammonia. The observed suppression, by ammonia, of ALC chemotaxis to cAMP supports our earlier hypothesis that ammonia is the tip-produced suppressor of such chemotaxis. We discuss implications of ammonia sensitivity of pst cells and ALC with regard to the movement and localization of ALC and pst cells in the slug and to the roles played by ALC in fruiting body formation. In addition, we suggest that a progressive decrease in sensitivity to ammonia is an important part of the maturation of ALC into pst cells.

Nitrosomethylurea induced streptomycin resistance in Lycopersicon esculentum Mill.

High frequency of streptomycin resistant variants of Lycopersicon esculentum were isolated on selective shoot regeneration medium supplemented with IAA (0.5 mg/L), zeatin (1.5 mg/L) and streptomycin sulphate (500 mg/L). Nonmutagenized (controls) and NMU treated cotyledons were placed on shoot regeneration medium supplemented with antibiotic streptomycin. Resistant shoots appeared at a high frequency in mutagenized cotyledons, whereas in controls morphogenesis was suppressed, accompanied by bleaching. Shoot regeneration occurred from the nodular tissues developed at the cut ends of cotyledons. Resistant shoots developed into complete plantlets on rooting medium containing selective concentration of antibiotic. Stability of streptomycin resistance was confirmed by leaf assay and reciprocal crosses between streptomycin-resistant and sensitive plants.

Enhancement of polygalacturonase activity during auxin induced para nodulation and endorhizosphere colonization of Azospirillum in rice roots.

Effect of different auxins, namely, 2,4-dichlorophenoxyacetic acid (2,4-D), naphthalene acetic acid (NAA) and indole acetic acid (IAA) and Azospirillum brasilense bioinoculation on the enhancement of polygalacturonase (PG) activity in rice roots during para nodulation and endorhizosphere colonization of Azospirillum was studied under in vitro condition. It was observed that Azospirillum bioinoculation could augment PG activity of rice roots to a lesser extent without any root morphogenesis whereas auxin application together with Azospirillum bioinoculation enhanced PG activity of rice roots to a higher level which resulted in better root morphogenesis (para nodule) and endorhizosphere colonisation of A. brasilense. Among the three auxins tested, 2,4-D, even at lower concentration (0.5 ppm) enhanced the rice root PG activity, root morphogenesis and endorhizosphere colonization of Azospirillum while it was 2.0 ppm with NAA and variable with IAA. It is concluded that there is a positive correlation existing among PG activity, degree of root morphogenesis and endorhizosphere colonization of Azospirillum brasilense in rice roots and the degree of correlation is determined by the chemical composition, concentration and mode of action of the auxin utilised.

Ação da insulina na morfogênese de embrioes de Gallus gallus domesticus / The action of insulin in the morphogenesis of Gallus gallus domesticus embryos

Aspectos concernentes à morfogênese de Gallus gallus domesticus viabilizam estudos relacionados à ação da insulina sobre estruturas e topografia embrionárias. Na temperatura de 37,5ºC, ovos foram incubados por 24 h, injetados com 5 ml de insulina de suínos em 3 concentrações e reincubados por mais 72 h. As características morfológicas de 80 embriões foram avaliadas e, de acordo com a organização apresentada, classificados em 5 níveis de morfogênese. Em 21 embriões submetidos aos testes com a insulina registrou-se dismorfismo generalizado (4o nível), enquanto nos de experimento de controle foi verificado morfogênese-padrão (1o nível) e dismorfismo localizado (3o nível). Aqueles espécimes mostraram corpo com dimensões reduzidas, caracterizado por limites ântero-dorsal organizados em uma projeção cefálica e regiões posterior-ventral alteradas, evidenciando um padrão de anormalidades na determinação do eixo ântero-posterior, que indica a ação específica da insulina na morfogênese embrionária no período de 96 horas de incubação.

Alteration of morphogenetic cell interactions by 1-beta-D-arabinofuranosylcytosine in Bufo arenarum embryo

Amphibian gastrulation was used as a model system to study the action of the nucleoside 1-beta-D-arabinofuranosylcytosine (Ara-C) on the early events of amphibian morphogenesis. Ara-C inhibits both glycoprotein and glycolipid synthesis and interferes with DNA synthesis. Thus, it is useful to investigate the importance of the cell surface and the nucleous during Bufo arenarum morphogenesis. Living embryos were incubated with Ara-C at blastula and gastrula stages. Treated-embryos undergo abnormal gastrulation, most of the embryos exogastrulate, although some do not gastrulate at all. This antimetabolite did not interfere with neural induction, as partial exogastrulae developed a small neural tube. We have proven that Area-C disturbs the typical intercellular organization and inhibits the radial intercalation of the blastocoelic roof. The mesodermal migration is the most affected morphogenetic process. The results described in this paper demonstrate that the timing of gastrulation movements strongly involves the participation of surface and extracellular molecules in cell recognition and cell interaction but does not involve a significant increase in cell division rate and can also occur in the absence of the cell division.

Development of cellular slime mould, Dictyostelium discoideum treated with a carbamate pesticide.

Dictyostelium cells when treated with 100 ppm carbaryl or placed on 20 ppm carbaryl agar showed profound changes in the developmental stages. The treated cells showed larger aggregate formations, inhibition of cAMP-chemotaxis and cAMP dependent extracellular phosphodiesterase activity. The fruiting body formations were also scarce. The developing Dictyostelium cells when placed on carbaryl agar showed aberrant morphogenesis with larger aggregates, abnormal slugs and large fruiting bodies. In all cases the development of the treated cells showed considerable delay when compared with controls.