Ethnobotany of seaweeds: clues to uses of seaweeds

Extensive uses of fresh and dried seaweeds by coastal populations over the world can furnish clues to potential food and other uses of seaweeds, just as the first extraction of a seaweed gelatin now used for bacteriological purposes was discovered by a housewife in search of a pudding. Ethnic uses as food depend heavily on closely related species suitable for making cool, gelatinous dishes or concoctions, or on species suitable for adding to soups or stews. Rarely, single species like cochajugo (Durvillea antarctica) in Chile and rimu (Durvillea antarctica) in New Zealand point to different kinds of food preparation. Oriental cuisine incorporates many different species of seaweeds in a wide variety of ways, whereas commercial western uses depend upon extracts of wall materials to suspend, emulsify or stabilize a broad variety of foods and products.     

pH mapping in transparent gel using color indicator videodensitometry

The colored pH indicator method introduced by Weisenseel et al. (1979) is particularly useful for localizing the zones along roots where acidification/alkalinization occurs. It can also be used to assess the direction and intensity of the proton fluxes. Because the method has not been quantitatively evaluated, however, it is nowadays little used or used in conjunction with other such as potentiometry. In the present study we examine the theoretical basis underlying this method of colorimetric visualization and show its similarity to spectrodensitometry. It thus becomes possible to quantify the luminous information and express it in terms of environmental pH. We describe the method used, emphasizing in particular the conditions required to achieve maximum accuracy of measurement, and an appropriate experimental device. pH distribution around roots can be mapped with a relative error of 0.03 pH units. The experimental device is easy to use and incorporates a computer-controlled video camera, thanks to which al acquisition and calculation procedures can be automated.     

Agar Analysis,nuclear genome quantification and characterization of four agarophytes (Gracilaria) from the Mexican Gulf Coast

DNA reassociation kinetics were used to determine nuclear genome organization and complexity in four species of Gracilaria (Gracilariales, Rhodophyta). In Gracilaria tikvahiae, G. caudata, G. cervicornis and G. divaricata, results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repetitive sequences varied from 13–46% and unique DNA ranged from 45–78%, Thermal denaturation (T _m) indicated guanine + cytosine (G + C) levels of 41.9–46.0 mol % G + C. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to quantify nuclear DNA content. Comparisons of mean nuclear DNA (I _f) values to chicken erythrocytes (RBC) resulted in an estimate of 0.37–0.40 pg/2C genomes for the four Gracilaria species. Total agar content following alkaline pretreatment ranged from 7–15% dry weight. Gel strengths were generally below commercial levels, ranging from 40–260 g cm⁻² Nuclear genome profiles developed from information for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity as previously speculated.     

Induction of shikonin formation by agar in Lithospermum erythrorhizon cell suspension cultures

Cultured cells of Lithospermum erythrorhizon capable of producing red naphthoquinone (shikonin) derivatives on Linsmaier-Skoog agar medium ceased s     

Specifically UV-sensitive photoreactivable mutant of Salmonella abony

A new type of UV-sensitive mutant was isolated in Salmonella abony. The war 12 mutation causing UV sensitivity did not affect photoreactivability of UV damage or sensitivity to γ-rays, methyl methanesulfonate (MMS), mitomycin (MC) or 4-nitro-quinoline I-oxide (4NQO).Mutation uvr I2 appeared to be near the uvr B gene of Salmonella: the frequencies of contransduction of uvr B2 and uvr I2 mutations with gal were found to be 3% and 6% respectively.Close localization of the uvr I2 and uvr B2 mutations, the possibility of recombination between them and their phenotypic differences (both uvr B2 and uvr I2 mutants show quantitatively different Hcr phenotypes and different sensitivities to MC and 4NQO) suggest that the uvr B2 and uvr I2 mutations might be localized in different cistrons of an operon controlling the first step of excision repair.     

Agars from Chilean Gelidiaceae

Cystocarpic, tetrasporic and vegetative thalli of Gelidium chilense were extracted with water at 95 °C. The contents of 3,6-anhydro-galactose and sulfate group of the hydrocolloids correspond to those of an agar-type polysaccharide. The percentages of 6-O-methyl-galactose and of pyruvic acid ranged between 5.7–6.2% and 0.42–0.54%, respectively. The gel melting and gelation temperatures of Gelidium chilense, G. rex and G. lingulatum agars were determined. A correlation between 6-O-methylgalactose content and gelation temperatures was not observed. It was found by anion-exchange chromatography that 19.8% of tetrasporic and 4.9% of vegetative G. chilense agars are unsulfated polymers. Structural studies on the neutral fraction from tetrasporic G. chilense agar by partial hydrolysis and ¹H NMR spectroscopy have shown that it is mainly composed of agarose. Methylation analysis, oxidative hydrolysis and partial hydrolysis, followed by ¹H NMR spectroscopy, have shown that the neutral fraction of the agar from tetrasporic Gelidium rex is agarose. The results obtained in this work are compared with previously reported data on studies of agars from Chilean Gelidium species.     

Quantification of cytotoxic hemocytes of Mytilus edulis using a cytotoxicity assay in agar

When a thin layer of agar containing a mixture of erythrocytes and Mytilus hemocytes is prepared on slides, the occurrence of plaques of lysed target cells can be observed around a limited number of hemocytes. These hemocytes remain completely intact cells and are viable as evidenced by their ability to phagocytose target cells and/or to form pseudopods. The number of hemocytes releasing cytotoxic molecules has been shown to vary greatly between different animals. The same holds true for the total number of circulating hemocytes, although no correlation exists between the number of hemocytes in the circulation and the percentage of cytotoxic blood cells.     

Media and gelling agent effect on cotton callus initiation from excised seed hypocotyls

A factorial experiment was performed to develop a medium which would support initiation and proliferation of callus in a diverse group of exotic lines of Gossypium hirsutum. Seed hypocotyls of T1, T25 and T133 were cultured on Linsmaier and Skoog (LS) basal medium (1965) with NAA or 2,4-D tested in combination with BA or kinetin. The best medium from this study was then compared to five published media for support of callus initiation and growth of the varieties Acala 1517-75, Coker 500, Dunn 120, Paymaster 303 and TM1. Furthermore, the effects of two gelling agents, Difco-Bacto agar and Kelco Gelrite, were investigated with each of the six media. Significantly more callus was initiated on media solidified with Gelrite than with agar. The best callus production occurred on LS medium supplemented with 30gl^-1 glucose, 0.1 mgl^-1 BA and 0.1 mgl^-1 2,4-D.