Evaluation of temporal, seasonal and geographic stability of the molluscicidal property of Euphorbia splendens latex

Laboratory tests with aqueous solutions of Euphorbia splendens var. hislopii latex have demonstrated seasonal stability of the molluscicidal principle, with LD90 values of 1.14 ppm (spring), 1.02 ppm (fall), 1.09 ppm (winter), and 1.07 ppm (summer) that have been determined against Biomphalaria tenagophila in the field. Assays on latex collected in Belo Horizonte and Recife yielded LD90 values similar to those obtained with the reference substance collected in Rio de Janeiro (Ilha do Governador), demonstrating geographic stability of the molluscicidal effect. The molluscicidal action of aqueous dilutions of the latex in natura, centrifuged (precipitate) and lyophilized, was stable for up to 124 days at room temperature (in natura) and for up to 736 days in a common refrigerator at 10 to 12ºC (lyophilized product). A 5.0 ppm solution is 100% lethal for snails up to 13 days after preparation, the effect being gradually lost to almost total inactivity by the 30th day. This observation indicated that the active principle is instable. These properties together with the wide distribution of the plant, its resistance and adaptation to the tropical climate, its easy cultivation and the easy obtention of latex and preparation of the molluscicidal solution, make this a promising material for large-scale use in the control of schistosomiasis

Physiological changes in Biomphalaria glabrata say, 1818 (Pulmonata: Planorbidae) caused by sub-lethal concentrations of the latex of Euphorbia splendens var. hislopii N.E.B (Euphorbiaceae)

Molluscides have been used as one of the strategies to control schistosomiasis. Many plant extracts with molluscidal effects have been tested, but the action of the latex of Euphorbia splendens var. hislopii is considered the most promising because it meets the recommendations of the World Health Organization (WHO). The objective of this study was to determine the lethal dose and identify the effects of the different doses of latex of E. splendens var. hislopii on the physiology of Biomphalaria glabrata submitted to treatment for 24 h. The concentrations of glucose, uric acid and total proteins in the hemolymph and of glycogen in the digestive gland and cephalopodal mass were determined. The LD50 value was 1 mg/l. The highest escape index was found to be at a concentration of 0.6 mg/l. The results showed that the latex of E. splendens var. hislopii caused a sharp reduction in the reserves of glycogen in the digestive gland and elevation of the protein content in the hemolymph of B. glabrata.

Optimization of preservation conditions of As (III) bioreporter bacteria.

Long-term preservation of bioreporter bacteria is essential for the functioning of cell-based detection devices, particularly when field application, e.g., in developing countries, is intended. We varied the culture conditions (i.e., the NaCl content of the medium), storage protection media, and preservation methods (vacuum drying vs. encapsulation gels remaining hydrated) in order to achieve optimal preservation of the activity of As (III) bioreporter bacteria during up to 12 weeks of storage at 4 degrees C. The presence of 2% sodium chloride during the cultivation improved the response intensity of some bioreporters upon reconstitution, particularly of those that had been dried and stored in the presence of sucrose or trehalose and 10% gelatin. The most satisfying, stable response to arsenite after 12 weeks storage was obtained with cells that had been dried in the presence of 34% trehalose and 1.5% polyvinylpyrrolidone. Amendments of peptone, meat extract, sodium ascorbate, and sodium glutamate preserved the bioreporter activity only for the first 2 weeks, but not during long-term storage. Only short-term stability was also achieved when bioreporter bacteria were encapsulated in gels remaining hydrated during storage.

Effect of Hevea brasiliensis latex sap gel on healing of acute skin wounds induced on the back of rats

Objective : to evaluate the effect of topical delivery of latex cream-gel in acute cutaneous wounds induced on the back of rats. Methods : we subjected sixteen rats to dermo-epidermal excision of a round dorsal skin flap, with 2.5cm diameter. We divided the animals into two groups: Latex Group: application of cream-gel-based latex throughout the wound bed on postoperative days zero, three, six and nine; Control group: no treatment on the wound. Photographs of the lesions were taken on the procedure day and on the 6th and 14th postoperative days, for analyzing the area and the larger diameter of the wound. We carried out euthanasia of all animals on the 14th postoperative day, when we resected he dorsal skin and the underlying muscle layer supporting the wound for histopathological study. Results : there was no statistically significant difference in the percentage of wound closure, in the histopathological findings or in the reduction of the area and of the largest diameter of the wounds among the groups studied on the 14th postoperative day. Conclusion : according to the experimental conditions in which the study was conducted, latex cream-gel did not interfere in the healing of acute cutaneous wounds in rats.

Study of the embryofeto-toxicity of Crown-of-Thorns (Euphorbia milii) latex, a natural molluscicide

The crude latex of Crown-of-Thorns (Euphorbia milii var. hislopii) is a potent plant molluscicide and a promising alternative to the synthetic molluscicides used in schistosomiasis control. The present study was undertaken to investigate the embryofeto-toxic potential of E. milii latex. The study is part of a comprehensive safety evaluation of this plant molluscicide. Lyophilized latex (0, 125, 250 and 500 mg/kg body weight) in corn oil was given by gavage to Wistar rats (N = 100) from days 6 to 15 of pregnancy and cesarean sections were performed on day 21 of pregnancy. The numbers of implantation sites, living and dead fetuses, resorptions and corpora lutea were recorded. Fetuses were weighed, examined for external malformations, and fixed for visceral examination, or cleared and stained with Alizarin red S for skeleton evaluation. A reduction of body weight minus uterine weight at term indicated that E. milii latex was maternally toxic over the dose range tested. No latex-induced embryolethality was noted at the lowest dose (125 mg/kg) but the resorption rate was markedly increased at 250 mg/kg (62.5%) and 500 mg/kg (93.4%). A higher frequency of fetuses showing signs of delayed ossification (control: 17.4%; 125 mg/kg: 27.4% and 250 mg/kg: 62.8%; P<0.05 vs control) indicated that fetal growth was retarded at doses ³ 125 mg latex/kg body weight. No increase in the proportion of fetuses with skeletal anomalies was observed at the lowest dose but the incidence of minor skeletal malformations was higher at 250 mg/kg body weight (control: 13.7%; 125 mg/kg: 14.8%; 250 mg/kg: 45.7%; P<0.05 vs control). Since a higher frequency of minor malformations was noted only at very high doses of latex which are embryolethal and maternally toxic, it is reasonable to conclude that this plant molluscicide poses no teratogenic hazard or, at least, that this possibility is of a considerably low order of magnitude

Potential of quixaba (Sideroxylon obtusifolium) latex as a milk-clotting agent

There are several obstacles to the use of chymosin in cheese production. Consequently, plant proteases have been studied as possible rennet substitutes, but most of these enzymes are unsuitable for the manufacture of cheese. The aim of this study was to evaluate the potential of latex from Sideroxylon obtusifolium as a source of milk-clotting proteases and to partially characterize the enzyme. The enzyme extract showed high protease and coagulant activities, with an optimal pH of 8.0 and temperature of 55 °C. The enzyme was stable in wide ranges of temperature and pH. Its activity was not affected by any metal ions tested; but was inhibited by phenylmethanesulfonyl fluoride and pepstatin. For the coagulant activity, the optimal concentration of CaCl2 was 10 µmol L- 1. Polyacrylamide gel electrophoresis showed four bands, with molecular weights between 17 and 64 kDa. These results indicate that the enzyme can be applied to the cheese industry.

The Utilization of Waste Latex Products in Styrene-Butadiene Rubber

Waste latex products are converted to a processabto material by a novel economical process developed in our laboratory , It contains rubber hydrocarbon of very high quality and Is lightly cross -linked. Styrene-butadlene rubber is mixed with latex reclaim In different proportions . The mechanical properties are found to be improved up to 60 percent replacement of styrene-butadlene rubber by latex reclaim . The curing of styrene-butadiene rubber Is found to be accelerated by the addition of latex reclaim. The processablllty study shows that the blends can be processed similar to SBRINR blends.

Design and Development of Instrumentation Systems to determine the Dry Rubber Content in Natural Rubber Latex

Hevea latex is a natural biological liquid of very complex composition .Besides rubber hydrocarbons,it contains many proteinous and resinous substances,carbohydrates,inorganic matter,water,and others.The Dry Rubber Content (DRC) of latex varies according to season, tapping system,weather,soil conditions ,clone,age of the tree etc. The true DRC of the latex must be determined to ensure fair prices for the latex during commercial exchange.The DRC of Hevea latex is a very familiar term to all in the rubber industry.It has been the basis for incentive payments to tappers who bring in more than the daily agreed poundage of latex.It is an important parameter for rubber and latex processing industries for automation and verious decesion making processes.This thesis embodies the efforts made by me to determine the DRC of rubber latex following different analytical tools such as MIR absorption,thermal analysis.dielectric spectroscopy and NIR reflectance.The rubber industry is still Looking for a compact instrument that is accurate economical,easy to use and environment friendly.I hope the results presented in this thesis will help to realise this goal in the near future.

Influence of compounding and process variables on quality of condams made from natural rubber latex

Condoms are widely accepted as a contraceptive for family planning and population control. It is also accepted as the most effective barrier against sexually transmitted diseases, especially AIDS, the incurable disease. But presence of pinholes and low film strength of condoms make it unsuitable for the purpose. Quality improvement of condoms by reducing the pinhole formation and increasing the film strength is thus an essential requirement for population control as well as for preventing the spread of sexually transmitted diseases. Strict implementation of WHO specification of condoms further increases the rejection percentage. This causes higher rejection loss to condom manufacturers because the defects could be identified only at the final stage of processing. If the influence of various factors which cause these defects is known, manufacturers can take remedial measures to reduce the defectives so that rejection loss can be decreased and quality of condoms increased. In the present study, it was proposed to conduct experiments to improve the quality of condoms by reducing the pinhole rejection percentage and increasing the tensile properties, burst volume, and burst pressure. Ageing property improvement also was an important target among other parameters. Until a cure for AIDS is found, a high quality latex condom is the only effective device in the prevention of the spread of HIV, AIDS and STD's. Hence it is all the more necessary to have high quality condoms.

Studies on prevulcanization of rubber latex with special reference to influence of storage and after treatments on properties of films

Systematic investigations on prevulcanization of NR latex with special reference to the influence of storage of latex and after-treatments of films, have been carried out. The other aspects studied include the effect of temperature on sulphur prevulcanization, the extent of crosslinking, tensile properties, stress relaxation characteristics, water absorption and leaching characteristics of prevulcanizcd latex films

Studies On Vulcanization, Rheology And Reinforcement Of Natural Rubber Latex With Special Reference To Accelerator Combinations, Surface Active Agents And Gamma Irradiation

In the present work, studies on vulcanization, rheology and reinforcement of natural rubber latex with special reference to accelerator combinations, surface active agents and gamma irradiation have been undertaken. In vulcanization, the choice of vulcanization system, the extent and mc-zie of vulcanization and network structure of the vulcanizate are important factors contributing to the overall quality of the product. The vulcanization system may be conventional type using elemental sulfur or a system involving sulfur donors. The latter type is used mainly in the manufacture of heat resistant products. For improving the technical properties of the products such as modulus and tensile strength, different accelerator combinations are used. It is known that accelerators have a strong effect on the physical properties of rubber vulcanizates. A perusal of the literature indicates that fundamental studies on the above aspects of latex technology are very limited. Thereforea systematic study on vulcanization, rheology and reinforcement of natural rubber latex with reference to the effect of accelerator combinations, surface active agents and gamma irradiation has been undertaken. The preparation and evaluation of some products like latex thread was also undertaken as a part of the study. The thesis consists of six chapter

Mineralised organic remains from cesspits at the Roman town of Silchester: Processes and preservation

Mineralised organic remains (including apple pips and cereal grains) collected during the ongoing excavations of Insula IX at the Roman town of Silchester, Hampshire have been analysed by a combination of SEM-EDX, powder XRD and IR spectroscopy. The experiments included mapping experiments using spatially resolved versions of each technique. IR and powder XRD mapping have been carried out utilising the synchrotron source at The Daresbury Laboratory oil stations 11.1 and 9.6. It is concluded that these samples are preserved by rapid mineralisation in the carbonate-substituted calcium phosphate mineral, dahllite. The rapid mineralisation leads to excellent preservation of the samples and a small crystal size. The value of IR spectroscopy in studying materials like this where the crystal size is small is demonstrated. A comparison is made between the excellent preservation seen in this context and the much poorer preservation of mineralised remains seen in Context 5276 or Cesspit 5251. Comments on the possible mechanism of mineralisation of these samples are made. (C) 2008 Elsevier B.V.. All rights reserved.

Mineralised organic remains from cesspits at the Roman town of Silchester: processes and preservation

Mineralised organic remains (including apple pips and cereal grains) collected during the ongoing excavations of Insula IX at the Roman town of Silchester, Hampshire have been analysed by a combination of SEM-EDX, powder XRD and IR spectroscopy. The experiments included mapping experiments using spatially resolved versions of each technique. IR and powder XRD mapping have been carried out utilising the synchrotron source at The Daresbury Laboratory oil stations 11.1 and 9.6. It is concluded that these samples are preserved by rapid mineralisation in the carbonate-substituted calcium phosphate mineral, dahllite. The rapid mineralisation leads to excellent preservation of the samples and a small crystal size. The value of IR spectroscopy in studying materials like this where the crystal size is small is demonstrated. A comparison is made between the excellent preservation seen in this context and the much poorer preservation of mineralised remains seen in Context 5276 or Cesspit 5251. Comments on the possible mechanism of mineralisation of these samples are made. (C) 2008 Elsevier B.V.. All rights reserved.

Structural characterization of blends containing both PVDF and natural rubber latex

Films containing different volumes of latex of natural rubber (NR) in a fixed mass of poly (vinylidene fluoride) (PVDF) powder were fabricated by compressing under annealing a mixture of both materials without using any solvent. This is an important issue keeping in mind that these films have to be used in the future as biomaterials in different applications once the solvents that are used to dissolve the PVDF become toxic to human. The films with different percentage of latex in PVDF were characterized using microRaman scattering and Fourier transform infrared absorption (FTIR) spectroscopies, thermomechanical techniques using thermogravimetry (TG), differential scanning calorimetry (DSC), dynamical-mechanical analysis (DMA) and scanning electron microscopy (SEM). The results showed that the latex of NR and PVDF do not interact chemically, leading to the formation of a polymeric blend with high thermal stability and mechanical properties suitable for applications involving bone (prostheses, for instance). Besides, the results recorded using the micro-Raman technique revealed that for a fixed amount of PVDF the higher the amount of latex in the blend, the better the miscibility between both materials. Copyright (c) 2005 John Wiley & Sons, Ltd.

Morphology and topography analysis of mesoporous titania templated by micrometric latex sphere arrays

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)