A contribution to the establishment of reference values for total mercury levels in hair and fish in amazonia.

Studies on mercury levels in the Amazonian Region have typically lacked background or reference parameters. A sectional study on Hg concentration in hair and fish was conducted, together with an assessment of the prevalence of signs and symptoms related to Hg poisoning, in four communities in the Amazon Basin not impacted by gold mining, located either by a river course (Santana do Ituqui and Caxiuanã) or by a lake (Aldeia do Lago Grande and Vila do Tabatinga). Mercury determinations in hair and fish were made by flameless atomic absorption spectrophotometry. Mean total Hg in hair was 4.33 microg/g (0.40-11.60 microg/g) in 321 individuals from Santana do Ituqui, 3.98 microg/g (0.40-11.76 microg/g) for 316 persons in Aldeia do Lago Grande, 5.46 microg/g (0.37-49.85 microg/g) for 504 individuals from Vila do Tabatinga and 8.58 microg/g (0.61-45.59 microg/g) for 203 inhabitants from Caxiuanã. Fish consumption was very high in all those communities but no signs or symptoms associated with Hg poisoning were found. Mean Hg concentration in fish varied from 0.006 to 2.529 microg/g for carnivores and from 0.008 to 0.871 microg/g for noncarnivores. These values suggest that further studies including a larger number of communities would eventually lead to values of "normal" Hg concentration in the Amazonian Region quite above the limits suggested by the World Health Organization.

Mercury contamination of fish and exposures of an indigenous community in Pará state, Brazil.

Fish consumption is an important source of protein among indigenous communities in Amazonian Brazil. Exposures to mercury via fish were studied in an indigenous community of the Munduruku reserve, located in the Tapajós River basin in the state of Pará, one of the oldest and most productive gold mining areas in the Amazon region. This study summarizes the results of mercury (Hg) analyses of fish consumed by inhabitants of the Munduruku settlement of Sai Cinza. The most frequently consumed fish, reported by 330 persons interviewed for this study, were tucunaré, pacu, jaraqui, traíra, aracu, matrinchã, and caratinga. The mean mercury concentration in carnivorous fish was 0.297 microg.g(-1) while in noncarnivorous fish mean mercury concentration was 0.095 microg.g(-1). Only in caratinga was there a significant relationship between fish size, weight, and mercury levels. Levels of methylmercury in the tucunaré averaged 0.170 microg.g(-1), while in traíra the mean level of methylmercury was 0.212 microg.g(-1). Although the levels of Hg in fish consumed by the Sai Cinza community are below the Brazilian limit value for consumption, the high rates and amounts of fish consumed by this population are relevant to evaluating risks of mercury contamination for communities with limited food resources.

Mercury exposures in riverside Amazon communities in Pará, Brazil.

Cross-sectional studies were conducted in three riverside communities in the state of Pará in the Amazon Region of Brazil. Two of these communities, Brasília Legal and São Luís do Tapajós, are located in a watershed exposed to mercury pollution from artisanal gold mining, and the third, Santana do Ituqui, is outside this area. The studies were based upon a community census and included all persons volunteering for participation in each community. All participants were surveyed by questionnaire for health history, occupation, residence, and diet. Clinical evaluations were also done on each subject, along with collection of blood, urine, feces, and hair. Fish samples were collected to represent the most frequently consumed species. Mercury was measured in hair and fish. Although no signs or symptoms of overt mercury intoxication were observed, persons in Brasília Legal and São Luís do Tapajós had higher levels of mercury in hair than residents of Santana de Ituqui, located out of the risk area. Levels of mercury in fish were below Brazilian health guidance limits, but the high rates of fish consumption among these populations raise concerns for the possible effects of chronic exposure, especially among young children and women of childbearing age.

[Mercury levels in fish consumed by the Sai Cinza indigenous community, Munduruku Reservation, Jacareacanga County, State of Pará, Brazil]. / Níveis de mercúrio em peixes consumidos pela comunidade indígena de Sai Cinza na Reserva Munduruku, Município de Jacareacanga, Estado do Pará, Brasil.

This study evaluated fish consumption and mercury levels in fish consumed by an indigenous community in the State of Pará. Eighty fish samples were collected (barbado, surubim, traíra, tucunaré, piranha, aruanã, caratinga, aracu, mandiá, jandiá, and pacu). Mercury analysis was performed using a Mercury Analyzer HG-3500. Average mercury concentration in carnivorous species was 0.293 (g/g (SD=0.104), while in non-carnivorous species it was 0.112 (g/g (SD=0. 036). Brazilian legislation establishes a maximum permissible limit of 0.5 (g/g for fish consumption. No significant correlation was found between fish length or weight and mercury concentration. Types of fish most frequently consumed by the community were tucunaré, pacu, jaraqui, traíra, aracu, matrinchã, and caratinga. Carnivorous species, especially tucunaré and traíra, amongst the most frequently eaten, had higher mercury levels than non-carnivorous species. Frequency of consumption is crucial to assess the risk of mercury contamination in communities who lack alternative food sources.

Anther culture in Helianthus annuus L., influence of genotype and culture conditions on embryo induction and plant regeneration.

Production of microspore-derived embryos from cultured anthers is now a well established technique for the isolation of homozygous lines in many crop plants. We describe here a culture method for embryo induction and plant regeneration from anthers of four sunflower genotypes. For preliminary experiments, anthers of uninucleate microspores were cultured on four types of basal media viz., Murashige and Skoog's MS, Gamborg's B5, Nitsch and Nitsch, and White's W, supplemented with 1.0 mg/l 2,4 dichlorophenoxy acetic acid and 0.5 mg/l 6-benzylaminopurine and 40 g/l sucrose. MS basal medium, being more responsive for embryo induction, was used for further experimentation. To optimise the culture requirement MS basal medium was supplemented with 0.2-2.0 mg/l 2,4 dichlorophenoxy acetic acid and 0.5 and 1.0 mg/l 6-benzylaminopurine. The effect of cold pretreatment, hormone regime and sucrose concentration were tested for embryogenic efficiency. Genotype had a significant effect on the capacity of embryo induction. Addition of silver nitrate (2.5 mg/l), an ethylene inhibitor, stimulated embryo germination. Plantlets were obtained (10-15%) from embryos of only one genotype.

Floral biology and breeding behavior in the bamboo Dendrocalamus strictus Nees.

Floral biology and breeding behavior were studied in the bamboo Dendrocalamus strictus Nees. The inflorescence in this species is a large branching panicle. Fertile florets are intermixed with smaller sterile ones. There are six stamens. The ovary is stipitate and turbinate. The style is long and the stigma is bifid and plumose. Dendrocalamus strictus is typically dichogamous and protogynous. The gynoecium matures 3-4 days before the androecium, effectively preventing self pollination. Flower bloom, which took place over a period of 2 to 3 h, was dependent on air temperature and only occurred between 0600 and 1300 h. Dendrocalamus strictus is anemophilous. Flowers in the male phase were visited by insects. These insects completely neglected the flowers at the female phase. The insects fed on the pollen and were not pollen vectors. When wind was excluded by enclosing the inflorescences in bags there was no seed set, indicating that cross pollination by wind is necessary for fertilization and that parthenocarpy and apomixis are not occurring in this species. Pollen fertility was about 98% as indicated by staining fresh pollen at the time of anther dehiscence and pollen release with Alexander's stain (Alexander 1969). When placed on a modified Brewbaker-Kwak medium containing 1% glucose, the pollen grains germinated well, and the pollen tubes grew to 15-20 times the diameter of mature pollen grains. Although profound protogyny has its disadvantages in times of sporadic flowering, it can be useful in breeding programs because it eliminates the need for emasculation.

Antibiotic prophylaxis in biliary surgery.

Early studies in which a higher incidence of wound infection and septic complications in biliary surgery was found demonstrated the need for antibiotic prophylaxis. In two studies, one retrospective and one prospective, the role of prophylactic antibiotics in biliary surgery was studied in "at risk" and "no risk" groups of patients. Twenty-eight percent of "no risk" patients had a positive bile culture. It was concluded that a single dose of 1 g cefotaxime, administered upon induction of anaesthesia, is a safe and effective prophylactic regimen in biliary surgery.

Plantlet production through high frequency somatic embryogenesis in long term cultures ofEucalyptus citriodora.

A highly embryogenic culture ofEucalyptus citriodora was obtained by repetitive embryogenesis from somatic embryos cultured in the dark on a medium containing 500 mg/l each of glutamine and casein hydrolysate, 30 g/l of sucrose and 5 mg/l of 1-napthaleneacetic acid. Cultures retained morphogenetic ability for upto 36 months when maintained at 27°C by subculture at intervals of 4-5 weeks. The subculture period could be extended beyond 9 months if cultures were incubated at 10°C. On a hormone free medium incubated in light 50% of the embryos germinated to plantlets of which 70% survived when transferred to a sand and soil mixture.

Occurrence and frequency of precocious germination of somatic embryos is a genotpye - dependent phenomenon in wheat.

Immature embryos of thirty-three genotypes of wheat were cultured on 2,4-D containing medium. Occurrence of precocious germination of the zygotic and somatic embryos simultaneously on the same medium was a striking feature observed during the course of work. The percentage of precocious germination was seen to vary extensively from 0-88% and 0-84% for zygotic and somatic embryos respectively. In the genotypes NI-5439 and NI-5643 which are characterized by a high tillering capacity, the phenomenon of precocious germination seems to take a different path from that observed in the other genotypes. This is evident since these two genotypes require total absence of hormone for shoot elongation although multiple shoot primordia are formed on auxin containing medium.Precocious germination also seems to be relevant to somatic embryogenesis and plantlet regeneration. This conclusion stems from the observation that a majority of the genotypes that show precocious germination of zygotic embryos have greater embryogenic potential. Consecutively, most of the genotypes that show precocious germination of somatic embryos exhibit a higher frequency and faster rate of plantlet regeneration.

In vitro plantlet formation by organogenesis in E. camaldulensis and by somatic embryogenesis in Eucalyptus citriodora.

Adventitious shoots were formed through callus on leaf explants of Eucalyptus camaldulensis Dehnh. (River red gum) taken from shoot cultures of mature trees. Callus formed in dark on a medium containing 1 g/l casein hydrolysate, 3 mg/l 1-naphthaleneacetic acid, 0.1 mg/l 6-benzyladenine and 50 g/l sucrose. Shoot initiation occurred in 4 weeks on calli shifted to light on a regeneration medium containing 10% coconut milk, 0.5 mg/l 6-benzyladenine and 20 g/l sucrose. Rooting occured in dark on a liquid medium containing 4 mg/l 1-naphthaleneacetic acid. Zygotic embryos of Eucalyptus citriodora Hook f. (Lemon scented gum) cultured in dark on a medium containing 3 mg/l 1-naphthaleneacetic acid and 50 g/l sucrose formed somatic embryoids which grew to normal plantlets on the same regeneration medium used for organogenesis.

Studies on endosperm culture of Annona squamosa Linn.

Mature endosperm tissue excised from germinated seeds (2-4 days after radicle emergence) of Annona squamosa grew and proliferated on White's basal medium supplemented with two cytokinins, an auxin and gibberellic acid. The callus obtained could be periodically subcultured. Shoot differentiation and root induction were obtained from callus on media of different compositions. Analyses of the root and young leaf tips showed triploid number of chromosomes (3n=21).

Biochemical aspects of shoot differentiation in sugarcane callus: I. Nitrogen assimilating enzymes.

The developmental patterns of the nitrogen assimilating enzymes were investigated and compared in the non-shoot forming and the shoot forming callus cultures of sugarane. In the shoot forming tissue the pre-emergence period od shoots was characterised by increasing activities of glutamine synthetase and glutamate synthase. The activity of these enzymes during the corresponding period in the non-shoot forming callus was found to decline. Although the activity of glutamate dehydrogenase in the shoot forming callus during the period of pre-emergence of shoots did not show any appreciable change, in the non-shoot forming callus, it increased during the corresponding period. The developmental patterns of nitrate reductase in both the programmes were identical except for the fact that in the shoot forming tissue the nitrate reductase activity was higher at all times than in the non-shoot forming callus. The data suggest that (a) shoot differentiation occurs concomitant with peak glutamine synthetase, glutamate synthase, and nitrate reductase activity, whereas the glutamate dehydrogenase activity is at its lowest, (b) better mobilization of nitrate occurs in the shoot forming callus and (c) the glutamine synthetase/glutamate synthase pathway becomes operative prior to shoot differentiation.

Studies on a drought resistant legume: The moth bean, Vigna aconitifolia (Jacq) marechal. I. Protoplast culture and organogenesis.

High yields of viable protoplasts were obtained from callus cultures derived from shoot apices of Vigna aconitifolia (JACQ) Marechal. The protoplasts divided and formed cell clusters on modified MS medium. The protoplast-derived callus formed multiple shoot buds on MS and B5 basal media without supplements, on MS medium containing supplements and on B5 medium containing charcoal (0.25%). Shoot formation occurred.

Studies on a drought resistant legume: The moth bean, Vigna aconitifolia (Jacq) marechal. II. morphogenetic studies.

Plantlets regenerated from shoot apices, cotyledons and callus cultures in Moth bean, Vigna aconitifolia (JACQ) Marechal, a drought resistant legume and pulse crop, were rooted and transferred to soil. Explants for these studies were derived from seedlings pre-conditioned by germination of seeds on B5BA and WMB (control).

In vivo nitrate reductase activity in dark- and light-grown sugarcane callus.

The in vivo nitrate reductase activity in 8 day old dark-grown sugarcane callus was over three fold that of the light-grown callus. NADH (0.3 mM) in the reaction system, increased the in vivo nitrate reductase activity by more than two fold both in the dark- and the light-grown callus tissues. The NADH dependence of nitrate reductase activity followed Michaelian kinetics. The apparent Km values for NADH were 0.083 mM and 0.20 mM, respectively, for the dark- and the light-grown callus. In vivo nitrate reductase activity in green sugarcane leaves (field grown) was unaffected by NADH in the reaction system. Under the standard conditions of assay up to 60% of the NADH penetrated into the sugarcane callus within 2 min. No penetration of NADH into the sugarcane leaf discs was, however, recorded under identical conditions.

Somatic embryogenesis and plants from zygotic embryos of coconut (Cocos nucifera L.) in vitro.

Complete plants were grown from zygotic embryos cultured on Y3 basal liquid medium supplemented with coconut milk, BA and NAA. Explants from stem, leaf and rachilla of mature coconut trees turned green and swelled on Y3 semi-solid basal media supplemented with 2,4-D, K, NAA, BA and activated charcoal. Callus was initiated in explants from the subapical regions of the stem on Y3 basal medium supplemented with 2,4-D (4.52×10(2)µM). Globular embryo-like structures were obtained when this callus was subcultured to auxinless medium. Root formation was obtained from leaf explants on Y3 basal medium containing citric acid, ascorbic acid and 2,4-D (4.52×10(2) µM). Globular embryo-like structures were also obtained directly from leaf explants on a Y3 basal medium supplemented with 2,4-D (2.26×10(2) µM). Callus isolated from rachilla explants on Y3 basal medium containing 2,4-D(4.52×10(2) µM), formed nodular structures when transferred to medium with 2,4-D (2.3×10(1) µM). These nodules developed roots from the base of the nodular growth whereas from the upper portion shoots were observed on Y3 basal liquid medium.