Are fundamental niches larger than the realized? Testing a 50-year-old prediction by Hutchinson.

For more than 50 years ecological niches have been defined as combinations of multidimensional environmental conditions permitting a species to survive and reproduce. A fundamental niche (NF) is defined as the set of conditions within which a species can live in the absence of competitors, and a realized niche (NR) is a NF hypothetically reduced by competitive interactions (and some other limiting factors). This definition implies that NF is "larger" than NR, something that has been nearly universally accepted by ecologists. However, there have been few attempts at empirical tests. Here, we present a novel quantitative test using one-dimensional estimates of NF for 105 species of reptiles and amphibians, and estimates of NR obtained from ~1.4 x 104 field observations. To specify our test, we operationalize the original classification of niche types. Our results predominantly support the hypothesis that NF 'is larger' than NR and we highlight the theoretical and practical importance of quantifying niches.

Purification and identification of antibacterial phenolics from Tripodanthus acutifolius leaves.

AIMS: To perform an activity-guided purification, identification and quantification of antibacterial compounds from Tripodanthus acutifolius infusion. To validate the antibacterial activity of purified substances. METHODS AND RESULTS: Bioautographic methods were employed as screening assays for purifying bioactive substances. Purification procedures included sephadex LH-20 column chromatography and reverse phase HPLC. Identification was achieved by spectroscopic methods (UV-Vis, MS, NMR and polarimetry) and chromatographic assays (paper chromatography and HPLC). Antibacterial activity was studied by microdilution, colony count and photometric assays, Sytox green stain and transmission electron microscopy (TEM). Four glycoflavonoids (rutin, nicotiflorin, hyperoside and isoquercitrin) and an unusual phenylbutanoid glycoside (tripodantoside) were purified and identified. Tripodantoside was found at 6.59 +/- 0.82 g per 100 g of dry leaves. The flavonoids showed bactericidal effect at a concentration of 4 mg ml(-1) against Staphylococcus aureus and Pseudomonas aeruginosa strains from American Type Culture Collection, while tripodantoside was almost four times more active than those compounds, with a minimum bactericidal concentration = 1.024 mg ml(-1) against these strains. Tripodantoside aglycone showed bacteriolytic effects on the assayed strains, causing evident damages on cell wall and membrane, while tripodantoside did not exhibit those effects. CONCLUSIONS: The antibacterial activity of T. acutifolius infusion would be partially attributed to the purified glycoflavonoids and mainly to tripodantoside. SIGNIFICANCE AND IMPACT: The high extraction yield and the antibacterial activity exhibited by tripodantoside makes this chemical structure of interest to support further studies dealing with chemical modifications to increase the antibacterial activity or to seek another activities.

Antibacterial activity of plant extracts from northwestern Argentina.

AIMS: To determine the antibacterial and cytotoxic activities of aqueous and ethanolic extracts of northwestern Argentinian plants used in folk medicine. To compare the mentioned activities with those of five commercial antibiotics. To identify the compounds responsible for the antibacterial activity. METHODS AND RESULTS: Plant extracts were prepared according to traditional uses in northwestern Argentina. Antibacterial activity was assayed by agar dilution in Petri dishes and broth dilution in 96-well plates. Lethal dose 50 (LD(50)) was determined by the Artemia salina assay. Phytochemical analysis was performed by sample adsorption on silica gel, thin-layer chromatography (TLC), bioautography and UV-visible spectra. The results showed that Tripodanthus acutifolius aqueous extracts have lower minimal inhibitory concentrations (MIC) (502 and 506 microg of extracted material (EM) per ml for infusion and decoction, respectively) than cefotaxim MIC (640 microg ml(-1)) against Acinetobacterfreundii (303). These data were lower than their LD(50). Tripodanthus acutifolius tincture showed lower MIC (110 microg of EM per ml) and minimal bactericidal concentration (MBC) (220 microg of EM per ml) than cefotaxim (MIC and MBC of 320 microg ml(-1)) for Pseudomonasaeruginosa. This extract also showed a MIC/MBC of 110/220 microg of EM per ml, lower than oxacillin (MIC/MBC of 160/220 microg ml(-1)) for Staphylococcus aureus (ATCC 25923). The cytotoxicity of all extracts were compared with that of commercial antibiotics. Rutin (3,3',4',5,7-pentahydroxyflavone 3-beta-rhamnosilglucoside), iso-quercitrin (3,3',4',5,7-pentahydroxyflavone 3-beta-glucoside) and a terpene would be partially responsible for the antibacterial activity of T. acutifolius infusion. CONCLUSIONS: Tripodanthus acutifolius extracts had the ability to inhibit bacterial growth. The antibacterial activity differs with the applied extractive method, and it could be partially attributed to glycoflavonoids. This paper contributes to the knowledge of antibacterial capacity of plants from northwestern Argentina. SIGNIFICANCE AND IMPACT OF THE STUDY: These antibacterial activities support further studies to discover new chemical structures that can contribute to alleviate or cure some illnesses.

Propolis from the northwest of Argentina as a source of antifungal principles.

AIMS: To determine the antimycotic and cytotoxic activities of partially purified propolis extract on yeasts, xylophagous and phytopathogenic fungi. To compare these activities with pinocembrin and galangin isolated from this propolis and with the synthetic drugs ketoconazole and clortrimazole. METHODS AND RESULTS: Ethanolic propolis extract was partially purified by cooling at -20 degrees C. Two of its components were isolated by HPLC and identified as pinocembrin and galangin. The antifungal activity was assayed by bioautography, hyphal radial growth, hyphal extent and microdilution in liquid medium. Cytotoxicity was studied with the lethality assay of Artemia salina. The obtained results were compared with the actions of ketoconazole and clortrimazole. The results showed that the antifungal potency of ketoconazole and clortrimazole is higher than pinocembrin, galangin and the partially purified propolis extract in this order. Otherwise, the cytotoxicity of the synthetic drugs is also the highest. CONCLUSIONS: Partially purified propolis extract inhibits fungal growth. The comparison of its relative biocide potency and cytotoxicity with synthetic drugs and two components of this propolis (pinocembrin and galangin) showed that the propolis from 'El Siambón', Tucumán, Argentina, is a suitable source of antifungal products. SIGNIFICANCE AND IMPACT OF THE STUDY: The partially purified propolis extract and its isolated compounds, pinocembrin and galangin, have the capacity of being used as antifungals without detriment to the equilibrium of agroecosystems. The impact of this study is that the preparation of agrochemicals with reduced economic costs using a partially purified preparation as the active principle is possible.

Absence of detectable transgenes in local landraces of maize in Oaxaca, Mexico (2003-2004).

In 2000, transgenes were detected in local maize varieties (landraces) in the mountains of Oaxaca, Mexico [Quist, D. & Chapela, I. H. (2001) Nature 414, 541-543]. This region is part of the Mesoamerican center of origin for maize (Zea mays L.), and the genetic diversity that is maintained in open-pollinated landraces is recognized as an important genetic resource of great cultural value. The presence of transgenes in landraces was significant because transgenic maize has never been approved for cultivation in Mexico. Here we provide a systematic survey of the frequency of transgenes in currently grown landraces. We sampled maize seeds from 870 plants in 125 fields and 18 localities in the state of Oaxaca during 2003 and 2004. We then screened 153,746 sampled seeds for the presence of two transgene elements from the 35S promoter of the cauliflower mosaic virus and the nopaline synthase gene (nopaline synthase terminator) from Agrobacterium tumefaciens. One or both of these transgene elements are present in all transgenic commercial varieties of maize. No transgenic sequences were detected with highly sensitive PCR-based markers, appropriate positive and negative controls, and duplicate samples for DNA extraction. We conclude that transgenic maize seeds were absent or extremely rare in the sampled fields. This study provides a much-needed preliminary baseline for understanding the biological, socioeconomic, and ethical implications of the inadvertent dispersal of transgenes from the United States and elsewhere to local landraces of maize in Mexico.

Evaluación y seguimiento de un brote de salmonellosis en una población urbano marginal / Assessment and monitoring of an outbreak of salmonellosis in a marginal urban population

Se realice el estudio de un brote de EDA causado por Salmonella enteritidis en un Centro Educativo (CE) de una población urbano marginal (José Gálvez-JG-, Unidad Territorial de Salud de Villa María del Triunfo-UTES VMT, Dirección Sub Regional de Salud II Lima Sur-DISURSII-LS-), en noviembre de 1992. Se buscó precisar la sintomatología y evolución; posteriormente se investigó la prevalencia de portadores asintomáticos. Se estudiaron 52 casos que presentaron los siguientes signos y síntomas: diarreas acuosas (100%), dolor abdominal (90.69%), vómitos (83.72%), y fiebre (79.06%). La sintomatología cedió en un tiempo máximo de 7 días, resolviéndose la mayoría de los casos entre el 3er y 5to día (60.46%). El uso de antibióticos prolongó la evolución clínica, con respecto a los que no los recibieron; la sintomatología del 90% de éstos últimos cedió en los primeros 4 días. A las 8 semanas se evaluaron 36 pacientes; el 50% de las muestras tomadas para coprocultivo fueron positivas a Salmonella enteritis, sin relación aparente con el tratamiento antibiótico. Se concluye que el probable consumo de productos derivados de huevos crudos contaminados fue la causa del presente brote. Se plantea que el tratamiento antibiótico prolongó la evolución del cuadro clínico. Cabe destacar el hallazgo de una alta prevalencia de portadores asintomáticos en relación a lo descrito en la literatura, lo que se podría estar condicionando por la deficiencia dele estado inmune, la meno acidez gástrica de los niños y la automedicación indiscriminada con antibióticos de amplio espectro.

An acute diarrhoeal outbreak caused caused by Salmonella enteridis in an urban-marginal schooll (Jose Galvez-JG-, Unidad Territorial de Salud de Villa Maria del Triunfo-UTES VMT, Direccion Sub Regional de Salud II Lima Sur-DISURSII-LS-) in November 1992 was studied. The symptoms, evolution and further asymptomatic carriers prevalence were reached. 52 cases were studied; they presented the following signs and symptoms: diarrhea (100%), abdominal pain (90.69%), vomiting (83.72%), and fever (79.06%). The symptomatology lasted up to 7 days and most cases were solved by the 3rd and 5th days (60.46%). The use of antibiotics prolonged the clinical evolution, compared to those who didn´t received them; the clinical evolution, compared to those who didnÆt received them; the lattersÆ symptoms disappeared during the first 4 days. By the 8th week, 36 patients were evaluated; 50% the culture were positive to Salmonella enteridis, apparently not related to antibiotics. The conclusion was that possibly contaminated raw egg products caused this outbreak. The study suggests that antibiotic therapy prolonged the clinical evolution. Is remarkable the high prevalence of the asymptomatic carriers in relation to literature reports and it could be conditioned by immune-deficiency, infantsÆ low gastric acidity and uncontrolled self-prescription with broad-spectrum antibiotics.