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E Ezcurra

Publications and source records attributed to E Ezcurra.

10 recordsLinked to original sources
PubMed2005

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.

Agrobacterium tumefaciens↗
PubMed2004

Interventions for emergency contraception.

BACKGROUND: In emergency contraception a drug or IUD is used to prevent pregnancy shortly after unprotected intercourse. Except for some Western-European countries and China, emergency contraception is largely under-utilised worldwide. In many developing countries lack of access to emergency contraception may subject women to unsafe abortions, which contribute significantly to maternal mortality and morbidity. Currently, several interventions (IUD, the Yuzpe regimen, levonorgestrel, mifepristone, danazol and some combination regimens) are available for emergency contraception. Information on the comparative efficacy, safety and convenience of these methods is crucial for reproductive health care providers and the women they serve. OBJECTIVES: To determine which emergency contraceptive method following unprotected intercourse is the most effective, safe and convenient to prevent pregnancy. SEARCH STRATEGY: The search included the Cochrane Controlled Trials Register, Popline, MEDLINE, Chinese biomedical databases and UNDP/UNFPA/WHO/World Bank Special Programme on Human Reproduction (HRP) emergency contraception database (July 2003). Content experts and pharmaceutical companies were contacted. SELECTION CRITERIA: Randomised controlled trials and controlled clinical trials including women attending services for emergency contraception following a single act of unprotected intercourse were eligible. DATA COLLECTION AND ANALYSIS: Data on outcomes and trial characteristics were extracted in duplicate and independently by two reviewers. Quality assessment was also done by two reviewers independently. Meta-analysis results are expressed as relative risk (RR) using a fixed-effects model with 95% confidence interval (CI). In the presence of significant heterogeneity a random-effect model was applied. MAIN RESULTS: Forty-eight trials with 33110 women were included. Most trials were conducted in China (37/48). Levonorgestrel is more effective than the Yuzpe regimen in preventing pregnancy (2 trials, RR: 0.51; 95% CI: 0.31 to 0.83). Single dose (1.5 mg) administration seems to have similar effectiveness as the standard 12 hours apart split-dose (0.75 mg twice) of levonorgestrel (2 trials, RR: 0.77, 95% CI: 0.45 to 1.30). Levonorgestrel has similar effectiveness to mid-dose (8 trials, RR: 1.64; 95% CI: 0.82 to 3.25) or low-dose (7 trials, RR: 1.38; 95% CI: 0.93 to 2.05) mifepristone. Low-dose (=< 10 mg) mifepristone is similarly effective as mid doses (25-50 mg) when only high quality trials are considered. Delay in the onset of subsequent menses is the main unwanted effect of mifepristone and seems to be dose-related. The Yuzpe regimen can be used when levonorgestrel and mifepristone are not available. Half-dose Yuzpe with single administration is associated with fewer side-effects but it is not clear whether it is as effective as the standard Yuzpe regimen (RR: 1.41; 95% CI: 0.76 to 2.61). REVIEWERS' CONCLUSIONS: Levonorgestrel 1.5 mg (two split doses or a single dose) and low and mid-doses (25-50 mg) of mifepristone offer high efficacy with an acceptable side-effect profile. Single dose simplifies the use of levonorgestrel for emergency contraception without an increase in side-effects. However, mifepristone might delay the following menstruation, which could increase anxiety, particularly in higher doses. The Yuzpe regimen could be used if levonorgestrel or mifepristone are not available. The intrauterine device (IUD) is another effective emergency contraceptive, and can be kept for ongoing contraception.

Contraception, Postcoital↗
PubMed2001

El Niño effects on the dynamics of terrestrial ecosystems.

New studies are showing that the El Niño Southern Oscillation (ENSO) has major implications for the functioning of different ecosystems, ranging from deserts to tropical rain forests. ENSO-induced pulses of enhanced plant productivity can cascade upward through the food web invoking unforeseen feedbacks, and can cause open dryland ecosystems to shift to permanent woodlands. These insights suggest that the predicted change in extreme climatic events resulting from global warming could profoundly alter biodiversity and ecosystem functioning in many regions of the world. Our increasing ability to predict El Niño effects can be used to enhance management strategies for the restoration of degraded ecosystems.

Journal Article↗
PubMed2000

Interventions for emergency contraception.

OBJECTIVES: To determine which emergency contraceptive method following unprotected intercourse is the most effective, safe and convenient for use in preventing pregnancy. SEARCH STRATEGY: The search strategy included electronic searches of the Cochrane Controlled Trials Register, Popline, Chinese biomedical databases and HRP emergency contraception database. In addition, references of retrieved papers were searched and researchers in the field and two pharmaceutical companies were contacted. SELECTION CRITERIA: Randomized or quasi-randomized studies including women attending services for emergency contraception following a single act of unprotected intercourse were eligible. DATA COLLECTION AND ANALYSIS: Data on outcomes and trial characteristics were extracted in duplicate by two reviewers. Results were expressed as relative risk using a fixed-effects model with 95 % confidence interval. MAIN RESULTS: Fifteen trials were included in the review. The majority (8/15) of the trials were conducted in China. Most comparisons between different interventions included one or two trials although some trials were appropriately sized with power calculations. Levonorgestrel appears to be more effective than Yuzpe regimen (2 trials, RR: 0.51, 95 % CI: 0.31-0.84) and causes less side-effects (RR: 0.80, 95 % CI: 0.76 to 0.84). Levonorgestrel was less effective than locally manufactured mifepristone in a single, large Chinese study (RR: 2.17, 95 % CI: 1.00 to 4.77). Effectiveness of different doses of mifepristone seem to be similar but the frequency of delay in onset of the subsequent menstrual period increases with increased dose. REVIEWER'S CONCLUSIONS: Levonorgestrel and mifepristone seem to offer the highest efficacy with an acceptable side-effect profile. One disadvantage of mifepristone is that it causes delays in onset of subsequent menses which may induce anxiety. However, this seems to be dose-related and low doses of mifepristone minimise this side-effect without compromising effectiveness. Future studies should compare the effectiveness of mifepristone with levonorgestrel.

Contraceptives, Postcoital↗
PubMed2000

Pollination ecology of Agave macroacantha (Agavaceae) in a Mexican tropical desert. I. Floral biology and pollination mechanisms.

In a study of sexual reproduction in long-lived semelparous plants, we observed Agave macroacantha in the tropical desert of Tehuacán-Cuicatlán, Mexico, describing duration of flowering, flower phenology, and nectar production patterns. We also performed two manipulative experiments evaluating (a) the seed production efficiency of different crossing systems (selfing, cross-pollination, apomixis, and control), and (b) the effect of different pollinators (diurnal exposure to pollinators, nocturnal exposure, exclusion, and control) on the seeds produced. Flowering occurred from early May to late July and had a mean duration of 29 days in the individual rosettes. The flowers were protandrous; anthesis occurred in the afternoon of the third day after floral opening, and the pistils matured in the afternoon of the fifth day. The stigmas remained receptive from dusk to the following morning. Pollination was mostly allogamous. Nectar was produced principally during the night, from the first stages of floral aperture until the stigmas wilted and flowering ceased. The flowers were visited during the day by hymenoptera, butterflies, and hummingbirds and during the night by bats and moths. Only the nocturnal visitors, however, were successful pollinators. Agave macroacantha is extremely dependent on nocturnal pollinators for its reproductive success.

Journal Article↗
PubMed2000

Pollination ecology of Agave macroacantha (Agavaceae) in a Mexican tropical desert. II. The role of pollinators.

We did a series of observational studies and manipulative experiments on the guild of nocturnal visitors of Agave macroacantha, including (1) a description of the hourly patterns of visits by moths and bats, (2) an evaluation of the relative contribution of bats and moths to flowering success, and (3) an evaluation of the pollination efficiency of the different bat species. Scapes exposed to moths but excluded to bats yielded ∼50% fewer fruits than those exposed to both pollinator groups. Flowers exposed to the bat species Leptonycteris curasoae showed similar fruiting success to those exposed to Choeronycteris mexicana and to those exposed to the whole nocturnal visitor guild. However, the fruits originated from flowers pollinated by Leptonycteris curasoae yielded significantly more seed than those exposed to Choeronycteris mexicana or to the whole pollinator guild. It is concluded that Agave macroacantha is extremely dependent on nocturnal pollinators for its reproductive success and that bats are especially important for successful pollination. Some of these pollinators are migratory and have been reported to be steadily declining. A continuing decline in the populations of pollinators may impede the successful sexual reproduction of the plant host and may put the long-term survival of this agave species under risk.

Journal Article↗
PubMed1989

Insulin response to a short stress period.

In 24 healthy volunteers (seven women, 17 men; mean age 23 +/- 5 years), we studied the insulin response to a short stress period of 30 min, induced by cognitive conflict under social pressure. Insulin, growth hormone (GH), blood glucose and blood pressure (BP) determinations were performed before and after the stress period. There was a significant increase in insulin levels following the stress period (p = 0.02, paired t-test). A multiple stepwise regression analysis, with insulin difference as the dependent variable and initial GH and blood sugar levels, their increments and body mass index as predictors, showed that insulin variation was independent of any of the predictors. We discuss the influence of autonomic innervation on insulin secretion and the possible change in insulin sensitivity during stress.

Adult↗