Fluoroquinolone resistance in clinical and environmental isolates of Escherichia coli in Mexico City

Aims:  To assess the different phenotypes and mechanisms of fluoroquinolone (FQ) resistance in clinical and environmental isolates of Escherichia coli .
Methods and Results:  We compared FQ-resistant E. coli isolates, measuring minimal inhibitory concentrations (MIC) of ciprofloxacin, along with susceptibility to other antibiotics. We also searched for the presence of efflux pumps, using efflux inhibitors, and for plasmid-borne FQ-resistance by PCR. We found that, aside from the higher FQ-resistance prevalence among clinical strains, environmental ones resist much lower concentrations of ciprofloxacin. Efflux pumps mediate fluoroquinolone resistance as frequently among environmental isolates than in clinical strains. Plasmid-borne qnrA genes were not detected in any resistant strain.
Conclusions:  Environmental FQ-resistant strains may have a nonclinical origin and/or a selective pressure different from the clinical use of FQs.
Significance and Impact of the Study:  The identification of the source of low-level FQ-resistant strains (ciprofloxacin MIC c . 8 μg ml⁻¹) in the environment could be important to curb the rapid emergence and spread of FQ-resistance in clinical settings, as these strains can easily become fully resistant to FQ concentrations achievable in fluids and tissues during therapy.     

Unilateral sectioning of the superior ovarian nerve of rats with polycystic ovarian syndrome restores ovulation in the innervated ovary

The present study tested the hypothesis that if polycystic ovary syndrome (PCOS) results from activating the noradrenergic outflow to the ovary, unilaterally sectioning the superior ovarian nerve (SON) will result in ovulation by the denervated ovary, and the restoration of progesterone (P4), testosterone (T) and estradiol (E2) normal serum level. A single 2 mg dose of estradiol valerate (EV) to adult rats results in the development of a syndrome similar to the human PCOS. Ten-day old rats were injected with EV or vehicle solution (Vh) and were submitted to sham surgery, unilateral or bilateral sectioning of the SON at 24-days of age. The animals were sacrificed at 90 to 92 days of age, when they presented vaginal estrus preceded by a pro-estrus smear. In EV-treated animals, unilateral sectioning of the SON restored ovulation by the innervated ovary and unilateral or bilateral sectioning of the SON normalized testosterone and estradiol levels. These results suggest that aside from an increase in ovarian noradrenergic tone in the ovaries, in the pathogenesis of the PCOS participate other neural influences arriving to the ovaries via the SON, regulating spontaneous ovulation. Changes in P4, T and E2 serum levels induced by EV treatment seem to be controlled by neural signals arising from the abdominal wall and other signals arriving to the ovaries through the SON, and presents asymmetry.     

Growth hormone restores aged diaphragm myosin composition and performance after chronic undernutrition.

The effects of growth hormone (GH) on diaphragm muscle myosin heavy chain (MHC) composition and mechanical performance were investigated in Fischer 344 male rats aged to senescence (24.5 mo of age). Chronic undernutrition (UN), refeeding (RF), and RF+GH were compared with ad libitum feeding by using a model of UN that produced a 50% decrease in body weight over a 12-mo period. The effect of aging was assessed by comparing MHC composition of ad libitum-fed rats at 12 and 24.5 mo of age. At senescence, significant decreases in slow type I (-23%) and fast type IIA (-31%) MHC had occurred with aging. Conversely, UN over this aging period increased types I (32-73%) and IIA (22-23%) MHC and decreased fast types IIB (32-54%) and IIX (30-31%) MHC. RF and RF+GH reversed these shifts back toward control values. At senescence, maximal specific force, maximal velocity, and specific power capacity were not different across treatment groups. During repetitive isotonic contraction trials, the diaphragms of UN rats maintained power production over time (54% of initial power at 60 s), whereas the power production of diaphragms of ad libitum-fed rats fell to 0% (P < 0.05). In comparison with UN rats, the diaphragms of RF and RF+GH rats produced 23 (not significant) and 11% (P < 0.05) of initial power, respectively, suggesting that RF+GH treatment restored performance characteristics after UN. We conclude that RF+GH can reverse alterations in MHC composition and mechanical performance produced by chronic UN in the aged rat diaphragm.     

Senescence in European Middle Pleistocene hominids: The Atapuerca evidence

The mandibular specimens AT-250 and AT-793 (individual IV) and AT-888 (individual XXI) from the Atapuerca Middle Pleistocene sample show a combination of traits interpreted as evidence of senescence. In order to explore age-related mandibular changes relevant to the interpretation of the Atapuerca hominids, the sample of known age and sex from Spitalfields (London) and the Neolithic sample from Abu Hureyra (Syria) were used as a baseline. Results obtained indicate that the occurrence of an enlarged and posteriorly located mental foramen, in association with high alveolar resorption in AT-250 and AT-888, support the hypothesis of senescence in individuals IV and XXI from the Atapuerca sample. The findings suggest that European Middle Pleistocene populations lived long enough to reach senescence. The age at death for Middle Pleistocene hominids and Neanderthals has previously been estimated at around 40–45 years in the oldest specimens. The appearance of senescence processes before this age is indicative of higher rates of morphological aging in the clade which gave rise to Neanderthals. The anatomical significance of ageing features when considered in the context of craniofacial remodelling can help in the understanding of the taxonomic status of these morphological traits.     

Les Néandertaliens d’El Sidrón (Asturies,Espagne). Actualisation d’un nouvel échantillon

This paper synthesizes and updates the information coming from the El Sidrón (Asturias, Northern Spain) neandertal site. Since 2000, a new sample of Homo neanderthalensis dated to at least 49,000 years old is being systematically recovered at the El Sidrón cave site. The bone assemblage is located in a secondary position, and certainly derives from a close location. The sample is almost exclusively composed of human remains. There is a moderate number of Middle Paleolithic stone tools (n ≈ 415) and very few macro-faunal remains. All skeletal parts are preserved, including some rare bones such as the hyoid bone. Teeth are abundant (n = 213), cranial and postcranial remains are also well represented, but fragmentary, with a special presence of foot and hand bones. A minimum number of thirteen individuals has been identified, comprising different developmental stages from infancy to adulthood: one infant, two juveniles, three adolescents, and seven adults. Paleobiology of the El Sidrón humans fits the pattern found in other neandertal samples: a high incidence of dental hypoplasia and interproximal grooves, yet no serious traumatic lesions are present. Moreover, unambiguous evidence of human-induced modifications (cannibalism) was found on the human remains: cut marks, percussion pitting, conchoidal scars and adhering flakes. Individuals seem to have been treated differentially. Morphologically, the El Sidrón humans show a large number of neandertal lineage-derived features even though certain traits place the sample at the limits of neandertal variation. Integrating the El Sidrón human mandibles and occipital bones into the larger neandertal sample reveals a possible geographic patterning, with southern Neandertals showing broader faces with increased lower facial heights. Ancient DNA analyses have been carried out, developing an anti-contamination protocol of excavation for minimizing the risk of modern human DNA contamination. As a result both mitochondrial and nuclear DNA have been extracted from dental and osteological remains. Curiously, mtDNA comparative analyses suggest a population affinity of Iberian Peninsula Neandertals with Central European Neandertals. Nuclear DNA analyses have permitted the identification of some functional genes such as the melanocortin 1 receptor (MC1R), which regulates hair and skin pigmentation; the FOXP2, a gene involved in the development of language; and the gene involved in the ABO blood group system. Nowadays the large El Sidrón sample is the most significant neandertal sample from the Iberian Peninsula, and augments the European evolutionary lineage fossil record, supporting ecogeographical variability across neandertal populations.     

Correlation between oxidative Stress and Alteration of Intracellular Calcium Handling in Isoproterenol-Induced Myocardial Infarction

Myocardial Ca²⁺ overload and oxidative stress are well documented effects associated to isoproterenol (ISO)-induced myocardial necrosis, but information correlating these two issues is scarce. Using an ISO-induced myocardial infarction model, 3 stages of myocardial damage were defined: pre-infarction (0–12 h), infarction (12–24 h) and post-infarction (24–96 h). Alterations in Ca²⁺ homeostasis and oxidative stress were studied in mitochondria, sarcoplasmic reticulum and plasmalemma by measuring the Ca²⁺ content, the activity of Ca²⁺ handling proteins, and by quantifying TBARs, nitric oxide (NO) and oxidative protein damage (changes in carbonyl and thiol groups). Free radicals generated system, antioxidant enzymes and oxidative stress (GSH/GSSG ratio) were also monitored at different times of ISO-induced cardiotoxicity. The Ca²⁺ overload induced by ISO was counterbalanced by a diminution in the ryanodine receptor activity and the Na⁺-Ca⁺² exchanger as well as by the increase in both calcium ATPases activities (vanadate- and thapsigargine-sensitive) and mitochondrial Ca²⁺ uptake during pre-infarction and infarction stages. Pro-oxidative reactions and antioxidant defences during the 3 stages of cardiotoxicity were observed, with maximal oxidative stress during the infarction. Significant correlations were found among pro-oxidative reactions with plasmalemma and sarcoplasmic reticulum Ca²⁺ ATPases, and ryanodine receptor activities at the onset and development of ISO-induced infarction. These findings could be helpful in the design of antioxidant therapies in this pathology.     

Trophic basis of production in tropical headwater streams,Puerto Rico: an assessment of the importance of allochthonous resources in fueling food webs

The relative importance of allochthonous and autochthonous resources in fueling tropical headwater streams remains an open topic. We combined estimates of secondary production and assessment of its trophic basis to determine which resources were responsible for animal production. We studied benthic insect assemblages in two streams in the Luquillo Experimental Forest, Puerto Rico. Habitat-weighted production estimates were similar in both streams (528.5 and 591.5 mg m⁻² year⁻¹), but production was over twice as high in pool versus riffle habitats. The mayfly Neohagenulus (Leptophlebiidae) was a major contributor to total production (259.1 and 352.2 mg m⁻² year⁻¹). All taxa relied heavily on amorphous detritus and plant tissue. Aquatic insect production was similar to that reported for shrimp assemblages in the same study area, but low relative to temperate region estimates. The trophic basis of production appears to be allochthonous organic matter, which agrees with the small size and closed canopy cover over the study streams. This is the first study quantifying the production and trophic basis of the non-shrimp macroinvertebrate assemblage in tropical island streams. We also provide support for the importance of riparian vegetation as the main energy sources for stream tropical stream food webs.