Prominent effect of soil network heterogeneity on microbial invasion.

Using a network representation for real soil samples and mathematical models for microbial spread, we show that the structural heterogeneity of the soil habitat may have a very significant influence on the size of microbial invasions of the soil pore space. In particular, neglecting the soil structural heterogeneity may lead to a substantial underestimation of microbial invasion. Such effects are explained in terms of a crucial interplay between heterogeneity in microbial spread and heterogeneity in the topology of soil networks. The main influence of network topology on invasion is linked to the existence of long channels in soil networks that may act as bridges for transmission of microorganisms between distant parts of soil.

Toxicity of Brazilian plant seed extracts to two strains of Aedes aegypti (Diptera: Culicidae) and nontarget animals.

Seed ethanolic extracts of 21 Brazilian plants were evaluated for ovicidal, larvicidal, and pupicidal activities against insecticide-susceptible (SS) and field-collected (FC) strains of Aedes aegypti (L.) (Diptera: Culicidae), as well as for their effects on nontarget organisms. Myracrodruon urundeuva Fr. Allemao extract was highly toxic to both mosquito strains. Schinopsis brasiliensis Engler extract showed low toxicity and was 38-68 times less toxic to Ae. aegypti larvae than was M. urundeuva extract. The pupicidal activity (LC50) of 14 plant seed extracts ranged between 9 and 433/g/ml, and toxicities were comparable to both mosquito strains. Piptadenia moniliformis Benth. and Luetzelburgia auriculata (Allemao) Ducke extracts showed the highest activities against pupae of FC and SS strains. None of the extracts showed 100% ovicidal activity. In addition, the active extracts did not show high acute toxicity to mice (LD50 > 1.5 g/kg), except that of Enterolobium contortisiliquum (Vell.) Morong. Most of the active extracts exhibited low toxicity against brine shrimp (Artemia sp.) nauplii. The extracts of M. urundeuva, P. moniliformis, and L. auriculata are promising sources of recognized classes of insecticidal compounds with good selectivity against immature stages of Ae. aegypti.

A computational approach to characterization of bovine sperm chromatin alterations.

We describe here a computational morphology-based approach to the investigation of possible causes of chromatin alterations in sperm. A comprehensive set of state-of-the-art and geometric measures are computationally extracted from toluidine blue stained images and analyzed to infer the possible processes leading to normal and abnormal chromatin formation while seeking a possible taxonomy of chromatin alterations and their influence on sperm head morphology. Using this methodology, we have identified higher chromatin fragility at some specific points of the sperm head. Despite the lack of correlation between morphologies of sperm head and chromatin structure, four main morphological types of chromatin alterations in bull spermatozoa have been identified and their possible causes discussed.

[The rates of postneonatal mortality and sudden infant death in Spain compared with other countries]. / Tasas de mortalidad postneonatal y de la muerte súbita del lactante en España comparada con otros países.

PIP: Studies of infant mortality permit evaluation of the level of health care enjoyed by a population. Official Spanish mortality statistics are based on the medical certificate of death required before burial and on the Statistical Bulletin of Mortality, both of which contain detailed information on the causes of death. The developed countries have similar rates of infant mortality achieved through effective medical treatment of infections and other early problems. In the latest series of infant mortality statistics, Spain's rates varied from 9.88/1000 live births in 1984 to 9.20 in 1986, levels similar to those of the UK, Federal Republic of Germany, Ireland, and Belgium and slightly higher than those of France, Denmark, and Holland which averaged 8/1000 during the same period. Spain's rates were favorable compared to those of Greece, which declined from 14.34/1000 in 1984 to 11.04 n 1988 and of Portugal, where the rate was 12.18 in 1989. Infant mortality decline depends on declines in postneonatal mortality. Postneonatal mortality rates in Spain declined from 3.15/1000 in 1984 to 3.01 in 1986. The latest available data, for 1988, showed postneonatal rates of 2.9 for Denmark and Greece, 2.2 for Holland, and 2.05 for Italy. Portugal's rate declined from 5.41 in 1984 to 4.11 in 1989. Studies of sudden infant death syndrome (SIDS) show a progressively increasing incidence. Rates of death from SIDS in 1988 ranged from 1.3 to 2.8/1000 in France, the Federal Republic of Germany, and the UK. Rates in Spain increased from .15/1000 in 1984 to .23 in 1986. The annual increase probably results from a greater number of deaths attributed to SIDS in death certificates in the absence of autopsy findings. SIDS is a main cause of postneonatal mortality in most of the world, especially among term infants of adequate birth weight.^ieng