The effect of the Hurnik-Morris (HM) system on sow reproduction, attrition, and longevity

Sows were randomly selected and assigned to either the Hurnik-Morris system (HM; n = 59) or a conventional gestation crate system (GC; n = 90) before breeding. The HM system provides housing for sows in small groups. All sows were bred to Duroc x Hampshire commercial boars. A common farrowing barn with 18 farrowing crates was used for the HM and GC sows. The HM sows had less (P<.001) backfat at farrowing. Average parity per sow (P<.046), lifetime number of pigs born per sow (P<.02), lifetime number of pigs born alive per sow (P<.02), and lifetime number weaned per sow (P<.045) were higher for sows housed in the HM system. The total number of sows removed from the GC system was higher (P<.025) than the number leaving the HM system. The higher parity level and lifetime production exhibited by the sows in the HM system indicates that this system supports greater longevity and may reflect the superior effect that this housing system has on animal well-being.     

Female preference for fly song: playback experiments confirm the targets of sexual selection

The courtship song of Drosophila is thought to be involved in sexual selection and species recognition. Because of the mating system of flies, however, directly demonstrating that song influences female preference is difficult. The majority of previous studies have used an experimental design that potentially confounds male and female reactions to song. In D. montana, correlational evidence has suggested that males that produce short sound pulses consisting of a high number of sound cycles (i.e. a high carrier frequency) have a higher mating success than other males. In this study, we played synthetic song that varied in pulse length and carrier frequency to individual females in the laboratory, both alone and in the presence of mute males. We scored female preference via an acceptance posture, 'wing spreading', which the females of this species usually display prior to mounting by a male. Females responded to synthetic song in the absence of males. The presence of mute males significantly increased their overall responsiveness, but the relative effectiveness of the songs did not change, eliminating male reaction to song as a possible confounding factor in the results. The interaction between pulse length and carrier frequency determined the discrimination between song types, with females responding most readily to song consisting of short pulses with a high carrier frequency. Thus, direct examination of female preferences supports the previous studies of male mating success, and confirms female song preference as a likely determinant of male mating success. Copyright 1998 The Association for the Study of Animal Behaviour     

Folate and vitamin B12 status in a group of preschool children

OBJECTIVES: The purpose of this investigation was to determine the prevalence of sound, decayed, filled, and sealed permanent tooth surfaces for children and adolescents from three fluoridated communities in British Columbia and to develop a predictive model of sealant use that included the dental caries status of tooth surfaces. METHODS: Children in grades 2 and 3 (n = 2,715) and adolescents in grades 8 and 9 (3,317) were surveyed to determine the prevalence of sound, decayed, filled, and sealed permanent tooth surfaces. The DMFS index, modified to include incipient (D1) and cavitated (D2) lesions, was used to measure the status of all tooth surfaces. The prevalence of D1D2MF and sealed tooth surfaces was estimated by age group and tooth type. Logistic regression models were developed to analyze the association between a number of independent variables and sealant use. RESULTS: About 60 percent of surveyed students had one or more sealants present, with a mean of 3.2 sealants per subject. Of all pit and fissure surfaces on permanent first molars, 23.4 percent and 20.1 percent were sealed for the 11 years and younger and 12 years and older age groups, respectively. For these same two age groups, the percentages of pit and fissure surfaces that were decayed and filled were 6.7 percent and 19.7 percent, respectively. For both age groups combined, 10.8 percent and 23.7 percent of all pit and fissure surfaces on second molars and premolars, respectively, were sealed. The prevalence of decayed and filled pit and fissure surfaces was 5.6 percent and 1.8 percent, respectively, for second molars and premolars. Premolars were being sealed at a rate of 13 to 1 compared to the number of decayed and filled surfaces. Logistic regression failed to identify meaningful predictors of sealant use. CONCLUSIONS: Results from this study found an increase in the prevalence of sealants in the three communities surveyed, yet failed to identify criteria used by dentists or auxiliaries when making decisions about sealant placement. Professional education in the appropriate use of sealants may be necessary.     

Heterodimer formation and crystal nucleation of gramicidin D

The linear pentadecapeptide antibiotic gramicidin D is a heterogeneous mixture of six components. Precise refinements of three-dimensional structures of naturally occurring gramicidin D in crystals obtained from methanol, ethanol, and n-propanol demonstrate the unexpected presence of stable left-handed antiparallel double-helical heterodimers that vary with the crystallization solvent. The side chains of Trp residues in the three structures exhibit sequence-specific patterns of conformational preference. Tyr substitution for Trp at position 11 appears to favor beta ribbon formation and stabilization of the antiparallel double helix that acts as a template for gramicidin folding and nucleation of different crystal forms. The fact that a minor component in a heterogeneous mixture influences aggregation and crystal nucleation has potential applications to other systems in which anomalous behavior is exhibited by aggregation of apparently homogeneous materials, such as the enigmatic behavior of prion proteins.     

The reconstructed evolutionary process

Phylogenies reconstructed from contemporary taxa do not contain information about lineages that have gone extinct. We derive probability models for such phylogenies, allowing real data to be compared with specified null models of evolution, and lineage birth and death rates to be estimated.