Exploring artificial cranial deformation using elliptic Fourier analysis of Procrustes aligned outlines

The anatomical effects of artificial cranial deformation on the face and the base have been subject to various metric approaches, including standard linear as well as finite element techniques, and have produced controversial results (Antón [1989] Am. J. Phys. Anthropol. 79:253-267; Kohn et al. [1993] Am. J. Phys. Anthropol. 90:147-158). It can be argued that diverging observations partly result from methodological constraints. The present study compares samples of intentionally deformed and undeformed human crania, using elliptic Fourier analysis (EFA), a morphometric approach which has been shown to be particularly appropriate for characterizing the shape of two-dimensional outlines and associated shape changes. We improve the standard EFA approach by adding a preliminary orientation of the outlines following the rotation parameters of a Procrustes superimposition, using multiple homologous landmarks called control points. The results confirm that circumferentially deformed skulls exhibit modifications of the basioccipital region, together with increased anterior and inferior facial projection. However, the degree to which basioccipital flattening is modified in circumferentially deformed Peruvians was found to be less marked than changes observed in the face. Some of the modifications observed here can be related to morphological trends existing in the population from which our sample was taken. The observation of other modifications may be subject to methodological constraints of standard morphometric approaches.     

The genetic background as a determinant of human T-cell leukemia virus type 1 proviral load

Human T-cell leukemia virus type 1 (HTLV-1) is etiologically linked with HTLV-1-associated diseases. HTLV-1 proviral load is higher in persons with adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis than in asymptomatic carriers. However there are little data available on the factors controlling HTLV-1 proviral load in carriers. To study the effect of genetic background on HTLV-1 proviral load, we employed a mouse model of HTLV-1 infection that we had established. Here we analyzed nine strains of mice and found there is a great variation of proviral load among mouse strains that is not necessarily dependent on major histocompatibility complex. The antibody response is also different among these strains. To our knowledge, this is the first demonstration of the importance of the genetic background other than major histocompatibility complex controlling the HTLV-1 proviral load.     

Abnormal anxiety-related behavior in serotonin transporter null mutant mice: the influence of genetic background

Serotonin transporter (5-HTT) null mutant mice provide a model system to study the role genetic variation in the 5-HTT plays in the regulation of emotion. Anxiety-like behaviors were assessed in 5-HTT null mutants with the mutation placed on either a B6 congenic or a 129S6 congenic background. Replicating previous findings, B6 congenic 5-HTT null mutants exhibited increased anxiety-like behavior and reduced exploratory locomotion on the light ↔ dark exploration and elevated plus-maze tests. In contrast, 129S6 congenic 5-HTT null mutant mice showed no phenotypic abnormalities on either test. 5-HTT null mutants on the 129S6 background showed reduced 5-HT_1A receptor binding (as measured by quantitative autoradiography) and reduced 5-HT_1A receptor function (as measured by 8-OH-DPAT-indcued hypothermia). These data confirm that the 5-HTT null mutation produced alterations in brain 5-HT function in mice on the 129S6 background, thereby discounting the possibility that the absence of an abnormal anxiety-like phenotype in these mice was due to a suppression of the mutation by 129 modifier genes. Anxiety-like behaviors in the light ↔ dark exploration and elevated plus-maze tests were significantly higher in 129S6 congenic +/+ mice as compared to B6 congenic +/+ mice. This suggests that high baseline anxiety-like behavior in the 129S6 strain might have precluded detection of the anxiety-like effects of the 5-HTT null mutation on this background. Present findings provide further evidence linking genetic variation in the 5-HTT to abnormalities in mood and anxiety. Furthermore, these data highlight the utility of conducting behavioral phenotyping of mutant mice on multiple genetic backgrounds.     

Osmotic tolerance of mouse spermatozoa from various genetic backgrounds: acrosome integrity, membrane integrity, and maintenance of motility

All cells have an intrinsic biophysical property related to their ability to undergo osmotically driven volume changes. This project is of fundamental importance to our understanding of the basic cryobiology of mouse spermatozoa. The objectives of this study were to determine the osmotic tolerance limits for (1) motility, (2) acrosome integrity, and (3) membrane integrity of mouse spermatozoa from multiple genetic backgrounds including: C57BL/6, BALB/c, FVB, C3H, 129/SVS2 hsd B6C3F1, CB6F1, and ICR. The maintenance of acrosomal and plasma membrane integrity was not affected by genetic background (p=0.13), however, there was an interaction between genetic background and osmolality. In addition, acrosome and plasma membrane integrity was highly correlated within each strain (p<0.01). In contrast to acrosome and plasma membrane integrity, the motility of spermatozoa from different genetic backgrounds fell sharply on both sides of isosmolality, both with and without return to isosmotic conditions. Exposure to hyposmotic conditions caused morphological changes in the spermatozoa, which inhibited motility. However, this morphological change was not reversible in all cases when returned to isosmotic conditions. The ability to maintain motility in an anisosmotic media was affected by genetic background, osmolality as well as the interaction between genetic background and osmolality (p<0.05). In conclusion, mice with different genetic backgrounds appear to have similar tolerance to osmotic changes in terms of sperm acrosome and plasma membrane integrity; however, the ability to maintain motility differs between genetic backgrounds.     

Modifiers of the jumonji mutation downregulate cyclin D1 expression and cardiac cell proliferation

Cell proliferation is an important factor in various developmental processes in tissue morphogenesis, and is strictly regulated spatiotemporally. jumonji (jmj) deficient mice with a C3H/He background show hyperproliferation of cardiac myocytes and die probably of the phenotype around embryonic day 11.5. Analyses of the abnormalities revealed that repression of cyclin D1 expression by jmj is necessary for downregulation of cardiac myocyte proliferation. On the other hand, jmj mutant mice with a BALB/c background die around E14.5, suggesting that genetic background modifies hyperproliferation in the heart and timing of lethality. Here, we demonstrated that the hyperproliferation was not observed, and that cell proliferation and expression of cyclin D1 were downregulated properly in the cardiac ventricles of jmj mutant mice with a BALB/c background. These results suggest the modifier(s) of the jmj mutation can downregulate cardiac cell proliferation by repressing cyclin D1 expression in the same way as jmj.     

Cultural niche construction and the evolution of small family size

A model of cultural niche construction with two culturally transmitted traits is examined. The frequency of individuals with a certain general predisposition, which is transmitted vertically, plays a role as the cultural background, or the cultural niche, of the population. The cultural background determines the rate of oblique, relative to vertical, transmission of another cultural trait that affects fertility of individuals. It is assumed that individuals with fewer offspring are more likely to achieve social roles that influence the succeeding generation and are therefore overrepresented as transmitters in the process of oblique transmission. Our model suggests that even a slight overrepresentation of those with fewer offspring can drive the evolution of small family size, provided that the rate of oblique transmission depends strongly on the cultural background. In addition, our model may help to explain the time lag between the decrease in death rates and the subsequent decrease in birth rates during the demographic transition of industrializing societies.     

Gene silencing in potato: allelic differences and effect of ploidy

Silencing of genes is mostly studied in diploid, homozygous, self-fertile and sexually propagated species. However, conclusions drawn for these species are not always applicable to crops like potato, which is an autotetraploid, highly heterozygous, vegetatively propagated species. Factors influencing the level of silencing in potato are discussed, with emphasis on inhibition of the granule-bound starch synthase I (GBSSI) gene. Type of construct, number of integrated T-DNA copies, structural arrangement of the T-DNA locus, integration site, target tissue and genetic background are important factors for all plant species. Ploidy level and multiple allelism are factors deserving special attention when the efficiency of silencing of endogenous genes is studied in polyploid, heterozygous species such as potato.     

Anthropogenic Metal Content and Natural Background of Overbank Sediments from the Mining District of Guanajuato,Mexico

In many mining districts, metal pollutants from mine tailings have historically been dumped into local streams. The purpose of this study was to determine the concentrations of Pb, Cu, Zn, Mo, Sb, Cs, Cr, Sc, Co, Ni, and Li in eight overbank-sediment profiles from the Guanajuato River, in the Guanajuato mining district and to establish geochemical background values using direct and indirect methods. The background levels calculated using the direct method in pristine overbank deposits were similar to or slightly higher than the upper crustal values for Sc, Cr, Co, Ni, Zn, and Mo (17.3, 108.7, 18.7, 44.4, 97.2, and 1.1 mg/kg, respectively). In contrast, levels of Cu, Cs, and Pb were up to two times higher than crustal values (93.1, 11.2, and 37.5 mg/kg, respectively), and the median concentration of Sb was 8.2 mg/kg, up to 20 times the crustal level. These natural anomalies can be explained by the presence of mineral deposits in the Guanajuato mining district. Ni and Cr were provided by the ultramafic rocks of the Sierra de Guanajuato. The geochemical backgrounds established with the indirect method of Sc, Cr, Co, Ni, and Mo were lower than those found in the natural background. Moreover, the geochemical backgrounds established with the indirect method of Cu, Zn, Sb, Cs, and Pb were higher than those found in the geochemical background established with the direct method. Contamination levels calculated by the geoaccumulation index (Igeo) indicated moderate to strong contamination for Cu, Zn, Sb, and Pb in more than half of the samples. This contamination may be attributable to historical discharges of mine tailings in the Guanajuato River and the use of Cu during the metallurgical process of amalgamation. Our results provide evidence that anthropogenic metals stored in the fluvial plain of the Guanajuato River represent a major potential source of pollutants to surface and groundwaters downstream from the study area in the Lerma-Santiago basin.     

The locomotor activities on sites covered by silk produced by related and unrelated spider mites in Tetranychus urticae (Acari: Tetranychidae)

The two-spotted spider mite Tetranychus urticae is a silk producer known to live in groups with a common silk web that can cover entire plants and protect mites against predators, rain and wind. Silk also plays an important role during collective migration by aerial dispersal or by walking. In this context, we studied the locomotor activity i.e. time in movement, in resting, and in static exploration (probing behaviour) of an individual confronted to clean places and/or places covered by silk coming from its own population or from another. Two populations were tested, one of the red form (Tunisia) and another of the green form (Belgium). The experimental results showed that the presence or the absence of silk did not influence the relative proportion of each behavioural item either for the red or the green population. Individuals of the green form population spent more time moving and less time resting than individuals of the red form population and this, whatever the substrate (red/green silk, clean). Moreover, the silk from the red form population attracted individuals from both populations, whereas the silk produced by the green form population did not attract any individual either from the red or the green form. This surprising result might have been due to a difference in the quantity and/or quality of silk woven by the two forms. We discuss how the differences observed in the behaviour of these two populations may result from differences in their strategy to rapidly increase the population of the colony and reinforce the silk nest.     

Fluctuations in food supply drive recruitment variation in a marine fish

Reproductive rates and survival of young in animal populations figure centrally in generating management and conservation strategies. Model systems suggest that food supply can drive these often highly variable properties, yet for many wild species, quantifying such effects and assessing their implications have been challenging. We used spatially explicit time series of a well-studied marine reef fish (black surfperch Embiotoca jacksoni) and its known prey resources to evaluate the extent to which fluctuations in food supply influenced production of young by adults and survival of young to subadulthood. Our analyses reveal: (i) variable food available to both adults and to their offspring directly produced an order of magnitude variation in the number of young-of-year (YOY) produced per adult and (ii) food available to YOY produced a similar magnitude of variation in their subsequent survival. We also show that such large natural variation in vital rates can significantly alter decision thresholds (biological reference points) important for precautionary management. These findings reveal how knowledge of food resources can improve understanding of population dynamics and reduce risk of overharvest by more accurately identifying periods of low recruitment.