Characterization of high-copy-number retrotransposons from the large genomes of the louisiana iris species and their use as molecular markers

The Louisiana iris species Iris brevicaulis and I. fulva are morphologically and karyotypically distinct yet frequently hybridize in nature. A group of high-copy-number TY3/gypsy-like retrotransposons was characterized from these species and used to develop molecular markers that take advantage of the abundance and distribution of these elements in the large iris genome. The copy number of these IRRE elements (for iris retroelement), is approximately 1 x 10(5), accounting for approximately 6-10% of the approximately 10,000-Mb haploid Louisiana iris genome. IRRE elements are transcriptionally active in I. brevicaulis and I. fulva and their F(1) and backcross hybrids. The LTRs of the elements are more variable than the coding domains and can be used to define several distinct IRRE subfamilies. Transposon display or S-SAP markers specific to two of these subfamilies have been developed and are highly polymorphic among wild-collected individuals of each species. As IRRE elements are present in each of 11 iris species tested, the marker system has the potential to provide valuable comparative data on the dynamics of retrotransposition in large plant genomes.

An accelerator based system for in vivo neutron activation analysis measurements of manganese in human hand bones

Manganese (Mn) is an essential nutrient for growth and development. Unfortunately, overexposure can lead to neurological damage, which is manifested as a movement disorder marked by tremors. Preclinical symptoms have been found in populations occupationally exposed to the element, and it is suggested that in late stages of the disorder, removing the Mn exposure will not prevent symptoms from progressing. Hence, it is desirable to have a means of monitoring Mn body burden. In vivo neutron activation analysis (IVNAA) is a technique which allows the concentration of some elements to be determined within sites of the body without invasive procedures. Data in the literature suggests that the Mn concentration in bone is greater than other tissues, and that it may be a long term storage site following exposure. Therefore, using the McMaster KN-accelerator to produce neutrons through the 7Li(p,n)7Be reaction, the feasibility of IVNAA for measuring Mn levels in the human hand bone was investigated. Mn is activated through the 55Mn(n,gamma)56Mn reaction, and the 847 keV gamma rays emitted when 56Mn decays are measured outside the body using NaI(Tl) detectors. An optimal incident proton energy of 2.00 MeV was determined from indium foil and microdosimetry measurements. Hand phantom data suggest a minimum detectable limit of approximately 1.8 ppm could be achieved with a reasonably low dose of 50 mSv to the hand (normal manganese levels in the human hand are approximately 1 ppm). It is recommended the technique be developed further to make human in vivo measurements.

Genetics and the fitness of hybrids

Over the years, the evolutionary importance of natural hybridization has been a contentious issue. At one extreme is the relatively common view of hybridization as an evolutionarily unimportant process. A less common perspective, but one that has gained support over the past decade, is that of hybridization as a relatively widespread and potentially creative evolutionary process. Indeed, studies documenting the production of hybrid genotypes exhibiting a wide range of fitnesses have become increasingly common. In this review, we examine the genetic basis of such variation in hybrid fitness. In particular, we assess the genetic architecture of hybrid inferiority (both sterility and inviability). We then extend our discussion to the genetic basis of increased fitness in certain hybrid genotypes. The available evidence argues that hybrid inferiority is the result of widespread negative epistasis in a hybrid genetic background. In contrast, increased hybrid fitness can be most readily explained through the segregation of additive genetic factors, with epistasis playing a more limited role.

Differential inhibitory effects of intravenous immunoglobulin preparations on HLA-alloantibodies in vitro

BACKGROUND

Treatment of allosensitized patients with intravenously administered pooled immunoglobulin preparations (IVIG) may lead to a long-lasting reduction of anti-HLA alloantibody titers. An inhibitory response of IVIG preparations on lymphocytotoxicity is suggested to depend on IgG and to predict a successful reduction of anti-HLA alloantibodies upon the administration of high-dose IVIG in vivo.

METHODS

In this study, we evaluated different IVIG preparations for their in vitro inhibitory capacity on lymphocytotoxicity and binding of anti-HLA alloantibodies to purified HLA antigens. For that purpose sera from 24 highly sensitized patients awaiting kidney transplantation and serological HLA testing reagents were used. Panel-reactive antibody (PRA) determinations using standard complement-dependent cytotoxicity testing and anti-HLA alloantibody determination by ELISA were carried out in the presence and absence of 50% (v/v) IVIG.

RESULTS

The addition of IgG-containing IVIG preparations gave only a moderate inhibitory response judging from the average decrease of PRA levels (absolute DeltaPRA range: -2% to 16%), whereas the largest inhibition of lymphocytotoxicity was seen after the addition of IgM/IgA-containing IVIG preparations (absolute DeltaPRA range: 19% to 44%). For both IgG and IgM/IgA-containing IVIG preparations, the reduction of lymphocytotoxicity occurred in a dose-dependent fashion without a preference for particular anti-HLA class I antibody specificities. Significantly lower inhibitory effects on anti-HLA antibody reactivity were observed when the effects of IVIG preparations were monitored by ELISA (absolute DeltaPRA range: 7% to 22%).

CONCLUSIONS

Our data suggest that the immunomodulatory capacity is largely caused by the IgM/IgA fraction of IVIG when analyzed by lymphocytotoxicity. The different effect on ELISA versus complement-dependent cytotoxicity testing suggests that interactions of IVIG with complement rather than anti-idiotypic antibodies may contribute to the inhibitory effects of IVIG in vitro.

Intimately linked or hardly speaking? The relationship between genotype and environmental gradients in a Louisiana Iris hybrid population

Several models of hybrid zone evolution predict the same spatial patterns of genotypic distribution whether or not structuring is due to environment-dependent or -independent selection. In this study, we tested for evidence of environment-dependent selection in an Iris fulva x Iris brevicaulis hybrid population by examining the distribution of genotypes in relation to environmental gradients. We selected 201 Louisiana Iris plants from within a known hybrid population (80 m x 80 m) and placed them in four different genotypic classes (I. fulva, I. fulva-like hybrid, I. brevicaulis-like hybrid and I. brevicaulis) based on seven species-specific random amplified polymorphic DNA (RAPD) markers and two chloroplast DNA haplotypes. Environmental variables were then measured. These variables included percentage cover by tree canopy, elevation from the high water mark, soil pH and percentage soil organic matter. Each variable was sampled for all 201 plants. Canonical discriminant analysis (CDA) was used to infer the environmental factors most strongly associated with the different genotypic groups. Slight differences in elevation (-0.5 m to +0.4 m) were important for distinguishing habitat distributions described by CDA, even though there were no statistical differences between mean elevations alone. I. brevicaulis occurred in a broad range of habitats, while I. fulva had a narrower distribution. Of all the possible combinations, I. fulva-like hybrids and I. brevicaulis-like hybrids occurred in the most distinct habitat types relative to one another. Each hybrid class was not significantly different from its closest parent with regard to habitat occupied, but was statistically unique from its more distant parental species. Within the hybrid genotypes, most, but not all, RAPD loci were individually correlated with environmental variables. This study suggests that, at a very fine spatial scale, environment-dependent selection contributed to the genetic structuring of this hybrid zone.

Adult generativity and the socialization of adolescents: relations to mothers' and fathers' parenting beliefs, styles, and practices

Mothers, fathers, and their adolescent children participated in two studies investigating the relations between Erikson's concept of generativityin adulthood and patterns of parenting. Study 1 involved 77 mothers and 48 fathers of 1st-year university students; Study 2 was part of an investigation of socialization processes in 35 families with an adolescent, aged 14-18. Parental generative concern was assessed by the Loyola Generativity Scale (LGS) of McAdams and de St. Aubin (1992) in each study. In both studies, mothers demonstrated positive relations between scores on the LGS and an authoritative style of parenting, as well as between generativity and more positive, optimistic views of adolescent development. In Study 2, these more positive views in turn mediated some aspects of autonomy-fostering practices used with the adolescent. Variations in fathers' levels of generative concern were less consistently related to these indices of parenting, however.

Age-specific fitness components in hybrid females of Drosophila pseudoobscura and D. persimilis

Most models of hybridization assume that hybrids are less fit than their parental taxa. In contrast, some researchers have explored the possibility that hybrid individuals may actually have higher fitness and so play an important role in the generation of new species or adaptations. By estimating age-specific fitness components, we can determine not only how hybrid fitness differs from parental taxa, but also whether the fitness of hybrids relative to parental taxa changes with age. Here we describe an analysis of age-specific fitness traits in two species of Drosophila, D. pseudoobscura and D. persimilis, and their F1 hybrids. At early ages, hybrid females lay as many eggs as parental individuals, on average, but produce far fewer offspring. By late ages, in contrast, parental taxa show a steep decline in production not seen in hybrids, such that hybrids produce more offspring, on average, than parental taxa. Furthermore, egg-adult survival in hybrids is negatively correlated with egg density, whereas these traits are only weakly correlated in parental taxa. The results are limited somewhat by the fact that we analyze only two strains, and that these may be partially inbred. Nonetheless, the results are certainly illustrative, pointing out not only that at least some hybrid individuals may be as fit or fitter than parental taxa, but also that the difference between hybrids and parental taxa varies with age.

Monte Carlo design study for in vivo bone aluminum measurement using a low energy accelerator beam

The need for aluminum monitoring exists in occupational medicine, as well as for the clinical monitoring of patients with renal dysfunction. After the development of an appropriate neutron source card, Monte Carlo simulations were made to design moderator/reflector assembly consisting of a polyethylene moderator (2 cm) and graphite reflector (30 cm), surrounded by a boronated (5%) wax (20 cm) and lead (1 cm) shield. This design should allow for the bone aluminum measurement of healthy subjects, but prior to that detailed microdosimetry is necessary to address a noticed disagreement between theoretical and experimental dose data.

System design for in vivo neutron activation analysis measurements of manganese in the human brain: based on Monte Carlo modeling

Manganese is an essential nutrient required by the human body, but conversely, over exposure to the element may cause central nervous system damage. The technique of in vivo neutron activation analysis, using the McMaster KN-accelerator, is being investigated as a possible method of noninvasively determining manganese concentrations within the human body. Since the brain is the primary target of damage from exposure it would be the ideal site for measurements. Thus, Monte Carlo simulations have been undertaken to define the optimum experimental parameters for such a measurement, examining the use of possible moderator, reflector and collimator materials.

Nectar Production in Louisiana Iris Hybrids

Nectar is an important attractant for pollinators, and a plant's success in sexual reproduction can be influenced by the amount and concentration of nectar produced by its flowers. We studied nectar production over flower lifetime in Iris fulva, Iris brevicaulis, and four classes of hybrids-reciprocal F1's and backcrosses-between these species. Iris fulva produced less concentrated nectar than did I. brevicaulis, whereas I. brevicaulis flowers had a shorter life span. Hybrids were not intermediate, but they had the high nectar concentration of I. brevicaulis combined with the long life span of I. fulva flowers. Nectar production and concentration declined after the first day in all classes, but flowers continued to produce nectar until they were completely wilted. Backcrosses did not show a shift in mean or increased variation for the characters that distinguished the parental species; backcrosses toward I. fulva retained the high nectar concentration of I. brevicaulis, and backcrosses toward I. brevicaulis did not have a reduced flower life span. Overall, F1 hybrid flowers produced the highest amounts of nectar and nectar sugar over their life spans. These results, together with previously obtained data on pollinator choice in mixed arrays of the same flower classes, show that F1 hybrids between these species do not suffer from reduced attractiveness to pollinators. F1 individuals produced more nectar and nectar sugar than did their parents, and thus, they are possibly even more attractive to pollinators that forage for nectar.

Frequency and spatial patterning of clonal reproduction in Louisiana iris hybrid populations

The plant genera in which natural hybridization is most prevalent tend to be outcrossing perennials with some mechanism for clonal (i.e., asexual) reproduction. Although clonal reproduction in fertile, sexually reproducing hybrid populations could have important evolutionary consequences, little attention has been paid to quantifying this parameter in such populations. In the present study, we examined the frequency and spatial patterning of clonal reproduction in two Louisiana iris hybrid populations. Allozyme analysis of both populations revealed relatively high levels of genotypic diversity. However, a considerable amount of clonality was apparent. Nearly half of all genets (47%) in one population and more than half (61%) in the other had multiple ramets. Furthermore, both populations exhibited relatively high levels of genetic structuring, a pattern that resulted from the aggregation of clonal ramets. The occurrence of clonal reproduction in hybrid populations could not only facilitate introgression through an increase in the number of flowering ramets per genet and/or the survivorship of early generation hybrids, but might also influence the mating system of such populations. Any potential increase in the selfing rate due to cross-pollination among ramets of the same genet may, in turn, increase the likelihood of homoploid hybrid speciation.

Generativity and moral development as predictors of value-socialization narratives for young persons across the adult life span: from lessons learned to stories shared

Little research so far has examined storytelling as a channel of value socialization. In the present study, 129 adults from 3 age groups (18-26, 28-50, 60-75) were asked to tell stories for adolescents about 2 of their past value-learning experiences. Generative concern (D. P. McAdams & E. de St. Aubin, 1992) and moral reasoning stage level were also assessed. Stronger generative concern was predictive of a greater sense of having learned important lessons from these past events, of stronger adult value socialization investment, and of more engaging narratives for adolescents as judged by a panel of uninstructed raters. Higher levels of moral reasoning were positively related to generative concern and to a stronger sense of past lessons learned. Generativity appears important to the project of value socialization across the adult life span.

Generativity and moral development as predictors of value-socialization narratives for young persons across the adult life span: from lessons learned to stories shared

Little research so far has examined storytelling as a channel of value socialization. In the present study, 129 adults from 3 age groups (18-26, 28-50, 60-75) were asked to tell stories for adolescents about 2 of their past value-learning experiences. Generative concern (D. P. McAdams & E. de St. Aubin, 1992) and moral reasoning stage level were also assessed. Stronger generative concern was predictive of a greater sense of having learned important lessons from these past events, of stronger adult value socialization investment, and of more engaging narratives for adolescents as judged by a panel of uninstructed raters. Higher levels of moral reasoning were positively related to generative concern and to a stronger sense of past lessons learned. Generativity appears important to the project of value socialization across the adult life span.

Developmental selection within the angiosperm style: using gamete DNA to visualize interspecific pollen competition

Among flowering plants, females often have little control over the genetic relatedness of pollen deposited on stigmas. Thus, postpollination processes are of primary importance for mate discrimination. The ability to screen and select among male gametes during pollen tube growth within the female tissues of the stigma, style, and ovary is critical to the process of mate choice and reproductive isolation. However, direct evidence of the mechanistic/developmental processes associated with mate choice in flowering plants is sparse. We studied the contribution of postpollination, prefertilization processes to reproductive isolation in two wind-pollinated species of birch (Betula) that commonly hybridize in nature. We exploited the 3-fold difference in ploidy level between these two species to determine the paternity of individual pollen tubes growing within female reproductive tissues. We then tracked their developmental fate in conspecific, heterospecific, and mixed-species crosses. This design allowed a direct comparison of developmental processes responsible for reproductive isolation in both single-species and mixed-species pollinations. Our results have important implications for the population genetic outcome of hybridization dynamics in natural populations. Paternity analysis of progeny from mixed-species pollinations revealed that conspecific pollen tubes sired more than 98% of seedlings. Biased siring success was not the result of differential embryo abortion. We detected strong, early postpollination barriers such as pollen tube incompatibility, slower pollen tube growth, and delayed generative cell mitosis. Conspecific fertilization precedence was mediated by favorable or unfavorable male-female interactions, but there was no evidence for antagonistic male-male interactions.

The feasibility of measuring manganese concentrations in human liver using neutron activation analysis

Manganese is an element which is required by the human body. However, as with most metals, in large amounts manganese can be toxic. People who suffer from severe manganese intoxication have symptoms similar to those of Parkinson's disease. Preclinical symptoms of manganese intoxication have recently been detected in individuals working in industries which have manganese dioxide dust in the air. The concentration of many toxic elements can be measured in vivo using neutron activation. A small dose of neutrons is delivered to the organ of interest, the neutrons are readily captured by the target nuclei, and the gamma rays given off can be detected outside of the body. A neutron activation analysis system is being developed to measure manganese concentrations in humans. The McMaster KN-accelerator supplies the neutron beam and the thermal neutron capture reaction 55Mn(n,gamma)56Mn is used. The half-life of 56Mn is 2.58 hr and thus counting can occur after irradiation. The 847 keV gamma ray given off when 56Mn decays is detected using a Nal detector. Calibration curves are made using phantoms with known concentrations of Mn. This system will be used to monitor manganese levels in individuals who have occupational exposure to the element. Preliminary measurements, using liver phantoms, give a minimum detectable limit for Mn in the liver of less than one part per million, which is well below normal levels.