An agreed statement on calculating lead concentration and uncertainty in XRF in vivo bone lead analysis.
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Algorithms↗
Biomedical subjects
M L Arnold
Publications and source records attributed to M L Arnold.
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.
Bone and Bones↗
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.
Adjuvants, Immunologic↗
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.
Altitude↗
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.
Adolescent↗
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.
Animals↗
Environment-dependent performance and fitness of Iris brevicaulis, I. fulva (Iridaceae), and hybrids.
We tested the relative fitness of two Louisiana Iris species (Iris brevicaulis and I. fulva) and their first-generation backcross hybrids in three experimental watering treatments: dry, field capacity, and flooded. Leaf area expansion rate, gas exchange (A(max), g(s), c(i)), and biomass at final harvest were measured for each species and hybrid class in all three environmental treatments. Fitness (based on total biomass) of the four genotypic classes differed significantly with environment. All genotypic classes performed most poorly in the dry treatment. The fitness ranking of genotypic class also changed across environments (significant genotypic class by treatment interaction) with hybrid genotype fitness shifting relative to parental genotypes. Integrating over all treatments, backcrosses to I. fulva showed the lowest fitness, whereas backcrosses to I. brevicaulis outperformed I. fulva. The differences in fitness were apparently achieved by a combination of differences in photosynthesis and allocation. In this system, hybrids are not necessarily less fit than their parents, and the relationship between hybrid and parental fitness is influenced by environmental conditions, lending support to the Hybrid Novelty model of hybrid zone evolution.
Journal Article↗
Anderson's paradigm: Louisiana irises and the study of evolutionary phenomena.
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Animals↗
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.
Biological Evolution↗
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.
Crosses, Genetic↗
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.
Adult↗
Wild chromosomal variants in Aspergillus nidulans.
Pulsed-field gel electrophoresis and a chromosome-specific cosmid DNA library were used to determine the karyotypes of wild-type Aspergillus nidulans isolates from around the world. Overall, little structural variation was found, with a few major exceptions. One isolate possessed a non-essential B-chromosome of about 1.0 million base pairs (mb). Another isolate had undergone a non-reciprocal translocation of about 1.6 mb of chromosome VI onto chromosome VIII. Other than these chromosomal differences, these isolates appeared phenotypically normal. To analyze its effects on meiosis, the translocation isolate was outcrossed with another wild-type derivative that had a normal electrophoretic karyotype. This cross produced a range of phenotypes, including duplicated progeny that had a barren phenotype similar to that described for Neurospora partial disomics. The duplication was somewhat vegetatively unstable. This is the first association of sterility with chromosomal duplication in A. nidulans.
Aspergillus nidulans↗
Loss of meiosis in Aspergillus.
If strictly mitotic asexual fungi lack recombination, the conventional view predicts that they are recent derivatives from older meiotic lineages. We tested this by inferring phylogenetic relationships among closely related meiotic and strictly mitotic taxa with Aspergillus conidial (mitotic) states. Phylogenies were constructed by using DNA sequences from the mitochondrial small ribosomal subunit, the nuclear ribosomal internal transcribed spacers, and the nuclear 5.8S ribosomal gene. Over 920 bp of sequence was analyzed for each taxon. Phylogenetic analysis of both the mitochondrial and nuclear data sets showed at least four clades that possess both meiotic and strictly mitotic taxa. These results support the hypothesis that strictly mitotic lineages arise frequently from more ancient meiotic lineages with Aspergillus conidial states. Many of the strictly mitotic species examined retained characters that may be vestiges of a meiotic state, including the production of sclerotia, sclerotium-like structures, and hülle cells.
Aspergillus↗
Columbines: a geographically widespread species flock.
Species in the columbine genus, Aquilegia, are known for their broad variation in ecology and floral morphology. Aquilegia is also known for the large degree of intercompatibility among its species, which has led to the suggestion that the genus has arisen recently. However, intercompatibility does not always imply recent divergence and the widespread distribution pattern of the genus has suggested an older age. We constructed phylogenies for Aquilegia plus its close relatives by using nucleotide sequence data from both nuclear and chloroplast DNA. The sequence data averaged over 1250 bp per species. Among the 14 columbine species sampled from Europe, Asia, and North America only 16-bp changes and one insertion/deletion event were detected. In contrast, related genera had from 3 to 45 times this level of variation. The phylogenies derived from the chloroplast and nuclear DNA sequences were highly concordant and suggest that the columbines are the result of a recent, rapid radiation. In contrast to other examples of species flocks, Aquilegia has radiated on a widespread geographical scale. By comparison with their related taxa, we suggest that the evolution of the nectar spur in Aquilegia was a key innovation for this genus and allowed rapid speciation through specialization to specific pollinators.
Base Sequence↗
Floral and ecological isolation between Aquilegia formosa and Aquilegia pubescens.
Habitat preference and pollination syndrome have been suggested as major factors in reproductive isolation among plant species. The columbine genus Aquilegia contains species that have been used as classic examples of reproductive isolation due to ecological and floral factors. In this analysis Aquilegia formosa, Aquilegia pubescens, and natural hybrid populations between these two species were assayed for genetic and morphological variation. Clinal variation was evident for three "random amplified polymorphic DNA" loci and five morphological characters along a transect extending from a lower altitude A. formosa population, through an intermediate hybrid population, to a higher altitude A. pubescens population. Similar clinal variation was also discovered for a transect that included A. formosa-like, hybrid, and A. pubescens-like populations at a single elevation. The change in the frequency of both sets of markers was closely associated with change in habitat. The molecular markers indicate the presence of bidirectional introgression between these two species. In contrast, there was apparently selection against introgression of four of the five alternate floral characters. Selection against the incorporation of floral characters from one species into the other species was suggested by the introgression of the DNA markers with little or no introgression of the four floral characters. These findings suggest the importance of adaptations associated with both pollination syndromes and habitat preference on species integrity.
Adaptation, Biological↗
Sexual origins of British Aspergillus nidulans isolates.
Aspergillus nidulans is a holomorphic fungus, capable of producing both meiotically and mitotically derived spores. Meiosis may be an evolutionary relic in this species because it is potentially capable of mitotic recombination and because most Aspergilli lack the ability to produce meiotic spores. We tested the null hypothesis that meiosis has been a major factor in the origin of strains of A. nidulans from Great Britain by estimating linkage disequilibrium among restriction fragment length polymorphisms. These strains belong to different heterokaryon compatibility groups and are thus incapable of undergoing mitotic recombination with one another, so any recombination evidenced by linkage equilibrium is assumed to be the result of meiosis. Eleven cosmid clones of known chromosomal origin were used to generate multilocus genotypes based on restriction-pattern differences for each heterokaryon compatibility group. Low levels of genetic variation and little linkage disequilibrium were found, indicating that the heterokaryon compatibility groups represent recently diverged lineages that arose via meiotic recombination. The null hypothesis that loci are independent could not be rejected. Additionally, low levels of electrophoretic karyotype variation were indicative of meiosis. We conclude that although A. nidulans probably propagates in a primarily clonal fashion, recombination events are frequent enough to disrupt the stable maintenance of clonal genotypes. We further conclude that the British heterokaryon compatibility groups arose via recombination and not through novel mutation.
Aspergillus nidulans↗
Multiple eruptive cephalic histiocytomas in a case of T-cell lymphoma. A xanthomatous stage of benign cephalic histiocytosis in an adult patient?
A 67-year-old woman had multiple, pinhead-sized, yellowish papules localized to her face, scalp, and neck. A previously diagnosed T-cell lymphoma of low malignancy had been treated with cytostatic drugs. Ultrastructurally the dermal infiltrate consisted predominantly of histiocytic cells in various degrees of differentiation. The cells revealed signs of high metabolic activity and contained well-developed mitochondria, rough endoplasmic reticulum, and lysosomes. Groups of worm-like bodies (comma-shape bodies) and great numbers of coated vesicles in various sizes could be regularly found. Microvillous cell processes formed close interdigitations, and desmosome-like structures occurred between adjacent cell membranes. Lipid storage was present in the form of neutral lipid vacuoles, cholesterol clefts, and myelin-like arrangements of phospholipid membranes. Some multinucleated histiocytic cells, mast cells, lymphocytes, and eosinophilic granulocytes were encountered in the infiltrate. No dermal Langerhans' cells with their characteristic granules were present. Similarities to and differences from benign cephalic histiocytosis, generalized eruptive histiocytoma, and other xanthomatous disorders are discussed.
Aged↗
Congenital ichthyosis with hypogonadism and growth retardation--a new syndrome with peculiar ultrastructural features.
A male patient presented with a congenital ichthyosis clinically characterized by generalized erythroderma, fine scaling on the trunk and palmoplantar hyperkeratoses with severely affected nails. The acanthotic epidermis was characterized by hyperproliferation with a large quantity of mitoses and extremely suppressed keratinization without a normal granular layer. The horny layer was parakeratotic and contained remnants of cell debris and lipid droplets. Ultrastructurally the prickle cell layer was characterized by binuclear cells, oedematization of the keratinocytes and isolated dyskeratotic cells. Some suprabasal cells showed unusual morphological features, containing nuclei with cytoplasmic pseudoinclusions, sometimes leading to a complete disintegration of the nuclear structure, and bowl- and lens-shaped accumulations of a filamentous material. Instead of normal tonofibrils, the aggregated material consisted of fine interlacing filaments. The latter are compared with the filamentous shells in ichthyosis hystrix Curth-Macklin and congenital reticular ichthyosiform erythroderma. The clinical symptomatology--congenital ichthyosis, growth retardation, secondary hypogonadism, hepatomegaly--and the ultrastructural characteristics of the keratinization disorder indicate that the present case cannot be considered as a subtype of the recessively inherited ichthyosis congenita group, but suggest a new syndrome as a separate nosologic entity.
Adult↗