Apolipoprotein AI and CIII gene polymorphisms and their association with lipid levels in Italian, Greek and Anglo-Irish populations of Australia

PRIMARY OBJECTIVE

The apolipoprotein (apo) AI-CIII-AIV gene cluster on chromosome 11 has been identified as a candidate region for hyperlipidaemia and in particular for hypertriglyceridaemia. Our aim was to detect associations between the apo AI and CIII polymorphisms and the plasma lipids, total cholesterol, triglycerides, high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol in normal, healthy, adults from three ethnic groups of Australia--Italian, Greek and Anglo-Irish, separately by gender.

METHODS AND PROCEDURES

The SstI restriction fragment length polymorphisms (RFLP) in the 3' untranslated region of the apo CIII gene and the MspI RFLP in the third intron of the apo AI gene were scored and the lipid concentrations were ascertained using standard methodologies. t-tests were used to compare lipid levels between sexes and between populations, and multivariate ANOVA was used to detect if the two RFLPs had an effect on any of the lipid concentrations.

MAIN OUTCOMES AND RESULTS

The two RFLPs exhibit strong linkage disequilibrium in all three populations (p < 0.001). There were some significant differences in allele frequencies among the populations: the minor S2 allele was more frequent in Italians (0.12) than Greeks (0.03) (p = 0.003), and the minor M2 allele was more common in Greeks (0.14) than Anglo-Irish (0.05) (p = 0.026). We found no significant association between either of the RFLPs and any of the lipid concentrations in either sex of all three populations. However, Kruskal-Wallis tests detected associations of borderline significance between apo AI MspI genotypes and triglycerides (p = 0.04) and between apo AI MspI genotypes and cholesterol levels (p = 0.03) in Anglo-Irish females.

CONCLUSIONS

Because only two statistically significant associations were detected among a number of comparisons, our data suggest that the apo AI and CIII polymorphisms play only a very limited role in mediating variation in lipid concentrations in these three ethnic groups.

Farm-related fatalities involving children in Australia, 1989-92

OBJECTIVE

To describe the types of and circumstances surrounding unintentional farm-related fatal injuries involving children aged less than 15 years in Australia.

METHODS

Information concerning 115 deaths were obtained from inspection of coronial files for the period 1989-92.

RESULTS

Children less than 15 years made up 20% of all unintentional farm-related fatalities in Australia, with children less than 5 years representing 63% of all child fatalities. The majority of children were fatally injured while bystanders to farm work and equipment used on the farm (including dams), with drowning the most common mechanism of the fatal incident for children aged both 5 years or less and 5-9 years. Vehicle accidents were common for children aged 10-14 years.

CONCLUSIONS

Children are exposed to various hazards in the farming environment and as such are at risk of being injured.

IMPLICATIONS

This study has highlighted a number of particular hazards for children on farms, with drowning, transport and tractor-related injuries of particular concern. A national strategy for child safety on farms has been developed by Farmsafe Australia aimed at providing a nationally co-ordinated plan for improving child safety on farms.

Further data on the microsatellite locus D12S67 in worldwide populations: an unusual distribution of D12S67 alleles in Native Americans

We report the frequencies of alleles at the microsatellite locus D12S67 in 2 widely separated ethnic groups of the world: 2 populations from Sulawesi, an island in the Indonesian archipelago, and 5 Native American tribes of Colombia, South America. The allele frequencies in the Minihasans and Torajans of Sulawesi are similar to each other (but the modal class allele is different) and in general agreement with those reported in mainland Asian groups, but different from both Europeans and Chinese Han of Taiwan. The 5 Native American tribes (Arsario, Kogui, Ijka, Wayuu, and Coreguaje) display different allele frequencies from those seen in Sulawesi populations, in other groups from Europe and mainland Asia, and in Chinese Han of Taiwan. Native Americans exhibit a bimodal distribution of alleles, unlike other groups, with significant differences among the tribes. The Arsario and Kogui have no admixture with Europeans or Africans and are the most distinctive, while the Wayuu have the most admixture and show most similarity to other groups. The data suggest that nonadmixed Native Americans may be quite distinctive with respect to this marker. The most common allele varies across the 5 tribes, from 249 base pairs to 261 base pairs. All samples exhibit Hardy-Weinberg genotype proportions; heterozygosities are lowest in the 2 nonadmixed Native American tribes. Examination of all the available data indicates that some east Asian and southeast Asian groups are characterized by a high frequency of smaller sized D12S67 alleles, while other populations have a greater proportion of the larger sized alleles. The cumulative, though still highly restricted, population data on locus D12S67 demonstrate that it may be of considerable value in anthropological genetic studies of ethnic groups. Data are required on Native Americans outside Colombia before this marker can be used in admixture studies of this group.

Distribution of the 3' VNTR polymorphism in the human dopamine transporter gene in world populations

A polymorphism with a variable number of tandem repeats (VNTR) found in the 3' untranslated region of the human dopamine transporter gene (DAT1) was scored in unrelated individuals drawn from 10 geographically widely dispersed populations in order to assess this marker's usefulness in human population genetics. The populations that were analyzed in this study included 4 indigenous groups of Siberia, natives of North and South America, as well as Caucasian and Oceanic groups, most of which represented small-scale societies. A total of 5 DAT1 alleles were seen overall, but only in one Siberian population, the Altai-Kizhi, were all 5 present, and in the Native Americans of Colombia the locus was monomorphic. The most common allele, DAT1*10, ranged in frequency from 52% in Greeks to 100% in South Americans. The high frequency of the DAT1*10 allele (approximately 90%) among Mongoloid groups of north and east Asia distinguishes them from most Caucasian groups. The presence of the rare DAT1*7 allele in relatively high frequency (approximately 5%) among all Siberian groups suggests a close affinity with north Asian groups, especially Mongolians. The presence of the even rarer DAT1*13 allele in one Siberian population, the Altai-Kizhi, reflects this group's long historical contact with Mongolians. The results demonstrated that the DAT1 VNTR polymorphism is useful in investigating population relationships, and that rare alleles at this locus may be particularly valuable in understanding the extent of genetic affinity between neighboring groups and in situations where admixture is suspected. However, because of both the association and linkage of this VNTR locus with attention-deficit hyperactivity disorder (ADHD) in children, and its highly restricted polymorphism (usually 3 alleles) in most human groups, the possibility of selection constraints on the DAT1 gene cannot be ignored.

A biosensor for the detection of gas toxicity using a recombinant bioluminescent bacterium

A whole-cell biosensor was developed for the detection of gas toxicity using a recombinant bioluminescent Escherichia coli harboring a lac::luxCDABE fusion. Immobilization of the cells within LB agar has been done to maintain the activity of the microorganisms and to detect the toxicity of chemicals through the direct contact with gas. Benzene, known as a representative volatile organic compound, was chosen as a sample toxic gas to evaluate the performance of this biosensor based on the bioluminescent response. This biosensor showed a dose-dependent response, and was found to be reproducible. The immobilizing matrices of this biosensor were stored at 4 degrees C and were maintained for at least a month without any noticeable change in its activity. The optimal temperature for sensing was 37 degrees C. A small size of this sensor kit has been successfully fabricated, and found to be applicable as a disposable and portable biosensor to monitor the atmospheric environment of a workplace in which high concentrations of toxic gases could be discharged.

A polymorphic L1 retroposon insertion in the centromere of the human Y chromosome

We have identified a novel polymorphic L1 retroposon insertion, designated LY1, in the centromeric alphoid array of the human Y chromosome. The element belongs to the transpositionally active Ta subset and its presence is compatible with normal centromere function. It was found at highest frequency in China, where it accounts for 23% of the Han sample, and was present at low frequencies in the surrounding areas, but was not found at all outside Asia. Chromosomes carrying LY1 show considerable microsatellite diversity, suggesting an ancient origin for the lineage at approximately 10 000 years ago (with wide confidence limits), but only limited subsequent migration.

Evaluation of an 8 hour versus a 12 hour shift roster on employees at a power station

Several studies exist that have conducted research into the effects of different shiftwork patterns on the individual, especially regarding 8 and 12 h rosters. The findings of these studies have been largely supportive of longer shifts, however, the effects on work performance are not as clear cut. This study aimed to examine the changeover from an 8 h roster to a 12 h roster in a power station via monitoring on-shift performance, general health and well-being, sleep and mood behaviour, as well as absence and accident data. Results suggest that the domestic and social life of workers was markedly improved under the 12 h roster. Improvements in physical health, sleeping behaviour and mood state of employees were also documented. On-shift performance measures showed an increase in error rates at the end of a 12 h shift. Ways of reducing the risk of error towards the end of a 12 h shift should be explored. The results of this study suggest that 12 h shifts are a valid alternative to 8 h shifts in this particular workplace, although tasks that require error-free activities should not be performed towards the end of a 12 h shift.

Y-chromosome-specific microsatellite variation in Australian aboriginals

The frequency distributions of 4 highly polymorphic Y-chromosome-specific microsatellites (DYS19, DYS390, DYS391, and DYS392) were determined in 79 unrelated Australian Aboriginal males from the Northern Territory. These results are compared with those observed in worldwide populations at both the locus and the haplotype level. Common alleles in Aboriginals are DYS19*15 (49%), DYS19*14 (28%), DYS390*19 (39%), DYS390*24 (20%), DYS391*10 (72%), DYS392*11 (63%), and DYS392*13 (28%). No evidence of reduced gene diversity was observed for these Y-chromosome alleles. DYS390 exhibits the most complex arrangement, displaying a bimodal distribution composed of common alleles (*22-*26), and rare short alleles (*18-*20), with an intermediate allele (*21) being absent. DYS390*20, previously reported only in Papuans and Samoans, is observed for the first time in Aboriginals. Compared with a recent study of Aboriginals, our sample exhibits considerable diversity in the haplotypes associated with the rare DYS390*19 allele, indicating that this allele is of considerable antiquity, if it arose as a single deletion event. Combining all 4 Y-chromosome-linked microsatellites produced 41 unique haplotypes, which were linked using a median-joining network. This network shows that most (78%) of our Aboriginal haplotypes fall into 2 distinct clusters, which likely represent 2 separate lineages. Seven haplotypes are shared with haplotypes found in a recent study of Aboriginals, and 7 are shared with a Spanish population. The cluster of Aboriginal haplotypes associated with the short DYS390 alleles does not share any haplotypes with the Spanish, indicating that this cluster of haplotypes is unique to Australian Aboriginals. Limited data from 4 worldwide populations used to construct haplotypes based on 3 loci (DYS19, DYS390, DYS392) show that only 4 of these haplotypes are seen in Australian Aboriginals. Shared haplotypes may be the result of admixture and/or recurrent mutation at these loci. Expanding the haplotype analysis to include biallelic markers on the Y chromosome will resolve this issue.

Deletion polymorphism in the human COL1A2 gene: genetic evidence of a non-African population whose descendants spread to all continents

We report the frequencies of a deletion polymorphism at the alpha 2 (1) collagen gene (COL1A2) and argue that this distribution has major implications for understanding the evolution of modern humans immediately after their exodus from sub-Saharan Africa as well as their subsequent spread to all continents. The high frequency of the deletion in non-African populations and its complete absence in sub-Saharan African groups suggest that the deletion event occurred just before or shortly after modern humans left Africa. The deletion probably arose shortly after the African exodus in a group whose descendants were among the ancestors of all contemporary populations, except for sub-Saharan Africans. This, of course, does not imply that there was a single migration out of Africa. The GM immunoglobulin haplotype GM*A,X G displays a similar distribution to that for the COL1A2 deletion, and these 2 polymorphisms suggest that the exodus from Africa may not have been a rapid dispersion to all other regions of the world. Instead, it may have involved a period of time for the savanna-derived gene pool to adapt to novel selective agents, such as bacteria, viruses, and/or environmental xenobiotics found in both animal and plant foods in their new environment. In this context these polymorphisms are indicators of the evolution that occurred before the diaspora of these populations to the current distribution of modern peoples.

Distribution of native legumes (Leguminoseae) in frequently burned longleaf pine (Pinaceae)-wiregrass (Poaceae) ecosystems

Legume species distribution and abundance and selected environmental variables were quantified across a complex gradient (varying in both water-holding capacity and fertility) for frequently burned longleaf pine (Pinus palustris)-wiregrass (Aristida stricta) ecosystems. Legumes were present in all months; however, abundance peaked in June and was minimal after killing frosts in October. Legume species were prominent in the flora (43 species encountered) ubiquitous (94% of 2-m(2) subplots had at least one legume species), and abundant (nearly 120 000 stems/ha). Although most species were widely distributed throughout the gradient, Lespedeza angustifolia was distinctly associated with the more hydric end of the gradient, while both Petalostemon pinnatum and Galactia microphylla were located in the more xeric extreme. The percentage variation in species that could be accounted for by environmental variation was low (27%). Of the variation that could be accounted for, a number of environmental variables were important, including soil moisture, pine basal area (i.e., light), and bivalent base cations (e.g., Ca(2+)). Although gradients in resource availability among sites did not affect the distribution of species or abundance of legumes strongly, variation in resources are likely to regulate N(2)-fixation rates of the various native legume species, and thereby affect ecological functions such as maintenance of N capital and productivity.

Expression of embryonic fibronectin isoform EIIIA parallels alpha-smooth muscle actin in maturing and diseased kidney

In this study we examined if an association exists between expression of an alternatively spliced "embryonic" fibronectin isoform EIIIA (Fn-EIIIA) and alpha-smooth muscle actin (alpha-SMA) in the maturing and adult rat kidney and in two unrelated models of glomerular disease, passive accelerated anti-glomerular basement membrane (GBM) nephritis and Habu venom (HV)-induced proliferative glomerulonephritis, using immunohistochemistry and in situ hybridization. Fn-EIIIA and alpha-SMA proteins were abundantly expressed in mesangium and in periglomerular and peritubular interstitium of 20-day embryonic and 7-day (D-7) postnatal kidneys in regions of tubule and glomerular development. Staining was markedly reduced in these structures in maturing juvenile (D-14) kidney and was largely lost in adult kidney. Expression of Fn-EIIIA and alpha-SMA was reinitiated in the mesangium and the periglomerular and peritubular interstitium in both models and was also observed in glomerular crescents in anti-GBM nephritis. Increased expression of Fn-EIIIA mRNA by in situ hybridization corresponded to the localization of protein staining. Dual labeling experiments verified co-localization of Fn-EIIIA and alpha-SMA, showing a strong correlation of staining between location and staining intensity during kidney development, maturation, and disease. Expression of EIIIA mRNA corresponded to protein expression in developing and diseased kidneys and was lost in adult kidney. These studies show a recapitulation of the co-expression of Fn-EIIIA and alpha-SMA in anti-GBM disease and suggest a functional link for these two proteins.

Tissue chemistry and carbon allocation in seedlings of Pinus palustris subjected to elevated atmospheric CO(2) and water stress

Longleaf pine (Pinus palustris Mill.) seedlings were grown in 45-l pots and exposed to ambient or elevated (365 or 730 &mgr;mol CO(2) mol(-1)) CO(2) concentration in open-top chambers for 20 months. Two water-stress treatments (target values of -0.5 or -1.5 MPa xylem pressure potential) were imposed 19 weeks after initiation of the study. At harvest, tissues (needles, stems, taproots, coarse roots, and fine roots) were analyzed for carbon (C), nitrogen (N), nonpolar extractives (fats, waxes, and oils), nonstructural carbohydrates (sugars and starch), structural components (cellulose and lignin), and tannins. The greatest dry weights and lowest N concentrations occurred in tissues of plants grown at elevated CO(2) or with adequate water. Although allocation of C fractions among tissues was generally unaffected by treatments, concentrations of the analyzed compounds were influenced by treatments in needles and taproots, but not in stems and lateral roots. Needles and taproots of plants exposed to elevated CO(2) had increased concentrations of nonstructural carbohydrates. Among plant tissues, elevated CO(2) caused reductions in structural C concentrations and foliar concentrations of fats, waxes and oils.

Differential expression of thrombospondin and cellular fibronectin during remodeling in proliferative glomerulonephritis

Thrombospondin-1 (TSP-1) and an alternatively spliced fibronectin (Fn)-EIIIA isoform are adhesive proteins associated with embryogenesis and tissue remodeling. We compared, by immunohistochemistry and in situ hybridization, the course of TSP-1 and Fn-EIIIA expression in a model of glomerulonephritis induced by Habu snake venom (HV) and characterized by mesangial cell migration, proliferation, and extracellular matrix (ECM) synthesis. At 24 hr after HV, TSP-1 and Fn-EIIIA proteins localized in the central aspects of lesions associated with platelets and macrophages and at the margins of lesions coinciding with mesangial cell migration (determined by Thy-1 staining). Mesangial cells at this time expressed TSP-1 but not Fn-EIIIA mRNA. TSP-1 protein and mRNA peaked in lesions at 48 hr and were associated with cell proliferation (determined by PCNA, alpha-smooth muscle actin phenotype, and expression of beta-PDGF receptor mRNA). TSP-1 expression declined at 72 hr when expression of ECM synthesis peaked, as determined by increased expression of collagen Type IV, laminin, and TGF-beta1 protein and mRNA. Mesangial cell expression of Fn-EIIIA was first observed at 48 hr and was most abundant at 72 hr after HV. Therefore, platelet- and macrophage-derived Fn-EIIIA and TSP-1 in early lesions are associated with mesangial cell migration. Mesangial cell upregulation of TSP-1 is associated with migration and proliferation but not maximal ECM accumulation, whereas mesangial cell expression of Fn-EIIIA is associated with proliferation and ECM accumulation. These results suggest distinctive temporal and spatial roles for TSP-1 and Fn-EIIIA in remodeling during glomerular disease. (J Histochem Cytochem 47:533-543, 1999)

The central Siberian origin for native American Y chromosomes

Y chromosomal DNA polymorphisms were used to investigate Pleistocene male migrations to the American continent. In a worldwide sample of 306 men, we obtained 32 haplotypes constructed with the variation found in 30 distinct polymorphic sites. The major Y haplotype present in most Native Americans was traced back to recent ancestors common with Siberians, namely, the Kets and Altaians from the Yenissey River Basin and Altai Mountains, respectively. Going further back, the next common ancestor gave rise also to Caucasoid Y chromosomes, probably from the central Eurasian region. This study, therefore, suggests a predominantly central Siberian origin for Native American paternal lineages for those who could have migrated to the Americas during the Upper Pleistocene.

Y-chromosome specific alleles and haplotypes in European and Asian populations: linkage disequilibrium and geographic diversity

Variation on the Y chromosome may permit our understanding the evolution of the human paternal lineage and male gene flow. This study reports upon the distribution and non random association of alleles at four Y-chromosome specific loci in four populations, three Caucasoid (Italian, Greek and Slav) and one Asian. The markers include insertion/deletion (p12f), point mutation (92R7 and pY alpha I), and repeat sequence (p21A1) polymorphisms. Our data confirm that the p12f/TaqI 8 kb allele is a Caucasoid marker and that Asians are monomorphic at three of the loci (p12f, 92R7, and pY alpha I). The alleles at 92R7 and pY alpha I were found to be in complete disequilibrium in Europeans. Y-haplotype diversity was highly significant between Asians and all three European groups (P < 0.001), but the Greeks and Italians were also significantly different with respect to some alleles and haplotypes (P < 0.02). We find strong evidence that the p12f/TaqI 8 kb allele may have arisen only once, as a deletion event, and, additionally, that the present-day frequency distribution of Y chromosomes carrying the p12f/8 kb allele suggests that it may have been spread by colonising sea-faring peoples from the Near East, possibly the Phoenicians, rather than by expansion of Neolithic farmers into continental Europe. The p12f deletion is the key marker of a unique Y chromosome, found only in Caucasians to date, labelled 'Mediterranean' and this further increases the level of Y-chromosome diversity seen among Caucasoids when compared to the other major population groups.

Genetic diversity at six short tandem repeat loci within the state of Victoria, Australia

A new multiplex PCR system, developed by the Forensic Science Service (FSS) in the United Kingdom, permits the coamplification and typing of six short tandem repeat (STR) loci: HUMFGA, D8S1179, HUMTHO1, HUMvWA, D18S51, D21S11 and the sex determining marker Amelogenin. Data are presented on these six STRs for two populations in the state of Victoria, Australia: Caucasian and Asian. Whilst several worldwide databases are already available for the STR loci HUMTHO1 and HUMvWA, only relatively few databases exist for D8S1179, D18S51, D21S11 and HUMFGA. Allele frequencies at each locus displayed some fluctuations between the two populations. This is particularly so for HUMTHO1. Generally, however, the most common allele at each locus was the same in all populations, at all loci. A novel D8S1179 allele was found in Asians, provisionally identified as allele 19. Results for the six loci were compared with similar data from three UK resident populations: Caucasian, Afro-Caribbean and Asian (Indian/Pakistani) populations. These indicated that ethnically similar populations display similar allele frequencies, while the Australian Asian and UK Afro-Caribbean were found to be distinct.

Variation at three short tandem repeat (STR) loci in Australians: forensic and ethnic considerations

We report the results of typing three short tandem repeat (STR) polymorphisms by a multiplex system in three forensically relevant populations of Australia; (i) a general Australian, (ii) a Caucasian, and (iii) an Asian sample. The STRs are tetranucleotide repeats in the following autosomal genes; CSF1PO, TPOX and THO1, and collectively comprise the CTT multiplex (Promega). In all three population samples, each of the loci exhibited genotype frequencies consistent with those expected under Hardy-Weinberg equilibrium, and, further, there was no significant deviation from random association of alleles across separate loci. These two characteristics, plus the high discrimination power values, demonstrate that the CTT multiplex system is a powerful tool for DNA profiling in Australian jurisdictions. Australian Asians and Caucasians exhibit frequencies of alleles at these three STR loci very similar to those in other Asian and Caucasian samples. While most of the variation exists within any single population, there are still considerable differences between Asians and Caucasians. This difference between the two groups is minimal with respect to TPOX and greatest for THO1 alleles.

An evaluation of selected DNA extraction strategies for short tandem repeat typing

Organic and Chelex extraction methods are compared to five commercially available DNA extraction kits. For forensic purposes, comparison of different extraction strategies is based on the ability of the methods to economically recover high yields of amplifiable DNA from small blood samples in a quick, simple and safe manner. The findings of this study indicate that resin-based methods, such as Chelex, are best able to meet these criteria.

Effects of atmospheric CO(2) on longleaf pine: productivity and allocation as influenced by nitrogen and water

Longleaf pine (Pinus palustris Mill.) seedlings were exposed to two concentrations of atmospheric CO(2) (365 or 720 micro mol mol(-1)) in combination with two N treatments (40 or 400 kg N ha(-1) year(-1)) and two irrigation treatments (target values of -0.5 or -1.5 MPa xylem pressure potential) in open-top chambers from March 1993 through November 1994. Irrigation treatments were imposed after seedling establishment (i.e., 19 weeks after planting). Seedlings were harvested at 4, 8, 12, and 20 months. Elevated CO(2) increased biomass production only in the high-N treatment, and the relative growth enhancement was greater for the root system than for the shoot system. In water-stressed trees, elevated CO(2) increased root biomass only at the final harvest. Root:shoot ratios were usually increased by both the elevated CO(2) and low-N treatments. In the elevated CO(2) treatment, water-stressed trees had a higher root:shoot ratio than well-watered trees as a result of a drought-induced increase in the proportion of plant biomass in roots. Well-watered seedlings consistently grew larger than water-stressed seedlings only in the high-N treatment. We conclude that available soil N was the controlling resource for the growth response to elevated CO(2) in this study. Although some growth enhancement was observed in water-stressed trees in the elevated CO(2) treatment, this response was contingent on available soil N.

The geographic distribution of human Y chromosome variation

We examined variation on the nonrecombining portion of the human Y chromosome to investigate human evolution during the last 200,000 years. The Y-specific polymorphic sites included the Y Alu insertional polymorphism or "YAP" element (DYS287), the poly(A) tail associated with the YAP element, three point mutations in close association with the YAP insertion site, an A-G polymorphic transition (DYS271), and a tetranucleotide microsatellite (DYS19). Global variation at the five bi-allelic sites (DYS271, DYS287, and the three point mutations) gave rise to five "YAP haplotypes" in 60 populations from Africa, Europe, Asia, Australasia, and the New World (n = 1500). Combining the multi-allelic variation at the microsatellite loci (poly(A) tail and DYS19) with the YAP haplotypes resulted in a total of 27 "combination haplotypes". All five of the YAP haplotypes and 21 of the 27 combination haplotypes were found in African populations, which had greater haplotype diversity than did populations from other geographical locations. Only subsets of the five YAP haplotypes were found outside of Africa. Patterns of observed variation were compatible with a variety of hypotheses, including multiple human migrations and range expansions.

Human evolution and the Y chromosome

The past two years have seen the increased study of Y-chromosome polymorphisms and their relationship to human evolution and variation. Low Y-chromosome sequence diversity indicates that the common ancestor of all extant Y chromosomes lived relatively recently and the consensus of estimates of time to the most recent common ancestor concur with estimates of the mitochondrial DNA ancestor; but we do not know where this 'Adam' lived. Though the reason for low nucleotide diversity on the Y-chromosome remains unresolved, some of the mutations are proving highly informative in tracing human prehistoric migrations and are generating new hypotheses on human colonizations and migrations. The recent discovery of highly polymorphic microsatellites on the Y offers new possibilities for the investigation of more recent human evolutionary events, including the identification of male founders.

Recurrent duplication and deletion polymorphisms on the long arm of the Y chromosome in normal males

Deletion of the 50f2/C (DYS7C) locus in interval 6 of Yq has previously been reported as a polymorphism in three males. We describe a survey of worldwide populations for further instances of this deletion. Of 859 males tested, 55 (approximately 6%) show absence of the 50f2/C locus; duplication of the locus was also detected in eight out of 595 males (approximately 1.4%). Populations having the deletion are confined to Asia, Australasia, and southern and northern Europe; of those of reasonable sample size, Finns had the highest deletion frequency (55%; n = 21). The deletions vary in size and the larger ones remove some of the RBM (RNA Binding Motif) genes, but none of the deletion males lack DAZ (Deleted in AZoospermia), a candidate gene for the azoospermia factor. On a tree of Y haplotypes, 28 deletion and eight duplication chromosomes fall into six and four haplotypic groups respectively, each of which is likely to represent an independent deletion or duplication event. Microsatellite and other haplotyping data suggest the existence of at least two further classes of deletion. Thus duplications and deletions in this region of Yq have occurred many times in human evolution, but remain useful markers for paternal lineages.

Setting reactions in dental amalgam. Part 2. The kinetics of amalgamation

The literature on the setting mechanisms of dental amalgams made from powders of silver-rich alloys of tin and/or copper has been critically reviewed. Part 2 is a review of the kinetics of the reactions that convert the mixture of alloy powder and liquid mercury to hardened amalgam containing the phases and microstructures described in Part 1. It is emphasized that amalgamation is a non-equilbrium process in which hardened microstructures are determined as much by kinetics as by chemistry. The setting reaction begins with dissolution of silver and tin into liquid mercury; most of the product phases precipitate in the liquid mercury. The processes that produce supersaturation in the liquid mercury and the subsequent nucleation and growth of solid phases are considered. Mass balance relationships that provide insight into the factors that control the volume fraction of the undesirable gamma 2 Sn-Hg phase are described. The nucleation and growth of eta' Cu-Sn crystals are also discussed; it is found that these crystals nucleate on copper-rich phases and grow into the liquid mercury. Finally, aspects of the setting reaction that are controlled by intergranular and interphase diffusion in the solid are discussed. These aspects include: the supersaturation of silver and tin within the liquid mercury, nucleation and growth of the beta 1 Ag-Hg phase in the surfaces of alloy particles, and the decomposition of initially formed gamma 2 Sn-Hg.

Effects of grinding, polishing, and overglazing on the flexure strength of a high-leucite feldspathic porcelain

The objective of this study was to determine how surface treatments and moisture affect the flexure strength of a high-leucite feldspathic porcelain. Uniaxial flexure strength was measured for porcelain beams whose surfaces were coarse ground, overglazed, or polished. Half of the specimens were stored in distilled water and tested while their surfaces were coated with distilled water. The other half were stored in a dry environment and tested immediately in dry air. The high-leucite feldspathic porcelain was found to be sensitive to roughness and surface stresses, similar to leucite-free and low-leucite feldspathic porcelains. The experimental method used, however, was not sensitive enough to detect susceptibility to moisture.

Setting reactions in dental amalgam. Part 1. Phases and microstructures between one hour and one week

The literature on the setting mechanisms of dental amalgams made from powders of silver-rich alloys of tin and/or copper has been critically reviewed. In Part 1 of the review, the microstructure and phase content of recently set amalgams are described. The composition, morphology, and location of product phases are emphasized, since these features are clues to the setting reaction. Thus, Part 1 provides the background needed to understand the kinetics of the setting reactions, which is the topic of Part 2 of the review.

Expression of alternatively spliced fibronectin variants during remodeling in proliferative glomerulonephritis

Fibronectin (Fn) plays an important role in tissue remodeling during embryogenesis, wound repair, and vascular disease, and is thought to regulate cellular processes such as cell adhesion, migration, proliferation, and differentiation through specialized domains within the molecule. In addition, Fn can be alternatively spliced at three regions: extradomains EIIIA, EIIIB, and a variable segment V, potentially giving rise to functionally distinct variants of the molecule. We have previously shown a sequential expression of cellular Fn first by platelets, followed by macrophages, then mesangial cells in habu snake venom-induced proliferative glomerulonephritis (Am J Pathol 145: 585-597, 1994). These studies examined the cellular sources and glomerular localization of Fn in general but did not distinguish between the various alternatively spliced isoforms. In this study, we examine by in situ hybridization and immunohistochemistry the temporal expression and cellular sources of EIIIA, EIIIB, and V in a model of proliferation glomerulonephritis that has cell migration, proliferation, and extracellular matrix synthesis as features of tissue remodeling. Macrophages were the first cells to express Fn mRNA showing an EIIIA+, EIIIB-, and V95+ pattern beginning at 8 hours after habu snake venom injection. Migrating mesangial cells at the margins of early lesions (8 and 24 hours) did not overexpress mRNA encoding these Fn variants, but immunofluorescence microscopy revealed V95 and EIIIA protein at the margins of lesions. EIIIB was absent in lesions at this time. At 48 hours and peaking at 72 hours after habu snake venom injection, mesangial cells in central aspects of glomerular lesions expressed abundant mRNA and protein for V95 and EIIIA. EIIIB mRNA and protein was slight in the mesangium at these times. Parietal epithelial cells, particularly adjacent to glomerular lesions, also expressed abundant mRNA and protein for all three variants throughout the course of the disease, beginning at 24 hours after habu snake venom injection. Expression of mRNA and protein for all three isoforms declined by 2 weeks after habu snake venom injection. These studies show that migrating mesangial cells do not require their own synthesis of Fn and suggest that they might rely on exogenous sources of Fn, particularly V95+ and EIIIA+ forms. Commencement of enhanced expression of EIIIA and EIIIB mRNA and protein by resident glomerular cells coincided with the temporal course of cell proliferation, acquisition of alpha-smooth muscle cell actin phenotype, and matrix synthesis, suggesting that Fn isoforms have specific functions during the course of glomerular remodeling.

Expression of plasminogen activator-inhibitor-1 (PAI-1) during cellular remodeling in proliferative glomerulonephritis in the rat

Pericellular proteolysis involves the plasminogen activator/plasmin system and plays an important role in cell remodeling involving cell migration and extracellular matrix turnover. Studies in this laboratory have previously characterized a model of proliferative glomerulonephritis induced by Habu snake venom (HSV) in the rat that involves cell migration, proliferation, and extracellular matrix accumulation. Because plasminogen activator-inhibitor-1 (PAI-1) has been used as a marker for cell migration as well as matrix accumulation, we were interested in examining the temporal and spatial expression and cellular sources of PAI-1 mRNA and translated protein over the course of HSV-induced proliferative glomerulonephritis. The results showed a highly localized and progressive expression of PAI-1 mRNA and translated protein by in situ hybridization and immunohistochemistry at the margins and periphery of glomerular lesions 8 and 24 hr after HSV. The expression of PAI-1 in glomerular lesions localized to the same sites as mesangial cell marker proteins, desmin and Thy-1.1, indicating that mesangial cells synthesize this important regulator proteolysis. Few cells expressed PAI-1 in the central aspects of glomerular lesions at later time intervals (48 and 72 hr) when cell proliferation and expression of extracellular matrix (fibronectin protein and mRNA) were maximal. Therefore, the expression of PAI-1 in this model was associated more with early events related to cell migration than with proliferation or extracellular matrix synthesis. These observations support the hypothesis that the plasminogen activator/plasmin system is involved in cell migration in early remodeling during glomerular disease.

A comparison of infrared- and torch-soldering of Au-Pd and Co-Cr metal-ceramic alloys using a high-fusing solder

PURPOSE

The purpose of this study was to compare the bond strengths and fracture modes of soldered joints formed by infrared and gas-oxygen torch heating of a high-fusing, gold-based solder in two metal-ceramic alloys.

MATERIALS AND METHODS

Pairs of half-dumbbell-shaped specimens of either an Au-Pd or a Co-Cr alloy were positioned with a 0.25-mm gap and were joined using a high-fusing, gold-based solder by either gas-oxygen torch heating or infrared heating. The resulting specimens were subjected to a heat treatment that simulated ceramic firing. Each specimen was fractured in tension at a loading rate of 0.5 cm/min, and its bond strength was measured. The halves of the specimen were rejoined using the other heating method and were heat treated, and the specimen's bond strength was again measured. Fractured cross-sections were examined at a magnification of 40x to determine the following: the fracture mode (adhesive, cohesive, or mixed); the percentage of adhesive fracture; the presence or absence of voids, porosities, or flux inclusions; and the percentage of the cross-section that was discolored.

RESULTS

Three-factor analyses of variance showed that neither the heating method, the particular specimen tested, nor the order of testing significantly affected the bond strength (P < .05). For each alloy, significantly fewer infrared-heated joints than torch-heated joints contained voids, porosities, or flux inclusions visible at 40x (chi 2 test, P < .05). All fractures were either entirely cohesive in the solder or mixed cohesive and adhesive. When infrared heating was used, entirely cohesive fractures occurred more frequently in the Au-Pd alloy specimens than in the Co-Cr alloy specimens (chi 2 test, P < .05). The coefficients of variation of the bond strengths for the infrared-heated joints were smaller than those for the torch-heated joints.

CONCLUSIONS

Although the two heating methods produced solder joints that had strengths that were not significantly different, infrared-heated joints showed less scatter in bond strengths. It was suggested that, in the hands of most technicians, fewer infrared-heated joints would contain defects visible at a magnification of 40x. The presence of such defects may increase the probability of in vivo failure caused by cyclic stresses.

DNA polymorphisms at the lipoprotein lipase gene and their association with quantitative variation in plasma high-density lipoproteins and triacylglycerides

Lipoprotein lipase (LPL) plays a critical role in the metabolism of lipoproteins because this enzyme hydrolyzes the triacylglycerides in chylomicrons and very low density lipoproteins. This process influences the production of high-density lipoprotein (HDL), which takes up tissue cholesterol for transport to the liver for excretion. Accordingly, LPL qualifies as a candidate gene for understanding lipid metabolic disorders and atherosclerosis. Studies on the relationship between genetic variation at the LPL locus and lipid phenotypes have produced equivocal results to date. To help clarify this issue, we investigated 144 outwardly healthy male Mediterranean migrants (from Italy and Greece), age between 40 and 70 years and resident in Australia, for associations between two common LPL restriction site polymorphisms and the following lipid and lipoprotein phenotypes: total plasma cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triacylglycerides. A series of analysis of variance tests, controlling for age, body mass index, and ethnicity, showed that the HindIII polymorphism at the LPL locus is significantly associated with both triacylglyceride and HDL cholesterol concentrations in this sample. The PvUII polymorphism, however, showed no association with any lipid. Kruskal-Wallis tests confirmed the significance of the associations between the HindIII RFLP and both HDL (p = 0.008) and triacylglycerides (p = 0.03). When the sample was subdivided into subjects who exhibited primary hypertriacylglyceridemia and normolipidemics, a significant difference was observed in the frequency of HindIII (p < 0.05) but not PvuII genotypes. HindIII heterozygotes (H1,H2) were least and H2,H2 individuals were most at risk for triacylglyceridemia. Examination of the normolipidemic sample revealed some evidence for an independent effect of the PvuII polymorphism on both LDL cholesterol and total cholesterol levels.

DNA polymorphisms of the cholesteryl ester transfer protein (CETP) gene in Italian and Greek migrants to Australia

The distribution of two common TaqI restriction fragment length polymorphisms (RFLPs) of the cholesteryl ester transfer protein (CETP) gene were determined in 271 Italian-born and 170 Greek-born migrants to Melbourne, Australia. A much smaller number were examined for the EcoNI RFLP of the same gene. Allele frequencies of the TaqI A RFLP exhibited the least variation in both ethnic groups, and no significant regional heterogeneity in allele or genotype frequencies of either TaqI RFLP was detected for Greece or Italy. There was no difference between Italians and Greeks for the TaqI A polymorphism and the variability at the B RFLP was of borderline significance. Comparisons with other Caucasian populations revealed that allele frequencies of all three CETP RFLPs are remarkably uniform within Caucasians, with the TaqI B polymorphism being the most variable.

Polymorphisms of the gene coding for the cholesteryl ester transfer protein and plasma lipid levels in Italian and Greek migrants to Australia

The relation between TaqI restriction fragment length polymorphisms (RFLPs) of the cholesteryl ester transfer protein (CETP) gene and plasma lipid and lipoprotein phenotypes was investigated in a sample of Italian and Greek migrants of both sexes, age 40-69 years. Italians display significantly higher mean triglyceride and lower mean high-density lipoprotein (HDL) cholesterol levels than Greeks. Greek females have significantly higher HDL cholesterol than Greek males, and Italian females have significantly higher low-density lipoprotein (LDL), HDL, and total cholesterol than Italian males. The differences in RFLP allele frequencies between the two ethnic groups and sexes are insignificant. Multivariate analyses show that in the Greek sample the TaqI B RFLP of the CETP gene has a highly significant effect on HDL cholesterol levels regardless of sex and that the TaqI A polymorphism has a significant effect on HDL levels in females but modulates LDL cholesterol concentrations in males. Among Italians, with the sexes considered separately or combined, no such effects of the CETP TaqI polymorphisms are detected. Kruskal-Wallis tests detected associations between the TaqI B polymorphism in all Greek samples but not in the Italian samples. Genotype CETP*B2 exhibits significantly higher HDL cholesterol concentrations than either of the other two TaqI B genotypes, but there is no evidence of a dosage effect of the *B2 allele. These data suggest that associations between the CETP gene and lipid phenotypes can be population specific. Further, they suggest that such associations are mediated in some way by gender.

Hydroxyapatite orbital implants. Scanning with technetium-99m MDP

Porous hydroxyapatite spheres are an ideal prosthetic device for orbital implantation because they are incorporated into soft tissues. Once vascularized, an eye prosthesis can be coupled to the sphere by a peg placed within a central motility hole. This hole should not be drilled while the sphere is avascular because of the risk of infection. Radionuclide scanning with Tc-99m methylene diphosphonate has been used to assess implant vascular ingrowth because radiophosphonate deposition within the sphere parallels vascularization. Using this technique, the authors examined the hydroxyapatite implants of 15 patients 6 months following insertion. Results showed that complete vascularization is best defined by planar imaging rather than SPECT. While the relative intensity of implant activity may be an important feature, uniformity of activity is probably more significant.

Genetic polymorphisms in the white population of Victoria, Australia

Genetic variation in the rural population of the State of Victoria, Australia, is demonstrated through the analysis of eight genetically independent red cell antigen, red cell enzyme and plasma protein systems in a sample of more than 2000 blood donors. The polymorphisms investigated were ABO, RH, KEL, esterase D (ESD), glyoxalase 1 (GLO1), phosphoglucomutase locus 1 (PGM1), haptoglobin (HP) and the third component of complement (C3). For genetic distance analysis the sample was subdivided into nine regions using the Victorian Government's Statistical Divisions. Considerable regional genetic heterogeneity exists; with the Goulburn and the Central Highlands divisions being the most distinct, not only from the other seven divisions, but also from each other. The pattern of micro-differentiation is complex and cannot be easily explained, but there is evidence of varying levels of systematic evolutionary pressure on the Victorian divisions. The investigation of the proportion born overseas in each division, and their respective countries of origin, did not help in the interpretation of the findings. Overall, rural Victorians exhibited allele frequencies very similar to the populations of both Melbourne, the Victorian capital, and the island State of Tasmania.

The effect of fatigue on the shear bond strength of resin bonded to porcelain

PURPOSE

The objective of this study was to determine whether fatigue cycling affects the shear bond strength of a resin that is initially strongly bonded to porcelain.

MATERIALS AND METHODS

Thirty-five disks of a feldspathic/leucite porcelain were fired on a phosphate-bonded investment material. Each disk was etched with hydrofluoric acid and treated with a silane solution and an adhesive. Resin cement composite cylinders were applied to the treated porcelain and light cured. All specimens were stored for 1 week in distilled water at 37 degrees C and then thermocycled for 1000 cycles in water between 2 degrees C and 50 degrees C. Fifteen of the specimens were randomly selected as control specimens. The remaining were subjected to fatigue cycling. A shear load was applied parallel to the bonded surface and cycled in a square wave between 0 and 26 N at 2 Hz for 27,500 cycles. All specimens were fractured in shear at 1.27 mm/min, and the shear bond strength was determined.

RESULTS

Fifteen percent of fatigued specimens and 6.7% of the control specimens showed at least partial adhesive failure. All other specimens in both groups failed cohesively in the porcelain. There was no significant difference in the mean bond strengths of the fatigued and control groups (analysis of covariance, P > .05).

CONCLUSIONS

For the conditions investigated, cyclic fatigue did not reduce the bond strength of this resin/porcelain system.

Two Y-chromosome-specific restriction fragment length polymorphisms (DYS11 and DYZ8) in Italian and Greek migrants to Australia

The part of the Y chromosome not involved in recombination has been found to exhibit an extremely low frequency of DNA restriction fragment length polymorphisms (RFLPs) compared with either the X chromosome or autosomes. Also, the few Y-chromosome-specific RFLPs that have been identified have rarely been examined in more than one population. In this study two Y-chromosome-specific RFLPs at loci DYS11 and DYZ8 are examined in Italian and Greek migrants to Australia. The frequency of the rarer (8.5-kb) TaqI allele at DYS11 was 21% in Italians and even greater (34%) in Greeks. There is an inverse relationship between the frequency of the 8.5-kb allele and latitude on the Italian mainland; the regional variation (based on subject's birthplace in Italy) was significant (p < 0.01). The incidence of the 8.5-kb allele in southern Italy may reflect Greek colonization during pre-Roman times when this region was part of Magna Graecia. The frequency of the variant TaqI allele (7, 4 kb) at the DYZ8 locus is much higher in both Greeks and Italians (31% in each) than in Germans (5%), the only previously examined population. DYZ8 shows considerably less variation than DYS11 across the regional divisions of both Greece and Italy. The present findings, when added to the few other data available, indicate that these two Y-chromosome-specific loci are useful markers for investigating population affinities through the paternal line. Also, heterogeneity at these two loci (and added to that at the DYS1 locus) suggests that Mediterranean populations, compared with other groups, exhibit a high level of diversity of Y-chromosome-specific RFLPs.

Effects of dentin age and bonding on microgap formation

This study compared the effectiveness of dentin adhesives in extracted molars from younger (16-26) and older (58-87) human subjects. Extracted molars were selected to be restored with one of two dentin bonding agents (n = 22 per group). Opposite sides of each molar were ground flat and a 3 mm x 3 mm cylindrical preparation was milled into each surface. The opposing surfaces of each molar were then randomly restored with either a dentin bonding system that adhered to the dentin smear layer or one which bonded to the dentin after the smear layer was removed. All samples were examined at x150 to determine both the maximum gap in micrometers and extent of the gap in degrees. There were significantly shorter (P < 0.05) microgaps in older dentin with a bonding system that removed smear layer. This bonding system also produced shorter gaps in older dentin than in younger dentin. However, there was no statistically significant difference in the percentage of gap-free margins between age groups.

Spatial and Temporal Variation in Competitive Effects on Soil Moisture and Pine Response

The effects of different plant life-forms, including a bunch grass species, Andropogon virginicus L. (broomsedge), and a sprouting deciduous tree species, Liquidambar styraciflua L. (sweetgum), on soil moisture and competitive responses of a transplanted coniferous tree seedling, Pinus taeda L. (loblolly pine), were investigated. Addition of the bunch grass and/or hardwood sprouts either had no effect or increased soil moisture in the surface soil (0-14 cm) depending on the time, while addition of sweetgum and/or broomsedge (greatest density alone) decreased soil moisture in deeper portions of the solum during the summer months. Soil moisture available to pine seedlings at various points in time was assessed by measuring predawn xylem pressure potential. Temporal variation in predawn xylem pressure potential was accounted for through a water stress integral approach. More than half of the variation in pine size after one growing season could be accounted for by the water stress integral.

Ethnicity and blood group polymorphisms in the population of Melbourne, Australia

In an investigation of the extent of genetic variation in Melbourne, Australia, blood samples were collected from 3 of the largest ethnic groups comprising the present population; 251 Australian born of Anglo-Irish descent, 270 Greek born and 239 Italian born. Each sample was analysed for 5 red cell antigen systems, ABO, MNS, RH, KEL and FY. The Australian born sample was more similar to the Italians than the Greeks except for KEL R matrix and genetic distance analyses indicated that the Greek immigrants were similar to Greeks in Greece, but that Italian immigrants to Melbourne were not as close to a Southern Italian sample as their origins would suggest.

Phosphoglucomutase 1 (PGM1) subtypes and ESD types in mothers and newborns from the island of Tasmania, Australia

PGM1 subtypes and ESD phenotypes of 600 mothers and their respective newborn infants residing in the northern part of the island of Tasmania were examined. The allele frequencies of PGM1 in the mothers were 1+ = 0.6525, 1- = 0.1250, 2+ = 0.1758 and 2- = 0.0467, and in the newborns were 1+ = 0.6675, 1- = 0.1275, 2+ = 0.01600 and 2- = 0.0450. Both samples were found to exhibit Hardy-Weinberg equilibrium conditions and there was no significant difference between them. Also, the frequencies of PGM1 alleles were overall similar to frequencies in neighbouring populations on the Australian mainland. The frequency of ESD*2 in both samples was similar (0.105) but the mothers' genotypes were not in Hardy-Weinberg equilibrium (due to an excess of type 2). The ESD allele frequencies in Tasmania are similar to those reported in other white Australian populations.

Restriction fragment length polymorphism at the CALCA locus identified by the probe pEMBL36 in immigrant populations of Australia

Restriction fragment length polymorphisms detected by the cDNA probe, pEMBL36, at the CALCA locus (calcitonin gene and calcitonin gene related peptide) on TaqI blots were examined in samples from Italian, Greek and Vietnamese migrants to Melbourne, Australia and in a sample of residents from the island of Tasmania, Australia. The frequency of the rarer of the two alleles of this polymorphism, A2 (8.0kb) varied between a low of 6% in Vietnamese to a maximum of 38% in Tasmanians. The frequency range of the A2 allele in European populations, however, was considerably less. Analysis revealed no significant heterogeneity for this polymorphism among either the European or European derived populations, and these combined data exhibited a frequency of 33% for the A2 allele. Though based on a very small Vietnamese sample this study suggests that the A2 allele is less frequent in those of Asian ancestry.

Etiology of temporomandibular disorders

Temporomandibular (TM) disorders include a variety of conditions and disorders of the masticatory muscles and TM joints. As such, it is not appropriate or possible to discuss etiology in terms of a unified theory, as some authors and clinicians have attempted to do in the past. Recent literature reflects this awareness, and most authors now define etiology and treatment of these disorders in terms consistent with their medical counterparts. As with other musculoskeletal disorders, injuries, as well as microtrauma through parafunctional and excess functional stresses, seem to play major roles in etiology.

An immunologic and genetic study of asthma in workers in an aluminum smelter

The cause or causes of asthma among employees in aluminum smelters is unknown. We attempted to ascertain whether such workers who developed asthma differed in respect to indices of immunological function and certain genetic markers. Data were collected from 33 asthmatic and 127 nonasthmatic potroom workers. Asthmatic workers had significantly lower mean serum levels of immunoglobulin (Ig)M; however, mean levels of IgG and IgA, median levels of IgE, the capacity for recall of delayed type hypersensitivity, levels of immune complexes, and frequency of antinuclear or other autoantibodies did not differ from values for nonasthmatic workers. Asthma was found to develop on a background of atopy in 21 workers (64%), whereas there were no features of atopy in 12 workers (36%). Cigarette smoking had independent effects on immunological function. In respect to genetic markers, there was a higher frequency among asthmatic workers of the alpha-1-anti-trypsin deficiency phenotype MS, but the frequency of blood groups, Gm allotypes, or human leucocyte antigen types was similar. The study established that the profile of immune function, or genetic markers tested, did not differ essentially for workers in an aluminum smelter who did or did not develop asthma; however, there was an indication of heterogeneity in causation, as judged by "atopy-related" and "non-atopy-related" groups in the asthma population.

Migration and genetic structure in Northumberland

To understand the genetic variation that occurs among regions of northern England, we estimated migration from places of birth and residence in the last two generations for a sample of 1367 families in Northumberland. There has been an increase in kinship among regions, compatible with the increased mobility of recent decades, but the kinship patterns suggest that any regional gene frequency differences have remained relatively undiluted. Comparison of kinship and geographic distance between regions indicates that geographic location is an important determinant of genetic structure.

Examining population structure through the use of surname matrices: methodology for visualizing nonrandom mating

The analysis of nonrandom mating using the frequency of marital isonymy indirectly measures the degree of population structure. However, population structure is the result of all matings in a population. Difficulties with large surname matrices have resulted in data being summarized into a single statistic or collapsed into brief tables, with considerable loss of information. By using sophisticated computer graphing procedures and displays, it is possible to directly analyze the mating structure of a community. If P is a vector of proportions for each male surname i (i = 1, 2, 3, ..., n), Q a similar vector of female surnames j(j = 1, 2, 3, ...,m), then the expected frequency matrix E of each possible mating is P x Q. The difference D between the observed frequency matrix O and the expected matrix is O-E. The D matrix is graphed with the x axis containing the male surnames, the y axis the female surnames, and the z axis the difference values dij. Negative values represent negative nonrandom mating and positive values positive nonrandom mating. From 5417 marriages (1840-1963) in the Midlands of Tasmania, those between spouses having 1 of 194 core names were extracted. We analyze these marriages utilizing the new technique and examine the surface of the graph and statistical analysis of its finer structure. Among the results was the demonstration of frequency-dependent selection of surnames. This finding has significant implications for microevolution of human populations, as surnames have existed for possibly 700 years.

Clinical acceptability of orthodontic retainers fabricated from stored alginate impressions

The purpose of this study was to determine the clinical acceptability of orthodontic retainers fabricated from stored alginate impressions. In the laboratory, alginate impressions were made of a standard dentoform. In the clinic, maxillary alginate impressions were made of the teeth of 20 dentate adults. In each case, sets of stone models were made either immediately or after the impressions had been stored for 24 or 72 hours at high humidity. The linear dimensions of the three sets of dentoform models were compared with one another and with the standard dentoform. No differences were found. Claspless acrylic retainers were fabricated on the models from the adult subjects. The retainers were positioned in the subjects' mouths and evaluated for snap fit, stability, cervical margin fit, and self-retention. With the use of these criteria, 95% of the retainers made from impressions that were poured immediately were clinically acceptable. When impressions were stored 24 and 72 hours, the percentages of acceptable retainers were 80% and 90%, respectively. The differences in percentage of clinically acceptable retainers were not statistically significant. When impressions are stored at high humidity, a large percentage of clinically acceptable orthodontic retainers can be made from models poured as long as 72 hours after the impression is made.