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PubMed1998

Synapsin III, a novel synapsin with an unusual regulation by Ca2+.

Synapsins I and II are synaptic vesicle proteins essential for normal Ca2+ regulation of neurotransmitter release. Synapsins are composed of combinations of common and variable sequences, with the central C-domain as the largest conserved domain. The C-domain is structurally homologous to ATPases, suggesting that synapsins function as ATP-dependent phosphotransfer enzymes. We have now identified an unanticipated third synapsin gene that is also expressed in brain. The product of this gene, synapsin IIIa, shares with synapsins Ia and IIa three conserved domains that are connected by variable sequences: the phosphorylated A-domain at the amino terminus, the large ATP-binding C-domain in the center, and the E-domain at the carboxyl terminus. Like other synapsins, synapsin IIIa binds ATP with high affinity and ADP with a lower affinity, consistent with a cycle of ATP binding and hydrolysis. ATP binding to the different synapsins is directly regulated by Ca2+ in a dramatically different fashion: Ca2+ activates ATP binding to synapsin I, has no effect on synapsin II, and inhibits synapsin III. Thus vertebrates express three distinct synapsins that utilize ATP but are specialized for different modes of direct Ca2+ regulation in synaptic function.

Adenosine Triphosphate↗

PubMed2003

Structural estimation of a principal-agent model: moral hazard in medical insurance.

Despite the importance of principal-agent models in the development of modern economic theory, there are few estimations of these models. I recover the estimates of a principal-agent model and obtain an approximation to the optimal contract. The results show that out-of-pocket payments follow a concave profile with respect to costs of treatment. I estimate the welfare loss due to moral hazard, taking into account income effects. I also propose a new measure of moral hazard based on the conditional correlation between contractible and noncontractible variables.

Contracts↗

PubMed2000

Etiology of limited transmission diseases among drug users: does recent migration magnify the risk of sharing injection equipment?

Epidemiological studies have attributed area-specific changes in infectious disease prevalence to human migration. There is a paucity of research investigating the postmigration adjustment period as an effect on risk behaviors that are required in limited transmission diseases. A two-group typology, derived by cluster analysis, allowed for an analytical differentiation in the postmigration period. The cluster variable and other possible cofactors were included in linear and logistic regression modeling of sharing drug injection equipment among drug users in Alaska. The results indicate that among participants who have injected drugs, those in the postmigration adjustment period are nearly six times more likely to share injection equipment than those drug users who are not in a postmigration period. Further research is suggested and limitations are discussed.

Alaska↗

PubMed2003

Socioeconomic status modifies heritability of IQ in young children.

Scores on the Wechsler Intelligence Scale for Children were analyzed in a sample of 7-year-old twins from the National Collaborative Perinatal Project. A substantial proportion of the twins were raised in families living near or below the poverty level. Biometric analyses were conducted using models allowing for components attributable to the additive effects of genotype, shared environment, and nonshared environment to interact with socioeconomic status (SES) measured as a continuous variable. Results demonstrate that the proportions of IQ variance attributable to genes and environment vary nonlinearly with SES. The models suggest that in impoverished families, 60% of the variance in IQ is accounted for by the shared environment, and the contribution of genes is close to zero; in affluent families, the result is almost exactly the reverse.

Biometry↗

PubMed2002

Molecular characterization of 22q11 deletion in a three-generation family with maternal transmission.

Haploinsufficiency of chromosome 22q11.2 is a well-established cause of both the DiGeorge anomaly and the velocardiofacial syndrome. This condition shows a continuous spectrum of phenotypic manifestations with a considerable inter- and intrafamilial variability. We report on a three-generation family with four members sharing the same 3 Mb long deletion but showing different phenotypic expression. In the first generation, the deleted patient has hypernasal speech and suffers from recurrent psychotic episodes. Two of her offspring inherited the deletion. One of these, a male, has hypernasal speech, low-set ears, hypocalcemia, severe development delay, and tetralogy of Fallot. The other, a female, has hypernasal speech, minor facial anomalies, and very mild mental retardation. Her daughter has tetralogy of Fallot, velopharyngeal insufficiency, and mild facial anomalies. This family is an example of the widely variable phenotypic expressivity of the 22q11.2 deletion. There is no correlation between the size of the deletion and the phenotypic manifestations. Genetic background and/or environmental factors could explain the different phenotypes observed in the affected members of the family.

Abnormalities, Multiple↗

PubMed2004

Relationship between the energetic cost of burrowing and genetic variability among populations of the pocket gopher, T. bottae: does physiological fitness correlate with genetic variability?

Many studies have reported relationships between genetic variability and fitness characters in invertebrates, but there is a paucity of such studies in mammals. Here, we use a statistically powerful paired sampling design to test whether the metabolic cost of burrowing, an important physiological trait in the pocket gopher, Thomomys bottae, correlates with genetic variability. Three pairs of pocket gopher populations were used, with each pair selected from a different subspecies and comprising one high genetic variability and one low genetic variability population. Genetic variability was measured using average allozyme heterozygosity and two measures of DNA fingerprint band sharing. In addition, the cost of burrowing for individuals from each population was determined from the oxygen consumption per gram of body mass per unit of work performed. Our results indicate that the cost of burrowing was significantly higher in populations with lower genetic variability (3-way ANCOVA, P=0.0150); mass-adjusted cost of burrowing in the low variability populations averaged 0.57+/-0.24 ml O2 g(-1) kgm(-1) and that in the high variability populations averaged 0.42+/-0.19 ml O2 g(-1) kgm(-1). The magnitude of the population differences in cost of burrowing was associated with the magnitude of difference in genetic variability. We conclude that population differences in genetic variability are reflected in physiological fitness differences for a trait that is essential to gopher survival.

Analysis of Variance↗

PubMed2001

DPB1*8601, a previously unrecognized DPB1 variant in the Caucasoid population.

A new, previously unrecognized DPB1* allele, DPB1*8601, was found in a Swedish family. The new allele was carried on the common North European haplotype HLA A1-B8-DR3. Both individuals carrying the new allele were initially typed as clear DPB1*4601,*6601 but after family studies and further typing with allele-specific primers it was concluded that a new allele was present together with the common DPB1*0401. The new allele was investigated by direct sequencing of exon 2 in both forward and reverse directions employing intron primers combined with either an allele-specific sense or anti-sense biotinylated primer for bi-directional sequencing. The new allele is identical to DPB1*1701 in the five first variable regions. In the sixth region, however, DPB1*8601 carries the GGPM motif shared by several common alleles such as DPB1*0201 and 0401and 0402.

Alleles↗

PubMed2000

The mutually reinforcing triad of depressive symptoms, cardiovascular disease, and erectile dysfunction.

The conditions of depression, erectile dysfunction (ED), and cardiovascular disease may seem at a superficial level as independent medical problems managed by 3 separate and unrelated healthcare disciplines. Various studies, however, have revealed significant associations between depression and cardiovascular disease, ED and cardiovascular disease, and depression and ED. The purpose of this research was to identify whether the 3 medical conditions share mutually reinforcing associations and predictors. Population-based epidemiologic studies were utilized where possible. Variables including age, heart disease, hypertension, sedentary behavior, related medications, cigarette smoking, and abnormal lipids have been found to be highly associated with depressive symptoms, cardiovascular disease, and ED. It was concluded that all 3 medical conditions share many of the same risk factors and etiologic associations and may be best modeled in a 3-way holistic, mutually reinforcing relation. Of particular relevance, patients with sexual dysfunction have a likely comorbidity of cardiovascular disease and depression, as well as the potential increased risk for cardiac morbidity and mortality.

Causality↗

PubMed1996

Geographic variation in human mitochondrial DNA control region sequence: the population history of Turkey and its relationship to the European populations.

The hypervariable segment I of the control region of the mtDNA (positions 16024-16383) was amplified from hair roots by PCR and sequenced in 45 unrelated individuals from Anatolia (Asian Turkey). Forty different sequences were found, defined by 56 variable positions, of which only one involves a transversion. The neighbor-joining tree of Kimura's distance matrix for all sequences shows four main clusters. Cluster D was found to be the most statistically robust of the four, and all the sequences in it shared a mutation that is present only in European and West Asian populations. The variability in cluster D could have originated between 37,000 and 107,000 years ago. No branch is unexpectedly long, denoting the absence of sequences that diverged much before the others. The pairwise difference distribution is bell-shaped, in accordance with a population expansion occurring roughly 35,000 to 100,000 years ago. When compared to other Caucasoid populations through the pairwise difference distribution, there is a pattern from the Middle East (older expansion) to the various European populations, with Turkey in an intermediate position; when Turkish sequences are compared through a neighbor-joining tree on a genetic distance matrix of populations, this position is again evidenced. Although there is a very low level of genetic divergence among Caucasoid populations as shown by mtDNA control region sequences, a geographic pattern of genetic variation emerges, denoting a stepping-stone position of Turkey between the Middle East and Europe, which is in agreement with the hypothesis of a replacement of Neanderthals by modern humans, which could be related to the Upper Paleolithic cultural expansion.

Base Sequence↗

PubMed1987

Statistical issues in the estimation of assigned shares for carcinogenesis liability.

Congress is currently considering adopting a mathematical formula to assign shares in cancer causation to specific doses of radiation, for use in establishing liability and compensation awards. The proposed formula, if it were sound, would allow difficult problems in tort law and public policy to be resolved by reference to tabulated "probabilities of causation." This article examines the statistical and conceptual bases for the proposed methodology. We find that the proposed formula is incorrect as an expression for "probability and causation," that it implies hidden, debatable policy judgments in its treatment of factor interactions and uncertainties, and that it can not in general be quantified with sufficient precision to be useful. Three generic sources of statistical uncertainty are identified--sampling variability, population heterogeneity, and error propagation--that prevent accurate quantification of "assigned shares." These uncertainties arise whenever aggregate epidemiological or risk data are used to draw causal inferences about individual cases.

Disease Susceptibility↗

PubMed2002

Genetic contributions to regional variability in human brain structure: methods and preliminary results.

Twin studies provide one approach for investigating and partitioning genetic and environmental contributions to phenotypic variability in human brain structure. Previous twin studies have found that cerebral volume, hemispheric volume, ventricular volume, and cortical gyral pattern variability were heritable. We investigated the contributions of genetic and environmental factors to both global (brain volume and lateral ventricular volume) and regional (parcellated gray matter) variability in brain structure. We examined MR images from 10 pairs of healthy monozygotic and 10 pairs of same-sex dizygotic twins. Regional gray matter volume was estimated by automated image segmentation, transformation to standard space, and parcellation using a digital atlas. Heritability was estimated by path analysis. Estimated heritability for brain volume variability was high (0.66; 95% confidence interval 0.17, 1.0) but the major effects on lateral ventricular volume variability were common and unique environmental factors. We constructed a map of regional brain heritability and found large genetic effects shared in common between several bilateral brain regions, particularly paralimbic structures and temporal-parietal neocortex. We tested three specific hypotheses with regard to the genetic control of brain variability: (i) that the strength of the genetic effect is related to gyral ontogenesis, (ii) that there is greater genetic control of left than of right hemisphere variability, and (iii) that random or fluctuating asymmetry in bilateral structures is not heritable. We found no evidence in support of the first two hypotheses, but our results were consistent with the third hypothesis. Finally, we used principal component (PC) analysis of the genetic correlation matrix, to identify systems of anatomically distributed gray matter regions which shared major genetic effects in common. Frontal and parietal neocortical areas loaded positively on the first PC; some paralimbic and limbic areas loaded negatively. Bilateral insula, some frontal regions, and temporal neocortical regions functionally specialized for audition and language loaded strongly on the second PC. We conclude that large samples are required for powerful investigation of genetic effects in imaging data from twins. However, these preliminary re. sults suggest that genetic effects on structure of the human brain are regionally variable and predominantly symmetric in paralimbic structures and lateral temporal cortex.

Algorithms↗

PubMed1990

Work site smoking cessation: a meta-analysis of long-term quit rates from controlled studies.

Meta-analytic techniques were applied to 20 controlled studies of work site smoking cessation yielding a total of 34 comparisons of long-term (average = 12 months) quit rate (QR). An overall weighted mean effect size (ES) of .21 +/- .07 was found, indicating a modest but significant overall effect (P less than .01). The weighted average follow-up QR from all interventions was 13%. Based on previous research, characteristics associated with interventions, work sites, employees, and research methodology were identified as potential moderator variables. Apart from methodological variables, interventions conducted in smaller work sites (ES = .45 +/- .17), which lasted 2 to 6 hours (ES = .42 +/- .13), and which contained heavy smokers (ES = .28 +/- .07) were associated with the largest effect sizes. We were also interested in absolute quit rates. After controlling for methodological quality, programs that included a cessation group component (partial r = .39), that were not overly complicated (partial r = -.42), and that shared company and employee time (partial r = -.48), as well as the above variables had the strongest associations with QR. Implications for public health policy and future research are discussed.

Case-Control Studies↗

PubMed1995

Interstitial deletions 4q21.1q25 and 4q25q27: phenotypic variability and relation to Rieger anomaly.

We describe clinical and chromosomal findings in two patients with del(4q). Patient 1, with interstitial deletion (4)(q21.1q25), had craniofacial and skeletal anomalies and died at 8 months of hydrocephalus. Patient 2, with interstitial deletion (4)(q25q27), had craniofacial and skeletal anomalies with congenital hypotonia and developmental delay. These patients shared certain manifestations with other del(4q) patients but did not have Rieger anomaly. Clinical variability among patients with interstitial deletions of 4q may be related to variable expression, variable deletion, or imprinting of genes within the 4q region.

Abnormalities, Multiple↗

PubMed1994

Comparative structure and genomic organization of the discontinuous mitochondrial ribosomal RNA genes of Chlamydomonas eugametos and Chlamydomonas reinhardtii.

We report that the mitochondrial ribosomal RNAs (rRNAs) of Chlamydomonas eugametos are discontinuously encoded in separate gene pieces that are scrambled in order and interspersed with protein coding genes. Individual transcripts of these mitochondrial rRNA gene pieces have the potential to form standard rRNA secondary structures through intermolecular base-pairing and they all have termini that are confined to previously defined variable rRNA domains. The C. eugametos and the previously described Chlamydomonas reinhardtii mitochondrial DNAs, therefore, share the unusual feature of highly fragmented and extensively rearranged rRNA coding regions, which contrasts with the conventional mitochondrial rRNA gene structure of land plants and other green algae. Although many of the sites of mitochondrial rRNA discontinuity are in corresponding variable regions in the two Chlamydomonas species, several variable rRNA regions are interrupted in one species but not the other and the 5' to 3' order of the C. eugametos and C. reinhardtii gene pieces is very different. Based on these results, we conclude that the last common ancestor of C. eugametos and C. reinhardtii had discontinuous mitochondrial rRNA genes and that processes responsible for the further division and scrambling of these coding regions have continued since the divergence of C. eugametos and C. reinhardtii. The presence of four group I introns within the C. eugametos mitochondrial rRNA gene pieces leads us to favour recombination rather than reverse-transcription as the mechanism giving rise to the scrambled arrangement of rRNA genes in Chlamydomonas mitochondria.

Animals↗

PubMed1999

Immunodeficiency-associated lymphoproliferative disorders.

The incidence of lymphoproliferative disease is significantly higher in individuals who have congenital, acquired, or iatrogenically induced immunodeficiency. The immunodeficiency-associated lymphoproliferative disorders are clinically and pathologically heterogeneous, are of variable clonal composition, and vary according to the immunodeficiency syndrome. Nonetheless, they share several features, including frequent origination in or involvement of extranodal sites, diffuse aggressive histology, B-cell lineage derivation, association with the Epstein-Barr virus (EBV), and, often, rapid clinical progression. Reactive and atypical lymphoid hyperplasias and malignant lymphomas occur in association with congenital (primary) immunodeficiency. Post-transplantation lymphoproliferative disorders are often comprised of a polymorphic cell population, making it difficult to identify their benign or malignant nature by histopathologic criteria alone. Recent studies suggest that they are divisible into plasmacytic hyperplasias, polymorphic lymphoproliferative disorders, and malignant lymphomas. The plasmacytic hyperplasias are polyclonal and generally regress spontaneously following withdrawal of immunosuppression. The malignant lymphomas are monoclonal, possess a variety of genetic alterations, and generally progress despite aggressive therapy. The polymorphic lymphoproliferative disorders are also monoclonal but display variable clinical behavior, their progression apparently correlating with bcl-6 gene mutation. Non-Hodgkin's lymphoma (NHL) is the second most common AIDS-related neoplasm and an AIDS-defining illness. AIDS-related NHLs are divisible by anatomic site of origin into systemic (nodal/extra nodal), primary central nervous system, and body cavity-based (primary effusion) lymphomas; and by histopathology into Burkitt's and Burkitt's-like lymphoma, large cell lymphoma, and large cell immunoblastic (plasmacytoid) lymphoma More than 90% are monoclonal B-cell neoplasms. The primary effusion lymphomas contain the Kaposi's sarcoma-associated herpesvirus. Multiple molecular pathways appear to operate in AIDS lymphomagenesis and some may be preferentially associated with specific histopathologic categories or anatomic sites of origin. In conclusion, the immunodeficiency-associated lymphoproliferative disorders often represent a significant diagnostic problem requiring correlative analysis of the clinical behavior of the patient with the histopathology, immunophenotype, clonal composition, viral content, and genetic alterations of the lymphoproliferative disorder. They also represent an important biological model for studying the development and progression of lymphoid neoplasia

Humans↗

PubMed2004

Somatic diversification of variable lymphocyte receptors in the agnathan sea lamprey.

Although jawless vertebrates are apparently capable of adaptive immune responses, they have not been found to possess the recombinatorial antigen receptors shared by all jawed vertebrates. Our search for the phylogenetic roots of adaptive immunity in the lamprey has instead identified a new type of variable lymphocyte receptors (VLRs) composed of highly diverse leucine-rich repeats (LRR) sandwiched between amino- and carboxy-terminal LRRs. An invariant stalk region tethers the VLRs to the cell surface by means of a glycosyl-phosphatidyl-inositol anchor. To generate rearranged VLR genes of the diversity necessary for an anticipatory immune system, the single lamprey VLR locus contains a large bank of diverse LRR cassettes, available for insertion into an incomplete germline VLR gene. Individual lymphocytes express a uniquely rearranged VLR gene in monoallelic fashion. Different evolutionary strategies were thus used to generate highly diverse lymphocyte receptors through rearrangement of LRR modules in agnathans (jawless fish) and of immunoglobulin gene segments in gnathostomes (jawed vertebrates).

Adaptation, Physiological↗

PubMed1999

Genetic and environmental contributions to size, color, shape, and other characteristics of melanocytic naevi in a sample of adolescent twins.

The presence of melanocytic naevi is the strongest known risk factor for malignant melanoma. We have developed a computer imaging system with which it is possible to make quantitative measures of the size, color, and shape of pigmented lesions. The objective of this study was to examine the genetic and environmental contributions to these characteristics of naevi as measured by computer image analysis in a sample of adolescent twins. We captured video images of the 5 most atypical pigmented skin lesions (i.e., the largest, darkest, or most irregularly shaped) on each individual from 322 Australian adolescent twin pairs. Features extracted by computer image analysis for each lesion included color, size, symmetry, elongation, boundary irregularity, and edge distinctness. We found major genetic influences on the color and size of lesions accounting for between 40 and 80% of total variance. There were significant components of shared environmental influence (22-45% of total variance) for the color variables, with sun exposure the most obvious explanation. Differences between individuals in naevus color and size are largely genetic in origin although there are significant environmental contributions to color as well.

Adolescent↗

PubMed2001

Widespread pain among 11-year-old Finnish twin pairs.

OBJECTIVE: To examine the prevalence of widespread musculoskeletal pain (WSP) symptoms in 11-year-old Finnish twins and to determine the relative role of genetic and environmental factors in the etiology of WSP. METHODS: Data on current pain items were collected from 1995 to 1998 from a national sample of Finnish families with 11-year-old twins born between 1984 and 1987. The presence of WSP was determined using a validated questionnaire method. Pairwise similarity was computed for 583 monozygotic (MZ) pairs, 588 same-sex dizygotic (DZ) pairs, and 618 opposite-sex DZ twin pairs. Variance components for genetic and environmental factors were estimated using biometric structural equation modeling techniques. RESULTS: The prevalence of WSP was 9.9%, with no sex difference. The majority of twin pairs with WSP were discordant. The tetrachoric correlations for male MZ (r = 0.38), male DZ (r = 0.37), female MZ (r = 0.59), female DZ (r = 0.54), and opposite-sex pairs (r = 0.43) showed little difference by zygosity. Female pairs were more concordant than male pairs among both MZ and DZ twins. Biometric model-fitting indicated that genetic factors did not account for the pattern of twin similarity. Among boys 35%, and among girls 56%, of the variation in liability to WSP could be attributed to shared familial environmental effects. The remainder was attributed to unshared environmental effects. CONCLUSION: Genetic factors seem to play at most a minor role in WSP in 11-year-old twins, and environmental factors shared by family members account for a substantial proportion of the variability in WSP.

Child↗