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At least 343 records · Page 19Linked to original sources
PubMed2002

Patterns of cranial shape variation in the Papionini (Primates: Cercopithecinae).

Traditional classifications of the Old World monkey tribe Papionini (Primates: Cercopithecinae) recognized the mangabey genera Cercocebus and Lophocebus as sister taxa. However, molecular studies have consistently found the mangabeys to be diphyletic, with Cercocebus and Mandrillus forming a clade to the exclusion of all other papionins. Recent studies have identified cranial and postcranial features which distinguish the Cercocebus-Mandrillus clade, however the detailed similarities in cranial shape between the mangabey genera are more difficult to reconcile with the molecular evidence. Given the large size differential between members of the papionin molecular clades, it has frequently been suggested that allometric effects account for homoplasy in papionin cranial form. A combination of geometric morphometric, bivariate, and multivariate methods was used to evaluate the hypothesis that allometric scaling contributes to craniofacial similarities between like-sized papionin taxa. Patterns of allometric and size-independent cranial shape variation were subsequently described and related to known papionin phylogenetic relationships and patterns of development. Results confirm that allometric scaling of craniofacial shape characterized by positive facial allometry and negative neurocranial allometry is present across adult papionins. Pairwise comparisons of regression lines among genera revealed considerable homogeneity of scaling within the Papionini, however statistically significant differences in regression lines also were noted. In particular, Cercocebus and Lophocebus exhibit a shared slope and significant vertical displacement of their allometric lines relative to other papionins. These findings give no support to narrowly construed hypotheses of uniquely shared patterns of allometric scaling, either between sister taxa or across all papionins. However, more general allometric trends do appear to account for a substantial proportion of papionin cranial shape variation, most notably in those features which have influenced traditional morphological phylogenies. Examination of size-uncorrelated shape variation gives no clear support to molecular phylogenies, but underscores the absence of morphometric similarities between the mangabey genera when size effects are controlled. Patterns of allometric and size-uncorrelated shape variation indicate conservatism of cranial form in non- Theropithecus papionins, and suggest that Papio represents the primitive morphometric pattern for the African papionins. Lophocebus exhibits a divergent morphometric pattern, clearly distinguishable from other papionins, most notably Cercocebus. These results clarify patterns of cranial shape variation among the extant Papionini and lay the groundwork for studies of related fossil taxa.

Animals↗
PubMed1998

Phylogenetics of social behavior in Australian gall-forming thrips: evidence from mitochondrial DNA sequence, adult morphology and behavior, and gall morphology.

Six species of Australian gall-forming thrips (Insecta: Thysanoptera) on Acacia exhibit soldier castes, individuals with reduced wings and enlarged forelegs that defend their gall against interspecific invaders. We used data from two mitochondrial genes (cytochrome oxidase I and 16S rDNA), adult morphology and behavior, and gall morphology to infer a phylogeny for Acacia gall-forming thrips with and without soldiers, and we used this phylogeny to evaluate hypotheses concerning soldier evolution. Phylogenies inferred from each data set analyzed separately yielded large numbers of most-parsimonious trees and weak support for most nodes. However, when analyzed together the data sets complemented and reinforced one another in such a way as to yield a well-resolved phylogeny. Our phylogeny implies that soldiers originated once or twice early in the history of this clade, that soldiers were lost once or twice, and that soldiers evolved from winged dispersers rather than from nonsoldier within-gall reproductive offspring of foundresses. The phylogeny also provides evidence for long-term morphological stasis, an ancient split between eastern and western gall thrips species, and a high degree of conservatism in host-plant affiliations.

Acacia↗
PubMed2002

A phylogenetic analysis of cordyliformes (Reptilia: Squamata): comparison of molecular and karyological data.

A karyological study and the analysis of two mitochondrial genes were conducted in several species of cordyliformes from Madagascar. Both studies confirmed the monophyly of cordyliformes. The karyological conservatism and small genetic distance among mitochondrial genes observed in these species are in line with the hypothesis that all cordyliformes should be included in a single family. The two studies yielded contrasting results with regard to the relationships between the Malagasy species and the Cordylidae and Gerrhosauridae. Nonetheless, the consistency between the data from mitochondrial gene analysis and those of taxonomic studies based on morphological characters is more in favor of an affinity between Malagasy Zonosaurinae and Gerrhosauridae and suggests that the karyological similarities between the former and the Cordylidae may be due to plesiomorphy. Interesting, though not conclusive, data were also obtained on interspecific relationships among Zono-

Animals↗
PubMed1993

Evaluating the adequacy of maximum contaminant levels as health-protective cleanup goals: an analysis based on Monte Carlo techniques.

At many sites in the United States, health-based remediation goals for contaminated groundwater have been set at levels far below USEPA's drinking water standards (i.e., maximum contaminant levels or MCLs). This is due to the fact that, while the USEPA must often consider technical and economic factors (e.g., cost of compliance, risk/benefit analysis) when setting MCLs for public water systems, cleanup goals for contaminated groundwater are often based solely on conservative "point" estimates of exposure. One of the more recent refinements in the risk assessment process is the use of ranges of exposure estimates or "probability density functions" (PDFs), rather than fixed point estimates, to estimate exposure and chemical uptake. This approach provides a more thorough description of the range of potential risks, rather than a single "worst-case" value, and allows one to understand the conservatism inherent in assessments based on regulatory default parameters. This paper uses a number of PDFs and the Monte Carlo technique to assess whether the USEPA's MCLs for drinking water are sufficiently low to protect persons exposed to these levels. A case study involving daily exposure to tapwater containing MCL concentrations of tetrachloroethylene, chloroform, bromoform, and vinyl chloride is presented. Several direct and indirect exposure pathways are evaluated, including inhalation and dermal contact while showering, direct ingestion, and inhalation of emissions from household fixtures and appliances. PDFs for each exposure factor are based on the most recent and applicable data available. Our analysis indicates that the estimated increased cancer risks at the 50th and 95th percentile of exposure are within the range of increased cancer risks typically considered acceptable at Superfund sites (10(-4)-10(-6)). These results suggest that, at least for some chemicals, groundwater need not be cleaned-up to concentrations less than drinking water standards (i.e., MCLs) to protect human health.

Air Pollutants↗
PubMed1996

Mortality from tobacco in developed countries: are indirect estimates reliable?

The ICRF and WHO recently published estimates of smoking-attributed deaths in almost 50 developed countries. These estimates are derived without using any available data on the prevalence of smoking or of other risk factors in the countries concerned. This paper describes and discusses the various assumptions on which the derivation depends and shows that they are unlikely to hold in practice. ICRF/WHO attempt to control for confounding by introducing a modification to the standard attributable risk formula which they admit is "crude and arbitrary" but state is "conservative." In fact, this modified formula carries no guarantee of conservatism at all and may overestimate deaths even where there is no confounding. The validity of the ICRF/WHO estimates of smoking-attributed deaths is further undermined by the lack of correlation seen in males between the smoking prevalence rates they estimate indirectly and smoking prevalence rates actually published. The ICRF/WHO estimates of smoking-attributed deaths are shown to have no scientific basis and to be unreliable.

Adult↗
PubMed1999

Estimating acute dietary intakes of chemicals.

In some cases a single dose above an acceptable daily intake could elicit an adverse effect. In other cases a cumulative dose over several days may be necessary before an effect is expressed. Estimates of acute intake must relate to what is known about the toxicokinetics of the substance, in relation to the toxicological studies associated with the relevant end point. This is because estimates of intake can vary considerably over even a few days in some circumstances. Acute reference doses should therefore be qualified by an exposure interval. Default values can introduce considerable conservatism into intake estimates. Techniques for estimating acute intakes are very varied. They can range in complexity from conservative screening methods to sophisticated techniques designed to simulate real situations. Monte Carlo models allow for the distributions of chemical concentrations and food consumption patterns to be taken into account. For acute dietary risk assessments very high upper percentile cutoffs are sometimes applied, even as high as 99.9%. However, assumptions applied in such methods can lead to misleading results. Great care must also be used when interpreting such statistics because uncertainty and inaccuracy in the data increase considerably in the upper "tail" of the distribution.

Animals↗
PubMed1999

Background to the ADI/TDI/PTWI.

International scientific committees such as the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and the Joint FAO/WHO Meeting on Pesticide Residues (JMPR), regional scientific committees such as those of the European Union, and national regulatory agencies generally use the safety factor approach for establishing acceptable or tolerable intakes of substances that exhibit thresholds of toxicity. The acceptable daily intake (ADI) is used widely to describe "safe" levels of intake; other terms that are used are the reference dose (RfD) and tolerable intakes that are expressed on either a daily (TDI or tolerable daily intake) or weekly basis. JECFA uses the term PTWI, or provisional tolerable daily intake, for contaminants that may accumulate in the body. The weekly designation is used to stress the importance of limiting intake over a period of time for such substances. When using this approach no-observed-effect levels (NOELs) or no-observed-adverse-effect levels (NOAELs) are identified in the critical studies, to which appropriate safety or uncertainty factors are applied. Although the value of safety factors varies depending upon a number of factors, 100 is most often used, which is designed to account for interspecies and intraspecies variations. Within the framework of the IPCS project on harmonization of approaches to the assessment of risk from exposure to chemicals, issues relating to uncertainty and variability are being addressed with the aim of relying, whenever appropriate, on data-derived safety/uncertainty factors. The ILSI Europe ADI Task Force has, for the past few years, been considering the scientific basis for the safety factor, which will be discussed by other speakers in the workshop. The value of the NOAEL is dependent on the design of the study. Because of the expense and time required conduct many studies, doses are usually spread over wide intervals. Thus, the no-observed-adverse-effect level may be considerably less than a marginally effective dose. In addition, use traditionally has not been made of the dose-response relationship when establishing ADIs. Newer approaches such as the benchmark dose may provide ways of making use of dose-response information. It is unlikely that consumption at the level of the ADI will result in significant risk to the consumer because of the conservatisms that are built into it. It usually is based on long-term studies that are intended to mimic consumption over the lifetime of humans. The ADI is applied to "discretionary" chemicals (food additives, veterinary drugs, and pesticides) by JECFA and JMPR, which are relatively easy to control if safety problems are identified. On the other hand, when tolerable intakes are derived for contaminants that are present in the environment at high levels, the use of standard safety factors could result in discarding large portions of the food supply. Thus, it is very important that the basis for the tolerable intake is fully described so that informed judgments can be made about the health consequences of exceeding it.

Animals↗
PubMed1980

Primary sex determination: genetics and biochemistry.

On the basis of widespread phylogenetic conservatism, it has been proposed that serologically-defined H-Y antigen is the inducer of primary sex differentiation in mammals, causing the initially indifferent gonad to become a testis rather than an ovary. The proposal has withstood extensive testing in a variety of biological circumstances: XX males have testes and are H-Y+ and fertile XY females lack testicular tissue and are H-Y-; soluble H-Y antigen induces testicular organogenesis in XX indifferent gonads of the fetal calf in culture; H-Y antibody blocks tubular reaggregation of dispersed XY testicular cells, causing them to organize follicular clusters. There is a gonadal receptor for H-Y antigen: fetal ovarian cells that have been exposed to soluble H-Y (released for example by testicular Sertoli cells) take up the molecule and acquire the H-Y+ phenotype; they absorb H-Y antibody in serological tests. Specific uptake of soluble H-Y does not occur in the extra-gonadal tissues. It may be inferred that H-Y antigen is disseminated during embryogenesis and bound by specific receptors in cells of the primordial gonad, and that reaction of H-Y and its receptor signals a program of testicular differentiation, regardless of karyotype. The several anomalies of primary sexual differentiation manifest in such conditions as the XX male, the XX true hermaphrodite, and the XY female can thus reasonably be viewed as specific errors of synthesis, dissemination, and binding of H-Y antigen. H-Y is secreted by 'Daudi' cells, cultured from a human XY Burkitt lymphoma. The Daudi-secreted moiety is a single hydrophobic protein of 18,000 molecular weight. Early attempts to characterize H-Y secreted by testicular Sertoli cells have yielded two molecules, one of 16,500 MW (corresponding to the Daudi-secreted 18,000 MW protein), and one of 31,000 MW. It remains to be ascertained whether both are in fact H-Y antigens, and if so, whether one is a polymer of the other, or whether each represents the product of genes with discrete testis-determining functions.

Animals↗
PubMed1983

Homologous genes for X-linked chondrodysplasia punctata in man and mouse.

X-linked dominant chondrodysplasia punctata is a human gene defect characterized by punctate foci of epiphyseal calcification, cataracts, ichthyosis, and systematized atrophoderma. In a comparative study, the murine X-linked mutant 'bare patches' was found to display strikingly similar skeletal, ocular, and cutaneous anomalies. The human as well as the murine phenotypes occur exclusively in the female sex, apparently because the underlying mutations are lethal for male embryos. In both traits, the cutaneous lesions are arranged in a linear and blotchy pattern reflecting lyonization. The observed similarities constitute strong evidence that the two genes are homologous. The proposed homology is a further example of the evolutionary conservatism of the X-chromosome in mammals.

Animals↗
PubMed1994

Stably DNA-bound chromosomal proteins.

DNA accomplishes its biological function in a complex with nuclear proteins. A minor protein fraction has been found in chromatin which could not be dissociated from DNA by reagents abolishing non-covalent type of interactions. The controversy surrounding the nature of the protein moiety and the nature of the bond linking the two components on the one hand, and the fact pointing to its evolutionary conservatism and metabolic stability on the other, make it necessary to critically evaluate the data in view of the possible biological function for such proteins.

Animals↗
PubMed1982

Joint segregation of biochemical loci in salmonidae. III. Linkage associations in Salmonidae including data from rainbow trout (Salmo gairdneri).

The results of 107 pairwise examinations of joint segregation of biochemical and skin color loci in rainbow trout, Salmo gairdneri, are presented. Three examinations revealed significant nonrandom assortment: Idh-3 with Me-2, Ada-1 with G3p-3, and Mdh-3, with Mdh-4. We believe the first two instances to be cases of classical linkage and the latter instance to reflect pseudolinkage based on similar findings in Salvelinus. All known salmonid linkage associations are reviewed. The results of this summary indicate a high degree of genome conservatism among genera within the Salmonidae, which would seem to be in contrast to the highly plastic genome of this family based on karyotypic data. Data are presented which negate the view that Robertsonian fusion of homologous acrocentric chromosome arms was the preferred mode of metacentric formation in salmonid evolution.

Albinism↗
PubMed1975

Personality patterns of white, black, and Mexican-American patrolmen as measured by the sixteen personality factor questionnaire.

The Sixteen Personality Factor Questionnaire was administered to 461 Los Angeles patrolmen to abtain a normative police profile. Multivariate analysis revealed that the average patrolman appeared brighter, more reserved, dominant, and tough-minded (p less than .001) than the average male. Comparisons were made for 29 black, 33 Mexican-American, and 399 white officers. Mexican-American officers emerged as more conservative and relaxed than whites, while black officers appeared more experimental, analytical, and group-oriented. A comparison with an idependent police sample revealed common traits of self-assurance and conservatism. Results were compared with a social workers' profile and discussed in relation to police officers' actual job activities and community needs.

Black or African American↗
PubMed1990

Evolving trends in steroid hormone receptor research.

Recent advances have challenged classical notions regarding the nature of steroid hormone receptors in the cell including localization, activation, configuration, and stability. Molecular biology has revealed a remarkable similarity in the primary structure of a wide variety of receptor classes that goes beyond steroid action. Post-translational modification of a primary unit, expressed in response to genetic conservatism, would appear to assure receptor dynamics specific to hormone-, organ-, and tissue-dependent processes, and may even lead to toxicity and oncogenicity.

Animals↗
PubMedDate not supplied

Civil commitment reform: context and consequences.

Laws and policies governing the care and treatment of the mentally ill are in part shaped by the sociopolitical climate in which they are formulated, and their outcomes are similarly shaped by the context in which they occur. Civil commitment laws were narrowed in a liberal era but later broadened in response both to the outcome of the initial reform and the trend toward social and fiscal conservatism which emerged in the late 1970s and 1980s. This study, which reports on the evolution of commitment law in the state of Washington, indicates that while recent changes in these laws mandate greater use of state hospitals, the retention of the procedural safeguards set in place by the initial reform coupled with limitations on resources available to state mental health systems will prevent a return to the state hospital as it appeared prior to the deinstitutionalization movement. These factors may promote the search for non-institutional alternatives, such as efforts underway in Washington and elsewhere to implement civil commitment of community-based services.

Commitment of Persons with Psychiatric Disorders↗
PubMed1990

Sex knowledge, attitudes, and experience of Chinese medical students in Hong Kong.

Sex knowledge, attitudes, and experience of 83 Chinese undergraduate medical students were assessed in their responses to the Sex Knowledge and Attitude Test. They were found to be relatively less knowledgeable especially in areas of social and cultural data-based knowledge and were less liberal especially in attitudes toward heterosexual relations and abortion. While increased knowledge tended to be associated with the repudiation of sexual myths, a general conservative outlook as assessed by the Wilson-Patterson Conservatism Scale was found to have the greatest influence on attitudes toward heterosexual relations, autoeroticism, and abortion. In contrast to the sexual practice of young Chinese of similar age based on another survey, the present sample of medical students was relatively heterosexually inexperienced. Implications for medical education with value reorientation are discussed.

Adaptation, Psychological↗
PubMed1976

Formal and informal sex education as determinants of premarital sexual behavior.

Controversies exist regarding the effects of sex education in the schools and informal sex education obtained from parents, peers, the mass media, and other sources. Similarly, there is widespread interest in premarital sexual behavior, especially its determinants. This study presents several issues reflecting these concerns which have been the subject of much speculation but which have received little attention by researchers. The purpose of this study was to investigate--through the use of respondent reports--how formal and informal sex education influences premarital sexual behavior during college. A national probability sample of 1177 college students was studied using face-to-face interviews with approximately equal numbers of males and females. These interviews, which were conducted for the Institute for Sex Research, included questions about past and present sexual involvement and other attitudinal, behavioral and background variables. Accordingly, the data about sexual behavior and attitudes are based on the interviewees' self-reports. Indices were created which operationalized independent variables such as familial sexual conservatism, exposure to eroticism, perceived sex knowledge, and sexual exposure and assault during childhood and adolescence. Individual items reflecting childhood sex play, masturbation, current religiosity, religiosity while growing up, social class, sources of sex information, sex education in classrooms, and high school and college dating were used. The dependent variable, premarital sociosexual involvement, is a composite measure of incidence and prevalence of premarital heterosexual involvement which meets Guttman scaling criteria. An Automatic Interaction Detector analysis was used to determine the relative influences of reported sexualization variables on premarital sexual behavior. Major findings can be summarized as follows: Heterosexual behavior progresses in stepwise fashion from elementary to advanced levels of involvement, with each level representing a threshold. Reports of current influences and pressures explain more variance in premarital sexual behavior than reports of past informal sexualization influences, which, in turn, explain more variance than reported formal sex-education experiences. Limited success was reported with the use of a four-stage AID analysis which attempted to ascertain whether variables represented in later stages of the sexualization process "mask" the effects of variables in earlier stages and whether a development process can be identified. It may be concluded that these data do not support the belief that exposure to sexuality through formal sex education influences premarital sexual behavior. Informal sex education has significantly more impact on premarital sexual behavior, but there are indications that pressures and experiences confronting young people in a given dating or peer group situation take precedence over all past sexual socialization influences.

Adolescent↗
PubMed1991

Sexual practices of heterosexual Asian-American young adults: implications for risk of HIV infection.

Epidemiologic patterns of reported AIDS cases suggest that at present Asian Americans in the United States are an ethnic minority group at lower risk for human immunodeficiency virus (HIV) infection than blacks, Hispanics, or whites. Yet little is known empirically about the sexual behaviors of Asian Americans. The present study explores rates of sexual activity and patterns of sexual behavior in a sample of young, unmarried, heterosexual Asian Americans. Results suggest that previously reported sexual conservatism within this ethnic group may be limited to the initiation of sexual activity. Once sexually active, behaviors appear to be similar to their non-Asian counterparts and facilitative of HIV infection should the virus become widely distributed within the young, heterosexual population. This underscores the need for HIV prevention interventions directed toward this ethnic minority group despite current low rates of HIV infection.

Adolescent↗
PubMed1979

Evolutionary diversification of structure and function in the family of intracellular calcium-binding proteins.

The maximum parsimony method was used to reconstruct the genealogical history of the family of intracellular calcium-binding proteins represented by six major present-day lineages, three of which--calcium dependent modulator protein, heart and skeletal muscle troponin Cs, and alkali light chains of myosin--were found to share a closer kinship with one another than with the other lineages. Similarly, parvalbumins and regulatory light chains of myosin were depicted as more closely related, whereas the branch of intestinal calcium-binding protein proved to have the most distant separation. The computer-generated amino acid sequence for the common ancestor of these six lineages described a four domain protein in which each domain of approximately 40 amino acid residues had a mid-region. 12 residue segment that bound calcium and had properties most resembling those of the calcium dependent modulator protein. It could then be deduced that parvalbumins evolved by deletion of domain I, inactivation of calcium-binding properties in domain II, and acquisition of increased affinity for Ca++ and Mg++ in domains III and IV. Regulatory light chains of myosin lost the cation binding property from three domains, retaining it in I, whereas alkali light chains of myosin lost this ability from each of the four domains. In skeletal muscle troponin C all domains retained their calcium-binding activity; however, like parvalbumins, domains III and IV acquired high affinity properties. Cardiac troponin C lost its binding activity from domain I but otherwise resembled the skeletal muscle form. Finally, intestinal calcium-binding protein evolved by deletion of domains III and IV. Positive selection could be implicated in these evolutionary changes in that the rate of fixation of mutations substantially increased in the mid portions of those domains which were loosing calcium-binding activity. Likewise, when the cation binding sites were changing from low to high affinity, an accelerated rate of fixed mutations was observed. Once this new functional parameter was selected these regions showed a remarkable conservatism, as did those binding sites which were maintaining the lower affinity. Moreover even in sequence regions not directly involved in cation binding, the lineage of troponin C because very conservative over the past 300 million years, perhaps becuase of the necessity for maintaining specific interfaces in order for the molecule to interact with troponin I and T in a functional thin myofilament. A similar phenomenon was observed in domain II of the regulatory light chains of the myosin lineage suggesting a possible binding site with the heavy chain of myosin.

Amino Acid Sequence↗