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PubMed2000

Genotype, phenotype, and developmental biology of molar tooth characters.

Primate molar shapes reflect developmental and ecological processes. Development may constrain as well as facilitate evolution of new tooth shapes, affecting how reliable dental characters are in phylogenetic studies. Much of the genetic machinery of development uses the same genes among different organs, including teeth, limbs, and feathers. Furthermore, within a tooth, the development of individual cusps repeatedly uses the same set of developmental genes, forming a "developmental module." The repeated activation of the developmental module can explain the cumulative variation in later-developing cusps. Therefore short, later-developing cusps may be evolvable but also more homoplastic. This patterning cascade mode of cusp development can be used to explain the variational properties of dental characters and character states related to cusp initiation. The developmental basis and variational properties of crown termination, cusp shape, and cusp configuration characters are currently less well understood. It is unlikely that there is a simple "gene to phenotype" map for dental characters. Rather, the whole cusp pattern is a product of a dynamic developmental program manifested in the activation of the developmental modules.

Animals↗
PubMed2002

Fabrication and use of a transient contractional flow device to quantify the sensitivity of mammalian and insect cells to hydrodynamic forces.

A microfluidic device was fabricated via photolithographic techniques which can create transient elongational and shear forces ranging over three orders of magnitude while still maintaining laminar flow conditions. The contractional fluid flow inside the microfluidic device was simulated with FLUENT (a computational fluid dynamics computer program) and the local deformation forces were characterized with the scalar quantity, local energy dissipation rate. The sensitivities of four cell lines (CHO, HB-24, Sf-9, and MCF7) were tested in the device. The results indicate that all four cell lines are able to withstand relatively intense energy dissipation rates (up to 10(4)-10(5) kW/m(3)), which is orders of magnitude higher than the maximum local energy dissipation rates generated by impellers in bioreactors, but comparable to that associated with small bursting bubbles. While the concept that suspended animal cells are relatively robust with respect to purely hydrodynamic forces in bioprocess equipment is well known, these results quantitatively demonstrate these observations.

Animals↗
PubMed2003

Nonspecific interaction forces at water-membrane interface by forced molecular dynamics simulations.

Nonspecific interactions are the main driving forces for the behavior of molecules with great affinity for biologic membranes. To investigate not only the molecular details of these interactions but to estimate their magnitude as well, the theoretical method of Forced Molecular Dynamics Simulations, based on the Atomic Force Spectroscopy experimental technique, was applied. In this approach, an additional one-dimensional elastic force, representing the cantilever probe, was incorporated to the force field of a Molecular Dynamics computational program. This force represents a spring fixed on one end to a selected atom of the molecule; the other end of the spring is displaced at constant velocity to pull the molecule out of the membrane. The force experimented by the molecule due to the spring, is proportional to the spring elongation relative to its equilibrium position. This value is registered during the entire simulation, and its maximum value will determine the molecule-membrane interaction force. Nonexplicit medium simulations were carried out. Polar and apolar media were considered according to their polarizability degree and a specific dielectric constant value was assigned. In this approach, the membrane was considered as the apolar region limited by two flat surfaces with a polar aqueous medium. The potential energy discontinuity at the interfaces was smoothed by considering the polarization-induced effects using the image method. The results of this methodology are presented using a small system, a single Alanine amino acid model, which enables extended simulations in a microsecond time scale. The confinement of this amino acid at the interface reduces its degrees of freedom and forces it to adopt one of the six defined conformations. A correlation between these stable structures at the water-membrane interface and the interaction force value was determined.

Alanine↗
PubMed1996

Topology prediction for helical transmembrane proteins at 86% accuracy.

Previously, we introduced a neural network system predicting locations of transmembrane helices (HTMs) based on evolutionary profiles (PHDhtm, Rost B, Casadio R, Fariselli P, Sander C, 1995, Protein Sci 4:521-533). Here, we describe an improvement and an extension of that system. The improvement is achieved by a dynamic programming-like algorithm that optimizes helices compatible with the neural network output. The extension is the prediction of topology (orientation of first loop region with respect to membrane) by applying to the refined prediction the observation that positively charged residues are more abundant in extra-cytoplasmic regions. Furthermore, we introduce a method to reduce the number of false positives, i.e., proteins falsely predicted with membrane helices. The evaluation of prediction accuracy is based on a cross-validation and a double-blind test set (in total 131 proteins). The final method appears to be more accurate than other methods published: (1) For almost 89% (+/-3%) of the test proteins, all HTMs are predicted correctly. (2) For more than 86% (+/-3%) of the proteins, topology is predicted correctly. (3) We define reliability indices that correlate with prediction accuracy: for one half of the proteins, segment accuracy raises to 98%; and for two-thirds, accuracy of topology prediction is 95%. (4) The rate of proteins for which HTMs are predicted falsely is below 2% (+/-1%). Finally, the method is applied to 1,616 sequences of Haemophilus influenzae. We predict 19% of the genome sequences to contain one or more HTMs. This appears to be lower than what we predicted previously for the yeast VIII chromosome (about 25%).

Algorithms↗
PubMed1997

A Potential Energy Surface for the Electronic Ground State of H2Te Derived from Experiment

We report here the determination of a new potential energy surface for the electronic ground state of the H2Te molecule by fitting to an extensive set of very recent experimental spectroscopic data (see J.-M. Flaud, P. Arcas, H. Burger, O. Polanz, and L. Halonen, J. Mol. Spectrosc. 183, 310-335 (1997), and references therein) by means of the MORBID (Morse Oscillator Rigid Bender Internal Dynamics) computer program. The fitting to all 1111 input data (involving rotation-vibrational states with J </= 10) had a standard deviation of 0.18 cm-1 and was obtained by varying 14 parameters. With the new potential energy function, the rotation-vibration energies of H2130Te have been calculated with the MORBID program. In particular, we have calculated the rotational energy manifolds for J </= 40 in the lowest vibrational states. Compared to previous potential energy functions for H2Te, the new function has substantially improved the reproduction of the rotational spacings in the excited vibrational states. An important aim of the present work is the further characterization of the anomalous "fourfold cluster effect" (i.e., the formation of four-member groups of nearly degenerate rotation-vibration energies at high rotational excitation) exhibited by the energy levels of H2Te. Comparison of our theoretical results with the experimental results of J.-M. Flaud, M. Betrencourt, P. Arcas, H. Burger, O. Polanz, and W. J. Lafferty (1997, J. Mol. Spectrosc. 182, 396-420) provides conclusive evidence for the existence of so-called Type II clusters (clusters formed by coalescence of two energy doublets belonging to two different vibrational states) in the nu1/nu3 vibrational states of H2130Te. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1995

An economic analysis of pregnancy resolution in Virginia: specific as to race and residence.

This study analyses an economic model of pregnancy resolution; that is, a model of the choice by a pregnant woman to abort her fetus or carry it to term. This analysis, using an analytical model derived from the household utility framework, adds to previous research by presenting race- and residence-specific estimates of how individual characteristics, history of abortion, and the community-based factors determine women's choices of giving birth vs. aborting. The main data for estimating the model were drawn from the 1984 vital statistics of all induced abortions and live births in the Commonwealth of Virginia. The major findings indicate that low parental education, high maternal age, previous early abortions, and the availability of abortion providers all significantly reduce the probability of choosing the live birth option. Married status and the availability of family planning clinics significantly increase the probability of the live birth option. The findings also suggest that women's choices between abortion and live birth vary substantially with race (White vs. Black) and residential (urban vs. rural) location.

Abortion, Induced↗
PubMed1993

Immigration policy and immigrant quality: empirical evidence from Canada.

"This paper examines the earnings of foreign-born and native-born men [in Canada] in an attempt to evaluate whether the decline in the quality [based on earnings] of Canadian immigrants is related to changes in the country-of-origin mix and the class (type) mix of immigrants....The analysis consists of two parts. The first part is based on individual data on earnings and socio-economic characteristics collected in the 1971 and 1986 Canadian Censuses.... In the second part of the analysis, additional regression equations are estimated, pertaining to the period 1968 to 1985, that relate these Census-based measures of immigrant quality to the country-of-origin and class mix of immigrants." The impact of changes brought about by the 1967 restructuring of the Canadian immigration system is analyzed.

Americas↗
PubMed1977

A psychological theory of child abuse.

This paper presents a detailed study of two patients hospitalized in a closed psychiatric unit on which the treatment program emphasized dynamically oriented individual psychotherapy and family therapy. The first patient was hospitalized following physical abuse of her four-year-old daughter, while the second was hospitalized for a postpartum depression eight weeks following the birth of her first child, a girl. Although the presenting pictures in these two patients were markedly different, the psychodynamic patterns were so similar that a detailed comparison of the two cases seems to offer useful insight into some of the psychological causes of child abuse.

Adult↗
PubMed1986

Targeting the adolescent male.

The National Urban League regards too early parenting among adolescents as an issue requiring high level, active attention from all segments of the Black community. Poverty, single parent households and adolescent pregnancies are not exclusively female problems. The role that males play has been missing from too many studies of these phenomena. In light of the fact that most sexual activity is male initiated, and most sexual behavior is male influenced, it becomes clear that there will be no resolution of the problem of teenage pregnancy without directing greater attention to the male. The issue of male responsibility is skirted too often due to parental pride on the part of mothers and fathers when their male children seek sexual relations with female partners. It is viewed as a sign that they are developing sexually within the norm. This is especially true, in many instances, in female headed households where the mother is concerned that she may not be providing her son with an adequate male role model. Sexual activity by female adolescents, however, is generally not condoned. This confusing double standard is further compounded by the disjointed fashion in which American society responds to adolescent sexuality on the whole. Although the home should be the focal point, many parents reluctantly admit an inability to communicate effectively about sex with their pre-adolescent children. Thus, the school, church, community and social agencies have all been enlisted in this task. The National Urban League's initiative in this area is expected to have significant impact on the course of adolescent sexuality and reproductive responsibility.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Adolescent pregnancy: networking and the interdisciplinary approach.

The networking approach to providing needed services to pregnant and parenting teenagers has numerous merits. An historical overview of the formation of the Brooklyn Teen Pregnancy Network highlights service agency need for information and resource sharing, and improved client referral systems as key factors in the genesis of the Network. The borough-wide approach and its spread as an agency model throughout New York City's other boroughs and several other northeastern cities is also attributed to its positive client impact, including: improved family communication and cooperation; early prenatal care with its concomitant improved pregnancy outcomes; financial support for teens; continued teen education; and parenting skills development. Resource information is provided regarding networks operating in the Greater New York metropolitan area. A planned Eastern Regional network initiative is under development.

Adolescent↗
PubMed1999

Computer modelling of the cerebrospinal fluid flow dynamics of aqueduct stenosis.

As the craniospinal space is a pressure loaded system it is difficult to conceptualize and understand the flow dynamics through the ventricular system. Aqueduct stenosis compromises flow, increasing the pressure required to move cerebrospinal fluid (CSF) through the ventricles. Under normal circumstances, less than one pascal (1 Pa) of pressure is required to move a physiological flow of CSF through the aqueduct. This is too small to measure using clinical pressure transducers. A computational fluid dynamics (CFD) program, CFX, has been used to model two forms of aqueduct stenosis: simple narrowing and forking of the aqueduct. This study shows that with mild stenoses, the increase in pressure required to drive flow becomes significant (86-125 Pa), which may result in an increased transmantle pressure difference but not necessarily an increased intraventricular pressure. Severe stenoses will result in both. Wall shear stresses increase concomitantly and may contribute to local damage of the aqueduct wall and further gliosis with narrowing.

Cerebrospinal Fluid↗
PubMedDate not supplied

Socio-biological factors in underfive deaths in a rural area.

In 1985-86, 286 underfive deaths occurred among a population of 30,000 in a rural area of Haryana. Two hundred and eighty one were analysed for socio-biological factors related to under five mortality. Females had a higher mortality. About 2/3 of the deaths were in infants, and 90% in first 3 years. Most of the deaths (94%) occurred in the village itself, 58.4% did not seek any medical care during the terminal illness, 80-90% did not receive even a single dose of BCG, DPT or O.P.V., and 36.7% died in the first attack of illness. Though 68% had at least one episode earlier, 31.0% had been admitted in hospitals for an earlier episode of illness. In 42.8% of deaths, the birth order was IV or above. Deaths in socially and economically disadvantaged cases constituted 77.6%. The triad of diarrhea, ARI and malnutrition claimed 56% deaths. In 93% of the deaths, the mothers were illiterate and 96.4% were house wives. There was a sibling death earlier in the family in 78.3%, and 60.1% deaths were of those living in poor housing conditions. About 50% had radio for communication, 85.8% had bicycle for conveyance, and in 66.9% the family had piped water supply. All these findings have been discussed in the study.

Age Factors↗
PubMed2002

Stream restoration and enhancement projects: is anyone monitoring?

Declines in salmon stocks and general watershed health in Washington State, USA, have led to an increase in stream restoration and enhancement projects initiated throughout the state. The increasing number of projects has also raised questions regarding the monitoring of these efforts. Project managers receiving hydraulic project approvals (HPAs) were surveyed to determine whether monitoring was taking place on their projects. About half the project managers surveyed reported the collection of baseline data and the use of biological, physical, chemical, or other water quality measures for their projects. Of those who reported collection of monitoring data, only 18% indicated that monitoring was required. Respondents were also asked to rank the importance of various project goals on a Likert scale. Project managers with projects focusing on "engineering" goals (e.g., roadbed stabilization) were less likely than other project managers to collect baseline monitoring data. Project managers with projects focusing on "restoration/ecological" or "fisheries" goals were more likely than other project managers to collect monitoring measures. Although monitoring appears to be taking place in slightly more than half of the projects surveyed, the nature of the data collected varies widely across projects, and in most cases the monitoring effort is voluntary. This suggests that project sponsors, funders, and managers must consider the issues involved in requiring appropriate monitoring, establishing standardized monitoring guidelines, the time frames in which to monitor, providing other incentives for conducting monitoring, and ensuring adequate funding for monitoring efforts.

Animals↗