The Production of Quality in Child-Care Centers: Another Look

Data from the Cost, Quality, and Outcomes Study (Helburn, 1995) are used to examine the effects of group size, staff-child ratio, and teacher qualifications on the quality of child care provided in day care centers. The Cost, Quality, and Outcomes data are from a representative 4-state sample of day care centers with a design that makes it possible to control for unobserved differences across centers that could cause biased estimates of the effects of interest. The empirical results indicate that group size has small and statistically insignificant effects on child-care quality. A higher staff-child ratio appears to have beneficial effects on child-care quality when unobserved differences across centers are not accounted for. These effects become much smaller when unobserved differences are accounted for. The effects of teacher education and training are also generally not robust, but some measures of education and training have quantitatively and statistically significant effects even accounting for unobserved differences across centers. The implications of the results for future research on the determinants of child-care quality and for public policy are discussed.     

Atlantic salmon growth in strongly food-limited environments: Effects of egg size and paternal phenotype?

I manipulated egg size and followed individual mass trajectories from the egg stage in Atlantic salmon to test for effects of size, and for interactions between size and paternal body mass, on offspring performance in strongly food-limited environments. Egg size had a strong effect on body mass at yolk absorption, causing juveniles originating from large eggs to outgrow their siblings from small eggs. This corroborates previous findings of egg size effects under more benign environments, and demonstrates that positive effects of egg size on offspring success are manifested even under strong food-limitation. Previously reported negative effects of being large during the critical period for survival in dense populations are thus likely related to social interactions, rather than to effects of density on total food abundance in the environment. The effect of egg size on offspring performance, and hence the optimal egg size, was independent of paternal body mass.     

IV. Discriminative stimulus effects of narcotics: Evidence for multiple receptor-mediated actions

Results of studies on the discriminative stimulus effects of narcotics are consistent with the hypothesis that multiple receptors mediate the effects of these compounds. In the rat, at least three subsets of discriminative effects exist, although some drugs appear to have effects that transcend more than one subset. The discriminative effects of morphine-like narcotics (μ agonists), for example, are often clearly distinguishable from the discriminative effects produced by κ agonists, such as ketazocine, and from those produced by phencyclidine-like agonists, such as SKF-10,047 and cyclazocine. Cyclazocine, however, has been reported to have discriminative effects in common with morphine (45) and fentanyl (17) and appears to have κ-like, in addition to phencyclidine-like, discriminative effects. The relative ability of pure narcotic antagonists to block the discriminative effects of these compounds also provides evidence for distinct pharmacologic actions of these drugs. In the rat, the discriminative effects of morphine are blocked by doses of naloxone that are considerably smaller than those that are needed to block the discriminative effects of cyclazocine (44). The discriminative effects of phencyclidine are not altered at all by naltrexone (63).     

The effect of cytosine arabinoside and bromodeoxyuridine on the appearance of tyrosine aminotransferase in cultured foetal hepatocytes of the rat.

1. The acquisition of dexamethasone-inducibility of tyrosine aminotransferase activity by hepatocytes cultured from 15-day-foetal rat liver is blocked in the presence of cytosine arabinoside. 2. Similar results are obtained in the presence of bormodeoxyuridine. 3. No effects on steroid-inducibility of tyrosine aminotransferase are obtained with either of the above compounds in hepatocytes cultured from 19-day-foetal liver. 4. the inhibitory effects of the agents are substantially reversed after their removal from the culture medium. 5. The effects of bromodeoxyuridine suggest that cell differentiation, with respect to tyrosine aminotransferase-inducibility, occurs in cultures of 15-day-doetal hepatocytes. 6. The effects of cytosine arabinoside suggest that such an event is dependent on mitosis.     

Metrics that differentiate the origins of osmolyte effects on protein stability: a test of the surface tension proposal

Osmolytes that are naturally selected to protect organisms against environmental stresses are known to confer stability to proteins via preferential exclusion from protein surfaces. Solvophobicity, surface tension, excluded volume, water structure changes and electrostatic repulsion are all examples of forces proposed to account for preferential exclusion and the ramifications exclusion has on protein properties. What has been lacking is a systematic way of determining which force(s) is(are) responsible for osmolyte effects. Here, we propose the use of two experimental metrics for assessing the abilities of various proposed forces to account for osmolyte-mediated effects on protein properties. Metric 1 requires prediction of the experimentally determined ability of the osmolyte to bring about folding/unfolding resulting from the application of the force in question (i.e. prediction of the m-value of the protein in osmolyte). Metric 2 requires prediction of the experimentally determined ability of the osmolyte to contract or expand the Stokes radius of the denatured state resulting from the application of the force. These metrics are applied to test separate claims that solvophobicity/solvophilicity and surface tension are driving forces for osmolyte-induced effects on protein stability. The results show clearly that solvophobic/solvophilic forces readily account for protein stability and denatured state dimensional effects, while surface tension alone fails to do so. The agreement between experimental and predicted m-values involves both positive and negative m-values for three different proteins, and as many as six different osmolytes, illustrating that the tests are robust and discriminating. The ability of the two metrics to distinguish which forces account for the effects of osmolytes on protein properties and which do not, provides a powerful means of investigating the origins of osmolyte-protein effects.     

Review of possible modulation-dependent biological effects of radiofrequency fields

The biological effects of modulated radiofrequency (RF) electromagnetic fields have been a subject of debate since early publications more than 30 years ago, suggesting that relatively weak amplitude-modulated RF electromagnetic fields have specific biological effects different from the well-known thermal effects of RF energy. This discussion has been recently activated by the increasing human exposure to RF fields from wireless communication systems. Modulation is used in all wireless communication systems to enable the signal to carry information. A previous review in 1998 indicated that experimental evidence for modulation-specific effects of RF energy is weak. This article reviews recent studies (published after 1998) on the biological effects of modulated RF fields. The focus is on studies that have compared the effects of modulated and unmodulated (continuous wave) RF fields, or compared the effects of different kinds of modulations; studies that used only one type of signal are not included. While the majority of recent studies have reported no modulation-specific effects, there are a few interesting exceptions indicating that there may be specific effects from amplitude-modulated RF fields on the human central nervous system. These findings warrant follow-up studies.     

The Effect of Plant Polygalaturonase-Inhibiting Protein on the Rate of Oligouronide Formation

The effects of the polygalacturonase-inhibiting protein (PGIP) on the rate of oligouronide formation were studied in a model system containing polygalacturonic acid and polygalacturonase (PG) from the culture medium of phytopathogenic fungi. PGIP preparations were prepared from stored potato tubers and sprouts and also from apple fruits. The PGIP effects on oligouronide synthesis depended markedly on the physiological state of the source plant. Apple cultivars differing in their earliness differed in PGIP effects as well. The PGIP from potato tubers, which were in deep dormancy, suppressed oligouronide formation. The inhibitory PGIP action was decreased after dormancy release and tuber sprouting, which resulted in the oligouronide accumulation. The effects of PGIP from apple fruits on the oligouronide synthesis in the system containing PG from various phytopathogenic fungi were not correlated with tissue damage induced by these fungi. The PGIP effects on oligouronide formation are evident; however, their role in plant-cell processes related to the pectin compound conversions and plant resistance to diseases remains to be elucidated.     

Influence of multiple global change drivers on terrestrial carbon storage: additive effects are common

The interactive effects of multiple global change drivers on terrestrial carbon (C) storage remain poorly understood. Here, we synthesise data from 633 published studies to show how the interactive effects of multiple drivers are generally additive (i.e. not differing from the sum of their individual effects) rather than synergistic or antagonistic. We further show that (1) elevated CO₂, warming, N addition, P addition and increased rainfall, all exerted positive individual effects on plant C pools at both single‐plant and plant‐community levels; (2) plant C pool responses to individual or combined effects of multiple drivers are seldom scale‐dependent (i.e. not differing from single‐plant to plant‐community levels) and (3) soil and microbial biomass C pools are significantly less sensitive than plant C pools to individual or combined effects. We provide a quantitative basis for integrating additive effects of multiple global change drivers into future assessments of the C storage ability of terrestrial ecosystems.     

Negative effects overpower the positive of kelp to exclude invertebrates from the understorey community

Marine macroalgal forests are one of the most widespread and studied habitats on subtidal coasts, but there remain challenges in understanding why many sessile invertebrates are anomalously absent from understorey communities. In a series of experiments on recruitment of invertebrates, I partitioned the habitat-modifying effects of kelp into their positive and negative effects. Experiments revealed that a reduction of light intensity and removal of sediment by canopies acted to facilitate recruitment, but physical abrasion by the canopy acted as a negative force to overpower these positive effects. Understorey assemblages, therefore, represent biased subsets of taxa from a local pool capable of colonization. On balance, negative effects acted to exclude invertebrates from the understorey community. The asymmetric strength of negative effects not only explains the enigma of exclusion but also indicates that, when it exists, understorey coexistence with canopy plants must reflect a more even match between positive and negative effects.     

Differential effects of amphiregulin and TGF-alpha on the morphology of MDCK cells

Although both amphiregulin and TGF-alpha are known to exert their effects through the EGF receptor, we find that concentrations of recombinant human amphiregulin and TGF-alpha that are equipotent in EGF receptor activation and mitogenesis exhibit markedly different effects on MDCK cell morphology. Amphiregulin induces a spindle-like morphology that is associated with a redistribution of E-cadherin from a Triton-insoluble to Triton-soluble pool. TGF-alpha does not affect epithelial morphology nor does it affect the distribution of the Triton-soluble or -insoluble pool of E-cadherin. The effects of amphiregulin on E-cadherin are associated with actin rearrangement. The morphological and biochemical effects of amphiregulin are prevented by EGF receptor blockade but require Src-family kinase activity and MAPK signaling. These results identify an action of amphiregulin that is distinct from TGF-alpha that may contribute to amphiregulin's participation in the pathogenesis of inflammatory disorders like psoriasis and cancer.     

Hydrogen bonding monitored by deuterium isotope effects on carbonyl 13C chemical shift in BPTI: intra-residue hydrogen bonds in antiparallel beta-sheet.

Deuterium isotope effects on carbonyl 13C magnetic shielding were measured for the backbone carbonyl groups in BPTI (basic pancreatic trypsin inhibitor), and interpreted as a measure of hydrogen bond energies. The effects originate from peptide amide proton deuterium substitution and were observed on carbonyl carbons separated by two or three covalent bonds from the amide H/D. Two-bond isotope effects depend on the energy of the hydrogen bond donated by NH/D. Calibration of the effect with model compound data leads to hydrogen bond enthalpies less than 4.7 kcal/mol. Isotope effects over three bonds from the amide H/D to the carbonyl carbon of the same amino acid residue are observed for seven carbonyl resonances in BPTI. The three-bond isotope effects are highly related to the various backbone conformations. The largest effects are observed for residues with an approximate syn- periplanar conformation of the H-N-C alpha-C = O atoms, as realized for many residues in the BPTI antiparallel beta-sheet. The residues that show measurable three-bond effects have unusually short distances between H and O. The size of this effect decreases rapidly with increased O..H distance in the open five-membered ring. This observation suggests appreciable interactions in these rings.     

Male-female differences in the effects of cannabinoids on sexual behavior and gonadal hormone function

The putative role of the endocannabinoid system and the effects of cannabis use in male and female sexual functioning are summarized. The influence of cannabis intake on sexual behavior and arousability appear to be dose-dependent in both men and women, although women are far more consistent in reporting facilitatory effects. Furthermore, evidence from nonhuman species indicate somewhat more beneficial than debilitating effects of cannabinoids on female sexual proceptivity and receptivity while suggesting predominantly detrimental effects on male sexual motivation and erectile functioning. Data from human and nonhuman species converge on the ephemeral nature of THC-induced testosterone decline. However, it is clear that cannabinoid-induced inhibition of male sexual behavior is independent of concurrent declines in testosterone levels. Investigations also reveal a suppression of gonadotropin release by cannabinoids across various species. Historical milestones and promising future directions in the area of cannabinoid and sexuality research are also outlined in this review.     

Direct investment by stepfathers can mitigate effects on educational outcomes but does not improve behavioural difficulties

In contemporary developed populations, stepfather presence has been associated with detrimental effects on child development. However, the proximate mechanisms behind such effects are yet to be fully explored. From a behavioural ecological perspective, the negative effects associated with stepfathers may be due to the reduced quantity and quality of investments children receive within stepfather households. Here, we build on previous studies by investigating whether the effects of stepfather presence on child outcomes are driven by differences in maternal and partner (i.e., father or stepfather) direct investments. We use data from the Avon Longitudinal Study of Parents and Children to explore stepfather effects on children’s educational achievement and behavioural difficulties at age 7. Our results indicate that, for educational achievement, stepfather effects are due to the lower levels of direct investments children receive. For behavioural difficulty, stepfather effects are due to multiple factors whereby stepfather presence is associated with greater difficulties independent of investment levels, and direct investments from stepfathers are ineffective. Our results suggest that the negative effects of stepfathers on child outcomes can be explained, in part, by the reduced quantity and the ineffectiveness of direct investments children receive from stepfathers. Furthermore, the effects of stepfather direct investments seem to vary between child outcomes.     

Parental environmental effects on life history traits in Arabidopsis thaliana (Brassicaceae)

Environmentally induced maternal effects on offspring phenotype are well known in plants. When genotypes or maternal lineages are replicated and raised in different environmental conditions, the phenotype of their offspring often depends on the environment in which the parents developed. However, the degree to which such maternal effects are maintained over subsequent generations has not been documented in many taxa. Here we report the results of a study designed to assess the effects of parental environment on vegetative and reproductive traits, using glasshouse-raised maternal lines sampled from natural populations of Arabidopsis thaliana . Replicates of five highly selfed lines from each of four wild populations were cultivated in two abiotic environments in the glasshouse, and the quality and performance of seeds derived from these two environments were examined over two generations. We found that offspring phenotype was strongly influenced by parental environment, but because the parental environments differed with respect to the time of seed harvest, it was not possible to distinguish clearly between parental environmental effects and the possible (but unlikely) effects of seed age on offspring phenotype. We observed a rapid decline in the expression of ancestral environmental effects, and no main environmental effects on progeny phenotype persisted in the second generation. The mechanism of transmission of environmental effects did not appear to be associated with the quantity or quality of reserves in the seeds, suggesting that environmental effects may be transmitted across subsequent generations via some mechanism that generates environment-specific gene expression.     

The influence of macromolecular crowding on thermodynamic activity: solubility and dimerization constants for spherical and dumbbell-shaped molecules in a hard-sphere mixture

Macromolecules in solution can have large effects on the properties of other solutes through nonideal excluded-volume (crowding) interactions. Minton has calculated such effects by treating the macromolecules as a hard-sphere fluid in a background of an inert structureless solvent. In the present paper these calculations are extended by including the primary solvent as a separate component in a hard-sphere mixture. The results are in good agreement with experimental data. However, some predictions of this model differ drastically from those based on Minton's approach. Thus, much smaller effects from macromolecular crowding, particularly by smaller molecules, are expected. The present results also predict a much larger dependence on the shape of the molecules under study; notably for a dimerization reaction, it is found that the excluded-volume effects actually can destabilize side-by-side binding of two spherical molecules, while a dimerization to a spherical complex is stabilized. Therefore there will exist intermediate shapes of complexes whose stability is insensitive to crowded-volume effects. The consequences for crowding effects inside the living cell are also discussed.     

Effects of high pressure on enzymatic activity

Effects of high pressure on enzymatic reactions are poised to revolutionize enzyme kinetics. The reason for this is that experimental designs are at hand to separate effects on equilibria between reactant states from effects on catalytic transition states and both yield new information. The first of the former runs contrary to Pauling's hypothesis that substrates are bound more tightly in the transition state, while the latter penetrates the 'black box' of catalysis, the stabilized transition state itself, and returns a precise measure of a physical parameter, deltaV. This in turn opens the door to new forms of structure-activity relationships. The first of these has been described, the effect of pressure on isotope effects, with the surprising finding that the entire isotope effect comes from a transition state phenomenon such as quantum mechanical hydrogen tunneling.     

Species richness and abundance of forest birds in relation to radiation at Chernobyl

The effects of low-level radiation on the abundance of animals are poorly known, as are the effects on ecosystems and their functioning. Recent conclusions from the UN Chernobyl forum and reports in the popular media concerning the effects of radiation from Chernobyl on animals have left the impression that the Chernobyl exclusion zone is a thriving ecosystem, filled with an increasing number of rare species. Surprisingly, there are no standardized censuses of common animals in relation to radiation, leaving the question about the ecological effects of radiation unresolved. We conducted standardized point counts of breeding birds at forest sites around Chernobyl differing in level of background radiation by over three orders of magnitude. Species richness, abundance and population density of breeding birds decreased with increasing level of radiation, even after controlling statistically for the effects of potentially confounding factors such as soil type, habitat and height of the vegetation. This effect was differential for birds eating soil invertebrates living in the most contaminated top soil layer. These results imply that the ecological effects of Chernobyl on animals are considerably greater than previously assumed.     

Do hormone‐modulating chemicals impact on reproduction and development of wild amphibians?

Globally, amphibians are undergoing a precipitous decline. At the last estimate in 2004, 32% of the approximately 6000 species were threatened with extinction and 43% were experiencing significant declines. These declines have been linked with a wide range of environmental pressures from habitat loss to climate change, disease and pollution. This review evaluates the evidence that endocrine‐disrupting contaminants (EDCs) – pollutants that affect hormone systems – are impacting on wild amphibians and contributing to population declines. The review is limited to anurans (frogs and toads) as data for effects of EDCs on wild urodeles (salamanders, newts) or caecilians (limbless amphibians) are extremely limited. Evidence from laboratory studies has shown that a wide range of chemicals have the ability to alter hormone systems and affect reproductive development and function in anurans, but for the most part only at concentrations exceeding those normally found in natural environments. Exceptions can be found for exposures to the herbicide atrazine and polychlorinated biphenyls in leopard frogs (Rana pipiens) and perchlorate in African clawed frogs (Xenopus laevis). These contaminants induce feminising effects on the male gonads (including ‘intersex’ – oocytes within testes) at concentrations measured in some aquatic environments. The most extensive data for effects of an EDC in wild amphibian populations are for feminising effects of atrazine on male gonad development in regions across the USA. Even where strong evidence has been provided for feminising effects of EDCs, however, the possible impact of these effects on fertility and breeding outcome has not been established, making inference for effects on populations difficult. Laboratory studies have shown that various chemicals, including perchlorate, polychlorinated biphenyls and bromodiphenylethers, also act as endocrine disrupters through interfering with thyroid‐dependent processes that are fundamental for amphibian metamorphosis. Perchlorate has also been shown to induce these effects in wild anuran populations from perchlorate‐contaminated environments. Overall, the published data available suggest that some health effects observed in wild anuran populations, most notably intersex, likely have a chemical aetiology; however they derive only from very few anuran species and for a few pesticides at field sites in the USA. To understand better the impacts of EDCs on wild anuran populations, as well as other amphibian groups, assessment of fertility in exposed animals are required. Development of non‐destructive biomarkers that are indicative of specific EDC‐effect mechanisms are also needed to allow the study of vulnerable populations. This will help to distinguish the effects of EDCs from other environmental and/or genetic influences on development and reproduction.     

The effect of externally applied electrostatic fields,microwave radiation and electric currents on plants and other organisms,with special reference to weed control

A wide-ranging review is presented of the effects of various forms of externally applied electrical energy upon plants and other organisms. Although investigations involving both small and large amounts of energy directed at the targets are considered, a particular emphasis of this review is the feasibility of each type of electrical stimulation for weed control. Electrostatic fields ranging from 100 V m^?1 to 800 kV m^?1 have been applied to plants under laboratory conditions and in field trials since the 1880’s. Some beneficial effects have been reported (e.g. increase in yield from both cereal and vegetable crops), but the results have been erratic and the electrical conditions leading to definite benefits on a large scale could not be confidently predicted from early studies. High electric fields are reported to damage plants if currents greater than 10^?6 A are induced to flow through leaves causing corona discharges from the tips. The nature of the damage and the effects on metabolic processes are discussed. The results from experiments on the growth of plants in which the density and charge of air ions have been varied are also reviewed. The effects of microwave radiation (mostly 2450 MHz) upon seeds, plants and other organisms in soil are discussed. These effects depend upon the power density of the radiation and the electrical properties of the targets. Factors such as size of seeds and plants, shape and moisture content are important, as are the properties of the soil irradiated (notably water content). Although microwaves can be effective in killing plants and also seeds that are buried several centimeters deep in soil, high power equipment is required and treatment times are long e.g. a 60 kW machine could take up to 92.6 hours per hectare. Other experiments reported show that microwave radiation can kill nematodes in the soil and that it is also very effective in killing fungi and bacteria. The potential of the various possible uses of microwave radiation in agriculture is also described. Electric currents have been caused to flow through plants by the application of electrodes to the leaves. The effects range from nil, when 50–100 V and 1 or 2 μA are used, to very striking when voltages from 5 to 15 kV are applied causing currents of several amperes to flow and resulting in the rapid destruction of the target. Small electric currents passed through soil containing plants are reported to increase their growth. The effects of small current on the growth of individual leaves are reviewed. The use of high voltage tractor-borne equipment for weed control is also considered.     

Assessing the impacts of wind farms on birds

The potential effects of the proposed increase in wind energy developments on birds are explored using information from studies of existing wind farms. Evidence of the four main effects, collision, displacement due to disturbance, barrier effects and habitat loss, is presented and discussed. The consequences of such effects may be direct mortality or more subtle changes to condition and breeding success. The requirements for assessing the impact of future developments are summarized, including relevant environmental legislation and appropriate methods for undertaking baseline surveys and post-construction monitoring, with particular emphasis on the rapidly developing area of offshore wind farm assessments. Mitigation measures which have the potential to minimize impacts are also summarized. Finally, recent developments in the monitoring and research of wind energy impacts on birds are outlined and some areas for future work are described.