Analysis by partitioning in aqueous two-phase systems of the loss of transferrin-binding capacity during maturation of rat reticulocytes

A decrease in the number of binding sites for¹²⁵I-transferrin, without an apparent modification of the association constant, has been observed during the maturation of reticulocytes into erythrocytes. As an experimental model, different red cell populations from phenylhydrazinic anaemic rates (95% to 12% reticulocyte-rich) have been used. The fractionation by multiple partition in two-phase systems of these red cell populations has been applied here to show the relationship between number of transferrin receptors and rate of reticulocyte maturation.     

Transforming Milk in a Global Economy

Large-scale milk production and consumption historically have been localized to Europe and countries with large European-derived populations. However, global patterns have now shifted, with dramatic increases in milk consumption in Asian countries and flat or declining consumption in European and European-derived countries. Efforts to market it around the world emphasize milk's positive effects on child growth, and, by extension, the individual and national benefits that derive from that growth. At the same time, milk has newly emerged in milk promotions in the United States as food that facilitates weight loss. Milk has been able to achieve a global presence and continuing relevance in populations in which its consumption has been declining by continually transforming and repositioning itself as a "special" food with properties able to alleviate the health concerns seen as most salient at the time.     

Immune responses to stress proteins: Applications to infectious disease and cancer

Heat shock proteins, or stress proteins have been identified as part of a highly conserved cellular defence mechanism mediated by multiple, distinct gene familes and corresponding gene products. As intracellular chaperones, stress proteins participate in many essential biochemical pathways of protein maturation and function active during times of stress and during normal cellular homeostasis. In addition to their well-characterized role as protein chaperones, stress proteins are now realized to possess another important biological property: immunogenicity. Stress proteins are now understood to play a fundamental role in immune surveillance of infection and malignancy and this body of basic research has provided a framework for their clinical application. As key targets of both humoral and cellular immunity during infection, stress proteins have accordingly received considerable research interest as prophylactic vaccines for infectious disease applications. The unique and potent immunostimulatory properties of stress proteins have similarly been applied to the development of new approaches to cancer therapy, including both protein and gene-based modalities.     

The conservation of critically endangered flightless birds in New Zealand

The current status of Kakapo Strigops habroptilus and Takahe Porphyrio mantelli is described along with recent developments in programmes for their conservation. Both species were (at different times) thought to be effectively extinct, and both have been temporarily reprieved by the discovery of new populations. Population declines have continued, with Kakapo now reduced to less than 50 individuals and Takahe to about 150. Kakapo are especially at risk; 87% of the remaining birds are over 14 years old and only 17 females are known. Research on relict populations of both species has identified predation and competition from introduced mammals as major threats. Both species have high rates of egg infertility and low survival of young. Increasingly intensive management of both Kakapo and Takahe over recent years has included translocation to predator-free island refuges, supplementary feeding to encourage breeding, clutch manipulation, captive rearing and predator control. All known Kakapo have now been transferred to three island refuges, where the overall rate of population decline has slowed and supplementary feeding has apparently encouraged more frequent breeding attempts. Takahe conservation has concentrated largely on attempts to increase the population in Fiordland, New Zealand, through clutch manipulation and release of captive-reared young, but birds have also been released on four islands, which now hold 19% of the total population. The relict Fiordland populations of both Kakapo and Takahe were confined to apparently suboptimal habitat. Both species have successfully adapted to novel environments and foods when translocated, and the populations which now exist present improved opportunities for intensive management using a range of conservation techniques to enhance productivity and survival. Recent population trends of Kakapo and Takahe are reconstructed, and the contribution of research to their conservation is reviewed.     

Harvest-induced maturation evolution under different life-history trade-offs and harvesting regimes

The potential of harvesting to induce adaptive changes in exploited populations is now increasingly recognized. While early studies predicted that elevated mortalities among larger individuals select for reduced maturation size, recent theoretical studies have shown conditions under which other, more complex evolutionary responses to size-selective mortality are expected. These new predictions are based on the assumption that, owing to the trade-off between growth and reproduction, early maturation implies reduced growth. Here we extend these findings by analyzing a model of a harvested size-structured population in continuous time, and by systematically exploring maturation evolution under all three traditionally acknowledged costs of early maturation: reduced fecundity, reduced growth, and/or increased natural mortality. We further extend this analysis to the two main types of harvest selectivity, with an individual's chance of getting harvested depending on its size and/or maturity stage. Surprisingly, we find that harvesting mature individuals not only favors late maturation when the costs of early maturation are low, but promotes early maturation when the costs of early maturation are high. To our knowledge, this study therefore is the first to show that harvesting mature individuals can induce early maturation.     

Fifty years of chimpanzee demography at Taronga Park Zoo

There has been a captive Pan troglodytes colony at Taronga Park Zoo in Sydney, Australia, since the mid-1930s. Demographic data on these animals were first analyzed in 1986; however, further information collected for 15 years since then is now available. The reproductive histories of 33 females in the colony have been recorded, and these data form the largest collection of captive chimpanzee data from a setting that has involved natural breeding conditions since the mid-1960s. These data were analyzed in conjunction with data from wild populations to establish the degree of variability present within chimpanzee reproductive parameters, and to identify which distinctive life history characteristics persist in well-provisioned, natural-fertility populations. The age at first birth for the chimpanzee females is 9.8 yr on average (n=16), which is 1-4.8 yr earlier than the average for wild populations. In line with this accelerated reproduction, birth intervals are also significantly shorter than those in noncaptive chimpanzee populations. The median birth interval for all surviving infants (based on a Kaplan-Meier survival analysis) is 49 months (n=43) compared to 62+ months for wild groups. At the same time, infant mortality remains high. The data confirm distinctive features of the life history of common chimpanzees, including later maturation, long birth intervals, a relatively invariant fertility schedule, and high juvenile mortality. However, aspects of both fertility and mortality are significantly related to social circumstances, indicating that in common chimpanzees, as in humans, life history characters may represent ecological and social adaptations rather than species-fixed characteristics.     

Sexual selection shapes development and maturation rates in Drosophila

Explanations for the evolution of delayed maturity usually invoke trade‐offs mediated by growth, but processes of reproductive maturation continue long after growth has ceased. Here, we tested whether sexual selection shapes the rate of posteclosion maturation in the fruit fly Drosophila melanogaster. We found that populations maintained for more than 100 generations under a short generation time and polygamous mating system evolved faster posteclosion maturation and faster egg‐to‐adult development of males, when compared to populations kept under short generations and randomized monogamy that eliminated sexual selection. An independent assay demonstrated that more mature males have higher fitness under polygamy, but this advantage disappears under monogamy. In contrast, for females greater maturity was equally advantageous under polygamy and monogamy. Furthermore, monogamous populations evolved faster development and maturation of females relative to polygamous populations, with no detectable trade‐offs with adult size or egg‐to‐adult survival. These results suggest that a major aspect of male maturation involves developing traits that increase success in sexual competition, whereas female maturation is not limited by investment in traits involved in mate choice or defense against male antagonism. Moreover, rates of juvenile development and adult maturation can readily evolve in opposite directions in the two sexes, possibly implicating polymorphisms with sexually antagonistic pleiotropy.     

Probabilistic maturation reaction norms assessed from mark–recaptures of wild fish in their natural habitat

Reaction norms are a valuable tool in evolutionary biology. Lately, the probabilistic maturation reaction norm approach, describing probabilities of maturing at combinations of age and body size, has been much applied for testing whether phenotypic changes in exploited populations of fish are mainly plastic or involving an evolutionary component. However, due to typical field data limitations, with imperfect knowledge about individual life histories, this demographic method still needs to be assessed. Using 13 years of direct mark–recapture observations on individual growth and maturation in an intensively sampled population of brown trout (Salmo trutta), we show that the probabilistic maturation reaction norm approach may perform well even if the assumption of equal survival of juvenile and maturing fish does not hold. Earlier studies have pointed out that growth effects may confound the interpretation of shifts in maturation reaction norms, because this method in its basic form deals with body size rather than growth. In our case, however, we found that juvenile body size, rather than annual growth, was more strongly associated with maturation. Viewed against earlier studies, our results also underscore the challenges of generalizing life‐history patterns among species and populations.     

Modulation of Adhesion Molecule Expression on Rat Cortical Astrocytes During Maturation

Abstract: During development of the vertebrate CNS the functional properties of astrocytes change significantly. Many of these functional changes result from modifications in the expression of cell surface adhesion molecules on astrocytes that mediate the interactions of astrocytes with other astrocytes, neurons, and growing axons. In this study we have compared the cell surface expression of HNK-1, NCAM, and laminin on rat cortical type-I-like astrocytes during maturation in vitro and in vivo. Both the proportion of immunoreactive cells and the relative levels of expression of these antigens on different aged astrocyte populations were assayed by flow cytometry. At birth, most cortical type-I astrocytes express high levels of HNK-1 and NCAM, while ∼50% of the cells express laminin. During maturation in vitro, the proportion of cortical astrocytes that expressed these surface molecules decreased over a period of 28 days, even though cell size and glial fibrillary acidic protein content increased. During maturation in vivo, a qualitatively and temporally similar decrease in antigen expression on astrocytes was observed. This reduction in the expression of specific cell surface molecules on maturing astrocytes results from maturation of a single population of astrocytes and not differential proliferation of a nonexpressing subpopulation of astrocytes, as shown by cell cycle analysis of both immunoreactive and nonimmunoreactive cell populations. These data indicate that during maturation of rat cortical type-I-like astrocytes, the expression of cell surface adhesion molecules is regulated. Furthermore, this regulation appears to be cell autonomous and not dependent on environmental factors. Such regulation of adhesion molecule expression may have profound consequences for the functional properties of astrocytes during CNS maturation.     

Nicotine and brain development

Preclinical studies, using primarily rodent models, have shown acetylcholine to have a critical role in brain maturation via activation of nicotinic acetylcholine receptors (nAChRs), a structurally diverse family of ligand-gated ion channels. nAChRs are widely expressed in fetal central nervous system, with transient upregulation in numerous brain regions during critical developmental periods. Activation of nAChRs can have varied developmental influences that are dependent on the pharmacologic properties and localization of the receptor. These include regulation of transmitter release, gene expression, neurite outgrowth, cell survival, and synapse formation and maturation. Aberrant exposure of fetal and neonatal brain to nicotine, through maternal smoking or nicotine replacement therapy (NRT), has been shown to have detrimental effects on cholinergic modulation of brain development. These include alterations in sexual differentiation of the brain, and in cell survival and synaptogenesis. Long-term alterations in the functional status and pharmacologic properties of nAChRs may also occur, which result in modifications of specific neural circuitry such as the brainstem cardiorespiratory network and sensory thalamocortical gating. Such alterations in brain structure and function may contribute to clinically characterized deficits that result from maternal smoking, such as sudden infant death syndrome and auditory-cognitive dysfunction. Although not the only constituent of tobacco smoke, there is now abundant evidence that nicotine is a neural teratogen. Thus, alternatives to NRT should be sought as tobacco cessation treatments in pregnant women.     

Evidence for genetic differentiation in timing of maturation among nine‐spined stickleback populations

Timing of maturation is an important life‐history trait that is likely to be subjected to strong natural selection. Although population differences in timing of maturation have been frequently reported in studies of wild animal populations, little is known about the genetic basis of this differentiation. Here, we investigated population and sex differences in timing of maturation within and between two nine‐spined stickleback (Pungitius pungitius) populations in a laboratory breeding experiment. We found that fish from the high‐predation marine population matured earlier than fish from the low‐predation pond population and males matured earlier than females. Timing of maturation in both reciprocal hybrid crosses between the two populations was similar to that in the marine population, suggesting that early timing of maturation is a dominant trait, whereas delayed timing of maturation in the pond is a recessive trait. Thus, the observed population divergence is suggestive of strong natural selection against early maturation in the piscine‐predator‐free pond population.     

Intake assessment of L-ergothioneine in some European countries and in the United States

L-ergothioneine is an amino acid synthetized by fungi and mycobacteria that cannot be synthesized by other species. It has been detected in plants, animals, and the human body. In the last few years, it has been recognized as a good antioxidant and, recently, it has also been related to other properties besides antioxidant properties. Even though few studies on the toxicity of L-ergothioneine have been carried out, evidence suggests that L-ergothioneine is not harmful to health. Considering that L-ergothioneine has increasingly been linked to positive effects on human health, coupled with the fact that it seems to be safe for human consumption, this molecule may be suitable for use as an ingredient in foods. On the other hand, despite the positive effects reported for this molecule, no estimate of L-ergothioneine intake has been carried out until now. Thus, the aim of this work is to estimate the intake of L-ergothioneine through food consumption of several European countries and the United States. Values were estimated by using the deterministic and probabilistic approach. Results show that the populations with the highest intake of L-ergothioneine correspond to Italian population, both for children and adults.     

Uncultured giant sulfur bacteria of the genus Achromatium

Achromatium is a genus of large unicellular sulfur bacteria. Despite being first described in the late 19th century, no Achromatium spp. have yet been isolated in culture, and for over 100 years, knowledge of their ecology, physiology and relationships to other bacteria has been scant. In recent years, the application of culture-independent techniques combined with in situ process measurements and single-cell activity measurements in sediments harbouring large Achromatium populations, has expanded our knowledge of these bacteria. Aspects of carbon and sulfur metabolism in Achromatium are now better understood, but their preferred electron acceptor(s) remain unknown. Unexpected diversity has been uncovered in Achromatium populations and it is now clear that the organism routinely described as Achromatium oxaliferum actually comprises several distinct Achromatium spp.     

Quantitative genetic analysis of natural populations

Quantitative genetic studies in natural populations have been rare because they require large breeding programmes or known pedigrees. The relatedness that has been estimated from molecular markers can now be used to substitute for breeding, allowing studies of previously inaccessible species. Many behavioural ecologists have a sufficient number of markers and study species with characteristics that are amenable to this approach. It is now time to combine studies of selection with studies of genetic variation for a more complete understanding of behavioural evolution.     

Energy metabolism of erythrocytes in pyruvate kinase enzymopathies

Until now pyruvate kinase enzymopathies have been described only for red blood cells. On the basis of these results special structural properties of the erythrocyte PK was assumed, which are not yet totally established. PK defects may cause a nonspherocytic hemolytic anemia. This enzymopathy is characterized by a polymorphism, which is expressed in more than 5 different pathological variants. Up to now 16 cases of PK deficiency have ben diagnozed in the GDR. The following parameters are used for the characterization of the PK: the PEP-dependance, the inhibition by ATP and alanine, the specificity to nucleotides, the stability to temperature and urea and the maturation dependence. Two pathological variants of the PK with a decreased PEP-affinity are described. Furthermore the differences in the energy metabolism of the red blood cells of these two patients under aerobic and anaerobic conditions are discussed.     

Reinforcement of reproductive isolation between adjacent populations in the Park Grass Experiment

It has been debated, ever since Charles Darwin and Alfred Russell Wallace disagreed about the matter, whether natural selection plays a role in reinforcing reproductive isolation during the earliest stages of speciation. Recent theory suggests that it can do so, but until now the empirical evidence has conspicuously lacked a case in which reinforcement has actually been observed to split a population. We show that this has occurred at least once in populations of the grass Anthoxanthum odoratum growing in the Park Grass Experiment where flowering time has shifted at the boundaries between plots. As a consequence, gene flow via pollen has been severely limited and adjacent populations that had a common origin at the start of the experiment in 1856 have now diverged at neutral marker loci.     

Recent advances using green and red fluorescent protein variants

Fluorescent proteins have proven to be excellent tools for live-cell imaging. In addition to green fluorescent protein (GFP) and its variants, recent progress has led to the development of monomeric red fluorescent proteins (mRFPs) that show improved properties with respect to maturation, brightness, and the monomeric state. This review considers green and red spectral variants, their paired use for live-cell imaging in vivo, in vitro, and in fluorescence resonance energy transfer (FRET) studies, in addition to other recent “two-color” advances including photoswitching and bimolecular fluorescence complementation (BiFC). It will be seen that green and red fluorescent proteins now exist with nearly ideal properties for dual-color microscopy and FRET.     

Phagocytosis: dynamin's dual role in phagosome biogenesis

Dynamins have a well-established role in the fission of vesicles at sites of endocytosis. In phagocytosis, however, a role for certain dynamin isoforms has been reported in the full extension of pseudopods during phagosome formation, not in fission of the phagocytic vacuole. Recent studies in Caenorhabditis elegans have now uncovered a new function of dynamin in phagosome maturation.     

Alterations in membrane surface properties during cell differentiation as measured by partition in aqueous two-polymer phase systems: Rat intestinal epithelial cells

Membrane surface properties of rat intestinal epithelial cells (crypt base to villus tips) were studied by cell partition in a two-polymer aqueous phase system. A higher partition generally reflects higher cell surface charge (or charge-associated properties) which is not necessarily the same as the charge determined by cell electrophoresis since the latter reflects only the charge at the plane of shear while the former gauges it deeper into the membrane [10]. Cells were prepared by the method of Weiser [22] which sequentially yields cell fractions from villus tips to crypt base. The isolated cells were subjected to countercurrent distribution in a dextran-polyethylene glycol aqueous two-phase system. Countercurrent distribution on the first fractions obtained by Weiser's method have a peak to the left and a smaller peak to the right indicating a surface membrane heterogeneity of upper villus cells; last fractions have a peak only to the right. When all fractions are pooled before countercurrent distribution two well-separated peaks are obtained with the right peak sometimes showing additional heterogeneities. Experiments combining isotope labeling of cells with countercurrent distribution lead us to conclude that the membrane charge (or charge-associated properties) of crypt base cells increases during differentiation and that the charge of the villus cells to which they give rise then diminishes during maturation. The charge of the bulk of the upper villus cells is the lowest of any in the intestinal cell population. The basis for the alteration in charge has not been established but the phenomenon of changing membrane surface charge (or charge-associated properties) as a function of cell differentiation, maturation and aging appears to be a general phenomenon having been found and traced in different cell populations [14, 16, 17, 28].     

Hormone-induced Maturation of Xenopus laevis oocytes: Effects of Different Steroids and Study of the Properties of a Progesterone Receptor

The ability of various steroids to induce maturation of Xenopus laevis oocytes after incubation or injection has been studied.
Only two of these hormones, hydrocortisone and testosterone, are active by injection as well as by incubation. Progesterone can induce maturation only when administered from the outside medium, which suggests the presence of a receptor in or near the membrane.
This progesterone-receptor has been localized in the melanosomes, and its properties and affinity for other steroids have been studied. The morphological and biochemical effects of the injection of the progesterone-receptor complex have been studied.