Evolution of Hawaiian drosophilidae. II. Patterns and rates of chromosome evolution in an antopocerus phylogeny

The phylogenetic relationships of seven species of the genus Antopocerus (Family Drosophilidae) have been determined by means of a study of the metaphase configurations and polytene chromosomes. Based on biogeographical, behavioral and cytogenetic information A. longiseta from Molokai is tentatively identified as the primitive species of the genus. The metaphase karyotypes of all Antopocerus species are either five pairs of rod chromosomes and a pair of dots (5R1D), or six rods (6R). Heterochromatin additions converted the dots to rods. Chromosome breakpoints for inversions also are clustered at heterochromatic loci. The chromosome segments between heterochromatic loci may represent sets of functionally related loci, evolving as a unit. The rate of chromosomal inversion substitution is estimated in the origin of the taxon (probably a subgenus of Drosophila rather than a separate genus). It averages no greater than one substitution per 1,000 years, or one per 5,000 generations. The average genetic death rate per generation of one individual per hundred is required to achieve this substitution rate. The rate of inversion substitution during radiation of this taxon may be only 4.4 X 10(-3) times as fast as that present in forming the taxon. Alternatively, radiation may have required only 250,000 years if rates of substitution are the same as in the origination of the taxon. Average rates of substitution reflect genetic accidents, selection pressures and rates of adaptation to new niches, as well as the rate of encountering new niches. Rate of adaptation probably is much greater in this instance than rate of encountering new niches. Rate of adaptation probably is much greater in this instance than rate of encountering new niches. Therefore, the average rate of evolution reflects more nearly biogeographic and ecological factors than genetic factors.     

Cognitive function in mammals: the evolutionary perspective

The work of behavioural pharmacologists has concentrated on small animals, such as rodents and pigeons. The validity of extrapolation of their findings to humans depends upon the existence of parallels in both physiology and psychology between these animals and humans. This paper considers the question whether there are in fact substantial cognitive parallels between, first, different non-human groups of vertebrates and, second, non-humans and humans. Behavioural data from 'simple' tasks, such as habituation and conditioning, do not point to species differences among vertebrates. Using examples that concentrate on the performance of rodents and birds, it is argued that, similarly, data from more complex tasks (learning-set formation, transitive inference, and spatial memory serve as examples) reveal few if any cognitive differences amongst non-human vertebrates. This conclusion supports the notion that association formation may be the critical problem-solving process available to non-human animals; associative mechanisms are assumed to have evolved to detect causal links between events, and would therefore be relevant in all ecological niches. In agreement with this view, recent advances in comparative neurology show striking parallels in functional organisation of mammalian and avian telencephalon. Finally, it is argued that although the peculiarly human capacity for language marks a large cognitive contrast between humans and non-humans, there is good evidence-in particular, from work on implicit learning--that the learning mechanisms available to non--humans are present and do play an important role in human cognition.     

Hormonal induction of thumb pads and the evolution of secondary sexual characteristics of the Southeast Asian fanged frog, Rana blythii

The fanged frogs of Southeast Asia do not express most of the hormone-dependent secondary sexual characteristics such as thumb pads that are common to other ranid frogs. At the same point in the evolutionary history of the group that these androgen-mediated characteristics are lost, male parental care first evolves. This behavior is often correlated with low androgen levels. Prior work indicates that in one of the fanged frogs, Rana blythii, adult males have low androgen levels compared to North Temperate species of Rana. This leads to the question of whether these low androgen levels are related to the unusual male parental care and the lack of expression of the thumb pad and other hormone-dependent secondary sexual characteristics in this species. We tested that hypothesis by examining the effects of exogenous dihydrotestosterone supplements on the expression of thumb pads in Rana blythii. Dihydrotestosterone injections appear to stimulate the expression of the thumb pad in R. blythii. These results support the hypothesis that low androgen levels are involved in the loss of the thumb pad in R. blythii. This work provides an example of how mapping characters on phylogenies can be a powerful approach for gaining insights into proximate physiological mechanisms of selection at the evolutionary level.     

Coercive and voluntary referrals: how ethnic minority adults get into mental health treatment

The relationship of oxidative stress with maximum life span (MLSP) in different vertebrate species is reviewed. In all animal groups the endogenous levels of enzymatic and non-enzymatic antioxidants in tissues negatively correlate with MLSP and the most longevous animals studied in each group, pigeon or man, show the minimum levels of antioxidants. A possible evolutionary reason for this is that longevous animals produce oxygen radicals at a low rate. This has been analysed at the place where more than 90% of oxygen is consumed in the cell, the mitochondria. All available work agrees that, across species, the longer the life span, the lower the rate of mitochondrial oxygen radical production. This is true even in animal groups that do not conform to the rate of living theory of aging, such as birds. Birds have low rates of mitochondrial oxygen radical production, frequently due to a low free radical leak in their respiratory chain. Possibly the low rate of mitochondrial oxygen radical production of longevous species can decrease oxidative damage at targets important for aging (like mitochondrial DNA) that are situated near the places of free radical generation. A low rate of free radical production can contribute to a low aging rate both in animals that conform to the rate of living (metabolic) theory of aging and in animals with exceptional longevities, like birds and primates. Available research indicates there are at least two main characteristics of longevous species: a high rate of DNA repair together with a low rate of free radical production near DNA. Simultaneous consideration of these two characteristics can explain part of the quantitative differences in longevity between animal species.     

Effects of ontogeny and sexual dimorphism on scapula morphology in the mountain gorilla (Gorilla gorilla beringei)

Scapular measurements were obtained from growth series of the sexually dimorphic mountain gorilla (Gorilla gorilla beringei). Juveniles, subadults, and adults were compared to determine if scapula morphology varies with age. Analyses reveal significant (P < 0.05) differences in scapula form for shape ratios of length vs. breadth, length vs. infraspinous fossa length, and length vs. spine length. Males and females were also compared to determine if sexual dimorphism in scapula morphology is a consequence of differential extension of common patterns of relative growth. Analyses reveal that scapula proportions are ontogenetically scaled. Data indicate that male scapulae grow at a faster rate and for a longer duration than females. Results of comparisons of males and females suggest that unique adaptations to different ecological niches have not evolved between the sexes despite sexual differences in frequency of patterns of locomotor behavior. By contrast, age-related variation in scapula morphology may be linked to differences in locomotor behavior during ontogeny.     

Behavioral thermoregulation in a sexually and developmentally dichromatic neotropical primate, the black-and-gold howling monkey (Alouatta caraya)

Behavioral thermoregulation in primates may provide a means for the conservation of heat during periods of low ambient temperature and/or food shortage as well as a way to dissipate heat under hot conditions. This article focuses on behavioral thermoregulation in a sexually dichromatic primate, the black-and-gold howling monkey (Alouatta caraya). Two models have been proposed to explain the evolution of sexual dichromatism in this species: thermoregulation and sexual selection. Five hypotheses associated with thermoregulatory behaviors are tested. These are as follows: (1) energy-conserving postures are used mainly under low ambient temperatures; (2) sunny resting places are selected during periods of low temperature; (3) exposure of the less-insulated ventral region to sunlight decreases with increasing temperature; (4) black-colored adult males use energy-conserving postures, sunny places, and exposure of the ventral region to sunlight less frequently than do blonde-colored adult females; and (5) smaller individuals use energy-conserving postures, sunny places, and exposure of the ventral region to sunlight in significantly greater frequency than do larger individuals. Over a 12-month period, behavioral data were collected on a free-ranging habituated group of 15-17 howlers of all age-sex classes. Ambient temperature was measured each hour. The results indicate that during resting, howlers showed a consistent use of heat-conserving postures, showed a preference for sunny places, and exposed their ventral region to sunlight under low ambient temperatures. A preference for shady places, heat-dissipating postures, and exposure of the back were observed under high ambient temperatures. Despite sex differences in adult color patterns and differences in size between age classes, no significant age or sex differences in thermoregulatory behaviors were detected. Failure to confirm a thermoregulation model implies that sexual selection may be responsible for sexual dichromatism in this species.     

Force and myosin content variation in isolated intact single muscle fibres from Rana temporaria

We studied the relation between force normalized by dry mass per unit length and the myosin fraction of muscle dry mass. The two tibialis anterior muscles were dissected from 12 frogs (Rana temporaria). Then, from one muscle, two single fast-twitch fibres were isolated. Each fibre was mounted isometrically in Ringer's solution, and electrically stimulated using a standardized protocol. Peak force production, normalized by the fibre's dry mass per unit length, varied by a factor of 1.4. Little variation in normalized force was measured between fibres from the same animal, whereas between animals a significant difference was found (P<0.05). The contralateral muscle was used to determine the myosin fraction of the dry mass. The relationship between the fraction myosin of the dry mass and force normalized by dry mass per unit length showed a high correlation (r = 0.81; n = 12). From this we conclude that variation in normalized tetanic force is determined greatly (65%) by variations in myosin content.     

Phylogenetic differences between particle-associated and planktonic ammonia-oxidizing bacteria of the beta subdivision of the class Proteobacteria in the Northwestern Mediterranean Sea

The aim of this study was to determine if there were differences between the types of ammonia-oxidizing bacteria of the beta subdivision of the class Proteobacteria associated with particulate material and planktonic samples obtained from the northwestern Mediterranean Sea. A nested PCR procedure performed with ammonia oxidizer-selective primers was used to amplify 16S rRNA genes from extracted DNA. The results of partial and full-length sequence analyses of 16S rRNA genes suggested that different groups of ammonia-oxidizing bacteria were associated with the two sample types. The particle-associated sequences were predominantly related to Nitrosomonas eutropha, while the sequences obtained from the planktonic samples were related to a novel marine Nitrosospira group (cluster 1) for which there is no cultured representative yet. A number of oligonucleotide probes specific for different groups of ammonia oxidizers were used to estimate the relative abundance of sequence types in samples of clone libraries. The planktonic libraries contained lower proportions of ammonia oxidizer clones (0 to 26%) than the particulate material libraries (9 to 83%). Samples of the planktonic and particle-associated libraries showed that there were depth-related differences in the ammonia oxidizer populations, with the highest number of positive clones in the particle-associated sample occurring at a depth of 700 m. The greatest difference between planktonic and particle-associated populations occurred at a depth of 400 m, where only 4% of the clones in the planktonic library were identified as Nitrosomonas clones, while 96% of these clones were identified as clones that were related to the marine Nitrosospira species. Conversely, all ammonia oxidizer-positive clones obtained from the particle-associated library were members of the Nitrosomonas group. This is the first indication that Nitrosomonas species and Nitrosospira species may occupy at least two distinct environmental niches in marine environments. The occurrence of these groups in different niches may result from differences in physiological properties and, coupled with the different environmental conditions associated with these niches, may lead to significant differences in the nature and rates of nitrogen cycling in these environments.     

Retrotransposable elements R1 and R2 in the rDNA units of Drosophila mercatorum: abnormal abdomen revisited

R1 and R2 retrotransposable elements are stable components of the 28S rRNA genes of arthropods. While each retrotransposition event leads to incremental losses of rDNA unit expression, little is known about the selective consequences of these elements on the host genome. Previous reports suggested that in the abnormal abdomen (aa) phenotype of Drosophila mercatorum, high levels of rDNA insertions (R1) in conjunction with the under-replication locus (ur), enable the utilization of different ecological conditions via a population level shift to younger age. We have sequenced the R1 and R2 elements of D. mercatorum and show that the levels of R1- and R2-inserted rDNA units were inaccurately scored in the original studies of aa, leading to several misinterpretations. In particular, contrary to earlier reports, aa flies differentially underreplicate R1- and R2-inserted rDNA units, like other species of Drosophila. However, aa flies do not undergo the lower level of underreplication of their functional rDNA units (general underreplication) that is seen in wild-type strains. The lack of general underreplication is expected to confer a selective advantage and, thus, can be interpreted as an adaptation to overcome high levels of R1 and R2 insertions. These results allow us to reconcile some of the apparently contradictory effects of aa and the bobbed phenotype found in other species of Drosophila.     

A New Darwinopterid Pterosaur from the Middle Jurassic of Western Liaoning,Northeastern China and its Ecological Implications

A new species of Darwinopterus, D. robustodens sp. nov. is described and named. Based on the new specimen, the diagnostic characters of Darwinopterus are amended and include: rostral dentition composed of well-spaced, spike-like teeth; the longest teeth are confined to the anterior half of the tooth row; tooth alveoli have raised margins; nasoantorbital fenestra confluent; inclined quadrate; elongate cervical vertebrae with low neural spine and reduced or absent ribs; long tail of more than 20 caudals partially enclosed by filiform extensions of the pre- and postzygapophyses; short metacarpus less than 60 per cent length of humerus, fifth toe with two elongate phalanges and curved second pedal phalanx of the fifth toe with the angle between the proximal and distal segments about 130 degrees. The complete specimen of the new pterosaur D. robustodens sp. nov. provides much more osteological information. The differences in tooth morphologies between Darwinopterus modularis and D. robustodens sp. nov. suggest that they filled different ecological niches. The hard integumentbearing Coleoptera may have been the main food source of Darwinopterus robustodens.     

Evolution of MHC class II beta chain-encoding genes in the Lake Tana barbel species flock (Barbus intermedius complex)

Major histocompatibility complex (MHC) class II protein polymorphism is maintained in allelic lineages which evolve in a trans-specific manner, passing from one species to descendant species. Selection pressure on peptide binding residues should be greatest during speciation, when organisms move into new environments and their MHC molecules encounter new pathogens. The isolation of MHC genes from teleost fishes, the most diverse group of vertebrates, has created possibilities for testing this hypothesis. The large barbels of Lake Tana have undergone an adaptive radiation within the last 5 million years, producing 14 morphotypes which inhabit different ecological niches within the lake. We studied the variability in class II beta chain-encoding genes of four of these morphotypes using polymerase chain reaction amplification and DNA sequencing. The sequences obtained were orthologous to four of the known class II genes from the common carp, from which barbels diverged approximately 32 million years ago. When subjected to phylogenetic analysis, the 48 sequences clustered into groups which represent allelic lineages. A comparison of nonsynonymous and synonymous substitutions between the peptide binding region codons and non-peptide binding region codons of these sequences revealed that they are under strong selective pressure.     

GABA(B)-receptor subtypes assemble into functional heteromeric complexes

B-type receptors for the neurotransmitter GABA (gamma-aminobutyric acid) inhibit neuronal activity through G-protein-coupled second-messenger systems, which regulate the release of neurotransmitters and the activity of ion channels and adenylyl cyclase. Physiological and biochemical studies show that there are differences in drug efficiencies at different GABA(B) receptors, so it is expected that GABA(B)-receptor (GABA(B)R) subtypes exist. Two GABA(B)-receptor splice variants have been cloned (GABA(B)R1a and GABA(B)R1b), but native GABA(B) receptors and recombinant receptors showed unexplained differences in agonist-binding potencies. Moreover, the activation of presumed effector ion channels in heterologous cells expressing the recombinant receptors proved difficult. Here we describe a new GABA(B) receptor subtype, GABA(B)R2, which does not bind available GABA(B) antagonists with measurable potency. GABA(B)R1a, GABA(B)R1b and GABA(B)R2 alone do not activate Kir3-type potassium channels efficiently, but co-expression of these receptors yields a robust coupling to activation of Kir3 channels. We provide evidence for the assembly of heteromeric GABA(B) receptors in vivo and show that GABA(B)R2 and GABA(B)R1a/b proteins immunoprecipitate and localize together at dendritic spines. The heteromeric receptor complexes exhibit a significant increase in agonist- and partial-agonist-binding potencies as compared with individual receptors and probably represent the predominant native GABA(B) receptor. Heteromeric assembly among G-protein-coupled receptors has not, to our knowledge, been described before.     

An improved approach to delivery of enteral nutrition in the intensive care unit

Using immunohistochemistry, vasoactive intestinal peptide (VIP) was visualized in taste bud cells of the carp, Cyprinus carpio, and the European catfish, Silurus glanis, by means of light and electron microscopy. Intracellular membrane systems, presumably smooth endoplasmic reticulum, of light (sensory) cells, but not of dark (supporting) cells and basal cells, were densely labelled with antibody. In the frog (four species: Rana temporaria, R. ridibunda, R. arvalis, R. pipiens), taste bud cells did not label. However, the dense basal nerve fibre plexus, some subepithelial ganglionic cells, but no ascending intragemmal fibres, were immunoreactive. In fish, the results support evidence that VIP is involved in the modulation of taste transduction at the level of receptor cells. In the frog, an indirect, possibly vasodilatatory effect on taste perception may be considered.     

Why do we work in public hospitals? Some ideas to keep in mind

Why do we work in public hospitals, what do we look for and what do we find working at these places? There are several answers. The heritage, the places where we learnt, the places where medicine is practiced. A model that feeds us. They cannot be improved and it is difficult to accept their limitations. However, many factors such as teaching, research and group work, encourage us to continue working in them. Variation and simultaneity, they are places with many variables, a living organism. The myth, the mother, that transmits its principles and behaviors, gives us a sense of life, feeds us and allows us to feed others. Economical reasons and performance. When performance of physicians is analyzed, positive values such as contact with patients, hours of discussion and study, quality of care, risks, dedication and training difficulties must be taken into consideration. Hospitals are not a patient assembly line. Fantasies and representations. We are participating in a health community and hospitals become a place for personal growth. Respect towards poverty. Helping the less fortunate. Knowledge and learning. Experiencing values. Forgotten words. Bioethics brought back several principles that are present in hospitals such as compassion, empathy, sweetness, service, humility, gratitude.     

Use of binaural cues for sound localization in two species of Phyllostomidae: The Greater spear-nosed bat (Phyllostomus hastatus) and the Short-tailed fruit bat (Carollia perspicillata).

Unlike humans, not all mammals use both of the binaural cues for sound localization. Whether an animal uses these cues can be determined by testing its ability to localize pure tones; specifically, low frequencies are localized using time-difference cues, and high frequencies are localized using intensity-difference cues. We determined the ability to use binaural cues in 2 New World bats, Phyllostomus hastatus, large omnivores, and Carollia perspicillata, small frugivores, by testing their tone-localization ability using a conditioned avoidance procedure. Both species easily localized high-frequency tones, indicating that they could use the interaural intensity-difference cue. However, neither species was able to use the phase-difference cue to localize either low-frequency pure tones or amplitude-modulated tones (which provided an envelope for additional time analysis). We now know of 3 bat species that cannot use binaural time cues and 2 that can. Further exploration of localization in bats may provide insight into the neural analysis of time cues in species that do not hear low frequencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Filtration Removals of Microorganisms and Particles

Filtration log removals (log?R’s) were determined by pilot plant seeding experiments for a selected array of organisms, i.e., protozoan cysts, algae, bacteria, and viruses, as well as turbidity/particles. Removals of these organisms and particles varied from one species to another within the range 1.4 ? log?R ? 5.1 for “reference,” i.e., specified, conditions. For other conditions, called here “excursion” conditions, log?R’s were found to be proportional to alum dose between zero and “optimum” the latter being defined as the smallest dosage that minimized filter effluent turbidity. Mono and dual media did not show performance differences, and conventional filtration showed slightly higher log?R’s than in-line filtration. The influent concentration did not show a “true” effect on log?R’s (but an “apparent” effect was seen when effluent values were consistently very low, making log?R’s proportional to influent concentration). log?R’s obtained in limited experiments at another site showed significant differences for two algae and two viruses when compared with log?R’s for reference conditions. The results illustrate the log?R variation that may be found among different groups of organisms/particles and indicate the influences of certain independent variables (e.g., influent concentration, dual media versus mono media, conventional filtration versus in-line, alum dose, zero alum dose, and filtration at a different site) on filtration removals. In addition, the importance of sampling repetitions was reinforced. The findings are significant to water treatment practice in that organism removals by filtration are likely to vary, depending on the organism/particle species as well as the filtration conditions. The implication is that a pilot plant study is advisable if confidence in log?R is desired for a given organism/particle.     

Is life stress more likely to provoke depressive episodes in women than in men?

One of the most consistent findings in psychiatric research is that rates of major depression are at least twofold higher among women than among men. Although there is considerable agreement in the literature that life events play a role in producing, triggering, or maintaining episodes of depression, less is known about the relationship among gender, life events, and depression. In the present study, we compared the rates, focus ("interpersonal" vs. "non-interpersonal"), and timing of stressful life experiences reported in rigorous interviews of male and female patients with unipolar recurrent depression and nondepressed contrast subjects. Consistent with hypotheses, female patients were more likely to experience stressful life experiences than their male counterparts; rates of stressful life experiences did not differ between female and male controls. Unexpectedly, rates of interpersonal stress did not differ among males and females regardless of patient or control status. We also found no significant differences in the timing of pre-onset events: stressful events were generally concentrated in the period immediately preceding onset for both men and women. Thus, although these data suggest that life stress may play a larger role in the provocation of recurrent episodes of depression for women than for men, there do not seem to be sex differences in the extent to which interpersonal vs. noninterpersonal events and difficulties are associated with depression onset or in the temporal distribution of events. Implications of these results are discussed in the context of research on other putative factors contributing to gender differences in rates of depression.