Do male ornaments signal immunity in the common yellowthroat?

Male ornaments may advertise genetic benefits to females choosingmates. These benefits may come in the form of genes for resistanceto parasites and disease. Thus, females that prefer more ornamentedmales as mates may receive genes for enhanced immune systemfunction for their offspring. The common yellowthroat (Geothlypistrichas) is the only species to date in which a male plumageornament (size of the black facial mask) is known to be relatedto extrapair mating, and extrapair young are more immunocompetentthan their within-pair half-sibs (at least in colder years).To investigate whether male mask size signals superior immunefunction, we examined male ornaments (mask and bib size andcolor) in relation to measures of overall health (hematocrit)and immune system function (plasma immunoglobulin G [IgG] concentrationand cutaneous immune activity). We also investigated the rolethat testosterone may play in mediating the relationship betweenornaments and immunity. Male mask size was correlated positivelywith IgG level, suggesting that male mask size may indicatehumoral immunity. However, mask size was correlated negativelywith hematocrit and cutaneous immune activity (our measure ofnestling immunocompetence). Bib size and color were not relatedto these indices of immune function or health. Plasma testosteronelevel was neither related to immune function or health nor tothe expression of male ornaments. These results suggest thatthere might be a trade-off between immune system components,as well as between immunity and the production or advertisementof male ornaments.     

Towards an understanding of the molecular basis of plants K+ transport: Characterization of cloned K+ transport cDNAs

Recently, two K⁺-transport cDNAs, KAT1 and AKT1, were cloned in Arabidopsis thaliana. These cDNAs had structural similarities to K⁺ channel genes in animals, and also conferred the ability for growth on micromolar levels of K⁺ when expressed in K⁺ transport-defective yeast mutants. In this study, we examined the possibility that KAT1 encodes the high-affinity K⁺ transport system that has been previously characterized in plant roots, by studying the concentration-dependent kinetics of K⁺ transport for KAT1 expressed in Xenopus oocytes and Saccharomyces cerevisiae. In both organisms, the K⁺ transport system encoded by KAT1 yielded Michaelis-Menten kinetics with a high K_m for K⁺ (35 mM in oocytes, 0.6 mM in yeast cells). Furthermore, Northern analysis indicated that KAT1 is expressed primarily in the Arabidopsis shoot. These results strongly suggest that the system encoded by KAT1 is not a root high-affinity K⁺ transporter.     

Blubber morphology in wild bottlenose dolphins (Tursiops truncatus) from the Southeastern United States: influence of geographic location, age class, and reproductive state

This study investigated blubber morphology and correlations of histological measurements with ontogeny, geography, and reproductive state in live, wild bottlenose dolphins (Tursiops truncatus) from the southeastern United States. Surgical skin-blubber biopsies (N=74) were collected from dolphins during capture-release studies conducted in two geographic locations: Charleston, SC (N=38) and Indian River Lagoon, FL (N=36). Histological analysis of blubber revealed stratification into superficial, middle, and deep layers. Adipocytes of the middle blubber were 1.6x larger in Charleston subadults than in Indian River Lagoon subadults (4,590+/-340 compared to 2,833+/-335 microm2 per cell). Charleston subadult dolphins contained higher levels of total blubber lipids than Charleston adult animals (49.3%+/-1.9% compared to 34.2%+/-1.7%), and this difference was manifested in more adipocytes in the middle blubber layer (19.2+/-0.9 compared to 14.9+/-0.5 cells per field). However, dolphins from Indian River Lagoon did not exhibit this pattern, and the adipocyte cell counts of subadults were approximately equal to those of the adults (16.0+/-1.4 compared to 13.4+/-0.8 cells per field). The colder year-round water temperatures in Charleston compared to Indian River Lagoon may explain these differences. Adipocytes in the deep blubber layer were significantly smaller in lactating and simultaneously pregnant and lactating animals compared to pregnant dolphins (840+/-179, 627+/-333, and 2,776+/-586 microm2 per cell, respectively). Total blubber lipid content and adipocyte size in the deep blubber of mothers with calves decreased linearly with calf length. Lactating females may utilize lipids from the deep blubber during periods of increased energetic demands associated with offspring care. This study demonstrates that ontogeny, geography, and reproductive state may influence morphological parameters such as structural fiber densities and adipocyte numbers and sizes, measured in bottlenose dolphin blubber.     

Membrane resistance change of the frog taste cells in response to water and Nacl

The electrical properties of the frog taste cells during gustatory stimulations with distilled water and varying concentrations of NaCl were studied with intracellular microelectrodes. Under the Ringer adaptation of the tongue, two types of taste cells were distinguished by the gustatory stimuli. One type, termed NaCl-sensitive (NS) cells, responded to water with hyperpolarizations and responded to concentrated NaCl with depolarizations. In contrast, the other type of cells, termed water-sensitive (WS) cells, responded to water depolarizations and responded to concentrated NaCl with hyperpolarizations. The membrane resistance of both taste cell types increased during the hyperpolarizing receptor potentials and decreased during the depolarizing receptor potentials, Reversal potentials for the depolarizing and hyperpolarizing responses in each cell type were a few millivolts positive above the zero membrane potential. When the tongue was adapted with Na-free Ringer solution for 30 min, the amplitude of the depolarizing responses in the NS cells reduced to 50% of the control value under normal Ringer adaptation. On the basis of the present results, it is concluded (a) that the depolarizing responses of the NS and WS cells under the Ringer adaptation are produced by the permeability increase in some ions, mainly Na+ ions across the taste cell membranes, and (b) that the hyperpolarizing responses of both types of taste cells are produced by a decrease in the cell membrane permeability to some ions, probably Na+ ions, which is slightly enhanced during the Ringer adaptation.     

The human neonatal small intestine has the potential for arginine synthesis; developmental changes in the expression of arginine-synthesizing and -catabolizing enzymes

Background  

Milk contains too little arginine for normal growth, but its precursors proline and glutamine are abundant; the small intestine of rodents and piglets produces arginine from proline during the suckling period; and parenterally fed premature human neonates frequently suffer from hypoargininemia. These findings raise the question whether the neonatal human small intestine also expresses the enzymes that enable the synthesis of arginine from proline and/or glutamine. Carbamoylphosphate synthetase (CPS), ornithine aminotransferase (OAT), argininosuccinate synthetase (ASS), arginase-1 (ARG1), arginase-2 (ARG2), and nitric-oxide synthase (NOS) were visualized by semiquantitative immunohistochemistry in 89 small-intestinal specimens.     

Physiological and molecular characterization of aluminum resistance in <Emphasis Type="Italic">Medicago truncatula</Emphasis>

Background  

Aluminum (Al) toxicity is an important factor limiting crop production on acid soils. However, little is known about the mechanisms by which legumes respond to and resist Al stress. To explore the mechanisms of Al toxicity and resistance in legumes, we compared the impact of Al stress in Al-resistant and Al-sensitive lines of the model legume, Medicago truncatula Gaertn.     

Molecular evidence for the rapid propagation of mouse t haplotypes from a single, recent, ancestral chromosome

Mouse t haplotypes are variant forms of chromosome 17 that exist at high frequencies in worldwide populations of two species of commensal mice. To determine both the relationship of t haplotypes to each other and the species within which they exist, 35 representative t haplotypes were analyzed by means of 10 independent molecular probes, including five DNA clones and five polypeptide spots identified by means of two- dimensional gel electrophoresis. All of the tested haplotypes were found to share restriction fragments and polypeptide spots that are absent in mice carrying wild-type forms of chromosome 17. This observation provides the first direct evidence that all of the known t haplotypes are descendents of a single ancestral chromosome. The absence of variation among t haplotypes could mean that this ancestral chromosome existed relatively recently, in which case it would be necessary to postulate introgressions of t haplotypes across species lines to explain their presence in both Mus domesticus and M. musculus. Alternatively, it is possible that the ancestral chromosome existed prior to the split between M. domesticus and M. musculus and that, by chance, our probes fail to detect polymorphisms that exist among the t haplotypes. A further result of our analysis is the characterization of a partial t haplotype in a wild population of Israeli mice.      

Phylogenetic analysis of the alpha-globin pseudogene-4 (Hba-ps4) locus in the house mouse species complex reveals a stepwise evolution of t haplotypes [published erratum appears in Mol Biol Evol 1994 Jan;11(1):158]

A parsimony analysis was performed on restriction sites at the Hba-ps4 pseudogene locus within one of four inversions associated with mouse t haplotypes. The results suggest that all t haplotypes form a monophyletic group and that the in (17)4 inversion originated before the radiation of the Mus musculus species complex but after the divergence of the lineages leading to M. spretus, M. abbotti, and M. hortulanus. A time frame based on the evolutionary rate of mouse pseudogenes places the origin of this t haplotype inversion at 1.5 Mya, or approximately 1.5 Myr after the origin of the more proximal t complex inversion, in (17)2. The accumulated evidence indicates that complete t haplotypes have been assembled in a stepwise manner, with each of these inversions occurring on separate chromosomal lineages and at different evolutionary times. In addition, the evolutionary relationships of pseudogene sequences resulting from genetic exchange between wild-type and t haplotype alleles were examined. Analysis of sequences from the 5' and 3' sides of a putative site of recombination resulted in cladograms with different topologies. The implications for hypotheses concerning the evolutionary forces acting on t haplotypes and their rapid propagation throughout worldwide populations of mice are discussed.      

Life Cycle Greenhouse Gas Emissions of Electricity Generated from Conventionally Produced Natural Gas

This research provides a systematic review and harmonization of the life cycle assessment (LCA) literature of electricity generated from conventionally produced natural gas. We focus on estimates of greenhouse gases (GHGs) emitted in the life cycle of electricity generation from natural gas‐fired combustion turbine (NGCT) and combined‐cycle (NGCC) systems. The smaller set of LCAs of liquefied natural gas power systems and natural gas plants with carbon capture and storage were also collected, but analyzed to a lesser extent. A meta‐analytical process we term “harmonization” was employed to align several system boundaries and technical performance parameters to better allow for cross‐study comparisons, with the aim of clarifying central tendency and reducing variability in estimates of life cycle GHG emissions. Of over 250 references identified, 42 passed screens for technological relevance and study quality, providing a total of 69 estimates for NGCT and NGCC. Harmonization increased the median estimates in each category as a result of several factors not typically considered in the previous research, including the regular clearing of liquids from a well, and consolidated the interquartile range for NGCC to 420 to 480 grams of carbon dioxide equivalent per kilowatt‐hour (g CO₂‐eq/kWh) and for NGCT to 570 to 750 g CO₂‐eq/kWh, with medians of 450 and 670 CO₂‐eq/kWh, respectively. Harmonization of thermal efficiency had the largest effect in reducing variability; methane leakage rate is likely similarly influential, but was unharmonized in this assessment as a result of the significant current uncertainties in its estimation, an area that is justifiably receiving significant research attention.