Membrane protein biosynthesis in bacteriophage BF23-infected Escherichia coli.

When Escherichia coli is infected with bacteriophage BF23, two new proteins with molecular weights greater than 10,000, as indicated by polyacrylamide gel electrophoresis, are found associated with the cells' membranes. One of these, found associated with both the inner and outer membrane, has a molecular weight of about 55,000 and is regulated by the A1 gene of this phage, a gene found on the spontaneously injected 8% piece of BF23 DNA, DNA that codes for the synthesis of proteins necessary for the injection of the whole phage genome. The other protein, often undetected in whole membrane preparations, is found exclusively associated with the inner membrane. Evidence indicates that this protein is also regulated by the initially injected 8% piece of the DNA.     

Obesity and labour market success in Finland: The difference between having a high BMI and being fat

This paper examines the relationship between obesity and labour market success in Finland, using various indicators of individual body composition along with body mass index (BMI). Weight, height, fat mass and waist circumference are measured by health professionals. We find that only waist circumference has a negative association with wages for women, whereas no obesity measure is significant in the linear wage models for men. However, all measures of obesity are negatively associated with women's employment probability and fat mass is negatively associated with men's employment probability. We also find that the use of categories for waist circumference and fat mass has a substantial influence on the results. For example, the category for high fat mass is associated with roughly 5.5% lower wages for men. All in all, the results indicate that in the absence of measures of body composition, there is a risk that labour market penalties associated with obesity are measured with bias.     

Nitrogen fixation (acetylene reduction) on a coral reef

Nitrogen fixation rates associated with various substrates on a fringing reef at Eilat, Red Sea, were estimated by in situ acetylene reduction. High rates of acctylene reduction were associated with bare substrates, such as sand and dead coral skeletons. Low rates of acetylene reduction were associated with substrates covered by macroalgae or living coral tissue. Estimates of nitrogen fixation in various reef zones, based on these measurements, indicate that the sand-covered lagoon is responsible for more than 70% of the fixation in the reef. Consequently, the lagoon may serve as an important source of nitrogen for the coral reef community.     

Quantitative genetic variance associated with chromosomal markers in segregating populations

Summary Use of chromosomal markers can accelerate genetic progress for quantitative traits in pedigree selection programs by providing early information on Mendelian segregation effects for individual progeny. Potential effectiveness of selection using markers is determined by the amount of additive genetic variance traced from parents to progeny by the markers. Theoretical equations for the amount of additive genetic variance associated with a marker were derived at the individual level and for a segregating population in joint linkage equilibrium. Factors considered were the number of quantitative trait loci linked to the marker, their individual effects, and recombination rates with the marker. Subsequently, the expected amount of genetic variance associated with a marker in a segregating population was derived. In pedigree selection programs in segregating populations, a considerable fraction of the genetic variance on a chromosome is expected to be associated with a marker located on that chromosome. For an average chromosome in the bovine, this fraction is approximately 40% of the Mendelian segregation variance contributed by the chromosome. The effects of interference and position of the marker on this expectation are relative small. Length of the chromosome has a large effect on the expected variance. Effectiveness of MAS is, however, greatly reduced by lack of polymorphism at the marker and inaccuracy of estimation of chromosome substitution effects. The size of the expected amount of genetic variance associated with a chromosomal marker indicates that, even when the marker is not the active locus, large chromosome substitution effects are not uncommon in segregating populations.     

Hard rock versus soft bottom: the fauna associated with intertidal mussel beds on hard bottoms along the coast of Chile,and considerations on the functional role of mussel beds

The fauna associated with hard bottom mussel beds along the exposed Pacific coast of Chile was examined. The abundance of adult (>10 mm body length) purple mussels Perumytilus purpuratus varied between 32 and 75 individuals per 50 cm², and their biomass between 4.8 and 8.6 g AFDW per 50 cm² at eight sampling sites between Arica (18°S) and Chiloé (42°S). At all sampling sites, the associated fauna was dominated by suspension-feeding organisms (cirripeds, spionid and sabellid polychaetes, a small bivalve) followed by grazing peracarids and gastropods. Predators and scavengers also reached high abundances while deposit- and detritus-feeding organisms were of minor importance. The majority of organisms associated with these hard bottom mussel beds feed on resources obtained from the water column or growing on the mussels rather than on materials deposited by the mussels. This is in contrast to the fauna associated with mussel beds on soft bottoms, which comprises many species feeding on material accumulated by mussels (faeces and pseudofaeces) and deposited within the mussel bed. Many of the organisms dwelling between mussels both on hard bottoms and on soft bottoms have direct development, but organisms with pelagic development also occur abundantly within mussel beds. We propose that species with direct development are disproportionately favoured by the structurally complex habitat with diverse interstitial spaces between the mussels, which provides ample shelter for small organisms. We conclude that mussels on hard-bottoms primarily provide substratum for associated fauna while mussels on soft bottoms provide both substratum and food resources. Electronic Publication     

Association of leucogenenol,a thymothyroid hormone,with carrier proteins in the thymus

Leucogenenol a heterocyclic enolic thymothyroid hormone (MW 383) whose concentration in the serum regulates the rate at which already committed cells of the bone marrow develop into functional cells, was found to be associated in the thymus with a carrier protein. The carrier protein for leucogenenol is not precipitated by heating to 80° but following this treatment leucogenenol is precipitated in association with proteins precipitated by acetone and then by saturated ammonium sulfate. On chromatography on Sephacryl G-200 it was found that leucogenenol was associated with proteins of MW approximately 38,000. Leucogenenol is not eluted from the chromatographic column if it is not associated with its carrier proteins. It is suggested that other hormones such as those associated with the reproductive cycle or compounds that result from tissue damage induce the liberation of leucogenenol from its carrier protein in the thymus to the circulation where it is associated as previously described, with a protein of approximately MW 300,000.     

Male-male competition and nuptial-colour displacement as a diversifying force in Lake Victoria cichlid fishes

We propose a new mechanism for diversification of male nuptial-colour patterns in the rapidly speciating cichlid fishes of Lake Victoria. Sympatric closely related species often display nuptial colours at opposite ends of the spectrum with males either blue or yellow to red. Colour polymorphisms within single populations are common too. We propose that competition between males for breeding sites promotes such colour diversification, and thereby speciation. We hypothesize that male aggression is primarily directed towards males of the common colour, and that rare colour morphs enjoy a negatively frequency-dependent fitness advantage. We test our hypothesis with a large dataset on the distributions and nuptial colorations of 52 species on 47 habitat islands in Lake Victoria, and with a smaller dataset on the within-spawning-site distributions of males with different coloration. We report that territories of males of the same colour are negatively associated on the spawning site, and that the distribution of closely related species over habitat islands is determined by nuptial coloration in the fashion predicted by our hypothesis. Whereas among unrelated species those with similar nuptial colour are positively associated, among closely related species those with similar colour are negatively associated and those with different colour are positively associated. This implies that negatively frequency-dependent selection on nuptial coloration among closely related species is a sufficiently strong force to override other effects on species distributions. We suggest that male-male competition is an important and previously neglected agent of diversification among haplochromine cichlid fishes.     

The binding of learning to action in motor adaptation

In motor tasks, errors between planned and actual movements generally result in adaptive changes which reduce the occurrence of similar errors in the future. It has commonly been assumed that the motor adaptation arising from an error occurring on a particular movement is specifically associated with the motion that was planned. Here we show that this is not the case. Instead, we demonstrate the binding of the adaptation arising from an error on a particular trial to the motion experienced on that same trial. The formation of this association means that future movements planned to resemble the motion experienced on a given trial benefit maximally from the adaptation arising from it. This reflects the idea that actual rather than planned motions are assigned 'credit' for motor errors because, in a computational sense, the maximal adaptive response would be associated with the condition credited with the error. We studied this process by examining the patterns of generalization associated with motor adaptation to novel dynamic environments during reaching arm movements in humans. We found that these patterns consistently matched those predicted by adaptation associated with the actual rather than the planned motion, with maximal generalization observed where actual motions were clustered. We followed up these findings by showing that a novel training procedure designed to leverage this newfound understanding of the binding of learning to action, can improve adaptation rates by greater than 50%. Our results provide a mechanistic framework for understanding the effects of partial assistance and error augmentation during neurologic rehabilitation, and they suggest ways to optimize their use.     

Immune Subversion and Quorum-Sensing Shape the Variation in Infectious Dose among Bacterial Pathogens

Many studies have been devoted to understand the mechanisms used by pathogenic bacteria to exploit human hosts. These mechanisms are very diverse in the detail, but share commonalities whose quantification should enlighten the evolution of virulence from both a molecular and an ecological perspective. We mined the literature for experimental data on infectious dose of bacterial pathogens in humans (ID50) and also for traits with which ID50 might be associated. These compilations were checked and complemented with genome analyses. We observed that ID50 varies in a continuous way by over 10 orders of magnitude. Low ID50 values are very strongly associated with the capacity of the bacteria to kill professional phagocytes or to survive in the intracellular milieu of these cells. Inversely, high ID50 values are associated with motile and fast-growing bacteria that use quorum-sensing based regulation of virulence factors expression. Infectious dose is not associated with genome size and shows insignificant phylogenetic inertia, in line with frequent virulence shifts associated with the horizontal gene transfer of a small number of virulence factors. Contrary to previous proposals, infectious dose shows little dependence on contact-dependent secretion systems and on the natural route of exposure. When all variables are combined, immune subversion and quorum-sensing are sufficient to explain two thirds of the variance in infectious dose. Our results show the key role of immune subversion in effective human infection by small bacterial populations. They also suggest that cooperative processes might be important for successful infection by bacteria with high ID50. Our results suggest that trade-offs between selection for population growth-related traits and selection for the ability to subvert the immune system shape bacterial infectiousness. Understanding these trade-offs provides guidelines to study the evolution of virulence and in particular the micro-evolutionary paths of emerging pathogens.     

Small Heat Shock Proteins and Distal Hereditary Neuropathies

Classification of small heat shock proteins (sHsp) is presented and processes regulated by sHsp are described. Symptoms of hereditary distal neuropathy are described and the genes whose mutations are associated with development of this congenital disease are listed. The literature data and our own results concerning physicochemical properties of HspB1 mutants associated with Charcot–Marie–Tooth disease are analyzed. Mutations of HspB1, associated with hereditary motor neuron disease, can be accompanied by change of the size of HspB1 oligomers, by decreased stability under unfavorable conditions, by changes in the interaction with protein partners, and as a rule by decrease of chaperone-like activity. The largest part of these mutations is accompanied by change of oligomer stability (that can be either increased or decreased) or by change of intermonomer interaction inside an oligomer. Data on point mutation of HspB3 associated with axonal neuropathy are presented. Data concerning point mutations of Lys141 of HspB8 and those associated with hereditary neuropathy and different forms of Charcot–Marie–Tooth disease are analyzed. It is supposed that point mutations of sHsp associated with distal neuropathies lead either to loss of function (for instance, decrease of chaperone-like activity) or to gain of harmful functions (for instance, increase of interaction with certain protein partners).     

Genomic regions associated with antibody response to sheep red blood cells in the chicken

F(1) and F(2) populations were generated by crossing two lines of chickens divergently selected from a common founder population for 32 generations for either high or low antibody response 5 days post-injection of a non-pathogenic antigen, sheep red blood cells (SRBCs). The number of loci with major effects on day 5 SRBC titers was estimated to be more than 7 in this population. There was a significant association between MHC haplotype and day 5 antibody titers as well as body weight at sexual maturity. A significant difference between reciprocal F(2) crosses for both 5- and 12-day antibody titers suggests that sex chromosome and/or parent of origin effects on autosomal loci have an important role in immune response. A single marker-trait association analysis on 1024 genetic markers and 128 F(2) individuals detected 11 genomic regions associated with antibody response traits and 17 regions associated with body weight gain. Several of the genomic regions identified as being associated with antibody response have been described previously, while novel regions associated with antibody response were identified on chromosomes 11 and 24. Based on the lack of overlap of the regions associated with body weight and antibody response, we conclude that while these phenotypes are inversely correlated in the selected lines, they are controlled by distinct genetic loci and may be reflective of intense selection pressure on loci affecting the partitioning of nutrients between the immune system and growth pathways.     

Biological roles of blood group antigens

Recognition and application of blood group differences on human red cells permitted the development of safe procedures for blood transfusion. Blood group antigens are markers on surface-exposed red cell proteins or the sugar moiety of glycoproteins or glycolipids. Apart from their presumed biological function, some antigens have been identified as receptors for host/parasite interactions. Thus, carbohydrates that determine P antigenicity are the binding receptor for certain strains of pyelonephritic coliforms. Other pathogenic coliforms bind to the membrane structure that carries the Dra antigen. A structure associated with Duffy antigens is the attachment receptor for the parasite of Plasmodium vivax malaria, while Plasmodium falciparum parasites bind to structures associated with membrane glycophorins. Structure/function relationships have been established by the finding that lack of Rh protein in red cells of Rhnull phenotype is associated with stomatocytic cell morphology and a hemolytic state. Absence of glycophorin C, and the Gerbich blood group antigens that it carries, is associated with elliptocytic red cells. Absence of Kx antigen protein in the Kell system is associated with the McLeod blood group phenotype, with acanthocytic cell morphology and reduced in vivo survival. McLeod individuals also have late-onset muscular dystrophy and neurological disorders.     

Do fatal infectious diseases eradicate host species?

In simple SI epidemic and endemic models, three classes of incidence functions are identified for their potential to be associated with host extinction: weakly upper density-dependent incidences are never associated with host extinction. Power incidences that depend on the number of susceptibles and infectives by powers strictly between 0 and 1 are associated with initial-constellation-dependent host extinction for all parameter values. Homogeneous incidences, of which frequency-dependent incidence is a very particular case, and power incidences are associated with global host extinction for certain parameter constellations and with host survival for others. Laboratory infection experiments with salamander larvae are equally well fitted by power incidences and certain upper density-dependent incidences such as the negative binomial incidence and do not rule out homogeneous incidences such as an asymmetric frequency-dependent incidence either.

     

Identification of intrinsic sialidase and sialoglycoprotein substrates in rat brain synaptic junctions

Sialidase activity associated with rat brain synaptic junctions (SJ) and synaptic membranes (SM) was determined. Both fractions released sialic acid from exogenous glycopeptides and gangliosides. SJ accounted for 5-10% of the total sialidase activity recovered from SM following extraction with Triton X-100, and the specific activity of SJ sialidase was 60% of that of the parent SM fraction. Intrinsic SJ sialidase hydrolysed 12-15% of the sialic acid associated with endogenous SJ glycoproteins. Sialic acid residues associated with SJ glycoproteins were labelled with sodium borotritide and SJ proteins fractionated by affinity chromatography on concanavalin A-agarose. SJ glycoproteins that reacted with concanavalin A (con A+ glycoproteins) accounted for 25% of the total SJ [3H]sialic acid. Intrinsic SJ sialidase hydrolysed 20% of the [3H]sialic acid associated with these glycoproteins. Each molecular weight class of con A+ glycoprotein previously shown to be a specific component of the postsynaptic apparatus contained sialic acid and was acted on by intrinsic SJ sialidase.     

Accumulation of P elements in minority inversions in natural populations of Drosophila melanogaster.

The accumulation of a transposable element inside chromosomal inversions is examined theoretically by a mathematical model, and empirically by counts of P elements associated with inversion polymorphisms in natural populations of Drosophila melanogaster. The model demonstrates that, if heterozygosity for an inversion effectively reduces element associated production of detrimental chromosome rearrangements, a differential accumulation of elements is expected, with increased copy number inside the minority inversion. Several-fold differential accumulations are possible with certain parameter values. We present data on P element counts for inversion polymorphisms on all five chromosome arms of 157 haploid genomes from two African populations. Our observations show significantly increased numbers of elements within the regions associated with the least common, or minority arrangements, in natural inversion polymorphisms.     

Membrane lipid domains distinct from cholesterol/sphingomyelin-rich rafts are involved in the ABCA1-mediated lipid secretory pathway

Efflux of excess cellular cholesterol mediated by lipid-poor apolipoproteins occurs by an active mechanism distinct from passive diffusion and is controlled by the ATP-binding cassette transporter ABCA1. Here we examined whether ABCA1-mediated lipid efflux involves the selective removal of lipids associated with membrane rafts, plasma membrane domains enriched in cholesterol and sphingomyelin. ABCA1 was not associated with cholesterol and sphingolipid-rich membrane raft domains based on detergent solubility and lack of colocalization with marker proteins associated with raft domains. Lipid efflux to apoA-I was accounted for by decreases in cellular lipids not associated with cholesterol/sphingomyelin-rich membranes. Treating cells with filipin, to disrupt raft structure, or with sphingomyelinase, to digest plasma membrane sphingomyelin, did not impair apoA-I-mediated cholesterol or phosphatidylcholine efflux. In contrast, efflux of cholesterol to high density lipoproteins (HDL) or plasma was partially accounted for by depletion of cholesterol from membrane rafts. Additionally, HDL-mediated cholesterol efflux was partially inhibited by filipin and sphingomyelinase treatment. Apo-A-I-mediated cholesterol efflux was absent from fibroblasts with nonfunctional ABCA1 (Tangier disease cells), despite near normal amounts of cholesterol associated with raft domains and normal abilities of plasma and HDL to deplete cholesterol from these domains. Thus, the involvement of membrane rafts in cholesterol efflux applies to lipidated HDL particles but not to lipid-free apoA-I. We conclude that cholesterol and sphingomyelin-rich membrane rafts do not provide lipid for efflux promoted by apolipoproteins through the ABCA1-mediated lipid secretory pathway and that ABCA1 is not associated with these domains.     

Energetics of reproduction and its evolutionary implications

The majority of invertebrates so far studied are more efficient converters of absorbed food energy to gametes than they are, as adults, to somatic tissues. Indeed, reproductive conversion efficiencies sometimes better the best conversion efficiencies associated with somatic production (usually in juveniles). Depending on species, this is achieved either by an increase in absorption relative to respiratory losses, or a reduction in respiratory losses relative to absorption, or by supplementing the energy absorbed from the food with that obtained from somatic stores and tissues, or by a combination of these. The fact that the metabolic processes associated with gamete production are distinct from those associated with the production of somatic tissues has implications for the theory of life-cycle evolution.