Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “TAILS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed2006

Variations in the unstructured C-terminal tail of interferons contribute to differential receptor binding and biological activity.

Type I interferons (IFNs) elicit antiviral, antiproliferative and immunomodulatory properties in cells. All of them bind to the same receptor proteins, IFNAR1 and IFNAR2, with different affinities. While the 13 known IFNalphas are highly conserved, the C-terminal unstructured tail was found to have large variation in its net charge, from neutral to +4. This led us to speculate that the tail may have a role in modulation of the IFN biological activity, through fine-tuning the binding to IFNAR2. To evaluate this hypothesis, we replaced the tail of IFNalpha2 with that of IFNalpha8 and IFNbeta tails, or deleted the last five residues of this segment. Mutations to the more positively charged tail of IFNalpha8 resulted in a 20-fold higher affinity to IFNAR2, which results in a higher antiviral and antiproliferative activity. Double and multiple mutant cycle analysis placed the tail near a negatively charged loop on IFNAR2, comprising of residues Glu 132-134. Deleting the tail resulted in only twofold reduction in binding compared to the wild-type. Next, we modeled the location of the tail using a two-step procedure: first we generated 200 models of the tail docked on IFNAR2 using HADDOCK, second the models were scored according to the fit between experimentally determined rates of association of nine mutant complexes, and their calculated rates using the PARE software. From the results we suggest that the unstructured tail of IFNalpha is gaining a specific structure in the bound state, binding to a groove below the 132-134 loop in IFNAR2.

Antineoplastic Agents↗
PubMed2005

Effects of sewage sludge on pH and plant availability of metals in oxidising sulphide mine tailings.

A field study was conducted adjacent to the tailings deposit of the Aitik copper mine in the north of Sweden to investigate the effects of sewage sludge on pH and plant availability of Al, Mn, Cu, Zn, Ni, Pb, As, Cr and Cd in the oxidising sulphide tailings. One treatment was supplied with sewage sludge, while the control received NPK-fertiliser. The tailings samples were collected at the beginning and the end of the growing season and extracted by NH(4)NO(3), NH(4)Ac-EDTA and HNO(3). Plant tissue concentrations of the elements were determined in the above-ground parts of barley (Hordeum vulgare) and red fescue (Festuca rubra). The application of sewage sludge resulted in higher crop yields compared to the control, although the buffering capacity and the metal immobilising effect of the sludge were limited. The pH decreased from 6.6 to 4.3 in the control and from 6.4 to 4.8 in the sludge-treated tailings during the growing season, probably due to sulphide oxidation in the tailings. This resulted in increased levels of soluble elements in all treatments studied. Application of sewage sludge resulted in elevated levels of soluble Zn and lower values of soluble As and Cd in the unaltered tailings but increased levels of specifically adsorbed Cu, Ni and As in the oxidised tailings. This was partly reflected in the plants, as the application of sewage sludge resulted in 67 mg Zn kg(-1) in barley grains and 60 mg Zn kg(-1) in red fescue shoots, both values twice as high as the corresponding values in the control, but lower As contents in both straw (0.3 mg kg(-1)) and grain (0.06 mg kg(-1)) of barley compared to the control (0.6 and 0.2 mg kg(-1), respectively). In addition, red fescue grown in sludge-treated plots contained significantly higher levels of Al, Cu, Pb, As and Cr compared to the control. The levels of several metals in barley and red fescue grown in both treatments exceeded background values found in the literature. The Cu content in barley straw exceeded 100 mg kg(-1) in both treatments and might be toxic to grazing animals. Thus, this study suggests that adding sewage sludge to the mine tailings at Aitik would not counteract the effects of the sulphide oxidation in the tailings. Furthermore, using a sequential extraction technique proved preferable to using total metal analysis in order to predict plant uptake of the elements in the tailings.

Biological Availability↗
PubMed2004

Large scale preparation of nucleosomes containing site-specifically chemically modified histones lacking the core histone tail domains.

The core histone tail domains are critical regulators of chromatin structure and function and modifications such as acetylation of lysine residues within the tails are central to this regulation. Studies have shown that the removal of core histone tail domains by trypsinization in which one-half to two-thirds of each core histone tail domain are removed in gross aspects mimics the acetylation of core histone tails. In addition, removal of the tails has been useful in understanding general tail function. Thus, removal of native core histone tails by trypsinization is a widely used method. In addition, many in vitro studies now employ core histones site-specifically modified with photo activatable cross-linking probes or fluorescent probes. However, in our experience, standard methods employing trypsinized donor chromatin for reconstitution of nucleosomes containing certain chemically modified histones lacking the core histone tail domains are not uniformly applicable. Here, we describe various methods for preparing nucleosomes containing a core histone modified with a cross-linking agent, APB, and lacking the core histone tail domains.

Animals↗
PubMed2001

Geochemical changes in sulfidic mine tailings stored under a shallow water cover.

The objective of this study was to assess the effectiveness of an engineered shallow water cover in reducing the oxidation of sulfidic mine tailings and thus preventing the development of acid rock drainage. Fresh tailings were submerged under a 0.3-m water cover in experimental field cells. From 1996 to 1998, we followed the chemistry of the interstitial water near the tailings-overlying water interface using in situ dialysis, and determined pH and dissolved oxygen (DO) profiles across the tailing water interface using micro-electrodes. Penetration of DO into the tailings was limited to <7 mm, even in the presence of DO produced by benthic periphyton. Anoxia in the tailings was further demonstrated by the appearance of dissolved sigmaH2S, Fe and Mn in pore water at depths -1.5 cm below the interface. However, there was clear evidence of surface oxidation of the mine tailings at the mm scale (i.e., DO depletion, coupled with localized increases in [H+] and [SO4(2-)]). Mobilization of Cd and Zn from this surface layer was indicated by the presence of sub-surface peaks in the concentrations of these two metals in the tailings interstitial water and by a change in their solid phase partitioning from refractory to more labile fractions. In contrast, mobilization of Cu from tailings was less evident. Unlike previous reports, which suggested that submerged tailings were effectively inert, our results show alteration of the superficial layer over time.

Geologic Sediments↗
PubMed2000

Punctuated recovery of sediments and benthic infauna: a 19-year study of tailings deposition in a British Columbia fjord.

Sediment organic and metal chemistry, benthic infauna and tissue contaminants surveys have been conducted over 19 years before and following tailings deposition from a metal (Mo, Pb, Zn) mine in Alice Arm, a British Columbia fjord. We found changes in benthic fauna and habitat after tailings disposal to be predictable in terms of sediment chemistry and faunal recolonization. What was not predictable was the timing and extent of slope failure or resuspension following abandonment. These events can have essentially the same or greater effect than the initial tailings disposal and produce long-term unpredictability particular to cases of submarine disposal on slopes. The present study focused on the submarine deposition of 4 x 10(6) tonnes of tailings during an 18-months period ending October 1982. When the mine closed, gross defaunation had occurred at three stations in the tailings path, and two others showed recent defaunation and recolonization. A year later, a large tailings slump near the outfall transported tailings to the deep basin; fauna were impoverished both in the slump region and through most of the deep basin. Declining metal concentrations in surface sediments was accompanied by considerable recovery of fauna 3 years after the mine closed. Nevertheless, fauna at the three stations defaunated at the time of mine closure could still be statistically distinguished from all other stations due to high abundances of small opportunistic polychaetes and bivalves. A resuspension in tailings between 1988 and 1990 coincided with a moderate decline in abundance of all macrofauna taxa. From 1989 to 1995 recovery toward natural sediment conditions was evident as increasing organic content together with the highest faunal biomass values found during the study. Small polychaetes were the first recolonizers in defaunated areas, whereas small bivalves were more tolerant of moderate tailings deposition. By 1989 and 1995 small colonizers had declined and amphipods and larger echinoderms had increased. Dominant species patterns and exceptionally high biomass values in 1995 show that the largest fauna did not recover until much later than smaller taxa. One genus of bivalve (Yoldia spp.) accumulated metals in a pattern similar to the sediment chemistry, indicating that the metals from the most recent mine had entered the benthic food chain. It is not possible to tell from this study whether biota were affected by toxicity from metals. However, many of the observed biotic effects could be caused by physical disruption from tailings.

Animals↗
PubMed2001

226Ra bioavailability to plants at the Urgeiriça uranium mill tailings site.

Large amounts of solid wastes (tailings) resulting from the exploitation and treatment of uranium ore at the Urgeiriça mine (north of Portugal) have been accumulated in dams (tailing ponds). To reduce the dispersion of natural radionuclides into the environment, some dams were revegetated with eucalyptus (Eucalyptus globolus) and pines (Pinus pinea). Besides these plants, some shrubs (Cytisus spp.) are growing in some of the dams. The objective of this study is to determine the 226Ra bioavailability from uranium mill tailings by quantifying the total and available fraction of radium in the tailings and to estimate its transfer to plants growing on the tailing piles. Plant and tailing samples were randomly collected and the activity concentration of 226Ra in plants (aerial part and roots) and tailings was measured by gamma-spectrometry. The exchangeable fraction of radium in tailings was quantified using one single step extraction with 1 mol dm-3 ammonium acetate (pH = 7) or 1 mol dm-3 calcium chloride solutions. The results obtained for 226Ra uptake by plants show that 226Ra concentration ratios for eucalyptus and pines decrease at low 226Ra concentrations in the tailings and appear relatively constant at higher radium concentrations. For shrubs, the concentration ratios increase at higher 226Ra solid waste concentrations approaching a saturation value. Percentage values of 16.0 +/- 8.3 and 12.9 +/- 8.9, for the fraction of radium extracted from the tailings, using 1 mol dm-3 ammonium acetate or calcium chloride solutions, respectively, were obtained. The 226Ra concentration ratios determined on the basis of exchangeable radium are one order of magnitude higher than those based on total radium. It can be concluded that, at a 95% confidence level, more consistent 226Ra concentration ratios were obtained when calculated on the basis of available radium than when total radium was considered, for all the dams.

Biological Availability↗
PubMed1995

Isolation and characterization of human milk bile salt-activated lipase C-tail fragment.

Glycosylation positions and oligosaccharide characteristics in the proline-rich, mucin-like, C-terminal region (C-tail) of human milk bile salt-activated lipase (BAL) were studied in order to assess the possible physiological functions of this region. A large-scale purification method has been devised to purify the C-tail fragment from human milk BAL. Chymotryptic, tryptic, and cyanogen bromide cleavages of partially purified BAL and subsequent molecular sieve chromatography yielded 20-30 mg of C-tail fragment from 1 L of human milk. The N-terminal sequence and amino acid composition of the purified C-tail fragment establish that it is derived from residues 528-712 of the enzyme. The O-glycosylated carbohydrates of the C-tail fragment contain fucose, galactose, glucosamine, galactosamine, and neuraminic acid in a molar ratio of 1:3:2:1:0.3, respectively. beta-Elimination reaction revealed that nine threonine residues and less than one serine residue were glycosylated. Edman degradation of C-tail fragment and its pronase subfragment suggest a number of glycosylation sites which are flanked by a consensus motif of PVPP. We suggest that this motif may serve as a signal for O-glycosylation in the C-tail region of BAL. Immunochemical studies indicated that the oligosaccharide chains in the C-tail region of BAL contain Lewis x and Lewis a antigens and, less prominently, sialyl Lewis x and sialyl Lewis a antigens. C-tail fragment was also found to bind jacalin lectin. These observations suggest the possibility that the C-tail region may contribute to adhesive activity in the physiological function of BAL.

Amino Acid Sequence↗
PubMed2003

State of the marine environment at Little Bay Arm, Newfoundland and Labrador, Canada, 10 years after a "do nothing" response to a mine tailings spill.

In 1989, the tailings pond dam at the site of a former copper mine near Little Bay, Newfoundland and Labrador, Canada, ruptured and tailings spilled into Little Bay Arm. At the time, no action was taken to arrest the flow of tailings or to mitigate the effects of the spill. To date, no action has been taken to repair the dam and tailings continue to flow into Little Bay Arm. As a result, the marine environment around Little Bay Arm has become contaminated with heavy metals from the tailings. However, the tailings are not the only source of heavy metals to the ecosystem. An old slag heap and what is presumably concentrated copper ore spilled during the loading of ore freighters, are also contributing to the ecosystem's metal load. Marine sediment throughout the Arm contained elevated concentrations of Cu, Ni, Zn, As, V, Co, and Mn. Beach material also contained elevated concentrations of metals with material near the slag heap being the most contaminated. At this site, Cu concentrations were in excess of 5000 mg kg(-1) dry weight, Zn greater than 3000 mg kg(-1) and Co concentrations exceeded 700 mg kg(-1). The highest concentrations of metals in biota were found near the slag heap, near the tailings dam breach, and at the site of the former concentrate loading dock. Despite elevated metal concentrations, the tailings and nearby sediment were not devoid of life. Bivalves and seaweed were abundant in the area and there were no obvious signs of tissue damage or disease in soft shell clams (Mya arenaria) living in the tailings. These clams may be suffering from chronic exposure to the tailings, however, evidence of lipid peroxidation in the clams was inconclusive.

Accidents↗
PubMed2005

Salt-dependent intra- and internucleosomal interactions of the H3 tail domain in a model oligonucleosomal array.

The core histone tail domains are known to be key regulators of chromatin structure and function. The tails are required for condensation of nucleosome arrays into secondary and tertiary chromatin structures, yet little is known regarding tail structures or sites of tail interactions in chromatin. We have developed a system to test the hypothesis that the tails participate in internucleosomal interactions during salt-dependent chromatin condensation, and here we used it to examine interactions of the H3 tail domain. We found that the H3 tail participates primarily in intranucleosome interactions when the nucleosome array exists in an extended "beads-on-a-string" conformation and that tail interactions reorganize to engage in primarily internucleosome interactions as the array successively undergoes salt-dependent folding and oligomerization. These results indicated that the location and interactions of the H3 tail domain are dependent upon the degree of condensation of the nucleosomal array, suggesting a mechanism by which alterations in tail interactions may elaborate different structural and functional states of chromatin.

Amino Acid Substitution↗
PubMed2006

Functions of the cytoplasmic tails of the human receptor activity-modifying protein components of calcitonin gene-related peptide and adrenomedullin receptors.

Receptor activity-modifying proteins (RAMPs) enable calcitonin receptor-like receptor (CRLR) to function as a calcitonin gene-related peptide receptor (CRLR/RAMP1) or an adrenomedullin (AM) receptor (CRLR/RAMP2 or -3). Here we investigated the functions of the cytoplasmic C-terminal tails (C-tails) of human RAMP1, -2, and -3 (hRAMP1, -2, and -3) by cotransfecting their C-terminal deletion or progressive truncation mutants into HEK-293 cells stably expressing hCRLR. Deletion of the C-tail from hRAMP1 had little effect on the surface expression, function, or intracellular trafficking of the mutant heterodimers. By contrast, deletion of the C-tail from hRAMP2 disrupted transport of hCRLR to the cell surface, resulting in significant reductions in (125)I-hAM binding and evoked cAMP accumulation. The transfection efficiency for the hRAMP2 mutant was comparable with that for wild-type hRAMP2; moreover, immunocytochemical analysis showed that the mutant hRAMP2 remained within the endoplasmic reticulum. FACS analysis revealed that deleting the C-tail from hRAMP3 markedly enhances AM-evoked internalization of the mutant heterodimers, although there was no change in agonist affinity. Truncating the C-tails by removing the six C-terminal amino acids of hRAMP2 and -3 or exchanging their C-tails with one another had no effect on surface expression, agonist affinity, or internalization of hCRLR, which suggests that the highly conserved Ser-Lys sequence within hRAMP C-tails is involved in cellular trafficking of the two AM receptors. Notably, deleting the respective C-tails from hRAMPs had no effect on lysosomal sorting of hCRLR. Thus, the respective C-tails of hRAMP2 and -3 differentially affect hCRLR surface delivery and internalization.

Amino Acid Sequence↗
PubMed1997

Xenopus actin depolymerizing factor/cofilin (XAC) is responsible for the turnover of actin filaments in Listeria monocytogenes tails.

In contrast to the slow rate of depolymerization of pure actin in vitro, populations of actin filaments in vivo turn over rapidly. Therefore, the rate of actin depolymerization must be accelerated by one or more factors in the cell. Since the actin dynamics in Listeria monocytogenes tails bear many similarities to those in the lamellipodia of moving cells, we have used Listeria as a model system to isolate factors required for regulating the rapid actin filament turnover involved in cell migration. Using a cell-free Xenopus egg extract system to reproduce the Listeria movement seen in a cell, we depleted candidate depolymerizing proteins and analyzed the effect that their removal had on the morphology of Listeria tails. Immunodepletion of Xenopus actin depolymerizing factor (ADF)/cofilin (XAC) from Xenopus egg extracts resulted in Listeria tails that were approximately five times longer than the tails from undepleted extracts. Depletion of XAC did not affect the tail assembly rate, suggesting that the increased tail length was caused by an inhibition of actin filament depolymerization. Immunodepletion of Xenopus gelsolin had no effect on either tail length or assembly rate. Addition of recombinant wild-type XAC or chick ADF protein to XAC-depleted extracts restored the tail length to that of control extracts, while addition of mutant ADF S3E that mimics the phosphorylated, inactive form of ADF did not reduce the tail length. Addition of excess wild-type XAC to Xenopus egg extracts reduced the length of Listeria tails to a limited extent. These observations show that XAC but not gelsolin is essential for depolymerizing actin filaments that rapidly turn over in Xenopus extracts. We also show that while the depolymerizing activities of XAC and Xenopus extract are effective at depolymerizing normal filaments containing ADP, they are unable to completely depolymerize actin filaments containing AMPPNP, a slowly hydrolyzible ATP analog. This observation suggests that the substrate for XAC is the ADP-bound subunit of actin and that the lifetime of a filament is controlled by its nucleotide content.

Actin Cytoskeleton↗
PubMed2002

Slo1 tail domains, but not the Ca2+ bowl, are required for the beta 1 subunit to increase the apparent Ca2+ sensitivity of BK channels.

Functional large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels can be assembled from four alpha subunits (Slo1) alone, or together with four auxiliary beta1 subunits to greatly increase the apparent Ca(2+) sensitivity of the channel. We examined the structural features involved in this modulation with two types of experiments. In the first, the tail domain of the alpha subunit, which includes the RCK2 (regulator of K(+) conductance) domain and Ca(2+) bowl, was replaced with the tail domain of Slo3, a BK-related channel that lacks both a Ca(2+) bowl and high affinity Ca(2+) sensitivity. In the second, the Ca(2+) bowl was disrupted by mutations that greatly reduce the apparent Ca(2+) sensitivity. We found that the beta1 subunit increased the apparent Ca(2+) sensitivity of Slo1 channels, independently of whether the alpha subunits were expressed as separate cores (S0-S8) and tails (S9-S10) or full length, and this increase was still observed after the Ca(2+) bowl was mutated. In contrast, beta1 subunits no longer increased Ca(2+) sensitivity when Slo1 tails were replaced by Slo3 tails. The beta1 subunits were still functionally coupled to channels with Slo3 tails, as DHS-I and 17 beta-estradiol activated these channels in the presence of beta1 subunits, but not in their absence. These findings indicate that the increase in apparent Ca(2+) sensitivity induced by the beta1 subunit does not require either the Ca(2+) bowl or the linker between the RCK1 and RCK2 domains, and that Slo3 tails cannot substitute for Slo1 tails. The beta1 subunit also induced a decrease in voltage sensitivity that occurred with either Slo1 or Slo3 tails. In contrast, the beta1 subunit-induced increase in apparent Ca(2+) sensitivity required Slo1 tails. This suggests that the allosteric activation pathways for these two types of actions of the beta1 subunit may be different.

Amino Acid Sequence↗
PubMed2006

The WD40-repeat protein Pwp1p associates in vivo with 25S ribosomal chromatin in a histone H4 tail-dependent manner.

The tails of core histones (H2A, H2B, H3 and H4) are critical for the regulation of chromatin dynamics. Each core histone tail is specifically recognized by various tail binding proteins. Here we screened for budding yeast histone H4-tail binding proteins in a protein differential display approach by two-dimensional gel electrophoresis (2DGE). To obtain highly enriched chromatin proteins, we used a Mg2+-dependent chromatin oligomerization technique. The Mg2+-dependent oligomerized chromatin from H4-tail deleted cells was compared with that from wild-type cells. We used mass spectrometry to identify 22 candidate proteins whose amounts were reduced in the oligomerized chromatin from the H4-tail deleted cells. A Saccharomyces Genome Database search revealed 10 protein complexes, each of which contained more than two candidate proteins. Interestingly, 7 out of the 10 complexes have the potential to associate with the H4-tail. We obtained in vivo evidence, by a chromatin immunoprecipitation assay, that one of the candidate proteins, Pwp1p, associates with the 25S ribosomal DNA (rDNA) chromatin in an H4-tail-dependent manner. We propose that the complex containing Pwp1p regulates the transcription of rDNA. Our results demonstrate that the protein differential display approach by 2DGE, using a histone-tail mutant, is a powerful method to identify histone-tail binding proteins.

Chromatin↗
PubMed2000

The effect of single residue substitutions of serine-283 on the strength of head-to-tail interaction and actin binding properties of rabbit skeletal muscle alpha-tropomyosin.

Vertebrate skeletal muscle alpha-tropomyosin polymerizes in a head-to-tail manner and binds cooperatively to actin. It has been postulated that the cooperative actin binding is governed by the strength of the head-to-tail interaction. In order to know the relationship between the head-to-tail affinity and actin binding, we studied the properties of tropomyosin variants with single residue substitutions at serine-283, the penultimate residue at the carboxyl terminus that is involved in the head-to-tail interaction. It has been shown that the phosphorylation of serine-283 strengthens the head-to-tail interaction. Viscometry was employed to compare the head-to-tail affinity of tropomyosin variants. Variant S283E showed higher viscosity whereas variant S283K showed lower viscosity compared with the wild type non-phosphorylated alpha-tropomyosin. The results confirm the idea that the interaction is sensitive to the ionic properties of residue 283. The strength of the head-to-tail interaction was assessed directly by sedimentation equilibrium using two pairs of tropomyosin variants designed so that only dimeric interactions were allowed within each pair. From one pair of variants with serine-283, the association constant was determined to be 2.6 x 10(4) M(-1) (SD =1.0 x 10(4)), whereas for the second pair with glutamate-283, the affinity was 3.9 x 10(4) M(-1) (SD =1.6 x 10(4)), slightly stronger than the former, consistent with the results of viscometry. The results indicate that the head-to-tail association is weak as previously implicated from light scattering measurements. Cosedimentation was employed to measure the cooperative actin binding of tropomyosin variants. Although previous results indicated the phosphorylation has no significant influence on the actin affinity, variant S283E shows a lower affinity compared with the control. Variants S283K and S283A show even lower affinities to actin, although these species bind to actin more cooperatively than does variant S283E. The results indicate that the affinity of the head-to-tail interaction between adjacent tropomyosin molecules is weak, and is substantially influenced by an extra charge at residue 283. On the other hand, the interaction with actin, the affinity and the cooperativity in actin binding, is dependent on amino acid residues at 283 and is not simply correlated with the strength of the head-to-tail interaction between Tm molecules in solution.

Actins↗
PubMed2001

Sexual selection of multiple handicaps in the red-collared widowbird: female choice of tail length but not carotenoid display.

Although sexual selection through female choice explains exaggerated male ornaments in many species, the evolution of the multicomponent nature of most sexual displays remains poorly understood. Theoretical models suggest that handicap signaling should converge on a single most informative quality indicator, whereas additional signals are more likely to be arbitrary Fisherian traits, amplifiers, or exploitations of receiver psychology. Male nuptial plumage in the highly polygynous red-collared widowbird (Euplectes ardens) comprises two of the commonly advocated quality advertisements (handicaps) in birds: a long graduated tail and red carotenoid coloration. Here we use multivariate selection analysis to investigate female choice in relation to male tail length, color (reflectance) of the collar, other aspects of morphology, ectoparasite load, display rate, and territory quality. The order and total number of active nests obtained are used as measures of male reproductive success. We demonstrate a strong female preference and net sexual selection for long tails, but marginal or no effects of color, morphology, or territory quality. Tail length explained 47% of male reproductive success, an unusually strong fitness effect of natural ornament variation. Fluctuating tail asymmetry was unrelated to tail length, and had no impact on mating success. For the red collar, there was negative net selection on collar area, presumably via its negative relationship with tail length. None of the color variables (hue, chroma, and brightness) had significant selection differentials, but a partial effect (selection gradient) of chroma might represent a color preference when tail length is controlled for. We suggest that the red collar functions in male agonistic interactions, which has been strongly supported by subsequent work. Thus, female choice targets only one handicap, extreme tail elongation, disregarding or even selecting against the carotenoid display. We discuss whether long tails might be better indicators of genetic quality than carotenoid pigmentation. As regards the evolution of multiple ornaments, we propose that multiple handicap signaling is stable not because of multiple messages but because of multiple receivers, in this case females and males.

Animals↗
PubMed1993

Ionic dependence of a slow inward tail current in rat dorsal raphe neurones.

1. The mechanism underlying a large slow inward tail current was studied in serotonergic dorsal raphe (DR) neurones. The tail current is most easily observed under conditions of suppressed K+ channel outward currents and follows the activation of a calcium current. This current may underlie a slow after-depolarizing potential (ADP) which follows action potentials observed in acutely isolated DR neurones. 2. The after-hyperpolarizing potential (AHP) following action potentials which should reverse at EK (the reversal potential for potassium) becomes an ADP at less negative potentials than expected due to contamination by the slow inward tail current. 3. DR neurones were acutely isolated enzymatically; the ADP in current clamp and the tail current underlying it in voltage clamp were studied using the patch clamp method. When the external Na+ was replaced with TEA or choline the slow inward tail current was completely abolished. Blocking K+ channels from the inside of the cell membrane with 40 mM TEACl or large concentrations of internal Cs+ also blocked the slow inward tail current. 4. The tail current proved to be independent of calcium influx or intracellular calcium release as it was not affected by inorganic calcium channel blockers or caffeine. 5. The tail grew exponentially upon lengthening the depolarizing test pulse and appeared to reverse close to 0 mV indicating that the current was carried by a nonselective cation conductance. Removal of external Na+ and replacement with Li+ ions reversibly blocked the tail current by 77%. 6. The data rule out several mechanisms for the generation of the current, namely: a calcium-activated chloride conductance, a calcium-activated non-selective cation conductance, a Na(+)-Ca2+ exchange pump current or a sodium-activated K+ conductance. 7. The slow tail current may be explained by postulating an inward movement of Na+ through a channel which is blocked by high concentrations of external TEA and Li+ or internal Cs+ or 40 mM TEA.

Animals↗
PubMed1993

Examination of Lipopolysaccharide (O-Antigen) Populations of Thiobacillus ferrooxidans from Two Mine Tailings.

Net acid-generating capacities of 39.74 kg of H(2)SO(4) per ton (ca. 0.05 kg/kg) (pH 2.68) for the Lemoine copper mine tailings (closed ca. 8 years ago; located 40 km west of Chibougamau, Quebec, Canada) and 16.07 kg of H(2)SO(4) per ton (ca. 0.02 kg/kg) (pH 3.01) for the Copper Rand tailings (in current use and 50 km distant [east] from those of Lemoine) demonstrate that these sulfide tailings can support populations of acidophilic thiobacilli. Oxidized regions in both tailings environments were readily visible, were extremely acidic (Lemoine, pH 2.36; Copper Rand, pH 3.07), and provided natural isolates for our study. A 10% (wt/vol) oxalic acid treatment, which solubilizes both ferric sulfate and ferric hydroxide precipitates (B. Ramsay, J. Ramsay, M. deTremblay, and C. Chavarie, Geomicrobiol. J. 6:171-177, 1988), enabled the recovery of intact bacterial cells from the tailings material and from liquid synthetic medium for lipopolysaccharide analysis. No viable cells could be cultured after this oxalic acid treatment. Sodium dodecyl sulfate-polyacrylamide gel electro-phoretic profiles of lipopolysaccharides extracted from the Lemoine tailings were complex, indicating a heterogeneous population of Thiobacillus ferrooxidans. Six T. ferrooxidans subspecies as identified by lipopolysaccharide analysis (i.e., lipopolysaccharide chemotypes) were eventually isolated from a total of 112 cultures from the Lemoine tailings. Using the same isolate and lipopolysaccharide typing techniques, we identified only a single lipopolysaccharide chemotype from 20 cultures of T. ferrooxidans isolated from the Copper Rand tailings. This homogeneity of lipopolysaccharide chemotype was much different from what was found for the older Lemoine tailings and may reflect a progressive lipopolysaccharide heterogeneity of Thiobacillus isolates as tailings leach and age.

Journal Article↗
PubMed1993

Mutations in the cytoplasmic tail of influenza A virus neuraminidase affect incorporation into virions.

The significance of the conserved cytoplasmic tail sequence of influenza A virus neuraminidase (NA) was analyzed by the recently developed reverse genetics technique (W. Luytjes, M. Krystal, M. Enami, J. D. Parvin, and P. Palese, Cell 59:1107-1113, 1989). A chimeric influenza virus A/WSN/33 NA containing the influenza B virus cytoplasmic tail rescued influenza A virus infectivity. The transfectant virus had less NA incorporated into virions than A/WSN/33, indicating that the cytoplasmic tail of influenza virus NA plays a role in incorporation of NA into virions. However, these results also suggest that the influenza A virus and influenza B virus cytoplasmic tail sequences share common features that lead to the production of infectious virus. Transfectant virus was obtained with all cytoplasmic tail mutants generated by site-directed mutagenesis of the influenza A virus tail, except for the mutant resulting from substitution of the conserved proline residue, presumably because of its contribution to the secondary structure of the tail. No virus was rescued when the cytoplasmic tail was deleted, indicating that the cytoplasmic tail is essential for production of the virus. The virulence of the transfectant viruses in mice was directly proportional to the amount of NA incorporated. The importance of the NA cytoplasmic tail in virus assembly and virulence has implications for use in developing antiviral strategies.

Amino Acid Sequence↗