bluuebunny/crossref_metadata_2025 huggingface dataset:
A Two-Component
covRS
Regulatory System Regulates Expression of Fructosyltransferase and a Novel Extracellular Carbohydrate in
Streptococcus mutans
Authors: Lee Song F. , Delaney Gillian D. , Elkhateeb Mohammad
Published: June 2004

The expression of fructosyltransferase (FTF), the enzyme that synthesizes fructan from sucrose, is regulated in the cariogenic bacterium
Streptococcus mutans
. However, the exact mechanism of FTF regulation is unknown. In this study, the role of a two-component regulatory system (
covRS
) in FTF expression was investigated. A CovR-defective mutant of
S. mutans
NG8 was constructed by homologous recombination. By use of immunoblotting, the mutant was shown to overexpress FTF in the absence of sucrose, while the wild type and a
covRS
-complemented mutant showed sucrose-inducible FTF expression. Reverse transcription-PCR showed that the
ftf
transcript levels were increased in the
covR
mutant, suggesting regulation at the transcriptional level. The
covR
mutant was also found to overproduce extracellular carbohydrate, and this phenotype was reversed by
covRS
complementation. Paper chromatographic studies and chemical tests showed that the extracellular carbohydrate contained glucose and glucuronic acid but not fructose. These results suggest that the extracellular carbohydrate was not fructan. The production of a glucose- and glucuronic acid-containing extracellular carbohydrate has not been reported for
S. mutans
and may be considered novel. In conclusion, the results indicate that the expression of FTF and a glucose- and glucuronic acid-containing carbohydrate was negatively regulated by the
covRS
two-component regulatory system in
S. mutans
.
The Two Murein Lipoproteins ofSalmonella entericaSerovar Typhimurium Contribute to the Virulence of the Organism
Authors: Sha J. , Fadl A. A. , Klimpel G. R. , Niesel D. W. , Popov V. L. , Chopra A. K.
Published: June 2004

Septic shock due toSalmonellaand other gram-negative enteric pathogens is a leading cause of death worldwide. The role of lipopolysaccharide in sepsis is well studied; however, the contribution of other bacterial outer membrane components, such as Braun (murein) lipoprotein (Lpp), is not well defined. The genome ofSalmonella entericaserovar Typhimurium harbors two copies of the lipoprotein (lpp) gene. We constructed a serovar Typhimurium strain with deletions in both copies of thelppgene (lpp1andlpp2) by marker exchange mutagenesis. The integrity of the cell membrane and the secretion of the effector proteins through the type III secretion system were not affected in thelppdouble-knockout mutant. Subsequently, the virulence potential of this mutant was examined in a cell culture system using T84 intestinal epithelial and RAW264.7 macrophage cell lines and a mouse model of salmonellosis. Thelppdouble-knockout mutant was defective in invading and inducing cytotoxic effects in T84 and RAW264.7 cells, although binding of the mutant to the host cell was not affected when compared to the wild-type (WT) serovar Typhimurium. The motility of the mutant was impaired, despite the finding that the number of flagella was similar in thelppdouble knockout mutant and the WT serovar Typhimurium. Deletion in thelppgenes did not affect the intracellular survival and replication ofSalmonellain macrophages and T84 cells. Induction of the proinflammatory cytokines tumor necrosis factor alpha and interleukin-8 (IL-8) was significantly reduced in macrophages and T84 cells infected with thelppdouble-knockout mutant. The levels of IL-8 remained unaffected in T84 cells when infected with either live or heat-killed WT andlppmutant, indicating that invasion was not required for IL-8 production and that Toll-like receptor 2 signaling might be affected in the Lpp double-knockout mutant. These effects of the Lpp protein could be restored by complementation of the isogenic mutant. Thelppdouble-knockout mutant was avirulent in mice, and animals infected with this mutant were protected from a lethal challenge dose of WT serovar Typhimurium. The severe combined immunodeficient mice, on the other hand, were susceptible to infection by thelppdouble-knockout mutant. The serovar Typhimurium mutants from which only one of thelpp(lpp1orlpp2) genes was deleted were also avirulent in mice. Taken together, our data indicated that Lpp specifically contributed to the virulence of the organism.
Chemotherapy for Schistosomiasis in Ugandan Fishermen: Treatment Can Cause a Rapid Increase in Interleukin-5 Levels in Plasma but Decreased Levels of Eosinophilia and Worm-Specific Immunoglobulin E
Authors: Fitzsimmons Colin M. , Joseph Sarah , Jones Frances M. , Reimert Claus M. , Hoffmann Karl F. , Kazibwe Francis , Kimani Gachuhi , Mwatha Joseph K. , Ouma John H. , Tukahebwa Edridah M. , Kariuki Henry. C. , Vennervald Birgitte J. , Kabatereine Narcis B. , Dunne David W.
Published: June 2004

Chemotherapy for blood-dwelling schistosomes kills the worms and exposes parasite antigen to the circulation. In many people from areas of endemicity, this treatment increases parasite-specific immunoglobulin E (IgE) and other Th2 responses in the months following therapy, responses that have been associated with subsequent resistance to reinfection. Here we investigate much earlier changes in immune reactions after praziquantel therapy inSchistosoma mansoni-infected fishermen working in an area of high transmission in Uganda. The subjects gave blood before treatment and at 1 and 21 days posttreatment. Blood cultures were incubated with schistosome soluble worm antigen (SWA) or soluble egg antigen (SEA). Interleukin-4 (IL-4), IL-5, IL-10, IL-13, gamma interferon, and transforming growth factor β levels were measured in the cultures and in plasma. A marked transient increase in plasma IL-5 levels was observed in 75% of the subjects (n= 48) by 1 day posttreatment. This response was dependent on pretreatment intensity of infection and was accompanied by a transient decrease in eosinophil numbers. One day posttreatment, blood cultures from the 16 subjects with the greatest increase in plasma IL-5 level (>100 pg/ml) displayed reduced IL-5, IL-13, and IL-10 responses to SWA, and in contrast to the rest of the cohort, these high-IL-5 subjects displayed reduced levels of SWA-specific IgE in plasma 21 days posttreatment. Twenty months after treatment, the intensity of reinfection was positively correlated with the increase in plasma IL-5 level seen 1 day posttreatment. These studies describe the heterogeneity in early immune reactions to treatment, identifying subgroups who have different patterns of reaction and who may have different capacities to mount the responses that have been associated with resistance to reinfection.
Inducible Nitric Oxide Synthase Is Not Essential for Control ofTrypanosoma cruziInfection in Mice
Authors: Cummings Kara L. , Tarleton Rick L.
Published: June 2004

Immune control of many intracellular pathogens, includingTrypanosoma cruzi, is reported to be dependent on the production of nitric oxide. In this study, we show that mice deficient in inducible nitric oxide synthase (iNOS or NOS2) exhibit resistance toT. cruziinfection that is comparable to that of wild-type mice. This is the case for two iNOS-deficient mouse strains, Nos2tm1Lauand Nos2 N5, infected with the Brazil or Tulahuen strain ofT. cruzi. In all cases, blood parasitemia, tissue parasite load, and survival rates are similar between wild-type and iNOS-deficient mice. In contrast, both wild-type and Nos2tm1Laumice died within 32 days postinfection when treated with the nitric oxide synthase inhibitor aminoguanidine. Increased transcription of NOS1 or NOS3 is not found in iNOS-knockout (KO) mice, indicating that the absence of nitric oxide production through iNOS is not compensated for by increased production of other NOS isoforms. However, Nos2tm1Laumice exhibit enhanced expression of tumor necrosis factor alpha, interleukin-1, and macrophage inflammatory protein 1α compared to that of wild-type mice, and these alterations may in part compensate for the lack of iNOS. These results clearly show that iNOS is not required for control ofT. cruziinfection in mice.
Antibodies Produced in Response toCryptococcus neoformansPulmonary Infection in Mice Have Characteristics of Nonprotective Antibodies
Authors: Zaragoza Oscar , Casadevall Arturo
Published: June 2004

Murine cryptocococcal pulmonary infection elicited serum immunoglobulin M (IgM) and IgG to the capsular polysaccharide, but only IgG stained yeast cells in alveoli. Both isotypes produced punctuate immunofluorescence patterns on yeast cells like those of nonprotective antibodies. The difficulties involved in associating humoral immunity with protection in murine cryptocococcal infection could reflect nonprotective antibody responses.
Numerical assessment and prediction method for the chemico-mechanical deterioration of ASR-affected concrete structures
Authors: Li Kefei , Coussy Olivier
Published: June 2004

The degradation of concrete structures by the alkali–silica reaction (ASR) is highlighted in recent years in civil engineering. To quantify the deterioration of concrete structures, one has the behavior modeling of affected concrete proposed by multiple approaches, on one side, and the expansion of the structure measured by the in situ engineers, on the other side. The task is to determine the progressive structure degradation from these two supports by a systematical method. Nevertheless, this method should not depend on the employed model so that a better one can always be added to the assessment. Moreover, one should also be able to analyze the credibility of the assessment result. All these points differentiate between a laboratory expertise and a structural assessment. This article proposes a time-scaled evaluation method and formulates it into an inverse problem. With an adopted chemico-mechanical model for ASR expansion and the analyzed structure observation data, the authors give the numerical solution for the established inverse problem. An ASR-affected suspension bridge is then evaluated using a finite element code for its durability by the achieved method. Some further discussions are given in the last section of this article. Key words: alkali–silica reaction, modeling, inverse problem, assessment, suspension bridge, durability.
A driver visual attention model. Part 1. Conceptual framework
Authors: Lim Clark , Sayed Tarek , Navin Francis
Published: June 2004

This paper describes a driver visual attention model that gathers information based on a selective process so that events such as distractions can be modelled. This model contains visual information gathering capabilities and visual attention mechanisms based on subjective and objective factors. As the research focused on applicability, the model's framework was designed to be integrated as a component processor within a microscopic computer traffic simulation. The model determines visual attention using two mechanisms: internal and external focusing. The internal focusing mechanism is a proactive attention director. This subjective-based mechanism moves the head and eye to a general direction such that information relevant to the current task is actively searched for based on the driver's expectancy. The external focusing mechanism is a reactive attention director based on the characteristics of the objects within the driver's visual field. External control allows for distractions to be modelled, since irrelevant information may objectively demand higher attention than relevant information. For each visible object, these two control mechanisms determine its attention demand value (ADV). Visual information from the object with the highest ADV is then acquired. The ADV also plays a role in determining the information processing time and amount of attention allocated to driving. With the use of this model and its input of various internal and external variables, it is hoped that a variety of driver types with varying visual abilities (age-related, intoxicated) can be simulated within visually detailed environments.Key words: driver behaviour, visibility, driver visual attention, attention demand value, driver simulation models
A survey of indigenous microbial hydrocarbon degradation genes in soils from Antarctica and Brazil
Authors: Luz A P , Pellizari V H , Whyte L G , Greer C W
Published: June 2004

Total community DNA from 29 noncontaminated soils and soils impacted by petroleum hydrocarbons and chloro-organics from Antarctica and Brazil were screened for the presence of nine catabolic genes, encoding alkane monooxygenase or aromatic dioxygenases, from known bacterial biodegradation pathways. Specific primers and probes targeting alkane monooxygenase genes were derived from Pseudomonas putida ATCC 29347 (Pp alkB), Rhodococcus sp. strain Q15 (Rh alkB1, Rh alkB2), and Acinetobacter sp. ADP-1 (Ac alkM). In addition, primers and probes detecting aromatic dioxygenase genes were derived from P. putida ATCC 17484 (ndoB), P. putida F1 (todC1), P. putida ATCC 33015 (xylE and cat23), and P. pseudoalcaligenes KF707 (bphA). The primers and probes were used to analyze total community DNA extracts by using PCR and hybridization analysis. All the catabolic genes, except the Ac alkM, were detected in contaminated and control soils from both geographic regions, with a higher frequency in the Antarctic soils. The alkane monooxygenase genes, Rh alkB1 and Rh alkB2, were the most frequently detected alk genes in both regions, while Pp alkB was not detected in Brazil soils. Genes encoding the aromatic dioxygenases toluene dioxygenase (todC1) and biphenyl dioxygenase (bphA) were the most frequently detected in Antarctica, and todC1 and catechol-2,3-dioxygenase (cat23) were the most frequent in Brazil soils. Hybridization analysis confirmed the PCR results, indicating that the probes used had a high degree of homology to the genes detected in the soil extracts and were effective in detecting biodegradative potential in the indigenous microbial population.Key words: catabolic genes, anthropogenic compounds, petroleum hydrocarbons, alkane monooxygenases, aromatic dioxygenases.
Isolation of antibiotic-resistant and antimetabolite-resistant mutants ofFrankiastrains EuI1c and Cc1.17
Authors: Myers Anna K , Tisa Louis S
Published: June 2004

Antibiotic-resistant and antimetabolite-resistant mutants of the nitrogen-fixing symbiotic bacterium Frankia were isolated to provide strains with genetic backgrounds amenable to genetic analysis. The lethal and mutagenic effects of ethyl methanesulfonate (EMS) and UV light on four Frankia strains were investigated. UV irradiation or EMS treatment of strain EuI1c cells resulted in the formation of two different colony types: rough and smooth. The smooth colonies were conditional sporulation mutants. In the case of EMS-induced cells of strain Cc1.17, resistance to lincomycin, ampicillin, and 5-fluorouracil occurred at a frequency of 1 × 10–5, 1 × 10–5, and 4 × 10–5, respectively. The lincomycin-resistant mutants produced a yellow–tan pigment that was released into the growth medium. Resistance to tetracycline and lincomycin with EMS-induced cells of strain EuI1c occurred at a frequency of 3.2 × 10–3and 4.7 × 10–4, respectively. These strains will be useful for the development of genetic methods for Frankia.Key words: genetics, genetic markers, Frankia, actinorhizal symbiosis, nitrogen fixation, mutagenesis, EMS, UV light.
Inhibition ofPseudomonas aeruginosaadhesion to fibronectin by PA-IL and monosaccharides: involvement of a lectin-like process
Authors: Rebiere-Huët Julie , Martino Patrick Di , Hulen Christian
Published: June 2004

Pseudomonas aeruginosa adherence to fibronectin has been shown to be important to bacterial colonization and infection. To better understand the mechanisms involved in this interaction, the role of the carbohydrate moiety of the fibronectin molecule in P. aeruginosa adhesion was studied. Strain NK 125 502 adhered to immobilized fibronectin with an adherence index of 4.8 × 105CFU/µg. Periodic oxidation of fibronectin markedly reduced the adhesion of P. aeruginosa, while a neuraminidase treatment increased bacteria adhesion. N-Acetylgalactosamine, N-acetylglucosamine, sialic acid, and also lectin PA-IL worked as efficient inhibitors in adhesion assays: 59%, 70.7%, 100%, and 60% of inhibition, respectively. We have demonstrated here the involvement of a lectin-like process in the interaction of P. aeruginosa NK 125 502 with immobilized fibronectin.Key words: Pseudomonas aeruginosa, fibronectin, adherence, lectins.
Ethnic differences in the frequency of distribution of serum cholinesterase activity in the Iranian population
Authors: Vahdati-Mashhadian Nasser , Hassanzadeh Mohammad K , Hosseini Javad , Saffareshargh Ali A
Published: June 2004

One thousand Iranians belonging to 5 different Iranian ethnic groups were tested for butyrylcholinesterase (BChE) activity and phenotype. The phenotype was measured as percent inhibition in the presence of dibucaine. It was found that the Iranian population had an extraordinarily high frequency of the atypical variant of butyrylcholinesterase. 70% to 80% of Iranians carried the atypical mutation (Asp70Gly) on one allele. This contrasts with European and American populations where only 4% carry the atypical allele. The atypical variant of butyrylcholinesterase is known to be associated with prolonged apnea after administration of the muscle relaxants succinylcholine and mivacurium, and is also thought to be associated with abnormal sensitivity to cocaine toxicity. This study demonstrates that the ethnic background of a person has an important role in a person's response to drugs.Key words: butyrylcholinesterase, dibucaine number, heterozygous genes, different Iranian ethnics, metabolic polymorphism.
Enhancement of hybrid-fiber types in rat soleus muscle after clenbuterol administration during hindlimb unloading
Authors: Picquet F , De-Doncker L , Falempin M
Published: June 2004

Our objective was to determine the effects of a clenbuterol (CB) treatment orally administered (2 mg per kg) to rats submitted to 14 days of hindlimb unloading (HU). The morphological and the contractile properties as well as the myosin heavy chain isoforms contained in each fiber type were determined in whole soleus muscles. As classically described after HU, a decrease in muscle wet weight and in body mass associated with a loss of muscular force, an evolution of the contractile parameters towards those of a fast muscle type, and the emergence of fast myosin heavy chain isoforms were observed. The CB treatment in the HU rats helped reduce the decrease in 1) muscle and body weights, 2) force and 3) the proportion of slow fibers, without preventing the emergence of fast myosin isoforms. Clenbuterol induced a complex remodelling of the muscle typing promoting the combination of both slow and fast myosin isoforms within one fiber. To conclude, our data demonstrate that CB administration partially counteracts the effects produced by HU, and they allow us to anticipate advances in the treatment of muscular atrophy.Key words: β2 agonist, clenbuterol, soleus, contractile parameters, myosin, immunohistochemistry, simulated microgravity, countermeasure.
Sex ratio estimation and survival analysis for Orthetrum coerulescens (Odonata, Libellulidae)
Authors: Kéry M , Juillerat L
Published: June 2004

There is controversy over whether uneven sex ratios observed in mature dragonfly populations are a mere artifact resulting from the higher observability of males. Previous studies have at best made indirect inference about sex ratios by analysis of survival or recapture rates. Here, we obtain direct estimates of sex ratio from capturerecapture data based on the CormackJollySeber model. We studied Orthetrum coerulescens (Fabricius, 1798) at three sites in the Swiss Jura Mountains over an entire activity period. Recapture rates per 5-day interval were 3.5 times greater for males (0.67, SE 0.02) than for females (0.19, SE 0.02). At two sites, recapture rate increased over the season for males and was constant for females, and at one site it decreased with precipitation for both sexes. In addition, recapture rate was higher with higher temperature for males only. We found no evidence for higher male survival rates in any population. Survival per 5-day interval for both sexes was estimated to be 0.77 (95% CI 0.750.79) without significant site-or time-specific variation. There were clear effects of temperature (positive) and precipitation (negative) on survival rate at two sites. Direct estimates of sex ratios were not significantly different from 1 for any time interval. Hence, the observed male-biased sex ratio in adult O. coerulescens was an artifact resulting from the better observability of males. The method presented in this paper is applicable to sex ratio estimation in any kind of animal.
Changes in the elemental composition of the stomach contents of the opossum shrimp Mysis relicta during diel vertical migration
Authors: Lasenby David , Shi Youqing
Published: June 2004

Clear differences in the elemental composition of the stomachs of adult Mysis relicta Lovén captured on or near the lake bottom during the day and those captured at night in the water column were observed using laser ablation – inductively coupled plasma – mass spectrometry. The elemental composition of the stomachs of mysids captured at night indicated that they were feeding on zooplankton and algae, whereas the stomachs of those captured during the day indicated sediment feeding. These results suggest that lake sediments may be a significant part of the mysid diet and that sediments transported vertically as gut contents may contribute to the transport of elements into the water column.
Species-level differentiation of two cryptic species pairs of wild cavies, generaCaviaandGalea, with a discussion of the relationship between social systems and phylogeny in the Caviinae
Authors: Trillmich Fritz , Kraus Cornelia , Künkele Joachim , Asher Matthias , Clara Mario , Dekomien Gabriele , Epplen Jörg T , Saralegui Alvaro , Sachser Norbert
Published: June 2004

Two little-known species of guinea-pig from the genera Cavia and Galea (Cavia magna Ximénez, 1980 and Galea sp. nov.) have recently been studied in more detail with respect to their behavior, social structure, and mating system. To determine the specific distinctness of these little-known species from Cavia aperea Erxleben, 1777 and Galea musteloides Meyen, 1832, crossbreeding between species was tried and it demonstrated that the two Cavia species will rarely cross in captivity to produce hybrids of much reduced fertility, whereas the Galea species could not be crossed. To analyze the phylogenetic position of C. magna and Galea sp. nov., we present an analysis based on major parts of the 12S (778 base pair) and 16S genes of mitochondrial RNA (1435 base pair) in conjunction with corresponding data on all other genera of the Caviinae. We also determined the relationship between C. magna and the sympatric wild guinea-pig (C. aperea) and its domestic form (Cavia aperea f. porcellus (Linnaeus, 1758)). Phylogenetic and distance analysis of all genera of cavies (Cavia (two species), Galea (two species), Kerodon, Microcavia) showed the close relationship of C. magna with C. aperea and the latter's particularly low genetic distance to C. aperea f. porcellus. Galea sp. nov. differed markedly from G. musteloides. Of the three genera, Galea appears most distinct. The genus Kerodon clustered with the genus Hydrochaeris, supporting the previous conclusion by Rowe and Honeycutt (2002. Mol. Biol. Evol. 19: 263–277) regarding the placement of the genus Hydrochaeris within the Caviidae. Recently published data on the social systems of the above-mentioned cavy species, however, show their great inter- and intra-specific social flexibility and contradict the interpretation of the same authors about a simple relationship between phylogeny and social systems in the Caviidae.
Tree swallow reproductive investment, stress, and parasites
Authors: Shutler Dave , Mullie Adele , Clark Robert G
Published: June 2004

We reduced or increased tree swallow, Tachycineta bicolor (Vieillot, 1808), clutch sizes by three eggs (50% of modal clutch size) to test experimentally for relationships between stress and parasite loads. In the first year of the study (1996), we enumerated two measures of stress (granulocyte to non-granulocyte ratios and heterophil to lymphocyte ratios), blood parasites, and ectoparasites living on birds (and not in nesting material). Stress indices increased for parents, but not for nestlings, associated with larger broods. Only one blood parasite (a trypanosome) was detected in blood smears from 221 different individuals. On individual birds, we found a median of 0 fleas, 0 lice, and 7 feather mites. In the second study (1998), we focused on parasites living in nesting material. Here, we found a median of 106 fleas and, of the parasites we observed, these probably had the greatest potential impact on the birds. Per capita flea loads were higher in nests that contained more young. However, despite higher stress to parents and higher per capita flea loads in enlarged broods, flea numbers were not associated with smaller nestlings or with reduced fledging success.
Genetic diversity and management of Nearctic rock ptarmigan (Lagopus mutus)
Authors: Holder Karen , Montgomerie Robert , Friesen Vicki L
Published: June 2004

Though the rock ptarmigan, Lagopus mutus (Montin, 1776), is a relatively common breeding bird in arctic regions worldwide, several Nearctic insular populations have become extinct or threatened in the past 250 years. In this study, we use patterns of DNA sequence variation in the mitochondrial control region and a nuclear intron (GAPDH) to reexamine the evolutionary history of Nearctic rock ptarmigan populations as a basis for conservation and management. The extent of genetic diversity within currently recognized subspecies varies widely, with many nonmigratory insular subspecies genetically invariant and continental subspecies moderately diverse. Our analyses suggest at least six evolutionarily significant units (ESUs) in the Nearctic and Iceland, four of which correspond to recognized subspecies: Lagopus mutus evermanni (Elliot, 1896) on Attu I., Alaska, Lagopus mutus welchi (Brewster, 1885) on Newfoundland, Lagopus mutus rupestris (Gmelin, 1789) in the Canadian Arctic, and Lagopus mutus islandorum (Faber, 1822) on Iceland. A fifth ESU comprises three central Aleutian subspecies. The remaining subspecies of the Aleutian archipelago, along with Lagopus mutus nelsoni (Stejneger, 1884) of mainland Alaska and Lagopus mutus captus (Peters, 1934) of Ellesmere I., Nunavut, constitute a sixth ESU, which we further subdivide into three management units based on patterns of genetic substructuring and geographic barriers to immigration.
Foraging patterns of male and female Double-crested Cormorants nesting in the Columbia River estuary
Authors: Anderson Cynthia D , Roby Daniel D , Collis Ken
Published: June 2004

The nesting colony of Double-crested Cormorants, Phalacrocorax auritus (Lesson, 1831), on East Sand Island in the Columbia River estuary is currently the largest for this species on the Pacific Coast of North America. We used radiotelemetry to investigate the spatial and temporal foraging patterns of nesting cormorants to better understand how this colony of piscivores meets its resource needs. We determined that nesting adults tended to forage >5 km from the colony and foraging distribution was distinctly different between the sexes. On average, males commuted nearly twice the distance to forage compared with females. Females typically foraged in the estuarine mixing zone, reportedly the region of the estuary with the greatest densities of schooling fishes, while males tended to commute more than 15 km to forage in the freshwater zone. Foraging intensity of both sexes varied by time of day, tide stage, and tide series; foraging generally intensified during ebb tides. These gender differences in foraging patterns, combined with the ability to forage at considerable distance from the colony on a wide variety of prey, may allow this large and growing colony to remain productive while potentially competing for food with many thousands of other piscivorous waterbirds that use East Sand Island.
Factors influencing the acquisition of rodent carrion by vertebrate scavengers and decomposers
Authors: DeVault Travis L , Brisbin, Jr. I Lehr , Rhodes, Jr. Olin E
Published: June 2004

Vertebrate scavengers and decomposers compete for animal carcasses in all temperate and tropical ecosystems. We examined the influence of carcass size, forest type, and air temperature on the fate of rodent carcasses at the Savannah River Site, South Carolina, USA. Three hundred rodent carcasses were placed at random locations in forested habitats and scavengers were identified using remote photography. Seventeen species of vertebrates removed 104 of 300 (35%) rodent carcasses over a year. Raccoons (Procyon lotor (Linnaeus, 1758)) and Virginia opossums (Didelphis virginiana Kerr, 1792) scavenged most frequently. For scavenged carcasses, the mean time to carcass removal was 2.58 days after placement. Carcass acquisition by scavengers and decomposers was influenced moderately by forest type and carcass size, although ambient air temperature considerably influenced the fate of carcasses. Vertebrates removed fewer carcasses as temperatures increased: only 28 of 144 (19%) carcasses were scavenged when temperatures exceeded 17 °C. The temporal pattern of carcass removal by vertebrates, however, did not vary with temperature. Consistent rates of carcass removal by vertebrates across the year and increased activity by insects during warm weather led to elevated levels of decomposition during summer months. This study confirms the complexity and dynamic nature of competitive relationships among scavengers and decomposers.
Chemosensory predator recognition induces defensive behavior in the slow-worm (Anguis fragilis)
Authors: Cabido Carlos , Gonzalo Adega , Galán Pedro , Martín José , López Pilar
Published: June 2004

Many antipredator adaptations are induced or mediated by the ability of the prey to recognize chemical cues from the predator. This ability is particularly advantageous for organisms whose environment precludes the effective use of other sensory systems, such as fossorial lizards. We tested the ability of the slow-worm, Anguis fragilis Linnaeus, 1758, a semifossorial legless lizard, to detect and discriminate chemical stimuli arising from potential predators. We compared rates of tongue-flicks to swabs impregnated with scents from the smooth snake (Coronella austriaca Laurenti, 1768), a sympatric predator, the grass snake (Natrix natrix (Linnaeus, 1758)), a sympatric but non-saurophagous predator, and the three-toed skink (Chalcides striatus (Cuvier, 1829)), a sympatric insectivorous, and thus innocuous, skink. Differential tongue-flick rates suggest that scents of smooth snakes were recognized by slow-worms. Moreover, scents of smooth snakes were quickly avoided and elicited defensive behaviors much more often than any other scent, suggesting that chemical cues are a reliable means of assessing the snake's presence. These chemosensory capacities would be evolutionarily advantageous to avoid predation by snakes and are likely to represent a component of the suite of adaptations associated with low-visibility habitats.
Host and host-site specificity of bat flies (Diptera: Streblidae and Nycteribiidae) on Neotropical bats (Chiroptera)
Authors: ter Hofstede Hannah M , Fenton M Brock , Whitaker, Jr. John O
Published: June 2004

Ectoparasite host specificity can be influenced by factors such as the degree of host isolation and ectoparasite mobility. Host-site specificity can result from factors such as proximity to mates, competition, and host grooming behaviour. Ectoparasitic bat flies on bats from the Lamanai area of Belize were collected from hosts captured in mist nets to determine host specificity and host-site specificity. Bat grooming behaviour was also recorded and quantified. From 455 bats (25 species in five families), 773 bat flies (32 species in two families) were collected. Of 32 bat fly species, 25 were only found on 1 bat species, 6 were found on 2 species of the same genus, and 1 was found on 2 species of different genera (the latter appearing to be an accidental association). Specificity of the bat flies tended to follow the taxonomy of the bat hosts, not the ecological isolation of the host species, since bat species that often roost in polyspecific groups did not share bat fly species. Mobility of the bat flies was not related to host specificity. Host-site specificity of bat flies occurred for either fur or membrane on the host, and long hind legs and ctenidia appear to be morphological adaptations for living in fur. Bat grooming behaviour was consistent with the assumptions of a simulation model, which suggested that host grooming could be responsible for host-site segregation of bat flies.
Unique temperature-activated neurons from pit viper thermosensors
Authors: Pappas Todd C. , Motamedi Massoud , Christensen Burgess N.
Published: June 2004

Rattlesnakes, copperheads, and other pit vipers have highly sensitive heat detectors known as pit organs, which are used to sense and strike at prey. However, it is not currently known how temperature change triggers cellular and molecular events that activate neurons supplying the pit organ. We dissociated and cultured neurons from the trigeminal ganglia (TG) innervating the pit organs of the Western Diamondback rattlesnake ( Crotalus atrox) and the copperhead ( Agkistrodon contortix) to investigate electrophysiological responses to thermal stimuli. Whole cell voltage-clamp recordings indicated that 75% of the TG neurons from C. atrox and 74% of the TG neurons from A. contortix showed a unique temperature-activated inward current ( IΔT). We also found an IΔT-like current in 15% of TG neurons from the common garter snake, a species that does not have a specialized heat-sensing organ. A steep rise in the current-temperature relationship of IΔT started just below 18°C, and cooling temperature-responsive TG neurons from 20°C resulted in an outward current, suggesting that IΔT is on at relatively low temperatures. Ion substitution and Ca2+ imaging experiments indicated that IΔT is primarily a monovalent cation current. IΔT was not sensitive to capsaicin or amiloride, suggesting that the current did not show similar pharmacology to other mammalian heat-sensitive membrane proteins. Our findings indicate that a novel temperature-sensitive conductance with unique ion permeability and low-temperature threshold is expressed in TG neurons and may be involved in highly sensitive heat detection in snakes.
Neutralization of tumor necrosis factor-α reverses insulin resistance in skeletal muscle but not adipose tissue
Authors: Borst Stephen E. , Lee Youngil , Conover Christine F. , Shek Eugene W. , Bagby Gregory J.
Published: June 2004

We examined the possible role of tumor necrosis factor-α (TNF-α) as a mediator of insulin resistance in maturing male Sprague-Dawley rats. Rats were treated either with goat anti-murine TNF-α IgG (anti-TNF-α) or goat nonimmune IgG (NI) for 7 days. Vascular catheters were implanted, and rats were fasted overnight before hyperinsulinemic euglycemic clamp (HUC) studies were performed. TNF-α neutralization increased the rate of glucose infusion required to maintain euglycemia by 68%. Insulin-stimulated glucose transport into individual tissues was measured after bolus administration of 2-deoxy-[14C]glucose during HUC. Anti-TNF-α administration increased glucose transport in muscles composed predominantly of fast-twitch fibers: white gastrocnemius muscle (68% increase) and tibialis anterior muscle (64% increase). There were nonsignificant trends for increased glucose transport in the slow-twitch soleus muscle and in the mixed-fiber red gastrocnemius muscle. Glucose transport was unchanged in visceral and subcutaneous fat. Anti-TNF treatment did not alter body weight, muscle mass, or fat mass. Anti-TNF-α did not alter the distribution of the 17-kDa and 26-kDa forms of TNF-α in either muscle or fat. However, anti-TNF-α treatment caused an ∼50% reduction in the secretion of TNF-α bioactivity in vitro by explants of visceral and subcutaneous fat. We conclude that TNF-α neutralization reversed insulin resistance substantially in fast-twitch muscle and may have done so in other muscles, while having little effect in fat. TNF-α neutralization was accompanied by reduced TNF-α bioactivity without tissue depletion of TNF-α protein.
Downregulation of renal vasopressin V2 receptor and aquaporin-2 expression parallels age-associated defects in urine concentration
Authors: Tian Ying , Serino Ryota , Verbalis Joseph G.
Published: June 2004

Renal concentrating ability is known to be impaired with aging. The antidiuretic hormone AVP plays an important role in renal water excretion by regulating the membrane insertion and abundance of the water channel aquaporin-2 (AQP2); this effect is primarily mediated via the V2 subtype of the AVP receptor (V2R). This study evaluated the hypothesis that decreased renal sensitivity to AVP, with subsequent altered renal AQP2 expression, contributes to the reduced urinary concentrating ability with aging. Our results show that under baseline conditions, urine osmolality is significantly lower in aged Fischer 344 and Brown-Norway F1 hybrid (F344BN) rats despite equivalent plasma AVP concentrations as in young rats. Levels of kidney V2R mRNA expression and AQP2 abundances were also significantly decreased in aged F344BN rats, as was AQP2 immunostaining in collecting duct cells. In response to moderate water restriction, urine osmolality increased by significantly lesser amounts in aged F344BN rats compared with young rats despite similar increases in plasma AVP levels. Moderate water restriction induced equivalent relative increases in renal AQP2 abundances in all age groups but resulted in significantly lower abundances in total kidney AQP2 protein in aged compared with young F344BN rats. These results therefore demonstrate a functional impairment of renal concentrating ability in aged F344BN rats that is not due to impaired secretion of AVP but rather appears to be related to impaired responsiveness of the kidney to AVP that is secondary, at least in part, to a downregulation of renal V2R expression and AQP2 abundance.
Presynaptic Calcium Measurements at Physiological Temperatures Using a New Class of Dextran-Conjugated Indicators
Authors: Beierlein Michael , Gee Kyle R. , Martin Vladimir V. , Regehr Wade G.
Published: June 2004

Presynaptic calcium (Capre) has been studied extensively because of its role in triggering and modulating neurotransmitter release. Although calcium regulation and calcium-driven processes can be strongly temperature dependent, technical difficulties have limited most studies of Capre to temperatures well below the physiological range. Here we assessed the use of membrane-permeant acetoxymethyl (AM) indicators and dextran-conjugated indicators for measuring Capre at physiological temperatures. A comparison of these two types of indicators loaded into parallel fibers of rat cerebellar slices revealed striking differences. AM indicators were rapidly extruded from axons and presynaptic terminals and therefore cannot be used for long-term measurements at high temperatures. In contrast, dextran-conjugated indicators were retained within parallel fibers and are therefore well suited to measuring Capre at physiological temperatures. The limited number of dextran indicators available prompted us to synthesize three new indicators that show peak emission in the red (575–600 nm). These indicators allow for simultaneous use of multiple calcium indicators that can be readily distinguished on the basis of excitation and emission wavelengths, use of excitation and emission wavelengths that are relatively insensitive to tissue autofluorescence, and measurements in systems with expression of green fluorescent protein (GFP). Thus we find that dextran-conjugated indicators are well suited to long-term recordings of Capre at physiological temperatures and that the development of new red indicators greatly extends their utility.
Layer Variations of Long-Term Depression in Rat Visual Cortex
Authors: Rao Yan , Daw Nigel W.
Published: June 2004

In vitro long-term depression (LTD) is thought to be a model for the loss of cortical responsiveness to an eye deprived of vision during the critical period. Using whole cell recording, the present study investigates the mechanisms of LTD in vitro across layers in developing rat visual cortex. LTD was induced in layers II/III, V, and VI but not layer IV with 10-min 1-Hz stimulation paired with postsynaptic depolarization. LTD in layers II/III and V could be blocked by the N-methyl-d-aspartate (NMDA) receptor antagonist d-aminophosphonovaleric acid (d-AP5) but not by 100 μM (2S)-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495), a metabotropic glutamate receptor inhibitor. In contrast, LTD in layer VI was blocked by 100 μM LY341495 and (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) but not d-AP5 and partially blocked by application of guanosine 5′- O-(2-thiodiphosphate) thilothium salt (GDP-β-S) in patch pipette, suggesting an involvement of postsynaptic group I metabotropic glutamate receptors (mGluRs). These results indicate that LTD in developing rat visual cortex varies with layer: LTD was absent in layer IV, suggesting a unique plasticity mechanism at geniculocortical synapses; LTD in layers II/III and V depends on NMDA receptors but not mGluRs, and LTD in layer VI requires mGluRs but not NMDA receptors.
Amyloid β Prevents Activation of Calcium/Calmodulin-Dependent Protein Kinase II and AMPA Receptor Phosphorylation During Hippocampal Long-Term Potentiation
Authors: Zhao Danyun , Watson Joseph B. , Xie Cui-Wei
Published: June 2004

Accumulation of amyloid β-peptides (Aβ) in the brain has been linked with memory loss in Alzheimer's disease and its animal models. However, the synaptic mechanism by which Aβ causes memory deficits remains unclear. We previously showed that acute application of Aβ inhibited long-term potentiation (LTP) in the hippocampal perforant path via activation of calcineurin, a Ca2+-dependent protein phosphatase. This study examined whether Aβ could also inhibit Ca2+/calmodulin dependent protein kinase II (CaMKII), further disrupting the dynamic balance between protein kinase and phosphatase during synaptic plasticity. Immunoblot analysis was conducted to measure autophosphorylation of CaMKII at Thr286and phosphorylation of the GluR1 subunit of AMPA receptors in single rat hippocampal slices. A high-frequency tetanus applied to the perforant path significantly increased CaMKII autophosphorylation and subsequent phosphorylation of GluR1 at Ser831, a CaMKII-dependent site, in the dentate area. Acute application of Aβ1–42inhibited dentate LTP and associated phosphorylation processes, but was without effect on phosphorylation of GluR1 at Ser845, a protein kinase A-dependent site. These results suggest that activity-dependent CaMKII autophosphorylation and AMPA receptor phosphorylation are essential for dentate LTP. Disruption of such mechanisms could directly contribute to Aβ-induced deficits in hippocampal synaptic plasticity and memory.
Two Distinct Types of Noisy Oscillators in Electroreceptors of Paddlefish
Authors: Neiman Alexander B. , Russell David F.
Published: June 2004

Our computational analyses and experiments demonstrate that ampullary electroreceptors in paddlefish ( Polyodon spathula) contain 2 distinct types of continuously active noisy oscillators. The spontaneous firing of afferents reflects both rhythms, and as a result is stochastically biperiodic (quasiperiodic). The first type of oscillator resides in the sensory epithelia, is recorded as approximately 26 Hz and ±70 μV voltage fluctuations at the canal skin pores, and gives rise to a noisy peak at fe≈ 26 Hz in power spectra of spontaneous afferent firing. The second type of oscillator resides in afferent terminals, is seen as a noisy peak at fa≈ 30–70 Hz that dominates the power spectra of spontaneous afferent firing, and corresponds to the mean spontaneous firing rate. Sideband peaks at frequencies of fa± feare consistent with epithelia-to-afferent unidirectional synaptic coupling or, alternatively, nonlinear mixing of the 2 oscillatory processes. External stimulation affects the frequency of only the afferent oscillator, not the epithelial oscillators. Application of temperature gradients localized the feand faoscillators to different depths below the skin. Having 2 distinct types of internal oscillators is a novel form of organization for peripheral sensory receptors, of relevance for other hair cell sensory receptors.
Detection of Injury-Induced Vascular Remodeling by Targeting Activated α
v
β
3
Integrin In Vivo
Authors: Sadeghi Mehran M. , Krassilnikova Svetlana , Zhang Jiasheng , Gharaei Amir A. , Fassaei Hooman Rastegar , Esmailzadeh Leila , Kooshkabadi Ali , Edwards Scott , Yalamanchili Padmaja , Harris Thomas D. , Sinusas Albert J. , Zaret Barry L. , Bender Jeffrey R.
Published: June 2004

Background—

The α
v
β
3
integrin plays a critical role in cell proliferation and migration. We hypothesized that vascular cell proliferation, a hallmark of injury-induced remodeling, can be tracked by targeting α
v
β
3
integrin expression in vivo.

Methods and Results—

RP748, a novel
111
In-labeled α
v
β
3
-specific radiotracer, was evaluated for its cell-binding characteristics and ability to track injury-induced vascular proliferation in vivo. Three groups of experiments were performed. In cultured endothelial cells (ECs), TA145, a cy3-labeled homologue of RP748, localized to α
v
β
3
at focal contacts. Activation of α
v
β
3
by Mn
2+
led to increased EC binding of TA145. Left common carotid artery wire injury in apolipoprotein E
−/−
mice led to vascular wall expansion over a period of 4 weeks. RP748 (7.4 MBq) was injected into groups of 9 mice at 1, 3, or 4 weeks after left carotid injury, and carotids were harvested for autoradiography. Relative autographic intensity, defined as counts/pixel of the injured left carotid area divided by counts/pixel of the uninjured right carotid area, was higher at 1 and 3 weeks (1.8±0.1 and 1.9±0.2, respectively) and decreased significantly by 4 weeks after injury (1.4±0.1,
P
<0.05). Carotid α
v
and β
3
integrin expression was maximal at 1 week and decreased by 4 weeks after injury. The proliferation index, as determined by Ki67 staining, followed a temporal pattern similar to that of RP748 uptake. Dynamic gamma imaging demonstrated rapid renal clearance of RP748.

Conclusions—

RP748 has preferential binding to activated α
v
β
3
integrin and can track the injury-induced vascular proliferative process in vivo.