bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytadherence-Deficient Mutants of
Mycoplasma gallisepticum
Generated by Transposon Mutagenesis
Authors: Mudahi-Orenstein Sigalit , Levisohn Sharon , Geary Steven J. , Yogev David 
Published: June 2003

ABSTRACT

Cytadherence-related molecules of
Mycoplasma gallisepticum
strain R-low were identified by Tn
4001
transposon mutagenesis with the hemadsorption (HA) assay as an indicator for cytadherence. Three Gm
r
HA-negative (HA
−
) colonies displaying a stable HA
−
phenotype through several successive generations in which gentamicin selection was maintained were isolated from four independent transformation experiments and characterized. Southern blot analysis showed that the transposon was inserted as a single copy within the genome of each of the HA
−
mutants, suggesting that the transposon insertion was directly responsible for their inability to attach to erythrocytes. Sequence analysis of the transposon insertion sites revealed that in two mutants, the transposon was inserted at two distinct sites within the
gapA
structural gene. In the third mutant, the insertion was mapped within the
crmA
gene, which is located immediately downstream of the
gapA
gene as part of the same operon. In vitro attachment experiments with the MRC-5 human lung fibroblast cell line showed that the cytadherence capabilities of the HA
−
mutants were less than 25% those of original strain R. Experimental infection of chickens, the natural host of
M
.
gallisepticum
, with each of the three mutants demonstrated significantly impaired colonization and host responses. These data demonstrate conclusively the role of both GapA and CrmA proteins in the adherence of
M
.
gallisepticum
to host cells in model systems and in vivo colonization. Furthermore, these results underscore the relevance of in vitro cytadherence model systems for studying the pathogenesis of natural infections in chickens.
Major Surface Protein 2 of
Anaplasma phagocytophilum
Facilitates Adherence to Granulocytes
Authors: Park Jinho , Choi Kyoung Seong , Dumler J. Stephen 
Published: June 2003

ABSTRACT

Anaplasma phagocytophilum
is an obligate intracellular bacterium that infects myeloid cells in the mammalian host. Msp2 (p44) is the major immunodominant outer-membrane protein of these bacteria. We hypothesized that Msp2 acts as an adhesin for
A. phagocytophilum
entry into granulocytes. This potential role was investigated by blocking binding with Msp2 monoclonal antibodies and by antagonizing binding and propagation with recombinant Msp2 (rMsp2) in vitro. With HL-60 cells, fresh human peripheral blood neutrophils, and a cell line devoid of the fucosylated platelet selectin glycoprotein ligand 1 (PSGL-1) receptor for
A. phagocytophilum
or one that was transfected to express this ligand, Msp2 monoclonal antibody and rMsp2 used as the antagonist caused concentration-dependent reductions in bacterial adhesion (
P
< 0.007 and
P
< 0.02, respectively) and propagation (
P
< 0.05 and
P
< 0.001), although inhibition of adhesion or propagation was moderate and incomplete. Likewise, rMsp2 bound to surfaces of the transfected cell at a level similar to that of extracellular
A. phagocytophilum
and significantly (
P
< 0.05) beyond that of nontransfected cells. Moreover, a dose-dependent reduction (
P
< 0.019) in PSGL-1 monoclonal antibody binding to HL-60 cells was elicited with rMsp2. We conclude that Msp2s of
A. phagocytophilum
are involved in bacterial adhesion to ligands on host myeloid cells before intracellular infection.
Synthesis of Melanin-Like Pigments by
Sporothrix schenckii
In Vitro and during Mammalian Infection
Authors: Morris-Jones Rachael , Youngchim Sirida , Gomez Beatriz L. , Aisen Phil , Hay Roderick J. , Nosanchuk Joshua D. , Casadevall Arturo , Hamilton Andrew J. 
Published: June 2003

ABSTRACT

Melanin has been implicated in the pathogenesis of several important human fungal pathogens. Existing data suggest that the conidia of the dimorphic fungal pathogen
Sporothrix schenckii
produce melanin or melanin-like compounds; in this study we aimed to confirm this suggestion and to demonstrate in vitro and in vivo production of melanin by yeast cells.
S. schenckii
grown on Mycosel agar produced visibly pigmented conidia, although yeast cells grown in brain heart infusion and minimal medium broth appeared to be nonpigmented macroscopically. However, treatment of both conidia and yeast cells with proteolytic enzymes, denaturant, and concentrated hot acid yielded dark particles similar in shape and size to the corresponding propagules, which were stable free radicals consistent with identification as melanins. Melanin particles extracted from
S. schenckii
yeast cells were used to produce a panel of murine monoclonal antibodies (MAbs) which labeled pigmented conidia, yeast cells, and the isolated particles. Tissue from hamster testicles infected with
S. schenckii
contained fungal cells that were labeled by melanin-binding MAbs, and digestion of infected hamster tissue yielded dark particles that were also reactive. Additionally, sera from humans with sporotrichosis contained antibodies that bound melanin particles. These findings indicate that
S. schenckii
conidia and yeast cells can produce melanin or melanin-like compounds in vitro and that yeast cells can synthesize pigment in vivo. Since melanin is an important virulence factor in other pathogenic fungi, this pigment may have a similar role in the pathogenesis of sporotrichosis.
Soluble Extracts fromHelicobacter pyloriInduce Dome Formation in Polarized Intestinal Epithelial Monolayers in a Laminin-Dependent Manner
Authors: Terrés A. M. , Windle H. J. , Ardini E. , Kelleher D. P. 
Published: June 2003

ABSTRACTHelicobacter pyloricolonizes the stomach at the interface between the mucus layer and the apical pole of gastric epithelial cells. A number of secreted and shed products from the bacteria, such as proteins and lipopolysaccharide, are likely to have a role in the pathogenesis at the epithelial level. To determine the physiological response of transporting polarized epithelia to released soluble factors from the bacterium, we used the T84 cell line. Monolayers of T84 cells were exposed to soluble extracts fromH. pylori.The extracts induced rapid “dome” formation as well as an immediate decrease in transepithelial electrical resistance. Domes are fluid-filled blister-like structures unique to polarized epithelia. Their formation has been linked to sodium-transporting events as well as to diminished adherence of the cells to the substrate.H. pylori-induced dome formation in T84 monolayers was exacerbated by amiloride and inhibited by ouabain. Furthermore, it was associated with changes in the expression of the laminin binding α6β4 integrin and the 67-kDa laminin receptor. Domes formed primarily on laminin-coated filters, rather than on fibronectin or collagen matrices, and their formation was inhibited by preincubating the bacterial extract with soluble laminin. This effect was specific toH. pyloriand independent of the urease, vacA, cagA, and Lewis phenotype of the strains. These data indicate that released elements fromH. pylorican alter the physiological balance and integrity of the epithelium in the absence of an underlying immune response.
Peripheral targets of centrally located putative accessory neurons of MRO in the isopodLigia exotica
Authors: Hama Noriyuki , Okada Yoshinori , Pollák Edit , Molnár László , Niida Akiyoshi 
Published: June 2003

SUMMARYThe three centrally located putative accessory neurons of the muscle receptor organ (MRO) of the isopod Ligia exotica were identified to the third segmental nerve (N3) of the thoracic ganglion by backfilling with Lucifer Yellow. These neurons were then studied intracellularly and extracellularly to determine whether they suppressed the stretch-activated responses of thoracic stretch receptors. Intracellular injection of depolarizing currents into these three putative accessory neurons revealed that only neuron #3 had an inhibitory effect, suggesting that it is an inhibitory accessory neuron related to thoracic stretch receptors. We searched for the peripheral targets of neurons #1 and #2 by intracellular filling with Lucifer Yellow or by recording of junctional potentials in extensor muscles,and show that they are motor neurons that innervate the deep extensor and superficial extensor muscles, respectively.
Probing the limits to muscle-powered accelerations: lessons from jumping bullfrogs
Authors: Roberts Thomas J. , Marsh Richard L. 
Published: June 2003

SUMMARYThe function of many muscles during natural movements is to accelerate a mass. We used a simple model containing the essential elements of this functional system to investigate which musculoskeletal features are important for increasing the mechanical work done in a muscle-powered acceleration. The muscle model consisted of a muscle-like actuator with frog hindlimb muscle properties, operating across a lever to accelerate a load. We tested this model in configurations with and without a series elastic element and with and without a variable mechanical advantage. When total muscle shortening was held constant at 30%, the model produced the most work when the muscle operated with a series elastic element and an effective mechanical advantage that increased throughout the contraction (31 J kg-1 muscle vs26.6 J kg-1 muscle for the non-compliant, constant mechanical advantage configuration). We also compared the model output with the dynamics of jumping bullfrogs, measured by high-speed video analysis, and the length changes of the plantaris muscle, measured by sonomicrometry. This comparison revealed that the length, force and power trajectory of the body of jumping frogs could be accurately replicated by a model of a fully active muscle operating against an inertial load, but only if the model muscle included a series elastic element. Sonomicrometer measurements of the plantaris muscle revealed an unusual, biphasic pattern of shortening, with high muscle velocities early and late in the contraction, separated by a period of slow contraction. The model muscle produced this pattern of shortening only when an elastic element was included.These results demonstrate that an elastic element can increase the work output in a muscle-powered acceleration. Elastic elements uncouple muscle fiber shortening velocity from body movement to allow the muscle fibers to operate at slower shortening velocities and higher force outputs. A variable muscle mechanical advantage improves the effectiveness of elastic energy storage and recovery by providing an inertial catch mechanism. These results can explain the high power outputs observed in jumping frogs. More generally,our model suggests how the function of non-muscular elements of the musculoskeletal system enhances performance in muscle-powered accelerations.
Regeneration of ultraviolet-sensitive cones in the retinal cone mosaic of thyroxin-challenged post-juvenile rainbow trout (Oncorhynchus mykiss)
Authors: Hawryshyn Craig W. , Martens Garnet , Allison W. Ted , Anholt Bradley R. 
Published: June 2003

SUMMARYPrevious studies in our laboratory have examined the loss of ultraviolet-sensitive (UVS) cones and UV sensitivity. This study looks at the question of regeneration of UVS cones and its topographic distribution, along with several other measures of the cone mosaic. Topography of the cone mosaic in rainbow trout smolts (post-metamorphic juveniles) was examined under normal growth conditions and during an exogenous thyroid hormone (TH) challenge. Growth of trout retina was studied over six weeks. Retinas sampled at 0, 3 and 6 weeks were embedded in EPON resin, and thick (1 μm) tangential sections were stained with Richardson's stain. Sites representing central ventral,ventral, temporal, dorsal and nasal retina were sampled. Variables measured were cone densities, mean double cone diameter and mean spacing between cones of the same type. These same variables were compared with those of fish that were challenged with l-thyroxin (T4), and regeneration of UVS cones was assessed. Principal components of the correlation matrix of all photoreceptor measurements were analysed using analysis of variance. Here, we show several interesting effects of thyroxin exposure on post-metamorphic rainbow trout: (1) controls at week 0 have a high density of UVS cones in the temporal and dorsal sampling regions and a high density of blue(short-wavelength)-sensitive (SWS) and double cones across all regions sampled; (2) both control and TH-treated fish had less abundant, larger and less tightly packed SWS and double cones and a lower density of UVS cones in the temporal and dorsal sampling regions three and six weeks into the experiment compared with the starting condition at week 0; (3) fish treated with TH had a higher UVS cone density in the nasal and ventral sampling regions and there were higher densities of SWS and double cones in the central ventral, temporal and ventral regions, but lower densities in the nasal sampling regions, relative to the controls. The regeneration of UVS cones into the ventral retinal hemisphere in post-juvenile salmonids has important implications for visually guided behavior.
Thermoregulation is the pits: use of thermal radiation for retreat site selection by rattlesnakes
Authors: Krochmal Aaron R. , Bakken George S. 
Published: June 2003

SUMMARY
Pitvipers (Viperidae: Crotalinae) possess unique sensory organs,the facial pits, capable of sensing subtle fluctuations in thermal radiation. Prey acquisition has long been regarded as the sole function of the facial pits. However, the ability to sense thermal radiation could also direct thermoregulatory behavior by remotely sensing nearby surface temperatures. Using a series of behavioral arenas of varying spatial complexity and ecological relevance, we surveyed the ability of the western diamondback rattlesnake Crotalus atrox to direct successful thermoregulatory movements with either functional or disabled facial pits. We found that western diamondback rattlesnakes could base thermoregulatory decisions on thermal radiation cues when their pits were functional, but not when blocked. Our results indicate that the facial pit is part of a generalized sense, and suggest thermoregulation as an alternative hypothesis to prey acquisition for the origin of facial pits.
Maturation of cardiovascular control mechanisms in the embryonic emu(Dromiceius novaehollandiae)
Authors: Crossley Dane A. , Bagatto Brian P. , Dzialowski Edward M. , Burggren Warren W. 
Published: June 2003

SUMMARY
Our understanding of avian embryonic cardiovascular regulation has been based on studies in chickens. The present study was undertaken to determine if the patterns established in chickens are generally applicable to the emu, a ratite bird species. We studied cardiovascular physiology over the interval from 60% to 90% of the emu's 50-day incubation period. During this period,embryonic emus exhibit a slight fall in resting heart rate (from 171 beats min-1 to 154 beats min-1) and a doubling of mean arterial pressure (from 1.2 kPa to 2.6 kPa). Exposures to 15% or 10%O2 initially decreased heart rate during the first period of emu incubation studied [60% of incubation (60%I)] but increased heart rate in the 90%I group. Arterial pressure responded to hypoxia with an initial depression(-1.6 kPa) at 60%I and 70%I but showed no response during the later periods of incubation (80%I and 90%I). In addition, tonic stimulation of both cholinergic and adrenergic (α and β) receptors was present on heart rate at 70%I, with the cholinergic and β-adrenergic tone increasing in strength by 90%I. Arterial pressure was dependent on a constant β-adrenergic and constant α-adrenergic tone from 60%I to 90%I. A comparison with embryonic white leghorn chickens over a similar window of incubation revealed that emus and white leghorn chickens both possess an adrenergic tone on heart rate and pressure but that only emus possess a cholinergic tone on heart rate. Collectively, these data indicate that the maturation of cardiovascular control systems differs between white leghorn chickens and emus, inviting investigation of additional avian species to determine other patterns.
Struktur‐Wirkungs‐Beziehungen von Oxazolidinonen: Grundlage der Entwicklung von Linezolid
Authors: Barbachyn Michael R. , Ford Charles W. 
Published: May 2003

AbstractDie zunehmende Resistenz von Bakterien gegen Antibiotika ist gegenwärtig eines der drängendsten Probleme in der Medizin. In dieser Hinsicht besonders bedenklich sind durch mehrfachresistente Gram‐positive Pathogene verursachte Infektionen, die signifikante Krankheits‐ und Sterblichkeitsziffern verursachen. Eine Reihe von Lösungsansätzen wurde zur Bekämpfung der Bakterienresistenz eingeführt. Der am häufigsten angewendete Ansatz beruht auf der Modifizierung existierender Klassen von Antibiotika zur Herstellung neuer Analoga mit verbesserten Eigenschaften. Weitere Strategien sind die Kombination von antibakteriellen mit anderen Wirkstoffen und die Anwendung von Zusatztherapeutika wie Immunmodulatoren. Die größte Bedeutung hat aber zweifellos die Entwicklung neuer Klassen antibakterieller Wirkstoffe mit neuartigen Wirkmechanismen, die sich durch das Fehlen von Kreuzresistenzen mit existierenden antimikrobiellen Wirkstoffen auszeichnen. Dieser Aufsatz schildert die Arbeiten, die zur Entwicklung von Linezolid führten, dem ersten klinisch nutzbaren Oxazolidinon‐Antibiotikum.
Oxazolidinone Structure–Activity Relationships Leading to Linezolid
Authors: Barbachyn Michael R. , Ford Charles W. 
Published: May 2003

AbstractThe development of bacterial resistance to currently available antibacterial agents is a growing global health problem. Of particular concern are infections caused by multidrug‐resistant Gram‐positive pathogens which are responsible for significant morbidity and mortality in both the hospital and community settings. A number of solutions to the problem of bacterial resistance are possible. The most common approach is to continue modifying existing classes of antibacterial agents to provide new analogues with improved attributes. Other successful strategies are to combine existing antibacterial agents with other drugs as well as the development of improved diagnostic procedures that may lead to rapid identification of the causative pathogen and permit the use of antibacterial agents with a narrow spectrum of activity. Finally, and most importantly, the discovery of novel classes of antibacterial agents employing new mechanisms of action has considerable promise. Such agents would exhibit a lack of cross‐resistance with existing antimicrobial drugs. This review describes the work leading to the discovery of linezolid, the first clinically useful oxazolidinone antibacterial agent.
Catalytic Synthesis of Ammonia—A “Never‐Ending Story”?
Authors: Schlögl Robert 
Published: May 2003

AbstractNitrogen atoms are essential for the function of biological molecules and thus are and important component of fertilizers and medicaments. Bonds to nitrogen also find nonbiological uses in dyes, explosives, and resins. The synthesis of all these materials requires ammonia as an activated nitrogen building block. This situation is true for natural processes and the chemical industry. Knowledge of the various techniques for the preparation of ammonia is thus of fundamental importance for chemistry. The Haber–Bosch synthesis was the first heterogeneous catalytic system employed in the chemical industry and is still in use today. Understanding the mechanism and the translation of the knowledge into technical perfection has become a fundamental criterion for scientific development in catalysis research.
Functional and prognostic relevance of the −173 polymorphism of the macrophage migration inhibitory factor gene in systemic‐onset juvenile idiopathic arthritis
Authors: De Benedetti Fabrizio , Meazza Cristina , Vivarelli Marina , Rossi Federica , Pistorio Angela , Lamb Rebecca , Lunt Mark , Thomson Wendy ,   the British Paediatric Rheumatology Study Group, Ravelli Angelo , Donn Rachelle , Martini Alberto 
Published: May 2003

AbstractObjectiveTo address the functional and prognostic relevance of the −173 single‐nucleotide G‐to‐C polymorphism of the macrophage migration inhibitory factor (MIF) gene in patients with systemic‐onset juvenile idiopathic arthritis (systemic‐onset JIA) by evaluating its association with serum and synovial fluid levels of MIF, with glucocorticoid requirement, and with the outcome of the disease.MethodsA total of 136 patients with systemic‐onset JIA were studied, including 98 patients from the British Paediatric Rheumatology Study Group's National Repository for JIA and 38 patients who were followed up at the IRCCS Policlinico San Matteo (Pavia, Italy) and the IRCCS G. Gaslini (Genoa, Italy). The MIF‐173 polymorphism was genotyped using SnaPshot ddNTP primer extension and capillary electrophoresis. MIF levels were measured by enzyme‐linked immunosorbent assay. The evaluation of the association of the MIF‐173 polymorphism with outcome was performed only in Italian patients who were followed up for >5 years, by analyzing retrospectively 1) the number of joints with active arthritis and the number of joints with limited range of motion; 2) the score, at the last visit, on the Italian version of the Childhood Health Assessment Questionnaire (C‐HAQ); and 3) data concerning the treatment regimens during the disease course.ResultsSystemic‐onset JIA patients carrying a MIF‐173*C allele had serum and synovial fluid levels of MIF significantly higher than those in patients with the GG genotype. The duration of glucocorticoid treatment on a daily regimen was significantly longer in patients carrying a MIF‐173*C allele than in MIF‐173 GG homozygous patients. Moreover, the duration of clinical response to intraarticular injection of triamcinolone hexacetonide was significantly shorter in patients carrying a MIF‐173*C allele. At the last visit, the numbers of joints with active arthritis, the C‐HAQ scores, and the numbers of joints with limited range of motion were significantly higher in patients carrying the MIF‐173*C allele.ConclusionOur study shows the functional relevance of the MIF‐173 polymorphism and suggests that the MIF‐173*C allele is a predictor of poor outcome in systemic‐onset JIA.