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1

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Complete asymptotic expansions of the Fermi–Dirac integrals Fp(η)=1/Γ(p+1)∫0∞[εp/(1+eε−η)]dε (2001)

Garoni, T. M. ; Frankel, N. E.

College Park, Md. : American Institute of Physics (AIP)

Journal of Mathematical Physics 42 (2001), S. 1860-1868

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ISSN: 1089-7658

Source: AIP Digital Archive

Topics: Mathematics , Physics

Notes: The complete asymptotic expansions, that is to say expansions which include any exponentially small terms lying beyond all orders of the asymptotic power series, are calculated for the Fermi–Dirac integrals. We present two methods to accomplish this, the first in the complex plane utilizing Mellin transforms and Hankel's representation of the gamma function, and the second on the real line using the known asymptotic expansions of the confluent hypergeometric functions. The complete expansions of Fp(η) are then used to investigate the effect that these traditionally neglected exponentially small terms have on physical systems. It is shown that for a 2 dimensional nonrelativistic ideal Fermi gas, the subdominant exponentially small series becomes dominant. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1350634

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Site-directed mutagenesis of intimin α modulates intimin-mediated tissue tropism and host specificity (2001)

Reece, Stephen ; Simmons, Cameron P. ; Fitzhenry, Robert J. ; [et al.]

Oxford, UK : Blackwell Science, Ltd

Molecular microbiology 40 (2001), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: The hallmark of enteropathogenic (EPEC) and enterohaemorrhagic (EHEC) Escherchia coli adhesion to host cells is intimate attachment leading to the formation of distinctive ‘attaching and effacing’ lesions. This event is mediated, in part, by binding of the bacterial adhesion molecule intimin to a second bacterial protein, Tir, delivered by a type III secretion system into the host cell plasma membrane. The receptor-binding activity of intimin is localized to the C-terminal 280 amino acids (Int280) and at least five distinct intimin types (α, β, γ, δ and ε) have been identified thus far. In addition to binding to Tir, intimin can also bind to a component encoded by the host. The consequence of latter intimin-binding activity may determine tissue tropism and host specificity. In this study we selected three amino acids in intimin, which are implicated in Tir binding, for site-directed mutagenesis. We used the yeast two-hybrid system and gel overlays to study intimin–Tir protein interaction. In addition, the biological consequences of the mutagenesis was tested using a number of infection models (cultured epithelial cells, human intestinal explants and a mouse model). We report that while an I237/897A substitution (positions numbered according to Int280α/whole intimin α) in intimin α did not have any affect on its biological activity, a T255/914A substitution attenuated intimin activity in vivo. In contrast, the mutation V252/911A affected tissue targeting in the human intestinal explant model and attenuated the biological activity of intimin in the mouse model. This study provides the first clues of the molecular basis of how intimin mediates tissue tropism and host specificity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02371.x

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3

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Numerical simulations of sound radiated from an axisymmetric premixed reacting jet (2001)

Zhao, Wei ; Frankel, Steven H.

[S.l.] : American Institute of Physics (AIP)

Physics of Fluids 13 (2001), S. 2671-2681

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ISSN: 1089-7666

Source: AIP Digital Archive

Topics: Physics

Notes: The sound radiated by an axisymmetric (two-dimensional) premixed reacting free jet was studied using direct numerical simulation. The jet was injected into cold combustion products. A narrow (in radial extent) high temperature pulse was specified at the jet inlet to stabilize the reacting jet. The computational domain included both the near-field flow and far-field acoustic regions. Both reacting and nonreacting cases were considered. The heat release associated with the reacting jet had a significant effect on the vortical structure, as well as the sound radiation level and pattern, within the jet. The sound radiation pattern and the source terms in Lighthill's equation were used to identify apparent sound source locations. Within the context of the assumptions of the present simulations, the results showed that the effect of heat release was to: (1) Stabilize the jet, (2) enhance sound radiation levels due to an increase in the entropy source, and (3) shift the frequency of the most unstable mode to lower values, resulting in a broader sound spectrum. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1386940

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4

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Inheritance of caudal peduncle banding in the spike-tailed paradisefish (2001)

Frankel, J. S.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 59 (2001), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Segregation patterns observed in the progenies from 13 different crosses of the spike-tailed paradisefish Pseudosphromenus cupanus support the hypothesis that caudal peduncle banding is controlled by a major effect gene exhibiting the classical monohybrid Mendelian pattern of inheritance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1095-8649.2001.tb00175.x

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SepL, a protein required for enteropathogenic Escherichia coli type III translocation, interacts with secretion component SepD (2004)

O'Connell, Colin B. ; Creasey, Elizabeth A. ; Knutton, Stuart ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 52 (2004), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: Enteropathogenic Escherichia coli (EPEC), an important cause of infantile diarrhoea in the developing world, disrupts host cell microvilli, causes actin rearrangements and attaches intimately to the host cell surface. This characteristic phenotype, referred to as the attaching and effacing (A/E) effect, is encoded on a 36 kb pathogenicity island called the locus of enterocyte effacement (LEE). The LEE includes genes involved in type III secretion and translocation, the eae gene encoding an outer membrane adhesin known as intimin, the tir gene for the translocated intimin receptor, a regulator and various genes of unknown function. Among this last group is sepL. To determine the role of SepL in EPEC pathogenesis, we constructed and tested a non-polar sepL mutant. We found that this sepL mutant is deficient for A/E and that it secretes markedly reduced quantities of those proteins involved in translocation (EspA, EspB and EspD), but normal levels of those proteins presumed to be effectors (Tir, EspF and EspG). Despite normal levels of secretion, the mutant strain was unable to translocate EspF and Tir into host cells and formed no EspA filaments. Fractionation studies revealed that SepL is a soluble cytoplasmic protein. Yeast two-hybrid and affinity purification studies indicated that SepL interacts with the LEE-encoded protein SepD. In contrast to SepL, we found that SepD is required for type III secretion of both translocation and effector proteins. Together, these results demonstrate that SepL has a unique role in type III secretion as a functional component of the translocation system that interacts with an essential element of the secretion machinery.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04101.x

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6

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The Effects of Supraoptimal Temperatures on Population Growth and Cortical Patterning in Tetrahymena pyriformis and Tetrahymena thermophila: A Comparison (2001)

FRANKEL, JOSEPH ; NELSEN, E. MARLO

Oxford, UK : Blackwell Publishing Ltd

The @journal of eukaryotic microbiology 48 (2001), S. 0

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ISSN: 1550-7408

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: . In this investigation, we compare the multiplication rates and morphogenetic responses of the two most studied Tetrahymena species, T. pyriformis and T. thermophila, at supraoptimal temperatures. Although the upper temperature limits differ greatly in the two species, the pattern of growth responses to high temperature is for the most part similar, with some differences in detail. The transient recovery of cell division at the highest temperature that allows cell division, characteristic of T. pyriformis, is observed in a less distinct form in T. thermophila. Moreover, there is a remarkable difference in developmental response, with drastic abnormalities in patterning of oral structures during the transient recovery of cell division in T. pyriformis, and far more limited abnormalities under similar conditions in T. thermophila. The abnormalities result from spatial disorder in the alignment and orientation of basal body pairs within the early oral primordium, followed by failures in the realignment that normally occurs as oral structures (membranelles and undulating membrane) mature. Both the initial spatial disorder and the failures in realignment are far more severe in T. pyriformis than in T. thermophila.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1550-7408.2001.tb00296.x

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7

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An Evaluation of Hsp90 as a Mediator of Cortical Patterning in Tetrahymena (2001)

FRANKEL, JOSEPH ; WILLIAMS, NORMAN E. ; NELSEN, E. MARLO ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

The @journal of eukaryotic microbiology 48 (2001), S. 0

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ISSN: 1550-7408

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: . This study asks two questions: 1) whether Hsp90 is involved in the regulation of cortical patterning in Tetrahymena, and 2) if it is, whether specific defects in this regulation can be attributed to functional insufficiency of the Hsp90 molecule. To address question I, we compared the effects of a specific inhibitor of Hsp90, geldanamycin, on population growth and on development of the oral apparatus in two Tetrahymena species, T. pyriformis and T. thermophila. We observed that geldanamycin inhibits population growth in both species at very low concentrations, and that it has far more severe effects on oral patterning in T. pyriformis than in T. thermophila. These effects are parallel to those of high temperature in the same two species, and provide a tentative affirmative answer to the first question. To address question 2, we ascertained the base sequence of the genes that encode the Hsp90 molecules which are induced at high temperatures in both Tetrahymena species, as well as corresponding sequences in Paramecium tetraurelia. Extensive comparative analyses of the deduced amino acid sequences of the Hsp90 molecules of the two Tetrahymena species indicate that on the basis of what we currently know about Hsp90 both proteins are equally likely to be functional. Phylogenetic analyses of Hsp90 amino acid sequences indicate that the two Tetrahymena Hsp90 molecules have undergone a similar number of amino acid substitutions from their most recent common ancestor, with none of these corresponding to any known functionally critical region of the molecule. Thus there is no evidence that the Hsp90 molecule of T. pyriformis is functionally impaired; the flaw in the control of cortical patterning is more likely to be caused by defects in mechanism(s) that mediate the response to Hsp90, as would be expected from the “Hsp90 capacitor” model of Rutherford and Lindquist.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1550-7408.2001.tb00297.x

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Nuclear and Cortical Regulation in Doublets of Paramecium: II. When and How do Two Cortical Domains Reorganize to One? (2001)

IFTODE, FRANCINE ; PRAJER, MALGORZATA ; FRANKEL, JOSEPH

Oxford, UK : Blackwell Publishing Ltd

The @journal of eukaryotic microbiology 48 (2001), S. 0

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ISSN: 1550-7408

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: . Homopolar doublets with twofold rotational symmetry were generated in Paramecium tetraurelia and in P. undecaurelia by electrofusion or by arrested conjugation. These doublets underwent a complex cortical reorganization over time, which led to their reversion to singlets. This reorganization involved a reduction in number of ciliary rows, a progressive inactivation and loss of one oral meridian, and a reduction and eventual disappearance of one cortical surface (semicell) situated between the two oral meridians. The intermediate steps of this reorganization included some processes that resemble those previously described in regulating doublets of other ciliates, and others that are peculiar to members of the “P. aurelia” species-group and some of its close relatives. The former included a disappearance of one cortical landmark (a contractile vacuole meridian) and transient appearance of another (a third cytoproct) within the narrower semicell. The latter included a reorganization of the paratene zone and the associated invariant (non-duplicating) region to occupy the entire narrower semicell and a redistribution of zones of most active basal-body proliferation within the opposite, wider semicell. The final steps of reorganization involved anterior displacement, invagination, and resorption of one of the two oral apparatuses and eventual disappearance of the associated oral meridian. An oral meridian deprived of its oral apparatus, either by spontaneous resorption or microsurgical removal, could persist for some time in “incomplete doublets” before regulating to the singlet condition. The phylogenetically widespread events encountered in the regulation of doublets to singlets suggest that Paramecium shares some of the global regulatory properties that are likely to be ancestral in ciliates. The more specific events are probably associated with the complex cytoskeletal architecture of this organism and with the frequent occurrence of autogamy that was described in the preceding study (Prajer et al. 1999).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1550-7408.2001.tb00210.x

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