bluuebunny/crossref_metadata_2025 huggingface dataset:
Early T lymphocytes. Differentiation in vivo of adult intrathymic precursor cells.
Authors: Fowlkes B J , Edison L , Mathieson B J , Chused T M
Published: June 2004

A minor subpopulation of adult murine thymocytes (less than 5%) that is Lyt-2-, L3T4-, and expresses low levels of Ly-1 (designated dLy-1 [dull] thymocytes) has been identified, isolated, and characterized. This study assesses the differentiation potential of dLy-1 thymocytes in the thymus in vivo. Using multiparameter flow cytometry, radiation chimeras of C57BL/6 mice congenic at the Ly-1 or Ly-5 locus, and allelic markers to discriminate host and donor, we showed that transferred dLy-1 cells were able to generate thymocytes expressing both cortical and medullary phenotypes in a sequential manner. The proportion of donor-derived thymocytes obtained was directly related to the number of dLy-1 thymocytes transferred. Transfer of purified Lyt-2+ or Lyt-2+ + L3T4+ thymocytes, which constitute greater than 94% of total thymocytes, failed to generate any donor-derived thymocytes in irradiated recipients. Transfer of bone marrow (BM) cells produced the same sequential pattern of differentiation as that produced by dLy-1 cells, but was delayed by 4-5 d. Transferred dLy-1 thymocytes exhibited a limited capacity for self-renewal, and resulted in a single wave of differentiation in irradiated hosts. Thus, thymic repopulation by donor-derived cells after transfer of dLy-1 thymocytes was transient, while repopulation by BM was permanent. These findings suggest that the isolated dLy-1 thymocytes described herein are precursor thymocytes that represent a very early stage in intrathymic development.
Long-term administration of massive doses of Sn-protoporphyrin in anemic mutant mice (sphha/sphha).
Authors: Sassa S , Drummond G S , Bernstein S E , Kappas A
Published: June 2004

The effects of long-term administration of very large doses of Sn-protoporphyrin on hematological indices, histological changes, plasma bilirubin levels, tissue heme oxygenase activity, and activities of heme biosynthetic enzymes, were examined in genetically anemic mutant mice with hemolytic anemia (sphha/sphha). Long-term weekly treatment with Sn-protoporphyrin (100 mumol/kg body weight for 32 wk) did not alter hematological indices, histological findings, or enzyme activities related to heme biosynthesis, even though it resulted in sustained decreases in microsomal heme oxygenase activity in the liver, kidney, and spleen, and a prolonged decrease in plasma bilirubin concentration. Inhibition of heme oxygenase did not alter the level of cytochrome P-450 in the liver and the kidney. The results indicate that long-term treatment with massive doses of Sn-protoporphyrin suppresses bilirubin formation but does not produce significant histopathological changes or appreciably interfere with heme synthesis, in this strain of genetically anemic mice. These findings provide further support for the idea that suppression of heme degradation to bile pigment by the inhibition of heme oxygenase may prove useful to the prevention of severe hyperbilirubinemia in humans.
Thymus-leukemia (TL) antigens of the mouse. Analysis of TL mRNA and TL cDNA TL+ and TL- strains.
Authors: Chen Y T , Obata Y , Stockert E , Old L J
Published: June 2004

A thymus-leukemia (TL)-specific probe, pTL1, has been generated from a TL-coding gene of BALB/c mice. Multiple species of TL mRNA were detected in TL+ cells by Northern blot analysis with pTL1, and different Tla haplotypes could be distinguished on the basis of characteristic patterns of TL mRNA. No TL-related message was found in normal or leukemic TL- cells, including thymocytes from Tlab mice. However, TL mRNA could be detected in TL+ leukemias occurring in Tlab mice. A cDNA library has been made from ASL1 (a TL+ leukemia of A mice [Tlaa]), and pTL1+ clones have been sequenced. At least three structurally distinct TL genes are expressed in ASL1. Sequence comparison of TL genes from three Tla haplotypes indicates that TL genes are highly conserved (greater than 90% homology) and are more distantly related to H-2 genes. Several polyadenylation sites have been found in the 3' untranslated region of TL genes, and differential polyadenylation contributes to the size heterogeneity of TL transcripts. The predicted amino acid sequence of TL products indicates that TL and H-2 are similar in domain structure and disulfide bonds, but differ in glycosylation sites and in cytoplasmic domain sequences.
Lack of K1b9 light chains in Basilea rabbits is probably due to a mutation in an acceptor site for mRNA splicing.
Authors: Lamoyi E , Mage R G
Published: June 2004

Rabbits of the Basilea strain do not produce normal K1b9 light chains but continue to produce immunoglobulins with light chains of the rare K2 isotype and of lambda type. To understand the molecular basis for this unusual expression of kappa light chains in Basilea rabbits, we undertook an analysis of their kappa genes. We isolated and sequenced the mutant kappa 1b9 gene and found a substitution of A for G in the highly conserved AG dinucleotide of the 3' acceptor splice site. Although we cannot rule out additional alterations of portions of the gene we did not sequence, this spontaneous change of the G found in the normal gene provides a likely molecular explanation for the loss of K1 light chain expression in Basilea rabbits.
Cysteine eliminates the feeder cell requirement for cultivation of Trypanosoma brucei bloodstream forms in vitro.
Authors: Duszenko M , Ferguson M A , Lamont G S , Rifkin M R , Cross G A
Published: June 2004

In all previous studies, bloodstream forms of Trypanosoma brucei could be grown in vitro only when supported by a feeder layer of mammalian fibroblasts. We have axenically cultivated bloodstream T. brucei by adding L-cysteine at regular intervals and appropriate concentrations. The optimum cysteine concentration depends on cell density and is close to physiological serum levels. At concentrations greater than 24 mg/liter (2 X 10(-4) M), cysteine was acutely toxic to trypanosome concentrations of 3 X 10(7)/ml. Toxicity was prevented by addition of pyruvate or catalase, which neutralize H2O2 produced by cysteine autoxidation. In uptake studies using [35S]cysteine and [35S]cystine, T. brucei efficiently incorporated only cysteine. The Km for cysteine uptake was 4 X 10(-4) M. Cystine supported axenic growth if low concentrations of 2-mercaptoethanol were added at regular intervals.
Human hematopoietic progenitor cells in long-term cultures express HLA-DR antigens and lack HLA-DQ antigens.
Authors: Falkenburg J H , Fibbe W E , Goselink H M , Van Rood J J , Jansen J
Published: June 2004

The expression of HLA-DR antigenic determinants on human hematopoietic progenitor cells (HPC) capable of differentiating into mature blood cells, as determined in semisolid cultures, has been demonstrated previously (3-7). Here, we investigated the expression of class II determinants on HPC responsible for the sustained proliferation of colony-forming units of granulocyte/macrophage (CFU-GM), of multilineage HPC (CFU-GEMM, granulocyte/erythrocyte/macrophage/megakaryocyte), and burst-forming units of erythroid cells (BFU-E) in liquid long-term cultures. Using both fluorescence-activated cell sorting and complement-dependent cytotoxicity assays, HLA-DR determinants could be identified on virtually all these HPC capable of proliferating in long-term cultures. Experiments in which the stromal layer had been irradiated provided evidence that the HPC themselves were truly HLA-DR+, and that the sustained proliferation of HPC was not due to activation of HLA-DR- residual HPC in the stromal layer by reinoculated HLA-DR+ accessory cells. Furthermore, it was shown that all HPC recognized in semisolid and liquid long-term cultures were HLA-DQ-. These results suggest that the human true pluripotential stem cell is HLA-DR+. These results open the possibility of studying class II-dependent regulation of hematopoiesis in liquid long-term cultures.
The hematopoietic system is a source of odorants that distinguish major histocompatibility types.
Authors: Yamazaki K , Beauchamp G K , Thomas L , Boyse E A
Published: June 2004

Radiation chimeras were made by restoring lethally irradiated inbred mice with bone marrow cells of F1 hybrid mice of crosses between that inbred strain and an H-2-congenic strain. The urine of these chimeras was tested by the Y maze method, and shown to have acquired a scent indicative of the reconstituting donors' H-2 type. Thus, cells of the hematopoietic system contribute to the H-2-related odorant properties that enable mice to distinguish one another according to their H-2 types.
Membranes replace irradiated blast cells as growth requirement for leukemic blast progenitors in suspension culture.
Authors: Nara N , McCulloch E A
Published: June 2004

The blast cells of acute myeloblastic leukemia (AML) may be considered as a renewal population, maintained by blast stem cells capable of both self-renewal and the generation of progeny with reduced or absent proliferative potential. Blast progenitor renewal is manifested in suspension culture by an exponential increase in clonogenic cells. This growth requires that two conditions be met: first, the cultures must contain growth factors in media conditioned either by phytohemagglutinin (PHA)-stimulated mononuclear leukocytes (PHA-LCM), or by cells of the continuous bladder carcinoma line HTB9 (HTB9-CM). Second, the cell density must be maintained at 10(6) blasts/ml; this may be achieved by adding irradiated cells to smaller numbers of intact blasts. We are concerned with the mechanism of the feeding function. We present evidence that (a) cell-cell contact is required. (b) Blasts are heterogeneous in respect to their capacity to support growth. (c) Fractions containing membranes from blast cells will substitute for intact cells in promoting the generation of new blast progenitors in culture. (d) This membrane function may be specific for AML blasts, since membranes from blasts of lymphoblastic leukemia or normal marrow cells were inactive.
Strain-specific silencing of a predominant antidextran clonotype family.
Authors: Froscher B G , Klinman N R
Published: June 2004

The immune response to dextran is characterized by marked phenotypic differences among murine strains. In particular, Igha strains, as opposed to strains of other Igh haplotypes, respond relatively vigorously to dextran B1355 fraction S (DEX), producing predominantly antibodies bearing the lambda light chain, and specific for the alpha(1----3) glucose linkage. We have investigated this disparity in BALB/c (Igha) vs. C.B20 (Ighb) mice at the individual precursor cell level. Consistent with previous findings (7-9, 35, 40, 42, 43), there was a 10-fold higher frequency of lambda-bearing splenic B cells specific for the alpha(1----3) linkage in Igha mice. As with previously studied (25-27) predominant specificities, the origin of this high frequency of lambda-bearing alpha(1----3) DEX-specific B cells appears to be a reflection of a high expression of this specificity in surface Ig (sIg)-negative cells emerging from the bone marrow generative cell pool. Surprisingly, although C.B20 mice (Ighb) have a low frequency of lambda-bearing alpha(1----3) DEX-specific B cells in their mature primary splenic population, the frequency of precursor cells of this clonotype in their sIg- bone marrow cell population is equivalent to that of BALB/c sIg- cells. These cells could only be stimulated in allotype allogeneic (Igha), as opposed to allotype syngeneic (Ighb), carrier-primed irradiated recipients. This finding was confirmed by the finding that a high proportion of antidextran hybridoma cell lines derived from C.B20 bone marrow cells produced lambda-bearing alpha(1----3) DEX-specific antibodies that were IdX+. These findings have led us to conclude that the well-established phenotypic difference between Igha and Ighb mice with respect to the expression of lambda-bearing alpha(1----3) DEX-specific antibody responses is not, as previously assumed, the result of an inability of Ighb mice to generate B cells of this clonotype, but rather, is the product of environmental, possibly antiidiotypic, silencing of cells of this clonotype as they mature in Ighb mice.
Widespread and selective induction of major histocompatibility complex-determined antigens in vivo by gamma interferon.
Authors: Skoskiewicz M J , Colvin R B , Schneeberger E E , Russell P S
Published: June 2004

gamma Interferon (IFN-gamma) caused remarkable increases in class I (H-2Kk) and class II (I-Ak) antigens throughout the body by 6-9 d. Heart, kidney, and adrenals showed increases of 4-8 times their previous levels of class I antigen content, while the pancreas and small intestine increased 13-17-fold. Lesser increases were found in spleen, liver, and lung, which showed higher resting antigenic potency. Increases of class II antigenicity of 6-10-fold were found in heart, kidney, pancreas, lung, liver, adrenal, and small intestine, with lesser increases in thymus and spleen, and none in lymph node. Topographical analysis revealed that IFN-gamma induced class I and II antigens on most tissues in a highly selective fashion. For example, the renal proximal tubules expressed large amounts of both class I and II antigens, whereas the distal tubules and collecting ducts did not. In some epithelial cells class I and II determinants were induced only on the basal aspects of the cell membrane. IFN-gamma caused a remarkable increase in class II-positive dendritic cells in the liver, pancreas, salivary glands, and thyroid. Whether these cells were of local or systemic origin is uncertain, but the finding of a simultaneous depletion of dendritic cells from lymph nodes and spleen raises the possibility that they may have been derived, at least in part, from these sites. The dynamic and selective induction of class I and II antigen expression by IFN-gamma is likely to be important in regulation of the immune response in tissues.
Specific unresponsiveness in rats with prolonged cardiac allograft survival after treatment with cyclosporine. Mediation of specific suppression by T helper/inducer cells.
Authors: Hall B M , Jelbart M E , Gurley K E , Dorsch S E
Published: June 2004

DA rats grafted with major histocompatibility complex-incompatible PVG heart grafts and treated with cyclosporine (CY) for 10 d do not reject their grafts, and develop a state of specific unresponsiveness toward PVG allografts. Cells from these animals tested in an adoptive transfer assay were incapable of restoring PVG graft rejection, and capable of specifically inhibiting the capacity of adoptively transferred normal lymph node cells (LNC) to do so. They effected third party Wistar/Furth (W/F) graft rejection, however. Adoptive transfer assays with purified subpopulations of the lymphocytes that mediated this effect showed that W3/25+ T cells of the helper/inducer subclass, when injected alone, failed to restore rejection, and were also able, when injected with normal LNC or the W/25+ cells separated from them, to prevent these cells from effecting rejection. MRC OX8+ T cells of the cytotoxic/suppressor subclass, B cells, and serum from rats with long-surviving grafts all failed to inhibit the allograft responsiveness of normal LNC, and thus were not identified as mediators of the state of specific unresponsiveness. These results show that the specific unresponsiveness that develops in rats with long-surviving grafts, and which, in part at least, is responsible for prolonged graft survival, is due to an alteration in the alloreactivity of the helper/inducer subclass of T cells. These cells not only lack the capacity to initiate a rejection response against the alloantigens of the graft, but also have the ability to inhibit the capacity of normal W3/25+ cells to do so.
Tolerance to parenchymal self. Regulatory role of major histocompatibility complex-restricted, OX8+ suppressor T cells specific for autologous renal tubular antigen in experimental interstitial nephritis.
Authors: Kelly C J , Silvers W K , Neilson E G
Published: June 2004

BN rats develop interstitial nephritis after immunization with rabbit, but not rat renal tubular antigen. Using RT1n rat strains that differentially express tubular antigen, we investigated the unresponsiveness of BN rats to BN tubular antigen (BN-TBM) using delayed-type hypersensitivity (DTH) responses to BN-TBM as a measure of cell-mediated immunity. Our results indicate that rat strains expressing tubular antigen respond to immunization with BN-TBM with the clonal expansion of antigen-specific, cyclophosphamide-sensitive, OX8+, MHC-restricted suppressor T cells. Such suppression appears to be relevant to the maintenance of tolerance to parenchymal self, since chronic cyclophosphamide therapy abrogates suppression and results in significant interstitial nephritis.
Encephalitogenic T cell clones specific for myelin basic protein. An unusual bias in antigen recognition.
Authors: Zamvil S S , Nelson P A , Mitchell D J , Knobler R L , Fritz R B , Steinman L
Published: June 2004

Class II-restricted T cell clones specific for myelin basic protein (MBP) have been generated from PL/J and (PL/J X SJL/J)F1 [((PLSJ)F1] mice following sensitization to rat MBP. Of 17 T cell clones generated from (PLSJ)F1 mice, 5 are I-Au(A alpha uA beta u) restricted, one is restricted to I-As(A alpha sA beta s), 10 are restricted to hybrid I-A(u X s)F1 (A alpha sA beta u) determinants, and one clone is restricted to hybrid I-E(u X s) (E alpha uE beta s) molecules. Thus, of 16 I-A-restricted T cell clones generated from (PLSJ)F1 mice, only one is I-As-restricted, reflecting a lack of priming to MBP in association with I-As. T cell clones restricted to I-Au and to I-E (E alpha u E beta s) molecules recognize mouse (self) MBP. Furthermore, only the five T cell clones restricted to I-Au molecules recognize a determinant in common with mouse (self) MBP within the encephalitogenic N-terminal peptide. Three such I-Au restricted T cell clones, derived independently, cause paralysis in 100% of (PL/J X SJL/J)F1 mice tested. Acute, chronic unremitting, and chronic relapsing paralysis are all induced following injection of these clones. Administration of greater numbers of cloned T cells causes acute and fatal experimental allergic encephalomyelitis, while administration of lower numbers of cloned T cells is associated with chronic unremitting and relapsing paralysis. Paralysis induced with T cell clones shares many clinical, immunologic, and histologic aspects with human demyelinating diseases such as multiple sclerosis. Histopathology reveals perivascular lymphocytic infiltration, demyelination, and remyelination. These studies demonstrate the utility of T cell clones for analyzing the association between class II major histocompatibility complex molecules and disease susceptibility.
Origin of human T-lymphotrophic virus I-positive T cell lines in adult T cell leukemia. Analysis of T cell receptor gene rearrangement.
Authors: Maeda M , Shimizu A , Ikuta K , Okamoto H , Kashihara M , Uchiyama T , Honjo T , Yodoi J
Published: June 2004

Using the clone-specific rearrangement of the T cell receptor gene as the genetic marker of the clonotype, we analyzed the clonal origin of the interleukin 2 (IL-2)-dependent human T-lymphotrophic virus I (HTLV-I)-positive T cell lines established from various adult T cell leukemia (ATL) patients. From a patient with chronic ATL, whose leukemic cells proliferated in vitro in response to IL-2, we repeatedly established leukemic T cell clones having the same rearrangement profile of the T beta chain gene as the leukemic cells. By contrast, established cell lines from acute ATL patients had different beta chain gene rearrangements from those of the leukemic cells. These HTLV-I+ T cell lines might not be the direct progeny of the leukemic cells, but that of T cells infected either in vivo or in vitro. These IL-2-reactive nonleukemic T cells might have been selected in vitro, because their leukemic cells failed to respond to IL-2, despite the expression of IL-2 receptor. The analysis of the T cell receptor gene rearrangement may give a new approach for the elucidation of the mechanism of leukemogenesis and the origin of the HTLV-I+ T cell lines in ATL.
Increasing Antibiotic Resistance of Streptococcus Species in New York City
Authors: Lin Karen , Tierno Philip M. , Komisar Arnold
Published: June 2004

Objective:
Streptococcus species are common pathogens in head and neck infections and are leading causes of morbidity and mortality. Emerging penicillin‐resistant streptococcal pathogens have shifted empirical antibiotic therapy in favor of valuable alternatives, including erythromycin and clindamycin. This study was undertaken to determine the magnitude of antimicrobial resistance to these antibiotics.

Study Design: Retrospective review.

Methods: A retrospective study of two streptococcal species isolates, Streptococcus pyogenes (163 specimens) and Streptococcus pneumoniae (164 specimens), collected between January 1, 2001 and January 1, 2002 at two academic institutions. The antibiotic susceptibility patterns were analyzed for penicillin, erythromycin, and clindamycin according to the National Committee for Clinical Laboratory Standards.

Results: Fourteen percent to 34% of S. pyogenes isolates were erythromycin‐resistant, and 0% to 28% were clindamycin‐resistant. None of the S. pyogenes isolates were resistant to penicillin. Of the S. pneumoniae isolates, 33% to 50% were resistant to erythromycin, and 18% to 33% were resistant to clindamycin. The penicillin resistance levels for S. pneumoniae were 0% to 45%.

Conclusions: Our antimicrobial resistance levels for S. pyogenes and S. pneumoniae significantly exceeded national and worldwide levels of erythromycin and clindamycin resistance. With a diverse population of over 8 million residents and high physician supply, our model is a microcosm for the study of antimicrobial use and susceptibility patterns and of clinical failure.
New Method of Using Reconstructed Images for Assessment of Patency of Intracochlear Spaces for Cochlear Implant Candidates
Authors: Karino Shotaro , Hayashi Naoto , Aoki Shigeki , Ohtomo Kuni , Yamasoba Tatsuya
Published: June 2004

Objective/Hypothesis: A new method of reconstruction using multidetector‐row helical computed tomography (MDCT) was applied for assessment of cochlear patency in cochlear implantation candidates.

Study Design: Descriptive study comparing radiologic and surgical findings in eight radiologically normal cochleas and four abnormal cases.

Methods: In unusual cases including cochlear ossification and misinsertion of electrodes, intracochlear space was evaluated on two types of reconstructed images: the “basal turn plane” that was vertical to the modiolus and contained whole basal turn was effective in the assessment of the lining of the inner bony wall of the otic capsule; “cochlear cross plane” images allowed evaluation of the patency of the intracochlear space and the location of inserted electrodes at the sections vertical to the direction of insertion of the electrodes.

Results: Preoperative evaluation was useful for predicting possible problems in electrode insertion and therefore helped in decision‐making in regards to surgical strategies, especially in candidates with a high probability of cochlear ossification such as those with meningitis and otosclerosis. Furthermore, the new reconstruction method also provided useful information on the position of the cochlear implant electrodes after surgery.

Conclusions: These unusual cases demonstrated that preoperative MDCT evaluation by our reconstruction method was useful for predicting possible problems in electrode insertion and decision‐making in regards to surgical strategies, especially in cochlear implantation candidates with a high probability of cochlear stenosis.
Office‐Based Endoscopic Procedure for Diagnosis in Conductive Hearing Loss Cases Using OtoScan Laser‐Assisted Myringotomy
Authors: Kakehata Seiji , Futai Kazunori , Kuroda Reiko , Shinkawa Hideichi
Published: June 2004

Objectives/Hypothesis: In conductive hearing loss (HL), even though preoperative examinations including audiometry, tympanometry, and computed tomography (CT) scan are applied, exploratory tympanotomy is necessary to make an exact diagnosis of ossicular interruption and stapes fixation. Precise preoperative diagnosis would be useful for patient counseling, surgical indications, and planning. The advantages of office‐based OtoScan laser‐assisted myringotomy (LAM), which makes a circular and non‐hemorrhagic perforation, prompted us to investigate other uses of LAM in addition to ventilation and drainage of the tympanic cavity. To make presurgical diagnosis in conductive HL, endoscopes with an outer diameter of 1.7 or 1.9 mm were used to inspect the middle ear pathology through perforations with a diameter of 2 mm made by LAM.

Methods: In the outpatient clinic, a circular perforation with a diameter of 2 mm was made in the tympanic membrane with LAM. An endoscopic view of the ossicular chain through a 70° angled tip endoscope held immediately to the outer side of the perforation was obtained to diagnose conduction disturbance loci in conductive HL cases.

Results: Ossicular chain abnormalities were easily and safely detected by clean endoscopic views obtained through a nonhemorrhagic circular perforation. When necessary, insertion of the tip of the endoscope into the tympanic cavity provided additional views of epitympanum.

Conclusion: We suggest that transtympanic endoscopy through the perforation made by LAM is an effective and safe office‐based procedure for diagnosis in conductive HL cases and could be an alternative procedure to replace exploratory tympanotomy.
Immunohistochemistry and Reverse Transcriptase–Polymerase Chain Reaction as Methods for Diagnostic Determination of Usher Syndrome Type IIa
Authors: Cohn Edward , Bhattacharya Gautam , Pearsall Nicole , Shendrik Igor , Kimberling William , Cosgrove Dominic
Published: June 2004

Objectives/Hypothesis: Patients having null mutations in the USH2A gene do not produce usherin and therefore are not positive for immunohistochemical staining of the usherin protein. Thus, immunostaining for usherin can serve as a reliable diagnostic tool for Usher syndrome type IIa.

Study Design: Prospective.

Methods: Immunohistochemical staining for usherin was carried out in basement membrane of minor salivary gland tissue from subjects with confirmed Usher syndrome type IIa and from archival minor salivary gland tissue from patients without Usher syndrome as control samples. Quantitative usherin messenger RNA analysis was performed using minor salivary gland biopsy tissue.

Results: Five subjects with Usher syndrome type IIa had no immunostaining in minor salivary gland tissue, whereas control minor salivary gland tissue did stain with usherin antibody. No usherin RNA was detected in biopsy specimens from patients with confirmed Usher syndrome IIa.

Conclusion: The feasibility was confirmed of diagnosing Usher syndrome type IIa using purified usherin antibody in subjects having two null USH2A mutations.
The effects of nonnative interactions on protein folding rates: Theory and simulation
Authors: Clementi Cecilia , Plotkin Steven S.
Published: June 2004

Proteins are minimally frustrated polymers. However, for realistic protein models, nonnative interactions must be taken into account. In this paper, we analyze the effect of nonnative interactions on the folding rate and on the folding free energy barrier. We present an analytic theory to account for the modification on the free energy landscape upon introduction of nonnative contacts, added as a perturbation to the strong native interactions driving folding. Our theory predicts a rate‐enhancement regime at fixed temperature, under the introduction of weak, nonnative interactions. We have thoroughly tested this theoretical prediction with simulations of a coarse‐grained protein model, by using an off‐lattice Cαmodel of the src‐SH3 domain. The strong agreement between results from simulations and theory confirm the nontrivial result that a relatively small amount of nonnative interaction energy can actually assist the folding to the native structure.
Trapping a 96° domain rotation in two distinct conformations by engineered disulfide bridges
Authors: Schultz‐Heienbrok Robert , Maier Timm , Sträter Norbert
Published: June 2004

Engineering disulfide bridges is a common technique to lock a protein movement in a defined conformational state. We have designed two double mutants of Escherichia coli 5′‐nucleotidase to trap the enzyme in both an open (S228C, P513C) and a closed (P90C, L424C) conformation by the formation of disulfide bridges. The mutant proteins have been expressed, purified, and crystallized, to structurally characterize the designed variants. The S228C, P513C is a double mutant crystallized in two different crystal forms with three independent conformers, which differ from each other by a rotation of up to 12° of the C‐terminal domain with respect to the N‐terminal domain. This finding, as well as an analysis of the domain motion in the crystal, indicates that the enzyme still exhibits considerable residual domain flexibility. In the double mutant that was designed to trap the enzyme in the closed conformation, the structure analysis reveals an unexpected intermediate conformation along the 96° rotation trajectory between the open and closed enzyme forms. A comparison of the five independent conformers analyzed in this study shows that the domain movement of the variant enzymes is characterized by a sliding movement of the residues of the domain interface along the interface, which is in contrast to a classical closure motion where the residues of the domain interface move perpendicular to the interface.
Observation of sequence specificity in the seeding of protein amyloid fibrils
Authors: Krebs Mark R.H. , Morozova‐Roche Ludmilla A. , Daniel Katie , Robinson Carol V. , Dobson Christopher M.
Published: June 2004

It is well established that the rate of formation of fibrils by amyloidogenic proteins is enhanced by the addition of preformed fibrils, a phenomenon known as seeding. We show that the efficiency of seeding fibril formation from solutions of hen lysozyme by a series of other proteins depends strongly on the similarity of their sequences. This observation is consistent with the importance of long‐range interactions in stabilizing the core structure of amyloid fibrils and may be associated with the existence of a species barrier observed in the transmissible spongiform encephalopathies. In addition, it is consistent with the observation of a single dominant type of protein in the deposits associated with each form of amyloid disease.
Determining the Causes and Durability of Transnational Labour Migration between Mexico and the United States: Some Empirical Findings
Authors: Pries Ludger
Published: June 2004

While the field of transnational migration studies is expanding, one important challenge is to broaden research from a mainly qualitative approach proving the existence of transnational migration phenomena toward efforts to quantify transnational migration and pay more attention to analysing its internal dynamics and interrelationships with other (ideal) types of migration. Based on a qualitative and quantitative empirical study of (trans)migrants moving between Puebla (Mexico) and the New York City region focused on the life and work trajectories of 648 individuals and on biographical life history interviews with about 40 Mexican migrants, the article is focused on analysing and explaining the number of trips as an important indicator for transnational migration (even if transmigration could be predominantly a subjective perception and practice without constant physical movement between countries). In order to establish the empirical existence of the transmigration phenomenon, a typology for distinguishing between different types of migrants is advanced and applied to those migrants captured in the survey. The influence of personal, familial, time‐, job‐, and community‐related factors on their decision‐making processes and the number of country trips are analysed. The empirical findings will be complemented by qualitative interview material to present the case of a transnationally organized family. This case study serves, first, to demonstrate that research on transmigrant household decision‐making strategies is complicated by the complexity of social and family networks, which make it difficult to clearly identify household units; second, it helps address the issue of the durability of the transmigration phenomenon by showing that transnational strategies can be adopted by family members over several generations, depending on individuals' changing needs and desires.
Loving America and Longing for Home: Isma'il al‐Faruqi and the Emergence of the Muslim Diaspora in North America
Authors: Ghamari‐Tabrizi Behrooz
Published: June 2004

In this paper, I weave the experience of an emerging community of Muslim diaspora around a biographical narrative of the Muslim activist and scholar Isma'il al‐Faruqi. Through this narrative, I illustrate that the diasporic experience begins in the place of origin and it does not inevitably lead toward a perpetual hybridization. The latter point is particularly significant because notions of diaspora and hybridity are conceptually linked and are often understood as a unidirectional cutting and mixing between the West and the East, or between the modern and the traditional. Al‐Faruqi's experience shows that, in a Fanonian sense of colonialism, diasporic experience conveys living as a “stranger”, at and away from home.

The postcolonial condition has made it possible for ethnically diverse communities of Muslims to reside in the West, but maintain strong connections with their place of origin. Adopting the allegory of the Prophet's migration or hijra, al‐Faruqi constructed a fantastic notion of the ummah and a normative homo islamicus subject. Although he was profoundly influenced by the diversity of the Muslim Student Associations' constituency, al‐Faruqi encouraged Muslims to transcend their differences and sought to conceive a discursively homogenous ummah. Ultimately, however, his project failed because it did not correspond to real life experiences of Muslims of the West. Historically, Muslim communities have negotiated the boundaries of Muslimhood and the social responsibilities it entails, both in their homelands and in their new home in the West — a new home that increasingly becomes hostile to their presence, and thereby further complicates their triangular diaspora/host society/homeland relationship.
Plastid differentiation and chlorophyll biosynthesis in different leaf layers of white cabbage (Brassica oleracea cv. capitata)
Authors: Solymosi Katalin , Martinez Krisztina , Kristóf Zoltán , Sundqvist Christer , Böddi Béla
Published: June 2004

The contents of protochlorophyllide, protochlorophyll and chlorophyll together with the native arrangements of the pigments and the plastid ultrastructure were studied in different leaf layers of white cabbage (Brassica oleracea cv. capitata) using absorption, 77 K fluorescence spectroscopy and transmission electron microscopy. The developmental stage of the leaves was determined using the differentiation of the stoma complexes as seen by scanning electron microscopy and light microscopy. The pigment content showed a gradual decrease from the outer leaf layer towards the central leaves. The innermost leaves were in a primordial stage in many aspects; they were large but had typical proplastids with few simple inner membranes, and contained protochlorophyllide and its esters in a 2 : 1 ratio and no chlorophyll. Short‐wavelength, not flash‐photoactive protochlorophyllide and/or protochlorophyll forms emitting at 629 and 636 nm were dominant in the innermost leaves. These leaves also had small amounts of the 644 and 654 nm emitting, flash‐photoactive protochlorophyllide forms. Rarely prolamellar bodies were observed in this layer. The outermost leaves had the usual characteristics of fully developed green leaves. The intermediary layers contained chlorophyll a and chlorophyll b besides the protochlorophyll(ide) pigments and had various intermediary developmental stages. Spectroscopically two types of intermediary leaves could be distinguished: one with only a 680 nm emitting chlorophyll a form and a second with bands at 685, 695 and 730 nm, corresponding to chlorophyll–protein complexes of green leaves. In these leaves, a large variety of chloroplasts were found. The data of this work show that etioplasts, etio‐chloroplasts or chloro‐etioplasts as well as etiolated leaves do exist in the nature and not only under laboratory conditions. The specificity of cabbage leaves compared with those of dark‐grown seedlings is the retained primordial or intermediary developmental stage of leaves in the inner layers for very long (even for a few month) period. This opens new developmental routes leading to formation of specially developed plastids in the various cabbage leaf layers. The study of these plastids provided new information for a better understanding of the plastid differentiation and the greening process.
The scientific status of metazoan cladistics: why current research practice must change
Authors: Jenner Ronald A.
Published: June 2004

Jenner, R. A. (2004). The scientific status of metazoan cladistics: why current research practice must change. —Zoologica Scripta,33, 293–310.

Metazoan phylogenetics is bustling with activity. The use of comprehensive morphological data sets in recent phylogenetic analyses of the Metazoa indicates that morphological evidence continues to play a key role in the reconstruction of metazoan deep history. In this paper I review the scientific status of morphological metazoan cladistics from the perspective of cladistic research cycles. Each research cycle consists of three main steps: (1) the compilation of a data matrix (2) the simultaneous evaluation of all possible cladograms in a character congruence test, and (3) the assessment of the relationship between evidence and hypothesis after finding the optimal tree. I identify a striking discrepancy between the sophistication of the analysis of given data sets (Step 2), and their compilation and the interpretation of the results (Steps 1 and 3). The latter two steps deserve far greater attention than is current practice. Uncritical and nonexplicit character selection, character coding, and character scoring seriously compromise Step 1. Careful comparative morphological study prior to data matrix construction is necessary to remedy this problem in future cladistic analyses. Step 2 is the locus of most recent advances in metazoan cladistics through the increasing availability of computing power, and the development of increasingly efficient phylogenetic software that allows analysis of large data sets. Failure to identify problems and errors generated in Step 1 of the research cycle is testament to the general failure of Step 3. Consequently, recent progress in metazoan cladistics is primarily analytical, while the only empirical anchor of the discipline receives surprisingly little attention. Not surprisingly, the first generation of modern metazoan phylogeneticists used computers principally as a relatively quick and easy means to generate abundant phylogenies from morphological data. The next phase should build on this foundation by critically testing these alternative hypotheses by a thorough qualitative reassessment and elaboration of morphological data matrices, and a more critical approach to data selection. A rigorous research program for metazoan cladistics can only be established when the cladistic research cycle is properly completed, and when subsequent research cycles are effectively linked to previous efforts.
Plate 494. Lechenaultia hirsuta Goodeniaceae
Authors: Morrison David , George Alex
Published: June 2004

Summary.  Lechenaultia hirsuta F. Muell. (Goodeniaceae) is the only hairy species of the genus. It is an openly branched plant with large, scarlet flowers.
Plate 495. Lechenaultia linarioides Goodeniaceae
Authors: Morrison David , George Alex
Published: June 2004

Summary.  Lechenaultia linarioides DC. (Goodeniaceae) is a tangled shrub with rather more woody stems than the other species. It has been grown in Europe since the 1840s.
Plate 497. Lechenaultia tubiflora Goodeniaceae
Authors: Morrison David , George Alex
Published: June 2004

Summary.  Lechenaultia tubiflora R.Br. (Goodeniaceae) heath leschenaultia has narrow, tubular flowers that show great variation in colour. It has proved difficult in cultivation.
Development of an in vitro, isolated, infected spore testing model for disinfectant testing of Microsporum canis isolates
Authors: MORIELLO KAREN A. , DEBOER DOUGLAS J. , VOLK LYNN M. , SPARKES ANDREW , ROBINSON ANN
Published: June 2004

Abstract  The isolated infected hair model is a commonly used technique to test the fungicidal efficacy of topical therapies against Microsporum canis. The most commonly used model uses mats of infective hairs, and results from various laboratories have differed. The objectives of this study were to develop a method to produce spores for testing when only mycelial forms were available and to develop a semiquantitative testing method that used only infective spores from hairs, and not pooled hair samples for testing. Ten isolates of M. canis were used in this study. Juvenile guinea pigs were easily infected using mycelial forms of M. canis and large numbers of spores were easily harvested for testing. Eight dilutions of disinfectants were tested. Fungal culture data were evaluated using an endpoint dilution at which there was 100% fungicidal activity, i.e. no growth on the plates. The 10 samples showed identical results. Chlorhexidine and Virkon® S were ineffective even when used at ×4 the manufacturer's recommended dilution. Lime sulphur (1 : 33), enilconazole (20 µL mL−1), and bleach (1 : 10) were consistently effective when used at the recommended dilution. In addition, lime sulphur and enilconazole were 100% fungicidal even when the recommended concentration was diluted 1 : 4 or ×4 as dilute as recommended.
Diversity of geometrid moths (Lepidoptera: Geometridae) along an Afrotropical elevational rainforest transect
Authors: Axmacher Jan C. , Holtmann Gabriele , Scheuermann Luis , Brehm Gunnar , Müller‐Hohenstein Klaus , Fiedler Konrad
Published: June 2004

Geometrid moths were investigated at 26 sites on 9 elevational levels along an elevational transect at Mt. Kilimanjaro (Tanzania), stretching from the fine‐grained mosaic of small agroforest plots with combined cultivation of trees, shrubs and crops at 1650 m through mountain rainforest to heathland at 3300 m. We sampled moths manually at light between 19 : 00 and 22 : 00 in the rainy seasons of March to May and October to January in the years 2000, 2001 and 2002.

Along the transect, the composition of moth communities changed from a domination by Sterrhinae and Ennominae to a dominance of Larentiinae with increasing elevation. Overall, alpha diversity was very low compared to other tropical mountain regions. Fisher's alpha showed a maximum of 30 in the agroforest mosaic at 1650 m and decreased to values around 12 in the mountain rainforest. Communities of geometrid moths within the forest belt were significantly dissimilar from communities outside the forest. The diversity patterns on Mt. Kilimanjaro can be related to the young age, island‐like position and history of the mountain. These factors have led to the formation of a homogeneous upper mountain rainforest habitat which in turn houses homogeneous moth communities with a low diversity compared to habitats at lower elevations. Here, a heterogeneous habitat mosaic allowing the intrusion of savannah species into this former forest habitat may account for an increased diversity. In the heath zone above the forest, climatic conditions are very harsh, permitting only few specialists to thrive in this ericaceous woodland. Edge effects were discernible at the forest–heathland boundary where some moth species from heathland invaded the closed forest. At the boundary between agroforest and a forest mosaic of exotic Acacia and Eucalyptus forest plantations and natural mountain forest, diversity values remained low as the dominant species Chiasmia fuscataria accounted for far higher proportions than other dominant species in any of the other habitats.
Quantitative trait, genetic, environmental, and geographical distances among populations of the C4 grass Trachypogon plumosus in Neotropical savannas
Authors: Baruch Zdravko , Nassar Jafet M. , Bubis José
Published: June 2004

Venezuelan savannas are exposed to land‐use changes and biological invasions which compromise their persistence and function. The native C4 grass Trachypogon plumosus is the most important component of the savannas under diverse combinations of climate and soils, suggesting substantial interpopulation variation. We examined quantitative traits and isozyme variation of nine populations of this grass and related these estimates to geographical and environmental features of sampled locations. Isozyme diversity estimates were based on 10 polymorphic enzyme systems whereas 21 quantitative traits, from field and controlled growth conditions, were evaluated. Distance matrices for quantitative traits, isozyme, geographical and environmental data were subjected to clustering analysis. Correspondence between quantitative trait distance and genetic distance, and their association to geographical and environmental distances were analysed with Mantel tests. All quantitative traits differed significantly among populations. The average QST calculated for eight quantitative traits measured in the greenhouse was 0.157. Isozyme diversity differed significantly among populations. About 28% of total isozyme variation occurred among populations. Significant positive associations were detected between environmental, quantitative field traits, and geographical distance as well as between the later and genetic distances. Genetic distances did not correspond significantly with quantitative traits nor did environmental distances. Ecologically meaningful associations were detected between field quantitative traits, environmental, and geographical data using cluster analysis. Our results support the hypothesis that processes of the neutral type are mainly responsible for the variation patterns observed in T. plumosus populations in Venezuelan savannas. Variation observed for quantitative traits among populations seems to be due to the effect of environmental conditions on phenotypically plastic traits, and not the result of directional selection favouring different phenotypes in different populations.
Reconstruction of the colonization route from glacial refugium to the northern distribution range of the European butterfly Polyommatus coridon (Lepidoptera: Lycaenidae)
Authors: Schmitt Thomas , Krauss Jochen
Published: June 2004

Genetic analyses are useful tools for reconstructing glacial distribution patterns and postglacial expansion corridors. However, little information is available about the latter. We reconstruct the expansion corridors of the butterfly Polyommatus coridon from its glacial refugium to the northern edge of its current distribution by comparing populations from southern Lower Saxony (central Germany) to other existing genetic data sets. The populations from Lower Saxony clearly belonged to a western lineage that expanded postglacially from the Adriatic‐Mediterranean region. They form part of a southern German group passing through the Burgundian Gap. In the southern German group, populations belong to a western subgroup. Therefore, expansion followed the Rhine valley and through Hesse, finally reaching southern Lower Saxony and western Thuringia in central Germany. Thus, we present a complete colonization route from the glacial refugium to the northern distribution range of P. coridon. Such data are useful for understanding the biogeographic structure and migration corridors for other mobile Mediterranean species.