Microbial iron transport via a siderophore shuttle: a membrane ion transport paradigm

A mechanism of ion transport across membranes is reported. Microbial transport of Fe(3+) generally delivers iron, a growth-limiting nutrient, to cells via highly specific siderophore-mediated transport systems. In contrast, iron transport in the fresh water bacterium Aeromonas hydrophila is found to occur by means of an indiscriminant siderophore transport system composed of a single multifunctional receptor. It is shown that (i) the siderophore and Fe(3+) enter the bacterium together, (ii) a ligand exchange step occurs in the course of the transport, and (iii) a redox process is not involved in iron exchange. To the best of our knowledge, there have been no other reports of a ligand exchange mechanism in bacterial iron transport. The ligand exchange step occurs at the cell surface and involves the exchange of iron from a ferric siderophore to an iron-free siderophore already bound to the receptor. This ligand exchange mechanism is also found in Escherichia coli and seems likely to be widely distributed among microorganisms.

Dynamic changes in Rad51 distribution on chromatin during meiosis in male and female vertebrates

Antibodies against human Rad51 protein were used to examine the distribution of Rad51 on meiotic chromatin in mouse spermatocytes and oocytes as well as chicken oocytes during sequential stages of meiosis. We observed the following dynamic changes in distribution of Rad51 during meiosis: (1) in early leptotene nuclei there are multiple, apparently randomly distributed, foci that by late leptonema become organized into tracks of foci. (2) These foci persist into zygonema, but most foci are now localized on Rad51-positive axes that correspond to lateral elements of the synaptonemal complex. As homologs synapse foci from homologous axes fuse. The distribution and involvement of Rad51 foci as contact points between homologs suggest that they may be components to early recombination nodules. (3) As pachynema progresses the number of foci drops dramatically; the temporal occurrence (mice) and physical and numerical distribution of foci on axes (chickens) suggest that they may be a component of late recombination nodules. (4) In early pachynema there are numerous Rad51 foci on the single axis of the X (mouse spermatocytes) or the Z (chicken oocytes) chromosomes that neither pair, nor recombine. (5) In late pachynema in mouse spermatocytes, but not oocytes, the Rad51 signal is preferentially enhanced at both ends of all the bivalents. As bivalents in spermatocytes, but not oocytes, begin to desynapse at diplonema they are often held together at these Rad51-positive termini. These observations parallel observations that recombination rates are exceptionally high near chromosome ends in male but not female eutherian mammals. (6) From diakinesis through metaphase I, Rad51 protein is detected as low-intensity fluorescent doublets that localize with CREST-specific antigens (kinetochores), suggesting that Rad51 participates, at least as a structural component of the materials involved, in sister kinetochore cohesiveness. Finally, the changes in Rad51 distribution during meiosis do not appear to be species specific, but intrinsic to the meiotic process.

Pan1p, End3p, and S1a1p, three yeast proteins required for normal cortical actin cytoskeleton organization, associate with each other and play essential roles in cell wall morphogenesis

The EH domain proteins Pan1p and End3p of budding yeast have been known to form a complex in vivo and play important roles in organization of the actin cytoskeleton and endocytosis. In this report, we describe new findings concerning the function of the Pan1p-End3p complex. First, we found that the Pan1p-End3p complex associates with Sla1p, another protein known to be required for the assembly of cortical actin structures. Sla1p interacts with the first long repeat region of Pan1p and the N-terminal EH domain of End3p, thus leaving the Pan1p-End3p interaction, which requires the second long repeat of Pan1p and the C-terminal repeat region of End3p, undisturbed. Second, Pan1p, End3p, and Sla1p are also required for normal cell wall morphogenesis. Each of the Pan1-4, sla1Delta, and end3Delta mutants displays the abnormal cell wall morphology previously reported for the act1-1 mutant. These cell wall defects are also exhibited by wild-type cells overproducing the C-terminal region of Sla1p that is responsible for interactions with Pan1p and End3p. These results indicate that the functions of Pan1p, End3p, and Sla1p in cell wall morphogenesis may depend on the formation of a heterotrimeric complex. Interestingly, the cell wall abnormalities exhibited by these cells are independent of the actin cytoskeleton organization on the cell cortex, as they manifest despite the presence of apparently normal cortical actin cytoskeleton. Examination of several act1 mutants also supports this conclusion. These observations suggest that the Pan1p-End3p-Sla1p complex is required not only for normal actin cytoskeleton organization but also for normal cell wall morphogenesis in yeast.

Separation orthogonality in temperature-programmed comprehensive two-dimensional gas chromatography

In a comprehensive two-dimensional gas chromatograph, a thermal modulator serially couples two columns containing dissimilar stationary phases. The secondary column generates a series of high-speed secondary chromatograms from the sample stream formed by the chromatogram eluting from the primary column. This series of secondary chromatograms forms a two-dimensional gas chromatogram with peaks dispersed over a retention plane rather than along a line. The method is comprehensive because the entire primary column chromatogram is transmitted through the secondary column with fidelity. One might expect that a two-dimensional separation in which both dimensions are basically the same technique, gas chromatography, would be inefficient because the two dimensions would behave similarly, generating peaks whose retentions correlate across dimensions. Applying a temperature program to the two columns, however, can tune the separation to eliminate this inefficiency. The temperature program reduces the retentive power of the secondary column as a function of progress of the primary chromatogram such that the retention mechanism of the primary column is eliminated from the second dimension. Retention of a substance in the second dimension is then determined by the difference in its interaction with the two stationary phases. Retention times in the second dimension then fall within a fixed range, and the whole retention plane is accessible. In a properly tuned comprehensive two-dimensional chromatogram, retention times in the two dimensions are independent of each other, and the two-dimensional chromatogram is orthogonal. Orthogonality is important for two reasons. First, an orthogonal separation efficiently uses the separation space and so has either greater speed or peak capacity than nonorthogonal separations. Second, retention in the two dimensions of an orthogonal chromatogram is determined by two different and independent mechanisms and so provides two independent measures of molecular properties.

Methods and strategies of peptide ligation

This review focuses on the concept, methods, and strategies of orthogonal peptide ligation. It updates our previous review in 1999 on the same subject matter in Biopolymers (Peptide Science, 1999, Vol. 51, p. 311). Orthogonal peptide ligation is an amino terminal specific method to couple chemically unprotected peptides or proteins derived from synthetic or biosynthetic sources. Unlike conventional chemical methods, peptide ligation methods do not require coupling reagents or protection schemes, but are achieved through a variable chemoselective capture step and then an invariable intramolecular acyl transfer reaction. It is also a convergent method with the fewest steps. More than a dozen orthogonal ligation methods have been developed based on captures by either imine or thioester chemistries to afford native and unusual amino acids at ligation sites of linear, branched, or cyclic peptides. The ligation strategies for multiple segments including sequential and tandem ligations are also discussed.

Phosphorylation of the hepatitis C virus NS5A protein in vitro and in vivo: properties of the NS5A-associated kinase

NS5A derived from a hepatitis C virus (HCV) genotype 1b isolate has previously been shown to undergo phosphorylation on serine residues (T. Kaneko, Y. Tanji, S. Satoh, M. Hijikata, S. Asabe, K. Kimura, and K. Shimotohno, Biochem. Biophys. Res. Commun. 205:320-326, 1994). In this report, phosphorylation of NS5A derived from HCV isolates of the 1a and distantly related 2a genotypes is demonstrated. Phosphoamino acid analysis of NS5A from the 1a isolate indicated that phosphorylation occurs predominantly on serine, with a minor fraction of threonine residues also being phosphorylated. NS5A phosphorylation was observed in diverse cell types, including COS-1, BHK-21, HeLa, and the hepatoma cell line HuH-7. Phosphorylation of a glutathione S-transferase (GST)/HCV-H NS5A fusion protein was also demonstrated in an in vitro kinase assay. This activity seemed to be highest when the pH of the reaction was neutral or slightly alkaline and displayed a preference for Mn2+ over Mg2+, with an optimum concentration of approximately 10 mM Mn2+. Somewhat surprisingly, in vitro phosphorylation of NS5A was inhibited by the addition of > or = 0.25 mM Ca2+ to reaction buffer containing Mn2+ and/or Mg2+. Comparison of phosphopeptide maps of NS5A phosphorylated in vitro and in cultured cells showed that most of the phosphopeptides comigrated, suggesting that one or more kinases involved in NS5A phosphorylation in vivo and in vitro are the same. The effects of various kinase inhibitors on NS5A phosphorylation were consistent with a kinase activity belonging to the CMGC group of serine-threonine kinases. The development of an in vitro kinase assay for NS5A phosphorylation should facilitate identification of kinase(s) responsible for its phosphorylation and of phosphorylation sites which may influence the function of NS5A in HCV propagation.

Pioneer factors, genetic competence, and inductive signaling: programming liver and pancreas progenitors from the endoderm

The endoderm is a multipotent progenitor cell population in the embryo that gives rise to the liver, pancreas, and other cell types and provides paradigms for understanding cell-type specification. Studies of isolated embryo tissue cells and genetic approaches in vivo have defined fibroblast growth factor/mitogen-activated protein kinase (FGF/MAPK) and bone morphogenetic protein (BMP) signaling pathways that induce liver and pancreatic fates in the endoderm. In undifferentiated endoderm cells, the FoxA and GATA transcription factors are among the first to engage silent genes, helping to endow competence for cell-type specification. FoxA proteins can bind their target sites in highly compacted chromatin and open up the local region for other factors to bind; hence, they have been termed "pioneer factors." We recently found that FoxA proteins remain bound to chromatin in mitosis, as an epigenetic mark. In embryonic stem cells, which lack FoxA, FoxA target sites can be occupied by FoxD3, which in turn helps to maintain a local demethylation of chromatin. By these means, a cascade of Fox factors helps to endow progenitor cells with the competence to activate genes in response to tissue-inductive signals. Understanding such epigenetic mechanisms for transcriptional competence coupled with knowledge of the relevant signals for cell-type specification should greatly facilitate efforts to predictably differentiate stem cells to liver and pancreatic fates.

A multicenter randomized controlled trial of a plant-based nutrition program to reduce body weight and cardiovascular risk in the corporate setting: the GEICO study

Background/objectives:

To determine the effects of a low-fat plant-based diet program on anthropometric and biochemical measures in a multicenter corporate setting.

Subjects/methods:

Employees from 10 sites of a major US company with body mass index ⩾25 kg/m² and/or previous diagnosis of type 2 diabetes were randomized to either follow a low-fat vegan diet, with weekly group support and work cafeteria options available, or make no diet changes for 18 weeks. Dietary intake, body weight, plasma lipid concentrations, blood pressure and glycated hemoglobin (HbA_1C) were determined at baseline and 18 weeks.

Results:

Mean body weight fell 2.9 kg and 0.06 kg in the intervention and control groups, respectively (P<0.001). Total and low-density lipoprotein (LDL) cholesterol fell 8.0 and 8.1 mg/dl in the intervention group and 0.01 and 0.9 mg/dl in the control group (P<0.01). HbA_1C fell 0.6 percentage point and 0.08 percentage point in the intervention and control group, respectively (P<0.01).

Among study completers, mean changes in body weight were −4.3 kg and −0.08 kg in the intervention and control groups, respectively (P<0.001). Total and LDL cholesterol fell 13.7 and 13.0 mg/dl in the intervention group and 1.3 and 1.7 mg/dl in the control group (P<0.001). HbA_1C levels decreased 0.7 percentage point and 0.1 percentage point in the intervention and control group, respectively (P<0.01).

Conclusions:

An 18-week dietary intervention using a low-fat plant-based diet in a corporate setting improves body weight, plasma lipids, and, in individuals with diabetes, glycemic control.

NAB domain is essential for the subunit assembly of both alpha-alpha and alpha-beta complexes of shaker-like potassium channels

There are at least five subfamilies of Shaker-like K+ channels. The diverse function of K+ channels are thought to be further modulated by hydrophilic beta subunits. Here we report that Kv beta 1 inactivates RCK4 and Shaker B K+ channels of the Kv1 subfamily, but not Shal2 of the Kv4 subfamily. This correlates the subfamily-specific bindings of Kv beta 1 to the cytoplasmic N-terminal domains of Kv1 alpha subunits. We map the Kv beta 1-binding site to a region overlapping NABKv1, a domain that specifies different Kv1 alpha subunits to form heterotetramers. Using chimeric alpha subunits, we demonstrate that NABKv1 is essential for the Kv beta 1-mediated inactivation. These results suggest that Kv beta 1 modulates a subset of K+ channels through the specific assembly of alpha-beta complexes and reveal the dual function of the NAB domain in mediating the assembly of both alpha-alpha and alpha-beta complexes.

Secondary follicle growth and oocyte maturation during encapsulated three-dimensional culture in rhesus monkeys: effects of gonadotrophins, oxygen and fetuin

BACKGROUND

An alginate-based matrix supports the three-dimensional (3D) architecture of non-human primate follicles and, in the presence of FSH, permits the in vitro development of pre-antral follicles to the small antral stage, including the production of ovarian steroids and paracrine factors. The current study investigated the ability of gonadotrophins, fetuin and oxygen (O₂) to improve primate follicle growth and oocyte maturation in vitro.

METHODS

Macaque secondary follicles were isolated from the early follicular phase ovaries, encapsulated in a sodium alginate matrix and cultured individually for 40 days in supplemented medium. The effects of recombinant human (rh) FSH (15, 3 and 0.3 ng/ml for high, medium and low FSH, respectively), bovine fetuin (1 or 0 mg/ml) and O₂ (5 or 20% v/v) were examined. Half of the follicles in each culture condition received rhLH on Day 30-40. Follicles that reached antral stage were treated with rh chorionic gonadotrophin for 34 h to initiate oocyte meiotic maturation. Media were analyzed for ovarian steroids and anti-müllerian hormone (AMH).

RESULTS

Improved culture conditions supported non-human primate, secondary follicle growth to the antral stage and, for the first time, promoted oocyte maturation to the MII stage. In the presence of fetuin at 5% O₂, follicles had the highest survival rate if cultured with high or medium FSH, whereas follicles grew to larger diameters at Week 5 in low FSH. Oocyte health and maturation were promoted under 5% O₂. High FSH stimulated steroid production by growing follicles, and steroidogenesis by follicles cultured with low FSH was promoted by LH. AMH biosynthesis was elevated with high compared with low FSH and for longer under 5% O₂ than under 20% O₂.

CONCLUSIONS

This encapsulated 3D culture model permits further studies on the endocrine and local factors that influence primate follicle growth and oocyte maturation, with relevance to enhancing fertility preservation options in women.

Twist1 promotes breast cancer invasion and metastasis by silencing Foxa1 expression

The heterogeneous breast cancers can be classified into different subtypes according to their histopathological characteristics and molecular signatures. Foxa1 expression is linked with luminal breast cancer (LBC) with good prognosis, whereas Twist1 expression is associated with basal-like breast cancer (BLBC) with poor prognosis owing to its role in promoting epithelial-to-mesenchymal transition (EMT), invasiveness and metastasis. However, the regulatory and functional relationships between Twist1 and Foxa1 in breast cancer progression are unknown. In this study, we demonstrate that in the estrogen receptor (ERα)-positive LBC cells Twist1 silences Foxa1 expression, which has an essential role in relieving Foxa1-arrested migration, invasion and metastasis of breast cancer cells. Mechanistically, Twist1 binds to Foxa1 proximal promoter and recruits the NuRD transcriptional repressor complex to de-acetylate H3K9 and repress RNA polymerase II recruitment. Twist1 also silences Foxa1 promoter by inhibiting AP-1 recruitment. Twist1 expression in MCF7 cells silenced Foxa1 expression, which was concurrent with the induction of EMT, migration, invasion and metastasis of these cells. Importantly, restored Foxa1 expression in these cells largely inhibited Twist1-promoted migration, invasion and metastasis. Restored Foxa1 expression did not change the Twist1-induced mesenchymal cellular morphology and the expression of Twist1-regulated E-cadherin, β-catenin, vimentin and Slug, but it partially rescued Twist1-silenced ERα and cytokeratin 8 expression and reduced Twist1-induced integrin α5, integrin β1 and MMP9 expression. In a xenografted mouse model, restored Foxa1 also increased Twist1-repressed LBC markers and decreased Twist1-induced BLBC markers. Furthermore, Twist1 expression is negatively correlated with Foxa1 in the human breast tumors. The tumors with high Twist1 and low Foxa1 expressions are associated with poor distant metastasis-free survival. These results demonstrate that Twist1's silencing effect on Foxa1 expression is largely responsible for Twist1-induced migration, invasion and metastasis, but less responsible for Twist1-induced mesenchymal morphogenesis and expression of certain EMT markers.

Identification of genes overexpressed in head and neck squamous cell carcinoma using a combination of complementary DNA subtraction and microarray analysis

OBJECTIVES/HYPOTHESIS

To discover unique genes specific for squamous cell carcinoma of the head and neck for eventual development as tumor markers and vaccine candidates.

STUDY DESIGN

Molecular biological analysis of fresh-frozen head and neck squamous cell cancer (HNSCC).

METHODS

A subtractive library was made from two HNSCC and six normal tissues using a polymerase chain reaction (PCR)-based approach. Genes from this library were PCR amplified and placed on a microarray glass slide. RNA was prepared or obtained from 16 fresh-frozen HNSCC and 22 normal tissue sources. Fluorescent probes were made from the polyA+ RNA derived from the tumor and normal tissues. The probes were hybridized to the glass slides and excited by a tuneable laser. One hundred seven of the genes showing the highest differential fluorescence value between tumor and normal tissue were identified by sequence analysis.

RESULTS

Thirteen independent genes were found to be overexpressed in tumor tissues. Of these, nine were previously known: keratins K6 and K16, laminin-5, plakophilin-1, matrix metalloproteinase-2 (MMP), vascular endothelial growth factor, connexin 26, 14-3-3 sigma, and CaN19. The level of polyA+ RNA of these genes in the tumors was significantly different from the levels in normal tissue (P < .05). Four previously unidentified genes were also discovered to have increased expression in tumor tissue. Comparing the total tumor group (n = 16) to the normal group (n = 22), only one of these genes showed significant overexpression.

CONCLUSION

We report the identification of nine known genes that are significantly overexpressed in HNSCC as compared to normal tissue using subtractive and microarray technology. In addition, we present four previously unidentified genes that are overexpressed in a subset of tumors. These genes will be developed as tumor markers and vaccine candidates.

The Gelation of CO(2): A Sustainable Route to the Creation of Microcellular Materials

Compounds with strong thermodynamic affinity for carbon dioxide (CO(2)) have been designed and synthesized that dissolve in CO(2), then associate to form gels. Upon removal of the CO(2), these gels produced free-standing foams with cells with an average diameter smaller than 1 micrometer and a bulk density reduction of 97 percent relative to the parent material.

The new function of circRNA: translation

Circular RNAs (circRNAs) have been considered a special class of non-coding RNAs without 5' caps and 3' tails which are covalently closed RNA molecules generated by back splicing of mRNA. For a long time, circRNAs have been considered to be directly involved in various biological processes as functional RNA. In recent years, a variety of circRNAs have been found to have translational functions, and the resultant peptides also play biological roles in the emergence and progression of human disease. The discovery of these circRNAs and their encoded peptides has enriched genomics, helped us to study the causes of diseases, and promoted the development of biotechnology. The purpose of this review is to summarize the research progress of the detection methods, translation initiation mechanism, as well as functional mechanism of peptides encoded by circRNAs, with the goal of providing the directions for the discovery of biomarkers for diagnosis, prognosis, and therapeutic targets for human disease.

Primary care, infant mortality, and low birth weight in the states of the USA

STUDY OBJECTIVE

The study tests the extent to which primary care physician supply (office based primary care physicians per 10 000 population) moderates the association between social inequalities and infant mortality and low birth weight throughout the 50 states of the USA.

DESIGN

Pooled cross sectional, time series analysis of secondary data. Analyses controlled for state level education, unemployment, racial/ethnic composition, income inequality, and urban/rural differences. Contemporaneous and time lagged covariates were modelled.

SETTING

Eleven years (1985-95) of data from 50 US states (final n = 549 because of one missing data point).

MAIN RESULTS

Primary care was negatively associated with infant mortality and low birth weight in all multivariate models (p<0.0001). The association was consistent in contemporaneous and time lagged models. Although income inequality was positively associated with low birth weight and infant mortality (p<0.0001), the association with infant mortality disappeared with the addition of sociodemographic covariates.

CONCLUSIONS

In US states, an increased supply of primary care practitioners-especially in areas with high levels of social disparities-is negatively associated with infant mortality and low birth weight.

Cloning and characterization of osteoactivin, a novel cDNA expressed in osteoblasts

Osteoblast development is a complex process involving the expression of specific growth factors and regulatory proteins that control cell proliferation, differentiation, and maturation. In this study, we used the rat mutation, osteopetrosis (op), to examine differences in skeletal gene expression between mutant op and normal littermates. Total RNA isolated from long bone and calvaria was used as a template for mRNA differential display. One of many cDNAs that were selectively expressed in either normal or mutant bone was cloned and sequenced and found to share some homology to the human nmb and Pmel 17 genes. This novel cDNA was named osteoactivin. Osteoactivin has an open reading frame of 1716 bp that encodes a protein of 572 amino acids with a predicted molecular weight of 63.8 kD. Protein sequence analysis revealed the presence of a signal peptide and a cleavage site at position 23. The protein also has thirteen predicted N-linked glycosylation sites and a potential RGD integrin recognition site at position 556. Northern blot analysis confirmed that osteoactivin was 3- to 4-fold overexpressed in op versus normal bone. RT-PCR analysis showed that osteoactivin is most highly expressed in bone compared with any of the other non-osseous tissues examined. In situ hybridization analysis of osteoactivin in normal bone revealed that it is primarily expressed in osteoblasts actively engaged in bone matrix production and mineralization. In primary rat osteoblast cultures, osteoactivin showed a temporal pattern of expression being expressed at highest levels during the later stages of matrix maturation and mineralization and correlated with the expression of alkaline phosphatase and osteocalcin. Our findings show that osteoactivin expression in bone is osteoblast-specific and suggest that it may play an important role in osteoblast differentiation and matrix mineralization. Furthermore, osteoactivin overexpression in op mutant bone may be secondary to the uncoupling of bone resorption and formation resulting in abnormalities in osteoblast gene expression and function.

Functional neuronavigation combined with intra-operative 3D ultrasound: initial experiences during surgical resections close to eloquent brain areas and future directions in automatic brain shift compensation of preoperative data

OBJECTIVE

The aims of this study were: 1) To develop protocols for, integration and assessment of the usefulness of high quality fMRI (functional magnetic resonance imaging) and DTI (diffusion tensor imaging) data in an ultrasound-based neuronavigation system. 2) To develop and demonstrate a co-registration method for automatic brain-shift correction of pre-operative MR data using intra-operative 3D ultrasound.

METHODS

Twelve patients undergoing brain surgery were scanned to obtain structural and fMRI data before the operation. In six of these patients, DTI data was also obtained. The preoperative data was imported into a commercial ultrasound-based navigation system and used for surgical planning and guidance. Intra-operative ultrasound volumes were acquired when needed during surgery and the multimodal data was used for guidance and resection control. The use of the available image information during planning and surgery was recorded. An automatic voxel-based registration method between preoperative MRA and intra-operative 3D ultrasound angiography (Power Doppler) was developed and tested postoperatively.

RESULTS

The study showed that it is possible to implement robust, high-quality protocols for fMRI and DTI and that the acquired data could be seamlessly integrated in an ultrasound-based neuronavigation system. Navigation based on fMRI data was found to be important for pre-operative planning in all twelve procedures. In five out of eleven cases the data was also found useful during the resection. DTI data was found to be useful for planning in all five cases where these data were imported into the navigation system. In two out of four cases DTI data was also considered important during the resection (in one case DTI data were acquired but not imported and in another case fMRI and DTI data could only be used for planning). Information regarding the location of important functional areas (fMRI) was more beneficial during the planning phase while DTI data was more helpful during the resection. Furthermore, the surgeon found it more user-friendly and efficient to interpret fMRI and DTI information when shown in a navigation system as compared to the traditional display on a light board or monitor. Updating MRI data for brain-shift using automatic co-registration of preoperative MRI with intra-operative ultrasound was feasible.

CONCLUSION

In the present study we have demonstrated how both fMRI and DTI data can be acquired and integrated into a neuronavigation system for improved surgical planning and guidance. The surgeons reported that the integration of fMRI and DTI data in the navigation system represented valuable additional information presented in a user-friendly way and functional neuronavigation is now in routine use at our hospital. Furthermore, the present study showed that automatic ultrasound-based updates of important pre-operative MRI data are feasible and hence can be used to compensate for brain shift.

Keratin filament suspensions show unique micromechanical properties

All epithelial cells feature a prominent keratin intermediate filament (IF) network in their cytoplasm. Studies in transgenic mice and in patients with inherited epithelial fragility syndromes showed that a major function of keratin IFs is to provide mechanical support to epithelial cell sheets. Yet the micromechanical properties of keratin IFs themselves remain unknown. We used rheological methods to assess the properties of suspensions of epidermal type I and type II keratin IFs and of vimentin, a type III IF polymer. We find that both types of IFs form gels with properties akin to visco-elastic solids. With increasing deformation they display strain hardening and yield relatively rapidly. Remarkably, both types of gels recover their preshear properties upon cessation of the deformation. Repeated imposition of small deformations gives rise to a progressively stiffer gel for keratin but not vimentin IFs. The visco-elastic moduli of both gels show a weak dependence upon the frequency of the input shear stress and the concentration of the polymer, suggesting that both steric and nonsteric interactions between individual polymers contribute to the observed mechanical properties. In support of this, the length of individual polymers contributes only modestly to the properties of IF gels. Collectively these properties render IFs unique among cytoskeletal polymers and have strong implications for their function in vivo.

Cloning and characterization of a mouse sigma1 receptor

A cDNA clone (S2-1a) isolated from a mouse brain cDNA library, using a guinea pig sigma1 cDNA as probe, has high homology to the predicted protein sequence of the guinea pig (88%) and human (90%) sigma1 receptors. Northern analysis revealed a major mRNA of approximately 1.8 kb in a wide range of mouse tissues, with highest levels in brain, liver, kidney, and thymus. Southern analysis and chromosomal mapping in the mouse suggested a single-copy gene in region A5-B2 of chromosome 4. Expression of the clone in MCF-7 and CHO cells led to a pronounced increase in (+)-[3H]pentazocine binding with a selectivity profile consistent with sigma1 receptors. In vitro translation yielded a protein of approximately 28 kDa, as did transfection of a probe containing the hemagglutinin (HA) epitope (S2-1a.HA) into CHO cells, as determined by western analysis using an antibody directed against HA. (+)-[3H]-Pentazocine binding to immunopurified HA-tagged receptor demonstrated conclusively that S2-1a.HA encodes a high-affinity (+)-[3H]pentazocine binding site with characteristics of a murine sigma1 receptor. An antisense oligodeoxynucleotide designed from S2-1a potentiated opioid analgesia in vivo.

Bovine viral diarrhea virus NS3 serine proteinase: polyprotein cleavage sites, cofactor requirements, and molecular model of an enzyme essential for pestivirus replication

Members of the Flaviviridae encode a serine proteinase termed NS3 that is responsible for processing at several sites in the viral polyproteins. In this report, we show that the NS3 proteinase of the pestivirus bovine viral diarrhea virus (BVDV) (NADL strain) is required for processing at nonstructural (NS) protein sites 3/4A, 4A/4B, 4B/5A, and 5A/5B but not for cleavage at the junction between NS2 and NS3. Cleavage sites of the proteinase were determined by amino-terminal sequence analysis of the NS4A, NS4B, NS5A, and NS5B proteins. A conserved leucine residue is found at the P1 position of all four cleavage sites, followed by either serine (3/4A, 4B/5A, and 5A/5B sites) or alanine (4A/4B site) at the P1' position. Consistent with this cleavage site preference, a structural model of the pestivirus NS3 proteinase predicts a highly hydrophobic P1 specificity pocket. trans-Processing experiments implicate the 64-residue NS4A protein as an NS3 proteinase cofactor required for cleavage at the 4B/5A and 5A/5B sites. Finally, using a full-length functional BVDV cDNA clone, we demonstrate that a catalytically active NS3 serine proteinase is essential for pestivirus replication.

Extracellular hmgb1 functions as an innate immune-mediator implicated in murine cardiac allograft acute rejection

Hmgb1, an evolutionarily conserved chromosomal protein, was recently re-discovered to be an innate immune-mediator contributing to both innate and adaptive immune responses. Here, we show a pivotal role for Hmgb1 in acute allograft rejection in a murine cardiac transplantation model. Extracellular Hmgb1 was found to be a potent stimulator for adaptive immune responses. Hmgb1 can be either passively released from damaged cells after organ harvest and ischemia/reperfusion insults, or actively secreted by allograft infiltrated immune cells. After transplantation, allografts show a significant temporal up-regulation of Hmgb1 expression accompanied by inflammatory infiltration, a consequence of graft destruction. These data suggest the involvement of Hmgb1 in acute allograft rejection. In line with these observations, treatment of recipients with rA-box, a specific blockade for endogenous Hmgb1, significantly prolonged cardiac allograft survival as compared to those recipients treated with either rGST or control vehicle. The enhanced graft survival is associated with reduced allograft expression of TNFalpha, IFNgamma and Hmgb1 and impaired Th1 immune response.

Impaired primary T cell responses in L-selectin-deficient mice

L-selectin is a homing receptor that mediates the selective attachment of leukocytes to specialized high endothelial venules. To study the potential role of L-selectin in immune responses in intact mice, we generated L-selectin-deficient mice by gene targeting. L-selectin-deficient mice are defective in cutaneous delayed-type hypersensitivity (DTH) responses when tested after conventional intervals of immunization (4 d). Primary T cell proliferative responses and cytokine production (interleukin [IL] 2, IL-4, and interferon gamma) were also compromised when tested after 5 d of immunization, indicating that L-selectin is important for the immune response to antigens. In contrast, after more prolonged immunization protocols (9 d), normal responses were observed, suggesting that L-selectin-independent compensatory mechanisms exist. Interestingly, humoral responses of L-selectin-deficient mice to keyhole limpet hemocyanin are indistinguishable from wild-type control mice, implying that L-selectin plays no rate-limiting role in T cell help of B cell function. Thus, our results suggest that L-selectin plays an important role in the generation of primary T cell responses but may not be essential for humoral and memory T cell responses. L-selectin does not appear to be rate limiting for the events leading to antigen-driven neutrophil recruitment, since normal DTH responses are obtained at late time points after immunization.

Technical Note: spektr 3.0-A computational tool for x-ray spectrum modeling and analysis

PURPOSE

A computational toolkit (spektr 3.0) has been developed to calculate x-ray spectra based on the tungsten anode spectral model using interpolating cubic splines (TASMICS) algorithm, updating previous work based on the tungsten anode spectral model using interpolating polynomials (TASMIP) spectral model. The toolkit includes a matlab (The Mathworks, Natick, MA) function library and improved user interface (UI) along with an optimization algorithm to match calculated beam quality with measurements.

METHODS

The spektr code generates x-ray spectra (photons/mm(2)/mAs at 100 cm from the source) using TASMICS as default (with TASMIP as an option) in 1 keV energy bins over beam energies 20-150 kV, extensible to 640 kV using the TASMICS spectra. An optimization tool was implemented to compute the added filtration (Al and W) that provides a best match between calculated and measured x-ray tube output (mGy/mAs or mR/mAs) for individual x-ray tubes that may differ from that assumed in TASMICS or TASMIP and to account for factors such as anode angle.

RESULTS

The median percent difference in photon counts for a TASMICS and TASMIP spectrum was 4.15% for tube potentials in the range 30-140 kV with the largest percentage difference arising in the low and high energy bins due to measurement errors in the empirically based TASMIP model and inaccurate polynomial fitting. The optimization tool reported a close agreement between measured and calculated spectra with a Pearson coefficient of 0.98.

CONCLUSIONS

The computational toolkit, spektr, has been updated to version 3.0, validated against measurements and existing models, and made available as open source code. Video tutorials for the spektr function library, UI, and optimization tool are available.

Combined analysis of hereditary prostate cancer linkage to 1q24-25: results from 772 hereditary prostate cancer families from the International Consortium for Prostate Cancer Genetics

A previous linkage study provided evidence for a prostate cancer-susceptibility locus at 1q24-25. Subsequent reports in additional collections of families have yielded conflicting results. In addition, evidence for locus heterogeneity has been provided by the identification of other putative hereditary prostate cancer loci on Xq27-28, 1q42-43, and 1p36. The present study describes a combined analysis for six markers in the 1q24-25 region in 772 families affected by hereditary prostate cancer and ascertained by the members of the International Consortium for Prostate Cancer Genetics (ICPCG) from North America, Australia, Finland, Norway, Sweden, and the United Kingdom. Overall, there was some evidence for linkage, with a peak parametric multipoint LOD score assuming heterogeneity (HLOD) of 1.40 (P=.01) at D1S212. The estimated proportion of families (alpha) linked to the locus was.06 (1-LOD support interval.01-.12). This evidence was not observed by a nonparametric approach, presumably because of the extensive heterogeneity. Further parametric analysis revealed a significant effect of the presence of male-to-male disease transmission within the families. In the subset of 491 such families, the peak HLOD was 2.56 (P=.0006) and alpha =.11 (1-LOD support interval.04-.19), compared with HLODs of 0 in the remaining 281 families. Within the families with male-to-male disease transmission, alpha increased with the early mean age at diagnosis (<65 years, alpha =.19, with 1-LOD support interval.06-.34) and the number of affected family members (five or more family members, alpha =.15, with 1-LOD support interval.04-.28). The highest value of alpha was observed for the 48 families that met all three criteria (peak HLOD = 2.25, P=.001, alpha=.29, with 1-LOD support interval.08-.53). These results support the finding of a prostate cancer-susceptibility gene linked to 1q24-25, albeit in a defined subset of prostate cancer families. Although HPC1 accounts for only a small proportion of all families affected by hereditary prostate cancer, it appears to play a more prominent role in the subset of families with several members affected at an early age and with male-to-male disease transmission.