Lifespan extension and delayed immune and collagen aging in mutant mice with defects in growth hormone production

Single-gene mutations that extend lifespan provide valuable tools for the exploration of the molecular basis for age-related changes in cell and tissue function and for the pathophysiology of age-dependent diseases. We show here that mice homozygous for loss-of-function mutations at the Pit1 (Snell dwarf) locus show a >40% increase in mean and maximal longevity on the relatively long-lived (C3H/HeJ × DW/J)F1 background. Mutant dwJ/dw animals show delays in age-dependent collagen cross-linking and in six age-sensitive indices of immune system status. These findings thus demonstrate that a single gene can control maximum lifespan and the timing of both cellular and extracellular senescence in a mammal. Pituitary transplantation into dwarf mice does not reverse the lifespan effect, suggesting that the effect is not due to lowered prolactin levels. In contrast, homozygosity for the Ghrhrlit mutation, which like the Pit1dw mutation lowers plasma growth hormone levels, does lead to a significant increase in longevity. Male Snell dwarf mice, unlike calorically restricted mice, become obese and exhibit proportionately high leptin levels in old age, showing that their exceptional longevity is not simply due to alterations in adiposity per se. Further studies of the Pit1dw mutant, and the closely related, long-lived Prop-1df (Ames dwarf) mutant, should provide new insights into the hormonal regulation of senescence, longevity, and late life disease.

Direct observation of extension and retraction of type IV pili

Type IV pili are thin filaments that extend from the poles of a diverse group of bacteria, enabling them to move at speeds of a few tenths of a micrometer per second. They are required for twitching motility, e.g., in Pseudomonas aeruginosa and Neisseria gonorrhoeae, and for social gliding motility in Myxococcus xanthus. Here we report direct observation of extension and retraction of type IV pili in P. aeruginosa. Cells without flagellar filaments were labeled with an amino-specific Cy3 fluorescent dye and were visualized on a quartz slide by total internal reflection microscopy. When pili were attached to a cell and their distal ends were free, they extended or retracted at rates of about 0.5 μm s−1 (29°C). They also flexed by Brownian motion, exhibiting a persistence length of about 5 μm. Frequently, the distal tip of a filament adsorbed to the substratum and the filament was pulled taut. From the absence of lateral deflections of such filaments, we estimate tensions of at least 10 pN. Occasionally, cell bodies came free and were pulled forward by pilus retraction. Thus, type IV pili are linear actuators that extend, attach at their distal tips, exert substantial force, and retract.

Adjoint modular Galois representations and their Selmer groups

In the last 15 years, many class number formulas and main conjectures have been proven. Here, we discuss such formulas on the Selmer groups of the three-dimensional adjoint representation ad(φ) of a two-dimensional modular Galois representation φ. We start with the p-adic Galois representation φ0 of a modular elliptic curve E and present a formula expressing in terms of L(1, ad(φ0)) the intersection number of the elliptic curve E and the complementary abelian variety inside the Jacobian of the modular curve. Then we explain how one can deduce a formula for the order of the Selmer group Sel(ad(φ0)) from the proof of Wiles of the Shimura–Taniyama conjecture. After that, we generalize the formula in an Iwasawa theoretic setting of one and two variables. Here the first variable, T, is the weight variable of the universal p-ordinary Hecke algebra, and the second variable is the cyclotomic variable S. In the one-variable case, we let φ denote the p-ordinary Galois representation with values in GL2(Zp[[T]]) lifting φ0, and the characteristic power series of the Selmer group Sel(ad(φ)) is given by a p-adic L-function interpolating L(1, ad(φk)) for weight k + 2 specialization φk of φ. In the two-variable case, we state a main conjecture on the characteristic power series in Zp[[T, S]] of Sel(ad(φ) ⊗ ν−1), where ν is the universal cyclotomic character with values in Zp[[S]]. Finally, we describe our recent results toward the proof of the conjecture and a possible strategy of proving the main conjecture using p-adic Siegel modular forms.

Deforming semistable Galois representations

Let V be a p-adic representation of Gal(Q̄/Q). One of the ideas of Wiles’s proof of FLT is that, if V is the representation associated to a suitable autromorphic form (a modular form in his case) and if V′ is another p-adic representation of Gal(Q̄/Q) “closed enough” to V, then V′ is also associated to an automorphic form. In this paper we discuss which kind of local condition at p one should require on V and V′ in order to be able to extend this part of Wiles’s methods.

On degree 2 Galois representations over

We discuss proofs of some new special cases of Serre’s conjecture on odd, degree 2 representations of Gℚ.

Sequence-specific arrest of primer extension on single-stranded DNA by an oligonucleotide-minor groove binder conjugate.

A minor groove binder (MGB) derivative (N-3-carbamoyl-1,2-dihydro-3H-pyrrolo[3,2-e]indole-7-carboxylate tripeptide; CDPI3) was covalently linked to the 5' or 3' end of several oligodeoxyribonucleotides (ODNs) totally complementary or possessing a single mismatch to M13mp19 single-stranded DNA. Absorption thermal denaturation and slot-blot hybridization studies showed that conjugation of CDPI3 to these ODNs increased both the specificity and the strength with which they hybridized. Primer extension of the same phage DNA by a modified form of phage T7 DNA polymerase (Sequenase) was physically blocked when a complementary 16-mer with a conjugated 5'-CDPI3 moiety was hybridized to a downstream site. Approximately 50% of the replicating complexes were arrested when the blocking ODN was equimolar to the phage DNA. Inhibition was unaffected by 3'-capping of the ODN with a hexanol group or by elimination of a preannealing step. Blockage was abolished when a single mismatch was introduced into the ODN or when the MGB was either removed or replaced by a 5'-acridine group. A 16-mer with a 3'-CDPI3 moiety failed to arrest primer extension, as did an unmodified 32-mer. We attribute the exceptional stability of hybrids formed by ODNs conjugated to a CDPI3 to the tethered tripeptide binding in the minor groove of the hybrid. When that group is linked to the 5' end of a hybridized ODN, it probably blocks DNA synthesis by inhibiting strand displacement. These ODNs conjugated to CDPI3 offer attractive features as diagnostic probes and antigene agents.

Heterogeneity of primer extension products in asymmetric PCR is due both to cleavage by a structure-specific exo/endonuclease activity of DNA polymerases and to premature stops.

In PCR, DNA polymerases from thermophilic bacteria catalyze the extension of primers annealed to templates as well as the structure-specific cleavage of the products of primer extension. Here we show that cleavage by Thermus aquaticus and Thermus thermophilus DNA polymerases can be precise and substantial: it occurs at the base of the stem-loop structure assumed by the single strand products of primer extension using as template a common genetic element, the promoter-operator of the Escherichia coli lactose operon, and may involve up to 30% of the products. The cleavage is independent of primer, template, and triphosphates, is dependent on substrate length and temperature, requires free ends and Mg2+, and is absent in DNA polymerases lacking the 5'-->3' exonuclease, such as the Stoffel fragment and the T7 DNA polymerase. Heterogeneity of the extension products results also from premature detachment of the enzyme approaching the 5' end of the template.

Formation of chimeric DNA primer extension products by template switching onto an annealed downstream oligonucleotide.

Oligodeoxynucleotide sequences are described that anneal to a template downstream of a priming site. During polymerase-catalyzed extension of the primer, the extending primer shifts from the original template to a segment of the annealed oligonucleotide that acts as an alternative template. The resulting chimeric extended primer has one segment that is complementary to the template and a second segment that is complementary to the oligonucleotide. The influence of the sequence elements of the oligonucleotide and the reaction conditions on template switching have been explored. The sequence requirements for template switching are compared to those for transposon excision.

Molecular cloning and sequence analysis of expansins--a highly conserved, multigene family of proteins that mediate cell wall extension in plants.

Expansins are unusual proteins discovered by virtue of their ability to mediate cell wall extension in plants. We identified cDNA clones for two cucumber expansins on the basis of peptide sequences of proteins purified from cucumber hypocotyls. The expansin cDNAs encode related proteins with signal peptides predicted to direct protein secretion to the cell wall. Northern blot analysis showed moderate transcript abundance in the growing region of the hypocotyl and no detectable transcripts in the nongrowing region. Rice and Arabidopsis expansin cDNAs were identified from collections of anonymous cDNAs (expressed sequence tags). Sequence comparisons indicate at least four distinct expansin cDNAs in rice and at least six in Arabidopsis. Expansins are highly conserved in size and sequence (60-87% amino acid sequence identity and 75-95% similarity between any pairwise comparison), and phylogenetic trees indicate that this multigene family formed before the evolutionary divergence of monocotyledons and dicotyledons. Sequence and motif analyses show no similarities to known functional domains that might account for expansin action on wall extension. A series of highly conserved tryptophans may function in expansin binding to cellulose or other glycans. The high conservation of this multigene family indicates that the mechanism by which expansins promote wall extensin tolerates little variation in protein structure.

Exception or extension? : reorienting the Peacock Room among James McNeill Whistler's interior designs

"Although famous for his paintings and etchings today, James McNeill Whistler (1834-1903) was also an important interior designer in the nineteenth-century British Aesthetic movement. Whistler‘s most famous and only extant interior design is Harmony in Blue and Gold: The Peacock Room (1876-77). It is also his most puzzling interior. Long considered an exception to the rule of Whistler‘s other interiors, the Peacock Room has often been overlooked in the few studies of the artist‘s interior designs"

Evaluating knowledge-based approaches to the multilingual extension of a temporal expression normalizer

The extension to new languages is a well known bottleneck for rule-based systems. Considerable human effort, which typically consists in re-writing from scratch huge amounts of rules, is in fact required to transfer the knowledge available to the system from one language to a new one. Provided sufficient annotated data, machine learning algorithms allow to minimize the costs of such knowledge transfer but, up to date, proved to be ineffective for some specific tasks. Among these, the recognition and normalization of temporal expressions still remains out of their reach. Focusing on this task, and still adhering to the rule-based framework, this paper presents a bunch of experiments on the automatic porting to Italian of a system originally developed for Spanish. Different automatic rule translation strategies are evaluated and discussed, providing a comprehensive overview of the challenge.

Multilingual extension of a temporal expression normalizer using annotated corpora

This paper presents the automatic extension to other languages of TERSEO, a knowledge-based system for the recognition and normalization of temporal expressions originally developed for Spanish. TERSEO was first extended to English through the automatic translation of the temporal expressions. Then, an improved porting process was applied to Italian, where the automatic translation of the temporal expressions from English and from Spanish was combined with the extraction of new expressions from an Italian annotated corpus. Experimental results demonstrate how, while still adhering to the rule-based paradigm, the development of automatic rule translation procedures allowed us to minimize the effort required for porting to new languages. Relying on such procedures, and without any manual effort or previous knowledge of the target language, TERSEO recognizes and normalizes temporal expressions in Italian with good results (72% precision and 83% recall for recognition).

Review and extension of the McCabe-Thiele method covering multiple feeds, products and heat transfer stages

The McCabe-Thiele method is a classical approximate graphical method for the conceptual design of binary distillation columns which is still widely used, mainly for didactical purposes, though it is also valuable for quick preliminary calculations. Nevertheless, no complete description of the method has been found and situations such as different thermal feed conditions, multiple feeds, possibilities to extract by-products or to add or remove heat, are not always considered. In the present work we provide a systematic analysis of such situations by developing the generalized equations for: a) the operating lines (OL) of each sector, and b) the changeover line that provides the connection between two consecutive trays of the corresponding sectors separated by a lateral stream of feed, product, or a heat removal or addition.

A secret sharing scheme based on exponentiation in Galois fields

To provide more efficient and flexible alternatives for the applications of secret sharing schemes, this paper describes a threshold sharing scheme based on exponentiation of matrices in Galois fields. A significant characteristic of the proposed scheme is that each participant has to keep only one master secret share which can be used to reconstruct different group secrets according to the number of threshold values.

Developing Semantic Rich Internet Applications with the Sm4RIA Extension for OIDE

This paper introduces the Sm4RIA Extension for OIDE, which implements the Sm4RIA approach in OIDE (OOH4RIA Integrated Development Environment). The application, based on the Eclipse framework, supports the design of the Sm4RIA models as well as the model-to-model and model-to-text transformation processes that facilitate the generation of Semantic Rich Internet Applications, i.e., RIA applications capable of sharing data as Linked data and consuming external data from other sources in the same manner. Moreover, the application implements mechanisms for the creation of RIA interfaces from ontologies and the automatic generation of administration interfaces for a previously design application.