New N,N-dimethylcarbamate inhibitors of acetylcholinesterase: design synthesis and biological evaluation

Abstract

A series of N,N-dimethylcarbamates containing a N,N-dibenzylamino moiety was synthesized and tested to evaluate their ability to inhibit Acetylcholinesterase (AChE). The most active compounds 4 and 8, showed 85 and 69% of inhibition at 50?μM, respectively. Furthermore, some basic SAR rules were outlined: an alkyl linker of six methylene units is the best spacer between the carbamoyl and dibenzylamino moieties; electron-withdrawal substituents on aromatics rings of the dibenzylamino group reduce the inhibitory power. Compound 4 produces a slow onset inhibition of AChE and this is not due to the carbamoylation of the enzyme, as demonstrated by the time-dependent inhibition assay of AChE with compound 4 and by MALDI-TOF MS analysis of trypsinized AChE inhibited by compound 4. Instead, compound 4 could act as a slow-binding inhibitor of AChE, probably because of its high conformational freedom due to the linear alkyl chain.     

A Basal Lithostrotian Titanosaur (Dinosauria: Sauropoda) with a Complete Skull: Implications for the Evolution and Paleobiology of Titanosauria

We describe Sarmientosaurus musacchioi gen. et sp. nov., a titanosaurian sauropod dinosaur from the Upper Cretaceous (Cenomanian—Turonian) Lower Member of the Bajo Barreal Formation of southern Chubut Province in central Patagonia, Argentina. The holotypic and only known specimen consists of an articulated, virtually complete skull and part of the cranial and middle cervical series. Sarmientosaurus exhibits the following distinctive features that we interpret as autapomorphies: (1) maximum diameter of orbit nearly 40% rostrocaudal length of cranium; (2) complex maxilla—lacrimal articulation, in which the lacrimal clasps the ascending ramus of the maxilla; (3) medial edge of caudal sector of maxillary ascending ramus bordering bony nasal aperture with low but distinct ridge; (4) ‘tongue-like’ ventral process of quadratojugal that overlaps quadrate caudally; (5) separate foramina for all three branches of the trigeminal nerve; (6) absence of median venous canal connecting infundibular region to ventral part of brainstem; (7) subvertical premaxillary, procumbent maxillary, and recumbent dentary teeth; (8) cervical vertebrae with ‘strut-like’ centroprezygapophyseal laminae; (9) extremely elongate and slender ossified tendon positioned ventrolateral to cervical vertebrae and ribs. The cranial endocast of Sarmientosaurus preserves some of the most complete information obtained to date regarding the brain and sensory systems of sauropods. Phylogenetic analysis recovers the new taxon as a basal member of Lithostrotia, as the most plesiomorphic titanosaurian to be preserved with a complete skull. Sarmientosaurus provides a wealth of new cranial evidence that reaffirms the close relationship of titanosaurs to Brachiosauridae. Moreover, the presence of the relatively derived lithostrotian Tapuiasaurus in Aptian deposits indicates that the new Patagonian genus represents a ‘ghost lineage’ with a comparatively plesiomorphic craniodental form, the evolutionary history of which is missing for at least 13 million years of the Cretaceous. The skull anatomy of Sarmientosaurus suggests that multiple titanosaurian species with dissimilar cranial structures coexisted in the early Late Cretaceous of southern South America. Furthermore, the new taxon possesses a number of distinctive morphologies—such as the ossified cervical tendon, extremely pneumatized cervical vertebrae, and a habitually downward-facing snout—that have rarely, if ever, been documented in other titanosaurs, thus broadening our understanding of the anatomical diversity of this remarkable sauropod clade. The latter two features were convergently acquired by at least one penecontemporaneous diplodocoid, and may represent mutual specializations for consuming low-growing vegetation.     

Synthesis of 8-Substituted Theophyllineβ-D-Ribofuranosides

Abstract

Methods for the synthesis of 8-chloro-and 8-bromotheophylline D-riboside triacetates by the chlorination of 7-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)-theophylline with N-chlorosuccinimide or by the glycosylation of 8-bromotheophylline with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose were found. Nucleophilic displacement of the halogen gave 8-amino-, 8-alkylamino-, 8-benzylamino-, and 8-hydrazinotheophyllineβ-D-ribofuranosides.     

Proteolytic Histone Modification by Mast Cell Tryptase,a Serglycin Proteoglycan-dependent Secretory Granule Protease

A hallmark feature of mast cells is their high content of cytoplasmic secretory granules filled with various preformed compounds, including proteases of tryptase-, chymase-, and carboxypeptidase A3 type that are electrostatically bound to serglycin proteoglycan. Apart from participating in extracellular processes, serglycin proteoglycan and one of its associated proteases, tryptase, are known to regulate cell death by promoting apoptosis over necrosis. Here we sought to outline the underlying mechanism and identify core histones as primary proteolytic targets for the serglycin-tryptase axis. During the cell death process, tryptase was found to relocalize from granules into the cytosol and nucleus, and it was found that the absence of tryptase was associated with a pronounced accumulation of core histones both in the cytosol and in the nucleus. Intriguingly, tryptase deficiency resulted in defective proteolytic modification of core histones even at baseline conditions, i.e. in the absence of cytotoxic agent, suggesting that tryptase has a homeostatic impact on nuclear events. Indeed, tryptase was found in the nucleus of viable cells and was shown to cleave core histones in their N-terminal tail. Moreover, it was shown that the absence of the serglycin-tryptase axis resulted in altered chromatin composition. Together, these findings implicate histone proteolysis through a secretory granule-derived serglycin-tryptase axis as a novel principle for histone modification, during both cell homeostasis and cell death.     

One-step Concentration and Partial Purification of Aspergillus kawachii Non-acidic Polygalacturonases by Adsorption to Glass Fiber Microfilters

The non-acidic polygalacturonases produced by Aspergillus kawachii in a glucose/tryptone medium were adsorbed to a glass fiber microfilter that was used to clarify the fermentation broth. Maximum adsorption occurred at pH 3 under low ionic strength conditions. The adsorbed activity could be readily released with a buffer solution at pH 5. Based upon these observations, a separation process was developed which enabled the broth to be clarified and, at the same time, the non-acidic polygalacturonases to be concentrated 20-fold and purified 100-fold in a unique filtration step. The practical advantage of recovering polygalacturonases by a filtration process lies in the simplicity and efficiency of the operation involved. Received 27 July 2005; Revisions requested 24 August 2005; Revisions received 16 November 2005; Accepted 16 November 2005     

Derangement of Erythrocytic AE1 in Beta-Thalassemia by Caspase 3: Pathogenic Mechanisms and Implications in Red Blood Cell Senescence

Considering its complex molecular pathophysiology, beta-thalassemia could be a good in vivo model to study some aspects related to erythrocyte functions with potential therapeutic implications not only within the frame of this particular hemoglobinopathy but also with respect to conditions in which the cellular milieu, altered by a deranged anion exchanger, could display a significant pathogenetic role (i.e., erythrocyte senescence, complications of red cell storage, renal tubular acidosis and some abnormal protein thesaurismosis). This work evaluates the anionic influx across band 3 protein in normal and beta-thalassemic red blood cells (RBCs) and ghosts. Since redox-mediated injury is an important pathway in the destruction of beta-thalassemic RBCs, we studied the anion transport and the activity of caspase 3 in the absence and presence of t-butylhydroperoxide in order to evaluate the effect of an increase of cellular oxidative stress. Interestingly, beta-thalassemic erythrocytes show a faster rate of anion exchange than normal RBCs and absence of any modulation mechanism of anion influx. These findings led us to formulate a hypothesis about the metabolic characteristics of beta-thalassemic erythrocytes, outlining that one of the main targets of caspase 3 in RBCs is the cytoplasmic domain of band 3 protein.