Citations

A pilot study on the extraction of three steroidal glucosiduronic acids from water into organic solutions of liquid ion-exchangers is reported. A single extraction of a 0.5mm aqueous solution of either 11-deoxycorticosterone 21-glucosiduronic acid or cortisone 21-glucosiduronic acid with 0.1m-tetraheptylammonium chloride in chloroform took more than 99% of the conjugate into the organic phase; under the same conditions, the very polar conjugate, β-cortol 3-glucosiduronic acid, was extracted to the extent of 43%. The presence of a small amount of chloride, acetate, or sulphate ion in the aqueous phase inhibited extraction, but making the aqueous phase 4.0m with ammonium sulphate promoted extraction strongly. An increase in the concentration of ion-exchanger in the organic phase also promoted extraction. The amount of cortisone 21-glucosiduronic acid extracted by tetraheptylammonium chloride over the pH range of 3.9 to 10.7 was essentially constant. Chloroform solutions of a tertiary, a secondary, or a primary amine hydrochloride also will extract cortisone 21-glucosiduronic acid from water. The various liquid ion exchangers will extract steroidal glucosiduronic acid methyl esters from water into chloroform, although less completely than the corresponding free acids. The extraction of the glucosiduronic acids from water by tetraheptylammonium chloride occurs by an ion-exchange process; extraction of the esters does not involve ion exchange.

The microtubule-associated protein, tau, is the principal component of paired helical filaments (PHFs) in Alzheimer's disease. PHF-tau is highly phosphorylated and a total of 25 sites of phosphorylation have so far been identified. Many of these sites are serine or threonine residues that are immediately followed in the sequence by proline residues, and hence are candidate phosphorylation sites for proline-directed kinases. In vitro, glycogen synthase kinase-3 (GSK-3), extracellular signal-related kinase-1 and -2, and mitogen-activated protein kinases, p38 kinase and c-jun N-terminal kinase, all phosphorylate many of these sites, although with different efficiencies for particular sites. Phosphorylation studies in transfected cells and neurons show that GSK-3 phosphorylates tau more extensively than do these other proline-directed kinases. Mutations in tau have been shown to affect in vitro phosphorylation of tau by GSK-3. The Arg406-->Trp (R406W) tau mutation also affects tau phosphorylation in cells.

Neurodegenerative diseases have traditionally been defined as clinico-pathological entities. The clinician observes characteristic clusters of symptoms that relate to the anatomical distribution of the lesion. Typically, these symptoms progress in a characteristic sequence allowing the clinician to make a provisional diagnosis. At autopsy, the pathologist examines the nature and distribution of the lesions, reads the clinical report and makes a definitive diagnosis. This structure is so deeply embedded in our concepts of neurodegenerative disease that we are hardly aware of it. It has become deeply embedded because it has been a useful construct that allows grouping of patients for research, especially in treatment trials. However this success has served to hide its limitations and molecular genetic analysis has clearly shown that there are other ways of thinking about neurodegenerative disease. In this review, I will summarize the limitations of the clinicopathological approach, and discuss how molecular genetics offers an alternative way of thinking about neurodegeneration. My intention is not to suggest that we should replace the clinicopathological approach (Newtonian physics is a perfectly good way of thinking about the world on a day-to-day basis even though we know it is only an approximation to the truth) but rather, to suggest that future treatments for these most devastating diseases may come from a deeper understanding of their related pathogenesis.

Several studies have demonstrated that the amino acid residues flanking the Arg-Gly-Asp (RGD) sequence of high-affinity ligands modulate their specificity of interaction with integrin complexes. Because of the absence of structural data for integrin complexes with bound ligand, the molecular basis for this specificity modulation remains obscure. In a previous paper [Rahman, Lu, Kakkar and Authi (1995) Biochem. J. 312, 223-232] we demonstrated that two genetically distinct venom-derived RGD proteins, kistrin and dendroaspin (both containing the sequence PRGDMP), were simple competitors, indicating the recognition of an identical binding site on the αIIbβ3 complex. Furthermore, both kistrin and dendroaspin inhibited the binding of the disintegrin elegantin (containing the sequence ARGDNP) via a non-competitive mechanism, suggesting that the binding of elegantin to the αIIbβ3 complex was at a remote site and down-regulated via an allosteric mechanism. Here we present further evidence for distinct RGD ligand recognition sites on the αIIbβ3 complex that exhibit a negative allosteric relationship. A panel of well-characterized recombinant dendroaspin and elegantin derivatives were employed for this study. These recombinant molecules were constructed as glutathione S-transferase fusion proteins with either an Ala or Pro residue N-terminal to the RGD sequence in combination with either a Met or an Asn residue immediately C-terminal. Equilibrium competition experiments showed that elegantin binding to ADP-treated platelets was inhibited by derivatives Eleg. AM (ARGDMP) and Eleg. PM (PRGDMP) via an allosteric competitive mechanism, providing direct evidence that modulation of the RGD motif can alter competitive behaviour. In addition, recombinant kistrin and dendroaspin both inhibited elegantin binding via a non-competitive mechanism, confirming our previous observations. Further evidence for distinct binding sites employing an independent approach was obtained by analysing the binding of the panel of venom proteins to the functionally defective heterodimer αIIbβ3 Ser123 → Ala expressed on Chinese hamster ovary cells. These studies demonstrated that simple competitors kistrin and dendroaspin bound with high affinity to the variant integrin complex. In contrast, the binding of elegantin and most significantly, recombinant Dendro. PN (PRGDNP) and Dendro. AN (ARGDNP) were abolished. These observations, taken together, are consistent with a model depicting the presence of distinct sites of RGD ligand recognition on the αIIbβ3 complex that show the preferential recognition of specific RGD motifs. Competition experiments demonstrate a negative allosteric relationship between these RGD recognition sites.

Glycosylphosphatidylinositol (GPI)-anchored proteins are resistant to solubilization with Triton X-100 at 4 °C, and they can be recovered in Triton-insoluble membranes (TIMs) that float to a characteristic buoyant density. Because the GPI structure itself has been shown to target GPI-anchored proteins to TIMs, we investigated the association of GPI-anchor intermediates with TIMs. GPI-anchor biosynthesis involves a pathway of some 10 steps that take place in the endoplasmic reticulum (ER). These intermediates include glucosaminyl-acylphosphatidylinositol [GlcN-(acyl)PI] and later mannosylated GPIs, denoted H6, H7 and H8, that are present not only in the ER but also in other cell compartments, including the plasma membrane. At least two-thirds of the GlcN-(acyl)PI in HeLa D cells and mannosylated GPIs in K562 cells were found in TIMs. Although previous reports have considered TIMs to be derived primarily from the plasma membrane, we recovered TIMs from subcellular fractions enriched in ER membranes. The ER marker calnexin and GPI-anchored proteins as well as N-acetylglucosaminyl-phosphatidylinositol and mannosylated GPIs were present in ER-TIMs. Interestingly, GlcN-PI and H7 were less enriched in ER-TIM than the other GPIs, suggesting that ER-TIMs might reflect a compartmentalization of the GPI-anchor biosynthetic pathway in the ER.

Glucosylceramide synthase (GCS) catalyses the transfer of glucose from UDP-glucose (UDP-Glc) to ceramide to form glucosylceramide, the common precursor of most higher-order glycosphingolipids. Inhibition of GCS activity has been proposed as a possible target of chemotherapeutic agents for a number of diseases, including cancer. Design of new GCS inhibitors with desirable pharmaceutical properties is hampered by lack of knowledge of the secondary structure or catalytic mechanism of the GCS protein. Thus we cloned the rat homologue of GCS to begin studies to identify its catalytic regions. The histidine-modifying agent diethyl pyrocarbonate (DEPC) inhibited recombinant rat GCS expressed in bacteria; this inhibition was rapidly reversible by hydroxylamine and could be diminished by preincubation of GCS with UDP-Glc. These data suggest that DEPC acts on histidine residues within or near the UDP-Glc-binding site of GCS. Mutant proteins were expressed in which the eight histidine residues in GCS were individually replaced by other amino acids. H193A (His193 → Ala) and H193N (His193 → Asn) mutants were unaffected by 0.1 mM DEPC, a concentration that inhibited other histidine mutants and the wild-type enzyme by at least 60%. These results indicate that His193 is the primary target of DEPC and is at, or near, the UDP-Glc-binding site of GCS. His193 mutants were also insensitive to the GCS inhibitor D - threo - 1 - phenyl - 2 - decanoylamino - 3 - morpholinopropan - 1 - ol, at concentrations which inhibited the wild-type enzyme by > 80%. These results have significance for both an understanding of the GCS active site and also for the possible design of new and specific inhibitors of GCS.

ObjectivesTo assess technical performance learning curves of teams performing transfemoral transcatheter aortic valve replacement (TF‐TAVR).BackgroundTF‐TAVR is a new procedure for treating severe aortic stenosis. The number of cases required for procedural efficiency is unknown.MethodsIn the PARTNER‐I trial, 1,521 patients underwent TF‐TAVR from 4/2007–2/2012. Learning curve analysis of technical performance metrics was performed using institution‐specific patient sequence number, interval between procedures, and institutional trial entry date. Learning curve characteristics were assessed using semi‐parametric and parametric mixed‐effects models.ResultsAs patient sequence number increased, average procedure time decreased from 154 to 85 minutes (P < 0.0001), and fluoroscopy time from 28 to 20 minutes (P < 0.0001). Procedure time plateaued at an average of 83 minutes (range 52–140). Procedure time plateau was dynamic during the course of the trial, averaging 25 cases (range 21–52) by its end. The later institutions enrolled in the trial, the shorter the initial procedure time. During the trial, percutaneous rather than surgical access increased from 7.9% to 69%.ConclusionsTechnical performance learning curves exist for TF‐TAVR; procedural efficiency increased with experience, with concomitant decreases in radiation and contrast media exposure. The number of cases needed to achieve efficiency decreased progressively, with optimal procedural performance reached after approximately 25 cases for late‐entering institutions. Knowledge and experience accumulated by early TF‐TAVR institutions were disseminated, shortening the learning curve of late‐entering institutions. Technological advances resulting from learning during the trial moved the field from initial conservative surgical cut‐down to percutaneous access for most patients. © 2015 Wiley Periodicals, Inc.

Crohn's disease is a chronic inflammatory bowel disease commonly diagnosed during the reproductive years. Disease management involves advocating conception during periods of stable clinical remission and continuing safe medications throughout pregnancy to achieve optimal maternal and fetal outcomes.

ObjectiveThe aim of the present case report was to describe the late onset of recurrent mania in a patient after ischemic injury to the cerebellum and dorsolateral medulla.MethodsWe studied an 86‐year‐old male with no prior psychiatric history who developed recurrent episodes of mania following a brain stroke. Additionally, he had neurological symptom constellation typical of Wallenberg syndrome.ResultsMagnetic resonance imaging of the brain revealed infarction in the inferomedial right cerebellar hemisphere and the right dorsolateral medulla in the right posterior inferior cerebellar artery (PICA) distribution. He was successfully managed with a combination of antipsychotic and mood‐stabilizer medications.ConclusionsPost‐stroke mania may be one of the rare manifestations of Wallenberg syndrome. This case adds to the emerging literature on cerebellar involvement in mood regulation and pathology of mania.