Functional importance of the different ubiquinones in the filarial parasite Setaria digitata

The cattle filarial parasite Setaria digitata is reported to have two ubiquinones, Q6 and Q8. These quinones are synthesized within the parasite itself and are not of host origin. Maximum concentration is found in the mitochondria of the parasite. When both Q6 and Q8 are formed and present in the adult stage, the microfilarial stage is now shown to contain only one quinone, namely Q6. Both in the adult and the mf stage, Q6 is associated with the process of electron transport. Though reduction of oxygen in S. digitata results in the generation of high concentrations of oxidants, antioxidants such as catalase and tocopherol are present in relatively lower concentrations. Hence it is proposed that the higher ubiquinone Q8 which is not involved in the electron transport process, is functioning as an antioxidant compensating for the reduced levels of classical antioxidants.     

Conformational polymorphism of the amyloidogenic peptide homologous to residues 113-127 of the prion protein

Conformational transitions are thought to be the prime mechanism of amyloid formation in prion diseases. The prion proteins are known to exhibit polymorphic behavior that explains their ability of "conformation switching" facilitated by structured "seeds" consisting of transformed proteins. Oligopeptides containing prion sequences showing the polymorphism are not known even though amyloid formation is observed in these fragments. In this work, we have observed polymorphism in a 15-residue peptide PrP (113-127) that is known to form amyloid fibrils on aging. To see the polymorphic behavior of this peptide in different solvent environments, circular dichroism (CD) spectroscopic studies on an aqueous solution of PrP (113-127) in different trifluoroethanol (TFE) concentrations were carried out. The results show that PrP (113-127) have sheet preference in lower TFE concentration whereas it has more helical conformation in higher TFE content (>40%). The structural transitions involved in TFE solvent were studied using interval-scan CD and FT-IR studies. It is interesting to note that the alpha-helical structure persists throughout the structural transition process involved in amyloid fibril formation implicating the involvement of both N- and C-terminal sequences. To unravel the role of the N-terminal region in the polymorphism of the PrP (113-127), CD studies on another synthetic peptide, PrP (113-120) were carried out. PrP(113-120) exhibits random coil conformation in 100% water and helical conformation in 100% TFE, indicating the importance of full-length sequence for beta-sheet formation. Besides, the influence of different chemico-physical conditions such as concentration, pH, ionic strength, and membrane like environment on the secondary structure of the peptide PrP (113-127) has been investigated. At higher concentration, PrP (113-127) shows features of sheet conformation even in 100% TFE suggesting aggregation. In the presence of 5% solution of sodium dodecyl sulfate, PrP (113-127) takes high alpha-helical propensity. The environment-dependent conformational polymorphism of PrP (113-127) and its marked tendency to form stable beta-sheet structure at acidic pH could account for its conformation switching behavior from alpha-helix to beta-sheet. This work emphasizes the coordinative involvement of N-terminal and C-terminal sequences in the self-assembly of PrP (113-127).     

Histological changes in intestine in semichronic diarrhoea induced by lactose enriched diet in rats: effect of Diarex-Vet

Efficacy of Diarex-Vet (The Himalaya Drug Company, Makali, Bangalore, India) was evaluated histologically in semichronic diarrhoea induced by lactose enriched diet in rats. The rats in different groups were given lactose enriched diet alone for 2 days before starting the treatment with Diarex-Vet at a dose of 250, 500 and 750 mg/kg body weight along with lactose enriched diet for 5 days. Animals were euthanised at the end of 5 days of treatment and histological changes were observed in the ileum, caecum and colon. Semiquantitative analysis of goblet cells in intestines showed dose dependent response among the treated groups. The morphological changes were comparable to normal in the group given 750 mg/kg body wt Diarex-Vet. The effects observed were attributed to the lactase like analogous activity of Diarex-Vet or the inhibition of the osmotic processes in the intestinal lumen thereby reducing the morphological changes in the intestines.     

Coreceptor phenotype of natural human immunodeficiency virus with nef deleted evolves in vivo,leading to increased virulence

The Sydney Blood Bank Cohort is a group of patients with slowly progressive infection by a human immunodeficiency virus strain containing spontaneous deletions within the nef long terminal repeat region. In 1999, 18 years after the initial infection, one of the members (D36) developed AIDS. In this work, we used an ex vivo human lymphoid cell culture system to analyze two viral isolates obtained from this patient, one prior to the onset of AIDS in 1995 and one after disease progression in 1999. Both D36 isolates were less potent in depleting CD4(+) T cells than a reference dualtropic, nef-bearing viral isolate. However, the 1999 isolate was measurably more cytotoxic to CD4(+) T cells than the 1995 isolate. Interestingly, although both isolates were nearly equally potent in depleting CCR5(+) CD4(+) T cells, the cytotoxic effect of the 1999 isolate toward CCR5(-) CD4(+) T cells was significantly higher. Furthermore, GHOST cell infection assays and blocking experiments with the CXCR4 inhibitor AMD3100 showed that the later D36 1999 isolate could infect both CCR5(+) and CCR5(-) CXCR4(+) cells efficiently, while infection by the 1995 isolate was nearly completely restricted to CCR5(+) cells. Sequence analysis of the V1/V2 and V3 regions of the viral envelope protein gp120 revealed that the more efficient CXCR4 usage of the later isolate might be caused by an additional potential N-glycosylation site in the V1/V2 loop. In conclusion, these data show that an in vivo evolution of the tropism of this nef-deleted strain toward an X4 phenotype was associated with a higher cytopathic potential and progression to AIDS.     

Synthesis and SAR of N-benzoyl-L-biphenylalanine derivatives: discovery of TR-14035, a dual alpha(4)beta(7)/alpha(4)beta(1) integrin antagonist

alpha(4)beta(1) and alpha(4)beta(7) integrins are key regulators of physiologic and pathologic responses in inflammation and autoimmune disease. The effectiveness of anti-integrin antibodies to attenuate a number of inflammatory/immune conditions provides a strong rationale to target integrins for drug development. Important advances have been made in identifying potent and selective candidates, peptides and peptidomimetics, for further development. Herein, we report the discovery of a series of novel N-benzoyl-L-biphenylalanine derivatives that are potent inhibitors of alpha4 integrins. The potency of the initial lead compound (1: IC(50) alpha(4)beta(7)/alpha(4)beta(1)=5/33 microM) was optimized via sequential manipulation of substituents to generate low nM, orally bioavailable dual alpha(4)beta(1)/alpha(4)beta(7) antagonists. The SAR also led to the identification of several subnanomolar antagonists (134, 142, and 143). Compound 81 (TR-14035; IC(50) alpha(4)beta(7)/alpha(4)beta(1)=7/87 nM) has completed Phase I studies in Europe. The synthesis, SAR and biological evaluation of these compounds are described.     

Inhibition of serine proteinases plasmin,trypsin, subtilisin A,cathepsin G,and elastase by LEKTI: a kinetic analysis

The human LEKTI gene encodes a putative 15-domain serine proteinase inhibitor and has been linked to the inherited disorder known as Netherton syndrome. In this study, human recombinant LEKTI (rLEKTI) was purified using a baculovirus/insect cell expression system, and the inhibitory profile of the full-length rLEKTI protein was examined. Expression of LEKTI in Sf9 cells showed the presence of disulfide bonds, suggesting the maintenance of the tertiary protein structure. rLEKTI inhibited the serine proteinases plasmin, subtilisin A, cathepsin G, human neutrophil elastase, and trypsin, but not chymotrypsin. Moreover, rLEKTI did not inhibit the cysteine proteinase papain or cathepsin K, L, or S. Further, rLEKTI inhibitory activity was inactivated by treatment with 20 mM DTT, suggesting that disulfide bonds are important to LEKTI function. The inhibition of plasmin, subtilisin A, cathepsin G, elastase, and trypsin by rLEKTI occurred through a noncompetitive-type mechanism, with inhibitory constants (K(i)) of 27 +/- 5, 49 +/- 3, 67 +/- 6, 317 +/-36, and 849 +/- 55 nM, respectively. Thus, LEKTI is likely to be a major physiological inhibitor of multiple serine proteinases.     

Effect of Ca2+ on the self assembly of a nonionic peptide aggregate

Conductometry, circular dichroism and fluorescence spectroscopy are thetechniques employed to investigate the effect of added calcium ions and other monovalent and divalent metal ions on aqueous solutions of nonionic peptide aggregates, Boc-Leu-Asn-OEt (1). It is observed that among all the metal ions studied, Ca²⁺ ions facilitate the aggregation of the peptide. The interior dielectric constant of the micelles () was found to depend upon the proportion of Ca²⁺ complexed peptide with the peptide monomers in the micelles. When Ca²⁺ ion becomes 1/4th of the peptide concentration, there is a structural transition leading to drastic change in the interior of the micro dielectric constant (_m).     

Formation of multilamellar vesicles ('onions') in peptide based surfactant

Concentration dependent morphological characteristics of a novel dipeptide derivative Lys-Asp-Lauryl.HBr (1) has been presented. Evidence for "onion" like vesicle formation at higher concentration (>8.2 x 10(-3) M) of peptide (1) in aqueous medium was obtained from conductance and 90 degrees light scattering measurements, and cryo-transmission electron microscopic studies.     

Anomalous temperature dependence of peptide films at air-water interface

The tetrapeptide derivative Tyr-Gly-Phe-Ala-OBz (1) forms monolayers as confirmed by compressibility studies carried out at various temperatures. Peptide 1 monolayer exhibits an anomalous structural transition at 40 degrees C as evidenced by pi-A isotherms recorded at different temperatures. The structural transition is also observed in aqueous solution of trifluoroacetate of peptide 1 as evidenced by fluorescence and Raman scattering intensity measurements.