Oligomerization of glycine and alanine catalyzed by iron oxides: implications for prebiotic chemistry.

Iron oxide minerals are probable constituents of the sediments present in geothermal regions of the primitive earth. They might have adsorbed different organic monomers (amino acids, nucleotides etc.) and catalyzed polymerization processes leading to the formation of the first living cell. In the present work we tested the catalytic activity of three forms of iron oxides (Goethite, Akaganeite and Hematite) in the intermolecular condensation of each of the amino acids glycine and L-alanine. The effect of zinc oxide and titanium dioxide on the oligomerization has also been studied. Oligomerization studies were performed for 35 days at three different temperatures 50, 90 and 120°C without applying drying/wetting cycling. The products formed were characterized by HPLC and ESI-MS techniques. All three forms of iron oxides catalyzed peptide bond formation (23.2% of gly2 and 10.65% of ala2). The reaction was monitored every 7 days. Formation of peptides was observed to start after 7 days at 50°C. Maximum yield of peptides was found after 35 days at 90°C. Reaction at 120°C favors formation of diketopiperazine derivatives. It is also important to note that after 35 days of reaction, goethite produced dimer and trimer with the highest yield among the oxides tested. We suggest that the activity of goethite could probably be due to its high surface area and surface acidity.

Assessment of dentifrices against Candida biofilm.

The invasion of opportunistic pleiomorphic Candida albicans into oral cavity environment leads to development and progression of its resistance to both naturally occurring antifungal peptides in human saliva as well as commercially available antifungal therapies. As a result of this, the usage and popularity of natural medicine and dentifrices had increased significantly in the last decade. In the present investigation, we have assessed the action of locally available dentifrices against C. albicans biofilm. Disk diffusion test showed maximum zone of inhibition (20 mm) by herbal dentifrice (D-5) as compared to other dentifrices when incubated at 37 °C and 48 h. Assessment of dentifrice D-5 for its effectiveness against C. albicans was further shown in MIC(90) (3.12 mg mL(-1)) and SMIC(90) (6.2 mg mL(-1)) values for planktonic and sessile cells (biofilm forming), respectively. Our data depicted 80% reduction in the cell surface hydrophobicity when 6.2 mg mL(-1) of herbal dentifrice D-5 was used against 48-h grown Candida biofilm at 37 °C. Visualization of herbal dentifrice D-5-treated C. albicans biofilm under SEM revealed drastic reduction in the dense network of yeast, hyphae, and pseudohyphae enclosed in its ECM as compared to its control biofilm. The data were further supported by CLSM analysis which depicted C. albicans architecture disruption by herbal dentifrices. From the above data, it is inferred that these studies would provide researchers and medical practitioners with better insight into the antifungal effect of natural herbal dentifrices.

Formation of nucleobases from formamide in the presence of iron oxides: implication in chemical evolution and origin of life.

Simple compounds like HCN, which have one C and one N, are proposed as the probable precursors for biomonomers. Formamide, a hydrolysis product of HCN, is known as the precursor of various biologically important compounds, for example, nucleobases (purines and pyrimidines). In this paper, we report our results on the synthesis of nucleobases, adenine, cytosine, purine, 9-(hydroxyacetyl) purine, and 4(3H)-pyrimidinone from formamide, using iron oxide (hematite) and oxide hydroxides (goethite and akaganeite) as a catalyst. Goethite and hematite produced purine in higher yield. The products formed were characterized by high-performance liquid chromatography and electrospray ionization mass spectrometry techniques. Results of our study reveal that iron oxides might have worked as efficient prebiotic catalysts.

Synthesis of new chalcone derivatives containing acridinyl moiety with potential antimalarial activity.

A series of novel chalcones bearing acridine moiety attached to the amino group in their ring A have been synthesized through noncatalyzed nucleophilic aromatic substitution reaction between various 3'-aminochalcone or 4'-aminochalcones and 9-chloroacridine. The synthesized chalcone derivatives have been characterized and screened for in vitro antimalarial activity against Plasmodium falciparum NF-54. All the chalcones showed complete inhibition at concentration of 10 microg/mL and above while three compounds showed significant inhibition at concentration of 2 microg/mL. The three most active chalcone derivatives were screened for in vivo activity as well, but no significant inhibition in parasitaemia was observed when given intraperitoneally to Plasmodium yoelii infected mice model.

Determination of cobalt ions at nano-level based on newly synthesized pendant armed macrocycle by polymeric membrane and coated graphite electrode.

Poly(vinylchloride) (PVC) based membranes of macrocycles 2,3,4:9,10,11-dipyridine-1,3,5,8,10,12-hexaazacyclotetradeca-2,9-diene (L(1)) and 2,3,4:9,10,11-dipyridine-1,5,8,12-tetramethylacrylate-1,3,5,8,10,12-hexaazacyclotetradeca-2,9-diene (L(2)) with NaTPB and KTpClPB as anion excluders and dibutylphthalate (DBP), benzyl acetate (BA), dioctylphthalate (DOP), o-nitrophenyloctyl ether (o-NPOE) and tri-n-butylphosphate (TBP) as plasticizing solvent mediators were prepared and investigated as Co(2+) selective electrodes. The best performance was observed with the membranes having the composition L(2):PVC:TBP:NaTPB in the ratio of 6:39:53:2 (w/w; mg). The performance of the membrane based on L(2) was compared with polymeric membrane electrode (PME) and coated graphite electrode (CGE). The PME exhibits detection limit of 4.7x10(-8)M with a Nernstian slope of 29.7 mV decade(-1) of activity between pH 2.5 and 8.5 whereas CGE exhibits the detection limit of 6.8x10(-9)M with a Nernstian slope of 29.5 mV decade(-1) of activity between pH 2.0 and 9.0. The response time for PME and CGE was found to be 11 and 8s, respectively. The CGE has been found to work satisfactorily in partially non-aqueous media up to 35% (v/v) content of methanol, ethanol and 25% (v/v) content of acetonitrile and could be used for a period of 4 months. The CGE was successfully applied for the determination of Co(2+) in real and pharmaceutical samples and as an indicator electrode in potentiometric titration of cobalt ion.

Synthesis and antimicrobial evaluation of new chalcones containing piperazine or 2,5-dichlorothiophene moiety.

Two new series of chalcones have been synthesized by reacting 1-(4-piperazin-1-yl-phenyl)ethanone and 1-(2,5-dichloro-3-thienyl)-1-ethanone with different substituted benzaldehydes in turn by Claisen-Schmidt condensation. The compounds have been characterized by IR, (1)H NMR spectral and microanalysis data. All the synthesized compounds have been evaluated for antimicrobial activity. Some of these derivatives are potentially active against Gram-positive bacteria, Staphylococcus aureus and Escherichia coli while the most potent compound (1) in this study showed MIC(50) value of 2.22 microg/mL against Candida albicans.

Inducible expression of the alpha2-macroglobulin signaling receptor in response to antigenic stimulation: a study of second messenger generation.

Thioglycollate (TG)-elicited murine, peritoneal macrophages express two receptors for activated forms of the proteinase inhibitor alpha2-macroglobulin (alpha2M*)--namely, the low density lipoprotein receptor-related protein (LRP) and the alpha2M signaling receptor (alpha2MSR). We now report that resident peritoneal macrophages express only 400+/-50 alpha2MSR receptors/cell compared to 5000+/-500 receptor/TG-elicited macrophage. By contrast, LRP expression is only 2-2.5-fold greater on elicited cells. The low level of alpha2MSR expression by resident cells is insufficient to trigger signal transduction in contrast to TG-elicited cells which when exposed to alpha2M* demonstrate a rapid rise in inositol 1,4,5-trisphosphate and a concomitant increase in cytosolic free Ca2+. We then studied a variety of preparations injected subcutaneously for their ability to upregulate alpha2MSR. Macroaggregated bovine serum albumin (macroBSA) injection upregulated alpha2MSR and triggered signaling responses by splenic macrophages. Nonaggregated BSA injection alone or in the presence of alum, by contrast, did not alter alpha2MSR expression. Recombivax (hepatitis B antigen adsorbed to alum) injection also upregulated alpha2MSR on splenic macrophages while the alum carrier had no effect. We conclude that macrophage alpha2M* receptors are inducible and their expression may be regulated, in part, by potential antigens.

Differential regulation of the fibroblast growth factor (FGF) family by alpha(2)-macroglobulin: evidence for selective modulation of FGF-2-induced angiogenesis.

The fibroblast growth factor (FGF) family has an important role in processes such as angiogenesis, wound healing, and development in which precise control of proteinase activity is important. The human plasma proteinase inhibitor alpha(2)-macroglobulin (alpha(2)M) regulates cellular growth by binding and modulating the activity of many cytokines and growth factors. These studies investigate the ability of native and activated alpha(2)M (alpha(2)M*) to bind to members of the FGF family. Both alpha(2)M and alpha(2)M* bind specifically and saturably to FGF-1, -2, -4, and -6, although the binding to alpha(2)M* is of significantly higher affinity. Neither alpha(2)M nor alpha(2)M* bind to FGF-5, -7, -9, or -10. FGF-2 was chosen for more extensive study in view of its important role in angiogenesis. It was demonstrated that FGF-2 binds to the previously identified TGF-beta binding site. The alpha(2)M* inhibits FGF-2-dependent fetal bovine heart endothelial cell proliferation in a dose-dependent manner. Unexpectedly, alpha(2)M* does not affect FGF-2-induced vascular tubule formation on Matrigel basement membrane matrix or collagen gels. Further studies demonstrate that FGF-2 partitions between fluid-phase alpha(2)M* and solid-phase Matrigel or collagen. These studies suggest that the ability of alpha(2)M* to modulate the activity of FGF-2 is dependent on an interplay with extracellular matrix components. (Blood. 2001;97:3450-3457)

Radiotherapy in carcinoma cervix.

The techniques of radiation treatment of cervical cancer with radium evolved empirically. During the last few decades a lot of technological breakthrough has occurred in the field of brachytherapy mainly due to revolutionary changes brought by computerisation. The difficulties encountered during intracavitary insertions and the practical problems have been discussed. The complications following acute and late reactions have also been discussed.

The conformation-dependent interaction of alpha 2-macroglobulin with vascular endothelial growth factor. A novel mechanism of alpha 2-macroglobulin/growth factor binding.

alpha(2)-Macroglobulin (alpha(2)M) is a highly conserved proteinase inhibitor present in human plasma at high concentration (2-4 mg/ml). alpha(2)M exists in two conformations, a native form and an activated, receptor-recognized form. While alpha(2)M binds to numerous cytokines and growth factors, in most cases, the nature of the alpha(2)M interaction with these factors is poorly understood. We examined in detail the interaction between alpha(2)M and vascular endothelial growth factor (VEGF) and found a novel and unexpected mechanism of interaction as demonstrated by the following observations: 1) the binding of VEGF to alpha(2)M occurs at a site distinct from the recently characterized growth factor binding site; 2) VEGF binds different forms of alpha(2)M with distinct spatial arrangement, namely to the interior of methylamine or ammonia-treated alpha(2)M and to the exterior of native and proteinase-converted alpha(2)M; and 3) VEGF (molecular mass approximately 40 kDa) can access the interior of receptor-recognized alpha(2)M in the absence of a proteinase trapped within the molecule. VEGF bound to receptor-recognized forms of alpha(2)M is internalized and degraded by macrophages via the alpha(2)M receptor, the low density lipoprotein receptor-related protein. Oxidation of both native and receptor-recognized alpha(2)M results in significant inhibition of VEGF binding. We also examined the biological significance of this interaction by studying the effect of alpha(2)M on VEGF-induced cell proliferation and VEGF-induced up-regulation of intracellular Ca(2+) levels. We demonstrate that under physiological conditions, alpha(2)M does not impact the ability of VEGF to induce cell proliferation or up-regulate Ca(2+).

Incorporation of non-proteolytic proteins by murine alpha2-macroglobulin.

Human alpha2-macroglobulin is a tetrameric glycoprotein with a molecular weight of 718 kDa that is present in human plasma at high concentrations. Murine alpha2-macroglobulin is homologous to human alpha2-macroglobulin but it undergoes post-translational cleavage in the subunits. Each subunit of alpha2-macroglobulin contains a thiolester which can be cleaved by small nucleophiles. In human alpha2-macroglobulin this results in a conformational change to a receptor-recognized form and a change in the electrophoretic mobility. Recent work has demonstrated that this process is reversible and during this reversal non-proteolytic proteins can become covalently trapped within the human alpha2-macroglobulin molecule. The present study further investigates this observation and examines the question whether reversal of thiolester cleavage occurs in mouse alpha2-macroglobulin. Previous studies suggest that small nucleophiles only partially convert mouse alpha2-macroglobulin to a receptor-recognized form. We demonstrate here that under appropriate conditions, mouse alpha2-macroglobulin is fully converted by NH3. We also demonstrate that despite structural and kinetic differences between human and mouse alpha2-macroglobulin, both molecules are able to incorporate non-proteolytic ligands in a similar manner. This leads us to propose a general model of ligand incorporation via nucleophilic exchange in multimeric alpha-macroglobulins.

Dynamic instability of microtubules assembled from microtubule-associated protein-free tubulin: neither variability of growth and shortening rates nor "rescue" requires microtubule-associated proteins.

The growth and shortening of microtubules in dynamic instability is known to be modulated by microtubule-associated proteins (MAPs). A full understanding of the mechanism of dynamic instability requires that one distinguish which of its aspects are mediated by microtubule-associated proteins (even in small residual concentrations) and which are intrinsic properties of the tubulin lattice itself. This paper addresses two of those aspects: whether MAPs cause the rescue events of dynamic instability (i.e., the transitions from shortening to growth) and whether MAPs are responsible for the marked variability of the rates at which microtubules grow and shorten. Very pure tubulin was prepared by sequential chromatographies on phosphocellulose and DEAE-Sephadex. Analysis by electrophoresis and immunoblotting showed it to be essentially MAP-free; it contained fewer than one MAP molecule per 10000 tubulin dimers. When its dynamic instability was studied by video-DIC microscopy, rescues were found to occur at a mean frequency of one per 4 microns of shortening. Variability of rates of growth and shortening, which is observed on the length scale of a few micrometers, was not changed by removal of MAPs. Because the mean distance between bound MAP molecules was calculated to be greater than 14 microns in these experiments, it is concluded that they cannot cause either rescue or variability of rates.

Influence of acute and chronic administration of methadone hydrochloride on NADPH-cytochrome c reductase and cytochrome P-450 of mouse liver microsomes.

Administration of a single acute dose (20 mg/kg body weight) of methadone hydrochloride to both male and female mice increased the specific activity of NADPH-cytochrome c reductase and did not change much the content of cytochrome P-450 of their liver microsomes. Administration of multiple acute doses of methadone in male mice increased the specific activity of cytochrome c reductase and the content of cytochrome P-450 of their liver microsomes. Chronic administration of progressively increasing doses of methadone (up to 40 mg/kg body weight) to male mice increased the specific activity of c reductase. Similar chronic administration of methadone up to 28 mg/kg body weight also increased the microsomal content of P-450, but with higher doses of methadone, the content of P-450 declined and finally dropped slightly below control levels. The levels of c reductase activity and P-450 content returned to normal about two weeks after discontinuation of methadone administration.