Hydrophobic surfaces in oligosaccharides: linear dextrins are amphiphilic chains.

Polysaccharide chains are usually considered to be highly hydrophilic, since they have no obvious nonpolar moieties in them. Yet, it is possible to realise conformations in these chains wherein all the hydroxy groups are disposed in one side or face of the chain and the hydrogens disposed in the other. We experimentally demonstrate that such an amphiphilic surface is present in linear oligomeric dextrins, i.e., alpha-1,4-linked D-glucosides, but not in alpha-1,6-D-glucosides (dextrans) or in beta-1,4-D-glucosides (cellulose). This amphiphilicity is generated as a consequence of the stereochemical constraints, which vary with the structure of the sugar and with the type of linkage. Oligosaccharide chains that can adopt incipient helical structures might display amphiphilicity. This property might be relevant to intermolecular recognition on cell surfaces, lectin-sugar binding, antigen-antibody interactions and the like, and might be manifested more in heteromolecular recognition process than as homomolecular self-aggregation.     

Apoptosis: mode of cell death induced in T cell leukemia lines by dexamethasone and other agents

Glucocorticoids can mediate the destruction of thymocytes and T cell-derived leukemia cells through a mechanism known as apoptosis. The characteristic feature of apoptosis is fragmentation of DNA at internucleosomal linkers through the activity of a specific endonuclease. In this study, an attempt was made to compare dexamethasone-induced apoptosis in two T cell-derived human leukemia lines (CEM-C1 and CEM-C7) to the cell killing brought about by selected cytotoxic agents. In the CEM-C7 cell line (dexamethasone-sensitive), apoptosis was induced not only by dexamethasone but by actinomycin D, cycloheximide, and 25-OH cholesterol. In the CEM-C1 cell line (dexamethasone-resistant) cycloheximide, 25-OH cholesterol, or cell starvation could induce apoptosis. It appears that in leukemic cells apoptosis may be induced by a variety of unrelated toxic agents and is not limited to glucocorticoids.     

New coumarins from the umbels of Seseli sibiricum

Three new coumarins, seselinal, sesibiricol and sibirinol, and 12 known coumarins have been isolated from the umbels of Seseli sibiricum. The new coumarins have been characterized as 5, 7-dimethoxy-8-(2-methyl-2-formylpropyl)-2H-1-benzopyran-2-one, 5-(3-methylbut-2-enyloxy)-7-methoxy-8-(2-hydroxy-3-methylbut-3-enyl)-2H-1-benzopyran-2-one and 5,7-dimethoxy-8-(2-hydroxy-3-methylbut-3-enyl)-2H-1-benzopyran-2-one,respectively. The known ones were identified as sesibiricin, isosibiricin, osthol, coumurrayin, sesebrin, sesebrinol, sibiricin, imperatorin, bergapten, xanthotoxin, isopimpinellin and mexoticin.     

A novel Z-structure for poly d(GC).poly d(GC)

A novel zig-zag (Z) structure is proposed for poly d(GC).poly d(GC). The proposed model closely resembles the crystal structure of d(CG)₃.     

Isolation and characterisation of cathepsin-B from bovine pancreas

A simple procedure for the isolation of cathepsin-B from bovine pancreas employing ammonium sulphate fractionation, DEAE cellulose chromatography and Sephadex G-200 gel filtration is described. The purified enzyme gave a single band on polyacrylamide gel electrophoresis. The molecular weight as determined by gel filtration of the enzyme was 26,850. ItsK _m andV _max values were 12.8 mM and 0.303 Μmol/min/mg, respectively. TheK _i for iodoacetamide was 0.16 mM.     

DIFFERENTIAL SENSITIVITY OF “DOUBLE” AND “SINGLE” FLOWERS OF NIGELLA DAMASCENA (RANUNCULACEAE) TO EMASCULATION AND TO GA3

In Nigella damascena “double” flower is inherited as a single-gene recessive to “single” flower. Early emasculation of “double” flowers greatly inhibits gynoecium development and, to a lesser degree, development of sepals and bracts. No comparable inhibition of gynoecia was induced in “single” flowers though some sepal and bract inhibition was detected. A differential nutritional requirement for organ initiation on cultured flower apices was also detected. Apices of both varieties initiated stamens and carpels if kinetin was added to the basal medium. However, in the absence of kinetin, GA₃ was required for organ initiation in “doubles” but completely inhibited stamen initiation in “singles.” Both these differential effects are thought to reflect rather different patterns of gibberellin metabolism in the two genetic strains.     

Testicular phosphatase activity in rats treated with cyproterone acetate & flutamide

Cyproterone acetate (CPA) and flutamide (F), 2 antiandrogens were tested in the rat, to determine their effect on acid (ACP) and alkaline (ALP) phosphatase activity. 70 fertile male rats were injected with either CPA, F, or testosterone propionate (TP) at either 2.5 or 10 mg. TP was injected either alone or in combination with the others. Histological examinations of the testes were performed. Spermatogenesis was arrested and Leydig cells atrophied in animals treated with CPA or F. Histochemical examination revealed that CPA enhanced ALP and ACP in the testes while F decreased ALP and ACP. TP treatment in combination with either antiandrogens was unable to overcome their effect. The changes in the 2 phosphatases depending on which antiandrogen was injected suggests different modes of action.     

Development and Validation of Real-Time PCR for Rapid Detection of Mecistocirrus digitatus

Hematophagous activity of Mecistocirrus digitatus, which causes substantial blood and weight loss in large ruminants, is an emerging challenge due to the economic loss it brings to the livestock industry. Infected animals are treated with anthelmintic drugs, based on the identification of helminth species and the severity of infection; however, traditional methods such as microscopic identification and the counting of eggs for diagnosis and determination of level of infection are laborious, cumbersome and unreliable. To facilitate the detection of this parasite, a SYBR green-based real-time PCR was standardized and validated for the detection of M. digitatus infection in cattle and buffaloes. Oligonucleotides were designed to amplify partial Internal Transcribed Spacer (ITS)-1 sequence of M. digitatus. The specificity of the primers was confirmed by non-amplification of DNA extracted from other commonly occurring gastrointestinal nematodes in ruminants. Plasmids were ligated with partial ITS-1 sequence of M. digitatus, serially diluted (hundred fold) and used as standards in the real-time PCR assay. The quantification cycle (Cq) values were plotted against the standard DNA concentration to produce a standard curve. The assay was sensitive enough to detect one plasmid containing the M. digitatus DNA. Clinical application of this assay was validated by testing the DNA extracted from the faeces of naturally infected cattle (n = 40) and buffaloes (n = 25). The results were compared with our standard curve to calculate the quantity of M. digitatus in each faecal sample. The Cq value of the assay depicted a strong linear relationship with faecal DNA content, with a regression coefficient of 0.984 and efficiency of 99%. This assay has noteworthy advantages over the conventional methods of diagnosis because it is more specific, sensitive and reliable.