An immunocytochemical study of the endocrine pancreas in the Australian fat-tailed dunnart (Sminthopsis crassicaudata)

Summary The endocrine pancreas of the Australian fattailed dunnart, Sminthopsis crassicaudata, was investigated by means of electron-microscopic immunocytochemistry using the protein A-gold technique on London resin (LR) white-embedded tissue. The primary antibodies used were raised against insulin, glucagon, somatostatin and pancreatic polypeptide. The morphology of the secretory granules differed in the four cell types. The insulin cells are pleomorphic, and the secretory granules composed of an electron-dense core surrounded by an electron-lucen halo. The glucago cells possess granules with an electron-dense core usually surrounded by a halo of less dense granular material. Somatostatin cells have large, less dense secretory granules. The pancreatic polypeptide cells show small, dense secretory granules. In order for an ultrastructural study to be considered reliable for the definite identification of endocrine cell types, it is essential that it be corroborated by immunocytochemical data at the light-or preferably electron-microscopic level. Recent developments in immuno-electron-microscopic techniques have contributed to a better knowledge of cells responsible for the secretion of a wide variety of hormones, as in this study.     

Nonesterified fatty acids inhibit iron-dependent lipid peroxidation

The effect of various fatty acids on lipid peroxidation of liver microsomes induced by different methods in vitro was studied using oxygen uptake and malonaldehyde (MDA) production. It was observed that fatty acids with a single double bond are effective inhibitors of peroxidation. Stereo and positional isomers of oleic acid were equally effective as oleic acid. There was an absolute requirement for a free carboxyl group, since methyl esters of fatty acids and long-chain saturated and unsaturated hydrocarbons could not inhibit peroxidation. Saturated fatty acids with a chain length of 12-16 carbon atoms showed inhibition, whereas more than 18 carbon atoms reduced the inhibitory capacity. Fatty acids of lower chain length such as capric and caprylic acids did not show inhibition. Fatty acid inhibition was partially reversed by increasing the concentration of iron in the system. Peroxidation induced by methods which were independent of iron was not inhibited by fatty acids. It was observed that intestinal microsomes which were resistant to peroxidation due to the presence of nonesterified fatty acids in their membrane lipids were able to peroxidise by methods which do not require iron. These results suggest that certain fatty acids inhibit peroxidation by chelating available free iron. In addition, they may also be involved in competing with the esterified fatty acids in the membrane lipids which are the substrates for peroxidation.     

Implications of Lag Time Concept in the Oxidation of LDL

Oxidation of low density lipoprotein (LDL) has been implicated in the pathogenesis of atherosclerosis. The most common technique for measuring the oxidation of lipoproteins is the continuos measurement of the formation of conjugated diene at OD 234 nm. The concept of “lag time”, derived from such measurements, has been used to test the efficacy of various antioxidants for their ability to inhibit the oxidation of LDL. This review will elaborate on some of the factors that might affect the lag time.     

An integrated genetic and physical map of the bovine X Chromosome

Genotypic data for 56 microsatellites (ms) generated from maternal full sib families nested within paternal half sib pedigrees were used to construct a linkage map of the bovine X Chromosome (Chr) (BTX) that spans 150 cM (ave. interval 2.7 cM). The linkage map contains 36 previously unlinked ms; seven generated from a BTXp library. Genotypic data from these 36 ms was merged into an existing linkage map to more than double the number of informative BTX markers. A male specific linkage map of the pseudoautosomal region was also constructed from five ms at the distal end of BTXq. Four informative probes physically assigned by fluorescence in situ hybridization defined the extent of coverage, confirmed the position of the pseudoautosomal region on the q-arm, and identified a 4.1-cM marker interval containing the centromere of BTX. Received: 14 July 1996 / Accepted: 19 September 1996     

Esterase activity of Candida species isolated from immunocompromised hosts

A total of 149 clinical isolates of Candida species isolated from immunocompromised patients were examined to ascertain their esterase activity by the Tween 80 opacity test, which is a biochemical test used mainly to differentiate between Candida albicans and Candida dubliniensis. Our results showed that C. albicans (92.3%), Candida tropicalis (92.3%), Candida parapsilosis (25%), C. dubliniensis (16.6%), Candida inconspicua (100%), and Candida lipolytica (100%) produced opacity halos through the 10-day post-inoculation period. The remaining Candida species did not produce a positive test response. These findings indicate that Tween 80 opacity test cannot be used as the sole phenotypic trait in the differentiation of C. albicans and C. dubliniensis.     

The YvfTU Two-component System is involved in plcR expression in Bacillus cereus

Background

Protein A, protein G and protein L are three well-defined immunoglobulin (Ig)-binding proteins (IBPs), which show affinity for specific sites on Ig of mammalian hosts. Although the precise functions of these molecules are not fully understood, it is thought that they play an important role in pathogenicity of bacteria. The single domains of protein A, protein G and protein L were all demonstrated to have function to bind to Ig. Whether combinations of Ig-binding domains of various IBPs could exhibit useful novel binding is interesting.

Results

We used a combinatorial phage library which displayed randomly-rearranged various-peptide-linked molecules of D and A domains of protein A, designated PA(D) and PA(A) respectively, B2 domain of protein G (PG) and B3 domain of protein L (PL) for affinity selection with human IgG (hIgG), human IgM (hIgM), human IgA (hIgA) and recombinant hIgG1-Fc as bait respectively. Two kinds of novel combinatorial molecules with characteristic structure of PA(A)-PG and PA(A)-PL were obtained in hIgG (hIgG1-Fc) and hIgM (hIgA) post-selection populations respectively. In addition, the linking peptides among all PA(A)-PG and PA(A)-PL structures was strongly selected, and showed interestingly divergent and convergent distribution. The phage binding assays and competitive inhibition experiments demonstrated that PA(A)-PG and PA(A)-PL combinations possess comparable binding advantages with hIgG/hIgG1-Fc and hIgM/hIgA respectively.

Conclusion

In this work, a combinatorial phage library displaying Ig-binding domains of protein A, protein G, or protein L joined by various random linking peptides was used to conducted evolutional selection in vitro with four kinds of Ig molecules. Two kinds of novel combinations of Ig-binding domains, PA(A)-PG and PA(A)-PL, were obtained, and demonstrate the novel Ig binding properties.     

Synthesis and in vitro evaluation of the antifungal activities of dihydropyrimidinones

Copper (II) chloride in the absence of any solvent, efficiently catalyses the synthesis of dihydropyrimidinones (80-96% yields) by the Biginelli reaction. Six compounds were selected and examined their antifungal activities against the radial growth of three fungal species viz., Trichoderma hammatum, Trichoderma koningii and Aspergillus niger.