A hepatobiliary scan was performed on a patient presenting with symptoms of acute cholecystitis. In addition to cystic duct obstruction, there was a focal area of intense uptake in the left lobe of the liver. Additional imaging studies confirmed a solid mass in the left lobe of the liver, which proved to be a hepatocellular carcinoma on surgery.

Acute Disease↗

PubMed1985

Castanospermine inhibits alpha-glucosidase activities and alters glycogen distribution in animals.

Castanospermine, an inhibitor of alpha-glucosidase activity, was injected into rats to determine its effects in vivo. Daily injections of alkaloid, at levels of 0.5 mg/g of body weight, or higher, for 3 days decreased hepatic alpha-glucosidase to 40% of control values, whereas alpha-glucosidase in brain was reduced to 25% of control values and that in spleen and kidney was reduced to about 40%. In liver, both the neutral (pH 6.5) and the acidic (pH 4.5) alpha-glucosidase activities were inhibited, but the former was more susceptible. On the other hand, beta-N-acetylhexosaminidase activity was elevated in the livers of treated animals, whereas beta-galactosidase activity was unchanged and alpha-mannosidase activity was somewhat inhibited. Livers of treated animals were examined by light and electron microscopy and compared to control animals to determine whether changes in morphology had occurred. In treated animals fed normal rat chow, the hepatocytes were smaller in size and simplified in structure, whereas the high-glucose diet lessened these alterations. Furthermore, in those animals receiving castanospermine at 1.0 mg or higher per g of body weight for 3 days, there was a marked decrease in the amount of glycogen in the cytoplasm, while a large number of lysosomes were observed that were full of dense, granular material. That this dense material was indeed glycogen was shown by the fact that it disappeared when blocks of fixed tissue were pretreated with alpha-amylase. Glycogen levels in liver, as measured either colorimetrically or enzymatically, were somewhat depressed at the higher levels of castanospermine.

Alkaloids↗

PubMed1984

Studies on the mechanism of castanospermine inhibition of alpha- and beta-glucosidases.

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine) is an indolizidine alkaloid that was isolated from the Australian plant, Castanospermum australe. This alkaloid was found to be a potent inhibitor of lysosomal alpha- and beta-glucosidases. In this report, the mechanism of inhibition of amyloglucosidase (an exo-1,4-alpha-glucosidase) and almond emulsin beta-glucosidase was examined. Castanospermine proved to be a competitive inhibitor of amyloglucosidase at both pH 4.5 and 6.0 when assayed with the p-nitrophenyl-alpha-D-glucoside. It was also a competitive inhibitor of almond emulsin beta-glucosidase at pH 6.5, but in this case previous studies had shown that inhibition was of the mixed type at pH 4.5 to 5.0. Th pH of the incubation mixture had a marked effect on the inhibition. Thus, in all cases, castanospermine was a much better inhibitor at pH 6.0 to 6.5 than it was at lower pH values. The pK for castanospermine was found to be 6.09, indicating that the alkaloid was probably more active in the unprotonated form. This was also suggested by the fact that the N-oxide of castanospermine, while still a competitive inhibitor, was 50 to 100 times less active than was castanospermine, and its activity was not markedly altered by pH. These results probably explain why castanospermine is a good inhibitor of the glycoprotein processing enzyme, glucosidase I, since this is a neutral enzyme.

Alkaloids↗

PubMed1983

Castanospermine inhibits the processing of the oligosaccharide portion of the influenza viral hemagglutinin.

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine) is a plant alkaloid that inhibits alpha- and beta-glucosidase in fibroblast extracts [Saul, R., Chambers, J. P., Molyneux, R. J., & Elbein, A. D. (1983) Arch. Biochem. Biophys. 221, 593-597]. In the present study, castanospermine also proved to be a potent inhibitor of glycoprotein processing by virtue of the fact that it inhibits glucosidase I. Thus, when influenza virus was raised in the presence of castanospermine, at 10 micrograms/mL or higher, 80-90% of the viral glycopeptides were susceptible to the action of endoglucosaminidase H, whereas in the normal virus 70% of the glycopeptides are resistant to this enzyme. The major oligosaccharide released by endoglucosaminidase H from castanospermine-grown virus migrated like a hexose10GlcNac on a calibrated Bio-Gel P-4 column. This oligosaccharide was characterized as a Glc 3 Man 7 GlcNAc on the basis of various enzymatic treatments, as well as by methylation analysis of the [2-3H]-mannose-labeled or [6-3H]galactose-labeled oligosaccharide. The presence of three glucose residues in the oligosaccharide was also confirmed by periodate oxidation studies of the [6-3H]galactose-labeled hexose10GlcNAc. Castanospermine did not inhibit the incorporation of [3H]leucine or [14C]alanine into protein in MDCK cells at levels as high as 50 micrograms/mL. In addition, influenza virus produced in the presence of this alkaloid were fully infective and apparently produced in similar amounts to that of control cells, as determined by plaque counts. Castanospermine did, however, cause considerable changes in cell surface properties, since MDCK cells grown in 10 micrograms/mL castanospermine were able to bind twice as much [3H]concanavalin A as were control cells.

Alkaloids↗

PubMed1983

Castanospermine, a tetrahydroxylated alkaloid that inhibits beta-glucosidase and beta-glucocerebrosidase.

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine) was tested against a variety of commercially available glycosidases and found to be a potent inhibitor of almond emulsin beta-glucosidase, and also to inhibit fungal beta-xylosidase. This alkaloid was inactive on yeast alpha-glucosidase, alpha- or beta-galactosidase, alpha-mannosidase, beta-N-acetylhexosaminidase, beta-glucuronidase, alpha-L-fucosidase. Fifty-percent inhibition of beta-glucosidase required about 10 micrograms/ml of castanospermine. The amount of inhibition was uniform throughout the time course, and the inhibition with regard to substrate concentration (p-nitrophenyl-beta-D-glucopyranoside) appeared to be of the mixed type. Castanospermine was also a potent inhibitor of beta-glucocerebrosidase when assayed with fibroblast extracts using either a fluorimetric or a radioactive assay. Interestingly enough, castanospermine also inhibited the lysosomal alpha-glucosidase, and this inhibition required comparable levels of alkaloid to that required for inhibition of beta-glucocerebrosidase. However, a number of other lysosomal glycosidases were not sensitive to castanospermine (i.e., alpha- or beta-galactosidase, alpha- or beta-mannosidase, alpha- or beta-L-fucosidase, beta-N-acetylhexosaminidase, beta-glucuronidase).

Alkaloids↗

PubMed1982

An analytical method for simple N-nitrosamides.

A clean-up method is described which sufficiently removes interfering chemicals from feces so that the colorimetric procedure of Preussmann & Schaper-Druckrey (1972), or HPLC with UV detection, can be used reliably to detect N-nitrosamides. The method has given reasonably good recoveries of four different N-nitrosamides intentionally added to feces. The method, or parts of it, should be applicable to the clean-up of other complex samples, such as food, biological tissues and body fluids.

Colorimetry↗

PubMed1979