Intestinal lactase (beta-galactosidase) and other disaccharidase activities of suckling and adult common brushtail possums, Trichosurus vulpecula (Marsupialia:Phalangeridae).

Small-intestinal disaccharidase activities of eight suckling T. vulpecula, aged from 34 to 150 days, and of two adult animals were investigated. Intestinal maltase, isomaltase and sucrase activities increased with age, whereas lactase activities decreased. Trehalase activities were relatively high in all animals and showed no obvious age-related changes. Three separate beta-galactosidase activities, one neutral and two acid, acted on lactose. The neutral beta-galactosidase activity appeared to be due to a brush border enzyme similar to that of eutherian mammals, whereas the acid beta-galactosidases were soluble and probably of lysosomal origin. One of these, acid beta-galactosidase-1, had similar properties to the sole intestinal beta-galactosidase of macropodid marsupials, whereas the other, acid beta-galactosidase-2, has not previously been described. Galactosyl oligosaccharides isolated from macropodid milk were readily hydrolysed by both acid beta-galactosidases but not by the neutral beta-galactosidase. The total intestinal lactase activity in animals aged up to 125 days was due mainly to acid beta-galactosidase-1, whereas in older animals it was due mostly to the neutral beta-galactosidase; this suggests that late in lactation the young T. vulpecula change from a macropodid mode of digestion of galactosyl oligosaccharides to a eutherian mechanism for the digestion of lactose. These findings may have implications for the hand-rearing of orphaned T. vulpecula.

Changes in milk carbohydrates during lactation in the common brushtail possum, Trichosurus vulpecula (Marsupialia:Phalangeridae).

Milk samples (186) were obtained at various stages of lactation from 27 common brushtail possums (Trichosurus vulpecula). Qualitative and quantitative changes in the milk carbohydrates during early and mid-lactation were similar to those previously seen in other marsupials; the principal carbohydrate was lactose early in lactation and higher oligosaccharides in mid-lactation, and the hexose concentration reached a peak during mid-lactation. However, the late-lactation milk was unusual in that the carbohydrate was mainly lactose and its concentration remained relatively high (3.5 to 5.5%). In contrast to earlier findings on the milk of the tammar wallaby (Macropus eugenii), little or no nucleotide pyrophosphatase, beta-galactosidase and alkaline phosphatase activities were detected late in lactation.

Intestinal lactase and other disaccharidase activities of a suckling crabeater seal (Lobodon carcinophagus).

1. The intestinal disaccharidase activities of a suckling crabeater seal were investigated. 2. Lactase, maltase, isomaltase and cellobiase activities were readily detected but trehalase and sucrase activities were absent. 3. The intestinal homogenates were separated into a soluble (S2) fraction and a particulate brush border (P2) fraction. The lactase activities of the two fractions had different properties corresponding to those of an acid and a neutral beta-galactosidase respectively. Approximately two-thirds of the total lactase activity measured at pH 6.0 was due to the acid beta-galactosidase. 4. The isomaltase and cellobiase activities were found almost exclusively in the particulate fractions but about one third of the maltase activity was in the S2 fraction. This soluble maltase activity appeared to be due to an acid maltase.

Studies on the carbohydrate content of milk of the crabeater seal (Lobodon carcinophagus).

1. The mean carbohydrate content of six samples of milk of the crabeater seal (a phocid), measured as total hexose, was 1.5 +/- 0.3% (w/v). Ultrafiltrates of the skim milk of these samples had a mean carbohydrate content of 1.9 +/- 0.2%. 2. Thin-layer chromatography of the ultrafiltrates showed that this carbohydrate consists mainly of various oligosaccharides of low chromatographic mobility; lactose and traces of free glucose and galactose were also detected. 3. These oligosaccharides consisted mainly of D-galactose and N-acetylhexosamine; L-fucose, D-glucose and sialic acid were additional minor components. 4. The mean lactose content of the ultrafiltrates, determined by a specific enzymic method, was 0.021 +/- 0.007% (w/v); this is similar to the levels which have been reported for the milk of otariids.

Absence of beta-galactosidase (lactase) activity from intestinal brush borders of suckling macropods: implications for mechanism of lactose absorption.

1. Neutral beta-galactosidase (lactase) activity was absent from crude brush borders of small intestines of three species of suckling macropods (kangaroos and wallabies), even though the intestinal mucosal homogenates had high beta-galactosidase activities. 2. These activities were entirely due to an intracellular acid beta-galactosidase, probably located in lysosomes. 3. The results suggest that the absorptive-digestive mechanism for lactose in macropods is fundamentally different from that in eutherian mammals.

Immunomodulatory effects of poly(I,C)-LC in cancer patients.

Poly(I,C)-LC was administered in low (1 mg/m2) and intermediate (4 mg/m2) doses to cancer patients by intramuscular injection or intravenous infusion to evaluate the immunomodulatory effects. Natural killer cell (NK) activity was elevated slightly at the low dose and remained unchanged overall, but some depression was observed at the 4 mg/m2 intravenous dose. Monocyte function was elevated in all groups of patients, as was the interferon-induced enzyme 2'5'-oligo-A synthetase. These increases were observed at the 1 mg/m2 intramuscular dose, despite a lack of detectable circulating serum interferon (IFN). In regard to cell surface markers, poly(I,C)-LC induced an increase in OKT10-positive cells and a small but consistent trend toward increases in the ratio of Leu-3/Leu-2-positive cells. Lymphocyte proliferation in response to concanavalin A was depressed by poly(I,C)-LC administration. Although an optimum immunomodulatory dose and schedule was not determined, the data indicate that low doses produce significant changes in immune function and that induction of detectable levels of circulating interferon is not required for poly(I,C)-LC to have biological effects.

The action of organic mercurials on the erythrocyte membrane.

The solubilisation of proteins from erythrocyte membranes by treatment with organic mercurials has been studied with different species. The marked solubilisation previously reported for human membranes does not seem to be a general phenomenon. All of the other species examined showed less than 50% of the solubilisation shown by human membranes. The protein-solubilising effect seems to be dependent on hydrophobic mercury derivatives carrying a net negative charge. Uncharged compounds like phenylmercuric acetate blocked the effect, although N-ethylmaleimide and iodoacetamide did not. With the aid of radioactively labelled compounds, and of atomic absorption spectrophotometry, the proteins reactive towards the mercurials were identified. The major integral protein, band 3, was the major protein capable of binding the mercurial. Reaction with the mercurial appears to disrupt interaction of band 3 with bands 2.1 and 4.2, allowing dissociation of the cytoskeleton from the membrane. In addition, band 4.9 was also found to react with the mercurials, possibly resulting in disruption of the cytoskeleton.