Combination of polydextrose and lactitol affects microbial ecosystem and immune responses in rat gastrointestinal tract.

The effects of various dietary fibres on gut health have been studied extensively but their combined effects are scarcely documented. In the present study the effects of 2 % (w/w) polydextrose (PDX), 2 % (w/w) disaccharide lactitol, or 2 % (w/w) PDX+2 % (w/w) lactitol on gut microflora, microbial metabolism and gut immune responses were investigated in rats. Both PDX and lactitol alone had an effect on many of the studied parameters, but their combination had stronger than additive effects in some parameters. The PDX+lactitol combination altered the microbial community structure as seen by a culture-independent method, percentage guanine+cytosine (%G+C) profiling, increasing the areas of %G+C 35-39 (P<0.0001) and %G+C 45-49 (P=0.0002), and decreasing %G+C 65-74 (P<0.0003). These changes were also reflected in the microbial metabolism so that the production of biogenic amines and branched volatile fatty acids was significantly reduced, by 12 (P=0.03) and 50 % (P=0.002), respectively, indicating a shift from putrefactive towards saccharolytic metabolism. PDX increased the secretion of IgA in the caecum (P=0.007). Secretion of IgA increased even more, almost ten-fold, with the combination of PDX+lactitol (P<0.0001) when compared with the control group. Lactitol increased the production of butyrate by caecal microbes by two- to three-fold when compared with the PDX or control group (P<0.0001). Butyrate is a preferred energy source for mucosal cells; thus a boost in the availability of energy for immune cells may have still added to the synergistic effects of PDX and lactitol on immune cells. It is noteworthy that improvement in the IgA secretion occurred without signs of mucosal inflammation.

The susceptibility of early developmental phases of an acid-tolerant and acid-sensitive fish species to acidity and aluminum.

The mortality of roach (Rutilus rutilus) embryos increased during the early embryonic phase following exposure to Al and acidity from pH 6.7 to 5.0. No roach hatched at pH<5.00 or at pH 5.00 in the presence of Al. By contrast, increased embryonic mortality in pike (Esox lucius) occurred mainly during and after the normal hatching period due to the acidity-dependent prolongation and inhibition of hatching at pH 4.00. Newly hatched fry of both species were more sensitive to Al than the embryos. A reduction in the development of yolk-sac fry occurred in pike at pH 4.00 and in roach at pH 5.00, and in the presence of Al at pH< or =5.00 and pH< or =5.75, respectively. Thus, the most susceptible early developmental phase to acidity differed between the acid-sensitive roach and the acid-tolerant pike, although the newly hatched fry was the developmental phase most sensitive to Al for both species.

Effects of temperature on the recovery of juvenile grayling (Thymallus thymallus) from exposure to Al+Fe.

One-summer-old graylings (Thymallus thymallus) were exposed for 6 days to water containing a mixture of 1 mg l(-1) Fe and 100 microg l(-1) Al at pH 5.5, with or without 15 mg l(-1) humic acid. A pH of 6.9 was used as a control. The experiment was performed at two test temperatures, 13 and 3 degrees C. After 1 week of exposure, half of the fish in the tank were taken for oxygen measurement and tissue sampling. The remaining half were maintained in metal-free water for a further week to assess their recovery at the two test temperatures. Fifty percent of the fish died under metal exposure at 13 degrees C, but none at 3 degrees C. Despite of the lack of mortalities at the lower temperature, surviving fish at both test temperatures suffered similar gill damage (adherence of lamellae), disturbances in ion regulation, increases in haematocrit value (Hct) and haemoglobin (Hb) concentration and reductions in oxygen consumption. The addition of humic acid prevented these changes. The reduced plasma chloride concentration, increased blood Hct value and Hb concentration recovered completely at 13 degrees C, whereas the lowered oxygen consumption recovered less completely, which may be attributed to the remaining minor gill damage (lamellar hypertrophy). At the lower temperature, the adherence of lamellae persisted after the recovery period, and oxygen consumption, therefore, remained at a very low level. The decreased plasma chloride concentration was also unable to recover. The accumulation of Al inside the gill tissue was greater at low temperature. We conclude that the acute toxicity of a mixture of Fe and Al to grayling and their subsequent ability to recovery is dependent on the exposure temperature.

Reproduction, blood and plasma parameters and gill histology of vendace (Coregonus albula L.) in long-term exposure to acidity and aluminum.

Vendace were exposed to pHs 4.75 and 5.25 with or without added aluminum (200 microg=7.4 micromol AlL(-1)) from late endogenous vitellogenesis in July through the spawning period. At the normal time of spawning, when 48% of the control females had already released their eggs, 50% of females at pH 4.75+Al had completely unovulated oocytes. The final proportions of completely ovulated females were 14%, 36%, 25%, 61%, and 81% at pH 4.75+Al, pH 4.75, pH 5.25+Al, pH 5.25, and in the control group, respectively. Delayed testes regression was seen in males at pH 4.75+Al. A clear decrease in plasma Na(+) and Cl(-) and an increase in blood glucose concentration was detected only near spawning time, from October to November, coincident with Al accumulation inside the gill tissue. It is concluded that seasonal changes, probably related to reproductive physiology or to the decrease in water temperature, are associated with the increase in Al toxicity in vendace.