Effect of enteral diets on whole body and gut growth in unstressed rats

The composition of enteral feeding formulas may have different effects on total body and gut growth. We studied the growth effects in rats of a complex solid fiber-based diet (Prolab Rodent Diet) with that of three isocaloric and isonitrogenous commercially available liquid feeding formulas which differ in their type of protein (Osmolite HN, an intact protein formula; Reabilan HN, a peptide formula; and Vivonex-TEN, an amino acid formula). Total body weight gain was greatest with the rodent diet (93 +/- 2 g/10 days), followed by the peptide diet (72 +/- 5 g/10 days) and intact protein diet (58 +/- 8 g/10 days). Weight gain was significantly lower on the amino acid diet (43 +/- 7 g/10 days). Proximal and mid gut mass was comparable with all four diets, but distal gut mass was significantly lower with the amino acid diet. Somatomedin C levels on the rodent diet (13.3 +/- 1.8 nM), and the peptide diet (14.0 +/- 3.3 nM) were significantly higher than somatomedin C levels on the amino acid diet (8.0 +/- 1.0 nM). Somatomedin C levels on the intact protein diet (9.6 +/- 1.4 nM) were intermediate between the rodent diet and amino acid diet. We conclude that growth effects vary with different enteral diets (unrelated to total calories and protein) and may result from differences in the generation of tissue growth factors.     

Influences of probiotic bacteria on organic acid production by pig caecal bacteria in vitro

The mechanism of action of probiotics is largely unknown. A potential mechanism should be to increase the production of short-chain fatty acids (SCFA), known modulators of gut functions, by the bacterial ecosystem in the large intestine. The present paper reviews our recent studies in which the capacity of probiotic bacteria to increase the production of SCFA by pig caecal bacteria was investigated using batch-culture and continuous-culture techniques. All four commercial probiotic preparations and three strains of probiotic bacteria dose-dependently accelerated the net production of SCFA, succinic acid and lactic acid without changing the acid profile, and slowed the net production of NH4. Effects on organic acid production did not vary among different probiotic species. Neither probiotic preparations nor probiotic bacteria affected the organic acid production from glucose, gastric mucin, starch or lactose, or organic acids produced:added saccharide. Glucose abolished these effects of probiotic preparations. However, the capacity of probiotics to increase SCFA production was not modified by gastric mucin, starch or lactose. These results indicate that probiotic bacteria increase SCFA production by accelerating the breakdown of carbohydrates that are resistant to indigenous bacteria, and suggest that the concept of prebiotics in terms of SCFA production as a measure of probiotic function is arguable.     

Effects of selenium diets on growth, accumulation and antioxidant response in juvenile carp

An 8-week feeding trial was undertaken with Cyprinus carpio to determine the effects of two commercial Se diets (HSe 1.0 mg kg⁻¹ and LSe 0.25 mg kg⁻¹) on growth, accumulation and antioxidant response in juveniles at time 0, 30 and 60 days. HSe carp had higher mean weight (W) values than LSe group at 60 days and the Fulton condition factor (K) indicated good fish health for both diet groups. Among the investigated HSe tissues, kidney and liver were mainly involved in Se accumulation, whereas the Se level in muscle indicated a very low Se contamination risk for human health. Selenium accumulation levels in HSe tissues followed this order: kidney>liver>muscle. Although growth was not impaired, biochemical antioxidant indicators in liver and kidney evidenced an oxidative stress condition in HSe juveniles. Furthermore, selenium supplementation levels, higher than the one employed in this study, might worsen the antioxidant status of carp.     

Availability to pigs of amino acids in cereal grains. 1. Endogenous levels of amino acids in ileal digesta and faeces of pigs given cereal diets

1. Endogenous levels of amino acids in ileal digesta were determined as the output from pigs given protein-free diets and by extrapolation to zero intake of linear regressions of ileal amino acid output v. dietary amino acid intake. The protein-free diets included 0 or 50 g cellulose/kg and extrapolations were made from two series of four diets which contained graded levels of wheat or barley as the only source of protein. Within each series, dietary fibre level (mg/g) was maintained at approximately 140 or 190 neutral-detergent fibre (NDF) respectively. Endogenous amino acid levels in faeces were also determined. 2. Endogenous amino acid output in faeces was linearly related to dietary fibre level; endogenous ileal output increased with dietary fibre up to approximately 100 mg NDF/g, after which endogenous output no longer increased. 3. The amino acid composition of endogenous ileal protein varied little among levels of output and among different experiments. The composition appears to be determined by the predominance of mucin protein, the slow absorption of some acids and the methods commonly used to measure output. The very high levels of proline and glycine in ileal digesta seemed characteristic only of protein-free and low-protein diets. 4. The amino acid composition of endogenous faecal protein also varied little among different estimates, but was considerably different from that of endogenous ileal protein. Furthermore, the similarity of bacterial and faecal proteins suggested that much of the endogenous faecal protein was of bacterial origin.     

Effects of ethanol, acetaldehyde, and acetic acid on histamine secretion in guinea pig lung mast cells.

We studied the direct effects of ethanol and its metabolites on the guinea pig lung mast cell, and the alterations caused in the histamine release induced by different stimuli. Guinea pig lungs cells dispersed by collagenase were used throughout. High concentrations of ethanol (100 mg/ml), acetaldehyde (0.3-3 mg/ml) and acetic acid (3 mg/ml) induced histamine release that was not inhibited by sodium cyanide (0.3 mM). Lower concentration of ethanol (10 mg/ml) and acetic acid (0.3 mg/ml), but not acetaldehyde, inhibited the histamine release induced by antigen and ionophore A23187. The histamine release induced by phorbol 12-miristate 13-acetate (1 microM) was also inhibited by ethanol (10 mg/ml). Changes in the levels of calcium, glucose and phosphatidic acid did not influence the effect of ethanol. We conclude that high doses of ethanol, acetaldehyde, and acetic acid cause a cytotoxic histamine release by independent mechanisms. Low concentrations of acetic acid inhibit the histamine release by pH reduction. Ethanol acts by a generalized effect that is independent of calcium and glucose suggesting a nonspecific effect that, nevertheless, is not cytotoxic since it can be reversed by washing the cells.     

Effects of disodium fumarate on in vitro rumen microbial growth, methane production and fermentation of diets differing in their forage:concentrate ratio

The effects of disodium fumarate on microbial growth, CH4 production and fermentation of three diets differing in their forage content (800, 500 and 200 g/kg DM) by rumen micro-organisms in vitro were studied using batch cultures. Rumen contents were collected from four Merino sheep. Disodium fumarate was added to the incubation bottles to achieve final concentrations of 0, 4 and 8 mm-fumarate, and (15)N was used as a microbial marker. Gas production was measured at regular intervals from 0 to 120 h of incubation. Fumarate did not affect (P>0.05) any of the measured gas production parameters. In 17 h incubations, the final pH and the production of acetate and propionate were increased linearly (P<0.001) by the addition of fumarate. Fumarate tended to increase (P=0.076) the organic matter disappearance of the diets and to decrease (P=0.079) the amount of NH3-N in the cultures. Adding fumarate to batch cultures tended (P=0.099) to decrease CH4 production, the mean values of the decrease being 5.4 %, 2.9 % and 3.8 % for the high-, medium- and low-forage diet, respectively. Fumarate tended to increase (P=0.082) rumen microbial growth for the high-forage diet, but no differences (P>0.05) were observed for the other two diets. These results indicate that the effects of fumarate on rumen fermentation depend on the nature of the incubated substrate, the high-forage diet showing the greatest response.     

生长激素对脓毒症大鼠肠黏膜屏障功能的影响

目的:研究生长激素(GH)对脓毒症大鼠肠黏膜屏障功能的影响。方法:将72只大鼠随机分对照组、脓毒症组、脓毒症加GH组,再将各组随机分为空肠组、回肠组和结肠组。空肠组大鼠取Treitz韧带处行空肠置管,距离Treitz韧带25 cm处造口;回肠组自回盲部向上25 cm处置管,末端回肠造口;结肠组行盲肠置管。各组分别于肠道置管造口灌入甘露醇/乳果糖(L/M),收集6 h全部尿液,采用高效液相色谱分析法(HPLC)测定尿L/M值。24 h后处死大鼠,分别取部分空肠、回肠、结肠肠管行体外肠黏膜通透性检测,于透射电镜观察肠上皮细胞间紧密连接(TJ)的超微结构改变。结果:脓毒症组大鼠肠黏膜TJ间隙增宽,肠道通透性增加,且回肠组更加明显;脓毒症加GH组肠黏膜TJ损伤和肠黏膜通透性的增加有所减轻。结论:GH能减轻脓毒症大鼠肠黏膜TJ损伤,改善肠黏膜屏障功能。     

Digestion of milk, fish and soya-bean protein in the preruminant calf: flow of digesta, apparent digestibility at the end of the ileum and amino acid composition of ileal digesta

1. Digesta were collected from eleven preruminant calves fitted with re-entrant (four calves in Expt 1 and three in Expt 2) or single cannulas (four calves in Expt 1) in the terminal ileum. Collection periods lasted 24 h (Expt 1) or 96 h (Expt 2). 2. Two milk-substitutes (fish and soya bean) and a control diet were given to the calves. In the control diet, protein was entirely provided by skim-milk powder. In the other two diets, protein was provided mainly by a partially hydrolysed white-fish protein concentrate or a soya-bean protein concentrate prepared by extracting soya-bean meal with hot aqueous ethanol. 3. In Expt 1, flow rates of fresh matter, dry matter, nitrogen and ash exhibited two maxima between 6 and 8 h after the morning meal and between 4 and 6 h (control and soya-bean diets) or 6 and 8 h (fish diet) after the evening meal. Minimum pH values were observed at times of maximum flow rate. Variations observed in the flow rates and pH values were larger with fish and especially soya-bean diets than with the control diet. 4. The apparent digestibility of the three diets in the terminal ileum was significantly higher in Expt 2 than in Expt 1: for N, the values were 0.92, 0.83 and 0.75 (Expt 1), and 0.94, 0.87 and 0.88 (Expt 2) with the control, fish and soya-bean diets respectively. 5. The amount of N apparently absorbed in the terminal ileum represented 90-96% of the amount that disappeared from the whole digestive tract in Expt 1 and 95-99% in Expt 2. 6. In Expt 1 the amino acid (AA) composition of digesta changed little with the flow rate when the calves were given the control diet (from 158 to 179 g glutamic acid/kg AA). With the fish and soya-bean diets the AA composition was similar to that observed with the control diet when the flow rate was minimum, but differences became apparent as the flow rate increased (281 and 161 g glutamic acid/kg AA for the soya-bean and control diets respectively with maximum flow rate). In Expt 2, the mean compositions of the digesta were very similar to the means obtained in Expt 1. 7. Different comparisons with dietary, endogenous and bacterial proteins indicated that for the three diets a common mixture containing approximately 65% endogenous and 35% bacterial proteins reached the terminal ileum.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of immunization of pregnant guinea pigs with guinea pig cytomegalovirus glycoprotein B on viral spread in the placenta

Background

Cytomegalovirus (CMV) is the most common cause of congenital virus infection. Infection of guinea pigs with guinea pig CMV (GPCMV) can provide a useful model for the analysis of its pathogenesis as well as for the evaluation of vaccines. Although glycoprotein B (gB) vaccines have been reported to reduce the incidence and mortality of congenital infection in human clinical trials and guinea pig animal models, the mechanisms of protection remain unclear.

Methods

To understand the gB vaccine protection mechanisms, we analyzed the spread of challenged viruses in the placentas and fetuses of guinea pig dams immunized with recombinant adenoviruses expressing GPCMV gB and β-galactosidase, rAd-gB and rAd-LacZ, respectively.

Results

Mean body weight of the fetuses in the dams immunized with rAd-LacZ followed by GPCMV challenge 3 weeks after immunization was 78% of that observed for dams immunized with rAd-gB. Under conditions in which congenital infection occurred in 75% of fetuses in rAd-LacZ-immunized dams, only 13% of fetuses in rAd-gB-immunized dams were congenitally infected. The placentas were infected less frequently in the gB-immunized animals. In the placentas of the rAd-LacZ- and rAd-gB-immunized animals, CMV early antigens were detected mainly in the spongiotrophoblast layer. Focal localization of viral antigens in the spongiotrophoblast layer suggests cell-to-cell viral spread in the placenta. In spite of a similar level of antibodies against gB and avidity indices among fetuses in each gB-immunized dam, congenital infection was sometimes observed in a littermate fetus. In such infected fetuses, CMV spread to most organs.

Conclusions

Our results suggest that antibodies against gB protected against infection mainly at the interface of the placenta rather than from the placenta to the fetus. The development of strategies to block cell-to-cell viral spread in the placenta is, therefore, required for effective protection against congenital CMV infection.     

Differential effects of dietary whey, casein and soya on colonic DNA damage and large bowel SCFA in rats fed diets low and high in resistant starch

Feeding higher levels of dietary animal protein (as casein or red meat) increases colonic DNA damage and thins the colonic mucus barrier in rats. Feeding resistant starch (RS) reverses these changes and increases large bowel SCFA. The present study examined whether high dietary dairy (casein or whey) or plant (soya) proteins had similar adverse effects and whether dietary RS was protective. Adult male rats were fed diets containing 15 or 25 % casein, whey or soya protein with or without 48 % high amylose starch (as a source of RS) for 4 weeks. DNA damage was measured in isolated colonocytes using the comet assay. Higher dietary casein and soya (but not whey) increased colonocyte DNA damage. DNA damage was highest with soya when fed at 15 or 25 % protein without RS. Dietary RS attenuated protein-induced colonocyte DNA damage in all groups but it remained significantly higher in rats fed 25 % soya compared with those fed 15 % protein. Dietary protein level did not affect colonic mucus thickness overall but the barrier was thinner in rats fed high dietary casein. This effect was reversed by feeding RS. Caecal total SCFA and butyrate pools were higher in rats fed RS compared with digestible starch. Caecal and faecal SCFA were unrelated to genetic damage but correlated with mucus thickness. The present data confirm that higher dietary protein affected colonocyte DNA and colonic mucus thickness adversely but that proteins differ in their effects on these indices of colon health. The data show also that these changes were reversed by RS.