The use of India ink and 51Cr-labeled microspheres in examining the function of the yolk stalk as a passageway between the yolk sac and intestine in posthatch broiler chicks.

India ink and radioactive 51Cr-labeled microspheres were used in separate trials to examine the role of the yolk stalk lumen as a distinct pathway between the yolk sac and gut through the first 5 d of posthatch growth in broiler chicks. Throughout this period, India ink was able to pass from the yolk sac through the yolk stalk and into the intestine, but was not able to pass from the intestine into the yolk stalk or yolk sac. Furthermore, labeled microspheres moved from the yolk sac via the yolk stalk into the gut; which caused the total counts per minute of the intestine, yolk stalk, and excreta to progressively increase. It was concluded that India ink and 51Cr-labeled microspheres were useful materials in establishing that the yolk stalk provides a direct one-way passage by which material in the yolk sac may move into the intestine of broiler chicks during the first 5 d after hatching.

Changes in serum lipid, lipoprotein and corticosterone concentrations during neonatal chick development.

Broiler chicks were given a standard commercial starter diet from day 0 (day of hatch) to 9 days of age. Body weight and concentrations of the following serum constituents were measured daily: glucose (GLU), triglycerides (TRI), corticosterone (CORT), cholesterol (CHOL), and high (HDL) and low (LDL) density lipoproteins. Serum GLU and TRI increased at each sampling day to reach a peak on days 3 and 4, respectively, and then decreased thereafter. However, CHOL, HDL, and LDL decreased sharply by day 1 and then gradually decreased to day 5. Conversely, CORT peaked on day 1 and then decreased to day 4. It peaked again on day 5 and remained at that level throughout the remainder of the experiment. In summary, serum concentrations of all constituents measured fluctuated drastically between 1 and 5 days of age, with few changes occurring between days 6 and 9.

Ontogeny of taurocholate accumulation in the terminal ileal mucosal cells of young chicks.

The everted, ileal ring technique of Little and Lester was utilized to study taurocholate accumulation against a concentration gradient in the terminal ileal mucosal cells of chicks from hatch to 6 wk of age. The chicks had low levels of taurocholate accumulation at hatch. A three- to fourfold increase in accumulation was observed at Day 3 posthatch, but taurocholate returned to baseline levels within 2 days. This peak has not been previously reported in any other species. The age-related peak in the ileal accumulation of taurocholate was not influenced by removal of the yolk sac at hatch, oral feeding of yolk, or supplementation of the diet with taurocholate or cholestyramine. Comparison of ileal uptake of proline versus uptake of taurocholate during the 1st wk posthatch indicated that the peak in ileal taurocholate accumulation is not the result of a general increase in absorptive capacity through cell proliferation. These data suggest that the age-related changes in taurocholate absorption are genetically determined and are not responsive to external influences.

Bile acid concentrations in serum, bile, jejunal contents, and excreta of male broiler chicks during the first six weeks posthatch.

Bile acid concentrations in serum, bile, jejunal contents, and excreta of male broiler chicks during the first six weeks posthatch were determined. Bile acid concentrations in serum, jejunum, and excreta declined significantly (P less than .05) during the 1st week after hatch. Serum and jejunal concentrations then rose through week 3, declined during Weeks 4 and 5, and by 6 weeks of age had returned to levels comparable to those seen at Week 3. After the 1st week, no further significant changes were seen in bile acid concentrations in excreta. Concentrations of bile acids in bile were significantly higher at Weeks 1, 3, 5, and 6 than at Weeks 2 and 4. Predictive polynomial equations were calculated for use in modeling applications. This study shows that concentration of bile acids in various body compartments varies significantly during the first 6 weeks posthatch.

Circulating androgen levels in the developing boar.

Circulating levels of serum androgens were studied for 11 Duroc boars. Jugular blood samples were collected at 2-wk intervals, beginning at 5 wk of age and continuing until 27 wk of age. Testosterone and androstenedione values were determined by radioimmunoassay. Analysis of variance indicated a significant difference among ages in testosterone and androstenedione concentrations. Plasma levels of testosterone were 1.5 to 1.9 ng/ml at 5 to 7 wk, decreased to 0.3 to 0.6 ng/ml between 7 and 17 wk, and then increased to 3.7 ng/ml by the 27th wk of age. Plasma androstenedione tended to be elevated during the 5th through 7th wk (3.5 to 4.9 ng/ml), decreased to 0.9 to 1.6 ng/ml through the 19th wk and then gradually increased through the 27th wk (1.4 to 2.4 ng/ml). A highly significant correlation was observed between testosterone and androstenedione (r=0.39). Testicular volume was shown to be highly correlated with testosterone concentration (r=0.48). During the early life of the pig, the predominant androgen is androstenedione with testosterone becoming the predominant androgen as the boar reaches maturity.

The effect of sample composition and vial type on Cerenkov counting in a liquid scintillation counter.

The effect of sample vial type and sample composition on the Cerenkov count rate detected from 32P and 36Cl was studied using a liquid scintillation counter. When counting was done in the noncoincident mode, glass vials allowed higher counting efficiency than plastic vials. In the coincident mode light scattering caused by polyethylene and polyproplyene vials allowed higher counting efficiency than glass vials. Highest coincident counting efficiency was from plastic minivials in a glass carrier vial. Increased solute concentration in samples caused increased counting efficiency due to changes in the refractive index of the solution. This can cause significant counting efficiency changes with no sample channel ratio change in density gradient fractions. The use of wavelength shifters is shown to be inappropriate when the sample pH varies, as this can change the fluorescent properties of the shifters and thereby the observed count rate.

Steroid balance and tissue cholesterol accumulation in germfree and conventional rats fed diets containing saturated and polyunsaturated fats.

Steroid balance studies were conducted on 24 conventional and 12 germfree male rats, 90-120 days old, fed diets containing either 20% safflower or 20% coconut oil. Both germfree and conventional rats fed the safflower oil diets had significantly lower serum cholesterol levels and significantly higher liver cholesterol levels than did the rats fed coconut oil. No significant differences in total fecal neutral sterols, coprostanol, Delta(7)-cholestenol, or total fecal bile acid excretion were seen between dietary groups of rats of either status. There was no evidence of qualitative differences in fecal bile acid excretion as a function of diet. The increased liver cholesterol was in the ester form, with cholesteryl linoleate the largest single component. There was no significant difference in the cholesterol content of the skin, muscle, adipose tissue, or gastrointestinal tract. The significance of a large increase in liver cholesteryl ester, lowered serum cholesterol, and no change in steroid excretion is discussed.

An improved spray reagent for detection of bile acids on thin-layer chromatoplates.

A spray reagent containing 8-hydroxy-1,3,6-pyrenetrisulfonic acid sodium salt is described, which allows detection of as little as 1 micro g of bile acids under long-wave UV light. The bile acids can be eluted directly from the sprayed plates with acetone without eluting the spray reagent.

Effect of bile acid deconjugation on the fecal excretion of steroids.

The effect of microbiological deconjugation of bile acids on total bile acid and neutral sterol fecal excretion by adult male rats has been studied. A screening method utilizing mice allowed selection of a Clostridium perfringens type A strain, which accelerated cholesterol catabolism in mice. When this species of bacteria was associated with germfree rats, the fecal bile acids were excreted as free bile acids (deconjugated), however the quantities of bile acids excreted were not increased compared with those of germfree rats. Conventional rats excrete twice as much bile acids (all deconjugated) as do the germfree and C. perfringens-associated rats. It is, therefore, unlikely that the microbiological deconjugation of bile acids is responsible for the increased fecal excretion of bile acids seen in conventional rats. The C. perfringens-associated rats excreted identical kinds and quantities of fecal neutral sterols as did the germfree rats.

Fecal neutral steroids and bile acids from germfree rats.

The amount and composition of fecal neutral sterols and bile acids excreted by adult male germfree and conventional rats have been determined. The amounts of neutral sterols excreted were 12.8 (germfree) and 19.5 (conventional) mg/kg of body wt per day. The germfree rats excreted cholesterol and lathosterol (methostenol was not assayed); the conventional rats excreted coprostanol and coprostanone in addition. The amounts of bile acids excreted were 11.3 (germfree) and 21.4 (conventional) mg/kg of body wt per day. The bile acids excreted by the rats were tentatively identified as tauro--muricholate, tauro-alpha-muricholate, and tauro-cholate, besides an unidentified component. The conventional rats excreted the corresponding unconjugated acids as well as many other unconjugated bile acids. No significant correlation was found between the amount of coprosterols and the total amount of neutral sterols excreted by the conventional rats. This suggests that bacterial reduction of cholesterol is not an important mechanism of increasing neutral sterol excretion of conventional rats as compared to germfree rats. Evidence is presented that suggests that this difference in neutral sterol excretion is due to changes in intestinal secretion and sloughing between the two types of animal. The factors reponsible for the differences in bile acid excretion have not been identified.