No abstract

Development of folate deficiency (FD) was evaluated in weanling rats fed diets containing mixtures of free amino acids or of vitamin-free casein and gelatin as sources of dietary nitrogen. FD could be produced in 21 d with amino acid diets that promoted maximum growth rate, were completely devoid of folate and contained 1% succinylsulfathiazole. Growth retardation and blood dyscrasia associated with FD could not be demonstrated in rats fed diets containing casein and gelatin as nitrogen sources because the vitamin-free casein contained low but measurable levels of folate. The most effective protocol to produce experimental FD in rats is to feed a folate-free diet that otherwise supports maximum growth in young animals. Additional modifications such as use of methotrexate or amino acid-imbalanced or protein-deficient diets are unnecessary.

Cyclic fatty acid monomers were analyzed by gas chromatography in commercial frying oils, obtained in this country and in the Middle East. Samples were obtained from food outlets in California and Illinois after varying periods of usage. The samples from Egypt and Israel were collected from street vendors frying vegetable patties (known as “fallafel”) in open‐air stands. The United States samples ranged from 0.1 to 0.5% cyclic monomers, and from 1 to 8% polar +noneluted thermal oxidation materials. The Middle Eastern samples showed significantly more heat abuse, with values for cyclic monomers from 0.2 to 0.7% and polar materials ranging from 2 to 22%.

Pharmacokinetic parameters of florfenicol were determined in 10 adult sheep (five wethers and five ewes) after a single 40 mg/kg intravenous (i.v.) dose, and three daily subcutaneous (s.c.) doses of 40 mg/kg of a commercial preparation (Nuflor((R))). The concentration of florfenicol in serum samples was assayed using a proprietary HPLC assay method, and pharmacokinetic parameters derived for individual animal data by each route using compartmental and noncompartmental approaches. Two animals (one male and one female) were excluded due to observed i.v. dosing problems, and a biexponential model was found to fit the i.v. data well for six of the other eight animals. Data from two males showed prolonged low concentrations of florfenicol in serum and were better fit by a three-compartment model. The mean +/- SD for the half-lives of the distribution and elimination phases for the six sheep best fit with a two-compartment model were 0.069 +/- 0.018 and 1.01 +/- 0.09 h respectively, and for the V(d(ss)) and clearances were 0.503 +/- 0.035 L/kg and 366 +/- 53 mL/h/kg respectively. The data collected during the s.c. multiple dose study were analyzed using noncompartmental methods only. The bioavailability (F%) after s.c. dosing was calculated in three ways to compare estimation methods as steady-state had not been reached and single dose s.c. data were not obtained past 24 h. Using the AUC(0--24) and AUC(0--> infinity ) from the first dose, the F% values averaged 27 and 40% respectively. Using the AUC(0--> infinity ) for all doses, the F% was 65%. Calculations of the mean time during which the serum concentration exceeded 0.5 and 1.0 microg/mL were 105 +/- 3.9 and 74.7 +/- 12.2 h respectively.

The capacity of rat intestinal epithelial cells for de novo purine synthesis and reutilization was studied in vitro with isolated cells and in vivo in functionally hepatectomized rats. De novo purine synthesis and purine reutilization were measured as the rate of incorporation of [14C]-glycine or [14C]-adenine, respectively, into the adenine and guanine pools of the intestinal cells. Isolated intestinal epithelial cells incubated with labeled purine or glycine incorporated only labeled adenine. Labeled glycine, guanine, hypoxanthine or xanthine were not incorporated into cellular adenine or guanine. Labeled glycine, given intravenously to functionally hepatectomized rats, was not incorporated into the adenine and guanine of intestinal villus or crypt cells. Labeled glycine was readily incorporated into hepatic adenine and guanine pools of a sham-operated rat. The failure of glycine to be incorporated into intestinal cells in vitro or in vivo demonstrated that these cells lack de novo purine synthesis. Since adenine was readily incorporated into the adenine pool of these cells, we believe that adenine, which is synthesized in the liver or supplied in the diet, was an important precursor for the nucleic acid synthesis in this study.