Disposition of sulfonamides in food-producing animals: pharmacokinetics of sulfamerazine in ewe lambs

Date from plasma and urine samples from four ewe lambs were analyzed after administration of sulfamerazine as single IV and oral doses. A two-compartment pharmacokinetic model was developed to describe the disposition of sulfamerazine. The drug was eliminated, primarily by renal excretion of (i) unchanged sulfamerazine and metabolism to an acetyl metabolite, (ii) polar conjugates, and (iii) a third metabolite. The biological half-life of the drug was 6.6 hours. The average value of the absorption rate constant was 0.433 hour-1 (half-life 1.60 hours). Sulfarmerazine was relatively completely absorbed (approx 81% of dose) after oral administration in solution.     

Sex difference in the morphology of erythrocyte nucleus and melanising activity of blood of one-day-old chicks

Erythrocyte nuclear breadth and area were found to be less in the male than in the female of 1‐d‐old chicks. The nuclear length and area of erythrocyte as a whole did not vary between sexes. The percentage of erythrocytes with narrow nuclei was higher in the male than in the female. Blood from males showed higher melanising activity than that from females.

From the results obtained it is suggested that these sex differences are due to the male's higher oxidation rate.     

Effects of unilateral castration and unilateral cryptorchidism of the Holstein bull on plasma gonadotropins, testosterone and testis anatomy

The effects of unilateral castration (UC) and induced unilateral cryptorchidism (CR) on plasma hormones and testis anatomy were studied in 36 Holstein bulls altered at either 3, 6 or 9 mo of age (n = 12). Plasma hormone concentrations were determined in six samples collected at hourly intervals on d 0, 1, 3, 7, 14 and 30, and then at monthly intervals through 6 mo after gonadal manipulation. Although plasma testosterone (T) showed a transient decrease (P less than .05) immediately after treatment, mean plasma concentrations of luteinizing hormone (LH) and T were unaffected by UC or CR over the 6-mo period (P greater than .05). Both hormones increased (P less than .05) in concentration with advancing age. Plasma follicle stimulating hormone (FSH) concentration was greater (P less than .05) in UC than in intact (IN) bulls overall, while FSH in CR bulls did not differ (P greater than .05) from either group. At slaughter, 11 mo after gonadal alteration, mean testis weight, ratio of testis weight to body weight and mean testis sperm cell numbers were increased (P less than .05) in UC bulls compared with mean testis values in intact (IN) bulls. Unilateral castration increased (P less than .05) seminiferous tubuler diameter and seminiferous epithelial cell height from basement membrane to the border of the lumen, but did not alter the ratio of tubuler to interstitial space within the testis. Seminiferous tubuler diameter and epithelial cell height were increased (P less than .05) in CR compared with IN bulls. Unilateral gonadal alteration at 3 mo of age caused a greater (P less than .05) hypertrophy of the scrotal testis in both UC and CR bulls than alteration at 6 or 9 mo of age. Results indicate that unilateral gonadal disruption is followed by rapid compensation in testis T production, little change in systemic LH and a rapid increase in secretion of FSH in the bull within those ages investigated. Further, UC elicits a greater compensatory hypertrophy than CR and the pituitary-testis endocrine axis is more responsive to alteration at 3 mo than at 6 or 9 mo of age in the bull.     

Circulating concentrations of 17-estradiol influence pattern of LH in circulation of cows

The objective of the research was to determine the relationship between circulating 17β-estradiol (E2) and secretion of luteinizing hormone (LH) in cows. A second objective was to determine if response to E₂ was influenced by interval between ovariectomy and the start of E₂ treatment. Thirty-one nulliparous cows 3 yr of age were randomly assigned to a 2 × 4 factorial arrangement of treatments. Sixteen cows were ovariectomized at 18 mo of age (long term), and the other 15 cows were ovariectomized at 36 mo of age (short term). At the time of ovariectomy of cows in the short term group, 11 cows in the short term group and 12 cows in the long term group were implanted subcutaneously with 1, 2 or 4 polydimethylsiloxane capsules containing E₂. The other eight cows served as non-implanted controls (n=4-short term, n=4-long term). All cows were fitted with jugular vein catheters on day 29 of treatment, and on day 30 blood samples were collected at 12-min intervals for 6 hr. At the end of 6 hr, luteinizing hormone-releasing hormone (LHRH) was administered and blood sampling continued at 12-min intervals for an additional hour. Serum was analyzed for LH and E₂. Variables of LH secretion analyzed were mean concentration, frequency of pulses, amplitude of pulses and maximum concentration after LHRH. There were no significant interactions for any of the variables of LH among cows ovariectomized for the long and short term. There was a significant linear increase in mean concentration of LH with increased circulating concentration of E₂. Frequency of LH pulses was not affected by circulating concentration of E₂. As circulating concentration of E₂ increased, amplitude of LH pulses increased and response to LHRH increased - resulting in an increase in mean LH. Interval from time of ovariectomy to the start of E₂ treatment only had a minor influence on mean concentration of LH and profile of LH concentrations in circulation.     

Advantages of a new agar medium in the primary isolation of Mycobacterium bovis

Suspect tuberculous lesions from 116 cattle were examined histologically and cultured for Mycobacterium bovis using 5 different media. The media used were: B83, an agar medium incorporating bovine blood and sodium pyruvate; Middlebrook's agar; 2 variations of Stonebrink's medium; L?wenstein-Jensen medium. The B83 medium and a modification of Stonebrink's medium which had a lowered concentration of malachite green were most successful, detecting 95.2% of tuberculous animals when used together. The B83 medium detected isolates approximately 1 week earlier and had more colonies than the Stonebrink's modification. A combination of 2 slopes of B83 and 2 slopes of modified Stonebrink's medium is recommended for routine culture of samples.     

A Rapid,High Throughput Micro Sugar‐Snap Cookie Quality Test Procedure Using Asymmetrical Centrifugal Mixing

A modified AACC 45‐g flour cookie procedure using asymmetrical centrifuge mixing as a replacement for conventional mixing has been developed. Ingredients are added to a pin cup in the same proportion as in the Approved Method 10‐50D (AACC 2000) sugar‐snap cookie test and mixed in a single step for 15 sec at 2,500 rpm. The dough is then processed and the resulting cookies are scored according to the AACC Approved Method 10–52 40‐g flour micro cookie test method. Cookies produced from a control cookie flour and four commercial soft wheat flours with the new mixing method did not show the characteristic surface cracking patterns normally obtained with conventional three‐stage mixing. However, with the exception of one spread value, no significant differences in spread, thickness, or the ratio of spread to thickness were evident when results were compared with those obtained with the AACC Approved Method 10‐50D 225‐g flour test method using a Hobart mixer equipped with a paddle. Cookies produced from two sets of advanced soft white spring wheat breeder lines, including control cultivars, using the asymmetrical centrifuge mixing procedure were also very comparable in spread, thickness, and ratio compared with those produced using 225 g of flour in the AACC Approved Method. Reproducibility of test results for all cookie parameters for both commercial and advanced plant breeder samples were comparable to the AACC Approved Method 10‐50D 225‐g flour test method. The very short mixing time and the ability to quickly clean or use multiple pin cups should allow very high throughput of flour samples relative to the use of conventional mixers for cookie testing.