Effect of tester on combining ability estimates of maize germplasm complexes

Eight maize complexes and varieties representing high and low yield levels were tested for their suitability as top cross testers by comparing the performance of the crosses in relation to the combining ability of the parents estimated by diallel analysis. The discriminating ability of the testers was compared by Schumann and Bradley test. In both cases the results clearly showed that the low performing testers were better and more reliable than the high performing complexes. The utility of per se performance as an indication of general combining ability of the complexes has been discussed.     

Pharmacokinetics of Enrofloxacin and Its Metabolite Ciprofloxacin after Intramuscular Administration of Enrofloxacin in Goats

The pharmacokinetics of enrofloxacin and its active metabolite ciprofloxacin were investigated in goats after a single intramuscular administration of enrofloxacin at 2.5 mg/kg body weight. The plasma concentrations of enrofloxacin and ciprofloxacin were determined simultaneously by a HPLC method. The peak concentrations (C _max) of enrofloxacin (1.13 g/ml) and ciprofloxacin (0.24 g/ml) were observed at 0.8 and 1.2 h, respectively. The elimination half-life (t _1/2), volume of distribution (V _d(area)), total body clearance (Cl_B) and mean residence time (MRT) of enrofloxacin were 0.74 h, 1.42 L/kg, 1329 ml/h per kg and 1.54 h, respectively. The t _1/2, area under the plasma concentration–time curve (AUC) and the MRT of ciprofloxacin were 1.38 h, 0.74 g h/ml and 2.73 h, respectively. The metabolic conversion of enrofloxacin to ciprofloxacin was appreciable (36%) and the sum of the plasma concentrations of enrofloxacin and ciprofloxacin was maintained at or above 0.1 g/ml for up to 4 h. Enrofloxacin appears to be useful for the treatment of goat diseases associated with pathogens sensitive to this drug.     

IBDV-induced bursal T lymphocytes inhibit mitogenic response of normal splenocytes

We examined the suppressive activity of bursal T cells induced by infectious bursal disease virus (IBDV) in inbred (15x7) and outbred commercial specific-pathogen-free (SPF) chickens. The suppressive activity was measured by the ability of bursal and splenic T cells from IBDV-infected chickens to inhibit mitogenic responses of normal splenocytes. The bursacytes but not the splenocytes of IBDV-infected chickens inhibited the mitogenic responses of normal splenocytes. The mitogenic inhibition by the bursacytes of IBDV-infected chickens was dose-dependent. The suppression was observed both in inbred and non-inbred chickens, and thus, was non MHC-restricted. Cell-sorting experiments revealed that both CD4(+) and CD8(+) cells from the bursa of IBDV-infected chickens, as well as cell-culture supernatants conditioned by these cells, mediated suppression. Suppressor T (Ts) cells may therefore be involved in the immunosuppression induced by IBDV.     

Polymerase chain reaction amplification of 16S-23S spacer region for rapid identification of Salmonella serovars

Polymerase chain reaction (PCR) was used to amplify the spacer regions between the 16S and 23S genes of rRNA genetic loci of Salmonella serovars for their rapid identification. These genetic loci revealed a significant level of polymorphism in length across the species/serovar lines. When the 16S-23S spacer region amplification products were subjected to agarose electrophoresis, the patterns observed could be used to distinguish all the serovars of Salmonella tested. Unique elements obtained in amplification products were mostly clustered at serovar level, although certain genus-specific patterns were also observed. On the basis of the results obtained, the amplification of 16S-23S ribosomal spacer region could suitably be used in a PCR-based identification method for Salmonella serovars.