Enzymatic amplification of expansion segment 5 sequences within domain IV of the large subunit ribosomal DNA generated distinct results among geographical isolates of Trichinella pseudospiralis from Russia, North America, and Australia from both avian and mammalian hosts. Discrete, multiple DNA fragments ranging in approximate size from 285 to 360 bp were observed within and among each of the isolates tested. Polymerase chain reaction performed on individual adult parasites from each isolate resulted in multiple DNA fragments that were comparable to those generated from pooled genomic DNA. Sequence analysis of cloned, representative amplified fragments demonstrated that fragment length variation resulted primarily from the dinucleotide (TG)n and trinucleotide (TGC)n microsatellite repeats present within the expansion segment. Results are consistent with both population differences within the species as well as the presence of multiple alleles of the large subunit ribosomal RNA genes within individual parasites.

Twenty-four Holstein cows, producing at least 21 kg of milk/d, were used in two replicate experiments to determine the effect of presence or absence of pulsation on loss of teat canal keratin during machine milking. Left quarters were milked without pulsation and right quarters were milked with pulsation. On d 0 and 10, keratin was collected from one left and from one right teat canal of each cow prior to milking and from the remaining two teat canals after milking. Milk was collected for assessment of SCC and bacteriological status on d 0 and approximately every 3 d until d 18. Quantity of keratin recovered before milking on d 10 did not differ between teats milked with or without pulsation, but loss of keratin because of milking was greater from teats milked with pulsation. By d 7, 30% (12 of 43) of quarters milked without pulsation had become infected, but no (0 of 47) quarters milked with pulsation were infected. By d 14 to 16, new infections had increased to 68% (28 of 41) of quarters milked without pulsation and 2% (1 of 43) in quarters milked with pulsation; mean SCC in pulsationless quarters increased sevenfold relative to pulsation quarters. Protein and water content of keratin did not differ because of treatment, and changes in lipid composition were minor. Histological analysis of the teats of 4 cows indicated that the mean diameter of the teat canal, within 2 h after milking, was greater without pulsation than with pulsation (680 vs. 483 microns).

cDNA generated from stimulated abomasal lymph node cells was used to amplify and clone the 35 kDa and 40 kDa subunits of bovine interleukin 12 (IL-12) using primers derived from semi-conserved regions between human and mouse IL-12 sequences. The deduced amino acid sequence of the 40 kDa subunit demonstrated 84.4% and 67.6% homology with human and mouse sequences, respectively. The deduced sequence of the 35 kDa subunit exhibited comparable similarities to the human 35 kDa subunit (82.2%) but differed significantly (58.6%) from mouse-derived sequences.