Effects of preconditioning on pre- and post-shipment performance of feeder calves

A preconditioning (PC) program that involved preweaning vaccination and preshipment weaning was evaluated utilizing 600 calves produced on four South Dakota ranches. Nonpreconditioned (NPC) controls were herd mates that were maintained with their dams during the preconditioning process. All calves were shipped from the ranch to the feedlot on the same date. In Exp. I, PC caused lower (P less than .001) preshipment gains. However, management x ranch and management x year effects indicated that response to PC was variable. Preconditioning reduced (P less than .001) transit shrink in Exp. I but caused greater (P less than .05) shrink in Exp. II. Ranch and management x ranch effects accounted for more of the variation in shrink than PC did. In the feedlot, PC calves consumed more feed initially (d 1 to 28; P less than .001) and during the entire (P less than .10) feeding period when fed to slaughter condition. During the 28-d postshipment period, calves fed higher-grain diets consumed more feed (P less than .001) and were less efficient (P less than .001) than calves fed corn silage. When fed for longer periods (greater than 28 d), higher-energy diets improved feedlot gains and feed efficiency independent of preconditioning. Health and performance responses to this preconditioning procedure were variable. Our preconditioning procedure did not improve beef production efficiency.     

Chlamydiosis in workers at a duck farm and processing plant

SUMMARY An outbreak of chlamydiosis was Investigated in workers at a duck farm and processing plant during winter 1989. Chlamydia psittaci was isolated from ducks, but there was little evidence of clinical chlamydiosis in the ducks. Serological tests showed that 76% of workers had been exposed to Infection, 12% recently, 16% had not been exposed and 8% had inconclusive test results. There was a strong association (P < 0.05) between years of employment and exposure to Infection. Infection appeared to be contracted during the first year of employment. Measures were Implemented to reduce shed contamination and control rodents and wild birds. At the same time, ducks were medicated, the processing plant was modified, work practices were altered and workers were advised about chlamydiosis to reduce the risk of human infection.     

An ion balance for ultra-high-precision atomic mass measurements

We have developed the analog of a double-pan balance for determining the masses of single molecular ions from the ratio of their two cyclotron frequencies. By confining two different ions on the same magnetron orbit in a Penning trap, we balance out many sources of noise and error (such as fluctuations of the magnetic field). To minimize the systematic error associated with the Coulomb interaction between the two ions, they are kept about 1 millimeter apart from each other, resulting in fractional uncertainty below 1 x 10(-11). Such precision opens the door to numerous applications of mass spectrometry, including metrology, fundamental physics, and weighing chemical bonds.     

Traces of human migrations in Helicobacter pylori populations

Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions. These modern populations derive their gene pools from ancestral populations that arose in Africa, Central Asia, and East Asia. Subsequent spread can be attributed to human migratory fluxes such as the prehistoric colonization of Polynesia and the Americas, the neolithic introduction of farming to Europe, the Bantu expansion within Africa, and the slave trade.     

Medulloblastoma growth inhibition by hedgehog pathway blockade

Constitutive Hedgehog (Hh) pathway activity is associated with initiation of neoplasia, but its role in the continued growth of established tumors is unclear. Here, we investigate the therapeutic efficacy of the Hh pathway antagonist cyclopamine in preclinical models of medulloblastoma, the most common malignant brain tumor in children. Cyclopamine treatment of murine medulloblastoma cells blocked proliferation in vitro and induced changes in gene expression consistent with initiation of neuronal differentiation and loss of neuronal stem cell-like character. This compound also caused regression of murine tumor allografts in vivo and induced rapid death of cells from freshly resected human medulloblastomas, but not from other brain tumors, thus establishing a specific role for Hh pathway activity in medulloblastoma growth.     

Genetic structure of human populations

We studied human population structure using genotypes at 377 autosomal microsatellite loci in 1056 individuals from 52 populations. Within-population differences among individuals account for 93 to 95% of genetic variation; differences among major groups constitute only 3 to 5%. Nevertheless, without using prior information about the origins of individuals, we identified six main genetic clusters, five of which correspond to major geographic regions, and subclusters that often correspond to individual populations. General agreement of genetic and predefined populations suggests that self-reported ancestry can facilitate assessments of epidemiological risks but does not obviate the need to use genetic information in genetic association studies.