多重聚合酶链反应筛选方法的研究

本文提出了筛选多重聚合酶链反应的常用方法，根据该法将56个牛微卫星组成的21个多重聚合酶链反应组合，其中14个三微卫星组合，7个二微卫星组合，这些多重聚合酶链反应组合可用于大批量测定微卫星的试验，如基因定位及亲子鉴定等。     

Expression of receptor tyrosine kinases VEGFR-1 (FLT-1), VEGFR-2 (KDR), EGFR-1, PDGFRa and c-Met in canine primary brain tumours

Inhibition of tumour growth and angiogenesis by targeting key growth factor receptors is a promising therapeutic strategy for central nervous system tumours. Characterization of these growth factor receptors in canine primary brain tumours has not been done. Using quantitative real‐time TaqMan polymerase chain reaction (PCR), we evaluated the expression of messenger RNA (mRNA) for five tyrosine kinase growth factor receptors (vascular endothelial growth factor receptor [VEGFR]‐1, VEGFR‐2, endothelial growth factor receptor [EGFR]‐1, platelet‐derived growth factor receptor a [PDGFRa], and c‐Met) relative to normal cerebral cortex in 66 spontaneous canine primary brain tumours. Increased expression of VEGFR‐1 and VEGFR‐2 mRNA was greatest in grade IV astrocytomas (glioblastoma multiforme) and grade III (anaplastic) oligodendrogliomas. EGFR‐1 mRNA expression was more consistently increased than the other receptors in all tumour types, while increased PDGFRa mRNA expression was mostly restricted to oligodendrogliomas. The similarities in increased expression of these tyrosine kinase growth factor receptors in these canine tumours, as compared to data from their human counterparts, suggest that common molecular mechanisms may be present.     

CNS mastitis: nothing to worry about?

In this paper, we analyzed a very large field data set on intramammary infections (IMI) and the associated somatic cell count (SCC) in dairy cows. The objective of the study was to analyze the impact of coagulase-negative staphylococci (CNS) IMI on cow SCC, both mean and variability, and on the potential of these infections to have a major impact on the bulk milk SCC (BMSCC). Data and milk samples for bacterial culture were collected by Quality Milk Production Services (QMPS) between 1992 and March of 2007. The QMPS program services dairy farms in New York State and other states in the Northeastern USA and operates in conjunction with Cornell University. Only records from cows where SCC and milk production data were available, and where only one organism was isolated from bacterial cultures of milk samples (or where culture was negative) were used for this analysis. A total of 352,614 records from 4200 whole herd mastitis screening sampling qualified for this study. Within herds an average of 15% (S.D. 12%) of cows sampled were infected with CNS, ranging between 0 and 100%. Average within herd prevalence of cows with a CNS IMI and an SCC over 200,000 cells/ml was 2% (S.D. 4%) with a minimum of 0% and a maximum of 50%. Results of linear mixed models showed three distinct populations of IMI statuses: negative cultures with the lowest SCC; CNS and Corynebacterium bovis with a moderate increase in SCC, and Streptococcus agalactiae, Streptococcus spp. and Staphylococcus aureus showing an important increase in SCC. Surprisingly, milk production was slightly but significantly higher in CNS infected cows compared to culture-negative cows, whereas it was strongly reduced in cows with a major pathogen IMI. The percentage contribution of CNS infections to the BMSCC was 17.9% in herds with a BMSCC less than 200,000 cells/ml. This value decreased to 11.9 and 7.9% in herds with bulk milk SCC between 200,000 and 400,000 and over 400,000 cells/ml, respectively. We concluded that very few herds with milk quality problems would have an important increase in BMSCC that could be mostly attributed to CNS infections. On the other hand, in herds with low BMSCC, CNS infections may be an important contributor to the total number of somatic cells in the bulk milk.     

The effect of feeding level and physiological status on total flow and amino acid composition of endogenous protein at the distal ileum in swine.

An experiment was conducted to investigate the effects of BW, feed intake, and the physiological condition of the animal on the loss and amino acid composition of endogenous protein in swine. Ten growing barrows and five multiparous sows were equipped with a T-cannula in the distal ileum for digesta collection. A protein-free diet was fed to all animals. The barrows were given free access to the experimental diet. The sows also were allowed to consume the diet on an ad libitum basis, and digesta were collected during lactation and in the following gestation period. In addition, digesta from the gravid sows were collected after restricting the sows to 2 kg of feed per day. For each animal group, the endogenous losses of protein and amino acids were calculated in relation to DMI, and the amino acid composition of endogenous protein was calculated. The total endogenous gut protein loss at the distal ileum of growing pigs, lactating sows, and gestating sows, given free access to feed, was 12.4, 9.4, and 11.2 g/kg DMI, respectively. These values were not different (P > .10). However, when gestating sows were fed only 2 kg/d, 17.8 g of endogenous protein was lost per kilogram of DMI, which was higher (P < .05) than for any of the other groups. This difference was mainly caused by higher (P < .05) losses of glycine, proline, and serine. There were no differences (P > .05) in amino acid composition of endogenous protein between growing pigs, lactating sows, and gestating sows given free access to feed, but restricted-fed gestating sows had an amino acid composition of endogenous protein that was significantly different from that of the other groups. The results from the experiment showed that age, BW, and the physiological condition of the animal have little or no effect on the amount of endogenous protein and amino acids lost at the distal ileum of hogs if calculated in relation to DMI. Likewise, the amino acid composition was not affected by the BW or physiological condition of the animal. However, DMI had a significant effect on endogenous protein losses in sows as well as on amino acid composition of endogenous protein.     

Genetic parameters for body weight, reproduction, and parasite resistance traits in the Creole goat

We estimated the genetic parameters for BW, reproduction, and parasite resistance traits to implement a breeding program for the Creole goat. The traits were preweaning BW at 70 d of age (BW70d), BW at 11 mo of age (BW11), fecal egg count at 11 mo of age (FEC11) for all animals, packed cell volumes of lactating does (PCV), and their fertility (FER) and litter size (LS). We analyzed about 30 yr of data, which included 18,450 records on 11,970 animals from the INRA experimental flock in Guadeloupe (French West Indies). Heritability estimates were low for reproduction traits (0.11 ± 0.02 for LS and FER) to moderate for production traits (0.32 ± 0.03 for BW11; 0.20 ± 0.03 and 0.08 ± 0.02 for the direct and maternal heritability estimates of BW70d, respectively). Heritability estimates for gastrointestinal nematode resistance traits were situated in an intermediate range (0.13 ± 0.05 for PCV and 0.18 ± 0.04 for FEC11). Genetic correlations between FER, PCV, BW11, and the maternal effect of BW70d were altogether positive, whereas LS and FEC11 were almost uncorrelated phenotypically and genetically. These correlations are very favorable for setting up a breeding program, making it possible to improve BW, reproduction, and parasite resistance traits simultaneously.