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1.
Hereford x Angus crossbred steers (n = 36) were stunned, exsanguinated, and infused via the carotid artery either with an aqueous solution containing 98.52% water, 0.97% saccharides, 0.23% sodium chloride, and 0.28% phosphates (MPSC; n = 12) or with 0.3 M CaCl2 (n = 12). The remaining 12 steers served as noninfused controls. At 48 h postmortem, the quadriceps muscles and subcutaneous fat were removed from the carcasses, frozen, and later made into ground beef (18 to 20% fat). The longissimus lumborum (LL), semimembranosus, and psoas major (PM) also were removed, vacuum packaged, aged until 14 d postmortem, and then one steak was sliced from each muscle for visual and instrumental color evaluations. The inside (ISM) and outside (OSM) portions of the SM were evaluated separately. The LL and OSM steaks from MPSC-infused carcasses had a lighter red (P < 0.05) initial appearance than steaks from the other treatments. The LL steaks from noninfused carcasses had the most (P < 0.05) uniform color; the MPSC treatment was intermediate, and the CaCl2 treatment was the most two-toned. Steaks from both infusion treatments had higher (P < 0.05) L* values for the LL, ISM, and OSM muscles compared with noninfused carcasses. In general, the LL from CaCl2-infused carcasses had lower (P < 0.05) a* values, saturation indices, and 630 nm to 580 nm reflectance values, and had larger (P < 0.05) hue angles. Infusion with MPSC increased (P < 0.05) hue angles in the LL and OSM. Display color stability was lowest (P < 0.05) for LL steaks from CaCl2-infused carcasses, whereas steaks from MPSC-infused carcasses were lighter red in initial color, but otherwise had display color stability similar to those from noninfused carcasses. No differences (P > 0.05) due to infusion were found for any color traits for the PM muscle and ground beef. Carotid artery vascular infusion of carcasses with CaCl2 resulted in undesirable meat colors, whereas the MPSC solution lightened loin and inside round color in a desirable way, but the color stability was slightly less compared to muscle from noninfused carcasses. Infusion effects were not consistent among muscles, and further research will be needed to determine what caused these differences.  相似文献   
2.
An enzyme-linked immunosorbent assay (ELISA) was developed for detecting antibody to type A avian influenza (AI) virus. The sensitivity and group specificity of the AI-ELISA were compared with those of the agar-gel-precipitin test (AGPT) and the hemagglutination-inhibition (HI) test under conditions of both controlled and field exposure. During the course of temporal experimental infection (0-76 days) of specific-pathogen-free (SPF) chickens with AI subtype Hav9N2, the AI-ELISA was able to detect specific AI antibody as early as 8 days postinoculation (PI), and it measured rising levels of antibody through 35 days PI, at which time the chickens were re-exposed to AI virus. Conversely, AGP tests were negative through 35 days PI, and HI tests began to detect low levels of AI antibody only at 21 days PI. Following a secondary infection at 35 days PI with the same AI subtype, all tests measured rising levels of AI-specific antibody (35-76 days PI). However, the AGP test was positive at only the 7- and 14-day samplings postsecondary immunization. Under field conditions, the AI-ELISA was able to detect serum AI antibody in flocks from which highly pathogenic AI was isolated, but the AGP tests of these sera were negative.  相似文献   
3.
Ceftiofur hydrochloride was tested for effectiveness against induced colibacillosis in neonatal swine. In this model, pigs less than 12 hours old were inoculated via stomach tube with a virulent, K99+, nalidixic acid-resistant strain of Escherichia coli. Six hours after challenge exposure, 1 dose of ceftiofur was administered either IM or orally in experiment 1 and orally only in experiment 2. Mortality, shedding of bacteria, fecal consistency scores, and body weight changes were monitored for 10 days. In experiment 1 (n = 383 pigs), all treatments at dosage that ranged between 0.5 and 64.0 mg of ceftiofur/kg of body weight significantly (P less than 0.001) reduced mortality, bacterial shedding, and diarrhea and increased weight gain, compared with findings in untreated controls. There were no detectable differences between oral and IM routes, except that there was greater reduction in bacteria shedding associated with the oral route of administration. In experiment 2 (n = 505 pigs), ceftiofur was administered orally either once at 6 hours after challenge exposure or twice at 6 and at 48 hours after the first dose. Dosage of ceftiofur was 0, 5, 10, 20, 30, or 60 mg/kg administered once, or half the same dose was administered at each of 2 times. At the optimal dosage (10 mg/kg), a single dose was as effective as 2 doses. The single administration at all dosages reduced mortality, bacterial shedding, and diarrhea scores and increased body weight gain, compared with findings in untreated pigs (P less than 0.01). In this induced infection model, the optimal treatment dosage was determined to be 10 mg/kg administered once.  相似文献   
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Two neutralizing monoclonal antibodies (MCAs), R63 and B69, were used in antigen-capture enzyme immunoassays to verify the presence of infectious bursal disease virus (IBDV) in infected bursal tissues. The intra-serotype-common neutralization site defined by the R63 MCA was present on all IBDV isolates and laboratory strains tested. However, the neutralization site defined by the B69 MCA was found on only classic or older IBDV strains; it was not found on recently isolated variants of IBDV or on a majority of recent field viruses examined. The data suggest that a major antigenic shift in IBDV has occurred in the field and that this shift involves, at a minimum, the deletion or alteration of one of two neutralization sites previously found on classic IBDV strains.  相似文献   
6.
Little information is available in the literature on the interrelationships and interactions among pH, aging time, marbling, and maturity on the flavor profile of some beef muscles commonly used for steaks. To investigate these effects on beef flavor, the infraspinatus (top-blade steak) from the chuck clod, the gluteus medius (top-sirloin steak) from the sirloin, and the psoas major (tenderloin steak) from the loin were obtained from A- (n = 80) and B-maturity (n = 60) carcasses with either Slight (n = 68) or Small (n = 72) marbling, and with either normal (< or = 5.7; n = 80) or high (> or = 6.0; n = 60) pH. Muscles were selected from two commercial processing plants at six different sampling times to evaluate factors that affect the flavor profile of cooked beef steaks. Muscles were vacuum-aged for 7, 14, 21, or 35 d, and a highly trained, flavor-profile sensory panel evaluated charbroiled steaks from these muscles. Numerous statistical interactions (P < 0.05) were detected for flavor attributes of the different muscles. In general, muscles from high pH (dark cutting) carcasses had less typical beef flavor identity and less brown-roasted flavor than those from carcasses with normal pH. Aging longer than 21 d generally decreased beef flavor identity. Top-blade steaks generally had less intense beef flavor identity and more intense bloody/serumy flavor than did top-sirloin and tenderloin steaks. Tenderloin and top-sirloin steaks of normal pH generally had the most brown-roasted flavor, especially when aged 21 d or less. Small degree of marbling generally resulted in a more rancid flavor compared with Slight marbling, but marbling had no other appreciable effects on the flavor profile. Aging steaks for 35 d increased (P < 0.05) the metallic flavor compared with aging for only 7 or 14 d. Top-sirloin steaks had a more intense (P < 0.05) sour flavor than did top-blade steaks, and steaks from carcasses with a high pH were more rancid (P < 0.05) than steaks from carcasses with normal pH. Vacuum-aging top-blade, top-sirloin, and tenderloin steaks to 21 or 35 d postmortem generally increased metallic and rancid flavors and increased sour flavor in top-sirloin steaks that were high in pH.  相似文献   
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The potential of using a QCDCR (quilA:cholesterol:dimethyl dioctadecyl ammonium bromide:carbopol:R1005 glycolipid) formulated CpG oligodeoxynucleotide (ODN), ODN 2007, to confer protection in Nile tilapia against Streptococcus iniae infection was evaluated in this study. At two days post treatment, QCDCR formulated ODN 2007 elicited significant (P<0.05) protection to Nile tilapia, with relative percent survival of 63% compared to fish treated by QCDCR alone. To understand the molecular mechanisms involved in the protective immunity elicited by ODN 2007, suppression subtractive cDNA hybridization technique was used to identify upregulated genes induced by ODN 2007. A total of 69 expressed sequence tags (ESTs) were identified from the subtractive cDNA library. Quantitative PCR revealed that 44 ESTs were significantly (P<0.05) upregulated by ODN 2007, including 29 highly (>10-fold) and 15 moderately (<10-fold) upregulated ESTs. Of all ESTs, putative peroxisomal sarcosine oxidase was upregulated the highest. The 69 ESTs only included six genes that had putative functions related to immunity, of which only two (putative glutaredoxin-1 and carboxypeptidase N catalytic chain) were confirmed to be significantly upregulated. Our results suggest that the protection elicited by ODN 2007 is mainly through innate immune responses directly or indirectly related to immunity.  相似文献   
9.
All-atom empirical molecular mechanics protein force fields, which have been developed to represent the energetics of peptide folding behavior in aqueous solution, have not been parameterized for protein interactions with solid material surfaces. As a result, their applicability for representing the adsorption behavior of proteins with functionalized material surfaces should not be assumed. To address this issue, we conducted replica-exchange molecular dynamics simulations of the adsorption behavior of structured peptides to functionalized surfaces using three protein force fields that are widely used for the simulation of peptide adsorption behavior: CHARMM22, AMBER94, and OPLS-AA. Simulation results for peptide structure both in solution and when adsorbed to the surfaces were compared to experimental results for similar peptide-surface systems to provide a means of evaluating and comparing the performance of these three force fields for this type of application. Substantial differences in both solution and adsorbed peptide conformations were found amongst these three force fields, with the CHARMM22 force field found to most closely match experimental results.  相似文献   
10.
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