Browsing by Subject "in vitro"

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    Effect of yeast, protected minerals and bismuth subsalicylate on in vitro fermentation by rumen microbes.
    (2012-04) Moreno, Martín Ruiz
    Three experiments were conducted using a dual flow continuous culture fermenter system. In Experiment I, two levels of active dry yeast at 0 or 2 mg/fermenter/day (NY and YS, respectively) were infused twice daily to fermenters in a completely randomized arrangement of treatments. Apparent and true OM digestion was not affected by yeast. No differences were obtained in NDF and ADF digestion. Total VFA concentrations were not affected by treatments. Addition of yeast did not affect VFA molar proportions or estimated CH4S production but resulted in a trend for a lower A:P ratio. Addition of yeast decreased NH3-N concentration and NH3-N daily flow, without affecting crude protein digestion and efficiency of microbial protein synthesis. Mean and minimum pH of fermenters did not differ between treatments but a trend for a lower maximum pH was obtained with yeast. In conclusion, a low dose of active dry yeast decreased NH3-N concentration and daily flow, without affecting any other of the in vitro rumen fermentation characteristics measured in this study. In Experiment II, effects of two levels of lignosulfonate and two sources of minerals (protected and unprotected) on rumen fermentation were evaluated using a 2 x 2 factorial arrangement of treatments. Addition of lignosulfonate tended to decrease daily flow of non NH3-N, efficiency of microbial protein synthesis, total VFA concentration and molar proportion of acetate, but increased molar proportion of propionate, valerate and caproate. Protected minerals decreased molar proportion of propionate. Addition of lignosulfonate increased ruminally soluble Cu and Mn, whereas protected minerals reduced ruminally soluble Cu. Concentrations of bacterial Cu and Zn increased with protected minerals in absence of lignosulfonate. Concentration of Mn was not affected by treatments. Addition of lignosulfonate resulted in higher enzymatic release of Zn from solids outflow but lower from bacterial pellets. Mean, minimum and maximum fermentation pH was higher with lignosulfonate, and not affected by mineral source. Addition of lignosulfonate induced major changes in ruminal fermentation. Protection of minerals decreased rumen soluble Cu and increased bacterial Cu and Zn without affecting postruminal release of minerals. In Experiment III, addition of bismuth subsalicylate (BSS) at 1% of DM and monensin (MON; 5 ppm) were used to assess their effects on rumen metabolism and H2S release by rumen microbes in a 2 x 2 factorial arrangement of treatments. Addition of BSS increased digestion of OM, NDF and ADF but decreased that of NFC and total VFA concentrations. Molar proportions of acetate and propionate increased with BSS in the diet, while that of butyrate decreased. Monensin decreased ADF digestion and A:P ratio, without affecting molar proportions of major VFA. Regarding nitrogen metabolism, MON increased non NH3-N outflow without affecting other measurements. Addition of BSS to the diet increased NH3-N concentration, NH3-N flow and dietary-N flow, while decreasing microbial-N outflow, CP digestion, and efficiency of microbial protein synthesis. Headspace H2S was reduced by 99% with BSS treatment but was not affected by MON. Only minor changes in fermentation pH were found with MON, but an increase in mean, minimum and maximum fermentation pH were found following addition of BSS. Results indicate that BSS can markedly reduce H2S production in short term and long term in vitro rumen incubations.
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    The effectiveness of anular repair as illustrated in an in vitro laboratory simulation
    (2010-05) Bartlett, Ashley Nicole
    Surgeries to repair herniated discs are one of the most performed spinal surgeries worldwide. During a lumbar discectomy the herniated portion of the intervertebral disc (IVD) is removed; however, the defect in the anulus fibrosus (AF) remains and can provide a pathway for future herniation. Repairing the anulus is shown to diminish reherniation rates. There is a lack of data regarding the ability of anular repair methods to withstand intradiscal pressures, especially in an in vitro laboratory setting. This study has focused on creating an in vitro laboratory apparatus to simulate intradiscal pressure, allowing for controlled and repeatable results. By using a commercially-available anular repair device, and developing a protocol to test the efficacy of this device, the benefit of anular repair with discectomy compared to an unrepaired defect was demonstrated. An artificial AF was developed and used in conjunction with a pressurization chamber to simulate herniation of the IVD. Four configurations were evaluated: 1) circular or slit defect (control); 2) a single tension band; 3) two tension bands in a cruciate pattern; and 4) two tension bands in a parallel configuration. Anular defects were repaired with the XcloseTM Tissue Repair System. Input pressure was increased until failure (i.e. extrusion of the NP) occurred. The maximum failure pressure, representing the pressure at herniation, was recorded. Maximum failure pressure for the non-repaired conditions were significantly different compared to the repaired conditions for both defect types. For the circular defect, the failure pressure increased by approximately 76 and 131 percent with one or two tension bands, respectively, as compared to the control. In addition, the failure pressure for two tension bands (in either configuration) was approximately 32 percent higher than that for one tension band; this difference was significant. For the slit defect, with one or two tension bands the maximum failure pressure increased by approximately 21 and 37 percent, respectively, as compared to the control. No significant difference was found between two tension bands in the cruciate and parallel configurations for either defect. Current literature and the results of this laboratory simulation suggest anular repair reduces reherniation after a lumbar discectomy. First, the significant differences found in the maximum failure pressures for repaired versus non-repaired groups suggest a reduced risk for reherniation when anular repair is performed. Second, this study indicated that defect size and shape are relevant when choosing a repair configuration. Finally, two tension bands were seen to improve the ability to retain disc material, especially for the circular defect. The use of a laboratory experiment such as this enabled control of variables that would normally be difficult to test in a surgical setting, and laid the groundwork for the use of laboratory simulations in evaluating anular repair and its respective techniques.