QUANTITATIVE ASSESSMENT OF SURGICALLY INDUCED MITRAL REGURGITATION USING RADIONUCLIDE VENTRICULOGRAPHY AND FIRST PASS RADIONUCLIDE ANGIOGRAPHY

Radionuclide ventriculography has been used in humans to evaluate valvular incompetency. The stroke volume ratio, derived from the radionuclide ventriculogram, is used to quantify the severity of mitral regurgitation (MR). Previous studies conducted in humans have shown that left to right stroke volume ratio increases as the severity of MR increases. In this study, we evaluated radionuclide ventriculography as a noninvasive method to detect MR in dogs with surgically created mitral insufficiency. Six male and three female adult, conditioned mongrel dogs were used. Scintigraphic studies were performed prior to and 4 weeks after surgically created MR. Because of the overlap of the left and right ventricles when viewed from a left lateral position, we combined data from a first-pass radionuclide angiocardiogram with the radionuclide ventriculogram to obtain a corrected stroke volume ratio. Blood flow transit parameters were also derived from the first-pass radionuclide angiocardiogram. Standard left ventricular functional indices were also measured from the radionuclide ventriculogram. On the left lateral view of the heart, 25 to 30% of the right ventricular volume overlaps the left ventricle. After correcting for the overlap, the stroke volume ratio of normal dogs was 1.17±0.178 (mean±SD), which increased to 2.06±0.41 (mean±SD) (p<.001) 4 weeks after creation of MR. The was no significant change in left ventricular ejection fraction or peak rate of ejection following MR. The transit times of blood through the left ventricle were measured from the first-pass radionuclide angiocardiogram and were expressed as half-time clearance, peak clearance rate, and time to peak clearance rate. The baseline half-time clearance was 2.07±0.71 s (mean±SD), which increased to 6.70±4.89 s (mean±SD) (p=.02) after creation of MR. The baseline peak clearance rate was 49.75±8.96 cts/s (mean±SD), which decreased to 23.12±6.84 cts/s (mean±SD) (p<.001) after creation of MR. Stroke volume ratios significantly increased following creation of MR. Blood flow transit through the left ventricle slowed following creation of MR. The variability of these parameters were small in the baseline studies, suggesting these techniques may be clinically useful to gauge the severity of MR in dogs.     

A Simple Apparatus for Frequent Measurement of Gastrointestinal Intraluminal PCO2

The accuracy and precision of an end-tidal infrared CO₂ monitor and customized capnography tubing system designed to measure gastrointestinal intraluminal CO₂ partial pressure (P_iCO₂) were tested in vitro. Samples were taken from the customized capnography tubing placed in either 5% or 10% CO₂ gas at discrete intervals ranging from one minute to twelve minutes. For a given time interval, the tubing PCO₂ measurement was a constant fraction of the actual PCO₂ (all standard errors < 0.02). For increasing time intervals, the ratio of the tubing PCO₂ to actual PCO₂ increased logarithmically. In the 5% and 10% CO₂, the regression coefficients were 0.89 and 0.85 for 8 French tubing and 0.99 and 0.91 for 6 French tubing. Beacuase of its accuracy and precision, this system may provide automated gastrointestinal CO₂ partial pressure monitoring at short intervals (e.g. 5 minutes), facilitating testing of the role of gastrointestinal P_iCO₂ information in treatment algorithms. (Vet Emerg & Crit Care, 1998; 8: 109–116)     

Heterosis retained in advanced generations of crosses among Angus and Hereford cattle

Data from 1,909 purebred, F1, backcross and F2 and F3 inter se combinations of Angus and Hereford were used to estimate average individual, maternal and grandmaternal genetic effects, individual and maternal heterosis, dominance and epistatic genetic effects. Models for evaluating heterosis and epistatic or recombination effects were discussed. Average individual effects indicate that Angus, compared with Hereford, had calves that were born earlier, had lighter birth weights, lower pre- and postweaning gains and lower pregnancy rates. Angus also produced lighter weight carcasses with more fat cover and marbling. Maternal effects of Angus were in the direction of reduced birth weight, greater calving ease, higher preweaning but lower postweaning growth rate and increased fatness when contrasted with Hereford. There was a tendency for opposite direction of maternal and grandmaternal effects for traits influenced by preweaning maternal environment. When additive X additive effects were ignored, total heterosis was significant for earlier day born, heavier birth weight, preweaning and postweaning gain, and heavier and fatter carcasses. Heterosis retained in F3 inter se vs F1 generation crosses indicated that net epistatic effects were relatively negligible for date of calving, birth weight, weaning gain and fat cover. There was a greater reduction of heterosis effects than expected from dominance alone for survival, pregnancy and marbling score. Loss of heterosis in F3 was less than expected for postweaning gain, carcass weight and rib eye area. Except for survival, pregnancy and marbling, these deviations from dominance expectations, or lack of them, are favorable for F3 composite populations.     

Comparison of Bos taurus-Bos indicus breed crosses with straightbred Bos indicus breeds of cattle for maternal and individual traits

Data were analyzed to compare crossbred females produced by crossing exotic Angus and Red Poll males to indigenous Ankole, Boran and Small East African Zebu (Zebu) females with straightbred females of the Ankole, Boran and Zebu breeds at the Ruhengere Field Station in the Ankole District of Southwestern Uganda. Progeny of the straightbred and crossbred dams were by Friesian, Brown Swiss and Simmental sires. Crossbred exotic X indigenous dams were favored over straightbred indigenous dams by 13.7% (P less than .01) in calf birth weight and by 14.8% (P less than .01) in calf weaning weight. Cross-bred cows exceeded (P less than .01) straightbred cows by 61.9% (48.5 kg) in calf weight weaned per cow exposed to breeding. Crossbred cows weighed 37, 46 and 42 kg more (P less than .01) than straightbred cows at parturition, weaning and cow mean weight, respectively. Angus X Boran and Red Poll X Boran crossbred dams were compared specifically with straightbred Boran dams. Exotic (Angus, Red Poll) X Boran crossbred dams exceeded straightbred Boran dams by 27.0% (P less than .05) in calf crop born, by 8.3% (P less than .05) in progeny birth weight and by 14.7% (P less than .01) in progeny weaning weight. Weight of calf weaned per cow exposed to breeding favored (P less than .01) the Angus X Boran and Red Poll X Boran crossbred dams over the straightbred Boran dams by 50.5% (50 kg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of amendments on soil structural development in a clay soil-forming material used as a cap for landfill restoration

Abstract. Restoration of landfill sites to a vegetated after-use is severely compromised if soil-forming materials (SFMs) have to be used as substitute growing media for the restoration cap, owing partly to their poorly-developed structure. The effects of crushed brick material (brick), composted green-waste organic matter (OM) and potassium chloride salt (KCl) in a clay SFM were assessed at the Brogborough Landfill Site (Shank Group plc) in the county of Bedfordshire, UK. Soil structure was characterized three times in a two-year experimental period through measuring drainage water release and aggregate stability and size distribution. Crushed brick and composted OM at 100 t ha⁻¹ improved the ability of the clay to release water by drainage. In addition, the composted OM was associated with an increase in the size of stable aggregates, whereas the brick amendment reduced the overall aggregate stability. The KCl amendment had no consistent effect. Some beneficial structural improvements were thus associated with the brick and OM amendments, although these were rarely significant at the 5% level and the effects declined over time in the absence of vegetation and re-application. Nevertheless, incorporation of crushed brick and organic amendments may offer a potential structure-improving option in clay SFMs prior to vegetation establishment.     

Annualized diameter and height growth equations for Pacific Northwest plantation-grown Douglas-fir, western hemlock, and red alder

Simulating the influence of intensive management and annual weather fluctuations on tree growth requires a shorter time step than currently employed by most regional growth models. High-quality data sets are available for several plantation species in the Pacific Northwest region of the United States, but the growth periods ranged from 2 to 12 years in length. Measurement periods of varying length complicate efforts to fit growth models because observed growth rates must be interpolated to a common length growth period or those growth periods longer or shorter than the desired model time step must be discarded. A variation of the iterative technique suggested by Cao [Cao, Q.V., 2000. Prediction of annual diameter growth and survival for individual trees from periodic measurements. Forest Sci. 46, 127–131] was applied to estimate annualized diameter and height growth equations for pure plantations of Douglas-fir, western hemlock, and red alder. Using this technique, fits were significantly improved for all three species by embedding a multi-level nonlinear mixed-effects framework (likelihood ratio test: p < 0.0001). The final models were consistent with expected biological behavior of diameter and height growth over tree, stand, and site variables. The random effects showed some correlation with key physiographic variables such as slope and aspect for Douglas-fir and red alder, but these relationships were not observed for western hemlock. Further, the random effects were more correlated with physiographic variables than actual climate or soils information. Long-term simulations (12–16 years) on an independent dataset using these annualized equations showed that the multi-level mixed effects models were more accurate and precise than those fitted without random effects as mean square error (MSE) was reduced by 13 and 21% for diameter and height growth prediction, respectively. The level of prediction error was also smaller than an existing similar growth model with a longer time step (ORGANON v8) as the annualized equations reduced MSE by 17 and 38% for diameter and height growth prediction, respectively. These models will prove to be quite useful for understanding the interaction of weather and silviculture in the Pacific Northwest and refining the precision of future growth model projections.     

Tree planting in Tigray, Ethiopia: the importance of human disease and water microdams

We examine the decision to plant trees and level of tree planting for two sites, public microdam areas and household agricultural land, and two species groups in Tigray, Ethiopia. Both sites are not perfect substitutes, as they vary with respect to distance from the household and tenure security. The role of permanent pooled water irrigation microdams to tree planting is important but unknown, because water borne diseases, which may influence household income and productivity, are thought to be enhanced by the dams. We find both disease and microdams to be important predictors to tree planting. Disease seems more important in determining whether households plant at all, and less important in the level of planting for those that do plant. For example, disease increases the probability of planting both eucalyptus and other species groups on household-own land, but households suffering from malaria plant higher-cost eucalyptus trees with lower probability at both sites, while planting of other lower-cost species increases at dam sites where other villagers can monitor the trees. We also establish a connection between planting and agricultural residues, finding a strong substitution effect on own-land. Microdam access and age are also important. Households living nearer to dam sites will plant both species groups there with higher probabilities, but the decision to plant on agricultural own-land is not affected. For older dams with more developed irrigation, households are more likely to grow crops rather than plant trees on their own land, but they plant more trees at the dam sites. This revised version was published online in June 2006 with corrections to the Cover Date.