The feasibility of determining the nitrogen content of farmyard manure using infrared spectroscopy was investigated. Fifteen samples each of cattle, pig, and turkey manure were analyzed by three infrared techniques: Fourier transform mid-infrared (MIR), using attenuated total reflection (ATR); near-infrared reflectance (NIR-R); and near-infrared optothermal photoacoustic (NIR-OT). The near-infrared measurements were made at wavelengths determined respectively by four (NIR-OT) and five (NIR-R) band-pass filters. The total nitrogen (using the Kjeldahl method) and volatile (ammoniacal) nitrogen contents of all samples were measured by wet chemistry. Internally cross-validated (ICV) partial least-squares (PLS) regression was then used to obtain calibrations for the nitrogen content. The data sets obtained by each technique were treated separately. Within these sets, data from each manure type were treated both separately and combined: the best predictive ability was obtained by combining data from all three manure types. From the combined data set, the residual standard deviations and correlation coefficients for the ICV-predicted versus actual Kjeldahl nitrogen content were, respectively, 6772 mg/kg dry wt, 0.862 (MIR); 9434 mg/kg dry wt, 0.771 (NIR-OT); and 8943 mg/kg dry wt, 0.865 (NIR-R). For the ammoniacal nitrogen content, the residual standard deviations and correlation coefficients were 3869 mg/kg dry wt, 0.899 (MIR); 6079 mg/kg dry wt, 0.820 (NIR-OT); and 3498 mg/kg dry wt, 0.961 (NIR-R).
In an isolated dog heart, perfused with blood from an anesthetized donor, left ventricular performance was observed during periods in which the left ventricle either contracted isovolumically or was allowed to eject saline. Heart rate and left ventricular end-diastolic pressure were comparable in both. Ventricular performance, as judged by peak systolic ventricular pressure, declined relatively rapidly during isovolumic loading when initial systolic pressures were higher. The efflux of norepinephrine (NE) from the heart was directly related to the systolic pressure of the left ventricle both when the NE concentration of the perfusing blood was normal and when it was reduced to undetectable levels by dialysis. Changes in heart rate did not affect NE efflux nor was NE efflux increased by isobaric loading when the ventricle was distended in diastole without developing pressure in systole. A pathway is described whereby ventricles developing a high systolic pressure may be depleted of NE.ADDITIONAL KEY WORDS systolic pressure isovolumic loading heart rate coronary flow ventricular performance isobaric loading canine heart • It has been reported that isolated, supported hearts perfused with the blood of an intact animal maintain left ventricular performance, as defined by their ability to maintain their stroke work at a near constant end-diastolic pressure for varying periods of time after isolation (1). Preliminary observations from this laboratory have confirmed these findings in that the left ventricular performance of hearts so perfused did not deteriorate provided the ventricle was allowed to eject a critical stroke volume of saline ( 2 ) . If, on the other hand, the ventricle was forced to contract isovolumically at a constant enddiastolic pressure, its performance as reflected by peak systolic pressure progressively declined. It was decided, then, to reexamine the performance of isovolumically contracting ventricles in comparison with those ejecting fluid and, insofar as possible, to explore causes for any discrepancies observed.Recent reports have indicated that the norepinephrine content is relatively low in ventricles that have been subjected to a high systolic pressure and subsequent failure compared with that of normal hearts (3). These findings imply that there is either a faster depletion of ventricular norepinephrine stores when the ventricle is subjected to the described stress, or that there is a diminution in the rate at which stores are reconstituted either by biosynthesis or uptake. Our studies were undertaken to determine the rate at which norepinephrine was released by the heart under various conditions of ventricular loading, particularly during the decline in ventricular performance which occurred when the ventricle was forced to contract isovolumically and produce a high systolic pressure. 774
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.