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Biomedical subjects

D A Wilson

Publications and source records attributed to D A Wilson.

241 records · Page 14Linked to original sources
PubMedDate not supplied

Case control and historical cohort study of diarrhea associated with administration of trimethoprim-potentiated sulphonamides to horses and ponies.

Trimethoprim-potentiated sulphonamides (TPS) are among the most frequently administered antimicrobials in equine medicine. Anecdotally, TPS has been implicated as a cause of mild to moderate diarrhea in horses. The purpose of this study was to document the prevalence of diarrhea in horses receiving TPS, to characterize the severity of the diarrhea, and to identify any other factors associated with the development of diarrhea. A 2-part study was designed to identify the prevalence of diarrhea associated with TPS in our clinic population. Part I was a case-control retrospective study of 135 records over a 10.5-year period from January 1, 1980 through June 30, 1990. Part II was a historical cohort study of 784 records over a 37-month period from July 1, 1990 through July 31, 1993. There was no significant difference in the occurrence of diarrhea associated with TPS therapy in either study. The occurrence of diarrhea was 21% and 3% in parts I and II, respectively. Significant factors identified in association with diarrhea in part I were duration of hospital stay, and antibiotic therapy other than TPS or penicillin. Significant factors identified in part II included other antibiotic therapy, penicillin therapy, and combined penicillin and TPS therapy. Diarrhea does occur after the administration of antibiotics, most likely because of the alteration of the patient's normal intestinal flora. Diarrhea was noted in association with administration of TPS in this study; however, its prevalence was not significantly different than that in horses receiving other antibiotics, such as penicillin and its derivatives.

Age Factors↗
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Transfer function measurement and analysis for a magnetic resonance imager.

The transfer function characteristics of a 1.5T imager have been determined. An edge response function (ERF) was obtained from a water/Plexiglas interface at various pixel widths ranging from 0.312 to 1.0 mm. An SE pulse sequence was used with a 5-mm transaxial slice. The ERF was smoothed, differentiated, and Fourier transformed to obtain MTF curves. The LSF was analyzed for skewness and kurtosis. The area under the MTF amplitude curves and the equivalent bandpass were calculated. All ERFs, LSFs, and MTFs were well behaved. The resulting LSF was Gaussian. All calculated MTFs had cutoff frequencies slightly less than the theoretical Nyquist limit. The MTF calculated from the theoretical Gaussian LSF is slightly superior to that calculated from experimental data and provides an upper limit to the MTF. Spatial resolution in our MR imager is dominated by the pixel size via the Nyquist sampling theorem. System performance is slightly less than theoretically predicted, possibly due to image processing algorithms during the reconstruction process.

Humans↗
PubMedDate not supplied

Natural history of experimental intracerebral hemorrhage: sonography, computed tomography and neuropathology.

The evolution of intracerebral hemorrhage was investigated in a canine model by high resolution sonography, computed tomography (CT), and neuropathologic examination. In 12 dogs, a parietal lobe hematoma was introduced by craniotomy. The sonographic appearance of acute hemorrhage was characteristic and consisted of a sharply circumscribed, homogeneous, highly echogenic lesion, the size and shape of which correlated closely to the area of increased density seen on the CT scan. This changed within 3-4 days to an echogenic rim surrounding a hypoechoic center. Histologically, this change corresponded to a loss of integrity of individual red blood cells. This occurred earliest in the hemorrhage center causing a hypoechoic center, while intact red blood cells at the periphery accounted for the echogenic rim. Shortly after the red blood cells lost their biconcave shape they began to lose their hemoglobin causing the hemorrhage to become isodense with surrounding brain on the CT scan. Faint contrast enhancement by CT was noted at this early stage and was related primarily to a mononuclear perivascular infiltrate at the edge of the hemorrhage. A collagen capsule formed around the hemorrhage over a 2 week period. This capsule slowly replaced intact red cells as the cause of the now shrinking echogenic rim. This capsule was also responsible for the increasing ring contrast enhancement around the resolving hemorrhage. The sequence of image changes seen on both CT and sonography in this experimental model closely resembled the findings seen in intracerebral hemorrhage in patients.

Animals↗
PubMedDate not supplied

Ultrasonic scanning of the kidneys.

Recent improvement in imaging technology has enabled ultrasound to assume an increasingly vital role in the identification and evaluation of renal disease. Renal masses can be differentiated. The nonfunctioning kidney can be imaged and obstruction or inflammation diagnosed. When further information is needed, an ultrasound guided biopsy or aspiration can be performed.

Adult↗