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Biomedical subjects

D A Wilson

Publications and source records attributed to D A Wilson.

At least 127 records · Page 7Linked to original sources
PubMed1991

Atlantoaxial malformation in a half-Arabian colt.

A 1-year-old half-Arabian colt was referred for evaluation of a cranial cervical abnormality. Physical examination revealed the left wing of the atlas to be more ventral than the right wing. A head tilt, with the pole deviated to the left, was present because of the malpositioned atlas. Neurologic examination identified symmetrical weakness, ataxia, and proprioceptive deficits in all four limbs. Radiographs of the cranial cervical region revealed fusion of the atlas and axis, and deviation of the atlantoaxial joint to the left of the median plane. Euthanasia was elected. Necropsy confirmed the radiographic findings. The atlas was rotated 20 degrees counterclockwise when viewed from the caudal aspect. Multifocal myelomalacia was present in the first and second cervical spinal cord segments. The malformation was believed to be due to a degenerative process or abnormal embryological development.

Animals↗
PubMed1991

Composition and morphologic features of the interosseous muscle in Standardbreds and Thoroughbreds.

Suspensory ligaments (SL) from 32 Thoroughbreds and 32 Standardbreds were collected to evaluate the variation in muscle content with respect to age, breed, sex, limb, and use. Six transverse sections, each 3 to 5 mm thick, were obtained from each SL. Four sections were taken from the body of the SL and 1 from the midportion of each branch. Sections were stained with van Gieson picric acid-fuchsin solution, then photographed, and black-and-white slides were made from the processed negatives. The transverse-sectional area of the SL and the contained muscle were determined by use of a computer with a color monitor and a digitizing device with its associated software. The percentage of muscle was then calculated for each section, for the entire ligament, and for each horse. Results were analyzed by multiple-regression analysis and Duncan multiple-range test, using the General Linear Model of SAS. Standardbreds had 40% more muscle in their SL than did Thoroughbreds. There was no significant difference in the percentage of SL muscle among sex, age, use, individual limb, or forelimb vs hind limb. For Standardbred horses, females had significantly greater muscle area content than intact males. Also, hind limb muscle area content was significantly greater than forelimb muscle content. Thoroughbred horses between 2 and 10 years of age not in training had significantly more muscle content than horses of the same age not in training. The reasons for these differences remain unclear.

Animals↗
PubMed1990

Modification of olfactory bulb synaptic inhibition by early unilateral olfactory deprivation.

Early unilateral olfactory deprivation produces large structural and neurochemical changes in the olfactory bulb, the first central relay for olfactory information. The functioning of deprived bulbs was examined in the present report by using paired-pulse stimulation of the lateral olfactory tract. Paired-pulse stimulation reflects interactions between mitral/tufted cells and granule cells, as well as the modulatory effects of centrifugal and intra-bulbar association fibers. Paired-pulse stimulation produced inhibition of mitral/tufted cells in control animals at PN20-PN22. This inhibition was significantly enhanced in littermates deprived of olfactory input from PN1 to PN20-PN22. Suppression of mitral/tufted cell single-unit spontaneous activity following single-pulse stimulation of the lateral olfactory tract (LOT) was similarly enhanced in deprived bulbs. These results suggest that early olfactory deprivation significantly modifies subsequent olfactory system function.

Animals↗
PubMed1990

Olfactory associative conditioning in infant rats with brain stimulation as reward. I. Neurobehavioral consequences.

In Experiment 1, infant rats were implanted with a stimulating electrode in the medial forebrain bundle/lateral hypothalamus (MFB/LH) on postnatal day 12 (PN12). Four to 6 hours later, the pups underwent associative olfactory conditioning, with half of the pups trained with 30 temporal pairings of odor (5 s) and MFB/LH stimulation (200 Hz, 300 ms), and the other half trained with random presentations of odor and MFB/LH stimulation. On PN13, pups were tested for: (1) behavioral preference for the conditioned odor; (2) focal glomerular layer 2-DG uptake to the odor; or (3) mitral/tufted cell single-unit response pattern to the odor. Odor-MFB/LH pairings produced a relative behavioral preference, enhanced focal 2-DG uptake and a modified mitral/tufted cell response pattern to the conditioned odor. Random training resulted in none of these changes. In Experiment 2, PN12 pups were anesthetized with urethane and single-unit responses of mitral/tufted cells to MFB/LH stimulation were examined. MFB/LH stimulation produced a brief suppression of mitral/tufted cell activity followed either by a prolonged excitation (18/30 cells; 8-10 s duration) or a prolonged suppression (12/30 cells; 10-30 s). These results suggest that pairing olfactory nerve input with MFB/LH stimulation modifies subsequent behavioral and physiological responses to olfactory nerve input alone. Furthermore, the prolonged olfactory bulb response to MFB/LH stimulation may be critical in this modification.

Animals↗
PubMed1990

Modified behavioral and olfactory bulb responses to maternal odors in preweanling rats.

Rat pups acquire an attraction for maternal odors, which can vary with maternal diet. In the two experiments reported here, maternal diet was modified and both pup behavioral responses and pup olfactory bulb neural responses [( 14C]2-DG uptake) to maternal odors were examined. In experiment 1, pups were reared from birth to postnatal day 19 with either a dam fed normal rat chow or a dam fed a sucrose-based diet which suppressed her normal maternal odor. In experiment 2, pups were raised from birth to postnatal day 19 with either a dam fed the sucrose-based diet adulterated with peppermint, or the non-scented sucrose-based diet. Pups selectively expressed both a behavioral attraction and an enhanced olfactory bulb neural response to odors that they experienced in the nest.

Action Potentials↗
PubMed1990

Cerebral cytochrome-C-oxidase copper band quantification in perfluorocarbon exchange transfused cats.

Rapid scanning near infrared spectroscopy (730-960 nm) was utilized to determine cat brain cytochrome-c-oxidase after blood-perfluorocarbon (FC-43) exchange. Spectra were carried out before, during, and after the exchange transfusion on cats with preserved somatosensory evoked potentials and microsphere determined cerebral blood flow (CBF). Carbon dioxide (8%) did not produce an increase in CBF. Difference spectra between the hypercapnic state (8% CO2-92% O2) and post mortem, demonstrated the presence of a broad absorption band centered around 820-845 nm which could be attributed to the oxidized low potential copper ion of cytochrome-c-oxidase. We were unable to further oxidize this band by adding carbon dioxide to the inspired gas mixture. This may be due to the near maximal CBF levels present in this preparation. The spectral data support the hypothesis that near infrared spectroscopy can quantify changes in the redox state of cytochrome-c-oxidase.

Animals↗
PubMed1990

Redox changes in cat brain cytochrome-c oxidase after blood-fluorocarbon exchange.

Rapid scanning near-infrared spectroscopy (730-960 nm) was utilized to determine cat brain cytochrome-c oxidase copper band by blood-perfluorochemical emulsion (Oxypherol) exchange. Spectra were carried out before, during, and after the exchange transfusion on animals with preserved somatosensory-evoked potentials and microsphere-determined cerebral blood flow. Remaining hemoglobin (less than 4% of control) was converted to carboxyhemoglobin that does not absorb in this spectral region. Difference spectra, between an hypercapnic status (8% CO2-92% O2) and postmortem, demonstrated the presence of a broad absorption band centered around 820-845 nm that could be attributed to the oxidized low potential copper ion (CuA) of cytochrome-c oxidase. However, we were unable to further oxidize this band by adding CO2 to the inspired gas mixture, but this inconsistency may be due to the near-maximal cerebral blood flow levels present in this preparation. Cytochrome oxidation by CO2 is normally attributed to increased O2 delivery to the tissue, secondary to an increased cerebral perfusion. We were unable to induce further increases in cerebral blood flow. In contrast, the cytochrome band could be reduced both by lowering fractional O2 concentration and by inducing circulatory arrest. The spectral data support the hypothesis that it is possible to quantify the cytochrome-c oxidase copper band in the near-infrared spectral region.

Animals↗
PubMed1990

Early unilateral deprivation modifies olfactory bulb function.

Unilateral olfactory deprivation during postnatal development produces significant structural and neurochemical modifications of the olfactory bulb. In the present report, we describe the functional consequences of such deprivation. Rat pups had a single naris occluded on postnatal day 2 (PN2) to deprive them of early olfactory stimulation. On PN20-22, the occluded naris was reopened, the previously open naris was sealed, and responses of the deprived olfactory bulb to odors were assessed using both single-unit recording from mitral/tufted cells and quantitative 14C-2-deoxyglucose (2-DG) autoradiography. While the response properties of individual odor-stimulated mitral/tufted cells were not altered by early deprivation, spontaneous activity was depressed, and there was a significantly higher incidence of odor-responsive mitral/tufted cells in deprived compared to nondeprived bulbs. In addition, odor-stimulated deprived bulbs demonstrated greater uptake of 2-DG than did non-deprived bulbs. Together, these data indicate that the olfactory system demonstrates an increased responsiveness to sensory cues following early deprivation.

Animals↗
PubMed1989

Small-colon rupture attributable to granulosa cell tumor in a mare.

A large granulosa cell tumor was believed to be responsible for causing obstruction and subsequent rupture of the small colon in a 10-year-old Quarter Horse mare. Two months earlier, a mass, tentatively diagnosed as granulosa cell tumor of the left ovary, had been identified by means of rectal palpation and ultrasonography. The mare was evaluated for clinical signs of acute, severe, abdominal pain, increased heart rate, cyanotic mucous membranes, clinical dehydration, with high PCV, leukopenia, and extreme abdominal distension. A large soft tissue mass and taut band that constricted the lumen of the small colon were palpable per rectum. Septic peritonitis was diagnosed on the basis of results of abdominocentesis. Exploratory surgery revealed extensive fecal contamination of the abdominal viscera, and the mare was euthanatized because of the resultant poor prognosis. At necropsy, the small colon was occluded by a taut, left broad ligament and the ovarian mass that was proved to be a granulosa cell tumor. The occlusion had caused impaction of the small colon, with subsequent perforation at the level of the broad ligament.

Animals↗
PubMed1989

Recurrence after strictureplasty or resection for Crohn's disease.

This study attempts to define whether there is an increased need for reoperation in patients with small bowel Crohn's disease treated by strictureplasty compared with those treated by small bowel resection. Previous studies of the rate of reoperation for small bowel Crohn's disease do not distinguish between reoperation performed because of a lesion at the original operation site and that undertaken because of a lesion at a distant site. This study analyses the need for reoperation only at the original site of operation and measures operation-free intervals. The site specific operation-free intervals in 41 patients with small bowel Crohn's disease treated by strictureplasty were not significantly different from the similar intervals in 41 patients treated by a small bowel resection.

Adult↗
PubMed1989

31P NMR spectroscopic and near infrared spectrophotometric studies of effects of anesthetics on in vivo RIF-1 tumors. Relationship to tumor radiosensitivity.

Mice with subcutaneous RIF-1 tumors were anesthetized with sodium pentobarbital (PB) or ketamine plus acepromazine (KA) before acquisition of in vivo 31P nuclear magnetic resonance (NMR) spectra from tumors. The area of the inorganic phosphate resonance was significantly greater (relative to phosphomonoesters or the alpha-phosphate resonance of nucleoside triphosphate) in spectra obtained under PB anesthesia, suggesting that the hypoxic fraction of the tumor increased following PB anesthesia. In vivo near-infrared laser spectroscopy directly demonstrated that tumor oxyhemoglobin was reduced by more than 20% following PB but was not significantly affected by KA. Total hemoglobin (tumor blood volume) was reduced by 11% following PB anesthesia, but was not significantly affected by KA. Tumor growth delay induced by gamma-irradiation was shorter when tumors were irradiated under PB anesthesia than when irradiated under KA, showing that PB anesthesia had a radioprotective effect. These studies demonstrate that both the 31P NMR and near infrared methods can detect metabolic or physiological changes associated with an increase in tumor radioresistance (i.e., an increase in the radiobiological hypoxic fraction).

Acepromazine↗
PubMed1989

Determination of cerebral venous hemoglobin saturation by derivative near infrared spectroscopy.

An "in vivo" method for non-invasive determination of cerebral venous hemoglobin O2 saturation (SvO2) was developed. A specially designed spectrophotometer recorded the Td near IR spectra of transilluminated brain tissue surrounding the SS. The accuracy of the method, based on the principle of DNIRS was tested on eight pentobarbital anesthetized dogs during hypoxic hypoxia (inspired O2 6-21%). Spectral data were transformed into first derivative for correlation with SvO2 data measured from the SS. Linear regression analyses were applied using data from 5 dogs, with SvO2 ranging from 1.5%-70%, to build a 3 wavelength algorithm for predicting brain SvO2. In three dogs, this regression equation was employed to predict SvO2 in 31 separate spectra of varying HH intensity. The standard deviation of differences between SvO2 and predicted values was 3.2%. The predicted values, when regressed against the sampled SvO2, yielded an r value of 0.97. The results demonstrate that it is possible to noninvasively quantify SvO2 utilizing IR spectroscopy.

Animals↗
PubMed1989

Near infrared determined cerebral transit time and oxy- and deoxyhemoglobin relationships during hemorrhagic hypotension in the dog.

The goal of the present study was to investigate the relationships among CBF, CMRO2, MTT and tissue/superior sagittal sinus hemoglobin saturations over a wide range of CPP using a canine model of hypotension. Microsphere-determined CBF was autoregulated in all tested cerebral regions over the 40-130 mmHg CPP range, but it decreased 50% around 30 mmHg. MTT, calculated by an indicator-dilution technique, progressively and proportionately increased over the 40-130 mmHg CPP range. The HbO2 content, measured in the same area by an optical method, parallely decreased. Around 30 mmHg CPP, MTT disproportionately lengthened (700% of control). CMRO2 maintenance was accompanied by a progressive decrease of tissue HbO2 and sagittal sinus hemoglobin saturation. In this framework, MTT measurement and tissue HbO2 monitoring by NIRS might give a sensitive evaluation of the hemodynamic reserve than CBF measurement in anesthesia and intensive care.

Animals↗
PubMed1989

Ultrasonographic evaluation of the healing of ventral midline abdominal incisions in the horse.

Ultrasonography was used to evaluate the ventral midline incisions of 21 ponies following exploratory laparotomy. The incisions were evaluated before surgery and at weekly intervals from one to seven weeks after surgery. Both 5.0 and 7.5 MHz linear array and 7.5 MHz sector transducers were used for the evaluations. The incisional complications observed were drainage, oedema, suture sinus formation, suture abscess, superficial dehiscence and incisional hernia. Ultrasonographic imaging of the ventral midline incision was an easy, reliable and objective method for detecting and monitoring the progression of incisional complications in a non-invasive manner.

Abdominal Muscles↗
PubMed1989

Noninvasive determination of hemoglobin saturation in dogs by derivative near-infrared spectroscopy.

An in vivo method utilizing derivative near-infrared spectroscopy was developed to noninvasively determine cerebral venous hemoglobin O2 saturation (SVO2). The method was tested on eight pentobarbital-anesthetized dogs ventilated with differing inspired O2 mixtures to force changes in SVO2 over a wide range. Spectral data obtained by transilluminating the tissues surrounding the superior sagittal sinus (SS) were transformed into first derivative units for correlation with SVO2 data measured from the SS. Linear regression analysis was applied to data obtained from five dogs and used to build a three-wavelength algorithm for predicting brain SVO2. In three dogs, SVO2 was varied to test this equation ability to predict SVO2. The standard deviation of differences between measured SVO2 and SVO2 predicted from 31 separate spectra was 3.2%. These predicted values, when regressed against the sampled SVO2, yielded an r value of 0.97. The results demonstrate that during hypoxic hypoxia (HH) it is possible to noninvasively quantify SVO2 with the use of infrared spectroscopy.

Animals↗
PubMed1989

Peripheral baroreceptor control of neurohypophysial blood flow during hemorrhage.

We measured neurohypophysial blood flow (NHBF) in dogs made hypotensive to study the time course of neurohypophysial autoregulation. We found that the neurohypophysis has a unique autoregulatory response in which blood flow increases transiently before establishing a stable perfusion level. During the "hyperemic" phase, the time course of the flow transient correlates with an increased plasma arginine vasopressin (pAVP) neurosecretory transient. However, unlike pAVP, blood flow does not remain elevated. The transitory nature of the flow response led us to evaluate the hypothesis that peripheral baroreceptor activity may be responsible for the hyperemic phase. Bilateral vagotomy and carotid sinus nerve denervation attenuated the increase in neural lobe blood flow (NLBF) to a standardized step to 80 mmHg mean arterial pressure. The pAVP response was enhanced both by vagotomy and carotid sinus denervation. Combined denervation abolished both the pAVP and the NLBF responses. We conclude that NHBF is autoregulated; however, control may be exerted at multiple levels, i.e., via nerves as well as local metabolic mechanisms. The peripheral baroreceptors influence NHBF primarily during periods of changing blood pressure. When blood pressure is stable, local mechanisms appear to be dominant.

Animals↗