Hyperadrenocorticism and hyperprogesteronemia in a cat with an adrenocortical adenocarcinoma.

A seven-year-old, neutered male domestic shorthair cat was evaluated for poorly regulated diabetes mellitus and increased skin fragility. Imaging studies revealed a right adrenal gland tumor, but cortisol testing did not support a diagnosis of hyperadrenocorticism. Serum concentrations of progesterone and testosterone were increased compared with a group of normal cats, and the clinical signs were attributed to hyperprogesteronemia. At necropsy, a diagnosis of adrenocortical adenocarcinoma was confirmed, and immunohistochemical staining confirmed the presence of progesterone within the tumor. Clinical signs of hyperadrenocorticism in cats may occur due to increased serum concentrations of hormones other than cortisol.

Surgical correction of polydactyly in a camel (Camelus dromedarius).

A 2-mo-old, 90-kg, intact male camel (Camelus dromedarius) was admitted for surgical removal of a supernumerary digit associated with the medial aspect of the right carpus and metacarpus. Radiographic views of the carpus and metacarpus revealed the supernumerary digit articulating with the middle carpal joint via an extra carpal bone. The supernumerary digit consisted of three bones. Surgical removal of the supernumerary digit was recommended to restore normal limb conformation, limit the possibility of future lameness, and improve the cosmetic appearance of the limb. Complete surgical removal of the digit was performed by disarticulating the extra carpal bone from its attachments to the second and radial carpal bones. One year after surgery, the leg appeared grossly normal and the camel showed no sign of lameness.

Discospondylitis in association with an intra-abdominal abscess in a dog.

An 11-year-old German shepherd dog cross was presented with a six-week history of weight loss and abdominal distension. A diagnosis of abdominal abscess and discospondylitis was made. The dog responded to surgical excision of the abscess and conservative medical treatment for discospondylitis.

Management of rupture of the gastrocnemius and superficial digital flexor muscles with a modified Thomas splint-cast combination in a horse.

A 6-month-old warmblood filly had traumatic rupture in the gastrocnemius and superficial digital flexor muscles of the left hind limb. A modified Thomas splint-cast combination, which was custom fitted to the limb, was placed to prevent further disruption of the caudal reciprocal apparatus. The external coaptation device was removed after 21 days. The horse developed lesions consistent with osteochondrosis of the femoropatellar articulation within 8 weeks of the initial injury. Examination of the horse 6 months after injury revealed fibrous healing of the muscles and restoration of caudal reciprocal apparatus function. There was no obvious difference in the external appearance of the hind limbs.

Use of two-dimensional real-time ultrasonography for diagnosing contracture and strain of the infraspinatus muscle in a dog.

A strain injury to the infraspinatus muscle was a potential cause of forelimb lameness in a dog. Ultrasonography was used for evaluation of infraspinatus muscle injury. The ultrasonographic appearance of a typical infraspinatus muscle, contracture of an infraspinatus muscle, acute strain of an infraspinatus muscle, and progression of healing of the infraspinatus muscle are described.

Effects of local reduction in pressure on distensibility and composition of cerebral arterioles.

This study examined effects of local reductions in mean and pulse pressures on cerebral arterioles in normotensive Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). WKY and SHRSP underwent clipping of one carotid artery at 1 month of age. At 10-12 months of age, mechanics of pial arterioles were examined in vivo in anesthetized rats. Bilateral craniotomies were performed to expose pial arterioles in the sham and clipped cerebral hemispheres. Stress-strain relations were calculated from measurements of pial arteriolar pressure (servo null), diameter, and cross-sectional area of the arteriolar wall. Point counting stereology was used to quantitate individual components in the arteriolar wall. Before deactivation of smooth muscle with EDTA, mean (Pm) and pulse (Pp) pressures were significantly less (p less than 0.05) in clipped than in sham arterioles in WKY (Pm, 63 +/- 2 versus 73 +/- 2 mm Hg; Pp, 23 +/- 3 versus 30 +/- 3 mm Hg) and SHRSP (Pm, 94 +/- 4 versus 110 +/- 4 mm Hg; Pp, 27 +/- 2 versus 38 +/- 3 mm Hg). Cross-sectional area of the arteriolar wall was less (p less than 0.05) in clipped than in sham arterioles in both groups of rats (1,403 +/- 125 versus 1,683 +/- 125 microns2 in WKY; 1,436 +/- 72 versus 1,926 +/- 134 microns2 in SHRSP). There was a correlation between cross-sectional area of the vessel wall and pulse pressure (r2 = 0.66), but not mean pressure (r2 = 0.09). During maximal dilatation with EDTA, the stress-strain curve was shifted to the left in clipped arterioles of SHRSP, but not of WKY, which indicates that carotid clipping in SHRSP reduces passive distensibility of cerebral arterioles. The proportion of distensible components in the vessel wall (smooth muscle, elastin, and endothelium) was reduced in clipped arterioles in SHRSP, but not in WKY. These findings suggest that 1) vascular hypertrophy of cerebral arterioles is related more closely to pulse pressure than to mean pressure, and 2) reduction of pial arteriolar pressure completely prevents cerebral vascular hypertrophy and attenuates increases in passive distensibility of cerebral arterioles in SHRSP.

Effects of aging on mechanics and composition of cerebral arterioles in rats.

The purpose of this study was to examine effects of aging on the mechanics and composition of cerebral arterioles. We measured pressure (servo-null) and diameter in pial arterioles in anesthetized adult (9-12 months old) and aged (24-27 months old) Fischer 344 rats. After deactivation of smooth muscle with EDTA, diameter of pial arterioles at 70 mm Hg pial arteriolar pressure was less in aged than in adult rats (67 +/- 4 vs. 81 +/- 4 microns [mean +/- SEM], p less than 0.05). The stress-strain relation and the slope of tangential elastic modulus versus stress (6.8 +/- 0.6 vs. 5.3 +/- 0.3, p less than 0.05) indicated that distensibility of pial arterioles was reduced in aged rats. Cross-sectional area of the vessel wall, measured histologically, was less in aged than adult rats (1,239 +/- 91 vs. 1,832 +/- 180 microns2, p less than 0.05). Point counting stereology was used to quantitate smooth muscle, elastin, collagen, and basement membrane in the arteriolar wall. Cross-sectional areas of smooth muscle and elastin were significantly less in aged than adult rats (744 +/- 57 vs. 1,291 +/- 119 microns2 for smooth muscle, 52 +/- 6 vs. 113 +/- 15 microns2 for elastin; p less than 0.05), whereas cross-sectional areas of collagen and basement membrane were not significantly different in aged and adult rats (4 +/- 1 vs. 3 +/- 1 microns2 for collagen, 236 +/- 17 vs. 258 +/- 31 microns2 for basement membrane). The ratio of nondistensible (collagen and basement membrane) to distensible (smooth muscle and elastin) components was greater in aged than adult rats (0.30 +/- 0.01 vs. 0.18 +/- 0.01, p less than 0.05). Thus, we conclude that, during aging, cerebral arterioles undergo atrophy, distensibility of cerebral arterioles is reduced, and the relative proportion of distensible elements, elastin and smooth muscle, is reduced in the arteriolar wall.

Effect of sympathetic nerves on composition and distensibility of cerebral arterioles in rats.

1. The goals of this study were to examine the effects of chronic sympathetic denervation on the mechanics and composition of cerebral arterioles in normotensive Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). 2. We used an in vivo method to examine the mechanics of pial arterioles in 10- to 12-month-old, anaesthetized WKY and SHRSP that had undergone unilateral removal of the superior cervical ganglion at 1 month of age. Bilateral craniotomies were performed in each rat to expose pial arterioles in the innervated and denervated cerebral hemispheres. Arterioles were deactivated with EDTA. Incremental distensibility and stress-strain relationships were calculated from measurements of pial arteriolar pressure (servo null), diameter and cross-sectional area of the arteriolar wall. Point counting stereology was used to quantify volume density and cross-sectional area of individual components in the arteriolar wall. 3. Chronic sympathetic denervation reduced cross-sectional area of the arteriolar wall by 16 +/- 2% (mean +/- S.E. of mean; P less than 0.05) in WKY and 44 +/- 3% in SHRSP. During maximal dilatation with EDTA, incremental distensibility was reduced and the stress-strain curve was shifted to the left in denervated arterioles of SHRSP, but not WKY. These findings indicate that sympathetic denervation in SHRSP attenuates the development of hypertrophy in pial arterioles and reduces arteriolar distensibility. The ratio of non-distensible (collagen and basement membrane) to distensible (smooth muscle, elastin and endothelium) components was reduced in denervated arterioles in SHRSP, but not WKY. 4. Thus, sympathetic nerves have trophic effects on cerebral arterioles in WKY and, to a greater degree, in SHRSP. Sympathetic nerves also contribute to increases in distensibility of cerebral arterioles in SHRSP, but not WKY. The increase in arteriolar distensibility is accompanied by a disproportionate increase in the more compliant elements of cerebral arterioles.

Effects of stimulation of fastigial nucleus on cerebral blood flow in cats.

The goal of this study was to examine effects of electrical stimulation of the rostral fastigial nucleus on cerebral blood flow. Anesthetized cats were studied, and arterial pressure and blood gases were maintained at control levels during fastigial stimulation. In one group, we measured vessel diameter and velocity of blood flow through a pial artery with a Doppler probe and calculated blood flow as the product of cross-sectional area and velocity. Electrical stimulation of the fastigial nucleus produced a small increase in pial arterial flow of 16 +/- 6% (means +/- SE, P less than 0.05). Pial vascular resistance increased during moderate hypertension and decreased during decreases in arterial pressure, which indicates that cerebral vascular responses were not impaired. In a second group, cerebral blood flow was measured with microspheres. Blood flow to the pons and medulla increased 25 +/- 11 and 21 +/- 11%, respectively, during stimulation of the fastigial nucleus, but blood flow to the cerebral cortex did not increase significantly. Stimulation produced decreases in flow to the renal cortex and duodenum of 39 +/- 10 and 39 +/- 15%, respectively, and flow to the heart increased 48 +/- 22%, which indicates that the stimulus was efficacious. Thus electrical stimulation of the rostral fastigial nucleus in cats elicits only a small increase in cerebral blood flow.

Role of molecular charge in disruption of the blood-brain barrier during acute hypertension.

Acute hypertension disrupts the blood-brain barrier and may neutralize the negative charge on cerebral endothelium. The goal of this study was to determine the effects of molecular charge on permeability of the blood-brain barrier during acute hypertension. Intravital fluorescent microscopy and fluorescein-labeled dextrans were used to evaluate disruption of the blood-brain barrier during acute hypertension in rats. Disruption of the blood-brain barrier was quantitated by calculating clearance of neutral dextran and of anionic dextran sulfate in two groups of rats. Pressure in pial venules, which are the primary site of disruption of the blood-brain barrier during acute hypertension, was measured using a servo-null device. When systemic arterial pressure was increased from 87 +/- 5 (mean +/- SEM) to 188 +/- 5 mm Hg, clearance of neutral dextran increased from 0.04 +/- 0.01 to 4.38 +/- 0.72 ml/sec x 10(-6). When systemic arterial pressure was increased from 91 +/- 4 to 181 +/- 3 mm Hg, clearance of anionic dextran sulfate increased from 0.02 +/- 0.01 to only 0.70 +/- 0.23 ml/sec x 10(-6). Increases in pial venular pressure were similar in the two groups. Thus, similar increases in systemic arterial pressure and pial venular pressure during acute hypertension produce less disruption of the blood-brain barrier to anionic dextran sulfate than neutral dextran. The findings suggest that 1) the net negative charge of cerebral vessels may be preserved during acute hypertension, and 2) molecular charge is an important determinant of the severity of disruption of the blood-brain barrier during acute hypertension.

Mechanics and composition of arterioles in brain stem and cerebrum.

The goal of this study was to compare mechanics and composition of arterioles in brain stem and cerebrum. We calculated stress and strain of pial arterioles in anesthetized rats from measurements of pial arteriolar pressure (servo-null), diameter, and cross-sectional area of the vessel wall. Composition of pial arterioles was quantitated using point-counting stereology. Before deactivation of smooth muscle with ethylenediaminetetraacetic acid (EDTA), pial arteriolar pressure and diameter were 28 and 30% greater (P less than 0.05) in brain stem than cerebrum. After EDTA, diameter of arterioles was similar in brain stem and cerebrum. Cross-sectional area of the arteriolar wall was 32% greater (P less than 0.05) in brain stem than cerebrum. Stress-strain curves indicated that distensibility of pial arterioles is greater in brain stem than cerebrum. The proportion of nondistensible (collagen and basement membrane) to distensible (elastin, smooth muscle, and endothelium) components was 20% less (P less than 0.05) in brain stem than cerebral arterioles. We conclude that 1) cross-sectional area of the vessel wall in arterioles of comparable size is greater in brain stem than cerebrum, 2) distensibility of arterioles is greater in brain stem than cerebrum, despite greater cross-sectional area of the arteriolar wall in brain stem, and 3) the proportion of elastic components is greater in brain stem than cerebral arterioles, which may contribute to greater arteriolar distensibility in brain stem.