A series of coupled differential equations was used to model the temporal dynamics of rabies in raccoons in the mid-Atlantic region of the United States. The model takes explicit account of the development of natural immunity to rabies and was used to evaluate culling and vaccination elimination strategies. For habitats typical of the mid-Atlantic states, and given the assumptions of the model, it was estimated that elimination of rabies in raccoons by culling may involve the annual removal of over 32% of the raccoon population or the yearly vaccination of up to 99% of the susceptible fraction. Assuming a constant marginal cost for both culling and vaccination, the model suggests that, whatever the actual cost of each method, the cheapest strategy will always involve either culling or vaccination alone. A combined strategy of culling and vaccination will be cheaper than culling alone only when the per capita cost of vaccination is around one-fifth or less the per capita cost of culling.

Neoplastic cells were isolated from 2 sibling Great Dane/Labrador Retriever mixed-breed dogs in which telangiectatic type osteosarcomas arose concurrently. Cells from various sites in the same osteosarcoma appeared similar in culture, but there were differences between the 2 osteosarcomas in growth characteristics and appearance of cells. Cells from 1 osteosarcoma had a small, but significant (P less than 0.05), cyclic adenosine monophosphate response to parathyroid hormone stimulation, indicating a low order of osteoblastic differentiation. Cells from the other osteosarcoma had no response to parathyroid hormone stimulation. Cells from both osteosarcomas and a concentrated cell-free filtrate from the osteosarcoma with osteoblastic differentiation were injected into nude mice, but osteosarcomas were not induced. Results of ultrastructural examination of osteosarcoma samples for viral particles were negative and supernatant fluids from cultured cells were considered negative for viral reverse transcriptase activity.

Custom-designed Hall-effect strain sensors (HES) were implanted surgically onto the superficial digital flexor tendons of the forelimbs of 4 adult Thoroughbreds. Strains were recorded at various gaits, using a portable amplifer and FM cassette recorder. Strain calculations used the original length (L) as the HES position with the forelimb in the relaxed neutral position during anesthesia. A characteristic deflection in the strain cycle recording was confirmed to correspond to initial hoof contact with the ground (heel strike) by simultaneous recording of weight bearing via a footswitch. Heel strike was used as the reference point to determine the magnitude of strain change during weight bearing and nonweight bearing under various conditions. The weight-bearing strains (heel strike to maximal strain) recorded in 2 horses (with a rider) were 3.1% and 7.6% at the walk, 6.5% and 10.1% at the trot, and 11.5% and 16.6% at the gallop. Strain rate during tendon loading at the gallop was approximately 200%/s. The magnitude of strain change during nonweight bearing (minimal strain to heel strike) was smaller than during weight bearing, but also increased with faster gaits. In 3 horses led at the walk and trot, modest increases in hoof angle (baseline, 52%) resulted in small increases in the magnitude of strain change during weight bearing at the trot, but the magnitude of strain change at the walk was not affected. Results of the study indicated that the HES can be successfully adapted to provide continuous strain measurement without subjective signs of discomfort or lameness in horses during or after instrumentation.

Eighteen strains of Escherichia coli serogroup O115:K"V165" isolated from 1- to 8-week-old pigs with diarrhea were tested for toxigenicity, pathogenicity in pigs and mice, serum resistance, mannose-resistant hemagglutination (MRHA), F165 and other surface antigens, colicin V (Col V), aerobactin, and biotype. Twelve strains were positive for heat-stable enterotoxin (STb), MRHA-negative, and F165-negative; 5 strains were enterotoxin-negative, MRHA-positive, and F165-positive; and 1 strain was MRHA-positive, but F165- and enterotoxin-negative. Six of the 12 STb-positive strains moderately colonized the ileum of newborn colostrum-deprived pigs within 24 hours after inoculation. Two of the colonizing strains were able to induce watery diarrhea. All 12 STb-positive strains were nonpathogenic for adult mice and were serum-sensitive; 11 of 12 were Col V-negative, 9 of 12 did not produce aerobactin, and 10 of 12 belonged to biotypes other than 1 or 2. All 6 enterotoxin-negative strains colonized the small and large intestines, associated with peritoneal serosal surfaces, and induced septicemia and polyserositis in newborn colostrum-deprived pigs 1 to 2 days after inoculation. In contrast, 3 STb-positive strains poorly colonized the intestines and did not induce septicemia in pigs at 3 days after inoculation. All 6 enterotoxin-negative strains were Col V-positive, produced aerobactin, and belonged to biotype 1 or 2. Of the 5 enterotoxin-negative, F165-positive strains, only 4 were pathogenic for intraperitoneally inoculated adult mice and were serum-resistant. The enterotoxin-negative, F165-negative strain was neither serum-resistant nor mouse-pathogenic. O-agglutinable mutants of the mouse-pathogenic strains were, for the most part, no longer pathogenic for adult mice, although these strains remained unchanged for biotype and production of MRHA, F165, and Col V, and 3 of 4 mutant strains were serum-resistant. Thus, E coli strains of the same serogroup isolated from diarrheic pigs may cause either intestinal or extraintestinal disease upon reinoculation of pigs, depending on the virulence attributes produced by the strains.

Strain gauge rosettes were bonded to the dorsal, lateral, medial, and plantar aspects of the third metatarsal bone in the hind limbs of 6 ponies. The maximal compressive principal strain was approximately -600 X 10(-6) m/m, and exceeded the amplitudes of the tensile strains at all aspects of the bone. After transformation, the shear strain and the principal strains parallel and perpendicular to the bone were obtained. The first peak in the bending strain was higher in the dorsal and lateral aspects, and the second peak was higher in the medial and plantar aspects. Young modulus of elasticity was determined in a 4-point bending test at the dorsal and plantar sides; it averaged 19.5 GPa in tension and compression. Applying linear bending theory, the eccentricity of an axial force parallel or a bending force perpendicular to the bone were calculated. The position where the total force penetrated the tarsometatarsal joint surface was largely within the joint surface, indicating that the joint is merely loaded in (eccentric) compression.

Functional capabilities of morphologically mature (segmented) and immature granulocytes (neutrophils and eosinophils) from bone marrow from cows were studied and compared with similar activities of segmented granulocytes from blood. Phagocytosis of Escherichia coli and postphagocytic oxidative metabolic stimulation, measured by nitroblue tetrazolium (NBT) reduction, were evaluated simultaneously. Phagocytosis was observed readily in segmented neutrophils, neutrophilic bands, and metamyelocytes and rarely in myelocytes. Phagocytosis was not seen in promyelocytes and myeloblasts. Neutrophilic bands and metamyelocytes were phagocytically less active than were segmented neutrophils. Washed segmented bone marrow neutrophils possessed phagocytic activity similar to that of blood neutrophils, whereas the activity of unwashed segmented bone marrow neutrophils was markedly less than that of blood neutrophils. Reduction of NBT was observed only in blood segmented neutrophils and bone marrow segmented neutrophils; the magnitude of NBT reduction was significantly (P = less than 0.005) less in bone marrow neutrophils than in blood neutrophils. Eosinophils were phagocytically less competent than were neutrophils. The NBT reduction was observed only in eosinophils from blood, but not in eosinophils from bone marrow.

Periosteal autografts were obtained from the medial aspect of the proximal portion of the tibia, and perichondrial autografts were obtained from the sternum. Using arthroscopic visualization, each autograft was placed as a loose body into 1 tarsocrural joint in 6 young horses (2 to 4 years old). Horses were hand-walked daily, starting the day after surgery, for a total of 6 h/wk for 8 weeks. Eight weeks after autograft implantation, radiographs were taken of each tarsocrural joint and were interpreted with regard to mineralization in the transplanted autografts. Autografts were then surgically removed, and examined macroscopically and microscopically for viability, size, and production of chondroid tissue. All autografts appeared viable and most had evidence of growth. Longest-by-shortest axis value, cross-sectional area, and perimeter were greater in perichondrial autografts than in their periosteal counterparts in 3 horses, but the difference was not significant. Neochondrogenesis was observed in 5 of 6 periosteal grafts and in 1 of 6 perichondrial grafts. Futhermore, the amount of chondroid tissue produced in periosteal autografts was significantly (P less than 0.05) greater than that produced in the 1 perichondrial graft. The chondroid tissue produced by periosteal autografts had morphologic and matrical staining properties similar to those of hyaline cartilage.

Keratinocytes from explants of the oral mucosa of dogs were grown in culture for five passages. The ultrastructure of primary cultures and fully developed subcultures passaged 1, 3, and 5 times was examined. At every stage, the cells had the morphologic characteristics of epithelial cells and formed a multilayered squamous epithelium. The basal cells had the characteristics of metabolically active cells, whereas the suprabasal cells and the cells at the media interface expressed many, but not all, of the organelles and cell surface characteristics associated with keratinocyte differentiation. Keratohyalin granules were located in the suprabasal and superficial cells. Cell size and shape and the relationship between cells in the layers also reflected the morphologic characteristics of the parent tissue. Cells maintained this typical structure through all passages and the cultures changed minimally for up to a week after development.

Eight adult Holstein cows were used to compare the effects of lumbar segmental epidural analgesia (SEA) and lumbar segmental subarachnoid analgesia (SSA). A modified 17-gauge Huber point (Tuohy) needle was used to place a catheter with stylet into either the epidural space at the thoracolumbar (T13-L1) intervertebral space or the tubarachnoid space at the lumbosacral intervertebral junction. The catheters were advanced so that their tips lay at the anterior lumbar (L1-L2) epidural space or at the thoracolumbar (T-13-L1) subarachnoid space. The position of the catheter was confirmed radiographically. A 5% solution of procaine HCl was used at mean doses of 300 mg (6 ml) to induce SEA and 84.4 +/- 12.9 mg (1.7 +/-0.3 ml) to induce SSA. Onset of analgesia to superficial and deep muscular pinprick stimulation was significantly (P less than 0.05) faster in cows with SSA than in those with SEA (10.4 +/- 2.3 minutes vs 15.9 +/- 3.8 minutes). Maximal thoracolumbar analgesia extended from spinal cord segments T12 to L4 on one or both sides of the vertebral column during SEA and from T10 to L3 on one or both sides during SSA. Duration of analgesia lasted significantly (P less than 0.05) longer in cows with SEA than in those with SSA (76.2 +/- 16.2 minutes vs 53.7 +/- 14.3 minutes). The advantages and disadvantages of the SEA catheter technique are discussed.

Five 5 to 6 month old horses were surgically prepared with silver electrodes sutured to the serosa of gastric antrum, duodenum and proximal portions of the jejunum. Normal migrating motility complex (MMC) periodicity was determined during daytime hours in horses that were fed and horses from which food was withheld for 24 hours. Periodicity was defined as time span from the end of one period of regular spike activity (RSA) to the end of the next RSA in the MMC. The periodicity was 120.5 +/- 9.5 (SEM) minutes in horses from which food was withheld, and was 125.7 +/- 20.3 minutes in horses fed hay free choice. Coincident with each duodenal RSA, antral spike activity ceased. Xylazine (0.25 and 0.5 mg/kg), given IV during the period of intermittent spike activity of the MMC to either fed or unfed horses induced, within 2 minutes, a RSA complex in the duodenum that migrated to the proximal portion of the jejunum. This was followed by a period of no spike activity of normal duration, which proceeded on to a period of intermittent spike activity of varying duration to complete the MMC cycle. Pretreatment IV administration of an alpha 2-adrenergic antagonist, tolazoline (1 mg/kg) also provoked a RSA complex, but blocked the xylazine effect. The results indicated that xylazine resets the duodenal MMC in the horse, but does not seriously disrupt proximal gastrointestinal tract motility, and that control of MMC periodicity in this region probably involves more than alpha 2-adrenergic receptors.