bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro efficacy of chemotherapeutics as determined by 50% inhibitory concentrations in cell cultures of mammary gland tumors obtained from dogs
Authors: Simon Daniella , Knebel Jan W. , Baumgärtner Wolfgang , Aufderheide Michaela , Meyer-Lindenberg Andrea , Nolte Ingo
Published: December 2005

Objective—To determine the 50% inhibitory concentration (IC-50) of carboplatin, cisplatin, and doxorubicin in cell cultures of mammary gland tumors obtained from dogs and to assess whether in vitro efficacy was within the range of clinically relevant concentrations.

Sample Population—30 mammary gland tumors excised from dogs.

Procedure—Cell cultures were established from the 30 tumors. Cultures then were treated with carboplatin, cisplatin, or doxorubicin. Growth inhibition of cultures was assessed via DNA measurement 24, 48, and 72 hours after treatment. The IC-50 values were calculated by use of linear interpolation.

Results—Cultures varied in their pattern of susceptibility. Doxorubicin induced significantly lower IC-50 values than the platinum derivatives. Cisplatin and carboplatin had comparable effects. The IC-50 values for carboplatin and doxorubicin were in the range of clinically relevant concentrations, but only part of the cisplatin cultures had IC-50 values within clinically relevant concentrations. We did not detect differences in the in vitro susceptibility among subtypes of tumors (ie, adenocarcinoma, solid carcinoma, malignant mixed tumor).

Conclusion and Clinical Relevance—The IC-50 values determined in this study allowed assessment of in vitro drug efficacy of chemotherapeutics in cultures of mammary gland tumors obtained from dogs. Variations in susceptibility were evident and emphasize the importance of assessing susceptibility and resistance patterns for each tumor. Prospective studies to assess direct correlations between in vitro and in vivo efficacy must be performed to determine the clinical predictive value of this in vitro chemosensitivity assay for treatment of dogs with mammary gland tumors. (Am J Vet Res2001;62:1825–1830)
Metabolism of amino acids in cats with severe cobalamin deficiency
Authors: Ruaux Craig G. , Steiner Jörg M. , Williams David A.
Published: December 2005

Objective—To validate an automated chemiluminescent immunoassay for measuring serum cobalamin concentration in cats, to establish and validate gas chromatography-mass spectrometry techniques for use in quantification of methylmalonic acid, homocysteine, cysteine, cystathionine, and methionine in sera from cats, and to investigate serum concentrations of methylmalonic acid, methionine, homocysteine, cystathionine, and cysteine as indicators of biochemical abnormalities accompanying severe cobalamin (vitamin B12) deficiency in cats.

Sample Population—Serum samples of 40 cats with severe cobalamin deficiency (serum cobalamin concentration < 100 ng/L) and 24 control cats with serum cobalamin concentration within the reference range.

Procedure—Serum concentrations of cobalamin were measured, using a commercial automated chemiluminescent immunoassay. Serum concentrations of methylmalonic acid, methionine, homocysteine, cystathionine, and cysteine were measured, using gas chromatography-mass spectrometry, selected ion monitoring, stable-isotope dilution assays.

Results—Cats with cobalamin deficiency had significant increases in mean serum concentrations of methylmalonic acid (9,607 nmol/L), compared with healthy cats (448 nmol/L). Affected cats also had substantial disturbances in amino acid metabolism, compared with healthy cats, with significantly increased serum concentrations of methionine (133.8 vs 101.1 µmol/L) and significantly decreased serum concentrations of cystathionine (449.6 vs 573.2 nmol/L) and cysteine (142.3 vs 163.9 µmol/L). There was not a significant difference in serum concentrations of homocysteine between the 2 groups.

Conclusions and Clinical Relevance—Cats with gastrointestinal tract disease may have abnormalities in amino acid metabolism consistent with cobalamin deficiency. Parenteral administration of cobalamin may be necessary to correct these biochemical abnormalities. (Am J Vet Res2001;62:1852–1858)
Effects of exercise on biomechanical properties of the superficial digital flexor tendon in foals
Authors: Cherdchutham Worakij , Meershoek Liduin S. , van Weeren Paul R. , Barneveld Albert
Published: December 2005

Objective—To determine the effects of exercise on biomechanical properties of the superficial digital flexor tendon (SDFT) in foals.

Animals—43 Dutch Warmblood foals.

Procedure—From 1 week until 5 months of age, 14 foals were housed in stalls and not exercised, 14 foals were housed in stalls and exercised daily, and 15 foals were maintained at pasture. Eight foals in each group were euthanatized at 5 months, and remaining foals were housed together in a stall and paddock until euthanatized at 11 months. After euthanasia, SDFT were isolated and fit in a material testing system. Mean cross-sectional area (CSA) was measured and traction forces recorded. Normalized force at rupture (forcerup), normalized force at 4% strain, strain at rupture, stress at 4% strain (stress4%strain), and stress at rupture were compared among and within groups.

Results—At 5 months, mean CSA and normalized forcerup were significantly greater and stress4%strainsignificantly less in the pastured group, compared with the other groups. At 11 months, CSA and normalized forcerupwere not significantly different among groups, because forcerupincreased significantly from 5 to 11 months in the nonexercised group and decreased significantly in the pastured group.

Conclusions and Clinical Relevance—Exercise significantly affected the biomechanical properties of the SDFT in foals. Evenly distributed moderate- and low-intensity exercise at a young age may be more effective for development of strong, flexible tendons in horses than single episodes of high-intensity exercise superimposed on stall rest. This effect may impact later susceptibility to SDFT injury. (Am J Vet Res2001;62:1859–1864)
Anticoagulant effects of repeated subcutaneous injections of high doses of unfractionated heparin in healthy dogs
Authors: Mischke Reinhard H. , Schüttert Christina , Grebe Susanne I.
Published: December 2005

Objective—To evaluate SC administration of unfractionated heparin (UFH) in accordance with a dosing regimen for high-dose treatment in dogs.

Animals—10 healthy adult Beagles.

Procedures—Two groups of dogs (5 dogs/group) were given 6 injections of heparin (500 units of UFH/kg of body weight, SC) at intervals of 8 (experiment 1) and 12 (experiment 2) hours. Blood samples were collected before and 4 hours after heparin injections to determine amidolytic heparin activity, activated partial thromboplastin time (APTT), thrombin time, antithrombin activity, platelet count, and Hct.

Results—For experiments 1 and 2, mean ± SD heparin activities before (experiment 1, 1.32 ± 0.20 U/ml; experiment 2, 0.69 ± 0.174 U/ml) and 4 hours after the last heparin injection (experiment 1, 1.71 ± 0.30 U/ml; experiment 2, 1.10 ± 0.30 U/ml) were higher than values calculated for the regimen used in experiment 1. Results of the investigated thrombin time test system with low thrombin activity were frequently beyond the measurement range, even with UFH activities ≥ 0.6 U/ml. Moreover, a severe decrease of antithrombin activity became evident during both experiments (eg, in experiment 2 from 95.6 ± 4.8 to 59.2 ± 6.6%). In each treatment group, 2 dogs developed hematomas.

Conclusions and Clinical Relevance—Calculations of the course of heparin activity after a single injection do not result in a reliable dosing regimen for highdose heparin treatment in dogs. High-dose treatment must be monitored for each dog. Thrombin time measured with low thrombin activity is unsuitable for this purpose. (Am J Vet Res2001;62:1887–1891)
Effects of oral administration of phenylbutazone to horses on in vitro articular cartilage metabolism
Authors: Beluche Lisa A. , Bertone Alicia L. , Anderson David E. , Rohde Carsten
Published: December 2005

Objective—To evaluate the effects of orally administered phenylbutazone on proteoglycan synthesis and chondrocyte inhibition by IL-1β in articular cartilage explants of horses.

Animals—11 healthy 1- to 2-year-old horses.

Procedure—Horses were randomly assigned to the control (n = 5) or treated group (4.4 mg of phenylbutazone/ kg of body weight, PO, q 12 h; n = 6). Articular cartilage specimens were collected before treatment was initiated (day 0), after 14 days of treatment, and 2 weeks after cessation of treatment (day 30). Proteoglycan synthesis and stromelysin concentration in cartilage extracts were assessed after 72 hours of culture in medium alone or with recombinant human interleukin-1β (IL-1β; 0.1 ng/ml).

Results—On day 0, proteoglycan synthesis was significantly less in cartilage explants cultured in IL-1β, compared with medium alone. Mean proteoglycan synthesis in explants collected on days 14 and 30 was significantly less in treated horses, compared with controls. However, incubation of explants from treated horses with IL-1β did not result in a further decrease in proteoglycan synthesis. Significant differences in stromelysin concentration were not detected between or within groups.

Conclusions and Clinical Relevance—Oral administration of phenylbutazone for 14 days significantly decreased proteoglycan synthesis in articular culture explants from healthy horses to a degree similar to that induced by in vitro exposure to IL-1β. Phenylbutazone should be used judiciously in athletic horses with osteoarthritis, because chronic administration may suppress proteoglycan synthesis and potentiate cartilage damage. (Am J Vet Res2001; 62:1916–1921)
Effects of acetylpromazine or morphine on urine production in halothane-anesthetized dogs
Authors: Robertson Sheilah A. , Hauptman Joseph G. , Nachreiner Ray F. , Richter Marlee A.
Published: December 2005

Objective—To assess the influence of preanesthetic administration of acetylpromazine or morphine and fluids on urine production, arginine vasopressin (AVP; previously known as antidiuretic hormone) concentrations, mean arterial blood pressure (MAP), plasma osmolality (Osm), PCV, and concentration of total solids (TS) during anesthesia and surgery in dogs.

Animals—19 adult dogs.

Procedure—Concentration of AVP, indirect MAP, Osm, PCV, and concentration of TS were measured at 5 time points (before administration of acetylpromazine or morphine, after administration of those drugs, after induction of anesthesia, 1 hour after the start of surgery, and 2 hours after the start of surgery). Urine output and end-tidal halothane concentrations were measured 1 and 2 hours after the start of surgery. All dogs were administered lactated Ringer's solution (20 ml/kg of body weight/h, IV) during surgery.

Results—Compared with values for acetylpromazine, preoperative administration of morphine resulted in significantly lower urine output during the surgical period. Groups did not differ significantly for AVP concentration, Osm, MAP, and end-tidal halothane concentration; however, PCV and concentration of TS decreased over time in both groups and were lower in dogs given acetylpromazine.

Conclusions and Clinical Relevance—Preanesthetic administration of morphine resulted in significantly lower urine output, compared with values after administration of acetylpromazine, which cannot be explained by differences in AVP concentration or MAP. When urine output is used as a guide for determining rate for IV administration of fluids in the perioperative period, the type of preanesthetic agent used must be considered.(Am J Vet Res2001;62:1922–1927)
In vitro responses of equine colonic arterial and venous rings to adenosine triphosphate
Authors: Tetens Joanne , Venugopal Changaram S. , Holmes Earnestine P. , Koch Catherine E. , Hosgood Giselle , Moore Rustin M.
Published: December 2005

Objective—To evaluate the in vitro effects of adenosine tryphosphate (ATP) on vasomotor tone of equine colonic vasculature.

Sample Population—Arteries and veins from the left ventral colon of 14 mixed-breed horses euthanatized for reasons unrelated to cardiovascular or gastrointestinal tract disease.

Procedures—Endothelium-intact and -denuded arterial and venous rings were precontracted with 10–7and 1.8 × 10–8Mendothelin-1, respectively. In 1 trial, endothelium-intact rings were also incubated with 10–4MNω-nitro-L-arginine methyl ester (L-NAME) to inhibit nitric oxide (NO) production. Adenosine triphosphate (10–8to 10–3M) was added in a noncumulative manner, and relaxation percentage versus time curves were generated. Areas under the curves (ie, percentage of relaxation time) were calculated.

Results—Relaxation response of arterial and venous rings to ATP was dose-dependent. Percentage of relaxation time in response to 10–4and 10–3MATP was significantly greater, compared with that for rings not treated with ATP. Removal of endothelium attenuated but did not eliminate the relaxation response. Addition of L-NAME did not attenuate the relaxation response in arteries. At higher concentrations, the vascular response to ATP was biphasic.

Conclusions and Clinical Relevance—ATP applied to equine colonic arterial and venous rings with and without intact endothelium induced a biphasic response characterized by transient contraction followed by slow, substantial, and sustained relaxation. This ATP-induced response is possibly mediated by a mechanism other than NO. Adenosine triphosphate may be a useful treatment to modulate colonic vasomotor tone in horses with strangulating volvulus of the ascending colon. (Am J Vet Res2001;62:1928–1933)
Effects of topical administration of 0.005% latanoprost solution on eyes of clinically normal horses
Authors: Willis A. Michelle , Diehl Kathryn A. , Hoshaw-Woodard Stacy , Kobayashi Ichirio , Vitucci Michael P. , Schmall L. Michael
Published: December 2005

Objective—To determine the effect of 0.005% latanoprost solution on intraocular pressure (IOP) of eyes of clinically normal horses and establish the frequency of adverse effects of drug administration.

Animals—20 adult clinically normal horses.

Procedure—IOP was recorded (7, 9, and 11 AM; 3, 5, and 7 PM) on days 1 and 2 (baseline), days 3 to 7 (treatment), and days 8 to 9 (follow-up). Latanoprost was administered to 1 randomly assigned eye of each horse every 24 hours during the treatment period, following the 7 AM IOP recording. Pupil size and the presence or absence of conjunctival hyperemia, epiphora, blepharospasm, blepharedema, and aqueous flare were recorded prior to IOP measurement.

Results—IOP was reduced from baseline by a mean value of 1.03 mm Hg (5%) in males and 3.01 mm Hg (17%) in females during the treatment period. Miosis developed in all treated eyes and was moderate to marked in 77% of horses, with the peak effect observed 4 to 8 hours after drug administration. Conjunctival hyperemia, epiphora, blepharospasm, and blepharedema were present in 100, 57, 42, and 12% of treated eyes, respectively, 2 to 24 hours following drug administration. Aqueous flare was not observed at any time point.

Conclusions and Clinical Relevance—Although IOP was reduced with every 24-hour dosing of latanoprost, the frequency of prostaglandin-induced adverse events was high. Because recurrent uveitis appears to be a risk factor for glaucoma in horses, topical administration of latanoprost may potentiate prostaglandin-mediated inflammatory disease in affected horses. (Am J Vet Res2001;62:1945–1951)
Methodology and validity of assessing kinematics of the thoracolumbar vertebral column in horses on the basis of skin-fixated markers
Authors: Faber Marjan , Schamhardt Henk , Weeren René van , Barneveld Ab
Published: December 2005

Objective—To determine the validity of using skin-fixated
markers to assess kinematics of the thoracolumbar
vertebral column in horses.

Animals—5 Dutch Warmblood horses without abnormalities
of the vertebral column.

Procedure—Kinematics of T6, T10, T13, T17, L1, L3,
L5, S3, and both tuber coxae were determined by use
of bone-fixated and skin-fixated markers. Threedimensional
coordinate data were collected while
horses were walking and trotting on a treadmill.
Angular motion patterns were calculated and compared
on the basis of 2-dimensional analysis of data
from skin-fixated markers and 3-dimensional analysis
of data from bone-fixated markers.

Results—Flexion-extension of thoracolumbar vertebrae
and axial rotation of the sacrum were satisfactorily
determined at both the walk and trot, using skinfixated
markers. Data from skin-fixated markers were
accurate for determining lateral bending at the walk in
the midthoracic and lower lumbar portion of the vertebral
column only. However, at the trot, data from
skin-fixated markers were valid for determining lateral
bending for all thoracolumbar vertebrae.

Conclusions and Clinical Relevance—Caution
should be taken when interpreting data obtained by
use of skin-fixated markers on lateral bending
motions during the walk in horses. For determination
of other rotations at the walk and all rotations at the
trot, use of skin-fixated markers allows valid calculations
of kinematics of the vertebral column.
Understanding to what extent movements of skin-fixated
markers reflect true vertebral motion is a compulsory
step in developing noninvasive methods for
diagnosing abnormalities of the vertebral column and
related musculature in horses. (Am J Vet Res
2001;62:301–306)
Comparative efficacy of tricaine methanesulfonate and clove oil for use as anesthetics in red pacu (Piaractus brachypomus)
Authors: Sladky Kurt K. , Swanson Clifford R. , Stoskopf Michael K. , Loomis Michael R. , Lewbart Gregory A.
Published: December 2005

Objective—To compare the anesthetic efficacy and
physiologic changes associated with exposure to tricaine
methanesulfonate and clove oil (100%
eugenol).

Animals—15 adult cultured red pacu (Piaractus
brachypomus).

Procedure—Fish were exposed to each of 6 anesthetic
concentrations in a within-subjects complete
crossover design. Stages of anesthesia and recovery
were measured, and physiologic data were collected
before and during anesthesia.

Results—Interval to induction was more rapid and
recovery more prolonged in fish exposed to eugenol,
compared with those exposed to tricaine methanesulfonate.
The margin of safety for eugenol was narrow,
because at the highest concentration, most fish
required resuscitation. Mixed venous-arterial PO2 consistently
decreased with anesthesia, while PCO2 consistently
increased with anesthesia in all fish regardless
of anesthetic agent. The increase in PCO2 was
accompanied by a decrease in pH, presumably secondary
to respiratory acidosis. Anesthesia was associated
with increased blood glucose, potassium, and
sodium concentrations as well as Hct and hemoglobin.
Fish anesthetized with eugenol were more likely
to react to a hypodermic needle puncture than fish
anesthetized with tricaine methanesulfonate.

Conclusions and Clinical Relevance—Anesthesia
induced with tricaine methanesulfonate or eugenol
contributes to hypoxemia, hypercapnia, respiratory
acidosis, and hyperglycemia in red pacu. Similar to tricaine
methanesulfonate, eugenol appears to be an
effective immobilization compound, but eugenol is
characterized by more rapid induction, prolonged
recovery, and a narrow margin of safety. Care must
be taken when using high concentrations of eugenol
for induction, because ventilatory failure may occur
rapidly. In addition, analgesic properties of eugenol
are unknown. (Am J Vet Res 2001;62:337–342)
Role of excessive maternal iron in the pathogenesis of congenital leukoencephalomalacia in captive black rhinoceroses (Diceros bicornis)
Authors: Paglia Donald E. , Kenny David E. , Dierenfeld Ellen S. , Tsu I-Hsien
Published: December 2005

Objective—To investigate the possibility that excessive maternal iron (overload) may contribute to development of congenital leukoencephalomalacia in captive black rhinoceroses.

Sample Population—Tissue specimens and serum samples from 18 rhinoceroses in 2 kindreds harboring 4 (possibly 5) affected female calves.

Procedure—Fresh and archival sera and necropsy tissue specimens were evaluated to determine the nature and extent of iron overload in captive and wild black rhinoceroses as well as other rhinoceros species.

Results—Quantitative serum and tissue assays of iron and iron analytes, corroborated by histopathologic findings, indicated that these kindreds carried the greatest body burdens of iron yet found among captive black rhinoceroses. Fourteen of 18 rhinoceroses had the highest serum ferritin concentrations measured among 64 black rhinoceroses in captivity in the United States. Dams of affected calves had serum ferritin concentrations 2 orders of magnitude higher than clinically normal humans, equids, or free-ranging rhinoceroses. A neonatal serum sample from 1 affected female calf had a high ferritin concentration (approx 100-fold increase), but a male sibling of another affected female did not, suggesting a possible sex disparity in fetal response to maternal iron overload. Morphologic hallmarks of hemochromatosis were prominent in dams and grandams of affected calves.

Conclusions and Clinical Relevance—Excessive maternal iron may affect female fetuses more than males, possibly inducing leukoencephalomalacia by catalyzing production of highly toxic hydroxyl free radicals during crucial periods of in utero development. Reduction of maternal iron overload may decrease the probability of developing leukoencephalomalacia and some other disorders commonly affecting rhinoceroses in captivity. (Am J Vet Res2001;62:343–349)
Spectral analysis of circadian rhythms in heart rate variability of dogs
Authors: Matsunaga Toshiyuki , Harada Takuma , Mitsui Takeshi , Inokuma Masanori , Hashimoto Masatoshi , Miyauchi Makoto , Murano Hiroyuki , Shibutani Yasunori
Published: December 2005

Objective—To determine characteristics of power
spectral analysis of heart rate variability (HRV) during
a 24-hour period in dogs and to evaluate the effects of
vagal and sympathetic tone on HRV.

Animals—16 healthy adult Beagles.

Procedure—Power spectral analysis of HRV was conducted,
using 24-hour ambulatory ECG recordings.
Circadian rhythms were evaluated in terms of
absolute units of low-frequency (LF) and high-frequency
(HF) powers, their ratio (LF:HF), and their
adjusted (normalized) units (LF[norm] and HF[norm]).
Three or 4 dogs were used for simultaneous measurement
of heart rate and respiratory waveform as
well as to evaluate treatment (propranolol, atropine,
or both) administered to cause blockade of the autonomic
nervous system.

Results—Values for LF and HF powers, LF:HF,
LF(norm), and HF(norm) had obvious rhythmicity in
clinically normal dogs. The HF power of HRV in dogs
was extremely high, compared with that of other
species, and HF peaks corresponded to peaks
obtained from respiratory waveforms. Blockade of
the autonomic nervous system documented that
HRV in dogs was mostly attributable to vagal activity.

Conclusion and Clinical Relevance—We determined
characteristics of power spectral analysis of
HRV in dogs, including circadian rhythm of the autonomic
nervous system. Power spectral analysis of
HRV may provide a useful noninvasive technique for
assessing the effect of drugs on activity of the autonomic
nervous system in dogs. ( Am J Vet Res
2001;62:37–42)
Antioxidant prevention of Heinz body formation and oxidative injury in cats
Authors: Hill Ana S. , O'Neill Sharron , Rogers Quinton R. , Christopher Mary M.
Published: December 2005

Objective—To determine the effectiveness of 3 antioxidants in preventing Heinz body anemia in cats.

Design—Prospective study.

Animals—44 specific-pathogen-free healthy cats.

Procedure—Cats were housed individually, divided randomly into 4 groups, and given the following orally every 12 hours: empty gelcaps (control cats), Nacetylcysteine (NAC, 100 mg/kg of body weight), vitamin E (d,l-α-tocopherol; 400 IU), or ascorbate (250 mg). After 2 weeks, Heinz bodies were induced by dietary onion powder (OP; 1% or 3% of dry matter) or propylene glycol (PG, 8% wt/vol in drinking water) for an additional 3 weeks. Intake of treated water or food was recorded daily. Body weight, PCV, Heinz body and reticulocyte percentages, reduced glutathione concentration, and total antioxidant status were measured twice weekly in all cats.

Results—Heinz body percentage and degree of anemia did not differ significantly among cats receiving antioxidants and control cats except in cats that ingested water containing PG, in which antioxidant supplementation was associated with a decrease in water intake. Of cats that were fed a diet that contained OP, cats that received NAC had significantly higher reduced glutathione concentrations, compared with other cats in the experiment. Total antioxidant status did not consistently correlate with antioxidant supplementation or type of oxidant administered (ie, OP or PG).

Conclusions and Clinical Relevance—Although the effect of antioxidant supplementation on Heinz body anemia in cats was minimal, antioxidants may have subclinical biochemical effects such as GSH sparing that may be important against milder forms of oxidative stress. (Am J Vet Res2001;62:370–374)
Aberrations of the p53 tumor suppressor gene in various tumors in dogs
Authors: Setoguchi Asuka , Sakai Tadashi , Okuda Masaru , Minehata Kenichi , Yazawa Mitsuhiro , Ishizaka Tomomichi , Watari Toshihiro , Nishimura Ryohei , Sasaki Nobuo , Hasegawa Atsuhiko , Tsujimoto Hajime
Published: December 2005

Objective—To evaluate aberrations of the p53 tumor suppressor gene in naturally developing tumors in dogs.

Sample Population—Tumor specimens from 15 dogs with various tumors, including malignant lymphoma (7 dogs), monocytic leukemia (1), mammary gland adenoma (1), mammary gland benign mixed tumor (1), rhabdomyosarcoma (1), colon cancer (1), and osteosarcoma (3).

Procedure—Aberrations of the p53 gene in these tumor tissues were examined by reverse transcriptase- polymerase chain reaction and single-strand conformation polymorphism analysis, using 3 fragments that covered the entire open reading frame of the canine p53 gene, followed by nucleotide sequencing of the abnormal bands.

Results—Point mutations, deletions, and insertions resulting in a number of amino acid substitutions of wild-type p53 were detected in 7 of the 15 tumor specimens from dogs with malignant lymphoma, monocytic leukemia, rhabdomyosarcoma, colon cancer, and osteosarcoma. Of these 7 dogs, 2 had aberrations of the p53 gene on both alleles, whereas 5 had aberrations of the p53 gene on 1 allele and concurrently lacked the wild-type p53 transcript. Many of the aberrations of the p53 gene detected in these tumors were located in the transactivation, DNA binding, and oligomerization domains.

Conclusions and Clinical Relevance—Various naturally developing tumors in dogs often have inactivation of the p53 tumor suppressor gene, which may be 1 of the multiple step-wise genetic changes during tumorigenesis. This study indicates that p53 gene can be a target for gene therapy for tumors in dogs. (Am J Vet Res2001;62:433–439)
Photoelastic stress analysis of strain patterns in equine hooves after four-point trimming
Authors: Dejardin Loic M. , Arnoczky Steven P. , Cloud Gary L. , Stick John A.
Published: December 2005

Objective—To evaluate changes in strain patterns in normal equine hooves following 4-point trimming, using photoelastic stress analysis.

Sample Population—15 equine front limbs with normal hoof configuration.

Procedure—Limbs were disarticulated at the carpometacarpal joint. Weight-bearing surfaces of each hoof were trimmed level to ensure 100% ground contact. Hoof walls were coated with a custom-made strain-sensitive plastic, and limbs were loaded to a third of body weight. Using a polariscope, strain distribution, magnitudes, and directions were evaluated in level hooves as well as before and after standardized 4-point trimming. Repeated-measures ANOVA was used to compare strain magnitudes and directions before and after trimming.

Results—In leveled specimens, strain fields were symmetrically distributed above the heels and at quarter-toe junctions along a line between the middle and distal thirds of the hoof wall. After 4-point trimming, strain epicenters localized above the contact points, whereas strain magnitudes significantly increased by approximately 50%. Decreasing contact area by 50% resulted in an additional significant increase (32%) in strain magnitude. Trimming did not have a significant effect on strain orientations.

Conclusion and Clinical Relevance—This study documents that 4-point trimming results in strain concentration above the hoof contact points and that strain magnitude is dependent on contact area. (Am J Vet Res2001;62:467–473)
Determination of differential cell counts in feline bone marrow by use of flow cytometry
Authors: Weiss Douglas J.
Published: December 2005

Objective—To evaluate the potential usefulness of 2
flow cytometric methods for determination of differential
cell counts in feline bone marrow.

Sample Population—10 bone marrow specimens
from client-owned cats.

Procedure—Bone marrow specimens were stained
with 3,3'-dihexyloxacarbocyanine iodide (DiOC6) and
evaluated by use of flow cytometry. Differential
counts were also determined by analysis of scatterplots
of forward-angle versus side-angle light scatter
of unstained specimens, obtained by use of flow
cytometry (scatterplot method). Results of both flow
cytometric methods were compared with differential
cell counts determined by manually counting 1,000
cells on slides of Wright-stained smears.

Results—Staining with DiOC6 resulted in identification
of mature and immature erythroid and myeloid
cells and lymphocytes. Use of the scatterplot method
resulted in identification of mature and immature erythroid
and myeloid cells and metamyelocytes.
However, to identify lymphocytes by use of the scatterplot
method, bone marrow specimens were first
labeled with an anti-major histocompatability class-II
antibody. Comparison of results of the scatterplot
method with manual counts yielded higher correlation
coefficients and more similar mean values than did
comparison of results of the DiOC6 method.

Conclusion and Clinical Relevance—The scatterplot
method provided more accurate and precise
results than the DiOC6 method for determination of
bone marrow differential cell counts in cats by use of
flow cytometry. When combined with fluorescent
labeling of lymphocytes, the scatterplot method has
potential to provide rapid semiquantitative assessment
of bone marrow differential cell counts in cats.
(Am J Vet Res 2001;62:474–478)
Density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses
Authors: Andrew Stacy E. , Ramsey David T. , Hauptman Joe G. , Brooks Dennis E.
Published: December 2005

Objective—To determine density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses.

Sample Population—52 normal eyes from 26 horses.

Procedure—Eyes were enucleated after horses were euthanatized. Eyes were examined to determine that they did not have visible ocular defects. Noncontact specular microscopy was used to determine density of corneal endothelial cells. Corneal thickness was measured, using ultrasonic pachymetry or specular microscopy.

Results—Mean density of corneal endothelial cells was 3,155 cells/mm2. Cell density decreased with age, but sex did not affect cell density. Values did not differ significantly between right and left eyes from the same horse. Cell density of the ventral quadrant was significantly less than cell density of the medial and temporal quadrants. Mean corneal thickness was 893 µm. Sex or age did not affect corneal thickness. Dorsal and ventral quadrants were significantly thicker than the medial and temporal quadrants and central portion of the cornea. We did not detect a correlation between corneal thickness and density of endothelial cells in normal eyes of horses.

Conclusion and Clinical Relevance—Density of corneal endothelial cells decreases with age, but corneal thickness is not affected by age or sex in normal eyes of horses. The technique described here may be useful for determining density of endothelial cells in the cornea of enucleated eyes. This is clinically relevant for analyzing corneal donor tissue prior to harvest and use for corneal transplantation. (Am J Vet Res2001;62:(479–482)
Disposition, elimination, and bioavailability of phenytoin and its major metabolite in horses
Authors: Soma Lawrence R. , Uboh Cornelius E. , Guan Fuyu , Birks Eric K. , Teleis Donna C. , Rudy Jeffrey A. , Tsang Deborah S. , Watson Anthony O.
Published: December 2005

Objective—To determine pharmacokinetics and excretion of phenytoin in horses.

Animals—6 adult horses.

Procedure—Using a crossover design, phenytoin was administered (8.8 mg/kg of body weight, IV and PO) to 6 horses to determine bioavailability (F). Phenytoin also was administered orally twice daily for 5 days to those same 6 horses to determine steadystate concentrations and excretion patterns. Blood and urine samples were collected for analysis.

Results—Mean (± SD) elimination half-life following a single IV or PO administration was 12.6 ± 2.8 and 13.9 ± 6.3 hours, respectively, and was 11.2 ± 4.0 hours following twice-daily administration for 5 days. Values for F ranged from 14.5 to 84.7%. Mean peak plasma concentration (Cmax) following single oral administration was 1.8 ± 0.68 µg/ml. Steady-state plasma concentrations following twice-daily administration for 5 days was 4.0 ± 1.8 µg/ml. Of the 12.0 ± 5.4% of the drug excreted during the 36-hour collection period, 0.78 ± 0.39% was the parent drug phenytoin, and 11.2 ± 5.3% was 5-(p-hydroxyphenyl)-5-phenylhydantoin (p-HPPH). Following twice-daily administration for 5 days, phenytoin was quantified in plasma and urine for up to 72 and 96 hours, respectively, and p-HPPH was quantified in urine for up to 144 hours after administration. This excretion pattern was not consistent in all horses.

Conclusion and Clinical Relevance—Variability in F, terminal elimination-phase half-life, and Cmaxfollowing single or multiple oral administration of phenytoin was considerable. This variability makes it difficult to predict plasma concentrations in horses after phenytoin administration. (Am J Vet Res2001;62:483–489)
Contact transmission of vesicular stomatitis virus New Jersey in pigs
Authors: Stallknecht David E. , Perzak Deborah E. , Bauer Leslie D. , Murphy Molly D. , Howerth Elizabeth W.
Published: December 2005

Objective—To determine how viral shedding and development or lack of clinical disease relate to contact transmission of vesicular stomatitis virus New Jersey (VSV-NJ) in pigs and determine whether pigs infected by contact could infect other pigs by contact.

Animals—63 pigs.

Procedure—Serologically naive pigs were housed in direct contact with pigs that were experimentally inoculated with VSV-NJ via ID inoculation of the apex of the snout, application to a scarified area of the oral mucosa, application to intact oral mucosa, or ID inoculation of the ear. In a second experiment, pigs infected with VSV-NJ by contact were moved and housed with additional naive pigs. Pigs were monitored and sampled daily for clinical disease and virus isolation and were serologically tested before and after infection or contact.

Results—Contact transmission developed only when vesicular lesions were evident. Transmission developed rapidly; contact pigs shed virus as early as 1 day after contact. In pens in which contact transmission was detected, 2 of 3 or 3 of 3 contact pigs were infected.

Conclusion and Clinical Relevance—Transmission was lesion-dependent; however, vesicular lesions often were subtle with few or no clinical signs of infection. Contact transmission was efficient, with resulting infections ranging from subclinical (detected only by seroconversion) to clinical (development of vesicular lesions). Long-term maintenance of VSV-NJ via contact transmission alone appears unlikely. Pigs represent an efficient large-animal system for further study of VSV-NJ pathogenesis and transmission. (Am J Vet Res2001;62:516–520)
Effects of intranasal inoculation with Bordetella bronchiseptica, porcine reproductive and respiratory syndrome virus, or a combination of both organisms on subsequent infection with Pasteurella multocida in pigs
Authors: Brockmeier Susan L. , Palmer Mitchell V. , Bolin Steven R. , Rimler Richard B.
Published: December 2005

Objective—To determine effects of intranasal inoculation
with porcine reproductive and respiratory syndrome
virus (PRRSV) or Bordetella bronchiseptica on
challenge with nontoxigenic Pasteurella multocida in
pigs.

Animals—Seventy 3-week-old pigs.

Procedure—In experiment 1, pigs were not inoculated
(n= 10) or were inoculated with PRRSV (10), P multocida
(10), or PRRSV followed by challenge with P
multocida (10). In experiment 2, pigs were not inoculated
(n = 10) or were inoculated with B bronchiseptica
(10) or PRRSV and B bronchiseptica (10); all pigs
were challenged with P multocida. Five pigs from
each group were necropsied 14 and 21 days after initial
inoculations.

Results—Pasteurella multocida was not isolated
from tissue specimens of pigs challenged with P multocida
alone or after inoculation with PRRSV.
However, in pigs challenged after inoculation with B
bronchiseptica, P multocida was isolated from specimens
of the nasal cavity and tonsil of the soft palate.
Number of bacteria isolated increased in pigs challenged
after coinoculation with PRRSV and B bronchiseptica,
and all 3 agents were isolated from pneumonic
lesions in these pigs.

Conclusion and Clinical Relevance—Infection of
pigs with B bronchiseptica but not PRRSV prior to
challenge with P multocida resulted in colonization of
the upper respiratory tract and tonsil of the soft palate
with P multocida. Coinfection with PRRSV and B
bronchiseptica predisposed pigs to infection of the
upper respiratory tract and lung with P multocida.
Porcine reproductive and respiratory syndrome virus
and B bronchiseptica may interact to adversely affect
respiratory tract defense mechanisms, leaving pigs
especially vulnerable to infection with secondary
agents such as P multocida. (Am J Vet Res 2001;
62:521–525)
Microvascular development and growth of uterine tissue during the estrous cycle in mares
Authors: Ferreira-Dias Graça M. , Serrão Paula M. , Durão José F. Costa , Silva José Robalo
Published: December 2005

Objective—To document uterine growth and microvascular development in the endometrium of uteri with differing degrees of fibrosis as well as uterine growth throughout the estrous cycle of mares.

Animals—30 mares.

Procedure—Uterine tissue was obtained during the breeding season from a slaughter facility. Stage of estrous cycle of the mares was assessed on the basis of ovarian structures and plasma progesterone concentrations. Endometrium was characterized by use of light microscopy, and blood vessel walls were marked by histochemical techniques. Microvascular development was evaluated by a computerized image analysis system. Growth of uterine tissue was based on cellular content of DNA and RNA, RNA:DNA, and protein:DNA.

Results—Significant differences in vascular density were not observed in the endometrium of uteri obtained from mares euthanatized during the follicular or luteal phase of the estrous cycle, regardless of whether endometrial classification of degree of fibrosis was considered. There was a 3-fold increase in amount of DNA and RNA of endometrial cells in the follicular phase when compared to myometrium. Hypertrophy of endometrial tissue during the luteal phase was reflected by a significant increase in cell protein content and protein:DNA.

Conclusion and Clinical Relevance—Endometrial growth of vascular tissues during the estrous cycle may be coordinated with development of nonvascular tissue. Estrogen and progesterone may play a role in regulation of uterine growth and angiogenesis. (Am J Vet Res2001;62:526–530)
Induction of specific cytotoxic T-cell activity against xenogeneic target cells in carp (Cyprinus carpio)
Authors: Yamamoto Kiyoe , Mukamoto Masafumi , Watarai Shinobu , Kodama Hiroshi , Nakayasu Chihaya , Okamoto Nobuaki
Published: December 2005

Objective—To investigate the induction of cytotoxic T cells in carp (Cyprinus carpio) after inoculation of fish with 2 xenogeneic line cells and to examine specificity of the cytotoxic activity.

Animals—22 carp.

Procedure—Fish were inoculated with mouse myeloma line cells P3.NS-1/1Ag4.1 (NS-1) or chicken Marek's disease tumor-derived lymphoma line cells (MDCC MSB-1). Cytotoxic activity of immune lymphocytes was evaluated by incubating effector cells with homologous and heterologous target cells. Populations of effector cells were identified by blocking T-lymphocytes from effector cells, using anti-carp T-cell monoclonal antibody and complement.

Results—Lymphocytes in blood, spleen, and head kidney of carp inoculated with NS-1 cells or MDCC MSB-1 cells had dose-dependent cytotoxic effects against homologous target cells but not against heterologous target cells. Lymphocytes from noninoculated carp did not have cytotoxic effects. Depletion of Tlymphocytes in spleen cells from NS-1-inoculated carp resulted in a decrease of cytotoxic activity against NS-1 cells. Cytotoxic activity of spleen lymphocytes from NS-1-inoculated or noninoculated carp was not evident when cytotoxic tests were performed after addition of anti-NS-1 carp serum.

Conclusion and Clinical Relevance—Inoculation with xenogeneic target cells induces a specific cytotoxic T-cell response in carp. Thus, cell-mediated immunity plays a role in defense against infection of parasitic organisms such as protozoa and helminths. (Am J Vet Res2001;62:599–603)
Use of a polymerase chain reaction assay to detect and differentiate two strains of Haemobartonella felis in naturally infected cats
Authors: Jensen Wayne A. , Lappin Michael R. , Kamkar Sherwin , Reagan William J.
Published: December 2005

Objective—To develop a polymerase chain reaction (PCR) assay that detects and differentiates the Ohio strain ofHaemobartonella felis(H felis-OH) and the California strain ofH felis(H felis-CA) and to apply the assay to blood samples from cats with and without suspected haemobartonellosis (suspect and control cats, respectively).

Sample Population—220 blood samples were examined; 82 were from suspect cats, and 138 were from control cats.

Procedure—A PCR assay was designed to detect and differentiateH felis-OH andH felis-CA.

Results—On the basis of PCR assay results, the overall prevalence ofH felisinfection was 19.5% (43/220). Suspect cats (28.0%; 23/82) were significantly more likely than control cats (14.5%; 20/138) to beH felisinfected. Significantly greater numbers of suspect cats wereH felis-OH infected (12.2%, 9/82) orH felis-OH andH felis-CA infected (4.9%, 4/82) than control cats (0% [0/138] and 0.7% [1/138], respectively). Significantly more anemic cats wereH felis-OH infected (14.3%; 4/28) orH felis-OH andH felis-CA infected (7.1%; 2/28) than nonanemic cats (2.3% [3/128] and 0.8% [1/128], respectively). The PCR assay was more accurate than cytologic examination for detection ofH felis.

Conclusion and Clinical Relevance—Haemobartonella felisinfections are more common in cats than previously recognized.Haemobartonella felis-OH is apparently more pathogenic thanH felis-CA. The PCR assay is more accurate than cytologic examination for detection ofH felisinfection and is an effective clinical tool for the detection and differentiation of bothH felisstrains known to infect cats. (Am J Vet Res2001;62:604–608)
Sedative, analgesic, and cardiovascular effects of levomedetomidine alone and in combination with dexmedetomidine in dogs
Authors: Kuusela Erja , Vainio Outi , Kaistinen Anu , Kobylin Sanna , Raekallio Marja
Published: December 2005

Objective—To determine whether a high dose of levomedetomidine had any pharmacologic activity or would antagonize the sedative and analgesic effects of dexmedetomidine in dogs.

Animals—6 healthy Beagles.

Procedure—Each dog received the following treatments on separate days: a low dose of levomedetomidine (10 µg/kg), IV, as a bolus, followed by continuous infusion at a dose of 25 µg/kg/h; a high dose of levomedetomidine (80 µg/kg), IV, as a bolus, followed by continuous infusion at a dose of 200 µg/kg/h; and a dose of isotonic saline (0.9% NaCl) solution, IV, as a bolus, followed by continuous infusion (control). For all 3 treatments, the infusion was continued for 120 minutes. After 60 minutes, a single dose of dexmedetomidine (10 µg/kg) was administered IV. Sedation and analgesia were scored subjectively, and heart rate, blood pressure, respiratory rate, arterial blood gas partial pressures, and rectal temperatures were monitored.

Results—Administration of levomedetomidine did not cause any behavioral changes. However, administration of the higher dose of levomedetomidine enhanced the bradycardia and reduced the sedative and analgesic effects associated with administration of dexmedetomidine.

Conclusion and Clinical Relevance—Results suggest that administration of dexmedetomidine alone may have some cardiovascular benefits over administration of medetomidine, which contains both dexmedetomidine and levomedetomidine. Further studies are needed to confirm the clinical importance of the effects of levomedetomidine in dogs. (Am J Vet Res2001;62:616–621)
Fecal shedding of Giardia duodenalis, Cryptosporidium parvum, Salmonella organisms, and Escherichia coli O157:H7 from llamas in California
Authors: Rulofson Franz C. , Atwill Edward R. , Holmberg Charles A.
Published: December 2005

Objective—To evaluate fecal shedding ofGiardia duodenalis, Cryptosporidium parvum, Salmonellaorganisms, andEscherichia coliO157:H7 from llamas in California with respect to host factors and management practices.

Animals—354 llamas from 33 facilities.

Procedure—Fecal specimens were collected and examined forG duodenalisandC parvumby means of immunofluorescent microscopy.Salmonellaorganisms were cultured by placing feces into selenite enrichment broth followed by selective media.Escherichia coliO157:H7 was cultured by use of modified tryptocase soy broth followed by sorbitol MacConkey agar, with suspect colonies confirmed by means of immunofluorescent microscopy.

Results—12 of 354 fecal specimens (3.4%) hadG duodenaliscysts. Younger llamas (crias) were more likely to be shedding cysts, compared with older llamas. Farm-level factors that increased the risk of shedding were large numbers of yearlings on the property (> 10), smaller pen sizes, large numbers of crias born during the previous year (> 10), and large pen or pasture populations (> 20). None of the 354 fecal specimens hadC parvumoocysts. Seventy-six (from 7 facilities) and 192 (from 22 facilities) llamas were tested forSalmonellaorganisms andE coliO157:H7, respectively. All fecal specimens had negative results for these bacteria.

Conclusion and Clinical Relevance—Shedding ofG duodenaliswas primarily limited to crias 1 to 4 months old. Llamas from properties with large numbers of crias born in the previous year, resulting in large numbers of yearlings in the current year, were at greater risk of infection. In addition, housing llamas in smaller pens or pastures and managing llamas and crias in large groups also increased the risk ofG duodenalisshedding. (Am J Vet Res2001;62:637–642)