Predicting use of habitat patches by spawning horseshoe crabs (Limulus polyphemus) along a complex coastline with field surveys and geospatial analyses

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Effects of abamectin on intracellular potassium ion activity and membrane potential in dipteran skeletal muscle

The effects of abamectin (AVMB₁) on intracellular potassium ion activity (aK_i) and resting membrane potential (E_m) of the skeletal muscle cells of final instar larvae of Phormia terraenovae (Diptera) were investigated using K⁺-selective micro-electrodes. Bathing the preparation in 10^? M AVMB₁(+ 1 ml litre^?1 dimethylsulfoxide) for 60 min caused a significant (31%) decrease in aK_i, whilst E_m depolarized on average by 19 mV (nearly 50% of the original control value). The difference E_K-E_m increased by 9 mV, although E_K (potassium equilibrium potential) remained more negative than E_m. These results could be due to a cationic effect of AVMB₁ possibly involving an increase in K⁺ and Na⁺ conductances of the muscle plasma membrane.     

Effect of oral administration of low doses of pentobarbital on the induction of cytochrome P450 isoforms and cytochrome P450-mediated reactions in immature Beagles

OBJECTIVE: To determine the effect of oral administration of low doses of pentobarbital on cytochrome P450 (CYP) isoforms and CYP-mediated reactions in immature Beagles. ANIMALS: 42 immature (12-week-old) Beagles. PROCEDURE: Dogs were grouped and treated orally as follows for 8 weeks: low-dose pentobarbital (50 microg/d; 4 males, 4 females), mid-dose pentobarbital (150 microg/d; 4 males, 4 females), high-dose pentobarbital (500 microg/d; 4 males, 4 females), positive-pentobarbital control (10 mg/kg/d; 2 males, 2 females), positive-phenobarbital control (10 mg/kg/d; 2 males, 2 females), and negative control (saline 10.9% NaCl] solution; 5 males, 5 females). Serum biochemical and hematologic values were monitored. On necropsy examination, organ weights were determined, and histologic evaluation of tissue sections of liver, kidney, small intestine, testes, epididymis, and ovaries was performed. Hepatic and intestinal drug-metabolizing enzyme activities were measured, and relative amounts of CYP isoforms were determined by western blot analysis. RESULTS: The amount of a hepatic CYP2A-related isoform in dogs from the high-dose pentobarbital treatment group was twice that of dogs from the negative control group. CYP2C was not detectable in small intestinal mucosa of dogs from the negative control group; measurable amounts of CYP2C were found in dogs from the various (low-, mid-, and high-dose) pentobarbital treatment groups and from positive-pentobarbital and positive phenobarbital control groups. Several CYP-mediated reactions increased in a dose-dependent manner. The lowest calculated effective dose of pentobarbital ranged from 200 to 450 microg/d. CONCLUSIONS AND CLINICAL RELEVANCE: Several CYP isoforms and their associated reactions were induced in dogs by oral administration of low amounts of pentobarbital.     

In vitro effects of osteotomy angle and osteotomy reduction on tibial angulation and rotation during the tibial plateau-leveling osteotomy procedure

OBJECTIVE: To determine the effect of osteotomy angle, reduction technique, and tibial plateau rotation angle on angular and rotational limb deformities. STUDY DESIGN: Geometric comparison using bone models. METHODS: Rotational osteotomies were made in the proximal metaphysis of artificial tibias at 0 degrees, 10 degrees, 20 degrees, -10 degrees, and -20 degrees from perpendicular with respect to either the proximodistal and craniocaudal tibial axes. Negative-numbered angles represented osteotomies made from distal to proximal or caudal to cranial. Changes in tibial angulation and torsion were measured using a 3-dimensional digitizing instrument at tibial plateau rotation angles from 0 degrees to 30 degrees at 5 degrees increments. Two osteotomy reduction techniques were used: complete osteotomy reduction and alignment of the medial cortex. The mean of 5 measurements of torsional and angular tibial deformity for each of the 9 osteotomy orientations in each reduction technique group was obtained. RESULTS: All had increasing angular and rotational deformity as tibial plateau rotation angle increased. In the medially aligned cortex group, all tibias had valgus deformity, and 8 of 9 tibias were internally rotated. In the reduced osteotomy group, minimal angular deformity was seen in tibias with osteotomy variation along the proximodistal axis; however, tibias with osteotomy variation along the craniocaudal axis had angular deformity ranging from 6.0 degrees of varus deformity to 14.3 degrees of valgus deformity. Rotational deformity was affected similarly by osteotomy variation along either axis. Reduction technique had greater affect on angular and rotational deformity than osteotomy angle variation. CLINICAL RELEVANCE: These results suggest that osteotomy reduction may play a greater role in angular and rotational deformity than osteotomy angle, although extreme osteotomy angles should be avoided. To decrease the severity of deformity, we recommend that the osteotomy be made perpendicular to the craniocaudal and proximodistal axes and be completely reduced with less regard for alignment of the medial cortex.     

Cerebellar infarcts in two dogs diagnosed with magnetic resonance imaging

Two dogs presented with severe, peracute-onset, neurological signs. Neuroanatomical localization was cerebellovestibular. Magnetic resonance imaging (MRI) was performed and revealed focal, wedge-shaped lesions in the cerebellum. Diagnosis of cerebellar infarctions was made based on peracute-onset, clinical signs, MRI, and outcome as well as ancillary diagnostic information. Both dogs recovered completely. Cerebellar infarction should be included in the differential of any dog with peracute-onset, central cerebellovestibular signs regardless of severity of clinical signs. Outcome was excellent in these dogs.     

Influence of vestibulovaginal stenosis,pelvic bladder,and recessed vulva on response to treatment for clinical signs of lower urinary tract disease in dogs: 38 cases (1990-1999)

OBJECTIVE: To determine influence of vestibulovaginal stenosis, pelvic bladder, and recessed vulva on response to treatment for clinical signs of lower urinary tract disease in dogs. DESIGN: Retrospective study. ANIMALS: 38 spayed female dogs. PROCEDURE: Medical records and client follow-up were reviewed for dogs evaluated via excretory urography because of clinical signs of lower urinary tract disease. Clinical signs, results of radiography, and response to surgical or medical treatment were analyzed. RESULTS: Clinical signs included urinary tract infection (n = 24), urinary incontinence (20), vaginitis (11), pollakiuria or stranguria (10), and perivulvar dermatitis (4). Vaginocystourethrographic findings included vestibulovaginal stenosis (n = 28), pelvic bladder (17), and ureteritis or pyelonephritis (4). Ten dogs had a vestibulovaginal ratio of < 0.20 (severe stenosis), 9 dogs had a ratio of 0.20 to 0.25 (moderate stenosis), 9 dogs had a ratio of 0.26 to 0.35 (mild stenosis), and 10 dogs had a ratio of > 0.35 (anatomically normal). Lower urinary tract infection, incontinence, and pelvic bladder were not associated with response to treatment for recessed vulva. Vestibulovaginal stenosis with a ratio < 0.20 was significantly associated negatively with response to treatment. Dogs without severe vestibulovaginal stenosis that received vulvoplasty for a recessed vulva responded well to treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Vestibulovaginal stenosis is likely an important factor in dogs with vestibulovaginal ratio < 0.20. Vaginectomy or resection and anastomosis should be considered in dogs with severe vestibulovaginal stenosis and signs of lower urinary tract disease.     

Blood lead levels of wild Steller's eiders (Polysticta stelleri) and black scoters (Melanitta nigra) in Alaska using a portable blood lead analyzer.

Sea duck populations are declining in Alaska. The reasons for the decline are not known; environmental lead exposure is one suspected cause. Thirty wild Steller's eider ducks (Polysticta stelleri) and 40 wild black scoter ducks (Melanitta nigra) were tested for blood lead levels using a portable blood lead analyzer (LeadCare; ESA, Inc., Chelmsford, Massachusetts 01824, USA). Sixty-seven and one-tenth percent of the sea ducks had undetectable blood lead levels, 30.0% had values indicating normal or background lead exposure, and 2.9% had values indicating lead exposure. None of the birds had values indicating lead toxicity, and no birds demonstrated clinical signs of toxicity. Birds in areas with higher human population density had higher blood lead levels than those in less densely populated areas. This is the first time a portable blood lead analyzer has been utilized with sea ducks in a field setting. Because it provides immediate results, it is valuable as a screening tool for investigators carrying out surgical procedures on birds in the field as well as establishing baseline blood lead data on sea ducks. Lead exposure does occur in wild sea ducks, and the study indicates that additional research is needed in order to determine the role environmental lead plays in declining sea duck populations.     

Nutritional management of grazing beef cows.

In grazing operations, forage quality and availability are sometimes limited, and cattle are unable to consume enough nutrients from pasture forage to fulfill requirements. During such situations, supplemental or replacement feeding is necessary to meet production goals. A fundamental understanding of ruminant nutrition and forage management is helpful in deciding which feed or supplement type (ie, energy versus protein) best fits the goals of a specific beef production system. It is important to choose a delivery method and supplement form that provide the targeted amount of desired nutrients to each animal in the herd and that minimize input costs. The objective of this article is to serve as a resource for veterinarians as they provide nutritional management support to beef cow producers.     

The effects of cooling and vitrification of embryos from mares treated with equine follicle-stimulating hormone on pregnancy rates after nonsurgical transfer

Equine embryos can remain viable for 12 to 24 hours when cooled and stored at 5°C.¹ Cryopreservation of embryos would allow for long-term preservation of genetic material and more efficient management of embryo recipients. This study compared pregnancy rates after transfer of equine embryos vitrified within 1 hour of collection or cooled for 12 to 19 hours before vitrification. Mares (N = 40) were superovulated using equine follicle-stimulating hormone (eFSH). Embryos were recovered 6.5 days after ovulation or 8 days after human chorionic gonadotropin. Forty morulae or early blastocysts with a grade of 1 to 2 and <300 mm in diameter were randomly assigned to 1 of 2 treatments: Group 1 (n = 20), washed 4 times in a commercial holding medium and then vitrified; Group 2 (n = 20), washed 3 times and then stored in the same holding medium at 5°C to 8°C in a passive cooling device for 12 to 19 hours before being vitrified. To thaw, embryos were warmed by holding the straw in air at room temperature for 10 seconds and then submerged in a water bath (20°C to 22°C) for an additional 10 seconds. The contents of the straw were transferred directly into a recipient that had ovulated 4 to 6 days previously. There were no differences (P > .05) in embryo diameter, grade, or morphology score between treatment groups before vitrification. Pregnancy rates (day 16) were not different (P > .05) between embryos vitrified immediately after collection (15 of 20; 75%) and embryos cooled for 12 to 19 hours before vitrification (13 of 20; 65%). Based on these results, small equine embryos (<300 mm) can be stored at 5°C to 8°C for 12 to 19 hours before vitrification without a significant loss of viability.     

Landscape attributes and life history variability shape genetic structure of trout populations in a stream network

Spatial and temporal landscape patterns have long been recognized to influence biological processes, but these processes often operate at scales that are difficult to study by conventional means. Inferences from genetic markers can overcome some of these limitations. We used a landscape genetics approach to test hypotheses concerning landscape processes influencing the demography of Lahontan cutthroat trout in a complex stream network in the Great Basin desert of the western US. Predictions were tested with population- and individual-based analyses of microsatellite DNA variation, reflecting patterns of dispersal, population stability, and local effective population sizes. Complementary genetic inferences suggested samples from migratory corridors housed a mixture of fish from tributaries, as predicted based on assumed migratory life histories in those habitats. Also as predicted, populations presumed to have greater proportions of migratory fish or from physically connected, large, or high quality habitats had higher genetic variability and reduced genetic differentiation from other populations. Populations thought to contain largely non-migratory individuals generally showed the opposite pattern, suggesting behavioral isolation. Estimated effective sizes were small, and we identified significant and severe genetic bottlenecks in several populations that were isolated, recently founded, or that inhabit streams that desiccate frequently. Overall, this work suggested that Lahontan cutthroat trout populations in stream networks are affected by a combination of landscape and metapopulation processes. Results also demonstrated that genetic patterns can reveal unexpected processes, even within a system that is well studied from a conventional ecological perspective.