Influence of Precipitation on Plant Production at Different Topographic Positions in the Nebraska Sandhills

Several studies have evaluated the spatial distribution of cool- and warm-season grasses across different topographic positions in the Nebraska Sandhills, but limited research has explored topographic differences in total plant production or production of plant functional groups in relation to variable amounts of precipitation. This study evaluated how spring and growing season precipitation influenced plant production at four topographic positions common in the eastern Nebraska Sandhills. Plant production data were collected from annually moved grazing exclosures in mid-June (peak cool-season grass production) and mid-August (peak warm-season grass production) during a 17-yr period from 2001 to 2017. Total plant production and precipitation use efficiency were 35 ? 58% greater on interdune positions, and precipitation marginal response for total plant production was more sensitive to increases in spring and growing season precipitation on interdune compared with dune positions in both mid-June and mid-August. The greater precipitation marginal response of total plant production on interdune positions was driven primarily by greater increases in cool-season grass production with increasing spring or growing season precipitation. Warm-season grass precipitation marginal response was not different among the topographic positions, but production was 23 ? 70% greater on interdune compared with dune topographic positions in mid-August. When differences in the amount of each topographic position at the study location were accounted for, growing season precipitation explained 49% of the variation for total plant production in mid-August, but spring precipitation only explained 23% of the variation for total plant production in mid-June. Because of the differential response of plant production at dune and interdune positions, incorporating the relative amount of each topographic position into estimates of plant production at the pasture or ranch scale will provide better information for adjusting stocking rates to more accurately match animal demand with forage availability.     

Diffusion weighted magnetic resonance imaging is a feasible method for characterizing regional lymph nodes in canine patients with head and neck disease

In dogs diagnosed with solid tumors, regional lymph node involvement or evidence of distant metastasis can predict worse prognoses and significantly decreased survival. Lymph node size alone has been shown to be insufficient as a predictor for the accurate clinical staging of some canine neoplasia. However, certain regional lymph nodes (including those of the oral cavity) are difficult to access for routine tissue sampling. Diffusion weighted magnetic resonance imaging (MRI) has demonstrated the ability to differentiate metastatic from inflammatory/benign lymph nodes in clinical studies with human cancer patients through the calculation of quantitative values of diffusion termed apparent diffusion coefficients (ADC). The objective of this prospective, exploratory study was to evaluate diffusion‐weighted MRI and ADC as potential methods for detecting metastatic lymph nodes in dogs with naturally occurring disease. We hypothesized that diffusion‐weighted MRI would identify significantly different ADC values between benign and metastatic lymph nodes in a group of canine patients with head or neck disease. Our study population consisted of eight client‐owned canine patients, with a total of 20 lymph nodes evaluated (six metastatic, 14 benign). Our results demonstrated that two of four observers identified a significant difference between the mean ADC values of the benign and metastatic lymph nodes. When data from all four observers were pooled, the difference between the mean apparent diffusion coefficients values of the benign and metastatic lymph nodes did not reach significance (P‐value = 0.0566). Findings indicated that diffusion‐weighted MRI is a feasible method for further characterizing enlarged lymph nodes in dogs with head and neck disease, however measured ADC values did not differ for benign vs. metastatic lymph nodes in this small sample of dogs.     

A double‐blind,placebo‐controlled,randomized study to evaluate the weight gain drug,mirtazapine transdermal ointment,in cats with unintended weight loss

Mirtazapine is classified as a weight gain drug in cats, and the purpose of this study was to evaluate its efficacy in cats experiencing unintended weight loss. This was a multi‐center, double‐blind, placebo‐controlled, randomized clinical study in client‐owned cats ≥1 year of age, weighing ≥2 kg, with a documented loss (≥5%) in body weight. Cats were treated once daily with either 2 mg/cat mirtazapine transdermal ointment (n = 83) or placebo (n = 94) (Per Protocol population) applied to the inner surface of the pinna for 14 ± 3 days. Physical examination, body weight, complete blood count, serum chemistry, and urinalysis were performed prior to treatment and on Day 14. Changes in body weight between the mirtazapine and placebo groups were evaluated from Day 1 to Day 14 and compared using a two‐sample t test. The mean percent change in body weight was +3.9% (standard deviation ±5.4%) in the mirtazapine group and +0.4% (±3.3%) in the placebo group (p < 0.0001). The most common adverse event was mild erythema at the application site in 17.4% of placebo and 10.4% of mirtazapine‐treated cats. Application of mirtazapine transdermal ointment was well tolerated both topically and systemically and resulted in significant weight gain in cats experiencing unintended weight loss associated with various underlying diseases.     

Induction of tetraploidy in meristematically active seeds of Japanese barberry (Berberis thunbergii var. atropurpurea) through exposure to colchicine and oryzalin

Japanese barberry (Berberis thunbergii DC) is an invasive shrub, widely naturalized across the United States, whose numerous cultivars remain an important horticultural commodity. Maintaining this crop for the future necessitates the development of sterile clones. Exposure to the mitotic inhibitors colchicine and oryzalin is a traditional method for inducing tetraploidy in breeding lines as a precursor to creating sterile genotypes. Treatments utilized pre-germinated B. t. var. atropurpurea seeds with emerged radicles. Seeds were immersed in aqueous solutions of colchicine (.02%, .05%, .1% and .2%) and oryzalin (.002%, .005%, .01% and .02%) dissolved in 1% DMSO for 6, 12 and 24 h durations. Seedling ploidy level was determined via flow cytometry following 6 and 52 weeks of growth in the greenhouse. Both anti-mitotic chemicals proved effective at inducing tetraploidy and produced comparable efficiency rates. The survival rate of treated seeds decreased in response to both increased mitotic inhibitor concentration and longer exposure duration. While exposure to oryzalin produced greater seed mortality than colchicine, most seedlings that survived had altered ploidy levels. The most efficient oryzalin concentration was 0.002% with a rating of 28%, while the most efficient colchicine concentrations were in the range from 0.05% to 0.2%. Duration of exposure to mitotic inhibitor was not a significant factor over the range from 6 to 24 h. Reversion of tetraploid plants to the diploid state occurred at a low frequency following a dormancy period. Some tetraploid seedlings derived from exposure to both chemicals displayed foliar abnormalities including irregular leaf margins and mottled lamina. The primary advantage of colchicine was low seedling toxicity, while oryzalin was notable for its ability to induce tetraploidy at low concentrations.