The pathogenesis of paraesophageal empyema in dogs and constancy of radiographic and computed tomography signs are linked to involvement of the mediastinal serous cavity

The mediastinal serous cavity is a normal anatomic space in the caudal mediastinum. Aims of this anatomic and case series study were to describe the signs of pathologic expansion of the mediastinal serous cavity observed during computed tomography (CT), review the underlying anatomy, perform a literature review, and evaluate the medical records of several dogs with mediastinal serous cavity empyema (paraesophageal empyema). The mesothelial lined mediastinal serous cavity is a cranial extension of the omental bursa, separated from the peritoneal cavity by the diaphragm, in the dorsal part of the caudal mediastinum, to the right of the esophagus, between the heart base and diaphragm. In five adult, large‐breed dogs with surgically and histologically confirmed paraesophageal empyema, macroscopic plant material was found at surgery in two dogs, adherence to adjacent lung was present in three different dogs, accessory lobectomy was performed in two dogs with subacute‐chronic pyogranulomatous pneumonia, and one dog had concurrent pyothorax and mediastinitis, but none had esophageal abnormalities. This study expands our understanding of the pathogenesis and basis for the imaging appearance of paraesophageal empyema in dogs by clarifying the underlying anatomic structures that direct development of this condition. The term empyema accurately describes this condition because the purulent material accumulates within an existing body cavity. The study also provides initial evidence that the development of paraesophageal empyema might be due to local extension of lung disease, such as foreign body migration or pneumonia. Computed tomography was helpful for diagnosis, assessing size, and determining the spread of disease.     

Effects of tillage systems and rotations on crop production for a thin Black Chernozem in the Canadian Prairies

Soil degradation is the single most important threat to global food production and security. Wind and water erosion are the main forms of this degradation, and conservation tillage represents an effective method for controlling this problem. The objective of this study was to quantify the effects of three tillage methods [zero (ZT), minimum (MT) and conventional (CT)] and three four-year crop sequences [spring wheat (Triticum aestivum L.)–spring wheat–winter wheat–fallow; spring wheat–spring wheat–flax (Linum usitatissimum L.)–winter wheat; spring wheat–flax–winter wheat–field pea (Pisum sativum L.] on crop establishment, plant height, seed weight, soil water storage, crop water use, crop water use efficiency and grain yield over a 12-year period under Canadian growing conditions. Plant establishment was not adversely affected by tillage systems or crop sequences except for flax, where a small reduction was observed with ZT and MT. Conservation tillage showed a yield benefit over CT of 7%, 12.5% and 7.4% for field pea, flax and spring wheat grown on cereal stubble, respectively over the 12 years of the study. Much of the yield increase was due to an increase in soil water in the 0–30 cm soil layer with ZT and MT. However, tillage systems had no effect on grain yield for spring wheat grown on fallow and field pea stubble due to a lack of differences in spring soil water content. Flax grown in sequence with cereals only yielded higher than when it was grown in the sequence which included field pea, even though flax was seeded on spring wheat stubble in both cases. Winter wheat yielded higher when grown on flax stubble than on spring wheat stubble. The results indicate that a one-year non-cereal break crop was enough to alleviate the negative effects of consecutive cereal crops on winter wheat. Spring wheat grown on field pea stubble always yielded more than when grown on cereal stubble. A 10% increase in water use efficiency was observed with flax grown with ZT and MT management. Crop sequence improved water use efficiency in flax and spring wheat. Growing spring wheat on field pea stubble as opposed to growing it on cereal stubble resulted in a 10% increase in water use efficiency. Overall, rainfall accounted for 73%, 72%, 67% and 65% of total water used by field pea, flax, winter wheat and spring wheat, respectively. This explains the large year effect as a result of variation in growing (May–August) season precipitation. The non-significant tillage system by year interaction implies that the positive benefits of ZT and MT occur over a wide range of growing conditions, while the absence of a tillage system by crop sequence interaction suggests that knowledge developed under CT management also applies to ZT and MT. The results of this study support the large shifts towards in conservation tillage being observed in the Canadian prairies.     

Screening events to reduce farmers' hazardous exposures

Dairy farmers may be exposed to high levels of noise and dust. Protections against these hazards exist, but many farmers do not use them. An intervention consisting of hearing and respiratory screenings combined with personalized education was implemented. This study evaluates the impact of this intervention on farmers' self-reported use of personal protective equipment (PPE) and implementation of noise and dust abatement. Participants were screened as to noise (n=209) or dust (n=392) hazards and use of PPE. Following this, they were counseled on PPE use, and identification and reduction of noise or dust hazards. Counselors sought a pledge from the farmers to eliminate hazards and increase PPE use. Farmers were subsequently surveyed and asked whether they had implemented the changes. At baseline, 70% (146/209) of farmers exposed to high levels of noise reported poor use ("sometimes", "rarely", or "never") of hearing protection. Results indicated that two months after intervention, 25.2% (28/111) of these subjects had successfully improved their PPE use. At baseline, 79% (311/392) offarmers reported poor use of respiratory protection, with 27.3% (41/150) showing improvement in PPE use within the same time. Strategies to reduce noise hazards were identified by 92.8% (194/209) of hearing screening attendees; 13.2% (18/136) successfully reduced or removed exposure. These values for dust screening attendees were 98.2% (385/392) and 30.7% (54/176), respectively. Use of this intervention appears to be an effective method for increasing PPE use on the farm. However, it is not effective for reducing noise hazards.     

Rollover protection on New York tractors and farmers' readiness for change

Tractor overturns contribute significantly to fatalities in New York State agriculture. On-site inspections a decade ago indicated that approximately 60% of tractors were without effective rollover protection. Our objectives were: to describe the current prevalence and distribution of rollover protective structures (ROPS) on New York farm tractors, to identify characteristics associated with the absence of ROPS, to explore segmenting the New York farm community on readiness for ROPS retrofitting, and to identify demographic characteristics that might assist in this segmenting. A random selection of 644 livestock, dairy, fruit, cash crop, vegetable, and organic farms were contacted for a telephone survey. Of 562 farms (87%) participating, 102 (18.1%) had all tractors equipped with ROPS and 138 (24.6%) had none. A disproportionate number of livestock, cash crop, and organic operations had no ROPS. Rates of ROPS-equipped tractors correlated directly with farm size and annual hours of tractor operation. Older farmers had a lower proportion of ROPS tractors. The presence of a child operator did not affect the proportion of ROPS tractors. After weighting the sample, the total number of non-ROPS tractors in New York is estimated at more than 80,000. In addition to providing key farm demographics, the survey enabled placement of farmers on a "stage of change" continuum related to readiness for retrofitting. Three-quarters of New York farmers are in the "precontemplation" stage of change relative to ROPS retrofitting, and this varies little by size of operation, age of farmer, or the presence of child tractor operators. Stage of change may relate to hours of tractor operation (p = 0.05) and does relate to commodity (p = 0.003) due primarily to the higher proportion of crop farmers in the earliest stage of change. The goal of retrofitting all New York farm tractors with ROPS appears nearly as daunting as it did a decade ago.     

Age‐Dependent Morphology of NADPH Diaphorase‐Positive Amacrine Cells in the Mouse Retina

NADPH diaphorase‐positive amacrine cells (NAC) were studied in retinal whole mount preparation of mice, ranging from 1 day to 30 months of age. Following a peak in number and size during early development at postnatal day 14, their number and distribution remained well preserved up to senescence. Functional considerations include immunological, vascular and neuro‐modulating aspects.     

Effects of sialidase knockout and complementation on virulence of Mycoplasma gallisepticum

Reannotation of the pathogenic Mycoplasma gallisepticum strain R(low) genome identified the hypothetical gene MGA_0329 as a homolog of the sialidase gene MS53_0199 of Mycoplasma synoviae strain MS53. Potent sialidase activity was subsequently quantitated in several M. gallisepticum strains. Because sialidase activity levels correlate significantly with differing M. synoviae strain virulence, we hypothesized this enzyme may also influence the virulence of M. gallisepticum. MGA_0329 was disrupted in strain R(low) to create mutants 6, 358 and P1C5, which resulted in the loss of sialidase activity in all three mutants. Chickens infected with the knockout mutants had significantly less severe (P<0.05) tracheal lesions and tracheal mucosal thickening than chickens infected with equal doses of strain R(low). Significantly fewer (P<0.05) CCU especially of strains 6 and P1C5 were recovered at necropsy. Mini-Tn4001tet plasmid pTF20 carrying a wild-type copy of MGA_0329 with its native promoter was used to complement the genetic lesion in strain P1C5. Three clones derived from P1C5, each having one copy of MGA_0329 stably transposed into a different site in its genome, expressed sialidase restored to wild-type activity levels (1.58×10(-8)U/CFU). Complementation of P1C5 with MGA_0329 did not restore it to wild-type levels of virulence, indicating that the contribution of sialidase to M. gallisepticum virulence is not straightforward.