In vitro culture of equine respiratory mucosa explants

An in vitro model of the upper respiratory tract of the horse was developed to investigate mechanisms of respiratory diseases. Four tissues of the upper respiratory tract of three horses were collected. Explants were maintained in culture at an air–liquid interface for 96 h. At 0, 24, 48, 72 and 96 h of cultivation, a morphometric analysis was performed using light microscopy, scanning electron microscopy and transmission electron microscopy. The explants were judged on morphometric changes of epithelium, basement membrane and connective tissue. Viability was evaluated using a fluorescent Terminal deoxynucleotidyl transferase-mediated dUTP Nick End Labelling (TUNEL) staining. No significant changes in morphometry and viability of any of the explants were observed during cultivation. Hence, the in vitro model may be useful to study infectious and non-infectious diseases at the level of the equine respiratory tract, with potential application to the development of vaccines and treatments for diseases of the respiratory tract.     

Larynx-associated lymphoid tissue (LALT) in young cattle

This paper describes the presence of lymphoid tissue in the mucosa of the bovine larynx. A total of 15 bovine larynges were examined both macroscopically after tissue fixation in acetic acid and microscopically using histology. It was found that no paraepiglottic tonsil was present in cattle, although a few lymphoid follicles were present in the mucosa at the base of the epiglottis. This result is in accordance with previous reports. In contrast, numerous lymphoid follicles were seen in the mucosa of the epiglottis and the corniculate processes of the arytenoid cartilages. This suggests that larynx-associated lymphoid tissue is present in cattle. Our observation could be of clinical importance, e.g. in the framework of the development of aerosolized vaccines.     

Dogs as vectors of Streptobacillus moniliformis infection?

Rat bite fever is a bacterial zoonosis transmitted through the bite of rats. One of the two etiological agents that cause rat bite fever is Streptobacillus moniliformis. Rat bite fever is rare and very likely under diagnosed but occurs worldwide. Other animals, like dogs and cats that have mouthed a rat are often mentioned in the literature as potential risks for the attraction of rat bite fever. However, rat bite fever caused by the bite of a dog or cat has very seldom been documented. Therefore, to identify the possible risk for humans to become infected with S. moniliformis after having been bitten by a dog that has been in contact with rats, the presence of S. moniliformis in the mouth of these dogs was tested with molecular methods. Swabs taken from the mouth of 18 dogs with proven contacts with rats were tested for the presence of S. moniliformis DNA by PCR. An amplicon of the right size was obtained in 10 of the 18 dogs. Nucleotide sequencing of five amplicons of PCR positive samples demonstrated the presence of S. moniliformis DNA in the mouth of three dogs. A bite by these dogs therefore might infect humans with S. moniliformis and cause rat bite disease.     

Colonization strategy of Campylobacter jejuni results in persistent infection of the chicken gut

Although poultry meat is now recognized as the main source of Campylobacter jejuni gastroenteritis, little is known about the strategy used by the bacterium to colonize the chicken intestinal tract. In this study, the mechanism of C. jejuni colonization in chickens was studied using four human and four poultry isolates of C. jejuni. The C. jejuni strains were able to invade chicken primary cecal epithelial crypt cells in a predominantly microtubule-dependent way (five out of eight strains). Invasion of cecal epithelial cells was not accompanied by necrosis or apoptosis in the cell cultures, nor by intestinal inflammation in a cecal loop model. C. jejuni from human origin displayed a similar invasive profile compared to the poultry isolates. Invasiveness of the strains in vitro correlated with the magnitude of spleen colonization in C. jejuni inoculated chicks. The C. jejuni bacteria that invaded the epithelial cells were not able to proliferate intracellularly, but quickly evaded from the cells. In contrast, the C. jejuni strains were capable of replication in chicken intestinal mucus. These findings suggest a novel colonization mechanism by escaping rapid mucosal clearance through short-term epithelial invasion and evasion, combined with fast replication in the mucus.     

Anatomical and histological aspects of the bovine lingual tonsil

The localization of the bovine lingual tonsil is described as a prerequisite for the removal of specified risk material from the tongue meat in order to restrict the risk arising from bovine spongiform encephalopathy (BSE) to public health. The major part of this tonsil can be located macroscopically by the openings of its follicular crypts at the root of tongue. This part consists of organized aggregations of lymph nodules. Additional solitary primary lymph nodules and diffuse accumulations of lymphocytes are macroscopically invisible but are bilaterally present in the area extending 2 cm caudal to 3 cm rostral to the last vallate papillae. By sectioning the tongue 3 cm rostral to the last vallate papillae, undermining the lingual mucosa to the level of these papillae and making a transverse cut towards the lingual process of the basihyoid bone, the greater part of the lingual tonsil can efficiently be removed. Finally, immunohistochemical staining demonstrated the presence of T and B lymphocytes, suggesting that the bovine lingual tonsil can be considered as a site where an immune response can be induced.     

Development of the conservation of Dutch coastal waters

1. Traditionally, the living and nonliving natural resources of the coastal waters of The Netherlands have been exploited. Part of this exploitation took the form of embankment and reclamation to produce new agricultural land. 2. The first nature reserve within the coastal waters was established in 1916. After this year the number of coastal nature reserves gradually increased. However, until about 1970 the status of a nature reserve provided little protection when other interests claimed the same area. 3. In the period 1965–1980 the situation changed drastically. The Dutch government took far-reaching decisions with regard to the protection of the Wadden Sea and the Oosterschelde estuary. 4. At the start of this century about 10 000 km² of coastal waters existed between the mainland coast and the three-miles territorial border of The Netherlands. Of these, 4500 km² have been embanked and reclaimed or changed into freshwater lakes, 4000 km² have protected status, and about 1500 km² within the former three-miles zone and in the Westerschelde estuary (250 km²) are still unprotected. 5. The present situation with regard to the conservation of coastal waters in The Netherlands is largely due to private initiatives. Scientists played an active part in the conservation movement by providing information, especially in the early phases of this development. © 1997 John Wiley & Sons, Ltd.     

Long-term organic farming fosters below and aboveground biota: Implications for soil quality, biological control and productivity

Organic farming may contribute substantially to future agricultural production worldwide by improving soil quality and pest control, thereby reducing environmental impacts of conventional farming. We investigated in a comprehensive way soil chemical, as well as below and aboveground biological parameters of two organic and two conventional wheat farming systems that primarily differed in fertilization and weed management strategies. Contrast analyses identified management related differences between “herbicide-free” bioorganic (BIOORG) and biodynamic (BIODYN) systems and conventional systems with (CONFYM) or without manure (CONMIN) and herbicide application within a long-term agricultural experiment (DOK trial, Switzerland). Soil carbon content was significantly higher in systems receiving farmyard manure and concomitantly microbial biomass (fungi and bacteria) was increased. Microbial activity parameters, such as microbial basal respiration and nitrogen mineralization, showed an opposite pattern, suggesting that soil carbon in the conventional system (CONFYM) was more easily accessible to microorganisms than in organic systems. Bacterivorous nematodes and earthworms were most abundant in systems that received farmyard manure, which is in line with the responses of their potential food sources (microbes and organic matter). Mineral fertilizer application detrimentally affected enchytraeids and Diptera larvae, whereas aphids benefited. Spider abundance was favoured by organic management, most likely a response to increased prey availability from the belowground subsystem or increased weed coverage. In contrast to most soil-based, bottom-up controlled interactions, the twofold higher abundance of this generalist predator group in organic systems likely contributed to the significantly lower abundance of aboveground herbivore pests (aphids) in these systems. Long-term organic farming and the application of farmyard manure promoted soil quality, microbial biomass and fostered natural enemies and ecosystem engineers, suggesting enhanced nutrient cycling and pest control. Mineral fertilizers and herbicide application, in contrast, affected the potential for top-down control of aboveground pests negatively and reduced the organic carbon levels. Our study indicates that the use of synthetic fertilizers and herbicide application changes interactions within and between below and aboveground components, ultimately promoting negative environmental impacts of agriculture by reducing internal biological cycles and pest control. On the contrary, organic farming fosters microbial and faunal decomposers and this propagates into the aboveground system via generalist predators thereby increasing conservation biological control. However, grain and straw yields were 23% higher in systems receiving mineral fertilizers and herbicides reflecting the trade-off between productivity and environmental responsibility.