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Biomedical subjects

A van der Linden

Publications and source records attributed to A van der Linden.

4 recordsLinked to original sources
PubMed2004

Amblyseius andersoni Chant (Acari: Phytoseiidae), a successful predatory mite on Rosa spp.

Roses on commercial nurseries commonly suffer from attacks by the two-spotted spider mite, Tetranychus urticae, which have a negative influence on growth and quality. The aim of this project is to find natural enemies that are well adapted to roses, and may improve biological control. At different sites such as a plant collection garden, public parks and field boundaries, leaves were sampled from roses to identify the indigenous species of predatory mites. Amblyseius andersoni was amongst other species frequently found, which suggests that this species thrives well on roses. The possibility for biological control of spider mites with A. andersoni was investigated both in container roses outdoors and in glasshouses. In plots of outdoor roses artificially infested with spider mites, the following treatments were carried out: spider mites alone (untreated plot), Amblyseius andersoni Amblyseius andersoni and ice plants, Neoseiulus californicus, Neoseiulus californicus and ice plants. There were four replications of the treatments. The ice plants, Delosperma cooperi, were added to some treatments to supply pollen as extra food for the predatory mites. Natural enemies such as Chrysoperla spp., Conwentzia sp., Orius sp., Stethorus punctillum, and Feltiella acarisuga occurred naturally and contributed to the control of spider mites. After one month the spider mites were eradicated in all treatments. At the end of the trial, predatory mites were collected from all plots for identification. The ratio of Amblyseius andersoni to Neoseiulus californicus was approximately 9:1. There was no obvious effect of the ice plants on the number of predatory mites. On a nursery, where new roses are bred and selected, Amblyseius andersoni was released in three glasshouses after one early treatment with bifenazate against two-spotted spider mite Tetranychus urticae. In two of these glasshouses Neoseiulus californicus was also released. Samples, which were taken in the summer months showed that the spider mites were kept at a very low level. Amblyseius andersoni was found, even if spider mites were absent. Rose plants infested with spider mites, that were brought in to the glasshouses later developed spider mite 'hotspots'. Phytoseiulus persimilis was introduced in the hot spots and contributed to the control along with Neoseiulus californicus, Amblyseius andersoni and naturally occurring Feltiella acarisuga. These observations showed that Amblyseius andersoni is a good candidate for preventing spider mite outbreaks, as it easily survives without spider mites. This predatory mite is able to survive on other food, including thrips and fungal spores.

Acaridae↗
PubMed2000

Mycobacterium xenopi infection of the spine: a case report and literature review.

STUDY DESIGN: A case report of Mycobacterium xenopi. OBJECTIVES: To present a case report of a vertebral osteomyelitis caused by M. xenopi and to review the world literature on the subject. SUMMARY OF BACKGROUND DATA: M. xenopi is most commonly a pulmonary pathogen in immunosuppressed patients or those with underlying lung disease. Infection of the spine is very rare, with only four cases reported. Three of these cases occurred in immunosuppressed patients, and the fourth in a patient with previous tuberculosis osteomyelitis of the spine. METHODS: The information was obtained from a review of the patient's clinical notes and follow-up appointments. RESULTS: The patient was a 73-year-old woman with an M. xenopi osteomyelitis of T6-T7, confirmed by magnetic resonance imaging and a computed tomography-guided biopsy. She was treated with surgical decompression and stabilization before a 2-year antibiotic regimen was begun. At follow-up assessment 1 year after the antibiotics were finished, she still had some ongoing back pain, but no evidence of relapse. CONCLUSIONS: This is the first reported case of an M. xenopi infection of the spine in a patient with no predisposing factors. This type of infection can be difficult to treat, with a high relapse rate reported despite prolonged courses of antibiotics.

Aged↗
PubMed1997

Watershed-based segmentation of 3D MR data for volume quantization.

The aim of this work is the development of a semiautomatic segmentation technique for efficient and accurate volume quantization of Magnetic Resonance (MR) data. The proposed technique uses a 3D variant of Vincent and Soilles immersion-based watershed algorithm that is applied to the gradient magnitude of the MR data and that produces small volume primitives. The known drawback of the watershed algorithm, oversegmentation, is strongly reduced by a priori application of a 3D adaptive anisotropic diffusion filter to the MR data. Furthermore, oversegmentation is a posteriori reduced by properly merging small volume primitives that have similar gray level distributions. The outcome of the proceeding image processing steps is presented to the user for manual segmentation. Through selection of volume primitives, the user quickly segments of first slice, which contains the object of interest. Afterwards, the subsequent slices are automatically segmented by extrapolation. Segmentation results are contingently manually corrected. The proposed segmentation technique is tested on phantom objects, where segmentation errors less than 2% are observed. In addition, the technique is demonstrated on 3D MR data of the mouse head from which the cerebellum is extracted. Volumes of the mouse cerebellum and the mouse brains in toto are calculated.

Algorithms↗