A New Natural Planthopper Vector of Stolbur Phytoplasma in the Genus Pentastiridius (Hemiptera: Cixiidae)

A new disease of sugar beet called Syndrome des Basses Richesses, which appeared in Burgundy and Franche-Comté, France, in 1991, is of uncertain aetiology. However, evidence for aerial transmission of the disease, symptom similarity with yellow wilt and preliminary results of phytoplasma detection, support the hypothesis of a phytoplasma being associated to the disease. A search for a natural phytoplasma vector, was conducted in Franche-Comté in 1997 and 1998, in an area where sugar beet crops had been affected since 1996. A cixiid, tentatively identified as Pentastiridius beieri, not described in the preceding years and not formerly reported as a phytoplasma vector, was present in sugar beet plots in high populations from June to August in 1997 and 1998. Individuals were captured and used for transmission experiments to periwinkle and sugar beet seedlings. They were further tested for the presence of a phytoplasma in their body, using PCR amplification of 16S rDNA of phytoplasmas. In 1997 and 1998, from 2% to 13.3% of the individuals carried a stolbur phytoplasma and insects which tested positive, appeared to have transmitted, through feeding, a stolbur phytoplasma to periwinkles and to sugar beets. This cixiid, whose vectoring capacity of stolbur phytoplasma to plants, is now clearly demonstrated, is available for experimental inoculations, in order to examine the role of phytoplasmas in the Syndrome des Basses Richesses, through the observation of symptom expression in phytoplasma-inoculated plants.     

Vertebral osteomyelitis in a calf--the significance of neurologic studies in veterinary medicine for newborn and young animals

By a 4 weeks old being laid up calf the possibilities of the clinician's neurologic examination and further diagnostic aids (radiography, tomography and myelography) are presented.     

Biochemical and morphological characterization of potato clones differing in their resistance to late blight

Summary Morphological and biochemical parameters that could be involved in resistance to late blight were studied in non-infected and in infected potato hybrids resulting from a cross betweenSolanum phureja, resistant toPhytophthora infestans, and a susceptibleSolanum tuberosum. Some morphological differences between resistant and susceptible hybrids, indicating a positive correlation between stem diameter and phloem thickness in the stem and resistance toP. infestans, were observed. The lignin content in the leaves of the resistant hybrid rose upon infection byP. infestans. In the leaves of the susceptible hybrid, a diminution of the lignin content could be observed upon infection byP. infestans. In the same context, peroxidasic activity raised upon infection byP. infestans in both resistant and susceptible hybrids. Further characterization of the hybrid clones based on the polymorphism of peroxidases was attempted using isoelectric focusing.     

Decreased nitrogen rates and irrigation effect on celery yield and internal quality

The effect of decreased nitrogen rates (90, 60 and 30 kg N/ha) with and without irrigation on celery yield quantity and internal quality were studied in field experiments in 1993 and 1994. The decreased nitrogen rates reduced yields in both years. In the dry and warm conditions of 1994 nitrogen × irrigation interaction was clearly observed; irrigation increased yield more at higher nitrogen rates than at lower nitrogen rates. In the rainy conditions of 1993 irrigation did not effect the yield level.On the other hand, in both years, decreased nitrogen rates increased dry matter, vitamin C and dietary fiber contents, and nitrogen had a minor effect on total sugar content. In 1994 alpha- and beta carotene and thiamin were also analyzed but nitrogen had no effect on them. Irrigation increased dry matter and total sugar contents at the two lowest nitrogen rates in 1994, but decreased vitamin C contents in both years. There was also slight evidence that irrigation might decrease alpha- and beta-carotene and thiamin contents.     

Cardiolipin polyspecific autoreactivity in two broadly neutralizing HIV-1 antibodies

The design of a human immunodeficiency virus-1 (HIV-1) immunogen that can induce broadly reactive neutralizing antibodies is a major goal of HIV-1 vaccine development. Although rare human monoclonal antibodies (mAbs) exist that broadly neutralize HIV-1, HIV-1 envelope immunogens do not induce these antibody specificities. Here we demonstrate that the two most broadly reactive HIV-1 envelope gp41 human mAbs, 2F5 and 4E10, are polyspecific autoantibodies reactive with the phospholipid cardiolipin. Thus, current HIV-1 vaccines may not induce these types of antibodies because of autoantigen mimicry of the conserved membrane-proximal epitopes of the virus. These results may have important implications for generating effective neutralizing antibody responses by using HIV-1 vaccines.