Virus adaptation to quantitative plant resistance: erosion or breakdown?

Adaptation of populations to new environments is frequently costly due to trade-offs between life history traits, and consequently, parasites are expected to be locally adapted to sympatric hosts. Also, during adaptation to the host, an increase in parasite fitness could have direct consequences on its aggressiveness (i.e. the quantity of damages caused to the host by the virus). These two phenomena have been observed in the context of pathogen adaptation to host's qualitative and monogenic resistances. However, the ability of pathogens to adapt to quantitative polygenic plant resistances and the consequences of these potential adaptations on other pathogen life history traits remain to be evaluated. Potato virus Y and two pepper genotypes (one susceptible and one with quantitative resistance) were used, and experimental evolutions showed that adaptation to a quantitative resistance was possible and resulted in resistance breakdown. This adaptation was associated to a fitness cost on the susceptible cultivar, but had no consequence either in terms of aggressiveness, which could be explained by a high tolerance level, or in terms of aphid transmission efficiency. We concluded that quantitative resistances are not necessarily durable but management strategies mixing susceptible and resistant cultivars in space and/or in time should be useful to preserve their efficiency.

Mode of reproduction and amplified fragment length polymorphism variation in purple needlegrass (Nassella pulchra): utilization of natural germplasm sources.

A dominant plant of the California grasslands, purple needlegrass [Nassella pulchra (Hitchc.) Barkworth] is an important revegetation species in its native range. The amplified fragment length polymorphism (AFLP) method was used to elucidate mode of reproduction and nucleotide variation among 11 natural populations and three selected natural germplasm releases of N. pulchra. A total of 12 co-dominant AFLPs, informative within eight populations, failed to reveal any heterozygous individuals, indicating very high selfing rates (S(H)=1). Estimates of nucleotide diversity within populations ranged from 0 to 0.00069 (0.00035 average), whereas the total nucleotide divergence among populations ranged from 0.00107 to 0.00382 (0.00247 average). Measures of population differentiation (GS) in terms of Shannon-Weaver diversity values and estimated nucleotide substitutions were 0.90 and 0.86, respectively. Although some of the sample populations contained a mixture of true breeding genotypes, most populations could be distinguished unambiguously. Moreover, geographical distance between the natural source populations was significantly correlated with genetic distance (r = 0.60) among the corresponding sample populations. Results indicate that inbreeding, combined with founder effects and/or selection, has contributed to the differentiation of N. pulchra populations. Foundation seed populations of the selected natural germplasm releases were genetically well defined and most similar to natural seed collected near the corresponding source populations. Thus, these commercial germplasm sources will be made practically available and useful for conservation plantings within the intended areas of utilization.

Defective trafficking and function of KATP channels caused by a sulfonylurea receptor 1 mutation associated with persistent hyperinsulinemic hypoglycemia of infancy.

The ATP-sensitive potassium channel (K(ATP)) regulates insulin secretion in pancreatic beta cells. Loss of functional K(ATP) channels because of mutations in either the SUR1 or Kir6.2 channel subunit causes persistent hyperinsulinemic hypoglycemia of infancy (PHHI). We investigated the molecular mechanism by which a single phenylalanine deletion in SUR1 (DeltaF1388) causes PHHI. Previous studies have shown that coexpression of DeltaF1388 SUR1 with Kir6.2 results in no channel activity. We demonstrate here that the lack of functional expression is due to failure of the mutant channel to traffic to the cell surface. Trafficking of K(ATP) channels requires that the endoplasmic reticulum-retention signal, RKR, present in both SUR1 and Kir6.2, be shielded during channel assembly. To ask whether DeltaF1388 SUR1 forms functional channels with Kir6.2, we inactivated the RKR signal in DeltaF1388 SUR1 by mutation to AAA (DeltaF1388 SUR1(AAA)). Inactivation of similar endoplasmic reticulum-retention signals in the cystic fibrosis transmembrane conductance regulator has been shown to partially overcome the trafficking defect of a cystic fibrosis transmembrane conductance regulator mutation, DeltaF508. We found that coexpression of DeltaF1388 SUR1(AAA) with Kir6.2 led to partial surface expression of the mutant channel. Moreover, mutant channels were active. Compared with wild-type channels, the mutant channels have reduced ATP sensitivity and do not respond to stimulation by MgADP or diazoxide. The RKR --> AAA mutation alone has no effect on channel properties. Our results establish defective trafficking of K(ATP) channels as a molecular basis of PHHI and show that F1388 in SUR1 is critical for normal trafficking and function of K(ATP) channels.

[Delayed hypersensitivity to evoked antigens: normal values in Chilean young adults]. / Hipersensibilidad retardada a antígenos de evocación: valores normales en adultos jóvenes chilenos.

Delayed hypersensitivity skin test are widely accepted as in vivo measure of cellular immunity. Since genetic and environmental factors may affect these tests, each population must establish its own normal values. The aim of this work was to study delayed hypersensitivity in Chilean normal young adults. We studied the response to eight antigens using the Multitest CMI (Rhodia Merieux) in 50 students (22 females, 28 males), aged 18 to 25 years old. Skin tests were read at 24, 48 and 72 hours. At 48 Hours, 60% of women responded to 3 and 68% of men to 4 antigens. A mean response to 3.6 antigens was observed. Total score in men and women were 19.5 +/- 7.3 and 12.2 +/- 6.5 mm respectively (p < 0.05). These figures are different from those published abroad and confirm the need for national standards.

[Reconstruction of the orbital floor using skull grafts obtained during the treatment of craniostenoses and irradiated by gamma rays]. / Reconstruction du plancher de l'orbite à l'aide de greffons de voûte crânienne récupérés lors du traitement des crâniosténoses et irradiés par les rayons gamma.

The authors use skull grafts obtained during the treatment of craniostenoses and sterilized by gamma radiation to reconstruct the orbital walls. They describe the practical modalities of this technique and report a series of 26 cases in which no incidents of complications were observed.

[Maxillofacial manifestations of systemic scleroderma. Apropos of a case]. / Les manifestations maxillo-faciales de la sclérodermie généralisée. A propos d'une observation.

The authors relate the case of one patient 54 years old having a progressive systemic sclerosis. It is a rare progressive disease of unknown etiology. The patient was first seen in 1983, with lesions on the face. The following is the report of this patient who demonstrated resorption of the angle of the mandible, atrophy of the zygomatic arches, characteristics facial muscles and cutaneous lesions.

[Anterior vertical insufficiency of maxillary origin]. / L'insuffisance verticale antérieure d'origine maxillaire.

The authors present 10 cases of anterior vertical insufficiency of maxillary origin. They analyse the principal clinical and radiological elements of this syndrome. They discuss possible therapy involving Lefort I lowering osteotomy with bone grafting and possible mandibular surgery.

[The value of fine needle biopsy in the diagnosis of tumors of the salivary glands]. / Intérêt de la cytoponction à l'aiguille fine dans le diagnostic des tuméfactions des glandes salivaires.

Aspiration biopsy by fine needle from the major salivary glands has been studied. To evaluate this form of biopsy, 34 patients with salivary gland enlargement were examined. By this technic, 29 has confirmative histology. The method proved complication free and accurate. The safety of this biopsy form has been proven. The accuracy of this method may be high, particularly, for the most common benign mixed tumor. Thus this procedure is suggested for initial examination of all lesions of the salivary gland.