José Díaz

Induction of shikimate dehydrogenase and peroxidase in pepper (Capsicum annuum L.) seedlings in response to copper stress and its relation to lignification

Pepper (Capsicum annuum L.) plants growing in a nutrient solution with excess copper, showed an increase in shikimate dehydrogenase (SKDH, EC 1.1.1.25) and peroxidase (EC 1.11.1.7) activities in the hypocotyl. In the roots, peroxidase was also induced, but SKDH activity per organ was depleted rather than enhanced. Copper stress caused stunting in the plants, reflected by a decrease in the fresh weight of all the organs. In the hypocotyl, the induction of both enzymatic activities was associated with the accumulation of soluble phenolics and lignin. The two SKDH isozymes present in the control hypocotyls (SKDH-3 and SKDH-4) increased in a similar proportion after copper stress. In the case of peroxidases, two new isozymes (PRX-A2 and PRX-A4) were detected in copper-stressed hypocotyls, and the other two isoperoxidases, PRX-B and PRX-A3, were enhanced c. 10 and three times, respectively, with respect to the control. The application of the chelator EDTA was able to counteract all the stress effects of the metal cited above. The role of these enzymes in phenolic metabolism under heavy metal stress is discussed.

Differential activation of defense-related genes in susceptible and resistant pepper cultivars infected with Phytophthora capsici

This study investigated the expression pattern of genes encoding for a basic PR-1 protein, a basic beta-1,3-glucanase, a peroxidase, and a sesquiterpene cyclase involved in defense responses in three pepper cultivars with different levels of resistance to Phytophthora capsici. All genes were up-regulated in infected stems of the pepper cultivars, with expression being detected 8h post-inoculation. mRNA levels of these genes increased markedly by 24h post-inoculation, and maximal induction levels were observed for the PR-1 and sesquiterpene cyclase genes. PR-1, peroxidase, and sesquiterpene genes were always expressed at higher levels in resistant cultivars than in the susceptible cultivar, although up-regulation was observed in both, suggesting that the differences between these pepper genotypes in susceptibility and resistance are a matter of the timing and magnitude of the defense response.

Long-Term Outcomes of Stereotactic Radiosurgery for Treatment of Cavernous Sinus Meningiomas

PURPOSE Patients with cavernous sinus meningiomas (CSM) have an elevated risk of surgical morbidity and mortality. Recurrence is often observed after partial resection. Stereotactic radiosurgery (SRS), either alone or combined with surgery, represents an important advance in CSM management, but long-term results are lacking. METHODS AND MATERIALS A total of 88 CSM patients, treated from January 1991 to December 2005, were retrospectively reviewed. The mean follow-up was 86.8 months (range, 17.1-179.4 months). Among the patients, 22 were followed for more than 10 years. There was a female predominance (84.1%). The age varied from 16 to 90 years (mean, 51.6). In all, 47 patients (53.4%) received SRS alone, and 41 patients (46.6%) had undergone surgery before SRS. A dose of 14 Gy was prescribed to isodose curves from 50% to 90%. In 25 patients (28.4%), as a result of the proximity to organs at risk, the prescribed dose did not completely cover the target. RESULTS After SRS, 65 (73.8%) patients presented with tumor volume reduction; 14 (15.9%) remained stable, and 9 (10.2%) had tumor progression. The progression-free survival was 92.5% at 5 years, and 82.5% at 10 years. Age, sex, maximal diameter of the treated tumor, previous surgery, and complete target coverage did not show significant associations with prognosis. Among the 88 treated patients, 17 experienced morbidity that was related to SRS, and 6 of these patients spontaneously recovered. CONCLUSIONS SRS is an effective and safe treatment for CSM, feasible either in the primary or the postsurgical setting. Incomplete coverage of the target did not worsen outcomes. More than 80% of the patients remained free of disease progression during long-term follow-up.

Hormonal regulation of the basic peroxidase isoenzyme from Zinnia elegans

Xylem differentiation in plants is under strict hormonal regulation. Auxins and cytokinins, together with brassinosteroids (BRs), appear to be the main hormones controlling vascular differentiation. In this report, we study the effect of these hormones on the basic peroxidase isoenzyme from Zinnia elegans (ZePrx), an enzyme involved in lignin biosynthesis. Results showed that auxins and cytokinins induce ZePrx, similarly to the way in which they induce seedling secondary growth (in particular, metaxylem differentiation). Likewise, the exogenous application of BR reduces the levels of ZePrx, in a similar way to their capacity to inhibit seedling secondary growth. Consistent with this notion, the exogenous application of BR reverses the auxin/cytokinin-induced ZePrx expression, but has no effect on the auxin/cytokinin-induced secondary growth. This differential hormonal response is supported by the analysis of the ZePrx promoter, which contains (a) cis-elements directly responsive to these hormones and (b) cis-elements targets of the plethora of transcription factors, such as NAC, MYB, AP2, MADS and class III HD Zip, which are up-regulated during the auxin- and cytokinin-induced secondary growth. Taken together, these results suggest that ZePrx is directly and indirectly regulated by the plethora of hormones that control xylem differentiation, supporting the role of ZePrx in xylem lignification.

Wound-induced shikimate dehydrogenase and peroxidase related to lignification in pepper (Capsicum annuum L.) leaves

Summary Wounding on non-excised Capsicum annuum leaves, maintained on the whole growing plant, causes an increase in shikimate dehydrogenase (SKDH, EC 1.1.1.25) and peroxidase (EC 1.11.1.7) activity. The observed induction of both enzymatic activities was related to lignin accumulation, and in the case of peroxidase, it was located in the vicinity of the wounds. However, wounding did not cause changes in soluble phenolic compounds. PAGE analysis showed that the shikimate dehydrogenase pattern was the same in both control and wounded leaves, but each isozyme was enhanced to a different degree: SKDH-1 = SKDH-2 > SKDH-5 > SKDH-4 > SKDH-3. The relationship between the degree of induction and both subcellular location and biosynthetic function is proposed. In the case of peroxidases, one new acidic isozyme (PRX-A2, pI 4.5) was detected by isoelectric focusing in wounded leaves, and another one (PRX-A4, pI 3.7) was enhanced more than 8 times with respect to control leaves. The possible role of these isozymes in lignin biosynthesis and wound healing is discussed.

Wounding induces local resistance but systemic susceptibility to Botrytis cinerea in pepper plants

Cotyledon wounding in pepper caused the early generation of hydrogen peroxide both locally (cotyledons) and systemically (upper true leaves). However, 72 h later there is a different wound response between local and systemic organs, as shown by resistance to the pathogenic fungus Botrytis cinerea, that increased locally and decreased systemically. Signaling by ethylene and jasmonic acid was assessed by using two inhibitors: 1-methylcyclopropene (MCP, inhibitor of ethylene receptors) and ibuprofen (inhibitor of jasmonate biosynthesis). MCP did not affect the modulation of resistance levels to Botrytis by wounding, ruling out the involvement of ethylene signaling. Ibuprofen did not inhibit wound-induced resistance at the local level, but inhibited wound-induced systemic susceptibility. Moreover, changes of biochemical and structural defenses in response to wounding were studied. Peroxidase activity and the expression of a peroxidase gene (CAPO1) increased locally as a response to wounding, but no changes were observed systemically. Lignin deposition was induced in wounded cotyledons, but was repressed in systemic leaves of wounded plants, whereas soluble phenolics did not change locally and decreased systemically. The expression of two other genes involved in plant defense (CABPR1 and CASC1) was also differentially regulated locally and systemically, pointing to a generalized increase in plant defenses at the local level and a systemic decrease as a response to wounding. Wound-induced defenses at the local level coincided with resistance to the necrotroph fungus B. cinerea, whereas depleted defenses in systemic leaves of wounded plants correlated to induced susceptibility against this pathogen. It may be that the local response acts as a sink of energy resources to mount a defense against pathogens, whereas in systemic organs the resources for defense are lower.

Outcome for Patients with Essential Trigeminal Neuralgia Treated with Linear Accelerator Stereotactic Radiosurgery

Background: Stereotactic radiosurgery (SRS) is one option for treatment of trigeminal neuralgia, after unsuccessful conservative approaches. Objectives: The objective of this study was to retrospectively evaluate our institutional results in the management of patients with idiopathic trigeminal neuralgia treated with linear accelerator SRS. Methods: Fifty-two patients were treated between January 1998 and December 2009 and were followed for more than 6 months (median: 26.6 months). Forty-seven patients (90%) had undergone previous surgery before SRS. The target dose ranged from 50 to 80 Gy. Results: After SRS, 9 patients presented complete remission of the pain, and 21 were pain free but still under medication. Eleven patients reported a relief of more than 50% in crisis frequency. In 9 patients, no significant improvements were seen, and 2 presented an exacerbation of the pain. After an average period of 20 months, 15 patients reported pain recurrence. Results were better in patients older than 60 years (p = 0.019). Nineteen patients presented facial numbness after SRS, with a trend toward favorable treatment response (p = 0.06). Conclusion: SRS is an effective alternative to the treatment of essential trigeminal neuralgia, with long-lasting pain relief in more than 50% of the patients. Better results were seen with patients aged more than 60 years.

New bricks on the wall of induced resistance: salicylic acid receptors and transgenerational priming

In nature, plants have to cope with different types of stress. Stress by pathogens can be avoided through a plant response called Systemic Acquired Resistance (SAR). SAR is regulated by salicylic acid amongst other signals. Recently, several findings help us to have a deeper knowledge of SAR. On one hand, two different research groups have reported three different putative salicylic acid receptors; on the other hand, another two groups of scientists have found evidence about the basis of transgenerational priming in inducing resistance against pathogens. All these discoveries are discussed in the frame of the recent literature.

Long-term outcomes after radiosurgery for glomus jugulare tumors

Aims and background: The treatment of glomus jugulare tumors (GJT) remains controversial due to high morbidity. Historically, these tumors have primarily been managed surgically. The purpose of this retrospective review was to assess the tumor and clinical control rates as well as long-term toxicity of GJT treated with radiosurgery. Methods: Between 1993 and 2014, 30 patients with GJT (31 tumors) were managed with radiosurgery. Twenty-one patients were female and the median age was 59 years. Twenty-eight patients (93%) were treated with radiosurgery, typically at 14 Gy (n = 26), and 2 patients (7%) with stereotactic radiosurgery. Sixteen cases (52%) had undergone prior surgery. Results: The mean follow-up was 4.6 years (range 1.5–12). Crude overall survival, tumor control, clinical control, and long-term grade 1 toxicity rates were 97%, 97%, 97%, and 13% (4/30), respectively. No statistically significant risk factor was associated with lower tumor control in our series. Univariate analysis showed a statistically significant association between patients having 1 cranial nerve (CN) involvement before radiosurgery and a higher risk of lack of improvement of symptoms (odds ratio 5.24, 95% confidence interval 1.06–25.97, p = .043). Conclusions: Radiosurgery is an effective and safe treatment modality for GJT. Patients having 1 CN involvement before radiosurgery show a higher risk of lack of improvement of symptoms.

Vanillyl nonanoate induces systemic resistance and lignification in pepper plants

The treatment of the cotyledons of pepper plants with vanillyl nonanoate (VNT), a synthetic capsinoid similar to capsiate, protected systemically the plant against a root pathogen (the hemibiotrophic oomycete Phytophthora capsici) and an aerial pathogen (the necrotrophic fungus Botrytis cinerea). VNT treatment reduced both the symptoms and the colonization by these pathogens. VNT induced systemically two PR (Pathogenesis-related) genes and a gene involved in phytoalexin biosynthesis. VNT also induced systemically the reinforcement of cell walls with lignin both in the roots and the leaves. The increase in lignin was correlated with an increase in peroxidase gene expression and activity, pointing to the role of this enzyme in lignin polymerization. The results suggest that VNT induces systemic resistance at least in part by means of lignification.