Browsing by Author "González, S"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    BRAF mutation -: A frequent event in benign, atypical, and malignant melanocytic lesions of the skin
    (2003) Uribe, P; Wistuba, II; González, S
    BRAF mutations have recently been detected with a high frequency (66%) in cutaneous melanoma. All those mutations are activating, with a single substitution (T1796A) at codon 599 (V599E) accounting for over 90%. To investigate the stage in which those mutations occur in the currently proposed sequential malignant transformation of melanocytes, 22 benign melanocytic nevi, 23 melanocytic atypical nevi, and 25 primary cutaneous melanoma from 63 different patients were examined for BRAF mutations using DNA extracted from microdissected formalin-fixed and paraffin-embedded tissues, and a two-round PCR-RFLP-based strategy. A subset of samples was sequenced for mutation confirmation. Sixteen benign (73%) and eleven atypical (52%) melanocytic nevi, and thirteen melanoma (56%) demonstrated BRAF mutations at codon 599, and no statistically significant differences were detected among all three types of lesions. No mutations were demonstrated in microdissected epidermal keratinocytes adjacent to melanocytic lesions having BRAF mutations. No correlation was detected between BPAF mutational status and age, sun exposure, and Clark's level in malignant melanoma. However, comparing only atypical nevi and melanoma lesions the frequency of BRAF mutation is significantly greater in male (78%) than female (35%) patients (P = 0.0194). The previously described T1796A point mutation was detected in 17 of 18 mutated samples, and a novel mutation consisting of a substitution of valine for lysine (GT1795-96AA) was detected in one melanoma case. Our findings of a high frequency of BRAF mutations at codon 599 in benign metanocytic lesions of the skin indicate that this mutation is not sufficient by itself for malignant transformation.
  • Thumbnail Image
    Item
    Continuum Foreground Polarization and NaI Absorption in Type Ia SNe
    (2017) Zelaya, P; Clocchiatti, Alejandro; Baade, D; Hoflich, P; Maund, J; Patat, F; Quinn, Jason Lee; Reilly, E; Wang, L; Wheeler, J; Forster, F; González, S
  • No Thumbnail Available
    Item
    Failure of high doses of calcitriol and hypercalcaemia to induce apoptosis in hyperplastic parathyroid glands of azotaemic rats
    (2001) Jara, A; González, S; Felsenfeld, AJ; Chacón, C; Valdivieso, A; Jalil, R; Chuaqui, B
    Background. Whether calcitriol administration, which is used to treat secondary hyperparathyroidism in dialysis patients, induces regression of parathyroid-gland hyperplasia remains a subject of interest and debate. If regression of the parathyroid gland were to occur, the presumed mechanism would be apoptosis. However, information on whether high doses of calcitriol can induce apoptosis of parathyroid cells in hyperplastic parathyroid glands is lacking. Consequently, high doses of calcitriol were given to azotaemic rats and the parathyroid glands were evaluated for apoptosis.
  • No Thumbnail Available
    Item
    Sn 2005bf
    (2006) Folatelli, G; Contreras, C; Phillips, MM; Woosley, SE; Blinnikov, S; Morrell, N; Suntzeff, NB; Lee, BL; Hamuy, M; González, S; Krzeminski, W; Roth, M; Li, WD; Filippenko, AV; Foley, RJ; Freedman, WL; Madore, BF; Persson, SE; Murphy, D; Boissier, S; Galaz, G; González, L; McCarthy, PJ; McWilliam, A; Pych, W
    We present u'g'r'i'BV photometry and optical spectroscopy of the Type Ib/Ic SN 2005bf covering the first similar to 100 days following discovery. The u'g'BV light curves displayed an unprecedented morphology among Type Ib/Ic supernovae, with an initial maximum some 2 weeks after discovery and a second, main maximum about 25 days after that. The bolometric light curve indicates that SN 2005bf was a remarkably luminous event, radiating at least 6.3 x 10(42) ergs s(-1) at maximum light and a total of 2.1 x 10(49) ergs during the first 75 days after the explosion. Spectroscopically, SN 2005bf underwent a unique transformation from a Type Ic-like event at early times to a typical Type Ib supernova at later phases. The initial maximum in u'g'BV was accompanied by the presence in the spectrum of high-velocity (> 14,000 km s(-1)) absorption lines of Fe II, Ca II, and H I. The photospheric velocity derived from spectra at early epochs was below 10,000 km s(-1), which is unusually low compared with ordinary Type Ib supernovae. We describe one-dimensional computer simulations that attempt to account for these remarkable properties. The most favored model is that of a very energetic (2 x 10(51) ergs), asymmetric explosion of a massive ( 8.3 M-circle dot) Wolf-Rayet WN star that had lost most of its hydrogen envelope. We speculate that an unobserved relativistic jet was launched producing a two-component explosion consisting of ( 1) a polar explosion containing a small fraction of the total mass and moving at high velocity and ( 2) the explosion of the rest of the star. At first, only the polar explosion is observed, producing the initial maximum and the high-velocity absorption-line spectrum resembling a Type Ic event. At late times, this fast- moving component becomes optically thin, revealing the more slowly moving explosion of the rest of the star and transforming the observed spectrum to that of a typical Type Ib supernova. If this scenario is correct, then SN 2005bf is the best example to date of a transition object between normal Type Ib/Ic supernovae and gamma-ray bursts.
  • No Thumbnail Available
    Item
    Subcellular localization of catalase in sea urchin (Tetrapigus niger) gametes
    (1997) Figueroa, C; Kawada, ME; Munizaga, A; González, S; Barros, C; Koenig, C; Santos, MJ
    Peroxisomes are essential subcellular organelles that appear to be derived from pre existing organelles. To test the presence of peroxisomes in sea urchin (Tetrapigus niger) sperm and eggs, we performed biochemical and morphological experiments to evaluate the subcellular distribution of catalase as the typical peroxisomal marker. In sea urchin sperm, we found that catalase is localized in the cell cytosol. In contrast, sea urchin eggs contain sedimentable catalase, presumably contained in peroxisome-like structures detected by immunomicroscopy and by cytochemistry. Our results show, for the first time, evidence for the presence of peroxisome-like structures in sea urchin eggs and provide evidence for the peroxisome biogenesis hypothesis by division of preexisting organelles. (C) 1997 Elsevier Science Inc.