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Biomedical subjects

L Burgos

Publications and source records attributed to L Burgos.

At least 19 recordsLinked to original sources
PubMed2004

Analysis of the S-locus structure in Prunus armeniaca L. Identification of S-haplotype specific S-RNase and F-box genes.

The gametophytic self-incompatibility (GSI) system in Rosaceae has been proposed to be controlled by two genes located in the S -locusan S-RNase and a recently described pollen expressed S -haplotype specific F-box gene (SFB). However, in apricot (Prunus armeniaca L.) these genes had not been identified yet. We have sequenced 21 kb in total of the S -locus region in 3 different apricot S -haplotypes. These fragments contain genes homologous to the S-RNase and F-box genes found in other Prunus species, preserving their basic gene structure features and defined amino acid domains. The physical distance between the F-box and the S-RNase genes was determined exactly in the S2-haplotype (2.9 kb) and inferred approximately in the S 1-haplotype (< 49 kb) confirming that these genes are linked. Sequence analysis of the 5' flanking regions indicates the presence of a conserved region upstream of the putative TATA box in the S-RNase gene. The three identified S-RNase alleles (S1, S2 and S4) had a high allelic sequence diversity (75.3 amino acid identity), and the apricot F-box allelic variants (SFB1, SFB2 and SFB4) were also highly haplotype-specific (79.4 amino acid identity). Organ specific-expression was also studied, revealing that S1- and S2-RNases are expressed in style tissues, but not in pollen or leaves. In contrast, SFB1 and SFB2 are only expressed in pollen, but not in styles or leaves. Taken together, these results support these genes as candidates for the pistil and pollen S-determinants of GSI in apricot.

5' Flanking Region↗
PubMed2003

Construction and application of a bacterial artificial chromosome (BAC) library of Prunus armeniaca L. for the identification of clones linked to the self-incompatibility locus.

To facilitate gene discovery in the Rosaceae, a bacterial artificial chromosome (BAC) library was constructed using high-molecular-weight (HMW) DNA from apricot leaves (Prunus armeniaca L.). The library contains 101,376 clones (264, 384-well plates) with an average insert size of 64 kb, equivalent to 22-fold genome coverage. In the first application of this library, high-density filters were screened for self-incompatibility genes using apricot DNA probes. Eight positive BAC clones were detected and fingerprinted to determine clone relationships and assemble contigs. These results demonstrate the suitability of this library for gene identification and physical mapping of the apricot genome.

Autoimmunity↗
PubMed2003

Ethylene inhibitors and low kanamycin concentrations improve adventitious regeneration from apricot leaves.

An improved method for adventitious regeneration from apricot leaves is described. The use of the ethylene inhibitors silver thiosulphate (30-60 micro M) or aminoethoxyvinylglycine (0.5 micro M) increased regeneration percentages in Helena and Canino apricot cultivars and also the consistency of results from different experiments. Use of "Pure Agar" also improved regeneration from Helena leaves as compared with agargel or agarose. Regeneration rates for Canino were dependent on the medium in which the shoots were micropropagated. When different antibiotics were tested for their influence on regeneration, the combination of cefotaxime (0.13 m M) plus vancomycin (0.63 m M), which efficiently controls Agrobacterium growth, also increased regeneration percentages in Helena two-fold but did not affect regeneration in Canino. Kanamycin, an antibiotic widely used for selection of nptII transformed cells, promoted more rapid regeneration and higher regeneration rates from Helena leaves when added at low concentrations (8.6 and 17.1 micro M). With this improved procedure, regeneration from apricot leaves has been increased more than 200% as compared with rates reported previously.

Anti-Bacterial Agents↗
PubMed2001

[Findings in surgical reinterventions for cancer of the gallbladder in patients with and without preoperative chemotherapy and radiotherapy].

BACKGROUND: The usefulness of surgery in the treatment of gallbladder cancer has not been clearly established. The benefits of chemo and radiotherapy are similarly dubious. AIM: To report the pathological findings in patients subjected to surgical reinterventions for gallbladder cancer. PATIENTS AND METHODS: We report 54 patients with gallbladder cancer that were subjected to a second surgical intervention for resection of liver segments IVb and V and lymph nodes corresponding to the liver hilar, portal, peripancreatic, celiac artery and periaortic territories. Thirteen of these patients were subjected to preoperative chemo-radiotherapy (4500 Gy and 5-fluouracil 500 mg/m2). RESULTS: Lymph node metastases were found in 25 and 38%, and liver metastases in 25 and 28% of patients with or without chemo-radiotherapy respectively. The most frequent pathological findings attributed to radiation in the liver were fatty infiltration in 75% of cases, vascular transformation in 83% of cases and minimal periportal lymphocyte infiltration in 40% of cases. Lymph nodes were atrophic in 67% of cases and had foci of cortical necrosis in 46% of cases. Three cases had regional lymph node and liver metastases. Most tumor cells were viable. CONCLUSIONS: No differences in the number of lymph node or liver metastases were observed between patients with and without chemo-radiotherapy. No effect of the treatment on residual tumor was observed either.

Chemotherapy, Adjuvant↗
PubMed2001

[Primary cholangiocarcinoma associated with Caroli disease].

A 68 years old male presented with right hypochondrium abdominal pain and jaundice with no other clinical finding. CAT Scan and Ultrasonography showed right lobe bile duct dilatation. Magnetic Resonance Cholangiopancreatography gave an outstanding vision of a restricted right lobe bile duct dilatation associated to choledocholithiasis. A right hepatectomy and bile duct exploration were performed. The histopathological study disclosed a Caroli disease associated to a primary cholangiocarcinoma. Caroli disease is a congenital disorder characterized by intrahepatic cystic bile duct dilatation with a high risk association with cholangiocarcinoma.

Aged↗
PubMed2000

Assessment of factors affecting adventitious shoot regeneration from in vitro cultured leaves of apricot.

Relatively high percentages of adventitious shoot regeneration have consistently been obtained from leaves of some apricot cultivars. For the cultivar 'Helena', explants from the proliferation medium were more reactive than those from the elongation medium. The best results were obtained with thidiazuron (TDZ). When 6-benzylamino-purine (BAP) was used instead of TDZ, the regeneration percentages were very low. High alpha-naphthaleneacetic acid (NAA) concentration had an important effect upon the decrease of the secretion of phenolic substances. Young expanding leaves with the adaxial side touching the culture medium, maintained for 2 or 3 weeks in darkness, produced the best results. There was a significant genotypic variability in adventitious bud formation. Several caulinar meristems arose from very small areas of the leaf but only one meristem developed to form a shoot when those buds were transferred to elongation medium. However, the fact that several caulinar meristems exist in early steps could be an advantage when genetically transforming these leaves, since a high number of cells would have the possibility of being transformed and producing adventitious transformed buds.

Journal Article↗
PubMed2000

[P53 tumor suppressor gene in digestive neoplasms].

Malignant diseases of the digestive tract cause more than 50% of deaths due to cancer in Chile. There is a high incidence of gastric and gallbladder cancer and an increasing frequency of colorectal cancer. P53 tumor suppressor gene has a great importance in carcinogenesis and its alterations are specially important in digestive tract tumors such as colorectal cancer. There is contradictory evidence about the frequency of p53 gene or protein alterations or their biological significance. There is little information about p53 in Chile and it is mostly limited to immunohistochemical studies. This revision analyzes the frequency of p53 alterations in digestive tract tumors in Chile, using immunohistochemical and molecular biology methods. A special emphasis is given to the prognostic importance of this gene.

Digestive System Neoplasms↗
PubMed1999

Preoperative chemoradiotherapy in the treatment of gallbladder cancer.

Gallbladder cancer is generally associated with a poor prognosis, with local recurrence being the main pattern of failure. In an attempt to improve on the present status of management, we evaluated a prospective Phase II study involving preoperative 5-fluorouracil and radiation. Among 27 eligible patients with a potentially resectable gallbladder cancer detected after cholecystectomy, 18 were treated with preoperative radiation (4500 cGy; 180 cGy/fraction, 5 days/week) concurrent with a continuous infusion of 5-fluorouracil (350 mg/m2/day, days 1-5 and 21-25). Toxicity included leukopenia (8 patients) and thrombocytopenia (7 patients). Delay in surgery due to hematological toxicity was seen in 6 patients. Of the 18 patients, 15 underwent a reoperation. Resection was performed in 13 (86%). Pathologic findings after reoperation revealed residual tumor in both liver and lymph nodes in 3 patients. At a median follow-up of 24 months, 7 patients are alive. Among the patients who died after curative resection, local recurrence was demonstrated in only 1. This is the first report concerning preoperative chemoradiation in gallbladder cancer. To assess its effect on survival, a prospective randomized trial will be necessary.

Adult↗
PubMed1998

[Advances in the diagnosis and treatment of pancreatic carcinoma].

Pancreatic carcinoma has a dismal prognosis. In the last years, great efforts have been made to improve diagnosis and preoperative staging of potentially curable carcinomas. Actually, the diagnosis of fairly small tumours is possible. Chemoradiation therapy protocols prior to pancreatectomy, aiming to improve survival, are currently being held. This therapy allows radiation to be distributed into well oxygenated cells before surgical devascularization. This procedure can be done with acceptable morbidity and mortality rates. In selected cases of irresectable carcinoma, surgical palliation allows a better quality of life. Pancreatoduodenal resection, along with other traditional oncological therapies, will continue to be the therapy of choice for patients with carcinoma of the head of the pancreas, without local or regional metastases. However, an intensive search for new therapeutic strategies, specially in the field of molecular biology, is being carried out.

Carcinoma↗
PubMed1996

[CAA 19-9 and carcinoembryonic antigen in gallbladder cancer].

The aim of this work was to assess the diagnostic yield of serum tumoral markers, Ca 19-9 and carcinoembryonic antigen, in patients with gallbladder cancer. We studied 54 patients of whom 33 had gallbladder cancer and in 21 the tumor was removed previously and were presently free of disease. Twenty one patients with cholelithiasis were used as controls. Ca 19-9 was over 37 U/ml in 22 (65%) patients with cancer, in two patients free of disease and in two controls. The sensitivity and specificity of Ca 19-9 was 0.66 and 0.90 respectively. Carcinoembryonic antigen was over 2.5 ng/ml in 25 patients with cancer (56%) and its sensitivity and specificity was 0.75 and 0.71 respectively. Using a cutoff point of 4 ng/ml, these figures were 0.51 and 0.9 respectively. The better predictive capacity was given by a Ca 19-9 over 37 U/ml or a carcinoembryonic antigen over 4 ng/ml. It is concluded that, although the sensitivity and specificity of these markers was adequate in this work, one must bear in mind that studied patients had advanced tumors.

Adult↗
PubMed1996

[Gallbladder cancer: a review].

In Chile, gallbladder cancer is the tumor with the highest mortality rates among women. Cholelithiasis is the most common associated factor and the reduction in cholecystectomy rates could be an important factor in the incidence of gallbladder cancer. Unfortunately, the disease is diagnosed late and the study of the surgical piece is the main form of early recognition. The degree of gallbladder wall infiltration by the tumor is the simplest and best staging method that has prognostic value. Gallbladder fat must be considered as a separate tissue, since its biological behavior differs from that of the subserous. The treatment of these tumors is based in their dissemination modality that is mainly local and regional. Surgical resection and radiotherapy are potentially effective. However the detection of high risk patients that should be subjected to cholecystectomy should be the better therapeutic alternative.

Female↗
PubMed1996

[Pancreas divisium as a cause of chronic pancreatitis. Clinical case].

We report a 6 years old girl with chronic pancreatitis, presenting as recurring bouts of abdominal pain and hyperamylasemia, secondary to a lack of communication between the main papilla and pancreatic duct (pancreas divisium). The diagnosis was made during an intraoperative pancreatography and treatment consisted in a sphincteroplasty of the secondary papilla.

Child↗
PubMed1995

[Hereditary chronic pancreatitis. Report of a case].

Childhood hereditary pancreatitis is a rare entity of uncertain etiology, characterized by recurrent episodes of acute pancreatitis, abdominal pain and other unspecific symptoms. Among several therapeutic alternatives, pancreatojejunostomy is presently the treatment of choice. We report a 17 years old male with chronic hereditary pancreatitis that was treated with pancreatojejunostomy drainage.

Adolescent↗
PubMed1995

[Gallbladder cancer. Case-control study].

Gallbladder cancer is the principal oncological cause of death in chilean women and cholelithiasis is a well recognized risk factor. Aiming to unravel other risk factors for gallbladder cancer, we compared 50 patients subjected to cholecystectomy in whom a gallbladder cancer was found with 50 age and sex matched operated controls without cancer. Subjects were clinically assessed and interrogated about demographic, obstetrical features and feeding features. Multiples and early pregnancies were factors significantly associated to the development of gallbladder cancer. Twenty subjects (44%) with cancer knew that they had cholelithiasis and 41 patients in each group were symptomatic. It is concluded that pregnancy may be a risk factor for gallbladder cancer probably due to the lithogenic effect of its hormonal changes. Also, early cholecystectomy in symptomatic individuals may be an effective preventive measure.

Adult↗