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Biomedical subjects

E Espinosa

Publications and source records attributed to E Espinosa.

At least 19 recordsLinked to original sources
PubMed1998

Mapping diplosporous apomixis in tetraploid Tripsacum: one gene or several genes?

Polyploids in Tripsacum, a wild relative of maize, reproduce through the diplosporous type of apomixis, an asexual mode of reproduction through seeds. Diplosporous apomixis involves both the failure of meiosis and the parthenogenetic development of the unreduced gametes, resulting in progenies that are exact genetic copies of the mother plant. Apomixis is believed to be controlled by one single dominant allele, responsible for the whole developmental process. Construction of a linkage map for the chromosome controlling diplosporous apomixis in Tripsacum was carried out in both tetraploid-apomictic and diploid-sexual Tripsacum species using maize restriction fragment length polymorphism (RFLP) probes. A high level of collinearity was observed between the Tripsacum chromosome carrying the control of apomixis and a duplicated segment in the maize genome. In the apomictic tetraploid, there was a strong restriction to recombination, as compared to the corresponding genomic segment in sexual plants and maize. This suggests that apomixis, although inherited as a single Mendelian allele, might really be controlled by a cluster of linked loci. The analysis also revealed the tetrasomic nature of the inheritance of the chromosomal segment controlling apomixis, which contradicts the usually accepted hypothesis of an allopolyploid origin of apomictic species. The implications of these data for the transfer of apomixis into cultivated crops are discussed, and a new approach to studying the genetics of apomixis, based on comparative mapping, is proposed.

Chromosome Mapping↗
PubMed1998

Non-Mendelian transmission of apomixis in maize-Tripsacum hybrids caused by a transmission ratio distortion.

Apomixis is a mode of asexual reproduction through seeds. The apomictic process bypasses both meiosis and egg cell fertilization, producing offspring that are exact genetic replicas of the mother plant. In the Tripsacum agamic complex, all polyploids reproduce through the diplosporous type of apomixis, and diploids are sexual. In this paper, molecular markers linked with diplospory were used to analyse various generations of maize-Tripsacum hybrids and backcross derivatives and to derive a model for the inheritance of diplosporous reproduction. The results suggest that the gene or genes controlling apomixis in Tripsacum are linked with a segregation distorter-type system promoting the elimination of the apomixis alleles when transmitted through haploid gametes. Hence, this model offers an explanation of the relationship between apomixis and polyploidy. The evolutionary importance of this mechanism, which protects the diploid level from being invaded by apomixis, is discussed.

Chimera↗
PubMed1997

Uracil and tegafur modulated with leucovorin: an effective regimen with low toxicity for the treatment of colorectal carcinoma in the elderly. Oncopaz Cooperative Group.

BACKGROUND: In spite of the high prevalence of cancer in the elderly, little information is available about the efficacy and toxicity of chemotherapy in elderly patients. In a previous study, the authors demonstrated that the combination of uracil and tegafur (UFT) with leucovorin (LV) was active and well tolerated in patients with advanced colorectal carcinoma (ACC). The objective of the current study was to determine the efficacy and toxicity of this regimen in elderly patients with ACC. METHODS: Thirty-eight unselected patients older than 70 years (median age, 74 years) with measurable ACC were included. All patients were evaluable for toxicity and response. The regimen consisted of intravenous LV 500 mg/m2 on Day 1, oral LV 15 mg every 12 hours on Days 2-14, and oral UFT 390 mg/m2 on Days 1-14. Treatment was repeated every 28 days for a minimum of 4 courses per patient. RESULTS: Two hundred eighty-eight cycles of chemotherapy were delivered (median, 7 per patient). Two patients (5%) achieved a complete response and 9 (24%) a partial response, for an overall response rate of 29%. Toxicity was mild, without dose-limiting myelosuppression. Four patients (10%) experienced Grade 3-4 diarrhea, 1 patient had Grade 3-4 nausea/vomiting, and 1 had Grade 3-4 mucositis. Grade 3-4 toxicity was more frequent among women than men (38% vs. 4%, P < 0.05). CONCLUSIONS: Treatment with oral UFT modulated with LV is effective, well tolerated, and feasible on an outpatient basis for elderly patients with ACC. However, elderly women should be followed closely for the early detection of toxicity.

Administration, Oral↗
PubMed1997

[Vascular protection with estrogen. In-vitro and in-vivo effects--mechanisms and clinical implication].

Myocardial infarction is the major cause of death in the western world. Men are more prone to develop coronary artery disease than women of the same age, in whom coronary disease is rare before menopause. Epidemiological data have shown that estrogens are vasoprotective--especially in the coronary circulation--but the underlying mechanisms have been investigated more thoroughly only in recent years. Only up to half of the protective effect of estrogen replacement therapy an be attributed to its positive effects of the lipid profile. However, a large part of this protection is caused by mechanisms distinct from lipid metabolism. It is now known that estrogens also exert effects on vascular function and structure of the vessel wall involving numerous cellular and molecular mechanisms. Actions of natural estrogens on human vascular cells and arteries will be discussed. Estrogens modulate vascular function by increasing nitric oxide production via stimulation of endothelial nitric oxide synthase (eNOS) and decreasing endothelin-1 levels in vivo. Furthermore, 17-beta estradiol is a potent inhibitor of vascular smooth muscle cell proliferation and migration, which play a major role in atherosclerotic vascular disease and in the remodeling process. 17-beta estradiol also acutely affects vascular tone in human arteries and attenuates constriction induced by contractile agonists. Finally, clinical studies showed that 17-beta estradiol can acutely and chronically ameliorate vascular function in women with and without vascular disease. In conclusion, results from clinical and in vitro studies showed positive effects of natural estrogens on vascular function which could explain in part their protective actions against coronary heart disease. Thus, primary prevention of coronary heart disease by estrogen replacement therapy after menopause appears to be a new approach to reduce cardiovascular mortality in women.

Adult↗
PubMed1997

Plasma atrial natriuretic peptide and natriuretic peptide receptor gene expression in adipose tissue of normotensive and hypertensive obese patients.

OBJECTIVE: Human and rat adipose tissue contain very high levels of natriuretic peptides clearance receptor messenger (m)RNA, and fasting inhibits its gene expression in adipose tissue. In this study we evaluated plasma atrial natriuretic peptide (ANP) and gene expression of biologically active type A natriuretic peptide receptor (NPr-A) and clearance natriuretic peptide receptor (NPr-C) in adipose tissue of obese hypertensive and obese normotensive patients. DESIGN AND METHODS: We studied 27 untreated obese hypertensives, 26 obese normotensives (body mass index > or = 30 kg/m2), 24 non-obese essential hypertensives and 23 lean healthy subjects (body mass index < or = 25 kg/m2). Blood samples were withdrawn for ANP, plasma renin activity and aldosterone radioimmunoassays. Subcutaneous peri-umbilical adipose tissue samples were obtained, by needle aspiration, in 13 obese hypertensives and in 12 obese normotensives and used for RNA extraction. Then, complementary synthesis and semiquantitative polymerase chain reaction (PCR) with primers complementary to sequences of different exons of the genes encoding for NPr-A, NPr-C and beta-actin, were performed. 32P-labeled PCR products were separated by electrophoresis, blotted onto nylon membranes, and the exposed autoradiographic films were analysed by densitometry. NPr signals were normalized by the beta-actin expression level. RESULTS: Plasma ANP was lower in obese hypertensives than in obese normotensives (37.5+/-7 versus 43.2+/-6 pg/ml, P< 0.05), but was higher in non-obese hypertensives than in non-obese normotensives. In contrast, plasma renin activity and aldosterone were higher in the obese hypertensives. Although NPr-A and NPr-C expression were not statistically different between the two obese groups, the NPr-A: NPr-C mRNA ratios were significantly lower in obese hypertensives (P < 0.03). CONCLUSIONS: Our data suggest that in obese hypertensives compared to obese normotensives, the lower NPr-A: NPr-C ratio might determine decreased biological activity and/or an increased clearance of natriuretic peptide in adipose tissue, suggesting that the natriuretic peptide and its receptor system may be important in obesity-related hypertension where ANP levels are lower.

Actins↗
PubMed1997

UFT modulated with leucovorin in advanced colorectal cancer: Oncopaz experience.

A phase II trial of UFT (Tegafur and Uracil) modulated by leucovorin was undertaken by the Oncopaz Cooperative Group to assess the efficacy and toxicity of this combination in patients with advanced colorectal cancer. A total of 75 patients were given 500 mg/m2 intravenous leucovorin and 195 mg/m2 of oral UFT on day 1, followed by oral leucovorin 15 mg/12 h and 195 mg/m2/12 h of oral UFT on days 2-14. An overall response rate of 39% was obtained, with seven complete responses (9%), and 22 partial responses (29%). The primary toxicity was gastrointestinal, with grade 1-2 diarrhea occurring in 8.5% of courses, and grade 3-4 in 3.5%. Hematologic toxicity was minimal, and there were no deaths due to toxicity. This regimen was active and well tolerated in patients with advanced colorectal cancer, including those 70 years of age or older.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Experience of Oncopaz Cooperative Group with oral fluoropyrimidines in tumors of the stomach, lung, head and neck, and breast.

The Oncopaz Cooperative Group designed a chemotherapy regimen to modulate UFT (Tegafur and Uracil) with leucovorin. The regimen consisted of a high intravenous dose of leucovorin, followed by oral UFT and oral leucovorin twice daily for 14 days. Based on the promising results obtained with this regimen in patients with advanced colorectal cancer, the Oncopaz group performed several phase II trials using this combination with other drugs to treat advanced gastric, lung, head and neck, and breast cancers. When combined with etoposide in gastric cancer, the regimen was shown to be active and well tolerated. However, when used with cisplatin to treat non-small cell lung cancer, a low response rate and high toxicity precluded its recommendation for further study. The addition of carboplatin in the treatment of head and neck cancer demonstrated moderate activity with low toxicity. In an ongoing trial of advanced breast cancer, preliminary results indicate that the combination of idarubicin, UFT, and leucovorin is active, with moderate, primarily hematologic toxicity. Trials of new combinations are warranted to take advantage of the pharmacokinetic properties and oral bioavailability of UFT and leucovorin.

Adenocarcinoma↗
PubMed1997

Bimodal effects of angiotensin II on migration of human and rat smooth muscle cells. Direct stimulation and indirect inhibition via transforming growth factor-beta 1.

Angiotensin II may be an important mediator of neointima formation in vascular disease. This study was designed to examine the mechanisms involved in angiotensin II-stimulated migration of human and rat aortic vascular smooth muscle cells (VSMCs). VSMCs were seeded in one corner of Nunc four-well culture chambers; angiotensin II within filter paper was glued onto the wall of the opposite side. After 48 hours of incubation in serum-free medium containing growth-arresting factor, migrated cells were counted using a light microscope. Angiotensin II (2 x 10(-11) to 2 x 10(-8) mol/L) increased migration of VSMCs in a concentration-dependent manner. Interestingly, at higher concentrations of angiotensin II (up to 2 x 10(-6) mol/L), migration was reduced to levels comparable with control levels. Losartan, an AT1 receptor antagonist, prevented migration, while PD123319, an AT2 receptor antagonist, had no significant inhibitory effect. Transforming growth factor-beta 1 (TGF-beta 1; 0.01 to 10.0 pg/mL) inhibited migration induced by angiotensin II (2 x 10(-8) mol/L) in a concentration-dependent manner. A neutralizing TGF-beta antibody unmasked migratory effects of high concentrations of angiotensin II. Furthermore, angiotensin II (10(-6) mol/L) upregulated TGF-beta 1 mRNA levels fivefold in rat and fourfold in human VSMCs; this effect was prevented by losartan but not by PD123319. Thus, the effects of angiotensin II on migration of VSMCs are bimodal, ie, both migratory and antimigratory pathways are activated. Autocrine release of TGF-beta 1 induced by angiotensin II exerts an antimigratory effect in rat and human VSMCs. The AT1 receptor is involved in regulation of both pathways.

Angiotensin II↗
PubMed1997

Pericardial tamponade as the first manifestation of adenocarcinoma.

We hereby report on 13 cases of pericardial tamponade as the first manifestation of an adenocarcinoma. The primary tumor was detected in 10 cases: 7 lung, 1 stomach, 1 breast and 1 thyroid. A first cytologic examination of the pericardial fluid yielded the diagnosis of adenocarcinoma in 10 cases, whereas a second cytology was needed in another two cases. The pericardial biopsy was positive in 7 out of 7 patients. The therapeutic procedures included pericardiocentesis in 9 patients (6 of whom had recurrent tamponade), a pericardial window in 4 and pericardiotomy in 4 (without recurrences). The mean survival was 4 months.

Adenocarcinoma↗
PubMed1997

[Clinical identification of hereditary ataxias. A study of 38 cases in Colombia].

INTRODUCTION: Hereditary ataxias are a complex group of degeneratives diseases of the CNS. Material and methods. We studied 38 patients who were diagnosed inherited ataxia according to recent classification and radiologic criteria. We proposed flow sheet in order to reduce the cost of the studies. RESULTS: The most frequent findings we encountered were the congenital ataxias and the late onset ataxia forms, olivopontocerebellar ataxias (OPCA) and the late cortical cerebellar ataxias (CCA), following were the Friedreich ataxias, the intermittent ataxias, and cerebellar ataxias with myoclonus. We found finally two multisystemic atrophies. We didn't find dominant inheritance in the late onset ataxias, some of these were recessive forms and the others could be the novo mutations or idiopathic cerebellar ataxias of adult onset. CONCLUSION: It would be appropriate to enlarge the studies in the metabolic and treatable forms and try to define the forms that have a known genetic mutation.

Adolescent↗
PubMed1997

The UFT/leucovorin/etoposide regimen for the treatment of advanced gastric cancer. Oncopaz Cooperative Group.

Gastric cancer is the most chemosensitive adenocarcinoma among digestive neoplasms. A few years ago, we performed a phase II trial with the FLEP regimen, in which fluorouracil (5-FU) and leucovorin are combined with etoposide and cisplatin (Platinol). This regimen resulted in a 39% response rate and high toxicity. Then we used the combination UFT (tegafur and uracil)/leucovorin/etoposide: UFT 390 mg/m2/day orally on days 1 to 14; leucovorin 500 mg/m2 i.v. day 1, and 15 mg/12 h orally on days 2 to 14; and etoposide 100 mg/m2 i.v. on day 1 and then 200 mg/m2/day orally on days 2 and 3. Forty-six patients received a median of five courses. Five patients (11%) achieved a complete response and 12 (26%) a partial response, for an overall response rate of 37%. The response rate was 50% in patients with an Eastern Cooperative Oncology Group performance status of 0 to 1. Grades 3 to 4 toxicities appeared as follow: 17% of patients had diarrhea, 11% had nausea/vomiting, and 13% of patients had anemia. One patient died of neutropenia and sepsis. The median survival time was 9 months. In summary, UFT/leucovorin/etoposide is effective and moderately toxic in patients with advanced gastric cancer. A new trial with UFT/leucovorin/epirubicin is ongoing.

Anemia↗
PubMed1996

[Action of natural estrogens on the vessel wall: molecular mechanisms and clinical implications].

Myocardial infarction is the major cause of death in the Western world. Men are more prone to develop coronary artery disease than women, who rarely develop coronary disease before menopause. Although epidemiological data has long been available showing a protective effect of estrogen on the vascular system, the underlying mechanisms have been investigated more thoroughly only in recent years. Meta-analysis studies have revealed that only half of the protective effect on estrogen replacement therapy is due to its positive effects on the lipid profile and that a large part of this protection is caused by mechanisms distinct from lipid metabolism. It is now known that estrogens also exert effects on vascular function and structure of the vessel wall involving numerous cellular and molecular mechanisms. Here we review actions of natural estrogens on human vascular cells and arteries. Estrogens can modulate vascular function by increasing nitric oxide production via stimulation of endothelial nitric oxide synthase (eNOS) and decreasing endothelin-1 levels in vivo. Furthermore, 17 beta-estradiol is an inhibitor of vascular smooth muscle cell proliferation and migration, phenomena that play a major role in atherosclerotic vascular disease and in the remodelling process. 17 beta-estradiol can also acutely affect vascular tone in human arteries and attenuates constriction induced by contractile agonists. Finally, clinical studies have shown that 17 beta-estradiol can acutely and chronically ameliorate vascular function in women with and without vascular disease. In conclusion, results from clinical and in vitro studies confirm the positive effects of natural estrogens on vascular function and protection from coronary heart disease. Thus, primary prevention of coronary heart disease by estrogen replacement therapy after the menopause appears to be a new and straightforward approach by which cardiovascular mortality in women can be reduced.

Adult↗
PubMed1996

Treatment of patients with advanced gastric carcinoma with the combination of etoposide plus oral tegafur modulated by uracil and leucovorin. A phase II study of the ONCOPAZ Cooperative Group.

BACKGROUND: Both the biochemical modulation and the continuous administration of 5-fluorouracil (5-FU) have achieved promising results in patients with gastric carcinoma. Conversely, several studies on gastric carcinoma have demonstrated that the combination of etoposide (VP-16), leucovorin (LV), and 5-FU (ELF) is efficacious and moderately toxic. UFT is a combination of uracil and tegafur (ftorafur) in a 4:1 molar ratio. It can be administered orally for several weeks, thus stimulating the effects of a continuous infusion of 5-FU. Its combination with LV increased the efficacy of UFT. We conducted a Phase II study on patients with gastric carcinoma using the combination VP-16-LV-UFT. This combination is administered mainly orally (p.o) and could yield a good response rate and low toxicity. METHODS: Forty-six patients with bidimensionally measurable disease were entered into the study. Patients received VP-16 100 mg/m2 IV on Day 1 and 200 mg/ m2 p.o. on Days 2 and 3; LV 500 mg/m2 administered intravenously (i.v.) on Day 1, followed by p.o. LV 15 mg every twelve hours on Days 2 to 14. Patients also received UFT p.o. 390 mg/m2/day on Days 1 to 14. Treatment was repeated every 28 days for a minimum of 3 courses per patient. All courses were given on an outpatient basis. RESULTS: Four patients (9%) had a complete response, and 12 a partial response (26%) for an overall response rate of 35% (95% confidence interval: 22-51%). The median duration of response was 10 months. The median overall survival was 9 months. The main side effects were gastrointestinal. Grade 3 to 4 toxicity was encountered as follows: diarrhea in 17% of the patients, nausea/vomiting in 11%, anemia in 13%, mucositis and leukopenia in 4% each, and thrombocytopenia in 2%. One patient died of sepsis and neutropenia. CONCLUSIONS: VP-16-LV-UFT has an activity comparable to that of other schemes and a low incidence of side effects. Furthermore, since it is administered mainly orally, hospitalization is avoided, which makes this scheme suitable for patients with advanced gastric carcinoma.

Administration, Oral↗