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Biomedical subjects

M Yáñez

Publications and source records attributed to M Yáñez.

At least 19 recordsLinked to original sources
PubMed2005

Density functional theory study of the hydrogen bond interaction between lactones, lactams, and methanol.

The structure and relative stability of methanol complexes with various cyclic ketones, lactones, lactams, and N-methyl lactams from three- to seven-membered rings have been investigated using the density functional theory method. The geometries, harmonic frequencies, and energies were calculated at the B3LYP/6-311+G(d,p) level. Three stable structures, cis-a, cis-b, and trans, with respect to the ring oxygen (nitrogen) atom, were found to be local minima of the potential energy surface. For lactones and N-methyl lactams, the most stable structure is trans; it is stabilized, as in cyclic ketones, through the conventional hydrogen bond (HB) interaction between the basic carbonyl oxygen and the acidic methanolic hydrogen and an unconventional HB interaction between the methanolic oxygen and the CH hydrogen, in the alpha position of the carbonyl group. For unsubstituted lactams, the cis-a structure, stabilized through a HB interaction between the NH group and the methanol oxygen in addition to the conventional HB interaction, is the most stable. The topological properties of the electron density ratify the existence of conventional (N,O-H. . .O) and unconventional (C-H. . .O) hydrogen bonding. A good correlation was found between the HB distances and the electron density at the HB critical point. The unsubstituted lactams yield more stable complexes with methanol than N-methyl lactams, lactones, and cyclic ketones. In the most stable complexes, both components behave simultaneously as a HB donor and as a HB acceptor.

Cyclization↗
PubMed2001

Acidity trends in alpha,beta-unsaturated alkanes, silanes, germanes, and stannanes.

The gas-phase acidity of ethyl-, vinyl-, ethynyl-, and phenyl-substituted silanes, germanes, and stannanes has been measured by means of FT-ICR techniques. The effect of unsaturation on the intrinsic acidity of these compounds and the corresponding hydrocarbons was analyzed through the use of G2 ab initio and DFT calculations. In this way, it was possible to get a general picture of the acidity trends within group 14. As expected, the acid strength increases down the group, although the acidity differences between germanium and tin derivatives are already rather small. As has been found before for amines, phosphines, and arsines, the carbon, silicon, germanium, and tin alpha,beta-unsaturated compounds are stronger acids( )than their saturated analogues. The acidifying effect of unsaturation is much larger for carbon than for Si-, Ge-, and Sn-containing compounds. The allyl anion is better stabilized by resonance than its Si, Ge, and Sn analogues, [CH(2)(-)(delta)--CH(+)(delta)(') --CH(2)(-)(delta)](-) vs [CH(2)(-)(delta)()II = CH(-)(delta)()III - XH(2)(-)(delta)()IV](-) (X = Si, Ge, Sn). The enhanced acid strength of unsaturated compounds is essentially due to a greater stabilization of the anion with respect to the neutral, because the electronegativity of the alpha,beta-unsaturated carbon group increases with its degree of unsaturation. The phenyl derivatives are systematically weaker acids than the corresponding ethynyl derivatives by 15-20 kJ mol(-)(1). Experimentally, toluene acidity is very close to that of propyne, because the deprotonation of propyne takes place preferentially at the =CH group rather than at the -CH(3) group.

Journal Article↗
PubMed2001

A phase II study of gemcitabine in gallbladder carcinoma.

BACKGROUND: Due to the high mortality rates from gallbladder carcinoma in Chile, we conducted a phase II trial to test the efficacy and safety of gemcitabine in patients with locally advanced or metastatic gallbladder carcinoma. PATIENTS AND METHODS: From January 1998 to February 2000, 26 patients with metastatic or unresectable gallbladder carcinoma and no prior chemotherapy received gemcitabine 1,000 mg/m2 over 30 minutes weekly for three weeks followed by a week of rest. RESULTS: Patients received a median of 4.2 cycles (range 1-10). Out of the 25 patients whose response could be evaluated, 9 went into partial remission, an overall response rate of 36% (95% confidence interval (95% CI): 17.1% to 57.9%). In six (25.0%) patients, the cancer remained stable, and in 10 (40%) it progressed. Median survival time was 30 weeks (range 7-80+. Hematological toxicities were mild, with no cases of febrile neutropenia or hemorrhage. However, four and one patient(s) had grades 1-2 and 3-4 neutropenia, respectively, and two patients had grade 2 thrombocytopenia. Nine patients experienced grade 1-2 nausea/vomiting, but were able to continue treatment. There were no toxic deaths. CONCLUSIONS: In this phase II trial, gemcitabine is an active chemotherapy in metastatic or inoperable gallbladder carcinoma, with a manageable toxicity profile.

Adult↗
PubMed2000

Dietary isoflavones affect sex hormone-binding globulin levels in postmenopausal women.

The studies presented in this report were designed to further investigate the causal association between phytoestrogen action and increase in sex hormone-binding globulin (SHBG) levels. Phytoestrogens include isoflavones that bind to estrogen receptors and therefore exert estrogenic action. This study included 20 postmenopausal women that ingested 30 g soy milk daily for 10 weeks. Plasma concentrations of isoflavones and SHBG were measured. Total isoflavones significantly increased from 0.014 +/- 0.01 micromol/L (baseline) to 0.53 +/- 0.19 ,micromol/L, and paired responses showed that some subjects clearly increased their SHBG levels. The percent change in SHBG showed a positive correlation with phytoestrogen concentration; all women who had circulating phytoestrogen levels above 0.6 micromol/L increased by at least 30% their SHBG values. Results suggest that phytoestrogens may significantly increase SHBG in subjects whose SHBG concentrations are in the low end of the concentration range.

Aged↗
PubMed2000

[Relationship between leptin and insulin blood levels in obese and lean Chilean women].

BACKGROUND: Leptin, a product of ob gene and insulin blood levels, are proportional to the amount of adipose tissue. Insulin could have an independent regulatory effect on leptin secretion. AIM: To assess the relationship between serum leptin and plasma insulin levels in obese and lean Chilean women. MATERIAL AND METHODS: One hundred forty five women, aged 20 to 60 years old, were studied. Weight, height, waist and hip circumference, fasting blood glucose, insulin and leptin levels were measured. Insulin resistance was assessed using the homeostasis model assessment. The relationship between different variables was determined using multiple linear regression, variance analysis and non parametric correlation. RESULTS: Leptin serum concentrations were positively correlated with body mass index, insulin plasma levels and degree of insulin resistance. The association of leptin with insulin was independent of body mass index and persisted after adjustments by body fat distribution and age. CONCLUSIONS: Insulin and insulin resistance are associated to high blood leptin levels and this association is independent of the degree of adiposity and body fat distribution.

Adult↗
PubMed2000

[Post exercise myalgias as presentation form of dystrophinopathy].

Cramps and myalgias are frequent presentations of many disorders whose diagnosis is generally difficult. Among the unusual causes stand the milder phenotypes of dystrophinopathies, which are caused, just as Duchenne and Becker's dystrophy, by mutations in the dystrophin gene. An 8 year-old boy presented severe muscle pain on exercise and serum rise in creatine kinase over 1000 U/l. He had normal muscle power and mild calf hypertrophy. The molecular analysis by polymerase chain reaction (PCR) of the dystrophin gene showed deletions of exons 45 to 51. Dystrophin analysis by Western blot revealed a dystrophin of reduced quantity and molecular weight. Emphasis is made to include dystrophinopathies in the differential diagnosis of myalgias and the usefulness of molecular genetic techniques in the identification of these disorders.

Blotting, Western↗
PubMed1999

[Bcl-2 gene protein expression in salivary gland tumors].

BACKGROUND: Salivary gland tumors have heterogeneous pathological features. Oncogene Bcl-2 product expression inhibits apoptosis and therefore is important for tumor proliferation. AIM: To assess the immunohistochemical gene Bcl-2 protein expression in salivary gland tumors. MATERIAL AND METHODS: Twenty seven salivary gland tumors were selected from the archives of the Pathology Department of Temuco Regional Hospital. There were 20 pleiomorphic adenomas, 4 cystic adenoid carcinomas and three mucoepidermoid carcinomas. Immunohistochemical gene Bcl-2 protein expression was determined in paraffin included pathological slices. RESULTS: All pleiomorphic adenomas expressed the protein, specially in tubulo ductal structures, solid and trabecular areas. All cystic adenoid carcinomas expressed the protein in myoepithelial cells. Two mucoepidermoid carcinomas were positive, only in the epidermoid areas. CONCLUSIONS: immunohistochemical gene Bcl-2 protein was expressed in virtually all benign and malignant salivary gland tumors. This observation suggest an important role of this protein in the development of these tumors.

Adenoma, Pleomorphic↗
PubMed1999

[Chronic sclerosing non-specific sialadenitis of the submandibular gland (Küttner tumor). Report of one case].

Chronic sclerosing unspecific sialadenitis or Küttner tumor, is an infrequent inflammatory lesion of submandibular gland. We report a 60 years old male presenting with a slowly growing, painless, bilateral submandibular tumor of two years of evolution. Pathological examinations showed marked atrophy of glandular parenchyma with increased fibrous connective tissue and an intense lymphocytic infiltration with lymphoid follicle formation. Lymphocyte population study with kappa, lambda, CD20 and CD45RO antibodies was similar to that observed in reactive lymph nodes. There was no over expression of Bcl-2 gene protein, involved in the phenomenon of apoptosis of glandular tissue, that could explain the pathogenesis of atrophy. This protein was positive only in lymphoid cells and glandular conducts. An immune etiology, with replacement of glandular tissue by lymphoid and fibrous connective tissue is suggested.

Chronic Disease↗
PubMed1998

[MALT lymphoma of the bladder: report of a case].

Primary malignant lymphomas of the bladder are infrequent. We report a 70 year old woman presenting with hematuria, dysuria, malaise and a 5 kg weight loss. Pelvic ultrasound examination showed a 8 x 8 x 8 cm solid and cystic mass adjacent to the bladder and uterus. Cystoscopic biopsy disclosed a low grade B cell non Hodgkin lymphoma. She was treated with 6 cycles of chemotherapy with disappearance of the mass. Two years after admission, the patient is free of disease.

Aged↗
PubMed1998

[Analgesic response and secondary effects in patients with osteoblastic metastasis, treated with Samarium 153 ethylenediaminotetramethylenephosphate].

BACKGROUND: Samarium153 EDTMP, a beta and gamma emitter, is used in the palliative therapy of painful bone metastases. AIM: To evaluate the analgesic effects and myelotoxicity of Samarium153 EDTMP in patients with prostate, breast and renal carcinoma. PATIENTS AND METHODS: Twenty patients with bone metastases (11 males), aged 65 years old as a mean, received a 1 to 2 mCi/kg intravenous dose of Samarium153 EDTMP, produced in Chile. Patients were followed thereafter during 4 to 40 weeks. Pain was assessed using a visual analogue scale. RESULTS: Pain decreased from a score of 6.4 prior to treatment, to 2.7 at the fourth week of therapy and the effect lasted a mean of 12.5 weeks. Myelotoxicity was observed in 68% of cases (WHO stage I in 21%, stage II in 37%, stage III in 11% and no patients in stage IV). Platelets were the most affected series and neutrophils the least affected. Cell counts returned to normal between the sixth and eighth week. Seventy nine percent of patients decreased their basal analgesic therapy at the sixth week and 88% did so at the eighth week. Forty one percent of these patients discontinued all analgesics. CONCLUSIONS: Samarium153 EDTMP is effective in the treatment of pain in patients with bone metastases and its myelotoxicity is low to moderate. It should be considered as a therapy for this type of pain, with the precaution of performing periodical bood counts.

Adult↗
PubMed1997

[Epidemiological transition in Latin America: a comparison of four countries].

BACKGROUND: In the last decade, Latin America has experienced important transformations in its health conditions, due to demographic changes and a rapid urbanization process. AIM: To analyze socioeconomic, demographic and epidemiological changes in Chile, Guatemala, Mexico and Uruguay and relate them to the different stages in the demographic and epidemiological transition of these countries. MATERIAL AND METHODS: Data was obtained from official information of local and international organizations such as Pan-American Health Organization, United Nations, Latin American Center for Demography (CELADE) and World Bank. RESULTS: Guatemala is in a pre-transition stage with a high proportion of communicable diseases as causes of death (61%) as compared with Mexico (22%), Chile (13%) and Uruguay (7%). Mexico is in a prolonged transition situation and Chile is close to Uruguay in a post-transitional stage. Despite decreasing rates of mortality, the proportion of deaths represented by chronic diseases and injuries has increased to over 30% in all countries, except Uruguay. Adjusted mortality rates for cardiovascular diseases are lower in Latin American countries, as compared to Canada. However, excepting Guatemala, there are differences in the pattern of cardiovascular disease, with a higher mortality due to cerebrovascular and a lower mortality due to coronary artery diseases. CONCLUSIONS: An increment in non communicable diseases is expected for the next decades in Latin America. Analysis of demographic and epidemiological transition is crucial to define health policies and to adequate health systems to the new situations.

Chile↗
PubMed1997

[Determination of DNA content in salivary gland tumors].

BACKGROUND: DNA content determination is a useful tool in the characterization of different malignant tumors. AIM: To measure DNA content in cells of salivary gland tumors as adjunct to histological diagnosis, correlating morphologic and biological features of these tumors. MATERIAL AND METHODS: From the archives of the Pathology service of a general hospital, 21 salivary gland tumors, 15 pleomorphic adenomas, 3 mucoepidermoid carcinomas and 3 cystic adenoid carcinomas were selected. DNA content was determined in the histological samples using a flow cytometric DNA analysis. RESULTS: All pleomorphic adenomas had a normal or diploid DNA content. Fifty percent of malignant tumors had an aneuploid DNA content (1 mucoepidermoid carcinoma and 2 cystic adenoid carcinomas). CONCLUSIONS: DNA determination may help in the histological diagnosis of salivary gland tumors. The presence of aneuploidy suggests malignity.

Adenoma, Pleomorphic↗
PubMed1996

Obesity as a protective factor for postmenopausal osteoporosis.

BACKGROUND: Obesity is considered a protective factor for osteoporosis improving bone mass and maintaining higher levels of estrogen during menopause. OBJECTIVE: To determine the association of obesity with bone mineral density (BMD), and its relationship with sex hormone levels. DESIGN: A case-control study in Caucasian obese and non obese postmenopausal women. SUBJECTS: 113 obese and 50 non-obese postmenopausal women. MEASUREMENTS: BMD (dual-photon X-ray absorptiometry) at cervical femur. Ward's triangle, proximal radius and lumbar spine. Plasma levels of glucose, insulin, total estrogen, follicle stimulating hormone (FSH), sex hormone binding globulin (SHBG), dehydroepiandrosterone sulfate (DHA-S) and testosterone. RESULTS: Mean BMD at femoral sites were significantly higher in obese women (femoral neck: 0.849 +/- 0.124 g/cm2 vs 0.753 +/- 0.095 g/cm2, P < 0.001; Ward's triangle: 0.634 +/- 0.134 g/cm2 vs. 0.553 +/- 0.100 g/cm2, P < 0.001). Mean BMD at lumbar spine was 0.906 +/- 0.138 g/cm2 in obese women and 0.849 +/- 0.137 g/cm2 in non obese, P < 0.017. A decreased risk of osteopenia in femoral neck (Age adjusted OR = 0.36, 95%CI 0.17-0.75) and in lumbar spine (Age adjusted OR = 0.43, 95%CI 0.20-0.91) in obese women was observed. Although total estrogen were similar in both groups, in obese women, SHBG was lower (68.6 +/- 26.84 nmol/l vs. 85.1 +/- 31.18 nmol/l, P < 0.001), and postglucose load insulin levels were higher, than in non obese (77.2 +/- 50.4 Ul/ml vs. 49.4 +/- 24.1 Ul/ml, P < 0.0005). CONCLUSION: The findings confirm a higher BMD in obese women and suggest that obesity exerts protection due to a decreased SHBG thus increasing free sex steroids. Besides, hyperinsulinemia may produce a decline in the production of IGFBG-1, leading to an increase of IGF-1, that may stimulate the proliferation of osteoblasts.

Bone Density↗
PubMed1996

Double mitral valve orifice. Two-dimensional and Doppler echocardiographic diagnosis.

The purpose of this study was to demonstrate the usefulness of two-dimensional and Doppler echocardiography for diagnosing double mitral valve orifices (DMVO) in addition to identifying associated pathologies. We report five cases, three male and two female with an age ranging from 4 to 44 years old (mean age: 17 years), with the diagnosis of DMVO according to the following characteristics: using two-dimensional echocardiography on the short parasternal axis, both orifices were observed; apical in which the "seagull sign" was identified in both chambers, in addition to identifying the flows of each orifice by pulsed and codified color Doppler obtaining the corresponding gradients. With respect to the associated pathologies, all patients presented some type of malformation, such as subaortic ring, patent ductus arteriosus, coarctation of the aorta, bicuspid aorta and pulmonary stenosis. Using the color Doppler echocardiography allows an adequate anatomical and functional definition of DMVO.

Abnormalities, Multiple↗
PubMed1996

[Tropisetron for the prevention of nausea and vomiting during chemotherapy: multicenter clinical study].

The antiemetic effect of tropisetron was studied in 97 cancer patients (67 men, 30 women) receiving cisplatin in doses of 75 mg/m2 or higher. On 279 chemotherapy cycles studied (max 6 per patient) 5 mg of tropisetron was administered once a day i.v on day 1 and p.o. on days 2 to 6. Efficacy preventing vomiting and nausea was measured in 24 hour period as: complete control O episodes, major control 1 to 2 episodes, minor control 3 to 4 episodes and no control 5 or more episodes. Satisfactory vomiting control (complete and major) was 69%, 63%, 82%, 88%, 96% and 96% in days 1 to 6 of cycle 1. Satisfactory nausea control (complete and major) for the same days was 70%, 66%, 72%, 85%, 92% and 97%. Similar data was obtained for the subsequent cycles. Complete vomiting control was obtained in 47%, 35%, 56%, 72%, 81% and 84% and for nausea in 42%, 39%, 48%, 64%, 81% and 87%. 19 patients presented adverse effects (19.6%). Only 2 headache episodes had a definite relation with the antiemetic drug. 12 patients discontinued the medication; 6 due to drug inefficacy, 2 to illness unrelated to the drug, 1 to lack of collaboration, and 3 due to other reasons. We conclude that tropisetron allows satisfactory control of acute and delayed vomiting in a high percentage of patients treated with high doses of cisplatin. The drug does not have significant secondary effects. Tropisetron administration in only one daily dose implies an evident advantage and a treatment cost reduction.

Adolescent↗
PubMed1996

[Methods to estimate body composition in the elderly: a critical analysis].

The objective of this study was to compare the values obtained for total body fat obtained with deuterium dilution, anthropometry and bioimpedance in 41 institutionalized elderly individuals (65-90 years old). The values obtained with each technique were compared using the graphic analysis proposed by Bland and Altman, that plots the difference between measurements with both methods against their average. In men (n = 20) and women (n = 21), the best degree of agreement was obtained between the values measured by deuterium dilution and those calculated from skinfolds (mean difference = 1.4% and 6.9%, respectively). The limits of agreement (+/-2SD), for skinfolds reached a maximum of 14.8% in men, and 16.8% in women. These values tend to underestimate fat in the obese and overestimate it in thinner subjects. For bioimpedance and deuterium dilution, the inter-method difference is significantly greater: 9.3% in men and 14.7% in women. This lack of agreement is attributed to the fact that the bioimpedance equipment utilizes equations validated for younger adults. In conclusion, estimation of body composition using skinfoids has the smallest difference compared to deuterium dilution, even though individual measurements are not clinically acceptable. Caution is recommended when using measurements of body composition in the elderly, due to large errors in the determinations.

Aged↗
PubMed1995

[Body fat distribution: anthropometric indicators].

There are two types of fat distribution in obese subjects. The abdominal, superior, android or apple shaped and the gluteo-femoral, gynecoid, inferior or pear shaped. In the former, fat is accumulated in the abdomen and in the latter, in the gluteal region. The superior distribution is associated with a higher risk of cardiovascular diseases. Among anthropometric measurements of fat distribution, the ratio between waist circumference measured at the level of the navel and hip circumference, measured at the level of greater trochanters, is the best indicator. Using the cutoff points of 0.8 for women and 1 for men, it has a good correlation with visceral fat.

Adipose Tissue↗