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Biomedical subjects

C Y Valenzuela

Publications and source records attributed to C Y Valenzuela.

At least 19 recordsLinked to original sources
PubMed2006

Malignant melanoma in Chile: an unusual distribution of primary sites in men from low socioeconomic strata.

BACKGROUND: Mortality from malignant melanoma (MM) has increased in Chile in the past decade. The location of MM lesions on the body has been correlated with prognosis and survival. AIM: To review body site and gender relationships with histopathologically confirmed primary MM in Chile. METHODS: Records of 575 cases presenting to 5 state hospitals from 1992 to 2001 were analysed. RESULTS: There were 360 women and 215 men. Women showed a significantly higher number of MM on the legs, cheeks and arms, and in the genital area, whereas men showed a significantly higher number on the ears, backs of the hands, soles and feet. Men had a predilection for MM with a poor prognosis. CONCLUSION: The different body site distribution of primary MM in men and women may be explained by a different pattern of sun exposure. Ethnic and genetic factors may also be involved. The predominant location of MM in women in Chile is similar to white populations, whereas the location in men is similar to that observed in black and Asian populations. These observations may be relevant to the high mortality of MM in Chilean men.

Chile↗
PubMed2001

Human Raphe Magnus Nucleus: a morphometric Golgi-Cox study with emphasis on sex differences.

The number and proportion of neurons according to their type and size in the Raphe Magnus Nucleus stained by the Golgi-Cox and Nissl methods were compared in male and female infants. Four female/male pairs aged from 2 to 150 days were studied. While females showed more neurons than males, males showed a higher proportion of large multipolar (more than 40 microm) and fusiform neurons (more than 20 microm) but not of ovoid neurons (more than 15 microm). These differences varied according to the type of cells and age of infants. Some of these results are similar to those found in the human Median Raphe Nucleus with the same methods.

Cell Count↗
PubMed2001

[Ontogenetic origin of the human individual from his genome].

Diverse propositions about the ontogenetic origin of a live organism, specially human beings, are examined. Unambiguous and objective propositions about this origin are that a live organism is an ontogenetically programmed and integrated organisation, that the origin condition has the greater influence on other processes, that in pluricellular organisms, no organ or tissue can be considered critical to establish origins and that the origin must be established by endogenous elements. Several hypotheses about the origin of life are discarded. The integration between oocyte cytoplasm and the genetic material that it receives, that culminates in the first genome replication, is proposed as the process that gives origin to the individual. This process occurs in all living organisms.

Embryonic and Fetal Development↗
PubMed2001

[Scientific ethics and frozen embryos].

BACKGROUND: Scientific Ethics is the theory and praxis of decisions. Philosophical Ethics is presented as the theory and praxis of the good. As the good differs among cultures, Philosophical Ethics is dependent on the endo-cultural good conception. The decision (included that one of adhesion or not to a world vision) depends on neuro-psychic specific factors: i) cognitive factors that include mostly the knowledge of the alternatives and their consequences and the ideological or religious conception of good in relation to the alternatives; ii) affective factors that make alternatives pleasant, unpleasant or neutral, attractive, repulsive or neutral; iii) emotional factors that associate to alternatives anger, peace or neutrality, sadness, happiness or neutrality; iv) value factors that assign importance, triviality or neutrality to alternatives, or assign them significance, irrelevancy or neutrality. There are unspecific factors such as the psychic energy, desire or others. Mixed factors such as attitude, motivation, intention and others. Scientific Ethics deals with the mind as a materio-energetic process which is different from the soul, eggs and embryos of any species are full individuals of that species, because, they have initiated a copy of their genome that specify, give autonomy and define them as individuals. For Scientific Ethics to leave frozen embryos like that for ever, to defrost and get rid of them or to use their cells for science are synonymous of killing them. To defrost them to use their cells as stem cells for somatic cell therapy or to implant them into uteri to continue their development is to maintain alive their cells, but only the implantation allows their maintenance as individuals, thus, being the only compatible with the Christian ethics. The compatibility of these alternatives with other ethics is discussed.

Cryopreservation↗
PubMed2000

Misconceptions and false expectations in neutral evolution.

Neutral evolution results from random recurrent mutation and genetic drift. A small part of random evolution, that which is related to protein or DNA polymorphisms, is the subject of the Neutral Theory of Evolution. One of the foundations of this theory is the demonstration that the mutation rate (m) is equal to the substitution rate. Since both rates are independent of population size, they are independent of drift, which is dependent upon population size. Neutralists have erroneously equated the substitution rate with the fixation rate, despite the fact that they are antithetical conceptions. The neutralists then applied the random walk stochastic model to justify alleles or bases that were fixated or eliminated. In this model, once the allele or base frequencies reach the monomorphic states (values of 1.0 or 0.0), the absorbing barriers, they can no longer return to the polymorphic state. This operates in a pure mathematical model. If recurrent mutation occurs (as in biotic real systems) fixation and elimination are impossible. A population of bacteria in which m = 10(-8) base mutation (or substitution)/site/generation and the reproduction rate is 1000 cell cycle/year should replace all its genome bases in approximately 100,000 years. The expected situation for all sites is polymorphism for the four bases rather than monomorphism at 1.0 or 0.0 frequencies. If fixation and elimination of a base for more than 500,000 years are impossible, then most of the neutral theory is untenable. A new complete neutral model, which allows for recurrent substitutions, is proposed here based on recurrent mutation or substitution and drift alone. The model fits a binomial or Poisson distribution and not a geometric one, as does neutral theory.

Bacteria↗
PubMed1999

[Annual school and menarche rhythms (vacation-study)].

BACKGROUND: It has been hypothesized that the yearly menarche rhythm could be caused by the seasonal variation of photoperiod and temperature or by the annual distribution of the scholar vacation and study periods. AIM: To test the hypothesis that the distribution of study vacation periods is a condition that modifies the annual menarche rhythm. SUBJECTS AND METHODS: Two thousand ninety four school girls from Chile, 2,356 girls from Madras, India, 3,454 girls from Medellin, Colombia and 2,627 girls from Debrecen, Hungary, were studied. They were asked about the month of their menarche. Vacation months were considered those with more than 6 days of leave from school. RESULTS: The seasonal hypothesis was refuted because there were contradictions with the expected antithetical behavior in both hemispheres, there was a significant heterogeneity of the yearly menarche among girls from the same region, the expected cline of the menarche frequency variance from equator to poles was not observed, finding an antithetical cline instead and there was a significant heterogeneity among months of the same season. On the other hand, months with vacation periods coincided significantly with peaks of menarche, while study months had lower proportion of menarche (total binomial probability < 10(-6)). Girls whose month of menarche was the same as their month of birth, did not agree completely with the vacation-study hypothesis as the rest of the sample. CONCLUSIONS: Vacation periods influenced menarche rhythm. However, these periods coincide with most cultural events and this strong association needs further study to be considered causal. It is not possible to assume school stress as the main explanatory variable. Ontogenetic factors such as birth imprinting also can influence the menarche rhythm, as shown in girls whose month of menarche coincided with their month of birth.

Adolescent↗
PubMed1999

[Sexual dimorphism in human medial raphe nuclei. Preliminary study with the Golgi cox method].

Brains from a female and a male newborn who died from an asphictic syndrome were examined to study the cytoarchitecture of the median raphe nucleus using the Golgi-Cox and morphometric methods. This nucleus is part of the serotonergic system. The morphometric analysis showed in the female newborn a significant increase of neurons. Also she had a higher proportion of ovoid and multipolar cells and a lower proportion of fusiform cells than the newborn male. Our findings suggest that this neuronal distribution may be the anatomical substrate for a serotonergic specific system in each sex.

Female↗
PubMed1998

Distribution of (CGG)n and FMR-1 associated microsatellite alleles in a normal Chilean population.

We report on the allele distribution in a normal Chilean population at 2 microsatellite loci neighbouring the FRAXA locus and at the CGG repeat in the 5' end of the FMR-1 gene, which causes the fragile X syndrome. The most common CGG repeat allele was 30 (41.7%), with 29 being second most common (30.2%). This distribution was similar from that seen in Caucasians but different from that observed in Chinese controls, where the most common allele was 29 repeats. Four alleles of FRAXAC1 and 6 of DXS548 were observed in the Chilean sample. A striking linkage disequilibrium of FMR-1 alleles with FRAXAC1 alleles was observed. In 90% of the 30 CGG repeat alleles only 31% of the 29 CGG repeat alleles had the FRAXAC1 154 bp allele. This result is in agreement with the suggestion that slippage between CGG repeat alleles 29 and 30 and between 152 and 154 FRAXAC1 alleles is very rare. This study suggests a founder chromosome effect in the Chilean population.

Alleles↗
PubMed1998

Intelligence and genetic markers in Chilean children.

Genetic markers and total intelligence quotient (IQ) assessed by WISC (Wechsler Intelligence Scale for Children) were studied in children of both sexes from Santiago, Chile. Heterozygous boys for phosphoglucomutase 1 (PGM) and heterozygous girls for haptoglobin (Hp) had lower IQ than homozygotes. For ABO system, B girls had lower and B boys had higher IQ than children with other ABO phenotypes. These differences were highly significant with the two tailed t'-test (Student's t-test with the Welch-Satterthwaite correction for degrees of freedom), and most of them remained significant after the correction for multiple comparisons. Girls had greater variance of IQ than boys. Relationships between homozygotes and heterozygotes were found in two independent studies. Thus, the genetic relationship found here seems likely to be a true biotic effect.

ABO Blood-Group System↗
PubMed1997

[Gm and Km allotypes in a Chilean urban population sample].

BACKGROUND: The knowledge of the genic structure of a population is of great importance for evolutive studies. AIM: To estimate in a Chilean population sample from the low-middle and low socioeconomic strata of Santiago, haplotypes and allele frequencies for Gm and Km loci. SUBJECTS AND METHODS: The sample included 460 controls of a case-control study of typhoid fever. RESULTS: The G1m-G2m-G3m most frequent haplotypes were: za;..;g or 1,17;(-);21 = 0.4493;fn;b or 3;23;5,13 = 0.2522; f-,..;b or 3;(-);5,13 = 0.1389; zax;..;g or 1,2,17;(-);21 = 0.0685; za;..;b or 1,17;(-);5,13 = 0.0454; za;n;g or 1,17;23;21 = 0.0207; f;..;g or 3;(-);21 = 0.0129. The frequencies of Km alleles were 0.2391 and 0.7609 for Km1 and Km3 respectively. CONCLUSIONS: These frequencies are within those found in Amerindian and Caucasian populations as expected from the origin of the Chilean population. Gm haplotypes did not differ from Hardy-Weinberg equilibrium, while a significant lack of homozygous Km1/km1 was found in Km.

Adolescent↗
PubMed1997

[Confidence of 100 per cent sensitivity and specificity].

A new strategy and four new methods are presented to calculate the limits of the confident interval for an estimate of a proportion equal to 1.0 or 0.0. A current formula which includes 1/(2n) for continuity correction leads to a confident interval which does not include the parameter estimate. Thus, it is proposed: 1) The exclusion of the factor 1/(2n) in that formula leads to correct most of its inconsistencies. The new strategy assumes that the upper limit of a confident interval when the estimates is 100%. The lower limit is calculated by assuming that there is a proportion in the population, from where the sample was taken, such as the probability of getting 100% in the sample is equal to the probability of falling into type I error of current statistics (0.05, 0.01, etc). Three methods are proposed with this strategy. 2) A combinatorial solution based in the knowledge of the number of individuals at whom the test can be applied. 3) A solution based on the binomial distribution. 4) A solution based on the Poisson distribution.

Binomial Distribution↗
PubMed1997

[Assessment of height as an indicator of population nutritional status].

BACKGROUND: Chilean girls of middle and low socioeconomic levels are shorter than their European or North American counterparts. AIM: To challenge the hypothesis that undernutrition is the cause of the shorter stature of Chilean girls. MATERIAL AND METHODS: Height, weight, sexual maturation, biacromial and bi-iliac diameters of low and middle socioeconomic level Chilean children aged 0 to 20 years old, were compared with data from French, English and North American children in the same age range. RESULTS: Chilean girls had an earlier sexual maturation, had bigger biacromial and bi-iliac diameters and had a higher weight for height than European girls. Weight for height of these girls was over the values proposed by the Chilean Ministry of Health, that are based in NCHS/WHO tables. Chilean girls with recent European ancestry were taller than girls without this ancestry. Chilean boys were smaller and had lower weights than their foreign counterparts. Bi-iliac diameters were similar to those of French boys and sexual maturation was similar to English boys. CONCLUSIONS: These results indicate that genetics and not undernutrition is involved in the shorter height of Chilean girls, when compared with their European or North American counterparts.

Adolescent↗
PubMed1997

[Scientific ethics of the origin of humans].

The analysis of the early human life from the view point of a scientific ethics is presented. Life is a historical materioenergetic process of specific organization. This phylo-ontogenetic process is a continuous process without interruption. Biology has demonstrated that human eggs or embryos are full human individuals, even though not all human conception is a human being. The contradictions involved in taking ethical decisions after knowing the percentage of conceptions obtained by in vitro or in fallopian tube fertilization that reach the birth are shown. The advantages of scientific ethics in the analysis of the origin of the different positions are indicated. These advantages come from the dissection of the different cognitive, affective-emotional and value attribution frames involved in the alternative decisions.

Embryo Transfer↗
PubMed1997

Non random DNA evolution.

A model for testing random molecular evolution is proposed. Randomness of recurrent mutation is defined based on isotropy and zero covariance among nucleotide sites. Assuming an equal rate of mutation for the bases A, T, G, and C, in both DNA strands, a mutational matrix of transformation A, T, G, and C with 6 parameters is developed. Under this model the equilibrium proportions (F) of the bases are FA = FT = (D + E)/[2(D + E + H + J)] and FG = FC = (H + J)/[2(D + E + H + J)], D, E, H, J being 4 of the 6 matrix parameters. Thus the expected (FA + FT)/(FG + FC) ratio can also be tested. If the average rate of mutation is 10(-8) per nucleotide site and cell replication, the equilibrium for every site, in most species, is reached in 10(8) years. Eight DNA segments from human, bacteria, fungus and insect genomes were chosen to test these proportions and their heterogeneity among coding and non coding subsegments. While FG was similar to FC as expected, FA was highly different from FT Huge heterogeneities were found between coding and non coding segments and among non coding segments. These results are a strong evidence for non randomness of molecular evolution.

Animals↗
PubMed1996

Polymorphisms and phyletic relationships of the Paisa community from Antioquia (Colombia).

The allelic frequencies of 14 polymorphic loci were obtained for the Paisa community (Antioquia, Colombia) and compared with those of Caucasoids, Negroids and Amerindians as an approach to better understand its ancestral origin. Data pertaining to Caucasoids included Basques, Spaniards and Jews, historically assumed to be the ancestors of Paisas. These comparisons suggested that the Paisa community is a Caucasoid group with very low Amerindian or Negroid contributions. Spaniards or Basques and, to a lesser extent, Sephardims seem to have been their most probable ancestors.

Adolescent↗