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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
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↗
PubMed1996

[Annual rhythm of menarche in Medellín, Colombia].

Hypotheses on seasonal, phylogenetic and ontogenetic factors or imprinting that may produce menarcheal rhythm were tested in a sample of school girls from Medellín, Colombia. The questionnaire included a net of important religious or national feasts and periods of vacation or study to prevent memory biases. European, Asian and Chilean samples showed peaks of menarche in December and January, but a few samples showed a second one in June, July and August. The winter short photoperiod and low temperature were assumed to be the cause of the winter peak in most European samples. However, this seasonal hypothesis was refuted when a Chilean sample also showed a peak in December, January and February (Summer). In the present study performed in a sample from a tropical country we found two peaks of menarche, one in July and the other in November, December and January; thus, the seasonal bypothesis can be hardly supported. Moreover, this sample showed a high coincidence between the month of menarche and the month of birth, and a different pattern of menarche when menarches are distributed according to their coincidence with the gestational development. Both facts affirm the ontogenetic hypothesis, because they were also found in several samples. Since this population is different from those already studied and its monthly distribution of menarches and births is also different from those other ones, the hypothetical phylogenetic factors find additional support. The possible influence of school stress and other environmental factors in the menarcheal rhythm are discussed.

Adolescent↗
PubMed1996

Gm and Km allotypes and typhoid fever.

Gm and Km allotypes of immunoglobulins were determined in children with typhoid fever (Cases), in children without infectious diseases (Con-1), and in children with fever but no Salmonella in their blood or bone marrow (Con-2). Children were sampled from the urban population of Santiago; and they belonged to the low and low-middle socioeconomic strata. Cases had a higher frequency of [f;(-);b1,b3 or 3;(-);5,13] G1m, G2m, G3m haplotype than Con-1 and Con-2. Con-1 and Con-2 did not differ in their Gm haplotype or Km allele frequencies, but they differed in phenotype distribution. Con-1 deviated from Hardy-Weinberg equilibrium for Km due to a lack of Km 1-1 homozygotes. The relationship among these results, the ethnic origin of Chileans, and the differential susceptibility to typhoid fever are discussed.

Adolescent↗
PubMed1996

Idiopathic epilepsy with generalized tonic clonic seizures in Antioquia, Colombia: is the joint Amerindian and Negroid racial admixture the cause of its high prevalence?

Most Colombian populations stem from the admixture of Caucasians, Amerindians and Negroids. In the world, these two latter ethnical groups show a significantly higher prevalence of epilepsy than the former one. We tested the hypothesis that the high prevalence of idiopathic epilepsy with generalized tonic clonic seizures found in the Antioquian population (Paisas), from Colombia, is due to their possible joint Negroid and Amerindian ethnic components. We have previously demonstrated that inheritance is the principal factor for developing epilepsy in this community. Analyses of racial admixture, heterogeneity between populations, genetic distance, and phyletic relationships were performed among epileptic and non epileptic samples from the Antioquian community. Also Caucasians, Spaniards, Basques, Jews, Chileans, Negroids, Amerindians and Mongoloids were included in the analysis. Four highly polymorphic blood systems were used as genetic markers: RH, MNS, ABO and FY. They were chosen because of their high discriminant power in these ethnic groups. In the population affected with idiopathic epilepsy, the estimated Negroid and Amerindian rates of admixture were low (3% and 14%, respectively). Although, these degrees of admixture can be explained due to common ancestral origins, the estimated proportion of Amerindian admixture in the epileptic affected population, was significantly higher than the estimated for the Non affected Antioquian population. The latter finding is consistent with the analysis of heterogeneity between populations that discriminated epileptic population from non epileptic Antioquian population (p < 0.05). Epileptic and non epileptic Paisas clustered in topology with Caucasians, very close to Spaniards and Basques and highly distant from Negroids and Amerindians. Thus, far, the origin of the high prevalence of idiopathic epilepsy in the Antioquian (Paisa) population cannot be explained by the hypothetical joint Negroid and Amerindian ethnical admixture, but using additional genetic markers and other methods of racial estimation of admixture it is necessary to corroborate if the Amerindian admixture component is significantly higher in the epileptic population than in the non epileptic Paisa population.

Black People↗
PubMed1996

A model of complete random molecular evolution by recurrent mutation.

A model for random molecular evolution based on recurrent mutation is proposed. Recurrent mutation replaces completely any original base in a nucleotidic site. This occurs if more than four times the number of reproductive cycles equal to the reciprocal of the mutation rate happen; no matter the population size, the number of nucleotides a genome has, or the taxa at which it belongs. The main results are: i) the expected distribution of DNA bases in a site is an isotetranomial distribution, where Adenine (A), Guanine (G), Cytosine (C) and Thymine (T) occur with probability equal to 0.25; ii) the distribution of bases in a site is independent from the distribution of bases in other sites. Several expected consequences that can be contrasted with actual data are generated. Species or operational taxonomic units (OTUs) that evolved in big populations should present distances equal to zero and similarities equal to one. OTUs evolving in small populations should present distances equal to 3/4 and similarities equal to 1/4. Thus, random molecular evolution by recurrent mutation cannot yield a tree at all. The only possible tree is that produced by random fluctuations of distances according to their variances (stochastic tree). Some consequences of the model on the expected primary structure of proteins are also analyzed. There are sufficient generations for any DNA segment evolving apart during the last four hundred million years, to reach those expected base distributions.

Chymotrypsinogen↗
PubMed1996

New evidence of non seasonal factors in the menarche rhythm.

The phylogenetic, ontogenetic and seasonal hypotheses on the annual periodicity of menarche were tested. Data from European, Asian (Caucasian, Mongolian and Caucaso-Mongolian people from the northern hemisphere) and Chilean (Caucaso-Amerindian from the southern hemisphere) populations were compared with data from Hungary (Caucaso-Mongolian Europeans from a northern temperature zone) and Madras, India (a complex ethnically originated people from a tropical northern area). Chileans were compared with those Caucaso-Mongolian people because Amerindians belong also to the Mongolian group. Hungarian girls showed peaks of menarche in the month of January (winter), June, July and August (summer), in contradiction with most European Caucasians who showed peaks only in winter months; and in agreement with Finns who showed both peaks. Indian girls had peaks in April, May and June (summer) and more extreme peaks and troughs than the Finnish girls (from a temperature arctic zone). These findings do not agree with the seasonal hypothesis, but they do with the phylogenetic hypothesis. Indian girls had a peak of menarche in the same month of birth and the arrangement of data according to the gestational-menarche coincidence showed a significant heterogeneity for the monthly peaks of menarche; thus, the ontogenetic hypothesis was also supported.

Adolescent↗
PubMed1995

Rh--plasma iron binding capacity association. New evidence.

The relationship between Rh phenotypes and the total iron binding capacity (TIBC) of plasma was studied in a sample from Medellín, Colombia. In a previous report from Santiago, Chile, children carrying the C Rh specificity had a higher level of TIBC than those having the specificity. The same association was found in young people from Medellín.

Chile↗
PubMed1994

Epistemic restrictions in population biology.

Biologists have believed that the application of statistical or mathematical models to population biology has always been a correct and helpful tool to acquire knowledge. The present article demonstrates that the standard interpretation of statistical results yielded by the application of mathematical models to some populational processes, not only hides knowledge, but may lead to wrong knowledge. These epistemic restrictions (type I and II errors). A new more versatile conditional interpretation of statistical results is proposed.

Genetics, Population↗