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Biomedical subjects

C Denniston

Publications and source records attributed to C Denniston.

18 recordsLinked to original sources
PubMed1990

Alternative fitness models with the same allele frequency dynamics.

For any set of one- or two-locus genotypic fitnesses there are alternative sets, usually frequency-dependent and often with quite different biological meanings, that give rise to the same equations for change of allele or haplotype frequencies. Therefore, it is not possible to distinguish among alternative fitness models from allele or haplotype frequency trajectories or equilibrium distributions. For a single locus and for two loci when linkage equilibrium can be assumed, a simple procedure generates some of the alternative fitness sets.

Alleles↗
PubMed1989

The nonrandom participation of human acrocentric chromosomes in Robertsonian translocations.

The present study explores the origin of human Robertsonian translocations (RT) and the causes of the nonrandom participation of the different acrocentrics in them. Satellite associations have been analysed in 966 cells from 8 persons, and 1266 RT with ascertainment have been collected from the literature. The observation that the chromosomes preferentially taking part in satellite associations vary between individuals is confirmed. However, since a preferred chromosome appears to associate at random with the others, this phenomenon should not add to the nonrandomness of the RT. Most RT presumably arise through adjacent chromatid exchanges corresponding to mitotic chiasmata, in the pericentric regions of the acrocentrics. Our working hypothesis is that there is a basic exchange rate between any two acrocentrics. The surplus of t(14q21q) is presumed to depend on these two chromosomes having a homologous pericentric region. The 10-20 times higher incidence of t(13q14q) as compared with other RT is best explained by crossing-over between homologous, but relatively inverted, segments in these chromosomes. Of the 246 RT ascertained through repeated abortions or infertility, 56 were found through the latter. Of these, chromosome 14 was involved in 51. The infertility may be caused by a small deletion of 14q, as is often the case in 15q in Prader-Willi syndrome. In all RT ascertained through 21 or 13 trisomy, respectively, the relevant chromosome is one of the participants. Our data thus do not give any support to the idea of interchromosomal effects exerted by RT.

Chromosomes, Human, Pair 13↗
PubMed1985

X chromatin, endomitoses, and mitotic abnormalities in human cervical cancer.

The incidence of X chromatin bodies and mitotic modifications and aberrations has been analyzed using Feulgen-squash preparations in 47 cervical cancers from Helsinki and 35 from Madison. Sixteen of the 82 tumors did not display any X chromatin bodies, and some others showed a lower than normal frequency, especially in the large nuclei. Different hypotheses to explain the absence of Barr bodies in female tumors have been reviewed. A new observation is that 44/82 tumors contained endomitoses. The metaphase/prophase ratio (M/P) was higher than 1.5 in all but three cases, reaching values as high as 23.0 (Madison) and 34.2 (Helsinki), and in one exceptional case, 51.8. The different types of cells, mitotic, endomitotic, and those with large to giant nuclei, form their own strands or layers. Cervical cancer is diagnosed earlier in Finland than in Madison due to a Pap mass screening program, and consequently, the survival of the patients after 5 years was 27/47 in Helsinki and 6/35 in Madison. No correlation could be established between the M/P (or other mitotic phenomena) or the stage and grade of the tumor, the age of the patient, or survival time.

Adult↗
PubMed1985

Screening program theory: decision functions and protocols.

A screening program is defined to include a set of tests, a decision function, and a protocol. The major characteristics of a screening program are the error rates of the individual tests, the overall error rates of the program, the costs of the individual tests, and the overall program costs. It is shown how to calculate the program error rates for any given decision function. The concept of a screening protocol is developed and a method for enumerating all protocols of a given decision function is given. A given protocol has two calculable costs: the average cost of testing a mutagen and the average cost of calculating a nonmutagen. A method for calculating these costs for any protocol is given. All decision functions utilizing up to five tests are enumerated.

Costs and Cost Analysis↗
PubMed1985

Mitotic chiasmata, gene density, and oncogenes.

Chromosomes with regions rich in mitotic chiasmata in Bloom syndrome (1,3,6,11,12,17,19, and 22) have been compared for various parameters to similar-sized chromosomes 2, 4, 7, 10, 9, 18, 20, and 21 with the following results: (1) The number of genes localized on the test chromosomes is significantly higher (248) than that in the control chromosomes (133). (2) The number of trisomic abortions is significantly lower (45) for the test chromosomes than for the control chromosomes (140). (3) Homogeneously stained regions in neuroblastoma lie at chiasma-containing regions on chromosome arms 1p, 6p, 17q, and 19p or q. (4) The average chiasma density of regions with at least one oncogene is 2.414, whereas that of regions containing no known oncogene is 1.137; however, the difference is not statistically significant. The association of constant cancer chromosome breaks is also in the positive direction, but is not statistically significant. Our tentative conclusion is that the chiasma-rich regions which are Q-dark and early-replicating, and therefore assumed to contain active "housekeeping" genes are extended in interphase. Thus they are available for mitotic crossing-over. In the trisomic state they act as trisomy lethals, leading to early abortions. Being gene-rich they are more likely to contain oncogenes which is reflected also in their agreement with cancer breakpoints. The very high incidence of cancer in Bloom syndrome is a further indication of the possible association of cancer-related phenomena and mitotic crossing-over.

Abortion, Spontaneous↗
PubMed1979

Position of the human X inactivation center on Xq.

In three women with a 46,XXq- chromosome constitution, the length of the deletion was expressed as the ratio of the remaining part of Xq to Xp c' over a + b. In one of them (KH) this ratio was 0.33, in another (GE) 0.59, and in the third (AP) the ratio fell between these values. The break in KH is more or less on the border of the Q-dark proximal region. A comparison with relevant X-autosomal translocations indicates that the X inactivation center lies near, but not at the border of, the Q-dark and the adjoining bright region (c and d).

Adult↗
PubMed1979

Genetic polymorphism of the major parotid salivary glycoprotein (Gl) with linkage to the genes for Pr, Db, and Pa.

Genetic polymorphism of the major glycoprotein (Gl) found in parotid saliva is determined by autosomal inheritance of one unexpressed and four expressed alleles. This hypothesis is supported by studies in 41 white families including 146 children. For 143 randomly collected salivas from whites and 82 randomly collected salivas from blacks, maximum likelihood estimates of the gene frequencies are as follows: for whites, Gl1 = 0.742, Gl2 = 0.040, Gl3 = 0.155, Gl4 = 0.017, Gl0 = 0.46; for blacks, Gl1 = 0.459, Gl2 = 0.050, Gl3 = 0.337, Gl4 = 0.044, Gl0 = 0.110. There is strong evidence for linkage of Gl/Pr (seven families, lod score at theta = 0 is 5.24) and G1/Db (eight families, lod score at theta = 0 is 4.45). The allelic products of Gl show evidence for linkage disequilibrium with the products of the Pr, Db, and Pa loci (P less than 0.0005). On the basis of varying degrees of linkage disequilibrium, Gl may be closer to Db than to Pr or Pa and on the "outside" of Db with respect to Pr or Pa. Amino acid analyses of Gl 1 and Gl 4 proteins show strong resemblances in composition to the major basic glycoprotein and the acidic proline-rich proteins of parotid saliva described by other workers. The polymorphic forms of the Gl proteins show microheterogeneity due to variability in charge and molecular weight. The electrophoretic polymorphism appears to be determined by apparent differences in molecular weights between the Gl proteins.

Alleles↗
PubMed1979

Genetic polymorphism of vitamin B12 binding (R) proteins of human saliva detected by isoelectric focusing.

Genetic polymorphism of the vitamin B12 binding (R) proteins of parotid saliva is determined by autosomal inheritance of codominant alleles. This hypothesis is supported by studies in 43 families including 152 children. For randomly collected salivas from 143 whites, 104 blacks, and 75 Chinese, gene frequencies are as follows: for whites, Rs1=0.88, Rs2=0.12; for blacks, Rs1=0.94, Rs2=0.06; for Chinese, Rs1=1.00. This genetic marker is also shared by R proteins of milk, tears, and leukocytes. In the Rs 1--2 salivary type there is less labeling of the protein products of Rs2 v. Rs1 with 57Co B12 as assessed by the intensity of the bands on the autoradiogram. There is no evidence for close linkage (theta less than 0.01) between Rs and TC II (transcobalamin II) or between Rs and salivary protein locus Pr, Db, Gl, or Ps.

Carrier Proteins↗
PubMed1978

Mitotic chiasmata in human diplochromosomes.

Three placental tissue cultures of spontaneous human abortions showed an unusually high frequency of metaphases with diplochromosomes. In 62 such cells, nine configurations were interpreted as mitotic chiasmata between the two sister chromosomes of a diplochromosome. One U-type exchange between two sister chromosomes was also found. This differs significantly from the 1 : 1 ratio of adjacent and alternate exchanges in translocations, thus supporting the idea that mitotic chiasmata are in principle different from chromatid translocations. The hypothesis is put forward that the frequency of homologous exchanges is determined by the intimacy of pairing which ranges from meiotic pairing through sister chromatid association, through sister chromosome association in diplochromosomes to accidental pairing of homologous regions in diploid cells.

Abortion, Spontaneous↗
PubMed1978

An incorrect definition of fitness revisited.

I have attempted to show that a certain mistaken definition of fitness, which surfaces occasionally, may turn out to have some merit. No claim is made that it is an improvement on, or should replace, the conventional definition of fitness; but it is different and has its own validity. Its generality is intriguing, its application is not limited either to selection or one locus models, and it may be easier to measure experimentally.

Biological Evolution↗
PubMed1977

Nonpairing of the X and Y chromosomes in the spermtocytes of BDF1 mice.

In the hybrid mouse strain BDF1, some 35--40% of spermatocytes had unpaired X and Y choromosomes in stages ranging from diplotene to first meiotic metaphase. This phenomenon varied significantly from mouse to mouse. In pooled material from Swiss Albino and CF1 mice, the corresponding frequency was 5.7%. In C57 BL/6 mice, one of the parent strains of BDF1 mice, the X and Y were separate in 7.7% of the spermatocytes. Based on the behavior of the X and Y in the BDF1 strain, it is concluded that they do not pair, rather than initially pairing and then precociously separating. The factor interfering with the pairing of the X and Y does not affect the autosomes; possibly it is an incompatibility of the two sex chromosomes, which come from different inbred lines.

Animals↗
PubMed1976

A possible active segment on the inactive human X chromosome.

An idic(Xp--) in which the two X chromosomes are attached short arm to short arm, and which thus has two b regions (the Q-dark segment next to the centromere on Xp) between the inactivation centers, assumed to be situated on the Q-dark region next to the centromere on Xq, showed 63.8% bipartite Barr bodies as compared with 22.2% formed by idic(Xq--). In addition, the mean distance of the two parts of the Barr bodies in the fibroblasts of a patient with idic(Xp--) is significantly greater than in the cases with one or no b region. Contrary to the other patients with abnormal X chromosomes, the buccal cells of a woman idic(Xp--) showed a number of bipartite Barr bodies. -- To explain these observations we have put forward the hypothesis that the b region on the Xp always remains active and thus, when the rest of the chromosome forms a Barr body, this segment is extended, allowing the two parts of the X chromatin to get farther apart and at the same time increasing the percentage of bipartite bodies.

Female↗
PubMed1976

A note on serological interpretations.

This paper deals with the interpretation of binary serological data. It attempts to render exact and answer two questions: 1) What are all the serological interpretations of a given set of data? 2) How can different interpretations be distinguished serologically? It is hoped that the formal analysis of serology presented herein will prove to be helpful to those working with complex immunological systems.

Antibody Specificity↗
PubMed1975

Probability and genetic relationship: two loci.

A method has been described for calculating the 15 k-coefficients required to completely specify the genetic identity relations between two individuals at two linked loci. These k-coefficients are then used to derive a general expression for the covariance between relatives for a trait involving two linked loci and arbitrary epistasis.

Consanguinity↗