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K Lange

Publications and source records attributed to K Lange.

At least 19 recordsLinked to original sources
PubMed1979

Continuous variation caused by genes with graduated effects.

The classical polygenic theory of inheritance postulates a large number of genes with small, and essentially similar, effects. We propose instead a model with genes of gradually decreasing effects. The resulting phenotypic distribution is not normal; if the gene effects are geometrically decreasing, it can be triangular. The joint distribution of parent and offspring genic value is calculated. The most readily testable difference between the two models is that, in the decreasing-effect model, the variance of the offspring distribution from given parents depends on the parents' genic values. The more the parents deviate from the mean, the smaller the variance of the offspring should be. In the equal-effect model the offspring variance is independent of the parents' genic values.

Genes↗
PubMed1979

An alternative model of recombination and interference.

A model of four-strand crossing-over is presented in which all non-randomness is attributed to the non-Poisson distribution of the number of exchanges. Nth order recombination fractions and the coefficient of coincidence are calculated in terms of the model. It is shown that coincidence may be greater or less than unity depending on the prior distribution of exchanges. An obligate exchange is a sufficient condition for coincidence to be less than unity if there is a maximum of four exchanges, but not necessarily if five or more are possible. It is also shown that marginal coincidence is an insufficient concept to explain the behaviour of coincidence over its entire two-dimensional domain.

Chromosome Mapping↗
PubMed1979

Application of a recombination model in calculating the variance of sib pair genetic identity.

Using a previously described model of crossing over (Risch & Lange, 1979), we have calculated analytically the variance in the proportion of genes identical by descent shared by two sibs. The prior distributions for numbers of chiasmata reported in Suarez et al. (1979) were used to calculate a standard deviation of 0.040 for the 22 human autosomes. It is also shown that any two identity by descent values within a sibship are uncorrelated.

Animals↗
PubMed1979

A new method for the analysis of age trends in CPK levels with application to Duchenne muscular dystrophy.

Measurement of serum creatine phosphokinase (CPK) is the most commonly applied test for carrier detection in Duchenne muscular dystrophy. About two thirds of all carriers have markedly elevated CPK levels. Age correction of CPK measurements would be straightforward if carriers of all ages could be unambiguously identified. Since such identification is impossible, we elaborate an indirect statistical method which is based on Haldane's theory of the balance between selection and mutation for X-linked lethals. We also apply this method to a large body of data gathered on female relatives of Duchenne muscular dystrophy patients and on controls. The results are compared with earlier partial findings.

Age Factors↗
PubMed1978

Release of glycolytic enzymes from cultivated tumor cells.

Several types of cultured cells release glycolytic enzymes into their suspending medium. This effect is most obvious with tumor cells, especially with their ascites forms. Erythrocytes do not release glycolytic enzymes. The total extracellular phosphoglucose isomerase activity consists of two components. One part is dissolved in the medium, the other one is sedimentable at 150 X g together with the cells. The latter seems to be localized at the cell surface. At densities of about 10(6) cells/ml maximum activity in the medium is reached within 5--10 min. After that no further release of enzyme activity can be observed. Serum reduces the rate of enzyme release considerably. This effect can be reversed by washing with protein free media. Treatment with trypsin leads to high extracellular phosphoglucose isomerase activities of the cells which originally show low external enzyme activity. Erythrocytes do not show any effect with trypsin, ascites tumor cells do not alter their high extracellular enzyme activity. At a density of 10(5) cells/ml, Yoshida acites tumor cells, cultured in vitro, release about 12% of originally intracellular phosphoglucose isomerase activity by 5 elutions with fresh medium. The process of enzyme release shows a certain selectivity in respect to different glycolytic enzymes. Aldolase exhibits the highest activity in the medium in relation to its homogenate activity.

Animals↗
PubMed1978

A goodness-of-fit test for the polygenic threshold model: application to pyloric stenosis.

A new test of goodness of fit for the polygenic threshold model is proposed. This test, when applied to disorders showing different incidence rates in males and females, is designed to account for ascertainment in more detail than previously done by other investigators. This is accomplished by computing the expected distribution of nuclear families with more than one affected sib conditioned on several family-dependent variables, including whether each family was ascertained via only affected boys or via at least one affected girl. A direct measure of the probability of observing a data set is thereby derived. The test, when applied to data on pyloric stenosis, exposes the critical nature of the ascertainment procedures. Different levels of statistical significance are obtained when mode of ascertainment is taken into account than when the mode of ascertainment is ignored.

Female↗
PubMed1978

Effects of 6-aminonicotinamide on growth and acetylcholinesterase activity during differentiation of neuroblastoma cells in vitro.

Addition of 6-AN (0.01 mg/ml) to growing cultures of C-1300 neuroblastoma cells strongly reduced cell division. This growth inhibition was accompanied by a higher cell volume and a lower protein content per cell as compared to controls. Concurrently the specific activity of AChE increased markedly incontrols and 6-AN-treated cultures. During the experimental periods the specific activity of AChE was significantly higher after 6-AN. Morphologically, 6-AN-treated cultures showed characteristic signs of differentiation, i.e. enlarged, flattened cells with long branched processes. The described effect of 6-AN on growth and differentiation of neuroblastoma cells was less pronounced if cells received the antimetabolite after a subcultivation period of 5 days.

6-Aminonicotinamide↗
PubMed1978

Effects of reproductive compensation and genetic drift on X-linked lethals.

A revival of interest in Haldane's equilibrium theory for X-linked lethals has been stimulated by the introduction of accurate tests for the detection of female heterozygotes in Lesch-Nyhan disease. Application of these tests appears to indicate an excess of familial cases. This excess can be attributed to ascertainment bias, a difference in female and male mutation rates, genetic drift, and reproductive compensation. Reproductive compensation will be particularly effective in increasing the proportion of familial cases if (1) birth control is widespread; (2) selection against affected males acts in utero; (3) affected sons show symptoms at an early age; and (4) sons are more highly valued than daughters. We demonstrate how only a few generations of reproductive compensation are sufficient to achieve an approximate equilibrium between selection and mutation showing a high proportion of familial cases. We also discuss the random fluctuations around equilibrium caused by genetic drift.

Contraception↗
PubMed1977

Comments on lack of interference in the four strand model of crossing over.

Assuming a four strand model and no chromatid interference, lack of chiasma interference is known to be equivalent to the assumption that the formation of chiasmata follows a Poisson process. We prove the lack of chiasma interference is also equivalent to the assumption that a random gamete shows recombination on any given interval of a chromosome independently of recombination on all disjoint intervals. Both assumptions are sufficient, but not necessary, for Haldane's formula relating recombination to map distance to be true, as we demonstrate by specific counterexamples. These issues are discussed in the context of the theory of stochastic point processes.

Chromatids↗
PubMed1977

Distribution of acridine orange-stained RNA in neuroblastoma cells during differentiation.

Vital staining of neuroblastoma cells with acridine orange produces a bright intracellular red-orange fluorescence most probably due to the occurrence of RNA. The distribution of this fluorescence depends on the state of morphological differentiation. The fluorescence is predominantly found in the perikaryon, the growth cones, and the endings of the processes of differentiated cells. This is of special interest in respect to the biochemistry of differentiation and the function of nerve cells. Comparative autoradiographical studies with 3H-uridine demonstrate that the newly synthesised RNA is transported into the endings of the cell processes.

Acridines↗
PubMed1977

Glucose metabolism in C-1300 neuroblastoma cells after inhibition of hexose monophosphate pathway.

1. Application of 6-AN (0.01 mg/ml) leads to a strong accumulation of 6-PG in C-1300 neuroblastoma cells which, however, only amounts to one third of that found in C-6 glial cells. 2. In C-1300 neuroblastoma cells dephosphorylation of the accumulated 6-PG causes a rise of the intracellular gluconate to eight times the value found for 6-PG. It is four times higher than the gluconate content observed in C-6 glial cells. 3. Although 6-PG is a competitive inhibitor of PGI it causes no reduction of glycolytic flux and ATP content in stationary phase C-1300 neuroblastoma cells in contrast to the strong reduction of glycolytic flux and ATP content observed in C-glial cells. 4. The intracellular Glc-6-P and Fru-6-P content of C-1300 neuroblastoma cells increases by four to five times after treatment with 6-AN. Both this increase and the decrease of Fru-1,6-P2 content point to an inhibition of the phosphofructokinase. 5. In contrast to C-6 glial cells no morphological changes could be observed in C-1300 neuroblastoma cells up to 24 h after administration of 6-AN.

6-Aminonicotinamide↗
PubMed1977

Estimation of the variance components for dermal ridge count.

Refinements of the scoring algorithm to estimate variance components from pedigree data are developed. Subsequent to these modifications, heritability estimates were readily obtained from data for over 50 traits, including total finger ridge count reported here. A significant contribution to the total variance of ridge count could be attributed to the effects of dominance, a finding not previously reported for this dermatoglyphic trait.

Analysis of Variance↗