Hot spots and functional organization of human chromosomes

Summary Our working hypothesis is that the Q-darker human chromosome segments have higher gene densities than the bright regions. Especially prominent in this respect are six hot spots, the short Q-dark regions in 3p, 6p, 11q, 12q, 17q, and 19 (p or q), which have been chosen because their density of mitotic chiasmata is above 5. Chromosomes with gene-rich segments would act as trisomy lethals in very early embryos, whose spontaneous abortions would not be recognized. Containing active genes, the regions would be looped out in interphase and thus be more easily available for mitotic pairing and crossing-over.To test this hypothesis, correlations and partial correlations of the following parameters have been determined: the density of mitotic chiasmata, the number and density of localized genes, the incidence of trisomic abortions, the length of chromosomes, and their Q-brightness. Overall, the correlations and partial correlations agree with, but do not prove, the working hypothesis. Far stronger evidence for our hypothesis comes from the highly significant negative effect of hot spots on trisomic abortions which would act as a kind of trisomy lethal. The gene numbers on the hot-spot chromosomes as compared with the controls, on the other hand, are in the right direction, but the difference is not significant.This is paper No. 2161 from the Genetics Laboratory, University of Wisconsin. It was supported by National Institutes of Health (Washington) grants GM 22881, GM 15422-09, and, to Dr. Hans Ris, GM 04738; by grant IN-35P from the American Cancer Society, and by the U. W. Graduate Research Committee (Grant 101-4403). The photography was done by Mr. Walter Kugler, Jr.     

Changes in the organization of chromosomes during the cell cycle: response to ultraviolet light.

Fusion between mitotic and interphase cells results in the premature condensation of the interphase chromosomes into a morphology related to the position in the cell cycle at the time of fusion. These prematurely condensed chromosomes (PCC) have been used in conjunction with u.v. irradiation to examine the interphase chromosome condensation cycle of HeLa cells. The following observations have been made: (I) There is a progressive decondensation of the chromosomes during G1 which is accentuated by u.v. irradiation: (2) The chromosomes become more resistant to u.v.-induced decondensation during G2 and mitosis. (3) There is a close correlation between the degree of chromosome decondensation and the amount of unscheduled DNA synthesis induced by u.v. irradiation during G1 and mitosis: (4) Hydroxyurea enhances the ability of u.v. irradiation to promote the decondensation of chromosomes during G1, G2 and mitosis. Hydroxyurea also potentiates the lethal action of u.v. irradiation during mitosis and G1. These data are discussed in relation to the suggestion that chromosomes undergo a progressive decondensation during G1 and condensation during G2.     

Dynamic organization of the cell nucleus

The dynamic organization of the cell nucleus into subcompartments with distinct biological activities represents an important regulatory layer for cell function. Recent studies provide new insights into the principles, by which nuclear organelles form. This process frequently occurs in a self-organizing manner leading to the assembly of stable but plastic structures from multiple relatively weak interaction forces. These can rearrange into different functional states in response to specific modifications of the constituting components or changes in the nuclear environment.     

Age and the structural organization of the EEG of children and adolescents in different functional states of the brain

The present paper deals with age characteristics of EEG reactions, at the level of integral cues, to functional loads in children of 7-14 years and juveniles. Modelling of tense and emotional states leads to a reconstruction of the organization of the EEG of quiet waking state, with formation of integral characteristics specific for these states and reflecting various mechanisms of the brain activity. At the age of 9-12 years emotional loads bring about disturbances of EEG integral characteristics, testifying to a lowering of brain reactivity.     

Identical functional organization of nonpolytene and polytene chromosomes in Drosophila melanogaster

Salivary gland polytene chromosomes demonstrate banding pattern, genetic meaning of which is an enigma for decades. Till now it is not known how to mark the band/interband borders on physical map of DNA and structures of polytene chromosomes are not characterized in molecular and genetic terms. It is not known either similar banding pattern exists in chromosomes of regular diploid mitotically dividing nonpolytene cells. Using the newly developed approach permitting to identify the interband material and localization data of interband-specific proteins from modENCODE and other genome-wide projects, we identify physical limits of bands and interbands in small cytological region 9F13-10B3 of the X chromosome in D. melanogaster, as well as characterize their general molecular features. Our results suggests that the polytene and interphase cell line chromosomes have practically the same patterns of bands and interbands reflecting, probably, the basic principle of interphase chromosome organization. Two types of bands have been described in chromosomes, early and late-replicating, which differ in many aspects of their protein and genetic content. As appeared, origin recognition complexes are located almost totally in the interbands of chromosomes.     

EMBO workshop report. An eclipse over the cell nucleus functional organization of the cell nucleus Prague, August 9-12, 1999

The EMBO workshop 'Functional Organization of the Cell Nucleus' held in Prague at the Hotel of the Postgraduate School of Medicine was attended by 110 participants (49 invited speakers and 61 selected participants) from 22 countries. Such a full range of topics devoted to the cell biology of the nucleus has not been discussed previously in such an intimate meeting in Europe. The workshop not only offered an opportunity for junior scientists to benefit from having an international meeting within Europe and a chance to discuss their work with internationally recognized experts, but it also offered a unique opportunity for interactions among the more established investigators. The fruits of a number of presentations are gathered together in a Special Issue of the Journal of Structural Biology which appeared in spring 2000. Last but not least, it is worth mentioning that while stepping through a packed scientific program, the participants did find the time to observe the solar eclipse just before the lunch break of August 11.     

Neural activity states in different forms of physiological tremor. Facts and hypotheses

This paper attempts to combine (and thereby briefly review) various sets of physiological data in order to outline a qualitative model of the different states of stochastic neural activity underlying different forms of physiological tremor. Particular emphasis in put on spatial distributions of the properties of neural elements and their interconnexions, and on discharge characteristics of motor units and muscle spindle afferents including so-called early discharges and nonlinearities. It is argued that the wide variety of internal anatomical and functional structures of skeletal muscles and of their reflex organization must be considered when dealing with stability problems. Computer simulations of stochastic population models of the involved neuromuscular elements are advocated as means to investigate the relative importance of the many factors possibly contributing to stabilizing or de-stabilizing neuromuscular systems.     

Ultrastructural characteristics of osteoclasts in different functional states

By electron microscopy and autoradiography, a study was made of osteoclasts in the metaphyseal zones of the femora of 1-7-day old rabbits and rats. It was established that depending on the intensity of resorptive processes osteoclasts noticeably differed in their morphology (shape, size, number of nuclei, degree of development of intracellular organelles, "brush border"), as well as in the level of biosynthetic activity registered by incorporation intensity of 3H-uridine and 3H-methionine in these. According to these indices, osteoclasts were classified as young, mature functionally active, and non-active osteoclasts, as well as perishing ones. The defined morpho-functional states represent successive stages of the life cycle of osteoclasts.