A method of rapid examination of meiosis in fruit-trees

Vypracování nové metody rychlého vy?et?ování meiose u jádrového ovoce bylo vynuceno rozsáhlostí materiálu, který bylo nutno zpracovat p?i cytologickém zhodnocení 40 soret ?eskoslovenského základního hru?ňového sortimentu. Metoda umo?ňuje během t?í dn? získat trvalé ?ezané preparáty p?ibli?né z 1800 pra?ník?. Této metody je mo?no pou?ít u v?ech rostlin, které mají v době pr?běhu reduk?ního dělení v pylovýeh mate?ských buěkách dostate?ně velké pra?níky k extirpaci.     

Changes in the anatomical structure of the shoot apex ofSenecio vulgaris L. during ontogenis in relation to the formation of leaves and inflorescence

An investigation was made of the anatomical structure of the shoot apex ofSenecio vulgaris L. a photoperiodically neutral plant, and compared with the formation of successive leaf primordia along the axis up to the initiation of the terminal inflorescence. In the shoot apex of a germinating plant a central zone can first be distinguished from the peripheral zone which is composed of small and intensely stained cells. Later, a rib meristem appears. At the time of the initiation of the middle (the largest) leaves, the shoot apex has a distinct small central zone and a well developed peripheral zone and rib meristem. Between these zones there is a group of cells dividing in all directions, the subcentral zone. At the time of initiation of the last leaves, the central zone extends to the flanks and gradually ceases to be distinguishable. At the same time, the subcentral zone increases in size. This is caused first by cell division and later, with the initiation of the last, most reduced leaves, by enlargement of the cells. Vacuolization in the inner part of the apex and the arrangement of the superficial cells in rows parallel to the surface of the apex, is a preparatory step to the initiation of the inflorescence.     

Note on the spread of a state in small social groups

A model is developed for the spread of a state in small social groups. Under suitable assumptions the model exhibits formal identity with Markov chain theory. The basic theorems and classifications of Markov chain theory are stated and interpreted in terms of the model. Finally, some procedures for testing the model are indicated.     

Interferon Induction in Rabbit Cells Irradiated with UV Light

UV irradiation of a continuous line of rabbit kidney cells (RK13) was used as a tool for the study of the mechanism of interferon induction. Irradiation of cells prior to their exposure to Newcastle disease virus (NDV) resulted in a dose-dependent decrease in interferon production. The inhibition of total cellular RNA synthesis by UV irradiation in uninduced cultures was similar to the inactivation curve of interferon production in NDV-induced cultures. In contrast, the production of interferon with polyinosinate-polycytidylate (poly[I].poly [C]) paradoxically was enhanced in cells irradiated with a wide range of doses of UV. However, in cells stimulated with poly(I).poly(C) and "superinduced" by the sequential addition of cycloheximide and actinomycin D, the rate of inactivation of interferon production by UV light was similar to that observed with NDV. These results are not inconsistent with the idea that both poly(I).poly(C) and NDV stimulate the same interferon gene(s), but indicate that the mechanism controlling its expression may be different for each inducer.     

The densitometric study of G bands on human metaphase chromosomes

Summary The method of densitometric measurement of G bands on human metaphase chromosomes is described, and some factors influencing the densitometric patterns are discussed. The densitometric patterns are reproducible and typical for a given chromosomal pair, although they display some degree of variability. Typical patterns of all human metaphase chromosomes are presented, with the patterns obtained from the measurement of some structurally abnormal chromosomes (t13q14q, t14q21q, Xp-).

---

Zusammenfassung Wir beschreiben die Methode der photometrischen Darstellung von G-Banden an menschlichen Chromosomen und diskutieren über einigen Faktoren, die das Resultat beeinflussen. Die photometrischen Kurven sind reproduzierbar und für jedes Chromosomenpaar typisch. Selbstverständlich muß man mit geringen Abstufungen ihrer Variabilität rechnen. Wir zeigen unsere typischen Kurven aller menschlichen Chromosomen, die mit Hilfe der ASG-Technik gefärbt wurden. Gleichzeitig geben wir einige Kurven abnormaler Chromosomen wieder, die auch in unserem Labordargestellt wurden (t(13q14q), t(14q21q), Xp-).