Unlike some other reproductions of classic texts (1) We have not used OCR(Optical Character Recognition), as this leads to bad quality books with introduced typos. (2) In books where there are images such as portraits, maps, sketches etc We have endeavoured to keep the quality of these images, so they represent accurately the original artefact. Although occasionally there may be certain imperfections with these old texts, we feel they deserve to be made available for future generations to enjoy.

The control of plant gene expression at the transcriptional level is the main subject of this volume. Genetics, molecular biology and gene technology have dramatically improved our knowledge of this event. The functional analysis of promoters and transcription factors provides more and more insights into the molecular anatomy of initiation complexes assembled from RNA polymerase and the multiplicity of helper and control proteins. Formation of specific DNA-protein complexes - activating or repressing transcription - is the crux of developmental or environmental control of gene expression. The book presents an up-to-date, critical overview of this rapidly advancing field.

L. Nover and L. Hightower Though the roots of experimental stress biology at the cellular and organismic level can be traced back to the middle of the last century (Nover 1989), a decisive breakthrough came only in 1962 with the report on stress-induced changes of gene activity in Drosophila (Ritossa 1962) and the subsequent identification of the newly synthesized heat stress proteins (Tissieres et al. 1974) and mRNAs, respectively (McKenzie et al1975; McKenzie and Meselson 1977). The selectivity of induction and the high rate of accumulation of Hsps facilitated the cloning and sequencing of the hs genes in Drosophila and the demonstration that all organisms react similarly when exposed to heat stress or chemical stressors (Ashbumer and Bonner 1979; Schlesinger et al. 1982; Nover 1984). The explosive development of molecular stress research in the following 10 years illustrated that the stress response represents a characteristic network of dramatic but transient changes at many levels of cellular structure and function, including gene expression (Atkinson and Walden 1985; Tomasovic 1989; Georgopoulos et al. 1990; Nover et al. 1990; Nover 1991). Besides the characterization of the hs genes and the mechanism of their induction, major interest concentrated on the heat stress proteins and their possible roles in induced stress tolerance. Rapidly, it became apparent that the major stress proteins are coded by five conserved multigene families (Lindquist and Craig 1988: Nover et al.

Three years have elapsed since the publication of the first edition of this book (in German). The continued interest of our readers and the rapid progress of our knowl edge in many fields necessitates a thoroughly revised and somewhat enlarged new edition. Cell differentiation is a prerequisite of life. It is defined as the prooess leading to the qualitatively and quantitatively selective realization of distinct parts of a given genetic material. Cell differentiation comprises five main aspects: (1) signal reception and transformation, (2) selective rearrangements of the genetic material, (3) differen tial gene expression, (4) organization of gene expression programs and (5) intercellular coordination of cell differentiation within the developmental programs of multicellular organisms. Despite the bewildering multiplicity of its results, i.e., the differentiated phenotypes of cells, there are apparently fundamental similarities with respect to the molecular mechanisms of the process itself. These mechanisms constitute the central subject of this book."

1. Secondary Metabolism and Differentiation In addition to the primary metabolic reactions, which are similar in all living beings (formation and breakdown of nucleic acids and proteins as well as of their precursors, of most carbohy drates, of some carboxylic acids, etc. ), a vast number of metab olic pathways lead to the formation of compounds peculiar to a few species or even to a single chemical race only. These reac tions, in accord with CZAPEK (1921) and PAECH (1950), are summed up under the term "secondary metabolism," and their products are called "secondary metabolites. " The wide variety of secondary products formed in nature includes such well-known groups as alkaloids, antibiotics, cardiac glyco sides, tannins, saponins, volatile oils, and others. A consider able number of them are of economic importance in therapeutics or technology. Although secondary products are produced by micro organisms, higher plants, and animals (cf. LUCKNER, 1972), most of the substances are found in the plant kingdom. The lack of mechanisms for true excretion in higher plants may result in this unequal distribution, the "waste products" of metabolism in plants instead being accumulated in the vacuoles, the cell walls, or in special excretory cells or spaces of the organism ("metabolic excretion," cf. FREY-WYSSLING, 1935, 1970; MOTHES, 1966a, b, 1972; LUCKNER et al., 1976. Many secondary substances have, however, a direct biologic func tion. They can be regulatory effectors, e. g."

Fragen nach dem Forschungsdesign sind immer auch Fragen nach der Gegenstandsangemessenheit. Die Qualitat ihrer Umsetzung zeigt sich darin, wie gut es gelingt, Design, Forschungsfrage und Forschungsfeld anzupassen. Die Autorinnen und Autoren dieses Buches beantworten die sich ihnen stellende Frage der Gegenstandsangemessenheit teils mit der Entwicklung neuer Methoden fur neue Herausforderungen in Pflege und Pflegewissenschaft, teils mit der Anwendung 'klassischer' Forschungsdesigns, wie sie Hermeneutische Verfahren, Metaphernanalyse, Praxeologie oder Ethnographie vorschlagen. Wie es gelingen kann, methodologische und forschungspraktische Anforderungen zu erfullen, zeigen diese funf sehr unterschiedlichen Antworten. Deutlich wird die Notwendigkeit, sich einzulassen auf den Gegenstand und qualitative Forschung als Prozess zu begreifen. Erganzt werden diese forschungspraktischen Beispiele durch einen Aufriss der theoretischen und methodologischen Implikationen, sowie der Frage danach, wie Methoden gelehrt werden koennen.

In der Ophthalmologie gibt es - wie in allen klinischen Fachern - eine nicht ubersehbare Anzahl von therapeutischen Vor- schlagen. In diesem Buche sollte nun der Versuch gemacht werden a) darzustellen, was an konservativer Therapie gesichert ist und b) zahlreiche fragliche Behandlungsmethoden kritisch zu be- leuchten. Dem therapeutischen Optimisten wird in diesem Buche moegli- cherweise zu wenig, dem therapeutischen Pessimisten dagegen zu- viel gebracht worden sein. Ziel des Buches ist nicht Vollstandig- keit, sondern kritische Auswahl nach persoenlicher Erfahrung. Da- mit wird das Buch selbst wieder Kritik herausfordern. Ich bitte, die - hoffentlich zahlreichen - Anregungen und Diskus- sionsbeitrage direkt an die Autoren der einzelnen Kapitel zu schicken. Dusseldorf, im Oktober 1977 Hans Pau Inhaltsverzeichnis Kapitel 1 5. Prophylaxe von Refraktionsfehlem 23 Refraktionsstoerungen (E. Aulhom) Literatur 24 1. Brillen 1 1.1 Fernbrille 2 Brechkraft der Brillenglaser 2 1.1.1 Kapitel 2 1.1.2 Lichtabsorption der Brillenglaser 5 Asthenopien (E. Aulhom) 25 1.1.3 Farbige Toenung der Brillenglaser 7 1.1.4 Glas oder Kunststoff? 7 1.1.5 Brillenfassung 8 Literatur 25 1.1.6 Prismatische Brillenglaser 9 1.1.7 Aniseikonieausgleich 9 1.2 Lesebrille 10 1.2.1 Unifokal, bifokal, trifokal oder Kapitel 3 multifokal? 12 Stoerungen des Farbensehens 1.3 Arbeitsbrille 14 (E. Aulhom) 1.4 Schutzbrille 15 Sportbrille 15 1.5 1.6 Schwachsichtigensehhiljen 15 Angeborene Stoerungen des Rot-Grun- 1.