摘要:

The sensitivity of the chick embryo to teratogenic agents and its suitability for screening tests of various substances are examined. Consideration is given to the results obtained in chick embryos by various authors when testing substances (e.g. antibiotics, pesticides) with methods bothin ovoandin vitro. The data presented suggest that the chick embryo is suitable for the testing of teratogens.

ISSN:0373-4137    

DOI:10.1080/11250008009438688

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The structure and function of ribosomes in the cell cycle and especially in embryonal differentiation is reviewed, some of their phylogenetic aspects being also considered. Data from different species suggest a correlation between modification of the nucleotide sequences and different evolutionary levels of the organisms.

ISSN:0373-4137    

DOI:10.1080/11250008009438689

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Evidence from organ culture, primary cell culture, and cell cloning shows that terminally differentiated iris epithelial cells of adult newts give rise to lens cells when they are activated in proliferation. The working hypothesis is discussed according to which the cell-type conversion is controlled by the number of cell cycles traversed by the cells after their re-entry in cell cycles. It is further argued that the neural retina plays the decisive role for conversion onlyin situand in organ culture, where the proliferation period is restricted, but it is dispensable for conversion in cell culture where the proliferation period is extended. The progression of iris epithelial cells through cell cycles is accompanied by exocytosis of melanosomes and alteration in cell surface properties. These changes are interpreted as dedifferentiative events which release the cells from their prior commitment in melanocytic differentiation. Possible roles of lysosomes, intracellular levels of Ca++and cyclic AMP in melanosome discharge are discussed.

ISSN:0373-4137    

DOI:10.1080/11250008009438690

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

For domestic animals, modern management technics lead to a way of life very different from the natural one.

ISSN:0373-4137    

DOI:10.1080/11250008009438691

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The male black goby,Gobius jozo, is known to possess a large mesorchial gland which synthesizes large amounts of 5β-reduced androgens conjugates, especially etiocholanolone glucuronide. When gravid females releasing eggs on stripping were exposed singly to this steroid in a tank monitored through a closed television circuit, most of them manifested appetitive behaviour with negative kinesis towards the steroid source and were stimulated to lay their eggs. The steroid stimulus was effective in low concentration (below 2μM), in still water, and in the absence of sensorial reinforcements by a male partner. Females were little or not responsive outside in the interval between ovulation and oviposition.

ISSN:0373-4137    

DOI:10.1080/11250008009438692

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An overall picture of the European elver's behaviour during coastward migration and entrance into inland waters emerges from a survey of the literature. The factors influencing trophic migration are discussed.

ISSN:0373-4137    

DOI:10.1080/11250008009438693

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A general definition of environmental indicators is given, and their characteristics and practicability are then analyzed.

ISSN:0373-4137    

DOI:10.1080/11250008009438694

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Present knowledge and practice of artificial fertilization (AF) in fish-farming, and the gaps remaining are considered. The fish examined are those most commonly reared in cold-water (i.e. Salmonidae) or warm-water ponds (i.e. Cyprinidae). Our prospects are excellent for the former because the complete life cycle is under hatchery control, but some genetic aspects remain to be investigated, and complete control over the spawning time remains to be achieved. For the latter, the traditional methods yield well though they should be updated. Hormonal stimulation (hypophysation) of spawners and subsequent mass incubation of fertilized eggs should be more widely applied. This should increase considerably the populations of warm-water fish and favour the establishment of hatcheries capable, for instance, of producing large quantities of fry free from infectious diseases.

ISSN:0373-4137    

DOI:10.1080/11250008009438695

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The evolution of methods used in the extraction, isolation and identification of insect sex pheromones is briefly described.

ISSN:0373-4137    

DOI:10.1080/11250008009438696

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Entomophagous arthropods useful in forestry and in the main agricultural ecosystems are briefly considered, as well as the main aspects of integrated pest control and its organization on a large-scale basis. Support from central and local government is invoked.

ISSN:0373-4137    

DOI:10.1080/11250008009438697

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor