Archiv für Entwicklungsmechanik der Organismen

Các blastomere của phôi cá vằn có thể được phân loại thành hai loại - tế bào được nhuộm đậm (D) hoặc nhuộm nhạt (L) bằng hỗn hợp xanh toluidin và xanh methylene (T-M). Việc nhuộm đậm của các tế bào D chủ yếu là do mật độ cao của ti thể, lưới nội bào thô và ribosome đa. Sự hiện diện của các tế bào nhuộm một phần trong giai đoạn blastula sớm cho thấy rằng các tế bào L đã được chuyển hóa thành các tế bào D. Vai trò của lớp hợp bào lòng đỏ (YSL) trong quá trình chuyển hóa này được gợi ý bởi sự gần gũi của các tế bào này với YSL và bởi sự định hướng không gian khác biệt của chúng với các vùng chất nhân được nhuộm đậm luôn hướng về phía bên trong của phôi.

Collagen types I and III were purified from the skin of 3-or 7-week-old chickens, collagen type IV from bovine skin or EHS mouse tumour, fibronectin from human serum, and laminin from EHS mouse tumour. Antibodies were produced in rabbits or sheep, and used in indirect immunofluorescence on frozen sections of 9-to 16-day-old normal or mutant (scaleless) chick-embryo foot skin. In normal scale-forming skin and inscaleless skin, the distribution of anti-laminin and anti-type IV collagen label was uniform along the dermal-epidermal junction and showed no stage-related variations, except for fluorescent granules located in the dermis of early scale rudiments. By contrast, in normal scale-forming skin, the density of anti-types I and III label decreased in the dermis within scale rudiments, whereas it gradually increased in interscale skin. Conversely, anti-fibronectin label accumulated at a higher density within scale rudiments than in interscale skin. In the dermis of thescaleless mutant, anti-types I and III label and antifibronectin label were distributed evenly: the density of anti-collagen label increased with age, while that of antifibronectin decreased and almost completely vanished in 16-day-old skin, except around blood vessels. The microheterogeneous distribution of some extracellular matrix components, namely interstitial collagen types I and III and fibronectin, is interpreted as part of the morphogenetic message that the dermis is known to transmit to the epidermis during the formation of scales. The even distribution of these components in mutantscaleless skin is in agreement with this view. Basement membrane constituents laminin and type-IV collagen do not appear to be part of the dermal morphogenetic message.

Of the many mutations known to affect the wing vein pattern we have selected the most extreme in 29 genes for study. Their phenotype can be classified in two major classes: lack-of-veins and excess-of-veins, and in several internally coherent groups. The study of multiple mutant combinations, within groups and between groups, reveals several genetic operations at work in the generation of the vein pattern. The finding that some of these mutations also affect cell proliferation in characteristic ways has prompted a generative model of wing morphogenetic and pattern formation based on cell behaviour properties defined by the corresponding wild-type genes.

We estimate the number of blastoderm cells which generate the thoracic imaginal discs ofDrosophila. At hatching the wing disc is twice the size of the haltere disc, but the results suggest that both discs develop from a similar number of blastoderm cells. Two homeotic mutations, which transform the haltere into wing, affect embryonic growth but not the primordial number. All the segmental primordia may be of similar size and each may be similarly subdivided into a larger anterior, and a smaller posterior polyclone.