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P Sengel

Publications and source records attributed to P Sengel.

10 recordsLinked to original sources
PubMed1992

Cellular and extracellular involvement in the regeneration of the rat lower vibrissa follicle.

The sequence of events leading to the reconstruction of a fibre-producing hair follicle, after microsurgical amputation of the lower follicle bulb, has been detailed by immunohistology and electron microscopy. The initial response was essentially found to be a wound reaction, in that hyperproliferative follicle epidermis quickly spread to below the level of amputation--associated with downward movement of mesenchymal (or dermal) sheath cells. Fibronectin was prominent in both dermis and epidermis at this stage and, as in wound repair, preceded laminin and type IV collagen in covering the lower dermal-epidermal junction. Once a new basal line of epidermis and a complete basement membrane were established, laminin and type IV collagen were detected below this junction and within the prospective papilla-forming mesenchyme. This coincided with ultrastructural observations of profuse sub-basement membrane extracellular material in the region of new papilla formation. The glassy membrane displayed extensive ultrastructural modifications at its lower level, and these corresponded with localized variations in staining intensities for all three antibodies over time. The membrane hung below the level of the epidermis, and was crossed by migrating cells from the mesenchymal dermal sheath of the follicle - it acted to segregate the inner group of follicular dermal cells from wound fibroblasts. Extracellular matrix may be a mediator of the dermal-epidermal interactions associated with this hair follicle regeneration phenomenon.

Animals↗
PubMed1992

Changes in fibronectin, laminin and type IV collagen distribution relate to basement membrane restructuring during the rat vibrissa follicle hair growth cycle.

Hair growth in adult mammals involves continuous dermal-epidermal interaction across the follicular basement membrane, and repeated reorganisation of lower follicle structure during the hair growth cycle. The immunolocalisation of 3 extracellular matrix components, fibronectin, laminin and type IV collagen was investigated during the course of the rat vibrissa follicle growth cycle, and their distribution correlated with changes in cellular and extracellular ultrastructure, particularly around the basement membrane zone. Laminin and type IV collagen were omnipresent at the follicular dermal-epidermal junction, but were also seen in granular extracellular form within the inner dermal component of the follicle, the dermal papilla. Both the inner papilla-epidermal junction and the thick specialised outer basement membrane (the glassy membrane) revealed labelling by these 2 antibodies around telogen (the period of nonfibre production). By contrast, fibronectin was abundant within the anagen dermal papilla but at telogen stained the dermal-epidermal junction heterogeneously, when it disappeared from the inner papilla-epidermal interface but intensified externally. These changes to extracellular matrix distribution coincided with a modification of basement membrane ultrastructure from a relatively uniform line at anagen, to one which became much broader and multilayered at telogen with a loss of definite structure within the papilla. This shows that the lower part of the vibrissa follicle retains the capacity for very rapid basement membrane modification and remodelling, and implies that it is part of the biological process which enables dermal-epidermal signalling, rather than a secondary product of physical changes to the appendage. The work supports the idea that dermal papilla cells could contribute to basement membrane formation, and also that fibronectin may be involved in regulating cellular activities within the follicle. In the vibrissa follicle, dynamic cellular activity clearly takes place throughout the duration of the hair cycle.

Animals↗
PubMed1990

Pattern formation in skin development.

The development of skin and cutaneous appendages in amniote embryos has been submitted to a large number of experimental investigations the results of which have led to a better understanding of the mechanisms whereby this multiform organ arises during embryonic development. In birds, the main appendages are the feathers and the foot scales. Their formation results from a series of inductive events between ectoderm (later epidermis) and subectodermal mesoderm (later individualized dermis). Morphogenetically, the mesodermal (mesenchymal) component of skin is the predominant tissue, insofar as it controls most morphological and physiological features of developing skin and appendages, notably transformation of ectoderm into epidermis, polarization, proliferation and stratification of epidermal cells, initiation, site, size and distribution pattern of epidermal placodes, species-specific architecture of appendages, regional specification of keratin synthesis. The ectodermal (epithelial) component is able to respond to the mesodermal inductive instructions by building feathers and scales in conformity with the specific origin of the dermis. In these epithelial-mesenchymal interactions, extracellular matrix and the microarchitecture of the dermal-epidermal junction appear to play an important role. Indeed extracellular matrix components (primarily collagens, proteoglycans and adhesive glycoproteins) and dermal cell processes close to the epidermal basement membrane become distributed in a microheterogeneous fashion, thus providing a changing substratum for the overlying epidermis. It is assumed that the latter is able to somehow sense the texture and composition of its substratum, and by doing so to appropriately engage in the formation of glabrous, feathered or scaly skin.

Animals↗
PubMed1988

Alpha-smooth muscle actin is transiently expressed in embryonic rat cardiac and skeletal muscles.

Actin isoform expression may change during development, and in certain physiological, experimental and pathological situations. It is accepted that during sarcomeric (skeletal and cardiac) muscle development, the alpha-skeletal and alpha-cardiac isoforms of actin accumulate rapidly at the onset of muscle fibre formation, while there is a rapid fall in the expression of nonmuscle (beta and gamma) actin isoforms. Here we show that, before birth, both skeletal and myocardial cells express significant amounts of alpha-smooth muscle actin mRNA and protein. This expression is transient and disappears over the 1-7 days following birth. Our findings show that the program regulating actin isoform expression in sarcomeric muscle development is complex and that alpha-smooth muscle actin participates in this process.

Actins↗
PubMed1986

Wound healing of human skin transplanted onto the nude mouse. I. An immunohistological study of the reepithelialization process.

Two months after transplantation of human skin onto the nude mouse, excisional wounds were made through the entire thickness of the skin, at the center of the graft, using a 2-mm punch. At various time intervals thereafter, ranging from 2 days to 9 weeks, the graft sites were harvested and processed for an immunohistological study. With a monoclonal antibody directed against HLA-ABC antigens, it was demonstrated that the healing epidermis is of human origin. Moreover, with three different monoclonal antibodies directed against human keratins, named respectively AE1, AE3, and KL1 and with an anti-involucrin antiserum, it is reported that the keratinization and involucrin distribution patterns observed in normal human epidermis are reconstituted, 2 months after transplantation, in the major part of the grafted epidermis, undergo changes during the reepithelialization process, and are restored in the healed epidermis 9 weeks after injury. This study indicates that the nude mouse/human skin model could be a valuable tool to study a major aspect of regeneration such as the reepidermization of human skin without recourse to human volunteers.

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PubMed1979

[Origin of cutaneous smooth muscles in birds (author's transl)].

The origin of smooth muscles in the skin of bird embryos has been analyzed in heterospecific quail/chick recombinants. The somitic mesoderm of the wing level of 2-day chick embryos was replaced by homotopic or heterotopic somitic mesoderm from quail embryos. The cellular constitution of tissues was observed in twelve recombinant embryos at 17 or 18 days of incubation. Results show that feather smooth muscles and vascular smooth muscles have the same origin as the cutaneous mesenchyme in which they differentiate. They are of somatopleural origin in the wing integument and of somitic (dermatomal) origin in the dorsal integument. This study further reveals that the muscular and connective tissue wall of blood vessels does not have the same embryonic origin as the endothelium. It is suggested that the latter originates from the primitive aorta.

Animals↗
PubMed1975

[Feather- and hair-forming properties of dermal cells of glabrous skin from bird and mammals].

The absence of cutaneous appendages in glabrous skin areas of birds and mammals rises from the incapacity of the dermis to trigger off the development of feather and hair buds. The dermal cells from avian or mammalian glabrous regions are however able to induce the continuation and completion of feather or hair morphogenesis respectively, provided the initiation of appendage bud formation has been triggered off by dermis from feather- or hair-forming regions.

Animals↗
PubMed1975

Feather pattern development.

Experiments on skin development in amniotes have shown conclusively that the pattern of cutaneous appendages is determined by the dermis. The following concept of feather pattern formation is proposed. The diameter of feather rudiments and the dermal cell density inside the dermal feather condensations are genetically fixed, region-specific parameters. The first feather rudiment is established along the middorsal line (in the lumbar region) as soon as a sufficient width of dense dermis is available. This occurs at about 6 1/2 days in the chick embryo. The next rudiments are formed in front of and behind the first one, within the longitudinal band of dense dermis. They are laid down as close as possible to the first one, given rudiment diameter and dermal condensation cell density. In other words, as they form, the middorsal rudiments are tangent circles.. Later they become separated from one another due to longitudinal growth. As progressively more dense dermis becomes available to the sides of the middorsal row of rudiments, new rudiments are being laid down lateral to the middorsal row, in successive longitudinal rows, until, by 9 or 10 days, all the available dense dermis has been used up. Again, the rudiments in the lateral rows, given their diameter and dermal condensation cell density, develop as close as possible to those of the preceding row, i.e. tangentially to two neighbouring rudiments of the preceding row, thus generating a hexagonal pattern.

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