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Biomedical subjects

M W Ferguson

Publications and source records attributed to M W Ferguson.

At least 91 records · Page 5Linked to original sources
PubMed1992

Sequential changes in histologic pattern and extracellular matrix deposition during the healing of chronic venous ulcers.

As part of a major clinical trial, sequential biopsies were taken from the margins of venous leg ulcers during their healing. The changing patterns of tissue architecture and extracellular matrix synthesis during healing were documented histologically and immunocytochemically. Initial biopsies were similar in appearance: prominent fibrin cuffs, variable inflammation, hemosiderin, and red blood cell extravasation. So called "fibrin cuffs" were highly organized structures composed of laminin, fibronectin, tenascin, and collagen as well as trapped leukocytes and fibrin. Fibronectin was absent from the ulcer tissue although collagen was abundant. Major histologic changes were observed after 2 weeks' pressure bandage therapy; hemosiderin, acute inflammation, and granulation tissue with the deposition of fibronectin had all increased and epithelial migration had commenced. Complete epithelialization was frequent by the fourth week of treatment, but the basement membrane was incomplete. At this time, hemosiderin and red blood cell extravasation had decreased and "fibrin cuffs" were virtually absent although chronic inflammation remained. The complex organization of the so-called "fibrin cuffs" may inhibit angiogenesis (but offer protection against increased venous pressure) in addition to their previously ascribed role in causing tissue ischemia.

Biopsy↗
PubMed1992

Differential expression of insulin-like growth factors I and II (IGF I and II), mRNA, peptide and binding protein 1 during mouse palate development: comparison with TGF beta peptide distribution.

Development of the mammalian secondary palate involves a series of epithelial mesenchymal interactions: during one of these, a mesenchymal signal specifies regionally distinct palatal epithelial differentiation. Extracellular matrix molecules and soluble growth factors may be involved in this signalling process. In this study, we have mapped the expression of the genes for insulin-like growth factors (IGF I and II), the peptides they encode, and the IGF binding protein 1 (IGF BP-1) during murine palatogenesis (embryonic days (E) 12-15). IGF-I gene expression was below detectable levels in the craniofacial region at all ages. IGF-I peptide was at the threshold of immunocytochemical detection and widely distributed in the palatal mesenchyme, decreasing in staining intensity from E12 to E14. By contrast, IGF-II mRNA was intensely localised in several tissues. IGF-II gene expression within the forming palate was developmentally regulated. In the vertical palatal shelves (E12 to E13) IGF-II gene expression was absent. On early E14, in the horizontal prefusion palate, significant expression was present in the palatal mesenchyme, but not the epithelium. Once palatal fusion had occurred, mesenchymal expression fell rapidly to undetectable levels. IGF-II mRNA was next detectable in the secondary palate on late E15 at sites of membranous bone formation. By contrast to the mRNA distribution, IGF-II peptide was localised predominantly in the palatal epithelia (particularly the nasal and medial edge epithelia) but also in the mesenchyme of the E14 prefusion palate. Significantly, the IGF binding protein had a similar distribution pattern to the IGF-II peptide. At all ages, the developing tongue myotubes labelled heavily for IGF-II mRNA, protein and binding protein. These data suggest that IGF-II may play a localised paracrine role during murine palatogenesis, perhaps in the mesenchymal signalling of epithelial differentiation. IGF-II may also serve to coordinate the development of the tongue and palate. The distribution of IGF-II peptide was very similar to that of TGF-beta, suggesting a possible interactive role of these growth factors during palate development. Finally, evidence that the IGF-II gene is imprinted (Ferguson-Smith et al. 1991) and may be the target for uniparental disomy in the human Beckwith Wiedemann syndrome (Henry et al. 1991), which is characterised by the overgrowth of tissues (especially the tongue) expressing IGF II in the embryo, indicates the necessity of reanalysing human cleft palate families for disruption (including uniparental disomy) of the genes encoding IGFs, their receptors and binding proteins.

Animals↗
PubMed1992

Mouse embryonic palatal epithelial sheets in culture: an immunocytochemical study of proliferative activity using bromodeoxyuridine.

Mouse secondary palate morphogenesis is accompanied by distinctive patterns of proliferation in the palatal epithelium which latterly reflect its region-specific differentiation into oral, nasal and medial edge phenotypes. Isolated intact embryonic palatal epithelial sheets were cultured prior to, and during, the critical period of epithelial differentiation in chemically defined culture medium with, and without, 10% donor calf serum. The spatial and temporal patterns of proliferative activity were investigated by immunocytochemistry in 'pulse' and 'continuous' labelling experiments using bromodeoxyuridine (BrdUrd). Continuously labelled cultures exhibited extensive proliferation throughout the oral, nasal and medial edge regions. Pulse labelled cultures demonstrated a shift in mitotic activity from nasal to oral epithelial cells probably representing the cell turnover associated with the respective differentiated phenotypes. Medial edge cells became post-mitotic within the first 19 h of culture. Our defined culture system coupled with the immunocytochemical detection of cell proliferation using BrdUrd offers a rapid and precise method for the further investigation of palatal epithelial proliferation and its regulation by extrinsic factors.

Animals↗
PubMed1992

Modulation of the epidermal growth factor receptor of mouse embryonic palatal mesenchyme cells in vitro by growth factors.

A single class of high-affinity receptors for EGF were detected on mouse embryonic palatal mesenchyme (MEPM) cells cultured in vitro. The degree of confluence of the cultured cells did not affect the number or affinity of the binding sites. Culture of MEPM cells in the presence of bFGF, IGF-II or TGF-beta 1 induced changes in 125I-EGF binding. TGF-beta 1 caused a marked reduction in binding to 40% of control levels. This reduction was achieved after 2 h and persisted for 24 h after addition of the growth factor. IGF-II induced a similar reduction but this effect was transitory; after a 12 h pretreatment with IGF-II, binding was restored to control levels. The effects of bFGF were biphasic. Initially, a short pre-treatment period (3-5 h) with bFGF caused a small reduction in 125I-EGF binding; longer periods of pre-incubation (24 h) resulted in a large increase in receptor number. Pre-incubation in medium containing both bFGF and TGF-beta 1 resulted in a decrease in EGF binding. Thus, TGF-beta 1 negated the large increase in receptor number induced by bFGF alone. Changes in receptor number were usually, but not always, directly related to changes in the biological activity of EGF, as assessed by a thymidine incorporation assay. This study highlights the possible interactive role of growth factors known to be present in the developing palate.

Animals↗
PubMed1991

Alveolar ridge resorption and mandibular atrophy. A review of the role of local and systemic factors.

Loss of alveolar bone from the edentulous jaws is a serious and common clinical problem, especially among the elderly. The retention and stability of dentures are reduced, but little is known about the pathogenesis of this bone loss. The existing data suggest that either local factors, for instance occlusal trauma, or systemic factors such as postmenopausal osteoporosis, contribute to edentulous alveolar bone resorption. This paper reviews the evidence for the aetiology of residual ridge resorption following tooth extraction.

Alveolar Bone Loss↗
PubMed1991

Immunolocalization of epidermal growth factor (EGF), EGF receptor and transforming growth factor alpha (TGF alpha) during murine palatogenesis in vivo and in vitro.

The distribution of epidermal growth factor, the epidermal growth factor receptor and transforming growth factor alpha during murine palatogenesis was investigated immunocytochemically. On embryonic day 12 staining for transforming growth factor alpha was present throughout the palatal mesenchyme, with little in the epithelia. On embryonic day 13 staining increased in the palatal epithelia and in the mesenchyme at the tip of the palate. As the palatal shelves fused together (embryonic day 14.5) intense staining for transforming growth factor alpha was seen in the midline epithelial seam and in the subjacent mesenchyme. On embryonic day 15 there was a generalised increase in palatal epithelial staining; this was most marked in the remnants of the degenerating epithelial seam. Mesenchymal staining was, however, uniform. Whilst palatal staining for epidermal growth factor was sparse, at all stages, staining for its receptor was present throughout the palatal epithelia and mesenchyme. This was most intense in the palatal medial edge epithelia at the time of midline epithelial seam degeneration. The regional and temporal differences in staining for the epidermal growth factor receptor and transforming growth factor alpha suggested that these molecules may play an important role in normal palate development in vivo, particularly in degeneration of the midline epithelial seam.

Animals↗
PubMed1991

Comparative biochemistry of mouse and chick secondary-palate development in vivo and in vitro with particular emphasis on extracellular matrix molecules and the effects of growth factors on their synthesis.

A biochemical study analysing the wet weight, dry weight, water, protein and DNA content, collagen and GAG composition of all stages of the developing secondary palate in vivo and in vitro was undertaken to investigate differences between a species in which the palatal shelves elevate (mouse) and one in which they do not (chick). The effects of EGF, bFGF, PDGF and TFG-beta 1 on collagen and GAG synthesis by cultured mouse and chick palatal shelves of different embryonic stages were also studied. The total GAG content of developing mouse palatal shelves decreased with developmental time; heparan sulphate proteoglycan formed the major species in early palates but hyaluronan was the major species in mid-late palates. There was a peak of hyaluronan synthesis in embryonic palatal shelves in vitro at day 13 (T.21), i.e. immediately before shelf elevation. By contrast the total GAG content of chick palates increased with development; chondroitin-6-sulphate formed the major GAG species and there was no peak in hyaluronan synthesis. The water content of developing murine palates rose rapidly at day 14 (T.22), i.e. the time of shelf elevation. No such peak was seen in the chick, where the water content rose exponentially with developmental time. Mouse palates synthesized chondroitin-4-sulphate and novel proteins around the time of shelf elevation; chick palates synthesized chondroitin-6-sulphate and no novel proteins at any developmental stage. Collagen synthesis also peaked in vitro in T.21 murine palates. EGF markedly stimulated murine palatal collagens and GAG synthesis between stages T.20-T.22, but had no effect thereafter. Basic FGF had similar but smaller stage-related effects. PDGF had no effect on mouse palatal collagen and GAG synthesis whilst TGF-beta 1 inhibited GAG synthesis at T.21. The ratios of collagens I, III and V produced by mouse palates were unaltered by the growth factors. All the growth factors had no effect on chick palatal collagen synthesis at any stage and minimal effect on GAG synthesis; TGF-beta 1 stimulated it in early but inhibited it in mid- to late-stage chick palates. These data indicate that extracellular matrix molecule metabolism within the palate is markedly different in the two species studied and suggest that the differing profiles of such molecules may be regulated at certain developmental stages by specific growth factors.

Animals↗
PubMed1991

Fetal diaphragmatic wounds heal with scar formation.

Fetal wound healing is fundamentally different from wound healing in the adult. Although experimental work in mice, rats, rabbits, monkeys, and sheep has demonstrated that fetal healing occurs without inflammation and scarring, all of these studies have been limited to fetal skin wounds. Whether all fetal tissues heal in a regenerative-like fashion is unknown. Amniotic fluid exposure may play an important role in scarless fetal skin wound healing, but the effect of amniotic fluid on fetal mesothelial wound healing has not been characterized. To investigate these questions we created bilateral linear diaphragmatic wounds in 100-day gestation fetal lambs (term = 145 days). The right thoracotomy was closed to exclude amniotic fluid. In contrast, the left thoracotomy was fashioned into an Eloesser flap which permitted the left diaphragmatic wound to be continually bathed in amniotic fluid. Wounds were harvested after 1, 2, 7, or 14 days and analyzed by light microscopy and immunohistochemistry with antibodies to collagen types I, III, IV, and VI. Whether bathed in or excluded from amniotic fluid, the mesothelial-lined diaphragm healed with scar formation and without evidence of muscle regeneration. Interestingly, diaphragmatic wounds exposed to amniotic fluid were covered by a thick fibrous collagen peel similar to that seen in gastroschisis bowel. These findings indicate that not all fetal tissues share the unique scarless healing properties of fetal skin.

Amniotic Fluid↗
PubMed1991

Immunohistochemical localization of growth factors in fetal wound healing.

Fetal wound healing occurs rapidly, in a regenerative fashion, and without scar formation, by contrast with adult wound healing, where tissue repair results in scar formation which limits tissue function and growth. The extracellular matrix deposited in fetal wounds contains essentially the same structural components as that in the adult wound but there are distinct differences in the spatial and temporal distribution of these components. In particular the organization of collagen in the healed fetal wound is indistinguishable from the normal surrounding tissue. Rapidity of healing, lack of an inflammatory response, and an absence of neovascularization also distinguish fetal from adult wound healing. The mechanisms controlling these differing processes are undefined but growth factors may play a critical role. The distribution of growth factors in healing fetal wounds is unknown. We have studied, by immunohistochemistry, the localization of platelet-derived growth factor (PDGF), transforming growth factor beta (TGF beta), and basic fibroblast growth factor (bFGF), in fetal, neonatal, and adult mouse lip wounds. TGF beta and bFGF were present in neonatal and adult wounds, but were not detected in the fetal wounds, while PDGF was present in fetal, neonatal, and adult wounds. This pattern correlates with the known effects in vitro of these factors, the absence of an inflammatory response and neovascularization in the fetal wound, and the patterns of collagen deposition in both fetal and adult wounds. The results suggest that it may be possible to manipulate the adult wound to produce more fetal-like, scarless, wound healing.

Aging↗
PubMed1991

Differentiation of mouse embryonic palatal epithelium in culture: selective cytokeratin expression distinguishes between oral, medial edge and nasal epithelial cells.

During normal murine palatogenesis, regional specific differentiation of the epithelium results in three cell phenotypes: nasal (ciliated pseudostratified columnar cells), oral (stratified squamous cells) and medial edge (migratory, epithelio-mesenchymally transformed cells). We have developed a defined, serum-free, culture system which supports the growth and differentiation of isolated murine embryonic palatal epithelia in vitro. Using immunofluorescence microscopy, an established panel of antibodies was used to characterise the cytokeratin intermediate filament profile of palatal epithelial sheets at a precise developmental stage, following culture in serum-free medium with and without either transforming growth factor alpha (TGF alpha) or 10% donor calf serum (DCS). The morphologically discernable oral, medial edge and nasal phenotypes exhibited distinctive cytokeratin profiles, which remained consistent for all culture conditions, and which correlated with the known differentiation states of the epithelial types. The oral epithelia stained positively for cytokeratin 19 and cytokeratins characteristic of multilayered epithelia (1, 5, 14). Nasal epithelia stained similarly but in addition expressed the simple-epithelial cytokeratin pair, 8 and 18. Medial edge epithelia also expressed cytokeratins 1, 5 and 14 but with the exception of a few isolated cells there was no staining for cytokeratins 8 and 18. Cytokeratin 19 was absent specifically from the medial edge epithelial cells: this result may be related to the loss of cytokeratin expression observed during epithelial-mesenchymal transformations. By exhibiting a complexity of expression linked to differentiation state and independent of culture conditions, cytokeratins constitute useful markers of palatal epithelial differentiation in vitro as well as in vivo.

Animals↗
PubMed1991

Expression of EGF-receptors on epithelial and stromal cells of normal and inflamed gingiva.

Immunolocalization techniques were used to examine the expression of the cell surface receptors of EGF in normal and inflamed gingival tissue. Detectable levels of receptor were not observed in any (0/6) of the normal tissue biopsies examined; in contrast, the EGF-receptor was expressed by both epithelial and stromal cells in 7/9 of the inflamed tissue biopsies. Receptor expression by epithelial cells in inflamed tissues exhibited a variable distribution pattern. In the majority of sections, staining was confined to cells in the spinous, granular and cornified cell layers, with little in the basal layer. Occasionally, isolated islands of stained epithelial cells were present, suggesting their clonal origin. Staining for the EGF receptor was also observed in fibroblasts and endothelial cells throughout the lamina propria of inflamed tissue. Positive staining for the receptor ligand (EGF) was observed in both normal and inflamed tissue. These data suggest that an up-regulation of cell surface receptors for EGF occurs during the inflammatory response, this resulting in an increased cellular responsiveness to EGF.

Adult↗
PubMed1991

The homeobox gene Hox 7.1 has specific regional and temporal expression patterns during early murine craniofacial embryogenesis, especially tooth development in vivo and in vitro.

Hox 7.1 is a murine homeobox-containing gene expressed in a range of neural-crest-derived tissues and areas of putative epithelial-mesenchymal interactions during embryogenesis. We have examined the expression of Hox 7.1 during craniofacial development in the mouse embryo between days 8 and 16 of development. Whereas facial expression at day 10 of gestation is broadly localised in the neural-crest-derived mesenchyme of the medial nasal, lateral nasal, maxillary and mandibular processes, by day 12 expression is restricted to the mesenchyme immediately surrounding the developing tooth germs in the maxillary and mandibular processes. Hox 7.1 expression in the mesenchyme of the dental papilla and follicle is maximal at the cap stage of development and progressively declines in the bell stage prior to differentiation of odontoblasts and ameloblasts. Hox 7.1 expression in tooth germs is independent of overall embryonic stage of development but is dependent on stage of development of the individual tooth. Similar patterns of transient Hox 7.1 expression can also be detected in tooth germs in vitro in organ cultures of day 11 first branchial arch explants cultured for up to 7 days. Hox 7.1 is also expressed early in development (days 10/11) in the epithelium of the developing anterior pituitary (Rathke's pouch), the connective tissue capsule and meninges of the developing brain, and specific regions of neuroepithelium in the developing brain.

Animals↗
PubMed1991

The extracellular matrix of lip wounds in fetal, neonatal and adult mice.

Wound healing in the fetus occurs rapidly, by a regenerative process and without an inflammatory response, resulting in complete restitution of normal tissue function. By contrast, in the adult, wounds heal with scar formation, which may impair function and inhibit further growth. The cellular mechanisms underlying these differing forms of wound healing are unknown but the extracellular matrix (ECM), through its effects on cell function, may play a key role. We have studied the ECM in upper lip wounds of adult, neonatal and fetal mice at days 14, 16 and 18 of gestation. The spatial and temporal distribution of collagen types I, III, IV, V and VI, fibronectin, tenascin, laminin, chondroitin and heparan sulphates were examined immunohistochemically. Results from the fetal groups were essentially similar whilst there were distinct differences between fetus, neonate and adult. Fibronectin was present at the surface of the wound in all groups at 1 h post-wounding. Tenascin was also present at the wound surface but the time at which it was first present differed between fetus (1 h), neonate (12 h) and adult (24 h). The time of first appearance paralleled the rate of wound healing which was most rapid in the fetus and slowest in the adult. Tenascin inhibits the cell adhesion effect of fibronectin and during development the appearance of tenascin correlates with the initiation of cell migration. During wound healing the appearance of tenascin preceded cell migration and the rapid closure of fetal wounds may be due to the early appearance of tenascin in the wound. Collagen types I, III, IV, V and VI were present in all three wound groups but the timing and pattern of collagen deposition differed, with restoration of the normal collagen pattern in the fetus and a scar pattern in the adult. This confirms that lack of scarring in fetal wounds is due to the organisation of collagen within the wound and not simply lack of collagen formation. The distribution of chondroitin sulphate differed between normal fetal and adult tissues and between fetal and adult wounds. Its presence in the fetal wound may alter collagen fibril formation. No inflammatory response was seen in the fetal wounds. The differences in the ECM of fetal and adult wounds suggests that it may be possible to alter the adult wound so that it heals by a fetal-like process without scar formation, loss of tissue function or restriction of growth.

Animals↗
PubMed1991

Hox-7 expression during murine craniofacial development.

We have used in situ hybridisation to establish the temporal and spatial expression patterns of the mouse homeobox-containing gene; Hox-7, in the developing embryonic cranium and nervous system of the mouse between embryonic days 9.5 (E9.5) and E15.5. Hox-7 has previously been associated with areas of mesenchymal-epithelial interaction and cell migration especially in neural crest ectomesenchymal cells. Aside from the expression patterns seen in the facial anlage at E9.5, Hox-7 transcripts were also detected in the neuroepithelium including cells of the dorsal midline of the neural tube. This expression pattern persisted throughout the embryonic time span studied. At E11.5, expression of Hox-7 became obvious in the neuroepithelium of the forming tela choroida and the telencephelii in areas destined to form the choroid plexus before any atrophy of the neuroepithelium took place. High expression of Hox-7 was also present in the mesenchyme cells invading the pouch formed by the involuting choroid plexus neuroepithelium. A second major site where Hox-7 was expressed was the anlage of the anterior pituitary; the Rathke's pouch. Expression became obvious at E10.5 throughout the pouch but by E12.5 became more regionalised in areas of the pouch destined to form the pars distalis. Hox-7 was also expressed in the forming meninges and skull bone precursors from E10.5 onwards. Expression of the Hox-7 gene is also seen in the external ear, the forming eye, the nasal pits and forming Jacobson's organs. When these expression patterns are considered together with characterised human and mouse retinoic acid embryopathies and the congenital malformations seen in human children associated with deletion of chromosome 4p16.1 (Wolf-Hirschhorn syndrome), Hox-7 may be a good candidate as one of the genes involved in the initiation of the choroid plexus phenotype and its subsequent formation, the formation of the outer ear, formation of the dentition and the differentiation of the cell types of the anterior pituitary. The expression pattern of Hox-7 in the dorsal midline of the neural tube further suggests that it may also be involved in the specification of the dorsal-ventral axis of the developing nervous system.

Animals↗
PubMed1991

Rapid epithelialisation of fetal wounds is associated with the early deposition of tenascin.

Wound healing is a complex process involving the interaction of many cell types with the extracellular matrix (ECM). Fetal skin wound healing differs from that in the adult in that it occurs rapidly and without scar formation. The mechanisms underlying these differing processes may be related to the fetal environment, the stage of differentiation of the fetal cells or the ECM deposited in the wound. The spatial and temporal distribution of two components of the ECM, fibronectin and tenascin, were studied by immunostaining of cryosections from trunk wounds of fetal and adult sheep. Epithelialisation was complete earlier in the fetal wound than in the adult. The distribution of fibronectin was similar in fetal and adult wounds but tenascin was present earlier in the fetal wound. Fibronectin has several roles in wound healing including acting as a substratum for cell migration and as a mediator of cell adhesion through cell surface integrins. The attachment of fibroblasts to fibronectin is inhibited by tenascin and during development the appearance of tenascin in the ECM of migratory pathways correlates with the initiation of cell migration. Similarly, the appearance of tenascin in healing wounds may initiate cell migration. Tenascin was present in these wounds prior to cell migration and the rapid epithelialisation of fetal wounds may be due to the early appearance of tenascin in the wound.

Animals↗
PubMed1991

Morphometric analysis of the developing murine molar tooth in vivo and in vitro.

A morphometric technique is described which has been used to measure morphogenesis and matrix synthesis of developing murine teeth in vivo and in vitro. The growth of bud and cap stage tooth germs in vitro was reduced considerably compared with in vivo. There was no growth of tooth germs explanted and cultured in vitro at the bell stage. The onset of dentine and enamel synthesis were however only slightly delayed in vitro compared with in vivo. The technique had been designed to be insensitive to orientation or artefactual folding of the cultured tissue.

Animals↗
PubMed1991

The development of enamel tubules during the formation of enamel in the marsupial Monodelphis domestica.

In Monodelphis domestica, although both processes from odontoblasts and projections from ameloblasts were found in developing enamel, the majority of the contents of enamel tubules were probably processes that originated from odontoblasts. Processes from odontoblasts penetrating into enamel touched part of the ameloblasts in the stage of enamel formation. No specialised cell junctions were seen at the adherence between the two. There were no enamel tubules in the aprismatic and pseudoprismatic enamel layer. It is likely that enamel tubules exist only in prismatic enamel. The majority of enamel tubules seemed to contain no cell processes in the stage of enamel maturation, indicating that the cell processes in the tubules probably degenerate after the stage of enamel formation.

Amelogenesis↗