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Biomedical subjects

M W Ferguson

Publications and source records attributed to M W Ferguson.

At least 19 recordsLinked to original sources
PubMed1992

Cloning and expression analysis of two ZFY-related zinc finger genes from Alligator mississippiensis, a species with temperature-dependent sex determination.

In order to investigate the molecular mechanism of temperature-dependent sex determination, a human zinc finger gene (ZFY), known to be highly conserved amongst other species, was used to isolate homologues from the genome of the American alligator, Alligator mississippiensis. ZFY was originally a candidate for the primary testis-determining gene in man, but is now thought to function further down the sex-determining cascade. Two alligator genes are described, Zfc and Znc6. Both code for zinc finger proteins and exhibit amino acid (aa) homologies to ZFY of 91% and 73%, respectively. Znc6 shows aa homology of 88% to the protein encoded by the zinc finger exon of the human ZFY-related gene, ZNF6, recently found on the X chromosome. Analysis of Zfc and Znc6 expression during embryonic development identified two major transcripts of 5.9 kb and 2.7 kb coding for Zfc, whilst only one transcript of 4.8 kb was detected for Znc6. Both genes are transcribed at all stages tested, from day 3 (post egg laying) throughout gestation. The expression level of all transcripts appears to decline towards the time of hatching (65-72 days). No sex-specific differences in the expression were observed. The extensive sequence conservation of the genes between reptiles and humans suggests major functional constraints. The expression patterns indicate that these genes do not play a primary role in temperature-dependent sex determination.

Alligators and Crocodiles↗
PubMed1992

Control of scarring in adult wounds by neutralising antibody to transforming growth factor beta.

Adult wounds heal with scar-tissue formation, whereas fetal wounds heal without scarring and with a lesser inflammatory and cytokine response. We injected the margins of healing dermal wounds in adult rats with neutralising antibody (NA) to transforming growth factor-beta (TGF-beta). All control wounds (irrelevant antibody, or TGF-beta, or no injection) healed with scarring, whereas the NA-treated wounds healed without scar-tissue formation; NA-treated wounds had fewer macrophages and blood vessels, lower collagen and fibronectin contents, but identical tensile strength and more normal dermal architecture than the other wounds. Early manipulation of the concentrations of selected cytokines may be a new approach to the control of scarring.

Animals↗
PubMed1992

Changes in the extracellular matrix of the normal human breast during the menstrual cycle.

The normal human mammary gland undergoes a well defined sequence of histological changes in both epithelial and stromal compartments during the menstrual cycle. Studies in vitro have suggested that the extracellular matrix surrounding the individual cells plays a central role in modulating a wide variety of cellular events, including proliferation, differentiation and gene expression. We therefore investigated the distribution of a number of extracellular matrix molecules in the normal breast during the menstrual cycle. By use of indirect immunofluorescence, with specific antibodies, we demonstrated that laminin, heparan sulphate proteoglycan, type IV collagen, type V collagen, chondroitin sulphate and fibronectin undergo changes in distribution during the menstrual cycle, whereas collagen types I, III, VI and VII remain unchanged. These changes were most marked in the basement membrane, sub-basement membrane zone and delimiting layer of fibroblasts surrounding the ductules where basement membrane markers such as laminin, heparan sulphate proteoglycan, and type IV and V collagens appear greatly reduced during the mid-cycle period (days 8 to 22). These results suggest that some extracellular matrix molecules may act as mediators in the hormonal control of the mammary gland, whereas others may have a predominantly structural role.

Adenofibroma↗
PubMed1992

The effects of epidermal growth factor, transforming growth factors alpha and beta and platelet-derived growth factor on murine palatal shelves in organ culture.

Palatal shelves isolated from day-13 embryonic mice were explanted on to the surfaces of collagen gels either singly or in pairs with their medial edges in contact, and cultured submerged in a 1:1 mixture of Dulbecco's modified Eagle's medium/Ham's F12 medium. The medium was supplemented with either 10 ng/ml epidermal growth factor (EGF), 10 ng/ml transforming growth factor alpha (TGF alpha), 1 ng/ml transforming growth factor beta (TGF beta 1) or 2 ng/ml platelet-derived growth factor (PDGF) all in the presence or absence of 2.5% donor calf serum (DCS). Cultures were terminated after 0, 24, 48 or 72 h and processed for histological and immunocytochemical examination. In serum-free medium and medium supplemented with 2.5% DCS the palatal epithelia differentiated in a manner similar to that seen in vivo (oral, keratinization; nasal, pseudostratified, ciliated columnar cells and medial edge, epithelial degeneration). A similar pattern was obtained in serum-free medium supplemented with either EGF or TGF alpha. However in cultures with either EGF or TGF alpha plus 2.5% DCS present in the medium, medial-edge epithelial degeneration was inhibited and the oral epithelia were more heavily keratinized. The mesenchyme of such cultures stained more intensely for various extracellular matrix molecules. In TGF beta 1-supplemented cultures (with, but especially without, serum supplementation) the epithelia were thin, medial-edge epithelial degeneration was marked, and the fibronectin content of the mesenchyme was increased. PDGF prevented medial-edge epithelial degeneration in the presence, but not in the absence, of serum; mesenchymal extracellular molecules were not as prevalent as with the EGF treatment. These results indicate that exogenous growth factors (including those present in serum) exert effects on organ-cultured mouse palatal shelves in a fashion similar to their effects in cell culture and that controlled physiological levels of such factors may be important in mouse palatal development.

Animals↗
PubMed1992

Immunofluorescent lectin binding patterns and glycoprotein co-localization in the developing murine molar tooth.

Fluorescein-conjugated lectins were used in conjunction with antibodies to laminin, tenascin and amelogenin to investigate saccharide expression in the developing tooth germ. At the bud stage, peanut agglutinin (PNA) binding demonstrated residues that may be D-galactose-(beta 1----3)DGalNAc, and this staining occurred after the expression of tenascin. Only the cap-stage enamel organ suprabasal cells and the enamel knot stained intensely with Ulex europeus agglutinin-I, but not Lotus tetragonolobus agglutinin, implying the transient presence of blood group H type I oligosaccharides. At the late stages of amelogenesis, enamel synthesis is preceded by en bloc loss of inner enamel basement membrane components. Before this, Bandeiraea (Griffonia) simplicifolia--I (BSL-I) staining was lost from postmitotic ameloblasts, suggesting that a glycosylated species is initially removed. Additionally, PNA was co-localized with amelogenin protein, suggesting that it may express beta-D-galactosyl sequences. These results indicate that the glycosylation patterns of matrix components during odontogenesis may be important as they vary in a manner similar to that of the well-known glycoproteins.

Acetylgalactosamine↗
PubMed1992

The effects of transforming growth factor-beta 1 on protein production by mouse embryonic palate mesenchymal cells in the presence or absence of serum.

Mouse embryonic palatal mesenchyme cells were cultured on a variety of substrata (plastic, on a collagen gel or within a collagen gel). On each substratum TGF-beta 1 (1 ng/ml) inhibited cell proliferation. Cells cultured within a collagen gel had the lowest rate of proliferation, but were metabolically the most active in terms of incorporation of [3H]-proline into both collagenous and non-collagenous proteins. TGF-beta 1, in the presence of 2.5% donor calf serum stimulated the production of fibronectin and the major collagen types I, III and V. However, in serum-free medium, TGF-beta 1 induced a large reduction in total collagen production, mainly due to an effect on type I collagen, whilst stimulating production of some non-collagenous proteins. Experiments involving combinations of TGF-beta 1 with other growth factors suggested that the different effects of TGF-beta 1 on collagen production, in the presence and absence of serum, may be due to an interaction with platelet-derived growth factor.

Animals↗
PubMed1992

Serum parathyroid hormone and calcitonin levels following ovariectomy in the adult rat.

The ovariectomized rat is a reasonably good and often utilized model of human post-menopausal osteoporosis (Devlin and Ferguson, 1989). Mature rats were either ovariectomized or underwent a sham operation, killed at intervals following operation and the serum concentration of parathyroid hormone and calcitonin at death related to the histomorphometry of the cancellous bone of the proximal ilium. The mean serum calcitonin concentration for all ovariectomized rats was 66.4 pg/ml (SD = 18) and for the control rats was 76.42 pg/ml (SD = 20). The serum calcitonin concentration in the ovariectomized rats was significantly negatively correlated with the extent of erosion cavities of the cancellous bone (r = -0.598, t = -2.36, p = 0.039). No significant correlation was observed for the control rats (r = -0.107, t = -0.357, p = 0.727). The mean extent of erosion cavities in the ovariectomized group was 6.81% (SD = 1.94) and in the control group was 6.47% (SD = 2.21), with no significant differences between the two groups (t = 0.41, p = 0.69). No significant correlations were observed in serum parathyroid hormone (PTH) concentration with the bone resorption parameters. From this study it was concluded that calcitonin may be of aetiological importance in bone loss in the ovariectomized rat.

Animals↗
PubMed1992

The fate of medial edge epithelial cells during palatal fusion in vitro: an analysis by DiI labelling and confocal microscopy.

Fusion of bilateral shelves, to form the definitive mammalian secondary palate, is critically dependent on removal of the medial edge cells that constitute the midline epithelial seam. Conflicting views suggest that programmed apoptotic death or epithelial-mesenchymal transformation of these cells is predominantly involved. Due in part to the potentially ambiguous interpretation of static images and the notable absence of fate mapping studies, the process by which this is achieved has, however, remained mechanistically equivocal. Using an in vitro mouse model, we have selectively labelled palatal epithelia with DiI and examined the fate of medial edge epithelial (MEE) cells during palatal fusion by localisation using a combination of conventional histology and confocal laser scanning microscopy (CLSM). In dynamic studies using CLSM, we have made repetitive observations of the same palatal cultures in time-course investigations. Our results concurred with the established morphological criteria of seam degeneration; however, they provided no evidence of MEE cell death or transformation. Instead we report that MEE cells migrate nasally and orally out of the seam and are recruited into, and constitute, epithelial triangles on both the oral and nasal aspects of the palate. Subsequently these cells become incorporated into the oral and nasal epithelia on the surface of the palate. We hypothesize an alternative method of seam degeneration in vivo which largely conserves the MEE population by recruiting it into the nasal and oral epithelia.

Animals↗
PubMed1992

Expression patterns of the homeobox gene, Hox-8, in the mouse embryo suggest a role in specifying tooth initiation and shape.

We have studied the expression patterns of the newly isolated homeobox gene, Hox-8 by in situ hybridisation to sections of the developing heads of mouse embryos between E9 and E17.5, and compared them to Hox-7 expression patterns in adjacent sections. This paper concentrates on the interesting expression patterns of Hox-8 during initiation and development of the molar and incisor teeth. Hox-8 expression domains are present in the neural crest-derived mesenchyme beneath sites of future tooth formation, in a proximo-distal gradient. Tooth development is initiated in the oral epithelium which subsequently thickens in discrete sites and invaginates to form the dental lamina. Hox-8 expression in mouse oral epithelium is first evident at the sites of the dental placodes, suggesting a role in the specification of tooth position. Subsequently, in molar teeth, this patch of Hox-8 expressing epithelium becomes incorporated within the buccal aspect of the invaginating dental lamina to form part of the external enamel epithelium of the cap stage tooth germ. This locus of Hox-8 expression becomes continuous with new sites of Hox-8 expression in the enamel navel, septum, knot and internal enamel epithelium. The transitory enamel knot, septum and navel were postulated, long ago, to be involved in specifying tooth shape, causing the inflection of the first buccal cusp, but this theory has been largely ignored. Interestingly, in the conical incisor teeth, the enamel navel, septum and knot are absent, and Hox-8 has a symmetrical expression pattern. Our demonstration of the precise expression patterns of Hox-8 in the early dental placodes and their subsequent association with the enamel knot, septum and navel provide the first molecular clues to the basis of patterning in the dentition and the association of tooth position with tooth shape: an association all the more intriguing in view of the evolutionary robustness of the patterning mechanism, and the known role of homeobox genes in Drosophila pattern formation. At the bell stage of tooth development, Hox-8 expression switches tissue layers, being absent from the differentiating epithelial ameloblasts and turned on in the differentiating mesenchymal odontoblasts. Hox-7 is expressed in the mesenchyme of the dental papilla and follicle at all stages. This reciprocity of expression suggests an interactive role between Hox-7, Hox-8 and other genes in regulating epithelial mesenchymal interactions during dental differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
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↗