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K B English

Publications and source records attributed to K B English.

14 recordsLinked to original sources
PubMed1994

Localization of nerve growth factor (NGF) and low-affinity NGF receptors in touch domes and quantification of NGF mRNA in keratinocytes of adult rats.

Touch domes are clearly delineated mechanoreceptors that are visible on the depilated skin of mammals. These structures consist of a sharply circumscribed disk of thickened epithelium surmounting a group of Merkel cells that are innervated by type I sensory neurons. These characteristic cutaneous structures provide an ideal opportunity for investigating whether the localization of nerve growth factor (NGF) in the skin is related to sites of sensory axon termination. For these reasons, we have used immunocytochemistry to study the distribution of NGF and the low-affinity NGF receptor (p75NGFR) in the touch domes of adult rat skin. Intense NGF-like immunoreactivity was sharply restricted to keratinocytes (excluding the stratum corneum) of the thickened epidermis of touch domes. The epidermis immediately surrounding touch domes and the epidermis of the tylotrich hair follicle associated with touch domes were not stained by anti-NGF antiserum. Merkel cells of the basal epidermis of touch domes were immunonegative for NGF but were immunopositive for p75NGFR as were the type I nerve endings innervating these cells. Quantitative Northern blotting revealed that the level of NGF mRNA was substantially higher in keratinocytes isolated from the stratum granulosum and stratum spinosum than in keratinocytes isolated from the stratum germinativum. These findings indicate that NGF synthesis in mature skin has a highly restricted regional distribution that is primarily associated with the innervation of a specialized touch receptor.

Animals↗
PubMed1992

Serotonin-like immunoreactivity in Merkel cells and their afferent neurons in touch domes from the hairy skin of rats.

Immunoreactivity to serotonin was observed in Merkel cells as well as the afferent type I nerves terminating upon them in touch domes excised from the belly skin of rats. Type I nerves were strongly immunoreactive and could be traced through the dermis of the domal papilla. Merkel cell immunoreactivity was sometimes seen in the entire cell, but was often localized in the Merkel cell cytoplasm adjacent to nerve terminals and may have been in the terminals themselves. Domes were fixed by immersion in 4% paraformaldehyde-lysine-sodium-m-periodate (PLP) fixative at 4 degrees C for 2.5-3 hours and cryoprotected in 30% sucrose overnight. Sections were processed with the avidin-biotin complex peroxidase (ABC), peroxidase-antiperoxidase (PAP), and indirect immunofluorescence techniques with rabbit antiserum generated against serotonin.

Afferent Pathways↗
PubMed1992

Tactile function in skin-equivalent grafts.

Cultured grafts are excellent wound covers; however, their somatosensory capabilities are unknown. This is a preliminary report of a study which determined whether grafts of cultured skin become innervated and also examined whether seeding grafts with target tissue improved nerve growth or functional recovery. Autologous skin for grafting was generated from adult rat biopsy tissue. Dissociated keratinocytes were seeded on top of fibroblast-contracted collagen gels (skin-equivalents). Some animals received grafts composed entirely of skin-equivalents. Others had grafts with 2-mm punch biopsies (normal skin or touch domes) inserted into them. Prior to sacrifice, whole nerve recordings of the cutaneous nerves supplying the grafts were made following tactile mechanical stimulation of the graft surfaces. Tissue was processed for light and electron microscopy as well as silver stained. Nerve fibers were present in the dermis (generated from the fibroblast contracted collagen gels) of all animals and often extended to the epidermis. Light brushing of the cultured areas of the grafts produced little or no activity in the cutaneous nerves; however, afferent impulses were generated after rubbing the skin with a glass rod or pinching it with fine forceps. The implanted regions within the skin-equivalents varied from this pattern. Lightly brushing their surface resulted in vigorous activity in the nerves. Elements in the skin therefore seemed to enhance nerve regeneration and function. However, the quality of the engraftment was also important. Implanted regions of grafts experiencing poor "takes" had compromised innervation.

Animals↗
PubMed1992

Functional innervation of cultured skin grafts.

The aims of the present study were to determine 1) if grafts of cultured skin become innervated; and 2) whether tactile function of these grafts could be improved by implanting target tissue into them. Autologous skin equivalents were generated in vitro (30 d) for individual adult Sprague-Dawley rats. Some animals received pure skin equivalent grafts; others had target tissue consisting of 2-mm punch biopsies (normal skin or touch domes) inserted into their skin equivalents at the time of grafting. After 83 d, physiologic recordings were obtained from afferent nerves innervating the grafts. Tissue was processed for histology at various intervals. Silver staining of the tissues demonstrated many isolated nerve fibers in the dermis of cultured areas of skin as well as in implant zones. When grafts were rubbed with a glass rod or pinched with watchmaker forceps, impulses were evoked in nerves innervating both implant and cultured regions. In contrast, the afferent response to gently stroking grafts with a camel hair brush was severely reduced in cultured areas but was vigorous in implanted skin. Neuronal activity characteristic of type I neurons innervating touch domes was only found in cutaneous nerves innervating implants originally possessing domal tissue. Furthermore, grafts with good takes had better return of sensory function than grafts undergoing episodes of crusting. These results suggest that structural components or trophic factors present in implants enhanced the return of neural function related to the sensory modality of light touch; and this was also affected by the engraftment quality.

Action Potentials↗
PubMed1991

Skin wound closure in athymic mice with cultured human cells, biopolymers, and growth factors.

Skin wound closure remains a major problem in acute and reconstructive skin grafting after large burns because of limited availability of donor skin. This report evaluates six protocols for preparation in vitro of skin substitutes composed of cultured human cells, biopolymers, and growth factors for wound closure. Full-thickness wounds in athymic mice treated in a single procedure with cultured skin substitutes were compared directly to treatments with murine skin autograft, human skin xenograft, or no graft. Rectilinear planimetry of healed wounds 6 weeks after surgery showed that skin substitutes cultured in serum-free medium, and for 24 hours before surgery in defined medium with basic fibroblast growth factor (100 ng/ml), were not statistically different (p less than 0.05) in size from treatment with human skin xenograft. Acceptance and persistence of skin substitutes cultured in serum-free media were 70% at 6 weeks after surgery, as determined by staining of healed skin with a fluorescein-labeled monoclonal antibody against human HLA-ABC antigens. Ultrastructural examination of wounds with cultured human skin 6 weeks after treatment showed complete basement membrane, including anchoring fibrils, presence of melanocytes and pigment transfer to keratinocytes, and innervation of healed skin adjacent to basement membrane. These findings demonstrate effectiveness of cultured skin substitutes for closure of skin wounds and illustrate important capabilities to modulate the natural processes of wound repair, to increase supply of materials used for wound repair, and to enhance quality of wound healing.

Animals↗
PubMed1990

Primary culture of cells arising from a neuroendocrine skin carcinoma.

A carcinoma arising in the skin of the lip metastasized to the lymph nodes in the neck of a 53-year-old white man. Electron microscopy of the initial excisional biopsy specimen revealed that the tumor cells contained dense-cored vesicles (100 nm in diameter) in their cytoplasm and were joined by simple junctions. Cells from the nodal metastases were found to be immunoreactive for neuronspecific enolase, keratin intermediate filaments, and chromogranin A, but not for neurofilaments. The tumor was thus classified as a neuroendocrine skin carcinoma. In addition, its metastatic cells shared immunoreactive and ultrastructural characteristics of Merkel cells, which are situated in the basal epidermis of normal skin. Primary cultures from a nodal metastasis were established and characterized. The cells attached and proliferated on culture flask surfaces. The population-doubling time was 2 days. This is the first report where cells from a neuroendocrine skin carcinoma have been demonstrated to retain their characteristic ultrastructure in an in vitro environment (10 days). Studies of cells cultured from neuroendocrine skin carcinomas may prove useful in understanding the pathobiology of this disease and help define the in vitro growth requirements of nontransformed Merkel cells as well.

Carcinoma↗
PubMed1983

Effects of chronic denervation in type I cutaneous mechanoreceptors (Haarscheiben).

Cutaneous type I receptor sites (Haarscheiben or tactile domes) were examined at intervals of 4 to 275 days after chronic denervation of the skin. The number of domes decreased with denervation time, and only about one-third of the domes originally present were still visible at 275 days. Most but not all of the Merkel cells from these domes were absent by 48 days, and the epithelium was significantly thinner than in nondenervated domes. Only a few of the examined domes appeared to be completely devoid of Merkel cells. It is concluded that after nerve transection, domes degenerate but do not always disappear entirely. The remnants may thus act as target sites which either attract regenerating type I nerve fibers or facilitate the formation of new dome structures after nerve regeneration.

Animals↗
PubMed1980

Development of rat Merkel cells.

The ultrastructure of Merkel cells and cutaneous nerves was examined in fetal, newborn, and 7-day-old rats. The earliest observation of cells having some, but not all, of the features of mature Merkel cells was at 16 days gestation in snout skin. These early presumptive Merkel cells resembled the neighboring keratocytes, except that they contained dense-cored vesicles scattered in the cytoplasm. Presumptive Merkel cells were seen only in the epidermis, although a careful search was made of the dermis. Developing neurons were not observed to penetrate the epidermal basal lamina when presumptive Merkel cells were first seen. The earliest observation of identifiable nerve axons in the snout epidermis was at 17-171/2 days gestation. Study of the presumptive Merkel cells through successively older gestational stages showed that the cells became innervated and progressively developed the characteristics of adult Merkel cells. We suggest that Merkel cells arise from keratocyte-like precursors in rat epidermis, at a time when skin nerves may still be several micrometers away.

Animals↗
PubMed1977

The ultrastructure of cutaneous type I mechanoreceptors (Haarscheiben) in cats following denervation.

Denervation of specialized cutaneous mechanoreceptors (Haarscheiben or domes) in cats was followed after 20 and 25 days by the following alterations in receptor structure: (1) reduced numbers of Merkel cells, (2) Merkel cells degenerating in situ, (3) fewer dense-core granules in the cytoplasm of Merkel cells, (4) an increased number of agranular dendritic cells and Langerhans cells in the dome, (5) the apparent phagocytosis of Merkel cells by Schwann and Langerhans cells, (6) fewer epithelial cell layers over the dome, and (7) a decrease in the number of transitional cells. Skin excised between the domes in the denervated nerve field appeared normal when compared to innervated skin, and it was considered unlikely that the alterations in dome structure were due to generalized nutritional changes in the skin caused by transection of sympathetic axons or to some other side effect of denervation. Since domes are formed in new locations on the skin after nerves have regenerated (Burgess et al., '74), changes in dome structure following nerve transection are probably due to loss of the "trophic" influence of the nerves supplying the dome.

Animals↗
PubMed1974

Patterning in the regeneration of type I cutaneous receptors.

1. Type I sensory fibres in cat hairy skin innervate structures characterized by twenty to fifty specialized epithelial (Merkel) cells aggregated in a small dome-shaped elevation. Only one fibre enters each dome and it branches repeatedly to supply at least one terminal to each Merkel cell. After the nerve is cut, the Merkel cells and the dome ultimately disappear.2. The distribution of domes on the posterior thigh was mapped before interruption of the femoral cutaneous nerve and after its regeneration. Regeneration after nerve crush was apparently complete, producing a coincidence pattern similar to those seen in control studies where the nerve was not damaged. After cutting the nerve fewer domes returned, but coincidence of regenerated femoral cutaneous domes with old sites generally was significantly greater than would be expected by chance alone. Non-femoral cutaneous fibres sprouting into the denervated femoral cutaneous field tended to form domes at old sites. Domes were also reformed on scars where domes had been excised.3. Domes appearing at new locations and on excision scars were often small and close together (clustered). Individual domes in a cluster could be innervated by different Type I fibres.4. Type I fibres are directed by some mechanism to sites formerly occupied by domes and to sites where domes are being induced.

Animals↗
PubMedDate not supplied

Cutaneous nerve distribution in adult rat hairy skin after thermal injury--an immunohistochemical study.

Regrowth of cutaneous nerves after thermal injury was examined in rat hairy skin with use of protein gene product 9.5, which has been shown to label nerves in skin preparations. Tissue biopsies were obtained from injured and control skin at postburn days 1, 7, 14, 28, and 120, fixed in 4% paraformaldehyde, cryoprotected, sectioned, and immunostained with rhodamine conjugated goat anti-rabbit immunoglobulin G. Immunoreactivity for protein gene product 9.5 was intense and illustrated the process of nerve regrowth in rat skin after thermal injury. No nerve growth was detectable in 1- and 7-day preparations. Variable regeneration was noted in 14-day preparations. The 28- and 120-day groups produced nerve counts that were similar to control sections. Results suggest that rat hairy skin has a capacity for nerve regrowth after thermal injury. Nerves were noted to regenerate from beneath the scar. Burn wounds in rats demonstrated vigorous cutaneous nerve regeneration.

Animals↗
PubMedDate not supplied

Chemosensitivity of the rat type I slowly adapting mechanoreceptor.

An in vitro lateral thoracic skin preparation of the adult rat was used to test the effect of serotonin (5, 50, 500 microM) and control solutions on the response of the type I slowly adapting mechanoreceptor to a standard mechanical stimulus. Serotonin (5-HT) significantly increased the magnitude of the type I response to mechanical indentation: 50 microM 5-HT infusion enhanced responsiveness more effectively than 5 microM 5-HT. In the absence of mechanical stimulation, little or no change in spontaneous discharge relative to control was observed, and recovery to baseline levels occurred within three stimulus trials. In vitro and in vivo control experiments showed no statistically significant change in responsiveness over a similar number of stimulus cycles. It was concluded that 5-HT modulates, but does not activate the rat type I receptor or alter its ability to encode the depth and/or velocity of mechanical displacement.

Adaptation, Physiological↗