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Results for “Merkel Cells”

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At least 1,711 records · Page 95Linked to original sources
PubMed1989

Mechanoreceptive units in the human infra-orbital nerve.

Eighty-four low-threshold mechanoreceptive afferents innervating facial hairy skin or the red zone of the lip were recorded with micro-electrodes from the human infra-orbital nerve. Based on their responses to skin indentations, the units were classified as slowly or fast-adapting, with small or large receptive fields. The responses to hair movement, skin stretching and contraction of facial muscles were also studied. Both hairy skin and the red zone were innervated by slowly and by fast-adapting units. The innervation density was found to be highest at the corner of the mouth and on the upper lip. Slowly adapting units with small fields in hairy skin were most common and included units responding to sustained hair displacement. These units are suggested to have two types of end-organs, either pilo-Ruffini endings or Merkel cell-neurite complexes. The slowly adapting units with large fields were spontaneously active stretch receptors and may have corresponded to Ruffini corpuscles, although the possibility of other, intramuscular, receptors could not be ruled out. Only one afferent possibly innervated a Pacinian corpuscle. Most mechanoreceptors were also activated by skin stretching or contraction of facial muscles. Many of the slowly adapting units with small fields responded to the onset and release of stretch, whereas their discharge in response to sustained stretching adapted more or less completely. Spontaneously active units had the most sustained stretch response. It is concluded that several types of cutaneous mechanoreceptors can operate as sensitive proprioceptors of importance for facial kinaesthesia and motor control.

Adult↗
PubMed1981

Light microscopic morphology of low resistance skin points in the guinea pig.

This study compares the light microscopic structure of low resistance skin points (LRSP) to high resistance skin points (HRSP) of the guinea pig, Previously, LRSP have been shown to coincide with acupuncture loci. Epidermal nuclei and dermal nuclei were counted at both LRSP and at control points or HRSP. In addition, hair follicles, blood vessels, and sebaceous nuclei were likewise quantitated. This data, collected in a blind manner, was then subjected to statistical analysis using a nested analysis of variance and a Student's "t" test. The former test indicated an increase in density of hair follicles at LRSP, while both demonstrated a decrease in dermal nuclei at LRSP. An interesting finding is that the epidermis at both LRSP and HRSP is indistinguishable at the light microscopic level. This was indicated by both statistical procedures. Finding of a Haarscheibe, an aggregation of Merkel cell-neurite complexes, only at HRSP tends to preclude its role as an acupuncture neurotransducer. Finally, there appeared to be no obvious qualitative differences between LRSP and HRSP observable at the light microscopic level.

Acupuncture Therapy↗
PubMed2005

Sensory abnormalities in unaffected relatives in familial adult-onset dystonia.

Somatosensory abnormalities are found in adult-onset primary torsion dystonia (PTD). Therefore we assessed spatial discrimination thresholds (SDT), a measure of spatial acuity, in four multiplex families with adult-onset PTD. In family members aged 20 to 45 years vs controls (mean + 2.5 SD), abnormal SDTs were found in four of five affected with adult-onset PTD and in 12 of 49 unaffected relatives. Sensory abnormalities may be an endophenotype, possibly expressed later as adult-onset PTD.

Adult↗
PubMed1993

Time course and characteristics of the capacity of sensory nerves to reinnervate skin territories outside their normal innervation zones.

Factors involved in the outcome of regeneration of the saphenous nerve after a cut or crush lesion were studied in adult rats with electrophysiological recordings of low-threshold mechanoreceptor activity and plasma extravasation of Evans blue after electrical nerve stimulation that activated C fibers. In the first series of experiments, saphenous and sciatic nerve section was combined with anastomosis of the transected proximal end of the saphenous nerve to the distal end of the cut tibial nerve. Regeneration of saphenous nerve fibers involved in plasma extravasation and low-threshold mechanoreceptor activity in the glabrous skin was observed 13 weeks after nerve anastomosis. Substance P-, calcitonin gene-related peptide-, and protein gene product 9.5 (PGP-9.5)-immunoreactive (IR) thin epidermal and dermal nerve endings, as well as coarse dermal PGP-9.5-IR nerve fibers and Meissner corpuscles and Merkel cell-neurite-like complexes, were observed in the reinnervated glabrous skin at this time. In a second series of experiments, the time course of the regeneration of saphenous nerve axons to the permanently sciatic-nerve-denervated foot sole was examined. Saphenous-nerve-induced plasma extravasation and low-threshold mechanoreceptor activity in the saphenous nerve were found in the normal saphenous nerve territory 2, 3, 4, and 6 weeks after sciatic nerve cut combined with saphenous nerve crush in the left hindlimb. Saphenous-nerve-induced plasma extravasation was also present in the glabrous skin normally innervated by the sciatic nerve 3, 4, and 6 weeks after the sciatic cut/saphenous crush lesion. However, no low-threshold mechanoreceptor activity was detected in the saphenous nerve when the glabrous skin area was stimulated. In a third series of experiments, the fate of the expansion of the saphenous nerve territory after saphenous nerve crush was examined when the crushed sciatic nerve had been allowed to regenerate. Nerve fibers involved in plasma extravasation were observed in the glabrous skin of the hindpaw after saphenous nerve, as well as after tibial nerve, C-fiber stimulation 3, 12, and 43 weeks after the saphenous crush/sciatic crush lesion. Low-threshold mechanoreceptors from the regenerated saphenous nerve, which primarily innervates hairy skin, seem to be functional in the glabrous skin if the axons are guided by the transected tibial nerve by anastomosis. Furthermore, the results indicate that fibers from the regenerating saphenous nerve that have extended into denervated glabrous skin areas can exist even if sciatic nerve axons are allowed to grow back to their original territory.

Afferent Pathways↗
PubMed1999

Intraepidermal nerves in human skin: PGP 9.5 immunohistochemistry with special reference to the nerve density in skin from different body regions.

The intraepidermal nerves of normal adult human skin were demonstrated by employing a powerful marker of neuronal elements, protein gene product (PGP) 9.5. There were two types of epidermal nerves, free nerve endings and nerves in the Merkel cell-neurite complex. The free nerve endings distributed to, and terminated in, all the strata basale, spinosum and granulosum, and they appeared as thin fibers, mostly varicose, branched or single processed, straight or bent. They existed at every site of the human body, including face, trunk and extremities. However, the densities of these nerves varied in different body parts and areas. The number of nerves decreased from the trunk to the distal parts of the limbs, and small denser 'innervation patches' showed up in the epidermis which were identified in confocal microscopy as one morphologic terminal field coming from the same dermal nerve bundle. This study has confirmed the existence of epidermal nerves in normal adult human skin, and presented a more clear picture than earlier. The difference between densities of epidermal nerves at different body areas implies area-specific functions of the intraepidermal nerve terminals. The observed intraepithelial nerve fibers may have a pain-perceiving role, however, also trophic or immunoregulatory roles can not be excluded.

Adult↗
PubMed2002

[Primitive cutaneous neuroendocrine carcinomas or Merkel's tumor. Clinical and therapeutic aspects in 22 patients].

INTRODUCTION: Primitive cutaneous neuroendocrine carcinoma (PCNC) is a rare tumor with poor prognosis. Surgery is the treatment of choice, but radiotherapy is taking a larger place in the management of these patients. METHODS: The files of 22 patients were studied retrospectively over a period of 14 years. RESULTS: The study included 17 women and 5 men with a mean age of 75.5 years. The localization of the tumor was the cephalic extremity in 12 cases. At the initial stage, the tumor in 3 of the 22 patients was of glandular or visceral localization. Thirteen stage I patients were treated surgically. Adjuvant radiotherapy was performed in 10 of these patients and only one relapsed (incomplete initial exeresis). The other three relapsed. Exclusive radiotherapy led to complete response in 4 patients who could not undergo surgery and in 2 with local relapses. Seven patients exhibited glandular involvement and 6 of them died (median 7 months) after the adenopathy had been discovered. DISCUSSION: Our series illustrates the clinical characteristics of this tumor of the elderly, which is predominantly cephalic and of rapid progression. From a therapeutic point of view, our results underline the benefit of radiotherapy as adjuvant to surgery. When surgery is impossible, and in the case of local relapse, radiotherapy gives good results.

Aged↗