A dichotomy of hair-cell types has been found in the bullfrog sacculus, and considerable evidence supports the view that one type ("peripheral") is transformed during macular growth to the other type ("central"). Between the periphery and the center of the macula, one finds a gradation of form from "peripheral" to "central" type. Occasionally in adults and more often in stage-26 tadpoles one finds the presumably younger peripheral type of hair cell occurring well beyond the limits of the macula proper. The apparent morphogenic sequence for saccular hair cells is (1) development of a kinocillum on a n endolymphatic epithelial cell, (2) gradual transformation of microvilli into stereocilia, (3) growth of the stereocilia and development of kinociliary bulb, (4) achievement of final size and form.The scanning electron microscope has been employed quite successfully in studies of the surfaces of ciliated cells in general (Barber and Boyde, '68) and of auditory and vestibular receptors in particular (Bredberg, Lindeman, Ades, West and Engstrom, '70; Hillman and Lewis, '71; Lim and Lane, '69; Marovitz, Arenberg and Thalman, '70). In a recently published scanning microscopy paper, Lewis and Nemanic ('72) reported two distinct types of hair cells in the saccular macula of the mudpuppy (Necturus maculosus). One type, which occurs at the periphery of the macula, is very similar to hair cells of the mudpuppy utricular macula. The other type, occurring throughout the center of the macula, is quite distinct. Following that study, we found a similar dichotomy among hair cells of the bullfrog saccular macula. One of us (C.W. Li) undertook a scanning microscopy examination of the development of the saccular macula during metamorphosis, and soon found evidence that the peripheral hair cells were involved in macular growth. Continuing this study, we have expanded the evidence. The work was greatly facilitated by an additional distinction, not found in the mudpuppy, between the peripheral and central types. The central type of hair cell exhibited the very obvious kinociliary bulb first reported by Hillman ('69) and later shown J. MORPH., in scanning micrographs by Hillman and Lewis ('71). MATERIALS AND METHODSTwenty adult bullfrogs (Rana catesbeiana) and ten stage-26 tadpoles (Gosner '60) were used in this study. The animals were killed by decapitation and then pithed to prevent movement during dissection and the early stages of fixation. The otic capsules were exposed from the roof of the mouth and perfused with osmium tetroxide solution in the manner employed by Hillman ('69). Proper osmolarities for the osmium solutions were determined by preliminary experiments. The effects of hyperosmotic and hyposmotic solutions on microvilli and cilia were quite marked, and the optimal osmolarities (measured on a Fiske Osmometer) were bracketed very easily. As others have found (Lombard '70), the optimal osmolarity for tadpoles was approximately one half that for adult frogs.After fixation, the otolith and gelatinous membrane were rem...
Increasing evidence supports that acupuncture intervention is an effective approach for intraoperative and postoperative pain. Neuron-microglia crosstalk, mediated by the purinergic P2X7 receptor (R)/fractalkine/CX3CR1 cascade in the spinal cord dorsal horn, plays a pivotal role in pain processing. However, its involvement in the analgesic effect of electroacupuncture (EA) remains unclear. In this study, a rat neck-incision pain model was established by making a longitudinal incision along the midline of the neck and subsequent repeated mechanical stimulation. EA stimulation was applied to bilateral LI18, LI4-PC6, or ST36-GB34. The thermal pain threshold, cervicospinal ATP concentration, expression levels of purinergic P2XR and P2YR subunits mRNAs, and fractalkine, CX3CR1 and p38 MAPK proteins, were detected separately. The neck incision induced strong thermal hyperalgesia and upregulation of spinal ATP within 48 h. No significant change was found in thermal hyperalgesia after a single session of EA intervention. However, a single session of EA dramatically enhanced the neck incision-induced upregulation of ATP and upregulated the expression of P2X7R, which was reversed by two sessions of EA. Two sessions of EA at bilateral LI18 or LI4-PC6 attenuated hyperalgesia significantly, accompanied with downregulation of P2X7R/fractalkine/ CX3CR1 signaling after three sessions of EA. EA stimulation of LI18 or LI4-PC6 alleviates thermal hyperalgesia in neck-incision pain rats, which may be associated with its effects in regulating the neck incision-induced increase of ATP and P2X7R and subsequently suppressing fractalkine/CX3CR1 signaling in the cervical spinal cord.
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