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Biomedical subjects

C D Fermin

Publications and source records attributed to C D Fermin.

At least 55 records · Page 3Linked to original sources
PubMed1989

Ultrastructural evidence of repair and neuronal survival after labyrinthectomy in the squirrel monkey.

Although the vestibular and cochlear branches of the VIIIth cranial nerve originate embryologically from the same primordia, results of the present investigation confirm previous findings indicating that the vestibular branch may be more plastic with respect to recovery after surgical insult than the cochlear division. In this report we show ultrastructural details of changes undergone by the vestibular nerve after surgery. Dendrites peripheral to the vestibular nerve ganglion (VNG) were severed by surgically removing the vestibular end organs; the squirrel monkeys were then allowed to recuperate, and tested for their vestibulospinal and vestibulo-oculomotor functions behaviorally. However, behavior deficits resulting from the injury are reported separately. The vestibular nerves excised from the internal acoustic meatus and the temporal bones were examined histologically for changes of VNG and fibers from day 1 to 1,247 days after labyrinthectomy. Light- and electron-microscopic examinations indicated that some perikarya and some fibers of the VNG remained in the ganglionic matrix for up to 1,247 days, the longest period studied, after the operation. Fibers extended toward the remodeled inner ear space in the absence of appropriate sensory cell targets. The surviving neurons and fibers exhibited various degrees of wallerian-like degeneration at first, but many of them retained ultracellular organelles and integrity even after 1,247 days. Since vestibular perikarya are bipolar, the unsevered fibers that project to the brainstem could retain functional synaptic connections, a possibility that is now under investigation. Schwann cells in the ganglionic matrix may also have contributed to vestibular neuron survival by providing the proper nourishment. Morphometric measurements determined that neurons remaining in the ganglion had significantly smaller cross-sectional areas than normal neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Localization of Na+, K+-ATPase activity in the tegmentum vasculosum of the chick cochlea.

We studied the localization of Na+, K+-ATPase activity in the chick cochlea, utilizing a cytochemical method of K+-p-nitrophenylphosphatase (K+-NPPase), and found that the enzyme activity was limited to the dark cells of the tegmentum vasculosum (TV). Our present results indicate that the dark cells of the TV play an essential role in the maintenance of the ionic composition of the cochlear endolymph.

Animals↗
PubMed1987

Ultrastructural changes of statoconia after segmentation of the otolithic membrane.

The chick vestibule transformed from a homogeneous epithelial layer at day 2 (stage 15) into a pseudo-stratified epithelial layer at day 4 (stage 24). The apical columnal appearance of sensory cells was evident by day 6 (stage 29). In the supporting cells of the saccule and utricle large rough endoplasmic reticulum cisterns filled with material similar to the primitive organic matrix. Fibrillar material of the otolithic membrane remained attached to the supporting cells and accumulated over the saccule and utricle. The primitive otolithic membrane acquired stress-like lines and statoconial units emerged from the upper surface without a central core. Statoconia thickened at the periphery and a central core formed. Calcium was deposited between the fibrils of older statoconia which were located on top of the segmenting membrane. DIAMOX inhibited statoconia formation and/or prevented calcium and the matrix from associating. Large statoconia (100-200 microns diameter) were formed in embryos injected with this carbonic anhydrase inhibitor. Gel electrophoresis of immature statoconial complexes yielded at least 5 major protein bands between 25 and 210 kDa. Ouabain-sensitive potassium-dependent p-nitrophenylphosphatase activity was demonstrated in the endolymphatic sac of newly hatched chicks.

Acetazolamide↗
PubMed1987

Morphometry and ultrastructure of the squirrel monkey (Saimiri sciureus) vestibular nerve.

Vestibular nerves of squirrel monkeys (Saimiri sciureus) embedded in plastics and epoxies were examined with light microscopy (LM) and transmission electron microscopy (TEM), and computerized measures were obtained and analyzed statistically. An average of 12,412 perikarya and 12,005 myelinated nerve fibers was obtained. Approximately 0.7% of the perikarya appeared unmyelinated under LM. About 500 unmyelinated fibers were counted. The cross-sectional area of 1,864 perikarya was 200-650 micron 2. The cross-sectional area of 1,346 nerve fibers was 3-11 micron 2 for the axoplasm and 11-12 micron 2 for the myelin sheath of the same fiber. Myelin thickness was directly proportional to the axoplasm cross-sectional area of the nerve fibers. The cross-sectional area of central axons and peripheral dendrites differed significantly (p less than 0.001). The initial segments of peripheral dendrites were usually smaller, but longer than the initial segments of the central axons. Both initial segments increased in diameter after the first node of Ranvier. Schmidt-Lantermann incisures were more abundant in thick and heavily myelinated fibers than in thin and lightly myelinated fibers. Larger perikarya usually had larger fibers and vice versa, within the first 100-200 micron from the first node of Ranvier. No major ultrastructural differences were found between myelinated and unmyelinated perikarya, except at the hillock region. The Nissl substance was preferentially located in the peripheral cytoplasm.

Animals↗
PubMed1986

Review of statoconia formation in birds and original research in chicks (Gallus domesticus).

This paper reviews published materials on statoconia formation in birds, and emphasizes works dealing with the embryonic chick (Gallus domesticus) saccule and utricule. Histological, biochemical and histochemical aspects of forming statoconial membranes and statoconial crystals of mammals are included. Results from our work with chick embryos permitted us to conclude that statoconia probably do not form by seeding of a subunit around central core. Instead, immature statoconia may emerge already formed, from a segmenting mass of organic material that seems to be secreted by the supporting cells of the saccular and utricular maculae. Crystallization of each statoconium may involve seeding of multiple subunits around many nucleation centers in the organic matrix. Following these processes, calcium (sometimes granular) attaches to immature statoconia and become subsequently incorporated between the fibrils of the organic matrix starting at the peripheral zone and advancing toward the central core. Our transmission electron microscopy findings, histochemistry and X-ray microanalysis complements of other investigators, who used chicks with light microscopic studies. These results agree with the notion that the secretion of an organic matrix constitutes the first step toward the formation of the statoconial membrane and statoconia. We show ultrastructurally how statoconia may be assembled from the organic matrix before they acquire their characteristic geometric shapes.

Animals↗
PubMed1985

Electron-microscopic observations of the gravity receptor epithelia of normal and spinner juvenile Octopus maya.

Light and electron microscopy of the gravity receptor epithelia (maculae) of statocysts of normal and "spinner" juvenile Octopus maya showed differences between the structures of the hair cells, supporting cells, and afferent neurons of these cephalopods. The maculae of spinner animals were approximately 30% smaller in their surface area and had 40% fewer hair cells. Moreover, the average distance between randomly-chosen hair bundles in scanning electron micrographs of maculae of normal animals was significantly greater (4.33 +/- 6.47 microns) than those of maculae of spinner animals (3.38 +/- 4.90 microns; P less than 0.0001). The sectional area of the supporting cell's microvilli in spinner maculae was larger (0.16 +/- 0.18 microns) than those of normal (0.10 +/- 0.10 micron; P less than 0.0001) O. maya. The morphological differences observed between certain structural components of the maculae of normal and spinner O. maya may be related to the absence and/or malformation of the neuroepithelial suprastructures in spinners. This may have direct or indirect effects to their inability to orient to gravity with these organs.

Acoustic Maculae↗
PubMed1985

Development of the embryonic chick's tectorial membrane.

The nascent tectorial membrane (TM) is identifiable as early as stage 33 (7th day) as thin, wispy material. By stage 37 (11th day), the dense mesh of the immature TM and fibrous webs (subtectorial threads) that attach the TM to the basilar papilla are distinct but scanty. The TM condenses slightly in its upper face. The growth of the columnar cells and basilar papilla during the following days pulls the TM, lifting it upward, and resembling the cables on a suspension bridge in cross-section. As a result, a large hollow wedge forms. During stages 40-44 (14th-18th days), the columnar cells secrete large amounts of fibrous material, which fills the hollow wedge and condenses into the dense meshes. The honeycombed patterns appear at this time. The supporting cells secrete the fibrous webs. Their secretory activity closely corresponds to that of the columnar cells. The secretory material from both cell types remains attached to the apical ends of their respective cells after secretory activity ends. By hatching (stage 46-21 days), the columnar cells have filled with fibrous material and their cytoplasmic organelles are restricted to the apices. The cytoplasm of supporting cells is relatively clear, with few cytoplasmic remnants of their intense secretory activity earlier.

Animals↗
PubMed1985

Development of otoconia in the embryonic chick (Gallus domesticus).

In the chick (Gallus domesticus) embryo, otoconium formation started first over the macula sacculi around the 4th day of incubation, and a day later over the macula utriculi. It was determined that each otoconium formed as a result of the segmentation of the immature otolithic membrane, and that the calcium responsible for otoconium calcification was incorporated into the organic matrix of each otoconium in the form of small electron-dense granules (20-150 nm in diameter). The presence of calcium in these granules was confirmed by histochemical staining with osmic-potassium pyroantimonate, by EDTA chelation, and by X-ray microanalysis under the electron microscope.

Animals↗
PubMedDate not supplied

Immunohistochemical localization of the neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP), in human and primate hypothalamus.

A 38 residue neuropeptide was recently isolated from ovine hypothalamus in our laboratory, and named pituitary adenylate cyclase activating polypeptide (PACAP38) based on its biological activity. Rabbit antisera against synthetic PACAP27 were characterized by ELISA for immunohistochemical use. PACAP-immunoreactive neuronal elements having similar distributions were demonstrated in both human and spider monkey hypothalami. Many PACAP-immunoreactive cell bodies were present in the supraoptic and paraventricular nuclei. Immunopositive nerve fiber networks were stained throughout the hypothalamus, including in both external and internal zones of the tuber cinereum, close to the transition of the pituitary stalk (median eminence). These results suggest that PACAP plays multifunctional roles as a hypophysiotropic hormone, neurohypophysial hormone, neurotransmitter or neuromodulator in higher vertebrate species including man.

Amino Acid Sequence↗
PubMedDate not supplied

Aminoglycoside ototoxicity in the chick (Gallus domesticus) inner ear: I. The effects of kanamycin and netilmicin on the basilar papilla.

A single dose (100 mg/kg of egg weight) of kanamycin or netilmicin was injected into the yolk sacs of 7-day-old chick (Gallus domesticus) embryos. Embryos were collected every 24 hours and processed for light and transmission electron microscopy. Morphologic study of the medial basilar papilla disclosed that both kanamycin and netilmicin are toxic to the hair cells in this region. Intoxication was manifested by an increased number of dense osmiophilic bodies, swollen mitochondria, agglomerated chromatin, and occasional disorganization of the kinocilium basal bodies. The cytologic changes observed in the hair cells of embryos injected with netilmicin and kanamycin were similar. However, mitochondrial damage was more severe in the chicks after kanamycin than after netilmicin injection. Some of the cytologic alterations described here are comparable to those already reported for aminoglycoside-intoxicated hair cells in several mammalian species. This study and previous work indicate that the chick embryo provides a satisfactory developmental model for testing ototoxicity of drugs in vivo.

Animals↗
PubMedDate not supplied

Vestibular ganglion of the squirrel monkey.

The vestibular ganglia of adult squirrel monkeys (Saimiri sciureus) were studied with the aid of light and electron microscopy. The vestibular ganglia are formed by small and large neurons (perikarya). The perikarya's outermost surface is surrounded by 2-20 lamellae of compact myelin. The compact myelin sheath varies its thickness around one perikaryon. The sheath generally thins out i the vicinity of the axon hillock. Occasionally, the compact myelin transforms completely into loose myelin for a length of 2-5 mu. Two to eight lamellae of loose myelin usually face the cytoplasm of the neurons. This myelin arrangement is constant in the majority of the cells examined regardless of shape and/or size. Large myelinated perikarya form the majority of the ganglion cells. There are, however, a few neurons that lack a true compact myelin sheath. Others are surrounded by very few lamellae of loose myelin. The general morphology of the neurons was compared to the available literature on other species. Possible variation on the myelination pattern due to fixation differences, and variation on the perikaryal size due to the angle of cut irregular shape of the cells are also discussed.

Animals↗
PubMedDate not supplied

The development of hair cells in the embryonic chick's basilar papilla.

During the 7th to 21st (hatching) days, hair cells of the embeyonic chick transform from an undifferentiated epithelium into cylindrically-shaped tall hair cells (THCs), pitcher-shaped short hair cells (SHCs), or intermediate hair cells that share structural characteristics of the first two. By the 11th day hair cell types are unambiguous. "Hairs" (stereocilia and a kinocilium) were first identified on the 7th day and resembled the adult pattern the 13th. The nucleus occupies relatively less volume as hair cells increase in size, becoming positioned centrally in THCs and basally in SHCs. Nucleoli, which are prominent throughout development, remain conspicuous even in newly hatched chicks. The cuticular cone begins to form the 11th day. By the 10th day, sensory nerve endings synapse on the bases of the HCs, which by the 11th day develop synaptic bars. Although efferent neurites were in evidence as early as the 11th day, synaptic contacts and their cisterns were identified by the 19th day but may form earlier. Supporting cells transform from cylindrically to flask-shaped cells with constricted necks and may secrete at least a portion of the tectorial membrane.

Afferent Pathways↗
PubMedDate not supplied

Development of the embryonic chick's statoacoustic ganglion.

During stage 25 (4 1/2 days of incubation), the embryonic chick's statoacoustic ganglion appeared as a homogeneous cell mass. By stage 29 (6 days)- perikarya could be distinguished from Schwann cells because the latter contained more endoplasmic reticulum and ribosome. Granular Schwann cells processes have formed loose boundaries around groups of neurites. During the next 7 days, the Schwann cells clutched the neurites more tightly and divided them into successively smaller bundles. By the 13th day (stage 39) the first compact myelin (2-6 layers) surrounded the larger dendrites, and by the 14th day (stage 40) compact myelin appeared regularly. Until the 17th day (stage 43), the perikaryal were covered by a few layers of loose myelin. Perikaryal compact myelin appeared a day later (stage 44); the larger perikaryl diameter (15-30x) probably accounts for the lag. At hatching (20-21 days), 12-18 myelin layers surrounded many dendrites, though the extent of myelination varied markedly among dendrites in adjacent bundles. By the 2nd week after hatching, large myelinated perikarya outnumbered the smaller and loosely myelinated ones. Perikaryonal myelination required the cooperation of several Schwann cells. The myelin regularly alternated from compact to loose around each perikaryon.

Animals↗
PubMedDate not supplied

Developmental gradients in the embryonic chick's basilar papilla.

The basilar papilla, the avian counterpart to Corti's organ, was examined cytologically in the embryonic chick (Gallus domesticus) from stages 31 through 46 (hatching). Developmental reconstructions were prepared by using light microscopy to analyse serial sections (1-5 microM) along the entire lagenar length and electron microscopy to examine representative thin sections from the proximal, medial and distal regions. We identified two gradients, the lateral and longitudinal. In the longitudinal gradient, the mid-basal basilar papilla, which lies directly above the statoacoustic ganglion, develops before the proximal and distal regions as evidenced by the maturation of hair cells and afferent synapses. Similarly, in the lateral gradient, tall hair cells and afferent synapses develop before short hair cells and their respective afferent terminals. Efferent synaptogenesis follows the same two gradients several days later than the afferents. Afferent synaptogenesis corresponds with the opening of the perilymphatic spaces and completion of the tectorial membrane.

Afferent Pathways↗
PubMedDate not supplied

Dendritic growth following labyrinthectomy in the squirrel monkey. Light and electron microscopic studies.

In the squirrel monkey (Saimiri sciureus) peripheral vestibular dendrites underwent degeneration after destruction of the vestibular end organs (labyrinthectomy). The dendrites subsequently grew into the remodelled area where the end organs, surrounding tissues and inner ear fluid spaces were previously located, and were progressively occupied by connective tissue, blood vessels and also new bone. This finding indicates that peripheral vestibular dendrites of adult squirrel monkey can grow, that Schwann cells migrate along with these dendrites, and that myelin can be formed in vivo in locations not previously destined for myelination. The importance of these findings in relation to the plastic properties of the squirrel monkey vestibular nerve is discussed.

Animals↗
PubMedDate not supplied

Ultracytochemical localization of Na+, K(+)-ATPase activity in the tegmentum vasculosum of the developing chick cochlea.

We studied the morphological changes and the precise localization of Na+, K(+)-ATPase activity in the developing chick tegmentum vasculosum (TV) with a cytochemical method utilizing K(+)-p-nitrophenylphosphatase (K(+)-NPPase). At stage 37, epithelial folds (lamellae) were relatively well developed, and the light and the dark cells were clearly identified. At stage 41 to 42, Na+, K(+)-ATPase activity appeared in the folded cytoplasmic processes of the dark cells which interdigitated with those of the light cells. The present results indicate that the TV is involved in the production of the cochlear endolymph prenatally (at least up to stage 41), and that the dark cell plays a central role in the maintenance of the ionic composition of the endolymph.

Animals↗
PubMedDate not supplied

Color threshold and ratio of S100 beta, MAP5, NF68/200, GABA & GAD. I. Distribution in inner ear afferents.

Afferents of chick embryos (Gallus domesticus) VIIIth nerve were examined at E3, E6, E9, E13, El7, and hatching (NH) for anti-S100 beta, anti-MAP5, anti-GABA, anti-GAD and anti-NF68/200 stain. Different ages were processed together to determine if the distribution of these antibodies changed during synaptogenesis and myelination. Color thresholding showed that saturation of pixels changed for S100 beta only 5%, for NF68/200 10%, and for MAP5, 10%, between E9-NH. Color ratio of NF68/200 over MAP5 was 1.00 at E13 and 0.25 at E16 and NH. S100 beta, GABA and GAD were co-expressed on nerve endings at the edge of the maculae and center of the cristae, whereas hair cells in the center of the maculae expressed either S100 beta or GABA, but not both. S100 beta/NF68/200 shared antigenic sites on the chalices, but NF68/200 expression was higher than S100 beta in the chalices at hatching. MAP5 was expressed in more neurons than NF68/200 at E11, whereas NF68/200 was more abundant than MAP5 at hatching. The results suggest that: 1) the immunoexpression of these neuronal proteins is modulated concomitantly with the establishment of afferent synapses and myelination; 2) S100 beta may serve a neurotrophic function in the chalices where it is co-expressed with the neurotransmitter GABA and its synthesizing enzyme GAD.

Animals↗