Tarsal navicular stress fracture in athletes

Stress fracture of the tarsal navicular bone is now frequently recognised. The majority of navicular stress fractures are partial fractures in the sagittal plane. They occur mainly in track and field athletes. A number of theories regarding the aetiology of this fracture have been proposed. Athletes with a history of vague, activity-related midfoot pain, with associated tenderness over the dorsal proximal navicular ('N' spot) should be suspected of having a navicular stress fracture. Plain radiography frequently fails to demonstrate the fracture, thus radionuclide scanning is the investigation of choice to detect navicular stress injury. A computed tomography (CT) scan should be performed to confirm the presence of the fracture. Various methods of treatment have been employed. A minimum of 6 weeks of strict non-weightbearing cast immobilisation is the treatment of choice. After removal of the cast, a further 6 week programme of rehabilitation with a graduated return to activity, joint mobilisation and soft tissue massage is required. Surgery for nonunion or delayed union is rarely required if initial treatment is appropriate.

Analysis of gamma-aminobutyric acidA receptor subunits in the mouse cochlea by means of the polymerase chain reaction

Thirteen GABAA receptor subunits were examined in the cochlea of the CBAJ mouse by PCR analysis. Total RNA was extracted from the auditory organs of 14-18-day-old animals, and mRNA was isolated using oligo-dT cellulose. After reverse transcription, resulting cDNA was amplified by PCR with primers specific for nucleotide sequences representing GABAA subunits. PCR products corresponding to subunits alpha 1-alpha 6, beta 1-beta 3, and gamma 2 were amplified, whereas those representing gamma 1, gamma 3, and delta were not amplified above background. These results provide the most direct evidence to date that GABAA receptors composed of the detected subunits are expressed in the mammalian cochlea, lending new support to previous studies implicating GABA as a cochlear transmitter. The pronounced expression of alpha 2 and alpha 6 subunits suggests type II and "cerebellar-type" benzodiazepine pharmacology in the cochlea.

Acetylcholinesterase activity is associated with efferent endings in the sensory epithelia of the utricle and semicircular canals of the rainbow trout inner ear

The mechanosensory hair cells of the utricle and semicircular canals of the trout inner ear are morphologically similar to type II hair cells of the avian and mammalian vestibular end organs. These cells are innervated by two types of nerve terminals. The nonvesiculated terminals are considered to be afferent, and the vesiculated endings are presumed to be efferent. The presumptive efferent endings contain numerous clear, round vesicles and a few that are dense-cored. Histocytochemical, electron microscopic analysis has localized acetylcholinesterase activity to plasma membranes of vesiculated, presumptive efferent nerve terminals in sensory epithelia of the utricle and semicircular canals. No reaction product was observed at the receptoneural synapse or found in nonvesiculated, presumptive afferent endings. Control specimens incubated in the presence of eserine sulfate, an inhibitor of acetylcholinesterase, were devoid of reaction product. These results support the tenet that vesiculated nerve endings in the sensory epithelia of the utricle and semicircular canals of the trout are cholinergic.

Immunohistochemical localization of S-100 protein in the saccule of the rainbow trout (Salmo gairdnerii R.)

The distribution of S-100-like immunoreactivity in the trout saccule (a presumed organ of hearing in fish) has been determined by means of immunohistochemistry. Within the sensory epithelium of the saccular macula, hair cells and myelinated saccular nerve fibers were found to be immunoreactive. Hair-cell immunoreactivity was relatively uniform throughout the macula except at the extreme periphery (rostral, caudal, ventral and dorsal), where staining was either decreased or absent. The immunoreactivity associated with myelinated nerve fibers was greatest at the peripheral edges of the nerve processes, a position corresponding to the location of Schwann cells. However, the nerve processes themselves (within and subjacent to the sensory epithelium), as well as cell bodies within the saccular nerve, were also immunoreactive. Thus, the immunoreactivity of the saccular nerve observed above the basal lamina can be attributed to the saccular nerve processes as well as to nerve-associated Schwann cells. Overall, the immunoreactivity displayed by hair cells was less intense than that associated with myelinated saccular nerve, as evidenced by a disappearance of signal in hair cells first, upon serial dilution of antibody. No S-100-like immunoreactivity was observed in supporting cells within the sensory epithelium or in epithelial cells in non-sensory regions. A concentration of S-100-like immunoreactivity in hair cells and saccular nerve is suggestive of the presence of S-100 calcium-binding protein-mediated activities in these cell types.

Stress fractures of the tarsal navicular bone: CT findings in 55 cases

OBJECTIVE

The purpose of this article is to present the CT findings in 55 cases of tarsal navicular stress fracture before and after treatment and to describe the CT protocol used.

MATERIALS AND METHODS

Fifty-five navicular stress fractures in 54 patients whose initial and follow-up CT scans were available for study were retrospectively reviewed. In most cases, contiguous 1.5-mm axial and 3-mm coronal scans of the navicular bone had been obtained. Both feet were scanned for comparison. Follow-up scans were obtained between 4 weeks and 6 years.

RESULTS

On review, fractures were evident in all cases, but six small fractures (11%) were missed at the initial interpretation. All fractures involved the central third of the proximal dorsal margin of the navicular bone. Fifty-three fractures (96%) were partial. Forty-three partial fractures were linear, five were linear with bone fragments, and five were rim defects with ossicles. In 13 cases (24%) the fracture was small, 10% or less of bone height. The earliest sign of healing, slight dorsal cortical bridging, was seen in three of eight cases in which follow-up was done at 6 weeks. Firm cortical union was noted in 10 (32%) of 31 by 4 months. Nonunion occurred in 12 and was indicated by the persistence of the fracture gap and lack of cortical healing. Medullary cysts (five) and cortical notching (two) were noted to persist after complete healing.

CONCLUSION

CT scanning is a suitable method for detecting navicular stress fracture and for performing follow-up examinations. Small fractures may be overlooked owing to lack of familiarity with their appearance.

Outcome of conservative and surgical management of navicular stress fracture in athletes. Eighty-six cases proven with computerized tomography

Eighty-two athletes with 86 clinical navicular stress fractures, all imaged with computerized tomography, were followed for an average of 33 months (range, 6 to 108) after diagnosis. Initial treatment consisted of at least 6 weeks of nonweightbearing cast immobilization for 22 fractures, at least 6 weeks of limitation of activity with continued weightbearing for 34 fractures, and a period of less than 6 weeks of conservative treatment for another 19 fractures. Five patients attempted to continue playing sports. Six patients had immediate surgery. Nineteen of 22 patients (86%) who had initial non-weightbearing cast immobilization treatment returned to sports, compared with only 9 of 34 patients (26%) who initially continued weightbearing with limited activity (P < 0.001). After failure of the latter treatment, successful outcomes were seen for 6 of 7 patients (86%) treated with nonweightbearing cast immobilization, while 11 of 15 patients (73%) who had one surgical procedure were able to return to sports. These results indicate that nonweightbearing cast immobilization is the treatment of choice for navicular stress fractures. Also, this treatment compares favorably with surgical treatment for patients who present after failed weightbearing treatments. Computerized tomographic appearances of healing fractures do not necessarily mirror clinical union, and postimmobilization management should be monitored clinically.

Lack of Alzheimer pathology after beta-amyloid protein injections in rat brain

In order to establish a direct relationship between beta-amyloid protein (beta AP) and in vivo neurotoxicity, we made intraparenchymal injections and Alzet pump infusions of beta AP into the hippocampus and cortex of adult rats. We tested a number of synthetic beta AP peptides (beta AP 1-40, 1-38, and 25-35) and peptide controls (scrambled and reversed 1-40, and scrambled and reversed 25-35) over a wide range of concentrations and in a variety of vehicles. The rats were sacrificed from 2-35 days following the implant, and the brains examined by standard immunohistochemical and histological methods used to evaluate the pathologies associated with Alzheimer's disease. We report the lack of Alzheimer related pathology and no significant morphological differences between the beta AP peptide and the peptide and vehicle control injections. These observations indicate that the simple intraparenchymal injection of beta AP in the rat brain is not an appropriate model of Alzheimer-related neurotoxicity.

The histochemical localization of acetylcholinesterase in the rainbow trout saccular macula by electron microscopy

The hair cells of the teleost saccular macula are morphologically similar to type II vestibular hair cells of higher vertebrates. The two types of nerve endings at the base of the saccular hair cells are the non-vesiculated endings, thought to be afferent, and the vesiculated terminals, presumed to be efferent. The vesicles in the presumptive efferent endings are predominantly round and clear, and a few are dense cored. The morphological characteristics of the vesiculated endings resemble those of presumptive efferent cholinergic endings present in the inner ear of higher vertebrates. In the present study, vesiculated nerve endings were examined histochemically for acetylcholinesterase. The reaction product was observed along the plasma membranes of the vesiculated nerve endings synapsing both with the hair cells and afferent endings, but was not seen at non-vesiculated endings on hair cells. No staining was observed in control specimens incubated in the presence of eserine sulfate, an inhibitor of acetylcholinesterase. These results suggest that the vesiculated nerve endings in the trout saccular macula contain cholinergic elements.

Carbohydrates associated with the cell coat surrounding cells of the rainbow trout saccular macula as revealed by lectin probes

The luminal surface of the saccular macula in the rainbow trout is covered with a glycoconjugate-rich cell coat. The aim of this study was to identify specific carbohydrate moieties present in this coat, using biotinylated lectins as probes. Saccular tissues were fixed in Karnovsky's fixative for 2 h at 1-2 degrees C, followed by incubation with biotinylated lectins for 12-16 h at 25 degrees C. Lectin binding was visualized by performing avidin-biotin-peroxidase reactions. As controls, specimens were reacted with solutions of lectins preincubated with their specific inhibitory sugars. Staining was observed that was consistent with the presence of glucose, galactose, fucose, mannose, N-acetylglucosamine, N-acetylneuraminic acid, and N-acetylgalactosamine in the cell coat. The variability in the intensity of staining associated with the lectin-carbohydrate complexes suggests quantitative differences among the various carbohydrate moieties detected. The presence of these carbohydrates in the cell coat of the trout saccular macula also suggests biochemical similarities between cell coats in teleost and mammalian inner ear structures.

The cell coat of the sensory and supporting cells of the rainbow trout saccular macula as demonstrated by reaction with ruthenium red and tannic acid

The surface of most cells is covered by glycoconjugates. The composition and thickness of the surface coat varies among different cell types. The purpose of the present study was to demonstrate the presence of and to characterize the cell coat surrounding the cells in the saccular macula of the rainbow trout. Tissues were fixed in Karnovsky's fixative containing either ruthenium red (0.5, 1, or 2%) or tannic acid (1, 2, or 4%). The apical surface of the sensory and supporting cells reacted with both agents. Varying the concentration of the compounds within a certain range did not significantly affect the degree of tissue staining. Whereas ruthenium red staining was distributed evenly along the luminal surface of the epithelium and along the length of the stereocilia, tannic acid formed electron-dense clumps on the luminal surface of sensory and non-sensory cells and in the basal region of the macular epithelium. The stereocilia of the sensory cells also exhibited tannic acid-positive, electrondense precipitate, particularly near the distal ends of these processes, while uniform staining of the plasma membrane was seen along their lengths. The results of this study suggest that the trout saccular macula is provided with extracellular microenvironments which may be necessary for functional integrity.

Proteins of the gelatinous layer of the trout saccular otolithic membrane

Although the otolithic membrane is thought to play an important role in the stimulation of vestibular hair cells, little is known about its chemical composition. We analyzed proteins of the gelatinous layer of this structure from the trout saccule, a probable organ of hearing in fish, by SDS-polyacrylamide gel electrophoresis. A relatively small number of major proteins were detected in homogenates of the 'membrane' layer, with apparent molecular weights ranging from 35 to greater than 300 kDa. Six bands, with molecular weights of 35, 43, 65, 94, 100, and 160 kDa, were particularly prominent. Periodic acid-Schiff (PAS) staining indicated that the 43, 94, 100, and 160 kDa bands were glycoproteins. Lectin binding on nitrocellulose blots confirmed the PAS results, and further suggested that the 35 and 65 kDa bands may be glycoproteins. Incubation of blots with human anti-collagen type II antibodies suggested that the 94 kDa band was a component of collagen type II or a related protein.

Sequestration and degradation of alpha 2u-globulin in rat kidney lysosomes

alpha 2u-Globulin (M.W. = 18,709) is the major protein synthesized in the liver of adult male rats. alpha 2u-Globulin, secreted from the liver, is filtered by the kidneys where about a half of the protein is reabsorbed and the remainder is excreted in the urine. Highly purified lysosomes from rat kidneys were subjected to immunoblot analysis using antiserum against alpha 2u-globulin. A major immuno-reactive band was observed at the position about 1 k dalton smaller than that of the authentic alpha 2u-globulin. The immuno-reactive band in SDS-polyacrylamide gel was excised and the protein, eluted from the gel, was subjected to amino acid sequence analysis by micro Edman method. The N-terminal amino acid sequence of the intralysosomal alpha 2u-globulin was found to be leu-asp-val-ala-lys-leu-asn-gly-... which exactly corresponded to the sequence from the 10th leucine residue of the authentic urinary alpha 2u-globulin. This result suggests that alpha 2u-globulin, sequestered into the kidney lysosomes, is cleaved intralysosomally between the 9th asparagine and the 10th leucine, and the degradative intermediate, thus produced, is accumulated in the lysosomes. The immuno-blot assay gave the value of 210 +/- 70 mg alpha 2u-globulin/g kidney lysosomal proteins. The molecular basis for the resistance of the degradative intermediate of alpha 2u-globulin against further degradation in the kidney lysosomes was discussed in the light of the computer-predicted secondary structure of alpha 2u-globulin.

Protein associated with the sensory cell layer of the rainbow trout saccular macula

A protein has been detected that is associated with the saccular hair cell layer of the rainbow trout, Salmo gairdnerii R. By one- and two-dimensional SDS polyacrylamide gel electrophoresis, the molecular weight and isoelectric point of this protein are estimated to be 13.6 and 8.8 kDa, respectively. The 13.6 kDa protein cannot be detected electrophoretically in brain, gill, liver, and fractions containing the basal lamina, non-sensory epithelium, and saccular nerve. This protein does not bind antibodies to bovine myelin basic protein, while trout myelin basic proteins in the same molecular weight range do. In addition, the protein does not bind concanavalin A or react with the periodic acid-Schiff reagent. The 13.6 kDa band represents about 1% of the total protein in saccular sensory epithelium, and may be a marker protein for the hair cell layer.

Degradation of aspartate aminotransferase in rat liver lysosomes

Highly purified lysosomes from the normal and leupeptin-treated rat livers were subjected to immunoblot analysis using antibodies against cytosolic and mitochondrial isozymes of aspartate aminotransferase (cAspAT and mAspAT). In the case of cAspAT (subunit M.W. = 46K), the leupeptin-treated lysosomes showed a major band of 46K and a minor band of 36K while normal lysosomes showed a major band of 36K and a minor band of 41K. In the case of mAspAT (subunit M.W. = 44K), the leupeptin-treated lysosomes showed a 44K band and the normal lysosomes showed a 40K band. These observations suggest that both cAspAT and mAspAT are sequestered into lysosomes with the original subunit molecular weights and are degraded in the lysosomes by way of sequential formation of relatively stable intermediates with distinct molecular weights.

Morphologic study of effects of kanamycin on the developing cochlea of the rat

The development of the rat inner ear starts about day 9 of a 22-day gestational period. The sensory and supporting cells are morphologically identifiable by day 18 of gestation; however, auditory function is not evident until day 9 postnatally. The organ of Corti attains adult maturity about day 16 postnatally. Morphologic and physiologic studies have shown that administration of sublethal doses of aminoglycosidic antibiotics, including kanamycin, damages the sensory and supporting cells of the inner ear in mammals. This results in the impairment of auditory function. This study was designed to determine the earliest stage in cochlear duct development at which kanamycin toxicity can be morphologically detected. A sublethal dose of kanamycin was administered to pregnant rats on days 10 through 20 of gestation and to neonates from days 1 to 8 or from days 8 to 16 postnatally. The inner ears were dissected and processed for light microscopic and ultrastructural observations. The cochlear ducts of fetuses exposed in utero to kanamycin and those of neonates exposed from days to 1 to 8 postnatally were unaffected. Kanamycin toxicity was evident in the cochlear ducts of neonates exposed from days 8 to 16 postnatally. The most severe damage occurred in the basal coil of the cochlea where in many instances sensory cells were totally absent. The sensory cells in the middle and apical coils exhibited abnormal morphology. These results suggest: (1) kanamycin does not have any permanent toxic effects on the rat cochlear duct during gestation and the first week of postnatal life. This provides a basis for further studies into the possible pharmacologic application of this finding in humans. (2) A correlation exists between the initiation of auditory function and the vulnerability of the organ of Corti to kanamycin toxicity.

Clinical and immunogenetic studies in rheumatoid arthritis from northern India

A total of 258 patients with classic rheumatoid arthritis seen over a 7-year period were included in this study. The majority of the patients had relatively mild disease at the time of presentation. The incidence of extraarticular manifestations such as subcutaneous nodules, vasculitis, amyloidosis and pulmonary involvement was low although one or two pulmonary function test parameters were abnormal in some. Seventy patients were tested for all three subclasses of rheumatoid factors - IgM, IgG and IgA. Of these, 23 patients had all three whilst four had only IgG. The 62 patients who had most typical and severe manifestations were typed for four major HLA loci A, B, C and DR. Of these 42 (67.7%) had DR4 antigen while DR3 antigen was detected in 14 (22.6%).

DNA content, mitotic activity, and incorporation of tritiated thymidine in the developing inner ear of the rat

The rat inner ear is ectodermally derived from a region adjacent to the developing hindbrain. Beginning on day 8 of a 22-day gestational period, This zone of ectoderm first forms the otic placode, then the otocyst, and ultimately the definitive membranous labyrinth. This report provides an estimation of total DNA content of the developing inner ear, and hence an estimation of the total number of cells that comprise the inner ear at each developmental stage. The incorporation of 3H-thymidine indicates that most cells of the inner ear undergo DNA synthetic activity during gestational days 13 to 15. Radioautographic observations indicate a zone of DNA synthetic activity at the base of the outpocketing cochlear duct during early development. At the later stages of development, DNA synthesis is restricted to the cristae ampullares of the semicircular canals and the maculae of the utricle and the saccule. In contradistinction to the findings of other investigators, the statoacoustic ganglion complex undergoes terminal mitosis during gestational days 17 and 18. The gestational period between days 13 and 15 may prove to be a critical stage in normal otic development. The normal values of total DNA content and the number of cells that comprise the inner ear during development, established by these methods, can be compared with pathologic inner ears to provide quantitative means of assessing the damage in malformed inner ears. These values also form the baseline for future experimental studies of inner ear development.

Effects of fluorodeoxyuridine on the developing inner ear of the rat

The inner ear in rats develops from the surface ectoderm on day 8 of a 22-day gestational period. Labeled thymidine incorporation studies have indicated that in the developing inner ear most of the cells undergo terminal mitosis between gestational days 13 and 15. During this period the developing inner ear would be particularly vulnerable to environmental hazards. To test this hypothesis, pregnant rats were given a single intraperitoneal injection of 5-fluoro-2'-deoxyuridine (FUdR), an antimitotic substance, on gestational days 12 to 16. The rats also received one injection of 3H-thymidine 1 h prior to the removal of the fetuses. The animals were killed after various time intervals following the treatment, and the otocysts or inner ears were prepared for morphologic observations and biochemical assays. The cells in the inner ear of rats exposed to FUdR exhibited pyknotic nuclei and chromatolytic degeneration, and they eventually died. By 4 h after the administration of FUdR, pyknotic nuclei were seen in the antiluminal zone of the otic epithelium, and there was a substantial decrease in the number of the otic cells. This decline in cell number was seen until 24 h after treatment. However, the inner ears from the fetuses exposed to FUdR during gestational days 12--15 showed complete recovery from the toxic effects of the drug when examined on day 21 of gestation. The phenomenon of programmed cell death observed in the developing inner ear of the rat indicates that more cells are produced during the earlier stages of development than are required for the definitive adult structures. This phenomenon may represent an important protective feature. The redundant production of cells perhaps allows the developing otocysts to respond to an environmental stress by subtotal destruction of cells from the pool of undifferentiated cells, resulting in relatively fewer congenital anomalies of the inner ear.

The effect of geometric errors in the reconstruction of iridium-192 seed implants

In the treatment of tumors using interstitial implants of radioactive seeds, the accuracy of computed dose distributions depends upon the accuracy with which the three-dimensional source geometries are reconstructed from radiographs of the implants. The effect of geometric reconstruction errors in iridium-192 seed implants were studied, using tumor dose as the measure. Tumor dose was defined as the average dose around the periphery of the treatment volume. Three ideal mathematical implants and five actual patient implants were used. The implants were distorted by randomly moving a specified number of seeds a specified distance. Tumor doses were directly calculated for the ideal implants. For the actual implants, isodose distributions were plotted and were read by a radiotherapist. For both types of implants, percentage errors in the tumor doses were calculated for the distorted reconstructions relative to the correct reconstructions. It was found that the tumor dose was accurate to within 5% if all the seeds were reconstructed to within 0.5 cm of their actual positions. Furthermore, up to 5% of the seeds could be mismatched between films, or otherwise incorrectly reconstructed, with position errors as large as 20 cm, and not change the tumor dose by more than 5%.

Pi meson radiotherapy for advanced head and neck neoplasms: preliminary results

Under the auspices of the University of New Mexico Cancer Research and Treatment Center, trials are under way at the Los Alamos Meson Physics Facility to evaluate the effects of pi meson irradiation on locally advanced human tumors. This paper summarizes the preliminary results in patients with locally advanced head and neck tumors treated under Phase 1 and Phase II studies. A total of 26 patients were treated between June 1977 and May 1979 with a minimum follow-up of 9 months and a maximum follow-up of 33 months. Sites of disease included the oropharynx in 10 cases (base of tongue in 7, tonsil in 2, and pharyngoepiglottic fold in 1), the supraglottic larynx in 4, the nasopharynx in 5, the oral cavity in 4, the hypopharynx in 2, and the sublingual salivary gland in 1. Twelve of the 26 patients are alive, and 10 survive with no evidence of disease. Doses employed ranged from a minimum of 1,000 peak pion rad in 7 fractions over 9 days to a maximum of 5,4000 peak pion rad in 51 fractions of 89 days. The minimum dose employed for any patients treated with peak pions alone was 3,000 rad. These data are analyzed according to dose, sit, histology, tumor response, local control, and survival. Results from these cases form the basis of the Phase III randomized trials for advanced squamous-cell carcinomas of the head and neck, which are currently in progress.

Intercellular junctions in the differentiating rat otocyst

Intercellular junctions between cells of the rat otocyst on the 12th day of gestation were studied using lanthanum tracer and freeze-fracture techniques. At the luminal surface, the intercellular space is closed by a series of tight junctions. Gap junctions are also present between cells both within and below the luminal junctional complex. The presence of tight and gap junctions at this early stage in the differentiating otocyst is probably essential for the development of a normally functioning adult ear.

Detection of H2-b and Thy-1.2 surface antigens on the differentiating murine otocyst using Nomarski optics

The 12th postcoital day otocyst appears as a hollow cellular ball of pseudostratified columnar epithelium that has entered into its inital stages of differentiation and organogenesis. H-2b antigen was demonstrated on the ectodermally derived epithelial cells of the otocysts and on the mesodermally derived cells of the surrounding mesenchyme. Thy-1.2 antigen was detected in the mesenchymal cells, but not on the epithelial cells of the otocyst. The use of Nomarski optics as a new method for detecting cell surface staining that would otherwise be undetected by bright field optics was demonstrated.

Ultrastructural development of the early rat otocyst

The ultrastructural development and differentiation of cells forming the rat otocyst were studied from the 9th to the 13th postcoital day (PCD). The earliest stage investigated was a simple ovoid structure with a connecting stalk to the surface ectoderm. A process of programmed cellular death involving surface ectoderm, connecting stalk, and lateral otocyst wall rapidly detached the otocyst. The cells forming the otocyst were roughly columnar, the organelles were polarized; mitochondria occurred in greatest number basally and in the supranuclear area; Golgi membranes when present were supranuclear. Luminal cells had many microvilli and cilia of various lengths were detected. The shorter, incompletely formed cilia terminated in small knob-like blebs. With each day the otocysts became more complicated and the endolymphatic duct made its appearance as an evagination of the otocyst. Many more cells were seen to have cilia in various stages of development, and by the 12th PCD possibly each cell of the main otocystic cavity had a kinocilium. Growth of the otocyst due to mitosis occurred to a great extent from a single ventromedial center. Cells in mitosis, although seen at other sites, were in greatest abundance in this area; cellular involution apparently was a related function. Together the process of over-production and programmed cellular involution of supranumerary cells not lost to other causes (e.g., environmental) may represent an evolutionary advantage.

Scanning electron microscopic appearance of rat otocyst of the twelfth postcoital day: elaboration of a method

A method for removal, fixation, microdissection, and drying of early rat otocyst for examination by the scanning electron microscope is elaborated. Tissues were dissected, fixed as for conventional transmission electron microscopy and dried by critical point evaporation using amylacetate as the transitional fluid and carbon dioxide as the pressure head. Otocysts were either dissected at the time of initial fixation, or subsequent to drying. The otocyst of the 12th postcoital day was used as a model system in this preliminary report. Critical point drying retained the overall configuration and the fine ultrastructural detail of the otocyst. The interior otocystic surface was visualized and cilia bearing cells of the luminal surface were identified. Most if not all of these cells had a comspicuous, but short kinocillum which terminated in an ovoid bulb. The scanning electron microscopic appearance was correlated to the transmission electron microscopic image seen in the second paper in this Supplement.

An improved method for processing early rat otocysts for the electron microscope

Various methods of dissection, fixation, osmication, sectioning and staining were tested in order to develop an acceptable technique for preparing 9, 10, 11, and 12-day-old rat otocysts for electron microscopic study. The general problems associated with embryonic tissue-difficult handling, high water content and poor stainability are discussed, and concrete methods of preparation which significantly decrease these difficulties are proposed. The specific fixation and sectioning requirements of rat otocyst are also described in the elaboration of a method which will be used in subsequent studies of the organogenesis of rodent ear.

Spiral migration theory of organ of Corti development

A mitotic zone has previously been demonstrated on the luminal surface of the posteromedial wall of the otocyst in the plane of the endolymphatic duct and at the junction of cochlea with primitive saccule. In this experiment the application of fluorodeoxyuridine (FudR) (an antimitotic agent) demonstrates the existence of a discrete synthetic zone for the otocyst which lies nearby to the otic zone of mitosis. Cells labeled by FudR and, therefore, in the mitotic synthetic (S) phase are always found away from the lumen (antiluminal surface) when the animals are sacrificed soon after injection. Cellular migration from synthetic zone through the luminal mitotic area and beyond is hypothesized. Once cellular division is completed the cells appear to follow a spiral course (from medial to lateral) over the anterior wall of the otocyst. The cells continue their spiral course entering the thin side of the cochlear base. From this strategic location the cells migrate around the sides of the cochlea to reach and to form the pseudostratified wall and complete the thin side of the cochlear duct. The pitch of this migration pattern is similar to the helical pitch of the mature cochlear duct and may be responsible for the adult configuration.

The role of cellular degeneration in the normal development of (rat) otocyst

From day 12 to 16 of gestation a highly circumscribed zone of cellular degeneration has been observed in the otocyst of more than 50 normal rats. This zone appears to be produced by selective or programmed cell death, and results in the elimination of unneeded cellular elements. That cells in this zone are also selectively destroying subcellular organelles as a first step in specialization is also discussed. Programmed cellular death has long been known in other systems and is often an obligatory companion to cellular specialization. The ear now joins the long list of organs which demonstrate this phenomenon.