Pattern formation of the otic placode and morphogenesis of the otocyst

The early embryonic development of the inner ear anlage, from the otic placode stage to formation of the otocyst, was documented in CBA/CBA mice by scanning electron microscopy. The otic placode is identified at the eight- to ten-somite stage, as revealed by the surface morphology of the developing ectoderm. The cells in the otic depression are considerably smaller than those of the adjacent ectodermal surface. Rapid invagination of the otic anlage occurs during the ninth gestational day (approximately eight to 20 somites). In most specimens from the tenth gestational day, the otic vesicle has closed toward the ectodermal surface. The surface of the otocyst on the 13th gestational day shows considerable specialization, with regional differences of the surface structure.     

Mechanisms in middle ear effusion production caused by irritation of the external auditory canal

In an animal model, a stream of chilled air blown into the external auditory canal evoked an edematous pars flaccida and accumulation of a serous effusion in the attic. The degree of inflammatory changes depended on the temperature of the stimuli. The nervous system appears to mediate the observed changes, as the vagus nerve, representing the parasympathetic system, potentiates vascular leakage, and the sympathetic nerves inhibit leakage.     

Tympanic membrane changes resulting from different methods of transmyringeal middle ear ventilation

This experimental study was designed to evaluate the morphologic changes of the tympanic membrane in the rat after different methods of transmyringeal ventilation. Artificial ventilation was obtained in two principal ways, either by making tympanic membrane perforations with delayed healing or by inserting a tympanostomy tube. Perforations occupying the upper rear quadrant of the tympanic membrane were made by diathermy or by a carbon dioxide laser with healing times of 12 to 15 days and 18 to 21 days, respectively. Compared with the healing times of perforations made by lancet (9 to 11 days), the healing pattern was considerably delayed. The structural changes of the healed tympanic membrane were minimal, but the connective tissue remained thickened for several months. Repeated insertion of tympanostomy tubes caused a remarkable thickening (30-fold) of the tubulated quadrants. The thickened tympanic membranes were characterized by a hyperplastic, dense connective tissue containing sclerotic plaques. Similar changes, though less pronounced, were also seen after reiterated myringotomies without tube insertion.     

Mast cells and middle ear effusion

The mast cell--an important component of connective tissue--carries in its cytoplasmic granules various biologically active substances, such as heparin, histamine, and a broad spectrum of enzymes. This cell type plays a prominent role in inflammatory and allergic conditions. In the middle ear, the mast cells are mainly localized in the pars flaccida of the tympanic membrane and beneath the tracts of secretory and ciliated cells in the middle ear mucosa. Degranulation of the mast cells by the histamine liberator compound 48/80 causes histamine-rich effusion material to accumulate in the middle ear. Plugging of the eustachian tube and/or tympanic isthmus will bring about a similar accumulation. It would thus seem that mast cells in some way participate in the production of middle ear effusion, probably via their potent mediators.     

Antidromically evoked facial nerve response

Facial nerve electrodiagnostic tests that are currently available indirectly assess the severity of injury to the intratemporal facial nerve. Antidromic conduction testing is an alternate approach that, if feasible, could provide direct and immediate assessment of proximal facial nerve function. This possibility was tested in a guinea pig model, in which near-field (intracranial) and far-field (extradural) recording techniques were used to assess antidromically evoked facial nerve activity. Response characteristics, topographical distribution, and lesion effects suggest that the recorded potentials represent antidromic activation of the facial nerve. If response amplitude and/or latency can be correlated with the functional state of the nerve, antidromic testing may provide a useful means of assessing proximal facial nerve function in pathologic states.     

Effect of alertness and visual attention on optokinetic nystagmus in humans

The effect of alertness and visual attention on optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN) was studied in 20 volunteers. Electroencephalographic (EEG) activity was recorded over the occipital lobe. Exposure to sound and vibration caused a significant increase in the mean slow-phase velocity of OKN, whereas its maximum slow-phase velocity remained unaffected. Vibration tended to increase the mean slow-phase velocity of OKN more than sound did, though the difference was not statistically significant. Vibration also significantly increased the OKAN. When alpha rhythm appeared in the occipital EEG during OKN, the velocity of concurrent slow phases was reduced. However, the periods of alpha rhythm did not differ between the different stimulus conditions. The findings suggest that sound and vibration activate the subcortical optokinetic mechanism, thus causing an increase in the mean velocity of OKN. Abatement of visual attention is reflected in temporary reduction of OKN in conjunction with the appearance of alpha waves and is to be interpreted as transient quiescence of the cortical optokinetic mechanism.     

Mediastinitis and neck abscess following cervical spinal fracture

Neck abscess and mediastinitis are rare complications of cervical spinal injury. Often there is a delay in diagnosis because the physical and laboratory signs of abscess are falsely attributed to the vertebral injury. Prognosis is directly related to the expediency of recognition of infection and surgical drainage. Three cases of neck abscess with mediastinitis that were seen over a four-year period at the spinal cord unit at Northwestern Memorial Hospital are reviewed.     

Bipedicled lingual flap for lip reconstruction

Full-thickness loss of the lower lip due to trauma or malignancy presents a difficult reconstructive problem. Numerous reconstructive techniques, including distant flaps, local pedicle flaps, advancements and skin-muscle composite transfers, have been described. The bipedicled lingual flap is a relatively simple procedure that offers many advantages over other techniques since it results in excellent cosmesis without donor site deformity. It causes negligible loss of labial and lingual function. Although it is performed in two stages, its simplicity of execution requires less operative time than many other techniques, and it allows satisfactory reconstruction of unusually large defects.     

Acoustic neuroma presenting as sudden hearing loss

Sudden hearing loss occurs as the initial symptom in 1 to 9 per cent of all acoustic neuromas. A case of an acoustic neuroma presenting with sudden hearing loss is described. In this case, the hearing thresholds returned to normal. To the authors' knowledge, this is the first case in which an acoustic neuroma presenting with sudden hearing loss exhibited a return to normal thresholds. This suggests that such tumors may have an initial reversible effect on hearing thresholds.     

Influence of gamma irradiation on developing otoconia

Thirty-two CBA/CBA mice were irradiated in utero on the 12th, 13th, or 16th gestational day with doses of 0.5, 1, and 2 Gy, respectively (1 Gy = 100 rads). One month after birth, the inner ears were examined by light microscopy and transmission and scanning electron microscopy. Otoconia with defective shapes was identified frequently. The strict hexagonal shape of normal otoconia seldom developed and, in exposed animals, had often been replaced with rounded, oval, or elongated shapes. The otoconial substructure was disarrayed, and fusion of two or three otoconia occurred. Degenerating otoconia appeared in the intercellular space of the dark-cell epithelium. Fetal gross structures of otoconia persisted into maturity.     

Barrett's esophagus: current views of etiology and treatment

Barrett's esophagus is now thought to be an acquired condition rather than a congenital condition. It has a dangerous potential for malignancy; yet, aggressive medical management, antireflux procedures, and diligent follow-up may reduce the incidence of malignancy in this condition.     

Analysis of human nasal mucous glycoproteins

Human nasal turbinates were cultured in the presence of 3H-glucosamine, which is incorporated into nasal mucous glycoproteins. Nasal mucous glycoprotein was then characterized biochemically, and the effects of various neurohormones and immunologic stimulation on mucous glycoprotein release were analyzed. Fractionation of nasal mucous glycoprotein by gel filtration chromatography revealed a molecular size range of 2 to 200 X 10(5) (as judged by protein markers) but displayed a single, acidic charge, as reflected both in a narrow elution pattern from DEAE-cellulose and a sharp isoelectric focusing point of 2.6. Highly enriched nasal mucous glycoprotein preparations consisted of 80 per cent carbohydrate and 20 per cent protein (by weight) and included enzymatically cleavable carbohydrate side chains with molecular weights of 1,600 to 1,800. Thus, nasal mucous glycoproteins are a family of molecules that express uniform acidic charge characteristics and a wide range of molecular sizes. Cholinergic stimulation of atropine-inhibitable muscarinic receptors increased nasal mucous glycoprotein release in a dose-related manner, as did alpha-adrenergic stimulation. However, beta-adrenergic stimulation did not affect mucous glycoprotein release. Immunologic stimulation of nasal mast cells by either reversed anaphylaxis or antigen challenge after passive sensitization caused both histamine release and increased mucous glycoprotein release. Thus, nasal turbinates provide an accessible source of tissue for the analysis of nasal mucus secretion and mast cell degranulation and may provide a model for the study of pharmacologic approaches to the universally experienced discomfort of rhinorrhea.