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Biomedical subjects

J B Snow

Publications and source records attributed to J B Snow.

At least 19 recordsLinked to original sources
PubMed1979

Effect of kanamycin sulfate on the endocochlear dc potential of guinea pigs.

The magnitudes of the endocochlear dc potential (EP) during adequate ventilation and during five minutes of anoxia were recorded in control guinea pigs and guinea pigs administered various dosages of kanamycin sulfate. The magnitudes of the EP after five minutes of anoxia were -44.6 +/- 5.9 mV in the controls and +26.6 +/- 9.9 mV in the guinea pigs that received kanamycin for seven or ten days. This change occurred after five or six days of administration of kanamycin. However, there was no significant change in the magnitude ot the EP with adequate ventilation with kanamycin intoxication. There is a significant correlation between the magnitude of the negative EP and the maximum output of the cochlear microphonics (r = -.770, P less than .001). These results suggest that the EP may not be the mathematical summation of the positive electrogenic potential and the negative diffusion potential. The mechanism for generating the negative EP during anoxia may have some relationship to hair cell integrity.

Animals↗
PubMed1979

Assessement of surgical procedures for Ménière's disease.

There are numerous surgical procedures for the treatment of Meniere's disease, and the current status of their efficacy is controversial. A review of the literature is presented as a basis for the evaluation of the relative merit of these procedures. Emphasis is placed on endolymphatic sac procedures, sacculotomy, vestibular neurectomy and labyrinthectomy. Vestibular neurectomy and surgical labyrinthectomy provide high rates of improvement in vertigo. The hearing is frequently made worse by vestibular neurectomy. Endolymphatic sac procedures result in improvement in vertigo less frequently. They are most likely to improve hearing. Although sacculotomies are associated with improvement in vertigo in approximately 80% of patients, they are associated with high rates of hearing loss.

Ear, Inner↗
PubMed1978

Electrical resistance of the cochlear partition.

The relationship between the calculated value of the effective electrical resistance of the cochlear partition and the distance between the electrode for measuring the EP and the stimulating electrodes has been studied. The calculated value of the effective electrical resistance of the cochlear partition declines linearly with increasing distance between these electrodes. The correlation coefficient (r) is -0.806. In calculations of the effective electrical resistance of the cochlear partition, attention must be paid to the distance between the microelectrodes.

Animals↗
PubMed1978

Etiologic factors in hypocalcemia secondary to operations for carcinoma of the pharynx and larynx.

Hypocalcemia, although a relatively uncommon sequela of operations for carcinoma of the larynx and pharynx, often presents as an acute medical emergency. In its chronic form, hypocalcemia may be a difficult disorder to control. Understanding the etiologic basis of hypocalcemia secondary to operations for carcinoma of the head and neck requires knowledge of the pathophysiology of the preoperative and postoperative factors affecting calcium homeostasis. These factors include thyroidectomy, hypoparathyroidism, hypomagnesemia, anticonvulsant therapy, estrogen replacement therapy, oral contraceptives, blood transfusions, hyperventilation alkalosis, hypoalbuminemia, corticosteroid therapy, depression, emotional stress and diet. Often the onset of symptoms and signs of hypocalcemia occurs within 24 to 48 hours after the operation. The symptoms may include mental depression, headache, tingling of the hands and perioral region and abdominal pain. Unrecognized chronic hypocalcemia may lead to the development of cataracts, convulsions and psychosis.

Alkalosis↗
PubMed1977

Central auditory imperception.

The development of clinically applicable techniques for the evaluation of hearing impairment caused by lesions of the central auditory pathways has increased clinical interest in the anatomy and physiology of these pathways. A conceptualization of present understanding of the anatomy and physiology of the central auditory pathways is presented. Clinical tests based on reduction of redundancy of the speech message, degradation of speech and binaural interations are presented. Specifically performance-intensity functions, filtered speech tests, competing message tests and time-compressed speech tests are presented with the emphasis on our experience with time-compressed speech tests. With proper use of these tests not only can central auditory impairments by detected, but brain stem lesions can be distinguished from cortical lesions.

Animals↗
PubMed1977

Neoplasms of the nasopharynx in children.

Neoplasms of the nasopharynx are rare in children, but they threaten the child's life when they do occur. The nasopharynx tends to harbor dysontogenetic neoplasms. After classification into benign and malignant groups, nasopharyngeal neoplasms in children can be further characterized according to the age of the patients in which the clinical manifestations usually appear. Dermoids and teratomas are the most frequently encountered neoplasms of the nasopharynx in infants and may produce airway obstruction and dysphagia. Among the benign tumors of the nasopharynx in children, the juvenile angiofibroma deserves the most attention. With the onset in puberty, these neoplasms may cause recurrent massive bleeding and orbital and intracranial complications. Evaluation of the extent of the neoplasm and the source of the blood supply has been improved with bilateral selective internal and external carotid angiography. Intracranial and orbital invasion is regarded as an indication for radiotherapy. Surgery has been made somewhat safer by preoperative estrogen therapy and angiographic embolization of the major arterial supply. Patients with squamous cell carcinoma of the nasopharynx have immunologic similarities to patients with Burkitt's lymphomia and infectious mononucleosis; The etiologic role of the Epstein-Barr virus is considered. The parts played by radiation therapy, surgery, chemotherapy, and cryosurgery in the treatment of children with carcinoma of the nasopharynx are discussed. The value of radical neck dissection after radiation therapy is critically reviewed. The prognosis in patients with carcinoma of the nasopharynx is better in females than in males and better in children than in adults.

Adolescent↗
PubMed1976

Effects of head blow on the development of hearing loss.

The effects of the direction and intensity of the head blow and the effects of the lapse of time after a head blow on the development of hearing loss were studied in guinea pigs. The electrical responses from the right inferior colliculus (ER) and from the left round window (CP) to acoustic stimuli were measured. The elevation in threshold of the ER in the presence of normal CP in guinea pigs after a head blow suggests that the site of the lesion is central to the cochlea.

Animals↗
PubMed1976

Histopathologic correlates of otoneurologic manifestations following head trauma.

The clinical course of patients dying of head trauma and the physiologic evaluation of audition in guinea pigs subjected to several forms of head trauma are correlated with the histopathologic findings in the brains and temporal bones. In the patients there was wide spread hemorrhage, edema, disorganization and disruption of neural tissue. Loss of Purkinje cells and other neural elements was prominent. The temporal bone findings in the patients included laceration of and hemorrhage into the VIIIth nerve as well as bleeding into the scala tympani. The membranous labyrinths demonstrated no specific changes secondary to the trauma. The guinea pigs developed a central form of hearing loss with elevated thresholds for evoked responses from the inferior colliculus and normal AC cochlear potentials. In the animals hemorrhage in the substance of the brain, necrosis of neural tissue, edema, disorganization and disruption were prominent. Although there was extravasation of blood in the tympanic and vestibular scalae, the membranous structures of the inner ears were well preserved.

Adolescent↗
PubMed1975

Parapharyngeal rhabdomyoma.

Rhabdomyoma is a benign tumor of striated muscle origin that is very rare in young children. Review of the world literature revealed 20 cases of extracardiac adult-type rhabdomyoma in the head and neck area. All reported cases have been encapsulated and easily excised. A 22 1/2-month-old girl with a parapharyngeal rhabdomyoma is unique in that her tumor had atypical histology and lacked a capsule; it could not be "shelled-out".

Age Factors↗
PubMed1975

Pathogenesis of hearing loss in head injury. Studies in man and experimental animals.

This study reports on the histopathologic findings in the temporal bones and brain of a patient who died of head injury. A common type of head injury in man was simulated in guinea pigs by shaking them. A hearing loss was demonstrated with Preyer reflex audiometry although the cochlear potential thresholds remained normal. Only minor pathologic changes were found in the membranous labyrinths. Laceration and hemorrhage in and around the cerebrum, rhombencephalon, and eighth nerves were noted in most of the experimental animals. Auditory manifestations following head injury may very frequently be due to damage to the central auditory pathways rather than to the end organ.

Animals↗