Literature review: the common cold.

Most colds are caused by rhinovirus infection, perhaps facilitated by chilling or stress. Virus infection begins in the nasopharynx and causes spotty destruction of the nasal ciliated epithelium. Transmission occurs chiefly via droplets of various sizes transported through the air, but some types of virus persist in moist secretions on handled objects and may retain their infectiousness. Living in crowded, poorly-ventilated quarters facilitates transmission. Not many virus particles survive in saliva and it is difficult to infect via the lips or mouth. Kissing does not efficiently spread cold infection. Prophylactic treatment with interferon does not protect against cold infection. Aspirin and acetaminophen reduced serum antibody response and increased nasal symptoms in a controlled Australian study. The combination of intranasal interferon and ipratropium with oral naproxen gave promising results in experimental rhinovirus inoculation. Basically, there has been little or no progress towards effective cold treatment in the past century.

Petrous apex and subarcuate fossa maturation.

During the first year of life, the bone of the petrous apex grows rapidly. At birth, only 5 mm of bone separates the cochlea from Dorello's canal as compared to 2 cm in the adult. More than half this growth occurs during the first year of life. The subarcuate fossa is a cavity within the superior semicircular canal which reaches from the posterior fossa to the future mastoid in fetuses and nearly to the mastoid antrum in newborns. During the second year of left it is nearly obliterated to form a shallow depression or slit on the posterior aspect of the temporal bone and the variable petromastoid canal which contains the subarcuate artery and vein. Clinical petrositis of infants less that 1 year of age is rare, and provides a challenge for surgery. A case is reported and discussed.

Tympanostomy tube complications and efficacy in children of a rural community.

In the pediatric group practice and the otolaryngologic practice of our rural community, 41 patients were seen in 1984 with 49 episodes of suppurative discharge after tympanostomy tube insertion. Streptococcus pneumoniae was the most common organism after upper respiratory tract infection. Staphylococcus or enteric organisms were most frequently encountered after bathing or swimming. Most patients regained hearing within normal limits. The benefits of tympanostomy tubes in terms of good hearing and reduced incidence of suppurative otitis media outweigh the risk of transitory suppuration for most patients.

Biological effects of ingested amosite asbestos, taconite tailings, diatomaceous earth and Lake Superior water in rats.

Because amphibole fibers were found in Lake Superior and in Duluth municipal water, this study was initiated to evaluate the carcinogenicity of ingested asbestos. Groups of 22-30 Sprague-Dawley rats were fed asbestos and related materials during their lifetime and were examined at autopsy after spontaneous death. Test materials were unfiltered Duluth city tap water, municipal water reservoir sediment suspension, taconite plant tailings, amosite asbestos (a "low-dose" group at 20 mg/rat . day an a high-dose group at 300 mg/rat . day) and diatomaceous earth; a control group drank fiber-free well water or filtered city tap water. Autopsy studies revealed no significant increase in the incidence of malignant tumors in any experimental group compared with that in the control group.

Development of the epithelium of the middle ear. Electron microscopic study of fine structure, including junctional complexes and basal lamina.

A detailed light and electron microscopic study of the development of the middle ear lining epithelium of the rat was undertaken in order to determine whether a portion of the middle ear lining is normally derived from a condensation of mesenchymal connective tissue. We learned that pharyngeal epithelium outpouches early in development and persists during the formation and growth of the ossicles and inner ear structures in a relatively constant anatomic relationship. We found no evidence of a contribution of mesodermal tissue to the lining epithelium itself. Certain features of the junctional complexes between adjacent cells were used as a means of identifying pharyngeal and middle ear epithelial cells. It is concluded that at no time is connective tissue found within the middle ear space (as defined by its epithelial limits); pneumatization occurs by absorption of mesenchymal tissue that occupied the space between the outer part of the epithelium and bone structures.

Pigmentation of the stria vascularis. The contribution of neural crest melanocytes.

Because all stages of melanogenesis (premelanosome, melanosome and melanin granules) were found in intermediate cells of the rat stria vascularis, they can be classified as melanocytes. The marginal and basal cells of these rat specimens contained no pigment. Early in development, the melanocytes or future intermediate cells are located beneath the strial basal lamina. They penetrate this lamina to insert themselves between marginal cells. Both the melanocytes and marginal cells are believed to participate actively in the tissue rearrangements which ultimately bring the two cell types into intimate structural relationship. The ingrowing melanocytes and the mature, pigmented, intermediate cells which they form are frequently associated with blood vessels. Pretreatment with Dopa to enhance the melanin content of early melanocytes did not enable us to identify their route of migration into the stria.

Glycogen in the cochlea during development.

A recently developed technique for demonstrating glycogen by electron microscopy was used to study its location at various stages of cochlear development. It appears first in dispersed form in most of the cells of the otocyst at the stage of the 14-day rat embryo. Glycogen clums were found in Reissner's membrane at 17 days and in the future pillar cells shortly afterwards. Near the time of birth, glycogen appeared in the stria vascularis. By a few days after birth, heavy deposits were evident in the stria but glycogen had faded from the pillar cells and Reissner's membrane. Ten days after birth glycogen is no longer apparent in any of the cells of the cochlear duct except the outer hair cells.

Development of the labyrinthine receptors in the guinea pig, cat and dog.

Light and electron microscope observations were made on the vestibular receptors in fetal guinea pigs and cats, and in kittens and puppies. In the guinea pig hair cells were recognizable by 30 DBB (days before birth), myelinated preganglionary nerve fibers by 25 DBB, and neuro-epithelial synapses by 15 DBB. These observations can be correlated with the early development of the righting reflex in fetal guinea pig. Similar ultrastructural observations were made on cats and dogs at different times in development. A direct comparison between development in the vestibular system and the auditory system is possible since development of the organ of Corti in the same animals has previously been documented.

Distribution of microtubules and microfilaments in developing vestibular sensory epithelium of mouse otocysts grown in vitro.

Otocysts explanted from 12th-gestation-day mice and maintained in organ culture under went a series of developmental changes which paralleled those that occurred in vivo and which resulted in the formation of a sensory epithelium of the vestibular type. At the time of explantation presumptive vestibular sensory epithelium consisted of cells that were undifferentiated, pseudostratified and rapidly proliferating. The only microtubules present were those of the mitotic apparatus. After 4 days of in vitro development cells comprising the presumptive vestibular sensory epithelium were less pseudostratified and more elongate; their nuclei had assumed a basal orientation and there was a clear maginal velum. Longitudinally oriented cytoplasmic microtubules were present at the apices of some cells; they were often grouped around a centriole which may have served as a nucleation centre for their assembly. After 7 days of in vitro development mitosis had ceased and supporting cells had innervated hair cells were present: both types of cells were always longer than they were broad and were often highly asymmetrical. Hair cells were flask- or columnar-shaped, with a nucleus situated in the basal third of the cell. Most mitochondria in hair cells were located in the apical third of the cell. The same distribution of mitochondria and nuclei was evident in supporting cells. Microtubules occurred throughout the length of the supporting cell and were always parallel to its longitudinal axis. In hair cells microtubules were more frequent than in supporting cells: the majority were parallel to the longitudinal axis of the cell but there were two exceptions. First, at the apex of hair cells some microtubules were oriented transversely and diagnonally: these were probably involved in the development and maintenance of the constricted apex of these cells. Secondly, microtubules appeared to be randomly arranged in the narrow region of the cytoplasm between the ventral surface of the nucleus and the base of the hair cells. Microfilaments were confined to the basal third of hair cells where their orientation paralleled that of microtubules. The possible functions of microtubules and microfilaments in the development of hair cells and supporting cells of the mouse vestibular epithelium are discussed.