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Biomedical subjects

J R Meyers

Publications and source records attributed to J R Meyers.

6 recordsLinked to original sources
PubMed2000

Solitary hair cells are distributed throughout the extramacular epithelium in the bullfrog's saccule.

The frog inner ear contains eight sensory organs that provide sensitivities to auditory, vestibular, and ground-borne vibrational stimuli. The saccule in bullfrogs is responsible for detecting ground- and airborne vibrations and is used for studies of hair cell physiology, development, and regeneration. Based on hair bundle morphology, a number of hair cell types have been defined in this organ. Using immunocytochemistry, vital labeling, and electron microscopy, we have characterized a new hair cell type in the bullfrog saccule. A monoclonal antibody that is specific to hair cells revealed that a population of solitary hair cells exists outside the sensory macula in what was previously thought to be nonsensory epithelium. We call these extramacular hair cells. There are 80-100 extramacular hair cells in both tadpole and adult saccules, which extend up to 1 mm from the edge of the sensory macula. The extramacular hair cells have spherical cell bodies and small apical surfaces. Even in adults, the hair bundles of the extramacular cells appear immature, with a long kinocilium (6-9 microm) and short stereocilia (0.5-2 microm). At least 90% of extramacular hair cells are likely to be innervated as demonstrated by labeling of nerve fibers with an antineurofilament antibody. The extramacular hair cells may differentiate in regionsjust beyond the edge of the macula at an early stage in development and then be pushed out via the interstitial growth of the epithelium that surrounds the macula. It is also possible that they may be produced from cell divisions in the extramacular epithelium that has not been considered capable of giving rise to hair cells.

Animals↗
PubMed1998

Comparison of fast startle responses between two elongate bony fish with an anguilliform type of locomotion and the implications for the underlying neuronal basis of escape behavior.

A comparative anatomical and behavioral approach was used to elucidate the role of medullary networks associated with Mauthner cells (M-cells) in determining the type of fast startle responses of elongate bony fish with an anguilliform type of locomotion. The M-cell initiates fast startle responses in goldfish and is thought to initiate such responses in other fish as well [Wilson, 1959; Eaton et al., 1977; Currie and Carlsen, 1987; Currie, 1991]. Goldfish M-cells have a specialized structure, termed an axon cap, that surrounds their axon hillock-initial segment region and is critical for the control of M-cell excitability. The M-cell axon cap is present in some elongate fish such as the African lungfish (Protopterus, Lepidosireniformes) and absent in others such as the American eel (Anguilla, Anguilliformes). The lungfish startle response is characterized by a rotation of the head and upper trunk, similar to the initial phase of the goldfish (Carassius, Cypriniformes) startle response. The American eel, on the other hand, displays a withdrawal-type startle response. We hypothesize that the withdrawal-type startle response of the American eel results from the absence of inhibitory networks associated with the M-cell axon cap. The correlation of the absence of an axon cap and a withdrawal-type startle response may be a general feature of all Anguilliformes and elongate ray-finned fish with an anguilliform type of locomotion.

Anguilla↗
PubMed1987

Alzheimer's disease with refluxes.

This is a report concerning a unique combination of Alzheimer's disease with the following refluxes: buccosalivary, gastroesophageal, vesicoureteral, urethroprostatic and urethrovesicular, along with neurogenic bowel and neuropathic bladder. A second patient with Alzheimer's disease and vesicoureteral reflux is reported. The possible etiopathology of these unusual refluxes and their relation to Alzheimer's disease are discussed.

Aged↗
PubMed1975

Changes in functional residual capacity of the lung after operation.

Functional residual capacity (FRC) of the lung was measured by the closed-circuit helium equilibration method before and for five days after upper abdominal operations in 28 patients (25 had cholecystectomies). Measurements in many were made with the patient both sitting in bed and sitting in a chair. Vital capacity (VC), residual volume (RV), and forced expiratory volume in one second (FEV1), as well as FRC, all decreased after operation, with the maximum decrease on days 1 and 2 and a gradual return toward preoperative values by day 5. Patients with 40% or less decrease in FRC after operation did not develop pulmonary complications. Change in position from bed to chair increased FRC 14.2% preoperatively and 17% postoperatively. The use of intermittent positive pressure breathing had no measurable effect on FRC. Similar changes in FEV1, VC, and RV also occurred, with maximum decreases on day 1.

Adolescent↗