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Biomedical subjects

D B Webster

Publications and source records attributed to D B Webster.

At least 37 records · Page 2Linked to original sources
PubMed1983

Auditory neuronal sizes after a unilateral conductive hearing loss.

The left external auditory meatus was removed in 4-day-old CBA/J mice; after killing at 45 days, serial sections of the cochleae and brain stem were prepared. From these, the cross-sectional areas of spiral ganglion neurons and of 14 auditory brain stem neuronal types were measured, using a total of 210 neurons of each of the 15 types from both the right and left sides. Nine neuronal types were significantly smaller (P less than 0.01) on the left side: spiral ganglion neurons; globular, small spherical, large spherical, octopus, multipolar, and granule cells of the ventral cochlear nucleus; Purkinje-like cells of the dorsal cochlear nucleus; and spindle cells of the lateral superior olivary nucleus. Two neuronal types were significantly smaller (P less than 0.01) on the right: principal cells of the medial nucleus of the trapezoid body (superior olivary complex), and spindle-shape principal neurons of the central nucleus of the inferior colliculus. The left ventral cochlear nucleus had significantly smaller volume (P less than 0.01) than the right but right and left dorsal cochlear nuclear volumes did not differ significantly (P greater than 0.05). Right and left sides were not significantly different (P greater than 0.05) for the following neuronal types: fusiform cells and coarse- and fine-Nissl deep cells of the dorsal cochlear nucleus, and rostral bipolar cells of the medial superior olivary nucleus. Neurons affected by unilateral conductive loss were not significantly different (P greater than 0.05) from the same cells in mice with bilateral conductive losses; neurons not affected by unilateral conductive loss were not significantly different (P greater than 0.05) from the same cells in normal mice.

Animals↗
PubMed1983

Auditory brainstem responses in neonatally sound deprived CBA/J mice.

Auditory brainstem responses (ABR) from ten normal (3 males, 7 females) and ten environmentally sound deprived CBA/J mice (6 males, 4 females) were elicited by 30 dB HL click stimuli delivered via specially constructed, matched insert earphones. The mice were tested at 44-49 days of age under chloral hydrate sedation using an electrode montage of vertex/linked bilateral bullae/presacrum. The deprived mice were killed immediately after testing and serial transverse sections were prepared from their brains. Examination of globular cells of the ventromedial ventral cochlear nuclei revealed significantly smaller cross-sectional areas of these cells than in previously studied normal mice. Although monaural thresholds did not differ between the two groups, significantly shorter mean latencies were observed in the ABRs of the sound deprived group in wave I as well as in the interpeak latencies of the later ABR components (I-IV, I-V, and III-V). These electrophysiologic alterations in brainstem conduction presumably reflect the anatomical changes demonstrated in neonatally sound deprived mice.

Animals↗
PubMed1983

A critical period during postnatal auditory development of mice.

CBA/J mice were given a 50 dB unilateral conductive hearing loss by removal of the left cartilaginous external auditory meatus. When the conductive loss extended from 12 to 24 days after birth, the left globular cells and left large spherical cells of the ventral cochlear nucleus were significantly smaller (P less than 0.01) than comparable cells on the right side. Right medial nucleus of the trapezoid body cells and right inferior colliculus cells were significantly smaller (P less than 0.01) than comparable left side cells. These same effects were found with conductive losses of 4-24, 4-45, and 4-90 days after birth. There were no significant differences (P greater than 0.05) between right and left cell sizes with conductive losses of 4-12 or 24-45 days after birth. There were significant right/left cell size differences (P less than 0.01) when the conductive loss was 4-18, 12-18, or 18-24 days, but these differences were of lesser magnitude than when the conductive loss included the full 12-24 day period. Since normally all these neurons have adult soma size by postnatal day 12, it is evident that adequate acoustic stimulation is necessary between 12 and 24 days postnatally in order to maintain normal brainstem auditory neuronal size in CBA/J mice.

Acoustic Stimulation↗
PubMed1982

Cochlear nuclear complex of mice.

Using serial sections stained with luxol fast blue-cresyl violet, the cochlear nuclei of CBA/J mice were parcellated into the same cytoarchitectonic areas and layers that Osen (1969) used in cats. Within the spherical cell areas, the distribution of Nissl substance is more reliable than soma shape in identifying the spherical cells. The area of large spherical cells is extremely small in CBA/J mice but does contain significantly larger neurons than the small spherical cell area. In Golgi preparations, bushy cells are found in all areas of the ventral cochlear nucleus except in the octopus cell area and granule cell layer. They are more numerous anteriorly than posteriorly and details of their morphology are quite variable. Stellate cells are found throughout the ventral cochlear nuclei but are present in greatest numbers in the multipolar cell area; they are rare in the large spherical cell area and octopus cell area. Because size, soma morphology, and dendritic arborization vary on a continuum rather than in discrete steps, we have not subcategorized these neurons. Octopus cells are restricted to the posterior, dorsomedial area of the ventral cochlear nucleus. In the central region of the dorsal cochlear nucleus, stellate cells abound and are categorized as vertical, elongate, or radiate cells. In the granule layer of the dorsal cochlear nucleus there are both fusiform and Purkinje-like neurons, so named because of their resemblance to cerebellar Purkinje cells. These Purkinje-like cells differ from fusiform cells in having 1) a smaller cell body, spherical in shape, 2) no basal dendrites, 3) a sagittal dendritic orientation, 4) elaborate dendritic branching, and 5) abundant dendritic spines.

Animals↗
PubMed1981

Spiral ganglion neuron loss following organ of Corti loss: a quantitative study.

The packing density of spiral ganglion neurons was measured in 2.5- and 13-15-month-old guinea pigs, in guinea pigs at various times after drug-deafening or acoustic trauma, and in Waltzing guinea pigs of various ages. Analysis of variance and Duncan's new multiple range tests were used to determine significant differences between treatment/survival groups. Spiral ganglion neurons in young and old normal ears did not have significantly different packing densities. Drug-deaf guinea pigs showed a significant loss of neurons by 2 weeks following treatment, a further significant loss by 2 months, and a marginally significant loss between 4 and 8 months. The neuronal population was then stable through 15 months, at about 13% of normal. Acoustic trauma ears showed the first significant loss isn the lower second turn at 1 month. Long-term (12-14 months post-exposure) trauma ears were highly variable. Waltzers lost about 50% of their normal neuronal population between 4 and 8 months; they showed an unexpected greater-than-normal density at 2 months, possible explanations of which are discussed. Thus, loss of the organ of Corti from various causes results in a slow but progressive loss of spiral ganglion neurons, the time course of which varies with the type of cochlear insult.

Animals↗
PubMed1981

A systems model for food purchasing.

The approach taken in this paper of isolating seasonal characteristics of products and then using that information to determine when those products should be ordered to minimize the system's purchasing costs appears to be valid. A drawback to using this approach, however, is acquiring appropriate data. The authors used data which they believed to be appropriate for thier market purchasing environment but which are not necessarily valid for other locations and/or environments. The prospective user of this model must find and obtain data suitable for the environment and isolate those products which appear seasonal. Only a small percentage of the items used possess any seasonal properties. There is also the obvious problem of using past data to determine future outcomes. Past price patterns do not necessarily continue into the future, although they should be at least indications, barring unusual farm and/or market situations. As with all decision modeling approaches, however, this model should be followed with caution. While the approach is valid, the procedure is no substitute for knowledgeable management of food service functions. Results from the model should provide additional input to guide food purchasing decisions but should not be used unequivocably. When property used, however, this procedure will allow food buyers to come closer to the goal of optimally purchasing food products from a systems point of view then is currently possible.

Alabama↗
PubMed1979

Aspects of planning and evaluation of children's dental care in Appalachia.

The dental public health literature contains almost no information on caries experience and treatment needs of Appalachian children, and little information concerning resource requirements for children's dental care programs in general. Data from three dental treatment programs in Appalachia are summarized for purposes of planning and evaluation of similar programs. Age specific caries and service experiences are presented, and evaluation criteria and planning considerations are discussed. Resource requirements, including time, cost and manpower are also presented, and special considerations for planning programs are discussed.

Adolescent↗
PubMed1979

The caries-preventive effect of amine fluorides and inorganic fluorides in a mouthrinse or dentifrice after 30 months of use.

The study groups using a dentifrice and mouthrinse both containing fluorides, a dentifrice containing stannous fluoride and a mouthrinse containing sodium fluoride, or a mouthrinse containing sodium fluoride with a placebo dentifrice had a 20.7% to 29.0% lower DMF increment than the control group after 30 months. These differences were significant. The study groups using a dentifrice containing amine fluorides and a placebo mouthrinse, a mouthrinse containing amine fluorides and a placebo dentifrice, or a dentifrice containing stannous fluoride and a placebo mouthrinse had a 13.6% to 22.4% lower DMF increment than the control group. These differences were not statistically significant. There was no significant difference in effectiveness against caries between the use of the organic or inorganic fluoride products.

Amines↗
PubMed1978

Anatomical consequences of CO2 laser surgery of the guinea pig ear.

A modified American Optical (Model 100) CO2 laser was used to produce lesions in the tympanic membranes, ossicles, and cochlear capsules of guinea pigs. Even with the lowest available intensities and durations (0.4 watts, 50 msec), there was damage to the inner ear. Although laser surgery of the ear can avoid mechanical trauma and bleeding as well as increase accuracy, the use of commercial lasers in ear surgery should be avoided until a proven unit is available.

Animals↗
PubMed1977

Neonatal sound deprivation affects brain stem auditory nuclei.

CBA/J mice deprived of airborne sound stimulation during postnatal development have smaller globular cells in the ventral cochlear nucleus and smaller neurons in the medial nucleus of the trapezoid body than do normal control mice. The sound deprivation in these mice is similar to that experienced by persons with pure congenital conductive hearing losses. Even more profound central neural changes were found in auditory nuclei in the brain stem of a congenitally sensorineural deaf human.

Acoustic Stimulation↗
PubMed1977

Effects of an amine fluoride mouthrinse and dentifrice on the gingival health and the extent of plaque of school children.

A study to test the efficacy of two amine fluoride products in reducing the extent of plaque and the degree of gingivitis was conducted with 6th-grade school children in Pensacola, Florida. The treatment regimens consisted of a daily supervised mouthrinse at school and the ad libitum home use of a dentifrice. Examinations were conducted at 12-week and 20-week intervals after the treatment had begun. There was no recognizable difference between the plaque and gingival reductions achieved with the use of the amine fluoride dentifrice or mouthrinse when compared either with their inorganic counterparts or with placebo treatment vehicles

Amines↗
PubMed1976

An evaluation of single and combined self-applied fluoride programs in schools.

1. The combined use of a twice-yearly, self-applied 2.2 percent phosphate fluoride prophylactic paste and a weekly 0.2 percent sodium fluoride mouthrinse resulted in a significantly lower caries prevalence at the same school after two years. 2. The use of a weekly 0.2 percent sodium fluoride mouthrinse alone resulted in a significantly lower caries prevalence among 11 year olds at the same school after two years. 3. The use of a twice-yearly 2.2 percent phosphate fluoride self-applied prophylactic paste did not result in a significant difference in caries prevalence at the same school after two years. 4. The combination of methods appeared to be more effective than either method used alone and the programs were more effective among nonwhites in this population with this type of analysis. 5. A study design which uses cross-sectional data to estimate incidence and to make prevalence comparisons at two different points in time can be useful when an evaluation of the effect of previously tested products is desired in school-based programs.

Child↗
PubMed1975

Auditory systems of Heteromyidae: functional morphology and evolution of the middle ear.

Middle ears (515) from 26 species of the rodent family Heteromyidae - genera Dipodomys, Microdipodops, Perognathus, and Liomys - were studied both grossly and histologically, for qualitative and quantitative comparisons. Middle ear modifications characteristic of each genus are qualitatively described. Quantitative comparisons are made among the 26 species in the study. Some correlations between middle ear size and other measurements are discussed. The middle ear is an acoustical transformer that for best efficiency must match the impedance of the cochlea to the impedance of the air in the external auditory meatus. It accomplishes this by a pressure increase and a velocity decrease through the combined effects of the lever and areal ratios; however, because the important consideration is a matching of two impedances rather than an absolute pressure increase, the pressure transformer ratio is a less informative measure of the middle ear's efficiency than is the impedance transform ratio. The impedance transformer mechanism is explained (from a morphological point of view), and equations are presented. Dipodomys, Microdipodops, and Perognathus have a theoretical transmission (at the resonant frequency) of 94-100% of the incident acoustical energy; Liomys, 78-80%. The areal ratio of stapes footplate to 2/3 tympanic membrane is remarkably constant among the species, varying only from 0.04 to 0.07: in Dipodomys and Microdipodops this small ratio is due to the very large tympanic membrane; in Perognathus and Liomys it is due to the extremely small stapes footplate. The lever ratio of incus to malleus varies from 0.28 to 0.33 in Dipodpmys and Microdipodops, from 0.37 to 0.46 in Perognathus, and from 0.55 to 0.60 in Liomys. In addition, the middle ear volumes and the morphology of tympanic membrane, ossicles, ligaments, and muscles, all combine to minimize both mass and stiffness. All these data suggest middle ear mechanisms which are very efficient over a broad frequency range. The middle ear modifications found in heteromyids are adaptive in predator avoidance, especially in areas of little natural cover; nevertheless, contrary to expectations, there is no firm relationship between habitat and the extent of these modifications in the 26 species. However, environment did apparently plan an important role in the evolution of the family, and this is discussed.

Acoustics↗