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Biomedical subjects

D B Webster

Publications and source records attributed to D B Webster.

At least 19 recordsLinked to original sources
PubMed1992

Degeneration followed by partial regeneration of the organ of Corti in deafness (dn/dn) mice.

The deafness mouse is a Mendelian recessive mutant which never hears and has no stimulus-related receptor or neural auditory responses. From birth through 12 days after birth (DAB), the organ of Corti develops normally as seen with light microscopy, except that the space of Nuel does not fully develop. The inner and outer hair cells are degenerating between 12 and 24 DAB and are gone by 45 DAB. As the hair cells degenerate, other cells of the organ of Corti become less recognizable, appear to collapse, and lose their identities as differentiated cells. By 45 DAB, from base to apex, the organ of Corti is composed of a low, roughly cuboidal epithelium with no distinguishing cell types; a hint of a tunnel of Corti remains at the apex. In the basal turn, the organ of Corti remains in this degenerated state through at least 460 DAB (senility for these mice). In the apical organ of Corti, considerable regeneration occurs between 45 and 90 DAB. By 90 DAB the apical turn of the organ of Corti has readily identifiable inner and outer pillar cells, inner and outer supporting cells, Hensen's cells, and Claudius' cells. A tunnel of Corti and space of Nuel are also present in the apex but there are no hair cells. Mechanisms are not known for either the degeneration or the regeneration.

Animals↗
PubMed1991

Neonatal conductive hearing loss does not compromise brainstem auditory function and structure in rhesus monkeys.

The effect of conductive hearing loss on the maturation of the auditory pathway was evaluated using the auditory brainstem response (ABR) in rhesus monkeys. Ten newborn rhesus monkeys were assigned to control (N = 4), unilateral hearing loss (N = 3), or bilateral hearing loss (N = 3) groups. Hearing loss was created by surgically excising a 3 mm section of the external auditory canal and suturing the canal. Auditory brainstem responses to click stimuli were recorded prior to and after the surgical procedure and bi-monthly or monthly for a 14 month follow-up period. Results showed that after surgery all ears developed an estimated 30-50 dB conductive hearing loss which was retained throughout the follow-up period. Contrary to expectations, the latencies of the ABR component waves decreased with age in all ears. When adjusted for hearing level, there were no differences between ears in maturation of the component waves of the ABR. These data suggest that, in primates, a conductive hearing loss does not affect the maturation of those aspects of the auditory pathway reflected in the ABR. Furthermore, the conductive losses were not accompanied by any discernible change in the neuronal sizes of brainstem auditory neurons or the volume of the cochlear nuclei.

Animals↗
PubMed1987

Morphological and electrophysiological study of the inner ear and the central auditory pathways following whole body fetal irradiation.

Pregnant CBA/CBA mice were whole body irradiated with 2 Gy on the 13th or 16th day of gestation, respectively. The exposed fetuses were raised to an age of 21 postnatal days. Auditory brainstem recordings of threshold levels showed a considerable elevation independent of if irradiation had been performed on either the 13th gestational day or the 16th gestational day. In exposed animals a latency difference occurs in the peaks that increases from peak 1 to peak 5, measuring in peak 5 up to 1.16 ms. Also the peak-to-peak length of waves 1-5 increases in irradiated animals. Scanning electron microscopy of the cochleae showed varying degrees of stereociliary derangement of both outer and inner hair cells, particularly in cochleae where irradiation had been performed on the 13th gestational day, but not loss of hair cells. Light microscopic analysis of auditory brainstem nuclei revealed normal conditions except that in inner ears exposed on the 16th gestational day the flocculus was fused to the lateral surface of the anterior ventral cochlear nucleus. It is concluded that the elevated threshold levels in irradiated animals are most likely due to pathological changes in the peripheral receptor organ whereas the increased latencies and the increased peak-to-peak length likewise reflect functional changes in the brainstem auditory nuclei.

Animals↗
PubMed1987

Caries and treatment patterns in children related to school lunch program eligibility.

This article presents the caries prevalence and treatment patterns of children relative to a classification of family economic status, based on the child's eligibility for the free or reduced-cost school lunch program. Dental caries prevalence is reported for children aged 8-11 years at the beginning of a longitudinal clinical trial in the nonfluoridated city of Tampa, Florida. These children were placed into one of three school lunch subsidy categories--poverty, near-poverty, and nonpoverty--using federal government income eligibility guidelines for the school lunch program. The results support an inverse relation of caries prevalence to economic status, as well as the expected direct relation of family income to treatment needs met. The nonpoverty group exhibited the lowest number of decayed surfaces and had nearly 70 percent of their treatment needs met. The poverty group had significantly higher scores both for total caries experience (DMFS) and decayed surfaces (DS) than either of the other groups. Filled surfaces (FS) scores were not significantly different for any of the groups. This method of classifying children by school lunch program eligibility is considered valid because of the rigorous requirements used in determining family income, as well as the thorough verification procedure that is applied. The method is easy to use once officials have been convinced that confidentiality will be maintained.

Child↗
PubMed1985

The spiral ganglion and cochlear nuclei of deafness mice.

Deafness mice (dn/dn) never develop hearing, but, except for the associated physical defects, have no other known abnormalities. For this study, cochleas and brains of five adult homozygotes (dn/dn) and five adult heterozygotes (+/dn), matched by weight and sex, were prepared for serial section light microscopy. In the homozygotes, the organ of Corti was totally degenerated basally, gradually improving toward the apex where supporting cells, border cells and pillar cells were present; however, the stria vascularis was dystrophic in the apex. The saccular macula was atrophied or dystrophic in seven of the ten homozygote ears. The homozygotes had only 23% of the number of spiral ganglion cells found in the heterozygotes, but they appeared robust. In six of the ears of each group there was clumping of apical spiral ganglion neurons. In the homozygotes, the volume of Rosenthal's canal was 121%, that of the dorsal nuclei was 90%, and that of the ventral cochlear nuclei was 63% of the comparable volumes in heterozygotes. The globular cells of the homozygote ventral cochlear nucleus were 72% of the size of those of heterozygotes. These quantitative morphological abnormalities of the homozygote spiral ganglion and cochlear nuclei may result from organ of Corti atrophy.

Animals↗
PubMed1984

Consultant evaluation of a hospital medication system: analysis of the existing system.

A consultant team's evaluation of a system for distributing and controlling medications in a large teaching hospital is described. Through interviews with key personnel from administration, pharmacy, nursing, and the medical staff, an interdisciplinary research group identified problems in the reliability and response times of the hospital's existing medication system. After assessing staff expectations regarding acceptable standards for medication errors and response times and their attitudes toward proposed changes in the medication system, medication-error rates were determined using a pharmacist-observer method. Observations during 34 five-hour periods on four nursing units were conducted over a 17-day period. Medication-error rates were calculated as the frequency of medication errors during the observation period divided by the total opportunities for error (OE), which were defined as doses ordered plus unauthorized doses given. Response times for processing "now," "stat," and routine orders were also determined using work-sampling methods. The total medication-error rate for the nursing units studied was 9% excluding wrong-time errors; more than a third of doses were given more than 30 minutes before or after their scheduled administration times. Response times for "now" and "stat" orders averaged about 23 minutes, in conformance with the desired standard of 30 minutes. However, processing of routine orders required an average of two hours and seven minutes, much of which was attributed to delays in the messenger service. The basic design of the existing unit dose medication system contributed to problems in the reliability and efficiency of the system.

Attitude of Health Personnel↗
PubMed1984

Consultant evaluation of a hospital medication system: synthesis of a new system.

Recommendations of consultants for the implementation of a new medication system at a large teaching hospital are described. Based on a previous analysis of the hospital's existing drug distribution and control system that revealed problems in reliability and response time, an interdisciplinary consultant group offered 14 recommendations, which included implementation of a computerized unit dose delivery system and selected clinical pharmacy services. Functions identified for which computerization would produce the greatest benefits included maintenance of patient census data, medication order entry and retrieval, and preparation of a medication administration record for nursing. Recommendations for improving the unit dose system in the hospital consisted of increasing the number of medications packaged in true unit dose form, increasing the frequency of daily deliveries of scheduled medications, sending p.r.n. medications on an on-call basis, decreasing the lead time for preparation of i.v. solutions, and using a pharmacist-manned portable medication cart to reduce workload on the central pharmacy during peak workload periods. Clinical pharmacy services identified as having the greatest cost-benefit ratio were discharge consults, drug therapy monitoring, and drug-use review. Using information from published studies and cost data from the hospital, a net annual savings of over +152,000 was projected with implementation of these services. Improvements in the unit dose system and implementation of clinical pharmacy services were expected to result in substantial cost savings in the study hospital.

Computers↗
PubMed1984

Consultant evaluation of a hospital medication system: implementation and evaluation of the new system.

The effects of consultant-recommended modifications in a hospital medication system on medication-error rates and response times were evaluated. Fourteen recommendations for improving the medication system in a large teaching hospital were implemented to varying extents over a period of 1.5 years. The response times and medication-error rates of the newly implemented system were then measured using pharmacist-observers as was done in the old medication system. Medication-error rates were then compared on one medical-nursing unit and two surgical-nursing units both before and after implementation of the new system on the medical unit alone. Response times for routine medication orders decreased by 55% compared with the previous system; for "now" and "stat" orders, response times were reduced by 57% for orders filled from the central pharmacy and by 70% for orders filled from medication carts on the nursing units. No significant differences in medication-error rates were found when the old and new medication systems were compared. This finding was attributed primarily to the hospital's failure to implement recommendations related to computer printing and sorting of orders, use of dispensing envelopes for delivering medications in true unit dose form, and packaging of all medications in unit dose form. This study illustrates how the benefits of a unit dose system can be compromised in implementation and the need for close monitoring to ensure that performance standards are maintained.

Consultants↗
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↗