Search PubMed⌕ Search

Biomedical subjects

K Horner

Publications and source records attributed to K Horner.

79 records · Page 5Linked to original sources
PubMed1988

Atypical simple bone cysts of the jaws. II: A possible association with benign fibro-osseous (cemental) lesions of the jaws.

Four cases are described of simple bone cysts of the mandible arising concurrently with benign fibro-osseous (cemental) lesions. Previous reports of such findings, and a possible relationship to the so-called 'cementoma' of the long bones, are considered. The relevance of this to the aetiology is addressed, and it is suggested that at least some cases diagnosed as simple bone cysts are closely related to the fibro-osseous lesions.

Adult↗
PubMed1988

Erbium filtration for dose reduction in dental radiography.

Previous work has suggested that rare-earth filtration of diagnostic X rays is an effective means of dose reduction in radiology. Erbium (atomic number 68) is particularly promising in this respect. The effects on the X-ray beam and surface dose of the addition of 0.1 mm of erbium foil to the conventional filtration of a GE1000 dental X-ray set were investigated. Filtration by 0.1 mm of erbium produced a beam of narrower spectrum, greater penetration but lower intensity than that filtered conventionally by aluminium alone. The overall dose reduction achieved in dental radiography was greater than 30% between 65 and 85 kVp with a maximum dose reduction of 42% at 65 kVp. The question of the cost-effectiveness of erbium filtration as a radiation protection measure is also addressed.

Erbium↗
PubMed1985

Electrical stimulation of the auditory system in animals profoundly deaf from birth.

Animals homozygous for the recessive deafness gene (dn/dn) have been used to study central responses to modiolar or round window electrical stimulation. Inferior colliculus evoked responses to contralateral constant current pulses are larger in mutants than in controls. In mutants, responses are largest in animals aged 5-7 months, compared with animals aged 42-50 days or 13.5-19 months. The spiral ganglion cell density is normal in the youngest group, but decreases significantly in older animals. Electrical stimulation of the round window is less effective than modiolar stimulation. Single unit recordings suggest that the larger evoked responses in deafness mice are produced by stronger discharges in neurones, rather than greater synchrony of discharge. The deafness mutation appears to provide a useful animal model for studying electrical stimulation of a central pathway which has never received stimulus-related input.

Age Factors↗
PubMed1983

Neural correlates of cubic difference tones in the medial geniculate body of the cat.

Single unit responses to the cubic difference tone CDT (2f1 - f2 = CF) and the difference tone DT (f2 - f1 = CF) were studied in the medial geniculate body (MGB) of the cat. Out of 66 units tested with CDT stimuli and having characteristic frequencies (CF) below 10 kHz, 77% gave a response to the two-tone combination stimulus. The component tones when presented alone evoked no responses, or in some cases a response pattern that was different from the one observed for the combination tone. The CDT response pattern was always similar to that seen for a pure tone at the CF. The threshold of response for the CDT was 10-70 dB higher than for a pure tone stimulus at the CF. The few units which were phase-locked could be synchronised with the CF, CDT, or DT, depending on the particular stimulus conditions. The index of synchrony was in many cases found to be higher for CDT responses than for a pure tone at CF.

Animals↗
PubMedDate not supplied

Localising maxillary canines using dental panoramic tomography.

Impacted maxillary canine teeth occur in about 2% of the population. Late detection of palatal canines may have treatment implications for the patient and medicolegal implications for the dental practitioner. Dental panoramic tomograms (DPT) are widely taken in practice. Image formation in dental panoramic tomography results in relative magnification of objects placed palatal to the image layer and relative diminution of objects buccal to it. This provides a possible means of bucco-palatal localisation of teeth. The aim of this study was assess the validity of DPTs in locating ectopic canines using the vertex occlusal view (VO) as the gold standard. One hundred pairs of radiographs showing 139 ectopic canines were examined. Using the DPT, it was possible to accurately predict the position of a palatally displaced crown in about 80% of cases. The DPT alone is not sufficient for canine localisation, but clinical evidence and suggestion of ectopic positioning on a DPT should warrant further radiographic investigation. Careful interpretation of a radiograph widely used in practice may lead to earlier detection of palatal canines.

Child↗
PubMedDate not supplied

No change detected on distortion products in awake or anesthetized guinea pigs.

Two pure tones presented simultaneously to one ear can produce physiologically and perceptively other tones called distortion products which originate in the inner ear. Notable differences exist between their physiological and perceptive features. In physiological experiments the anesthesia may alter the functioning of the cochlea, especially its efferent system. Physiological measurements made of distortion products taken from the same animals under anesthesia or in the awake state were compared using round window cochlear microphonic responses and evoked potentials from the eighth nerve and the auditory cortex. The physiological measures appeared unaltered by anesthesia, but in both the awake and anesthetized states, repeated measuring at intervals of several minutes could show apparently random variations of a few decibels.

Acoustic Stimulation↗