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Biomedical subjects

P Kwok

Publications and source records attributed to P Kwok.

At least 19 recordsLinked to original sources
PubMed2005

Safety of gold in stapes surgery.

Gold prostheses in middle ear surgery were found to have a higher extrusion rate than prostheses made from titanium. Incidences of deafness after insertion of a gold piston into the vestibule during stapes surgery have been observed. The aim of this study was to find out to what degree gold cations can diffuse from the prosthesis piston into the perilymph. For this, gold prostheses were incubated in artificial perilymph for four months, after which the gold content of the perilymph was analysed. As gold exhibits a special behaviour in complex fluids like the perilymph, a new analysing method was developed. The results show that gold does leak out of the pistons, that it can be reliably measured and that the amount of gold reaching the perilymph depends on the contact area. As the amount of gold measured in the perilymph stays far below the toxic level, it is very unlikely that the gold cations diffusing from a stapes prosthesis into the perilymph have a toxic effect on the inner ear hair cells. Inflammatory or allergic reactions to gold induced by direct tissue contact, however, cannot be excluded.

Animals↗
PubMed2003

[How do metallic middle ear implants behave in the MRI?].

BACKGROUND: Magnetic resonance imaging (MRI) has gained in frequency and importance as a diagnostic procedure. In respect to the close anatomical relationship in the temporal bone it is necessary to know whether it is hazardous to patients with metallic middle ear implants regarding displacement and rise in temperature. For the MR image quality artefacts caused by metallic prostheses should be low. METHODS: Four different stapes prostheses made from titanium, gold, teflon/platinum and teflon/steel, a titanium total ossicular reconstruction prosthesis (TORP) and two ventilation tubes (made from titanium and gold) were tested in a 1.5 Tesla MRI machine regarding their displacement. All objects were first placed in a petri dish, then suspended from a thread and finally immersed in a dish filled with Gadolinium. Temperature changes of the implants were recorded by a pyrometer. RESULTS: None of the implants moved when they were placed in the petri dish or suspended from the thread. On the water surface the teflon/platinum and the teflon/steel pistons adjusted their direction with their axis longitudinally to the MRI scanner opening and the teflon/steel piston floated towards the MRI-machine when put close enough to the scanner opening. No rise in temperature was recorded. All implants showed as little artefacts that would still make an evaluation of the surrounding tissue possible. CONCLUSION: Patients with any of the metallic middle ear implants that were examined in this study may undergo MRI-investigations without significant adverse effects.

Artifacts↗
PubMed2001

Comparative electron microscopic study of the surface structure of gold, Teflon, and titanium stapes prostheses.

HYPOTHESIS: The goal of this study was to compare stapes prostheses of different materials with respect to their surface structures and to discuss their suitability for their use in stapes surgery. BACKGROUND: The surface condition of a stapes prosthesis plays an important role in relation to the type of membrane that forms between the stapes piston and the bony edge of the stapedotomy opening. The quality of this membrane in thickness and mobility is one of the determinants for postoperative hearing improvement. METHODS: The surface conditions of gold, Teflon/steel, Teflon/platinum, and titanium stapes prostheses were examined with a scanning electron microscope. The loop, shaft, and end of each prosthesis were studied. RESULTS: The gold piston was the smoothest of the four pistons examined. When it was cut with a scalpel, a very smooth surface was achieved at the end area. The Teflon piston had the roughest surface. However, when it was cut, a smooth surface with a parallel arrangement of fibers resulted. Its steel loop was the smoothest, followed by gold and platinum. The titanium shaft had a scaly surface, which remained when the end of the shaft was shortened. CONCLUSION: Because a certain roughness of the piston surface is necessary for the development of a stable membrane between the piston and the edge of the stapedotomy opening, the titanium prosthesis is considered to be the most suitable for stapes surgery of the three pistons examined.

Gold↗
PubMed1994

Computer generated three-dimensional reconstruction of the bony labyrinth in Mondini's dysplasia.

The bony labyrinth obtained at necropsy in four cases was studied by a new computer-generated three-dimensional (3-D) system. One case was normal (control) and the other three were histopathologically confirmed cases of Mondini's dysplasia. In case 1, the cochlea had only 2 turns and the lateral semicircular canal did not make a circle but appeared as a spherical mass projecting from the utricle even though the posterior semicircular canal made a normal circle. In case 2, there were no turns in the cochlea even though the semicircular canals and the vestibule appeared normal. In case 3, the cochlea showed 1 to 1 and 1/2 turns and the semicircular canals were premature showing only bud-like projections. This 3-D imaging system, which utilizes the toggling method, provides a way of obtaining satisfactory images without markers, and the time required to obtain these 3-D images was reduced by using a video camera instead of a digitizer. One of the problems associated with the use of 3-D imaging is the long processing time. We resolved this by inputting the section images with a video camera and by picking up structures using density segmentation instead of tracing with a digitizer.

Child, Preschool↗
PubMed1992

Swirls, wrinkles and the whole ball of wax (the source of keratin in cerumen).

Recent work carried out at the Ear Pathology Research Laboratory has demonstrated that cerumen plugs consist of a large amount of keratin debris. In this study the site of origin of this keratin was investigated. This was done by histologically examining these cerumen plugs without disturbing the natural relationship between the plug and the surrounding epithelium. We have clearly demonstrated that a cerumen plug consists of keratin arising from the migratory epithelium of the deep external auditory canal and epithelium of the superficial external auditory canal.

Cadaver↗
PubMed1992

Granular myringitis: a review.

Granular myringitis is the result of a localized chronic inflammation of the lateral surface of the tympanic membrane which is characterized by the development and persistence of granulation tissue over the involved area. The onset of the disease is insidious, and the symptoms, which are minor, are usually confined to chronic otorrhea and mild discomfort in the involved ear. Granular myringitis is a disease which is poorly understood and has received relatively little attention in the literature. The clinical features of this disease are outlined, the pathologic changes in the tympanic membrane illustrated, the literature reviewed and a strategy for treatment presented.

Chronic Disease↗
PubMed1991

The embryonic development of the lateral nasal wall from 8 to 24 weeks.

This histological study of 20 fetal heads aged between 8 and 24 weeks of gestation demonstrates and describes the embryonic development of the lateral wall of the nose. The three turbinates (inferior, middle, and superior) arise as soft-tissue swellings (preturbinates) by 8 weeks' gestation. A cartilage capsule surrounds the nose at 8 weeks and by 9 weeks, medially directed flanges of cartilage have invaded all three preturbinates. The uncinate process arises from the medial surface of the lateral cartilaginous capsule and is first identifiable by 10 weeks. An "air space" progressively develops from 11 to 12 weeks lateral to the cartilaginous uncinate process and from this space, the embryonic channel to the maxillary sinus develops. The embryonic woven bone of the maxilla can be identified from 9 to 10 weeks and enlarges both absolutely and relatively to the nasal cavity, so that by 13 to 14 weeks, this expanding bone forms the lateral wall of the inferior meatus as the cartilaginous nasal capsule regresses.

Embryonic and Fetal Development↗
PubMed1991

Persistence of the foramen of Huschke in the adult: an osteological study.

The foramen of Huschke, which appears during the embryological development of the tympanic bone, usually closes by the age of five years. A review of 377 dried skulls revealed that the foramen of Huschke was present in adult life in 7% of the skulls examined. A patent foramen of Huschke in the adult may, in rare cases, be the cause of temporomandibular joint herniation or fistulization through the anterior wall of the bony external canal.

Adult↗
PubMed1989

The immunosuppressant FK506 selectively inhibits expression of early T cell activation genes.

FK506, a neutral macrolide with immunosuppressive properties, was shown to selectively and rapidly inhibit the accumulation of IL-2 mRNA, as well as the mRNAs of other early (E) phase T cell activation genes such as IL-3, IL-4, GM-CSF, TNF alpha, IFN-gamma, and c-myc in activated human peripheral blood T cells. The activity of FK506, when compared to Cyclosporin A, another immunosuppressant, was 10 to 100x more potent in its ability to inhibit IL-2 mRNA synthesis. FK506 inhibited IL-2 mRNA accumulation in Con A, Con A plus PMA, Ionomycin plus PMA, anti-CD3, and anti-CD3 plus PMA activated T cells. Transcripts from other T cell gene classes such as the immediate early (IE) phase gene, c-fos, the late phase (L) genes, transferrin receptor, IL-2R alpha-chain, and TNF-beta, and the constitutive class genes glyceraldehyde-3-phosphate dehydrogenase and class I MHC HLA-B7 were not affected by FK506. The macrolide Rapamycin, which is structurally related to FK506, had no inhibitory effect on IE, E, L, or constitutive class mRNAs, but it appeared to increase the levels of the E-phase transcripts that were inhibited in FK506 treated T cells. The effect of FK506 on inducible genes in non-T and non-lymphoid human cells was studied in LPS-induced monocytes and PMA or IL-1 activated synovial fibroblasts. FK506 did not affect expression of the mRNAs for IL-1 alpha or IL-1 beta in human monocytes, or of stromelysin, collagenase, or TIMP in synovial fibroblasts. Nuclear run-off transcription studies indicate that FK506 inhibits transcription of the IL-2 gene. These studies suggest that Cyclosporin A and FK506 may effect a common early event in the T cell activation pathway.

Base Sequence↗
PubMed1989

Neurothekeoma (peripheral nerve sheath myxoma) of the external auditory canal.

A patient who presented with an isolated soft-tissue tumor in the lateral portion of the external auditory canal, which after removal was diagnosed histopathologically as a peripheral nerve sheath neurothekeoma, is presented. Peripheral nerve sheath myxomas (neurothekeomas or perineural myxomas) have been reported to occur on the central area of the face, arms and shoulders. This is the first case in which a tumor of this type has been reported to develop in the external auditory canal. The distinguishing histopathological characteristics and the differential diagnosis of this tumor are discussed.

Ear Canal↗
PubMed1988

Severe sensorineural hearing loss caused by lightning. A temporal bone case report.

To our knowledge, this article represents the second temporal bone case report in the literature of profound bilateral sensorineural deafness resulting from a lightning strike to the neck. Initial survival permitted antemortem audiologic testing, the results of which suggested severe cochlear abnormalities. Both temporal bones showed widespread inner-ear changes with absent organs of Corti, rupture and collapse of Reissner's membrane, strial degeneration, and a decreased spiral ganglion cell population. The occurrence of inner-ear trauma with an intact tympanic membrane and normal middle-ear structures suggests that a mechanism other than blast injury was responsible for the pathologic changes in this case.

Adult↗
PubMed1988

Epidermal cyst attached to the chorda tympani nerve.

The incidental post-mortem finding of a small epidermal cyst in the middle ear of a 78-year-old female is presented. The epidermal cyst was attached to the chorda tympani nerve adjacent to the body of the incus, but was not associated with bony erosion or any other suggestion of enlargement or invasive growth. The pathological relationship of this lesion to previously reported "congenital cholesteatomas" of the middle ear is discussed.

Aged↗
PubMed1988

Intradermal nevus of the ear canal.

While intradermal nevi are common benign pigmented skin tumors, their occurrence within the external auditory canal is uncommon. The clinical and pathologic features of an intradermal nevus arising within the external auditory canal are presented, and the literature reviewed.

Adult↗
PubMed1988

Benign osteitis of the external auditory meatus.

Benign osteitis of the external auditory canal is a distinct clinical entity characterized by localized ulceration in the skin of the floor of the bony external auditory meatus with underlying osteitis and sequestration of the underlying tympanic bone. Consideration of clinical and pathological data suggests that continued self-inflicted minor trauma is an etiological factor in at least some cases. The purpose of this paper is to review benign osteitis of the external auditory canal, presenting further clinical documentation and to offer etiological suggestions based upon clinical, pathological and experimental observations. The benign nature of this condition is emphasized.

Aged↗