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Biomedical subjects

W K Low

Publications and source records attributed to W K Low.

16 recordsLinked to original sources
PubMed1998

Skin-type antifreeze protein from the shorthorn sculpin, Myoxocephalus scorpius. Expression and characterization of a Mr 9, 700 recombinant protein.

A cDNA clone encoding a presumptive antifreeze protein was isolated from a skin library from shorthorn sculpin, Myoxocephalus scorpius. The clone encodes a 92-residue mature polypeptide (sssAFP-2) without any signal and prosequence, which suggests an intracellular localization. It is the largest alanine-rich, alpha-helical type I antifreeze protein known. A recombinant fusion protein containing an N-terminal-linked His-tag was produced and purified from Escherichia coli. This protein is alpha-helical at 0 degreesC and exhibits significant antifreeze activity. Northern blot and reverse transcription-polymerase chain reaction analyses indicate that sssAFP-2 mRNA has limited tissue distribution and is present in peripheral tissues such as skin and dorsal fin, but is notably absent in the liver. These studies reinforce recent evidence that indicate that the external tissues of cold water marine fishes are major organs for antifreeze protein synthesis and are likely the first line of defense against the threat of freezing.

Amino Acid Sequence↗
PubMed1998

Long-term hearing status after radiotherapy for nasopharyngeal carcinoma.

This paper evaluates the hearing status in the long-term, of patients who have had radiotherapy for nasopharyngeal carcinoma (NPC) and also discusses the hearing losses from a disability point of view, which takes into account binaural hearing. Forty patients who have had NPC successfully treated by a single radical course of radiotherapy of 70-80 Gy were studied at 2-12 years (mean 6.2 years) after radiotherapy. Each patient was examined clinically and with a pure-tone audiogram. Averaged hearing thresholds over 0.5, 1.0, 2.0 and 4.0 kHz were evaluated and a value > 30 dB was considered abnormal. The findings were compared with age-matched controls. The median hearing threshold for each ear in NPC patients was found to be 31.9 dB (range 10.0-86.3 dB) and that for controls 17.5 dB (7.5-38.8 dB) (P < 0.0005, Wilcoxon's matched pairs test). In NPC patients, 44 ears (55.0%) had abnormal hearing, of which 17 (21.3%), 5 (6.3%) and 22 (27.5%) ears had predominantly sensori-neural, conductive and mixed hearing losses, respectively. Nineteen ears had middle ear effusions, accounting for the majority of mixed and conductive hearing losses. In terms of individual patients, 8 (20.0%) and 18 (45.0%) patients had abnormal hearing in one year (monaural hearing disability) and both ears (binaural hearing disability), respectively. In conclusion, a substantial proportion of patients who have had radiotherapy for NPC, have hearing disability in the long-term, as compared to normal controls.

Adult↗
PubMed1998

Long-term post-irradiation middle ear effusion in nasopharyngeal carcinoma.

This study aimed to find out if there were factors which influenced the development of long-term middle ear effusion (MEE) in patients irradiated for nasopharyngeal carcinoma. Thirty-five patients (70 ears) were studied for 2-8 years (mean 5.5 years) post-radiotherapy. The factors studied were (a) sex (b) age (c) tumour size and (d) presence of pre-radiotherapy MEE. Only the presence of pre-radiotherapy MEE was found to be statistically significant (P = 0.004, Fisher's exact test). Stepwise multiple regression analysis showed the presence of pre-radiotherapy MEE was a predictor of post-radiotherapy MEE with an odds ratio of 0.67. It is postulated that irreversible Eustachian tube dysfunction occurs when the tube which has been damaged by tumour is further damaged by irradiation. This may explain the frequent persistent otorrhea when ventilation tubes are used to treat post-radiotherapy MEE in patients with nasopharyngeal carcinoma. In conclusion, an ear with pre-irradiation MEE was almost seven times more likely to have long-term post-irradiation MEE than an ear without pre-irradiation MEE.

Ear, Middle↗
PubMed1997

The contact bleeding sign of nasopharyngeal carcinoma.

BACKGROUND: The nasopharynx has lymphoepithelium frequently resulting in mucosal irregularities. Therefore, it is often difficult by mere inspection to clinically differentiate nasopharyngeal carcinoma (NPC) from normal tissue. The present study aimed to determine if contact bleeding could be used as a reliable sign to help differentiate the two. METHODS: Fifty consecutive Chinese adult patients with mucosal masses in the nasopharynx suspicious of being NPC were studied. Contact bleeding, if present, was elicited with a swab stick and viewed with a nasal endoscope. Each mass was then biopsied and examined histologically. RESULTS: Twenty-one patients were histologically proven to have NPC and all had contact bleeding (sensitivity rate of 100%). Of those patients who did not have NPC, 10 had contact bleeding (specificity rate of 65.5%) but 90.0% of them exhibited signs and/or symptoms of rhinosinusitis. After the rhinosinusitis was successfully treated, the masses either resolved or exhibited no further contact bleeding. CONCLUSIONS: Illiciting contact bleeding on masses in the postnasal space is inexpensive, safe, and easy. In many cases, it helps the clinician decide if certain masses warrant biopsies to exclude NPC.

Adult↗
PubMed1997

Pathogenesis of middle-ear effusion in nasopharyngeal carcinoma: a new perspective.

The theory that middle-ear effusion (MEE) associated with nasopharyngeal carcinoma (NPC) is merely the result of tensor veli palatinus destruction is deficient because recent studies have shown that many patients with NPC have MEE but no tensor veli palatinus dysfunction. The present study evaluates the relationship between MEE and Eustachian cartilage erosion by NPC and examines the pathogenesis of NPC-associated MEE from a new perspective. Thirty-five patients with NPC were studied by magnetic resonance scans taken along the lengths of the Eustachian tubes. Twenty-four patients had tumour involvement of both sides of the nasopharynx so that 59 ears were available for study. Eighteen ears had MEE of which 12 had Eustachian cartilage erosion (p < 0.00001), Fischer's Exact Test). In ears with MEE, Eustachian cartilage erosion was frequently but not necessarily associated with tensor veli palatinus destruction. We postulate that altered Eustachian tubal compliance as a result of cartilage erosion by tumour is an important reason why middle-ear effusions develop in patients with NPC.

Adult↗
PubMed1996

Hearing disability before and after radiotherapy for nasopharyngeal carcinoma.

This paper evaluates post-irradiation hearing changes in patients with nasopharyngeal carcinoma (NPC) from a disability orientated approach, which takes into account binaural hearing. Newly diagnosed patients with NPC were studied before radiotherapy, and at four to 12 months (mean 9.2 months) after radiotherapy, provided they remained disease-free. Each patient was examined clinically and with pure tone audiograms. Tympanometry was used to confirm middle ear effusion. Averaged hearing thresholds over 0.5, 1 and 2 kHz were evaluated. If abnormal (> 30 dB), the resultant hearing disability was illustrated by a modified Glasgow Plot. Twenty-three males and 10 females completed the study. Middle ear effusions resulted in 39.3 per cent (binaural in two patients) and 33.3 per cent (binaural in five patients) of patients having hearing disability pre- and post-irradiation respectively. No patient had hearing disability as a result of a sensorineural loss. It is recommended that future reporting of post-irradiation hearing changes in patients with NPC, as in middle ear surgery, be considered from a disability-orientated approach.

Adult↗
PubMed1995

Middle ear pressures in patients with nasopharyngeal carcinoma and their clinical significance.

There is a paucity of studies investigating middle ear pressures (MEPs) in patients with nasopharyngeal carcinoma (NPC). This paper prospectively examines MEPs in patients with nasopharyngeal carcinoma before and after radiotherapy and discusses their clinical significance. Newly diagnosed patients with nasopharyngeal carcinoma were studied before and at three to 12 months (mean 7.5 months) after radiotherapy. MEPs were measured by tympanometry. Thirty-three patients completed the study. The mean MEP before and after radiotherapy was -55.2 mm water (range -250 to 45 mm water) and -73.1 mm water (range -215 to 35 mm water) respectively. About two-thirds of assessable ears had an increase in negative MEPs after irradiation and the rest had less negative MEPs after irradiation. Those ears which developed post-irradiation middle ear effusions were found to have pre-irradiation negative middle ear pressures of at least -45 mm water. These findings provide possible explanations for some unexplained audiometric observations previously made in patients with nasopharyngeal carcinoma after radiotherapy. Tympanometry before radiotherapy may prove to be useful in identifying ears with a high risk of developing post-irradiation middle ear effusion.

Adult↗
PubMed1995

The influence of race on the position of the jugular bulb.

The position of the jugular bulb (JB) is of great clinical significance to the otologist. A high and laterally situated jugular bulb may pose difficulties when dealing with the middle ear while a high and medially sited jugular bulb can create problems in neuro-otological surgery. This paper aims to study possible racial differences in the position of the jugular bulb. Fine-cut computed tomogram (CT) scans of temporal bones (in the axial plane) of 34 Caucasians and 34 Chinese were studied. The position of the jugular bulb was determined with reference to the midpoint of the lumen at the inferior limit of the cochlea (mpC). Of the 60 Caucasian and 58 Chinese temporal bones with identifiable jugular bulbs, 33 jugular bulbs of the Caucasian (55 per cent) and 34 jugular bulbs of the Chinese (58.6 per cent) were at the same height or higher than the mpC (p = 0.2; chi-squared test). The midpoint of the jugular bulb was 8.67 +/- 1.73 and 8.61 +/- 2.49 mm posterior to the mpC for the Caucasian and Chinese respectively (p = 0.2; t-test). However, the midpoint of the jugular bulb of eight Caucasian (24.2 per cent) and 22 Chinese (64.7 per cent) were medial to the mpC (p < 0.001; chi-squared test). Race does not influence the height of the jugular bulb nor its position in the sagittal plane but can influence whether a high jugular bulb is medially or laterally situated.

Adult↗
PubMed1995

Complications of the Caldwell-Luc operation and how to avoid them.

The complications of the Caldwell-Luc operation were retrospectively studied in 1990. The case records were analysed and updated information from telephone interviews and posted questionnaires were available for most patients. One hundred and eighty-five patients with 216 procedures with a mean postoperative follow-up period of 33.5 months were studied. The commonest indication for the operation was for chronic sinusitis. There were three common complications found: facial swelling (61.9%), pain and/or numbness of the face (46.0%) and pain and/or numbness of the teeth/gums (30.9%). Rare complications are postoperative epistaxis (0.4%), oroantral fistulae (0.4%), epiphora (0.4%) and dental discoloration (0.4%). This paper discusses the pathophysiology of these complications and surgical techniques on how to avoid them. Although the use of the Caldwell-Luc operation has declined in recent years with the development of endoscopic sinus surgery, it still has occasional indications and a set of practical guidelines on how to prevent complications would be useful. The basis for treating chronic sinusitis with functional endoscopic sinus surgery at the expense of the more traditional form of treatment is also discussed.

Chronic Disease↗
PubMed1995

Racial considerations in acoustic neuroma removal with hearing preservation via the retrosigmoid approach.

Racial differences in the size, shape and structure of the cranium exist. This paper evaluates the importance of race in influencing the required sizes of craniotomies for gaining access to the lateral end of the internal auditory meatus without breaching the labyrinth via the retrosigmoid approach. Fine-cut CT scans of the temporal bones (axial cuts) of 34 Chinese and 34 Europeans were studied. The relevant distances and angles of the posterior cranial fossa and temporal bone were measured and statistically significant differences between the two races were found. This led us to the conclusion that a larger craniotomy is required in Europeans than in Chinese. In recommending an optimal size for a retrosigmoid craniotomy to remove acoustic neuromas completely and preserve hearing, the racial factor must be considered.

Adult↗
PubMed1994

Palatine tonsillar metastasis from carcinoma of the colon.

Metastatic carcinoma of the palatine tonsil is rare, with only 92 cases reported in the world literature. We report a case of tonsillar metastasis from the colon. This is an unusual case not only because it is the first case report of tonsillar metastasis from this site but also because the tonsillar secondary is the first sign of the primary disease.

Adenocarcinoma↗
PubMed1994

Can snoring relief after nasal septal surgery be predicted?

Patients with nasal obstruction often have associated snoring. This study aims to find out if there are reliable predictors for the success or failure of septal surgery in relieving snoring in patients with symptomatic nasal obstruction secondary to a deviated nasal septum and who have associated snoring. Thirty patients were studied pre-operatively and at 4-12 months (mean 6 months) post-operatively. The intensity of snoring was measured on a visual analogue scale. Nasal patency was measured with a peak nasal inspiratory flow meter. The collapsibility of the soft palate was gauged by the degree of velopharyngeal closure on the Muller manoeuvre. Fifteen patients (50%) achieved snoring relief after septal surgery. The severity of nasal obstruction and intensity of snoring pre-operatively, the magnitude of nasal obstruction relief post-operatively and the degree of collapsibility of the soft palate were found not to influence the outcome of septal surgery on snoring. The relationship between nasal obstruction and snoring is complex and the alteration of airflow patterns after septal surgery is postulated to be important in influencing snoring relief.

Adult↗
PubMed1993

The relationship between middle ear pressure and deviated nasal septum.

The deviated nasal septum may be associated with middle ear problems, particularly on the side of nasal obstruction. This study aims to find out whether middle ear pressure (MEP) correlates with the degree of nasal obstruction secondary to a deviated nasal septum, and to examine changes in MEP following septal surgery. Patencies of the nasal passages (measured with a peak nasal inspiratory flowmeter) and MEP (measured with a tympanometer) of 55 patients were obtained prior to surgery and 7.5 (6-10) months post-operatively [median (range)]. Forty patients completed the study. Results were analysed by linear regression. In the ear on the side of nasal blockage, MEP was -25.7 +/- 28.4 mm water pre-operatively, and following surgery increased significantly to -2.9 +/- 30.4 mm water (mean +/- SD) (P < 0.001). Pre-operatively, it was inversely related to the difference in patencies between the two nasal passages (r = -0.32, P < 0.02). Post-operatively, its improvement correlated with the degree of reduction of asymmetry of airway patency (r = 0.56, P < 0.001).

Acoustic Impedance Tests↗
PubMed1992

Submucous resection for deviated nasal septum: a critical appraisal.

Submucous resection (SMR) for the deviated nasal septum had been criticised to have a higher complication rate and less patient satisfaction than septoplasty. Seventy-five patients who underwent SMR were studied and followed up at 6 months to 56 months post-operatively. The rates of short and long term complications were relatively low: septal haematoma 1.3%, nasal infection 1.3%, epistaxis 2.6%, external nasal deformity 9.3% and septal perforation 2.7%. While most patients achieved short term relief of nasal obstruction (93.4%), about 30% had persistent/recurrent nasal obstruction on long term follow-up. Similar rates had been quoted for the operation of septoplasty. We postulated that this was due to unfavourable airflow patterns as a result of minor residual septal deviation. Some patients had associated pre-operative symptoms of snoring (57.3%), headache (48.0%), rhinorrhoea (38.7%), sneezing (30.7%), hyposmia (30.7%) and epistaxis (21.3%). Frequencies of cure/improvement of these symptoms after SMR were 34.9%, 33.3%, 24.1%, 30.4%, 60.9% and 43.8% respectively. The overall post-operative long term (average 23.5 months) satisfaction rate was almost 70%. SMR, being relatively easy to perform, and having similar complication and patient satisfaction rates as septoplasty, should be retained in the surgical armamentarium for the deviated nasal septum.

Adolescent↗
PubMedDate not supplied

Headaches associated with nasal obstruction due to deviated nasal septum.

A deviated nasal septum not only can cause a blocked nose, but may also be associated with headaches. This study evaluates the nature of these headaches, the effect of submucous resection of the nasal septum, and the factors associated with postoperative headache relief. Deviated nasal septa were corrected by submucous resection in 99 men and 17 women. Patients were studied at 4 to 48 months (mean 18 months) postoperatively. Fifty-five of the 116 patients studied (47.4%) had preoperative recurring headaches. Thirty-five of the 55 patients with headaches (63.6%) experienced relief (complete or partial) of their headaches at a mean follow-up period of 18 months. Patients were more likely to be relieved of their headaches following submucous resection if the headaches were most intense over the frontal region, pressurelike in nature, and if the submucous resection resulted in relief of nasal obstruction. It is possible that headaches recur in the long term, and it is postulated that central mechanisms play a role.

Adolescent↗