Biomedical subjects
Publications and source records attributed to M J Porter.
The use of polyamino acids in asymmetric organic synthesis is reviewed. Particular emphasis is placed on the asymmetric epoxidation of alpha,beta-unsaturated ketones with hydrogen peroxide in the presence of polyalanine or polyleucine, and further transformations of the epoxide products.
The great auricular nerve is routinely divided during the operation of parotidectomy, however, some surgeons have suggested that preserving the posterior branches reduces the area of post-operative anaesthesia. A prospective study was performed comparing the area of anaesthesia and hypoaesthesia in patients undergoing parotidectomy. In 20 patients the great auricular nerve was preserved and in 11 it was sacrificed. Mapping of the area of sensory loss at 2 weeks, 3, 6, 9 and 12 months showed that there was no difference between the two groups. The area of sensory loss decreased in an exponential fashion in both groups. The majority of the change occurred within 6 months. We conclude that preservation of the posterior branches of the great auricular nerve is unnecessary.
Almost all the pathological and physiological process that effect the nose will change the volume of the airspace within it. This volume has previously been difficult to measure but a new method that calculates this space has been developed. A mechanical model was built to test the physical parameters involved in making volume measurements. The model demonstrated that a model sinus could be detected if the ostium was only 0.5 mm in diameter. It also showed that a mathematical model which described the volume of the space could be constructed. In vivo experiments showed that nasal volume can be measured in children as young as 4. In children, nasal volume correlates with age, height, and weight. They had a low coefficient of variation (7.1%) and a high test-retest correlation (r = 0.94). Adult nasal volume averaged 138 ml. The method is sensitive enough to detect the decongestant effect of xylometazoline in a group of 17 healthy volunteers (p < 0.01). There is no significant difference in the sensitivity to detect the decongestant effect of xylometazoline when compared with active anterior rhinometry, nasal peak flow, and acoustic rhinometry (range 80-95%).
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A new method of measuring nasal volume has been developed called 'Manometric Rhinometry'. We describe the principle behind its use and present the results of measuring two groups of normal children aged 4-10. The total volume of the nasal cavity, paranasal sinuses and postnasal space in these children averaged 81 ml in 4-year olds and 140 ml in 10-year olds when measured using an open cell foam plug. Where a rigid nasal tip was used the volume averaged 67 ml in 4-year olds rising to 99 ml in 8-year olds. Correlation with age, weight, height and head circumference showed the greatest correlation with height (r = 0.66). Multiple regression analysis did not add further explanatory power.
A study comparing the pre- and post-radiotherapy computed tomographic scans of patients treated for nasopharyngeal carcinoma revealed that the incidence of major mucosal abnormality was significantly increased and approximately doubled after radiotherapy. The most significant factor predicting major mucosal abnormality after radiotherapy was the presence of tumour in the sinus before treatment. In the maxillary sinus there was significant association of major mucosal abnormality before and after radiotherapy although this was not so for the other sinuses. The mucosal changes observed were evident as early as six months after radiotherapy.
A retrospective study of computed tomography scans of the paranasal sinuses of 131 control subjects in Hong Kong revealed minor mucosal abnormalities in more than half of the ethmoid sinuses. Major abnormalities were present in seven per cent of maxillary, five per cent of anterior ethmoid and four per cent of posterior ethmoid sinus. In 85 patients with nasopharyngeal carcinoma the prevalence of minor mucosal abnormalities in the sinuses was similar to that of the control group but major mucosal abnormalities were significantly more common in the anterior and posterior ethmoids at 15 per cent and 21 per cent of the respective sinuses (p < 0.001).
A study has been undertaken to compare the sensitivity of manometric rhinometry, rhinomanometry, nasal peak flow and acoustic rhinometry to detect the decongestant effect of xylometazoline. Twenty healthy volunteers were investigated before and after decongestion. The sensitivity of all four methods varied from 80 to 95%. These differences were not significant. Manometric rhinometry, a new method of investigating nasal physiology, is as sensitive as more established methods.
The Glasgow benefit plot has encouraged surgeons to look at the results of their surgery from a more functional standpoint rather than in purely technical terms. Our aim was to use the plot to examine the efficacy of second side stapedectomy. A retrospective study of 17 second side stapedectomies showed that the addition of the second operation significantly increased the chances of achieving at least one 'normal' hearing ear and made 'normal' and symmetrical hearing possible.
A new method of measuring nasal volume is described. It works by extracting air from a closed cavity and measuring the resultant pressure change. To validate this method in the nose, 17 healthy volunteers were examined before and after application of xylometazoline. The apparent volume before decongestion was a mean of 204 ml. After decongestion the average volume was 228 ml. The difference is highly significant (P < 0.01). We conclude that manometric rhinometry is a valid method of investigating the nose and sinuses.
Tumours of the parapharyngeal space are not common. The majority arise from the deep lobe of the parotid gland or neurovascular structures. We describe a case of fibromatosis, which has not previously been reported at this site.
Forty-one paraffin embedded specimens of primary nasopharyngeal carcinoma (NPC) were examined to investigate the expression of c-myc and ras oncogenes. Sections were stained with the monoclonal antibodies myc 1-9E10 or ras Y13-259 and binding was detected using the ABC method. The intensity of staining for each tumour was assessed as nil, moderate or intense. The results indicated that 9 (22%) had intense staining for the c-myc oncogene, 28 (68%) had moderate staining and only 4 (10%) showed no staining. For the ras oncogene, 8 (19%) had intense staining, 22 (54%) moderate staining and 11 (27%) showed no staining. The patient's clinical data indicated no correlation between the expression of either c-myc or ras p21 and age, sex, smoking, tumour stage, antibody titre to EBV, or family history. No correlation was found between ras p21 expression and survival; however, overexpression of the c-myc oncogene correlated with a poor prognosis (p < 0.05). This study is consistent with investigations demonstrating that c-myc expression correlates with poor survival in head and neck tumours.
We present the case of a 55-year-old man who presented with intermittent, profuse bleeding from the ear five years following radiotherapy for a nasopharyngeal carcinoma. He had developed osteoradionecrosis of the temporal bone, and the bleeding was shown to originate from an aneurysm of the internal carotid artery within his temporal bone. This has not previously been reported as a complication of radiotherapy for nasopharyngeal cancer.
Since the introduction of stapedectomy with reconstruction of the ossicular chain to Great Britain, many modifications in practice have taken place. The changes include patient selection, operative technique and the type of prosthesis used, as well as the number of operations performed yearly. The aim of this study is to attempt to establish the actual practice among British otolaryngology consultants by means of a simple questionnaire. Two hundred (50.3%) forms were analysed anonymously. The study confirms the decrease in the number of operations performed annually, the absence of centralization for this type of surgery in Great Britain and also demonstrated the trends towards stapedotomy and the practice of bilateral surgery amongst younger consultants.
The differing effects of halothane and isoflurane on nasal mucosal blood-flow was investigated by means of laser-doppler flowmetry in a total of fourteen patients who received one of these inhalational agents during anaesthesia. A trend towards lower nasal flux was seen in the halothane group but, due to insufficient numbers, significance could not be demonstrated. These changes in flux appeared not to be related to the falls in perfusion pressure which were seen in both groups of patients and were thought to be due to locally vasoactive effects.
The diagnosis of CSF rhinorrhoea on clinical grounds alone can be difficult. We describe how the use of non-invasive electrophoretic analysis of nasal secretions for tau protein (asialotransferrin) helped in the management of cases where the existence of a CSF leak was in doubt. Patients were thus saved unnecessary invasive investigations or surgery. A modification of the method of analysis, which improves diagnostic accuracy, is described.
Cocaine is commonly used in ENT practice for its vasoconstrictor and anaesthetic properties. It is sometimes combined with adrenaline. The laser Doppler Flowmeter was used to compare the effect of 5 per cent cocaine alone or with adrenaline (1 in 1,000) on nasal mucosal blood flow. The results show an average fall in blood flow of 76.7 per cent for cocaine with adrenaline, compared to 61.2 per cent with cocaine alone. The difference is significant (P less than 0.05). The time taken for the blood flow to fall was an average of 131 s and 160 s respectively. These differences are not significant.
The submucosal temperature in the inferior turbinate was measured in 13 subjects. It was found that giving ice cubes to suck produced a significantly greater fall in nasal temperature than did the application of ice packs to the forehead. In only seven out of the 13 subjects did an ice pack reduce nasal temperature.