Selection of mutations altering specificity in restriction-modification enzymes using the bacteriophage P22 challenge-phage system.

A method for selecting mutants of site-specific DNA-binding proteins has been applied to the study of the EcoRI and RsrI restriction-modification enzymes. Catalytically inactive variants of both endonucleases are shown to function as pseudo-repressors in the bacteriophage P22 challenge-phage assay, and, upon further mutagenesis of the gene encoding R.EcoRI, a variant of that enzyme has been selected which appears to bind EcoRI-methylated GAATTC sequences to the exclusion of unmethylated sites: this specificity is the opposite of that belonging to the native enzyme. Variants of the EcoRI methylase have also been found that lack either catalytic activity or both binding and catalytic activities.

Assessment of the otoscopic skills of general practitioners and medical students: is there room for improvement?

Ear, nose and throat problems are common in general practice, yet undergraduate and postgraduate teaching in the subject is variable and often sparse. The assumption that direct experience in otoscopy in practice will compensate for inadequate previous tuition was tested by assessing a group of 53 general practitioners and 59 medical students. Confidence in otoscopy was assessed using a visual analogue scale and skill was assessed by clinical examination of four ears. Otoscopy was divided into identifying the tympanic membrane, distinguishing a normal from an abnormal membrane and identifying specific features of the membrane. The medical students and general practitioners were comparable in both confidence and skill for all parameters except skill in identification of specific features of the tympanic membrane, in which the students' ability was greater (Student's t-test, P < 0.01). In both groups the percentage of false negative observations was reassuringly low--for students the mean was 3.0%; and for general practitioners 4.3%. There is room for improvement in general practitioner's training in otoscopy. Supervised tuition is essential and cannot be compensated for by unsupervised experience. More involvement with ear, nose and throat problems in vocational training or attendance at continuing education courses is suggested.

Neplanocin A inhibition of S-adenosylhomocysteine hydrolase in Alcaligenes faecalis has no effect on growth of the microorganism.

Neplanocin A, a cyclopentenyl analog of adenosine, is a naturally occurring antibiotic possessing potent inhibitory activity toward the enzyme S-adenosylhomocysteine (AdoHcy) hydrolase. In the present study, we examined whether there was a correlation between the inhibition of prokaryotic AdoHcy hydrolase and the reported antibacterial activity of neplanocin A, e.g. Alcaligenes faecalis (Yaginuma et al., J. Antibiotics 34: 359 approximately 366, 1981). Of 16 bacterial species screened, only 2 organisms (both of which contained AdoHcy hydrolase) were sensitive to 10 nM neplanocin A when grown on agar plates. None of the 16 strains showed any growth sensitivity in broth culture to concentrations of the antibiotic as high as 4 mM. However, treatment of A. faecalis in broth culture with 14 microM neplanocin A resulted in complete inhibition of cellular AdoHcy hydrolase and subsequent elevation of intracellular AdoHcy. No alternative method for degrading or removing the excess AdoHcy from these cells was detected. Bacillus subtilis, which exhibited no AdoHcy hydrolase activity showed no alteration of AdoHcy metabolism when treated with the same concentration of the antibiotic. These results indicate that inhibition of AdoHcy hydrolase is not related to the antibacterial activity of neplanocin A and suggest that using this enzyme as a target for the design of antimicrobial agents is not likely to prove a productive approach.

Rhinological manifestations of Paget's disease of bone (Osteitis deformans).

Two cases of Paget's disease of bone are presented in which nasal symptoms were prominent. The clinical and radiographic features of Paget's disease of the maxilla and ethmoids are described. Medical and surgical treatment is discussed with the recommendation that surgery is kept to a minimum and covered by prophylactic antibiotics to prevent osteomyelitis. Sudden enlargement of the involved bones should raise the suspicion of malignancy.

Aspects of body fluid dynam1cs of neonatal calf diarrhoea.

The results of balance studies upon 26 calves, most of which were diarrhoeic and some of which died, demonstrated that: (a) milk intake helped to maintain plasma volume but calves still died: (b) changes in haematocrit were related to milk intake but not to faecal output; (c) the kidney tended to compensate for excess faecal water output. but this function was dependent on the maintenance of adequate plasma volume and therefore on milk intake.

The nasal cycle after deprivation of airflow: a study of laryngectomy patients using acoustic rhinometry.

Previous studies of the nasal cycle in laryngectomy patients using rhinomanometric techniques concluded that the cycle was abolished as a result of the cessation of airflow after laryngectomy. This study was performed with 20 postoperative laryngectomy patients (mean time after surgery 4 years, range: 2 weeks to 10 years) and 10 control subjects matched for age and sex (including 2 preoperative patients). Acoustic rhinometry was used to determine minimum nasal cross-sectional area and nasal cavity volume as the indices of nasal patency. Testing was repeated at intervals of 15-30 min over a period of 3-8 h. Fluctuations in nasal patency were observed in all laryngectomees and controls. The fluctuations were classified as 'classical' (reciprocal alternating) in 5 (25%) laryngectomees and 5 (50%) controls. An 'irregular' pattern of fluctuation was seen in 8 (40%) laryngectomees and 2 (20%) controls. An 'in concert' cyclical pattern was seen in 7 (35%) laryngectomees and 3 (30%) controls. This is the first demonstration of retention of the nasal cycle after airflow deprivation. Whilst the cycle may in some instances be modified after operation, it is not abolished. The central generation of the cycle is confirmed, although afferent input from airflow receptors may play a role in modulating the cycle's pattern and amplitude.

Experimental studies of the resolution of acoustic rhinometry in vivo.

The ability of acoustic rhinometry to detect objects of defined size in nasal cavities has hitherto been investigated only in cadavers and models. We aimed to determine the resolution of the technique in the nose of living subjects. Silicone spheres of 3.0, 5.0, and 7.0 mm diameter were placed at two sites in the decongested and locally anaesthetised nasal cavities of 3 healthy adults. Acoustic rhinometry area-distance functions were obtained before and after insertion of the spheres, with further control data obtained after removal of the sphere from the nasal cavity. Six nasal cavities were studied in each test state on two separate occasions. The 3.0 mm sphere caused a statistically significant change in cavity volumes in only 17% of cases when placed in the middle meatus and in 8% at the nasal value (Mann-Whitney U-test; p < 0.05). The detection rates for the 5.0 mm sphere were 50% in the middle meatus and 50% at the nasal valve. When the control and test curves were compared by superimposition and the cross-sectional areas at the site of perturbations compared statistically (Mann-Whitney U-test) the detection rates in the middle meatus were: 33%-3.0 mm and 67%-5.0 mm sphere. The detection rate at the nasal valve region was 25%-3.0 mm sphere and 58%-5.0 mm. The 7.0 mm sphere was detected in 100% cases by volume changes, and 80% by area changes. Acoustic rhinometry can reliably detect changes of volume and area in the living nose resulting from the introduction of a 7 mm sphere into the nasal valve or middle meatal region in most cases. Smaller spheres are detected in only a fraction of cases. The resolution of the technique is therefore close to 7.0 mm (1.44 cm3). These findings are important when interpreting acoustic rhinometry data in monitoring patients with nasal pathology.

Acoustic rhinometry in the pre-operative assessment of adenoidectomy candidates.

Claims have been made for the potential of acoustic rhinometry (AR) in the evaluation of adenoidectomy patients. Little evidence has been presented to support such claims, and evidence is accumulating that AR is inaccurate in reflecting anatomical reality in the nasopharynx. We set out to establish whether acoustic rhinometry studies could predict operative decision-making sufficiently for it to be of assistance to the clinician, despite these theoretical and practical obstacles. A total of 101 patients aged 2-13 years were examined by AR using the impulse technique. Parameters were chosen from the area-distance function to indicate nasopharyngeal volumes and areas (decongested and non-decongested). This information was compared with findings at EUA (examination under anaesthesia-obstruction categories: A-'good airway' to D-'severe obstruction'), operative decision (2 categories-'obstructive' = remove, versus 'non obstructive' = leave in situ) and parents' symptom scores. Twenty-one patients were also evaluated post-operatively. There was considerable overlap between the AR parameters in the groups classified at EUA as 'obstructive' or 'non obstructive', but this overlap diminished after decongestion. Logistic regression demonstrated that the decongested volume and area parameters were of significant predictive value with respect to operative decision (odds ratio for unit change in volume = 0.82; 95% C.I. = 0.70-0.97; p = 0.018). Parents' analogue scores for snoring and for [snoring+obstruction+ mouthbreathing] were also of significant predictive value. The presence of rhinitis diminishes the predictive value of AR. Acoustic rhinometry has potential as a pre-operative evaluation of the nasopharyngeal airway in adenoidectomy candidates, but the predictive value is low unless combined with clinical factors.

The human nasal mucosa after deprivation of airflow: a study of laryngectomy patients.

The effects on the human nasal mucosa of airflow cessation can be studied conveniently in the laryngectomy patient. We studied 39 laryngectomy patients and 50 healthy adults. Mucociliary clearance was measured using the saccharin test, ciliary beat frequency (CBF) analyzed in inferior meatal brushings and transmission electron microscopical observations made in similar nasal brushings. Mucociliary clearance was no faster in laryngectomees (mean 15.4 +/- 7.8 min); however, CBF was higher in the laryngectomees (means 15.0 and 14.1 Hz; p less than 0.05), especially in the first weeks after surgery (mean 16.8 Hz; p less than 0.01). Mucus-producing cells gradually decreased in proportion over the first postoperative year. The changes in the nasal mucosa after airflow cessation are dynamic and require months to equilibrate. This has implications for the timing of postoperative assessment of patients undergoing airway surgery.

The role of acoustic rhinometry in studying the nasal cycle.

The nasal cycle has been demonstrated in man using several techniques, including magnetic resonance imaging, anterior rhinoscopy, rhinomanometry, all of which have limitations due to expense, discomfort, limited scope or poor reproducibility. Acoustic rhinometry is a new technique which analyses nasal geometry throughout the nasal cavity, not just at the flow-limiting segment. Six adult volunteers were examined at 15-to 30-min intervals using acoustic rhinometry. The classical alternating cycle was seen in three subjects, a non-classical cycle was seen in two, and no cycle seen in one subject. Changes occurred throughout the nasal cavity and corresponded with fluctuations in subjective scores of obstruction and, in one case, with nasal resistance measurements. Acoustic rhinometry is a rapid, reproducible and non-invasive technique. This pilot study demonstrates that it has potential for studying in detail the physiology of the nasal cycle.

Practical aspects of acoustic rhinometry: problems and solutions.

Acoustic rhinometry now has an established place in the rhinology laboratory as a measure of nasal geometry. We aimed to investigate several aspects of technique in order to offer some guidance on preferred procedures. We studied the effects of nosepiece seal quality, nosepiece aperture diameter, angle of inclination of the wave tube (in two planes), palate position and inter-observer variation on the nasal area-distance function. One hundred nasal cavities in adults and children were examined: 50 normal and 50 pathological. Each factor was examined intensively in 20 cavities, and reproducibility data obtained on all 100 cavities. The baseline mean coefficient of variation for nasal cavity volume (V1) was 6% and for minimum cross-sectional area (MCA) was 8%. Altering the angle of incidence of the wave tube in the axial and coronal planes caused considerable change in the traces from the anterior nasal cavity, including the I- and C-notches, and affected the MCA significantly (p < 0.01, Wilcoxon signed rank test). Using a small nosepiece aperture accentuated the I-notch, and the nosepiece in some cases became the site of the minimal area. Addition of a silicone-based sealant to the standard nosepiece caused a mean reduction of 14.3% in nasal volume, if the seal quality was suspected to be suboptimal. Nasopharyngeal volume decreased by a mean of 28.6% when the palate is raised by the modified Valsalva manoeuvre, and no difference was found between quiet oral respiration and cessation of nasal respiration. Acoustic rhinometry is sensitive to minor changes in the details of technique. We recommend using an intermediate range of angles in both planes, the addition of a sealant where the nosepiece seal is suspect, use of newer improved nosepieces and synchronizing readings with either cessation of nasal respiration or with quiet oral respiration. There is a pressing need for international agreement on such details if collaboration and clinical application of acoustic rhinometry is to flourish.

Reduction in junior doctors' hours in an otolaryngology unit: effects on the 'out of hours' working patterns of all grades.

This study aimed to assess the effects of recent controls on juniors' duty hours (the 'New Deal') on the work performed by all grades of ENT medical staff 'out of hours'. For 100 days in 1993 the out of hours duties of all grades of doctor in the Otolaryngology Unit were monitored using daily logs. Three patterns of cover were run in parallel and subjected to comparison: Light: Senior House Officer (SHO)--Consultant (CON); Traditional: SHO-Intermediate (Registrar or Senior Registrar)--Consultant; Cross-cover--Pre-Registration House Officer (PRHO)--Intermediate-Consultant. The SHO 'out of hours' daily workload did not differ significantly between the traditional and light systems (median hours: 5.6 versus 5.0). There was an increase in working hours for the intermediate (registrar or senior registrar) grade of 84 per cent when the cross-cover system was in operation compared with the traditional system (median hours: 5.0 versus 2.8; p < 0.0001--Mann-Whitney U test). Consultant working hours increased by an average of 132 per cent as a result of removal of the intermediate tier (median hours: 1.7 versus 0.80; p < 0.0001). Reduction in on-call hours of junior staff resulted in a need for cross-cover and also in the frequent removal of an intermediate tier of staff. This has been shown to have a considerable effect on working patterns for intermediate and senior grades in an ENT unit of average size. Further reductions would be expected to have major effects on the working patterns of the consultant grade and considerably dilute the emergency experience of trainees.

Osteoma of the external auditory meatus presenting as an aural polyp.

Isolated osteomata of the external auditory canal are benign and often symptomless lesions, and are distinct from the much commoner exostoses. A case is reported in which an osteoma presented as a recurrent 'aural polyp' due to a fibroepithelial polypoid reaction in the overlying skin. The polyp and the osteoma were excised surgically. We believe this to be the first reported case to present in this manner.

Percutaneous tracheostomy in a head and neck unit.

A recent innovation in the technique of tracheostomy is now available as a commercial kit. A standard tracheostomy tube is inserted using a guidewire and dilator as in the Seldinger technique. The kit was used in nine cases in a unit with a head and neck oncology interest. Two failures were experienced but no serious or fatal complications. The technique is limited when applied to necks which are not anatomically 'ideal', and hence will have application in head and neck surgery only after careful patient selection.

Antroscopy: current practice--a survey of UK otolaryngologists.

The use of antroscopy by otolaryngologists in the UK was assessed by means of a postal questionnaire. A response of 70 per cent was obtained. Thirty-three per cent of otolaryngologists currently perform antroscopy; the principal reason for not using the technique being lack of suitable equipment. Twenty-four per cent of non-users believed that antroscopy would not alter their management of patients, and 19 per cent of all responders thought that antroscopy had no proven clinical role. Few surgeons recognized a role for antroscopy in the treatment of antral disease. Antroscopists preferred to operate on in-patients (73 per cent), under a general anaesthetic (60 per cent) and via the inferior meatus (66 per cent); 76 per cent consider that morbidity is insignificant. There is clearly a need for studies clarifying the role of antroscopy in clinical practice and to establish the cost-effectiveness of the technique.

Surgery for external auditory canal exostoses and osteomata.

The popularity of water sports in Western Australia results in a high demand for surgery for meatal exostoses when compared to Europe or North America, and such procedures for advanced exostoses present a technical challenge. We report on a decade of experience in exostosis and osteoma surgery consisting of 127 procedures on 102 patients. Exostectomy was an access manoeuvre for other otological procedures in 13 cases and five procedures were for regrowth of exostoses. Minor complications were seen after 22 per cent of operations. Major complications were experienced after five per cent for example canal stenosis, temporomandibular joint prolapse, sensorineural loss, persistent deep bony lip and persistent tympanic membrane perforation. There were no facial palsies. Exostosis surgery should be reserved for failed conservative treatment and attention focused on adequate access, meatal skin preservation and tympanic membrane protection. An approach which concentrates on safe anterior landmarks and wide exposure is recommended to avoid serious complications.

Improving the reproducibility of acoustic rhinometry: a customized stand giving control of height and angle.

Control and recording of the position of the acoustic rhinometer in relation to the nostrils is important for serial measurements. Several technical factors must be controlled, including the angle of the incident acoustic wave. We describe a simple, newly-designed, rhinometer stand which allows control of height and angle, and hence improves the reliability of serial measurements in clinical and physiological work.

Pulmonary tuberculosis presenting as suspected foreign body aspiration.

Tuberculosis is a disease of protean manifestations, and despite a falling incidence is still prevalent in our society. We present a case of a child whose history and preoperative chest radiograph suggested the presence of a foreign body, but subsequent examination of the material removed at endoscopy revealed a diagnosis of tuberculosis. We suggest that all friable material removed from the lower respiratory tract be submitted for microscopy, culture and histopathology with this diagnosis in mind.

Prophylaxis of nasolacrimal duct obstruction after major sinus surgery using a silicone stent.

Damage to the nasolacrimal duct during major sinus procedures results in troublesome symptoms of epiphora and acute infection. Prophylactic stenting of the lacrimal apparatus using a silicone stent is described as a means of preventing such complications.