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Biomedical subjects

A Tomkinson

Publications and source records attributed to A Tomkinson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Acoustic rhinometry: an explanation of some common artefacts associated with nasal decongestion.

The nasal cavities of 51 healthy volunteers were examined using acoustic rhinometry before and after nasal decongestant. Several specific dimensions were studied, which included the minimum cross-sectional area, and three volumes corresponding to the anterior, middle and posterior regions of the nasal airway. An average acoustic rhinometry trace was constructed for the whole group of subjects, before and after decongestion, from data extracted from the raw data files written to the computer hard disk for each subject. A 27.5% (P < 0.0001) increase in the minimum cross-sectional area was observed, with no shift in its position. The greatest increase in nasal dimensions was seen in the anterior and middle parts of the nose, however, significant changes were also seen in the posterior nasal cavity and post nasal space. There are a number of possible sources of artefact. First, confusion of the first and second minima may produce apparent movement of the minimum cross-sectional area following nasal decongestion. Second, a postulated change in the acoustic path length may lead to apparent changes in volume in certain regions of the nose. Third, a variable and uncontrollable degree of sound energy loss will occur into the opposite nasal cavity beyond the posterior border of the septum. An apparent increase in the dimensions of this region will be seen as the opposite cavity decongests. We feel that all users of the acoustic rhinometer need to be aware of these potential sources of artefact, and attention needs to be focused on an agreed definition of the components of the acoustic rhinometry trace.

Acoustics↗
PubMed1998

Supracricoid laryngectomy: a significant advance in the management of laryngeal cancer.

Supracricoid laryngectomy is a new development in the treatment of laryngeal cancer in Australia. It allows the removal of both vocal cords, vestibular folds, and the entire thyroid cartilage including the paraglottic space without the loss of laryngeal function. This technique may offer a significant advance in the treatment of squamous cell carcinoma of the larynx. This paper reviews the surgical management of laryngeal cancer and discusses this new technique with modifications, indications for its use and the advantages of supracricoid laryngectomy. Case reports of seven patients operated on in our institution are included.

Carcinoma, Squamous Cell↗
PubMed1998

The role of estrogen in the control of rat osteocyte apoptosis.

We have previously shown that estrogen withdrawal by gonadotrophin-releasing hormone analogs (GnRHa) induces osteocyte death via apoptosis in human bone. Although it is likely that the increase in osteocyte death via apoptosis was related to the loss of estrogen, these experiments could not rule out a direct role for the GnRHa. Therefore, in this study, we have used a rat model of ovariectomy (OVX) to determine whether the effect of estrogen withdrawal extends to other species and to clarify the role of estrogen in the maintenance of osteocyte viability. Twelve 9-week-old rats were divided into three treatment groups: sham operated (SHAM) (n = 4), OVX (n = 4), and OVX + estrogen (E2) (25 microg/day) (n = 4). At 3 weeks following the start of treatment, tibial bones were removed. The percentage of osteocytes displaying DNA breaks, using an in situ nick-translation method, was significantly higher in the OVX group compared with the SHAM control in both cortical bone (10.04% vs. 2.31%, respectively; p < 0.0001) and trabecular bone (6.44% vs. 1.58%, respectively; p = 0.003). Addition of estrogen in the OVX animals completely abrogated the increase in osteocyte apoptosis in cortical bone (0.78%) and trabecular bone (1.17%). The percentage of apoptotic osteocytes decreased with increasing distance from the primary/secondary spongiosa interface below the growth plate in the OVX model and the OVX + E2 model. Nuclear morphology and electrophoresis of DNA confirmed the presence of apoptotic cells in the samples. In conclusion, OVX in the rat results in an increase in osteocyte apoptosis as a direct or indirect result of E2 loss. Addition of estrogen in the OVX animals prevents this increase in osteocyte apoptosis. These data confirm an important role for estrogen in the control of osteocyte apoptosis and the maintenance of osteocyte viability. Estrogen deficiency might, through compromising the viability of osteocyte networks, reduce the ability of bone to respond appropriately to loading.

Animals↗
PubMed1997

The pathophysiology of otitic hydrocephalus.

The pathophysiology of otitic hydrocephalus remains controversial. It has been argued that involvement of the superior sagittal sinus, by, at least, a mural thrombus is a necessary component of this disease. We present a case of otitic hydrocephalus where on magnetic resonance imaging (MRI) normal luminal and mural flow within the superior sagittal sinus is demonstrated. The presence of thrombus in the lateral venous sinus alone appears sufficient in this case to impede venous drainage of the intracranial contents into the neck and produce a rise in the cerebral venous pressure and a subsequent increase in the CSF pressure. The presence of a superior sagittal sinus mural thrombus is not required.

Child↗
PubMed1997

The death of osteocytes via apoptosis accompanies estrogen withdrawal in human bone.

Estrogen withdrawal in women leads initially to rapid bone loss caused by increased numbers or activity of osteoclasts. We previously have noted apoptosis of lacunar osteocytes associated with conditions of high bone turnover. Therefore, in this study, we investigated whether the increased bone loss associated with GnRH analogue (GnRH-a)-induced estrogen withdrawal affects osteocyte viability in situ in a way that would be directly contrary to the effect of estrogens on osteoclast viability. Transiliac biopsies were obtained from six premenopausal women, between 30-45 yr old, diagnosed as having endometriosis. Biopsies were taken before and after 24 weeks of GnRH-a therapy. Biopsies were snap-frozen and cryostat sectioned. Osteocyte viability, determined by the presence of lactate dehydrogenase (LDH) activity, was reduced in all but one subject after treatment. Furthermore, in every subject, the proportion of osteocytes showing evidence of DNA fragmentation typical of apoptosis increased, as demonstrated using in situ DNA nick translation (P = 0.008). Gel electrophoresis of extracted DNA and morphological studies of chromatin condensation and nuclear fragmentation confirmed that changes typical of apoptosis were affecting the osteocytes. It was concluded that GnRH-a therapy caused a higher prevalence of dead osteocytes in iliac bone, probably caused by the increase in the observed proportion of osteocytes showing apoptotic changes. The capacity of bone to repair microdamage and to modulate the effects of mechanical strain is currently believed to be dependent on osteocyte viability. Our findings have therefore revealed a possible mechanism whereby estrogen deficiency could lead to increased bone fragility with or without an accompanying net bone loss.

Adult↗
PubMed1997

Patterns of hospital attendance with epistaxis.

The age and sex distribution of epistaxis admissions to hospital was examined. A retrospective analysis of 6,885 patients admitted to hospitals in the whole of Wales was performed, over a period of five years. The findings were compared with data from the 1991 National Population Census for the same region, thus providing a more representative estimate of the behaviour of this disease. A clear age relationship is demonstrated, with the incidence of epistaxis increasing rapidly after the age of 40 years. The female-to-male ratio is also age dependent. In the group aged between 20 to 49 years twice as many males as females were admitted, where no sex difference was expected from the population data. This difference was not present in the group aged 50 years and over where the ratio was similar to that in the underlying population. There was a 1.6 fold difference between the sex ratios of the two groups (95% confidence intervals of 1.9 to 1.4; p < 0.0001). It is possible that the female pre-menopausal state may provide a significant protection from this disease. The mechanism for this is unknown, but may be secondary to a direct effect of oestrogen on the nasal mucosa or vasculature, or the healing of vessels in this region. Alternatively, this observation may simply be a reflection of protection the pre-menopausal state provides against cardiovascular disease in general.

Adolescent↗
PubMed1996

Tympanic thermometry and minor ear surgery.

Infra-red tympanic thermometry is a relatively new technique for measuring body temperature which requires the minimum of co-operation and is quick and easy to use. It is therefore ideal for use in children. Its use is becoming more widespread and as it is theoretically possible that minor ear surgery may interfere with function its reliability in these patients may be in question. Twenty-two children (mean age 5.3 years) who underwent myringotomy +/- grommet insertion had the tympanic temperature of each ear measured immediately before, and 15 minutes after, surgery on the recovery ward. No difference was found between the pre- and post-operative temperatures (mean difference--0.1 degree C, p > 0.1, paired t-test, hypothesized difference of 0). This thermometer appears to be a reliable way of monitoring body temperature on a paediatric ENT recovery ward in patients who have undergone minor ear surgery.

Adolescent↗
PubMed1996

Treatment of acute auricular haematoma.

Auricular haematoma is a problem frequently complicated by recurrence due to failure to apply adequate pressure over the pinna following simple drainage. We describe a simple method of splinting the pinna using silicone putty which overcomes this problem.

Acute Disease↗
PubMed1996

Pharyngocutaneous fistula following total laryngectomy and post-operative vomiting.

The significance of post-operative vomiting as a risk factor in the development of a pharyngocutaneous fistula was examined. The case records of 50 consecutive patients undergoing laryngectomies (39 men, 11 women, average age 64 years) were examined, 17 also underwent a simultaneous radical neck dissection. A fistula developed in eight patients (16%) and the median time to its diagnosis was 11 days (range 3-15 days). Several potential risk factors were examined including age, gender, previous radiotherapy, TNM stage, differentiation of tumour, simultaneous radical neck dissection and also the occurrence of vomiting post-operatively. In this series of patients only vomiting in the early post-operative period appeared to be related to the development of a fistula (regression summary: R2 = 0.6, t-value 5.6, P < 0.0001). An episode of vomiting was recorded in eight patients and of these six (75%) subsequently developed a fistula. The median time of post-operative vomiting was 7.5 days (range 1-10 days) and the diagnosis of a fistula occurred at a mean of 1.2 +/- 0.4 days after the episode of vomiting. In a study of this nature it is not possible to conclude that a causal relationship exists between vomiting and fistula development. However, if this is the case a potential means of decreasing the incidence of fistulae following laryngectomy may be available.

Female↗
PubMed1996

Acoustic rhinometry: do we need a standardized operating procedure?

The usefulness of a standardized operating procedure for acoustic rhinometry was assessed in a study on 51 healthy volunteers. Nasal measurements were made with acoustic rhinometry before and after application of a topical nasal decongestant. Our standard operating procedure used three consecutive readings of anterior nasal volume to obtain a valid estimate of mean nasal dimensions. The mean measurement was only accepted as valid if the three readings had a coefficient of variation (CV) of less than 20%. Twenty-two out of 192 (11.5%) nasal cavities required more than three consecutive readings to achieve this. Our data show that the error encountered by relying on a single reading of an acoustic trace can be greater than the changes caused by the topical nasal decongestant and that multiple readings using a standard operating procedure are essential to obtain valid data.

Acoustics↗
PubMed1996

The effect of isoenzyme-selective PDE inhibitors on methacholine-induced contraction of guinea-pig and rat ileum.

1. We have examined the effects of the isoenzyme-selective phosphodiesterase (PDE) inhibitors, vinpocetine (type 1), siguazodan (type 3), rolipram (type 4) and zaprinast (type 5) and the non-selective PDE inhibitor enprofylline on methacholine (MCh) contractile concentration-response curves on guinea-pig and rat isolated ileum. 2. In guinea-pig ileum, vinpocetine (10-300 microM), zaprinast (1-300 microM) and enprofylline (100-1000 microM) produced a concentration-dependent depression of the maximum response (Emax) to MCh only without effect on the MCh EC50 values (rank order of potency: zaprinast > vinpocetine > enprofylline). In contrast, siguazodan (10-300 microM) and rolipram (10-300 microM) produced a rightward displacement of the MCh concentration-response curve (increase in EC50: rank order; rolipram > siguazodan), with effects on the MCh maximum seen only at higher concentrations. 3. In the rat ileum, vinpocetine (10-300 microM), zaprinast (0.1-300 microM) and enprofylline (100-1000 microM) caused depression of the MCh maximum contraction (rank order: zaprinast > vinpocetine > enprofylline). Low concentrations of rolipram and siguazodan had no significant effect on the MCh maximum. In the presence of higher concentrations (> 100 microM) of rolipram and siguazodan, a maximum response was not achieved at the highest concentration of MCh tested. As in the guinea-pig ileum, only rolipram (10-300 microM) and siguazodan (10-300 microM) produced a significant, concentration-dependent, rightward displacement of the MCh concentration-response curve (increase in EC50: rank order: rolipram > siguazodan). 4. In the guinea-pig ileum, isoprenaline (0.1 microM) produced a rightward displacement (approximately 3 fold) of the MCh concentration-response curve, accompanied by a significant depression of the maximum response. Increasing the isoprenaline concentration (1 microM) had no further effect on either parameter. Sodium nitroprusside (SNP, > or = 10 microM) produced a concentration-dependent depression of the MCh maximum without an effect on the EC50. 5. In the rat ileum, isoprenaline (1 microM) produced a concentration-dependent rightward displacement (approximately 2.8 fold) of the MCh concentration-response curve with depression of the MCh maximum at higher (> or = 100 microM) concentrations. SNP produced depression of the MCh maximum at a concentration of 10 microM and above. Effects on the MCh EC50 were seen only at 100 and 300 microM. 6. In guinea-pig ileum, isoprenaline (0.1 microM) in combination with rolipram (10 microM) further increased the MCh EC50 and reduced the MCh maximum. The combination of SNP (10 microM) with zaprinast (0.1 microM) produced no further significant effect than SNP alone. 7. In rat ileum, isoprenaline (1 microM) in combination with rolipram (10 microM) further increased the EC50 and reduced the maximum. SNP (10 microM) had no significant effect on either the MCh maximum or EC50. A combination with zaprinast (1 microM) had no further effect. 8. In conclusion, all the PDE inhibitors tested produced a concentration-dependent inhibition of the MCh concentration-response curve, indicating a modulator role for the PDE isoenzymes in gastrointestinal smooth muscle contractility. The PDE inhibitors that elevate cyclic GMP produced a depression of the MCh maximum response only, whilst those that elevate cyclic AMP produced a rightward displacement of the MCh concentration-response curve. This was confirmed by the use of isoprenaline and SNP. This difference in the type of inhibition produced by these PDE isoenzyme inhibitors may reflect a different intracellular site/mechanism by which the cyclic AMP- and cyclic GMP-activated kinases act functionally to antagonize the contractile response.

Animals↗
PubMed1996

The effect of changes in ambient temperature on the reliability of acoustic rhinometry data.

The effect of changing ambient temperature on the reliability of acoustic rhinometer data was examined. The acoustic rhinometer was set up in a climate chamber, and connected to a simple cylindrical model containing a constriction. This constriction was at 22.5 cm from the microphone. This would be the position of the tip of a 7.5-cm nose piece, relative to the microphone, when attached to the rhinometer. The ambient temperature was increased from 10 degrees C to 40 degrees C. The position of the constrictions as recorded by the acoustic rhinometer was compared in the same stable model at intervals during the temperature increase. The point of identification of the constriction varied with ambient temperature and the change almost perfectly followed the expected changes in the readings given the relationship of the speed of sound in air to ambient temperature. A shift of approximately 1 mm along the X-axis per 2.5 degrees C change in temperature is seen for this constriction. In a human subject the whole acoustic rhinometry trace would shift along the X-axis to the same degree when using a 7.5-cm nose piece. Volume estimates are calculated between two fixed points on the X-axis and may be profoundly affected by even a small shift of the acoustic reading along this axis. Acoustic rhinometry data should always be collected under the same stable environmental conditions.

Acoustics↗
PubMed1995

Palatal myoclonus affected by neck position.

Palatal myoclonus is defined as a continuous, rhythmic contraction of the palatal musculature. Reverberant neuronal activity in a region of the brain stem known as the Guillain-Mollaret triangle is believed to underlie this condition. We present a case of palatal myoclonus which could be abolished by anterior neck flexion. The pathology and management of this condition is briefly discussed.

Female↗
PubMed1995

External facial dimensions and minimum nasal cross-sectional area.

The relationship of the total minimum nasal cross-sectional area of the decongested nasal cavity to specific, easily measured, facial dimensions was examined. The nasal cavities of 51 healthy volunteers were examined using acoustic rhinometry following nasal decongestant and their minimum nasal cross-sectional area was estimated. This was compared with several personal characteristics, including height and weight, facial width and height, inter-canthal width, and nasal height, alar breadth and the nasal triangular area (half the product of nasal height and alar breadth). The total minimum nasal cross-sectional area showed a good correlation with both the alar breadth, 0.55 (P < 0.0001) and the nasal triangular area, 0.62 (P < 0.0001). No significant correlation was seen with the remaining personal characteristics. The results suggest that it may be possible to produce a clinically useful formula that would be able to predict the expected normal total minimum cross-sectional area of the nasal cavity from these external dimensions. This predicted cross-sectional area could be compared with that measured by acoustic rhinometry. This may prove of value to a clinician wishing to establish if a given patient has a pathologically narrow nasal cavity.

Adolescent↗