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Biomedical subjects

D W Morgan

Publications and source records attributed to D W Morgan.

At least 91 records · Page 5Linked to original sources
PubMed1990

Cellular and extracellular phospholipase A2 activity in zymosan pleurisy in rat.

The pleural exudate from rats treated intrapleurally with zymosan contains phospholipase A2 (PLA2) activity which is Ca2(+)-independent and optimally active at a neutral pH. This PLA2 activity was found in approximately equal amounts in both the cellular and extracellular fractions of the exudate. The Ca2(+)-independency of the PLA2's in the pleural exudate distinguishes them from plasma PLA2's and this suggests that the source of the exudate PLA2's is not plasma. The appearance of PLA2 activity in zymosan-induced pleural exudate correlates temporally with increases in exudate volume and pleural cell number. In all cases, the maximum response was seen 24 hr after zymosan challenge. All parameters of pleurisy and PLA2 activity are similarly sensitive to the steroid dexamethasone which has been hypothesized to act, in part, through the synthesis of PLA2 inhibitory peptides. In its entirety, this information suggests that there is a relationship between pleural PLA2 activity and the appearance of pleural inflammation (exudate volume and cells) and that PLA2 may play an important role in the initiation and propagation of this inflammatory process in rats. Furthermore, the zymosan-induced pleurisy model may serve as a useful model for the identification of PLA2 inhibitors with antiinflammatory activity.

Animals↗
PubMed1990

Current management of choanal atresia.

Recent advances in the management of choanal atresia are outlined in the context of our experience at the Hospital for Sick Children, Great Ormond Street, London. Fifty cases were treated over the 6-year period 1982-1988. There was a 72% incidence of other associated congenital anomalies and 30% of patients had the CHARGE association. The advantages and pitfalls of pre-operative computerised axial tomography are illustrated. The surgical results and complications following the trans-nasal approach are discussed. Eighty-four percent of patients had their atresias successfully corrected, 12% restenosed to some extent, and 4% obliterated. The most significant complications were palatal fistulae (8%) and columella ulceration from the Portex tube stents (8%).

Choanal Atresia↗
PubMed1990

Unusual case of bilateral conductive deafness.

A 30-year-old female presented with a ten-year history of bilateral conductive deafness. A pre-operative diagnosis of otosclerosis was made but at tympanotomy, the stapes crura in each ear was found to be disconnected from the footplate, the ossicular chain being otherwise normal. A Teflon-wire prosthesis was used to join incus and footplate, with good results. In the absence of a history of trauma or sepsis this may be a late presentation of a congenital stapedial anomaly which has not previously been reported.

Adult↗
PubMed1990

Hearing loss due to cranio-metaphysial dysplasia.

Craniometaphysial dysplasia is a rare cause of conductive hearing loss. It is a genetic disorder of bone due to decreased osteoclastic activity in the endosteal and periosteal regions of craniofacial and long bones. The characteristic temporal bone abnormalities are attic fixation, abnormally shaped ossicles and obliterated foramina ovale. Computerised tomography is helpful in predicting operative findings; surgery should be reserved for those with a severe hearing loss.

Adult↗
PubMed1990

Developmental nasal anomalies.

Despite the complex embryological development of the nose and surrounding structures, significant developmental nasal anomalies are rare. We therefore present our experience in the management of such anomalies (excluding choanal atresia) over the past 10 years. Fifty cases were surgically treated; two nasopharyngeal cysts, four hairy polyps, two meningoencephalocoeles, seven gliomata, 20 dermoids, two capillary haemangiomata, four fibromas, one fibromyxyoma, one mucocoele, one granuloma, one lipoma, two nasal aplasias, two nasal clefts and one nasal web. All cases presented with nasal obstruction and/or as a nasal mass. Computerized tomography and magnetic resonance imaging aided diagnosis determining the extent of intracranial involvement. Various surgical techniques were used ranging from simple excision to the lateral rhinotomy and Goodman's external rhinoplasty approach. Only five patients (10 per cent) suffered complications; two CSF leaks and three recurrences, all treated successfully.

Child↗
PubMed1990

Who's in CHARGE? Multidisciplinary management of patients with CHARGE association.

Clinical experience of 50 patients with the CHARGE association is reviewed and problems with management of children born with multiple system involvement is highlighted. It was found that the outlook for survival was poor if more than one of the following three features was present: cyanotic cardiac lesions, bilateral posterior choanal atresia, or tracheo-oesophageal fistula. Mortality was largely due not to the structural heart defects or choanal abnormalities, but reflected underlying pharyngeal and laryngeal incoordination, which resulted in aspiration of secretions. Outcome is likely to be improved if collaboration between specialist surgical teams allows necessary procedures to be performed using the minimum number of anaesthetics. Examination of both the short and long term management of these children has stressed the importance of a multidisciplinary approach to their care.

Abnormalities, Multiple↗
PubMed1990

Effects of a prolonged maximal run on running economy and running mechanics.

The purpose of this study was to document the effects of a prolonged (30 min) maximal run (PMR) on running economy (RE) and running mechanics in 16 male runners (mean VO2max = 59.0 +/- 4.5 ml.kg-1.min-1). After completing 60 min of treadmill accommodation, each subject performed two 10 min economy runs at 200 m.min-1. Subjects were also filmed at 100 fps during the last 30 s of each run in order to quantify 20 temporal, kinematic, and kinetic gait descriptors previously associated with RE variation. Following the second run, each subject completed the PMR at 85% of his predicted velocity at VO2max (89% VO2max). One, two, and four days after the PMR, subjects repeated the 10 min economy run. No significant difference (P greater than or equal to 0.05) in RE (range = 42.3-42.6 ml.kg-1.min-1) was observed following the PMR. Biomechanical analyses also indicated that, with the exception of one variable (plantar flexion angle at toe-off), gait characteristics remained unaltered after the PMR. When considered from a cross-disciplinary perspective, these data suggest that a 30 min maximal run does not increase the aerobic demand of running or disrupt the running mechanics of moderately trained male subjects who perform subsequent submaximal runs over the short term.

Adult↗
PubMed1989

Clinical evaluation of propofol as an intravenous anaesthetic agent in cats and dogs.

The clinical efficacy and safety of an emulsion containing 10 mg/ml of the intravenous anaesthetic propofol were evaluated in cats and dogs by veterinary surgeons in eight practices in the United Kingdom. A total of 290 dogs and 207 cats were anaesthetised with propofol either as a single injection for procedures of short duration, or as an induction agent with maintenance provided by further incremental injections or as an induction agent with maintenance by gaseous agents. The mean induction doses of propofol for unpremedicated dogs and cats were respectively 6.55 mg/kg and 8.03 mg/kg. The mean induction doses after premedication with a tranquilliser were 4.5 mg/kg and 5.97 mg/kg for dogs and cats, respectively. Mean recovery times ranged, depending on the method of anaesthesia, from 23 to 40 minutes in dogs and from 27 to 38 minutes in cats; recovery was defined as the time at which the animals were alert and able to stand. Adverse side effects were infrequent, apnoea during induction being the commonest. Acepromazine and atropine were most often used as premedicants although in a few cases diazepam, xylazine and other agents were employed. No clinical incompatibility was observed between propofol and any of the other agents administered during the study. The rapid and usually excitement-free recovery of the animals was a valuable feature of anaesthesia with propofol.

Anesthesia, Intravenous↗
PubMed1989

Experience with the home-care of tracheotomised paediatric patients.

Many infants with tracheotomies remain cannulated for prolonged periods while the underlying cause of airway obstruction is either treated or natural resolution is awaited (usually by growth). To enable these children to enjoy a relatively normal family environment despite a tracheotomy, it is desirable that they should be managed at home for at least part of the time. For the past 8 years we have routinely used soft polyvinyl chloride paediatric tracheotomy tubes (Shiley) in our patients. These tubes have proved to be relatively resistant to obstruction with secretions and are changed at 1- to 2-week intervals. They can be modified by making a series of three to four 2-mm through-and-through fenestrations around the shoulder in order to improve speech production and facilitate decannulation. Parents are tutored in tracheotomy care, which includes tube changing, humidification and suction. They are then permitted to take their child home from hospital when they are considered to be competent. Twenty-eight children (13 boys, 15 girls) with a mean age of 14.5 weeks (range 1-525 weeks) at the time of tracheotomy have been managed at home using this system. The median period of hospitalisation was 12 weeks (range 5-75 weeks), and the median duration of home management was 94 weeks (range 13-394 weeks). Sixteen patients have been successfully decannulated, 11 remain cannulated and 1 died at home from sudden infant death syndrome. Despite supportive measures, the majority of the children developed intermittent chest infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1989

Swimming in chlorinated water and its effect on Eustachian tube function.

Middle-ear effusion in children is considered to be the result of multiple factors. Swimming in chlorinated water has been incriminated as one such possible aetiological factor. To test the hypothesis that the chemical disinfectant in the swimming pool is probably responsible for the Eustachian tube dysfunction, 30 children between the ages of four and eight years were selected at random from the community health department computer records and were randomly allocated into two groups. Eustachian tube function was assessed by standard tympanometry both immediately prior to swimming (control) and 30 to 45 minutes following swimming in Group 1 and approximately 14 hours following swimming in Group 2. The results of the study showed no significant change (p greater than 0.05) between pre- and post-swimming tympanometry. It is therefore concluded that swimming on the surface of chlorinated water does not compromise the Eustachian tube function in children with healthy middle ears.

Acoustic Impedance Tests↗
PubMed1989

Nasal polyps and sinusitis in children with cystic fibrosis.

Eighteen children suffering from cystic fibrosis and nasal polyps were studied. Two patients presented with nasal polyps at two years of age; the remaining patients had an initial polypectomy at any age up to fifteen years (mean age of seven and a half years). There were no obvious correlations between the cultures of the sinus washouts and the corresponding sputum samples. Organisms were only grown from five of the fifteen wash outs and from nine of the sputum samples. The patients with severe polyposis were not obviously more atopic.

Adolescent↗
PubMed1989

Longitudinal changes in distance-running performance of young males.

Longitudinal studies of adolescent males have shown that absolute maximal aerobic power (VO2max) and distance-running performance improve with age, while VO2max expressed relative to body mass remains stable. These earlier studies used subjects that were engaged in distance-run training; therefore, it was not possible to assess the relative importance of growth and/or run training to improved performance. The purpose of this study, therefore, was to quantify longitudinal changes in VO2max, running economy (RE), and distance-running performance in non-run-trained young males. Six subjects were tested at mean ages of 9.9 (T1) and 16.8 years (T2). Statistical tests of mean values revealed that over the 7-year period, relative VO2max remained unchanged (T1, 48.9 ml.kg-1.min-1; T2, 47.8 ml.kg-1.min-1) and RE improved (T1, 234.2; T2, 202.8 ml.kg-1.km-1), 9-min run distance increased (T1, 1637 m; T2, 2115 m), and the estimated percent of VO2max incurred during the 9-min run increased from 85.8% (T1) to 99.5% (T2). It was concluded that the improvement in distance-running performance observed in adolescent boys was not dependent upon run training. In view of the fact that maximal aerobic power remained stable, this change appears to be attributable to better running economy and an ability in runs of a fixed duration to perform at a higher relative work load.

Adolescent↗
PubMed1989

Ten kilometer performance and predicted velocity at VO2max among well-trained male runners.

Previous research (study 1) has shown that a significant relationship exists between 10 km run time (RT) and predicted running velocity at VO2max (vVO2max) among well-trained males heterogeneous in VO2max. Since competitive runners often display a homogeneous fitness profile, the purpose of this study was to determine the association between 10 km RT and vVO2max among a group of trained runners exhibiting nearly identical VO2max values (study 2). Running economy (RE), vVO2max, and velocity at a 4 mM blood lactate concentration (v at 4 mM BL) were calculated in both studies. Correlations were obtained as shown in Table 2. The relationship between VO2max and 10 km RT achieved statistical significance only in study 1, while RE explained a greater amount of performance variation in study 2. In both studies, variation in 10 km RT attributable to vVO2max was similar and exceeded that due to either VO2max or RE. vVO2max also accounted for essentially the same amount of variation in 10 km RT as did v at 4 mM BL. It was concluded that, among well-trained subjects homogeneous in VO2max, a strong relationship exists between 10 km RT and vVO2max that appears to be mediated to a large extent by RE.

Adult↗
PubMed1989

Factors affecting running economy.

Running economy, defined as the steady-state VO2 for a given running velocity, has been shown to account for a large and significant proportion of variation in distance-running performance among runners roughly comparable in VO2 max. Despite this recognition, relatively little is known regarding the potpourri of physiological, environmental, structural and mechanical factors potentially associated with a lower aerobic demand of running. Early attempts at quantifying the energy expenditure of exhaustive runs incorporated measurements of oxygen consumption before, during, and after exercise. The validity of this approach has been questioned, however, since recent evidence has demonstrated that only a moderate relationship exists between postexercise VO2 and anaerobic metabolism. The energy demands for submaximal running (i.e. running economy) can be quantified by calculating the steady-state VO2, expressed with respect to body mass and time, for a standardised, submaximal running speed. Since this variable represents the aerobic demand of running, the generation of energy must derive wholly from cell respiration and not from substantial protein catabolism. Research has indicated that at low to moderate work rates, the steady-state energy condition is attained in about 3 minutes. Trained individuals reach steady-state sooner than unfit subjects. While limited by methodological constraints, the existence of a steady-state has also been verified by the lack of blood lactate accumulation and the presence of a respiratory exchange ratio of less than 1.00. The ability of economy, either singly or in combination with VO2 max, to account for a substantial portion of performance variation among trained distance runners and untrained subjects of comparable ability and fitness level has been demonstrated in recent cross-sectional studies. Limited data from short and long term longitudinal research also suggests that endurance running success is linked to training and growth-related improvements in economy. Intraindividual variation in economy has been shown to vary between 2% and 11% for a given speed. Most of this variation can probably be attributed to biological error. While the majority of evidence does not support a gender difference in running economy, data from some studies suggest that males may be more economical than women. Prepubescent children are less economical than older children and adults, whereas older adults exhibit the same trend when compared to younger counterparts. Because of air and wind resistance, the aerobic demands of indoor treadmill running significantly underestimate the cost of overground running, especially at higher speeds.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical Phenomena↗
PubMed1989

Tumors of the minor salivary glands.

Ten to 15% of all salivary gland tumors arise from the minor salivary glands, which are distributed throughout the upper aerodigestive tract. Most of these tumors occur in the oral cavity, and there is a much higher incidence of malignancy than is the case with the major salivary glands. The pathologic appearance, clinical features, treatment, and prognosis of minor salivary gland tumors are discussed. Particular reference is made to the role of adjuvant radiotherapy in improving the control rate after surgical excision.

Humans↗
PubMed1989

Salivary disease in childhood.

Salivary disease in childhood is uncommon. Clinical features are much the same as in adult disease, however, congenital, inflammation, and functional disease is more common. Management is governed by the same general principles in all age groups. Congenital abnormalities are rare. Inflammation, either bacterial or viral, is the most common disease. Chronic sialadenitis usually resolves at puberty. Neoplasia is rare, and the majority of tumors are benign and occur in the parotid gland. Malignancy is suggested by rapid growth, pain, skin fixation, and lymphadenopathy. Surgical treatment of sialorrhea should only be considered after careful assessment. Relocation of the submandibular ducts is the treatment of choice.

Adolescent↗
PubMed1988

Salivary gland tumours studied by means of the AgNOR technique.

Difficulty is sometimes encountered in distinguishing between pleomorphic adenoma, adenoid cystic carcinoma and adenocarcinoma, especially in small biopsies from salivary glands. The argyrophil (AgNOR) staining technique for nucleolar organizer regions (NORs) has been applied to a series of benign and malignant salivary gland tumours. We studied 35 salivary gland tumours, 13 benign and 22 malignant. In all specimens clearly defined silver-stained intranuclear AgNOR dots were visible. The differences between the numbers of AgNORs in the benign and malignant groups, notably pleomorphic adenomas, adenoid cystic carcinoma and adenocarcinoma, were highly significant. In view of this difference we propose that the AgNOR staining technique is of diagnostic help in distinguishing between these salivary gland tumours.

Histocytochemistry↗