Biomedical subjects
Publications and source records attributed to D B Mitchell.
In assessing the usefulness of the acoustic reflectometer we have evaluated its performance on a selected group of patients, finding it to be of equivalent predictive value to those screening tests in common use. We feel that the advantages of the instrument combined with its performance will provide the general practitioner with a useful diagnostic aid.
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Larsen's syndrome is known to have an association with laryngomalacia and tracheomalacia. We report a case of Larsen's syndrome with respiratory difficulty due to a tracheal stenosis. To our knowledge, this association has not previously been reported.
We report 3 cases of severe tracheobronchomalacia associated with laryngeal cleft. Each of these children had a major cleft, type 3 in Evans' classification. Separately each of these conditions are difficult to treat, in combination these major airway anomalies caused management problems of great complexity. We describe the presentation of these cases, the diagnosis of the lesions and the management paths we followed. We discuss the pathology of the conditions and the diagnostic options which are available for defining the extent of responsibility of each component to the overall clinical picture. We discuss the therapeutic options available and describe our own management regime.
Recurrent meningitis in children is not only a potentially life threatening condition, but often involves the child in the trauma of repeated hospital admissions and multiple and invasive investigations to try and find an underlying cause. Symptoms and signs of CSF rhinorrhoea or otorrhoea are infrequent in these patients. Unilateral deafness may be difficult to diagnose in the young child. Full ENT examination may be normal. We report seven cases of children with recurrent meningitis in whom inner ear abnormalities were only indicated as the site of entry of infection by hypocycloidal tomography or high resolution CT scanning of the temporal bone. Subsequent tympanotomy confirmed the site of the CSF leak as the oval window in the majority of cases; packing the vestibule with muscle halted further attacks in these patients.
The present research tested Tulving's (1985) ternary memory theory. Young (ages 19-32) and older (ages 63-80) adults were given procedural, semantic, and episodic memory tasks. Repetition, lag, and codability were manipulated in a picture-naming task, followed by incidental memory tests. Relative to young adults, older adults exhibited lower levels of recall and recognition, but these episodic measures increased similarly as a function of lag and repetition in both age groups. No age-related deficits emerged in either semantic memory (vocabulary, latency slopes, naming errors, and tip-of-the-tongue responses) or procedural memory (repetition priming magnitude and rate of decline). In addition to the age by memory task dissociations, the manipulation of codability produced slower naming latencies and more naming errors (semantic memory), yet promoted better recall and recognition (episodic memory). Finally, a factor analysis of 11 memory measures revealed three distinct factors, providing additional support for a tripartite memory model.
This prospective study was designed to asses whether the results of reducing simple fractures of the nasal bones were different using local or general anaesthesia. Two consecutive groups of 50 patients had their fractures manipulated under (a) general, or (b) local anaesthesia. The results of reduction as assessed by the patients and surgeons were not significantly different between the 2 groups. The reoperation rate for nasal obstruction and external deformity was similar in the 2 groups. We suggest that fractured nasal bones may be reduced under local anaesthesia without detriment to the results. This represents a significant saving of hospital resources.
We focus on the issue of whether cognitive effort is causally related to memory. We begin with a discussion of the concept of cognitive effort as derived from capacity models of attention. We then suggest that the theoretical analysis of memory may involve concepts from different levels of psychological analysis, and we draw a distinction between concepts that represent boundary conditions and sufficient cause. When applied to memory phenomena, attentional concepts serve only as a boundary--or limiting--function in memory theory. In contrast, concepts that represent memorial processes serve as a sufficient cause function. In some instances, cognitive effort appears to have been used as a sufficient cause concept, resulting in some confusion. A review of the literature reveals a haphazard correlation between indexes of cognitive effort and of memory performance. Alternatively, the application of cognitive effort or capacity to the memory performance of certain populations (clinical, children, and elderly) illustrates a potentially more appropriate use of the concept.
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Laryngeal carcinoma in childhood is rare and most commonly classified as squamous cell carcinoma. Although mucoepidermoid carcinoma of the larynx has been noted in adults, it has not previously been reported in a child. A 13-year-old boy presented to our department with an epiglottic mass which was determined histologically to be mucoepidermoid carcinoma. A total epiglottectomy was performed and one year postoperatively the child is without disease.
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The current experiments investigated the longevity of repetition priming and dissociations between different memory measures. Picture-naming latencies revealed robust repetition priming in four separate studies: Previously named pictures were named faster than new pictures. The magnitude of this naming facilitation was stable across 1 to 6 weeks. The apparent temporal invulnerability of repetition priming was in marked contrast to the decline in episodic recognition memory across 6 weeks, suggesting a dissociation between implicit and explicit memory. Additional evidence of this dissociation was observed within each session: Naming facilitation for repeated pictures occurred regardless of whether those particular pictures were consciously recognized.
We assessed the utility of liver-targeted vesicles as a drug delivery system for the treatment of liver diseases. Small, unilamellar vesicles (mean diameter, 60-80 nm) composed of dipalmitoylphosphatidylcholine, cholesterol, dipalmitoylphosphatidylglycerol and digalactosyldiacylglycerol (mol ratios, 40:40:5:15) are rapidly cleared from the blood in rats after intravenous injection. In vivo organ distribution shows that the liver is the major site of vesicle accumulation, with roughly 60-80% of the vesicle contents delivered to the liver. Isolated, perfused rat liver experiments show that the uptake is due to the hepatic asialoglycoprotein receptor, and the uptake process occurs with minimal vesicle leakage. At low doses of the vesicles, the single pass extraction by the liver is around 50%, which means that this vesicle formulation operates close to optimal efficiency as a drug delivery system to the liver. Binding of vesicles to the liver was determined to saturate at 6.5 mg total lipid/kg body weight, with a maximum steady-state turnover rate of vesicles at 37 degrees C of 79 micrograms lipid/min per kg body weight. This gives a receptor recycling time of around 80 min. We have incorporated this information into a pharmacokinetic model of vesicle distribution which quantitatively predicts the kinetics and dose dependence of vesicle uptake by the liver in vivo. This information can be used to optimize vesicle-mediated drug delivery to the liver.
The natural growth of a frontal sinus osteoma is documented in a series of radiographs taken over a period of 17 years in a patient attending St. Thomas' Hospital with untreated acromegaly.
We report the largest single-centre series in the literature of laryngeal cysts in infants. Most of these children presented with stridor within the first two weeks of life, and were found to have a supraglottic or vallecular cyst. Early endoscopic de-roofing of the cyst is the recommended form of treatment.
Younger adult students between 19 and 24 years of age (M = 21.3 years), older adult students between 61 and 76 years of age (M = 67.9 years), and older adult nonstudents between 62 and 76 years of age (M = 68.5 years) were assessed for health (self-ratings of physical and mental health), social functioning (self-ratings of physical and mental activity, perceived role activity level, perceived roles, locus of control, and age-norm expectations), and cognitive functioning (Wechsler Adult Intelligence Scale-Revised vocabulary and block design, and paired associate memory). Age differences were observed in self-ratings of health, social roles, intellectual performance, and memory. No student status differences were observed. The results are discussed in terms of plasticity of intellectual function and characteristics of student status in later adulthood.
The role of semantic memory activation in accounting for generation effects and reality monitoring was investigated in young and old normal adults and in patients with dementia of the Alzheimer's type (DAT). Both young and old normal adults demonstrated higher recall for internally generated information than for externally presented information, whereas the DAT patients failed to demonstrate a generation effect. Similarly, reality monitoring scores (discrimination between internal and external items) were high for both age groups of normals, but near chance levels for the DAT group. These results implicate semantic memory as an important factor in generation effects.
A major goal of our laboratory has been the development of primary culture systems that retain differentiated functions and responses characteristic of intact tissues in vivo. Specifically, we have developed cellular models of primary cultures of rat heart, liver, and kidney cells to explore the mechanisms by which drugs or chemicals may be toxic to key organs of the body and to develop new techniques by which xenobiotics may be evaluated or identified as potential toxicants to living systems. The purpose of this paper is to describe our rationale and approach to the study of target organ toxicology with in vitro cellular systems.