Biomedical subjects
Publications and source records attributed to A Richards.
This report describes a young male patient who had enamel hypoplasia, persistent oral candidiasis, skin hyperpigmentation, and vitiligo, and was thus suspected of having candidiasis endocrinopathy syndrome. The clinical and laboratory investigations employed to confirm the diagnosis are detailed.
Laryngeal involvement with candida is usually secondary to pulmonary candidiasis and is seen in patients with impaired immunity. We report a case of isolated laryngeal candidiasis involving the vestibular folds and presenting with stridor in a one-year-old child with Down's syndrome and hypogammaglobulinaemia. Vestibular fold reduction and fluconazole achieved resolution of the disease. Candidiasis should be considered in any potentially immunodeficient child presenting with symptoms of laryngeal disease.
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.
Three experiments are reported comparing high- and low-trait anxious subjects in terms of their patterns of semantic activation in response to ambiguous primes, with one threat-related and one neutral meaning. Such primes were followed by targets related to either their threat or neutral meaning, or by unrelated targets, in a lexical decision task. Experiments 1 to 3 employed stimulus onset asynchronies (SOAs) of 750 msec, 500 msec, and 1250 msec, respectively. At 500-msec SOA all subjects showed facilitation for both meanings. At 750-msec SOA the only significant priming effect was that for the threat-related meaning in the high-anxiety group, and a similar trend was found at 1250-msec SOA. Consideration of the patterns of priming for targets following ambiguous threat/neutral primes suggest that at the longer SOAs, high-anxiety subjects consciously "lock on" to a threatening interpretation if one has been made available by earlier automatic spreading activation.
In Study 1 subjects high and low in trait anxiety were asked to identify the colour of anxiety-related, anxiety-matched neutral, happiness-related and happiness-matched neutral words. There were two types of stimulus presentation: blocked trials, where stimuli were blocked with respect to their valence, and mixed trials, where stimuli were mixed with respect to their valence. Subjects high in trait anxiety took longer to identify the colour of anxiety-related compared to matched neutral words for blocked-trial presentation only. In Study 2 subjects were exposed to either a positive or a negative mood-manipulation followed by a mixed-trial Stroop task. The mood manipulation procedure was successful in producing predicted changes in self-reported state anxiety. Analyses showed that high-trait-anxiety subjects exhibited interference effects consistent with the induced mood. No such effects were observed for the low-trait-anxiety subjects.
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Unerupted fluorotic human enamel was obtained from teeth surgically removed from patients with dental fluorosis. Fluoride was measured in samples produced by serial acid etching from the surface to the interior of blocks of buccal and lingual enamel. The severity of fluorosis, according to the TF index, was determined from the macroscopic and microradiographic appearance of the specimens. The shape of the fluoride profiles was not affected by the degree of severity of fluorosis, but the fluoride concentrations increased with increasing severity of lesions. Fluoride concentrations were similar to those previously recorded in erupted fluorotic enamel and were not related to the length of time the teeth had been present in the jaws. It was concluded that the fluoride content of erupted fluorotic enamel represents fluoride acquired during tooth formation and that further uptake prior to eruption may be negligible.
We have compared the size and arrangement of the primary somatic sensory cortex (SI) and its constituent parts in juvenile (1 week old) and mature (10-12 weeks old) rats using succinic dehydrogenase histochemistry and digital image analysis. Our goal was to determine whether some regions of the maturing cortex grow more than others. To this end, we examined (1) the growth of barrels and the surrounding (interbarrel) cortex, (2) the growth of the major somatic representations within SI, and (3) the overall growth of SI compared to the neocortex as a whole. With respect to the first of these issues, SI barrels and barrel-like structures grow more than the intervening cortex. The growth of these elements varies according to region: barrels in the head representation more than double in size, whereas the barrel-like structures in the paw representations increase by only about half this amount. The growth of the major somatic representations within SI is also heterogeneous, the representation of the head enlarging to a greater extent than the representations of the paws. Thus, the ratio of the total area of head representation to the combined paw representation is 15% greater in adults than in juveniles. Finally, the primary somatic sensory cortex grows to a somewhat greater extent than the neocortex as a whole. These observations demonstrate that postnatal cortical growth is not uniform; it varies among cortical barrels and the immediately surrounding (interbarrel) cortex, among the representations of different body parts, and between SI and the rest of the neocortex. As an explanation of this differential growth, we suggest that the neuropil of metabolically (and/or electrically) more active cortical regions grows to a greater extent during maturation than that of less active regions.
In the 1st of 2 experiments, currently clinically anxious, recovered clinically anxious, and normal control subjects were presented with a mixture of unambiguous and ambiguous sentences; both threatening and nonthreatening interpretations were possible for the latter. A subsequent recognition-memory test indicated that the currently anxious subjects were more likely than normal control and recovered anxious subjects to interpret the ambiguous sentences in a threatening fashion rather than in a nonthreatening fashion. This suggests that the biased interpretation of ambiguity found in currently anxious subjects reflected their anxious mood state. A 2nd experiment established that the difference in interpretative processes between currently anxious and control subjects was not due to response bias and that the interpretative bias was a reasonably general one.
Epstein syndrome is a rare dominantly inherited disorder in which the main features are nephritis, deafness and macrothrombocytopathic thrombocytopenia. A case with oral haemorrhage and purpuric lesions is reported. This appears to be the first report of this syndrome in the dental literature.
A considerable number of agents have been proposed as causing ligneous conjunctivitis. We report the first case to arise as a side effect of tranexamic acid (Cyclokapron), an anti-fibrinolytic drug used in the treatment of menorrhagia. In addition to the typical conjunctival changes our patient had lesions affecting the gingiva and the peritoneum the last causing considerable protein loss into the peritoneal cavity.
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In phase 1 of the study subjects high and low in trait anxiety were exposed to a novel mood manipulation technique. This involved the presentation of either pleasant or unpleasant newspaper photographs. Subjects exposed to the positive and negative manipulations reported corresponding state anxiety decreases and increases respectively. In phase 2, subjects were required to recall specific personal memories to anxiety-related and happiness-related cue words. It was found that the high trait anxiety group were faster in response to anxiety-related as compared with happiness-related cue words. Retrieval latencies were not affected by type of cue word for the low trait group. Further analyses showed that the two groups differed in terms of their retrieval latencies rather than their retrieval strategies. Multiple regression analyses revealed that, whereas state anxiety is related to an enhanced retrieval of memories to anxiety-related cue words, depression is associated with a slowing of responses to happiness-related cue words. The content specificity hypothesis is offered as an explanation for this pattern of results.
State and trait anxiety were found to be unrelated to the handedness categories distinguished by Annett (1970) in a sample of volunteers (N = 385). Furthermore, mean scores for 99 male subjects did not differ significantly from those of 293 females. The mean anxiety levels in this study were much more representative of the general population than those reported in a previous similar study by Beaton & Moseley (1984). A suggestion that subjects classified as mixed-handed might show a tendency to avoid extreme responses was not supported.
Recent studies of dental fluorosis in animals have been reviewed. The aim was to describe studies which have provided information which may be relevant to explaining the mechanisms involved in human dental fluorosis. Studies on rats, sheep, and pigs have provided details of dosage regimens which produce lesions which resemble those described in human fluorosis. In the pig and rat, the plasma fluoride concentrations associated with these dental lesions are of the same order of magnitude as those which may occur in man. Three different kinds of studies in different species have shown that fluoride affects processes occurring during enamel maturation. One study on rats has indicated that fluoride may reduce matrix removal during maturation by an effect on enamel proteases. Many studies have demonstrated accumulation of fluoride in secretory enamel and that fluoride concentrations in maturation enamel are lower than in secretory enamel. This phenomenon had previously been explained by the binding of fluoride to enamel proteins, but recent studies indicate that such binding does not occur. The hypothesis that enamel fluorosis might be caused by general effects of fluoride on calcium metabolism has not been supported by more recent studies. It was concluded that, although the mechanisms involved in dental fluorosis remain obscure, recent animal studies do seem to have provided new information which may prove to be important for our understanding of mechanisms whereby fluoride causes dental fluorosis in man.
The purpose of the experiment was to assess the effects of fluoride (F-) on the remodeling process of cortical bone. Sixteen pigs, eight experimental animals receiving a supplement of 2 mg F-/kg b.w. and eight controls, were studied in individual sites from age 8 to 14 months. At slaughter samples of cortical bone were obtained from the right femur and embedded undecalcified. A new stereologic model based on fluorochrome tissue time markers and isotropic uniform random histologic sections was implied in order to obtain information in three-dimensional terms about dynamic aspects of remodeling. The rate of remodeling was increased in cortical bone from pigs receiving F- due to an increased activation of new remodeling. A doubling of the length density of resorptive and formative osteons was observed, although the change was statistically significant for the formative osteons only. An 11% decrease in depth of resorption and an 8% decrease in thickness of new bone formed led to a small decrease in the radius of Haversian canals in the fluorotic bone. The porosity of cortical bone was slightly but significantly increased. At formative sites the osteoid thickness and the mineralization rate were not significantly changed by F-. It was concluded that the observed changes cannot be explained by F- induced changes in a single cell. Fluoride appears to affect all cells involved in remodeling by direct or indirect mechanisms.
In previous studies, we have established that anxiety states are characterized by an attentional bias that favors the processing of threatening stimuli. In the present study we extend this finding to ambiguous stimuli, specifically, homophones with spellings that correspond to either a threatening or a neutral meaning. As predicted, clinically anxious subjects used the threatening spellings relatively more than did controls, whereas recovered subjects were intermediate in this respect. Threatening words were associated with greater skin conductance responses than were neutral words, but the groups did not differ in their electrodermal reactions to homophones. We take these findings as evidence that, although the different meanings of ambiguous stimuli may be processed in parallel by all subjects, an interpretive bias operates such that anxiety-prone individuals tend to become preferentially aware of the more threatening meaning of such events.