Biomedical subjects
M Cook
Publications and source records attributed to M Cook.
A distinct Hox code for the branchial region of the vertebrate head.
The branchial region of the vertebrate head forms through complex interactions involving rhombomeric segments, neural crest and branchial arches. It is though that aspects of their patterning mechanisms are linked and involve Hox-2 genes, whose overlapping and spatially restricted expression domains represent a combinatorial code for generating regional diversity. Vertebrates possess four Hox clusters of Antennapedia class homeobox genes, related to each other by duplication and divergence from a common ancestral complex. In consequence, at equivalent positions in different clusters there are highly related genes known as subfamilies or paralogous groups. As Hox-2 genes cannot fully account for patterning individual rhombomeres, we investigated whether offsets in expression limits of paralogous genes could account for the generation of regional diversity. We report here that, with the exception of the labial subfamily, paralogues show identical expression limits in rhombomeres, cranial ganglia and branchial arches, providing a combinatorial Hox code for the branchial region that seems to be different in organization to that of the trunk.
Multiple spatially specific enhancers are required to reconstruct the pattern of Hox-2.6 gene expression.
Murine Hox genes are organized into four clusters that share many features with the homeotic clusters of Drosophila. This evolutionary conservation and the clear relationships between the position of a gene within a cluster and its expression pattern have led to the suggestion that the structure of the cluster is essential for proper regulation. Using a Hox-2.6-lacZ reporter gene in transgenic mice we have shown that the overall expression pattern of the endogenous Hox-2.6 gene can be reconstructed when it is isolated from the complex. The transgene was expressed in the proper tissues, with the correct spatial distribution and temporal pattern. Furthermore, direct comparison by in situ hybridization revealed that the levels of transgene expression are similar to those of the endogenous gene. This has allowed us to define three elements that regulate particular aspects of the Hox-2.6 pattern, two of which act as spatially specific enhancers. One enhancer, region A, directed expression only in the neural tube, whereas the other, region C, specified the majority of the Hox-2.6 pattern. Both were also capable of imposing the correct boundaries of expression on heterologous promoters. The definition of such elements will allow the characterization of the trans-acting factors that mediate spatial regulation in the mammalian embryo.
Denture bases reinforced with carbon fibres.
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Attentional deficit in the siblings of schizophrenics.
A study of attentional deficit in the relatives of schizophrenics and in a matched control group is reported, in which the relatives are found to have poorer scores on a vigilance test and on a choice reaction time test. It is concluded that this deficit points to one of the primary symptoms of schizoprenia, and suggestions for further research are made.
Gaze patterns of mentally retarded adults in two contrasting environments.
Two matched samples of mentally retarded adults were video recorded on two occasions, before and after one group was transferred to a different type of hospital, and their gaze patterns analyzed. Overall, only slight changes after transfer were found, but analysis according to amount of looking at the interviewer on the first occasion showed that those transferred subjects who initially looked little of the time significantly increased their amount of looking after transfer. Some correlations with the Adaptive Behavior Scale were also reported.
The judgment of distance on a plane surface.
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The perception of solid form in early infancy.
Day and McKenzie determined the rate of habituation of fixation of young infants to repeated visual presentations of a cube. They found the habituation rate to be the same when the stimulus orientation changed between presentations as when it was fixed, and they interpreted this as evidence of shape constancy. However, a failure to discriminate between cubes in different orientations is only evidence of shape constancy if the infant can at the same time discriminate the cube from other cubelike forms. The experiment described here contrasted the rate of habituation of fixation of 12-week-old infants to a homogenous stimulus series (a cube presented in different orientations) with the rates of habituation to various heterogeneous series, in each of which a cube was alternated with some other solid. It was found that, while the infant could distinguish a cube from a photograph of a cube and a concave solid (an L-form), there was no evidence of discrimination between the cube and either a wedge or a truncated pyramid. The results imply limits to the young infants capacity to resolve solid form.
Esterase isozyme patterns in developing embryos of Brachydanio rerio (zebra danio), Brachydanio abolineatus (pearl danio), and their hybrids.
The ontogeny of esterase isozymes in Brachydanio rerio (zebra danio), Brachydanio albolineatus (pearl danio), and hybrids formed by their reciprocal crosses was investigated using polyacrylamide disc electrophoresis. Seven esterase isozymes were identified in each species from the unfertilized egg stage to nine days posthatch. Electrophoretic analysis of qualitative changes in enzyme pattern indicated that some esterases were present at all stages of development while other esterases abruptly appeared at a specific stage of morphological differentiation. The esterases of both species were classified on the basis differential substrate and inhibitor specificities. In developing hybrids formed by B. rerio eggs inseminated with B. albolineatus sperm, the maternal isozyme pattern persisted until Stage 17 (gastrulation). Embryonic extracts from Stage 17 onward showed a slow-moving, DFP-sensitive carboxylesterase of paternal origin. In developing hybrids formed by B. albolineatus eggs inseminated with B. rerio sperm, a paternal contribution to the esterase pattern was probably present by the end of gastrulation; esterase activity of distinctively paternal origin was present by Stage 22 (retinal pigmentation) The maternal contribution to the total esterase profile appeared to remain high through hatching. Additional evidence for gene activity at gastrulation was obtained in experiments utilizing actinomycin-D and cycloheximide. Results of exposing embryos of B. rerio to 15 mug/ml of actinomycin-D indicated that transcription of the template RNA coding for cholinesterase occurred during gastrulation or some 20-30 hours prior to the appearance of the isozyme at Stage 22. This template RNA was translated sometime during that 10-hour interval immediately preceding Stage 22.
The uptake of [1-3H]glucosamine and sodium [35S]sulphate into glycoproteins secreted by mucus glands of the common sea mussel Mytilus edulis [proceedings].
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Preliminary examination of assessment of assertive behavior in retarded persons.
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Comparative analysis of tissue esterases of the zebra danio (Brachydanio rerio) and the pear danio (B. albolineatus) by disc gel electrophoresis.
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The role of gaze in impression formation.
Three hypotheses about the effects of amount of gaze on the impression created of six confederates were tested, using rating scales and free descriptions. The first hypothesis--that favourableness of impression would be a linear function of amount of gaze--was partly confirmed. The second hypothesis--that favourableness of impression would be a curvilinear function of amount of gaze--was not confirmed, nor was the third hypothesis--that effect of gaze would be a complex function of sex of subject and sex of gazer. The effects of gaze were not as marked as had been predicted. The free descriptions also provided data on the number and type of subjects who commented on the amount of gaze of the confederate. Three possible explanations of the results are discussed.
Anxiety and ritualized speech.
The experiment examines the effects on a number of words that seem irrevelant to semantic communication. The Units of Ritualized Speech (URSs) considered are: 'I mean', 'in fact', 'really', 'sort of', 'well', and 'you know'. Two hypotheses are tested: (i) that URS rate will increase with anxiety; and (ii) that the speaker's preferred URS will increase with anxiety. Subjects were interviewed on topics they had previously rated as anxiety-provoking and non-anxiety-provoking. Hypothesis (i) was supported, but hypothesis (ii) was not. More specifically, the use of 'I mean' and 'well' increases when the speaker is anxious. Explanation for this is sought in the grammatical location of these two units. Sex differences in the use of URSs, correlations between URSs and their relationship to other forms of disfluency are also considered.
Changing to an automated information system.
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Proceedings: Effects of truncal vagotomy on the muscle layers of dog stomach.
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