Showing papers by "University of St Andrews published in 1992"

Organization and functions of cells responsive to faces in the temporal cortex.

Abstract: Cells selectively responsive to the face have been found in several visual sub-areas of temporal cortex in the macaque brain. These include the lateral and ventral surfaces of inferior temporal cortex and the upper bank, lower bank and fundus of the superior temporal sulcus (STS). Cells in the different regions may contribute in different ways to the processing of the facial image. Within the upper bank of the STS different populations of cells are selective for different views of the face and head. These cells occur in functionally discrete patches (3-5 mm across) within the STS cortex. Studies of output connections from the STS also reveal a modular anatomical organization of repeating 3-5 mm patches connected to the parietal cortex, an area thought to be involved in spatial awareness and in the control of attention. The properties of some cells suggest a role in the discrimination of heads from other objects, and in the recognition of familiar individuals. The selectivity for view suggests that the neural operations underlying face or head recognition rely on parallel analyses of different characteristic views of the head, the outputs of these view-specific analyses being subsequently combined to support view-independent (object-centred) recognition. An alternative functional interpretation of the sensitivity to head view is that the cells enable an analysis of 'social attention', i.e. they signal where other individuals are directing their attention. A cell maximally responsive to the left profile thus provides a signal that the attention (of another individual) is directed to the observer's left. Such information is useful for analysing social interactions between other individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Thioredoxin regulates the DNA binding activity of NF-kappa B by reduction of a disulphide bond involving cysteine 62.

Abstract: A role for redox regulation in activation of the NF-kappa B transcription factor was suggested by the observation that DNA binding activity of free protein, but not preformed DNA-protein complex, is inhibited by -SH modifying agents but enhanced by reducing agents. Mutagenesis of conserved cysteine residues in the p50 subunit identified amino acid 62 as being important for DNA binding, as a serine substitution at this position reduces DNA binding affinity, but renders the protein insensitive to -SH modifying agents. DNA binding activity of the wild type protein but not the amino acid 62 mutant was also stimulated by thioredoxin while detection of disulphide cross linked dimers in p50 but not the amino acid 62 mutant suggests that thioredoxin stimulates DNA binding by reduction of a disulphide bond involving cysteine 62. The physiological relevance of these findings was supported by the observation that cotransfection of a plasmid expressing human thioredoxin and an HIV LTR driven reporter construct resulted in an NF-kappa B dependent increase in expression of the reporter gene. Thus modification of p50 by thioredoxin, a gene induced by stimulation of T-lymphocytes in parallel with NF-kappa B translocation, is a likely step in the cascade of events leading to full NF-kappa B activation.

Plant invasions, interspecific hybridization and the evolution of new plant taxa

Abstract: Interspecific hybridization between a native and an invading plant species, or two invading species, sometimes results in a new, sexually reproducing taxon. Several examples of such taxa have been confirmed by recent molecular and isozyme analyses. Further study of these new taxa, when recognized soon after their origin, should aim to elucidate the factors that influence their subsequent establishment and spread, thus leading to a better understanding of the processes that lead to successful speciation. Plant hybrids formed following a plant invasion provide great potential for the study of ‘evolution in action'.

Time course of neural responses discriminating different views of the face and head.

Abstract: 1. Measurements of the magnitude and time course of response were made from 44 cells responsive to static head views at different levels of stimulus effectiveness. In this way responses to complex stimulus patterns evoking good, poor, and midrange responses could be compared across the cell population. 2. Cells exhibiting both good and poor initial discrimination between head views were found at short and long latencies; there was no correlation of any of the temporal response parameters measured with cell response latency. 3. The time course of the population response to the most effective stimuli showed a rapid increase to a peak firing rate (onset to peak, rise time, 58 ms) that was on average 115 spikes/s above spontaneous activity (S/A), followed by slower decay (decay time, 93 ms) to a maintained discharge rate (15% of the peak rate above S/A). 4. Discrimination between responses to different head views exhibited by the population showed a sharp rise and reached highly significant levels within 25 ms after the population's response onset. 5. On average, activity in a single neuron (the Average Cell) rises to 44% of its peak response rate within 5 ms of the response onset. 6. The Average Cell also showed exceptionally fast discrimination between views, significant within 5 ms of response onset. 7. It is argued that the fast rise in firing rate, followed by a decay to a lower rate and the very fast emergence of discrimination are features of pattern processing present in real neural systems that are lacking in many processing models based on artificial networks of neuronlike elements, particularly those where discrimination relies on top-down and/or lateral competitive inhibition. 8. It is concluded that the only way to account for the rapid discrimination is to consider a coding system in which the first spike from multiple sources is used to transmit information between stages of processing.

On Reading Organizational Culture

Abstract: The study of organizational cultures has been dominated by an interpretative approach which has emphasized the production of culture at the expense of the creativity shown by the consumers of cuiture, organizational members. 'Corpor ate culture' is distinguished from 'workplace' or 'organizational' cultures, and a number of other problems emerging within the literature are identified. These are presented as organizational culture versus cultural organization; cultural plurali ties ; rationality and the irrational; common knowledge and its constitution; power and ideology; and individualism and subjectivity. It is then argued, after a detailed discussion of concepts drawn primarily from a close reading of the work of Jacques Derrida, that a postmodern approach to organizational culture would recast the problems in terms of a revised conceptualization of subjectivity, and would formulate culture as paradox, otherness, seduction, and discourse. This would entail studying the 'bricolage' of organizational mem...

Thinking Translation: A Course in Translation Method: French to English

Abstract: Thinking Translation is a comprehensive and revolutionary 20-week course in translation method. It has been fully and successfully piloted at the University of St. Andrews. The course offers a challenging and entertaining approach to the acquisition of translation skills. Translation is presented as a problem-solving discipline. Discussion, examples and a full range of exercise work allows students to acquire the skills necessary for a broad range of translation problems. Thinking Translation draws on a wide range of material from technical texts to poetry and song.

Dialects in wild chimpanzees

Abstract: Chimpanzees emit a loud, species-typical long distance call known as the pant hoot. Geographic variation between the pant hoots of chimpanzees living in two neighboring populations, the Mahale Mountains and Gombe Stream National Parks, Tanzania, was examined. Analysis of six acoustic features revealed subtle differences in the way chimpanzees from the two populations called. Individuals from the Mahale study site uttered one section of their pant hoots at a faster rate and with shorter elements than animals from Gombe Stream. In addition, individuals at Mahale delivered broader-band, higher pitched "climax" elements than males from Gombe. While genetic factors, anatomical differences, variations in the use of calls at the two sites, and changes in calling over time may account for the variability between populations, we suggest the additional possibility that differences in pant hooting may be due to learning. © 1992 Wiley-Liss, Inc.

Event-related potentials and recognition memory for low-and high-frequency words

Abstract: Event-related potentials (ERPs) were recorded while subjects made recognition judgments on high-and low-frequency words, half of which had previously been presented in an incidental study task. Compared to high-frequency items, low-frequency words were associated with superior recognition performance, and attracted a higher proportion of confident judgments. In the case of the low-frequency words only, the region of the ERPs post-500 msec evoked by correctly classified, previously studied (old) words was more positive-going than was the same region of the EWs to nonstudied (new) words. These “old/new” ERP differences were larger from electrodes over the left than over the right hemisphere. This old/new by frequency interaction held when EWs were formed only from words that attracted confident judgments. It is argued that these data are consistent with the ideas that (1) post-500 msec “old/ new” EW differences in recognition memory tasks reflect differences in old and new words' levels of relative familiarity, and (2) the recognition memory advantage for low-frequency words results, at least in part, from the higher level of relative familiarity engendered at test by previously studied low-frequency items. The data are interpreted as providing support for “two-process” models of recognition memory.

Construction of solid matrix-antibody-antigen complexes containing simian immunodeficiency virus p27 using tag-specific monoclonal antibody and tag-linked antigen.

Abstract: We have previously shown that immunization with solid matrix-antigen-antibody (SMAA) complexes induces both vigorous humoral and cell-mediated immune responses and have suggested that this method of vaccination may be developed for use in humans, and potentially as a vaccine against AIDS. Here we demonstrate that a small oligopeptide can act as a tag for the construction of SMAA complexes using a tag-specific monoclonal antibody and tag-linked antigens. We show that a 14-amino acid oligopeptide, present in the phospho (P) and V proteins of simian virus 5 (SV5), retains its antigenicity when attached to the C terminus of three ‘foreign’ proteins [p27 and gp110 of simian immunodeficiency virus (SIV) and glutathione S-transferase] such that these proteins can be incorporated into SMAA complexes using a monoclonal antibody (MAb) that was originally raised against the native SV5 P and V proteins. Mice were immunized with SMAA complexes containing recombinant p27-TAG and MAbs have been isolated that recognized native SIV p27. The significance of these results in terms of the development of SMAA complexes as human vaccines is discussed.

Multiple origins and genetic diversity in the newly arisen allopolyploid species, Senecio cambrensis Rosser (Compositae)

Abstract: A survey of allozyme variation was conducted in populations of the newly arisen allopolyploid species Senecio cambrensis and its two parental species S. vulgaris and S. squalidus sampled from the three locations in Britain where S. cambrensis is known to occur, i.e. at Wrexham and Mochdre in Wales, and Edinburgh in Scotland. Electrophoretic variation at the Acp-1 and αEst-1 loci provided strong evidence of separate origins of S. cambrensis in Wales and Edinburgh. The possibility of two additional independent origins of the species in Wales was indicated by the variation pattern at the Aat-3 locus, although this variation could be explained as a result of segregation from a fixed heterozygote (representative of a single origin) following pairing between homoeologous chromosomes, as could the pattern of variation recorded at the βEst-3 locus. For no enzyme system were additional allozymes found in S. cambrensis which were not present in one of the respective parents. The ability of S. cambrensis to originate at different locations and to generate genetic diversity following recombination between its parental genomes, might act in favour of its establishment and diversification in Britain.

Interval estimation for mark-recapture studies of closed populations.

Abstract: Textbooks continue to recommend the use of an asymptotic normal distribution to provide an interval estimate for the unknown size, N, of a closed population studied by a mark-recapture experiment or multiple-record system. A likelihood interval approach is proposed and its implementation demonstrated for a range of models for such studies, including all main effect and interaction models for incomplete contingency tables.

Antipeptide antisera define neutralizing epitopes on the adenovirus hexon.

Abstract: The adenovirus (Ad) hexon contains both group- and type-specific antigenic determinants. To identify the latter, peptides were synthesized corresponding to residues 281 to 292 from loop 1 and 441 to 455 from loop 2 of the Ad2 hexon. These sequences display type-specific variation and have been shown by X-ray crystallography to be present on the surface of the virion. Antisera raised against the peptides bound both peptide and the native hexon in ELISA, and blocked virus infectivity, as determined by immunofluorescence or neutralization assays. The loop 1 peptide was shown to inhibit binding of the corresponding antiserum to the native hexon in ELISA and to abolish its neutralizing activity. Neither the loop 1- nor loop 2-specific antiserum neutralized the infectivity of Ad4 or Ad40. Neutralization did not appear to result from aggregation of virus particles and thus their inability to attach to the cell, because virions treated with immune serum were internalized to the same extent as those treated with preimmune serum. Examination of the immune response elicited by Ad2 infection revealed that antibodies directed against the L1 and L2 epitopes were also present in human serum. Thus, the variable regions exposed on the surface of the Ad2 hexon represent type-specific neutralizing antigenic determinants.

Patterns of movement by baboons in the Drakensberg mountains: Primary responses to the environment

Abstract: The movement patterns of two chacma baboon troops in the Drakensberg mountains of South Africa were studied over an 18-month period. One of these troops (HIGH) lived on the escarpment slopes (1920–2980 m), while the other (LOW) lived primarily in the montane belt (1560–2000 m). In this paper we analyze the effects of environmental variables on day journeys and home range use. We found the troops to be similar in the temporal patterning of their daily movement, in the resistance of travel speed to variations in local climatic conditions, and in their response to the nutritional bottleneck at the end of the austral winter. While both troops traveled farther as food became scarcer, HIGH troop undertook longer day journeys than LOW troop. This was probably due to the interactive effects of absolutely lower food availability and lower ambient temperatures. HIGH troop traveled farther when food was scarcer and when minimum temperatures were higher. Neither variable accounted for variance in the day journeys of LOW troop. Both troops used some areas of their home ranges preferentially. For LOW troop this preference followed the spatial distribution of food. While the same was generally true for HIGH troop, its home range use was complicated by the adverse temperatures of winter and spring. It abandoned the higher, more productive part of its range once temperatures became severe, returning only after minimum ground temperatures had risen above 0°C. These usage patterns differ from those described for eastern African baboon populations and reflect both the severity and sesonality of climate and the poor quality and extreme dispersion of food that characterize these southern mountains.

Iron‐sulphur cluster nitrosyls, a novel class of nitric oxide generator: mechanism of vasodilator action on rat isolated tail artery

Abstract: 1. Two iron-sulphur cluster nitrosyls have been investigated as potential nitric oxide (NO.) donor drugs (A: tetranitrosyltetra-mu 3-sulphidotetrahedro-tetrairon; and B: heptanitrosyltri-mu 3-thioxotetraferrate(1-)). Both compounds are shown to dilate precontracted, internally-perfused rat tail arteries. 2. Bolus injections (10 microliters) of compound A or B generate two kinds of vasodilator response. Doses below a critical threshold concentration (DT) evoke transient (or T-type) responses, which resemble those seen with conventional nitrovasodilators. Doses > DT produce sustained (or S-type) responses, comprising an initial, rapid drop of pressure, followed by incomplete recovery, resulting in a plateau of reduced tone which can persist for several hours. 3. T- and S-type responses are attenuated by ferrohaemoglobin (Hb) and by methylene blue (MB), but not by inhibitors of endothelial NO. synthase. Addition of either Hb or MB to the internal perfusate can restore agonist-induced tone when administered during the plateau phase of an S-type response. Moreover, subsequent removal of Hb causes the artery to re-dilate fully. 4. We conclude that T- and S-type responses are both mediated by NO.. It is postulated that S-type responses represent the sum of two vasodilator components: a reversible component, superimposed upon a non-recoverable component. The former is attributed to free NO., preformed in solution at the time of injection; and the latter to NO. generated by gradual decomposition of a 'store' of iron-sulphur-nitrosyl complexes within the tissue. This hypothesis is supported by histochemical studies which show that both clusters accumulate in endothelial cells.

Influence of temperature on muscle-fibre development in larvae of the herring Clupea harengus

Abstract: The development of swimming (myotomal) muscles was studied in herring larvae (Clupea harengus L.) caught in the Firth of Clyde, Scotland, in spring 1990 and reared at either 5, 10 or 15°C. Two muscle-fibre types can be distinguished in the myotomes of herring larvae using ultrastructural criteria. A single layer of small-diameter muscle fibres, packed with mitochondria, is present beneath the entire surface of the skin (superficial muscle fibres). The remaining bulk of the muscle is composed of larger diameter fibres (inner muscle fibres) containing significantly more myofibrils than the superficial fibres. In 1 d-old larvae, the number of inner muscle fibres in myotomes immediately posterior to the yolk-sac was 311±41 at 15°C, 257±22 at 10°C and 187±22 at 5°C (mean±SD,n=6). The average diameter of inner muscle fibres increased with decreasing temperature, so that the total cross-sectional area of muscle was similar at each temperature. After 6 to 7 d, the number of muscle fibres had significantly increased at 15°C (383±25), but not at 10°C (281±32) or 5°C (192±17). In contrast, the average cross-sectional area of inner muscle fibres had increased by 19% at 15°C, 34% at 10°C, and 26% at 5°C. Temperature also influenced the relative proportions and spatial distributions of muscle-fibre organelles. For example, in 1 d-old larvae, the fraction of muscle-fibre volume (volume density) occupied by mitochondria in the superficial fibres was significantly higher at 15°C (46.0%) than at either 5°C (37.6%) or 10°C (38.8%). In the inner muscle fibres, the volume density of mitochondria was 26.1% at 15°C, 20.5% at 10°C and 15.9% at 5°C, whereas the volume density of myofibrils was similar at the three temperatures (33 to 38%). Typically, inner muscle fibres from 10°C larvae, but not from 5 or 15°C larvae contained a large central mitochondrion.

Resonant generation of biexcitons in a GaAs quantum well.

Abstract: Generation of cold excitons in GaAs quantum wells is shown to lead to enhanced condensation to the biexciton state under cw illumination. Resonant two-photon absorption to the biexciton state in the same structure is found to account for a quantum beating phenomenon involving the biexciton and exciton states in a more complex three-level system than hitherto investigated.

Derivation of a single-band model for CuO2 planes by a cell-perturbation method.

Abstract: A cell-perturbation method is developed for ${\mathrm{CuO}}_{2}$ planes in the cuprate superconductors described by a d-p model. It is shown that a single-band t-t'-J-J' model accurately describes the low-energy physics and how the parameters of this model vary with those of the underlying d-p model. The method is similar in spirit to Anderson's original treatment of superexchange [Phys. Rev. 115, 2 (1959)], where the exchange interaction is obtained in second order rather than given by the usual fourth-order result of ordinary perturbation theory (a poor approximation). It is shown that O-O hopping can appreciably affect the absolute and relative magnitudes of the effective single-band parameters and that a regime with J\ensuremath{\sim}t is quite conceivable. Although triplet (intermediate) states can appreciably enhance the magnitude of the ``diagonal'' effective hopping t', an effective single-band description should remain valid for all reasonable estimates of the underlying d-p parameters. Correction terms involving hole pairs on neighboring cells are derived and shown to be small. For the ``undoped'' case, an estimate is made of the critical charge-transfer energy for an insulator-metal transition.

Glacier response to climatic change during the Loch Lomond Stadial and early Flandrian: Geomorphological and palynological evidence from the Isle of Skye, Scotland

Abstract: The deglaciation of Skye at the close of the Loch Lomond Stadial is assessed on the basis of detailed geomorphological mapping and pollen-stratigraphic correlations. It is concluded that deglaciation proceeded in two distinct stages. The first was marked by numerous glacier stillstands and readvances, while uninterrupted retreat and local glacier stagnation occurred during the second and final stage. The pollen evidence indicates that the first stage was well advanced before the marked thermal improvement at the start of the Flandrian, and it is inferred that initial glacier retreat occurred in response to a decline in precipitation in the later part of the Loch Lomond Stadial. The first stage of glacier retreat continued into the early Flandrian, during which climatic amelioration was interrupted briefly. Final deglaciation appears to have occurred rapidly in response to sustained temperature increases. The collective evidence also indicates spatial variations in the timing of deglaciation, which appear to reflect differences in glacier morphology.

Recognition of the adenovirus type 2 origin of DNA replication by the virally encoded DNA polymerase and preterminal proteins.

Abstract: Initiation of adenovirus DNA synthesis is preceded by the assembly of a nucleoprotein complex at the origin of DNA replication containing three viral proteins, preterminal protein, DNA polymerase and DNA binding protein, and two cellular proteins, nuclear factors I and III. While sequence specific interactions of the cellular proteins with their cognate sites in the origin of DNA replication are well characterized, the question of how the viral replication proteins recognize the origin has remained unanswered. Preterminal protein and DNA polymerase were therefore purified to homogeneity from recombinant baculovirus infected insect cells. Gel filtration demonstrated that while DNA polymerase existed in monomeric and dimeric forms, preterminal protein was predominantly monomeric and when combined the proteins formed a stable heterodimer. In a gel electrophoresis DNA binding assay each of the protein species recognized DNA within the origin of DNA replication with unique specificity. Competition analysis and DNase I protection experiments revealed that although each protein could recognize the origin, the heterodimer did so with enhanced specificity, protecting bases 8-17 from cleavage with the nuclease. Thus the highly conserved 'core' of the origin of DNA replication, present in all human adenoviruses, is recognized by the preterminal protein--DNA polymerase heterodimer.