The current investigation examined perturbation and adaptation during language comprehension in young normal subjects. Using a dynamic system framework, induced instability was studied by increasing perceptual demand (compressed sentences), syntactic demand, or both. Two experiments were conducted, one behavioral and one using fMRI technology, to explore the relations between brain responses and behavior. This study examines if changes in rate of speech, syntax, or both induce an instability, or perturbation, with subsequent adaptation in which subjects regain a previous stable state. Dependent measures in the behavioral study were accuracy and reaction time based indices of perturbation, adaptation, and stability. Results of the behavioral study demonstrated that language comprehension can be perturbed by changes in syntactic complexity or syntactic + perceptual complexity. Further, it was found that subjects adapted to being perturbed. The more complex the stimulus, the longer it took for subjects to adapt. The second experiment used fMRI to measure brain activation associated with perturbation and adaptation of language. Several brain regions showed increases in activation with increasing complexity (i.e., perturbation). Some regions (e.g., the superior parietal lobule) appeared more active when the perturbation was perceptual and others (e.g., the left inferior frontal gyrus) more active when the perturbation was syntactic in nature. These regions either remained active during the adaptation process, or reduced in activation during adaptation suggesting a role specific role in perturbation. These results suggest that subjects develop and maintain a representation of either the syntactic frame (i.e., via priming), a conscious strategy for accommodating syntactic complexity, or rate normalization schema. Thus, the brain regions that remain active during adaptation may be used to maintain the linguistic or perceptual frame. Within a dynamic system framework, the development of these representations, which occurs over a few items, serves as an attractor to which subjects are drawn each time they are perturbed. Like other complex systems, once instability occurs, there needs to be a strong attractor state to pull subjects into stability that permits appropriate performance to continue.

The purpose of this study was to investigate the relationship between aphasia severity and cerebral perfusion and lesion size in stroke. Nine subjects with acute ischemic stroke were examined within 24 hours of symptom onset and six were reexamined at one-month post-stroke. Examination included aphasia testing, testing of face discrimination ability, administration of the National Institutes of Health Stroke Scale, and perfusion MRI (PI), diffusion MRI (DWI), and T2-weighted MRI (T2-MRI). Subjects with a variety of aphasia types and a large range of aphasia severity participated in the study. MR images were visually inspected to verify perfusion and diffusion abnormalities. Perfusion abnormality was quantified by calculating a perfusion signal ratio of the affected hemisphere over the whole image (left/whole = ratio). Lesion volume was calculated from the DWI and T2-MRI. A perfusion abnormality larger than a DWI lesion was observed in 8 of 9 subjects. Minimal lesions were observed on DWI in three of the subjects while their PI revealed significant perfusion abnormality. Correlation coefficients (Spearman) between aphasia severity and hypoperfusion were significant in the acute stage and again at one-month post-stroke. Five of six subjects that were reexamined at one-month post-stroke experienced significant aphasia recovery. Visual inspection of their PI scans suggests that aphasia recovery was accompanied by increase in cerebral perfusion. The correlation between aphasia severity and lesion size was not statistically significant in the acute stage or at one-month post-stroke. Consequently, it is probable that cerebral hypoperfusion is a better predictor of aphasia severity and recovery in early stroke than lesion volume.

Today genetic services including genetic counselling are widespread across the world. Although developing countries, like Colombia, have started to apply genetic knowledge to the health area, genetic counselling is usually integrated in the routine clinical genetic consultation, however, before this study the process of communication involved in it had not been explored. In collaboration with the Colombian Association of Medical Genetics, the Bogotá Health Service, and the University of Warwick (UK), I observed 25 genetic consultations in five Colombian genetic clinics. I undertook semi-structured interviews with patients / families before and after the consultation. Thematic analysis of the interview transcripts established mismatches between physician perception and patient comprehension. Efficient communication was affected by patient, relatives, practitioner and external factors. Among these environmental factors were excessive administrative procedures, interruptions during the encounter, patients‟ lack of interest to medical terminology, doctors using scientific language, excessive information given in one session, beliefs and education level of the patient and/or relatives, patient distress caused by bad news, unfulfilled expectations and no availability/accessibility of treatment. I also interviewed 20 medical practitioners working in genetics services. There was general agreement that genetic counselling in Colombia was challenging, and that more training in communication skills was required at Medical schools at undergraduate and postgraduate level. Many physicians did not believe that other health professionals should work as genetic counsellors. There was a general recognition of limited genetic knowledge, awareness and understanding in most medical specialities. These results have made a valuable contribution to describe the current situation with genetics consultation and counselling in Colombian genetic clinics, and have already influenced the future development of an effective and robust genetic counselling service in Colombia. They will also be used in the development of the academic curriculum related to basic and clinical genetics at Colombian Universities.

<p> Endothelial cells play a vital role in the normal physiology of the vasculature. The cerebrovascular region is highly populated by endothelial cells with distinct morphology and functions. However, endothelial cells are also a vital region in the pathophysiology of the vasculature, such as aneurysm formation, due to reactive oxygen species (ROS) production. To study the effects of glucose and flow on ROS production in brain arterial endothelial cells, ROS production was measured. This thesis is divided into three parts: glucose effect on ROS, flow effect on ROS, and glucose effect on flow-induced ROS. Previous endothelial cultures were provided by Joeseph Moran-Guiati and Jason Kushner. The effect of high glucose on static endothelial cells was shown to increase ROS production as compared to the effect of normal glucose. Under chronic treatment of endothelial cells with high flow, ROS production was significantly greater that in endothelial cells under chronic treatment of normal flow. High glucose was shown to exacerbate the high flow response. These studies provide insight to a possible connection between intracranial aneurysm formation and a major risk factor, Diabetes Mellitus.</p>

3 pp. / This publication describes the factors affecting development of downy mildew of lettuce and provides disease management strategies.

In this study, Red clover necrotic mosaic virus (RCNMV) was used to better understand the functions of replication proteins and to identify the terminal promoter element involved in viral replication. RCNMV genome contains two positive-sense, single-stranded RNAs. RNA-1 encodes two proteins essential for viral replication: p27 and p88. p88 is a fusion protein containing p27 at its N terminus and RNA dependent RNA polymerase motifs at its C-terminal domain. The function of p27 is not known. In this work, studies of RNA-1 chimerical clones between a highly infectious clone and a poorly infectious clone and subsequent mutagenesis demonstrated that the N-terminal 14 amino acids of p27 and p88 were required for efficient RNA replication. Sequence analysis indicated that it is possibly involved in membrane interaction. Another important aspect of viral replication is template recognition by the replicase at the 3' promoter. The 3' -29 nucleotides of both RCNMV RNA-1 and RNA-2 can be predicted to form an identical stem-loop structure (SLS). Mutational analysis of the SLS indicated that both the structure and the loop sequence were required for viral replication. Within the 5-nt loop region, three discontinuous nucleotides were identified as critical nucleotides for RNA-replicase interaction. The functional groups in these key nucleotides involved in replicase recognition are predicted. The 3' promoter element of RCNMV not only affects viral RNA replication but also influences transgenic recombination. RCNMV RNA-2 encodes a movement protein (MP) that is required for viral cell-to-cell movement and systemic infection. Transgenic Nicotiana benthamiana plants expressing different versions of MP mRNA neither resisted RCNMV nor complemented RNA-1 infection. However, systemic infection was observed in transgenic lines expressing 5' truncated MP mRNA when only RNA-1 was inoculated. Further analysis showed that the infection was resulted from nonhomologous RNA recombination events between infecting RNA-1 and MP transgene mRNA. A replicase-mediated template switch model of the transgenic recombination was proposed. The presence of the 3' promoter element in the transgene mRNA thus was a major factor determining transgenic recombination frequencies. As predicted from the model, transgene mRNA lacking the 3' promoter element would not be a good donor RNA for transgenic recombination. Consequently, no transgenic recombination was detected in transgenic plants expressing the 3' truncated MP mRNA upon inoculation with RCNMV RNA-1.

This study investigated the fast-mapping ability of young children with normal language (NL) and specific language impairment (SLI). It compared their ability to fast-map semantic and lexical information in different conditions. Children had to fast map visual information only, visual plus non-linguistic auditory information, and visual plus linguistic auditory information. Children with SLI performed worse than children with NL overall. They showed specific deficits when the task did not meet their expectations and when they were asked to map phonologically infrequent linguistic information. A nonword repetition task was correlated with both semantic and lexical fast-mapping. The findings are discussed in light of their support for a limited capacity model of processing, and for the need to evaluate children with SLI for semantic deficits.

Purpose. The purpose of this study was to examine the influence of visual information on the intelligibility of dysarthric speech. The two research questions posed by this study were: (1) Does the presentation mode (auditory-only versus auditory-visual) influence the intelligibility of a homogeneous group of speakers with dysarthria? and (2) Does the experience of the listener (experienced versus inexperienced with dysarthric speech) influence the intelligibility scores of these speakers? Background. Investigations of speakers with hearing impairment and laryngectomy have indicated that intelligibility scores are higher in an auditory-visual mode compared to an auditory-only mode of presentation. Studies of speakers with dysarthria have resulted in mixed findings. Methodological issues such as heterogeneity of speaker groups and factors related to the stimuli may have contributed to these mixed findings. Method. Eight speakers with dysarthria related to Parkinson disease were audio and video tape-recorded reading sentences. Movie files were created in which an auditory-only condition containing the speaker's voice but no visual image of the speaker and an auditory-visual condition containing the speaker's voice and a view of his/her face. Two groups of listeners (experienced and inexperienced with dysarthric speech) completed listening sessions in which they listened to (auditory-only) and watched and listened to (auditory-visual) the movies and transcribed what they heard each speaker say. Results. Although auditory-visual scores were significantly higher than auditory-only intelligibility scores, the difference between these scores was influenced by the order in which the two conditions were presented. A speaker effect was found across presentation modes, with less intelligible speakers demonstrating greater benefit from the inclusion of visual information. No statistically significant difference was found between the two listener groups in this study. Conclusions. These findings suggest that clinicians should include assessment of both auditory-only and auditory-visual intelligibility measures in speakers with Parkinson disease. Management of intelligibility impairment in these individuals should consider whether visual information is beneficial to listeners.

Considering the economic importance of asparagus as a crop and the historical association of Fusarium spp. as a principal cause of stand decline of this crop, a study was conducted from 1995-1997 in Southern California and Northern Mexico. The main objectives were to determine the causal agent of asparagus crown rot and the study the etiology of the causal agents which affects asparagus spears in these two important growing regions. Asparagus crowns exhibiting symptoms of crown decay were selected from each of the above production regions and processed in the laboratory. Based on morphological characteristics, F. proliferatum and F. oxysporum were the dominant species isolated from crowns. F. proliferatum produced mono and polyphialides and conidia in long chains. F. oxysporum was distinguished by the production of chlamydospore and conidia not produced in chains. Both species were recovered from marketable spears with an incidence ranged from 20-90%. Pathogenicity test on asparagus seedlings with isolates of F. proliferatum and F. oxysporum obtained from spears were positive. To determine the source of spear infection in commercial asparagus plantings, crowns and spears were collected from two fields in the Imperial Valley of California. Both F. proliferatum and F. oxysporum were recovered from crown tissues and from spears. However, F. proliferatum was the most prevalent species of Fusarium isolated from both spears and crowns. Evaluation of the influence of Fusarium species on quality characters of marketable asparagus was also studied. The quality of marketable spears infected with F. proliferatum and F. oxysporum was found to decrease significantly as the length of storage increased from five to ten days and as temperature of storage was increased from 5 C to 26 C. Since some species of Fusarium are known to produce fumonisins (a mycotoxin), and investigation of the possible presence of fumonisins in commercial asparagus spears was conducted. Spears were obtained from two different geographic regions of Mexico and two in California. Spear samples naturally colonized by Fusarium spp. were analyzed for fumonisin B1, B2 and B3. No detectable levels of fumonisin, regardless of geographic location of samples, were founded.

The temporal and spatial population genetics of Phytophthora infestans, the causal agent of the potato and tomato late blight, was analyzed in a mixed potato and tomato production area in the Del Fuerte Valley, Sin., Mexico. Isolates of P. infestans were characterized by mating type, allozyme analysis at the glucose-6-phosphate isomerase (GPI) and peptidase (PEP) loci, restriction fragment length polymorphism (RFLP) with probe RG57, metalaxyl sensitivity, and aggressiveness to tomato and potato. Spatial patterns of P. infestans genotypes were analyzed using Geographical Information Systems (GIS) and Geostatistics during the seasons 1994-1995 to 1996-1997. A temporal analysis of the P. infestans genetic structure from 1990-1991 to 1996-1997 suggests an asexual or clonal population with frequent introductions from outside the valley. In the period from 1990-1991 to 1994-1995, the A2 mating type was predominant in both tomato and potato crops, with a very low frequency of the A1 mating type occurring either on tomato or on potato. Conversely, by the 1995-1996 season the predominant mating type was the A1, with low frequency of the A2 on tomato. By 1996-1997 only the A1 mating type was found. This suggests sexual reproduction is unlikely to be occurring in this area. Genotype variation, based on mating type, allozymes, and RFLP was, in general, very low with one predominant genotype affecting both crops each year. These predominant genotypes were highly aggressive to both tomato and potato in an in vitro detached leaf aggressiveness test. Other genotypes found on either potato or tomato, but not on both hosts, were non-aggressive to either tomato or potato. Data on metalaxyl sensitivity indicates that allozyme analysis can accurately discriminate between sensitive and resistant isolates. RFLP analysis showed that, in 1995-1996, there was greater diversity than could be determined by allozyme analysis alone. Spatial analysis of the genetic structure of P. infestans indicates that geographic substructuring of this pathogen does occur in this area. Maps displaying the probabilities of occurrence of mating types and genotypes of P. infestans, and of disease severity in a regional scale were obtained. Some genotypes, which exhibited differences in epidemiologically important features such as metalaxyl sensitivity and aggressiveness to tomato and potato, had a restricted spread and were localized in separated areas. Analysis of late blight severity demonstrates recurrent patterns such as the early onset of the disease in the area where both potato and tomato are growing, strengthening the hypothesis that infected potato tubers are the main source of primary inoculum. The information that geostatistics can provide together with the power of GIS and molecular biology techniques can help improve management programs for late blight in the Del Fuerte Valley.