APLF is a forkhead associated (FHA) domain-containing protein with unique poly(ADP)-ribose (PAR)-binding zinc finger (PBZ) domains that are involved in the DNA damage response. The interaction of the APLF PBZ domains with PAR is essential for the rapid recruitment of APLF to sites of DNA double strand breaks (DSBs), while the FHA domain facilitates non-homologous end-joining. In response to ionizing radiation (IR), APLF is phosphorylated at Serine-116 (APLFS116), although the function of this post-translational modification has yet to be defined. Here we provide a detailed characterization of the IR-induced and ATM- dependent phosphorylation of endogenous APLF at Serine-116 in the context of DNA damage. We additionally examine a novel APLF FHA-dependent interaction with 53BP1 (p53 Binding protein 1). Together, we illustrate that APLFS116 phosphorylation is dependent upon both the tandem PBZ domains, as well as the FHA-domain, and that the depletion of either PARP3 or 53BP1, similarly affected APLFS116 phosphorylation. Furthermore, we show that DSB-repair was compromised in cells expressing the APLFS116A mutation. Collectively, our findings provide a detailed understanding of the molecular pathway that leads to the phosphorylation of APLF following DNA damage and suggest that APLFS116 phosphorylation facilitates APLF-dependent DSB repair.

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This thesis demonstrates the effect of micro-damage healing on stress and displacement fields in the vicinity of a crack tip in the material that tend to self-heal. The micro-damage healing model is modeled by incorporating time-dependent traction within the crack faces. This time-dependent traction occurs in a small zone referred to as healing process zone. The effect of the micro-damage healing on crack propagation in elastic media is investigated by deriving analytical relations for Stress Intensity Factor (SIF) when micro-damage healing mechanism is in effect. It is shown that the larger values of both healing process zone and bonding strength decrease the value of SIF near the crack tip. In order to clearly capture this phenomenon, a novel technique based on complex variables is used to derive the equations to calculate the stress and displacement fields in elastic media. Using the third correspondence principle, which is suitable in analyzing the crack shortening (healing phenomenon), the corresponding results of stress and displacement fields in elastic media are converted into viscoelastic media. Since asphalt has time-dependent material properties, the viscoelastic result is more accurate than the elastic. It is shown that an increase in the value of both healing process zone and bonding strength results in a decrease in the stress and displacement fields near the crack tip. Finally, the effect of using different coefficients in defining the bonding strength and relaxation time is evaluated. Asphalt concrete pavements are concurrently subjected to mechanical and environmental loading conditions during their service life. Applied mechanical and environmental loadings gradually degrade properties of asphalt concrete pavements. However, under specific conditions, asphalt concrete has the potential to heal and regain part of its strength. Identifying a model for the healing process is crucial. This proposed model is not dependent on the test methods that empower its usage in computational modeling. Moreover, this research considers both effects of instantaneous healing (a result of wetting) and time-dependent bond strength (a result of molecular diffusion between the crack faces), using the complex-variable method. Schapery (1989) considered only instantaneous healing and regarded it as the total bond strength. Therefore, considering both effects of instantaneous and time-dependent bond-strength makes this model superior with respect to the analogous model. It is hoped that this research provides insight on the healing mechanism at micro-scale.

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The project was to clone the gene encoding a nuclear enzyme poly-ADP-ribose polymerase (PARP) involved in the posttranslational modification of nuclear proteins. This modification is important in the regulation of various cellular processes such as cell differentiation, proliferation and in the molecular events involved in the recovery of cells from DNA damage. At the start of this project this enzyme had been well characterized in animal systems but had not as yet been explored in plants. Firstly, I showed the enzyme to be present in higher plant nuclei, by a series of experiments including enzyme assays and western blotting (probed with a polyclonal antibody specific to the protein). Molecular biology approaches were used to isolate the gene encoding the PARP enzyme. These techniques included screening of cDNA libraries, constructed in λZAPII, with both the polyclonal antibody and a gene probe (a restriction digest of a human PARP gene was performed and a 1.4Kb fragment containing the C-terminal region of the gene used as a probe). This identified a number of bacteriophages from which sequence information was obtained (by making and extracting phagemids). Subsequent translation of these nucleotide sequences revealed that one of the sequences (245941) obtained in this manner showed homology to the PARP protein. Degenerate oligonucleotide primers, designed to the conserved C-terminal region of the gene, were also used in an attempt to amplify a 375bp region of the gene thought to contain the PARP signature. PCR products of the expected size (375bp) were obtained from an SST cDNA library. These PCR products hybridized to the gene probe (mentioned earlier). Subsequent subcloning revealed multiple products of 375bp comigrating in the agarose gels. Two different sequences were obtained which were, upon translation, shown not be PARP-like sequence.

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Computerized cognitive retraining is a technique for remediation of the cognitive and behavioral changes which follow a traumatic brain injury. The technique utilizes specifically developed computer software which builds on the basic foundations of intellectual functioning. While the injured patient is the target of treatment, the method appeared to have an impact on the patient's family as well. Families of patients who participated in computerized cognitive retraining initially appeared to have fewer difficulties with anxiety, depression, and family problems. They also appeared to be more involved in the patient's treatment than were similar families who had not had this experience.The experiment evaluated the secondary psychological effects of computerized cognitive retraining on the brain injured patient's primary caretaker in the family. The dependent variables studied were perception of family involvement in patient treatment, anxiety, depression and perception of family problems.Subjects were recruited from the outpatient case load of the Psychology Department of Fort Sanders Regional Medical Center in Knoxville, Tennessee and from a local support group for families of patients who have experienced a traumatic brain injury. The injured patients and family members participated in the retraining technique. A total of seventeen patient/family member pairs participated in the study.Subjects participated in either the experimental or control treatments. The experimental group underwent five sessions of approximately one hour in length. The patient and family member worked together during the course of the retraining. Brief counseling followed each session. The treatment group used an Atari 800 computer and Bracy's "Foundations" cognitive retraining software package ( Psychological Software Services, Indianapolis, Indiana). The control group was a waiting list, minimum contact group, whose participation was limited to completion of the pre and posttest materials.Family members in both groups completed pre and posttesting packages. These included: a demographic questionnaire, the "Problem Solving Inventory" (Heppner, 1982a, 1982b), the "State/Trait Anxiety Inventory" (Speilberger, 1983), the "Beck Depression Inventory" (Beck, 1961), and the "Scale of Marriage Problems" (Swenson & Fiore, 1982).The experiment utilized Kerlinger's pretest-posttest control group design (Kerlinger, 1973). Patient/family pairs were randomly selected from the available subject pool. Control or experimental treatment groupings were assigned by stratified random sampling. Data were analyzed by the use of two way analysis of variance with repeated measures on one factor. Throughout the analysis, a level of R < .05 was required to infer statistical significance.The results of this experiment did not support the effectiveness of computerized cognitive retraining as a specific intervention method for the families of brain injured individuals. The findings revealed that there were no statistically significant differences between the control and treatment groups on measures of perception of family involvement, depression, or perception of family problems. The treatment group experienced a statistically significant increase in state anxiety following the experimental treatment. The validity, generalizability and implications for these findings were discussed in light of prior research.Recommendations for further research in the area of family response to computerized cognitive retraining include replication of the study with greater numbers of subjects and more sophisticated evaluation and treatment methodology. It is also suggested that future research address the patient's cognitive level, the utilization of varied retraining protocols specific to the patient's level of function, and premorbid psychosocial factors which may influence the process of cognitive remediation.

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No description available.