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J T Parsons

Publications and source records attributed to J T Parsons.

At least 19 recordsLinked to original sources
PubMed1999

Cytoskeletal changes induced by GRAF, the GTPase regulator associated with focal adhesion kinase, are mediated by Rho.

Graf, the GTPase regulator associated with focal adhesion kinase was previously shown to have GAP activity for &Rgr; A and Cdc42 in vitro (Hildebrand et al 1996 Mol. Cell Biol. 16: 3169-3178). In this study we sought to determine whether Graf acted at the level of Cdc42, Rho, or both in vivo and whether Graf was a signal terminator or transducer for these proteins. Microinjection of Graf cDNA into subconfluent Swiss 3T3 cells (in the presence of serum) has marked effects on cell shape and actin localization. Graf expression causes clearing of stress fibers followed by formation of long actin based filopodial-like extensions. Similar phenotypes were observed following injection of the Rho-inhibitor, C3 into these cells. The Graf response was dependent on GAP activity, since injection of Graf cDNA containing point mutations in the GAP domain (R236Q or N351V) which block enzymatic activity, does not confer this phenotype. Injection of Graf into Swiss 3T3 cells in which Rho has been down-regulated by serum starvation has no effect on cell morphology. Using this system, we demonstrate that Graf blocks sphingosine-1-phosphate (SPP) stimulated (Rho-mediated) stress fiber formation. Conversely, Graf expression does not inhibit bradykinin stimulated (Cdc42-mediated) filopodial extensions. These data indicate that Graf is a GAP for Rho in vivo. To further substantiate these results we examined the effect of Graf over-expression on Rho-mediated neurite retraction in nerve growth factor (NGF)-differentiated PC12 cells. In PC12 cells, which express relatively high levels of endogenous Graf, overexpression of Graf (but not Graf containing the R236Q mutation) enhances SPP-induced neurite retraction. These data indicate the possibility that Graf may be an effector for Rho in certain cell types.

3T3 Cells↗
PubMed1998

Separation of radiolabeled orthophosphate and adenosine 5'-triphosphate by 20% polyacrylamide gel electrophoresis: an assay for brain microsomal Mg2+/Ca2+ ATPase activity.

Measuring orthophosphate is an important tool in biochemical analyses used to study membrane transport ATPases essential for calcium homeostasis. Current techniques involve extraction of radioactive phosphate with organic solvents, a technique that results in large quantities of hazardous radioactive waste. Other colorimetric assays are less sensitive and are complicated by interference of background absorbance from membrane tissue and unutilized ATP. This report describes a unique assay for the detection of inorganic phosphate and its application to the study of rat brain microsomal Mg2+/Ca2+ ATPase from a membrane fraction. The technique involves the separation of radioactive phosphate from unused gamma-radiolabeled ATP by resolution on 20% polyacrylamide gels. Both are visualized with X-ray film and quantitated by liquid scintillation counting after extraction from the gels. The assay can detect as little as 4.1 pmol of radiolabeled ATP and ATPase activity in 3.5 ng/microliter of membrane protein. This method offers the advantage of simultaneous quantitation of radiolabeled ATP and radioactive orthophosphate without the generation of large quantities of radioactive waste. The results demonstrate the development of a novel assay procedure for quantitating orthophosphate that is extremely sensitive, reproducible, and applicable to the study of any phosphate liberating enzyme.

Adenosine Triphosphate↗
PubMed1998

Expression and characterization of splice variants of PYK2, a focal adhesion kinase-related protein.

Focal adhesion kinase and the recently identified proline-rich tyrosine kinase 2 (PYK2), also known as cell adhesion kinase &bgr ;, related adhesion focal tyrosine kinase or calcium-dependent protein tyrosine kinase, define a new family of non-receptor protein tyrosine kinases. Activation of PYK2 has been implicated in multiple signaling events, including modulation of ion channels, T- and B-cell receptor signaling and cell death. Mechanisms underlying the functional diversity of PYK2 are unclear. Here, we provide evidence for two novel alternatively expressed isoforms of PYK2. One isoform, designated PYK2s (PYK2 splice form), appears to be a splice variant of PYK2 lacking 42 amino acids within the C-terminal domain. A second isoform, referred to as PRNK (PYK2-related non-kinase), appears to be specified by mRNAs that encode only part of the C-terminal domain of PYK2. Northern blot analysis indicates that the unspliced PYK2 is expressed at high levels in the brain and poorly expressed in the spleen, whereas PYK2s and PRNK are expressed in the spleen. In situ hybridization studies of rat brain demonstrate that the unspliced PYK2 is selectively expressed at high levels in hippocampus, cerebral cortex and olfactory bulb, whereas PYK2s and PRNK are expressed at low levels in all regions of rat brain examined. Immunofluorescence analysis of ectopically expressed PRNK protein shows that PRNK, in contrast to full-length PYK2, is localized to focal adhesions by sequences within the focal adhesion targeting domain. In addition, PYK2, but not PRNK, interacts with p130(cas )and Graf. These results imply that PRNK may selectively regulate PYK2 function in certain cells by binding to some but not all PYK2 binding partners, and the functional diversity mediated by PYK2 may be due in part to complex alternative splicing.

3T3 Cells↗
PubMed1998

Characterization of graf, the GTPase-activating protein for rho associated with focal adhesion kinase. Phosphorylation and possible regulation by mitogen-activated protein kinase.

Graf is a GTPase-activating protein for Rho that interacts with focal adhesion kinase and co-localizes with the actin cytoskeleton (Hildebrand, J. D., Taylor, J. M. and Parsons, J. T. (1996) Mol. Cell. Biol. 16, 3169-3178). We examined the expression and regulation of Graf as a prelude to understanding the role of Graf in mediating signal transduction in vivo. We demonstrated that Graf is a ubiquitously expressed 95-kDa protein with high levels observed in heart and brain and cells derived from these tissues. Stimulation of PC12 cells with epidermal growth factor or nerve growth factor induced a phosphatase-reversible mobility shift upon gel electrophoresis, indicative of phosphorylation. In vitro, purified mitogen-activated protein (MAP) kinase catalyzed the phosphorylation of Graf on serine 510, suggesting that Graf phosphorylation may be mediated through MAP kinase signaling. In addition, the mutation of serine 510 to alanine inhibited the epidermal growth factor-induced mobility shift of mutant Graf protein in vivo, consistent with serine 510 being the site of in vivo phosphorylation. Based on these data we suggest that phosphorylation of Graf by MAP kinase or related kinases may be a mechanism by which growth factor signaling modulates Rho-mediated cytoskeletal changes in PC12 and perhaps other cells.

Amino Acid Sequence↗
PubMed1998

T4 laryngeal carcinoma: radiotherapy alone with surgery reserved for salvage.

PURPOSE: To review the results of primary radiation therapy for patients with T4 squamous cell carcinoma of the larynx. METHODS AND MATERIALS: Between October 1964 and October 1994, 43 patients with T4 invasive squamous cell carcinoma of the larynx received radiotherapy with curative intent in the University of Florida Department of Radiation Oncology. All patients had a minimum of 2 years follow-up. There were 26 primary cancers of the supraglottic larynx, 11 of the glottic larynx, and 6 of the subglottic larynx. RESULTS: The 5-year actuarial rate of local control was 52%. By direct calculation, local control was achieved in 8 (38%) of 21 supraglottic carcinomas, 8 (89%) of 9 glottic tumors, and 2 of 6 subglottic tumors. Local control of nonbulky lesions was achieved in 67%, and 38% of bulky lesions were locally controlled. Only 3 (17%) of 18 local recurrences were successfully salvaged by subsequent surgery. There were 2 (5%) severe complications of irradiation. CONCLUSION: From our series, as well as a review of the literature, local control by primary irradiation has been achieved in approximately 50% of patients with T4 laryngeal cancer. Selection factors for choosing irradiation have not been well described: the present series contains a small amount of information suggesting that tumor volume may be a reliable predictor of control, but further substantiation is required.

Adult↗
PubMed1998

Evaluation of pretreatment computed tomography as a predictor of local control in T1/T2 pyriform sinus carcinoma treated with definitive radiotherapy.

BACKGROUND: This study was undertaken to determine whether pretreatment computed tomography (CT) findings can predict local control in pyriform sinus carcinoma treated with definitive radiotherapy (RT). METHODS: Twenty-three patients with pyriform sinus carcinoma (T1: n = 5; T2: n = 18) were treated with high-dose RT and followed for a minimum of 2 years. Tumor volumes and extent were determined on pretreatment CT studies. The specific CT parameters assessed were analyzed as predictors of local control. RESULTS: There was a significant decrease in local control rate for tumors over 6.5 mL (1 of 4 [25%]) relative to tumors under 6.5 mL (17 of 19 [89%]; p = .021). Sensitivity and specificity for local control using this cutoff were 94% and 60%, respectively. Tumor score, as a measure of anatomic extent, was also found to be a significant predictor of local control (p = .033). The local control rate was not influenced significantly by the presence of "minimal" apex disease (< 10 mm in greatest dimensions as measured on CT) but decreased significantly when "bulk" apex disease (> OR = 10 mm) was present (p = .027). Laryngeal cartilage sclerosis was not a significant predictor of outcome. CONCLUSION: Computed tomography can stratify pyriform sinus carcinomas into groups more or less likely to be locally controlled with definitive RT.

Carcinoma, Squamous Cell↗
PubMed1998

Carcinoma of the skin metastatic to the parotid area lymph nodes.

BACKGROUND: We performed an analysis of treatment outcome at the University of Florida for 77 patients with previously untreated carcinoma of the skin metastatic to parotid area lymph nodes. METHODS: Seventy-seven patients with 79 parotid node metastases were treated with curative intent between 1966 and 1994. All patients had a minimum 2-year follow-up. Treatment consisted of radiotherapy alone in 18 patients, preoperative radiotherapy in 6 patients (7 parotids), and postoperative radiotherapy in 53 patients (54 parotids). RESULTS: Overall rate of disease control in the parotid area at 5 years was 82%. Parotid area disease control according to treatment group revealed: surgery and postoperative radiotherapy, 43 of 48 (90%); preoperative radiotherapy and surgery, 4 of 5 (80%); and radiotherapy alone, 8 of 15 (53%). Multivariate analysis of parotid disease control revealed the following: treatment method (p = .0037), N stage (p = .0726), cranial nerve involvement (p = .1851), fixation (p = .1820), skin involvement (p = .1771), and sex (p = .5782). Overall 5-year absolute and cause-specific survival rates were 54% and 68%, respectively. The 5-year cause-specific survival rate was 72% after surgery and postoperative radiotherapy and 59% following radiotherapy alone. Multivariate analysis of cause-specific survival revealed the following: skin involvement (p = .0215), cranial nerve involvement (p = .1549), fixation (p = .0347), N stage (p = .4302), sex (p = .6806), and treatment method (p = .9599). CONCLUSIONS: Our current policy is to treat patients with tumor that is initially resectable with surgery followed by radiotherapy, whereas those who have initially unresectable disease undergo preoperative radiotherapy followed by surgical resection if the tumor becomes resectable. If surgery cannot be performed for medical reasons, patients still have better than a 50% chance of being cured with radiotherapy alone.

Adult↗
PubMed1998

Radiotherapy in the management of chemodectomas of the carotid body and glomus vagale.

BACKGROUND: Because only limited data are available pertaining to radiotherapy for chemodectomas of the carotid body and glomus vagale, we reviewed our experience. METHODS: Fifteen patients with 23 chemodectomas of either the carotid body or glomus vagale were treated with radiotherapy at the University of Florida between 1981 and 1995. Eighteen lesions were previously untreated. One patient had received prior radiotherapy at another institution and four patients had received prior surgery. RESULTS: The local control rate at 10 years, calculated by the Kaplan-Meier product-limit method, was 96% for the overall group of 23 lesions and 100% for the subset of 22 lesions without prior radiotherapy. The 10-year cause-specific survival rate was 89% for all 15 patients and 100% for the 14 patients who had received no prior radiotherapy. No patient experienced a significant complication secondary to irradiation. CONCLUSIONS: Irradiation offers a high probability of tumor control with relatively minimal risks for patients with chemodectomas of the carotid body and glomus vagale.

Adult↗
PubMed1998

Diagnostic evaluation of squamous cell carcinoma metastatic to cervical lymph nodes from an unknown head and neck primary site.

BACKGROUND: The purpose of this study was to evaluate the efficacy of the modern diagnostic evaluation for squamous cell carcinoma metastatic to cervical lymph nodes from an unknown head and neck primary site. METHODS: One hundred thirty patients were evaluated between June 1983 and June 1997. All underwent head and neck examinations, head and neck computed tomography (CT), and/or magnetic resonance imaging (MRI) scans, panendoscopies, and biopsies of head and neck mucosal sites. Twenty-four patients underwent 2-[fluorine-18]-2-deoxy-D-glucose (FDG) single photon emission computed tomography (SPECT); 34 patients underwent tonsillectomy. RESULTS: The primary site was identified in 56 patients (43%); the likelihood was increased in patients with suggestive findings on physical examination and/or radiographic evaluation. Eighty-three percent of the lesions were located in the tonsillar fossa and base of tongue. Results of FDG-SPECT scans were positive in 20 patients (83%); the primary tumor was detected in 7 patients (35%). Twelve (35%) of 34 patients who underwent tonsillectomy had a primary tumor discovered in the tonsillar fossa. Multivariate analysis of successful primary site detection revealed that suggestive findings on physical examination (p= .0225) and suggestive findings on CT and/or MRI (p = .0013) were significantly related to this end point. CONCLUSION: The primary lesion will be detected in over 40% of patients with physical examination of the head and neck and CT and/or MRI followed by panendoscopy and biopsies. Limited data pertaining to FDG-SPECT suggest that this provides additional useful information in a small subset of patients. Tonsillectomy is useful for those with suggestive findings on physical examination and/or radiographic evaluation.

Adult↗
PubMed1998

Merkel cell carcinoma of the skin.

Merkel cell carcinoma is a rare, aggressive neuroendocrine tumor of the skin with a predisposition for local regional and distant spread. Radiotherapy after wide local excision has improved local control, but distant spread continues to be a significant problem. This is an update of our experience in the treatment of Merkel cell carcinoma at the University of Florida. Of 24 patients who were treated for Merkel cell carcinoma between 1984 and 1996, 18 patients were treated at the time of the initial diagnosis, and six were treated after local-regional recurrence. Of the 18 previously untreated patients, 13 had primary sites in the head and neck region, and five had primary sites elsewhere. Minimum follow-up was 1 year; no patient was lost to follow-up. The 5-year absolute survival, cause-specific survival, and local-regional control rates for the entire group were 27%, 31%, and 78%, respectively. Patients who were treated with radiotherapy at the time of initial presentation had 5-year absolute survival, cause-specific survival, and local-regional control rates of 38%, 44%, and 73%, respectively. Most deaths were due to distant metastasis. Site of the primary tumor (head and neck versus other) was not associated with any difference in the outcome. Of six patients who were treated at the time of local-regional recurrence, five developed distant metastasis at 3-19 months (median 8 months) from the time of treatment. One patient was alive and without evidence of disease 13 months after treatment. All patients who were treated at the time of local-regional recurrence had local-regional control after radiotherapy at 3-30 months (median 8 months). Wide local excision and radiotherapy is effective local-regional treatment for Merkel cell carcinoma of the skin, but distant metastasis remains a significant problem in this disease. The role and effectiveness of chemotherapy as part of the initial treatment remains to be defined.

Aged↗
PubMed1998

The role of the family system in HIV risk reduction: youths with hemophilia and HIV infection and their parents. Adolescent Hemophilia Behavioral Intervention Evaluation Project (HBIEP) Study Group.

OBJECTIVE: To examine the relationship between family communication and HIV risk reduction behaviors among a multisite sample of 125 male youths (ages 12-25) with hemophilia and HIV- infection, as well as their parents. METHODS: Participants completed self-report surveys assessing communication and attitudes regarding HIV risk reduction interventions; adolescents also provided data about their sexual behaviors. RESULTS: Adolescents with parents who discuss sexual issues were more likely to report HIV status disclosure to sexual partners. Most parents were supportive of HIV risk reduction interventions for their adolescents, but the youths themselves tended to endorse only interventions that offered opportunities for recreational activities and socialization with peers. CONCLUSIONS: Findings are discussed in terms of intervention implications and the need for family systems-based programs.

Adolescent↗
PubMed1998

Identification of a novel cortactin SH3 domain-binding protein and its localization to growth cones of cultured neurons.

Cortactin is an actin-binding protein that contains several potential signaling motifs including a Src homology 3 (SH3) domain at the distal C terminus. Translocation of cortactin to specific cortical actin structures and hyperphosphorylation of cortactin on tyrosine have been associated with the cortical cytoskeleton reorganization induced by a variety of cellular stimuli. The function of cortactin in these processes is largely unknown in part due to the lack of information about cellular binding partners for cortactin. Here we report the identification of a novel cortactin-binding protein of approximately 180 kDa by yeast two-hybrid interaction screening. The interaction of cortactin with this 180-kDa protein was confirmed by both in vitro and in vivo methods, and the SH3 domain of cortactin was found to direct this interaction. Since this protein represents the first reported natural ligand for the cortactin SH3 domain, we designated it CortBP1 for cortactin-binding protein 1. CortBP1 contains two recognizable sequence motifs within its C-terminal region, including a consensus sequence for cortactin SH3 domain-binding peptides and a sterile alpha motif. Northern and Western blot analysis indicated that CortBP1 is expressed predominately in brain tissue. Immunofluorescence studies revealed colocalization of CortBP1 with cortactin and cortical actin filaments in lamellipodia and membrane ruffles in fibroblasts expressing CortBP1. Colocalization of endogenous CortBP1 and cortactin was also observed in growth cones of developing hippocampal neurons, implicating CortBP1 and cortactin in cytoskeleton reorganization during neurite outgrowth.

3T3 Cells↗
PubMed1998

Translocation of cortactin to the cell periphery is mediated by the small GTPase Rac1.

Small GTPases of the Rho family regulate signaling pathways that control actin cytoskeletal structures. In Swiss 3T3 cells, RhoA activation leads to stress fiber and focal adhesion formation, Rac1 to lamellipoda and membrane ruffles, and Cdc42 to microspikes and filopodia. Several downstream molecules mediating these effects have been recently identified. In this report we provide evidence that the intracellular localization of the actin binding protein cortactin, a Src kinase substrate, is regulated by the activation of Rac1. Cortactin redistributes from the cytoplasm into membrane ruffles as a result of growth factor-induced Rac1 activation, and this translocation is blocked by expression of dominant negative Rac1N17. Expression of constitutively active Rac1L61 evoked the translocation of cortactin from cytoplasmic pools into peripheral membrane ruffles. Expression of mutant forms of the serine/threonine kinase PAK1, a downstream effector of Rac1 and Cdc42 recently demonstrated to trigger cortical actin polymerization and membrane ruffling, also led to the translocation of cortactin to the cell cortex, although this was effectively blocked by coexpression of Rac1N17. Collectively these data provide evidence for cortactin as a putative target of Rac1-induced signal transduction events involved in membrane ruffling and lamellipodia formation.

3T3 Cells↗
PubMed1998

Altered fractionation in radiation therapy for squamous-cell carcinoma of the head and neck.

Following is a review of altered fractionation in radiation therapy for head and neck cancer. The goals of altered fractionation are to increase local-regional control and/or reduce the risk of late complications. Altered fractionation schedules can be broadly classified as accelerated fractionation and hyperfractionation. Data indicate that some of these schedules, particularly hyperfractionated radiation therapy, offer improved results compared to conventionally fractionated radiation therapy. Most investigators have observed no significant increased risk of late complications with the dose-fractionation schedules described.

Carcinoma, Squamous Cell↗
PubMed1998

CT findings in chondroradionecrosis of the larynx.

PURPOSE: Our goal was to describe the CT findings before and after radiation therapy in a series of patients with laryngeal chondroradionecrosis. METHODS: The CT studies obtained before and after radiation therapy in nine patients with the diagnosis of laryngeal chondroradionecrosis were reviewed retrospectively. RESULTS: CT scans revealed abnormalities in all patients. A variable degree of laryngeal soft-tissue swelling was seen in eight of the patients. In four patients, cartilaginous abnormalities were visible initially, and appeared in three of four other patients who had further follow-up CT studies. Six patients had involvement of the thyroid cartilage; collapse of the thyroid cartilage was seen in two cases and gas bubbles were visible adjacent to the thyroid cartilage in three cases. Four patients with involvement of the thyroid cartilage eventually underwent total laryngectomy, and one died suddenly in severe respiratory distress. In all three patients with arytenoidal involvement, anterior dislocation of this cartilage was seen; in two of these patients, the adjacent part of the cricoid cartilage showed some sclerosis. Two patients with arytenoidal necrosis (both with cricoidal sclerosis) kept a functional larynx. In one case, cricoidal sclerosis was seen in association with lysis of the thyroid cartilage. CONCLUSION: The CT appearance of laryngeal chondroradionecrosis is nonspecific, but the diagnosis can be strongly suggested in cases of sloughing of the arytenoid cartilage, fragmentation and collapse of the thyroid cartilage, and/or in the presence of gas bubbles around the cartilage.

Adult↗
PubMed1997

Induction of apoptosis after expression of PYK2, a tyrosine kinase structurally related to focal adhesion kinase.

Many cells (e.g., epithelial cells) require attachment to the extracellular matrix (ECM) to survive, a phenomenon known as anchorage-dependent cell survival. Disruption of the cell-ECM interactions mediated by the integrin receptors results in apoptosis. Focal adhesion kinase (FAK), a 125-kD protein tyrosine kinase activated by integrin engagement, appears to be involved in mediating cell attachment and survival. Proline-rich tyrosine kinase 2 (PYK2), also known as cellular adhesion kinase beta (CAKbeta) and related adhesion focal tyrosine kinase, is a second member of the FAK subfamily and is activated by an increase in intracellular calcium levels, or treatment with TNFalpha and UV light. However, the function of PYK2 remains largely unknown. In this study, we show that over-expression of PYK2, but not FAK, in rat and mouse fibroblasts leads to apoptotic cell death. Using a series of deletion mutants and chimeric fusion proteins of PYK2/FAK, we determined that the NH2-terminal domain and tyrosine kinase activity of PYK2 were required for the efficient induction of apoptosis. Furthermore, the apoptosis mediated by PYK2 could be suppressed by over-expressing catalytically active v-Src, c-Src, phosphatidylinositol-3-kinase, or Akt/protein kinase B. In addition, it could also be suppressed by overexpressing an ICE or ICE-like proteinase inhibitor, crmA, but not Bcl2. Collectively, our results suggest that PYK2 and FAK, albeit highly homologous in primary structure, appear to have different functions; FAK is required for cell survival, whereas PYK2 induces apoptosis in fibroblasts.

Animals↗