Protein Phosphatase 1 binds strongly to the retinoblastoma protein but not to p107 or p130 in vitro and in vivo

PURPOSE: To identify and characterize retinoblastoma protein (pRb) binding proteins that may influence retinoblast proliferation and retinal pigment epithelial cell survival. METHODS: The yeast two-hybrid system was used to screen a bovine retinal cDNA library and to characterize positive clones. DNA sequencing and site-directed mutagenesis were used for further analysis. Co-immunoprecipitation experiments were used to confirm the results of the two-hybrid system in vivo. RESULTS: In the two-hybrid system, Protein Phosphatase 1alpha1 (PP1alpha1) binds the retinoblastoma protein. Unlike several other pRb binding proteins, PP1alpha1 binds only weakly to the Rb family member p107, and does not demonstrate detectable binding to p130. Confirming the two-hybrid results, endogenous PP1 in a human retinal pigment epithelial (RPE) cell line co-immunoprecipitates with endogenous pRb but not p107 or p130. Site directed mutagenesis of two pRb binding motifs in PP1alpha1 from LXSXE to LXCXE leads to slight increases in its two-hybrid interaction with pRb but does not alter its binding preference for pRb over the other family members. The complete sequence of bovine PP1alpha1 is reported. CONCLUSIONS: The strong two-hybrid interaction between PP1alpha1 and pRb, but not p107 or p130, suggests that the phosphorylation status of members of the pRb family may be regulated by different phosphatases, contributing to fine control of cell cycle progression. Conversely, PP1 activity may be specifically regulated by pRb and not p107 or p130. Mutagenesis studies suggest that PP1alpha1's LXSXE motif is not responsible for its binding preference for pRb over p107 and p130. Disruption of the PP1-pRb interaction may influence retinoblastoma tumorigenesis as well as RPE cell proliferation and survival.     

The changing psychological contract at work and employee burnout

Today we stand in a vortex of technological, economic, and cultural changes that altered dramatically the world of labor and with it the psychological contract between employers and employees. While the effects of the changed contract at work are usually addressed from an organizational, social or economic perspective, the current article addresses it from a psychological perspective from which one noteworthy cost of the changed psychological contract is employee burnout. The article describes burnout, differentiates it from stress, and proposes an existential perspective to explain its underlying dynamic, using the results of a cross-cultural study of Israeli and American managers as an example. Recent studies on gender differences in management are used to point in the recommended for preventing employee burnout, despite the new psychological contract, namely--a democratic, egalitarian management style.     

Mechanism of immune dysfunction in sepsis: inducible nitric oxide-meditated alterations in p38 MAPK activation

BACKGROUND: After the onset of sepsis, there is a marked dysfunction in cell-mediated immunity that contributes to the morbidity and mortality seen in this condition. Although both nitric oxide (NO) from inducible NO synthase (iNOS) and the activation of p38 mitogen-activated protein kinase (p38 MAPK) appear to contribute to this immune dysfunction, the extent to which NO regulates p38 MAPK activity in sepsis remains unknown. METHODS: To examine this, we induced sepsis by cecal ligation and puncture (CLP) in iNOS knockout (iNOS -/-) or C57BL/6 control mice. Twenty-four hours after CLP or sham operation, splenic T cells and macrophages were isolated and then stimulated with monoclonal antibody against the T-cell marker CD3 (anti-CD3) or lipopolysaccharide. At 4 or 24 hours after stimulation, cytokine release was determined by enzyme-linked immunosorbent assay, and p38 MAPK phosphorylation (activation) was determined by immunoblotting with antibody specific to phosphorylated p38 MAPK. RESULTS: Splenic T-cell p38 MAPK activation and interleukin (IL)-10 release was increased by CLP, whereas Th1 cytokine (IL-2, interferon-gamma) release was depressed. iNOS gene deficiency inhibited p38 MAPK activation in splenic T cells taken from septic mice, and also suppressed IL-10 release in both sham and septic mice. Interestingly, although deficiency of iNOS restored IL-2 release after CLP, both sham and CLP T cells remained depressed in their ability to release interferon-gamma. Septic insult markedly suppressed C57BL/6 splenic macrophage release of proinflammatory agents tumor necrosis factor, IL-12, and IL-1, while augmenting the release of IL-10. However, although deficiency of iNOS concomitantly restored the ability to produce tumor necrosis factor while suppressing the rise in IL-10 release and p38 MAPK activation, it only partially restored IL-1 release and had no effect on IL-12 production seen after CLP. CONCLUSION: These data suggest that NO release from iNOS regulates aspects of sepsis-induced immune dysfunction by the activation of p38 MAPK.     

Infraclavicular brachial plexus block using a multiple injection technique and an approach in the cranial direction in a patient with anticipated difficulties in tracheal intubation

A man with a pathologic diaphysial fracture of the middle third of the left humerus underwent emergency surgery for osteosynthesis of the fracture. Preoperative examination revealed that intubation would be difficult due to a history of radical surgery for epidermoid carcinoma of the oropharynx, and local-regional anesthesia was therefore considered. An interscalene approach was contraindicated because of the presence of an ulcerated metastatic cutaneous lesion in the area of puncture; and axillary block was also ruled out given that the fracture made movement painful. However, a satisfactory block and optimal conditions for surgery were achieved through an infraclavicular block using a cephalad multiple injection technique. Among the various levels of brachial plexus blockade, the infraclavicular option is little known and the least utilized, considering that one of its advantages is that the upper limb does not need to be moved for referencing (giving it an advantage over the axillary block) and that it has a lower incidence of pneumothorax (in comparison with a supraclavicular approach). Combined with a multiple injection technique and puncture in a cephalad direction, this solution allowed proximal surgery to be performed on the arm of a patient in whom intubation would have been difficult.     

Bilateral testicular germ cell tumors: twenty-year experience at M. D. Anderson Cancer Center

BACKGROUND: The incidence of testicular carcinoma in the United States has increased significantly over the last two decades. Germ cell tumors form the majority of malignant testicular tumors. With advances in diagnosis and therapeutic approaches, germ cell tumors are now highly sensitive to treatment, providing long-term survival. It has been speculated that the incidence of bilateral germ cell tumors may increase due to the improved survival of patients with unilateral germ cell tumors. In this report, the authors present a study of bilateral germ cell tumors of the testis in men who were treated at The University of Texas M. D. Anderson Cancer Center over a 20-year period with emphasis on their incidence, histologic features, and clinical features. METHODS: Between 1978 and 1999, 2431 patients with testicular germ cell tumors were treated at The University of Texas M. D. Anderson Cancer Center. Among these, 24 patients with bilateral germ cell tumors were identified. Clinical records and all available pathology slides of the tumors were reviewed. RESULTS: The overall incidence of bilateral germ cell tumors in the patients with testicular germ cell tumors was 1% (24 of 2431 patients). The incidence was 1.8% (14 of 776 patients) in patients with seminoma and 0.6% (10 of 1655 patients) in patients with nonseminomatous germ cell tumors. Patients with seminoma who were age 相似文献   

Can cure in patients with osteosarcoma be achieved exclusively with chemotherapy and abrogation of surgery?

BACKGROUND: Contemporary therapy for osteosarcoma is comprised of initial treatment with chemotherapy and surgical extirpation of the primary tumor in the affected bone. In view of the major advances forged by chemotherapy in the treatment of the primary tumor, an attempt was made to destroy the tumor exclusively with this therapeutic modality and abrogate surgery. METHODS: Thirty-one consecutive patients were treated. All had localized disease (absence of metastases) at the time of diagnosis. Initial treatment with chemotherapy was comprised of high-dose methotrexate and leucovorin rescue (MTX-LF) in 3 patients and intraarterial cisplatin in 28 patients. Clinical, radiologic, angiographic, radionuclide, and histologic investigations were utilized to assess the efficacy of treatment. After a response at 3 months, entry into the study was permitted and treatment was maintained for a total of 18-21 months with a combination of agents comprised of MTX-LF, intraarterial cisplatin, and doxorubicin. Patients were monitored closely for disease recurrence with the investigations outlined earlier. Two informed consents were required: one at the time of diagnosis and another at 3 months after the initial response had been attained. RESULTS: Only 3 of 31 patients were cured with the administration of chemotherapy alone. Local recurrence and pulmonary metastases were not reported to develop in these 3 patients during a follow-up period of 204+ to 225+ months. Four other patients also possibly were cured with chemotherapy alone. At their request, several months after the cessation of chemotherapy, they underwent surgical extirpation of the tumor. No evidence of viable tumor was found. These patients remained free of disease for 192+ to 216+ months. Thus, only seven patients did not develop local recurrence and/or pulmonary metastases. Among the remaining 24 patients, 9 developed local recurrences without pulmonary metastases 14-74 months (median, 30 months) after the initial response. Eight of the nine patients were rendered tumor free by extirpation of the local recurrence. Two of these eight patients subsequently died, one of the acquired immunodeficiency syndrome (AIDS) and the other of varicella septicemia. The ninth patient refused amputation and died of metabolic complications. Three other patients developed local recurrences 20-69 months and pulmonary metastases 10-98 months after achievement of the initial response. These patients were rendered tumor free by extirpation of the local recurrence and metastasectomy. One of these patients also later died of AIDS. In the remaining 12 patients, local recurrences developed 5-29 months (median, 14 months) after the initial response was achieved. The patients also developed pulmonary metastases 11-60 months after the initial response. In eight patients the local recurrences were extirpated and metastasectomy was performed; however, these patients later died of recurrent pulmonary metastases. The remaining four patients refused to undergo extirpation of the local recurrence. The pulmonary metastases were not resected. They failed to respond to alternate therapy. Thus, the tumor-free survival rate was 23% (7 of 31 patients): 3 patients who were treated with chemotherapy only and 4 patients who were treated with chemotherapy plus surgery. The overall survival rate (patients who remained free of disease and those who underwent resection for local recurrence and metastasectomy) was 48% (15 of 31 patients). Prior to the deaths from AIDS and varicella septicemia, the overall survival was 58% (18 of 31 patients). CONCLUSIONS: Utilizing the regimen employed in the current study, only 3 of 31 patients with osteosarcoma (10%) were cured exclusively with chemotherapy. Four additional patients who underwent extirpation of the primary tumor without disease recurrence and in whom no viable tumor was found in the resected specimens possibly could increase the number of patients who potentially were cured with chemotherapy to 7 (23%). With an overall expected cure rate of 50-65% with "conventional" sin whom no viable tumor was found in the resected specimens possibly could increase the number of patients who potentially were cured with chemotherapy to 7 (23%). With an overall expected cure rate of 50-65% with "conventional" strategies, the results of the current study do not justify the adoption of current forms of chemotherapy as exclusive treatments for osteosarcoma.     

Decrease of 1-methyl-1,2,3,4-tetrahydroisoquinoline synthesizing enzyme activity in the brain areas of aged rat

1-Methyl-1,2,3,4-tetrahydroisoquinoline (1-MeTIQ), an endogenous monoamine, which prevents the neurotoxic effect of 1-methyl-4-phenylpyridinium ion (MPP(+)) and other endogenous neurotoxins, has been described as being enzymatically formed in the brain by the 1-MeTIQ synthesizing enzyme (1-MeTIQse). In this paper, we report the brain's regional distribution of this enzyme in 3- and 24-month-old rats. The results show that the activity is spread throughout the brain, the highest activity being in the dopaminergic areas (striatum and substantia nigra) and in the cortex. During aging there was a 1-MeTIQse activity reduction ( approximately 50%) in the areas implicated in the ethyology of Parkinson disease (substantia nigra, striatum) and in the cerebral cortex.     

A methodological bias toward overestimation of molecular evolutionary time scales

There is presently a conflict between fossil- and molecular-based evolutionary time scales. Molecular approaches for dating the branches of the tree of life frequently lead to substantially deeper times of divergence than those inferred by paleontologists. The discrepancy between molecular and fossil estimates persists despite the booming growth of sequence data sets, which increasingly feeds the interpretation that molecular estimates are older than stratigraphic dates because of deficiencies in the fossil record. Here we show that molecular time estimates suffer from a methodological handicap, namely that they are asymmetrically bounded random variables, constrained by a nonelastic boundary at the lower end, but not at the higher end of the distribution. This introduces a bias toward an overestimation of time since divergence, which becomes greater as the length of the molecular sequence and the rate of evolution decrease.     

Pyrrolidine dithiocarbamate protects against thioacetamide-induced fulminant hepatic failure in rats

BACKGROUND/AIMS: Reactive oxygen species and nuclear factor kappa B (NF-kappaB) activation have been implicated in the pathogenesis of cell injury in experimental models of liver damage. The aim of the present study was to examine whether pyrrolidine dithiocarbamate (PDTC), an anti oxidant and inhibitor of NF-kappaB activation, would prevent hepatic damage induced in a rat model of thioacetamide (TAA)-induced liver failure. METHODS: Fulminant hepatic failure was induced in the control and treatment groups by two intraperitoneal injections of TAA (either 300 or 400 mg/kg) at 24-h intervals. In the treatment groups, rats were treated also with PDTC (60 mg/kg/24 h, i.p.), initiated 24 h prior to TAA. RESULTS: Liver enzymes, blood ammonia, and hepatic levels of thiobarbituric acid reactive substances (P<0.001) and protein carbonyls (P<0.05) were significantly lower in rats treated with PDTC compared to TAA only. Liver histology and the survival rate in the PDTC-treated rats were also improved (P<0.01 compared to TAA only). NF-kappaB activation, 2 and 6 h after TAA administration, was inhibited by PDTC. CONCLUSIONS: In a rat model of fulminant hepatic failure, the administration of PDTC attenuated liver damage and improved survival. This effect may be due to decreased oxidative stress and inhibition of NF-kappaB activation.