S. typhimurium encodes an activator of Rho GTPases that induces membrane ruffling and nuclear responses in host cells

S. typhimurium stimulates signaling pathways leading to membrane ruffling, actin cytoskeleton rearrangements, and nuclear responses. The stimulation requires a protein secretion system (type III) that translocates bacterial proteins into the host cell. We show that SopE, a substrate of this secretion system, stimulates cytoskeletal reorganization and JNK activation in a CDC42- and Rac-1-dependent manner. A lambda gt11 cDNA library screen for proteins that interact with SopE identified Rac-1 and CDC42. Furthermore, purified SopE was shown to stimulate GDP/GTP nucleotide exchange in several Rho GTPases in vitro, including Rac-1 and CDC42. These findings establish a paradigm for microbial stimulation of cellular responses in which the pathogen induces signaling events by directly engaging the signaling machinery within the host cell.     

Differential effects of interleukin-12, interleukin-15, and interleukin-2 on human immunodeficiency virus type 1 replication in vitro

Cytokines may have clinical utility as therapeutic agents for human immunodeficiency virus type 1 (HIV-1) infection and as an adjuvant for vaccines. The effect of interleukin-12 (IL-12) and IL-15 on in vitro HIV-1 replication was investigated. IL-12 and IL-15 at doses up to 10 ng/ml had little effect on basal HIV-1 p24 antigen production by chronically HIV-infected T (ACH-2) and monocytic (U1) cell lines. For ACH-2 cells stimulated with phorbol 12-myristate 13-acetate (PMA; 50 ng/ml), IL-12 and IL-15 significantly increased p24 antigen production by 20 and 30%, respectively (n = 6). In contrast, IL-12 and IL-15 (10 ng/ml) treatment of PMA-stimulated U1 cells decreased p24 antigen production by 16 and 15%, respectively (n = 6). We next studied the effect of IL-12 and IL-15 on HIV-infected peripheral blood mononuclear cells (PBMCs). In 10 HIV-seropositive patients' PBMCs cocultured with mitogen-activated HIV-seronegative donor cells, two patterns of p24 antigen production were observed in response to IL-2: low (p24 antigen production < 10(3) pg/ml; n = 8) and high (p24 antigen production > 10(3) pg/ml; n = 2) response. For the low-response pattern, IL-12 and IL-15 increased viral replication by 97-fold and 100-fold, respectively (P = 0.05 and 0.004, respectively). For the high-response pattern, both IL-12 and IL-15 suppressed HIV replication. The effect of IL-2, IL-12, and IL-15 on acute in vitro infection by HIV-1JRCSF was also examined. IL-12 did not increase p24 antigen production above basal levels while IL-2 and IL-15 significantly enhanced p24 antigen production (by approximately 2-fold). In conclusion, IL-12 and IL-15 may have differential effects on latent and acute HIV infection, and their ability to enhance HIV production may depend on cell activation. Thus, the use of these cytokines may be dictated by the clinical state of the patient.     

Nucleus gracilis: an integrator for visceral and somatic information

The nucleus gracilis (NG) receives an abundance of visceral input from various abdominal organs and is proposed to play an important role in visceral pain processing. The purpose of this study was to investigate the necessity of the NG for colorectal input into the ventral posterolateral (VPL) nucleus of the thalamus. Single-cell recordings were made from nine VPL cells isolated in nine different male Sprague Dawley rats anesthetized with pentobarbital sodium. Responses of the VPL cells to colorectal distension (CRD) and to cutaneous stimuli were obtained before and after lesioning of the NG. Electrolytic (n = 5) and chemical (n = 4) lesions of the NG were made in different preparations. The chemical lesions were made by injecting a solution of kainic acid into the NG. Kainic acid presumably kills neuronal cell bodies and spares axons of passage. The results indicate that a lesion of the NG, regardless of its type, reduces dramatically the responses of VPL neurons to innocuous cutaneous stimuli, and, to a lesser extent, the responses to CRD. Attenuation of VPL neuronal responses to CRD as well as to innocuous cutaneous stimuli by the NG lesions emphasizes the role of the dorsal column in visceral nociception and suggests that the NG is an integration center for visceral and cutaneous information flowing into the VPL nucleus.     

Comparison of thoracoscopic and open thoracic discectomy in a live ovine model for anterior spinal fusion

STUDY DESIGN: The authors undertook a randomized comparison of 30 thoracoscopic and 30 open thoracic discectomies for anterior spinal fusion in a live sheep model. OBJECTIVES: To compare in a live sheep model discectomies performed using a thoracoscopic technique with those using an open thoracotomy technique to validate the efficacy of thoracoscopic disc and end plate removal for potential fusion. SUMMARY OF BACKGROUND DATA: In 1993, Mack and Regan described a technique for video-assisted thoracic surgery that resulted in less morbidity than open techniques. Subsequent reports support the finding that thoracoscopic spinal surgery results in less morbidity. METHODS: Sixty discectomies were performed in 10 live sheep. In each sheep, three randomly selected discectomies were performed thoracoscopically, and, subsequently, three open discectomies were performed. The animal then was killed, and the spine was sectioned and analyzed by computer imaging. RESULTS: Statistical analysis found no significant difference in the amount of disc resected (t' = 1.9639, t0.025, 60 = 2.000, alpha = 0.05). The mean percentage of disc resected was 67.8% (range, 0-92.2%) in the thoracoscopic group and 76.1% (range, 44.9-95.4%) in the open group. More than 50% of the disc was excised in 27 of 30 spines (90%) in the thoracoscopic group and in 29 of 30 (96.7%) in the open group. This difference was not statistically significant (theta 2(0.05, 1) = 3.84, theta 2' = 1.07). CONCLUSION: The findings in this study indicate that the thoracoscopic discectomy technique is equivalent to the open technique in the amount of disc and end plate resected. In addition, these findings suggest that thoracoscopic discectomies provide adequate disc resection to provide for an acceptable fusion rate according to the criteria demonstrated by Bunnell in 1982 and therefore support the efficacy of a thoracoscopic technique for anterior spinal fusion.