Manganese activates the mitochondrial apoptotic pathway in rat astrocytes by modulating the expression of proteins of the Bcl-2 family

Manganese induces the central nervous system injury leading to manganism, by mechanisms not completely understood. Chronic exposure to manganese generates oxidative stress and induces the mitochondrial permeability transition. In the present study, we characterized apoptotic cell death mechanisms associated with manganese toxicity in rat cortical astrocytes and demonstrated that (i) Mn treatment targets the mitochondria and induces mitochondrial membrane depolarization followed by cytochrome c release to the cytoplasm, (ii) Mn induces both effector caspases 3/7 and 6 as well as PARP-1 cleavage and (iii) Mn shifts the balance of cell death/survival of Bcl-2 family proteins to favor the apoptotic demise of astrocytes. Our model system using cortical rat astrocytes treated with Mn would emerge as a good tool for investigations aimed to elucidate the role of apoptosis in manganism.     

Human immunodeficiency virus-specific CD8+ T-cell activity is detectable from birth in the majority of in utero-infected infants

Human immunodeficiency virus (HIV)-infected infants in sub-Saharan Africa typically progress to AIDS or death by 2 years of life in the absence of antiretroviral therapy. This rapid progression to HIV disease has been related to immaturity of the adaptive immune response in infants. We screened 740 infants born to HIV-infected mothers and tracked development and specificity of HIV-specific CD8⁺ T-cell responses in 63 HIV-infected infants identified using gamma interferon enzyme-linked immunospot assays and intracellular cytokine staining. Forty-four in utero-infected and 19 intrapartum-infected infants were compared to 45 chronically infected children >2 years of age. Seventy percent (14 of 20) in utero-infected infants tested within the first week of life demonstrated HIV-specific CD8⁺ T-cell responses. Gag, Pol, and Nef were the principally targeted regions in chronic pediatric infection. However, Env dominated the overall response in one-third (12/36) of the acutely infected infants, compared to only 2/45 (4%) of chronically infected children (P = 0.00083). Gag-specific CD4⁺ T-cell responses were minimal to undetectable in the first 6 months of pediatric infection. These data indicate that failure to control HIV replication in in utero-infected infants is not due to an inability to induce responses but instead suggest secondary failure of adaptive immunity in containing this infection. Moreover, the detection of virus-specific CD8⁺ T-cell responses in the first days of life in most in utero-infected infants is encouraging for HIV vaccine interventions in infants.     

Use of fine needle aspiration biopsy in radiofrequency ablation

OBJECTIVE: To demonstrate the utility of fine needle aspiration biopsy (FNAB) in radiofrequency ablation (RFA) of suspected metastatic tumors at various sites. STUDY DESIGN: Eighteen patients referred for RFA underwent 21 aspirations prior to the procedure. A radiologist performed the FNAB and RFA with radiographic guidance. On-site preliminary evaluation of Diff-Quik-stained smears were followed with Papanicolaou staining. A final diagnosis was rendered and compared to the preliminary diagnosis. RESULTS: Liver was aspirated in 17 cases, lung in 3 cases and pubic bone in 1. Fifteen aspirates were deemed on site as positive or suspicious for malignancy. A preliminary, on-site diagnosis of benign was given in one case and adequate with deferment for review of all slides in four others. One FNAB was unsatisfactory. All but one (patient with benign diagnosis) then immediately proceeded to RFA of the lesion. After review of additional slides, the final diagnosis confirmed metastatic adenocarcinoma in 16, hepatocellular carcinoma in 2 and metastatic squamous cell carcinoma in 1. One FNAB yielded benign hepatocytes, and one was unsatisfactory. CONCLUSION: FNAB is an accurate, safe and rapid method of confirming disease in patients just prior to undergoing RFA.     

Solution structure of the major (Spy0128) and minor (Spy0125 and Spy0130) pili subunits from Streptococcus pyogenes

Adhesion of the serotype M1 Streptococcus pyogenes strain SF370 to human tonsil explants and cultured keratinocytes requires extended polymeric surface structures called pili. In this important human pathogen, pili are assembled from three protein subunits: Spy0125, Spy0128 and Spy0130 through the action of sortase enzymes. For this study, the structural properties of these pili proteins have been investigated in solution. Spy0125 and Spy0128 display characteristics of globular, folded proteins. Circular dichroism suggests a largely β-sheet composition for Spy0128 and Spy0125; Spy0130 appears to contain little secondary structure. Each of the proteins adopts a monodisperse, monomeric state in solution as assessed by analytical ultracentrifugation. Further, small-angle X-ray scattering curves for Spy0125, Spy0128 and Spy0130 suggest each protein adopts an elongated shape, likely comprised of two domains, with similar maximal dimensions. Based on the scattering data, dummy atom models of each of the pili subunits have been reconstructed ab initio. This study provides the first insights into the structure of Streptococcus pyogenes minor pili subunits, and possible implications for protein function are discussed.     

Single-dose murine monoclonal antibody ricin A chain immunotoxin in the treatment of metastatic melanoma: a phase I trial.

To determine the maximally tolerated dose of a ricin A chain-conjugated antimelanoma antibody (XomaZyme-Mel), 20 patients with metastatic melanoma were treated with escalating doses of the murine immunotoxin given as single intravenous infusion over 30 minutes. The starting dose was 0.6 mg/kg and was escalated in five groups to a maximum of 1.6 mg/kg. The maximally tolerated dose was 1.25 mg/kg as three of six patients treated at 1.6 mg/kg developed unacceptable toxicity. The dose-limiting toxicity consisted of profound fatigue, myalgias, and arthralgias. These occurred within 4 days and resolved in 7 to 10 days. Other non-dose-limiting toxicities encountered consisted of hypoalbuminemia, weight gain, peripheral edema, mild hypotension, and flu-like syndrome; the severity of these was also dose related. In addition, two allergic reactions occurred, one severe. There was one durable complete response of 12+ months' duration and one brief mixed response lasting 3 months. We conclude that the maximum tolerated single dose of XomaZyme-Mel is 1.25 mg/kg. Phase I studies evaluating 1.25 mg/kg given in multiple doses at 2- to 4-week intervals and phase II studies to determine the response rate of a single 1.25 mg/kg dose are warranted.     

Mesenteric microvascular inflammatory responses to systemic hypoxia are mediated by PAF and LTB4.

Systemic hypoxia produces a rapid microvascular inflammatory response characterized by increased reactive oxygen species (ROS) levels, leukocyte-endothelial adherence and emigration, and increased vascular permeability. The lipid inflammatory mediator leukotriene B(4) (LTB(4)) is involved in the early hypoxia-induced responses (ROS generation and leukocyte adherence). Whether other lipid inflammatory mediators participate in this phenomenon is not known. The objective of these experiments was to study the role of platelet-activating factor (PAF) in the microvascular inflammatory response to hypoxia and its potential interactions with LTB(4) in this response. Intravital microscopy was used to examine mesenteric venules of anesthetized rats. We found that WEB-2086, a PAF receptor antagonist, completely prevented the increase in ROS levels and leukocyte adherence during a brief reduction in inspired Po(2) to anesthetized rats; administration of either WEB-2086 or the LTB(4) antagonist LTB(4)-DMA attenuated leukocyte emigration and the increase in vascular permeability to the same extent during prolonged systemic hypoxia in conscious rats. Furthermore, no additive effect was observed in either response when both antagonists were administered simultaneously. This study demonstrates a role for PAF in the rapid microvascular inflammatory response to hypoxia, as well as contributions of PAF and LTB(4) to the slowly developing responses observed during sustained hypoxia. The incomplete blockade of the hypoxia-induced increases in vascular permeability and leukocyte emigration by combined administration of both antagonists indicates that factors in addition to LTB(4) and PAF participate in these phenomena.     

Fractal analysis of plant spatial patterns: a monitoring tool for vegetation transition shifts

Spatial heterogeneity, like species diversity, is an important ecosystem property. We examine the effects of land use on the diversity and spatial distribution of plants in five semi-arid communities of eastern Spain using non-linear methods to assess the spatialtemporal dynamics of plant populations. Specifically, we are interested in detecting long-term structural changes or drift in an ecosystem before it is too late to prevent irreversible degradation. Fractal analysis is used to characterize the complexity of plant spatial patterns and Information Theory indices are used to measure change in information flow with land use changes and soil substrate. We found that grazing favored diversity and heterogeneity of species distribution on the impoverished gypsum and saline substrate community, as opposed to the detrimental effect of grazing in the Alpha steppe community. Indeed, old-field succession after 30 years of abandonment showed a recovery of species diversity but not the spatial structure of the vegetation. Further, Information Fractal Dimension, representing the unpredictability of plant spatial patterns in the landscape, increased as we moved from a highly diverse to a less diverse community, revealing the change to a more scattered and homogeneous spatial plant distribution. The Information Fractal Dimension is a good estimator of ecosystem disturbance, independent of scale, and thus can be used to monitor ecosystem dynamics.