Lipopolysaccharide attenuates thrombolysis in batroxobin-induced lung vasculature fibrin deposition but not in ferrous chloride-induced carotid artery thrombus in rats: role of endogenous PAI-1

In this study, we investigated if elevation of endogenous plasminogen activator inhibitor type 1 (PAI-1) by lipopolysaccharide (LPS) can retard thrombolysis in both a rat model of lung vasculature fibrin deposition and a platelet-rich thrombus model induced by endothelial injury. By 3 h following an intravenous bolus injection of 0.5 mg/kg LPS, the plasma PAI-1 level had increased to 8 ng/ml. ¹²⁵I-labeled fibrinogen was injected intravenously followed by an injection of batroxobin. Batroxobin converts fibrinogen into insoluble fibrin, which was then deposited in the lungs within 5 min, followed by spontaneous fibrinolysis that completely cleared fibrin deposition in the lungs by 30 min. In rats pre-treated with LPS, spontaneous fibrinolysis was significantly retarded. In the endothelial injury model, topical application of FeCl₂ on the carotid artery induced an occlusive platelet-rich thrombus, which was not sensitive to endogenous thrombolysis. Exogenous tissue-type plasminogen activator (tPA) was required to recanalize the occlusive thrombus in a dose-dependent manner. Pre-treatment with LPS did not alter the dose–response curve of exogenous tPA-induced thrombolysis. These data indicate that batroxobin-induced lung vasculature fibrin deposition in rats, unlike the FeCl₂ model, is sensitive to the impact of endogenous PAI-1 on fibrinolysis.     

Effects of GCP-II inhibition on responses of dorsal horn neurones after inflammation and neuropathy: an electrophysiological study in the rat

N-Acetylaspartylglutamate (NAAG) is a peptide neurotransmitter present in the brain and spinal cord. It is hydrolysed by glutamate carboxypeptidase II (GCPII); thus, the GCP-II inhibitor 2-[phosphono-methyl]-pentanedioic acid (2-PMPA) protects endogenous NAAG from degradation, allowing its effects to be studied in vivo. We recorded the effect of spinal 2-PMPA (50-1000 microg) on the electrical-evoked activity of dorsal horn neurones in normal and carrageenan-inflamed animals, and in the spinal nerve ligation (SNL) model of neuropathy and sham-operated animals. In normal animals, 1000 microg 2-PMPA selectively inhibited noxious-evoked activity (input, post-discharge and C- and Adelta-fibre-evoked responses), and not low threshold Abeta-fibre-evoked responses. After carrageenan inflammation, the lower dose of 100 microg 2-PMPA inhibited input, post-discharge, C- and Adelta-fibre-evoked responses by a significantly greater amount than the same dose in normal animals. 2-PMPA inhibited neuronal responses less consistently in sham-operated and SNL animals, and effects were not significantly different from those seen in normal animals. NAAG is an agonist at the inhibitory metabotropic glutamate receptor mGluR3, and 2-PMPA may inhibit nociceptive transmission in normal animals by elevating synaptic NAAG levels, allowing it to activate mGluR3 and thus reducing transmitter release from afferent nerve terminals. mGluR3 expression in the superficial dorsal horn is upregulated after peripheral inflammation, perhaps explaining the greater inhibition of neuronal responses we observed after carrageenan inflammation. These results support an important role of endogenous NAAG in the spinal processing of noxious information.     

Hysteresis drives cell-cycle transitions in Xenopus laevis egg extracts

Cells progressing through the cell cycle must commit irreversibly to mitosis without slipping back to interphase before properly segregating their chromosomes. A mathematical model of cell-cycle progression in cell-free egg extracts from frog predicts that irreversible transitions into and out of mitosis are driven by hysteresis in the molecular control system. Hysteresis refers to toggle-like switching behavior in a dynamical system. In the mathematical model, the toggle switch is created by positive feedback in the phosphorylation reactions controlling the activity of Cdc2, a protein kinase bound to its regulatory subunit, cyclin B. To determine whether hysteresis underlies entry into and exit from mitosis in cell-free egg extracts, we tested three predictions of the Novak-Tyson model. (i) The minimal concentration of cyclin B necessary to drive an interphase extract into mitosis is distinctly higher than the minimal concentration necessary to hold a mitotic extract in mitosis, evidence for hysteresis. (ii) Unreplicated DNA elevates the cyclin threshold for Cdc2 activation, indication that checkpoints operate by enlarging the hysteresis loop. (iii) A dramatic "slowing down" in the rate of Cdc2 activation is detected at concentrations of cyclin B marginally above the activation threshold. All three predictions were validated. These observations confirm hysteresis as the driving force for cell-cycle transitions into and out of mitosis.     

The Effect of altering ADL thresholds on active life expectancy estimates for older persons

OBJECTIVES: Research on disability and active life expectancy (ALE) has often criticized the measurement of disability but has rarely empirically investigated the effect of changing measurement. The purpose of this study was to determine whether altering the number of activities of daily living (ADLs) required to consider an individual "disabled" affects population-based ALE estimates after considering parametric uncertainty and sampling error. METHODS: The authors develop a Bayesian approach to estimating multistate life tables for a three-dimensional state space, using data on community-dwelling older adults from the 1989 and 1994 National Long Term Care Survey analytic files. Empirical confidence intervals for ALE are compared across 6 models using successively higher ADL cutoffs for defining individuals as being disabled. RESULTS: After considering sampling and other errors in the estimation of transition probabilities, the authors found that altering the threshold for measuring disability has relatively little effect on ALE estimates, especially with higher ADL-level thresholds and at older ages. DISCUSSION: The implications of the results include that disability measurement, including altering the definition of being disabled and possibly expanding the state space of a model, may not affect population-based estimates of ALE.     

Concurrent validity and classification accuracy of the Leiter and Leiter-R in low-functioning children with autism

The concurrent validity of the Leiter International Performance Scale (Leiter) and Leiter International Performance Scale–Revised (Leiter-R) was examined in a sample of children with autism who could not be assessed with more traditional measures of intelligence (e.g., the Wechsler scales). The sample consisted of 26 children ranging in age from 4 to 16 years. The correlation between the Leiter scales was high (r = .87), and there was a difference of 3.7 points between the two mean scores, nonsignificant at both statistical and clinical levels. However, significant intraindividual discrepancies were present in 10 cases, 2 of which were both large (24 and 36 points) and clinically meaningful. The mean profile of performance on Leiter-R subtests is also presented for this sample of children with autism, to allow for comparison with other groups. Based on the results of this initial evaluation, together with the current normative data, good psychometric properties, and availability of global and subtest scores with the Leiter-R, the instrument is generally recommended for use with children with autism. However, because of changes in the design of the Leiter-R, there may be greater clinical success with the original Leiter for those children who are very low functioning and severely affected, particularly younger children.     

How surgeon age affects surveillance strategies for extremity soft tissue sarcoma patients after potentially curative treatment

BACKGROUND: The optimal strategy for follow-up of extremity soft tissue sarcoma patients after potentially curative treatment remains unknown. We investigated whether the date of completion of formal surgical training affects choice of surveillance strategy. MATERIALS AND METHODS: The 1,592 members of the Society of Surgical Oncology were asked how often they use 12 separate surveillance modalities during years 1-5 and 10 postsurgery. The motivation underlying follow-up was assessed separately. Repeated-measures analysis of variance was used to compare practice patterns by the year in which the surgeon's formal surgery training was completed, controlling for tumor grade, tumor size, and year postsurgery. RESULTS: Of the 716 respondents, 318 performed surgery and also provided long-term postoperative surveillance for their patients. These respondents were considered evaluable. Erythrocyte sedimentation rate, extremity X ray, and bone scan were the follow-up tests which differed significantly among physician age groups. Surgeons who completed training more than 30 years ago ordered erythrocyte sedimentation rate more frequently (P < 0.001). Surgeons in the 21-30 year category ordered extremity X ray and bone scan more frequently (P < 0.05), but the absolute differences among age groups were quite small. Older surgeons were also significantly more likely to believe that follow-up is clinically worthwhile. CONCLUSIONS: The posttreatment surveillance practice patterns of the members of the Society of Surgical Oncology caring for extremity soft tissue sarcoma patients vary only marginally with the length of time since completion of training. Postgraduate education may be one factor homogenizing surgeon behavior in this important aspect of cancer patient care.     

Toll-like receptor-4 signaling mediates pulmonary neutrophil sequestration in response to gram-positive bacterial enterotoxin

BACKGROUND: Toll-like receptors (TLRs) serve as mediators of innate immune responses to pathogen-associated molecular patterns (PAMPs) which include lipopolysaccharide (LPS) and staphylococcal enterotoxin B (SEB). TLR-4 is thought to act as the primary effector of LPS recognition and TLR-2 is thought to mediate responses to Gram-positive bacterial proteins. Chemokines such as macrophage inflammatory protein (MIP-2) are peptides that are responsible for lung neutrophil (PMN) sequestration following an infectious or inflammatory insult. Given the Gram-positive origin of SEB, we hypothesized that mice with altered TLR-4 signaling would exhibit no difference in lung PMN sequestration following SEB when compared to wild-type mice. METHODS: Wild-type and TLR-4 mutant mice were administered intratracheal saline, LPS (Escherichia coli 0.1 mg/kg), or SEB (1 mg/kg). After 24 h, lung PMN accumulation was determined by myeloperoxidase (MPO) assay and bronchoalveolar lavage fluid cell count (BALfcc). Total lung and BALf MIP-2 was measured by enzyme-linked immunosorbent assay. RESULTS: There was an increase in lung PMN accumulation (by both MPO and BALfcc) and MIP-2 following LPS and SEB in wild-type mice compared to saline-treated controls. In contrast, TLR-4 mice failed to exhibit an increase in lung MIP-2 or PMN accumulation following either LPS or SEB compared to wild-type mice. CONCLUSIONS: TLR-4 mutant mice are unresponsive to intratracheal LPS. SEB elicited an increase in lung MIP-2 and PMN accumulation in wild-type mice. However, TLR-4 mutant mice were protected from this process. This suggests that TLR-4 signaling may mediate the responses to other PAMPs in addition to LPS.