Studies of antibacterial activity (in vitro and in vivo) and mode of action for des-acyl tridecaptins (DATs)

Tridecaptins comprise a class of linear cationic lipopeptides with an N-terminal fatty acyl moiety. These 13-mer antimicrobial peptides consist of a combination of d- and l-amino acids, conferring increased proteolytic stability. Intriguingly, they are biosynthesized by non-ribosomal peptide synthetases in the same bacterial species that also produce the cyclic polymyxins displaying similar fatty acid tails. Previously, the des-acyl analog of TriA1 (termed H-TriA1) was found to possess very weak antibacterial activity, albeit it potentiated the effect of several antibiotics. In the present study, two series of des-acyl tridecaptins were explored with the aim of improving the direct antibacterial effect. At the same time, overall physico-chemical properties were modulated by amino acid substitution(s) to diminish the risk of undesired levels of hemolysis and to avoid an impairment of mammalian cell viability, since these properties are typically associated with highly hydrophobic cationic peptides. Microbiology and biophysics tools were used to determine bacterial uptake, while circular dichroism and isothermal calorimetry were used to probe the mode of action. Several analogs had improved antibacterial activity (as compared to that of H-TriA1) against Enterobacteriaceae. Optimization enabled identification of the lead compound 29 that showed a good ADMET profile as well as in vivo efficacy in a variety of mouse models of infection.

Discovery of Novel UDP-N-Acetylglucosamine Acyltransferase (LpxA) Inhibitors with Activity against Pseudomonas aeruginosa

This study describes a novel series of UDP-N-acetylglucosamine acyltransferase (LpxA) inhibitors that was identified through affinity-mediated selection from a DNA-encoded compound library. The original hit was a selective inhibitor of Pseudomonas aeruginosa LpxA with no activity against Escherichia coli LpxA. The biochemical potency of the series was optimized through an X-ray crystallography-supported medicinal chemistry program, resulting in compounds with nanomolar activity against P. aeruginosa LpxA (best half-maximal inhibitory concentration (IC₅₀) <5 nM) and cellular activity against P. aeruginosa (best minimal inhibitory concentration (MIC) of 4 μg/mL). Lack of activity against E. coli was maintained (IC₅₀ > 20 μM and MIC > 128 μg/mL). The mode of action of analogues was confirmed through genetic analyses. As expected, compounds were active against multidrug-resistant isolates. Further optimization of pharmacokinetics is needed before efficacy studies in mouse infection models can be attempted. To our knowledge, this is the first reported LpxA inhibitor series with selective activity against P. aeruginosa.

The regression of the bovine tuberculin reaction: Results from the Reactor Quality Assurance study in Northern Ireland

Tuberculin skin tests remain widely used in the control of bovine tuberculosis (bTB) in cattle. Little is known about the rate of regression of tuberculin reactions after the comparative intradermal cervical test (CICT) in cattle. This study aimed to collect data to describe tuberculin regression in reactors following the CICT at 72 ± 4 h post injection. Reactors were also tested using the interferon gamma (IFN-γ) assay to establish if any pattern existed between these results and the CICT reaction regression. The data were derived from 108 herds, 112 herd-level CICTs and 1008 animals. A multivariable linear mixed model was built to explore the regression of the bovine tuberculin reaction over time and the influence of potential predictors. The results confirmed a proportional decline in the bovine tuberculin reaction occurred over time. The predictors in the final model demonstrated that regression of the tuberculin reaction differed between reactors according to their IFN-γ test results and whether visible lesions were present at slaughter. Follow-up measurement of tuberculin reactions and the serial use of the IFN-γ assay in large breakdowns has the potential to provide both a mechanism for quality assurance of the current CICT bTB surveillance and the identification of atypical breakdowns or reactors requiring further investigation.

A Bayesian analysis of a Test and Vaccinate or Remove study to control bovine tuberculosis in badgers (Meles meles)

A novel five year Test and Vaccinate or Remove (TVR) wildlife research intervention project in badgers (Meles meles) commenced in 2014 in a 100km2 area of Northern Ireland. It aimed to increase the evidence base around badgers and bovine TB and help create well-informed and evidence-based strategies to address the issue of cattle-to-cattle spread and spread between cattle and badgers. It involved real-time trap-side testing of captured badgers and vaccinating those that tested negative for bTB (BadgerBCG-BCG Danish 1331) and removal of those that tested bTB positive using the Dual-Path Platform VetTB test (DPP) for cervids (Chembio Diagnostic Systems, Medford, NY USA). Four diagnostic tests were utilised within the study interferon gamma release assay (IGRA), culture (clinical samples and post mortem), DPP using both whole blood and DPP using serum. BCG Sofia (SL222) was used in the final two years because of supply issues with BadgerBCG. Objectives for this study were to evaluate the performance of the DPP in field conditions and whether any trend was apparent in infection prevalence over the study period. A Bayesian latent class model of diagnostic test evaluation in the absence of a gold standard was applied to the data. Temporal variation in the sensitivity of DPP and interferon gamma release assay (IGRA) due to the impact of control measures was investigated using logistic regression and individual variability was assessed. Bayesian latent class analysis estimated DPP with serum to have a sensitivity of 0.58 (95% CrI: 0.40-0.76) and specificity of 0.97 (95% CrI: 0.95-0.98). The DPP with whole blood showed a higher sensitivity (0.69 (95% CrI: 0.48-0.88)) but similar specificity (0.98 (95% Crl: 0.96-0.99)). The change from BCG Danish to BCG Sofia significantly impacted on DPP serum test characteristics. In addition, there was weak evidence of increasing sensitivity of IGRA over time and differences in DPP test sensitivity between adults and cubs. An exponential decline model was an appropriate representation of the infection prevalence over the 5 years, with a starting prevalence of 14% (95% CrI: 0.10-0.20), and an annual reduction of 39.1% (95% CrI: 26.5-50.9). The resulting estimate of infection prevalence in year 5 of the study was 1.9% (95% CrI: 0.8-3.8). These results provide field evidence of a statistically significant reduction in badger TB prevalence supporting a TVR approach to badger intervention. They give confidence in the reliability and reproducibility in the DPP Whole Blood as a real time trap-side diagnostic test for badgers, and describe the effect of vaccination and reduced infection prevalence on test characteristics.

Transient shear banding in the nematic dumbbell model of liquid crystalline polymers

In the shear flow of liquid crystalline polymers (LCPs) the nematic director orientation can align with the flow direction for some materials but continuously tumble in others. The nematic dumbbell (ND) model was originally developed to describe the rheology of flow-aligning semiflexible LCPs, and flow-aligning LCPs are the focus in this paper. In the shear flow of monodomain LCPs, it is usually assumed that the spatial distribution of the velocity is uniform. This is in contrast to polymer solutions, where highly nonuniform spatial velocity profiles have been observed in experiments. We analyze the ND model, with an additional gradient term in the constitutive model, using a linear stability analysis. We investigate the separate cases of constant applied shear stress and constant applied shear rate. We find that the ND model has a transient flow instability to the formation of a spatially inhomogeneous flow velocity for certain starting orientations of the director. We calculate the spatially resolved flow profile in both constant applied stress and constant applied shear rate in start up from rest, using a model with one spatial dimension to illustrate the flow behavior of the fluid. For low shear rates flow reversal can be seen as the director realigns with the flow direction, whereas for high shear rates the director reorientation occurs simultaneously across the gap. Experimentally, this inhomogeneous flow is predicted to be observed in flow reversal experiments in LCPs.

Clinical dashboard: use in older adult mental health wards

Aims and method

To explore the experiences and attitudes of mental health professionals working in acute elderly care to a new clinical dashboard system. Metrics were identified from the Royal College of Psychiatrists' Accreditation for Inpatient Mental Health Services – Older People (AIMS-OP); these were tracked from baseline to 6 months. A questionnaire was developed and distributed across the three clinical areas involved in the clinical dashboard mental health pilot.

Results

Staff completed the questionnaire 3 months after the initial implementation. At this point the benefits of the introduction of the dashboard were suggested as: improved access to information, increased communication and information-sharing, increased staff awareness, and data quality.

Clinical implications

The introduction of the clinical dashboard in older adult mental health services allowed for better data availability and resulted in better data quality.

Listeria monocytogenes Has Both Cytochrome bd-Type and Cytochrome aa 3-Type Terminal Oxidases, Which Allow Growth at Different Oxygen Levels, and Both Are Important in Infection

Listeria monocytogenes is a foodborne pathogen responsible for a number of life-threatening infections of humans. During an infection, it invades epithelial cells before spreading from the intestine to the cells of the liver and spleen. This requires an ability to adapt to varying oxygen levels. Here, we demonstrate that L. monocytogenes has two terminal oxidases, a cytochrome bd-type (CydAB) and a cytochrome aa 3-type menaquinol (QoxAB) oxidase, and that both are used for respiration under different oxygen tensions. Furthermore, we show that possession of both terminal oxidases is important in infection. In air, the CydAB bd-type oxidase is essential for aerobic respiration and intracellular replication, and cydAB mutants are highly attenuated in mice. In contrast, the QoxAB aa 3-type oxidase is required neither for aerobic respiration in air nor for intracellular growth. However, the qoxAB mutants are attenuated in mice, with a delay in the onset of disease signs and with increased survival time, indicating a role for the QoxAB aa 3-type oxidase in the initial stages of infection. Growth of bacteria under defined oxygen conditions revealed that at 1% (vol/vol), both oxidases are functional, and the presence of either is sufficient for aerobic respiration and intracellular replication. However, at 0.2% (vol/vol), both oxidases are necessary for maximum growth. These findings are consistent with the ability of L. monocytogenes to switch between terminal oxidases under different oxygen conditions, providing exquisite adaptation to different conditions encountered within the infected host.

In vitro susceptibility of Clostridium difficile to SMT19969 and comparators, as well as the killing kinetics and post-antibiotic effects of SMT19969 and comparators against C. difficile

OBJECTIVES

SMT19969 is a novel antimicrobial under clinical development for the treatment of Clostridium difficile infection (CDI). The objective was to determine the comparative susceptibility of 82 C. difficile clinical isolates (which included ribotype 027 isolates and isolates with reduced metronidazole susceptibility) to SMT19969, fidaxomicin, vancomycin and metronidazole and to determine the killing kinetics and post-antibiotic effects of SMT19969, fidaxomicin and vancomycin against C. difficile.

METHODS

MICs were determined by agar incorporation. Killing kinetics and post-antibiotic effects were determined against C. difficile BI1, 630 and 5325 (ribotypes 027, 012 and 078, respectively).

RESULTS

SMT19969 showed potent inhibition of C. difficile (MIC90=0.125 mg/L) and was markedly more active than either metronidazole (MIC90 = 8 mg/L) or vancomycin (MIC90 = 2 mg/L). There were no differences in susceptibility to SMT19969 between different ribotypes. Fidaxomicin was typically one doubling dilution more active than SMT19969 and both agents maintained activity against isolates with reduced susceptibility to metronidazole. In addition, SMT19969 was bactericidal against the C. difficile strains tested, with reductions in viable counts to below the limit of detection by 24 h post-inoculation. Vancomycin was bacteriostatic against all three strains. Fidaxomicin was bactericidal although reduced killing was observed at concentrations <20 × MIC against C. difficile BI1 (ribotype 027) compared with other strains tested.

CONCLUSIONS

These data demonstrate that SMT19969 is associated with potent and bactericidal activity against the strains tested and support further investigation of SMT19969 as potential therapy for CDI.

Predictors of low bone mineral density of the stroke-affected hip among ambulatory individuals with chronic stroke

Risk of hip fracture is greater poststroke than in an age-matched healthy population, in part because of declining hip BMD. We found that individuals may be at risk of loss of hip BMD from muscle atrophy, asymmetrical gait, and poor affected-side ankle dorsiflexor strength. These impairments may be targeted during rehabilitation.

INTRODUCTION

This study aimed to determine predictors of low hip BMD on the stroke-affected side in people living in the community.

METHODS

Forty-three participants (female; 27.9%), mean age 62.4 ± 13.5 and 17.9 ± 32.8 months, poststroke with motor impairments underwent dual energy X-ray absorptiometry scans. Gait characteristics, isometric strength, body composition, and fasting plasma lipids were measured.

RESULTS

At entry, 34.9% (15/43) of the participants had low total hip BMD on the stroke-affected side. Of those with low BMD, 93.3% (14/15) had a step length symmetry ratio >1, indicating greater reliance on the non-paretic leg for weight bearing. Logistic regression analysis revealed that lower affected-side ankle dorsiflexor strength (ß = 0.700, p = 0.02), lower total body fat-free mass index (ß = 0.437, p = 0.02), and greater step length symmetry ratio during walking (ß = 1.135 × 10(3), p = 0.03) were predictors of low hip BMD.

CONCLUSION

Low BMD of the stroke-affected side hip is prevalent in over a third of individuals with lower limb motor impairments. These individuals may be at particular risk of accelerated loss of BMD at the hip from asymmetrical gait pattern and poor affected-side ankle dorsiflexor strength. These impairments are intervention targets that may be addressed during rehabilitation which includes resistance training and addresses gait impairments.

Inhibition of calpain blocks the phagosomal escape of Listeria monocytogenes

Listeria monocytogenes is a gram-positive facultative intracellular bacterium responsible for the food borne infection listeriosis, affecting principally the immunocompromised, the old, neonates and pregnant women. Following invasion L. monocytogenes escapes the phagosome and replicates in the cytoplasm. Phagosome escape is central to L. monocytogenes virulence and is required for initiating innate host-defence responses such as the secretion of the cytokine interleukin-1. Phagosome escape of L. monocytogenes is reported to depend upon host proteins such as γ-interferon-inducible lysosomal thiol reductase and the cystic fibrosis transmembrane conductance regulator. The host cytosolic cysteine protease calpain is required in the life cycle of numerous pathogens, and previous research reports an activation of calpain by L. monocytogenes infection. Thus we sought to determine whether host calpain was required for the virulence of L. monocytogenes. Treatment of macrophages with calpain inhibitors blocked escape of L. monocytogenes from the phagosome and consequently its proliferation within the cytosol. This was independent of any direct effect on the production of bacterial virulence factors or of a bactericidal effect. Furthermore, the secretion of interleukin-1β, a host cytokine whose secretion induced by L. monocytogenes depends upon phagosome escape, was also blocked by calpain inhibition. These data indicate that L. monocytogenes co-opts host calpain to facilitate its escape from the phagosome, and more generally, that calpain may represent a cellular Achilles heel exploited by pathogens.

Letter - Response to 'Future-proofing primary health care: GP recruitment and retention in the new NHS'

I am increasingly bemused by the narrowing and blinkered view of training to becoming a GP. Rosenthal and Chana1 comment 'many trainees still spend part of this time in posts that offer traditional hospital-based experience that may not reflect the context of new community based service models'. Cautiously I would like to add the comment 'so what?' We do want 'well rounded' GPs, people open to new ideas, and who are open to 'lifelong learning.' Many who qualified at a similar time to me will have done hospital jobs as 'part of the team.' Six months at the end of which we were hopefully competent but also confident. Confident. Now that's a word we haven't been using too much recently but, as long as not false, important.Doing 6 months and making a good job of a delivery or episiotomy repair, doing pleural taps or biopsies, covering the paediatric clinic when the consultant had to rush off. Not perhaps relevant to my job now but it did instill a confidence and satisfaction to my work. There is now much less 'hands on'.Interestingly a local gastroenterologist recently told me he used to teach his GP trainees to do endoscopies, no longer, as 4 months is 'not enough.' We now have tasters that might encourage some degree of competence ('please sign me up' ) but are we creating doctors with no confidence in their own abilities?I like the idea of First5, encouraging doctors as they start their careers as GPs, dealing with issues, and educating around the GP mantle. It is a long career and may become longer so we need to generically give new GPs the tools to handle the future. Are we narrowing so much and trying too hard with training that we're taking the enjoyment out of the process, when perhaps some of this could be done later? It is now rare to have colleagues, who had done several years as gynaecologists/surgeons, join our ranks and I think we have lost something here.In my GP career I have been very grateful for sabbaticals to try working in different places/environments. This also seems to becoming more difficult and not encouraged generally while trying to achieve CCT. That great idea of learner-led education, particularly for trainees, seems to have gone out of the window.I suppose I am saying, can we be a bit more generic in our training years, widen our horizons again, and use First5 to help settle doctors into the rewarding job we do?

The Effect of Mycobacterium avium Complex Infections on Routine Mycobacterium bovis Diagnostic Tests

Bovine tuberculosis (bTB) is diagnosed in naturally infected populations exposed to a wide variety of other pathogens. This study describes the cell-mediated immune responses of cattle exposed to Mycobacterium avium subspecies paratuberculosis (Map) and Mycobacterium avium subspecies avium with particular reference to routine antefmortem Mycobacterium bovis diagnostic tests. The IFN-γ released in response to stimulated blood was found to peak later in the Map-exposed group and was more sustained when compared to the Maa-exposed group. There was a very close correlation between the responses to the purified protein derivatives (PPD) used for stimulation (PPDa, PPDb, and PPDj) with PPDa and PPDj most closely correlated. On occasion, in the Map-infected cattle, PPDb-biased responses were seen compared to PPDa suggesting that some Map-infected cattle could be misclassified as M. bovis infected using this test with these reagents. This bias was not seen when PPDj was used. SICCT results were consistent with the respective infections and all calves would have been classed skin test negative.

The combined actions of the copper-responsive repressor CsoR and copper-metallochaperone CopZ modulate CopA-mediated copper efflux in the intracellular pathogen Listeria monocytogenes

We have characterized the csoR-copA-copZ copper resistance operon of the important human intracellular pathogen Listeria monocytogenes. Transcription of the operon is specifically induced by copper, and mutants lacking the P₁-type ATPase CopA have reduced copper tolerance and over-accumulate copper relative to wild type. The copper-responsive repressor CsoR autoregulates transcription by binding to a single 32 bp site spanning the -10 and -35 elements of the promoter. Copper co-ordination by CsoR derepresses transcription of the operon and alters CsoR:DNA complex assembly as determined by DNase I footprinting and electrophoretic mobility shift assays, with some DNA-binding capacity being retained in the presence of 2 mole equivalents of copper. Analysis of the CsoR copper sensory site demonstrated that substitution of Cys⁴² with Ala generated a CsoR variant that was unresponsive to copper. Importantly, in the absence of CopZ, copper responsiveness of csoR-copA-copZ expression is substantially increased, implying that CopZ reduces the access of CsoR to copper. Furthermore, CopZ is shown to confer copper resistance in mutants lacking copper-inducible csoR-copA-copZ expression, thus providing protection from the deleterious effects of copper within the cytoplasm.

A New Experimental Infection Model in Ferrets Based on Aerosolised Mycobacterium bovis

There is significant interest in developing vaccines to control bovine tuberculosis, especially in wildlife species where this disease continues to persist in reservoir species such as the European Badger (Meles meles). However, gaining access to populations of badgers (protected under UK law) is problematic and not always possible. In this study, a new infection model has been developed in ferrets (Mustela furo), a species which is closely related to the badger. Groups of ferrets were infected using a Madison infection chamber and were examined postmortem for the presence of tuberculous lesions and to provide tissue samples for confirmation of Mycobacterium bovis by culture. An infectious dose was defined, that establishes infection within the lungs and associated lymph nodes with subsequent spread to the mesentery lymph nodes. This model, which emphasises respiratory tract infection, will be used to evaluate vaccines for the control of bovine tuberculosis in wildlife species.

Anisotropic response of glassy splay-bend and twist nematic cantilevers to light and heat

A gradient of director through the thickness of a nematic glass cantilever gives a gradient in the large distortions such materials suffer in response to temperature or illumination changes. We first sketch, within isotropic elasticity, how such gradients cause these cantilevers to respond by bending. We then derive the response within the anisotropic elasticity expected for uniaxial solids. Because, in general, spontaneously bending cantilevers have regions of elongation and contraction (with respect to their neutral state), internal stresses are generated, the magnitude of which depends on the anisotropic, fourth rank modulus tensor and in particular on its local alignment arising from the director's spatial distribution. We show that despite elastic complexity, bend is simply linear in the anisotropy of thermo-optical response, with a slope depending on the structure of the modulus tensor, justifying the previous literature on spontaneously bending cantilevers. We also explicitly consider two important director distributions--splay-bend and twist. Splay-bend cantilevers have no anticlastic (double-bend, saddle) response in the isotropic case or for some values of the anisotropic modulus tensor. Twist cantilevers have maximal anticlasticity in the isotropic case which we show to be weakly modified by anisotropy of elastic moduli.

Curvature in nematic elastica responding to light and heat

Nematic elastic bodies can develop a gradient of response to heat, light and other stimuli. They then bend and develop curvature in a complex manner depending on director field distributions, on whether they are monodomain or polydomain structures and on linear or nonlinear light absorptive processes. In each case, we derive the general weak response where bend in each direction is treated independently of that in others. In a subsequent paper, we address the reverse phenomenon, that is of strong spontaneous distortion leading to curvature suppression.

Suppression of curvature in nematic elastica

Nematic elastic bodies can develop a gradient of response to heat, light and other stimuli. They then bend and develop curvature in a complex manner. Using the results for a general weak response derived in the preceding paper, we solve for strong spontaneous distortion where bend in one direction causes stretch in another direction if that too is bending, and vice versa. Since stretch is elastically expensive, it can cause suppression of one of the bends (we determine which), thus eliminating Gaussian curvature. This is the spontaneous distortion equivalent of the classical Lamb calculation of the anti-clastic suppression when large distortions are imposed in classical elastica. In practice, spontaneously deforming nematic solids, e.g. in actuation, are in this strong bend limit.

Co-Infection of cattle with Fasciola hepatica and Mycobacterium bovis- immunological consequences

Fasciola hepatica, the liver fluke, is a common parasite of cattle in much of the world. Previously, we have shown that cattle infected with F. hepatica have altered responsiveness (delayed type hypersensitivity reaction and cytokine responses) to M. bovis BCG infection. We hypothesized that co-infection with F. hepatica would, likewise, alter the immune response of cattle to virulent M. bovis infection, with possible implications for disease diagnosis and disease progression. Our previous work with F. hepatica/M. bovis BCG-infected cattle demonstrated a reduction in interferon (IFN)-gamma responsiveness in co-infected animals. Similar findings are reported here with virulent M. bovis following aerosol infection. The epidemiological significance of these findings, also, require exploration, particularly in view of the considerable resources devoted to the diagnosis and eradication of bovine tuberculosis, and the high prevalence of F. hepatica infection in areas where eradication has proved difficult.

The role of microbial polysaccharides in host-pathogen interaction

Bacteria are capable of expressing a diverse range of cell surface polysaccharides from capsules and lipopolysaccharides through teichoic acid molecules to lipoarabinomannans. This review will focus on the expression of capsular polysaccharides and their interaction with the host. In particular, it will focus on the role of capsular polysaccharides as immunomodulatory molecules.

Polarization dependence of optically driven polydomain elastomer mechanics

We model how polarized and unpolarized light can cause mechanical response in polydomain nematic and related photoelastomers. The reduction of order by heating and the consequential large strains that are known from nematic elastomers can alternatively be caused by light-induced bending of rodlike dye molecules which then equally reduce the order of their nematic hosts. While there is no mechanical response to heating of polydomain elastomers, mechanical response to light is possible by the selective absorption of light according to how domains are aligned with respect to the polarization direction or with respect to the propagation direction in the case of unpolarized light. We find large contractions or elongations, depending on the nature of polarization. The responses are nonmonotonic with light intensity.

Bleaching and stimulated recovery of dyes and of photocantilevers

We examine how intense optical beams can penetrate deeply into highly absorbing media by a nonlinear, photobleaching process. The role of stimulated recovery to the dye ground state can be important and is delineated. This analysis of nonlinear absorption processes is applicable in general to situations where chromophores are irradiated, for instance, in biology. We examine the implications for the bending of cantilevers made of heavily dye-loaded nematic photosolids, that is nematic glasses and elastomers that have large mechanical reactions to light. In particular we describe the bending of cantilevers sufficiently absorbing that they would not bend if Beer's law were applicable. We quantify the role of optically generated heat in determining the mechanical response and conclude that in general it is minor in importance compared with optical effects.

Thermal diffusion and bending kinetics in nematic elastomer cantilever

Vertically aligned monodomain nematic liquid-crystal elastomers contract when heated. If a temperature gradient is applied across the width of such a cantilever, inhomogeneous strain distribution leads to bending motion. We modelled the kinetics of thermally induced bending in the limit of a long thin strip and the predicted time variation of curvature agreed quantitatively with experimental data from samples with a range of critical indices and nematic-isotropic transition temperatures. We also deduced a value for the thermal diffusion coefficient of the elastomer.

Linear and nonlinear photoinduced deformations of cantilevers

Glassy and elastomeric nematic networks with dye molecules present can be very responsive to illumination, huge reversible strains being possible. If absorption is appreciable, strain decreases with depth into a cantilever, leading to bend that is the basis of micro-opto-mechanical systems (MOMS). Bend actually occurs even when Beer's law suggests a tiny penetration of light into a heavily dye-doped system. We model the nonlinear opto-elastic processes behind this effect. In the regime of cantilever thickness giving optimal bending for a given incident light intensity, there are three neutral surfaces. In practice such nonlinear absorptive effects are very important since heavily doped systems are commonly used.

SlyA and H-NS regulate transcription of the Escherichia coli K5 capsule gene cluster, and expression of slyA in Escherichia coli is temperature-dependent, positively autoregulated, and independent of H-NS

In this paper, we present the first evidence of a role for the transcriptional regulator SlyA in the regulation of transcription of the Escherichia coli K5 capsule gene cluster and demonstrate, using a combination of reporter gene fusions, DNase I footprinting, and electrophoretic mobility shift assays, the dependence of transcription on the functional interplay between H-NS and SlyA. Both SlyA and H-NS bind to multiple overlapping sites within the promoter in vitro, but their binding is not mutually exclusive, resulting in a remodeled nucleoprotein complex. In addition, we show that expression of the E. coli slyA gene is temperature-regulated, positively autoregulated, and independent of H-NS.

Enriched environment enhances transplanted subventricular zone stem cell migration and functional recovery after stroke

Stroke patients suffer from severe impairments and significant effort is under way to develop therapies to improve functional recovery. Stem cells provide a promising form of therapy to replace neuronal circuits lost to injury. Indeed, previous studies have shown that a variety of stem cell types can provide some functional recovery in animal models of stroke. However, it is unlikely that replacement therapy alone will be sufficient to maximize recovery. The aim of the present study was to determine if rodent stem cell transplants combined with rehabilitation resulted in enhanced functional recovery after focal ischemia in rats. Middle cerebral artery occlusion was induced by injection of the vasoconstrictive peptide endothelin-1 adjacent to the middle cerebral artery. Seven days after stroke the rats received adult neural stem cell transplants isolated from mouse subventricular zone or vehicle injection and then subsequently were housed in enriched or standard conditions. The rats in the enriched housing also had access to running wheels once a week. Enriched housing and voluntary running exercise enhanced migration of transplanted stem cells toward the region of injury after stroke and there was a trend toward increased survival of stem cells. Enrichment also increased the number of endogenous progenitor cells in the subventricular zone of transplanted animals. Finally, functional recovery measured in the cylinder test was facilitated only when the stem cell transplants were combined with enrichment and running exercise 7 days after the transplant. These results suggest that the ability of transplanted stem cells in promoting recovery can be augmented by environmental factors such as rehabilitation.

Nonlinear photoresponse of disordered elastomers

We model the polarization-dependent photocontractions of polydomain nematic elastomers. Contraction initially arises by light-induced director rotation. At higher light intensity, strain recovers because the local order parameter diminishes. Thus we predict photostrains to be nonmonotonic with light intensity and predict the induction of a negative global order parameter for the system of polydomains. Nonmonotonic strains would give curvature reversal in thick samples. Our model also predicts an elongational strain response to nonpolarized light.

Delayed minocycline treatment reduces long-term functional deficits and histological injury in a rodent model of focal ischemia

The absence of effective treatments for stroke presents a critical need for novel strategies that can reduce ischemic injury. Neuroinflammation following focal ischemia induces secondary injury in the region surrounding the insult, thus anti-inflammatory agents are potential neuroprotectants. Minocycline is one such agent possessing neuroprotective properties, however many studies examining minocycline after ischemia have used minimal delays between ischemia and treatment, short survival periods, and lack measures of functional outcome. Such studies do not distinguish whether minocycline provides sustained protection or merely delays cell death. This study was designed to address some of these concerns. Male Sprague-Dawley rats were treated with multiple doses of minocycline (45 mg/kg i.p.) or vehicle beginning 2.5 h after endothelin-1-induced focal ischemia. Measures of forelimb asymmetry and skilled reaching (staircase test) were used to determine functional outcome 7, 15 and 28 days after ischemia. Long-term functional assessment indicates that minocycline provides limited benefit in the staircase test, but confers long-term benefit in the forelimb asymmetry test. Subcortical and whole hemisphere infarct volumes were reduced by 41 and 39% respectively in minocycline-treated animals. Further analysis revealed that minocycline attenuated long-term white matter damage adjacent to the striatal injury core, which correlated with sustained functional benefits. This study indicates that delayed minocycline treatment improves long-term functional outcome which is linked to protection of both white and gray matter.

Temperature modulation (hypothermic and hyperthermic conditions) and its influence on histological and behavioral outcomes following cerebral ischemia

Core temperature (T(C)) is a critical determinant of the severity of neural damage that results from focal or global ischemia. Former studies indicated that especially intra-ischemic but also post ischemic mild hypothermia significantly decreased necrotic neural damage of a focal or global insult, as assessed between 3-7 days post-insult. More recent work shows that prolonged post-ischemic hypothermia reduces neural damage and inhibits associated behavioral deficits for up to one year after the insult (i.e. true neuroprotection with behavioral preservation). Alternatively, increases in core temperature via external heating or with pyrogens resulting from bacterial infections, at the time of the global ischemia insult worsen the neural damage of ischemic animals from those of respective normothermic controls given the same insult. This is paralleled in the clinical setting whereby approximately 50% of ischemic patients develop fevers within 2 days of the insult and have worsened neurological outcomes than non-febrile patients. The review discusses the possible mechanisms of neuroprotection of hypothermic therapy from cerebral ischemia as well as mechanisms involved in the exacerbation of neural damage of hypoxic ischemia under hyperthermic conditions. Questions are raised as to whether the medical community has sufficient evidence to begin appropriate hypothermic therapy of acute stroke patients. The importance of accurate monitoring core temperatures of all suspected stroke patients is emphasized, noting the differences in temperature that can occur with age, sex, medication or lifestyle so that appropriate temperature treatment could be implemented, if required.

Endurance exercise regimens induce differential effects on brain-derived neurotrophic factor, synapsin-I and insulin-like growth factor I after focal ischemia

The optimal amount of endurance exercise required to elevate proteins involved in neuroplasticity during stroke rehabilitation is not known. This study compared the effects of varying intensities and durations of endurance exercise using both motorized and voluntary running wheels after endothelin-I-induced focal ischemia in rats. Hippocampal levels of brain-derived neurotrophic factor, insulin-like growth factor I and synapsin-I were elevated in the ischemic hemisphere even in sedentary animals suggesting an intrinsic restorative response 2 weeks after ischemia. In the sensorimotor cortex and the hippocampus of the intact hemisphere, one episode of moderate walking exercise, but not more intense running, resulted in the greatest increases in levels of brain-derived neurotrophic factor and synapsin-I. Exercise did not increase brain-derived neurotrophic factor, insulin-like growth factor I or synapsin-I in the ischemic hemisphere. In voluntary running animals, both brain and serum insulin-like growth factor I appeared to be intensity dependent and were associated with decreasing serum levels of insulin-like growth factor I and increasing hippocampal levels of insulin-like growth factor I in the ischemic hemisphere. This supports the notion that exercise facilitates the movement of insulin-like growth factor I across the blood-brain barrier. Serum corticosterone levels were elevated by all exercise regimens and were highest in rats exposed to motorized running of greater speed or duration. The elevation of corticosterone did not seem to alter the expression of the proteins measured, however, graduated exercise protocols may be indicated early after stroke. These findings suggest that relatively modest exercise intervention can increase proteins involved in synaptic plasticity in areas of the brain that likely subserve motor relearning after stroke.

Environmental enrichment enhances recovery of function but exacerbates ischemic cell death

Prior exposure to brief 'conditioning' episodes of ischemia protects hippocampal CA1 neurons against a subsequent more severe ischemic insult. However, protected cells exhibit abnormal function and as survival times are extended this ischemic tolerance dissipates and cells begin to die. In this study, we sought to determine whether environmental enrichment could alter the above pattern of delayed cell death and functional impairment in a gerbil model of ischemic tolerance. Gerbils received either ischemic preconditioning, 5 min of ischemia without preconditioning or sham surgery. Three days after ischemia, gerbils were placed in either an enriched environment or standard laboratory housing. Open field habituation was assessed 3, 7, 10, 30 and 60 days after ischemia. Subsequently, animals were trained in two versions (win-shift and win-stay) of a T-maze task. Following behavioral testing, extracellular CA1 field potential amplitudes and CA1 cell counts were determined. Initial open field activity was significantly higher in all experimental groups compared to sham animals (P<0.001). By 60 days, enriched ischemic preconditioned and enriched ischemic gerbils were not different than shams whereas non-enriched, ischemic preconditioned and ischemic gerbils continued to have higher activity scores (P<0.05). Preconditioned and enriched ischemic animals learned the win-shift T-maze problem as quickly as shams while non-enriched ischemic gerbils were severely impaired compared with all other groups (P<0.001). Only the sham and enriched preconditioned groups readily acquired the win-stay paradigm. CA1 field potential amplitudes were lower (P<0.05) in ischemic than sham gerbils irrespective of treatment. Surprisingly, CA1 cell counts were significantly lower (P<0.01) in enriched versus non-enriched ischemic preconditioned animals. These data demonstrate that early, intensive intervention after ischemia can improve functional outcome but that this is accompanied by increased brain damage. Careful consideration needs to be given to the timing of rehabilitation after stroke and related types of brain injury.

Basaloid/follicular hyperplasia overlying connective tissue/mesenchymal hamartomas simulating basal cell carcinomas

BACKGROUND

Basaloid hyperplasia has been described overlying dermatofibromas as well as in the epidermis overlying nevus sebaceus. Although the morphology of these areas may resemble that of basal cell carcinoma (BCC), in the majority of cases aggressive behavior of the proliferation is not seen. In fact, the basaloid proliferation often shows follicular differentiation and may be stimulated and maintained by its relationship with the underlying stromal cells.

OBJECTIVE

We wanted to determine whether immunohistochemical staining for antibodies, which may suggest differences in pathogenesis, were different in basaloid hyperplasia overlying connective tissue/mesenchymal hamartomas and BCC.

METHODS

We report 3 cases of connective tissue/mesenchymal hamartomas with overlying basaloid hyperplasia, in which the areas of the basaloid proliferation showed follicular differentiation. Immunohistochemical stains included Ber-EP4, PCNA, Ki-67, Bcl-2, p53, SM-Actin, CD31, factor XIIIa, KP-1, and CD34.

RESULTS

There was a diffuse positive reaction for Ber-EP4 in all specimens and there was increased nuclear staining for PCNA and Ki-67. There was focal cytoplasmic staining for Bcl-2 in the areas of basaloid hyperplasia. Immunohistochemical staining for p53 showed only scattered positive cells except in a small focus in the areas of basaloid hyperplasia. The connective tissue component of all lesions showed diffuse staining for CD34 surrounding areas of basaloid hyperplasia in the mesenchymal component as well as in abundant S-100(+) nerves.

CONCLUSION

The areas of basaloid hyperplasia in these hamartomas exhibited an immature phenotype similar to that seen in both BCCs and follicular tumors; however, the patterns of proliferation markers, p53, Bcl-2, and the surrounding stromal cell markers were similar to those of benign follicular tumors. Thus the staining pattern for this group of antibodies suggests that areas of basaloid hyperplasia are not BCC.

A serial MR study of cerebral blood flow changes and lesion development following endothelin-1-induced ischemia in rats

The vasoconstrictive peptide endothelin-1 (ET-1) has been used previously to transiently occlude the middle cerebral artery (MCA) in rats. However, the duration of the resulting reduction in cerebral blood flow (CBF) and the reperfusion characteristics are poorly understood. In this study perfusion and T(2)-weighted MRI were used together with histology to characterize the cerebral perfusion dynamics and lesion development following ET-1 injection. Twenty-two rats received an intracerebral injection of ET-1 adjacent to the MCA. CBF was reduced to 30-50% of control levels, and a significant reduction persisted for 16 h in the cortex and 7 h in the striatum. The lesion size measured by T(2)-weighted imaging at 48 h correlated with the final infarct size measured by histology at 7 d. The sustained reduction in CBF and the gradual development of the ischemic lesion resemble human stroke evolution, suggesting that this model may be useful for evaluating therapeutic agents, particularly when treatment is delayed.

Enriched rehabilitative training promotes improved forelimb motor function and enhanced dendritic growth after focal ischemic injury

Chronic impairment of forelimb and digit movement is a common problem after stroke that is resistant to therapy. Previous studies have demonstrated that enrichment improves behavioral outcome after focal ischemia; however, postischemic enrichment alone is not capable of enhancing fine digit and forelimb function. Therefore, we combined environmental enrichment with daily skilled-reach training to assess the effect of intensive task-specific rehabilitation on long-term functional outcome. Rats were subjected to either endothelin-1-induced focal ischemia or sham surgery and subsequently designated to enriched-rehabilitation or standard-housing treatment groups starting 15 d after ischemia. Functional assessment of the affected forelimb at 4 and 9 weeks after treatment revealed that ischemic plus enrichment (IE) animals had improved approximately 30% on the staircase-reaching task and were indistinguishable from sham animals for both latency and foot faults in a beam-traversing task. In contrast, ischemic plus standard (IS) animals remained significantly impaired on both tasks. Interestingly, both ischemic groups (IE and IS) relied on the nonaffected forelimb during upright weight-bearing movements, a pattern that persisted for the duration of the experiment. Dendritic arborization of layer V pyramidal cells within the undamaged motor cortex was examined using a Golgi-Cox procedure. IE animals showed enhanced dendritic complexity and length compared with both IS and sham groups. These results suggest that enrichment combined with task-specific rehabilitative therapy is capable of augmenting intrinsic neuronal plasticity within noninjured, functionally connected brain regions, as well as promoting enhanced functional outcome.

Rat middle cerebral artery occlusion: Correlations between histopathology, T2-weighted magnetic resonance imaging, and behavioral indices

During attempts to develop the intraluminal suture model of transient middle cerebral artery occlusion (MCAO) in the Sprague Dawley strain of rats, we noticed a wide variability in lesion size seen with T2-weighed magnetic resonance imaging (MRI) or histopathology, as well as in scores for behavioral indices. It was our intent to examine the results of the study carefully and determine whether there were strong point-to-point correlations between the degree of lesion size determined from T2-weighted MRI or histopathology and intermediate or long-term neurologic/behavioral assessments. Baseline behavioral scores for forelimb dexterity (staircase test) were obtained on all animals in the period before receiving 60 minutes of transient MCAO. After MCAO, animals were tested at specified intervals from 1 to 21 days for composite neurologic deficits. T2-weighted MRI was taken at 2 and 7 days post-MCAO. At 30 and 60 days post-MCAO, animals were retested in the staircase test with subsequent histopathologic examination of the brains. Indeed, there were highly significant correlations between lesion size determined by MRI and histopathology. The damage observed in the T2-weighted MRI, as well as the size of the histopathologic lesions, were in turn highly correlated to deficiencies observed in the composite neurologic assessments, as well as to deficits at 30 and 60 days post-MCAO for skilled use of the contralateral forepaw (damaged side). In the latter test, the correlations were somewhat less significant for the ability of rats to reach for food with the ipsilateral forepaw (undamaged side).

T2-weighted MRI correlates with long-term histopathology, neurology scores, and skilled motor behavior in a rat stroke model

The intraluminal suture model of transient middle cerebral artery occlusion (MCAO) in the Sprague Dawley strain of rats characteristically results in an inconsistently sized brain lesion. The purpose of the investigation reported here was to determine whether there were strong point-to-point correlations between the degree of cortical lesion size, as assessed in vivo using T2-weighted magnetic resonance imaging (MRI) and corresponding cortical lesion size using routine histopathological techniques. Moreover, we aimed to investigate if cortical lesion size as determined by these two modalities correlates with neurological and/or skilled motor deficits observed in individual animals. Baseline behavioral scores were obtained on the animals prior to receiving 60 min of transient MCAO. Following MCAO, animals were tested for 1-21 days for neurological deficits. T2-weighted MRIs of the cortex were taken at two and seven days post-MCAO. At 30 and 60 days the rats were retested for forelimb dexterity in the staircase test. Subsequently, the cortex was examined for histopathological damage. Indeed, there were highly significant correlations between lesion size determined by MRI and histopathology. The degree of cortical damage observed in the T2-weighted MRI, as well as the size of the histopathological lesions were, in turn, highly correlated with the degrees of deficiencies observed in the composite neurological assessments and with the deficits involving skilled use of the contralateral forepaw (damaged side).

Microcystic adnexal carcinoma: an immunohistochemical study including markers of proliferation and apoptosis

Microcystic adnexal carcinoma (MAC) is the prototype for a subset of locally aggressive adnexal carcinomas (LAACs). Ultraviolet radiation (UVR) and UVB signature p53 mutations are implicated in the etiology of the most common cutaneous carcinomas. However in MACs, the role of UVR and p53 mutations is unknown. In addition, controversy still exists regarding the patterns of differentiation within these tumors. The objective of this study was to determine the expression patterns of immunohistochemical markers for p53, Ki-67, c-erbB-2, and Bcl-2 in MACs, and to compare these patterns with two MAC histologic stimulants: sclerosing type basal cell carcinomas (sBCCs) and desmoplastic trichoepitheliomas (dTEs). Other objectives were to compare expression patterns of cytokeratin (CK) AE1/AE3, CK7, CD20, endothelial membrane antigen (EMA), Ber-EP4, CD34, alpha-smooth muscle actin (SMA), and S-100 protein in MACs with its histologic simulators, and to determine the usefulness of all the immunohistochemical studies in diagnosis. Immunohistochemical markers were performed on 10 MACs, 10 sBCCs, and four dTEs. They included p53, Ki-67, c-erbB-2, Bcl-2, CK AE1/AE3, CK7, CD20, EMA, Ber-EP4, CD34, S-100 protein, and alpha-SMA. MACs expressed p53 in less than 25% of the tumor cells in only two cases (20%), and both cases showed only moderately intense staining, whereas 80% of the sBCCs were positive and showed intense staining, and all dTEs were negative. In MACs, less than 5% of the tumor cells were Ki-67 positive, whereas the sBCCs showed 20% to 40% Ki-67-positive tumor cells and dTEs showed rare Ki-67-positive cells. Bcl-2 was expressed focally in MACs, diffusely in sBCCs, and in scattered cells in dTEs. All tumors were negative for c-erbB-2. CD34, CK7, EMA, Ber-EP4, S-100 protein, and alpha-SMA all showed a distinctive pattern of staining in MACs. Although MACs arise commonly in chronically sun-exposed skin, increased expression of p53 is not found frequently. Overexpression of c-erbB-2 does not appear to be a factor in the development and progression of these adnexal tumors. Bcl-2 is expressed in MACs, but not diffusely as in sBCCs. The low level of Ki-67 supports a low proliferative rate, and other immunohistochemical markers support divergent patterns of adnexal differentiation in MACs. Immunohistochemical studies may help to differentiate MAC from sBCCs and dTEs.

Efficacy of disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059), a free radical trapping agent, in a rat model of hemorrhagic stroke

Because free radical mechanisms may contribute to brain injury in hemorrhagic stroke, the effect of the free radical trapping agent disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059) was investigated on outcome following intracerebral hemorrhage (ICH) in rat. ICH was induced in 20 adult rats by infusion of collagenase into the caudate-putamen. Thirty minutes later rats were treated with NXY-059 (50 mg/kg subcutaneous plus 8.8 mg/kg/h for 3 days subcutaneous delivered via implanted osmotic pumps) or saline (equivalent volumes). Magnetic resonance imaging 24 h after ICH confirmed that the hemorrhage was uniform in the two groups, and subsequent imaging at 7 and 42 days post-ICH showed that the hematoma resolved similarly in the two groups. Behavioral testing on days 1, 3, 7, 14, and 21 after ICH showed that rats treated with NXY-059 had significantly decreased neurological impairment at all times. Deficits in skilled forelimb use 4-5 weeks post-ICH, and in striatal function 6 weeks post-ICH, were not reduced by treatment with NXY-059. Treatment with NXY-059 significantly reduced the neutrophil infiltrate observed 48 h post-hemorrhage in the vicinity of the hematoma, and the number of TUNEL-positive cells 48 h post-hemorrhage at the hematoma margin. However, by 6 weeks there were no differences in neuronal densities in treated and control rats.

Therapeutic implications of hypothermic and hyperthermic temperature conditions in stroke patients

Brain temperature is an important variable in determining the outcome of cerebral ischemia; increases in core temperature escalate neural damage whereas decreases in core temperature reduce damage. Fever induction often occurs in patients prior to or as a direct or indirect result of the ischemic insult, with a worsened stroke outcome, compared with non-febrile ischemic patients. Most importantly, post-ischemic hypothermia reduces long term neural damage and associated behavioral deficits in animals studied for up to a year after the ischemic insult. This review discusses the importance of monitoring the brain temperature of stroke patients and implemention of therapeutic thermoregulatory strategies to reduce the temperature of ischemic patients.

Electrophysiological properties of CA1 neurons protected by postischemic hypothermia in gerbils

BACKGROUND AND PURPOSE

Recent studies show that prolonged (eg, 24-hour) postischemic hypothermia confers lasting histological and behavioral protection against severe global cerebral ischemia. However, functional abnormalities may be compensated for by undamaged brain regions and thus not detected by behavioral tests. To determine whether hypothermia preserves CA1 functional integrity, we measured synaptic and membrane properties of CA1 neurons in ischemic gerbils treated with postischemic hypothermia.

METHODS

Gerbils were subjected to 5 minutes of forebrain ischemia and were either left untreated or exposed to 2 days of hypothermia (32 degrees C for 24 hours and then 34 degrees C for 24 hours). Sham animals were operated on but not made ischemic, then either allowed to recover at room temperature or subjected to hypothermia for 2 days. Approximately 5 weeks after ischemia or sham surgery, patch-clamp recordings were obtained from the CA1 region of hippocampal slices.

RESULTS

There was approximately 95% CA1 cell loss in untreated ischemic animals, whereas ischemic gerbils treated with hypothermia had cell counts similar to sham animals. Resting membrane potential, action potential amplitude and duration, input resistance, and synaptic currents evoked by Schaffer collateral stimulation were similar between pyramidal cells obtained from ischemic gerbils treated with hypothermia and sham-operated animals (P:>0.05).

CONCLUSIONS

These data demonstrate that postischemic hypothermia preserves the measured electrophysiological properties of CA1 neurons in the absence of any apparent functional abnormalities. This study provides further support for the use of hypothermia as a treatment for cerebral ischemia.

Identification of parasitoses in a child burial from Adak Island (Central Aleutian Islands, Alaska)

Bothriocephalid (Diphyllobothrium pacificum) and Ascarid (Ascaris lumbricoides) eggs have been identified in a sample taken in the abdominal cavity of a child skeleton found in Zeto Point (ADK-011), an archaeological site on Adak Island in the Central Aleutian Islands (Alaska).

Effect of FK-506 on inflammation and behavioral outcome following intracerebral hemorrhage in rat

Beginning 15 min after induction of intracerebral hemorrhage (ICH) by intrastriatal administration of collagenase, rats were treated intramuscularly with FK-506 (3 mg/kg) or with vehicle. Treatment was repeated daily for 7 days. MR imaging 1, 7, and 28 days post-ICH showed that treatment did not affect hematoma size or its subsequent resolution. Two days post-ICH, neutrophil infiltration around the hematoma was decreased in the FK-506-treated rats, as was the number of TUNEL-positive cells at the edge of the hematoma and in the peripheral region. The decreased inflammatory response was accompanied by functional improvement in the treated rats. The neurological deficit induced by the ICH (beam walking ability, postural reflex, spontaneous circling) was significantly decreased from 3 to 21 days post-ICH by treatment with FK-506. Skilled use of the forelimb ipsilateral to the ICH was improved and sensory neglect of the same limb was decreased 8-9 weeks post-ICH in rats treated with FK-506. However, neuronal loss assessed 9 weeks post-ICH was not different in the treated and untreated rats.

HIV-1 Tat neurotoxicity is prevented by matrix metalloproteinase inhibitors

The release of potentially neurotoxic molecules by HIV-infected brain macrophages is accompanied by neuronal injury and death that results in the development of HIV-associated dementia (HAD). Among the potential neurotoxins implicated in the development of HAD is the HIV-1 transactivating protein, Tat. To investigate the mechanism by which Tat causes neurotoxicity, brain-derived Tat sequences from nondemented (Tat-ND) and demented (Tat-HAD) AIDS patients, which differed primarily in the augmenting region of Tat, were expressed in U937 monoblastoid cells and primary human macrophages. Cells expressing Tat-HAD protein exhibited elevated matrix metalloproteinase (MMP)-2 and -7 release and activation, but cells expressing Tat-ND did not exhibit enhanced MMP expression. Conditioned media from Tat-HAD-transfected cells caused significantly greater neuronal death (15.4 +/- 4.3%) than did Tat-ND (4.4 +/- 2.1%) or nontransfected (2.1 +/- 0.8%) cell-derived conditioned media. The neurotoxicity induced by Tat-HAD was inhibited by anti-MMP-2 or -7 antibodies (p < 0.005) but not by antibodies against MMP-9 or Tat. Similarly, scid/nod mice receiving striatal implants of Tat-HAD-transfected cells exhibited greater neurobehavioral abnormalities and neuronal loss (p < 0.005) than did animals receiving Tat-ND or nontransfected cells, which were reduced by treatment with the MMP inhibitor prinomastat (p < 0.005). These findings indicate that Tat causes neuronal death through an indirect mechanism that is Tat sequence dependent and involves the induction of MMPs.

Prolonged but delayed postischemic hypothermia: a long-term outcome study in the rat middle cerebral artery occlusion model

Delayed but prolonged hypothermia persistently decreases cell death and functional deficits after global cerebral ischemia in rodents. Postischemic hypothermia also reduces infarction after middle cerebral artery occlusion (MCAO) in rat. Because initial neuroprotection is sometimes transient and may not subserve functional recovery, especially on demanding tasks, the authors examined whether postischemic cooling would persistently reduce infarction and forelimb reaching deficits after MCAO. Male spontaneously hypertensive rats were trained to retrieve food pellets in a staircase test that measures independent forelimb reaching ability. Later, rats underwent 90 minutes of normothermic MCAO, through a microclip, or sham operation. In some rats, prolonged cooling (33 degrees C for 24 hours and then 35 degrees C for 24 hours) began 2.5 hours after the onset of ischemia (60 minutes after the start of reperfusion; n = 17 with subsequently 1 death) or sham procedures (n = 4), whereas untreated sham (n = 4) and ischemic (n = 16 with subsequently 1 death) rats maintained normothermia. An indwelling abdominal probe continually measured core temperature, and an automated fan and water spray system was used to produce hypothermia. One month later rats were reassessed in the staircase test over five days and then killed. The contralateral limb impairment in food pellet retrieval was completely prevented by hypothermia (P = 0.0001). Hypothermia reduced an infarct volume of 67.5 mm3 after untreated ischemia to 35.8 mm3 (P < 0.0001). These findings of persistent benefit encourage the clinical assessment of hypothermia.

Persistent neuroprotection with prolonged postischemic hypothermia in adult rats subjected to transient middle cerebral artery occlusion

Postischemic hypothermia provides long-lasting neuroprotection against global cerebral ischemia in adult rats and gerbils. Studies indicate that hypothermia must be prolonged (e.g., 24 h) to indefatigably salvage hippocampal CA1 neurons. Delayed hypothermia also reduces focal ischemic injury. However, no study has examined long-term outcome following postischemic hypothermia in adult animals. Furthermore, most studies examined only brief hypothermia (e.g., 3 h). Since previous studies may have overestimated long-term benefit and have likely used suboptimal durations of hypothermia, we examined whether prolonged cooling would attenuate infarction at a 2-month survival time following middle cerebral artery occlusion (MCAo) in rats. Adult male Wistar rats were implanted with telemetry brain temperature probes and later subjected to 30 min of normothermic MCAo (contralateral to side of probe placement) or sham operation. Ischemia was produced by the insertion of an intraluminal suture combined with systemic hypotension (60 mm Hg). Sham rats and one ischemic group controlled their own postischemic temperature while another ischemic group was cooled to 34 degrees C for 48 h starting at 30 min following the onset of reperfusion. The infarct area was quantified after a 2-month survival time. Normothermic MCAo resulted in almost complete striatal destruction (91% loss +/- 12 SD) with extensive cortical damage (36% +/- 16 SD). Delayed hypothermia treatment significantly reduced cortical injury to 10% +/- 10 SD (P < 0.001) while striatal injury was marginally reduced to 79% loss +/- 17 SD (P < 0.05). Delayed hypothermia of only 34 degrees C provided long-lasting cortical and striatal protection in adult rats subjected to a severe MCAo insult. These results strongly support the clinical assessment of hypothermia in acute stroke.