Stroke Rehabilitation In The United States

Stroke rehabilitation currently is a very exciting area in which to be involved.There is much going on with regard to clinical research,and much more to come.     

In Vitro and In Vivo Antifungal Activity of Amphotericin B Lipid Complex: Are Phospholipases Important?

Amphotericin B lipid complex for injection (ABLC) is a suspension of amphotericin B complexed with the lipids l-α-dimyristoylphosphatidylcholine (DMPC) and l-α-dimyristoylphosphatidylglycerol. ABLC is less toxic than amphotericin B deoxycholate (AmB-d), while it maintains the antifungal activity of AmB-d. Active amphotericin B can be released from ABLC by exogenously added (snake venom, bacteria, or Candida-derived) phospholipases or by phospholipases derived from activated mammalian vascular tissue (rat arteries). Such extracellular phospholipases are capable of hydrolyzing the major lipid in ABLC. Mutants of C. albicans that were resistant to ABLC but not AmB-d in vitro were deficient in extracellular phospholipase activity, as measured on egg yolk agar or as measured by their ability to hydrolyze DMPC in ABLC. ABLC was nevertheless effective in the treatment of experimental murine infections produced by these mutants. Isolates of Aspergillus species, apparently resistant to ABLC in vitro (but susceptible to AmB-d), were also susceptible to ABLC in vivo. We suggest that routine in vitro susceptibility tests with ABLC itself as the test material may not accurately predict the in vivo activity of ABLC and that the enhanced therapeutic index of ABLC relative to that of AmB-d in vivo may be due, in part, to the selective release of active amphotericin B from the complex at sites of fungal infection through the action of fungal or host cell-derived phospholipases.Amphotericin B has been the agent of choice for the treatment of serious fungal infections for more than 35 years. However, administration of the most common preparation of amphotericin B (a sodium deoxycholate colloidal suspension) is associated with severe, dose-limiting acute and chronic toxicities, particularly nephrotoxicity.Amphotericin B lipid complex for injection (ABLC) is a suspension of amphotericin B complexed with the lipids l-α-dimyristoylphosphatidylcholine (DMPC) and l-α-dimyristoylphosphatidylglycerol (DMPG) (11). The safety and efficacy of ABLC have been extensively evaluated in laboratory (4–6, 14) and clinical (7, 24, 25) studies. Those studies have shown that ABLC is, in general, markedly less toxic than amphotericin B deoxycholate (AmB-d) and has antifungal activity at least comparable to and sometimes enhanced over that of AmB-d.Complexation with lipids appears to stabilize amphotericin B in a self-associated state so that it is not available to interact with cellular membranes (the presumed major site of its antifungal activity and its mammalian toxicity) (12, 17). It was previously demonstrated that ABLC is more than 1,000-fold less hemolytic to erythrocytes in vitro than AmB-d and that active (hemolytic) amphotericin B can be released from ABLC by a heat-labile, extracellular fungal product (lipase) (17). It has also been demonstrated that in vitro the MICs of ABLC for certain phospholipase-deficient non-Candida albicans Candida species and phospholipase-deficient mutants of C. albicans are higher than those of AmB-d (13). In the present study we further evaluated the role of phospholipases in the in vitro and in vivo antifungal activity of ABLC.     

In Vitro and In Vivo Efficacy of β-Lactams against Replicating and Slowly Growing/Nonreplicating Mycobacterium tuberculosis

Beta-lactams, in combination with beta-lactamase inhibitors, are reported to have activity against Mycobacterium tuberculosis bacteria growing in broth, as well as inside the human macrophage. We tested representative beta-lactams belonging to 3 different classes for activity against replicating M. tuberculosis in broth and nonreplicating M. tuberculosis under hypoxia, as well as against streptomycin-starved M. tuberculosis strain 18b (ss18b) in the presence or absence of clavulanate. Most of the combinations showed bactericidal activity against replicating M. tuberculosis, with up to 200-fold improvement in potency in the presence of clavulanate. None of the combinations, including those containing meropenem, imipenem, and faropenem, killed M. tuberculosis under hypoxia. However, faropenem- and meropenem-containing combinations killed strain ss18b moderately. We tested the bactericidal activities of meropenem-clavulanate and amoxicillin-clavulanate combinations in the acute and chronic aerosol infection models of tuberculosis in BALB/c mice. Based on pharmacokinetic/pharmacodynamic indexes reported for beta-lactams against other bacterial pathogens, a cumulative percentage of a 24-h period that the drug concentration exceeds the MIC under steady-state pharmacokinetic conditions (%T_MIC) of 20 to 40% was achieved in mice using a suitable dosing regimen. Both combinations showed marginal reduction in lung CFU compared to the late controls in the acute model, whereas both were inactive in the chronic model.     

In Vitro and In Vivo Structure–Property Relationship of 68Ga-Labeled Schiff Base Derivatives for Functional Myocardial PET Imaging

Purpose

SPECT (e.g., with ^99mTc-sestamibi) is routinely used for imaging myocardial damage, even though PET could offer a higher spatial resolution. Using the generator-gained isotope ⁶⁸Ga would allow a rapid supply of the tracer in the diagnostic unit. For this reason, the aim of the study was to develop ⁶⁸Ga-labeled PET tracers based on different Schiff base amines and to evaluate the cardiomyocyte uptake in vitro as well as the biodistribution of the tracers in vivo.

Procedures

Fifteen different Schiff bases (basing on 3 different backbones) were synthesized and labeled with ⁶⁸Ga. Lipophilicity varied between 0.87?±?0.24 and 2.72?±?0.14 (logD value). All tracers were positively charged and stable in plasma and apo-transferrin solution. In vitro uptake into cardiomyocytes was assessed in HL-1 cells in the absence and presence of the ionophor valinomycin. In vivo accumulation in the heart and in various organs was assessed by small animal PET imaging as well as by ex vivo biodistribution. The results were compared with ^99mTc-sestamibi and ¹⁸F-flurpiridaz.

Results

All cationic Schiff bases were taken up into cardiomyocytes but the amount varied by a factor of 10. When destroying the membrane potential, the cellular uptake was markedly reduced in most of the tracers, indicating the applicability of these tracers for identifying ischemic myocardium. PET imaging revealed that the in vivo myocardial uptake reached a constant value approximately 10 min after injection but the intracardial amount of the tracer varied profoundly (SUV 0.46 to 3.35). The most suitable tracers showed a myocardial uptake which was comparable to that of ^99mTc-sestamibi.

Conclusions

⁶⁸Ga-based Schiff bases appear suitable for myocardial PET images with uptake comparable to ^99mTc-sestamibi but offering higher spatial resolution. By systematical variation of the backbone and the side chains, tracers with optimal properties can be identified for further clinical evaluation.     

Validation of an Engineered Cell Model for In Vitro and In Vivo HIF-1α Evaluation by Different Imaging Modalities

Purpose

The aim of this study was to characterize a cell-based model for the molecular study of hypoxia-inducible factor (HIF)-1α activity, in the context of hypoxia, by means of different imaging techniques.

Procedures

Engineered U251-HRE glioma cells were used to analyze the molecular mechanisms underlying HIF-1α activity in vitro in relation to luciferase expression. The same cells were orthotopically implanted in mice to evaluate tumor progression and hypoxia induction by bioluminescence imaging, fluorescence imaging, positron emission tomography (PET), and magnetic resonance imaging (MRI).

Results

In vitro analyses highlighted the relationship between HIF-1α and luciferase activity in hypoxic conditions and after pharmacological treatments in U251-HRE cells. Through in vivo studies, it was possible to assess hypoxia establishment in relation to tumor growth by optical imaging, PET and MRI.

Conclusions

The findings of this study indicate that the U251-HRE orthotopic murine model can be used to reliably evaluate processes modulating HIF-1α activity, using both molecular and preclinical non-invasive imaging techniques.     

Can Power Motion Imaging Mode Combined with Contrast Agent Assess Myocardial Contraction and Perfusion? In Vitro and In Vivo Studies

Power motion imaging (PMI) is a new Doppler imaging technology that can enhance contrast agent visualization. We hypothesized that PMI combined with Albunex injection (CPMI) could provide new insights into myocardial contractility and perfusion. In a first step, PMI signal was studied with an in vitro phantom. In a second step, PMI signal was studied in 10 rabbits at different workloads. In a third step, 10 rabbits were studied before and after ischemia produced by coronary ligation and finally during reperfusion. During the latter protocol, epicardial echocardiography analyzed by PMI and fundamental mode was performed before and after Albunex injection. PMI signal was well correlated with phantom velocity. PMI signal and myocardial wall thickening were well correlated, particularly in the septal area. On the coronary occlusion model, ischemia was associated with a significant decrease in PMI and CPMI signals, whereas reperfusion was associated with a significant decrease in PMI signals only, indicating stunning. We conclude that PMI combined with CPMI is a powerful tool to assess myocardial contractility and perfusion.     

Comparison of the Adsorption Capacities of an Activated-Charcoal–Yogurt Mixture Versus Activated-Charcoal–Water Slurry In Vivo and In Vitro

Background. An activated charcoal–yogurt mixture was evaluated in vivo to determine the effect on the gastrointestinal absorption of paracetamol, as compared to activated-charcoal–water slurry. The potential advantage of the activated-charcoal–yogurt mixture is a better palatability and general acceptance by the patients without loss of efficacy. In addition, paracetamol adsorption studies were carried out in vitro to calculate the maximum adsorption capacity of paracetamol to activated-charcoal–yogurt mixture. Methods. In vivo: A randomized crossover study on 15 adult volunteers, using paracetamol 50 mg/kg as a simulated overdose. Each study day volunteers were given a standard meal 1 h before paracetamol, then 50 g activated charcoal 1 h later in either of two preparations: standard water slurry or mixed with 400 mL yogurt. Paracetamol serum concentrations were measured using HPLC. The areas under the concentration-time curve (AUC) of the two preparations were compared and used to estimate the efficacy of each preparation. The palatability of both preparations was evaluated using a visual-analogue scale where the volunteers were asked to evaluate the appearance, smell, flavor, texture, ability to swallow, and overall impression of the mixtures. The time spent to consume the activated charcoal was also registered. In vitro: Activated charcoal, simulated gastric (pH 1.2) or intestinal (pH 7.2) fluid, and paracetamol were mixed with yogurt followed by 1 h incubation. The maximum adsorption capacity of paracetamol to activated charcoal was calculated using Langmuir's adsorption isotherm. Paracetamol concentration was analyzed using HPLC. Results. In vivo there was no significant difference (p > 0.05) in the AUC of paracetamol between the two activated-charcoal preparations. Geometric mean values and 95% CI for the AUCs were (in mg/l · min): 6307 (4932–8065) for the activated charcoal–water slurry and 6525 (5111–8330) for the activated charcoal–yogurt mixture. The palatability study showed significant difference (p < 0.05) only in duration of administration, in favor of the activated charcoal-water slurry. In vitro the maximum adsorption capacity of activated charcoal with added yogurt was 544 mg paracetamol/g activated charcoal (pH 1.2), and 569 mg paracetamol/g activated charcoal (pH 7.2). Conclusion. The two activated-charcoal preparations showed equal (NS) absorption reduction of paracetamol in vivo. Mixing activated charcoal with yogurt rather than water prolonged the ingestion time, but did not improve the palatability in adults. The presence of yogurt reduced the adsorption capacity in vitro by 9–13% (p < 0.05) compared to control without yogurt (previous study with the same setup).