<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> Evasion of Host Immunity in the Setting of Prosthetic Joint Infection: Biofilm and Beyond

Purpose of Review

The incidence of complications from prosthetic joint infection (PJI) is increasing, and treatment failure remains high. We review the current literature with a focus on Staphylococcus aureus pathogenesis and biofilm, as well as treatment challenges, and novel therapeutic strategies.

Recent Findings

S. aureus biofilm creates a favorable environment that increases antibiotic resistance, impairs host immunity, and increases tolerance to nutritional deprivation. Secreted proteins from bacterial cells within the biofilm and the quorum-sensing agr system contribute to immune evasion. Additional immunoevasive properties of S. aureus include the formation of staphylococcal abscess communities (SACs) and canalicular invasion. Novel approaches to target biofilm and increase resistance to implant colonization include novel antibiotic therapy, immunotherapy, and local implant treatments.

Summary

Challenges remain given the diverse mechanisms developed by S. aureus to alter the host immune responses. Further understanding of these processes should provide novel therapeutic mechanisms to enhance eradication after PJI.

     

Effect of synbiotic therapy on the incidence of ventilator associated pneumonia in critically ill patients: a randomised,double-blind,placebo-controlled trial

Objective

To investigate the effect of enteral Synbiotic 2000 FORTE^® (a mixture of lactic acid bacteria and fibre) on the incidence of ventilator associated pneumonia (VAP) in critically ill patients.

Design

Prospective, randomised, double blind, placebo controlled trial.

Setting

Tertiary referral centre, general Adult Intensive Care Unit (ICU).

Patients and participants

259 enterally fed patients requiring mechanical ventilation for 48 h or more were enrolled.

Intervention

All patients were enterally fed as per a standard protocol and randomly assigned to receive either synbiotic 2000 FORTE^® (twice a day) or a cellulose-based placebo for a maximum of 28 days.

Measurements and results

Treatment group (n = 130) was well matched with placebo group (n = 129) for age (mean 49.5 and 50 years, respectively) and APACHE II score (median 17 for both). Oropharyngeal microbial flora and colonisation rates were unaffected by synbiotics. The overall incidence of VAP was lower than anticipated (11.2%) and no statistical difference was demonstrated between groups receiving synbiotic and placebo in the incidence of VAP (9 and 13%, P = 0.42), VAP rate per 1,000 ventilator days (13 and 14.6, P = 0.91) or hospital mortality (27 and 33%, P = 0.39), respectively.

Conclusions

Enteral administration of Synbiotic 2000 FORTE^® has no statistically significant impact on the incidence of VAP in critically ill patients.

     

Bioluminescence Imaging of Colonization and Clearance Dynamics of <Emphasis Type="Italic">Brucella Suis</Emphasis> Vaccine Strain S2 in Mice and Guinea Pigs

Purpose

The goal of this study was to develop a plasmid-based lux bio-reporter for use to obtain in vivo images of Brucella suis vaccine strain 2 (B.suis S2) infection with high resolution and good definition.

Procedures

The pBBR-lux (pBBR1MCS-2-lxCDABE) plasmid that carries the luxCDABE operon was introduced into B. suis S2 by electroporation yielding B. suis S2-lux. The spatial and temporal transit of B. suis S2 in mice and guinea pigs was monitored by bioluminescence imaging.

Results

The plasmid pBBR-lux is stable in vivo and does not appear to impact the virulence or growth of bacteria. This sensitive luciferase reporter could represent B. suis S2 survival in real time. B. suis S2 mainly colonized the lungs, liver, spleen, and uterus in mice and guinea pigs as demonstrated by bioluminescence imaging.

Conclusion

The plasmid-based lux bioreporter strategy can be used to obtain high resolution in vivo images of B. suis S2 infection in mice and guinea pigs.

     

<Emphasis Type="Italic">L</Emphasis><Subscript><Emphasis Type="Italic">p</Emphasis></Subscript> Regularization for Bioluminescence Tomography Based on the Split Bregman Method

Purpose

Bioluminescence tomography (BLT) is a promising in vivo optical imaging technique in preclinical research at cellular and molecular levels. The problem of BLT reconstruction is quite ill-posed and ill-conditioned. In order to achieve high accuracy and efficiency for its inverse reconstruction, we proposed a novel approach based on L _p regularization with the Split Bregman method.

Procedures

The diffusion equation was used as the forward model. Then, we defined the objective function of L _p regularization and developed a Split Bregman iteration algorithm to optimize this function. After that, we conducted numerical simulations and in vivo experiments to evaluate the accuracy and efficiency of the proposed method.

Results

The results of the simulations indicated that compared with the conjugate gradient and iterative shrinkage methods, the proposed method is more accurate and faster for multisource reconstructions. Furthermore, in vivo imaging suggested that it could clearly distinguish the viable and apoptotic tumor regions.

Conclusions

The Split Bregman iteration method is able to minimize the L _p regularization problem and achieve fast and accurate reconstruction in BLT.

     

Reactive Oxygen Species Imaging in a Mouse Model of Inflammatory Bowel Disease

Purpose

Reactive oxygen species (ROS) are important contributors to inflammatory bowel disease (IBD); however, there are insufficient tools for their in vivo evaluation.

Procedures

To determine if a chemiluminescent ROS reporter, coelenterazine, would be a useful tool for the detection of immune cell activation, the macrophage cell line (RAW 264.7) was treated with phorbol myristate acetate (PMA). Additionally, coelenterazine was used to monitor the changes in ROS production over time in a mouse model of IBD.

Results

In vitro, coelenterazine enabled the dynamic monitoring of the RAW 264.7 cell oxidative burst. In vivo, there were early, preclinical, changes in the localization and magnitude of coelenterazine chemiluminescent foci.

Conclusions

Coelenterazine offers a high-throughput method for assessing immune cell activation in culture and provides a means for the in vivo detection and localization of ROS during IBD disease progression.

     

Quantitative [<Superscript>18</Superscript>F]FMISO PET Imaging Shows Reduction of Hypoxia Following Trastuzumab in a Murine Model of HER2+ Breast Cancer

Purpose

Evaluation of [¹⁸F]fluoromisonidazole ([¹⁸F]FMISO)-positron emission tomography (PET) imaging as a metric for evaluating early response to trastuzumab therapy with histological validation in a murine model of HER2+ breast cancer.

Procedures

Mice with BT474, HER2+ tumors, were imaged with [¹⁸F]FMISO-PET during trastuzumab therapy. Pimonidazole staining was used to confirm hypoxia from imaging.

Results

[¹⁸F]FMISO-PET indicated significant decreases in hypoxia beginning on day 3 (P?<?0.01) prior to changes in tumor size. These results were confirmed with pimonidazole staining on day 7 (P?<?0.01); additionally, there was a significant positive linear correlation between histology and PET imaging (r ² ?=?0.85).

Conclusions

[¹⁸F]FMISO-PET is a clinically relevant modality which provides the opportunity to (1) predict response to HER2+ therapy before changes in tumor size and (2) identify decreases in hypoxia which has the potential to guide subsequent therapy.

     

Multimodal Genetic Approach for Molecular Imaging of Vasculature in a Mouse Model of Melanoma

Purpose

In this study, we evaluated a genetic approach for in vivo multimodal molecular imaging of vasculature in a mouse model of melanoma.

Procedures

We used a novel transgenic mouse, Ts-Biotag, that genetically biotinylates vascular endothelial cells. After inoculating these mice with B16 melanoma cells, we selectively targeted endothelial cells with (strept)avidinated contrast agents to achieve multimodal contrast enhancement of Tie2-expressing blood vessels during tumor progression.

Results

This genetic targeting system provided selective labeling of tumor vasculature and showed in vivo binding of avidinated probes with high specificity and sensitivity using microscopy, near infrared, ultrasound, and magnetic resonance imaging. We further demonstrated the feasibility of conducting longitudinal three-dimensional (3D) targeted imaging studies to dynamically assess changes in vascular Tie2 from early to advanced tumor stages.

Conclusions

Our results validated the Ts-Biotag mouse as a multimodal targeted imaging system with the potential to provide spatio-temporal information about dynamic changes in vasculature during tumor progression.

     

Effet des extraits de quelques plantes sur les bactéries pathogènes responsables de gastroentérites

Background

Phytochemicals are natural bioactive compounds that protect plants against the stress. These phytochemicals may also have other biological activities like, antibacterial activity.

Objective

The objective of this work is to study the antibacterial effect of aqueous and hydro-alcoholic extracts prepared from Thymus vulgaris, Aloysia triphylla, Pistacia lentiscus, Olea europaea leaves and Trigonella foenum-graecum seeds on some pathogenic bacteria responsible for gastroenteritis.

Result

The results obtained from the antibacterial effect showed a moderate activity against the strains studied with a diameters of inhibition zones ranging from 07.00 ± 0.8 to 16.00 ± 1.0 mm for aqueous extracts and vary between 07.00 ± 0.9 and 13.00 ± 1.0 mm for hydro-alcoholic extracts.

Conclusion

This study confirms the possibility of using these plants or components in the prevention of several diseases like, gastroenteritis.

     

High Impact of <Superscript>18</Superscript>F-FDG-PET on Management and Prognostic Stratification of Newly Diagnosed Small Cell Lung Cancer

Purpose

We evaluated whether ¹⁸F-FDG-PET altered stage classification, management, and prognostic stratification of newly diagnosed small cell lung cancer (SCLC).

Procedures

We identified 46 consecutive patients undergoing staging positron emission tomography for SCLC from 1993–2008 inclusive. Updated survival data from the state Cancer Registry was available on 42 of 46 patients.

Results

PET altered stage classification in 12 of 46 (26%) patients. PET altered treatment modality in nine patients, and the target mediastinal radiation field in another three patients. Therefore, PET altered management in 12 of 46 (26%) patients. Patients with limited disease (LD) on pre-PET staging had significantly longer overall survival (OS) than those upstaged to extensive disease (ED; median 18.6 months versus 5.7 months; log-rank p?versus 5.9 months; log-rank p?=?0.037).

Conclusion

PET had a major impact on stage classification, management, and prognostic stratification of newly diagnosed SCLC.

     

Detection of Enzyme Activity and Inhibition during Studies in Solution, <Emphasis Type="Italic">In Vitro</Emphasis> and <Emphasis Type="Italic">In Vivo</Emphasis> with CatalyCEST MRI

Purpose

The detection of enzyme activities and evaluation of enzyme inhibitors have been challenging with magnetic resonance imaging (MRI). To address this need, we have developed a diamagnetic, nonmetallic contrast agent and a protocol known as catalyCEST MRI that uses chemical exchange saturation transfer (CEST) to detect enzyme activity as well as enzyme inhibition.

Procedures

We synthesized a diamagnetic MRI contrast agent that has enzyme responsive and enzyme unresponsive CEST signals. We tested the ability of this agent to detect the activity of kallikrein 6 (KLK6) in biochemical solutions, in vitro and in vivo, with and without a KLK6 inhibitor.

Results

The agent detected KLK6 activity in solution and also detected KLK6 inhibition by antithrombin III. KLK6 activity was detected during in vitro studies with HCT116 colon cancer cells, relative to the detection of almost no activity in a KLK6-knockdown HCT116 cell line and HCT116 cells treated with antithrombin III inhibitor. Finally, strong enzyme activity was detected within an in vivo HCT116 tumor model, while lower enzyme activity was detected in a KLK6 knockdown tumor model and in the HCT116 tumor model treated with antithrombin III inhibitor. In all cases, comparisons of the enzyme responsive and enzyme unresponsive CEST signals were critical for the detection of enzyme activity.

Conclusions

This study has established that catalyCEST MRI with an exogenous diaCEST agent can evaluate enzyme activity and inhibition in solution, in vitro and in vivo.

     

Novel Approach to Repeated Arterial Blood Sampling in Small Animal PET: Application in a Test-Retest Study with the Adenosine A1 Receptor Ligand [<Superscript>11</Superscript>C]MPDX

Purpose

Small animal positron emission tomography (PET) can be used to detect small changes in neuroreceptor availability. This often requires rapid arterial blood sampling. However, current catheterization procedures do not allow repeated blood sampling. We have developed a procedure which allows arterial sampling on repeated occasions in the same animal.

Procedures

Eleven male Wistar rats were two times catheterized via a superficial branch of a femoral artery and scanned with [¹¹C]MPDX and blood sampling. PET images were co-registered to a magnetic resonance imaging (MRI) template. Regional tracer distribution volumes (V _T) in the brain were calculated by the Logan analysis. The procedure was repeated after 1 week.

Results

Surgery was successful in 90 % of the cases, and discomfort was minor. The V _T data showed small differences between test and retest, low between subject variability, and a strong agreement between and within subjects.

Conclusion

Repeated quantitative imaging with a high reproducibility is possible with this approach.

     

Rate of bacterial eradication by ophthalmic solutions of fourth-generation fluoroquinolones

Introduction

Antibacterial activity of ophthalmic fourth-generation fluoroquinolones has traditionally been evaluated by comparing only their active ingredients, gatifloxacin and moxifloxacin. However, ophthalmic formulations of fourth-generation fluoroquinolones differ in terms of the inclusion of preservatives. While gatifloxacin ophthalmic solution 0.3% (Zymar®; Allergan, Inc., Irvine, CA, USA) contains 0.005% benzalkonium chloride (BAK), moxifloxacin ophthalmic solution 0.5% (Vigamox®; Alcon Laboratories, Inc., Fort Worth, TX, USA) is preservative-free. Recent studies have demonstrated that the presence of BAK dramatically affects the antibacterial activity of the ophthalmic formulation of gatifloxacin. This study was designed to compare the kill rates of ophthalmic solutions of fourth-generation fluoroquinolones against isolates of common ocular bacterial pathogens.

Methods

Approximately 5.6 log₁₀ colony-forming units (CFU)/mL of Haemophilus influenzae (n=1), Streptococcus pneumoniae (n=1), Staphylococcus aureus (n=2), methicillin-resistant Staphylococcus aureus (MRSA) (n=4), methicillinresistant Staphylococcus epidermidis (MRSE) (n=4), and fluoroquinolone-resistant S. epidermidis (n=1) were incubated with ophthalmic solutions of either gatifloxacin or moxifloxacin. Viable bacteria were quantified at specific time points up to 60 minutes.

Results

Gatifloxacin 0.3% completely eradicated H. influenzae and Strep. pneumoniae in 5 minutes, one of two S. aureus isolates in 15 minutes, and the other S. aureus isolate in 60 minutes. Gatifloxacin 0.3% completely killed all MRSA, MRSE, and fluoroquinolone-resistant S. epidermidis isolates in 15 minutes. Moxifloxacin 0.5% completely eradicated Strep. pneumoniae and one of four MRSA isolates in 60 minutes. All other isolates incubated with moxifloxacin 0.5% retained viable bacteria ranging from 1.8 to 4.4 log₁₀ CFU/mL.

Conclusions

The ophthalmic solution of gatifloxacin 0.3% eradicated bacteria that frequently cause postoperative ocular infections substantially faster than did the ophthalmic solution of moxifloxacin 0.5%.

     

Selecting Patients with Ovarian Cancer for Germline <Emphasis Type="Italic">BRCA</Emphasis> Mutation Testing: Findings from Guidelines and a Systematic Literature Review

Introduction

One of the most significant risk factors for the development of ovarian cancer (OC) is a genetic mutation in BRCA1 (breast cancer gene 1) or BRCA2. Here we describe the impact of previous and current guidance on BRCA testing practices and provide evidence about which characteristics best identify patients with OC and an underlying germline BRCA mutation.

Methods

A search was conducted for guidelines recommending genetic testing to identify constitutional pathogenic mutations in the BRCA genes. In addition, a systematic literature search of studies published in 2003–2015 was performed to assess BRCA mutation frequency in population-based OC patients unselected for patient characteristics (personal history, family history, and Ashkenazi Jewish ethnicity) and to describe the association of patient characteristics with BRCA mutation. Exclusively, studies assessing epithelial OC or invasive epithelial OC with full-gene screening of both BRCA1 and BRCA2 mutations were evaluated.

Results

Of 15 guidelines recommending genetic testing for OC patients, only 5 do not require co-occurrence of specific patient or family characteristics. Twenty-two full publications were identified that assessed germline BRCA mutation frequency in women with OC, utilizing a range of different full mutation detection methods. Germline BRCA mutation prevalence in patients with OC was 5.8–24.8%. Using criteria recommended in guidelines that are yet to be updated, we estimated that 27.5% of all germline BRCA mutations present in patients with OC may be missed because patients do not meet appropriate criteria.

Conclusion

With the availability of BRCA mutation-targeted therapies, identification of patients with OC with germline BRCA mutations has potential therapeutic consequences. For identified gene carriers, predictive testing to allow cancer prevention strategies, including bilateral salpingo-oophorectomy, provides wider benefit to identifying such gene carriers. Updating guidelines will increase the opportunity for targeted treatment among patients and risk reduction in relatives.

Funding

AstraZeneca

     

Influence of cancer treatment on the <Emphasis Type="Italic">Candida albicans</Emphasis> isolated from the oral cavities of cancer patients

Purpose

Cancer treatment causes mucositis and the manifestation of oral candidiasis. This study investigated the virulence properties and antifungal susceptibilities of Candida albicans isolated from cancer patients undergoing therapy.

Methods

C. albicans were isolated from 49 patients on cancer treatment and 21 healthy individuals and their virulence attributes measured. A correlation was determined between the length of treatment and the fungal counts and their virulence factors.

Results

Although Candida carriage was similar in all the study groups, high quantities of C. albicans and variety of Candida were found in cancer patients. Germ tubes were produced by all the strains. Significantly high number of yeast isolated from radiotherapy and chemotherapy produced large quantities of phospholipase compared to healthy individuals (p?<?0.01). The length of chemotherapy was associated with an increase in the phospholipase production (p?=?0.03) by the C. albicans. Proteinase production was seen in a significant number of isolates from the radiotherapy group (p?<?0.01). Type of cancer treatment had no effect. Resistance to antifungal agents was low.

Conclusions

High quantities of phospholipase were produced by C. albicans in cancer patients on therapy which also increased with the length of chemotherapy suggesting enhanced risk of oral and systemic infection. Therefore, during treatment, prophylactic topical antifungal therapy may be considered.

     

<Emphasis Type="Italic">In Vitro</Emphasis> and <Emphasis Type="Italic">In Vivo</Emphasis> Comparison of Selected Ga-68 and Zr-89 Labelled Siderophores

Purpose

Some [⁶⁸Ga]siderophores show promise in specific and sensitive imaging of infection. Here, we compare the in vitro and in vivo behaviour of selected Ga-68 and Zr-89 labelled siderophores.

Procedures

Radiolabelling was performed in HEPES or sodium acetate buffer systems. Radiochemical purity of labelled siderophores was determined using chromatography. Partition coefficients, in vitro stability and protein binding affinities were determined. Ex vivo biodistribution and animal imaging was studied in mice.

Results

Certain differences among studied siderophores were observed in labelling efficiency. Protein binding and stability tests showed highest stabilities and lowest protein binding affinities for Ga-68 and [⁸⁹Zr]triacetylfusarinine C (TAFC). All studied Ga-68 and [⁸⁹Zr]siderophores exhibited a similar biodistribution and pharmacokinetics in mice with the exception of [⁸⁹Zr]ferrioxamine E (FOXE).

Conclusions

Zr-89 and [⁶⁸Ga]siderophores showed analogous in vitro and in vivo behaviour. Tested [⁸⁹Zr]siderophores could be applied for longitudinal positron emission tomography (PET) studies of fungal infections and especially TAFC for the development of novel bioconjugates.

     

Effects of a self-managed home-based walking intervention on psychosocial health outcomes for breast cancer patients receiving chemotherapy: a randomised controlled trial

Purpose

This study evaluated the effectiveness of a self-managed home-based moderate intensity walking intervention on psychosocial health outcomes among breast cancer patients undergoing chemotherapy.

Methods

The randomised controlled trial compared a self-managed, home-based walking intervention to usual care alone among breast cancer patients receiving chemotherapy. Outcome measures included changes in self-report measures of anxiety, depression, fatigue, self-esteem, mood and physical activity. Fifty participants were randomised to either the intervention group (n?=?25), who received 12 weeks of moderate intensity walking, or the control group (n?=?25) mid-way through chemotherapy. Participants in the intervention group were provided with a pedometer and were asked to set goals and keep weekly diaries outlining the duration, intensity and exertion of their walking. Levels of psychosocial functioning and physical activity were assessed pre- and post-intervention in both groups.

Results

The intervention had positive effects on fatigue (F?=?5.77, p?=?0.02), self-esteem (F?=?8.93, p?≤?0.001), mood (F?=?4.73, p?=?0.03) and levels of physical activity (x ²?=?17.15, p?=?0.0011) but not anxiety (F?=?0.90, p?=?0.35) and depression (F?=?0.26, p?=?0.60) as assessed using the HADS. We found an 80 % adherence rate to completing the 12-week intervention and recording weekly logs.

Conclusion

This self-managed, home-based intervention was beneficial for improving psychosocial well-being and levels of physical activity among breast cancer patients treated with chemotherapy.

Trial registration

Current Controlled Trials ISRCTN50709297.

     

Short-Term Effects of a Combined Nutraceutical on Lipid Level,Fatty Liver Biomarkers,Hemodynamic Parameters,and Estimated Cardiovascular Disease Risk: A Double-Blind,Placebo-Controlled Randomized Clinical Trial

Introduction

There is a growing interest in nutraceuticals improving cardiovascular risk factor levels and related organ damage.

Methods

This double-blind, placebo-controlled randomized clinical trial aims to compare the effect of a combined nutraceutical containing red yeast rice (10 mg), phytosterols (800 mg), and l-tyrosol (5 mg) on lipid profile, blood pressure, endothelial function, and arterial stiffness in a group of 60 patients with polygenic hypercholesterolemia resistant to Mediterranean diet.

Results

After 8 weeks of treatment, when compared to the placebo group, the active treated patients experienced a more favorable percentage change in total cholesterol (?16.3% vs 9.9%, P < 0.001 always), LDL-C (?23.4% vs ?13.2%, P < 0.001 always), and hepatic steatosis index (?2.8%, P < 0.01 vs ?1.8%, P < 0.05). Moreover, ALT (?27.7%, P < 0.001), AST (?13.8%, P = 0.004), and serum uric acid (?12.3%, P = 0.005) were reduced by the tested nutraceutical compound both compared to randomization and to placebo, which did not affect these parameters (P < 0.01 for all). Regarding the hemodynamic parameters, there was a decrease of systolic blood pressure (?5.6%) with the active treatment not observed with placebo (P < 0.05 vs baseline and placebo) and endothelial reactivity improved, too (?13.2%, P < 0.001 vs baseline). Consequently, the estimated 10-year cardiovascular risk score improved by 1.19% (SE 0.4%) (P = 0.01) in the nutraceutical-treated patients.

Conclusion

The tested nutraceutical association is able to improve the positive effects of a Mediterranean diet on a large number of CV risk factors and consequently of the estimated CV risk.

Trial registration

ClinicalTrials.gov identifier NCT02492464.

Funding

IBSA Farmaceutici.

     

Preclinical Evaluation of [<Superscript>18</Superscript>F]THK-5105 Enantiomers: Effects of Chirality on Its Effectiveness as a Tau Imaging Radiotracer

Purpose

Noninvasive imaging of tau and amyloid-β pathologies would facilitate diagnosis of Alzheimer’s disease (AD). Recently, we have developed [¹⁸F]THK-5105 for selective detection of tau pathology by positron emission tomography (PET). The purpose of this study was to clarify biological properties of optically pure [¹⁸F]THK-5105 enantiomers.

Procedures

Binding for tau aggregates in AD brain section was evaluated by autoradiography (ARG). In vitro binding assays were performed to evaluate the binding properties of enantiomers for AD brain homogenates. The pharmacokinetics in the normal mouse brains was assessed by ex vivo biodistribution assay

Results

The ARG of enantiomers showed the high accumulation of radioactivity corresponding to the distribution of tau deposits. In vitro binding assays revealed that (S)-[¹⁸F]THK-5105 has slower dissociation from tau than (R)-[¹⁸F]THK-5105. Biodistribution assays indicated that (S)-[¹⁸F]THK-5105 eliminated faster from the mouse brains and blood compared with (R)-[¹⁸F]THK-5105.

Conclusion

(S)-[¹⁸F]THK-5105 could be more suitable than (R)-enantiomer for a tau imaging agent.

     

Sigma-1 Agonist Binding in the Aging Rat Brain: a MicroPET Study with [<Superscript>11</Superscript>C]SA4503

Purpose

Sigma-1 receptor ligands modulate the release of several neurotransmitters and intracellular calcium signaling. We examined the binding of a radiolabeled sigma-1 agonist in the aging rat brain with positron emission tomography (PET).

Procedures

Time-dependent uptake of [¹¹C]SA4503 was measured in the brain of young (1.5 to 3 months) and aged (18 to 32 months) Wistar Hannover rats, and tracer-kinetic models were fitted to this data, using metabolite-corrected plasma radioactivity as input function.

Results

In aged animals, the injected probe was less rapidly metabolized and cleared. Logan graphical analysis and a 2-tissue compartment model (2-TCM) fit indicated changes of total distribution volume (V _T) and binding potential (BP _ND) of the tracer. BP _ND was reduced particularly in the (hypo)thalamus, pons, and medulla.

Conclusions

Some areas showed reductions of ligand binding with aging whereas binding in other areas (cortex) was not significantly affected.