Potential involvement of Streptococcus mutans possessing collagen binding protein Cnm in infective endocarditis.

Streptococcus mutans, a significant contributor to dental caries, is occasionally isolated from the blood of patients with infective endocarditis. We previously showed that S. mutans strains expressing collagen-binding protein (Cnm) are present in the oral cavity of approximately 10-20% of humans and that they can effectively invade human umbilical vein endothelial cells (HUVECs).

Effects of exogenous lactate administration on fat metabolism and glycogen synthesis factors in rats.

Purpose: Lactate has several beneficial roles as an energy resource and in metabolism. However, studies on the effects of oral administration of lactate on fat metabolism and glycogen synthesis are limited. Therefore, the purpose of the present study was to investigate how oral administration of lactate affects fat metabolism and glycogen synthesis factors at specific times (0, 30, 60, 120 min) after intake.

Contribution of Severe Dental Caries Induced by Streptococcus mutans to the Pathogenicity of Infective Endocarditis.

, a major pathogen of dental caries, is regarded as a causative agent of infective endocarditis (IE), which mainly occurs in patients with underlying heart disease. However, it remains unknown whether severe dental caries that extend to pulp space represent a possible route of infection. In the present study, we evaluated the virulence of for IE development using rats with concurrent severe dental caries and heart valve injury.

Contribution of Streptococcus mutans Strains with Collagen-Binding Proteins in the Presence of Serum to the Pathogenesis of Infective Endocarditis.

, a major pathogen of dental caries, is considered one of the causative agents of infective endocarditis (IE). Recently, bacterial DNA encoding 120-kDa cell surface collagen-binding proteins (CBPs) has frequently been detected from -positive IE patients. In addition, some of the CBP-positive strains lacked a 190-kDa protein antigen (PA), whose absence strengthened the adhesion to and invasion of endothelial cells.

Noninvasive quantification of cerebral metabolic rate for glucose in rats using (18)F-FDG PET and standard input function.

Measurement of arterial input function (AIF) for quantitative positron emission tomography (PET) studies is technically challenging. The present study aimed to develop a method based on a standard arterial input function (SIF) to estimate input function without blood sampling. We performed (18)F-fluolodeoxyglucose studies accompanied by continuous blood sampling for measurement of AIF in 11 rats.

Contribution of the interaction of Streptococcus mutans serotype k strains with fibrinogen to the pathogenicity of infective endocarditis.

Streptococcus mutans, a pathogen responsible for dental caries, is occasionally isolated from the blood of patients with bacteremia and infective endocarditis (IE). Our previous study demonstrated that serotype k-specific bacterial DNA is frequently detected in S. mutans-positive heart valve specimens extirpated from IE patients.

Tissue-engineered stent-graft integrates with aortic wall by recruiting host tissue into graft scaffold.

Objective: To prevent postoperative migration and endoleaks after endovascular aneurysm repair, we developed a tissue-engineered vascular graft that integrates with the aortic wall by recruiting the host tissue into the graft scaffold. In the present study, we assessed the mechanical properties of the new graft and evaluated the integration between the graft and aortic wall histologically and mechanically in canine models.

Methods: The tissue-engineered vascular graft was woven to be partially degradable with a double-layered fiber (core; polyethylene terephthalate [PET], and sheath; polyglycolic acid [PGA]).

Adequacy of a compartment model for CMRO₂ quantitation using ¹⁵O-labeled oxygen and PET: a clearance measurement of ¹⁵O-radioactivity following intracarotid bolus injection of ¹⁵O-labeled oxyhemoglobin on Macaca fascicularis.

We aimed at evaluating the adequacy of the commonly employed compartmental model for quantitation of cerebral metabolic rate of oxygen (CMRO2) using (15)O-labeled oxygen ((15)O2) and positron emission tomography (PET). Sequential PET imaging was carried out on monkeys following slow bolus injection of blood samples containing (15)O2-oxyhemoglobin ((15)O2-Hb), (15)O-labeled water (H2(15)O), and C(15)O-labeled hemoglobin (C(15)O-Hb) into the internal carotid artery (ICA). Clearance slopes were assessed in the middle cerebral artery territory of the injected hemisphere.

Rapid quantitative CBF and CMRO(2) measurements from a single PET scan with sequential administration of dual (15)O-labeled tracers.

Positron emission tomography (PET) with (15)O tracers provides essential information in patients with cerebral vascular disorders, such as cerebral blood flow (CBF), oxygen extraction fraction (OEF), and metabolic rate of oxygen (CMRO(2)). However, most of techniques require an additional C(15)O scan for compensating cerebral blood volume (CBV). We aimed to establish a technique to calculate all functional images only from a single dynamic PET scan, without losing accuracy or statistical certainties.

Quantification of regional cerebral blood flow in rats using an arteriovenous shunt and micro-PET.

Introduction: Measurement of regional cerebral blood flow (rCBF) in rodents can provide knowledge of pathophysiology of the cerebral circulation, but generally requires blood sampling for analysis during positron emission tomography (PET). We therefore tested the feasibility of using an arteriovenous (AV) shunt in rats for less invasive blood analysis.

Methods: Six anesthetized rats received [15O]H2O and [15O]CO PET scans with their femoral artery and vein connected by an AV shunt, the activity within which was measured with a germanium ortho-oxysilicate scintillation detector.

Three-dimensional quantitation of regional cerebral blood flow in mice using a high-resolution pinhole SPECT system and 123I-iodoamphetamine.

Introduction: This study is intended to evaluate the feasibility of using a high-resolution pinhole SPECT system and iodine-123-N-isopropyl-4-iodoamphetamine ((123)I-IMP) for three-dimensional (3D) absolute quantitation of regional cerebral blood flow (rCBF) in mice.

Methods: The pinhole SPECT system consists of a rotating stage and a pinhole collimator attached to a clinical gamma camera. The collimator's focal length is 251 mm.

Experimental pig model of old myocardial infarction with long survival leading to chronic left ventricular dysfunction and remodeling as evaluated by PET.

Unlabelled: A pig model of reduced left ventricular (LV) function and remodeling or chronic heart failure with long survival after myocardial infarction (MI) has not been established. The aim of this study was to evaluate the pathophysiologic status of a pig model of old MI using a series of PET studies.

Methods: Twenty-seven male farm pigs were divided into 2 groups: 7 animals in the control group and 20 animals that underwent a proximal coronary artery (CA) occlusion using an ameroid constrictor after distal CA ligation.

Long-term in vivo magnetic resonance imaging tracking of endothelial progenitor cells transplanted in rat ischemic limbs and their angiogenic potential.

Stem cell therapy has been used to repair ischemic tissues in the limbs, in myocardial infarctions, and in the brain. To understand the mechanisms of healing, a contrast agent capable of inducing sufficient magnetic resonance (MR) contrast would be useful in providing fundamental information about the cell migration and incorporation into the ischemic tissue. A magnetic resonance imaging contrast agent composed of dextran and gadolinium chelate was synthesized.

Impaired myocardium regeneration with skeletal cell sheets--a preclinical trial for tissue-engineered regeneration therapy.

Background: We hypothesized that autologous skeletal cell (SC) sheets regenerate the infract myocardium in porcine heart as a preclinical trial.

Methods And Results: The impaired heart was created by implantation of ameroid constrictor on left anterior descending for 4 weeks. SCs isolated from leg muscle were cultured and detached from the temperature-responsive domain-coated dishes as single monolayer cell sheet at 20 degrees C.

Long-term observation of auto-cell transplantation in non-human primate reveals safety and efficiency of bone marrow stromal cell-derived Schwann cells in peripheral nerve regeneration.

Based on their differentiation ability, bone marrow stromal cells (MSCs) are a good source for cell therapy. Using a cynomolgus monkey peripheral nervous system injury model, we examined the safety and efficacy of Schwann cells induced from MSCs as a source for auto-cell transplantation therapy in nerve injury. Serial treatment of monkey MSCs with reducing agents and cytokines induced their differentiation into cells with Schwann cell properties at a very high ratio.

Measurement of density and affinity for dopamine D(2) receptors by a single positron emission tomography scan with multiple injections of [(11)C]raclopride.

Positron emission tomography (PET) with [(11)C]raclopride has been used to investigate the density (B(max)) and affinity (K(d)) of dopamine D(2) receptors related to several neurological and psychiatric disorders. However, in assessing the B(max) and K(d), multiple PET scans are necessary under variable specific activities of administered [(11)C]raclopride, resulting in a long study period and unexpected physiological variations. In this paper, we have developed a method of multiple-injection graphical analysis (MI-GA) that provides the B(max) and K(d) values from a single PET scan with three sequential injections of [(11)C]raclopride, and we validated the proposed method by performing numerous simulations and PET studies on monkeys.

Quantification of regional myocardial oxygen metabolism in normal pigs using positron emission tomography with injectable (15)O-O (2).

Purpose: Although (15)O-O(2) gas inhalation can provide a reliable and accurate myocardial metabolic rate for oxygen by PET, the spillover from gas volume in the lung distorts the images. Recently, we developed an injectable method in which blood takes up (15)O-O(2) from an artificial lung, and this made it possible to estimate oxygen metabolism without the inhalation protocol. In the present study, we evaluated the effectiveness of the injectable (15)O-O(2) system in porcine hearts.

Quantitative evaluation of changes in binding potential with a simplified reference tissue model and multiple injections of [11C]raclopride.

Positron emission tomography (PET) with [(11)C]raclopride is widely used to investigate temporal changes in the dopamine D(2) receptor system attributed to the dopamine release. The simplified reference tissue model (SRTM) can be used to determine the binding potential (BP(ND)) value using the time-activity curve (TAC) of the reference region as input function. However, in assessing temporal changes in BP(ND) using the SRTM, multiple [(11)C]raclopride PET scans are required, and a second scan must be performed after the disappearance of the [(11)C]raclopride administered in the first scan.

A physiologic model for recirculation water correction in CMRO2 assessment with 15O2 inhalation PET.

Cerebral metabolic rate of oxygen (CMRO(2)) can be assessed quantitatively using (15)O(2) and positron emission tomography. Determining the arterial input function is considered critical with regards to the separation of the metabolic product of (15)O(2) (RW) from a measured whole blood. A mathematical formula based on physiologic model has been proposed to predict RW.

Use of a compact pixellated gamma camera for small animal pinhole SPECT imaging.

Objectives: Pinhole SPECT which permits in vivo high resolution 3D imaging of physiological functions in small animals facilitates objective assessment of pharmaceutical development and regenerative therapy in pre-clinical trials. For handiness and mobility, the miniature size of the SPECT system is useful. We developed a small animal SPECT system based on a compact high-resolution gamma camera fitted to a pinhole collimator and an object-rotating unit.

Development of a hyperpolarized 129Xe system on 3T for the rat lungs.

MRI (magnetic resonance imaging) with 129Xe has gained much attention as a diagnostic methodology because of its affinity for lipids and possible polarization. The quantitative estimation of net detectability and stability of hyperpolarized 129Xe in the dissolved phase in vivo is valuable to the development of clinical applications. The goal of this study was to develop a stable hyperpolarized 129Xe experimental 3T system to statistically analyze the dissolved-phase 129Xe signal in the rat lungs.

Parametric imaging of myocardial blood flow with 15O-water and PET using the basis function method.

Unlabelled: Regional myocardial blood flow (MBF) can be measured with 15O-water and PET using the 1-tissue-compartment model with perfusable tissue fraction, which provides an MBF value that is free from the partial-volume effect. Studies with 15O-water have several advantages, such as the ability to repeat a scan. However, because of the short scanning time and the small distribution volume of 15O-water in the myocardium, the image quality of 15O-water is limited, impeding the computation of MBF and perfusable tissue fraction at the voxel level.

Understanding of cerebral energy metabolism by dynamic living brain slice imaging system with [18F]FDG.

Recently, lactate has been receiving great attention as an energy substrate in the brain. In this study, the role of lactate was evaluated by "bioradiography" system with 2-deoxy-2-[(18)F]fluoro-d-glucose ([(18)F]FDG), which is a positron emitting radiotracer for glucose uptake quantification. "Bioradiography" is the dynamic living tissue slice imaging system for positron-emitter labeled compounds.

Rapid quantitative measurement of CMRO(2) and CBF by dual administration of (15)O-labeled oxygen and water during a single PET scan-a validation study and error analysis in anesthetized monkeys.

Cerebral blood flow (CBF) and rate of oxygen metabolism (CMRO(2)) may be quantified using positron emission tomography (PET) with (15)O-tracers, but the conventional three-step technique requires a relatively long study period, attributed to the need for separate acquisition for each of (15)O(2), H(2)(15)O, and C(15)O tracers, which makes the multiple measurements at different physiologic conditions difficult. In this study, we present a novel, faster technique that provides a pixel-by-pixel calculation of CBF and CMRO(2) from a single PET acquisition with a sequential administration of (15)O(2) and H(2)(15)O. Experiments were performed on six anesthetized monkeys to validate this technique.

Long-term effect of motor cortical repetitive transcranial magnetic stimulation [correction].

Repetitive transcranial magnetic stimulation (rTMS) recently has been assessed as a noninvasive treatment modality for movement and psychiatric disorders, whereas the mechanism underlying the therapeutic effects is not fully understood. Studies in rodents showed lasting functional changes in some selected regions, such as limbic-associated structures, but unfocused brain stimulation did not clarify the regional effects. To address the topographical and temporal profiles of the effects on glucose metabolism in primate brain, we performed rTMS and repeated (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) before, during, and up to 16 days after rTMS in anesthetized cynomologous monkeys.