New-onset schizophrenia in an adolescent after COVID-19.

Schizophrenia develops during adolescence. Maternal infections during the fetal period increase the incidence of schizophrenia in children, which suggests that the pathogenesis involves neuroinflammation. Here, we report a case of new-onset schizophrenia in a 16-year-old boy after COVID-19. After developing COVID-19, he entered a catatonic state 4 days later and was hospitalized. Benzodiazepines alleviated his catatonia, but hallucinations and delusions persisted. Encephalitis and epilepsy were excluded by magnetic resonance imaging (MRI), encephalography, and cerebrospinal fluid examination. Psychosis persisted after the virus titer declined and the inflammatory response subsided. Moreover, the patient exhibited delusions of control-a Schneider's first-rank symptom. Schizophrenia was diagnosed, and olanzapine improved his symptoms. He had a brief history of insomnia before COVID-19 but his symptoms did not satisfy the ultra-high-risk criteria. However, COVID-19 may have facilitated development of schizophrenia through neuroinflammation and volume reduction in the gray matter of the right medial temporal lobe. This case demonstrates that infectious diseases in adolescents should be carefully managed, to prevent schizophrenia.

Development of an In Vivo Method to Estimate Effective Drug Doses and Quantify Fatty Acid Amide Hydrolase in Rodent Brain using Positron Emission Tomography Tracer [11C]DFMC.

Fatty acid amide hydrolase (FAAH) is a key enzyme in the endocannabinoid system. N-(3,4-Dimethylisoxazol-5-yl)piperazine-4-[4-(2-fluoro-4-[11C]methylphenyl)thiazol-2-yl]-1-carboxamide ([11C]DFMC) was developed as an irreversible-type positron emission tomography (PET) tracer for FAAH. Here, we attempted to noninvasively estimate rate constant k3 (rate of transfer to the specifically-bound compartment) as a direct index for FAAH in the rat brain. First, the two-tissue compartment model analysis including three parameters [K1-k3, two-tissue compartment model for the irreversible-type radiotracer (2TCMi)] in PET study with [11C]DFMC was conducted, which provided 0.21 ± 0.04 ml·cm-3·min-1 of the net uptake value (Ki), an indirect index for FAAH, in the FAAH-richest region (the cingulate cortex). Subsequently, to noninvasively estimate Ki value, the reference model analysis (Patlak graphical analysis reference model) was tried using a time-activity curve of the spinal cord. In that result, the noninvasive Ki value (KREF) was concisely estimated with high correlation (r > 0.95) to Ki values based on 2TCMi. Using estimated KREF value, we tried to obtain calculated-k3 based on previously defined equations. The calculated k3 was successfully estimated with high correlation (r = 0.95) to direct k3 in 2TCMi. Finally, the dose relationship study using calculated k3 demonstrated that in vivo ED50 value of [3-(3-carbamoylphenyl)phenyl] N-cyclohexylcarbamate, a major inhibitor of FAAH, was 66.4 µg/kg in rat brain. In conclusion, we proposed the calculated k3 as an alternative index corresponding to regional FAAH concentrations and suggested that PET with [11C]DFMC enables occupancy study for new pharmaceuticals targeting FAAH. SIGNIFICANCE STATEMENT: In the present study, we proposed calculated k3 as an alternative index corresponding with fatty acid amide hydrolase concentration. By using calculated k3, in vivo ED50 of [3-(3-carbamoylphenyl)phenyl] N-cyclohexylcarbamate was successfully estimated to be 66.4 µg/kg for rats. Thus, we demonstrated the pharmacological utility of positron emission tomography with N-(3,4-dimethylisoxazol-5-yl)piperazine-4-[4-(2-fluoro-4-[11C]methylphenyl)thiazol-2-yl]-1-carboxamide.

Development of a remote purification apparatus with disposable evaporator for the routine production of high-quality 64Cu for clinical use.

We developed a new apparatus for the routine production of 64Cu in clinical use. The apparatus has many disposable parts that stabilize the product quality (such that there is a low deviation of the concentrations of impurity metals in the product) and reduce the work load of preparation for routine production. We also developed a new evaporator using near-infrared heaters for disposable use. We conducted a production test using the new apparatus and evaluated product quality. The product yield was 6.3 ±â€¯0.32 GBq (end of bombardment) (N = 4), the product quality in terms of the concentrations of impurity metals (Cu2+, Ni2+, Fe3+, Zn2+, Mn2+) was as good as that usually achieved, likely on the order of parts per billion, and the preparation time was reduced from 2 days to 1 day.

First demonstration of in vivo mapping for regional brain monoacylglycerol lipase using PET with [11C]SAR127303.

Monoacylglycerol lipase (MAGL) is a main regulator of the endocannabinoid system within the central nervous system (CNS). Recently, [11C]SAR127303 was developed as a promising radioligand for MAGL imaging. In this study, we aimed to quantify regional MAGL concentrations in the rat brain using positron emission tomography (PET) with [11C]SAR127303. An irreversible two-tissue compartment model (2-TCMi, k4 = 0) analysis was conducted to estimate quantitative parameters (k3, Ki2-TCMi, and λk3). These parameters were successfully obtained with high identifiability (<10 %COV) for the following regions ranked in order from highest to lowest: cingulate cortex > striatum > hippocampus > thalamus > cerebellum > hypothalamus ≈ pons. In vitro autoradiographs using [11C]SAR127303 showed a heterogeneous distribution of radioactivity, as seen in the PET images. The Ki2-TCMi and λk3 values correlated relatively highly with in vitro binding (r > 0.4, P < 0.005). The Ki2-TCMi values showed high correlation and low underestimation (<10%) compared with the slope of a Patlak plot analysis with linear regression (KiPatlak). In conclusion, we successfully estimated regional net uptake value of [11C]SAR127303 reflecting MAGL concentrations in rat brain regions for the first time.

Small-scale production of 67Cu for a preclinical study via the 64Ni(α, p)67Cu channel.

INTRODUCTION: Copper-67 is an attractive beta emitter for targeted radionuclide therapy. However, the availability of 67Cu limits its potential use in a wide range of applications. In this study, we propose an easy small-scale production of 67Cu using 64Ni target for a preclinical study. METHODS: 67Cu was produced from an electrodeposited 64Ni target via the 64Ni(α, p)67Cu-reaction with a 36 MeV alpha beam at 15 eµA (electrical microampere) conducted for 7 h. The chemical separation process of 67Cu from the 64Ni target was performed following by our routine procedure of 64Cu production using cation exchange resin, AG50W-X8, with minor modification. The target and its holder were redesigned in the preparation. RESULTS: The 67Cu product was obtained with a yield of 55 ±â€¯10 MBq at the end of bombardment (EOB), and the yield was 527 ±â€¯96 kBq/µAh at the EOB. The copper impurity in the product was low (0.71 ±â€¯0.21 µg) and the product was suitable for a preclinical study. CONCLUSIONS: We produced 67Cu with sufficient activity and quality for a preclinical study using a 64Ni-target. This production method also showed advantages as a routine method, i.e., shorten the processing time, reducing the radiation exposure and ready target recycling, when compared with that of a conventional Zn-target used for 67Cu production.

67Cu-Radiolabeling of a multimeric RGD peptide for αVß3 integrin-targeted radionuclide therapy: stability, therapeutic efficacy, and safety studies in mice.

OBJECTIVE: Copper-67 (Cu) is one of the most promising radionuclides for internal radiation therapy. Globally, several projects have recently been initiated for developing innovative approaches for the large-scale production of Cu. Encouraged by these, we performed Cu-radiolabeling of a tetrameric cyclic Arg-Gly-Asp (cRGD) peptide conjugate, cyclam-RAFT-c(-RGDfK-)4, which selectively targets αVß3 integrin (αVß3), the transmembrane receptor involved in tumor invasion, angiogenesis, and metastasis. We also evaluated the therapeutic potential and safety of this radiocompound. MATERIALS AND METHODS: Cu, produced through the Ni(α, p)Cu reaction, was used for the radiolabeling of cyclam-RAFT-c(-RGDfK-)4 at 70°C for 10 min. The radiolabeling efficiency and product stability were assessed using reversed-phase high-performance liquid chromatography and/or thin-layer chromatography. Mice with subcutaneous αVß3-positive U87MG-glioblastoma xenografts received a single intravenous injection of one of the following: Cu-cyclam-RAFT-c(-RGDfK-)4 (11.1 MBq), peptide control, or vehicle solution. The tumor volumes were measured, side effects were assessed in terms of body weight, routine hematology, and hepatic and renal functions, and the mouse radiation dosimetry was estimated. RESULTS: Cu-cyclam-RAFT-c(-RGDfK-)4 was produced with a radiochemical purity of 97.9±2.4% and a specific activity of 2.7±0.6 MBq/nmol and showed high in-vitro and in-vivo plasma stability. The administration of a single dose of Cu-cyclam-RAFT-c(-RGDfK-)4 resulted in significant tumor growth delay in comparison with that observed upon vehicle or peptide control administration, with an estimated tumor-absorbed dose of 0.712 Gy. No significant toxicity was observed in Cu-cyclam-RAFT-c(-RGDfK-)4-treated mice. CONCLUSION: Cu-cyclam-RAFT-c(-RGDfK-)4 would be a promising therapeutic agent for αVß3 integrin-targeted internal radiotherapy.

Efficient preparation of high-quality 64Cu for routine use.

INTRODUCTION: Copper-64 is an attractive radionuclide for positron emission tomography and is emerging as a radiotherapeutic agent. The demand of 64Cu with low metallic impurities has increased because of its wide applications when incorporated with antibodies, peptides, and proteins. In this study, we propose a new separation method to produce high-quality 64Cu using a cation exchange column, as well as an automated separation system suitable for large-scale production. METHODS: 64Cu was produced from an electrodeposited 64Ni target via the 64Ni(p,n)-reaction with a 24MeV HH+ beam at 10eµA (electrical microampere) conducted for 1-3h. The irradiated target was transported to a hot cell and disassembled remotely. 64Cu was separated by a solvent mixture of HCl and acetone on a cation-exchange resin, AG50W-X8. The chemical purity of 64Cu final product was evaluated using ion-chromatography coupled with a UV detector and inductively coupled plasma mass spectroscopy for quality as well as metallic impurities. RESULTS: We obtained 64Cu in dried form at a yield of 5.2-13GBq at the end of separation, or 521±12MBq/eµAh as the final product within 2.5h of processing time. The metallic impurities were a satisfactory low level in the order of ppb. Major contaminants of Co and Ni were lower than those samples obtained by a widely accepted separation using an anion-exchange resin. CONCLUSION: Using a cation-exchange resin and a systematic operation, we successfully reduced the contamination level of the 64Cu product. As a straightforward separation method, which shortened the entire processing time, we obtained a satisfactory amount of high-quality 64Cu available for routine use.

Production of scandium-43 and -47 from a powdery calcium oxide target via the (nat/44)Ca(α,x)-channel.

We produced (43)Sc and (47)Sc via the (nat/44)Ca(α,x)-channel using a vertical beam coupled with a ceramic target box. After activation, the powdery CaO target material was dissolved in HCl in the target box in situ and remotely recovered as a radio-Sc solution. The respective yields of (43)Sc and (47)Sc following isolation via a precipitation method with a typical 0.22µm sterile filter were 54.8MBq/µAh (1.48mCi/µAh) and 780kBq/µAh (21.1µCi/µAh) at the end of separation (approximately 1.5h from the EOB). In addition, we discuss the recycling of target Ca.

Improved Visualization and Specific Binding for Metabotropic Glutamate Receptor Subtype 1 (mGluR1) Using [11C]ITMM with Ultra-High Specific Activity in Small-Animal PET.

Metabotropic glutamate receptor subtype 1 (mGluR1) is a crucial target in the development of new medications to treat central nervous system (CNS) disorders. Recently, we developed N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-4-[11C]methoxy-N-methyl-benzamide ([11C]ITMM) as a useful positron emission tomography (PET) probe for mGluR1 in clinical studies. Here, we aimed to improve visualization and threshold of specific binding for mGluR1 using [11C]ITMM with ultra-high specific activity (SA) of > 3,500 GBq/µmol in rat brains. A two-tissue compartment model indicated large differences between the two SAs in the constants k3 and k4, representing binding ability for mGluR1, while constants K1 and k2 showed no differences. The total distribution volume (VT) values of conventional and ultra-high SA were 9.1 and 11.2 in the thalamus, 7.7 and 9.7 in the striatum, and 6.4 and 8.5 mL/cm3 in the substantia nigra, respectively. The specific binding of [11C]ITMM with ultra-high SA was significantly higher than the conventional SA, especially in the basal ganglia. Parametric PET images scaled with VT of the ultra-high SA clearly identified regional differences in the rat brain. In conclusion, PET studies using [11C]ITMM with ultra-high SA could sufficiently improve visualization and specific binding for mGluR1, which could help further understanding for mGluR1 functions in CNS disorders.

Non-input analysis for incomplete trapping irreversible tracer with PET.

INTRODUCTION: When using metabolic trapping type tracers, the tracers are not always trapped in the target tissue; i.e., some are completely trapped in the target, but others can be eliminated from the target tissue at a measurable rate. The tracers that can be eliminated are termed 'incomplete trapping irreversible tracers'. These incomplete trapping irreversible tracers may be clinically useful when the tracer ß-value, the ratio of the tracer (metabolite) elimination rate to the tracer efflux rate, is under approximately 0.1. In this study, we propose a non-input analysis for incomplete trapping irreversible tracers based on the shape analysis (Shape), a non-input analysis used for irreversible tracers. METHODS: A Monte Carlo simulation study based on experimental monkey data with two actual PET tracers (a complete trapping irreversible tracer [(11)C]MP4A and an incomplete trapping irreversible tracer [(18)F]FEP-4MA) was performed to examine the effects of the environmental error and the tracer elimination rate on the estimation of the k3-parameter (corresponds to metabolic rate) using Shape (original) and modified Shape (M-Shape) analysis. The simulation results were also compared with the experimental results obtained with the two PET tracers. RESULTS: When the tracer ß-value was over 0.03, the M-Shape method was superior to the Shape method for the estimation of the k3-parameter. The simulation results were also in reasonable agreement with the experimental ones. CONCLUSIONS: M-Shape can be used as the non-input analysis of incomplete trapping irreversible tracers for PET study.

A method to predict the ratio of the tracer conversion rate to the tracer back-diffusion rate of an irreversible-type radiotracer in humans by preclinical evaluations.

OBJECTIVE: The aim of this study was to develop a method to predict a tracer's α-value in the human brain on the basis of animal data. The α-value is the ratio of the conversion rate and the back-diffusion rate (k3/k2) and is one of the critical kinetic features of the detection sensitivity of target molecule activity, such as enzyme activity, in the measurement of PET and single-photon emission computed tomography using an irreversible-type radiotracer. METHOD: The α-value in the rat brain was estimated by a simultaneous assay of the tracer uptake and the target biochemical activity using N-[C]-methylpiperidin-4-yl acetate ([C]MP4A) and N-[C]-methylpiperidin-4-yl propionate ([C]MP4P) as test tracers, both of which are metabolic trapping tracers for measurement of brain acetylcholinesterase. The α-value in humans was then extrapolated from the α-value in rats by considering the differences between the species. The predicted human α-values were compared with those obtained from the kinetic analyses of human PET studies using [C]MP4A and [C]MP4P. RESULT: The α-values in the human brain cortex were predicted to be 0.51±0.1 for MP4A and 0.25±0.05 for MP4P. These results were close to values reported in other PET studies: 0.48±0.1 to 0.73±0.2 for MP4A and 0.15±0.04 to 0.18±0.04 for MP4P. CONCLUSION: The α-value predicted by this method would be used for practical selection or development of irreversible-type radiotracers for human use.

In vivo measurement of the affinity and density of metabotropic glutamate receptor subtype 1 in rat brain using 18F-FITM in small-animal PET.

UNLABELLED: Metabotropic glutamate receptor subtype 1 (mGluR1) is a crucial molecular target in the central nervous system disorders. 4-(18)F-fluoro-N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide ((18)F-FITM) has been recently developed as a useful PET ligand for mGluR1 imaging in our laboratory. In this study, we aimed to measure the affinity and density of mGluR1 using PET with (18)F-FITM in rat brain under the in vivo conditions. METHODS: Binding potentials (BP(ND)) and amounts of specific binding (bound ligand concentration) at equilibrium state in brain regions were noninvasively estimated using the equilibrium analysis combined with the receptor-blocked approach (EA RBA) for kinetic analysis of (18)F-FITM PET results in place of reference tissue methods. Using BP(ND) and specific binding values of rats treated with multidose ligand, we performed Scatchard analyses for in vivo measurements of mGluR1 density (maximum number of binding sites, or B(max)) and ligand affinity (dissociation constant, or K(d)) in brain regions, respectively. RESULTS: The pretreatment of rats with unlabeled FITM (1 mg/kg) occupied an mGluR1 binding site of (18)F-FITM by more than 99% and did not affect the input function. Hence, we used the tissue time-activity curve for receptor-blocked rats as representative of the nondisplaceable (free and nonspecific binding of radioligand) compartment. The BP(ND) based on EA RBA showed a high correlation with the BP(ND) based on invasive Logan plot graphical analysis in the thalamus, hippocampus, striatum, and cingulate cortex. The K(d) (nM) and B(max) (pmol/mL) obtained by the Scatchard analyses with the multidose ligand assays were 2.1 and 36.3, respectively, for the thalamus; 2.1 and 27.5, respectively, for the hippocampus; 1.5 and 22.2, respectively, for the striatum; and 1.5 and 20.5, respectively, for the cingulate cortex with a high confidence. CONCLUSION: Our study is the first to our knowledge to measure the in vivo affinity (K(d) and binding potential) of (18)F-FITM and mGluR1 density (B(max)) with a high correlation to in vitro values in rat brain regions. This measurement using PET with (18)F-FITM would be a useful index for research about mGluR1 functions in central nervous system disorders and development of new pharmaceuticals.

Effect of radiolabeled metabolite elimination from the brain on the accuracy of cerebral enzyme activity estimation using positron emission tomography with substrate tracers.

Cerebral enzyme activity can be quantified using positron emission tomography (PET) in conjunction with a radiolabeled enzyme substrate. We investigated the relationship between the elimination rate (k(el)) of tracer metabolites from the brain and the precision of target enzyme activity estimation (k(3)). An initial simulation study indicated that the precision of k(3) estimates was highly dependent on k(el), and was characterized by several kinetic parameters including the ratio of k(el) and the efflux rate (k(2)) of authentic tracer (ß≡k(el)/k(2)). The optimal tracer condition for high sensitivity was found to be ß<0.1. To verify the simulation results, we performed a PET study with a single monkey using two PET tracers, N-[(18)F]fluoroethylpiperidin-4-ylmethyl acetate ([(18)F]FEP-4MA) and N-[(11)C]methylpiperidin-4-yl acetate ([(11)C]MP4A). Both of these substrate type tracers were developed for measuring cerebral acetylcholinesterase activity. There was good retention of the radioactive metabolite of [(11)C]MP4A in the brain (k(el)=0.0036±0.0013 min(-1), ß=0.028), whereas that of [(18)F]FEP-4MA was eliminated from the brain (k(el)=0.012±0.0010 min(-1), ß=0.085). A non-linear least square analysis for simultaneous estimation of all parameters showed that the precision of the k(3) estimate for [(18)F]FEP-4MA was as high (7.4%) as that for [(11)C]MP4A (10%). These results indicate that tracers with metabolites that are eliminated from the brain at a slow rate (ß<0.1) may be useful for the quantitative measurement of target enzyme activity.

An analysis of long-distance water transport in the soybean stem using H215O.

The lateral water movement in the intact stem of a transpiring soybean plant was analyzed quantitatively by a real-time measurement system utilizing labeled water, H(2)(15)O and gamma ray detectors. A large volume of water escaping from xylem vessels during its transport was detected. The escape of water was not influenced by evaporation from the stem surface or mass flow in the sieve tubes. It was assumed that the total amount of water transported through xylem vessels was kept almost completely constant along the internode. As a result, most of the escaped water was found to re-enter the xylem vessels, i.e. water exchange occurred. The analysis of radiographs of tritiated water suggested that the self-diffusion effect of water was strong for lateral water movement, although another driving force besides thermal motion was included in the process, and that the process was also affected by the water permeability of the plasma membrane. An analysis based on a mathematical model showed that the net volume of water which escaped from xylem vessels was not dependent on the transpiration rate of the plant.

Spectroscopic study of water-NaCl-benzene mixtures at high temperatures and pressures.

Near-infrared and ultraviolet spectra of water-NaCl-benzene mixtures have been measured in the 473-573 K and 100-400 bar range and 373-498 K and 50-300 bar range, respectively. Concentrations of water in the benzene-rich phase and benzene in the water-rich phase were estimated from integrated intensities of the absorption bands. It is found that addition of NaCl in the aqueous phase suppresses transfer of water into the benzene-rich phase, and the relative decrease in water solubility in benzene exhibits good correlation with an increase in density of the aqueous NaCl solution relative to that of neat water. The salting-out constant for the water-NaCl-benzene system, which is estimated from a relative decrease in benzene solubility in the aqueous phase by addition of sodium chloride, increases significantly with increasing temperature. It is suggested that the effect of sodium chloride on the water-benzene mutual solubilities can be explained by ion-induced electrostriction of the aqueous phase.

An aluminum influence on root circumnutation in dark revealed by a new super-HARP (high-gain avalanche rushing amorphous photoconductor) camera.

The circumnutation of a rice root under dark conditions was observed using a highly sensitive camera, a new super-HARP camera. A rice root showed regular rhythmic movement with fixed angle. When treated with Al (5 microM AlCl3), the rotation angle of the root tip was drastically decreased and then the movement was resumed again, whereas the root elongation rate was constant. With the increase of Al concentration, the cycle-fading period became shorter. This is the first report to show that an Al treatment ceased the rotation movement of the root but not elongation.