Long-Term Comparison of Esthetic Outcomes Between Hatchet and Transposition Flaps in Facial-Defect Reconstruction.

BACKGROUND: Transposition flaps are commonly used for facial-defect repair after wide excision of skin cancers. However, such repair often causes excessive tension at the donor site that can result in distortion of the adjacent area. The hatchet flap, a rotation-advancement flap, can prevent distortion by redistributing the donor site tension evenly to the recipient site. This study aims to compare the esthetic outcomes of the hatchet flap and transposition flap in facial-defect reconstruction. METHODS: We retrospectively included 50 patients who underwent facial reconstruction with the hatchet flap or transposition flap after excision of skin cancer. They were followed up for more than 6 months. At the last follow-up visit, the esthetic outcome was evaluated by subjective and objective assessments using the patients and observer scar assessment scale and Manchester scar scale. RESULTS: Thirty patients and 20 patients underwent reconstruction using the hatchet flap and the transposition flap, respectively. The total score from the patient and observer scar assessment scale was significantly lower in the hatchet flap group compared with the transposition flap group (p = 0.009). The Manchester scar scale showed a total score of 7.67 ± 2.2 for the hatchet flap and 9.95 ± 1.99 for the transposition flap: in the color (p < 0.001), distortion (p < 0.001), and texture (p < 0.02) categories, the hatchet flap yielded significantly better outcomes than the transposition flap. CONCLUSIONS: The hatchet flap had good esthetic outcome for facial reconstruction and could be a valuable option for reconstructing facial defects. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these evidence-based medicine ratings, please refer to Table of Contents or online Instructions to Authors www.springer.com/00266.

Predicting leachate impact on groundwater using electrical conductivity and oxidation-reduction potential measurements: An empirical and theoretical approach.

This study developed innovative predictive models of groundwater pollution using in situ electrical conductivity (EC) and oxidation-reduction potential (ORP) measurements at livestock carcass burial sites. Combined electrode analysis (EC and ORP) and machine learning techniques efficiently and accurately distinguished between leachate and background groundwater. Two models-empirical and theoretical-were constructed based on a supervised classification framework. The empirical model constructs a classifier with high accuracy, sensitivity, and specificity, utilizing the comprehensive in situ EC and ORP measurements. The theoretical model with only two end members achieves comparable performance by simulating the leachate-groundwater interactions using a geochemical mixing model. Besides enhancing the early detection capabilities, our approach considerably reduces the reliance on extensive hydrochemical analyses, thus streamlining the monitoring process. Moreover, the use of field parameters was found to proactively identify potential pollution incidents, enhancing the efficiency of groundwater monitoring strategies. Our approach is applicable to various waste disposal sites, indicating its extensive potential for environmental monitoring and management.

Strain-invariant stretchable radio-frequency electronics.

Wireless modules that provide telecommunications and power-harvesting capabilities enabled by radio-frequency (RF) electronics are vital components of skin-interfaced stretchable electronics1-7. However, recent studies on stretchable RF components have demonstrated that substantial changes in electrical properties, such as a shift in the antenna resonance frequency, occur even under relatively low elastic strains8-15. Such changes lead directly to greatly reduced wireless signal strength or power-transfer efficiency in stretchable systems, particularly in physically dynamic environments such as the surface of the skin. Here we present strain-invariant stretchable RF electronics capable of completely maintaining the original RF properties under various elastic strains using a 'dielectro-elastic' material as the substrate. Dielectro-elastic materials have physically tunable dielectric properties that effectively avert frequency shifts arising in interfacing RF electronics. Compared with conventional stretchable substrate materials, our material has superior electrical, mechanical and thermal properties that are suitable for high-performance stretchable RF electronics. In this paper, we describe the materials, fabrication and design strategies that serve as the foundation for enabling the strain-invariant behaviour of key RF components based on experimental and computational studies. Finally, we present a set of skin-interfaced wireless healthcare monitors based on strain-invariant stretchable RF electronics with a wireless operational distance of up to 30 m under strain.

Complete Preservation of Orbital Fat by Restoration of Attenuated Orbital Septa Using an Acellular Dermal Matrix in Lower Blepharoplasty.

BACKGROUND: We hypothesized that application of acellular dermal matrix (ADM) over the orbital septum overlying the herniated orbital fat to tighten and strengthen the attenuated orbital septum in lower blepharoplasty would allow successful repositioning of the herniated orbital fat within the bony orbit. METHODS: The author prospectively compared the cosmetic outcomes of lower blepharoplasty using ADM with standard blepharoplasty. We evaluated recurrence of eyelid bulging and tear trough deformity, volume of the lower periorbital region, and enophthalmos and eyelid droop 1 year after surgery. RESULTS: Twenty-two of the 24 enrolled patients completed the study. There was no significant difference in recurrence of eyelid bulging and tear trough deformity between standard blepharoplasty and blepharoplasty with ADM graft groups. In the standard blepharoplasty group, the volume of the lower periorbital region decreased significantly after surgery. In the blepharoplasty with ADM graft group, there was no significant change in the volume of the lower periorbital region after surgery. In the standard blepharoplasty group, there was no significant change in eyelid droop on either side after surgery. In the blepharoplasty with ADM graft group, the eyelid droop decreased significantly after surgery on the right side but showed no significant change on the left side. There was no significant change in enophthalmos after surgery for either group. CONCLUSIONS: This study demonstrated that ADM graft provided effective support for maintaining the replaced orbital fat in lower blepharoplasty. In the long-term, blepharoplasty with ADM graft might be effective in slowing development of age-related enophthalmos. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Orthogonal inducible control of Cas13 circuits enables programmable RNA regulation in mammalian cells.

RNA plays an indispensable role in mammalian cell functions. Cas13, a class of RNA-guided ribonuclease, is a flexible tool for modifying and regulating coding and non-coding RNAs, with enormous potential for creating new cell functions. However, the lack of control over Cas13 activity has limited its cell engineering capability. Here, we present the CRISTAL (Control of RNA with Inducible SpliT CAs13 Orthologs and Exogenous Ligands) platform. CRISTAL is powered by a collection (10 total) of orthogonal split inducible Cas13 effectors that can be turned ON or OFF via small molecules in multiple cell types, providing precise temporal control. Also, we engineer Cas13 logic circuits that can respond to endogenous signaling and exogenous small molecule inputs. Furthermore, the orthogonality, low leakiness, and high dynamic range of our inducible Cas13d and Cas13b enable the design and construction of a robust incoherent feedforward loop, leading to near-perfect and tunable adaptation response. Finally, using our inducible Cas13 effectors, we achieve simultaneous multiplexed control of multiple genes in vitro and in mice. Together, our CRISTAL design represents a powerful platform for precisely regulating RNA dynamics to advance cell engineering and elucidate RNA biology.

Improving Facial Fat Graft Survival Using Stromal Vascular Fraction-Enriched Lipotransfer: A Multicenter Randomized Controlled Study.

BACKGROUND: Although previous clinical studies have reported that cell-assisted lipotransfer increases the fat survival rate in facial fat transplants, most were case studies without quantitative evaluation. A multicenter randomized controlled study was performed to evaluate the safety and efficacy of the stromal vascular fraction (SVF) in facial fat grafts. METHODS: Twenty-three participants were enrolled for autologous fat transfer in the face, and assigned randomly to the experimental ( n = 11) or control ( n = 12) group. Fat survival was assessed using magnetic resonance imaging at 6 and 24 weeks postoperatively. Subjective evaluations were performed by the patients and surgeons. To address safety concerns, results of an SVF culture and the postoperative complications were recorded. RESULTS: The overall fat survival rate was significantly higher in the experimental group than in the control group (6 weeks, 74.5% ± 9.99% versus 66.55% ± 13.77%, P < 0.025; 24 weeks, 71.27% ± 10.43% versus 61.98% ± 13.46%, P < 0.012). Specifically, graft survival in the forehead was 12.82% higher in the experimental group when compared with that in the control group at 6 weeks ( P < 0.023). Furthermore, graft survival in the forehead ( P < 0.021) and cheeks ( P < 0.035) was superior in the experimental group at 24 weeks. At 24 weeks, the aesthetic scores given by the surgeons were higher in the experimental group than in the control group ( P < 0.03); however, no significant intergroup differences were noted in the patient-evaluated scores. Neither bacterial growth from SVF cultures nor postoperative complications were noted. CONCLUSION: SVF enrichment for autologous fat grafting can be a safe and effective technique for increasing the fat retention rate. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, II.

Advancing structural batteries: cost-efficient high-performance carbon fiber-coated LiFePO4 cathodes.

Structural batteries (SBs) have gained attention due to their ability to provide energy storage and structural support in vehicles and airplanes, using carbon fibers (CFs) as their main component. However, the development of high-performance carbon fiber-based cathode materials for structural batteries is currently limited. To address this issue, this study proposes a cost-efficient and straightforward method for creating a high-performance structural lithium iron phosphate (LiFePO4) positive electrode by coating carbon fibers at mild temperatures and pressures. The resulting cathode demonstrated a high LiFePO4 loading (at least 74%) and a smooth coating, as confirmed by X-ray spectroscopy, scanning electron microscopy, and Raman spectroscopy. This structural cathode exhibited a capacity of 144 mA h g-1 and 108 mA h g-1 at 0.1 C and 1.0 C, respectively. Additionally, the LiFePO4 cathode displayed excellent electrochemical properties, with a capacity retention of 96.4% at 0.33 C and 81.2% at 1.0 C after 300 cycles. Overall, this study presents a promising approach for fabricating high-performance structural batteries with enhanced energy storage and structural capabilities.

The future of wearable EEG: a review of ear-EEG technology and its applications.

Objective.This review paper provides a comprehensive overview of ear-electroencephalogram (EEG) technology, which involves recording EEG signals from electrodes placed in or around the ear, and its applications in the field of neural engineering.Approach.We conducted a thorough literature search using multiple databases to identify relevant studies related to ear-EEG technology and its various applications. We selected 123 publications and synthesized the information to highlight the main findings and trends in this field.Main results.Our review highlights the potential of ear-EEG technology as the future of wearable EEG technology. We discuss the advantages and limitations of ear-EEG compared to traditional scalp-based EEG and methods to overcome those limitations. Through our review, we found that ear-EEG is a promising method that produces comparable results to conventional scalp-based methods. We review the development of ear-EEG sensing devices, including the design, types of sensors, and materials. We also review the current state of research on ear-EEG in different application areas such as brain-computer interfaces, and clinical monitoring.Significance.This review paper is the first to focus solely on reviewing ear-EEG research articles. As such, it serves as a valuable resource for researchers, clinicians, and engineers working in the field of neural engineering. Our review sheds light on the exciting future prospects of ear-EEG, and its potential to advance neural engineering research and become the future of wearable EEG technology.

Comprehensive Lipid Profiling Recapitulates Enhanced Lipolysis and Fatty Acid Metabolism in Intimal Foamy Macrophages From Murine Atherosclerotic Aorta.

Lipid accumulation in macrophages is a prominent phenomenon observed in atherosclerosis. Previously, intimal foamy macrophages (FM) showed decreased inflammatory gene expression compared to intimal non-foamy macrophages (NFM). Since reprogramming of lipid metabolism in macrophages affects immunological functions, lipid profiling of intimal macrophages appears to be important for understanding the phenotypic changes of macrophages in atherosclerotic lesions. While lipidomic analysis has been performed in atherosclerotic aortic tissues and cultured macrophages, direct lipid profiling has not been performed in primary aortic macrophages from atherosclerotic aortas. We utilized nanoflow ultrahigh-performance liquid chromatography-tandem mass spectrometry to provide comprehensive lipid profiles of intimal non-foamy and foamy macrophages and adventitial macrophages from Ldlr-/- mouse aortas. We also analyzed the gene expression of each macrophage type related to lipid metabolism. FM showed increased levels of fatty acids, cholesterol esters, phosphatidylcholine, lysophosphatidylcholine, phosphatidylinositol, and sphingomyelin. However, phosphatidylethanolamine, phosphatidic acid, and ceramide levels were decreased in FM compared to those in NFM. Interestingly, FM showed decreased triacylglycerol (TG) levels. Expressions of lipolysis-related genes including Pnpla2 and Lpl were markedly increased but expressions of Lpin2 and Dgat1 related to TG synthesis were decreased in FM. Analysis of transcriptome and lipidome data revealed differences in the regulation of each lipid metabolic pathway in aortic macrophages. These comprehensive lipidomic data could clarify the phenotypes of macrophages in the atherosclerotic aorta.

Decoding auditory-evoked response in affective states using wearable around-ear EEG system.

Objective.In this paper, an around-ear EEG system is investigated as an alternative methodology to conventional scalp-EEG-based systems in classifying human affective states in the arousal-valence domain evoked in response to auditory stimuli.Approach.EEG recorded from around the ears is compared to EEG collected according to the international 10-20 system in terms of efficacy in an affective state classification task. A wearable device with eight dry EEG channels is designed for ear-EEG acquisition in this study. Twenty-one subjects participated in an experiment consisting of six sessions over three days using both ear and scalp-EEG acquisition methods. Experimental tasks consisted of listening to an auditory stimulus and self-reporting the elicited emotion in response to the said stimulus. Various features were used in tandem with asymmetry methods to evaluate binary classification performances of arousal and valence states using ear-EEG signals in comparison to scalp-EEG.Main results.We achieve an average accuracy of 67.09% ± 6.14 for arousal and 66.61% ± 6.14 for valence after training a multi-layer extreme learning machine with ear-EEG signals in a subject-dependent context in comparison to scalp-EEG approach which achieves an average accuracy of 68.59% ± 6.26 for arousal and 67.10% ± 4.99 for valence. In a subject-independent context, the ear-EEG approach achieves 63.74% ± 3.84 for arousal and 64.32% ± 6.38 for valence while the scalp-EEG approach achieves 64.67% ± 6.91 for arousal and 64.86% ± 5.95 for valence. The best results show no significant differences between ear-EEG and scalp-EEG signals for classifications of affective states.Significance.To the best of our knowledge, this paper is the first work to explore the use of around-ear EEG signals in emotion monitoring. Our results demonstrate the potential use of around-ear EEG systems for the development of emotional monitoring setups that are more suitable for use in daily affective life log systems compared to conventional scalp-EEG setups.

"Fruiting Liquid" of Mushroom-Forming Fungi, A Novel Source of Bioactive Compounds - Fruiting-Body Inducer and HIF and Axl Inhibitors.

In general, mushroom-forming fungi secrete liquid on the surface of mycelia just before fruiting-body formation. However, no researchers in mushroom science have paid attention to the liquid until now. We formulated a hypothesis that the liquid plays an important role(s) in the formation of the fruiting body and produces various bioactive compounds and named it the "fruiting liquid (FL)". Four novel compounds (1-4) were isolated from FL of Hypholoma lateritium and Hericium erinaceus. The structures of 1-4 except for their stereochemistry were determined by interpretation of MS and NMR data. The absolute configurations of compounds 1-4 were determined by quantum chemical calculation of the ECD spectrum, by single-crystal X-ray diffraction analyses, or by chemical syntheses. Compounds 1, 3, and 4 induced fruiting body formation of Flammulina velutipes. Compound 4 inhibited the activity of hypoxia-inducible factor, and compounds 2-4 suppressed receptor tyrosine kinase (Axl) expression.

Comprehensive ECG reference intervals in C57BL/6N substrains provide a generalizable guide for cardiac electrophysiology studies in mice.

Reference ranges provide a powerful tool for diagnostic decision-making in clinical medicine and are enormously valuable for understanding normality in pre-clinical scientific research that uses in vivo models. As yet, there are no published reference ranges for electrocardiography (ECG) in the laboratory mouse. The first mouse-specific reference ranges for the assessment of electrical conduction are reported herein generated from an ECG dataset of unprecedented scale. International Mouse Phenotyping Consortium data from over 26,000 conscious or anesthetized C57BL/6N wildtype control mice were stratified by sex and age to develop robust ECG reference ranges. Interesting findings include that heart rate and key elements from the ECG waveform (RR-, PR-, ST-, QT-interval, QT corrected, and QRS complex) demonstrate minimal sexual dimorphism. As expected, anesthesia induces a decrease in heart rate and was shown for both inhalation (isoflurane) and injectable (tribromoethanol) anesthesia. In the absence of pharmacological, environmental, or genetic challenges, we did not observe major age-related ECG changes in C57BL/6N-inbred mice as the differences in the reference ranges of 12-week-old compared to 62-week-old mice were negligible. The generalizability of the C57BL/6N substrain reference ranges was demonstrated by comparison with ECG data from a wide range of non-IMPC studies. The close overlap in data from a wide range of mouse strains suggests that the C57BL/6N-based reference ranges can be used as a robust and comprehensive indicator of normality. We report a unique ECG reference resource of fundamental importance for any experimental study of cardiac function in mice.

Roles of Vascular Smooth Muscle Cells in Atherosclerotic Calcification.

The accumulation of calcium in atherosclerotic plaques is a prominent feature of advanced atherosclerosis, and it has a strong positive correlation with the total burden of atherosclerosis. Atherosclerotic calcification usually appears first at the necrotic core, indicating that cell death and inflammatory processes are involved in calcification. During atherosclerotic inflammation, various cell types, such as vascular smooth muscle cells, nascent resident pericytes, circulating stem cells, or adventitial cells, have been assumed to differentiate into osteoblastic cells, which lead to vascular calcification. Among these cell types, vascular smooth muscle cells are considered a major contributor to osteochondrogenic cells in the atherosclerotic milieu. In this review, we summarize the molecular mechanisms underlying the osteochondrogenic switch of vascular smooth muscle cells in atherosclerotic plaques.

Fat graft survival requires metabolic reprogramming toward the glycolytic pathway.

BACKGROUND: Fat grafts are widely used as natural fillers in reconstructive and cosmetic surgery. However, the mechanisms underlying fat graft survival are poorly understood. Here, we performed an unbiased transcriptomic analysis in a mouse fat graft model to determine the molecular mechanism underlying free fat graft survival. METHODS: We conducted RNA-sequencing (RNA-seq) analysis in a mouse free subcutaneous fat graft model on days 3 and 7 following grafting (n = 5). High-throughput sequencing was performed on paired-end reads using NovaSeq6000. The calculated transcripts per million (TPM) values were processed for principal component analysis (PCA), unsupervised hierarchically clustered heatmap generation, and gene set enrichment analysis. RESULTS: PCA and heatmap data revealed global differences in the transcriptomes of the fat graft model and the non-grafted control. The top meaningful upregulated gene sets in the fat graft model were related to the epithelial-mesenchymal transition, hypoxia on day 3, and angiogenesis on day 7. Mechanistically, the glycolytic pathway was upregulated in the fat graft model at days 3 (FDR q = 0.012) and 7 (FDR q = 0.084). In subsequent experiments, pharmacological inhibition of the glycolytic pathway in mouse fat grafts with 2-deoxy-D-glucose (2-DG) significantly suppressed fat graft retention rates, both grossly and microscopically (n = 5). CONCLUSIONS: Free adipose tissue grafts undergo metabolic reprogramming toward the glycolytic pathway. Future studies should examine whether targeting this pathway can enhance the graft survival rate.

Neural Applications Using Immersive Virtual Reality: A Review on EEG Studies.

Recent advancements in immersive virtual reality head-mounted displays allowed users to better engage with simulated graphical environments. Having the screen egocentrically stabilized in a way such that the users may freely rotate their heads to observe virtual surroundings, head-mounted displays present virtual scenarios with rich immersion. With such an enhanced degree of freedom, immersive virtual reality displays have also been integrated with electroencephalograms, which make it possible to study and utilize brain signals non-invasively, to analyze and apply their capabilities. In this review, we introduce recent progress that utilized immersive head-mounted displays along with electroencephalograms across various fields, focusing on the purposes and experimental designs of their studies. The paper also highlights the effects of using immersive virtual reality discovered through the electroencephalogram analysis and discusses existing limitations, current trends as well as future research opportunities that may hopefully act as a useful source of information for further improvement of electroencephalogram-based immersive virtual reality applications.

Role of hypoxanthine-guanine phosphoribosyltransferase in the metabolism of fairy chemicals in rice.

Fairy chemicals (FCs), 2-azahypoxanthine (AHX), imidazole-4-carboxamide (ICA), and 2-aza-8-oxohypoxanthine (AOH), are molecules with many diverse functions in plants. The defined biosynthetic pathway for FCs is a novel purine metabolism in which they are biosynthesized from 5-aminoimidazole-4-carboxamide. Here, we show that one of the purine salvage enzymes, hypoxanthine-guanine phosphoribosyltransferase (HGPRT), recognizes AHX and AOH as substrates. Two novel compounds, AOH ribonucleotide and its ribonucleoside which are the derivatives of AOH, were enzymatically synthesized. The structures were determined by mass spectrometry, 1D and 2D NMR spectroscopy, and X-ray single-crystal diffraction analysis. This report demonstrates the function of HGPRT and the existence of novel purine metabolism associated with the biosynthesis of FCs in rice.

Bioactive Compounds from the Mushroom-Forming Fungus Chlorophyllum molybdites.

A novel compound (1) along with two known compounds (2 and 3) were isolated from the culture broth of Chlorophyllum molybdites, and three known compounds (4-6) were isolated from its fruiting bodies. The planar structure of 1 was determined by the interpretation of spectroscopic data. By comparing the specific rotation of the compound with that of the analog compound, the absolute configuration of 1 was determined to be R. This is the first time that compounds 2-4 were isolated from a mushroom-forming fungus. Compound 2 showed significant inhibition activity against Axl and immune checkpoints (PD-L1, PD-L2). In the bioassay to examine growth inhibitory activity against the phytopathogenic bacteria Peptobacterium carotovorum, Clavibacter michiganensis and Burkholderia glumae, compounds 2 and 3 inhibited the growth of P. carotovorum and C. michiganensis. In the bioassay to examine plant growth regulatory activity, compounds 1-4 showed a significant regulatory activity on lettuce growth.

Orthogonal inducible control of Cas13 circuits enables programmable RNA regulation in mammalian cells.

RNA plays an indispensable role in mammalian cell functions. Cas13, a class of RNA-guided ribonuclease, is a flexible tool for modifying and regulating coding and non-coding RNAs, with enormous potential for creating new cell functions. However, the lack of control over Cas13 activity has limited its cell engineering capability. Here, we present the CRISTAL ( C ontrol of R NA with Inducible S pli T C A s13 Orthologs and Exogenous L igands) platform. CRISTAL is powered by a collection (10 total) of orthogonal split inducible Cas13s that can be turned ON or OFF via small molecules in multiple cell types, providing precise temporal control. Also, we engineered Cas13 logic circuits that can respond to endogenous signaling and exogenous small molecule inputs. Furthermore, the orthogonality, low leakiness, and high dynamic range of our inducible Cas13d and Cas13b enable the design and construction of a robust incoherent feedforward loop, leading to near-perfect and tunable adaptation response. Finally, using our inducible Cas13s, we achieve simultaneous multiplexed control of multiple genes in vitro and in mice. Together, our CRISTAL design represents a powerful platform for precisely regulating RNA dynamics to advance cell engineering and elucidate RNA biology.

The role of xanthine dioxygenase in the biosynthetic pathway of 2-aza-8-oxohypoxanthine of Lepista sordida.

2-Azahypoxanthine (AHX) and 2-aza-8-oxohypoxanthine (AOH), discovered as causal substances of fairy rings are known to be endogenous in the fairy ring-forming Lepista sordida. In this study, we showed that xanthine dioxygenase, an a-ketoglutarate-dependent dioxygenase, might catalyze the conversion of AHX to AOH in the fungus. Furthermore, this enzyme is the first reported molybdopterin-independent protein of hypoxanthine metabolism.

Identification of Biosynthetic and Metabolic Genes of 2-Azahypoxanthine in Lepista sordida Based on Transcriptomic Analysis.

2-Azahypoxanthine was isolated from the fairy ring-forming fungus Lepista sordida as a fairy ring-inducing compound. 2-Azahypoxanthine has an unprecedented 1,2,3-triazine moiety, and its biosynthetic pathway is unknown. The biosynthetic genes for 2-azahypoxanthine formation in L. sordida were predicted by a differential gene expression analysis using MiSeq. The results revealed that several genes in the purine and histidine metabolic pathways and the arginine biosynthetic pathway are involved in the biosynthesis of 2-azahypoxanthine. Furthermore, nitric oxide (NO) was produced by recombinant NO synthase 5 (rNOS5), suggesting that NOS5 can be the enzyme involved in the formation of 1,2,3-triazine. The gene encoding hypoxanthine-guanine phosphoribosyltransferase (HGPRT), one of the major phosphoribosyltransferases of purine metabolism, increased when 2-azahypoxanthine content was the highest. Therefore, we hypothesized that HGPRT might catalyze a reversible reaction between 2-azahypoxanthine and 2-azahypoxanthine-ribonucleotide. We proved the endogenous existence of 2-azahypoxanthine-ribonucleotide in L. sordida mycelia by LC-MS/MS for the first time. Furthermore, it was shown that recombinant HGPRT catalyzed reversible interconversion between 2-azahypoxanthine and 2-azahypoxanthine-ribonucleotide. These findings demonstrate that HGPRT can be involved in the biosynthesis of 2-azahypoxanthine via 2-azahypoxanthine-ribonucleotide generated by NOS5.