Associated factors of undernutrition in children with congenital heart disease: a cross-sectional study.

Objective: To evaluate the prevalence and associated factors of undernutrition among children with congenital heart disease (CHD) who have not undergone surgeries in China. Methods: This cross-sectional study included 734 CHD children along with their parents. The outcome of interest was undernutrition, including underweight, wasting, and stunting, defined as Z-scores (i.e., weight-for-age, weight-for-height, and height-for-age) ≤-2, according to the World Health Organization (WHO) growth standard. Exposures of interest, containing demographics, obstetric factors, maternal dietary factors, parents' life behaviors and habits, birth-related factors, cardiac-related factors, and preoperative factors, were analyzed using a multivariate logistic regression model to test their associations with undernutrition in CHD children. Results: Overall, 36.1%, 29.7%, and 21.3% of cases were underweight, wasted, and stunted, respectively. Multivariate logistic regression indicated that underweight was associated with demographic factors (including parents' occupational status, family income, and maternal body mass index pre-pregnancy), low birth weight (OR = 4.60, 2.76-7.70), pulmonary hypertension (OR = 4.46, 3.09-6.43), and pneumonia (OR = 1.88, 1.28-2.76). Artificially-fed children were 2.34 (1.36-4.01) times more likely to be underweight. Occupied mothers (OR = 0.62, 0.44-0.88) and fathers (OR = 0.49, 0.26-0.92) served as protective factors, while mothers having gestational complications (OR = 1.56, 1.11-2.18) and exposed to noisy environment (OR = 1.64, 1.11-2.42) during this pregnancy, and pulmonary hypertension (OR = 3.21, 2.30-4.49) increased the chance of wasting in offspring. The odds of being stunted were greater in families with >2 children (OR = 1.88, 1.13-3.14), placental abruption during this pregnancy (OR = 25.15, 2.55-247.89), preterm births (OR = 1.84, 1.02-3.31), low birth weight (OR = 3.78, 2.16-6.62), pulmonary hypertension (OR = 2.35, 1.56-3.53) and pneumonia (OR = 1.93, 1.28-2.90). In subgroup analyses, the associations differed between patients with different feeding patterns (breastfeeding vs. non-breastfeeding), CHD classifications (cyanotic vs. acyanotic), and prematurity (preterm vs. non-preterm). Conclusion: Undernutrition is common in preoperative CHD children. Familial demographics, maternal factors (including having gestational complications and exposure to noisy environment during pregnancy), and patient-related factors (encompassing preterm births, low birth weight, pulmonary hypertension, pneumonia, and feeding pattern) were found to contribute to undernutrition in CHD cases. However, associated factors among the three subgroups of distinct feeding patterns, CHD categorization, and prematurity exhibited varied outcomes, suggesting the necessity for targeted interventions.

Maternal anaemia during early pregnancy and the risk of neonatal outcomes: a prospective cohort study in Central China.

BACKGROUND: The purpose of this study was to explore the association between anaemia during early pregnancy and the risk of neonatal outcomes. METHODS: We collected clinical data from pregnant women (≥18 years) who received their first antenatal care between 8 and 14 weeks of gestation in Hunan Provincial Maternal and Child Health Care Hospital. Multiple logistic regression models and restricted cubic spline regression models were used to analyse the association between anaemia during early pregnancy and the risk of neonatal outcomes. In addition, sensitivity analysis was further performed to assess the robustness of the results. RESULTS: The prospective cohort study ultimately included 34 087 singleton pregnancies. In this study, the rate of anaemia during early pregnancy was 16.3%. Our data showed that there was a positive relationship between the rate of preterm birth, low birth weight as well as small for gestational age (SGA) and the severity of maternal anaemia (Ptrend<0.05). After adjustment, the association of early pregnancy anaemia and haemoglobin (Hb) levels with the risk of preterm birth (mild anaemia adjusted OR (aOR) 1.37 (95% CI 1.25 to 1.52), moderate anaemia aOR 1.54 (95% CI 1.35 to 1.76) and severe anaemia aOR 4.03 (95% CI 2.67 to 6.08), respectively), low birth weight (mild anaemia aOR 1.61 (95% CI 1.44 to 1.79), moderate anaemia aOR 2.01 (95% CI 1.75 to 2.30) and severe anaemia aOR 6.11 (95% CI 3.99 to 9.36), respectively) and SGA (mild anaemia aOR 1.37 (95% CI 1.25 to 1.52), moderate anaemia aOR 1.54 (95% CI 1.35 to 1.76) and severe anaemia aOR 2.61 (95% CI 1.74 to 4.50), respectively; Pnon-linear<0.05) was observed. However, no association was found between early pregnancy anaemia or Hb levels and the risk of congenital malformations. Sensitivity analysis verified the stability of the results. CONCLUSIONS: Maternal anaemia during early pregnancy was associated with an increased risk of preterm birth, low birth weight and SGA and their rates may increase with the severity of maternal anaemia. TRIAL REGISTRATION NUMBER: ChiCTR1800016635.

The risk of attention-deficit hyperactivity disorder among children with congenital heart disease: A systematic review and meta-analysis.

BACKGROUND: Although current treatments are effective in dealing with congenital heart disease (CHD), non-cardiac comorbidities such as attention-deficit hyperactivity disorder (ADHD) have received widespread attention. The purpose of this systematic review and meta-analysis is to assess the risk of ADHD associated with CHD. METHODS: The literature search was carried out systematically through eight different databases by the end of September 2022. Either a fixed- or a random-effects model was used to calculate the overall combined risk estimates. The heterogeneity of the studies was assessed by the Cochran Q test and the I2 statistic. Subgroup and sensitivity analyses were used to explore the potential sources of heterogeneity. RESULTS: Eleven studies were included in this study, which involved a total of 296 741 participants. Our study showed that the children with CHD were at a significantly increased risk of ADHD compared with the reference group (OR = 2.98, 95% CI: 2.18-4.08). The results were moderately heterogeneous. These factors including study design, geographic region and study quality were identified as the first three of the most relevant heterogeneity moderators by subgroup analyses. Sensitivity analysis yielded consistent results. There was no evidence of publication bias. CONCLUSIONS: The present study suggests that CHD children have a significantly higher risk of ADHD when compared with those without CHD. Early identification and intervention of ADHD is important to reduce its symptoms and adverse effects; therefore, clinicians should increase screening for ADHD in children with CHD and intervene promptly to reduce its effects whenever possible.

Association of Maternal Folate Intake and Offspring MTHFD1 and MTHFD2 Genes with Congenital Heart Disease.

Existing evidence supported that congenital heart defect (CHD) was associated with a combination of environmental and genetic factors. Based on this, this study aimed at assessing the association of maternal folic acid supplementation (FAS), genetic variations in offspring methylenetetrahydrofolate dehydrogenase (MTHFD)1 and MTHFD2 genes, and their interactions with CHD and its subtypes. A hospital-based case-control study, including 620 cases with CHD and 620 healthy children, was conducted. This study showed that the absence of FAS was significantly associated with an increased risk of total CHD and its subtypes, such as atrial septal defect (ASD). FAS during the first and second trimesters was associated with a significantly higher risk of CHD in offspring compared to FAS during the three months prior to conception. The polymorphisms of offspring MTHFD1 and MTHFD2 genes at rs2236222, rs11849530, and rs828858 were significantly associated with the risk of CHD. Additionally, a significantly positive interaction between maternal FAS and genetic variation at rs828858 was observed for the risk of CHD. These findings suggested that pregnant women should carefully consider the timing of FAS, and individuals with higher genetic risk may benefit from targeted folic acid supplementation as a preventive measure against CHD.

Presence of immune factors in freshwater mussel (Hyriopsis cumingii) entails autologous serum an essential component in the culture of mantle cells.

Mussel cell culture is a challenging problem and serum serves a crucial biological role in cell culture as an autologous supply and an immunizing agent. In this study, the biology (calcium ions, total protein, pH, and osmotic pressure) of fetal bovine serum (FBS) and Hyriopsis cumingii serum (HCS) was investigated, and the development of Hyriopsis cumingii (H. cumingii) mantle cells in HCS and FBS systems was examined. The results showed that total protein, calcium ions, and osmotic pressure varied significantly (p<0.05). The activity of mantle cells was superior in the HCS culture system to that in the FBS culture system. The label-free technique was used to distinguish the two serum proteins to investigate the supportive effect of autologous serum on cell culture. These were examined for 109 unique proteins and 35 particular HCS proteins. Most differentially expressed proteins (DEPs) were involved in immune response, cell differentiation, and calcium ion binding. Furthermore, immune factors such as HSP, CALR, APOB, C3 were identified with significant differences. HSP was significantly more present in HCS than in FBS as an endogenous protective protein that regulates immune system function, cell differentiation, transport, and activity regulation. Parallel reaction monitoring (PRM) analysis was carried out to validate the expression levels of 19 DEPs, indicating high reliability of the proteomic results. This study reveals the important role of immune factors in mussel cell culture, providing a theoretical basis for explaining the applicability of autologous serum in cell culture. It is also helpful in improving the cell culture conditions of mussels.

Correction: Li et al. Identification and Functional Analysis of the Cell Proliferation Regulator, Insulin-like Growth Factor 1 (IGF1) in Freshwater Pearl Mussel (Hyriopsis cumingii). Biology 2022, 11, 1369.

In the original publication [...].

2,5-Hexanedione Affects Ovarian Granulosa Cells in Swine by Regulating the CDKN1A Gene: A Transcriptome Analysis.

N-hexane, a common industrial organic solvent, causes multiple organ damage owing to its metabolite, 2,5-hexanedione (2,5-HD). To identify and evaluate the effects of 2,5-HD on sows' reproductive performance, we used porcine ovarian granulosa cells (pGCs) as a vehicle and carried out cell morphology and transcriptome analyses. 2,5-HD has the potential to inhibit the proliferation of pGCs and induce morphological changes and apoptosis depending on the dose. RNA-seq analyses identified 4817 differentially expressed genes (DEGs), with 2394 down-regulated and 2423 up-regulated following 2,5-HD exposure treatment. The DEG, cyclin-dependent kinase inhibitor 1A (CDKN1A), according to the Kyoto Encyclopedia of Genes and Genomes enrichment analysis, was significantly enriched in the p53 signaling pathway. Thus, we evaluated its function in pGC apoptosis in vitro. Then, we knocked down the CDKN1A gene in the pGCs to identify its effects on pGCs. Its knockdown decreased pGC apoptosis, with significantly fewer cells in the G1 phase (p < 0.05) and very significantly more cells in the S phase (p < 0.01). Herein, we revealed novel candidate genes that influence pGCs apoptosis and cell cycle and provided new insights into the role of CDKN1A in pGCs during apoptosis and cell cycle arrest.

Copy Number Variation Analysis Revealed the Evolutionary Difference between Chinese Indigenous Pigs and Asian Wild Boars.

Copy number variation (CNV) has been widely used to study the evolution of different species. We first discovered different CNVs in 24 Anqingliubai pigs and 6 Asian wild boars using next-generation sequencing at the whole-genome level with 10× depth to understand the relationship between genetic evolution and production traits in wild boars and domestic pigs. A total of 97,489 CNVs were identified and divided into 10,429 copy number variation regions (CNVRs), occupying 32.06% of the porcine genome. Chromosome 1 had the most CNVRs, and chromosome 18 had the least. Ninety-six CNVRs were selected using VST 1% based on the signatures of all CNVRs, and sixty-five genes were identified in the selected regions. These genes were strongly correlated with traits distinguishing groups by enrichment in Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways, such as growth (CD36), reproduction (CIT, RLN), detoxification (CYP3A29), and fatty acid metabolism (ELOVL6). The QTL overlapping regions were associated with meat traits, growth, and immunity, which was consistent with CNV analysis. Our findings increase the understanding of evolved genome structural variations between wild boars and domestic pigs, and provide new molecular biomarkers to guide breeding and the efficient use of available genetic resources.

Detection of Selection Signatures in Anqing Six-End-White Pigs Based on Resequencing Data.

As a distinguished Chinese indigenous pig breed that exhibits disease resistance and high meat quality, the Anqing six-end-white (AQ) pig represents a valuable germplasm resource for improving the quality of the pig breeding industry. In this study, 24 AQ pigs that were distantly blood-related and 6 Asian Wild Boar (AWB) were selected for 10× deep-genome resequencing. The signatures of the selection were analyzed to explore the genetic basis of their germplasm characteristics and to identify excellent germplasm-related functional genes based on NGS data. A total of 49,289,052 SNPs and 6,186,123 indels were detected across the genome in 30 pigs. Most of the genetic variations were synonym mutations and existed in the intergenic region. We identified 275 selected regions (top 1%) harboring 85 genes by applying a crossover approach based on genetic differentiation (FST) and polymorphism levels (π ratio). Some genes were found to be positively selected in AQ pigs' breeding. The SMPD4 and DDX18 genes were involved in the immune response to pseudorabies virus (PRV) and porcine reproductive and respiratory syndrome virus (PRRSV). The BCL6 and P2RX6 genes were involved in biological regulation of immune T cells and phagocytes. The SLC7A4 and SPACA4 genes were related to reproductive performance. The MSTN and HIF1A genes were related to fat deposition and muscle development. Moreover, 138 overlapping regions were detected in selected regions and ROH islands of AQ pigs. Additionally, we found that the QTLs with the most overlapping regions were related to back fat thickness, meat color, pH value, fatty acid content, immune cells, parasitic immunity, and bacterial immunity. Based on functional enrichment analysis and QTLs mapping, we conducted further research on the molecular genetic basis of germplasm traits (disease resistance and excellent meat quality). These results are a reliable resource for conserving germplasm resources and exploiting molecular markers of AQ pigs.

Possible realization of optical Dirac points in woodpile photonic crystals.

The simulation of fermionic relativistic physics, e.g., Dirac and Weyl physics, has led to the discovery of many unprecedented phenomena in photonics, of which the optical-frequency realization is, however, still challenging. Here, surprisingly, we discover that the woodpile photonic crystals commonly used for optical frequency applications host exotic fermion-like relativistic degeneracies: a Dirac nodal line and a fourfold quadratic point, as protected by the nonsymmorphic crystalline symmetry. Deforming the woodpile photonic crystal leads to the emergence of type-II Dirac points from the fourfold quadratic point. Such type-II Dirac points can be detected by its anomalous refraction property which is manifested as a giant birefringence in a slab setup. Our findings provide a promising route towards 3D optical Dirac physics in all-dielectric photonic crystals.

Identification and Functional Analysis of the Cell Proliferation Regulator, Insulin-like Growth Factor 1 (IGF1) in Freshwater Pearl Mussel (Hyriopsis cumingii).

Insulin-like growth factor 1 (IGF1) plays an important regulatory role in the regulation of growth, differentiation, and anabolism in a variety of cells. In this study, the full-length cDNA of the IGF1 gene was cloned from Hyriopsis cumingii, named HcIGF1. The expression level of HcIGF1 in six tissues (adductor muscle, foot, hepatopancreas, gill, mantle, and gonad) was determined. In addition, the localization of HcIGF1 in the mantle was analyzed by in situ hybridization, and finally the function of HcIGF1 was explored by RNA interference and prokaryotic expression. The results showed that the amino acid sequence contained a typical IIGF structural domain. The phylogenetic tree showed that HcIGF1 clustered with other marine bivalve sequences. Quantitative real-time PCR and in situ hybridization analysis showed that HcIGF1 was expressed in all tissues. The highest expression was in the foot and the lowest was in the mantle. In the mantle tissue, the hybridization signal was mainly concentrated in the outer mantle. After RNA interference, the expression of IGF1 was found to be significantly decreased (p < 0.05), and its related genes IGF1R, AKT1, and cyclin D2 were downregulated, while MAPK1 were upregulated. The recombinant HcIGF1 protein was purified and its growth-promoting effect was investigated. The results showed that the recombinant HcIGF1 protein could significantly promote the proliferative activity of the mantle cells of mussels, with the best proliferative effect at 12.5 µg/mL. The results of this study provide a new method to solve the problem of weak proliferation of shellfish cells in vitro and lay the foundation for further understanding of the growth regulation mechanism of H. cumingii, as well as a better understanding of the physiological function of IGF1 in mollusks.

A proteomic approach reveals biomineralization and immune response for mantle to pearl sac in the freshwater pearl mussel (Hyriopsis cumingii).

In the process of production of freshwater pearl, implanted mantle pieces undergo a series of complex physiological and biochemical processes to form pearl sac, which produce pearl. This is a very important site of occurrence due to immune-induced biomineralization, while its molecular regulatory mechanism is still unclear. Here, we use proteomics to identify differentially expressed proteins (DEPs) of the mantle and pearl sac and examine the biomineralization and immune response of the pearl sac formation process in Hyriopsis cumingii. Using iTRAQ technology and bioinformatics analysis, we obtained DEP profiles between the mantle and pearl sac. A total of 1871 proteins were identified. Of these, 74 DEPs were found between the pearl sac and outer mantle, 112 DEPs between the pearl sac and inner mantle, and 124 DEPs between the outer and inner mantles. Bioinformatics analysis revealed that the screened biomineralization-related DEPs were mainly enriched in signaling pathways associated with calcium signaling, regulation of the actin cytoskeleton and protein processing in the endoplasmic reticulum, while the immune-related DEPs were mainly enriched in the Notch, Hippo, nuclear factor kappa-B (NF-κB), and transforming growth factor-ß (TGF-ß) signaling pathways. In addition, the expression of six biomineralization-related and four immune-related proteins were verified at the transcriptional level using quantitative real-time PCR. Our findings contribute to furthering the understanding of the mechanisms of pearl formation and immune response, and have long-term implications for future studies on the production of high-quality freshwater pearls and development of the freshwater pearl industry.

High-Yield and High-Efficiency Conversion of HMF to Levulinic Acid in a Green and Facile Catalytic Process by a Dual-Function Brønsted-Lewis Acid HScCl4 Catalyst.

Lignocellulosic biorefineries have received considerable attention for the purpose of producing high-value chemicals and materials. Levulinic acid (LA) is an important biomass-derived platform chemical that is produced from sugar-based biomass. Unfortunately, the catalysts reported thus far have shortcomings, such as expensive starting materials, complicated synthesis or purification operations, and a low LA yield under harsh reaction conditions. Herein, we develop a novel dual-functional catalyst, HScCl4, by combining Brønsted acid (HCl) and Lewis acid (ScCl3) sites. The as-prepared HScCl4 catalyst shows high efficiency and high selectivity for converting 5-hydroxymethylfurfural (HMF) to LA in a biphasic system consisting of methyl isobutyl ketone (MIBK) and water. The density functional theory (DFT) results show that the synergistic catalytic effect, originating from the Brønsted and Lewis acidic sites of HScCl4, significantly decreases the energy barriers of reactants and intermediates, thus facilitating the conversion of HMF to LA. Moreover, the efficient separation of LA in the water-MIBK biphasic system by extracting LA to the MIBK phase minimizes the side reactions of LA and thus the formation of humins while significantly improving the LA yield. The conversion of HMF and the selectivity for LA are 100 and 95.6% at 120 °C for 35 min, respectively. The free energy (ΔG) and activation energy (E a) of the reaction are -30 kcal mol-1 and 13.7 kJ mol-1, respectively. The developed process provides a green, sustainable, and efficient pathway to produce LA from biomass-derived HMF under mild conditions.

MiR-21-5p actions at the Smad7 gene during pig ovarian granulosa cell apoptosis.

MicroRNAs (miRNAs) are endogenous non-coding RNAs in eukaryotic cells that modulate apoptosis of ovarian granulosa cells (GCs), which is an important cause of mammalian follicular atresia. In the present study, associations were evaluated between miR-21-5p and the extent of Smad7 protein production in regulation of ovarian granulosa cell (pGC) apoptosis. There was detection of miR-21-5p and Smad7 primarily in the cytoplasm and nucleus of pGCs, respectively. When there was an enhanced abundance of miR-21-5p and decreased abundance of Smad7 there were similar effects in pGCs, including inducing proliferation, inhibiting apoptosis, increasing the number of cells in S and G2/M phases, increasing serum estradiol, and decreasing serum progesterone concentrations. Furthermore, the Smad7 mRNA transcript was identified as a target for miR-21-5p actions, with enhanced abundances of miR-21-5p being associated with a lesser abundance of Smad7 mRNA transcript and protein in pGCs. Overall, results from the present study indicate that miR-21-5p has actions on the Smad7 mRNA transcript during the process of ovarian granulosa cell apoptosis in pigs.

A three-dimensional electrochemical oxidation system with α-Fe2O3/PAC as the particle electrode for ammonium nitrogen wastewater treatment.

A three-dimensional particle electrode loaded with α-Fe2O3 on powdered activated carbon (PAC) (α-Fe2O3/PAC) was synthesized by the microwave method for removing ammonium nitrogen from wastewater in a three-dimensional electrode system. The α-Fe2O3/PAC electrode was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of the added α-Fe2O3/PAC on the removal of ammonium nitrogen from simulated wastewater was studied by changing the cell voltage, particle dosage, and particle electrode synthesis conditions. Simulated experiments were also carried out on different pollutants under the best experimental conditions and the actual domestic sewage was tested. The results show that the optimal synthesis conditions of the particle electrode are as follows: the ratio of PAC to anhydrous FeCl3 is 1 : 2, and the microwave power is 1000 W for 60 s. After 20 min of electrolysis at 20 V, the ammonium nitrogen removal rate can reach 95.30%.

MiR-222 inhibits apoptosis in porcine follicular granulosa cells by targeting the THBS1 gene.

Apoptosis of granulosa cells affects follicular atresia and reproduction and is regulated by miRNAs and the expression of certain genes. For the present study, we investigated the regulatory relationship between microRNA-222 (miR-222) and THBS1 in porcine follicular granulosa cells (pGCs) and its effects on apoptosis to provide empirical data for developing methods to improve pig fecundity. Results revealed that miR-222 promotes the proliferation of pGCs. MiRNA mimics and luciferase reporter assays revealed that miR-222 functions as an anti-apoptotic factor in pGCs. MiR-222 mimics in pGCs result in the upregulation of the anti-apoptotic BCL-2 gene, down-regulation of the proapoptotic caspase-3 gene, and inhibition of apoptosis. MiR-222 inhibitors reduced BCL-2 and had no significant effect on caspase-3. MiR-222 mimics promoted estrogen levels. Inhibition of THBS1 inhibited pGC apoptosis. Transfection of THBS1-siRNA reduced the proapoptotic BAX gene. MiR-222 can directly target the 3'-untranslated region of the THBS1 gene. MiR-222 mimics suppressed THBS1 mRNA and proteins, but these were upregulated by the miR-222 inhibitor. Transfection of THBS1-siRNA resulted in the inhibition of the miR-222 inhibitor, which suggests that miR-222 inhibits pGC apoptosis by targeting THBS1. These findings suggest that miR-222 and THBS1 play important roles in follicular atresia, ovarian development, and female reproduction.

[Investigation on level and influencing factors of first aid knowledge among dentists in Sichuan province].

OBJECTIVE: The study aims to investigate the cognition degree and influencing factors of first aid knowledge among dentists in Sichuan province, and to provide suggestions for the training of oral clinician. METHODS: A questionnaire was designed for this study. It included the basic situation of population, first aid knowledge level, emergency situation often encountered in stomatology clinic, first aid training situation, learning approach and attitude of first aid knowledge, etc. This questionnaire was used to investigate the dentists of medical institutions in various cities in Sichuan province. The survey results was statistical analyzed. RESULTS: There were 245 valid questionnaires. 1) The level of first aid knowledge of dentists was generally lower in Sichuan province. Work department and other departments work experience were the influencing factors of knowledge level of first aid knowledge among dentists. 2) 87.3% of dentists believed that it was very necessary to master the knowledge of first aid, but in the event of an emergency situation, 73.5% of dentists only can find other doctors to guide themselves to help. 3) The most common way to learn first aid knowledge was through work experience and medical school's first aid course. CONCLUSIONS: Dentists should strengthen the learning and training to improve the first aid skill.

Elemental Topological Dirac Semimetal: α-Sn on InSb(111).

Three-dimensional (3D) topological Dirac semimetals (TDSs) are rare but important as a versatile platform for exploring exotic electronic properties and topological phase transitions. A quintessential feature of TDSs is 3D Dirac fermions associated with bulk electronic states near the Fermi level. Using angle-resolved photoemission spectroscopy, we have observed such bulk Dirac cones in epitaxially grown α-Sn films on InSb(111), the first such TDS system realized in an elemental form. First-principles calculations confirm that epitaxial strain is key to the formation of the TDS phase. A phase diagram is established that connects the 3D TDS phase through a singular point of a zero-gap semimetal phase to a topological insulator phase. The nature of the Dirac cone crosses over from 3D to 2D as the film thickness is reduced.

Topological crystalline metal in orthorhombic perovskite iridates.

Since topological insulators were theoretically predicted and experimentally observed in semiconductors with strong spin-orbit coupling, increasing attention has been drawn to topological materials that host exotic surface states. These surface excitations are stable against perturbations since they are protected by global or spatial/lattice symmetries. Following the success in achieving various topological insulators, a tempting challenge now is to search for metallic materials with novel topological properties. Here we predict that orthorhombic perovskite iridates realize a new class of metals dubbed topological crystalline metals, which support zero-energy surface states protected by certain lattice symmetry. These surface states can be probed by photoemission and tunnelling experiments. Furthermore, we show that by applying magnetic fields, the topological crystalline metal can be driven into other topological metallic phases, with different topological properties and surface states.