Sustainable approach of La doped CuFe2O4 nanomaterial for electrochemical lead and paracetamol sensing action with multiple applications.

This present research aimed to investigate the novel applications of synthesized La doped CuFe2O4 nanomaterial (LCF NMs) using renewable bio-fuel (Aegle Marmelos extract) by combustion process. The sensor applications were accomplished by modified electrode using LCF NMs with graphite powder and examined its excellent sensing action towards heavy metal (Lead content) and drug chemical (Paracetamol) substances. The thermodynamics of redox potential and super-capacitor behavior of LCF NMs were investigated through Cyclic Voltametric (CV) and Electrochemical Impedance Spectral (EIS) methods under specific conditions at scan rate of 1 to 5 mV/s. The heterogeneous photo-catalytic process of prepared NMs on Fast orange Red (FOR) dye-decolouration was investigated and noted its excellent degradation (91.7%) at 90 min using 20 ppm of dye solution and 40 mg of synthesized samples under Sun-light irradiation. Further, the antibacterial activity of synthesized NMs is investigated against various strains of gram positive (Bacillus subtillis) and gram negative bacteria (Pseudomonas aeruginosa), which confirms that the LCF NMs have higher activity towards gram positive bacteria with an average inhibition zone of 19 mm. This synthesized LCF NMs is a multi-functional material with stable and eco-friendly materials.

Synergistic effect of a Bi2Zr2O7 and hydroxyapatite composite: organic pollutant remediation, antibacterial and electrochemical sensing applications.

Global concern regarding the energy crisis and environmental pollution is increasing. The fabrication of efficient catalysts remains a long-term goal. Recently, green synthesis methods for catalyst fabrication have attracted the scientific community. Herein, a simple approach to synthesize bismuth zirconate-hydroxyapatite (BZO-HA) nanocomposites using Mentha spicata (mint) leaves as a reducing agent via a combustion method has been reported. The use of a green reducing agent provided economic attributes to this work. Among the prepared samples, the BZO-HA (20%) composite exhibited superior photocatalytic activity. The photodegradation efficiency of the composite reached 90.3% and 98.4% for methylene blue (MB) and rose Bengal (RB) dyes, respectively. The results showed the excellent optical performance of the prepared composites. The constructed sensor (BZO-HA 20%) for the very first time showed outstanding selectivity and performance towards sensing lead nitrate and dextrose compared to bare bismuth zirconate (BZO) and hydroxyapatite (HA). A three-electrode system using 0.1 M KCl was used for the study. The synthesized composite BZO-HA (20%) can sense lead nitrate and dextrose over the concentration range of 1-5 mM in the potential range from -1.0 V to +1.0 V. The BZO-HA composite was also investigated against Gram-negative (S. typhi) and Gram-positive (S. aureus) bacteria for antibacterial activity studies. Enhanced antibacterial activity was observed compared to bare BZO and HA catalysts. Thus, the prepared BZO-HA nanocomposite exhibited multifunctional applications.

Influence of Ag on the Structural, Electrochemical, Antibacterial, and Photocatalytic Performance of the (CuO-Cu2O)Cu Nanocomposite.

The cost-effective novel Ag-doped (1-7%) (CuO-Cu2O)Cu (C3) heterostructured nanocomposites are successfully synthesized by the facile solution combustion process using the Leucas aspera extract as a green fuel. The structural properties of fabricated nanocomposites were well-characterized by specific spectral techniques for enhanced electrochemical sensor detection, antibacterial activities, and sunlight-driven photocatalytic dye decoloration studies. The existence of Ag+ ions has been confirmed by the appearance of two peaks of Ag 3d5/2 (367.9 eV) and Ag 3d3/2 (373.9 eV), with the chemical binding nature and exchange of the Ag+ state in the nanocomposite lattice as revealed by X-ray photoelectron spectroscopy analysis. The energy band gap value of the doped nanocomposite decreases from 2.2 to 1.8 eV, as measured by the UV-visible absorption spectral technique, hindering the recombination of electron-holes pairs by trapping e- and h+. This result supports that the C3Ag5 nanocomposite has a great potential as a sunlight photocatalyst toward the Alizarin Red (AR) dye, for which an excellent degradation activity of 98% at 180 min was achieved compared to that of the host nanocomposite (78% at 180 min). The variation of redox peak potentials of the prepared graphite nanocomposite working electrode is an effective tool for paracetamol sensing activity in 0.1 M KCl using electrochemical spectral studies. In addition, the antibacterial activities of the C3Ag5 nanocomposite against Escherichia coli and Staphylococcus aureus were successfully studied. The C3Ag5 nanocomposite exhibited a better performance than C3. The increase in activity is attributed to the presence of Ag as a dopant.

A cone-beam computed tomographic study of root and root canal morphology of primary maxillary and mandibular second molars in Indian Children: An in vitro study.

Introduction: The root canal system in primary molars is considered to be complex. The aim of the present study was to assess the morphology of roots and root canals of primary maxillary and mandibular second molars using the cone-beam computed tomography (CBCT). Materials and Methods: From a total of 104 collected primary maxillary and mandibular molars (51 maxillary second molars and 53 mandibular second molars), 60 teeth (30 each of maxillary and mandibular second molars) were selected randomly and accordingly assigned into two groups: MAX2M (primary maxillary second molars) and MAN2M (primary mandibular second molars). CBCT was used to assess the number of roots and root canals, length of root, mesiodistal and buccolingual width of the canal, shape of the canal, and intercanal communications. Descriptive statistical analysis was performed using the SPSS software version 17.0. Results: The mandibular second molars showed the presence of two roots in 27 sample molars while the presence of three roots was observed in three MAN2M group. In these molars, all three roots exhibited Type I root canal configuration. The maxillary second molars exhibited three roots. A total of nine intercanal communications were seen in MAX2M group, whereas two communications were seen in MAN2M group. The palatal root in MAX2M group was more angulated (mean value: 127.21 ± 9.10) as compared to mesial (mean value: 95.39 ± 8.64) and distal roots (114 ± 11.24). Conclusion: The comprehensive knowledge of root and canal morphology of primary molars and anatomic variations is essential for successful endodontic therapy.

DeepLumina: A Method Based on Deep Features and Luminance Information for Color Texture Classification.

Color texture classification is a significant computer vision task to identify and categorize textures that we often observe in natural visual scenes in the real world. Without color and texture, it remains a tedious task to identify and recognize objects in nature. Deep architectures proved to be a better method for recognizing the challenging patterns from texture images. This paper proposes a method, DeepLumina, that uses features from the deep architectures and luminance information with RGB color space for efficient color texture classification. This technique captures convolutional neural network features from the ResNet101 pretrained models and uses luminance information from the luminance (Y) channel of the YIQ color model and performs classification with a support vector machine (SVM). This approach works in the RGB-luminance color domain, exploring the effectiveness of applying luminance information along with the RGB color space. Experimental investigation and analysis during the study show that the proposed method, DeepLumina, got an accuracy of 90.15% for the Flickr Material Dataset (FMD) and 73.63% for the Describable Textures dataset (DTD), which is highly promising. Comparative analysis with other color spaces and pretrained CNN-FC models are also conducted, which throws light into the significance of the work. The method also proved the computational simplicity and obtained results in lesser computation time.

Root and Root Canal Anatomy of Primary Mandibular Central Incisor, Lateral Incisor, and Canine in Indian Children: A Cone Beam Computed Tomography Study.

Background: A thorough knowledge of root and root canal morphology in primary dentition is essential for success of endodontic therapy. This information also finds importance in anthropological research in reconstructing human population history. Lack of studies of root and root canal morphology in mandibular anterior teeth prompted us to the present study. Methods: A total of 109 extracted primary mandibular incisors and canines were collected, out of which 90 teeth were selected for this study and divided into 3 groups: CI, mandibular central incisor; LI, mandibular lateral incisor; C, mandibular canine. All the sample teeth were scanned using cone beam computed tomography (CBCT). Number of roots, number of root canals, length of root, mesiodistal (MD), and buccolingual (BL) width of canal, shape of canal, and presence of accessory canals were assessed. Collected data were statistically compared using one-way ANOVA and chi-square tests. Results: All teeth studied displayed single root with single root canal conforming to type I Vertucci's classification. Root length of CI was significantly shorter than both LI and C, with no significant difference between LI and C. Straight root canals were more common in CI and LI, whereas curved canals were more common in C. S-shaped canals were seen in a few CI and C. BL canal width was more than MD width in all teeth, C showing significantly larger dimensions than both CI and LI. Conclusion: This study presents root and root canal characteristics of primary mandibular central incisor, lateral incisor, and canine in children from Indian ethnicity.

Prevalence of molar incisor hypomineralization in India: A systematic review and meta-analysis.

Research Question: To estimate the pooled prevalence of molar incisor hypomineralization (MIH) in children from India. Research Protocol: The PRISMA guidelines were followed. Literature Search: An electronic search of the databases was performed to find prevalence studies of MIH in children above age 6 years in India. Data Extraction: Two authors independently extracted the data from the 16 included studies. Quality Appraisal: The risk of bias was assessed using a modified version of the Newcastle-Ottawa Scale adapted for cross-sectional studies. Data Analysis: The pooled prevalence estimate of MIH was calculated using logit transformed data with inverse variance approach in a random-effects model with 95% confidence interval (CI). Heterogeneity was assessed with the I2 statistic. The subgroups were analyzed to assess the pooled prevalence of MIH according to sex, arch-wise proportion of MIH-affected teeth, and proportion of children with the MIH phenotypes. Results and Interpretation of Results: Sixteen studies included in the meta-analysis represented 7 states of India. A total of 25,273 children were included in the meta-analysis. The pooled prevalence of MIH in India was estimated to be 10.0% (95% CI: 0.07, 0.12) with significantly high heterogeneity between the included studies. The pooled prevalence did not vary according to sex. The pooled proportions of MIH-affected teeth were similar in the maxillary and mandibular arches. The pooled proportion of children with MH phenotype was higher (56%) than those with M + IH phenotype (44%). Further studies with standardized criteria for recording MIH are needed to ascertain the prevalence of MIH in India.

Dietary Sugar Exposure and Oral Health Status in Children with Autism Spectrum Disorder: A Case-control Study.

This case-control study compared dietary sugar exposure and oral health status between children with and without Autism Spectrum Disorder (ASD), aged 5-12 years (n = 136, each). Data regarding socio-demographics, child's oral hygiene practices and behavior, diet-related behavior, oral habits and dental trauma were obtained. Child's diet on the previous day was recorded using 24-h recall method and sugar exposure was calculated using Dental Diet Diary (D3) mobile application. Oral Hygiene Index-Simplified (OHI-S), deft and DMFT were recorded. Results showed no significant differences in sugar exposure, deft and DMFT between the groups. Although oral hygiene practices were significantly better in children with ASD, their OHI-S was significantly worse. Significantly more children with ASD reported mouth-breathing, bruxism and self-injurious habits.

Does maternal tooth brushing-related sef-efficacy predict child's brushing adherence?

BACKGROUND: Dental plaque is a root cause of dental caries. Effective plaque control in young children can be achieved with twice-daily assisted tooth brushing. Self-efficacy relates to one's confidence in performing a task. Self-efficacy is shown to facilitate the behavior change in treatments for lifestyle diseases. The influence of maternal self-efficacy in children's oral health behaviors is less studied. AIM: The aim of this study is to evaluate an association between maternal tooth brushing-related self-efficacy (MTBSE) and child's brushing adherence. SETTINGS AND DESIGN: This cross-sectional study was conducted in schools and included 781 mother-child dyads with children between the age group of 2 and 6 years. METHODS: Selected mothers were asked to complete the questionnaires on sociodemographic data, mother's oral health knowledge (MOHK), tooth-brushing practices, and MTBSE. Brushing adherence was evaluated as complete adherence if the child followed twice daily assisted brushing using the toothbrush and toothpaste. STATISTICAL ANALYSIS: Nonparametric tests were used to compare the variables. Binary logistic regression was used to evaluate the predictors of brushing adherence. RESULTS: Complete brushing adherence (assisted brushing with toothbrush and toothpaste at least twice per day) was seen only in 26.9% children. More children with complete brushing adherence were single children (P < 0.001). Children with complete brushing adherence had mothers with significantly higher MTBSE (P < 0.001). The presence/absence of siblings, MOHK, and MTBSE were found to be strong and significant predictors of brushing adherence in children. CONCLUSIONS: MTBSE plays a significant role in complete adherence to toothbrushing in children aged 2-6 years.

Constituents, properties and clinical applications of OrthoMTA & RetroMTA: A systematic review.

Aim: OrthoMTA and RetroMTA are newly developed mineral trioxide aggregates that were developed to achieve maximum benefits and clinical performance. This systematic review aimed at assessing and describing the constituents, properties and uses of OrthoMTA and RetroMTA. Methodology: Literature search was performed using the keywords, "OrthoMTA", "RetroMTA", "BioMTA", "constituents" and "properties" in the databases, PubMed, Cochrane, Semantic scholar and Europe PubMed Central. Original articles in English describing the properties, constituents, uses/indications, history and recent advances on OrthoMTA and RetroMTA were considered for the study. Results: A total of 35 articles were selected for the systematic review based on keywords selected. Among the 35 articles, 5 articles described the composition and properties of OrthoMTA and RetroMTA, 7 articles depicted the usage of OrthoMTA and RetroMTA and the remaining articles discussed on the various properties of both OrthoMTA and RetroMTA. Conclusion: The present review confirmed that RetroMTA exhibits an excellent property, namely, short setting time, less tooth discoloration, high compressive strength, higher shear bond strength with time, higher push-out bond strength, low solubility, low cytotoxicity, biocompatibility, antibacterial property, and can be used in reparative processes in case of blood contamination. However, even OrthoMTA showed less microleakage, is biocompatible and possesses antibacterial properties.

Comparison of the effectiveness of Bach flower therapy and music therapy on dental anxiety in pediatric patients: A randomized controlled study.

BACKGROUND: Dental anxiety is a primary cause of missed dental appointments, delayed treatment, and untreated dental caries in children. Alternative techniques such as music therapy (MT) and Bach flower therapy (BFT) have potential to reduce anxiety. Lack of randomized controlled studies evaluating effectiveness of these methods in reducing dental anxiety led us to this study. AIM: To compare the effectiveness of BFT and MT on reduction of dental anxiety in pediatric patients. MATERIALS AND METHODS: A total of 120 children (aged 4-6 years) were selected and randomly allocated to three groups: BFT, MT, and control. All children received oral prophylaxis and fluoride treatment. Dental anxiety was evaluated using North Carolina Behavior Rating Scale, Facial Image Scale (FIS), and physiological parameters. RESULTS: Significantly better behavior was seen in children from the BFT group as compared to the control group (P = 0.014). FIS scores measured postoperatively did not show significant differences among the groups. Children from the BFT and MT groups showed a significant decrease in the pulse rates intraoperatively from the preoperative period. Intraoperative systolic blood pressure in children from the MT group was significantly lower than both the BFT and the control groups. Diastolic blood pressure significantly increased in the control group intraoperatively, whereas other groups showed a decrease. CONCLUSION: The results of this study demonstrate significant effects of both single dose of BFT and exposure to MT, on reduction of dental anxiety in children aged between 4 and 6 years.

A Nondimensional Model Reveals Alterations in Nuclear Mechanics upon Hepatitis C Virus Replication.

Morphology of the nucleus is an important regulator of gene expression. Nuclear morphology is in turn a function of the forces acting on it and the mechanical properties of the nuclear envelope. Here, we present a two-parameter, nondimensional mechanical model of the nucleus that reveals a relationship among nuclear shape parameters, such as projected area, surface area, and volume. Our model fits the morphology of individual nuclei and predicts the ratio between forces and modulus in each nucleus. We analyzed the changes in nuclear morphology of liver cells due to hepatitis C virus (HCV) infection using this model. The model predicted a decrease in the elastic modulus of the nuclear envelope and an increase in the pre-tension in cortical actin as the causes for the change in nuclear morphology. These predictions were validated biomechanically by showing that liver cells expressing HCV proteins possessed enhanced cellular stiffness and reduced nuclear stiffness. Concomitantly, cells expressing HCV proteins showed downregulation of lamin-A,C and upregulation of ß-actin, corroborating the predictions of the model. Our modeling assumptions are broadly applicable to adherent, monolayer cell cultures, making the model amenable to investigate changes in nuclear mechanics due to other stimuli by merely measuring nuclear morphology. Toward this, we present two techniques, graphical and numerical, to use our model for predicting physical changes in the nucleus.

Efficacy of Intraosseous Local Anesthesia for Restorative Procedures in Molar Incisor Hypomineralization-Affected Teeth in Children.

BACKGROUND: Treatment of teeth affected with molar incisor hypomineralization (MIH) in young patients is challenging due to chronic subclinical pulpal inflammation caused by porous enamel and exposed dentin. Hypersensitivity of the teeth and difficulty in achieving local anesthesia due to altered nerve potential affects the successful completion of the treatment. AIM: The aim of the study was to compare the anesthetic efficacy of the intraosseous (IO) anesthetic technique with conventional local infiltration technique in anesthetizing first permanent molars (FPMs) affected by MIH for restorative procedures in children. MATERIALS AND METHODS: This randomized controlled clinical trial recruited 54 MIH-affected mandibular or maxillary FPMs requiring restorations or stainless steel crowns. The teeth were randomly allocated to two equal groups to receive either IO injection or buccal infiltration (control), both using 4% articaine. Onset, time required, and pain experienced for administration, need for repeat, efficacy of anesthetic technique, heart rate, and postoperative complications were recorded in both the groups. Collected data were subjected to statistical analysis. RESULTS: Onset was significantly faster and pain experienced during administration was significantly lower with IO technique. Need for repeat of anesthesia was significantly more with infiltration (44.4% vs. 7.4% in IO, P = 0.004). Local infiltration failed to produce profound anesthesia in 74.1% MIH-affected teeth. IO anesthesia profoundly anesthetized 88.9% MIH-affected teeth. Anesthetic efficacy was significantly better with IO anesthesia (P < 0.001). Postoperative complications were significantly lower with IO anesthesia (P = 0.003). CONCLUSION: IO local anesthesia was found to be an effective and safe technique to achieve profound anesthesia in MIH-affected teeth in children in comparison to local infiltration.

The blalock and taussig shunt revisited.

The systemic to pulmonary artery shunts are done as palliative procedures for cyanotic congenital heart diseases ranging from simple tetralogy of Fallots (TOFs)/pulmonary atresia (PA) to complex univentricular hearts. They allow growth of pulmonary arteries and maintain regulated blood flow to the lungs till a proper age and body weight suitable for definitive corrective repair is reached. We have reviewed the BT shunt with its anaesthtic considerations and management of associated complications.

Skin score correlates with global DNA methylation and GSTO1 A140D polymorphism in arsenic-affected population of Eastern India.

Arsenic is a potent environmental toxicant causing serious public health concerns in India, Bangladesh and other parts of the world. Gene- and promoter-specific hypermethylation has been reported in different arsenic-exposed cell lines, whereas whole genome DNA methylation study suggested genomic hypo- and hypermethylation after arsenic exposure in in vitro and in vivo studies. Along with other characteristic biomarkers, arsenic toxicity leads to typical skin lesions. The present study demonstrates significant correlation between severities of skin manifestations with their whole genome DNA methylation status as well as with a particular polymorphism (Ala 140 Asp) status in arsenic metabolizing enzyme Glutathione S-transferase Omega-1 (GSTO1) in arsenic-exposed population of the district of Nadia, West Bengal, India.

Prevalence of Dental Fluorosis and associated Risk Factors in Bagalkot District, Karnataka, India.

INTRODUCTION: An earlier epidemiological study by these authors revealed fluorosis at very low levels of fluoride concentrations in drinking water. AIM: The objective of present study was to investigate risk factors of dental fluorosis in permanent teeth in the villages of northern Karnataka, India. MATERIALS AND METHODS: The present survey was carried out in three villages of Hungund Taluk, Bagalkot District, Karnataka, India, with the fluoride concentration of 0.136, 0.381, and 1.36 ppm. Children aged between 9 and 15, with permanent teeth, were examined for dental fluorosis using Dean's index, as per WHO criteria. Required relevant information regarding risk factors was obtained through a questionnaire. STATISTICAL ANALYSIS: Data entry and analysis were performed using SPSS for Windows 16.0. Comparison of means of different indices by the three groups was performed using ANOVA and t-test (p < 0.05). Bivariate analysis was performed to identify significant risk factors that affected prevalence and severity of dental fluorosis. Those variables showing a statistically significant association (p < 0.05) on χ2 were entered into multiple logistic regressions to assess their independent effects. RESULTS: In this study, we analyzed risk factors for both prevalence and severity of fluorosis. From multiple logistic regression analysis, only fluoride concentration in drinking water was found significant with prevalence of fluorosis and only nutritional status showed significant association with severity of fluorosis. CONCLUSION: Presence or absence of dental fluorosis in permanent teeth was significantly associated with fluoride concentration in drinking water. Once present, its severity was determined by nutritional status of the children - malnourished children exhibiting severe form of fluorosis. HOW TO CITE THIS ARTICLE: Mahantesha T, Dixit UB, Nayakar RP, Ashwin D Ramagoni NK, Ellore VPK. Prevalence of Dental Fluorosis and associated Risk Factors in Bagalkot District, Karnataka, India. Int J Clin Pediatr Dent 2016;9(3):256-263.

The Water Fraction of Calendula officinalis Hydroethanol Extract Stimulates In Vitro and In Vivo Proliferation of Dermal Fibroblasts in Wound Healing.

The active fraction and/or compounds of Calendula officinalis responsible for wound healing are not known yet. In this work we studied the molecular target of C. officinalis hydroethanol extract (CEE) and its active fraction (water fraction of hydroethanol extract, WCEE) on primary human dermal fibroblasts (HDF). In vivo, CEE or WCEE were topically applied on excisional wounds of BALB/c mice and the rate of wound contraction and immunohistological studies were carried out. We found that CEE and only its WCEE significantly stimulated the proliferation as well as the migration of HDF cells. Also they up-regulate the expression of connective tissue growth factor (CTGF) and α-smooth muscle actin (α-SMA) in vitro. In vivo, CEE or WCEE treated mice groups showed faster wound healing and increased expression of CTGF and α-SMA compared to placebo control group. The increased expression of both the proteins during granulation phase of wound repair demonstrated the potential role of C. officinalis in wound healing. In addition, HPLC-ESI MS analysis of the active water fraction revealed the presence of two major compounds, rutin and quercetin-3-O-glucoside. Thus, our results showed that C. officinalis potentiated wound healing by stimulating the expression of CTGF and α-SMA and further we identified active compounds. Copyright © 2016 John Wiley & Sons, Ltd.

An anaesthesiologist's encounter with purple glove syndrome.

Purple glove syndrome (PGS) is a devastating complication of intravenous (IV) phenytoin administration. Anaesthetic management during the amputation of the limb for such patients is very challenging due to limited clinical experience. A 65-year-old woman developed PGS of left upper extremity after IV administration of phenytoin following generalised tonic-clonic seizures. The condition progressed rapidly leading to gangrene of left hand extending to the mid arm. Amputation was carried out under general anaesthesia with a supraglottic airway device. We discuss the prevention and alternate managements in PGS, which is a rare clinical entity with limited data in the literature.

Anesthetic management for bronchoscopy and debulking of obstructing intratracheal tumor.

Primary tracheal tumors comprise a rare group of benign and malignant tumors. Bronchoscopy is required for diagnosis and staging of tracheal neoplasms as well as debulking of the tumor. The management of anesthesia for rigid bronchoscopy in a patient with tracheal neoplasm presents with many challenges to the anesthetist. We present anesthetic management of an 18-year-old female who presented with orthopnea. Computed tomography scan of the thorax revealed a polypoidal lesion in the trachea proximal to carina and consolidation in the right middle lobe. The patient was scheduled for rigid bronchoscopy and debulking of the tumor. Case was successfully managed by providing positive pressure ventilation and oxygenation during rigid bronchoscopy using manual ventilation through the side port of the rigid bronchoscope. The procedure was uneventful, and patient improved symptomatically in the immediate postoperative period. The successful management of this case demonstrates the airway management in a patient with tracheal tumor for rigid bronchoscopy.

Allorecognition proteins in an invertebrate exhibit homophilic interactions.

Sessile colonial invertebrates-animals such as sponges, corals, bryozoans, and ascidians-can distinguish between their own tissues and those of conspecifics upon contact [1]. This ability, called allorecognition, mediates spatial competition and can prevent stem cell parasitism by ensuring that colonies only fuse with self or close kin. In every taxon studied to date, allorecognition is controlled by one or more highly polymorphic genes [2-8]. However, in no case is it understood how the proteins encoded by these genes discriminate self from non-self. In the cnidarian Hydractinia symbiolongicarpus, allorecognition is controlled by at least two highly polymorphic allorecognition genes, Alr1 and Alr2 [3, 5, 9-12]. Sequence variation at each gene predicts allorecognition in laboratory strains such that colonies reject if they do not share a common allele at either locus, fuse temporarily if they share an allele at only one locus, or fuse permanently if they share an allele at both genes [5, 9]. Here, we show that the gene products of Alr1 and Alr2 (Alr1 and Alr2) are self-ligands with extraordinary specificity. Using an in vitro cell aggregation assay, we found that Alr1 and Alr2 bind to themselves homophilically across opposing cell membranes. For both proteins, each isoform bound only to itself or to an isoform of nearly identical sequence. These results provide a mechanistic explanation for the exquisite specificity of Hydractinia allorecognition. Our results also indicate that hydroids have evolved a molecular strategy of self-recognition that is unique among characterized allorecognition systems within and outside invertebrates.