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A. Objectives Contractile function in the normally perfused infarct borderzone (BZ) is depressed. However, the impact of reduced BZ contractility on left ventricular (LV) pump function is unknown. As a consequence, there have been no therapies specifically designed to improve BZ contractility. We tested the hypothesis that an improvement in borderzone contractility will improve LV pump function.B. Methods From a previously reported study, magnetic resonance (MRI) images with non-invasive tags were used to calculate 3D myocardial strain in five sheep 16 weeks after anteroapical myocardial infarction. Animal specific finite element (FE) models were created using MRI data and LV pressure obtained at early diastolic filling. Analysis of borderzone function using those FE models has been previously reported. Chamber stiffness, pump function (Starling’s law) and stress in the fiber, cross fiber and circumferential directions were calculated. Animal-specific FE models were performed for three cases: a) impaired BZ contractility (INJURED); b) BZ contractility fully restored (100% BZ IMPROVEMENT); or c) BZ contractility partially restored (50% BZ IMPROVEMENT).C. Results 100% BZ IMPROVEMENT and 50% BZ IMPROVEMENT both caused an upward shift in the Starling relationship, resulting in a large (36% and 26%) increase in stroke volume at LVPED = 20 mm Hg (8.0 ml, p

Background: Transgender men (TGM) are underrepresented in genital microbiome research. Our prospective study in Birmingham, AL investigated genital microbiota changes over time in TGM initiating testosterone, including the development of incident bacterial vaginosis (iBV). Here, we present lessons learned from recruitment challenges encountered during the conduct of this study., Methods: Inclusion criteria were assigned female sex at birth, TGM or non-binary identity, age ≥18 years, interested in injectable testosterone but willing to wait 7 days after enrollment before starting, and engaged with a testosterone-prescribing provider. Exclusion criteria were recent antibiotic use, HIV/STI infection, current vaginal infection, pregnancy, or past 6 months testosterone use. Recruitment initiatives included community advertisements via flyers, social media posts, and referrals from local gender health clinics., Results: Between February 2022 and October 2023, 61 individuals contacted the study, 17 (27.9%) completed an in-person screening visit, and 10 (58.8%) of those screened were enrolled. The primary reasons for individuals failing study screening were having limited access to testosterone-prescribing providers, already being on testosterone, being unwilling to wait 7 days to initiate testosterone therapy, or desiring the use of topical testosterone. Engagement of non-White TGM was also minimal., Conclusion: Despite robust study inquiry by TGM, screening and enrollment challenges were faced including engagement by TGM not yet in care and specific study eligibility criteria. Excitement among TGM for research representation should be leveraged in future work by engaging transgender community stakeholders at the inception of study development, particularly regarding feasibility of study inclusion and exclusion criteria, as well as recruitment of TGM of color. These results also highlight the need for more clinical resources for prescribing gender-affirming hormone therapy, especially in the Southeastern US., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Van Gerwen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Structural harm reduction is an approach to care for people who use drugs (PWUD) that incorporates services and resources (e.g., naloxone, sterile syringes). As conceptualized in our previous research, harm reduction is also "relational," encompassing a patient-provider relationship that is non-judgmental and respectful of patients' autonomy. Little is known about health care workers' (HCW) knowledge or attitudes towards harm reduction beyond structural strategies, whose availability and legality vary across geographical settings. To operationalize how relational harm reduction is both characterized and employed in HIV care settings, where nearly half of patients have a diagnosed substance use disorder, we qualitatively explored HCWs' knowledge of and use of harm reduction via individual in-depth interviews., Methods: Our study sample included three HIV clinics, one in Birmingham, Alabama (AL) and two in Pittsburgh, Pennsylvania (PA). We conducted individual interviews with n = 23 health care workers via Zoom, using a semi-structured interview guide to probe for questions around health care workers' attitudes towards and experiences with providing care to PWH who use drugs and their knowledge of and attitudes towards relational and structural harm reduction. Data was analyzed in Dedoose using thematic analysis., Results: Qualitative analyses revealed two primary themes, Continuum of Relational Harm Reduction in Practice and Limited Harm Reduction Training. Nearly all HCWs (n = 19, 83%) described a patient interaction or expressed a sentiment that corresponded with the principles of relational harm reduction. Yet, over half of participants (n = 14, 61%) used language to describe PWH who use drugs that was stigmatizing or described an interaction that was antithetical to the principles of relational harm reduction. Five HCWs, all from Birmingham, were unaware of the term 'harm reduction.' Few HCWs had any harm reduction training, with most learning about harm reduction from webinars/conferences or on the job., Conclusion: Our findings suggest that relational harm reduction in HIV care settings is practiced along a continuum, and that a range of behaviors exist even within individual HCWs (e.g., used stigmatizing terms such as "addict" but also described patient interactions that reflected patients' autonomy). Given that harm reduction is typically described as a structural approach, a broader definition of harm reduction that is not dependent on policy-dependent resources is needed., (© 2024. The Author(s).)

Injection-related infections continue to rise, particularly in the South. People who inject drugs are increasingly utilizing hospital services for serious injection-related infections but may be discharged to areas without harm reduction services. We explored the availability and travel time to services for HIV and substance use in Alabama., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: Pervasive health and healthcare disparities experienced by transgender (trans) and gender diverse (TGD) people require innovative solutions. Peer-based interventions may address disparities, and are an approach endorsed by TGD communities. However, the scope of the literature examining peer-based interventions to address health and healthcare access inclusive of TGD people is uncharted. Aim: This scoping review aimed to understand the extent of the literature about peer-based interventions conducted with and/or inclusive of TGD populations; specifically, study participants (e.g. sociodemographics), study designs/outcomes, intervention components (e.g. facilitator characteristics), and intervention effectiveness. Methods: Underpinned by Arksey and O'Malley's framework: (1) identifying the research question; (2) identifying studies; (3) study selection; (4) charting data; and (5) collating, summarizing, and reporting results, eligible studies were identified, charted, and thematically analyzed. Databases (e.g. ProQuest) and snowball searching were utilized to identify peer-reviewed literature published within 15 years of February 2023. Extracted data included overarching study characteristics (e.g. author[s]), methodological characteristics (e.g. type of research), intervention characteristics (e.g. delivery modality), and study findings. Results: Thirty-six eligible studies documented in 38 peer-reviewed articles detailing 40 unique peer-based interventions were identified. Forty-four percent ( n  = 16/36) of studies took place in United States (U.S.) urban centers. Over half ( n  = 23/40, 58%) focused exclusively on TGD people, nearly three-quarters of which ( n  = 17/23, 74%) focused exclusively on trans women/transfeminine people. Ninety-two percent ( n  = 33/36) included quantitative methods, of which 30% ( n  = 10/33) were randomized controlled trials. HIV was a primary focus ( n  = 30/36, 83.3%). Few interventions discussed promotion of gender affirmation for TGD participants. Most studies showed positive impacts of peer-based intervention. Discussion: Although promising in their effectiveness, limited peer-based interventions have been developed and/or evaluated that are inclusive of gender-diverse TGD people (e.g. trans men and nonbinary people). Studies are urgently need that expand this literature beyond HIV to address holistic needs and healthcare barriers among TGD communities., Competing Interests: The authors have no conflicts of interest to disclose., (© 2023 Taylor & Francis Group, LLC.)

Background: Achieving early and sustained viral suppression (VS) following diagnosis of HIV infection is critical to improving outcomes for persons with HIV (PWH). The Deep South of the United States (US) is a region that is disproportionately impacted by the domestic HIV epidemic. Time to VS, defined as time from diagnosis to initial VS, is substantially longer in the South than other regions of the US. We describe the development and implementation of a distributed data network between an academic institution and state health departments to investigate variation in time to VS in the Deep South., Methods: Representatives of state health departments, the Centers for Disease Control and Prevention (CDC), and the academic partner met to establish core objectives and procedures at the beginning of the project. Importantly, this project used the CDC-developed Enhanced HIV/AIDS Reporting System (eHARS) through a distributed data network model that maintained the confidentiality and integrity of the data. Software programs to build datasets and calculate time to VS were written by the academic partner and shared with each public health partner. To develop spatial elements of the eHARS data, health departments geocoded residential addresses of each newly diagnosed individual in eHARS between 2012-2019, supported by the academic partner. Health departments conducted all analyses within their own systems. Aggregate results were combined across states using meta-analysis techniques. Additionally, we created a synthetic eHARS data set for code development and testing., Results: The collaborative structure and distributed data network have allowed us to refine the study questions and analytic plans to conduct investigations into variation in time to VS for both research and public health practice. Additionally, a synthetic eHARS data set has been created and is publicly available for researchers and public health practitioners., Conclusions: These efforts have leveraged the practice expertise and surveillance data within state health departments and the analytic and methodologic expertise of the academic partner. This study could serve as an illustrative example of effective collaboration between academic institutions and public health agencies and provides resources to facilitate future use of the US HIV surveillance system for research and public health practice., (© 2023. The Author(s).)

Background: Persons with HIV (PWH) can now achieve a near-normal life expectancy due to antiretroviral therapy (ART). Despite widespread availability of ART in the United States (US), many of the country's approximate 1.1 million PWH are not achieving viral suppression due to poor ART adherence. Viral suppression rates are particularly low in Alabama (AL, 62%) and New York City (NYC, 67%). There is mixed evidence on the efficacy of community health workers (CHW) and mHealth interventions for improving ART adherence and viral suppression in PWH thus, we sought to combine these interventions and test the efficacy for improving health outcomes in PWH., Methods: The CHAMPS study is a two-arm randomized controlled trial among 300 PWH with suboptimal primary care appointment adherence (n = 150 in AL and 150 in NYC) over the course of 12 months. Participants are randomly assigned to CHAMPS (intervention) or a standard-of-care (control) arm. Participants in the intervention arm are given a CleverCap pill bottle that syncs to the WiseApp to track medication adherence, reminds users to take their medication at a set time, and enables communication with CHW. All participants complete baseline, 6-month, and 12-month follow-up visits where surveys are administered and, CD4 and HIV-1 viral load are obtained through blood draw., Discussion: Maintaining ART adherence has significant implications in HIV management and transmission. mHealth technologies have been shown to optimize the provision of health services, produce positive changes in health behavior, and significantly improve health outcomes. CHW interventions also provide personal support to PWH. The combination of these strategies may provide the necessary intensity to increase ART adherence and clinic attendance among PWH at highest risk for low engagement. Delivering care remotely enables CHW to contact, assess, and support numerous participants throughout the day, reducing burden on CHW and potentially improving intervention durability for PWH. The adoption of the WiseApp coupled with community health worker sessions in the CHAMPS study has the potential to improve HIV health outcomes, and will add to the growing knowledge of mHealth and CHW efforts to improve PWH medication adherence and viral suppression., Trial Registration: This trial was registered with Clinicaltrials.gov (NCT04562649) on 9/24/20., (© 2023. The Author(s).)

Introduction: Our previous pilot work suggests relational harm reduction strengthens relationships between people with HIV (PWH) who use drugs and their healthcare providers and improves HIV health outcomes. However, there is limited research examining ways that structural (eg, strategies like syringe service programmes) and/or relational (patient-provider relationship) harm reduction approaches in HIV clinical settings can mitigate experiences of stigma, affect patient-provider relationships and improve outcomes for PWH who use drugs. Our mixed methods, multisite, observational study aims to fill this knowledge gap and develop an intervention to operationalise harm reduction care for PWH who use drugs in HIV clinical settings., Methods and Analysis: Aim 1 will explore the relationship between healthcare providers' stigmatising attitudes towards working with PWH who use drugs and providers' acceptance and practice of structural and relational harm reduction through surveys (n=125) and interviews (n=20) with providers. Aim 2 will explore the interplay between patient-perceived harm reduction, intersectional stigma and clinical outcomes related to HIV, hepatitis C (if applicable) and substance use-related outcomes through surveys (n=500) and focus groups (k=6, total n=36) with PWH who use drugs. We will also psychometrically evaluate a 25-item scale we previously developed to assess relational harm reduction, the Patient Assessment of Provider Harm Reduction Scale. Aim 3 will use human-centred design approaches to develop and pretest an intervention to operationalise harm reduction care for PWH who use drugs in HIV clinical settings., Ethics and Dissemination: This study was approved via expedited review by the University of Pittsburgh Institutional Review Board (STUDY21090002). Study findings will be presented in peer-reviewed journals and public health conferences as well as shared with patient participants, community advisory boards and harm reduction organisations., Trial Registration Number: NCT05404750., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Introduction/objectives: Across the United States, and particularly in the South, there is an urgent need to improve health outcomes for people with HIV. In response, the Southeast AIDS Education & Training Center (AETC) conducted a 4-year Practice Transformation (PT) initiative (2015-2018) in 12 mostly primary care clinics across 4 states in the region. Drawing on the leadership of PT facilitators ("coaches") from AETC partner sites throughout the region and specific clinic staff members ("champions"), clinics worked toward self-selected organizational goals to increase their HIV care capacity and improve HIV health outcomes., Methods: To explore coaches' and champions' experiences and perspectives of PT, we conducted 2 focus group sessions, 1 tailored for coaches (n = 5) and another for champions (n = 9)., Results: Content analysis of qualitative data revealed 4 major themes around coaches' and champions' experiences and perspectives of PT. These themes include Challenges, Facilitators, Successes, and Suggestions for PT Improvement., Conclusion: Primary care and infectious diseases/HIV clinics can help improve HIV Care Continuum outcomes through increasing their capacity to serve the needs of their clients, as facilitated through coaches and clinic champions. Since no single clinic or clinic patient population is alike, it is important work within organizations to address specific needs and leverage unique skillsets. Future PT initiatives can learn from experiences of this PT program to optimize the effectiveness of their programs.

Background: Low levels of pre-exposure prophylaxis (PrEP) uptake continue among the most vulnerable (e.g., men who have sex with men) for HIV exposure in the USA. Providers of social and public health services ("psychosocial providers") can help improve this situation by educating patients about PrEP before linking them to primary care providers (PCPs)., Objective: To identify predictors of psychosocial providers offering PrEP education to patients vulnerable to HIV infection by determining the frequency with which psychosocial providers offer PrEP education to patients., Design: Longitudinal overview of PrEP implementation in New York City., Participants: Psychosocial providers of HIV prevention and adjunct treatment services, such as medication adherence counseling in 34 community settings., Main Measures: Longitudinal survey data collected in 2014-2016 (baseline) and 2015-2017 (1-year follow-up) from a 5-year longitudinal repeated measures study. Logistic regression modeling tested associations between baseline psychosocial provider-level and organization-level characteristics and frequency of PrEP education at baseline and 1-year follow-up., Key Results: Out of 245 participants, the number of psychosocial providers offering PrEP education at least once in the past 6 months increased significantly from baseline (n = 127, 51.8%) to 1-year follow-up (n = 161, 65.7%). Participants with higher odds of offering PrEP education at baseline and at one1-year follow-up were more likely to have reported high levels of interprofessional collaboration (IPC) and were also more likely to have received formal HIV prevention training., Conclusions: Both IPC and HIV training are predictive of PrEP education, and this association was maintained over time. We recommend expanding educational outreach efforts to psychosocial providers to further improve PrEP education and also training in interprofessional collaboration. This is an important first step toward linking patients to PCPs who prescribe PrEP and may help improve PrEP uptake.

Clinical trials have demonstrated that preexposure prophylaxis (PrEP) protects against HIV infection; yet, even with its approval by the Food and Drug Administration (FDA) in 2012, less than 10% of eligible users in the United States are currently taking PrEP.While there are multiple factors that influence PrEP uptake and pose barriers to PrEP implementation, here we focus on PrEP's cost in the United States, which, at the current list price of $2000 per month and with high levels of cost sharing, can leave insured users with more than $1000 in out-of-pocket costs every year. We discuss how patient deductibles, monthly premiums, copayments, and coinsurance vary widely and may increase the financial burden. Although drug payment-assistance programs have made PrEP more affordable to uninsured and underinsured users, lack of insurance is a barrier to PrEP accessibility. The FDA approved a generic version in 2017; however, that version has not been distributed to US consumers and may not be more affordable.As other countries begin implementing PrEP programs, the extent of PrEP's availability as a tool in the global fight against HIV remains to be seen.

Background: To obtain optimal health outcomes, persons living with human immunodeficiency virus (HIV) must be retained in clinical care. We examined the relationships between 4 possible combinations of 2 separate retention measures (missed visits and the Institute of Medicine [IOM] indicator) and all-cause mortality., Methods: The sample included 4162 antiretroviral therapy (ART)-naive patients who started ART between January 2000 and July 2010 at any of 5 US sites of the Center for AIDS Research Network of Integrated Clinical Systems. The independent variable of interest was retention, captured over the 12-month period after the initiation of ART. The study outcome, all-cause mortality 1 year after ART initiation, was determined by querying the Social Security Death Index or the National Death Index. We evaluated the associations of the 4 categories of retention with all-cause mortality, using the Cox proportional hazards models., Results: Ten percent of patients did not meet retention standards for either measure (hazard ratio [HR], 2.26; 95% confidence interval [CI], 1.59-3.21). Patients retained by the IOM but not the missed-visits measure (42%) had a higher HR for mortality (1.72; 95% CI, 1.33-2.21) than patients retained by both measures (41%). Patients retained by the missed-visits but not the IOM measure (6%) had the same mortality hazards as patients retained by both measures (HR, 1.01; 95% CI, .54-1.87)., Conclusions: Missed visits within the first 12 months of ART initiation are a major risk factor for subsequent death. Incorporating missed visits in clinical and public health retention and viral suppression programming is advised.

Introduction: There are multiple dimensions of HIV-related stigma that can compromise the mental and physical health of people living with HIV. We focused on the dimension of experienced stigma, defined as exposure to acts of discrimination, devaluation, and prejudice, and investigated its relationship with HIV health and psychosocial outcomes., Methods: We examined associations between experienced stigma in the community and health care settings and psychosocial and health outcomes for people living with HIV (N = 203) receiving care at an urban HIV clinic in the Southeastern United States. We also investigated whether those effects are unique to experienced stigma or are mediated by other dimensions of HIV-related stigma., Results: Experienced stigma was associated with suboptimal clinical outcomes such as viral nonsuppression, as well as poor affective, cognitive, and mental health outcomes (self-esteem, depressive symptoms, avoidance coping, and blame coping) and interpersonal outcomes such as social support and physician trust. Furthermore, serial mediation models suggested significant indirect effects of experienced stigma through internalized stigma and anticipated stigma from various theoretically expected sources of stigma (eg, community members, friends and family, and health care workers), with varying effects depending on the source., Conclusions: These findings suggest nuanced mechanisms for the effects of experienced HIV-related stigma, especially in health care settings, and may be used to inform stigma-reduction interventions. Interventions designed to address experienced stigma in health care settings might be more tailored to specific outcomes, such as depression and physician trust, than interventions designed to address experienced stigma in the community.

The HIV care continuum is a framework that models the dynamic stages of HIV care. The continuum consists of five main steps, which, at the population level, are depicted cross-sectionally as the HIV treatment cascade. These steps include diagnosis, linkage to care (LTC), retention in care (RiC), adherence to antiretroviral therapy (ART), and viral suppression. Although the HIV treatment cascade is represented as a linear, unidirectional framework, persons living with HIV (PLWH) often experience the care continuum in a less streamlined fashion, skip steps altogether, or even exit the continuum for a period of time and regress to an earlier stage. The proportion of PLWH decreases at each successive step of the cascade, beginning with an estimated 86% who are diagnosed and dropping dramatically to approximately 30% of PLWH who are virally suppressed in the United States (US). In this current issues review, we describe each step in the cascade, discuss targeted interventions that address weak points in the continuum, review domestic and international policies that help shape and direct HIV care strategies, and conclude with recommendations and future directions for HIV providers and policymakers. While we primarily examine issues related to domestic HIV care in the US, we also discuss international applications of the continuum in order to provide broader context.

Background: Pleural empyema is a collection of pus between the lungs and the chest wall. There is debate about treatment options with the advent of both fibrinolytic enzymes to facilitate tube drainage and less invasive video-assisted thoracoscopic surgery (VATS)., Objectives: To determine which was more effective: surgical (using thoracoscopy or thoracotomy) or non-surgical techniques (thoracocentesis, chest tube drainage); and to establish whether there was an optimum time for intervention., Search Strategy: In this updated review we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2005, issue 3) which contains the Acute Respiratory Infections Group's specialized register; MEDLINE (January 2002 to July Week 4, 2005); and EMBASE (January 2001 to 3rd Quarter 2005). Bibliographies, reference lists of identified studies and review articles were handsearched. Personal communication with authors is ongoing. There were no language restrictions., Selection Criteria: Randomised controlled trials (RCTs) of surgical techniques versus non-surgical approaches for treatment of pus in the pleural cavity in children and adults but not neonates. Studies of empyema associated with tuberculosis or malignancy were excluded., Data Collection and Analysis: Trial quality was assessed using Jadad criteria (Jadad 1996). Authors were contacted for missing information. The primary outcomes were death or resolution of the empyema. Secondary outcomes addressed the length of time chest tubes were required, pain, hospital stay and any complications., Main Results: Only one small randomised study was identified. Some methodological quality considerations cast doubt on the validity of the study with regard to patient selection, unclear allocation concealment and outcome assessor blinding and it scored 'B' overall (Jadad score 3). When compared with chest tube drainage combined with streptokinase, video-assisted thoracoscopic surgery (VATS) had a significantly higher primary treatment success and patients spent less time in hospital. Each treatment group suffered one mortality. The latest search revealed no further published randomised studies but communication with authors revealed two ongoing studies comparing conventional chest tube drainage plus antibiotics with and without fibrinolytics with video-assisted thorascopic surgery (VATS). A small unpublished study is awaiting assessment that compared chest tube drainage and antibiotics with thoracoscopy or thoracotomy plus antibiotics., Authors' Conclusions: It seems that for large, loculated pleural empyemas VATS is superior to chest tube drainage in terms of duration of chest tubes in situ and length of hospital stay. However, there are questions about validity in the one study which met the inclusion criteria and the study has too few participants to draw conclusions. There are risks of complications (associated with all treatments) which may not be apparent with small numbers. Larger studies are needed.

We have identified sequence variants in the 3' untranslated region of the insulin promoter factor 1 (Ipf1) cDNA sequence in mice and used a PCR-based oligonucleotide hybridization assay to map the Ipf1 gene to distal mouse chromosome (Chr) 5. An identical 12-bp insertion in the 3' untranslated region of the mouse Ipf1 gene sequence is present in Mus spretus and Mus m. musculus Czech II mice, two feral strains used for meiotic mapping by backcross analysis. The human IPF1 gene homolog would be expected to map to either chromosome 13q12-q14 or 7pter-q21 based on homology of synteny of other loci in this region of mouse Chr 5. Given its genetic map position, the Ipf1 gene may be part of a cassette of homeodomain-containing transcription factors involved in the development of the pancreas and other foregut-derived organs.

Fertilization of the sea urchin egg is accompanied by the assembly of an extracellular glycoprotein coat, the fertilization membrane. Assembly of the fertilization membrane involves exocytosis of egg cortical granules, divalent cation-mediated association of exudate proteins with the egg glycocalyx (the vitelline layer), and cross-linking of the assembled structure by ovoperoxidase, a fertilization membrane component derived from the cortical granules. We have identified and isolated a new protein, which we call proteoliaisin, that appears to be responsible for inserting ovoperoxidase into the fertilization membrane. Proteoliaisin is a 250,000-Mr protein that binds ovoperoxidase in a Ca2+-dependent manner, with half-maximal binding at 50 microM Ca2+. Other divalent cations are less effective (Ba2+, Mn2+, and Sr2+) or ineffective (Mg2+ and Cd2+) in mediating the binding interaction. Binding is optimal over the physiological pH range of fertilization membrane assembly (pH 5.5-7.5). Both proteoliaisin and ovoperoxidase are found in isolated, uncross-linked fertilization membranes. We have identified several macromolecular aggregates that are released from uncross-linked fertilization membranes after dilution into divalent cation-free buffer. One of these is an ovoperoxidase-proteoliaisin complex that is further disrupted only upon the addition of EGTA. These results suggest that a Ca2+-stabilized complex of ovoperoxidase and proteoliaisin forms one structural subunit of the fertilization membrane.

The ovoperoxidase from the egg of the sea urchin, Strongylocentrotus purpuratus, has been purified to apparent homogeneity. Ovoperoxidase is secreted from the egg at fertilization and is responsible, in vivo, for hardening of the fertilization membrane by forming cross-links between protein tyrosyl residues. Purification was accomplished by activation of cortical granule exocytosis with acetic acid, followed by NH4SO4 precipitation, DEAE-Sephacel chromatography in the absence of divalent cations, and CM-Sephadex chromatography. The purified enzyme is a glycoprotein of Mr 70,000, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme exhibits a UV-visible spectrum typical of heme peroxidases (epsilon 412 = 1.19 X 10(5) M-1 cm-1). Ovoperoxidase catalyzes the oxidation of tyrosine, guaiacol, iodide, and bromide, but not chloride, and can employ either H2O2 or, with 8% relative efficiency, ethyl peroxide as an oxidative substrate. Phenylhydrazine, 3-amino-1,2,4-triazole, azide, and sulfite all inhibit purified ovoperoxidase at concentrations similar to those that inhibit hardening in vivo. Inhibition by 3-amino-1,2,4-triazole is reversible, requires H2O2, and is slow relative to substrate turnover. The purified enzyme is sensitive to protease cleavage in the native state, yielding an active product of Mr approximately 50,000 which varies slightly depending upon the protease employed. Ovoperoxidase should provide a useful tool for the study of fertilization membrane formation as a paradigm of macromolecular assembly and modification.