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Curriculum change involves struggles among political actors and interest groups, and those efforts related to sex education have been noted for their particularly vexatious character. When Doug Ford was elected Premier of Ontario, Canada in 2018, he immediately repealed the comprehensive health curriculum of 2015 and attempted to muzzle teachers during the 2018-2019 school year, only to unveil a strikingly similar "new" curriculum for 2019-2020. This article analyses Ford's treatment of sex education as part of a conservative populist agenda. Using Critical Discourse Analysis, we divide the government's approach into six components that illustrate how anti-elitism and fact-bending drove curriculum policy. Our analysis contributes to discussions in curriculum studies and educational politics by connecting the recently ascendant political ideologies in the West with the already contentious area of sex education.

Vaccination and infection promote the formation, tissue distribution, and clonal evolution of B cells, which encode humoral immune memory. We evaluated pediatric and adult blood and deceased adult organ donor tissues to determine convergent antigen-specific antibody genes of similar sequences shared between individuals. B cell memory varied for different pathogens. Polysaccharide antigen-specific clones were not exclusive to the spleen. Adults had higher clone frequencies and greater class switching in lymphoid tissues than blood, while pediatric blood had abundant class-switched convergent clones. Consistent with reported serology, prepandemic children had class-switched convergent clones to severe acute respiratory syndrome coronavirus 2 with weak cross-reactivity to other coronaviruses, while adult blood or tissues showed few such clones. These results highlight the prominence of early childhood B cell clonal expansions and cross-reactivity for future responses to novel pathogens., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

This proof-of-concept study tests the initial efficacy of the Building a Strong Identity and Coping Skills (BaSICS) intervention, a selective prevention of internalizing problems program for early adolescents exposed to high levels of poverty-related stress. Eighty-four early adolescents (M age  = 11.36 years) residing in very low-income neighborhoods were randomized to receive the 16-session intervention (n = 44) or to an assessment-only control condition (n = 40). BaSICS teaches coping skills, social identity development, and collective social action to empower youth with the ability to connect with members of their communities and cope with poverty-related stress in positive and collaborative ways. Pretest-posttest analyses showed that intervention adolescents acquired problem-solving and cognitive-restructuring skills and reduced their reliance on avoidant coping. In addition, HPA reactivity was significantly reduced in the intervention youth, but not controls. Finally, intervention youth's internalizing and somatic symptoms as reported by both youth and their parents, showed significant reductions over time, whereas control youth had no such changes. Results provide strong support for this approach to strength-building and symptom reduction in a population of early adolescents exposed to poverty-related stress., (© 2019 Society for Community Research and Action.)

This article aims to integrate theory and empirical findings about understanding and fostering the process of resilience and adaptation in children and families who live in poverty. In this article, we draw from multiple, somewhat distinct, scholarly streams to identify sources of protection, integrating across the literatures on stress and coping, psychophysiology, cultural identity development, and empowerment theory. Because living in poverty cuts across other dimensions of social differentiation and structural inequality, intersectionality theory frames our discussion of how to leverage poverty-affected youths' diverse experiences. We present a framework to guide intervention and research on resiliency promotion, describe the Building a Strong Identity and Coping Skills intervention stemming from the framework, and suggest possible avenues and next steps for both interventions and research.

Objectives: Although chemoradiation is the standard of care for anal cancer, limited data exist regarding pelvic reirradiation (re-RT) for recurrent disease. We investigated toxicity and outcomes in patients who received prior pelvic radiation therapy (RT), and subsequently underwent hyperfractionated accelerated re-RT to the pelvis for recurrent anal cancer., Materials and Methods: We reviewed records of 10 patients with recurrent anal squamous cell carcinoma who previously received pelvic RT to at least 30 Gy as a component of their chemoradiation and underwent re-RT in 1.5 Gy twice daily fractions to the pelvis, with either preoperative (N=7) or definitive (N=3) intent., Results: The 3-year disease-free survival and 3-year overall survival rates were 40% and 60%. Four patients recurred within the reirradiated field, with a 3-year freedom from local progression rate of 56%. Of the 7 patients treated with preoperative intent, 5 proceeded to surgery, of whom 3 are alive and disease-free at a median duration of 43 months. Of the 3 patients treated definitively with no surgery, all are alive and disease-free at a median duration of 84 months. Re-RT resulted in one grade 3 acute toxicity and no grade 3 or higher late complications., Conclusions: Hyperfractionated accelerated re-RT was well-tolerated in patients with previously irradiated anal cancer. Patients treated with either definitive re-RT or re-RT followed by surgical resection had excellent rates of overall survival and freedom from local progression.

To determine whether pre-treatment neutrophil/lymphocyte (NLR) or platelet/lymphocyte ratios (PLR) are predictive for progression in early-stage classical Hodgkin lymphoma (cHL), we derived NLR and PLR values for 338 stage I/II cHL patients and appropriate cut-off point values to define progression. Two-year freedom from progression (FFP) for patients with NLR ≥6·4 was 82·2% vs. 95·7% with NLR <6·4 (P < 0·001). Similarly, 2-year FFP was 84·3% for patients with PLR ≥266·2 vs. 96·1% with PLR <266·2 (P = 0·003). On univariate analysis, both NLR and PLR were significantly associated with worse FFP (P = 0·001). On multivariate analysis, PLR remained a significant, independent prognostic factor (P < 0·001)., (© 2017 John Wiley & Sons Ltd.)

The presence of bulky disease in Hodgkin lymphoma (HL), traditionally defined with a 1-dimensional measurement, can change a patient's risk grouping and thus the treatment approach. We hypothesized that 3-dimensional measurements of disease burden obtained from baseline 18 F-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) scans, such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG), would more accurately risk-stratify patients. To test this hypothesis, we reviewed pretreatment PET-CT scans of patients with stage I-II HL treated at our institution between 2003 and 2013. Disease was delineated on prechemotherapy PET-CT scans by 2 methods: (1) manual contouring and (2) subthresholding of these contours to give the tumor volume with standardized uptake value ≥2.5. MTV and TLG were extracted from the threshold volumes (MTV t , TLG t ) and from the manually contoured soft-tissue volumes. At a median follow-up of 4.96 years for the 267 patients evaluated, 27 patients were diagnosed with relapsed or refractory disease and 12 died. Both MTV t and TLG t were highly correlated with freedom from progression and were dichotomized with 80th percentile cutoff values of 268 and 1703, respectively. Consideration of MTV and TLG enabled restratification of early unfavorable HL patients as having low- and high-risk disease. We conclude that MTV and TLG provide a potential measure of tumor burden to aid in risk stratification of early unfavorable HL patients., (© 2018 by The American Society of Hematology.)

Early-stage classical Hodgkin lymphoma (HL) patients are evaluated by an end-of-chemotherapy positron emission tomography-computed tomography (eoc-PET-CT) after doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) and before radiation therapy (RT). We determined freedom from progression (FFP) in patients treated with ABVD and RT according to the eoc-PET-CT 5-point score (5PS). Secondarily, we assessed whether patients with a positive eoc-PET-CT (5PS of 4-5) can be cured with RT alone. The cohort comprised 174 patients treated for stage I-II HL with ABVD and RT alone. ABVD was given with a median of four cycles and RT with a median dose of 30·6 Gy. Five-year FFP was 97%. Five-year FFP was 100% (0 relapses/98 patients) for patients with a 5PS of 1-2, 97% (2/65) for a 5PS of 3, 83% (1/8) for a 5PS of 4, and 67% (1/3) for a 5PS of 5 (P < 0·001). Patients with positive eoc-PET-CT scans who were selected for salvage RT alone had experienced a very good partial response to ABVD. Risk factors for recurrence in this subgroup included a small reduction in tumour size and a 'bounce' in ≥1 PET-CT parameter (reduction then rise from interim to final scan). Thus, a positive eoc-PET-CT is associated with inferior FFP; however, appropriately selected patients can be cured with RT alone., (© 2017 John Wiley & Sons Ltd.)

Purpose: Treatment for locoregionally advanced cervical cancer has changed dramatically since 2000. In that year, delivery of radiation therapy with concurrent chemotherapy became standard, and in the early 2000s, use of intensity modulated RT (IMRT) and positron emission tomography (PET) became more prevalent. We sought to determine the impact of these changes on disease-specific survival (DSS) and treatment-related adverse effects in patients with cervical cancer with para-aortic lymph node (PAN) metastases treated with definitive extended-field radiation therapy., Methods and Materials: We reviewed the medical records of 103 patients with cervical cancer with PAN metastases treated with curative intent at our institution during 2000 to 2013. DSS, disease control in PANs, and treatment-associated adverse effects were compared between patient groups defined by treatment year., Results: The 5-year DSS rate was 23% (95% confidence interval, 9%-38%) for the 34 patients treated from 2000 to 2004, and 47% (95% confidence interval, 36%-59%) for the 69 patients treated from 2005 to 2013 (P = .005). Factors associated with improved DSS included concurrent chemoradiation (P = .001), baseline PET imaging (P = .01), and treatment of PANs with IMRT (P = .02). Only 3 patients (4%) treated from 2005 to 2013 versus 6 patients (18%) treated from 2000 to 2004 had recurrence in PANs (P = .03). Most recurrences in patients treated from 2005 to 2013 were at distant sites. The crude rate of grade 3 or higher late treatment-related adverse effects was 17%; of the 18 patients who developed serious adverse effects, 8 were being treated for recurrent disease at the time. Adverse effects most frequently involved the gastrointestinal and genitourinary systems., Conclusions: Outcomes for patients with cervical cancer with PAN metastases have improved concurrently with advances in treatment, including PET and IMRT. Future studies should focus on ways to improve systemic treatments and reduce late adverse effects without compromising local control., (Copyright © 2016 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.)

Purpose: In early-stage classical Hodgkin lymphoma, fluorodeoxyglucose positron emission tomography (PET)-computed tomography (CT) scans are performed routinely after chemotherapy, and the 5-point Deauville score is used to report the disease response. We hypothesized that other PET-CT parameters, considered in combination with Deauville score, would improve risk stratification., Methods and Materials: Patients treated for stage I to II Hodgkin lymphoma from 2003 to 2013, who were aged ≥18 years and had analyzable PET-CT scans performed before and after chemotherapy, were eligible. The soft tissue volume (STV), maximum standardized uptake value, metabolic tumor volume, and total lesion glycolysis were recorded from the PET-CT scans before and after chemotherapy. Reductions were defined as 1 - (final PET-CT value)/(corresponding initial PET-CT value). The primary endpoint was freedom from progression (FFP)., Results: For 202 patients treated with chemotherapy with or without radiation therapy, the 5-year FFP was 89% (95% confidence interval 85%-93%). All PET-CT parameters were strongly associated with the Deauville score (P<.001) and FFP (P<.0001) on univariate analysis. The Deauville score was highly predictive of FFP (C-index 0.89) but was less discriminating in the Deauville 1 to 4 subset (C-index 0.67). Therefore, we aimed to identify PET-CT parameters that would improve risk stratification for this subgroup (n=187). STV reduction was predictive of outcome (C-index 0.71) and was dichotomized with an optimal cutoff of 0.65 (65% reduction in STV). A model incorporating the Deauville score and STV reduction predicted FFP more accurately than either measurement alone in the Deauville 1 to 4 subset (C-index 0.83). The improvement in predictive accuracy of this composite measure compared with the Deauville score alone met statistical significance (P=.045)., Conclusions: The relative reduction in tumor size is an independent predictor of outcome. Combined with the Deauville score, it might improve risk stratification and contribute to response-adapted individualization of therapy., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: The German Hodgkin Study Group HD11 trial validated 4 cycles of doxorubicin, bleomycin, vinblastine, dacarbazine (ABVD) chemotherapy followed by involved field radiation therapy (IFRT) for early unfavorable Hodgkin lymphoma (HL) patients. However, practitioners often recommend 6 cycles followed by RT, especially for bulky disease. We compared patient outcomes after treatment with 4 or 6 cycles of ABVD followed by RT (IFRT and involved site RT [ISRT])., Methods and Materials: We identified 128 patients treated for early unfavorable HL (GHSG criteria) between 2000 and 2013. Clinical outcomes (overall survival [OS] and freedom from relapse [FFR]) were estimated using Kaplan-Meier analysis. Toxicities were evaluated., Results: The median follow-up time was 5.0 years. Patients received 4 (70 patients, 55%) or 6 (58 patients, 45%) cycles of chemotherapy. Bulky disease was present in 22 patients (31%; 0 stage IA, 3 stage IB, 19 stage IIA) of the 4-cycle group and 42 patients (72%; 5 stage IA, 3 stage IB, 34 stage IIA) of the 6-cycle group. For patients receiving 4 and 6 cycles, the 6-year OS was 100% and 97% (P=.35), respectively, and the 6 year FFR was 100% and 98% (P=.28), respectively. More patients received 6 cycles if they were treated before 2010 (HD11 report) (P=.01) and if they had bulky disease (P<.01). Sixty-eight percent of patients received ISRT. The 6-year FFR was 99% and 100% for patients receiving ISRT and IFRT, respectively (P=.58). More patients experienced bleomycin pulmonary toxicity in the 6-cycle group (20% vs 31%, P=.16). For patients with bulky disease, the 4-year FFR was similar with receipt of 4 (100%) or 6 (98%) cycles (P=.48) and IFRT (100%) or ISRT (98%) (P=.52). There were no deaths among patients with bulky disease., Conclusions: Patients with early unfavorable HL have excellent outcomes with 4 cycles of ABVD chemotherapy followed by ISRT. Six cycles of chemotherapy does not appear superior for disease control, even for bulky disease., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Importance: The management of lymphoma diagnosed during pregnancy is controversial and has been guided largely by findings from case reports and small series., Objective: To determine maternal and fetal outcomes of women diagnosed with Hodgkin lymphoma (HL) or non-Hodgkin lymphoma (NHL) during pregnancy., Design, Setting, and Participants: This retrospective analysis studied a cohort of 39 pregnant women diagnosed with HL and NHL (31 HL and 8 NHL) at a single specialized cancer institution between January 1991 and December 2014., Main Outcomes and Measures: We examined data on disease and treatment characteristics, as well as maternal and fetal complications and outcomes. The Kaplan-Meier method was used to compare progression free survival (PFS) and overall survival (OS) according to receipt of antenatal therapy and other clinical factors. Univariate and multivariate analyses were performed by using Cox proportional hazard regression models to identify potential associations between clinical and treatment factors and survival., Results: The median (range) age of the 39 women in the patient cohort was 28 (19-38) years; 32 women (82%) had stage I or II disease at diagnosis, and 13 had bulky disease. Three women electively terminated the pregnancy to allow immediate systemic therapy; of the remaining 36 women, 24 received antenatal therapy (doxorubicin based combination chemotherapy in 20 of 24 patients), and 12 deferred therapy until after delivery. Four women experienced miscarriage, all of whom had received antenatal systemic therapy and 2 during the first trimester. Delivery occurred at a median (range) of 37 (32-42) weeks and was no different based on receipt of antenatal (median [range], 37 [33-42] weeks) vs postnatal (median [range], 37 [32-42] weeks) therapy (P = .21). No gross fetal malformations or anomalies were detected. At a median (range) follow-up time of 67.9 (8.8-277.5) months since the diagnosis of lymphoma, 5-year rates of PFS and OS were 74.7% and 82.4%, respectively; these rates did not differ according to timing of therapy. On univariate analysis, bulky disease (>10 cm), extranodal nonbone marrow involvement, and poor performance status (Eastern Cooperative Oncology Group score, ≥2) predicted increased risk of disease progression. On multivariate analysis, extranodal nonbone marrow disease and performance status remained significant for both PFS and OS., Conclusions and Relevance: Systemic therapy given for lymphoma after the first trimester of pregnancy is likely safe and results in acceptable maternal and fetal outcomes.

Background and Purpose: Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive malignancy. We report survival rates and toxicity associated with sequential multimodality treatment including whole abdominopelvic radiation therapy (WART)., Material and Methods: Medical records of 32 patients with DSRCT treated at our institution were reviewed. Patients underwent chemotherapy, cytoreductive surgery with hyperthermic intraperitoneal chemoperfusion (HIPEC), followed by WART with intensity-modulated radiation or volumetric-modulated arc therapy., Results: Median overall survival (OS) was 60months. After 18months of follow-up, 20 patients (62.5%) had disease recurrence and median disease-free survival (DFS) was 10months. Median time to extrahepatic abdominal failure was 19.4months. Factors affecting time to local progression included liver metastases at diagnosis, and an interval of greater than 5.6months between diagnosis and HIPEC or greater than 2.1months between HIPEC and WART. None of these factors altered OS. Grade 3 or higher toxicities occurred in 84% of patients., Conclusions: WART following chemotherapy, surgical cytoreduction and HIPEC is an aggressive treatment for DSRCT patients and can result in severe side effects. Our median OS of 5years is favorable compared to prior studies, despite a median DFS of only 10months, which may be due to improved salvage therapies., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Primary cutaneous B cell lymphomas (PCBCL) are rare; although data on outcomes and treatment are limited, traditionally they have been treated with radiation doses in excess of 24 Gy. We retrospectively identified and reviewed all cases of PCBCL treated at our institution from 2002-2014. Thirty-nine patients with PCBCL (42 lesions) were identified. Radiation was the only treatment for most patients. All lesions had a complete response and none had in-field failures; seven patients had out-of-field relapses, three of which were salvaged with radiation therapy. No differences in PFS or OS were found for patients given low-dose (≤ 12 Gy) versus high-dose (> 12 Gy) radiation. PCBCL is an indolent entity with a long clinical course and excellent response to radiation therapy and successful salvage of recurrent disease, even when doses are as low as 4 Gy. Given the above findings, we recommend the initial use of low-dose irradiation for PCBCL.

Background: Treatment of stage IIB bulky Hodgkin lymphoma (HL) is controversial, with treatment varying by institution. We evaluated patients with IIB bulky disease treated with combined-modality therapy at our institution by describing their long-term outcomes., Patients and Methods: We identified 149 consecutive patients with stage IIB bulky HL treated between 1971 and 2012. Clinical, pathologic, and treatment characteristics were extracted from medical records. Actuarial overall survival (OS) and relapse-free survival (RFS) were calculated by the Kaplan-Meier method. Independent factors associated with these outcomes were identified by a multivariate Cox regression model. Outcomes were further compared against comparison groups of both advanced-stage and stage IIB patients treated between 1971 and 2009., Results: The 8-year OS rate for patients with stage IIB bulky disease who received combined-modality ABVD (doxorubicin, bleomycin, vinblastine, dacarbazine) and radiation was 88.8%; the 8-year RFS rate was 76.8%. On multivariate analysis, age < 40 years (hazard ratio [HR], 0.28; 95% confidence interval [CI], 0.14-0.57; P = .001), receipt of ABVD (vs. MOPP [mechlorethamine, vincristine, procarbazine, prednisone]; HR, 0.32; 95% CI, 0.10-0.88; P = .028), and radiation dose ≥ 30.1 Gy (HR, 0.25; 95% CI, 0.11-0.65; P = .006) were associated with improved OS. Cardiac events (n = 11) and secondary malignancies (n = 11) only occurred in patients treated before 1995. A subgroup analysis demonstrated significantly improved survival in IIB bulky versus advanced-stage patients (8-year OS, 73.4% vs. 57.4%; P = .008). Improved outcomes in patients with in IIB bulky disease were especially evident in the modern era (> 1995; P = .004)., Conclusion: Patients with stage IIB bulky HL had excellent outcomes after combined-modality therapy. Treatment strategies have changed substantially over time, with concomitant improvements in disease outcomes and long-term toxicities., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: Few studies to date have evaluated factors associated with the development of radiation pneumonitis (RP) in patients with Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL), especially in patients treated with contemporary radiation techniques. These patients represent a unique group owing to the often large radiation target volumes within the mediastinum and to the potential to receive several lines of chemotherapy that add to pulmonary toxicity for relapsed or refractory disease. Our objective was to determine the incidence and clinical and dosimetric risk factors associated with RP in lymphoma patients treated with intensity modulated radiation therapy (IMRT) at a single institution., Methods and Materials: We retrospectively reviewed clinical charts and radiation records of 150 consecutive patients who received mediastinal IMRT for HL and NHL from 2009 through 2013. Clinical and dosimetric predictors associated with RP according to Radiation Therapy Oncology Group (RTOG) acute toxicity criteria were identified in univariate analysis using the Pearson χ(2) test and logistic multivariate regression., Results: Mediastinal radiation was administered as consolidation therapy in 110 patients with newly diagnosed HL or NHL and in 40 patients with relapsed or refractory disease. The overall incidence of RP (RTOG grades 1-3) was 14% in the entire cohort. Risk of RP was increased for patients who received radiation for relapsed or refractory disease (25%) versus those who received consolidation therapy (10%, P=.019). Several dosimetric parameters predicted RP, including mean lung dose of >13.5 Gy, V20 of >30%, V15 of >35%, V10 of >40%, and V5 of >55%. The likelihood ratio χ(2) value was highest for V5 >55% (χ(2) = 19.37)., Conclusions: In using IMRT to treat mediastinal lymphoma, all dosimetric parameters predicted RP, although small doses to large volumes of lung had the greatest influence. Patients with relapsed or refractory lymphoma who received salvage chemotherapy and hematopoietic stem cell transplantation were at higher risk for symptomatic RP., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

O-Phosphoserine (Sep), the most abundant phosphoamino acid in the eukaryotic phosphoproteome, is not encoded in the genetic code, but synthesized posttranslationally. Here, we present an engineered system for specific cotranslational Sep incorporation (directed by UAG) into any desired position in a protein by an Escherichia coli strain that harbors a Sep-accepting transfer RNA (tRNA(Sep)), its cognate Sep-tRNA synthetase (SepRS), and an engineered EF-Tu (EF-Sep). Expanding the genetic code rested on reengineering EF-Tu to relax its quality-control function and permit Sep-tRNA(Sep) binding. To test our system, we synthesized the activated form of human mitogen-activated ERK activating kinase 1 (MEK1) with either one or two Sep residues cotranslationally inserted in their canonical positions (Sep(218), Sep(222)). This system has general utility in protein engineering, molecular biology, and disease research.

Potential metal interactions with the cleavage site of a minimal hammerhead ribozyme (mHHRz) were probed using (31)P NMR-detected Cd(2+) titration studies of HHRz constructs containing a phosphorothioate (PS) modification at the cleavage site. The mHHRz nucleophile position was replaced by either a 2'-F or a 2'-NH(2) in order to block cleavage activity during the study. The 2'-F/PS cleavage site mHHRz construct, in which the 2'-F should closely imitate the atom size and electronegativity of a 2'-OH, demonstrates low levels of metal ion association (<1 ppm (31)P chemical shift changes). This observation indicates that having an atom size and electrostatic properties that are similar to the 2'-OH are not the governing factors in allowing metal interactions with the scissile phosphate of the mHHRz. With a 2'-NH(2) substitution, a large upfield change in (31)P NMR chemical shift of the phosphorothioate peak (Delta approximately 3 ppm with 6 equiv of added Cd(2+)) indicates observable Cd(2+) interactions with the substituted site. Since a 2'-NH(2), but not a 2'-F, can serve as a metal ligand, these data suggest that a metal ion interaction with the HHRz cleavage site may include both the scissile phosphate and the 2' nucleophile. Control samples in which the 2'-NH(2)/PS unit is placed either next to the mHHRz cleavage site (at U16.1), in a duplex, or in a (am)U(PS)U dinucleotide show much weaker interactions with Cd(2+). Results with these control samples indicate that simply the presence of a 2'-NH(2)/PS unit does not create a strong metal binding site, reinforcing the possibility that the 2'-NH(2)-moderated Cd-PS interaction is specific to the mHHRz cleavage site. Upfield chemical shifts of both (31)P and H-2' (1)H resonances in (am)U(PS)U are observed with addition of Cd(2+), consistent with the predicted metal coordination to both 2'-NH(2) and phosphorothioate ligands. These data suggest that metal ion association with the HHRz cleavage site may include an interaction with the 2'-OH nucleophile.

A recent re-examination of the role of the helices surrounding the conserved core of the hammerhead ribozyme has identified putative loop-loop interactions between stems I and II in native hammerhead sequences. These extended hammerhead sequences are more active at low concentrations of divalent cations than are minimal hammerheads. The loop-loop interactions are proposed to stabilize a more active conformation of the conserved core. Here, a kinetic and thermodynamic characterization of an extended hammerhead sequence derived from Schistosoma mansoni is performed. Biphasic kinetics are observed, suggesting the presence of at least two conformers, one cleaving with a fast rate and the other with a slow rate. Replacing loop II with a poly(U) sequence designed to eliminate the interaction between the two loops results in greatly diminished activity, suggesting that the loop-loop interactions do aid in forming a more active conformation. Previous studies with minimal hammerheads have shown deleterious effects of Rp-phosphorothioate substitutions at the cleavage site and 5' to A9, both of which could be rescued with Cd2+. Here, phosphorothioate modifications at the cleavage site and 5' to A9 were made in the schistosome-derived sequence. In Mg2+, both phosphorothioate substitutions decreased the overall fraction cleaved without significantly affecting the observed rate of cleavage. The addition of Cd2+ rescued cleavage in both cases, suggesting that these are still putative metal binding sites in this native sequence.

The risk of contracting HIV infection as a result of rape is unknown. We describe 4 female patients who were found to have antibodies to HIV-1 following rape, only one of whom had another recognized risk factor for HIV infection. The need for careful follow-up of rape victims, and the potential for HIV acquisition by the assailant is discussed.