Causes of loss to follow-up from drug-resistant TB treatment in Khayelitsha, South Africa.

Patients initiated on drug-resistant TB(DR-TB) treatment in 2019 in Khayelitsha, South Africa, with a loss to follow-up outcome were evaluated to better understand reasons for loss to follow-up and to determine if any had returned to care. Of a total of 187 patients, 28 (15%) were lost to follow-up (LTFU), 24 (86%) of whom were traced: 20/24 (83%) were found when they re-presented to facilities and 8/28 (29%) were linked back to DR-TB care. People with DR-TB continue to seek care even after being LTFU; thus better coordination between different components of the healthcare system are required to re-engage with these patients. Interventions to mitigate the socio-economic challenges of people on DR-TB treatment are needed. Many people who were LTFU and symptomatic were willing to re-engage with DR-TB care, which highlights the importance of for compassionate interventions to welcome them back.

Les patients placés sous traitement pour TB pharmacorésistante (DR-TB) en 2019 à Khayelitsha, Afrique du Sud, et ayant été perdus de vue ont été évalués afin de mieux comprendre les raisons de la perte de vue et de déterminer si certains étaient de nouveau suivis. Sur 187 patients, 28 (15%) ont été perdus de vue, dont 24 (86%) ont été retrouvés : 20/24 (83%) ont été retrouvés lorsqu'ils se sont de nouveau présentés en consultation et 8/28 (29%) ont été réinsérés dans le parcours de soins de la DR-TB. Les patients atteints de DR-TB sont toujours en demande de soins, même après avoir été perdus de vue. Ainsi, une meilleure coordination entre les différentes composantes du système de santé est nécessaire afin de rétablir le lien avec ces patients. Des interventions visant à atténuer les problèmes socio-économiques des patients sous traitement pour DR-TB sont nécessaires. De nombreux patients symptomatiques ayant été perdus de vue étaient enclins à reprendre leur traitement de la DR-TB. Il est donc important de mettre en place des programmes compassionnels afin de les réinsérer dans le parcours de soins.

Leveraging nurse practitioner capacities to achieve global health for all: COVID-19 and beyond.

AIM: To argue that nurse practitioners have been under-utilized generally in the current global health environment, creating barriers to achieving universal health coverage and the Sustainable Development Goals. BACKGROUND: Nurse practitioners are advanced practice nurses possessing expert knowledge and leadership skills that can be optimized to narrow disparities and ensure access to high-quality health care globally. Nurses worldwide have been challenged to meet global public health needs in the context of COVID-19 (SARS-CoV-2 virus), and there are early indications that nurse practitioners are being called upon to the full extent of their capabilities in the current pandemic. SOURCES OF EVIDENCE: PubMed; Google Scholar; the International Council of Nurses; World Health Organization; United Nations; and the experiences of the authors. DISCUSSION: Several international reports, nursing and health organizations have called for continued investment in and development of nursing to improve mechanisms that promote cost-effective and universally accessible care. Expanding nurse practitioner scopes of practice across nations will leverage their clinical capacities, policy and advocacy skills, and talents to lead at all levels. CONCLUSION: Ongoing empirical data and policy change is needed to enable the full scope and strategic utilization of nurse practitioners across healthcare systems and contexts. IMPLICATIONS FOR NURSING PRACTICE, AND NURSING AND HEALTH POLICY: Widespread education regarding nurse practitioner capacities for interdisciplinary partners, policymakers and the public is needed. Policies that safely expand their roles are critical. Role titles and remuneration reflective of their scope and service are required to lead, sustain and grow the workforce internationally.

Crystal structure of an Xrcc4-DNA ligase IV complex.

A complex of two proteins, Xrcc4 and DNA ligase IV, plays a fundamental role in DNA non-homologous end joining (NHEJ), a cellular function required for double-strand break repair and V(D)J recombination. Here we report the crystal structure of human Xrcc4 bound to a polypeptide that corresponds to the DNA ligase IV sequence linking its two BRCA1 C-terminal (BRCT) domains. In the complex, a single ligase chain binds asymmetrically to an Xrcc4 dimer. The helical tails of Xrcc4 undergo a substantial conformational change relative to the uncomplexed protein, forming a coiled coil that unwinds upon ligase binding, leading to a flat interaction surface. A buried network of charged hydrogen bonds surrounded by extensive hydrophobic contacts explains the observed tightness of the interaction. The strong conservation of residues at the interface between the two proteins provides evidence that the observed mode of interaction has been maintained in NHEJ throughout evolution.

Development and characterization of tissue-engineered aortic valves.

Tissue-engineered aortic valves, known as recellularized heart valves, were developed by seeding human neonatal fibroblasts onto decellularized, porcine aortic valves. Recellularized heart valves were cultured up to 8 weeks in a novel bioreactor that imposed dynamic pulsatile fluid flow to expose the dermal fibroblasts to mechanical forces. Our data showed that, under static or dynamic flow conditions, dermal fibroblasts attached to and migrated into the decellularized, porcine valve scaffolding. The human cells remained viable as indicated by MTT viability staining. Gradual colonization of the decellularized porcine scaffolding by the human dermal fibroblasts was shown histologically by hematoxylin & eosin staining, immunocytochemically using a monoclonal antibody directed against prolyl-4-hydroxylase (an intracellular enzyme expressed by human fibroblasts synthesizing collagen), and quantitative digital image analyses. Thymidine and proline radiolabeled analog studies at 1, 2 and 4 weeks of individual leaflets cultured statically demonstrated that the human fibroblasts were mitotic and synthesized human extracellular matrix proteins, thereby supplementing the existing porcine matrix. The overall approach results in a heart valve populated with viable human cells. In the development of valves that perform in a similar manner as natural biological structures, this approach may present some unique benefits over current medical therapies.

Protein-protein interactions in receptor activation and intracellular signalling.

We review here signalling complexes that we have defined using X-ray analysis in our laboratory. They include growth factors and their receptors: nerve growth factor (NGF) and its hetero-hexameric 7S NGF storage complex, hepatocyte growth factor/scatter factor (HGF/SF) NK1 dimers and fibroblast growth factor (FGF1) in complex with its receptor (FGFR2) ectodomain and heparin. We also review our recent structural studies on intracellular signalling complexes, focusing on phosducin transducin GPry, CK2 protein kinase and its complexes, and the cyclin D-dependent kinase, Cdk6, bound to the cell cycle inhibitor p19INK4d. Comparing the structures of these complexes with others we show that the surface area buried in signalling interactions does not always give a good indication of the strength of the interactions. We show that conformational changes are often important in complexes with intermediate buried surface areas of 1500 to 2000 A2, such as Cdk6INK4 interactions. Some interactions involve recognition of continuous epitopes, where there is no necessity for a tertiary structure and very often the binding conformation is induced during the process of interaction, for example phosducin binding to the betagamma subunits (Gtbetagamma) of the heterotrimeric G protein transducin.

Crystal structure of aspartate decarboxylase at 2.2 A resolution provides evidence for an ester in protein self-processing.

The structure of L-aspartate-alpha-decarboxylase from E. coli has been determined at 2.2 A resolution. The enzyme is a tetramer with pseudofour-fold rotational symmetry. The subunits are six-stranded beta-barrels capped by small alpha-helices at each end. The active sites are located between adjacent subunits. The electron density provides evidence for catalytic pyruvoyl groups at three active sites and an ester at the fourth. The ester is an intermediate in the autocatalytic self-processing leading to formation of the pyruvoyl group. This unprecedented structure provides novel insights into the general phenomenon of protein processing.

A stereotypic, transplantable liver tissue-culture system.

A method of coculturing adult rat hepatic parenchymal cells (PC) and stromal cells in a three-dimensional framework of nylon filtration screens or biodegradable polymer meshes was developed in our laboratory. Rat liver stroma, which includes vascular and bile duct endothelial cells, fat-storing cells, fibroblasts, and Kupffer cells, were isolated by gradient centrifugation after in situ liver perfusion and expanded in monolayer culture prior to seeding onto nylon screens or bioresorbable polyglycolic acid (PGA) polymers oriented into a felt-like construct. A second inoculum of freshly isolated PC was applied after the stromal cells became established. Histological analyses revealed that PC proliferation occurred until all available space for expansion within the template was exhausted. These cells retained their rounded morphology, and after 4-5 wk 7-9 "layers" of PC filled the 140-microns deep template. Dioxin-inducible cytochrome P450 activity was detected for up to 58 d in culture, and albumin, fibrinogen, transferrin, and soluble fibronectin were detected in the medium by enzyme-linked immunosorbent assay (ELISA) for 48 d in vitro. Immunohistochemical analysis of sections through the cultures confirmed the presence of these proteins as well as cytokeratin at the cellular level; the extracellular matrix stained for both collagen type III and laminin. Long-term PC proliferation and function were enhanced by the presence of stromal cells as well as by a meshwork template whose geometry allows the interaction of PC with stroma and matrix on several different planes. To permit transplantation, cocultures of hepatic PC and stromal cells were established on PGA felt constructs instead of nylon screens. After approximately 24 d in vitro, these constructs were grafted into sites in the mesentery, omentum, and subcutaneous tissues of adult Long-Evans rats. The growth of hepatocytes after 30 d in situ was evident by histological analysis; grafts of cocultures regenerated a liver-like architecture consisting of sinusoids and putative biliary structures. In addition, PC at these extrahepatic graft sites were positive for albumin, transferrin, and fibrinogen synthesis by immunohistochemistry. Graft survival was enhanced when recipients were subjected to approximately 40% hepatectomy. Hepatic PC:stromal cell cocultures may prove useful in the restoration of liver function either by direct transplantation using PGA or similar templates, or as extracorporeal devices, using nylon screens.

Stereotypic culture systems for liver and bone marrow: evidence for the development of functional tissue in vitro and following implantation in vivo.

Stromal cell-associated liver cell and bone marrow (BM) culture on three-dimensional nylon screen or polyglycolic acid (PGA) felt templates conveys certain functional advantages to the parenchyma of these tissues. Hepatic parenchymal cells (PC) manifest long-term ( approximately 2 month) expression of liver-specific activities including cytochrome P450 enzyme activity and the synthesis of albumin, fibrinogen, transferrin, and other proteins. PC also undergo proliferation in association with stromal cells that were pre-established on these templates. PC mitoses are directly proportional to available space within the template for their expansion indication that geometric or sterotypic parameters influence the growth of these cells in vitro. BM cultured on a similar template exhibits long-term multilineage hematopoietic expression and limited expansion of progenitor cell numbers. Progenitor cell concentration within the cultures can be substantially enhanced if these cells are liberated from co-culture and reseeded onto a template containing fresh stromal cells. BM and liver cel cultures established on felt composed of bioresorbable PGA filaments was grafted into various sites in rats. Liver co-cultures generated sinusoids and other liver-like structures in situ; active hematopoietic blasts were observed at sites of BM co-culture grafts. Biodegradable polymer constructs may prove useful for certain clinical applications as vehicles for the delivery of tissues that were engineered in culture.

Accommodating sequence changes in beta-hairpins in proteins.

A systematic study of homologous beta-hairpins in proteins of known structure reveals how insertions and deletions (herein known as indels) in the sequence are accommodated. The study was made for 12 protein families comprising 50 different structures, in which there were 49 independent hairpins. Each hairpin was classified according to its loop length and hydrogen bonding pattern. Most indels were found to occur in the loops and their frequency decreases rapidly with the size of the indel and approximately halves for each extra residue inserted. In very short loops, critical glycines are the primary determinants of loop structure and conversions between the two classic two-residue hairpin loops (with type I' and II' beta-turns) are quite common. Longer insertions are often accommodated by extending the beta-ladder and forming extra hydrogen bonds. There are also several indels that are not accommodated in the loop, but by forming a beta-bulge in one of the strands. This study should provide a useful aid to modelling hairpins in homologous structures.

Long-term expression of a retrovirally introduced beta-galactosidase gene in rodent cells implanted in vivo using biodegradable polymer meshes.

Grafts of various types of cells have been performed using bioresorbable polymer matrices. These synthetic fibers are degraded by hydrolysis into normal metabolic intermediates and induce a number of events that are conductive to healing and/or repair, the most important of which may be angiogenesis. The use of biodegradable meshes to deliver genetically altered cells was studied. A beta-galactosidase gene was inserted into Long-Evans rat bone marrow stromal (BMS) cells or fibroblasts derived from C57BL/6J mouse embryos using the retroviral vector LNL-SLX beta gal. Expression was monitored using X-gal staining. X-gal+ cells from monolayer cultures were seeded onto either polyglycolic acid (PGA) or polyglactin (PGL) biodegradable meshes and grown to confluence. Two types of grafts were performed: (1) embryonic C57BL/6J mouse fibroblasts (EMF) into either nude mice or adult C57BL/6J mice, and (2) Long-Evans rat BMS into Long-Evans rats. Beta-Galactosidase activity was found for up to 152 days for EMF in nude mice, 123 days for EMF in adult C57BL/6J mice, and 90 days for grafts of syngeneic BMS cells into Long-Evans rats. Noninfected cells grafted using the same methods did not stain with X-gal.

X-ray analyses of peptide-inhibitor complexes define the structural basis of specificity for human and mouse renins.

X-ray analyses have defined the three-dimensional structures of crystals of mouse and human renins complexed with peptide inhibitors at resolutions of 1.9 and 2.8 A, respectively. The exquisite specificity of renin arises partly from ordered loop regions at the periphery of the binding cleft. Although the pattern of main-chain hydrogen bonding in other aspartic proteinase inhibitor complexes is conserved in renins, differences in the positions of secondary structure elements (particularly helices) also lead to improved specificity in renins for angiotensinogen substrates.

Differential effects of drugs upon hematopoiesis can be assessed in long-term bone marrow cultures established on nylon screens.

Hematotoxicity is associated with exposure to chemotherapeutic drugs and numerous other agents. Most measurements of the hematopoietic effects of prospective therapeutic drugs and environmental agents have been made in animal models. We tested the influence of various drugs on hematopoiesis in long-term cultures of Long-Evans rat bone marrow cells. These cultures were established on nylon screen-bone marrow stromal cell templates that were suspended in liquid medium. Previous phenotypic analyses of adherent zone cells of suspended nylon screen bone marrow cultures (NSBMC) using monoclonal antibodies and flow cytometry indicated that they maintain a multilineage character for extended periods in culture and display continuous proliferation of hematopoietic progenitors (colony-forming unit culture [CFU-C]). NSBMC of various ages were incubated for 21 hr with several concentrations of beta-D-cytosine arabinofuranoside, 5-fluorouracil, cyclophosphamide, or methotrexate. Adherent zone cells were dissociated enzymatically, phenotyped by flow cytometry, and assayed for colony-forming unit culture content. beta-D-cytosine arabinofuranoside, 5-fluorouracil, and methotrexate treatment of bone marrow cultures resulted in a dose-related diminution in colony-forming unit culture numbers in the adherent zones of NSBMC. Phenotypic analyses revealed similar trends but certain of these drugs manifested lineage specificities. Toxicity was also related to cyclophosphamide dose, but the presence of bone marrow stroma was necessary to demonstrate this effect in vitro. A subpopulation of these cells was found to metabolize ethoxyfluorescein ethyl ester to fluorescein after induction with 2,3,7,8-tetrachlorodibenzo-p-dioxin, an effect which was quantified by flow cytometry. NSBMC may be used to ascertain lineage-specific toxicities and evaluate the effects of drugs on the proliferation of hematopoietic progenitor cells.

Crystallization and preliminary X-ray analysis of complexes of peptide inhibitors with human recombinant and mouse submandibular renins.

Inhibitor-complexed crystals of mouse and human renins suitable for X-ray analysis have been prepared. The mouse renin is complexed with a non-hydrolysable decapeptide analogue of rat angiotensinogen containing a hydroxyethylene isostere in place of the scissile bond. The crystals are monoclinic, space group P2(1) with cell dimensions a = 78.3 A, b = 117.8 A, c = 85.9 A, beta = 101.18 degrees containing four molecules per asymmetric unit. The human renin is fully glycosylated and complexed with a tetrapeptide containing norstatine. The complex crystallises in the cubic space group P2(1)3 with a = 143.1 A and has two molecules in the asymmetric unit. The rotation function of the mouse renin complex indicates pseudo 222 symmetry while that of human renin indicates a pseudo 2-fold axis. Full structural analyses of the two complexes are underway.

Hematopoiesis on suspended nylon screen-stromal cell microenvironments.

A three-dimensional culture system for the growth of primate and rodent bone marrow was developed in our laboratory. This method involves the seeding of stromal cells onto a nylon screen and the inoculation of fresh or cryopreserved bone marrow hematopoietic cells after stromal cell processes had extended across 3 to 4 out of every 5 mesh openings. Stromal cells attach, grow, and secrete matrix proteins which contribute to an intricate microenvironment for the support of multilineage hematopoiesis, which was observed for greater than 270 days in the rat model and for greater than 12 weeks in the human system, as evidenced by flow cytometry analysis and in vitro clonogenic assays. The adherent zones of these suspended nylon screen cultures consisted primarily of immature cells. These cultures could also be used as substrates for cytotoxicity measurements; treatment of rat bone marrow cultures of various ages with cytosine beta-D arabinofuranoside, cyclophosphamide, 5-fluorouracil, or methotrexate resulted in a dose-dependent decrease in CFU-C numbers and altered the phenotypic distribution of hematologic cells in the adherent zone. The use of a modification of this method to generate large numbers of active cytolytic cells after greater than 75 days culture of rat bone marrow-derived natural killer cells is described also. Suspended nylon screen bone marrow culture also has potential uses in genetic insertion and graft vs. host disease studies, blood component therapy, the evaluation of ex vivo purging programs, and in marrow expansion for transplantation.

Rat bone-marrow cell proliferation and differentiation as an index of the effects of xenobiotics in vitro.

A three-dimensional bone-marrow culture system was utilized for assessing the toxicity of various chemotherapeutic agents. This model, which exhibits multilineage haematopoiesis and promotes the growth of progenitor cells for extended periods, was treated with various concentrations of beta-d cytosine arabinofuranoside (Ara-C), cyclophosphamide (CP), methotrexate (MTX) or 5-fluorouracil (5-FU). The effects of these agents on the phenotypes of adherent zone cells was ascertained by labelling with monoclonal antibodies against rat leucocytes and evaluating by flow cytometry. Adherent zones also were assayed for content of colony-forming unit culture (CFU-C) and cellular viability after drug exposure was measured using the neutral red (NR) assay. The results indicated that Ara-C, CP, MTX and 5-FU treatment caused dose-dependent decreases in the CFU-C concentration of adherent zones in cultures of various ages. These agents also altered the phenotypic distribution of adherent zone cells and displayed differential lineage specificities. A dose-related decrease in viability also was observed with the NR assay, albeit at higher drug doses than those which induced measurable CFU-C and phenotypic alterations. These three-dimensional cultures may prove to be ideal substrates for toxicity testing as they contain all of the cell types present in vivo, are physiological with respect to their growth patterns, are easily manipulable, and can be maintained for extended periods.

A pilot study for an HIV prevention programme among commercial sex workers in Bulawayo, Zimbabwe.

In a health education pilot study for a programme to reduce HIV transmission among commercial sex workers (CSWs), 113 CSWs were interviewed and observed in Bulawayo, Zimbabwe during 1989. The educational level of the sample was low and less than a quarter had another job, either as a self-employed vendor/hawker or a domestic servant. Inability to earn income in other ways was the major reason cited for engaging in commercial sex. Nearly half the sample went for check-ups every 3 months or more often. All interviewees had heard about AIDS, but they were uniformed about several facets of AIDS. CSWs reported that they worked an average of 3.6 nights a week, averaged 1.3 clients a night and charged a mean of U.S. $2.8 a session and U.S. $6.5 a night. CSWs reportedly saw a total of 221 clients in the past 7 days and used condoms with 87 (39.3%) clients. Nearly all CSWs said they had done something to reduce the risk of getting AIDS, but when asked what they had done, only 40% said they were using condoms more frequently and many cited ineffective precautions. CSWs who had a job, charged higher fees, experienced little client violence and believed that they were susceptible to AIDS were more likely to use condoms. Clients were a cross-section of Bulawayo society, with widely varying education, incomes and occupations and shared little except an interest in commercial sex. Ethnographic approaches demonstrated a lack of cohesion among CSWs and a consequent need to foster organized, motivated groups for health education, the importance of incorporating clients in health education and the feasibility of using bar security and sales personnel as health educators. It is concluded that health education is urgently needed among CSWs, but that it is equally important to direct health interventions at clients, many of whom are resistant to condom use.