A COVID-19 monitoring process for healthcare workers utilizing occupational health.

BACKGROUND: Hospital-based occupational health (HBOH) is uniquely positioned to not only prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission, but to care for healthcare workers (HCWs) sick with coronavirus disease 2019 (COVID-19). AIMS: The primary objective of this study is to describe a system where HBOH services were adapted to provide a monitoring programme whereby HCWs with SARS-CoV-2 received daily evaluations and treatment options in order to improve access to care, and to report the clinical outcomes and predictors of hospitalization in HCWs enrolled in the programme. A secondary objective is to compare clinical outcomes to data on national HCWs with COVID-19. METHODS: This retrospective cohort study used survey data collected on HCWs at a university health system with COVID-19 from 1 March 2020 through 1 December 2021. A firth regression model was used to examine the unadjusted and adjusted association between clinical factors and hospitalization. RESULTS: The study cohort included 4814 HCWs with COVID-19. Overall hospitalizations were 119 (2%), and there were six deaths (0.12%). Predictors of hospitalization include several co-morbidities and symptoms. A total of 1835 HCWs monitored before vaccine or monoclonal antibody availability were compared with data on U.S. HCWs in a similar time period. The monitored HCWs had a lower rate of co-morbidities (19% versus 44%, P < 0.001), a lower hospitalization rate (3% versus 8% P < 0.001) and case-fatality rate (0.11% versus 0.95% P < 0.001). CONCLUSIONS: This monitoring strategy for COVID-19 may be feasible for HBOH systems to implement and improve access to care, but more data are needed to determine if it improves outcomes.

First Observation of the Four-Proton Unbound Nucleus

^{18}Mg was observed, for the first time, by the invariant-mass reconstruction of ^{14}O+4p events. The ground-state decay energy and width are E_{T}=4.865(34) MeV and Γ=115(100) keV, respectively. The observed momentum correlations between the five particles are consistent with two sequential steps of prompt 2p decay passing through the ground state of ^{16}Ne. The invariant-mass spectrum also provides evidence for an excited state at an excitation energy of 1.84(14) MeV, which is likely the first excited 2^{+} state. As this energy exceeds that for the 2^{+} state in ^{20}Mg, this observation provides an argument for the demise of the N=8 shell closure in nuclei far from stability. However, in open systems this classical argument for shell strength is compromised by Thomas-Ehrman shifts.

Between-limb asymmetry in kinetic and temporal characteristics during bilateral plyometric drop jumps from different heights.

This study investigated the between-limb asymmetry in kinetic and temporal characteristics during bilateral plyometric drop jumps from different heights. Seventeen male basketball players performed drop jumps from 3 heights on two platforms in randomized orders. Vertical ground reaction force data were analysed with respect to the lead limb (i.e. the limb stepping off the raised platform first) and trail limb. Peak forces and loading rates of each limb were calculated. The absolute time differential between the two limbs at initial ground contact and takeoff were determined. The frequency of symmetrical landing and taking off with "both limbs together" were counted using 3 time windows. Results showed that the lead limb displayed higher peak forces and loading rates than the trail limb across all heights (p <.05). As drop height increased, the absolute time differentials decreased at initial ground contact (p <.001) but increased at takeoff (p =.035). The greater the preset time window, the more landings and takeoffs were classified as bilaterally symmetrical. In conclusion, higher drop heights allowed subjects to become more bilaterally symmetrical in the timing of landing but this reduction in temporal asymmetry did not accompany with any reduction in kinetic asymmetry.

Chimaeric analysis reveals role of Pdgf receptors in all muscle lineages.

Blood vessels originate as simple endothelial cell tubes. It has been proposed that platelet-derived growth factor B polypeptide (Pdgfb) secreted by these endothelial cells drives the formation of the surrounding muscular wall by recruiting nearby mesenchymal cells. However, targetted inactivation of the Pdgfb gene or the Pdgf receptor beta (Pdgfrb) gene, by homologous recombination, does not prevent the development of apparently normal large arteries and connective tissue. We have used an in vivo competition assay in which we prepared chimaeric blastocysts, composed of a mixture of wild-type (Pdgfrb[+/+]) and Pdgfrb(+/-) or wild-type and Pdgfrb(-/-) cells, and quantified the relative success of cells of the two component genotypes in competing for representation in different cell lineages as the chimaeric embryos developed. This study revealed that the participation of Pdgfrb(-/-) cells in all muscle lineages (smooth, cardiac, skeletal and pericyte) was reduced by eightfold compared with Pdgfrb(+/+) cells, and that participation of Pdgfrb(+/-) cells was reduced by twofold (eightfold for pericytes). Pdgfrb inactivation did not affect cell contribution to non-muscle mesodermal lineages, including fibroblasts and endothelial cells. Chimaera competition is therefore a sensitive, quantitative method for determining developmental roles of specific genes, even when those roles are not apparent from analysis of purebred mutants; most likely because they are masked by homeostatic mechanisms.

Metabolic consequences of adenosine deaminase deficiency in mice are associated with defects in alveogenesis, pulmonary inflammation, and airway obstruction.

Adenosine deaminase (ADA) is a purine catabolic enzyme that manages levels of the biologically active purines adenosine and 2'-deoxyadenosine in tissues and cells. ADA-deficient mice die at 3 wk of age from severe respiratory distress. This phenotype is progressive and is linked to perturbations in pulmonary purine metabolism. The inflammatory changes found in the lungs of ADA-deficient mice included an accumulation of activated alveolar macrophages and eosinophils. These changes were accompanied by a pronounced enlargement of alveolar spaces and increases in mucus production in the bronchial airways. The alveolar enlargement was found to be due in part to abnormal alveogenesis. Lowering adenosine and 2'-deoxyadenosine levels using ADA enzyme therapy decreased the pulmonary eosinophilia and resolved many of the lung histopathologies. In addition, genetically restoring ADA to the forestomach of otherwise ADA-deficient mice prevented adenine metabolic disturbances as well as lung inflammation and damage. These data suggest that disturbances in purinergic signaling mediate the lung inflammation and damage seen in ADA-deficient mice.

Localization of components involved in protein transport and processing through the yeast Golgi apparatus.

Saccharomyces cerevisiae sec7 mutants exhibit pleiotropic deficiencies in the transit of proteins through the Golgi apparatus, and elaborate an array of Golgi apparatus-like cisternae at a restrictive growth temperature (37 degrees C). The SEC7 gene encodes an essential high-molecular weight protein (227 kD) that is phosphorylated in vivo. In cell lysates, Sec7 protein (Sec7p) is recovered in both sedimentable and soluble fractions. A punctate immunofluorescent pattern of Sec7p-associated structures seen in SEC cells coalesces in sec14 mutant yeast that accumulate exaggerated Golgi cisternae at 37 degrees C. Sec7p may function as a peripheral membrane protein that cycles between a soluble, cytosolic pool and a sedimentable, membrane-associated complex for its essential role in vesicular traffic through the Golgi apparatus. The transmembrane Kex2 protease, which processes precursors of secreted peptides within the yeast secretory pathway, is also localized by indirect immunofluorescence to multiple structures in the yeast cell (Redding, K., and R. Fuller, manuscript submitted for publication). In double-immunofluorescence labeling experiments, significant colocalization of Sec7 and Kex2 proteins was found. Colocalization of the two antigens, one implicated in protein transport through the Golgi apparatus and the other in processing within a late Golgi compartment, supports the conclusion that we have visualized the yeast Golgi apparatus.

A cytosolic complex of p62 and rab6 associates with TGN38/41 and is involved in budding of exocytic vesicles from the trans-Golgi network.

TGN38/41, an integral membrane protein predominantly localized to the trans-Golgi network, has been shown to cycle to the plasma membrane and return to the TGN within 30 min. (Ladinsky, M. S., and K. E. Howell. 1992. Eur. J. Cell Biol. 59:92-105). In characterizing the proteins which associate with TGN38/41, a peripheral 62-kD protein, two forms of rab6 and two other small GTP-binding proteins were identified by coimmunoprecipitation. However, approximately 90% of the 62-kD protein is cytosolic and is associated with the same subset of small GTP-binding proteins. Both the membrane and cytoplasmic complexes were characterized by sizing column fractionation and velocity sedimentation. The membrane complex was approximately 250 kD (11.6 S) consisting of the cytosolic complex and a heterodimer of TGN38/41 (160 kD). The cytosolic complex was approximately 86 kD (6.1 S) consisting of p62 and one small GTP-binding protein. Preliminary evidence indicates that phosphorylation of the p62 molecule regulates the dissociation of the cytosolic complex from TGN38/41. Functionally the cytosolic p62 complex must bind to TGN38/41 for the budding of exocytic transport vesicles from the TGN as assayed in a cell-free system (Salamero, J., E. S. Sztul, and K. E. Howell. 1990. Proc. Natl. Acad. Sci. USA. 87:7717-7721). Interference with p62, rab6 or TGN38, and TGN41 cytoplasmic domains by immunodepletion or competing peptides completely inhibited the budding of exocytic transport vesicles. These results support an essential role for interaction of the cytosolic p62/rab6 complex with TGN38/41 in budding of exocytic vesicles from the TGN.

Stress-Induced Translational Control in Potato Tubers May Be Mediated by Polysome-Associated Proteins.

Potato tubers exhibit distinct responses to wounding and hypoxia that include selective translation of stress-induced mRNAs. Newly synthesized wound-response mRNAs are bound to polysomes, whereas preexisting mRNAs are displaced and degraded. mRNAs that are induced and translated during hypoxic conditions are bound to ribosomes as expected. However, preexisting wound-response mRNAs whose translation is inhibited during hypoxia remain bound to polysomes, indicating that there are at least two distinct mechanisms by which translation is regulated in response to stress conditions. A 32-kD phosphoprotein is associated with polyribosomes from wounded tubers. This protein remains polysome bound as long as wound-response mRNAs are present, even during hypoxia when these mRNAs are no longer translated. However, association of the 32-kD protein with polysomes is not elicited by hypoxic stress alone. The kinase that phosphorylates this protein is active only for the first 24 hr after wounding and is not active during periods of hypoxia. This protein may mediate recognition of the wound-response mRNAs by ribosomes.

Erythroid expression of the heme-regulated eIF-2 alpha kinase.

The role of heme-regulated eIF-2 alpha kinase (HRI) in the regulation of protein synthesis in rabbit reticulocytes is well documented. Inhibitors of protein synthesis with properties similar to those of HRI have been described in some nonerythroid cell types, but it has not yet been determined whether these eIF-2 alpha kinase activities are mediated by HRI or one or more as yet uncharacterized kinases. We have studied the expression of mRNA, polypeptide, and kinase activities of HRI in various tissues from both nonanemic and anemic rabbits. Our results indicate that HRI is expressed in an erythroid cell-specific manner. HRI is present in the bone marrow and peripheral blood of both nonanemic and anemic rabbits but not in any of the other tissues tested. HRI mRNA is present at low levels in uninduced mouse erythroleukemic (MEL) cells and human K562 cells and accumulates to higher levels upon induction. The accumulation of HRI mRNA in differentiating MEL cells is dependent upon the presence of heme. The addition of 3-amino-1,2,4-triazole (AT), an inhibitor of heme biosynthesis, to the induction medium markedly reduced HRI mRNA accumulation. Simultaneous addition of hemin and AT to the dimethyl sulfoxide induction medium largely prevented the inhibition of HRI mRNA induction by AT. These findings indicate that HRI is expressed in an erythroid cell-specific manner and that the major physiologic role of HRI is in adjusting the synthesis of globins to the availability of heme.

Endothelial cells of hematopoietic origin make a significant contribution to adult blood vessel formation.

Granulation tissue formation is an example of new tissue development in an adult. Its rich vascular network has been thought to derive via angiogenic sprouting and extension of preexisting vessels from the surrounding tissue. The possibility that circulating cells of hematopoietic origin can differentiate into vascular endothelial cells (ECs) in areas of vascular remodeling has recently gained credibility. However, no quantitative data have placed the magnitude of this contribution into a physiological perspective. We have used hematopoietic chimeras to determine that 0.2% to 1.4% of ECs in vessels in control tissues derived from hematopoietic progenitors during the 4 months after irradiation and hematopoietic recovery. By contrast, 8.3% to 11.2% of ECs in vessels that developed in sponge-induced granulation tissue during 1 month derived from circulating hematopoietic progenitors. This recruitment of circulating progenitors to newly forming vessels would be difficult to observe in standard histological studies, but it is large enough to be encouraging for attempts to manipulate this contribution for therapeutic gain.

Lipid-mediated protein functionalization of electrospun polycaprolactone fibers.

In this study, electrospun polycaprolactone (PCL) fibers are plasma-treated and chemically conjugated with cholesteryl succinyl silane (CSS). In addition to Raman spectroscopy, an immobilization study of DiO as a fluorescent probe of lipid membranes provides evidence supporting the CSS coating of plasma-treated PCL fibers. Further, anti-CD20 antibodies are used as a model protein to evaluate the potential of lipid-mediated protein immobilization as a mechanism to functionalize the CSS-PCL fiber scaffolds. Upon anti-CD20 functionalization, the CSS-PCL fiber scaffolds capture Granta-22 cells 2.4 times more than the PCL control does, although the two fiber scaffolds immobilize a comparable amount of anti-CD20. Taken together, results from the present study demonstrate that the CSS coating and CSS-mediated antibody immobilization offers an appealing strategy to functionalize electrospun synthetic polymer fibers and confer cell-specific functions on the fiber scaffolds, which can be mechanically robust but often lack biological functions.

Influencing factors for port-site hernias after single-incision laparoscopy.

PURPOSE: Single-incision laparoscopic surgery (SILS) has been demonstrated to be a feasible alternative to multiport laparoscopy, but concerns over port-site incisional hernias have not been well addressed. A retrospective study was performed to determine the rate of port-site hernias as well as influencing risk factors for developing this complication. METHODS: A review of all consecutive patients who underwent SILS over 4 years was conducted using electronic medical records in a multi-specialty integrated healthcare system. Statistical evaluation included descriptive analysis of demographics in addition to bivariate and multivariate analyses of potential risk factors, which were age, gender, BMI, procedure, existing insertion-site hernia, wound infection, tobacco use, steroid use, and diabetes. RESULTS: 787 patients who underwent SILS without conversion to open were reviewed. There were 454 cholecystectomies, 189 appendectomies, 72 colectomies, 21 fundoplications, 15 transabdominal inguinal herniorrhaphies, and 36 other surgeries. Cases included 532 (67.6 %) women, and among all patients mean age was 44.65 (±19.05) years and mean BMI of 28.04 (±6). Of these, 50 (6.35 %) patients were documented as developing port-site incisional hernias by a health care provider or by incidental imaging. Of the risk factors analyzed, insertion-site hernia, age, and BMI were significant. Multivariate analysis indicated that both preexisting hernia and BMI were significant risk factors (p value = 0.00212; p value = 0.0307). Morbidly obese patients had the highest incidence of incisional hernias at 18.18 % (p value = 0.02). CONCLUSIONS: When selecting patients for SILS, surgeons should consider the presence of an umbilical hernia, increased age and obesity as risk factors for developing a port-site hernia.

Polyketide synthase acyl carrier proteins from Streptomyces: expression in Escherichia coli, purification and partial characterisation.

Acyl carrier proteins (ACPs) of the type II polyketide synthases for the aromatic antibiotics actinorhodin, granaticin, frenolicin and oxytetracycline were expressed in Escherichia coli downstream of an inducible phage T7 promoter. For the act and otc genes, several of the first eight codons were changed to synonymous codons used in highly expressed E. coli genes. Correlated with these changes, the amounts of the act and otc ACPs purified from the recombinant E. coli cultures were an order of magnitude greater than for the gra and fren ACPs expressed from the unmodified genes. Electrospray mass spectrometry (ESMS) of the purified proteins confirmed their calculated M(r) based on the DNA sequences while also revealing that, in the act and gra ACP samples, some 2% and 30% of the holo-form of the protein was present (i.e., carrying the 4'-phosphopantetheine prosthetic group), with the remainder (and 100% of the otc and fren samples) being in the apo-form. Increasing incubation time post heat induction led to an increase in act holo-ACP. The recombinant act and gra ACPs could function in vitro as substrates for an S. coelicolor malonyl CoA:ACP acyl transferase, as measured by the coupling of a labelled malonyl unit to the ACP; their quantitative abilities to do so correlated with the proportions of deduced holo form in the two samples.

Cloning and characterization of cDNAs encoding the epsilon-subunit of eukaryotic initiation factor-2B from rabbit and human.

A rabbit reticulocyte lysate cDNA library was screened with a polyclonal antiserum directed against eukaryotic initiation factor eIF-2B (eIF-2B). A 2508 base pair cDNA (pA1) was isolated and determined to encode the epsilon-subunit of eIF-2B based on the immunoreactivity of the fusion protein expressed from the cDNA in Escherichia coli and the presence of two peptide sequences obtained from two V8 fragments of purified nonrecombinant eIF-2B epsilon in the deduced amino acid sequence of the cDNA. The open reading frame of the cDNA began with the third nucleotide of the cDNA with the first AUG codon at nucleotide 522. Mutational analysis of pA1 indicated that the cDNA did not code for full-length eIF-2B epsilon. Seven missing codons of the reading-frame and the 71 nucleotide 5' non-coding region of the eIF-2B epsilon mRNA were obtained by 5' RACE. A human eIF-2B epsilon cDNA fragment, which corresponded to a similar 2.3 kb fragment generated by digestion of the rabbit pA1 cDNA with EcoRI, was isolated from a human histiocytic lymphoma (U-937) cell cDNA library constructed in lambda gt10. The nucleotide and amino acid sequences were highly conserved between the rabbit and human cDNAs, showing approx. 90% sequence identity within the open reading frame. Northern and Western blot analyses of reticulocyte lysate and other rabbit tissue extracts indicated that the eIF-2B epsilon polypeptide has a similar apparent molecular weight in all tissues examined, and is coded for by a single approximately 2.8 kilobase mRNA species which is ubiquitously expressed.

Disorganization is a completely dominant gain-of-function mouse mutation causing sporadic developmental defects.

Disorganization (Ds) is an exceptional mutation because of its diverse and profound developmental effects. Although other mouse mutations produce similar congenital defects, extreme pleiotropism, random occurrence, developmental independence of multiple defects, and type of anomaly make Ds unique. Examples of developmental defects include cranioschisis, rachischisis, thoracoschisis, exencephaly, hamartomas, and anomalies of appendages, digestive, genital and urinary tracts, sense organs, limbs and girdles, tail and pharynx. No other mutation in the mouse has such broad effects. Ds is therefore an important model for studying not only the genetic control of lineage determination and pattern formation, but also the occurrence of sporadic congenital defects. To characterize the effects of gene dosage, we examined the viability and phenotype of Ds homozygotes and the phenotype of +/+/Ds trisomic fetuses. Occurrence of homozygotes was tested by intercrossing Ds/+ heterozygotes, typing genetic markers that flank Ds, and examining homozygotes for morphological abnormalities. Not only were Ds homozygotes found in their expected frequency, homozygotes were not more severely affected than heterozygotes. Trisomies provide a direct test for determining whether Ds is a gain-of-function mutation. Trisomic fetuses were derived by crossing Ds/Ds homozygous mice to hybrid mice that were heterozygous for two related Robertsonian translocations. Two trisomic fetuses had developmental defects characteristic of Ds mice. Together these results demonstrate that Ds is a completely dominant, gain-of-function mutation.

MCAT is not required for in vitro polyketide synthesis in a minimal actinorhodin polyketide synthase from Streptomyces coelicolor.

BACKGROUND: It has been proposed that Streptomyces malonyl CoA: holo acyl carrier protein transacylases (MCATs) provide a link between fatty acid and polyketide biosynthesis. Two recent studies have provided evidence that the presence of MCAT is essential for polyketide synthesis to proceed in reconstituted minimal polyketide synthases (PKSs). In contrast to this, we previously showed that the holo acyl carrier proteins (ACPs) from type II PKSs are capable of catalytic self-malonylation in the presence of malonyl CoA, which suggests that MCAT might not be necessary for polyketide biosynthesis. RESULTS: We reconstituted a homologous actinorhodin (act) type II minimal PKS in vitro. When act holo-ACP is present in limiting concentrations, MCAT is required by the synthase complex in order for polyketide biosynthesis to proceed. When holo-ACP is present in excess, however, efficient polyketide synthesis proceeds without MCAT. The rate of polyketide production increases with holo-ACP concentration, but at low ACP concentration or equimolar AC:KS:CLF (KS, ketosynthase; CLF, chain length determining factor) concentrations this rate is significantly lower than expected, indicating that free holo-ACP is sequestered by the KS/CLF complex. CONCLUSIONS: The rate of polyketide biosynthesis is dictated by the ratio of holo-ACP to KS and CLF, as well as by the total protein concentration. There is no absolute requirement for MCAT in polyketide biosynthesis in vitro, although the role of MCAT during polyketide synthesis in vivo remains an open question. MCAT might be responsible for the rate enhancement of malonyl transfer at very low free holo-ACP concentrations or it could be required to catalyse the transfer of malonyl groups from malonyl CoA to sequestered holo-ACP.

Catalytic self-acylation of type II polyketide synthase acyl carrier proteins.

BACKGROUND: Aromatic polyketides are synthesised in streptomycetes by the successive condensation of simple carboxylic acids, catalysed by multienzyme complexes--the polyketide synthases (PKSs). Polyketide assembly intermediates are covalently linked as thioesters to the holo-acyl carrier protein (ACP) subunit of these type II PKSs. The ACP is primed for chain elongation by the transfer of malonate from malonyl CoA. Malonylation of fatty acid synthase (FAS) ACPs is catalysed by specific malonyl transferase (MT) enzymes. The type II PKS gene clusters apparently lack genes encoding such MT proteins, however. It has been proposed that the MT subunit of the FAS in streptomycetes catalyses malonylation of both FAS and PKS ACPs in vivo. RESULTS: We demonstrate that type II PKS ACPs catalyse self-malonylation upon incubation with malonyl CoA in vitro. The self-malonylation reaction of the actinorhodin C17S holo-ACP has a K(m) for malonyl CoA of 219 microM and a kcat of 0.34 min-1. Complete acylation of the PKS ACPs was observed with malonyl, methylmalonyl and acetoacetyl CoAs. No reaction was observed with acetyl and butyryl CoAs and FAS ACPs did not react with any of the substrates. Recombinant FAS MT from Streptomyces coelicolor did not accelerate the rate of malonylation. CONCLUSIONS: The catalytic self-acylation of type II PKS ACPs is an unprecedented reaction. We propose a reaction mechanism in which conserved arginines form a salt bridge with the acyl moiety and sequester it from bulk solvent. This work suggests that the beta-ketoacyl synthase, chain length factor and ACP may constitute a truly minimal PKS in vivo.

Herpetic tracheobronchitis. Cytologic and virologic detection.

Tracheobronchitis due to herpes simplex virus is a well-recognized finding in cases of burns, debilitation, or immunosuppression. Nearly all reported cases have been diagnosed at necropsy despite the possibility for clinical detection of such infections by exfoliative cytological studies, virus isolation and identification, or both. The present report details the cytologic and virologic diagnosis of herpetic tracheobronchitis in a patient with carcinoma of the lung and alcoholic fatty liver. Respiratory cells with herpetic infection cytologically showed less tendency to multinucleation than the characteristic herpes-infected cells of squamous epithelium, which may be a source of diagnostic confusion.

Factors associated with embryo splitting and clinical outcome of monozygotic twins in pregnancies after IVF and ICSI.

STUDY QUESTION: What factors are associated with monozygotic twins (MZT) after autologous IVF/ICSI with fresh and frozen/thawed single embryo transfer (SET) and what is the outcome of MZT? SUMMARY ANSWER: Factors associated with increased MZT were blastocyst transfer and elective single embryo transfer (eSET), with MZT showing a lower gestational age at birth and neonatal weight but higher perinatal mortality only after fresh transfer. WHAT IS KNOWN ALREADY: ART is associated with an increased incidence of MZT, which carries higher perinatal mortality. However, risk factors associated with MZT are still controversial. STUDY DESIGN SIZE DURATION: A population-based retrospective analysis of data extracted from ART cycles reported to the Latin American Registry of ART between January 2012 and December 2016 was used in order to study the frequency and outcome of MZT after SET. PARTICIPANTS/MATERIAL SETTING METHODS: In total, 2925 clinical pregnancies obtained after autologous IVF/ICSI with fresh SET were used to study biomedical factors possibly associated with MZT, such as maternal age, type of insemination, use of assisted hatching, stage of embryo development at transfer, elective or non-elective SET and preimplantation genetic testing. Another group of 3085 clinical pregnancies obtained after SET of frozen-thawed embryo transfer (FET) was also used to study the possible association between embryo freezing and MZT. Only pregnancies with complete follow-up until birth were included in this analysis. The diagnosis of MZT was established by transvaginal ultrasound performed at 6­8 weeks of amenorrhea. The rate of MZT for each potential risk factor was obtained and a multivariable logistic regression was performed in order to account for the above-mentioned factors. Pregnancies were followed until birth and the early neonatal period in order to assess the rate of miscarriage and stillbirths, gestational age at birth, neonatal weight and early neonatal mortality. MAIN RESULTS AND ROLE OF CHANCE: There were 76 MZT out of 2925 clinical pregnancies with fresh SET (2.6%) and 69 MZT out of 3085 clinical pregnancies after FET (2.2%) (odds ratio (OR) = 0.85, 95% CI 0.61­1.19). A statistically significantly increase in MZT rate was observed with blastocyst compared with cleavage stage ET (3.4 versus 2.0%, respectively; OR = 1.70, 95% CI 1.05­2.76). When confounding variables were considered, eSET was also significantly associated with an increase in the odds of MZT (OR = 1.74, 95% CI 1.04­2.92). Overall perinatal mortality was higher in MZT compared with singletons, but this rise was only significant after fresh ET. LIMITATIONS REASONS FOR CAUTION: Limitations of the current study result from the fact that MZT were diagnosed with ultrasound performed at 6­8 weeks of amenorrhea; therefore, spontaneous embryo reductions taking place earlier were missed. WIDER IMPLICATIONS OF THE FINDINGS: Reproductive health providers must inform their patients that blastocyst transfer and eSET of fresh embryos are associated with a statistically significantly increase in the odds of MZT and that perinatal mortality after fresh ET is significantly higher in MZT than in singletons. STUDY FUNDING/COMPETING INTERESTS: The Latin American Registry of ART receives direct funding from Ferring Pharmaceuticals, but no specific funding was received to undertake this study. None of the authors declare conflict of interest.

Conserved secondary structure in the actinorhodin polyketide synthase acyl carrier protein from Streptomyces coelicolor A3(2) and the fatty acid synthase acyl carrier protein from Escherichia coli.

The acyl carrier protein (ACP) of Streptomyces coelicolor A3(2) functions as a molecular chaperone during the biosynthesis of the polyketide actinorhodin (act). Here we compare structural features of the polyketide synthase (PKS) ACP, determined by two-dimensional 1H-NMR, with the Escherichia coli fatty acid synthase (FAS) ACP. The PKS ACP contains four helices (residues 7-16 [A], 42-53 [B], 62-67 [C], 72-86 [D]), and a large loop (residues 17-41) having no defined secondary structure with the exception of a turn between residues 21 and 24. The act ACP shows 47% sequence similarity with the E. coli FAS ACP and the results demonstrate that the sequence homology is extended to the secondary structure of the proteins.