1
|
Joshi R, Singla R, Mishra A, Kumar M, Singh RS, Singh A, Bansal S, Sharma AR, Sarma P, Prakash A, Medhi B. A systematic review on SARS-CoV-2 remission: an Emerging challenge for its management, treatment, immunization strategies and post-treatment guidelines. New Microbes New Infect 2022; 45:100949. [PMID: 35018221 PMCID: PMC8739778 DOI: 10.1016/j.nmni.2022.100949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 05/12/2021] [Accepted: 01/04/2022] [Indexed: 02/05/2023] Open
Abstract
The COVID-19 disease caused by severe acute respiratory syndrome coronavirus -2 (SARS-CoV-2) has posed as a major health concern for people all across the globe. Along with the increasing confirmed patients being readmitted with complaints for fever, cough, cold, the effective monitoring of 'relapse' of the SARS-CoV-2 virus in the previously discharged patients have become the next area of focus. However, availability of limited data on reactivation of SARS-CoV-2 makes the disease prognosis as well as the effective control of re-infection an immense challenge. Prompted by these challenges, we assessed the possibility of re-infection in discharged patients and the risk of the transmission, proficiency of RT-PCR results and approximate period required for the quarantine and the real challenges for the development of vaccine. In the present review, the published literature on all the possible cases of re-infection from February to July were reported, thereby selected 142 studies from a hub of overall 669 studies after full text screening. The incomplete virus clearance, poor sensitivity of the present diagnostic testing, emergence of mutant strains, insufficient mucus collection from the throat swab etc. are some of the possible causes of re-infection. The new protocols for management of COVID-19 discharged patients should be revised in the guidelines.
Collapse
Affiliation(s)
- Rupa Joshi
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Rubal Singla
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Abhishek Mishra
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Mukesh Kumar
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Rahul Soloman Singh
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Ashutosh Singh
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Seema Bansal
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Amit Raj Sharma
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Phulen Sarma
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Ajay Prakash
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| | - Bikash Medhi
- Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh
| |
Collapse
|
2
|
Imad HA, Ali AA, Nahuza M, Gurung R, Ubaid A, Maeesha A, Didi SA, Dey RK, Hilmy AI, Hareera A, Afzal I, Matsee W, Nguitragool W, Nakayama EE, Shioda T. Acalculous Cholecystitis in a Young Adult with Scrub Typhus: A Case Report and Epidemiology of Scrub Typhus in the Maldives. Trop Med Infect Dis 2021; 6:tropicalmed6040208. [PMID: 34941664 PMCID: PMC8707333 DOI: 10.3390/tropicalmed6040208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/05/2021] [Accepted: 12/06/2021] [Indexed: 11/21/2022] Open
Abstract
Scrub typhus is a neglected tropical disease predominantly occurring in Asia. The causative agent is a bacterium transmitted by the larval stage of mites found in rural vegetation in endemic regions. Cases of scrub typhus frequently present as acute undifferentiated febrile illness, and without early diagnosis and treatment, the disease can develop fatal complications. We retrospectively reviewed de-identified data from a 23-year-old woman who presented to an emergency department with complaints of worsening abdominal pain. On presentation, she appeared jaundiced and toxic-looking. Other positive findings on abdominal examination were a positive Murphey’s sign, abdominal guarding and hepatosplenomegaly. Magnetic resonance cholangiopancreatography demonstrated acalculous cholecystitis. Additional findings included eschar on the medial aspect of the left thigh with inguinal regional lymphadenopathy. Further, positive results were obtained for immunoglobulins M and G, confirming scrub typhus. The workup for other infectious causes of acute acalculous cholecystitis (AAC) detected antibodies against human herpesvirus 4 (Epstein–Barr virus), suggesting an alternative cause of AAC. Whether that represented re-activation of the Epstein–Barr virus could not be determined. As other reports have described acute acalculous cholecystitis in adult scrub typhus patients, we recommend doxycycline to treat acute acalculous cholecystitis in endemic regions while awaiting serological confirmation.
Collapse
Affiliation(s)
- Hisham Ahmed Imad
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand;
- Department of Viral Infections, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan; (E.E.N.); (T.S.)
- Correspondence: or ; Tel.: +66-631501402
| | - Aishath Azna Ali
- Department of Surgery, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.A.A.); (M.N.); (R.G.); (A.U.)
| | - Mariyam Nahuza
- Department of Surgery, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.A.A.); (M.N.); (R.G.); (A.U.)
| | - Rajan Gurung
- Department of Surgery, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.A.A.); (M.N.); (R.G.); (A.U.)
| | - Abdulla Ubaid
- Department of Surgery, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.A.A.); (M.N.); (R.G.); (A.U.)
| | - Aishath Maeesha
- Department of Medicine, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.M.); (S.A.D.); (R.K.D.); (A.I.H.)
| | - Sariu Ali Didi
- Department of Medicine, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.M.); (S.A.D.); (R.K.D.); (A.I.H.)
| | - Rajib Kumar Dey
- Department of Medicine, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.M.); (S.A.D.); (R.K.D.); (A.I.H.)
| | - Abdullah Isneen Hilmy
- Department of Medicine, Indira Gandhi Memorial Hospital, Malé 20002, Maldives; (A.M.); (S.A.D.); (R.K.D.); (A.I.H.)
- Gastrointestinal Unit, Department of Medicine, Groote Schuur Hospital, University of Cape Town, Cape Town 7935, South Africa
| | - Aishath Hareera
- Health Protection Agency, Ministry of Public Health, Malé 20002, Maldives; (A.H.); (I.A.)
| | - Ibrahim Afzal
- Health Protection Agency, Ministry of Public Health, Malé 20002, Maldives; (A.H.); (I.A.)
| | - Wasin Matsee
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand;
| | - Wang Nguitragool
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand;
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand
| | - Emi. E. Nakayama
- Department of Viral Infections, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan; (E.E.N.); (T.S.)
| | - Tatsuo Shioda
- Department of Viral Infections, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan; (E.E.N.); (T.S.)
| |
Collapse
|
3
|
Franceschini E, Cozzi-Lepri A, Santoro A, Bacca E, Lancellotti G, Menozzi M, Gennari W, Meschiari M, Bedini A, Orlando G, Puzzolante C, Digaetano M, Milic J, Codeluppi M, Pecorari M, Carli F, Cuomo G, Alfano G, Corradi L, Tonelli R, De Maria N, Busani S, Biagioni E, Coloretti I, Guaraldi G, Sarti M, Luppi M, Clini E, Girardis M, Gyssens IC, Mussini C. Herpes Simplex Virus Re-Activation in Patients with SARS-CoV-2 Pneumonia: A Prospective, Observational Study. Microorganisms 2021; 9:microorganisms9091896. [PMID: 34576791 PMCID: PMC8465957 DOI: 10.3390/microorganisms9091896] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 09/02/2021] [Accepted: 09/03/2021] [Indexed: 12/15/2022] Open
Abstract
Background: Herpes simplex 1 co-infections in patients with COVID-19 are considered relatively uncommon; some reports on re-activations in patients in intensive-care units were published. The aim of the study was to analyze herpetic re-activations and their clinical manifestations in hospitalized COVID-19 patients, performing HSV-1 PCR on plasma twice a week. Methods: we conducted a prospective, observational, single-center study involving 70 consecutive patients with severe/critical SARS-CoV-2 pneumonia tested for HSV-1 hospitalized at Azienda Ospedaliero-Universitaria of Modena. Results: of these 70 patients, 21 (30.0%) showed detectable viremia and 13 (62%) had clinically relevant manifestations of HSV-1 infection corresponding to 15 events (4 pneumonia, 5 herpes labialis, 3 gingivostomatitis, one encephalitis and two hepatitis). HSV-1 positive patients were more frequently treated with steroids than HSV-1 negative patients (76.2% vs. 49.0%, p = 0.036) and more often underwent mechanical ventilation (IMV) (57.1% vs. 22.4%, p = 0.005). In the unadjusted logistic regression analysis, steroid treatment, IMV, and higher LDH were significantly associated with an increased risk of HSV1 re-activation (odds ratio 3.33, 4.61, and 16.9, respectively). The association with the use of steroids was even stronger after controlling for previous use of both tocilizumab and IMV (OR = 5.13, 95% CI:1.36–19.32, p = 0.016). The effect size was larger when restricting to participants who were treated with high doses of steroids while there was no evidence to support an association with the use of tocilizumab Conclusions: our study shows a high incidence of HSV-1 re-activation both virologically and clinically in patients with SARS-CoV-2 severe pneumonia, especially in those treated with steroids.
Collapse
Affiliation(s)
- Erica Franceschini
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
- Correspondence: (E.F.); (C.M.)
| | - Alessandro Cozzi-Lepri
- Centre for Clinical Research, Epidemiology, Modelling and Evaluation, Institute for Global Health, University College London, London NW3 2PF, UK;
| | - Antonella Santoro
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Erica Bacca
- Department of Infectious Diseases, University of Modena and Reggio Emilia, 41124 Modena, Italy; (E.B.); (G.L.); (J.M.); (G.G.)
| | - Guido Lancellotti
- Department of Infectious Diseases, University of Modena and Reggio Emilia, 41124 Modena, Italy; (E.B.); (G.L.); (J.M.); (G.G.)
| | - Marianna Menozzi
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - William Gennari
- Microbiology and Virology Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (W.G.); (M.P.); (M.S.)
| | - Marianna Meschiari
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Andrea Bedini
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Gabriella Orlando
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Cinzia Puzzolante
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Margherita Digaetano
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Jovana Milic
- Department of Infectious Diseases, University of Modena and Reggio Emilia, 41124 Modena, Italy; (E.B.); (G.L.); (J.M.); (G.G.)
| | - Mauro Codeluppi
- Infectious Diseases Unit, G. da Saliceto Hospital, 29121 Piacenza, Italy;
| | - Monica Pecorari
- Microbiology and Virology Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (W.G.); (M.P.); (M.S.)
| | - Federica Carli
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Gianluca Cuomo
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Gaetano Alfano
- Nephrology, Dialysis and Transplant Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy;
| | - Luca Corradi
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
| | - Roberto Tonelli
- Respiratory Diseases Unit, University of Modena and Reggio Emilia, 41124 Modena, Italy; (R.T.); (E.C.)
| | - Nicola De Maria
- Gastroenterology Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy;
| | - Stefano Busani
- Intensive Care Unit, Department of Anaesthesia, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (S.B.); (E.B.); (I.C.); (M.G.)
| | - Emanuela Biagioni
- Intensive Care Unit, Department of Anaesthesia, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (S.B.); (E.B.); (I.C.); (M.G.)
| | - Irene Coloretti
- Intensive Care Unit, Department of Anaesthesia, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (S.B.); (E.B.); (I.C.); (M.G.)
| | - Giovanni Guaraldi
- Department of Infectious Diseases, University of Modena and Reggio Emilia, 41124 Modena, Italy; (E.B.); (G.L.); (J.M.); (G.G.)
| | - Mario Sarti
- Microbiology and Virology Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (W.G.); (M.P.); (M.S.)
| | - Mario Luppi
- Hematology Unit, University of Modena and Reggio Emilia, 41124 Modena, Italy;
| | - Enrico Clini
- Respiratory Diseases Unit, University of Modena and Reggio Emilia, 41124 Modena, Italy; (R.T.); (E.C.)
| | - Massimo Girardis
- Intensive Care Unit, Department of Anaesthesia, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (S.B.); (E.B.); (I.C.); (M.G.)
| | - Inge C. Gyssens
- Radboud Center for Infectious Diseases, Department of Internal Medicine, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands;
- Faculty of Medicine and Life Sciences, Hasselt University, 3500 Hasselt, Belgium
| | - Cristina Mussini
- Infectious Diseases Unit, Azienda Ospedaliero-Universitaria Policlinico, 41124 Modena, Italy; (A.S.); (M.M.); (M.M.); (A.B.); (G.O.); (C.P.); (M.D.); (F.C.); (G.C.); (L.C.)
- Department of Infectious Diseases, University of Modena and Reggio Emilia, 41124 Modena, Italy; (E.B.); (G.L.); (J.M.); (G.G.)
- Correspondence: (E.F.); (C.M.)
| |
Collapse
|
4
|
Abstract
Antigen-driven activation of CD8+ T cells results in the development of a robust anti-pathogen response and ultimately leads to the establishment of long-lived memory T cells. During the primary response, CD8+ T cells interact multiple times with cognate antigen on distinct types of antigen-presenting cells. The timing, location and context of these antigen encounters significantly impact the differentiation programs initiated in the cells. Moderate re-activation in the periphery promotes the establishment of the tissue-resident memory T cells that serve as sentinels at the portal of pathogen entry. Under some circumstances, moderate re-activation of T cells in the periphery can result in the excessive expansion and accumulation of circulatory memory T cells, a process called memory inflation. In contrast, excessive re-activation stimuli generally impede conventional T-cell differentiation programs and can result in T-cell exhaustion. However, these conditions can also elicit a small population of exhausted T cells with a memory-like signature and self-renewal capability that are capable of responding to immunotherapy, and restoration of functional activity. Although it is clear that antigen re-encounter during the primary immune response has a significant impact on memory T-cell development, we still do not understand the molecular details that drive these fate decisions. Here, we review our understanding of how antigen encounters and re-activation events impact the array of memory CD8+ T-cell subsets subsequently generated. Identification of the molecular programs that drive memory T-cell generation will advance the development of new vaccine strategies that elicit high-quality CD8+ T-cell memory.
Collapse
Affiliation(s)
- Shiki Takamura
- Department of Immunology, Faculty of Medicine, Kindai University, Ohno-Higashi, Osaka-Sayama, Osaka, Japan
| |
Collapse
|
5
|
Kabekkodu SP, Shukla V, Varghese VK, Adiga D, Vethil Jishnu P, Chakrabarty S, Satyamoorthy K. Cluster miRNAs and cancer: Diagnostic, prognostic and therapeutic opportunities. Wiley Interdiscip Rev RNA 2019; 11:e1563. [PMID: 31436881 DOI: 10.1002/wrna.1563] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 07/05/2019] [Accepted: 07/25/2019] [Indexed: 02/06/2023]
Abstract
MiRNAs are class of noncoding RNA important for gene expression regulation in many plants, animals and viruses. MiRNA clusters contain a set of two or more miRNA encoding genes, transcribed together as polycistronic miRNAs. Currently, there are approximately 159 miRNA clusters reported in the human genome consisting of miRNAs ranging from two or more miRNA genes. A large proportion of clustered miRNAs resides in and around the fragile sites or cancer associated genomic hotspots and plays an important role in carcinogenesis. Altered expression of miRNA cluster can be pro-tumorigenic or anti-tumorigenic and can be targeted for clinical management of cancer. Over the past few years, manipulation of miRNA clusters expression is attempted for experimental purpose as well as for diagnostic, prognostic and therapeutic applications in cancer. Re-expression of miRNAs by epigenetic therapy, genome editing such as clustered regulatory interspaced short palindromic repeats (CRISPR) and miRNA mowers showed promising results in cancer therapy. In this review, we focused on the potential of miRNA clusters as a biomarker for diagnosis, prognosis, targeted therapy as well as strategies for modulating their expression in a therapeutic context. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Processing > Processing of Small RNAs RNA in Disease and Development > RNA in Disease Regulatory RNAs/RNAi/Riboswitches > Biogenesis of Effector Small RNAs.
Collapse
Affiliation(s)
- Shama Prasada Kabekkodu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Vaibhav Shukla
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Vinay Koshy Varghese
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Divya Adiga
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Padacherri Vethil Jishnu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Kapaettu Satyamoorthy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| |
Collapse
|
6
|
Panchenko VN, Babushkin DE, Bercaw JE, Brintzinger HH. Catalyst Speciation During ansa-Zirconocene-Catalyzed Polymerization of 1-Hexene Studied by UV-vis Spectroscopy-Formation and Partial Re-Activation of Zr-Allyl Intermediates. Polymers (Basel) 2019; 11:E936. [PMID: 31146475 DOI: 10.3390/polym11060936] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 05/22/2019] [Accepted: 05/24/2019] [Indexed: 11/24/2022] Open
Abstract
Catalyst speciation during polymerization of 1-hexene in benzene or toluene solutions of the catalyst precursor SBIZr(μ-Me)2AlMe2+ B(C6F5)4− (SBI = rac-dimethylsilyl-bis(1-indenyl)) at 23 °C is studied by following the accompanying UV-vis-spectral changes. These indicate that the onset of polymerization catalysis is associated with the concurrent formation of two distinct zirconocene species. One of these is proposed to consist of SBIZr-σ-polyhexenyl cations arising from SBIZr-Me+ (formed from SBIZr(μ-Me)2AlMe2+ by release of AlMe3) by repeated olefin insertions, while the other one is proposed to consist of SBIZr-η3-allyl cations of composition SBIZr-η3-(1-R-C3H4)+ (R = n-propyl), formed by σ-bond metathesis between SBIZr-Me+ and 1-hexene under release of methane. At later reaction stages, all zirconocene-σ–polymeryl cations appear to decay to yet another SBIZr-allyl species, i.e., to cations of the type SBIZr-η3-(x-R-(3-x)-pol-C3H3)+ (pol = i-polyhexenyl, x = 1 or 2). Renewed addition of excess 1-hexene is proposed to convert these sterically encumbered Zr-allyl cations back to catalytically active SBIZr-σ–polymeryl cations within a few seconds, presumably by initial 1-hexene insertion into the η1- isomer, followed by repeated additional insertions, while the initially formed, less crowded allyl cations, SBIZr-η3-(1-R-C3H4)+ appear to remain unchanged. Implications of these results with regard to the kinetics of zirconocene-catalyzed olefin polymerization are discussed.
Collapse
|
7
|
Shupp AB, Kolb AD, Mukhopadhyay D, Bussard KM. Cancer Metastases to Bone: Concepts, Mechanisms, and Interactions with Bone Osteoblasts. Cancers (Basel) 2018; 10:E182. [PMID: 29867053 PMCID: PMC6025347 DOI: 10.3390/cancers10060182] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 05/29/2018] [Accepted: 05/31/2018] [Indexed: 12/31/2022] Open
Abstract
The skeleton is a unique structure capable of providing support for the body. Bone resorption and deposition are controlled in a tightly regulated balance between osteoblasts and osteoclasts with no net bone gain or loss. However, under conditions of disease, the balance between bone resorption and deposition is upset. Osteoblasts play an important role in bone homeostasis by depositing new bone osteoid into resorption pits. It is becoming increasingly evident that osteoblasts additionally play key roles in cancer cell dissemination to bone and subsequent metastasis. Our laboratory has evidence that when osteoblasts come into contact with disseminated breast cancer cells, the osteoblasts produce factors that initially reduce breast cancer cell proliferation, yet promote cancer cell survival in bone. Other laboratories have demonstrated that osteoblasts both directly and indirectly contribute to dormant cancer cell reactivation in bone. Moreover, we have demonstrated that osteoblasts undergo an inflammatory stress response in late stages of breast cancer, and produce inflammatory cytokines that are maintenance and survival factors for breast cancer cells and osteoclasts. Advances in understanding interactions between osteoblasts, osteoclasts, and bone metastatic cancer cells will aid in controlling and ultimately preventing cancer cell metastasis to bone.
Collapse
Affiliation(s)
- Alison B Shupp
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
| | - Alexus D Kolb
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
| | - Dimpi Mukhopadhyay
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
| | - Karen M Bussard
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
| |
Collapse
|