Author: Crispian Scully
Publisher: Academic Press
ISBN: 0128136820
Category : Medical
Languages : en
Pages : 124
Book Description
Saliva Protection and Transmissible Diseases provides a review of saliva protection, raising debate on micro-organisms potentially transmissible in saliva, and also considering the evidence on diseases that may be transmitted by kissing. Saliva is a complex body fluid essential to health, especially mastication, swallowing and speech, and hyposalivation can lead to dysfunction and even infection. More serious pathogens, such as herpes viruses and papillomaviruses can be conveyed by kissing, as can potentially lethal micro-organisms present in some saliva, such as meningococci, fungal organisms and Ebola viruses. - Stipulates the defensive roles of saliva, an important topic not previously reviewed in-depth in literature - Provides awareness that saliva also transmits infectious agents that can produce serious or even lethal diseases - Gives understanding that kissing may be an at-risk practice
Saliva Protection and Transmissible Diseases
Author: Crispian Scully
Publisher: Academic Press
ISBN: 0128136820
Category : Medical
Languages : en
Pages : 124
Book Description
Saliva Protection and Transmissible Diseases provides a review of saliva protection, raising debate on micro-organisms potentially transmissible in saliva, and also considering the evidence on diseases that may be transmitted by kissing. Saliva is a complex body fluid essential to health, especially mastication, swallowing and speech, and hyposalivation can lead to dysfunction and even infection. More serious pathogens, such as herpes viruses and papillomaviruses can be conveyed by kissing, as can potentially lethal micro-organisms present in some saliva, such as meningococci, fungal organisms and Ebola viruses. - Stipulates the defensive roles of saliva, an important topic not previously reviewed in-depth in literature - Provides awareness that saliva also transmits infectious agents that can produce serious or even lethal diseases - Gives understanding that kissing may be an at-risk practice
Publisher: Academic Press
ISBN: 0128136820
Category : Medical
Languages : en
Pages : 124
Book Description
Saliva Protection and Transmissible Diseases provides a review of saliva protection, raising debate on micro-organisms potentially transmissible in saliva, and also considering the evidence on diseases that may be transmitted by kissing. Saliva is a complex body fluid essential to health, especially mastication, swallowing and speech, and hyposalivation can lead to dysfunction and even infection. More serious pathogens, such as herpes viruses and papillomaviruses can be conveyed by kissing, as can potentially lethal micro-organisms present in some saliva, such as meningococci, fungal organisms and Ebola viruses. - Stipulates the defensive roles of saliva, an important topic not previously reviewed in-depth in literature - Provides awareness that saliva also transmits infectious agents that can produce serious or even lethal diseases - Gives understanding that kissing may be an at-risk practice
Human Herpesviruses
Author: Ann Arvin
Publisher: Cambridge University Press
ISBN: 1139461648
Category : Medical
Languages : en
Pages : 1325
Book Description
This comprehensive account of the human herpesviruses provides an encyclopedic overview of their basic virology and clinical manifestations. This group of viruses includes human simplex type 1 and 2, Epstein–Barr virus, Kaposi's Sarcoma-associated herpesvirus, cytomegalovirus, HHV6A, 6B and 7, and varicella-zoster virus. The viral diseases and cancers they cause are significant and often recurrent. Their prevalence in the developed world accounts for a major burden of disease, and as a result there is a great deal of research into the pathophysiology of infection and immunobiology. Another important area covered within this volume concerns antiviral therapy and the development of vaccines. All these aspects are covered in depth, both scientifically and in terms of clinical guidelines for patient care. The text is illustrated generously throughout and is fully referenced to the latest research and developments.
Publisher: Cambridge University Press
ISBN: 1139461648
Category : Medical
Languages : en
Pages : 1325
Book Description
This comprehensive account of the human herpesviruses provides an encyclopedic overview of their basic virology and clinical manifestations. This group of viruses includes human simplex type 1 and 2, Epstein–Barr virus, Kaposi's Sarcoma-associated herpesvirus, cytomegalovirus, HHV6A, 6B and 7, and varicella-zoster virus. The viral diseases and cancers they cause are significant and often recurrent. Their prevalence in the developed world accounts for a major burden of disease, and as a result there is a great deal of research into the pathophysiology of infection and immunobiology. Another important area covered within this volume concerns antiviral therapy and the development of vaccines. All these aspects are covered in depth, both scientifically and in terms of clinical guidelines for patient care. The text is illustrated generously throughout and is fully referenced to the latest research and developments.
Human Herpesviruses
Author: Yasushi Kawaguchi
Publisher: Springer
ISBN: 9811072302
Category : Medical
Languages : en
Pages : 498
Book Description
This book introduces and reviews several topics for each human herpesvirus. One of the most important features of the book is that it covers aspects of both basic research and clinical medicine. Herpesviridae, a family of double-strand DNA viruses, has unique biological features by which these viruses establish latency after primary infection and reactivate in later life. Nine human herpesviruses are known so far, and each of them causes a variety of diseases in both primary infection and reactivation. Since the discovery of each human herpesvirus, an abundance of findings related to them has accumulated in basic research and clinical medicine. However, the vast majority of biological features is still masked in mystery. Furthermore, a strategy of treatment and prevention has not yet been established for most human herpesviruses. A wide range of readers will be interested in this volume with its treatment of problematic points and latest findings in the field.
Publisher: Springer
ISBN: 9811072302
Category : Medical
Languages : en
Pages : 498
Book Description
This book introduces and reviews several topics for each human herpesvirus. One of the most important features of the book is that it covers aspects of both basic research and clinical medicine. Herpesviridae, a family of double-strand DNA viruses, has unique biological features by which these viruses establish latency after primary infection and reactivate in later life. Nine human herpesviruses are known so far, and each of them causes a variety of diseases in both primary infection and reactivation. Since the discovery of each human herpesvirus, an abundance of findings related to them has accumulated in basic research and clinical medicine. However, the vast majority of biological features is still masked in mystery. Furthermore, a strategy of treatment and prevention has not yet been established for most human herpesviruses. A wide range of readers will be interested in this volume with its treatment of problematic points and latest findings in the field.
Emerging Transplant Infections
Author: Michele I. Morris
Publisher: Springer
ISBN: 9783030258689
Category : Medical
Languages : en
Pages : 0
Book Description
The field of transplant medicine has evolved significantly since the first kidney transplant was performed in 1954. Innovations in transplant immunosuppression have lowered the risk of organ rejection so that infectious complications are now the leading cause of hospitalization and mortality after solid organ transplant. Infection is also cited as the leading cause of non-relapse mortality after stem cell transplantation. As transplant centers have recognized the importance of transplant specific expertise in patient outcomes, the field of transplant infectious diseases has expanded into a recognized and highly valued subspecialty. International growth in solid organ and stem cell transplantation has outpaced access to such expertise, with some centers employing microbiology laboratory directors and transplant nephrologists as their lead infectious diseases consultants. This has been a particular challenge as the use of novel immunosuppressive regimens in new geographic and immigrant populations have fueled the emergence of new infection syndromes, with the initial presentation sometimes occurring in this most vulnerable patient population. This digital-first book is designed to meet the needs of practitioners engaged in transplant infectious disease practice who need more depth than they are able to find in UpToDate. It provides an overview of emerging infectious disease challenges with clinically relevant information regarding the epidemiology, diagnosis, management, and prevention of infections in solid organ and stem cell transplant recipients. Each chapter focuses on a clinical syndrome or pathogen with new or emerging implications for transplant patients. Given the rapidly evolving nature of emerging infections and topics in transplant infections, no resource has been published on these increasingly notorious issues; this this text is written by top, global experts who regularly update the material to ensure that readers will always have access to the most cutting edge material available. The editorial team consists of three experienced leaders in the field, all of whom have a strong record of scholarship and publication, as well as an international reputation. All three have focused their academic careers on emerging infectious diseases in transplantation, including a current and a past president of various infectious diseases and transplantation societies. The editors are also experienced reviewers and authors who have collaborated on multiple previous projects. All are committed to this project as a unique opportunity to make an important contribution to their field.
Publisher: Springer
ISBN: 9783030258689
Category : Medical
Languages : en
Pages : 0
Book Description
The field of transplant medicine has evolved significantly since the first kidney transplant was performed in 1954. Innovations in transplant immunosuppression have lowered the risk of organ rejection so that infectious complications are now the leading cause of hospitalization and mortality after solid organ transplant. Infection is also cited as the leading cause of non-relapse mortality after stem cell transplantation. As transplant centers have recognized the importance of transplant specific expertise in patient outcomes, the field of transplant infectious diseases has expanded into a recognized and highly valued subspecialty. International growth in solid organ and stem cell transplantation has outpaced access to such expertise, with some centers employing microbiology laboratory directors and transplant nephrologists as their lead infectious diseases consultants. This has been a particular challenge as the use of novel immunosuppressive regimens in new geographic and immigrant populations have fueled the emergence of new infection syndromes, with the initial presentation sometimes occurring in this most vulnerable patient population. This digital-first book is designed to meet the needs of practitioners engaged in transplant infectious disease practice who need more depth than they are able to find in UpToDate. It provides an overview of emerging infectious disease challenges with clinically relevant information regarding the epidemiology, diagnosis, management, and prevention of infections in solid organ and stem cell transplant recipients. Each chapter focuses on a clinical syndrome or pathogen with new or emerging implications for transplant patients. Given the rapidly evolving nature of emerging infections and topics in transplant infections, no resource has been published on these increasingly notorious issues; this this text is written by top, global experts who regularly update the material to ensure that readers will always have access to the most cutting edge material available. The editorial team consists of three experienced leaders in the field, all of whom have a strong record of scholarship and publication, as well as an international reputation. All three have focused their academic careers on emerging infectious diseases in transplantation, including a current and a past president of various infectious diseases and transplantation societies. The editors are also experienced reviewers and authors who have collaborated on multiple previous projects. All are committed to this project as a unique opportunity to make an important contribution to their field.
Virology E-Book
Author: Stephen N J Korsman
Publisher: Elsevier Health Sciences
ISBN: 1455742139
Category : Medical
Languages : en
Pages : 149
Book Description
This is a concise, highly accessible introduction to medical virology, incorporating essential basic principles as well as a systematic review of viruses and viral diseases. It pays particular attention to developments in anti-viral therapy that are becoming increasingly effective in modern medicine. It is an ideal textbook for the information-overloaded student and an invaluable everyday companion for the busy professional who needs a good understanding of the current state of medical virology. In keeping with the highly successful format of other Illustrated Colour Texts, it presents the subject as a series of succinct 2 page 'learning units', using a superb collection of clear illustrations and clinical photographs, concise yet comprehensive text and key point boxes to aid quick access to information and examination preparation. So whether you are a medical student, junior doctor, medical scientist, trainee in infectious diseases or student on another allied medical course, this book is here to make your life easier! It will also provide a very solid foundation for any who plan to delve deeper into this fascinating field. - Part of the popular Illustrated Colour Text series - Information presented in double page spreads for easy learning - Highly illustrated with both full colour graphics and clinical photographs - Each spread includes a key point box for exam preparation
Publisher: Elsevier Health Sciences
ISBN: 1455742139
Category : Medical
Languages : en
Pages : 149
Book Description
This is a concise, highly accessible introduction to medical virology, incorporating essential basic principles as well as a systematic review of viruses and viral diseases. It pays particular attention to developments in anti-viral therapy that are becoming increasingly effective in modern medicine. It is an ideal textbook for the information-overloaded student and an invaluable everyday companion for the busy professional who needs a good understanding of the current state of medical virology. In keeping with the highly successful format of other Illustrated Colour Texts, it presents the subject as a series of succinct 2 page 'learning units', using a superb collection of clear illustrations and clinical photographs, concise yet comprehensive text and key point boxes to aid quick access to information and examination preparation. So whether you are a medical student, junior doctor, medical scientist, trainee in infectious diseases or student on another allied medical course, this book is here to make your life easier! It will also provide a very solid foundation for any who plan to delve deeper into this fascinating field. - Part of the popular Illustrated Colour Text series - Information presented in double page spreads for easy learning - Highly illustrated with both full colour graphics and clinical photographs - Each spread includes a key point box for exam preparation
Endometrial Gene Expression
Author: Joanne Kwak-Kim
Publisher: Springer
ISBN: 9783030285869
Category : Health & Fitness
Languages : en
Pages : 0
Book Description
The endometrium goes through cyclical changes under the influence of hormones, and immune effectors in the endometrium change their populations cyclically as well. Dynamic changes in immune effectors determine endometrial cytokine and chemokine milieus and, consequently, the endometrial immune response. Endometrial immune responses have been shown to be important for trophoblast invasion and early pregnancy. Indeed, dysregulated endometrial inflammatory immune responses are associated with reproductive failures, such as recurrent pregnancy losses, repeated implantation failure, and gynecological diseases with oncogenic potential. Hence, the investigation of endometrial gene expression may predict infertility, gynecological and oncological conditions. This book presents the state of the art in endometrial gene expression as well as recent developmental findings relating to reproduction and reproductive disorders. It begins with a review of the genetic regulation of urogenital tract formation and molecular mechanism underlying the physiology of menstrual cycle before moving on to the current and emerging technological advances in molecular biology. Endometrial gene expressions of immune inflammatory conditions, viral infection, metabolic and nutritional conditions, and reproductive disorders are then presented in following chapters. Examples of the use and interpretation of gene expression in clinical scenarios including recurrent pregnancy losses, infertility and multiple implantation failures are presented with currently available endometrial gene analysis. Utilizing the latest evidence and clinical guidelines, Endometrial Gene Expression will be a cutting-edge resource for gynecologist, reproductive immunologist, reproductive endocrinologists, obstetrician, maternal fetal medicine specialist and other health care providers in the field of reproductive medicine.
Publisher: Springer
ISBN: 9783030285869
Category : Health & Fitness
Languages : en
Pages : 0
Book Description
The endometrium goes through cyclical changes under the influence of hormones, and immune effectors in the endometrium change their populations cyclically as well. Dynamic changes in immune effectors determine endometrial cytokine and chemokine milieus and, consequently, the endometrial immune response. Endometrial immune responses have been shown to be important for trophoblast invasion and early pregnancy. Indeed, dysregulated endometrial inflammatory immune responses are associated with reproductive failures, such as recurrent pregnancy losses, repeated implantation failure, and gynecological diseases with oncogenic potential. Hence, the investigation of endometrial gene expression may predict infertility, gynecological and oncological conditions. This book presents the state of the art in endometrial gene expression as well as recent developmental findings relating to reproduction and reproductive disorders. It begins with a review of the genetic regulation of urogenital tract formation and molecular mechanism underlying the physiology of menstrual cycle before moving on to the current and emerging technological advances in molecular biology. Endometrial gene expressions of immune inflammatory conditions, viral infection, metabolic and nutritional conditions, and reproductive disorders are then presented in following chapters. Examples of the use and interpretation of gene expression in clinical scenarios including recurrent pregnancy losses, infertility and multiple implantation failures are presented with currently available endometrial gene analysis. Utilizing the latest evidence and clinical guidelines, Endometrial Gene Expression will be a cutting-edge resource for gynecologist, reproductive immunologist, reproductive endocrinologists, obstetrician, maternal fetal medicine specialist and other health care providers in the field of reproductive medicine.
New Drug Development for Known and Emerging Viruses
Author: Helga Rübsamen-Schaeff
Publisher: John Wiley & Sons
ISBN: 3527810706
Category : Medical
Languages : en
Pages : 530
Book Description
Discusses how to fight Ebola, SARS Corona, and other known or emerging human viruses by building on the successes in antiviral therapy of the past decades Written by leading medicinal chemists from academia and industry, this book discusses the entire field of antiviral drug discovery and development from a medicinal chemistry perspective, focusing on antiviral drugs, targets, and viral disease mechanisms. It provides an outlook on emerging pathogens such as Ebola, Zika, West Nile, Lassa, and includes a chapter on SARS Coronoavirus-2 causing the present pandemic. New Drug Development for Known and Emerging Viruses describes the discovery and development process for antiviral agents for different classes of viruses and targets based on the experiences from the nine human viruses for which approved drugs are on the market (HIV, HCV, Influenza, RSV, HBV, HPV, HCMV, HSV, and VZV). It covers the properties and potential of 20 classes of currently approved antivirals, including combination drugs, and looks at novel antiviral strategies against emerging viruses. Covers the entire field of antiviral drug discovery and development Addresses the need for antiviral drugs to combat major health threats such as Ebola, Zika, West Nile, and SARS Coronavirus-2 Summarizes the successes of the past 15 years in developing ground-breaking medicines against 9 major human viruses, both from the medicinal chemistry and the pharmacological angle Discusses practical and strategic challenges in the drug discovery and development process, including screening technologies, latency, and toxicity issues New Developments in Antiviral Drugs is an important book for medicinal chemists, pharmaceutical chemists, virologists, and epidemiologists, and will be of great interest to those in the ;pharmaceutical industry and public health agencies.
Publisher: John Wiley & Sons
ISBN: 3527810706
Category : Medical
Languages : en
Pages : 530
Book Description
Discusses how to fight Ebola, SARS Corona, and other known or emerging human viruses by building on the successes in antiviral therapy of the past decades Written by leading medicinal chemists from academia and industry, this book discusses the entire field of antiviral drug discovery and development from a medicinal chemistry perspective, focusing on antiviral drugs, targets, and viral disease mechanisms. It provides an outlook on emerging pathogens such as Ebola, Zika, West Nile, Lassa, and includes a chapter on SARS Coronoavirus-2 causing the present pandemic. New Drug Development for Known and Emerging Viruses describes the discovery and development process for antiviral agents for different classes of viruses and targets based on the experiences from the nine human viruses for which approved drugs are on the market (HIV, HCV, Influenza, RSV, HBV, HPV, HCMV, HSV, and VZV). It covers the properties and potential of 20 classes of currently approved antivirals, including combination drugs, and looks at novel antiviral strategies against emerging viruses. Covers the entire field of antiviral drug discovery and development Addresses the need for antiviral drugs to combat major health threats such as Ebola, Zika, West Nile, and SARS Coronavirus-2 Summarizes the successes of the past 15 years in developing ground-breaking medicines against 9 major human viruses, both from the medicinal chemistry and the pharmacological angle Discusses practical and strategic challenges in the drug discovery and development process, including screening technologies, latency, and toxicity issues New Developments in Antiviral Drugs is an important book for medicinal chemists, pharmaceutical chemists, virologists, and epidemiologists, and will be of great interest to those in the ;pharmaceutical industry and public health agencies.
Persistent Viral Infections
Author: R. Ahmed
Publisher: Wiley-Blackwell
ISBN:
Category : Medical
Languages : en
Pages : 754
Book Description
Persistent Viral Infections Edited by Rafi Ahmed Emory Vaccine Center, Atlanta, USA and Irvin S. Y. Chen UCLA School of Medicine, Los Angeles, USA During the past decade much of our attention has focused on diseases associated with viral persistence. Major breakthroughs in immunology, and the advent of molecular approaches to study pathogenesis have increased our understanding of the complex virus-host interactions that occur during viral persistence. Persistent Viral Infections focuses on: * The pathogenesis and immunology of chronic infections * Animal models that provide, or have the potential to provide, major insights This volume will be essential reading for virologists, immunologists, oncologists and neurologists.
Publisher: Wiley-Blackwell
ISBN:
Category : Medical
Languages : en
Pages : 754
Book Description
Persistent Viral Infections Edited by Rafi Ahmed Emory Vaccine Center, Atlanta, USA and Irvin S. Y. Chen UCLA School of Medicine, Los Angeles, USA During the past decade much of our attention has focused on diseases associated with viral persistence. Major breakthroughs in immunology, and the advent of molecular approaches to study pathogenesis have increased our understanding of the complex virus-host interactions that occur during viral persistence. Persistent Viral Infections focuses on: * The pathogenesis and immunology of chronic infections * Animal models that provide, or have the potential to provide, major insights This volume will be essential reading for virologists, immunologists, oncologists and neurologists.
Essential Human Virology
Author: Jennifer Louten
Publisher: Academic Press
ISBN: 0323914926
Category : Science
Languages : en
Pages : 412
Book Description
Essential Human Virology, Second Edition focuses on the structure and classification of viruses, virus transmission and virus replication strategies based upon type of viral nucleic acid. Several chapters focus on notable and recognizable viruses and the diseases caused by them, including influenza, HIV, hepatitis viruses, poliovirus, herpesviruses and emerging and dangerous viruses. Additionally, how viruses cause disease (pathogenesis) is highlighted, along with discussions on immune response to viruses, vaccines, anti-viral drugs, gene therapy, the beneficial uses of viruses, research laboratory assays and viral diagnosis assays. Fully revised and updated with new chapters on coronaviruses, nonliving infectious agents, and notable non-human viruses, the book provides students with a solid foundation in virology. - Focuses on human diseases and the cellular pathology that viruses cause - Highlights current and cutting-edge technology and associated issues - Presents real case studies and current news highlights in each chapter - Features dynamic illustrations, chapter assessment questions, key terms, and a summary of concepts, as well as an instructor website with lecture slides, a test bank and recommended activities - Updated and revised, with new chapters on coronaviruses, nonliving infectious agents, and notable non-human viruses
Publisher: Academic Press
ISBN: 0323914926
Category : Science
Languages : en
Pages : 412
Book Description
Essential Human Virology, Second Edition focuses on the structure and classification of viruses, virus transmission and virus replication strategies based upon type of viral nucleic acid. Several chapters focus on notable and recognizable viruses and the diseases caused by them, including influenza, HIV, hepatitis viruses, poliovirus, herpesviruses and emerging and dangerous viruses. Additionally, how viruses cause disease (pathogenesis) is highlighted, along with discussions on immune response to viruses, vaccines, anti-viral drugs, gene therapy, the beneficial uses of viruses, research laboratory assays and viral diagnosis assays. Fully revised and updated with new chapters on coronaviruses, nonliving infectious agents, and notable non-human viruses, the book provides students with a solid foundation in virology. - Focuses on human diseases and the cellular pathology that viruses cause - Highlights current and cutting-edge technology and associated issues - Presents real case studies and current news highlights in each chapter - Features dynamic illustrations, chapter assessment questions, key terms, and a summary of concepts, as well as an instructor website with lecture slides, a test bank and recommended activities - Updated and revised, with new chapters on coronaviruses, nonliving infectious agents, and notable non-human viruses
The Epstein-Barr Virus
Author: M. A. Epstein
Publisher: Springer Science & Business Media
ISBN: 3642672361
Category : Medical
Languages : en
Pages : 467
Book Description
The Epstein-Barr virus was discovered 15 years ago. Since that time an immense body of information has been accumu lated on this agent which has come to assume great signifi cance in many different fields of biological science. Thus, the virus has very special relevance in human medicine and oncology, in tumor virology, in immunology, and in mole cular virology, since it is the cause of infectious mononu cleosis and also the first human cancer virus, etiologically related to endemic Burkitt's lymphoma and probably to nasopharyngeal carcinoma. In addition, continuous human lymphoid cell lines initiated and maintained by the transform ing function of the virus genome provide a laboratory tool with wide and ever-growing applications. Innumerable papers on the Epstein-Barr virus have ap peared over recent years and reports of work with this agent now constitute a veritable flood. The present book provides the first and only comprehensive, authoritative over-view of all aspects of the virus by authors who have been the original and major contributors in their particular disciplines. A complete and up-to-date survey of this unique and important agent is thus provided which should be of great interest to experts, teachers, and students engaged in cancer research, virology, immunology, molecular biology, epide miology, and cell culture. Where topics have been dealt with from more than one of these viewpoints, some inevitable overlap and duplication has resulted; although this has been kept to a minimum, it has been retained in some places because of positive usefulness.
Publisher: Springer Science & Business Media
ISBN: 3642672361
Category : Medical
Languages : en
Pages : 467
Book Description
The Epstein-Barr virus was discovered 15 years ago. Since that time an immense body of information has been accumu lated on this agent which has come to assume great signifi cance in many different fields of biological science. Thus, the virus has very special relevance in human medicine and oncology, in tumor virology, in immunology, and in mole cular virology, since it is the cause of infectious mononu cleosis and also the first human cancer virus, etiologically related to endemic Burkitt's lymphoma and probably to nasopharyngeal carcinoma. In addition, continuous human lymphoid cell lines initiated and maintained by the transform ing function of the virus genome provide a laboratory tool with wide and ever-growing applications. Innumerable papers on the Epstein-Barr virus have ap peared over recent years and reports of work with this agent now constitute a veritable flood. The present book provides the first and only comprehensive, authoritative over-view of all aspects of the virus by authors who have been the original and major contributors in their particular disciplines. A complete and up-to-date survey of this unique and important agent is thus provided which should be of great interest to experts, teachers, and students engaged in cancer research, virology, immunology, molecular biology, epide miology, and cell culture. Where topics have been dealt with from more than one of these viewpoints, some inevitable overlap and duplication has resulted; although this has been kept to a minimum, it has been retained in some places because of positive usefulness.