1225
different approach, using a plasmid vector present at low copy number in the bacteria to prevent accumulation of the toxic protein.2 They synthesised CFTR in vitro and also expressed the recombinant protein in fibroblast cells (which do not normally express CFTR). CFTR was found to have many of the features predicted from the protein sequence: it is associated with cell membranes, can be phosphorylated,
a
and is normally glycosylated. A characteristic feature of CF epithelia is the lack of response to cyclic AMP (cAMP) induction of chloride efflux. Expression of recombinant CFTR under the control of viral promoters restored normal function to both pancreatic and airway cells from CF patients. 1,3 A recombinant molecule encoding mutant CFTR (deleted for the phenylalanine at position 508) is transcribed and translated like the normal sequence, but the resultant protein does not restore response to cAMP.3 These experiments show at the physiological level that the sequence identified solely by genetic means is the CF gene. Evidence that the expression of a single copy of the normal gene can correct the CF defect raises once again the possibility of gene therapy as a treatment for CF. To date, gene therapy stratagems have focused on the immune system, where the cells which must be "cured" can be accessed before differentiation, infected with a recombinant retrovirus in the laboratory, and returned to the patient. In CF morbidity is mainly due to respiratory failure following massive infection of the lung by microorganisms. These infections become increasingly difficult to treat whereas the gastrointestinal complications associated with CF can largely be controlled with enzyme supplements. The lung, therefore, is the organ that is most likely to be targeted in any gene therapy procedure. It is not yet known which cell type in the lung expresses CFTR and, by contrast with bone marrow, surgical removal of pulmonary stem cells does not seem to be feasible. Genes can be introduced into airway epithelial cells by retrovirus-mediated gene transfer but cell division is required for expression of the recombinant gene. However, adenoviruses do not require cell division to express genes introduced into the viral genome. Moreover, adenoviruses are normally present in the respiratory tract and are trophic for lung cells. Portions of the viral genome essential for replication can be deleted and replaced with the gene one wishes to express. The virus remains capable of infecting cells but cannot replicate itself, lyse the host cells, and infect other cells. Preliminary experiments in rats have shown that a modified type 5 adenovirus can infect lung cells in vivo after introduction of the virus into the trachea. The virus directed expression of a recombinant gene in these cells and the protein product was secreted by the cells as expected.4 Another virus that may be useful is the adeno-associated virus (AAV). This virus is defective, cannot grow in the absence of helper virus, and does not cause any known disease in man. Preliminary experiments have confirmed the possibilities of using recombinant viruses to direct gene expression in airway epithelial cells.5 The hurdles that have still to be overcome, especially with respect to recombinant viruses, should not be underestimated. Gene therapy requires the most stringent safety standards and a suitable animal model of CF to test possible therapies will not be available for some time. Consequently it is essential that clinicians and scientists do not raise the hopes of patients and parents prematurely. Many more children will be born with, and die
from, cystic fibrosis before any are cured by gene therapy. 1. Drumm ML, Pope HA, Cliff WK, et al. Correction of the cystic fibrosis defect in vitro by retrovirus-mediated gene transfer. Cell 1990; 62: 1227-33. 2. Gregory RJ, Cheng SH, Rich DP, et al. Expression and characterisation of the cystic fibrosis transmembrane conductance regulator. Nature 1990; 347: 382-86. 3. Rich DP, Anderson MP, Gregory RJ, et al. Expression of cystic fibrosis transmembrane conductance regulator corrects defective chloride channel regulation in cystic fibrosis airway epithelial cells. Nature 1990; 347: 358-63. 4. Crystal RG, Rosenfeld M, Siegfried W, et al. New viral transfer systems. Pediatr Pulmonol 1990; 5 (suppl): 103. 5. Carter BJ, Flotte TR, Owens RA. Adeno-associated viruses for gene transfer. Pediatr Pulmonol 1990; 5 (suppl): 104-05.
CLINICAL ULTRASOUND IN DEVELOPING COUNTRIES
practitioners appreciate that acquisition of the knowledge necessary to provide an accurate service which clinical colleagues value and act upon, without recourse to countless other investigations, is long and difficult but very rewarding. In Africa and other developing countries disease often presents so late that the lesions revealed by ultrasound are huge and bizarre. Scan abnormalities are so abundant and complicated by manifestations of endemic disease that ultrasound practitioners trained in a western country may be both amazed. Nevertheless, those who hold that ultrasound should be the first (and often only) investigation will have that view enhanced if the setting is Africa. The cost of X-ray equipment and the training abroad of radiologists is a great burden on the economy of developing countries. Equipment may not be serviced regularly, breakdowns are frequent, and repairs can take for ever. The lure of private practice, chronic staff shortages, and poor pay lead to low morale and, in turn, low standards. In many third-world countries the belief, long outdated elsewhere, that diagnostic radiology belongs in the basement (from where films emerge for the critical scrutiny of the clinicians upstairs) still persists. Techniques such as computerised tomography and magnetic resonance imaging that, with ultrasound, have done so much to improve the standing of radiology elsewhere, remain unfulfilled ambitions or very expensive luxuries. Ultrasound, on the other hand, is inexpensive, mobile, and requires little servicing and no installation other than a 13 amp plug. It is very accurate in experienced hands and can replace many conventional investigations. An ultrasound scan can, and should, be the first line of investigation for virtually all biliary, gynaecological, and genitourinary lesions, abdominal and pelvic masses, thyroid, salivary gland, and lymph-node Ultrasound
tumours, and scrotal lesions. In babies and young children it can be used to diagnose pyloric stenosis, congenital hip dislocation, intussusception, and brain lesions. The place of ultrasound in cardiology is well established. A complete "tour" of the abdomen and/or pelvis can be done in a few minutes or up to half an hour, depending on whether there are complicating lesions. A typical "list" for an ultrasound session at a hospital in Africa will be dominated by abdominal masses, renal failure, and gross gynaecological conditions; and in children huge abdominal or pelvic masses, tumours of the orbit and retro-orbital space, and the tragic consequences of meningitis (only too obvious when viewed through the open fontanelle) will predominate. The size of the lesions and the massive ascites that often accompanies them may be
1226
daunting at first, but if the principles of ultrasound are well understood and intelligently applied, the complexities encountered are soon overcome. Ultrasound diagnosis demands a good knowledge of anatomy, pathology, medicine, and surgery, and that means a medical training, preferably as a radiologist. Because the picture produced differs completely from that of all the other imaging facilities, it is usually unintelligible to anyone (clinician, technician, and radiologist specialising in different techniques) other than the operator. There is, then, a risk of misuse. If ultrasound is used to sex fetuses its standing will he harmed. Where there is a shortage of doctors (and radiologists) an attachment of, perhaps, 18 months to an ultrasound unit for a doctor with several years’ clinical experience can produce the skill needed to provide a diagnostic service of a high standard within the sphere of a radiology department. The aspiring radiologist who leaves Africa to acquire experience overseas and returns with limited hands-on ultrasound training and a first-world insight cannot hope to provide the sort of service that is needed to earn the confidence of referring clinicians. If the full potential of ultrasound1 is to be realised, consideration should be given to extending the service to provincial and other peripheral hospitals. In combination with WHO-BRS machines,2a considerable workload could be lifted from the main hospitals by, say, one day a week visits from ultrasound specialists. The successful conversion from conventional X-ray methods requires the confidence that only a skilled person can inspire. 1. Mindel S. The full potential of ultrasound. Lancet 1988; i: 244. 2. Editorial. X rays for the developing world. Lancet 1989; ii: 960.
ON-LINE CARTOGRAPHY IN OXFORD The latest in a series of international human gene mapping workshops, HMG 10 5, held in St John’s College, Oxford, in September provided an opportunity for experts in a wide variety of gene mapping activities to evaluate a new database system and to update the human gene map in preparation for HGM 11 (London) next August and subsequent meetings in Japan in 1992 and 1993. The human genome project has been fiercely debated. The long-term objective of this mammoth enterprise is to establish the sequence of the 3 billion nucleotides that comprise the genetic information in one human egg or sperm; however, the estimated number of human genes (50 000-100 000) is believed to account for only about 5% of this DNA. Human gene mapping workshops, through their international network of committees, are involved-in the less ambitious, but to some minds more practical, task of identifying and locating the genes in this essential fraction of the human genome. Progress has already been remarkable: over 1800 genes and about 5000 other DNA markers were recorded in the database by the end of the Oxford meeting. Although these figures are impressive, more than 95 % of coding sequences still remain to be fitted into the chromosomal maps. Within the workshop structure, the data are handled by a series of committees (one for each chromosome and others with special skills-eg, in nomenclature, DNA markers, and clinical disorders). Computers have played an increasingly important part in chromosome mapping. In Oxford, more than fifty rooms in St John’s College were connected via high-transmission optic-fibre cable for the meeting, and the College itself was linked to the University computing centre. In response to
the demand for an increasingly complex relational database, system known as the genome database (GDB) has been developed. This is a Howard Hughes Medical Institute project in collaboration with the Johns Hopkins University School of Medicine and the William H. Welch Medical Library in Baltimore, USA. The introduction and application of GDB to the chromosome committees for the workshop was undertaken with the help of human gene mapping computing team at the Imperial Cancer Research Fund (London) and the HGM 10-5 organisers; a highly important contribution was made by a team of trained local assistants, mostly graduate students, who worked closely with each of the workshop committees. Since the last published report in 1989 (in a special edition of Cytogenet Cell Genet, volume 51), several genes associated with disorders have been characterised, mapped, and incorporated into the database. Examples include an autosomal dominant form of retinitis pigmentosa (attributed to mutations within the rhodopsin gene on chromosome 3); facioscapulohumeral muscular dystrophy (chromosome 4); a form of spinal muscular atrophy (chromosome 5); and Marfan’s syndrome (chromosome 15). Knowledge of chromosomal position for a genetic disorder can allow a direct approach to the isolation and characterisation of the genes involved-eg, the cystic fibrosis gene (chromosome 7) and the candidate gene for von Recklinghausen’s neurofibromatosis, NF1 (chromosome 17). The proceedings of the Oxford Workshop will be published as an update to the human gene map and it is intended that the entire database should also be available, together with McKusick’s Mendelian Inheritance in Man, for on-line access (OMIM) in the near future through the Human Genome Resource Centre at Northwick Park; GDB and the OMIM database are already available in Baltimore and it is planned that Japan and another centre, possibly in Europe, will follow. a new
BREVITY IN THE LANCET In medical writing short can be very sweet. According to the citation analysts some of the most impactful items in The Lancet appear as Letters to the Editor; many an impressive observation has been recorded in half a page or so. Half a page, however, is often too painful a squeeze for otherwise suitable items; furthermore, some authors hesitate to consign their results to a correspondence section that does not have (and never can have) the cachet of 100% peer review. From January, therefore, we are offering a halfway house for contributions that lie somewhere between the letter and the full-scale paper. This idea of publishing Short Reports is hardly revolutionary. Where The Lancet’s scheme breaks new ground is in the offer to store, rather than print, the fine detail. After scrutiny by the external reviewers, part of the article (eg, comprehensive information on technical methods or detailed tables) may be kept in the editorial office for onward transmission to those few readers who require it. The dimensions of a Short Report? The published length should not exceed 2tcolumns of the journal. As pure text this would allow 1250 words; but, from this total, authors would have to deduct for the heading, the summary (not more than 100 words), figures, tables, and references (a maximum of 10), so they might well have no more than 800 words to play with. The correspondence columns will continue much as before.
different approach, using a plasmid vector present at low copy number in the bacteria to prevent accumulation of the toxic protein.2 They synthesised CFTR in vitro and also expressed the recombinant protein in fibroblast cells (which do not normally express CFTR). CFTR was found to have many of the features predicted from the protein sequence: it is associated with cell membranes, can be phosphorylated,
a
and is normally glycosylated. A characteristic feature of CF epithelia is the lack of response to cyclic AMP (cAMP) induction of chloride efflux. Expression of recombinant CFTR under the control of viral promoters restored normal function to both pancreatic and airway cells from CF patients. 1,3 A recombinant molecule encoding mutant CFTR (deleted for the phenylalanine at position 508) is transcribed and translated like the normal sequence, but the resultant protein does not restore response to cAMP.3 These experiments show at the physiological level that the sequence identified solely by genetic means is the CF gene. Evidence that the expression of a single copy of the normal gene can correct the CF defect raises once again the possibility of gene therapy as a treatment for CF. To date, gene therapy stratagems have focused on the immune system, where the cells which must be "cured" can be accessed before differentiation, infected with a recombinant retrovirus in the laboratory, and returned to the patient. In CF morbidity is mainly due to respiratory failure following massive infection of the lung by microorganisms. These infections become increasingly difficult to treat whereas the gastrointestinal complications associated with CF can largely be controlled with enzyme supplements. The lung, therefore, is the organ that is most likely to be targeted in any gene therapy procedure. It is not yet known which cell type in the lung expresses CFTR and, by contrast with bone marrow, surgical removal of pulmonary stem cells does not seem to be feasible. Genes can be introduced into airway epithelial cells by retrovirus-mediated gene transfer but cell division is required for expression of the recombinant gene. However, adenoviruses do not require cell division to express genes introduced into the viral genome. Moreover, adenoviruses are normally present in the respiratory tract and are trophic for lung cells. Portions of the viral genome essential for replication can be deleted and replaced with the gene one wishes to express. The virus remains capable of infecting cells but cannot replicate itself, lyse the host cells, and infect other cells. Preliminary experiments in rats have shown that a modified type 5 adenovirus can infect lung cells in vivo after introduction of the virus into the trachea. The virus directed expression of a recombinant gene in these cells and the protein product was secreted by the cells as expected.4 Another virus that may be useful is the adeno-associated virus (AAV). This virus is defective, cannot grow in the absence of helper virus, and does not cause any known disease in man. Preliminary experiments have confirmed the possibilities of using recombinant viruses to direct gene expression in airway epithelial cells.5 The hurdles that have still to be overcome, especially with respect to recombinant viruses, should not be underestimated. Gene therapy requires the most stringent safety standards and a suitable animal model of CF to test possible therapies will not be available for some time. Consequently it is essential that clinicians and scientists do not raise the hopes of patients and parents prematurely. Many more children will be born with, and die
from, cystic fibrosis before any are cured by gene therapy. 1. Drumm ML, Pope HA, Cliff WK, et al. Correction of the cystic fibrosis defect in vitro by retrovirus-mediated gene transfer. Cell 1990; 62: 1227-33. 2. Gregory RJ, Cheng SH, Rich DP, et al. Expression and characterisation of the cystic fibrosis transmembrane conductance regulator. Nature 1990; 347: 382-86. 3. Rich DP, Anderson MP, Gregory RJ, et al. Expression of cystic fibrosis transmembrane conductance regulator corrects defective chloride channel regulation in cystic fibrosis airway epithelial cells. Nature 1990; 347: 358-63. 4. Crystal RG, Rosenfeld M, Siegfried W, et al. New viral transfer systems. Pediatr Pulmonol 1990; 5 (suppl): 103. 5. Carter BJ, Flotte TR, Owens RA. Adeno-associated viruses for gene transfer. Pediatr Pulmonol 1990; 5 (suppl): 104-05.
CLINICAL ULTRASOUND IN DEVELOPING COUNTRIES
practitioners appreciate that acquisition of the knowledge necessary to provide an accurate service which clinical colleagues value and act upon, without recourse to countless other investigations, is long and difficult but very rewarding. In Africa and other developing countries disease often presents so late that the lesions revealed by ultrasound are huge and bizarre. Scan abnormalities are so abundant and complicated by manifestations of endemic disease that ultrasound practitioners trained in a western country may be both amazed. Nevertheless, those who hold that ultrasound should be the first (and often only) investigation will have that view enhanced if the setting is Africa. The cost of X-ray equipment and the training abroad of radiologists is a great burden on the economy of developing countries. Equipment may not be serviced regularly, breakdowns are frequent, and repairs can take for ever. The lure of private practice, chronic staff shortages, and poor pay lead to low morale and, in turn, low standards. In many third-world countries the belief, long outdated elsewhere, that diagnostic radiology belongs in the basement (from where films emerge for the critical scrutiny of the clinicians upstairs) still persists. Techniques such as computerised tomography and magnetic resonance imaging that, with ultrasound, have done so much to improve the standing of radiology elsewhere, remain unfulfilled ambitions or very expensive luxuries. Ultrasound, on the other hand, is inexpensive, mobile, and requires little servicing and no installation other than a 13 amp plug. It is very accurate in experienced hands and can replace many conventional investigations. An ultrasound scan can, and should, be the first line of investigation for virtually all biliary, gynaecological, and genitourinary lesions, abdominal and pelvic masses, thyroid, salivary gland, and lymph-node Ultrasound
tumours, and scrotal lesions. In babies and young children it can be used to diagnose pyloric stenosis, congenital hip dislocation, intussusception, and brain lesions. The place of ultrasound in cardiology is well established. A complete "tour" of the abdomen and/or pelvis can be done in a few minutes or up to half an hour, depending on whether there are complicating lesions. A typical "list" for an ultrasound session at a hospital in Africa will be dominated by abdominal masses, renal failure, and gross gynaecological conditions; and in children huge abdominal or pelvic masses, tumours of the orbit and retro-orbital space, and the tragic consequences of meningitis (only too obvious when viewed through the open fontanelle) will predominate. The size of the lesions and the massive ascites that often accompanies them may be
1226
daunting at first, but if the principles of ultrasound are well understood and intelligently applied, the complexities encountered are soon overcome. Ultrasound diagnosis demands a good knowledge of anatomy, pathology, medicine, and surgery, and that means a medical training, preferably as a radiologist. Because the picture produced differs completely from that of all the other imaging facilities, it is usually unintelligible to anyone (clinician, technician, and radiologist specialising in different techniques) other than the operator. There is, then, a risk of misuse. If ultrasound is used to sex fetuses its standing will he harmed. Where there is a shortage of doctors (and radiologists) an attachment of, perhaps, 18 months to an ultrasound unit for a doctor with several years’ clinical experience can produce the skill needed to provide a diagnostic service of a high standard within the sphere of a radiology department. The aspiring radiologist who leaves Africa to acquire experience overseas and returns with limited hands-on ultrasound training and a first-world insight cannot hope to provide the sort of service that is needed to earn the confidence of referring clinicians. If the full potential of ultrasound1 is to be realised, consideration should be given to extending the service to provincial and other peripheral hospitals. In combination with WHO-BRS machines,2a considerable workload could be lifted from the main hospitals by, say, one day a week visits from ultrasound specialists. The successful conversion from conventional X-ray methods requires the confidence that only a skilled person can inspire. 1. Mindel S. The full potential of ultrasound. Lancet 1988; i: 244. 2. Editorial. X rays for the developing world. Lancet 1989; ii: 960.
ON-LINE CARTOGRAPHY IN OXFORD The latest in a series of international human gene mapping workshops, HMG 10 5, held in St John’s College, Oxford, in September provided an opportunity for experts in a wide variety of gene mapping activities to evaluate a new database system and to update the human gene map in preparation for HGM 11 (London) next August and subsequent meetings in Japan in 1992 and 1993. The human genome project has been fiercely debated. The long-term objective of this mammoth enterprise is to establish the sequence of the 3 billion nucleotides that comprise the genetic information in one human egg or sperm; however, the estimated number of human genes (50 000-100 000) is believed to account for only about 5% of this DNA. Human gene mapping workshops, through their international network of committees, are involved-in the less ambitious, but to some minds more practical, task of identifying and locating the genes in this essential fraction of the human genome. Progress has already been remarkable: over 1800 genes and about 5000 other DNA markers were recorded in the database by the end of the Oxford meeting. Although these figures are impressive, more than 95 % of coding sequences still remain to be fitted into the chromosomal maps. Within the workshop structure, the data are handled by a series of committees (one for each chromosome and others with special skills-eg, in nomenclature, DNA markers, and clinical disorders). Computers have played an increasingly important part in chromosome mapping. In Oxford, more than fifty rooms in St John’s College were connected via high-transmission optic-fibre cable for the meeting, and the College itself was linked to the University computing centre. In response to
the demand for an increasingly complex relational database, system known as the genome database (GDB) has been developed. This is a Howard Hughes Medical Institute project in collaboration with the Johns Hopkins University School of Medicine and the William H. Welch Medical Library in Baltimore, USA. The introduction and application of GDB to the chromosome committees for the workshop was undertaken with the help of human gene mapping computing team at the Imperial Cancer Research Fund (London) and the HGM 10-5 organisers; a highly important contribution was made by a team of trained local assistants, mostly graduate students, who worked closely with each of the workshop committees. Since the last published report in 1989 (in a special edition of Cytogenet Cell Genet, volume 51), several genes associated with disorders have been characterised, mapped, and incorporated into the database. Examples include an autosomal dominant form of retinitis pigmentosa (attributed to mutations within the rhodopsin gene on chromosome 3); facioscapulohumeral muscular dystrophy (chromosome 4); a form of spinal muscular atrophy (chromosome 5); and Marfan’s syndrome (chromosome 15). Knowledge of chromosomal position for a genetic disorder can allow a direct approach to the isolation and characterisation of the genes involved-eg, the cystic fibrosis gene (chromosome 7) and the candidate gene for von Recklinghausen’s neurofibromatosis, NF1 (chromosome 17). The proceedings of the Oxford Workshop will be published as an update to the human gene map and it is intended that the entire database should also be available, together with McKusick’s Mendelian Inheritance in Man, for on-line access (OMIM) in the near future through the Human Genome Resource Centre at Northwick Park; GDB and the OMIM database are already available in Baltimore and it is planned that Japan and another centre, possibly in Europe, will follow. a new
BREVITY IN THE LANCET In medical writing short can be very sweet. According to the citation analysts some of the most impactful items in The Lancet appear as Letters to the Editor; many an impressive observation has been recorded in half a page or so. Half a page, however, is often too painful a squeeze for otherwise suitable items; furthermore, some authors hesitate to consign their results to a correspondence section that does not have (and never can have) the cachet of 100% peer review. From January, therefore, we are offering a halfway house for contributions that lie somewhere between the letter and the full-scale paper. This idea of publishing Short Reports is hardly revolutionary. Where The Lancet’s scheme breaks new ground is in the offer to store, rather than print, the fine detail. After scrutiny by the external reviewers, part of the article (eg, comprehensive information on technical methods or detailed tables) may be kept in the editorial office for onward transmission to those few readers who require it. The dimensions of a Short Report? The published length should not exceed 2tcolumns of the journal. As pure text this would allow 1250 words; but, from this total, authors would have to deduct for the heading, the summary (not more than 100 words), figures, tables, and references (a maximum of 10), so they might well have no more than 800 words to play with. The correspondence columns will continue much as before.
