Searching the literature. A beginners' guide

A number of questions will arise as you develop a research question. Has the question you are asking already been answered? Have other attempts been made to answer the question? If so, what techniques have been tried and what problems have arisen? Is there work in this area that will assist in developing your proposal? To find out you need to review the literature, that is, conduct a literature search. The idea of sitting in a medical library reading a few journal articles sounds interesting and easy. It is, but it is not a literature search. With so many medical journals published each year it is necessary to conduct a formal search of the published literature and the advent of electronic databases has simplified the process. However, there are a number of traps for beginners. As a beginner and having made most of the mistakes, I have been asked to write this article so that you can avoid the traps.

A critical review of the role of neonatal hearing screening in the detection of congenital hearing impairment

BACKGROUND

This review was commissioned because of the increasing doubt about the ability of existing screening programmes (mainly the health visitor distraction test (HVDT) at 7-8 months) to identify children with congenital hearing impairment, and technological advances which have made neonatal hearing screening an alternative option.

OBJECTIVES

To review the available literature on the screening of permanent childhood hearing impairment. To provide commissioners and providers of health care with information about how to deliver a more uniform service, better outcomes, and more cost-effective screening. To identify areas for further research and service development.

HOW THE RESEARCH WAS CONDUCTED

The research involved a review of the available published and unpublished literature, and a comprehensive survey of current pre-school hearing screening provision in the UK coupled with a health economics study of hearing screening costs. The research also included a number of focus groups and visits to key centres in the UK and North America.

RESEARCH FINDINGS

EPIDEMIOLOGY OF PERMANENT CHILDHOOD HEARING IMPAIRMENT: There are approximately 840 children a year born in the UK with significant permanent hearing impairment likely to affect their own and their family's quality of life. Present services will miss about 400 of these children by 1 1/2 years of age, and about 200 of these children by 3 1/2 years of age. Such late identification of hearing impairment greatly reduces the responsiveness of the services for individual children.

EVIDENCE FOR IMPROVED OUTCOMES WITH EARLIER IDENTIFICATION

Hearing-impaired children identified late are at risk of substantial delay in their acquisition of language and communication skills, with consequent longer-term risk to education achievement, mental health and quality of life. Theoretical arguments on neural development support the limited evidence here for the increased benefit for child and family associated with very early identification. In general, parents and professionals want very early identification, which, if implemented properly, does not cause undue anxiety.

CURRENT UK PRACTICE

The survey of current practice indicated a major problem with poor information systems. This problem was further highlighted as a major concern by the multi-disciplinary focus groups. Practice varies. There are two District-wide programmes in which all newborn babies are neonatally screened, a large number of ad hoc programmes for neonatal screening of 'at-risk' babies, a variety of early surveillance programmes, and widespread use of the HVDT. Intervention and habilitation for the majority of those screened neonatally is routinely undertaken within 6 months of birth. For those screened only by the health visitor, identification was on average at about 26 months of age with intervention at about 32 months on average. (ABSTRACT TRUNCATED)

Sonographic features of mucinous biliary papillomatosis: case report and review of imaging findings

Because of its indolent course, high recurrence rate, and risk of malignant transformation, mucinous biliary papillomatosis is an important consideration in the differential diagnosis of bile duct obstruction. We report a case of mucinous biliary papillomatosis and review the sonographic and other imaging findings previously reported in the literature. On sonography, these tumors appear as nonshadowing intrabiliary masses that are clearly defined and associated with proximal biliary dilatation. They may be multiple and associated with mucoid sludge. The imaging findings reflect the macroscopic appearance of a doughy papilliferous tumor of a bile duct. Associated findings include cholelithiasis, choledocholithiasis, and gallbladder dysplasia.

An investigation of laser scanning techniques for quantifying changes in facial soft-tissue volume

This paper describes a laser scanning technique to measure accurately changes in facial volume. Three potential sources of error were identified: the registration algorithm, the inherent accuracy of the scanner, and the natural minute-to-minute variability of the human face. In experiments performed to discover the relative magnitude and significance of each source of error, the performance of the registration algorithm was found to be limited by the accuracy of the data, being 1.6 cc, on average, measured over the entire face of a plaster model. Scan-to-scan variability in the shape of the human face was measured at 3.3 cc on average. We conclude that laser scanning is a simple, non-invasive, accurate, and reproducible means of assessing changes in facial volume.

Potential salvage therapy for inadvertent intrathecal administration of vincristine

Vincristine is an anti-neoplastic agent for intravenous use. Inadvertent intrathecal administration of vincristine tends to follow a predictable clinical sequence of a progressive ascending radiculomyeloencephalopathy, usually fatal in outcome. We report a case of a 10-year-old girl who suffered an inadvertent intrathecal vincristine administration. We have outlined the management strategy used and her consequent neurological progress. She has survived but with a significant neurological deficit. Her outcome is, however, less severe than in previous literature reports; this may in part be attributable to early aggressive neurological management. This case also serves to highlight the tragic consequences of human error when handling chemotherapeutic agents of this nature.

Internet conferences in glycobiology

In this article we describe recent activities in the use of electronic conferencing in glycobiology focusing on our experiences with the organization and development of the Second Electronic Glycoscience Conference (EGC-2), which was held on the Internet and World Wide Web in September 1996. EGC-2 involved the presentation and discussion of scientific research results in a virtual conferencing environment which incorporated virtual replicas of many activities usually observed at a physical conference in addition to features unique to the electronic medium. Highlights of the scientific program and technical developments in the design and use of these facilities are briefly described. EGC-3 will be held in October 1997.

Signalling pathways: a common theme in plants and animals?

The unexpected notion that disease resistance mechanisms may use similar regulatory pathways to developmental processes has emerged from recent advances in understanding signal transduction pathways in insects, mammals and plants.

Optimising the removal of inhaled plutonium and americium from the rat by administration of ZnDTPA in drinking water

1. The efficacy of ZnDTPA administered in drinking water has been investigated for removing 238Pu and 241Am from the rat after their simultaneous inhalation as nitrates. 2. The continual administration of ZnDTPA 95 mumol kg-1 d-1 over a 21 d interval commencing 1 h after exposure reduced the 238Pu content of the lungs and total body to 2% and 8% of those in untreated animals; the corresponding values for 241Am were 3% and 5%. 3. The continual intakes of 950 mumol kg-1 d-1, intermittent intakes of 3600 mumol kg-1 d-1 and the repeated injection of 30 mumol kg-1 body weight were considered no more effective. 4. All orally administered concentrations of ZnDTPA, commencing 7 d after exposure, reduced the total body contents of 238Pu and 241Am to 17% and 20% of controls by 28 d. 5. Histopathological examination of the kidneys, liver and gastrointestinal tract showed no apparent effects of these treatment protocols. 6. It is concluded that the oral administration of ZnDTPA could be an effective treatment for the removal of inhaled transportable forms of Pu and Am after human exposure.

Agnathia (severe micrognathia), aglossia and choanal atresia in an infant

A neonate is reported here, who was born with severe mandibular hypoplasia, complete absence of the tongue, unilateral choanal atresia, contralateral choanal stenosis and developed severe airway obstruction at birth. Arrested development of the ventral first branchial arch most likely underlies the clinical deficits. Most reported cases of agnathia have been lethal but the infant reported here has survived into infancy with a tracheostomy and feeding gastrostomy. Her clinical features, assessment and management are discussed.

Genealogies and geography

Any sample of genes traces back to a single common ancestor. Each gene also has other properties: its sequence, its geographic location and the phenotype and fitness of the organism that carries it. With sexual reproduction, different genes have different genealogies, which gives us much more information, but also greatly complicates population genetic analysis. We review the close relation between the distribution of genealogies and the classic theory of identity by descent in spatially structured populations, and develop a simple diffusion approximation to the distribution of coalescence times in a homogeneous two-dimensional habitat. This shows that when neighbourhood size is large (as in most populations) only a small fraction of pairs of genes are closely related, and only this fraction gives information about current rates of gene flow. The increase of spatial dispersion with lineage age is thus a poor estimator of gene flow. The bulk of the genealogy depends on the long-term history of the population; we discuss ways of inferring this history from the concordance between genealogies across loci.

Bilateral sequential lung transplantation for end stage septic lung disease

BACKGROUND

Bilateral sequential lung transplantation (BSLT) has been widely adopted as an alternative to combined heart and lung transplantation for the management of end stage septic lung disease in many transplant centres.

METHODS

A retrospective review was undertaken of the first 32 consecutive patients with septic lung disease to undergo BSLT at the Freeman Hospital.

RESULTS

Between April 1988 and October 1994 32 patients underwent BSLT. Survival at 30 days was 85% and actuarial survival at one year was 70%. Improved pulmonary function was seen in all surviving patients.

CONCLUSION

BSLT for septic lung disease offers comparable survival to heart-lung transplantation, with excellent functional results. Long term results may be superior because the disadvantages of transplanting the heart are avoided.

Decorporation of thorium-228 from the rat by 3,4,3-LIHOPO and DTPA after simulated wound contamination

1. With DTPA as a comparison, the siderophore analogue 3,4,3-LIHOPO has been examined for its ability to remove 228Th nitrate from the rat after subcutaneous (sc) and intramuscular (im) injection to simulate wound contamination. The commencement of treatment was delayed 30 min, 6 h or 1 d and the animals killed at 7 d. 2. In all cases 3,4,3-LIHOPO was appreciably more effective than DTPA although the efficacy of treatment and the relative effectiveness of the ligands decreased rapidly with their delay in administration. 3. Optimum removal with both ligands occurred when initial local administration at 30 min after exposure was followed by repeated intraperitoneal injection at 6 h, 1, 2 and 3 d. Under these conditions the body content of 228Th was reduced to 20% of controls after sc injection and 15% after im injection. The corresponding values using repeated DTPA administration were 80% and 54%. 4. It is concluded that 3,4,3-LIHOPO represents, potentially, a considerable advance on DTPA, the current agent of choice for the treatment of wounds contaminated by 228Th.

Maternal inheritance of extrachromosomal DNA in malaria parasites

Plasmodium falciparum has two extrachromosomal genomes, the mitochondrial 6-kb DNA element and the 35-kb circular DNA. The mitochondrial gene cytochrome b on the 6-kb element has been shown to be inherited uniparentally. In order to ascertain whether the route is maternal or paternal we have examined preparations of male and female gametes of the closely related Plasmodium gallinaceum for the presence of extrachromosomal DNA. DNA from purified preparations of gametes was hybridised to probes for both the 6-kb and 35-kb extrachromosomal genomes. Both probes hybridised to the preparation of Plasmodium gallinaceum female gametes but not to that of the males. We conclude that the extrachromosomal DNAs of malaria parasites are transmitted maternally.

Screening a state middle school for asthma using the free running asthma screening test

The free running asthma screening test (FRAST) was used to screen children in a state middle school during a normal physical education lesson. The test was conducted by the teachers with a general practitioner available via a radiopager. Of the 249 children attending the school, aged 8-12 years, 237 (95%) were tested. Twenty two (9%) children were known to have asthma, of whom 18 were tested. Thirty one children had a significant decrease (> 15%) in their peak expiratory flow rate (PEFR) after exercise. Six of these children were known to have asthma, indicating that their asthma treatment may be suboptimal. A further six children assessed clinically had false positive results. The 31 children with significant decreases in their PEFR were matched for age and sex with a control group of 30 children who were considered to have a normal result. Of the control group, one child had clinical asthma. In total, 19 (8%) new cases of asthma were identified, giving an overall prevalence of asthma in the school of 16%. These results indicate that it is feasible to screen schools for asthma using the FRAST. Children with undiagnosed asthma can be identified and the control of children with known asthma monitored.

Inhibition of neutrophil adherence improves postischemic ventricular performance of the neonatal heart

BACKGROUND

Reduction of the leukocyte population during postischemic coronary reperfusion results in decreased neutrophil-mediated tissue injury. However, the importance of leukocyte adhesion to coronary endothelium for postischemic ventricular dysfunction after global hypothermic myocardial ischemia is unknown. Neutrophil integrins (CD11b/CD18) upregulate in response to cardiopulmonary bypass and ischemic stress, and their role in generating postoperative ventricular dysfunction was examined in this study.

METHODS AND RESULTS

An in vivo, in situ model of neonatal cardiac surgery was established in which neutrophil adherence was manipulated by administering NPC 15669 (an inhibitor of neutrophil CD11b/CD18 surface receptor upregulation). Seventeen 3- to 5-day-old piglets (8 controls and 9 NPC 15669-treated animals) were instrumented with a coronary sinus catheter, sonomicrometry crystals across the short axis of the left ventricle (LV), and a micromanometer positioned in the LV. Hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Myocardial granulocyte accumulation during ischemia and reperfusion was reduced in NPC animals compared with controls (myeloperoxidase activity, 43.4 +/- 2.6 and 75.8 +/- 6.3 mumol/10 mg tissue, respectively; P < or = .005). This was associated with a reduction in coronary vascular resistance in NPC animals compared with controls (P < or = .02) and decreased release of myocardial creatine phosphokinase throughout reperfusion (P < or = .05). NPC animals demonstrated an improved preservation of the end-systolic pressure-volume relation after discontinuation of cardiopulmonary bypass (71 +/- 6% and 96 +/- 6% at 60 minutes, respectively; P < or = .05). There was no difference in ventricular compliance between groups.

CONCLUSIONS

These data demonstrate that inhibition of neutrophil CD11b/CD18 surface adherence receptor upregulation reduces granulocyte accumulation in myocardium after hypothermic global ischemia, reduces myocyte damage, and improves ventricular systolic function.

Comparative efficacies of 3,4,3-LIHOPO and DTPA for enhancing the excretion of plutonium and americium from the rat after simulated wound contamination as nitrates

With DTPA as a comparison, the siderophore analogue 3,4,3-LIHOPO has been examined for its ability to remove 238Pu and 241Am from the rat after subcutaneous (s.c.) and intramuscular (i.m.) injection of about 200 Bq of each actinide (0.3 ng Pu, 1.6 ng Am). After the s.c. deposition of 238Pu and 241Am, both ligands were more effective after local administration than (in decreasing order) their repeated interperitoneal (i.p.) injection, single i.p. injection and continuous infusion. Dosages of 3 mumol kg-1 of 3,4,3-LIHOPO were at least as effective as 30 mumol kg-1 DTPA after each mode of administration. The most effective regimen of those investigated for s.c. 238Pu and 241Am involved local administration of 30 mumol kg-1 of 3,4,3-LIHOPO at 30 min followed by i.p. injections at 6 h, 1, 2 and 3 day. By day 7 after exposure, the amounts of 238Pu and 241Am retained in the body were 2 and 7% of those in controls, respectively and 10 and four times less than when DTPA was administered using the same regimen. The ligand 3,4,3-LIHOPO was more effective for 238Pu and 241Am after their i.m. injection. This was attributed to the greater retention of these actinides at the wound site (97 versus 67%) when treatment commenced. After a single local injection of 30 mumol kg-1 at 30 min, the amounts of 238Pu and 241Am retained in the body at 7 day were 0.9 and 0.8% of controls. These values were 34 and 27 times less than after local and repeated i.p. injections of DTPA at dosages of 30 mumol kg-1. It is concluded that the administration of 3,4,3-LIHOPO represents potentially a most significant advance in the treatment of wound contamination by 238Pu and 241Am by chelating agents.

Health-related quality of life in persons with acquired immune deficiency syndrome

Assessing health-related quality of life in persons infected with human immunodeficiency virus (HIV) is extremely important, but most available scales are too long, contain items that are not relevant for such persons, or do not assess important signs and symptoms of HIV infection. This study presents a new set of scales for assessing the symptoms and functioning of persons infected with HIV and reports data on their reliability and validity collected in face-to-face interviews with 189 patients receiving primary care. This study also assesses the associations among systems, functional impairment, and global health assessments. The scales are easy to administer, are reliable, and serve as valid measures of quality of life. Fatigue, functional status, and average severity of all symptoms were the best predictors of overall perceived health status. Psychological well-being and perceived health status were the best predictors of overall perceived health status. Psychological well-being and perceived health status were the strongest correlates of life satisfaction. When assessing the health-related quality of life of persons infected with HIV, this study recommends utilizing a comprehensive set of measures that allows one to examine both discrete symptoms and the more diffuse impact of illness on functioning, mental health, and quality of life.

Removal of inhaled plutonium and americium from the rat by administration of ZnDTPA in drinking water

This study has examined the efficacy of ZnDTPA administered in drinking water for removing 238Pu and 241Am from the rat after their simultaneous inhalation as nitrates; the dosage used was 95 mumol kg-1d-1. The continuous administration of ZnDTPA over a 14 d interval, commencing 1 h after exposure, reduced the lung and total body contents of 238Pu to, respectively, 11% and 18% of those in untreated rats; the corresponding values for 241Am were 11% and 14%. After the continuous administration of 95 mumol kg-1 from 4 d to 28 d post exposure, the lung and total body contents of 238Pu were, respectively, 5% and 16% of those in controls; the corresponding values for 241Am were 7% and 19%. Further reductions in the actinide contents of body tissues were found when treatment was extended to 52 d or 76 d. These regimens were as effective as twice weekly injections of 30 mumol kg-1 ZnDTPA commencing at 4 d. After the continuous administration of 95 mumol kg-1 d-1 for 72 d, some pathological changes to the gastrointestinal tract were observed but these were considered to be reparable. It was concluded that further work is required to evaluate the toxicity of the ligand and to establish the optimal treatment regimen.

Complement inhibition with soluble complement receptor type 1 in cardiopulmonary bypass

Although complement activation during cardiopulmonary bypass (CPB) is well documented, its pathogenic role in postperfusion organ injury is unproven. In this study, soluble human complement receptor type 1 (sCR1), a potent inhibitor of complement activation, was used to determine the contribution of complement activation to pulmonary injury in a porcine model of CPB. In vitro experiments demonstrated that sCR1 inhibits both classic and alternative complement pathways in the pig. Seven control piglets and 6 piglets treated with sCR1 (12 mg/kg intravenously) underwent 2 hours of hypothermic (28 degrees C) CPB followed by 2 hours of observation. In control piglets, total hemolytic complement activity and functional activities of C3 and C5 declined to 61.3%, 67.8%, and 61.4% of prebypass values, respectively, after 2 hours of CPB. Plasma from animals treated with sCR1 had virtually no hemolytic activity (total hemolytic complement activity < 5% of baseline), demonstrating effective complement inhibition. Similar degrees of neutropenia developed in the two groups during CPB, and there was no difference in post-CPB lung tissue myeloperoxidase level. Two hours after CPB, pulmonary vascular resistance increased 338% in control piglets but only 147% in piglets pretreated with sCR1 (p < 0.05); the alveolar-arterial gradient was not significantly different between controls (331 +/- 52 mm Hg) and piglets receiving sCR1 (290 +/- 85 mm Hg). Histologic examination revealed similar degrees of pulmonary edema in both groups. These data constitute direct evidence that complement activation plays a pathogenic role in lung injury after CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Antimalarial activity of rifampicin in vitro and in rodent models

The antimalarial activity of rifampicin, a specific inhibitor of bacterial ribonucleic acid (RNA) polymerase, was confirmed with Plasmodium falciparum in vitro and with P. chabaudi in vivo. The viability of ring forms of P. falciparum, measured by [3H]hypoxanthine and [14C]isoleucine uptake, was significantly reduced within 5 h of exposure to 2.5 microM rifampicin, the 50% inhibitory concentration. Streptolydigin and tagetitoxin, other specific inhibitors of bacterial RNA polymerase, were much less effective as antimalarials. A rifampicin-tolerant sub-line of P. falciparum was selected in vitro. When released from drug pressure, the tolerant line showed appreciably greater rates of incorporation of precursors and growth than the parent line, but over a period of months these characteristics gradually reverted. Rifampicin was effective against a chloroquine-resistant line of P. falciparum and the rifampicin-tolerant line had increased chloroquine sensitivity. Treatment of patent parasitaemias of P. chabaudi in mice with more than 100 mg/kg rifampicin twice daily significantly reduced the parasitaemia within 24 h and parasites were barely detectable on blood films by the fourth day. Recrudescence occurred on release of drug pressure.