Justification of radiological procedures: Radiographers' experiences at two public hospitals

BACKGROUND

Justification is a process conducted by the radiographer in consultation with the radiologist to evaluate radiological procedures ordered by doctors. The main purpose for justifying all radiologic procedures is to assess the benefits and risks of a requested radiographic procedure and determine whether exposure will continue. Furthermore, justification helps to prevent unnecessary radiation exposure and reduce the chances of harmful effects of ionizing radiation.

OBJECTIVES

The study aimed to explore the experiences of radiographers regarding the justification of radiological procedures at two public hospitals in Namibia METHODS: This study made use of a qualitative, exploratory design. A total number of 13 purposefully selected radiographers from radiology departments in two tertiary public - hospitals in Namibia were interviewed using a semi-structured interview guide and audio recorder. All interviews were conducted face-to-face until data saturation was achieved. Data were analysed using Atlas.ti Windows (version 9.0 using Tesch's 8-step method of qualitative data analysis to generate themes and subthemes.

FINDINGS

The participants experienced an enhancement of patient care through enhanced radiation protection and optimised patient care. They also experienced defunct communication systems through deficient communication between radiographers and referrers, professional role conflict and incomplete referrals.

CONCLUSION

The study revealed that the justification of radiological procedures was linked to both negative and positive experiences. Enhanced patient-centred care was a positive experience related to the radiographers' job responsibilities. The defunct communication support system was a negative experience as it related to the limited availability and utilisation of communication systems that are meant to enhance and support justification by radiographers. The study recommends an in-depth study to quantify unjustified procedures in these two hospital departments. Continuous professional development focusing on justification and referral protocols must be conducted jointly between radiographers and referrers to create awareness and a platform for shared decision-making models.

London Trauma Conference 2015

I1: Trauma, Pre-hospital and Cardiac Arrest Care 2015

Pascale Avery, Leopold Salm, Flora Bird

A1: Retrospective evaluation of HEMS ‘Direct to CT’ protocol

Anja Hutchinson, Ashley Matthies, Anthony Hudson, Heather Jarman

A2 Rush hour – Crush hour: temporal relationship of cyclist vs. HGV trauma admissions. A single site observational study

Maria Bergman Nilsson, Tom Konig, Nigel Tai

A3 Semiprone position endotracheal intubation during continuous cardiopulmonary resuscitation in drowned children with regurgitation: a case report and experimental manikin study

Espen Fevang, Børge Hognestad, Håkon B. Abrahamsen

A4 An audit of CO2 A-a gradient in non-trauma patients receiving pre-hospital anaesthesia

Olivia V Cheetham, Matthew JC Thomas, Kieron D Rooney

A5 Can the use of c-spine immobilisation collars be avoided in non-trauma patients presenting to the Emergency Department?

Josephine Murray, Malcolm Tunnicliff

A6 Curriculum mapping in ED point of care simulation

Joseph W Collinson, Thomas Brown, Christopher Pritchett

A7 Point of care multidisciplinary trauma team simulation & participant satisfaction in a geographically remote trauma unit in Cornwall

Christopher SA Pritchett, Mark Jadav, Gareth Meredith, Jamie Plumb, Steve Harris, Roger Langford

A8 Conservative management of head injury inpatients - the challenge of simplifying injury management in a non-neurosurgical hospital

JG Hunter, A Sage, R Madden, O Flamank, B Broadbent, S Marsh, H Lewis, E Daniels, N Roberts

A9 Improving the care of traumatic brain injury at non-neurosurgical hospitals: Introducing a head injury pathway and single place of care is associated with significant improvements in neurological observation

JG Hunter, A Sage, R Madden, O Flamank, B Broadbent, S Marsh, H Lewis, E Daniels, N Lin, N Roberts

A10 The experience of inter-disciplinary students undertaking cardiac arrest moulage training

Samuel Bulford, Silas Houghton-Budd, Sam Pearson, Megan Clear-Hill

A11 Impact brain apnoea – nine cases

David J Menzies, James P Leonard, Conor Keogh, Ray Quinn, John D Hinds

A12 Time well spent? Improving the performance improvement programme in a busy Trauma Unit

N Roberts, D Ashton-Cleary, M Jadav

A14 Clinical significant and outcome of pulmonary contusions in patients with blunt chest trauma

Ismail Mahmood, Ayman El-Menyar, Basil Younis, Ahmed Khalid, Syed Nabir, Mohamed Nadeem Ahmed, Omer Al-Yahri, Hassan Al-Thani

A15 Plastics operative workload in major trauma centres: a national prospective survey

Katie Young, Susan A. Hendrickson, Georgina Phillips, Matthew D. Gardiner, Shehan Hettiaratchy

A16 A survey to assess the accuracy of estimating height by pre-hospital clinicians: can we reliably predict those most at risk of serious injury?

Alexandra Alice Crossland, Anthony Hudson

A17 An audit of the cause, outcome and adherence to treatment Standard Operating Procedure (SOP) for all traumatic cardiac arrests at a Helicopter Emergency Medical Service over a 12-month period

Nicholas C Brassington, Anthony Hudson, Emily McWhirter

A18 Should we “stay-and-play? A study of patient physiology in Norwegian Helicopter Emergency Services

Bjørn O Reid, Marius Rehn, Oddvar Uleberg, Andreas J Krüger

A19 Training in resuscitative thoracotomy: have we cracked it? A survey of higher Emergency Medicine trainees in London

Cara Jennings, Yasmin Kapadia, Duncan Bew

A20 London’s Air Ambulance (LAA): 25-years of drownings in an urban environment

Jenny Townsend, Tom P Hurst, Elizabeth A Foster

A21 Live patients in trauma simulation – more than just simulation on a shoestring?

Thomas B Brown, Joseph Collinson, Christopher Pritchett, Toby Slade

A22 Collecting core data in pre-hospital critical care using a consensus based template

Kristin Tønsager, Marius Rehn, Kjetil G.Ringdal, Andreas J.Krüger

A23 Prehospital interventions before and after implementation of a physician staffed helicopter

Rasmus Hesselfeldt, Sandra Wulffeld, Asger Sonne, Lars S. Rasmussen, Jacob Steinmetz

A24 Duration of ventilation following prehospital drug assisted intubation; a retrospective review

Thomas J Renninson, Nadine Thomson, Harvey Pynn, Timothy J Hooper

A25 Non-haemorrhagic shock in trauma: a novel guideline for management in ED

Anthony Hudson, Jacinta Dawson, Ashley Matthies

A26 Patient-tailored triage decisions by anaesthetist-staffed pre-hospital critical care teams

Morten Langfeldt Friberg, Leif Rognås

A27 Anatomical accuracy and appropriate sizing of pre-hospital thoracostomies

Jessica FG Wills, Anthony Hudson

A28 Pre-hospital management of mass casualty civilian shootings

Conor DA Turner, Marius Rehn

A30 The prevalence of alcohol-related trauma recidivism: a systematic review

James Nunn, Mete Erdogan, Robert S. Green

A31 Development of a hospital-wide program for simulation-based training in trauma care and management

Samuel Minor, Mete Erdogan, Kathy Hartlen, Robert S. Green

A32 Out of Hospital Cardiac Arrests (OOHCA); lessons from Hollywood

Ruth Bird, Rachael L. Grupping

A33 Mechanism of injury as a predictor of severity of injury in road traffic collisions: a literature review

Amelia M. Stacey, Marius Rehn, David J. Lockey

A34 Lessons to be learned from prehospital airway intervention documentation? Are airway intervention documentation templates as successful in-hospital as prehospitally?

S. Abiks, L. Cutler, K. Monaghan, A. Al-Rais, C. Hymers, R. Bloomer, Y. Kapadia

A35 Novel biomarkers in prehospital management of traumatic brain injury (the PreTBI study protocol)

Sophie-Charlott Seidenfaden, Ingunn S. Riddervold, Hans Kirkegaard, Niels Juul, Morten T. Bøtker

A36 Hospital outcomes of traumatic railway incidents: a seven-year observational retrospective study of a major trauma centre

Alice Gao, Zane Perkins; Gareth Grier, Alex Tzannes

A37 Does taking a third crew member affect the on-scene time of HEMS jobs?

Nathan Hudson-Peacock, Quentin Otto, Laurie Phillipson, Rik Thomas, Ainsley Heyworth

A38 Does pre-hospital rapid sequence induction affect on-scene time of HEMS jobs?

Quentin Otto, Nathan Hudson-Peacock, Laurie Phillipson, Ainsley Heyworth, Erica Ley

A39 Code red: shock index as a prehospital indicator of massive haemorrhage

Daniel Banner, Ainsley Heyworth, Erica Ley

A40 Air ambulance tasking: how accurate are our current methods?

Madeleine Benson, Nathan Hudson-Peacock, Tony Stone, Erica Ley, Louise Rousson, Ainsley Heyworth

A41 Modern trauma burden in a district general hospital

Beth A Lineham, Matthew J Lee, Martin Gough

A42 Establishing a legal service for major trauma patients in two UK major trauma centres

William H Seligman, Hannah E Thould, Andrew Dinsmore, Charlotte Tan, Julian Thompson, C Andy Eynon, David J Lockey

A43 Prehospital assessment and care of patients – a study of the use of guidelines when assessing head trauma

Rebecka M Rubenson Wahlin, Veronica Lindström, Sari Ponzer, Veronica Vicente

A44 An audit of pre-hospital blood pressure management resulting from head injury

Pamela Eligio, Anthony Hudson

A45 The surgical contribution of surface shading volumetric rendering techniques in rib fracture management

Robert Young, Dimitri Amiras, Ian Sinha

Hoarse voice in adults: an evidence-based approach to the 12 minute consultation

BACKGROUND

The hoarse voice is a common presentation in the adult ENT clinic. It is estimated that otolaryngology/voice clinics receive over 50 000 patients with dysphonia each year. Good vocal function is estimated to be required for around 1/3 of the labour force to fulfil their job requirements. The assessment and management of the patient with a hoarse voice is potentially a complex and protracted process as the aetiology is often multi-factorial. This article provides a guide for the clinician in the general ENT clinic to make a concise, thorough assessment of the hoarse patient and engage in an evidence based approach to investigation and management.

METHOD

Literature search performed on 4 October 2008 using EMBASE, MEDLINE, Cochrane databases using subject headings hoarse voice or dysphonia in combination with diagnosis, management, investigation, treatment, intervention and surgery.

RESULTS

General vocal hygiene is beneficial for non organic dysphonia but the evidence base for individual components is poor. There is a good evidence base for the use of voice therapy as first line treatment of organic dysphonia such as vocal fold nodules and polyps. There is little evidence for surgical intervention as first line therapy for most common benign vocal fold lesions. Surgery is, however, the treatment of choice for hoarseness due to papillomatosis. Both CO(2) laser and microdissection are equally acceptable modalities for surgical resection of common benign vocal fold lesions. Laryngopharyngeal reflux is commonly cited as a cause of hoarseness but the evidence base for treatment with gastric acid suppression is poor. Despite the widespread use of proton pump inhibitors for treating laryngopharyngeal reflux, there is high quality evidence to suggest that they are no more effective than placebo.

CONCLUSION

A concise and thorough approach to assessment in the general ENT clinic will provide the diagnosis and facilitate the management of the hoarse voice in the majority of cases. Voice therapy is an important tool that should be utilised in the general ENT clinic and should not be restricted to the specialist voice clinic. If there is no improvement after initial measures, the larynx appears normal and/or the patient has failed initial speech & language therapy, referral to a specialist voice clinic may be helpful. More research is still required particularly with regard to laryngopharyngeal reflux which is often cited as an important cause of hoarseness but is still poorly understood.

The development of a palliative care program for managed care patients: a case example

Palliative care is emerging as an important new field. Although programs are developing in hospital environments, little is known about development of programs in outpatient practices or those serving large managed care populations. This article provides a framework for the development of a comprehensive palliative care program in a large multispecialty group practice that serves managed care patients. The article addresses guiding principles, the need for obtaining baseline data, how the clinical consultation service was established, development of outcomes measures, and information on current program status. Five themes emerged as key to successful program development, most importantly the close collaboration between administrative and clinical staff in all aspects of program development.

Health-related quality of life in narcolepsy

Narcolepsy is a chronic sleep disorder characterised by symptoms of excessive daytime sleepiness and cataplexy. The aim of this study was to describe the health-related quality of life of people with narcolepsy residing in the UK. The study comprised a postal survey of 500 members of the UK narcolepsy patient association, which included amongst other questions the UK Short Form 36 (SF-36), the Beck Depression Inventory (BDI), and the Ullanlinna Narcolepsy Scale (UNS). A total of 305 questionnaires were included in the final analysis. The results showed that the subjects had significantly lower median scores on all eight domains of the SF-36 than normative data, and scored particularly poorly for the domains of role physical, energy/vitality, and social functioning. The BDI indicated that 56.9% of subjects had some degree of depression. In addition, many individuals described limitations on their education, home, work and social life caused by their symptoms. There was little difference between the groups receiving different types of medication. This study is the largest of its type in the UK, although the limitations of using a sample from a patient association have been recognised. The results are consistent with studies of narcolepsy in other countries in demonstrating the extensive impact of this disorder on health-related quality of life.

Underestimation of Mycobacterium tuberculosis infection in HIV-infected subjects using reactivity to tuberculin and anergy panel

BACKGROUND

This study aimed to evaluate purified protein derivative (PPD) reactivity and its interrelationship with anergy panel and CD4+ lymphocytes in HIV-infected subjects as compared to PPD reactivity in HIV-uninfected individuals in a tuberculosis endemic and high Bacillus Calmette-Guérin (BCG) coverage environment.

METHODS

Clients of four Mexico City HIV detection centres were screened for HIV-1 antibodies (ELISA or haemagglutination, Western Blot); reactivity to PPD (Mantoux PPD, 5TU RT-23), Candida (1:1000, 0.1 ml), and tetanus toxoid (10Lf, 0.1 ml); and CD4+ T cells. Active tuberculosis was excluded. Informed consent was obtained.

RESULTS

From 5130 clients 1168 subjects were enrolled; of these 801 (68.6%) were HIV positive. Reactivity to PPD among HIV-positive subjects was found in 174 (22%), 261 (32.6%), and 296 (37%), at PPD cutoff levels of > or =10 mm, > or =5 mm, and > or =2 mm as compared to 224 (61%) of 367 HIV-negative individuals' reactors to PPD (> or =10 mm) (P < 0.001). After exclusion of anergic individuals using two cutoff levels for cutaneous allergens (< or =2 mm and < or =5 mm), PPD reactivity between HIV-infected and uninfected individuals continued to be significantly different. Only HIV-infected individuals with CD4+ T cells > or =500 cells/mm3 had similar reactivity to PPD as HIV-uninfected individuals. Variables associated with PPD reactivity were CD4+ T cell counts, BCG scar, HIV infection and age.

CONCLUSIONS

PPD reactivity was useful to diagnose tuberculosis infection only among HIV-infected individuals with CD4+ counts > or =500 cells/mm3. Among individuals with lower counts, lowering cutoff levels or using anergy panel did not permit comparable reactivity as that observed among HIV-uninfected individuals.

Transmission thresholds for dengue in terms of Aedes aegypti pupae per person with discussion of their utility in source reduction efforts

The expense and ineffectiveness of drift-based insecticide aerosols to control dengue epidemics has led to suppression strategies based on eliminating larval breeding sites. With the notable but short-lived exceptions of Cuba and Singapore, these source reduction efforts have met with little documented success; failure has chiefly been attributed to inadequate participation of the communities involved. The present work attempts to estimate transmission thresholds for dengue based on an easily-derived statistic, the standing crop of Aedes aegypti pupae per person in the environment. We have developed these thresholds for use in the assessment of risk of transmission and to provide targets for the actual degree of suppression required to prevent or eliminate transmission in source reduction programs. The notion of thresholds is based on 2 concepts: the mass action principal-the course of an epidemic is dependent on the rate of contact between susceptible hosts and infectious vectors, and threshold theory-the introduction of a few infectious individuals into a community of susceptible individuals will not give rise to an outbreak unless the density of vectors exceeds a certain critical level. We use validated transmission models to estimate thresholds as a function of levels of pre-existing antibody levels in human populations, ambient air temperatures, and size and frequency of viral introduction. Threshold levels were estimated to range between about 0.5 and 1.5 Ae. aegypti pupae per person for ambient air temperatures of 28 degrees C and initial seroprevalences ranging between 0% to 67%. Surprisingly, the size of the viral introduction used in these studies, ranging between 1 and 12 infectious individuals per year, was not seen to significantly influence the magnitude of the threshold. From a control perspective, these results are not particularly encouraging. The ratio of Ae. aegypti pupae to human density has been observed in limited field studies to range between 0.3 and >60 in 25 sites in dengue-endemic or dengue-susceptible areas in the Caribbean, Central America, and Southeast Asia. If, for purposes of illustration, we assume an initial seroprevalence of 33%, the degree of suppression required to essentially eliminate the possibility of summertime transmission in Puerto Rico, Honduras, and Bangkok, Thailand was estimated to range between 10% and 83%; however in Mexico and Trinidad, reductions of >90% would be required. A clearer picture of the actual magnitude of the reductions required to eliminate the threat of transmission is provided by the ratio of the observed standing crop of Ae. aegypti pupae per person and the threshold. For example, in a site in Mayaguez, Puerto Rico, the ratio of observed and threshold was 1.7, meaning roughly that about 7 of every 17 breeding containers would have to be eliminated. For Reynosa, Mexico, with a ratio of approximately 10, 9 of every 10 containers would have to be eliminated. For sites in Trinidad with ratios averaging approximately 25, the elimination of 24 of every 25 would be required. With the exceptions of Cuba and Singapore, no published reports of sustained source reduction efforts have achieved anything near these levels of reductions in breeding containers. Practical advice on the use of thresholds is provided for operational control projects.

Comparison of expression patterns and cell adhesion properties of the mouse biliary glycoproteins Bbgp1 and Bbgp2

Biliary glycoproteins are members of the carcinoembryonic antigen (CEA) family and behave as cell adhesion molecules. The mouse genome contains two very similar Bgp genes, Bgp1 and Bgp2, whereas the human and rat genomes contain only one BGP gene. A Bgp2 isoform was previously identified as an alternative receptor for the mouse coronavirus mouse hepatitis virus. This isoform consists of two extracellular immunoglobulin domains, a transmembrane domain and a cytoplasmic tail of five amino acids. In this report, we have examined whether the Bgp2 gene can express other isoforms in different mouse tissues. We found only one other isoform, which has a long cytoplasmic tail of 73 amino acids. The long cytodomain of the Bgp2 protein is highly similar to that of the Bgp1/4L isoform. The Bgp2 protein is expressed in low amounts in kidney and in a rectal carcinoma cell line. Antibodies specific to Bgp2 detected a 42-kDa protein, which is expressed at the cell surface of these samples. Bgp2 was found by immunocytochemistry in smooth muscle layers of the kidney, the uterus, in gut mononuclear cells and in the crypt epithelia of intestinal tissues. Transfection studies showed that, in contrast with Bgp1, the Bgp2 glycoprotein was not directly involved in intercellular adhesion. However, this protein is found in the proliferative compartment of the intestinal crypts and in cells involved in immune recognition. This suggests that the Bgp2 protein represents a distinctive member of the CEA family; its unusual expression patterns in mouse tissues and the unique functions it may be fulfilling may provide novel clues about the multiple functions mediated by a common BGP protein in humans and rats.

Simulation of management strategies for the blacklegged tick (Acari: Ixodidae) and the Lyme disease spirochete, Borrelia burgdorferi

A computer model (LYMESIM) was developed to simulate the effects of management technologies on populations of the blacklegged tick, Ixodes scapularis Say, and the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner in eastern North America. Technologies considered in this study were area-wide acaricide, acaricide self-treatment of white-footed mice and white-tailed deer, vegetation reduction, and white-tailed deer density reduction. Computer simulations were run with normal weather patterns for coastal Connecticut and New York. Results showed that area-wide acaricide, vegetation reduction, or a combination of these technologies would be useful for short-term seasonal management of ticks and disease in small recreational or residential sites. Acaricide self-treatment of deer appears to be the most cost-effective technology for use in long-term management programs in large areas. Simulation results also suggested that deer density reduction should be considered as a management strategy component. Integrated management strategies are presented that could be used in pilot tests and operational tick and tick-borne disease programs.

Dynamics of the emergence of genetic resistance to biocides among asexual and sexual organisms

A stochastic, agent based, evolutionary algorithm, modeling mating, reproduction, genetic variation, phenotypic expression and selection was used to study the dynamic interactions affecting a multiple-gene system. The results suggest that strong irreversible constraints affect the evolution of resistance to biocides. Resistant genes evolve differently in asexual organisms compared with sexual ones in response to various patterns of biocide applications. Asexual populations (viruses and bacteria) are less likely to develop genetic resistance in response to multiple pesticides or if pesticides are used at low doses, whereas sexual populations (insects for example) are more likely to become resistant to pesticides if susceptibility to the pesticide relates to mate selection. The adaptation of genes not related to the emergence of resistance will affect the dynamics of the evolution of resistance. Increasing the number of pesticides reduces the probability of developing resistance to any of them in asexual organisms but much less so in sexual organisms. Sequential applications of toxins, were slightly less efficient in slowing emergence of resistance compared with simultaneous application of a mix in both sexual and asexual organisms. Targeting only one sex of the pest speeds the development of resistance. The findings are consistent to most of the published analytical models but are closer to known experimental results, showing that nonlinear, agent based simulation models are more powerful in explaining complex processes.

Simulation of blacklegged tick (Acari:Ixodidae) population dynamics and transmission of Borrelia burgdorferi

A model (LYMESIM) was developed for computer simulation of blacklegged tick, Ixodes scapularis Say, population dynamics and transmission of the Lyme disease agent. Borrelia burgdorferi Johnson. Schmid, Hyde, Steigerwalt & Brenner, LYMESIM simulates the effects of ambient temperature, saturation deficit, precipitation, habitat type, and host type and density on tick populations. Epidemiological parameters including host infectivity, tick infectivity, transovarial transmission, and transstadial transmission are included in the model to simulate transmission of the Lyme disease spirochete between vector ticks and vertebrate hosts. Validity of LYMESIM was established by comparing simulated and observed populations of immature I. scapularis on white-footed mice. Peromyscus leucopus, (Rafinesque), at 2 locations in Massachusetts. Validity also was indicated by comparisons of simulated and observed seasonality of blacklegged ticks in New York, Massachusetts, Florida, and Oklahoma-Arkansas. Further model validity was shown by correlation between simulated and observed numbers of immature ticks engorging on white-footed mice at 3 sites in Massachusetts. The model produced acceptable values for initial population growth rate, generation time, and 20-yr population density when historical meteorological data for 16 locations in eastern North America were used. Realistic rates of infection in ticks were produced for locations in the northeastern and northcentral United States. LYMESIM was used to study the effect of white-footed mouse and white-tailed deer, Odocoileus virginianus (Zimmerman), densities on tick density and infection rates. The model was also used to estimate tick density thresholds for maintenance of B. burgdorferi.

Optimal ratios of biliary glycoprotein isoforms required for inhibition of colonic tumor cell growth

Rodent biliary glycoprotein (Bgp), also known as C-CAM, has recently been shown to function as a tumor suppressor in colon, prostate, and bladder cancers. This glycoprotein is a member of the carcinoembryonic antigen family and is one of the only proteins in this family to encode either a long (71-73 amino acids) or short (10 amino acids) cytoplasmic domain. We and others have shown that the growth-inhibitory properties of Bgp depend upon the expression of its long cytoplasmic domain. However, the two Bgp isoforms normally coexist in most cell types surveyed; the longer variant is usually present in lower amounts than the shorter one. In this study, we have examined the in vitro and in vivo growth properties of both mouse Bgp variants separately and in combination. To determine the physiologically relevant expression levels and ratios of the two Bgp variants, we have quantified the amount of the longer variant in normal colonic epithelial cells and showed that it constitutes 15-20% of total Bgp expressed in this tissue. To mimic the in vivo situation, we have generated double transfectant cell lines expressing the longer and shorter Bgp isoforms coordinately in tumorigenic CT51 mouse colonic carcinoma cells and demonstrated that the longer Bgp isoform exhibits a dominant tumor growth inhibition phenotype over that of the shorter variant within physiological levels of expression of Bgp. Unexpectedly, significant overexpression of the longer Bgp isoform alone led to reversal of the tumor inhibition phenotype. These results, therefore, suggest that there may be a limiting threshold of Bgp expression or Bgp-associating proteins mediating the tumor inhibition phenotype.

Association of biliary glycoprotein with protein tyrosine phosphatase SHP-1 in malignant colon epithelial cells

Biliary glycoprotein (Bgp) is a member of the immunoglobulin superfamily and the carcinoembryonic antigen family. Previous studies have shown that Bgp functions as an intercellular adhesion molecule and a canalicular bile salt transporter. Moreover, we and others demonstrated that Bgp can inhibit colonic and prostatic tumor cell growth in vivo, through a mechanism which depends on sequences present in its cytoplasmic domain. In this study, we have examined the possibility that the cytoplasmic domain of Bgp can interact with signal transduction molecules. We showed that tyrosine phosphorylated Bgp, expressed in mouse colon carcinoma CT51 cells, could reversibly associate with protein tyrosine phosphatase SHP-1. Mutation of either of two tyrosine residues present in the cytoplasmic domain of Bgp abrogated SHP-1 binding, suggesting that this association was mediated by both tyrosine residues. Similarly, we noted that either of the two SH2 domains of SHP-1 could bind tyrosine phosphorylated Bgp in vitro. It is therefore conceivable that some of the functions of Bgp are mediated through its ability to induce intracellular protein tyrosine dephosphorylation.

Biliary glycoprotein 1 expression during embryogenesis: correlation with events of epithelial differentiation, mesenchymal-epithelial interactions, absorption, and myogenesis

Biliary glycoprotein (Bgp1), a carcinoembryonic antigen-related family member of the immunoglobulin superfamily, is involved in normal and neoplastic events. Analysis of Bgp1 expression throughout post-implantation mouse embryogenesis using reverse transcription-polymerase chain reactions, immunostaining with anti-Bgp1 monoclonal antibodies, and in situ hybridization with specific Bgp1 cDNA fragments revealed that Bgp1 may be involved in a number of specific embryonic processes. Immunoblot analysis of Bgp1 deletion mutant proteins indicated that distinguishable epitopes of the molecule were preferentially identified by the three Bgp1 antibodies used in this study. This distinction is supported by our immunolocalization studies during mouse embryogenesis in which the three antibodies revealed specific patterns of Bgp1 expression. Bgp1 is not expressed in early post-implantation embryos (7.5 dpc), but is found in the placenta and extra-embryonic tissues (decidual endothelial cells, giant trophoblasts, yolk sac visceral endoderm, and endometrial glands) at this time. The primitive gut epithelium and surface ectoderm were the first embryonic tissues to express Bgp1. Significant Bgp1 expression was also observed later during epithelial-mesenchymal interactions (skin, meninges, lung, kidney, salivary glands, pancreas). A unique epitope of Bgp1, detectable by the monoclonal antibody CC1, was also associated with mesenchymal expression and was prominent during myogenesis (secondary myotube formation) at sites of terminal differentiation. These studies suggest multiple roles for isoforms and glycoforms of the Bgp1 proteins localized in specific sites during prenatal development.

A simulation model of the epidemiology of urban dengue fever: literature analysis, model development, preliminary validation, and samples of simulation results

We have developed a pair of stochastic simulation models that describe the daily dynamics of dengue virus transmission in the urban environment. Our goal has been to construct comprehensive models that take into account the majority of factors known to influence dengue epidemiology. The models have an orientation toward site-specific data and are designed to be used by operational programs as well as researchers. The first model, the container-inhabiting mosquito simulation model (CIMSiM), a weather-driven dynamic life-table model of container-inhabiting mosquitoes such as Aedes aegypti, provides inputs to the tranmission model, the dengue simulation model (DENSiM); a description and validation of the entomology model was published previously. The basis of the transmission model is the simulation of a human population growing in response to country- and age-specific birth and death rates. An accounting of individual serologies is maintained by type of dengue virus, reflecting infection and birth to seropositive mothers. Daily estimates of adult mosquito survival, gonotrophic development, and the weight and number of emerging females from the CIMSiM are used to create the biting mosquito population in the DENSiM. The survival and emergence values determine the size of the population while the rate of gonotrophic development and female weight estimates influence biting frequency. Temperature and titer of virus in the human influences the extrinsic incubation period; titer may also influence the probability of transfer of virus from human to mosquito. The infection model within the DENSiM accounts for the development of virus within individuals and its passage between both populations. As in the case of the CIMSiM, the specific values used for any particular phenomenon are on menus where they can be readily changed. It is possible to simulate concurrent epidemics involving different serotypes. To provide a modicum of validation and to demonstrate the parameterization process for a specific location, we compare simulation results with reports on the nature of epidemics and seroprevalence of antibody in Honduras in low-lying coastal urbanizations and Tegucigalpa following the initial introduction of dengue-1 in 1978 into Central America. We conclude with some additional examples of simulation results to give an indication of the types of questions that can be investigated with the models.

Mycobacterium tuberculosis infection in pregnant and nonpregnant women infected with HIV in the Women and Infants Transmission Study

BACKGROUND

Prevalence of Mycobacterium tuberculosis (TB) infection and anergy were evaluated in a cohort of pregnant and nonpregnant women infected with the human immunodeficiency virus who were enrolled in a prospective natural history study (the Women and Infants Transmission Study) conducted in New York, NY; Boston and Worcester, Mass; Chicago, Ill; and San Juan, Puerto Rico.

METHODS

One hundred eighty-three women (65 pregnant, 118 nonpregnant) were evaluated for TB. The TB history and risk factors were assessed by interview and medical record review. Intradermal skin testing with tuberculin, mumps, and tetanus antigens and CD4+ lymphocyte count were performed.

RESULTS

Overall prevalence of TB infection or disease by documented medical history and/or a tuberculin skin test induration of 5 mm or more was 14% (26 of 183). History of TB infection or disease was documented in 11% of the women who were interviewed. Tuberculin and anergy skin test results were evaluable for 124 women; 6% (seven of 124) had tuberculin skin test induration of 5 mm or more, including 11% (five of 46) of the pregnant women who were tested. Induration between 2 and 5 mm was observed in four more women, three of whom were pregnant. Anergy was observed in 42% (52 of 124); prevalence of anergy was higher in nonpregnant women (38 [49%] of 78) than in pregnant women (14 [30%] of 46). While anergy was more common in women with a CD4+ cell count of 0.5 x 10(9)/L or less, 27% of those with a CD4+ cell count of more than 0.5 x 10(9)/L were also anergic.

CONCLUSION

These data support current Public Health Service recommendations for tuberculin skin testing in persons infected with the human immunodeficiency virus, and emphasize that evaluation should include pregnant as well as nonpregnant women. The prevalence of anergy does not appear increased in pregnancy in women infected with the human immunodeficiency virus. Health care providers should include tuberculin and anergy skin testing as part of the standard prenatal care for women infected with the human immunodeficiency virus.

Bgp2, a new member of the carcinoembryonic antigen-related gene family, encodes an alternative receptor for mouse hepatitis viruses

Murine coronaviruses such as mouse hepatitis virus (MHV) infect mouse cells via cellular receptors that are isoforms of biliary glycoprotein (Bgp) of the carcinoembryonic antigen gene family (G. S. Dveksler, C. W. Dieffenbach, C. B. Cardellichio, K. McCuaig, M. N. Pensiero, G.-S. Jiang, N. Beauchemin, and K. V. Holmes, J. Virol. 67:1-8, 1993). The Bgp isoforms are generated through alternative splicing of the mouse Bgp1 gene that has two allelic forms called MHVR (or mmCGM1), expressed in MHV-susceptible mouse strains, and mmCGM2, expressed in SJL/J mice, which are resistant to MHV. We here report the cloning and characterization of a new Bgp-related gene designated Bgp2. The Bgp2 cDNA allowed the prediction of a 271-amino-acid glycoprotein with two immunoglobulin domains, a transmembrane, and a putative cytoplasmic tail. There is considerable divergence in the amino acid sequences of the N-terminal domains of the proteins coded by the Bgp1 gene from that of the Bgp2-encoded protein. RNase protection assays and RNA PCR showed that Bgp2 was expressed in BALB/c kidney, colon, and brain tissue, in SJL/J colon and liver tissue, in BALB/c and CD1 spleen tissue, in C3H macrophages, and in mouse rectal carcinoma CMT-93 cells. When Bgp2-transfected hamster cells were challenged with MHV-A59, MHV-JHM, or MHV-3, the Bgp2-encoded protein served as a functional MHV receptor, although with a lower efficiency than that of the MHVR glycoprotein. The Bgp2-mediated virus infection could not be inhibited by monoclonal antibody CC1 that is specific for the N-terminal domain of MHVR. Although CMT-93 cells express both MHVR and Bgp2, infection with the three strains of MHV was blocked by pretreatment with monoclonal antibody CC1, suggesting that MHVR was the only functional receptor in these cells. Thus, a novel murine Bgp gene has been identified that can be coexpressed in inbred mice with the Bgp1 glycoproteins and that can serve as a receptor for MHV strains when expressed in transfected hamster cells.

Integrated management strategies for Amblyomma americanum (Acari: Ixodidae) on pastured beef cattle

Data on tick control and knowledge of the damage caused to beef cattle by tick feeding were incorporated into a computerized dynamic life table model (LSTSIM) for Amblyomma americanum (L.). Simulations were made to determine economically feasible, 5-yr integrated pest management (IPM) strategies for A. americanum in forage areas utilized by Bos taurus, Bos indicus, and crossbred cattle (B. taurus x B. indicus). The effects of host resistance, pasture rotation, habitat conversion, topical acaricides, systemic acaricides, and the area-wide application of acaricides to pastures on populations of parasitic female ticks were simulated as individual control technologies and as components of multiple-factor IPM strategies. The most effective, single-factor control strategy for A. americanum in beef cattle forage areas is the use of tick-resistant B. indicus cattle. Pasture rotation combined with area-wide acaricide applications was the only economically feasible IPM strategy for B. indicus cattle and reduced tick densities by 89% after 5 yr. Thirteen economically feasible IPM strategies were identified for use with B. taurus cattle. Of these, the most efficacious was pasture rotation in May combined with systemic or topical acaricide applications. Other strategies included systemic acaricides with area-wide acaricide applications to pastures, topical acaricides with area-wide acaricide applications, pasture rotation with habitat conversion and topical acaricides, and pasture rotation with habitat conversion, topical acaricides, and area-wide acaricide applications. Each technology reduced tick densities on B. taurus cattle by > 80% over a 5-yr period. Nine IPM strategies were economically feasible for use with crossbred cattle. Of these, pasture rotation combined with systemic or topical acaricide applications reduced the number of female ticks on cattle by > 84%; pasture rotation combined with habitat conversion reduced tick numbers by 77%. The most effective nonacaricide-based IPM strategy for B. taurus and crossbred cattle was pasture rotation combined with habitat conversion. No acaricide-free IPM strategy was economically feasible for use with B. indicus cattle.

Educating primary care providers about HIV disease: multidisciplinary interactive mechanisms

As HIV-related prophylactic and therapeutic research findings continue to evolve, the Health Resources and Services Administration (HRSA) of the Public Health Service has created multidisciplinary mechanisms to disseminate new treatment options and educate primary care providers at rural and urban sites throughout our nation's health care system. HRSA has implemented (a) the International State-of-the-Art HIV Clinical Conference Call Series, (b) the national network of AIDS Education and Training Centers, (c) the nationwide HIV Telephone Consultation Service, and (d) the Clinical Issues Subcommittee of the HRSA AIDS Advisory Committee. These collaborative and comprehensive efforts at HIV information dissemination target physicians, nurses, physician assistants, dentists, clinical pharmacists, mental health care providers, case managers, and allied health professionals. The sites where they provide care include public health clinics; county, State and Federal correctional facilities; private practice offices; community and academic hospitals; military and Veterans Administration facilities; hemophilia centers; schools of medicine, nursing, and dentistry; departments of health; chronic care facilities; visiting nurse and home care agencies; health maintenance organizations; and Indian Health Service clinics and hospitals.

Dynamic life table model for Aedes aegypti (Diptera: Culicidae): analysis of the literature and model development

The container-inhabiting mosquito simulation model (CIMSiM) is a weather-driven, dynamic life table simulation model of Aedes aegypti (L.). It is designed to provide a framework for related models of similar mosquitoes which inhibit artificial and natural containers. CIMSiM is an attempt to provide a mechanistic, comprehensive, and dynamic accounting of the multitude of relationships known to play a role in the life history of these mosquitoes. Development rates of eggs, larvae, pupae, and the gonotrophic cycle are based on temperature using an enzyme kinetics approach. Larval weight gain and food depletion are based on the differential equations of Gilpin & McClelland compensated for temperature. Survivals are a function of weather, habitat, and other factors. The heterogeneity of the larval habitat is depicted by modeling the immature cohorts within up to nine different containers, each of which represents an important type of mosquito-producing container in the field. The model provides estimates of the age-specific density of each life stage within a representative 1-ha area. CIMSiM is interactive and runs on IBM-compatible personal computers. The user specifies a region of the world of interest; the model responds with lists of countries and associated cities where historical data on weather, larval habitat, and human densities are available. Each location is tied to an environmental file containing a description of the significant mosquito-producing containers in the area and their characteristics. In addition to weather and environmental information, CIMSiM uses biological files that include species-specific values for each of the parameters used in the model. Within CIMSiM, it is possible to create new environmental and biological files or modify existing ones to allow simulations to be tailored to particular locations or to parameter sensitivity studies. The model also may be used to evaluate any number and combination of standard and novel control methods.

Dynamic life table model for Aedes aegypti (diptera: Culicidae): simulation results and validation

The container-inhabiting mosquito simulation model (CIMSiM) is a weather-driven, dynamic life table simulation model of Aedes aegypti (L.) and similar nondiapausing Aedes mosquitoes that inhabit artificial and natural containers. This paper presents a validation of CIMSiM simulating Ae. aegypti using several independent series of data that were not used in model development. Validation data sets include laboratory work designed to elucidate the role of diet on fecundity and rates of larval development and survival. Comparisons are made with four field studies conducted in Bangkok, Thailand, on seasonal changes in population dynamics and with a field study in New Orleans, LA, on larval habitat. Finally, predicted ovipositional activity of Ae. aegypti in seven cities in the southeastern United States for the period 1981-1985 is compared with a data set developed by the U.S. Public Health Service. On the basis of these comparisons, we believe that, for stated design goals, CIMSiM adequately simulates the population dynamics of Ae. aegypti in response to specific information on weather and immature habitat. We anticipate that it will be useful in simulation studies concerning the development and optimization of control strategies and that, with further field validation, can provide entomological inputs for a dengue virus transmission model.

New version of LSTSIM for computer simulation of Amblyomma americanum (Acari: Ixodidae) population dynamics

A previous version of Lone Star Tick Simulation Model (LSTSIM) for a wildlife ecosystem was revised and expanded to include a beef cattle forage area and improved handling of tick-host-habitat interactions. Relationships between environmental and biological variables were also refined in the new version. General validity of the revised model was established by comparing simulated and observed host-seeking populations of Amblyomma americanum (L.) at five geographic locations, three in Oklahoma and two in Kentucky-Tennessee. Additional validity was indicated from comparisons of simulated and observed seasonality of lone star ticks at one location in Kentucky. The model produced acceptable values for initial population growth rate, generation time, and 15-yr population density when historical weather files for 14 locations in the United States were used. The model of A. americanum population dynamics was used to study the relationship between tick density and density of white-tailed deer, Odocoileus virginianus (Zimmerman), and cattle. The revised model can be used for additional simulation studies on effects of tick control technologies and integrated management strategies.

Effects of interleukin-3 on murine fetal liver hemopoiesis in utero

The normal regulation of primitive hemopoietic stem cells (PHSCS) throughout development involves locally produced factors and humoral factors. While considerable information is available on the effects of candidate hemopoietic growth factors (HGFs) on postnatal hemopoietic tissues, little is known about the regulatory events of developing hemopoietic stem cells within fetal microenvironments. Fetal hemopoiesis represents expanding populations and may be under different regulatory control mechanisms. The microinjection of purified interleukin-3 (IL-3), a candidate HGF, into 13-day-old mouse fetuses via the yolk sac, allowed us to evaluate its effects on morphogenetic events and, more specifically, on fetal liver populations using quantitative in vitro clonal assays for hemopoietic precursors. In view of the sensitivity of fetal development during the early organogenetic period, considerable care was taken to identify the stress effects of the surgical laparotomy and the microinjection procedure. Control studies, required to distinguish stress effects of surgical laparotomy and microinjection, clearly revealed that the fetal liver is a sensitive organ responding with limited tissue disorganization, reduced cellularity and erythropoietic activity, as monitored 24 h after experimental intervention. The microinjection of 15 units of IL-3 promoted a significant expansion of depleted liver hemopoietic-cell populations and had stimulatory effects on the distribution of connective tissue mast cells and absolute cell numbers, including hemopoietic precursors (erythroid, granulocyte, macrophage, megakaryocyte), compared to controls. These studies suggest that (1) fetal liver hemopoiesis is selectively sensitive to maternal stress but has an effective regenerative capacity to maintain essential hemopoiesis in utero, and (2) fetal hemopoietic cells require an ability to respond to IL-3 early in fetal development.

Spatiotemporal expression of murine carcinoembryonic antigen (CEA) gene family members during mouse embryogenesis

Carcinoembryonic antigen is a glycosylated protein used as a human tumor marker to assess recurrences of gastrointestinal, breast and lung cancers. This protein is a member of the immunoglobulin supergene family and has been shown to function as a homophilic and heterophilic cell adhesion molecule. We have studied the spatial and temporal expression of two cloned mouse CEA gene family members during development using Northern analyses and in situ hybridization. Transcripts detected by the mouse CEA probes are expressed from 10.5 days post coitum (p.c.) to birth in mouse embryos and fetuses and are present from 16.5 days p.c. to adulthood in intestine and colon as evaluated by Northern analyses. The RNA is also present in many other tissues including meninges, cartilage and bone, blood vessel walls, placenta, dermis, muscle layers of the stomach and intestine and bronchioles of developing mouse embryos and fetuses. This expression pattern is similar to that of proteins of the Transforming Growth Factor beta gene family. The role of mouse CEA gene family members is unclear; however, the localizations of these CEA family members in the mouse embryo and fetus suggest an important functional role during active morphogenesis, a complex process in which cell adhesion molecules are significantly involved.

Passive immunisation of children with bovine colostrum containing antibodies to human rotavirus

The efficacy of a 10-day course of bovine colostrum with high antibody titre against the four known human rotavirus serotypes in protecting children against rotavirus infection was examined in patients admitted to hospital. Children aged 3 to 15 months were blocked in pairs according to ward accommodation (ie, isolation or open area). Each block contained 1 treated and 1 control child. The allocation to treatment or control (an artificial infant formula) was randomised. 9 of 65 control children but none of 55 treated children acquired rotavirus infection during the treatment period (p less than 0.001). The importance of protecting against rotavirus infection was highlighted by the fact that parents of symptomatic rotavirus-positive children sought medical attention seven times more often than did parents of symptomatic rotavirus-negative children (p less than 0.05).

Passive immunisation of children with bovine colostrum containing antibodies to human rotavirus

The efficacy of a 10-day course of bovine colostrum with high antibody titre against the four known human rotavirus serotypes in protecting children against rotavirus infection was examined in patients admitted to hospital. Children aged 3 to 15 months were blocked in pairs according to ward accommodation (ie, isolation or open area). Each block contained 1 treated and 1 control child. The allocation to treatment or control (an artificial infant formula) was randomised. 9 of 65 control children but none of 55 treated children acquired rotavirus infection during the treatment period (p less than 0.001). The importance of protecting against rotavirus infection was highlighted by the fact that parents of symptomatic rotavirus-positive children sought medical attention seven times more often than did parents of symptomatic rotavirus-negative children (p less than 0.05).

Comparison of direct electron microscopy and enzyme immunoassay for the detection of rotaviruses in calves, lambs, piglets and foals

Direct electron microscopy (EM) and enzyme-immunoassay (rotazyme) results for the detection of rotaviruses in 346 enteric specimens from calves, lambs, piglets and foals were compared. The rotazyme test was at least 3 times more sensitive than direct EM in diagnosing infection. Rotavirus antigen was demonstrated by rotazyme in 22% of 280 scour samples and in 27% of 66 samples from non-scouring animals. There was an association between diarrhoea and higher amounts of rotavirus antigen. This prevalence of rotaviruses detected in animals with diarrhoea highlights the significant involvement of other pathogens identified in the study including Eimeria, Cryptosporidia, Escherichia coli, Campylobacter, and other viruses.

Caprine arthritis-encephalitis virus infection of goats in South Australia

Caprine arthritis-encephalitis virus (CAEV) infection of dairy goats was shown by virus isolation and serology to be widespread in South Australia. CAEV was isolated at necropsy from 24 of 27 dairy goats with swollen joints from 13 herds, and from 9 of 30 liver dairy goats in 7 herds. Virus was isolated most frequently from synovial membranes, and occasionally from mammary glands, mammary lymph nodes, choroid plexus, lungs, spleen, bone marrow, salivary glands, leucocytes, synovial fluid and milk. Antibody to CAEV was detected in the serum of 13 of 17 of the necropsied goats tested in a single-line gel diffusion test, and in another 3 retested with a modified double-line technique. Serum antibody was also demonstrated in 61 of 77 dairy goat herds, many with histories of arthritis. In 1984 to 1986 the annual number of serologically positive serums and proportions of the numbers tested were 134 (40%), 121 (45%) and 42 (18%), respectively. CAEV was isolated from leucocytes of 8 live goats in 6 of these herds. In fibre goats antibody was detected in the serum of 25 Angora and 19 crossbreds (0.1%) from the 33,279 Angora, 1,705 Cashmere, 8,715 crossbred and 904 feral goats tested.

Transluminal angioplasty of the abdominal aorta

Transluminal angioplasty of the abdominal aorta was performed in 6 women between 49 and 69 years of age with histories of cigarette smoking. Five had a relatively small aorta. This procedure is effective in treating focal aortic stenoses.

A comparison of three-dimensional growth characteristics of cultured primitive marrow stroma derived from genetically anemic and normal mice

This study examines the ultrastructure of mouse defective marrow stroma when cultured as a three-dimensional organization of cells. Gelfoam sponges impregnated with agar medium allowed the three-dimensional organization of newly formed stromal cells derived from the crevices of marrow-depleted bones of Steel mutant mice (Sl/Sld) with defective stroma and also from mice with normal stroma (Sl +/+, W/Wv, and W +/+. Ultrastructural comparisons of 5- to 14-day cultures revealed that the mutant defective stromal cells developed normally, viz. i) proliferated and formed a three-dimensional organization of stroma, ii) stimulated residual hemopoietic precursors to form myeloid cells, and iii) formed a variety of stromal cell types characterized by variable quantities of Golgi bodies and ER, glycogen, filaments, and round cytoplasmic granules. The Steel-Dickie strain, however, included bacilliform electron-dense granules in both normal and mutant stroma. The only ultrastructural deficiency in Sl/Sld stroma was the absence of a category of "activated" cells that occurred within normal cell populations.

The diagnosis of meniscus pathology

A study of 281 patients evaluated for a meniscus pathologic condition was performed to assess the accuracy of the clinical diagnosis and arthrogram and delineate the role of arthroscopy. Following the clinical examination, the surgeon stated his level of confidence in his diagnosis, as did the radiologist in his interpretation of the arthrogram. In 134 cases inspected by arthroscopy or arthrotomy, the clinician proved to be correct 74% of the time, and the arthrogram accuracy in evaluating the medial meniscus was 89%; the majority of the errors were false positive diagnoses. In the 82 meniscus tears in which an arthrogram was performed the diagnosis was made in 80 cases, or 98%. The arthrogram accuracy in the lateral compartment was 81%; however, of the 31 lateral meniscus tears in which an arthrogram was performed, a positive diagnosis was yielded by arthrogram in only ten cases. In 34 lateral meniscus tears, a positive clinical diagnosis was made in only 12 cases. Arthroscopy was performed in 117 cases and proved helpful in patient management in 65 cases (55%). Arthroscopy was performed in 25 patients with lateral meniscus tears and a diagnosis of a lateral meniscus tear was made in all cases. The observations suggest that prior to performing an arthrotomy, arthroscopic examination of the knee should be performed routinely in patients suspected of having meniscus tears.

Characteristics of synthesis and distribution of 3H-fucose-containing glycoproteins by marrow stromal cells cocultured with hemopoeitic cells in gelfoam sponges. An electron microscope radioautographic study

Gelfoam sponge cultures of stromal cells, derived from guinea pig marrow-depleted bone fragments, support the growth of myeloid precursors in the absence of exogenous stimulants. EM radioautographic studies were undertaken to identify active synthesis and distribution of 3H-fucose-containing glycoproteins within the 3-D organization of cultured hemopoietic tissue. Labeling of 5-14 day cultures with tritiated fucose for 20 min revealed an intracellular localization of silver grains over the endoplasmic reticulum and Golgi bodies of all stromal cells. Cumulative labeling (1-48 h) of similar cultures indicated that (i) silver grains subsequently accumulated in plasma membranes, large cytoplasmic granules and also within lipid droplets, (ii) primitive and myeloid cells were also labeled. Localized extracellular concentrations of silver grains were facilitated by the multiple inter-stromal cell contacts and by the accumulation of fine labeled cytoplasmic processes. Mechanisms whereby stromal cells may actively influence physiochemical changes in the hemopoietic inductive microenvironment are suggested.

Ultrastructural observations on the three-dimensional reorganization and growth of newly-formed candidate stromal cells and residual hemopoietic cells in culture

Gelfoam sponges were used as three-dimensional culture supports to allow the migration, reorganization and growth of regenerative cells derived from bone fragments previously depleted of marrow by curettage. The explants and sponges, cultured in 0.3% agar-medium, were analysed ultrastructurally throughout a 14 day culture period. By day 5 the gelfoam sponge was infiltrated by large cells with extensive cytoplasmic processes (stromal cells) and primitive round cells. The stromal cells were pleomorphic and varied in their content of rough endoplasmic reticulum, mitochondria, cytoplasmic granules, microfilaments, lipid droplets and glycogen. The cytoplasmic processes made multiple intercellular contacts with other stromal cells thereby forming a stromal network. Close and direct associations of stromal cells with primitive hemopoietic cells and various stages of myeloid cells were identified. The identification of proliferating granulocytes and mononuclear phagocytes on days 7--14 in these unstimulated cultures suggests that the organization of stromal cells is able to maintain primitive cells and supports the proliferation and differentiation of myeloid cells. It is proposed that this three-dimensional culture technique (i) allows the development of primitive stromal precursors and primitive residual hemopoietic cells; (ii) provides a model for the analysis of early stromal cell-hemopoietic cell interactions.

The isolation of newly formed bone associated cells in vitro: preliminary observations on origin and morphology

Agar-medium suspensions were used to culture guinea-pig femoral bone fragments which had been physically depleted of marrow. A sequential study of the histological events occurring within the regenerating shaft, in the agar wholemount preparations and on the underlying coverglass allowed (1) the localization of the early regenerative cells within the endosteal crevices and their rapid proliferation to fill and 'encapsulate' the explant; (2) the detection of residual marrow granulocytic and mononuclear precursors amidst the regenerative non-hemopoietic cells within the endosteal crevices of bone; (3) a study of the development of the adherent cells on the coverglasses. Cumulative labeling studies indicated that almost all the migrating cells were newly formed cells with a small fraction (less than 5%) within the endosteal crevices observed as unlabeled cells after 5 days of culture. The adherent mononuclear cells were derived directly from the regenerating bone fragment and showed similar morphology and proliferative characteristics (97% cumulative labeling index) to the bone associated cells. A unique feature of these monolayers was the formation of an extensive network of extracellular material between cells. These observations have not been described in monolayers derived from marrow suspensions and appear to be a characteristic of the monolayers derived from regenerating bone fragments.

Early chick neuroretinal responses following direct exposure to methotrexate

Explants of 4.5-day-old chick embryonic neuroretinas with mesenchyme were exposed to Methotrexate (MTX) in medium 199 with embryo extract. Proliferative responses of the cultured neuroretinas were followed radioautographically by administration of 3H-thymidine to the cultures. The DNA synthetic, mitotic and pyknotic responses of the ventricular cells of the neuroretina were followed over a 16-hour period. The responses observed suggested that MTX caused a synchronization of the ventricular cells in the pre-mitotic phases with no direct inhibition of mitosis. Furthermore, prolonged exposure to MTX resulted in the accumulation of labeled pyknotic cells, indicating a decline in the regenerative capacity of the proliferative ventricular cells.