Radiation leukemia in C57BL/6 mice. I. Lack of serological evidence for the role of endogenous ecotropic viruses in pathogenesis.

The humoral immune response against endogenous ecotropic murine leukemia viruses (MuLV) was examined in irradiated and control C57BL/6 mice. Control mice developed antibodies against MuLV slowly throughout life. In contrast, within 2-3 mo after irradiation 90% of irradiated C57BL/6 mice had developed detectable antibodies against MuLV. The characteristics of this immune response, however, were identical in control and irradiated mice in terms of peak titers, specificity for endogenous ecotropic MuLV, and reactivity against the ecotropic viruses' glycoprotein (gp71). Moreover, the rate of appearance of antibodies against MuLV in irradiated mice and the peak titers were generally not affected by age at irradiation, dose of irradiation (two, three, or four treatments of 175 R), or bone marrow reconstitution. Although the ability of irradiation to accelerate the appearance of antibody in a population of C57BL/6 mice suggested activation of endogenous ecotropic MuLV, there was no apparent correlation between the appearance of this immune response or its persistence and the development of lymphoma. Thus, the incidence of lymphoma was comparable in mice that: (a) developed no immune response; (b) developed an immune response only transiently after irradiation; or (c) developed an immune response which persisted until death from lymphoma. Moreover, experimental conditions that alter the ability of irradiation to induce leukemia, such as age, dose, or bone marrow reconstitution did so without significantly altering either the rate of appearance of a humoral immune response to MuLV or its peak titers. The results, therefore, fail to demonstrate any seroepidemological relationship between endogenous ecotropic MuLV and radiation-induced leukemia.

Radiation leukemia in C57BL/6 mice. III. Correlation of altered expression of terminal deoxynucleotidyl transferase to induction of leukemia.

The expression of terminal deoxynucleotidyl transferase (TdT) in the thymus and bone marrow of irradiated mice has been examined. Mice given the leukemogenic regimen of irradiation of four weekly doses of 175 rads starting at 1 mo of age show a long-term elimination of TdT activity in the bone marrow and a reduction of TdT activity in thymocytes. In such mice, the reappearance of normal levels of TdT in the thymus appears to only be associated with the onset of overt leukemia. This effect on TdT expression was shown to be uniquely associated with the leukemogenic regimen of irradiation in that nonleukemogenic irradiation or variations such as bone marrow reconstitution or age which reduce leukemias did not show the same phenotypic effects on TdT expression. The basis for the loss of TdT-positive cells was shown not to be due to the lack of the requisite factors involved in differentiation, but rather to the ability of leukemogenic doses of irradiation to reduce or eliminate an inducible bone marrow stem cell. These results are discussed with respect to the possible mechanisms involved in radiation-induced leukemias in mice.

Expression and amplification of engineered mouse dihydrofolate reductase minigenes.

We constructed mouse dihydrofolate reductase (DHFR) minigenes (dhfr) that had 1.5 kilobases of 5' flanking sequences and contained either none or only one of the intervening sequences that are normally present in the coding region. They were greater than or equal to 3.2 kilobase long, about one-tenth the size of the corresponding chromosomal gene. Both of these minigenes complemented the DHFR deficiency in Chinese hamster ovary dhfr-1-cells at a high frequency after DNA-mediated gene transfer. The level of DHFR enzyme in various transfected clones varied over a 10-fold range but never was as high as in wild-type Chinese hamster ovary cells. In addition, the level of DHFR in primary transfectants did not vary directly with the copy number of the minigene, which ranged from fewer than five to several hundred per genome. The minigenes could be amplified to a level of over 2,000 copies per genome upon selection in methotrexate, a specific inhibitor of DHFR. In one case, the amplified minigenes were present in a tandem array; in two other cases, a rearranged minigene plasmid and its flanking chromosomal DNA sequence were amplified. Thus, the mouse dhfr minigenes could be transcribed, expressed, and amplified in Chinese hamster ovary cells, although the efficiency of expression was generally low. The key step in the construction of these minigenes was the generation in vivo of lambda phage recombinants by overlapping regions of homology between genomic and cDNA clones. The techniques used here for dhfr should be generally applicable to any gene, however large, and could be used to generate novel genes from members of multigene families.

Analysis of the mouse dhfr promoter region: existence of a divergently transcribed gene.

The use of murine dihydrofolate reductase (dhfr) gene amplification mutants enabled us to identify important structural and functional features of the dhfr promoter region. We found another transcription unit, at least 14 kilobases in size, which initiates within 130 base pairs of the major dhfr transcript and is transcribed divergently. The 5' ends of both transcripts were analyzed and found to have multiple initiation sites. The major dhfr transcript and the divergent transcript appear to share the same promoter region; the longer transcripts of the dhfr gene overlap with the divergent transcripts and use a different promoter region. The divergent transcript appears to code for a protein; an homologous sequence to its first exon is found in the corresponding location near the human dhfr gene.

A rapid in vitro assay for quantitating the invasive potential of tumor cells.

We have reconstituted a matrix of basement membrane onto a filter in a Boyden chamber and assessed the ability of various malignant and nonmalignant cells to penetrate through the coated filter. Cells from all the malignant cell lines tested were able to cross the matrix in 5-6 h, whereas human fibroblasts as well as mouse 3T3 and 10T1/2 cell lines, which are not tumorigenic, were not invasive. In addition, normal primary prostate epithelial cells and benign prostatic hyperplasia cells were not invasive when tested in this assay, whereas malignant prostate carcinoma cells were highly invasive. Parallel experiments with these prostatic cells using the intrasplenic assay for metastasis detection in the nude mouse confirmed the benign behavior of the former cells and the metastatic phenotype of the latter ones. These results suggest that this in vitro test allows the rapid and quantitative assessment of invasiveness and a means to screen for drugs which alter the invasive phenotype of tumor cells.

The incidence of hypomagnesaemia following abdominal aortic aneurysm surgery.

INTRODUCTION: Magnesium is important for cardiac function. Hypomagnesaemia is associated with a higher incidence of arrhythmias and poorer outcomes in cardiac surgery. No studies have investigated the incidence or impact of postoperative hypomagnesaemia after abdominal aortic aneurysm (AAA) surgery. We aim to assess the incidence of hypomagnesaemia after AAA repair in our population. METHODS: Retrospective analysis was performed of patients who underwent elective AAA surgery at a single vascular centre. The last 110 patients undergoing open or endovascular AAA repair were identified. The hospital pathology system was used to identify the immediate postoperative serum magnesium levels as well as patient demographics and admission details. Hypomagnesaemia was defined as serum magnesium of <0.7 mmol/l. RESULTS: A total of 211 patients were studied and there were 3 deaths. Of the patients included, 101 underwent open elective AAA repair and 110 underwent endovascular repair. In the elective open repair group, 73 patients (73%) were hypomagnesaemic. In the endovascular repair group, 35 (32%) had hypomagnesaemia. A t-test showed a statistically significant difference in hypomagnesaemia between the open and endovascular groups (p<0.001). CONCLUSIONS: AAA surgery is associated with a high incidence of postoperative hypomagnesaemia, which is significantly greater among open repair patients. This is likely to have an effect on cardiac activity and lead to cardiac complications such as arrhythmias and poorer postoperative outcomes, especially in the open AAA repair subgroup. This stresses the importance of serum magnesium and cardiac monitoring in the postoperative phase. A prospective study is proposed to further investigate these findings, and their potential implications on perioperative morbidity and mortality.

Cohorting of infants with respiratory syncytial virus.

During two winter periods (1994-1995 and 1995-1996), nasopharyngeal aspirates were obtained from infants and young children with an acute respiratory illness, after initial assessment in an area with six cubicles which serves as an admissions unit. Aspirates were sent for rapid diagnostic testing. Respiratory syncytial virus (RSV) positive patients were cohorted into two six-bedded bays on the paediatric wards. Over the two successive winter periods studied, 347 RSV positive patients were assigned to the cohort. No nosocomial infections were identified during the first winter; in the second, two were identified. Cohorting at admission eased clinical management, with one area used for high-dependency care and cubicles being freed for children with other infectious diseases. Nosocomial infection was minimized.

A review of the literature examining the relationship between alcohol use and HIV-related sexual risk-taking in young people.

Young people have been targeted as a potentially vulnerable population for the spread of HIV. The influence of alcohol on sexual behaviour is part of popular knowledge. More recently, studies have attempted to illuminate the relationship between alcohol use and sexual risk-taking in relation to HIV transmission. In our review of the literature three important points are highlighted for researchers in this area. First, methodological problems make establishing any relationship extremely difficult. Secondly, the concept of sexual risk-taking has to be developed to include acknowledgement of the context in which sex takes place rather than defining risk only in terms of sexual acts. Finally, populations of gay men and men who have sex with men and lesbians are sufficiently different from heterosexuals, with regard to the influence of alcohol on sexual behaviour, to make generalizations about one population inappropriate for the other.

Screening elderly people in primary care: a randomized controlled trial.

A randomized controlled trial was carried out to test the effectiveness of a screening programme carried out by nurses for elderly people aged 75 years and over in a general practice. A total of 151 people were randomly allocated to the test group and 145 to the control group. The test group received a home visit from a nurse at which an assessment lasting 45 minutes was made of: activities of daily living, social functioning, sensory functions, mental and emotional problems, current medical problems, blood pressure, urinalysis, haemoglobin level and compliance with medication. Both groups completed a selection of items from four health indices before and 20 months after the intervention. At follow up, the test group scored significantly better than the control group on a morale scale. However, this trial provided no evidence for better resolution of physical problems or finding activities of daily living easier in the test group compared with the control group. It is suggested that the main benefit of such a screening process is that the special attention and education provided improves adaptation to old age and awareness of the support systems available. The government has proposed an annual review of elderly people in their own home and this study suggests that the objectives of this scheme should be clarified.

Identification and certification of extracorporeal membrane oxygenation specialists in the United States.

Extracorporeal membrane oxygenation (ECMO) is a highly specialized technique widely practiced in many hospitals. Despite the proliferation of ECMO, little information has been generated relating to ECMO specialists, a new professional group responsible for managing the extracorporeal life support (ELS) system. A telephone survey of ECMO centers in the United States was conducted to determine the number of ECMO specialists, team composition by profession, and clinical components of ECMO specialist certification. Data were obtained in May 1991 from all 63 (100%) active ELS centers. The survey found that the average ECMO program performs 3,770 +/- 1,019 clinical hours of ELS per year with a team of 23 +/- 11 specialists. There are 1,431 practicing ECMO specialists in the United States: 73% registered nurses, 22% respiratory therapists, and 5% others. Most ECMO specialist teams (56%) are comprised of a single profession, with 44% of programs using a mixture of professions. The average ECMO specialist manages the ELS system 171 +/- 91 hr/yr. Thirty-six (57%) programs have a mean yearly clinical requirement of 77 +/- 23 ELS hours per specialist. These results represent the first complete report identifying the number of ECMO specialists in the United States. In addition, program demographics demonstrate variability in ECMO experience and certification requirements.

Students' knowledge and behavior concerning safer sex: a UK study.

Most students in institutions of further and higher education in the northeast of England who responded to a 1989 survey dealing with sexual behavior and safer sex were heterosexual and had been sexually active or intended to have sexual intercourse. Many students, however, believed that safer sex implied having no sex at all or were unaware of the role of nonpenetrative sex in preventing human immunodeficiency virus (HIV) infection. They did not use condoms, in spite of having positive attitudes about condom use, and they engaged in one or more sexual activities that increased the risk of acquiring HIV infection. In view of the increasing incidence of acquired immunodeficiency syndrome (AIDS), the authors assert, these findings are cause for concern and require concerted action by health educators and society to encourage safer sex practices and to prevent the spread of HIV infection.

PIP: 666 university students, 666 polytechnic students, and 542 college students in the Tyne-Tees area to the northeast of England were surveyed about safer sex and their sexual behavior. More than 47,000 full-time students attended 37 further and higher education establishments in the area in 1989. The survey was part of an evaluation of the 1989 Health Education Authority national initiative to increase students' awareness of HIV and AIDS through the use of information packs. 1388 responses were obtained from students of mean age 20.3 years. 97.7% considered themselves heterosexual, 72% were living away from home, and 70% had experienced penetrative sexual intercourse. Although the students were generally positive about condom use, only 19% always used condoms and 47% never did. Younger students aged 16-17 years tended to be the ones who used them consistently. Many had, however, modified their sexual behaviors because of publicity about AIDS. Those who had taken steps to reduce their risk of HIV infection were typically younger, women, and students in college. They had reduced the number of sex partners, become monogamous, reduced their participation in anal and casual sex and/or used condoms. The authors express concern over the finding that youths believe that safer sex implies abstinence and that many were unaware of the role of nonpenetrative sex in preventing HIV infection. Health educators and society are strongly urged to take measures capable of preventing further HIV infection.

Impact of the London 2012 Olympic and Paralympic Games on demand for microbiology gastrointestinal diagnostic services at the Public Health Laboratory London.

Planning for the London 2012 Olympic and Paralympic Games at the Public Health Laboratory London was based on the requirement to meet potential increased demand with scalable capacity. The aim of this study was to determine the impact on demand for microbiology gastrointestinal diagnostic services during the Games period. Retrospective cross-sectional time-series data analysis was used to assess the number of gastrointestinal specimens received in the laboratory and the number of positive results. There was no increase in the number of gastrointestinal specimens received during the Games period, thus the Games had no impact on demand for microbiology gastrointestinal diagnostic services at the laboratory. There was a decrease in the number of public health specimens received for culture [incidence rate ratio = 0.34, 95% confidence interval (CI) = 0.13-0.86, P = 0.02] and a decrease in the number of culture positive community specimens (odds ratio = 0.59, 95 % CI = 0.40-0.85, P = 0.005), suggesting a decrease in gastrointestinal illness during the Games period. As previous planning assumptions were not based on actual specimen activity, the results of this study may modify the extent of additional planning for microbiological services required for mass gatherings.

Issues in evaluation: evaluating assessments of elderly people using a combination of methods.

In evaluating a health service, individuals will give differing accounts of its performance, according to their experiences of the service, and the evaluative perspective they adopt. The value of a service may also change through time, and according to the particular part of the service studied. Traditional health care evaluations have generally not accounted for this variability because of the approaches used. Studies evaluating screening or assessment programmes for the elderly have focused on programme effectiveness and efficiency, using relatively inflexible quantitative methods. Evaluative approaches must reflect the complexity of health service provision, and methods must vary to suit the particular research objective. Under these circumstances, this paper presents the case for the use of multiple triangulation in evaluative research, where differing methods and perspectives are combined in one study. Emphasis is placed on the applications and benefits of subjectivist approaches in evaluation. An example of combined methods is provided in the form of an evaluation of the Newcastle Care Plan for the Elderly.

Gene manipulation by homologous recombination in Escherichia coli.

The use of homologous recombination in Escherichia coli is described as a tool for DNA manipulation. The utility of the method is illustrated by the addition of 3'-flanking sequences to a dhfr minigene by plasmid-phage recombination involving a supF-containing dhfr minigene plasmid and a lambda Charon4A phage containing the 3' end of the dhfr gene. In addition, other uses of both plasmid-phage and phage-phage recombination in gene manipulation are described.

A review of the costs and effectiveness of assessing the elderly in general practice.

The 1990 contract for general practitioners made annual health checks for people aged 75 and over compulsory. We review the costs and effects of different approaches to the health check, focusing on the method advised in the 1990 contract. This involves an annual home-based functional assessment by a member of the primary health care team, known as a blanket assessment. Our review of published randomized controlled trials shows such assessments have few consistent benefits. Data on the costs of assessment are usually reported in summary form, with little or no information on which costs are included. In studies where average costs are given for assessments, because of salary and travel expenses, the costs are high. Several promising methods for reducing costs in assessment, and a method with potential to improve effectiveness, are currently outside the terms of the 1990 contract. These methods are described. Revision of the 1990 contract should incorporate the flexibility to encourage more cost-effective approaches to assessing the elderly such as a two-stage assessment or using volunteers. A monitoring group is needed to establish how health checks are being implemented. This group could co-ordinate and advise on standardized criteria for methods of costing and assessing effectiveness in assessment programmes.