Cooperative breeding and monogamy in prairie voles: influence of the sire and geographical variation

Mammalian monogamy is characterized by pair bonding and a relative absence of sexual dimorphism in body size. Alloparental behaviour is a characteristic of mammalian cooperative breeding systems. Studies of prairie voles, Microtus ochrogaster, from stock captured in a resource-abundant habitat in Illinois have supported the assumption that this species is a monogamous, cooperative breeder, while other studies of prairie voles from a more arid habitat in Kansas have called this assumption into question. We hypothesized that reported differences between these populations represented true intraspecific variation. Patterns of sexual dimorphism in body size, partner preferences and parental contact behaviour were compared in prairie voles from stocks originating in Illinois or Kansas. Both Illinois and Kansas voles showed a strong preference for a familiar partner, which is suggestive of monogamy. Sexual dimorphism in body size was observed in Kansas, but not Illinois voles. Illinois voles displayed significantly higher levels of parental contact behaviour than did voles from Kansas. When animals from Illinois and Kansas were crossed, the expression of parental contact behaviour of the 'hybrid' offspring followed the pattern seen in the population of origin of the sire. Removal of the sire prior to the birth of the litter increased alloparenting in Kansas voles, but removal of the sire was associated with lower levels of alloparenting in Illinois voles. Thus, some traits associated with the social system may show intraspecific variation and can be influenced by the presence or absence of the sire during rearing. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Apoptosis in human primary brain tumours: actions of arachidonic acid

It has been postulated that loss of proliferative control in tumour cells is a consequence of depletion of cellular arachidonic acid (AA) and that exogenous AA and n-6 fatty acids may restore control of proliferation. To test this hypothesis and to investigate the activity of AA, apoptosis in human primary brain tumour cells was analysed using flow terminal deoxynucleotide transferase uridine nick end-labelling (TUNEL). The effect of exogenous AA (30 microM) was analysed in collagenase-dispersed tissue from seven human primary brain tumours and in the normal brain tissue surrounding one of the tumours. Exogenous AA stimulated apoptosis in tumour tissue. A rapid three-fold increase in endonuclease activity was detected in tumour cells incubated with AA. The increase in apoptosis was significantly greater than the contemporary (< 15%) increase in necrosis detected using propidium iodide permeability and was greater than AA effects on normal brain tissue. These results are consistent with activation of the pathways of apoptosis by AA.

Clinical and pathologic findings in hemochromatosis hip arthropathy

During a 9-year period, 15 patients with hemochromatosis hip arthropathy required 19 total hip arthroplasties for disabling hip pain. Preoperative presentation, hip function, pathologic evaluation of the femoral head, and radiographic findings were reviewed. Postoperative followup averaging 5.7 years (range, 2-11 years) was performed to assess hip pain and function after total hip arthroplasty. The average preoperative Hospital for Special Surgery hip score was 15 points (range, 4-24 points), and this improved to 30 points (range, 4-38 points) after total hip arthroplasty. Only one of 15 patients required revision surgery at 10 years for acetabular loosening. All other patients were pain free, with improved function at latest followup. Histologic evaluation of the resected femoral heads revealed evidence of primary or secondary osteonecrosis in seven of 19 (37%) specimens. Articular cartilage avulsion at the level of the tidemark was identified in eight of 19 (42%) specimens, and calcium pyrophosphate deposition was identified in five of 19 (26%) specimens. These pathologic findings suggest a predictable progression of the arthritic process in patients with hemochromatosis.

Photodynamic tumor therapy: mitochondrial benzodiazepine receptors as a therapeutic target

BACKGROUND

Photodynamic therapy employs photosensitive agents such as porphyrins to treat a variety of tumors accessible to light-emitting probes. This approach capitalizes on the selective retention of porphyrins by cancer cells. Cancer cells also have elevated levels of mitochondrial benzodiazepine receptors which bind porphyrins with high affinity.

METHODS

Cultured cancer cell lines were exposed to porphyrin and porphyrin-like compounds and then irradiated with light. Cytotoxicity of this treatment was measured via clonogenic assays. Mitochondrial benzodiazepine receptor pharmacology was studied using [3H] PK11195 binding to cancer cell homogenates and isolated kidney mitochondrial membranes.

RESULTS

We show that therapeutic potencies of porphyrins correlate closely with affinities for mitochondrial benzodiazepine receptors. Sensitivities of tumor cell lines to photodynamic therapy parallel their densities of these receptors.

CONCLUSION

We propose that porphyrin photodynamic therapy is mediated by mitochondrial benzodiazepine receptors.

Activated Raf-1 causes growth arrest in human small cell lung cancer cells

Small cell lung cancer (SCLC) accounts for 25% of all lung cancers, and is almost uniformly fatal. Unlike other lung cancers, ras mutations have not been reported in SCLC, suggesting that activation of ras-associated signal transduction pathways such as the raf-MEK mitogen-activated protein kinases (MAPK) are associated with biological consequences that are unique from other cancers. The biological effects of raf activation in small cell lung cancer cells was determined by transfecting NCI-H209 or NCI-H510 SCLC cells with a gene encoding a fusion protein consisting of an oncogenic form of human Raf-1 and the hormone binding domain of the estrogen receptor (DeltaRaf-1:ER), which can be activated with estradiol. DeltaRaf-1:ER activation resulted in phosphorylation of MAPK. Activation of this pathway caused a dramatic loss of soft agar cloning ability, suppression of growth capacity, associated with cell accumulation in G1 and G2, and S phase depletion. Raf activation in these SCLC cells was accompanied by a marked induction of the cyclin-dependent kinase (cdk) inhibitor p27(kip1), and a decrease in cdk2 protein kinase activities. Each of these events can be inhibited by pretreatment with the MEK inhibitor PD098059. These data demonstrate that MAPK activation by DeltaRaf-1:ER can activate growth inhibitory pathways leading to cell cycle arrest. These data suggest that raf/MEK/ MAPK pathway activation, rather than inhibition, may be a therapeutic target in SCLC and other neuroendocrine tumors.

Alcohol reduces neurofilament protein levels in primary cultured hippocampal neurons

High concentrations of alcohol (> or = 1.8%) were shown previously to impair health and viability of cultured hippocampal neurons. Because neurofilament proteins are essential for neuronal process outgrowth and differentiation, the effects of alcohol on these proteins were determined in the neuronal processes of primary cultured gestational day 18 rat hippocampal neurons. At the relatively lower concentrations used in the present study, alcohol caused a concentration-dependent reduction (< or = 47%) in 68 and 200 kDa neurofilament proteins (p < 0.05). Alcohol caused a 32% downward trend in 160 kDa neurofilament protein levels. Alcohol up to 1% (72-h exposure) produced no obvious alterations in neurite extension or explant morphology, and there were no visual signs of cell death. The sensitive MTT dye reduction assay showed no biochemical evidence of decreased cell viability at < or = 0.5% alcohol. The 32-47% reductions in neurofilament protein levels in vitro may hold implications for later hippocampal neuronal differentiation events in animals prenatally exposed to alcohol.

The interdependence of staff and patient doses in interventional radiology

Staff doses arising from the use of X-rays are principally due to scattered radiation. This is related to the dose received by the patient expressed as the dose-area product (DAP). Doses to patients in interventional radiology are generally higher than for other fluoroscopically guided procedures. Doses to interventional radiologists are, therefore, amongst the highest associated with the use of diagnostic X-rays. The results of staff dose monitoring normalized to DAP should provide an indicator of those procedures which are associated with particularly high radiation exposures to staff, and should help to identify those radiologists whose practice may result in unnecessarily high doses to themselves. A study has been made of patient doses in two X-ray rooms used for interventional procedures associated with vascular and liver diseases. Doses to radiologists in these rooms were normalized to DAP. It was found that the average doses to the body, neck and hands were 0.05, 0.89 and 2.45 microSv/(Gy cm2), respectively for those radiologists with no significant involvement in hepatobiliary procedures. Higher doses were found for one radiologist whose workload included biliary drainage. The whole body dose was 0.17 microSv/(Gy cm2) or 5.8 mSv per year. It was shown that the doses to the neck and hands for the biliary drainage work was 6.59 and 29.0 microSv/(Gy cm2), respectively. This study has demonstrated the value of DAP as a measure of radiologist workload in respect of its significance in terms of staff dose.

Changes in L1 antigen expression in the rat striatum after substantia nigra lesions

L1 antigen promotes neurite outgrowth from dopaminergic neurons in tissue culture. In the present study, we examined the effects of dopaminergic deafferentation of the striatum on L1 expression. In the medial-periventricular part of the striatum, both complete and partial substantia nigra (SN) lesions decreased L1 expression. Complete lesions increased L1 expression in the dorso-medial and ventro-lateral parts of the striatum on the lesioned side when compared with that on the non-lesioned side. The decrease in the ventro-lateral area was maintained in animals examined three months after the lesioning. Animals with partial SN lesions showed a different pattern of altered L1 expression. After frontal cortex lesions, changes in L1 expression also occur preferentially in the dorso-medial and periventricular striatum. Therefore, the results indicate a complex regulation of L1 expression after damage of striatal circuitry, manifested by a preferential occurrence of changes in periventricular regions.

Arachidonic acid activation of monocyte and neutrophil reactive oxygen in lung cancer patients undergoing pulmonary resection

Reactive oxygen intermediate (roi) generation was investigated in phagocytes of 39 patients undergoing pulmonary resection for lung cancer and 39 paired healthy controls. Generation of roi in monocytes and neutrophils was monitored using 2',7'-dichlorofluorescin diacetate. Activation associated with hydrophobic interactions was probed by analysis of phagocyte roi activation by arachidonic acid and gamma-linolenic acid. Patient roi was measured pre-operatively and 2 and 7 days post-operatively. Elevated (P < 0.01) roi production was detected in neutrophils of lung cancer patients. Surgery was associated with an increase (P < 0.05-P < 0.01) in phagocyte roi at 2 and 7 days post-op. Phagocyte roi was stimulated by arachidonic acid and gamma-linolenic acid (1-40 microM) both pre- and post-operatively. Differences in arachidonic acid and gamma-linolenic acid stimulation between patient and control and pre- and post-op patient phagocytes suggest arachidonic acid involvement in phagocyte activation during reactive responses to lung carcinoma and surgery.

Targeted hepatitis B vaccination--a cost effective immunisation strategy for the UK?

OBJECTIVE

To compare the potential cost effectiveness of vaccination against hepatitis B virus (HBV) targeted at genitourinary clinic (GU) attendees with that of universal infant vaccination.

DESIGN

A mathematical model of sexual and perinatal transmission of HBV was used to compare the effectiveness among heterosexual and homosexual populations of programmes of mass infant vaccination and targeted immunisation of genitourinary medicine (GU) clinic attendees. Each was applied to 90% of the eligible population with differing assumptions about rates of compliance and seroconversion - problems of delivery (obtaining high compliance) was considered a significant drawback of targeted vaccination. Observed relationships between GU clinic attendance and sex partner change rates for heterosexuals and for homosexuals were used to define the rates of vaccination uptake within sexual activity risk groups.

SETTING

England and Wales.

RESULTS

Model results showed that for heterosexuals universal infant vaccination became more effective than clinic based vaccination only approximately 40 years after the start of the programme and that the predicted cost effectiveness of GU clinic vaccination was greater at all times. For homosexuals, clinic vaccination was always more effective over the time frame considered, but by 50 years if it were carried out without prior screening it had become appreciably less cost effective than a mass infant programme. With prior screening in GU clinics this cost effectiveness deficit was only marginal.

CONCLUSIONS

Targeted vaccination might have a much greater potential than is realised at present, particularly if it were possible to improve compliance of clinic attendees. A fuller comparison between mass infant and targeted vaccination must await the specific inclusion in the model of other risk groups such as intravenous drug users. An important determinant of the relative merits of the two approaches is the relationship between rates of attendance and of changing sexual partners. Further research on this is required.

Scatter dose estimation based on dose-area product and the specification of radiation barriers

Scatter dose as a function of dose-area product (DAP) has been studied over a range of tube potentials and scattering angles. Data are presented to permit the calculation of scatter dose from DAP at distances of 1 m or more from the patient. This method has been used to calculate absorbed dose to the walls of six existing X-ray rooms which are used for interventional radiology, angiography or barium contrast studies. These calculations have been compared with measurements using thermoluminescent dosemeters. The median ratio of measured to calculated dose was 0.50 and the maximum value was 1.26. It was concluded that the calculation of scatter dose from DAP using the factors derived in this report can be used as the basis for the specification of radiation protection barriers. The busiest room in this study in terms of DAP had a DAP rate of 224 Gy cm2 per day. From the scatter factors presented here, it was shown that the room walls did not need to have more than 1.2 mm of lead equivalence.

Density-dependent processes in the transmission of human onchocerciasis: relationship between microfilarial intake and mortality of the simuliid vector

In order to construct an analytical model of onchocerciasis transmission, it is necessary to elucidate the functional relationships of the various population rate processes taking place within the human and vector hosts. Two previous papers have explored the evidence for density-dependent regulation in relation to microfilarial intake by, and larval development within, the Simulium host. This paper investigates the survivorship of wild-caught blackfly samples fed on subjects with different intensities of Onchocerca volvulus microfilarial infection. Analyses were based on data for Guatemalan S. ochraceum s.l. (possessing a well-developed cibarial armature), West African S. damnosum s.l. (forest species), and South Venezuelan S. guianense (the latter two lacking a toothed cibarium). The mean survival times of samples of the 3 species, kept under laboratory conditions, decreased as parasite intake increased, the rate of mortality being dependent on the fly's age (measured as time post-feeding) and on the worm load acquired. An empirical, time-dependent hazard function was fitted to observed death rates/fly/day which rose very shortly after engorgement, declined subsequently, and rose again throughout the extrinsic incubation period of the parasite. The parameters of this hazard model were all positively correlated with the density of microfilariae in the bloodmeal. Expressions of survivorship and life-expectancy as explicit functions of time post-feeding and mean parasite intake were derived. The average expectation of life at engorgement for uninfected flies in the laboratory was estimated to be around 1 week for both, armed and unarmed blackflies. Residual life-expectancy decreased with time post-feeding and microfilarial load in both categories of vectors. This decline (resulting from age- and parasite-dependent mortality rates) was much more pronounced in those species lacking a toothed fore-gut. Whilst a fraction of heavily infected S. ochraceum was able to survive the latent period of the parasite, being therefore potentially capable of transmitting the infection, equivalent worm loads in S. guianense resulted in a drastic reduction of the expectation of infective life. These results provide additional evidence to support the hypothesis that, in the case of intrinsically susceptible vectors, unarmed simuliids are more efficient at low microfilarial loads, when the transmission rate from human to vector host is higher, and parasite-induced fly mortality is negligible. The opposite takes place in armed flies, which perform poorly at low parasite burdens and better at heavier loads, with little parasite-induced vector death.

The genotype of the human cancer cell: implications for risk analysis

An extremely large database describes genotypes associated with the human cancer phenotype and genotypes of human populations with genetic predisposition to cancer. Aspects of this database are examined from the perspective of risk analysis, and the following conclusions and hypotheses are proposed: (1) The genotypes of human cancer cells are characterized by multiple mutated genes. Each type of cancer is characterized by a set of mutated genes, a subset from a total of more than 80 genes, that varies between tissue types and between different tumors from the same tissue. No single cancer-associated gene nor carcinogenic pathway appears suitable as an overall indicator whose induction serves as a quantitative marker for risk analysis. (2) Genetic defects that predispose human populations to cancer are numerous and diverse, and provide a model for associating cancer rates with induced genetic changes. As these syndromes contribute significantly to the overall cancer rate, risk analysis should include an estimation of the effect of putative carcinogens on individuals with genetic predisposition. (3) Gene activation and inactivation events are observed in the cancer genotype at different frequencies, and the potency of carcinogens to induce these events varies significantly. There is a paradox between the observed frequency for induction of single mutational events in test systems and the frequency of multiple events in a single cancer cell, suggesting events are not independent. Quantitative prediction of cancer risk will depend on identifying rate-limiting events in carcinogenesis. Hyperproliferation and hypermutation may be such events. (4) Four sets of data suggest that hypermutation may be an important carcinogenic process. Current mechanisms of risk analysis do not properly evaluate the potency of putative carcinogens to induce the hypermutable state or to increase mutation in hypermutable cells. (5) High-dose exposure to carcinogens in model systems changes patterns of gene expression and may induce protective effects through delay in cell progression and other processes that affect mutagenesis and toxicity. Paradigms in risk analysis that require extrapolation over wide ranges of exposure levels may be flawed mechanistically and may underestimate carcinogenic effects of test agents at environmental levels. Characteristics of the human cancer genotype suggest that approaches to risk analysis must be broadened to consider the multiplicity of carcinogenic pathways and the relative roles of hyperproliferation and hypermutation. Further, estimation of risk to general human populations must consider effects on hypersusceptible individuals. The extrapolation of effects over wide exposure levels is an imprecise process.

After 4 years' work, revised Code of Ethics goes to General Council for decision

The CMA's Committee on Ethics will present a revised Code of Ethics for consideration by General Council during the annual meeting in Sydney, NS, later this month. This article outlines the reasons for updating the current (1990) version of the code and explains some of the significant changes and omissions. If approved by General Council, the revised code will take effect immediately.

Delivery of albuterol in a pediatric emergency department

STUDY OBJECTIVE

To determine if albuterol delivery by the combination of a metered-dose inhaler (MDI) with a spacer is equal in effectiveness to nebulization in a pediatric emergency department setting.

DESIGN

Prospective series.

SETTING

Urban children's hospital emergency department.

PARTICIPANTS

Patients > or = six years of age with the diagnosis of acute asthma exacerbation. Exclusion criteria consisted of impending respiratory failure and corticosteroid administration within the preceding seven days.

INTERVENTIONS

Patients were randomized into either the nebulizer treatment group or one of two MDI-spacer treatment groups (two spacers were evaluated). Each patient received three albuterol treatments administered evenly over one hour. The dose ratio for albuterol by nebulizer versus MDI-spacer was 6.9:1. Outcome was assessed by comparing the pre- and posttreatment percent predicted respiratory rate and percent predicted peak expiratory flow rate (PEFR) for each patient.

RESULTS

Sixty patients were enrolled in the study. All three treatment groups showed significant improvement following albuterol therapy in both percent predicted respiratory rate and percent predicted PEFR. When comparing the three groups against each other in regard to outcome, no significant differences were found in improvement of percent predicted respiratory rate (P = 0.3258) or percent predicted PEFR (P = 0.9362).

CONCLUSION

In a pediatric emergency department setting, aerosolized albuterol delivered by MDI-spacer was equal in effectiveness to nebulization in the acute asthma management of children > or = six years of age.

Bioethics for clinicians: 1. Consent

Patients are entitled to make decisions about their medical care and to be given relevant information on which to base such decisions. The physicians obligation to obtain the patient's consent to treatment is grounded in the ethical principles of patient autonomy and respect for persons and is affirmed by Canadian law and professional policy. A large body of research supports the view that the process of obtaining consent can improve patient satisfaction and compliance and, ultimately, health outcomes. An exception to the requirement to obtain consent is the emergency treatment of incapable persons, provided there is no reason to believe that the treatment would be contrary to the person's wishes if he or she were capable.

Ethics for regional boards

When regional health boards choose how to allocate limited resources on the public's behalf, they are exercising ethical judgment. When board members are familiar with the study of ethics and the tools it has produced, they are able to make informed and consistent ethical choices. One board in P.E.I. drew upon ethical principles to first codify its core values, and then develop a process for making decisions which conformed to those values. As boards across Canada assume greater authority and responsibility for public health, a clear understanding of ethical principles can guide their difficult choices.

Pulmonary nodules: effect on detection of spiral CT pitch

PURPOSE

To compare spiral computed tomography (CT) performed at increased pitch with spiral CT performed at standard pitch in the detection of pulmonary nodules.

MATERIALS AND METHODS

Spiral CT scanning of the thorax was performed with a pitch of 1.0 in 109 patients with pulmonary nodules due to metastases. The patients were also randomly assigned to undergo further scanning with a pitch of 1.2 (n = 34), 1.5 (n = 37), 2.0 (n = 38) at the same scanning session. The scan pairs were analysed for number, size, and distribution of nodules.

RESULTS

A bias toward undercounting was noted on scans with a pitch of 1.5 and 2.0; however, this was not statistically significant. Correlation coefficients were r = .982, r = .977, and r = .989 for scans of pitch 1.2, 1.5, and 2.0, respectively. Disease in one patient would have been prospectively understaged from findings on a scan of pitch 2.0 because of poor conspicuity of a small solitary nodule.

CONCLUSION

Findings from scans with increased pitch generally agree well with those from scans with standard pitch; however, there is a greater risk of understaging of disease in patients with solitary nodules as pitch increases. Pitch should be limited to no greater than 1.5 for initial staging of pulmonary metastatic disease.

Optic neuritis in a child

A previously healthy four-year-old girl developed bilateral loss of vision over one day. Her course of optic nerve abnormalities, a related neurologic episode, and the response to corticosteroid therapy is presented. The diagnosis of optic neuritis in a child is made infrequently in an emergency department, but it must be considered in any patient presenting with an acute nontraumatic loss of vision. The characteristic findings associated with optic neuritis, and a review of childhood cases, are discussed.