In vitro identification and functional characterization of glial precursor cells in human gliomas

Human gliomas including astrocytomas and oligodendrogliomas are defined as being composed of neoplastic astrocytes and oligodendrocytes respectively. Here, on the basis of in vitro functional assays, we show that gliomas contain a mixture of glial progenitor cells and their progeny. We have set up explant cultures from pilocytic astrocytomas, glioblastomas and oligodendrogliomas and studied antigens that characterize glial lineage, from the precursor cells (glial restricted precursors and oligodendrocyte-type2-astrocyte/oligodendrocyte precursor cells expressing the A2B5 ganglioside) to the differentiated cells (oligodendrocyte and type-1 and type-2 astrocytes). All tumoral explants contain A2B5+ cells and can generate migrating cells with distinctive functional properties according to glioma subtypes. In pilocytic astrocytomas, very few migrating cells are dividing and can differentiate in type-2 astrocytes or towards the oligodendrocyte lineage. In glioblastomas, most migrating cells are dividing, express A2B5 or glial fibrillary acid protein (GFAP) and can generate oligodendrocytes and type-1 and type-2 astrocytes in appropriate medium. Oligodendroglioma explants are made by actively dividing glial precursor cells expressing A2B5 or PSA-NCAM. Only few cells can migrate and differentiation towards oligodendrocyte lineage does not occur. Isolated A2B5+ cells from both glioblastomas and oligodendrogliomas showed similar genetic alterations as the whole tumour. Therefore, pilocytic astrocytomas contain slowly dividing oligodendrocyte-type2-astrocyte/oligodendrocyte precursor cells in keeping with their benign behaviour whereas both glioblastomas and oligodendrogliomas contain neoplastic glial restricted precursor cells. In oligodendrogliomas, these cells are trapped in undifferentiated and proliferating state. The precursor cells properties present in gliomas give new insight into their histogenesis and open up new avenues for research in the field of gliomagenesis.

The threat to scientific integrity in environmental and occupational medicine

Over the last century, environmental and occupational medicine has played a significant role in the protection and improvement of public health. However, scientific integrity in this field has been increasingly threatened by pressure from some industries and governments. For example, it has been reported that the tobacco industry manipulated eminent scientists to legitimise their industrial positions, irresponsibly distorted risk and deliberately subverted scientific processes, and influenced many organisations in receipt of tobacco funding. Many environmental whistleblowers were sued and encountered numerous personal attacks. In some countries, scientific findings have been suppressed and distorted, and scientific advisory committees manipulated for political purposes by government agencies. How to respond to these threats is an important challenge for environmental and occupational medicine professionals and their societies. The authors recommend that professional organisations adopt a code of ethics that requires openness from public health professionals; that they not undertake research or use data where they do not have freedom to publish their results if these data have public health implications; that they disclose all possible conflicts; that the veracity of their research results should not be compromised; and that their research independence be protected through professional and legal support. The authors furthermore recommend that research funding for public health not be directly from the industry to the researcher. An independent, intermediate funding scheme should be established to ensure that there is no pressure to analyse data and publish results in bad faith. Such a funding system should also provide equal competition for funds and selection of the best proposals according to standard scientific criteria.

Climatic, high tide and vector variables and the transmission of Ross River virus

This report assesses the impact of the variability in environmental and vector factors on the transmission of Ross River virus (RRV) in Brisbane, Australia. Poisson time series regression analyses were conducted using monthly data on the counts of RRV cases, climate variables (Southern Oscillation Index and rainfall), high tides and mosquito density for the period of 1998-2001. The results indicate that increases in the high tide (relative risk (RR): 1.65; 95% confidence interval (CI): 1.20-2.26), rainfall (RR: 1.45; 95% CI: 1.21-1.73), mosquito density (RR: 1.17; 95% CI: 1.09-1.27), the density of Culex annulirostris (RR: 1.25; 95% CI: 1.13-1.37) and the density of Ochlerotatus vigilax (RR: 2.39; 95% CI: 2.30-2.48), each at a lag of 1 month, were statistically significantly associated with the rise of monthly RRV incidence. The results of the present study might facilitate the development of early warning systems for reducing the incidence of this wide-spread disease in Australia and other Pacific island nations.

Investigation of the effects of ischemic preconditioning on the HRV response to transient global ischemia using linear and nonlinear methods

Ischemic preconditioning (IP) has been used as a strategy to prevent cell death in various organs, including the brain and the heart. Investigation of the effects of ischemic preconditioning mostly employed models with reduced complexity, such as cell cultures, tissue slices or perfused organ preparations. Although such models can provide valuable insight into the protective mechanism of preconditioning, the functional (re)organization of the control mechanisms at the level of the living organism cannot be assessed. The purpose of the present animal model study was to evaluate the effect of global ischemic preconditioning on the heart rate variability (HRV) response to the asphyxia insult. The data consisted of 4 h RR interval measurements recorded in five preconditioned and five non-preconditioned Wistar rats. Using linear (time and frequency domain) and nonlinear (approximate entropy and parameters of Poincare plots) measures, we evaluated the dynamic time course of the HRV response to the asphyxia insult and the effect of preconditioning on the autonomic neurocardiac control. Both the linear and nonlinear parameters indicate a faster recovery of the baseline HRV corresponding to the preconditioned groups, though only the spectral analysis identifies a statistically significant difference between the two groups. For the preconditioned group, at about 90 min after the asphyxic insult, the autonomic neural balance (measured by LF/HF ratio) appears fully recovered. The small variation of the rest of the parameters indicates the necessity of further investigation including the design of a larger study with a higher statistical power. Our results show for the first time that global ischemic preconditioning influences the HRV response to the asphyxia injury. The neuroprotective effect of preconditioning translates into a faster recovery of the basal HRV and the autonomic modulation of the heart.

Would general practitioners support a population-based colorectal cancer screening programme of faecal-occult blood testing?

BACKGROUND

The success of a population-based screening for colorectal cancer (CRC) is determined to a large extent by general practitioner (GP) attitudes, beliefs and support. The extent to which GPs support population-based CRC screening remains unclear.

AIMS

To assess the knowledge, attitudes and practices of GPs in relation to CRC screening, and to identify the determinants of GP support for population-based faecal-occult blood testing (FOBT).

METHODS

A cross-sectional postal survey was conducted with a random sample of 692 GPs in Queensland, -Australia. We assessed GP knowledge, attitudes and practices concerning CRC screening in relation to their stance on population-based FOBT screening.

RESULTS

Although the response rate was low (41%), participants were representative of Queensland GPs in general. Of 284 participating GPs, 143 (50.5%) indicated that they would support a population-based FOBT screening programme, 42 (14.8%) would not and 98 (34.6%) were unsure. Belief in FOBT test efficacy (P <0.001), possession of CRC guidelines (P <0.05) and belief in earlier stage detection (P <0.05) were major determinants of support for population-based FOBT screening. No significant association was observed for doctor's sex, location of practice, age, year completed medical training, membership of a Division of General Practice, number of weekly consultations, number of patients investigated for CRC per month, size of practice, own family history of CRC, interest in further information on CRC screening or treatment, and current use of FOBT with asymptomatic patients aged > or =40 years.

CONCLUSIONS

GP support for FOBT population-based screening appears to have increased over recent years. The knowledge and attitudes/beliefs of GPs are key determinants of their support.

Ross River virus disease in Australia: epidemiology, socioecology and public health response

Societal and ecosystem change have a potentially profound impact of on human health and well-being. Alteration in the pattern of infectious diseases could be one of the most significant results of this process. Arboviral infections are a global public health issue with significant morbidity and mortality burden in the human population. Ross River virus (RRV) infection is the most common arboviral disease in Australia and some Pacific island nations. The present paper aims to illustrate the epidemiological and socioecological implications of RRV infection in Australia and to make recommendations for public health response to this disease.

Characterization of heart rate variability changes following asphyxia in rats

OBJECTIVES

A non-invasive method to monitor the functioning of the autonomous nervous system consists in heart rate variability (HRV) analysis. The aim of this study was to investigate the changes on HRV after an asphyxia experiment in rats, using several linear (time and frequency domain) and nonlinear parameters (approximate entropy, SD1 and SD2 indices derived from Poincare plots).

METHODS

The experiments involved the study of HRV changes after cardiac arrest (CA) resulting from 5 min of hypoxia and asphyxia, followed by manual resuscitation and return of spontaneous circulation. 5 min stationary periods of RR intervals were selected for further analysis from 5 rats in following distinct situations: 1) baseline, 2) 30 min after CA, 3) 60 min after CA, 4) 90 min after CA, 5) 120 min after CA, 6) 150 min after CA. The ANS contribution has been delineated based on time and frequency domain analysis.

RESULTS AND CONCLUSIONS

The results indicate that the recovery process following the asphyxia cardiac arrest reflects the impaired functioning of the autonomic nervous system. Both linear and nonlinear parameters track the different phases of the experiment, with an increased sensitivity displayed by the approximate entropy (ApEn). After 150 min the ApEn RRI parameter recovers to its baseline value. The results forward the ApEn as a more sensitive parameter of the recovery process following the asphyxia.

Determining zygosity in early pregnancy by ultrasound

OBJECTIVES

First-trimester ultrasound can reliably determine chorionicity but not zygosity. We set out to investigate whether it may be possible to determine zygosity using ultrasound by noting the number of corpora lutea (CLs), structures which reflect ovulation. In the presence of a dichorionic twin pregnancy, the identification of one CL would suggest that twins are monozygotic whereas two CLs implies dizygosity.

METHODS

This was a retrospective analysis of predominantly spontaneous twin pregnancies presenting for an early pregnancy ultrasound at 5-8-completed weeks of gestation. Placentation was correlated with presumed zygosity as predicted by the number of CLs present.

RESULTS

Of 33 twin gestations, chorionicity was compatible in all cases with the predicted zygosity. In 15 cases one CL was seen and these were designated monozygotic. Of these, four were of monochorionic placentation and 11 dichorionic. The remaining 18 cases had two CLs and were presumed dizygotic; all were of dichorionic placentation.

CONCLUSION

We propose a novel technique of zygosity determination during very early pregnancy which may have implications both clinically and in genetic research involving twins. However, this study requires further verification by comparing ultrasound results with DNA evidence taken after birth.

Abnormal pancreatic isoamylases in the serum of children with choledochal cyst

PURPOSE

To investigate the changes of pancreatic isoamylases in the serum of children with choledochal cyst.

METHODS

Serum and bile from 20 children with choledochal cyst were studied for total amylase activity and isoamylases. Using electrophoresis, the assay of pancreatic isoamylases was expressed by peak appearance rate (PAR) and ratio of isoenzyme activity (RIA). Serum from 20 healthy children and 12 adults with acute pancreatitis served as a comparison.

RESULTS

The total amylase activity in the serum of children with choledochal cyst was slightly higher than that of healthy controls, but dramatically lower than that of acute pancreatitis. The serum of children with choledochal cyst showed 5 pancreatic peaks (PAR: P1, 100 %; P2, 100 %; P3, 100 %; P4, 75 %; P5, 45 %) without any major peak. In healthy controls, only P1 and P2 were present (PAR: P1, 40 %; P2, 100 %) with the latter being a major peak (RIA: 81.8 +/- 25.3 %). These results in children with choledochal cyst differed from those of patients with acute pancreatitis who presented with the less common P4 and no P5 (PAR: P1, 100 %; P2, 100 %; P3, 91.6 %; P4, 8.3 %). The pattern of pancreatic isoenzymes in bile was similar to that in the serum from patients with choledochal cyst. These abnormal pancreatic isoamylases gradually disappeared after operation.

CONCLUSIONS

Abnormal pancreatic isoamylases, especially P4 and P5, are found in the serum of patients with choledochal cyst, which would point to a reflux of pancreatic juice into the biliary tract.

Time-dependent entropy estimation of EEG rhythm changes following brain ischemia

Our approach is motivated by the need to generate a rigorous measure of the degree of disorder (or complexity) of the EEG signal in brain injury. Entropy is a method to quantify the order/disorder of a time series. It is the first time that a time-dependent entropy (TDE) is used in the quantification of brain injury level. The TDE was sensitive enough to monitor the significant changes in the subject's brain rhythms during recovery from global ischemic brain injury. Among the different entropy measures, we used Tsallis entropy. This entropy is parametrized and is able to match with the particular properties of EEG, like long-range rhythms, spikes, and bursts. The method was tested in a signal composed of segments of synthetic signals (Gaussian and uniform distributions) and segments of real signals. The real signal segments were extracted from normal EEG, EEG recordings from early recovery, and normal EEG corrupted by simulated spikes and bursts. Adult Wistar rats were subjected to asphyxia-cardiac arrest for 3 and 5 min. The TDE detected the pattern of ischemia-induced EEG alterations and was able to discriminate the different injury levels. Two parameters seem to be good descriptors of the recovery process; the mean entropy and the variance of the estimate followed opposite trends, with the mean entropy decreasing and its variance increasing with injury.

Different responses of Ross River virus to climate variability between coastline and inland cities in Queensland, Australia

AIMS

To examine the potential impact of climate variability on the transmission of Ross River virus (RRv) infection, and to assess the difference in the potential predictors of RRv incidence in coastline and inland regions, Queensland, Australia.

METHODS

Information on the RRv cases notified between 1985 to 1996 was obtained from the Queensland Department of Health. Climate and population data were supplied by the Australian Bureau of Meteorology and the Australia Bureau of Statistics, respectively. The function of cross correlations was used to compute a series of correlations between climate variables (rainfall, maximum temperature, minimum temperature, relative humidity, and high tide) and the monthly incidence of RRv disease over a range of time lags. Time series Poisson regression models were performed to adjust for the autocorrelations of the monthly incidences of RRv disease and the confounding effects of seasonality, the case notification time, and population sizes.

RESULTS

The cross correlation function shows rainfall, maximum temperature, minimum temperature, and relative humidity at a lag of 1-2 months and high tide in the current month were significantly associated with the monthly incidence of RRv in the coastline region. Relative humidity and rainfall at a lag of two months was also significantly associated with the monthly incidence of RRv in the inland region. The results of Poisson regressive models show that the incidence of RRv disease was significantly associated with rainfall, maximum temperature, minimum temperature, relative humidity, and high tide in the coastline region, and with rainfall and relative humidity in the inland region. There was a significant interaction between climate variables and locality in RRv transmission.

CONCLUSIONS

Climate variability may have played a significant role in the transmission of RRv. There appeared to be different responses of RRv to climate variability between coastline and inland cities in Queensland, Australia. Maximum temperature appeared to exhibit a greater impact on the RRv transmission in coastline than in inland cities. Minimum temperature and relative humidity at 3 pm inland seemed to affect the RRv transmission more than at the coastline. However, the relation between climate variables and RRv needs to be viewed within a wider context of other social and environmental factors, and further research is needed.

Regulation of fusion activity by the cytoplasmic domain of a paramyxovirus F protein

SER virus is a member of the family Paramyxoviridae, genus Rubulavirus, which has been isolated from pigs. It is very closely related to SV5 virus serologically, in protein profile, and in nucleotide sequence. However, unlike SV5, SER induces minimal syncytium formation in infected CV-1 or BHK cells. Fluorescence transfer experiments between labeled erythrocytes and infected MDBK cells revealed that SER also induces hemifusion and pore formation with reduced efficiency. The virion polypeptide profiles of SER and SV5 are very similar, except that the SER F1 subunit shows an apparent molecular weight that is about 2 kDa higher than that of SV5. Comparison of the deduced amino acid sequences revealed the SER F (551 aa) to be longer than SV5 F (529 aa) by 22 residues in the cytoplasmic tail (CT) domain. The HN and M gene sequences of the viruses were found to be very similar. The SER F showed minimal fusion activity when coexpressed with either SV5 or SER HN. In contrast, SV5 F was highly fusogenic when coexpressed with either HN protein, indicating that the restricted fusion capacity of SER virus is a property of its F protein. Truncation in the CT of SER F by 22 residues completely rescued its ability to cause syncytium formation, whereas other truncations rescued syncytium formation partially. These results demonstrate that an elongated CT of a paramyxovirus F protein suppresses its membrane fusion activity.

Maternal and foetal activin A levels: associations with normal and abnormal labour

In pregnancy the feto-placental unit is the major source of activin A. However, the role(s) of activin A in late pregnancy remain uncertain and controversial. In particular, whether activin A levels alter in association with labour is unclear. In a cross-sectional cohort study, maternal serum samples were collected from women at term prior to elective Caesarean section (n=11), during labour prior to a spontaneous vaginal delivery (n=31), an instrumental vaginal delivery (n=16) or an emergent Caesarean section (n=7). Umbilical artery blood samples were collected from 75 pregnancies, after an elective Caesarean section (n=9), a normal vaginal delivery (n=37), an instrumental vaginal delivery (n=15) or an emergent Caesarean section (n=14). Levels of activin A were measured and compared according to modes of delivery.Maternal, but not foetal, serum activin A was increased significantly in women who were delivered by an intrapartum Caesarean section compared to other modes of delivery. Foetal, but not maternal, serum activin A was significantly correlated with umbilical artery pH. Maternal serum activin A is increased in women undergoing an intrapartum Caesarean section compared to either a vaginal delivery or an elective Caesarean section. The mechanism(s) underlying this observation are not clear.

Climate variability and Ross River virus transmission

OBJECTIVES

(1) To examine the feasibility to link climate data with monthly incidence of Ross River virus (RRv). (2) To assess the impact of climate variability on the RRv transmission.

DESIGN

An ecological time series analysis was performed on the data collected between 1985 to 1996 in Queensland, Australia.

METHODS

Information on the notified RRv cases was obtained from the Queensland Department of Health. Climate and population data were supplied by the Australian Bureau of Meteorology and the Australian Bureau of Statistics, respectively. Spearman's rank correlation analyses were performed to examine the relation between climate variability and the monthly incidence of notified RRv infections. The autoregressive integrated moving average (ARIMA) model was used to perform a time series analysis. As maximum and minimum temperatures were highly correlated with each other (r(s)=0.75), two separate models were developed.

RESULTS

For the eight major cities in Queensland, the climate-RRv correlation coefficients were in the range of 0.12 to 0.52 for maximum and minimum temperatures, -0.10 to 0.46 for rainfall, and 0.11 to 0.52 for relative humidity and high tide. For the whole State, rainfall (partial regression coefficient: 0.017 (95% confidence intervals 0.009 to 0.025) in Model I and 0.018 (0.010 to 0.026) in Model II), and high tidal level (0.030 (0.006 to 0.054) in Model I and 0.029 (0.005 to 0.053) in Model II) seemed to have played significant parts in the transmission of RRv in Queensland. Maximum temperature was also marginally significantly associated with the incidence of RRv infection.

CONCLUSION

Rainfall, temperature, and tidal levels may be important environmental determinants in the transmission cycles of RRv disease.