Rapid loss of Oct-4 and pluripotency in cultured rodent blastocysts and derivative cell lines.

The POU transcription factor Oct-4 is essential for the pluripotent character of the mouse inner cell mass (ICM) and derivative embryonic stem (ES) cells. We analyzed the expression of Oct-4 during culture and establishment of cell lines from mouse and rat preimplantation embryos. Oct-4 was rapidly lost in primary outgrowths of the majority of cultured embryos prior to any evidence of morphological differentiation. Oct-4 persisted in only a minority of strain 129 cultures, which can go on to give ES cells. We used transgenic rats in which the dual reporter/selection marker beta-geo is under control of Oct-4 regulatory elements to investigate the effect of direct selection for Oct-4 expressing cells. Ablation of all cells occurred, consistent with complete downregulation of Oct-4. Without selection, in contrast, continuous cultures of morphologically undifferentiated cells could be derived readily from rat blastocysts and ICMs. However, these cells did not express significant Oct-4 and, although capable of differentiating into extraembryonic cell types, appeared incapable of producing fetal germ layer derivatives. Downregulation of Oct-4 appears to be a limiting factor in attempts to derive pluripotent cell lines from preimplantation embryos.

Murray Valley encephalitis virus surveillance and control initiatives in Australia. National Arbovirus Advisory Committee of the Communicable Diseases Network Australia.

Mechanisms for monitoring Murray Valley encephalitis (MVE) virus activity include surveillance of human cases, surveillance for activity in sentinel animals, monitoring of mosquito vectors and monitoring of weather conditions. The monitoring of human cases is only one possible trigger for public health action and the additional surveillance systems are used in concert to signal the risk of human disease, often before the appearance of human cases. Mosquito vector surveillance includes mosquito trapping for speciation and enumeration of mosquitoes to monitor population sizes and relative composition. Virus isolation from mosquitoes can also be undertaken. Monitoring of weather conditions and vector surveillance determines whether there is a potential for MVE activity to occur. Virus isolation from trapped mosquitoes is necessary to define whether MVE is actually present, but is difficult to deliver in a timely fashion in some jurisdictions. Monitoring of sentinel animals indicates whether MVE transmission to vertebrates is actually occurring. Meteorological surveillance can assist in the prediction of potential MVE virus activity by signalling conditions that have been associated with outbreaks of Murray Valley encephalitis in humans in the past. Predictive models of MVE virus activity for south-eastern Australia have been developed, but due to the infrequency of outbreaks, are yet to be demonstrated as useful for the forecasting of major outbreaks. Surveillance mechanisms vary across the jurisdictions. Surveillance of human disease occurs in all States and Territories by reporting of cases to health authorities. Sentinel flocks of chickens are maintained in 4 jurisdictions (Western Australia, the Northern Territory, Victoria and New South Wales) with collaborations between Western Australia and the Northern Territory. Mosquito monitoring complements the surveillance of sentinel animals in these jurisdictions. In addition, other mosquito monitoring programs exist in other States (including South Australia and Queensland). Public health control measures may include advice to the general public and mosquito management programs to reduce the numbers of both mosquito larvae and adult vectors. Strategic plans for public health action in the event of MVE virus activity are currently developed or being developed in New South Wales, the Northern Territory, South Australia, Western Australia and Victoria. A southern tri-State agreement exists between health departments of New South Wales, Victoria and South Australia and the Commonwealth Department of Health and Aged Care. All partners have agreed to co-operate and provide assistance in predicting and combatting outbreaks of mosquito-borne disease in south-eastern Australia. The newly formed National Arbovirus Advisory Committee is a working party providing advice to the Communicable Diseases Network Australia on arbovirus surveillance and control. Recommendations for further enhancement of national surveillance for Murray Valley encephalitis are described.

Hyperinsulinaemia in ischaemic heart disease: the importance of myocardial infarction and left ventricular function.

Elevated circulating insulin levels have been reported in ischaemic heart disease, and may be of aetiological importance. Previous studies have not considered the potential influence of heart failure or of previous myocardial infarction, as opposed to stable angina. We therefore measured the insulin response to a 75 g oral glucose tolerance test in five groups with normal glucose tolerance, comparing normal male controls to men with chronic stable angina, men with recent myocardial infarction (two groups, 3 weeks and 3 months post infarction), and men with chronic severe heart failure. Only patients with chronic heart failure had fasting hyperinsulinaemia, probably reflecting associated neuroendocrine abnormalities. Stimulated hyperinsulinaemia was present in all patient groups, but was less pronounced and of shorter duration in patients with angina. At 120 min, only patients with heart failure or previous myocardial infarction were hyperinsulinaemic. The degree of stimulated hyperinsulinaemia was not influenced by the presence of heart failure or by the length of time from infarction. Hyperinsulinaemia is associated with impaired peripheral muscle glucose uptake and metabolism, and might contribute to muscular fatigue on exertion in patients with previous myocardial infarction or heart failure.

The long-term effects of metoprolol and epanolol on tissue-type plasminogen activator and plasminogen activator inhibitor 1 in patients with ischaemic heart disease.

This double-blind, randomized parallel group study investigated the effect of 6 months beta-adrenoceptor antagonist therapy with either metoprolol (beta 1-selective without intrinsic sympathomimetic activity [ISA]) or epanolol (beta 1-selective with ISA) on markers of endogenous fibrinolysis in 20 patients with chronic stable angina receiving concurrent treatment with nifedipine. Neither drug had an effect on tissue-type plasminogen activator or plasminogen activator inhibitor type 1 (PAI-1). A significant correlation between fasting insulin and PAI-1 has previously been described and was confirmed in this study. The group treated with metoprolol showed a significant rise in fasting insulin after 6 months with no change in PAI-1. This suggests that the previously described link between these two may not be causal.

Investigation of cell patterning in the asexual fruiting body of Dictyostelium discoideum using haploid and isogenic diploid strains.

The cell patterning (proportion of spores, stalk cells, and basal disk cells) of individual asexual fruiting bodies of haploid and isogenic diploid strains of D. discoideum was examined to test the hypothesis that the patterning mechanism is based on the 'sensing' of only a single parameter, e.g., cell volume, in dividing the aggregate into the three cell types. If cell patterning is based on sensing only a single parameter, there is no reason to predict a change in cell patterning with ploidy change, and thus haploid and isogenic diploid strains should not differ in their cell patterning. The cell patterning of each of the three pairs of haploid and isogenic diploid strains examined was different. Therefore we conclude that the cell patterning mechanism must involve at least two components not changing in the same way with change in ploidy. The cell patterning of both the haploid and the diploid strains was qualitatively similar, i.e., relationships between the three cell types were described by equations of the same form in the haploid and diploid strains. However a quantitative change in cell patterning led to an increased percentage of stalk and basal disk cells in each diploid compared to its parent haploid. The ratio of basal disk to stalk cell was also greater in the diploids than in their parent haploids. We conclude that these are general ploidy-related changes because the cell patterning of each of the three parent haploid strains was different; the average percentage of stalk cells was 11.6% for X22 (12.4% for its diploid DU162), 20.5% for NP73 (27.2% for its diploid DP62), and 24.5% for HU127 (29.1% for its diploid DU310). One possible patterning mechanism could involve a diffusible signal (s), which shows gene dosage, interacting with cell-surface molecules which we predict occupy a limited number of sites per unit area of the cell membrane. The observed change in cell patterning leading to an increased percentage of stalk cells in diploid strains is predicted from such a model involving diffusible signal interacting with cell-surface molecules.