Predictions of quantum mechanics and stochastic electrodynamics in travelling wave second harmonic generation

We show that stochastic electrodynamics and quantum mechanics give quantitatively different predictions for the quantum nondemolition (QND) correlations in travelling wave second harmonic generation. Using phase space methods and stochastic integration, we calculate correlations in both the positive-P and truncated Wigner representations, the latter being equivalent to the semi-classical theory of stochastic electrodynamics. We show that the semiclassical results are different in the regions where the system performs best in relation to the QND criteria, and that they significantly overestimate the performance in these regions. (C) 2001 Published by Elsevier Science B.V.

Mechanisms of drought-induced population decline in an endangered wallaby

The bridled nailtail wallaby is restricted to one locality in central Queensland, Australia. The population declined severely during a major drought between 1991 and 1995. We investigated age-specific covariates of survival and proximate causes of mortality from 1994 to 1997, using mark-recapture and radio-tagging techniques at two study sites. Using a matrix population model, we also modelled the effect of drought on age-specific survival and the intrinsic rate of population increase,;,. The only significant covariate of survival for adults was a measure of health unrelated to drought. Rainfall, food, predator activity, year, sex and habitat were not associated with variation in adult survival. Juvenile survival was negatively affected by drought, and predation was the proximate cause of most juvenile deaths. The matrix projection model showed that the observed juvenile survivorship during the drought was low enough to have produced a population decline, although fecundity and survival of other age classes was high throughout the study. (C) 2001 Elsevier Science Ltd. All rights reserved.

Increased susceptibility to streptozotocin-induced beta-cell apoptosis and delayed autoimmune diabetes in alkylpurine-DNA-N-glycosylase-deficient mice

Type I diabetes is thought to occur as a result of the loss of insulin-producing pancreatic beta cells by an environmentally triggered autoimmune reaction. In rodent models of diabetes, streptozotocin (STZ), a genotoxic methylating agent that is targeted to the beta cells, is used to trigger the initial cell death. High single doses of STZ cause extensive beta -cell necrosis, while multiple low doses induce limited apoptosis, which elicits an autoimmune reaction that eliminates the remaining cells. We now show that in mice lacking the DNA repair enzyme alkylpurine-DNA-N-glycosylase (APNG), beta -cell necrosis was markedly attenuated after a single dose of STZ. This is most probably due to the reduction in the frequency of base excision repair-induced strand breaks and the consequent activation of poly(ADP-ribose) polymerase (PARP), which results in catastrophic ATP depletion and cell necrosis. Indeed, PARP activity was not induced in A-PNG(-/-) islet cells following treatment with STZ in vitro. However, 48 h after STZ treatment, there was a peak of apoptosis in the beta cells of APNG(-/-) mice. Apoptosis was not observed in PARP-inhibited APNG(+/+) mice, suggesting that apoptotic pathways are activated in the absence of significant numbers of DNA strand breaks. Interestingly, STZ-treated APNG(-/-) mice succumbed to diabetes 8 months after treatment, in contrast to previous work with PARP inhibitors, where a high incidence of beta -cell tumors was observed. In the multiple-low-dose model, STZ induced diabetes in both APNG(-/-) and APNG(-/-) mice; however, the initial peak of apoptosis was 2.5-fold greater in the APNG(-/-) mice. We conclude that APNG substrates are diabetogenic but by different mechanisms according to the status of APNG activity.

The effects of pregnancy on myelin basic protein-induced experimental autoimmune encephalomyelitis in Lewis rats: Suppression of clinical disease, modulation of cytokine expression in the spinal cord inflammatory infiltrate and suppression of lymphocyte p

Problem: The present study was performed to explore the effects of pregnancy on experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats by inoculation with myelin basic protein (MBP) (MBP-EAE). Method of study: MBP-EAE was induced in pregnant and non-pregnant rats and severity of disease evaluated. Serum from pregnant and non-pregnant rats was used in standard lymphocyte proliferation assays. Real-time polymerase chain reaction (PCR) was used to investigate the expression of cytokine mRNA in the inflammatory cells obtained from the spinal cord of rats on day 15 after inoculation. Results: Pregnant rats developed less severe disease than non-pregnant rats. Serum from pregnant rats suppressed the proliferation of T lymphocytes in response to MBP. There was significantly increased expression of IL-4. IL-10 and TNF-alpha mRNA in the spinal cord infiltrate of pregnant rats. Conclusion: Circulating humoral factors and alteration in cytokine production by inflammatory cells may contribute to the suppression of EAE in pregnant rats.

Route of administration of chimeric BPV1VLP determines the character of the induced immune responses

To examine the mucosal immune response to papillomavirus virus-like particles (PV-VLP), mice were immunized with VLP intrarectally (i.r.), intravaginally (i.va.) or intramuscularly (i.m.) without adjuvant. PV-VLP were assembled with chimeric BPV-1 L1 proteins incorporating sequence from HIV-1 gp 120, either the V3 loop or a shorter peptide incorporating a known CTL epitope (HIVP18I10). Antibody specific for BPV-1 VLP and P18 peptide was detected in serum following i.m., but not i.r. or i.va. immunization. Denatured VLP induced a much reduced immune response when compared with native VLP, Immune responses following mucosal administration of VLP were generally weaker than following systemic administration. VLP specific IgA was higher in intestine washes following i.r. than i.va. immunization, and higher in vaginal washes following i.m. than i.r. or i.va. immunization. No differences in specific antibody responses were seen between animals immunized with BPV-1 P18 VLP or with BPV-1 V3 VLP. Cytotoxic T lymphocyte precursors specific for the P18 CTL epitope were recovered from the spleen following i.m., i.va. or i.r. immunization with P18 VLP, and were similarly detected in Peyer's patches following i.m. or i.r. immunization. Thus, mucosal or systemic immunization with PV VLP induces mucosal CTL responses and this may be important for vaccines for mucosal infection with human papillomaviruses and for other viruses.

Corticosteroid-induced glaucoma in a child after a scleral reinforcement procedure

Corticoteroid-induced glaucoma can result from either topical or systemic corticosteroid use. Compared with adults, the corticosteroid response in children is less well known. The case is reported of a child who developed glaucoma after receiving topical corticosteroids following a scleral re-inforcement procedure. The raised intraocular pressure was controlled after cessation of the corticosteroids and with the use of antiglaucoma therapy. As many forms of cortico-steroids are widely used, children on corticosteroids should have regular intraocular pressure measurements as part of their management.

A clonal culture system demonstrates that IL-4 induces a subpopulation of noncytolytic T cells with low CD8, perforin, and granzyme expression

Immune deviation of cytolytic T cell function, induced by type 2 cytokines like IL-4, is an attractive concept to explain failure of the immune system in some diseases. However, this concept is challenged by previous conflicting results on whether type 2 cytokine-producing CD8(+) T cells are cytolytic. Therefore, we have analyzed the relationship between cytolytic activity and cytokine production among large numbers of primary CD8(+) T cell clones. Single murine CD8(+) T cells of naive phenotype were activated at high efficiency with immobilized Abs to CD3, CD8, and CD11a in the presence of IL-2 (neutral conditions) or IL-2, IL-4, and anti-IFN-gamma Ab (type 2-polarizing conditions) for 8-9 days. Under neutral conditions, most clones produced IFN-gamma without IL-4 and were cytolytic. Under type 2-polarizing conditions, most clones produced IFN-gamma and IL-4 but displayed variable cytolytic activity and CD8 expression. Separation on the basis of surface CD8 levels revealed that, compared with CD8(high) cells from the same cultures, CD8(low) cells were poorly cytolytic and expressed low levels of perforin mRNA and protein and granzyme A, B, and C mRNA. A similar, smaller population of noncytolytic CD8(low) cells was identified among CD8(low) T cells activated in mixed lymphocyte reaction with IL-4. Variable efficiency of generation of the noncytolytic cells may account for the differing results of earlier studies. We conclude that IL-4 promotes the development of a noncytolytic CD8(low) T cell phenotype that might be important in tumor- or pathogen-induced immune deviation.

Electric-field-induced Mott insulating states in organic field-effect transistors

We consider the possibility that the electrons injected into organic field-effect transistors are strongly correlated. A single layer of acenes can be modeled by a Hubbard Hamiltonian similar to that used for the κ-(BEDT-TTF)2X family of organic superconductors. The injected electrons do not necessarily undergo a transition to a Mott insulator state as they would in bulk crystals when the system is half-filled. We calculate the fillings needed for obtaining insulating states in the framework of the slave-boson theory and in the limit of large Hubbard repulsion U. We also suggest that these Mott states are unstable above some critical interlayer coupling or long-range Coulomb interaction.

Magnetic-field-induced superconductivity in layered organic molecular crystals with localized magnetic moments

l-(BETS)2FeCl4 undergoes transitions from an antiferromagnetic insulator to a metal and then to a superconductor as a magnetic field is increased. We use a Hubbard-Kondo model to clarify the role of the Fe31 magnetic ions in these phase transitions. In the high-field regime, the magnetic field acting on the electron spins is compensated by the exchange field He due to the magnetic ions. We show how He can be extracted from the observed splitting of the Shubnikov–de Haas frequencies. We predict the field range for field-induced superconductivity in other materials.