D‐Serine metabolism in C6 glioma cells: Involvement of alanine‐serine‐cysteine transporter (ASCT2) and serine racemase (SRR) but not D‐amino acid oxidase (DAO)

D‐serine is an endogenous N‐methyl‐D‐aspartate (NMDA) receptor coagonist. It is synthesized from L‐serine by serine racemase (SRR), but many aspects of its metabolism remain unclear, especially in the forebrain, which lacks active D‐amino acid oxidase (DAO), the major D‐serine degradative enzyme. Candidate mechanisms include SRR operating in α,β‐eliminase mode (converting D‐serine to pyruvate) and regulation by serine transport, in which the alanine‐serine‐cysteine transporter ASCT2 is implicated. Here we report studies in C6 glioma cells, which “simulate” the forebrain, in that the cells express SRR and ASCT2 but lack DAO activity. We measured D‐serine, ASCT2, SRR, and DAO expression and DAO activity in two situations: after incubation of cells for 48 hr with serine isomers and after increased or decreased SRR expression by transfection and RNA interference, respectively. Incubation with serine enantiomers decreased [³H]D‐serine uptake and ASCT2 mRNA and increased SRR immunoreactivity but did not alter DAO immunoreactivity, and DAO activity remained undetectable. SRR overexpression increased D‐serine and pyruvate and decreased [³H]D‐serine uptake and ASCT2 mRNA but did not affect DAO. SRR knockdown did not alter any of the parameters. Our data suggest that D‐serine transport mediated by ASCT2 contributes prominently to D‐serine homeostasis when DAO activity is absent. The factors regulating D‐serine are important for understanding normal NMDA receptor function and because D‐serine, along with DAO and SRR, is implicated in the pathogenesis and treatment of schizophrenia. © 2010 Wiley‐Liss, Inc.     

Racism and cardiovascular disease in African Americans

This article provides an overview of the evidence on the ways racism can affect the disproportionate rates of cardiovascular disease (CVD) in African Americans. It describes the significant health disparities in CVD for blacks and whites and suggests that racial disparities should be understood within the context of persistent inequities in societal institutions and relations. Evidence and potential pathways for exploring effects of 3 levels of racism on cardiovascular health risk factors and outcomes are reviewed. First, institutional racism can lead to limited opportunities for socioeconomic mobility, differential access to goods and resources, and poor living conditions that can adversely affect cardiovascular health. Second, perceived/personally mediated racism acts as a stressor and can induce psychophysiological reactions that negatively affect cardiovascular health. Third, in race-conscious societies, such as the United States, the negative self-evaluations of accepting negative cultural stereotypes as true (internalized racism) can have deleterious effects on cardiovascular health. Few population-based studies have examined the relationship between racism and CVD. The findings, though suggestive of a positive association, are neither consistent nor clear. The research agenda of the Jackson Heart Study in addressing the role of racism in CVD is presented.     

Caspofungin and liposomal amphotericin B therapy of experimental murine scedosporiosis

Immunosuppressed mice were infected intravenously with conidia of Scedosporium prolificans. Treatment was begun 1 day later with liposomal amphotericin B, caspofungin, or both drugs initiated concurrently. Amphotericin B and caspofungin were each effective, but combined therapy did not appear to offer advantages over liposomal amphotericin B alone.     

NMDA receptor antagonist treatment at the time of nerve injury prevents injury-induced changes in spinal NR1 and NR2B subunit expression and increases the sensitivity of residual pain behaviours to subsequently administered NMDA receptor antagonists

Spinal NMDA receptors (NMDA R) are important in neuropathic sensitisation and acute administration of antagonists can provide temporary attenuation of sensitisation. If establishment of the chronic pain state could be prevented by brief administration of such agents at or around the time of nerve injury (pre-emptive analgesia) it might be possible to avoid many of the unacceptable side effects associated with repeated administration of these or other antagonists. Several reports describe aspects of effective pre-emptive analgesia from NMDA R antagonists in animal models of neuropathic pain. The first aim of the present study was to make a direct comparison of changes in mechanical allodynia, cold allodynia and thermal hyperalgesia following nerve injury, demonstrating their increasing degree of susceptibility to pre-emptive NMDA R antagonist treatment. Secondly, we used immunoblotting and immunohistochemistry to investigate the effects of nerve injury on NMDA receptor subunit expression, revealing increased expression of NR2B, but not NR2A and reduced NR1 in the superficial dorsal horn. These changes were attenuated following NMDA receptor antagonist pre-treatment. Thirdly, we investigated the pharmacological properties of residual mechanical allodynia and cold allodynia that remained after pre-emptive treatment and revealed a greater sensitivity to NMDA R antagonists. These findings indicate that in addition to a marked suppression of thermal hyperalgesia and cold allodynia, pre-emptive treatment with NMDA R antagonist causes a lasting change in spinal NMDA R complexes such that remaining mechanical allodynia should be more effectively targeted by NMDA R antagonists.     

Increased dry-season length over southern Amazonia in recent decades and its implication for future climate projection

We have observed that the dry-season length (DSL) has increased over southern Amazonia since 1979, primarily owing to a delay of its ending dates (dry-season end, DSE), and is accompanied by a prolonged fire season. A poleward shift of the subtropical jet over South America and an increase of local convective inhibition energy in austral winter (June–August) seem to cause the delay of the DSE in austral spring (September–November). These changes cannot be simply linked to the variability of the tropical Pacific and Atlantic Oceans. Although they show some resemblance to the effects of anthropogenic forcings reported in the literature, we cannot attribute them to this cause because of inadequate representation of these processes in the global climate models that were presented in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report. These models significantly underestimate the variability of the DSE and DSL and their controlling processes. Such biases imply that the future change of the DSE and DSL may be underestimated by the climate projections provided by the Intergovernmental Panel on Climate Change’s Fifth Assessment Report models. Although it is not clear whether the observed increase of the DSL will continue in the future, were it to continue at half the rate of that observed, the long DSL and fire season that contributed to the 2005 drought would become the new norm by the late 21st century. The large uncertainty shown in this study highlights the need for a focused effort to better understand and simulate these changes over southern Amazonia.Fifteen percent of global photosynthesis occurs in the Amazon rainforest (1), where 25% of plant species are found (2). This rainforest ecosystem normally removes C from the atmosphere but released more than 1 Pg of C to the atmosphere in the 2005 drought (3). Consequently, even a partial loss of these forests would substantially increase global atmospheric CO₂ (4, 5) and reduce biodiversity. The dry-season length (DSL) is among the most important climate limitations for sustaining rainforests (6–9), especially in southern Amazonia, where rainforests are exposed to relatively long dry seasons and vulnerable to increasing conversion of native forests to cultivated crops (10–12). The extreme droughts in 2005 and 2010 had strong impacts on the rainforest and its C cycle (3, 13, 14). These unusual events, along with possible increase of drought severity and DSL during the past few decades (e.g., refs. 15 and 16) heighten the urgency of understanding what causes these dry anomalies and whether they will continue into the future. Contrary to the observed drying, some global climate models that previously projected strong drying over Amazonia now project much weaker drying by the end of the 21st century as these models evolve (17). Do these observed events represent the extremes of natural climate variability, or do climate projections underestimate potential future changes? This study explores one aspect of these questions by focusing on the change of DSL.     

In vitro and in vivo activities of posaconazole against Coccidioides immitis

Posaconazole (SCH 56592) was tested against 25 strains of Coccidioides immitis to determine their in vitro susceptibilities. The geometric mean 48-h MIC of posaconazole (POSA) was 0.5 microg/ml, the MIC range was 0.25 to 1 microg/ml, and the MIC at which 50% of the isolates tested are inhibited (MIC50) and the MIC90 were 0.5 and 1 microg/ml, respectively. The geometric mean 48-h MIC of itraconazole (ITRA) was 0.23 microg/ml, the MIC range was 0.125 to 0.5 microg/ml, and the MIC50 and MIC90 were both 0.25 microg/ml. Two strains of C. immitis were selected for in vivo studies on the basis of the POSA 48-h MICs for the isolates. POSA orally administered at 0.01, 0.1, 0.5, 1, 5, and 10 mg/kg of body weight/day was compared with ITRA administered at 10 and 30 mg/kg three times a day. The spleens and livers of mice that died or survived to day 50 were removed to measure the fungal burdens. Mice had >or=90% survival when they were treated with >or=0.5 mg of POSA per kg or 30 mg of ITRA per kg. Cultures of whole spleens and livers from mice treated with 10 mg of POSA per kg showed >or=70% sterilization. No sterilization of whole spleens and livers from mice treated with ITRA was seen. POSA displayed potent in vivo activity against the two strains of C. immitis tested.     

HIV and COPD: a conspiracy of risk factors

Chronic obstructive pulmonary disease (COPD) is an under recognized complication of HIV infection. It is estimated that up to 25% of HIV infected people may have COPD. HIV is associated with COPD as a result of a complex interplay of multiple factors such as pulmonary inflammation, recurrent pulmonary infections especially tuberculosis (TB), increased cigarette smoking, socio‐economic status, childhood respiratory illnesses and industrial and environmental exposures; each of which are risk factors for COPD in their own right. COPD presents at an earlier age in people with HIV infection. There are over 35 million people living with HIV, and most people infected with HIV live in developing regions of the world where they are faced with multiple risk factors for COPD and suboptimal access to health care. TB is the commonest infectious complication of HIV, and HIV infected persons often experience multiple episodes of TB. Cigarette smoking is increasing in developing countries where the greatest burden of TB and HIV is experienced. Cigarette smoking is associated with increased risk of TB and may be associated with acquisition of HIV infection and progression. It is not clear whether non‐infectious pulmonary inflammation persists in the lung when immune reconstitution occurs. Prevention and control of HIV infection must be part of the multiple interventions to reduce the global burden of COPD. A multidisciplinary approach, including behavioural science is required to address this challenge. It presents research opportunities that should be driven by the pulmonology community.     

Culling and cattle controls influence tuberculosis risk for badgers

Human and livestock diseases can be difficult to control where infection persists in wildlife populations. In Britain, European badgers (Meles meles) are implicated in transmitting Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), to cattle. Badger culling has therefore been a component of British TB control policy for many years. However, large-scale field trials have recently shown that badger culling has the capacity to cause both increases and decreases in cattle TB incidence. Here, we show that repeated badger culling in the same area is associated with increasing prevalence of M. bovis infection in badgers, especially where landscape features allow badgers from neighboring land to recolonize culled areas. This impact on prevalence in badgers might reduce the beneficial effects of culling on cattle TB incidence, and could contribute to the detrimental effects that have been observed. Additionally, we show that suspension of cattle TB controls during a nationwide epidemic of foot and mouth disease, which substantially delayed removal of TB-affected cattle, was associated with a widespread increase in the prevalence of M. bovis infection in badgers. This pattern suggests that infection may be transmitted from cattle to badgers, as well as vice versa. Clearly, disease control measures aimed at either host species may have unintended consequences for transmission, both within and between species. Our findings highlight the need for policymakers to consider multiple transmission routes when managing multihost pathogens.