Potential methane reservoirs beneath Antarctica.

Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick and an estimated 21,000 petagrams (1 Pg equals 10(15) g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage.

Mycobacterial adenitis: role of Mycobacterium bovis, non-tuberculous mycobacteria, HIV infection, and risk factors in Arusha, Tanzania.

OBJECTIVE: To assess risk factors and mycobacterial agents in mycobacterial adenitis. DESIGN: Cross sectional involving comparison analysis of high-risk groups. SETTING: Seven hospitals in rural and semi-rural districts of Arusha. SUBJECTS: The study comprised of 457 patients of clinically diagnosed mycobacterial adenitis. INTERVENTIONS: Biopsy materials were cultured and identification of mycobacterial isolates, and HIV infection testing were performed using standard methods. A questionnaire was used to establish information for assessing risk factors. MAIN OUTCOME MEASURES: Proportions of mycobacterial isolates, risk factors and odds ratios. RESULTS: Of the 457 specimens, 65(14.2%) were culture positive. Isolates identified were M. bovis, 7(10.8%) M. tuberculosis, 27(41.5%) and non-tuberculous mycobacteria 31(47.7%). HIV infection and ingestion of raw milk were linked with increased risk of M. bovis infection by OR of 13.6 (95% CI, 1.7 - 109.9) and 15.28 (3.26 - 71.7), respectively. On multivariate analysis, an OR of 16.2 (1.3 - 201.3) for having M. bovis adenitis was linked to HIV infection, raw milk and houses with poor ventilation. An OR of 5.2 (1.2 - 20.6) for non-tuberculous mycobacterial adenitis was linked to history of TB in the family, HIV infection, raw milk, raw animal products and poor knowledge on transmission of tuberculosis. CONCLUSIONS: M. bovis caused one out of ten cases of culture positive mycobacterial adenitis. Non-tuberculous mycobacteria were more common than M. tuberculosis (50% and 40% of the cases, respectively). HIV infection and raw animal products are among the risk factors identified for M. bovis and non-tuberculous mycobacterial adenitis.

Fracture and fortified breast milk in an extremely preterm infant.

Metabolic bone disease (MBD) in the newborn predominantly affects preterm infants. The risk of MBD is inversely proportional to gestational age and birthweight, and directly related to postnatal complications. Poor bone mineralization has been shown in 55% of infants born at less than 1000 g. Optimal nutrition for very preterm infants is thought to be mother's own milk but supplementation is required to meet dietary requirements. However, there is insufficient evidence to determine that supplementation of human milk with commercial fortifiers has an effect on bone mineral content. We report a case of severe MBD with fractures in an extremely preterm infant who was fed with fortified mother's milk.

Specific patterns of responsiveness to microbial antigens staphylococcal enterotoxin B and purified protein derivative by cord blood mononuclear cells are predictive of risk for development of atopic dermatitis.

BACKGROUND: Mononuclear cells from children with active atopic dermatitis (AD) have been reported to be hyper-responsive to certain microbial stimuli, in particular staphylococcal enterotoxin B (SEB). However, it is not known whether this responsiveness is acquired during disease development, or is inherent. We investigated this question in a cohort of children at high risk of atopy followed prospectively from birth to age 3 years. We asked whether their cord blood mononuclear cell (CBMC) cytokine responses to SEB, to an unrelated microbial stimulus purified protein derivative (PPD), or to common allergens, were predictive of risk for subsequent AD development during infancy. METHODS: Children at high risk of developing atopy were randomly selected from an ongoing prospective cohort. Cord blood was collected at birth. The children were seen at 6 months, 1, 2 and 3 years and examined for the development of AD. IFN-gamma, IL-5, IL-10 and IL-13 production by CBMC cultured in the presence of SEB, PPD, PHA, house dust mite (HDM) allergen, ovalbumin (OVA) and cat allergen was determined. RESULTS: SEB-induced IL-5 production by CBMC was elevated in children who developed AD at 6 months (P = 0.01) and 2 years (P = 0.009). PPD-induced IL-5 responses were also elevated in CBMC from children who developed AD at 6 months, 2 years and 3 years (P = 0.05, P = 0.06 and P = 0.06, respectively), as were PPD-induced IL-10 responses (P = 0.05 at 1 years, P = 0.007 at 2 years, P = 0.003 at 3 years) and corresponding IFN-gamma responses (P = 0.05 at 6 months, P = 0.003 at 2 years, P = 0.0004 at 3 years). Increased IL-10 responses to HDM allergen were also observed throughout the observation period in CBMC from children who developed AD. CONCLUSION: Children who develop infantile AD appear to have a predisposition to respond to SEB in a Th2-dominant manner involving selective stimulation of IL-5 production. The increased IL-10 and IFN-gamma induced in response to PPD by children with AD may point to additional intrinsic differences in responses to microbial stimuli between those at high vs. those at low risk for AD, which merit more detailed investigations.

Microbial life beneath a high arctic glacier.

The debris-rich basal ice layers of a high Arctic glacier were shown to contain metabolically diverse microbes that could be cultured oligotrophically at low temperatures (0.3 to 4 degrees C). These organisms included aerobic chemoheterotrophs and anaerobic nitrate reducers, sulfate reducers, and methanogens. Colonies purified from subglacial samples at 4 degrees C appeared to be predominantly psychrophilic. Aerobic chemoheterotrophs were metabolically active in unfrozen basal sediments when they were cultured at 0.3 degrees C in the dark (to simulate nearly in situ conditions), producing (14)CO(2) from radiolabeled sodium acetate with minimal organic amendment (> or =38 microM C). In contrast, no activity was observed when samples were cultured at subfreezing temperatures (< or =-1.8 degrees C) for 66 days. Electron microscopy of thawed basal ice samples revealed various cell morphologies, including dividing cells. This suggests that the subglacial environment beneath a polythermal glacier provides a viable habitat for life and that microbes may be widespread where the basal ice is temperate and water is present at the base of the glacier and where organic carbon from glacially overridden soils is present. Our observations raise the possibility that in situ microbial production of CO(2) and CH(4) beneath ice masses (e.g., the Northern Hemisphere ice sheets) is an important factor in carbon cycling during glacial periods. Moreover, this terrestrial environment may provide a model for viable habitats for life on Mars, since similar conditions may exist or may have existed in the basal sediments beneath the Martian north polar ice cap.

Self-process in comorbid mental illness and drug abuse.

A theory of social influence is proposed as a framework within which to examine the psychosocial processes that underlie substance abuse among persons with severe mental illness. The theory's potential to account for some of the empirical findings in the mental health and substance abuse literatures is discussed, and implications for research are offered.

Efficient construction of 6-azasteroids: dual inhibitors of steroidal 5 alpha-reductase.

A new route to 17 beta-substituted-6-azaandrost-4-en-3-ones, potent dual inhibitors of type 1 and 2 steroidal 5 alpha-reductase, is described.

The physician survey on the post-concussion and whiplash syndromes.

BACKGROUND: The post-concussion syndrome (PCS) and whiplash syndrome (WS) have been controversial topics among physicians for many decades. There is little information available on the opinions and practices of physicians. METHODS: In June of 1992, we performed a national survey by mail of the four physician groups most commonly treating these problems. The number of respondents and response rates were as follows: family physicians, 118, 16%; neurologists, 100, 21%; neurosurgeons, 97, 23%; orthopedists, 82, 13%. The survey instrument contained items on demographics, definitions, causation, prognosis, medico-legal aspects, testing, and treatment. RESULTS: Only a minority of respondents believe that PCS and WS are clearly defined syndromes. A substantial minority report that psychogenic and litigation factors are most responsible for the conditions. Most of the physicians believe that PCS and WS have a 3-6 month recovery time. A significant minority concur that symptoms of the two syndromes resolve when litigation is settled. Most of the physicians order tests to rule out pathology although a minority order tests to reassure patients or because of litigation concerns. Only a minority of respondents believe that effective treatments are available. Not surprisingly, a multitude of conventional and unconventional treatments are sometimes recommended. CONCLUSIONS: Many aspects of PCS and WS are controversial among treating physicians. This controversy can have a profound impact on the quality and cost of patient care. Ongoing research is required to discover more effective treatments for mild brain injury and chronic pain.

Pumiliotoxin alkaloids: a new class of sodium channel agents.

Pumiliotoxin B (PTX-B) and a variety of congeneric alkaloids and synthetic analogs stimulated sodium flux and phosphoinositide breakdown in guinea pig cerebral cortical synaptoneurosomes. The effects of PTX-B and active congeners and analogs on sodium flux in synaptoneurosomes were potentiated markedly by scorpion venom (Leiurus quinquestriatus). In neuroblastoma cells, PTX-B and active congeners had no effect on sodium flux unless synergized by alpha-scorpion toxin or scorpion venom. Certain inactive congeners, lacking hydroxyl groups in the 6-alkylidene side chain, inhibited sodium flux elicited by PTX-B, scorpion venom, or the sodium channel activator batrachotoxin. Such inhibition appeared different from inhibition by local anesthetics, since pumiliotoxins, unlike local anesthetics, had little or no effect on binding of [3H]batrachotoxinin A benzoate to sodium channels. Thus, it appears likely that some "inactive" congeners bind to the PTX-B binding site, but do not activate sodium channels. In the absence of scorpion venom the stimulation of phosphoinositide breakdown in synaptoneurosomes was consonant with the stimulatory effects of these compounds on sodium flux through voltage-dependent sodium channels.

Sonographic detection of portal venous gas in infants with necrotizing enterocolitis.

A characteristic pattern of hepatic parenchymal and portal venous abnormalities was seen with sonography in 12 infants with necrotizing enterocolitis (NEC). In five cases these changes were seen before any radiographic abnormalities were observed. Sonography of 232 infants without NEC did not show these changes. The sonographic abnormalities are believed to be caused by small amounts of gas within the portal venous system and hepatic parenchyma. Because of the simplicity of the sonographic examination and the sensitivity and specificity of the findings, abdominal sonography may be of great value in the early evaluation of infants suspected of having NEC.

Choline incorporation into lecithin in response to insulin or dexamethasone in homogeneous cell cultures of rat lung epithelial cells and fibroblasts.

Labeled choline incorporation into adult rat lung alveolar epithelial cells and adult rat lung fibroblasts in monolayer culture was determined after incubation with insulin (Ins) 10 micrograms/ml, Dexamethasone (Dex) 10(-6)M, or no drug (ND). Incubation periods were 1, 3, 4, and 5 hours. The lecithin (phosphatidyl choline - PC) recovered was separated inot disaturated phosphatidyl choline (DSPC) and unsaturated phosphatidyl choline (USPC). Results expressed as specific activity per hour (see Table) indicate that the incorporation of choline into PC and USPC was greater in fibroblasts (F) than in epithelial cells (E) whether ND, Dex or Ins was present. For incorporation into DSPC, there was no difference between E and F whether ND, Dex or Ins was present. There was significant increase in choline incorporation into PC or USPC for both cell types when Ins was present, whereas there was no difference for either cell type when Dex was present. Insulin significantly increased choline incorporation into DSPC in E cells only. Dex was no different from ND in DSPC incorporation in either cell type. We attribute the greater lecithin synthesis of the F cells to a more rapid increase in cellular structural lipids in the fibroblast cell. Dex had no effect on either cell type possibly from the short-term exposure or possibly because the effect of dexamethasone on alveolar epithelial cells is mediated by product(s) from other lung cells, and thus requires a mixed cell culture to have its effect. We suggest that further study of isolated homogeneous cell lines will not be fruitful in the evaluation of mechanisms of acceleration of lung maturation.

Rapid detection of neonatal intracranial hemorrhage by transillumination.

Using transillumination and a sensitive cadmium sulfide light meter, 145 newborns were screened for the presence of intracranial hemorrhage. Intracranial hemorrhage (ICH) was suspected when the light meter could not detect any light passing through the anterior fontanel when the light beam was directed through the frontal eminence. ICH was confirmed by branial computed tomography or postmortem examination in all 17 infants not transmitting light. Spectrophotometry was performed on samples of cerebrospinal fluid (CSF) to demonstrate the mechanism through which blood in the CSF blocks light transmission.