Dressed neurons: modeling neural-glial interactions

Based on recent experimental data, we design a model for neuronal membrane potentials that incorporates the influence of the surrounding glia (dressed neurons). A neurotransmitter released into the synaptic cleft triggers a Ca(2+) response in nearby glial cells that spreads as a Ca(2+) wave and interacts with other synapses via the release of glutamate from astrocytes. We consider the simple case of a neuron-glia circuit that consists of a single neuron that triggers a Ca(2+) response in the glial cell which in turn feeds back into synapses of the same neuron. It is shown that persistent spiking can occur if the glutamate receptors on the astrocytes are overexpressed--a condition that has been reported from patients suffering from mesial-lobe epilepsy.     

Interception and retention of macroscopic bryophyte fragments by branch substrates in a tropical cloud forest: an experimental and demographic approach

Although the significance of canopy plant communities to ecosystem function is well documented, the process by which such communities become established in trees remains poorly known. Colonization of tree surfaces by canopy-dwelling plants often begins with the establishment of bryophytes, so the conditions that affect the dispersal of bryophytes in the forest canopy merit study. We assessed success rates of one mechanism of bryophyte propagation, the aerial dispersal of macroscopic fragments, using an experimental approach. We quantified interception and retention of marked fragments released from a 36 cm×36 cm grid 50 cm above branches of saplings and mature trees of the species Ocotea tonduzii in a montane cloud forest in Costa Rica. Only 1% of bryophyte fragments dropped over sapling crowns in this manner were retained for the 6-month duration of the study, while branches in the forest canopy with intact epiphyte loads and branches that had been stripped of their epiphytes retained 24% and 5%, respectively. Our results suggest that larger-diameter branches and the presence of other epiphytes can both improve the retention of bryophyte fragments on canopy branches. Further work will be needed to address the relative roles of other dispersal mechanisms (spores, gemmae, microscopic bryophyte fragments) and the dynamics of growth and establishment of macroscopic bryophyte fragments following their interception. Received: 1 March 1999 / Accepted: 24 August 1999     

Ocimum basilicum seeds as a pellicular support for immobilizing enzymes

Summary The swollen seeds ofOcimum basilicum consist of a hard core with a pectious porous outer layer to which urease was bound after epoxy activation, through ethylenediamine-glutaraldehyde arm. These seeds can serve as an inexpensive ready to use natural pellicular polysaccharide support for immobilizing enzymes.     

Plasma orosomucoid metabolism and susceptibility to malarial infection in rodents

The effects of Plasmodium berghei infection on liver function and plasma orosomucoid metabolism were investigated in Wistar rats. Infected rats with 20-25% parasitaemia manifested increased serum transaminase levels, hypoalbuminaemia and hypoproteinaemia. In spite of such indications of deranged liver function, the hepatic synthesis rate (as measured by 14C-amino acid incorporation) of seromucoids predominantly orosomucoid or alpha 1-acid glycoprotein) was increased by 73%. The circulating levels of this glycoprotein were also doubled in infected animals. The albumin synthesis rate was not increased. This preferential synthesis and increase in circulating levels of orosomucoid may have in vivo significance in malarial infection, in view of reports that orosomuocid has influence on in vitro invasion of red cells by malarial parasites.     

Association of BMI and cardiovascular risk stratification in the elderly African-American females

We aimed to estimate the association of BMI and risk of systemic hypertension in African-American females aged 65 years and older. In this retrospective, cross-sectional study, medical charts were randomly reviewed after obtaining institutional review board approval and data collection was conducted for height, weight, BMI, age, ethnicity, gender, and hypertension. A multivariable logistic regression analysis was performed. The mean BMI was significantly higher in hypertensive subjects than normotensives (30.3 vs. 29 kg/m2; P = 0.003). A higher proportion of hypertensive subjects had a BMI >23 kg/m2 as compared to normotensives (88.9% vs. 83.5%; P = 0.023). When the log odds of having a history of hypertension was plotted against BMI as a continuous variable, we found that the odds showed an increasing trend with increasing BMI and a steep increase after a BMI of 23 kg/m2. When BMI was analyzed as a categorical variable, a BMI of 23-30 kg/m2 was found to have an odds ratio of 1.43 (95% confidence interval 1.01-2.13; P = 0.05) and a BMI of >30 kg/m2 had an odds ratio of 1.76 (95% confidence interval 1.17-2.65; P = 0.007) when compared to a BMI of <23 kg/m2. This association remained significant in both univariate and multivariate analysis. We conclude that BMI is an independent predictor of hypertension in elderly African-American females. Our results indicate that the risk of hypertension increased significantly at BMI of >23 kg/m2 in this ethnic group. Weight reduction to a greater extent than previously indicated could play an integral role in prevention and control of high blood pressure in this particular population.     

Early mortality in adults initiating antiretroviral therapy (ART) in low- and middle-income countries (LMIC): a systematic review and meta-analysis

Background

We systematically reviewed observational studies of early mortality post-antiretroviral therapy (ART) initiation in low- and middle-income countries (LMIC) in Asia, Africa, and Central and South America, as defined by the World Bank, to summarize what is known.

Methods and Findings

Studies published in English between January 1996 and December 2010 were searched in Medline and EMBASE. Three independent reviewers examined studies of mortality within one year post-ART. An article was included if the study was conducted in a LMIC, participants were initiating ART in a non-clinical trial setting and were ≥15 years. Fifty studies were included; 38 (76%) from sub-Saharan Africa (SSA), 5 (10%) from Asia, 2 (4%) from the Americas, and 5 (10%) were multi-regional. Median follow-up time and pre-ART CD4 cell count ranged from 3–55 months and 11–192 cells/mm³, respectively. Loss-to-follow-up, reported in 40 (80%) studies, ranged from 0.3%–27%. Overall, SSA had the highest pooled 12-month mortality probability of 0.17 (95% CI 0.11–0.24) versus 0.11 (95% CI 0.10–0.13) for Asia, and 0.07 (95% CI 0.007–0.20) for the Americas. Of 14 (28%) studies reporting cause-specific mortality, tuberculosis (TB) (5%–44%), wasting (5%–53%), advanced HIV (20%–37%), and chronic diarrhea (10%–25%) were most common. Independent factors associated with early mortality in 30 (60%) studies included: low baseline CD4 cell count, male sex, advanced World Health Organization clinical stage, low body mass index, anemia, age greater than 40 years, and pre-ART quantitative HIV RNA.

Conclusions

Significant heterogeneity in outcomes and in methods of reporting outcomes exist among published studies evaluating mortality in the first year after ART initiation in LMIC. Early mortality rates are highest in SSA, and opportunistic illnesses such as TB and wasting syndrome are the most common reported causes of death. Strategies addressing modifiable risk factors associated with early death are urgently needed.     

A Comparison of Methods to Measure the Magnetic Moment of Magnetotactic Bacteria through Analysis of Their Trajectories in External Magnetic Fields

Magnetotactic bacteria possess organelles called magnetosomes that confer a magnetic moment on the cells, resulting in their partial alignment with external magnetic fields. Here we show that analysis of the trajectories of cells exposed to an external magnetic field can be used to measure the average magnetic dipole moment of a cell population in at least five different ways. We apply this analysis to movies of Magnetospirillum magneticum AMB-1 cells, and compare the values of the magnetic moment obtained in this way to that obtained by direct measurements of magnetosome dimension from electron micrographs. We find that methods relying on the viscous relaxation of the cell orientation give results comparable to that obtained by magnetosome measurements, whereas methods relying on statistical mechanics assumptions give systematically lower values of the magnetic moment. Since the observed distribution of magnetic moments in the population is not sufficient to explain this discrepancy, our results suggest that non-thermal random noise is present in the system, implying that a magnetotactic bacterial population should not be considered as similar to a paramagnetic material.