Limnology of Crater Lakes in Los Tuxtlas,Mexico

Investigations on the abundance, biomass and position of heterotrophic flagellates (HF) in the benthic microbial food web of a melt water stream on King George Island, Antarctic Peninsula, were undertaken during the Antarctic summer from 23rd December 1997 until 13th March 1998. Abundance and biomass of potential HF resources (picophotoautotrophic and non-photoautotrophic bacteria) as well as potential predators on HF (ciliates and meiofauna) were also investigated. HF abundance ranged from approximately 9 × 10³ to 81 × 10³ cells cm^–3, values which fall into the same range as those found in lower latitudes. Numerically important benthic HF were euglenids, kinetoplastids, thaumatomastigids and especially chrysomonads. Most species identified have been shown to have a worldwide distribution. Abundance of the benthic ciliates ranged from 27 to 950 cells cm^–3. Mean bacterial abundance was 1.9 × 10⁷ and 5.2 × 10⁸ cells cm^–3 for picophotoautotrophic and non-photoautotrophic benthos, respectively. The well-developed microbial community was able to support the large number of nematods, gastotrichs, tardigrads and rotifers with abundances reaching more than 1000 individuals cm^–3. The largest portion of heterotrophic biomass was formed by the meiofauna with a mean of 63 g C cm^–3, followed by that of the heterotrophic bacteria with 4.80 g C cm^–3. Picophotoautotrophic bacteria contributed a mean of 1.37 g C cm^–3. HF and ciliates mean biomass was 0.61 and 1.99 g C cm^–3, respectively, with the HF biomass comprising between <10 and 70% of the total protozoan biomass. The data obtained in this study identify the melt water stream as a hot-spot of heterotrophic microbial and meiofaunal activity during the austral summer. The HF in the melt water stream formed a diverse group in terms of taxa and potential feeding types. Chrysomonads, kinetoplastids, euglenids and thaumatomastigida were the most abundant taxa. A classification into feeding types identified an average of 34% of the total HF as bacterivorous while all others were able to utilise other, larger organisms as resources. Potential trophic interactions between HF and bacteria and higher trophic levels are discussed.     

Thermostable Pyrococcus furiosus DNA ligase catalyzes the synthesis of (di)nucleoside polyphosphates

DNA ligase from the hyperthermophilic marine archaeon Pyrococcus furiosus (Pfu DNA ligase) synthesizes adenosine 5'-tetraphosphate (p4A) and dinucleoside polyphosphates by displacement of the adenosine 5'-monophosphate (AMP) from the Pfu DNA ligase-AMP (E-AMP) complex with tripolyphosphate (P3), nucleoside triphosphates (NTP), or nucleoside diphosphates (NDP). The experiments were performed in the presence of 1-2 microM [alpha-32P]ATP and millimolar concentrations of NTP or NDP. Relative rates of synthesis (%) of the following adenosine(5')tetraphospho(5')nucleosides (Ap4N) were observed: Ap4guanosine (Ap4G) (from GTP, 100); Ap4deoxythymidine (Ap4dT) (from dTTP, 95); Ap4xanthosine (Ap4X) (from XTP, 94); Ap4deoxycytidine (Ap4dC) (from dCTP, 64); Ap4cytidine (Ap4C) (from CTP, 60); Ap4deoxyguanosine (Ap4dG) (from dGTP, 58); Ap4uridine (Ap4U) (from UTP, <3). The relative rate of synthesis (%) of adenosine(5')triphospho(5')nucleosides (Ap3N) were: Ap3guanosine (Ap3G) (from GDP, 100); Ap3xanthosine (Ap3X) (from XDP, 110); Ap3cytidine (Ap3C) (from CDP, 42); Ap3adenosine (Ap3A) (from ADP, <1). In general, the rate of synthesis of Ap4N was double that of the corresponding Ap3N. The enzyme presented optimum activity at a pH value of 7.2-7.5, in the presence of 4 mM Mg2+, and at 70 degrees C. The apparent Km values for ATP and GTP in the synthesis of Ap4G were about 0.001 and 0.4mM, respectively, lower values than those described for other DNA or RNA ligases. Pfu DNA ligase is used in the ligase chain reaction (LCR) and some of the reactions here reported [in particular the synthesis of Ap4adenosine (Ap4A)] could take place during the course of that reaction.     

Total sleep deprivation does not significantly degrade semantic encoding

ABSTRACT

Sleep deprivation impairs performance on cognitive tasks, but it is unclear which cognitive processes it degrades. We administered a semantic matching task with variable stimulus onset asynchrony (SOA) and both speeded and self-paced trial blocks. The task was administered at the baseline and 24 hours later after 30.8 hours of total sleep deprivation (TSD) or matching well-rested control. After sleep deprivation, the 20% slowest response times (RTs) were significantly increased. However, the semantic encoding time component of the RTs remained at baseline level. Thus, the performance impairment induced by sleep deprivation on this task occurred in cognitive processes downstream of semantic encoding.     

Regulatory T Cell Expansion in HTLV-1 and Strongyloidiasis Co-infection Is Associated with Reduced IL-5 Responses to Strongyloides stercoralis Antigen

Background

Human strongyloidiasis varies from a chronic but limited infection in normal hosts to hyperinfection in patients treated with corticosteroids or with HTLV-1 co-infection. Regulatory T cells dampen immune responses to infections. How human strongyloidiasis is controlled and how HTLV-1 infection affects this control are not clear. We hypothesize that HTLV-1 leads to dissemination of Strongyloides stercoralis infection by augmenting regulatory T cell numbers, which in turn down regulate the immune response to the parasite.

Objective

To measure peripheral blood T regulatory cells and Strongyloides stercoralis larval antigen-specific cytokine responses in strongyloidiasis patients with or without HTLV-1 co-infection.

Methods

Peripheral blood mononuclear cells (PBMCs) were isolated from newly diagnosed strongyloidiasis patients with or without HTLV-1 co-infection. Regulatory T cells were characterized by flow cytometry using intracellular staining for CD4, CD25 and FoxP3. PBMCs were also cultured with and without Strongyloides larval antigens. Supernatants were analyzed for IL-5 production.

Results

Patients with HTLV-1 and Strongyloides co-infection had higher parasite burdens. Eosinophil counts were decreased in the HTLV-1 and Strongyloides co-infected subjects compared to strongyloidiasis-only patients (70.0 vs. 502.5 cells/mm³, p = 0.09, Mann-Whitney test). The proportion of regulatory T cells was increased in HTLV-1 positive subjects co-infected with strongyloidiasis compared to patients with only strongyloidiasis or asymptomatic HTLV-1 carriers (median = 17.9% vs. 4.3% vs. 5.9 p<0.05, One-way ANOVA). Strongyloides antigen-specific IL-5 responses were reduced in strongyloidiasis/HTLV-1 co-infected patients (5.0 vs. 187.5 pg/ml, p = 0.03, Mann-Whitney test). Reduced IL-5 responses and eosinophil counts were inversely correlated to the number of CD4+CD25+FoxP3+ cells.

Conclusions

Regulatory T cell counts are increased in patients with HTLV-1 and Strongyloides stercoralis co-infection and correlate with both low circulating eosinophil counts and reduced antigen-driven IL-5 production. These findings suggest a role for regulatory T cells in susceptibility to Strongyloides hyperinfection.     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.     

Valid and reliable instruments for arm-hand assessment at ICF activity level in persons with hemiplegia: a systematic review

Background

Loss of arm-hand performance due to a hemiparesis as a result of stroke or cerebral palsy (CP), leads to large problems in daily life of these patients. Assessment of arm-hand performance is important in both clinical practice and research. To gain more insight in e.g. effectiveness of common therapies for different patient populations with similar clinical characteristics, consensus regarding the choice and use of outcome measures is paramount. To guide this choice, an overview of available instruments is necessary. The aim of this systematic review is to identify, evaluate and categorize instruments, reported to be valid and reliable, assessing arm-hand performance at the ICF activity level in patients with stroke or cerebral palsy.

Methods

A systematic literature search was performed to identify articles containing instruments assessing arm-hand skilled performance in patients with stroke or cerebral palsy. Instruments were identified and divided into the categories capacity, perceived performance and actual performance. A second search was performed to obtain information on their content and psychometrics.

Results

Regarding capacity, perceived performance and actual performance, 18, 9 and 3 instruments were included respectively. Only 3 of all included instruments were used and tested in both patient populations. The content of the instruments differed widely regarding the ICF levels measured, assessment of the amount of use versus the quality of use, the inclusion of unimanual and/or bimanual tasks and the inclusion of basic and/or extended tasks.

Conclusions

Although many instruments assess capacity and perceived performance, a dearth exists of instruments assessing actual performance. In addition, instruments appropriate for more than one patient population are sparse. For actual performance, new instruments have to be developed, with specific focus on the usability in different patient populations and the assessment of quality of use as well as amount of use. Also, consensus about the choice and use of instruments within and across populations is needed.     

E2→E1 transition and Rb(+) release induced by Na(+) in the Na(+)/K(+)-ATPase. Vanadate as a tool to investigate the interaction between Rb(+) and E2

This work presents a detailed kinetic study that shows the coupling between the E2→E1 transition and Rb(+) deocclusion stimulated by Na(+) in pig-kidney purified Na,K-ATPase. Using rapid mixing techniques, we measured in parallel experiments the decrease in concentration of occluded Rb(+) and the increase in eosin fluorescence (the formation of E1) as a function of time. The E2→E1 transition and Rb(+) deocclusion are described by the sum of two exponential functions with equal amplitudes, whose rate coefficients decreased with increasing [Rb(+)]. The rate coefficient values of the E2→E1 transition were very similar to those of Rb(+)-deocclusion, indicating that both processes are simultaneous. Our results suggest that, when ATP is absent, the mechanism of Na(+)-stimulated Rb(+) deocclusion would require the release of at least one Rb(+) ion through the extracellular access prior to the E2→E1 transition. Using vanadate to stabilize E2, we measured occluded Rb(+) in equilibrium conditions. Results show that, while Mg(2+) decreases the affinity for Rb(+), addition of vanadate offsets this effect, increasing the affinity for Rb(+). In transient experiments, we investigated the exchange of Rb(+) between the E2-vanadate complex and the medium. Results show that, in the absence of ATP, vanadate prevents the E2→E1 transition caused by Na(+) without significantly affecting the rate of Rb(+) deocclusion. On the other hand, we found the first evidence of a very low rate of Rb(+) occlusion in the enzyme-vanadate complex, suggesting that this complex would require a change to an open conformation in order to bind and occlude Rb(+).