Clinical and Epidemiological Features of Typhoid Fever in Pemba,Zanzibar: Assessment of the Performance of the WHO Case Definitions

Background

The gold standard for diagnosis of typhoid fever is blood culture (BC). Because blood culture is often not available in impoverished settings it would be helpful to have alternative diagnostic approaches. We therefore investigated the usefulness of clinical signs, WHO case definition and Widal test for the diagnosis of typhoid fever.

Methodology/Principal Findings

Participants with a body temperature ≥37.5°C or a history of fever were enrolled over 17 to 22 months in three hospitals on Pemba Island, Tanzania. Clinical signs and symptoms of participants upon presentation as well as blood and serum for BC and Widal testing were collected. Clinical signs and symptoms of typhoid fever cases were compared to other cases of invasive bacterial diseases and BC negative participants. The relationship of typhoid fever cases with rainfall, temperature, and religious festivals was explored. The performance of the WHO case definitions for suspected and probable typhoid fever and a local cut off titre for the Widal test was assessed. 79 of 2209 participants had invasive bacterial disease. 46 isolates were identified as typhoid fever. Apart from a longer duration of fever prior to admission clinical signs and symptoms were not significantly different among patients with typhoid fever than from other febrile patients. We did not detect any significant seasonal patterns nor correlation with rainfall or festivals. The sensitivity and specificity of the WHO case definition for suspected and probable typhoid fever were 82.6% and 41.3% and 36.3 and 99.7% respectively. Sensitivity and specificity of the Widal test was 47.8% and 99.4 both forfor O-agglutinin and H- agglutinin at a cut-off titre of 1∶80.

Conclusions/Significance

Typhoid fever prevalence rates on Pemba are high and its clinical signs and symptoms are non-specific. The sensitivity of the Widal test is low and the WHO case definition performed better than the Widal test.     

IgG responses to Anopheles gambiae salivary antigen gSG6 detect variation in exposure to malaria vectors and disease risk

Assessment of exposure to malaria vectors is important to our understanding of spatial and temporal variations in disease transmission and facilitates the targeting and evaluation of control efforts. Recently, an immunogenic Anopheles gambiae salivary protein (gSG6) was identified and proposed as the basis of an immuno-assay determining exposure to Afrotropical malaria vectors. In the present study, IgG responses to gSG6 and 6 malaria antigens (CSP, AMA-1, MSP-1, MSP-3, GLURP R1, and GLURP R2) were compared to Anopheles exposure and malaria incidence in a cohort of children from Korogwe district, Tanzania, an area of moderate and heterogeneous malaria transmission. Anti-gSG6 responses above the threshold for seropositivity were detected in 15% (96/636) of the children, and were positively associated with geographical variations in Anopheles exposure (OR 1.25, CI 1.01-1.54, p?=?0.04). Additionally, IgG responses to gSG6 in individual children showed a strong positive association with household level mosquito exposure. IgG levels for all antigens except AMA-1 were associated with the frequency of malaria episodes following sampling. gSG6 seropositivity was strongly positively associated with subsequent malaria incidence (test for trend p?=?0.004), comparable to malaria antigens MSP-1 and GLURP R2. Our results show that the gSG6 assay is sensitive to micro-epidemiological variations in exposure to Anopheles mosquitoes, and provides a correlate of malaria risk that is unrelated to immune protection. While the technique requires further evaluation in a range of malaria endemic settings, our findings suggest that the gSG6 assay may have a role in the evaluation and planning of targeted and preventative anti-malaria interventions.     

New insights into the fundamental role of topological constraints as a determinant of two-way junction conformation

Recent studies have shown that topological constraints encoded at the RNA secondary structure level involving basic steric and stereochemical forces can significantly restrict the orientations sampled by helices across two-way RNA junctions. Here, we formulate these topological constraints in greater quantitative detail and use this topological framework to rationalize long-standing but poorly understood observations regarding the basic behavior of RNA two-way junctions. Notably, we show that the asymmetric nature of the A-form helix and the finite length of a bulge provide a physical basis for the experimentally observed directionality and bulge-length amplitude dependence of bulge induced inter-helical bends. We also find that the topologically allowed space can be modulated by variations in sequence, particularly with the addition of non-canonical GU base pairs at the junction, and, surprisingly, by the length of the 5' and 3' helices. A survey of two-way RNA junctions in the protein data bank confirms that junction residues have a strong preference to adopt looped-in, non-canonically base-paired conformations, providing a route for extending our bulge-directed framework to internal loop motifs and implying a simplified link between secondary and tertiary structure. Finally, our results uncover a new simple mechanism for coupling junction-induced topological constraints with tertiary interactions.     

Unraveling the structural complexity in a single-stranded RNA tail: implications for efficient ligand binding in the prequeuosine riboswitch

Single-stranded RNAs (ssRNAs) are ubiquitous RNA elements that serve diverse functional roles. Much of our understanding of ssRNA conformational behavior is limited to structures in which ssRNA directly engages in tertiary interactions or is recognized by proteins. Little is known about the structural and dynamic behavior of free ssRNAs at atomic resolution. Here, we report the collaborative application of nuclear magnetic resonance (NMR) and replica exchange molecular dynamics (REMD) simulations to characterize the 12 nt ssRNA tail derived from the prequeuosine riboswitch. NMR carbon spin relaxation data and residual dipolar coupling measurements reveal a flexible yet stacked core adopting an A-form-like conformation, with the level of order decreasing toward the terminal ends. An A-to-C mutation within the polyadenine tract alters the observed dynamics consistent with the introduction of a dynamic kink. Pre-ordering of the tail may increase the efficacy of ligand binding above that achieved by a random-coil ssRNA. The REMD simulations recapitulate important trends in the NMR data, but suggest more internal motions than inferred from the NMR analysis. Our study unmasks a previously unappreciated level of complexity in ssRNA, which we believe will also serve as an excellent model system for testing and developing computational force fields.     

原代培养过程中壳聚糖衍生物对CTCF/YB-1/C-myc和p53蛋白表达的影响

成功建立了人增生性瘢痕细胞和正常皮肤成纤维细胞的原代培养, 并利用热休克蛋白(HSP47)和成纤维细胞特异蛋白(FSP)标记物进行了鉴定。研究发现, 经过壳聚糖衍生物处理, 人增生性瘢痕成纤维细胞和正常皮肤成纤维细胞在培养中均出现了不同类型的蛋白表达。多功能转录因子蛋白(CTCF)在壳聚糖衍生物处理的增生性瘢痕成纤维细胞中出现表达上调; 在聚糖衍生物处理的正常皮肤成纤维细胞中数量无变化。YB-1结合蛋白在经壳聚糖处理的正常皮肤成纤维细胞与人增生性瘢痕细胞中的表达几乎无异, 但在未经壳聚糖处理的细胞中表达不同。C-MYC和P53蛋白在壳聚糖衍生物处理的增生性瘢痕纤维细胞中表达上调, 但在正常皮肤成纤维细胞中, 无论是否经过壳聚糖衍生物处理, 这两种蛋白都没有表达。上述4种蛋白在人增生性瘢痕细胞和正常皮肤成纤维细胞中表现出不同的表达方式, 这种新型壳聚糖衍生物可能在控制人增生性瘢痕细胞和正常皮肤成纤维细胞生长和增殖过程中起着重要作用。这些蛋白因子的表达机制目前还不是完全清楚, 有待于进一步研究。     

Calcium and Magnesium ATPase Activities in Women with Varying BMIs

Objective: Intracellular calcium (Ca) is increased in obese humans, and magnesium (Mg)‐ATPase activity is increased in monosodium glutamate‐induced obese rats. The aims of this study were to test the hypotheses that Ca‐ATPase activity is negatively correlated with BMI, and that Mg‐ATPase activity is positively correlated with BMI and Ca‐ATPase activity in obese women. Research Methods and Procedures: Thirty healthy adult women, with BMIs of 20 to 40, donated a single sample of whole blood and were interviewed as to medical history and family history of obesity. Erythrocyte membranes were isolated and assayed for Ca‐ATPase and Mg‐ATPase. Weight and height were self‐reported. Regression analysis was used to determine relationship between BMI and enzyme activity. Family history of obesity served as a covariant. Results: Ca‐ATPase was negatively correlated with increasing BMI (r = ? 0.38, p = 0.02). The relationship between BMI and Ca‐ATPase remained valid after controlling for family history of obesity (r = ?0.36, p = 0.03). There was a positive correlation between Mg‐ATPase activity and Ca‐ATPase (r = 0.42, p = 0.024), and this relationship remained valid after controlling for BMI and family history of obesity (r = 0.41, p = 0.03). Discussion: Ca‐ATPase activity decreases as BMI increases. Decreased ATPase activity may contribute to increased intracellular calcium, previously reported in obese persons. Further studies are needed to determine whether a drop in Ca‐ATPase activity can serve as a marker for the development of obesity.     

Porphyromonas gingivalis regulates the RANKL-OPG system in bone marrow stromal cells

Porphyromonas gingivalis is a Gram-negative anaerobe implicated in chronic periodontitis, a bacterial-induced inflammatory condition that causes destruction of the periodontal connective tissues and underlying alveolar bone. The receptor activator of nuclear factor-kappaB ligand (RANKL) is a cytokine that directly stimulates osteoclastogenesis and bone resorption, whereas its decoy receptor osteoprotegerin (OPG) blocks this action. This study aimed to investigate the effects of P. gingivalis culture supernatants on RANKL and OPG expression in W20-17 bone marrow stromal cells, and evaluate the involvement of its virulence factors, particularly gingipains and lipopolysaccharide. P. gingivalis up-regulated RANKL and down-regulated OPG mRNA expression and protein production. These effects were blocked by indomethacin, suggesting mediation by prostaglandins. Furthermore, P gingivalis induced the production of prostaglandin E(2). Heat-inactivation, or chemical inhibition of P. gingivalis gingipains did not affect RANKL and OPG regulation. However, lipopolysaccharide depletion by polymyxin B abolished RANKL induction, and partly rescued the suppression of OPG. In conclusion, P. gingivalis regulates the RANKL-OPG system via prostaglandin E(2) in bone marrow stromal cells, in a manner that favours osteoclastogenesis. A non-proteolytic and non-proteinaceous P. gingivalis component is involved in these events, most probably its lipopolysaccharide. This activity may contribute to the bone loss characteristic of periodontitis.     

Venom induces alarm behaviour in the social wasp Polybioides raphigastra (Hymenoptera: Vespidae): an investigation of alarm behaviour, venom volatiles and sting autotomy

Chemicals from the venom gland elicited alarm behaviour and attack in the Asian polistine wasp Polybioides raphigastra. When presented with crushed venom glands workers of this wasp respond with a mass stinging attack. Gas chromatography–mass spectrometry analyses show that the major volatiles in the venom gland are alkanes, monounsaturated alkenes and 2-alcohols. Several pyrazines, a spiroacetal and aromatics were also identified as trace compounds. The anatomy and morphology of the sting apparatus are reported, and we describe sting autotomy in this wasp. This is the first such report for the Ropalidiinae. The structures responsible for autotomy are likely to be large barbs present on the sting lancets, and a conspicuous tooth present on the medial side of the left lancet. Sting autotomy in P. raphigastra probably plays an important role in the localization of sites of attack by wasps defending the nest.     

Topological constraints are major determinants of tRNA tertiary structure and dynamics and provide basis for tertiary folding cooperativity

Recent studies have shown that basic steric and connectivity constraints encoded at the secondary structure level are key determinants of 3D structure and dynamics in simple two-way RNA junctions. However, the role of these topological constraints in higher order RNA junctions remains poorly understood. Here, we use a specialized coarse-grained molecular dynamics model to directly probe the thermodynamic contributions of topological constraints in defining the 3D architecture and dynamics of transfer RNA (tRNA). Topological constraints alone restrict tRNA''s allowed conformational space by over an order of magnitude and strongly discriminate against formation of non-native tertiary contacts, providing a sequence independent source of folding specificity. Topological constraints also give rise to long-range correlations between the relative orientation of tRNA''s helices, which in turn provides a mechanism for encoding thermodynamic cooperativity between distinct tertiary interactions. These aspects of topological constraints make it such that only several tertiary interactions are needed to confine tRNA to its native global structure and specify functionally important 3D dynamics. We further show that topological constraints are conserved across tRNA''s different naturally occurring secondary structures. Taken together, our results emphasize the central role of secondary-structure-encoded topological constraints in defining RNA 3D structure, dynamics and folding.     

Studies on Gracilaria changii (Gracilariales,Rhodophyta) from Malaysian mangroves

Gracilaria changii, recorded from Malaysia and Thailand, is one of the more abundant agarophytic seaweeds found in Malaysia. A wild population of Gracilaria changii growing in mangroves was monitored for seasonal variation in agar content and gel strength as well as spore production. Agar yield and gel strength ranged from 12 to 25% dry weight and 294 to 563 g cm^–2, respectively, over a 15-month period. Gel strength but not yield was positively correlated with amount of rainfall. Cystocarps were observed throughout the study, but use of sporetraps showed that spore release peaked around July–August and January–February after the two monsoon periods.Mariculture of Gracilaria changii in shallow ponds in the mangroves, in an irrrigation canal and in a shrimp farm pond was conducted. Average growth rate of cuttings tied to monofilament lines was 3.3 ± 1.7% d^–1, 8.4 ± 1.8% d^–1 and 3.6 ± 1.6% d^–1 respectively. Cuttings were lost to siltation, wave action, predation and heavy epiphytisation.These studies show that Gracilaria changii has potential commercial application in the agar industry.