More on Nei and Roychoudhury''s Sampling Variances of Heterozygosity and Genetic Distance

The inequality relationship between the expected values of ( j_x-g)² and (ĝ-g) ², where j_x is a biased and ĝ is an unbiased estimate of population homozygosity g, were examined earlier by Nei and Roychoudhury (1974) and later by Mitra (1975). The improvement in the inequality still left much to be desired. In this paper a lower boundary of g has been obtained which may be regarded as ultimate for ensuring a smaller expected value of ( j_x-g)² than the corresponding value of ( ĝ-g)².     

On washout in nonlinear compartmental systems

Let x(t) be a solution of a compartmental system. If, for some compartment j, x_j(t)→0 as t→∞, then we say that the compartment j washes out. We show that a compartment washes out if it always reaches (along a fixed path) either the environment or another compartment for which there is no return path. Additional criteria, particularly regarding exponential convergence, are also presented. Examples are drawn from tracer kinetics, enzyme reactions, and epidemic models.     

On Nei and Roychoudhury''s Sampling Variances of Heterozygosity and Genetic Distance

Nei and Roychoudhury have developed an inequality relationship between the expected values of (j_x- g)² and (ĝ-g)² where j_x is a biased and ĝ is an unbiased estimate of population homozygosity g. Their inequality is somewhat weak and can be improved, as is demonstrated in this paper.     

Sites of the 5s Ribosomal Genes in Drosophila. I. the Multiple Clusters in the VIRILIS Group

Drosophila melanogaster ¹²⁵I-5S RNA was annealed to salivary gland preparations of 6 species in the virilis group of Drosophila. Two patterns of annealing were found. D. virilis, D. montana and D. borealis showed three 5S gene clusters on chromosome 5; S_d–f and W_c–j were strongly labeled, but X_a–e was weakly labeled. D. montana and D. borealis have a greater percentage of their total 5S cistrons at S _d–f than does D. virilis. D. americana americana, D. americana texana and D. novamexicana showed 2 sites labeled; no label was seen at S_d–f while W_c–j was weakly labeled and X_a–e was strongly labeled, the reciprocal of the previous pattern in the W-X region. Hybrids between D. a. americana and D. virilis showed no difference in chromosome banding at the sites of the 5S clusters despite their pattern differences. D. a texana x D. virilis, on the other hand, did show a difference in staining the X_a–e region. These patterns fall squarely into the biosystematic groupings deduced by many previous workers.     

Epiphytic lichens as biomonitors of airborne heavy metal pollution

The research aims to assess the performance of the lichen Parmotrema reticulatum as an air pollution biomonitor of four heavy metals, namely, chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn). Four contrasting land use sites within the greater Auckland region of New Zealand are used. One site is located within the relatively clean air shed of conservation land, the others within residential, commercial, and industrial areas, characterised by increasingly polluted air sheds, respectively. Three groups of lichens are monitored over a two-year period using active and passive biomonitoring methods to assess ‘on-thallus’ and ‘in-thallus’ concentrations of heavy metals. Seasonal transplants are used to quantify heavy metals accumulated by the lichen during each season. Long-term transplants are used to measure how fast lichens accumulate heavy metals and to better understand how and when heavy metals within the lichen thallus achieve equilibrium with air pollutant concentrations over time. The results show that the lichens continuously accumulates pollutants from the air until equilibrium is reached, thus transplanted lichens are useful for monitoring air pollution concentrations over time. Since pollutant concentration in the transplanted lichen at equilibrium stabilises, at this point the lichen ceases to be useful for monitoring temporal trends in air pollution, but may useful for spatial air pollution monitoring. The industrial location has the highest total accumulation for all four heavy metals, followed by the commercial and residential locations, respectively. Overall, the results show that the lichen P. reticulatum may be successfully used to monitor spatial and temporal pollution patterns caused by even very low concentrations of Cr, Cu, Pb and Zn.     

Risk Assessment for a Flood Control Engineering System Using Fuzzy Theory: A Case in China

Flood control engineering system risk assessment entails fuzziness. An assessment model is developed, based on the improved fuzzy comprehensive assessment method that developed a new index (S_fin ) to judge the assessment class. The model is used to assess the flood control engineering risk of a case in China. The results show that the proposed model in the present article can rationally determine the risk status of a flood control engineering system, and has higher resolution compared to the two conventional methods, fuzzy comprehensive assessment and matter-element model method. The proposed model is flexible and adaptable for determining flood control engineering system risk status.     

The role of amino terminus of mouse Cx50 in determining transjunctional voltage-dependent gating and unitary conductance

Amino-terminus and carboxyl-terminus of connexins have been proposed to be responsible for the transjunctional voltage-dependent gating (V_j-gating) and the unitary gap junction channel conductance (γ_j). To better understand the molecular structure(s) determining the V_j-gating properties and the γ_j of Cx50, we have replaced part of the amino-terminus of mCx50 by the corresponding domain of mCx36 to engineer a chimera Cx50-Cx36N, and attached GFP at the carboxyl-terminus of mCx50 to construct Cx50-GFP. The dual whole-cell patch-clamp technique was used to test the resulting gap junction channel properties in N2A cells. The Cx50-Cx36N gap junction channel lowered the sensitivity of steady-state junctional conductance to V_j (G_j/V_j relationship), slowed V_j-gating kinetics, and reduced γ_j as compared to Cx50 channel. Cx50-GFP gap junction channel showed similar V_j-gating properties and γ_j to Cx50 channel. We further characterized a mutation, Cx50N9R, where the Asn (N) at the ninth position of Cx50 was replaced by the corresponding Arg (R) at Cx36. The G_j/V_j relationship of Cx50N9R channel was significantly changed; most strikingly, the macroscopic residual conductance (G_min) was near zero. Moreover, the single Cx50N9R channel only displayed one open state (γ_j = 132 ± 4 pS), and no substate could be detected. Our data suggest that the NT of Cx50 is critical for both the V_j-gating and the γ_j, and the introduction of a positively charged Arg at the ninth position reduced the G_min with a correlated disappearance of the substate at the single channel level.     

Coordination of poly(1-vinylimidazole) by Hemin

It is shown that when hemin (Fe) coordinates imidazole groups (L) attached to a polymer such as poly(1-vinylimidazole) (PVI), then the experimentally observed equilibrium will correspond to the apparent equilibrium constant K_x = [FeL_x]/[Fe][L] and the plot of log ([FeL_x]/[Fe]) against log [L] will give a slope (n) of unity both when x = 1 and, provided both imidazole groups are attached to the same polymer molecule, when x = 2. In agreement with this, hemin reacts with PVI in dimethylsulfoxide at 25°C to give a single product that has a spectrum identical to that of the bisimidazole adduct and the equilibrium corresponds to n = 1.     

A Stochastic Four-State Model of Contingent Gating of Gap Junction Channels Containing Two “Fast” Gates Sensitive to Transjunctional Voltage

Connexins, a family of membrane proteins, form gap junction (GJ) channels that provide a direct pathway for electrical and metabolic signaling between cells. We developed a stochastic four-state model describing gating properties of homotypic and heterotypic GJ channels each composed of two hemichannels (connexons). GJ channel contain two “fast” gates (one per hemichannel) oriented opposite in respect to applied transjunctional voltage (V_j). The model uses a formal scheme of peace-linear aggregate and accounts for voltage distribution inside the pore of the channel depending on the state, unitary conductances and gating properties of each hemichannel. We assume that each hemichannel can be in the open state with conductance γ_h,o and in the residual state with conductance γ_h,res, and that both γ_h,o and γ_h,res rectifies. Gates can exhibit the same or different gating polarities. Gating of each hemichannel is determined by the fraction of V_j that falls across the hemichannel, and takes into account contingent gating when gating of one hemichannel depends on the state of apposed hemichannel. At the single-channel level, the model revealed the relationship between unitary conductances of hemichannels and GJ channels and how this relationship is affected by γ_h,o and γ_h,res rectification. Simulation of junctions containing up to several thousands of homotypic or heterotypic GJs has been used to reproduce experimentally measured macroscopic junctional current and V_j-dependent gating of GJs formed from different connexin isoforms. V_j-gating was simulated by imitating several frequently used experimental protocols: 1), consecutive V_j steps rising in amplitude, 2), slowly rising V_j ramps, and 3), series of V_j steps of high frequency. The model was used to predict V_j-gating of heterotypic GJs from characteristics of corresponding homotypic channels. The model allowed us to identify the parameters of V_j-gates under which small changes in the difference of holding potentials between cells forming heterotypic junctions effectively modulates cell-to-cell signaling from bidirectional to unidirectional. The proposed model can also be used to simulate gating properties of unapposed hemichannels.     

Atrial fibrillation-associated Connexin40 mutants make hemichannels and synergistically form gap junction channels with novel properties

Mutations of Cx40 (GJA5) have been identified in people with lone chronic atrial fibrillation including G38D and M163V which were found in the same patient. We used dual whole cell patch clamp procedures to examine the transjunctional voltage (V_j) gating and channel conductance properties of these two rare mutants. Each mutant exhibited slight alterations of V_j gating properties and increased the gap junction channel conductance (γ_j) by 20–30 pS. While co-expression of the two mutations had similar effects on V_j gating, it synergistically increased γ_j by 50%. Unlike WTCx40 or M163V, G38D induced activity of a dominant 271 pS hemichannel.     

Preparation and structure of [Ru2(O2CMe)4]2[Fe(CN)5NO] and magnetically ordered Hx[Ru2(O2CMe)4]3−x[Cr(CN)5NO] possessing interpenetrating lattices

Reaction of [Ru₂(O₂CMe)₄]Cl with K₃[Cr(CN)₅NO] in water forms H_x[Ru^II/III₂(O₂CMe)₄]_3−x-[Cr(CN)₅NO]·zH₂O (x = 0.2) that magnetically orders at 4.0 K and possesses an interpenetrating body centered cubic [a = 13.2509(2) Å] structure with random locations of the bridging nitrosyl ligands, and x/3 vacant cation sites. Similarly, the aqueous reaction of [Ru₂(O₂CMe)₄]Cl with Na₂[Fe(CN)₅NO] forms paramagnetic [Ru₂(O₂CMe)₄]₂[Fe(CN)₅NO]·H₂O, which has a similar tetragonal interpenetrating structure [a = 13.0186(1) Å, c = 13.0699(2) Å] where the NO ligands are presumably nonbridging and 1/3 of the expected cation sites are unoccupied. The presence of uncoordinated NO sites in addition to missing neighboring [Ru₂(O₂CMe)₄]⁺ units, results in significant vacancies (or holes) in the lattice.     

Improved coordinate reconstruction from stereo diagrams

A program has been written that reconstructs three-dimensional coordinates for a protein structure given a stereo C_α diagram. Initial three-dimensional coordinates are determined using an algorithm similar to the one used by Rossmann in the program STEREO. Thereafter the coordinates are refined such that the stereo image based on the reconstructed three-dimensional coordinates optimally fits the scanned stereo image while normal C_α stereochemistry is enforced.     

Genetic Mapping of Genes Required for Motility in CAULOBACTER CRESCENTUS

Mutations in more than 30 genes affect motility in Caulobacter crescentus. We have determined the chromosomal map locations for 27 genes involved in flagellar morphogenesis (fla), three genes involved in flagellar function (mot), and three genes that have a pleiotropic effect on both motility and bacteriophage resistance (ple). Three multigene clusters have been detected at widely separated chromosomal locations, but in addition, there are 12 fla and mot genes that are found at eight additional sites scattered around the C. cresentus chromosome. Thus, there is more scatter of genes involved in flagellar structure and function than has been observed in other bacterial systems.     

Genetic hazards of ionizing radiations: cytogenetic extrapolations from mouse to man

The frequencies of X-ray induced asymmetrical interchanges (dicentrics) and acentric fragments (deletions) at several doses were measured in the circullating leukocytes of six species. The leukocytes of the species used had similar DNA contents but different chromosome and chromosome arm numbers. The data for dicentrics were fitted separately for each species by regression analysis to the model Y_j = b_jD + c_jD². All species gave a good fit to this model. As expected, when the dicentric data for all species were pooled and fitted to this model a poor fit was obtained. However, if a term for arm number was included, so that the model Y_j = (N_j?1) (bD+cD²) was fitted, a significant amount of the variation among species could be accounted for. At each dose there was an approximately linear relationship between the yield of dicentrics and the arm number. Man, with an effective arm number of 81, had twice as many dicentrics as the mouse, with an effective arm number of. These results strongly suggest that the chromosome arm number of a species influences the yield of asymmetrica interchanges. The chromosome arm number did not appear to influence the yield of deletions, and the yields induced in the mouse and man at easch dose were equal.These results show that man is twice as sensitive as the mouse to the induction of translocations, whereas the two species are equally sensitive to the indcution of deletions and, in all probability, to the production of mutations.     

Leg stiffness and joint stiffness while running to and jumping over an obstacle

During running, muscles of the lower limb act like a linear spring bouncing on the ground. When approaching an obstacle, the overall stiffness of this leg-spring system (k_leg) is modified during the two steps preceding the jump to enhance the movement of the center of mass of the body while leaping the obstacle. The aim of the present study is to understand how k_leg is modified during the running steps preceding the jump. Since k_leg depends on the joint torsional stiffness and on the leg geometry, we analyzed the changes in these two parameters in eight subjects approaching and leaping a 0.65 m-high barrier at 15 km h⁻¹. Ground reaction force (F) was measured during 5–6 steps preceding the obstacle using force platform and the lower limb movements were recorded by camera. From these data, the net muscular moment (M_j), the angular displacement (θ_j) and the lever arm of F were evaluated at the hip, knee and ankle. At the level of the hip, the M_j–θ_j relation shows that muscles are not acting like torsional springs. At the level of the knee and ankle, the M_j–θ_j relation shows that muscles are acting like torsional springs: as compared to steady-state running, the torsional stiffness k_j decreases from ~1/3 two contacts before the obstacle, and increases from ~2/3 during the last contact. These modifications in k_j reflect in changes in the magnitude of F but also to changes in the leg geometry, i.e. in the lever arms of F.     

Sequence determinants for the tandem recognition of UGU and CUG rich RNA elements by the two N--terminal RRMs of CELF1

CUGBP, Elav-like family member 1 (CELF1) is an RNA binding protein with important roles in the regulation of splicing, mRNA decay and translation. CELF1 contains three RNA recognition motifs (RRMs). We used gel retardation, gel filtration, isothermal titration calorimetry and NMR titration studies to investigate the recognition of RNA by the first two RRMs of CELF1. NMR shows that RRM1 is promiscuous in binding to both UGU and CUG repeat sequences with comparable chemical shift perturbations. In contrast, RRM2 shows greater selectivity for UGUU rather than CUG motifs. A construct (T187) containing both binding domains (RRM1 and RRM2) was systematically studied for interaction with tandem UGU RNA binding sites with different length linker sequences UGU(U)_xUGU where x = 1–7. A single U spacer results in interactions only with RRM1, demonstrating both steric constraints in accommodating both RRMs simultaneously at adjacent sites, and also subtle differences in binding affinities between RRMs. However, high affinity co-operative binding (K_d ~ 0.4 µM) is evident for RNA sequences with x = 2–4, but longer spacers (x ≥ 5) lead to a 10-fold reduction in affinity. Our analysis rationalizes the high affinity interaction of T187 with the 11mer GRE consensus regulatory sequence UGUUUGUUUGU and has significant consequences for the prediction of CELF1 binding sites.     

Health Risk Map of a Petrochemical Complex through GIS-Fuzzy Integration of Air Pollution Monitoring Data

From the mid-1990s, a network of surveillance and prevention of atmospheric contamination has been running to control the levels of airborne pollution in urban and industrial (petrochemical) areas of Tarragona (Catalonia, Spain). Airborne concentrations of SO₂, NO₂, O₃, H₂S, and CO, as well as PM_10, are routinely analyzed and used to establish the air quality. However, only single substances, rather than the global incidence of all contaminants as a whole, are taken into account. Moreover, specific data from the population are not considered. In the present study, a modified version of a previously developed fuzzy-based risk evaluation technique was developed. The method was fed with real monitoring data, instead of theoretical results from modeling. Hazard (air levels) and Exposure parameters (location sensitivity and population density) were used to create fuzzy sets and, subsequently, to generate a risk map. This tool was subsequently applied to the case-study of the petrochemical area of Tarragona by means of generating risk maps. The combination of geographic information system (GIS) and fuzzy logic tools proved to be successful as a help for stakeholders involved in the decision-making process.     

Reaction of a bulky phosphite with [Ru3(CO)12]: The molecular structure of one of the decomposition products

Mono- and bis-substituted phosphite complexes [Ru₃(CO)_12−x L_x] (L = tris(2,4-di-tert-butylphenyl) phosphite; x = 1, 2) were synthesized by simple substitution reactions, and were characterized by spectroscopic methods. The monosubstituted ruthenium complex disproportionates in acetone producing a mononuclear ruthenium complex as one of the decomposition products. Single crystal X-ray diffraction analysis established the molecular structure of this new compound.     

Contributions of different mosquito species to the transmission of lymphatic filariasis in central Nigeria: implications for monitoring infection by PCR in mosquito pools

Background

Monitoring and evaluation are essential to the successful implementation of mass drug administration programmes for LF elimination. Monitoring transmission when it is low requires both large numbers of mosquito vectors and sensitive methods for detecting Wuchereria bancrofti infections in them. PCR-based methods are preferred over classical dissections but the best protocol so far achieved detection of one L₃ Wuchereria bancrofti larva in a pool of 35–50 Anopheles mosquitoes. It also lacks consistency and remains still a costly tool. Hence we decided to improve upon this to achieve detection in a pool of 100 or more by enhancing the quality of the template DNA. Prior to this we also evaluated three vector sampling methods in the context of numbers for monitoring.

Methods

Human landing, pyrethrium spray and light traps catches were conducted concurrently at sites in an LF endemic district in Ghana and the numbers obtained compared. Two DNA extraction methods; Bender buffer and phenol/chloroform purification, and DNAeasy Tissue kit (Quaigen Inc) were used on pools of 25, 50, 75 100 and 150 mosquitoes each seeded with one L₃ or its quivalent amount of DNA. Then another set of extracted DNA by the two methods was subjected to Dynal bead purification method (using capture oligonucleotide primers). These were used as template DNA in PCR to amplify W. bancrofti sequences. The best PCR result was then evaluated in the field at five sites by comparing its results (infections per 1000 mosquitoes) with that of dissection of roughly equal samples sizes.

Results

The largest numbers of mosquitoes were obtained with the human landing catches at all the sites sampled. Although PCR detection of one L₃ in pools of 25, 50 and 75 mosquitoes was consistent irrespective of the extraction method, that of one L₃ in 100 was only achieved with the kit-extracted DNA/Dynal bead purification method. Infections were found at only two sites by both dissection and pool-screening being 14.3 and 19 versus 13.4 and 20.1 per 1000 Anopheles mosquitoes respectively, which were not statistically significant

Discussion and conclusion

HLC still remains the best option for sampling for the large numbers of mosquitoes required for monitoring transmission during MDA programmes, when vector population densities are high and classical indices of transmission are required. One – in – 100 detection is an improvement on previous PCR pool-screening methods, which in our opinion was a result of the introduction of the extra step of parasite DNA capture using Dynal/beads. As pool sizes increase the insects DNA will swamp parasite DNA making the latter less available for an efficient PCR, therefore we propose either additional steps of parasite DNA capture or real-time PCR to improve further the pool screening method. The study also attests also to the applicability of Katholi et al's algorithm developed for determining onchocerciasis prevalence in LF studies.