New Karyological and Morphometric Data on Poorly Known Bufo surdus and Bufo luristanicus in Comparison with Data of Diploid Green Toads of the Bufo viridis Complex from South of Iran

Previous studies on the Bufo viridis complex, which is distributed broadly across Iran, are incomplete and restricted to a few regions or a few samples. In this paper a new detailed study on the B. viridis complex in southern of Iran （from West to East） is presented. The analysis of 18 morphometric characters with univariate and multivariate methods reveals significant differences between three members of the B. viridis complex namely B. variabilis, B. luristanicus, and B. surdus distributed in southern part of Iran. Our result help to resolve an old taxonomic problem about B. surdus subgroup （taxa closely related to B. surdus） confirming that B. luristanicus and B. surdus are distinct species. Moreover, for the first time we report and describe karyotype details of B. luristanicus and B. surdus which confirmed that they are diploid. Karyological studies demonstrate that all toads from three mentioned species have 2n = 22 chromosomes. These chromosomes are arranged into two groups. First group has six large chromosomes and the second group is composed of five small chromosomes. These chromosomes are metacentric or submetacentric. The number of submetacentric chromosomes is different in three mentioned species of B. viridis complex. Neither sexual heteromorphism, nor secondary constriction was observed in any pairs of chromosomes.     

Immunofluorescent labeling of CD20 tumor marker with quantum dots for rapid and quantitative detection of diffuse large B-cell non-Hodgkin's lymphoma

Fluorescent semiconductor quantum dots (QDs) are newfound nanocrystal probes which have been used in bioimaging filed in recent years. The purpose of this study is to evaluate the diagnostic value of specific QDs coupled to rituximab monoclonal antibody against CD20 tumor markers for patients with diffuse large B-cell lymphoma (DLBCL). In current study rituximab-conjugated quantum dots (QDs-rituximab) were prepared against CD20 tumor markers for detection of CD20-positive cells (human Raji cell line) using flowcytometry. A total of 27 tumor tissue samples were collected from patients with DLBCL and 27 subjects with negative pathological tests as healthy ones, which stained by QD-rituximab. The detection signals were obtained from QDs using fluorescence microscopy. The flowcytometry results demonstrated a remarkable difference in fluorescent intensity and FL2-H + (CD20-positive cells percentage) between two groups. Both factors were significantly higher in Raji in comparison with K562 cell line (P < 0.05). Lot of green fluorescence signals was observed due to the selectively binding of QD-rituximab to CD20 tumor markers which overexpressed in tumor tissues and a few signals observed on the defined healthy ones. Based on these observations the cut-off point was 46.8 dots and the sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 89.5%, 91.3%, and 100%, respectively (LR+, 9.52; LR−, 0). The QD - rituximab could be beneficial as a bioimaging tool with high sensitivity to provide an accurate molecular imaging technique for identifying CD20 tumor markers for early diagnosis of the patients with DLBCL.     

Elucidating the molecular interaction of serum albumin with nizatidine and the role of β-cyclodextrin: multi-spectroscopic and computational approach

Abstract

Nizatidine is a histamine H2 receptor antagonist which act by inhibiting the production of stomach acid, thereby, finds its application in treating various diseases related to the gastrointestinal tract. Studying albumin–drug interaction is important for understanding the pharmacokinetics and pharmacodynamics of therapeutic candidates. In the present work, the interaction of nizatidine with BSA was investigated by employing multi-spectroscopic and computational studies. The formation of BSA–nizatidine complex was characterised by UV-visible and fluorescence based-spectroscopic studies. Steady-state fluorescence demonstrated the static mode of quenching of BSA by nizatidine. The interaction was spontaneous and nizatidine binds to BSA with a stoichiometry of 1:1. Forster resonance energy transfer calculations revealed that there was a high possibility of energy transfer between nizatidine and BSA. The resultant secondary structural change in BSA on the addition of nizatidine was studied by circular dichroism spectroscopy. Moreover, synchronous and three-dimensional fluorescence spectroscopy was used to determine the conformational changes occurred in the structure of albumin on the binding of nizatidine. Competitive-site marker experiments suggested that nizatidine binds in the Sudlow site II of BSA. Additionally, the effect of β-cyclodextrin as an inclusion compound on the interaction was studied. Furthermore, molecular modelling and simulation studies were performed to corroborate the results obtained above.

Communicated by Ramaswamy H. Sarma     

Evaluation of the performance of protein separation in figure-8 centrifugal counter-current chromatography

The performance of protein separation using the figure-8 column configuration in centrifugal counter-current chromatography was investigated under various flow rates and revolution speeds. The separation was performed with a two-phase solvent system composed of polyethylene glycol 1000/potassium phosphate each at 12.5% (w/w) in water and with lysozyme and myoglobin as test samples. In order to improve tracing of the elution curve, a hollow fiber membrane dialyzer was inserted at the inlet of the UV detector. The results showed that the retention of stationary phase (Sf) and resolution (Rs) increased with decreased flow rate and increased revolution speed. The highest Rs of approximately 1 was obtained at a flow rate of 0.01 mL/min under a revolution speed of 1200 rpm with a 3.4 mL capacity column.     

Ecological implications of a flower size/number trade-off in tropical forest trees

BACKGROUND: In angiosperms, flower size commonly scales negatively with number. The ecological consequences of this trade-off for tropical trees remain poorly resolved, despite their potential importance for tropical forest conservation. We investigated the flower size number trade-off and its implications for fecundity in a sample of tree species from the Dipterocarpaceae on Borneo. METHODOLOGY/PRINCIPAL FINDINGS: We combined experimental exclusion of pollinators in 11 species, with direct and indirect estimates of contemporary pollen dispersal in two study species and published estimates of pollen dispersal in a further three species to explore the relationship between flower size, pollinator size and mean pollen dispersal distance. Maximum flower production was two orders of magnitude greater in small-flowered than large-flowered species of Dipterocarpaceae. In contrast, fruit production was unrelated to flower size and did not differ significantly among species. Small-flowered species had both smaller-sized pollinators and lower mean pollination success than large-flowered species. Average pollen dispersal distances were lower and frequency of mating between related individuals was higher in a smaller-flowered species than a larger-flowered confamilial. Our synthesis of pollen dispersal estimates across five species of dipterocarp suggests that pollen dispersal scales positively with flower size. CONCLUSIONS AND THEIR SIGNIFICANCE: Trade-offs embedded in the relationship between flower size and pollination success contribute to a reduction in the variance of fecundity among species. It is therefore plausible that these processes could delay competitive exclusion and contribute to maintenance of species coexistence in this ecologically and economically important family of tropical trees. These results have practical implications for tree species conservation and restoration. Seed collection from small-flowered species may be especially vulnerable to cryptic genetic erosion. Our findings also highlight the potential for differential vulnerability of tropical tree species to the deleterious consequences of forest fragmentation.     

Diel variation of zooplankton in the tropical coral-reef water of Tioman Island,Malaysia

Zooplankton was sampled at 3-h intervals for a 48-h period from a coral reef of Tioman Island, Malaysia. It was size-fractionated into three size classes: 100–200, 200–335, and >335 μm using different sieves with different mesh sizes. Total zooplankton (>100 μm) abundance and biomass in the water column were high later at night (0300 h), not just after sunset as previously described in other studies. Only the largest size-fraction (>335 μm) of zooplankton significantly differed in biomass and abundance between day and night. The increase in the large zooplankton later in the night is suggested to be caused by the advection of pelagic species into the reef. This work has provided a measurement of the variation of zooplankton community over coral reef that can exist on a scale of hours.     

Three-dimensional structure of Wza, the protein required for translocation of group 1 capsular polysaccharide across the outer membrane of Escherichia coli

Wza is a highly conserved multimeric outer membrane protein complex required for the surface expression of the serotype K30 group 1 capsular polysaccharide in Escherichia coli. Here we present the first three-dimensional structure of this type of polysaccharide exporter at a 15.5-A resolution obtained using single particle averaging on a dataset of cryo-negatively stained protein. Previous structural studies on purified Wza have revealed a homo-oligomeric ring structure that is most probably composed of eight subunits. Symmetry analysis of the three-dimensional structure combined with biochemical two- and three-dimensional crystallographic data strongly suggest that Wza is an octameric complex with a C4 quasi-rotational symmetry and is organized as a tetramer of dimeric subunits. Wza is best described as a stack of two 4-A high rings with differing diameters providing a mushroom-like aspect from the side. The larger ring has a distinctive square shape with a diameter of 115 A, whereas the smaller is almost circular with a diameter of 90 A. In the center of the complex and enclosed by the four symmetrical arms is a small elliptical cagelike cavity of approximately 40 A in diameter. The central cavity is effectively sealed at the top and bottom of the complex but has small inter-arm holes when viewed from the side. We discuss the structure of this complex and implications in the surface translocation of cell-surface polysaccharide.     

Effects of progesterone on apneic events during behaviorally defined sleep in male rats

Drug therapy with progesterone has been applied to the patients with sleep apnea syndrome, but its clinical efficacy is equivocal. In the present study, we examined the effects of progesterone (1 and 30 mg/kg, i.p.) on the apneic events during behaviorally defined sleep in male rats at 4, 14 and 26 weeks of age by using a whole body plethysmographic measurement. The number of events of spontaneous apnea (SA) and post-sigh apnea (PSA) increased with aging. The duration of SA or PSA was also prolonged in old rats. A low dose (1 mg/kg) of progesterone significantly decreased the number of both SA and PSA, and this effect increased in an age-dependent manner. However, progesterone had no effect on the duration of SA and PSA. Neither the basal respiratory rate nor the total sleep time was changed. On the other hand, a higher dose (30 mg/kg) of progesterone had no effect on the number of SA and PSA, while it prolonged the duration of PSA. It also prolonged the total sleep time without affecting the basal respiratory rate. Pretreatment with mifepristone (5 mg /kg, i.p.), an antagonist of progesterone receptors, inhibited the effects of the low dose of progesterone, but did not show any antagonistic effect on the high dose-induced changes. These results suggest that the progesterone-mediated mechanisms are involved, at least partly, in respiratory function during sleep and the progesterone therapy is possibly effective within an appropriate dose range for the sleep apnea syndrome.