Peripheral membrane molecules of leukocytes and NK cytotoxicity

Some leukocyte effector cell-surface molecules movement toward the adjoining target cells takes place during the reaction of NK cytotoxicity (NK R). The majority of the moving molecules are usually anchoredvia a divalent-ion-dependent interaction (PMM-M²⁺). The released PMM-M²⁺ can interact also with the secreted tumor necrosis factor alfa (TNF-α). In agreement with PMM-M²⁺ movement, the number of TNF-α binding sites on the target cell surface increases during NK R. In addition, antibodies against PMM-M²⁺, as well asd-mannose- or N-acetyl-d-glucosamine-terminated oligosaccharides of PMM-M²⁺ inhibit NK R. A more detailed analysis of PMM-M²⁺ with monoclonal antibodies used flow cytometry and cell-surface biotinylation. Only 3 of 31 tested CD antigens (CD2, LAK-1 and CD45) were passed through this first strongly restricted experimental screening. The EDTA-released LAK-1 antigen, but not CD2 and CD45, interact with TNF-α and cell surfacevia a mannose-inhibitable interaction dependent on the presence of Ca²⁺ ions. The mechanism of possible participation of PMM-M²⁺ in cytotoxic events is discussed in relation to Ca²⁺ influx and subsequent cytolysin secretion.     

Altered Transition Between Agonist-and Antagonist-Favoring States of μ-Opioid Receptor in Brain Membranes with Modified Microviscosity

Abstract: In unmodified synaptosomal brain membranes the presence of NaCl inhibited the binding to μ receptors of the tritiated opioid agonists etorphine, Tyr-D-Ala-Gly-(Me)Phe-Gly-ol, and sufentanil by 53, 43, and 37%, respectively, and increased that of the antagonist [³H]naltrexone by 54%. On the other hand, in membranes whose microviscosity was increased by incorporation of cholesteryl hemi-succinate (CHS) the effects of sodium on opioid agonist and antagonist binding were abolished and strongly reduced, respectively. Furthermore, in the modified membranes the ability of sodium to protect the opioid receptor from inactivation by the sulfhydryl-reactive agent N -ethyl-maleimide (NEM) was diminished. In CHS-treated membranes whose elevated microviscosity was reduced by the incorporation of oleic acid, the effectiveness of sodium in modulating opioid binding and attenuating receptor inactivation by NEM was restored. The results implicate membrane microviscosity in the mechanism by which sodium modulates the conversion between agonist-and antagonist-favoring states of μ opioid receptor.     

iTRAQ-based proteomic study of the effects of microcystin-LR on medaka fish liver

Microcystins are cyanotoxins that occur in ground water and thus pose a potential health risk. Microcystin-LR (microcystin-leucine-arginine) is a potent hepatotoxin, and is suspected of being a tumour promoter. Poisoning with this toxin causes several dysfunctions in hepatocytes by inhibiting protein phosphatases 1 and 2A, and notably produces oxidative stress, disrupts the cytoskeleton, and deregulates mitogen-activated protein kinase pathway. Medaka fish (Oryzias latipes) was chosen as a model for studying the effects of this cyanotoxin on liver proteins using a gel-free approach, iTRAQ. Fish were gavaged with microcystin-LR. Two hours later, 325 proteins could be identified by Scaffold Q+ and 32 proteins revealed statistically significant variations above a ∣0.2∣ threshold of log(2) ratio by comparison with control. These proteins are mostly involved in the translation and maturation of proteins, lipid metabolism and detoxification. Notably, apolipoproteins are deregulated which indicates a possible alteration of chylomicron-mediated transport.     

Modification of the structure of plasmatic membranes of the liver by the action of α-tocopherol in vitro

Biophysics - The effect of the natural antioxidant α-tocopherol in a broad concentration range (10?4–10?25 M) on the viscosity characteristics and thermally induced...     

Developmentally regulated cleavage of tRNAs in the bacterium Streptomyces coelicolor

The ability to sense and respond to environmental and physiological signals is critical for the survival of the soil-dwelling Gram-positive bacterium Streptomyces coelicolor. Nutrient deprivation triggers the onset of a complex morphological differentiation process that involves the raising of aerial hyphae and formation of spore chains, and coincides with the production of a diverse array of clinically relevant antibiotics and other secondary metabolites. These processes are tightly regulated; however, the genes and signals involved have not been fully elucidated. Here, we report a novel tRNA cleavage event that follows the same temporal regulation as morphological and physiological differentiation, and is growth medium dependent. All tRNAs appear to be susceptible to cleavage; however, there appears to be a bias towards increased cleavage of those tRNAs that specify highly utilized codons. In contrast to what has been observed in eukaryotes, accumulation of tRNA halves in S. coelicolor is not significantly affected by amino acid starvation, and is also not affected by induction of the stringent response or inhibition of ribosome function. Mutants defective in aerial development and antibiotic production exhibit altered tRNA cleavage profiles relative to wild-type strains.     

Egg sac silk of Theridiosoma gemmosum (Araneae: Theridiosomatidae)

Cocoons of Theridiosoma gemmosum consist of two main parts, the egg sac case and the stalk. The inner space of the egg sac case is filled with nonsticky flocculent silk. Measuring 600–800 nm in diameter, the flocculent threads are never made up of bundles of longitudinally oriented nanofibrils. The egg case wall consists of a lower layer of highly ordered threads and an upper layer of cover silk. The lower, permanently white layer consists of threads in a mesh‐like arrangement, the thicker threads being 4–6 μm and the thinner threads being 2–3 μm in diameter. Each thread is a bundle of parallel nanofibrils, with a diameter between 150 and 300 nm. The silk secretions of these fibers, emitted from spigots, are processed by legs. The upper layer of the egg case is applied to the threads of the lower layer by direct rubbing against its surface, i.e. without the use of legs. In the lower and middle part of the egg case, the accumulated secretion forms a virtually compact encrustation, whereas in the upper, conically shaped, part of the egg case where it becomes the stalk, this secretion becomes substantially scarcer. The stalk is a continuation of the egg case, its proximal part made of fibers similar to those forming the inner layer of the egg case wall. The distal part of the stalk continues towards the suspension area either as a compact bundle of parallel fibers, or the stalk forks into two bundles of roughly the same thickness, which continue towards the suspension area separately. On the surface of objects onto which cocoons are attached, the secretion of the piriform glands acts as an adhesive sheet. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Validation of HPTLC method for the analysis of taraxerol in Clitoria ternatea

A new, simple, sensitive, selective and precise HPTLC method has been developed for the determination of taraxerol in Clitoria ternatea L. Determination of taraxerol was performed on TLC aluminium plates. Linear ascending development was carried out in twin trough glass chamber saturated with hexane and ethyl acetate (80:20 v/v). The plate was then dried and sprayed with anisaldehyde reagent. A Camag TLC scanner III was used for spectrodensitometric scanning and analysis at 420 nm. The system was found to give compact spots for taraxerol (R(f) 0.53). The calibration plot was linear in the range of 100-1200 ng of taraxerol. The correlation coefficient of 0.9961 was indicative of good linear dependence of peak area on concentration. The concentration of taraxerol was found to be 12.4 mg/g w/w in the hydroalcoholic extract of C. ternatea root. To study the accuracy and precision of the method, recovery studies were performed. Recovery values from 99.65 to 99.74% showed excellent reliability and reproducibility of the method. The limits of detection and quantification were determined to be 31 and 105 ng/spot, respectively. The proposed HPTLC method for quantitative monitoring of taraxerol in C. ternatea can be used for routine quality testing of C. ternatea extract used in Ayurvedic formulations.     

Primate population decline in response to habitat loss: Borajan Reserve Forest of Assam, India

Systematic studies of the Borajan Reserve Forest in Assam, India, were conducted in 1995, 1997, and 1998. Initially this small (5 km²) forest was inhabited by substantial numbers of five species of diurnal primates and the forest was typical of Reserve Forests in northwest upper Assam. About two thirds of the forest had canopy cover of 20 – 50% or more. Civil unrest, political problems and a lack of resources for Forest Department personnel, however, resulted in rapid degradation of the area. After three years less than one third of the forest had more than 20% canopy cover; all primate populations had declined dramatically and the small percentage of juveniles in each species indicated that all were in imminent danger of local extinction. There was no evidence of hunting or trapping nor any large scale logging. Forest degradation was due primarily to small scale harvesting of forest products, selective cutting, and collection of firewood. Although only hand tools were employed, the forest inexorably declined in response to these steady pressures. Borajan may be an object lesson as to what can happen but it need not be the harbinger of Assam’s future.