Versatility of thermoluminescence materials and radiation dosimetry – A review

Thermoluminescence (TL) materials exhibit a wide range of applications in different areas such as personal dosimetry, environmental dosimetry, medical research etc. Doping of different rare earth impurities in different hosts is responsible for changing the properties of materials useful for various applications in different fields. These materials can be irradiated by different types of beams such as γ‐rays, X‐rays, electrons, neutrons etc. Various radiation regimes, as well as their dose–response range, play an important role in thermoluminescence dosimetry. Several TL materials, such as glass, microcrystalline, nanostructured inorganic materials and recently developed materials, are reviewed and described in this article.     

Ecdysteroid glycosides from Sida rhombifolia L

Seven ecdysteroids, including the three new compounds 1-3, were isolated from Sida rhombifolia L. Their structures and configurations were determined by extensive spectroscopic techniques in combination with chemical derivatization. The four known compounds--ecdysone (4), 20-hydroxyecdysone (5), 2-deoxy-20-hydroxyecdysone-3-O-beta-D-glucopyranoside (6), and 20-hydroxyecdysone-3-O-beta-D-glucopyranoside (7)--are reported for the first time from this plant.     

Developmental inhibition and reproductive potential impairment in Musca domestica L. by heavy metals

Post embryonic development and adult emergence of housefly, M. domestica L. was adversely affected in varying degrees on exposure of larvae to 6 different heavy metals. Of these, salts of mercury, aluminium and cadmium exhibited significant reduction in normal adult emergence. High decline in reproductive potential in terms of female fecundity and egg hatchability was also observed in the F1 progenies of treated larvae. The results are discussed in light of heavy pollution of environment by such contaminants.     

Biotransformation of lantadene A (22β-angeloyloxy-3-oxoolean-12-en-28-oic acid), the pentacyclic triterpenoid, by Alcaligenes faecalis

A bacterial strain capable of biotransformation oflantadene A(22-angeloyloxy-3-oxo-olean-12-en-28-oic acid),the pentacyclic hepatotoxin of lantana (Lantanacamara var. aculeata) has been isolated fromsoil using lantadene A as the sole carbon source. Theorganism is Gram negative, rod shaped, motile,catalase positive and has been identified as Alcaligenes faecalis. The isolate has been found tobe specific for lantadene A and did not utilizelantadene B. In studies using sucrose as an additionalcarbon source, A. faecalis elicitedbiotransformation of lantadene A to its trans isomer22-tigloyloxy-3-oxoolean-12-en-28-oic acid,designated as lantadene X and two other minormetabolites which could not be isolated in pure state.     

Crystallo-co-agglomeration: A novel technique to obtain ibuprofen-paracetamol agglomerates

The purpose of this research was to obtain directly compressible agglomerates of ibuprofen-paracetamol containing a desired ratio of drugs using a crystallo-co-agglomeration technique. Crystallo-co-agglomeration is an extension of the spherical crystallization technique, which enables simultaneous crystallization and agglomeration of 2 or more drugs or crystallization of a drug and its simultaneous agglomeration with another drug or excipient. Dichloromethane (DCM)-water system containing polyethylene glycol (PEG) 6000, polyvinyl pyrollidone, and ethylcellulose was used as the crystallization system. DCM acted as a good solvent for ibuprofen and bridging liquid for agglomeration. The process was performed at pH 5, considering the low solubility of ibuprofen and the stability of paracetamol. Loss of paracetamol was reduced by maintaining a low process temperature and by the addition of dextrose as a solubility suppressant. The agglomerates were characterized by differential scanning calorimetry, powder x-ray diffraction (PXRD), and scanning electron microscopy and were evaluated for tableting properties. The spherical agglomerates contained an ibuprofen-paracetamol ratio in the range of 1.23 to 1.36. Micromeritic, mechanical, and compressional properties of the agglomerates were affected by incorporated polymer. The PXRD data showed reduction in intensities owing to dilution and reduced crystallinity. Thermal data showed interaction between components at higher temperature. Ethylcellulose imparted mechanical strength to the agglomerates as well as compacts. The agglomerates containing PEG have better comparessibility but drug release in the initial stages was affected owing to asperity melting, yielding harder compacts. The agglomeration and properties of agglomerates were influenced by the nature of polymer.     

Single disulfide and linear analogues corresponding to the carboxy-terminal segment of bovine beta-defensin-2: effects of introducing the beta-hairpin nucleating sequence d-pro-gly on antibacterial activity and Biophysical properties

Mammalian defensins (alpha as well as beta forms) have a beta-hairpin structural motif spanning approximately 20 residues at the carboxy-terminal end. We have investigated the antibacterial activity and biophysical properties of synthetic peptides corresponding to the carboxy-terminal segment of bovine beta-defensin-2 (BNBD-2): VRNHVTC(1)RINRGFC(2)VPIRC(3)PGRTRQIGTC(4)FGPRIKC(5)C(6)RSW (positions of disulfide bonds are C(1)[bond]C(5), C(2)[bond]C(4), and C(3)[bond]C(6)). The parent sequence chosen was RCPGRTRQIGTIFGPRIKCRSW (P1), which spans the carboxy-terminal region of BNBD-2. Since the dipeptide sequence D-Pro-Gly favors nucleation of beta-hairpin structures even in acyclic peptides, analogues of P1 with one D-Pro-Gly at the central portion and two D-Pro-Gly segments near the N- and C-terminal ends were generated. An analogue in which GP (residues 14 and 15) in P1 was switched to PG was also synthesized. It was observed that the cyclic form as well as their linear forms exhibited antibacterial activity. Circular dichroism and theoretical studies indicated that while the beta-hairpin conformation is populated, there is conformational plasticity in the cyclic and linear peptides. The mode of bacterial killing was by membrane permeabilization. The entire mammalian defensin sequence does not appear to be essential for manifestation of antibacterial activity. Hence, short peptides corresponding to the C-terminal segments of mammalian defensins could have potential as therapeutic agents.     

Associative diazotrophs of pearl millet (Pennisetum glaucum) from semi arid region--isolation and characterization

Diversity of the native diazotrophs associated with the rhizosphere of pearl millet (P. glaucumn), grown in nutritionally poor soils of semi-arid regions was studied with a view to isolate effective nitrogen fixing and plant growth stimulating bacteria with root associative characteristics. The native population varied from 10(3)-10(4) g(-1) of rhizosphere soil after 40 d growth and belonged to genera Azospirillum, Azotobacter and Klebsiella. Another non-diazotrophic root associative group was Pseudomonas sp., which also produced IAA and enhanced plant growth. Some of these rhizobacteria showed high in vitro acetylene reduction activity along with production of indole acetic acid. Out of 11 selected diazotrophs used as seed inoculants, M10B (Azospirillum sp.), M11E (Azotobacter sp.) and M12D4 (Klebsiella sp.) resulted in significant increase in total root and shoot nitrogen at 45 and 60 days of plant growth under pot culture conditions.