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ABSTRACT An attempt has been made here to find out the effect chloramphenicol has on the protein synthesis of the germinating pollen of Chlorophytum tuberosum. Three factors have been studied viz., effect on the percentage of germination, effect on the rate of tube growth and division of the generative nucleus and its behaviour during germination. Though 0.3% of chloramphenicol affects %age of germination and the rate of tube growth, it has no inhibitory effect on the division of the generative nucleus. 0.6% of chloramphenicol certainly inhibits the division of the generative nucleus as no male gametes are formed after 20 hours of treatment. This is an indicator that protein synthesis which takes place before cell division is inhibited

Influence of bond orientational order on the switching time of ferroelectric smectics

We report studies of the bulk switching time as a function of temperature in the chiral smectic C (C∗ ) and chiral smectic I (I∗) phases of 4-(2-methylbutyl) phenyl 4'-(octyloxy)-(1,1')-biphenyl-4-carboxylate (8OSI) which shows a continuous evolution from the fluid C∗ to the hexatic I∗ phase. The thermal variation of the switching time is found (to our knowledge for the first time) to scale remarkably well with the hexatic order parameter for the two phases determined experimentally by Brock et al for 8OSI, the racemic form of 8OSI. Similar correlation is observed in the case of 8SI∗, the alkyl analog of 8OSI∗, which shows a first order C∗-I∗ transition

Schlieren textures in biaxial nematic liquid crystals

The optical textures exhibited by the mesophases of three compounds, all of which are reported to show the biaxial nematic phase, have been examined. The textures are of the usual nematic schlieren type, except that they consist entirely of disclinations of strength |s| = 1/2. It is suggested that the absence of disclinations of unit strength is diagnostic of biaxiality

Pressure induced twist grain boundary phase

We report high pressure studies on a binary system of 4-(2'-methyl butyl)phenyl 4'-n-octyl biphenyl-4-carboxylate (CE8 from BDH) and 4-n- dodecyloxy biphenyl-4'-(2'-methyl butyl)benzoate (C12). For the concentration range 0.32<X<0.62, where X is the weight fraction of C12, the system shows the following sequence of transitions at room pressure: Isotropic- Cholesteric (Ch)-Twist Grain Boundary (TGB)-Smectic A (A)Smectic C− (C∗ ). For X=0.25, the Ch phase transforms directly to the A phase at 1 bar, but there is an induced TGB phase between the Ch and A phases at elevated pressures. Analysis of the topology of the pressure-temperature diagram in the vicinity of the Ch-TGB-A meeting point indicates that is a critical end point rather than a bicritical point as expected from the mean field theory. At X=0.64 there is a direct TGB-C∗ transition at 1 bar, but there appears a pressure induced A phase between the TGB and C∗ phases. The topology of the phase diagram suggests that the TGB-A-C∗ meeting point is a bicritical point

Sesquiterpene Lactones Isolated from Elephantopus scaber L. Inhibits Human Lymphocyte Proliferation and the Growth of Tumour Cell Lines and Induces Apoptosis In Vitro

This study was designed to isolate the compounds responsible for the cytotoxic properties of South Indian Elephantopus scaber L. and further investigate their effects on quiescent and proliferating cells. Bioassay-guided isolation of the whole plant of chloroform extract of South Indian Elephantopus scaber afforded the known sesquiterpene lactone, deoxyelephantopin, and isodeoxyelephantopin whose structures were determined by spectroscopic methods. These compounds caused a dose dependent reduction in the viability of L-929 tumour cells in 72 h culture (IC50 value of 2.7 μg/mL and 3.3 μg/mL) by the cell viability assay. Both the compounds act selectively on quiescent and PHA-stimulated proliferating human lymphocytes and inhibited tritiated thymidine incorporation into cellular DNA of DLA tumour cells. The compound deoxyelephantopin at a concentration of 3 μg/mL caused maximum apoptotic cells. It also exhibited significant in vivo antitumour efficacy against DLA tumour cells. The results, therefore, indicate that the antiproliferative property of deoxyelephantopin and isodeoxyelephantopin could be used in regimens for treating tumors with extensive proliferative potencies

Electrooptic and viewing angle characteristics of a display device employing a discotic nematic liquid crystal

Recently we developed a novel liquid crystal display device employing discotic nematic material. This device exhibits the following improvements over a conventional twisted nematic (TN) display device using a calamitic nematic material. The device (i) is simple to fabricate and (ii) has excellent viewing angle characteristics showing a wide and symmetric viewing angle profile, (iii) has much less difference in the pixel capacitance between the ON and OFF states resulting in reduced cross talk problem. However the response time of the device is slower than conventional TN devices. An obvious solution to this problem is to reduce the viscosity of the material. To achieve this we have doped, in small concentrations, a long chain alkane compound to the parent room-temperature discotic nematic material. Systematic studies show that both the switch ON and switch OFF response times show a significant decrease, i.e., the device switches faster, in the case of the mixtures. It should be mentioned that wide and symmetric viewing angle characteristics remain unaffected by the addition of the dopant material. However both the switch ON and switch OFF response times are still an order of magnitude slower compared to that of conventional TN devices. Considering the fact that these response times are not very different from those for the STN displays, the achievement of symmetric and wide viewing angle characteristics with a simple fabrication process makes this device quite interesting. To make them attractive enough to be considered for commercial applications new materials with faster response have to be developed. Efforts in this direction are underway in our laboratory

Schlieren textures in free-standing nematic films: evidence of biaxiality

Conoscopic studies reveal that the nematic phase of 4,4-( p -terphenyl)-bis\[2,3,4-tri(dodecyloxy)benzal]imine is biaxial, the biaxial angle increasing with schlieren textures exhibited by the nematic phase have been between glass plates, as well as free-standing consisting entirely of s or 2-brush disclinations, confirming an earlier suggestion that the absence of 4-brush disclinations is evidence of biaxiality. decreasing temperature. The examined. Films sandwiched films, exhibit a nematic schlieren texture

A first low-molar-mass, monodispersive, bent-rod dimer exhibiting biaxial nematic and smectic A phases

A "peelable banana" is formed when a bent-core molecule is linked to a rodlike mesogen through a flexible aliphatic spacer. This is an appropriate description of this novel low-molar-mass organic system, which displays a transition from a biaxial nematic (Nb) phase to a biaxial smectic A phase. The illustration gives a schematic representation of the dimeric molecules in the Nb phase as well as the corresponding textural and conoscopic patterns obtained

COMBINATORIAL EFFECT OF D-AMINOACIDS AND TETRACYCLINE AGAINST PSEUDOMONAS AERUGINOSA BIOFILM

Objective: The present study attempted to evaluate the anti-biofilm activity of D-amino acids (D-AAs) on Pseudomonas aeruginosa and determine if the combination of D-AAs with tetracycline enhances the anti-biofilm activity in vitro and ex vivo.Methods: Different D-AAs were tested for antibiofilm activity against wild type P. aeruginosa PAO1 and two multidrug resistant P. aeruginosa clinical strains in the presence of sub inhibitory concentrations of tetracycline using crystal violet microtitre plate assay. Results were further validated using in vitro wound dressing and ex vivo porcine skin models followed by cytotoxicity and hemocompatibility studies.Results: D-tryptophan (5 mmol) showed 61 % reduction in biofilm formation of P. aeruginosa. Interestingly combinatorial effect of 5 mmol D-tryptophan and 0.5 minimum inhibitory concentration (MIC) (7.5µg/ml) tetracycline showed 90% reduction in biofilm formation. 5 mmol D-methionine shows 28 % reduction and combination with tetracycline shows 41% reduction in biofilm formation of P. aeruginosa. D-leucine and D-tyrosine alone or in combination with tetracycline did not show significant anti-biofilm activity. D tryptophan-tetracycline combination could reduce 80 % and 77 % reduction in biofilm formation in two multi drug resistant P. aeruginosa clinical strains. D-tryptophan-tetracycline-combination could also reduce 76% and 66% reduction in biofilm formation in wound dressing model and porcine skin explant respectively. The cytotoxicity and hemocompatibility studies did not show significant toxicity when this combination was used.Conclusion: The results established the potential therapeutic application of D-tryptophan alone or in combination with tetracycline for treating biofilm associated clinical problems caused by P. aeruginosa

Phytoplankton Blooms along the Indian Coasts-some highlights

The present article embodies a critical appraisal of the blooms observed at Karwar, Mangalore, Cochin, Vizhinjam, Tuticorin and Madras from 1982 to 1987. Noctiluca miliaris, Coscinodiscus sp. and Fragilaria oceanica are the three common species which appear in blooms regularly. There are some other phytoplankters also which bloom occasionally at restricted areas. These include species of Ceratium, Chaetoceros, Rhizosolenia, Biddulphia, Skeletonema, Thalassionema, Thalassiosira subtilis, Thalassiothrix and Trichodesmium