Studies on the extent of gill surface in a fresh water cat-fish Bagarius bagarius (Ham.).

The total gill area of the fish ranges from 37,537 to 56,551 lamellae. The number of lamellae per mm of the gill filament and area of lamellae knowing the respiratory gill area, the gill area per g of body weight and per cm3 of body volume were calculated to correlate the variation in gill surface area per unit weight and volume of the fish. The fish can survive for quite long out of water as the lamallae are spaced wide apart and do not adhere together.     

Analysis of chromatin of the brain of young and old rats by micrococcal nuclease and DNase I

Micrococcal nuclease (MCN) and DNase I were used to study the conformational changes in chromatin of the brain of rats of different ages. Purified nuclei and chromatin were digested separately by MCN and DNase I. Kinetics of digestion of chromatin by MCN are similar for young, adult and old rats. Also agarose gel electrophoresis of DNA fragments do not show any differences. The kinetics of digestion with DNase I, on the other hand, are greater and faster for 20-week old rats than for 90-week old rats. High performance denaturing polyacrylamide gel electrophoresis reveals that a greater amount of smaller fragments of DNA are produced in the 20-week old rats than in the 90-week. These conformational changes occur in the chromatin during aging.     

Substitution of Torpedo acetylcholine receptor alpha 1-subunit residues with snake alpha 1- and rat nerve alpha 3-subunit residues in recombinant fusion proteins: effect on alpha-bungarotoxin binding.

A fusion protein consisting of the TrpE protein and residues 166-211 of the Torpedo acetylcholine receptor alpha 1 subunit was produced in Escherichia coli using a pATH10 expression vector. Residues in the Torpedo sequence were changed by means of oligonucleotide-directed mutagenesis to residues present in snake alpha 1 subunit and rat nerve alpha 3 subunit which do not bind alpha-bungarotoxin. The fusion protein of the Torpedo sequence bound 125I-alpha-bungarotoxin with high affinity (IC50 = 2.5 x 10(-8) M from competition with unlabeled toxin, KD = 2.3 x 10(-8) M from equilibrium saturation binding data). Mutation of three Torpedo residues to snake residues, W184F, K185W, and W187S, had no effect on binding. Conversion of two additional Torpedo residues to snake, T191S and P194L, reduced alpha-bungarotoxin binding to undetectable levels. The P194L mutation alone abolished toxin binding. Mutation of three Torpedo alpha 1 residues to neuronal alpha 3-subunit residues, W187E, Y189K, and T191N, also abolished detectable alpha-bungarotoxin binding. Conversion of Try-189 to Asn which is present in the snake sequence (Y189N) abolished toxin binding. It is concluded that in the sequence of the alpha subunit of Torpedo encompassing Cys-192 and Cys-193, Try-189 and Pro-194 are important determinants of alpha-bungarotoxin binding. Tyr-189 may interact directly with cationic groups or participate in aromatic-aromatic interactions while Pro-194 may be necessary to maintain a conformation conductive to neurotoxin binding.     

Spin label reduction kinetics,a procedure to study the effect of drugs on membrane permeability: The effects of monosodium urate,dimethyl sulfoxide and amphotericin B

A method is presented to study the effect of drugs on membrane permeability. It is based on the reduction of a spin label trapped in the internal aqueous compartment(s) of membranes by ascorbate ions added to the bulk aqueous phase. The decay of the electron spin resonance signal of the spin label as a function of time gives an indication of the effect of added agents on the permeability of membranes. To demonstrate the technique, the effect on model membranes of egg phosphatidylcholine of the gout-implicated compound monosodium urate, the aprotic solvent dimethyl sulfoxide and the polyene antibiotic amphotericin B were examined. Monosodium urate did not affect the permeability, casting doubt on a proposed mechanism whereby the agent disrupts the membranes via hydrogen bonding. Dimethyl sulfoxide promoted a gradual increase in rate of solute passage across cholesterol-containing model membranes. Amphotericin B had pronounced effect on the permeability of cholesterol-containing membranes, causing nearly total loss of paramagnetism immediately after addition. Some aspects of the mechanism of action of the drugs are discussed as well as the advantages and disadvantages of the method. The experiments also allow the evaluation of the effect of surface charge and cholesterol on the dimensions of model membranes.     

Knowledge-based annotation of small molecule binding sites in proteins

Background  

The study of protein-small molecule interactions is vital for understanding protein function and for practical applications in drug discovery. To benefit from the rapidly increasing structural data, it is essential to improve the tools that enable large scale binding site prediction with greater emphasis on their biological validity.     

Effect of complete feed blocks or grazing and supplementation of lambs on performance, nutrient utilisation, rumen fermentation and rumen microbial enzymes

A study to compare two feeding systems, stall feeding (SF) and grazing plus supplementation (GR) was carried out, based on intake, performance and rumen fermentation characteristics of lambs. While SF animals received ad libitum complete feed blocks (CFB), GR animals were allowed grazing for 8 h on a pasture and supplemented with concentrate mixture at 250 g per head per day. Intake in grazing animals was determined using chromium III oxide as internal marker. Intake of dry matter (DM), crude protein (CP) and organic matter (OM) were higher ( P < 0.01) in SF than in GR animals. Similarly, digestibility of OM, CP and energy were higher ( P < 0.01) in SF animals. Average daily gain in SF animals (101 g) was significantly ( P < 0.01) higher than in GR animals (78 g) but total wool yield was similar for the two groups (856 g, SF; 782 g, GR). The pH of the rumen content, concentration of total volatile fatty acids and total activities of carboxymethyl cellulase, xylanase and esterase in the rumen liquor were similar. The concentrations (mg/dl) of total nitrogen (125, SF; 63, GR) and NH₃-nitrogen (42, SF; 31, GR) were higher in SF animals than that of GR animals. A significantly higher activity ( P < 0.05) of microcrystalline cellulase (24.5 v. 7.7 units) and lower activity ( P < 0.05) of protease (309 v. 525 units), was observed in the rumen of SF animals than in GR animals. SF animals could therefore harness more energy through degradation of plant cell walls thus reducing breakdown of plant proteins as gluconeogenic source. The SF system of feeding where CFB was offered to sheep appeared superior to GR in terms of intake, nutrient utilisation and animal performance. Therefore the SF feeding system where CFB are offered to animals can be advocated as an alternative to grazing and supplementation feeding strategy for sheep production, especially where the pastures are highly eroded and need resting for regeneration or curing. The CFB feeding can also be adopted under adverse conditions like drought and famine, a common phenomenon in arid and semiarid conditions.     

Sec14-nodulin proteins and the patterning of phosphoinositide landmarks for developmental control of membrane morphogenesis

Polarized membrane morphogenesis is a fundamental activity of eukaryotic cells. This process is essential for the biology of cells and tissues, and its execution demands exquisite temporal coordination of functionally diverse membrane signaling reactions with high spatial resolution. Moreover, mechanisms must exist to establish and preserve such organization in the face of randomizing forces that would diffuse it. Here we identify the conserved AtSfh1 Sec14-nodulin protein as a novel effector of phosphoinositide signaling in the extreme polarized membrane growth program exhibited by growing Arabidopsis root hairs. The data are consistent with Sec14-nodulin proteins controlling the lateral organization of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P₂) landmarks for polarized membrane morphogenesis in plants. This patterning activity requires both the PtdIns(4,5)P₂ binding and homo-oligomerization activities of the AtSfh1 nodulin domain and is an essential aspect of the polarity signaling program in root hairs. Finally, the data suggest a general principle for how the phosphoinositide signaling landscape is physically bit mapped so that eukaryotic cells are able to convert a membrane surface into a high-definition lipid-signaling screen.