Mechanistic studies on carboxypeptidase a from goat pancreas — part II: Evidence for carboxyl group

Studies with substrate analogues and the pH optimum indicated the involvement of carboxyl group in the active site of goat carboxypeptidase A. Chemical modification of the enzyme with 1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide methoI -p-toluene sulphonate, a carboxyl specific reagent, led to loss of both esterase and peptidase activities. Protection studies showed that this carboxyl group was in the active site and was protected by Βp-phenylpropionic acid and glycyl-L-tyrosine. Kinetic studies also confirmed the involvement of carboxylic group because the enzyme modification with water soluble carbodiimide was a two step reaction which excluded the possibility of tyrosine or lysine which are known to give a one step reaction with this reagent     

Population Changes of Heterodera glycines and Soybean Yields Resulting from Soil Treatment with Alachlor,Fenamiphos, and Ethoprop

The population dynamics of Heterodera glycines as influenced by alachlor, fenamiphos, and ethoprop alone and in herbicide-nematicide combinations were studied in the field. Numbers of H. glycines juveniles and eggs were higher at midseason and harvest where nematicides were applied. Fenamiphos alone or in combination with alachlor provided better control of H. glycines and greater seed yields than treatments with ethoprop. Numbers of H. glycines eggs at harvest in 1980 were positively correlated with numbers of juveniles at planting in 1981 and negatively related to seed yield in 1981.     

Relative growth rate correlates negatively with pathogen resistance in radish: the role of plant chemistry

Plant growth rate has frequently been associated with herbivore defence: a large investment in quantitative defence compounds occurs at the expense of growth. We tested whether such a relationship also holds for growth rate and pathogen resistance. For 15 radish (Raphanus sativus L.) cultivars, we determined the potential growth rate and the resistance to fungal wilt disease caused by Fusarium oxysporum. We subsequently aimed to explain a putative negative relationship between growth rate and resistance based on plant chemical composition. Both growth rate and resistance level varied greatly among cultivars. Moreover, there was a strong negative correlation between growth rate and resistance, i.e. there are costs associated with a high resistance level. Roots of slow-growing, resistant cultivars have a higher biomass density. Using pyrolysis mass spectrometry. we part1y explained variation in both growth rate and resistance in terms of the same change in chemical composition. Leaves of slow-growing, resistant cultivars contained more cell wall material. Surprisingly, roots of slow-growing, highly resistant cultivars contained significantly less cell wall material, and more cytoplasmic elements (proteins). We speculate that this higher protein concentration is related to high construction and turn-over costs and high metabolic activity. The latter in turn is thought to be responsible for a rapid and adequate resistance reaction, in which phenols may be involved.     

Three-dimensional perfused cell culture

Compelling evidence suggests the limitation and shortcomings of the current and well established cell culture method using multi-well plates, flasks and Petri dishes. These are particularly important when cell functions are sensitive to the local microenvironment, cell–cell and cell–extracellular matrix interactions. There is a clear need for advanced cell culture systems which mimic in vivo and more physiological conditions. This review summarises and analyses recent progress in three dimensional (3D) cell culture with perfusion as the next generation cell culture tools, while excluding engineered tissue culture where three dimensional scaffold has to be used for structural support and perfusion for overcoming mass transfer control. Apart from research activities in academic community, product development in industry is also included in this review.     

Foraging Efficacy of a Larval Parasitoid in a Cotton Patch: Influence of Chemical Cues and Learning

Plant-herbivore chemical signals and behavioral plasticity may enhance parasitoid host-foraging efficacy in the field; however, no studies have quantified the potential benefits from these factors under field-type conditions. The effect of plant-herbivore signals and learning on the foraging efficacy of Microplitis croceipes was quantified by directly observing and recording total and sequential duration of various foraging behaviors relative to 5 randomly placed herbivore-damaged and host-infested cotton plants and 20 undamaged and non-host-infested plants. Microplitis croceipes spent significantly more time searching (flying and antennation) on host infested versus uninfested plants. Antennation time was significantly and negatively correlated with successive host stings. Contrary to expectations of increased duration, flight time remained constant throughout the foraging bout, which may indicate that there was some learning associated with flight. These results suggest that plant-herbivore chemical signals and learning enhances the foraging efficacy of M. croceipes.     

Production, crystallization, and preliminary X-ray analysis of rabbit skeletal muscle troponin complex consisting of troponin C and fragment (1-47) of troponin I.

Troponin is a ternary protein complex consisting of subunits TnC. TnI, and TnT, and plays a key role in calcium regulation of the skeletal and cardiac muscle contraction. In the present study, a partial complex (CI47) was prepared from Escherichia coli-expressed rabbit skeletal muscle TnC and fragment 1-47 of TnI, which is obtained by chemical cleavage of an E. coli-expressed mutant of rabbit skeletal muscle TnI. Within the ternary troponin complex, CI47 is thought to form a core that is resistant to proteolytic digestion, and the interaction within CI47 likely maintains the integrity of the troponin complex. Complex CI47 was crystallized in the presence of sodium citrate. The addition of trehalose improved the diffraction pattern of the crystals substantially. The crystal lattice belongs to the space group P3(1)(2)21, with unit cell dimensions a = b = 48.2 A, c = 162 A. The asymmetric unit presumably contains one CI47 complex. Soaking with p-chloromercuribenzenesulfonate (PCMBS) resulted in loss of isomorphism, but enhanced the quality of the crystals. The crystals diffracted up to 2.3 A resolution, with completeness of 91% and R(merge) = 6.4%. The crystals of PCMBS-derivative should be suitable for X-ray studies using the multiple-wavelength anomalous diffraction technique. This is the first step for elucidating the structure of the full troponin complex.     

Sperm cell surface characteristics of Plumbago zeylanica L. in relation to transport in the embryo sac

Myosin associated with the male germ cells of angiosperms interacts with actin, promoting transport of the non-motile generative and later sperm cells in the pollen tube. Myosin localizing on the sperm cell plasma membrane seems negligible in Plumbago, as reflected by the absence of: (i) anti-myosin labeling using immunoelectron microscopy, (ii) sperm motility on actin matrices, and (iii) electrophoretic movement changes after addition of antibody. Sperm cells injected directly into actively streaming Nitella internodal cells, however, follow actin bundles and their movement is sensitive to ATP and Mg²⁺. This may be based on simple charge binding since negatively charged latex beads also migrate on actin, whereas neutral or positively-charged latex beads do not. Sperm cells are negatively charged according to capillary microelectrophoresis, whereas killed sperm cells, which are positively charged do not migrate. The sperm cell that normally fertilizes the egg has a higher calculated charge (8.277 × 10³ esu/cm²) compared with the sperm cell that fuses with the central cell (6.120 × 10³ esu/cm²). Received: 15 December 1998 / Accepted: 21 January 1999     

The Use of Proton Chemical Shifts to Define the Solution Structure of a Dimeric Peptide

For flexible peptides, nuclear Overhauser Effects (NOE) experiments do not provide enough information to ensure a correct definition of their solution structure. The use of distance constraints, derived from the knowledge of proton chemical shifts, is developed to restrict the number of possible conformations. In the case of flexible molecules, randomization appears as an important factor of the correct estimation of the chemical shifts from the 3D structure. The refinement of the solution structure of the highly flexible AVP-like parallel dimer is described to illustrate this process.     

The potential utility of postnatalskeletal developmental patterns in squamate phylogenetics

Postnatal patterns of skeletal development, includingthe sequence of appearance of ossification centres and the distributionof sesamoids, appear to be highly conserved species-level phenomenain squamates. As such, they are a potential source of charactersfor phylogenetic inquiry. These patterns, from 21 species representing14 crown squamate clades, form the basis for two analyses. In thefirst, the sequence of postnatal skeletal events is coded as charactersusing the sequence unit approach. This analysis reveals that thesequence of postnatal skeletal events might be useful for determiningrelationships at or above the level of crown clades, but not amongthem. The second analysis utilizes discrete data from postnatalskeletal development, such as the presence/absence of sesamoidsand the number of secondary centres in epiphyseal cartilages. Thesediscrete data appear capable of recovering the deeper divergenceswithin Squamata, but evolve too slowly to be informative at thelevel of crown clades. Thus, patterns of postnatal skeletal developmenthave the potential to help illuminate relationships throughout thesquamate tree. Further progress in this area will require the examinationof additional squamate species, the exploration of alternative codingschemes for developmental sequences, and comparable postnatal datafor Sphenodon .  © 2002 The Linnean Societyof London, Zoological Journal of the Linnean Society, 2002, 136 ,277−313.