Are economic selection indices always superior to a desired gains index?

Conclusions The comparison of different selection indices is justified only if the indices are constrated to achieve the same profit function, even when each index is not optimized with respect to that profit function.When a profit function is known and is non-linear, the desired gains index may be more efficient than the economic index. The optimum desired gains index should be determined by iterative techniques over several generations to compare the genetic progress with the economic index, because gains by the economic index are not linear and the changes observed in the initial generations of selection are not the same rates in future generations, although those changes are linear in the case of the desired gains index.     

Analysis of several key active site residues of ricin A chain by mutagenesis and X-ray crystallography.

Active site residues of ricin A chain were analyzed by site-directed mutagenesis and X-ray diffraction to help assess their roles in the mechanism of action of this toxic N-glycosidase enzyme. Arg180 is thought, from X-ray studies, to protonate the adenine substrate at N3; this facilitates bond cleavage and is crucial to the mechanisms of action. The residue was converted to Gln and initial rate data measured. Km for the mutant is not significantly affected, increasing only 2-fold. The kcat, however, is decreased approximately 1000-fold. This is consistent with a simple interpretation that Arg180 is involved more in transition state stabilization than in substrate binding. Tyrosines 80 and 123 are known from X-ray models to stack on either side of the substrate adenine ring. When they were each converted to serine overall activity was reduced 160- and 70-fold respectively against ribosomes from Artemia salina. These effects are each approximately 10 times greater than when the residues were previously converted to phenylalanines. Sufficient protein for the Tyr80 to Phe mutant was obtained to carry out an X-ray analysis. Together with mutagenesis data, the structure suggests that the invariance of the two active site Tyr residues is largely caused by structural stability.     

Effects of some ionophore antibiotics and polyoxins on the growth of anaerobic rumen fungi

The growth of mixed rumen fungi in vitro was suppressed by both ionophore antibiotics (salinomycin, monensin and portmicin) and polyoxins (polyoxin B and D: inhibitors of chitin synthesis). The fungistatic effect of the ionophores on a Piromonas spp. was more pronounced than on a Neocallimastix spp. The polyoxins, however, were more potent fungistatically against the Neocallimastix spp. than the Piromonas spp. Higher concentrations of the polyoxins were required to elicit the same effect as that observed with the ionophores. Salinomycin administration decreased fungal count in the rumen of sheep, but fungal count increased after the cessation of the feeding of the antibiotic. Polyoxin D also suppressed the growth of fungi in vivo, but the effect was short-lived. Nevertheless, both bacterial and protozoal counts tended to increase during and after the administration of polyoxin D. Total volatile fatty acid concentrations in the rumen tended to increase during the period of polyoxin D administration. This increasing tendency was maintained for 10 d after the cessation of antibiotic administration. Offering polyoxin D to sheep increased production of propionate ( P < 0·05), while decreasing that of acetate. The results indicate that the rumen fungi are sensitive to chitin synthesis inhibitors as well as ionophores, and are essential members of microbes in the rumen ecosystem.     

Phylogenetic analysis of the cadherin superfamily.

Cadherins are a multigene family of proteins which mediate homophilic calcium-dependent cell adhesion and are thought to play an important role in morphogenesis by mediating specific intercellular adhesion. Different lines of experimental evidence have recently indicated that the site responsible for mediating adhesive interactions is localized to the first extracellular domain of cadherin. Based upon an analysis of the sequence of this domain, I show that cadherins can be classified into three groups with distinct structural features. Furthermore, using this sequence information a phylogenetic tree relating the known cadherins was assembled. This is the first such tree to be published for the cadherins. One cadherin subtype, neural cadherin (N-cadherin), shows very little sequence divergence between species, whereas all other cadherin subtypes show more substantial divergence, suggesting that selective pressure upon this domain may be greater for N-cadherin than for other cadherins. Phylogenetic analysis also suggests that the gene duplications which established the main branches leading to the different cadherin subtypes occurred very early in their history. These duplications set the stage for the diversified superfamily we now observe.     

Kinetics of Escherichia coli destruction by microwave irradiation.

The kinetics of destruction of Escherichia coli cells suspended in a solution by microwave irradiation with a microwave oven were studied. During radiation at several powers, the temperature of 0.01 M phosphate buffer (PB), pH 7.0, in a glass beaker increased linearly at a rate of A (degrees Centigrade per second) according to the exposure time. When E. coli cells suspended in PB were exposed in the same beaker, the number of viable cells decreased according to the exposure time and the power used. The survival curve was approximated to a set of three linear parts. For each part, a rate constant of destruction (k) and an extrapolated starting temperature (T0) at several powers were estimated. Thereafter, the relationships between A and k and between A and T0 were studied. When a flat petri dish was used, the A value of exposed PB was lower and bacterial destruction was inhibited; the survival curve was similar to a curve predicted from the A value by using the relationships between the parameters. As the concentration of salt in the solution increased (from 0 to 1.35 M), the A value decreased and bacterial destruction was more suppressed. No remarkable difference between the destruction profiles for microwave exposure and conventional heating, which had the potential to generate an equal A value, was detected. These results showed that the parameter A of an irradiated solution is essential when kinetics of bacterial destruction by microwave exposure are studied and that the destruction profile can be interpreted mostly by means of thermal effects.     

D-lactate concentrations in blood, urine and sweat before and after exercise.

The purpose of this study was to investigate changes in the concentrations of D-lactate, L-lactate, pyruvate and methylglyoxal (MG) in body fluids after exercise. Eight untrained male students and five male students who were boat club members engaged in the exercise. Each subject performed runs of short and long duration. Compared to pre-exercise values plasma concentrations of D-lactate, L-lactate and pyruvate increased after running; in trained men by 3.6, 5.0, 3.4 times after short runs and by 1.5, 4.6, 2.0 times after long runs, and in untrained men by 3.0, 12.0, 1.6 times after short runs and 2.5, 5.6, 1.6 times after long runs, respectively. In all cases, the increase of L-lactate was always higher than that of D-lactate after running. The MG contents in red blood cells decreased markedly after running, especially in the untrained students. After short runs the MG concentration had decreased to 13% in the untrained men and 30% in the trained men, and after long runs the concentration had decreased to 41% in the untrained and 60% in the trained men. The MG in plasma and red blood cells appeared to have been utilized during relatively anaerobic exercise, especially by the untrained subjects. The D-lactate and related substances were also determined in urine, but the concentration of these substances showed no relationship to exercise. The D-lactate concentration in sweat samples tripled after short periods of running but the relative concentration to sodium ion concentration was not altered.(ABSTRACT TRUNCATED AT 250 WORDS)     

Germination of Monocolpate Angiosperm Pollen: Effects of Inhibitory Factors and the Ca2+-Channel Blocker, Nifedipine

Hydration of pollen of Narcissus pseudonarcissus was retardedand germination blocked in media with supra-optimal concentrationsof osmoticum. Activation of the grains, expressed in circulatorymovement in the vegetative cell, was not blocked. Wall developmentwas disrupted, and pectic material and callose were depositedthroughout. In the absence of calcium many grains burst on hydration.The survivors showed evidence of activation, but few tubes wereformed. In medium with supra-optimal Ca²⁺, activation proceeded,but where tube tips were produced they became occluded withcallose, which eventually formed a general lining to the intine.Nifedipine, a Ca²⁺-blocker, did not prevent activation at 10^–4M, but reduced callose deposition and inhibited polarized movementin the vegetative cell. Prominences formed at the germinationsites were mostly low and rounded. During recovery in normalmedium, tube tips with normal callose linings were formed. Colchicine,a microtubule inhibitor, had no effect on activation or germination.Cytochalasin D, an actin inhibitor, prevented activation ofthe vegetative cell, but did not arrest all wall deposition.Movement began soon after transfer to normal medium, and somegrains produced adventitious tube tips. While Ca²⁺ appears notto be essential for activation, these results may be interpretedas indicating links in the normal course of germination betweenthe initial Ca²⁺ influx at the potential germination sites and:(a) polarization of movement in the vegetative cell, probablyrelated to re-orientation of the actin cytoskeleton; and (b)patterned deposition of callose, which appears to have an importantmorphogenetic role. Narcissus pseudonarcissus, pollen activation, pollen germination, osmotic effects, actin cytoskeleton, nifedipine, cytochalasin D, colchicine, role of Ca²⁺ flux