Using group testing to estimate a proportion, and to test the binomial model

Group testing has been extensively studied as an efficient way to classify units as defective or satisfactory when the proportion (p) of defectives is small. It can also be used to estimate p, often substantially reducing the mean squared error (MSE) of p and cost per unit information. Group testing is useful for larger p in the estimation problem than in the classification problem, but for larger p more care must be taken in choosing the group size (k); k being too large not only increases MSE (p), but adversely affects the robustness of p to both errors in testing (misclassification) and errors in the assumed binomial model. Procedures that retest units from defective groups, if even feasible, are shown to reduce cost per unit information very little in the estimation problem, but can provide useful information for testing the model. Methods are given for using data from tests of unequal-sized groups to estimate p and for testing the validity of the binomial model.     

Free ADP levels in transgenic mouse liver expressing creatine kinase. Effects of enzyme activity, phosphagen type, and substrate concentration

ADP is an important regulator of hepatic metabolism. Despite its importance the level of free ADP in the liver remains controversial. Recently, we engineered transgenic mice which express high levels of creatine kinase in liver. The reaction catalyzed by creatine kinase was assumed to be at equilibrium and used to calculate a free ADP level of 0.059 mumol/g wet weight. In this report we test the equilibrium assumption by studying the free ADP level as a function of enzyme activity or substrate content. Over a 5-fold range of creatine kinase activity, from 150-800 mumol/min/g wet weight, there was no change in the free ADP level. The average value of ADP for these mice was 0.061 +/- 0.016 mumol/g wet weight. Similarly, altering hepatic creatine content from 1.6 to 30 mumol/g wet weight had no effect on the calculated total free ADP level. The average value of ADP for the creatine levels was 0.048 +/- 0.015 mumol/g wet weight. Finally, the free ADP level was calculated using the equilibrium with cyclocreatine rather than creatine as substrate. The equilibrium of the reaction with cyclocreatine lies 30 times more toward phosphorylation than does the equilibrium with creatine. A free ADP level of 0.063 +/- 0.031 mumol/g wet weight was calculated using cyclocreatine. This value is not different from that found with creatine. These results show that the equilibrium assumption used to calculate free ADP levels in transgenic mouse liver is valid, and the presence of creatine kinase does not affect ADP levels.     

Transport and deamination of amino acids by a gram-positive, monensin-sensitive ruminal bacterium.

Strain F, a recently isolated ruminal bacterium, grew rapidly with glutamate or glutamine as an energy source in the presence but not the absence of Na. Monensin, a Na+/H+ antiporter, completely inhibited bacterial growth and significantly reduced ammonia production (85%), but 3,3',4',5-tetrachlorosalicylanide (a protonophore) and valinomycin had little effect on growth or ammonia production. Dicyclohexylcarbodiimide, a H(+)-ATPase, inhibitor had no effect. The kinetics of glutamate and glutamine transport were biphasic, showing unusually high rates at high substrate concentrations. On the basis of low substrate concentrations (less than 100 microM), the Km values for glutamate and glutamine were 4 and 11 microM, respectively. Strain F had separate carriers for glutamate and glutamine which could be driven by a chemical gradient of Na. An artificial delta psi was unable to drive transport even when Na was present. The glutamate carrier had a single binding site for Na with a Km of 21 mM; the glutamine carrier appeared to have more than one binding site, and the Km was 2.8 mM. Neither carrier could use Li instead of Na. Histidine and serine were also rapidly transported by Na-dependent systems, but serine alone did not allow growth even when Na was present. Because exponentially growing cells at pH 6.9 had little delta psi (-3 mV) and a slightly reversed Z delta pH (+17 mV), it appeared that the membrane bioenergetics of strain F were solely dependent on Na circulation.     

Brugia pahangi: Feeding and nutrient uptake in vitro and in vivo

Incubation in vitro of adult Brugia pahangi in an apparatus which permitted the separate exposure of the anterior, middle, or posterior region of the worms to medium-containing radioactively labeled d-glucose, l-leucine, and adenosine has provided evidence that these materials are taken up in physiologically significant amounts by a transcuticular route. No evidence for an oral ingestion of materials has been obtained from worms in vitro, but in vivo an oral uptake of Trypan blue has been demonstrated. The ultrastructure and cytochemical staining reactions for nonspecific esterase, acid phosphatase (EC-3.1.3.2), and leucine naphthylamidase of the gut and body wall are described.     

Substrate utilization kinetic model for biological treatment process

The applicability of Contois' kinetic equation to aerobic and anaerobic treatments of organic wastes is investigated. A refractory coefficient to account for the nonbiodegradable portion of the organic substrates in the digester is incorporated into the kinetic equation. The kinetic equation is applied to the data for aerobic digestions of organic substrates and for anaerobic treatment of dairy wastes. They all show a very good fit of the kinetic equation to the data. Furthermore, the kinetic parameters and the refractory coefficients are shown to be independent of influent organic substrate concentration. This study confirms previous reports that the effluent quality of biological treatment systems for organic wastes depends on influent organic waste concentration. The effect of temperature on the kinetic parameters and the refractory coefficient for anaerobic treatment of sewage sludge are studied. It shows that the kinetic parameters vary with temperature, while the refractory coefficient remains fairly constant. Equations to predict biodegradable treatment efficiency and volumetric substrate utilization rate are also briefly discussed.     

The nucleotide sequence of rat liver tRNAAsn

The major species of asparagine specific tRNA was isolated from rat liver, degraded to oligonucleotides, and shown to have the nucleotide sequence pG-U-C-U-C-U-G-U-m¹G-m²G-C-G-C- A-A-D-C-G-G-D-X-A-G-C-G-C-m²G-ψ-ψ-C-G-G-C-U-Q-U-U-t⁶A-A-C-C-G- A-A-A-G-m⁷G-D-U-G-G-U-G-G-Z-ψ-C-G-m¹A-G-C-C-C-A-C-C-C-A-G-G-G- A-C-G-C-C-A_OH. Although this tRNA contains several modified nucleotides in their expected positions, it is unique in having X, 3-(3-Amino-3-carboxy-n-propyl)uridine in loop I rather than in loop III; Q, 7-(4,5-cis-dihydroxyl-1-cyclopenten-3-yl-aminomethyl)-7-deazaguanosine in the wobble position of loop II; and Z, an unknown, and presently uncharacterized nucleoside, at position 23 from the 3′ terminus usually occupied by ribothymidine.     

Inhibition of protein phosphorylation and induction of protein cross-linking in erythrocyte membranes by diamide

This report presents studies on the effect of diamide on protein phosphorylation in erythrocyte membranes. Diamide, a thiol-oxidizing reagent, nonspecifically inhibits cyclic Amp-dependent and -independent autophosphorylation of red cell memvranes, but not the activity of the solubilized membrane cycle AMP-independent protein kinases. Analysis of diamide-treated membranes by gel electrophoresis indicates that diamide is capable of inducing cross-linking of membrane proteins. The action of diamide, both in the inhibition of membrane autophosphorylation and in the cross-linking of membrane proteins, is very similar to that of Cu2+. o-phenanthroline complex. Our data indicate that diamide inhibits erythrocyte membrane autophosphorylation by perturbing the protein substrates.     

Differentiation of channel models by noise analysis.

Differentiation of membrane channel models based on fluctuation (or noise) analysis is discussed. The theory is particularly useful in distinguishing a single-conductance model (Hodgkin-Huxley formalism) from a multiconductance model. When applied to the frog node of Ranvier, it seems likely that the potassium channels of the membrane may have multiconductance states.