Prediction Intervals in Nonlinear Regression

By treating the nonlinear model as if it were linear in the parameterization θ in the neighbourhood of the least squares estimate θ, we construct two-sided nominally-q-prediction intervals by applying the usual linear model theory. The derivation of the truncated series expansion of the expected coverage of the prediction intervals at a feasible value of the parameter vector is described. The quadratic approximation of the expected coverage is then obtained for a two-parameter nonlinear model. Finally we show how we may construct the prediction intervals when a certain type of nonlinear transformation of the parameter vector has been applied.     

Chromatographic methods for large-scale preparation of immunoglobulin G2a monoclonal antibodies Lym-1 and TNT-1 F(ab')2 fragments

Lym-1 and TNT-1 are two murine immunoglobulin G_2a monoclonal antibodies (MAbs) which have been used for clinical trials in cancer patients. This paper describes methods for large-scale preparation of F(ab')₂ fragments from 50 mg to 4 g of MAbs Lym-1 and TNT-1. Digestion of MAbs with pepsin was optimized and performed at pH 3.8, a pepsin/antibody ratio of 1:250, and 3–4 h of incubation at 37°C. The F(ab')₂ fragments were purified by tandem column procedures using fast protein liquid chromatography. Quality control analyses of the products included protein purity, isoelectric point, immunoreactivity, and endotoxin level. The results revealed that the chromatographic procedures are practical, simple, and effective, and can be used to produce gram quantities of clinical-grade F(ab')₂ fragments for the diagnosis of cancer in patients.     

Interaction of menadione and duroquinone with Q-cycle during DT-diaphorase function]

The interaction of quinones (menadione and duroquinone) with DT-diaphorase and mitochondrial electron transport chain translocators at low (120 mosM) and high (400 mosM) values of the medium tonicity in the quinone concentration range of 6-90 microM was studied. It was shown that with a rise in menadione (K3) concentration the number of electron transport carriers interacting with it increase. At K3 concentration of 6 microM the latter is reduced by DT-diaphorase and fully oxidized via the Q-cycle. At K3 concentration of 15 microM the latter is also reduced by DT-diaphorase via the Q-cycle, but in this case the oxidation is incomplete (about 30% K3H2 is oxidized by the terminal part of the respiratory chain). At 90 microM K3 50% of quinone is reduced by DT-diaphorase and 50% by the respiratory chain NADH dehydrogenase complex enzymes; about 30% of K3H2 is oxidized via the Q-cycle, about 20%--by the terminal part of the respiratory chain and about 50%--by O2 without cytochrome oxidase. Unlike menadione, duroquinone (6-90 microM) is reduced only by DT-diaphorase and is oxidized in all cases by cytochrome oxidase. It was shown that the increase in the mitochondrial matrix volume in low tonicity media decreases the rate of the DT-diaphorase shunt operation.     

Analysis of synaptonemal complexes in a heterozygous human male carrier of a reciprocal translocation involving an acrocentric chromosome: heterosynapsis without previous homosynapsis

Summary Silver-stained synaptonemal complexes in surface-spread pachytene nuclei from an oligospermic man, heterozygous for a reciprocal translocation involving an acrocentric chromosome, were analyzed by electron microscopy. Contrary to the classically expected configuration, nonhomologous pairing was observed with asymetrical association of the lateral elements of the nonhomologous arms of the quadrivalents. A possible role of heterosynapsis in germ cell conservation is discussed.     

The effect of high hydrostatic pressure on the modulation of regulatory enzymes from spinach chloroplasts.

High hydrostatic pressure enhanced the specific activity of regulatory enzymes of the Benson-Calvin cycle (fructose-1,6-bisphosphatase, glyceraldehyde-3-P dehydrogenase, phosphoribulokinase) which are modulated by the ferredoxin-thioredoxin system. High activity of chloroplast fructose-1,6-bisphosphatase required dithiothreitol, fructose 1,6-bisphosphate, and Ca2+. At 100 bar the A0.5 for fructose 1,6-bisphosphate (0.3 mM) was lower than that at 1 bar (1.5 mM), whereas similar variations of pressure did not alter the A0.5 for Ca2+ (55 microM). The response of chloroplast glyceraldehyde-3-P dehydrogenase exposed to 500 bar was a 4-fold increase in the NADP-linked activity; conversely, the NAD-dependent activity remained unchanged. The concerted action of high pressure and Pi (or ATP), both activators of chloroplast glyceraldehyde-3-P dehydrogenase, led to inactivation. On the other hand, the activity of phosphoribulokinase increased 10-fold when the enzyme was incubated at 1500 bar; the activation process was strictly dependent on the presence of dithiothreitol. At variance with these enzymes, bovine liver fructose-1,6-bisphosphatase, yeast glyceraldehyde-3-P dehydrogenase, and chloroplast ribulose 1,5-bisphosphate carboxylase, whose activities are not modulated by reduced thioredoxin, were inactivated by high pressure. The comparison of oligomeric enzymes revealed that the stimulation of specific activity by high pressure correlated with thioredoxin-mediated activation, and it did not depend on a particular subunit composition. Present results show that high pressure resembled thioredoxin, cosolvents, and chaotropic anions in its action on regulatory enzymes of the Benson-Calvin cycle. The comparison of physiological and non-physiological modulators suggested that thioredoxin-mediated modifications of noncovalent interactions is an important event in light-dependent regulation of chloroplast enzymes.     

Identification of a hypervariable region in the long terminal repeat of equine infectious anemia virus.

An avirulent, field-derived isolate of equine infectious anemia virus (EIAV), designated MA-1, was molecularly cloned, and the complete nucleotide sequence was determined for the 3' half of the viral genome. Comparisons between MA-1 and the prototype Wyoming strain of EIAV identified a 66-nucleotide stretch between CAAT (-91) and TATAA (-25) in the U3 region of the long terminal repeat, where sequence divergence was as high as 39.3%. The polymerase chain reaction was used to amplify and clone long terminal repeat sequences from Th-1, the in vivo parental stock of MA-1. Results indicated that the nucleotide sequences of MA-1 and Th-1 clones were less variable than was observed between MA-1 and Wyoming. However, MA-1 and Th-1 markedly differed in the types of enhancer sequences located in the hypervariable region. These results suggest that variation in lentivirus regulatory sequences may be important in EIAV host cell tropism and pathogenesis.