An equilibrium between distorted and undistorted DNA in the adult chicken beta A-globin gene

We have used single strand specific nucleases to map DNA distortion in the adult chicken beta A-globin gene. We have detected two structures of that kind and have mapped nuclease-cutting sites at one base resolution. One prominent site is centered at -190 relative to the RNA capping site and is positioned at the center of a stretch of contiguous C residues. The second site is near the first intron/exon junction (+620) and appears as a series of discrete 1-base-long enzyme-cutting sites. Based upon the pattern of nuclease cutting and the kinetics of nuclease cutting we conclude that the "poly(C)" stretch may assume a looped geometry in supertwisted DNA molecules which is similar to that proposed by Felsenfeld (Nickol, J. M., and Felsenfeld, G. (1983) Cell 35, 467-477). We show that S1 nuclease cuts within the intron occur mainly at the end points of polypurine segments and suggest that such end points may assume a distorted transitional geometry. We find that Neurospora crassa endonuclease cuts both the promotor and intron sites in linear DNA molecules but that in linear DNA the cutting process is limited by a first order conformation change of the DNA substrate. Based upon those kinetics we propose that in unstressed DNA, each of the two sites can convert between a distorted and undistorted geometry. In the enzyme assay buffer at 37 degrees C, the time constant for the equilibrium is nearly 10 h for the promotor site and 7 h for the intron.     

Modulation induction of the T3 antigen by OKT3 antibody is monocyte dependent

We investigated the influence of monocytes on the susceptibility of the T3 antigen on human T cells to modulation induction by OKT3 antibody. In the absence of monocytes, the T3 antigen was only minimally susceptible to modulation. After the addition of 20% monocytes to the culture, however, complete modulation was readily observed. Furthermore, we found that even in the absence of OKT3 antibody, monocytes were able to down-regulate the expression of the T3 antigen, although to a lesser extent. The ability of monocytes to enhance antigenic modulation proved to be a more general phenomenon. Each individual T cell antigen, however, differed in its susceptibility to modulation by antibody, monocytes, or both, thereby establishing its own characteristic pattern. In addition, after complete modulation of the T3 antigen, the addition of monocytes to the culture thereafter had a distinct inhibitory effect on the reexpression of the T3 antigen. Monocyte enhancement of T3 modulation is significantly reduced when using the OKT3 F(ab')2 fragment, as is OKT3 mitogenesis. After pulsing the monocytes with OKT3 antibody before adding them to the culture, T3 modulation became nearly complete even in the absence of added OKT3 antibody. Monocyte-induced modulation proved not to be MHC restricted, thus allowing for comparative analysis of this effect between monocytes and other cell types. A moderate, however, incomplete modulation enhancement was observed with the human monocyte cell line U937 and with Daudi cells. This finding proved to coincide with the distinct ability of these cell lines to bind OKT3 antibody by their Fc receptors, as was the case with monocytes. In contrast, neither Fc receptor binding nor T3 modulation enhancement was observed with the cell lines Cess and G7. In addition, no effective T3 modulation was observed with glutaraldehyde-fixed monocytes. The overall results seem to indicate that effective modulation of the T3 antigen by OKT3 antibody requires the active participation of Fc receptors on monocytes.     

Application of macroscopic balances to the identification of gross measurement errors

A systematic method is presented which is capable of both detecting the presence of grossly biased measurement errors and locating the source of these errors in a bioreactor through statistical hypothesis testing. Equality constraints derived from material and energy balances are employed for the detection of data inconsistencies and for the subsequent identification of the suspect measurements by a process of data analysis and rectification. Maximum likelihood techniques are applied to the estimation of the states and parameters of the bioreactor after the suspect measurements have been eliminated. The level of significance is specified by the experimenter while the measurments are assumed to be randomly, normally distributed with zero mean and known variances. Two different approaches of data analysis, batchwise and sequential, that lead to a consistent set of adjustments on the experimental values, are discussed. Several examples based on the fermentation data taken from literature sources are presented to demonstrate the utility of the proposed method, and one set of data is solved numerically to illustrate the computational aspect of the algorithm.     

高胆固醇高脂肪膳食对家兔β-VLDL组成及其与巨噬细胞相互作用的影响的初步研究

给家兔喂以1％胆固醇及10％菜油(A组)或猪油(B组)50多天后A组血胆固醇水平(824.2±265.1mg/dl)明显低于B组(1666±693.8mg/dl);A组甘油三酯水平(51.9±19.1mg/dl)亦低于B组(104±40.2mg/dl)。二组家兔的β—VLDL的脂类组成无差别,但A组β—VLDL的apoE高于B组,分别为45.2％及37.5％。高分子量apoB(apoB_h)为33.6％,低于B组β-VLDL(47.3％)。A组β-VLDL促进小鼠腹腔巨噬细胞胆固醇堆积的程度大于B组,可能与apoE含量高有关。我们认为多不饱和脂酸减轻动脉粥样硬化(As)的作用不在于改变脂蛋白构成后阻碍泡沫细胞的形成而是促进β—VLDL从体内清除。     

Complement phenotypes in patients with psoriasis

Phenotype frequencies for the complement proteins C4A, C4B, Bf (factor B) and C3 were performed for 49 Caucasian patients with psoriasis. The C4*A6 allele was present in 26.6% of the patients as compared to 5.4% of healthy regional Caucasian controls, p less than 0.001, relative risk = 6.28. The C4*A6 allele is known to be in linkage disequilibrium with the HLA B17 allele and to produce a non-functional gene product when it occurs with the B17 allele. HLA B17 is known to be associated with psoriasis in many Caucasian populations. Additional findings in the present study were a significant reduction in the C4B*2 allele frequency, a non-significant increase in the Bf*F allele frequency and no difference for Bf or C3 phenotype frequencies in the patients with psoriasis as compared to the controls.     

Transposon mutagenesis of baculoviruses: analysis of TFP3 lepidopteran transposon insertions at the FP locus of nuclear polyhedrosis viruses

We report the complete sequences of two representatives of the TFP3 transposable element family of the lepidopteran, Trichoplusia ni. These elements were isolated as insertions mobilized from the Lepidopteran host genome into two closely related nuclear polyhedrosis viruses (NPV) during infection. Both elements inserted within the 500-bp FP locus of the respective viral genomes (map units 36.0 to 37.0), causing a distinctive plaque morphology phenotype and the loss of a 25-kDa viral-specific protein. Both insertions occurred at the identical TTAA target site in the respective genomes, in the same relative orientation, and are flanked by 15-bp imperfect inverted repeats. The inserted elements interrupt the 25K open reading frame (ORF). One of these FP mutants undergoes spontaneous reversion. Sequence analysis at the excision site of a spontaneous revertant demonstrates that the TFP3 elements are capable of precise excision, restoring the expression of the 25-kDa protein. We also compare the sequences of the 25K genes of the Autographa californica and Galleria mellonella viruses (AcMNPV and GmMNPV, respectively). The 25K gene sequences diverge in five areas, resulting in an additional EcoRV and TaqI site within the GmMNPV 25K gene, and extension of the ORF for an additional 2 amino acids at the C-terminus of the predicted GmMNPV 25 kDa protein. The phenomenon of transposon mutagenesis of Baculovirus genomes provides a unique opportunity for analysis of transposon mobility.