Background: Nonlinear regression, like linear regression, assumes that the scatter of data around the ideal curve follows a Gaussian or normal distribution. This assumption leads to the familiar goal of regression: to minimize the sum of the squares of the vertical or Y-value distances between the points and the curve. Outliers can dominate the sum-of-the-squares calculation, and lead to misleading results. However, we know of no practical method for routinely identifying outliers when fitting curves with nonlinear regression.

A low molecular weight inhibitor of cell-free protein synthesis effective at subnanomolar concentrations is formed on incubation of cytoplasmic extracts from interferontreated cells with double-stranded RNA and ATP. It can be conveniently synthesized by incubating a poly(I)poly(C)-Sepharose-bound enzyme fraction from such cels with [:IH or [a-or y-32P]ATP. The radioactive inhibitor has been characterized by its behavior on DEAE-Sephadex in the presence of urea and on the basis of the products obtained on enzymic, alkaline, and sequential degradation by periodate oxidation and ft elimination. Its structure appears to be pppA2'p5'A2'p5'A. We have found no evidence for any modification or abnormality other than the 2'-5' linkage. On occasion the inhibitor preparations have included what seems to be the corresponding dimeran higher oligomers in decreasing amounts. The trimer, tetramer, and pentamer are similar in activity, but the dimer is less potent if active at all. Protein synthesis in extracts from interferon-treated cells shows an enhanced sensitivity to inhibition by double-stranded RNA (dsRNA) (1, 2). A protein kinase(s), a nuclease(s), and a low molecular weight inhibitor(s) seem likely to be involved (3-8).The kinase is thought to phosphorylate one of the initiation factors in protein synthesis, as appears to be the case in rabbit reticulocyte lysates on inhibition of protein synthesis by a number of agents, including dsRNA (9-13). The roles of the nuclease and low molecular weight inhibitor are not known. The latter is formed in appropriate cell-free systems in response to dsRNA and is effective at subnanomolar concentrations in the inhibition of protein synthesis in reticulocyte lysates or mouse L cell-free systems (3-5). From our previous work it appeared to be an oligonucleotide of unusual structure. It was shown to contain two or more AMP residues in alkali-and snake venom phosphodiesterase (SVPD)-labile linkage, but to be resistant to digestion with a variety of other nucleases (5). A further characterization of the inhibitor is presented, leading to the proposed structure pppA2'p5'A2'p5'A.MATERIALS AND METHODS Treatment of mouse L cells with low doses (5-30 effective units/ml) of highly purified (>107 units/mg of protein) interferon, preparation of extracts from interferon-treated cells, synthesis and radioactive labeling of the oligonucleotide inhibitor, its initial purification on DEAE-cellulose and assay for inhibition of "4C-labeled amino acid incorporation in the L cell-free system programmed with encephalomyocarditis virus RNA, were as previously described (2-5

This study demonstrates both reduced maximal coronary vasodilation and impairment in the regulation of coronary flow in response to submaximal increases in myocardial demand in patients with diabetes mellitus. These microvascular abnormalities may lead to myocardial ischemia in the absence of epicardial coronary atherosclerosis in some circumstances, and thus contribute to adverse cardiovascular events in diabetic patients.

No abstract

No abstract

The enzyme (2-5A synthetase) which synthesizes ppp(A2'p)nA where n=2 to 4 (collectively referred to as 2-5A) is widely distributed in a variety of cells and tissues in amounts which increase response to interferon and vary with growth and hormone status. 2-5A activates a nuclease which inhibits protein synthesis. The non-phosphorylated 'core' of 2-5A ((A2'p)nA, n=2 to 4) can inhibit DNA synthesis and cell growth. Here we describe convenient and sensitive radioimmune (RI) and radiobinding (RB) assays for core and 2-5A. In combination with more satisfactory high performance liquid chromatography (HPCL) methods using reverse-phase C18 columns, these assays have been used to detect core and 2-5A in crude extracts from interferon-treated cells. The novel 2-5A synthetase products NAD2'p5' A2'p5'A and A5'p45'A2'p5'A2'p5'A (ref. 13), which can also be detected using the RB assay, were not found in significant amounts. The natural occurrence of core has not been described previously.

No abstract

No abstract