Detection of impaired left ventricular function in coronary artery disease with acceleration index in the first derivative of the transthoracic impedance change

In order to detect impaired left ventricular (LV) function in coronary artery disease (CAD) patients using acceleration index (Ac) of impedance cardiography (ICG), exercise ICG was performed in 29 patients with chest pain but without CAD (Group 1) and 21 patients with CAD (Group 2), and their resting values were compared with 30 healthy controls (Group 3). The acceleration index, which reflects indirectly aortic blood flow acceleration, was calculated as the ratio of dZ/dtmax to its accelerating time (AT). At rest, the values for Ac in Groups 1, 2, and 3 were 23 +/- 10, 15 +/- 6, and 36 +/- 13 omega/s2, respectively. There were significant differences between Group 1 versus 3, 2 versus 3, and 1 versus 2 (all p less than 0.001). At maximal exercise, Ac showed the largest percent change among the various indices used in this study. An increase of 198% for Group 2 was markedly lower than that of 250% in Group 1 (40 +/- 14 vs. 68 +/- 24 omega/s2, p less than 0.001). With a value of less than or equal to 40 omega/s2, Ac can detect the CAD patients, with a sensitivity of 62% and specificity of 90%, superior to stress ECG using CM5 lead. It is concluded that: (1) Ac is the sole index capable of distinguishing not only between the normals and diseased groups, but also between CAD patients and suspected CAD cases at rest. (2) Ac is a remarkably sensitive index for detecting impaired LV function at maximal exercise. (3) Exercise ICG is useful for predicting CAD from the population predisposing to CAD.(ABSTRACT TRUNCATED AT 250 WORDS)

HIV-1 tat trans-activation requires the loop sequence within tar

Human immunodeficiency virus (HIV-1) is the primary retroviral agent responsible for AIDS and related disorders worldwide. One of its identified gene products, tat protein, stimulates in trans the expression of all HIV-1 genes by several orders of magnitude. Cells infected with HIV-1 require tat protein to produce virus, suggesting that trans-activation is crucial for viral replication. The essential cis-acting site for trans-activation, termed tar, resides within the R region of the HIV-1 long terminal repeat (LTR), between -17 and +54 with respect to the initiation site of viral transcription. It is striking that the RNA encoded between +1 and +59 has the potential to form an extensive stem-loop secondary structure which, as a portion of the untranslated leader RNA, would be common to all HIV-1 mRNAs. We now present the results of nucleotide substitution experiments which suggest that tat trans-activation requires presentation of the sequence +30CUGGG+34 in tar within the loop of a RNA hairpin structure.

Concanavalin A receptor ‘tipping’ in Tetrahymena and its relationship to cell adhesion during conjugation

Shortly after mixing cells of complementary mating types of Tetrahymena, the cells develop the ability to pair, a process inhibited by ConA, and the region joining the cells becomes ringed with ConA receptors. This study examines the arrival of ConA receptors at the conjugation junction by looking at cells in the period between mixing and pairing. By brief incubations with F-ConA at intervals after mixing, it was ascertained that some cells had fluorescent tips as early as 15min. A kinetic analysis revealed that ‘tipping’ occurs in a manner that appears to be related to subsequent cell pairing. Cytoskeletal frameworks (CFs) were isolated under conditions in which ConA receptors remain attached. Western blot analysis of these structures revealed four major and several minor ConA-binding proteins. However, between mixing and the establishment of over 80% paired cells, changes occurring in the banding pattern were slight. This indicates that new populations of ConA receptors are not produced to any great extent after mixing. Head- on examination of CFs showed that it was possible to monitor simultaneously the process of tip transformation (widening of the nonciliated area of the tip) and ConA-receptor localization. ConA receptors originate posterior to the tip, begin to occupy the surface of the tip in clusters as the tip widens and eventually coat the transformed tip. Finally, as cells join pairs, the receptors relocate to a ring around the conjugation junction. These data suggest that ConA receptors accumulate at the anterior tips and then concentrate at the edge of the junction. This could provide a mechanism for controlling cell-cell adhesion.

Intracellular morphogenesis of bacteriophage T4. II. Head morphogenesis

The relative phage yields of cells of Escherichia coli infected with both wild-type and amber mutant phages deficient in head morphogenesis were determined. The decrease in burst size as a function of the ratio of mutant:wild-type-infecting phage was linear and proportional for mutants in genes 20, 22, and 23, while for mutants in genes 21, 31, and 24 the results suggest an excess of intracellular gene product. The initiation of assembly of phage particles was not delayed at reduced gene product levels; only a reduction in the rate of phage assembly was observed. The effects on burst size of pairs of mutations in genes 20 and 23, 22 and 23, and 22 and 24, in both cis and trans arrangements, were identical. Experiments using the mutant E920g in gene 23 show that varying the kind and intracellular amounts of the major capsid protein (gp23) with respect to the major core or scaffold protein (gp22) had a profound effect on the length of the T4 head. Head length determination must therefore depend on the proper intracellular balance between these two proteins.