Structural and functional heterogeneity of cardiomyocytes during hemodynamic loading of the rat heart

Ultrastructural studies of cardiomyocytes during experimental aorta coarctation enabled one to divide them into 6 types: with mitochondrial swelling and enlargement of the sarcoplasmic reticulum; with primary damage to myofibrils; with disintegration of ultrastructure because of edema; with hypertrophy and hyperplasia of ultrastructures; without essential changes in organelles; and with concomitant changes in mitochondria and myofibrils. Such different reactions of cardiomyocytes are regarded as an adaptation mechanism that ensures the maintenance of heart function under extreme conditions.     

Change in activity of enzymes for purine metabolism and RNA and DNA biosynthesis in macrophages, reflecting impairment of their functions in neoplastic growth

The changes in the biochemical parameters of peritoneal macrophages and their coupling to the secretory and phagocytic functions in CH3A mice during the growth of the reinoculated solid hepatoma 22a were studied. The DNA and RNA synthesis during the active tumour growth was more intense than that in resident macrophages. The activity of uridine kinase increased up to 156.0 +/- 12.0 nmol/hour/10(8) but was absent in resident macrophages. This was accompanied by a 7.2-fold increase of interleukin-1 synthesis as determined by the [3H]thymidine incorporation into thymocyte DNA in response to concanavalin A administration to C3H mice. Similar changes were observed in peptone-stimulated macrophages. A specific feature of macrophages from tumour-bearing mice was the impairment of activity of purine exchange enzymes and the efficiency of phagocytosis that were unobserved in peptone-stimulated macrophages. The activity of adenosine deaminase and purine nucleoside phosphorylase was inhibited as a result of their preincubation with zymosan, a phagocytosis-stimulating agent. This was accompanied by a significant decrease of the first chemiluminescence peak resulting from disturbances in Fc-reception. Macrophages of tumour-bearing animals possessed an increased 2.2-fold activity of membrane-bound AMP 5'-nucleotidase concomitant with the lack or decrease of the amplitude of the second chemiluminescence peak reflecting the disturbances in digestion resulting from phagocytosis.     

Triaminotricarboxylic amino acid oxidation productions of actinoidin and ristomycin]

Aromatic acids with three benzene nuclei bound through oxygen were obtained from actinoidin and ristomycin on their oxydation with permanganates of methylated aglycones and peptides. The structures of the methyl esters of these acids were determined by spectral methods. They are the following: methyl-3,5-bis-(4-methoxycarbonyl-phenoxy)-4-methoxybenzoate (from ristomycin) and methyl-3-(2-chlor-4-methoxycarbonyl-phenoxy)-5-(4-methoxycarbonyl-phenoxy)-4-methoxybenzoate (from actinoidin). The compounds are the aromatic parts of the molecules of the unusual triaminotricarboxylic amino acids present in the aglycones of all antibiotics of the group of polycyclic glycopeptides.     

Autocrine A2 in the T-System of Ventricular Myocytes Creates Transmural Gradients in Ion Transport: A Mechanism to Match Contraction with Load?

Transmural heterogeneities in Na/K pump current (I_P), transient outward K⁺-current (I_to), and Ca²⁺-current (I_CaL) play an important role in regulating electrical and contractile activities in the ventricular myocardium. Prior studies indicated angiotensin II (A2) may determine the transmural gradient in I_to, but the effects of A2 on I_P and I_CaL were unknown. In this study, myocytes were isolated from five muscle layers between epicardium and endocardium. We found a monotonic gradient in both I_p and I_to, with the lowest currents in ENDO. When AT₁Rs were inhibited, EPI currents were unaffected, but ENDO currents increased, suggesting endogenous extracellular A2 inhibits both currents in ENDO. I_P- and I_to-inhibition by A2 yielded essentially the same K_0.5 values, so they may both be regulated by the same mechanism. A2/AT₁R-mediated inhibition of I_P or I_to or stimulation of I_CaL persisted for hours in isolated myocytes, suggesting continuous autocrine secretion of A2 into a restricted diffusion compartment, like the T-system. Detubulation brought EPI I_P to its low ENDO value and eliminated A2 sensitivity, so the T-system lumen may indeed be the restricted diffusion compartment. These studies showed that 33–50% of I_P, 57–65% of I_to, and a significant fraction of I_CaL reside in T-tubule membranes where they are transmurally regulated by autocrine secretion of A2 into the T-system lumen and activation of AT₁Rs. Increased AT₁R activation regulates each of these currents in a direction expected to increase contractility. Endogenous A2 activation of AT₁Rs increases monotonically from EPI to ENDO in a manner similar to reported increases in passive tension when the ventricular chamber fills with blood. We therefore hypothesize load is the signal that regulates A2-activation of AT₁Rs, which create a contractile gradient that matches the gradient in load.     

Propagation of electrical potential changes in filamentous cyanobacteria

Possible energy transmission along conjugating membranes was investigated. It was found by extracellular electrodes that under local illumination of blue-green algae Phormidium uncinatum the electrical current propagated along trichomes. The form and sign of the responses show that e. m. f. appears in the illumination region, which generates on the cellular membrane the potential difference with a negative charge inside the cell. The initiated transmembrane potential difference propagates along the filament of Ph, uncinatum like along a cable. The hypothesis concerning a cable structure of Ph, uncinatum was supported in the experiments with intersection of algae, and with intracellular injection of fluorescein showing the existence of direct diffusion exchange through cellular interfaces.