A METHOD OF CORONARY RETROPERFUSION FOR THE TREATMENT OF ACUTE MYOCARDIAL ISCHEMIA

A method of retrograde perfusion of the myocardium has been developed in dogs. It consists of a double lumen balloon-tipped catheter inserted transvenously into the coronary sinus, with one lumen connected to a roller pump, the other to a helium counterpulsing pump. Oxygenated heparinized blood is obtained from the femoral artery and pumped continuously into the coronary sinus at a pressure of 50-75 mm Hg. The balloon is inflated during diastole, sealing the coronary sinus and promoting retrograde flow, and is deflated during systole, allowing blood drainage into the right atrium and preventing venous congestion. Thirteen anesthetized open-chest dogs were subjected to 15 minutes of proximal LAD artery occlusion and 30 minutes of diastolic coronary sinus perfusion (DCSP). The area of ischemia was mapped by means of platinum electrodes capable of simultaneously measuring myocardial tissue oxygen tension M(p)O(2)) and electrograms. Reduction of M(p)O(2) with simultaneous elevation of the ST segment on the corresponding electrogram was considered an indication of ischemia. Diastolic coronary sinus perfusion improved myocardial oxygen tension in the ischemic myocardium, reduced ST segment elevation, and tended to restore arterial blood pressure. Histologically, there was no intramyocardial hemorrhage.     

Studies on the activity and activation of rat liver microsomal glutathione transferase with a series of glutathione analogues

The substrate specificity of rat liver microsomal glutathione transferase toward glutathione has been examined in a systematic manner. Out of a glycyl-modified and eight gamma-glutamyl-modified glutathione analogues, it was found that four (glutaryl-L-Cys-Gly, alpha-L-Glu-L-Cys-Gly, alpha-D-Glu-L-Cys-Gly, and gamma-L-Glu-L-Cys-beta-Ala) function as substrates. The kinetic parameters for three of these substrates (the alpha-D-Glu-L-Cys-Gly analogue gave very low activity) were compared with those of GSH with both unactivated and the N-ethylmaleimide-activated microsomal glutathione transferase. The alpha-L-Glu-L-Cys-Gly analogue is similar to GSH in that it has a higher kcat (6.9 versus 0.6 s-1) value with the activated enzyme compared with the unactivated enzyme but displays a high Km (6 versus 11 mM) with both forms. Glutaryl-L-Cys-Gly, in contrast, exhibited a similar kcat (8.9 versus 6.7 s-1) with the N-ethylmaleimide-treated enzyme but retains a higher Km value (50 versus 15 mM). Thus, the alpha-amino group of the glutamyl residue in GSH is important for the activity of the activated microsomal glutathione transferase. These observations were quantitated by analyzing the changes in the Gibbs free energy of binding calculated from the changes in kcat/Km values, comparing the analogues to GSH and each other. It is estimated that the binding energy of the alpha-amino group of the glutamyl residue in GSH contributes 9.7 kJ/mol to catalysis by the activated enzyme, whereas the corresponding value for the unactivated enzyme is 3.2 kJ/mol. The importance of the acidic functions in glutathione is also evident as shown by the lack of activity with 4-aminobutyric acid-L-Cys-Gly and the low kcat/Km values with gamma-L-Glu-L-Cys-beta-Ala (0.03 and 0.01 mM-1s-1 for unactivated and activated enzyme, respectively). Utilization of binding energy from a correctly positioned carboxyl group in the glycine residue (10 and 17 kJ/mol for unactivated and activated enzyme, respectively) therefore also appears to be required for optimal activity and activation. A conformational change in the microsomal glutathione transferase upon treatment with N-ethylmaleimide or trypsin, which allows utilization of binding energy from the alpha-amino group of GSH as well as the glycine carboxyl in catalysis, is suggested to account for at least part of the activation of the enzyme.     

Steroid modulation of oxytocin/vasopressin receptors in the uterus

Oxytocin (OT) and V1 vasopressin (VP) receptors are present simultaneously in several tissues, including the uterus. In myometrium these receptors mediate contractility, while in endometrium they mediate the release of other uterotonic substances as endothelin (ET). In rabbit myometrium, estrogens increase, while progesterone blunts neurohypophysial hormone receptors. However, the action of sex steroids on OT and V1 VP receptors differs in terms of the ED₅₀ and maximal effect. Therefore, at parturition, only OT receptors show a dramatic rise, while V1 VP receptors do not change, suggesting a major role for OT in labor. ET is a potent stimulator of uterine activity acting through specific receptors present on myometrial cells. These receptors as well as the endometrial localization of ET are modulated by sex steroids, indicating that ET might represent a paracrine regulator of uterine activity. In humans, OT but not V1 VP receptors increase as pregnancy progresses, confirming the primary relevance of OT in timing delivery.     

Quaternary structure of ATP synthases: Symmetry and asymmetry in the F1 moiety

It has been proposed that during ATP synthesis/hydrolysis F₁ ATPases experience a complex pattern of nucleotide binding and release during the catalytic cycle (binding change mechanism). This type of mechanism has implications that can be correlated with the structure of the enzyme. F₁-ATPases (stoichiometry ₃₃) are essentially a symmetrical trimer of pairs of the major subunits ( and ); the minor subunits (, and ) are in single copies and interact with the trimer in an asymmetrical fashion. The asymmetry introduced by the minor subunits has important structural and functional consequences: (1) it introduces differences between the potentially equivalent binding and catalytic sites in the major subunits, (2) it restricts the ways in which a binding change mechanism can occur, and (3) it governs the way in which the F₁ interacts with the (asymmetrical) F₀ sector.     

Aldosterone regulation of active sodium chloride transport in the lizard colon (Gallotia galloti)

Summary Bioelectrical parameters and unidirectional sodium and chloride fluxes were measured under voltageclamp conditions in groups of lizards submitted to single or chronic aldosterone treatment. Both acute (AT) and chronic (CT) treatment induced significant increases in the short-circuit current (I _sc), as well as in the mucosa-to-serosa (J _m-s ^Na ) and net sodium flux (J _net ^Na ). In AT tissues, aldosterone did not change net chloride flux (J _net ^Cl ) but did so in CT tissues. Amiloride reduced the aldosterone-increased I _sc in AT and CT tissues, inhibited J _net ^Na in AT tissues and abolished it in CT colons. J _net ^Cl was also reduced by the diuretic in the group of AT colons, whereas no changes were observed in the CT tissues. Addition of luminal DIDS reduced Na⁺ absorption and totally inhibited Cl^- absorption in the AT tissues, but did not change I _sc. However, in CT tissues neither Na⁺ nor Cl^- transport were affected by DIDS. A good relationship between I _sc and J _m-s ^Na was apparent after DIDS treatment in AT tissues. In this group, simultaneous addition of DIDS and amiloride totally abolished J _net ^Na and reduced I _sc to untreated control values. Addition of serosal ouabain abolished I _sc and Na⁺ absorption in AT and CT colons, but Cl^- absorption was only altered in AT tissues. These results support the hypothesis that aldosterone induces an electrogenic, amiloride-sensitive sodium absorption, and in a dose-dependent fashion suppresses electroneutral NaCl absorption in the lizard colon.Abbreviations AT acutely treated - CT chronically treated animals - DIDS 4-4-diisothiocyanatostibene-2-2-disulfonic acid - DMSO dimethylsulphoxide - G _t tissue conductance - I _sc short circuit current - PD transepithelial potential difference - SITS 4-acetamido-4-isothiocyanatostilbene-2-2-disulfonic acid - UC untreated controls Preliminary results of this paper were presented at the X ^th meeting of the European Intestinal Transport Group (EITG), Askov Hojskole, Denmark, 16–19 September 1990     

Culture and growth of Lessonia trabeculata (Phaeophyta,Laminariales) juvenile sporophytes in La Herradura de Guayacan Bay,northern Chile

Lessonia trabeculata is one of the major kelps found along the northern coast of Chile. In addition to its ecological and economic importance, L. trabeculata may be severely affected by environmental disturbances such as El Níño, which during 1982–1983 cleared wide areas along the coast of Peru and Chile. The main goal of this work was to mass culture L. trabeculata and to observe the growth of sporophytes obtained in the laboratory and cultured in the sea. Juvenile sporophytes obtained in the laboratory were attached between 1 and 6 m in depth. The linear growth rate, as blade elongation, was recorded weekly for seven months. No significant differences (p < 0.05) were found in sporophyte blade linear growth at different depths. The best elongation growth rate was 7.5 ± 1.6 mm d^–1 at 3 m during March. This preliminary work suggests that L. trabeculata follows an annual growth cycle similar to that of other Laminariales with a high rate of blade elongation during the summer and decreasing towards autumn. This species can be considered a potential candidate for aquaculture to increase the availability of raw material and aid in repopulation of overexploited areas.     

The origin of the membrane convolute in degranulating platelets. A comparative study of normal and "gray" platelets

Thrombin-stimulated normal platelets contain a membrane system of dilated channels with openings to the exterior. Whether these membranes originate from the surface connected system (SCS), the alpha-granules or internalized portions of the plasmalemma has not yet been defined. The present study traces in series of ultrathin sections the rearrangement of these membranes during shape change, degranulation and internalization of surface membranes in washed normal and "gray" platelets upon the stimulation with thrombin (1 IU/ml). Cationized ferritin (CF) was used as a surface marker in order to recognize internalized portions of the plasmalemma. Within the first seconds after stimulation, both normal and gray platelets changed their shape by extrusion of the SCS membranes. Simultaneously they started to internalize surface membrane and formed surface membrane invaginations closely attached to the outer rim of the cytoskeletal sphere which developed during the internal contraction. CF was internalized in these invaginations. CF was not observed within the system of dilated channels of stimulated platelets, however. Thrombin-stimulated gray platelets showed a markedly reduced number of dilated channels or none at all. This observation may be due to the fact "gray" platelets are deficient in alpha-granules. It is concluded that the dilated system of membranes in degranulated normal platelets originates from membranes of the alpha-granules which have performed compound exocytosis.     

Comparison of two molecular species of ethanolamine plasmalogen in multiple sclerosis and normal myelin

A TLC procedure which resolves two molecular species of ethanolamine plasmalogen, Pl-PE-1 and Pl-PE-2, was used to compare the ratio of these two species in myelin isolated from normal appearing white matter from brains of 17 multiple sclerosis (MS) patients, 17 normal (N) individuals, 1 patient with subacute sclerosing panencepha itis (SSPE) and 1 patient with a non-demyelinating neurological disease (OND). One of these species (Pl-PE-2) has been reported to be unique to myelin and has primarily 181 in both the 1 and 2 positions of glycerol. The other species (Pl-PE-1) is also present in other membranes and has primarily a saturated chain in the 1 position and a polyunsaturated chain in the 2 position. The Pl-PE-1 to Pl-PE-2 ratio was quantitated by scanning the plates with a densitometer. The ratio was similar to normal in most of the MS samples, 0.88±0.09, but was much less than normal in 4 of the MS samples and the SSPE sample. This is attributed to increased decomposition or hydrolysis of Pl-PE-1 relative to Pl-PE-2 at some stage, either during the disease process or due to post-mortem decomposition. Although the reason for the enhanced decomposition of Pl-PE-1 is not known it suggests that Pl-PE-2 is more stable chemically. This may be related to the unique occurrence of Pl-PE-2 in myelin.     

Structural regularities in tetraether lipids of Caldariella and their biosynthetic and phyletic implications

Individual di(biphytanyl) diglycerol tetraether lipids from thermoacidophile archaebacteria of the Caldariella series, with differently cyclized biphytanyl components, are separated and shown to have structures 8–12, with the glycerol and biphytanyl components demonstrably both antiparallel and with partial assignments of stereochemistry. Tetraethers with alternative arrangements of the components are absent. The structures allow previous observations on these and related lipids to be rationalized both biosynthetically and phyletically.