Shock Following Myocardial Infarction: A Clinical Survey of 140 Cases

All admissions for acute myocardial infarction to a metropolitan general hospital over a 10-year period have been reviewed. One hundred and forty patients developed complications meeting the criteria for cardiogenic shock. The mortality rate in this group of patients was 83%. The mortality rate in 95 patients who received treatment with intravenous noradrenaline was no different from that in 45 patients who did not receive this type of therapy (p = >0.8). Patients dying from cardiogenic shock were younger than those dying of other complications. Autopsy study of this group of shocked patients revealed a significantly lower incidence of previous healed myocardial infarction (p = <0.01).A decline in the annual incidence of cardiogenic shock was noted over the decade surveyed. It is suggested that this may be due to the earlier and more frequent use of intravenous noradrenaline. Despite the reduction in the incidence of shock, the annual mortality rate from myocardial infarction has remained unaltered.     

Binary phase diagram of hydrated dimyristoylglycerol-dimyristoylphosphatidylcholine mixtures

The thermotropic phase behavior of binary mixtures of dimyristoylphosphatidylcholine with dimyristoyl glycerol (DMPC-DMG) has been studied in aqueous dispersion by using differential scanning calorimetry and spin label electron spin resonance spectroscopy. Phase identifications have been made by means of ³¹P nuclear magnetic resonance spectroscopy and x-ray diffraction. The binary phase diagram of DMPC-DMG mixtures displays three regions corresponding to the existence of compounds (C1 and C2, respectively) with approximately 1:1 and 1:2 mol/mol DMPC:DMG stoichiometries. The first region displays immiscibility between DMPC and C1 in the low temperature lamellar phase and miscibility of the components in the fluid phase that is lamellar. The second region displays immiscibility between C1 and C2 in the low temperature phase that is lamellar, whereas the fluid phase is of the inverted hexagonal type (H_II). The third region displays immiscibility between C2 and DMG in the low temperature phase that is lamellar, whereas the fluid phase is isotropic. The presence of immiscible DMG in the low temperature phase of the third region is indicated by hysteresis in the temperature scans corresponding to conversion between the stable and metastable crystalline polymorphs. Analysis of the first region of the phase diagram using regular solution theory further demonstrates the existence of a DMPC:DMG complex with approximately 1:1 stoichiometry and provides parameters for the nonideality of mixing in the fluid phase.     

Thorns as induced defenses: experimental evidence

Summary We report evidence from controlled experiments that long straight thorns deter herbivory by browsers. Cut branches of three woody species that had their thorns removed suffered significantly greater herbivory by a tethered goat than did paired intact branches. Branches on living Acacia seyal plants that had their thorns removed suffered significantly greater herbivory by a wild population of free-ranging giraffes than did intact branches on the same plants. These differences in herbivory resulted in long term losses of branch length in clipped as opposed to control branches. In addition, branches within reach of giraffes produced longer thorns and a greater density of thorns than did higher branches. These results imply that increased thorn length is an induced defense.No significance should be attached to order of authorship     

Whole-cell and single-channel currents across the plasmalemma of corn shoot suspension cells

Summary Whole-cell sealed-on pipettes have been used to measure electrical properties of the plasmalemma surrounding protoplasts isolated from Black Mexican sweet corn shoot cells from suspension culture. In these protoplasts the membrane resting potential (V _m ) was found to be –59±23 mV (n=23) in 1mm K _o ^– . The meanV _m became more negative as [K^–] _o decreased, but was more positive than the K⁺ equilibrium potential. There was no evidence of electrogenic pump activity. We describe four features of the current-voltage characteristic of the plasmalemma of these protoplasts which show voltagegated channel activity. Depolarization of the whole-cell membrane from the resting potential activates time- and voltage-dependent outward current through K⁺-selective channels. A local minimum in the outward current-voltage curve nearV _m =150 mV suggests that these currents are mediated by two populations of K⁺-selective channels. The absence of this minimum in the presence of verapamil suggests that the activation of one channel population depends on the influx of Ca²⁺ into the cytoplasm. We identify unitary currents from two K⁺-selective channel populations (40 and 125 pS) which open when the membrane is depolarized; it is possible that these mediate the outward whole-cell current. Hyperpolarization of the membrane from the resting potential produces time- and voltage-dependent inward whole-cell current. Current activation is fast and follows an exponential time course. The current saturates and in some cases decreases at membrane potentials more negative than –175 mV. This current is conducted by poorly selective K⁺ channels, whereP _Cl/P _K=0.43±0.15. We describe a low conductance (20 pS) channel population of unknown selectivity which opens when the membrane is hyperpolarized. It is possible that these channels mediate inward whole-cell current. When the membrane is hyperpolarized to potentials more negative than –250 mV large, irregular inward current is activated. A third type of inward whole-cell current is briefly described. This activates slowly and with a U-shaped current-voltage curve over the range of membrane potentials –90<V _m <0 mV.     

Local anesthetics: A new class of partial inhibitors of mitochondrial ATPase

The following characteristics are reported for mitochondrial ATPase prepared by the chloroform extraction method: (1) The pH optimum for enzyme activity is at 8.0. (2) The neutral anesthetic benzocaine inhibits the enzyme at all pH values. (3) Reciprocal plots of 1/v versus 1/[ATP] show that inhibition by lidocaine, tetracaine, dibucaine, and chlorpromazine is noncompetitive; slope and intercept replots are hyperbolic, showing that the inhibition is partial rather than complete.     

Steroid antagonism of the ‘hypertensinogenic’ activity of 9α-fluoroprednisolone

We have previously reported that adrenocortical steroids raise blood pressure by a ‘hypertensinogenic’ mechanism of action which is not simply related to their classical ‘mineralocorticoid’ or ‘glucocorticoid’ actions. This study presents evidence for specific antagonism of this ‘hypertensinogenic’ activity. The effects of separate IV infusions of prednisolone (P) 100 mg/d and 9α-fluoro-prednisolone (9αF-P) 0.6 mg/d on mean arterial pressure (MAP), plasma [K], plasma [glucose] and urinary NA excretion (UNaV) after 2 days were studied in sheep. In the same group of sheep which received P alone for 2 days, 9αF-P was given for a further 2 days while continuing the P infusion (P + 9αF-P). P alone had no effect on MAP or plasma [K] or U_NaV but increased plasma [glucose], effects which are characteristic of ‘glucocorticoid’ activity. 9αF-P alone increased MAP by 14 mmHg (P<0.001) and reduced plasma [K] and U_NaV but had no effect on plasma [glucose]. Thus 9αF-P exhibited both ‘hypertensinogenic’ and ‘mineralocorticoid’ activity. In the sheep which received the combined P + 9αF-P infusion, the increase in MAP normally produced by 9αF-P was blocked. Although pretreatment with P blocked the pressor effect of 9αF-P, it did not alter the ‘mineralocorticoid’ effects, namely hypokalaemia and urinary Na retention, produced when 9αF-P was infused alone. These results provide further evidence for our concept of a ‘hypertensinogenic’ class of steroid activity and are the first demonstration of specific antagonism of steroid induced hypertension.     

Selectivity of lipid-protein interactions

The spin label ESR and intrinsic fluorescence quenching methods of determining the selectivity of interactions of lipids with integral membrane proteins are summarized. The selectivity patterns of phospholipids, fatty acids, and steroids are reviewed for a variety of integral proteins. Where appropriate, correlations are established with biochemical assays of the effects of specific lipids on enzymatic activity and transport function.     

The evolution of migration and some life history parameters in marine fishes

Synopsis Migration is a common phenomenon in marine fishes but the consequences with respect to life history variation have been little explored. Migration both influences the evolution of other traits and is contigent upon the evolution of other behavioural and demographic characters. The interaction between such factors is illustrated by considering the relationship between the cost of migration in relation to fecundity and the advantages and disadvantages of schooling, a phenomenon hypothesized to favour the evolution of migration. These analyses predict that migratory species will be relatively large, mature late and at a relatively large size and grow relatively fast. Data from north temperate marine fish support these predictions.     

[3H]Arachidonic acid metabolism in rat brain minces: Effects of nucleotide triphosphates,CDPcholine and CMP

Rat brain minces were used to investigate the effects of nucleotides on the metabolism of arachidonic acid in nerve tissue. Brain free fatty acids, neutral lipids and phospholipids, were radiolabeled in vivo following intracerebral injection of [³H]arachidonic acid. Minces were prepared from the radiolabeled cerebra and were incubated in a modified Krebs-Ringer buffer with and without various nucleotides. The incubation-induced accumulation of unesterified [³H]arachidonate was reduced in the presence of CDPcholine, ATP, CTP, GTP, and UTP. These nucleotides inhibited choline and inositol glycerophospholipid hydrolysis. They also reduced the amount of labeled diglycerides. However, CDPethanolamine had no effect on arachidonic acid metabolism in the mince preparation and CMP appeared to stimulate further hydrolysis of choline glycerophospholipids, resulting in increased accumulation of [³H]arachidonic acid and labeled diglycerides. We suggest that the production of unesterified [³H]arachidonate and labeled diglycerides is due to the involvement of more than one catabolic reaction, since the high energy nucleotides had similar effects on fatty acid accumulation, but different effects on phospholipid labeling.