Two types of hydrocarbon chain interdigitation in sphingomyelin bilayers

Vibrational Raman spectroscopic experiments have been performed as a function of temperature on aqueous dispersions of synthetic DL-erythro-N-lignoceroylsphingosylphosphocholine [C(24):SPM], a racemic mixture of two highly asymmetric hydrocarbon chain length sphingomyelins. Raman spectral peak-height intensity ratios of vibrational transitions in the C-H stretching-mode region show that the C(24):SPM-H2O system undergoes two thermal phase transitions centered at 48.5 and 54.5 degrees C. Vibrational data for fully hydrated C(24):SPM are compared to those of highly asymmetric phosphatidylcholine dispersions. The Raman data are consistent with the plausible model that the lower temperature transition can be ascribed to the conversion of a mixed interdigitated gel state (gel II) to a partially interdigitated gel state (gel I) and that the higher temperature transition corresponds to a gel I----liquid-crystalline phase transition. The observation of a mixed interdigitated gel state (gel II) at temperatures below 48.5 degrees C implies that biological membranes may have lipid domains in which some of the lipid hydrocarbon chains penetrate completely across the entire hydrocarbon width of the lipid bilayer.     

Autolysis of psychrophilic bacteria from marine fish.

Two psychrophillic bacterial isolates of marine fish origin unable to grow at 20 degrees C or above were found to be distinguishable on the basis of autolysis at elevated temperature in various buffer systems. Isolate OP2 exhibited autolysis at 30 degrees C and above, while isolate OP7 underwent autolysis only at 35 degrees C and above. Tris buffer at pH 7.0 and 8.0 and at 35 degrees C significantly protected isolate OP2 from autolysis and failed to do so with isolate OP7. At pH 5.0, suspension phosphate buffer resulted in significantly greater autolysis of both isolates than did suspension in succinate buffer.     

Compartmental analysis of the efflux of l-[3H]norepinephrine from isolated perfused rat lungs

Isolated rat lungs, pretreated with 100 microM pargyline and 100 microM U-0521 (3',4'-dihydroxy-2-methylpropriophenone) to block metabolism of norepinephrine (NE), were perfused with 0.3 microM 3H-labeled l-norepinephrine (1-[3H]-NE) for 30 min. Efflux samples were then collected for 30 min during washout of the tissue with amine-free Krebs solution. Compartmental analysis (nonlinear least-squares regression) of the efflux of tissue l-[3H]NE content vs. time indicates that NE is accumulated in a large slowly equilibrating compartment (t 1/2 = 58.15 +/- 6.84 min) in addition to distribution in the vascular (blue dextran tracer) and extracellular ([3H]sorbitol tracer) fluid compartments of the lung. Pretreatment of the lungs with 100 microM cocaine hydrochloride reduces the total l-[3H]NE space from 7.44 +/- 1.91 to 2.48 +/- 0.23 ml/g (P less than 0.05) by selectively decreasing the size of the slow NE compartment from 6.99 +/- 1.97 to 1.67 +/- 0.14 ml/g (P less than 0.05). The large size, cocaine sensitivity, and long efflux half time of this compartment suggest that neuronal uptake contributes to the pulmonary vascular inactivation of l-[3H]NE.     

Platelet immune complex interaction in pathogenesis of Kawasaki disease and childhood polyarteritis.

The role of platelets in the pathogenesis of vasculitis and the formation of coronary artery aneurysms was studied in 19 children with Kawasaki disease and five with polyarteritis. All patients with Kawasaki disease developed thrombocytosis in the third week of illness. The peak platelet count was significantly correlated (p less than 0.005) with the subsequent development of coronary artery aneurysms. The rise in platelet count was associated with the appearance in the circulation of a factor that induced aggregation and serotonin release in normal platelets. This factor was shown to be of high molecular weight, and its activity was lost at low pH--features suggestive of an immune complex. Immune complexes, detected by precipitation with polyethylene glycol, also appeared in the circulation as the platelet count increased. These complexes induced platelet aggregation, and there was a significant correlation (p less than 0.001) between the concentrations of IgG and IgA in the polyethylene glycol precipitated material and the platelet aggregating activity. Similar platelet aggregating activity was also detected in patients with polyarteritis but followed a different time course, persisting in the circulation for several months in association with continued disease activity. These findings imply that different mechanisms have a role in distinct phases of Kawasaki disease. The initial feverish phase (probably infective) is probably followed by an immune complex vasculitis that occurs when antibodies to the initiating agent appear in the circulation. The immune complexes aggregate platelets and induce release of serotonin. Platelet derived vasoactive mediators may increase vascular permeability and facilitate further deposition of complexes in the tissues.     

Antiepileptic effects of amphetamine may require GABA (benzodiazepine) activity

Secondary components of visual evoked potentials (slow negative wave-SNW, and photically-evoked sensory afterdischarge-SAD) are known to be precursors of experimentally activated wave-spike discharges, similar to wave-spikes of petit mal epilepsy. Both SNW and SAD may be potently suppressed wither by amphetamine or GABAergic compounds such as diazepam and sodium valproate. A hypothesis was tested in the present study, that amphetamine-induced suppression of wave-spike discharges may require GABA-benzodiazepine activity for its expression.Electrocortical activity was recorded and averaged in unrestrained albino rats with chronically implanted epicortical electrodes. SNW and SAD obtained in habituated rats in the predrug state were potently suppressed by amphetamine (1 mg/kg, i.p.). Fifteen minutes after amphetamine injection, a challenging drug (metrazol, picrotoxin, convulsant benzodiazepine, Ro 5-3663, or imidazodiazepine, Ro 15-1788) was administered intraperitoneally. Subconvulsive doses of metrazol (10 mg/kg) reversed amphetamine suppression; imidazodiazepine (20 mg/kg) and picrotoxin (1.5 mg/kg) reliably opposed the SNW suppression; convulsant benzodiazepine, Ro 5-3663 (2 mg/kg), showed modest and nonsignificant effect in the same direction. It is proposed that the antiepileptic potency of amphetamine may be associated with its ability, apparently via modulatory effect of norepinephrine, to facilitate the activation of benzodiazepine-GABA receptors.     

Analysis of cloned mRNA sequences encoding subfragment 2 and part of subfragment 1 of alpha- and beta-myosin heavy chains of rabbit heart

Two cardiac myosin heavy chain cDNA clones, pMHC alpha 252 and pMHC beta 174, were constructed using rabbit ventricular mRNA isolated from adult thyrotoxic and normal hearts, respectively. The complete DNA sequences of the 2.2- and 1.4-kilobase inserts of pMHC beta 174 and pMHC alpha 252, respectively, were obtained. The 736 amino acids specified by pMHC beta 174 begin 439 (1.3 kilobases) residues from the heavy chain NH2 terminus and include a 400-amino acid segment of subfragment 1 and the entire subfragment 2 region. Clone pMHC alpha 252 encodes 465 amino acids encompassing all of subfragment 2 and a portion of light meromyosin. Comparison of these two clones revealed extensive sequence overlap which included 1107 nucleotides specifying a 369-amino acid segment corresponding to subfragment 2. Within this region 78 (7%) base and 32 (8.7%) amino acid mismatches were noted. These differences were clustered within discrete regions, with the subfragment 1/subfragment 2 junctional region being particularly divergent. Structural differences between pMHC alpha 252 and pMHC beta 174 indicate that these two clones represent two similar but distinct myosin heavy chain genes whose expression is responsible for ventricular myosin heavy chain isoforms alpha and beta, respectively. The derived amino acid sequences of both clones exhibit extensive homology (greater than 81%) with sequences obtained by direct analysis of adult rabbit skeletal muscle myosin heavy chain protein. The sequences corresponding to the subfragment 2 region are consistent with an alpha-helical conformation with a characteristic 7-residue periodicity in the linear distribution of nonpolar amino acids. Conversely, subfragment 1 sequences specified by pMHC beta 174 suggest a folded highly irregular structure.     

Endogenous opioid peptides: do they mediate the acute antihypertensive action of clonidine in humans?

The involvement of endogenous opioid peptides in the antihypertensive action of acutely administered clonidine, a centrally acting adrenergic agonist, was studied in humans. Eight hypertensive subjects received clonidine 0.2 mg orally, naloxone 8 mg i.v. followed by a 0.13 mg/min infusion, and both drugs together on separate days. Clonidine resulted in a significant decrease in mean blood pressure, which was not affected by concomitant treatment with naloxone. Naloxone alone or with clonidine caused significant elevations in plasma aldosterone, not mediated by increased plasma renin activity. Plasma beta-endorphin was not increased after clonidine administration. In humans, the antihypertensive effects of acute clonidine administration do not appear to be mediated by the release or action of endogenous opioids.     

Changes in the concentration of metalloproteins in the blood plasma in hypoxia and hyperbaric oxygenation

Dynamics of hemoglobin, ceruloplasmin concentration, the changes of chemiluminescence in blood plasma and kinetics of rat erythrocyte heat denaturation during consequent exposition of high altitude hypoxia and hyperbaric oxygenation have been studied. Severe hypoxia causes the decrease of extraerythrocyte hemoglobin and oxidase activity of ceruloplasmin. Reoxygenation results in significant increase of blood plasma chemiluminescence with simultaneous increase of extraerythrocyte hemoglobin level and with modification of surface structure of the erythrocyte membranes. Possible pathways of activation of oxygen-dependent of free-radical processes during reoxygenation are discussed.     

Lack of endotoxin in Borrelia hispanica and Treponema pallidum

Borrelia hispanica from infected guinea pigs and Treponema pallidum from testicular syphilomas of rabbits were assayed for the presence of endotoxin with the Limulus lysate test. A suspension of Borrelia, containing 1.3 X 10(8) spirochetes/ml, was nonreactive both when it was tested as intact organisms, and when tested after disruption of the spirochetes by sonication. Eight different suspensions of treponemes, ranging from 0.6 X 10(9) to 3 X 10(9) treponemes/ml, were negative at a 1:10 dilution and were no more active than control suspensions of normal rabbit testes. Therefore, it was concluded that T. pallidum, as well as the Borrelia, possessed no endotoxin.