Central transmural venous pressure and plasma arginine vasopressin during negative pressure breathing in man

After overnight food and fluid restriction, 8 normal healthy males were examined in the upright sitting position before (prestudy), during and after (recovery) negative pressure breathing (NPB) with a pressure (P = difference between airway pressure and barometric pressure) of -9.6 +/- 0.5 to -10.4 +/- 0.4 mm Hg for 30 min. Plasma arginine vasopressin (pAVP) did not change significantly comparing prestudy with 10 and 30 min of NPB or comparing recovery with NPB at 10, 20 or 30 min. However, at 20 min of NBP, pAVP was slightly lower than at prestudy (p less than 0.05). Central venous pressure (CVP) decreased significantly during NPB, and central transmural venous pressure (CVP-P) increased significantly from -0.9 +/- 0.8 mm Hg to 3.8 +/- 0.7, 4.3 +/- 0.7 and 4.5 +/- 0.6 mm Hg (p less than 0.001) after 10, 20 and 30 min, respectively. Systolic, diastolic and mean arterial pressure and heart rate did not change significantly during NPB. Diuresis, natriuresis, kaliuresis, osmotic excretion and clearance were slightly increased during the recovery hour after NPB compared to prestudy, while urine osmolality decreased during NPB (n = 6). However, none of these changes were significant. There was no significant correlation between CVP-P and pAVP. In conclusion, -10 mm Hg NPB for 30 min in upright sitting subjects did not change pAVP consistently, while CVP-P was significantly increased and HR and arterial pressures were unchanged. This lends support to the concept that arterial baroreceptors and not cardiopulmonary mechanoreceptors are of importance in regulating AVP secretion in man.     

Germination,reproduction and interference in the amphicarpic annual Emex spinosa (L.) Campd

Summary A comparison was made of the dimorphic subterranean and aerial achenes of the annual Emex spinosa (L.) Campd. Subterranean achenes were less dormant, had a higher percentage of viability, germinated at a faster rate, were less temperature-dependent in germination and produced larger seedlings than aerial achenes. Subterranean achenes germinated, equally well in light or dark but aerial achenes had a strong light requirement. There was a linear relationship between numbers of weight of aerial achenes and plant size in the field. More resources were allocated to reproduction in plants restricted in size because of environmental conditions. Subterranean achene production was less affected than aerial by density, nitrogen levels, varying field conditions and interference between plants grown, from subterranean and aerial achenes. In mixtures of such plants, those from subterranean achenes had larger leaf area and stems and more aerial achenes. These differences were not apparent in monocultures by the time of harvest. Seed dimorphism is more likely in short-lived fugitive species and the different roles associated with dimorphism (persistence in situ versus dispersal in E. spinosa) are seen as an ecological advantage in such species.     

Further evidence for heterogeneity of glucose-6-phosphate dehydrogenase deficiency in Papua New Guinea

Summary Four new G6PD variants have been characterized in individuals from Papua New Guinea. This study demonstrates that the previously reported Markham variant and the newly characterized Salata variant may be widely distributed in Papua New Guinea. The data presented here together with those of previously published studies demonstrate a degree of heterogeneity of G6PD deficiency that is much higher than that in other regions of the world where G6PD deficiency is common.     

Calcium ion stimulated endogenous protein kinase catalyzed phosphorylation of basic proteins in myelin subfractions and myelin-like membrane fraction from rat brain

Polypeptide composition and endogenous phosphorylation were investigated in the subfractions of rat brain myelin isolated by either discontinuous or continuous sucrose density gradient centrifugation of myelin. Similarly, a myelin-like membrane fraction (SN4) was also studied. Observations were made that strongly indicated the presence of a calcium-stimulated protein kinase in a highly purified myelin preparation and which exclusively phosphorylated myelin basic proteins of the membrane preparation. Adenosine cyclic 3',5'-phosphate (cAMP) stimulated kinase on the other hand was found to be considerably enriched in the myelin-like membrane fraction. Although this latter enzyme is also capable of phosphorylating the basic proteins, its effect was at least 5 times weaker compared to the calcium-stimulated myelin protein kinase. Within the gradient subfractions there appeared a close relation between the amount of basic proteins and their calcium-stimulated phosphorylation; a similar relationship, however, was not obtained in the case of cAMP-dependent phosphorylation of myelin basic proteins. The former (i.e., Ca2+-stimulated phosphorylation) was found to require a protein factor that functionally resembled calmodulin. The results thus raises an interesting possibility of the presence of calmodulin-like proteins and a calcium-stimulated protein kinase in adult myelin membrane from mammalian brain, both of which have been hitherto unrecognized constituents of myelin membranes.     

Synthesis of novel acetylene-containing amino acids

Summary.  Novel synthetic procedures for the modification of non-proteinogenic acetylene-containing amino acids have been developed. The functionalization either proceeds via zinc/copper-mediated introduction of alkyl substituents, or via tungsten-catalyzed ring-closing alkyne metathesis reactions. Received March 28, 2002 Accepted October 3, 2002 Published online December 18, 2002 Acknowledgements These investigations are supported (in part) by the Netherlands Research Council for Chemical Sciences (CW) with financial aid from the Netherlands Technology Foundation (STW). Authors' address: Floris P. J. T. Rutjes, Prof. Dr., Department of Organic Chemistry, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands, E-mail: rutjes@sci.kun.nl  2, selected data: ¹H NMR (300 MHz, CDCl₃) δ 5.32 (d, J = 7.7 Hz, 1H), 4.44–4.40 (m, 1H), 3.76 (s, 3H), 2.75–2.73 (d, J = 5.0 Hz, 2H), 1.44 (s, 9H); ¹³C NMR (75 MHz, CDCl₃) δ 171.0, 155.0, 80.3, 74.6, 52.6, 51.9, 41.7, 28.3, 24.0; mp = 55°C.  Typical procedure for 5: zinc dust (116 mg, 1.408 mmol) was weighed into a 20 mL flask, which was repeatedly evacuated (with heating using a heat gun) and flushed with argon. Dry DMF (0.5 mL, distilled from CaH₂) and 1,2-dibromoethane (9.2 μL, 0.106 mmol) were added and the flask was heated at 80°C for 40 min. The reaction mixture was allowed to cool to room temperature, trimethylsilyl chloride (4 μL, 0.035 mmol) was added and the resulting mixture was stirred vigorously for a further 30 min under argon. Iodocyclohexane (69 μl, 0.528 mmol) was added and stirred at room temperature for 3 h more after which stirring was ceased to settle the zinc. CuCN (41 mg, 0.458 mmol) and LiCl (40 mg, 0.915 mmol) were heated to 150°C for 2 h and cooled to room temperature. Addition of DMF (1 mL) formed a soluble CuCN·2LiCl complex within 5 min. After cooling the Cu-complex to −15°C, the organozinc reagent was added dropwise followed by the bromoacetylene 2 (116 mg, 0.352 mmol). The mixture was allowed to stir overnight at room temperature. Water was added and the suspension was extracted using heptane, washed with brine, dried (MgSO₄) and concentrated. Purification using flash column chromatography (10% EtOAc in heptane) yielded 5 (100 mg, 81%) as a colorless oil. 5: IR ν 3355, 2929, 2852, 2359, 2337, 1749, 1717, 1498, 1447, 1365, 1251, 1181, 1060; ¹H NMR (300 MHz, CDCl₃) δ 5.28 (d, J = 7.7 Hz, 1H), 4.43–4.38 (m, 1H), 3.73 (s, 3H), 2.69–2.63 (m, 2H), 2.13 (m, 1H), 1.73–1.22 (m, 10H), 1.43 (s, 9H); ¹³C NMR (75 MHz, CDCl₃) δ 171.4, 155.0, 88.1, 79.9, 73.8, 52.3, 32.7, 32.7, 28.8, 28.2, 25.8, 24.6, 23.1; HRMS (EI): calculated for C₁₇H₂₇NO₄ 309.1940, found 309.1937.  A solution of the tungsten catalyst (7 mg, 10 mol%) in C₆H₅Cl (2 mL) was treated with a solution of 14 (49.0 mg, 0.120 mmol) in C₆H₅Cl (5.0 mL) under an argon atmosphere and the resulting mixture was heated at 80°C for 3 h. Evaporation followed by flash column chromatography (80% EtOAc in heptane) afforded 15 (21.0 mg, 50%; 64% after correction for starting material) and 14 (16 mg, 33%) as colorless oils. 15: [α]_D =–14.6 (c = 1, CH₂Cl₂); IR ν 3313, 2931, 2865, 2249, 1744, 1667, 1520, 1366, 1170; ¹H NMR (400 MHz, CDCl₃) δ 7.14 (d, J = 8.7 Hz, 1H), 6.08 (d, J = 8.3 Hz, 1H), 4.78 (q, J = 6.8 Hz, 1H), 4.27 (q, J = 7.9 Hz, 1H), 3.73 (s, 3H), 2.17–2.15 (m, 4H), 2.07–1.96 (m, 2H), 1.79–1.52 (m, 4H), 1.45 (s, 9H), 0.89–0.83 (m, 2H); ¹³C NMR (100 MHz, CDCl₃) δ 173.2, 171.8, 155.8, 80.4, 80.2, 79.3, 53.8, 52.5, 51.2, 32.8 (2×), 28.1, 24.6, 24.2, 18.3 (2×); HRMS (EI): calculated for C₁₈H₂₈N₂O₅     

Biosynthesis of rat insulin-like growth factor II. I. Immunochemical demonstration of a approximately 20-kilodalton biosynthetic precursor of rat insulin-like growth factor II in metabolically labeled BRL-3A rat liver cells

BRL-3A rat liver cells synthesize mature 7484-dalton rat insulin-like growth factor II (rIGF-II) as a approximately 22-kDa precursor, presumably prepro-rIGF-II. In the present study, we have biosynthetically labeled intact BRL-3A cells with [35S]cysteine and immunoprecipitated cell lysates and media with antisera to rIGF-II. A approximately 20-kDa protein was identified in immunoprecipitates of cell lysates having properties consistent with pro-rIGF-II. The approximately 20-kDa protein is precipitated by immune sera but not by nonimmune serum. Its immunoprecipitation is specifically inhibited by unlabeled rIGF-II but not by insulin. It is not precipitated from labeled lysates of a subclone of BRL-3A cells (BRL-3A2) that does not synthesize rIGF-II. The approximately 20-kDa protein is rapidly labeled intracellularly (10 min) but is not detected in BRL-3A media. In pulse-chase experiments, radioactivity in the approximately 20-kDa protein disappears during the chase and appears, at later times, in specifically immunoprecipitated approximately 19-, approximately 10-, approximately 8-, and approximately 7-kDa proteins in media and, to a limited extent, intracellularly. A protein with electrophoretic mobility identical to that of the approximately 20-kDa protein observed in cell lysates is immunoprecipitated from 35S-proteins whose synthesis is directed by BRL-3A RNA in a reticulocyte lysate cell-free translation system supplemented with microsomal membranes, and presumably arises by cotranslational removal of the signal peptide from approximately 22-kDa prepro-rIGF-II. Processing of the approximately 20-kDa protein in intact BRL-3A cells to intermediate and mature rIGF-II species appears to occur at the time of secretion and/or shortly thereafter, with the different forms appearing at approximately the same time.     

Separation of metabolically radiolabeled O-methylmannitols and O-methylfucitol by reverse-phase high-performance liquid chromatography: applications to animal cell oligosaccharide structural analysis

Reverse-phase high-performance liquid chromatography was utilized to separate efficiently and rapidly a standard mixture of various radiolabeled O-methylated mannitols and O-methylfucitol commonly encountered when vertebrate asparagine-linked oligosaccharides are subjected to permethylation, hydrolysis, and reduction with NaBH4. The following reduced, radioactive O-methylhexitols were resolved: 2,4-, 3,4-, and 3,6-di-O-methylmannitols; 3,4,6-tri-O-methylmannitol, 2,3,4-tri-O-methylfucitol, and 2,3,4,6-tetra-O-methylmannitol. To demonstrate the utility of this separation method in the analysis of metabolically radiolabeled asparagine-linked oligosaccharides, mouse lymphoma BW 5147 cells were metabolically radiolabeled with [2-3H]mannose and their glycopeptides prepared by Pronase digestion and fractionated by serial chromatography on immobilized lectins. Each fraction was subjected to methylation and hydrolysis, the released monosaccharides were reduced, and the radioactive O-methylhexitols were separated by reverse-phase HPLC. The relative amounts of the O-methylhexitols in each glycopeptide fraction analyzed were similar to those values determined by a combination of other separation systems.     

Recent advances in identifying the functions of gangliosides

The recent development of several new approaches has proven extremely useful in identifying functions for gangliosides, the sialic-acid containing glycosphingolipids. The first is the incorporation of exogenous gangliosides into the plasma membrane of ganglioside-deficient cells. Using this approach, specific gangliosides have been identified as the receptors for certain bacterial toxins and viruses and as important factors in the organization of fibronectin into an extracellular matrix. The second approach has been a ligand blotting technique which allows detection of ganglioside-binding proteins such as toxins and antibodies. Gangliosides are separated by thin-layer chromatography and overlain with the protein of interest. Specific binding of the ligand to gangliosides can then be detected by either direct or indirect methods. The third approach is the use of the B or binding subunit of cholera toxin as a specific probe for endogenous plasma membrane ganglioside function. The ability of the B subunit to alter the growth of cells directly demonstrates a role for gangliosides as biotransducers of signals for the regulation of cell growth.