Cerebrovascular Occlusive Disease—Experience with Panarteriography in 300 Consecutive Cases

Three hundred patients with cerebrovascular occlusive disease have had cerebral angiographic examination at the Veterans Administration Hospital, San Francisco, in the last five years. The present technique consists of preliminary visualization of the aortic arch and the major extracranial branches, followed by selective study of the subclavian and carotid arteries as necessary for evaluation of the intracranial circulation.Nine major complications occurred (an over-all incidence of 3 per cent). Two patients died after angiography and seven had major neurologic deficits persisting for more than 24 hours. Three of these patients had permanent damage, but four recovered completely.One-third of the patients had extracranial disease and one-third had intracranial disease. No significant lesion was found in the remainder. In the 212 patients with lesions, multiple lesions were common, the average number being three. Six patients had brain tumors and five had aneurysms.The mechanism of the stroke could be ascertained readily in most of the patients, but the extent of the disease and the resulting symptoms varied considerably. Several patients with occlusion of most of the cerebral vessels had minimal symptoms, while others had catastrophic symptoms but only minimal findings at arteriography.     

Regulation of Gi and Go by mastoparan, related amphiphilic peptides, and hydrophobic amines. Mechanism and structural determinants of activity

Mastoparan (MP), a cationic, amphiphilic tetradecapeptide, stimulates guanine nucleotide exchange by GTP-binding regulatory proteins (G proteins) in a manner similar to that of G protein-coupled receptors. 1) MP stimulated exchange by isolated G protein alpha subunits and alpha beta gamma trimers. Relative stimulation was greater with alpha beta gamma trimers and beta gamma subunits could increase net MP-stimulated activity. 2) MP action was enhanced by reconstitution of trimeric G protein into phospholipid vesicles. Hill coefficients for activation were 2-4. The membrane-bound alpha-helical conformation of MP appeared to be the activating species. 3) MP blocked the ability of Go to increase the affinity of muscarinic receptors for agonist ligands, suggesting that MP and the receptor may compete for a common binding site on Go. 4) MP stimulated steady state GTPase activity at less than 1 microM Mg2+ and stimulated the dissociation of both GDP and guanosine 5'-O-(3-thiotriphosphate) at less than 1 nM Mg2+. Millimolar Mg2+ blocked the stimulatory effect of MP. Both high and low affinity Mg2+ binding sites are on the alpha subunit. 5) Increasing the amphiphilicity or hydrophobicity of MP enhanced its regulatory activity more than 2-fold and lowered the EC50 more than 10-fold. Several natural amphiphilic peptides also displayed modest stimulatory activity. 6) Benzalkonium chloride competitively antagonized the stimulation of Gi by MP but potently stimulated nucleotide exchange on Go. Because cationic, amphiphilic sequences on the cytoplasmic faces of receptors are required for G protein regulation, these findings suggest that nucleotide exchange on G proteins is regulated by the presentation of multiple cationic structures on the inner face of the plasma membrane.     

A novel sialidase which releases 2,7-anhydro-alpha-N-acetylneuraminic acid from sialoglycoconjugates

The leech (Macrobdella decora) was found to contain two sialic acid-cleaving enzymes: an ordinary sialidase and a novel sialic acid-cleaving enzyme. This novel enzyme released 2,7-anhydro-alpha-N-acetylneuraminic acid (Neu2,7-anhydro5Ac) instead of alpha-N-acetylneuraminic acid (Neu5Ac) from 4-methylumbelliferyl-Neu5Ac, glycoproteins, and gangliosides. We have partially purified this novel sialidase from M. decora. We have also isolated Neu2,7-anhydro5Ac released from 4-methylumelliferyl-Neu5Ac and whale nasal keratan sulfate in pure form. The novel sialidase produced Neu2,7-anhydro5Ac only from sialoglycoconjugates, but not from free Neu5Ac. The structure of Neu2,7-anhydro5Ac produced by the novel sialidase was established by chemical analysis, mass spectrometry, and NMR spectroscopy. NMR analysis showed that instead of the original 2C5 conformation, the pyranose ring of Neu2,7-anhydro5Ac was in the 5C2 conformation, which makes the formation of the 2,7-anhydro bridge possible.     

Recent insights in phosphatidylinositol signaling

Studies of phosphatidylinositol signaling pathways are entering a new phase in which molecular genetic techniques are providing powerful tools to dissect the functions of various metabolites and pathways. Studies with phospholipase C are most advanced and clearly indicate that phosphatidylinositol turnover is critical for vision in Drosophila and cell proliferation in various cultured cells. Expression of cDNA constructs and microinjection of PLC or antibodies against it clearly establish a role for PtdIns signaling distinct from its role in calcium mobilization and protein kinase C activation. The importance of inositol cyclic phosphates is also beginning to be realized from the study of cyclic hydrolase using similar techniques. Elucidation of the function of the 3-phosphate inositol phospholipid pathway awaits similar studies. The recent cDNA cloning of inositol monophosphatase (Diehl et al., 1990), Ins(1,4,5)P3 3-kinase (Choi et al., 1990), and inositol polyphosphate 1-phosphatase (York and Majerus, 1991) should provide tools to define further the cell biology of the phosphatidylinositol signaling pathway.     

Tissue factor and its extracellular soluble domain: the relationship between intermolecular association with factor VIIa and enzymatic activity of the complex.

We find that the isolated, extracellular domain of tissue factor (TF1-218; sTF) exhibits only 4% of the activity of wild-type transmembrane TF (TF1-263) in an assay that measures the conversion of factor X to Xa by the TF:VIIa complex. Further, the activity of sTF is manifest only when vesicles consisting of phosphatidylserine and phosphatidylcholine (30/70 w/w) are present. To determine whether the decreased activity results from weakened affinity of sTF for VIIa, we studied their interaction using equilibrium ultracentrifugation, fluorescence anisotropy, and an activity titration. Ultracentrifugation of the sTF:VIIa complex established a stoichiometry of 1:1 and an upper limit of 1 nM for the equilibrium dissociation constant (Kd). This value is in agreement with titrations of dansyl-D-Phe-L-Phe-Arg chloromethyl ketone active site labeled VIIa (DF-VIIa) with sTF using dansyl fluorescence anisotropy as the observable. Pressure dissociation experiments were used to obtain quantitative values for the binding interaction. These experiments indicate that the Kd for the interaction of sTF with DF-VIIa is 0.59 nM (25 degrees C). This value may be compared to a Kd of 7.3 pM obtained by the same method for the interaction of DF-VIIa with TF1-263 reconstituted into phosphatidylcholine vesicles. The molar volume change of association was found to be 63 and 117 mL mol-1 for the interaction of DF-VIIa with sTF and TF1-263, respectively. These binding data show that the sTF:VIIa complex is quantitatively and qualitatively different from the complex formed by TF1-263 and VIIa.     

Sexual asymmetry in hermaphroditic plants

Populations of hermaphroditic plants show variation in ovule and pollen production, so that the implicit assumption that hermaphrodite individuals function half as male and half as female is not valid. Such variation in gamete production results in sexual asymmetry, defined as nonconstant ratios of pollen to ovule production among plants of a population. This article reviews (1) some of the considerable amount of recent evidence for sexual asymmetry and non-equal malelfemale sex functioning in hermaphroditic seed plants, and (2) some models of asymmetry and sex functioning, with emphasis on their biological and evolutionary relevance.