Long survival in acute myelogenous leukaemia: an international collaborative study.

A group of 82 adult patients with acute myelogenous leukaemia had survived in continuous first remission for more than three years was studied. These long-surviving patients were being treated at 12 referral centres in Europe and the USA, and they were compared with other patients with acute myelogenous leukaemia from 10 of these centres. There was no clear difference in the amount of induction chemotherapy or the time taken to achieve remission. Immunotherapy was not found to improve chances of long-term survival. The 82 patients were also compared with a group of 115 patients who had no appreciable difference in the number of blood or marrow myeloblasts between these two groups at presentation, but the long survivors had significantly higher initial platelet counts and were slightly younger. The long survivors also tended to have a lower total white cell count at presentation and lower granulocyte counts; there was no obvious explanation for these differences. Eight of the 82 patients relapsed from three to four years after remission and two (of 69 patients) after four to five year. Thereafter relapse was rare, and it seems likely that some of the 40 patients who have survived for five years or more are cured.     

Isolation of metabolically active Petite mutants of Kluyveromyces lactis, a petite-negative yeast

Summary Conditions under which complete cultures of the petite-negative yeast Kluyveromyces lactis can be converted to metabolically active petite mutants have been found. These mutants, which lack mitochondrial protein synthesis have been shown to be metabolically active by their ability to exclude the dye trypan blue. They appear to possess a functional protein synthesising system, which is sensitive to the inhibitor trichodermin. However, on transfer to solid nutrient medium, these mutants fail to grow normally, and give rise to microcolonies composed of up to a thousand cells. These colonies autolyse after several days.     

Valine-sensitive acetohydroxy acid synthases in Escherichia coli K-12: unique regulation modulated by multiple genetic sites.

Summary Spontaneous mutants (146) of Escherichia coli K-12 were selected that were resistant to inhibition of growth by 1.2 mM L-valine (Val^r). The Val^r isolates, containing acetohydroxy acid synthase resistant to feedback inhibition by L-valine (AHAS^r), were classed according to cotransduction of the mutation with leu. Several mutations resulting in an AHAS^r phenotype were found to be cotransducible with glyA. However, no mutations causing a Val^r phenotype were linked to ilv. AHAS activity was more closely examined in representatives of three classes of mutants with Val^r linked to leu, labeled ilv-660, ilv-661, and ilv-662. The ilvE503 allele in E. coli K-12, known to cause a two- to three-fold derepression of AHAS, was found to affect regulation of synthesis of both valine-sensitive AHAS (AHAS^s) and AHAS^r in the mutants containing ilv-660 and ilv-661, whereas it affected repression of AHAS^s, only, in the mutant containing ilv-662. Further, both AHAS^s and AHAS^r in the ilv-661 mutant were repressed by valine, whereas valine did not repress AHAS^r synthesis in the strain carrying ilv-660 and only partially repressed AHAS^r in the strain carrying ilv-662. Unexpectedly, AHAS^r synthesis in strains carrying ilv-660 or ilv-662 was repressible by leucine. The ilv-660 locus appears to be similar in position to ilvH and encodes a product that confers valine-sensitivity upon AHAS activity in the wild-type E. coli K-12. The ilv-660 and ilv-662 loci may normally encode products that influence both the feedback sensitivity of AHAS and control of AHAS biosynthesis.     

VESICULAR STORAGE AND RELEASE OF ACETYLCHOLINE IN TORPEDO ELECTROPLAQUE SYNAPSES

Abstract— The disposition of newly synthesized ACh subsequent to depletion of vesicular endogenous ACh by stimulation was studied in the electromotor nerve terminals of Torpedo marmorata using [³H]acetate as a precursor of ACh. Little vesicular [³H]ACh could be isolated from tissue immediately after stimulation at 1 Hz. After 3 h post-stimulation recovery the newly synthesized [³H]ACh is found predominantly in a subpopulation of vesicles distinct from the vesicles containing most of the endogenous poorly labelled ACh. Restimulation of the tissue causes release of highly labelled ACh with a specific radioactivity (SRA) comparable to that of the newly synthesized [³H]ACh in the highly labelled subpopulation of vesicles and significantly greater than the SRA of ACh in the main vesicular pool or the total tissue.     

Precipitation and 13C-NMR relaxation enhancement measurements of the interactions of bile acids with synthetic cationic bile acid derivatives, and with spin labelled fatty acids.

In an investigation of novel potential bile acid sequestrants, the affinities of the sodium salts of the glycine and taurine conjugates of naturally occurring bile acids (cholate, deoxycholate, chenodeoxycholate and lithocholate) for several cationic ammonium bile acid derivatives have been investigated by measurements of the extent to which the derivatives are able to precipitate the bile acids. This is roughly proportional to the lipophilicity of the interacting species. Thus, amino and ammonium derivatives of cholic acid do not precipitate taurocholate or glycocholate to any great extent, whereas ammonium derivatives of deoxycholate and lithocholate are much more effective. To complement the precipitation measurements, high resolution 13C-NMR has been applied to investigate the weaker interactions between the ammonium cholate derivative and glycocholate, glycodeoxycholate and glycochenodeoxycholate. Addition of either of the latter two bile acids to the cationic ammonium compound results in considerable broadening of the 13C resonances of both species, indicating the formation of relatively rigid structures. In addition, we have used T2 relaxation enhancement induced by spin-labelled fatty acids to examine the mechanism of interaction with bile acids of amphiphilic anions, which might compete with bile acids for sites on bile acid sequestrants. Low concentrations of 16-DOXY L-Stearate dramatically broaden the 13C-NMR resonances of deoxycholate carbons 19, 18 and 7 in particular, while 5-DOXY L-Stearate exerts much less specific effects. These results have been incorporated into a snapshot model of bile acid-fatty acid interactions.     

Type VI collagen microfibrils: evidence for a structural association with hyaluronan

Type VI collagen, a widespread structural component of connective tissues, has been isolated in abundance from fetal bovine skin by a procedure involving bacterial collagenase digestion under nonreducing, nondenaturing conditions and gel filtration chromatography. Rotary shadowing electron microscopic analysis revealed that the collagen VI was predominantly in the form of extensive intact microfibrillar arrays. These microfibrils were seen in association with hyaluronan, which was identified by its ability to bind the G1 fragment of cartilage proteoglycan. Treatment with highly purified hyaluronidase largely disrupted the collagen VI microfibrils into component tetramers, double tetramers, and short microfibrillar sections. Subsequent incubation of disrupted collagen VI in the presence of hyaluronan facilitated a partial repolymerization of the microfibrils. In vitro binding studies have also demonstrated that type VI collagen binds hyaluronan with a relatively high affinity. These studies demonstrate that a specific structural relationship exists between type VI collagen and hyaluronan. This association is likely to be of primary importance in the growth and remodeling processes of connective tissues.     

A tyrosine-derived free radical in apogalactose oxidase

Oxidation of apogalactose oxidase with ferricyanide leads to the formation of a stable free radical exhibiting distinctive optical absorption and EPR spectral features. The radical is associated with absorption in both near-UV and near-IR spectral regions, and its EPR spectrum is characteristic of an aromatic free radical with gav = 2.005. Reconstitution of both the apoenzyme and the free radical-containing form with copper substantially restores both the absorption spectra and the catalytic activity of the active enzyme, indicating that the preparation of the radical species does not significantly damage the protein. The absence of a free radical EPR signal in reconstituted and activated galactose oxidase containing nearly stoichiometric copper suggests the radical is an active site species relating to the free radical-coupled copper site previously proposed for this enzyme. Isotopic labeling experiments demonstrate that the radical derives from a tyrosine residue. The distinctive spectra associated with this radical indicate an environment which is different from that associated with the tyrosyl phenoxyl sites in other free radical enzymes.     

2-pyrone-4,6-dicarboxylic acid, a catabolite of gallic acids in Pseudomonas species.

2-Pyrone-4,6-dicarboxylate hydrolase was purified from 4-hydroxybenzoate-grown Pseudomonas testosteroni. Gel filtration and electrophoretic measurements indicated that the preparation was homogeneous and gave a molecular weight of 37,200 for the single subunit of the enzyme. Hydrolytic activity was dependent upon a functioning sulfhydryl group(s) and was freely reversible; the equilibrium position was dependent upon pH, with equimolar amounts of pyrone and open-chain form present at pH 7.9. Since the hydrolase was strongly induced when the nonfluorescent organisms P. testosteroni and P. acidovorans grew with 4-hydroxybenzoate, it is suggested that 2-pyrone-4,6-dicarboxylate is a normal intermediate in the meta fission degradative pathway of protocatechuate. Laboratory strains of fluorescent pseudomonads did not metabolize 2-pyrone-4,6-dicarboxylate, but a strain of P. putida was isolated from soil that utilized this compound for growth; the hydrolase was then induced, but it was absent from extracts of 4-hydroxybenzoate-grown cells that readily catabolized protocatechuate by ortho fission reactions. 2-Pyrone-4,6-dicarboxylic acid was the major product formed when gallic acid was oxidized by purified protocatechuate 3,4-dioxygenase. Protocatechuate 4,5-dioxygenase gave only the open-chain ring fission product when gallic acid was oxidized, but the enzyme attacked 3-O-methylgallic acid, giving 2-pyrone-4,6-dicarboxylic acid as the major product. Cell suspensions of 4-hydroxybenzoate-grown P. testosteroni readily oxidized 3-O-methylgallate with accumulation of methanol.     

Identification of a Cholinergic-Specific Antigen Chol-1 as a Ganglioside

Abstract: An antiserum specific for cholinergic terminals was used to identify an antigen conserved between Elasmobranchs and mammals. Immunohistochemistry and a cytotoxicity test were used to assay the binding of antibody to mammalian terminals. Torpedo electric organ gangliosides totally abolished antibody binding. The highest inhibitory activity was associated with a single polysialoganglioside band on TLC plates. Neuraminidase altered the migration of the inhibitory activity on TLC plates. Antibody binding was inhibited by ganglioside fractions derived from chicken and mammalian brains. A summary of those tissues in which the antigen has been detected is presented. The possible function of the antigen is discussed.     

Some properties of human erythrocyte pyrimidine 5'-nucleotidase

In haemolysates human erythrocyte pyrimidine 5'-nucleotidase had a single optimum at pH 7.2 with CMP and 6.75 with UMP as substrate. The purified enzyme showed two pH optima at pH 6.25 and 7.2 with UMP as substrate. The enzyme was inhibited by both its products - inorganic phosphate and pyrimidine nucleoside. The inhibition by inorganic phosphate appeared to be non-competitive with Ki = 1.5 mM. Contrary to previous reports adenosine and inosine did not inhibit the enzyme.