The Structures of Myocotrienins I. and II,a Novel Class of Ansamycin Antibiotic

Endopolygalacturonase I [EC 3.2.1.15], the major component of endopolygalacturonases causing silver-leaf symptoms, was purified from culture liquids of Stereum purpureum by column chromatographies on CM-52 and Sephadex G-100. The purified enzyme was homogeneous on Polyacrylamide gel electrophoresis and ultracentrifugation. The sedimentation coefficient (S_20,W) was determined to be 3.21 S, and the molecular weight was estimated to be 40,000 by gel filtration, 41,000 by SDS-polyacrylamide gel electrophoresis and 44,000 by sedimentation equilibrium. The enzyme had an isoelectric point of pH 8.5. The optimal pH of the enzyme was 3.5 for trigalacturonic acid, 4.0 for tetragalacturonic acid, and 4.5 for pectic acid. The enzyme was stable in the range of pH 4.0 to 9.0 and up to 70%C for 30 min. The amount of the enzyme which was required to induce silver-leaf symptoms on apple trees was 20 μg/tree.     

Amyloid β-Peptide Inhibits High-Affinity Choline Uptake and Acetylcholine Release in Rat Hippocampal Slices

Abstract: The characteristic pathological features of the postmortem brain of Alzheimer's disease (AD) patients include, among other features, the presence of neuritic plaques composed of amyloid β-peptide (Aβ) and the loss of basal forebrain cholinergic neurons, which innervate the hippocampus and the cortex. Studies of the pathological changes that characterize AD and several other lines of evidence indicate that Aβ accumulation in vivo may initiate and/or contribute to the process of neurodegeneration and thereby the development of AD. However, the mechanisms by which Aβ peptide influences/causes degeneration of the basal forebrain cholinergic neurons and/or the cognitive impairment characteristic of AD remain obscure. Using in vitro slice preparations, we have recently reported that Aβ-related peptides, under acute conditions, potently inhibit K⁺-evoked endogenous acetylcholine (ACh) release from hippocampus and cortex but not from striatum. In the present study, we have further characterized Aβ-mediated inhibition of ACh release and also measured the effects of these peptides on choline acetyltransferase (ChAT) activity and high-affinity choline uptake (HACU) in hippocampal, cortical, and striatal regions of the rat brain. Aβ_1–40 (10^?8M) potently inhibited veratridine-evoked endogenous ACh release from rat hippocampal slices and also decreased the K⁺-evoked release potentiated by the nitric oxide-generating agent, sodium nitroprusside (SNP). It is interesting that the endogenous cyclic GMP level induced by SNP was found to be unaltered in the presence of Aβ_1–40. The activity of the enzyme ChAT was not altered by Aβ peptides in hippocampus, cortex, or striatum. HACU was reduced significantly by various Aβ peptides (10^?14 to 10^?6M) in hippocampal and cortical synaptosomes. However, the uptake of choline by striatal synaptosomes was altered only at high concentration of Aβ (10^?6M). Taken together, these results indicate that Aβ peptides, under acute conditions, can decrease endogenous ACh release and the uptake of choline but exhibit no effect on ChAT activity. In addition, the evidence that Aβ peptides target primarily the hippocampus and cortex provides a potential mechanistic framework suggesting that the preferential vulnerability of basal forebrain cholinergic neurons and their projections in AD could relate, at least in part, to their sensitivity to Aβ peptides.     

The polypeptide encoded by the cDNA for human cell surface antigen Fas can mediate apoptosis.

Mouse anti-Fas monoclonal antibody has a cytolytic activity on human cells that express the antigen. Complementary DNAs encoding the cell surface antigen Fas were isolated from a cDNA library of human T cell lymphoma KT-3 cells. The nucleotide sequence of the cDNAs revealed that the molecule coding for the Fas antigen determinant is a 319 amino acid polypeptide (Mr 36,000) with a single transmembrane domain. The extracellular domain is rich in cysteine residue, and shows a similarity to that of human tumor necrosis factor receptors, human nerve growth factor receptor, and human B cell antigen CD40. Murine WR19L cells or L929 cells transformed with the human Fas antigen cDNA were killed by the anti-Fas antibody in the process known as apoptosis.     

A human Fab fragment specific for thyroid peroxidase generated by cloning thyroid lymphocyte-derived immunoglobulin genes in a bacteriophage lambda library.

A human Fab fragment (SP2) which binds specifically to human thyroid peroxidase has been generated by expressing random combinations of heavy and light chain immunoglobulin genes (derived from Graves' thyroid cDNA) in a bacteriophage lambda library. In common with many serum TPO autoantibodies, the cloned Fab fragment is IgG1 kappa and has a high affinity for TPO (approximately 10(-9) M). On the basis of their nucleotide sequences, the heavy and light chain genes coding for SP2 belong to families VHI, (D), JH3 and VKI, JK2, respectively. These data provide the first characterization at a molecular level of a human thyroid peroxidase antibody associated with autoimmune thyroid disease.     

Heptaprenyl pyrophosphate synthetase from Bacillus subtilis

Heptaprenyl pyrophosphate synthetase was detected in partially purified extracts of Bacillus subtilis. The enzyme catalyzed the synthesis of all-trans C35 prenyl pyrophosphate from isopentenyl pyrophosphate and farnesyl or geranylgeranyl pyrophosphate, but it did not catalyze a reaction between isopentenyl pyrophosphate and either dimethylallyl or geranyl pyrophosphate. The enzyme reaction proceeded with an elimination of 2-pro-R hydrogen of isopentenyl pyrophosphate without accumulation of any prenyl pyrophosphate shorter than C35. The molecular weight of the enzyme was estimated by gel filtration to be 45,000. Michaelis constants for isopentenyl, farnesyl, and geranylgeranyl pyrophosphate were 12.8, 13.3, and 8.3 microM, respectively.     

Significance of Antibody to Hepatitis B Core Antigen in a Hemodialysis Unit

Serum hepatitis B surface antigen (HB_sAg), antibody to HB_sAg (anti-HB_s) and antibody to hepatitis B core antigen (anti-HB_c) were determined serially in patients and staff in a hemodialysis unit. A low prevalence of HB_sAg (2.8 percent) was found. However, in patients without HB_sAg, anti-HB_c alone was present in 9.2 percent, and coexistent anti-HB_s and anti-HB_c in 19.2 percent. In persons with anti-HB_c only, the levels of anti-HB_c correlate positively with abnormal results on liver function studies (LFS). In all subjects with abnormal LFS findings, anti-HB_c levels were greater than 6.04 radioimmunoassay (RIA) units. In subjects with both anti-HB_s and anti-HB_c, all five subjects with higher anti-HB_c relative levels had abnormal LFS results and all subjects with normal LFS results had higher anti-HB_s relative levels. Along with other recent reports in the literature, these findings suggest a hepatitis B prevalence in this hemodialysis unit far in excess of that anticipated on the basis of HB_sAg prevalence.     

Nucleotide sequence of a carboxyphosphonoenolpyruvate phosphonomutase gene isolated from a bialaphos-producing organism, Streptomyces hygroscopicus, and its expression in Streptomyces lividans.

Summary The carboxyphosphonoenolpyruvate (CPEP) phosphonomutase gene of bialaphos-producing Streptomyces hygroscopicus, which encodes a C-P bond forming enzyme was cloned into Streptomyces lividans and sequenced. The amino acid composition of the protein coded in an open reading frame of 295 codons and its calculated molecular mass, 32,800 Da, coincided well with those of the purified enzyme. Introduction of the CPEP phosphonomutase gene, the expression of which is controlled by the promoter of the aph gene, into S. lividans resulted in the production of this enzyme at a level almost equivalent to that in the parent strain.