In vivo phosphorylation of isocitrate lyase inEscherichia coli andAcinetobacter calcoaceticus

Isocitrate lyase inEscherichia coli and inAcinetobacter calcoaceticus is phosphorylated when the cells are grown with acetate as the sole carbon source in low-phosphate mineral salts medium containing³²P inorganic phosphate. The level of³²P incorporation into the enzyme in both microorganisms appears to be constant throughout the entire growth cycle. Further, theresults of immunoblots and rocket immunoelectrophoresis suggest that the amount of isocitrate lyase protein, although at different levels in each microorganism, also remains constant throughout the growth cycle.     

Pharmacological and Physicochemical Properties of Pre-Versus Postsynaptic 5-Hydroxytryptamine1A Receptor Binding Sites in the Rat Brain: A Quantitative Autoradiographic Study

Numerous data suggested that the pharmacological and biochemical properties of 5-hydroxytryptamine1A (5-HT1A) receptors exhibit some regional differences in the CNS, notably within the raphe nuclei compared with various forebrain areas (such as the hippocampus). This possibility has been further investigated in the dorsal raphe nucleus and two areas within the hippocampus, the dentate gyrus and the CA1 area, using the quantitative autoradiographic technique. The potencies of 5'-guanylylimidodiphosphate to inhibit the specific binding of 125I-Bolton-Hunter-8-methoxy-2-(N-propyl-N-propylamino)tetralin (125I-BH-8-MeO-N-PAT) to 5-HT1A sites and of N-ethylmaleimide to block these sites irreversibly were identical in the dorsal raphe nucleus and the hippocampal areas in rat brain sections. In contrast, slight but significant differences were noted in the pH dependence and pharmacological properties of 5-HT1A sites labeled by 125I-BH-8-MeO-N-PAT in these three regions. Similarly, heat denaturation experiments and tissue exposure to either phospholipase A2 or the alkylating agent 8-methoxy-2-(N-2'-chloropropyl,N-propyl)aminotetraline revealed regional differences in the properties of 5-HT1A sites. However, in most cases, the observed variations were of greater amplitude between the CA1 area and the dentate gyrus, where 5-HT1A sites are located postsynaptically, than between any one of these areas and the dorsal raphe nucleus where they act as (presynaptic) somatodendritic autoreceptors. These data further support that subtypes of 5-HT1A receptors probably exist in the rat brain, but this heterogeneity seems unrelated to the pre- or post-synaptic location of these receptors.     

Effect of tween 80 on exploratory behavior and locomotor activity in rats

Exploratory behavior and locomotor activity is enhanced in male rat pups (aged 10 to 20 days) whose dams received a chronic dose (1.25 ml/l) of Tween 80 via their drinking water. This enhancement manifests itself during the diurnal period of the day. These data suggest that Tween 80 has an effect on the CNS which could lead to misinterpretation of results in toxicology studies that use this compound as a dosage vehicle.     

Mutual recognition between polymerized liposomes. IV. Polysaccharide-lectin system.

As a model of cell-cell recognition processes, the association processes of a polysaccharide (mannan)-carrying liposome with a lectin (Concanavalin A, Con A)-carrying polymerized liposome were followed by turbidimetry. The association process was strongly inhibited by the addition of a low molecular weight sugar, methyl-alpha-D-mannopyranoside, which shows that the association between the liposomes is due to the specific interaction between Con A and mannan. The association rate constant obtained was much smaller than the theoretical value for a diffusion-controlled binary association process. This implies that the association rate of liposomes is limited by the recognition between complementary ligands bound on the liposome surfaces. Another reason for the smaller association rate constant in the liposome-liposome system is the repulsive hydration effect. The effect of the surface density of the lectin immobilized on the liposome on the recognition was also examined.     

Fate of recombinants of the rat mandibular epithelium with cranial ectomesenchymal cells of different sources in vitro

The recombinants of the mandibular molar bud epithelia with cranial ectomesenchymal cell groups from several different sources--mandibular molar area, tongue anlagen, and lateral nasal process--were cultured. Dental laminalike buds were developed in each of the recombinants (incidence of development 38-86%). In the heterotrophic recombinants, heterotypic differentiation of mandibular epithelium was also induced. However, the foreign ectomesenchymal cells were not induced heterotypically by the epithelial genetic factor, but the mesenchymal genetic factor is maintained. It is suggested that mandibular molar bud epithelia have potency to proliferate into mesenchyme under non-organ-specific influences of ectomesenchymal cells and that presumptive mandibular mucosal epithelia have multipotency for differentiation sensitive to inductive influences by the heterotypic cranial ectomesenchymal cells but that the mandibular molar bud epithelia have no heterotypic inductive activity for the differentiation of cranial ectomesenchymal cells.     

Decoding at the ribosomal A site: antibiotics, misreading and energy of aminoacyl-tRNA binding

The binding of Phe-tRNAPhe at the programmed ribosomal A site has been investigated using antibiotics that influence this binding in different ways. The adhesion of Phe-tRNAPhe, the consumption of GTP and the extent of the peptidyl transfer reaction were monitored. All of the five known misreading-inducing antibiotics that were tested stabilised the binding of Phe-tRNAPhe after its affixture to the A site by EF-Tu with GTP hydrolysis. The stabilisation was sufficient to overcome a single mismatch in the codon-anticodon interaction. Combinations of stabilising and destabilising influences were found to be additive, thus supporting the concepts: (1) that there is a 'correct' binding energy for aminoacyl tRNA in the A site, whose reduction hampers polypeptide synthesis and whose increase makes it inaccurate by by-passing proofreading; and (2) that the different antibiotics affect the bound aminoacyl tRNA at different points.     

Pentazocine-induced agranulocytosis.

A 46-year-old man with pentazocine-induced agranulocytosis is described. In previously reported cases of a complete absence of mature neutrophils in the peripheral blood and bone marrow the patients had undergone marrow-depressing treatment with radiation and antineoplastic drugs. This case is unique in that the patient had complete agranulocytosis without predisposing factors.     

Subunit composition and ATP site labeling of the coated vesicle proton-translocating adenosinetriphosphatase

The partially purified proton-translocating adenosinetriphosphatase [(H+)-ATPase] from clathrin-coated vesicles has been reported to contain eight polypeptides of molecular weights 15,000-116,000 [Xie, X.S., & Stone, D.K. (1986) J. Biol. Chem. 261, 2492-2495]. To determine whether these polypeptides form a single macromolecular complex, we have isolated three monoclonal antibodies which recognize the reconstitutively active (H+)-ATPase in the native, detergent-solubilized state. All three monoclonal antibodies precipitate the same set of polypeptides from either the partially purified enzyme or the detergent-solubilized coated vesicle membrane proteins. The immunoprecipitated polypeptides have molecular weights of 100,000, 73,000, 58,000, 40,000, 38,000, 34,000, 33,000, 19,000, and 17,000. These results thus indicate that this set of polypeptides forms a single macromolecular complex and suggest that they correspond to subunits of the coated vesicle (H+)-ATPase. To identify the ATP-hydrolytic subunit of the coated vesicle (H+)-ATPase, the purified enzyme was reacted with N-ethylmaleimide (NEM) and 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl), both of which inhibit activity in an ATP-protectable manner. Labeling was carried out by using [3H]NEM or [14C]NBD-Cl, and the specificity of the reaction was increased by prelabeling of the protein with the nonradioactive reagents in the presence of ATP and by taking advantage of the nucleotide specificity of protection. The principal polypeptide labeled by both [3H]NEM and [14C]NBD-Cl had a molecular weight of 73,000. In addition, this protein was the only polypeptide whose labeling was significantly reduced in the presence of ATP.(ABSTRACT TRUNCATED AT 250 WORDS)