Transplacental action of sodium nitrite on embryonic cells of Syrian golden hamster

Hamster embryos were treated with various doses of NaNO2 in utero, by its oral administration to the mothers, and then the embryonic cells were examined for micronucleus formation, chromosomal aberrations, morphological or malignant transformation and drug-resistant mutations. For induction of resistant mutations, the cells were cultured in normal medium for 72 h, and then selected in media containing 8-azaguanine (10 or 20 microgram/ml) or 1 mM ouabain. This treatment with NaNO2 caused marked dose-dependent induction of 8-azaguanine- and ouabain-resistant mutations. Cultured embryonic fibroblasts in the resting state also showed a marked dose-dependent increase in micronucleus formation but not an increase in chromosomal aberrations. This treatment also caused morphological and neoplastic transformation of the cells. Transplacental oral treatment with DMN, as a positive control, caused changes of similar extent in biological effects of embryonic fibroblasts, and in addition it caused chromosomal aberrations in metaphase plates. On the contrary, transplacental oral application of NaNO2 did not induce any biological change in cultured embryonic fibroblasts.     

Localization of intestinal sucrase-isomaltase complex on the microvillous membrane by electron microscopy using nonlabeled antibodies

Microvillous vesicles isolated from rabbit small intestine showed a trilaminar membrane with a rather smooth surface, which was apparently not affected by papain solubilizing sucrase-isomaltase complex or by trypsin unable to solubilize it. When microvilous vesicles or trysinized ones were incubated with immunoglobulin G against the sucrase-isomaltase complex or monovalent fragments therefrom, an apparently continuous electron-opaque layer approximately 180 A in width appeared around the external surface of vesicles. Such a layer was not formed on papainized vesicles. Microvillous vesicles and trypsinized ones negatively stained with phosphotungate showed a great number of particles protruding approximately 150 A from the membrane surface, but papainized vesicles did not. The particles existed close to one another and appeared to form a particulate layer 150 A in width on the surface. The antibodies, whether they were divalent or monovalent, increased the width of the layer to approximately 200 A and obscured the fine particulate structure of intact and trypsinized vesicles. Papainized vesicles retained their smooth surface upon interaction with antibodies. These results, together with those with the Triton-solubilized sucrase- isomaltase complex (Nishi and Takesue, 1978), J. Ultra-struct. Res., 62:1- 12), indicate not only that sucrase-isomaltase complexes are located close to one another on the membrane, but also that they or at least their protein portions protrude approximately 150 A from the surface of the trilaminar membrane.     

Topographical studies on intestinal microvillous leucine β-naphthylamidase on the outer membrane surface

Summary The location of leucine -naphthylamidase on the outer surface of the microvillous membrane of rabbit small intestine was examined by analyzing the interaction of antibodies against leucine -naphthylamidase or another microvillous enzyme, sucrase-isomaltase complex, with microvillous vesicles having different relative amounts of these enzymes, in respect to vesicle agglutination, inhibition of enzyme activity, and electron-microscopic morphology. The results obtained indicate that leucine -naphthylamidase, or at least its antigenic sites, protrude about 10 nm from the outer surface of the microvillous membrane.     

Synthesis of a polymide containing a glucose unit in the main chain

A new type polyamide containing a glucose unit in the main chain has been synthesized by the polymerization of C₁, C₃, C₄ blocked C₆-carboxymethylglucosamine, prepared from chitin. The deblocking procedure gave the water-soluble polyamide, of MW 1.5 × 10⁴, which can be regarded as a model for the recognition site of lectin.     

Actin polymerization promoted by a heptapeptide, an analog of the actin-binding S site on myosin head

Polymerization of G-actin to F-actin was indicated by an increase in light-scattering intensity after the addition of a heptapeptide (Ile-Arg-Ile-Cys(MT)-Arg-Lys-Gly-OEt), an analog of the actin-binding S-site on S-1 heavy chain. The half-maximal concentration of the heptapeptide which induced an increase in the light-scattering intensity at 25 degrees C was about 110 microM, which was in the range of the dissociation constant of this peptide with F-actin. The polymerization of G-actin to F-actin by binding of the heptapeptide was further demonstrated by ultracentrifugal separation, Pi liberation, and electron microscopy. The polymerization of G-actin was induced only by the heptapeptide, but not by fragments of the heptapeptide. The well known acceleration of polymerization of G-actin by the myosin head may be due to the binding of G-actin with the S-site on the myosin head.     

Ca2(+)-calmodulin-dependent protein kinase II phosphorylates various types of non-epithelial intermediate filament proteins

We have investigated the actions of Ca2(+)-calmodulin (CaM)-dependent protein kinase II on various types of non-epithelial intermediate filament proteins, vimentin, desmin, glial fibrillary acidic protein (GFAP) and neurofilament triplet proteins. Most of these filament proteins could serve as substrates. The effects of phosphorylation on the filamentous structure of vimentin were investigated in sedimentation experiments and by using electron microscopy. The amount of unassembled vimentin increased linearly with increased phosphorylation. However, the extent of the effect of phosphorylation on the potential to polymerize was also affected by the MgCl2 concentration, under conditions for reassembly. The actions of Ca2(+)-CaM-dependent protein kinase II on non-epithelial intermediate filaments under physiological conditions are given attention.     

Temperature dependency of induction of sexual agglutinability by α pheromone in the yeast Saccharomyces cerevisiae

When pheromone-pretreated cells of an inducible a strain of Saccharomyces cerevisiae carrying the inducible gene saa1 were incubated in a growth medium at 28°C, induction of sexual agglutinability began after a 10 min lag period. If the cells were incubated at 38°C during the lag period, no induction occurred even after incubation at 28°C. Contrary to this, if the cells were incubated at 28°C during the lag period, almost complete induction occurred, even after transfer to 38°C. Temperature shift experiments revealed that 5 min incubation at 28°C was necessary for the initiation of the temperature-sensitive period and further 5 min incubation for the completion of the period. The temperature-sensitive period was sensitive to phenylmethylsulfonyl fluoride.Non-common abbreviations PBS 10^-2 M phosphate buffer solution, pH 5.5 - PMSF phenylmethylsulfonyl fluoride     

pKJ1, a naturally occurring conjugative plasmid coding for toluene degradation and resistance to streptomycin and sulfonamides.

Pseudomonas sp. TA8 isolated by m-toluate enrichment from an aqueous sample metabolized toluene and m- and p-xylenes via the meta cleavage pathway, and manifested specific resistance to streptomycin and sulfonamides. A variety of experiments revealed that the pKJ1 plasmid of about 150 megadaltons carried by TA8 specified both the toluene and xylene degradative function (the Tol function) and streptomycin/sulfonamide resistance. The deletion of a segment of pKJ1 (about 22 megadaltons) resulted in the loss of the Tol function. pKJ1 was not assigned to Pseudomonas incompatibility group P-1, P-2, P-3, or P-9.