The xylanase introns from Cryptococcus albidus are accurately spliced in transgenic tobacco plants

The xylanase gene from Cryptococcus albidus contains seven introns. Genomic and cDNA clones under the control of the CaMV 35S promoter were transferred into tobacco plants using Agrobacterium-mediated cell transformation. The genes were transcribed and the mRNAs were amplified by the polymerase chain reaction using primers on each side of the intron region. About 90% of the amplification products from plants transformed with the genomic clone corresponded to the size of the pre-mRNA (1.2 kb) and 10% represented the spliced product (0.85 kb). The 0.85 kb fragment was cloned and sequenced and the result indicated that the introns from the xylanase gene were accurately spliced by the plant cells.     

Thiamine and Cholinergic Transmission in the Electric Organ of Torpedo

The electric organ of Torpedo marmorata was found to contain as much as 120 +/- 24 nmol of thiamine per g of fresh tissue. The vitamin was distributed as nonesterified thiamine (32%), thiamine monophosphate (22%), thiamine diphosphate (8%), and an important proportion of thiamine triphosphate (38%). A high level of thiamine triphosphate was found in synaptosomes isolated from the electric organ. In contrast, the synaptic vesicles did not show any enrichment in thiamine, whereas they contained a marked peak of acetylcholine (ACh) and ATP. Thus thiamine seems to be very abundant in cholinergic nerve terminals; its localization is apparently extravesicular, either in the axoplasm or in association with plasma membrane. When calcium was reduced and magnesium increased in the external medium, the efficiency of transmission was diminished, owing to inhibition of ACh release; in a parallel manner the degree of thiamine phosphorylation was found to increase--this condition is known to modify the repartition of ACh between vesicular and extravesicular compartments. Electrical stimulation, which causes periodic variations of the level of ACh and ATP, also caused significant changes in thiamine esters. In addition, related changes of the vitamin and the transmitter were observed under other conditions, suggesting a functional link between the metabolism of thiamine and that of ACh in cholinergic nerve terminals.     

The effects of membrane lipid order and cholesterol on the internal and external cationic sites of the Na+−K+ pump in erythrocytes

Cholesterol depletion alters the apparent affinity of the internal cationic sites and the maximal translocation rate but not the affinity of the external cationic sites of the $\text{Na}{}^{\mathrm{+}}\text{?K}{}^{\mathrm{+}}$ pump in human erythrocytes. To test whether these effects were mediated by a direct cholesterol-internal site interaction or by a change in membrane lipid order, the effects of five fluidizing amphiphiles (chlorpromazine, imipramine, benzyl alcohol, sodium oleate and sodium benzenesulphonate) on the kinetic parameters of the $\text{Na}{}^{\mathrm{+}}\text{?K}{}^{\mathrm{+}}$ pump were determined. The cholesterol removal and all the agents used induced dose-response decreases in membrane lipid order as measured by fluorescence polarization or ESR. Positive and neutral amphiphiles mimicked the effects of cholesterol removal on the affinity of the internal sites of the pump and to a lesser extent on the maximal translocation rate. Anionic amphiphiles had no effect on internal sites, probably because they distributed preferentially within the outer leaflet on the membrane. These results indicate that cholesterol controls the affinity of the internal sites of the $\text{Na}{}^{\mathrm{+}}\text{?K}{}^{\mathrm{+}}$ pump by altering the membrane lipid order. In contrast, neither cholesterol depletion nor the agents used altered the affinity of the external sites of the $\text{Na}{}^{\mathrm{+}}\text{?K}{}^{\mathrm{+}}$ pump. This difference in sensitivity to membrane lipid order suggests that internal and external cationic sites, although borne by the same protein, are in different lipid environments.     

A lipopolysaccharide fromAspergillus flavus conidia

A lipopolysaccharide was isolated by extraction ofAspergillus flavus conidia with 45 % phenol at 68–70 °C. Quantitative analysis revealed 7 % nucleic acids, 5.5 % proteins, 46 % polysaccharides and 49 % lipids, of which 12 % were covalently bound. Glucose, mannose, galactose and fucose were detected as monosaccharide components of the polysaccharide moiety by gas chromatography; palmitic acid, stearic acid, oleic acid, linoleic acid and myristic acid were mainly present in the lipidic fraction. This material differs from the bacterial lipopolysaccharides, both in composition of the polysaccharide moiety and representation of fatty acids in the lipidic fraction.     

A fast and simple radiometric assay for adenosine deaminase using reversed-phase thin-layer chromatography

A new quantitative radiometric assay for adenosine deaminase is described. The reaction conditions are similar to those used in other radioassays and are shown to result in an activity which increases linearly with time and with enzyme concentration. An original feature of the technique resides in the use of reversed-phase thin-layer chromatography to separate adenosine from inosine. The separation is complete, fast, and reproducible. Both compounds can be recovered almost quantitatively from the plates. The assay is very simple and allows the determination of up to 36 samples in 3 h.     

Iron-porphyrin catalysis of the oxidative dealkylation of para-nitro-anisole and 7-ethoxycoumarin by cumylhydroperoxide: a possible model for the corresponding cytochrome P 450-dependent reactions

A biphasic system containing an iron porphyrin, Fe (TPP) (C1)¹ or [Fe(TPP)]₂O, efficiently catalyzes the cumyl-or tertiobutyl-hydroperoxide-supported dealkylation of p-nitroanisole and 7-ethoxycoumarin to the corresponding phenol and formaldehyde. Stoichiometric amounts of iron porphyrin and hydroperoxide give a quantitative reaction. Catalytic amounts of iron porphyrin give reaction rates and yields which are proportional to substrate concentration. With increasing hydroperoxide concentrations, the rates level offto limit values and the yield rapidly decreases. The maximum rates obtained approach those of the reactions mediated by cytochrome P 450-dependent monooxygenases.