Cholinesterase activity in some species of theAllium genus

In partly purified protein complexes obtained from 22 species of theAllium genus and 6 cultivars ofAllium cepa the activity of cholinesterases was detected and measured using the method of Ellman et al. The degree of its inhibition with 10^-4 M neostigmine was also tested. It was found that the activity of cholinesterase differed in individual species up to two hundred times, while the differences in the inhibitory activity of 10^-4 M neostigmine occurred only in a few cases. Individual sections and cultivars could not be characterized on the basis of the differences in the activities of the cholinesterases. Of all the sections that ofPhyllodolon shows the highest average activity. In the case of the tested cultivars distinctly the lowest activity was observed in cv. Kastická. The values of the enzymatic activity measured by Ellman’s method in this plant material include the activity of specific and unspecific cholinesterases and the part uninhibitable by neostigmine.     

The comparison of seed protein patterns within the genusArachis by polyacrylamide gel electrophoresis

The seed protein patterns of 12Arachis species were compared by polyacrylamide gel electrophoresis (PAGE), similarities between patterns were measured by the Jaccard index. Results obtained confirm the close relationships established between members of the genus on morphological grounds and support the more recent classification schemes.A. villosa andA. correntina could well be regarded as distinct species on grounds of protein differences whileA. macedoi andA. villosulicarpa (although members of the same section, Extranervosae) show considerable differentiation of their protein patterns. Surprisingly, the formA. ×batizogaea showed less similarity in protein pattern to those of its parental species than might have been expected. The principle value of seed protein pattern data appears to be in distinguishing species within sections.     

Electro-optical measurements on aqueous suspension of purple membrane from Halobacterium halobium

The permanent dipole moment, polarizability, and the retinal angle of Halobacterium halobium purple membranes were determined at different pH values. All of the parameters have a maximum between pH 5 and 6. There is a reversal in the direction of the permanent dipole moment near pH 5. The value of permanent dipole moment was determined to be 60 D/protein at pH 6.6, and the value obtained for polarizability was 3 X 10(-28) Fm2/membrane fragment. The retinal angle of all-trans retinal was 0.8 degrees smaller than that of the 13-cis conformation.     

Analysis of two chloride requirements for sodium-dependent amino acid and glucose transport by intestinal brush-border membrane vesicles of fish

Intestinal brush border vesicles of a Mediterranean sea fish (Dicentrarchus labrax) were prepared using the Ca²⁺-sedimentation method. The transport of glucose, glycine and 2-aminoisobutyric acid is energized by an Na⁺ gradient ($\text{out > in}$). In addition, amino acid uptake requires Cl^? in the extravesicular medium (2-aminoisobutyric acid more than glycine). This Na⁺- and Cl^?-dependent uptake is electrogenic, since it can be stimulated by negative charges inside the vesicles. The specific Cl^? requirement of glycine and 2-aminoisobutyric acid transport is markedly influenced by pH, a change from 6.5 to 8.4 reducing the role played by Cl^?. In the presence of Cl^?, the $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ of 2-aminoisobutyric acid uptake is reduced and its $\text{V}{}_{\mathrm{<mtext>max</mtext>}}$ is enhanced. Cl^? affects also a non-saturable Na⁺-dependent component of this amino acid uptake. Amino acid transport is also increased by intravesicular Cl^? (2-aminoisobutyric acid less than glycine). This effect is more concerned with glucose uptake, which can be then multiplied by 2.3. A concentration gradient ($\text{in > out}$) as well as the presence of Na⁺ in the incubation medium seems to enter into this requirement. This intravesicular Cl^? effect is not influenced by pH between 6.5 and 8.4.     

Chromophoric peptide substrates for activity determination of animal aspartic proteinases in the presence of their zymogens: A novel assay

Solid-phase synthesis was used for the preparation of pyroglutamyl-histidyl-p-nitrophenylalanyl-phenylalanyl-alanyl-leucine amide (I) and glycyl-glycyl-histidyl-p-nitrophenylalanyl-phenylalanyl-alanyl-leucine amide (II), two water-soluble and sensitive chromophoric substrates of chicken pepsin, hog pepsin A, and bovine spleen cathepsin D. The kinetic constants of hydrolysis of the p-nitrophenylalanyl-phenylalanyl bond of the substrates were measured by difference spectrophotometry at 308 nm (Δ? = 860 m^?1 cm^?1) and by ninhydrin colorimetry (substrate I, ?₅₇₀ = 2.31 × 10⁴m^?1 cm^?1). The pH optimum of cleavage is 5 for the pepsins and 3.7 for cathepsin D. Since all three proteinases still have a significant activity at pH 5.5–6 a new, simple assay was designed for submicrogram quantities of pepsins in the presence of pepsinogens without interference of the latter. The method is particularly suitable for the analyses of the zymogen activation mixtures.     

Bumetanide-sensitive potassium transport and volume regulation in turkey erythrocytes

The bumetanide-sensitive (K+ + Na+ + 2Cl-)-cotransport system in turkey erythrocytes is activated by either of two treatments: addition of epinephrine or an increase in osmolarity. At elevated (20 mM) K+ concentration, cotransport activity induced by epinephrine slowly (within 90 min) declines to background level again. This time-dependent inactivation has been linked to bumetanide-sensitive cell swelling. We have compared both the initial rate of cotransport activity and its time dependence after induction by either epinephrine, increased osmolarity or a combination of the two treatments. As a measure of cotransport activity we took the bumetanide-sensitive fraction of 86Rb+ influx. Immediately after activation, several kinetic characteristics of this flux (Vmax; Km towards K+; Ki towards bumetanide; pH profile) were identical in cells activated by either treatment. By contrast, cotransport activated by hypertonicity was significantly more resistant towards subsequent inactivation. We show this to be due to the increase in intracellular ion concentrations brought about by hypertonic cell shrinkage. This tended to reverse the driving force for cotransport, and thereby prevented the bumetanide-sensitive swelling associated with inactivation. Our data support the notion that cell volume plays a key role both in the activation and in the time-dependent inactivation of bumetanide-sensitive transport.     

Peripheral benzodiazepine binding sites: Effect of PK 11195, 1-(2-chlorophenyl)-n-methyl-n-(1-methylpropyl)-3-isoquinolinecarboxamide: I. In vitro studies

[³H] R05-4864 binding sites have been characterized in kidney, heart, brain, adrenals and platelets in the rat. In all these organs the following order of potency in the R05-4864 displacement was found : R05-4864 > diazepam > clonazepam indicating that they correspond to the “peripheral type” of benzodiazepine binding sites. PK 11195, an isoquinoline carboxamide derivative, displaces [³H] R05-4864 from its binding sites in all the organs. PK 11195 was as potent as R05-4864 in the platelets, heart, adrenals, kidney and several brain regions (midbrain, hypothalamus, medulla + pons and hippocampus. However it was 5 to 10 times more effective in cortex and striatum. In conclusion PK 11195 might represent a new tool to elucidate the physiological relevance of “peripheral type” benzodiazepine binding sites and might help to discriminate the hypothetical subclasses of these binding sites.     

A heteroplasmic state induced by protoplast fusion is a necessary condition for detecting rearrangements in Nicotiana mitochondrial DNA

Theoretical and Applied Genetics - Mitochondrial DNA (mtDNA) restriction patterns were studied in mutant, cybrid and somatic hybrid plants regenerated from Nicotiana protoplasts. It has been shown...