Condensed tannins: co-occurrence of procyanidins,prodelphinidins and profisetinidins in the heartwood of Acacia baileyana

The flavonoids and condensed tannins of the heartwood of Acacia baileyana var. purpurea are described. In conformity with other Acacia species, the hydroxylation pattern of the flavonoids is of the resorcinol type but, in sharp contrast, the tannins are heterogeneous consisting of a mixture of the resorcinol and phtoroglucinol series. Dimeric proanthocyanidins of the phloroglucinol type were absent and this exception to the general observation that they invariably co-occur with the polymers may be explained by the relative nucleophilicity of the aromatic A-rings.     

Changes in key regulatory enzymes of hepatic carbohydrate metabolism after glucose loading of starved rats

When glucose was given to starved rats there was an increase in both 6-phosphofructo 2-kinase and pyruvate kinase activity and a decrease in fructose 2,6-bisphosphatase activity 30 min and 60 min later. These changes were accompanied by an increase in glycogen deposition and by modest, but significant increases in fructose 2,6-bisphosphate levels at the same time. Metabolite measurements indicated that flux through 6-phosphofructo 1-kinase and pyruvate kinase were increased. These results suggest that although glycogen deposition may occur via the gluconeogenic pathway, glycolysis is activated at the same time by changes in the phosphorylation state of key regulatory enzymes as well as by the small rise in fructose 2,6-bisphosphate.     

Simultaneous radioimmunoassay of testosterone,dihydrotestosterone, 5α-androstane-3α, 17β-diol and 5α-androstane-3β, 17β-diol in the plasma of adult male rats

A single thin layer chromatography and three antibodies were used for the specific radioimmunoassay of four androgens in pooled rat plasma (Sprague-Dawley adult males). The following values were found (pg/ml ± SD). Testosterone : 3, 138 ± 173; dihydrotestosterone : 374 ± 20; 5α-androstane-3α 17β-diol : 284 ± 24; 5α-androstane-3β, 17β-diol : 223 ± 11.     

Sulphydryl groups of (Na+ + K+)-ATPase from rectal glands of Squalus acanthias: Detection of ligand-induced conformational changes

1. Modification of the Class II sulphydryl groups on the (Na⁺ + K⁺)-ATPase from rectal glands of Squalus acanthias with N-ethylmaleimide has been used to detect conformational changes in the protein. The rates of inactivation of the enzyme and the incorporation of N-ethylmaleimide depend on the ligands present in the incubation medium. With 150 mM K⁺ the rate of inactivation is largest (k₁ = 1.73 mM^?1 · min^?1) and four SH groups per α-subunit are modified. The rate of inactivation in the presence of 150 mM Na⁺ is smaller (k₁ = 1.08 mM^?1 · min^-1) but the incorporation of N-ethylmaleimide is the same as with K⁺. 2. ATP in micromolar concentrations protects the Class II groups in the presence of Na⁺ (k₁ = 0.08 mM^?1 · min^?1 at saturating ATP) and the incorporation id drastically reduced. ATP in millimolar concentrations protects the Class II groups partially in the presence of K⁺ (k₁ = 1.08 mM^?1 · min^?1) and three SH groups are labelled per α subunit. 3. The K⁺ -dependent phosphatase is inhibited in parallel to the (Na⁺ + K⁺)-ATPase under all conditions, and the ligand-dependent incorporation of N-ethylmaleimide was on the α-subunit only. 4. It is shown that the difference between the Na⁺ and K⁺ conformations sensed with N-ethylmaleimide depends on the pH of the incubation medium. At pH 6 there is a very small difference between the rates of inactivation in the presence of Na⁺ and K⁺, but at higher pH the difference increases. It is also shown that the rate of inactivation has a minimum at pH 6.9, which suggests that the conformation of the enzyme changes with pH. 5. Modification of the Class III groups with N-ethylmaleimide-whereby the enzyme activity is reduced from about 16% to zero-shows that these groups are also sensitive to conformational changes. As with the Class II groups, ATP in micromolar concentrations protects in the presence of Na⁺ relative to Na⁺ or K⁺ alone. ATP in millimolar concentrations with K⁺ present increases the rate of inactivation relative to K⁺ alone, in contrast to the effect on the Class II groups. 6. Modification of the Class II groups with a maleimide spin label shows a difference between Class II groups labelled in the presence of Na⁺ (or K⁺) and Class II groups labelled in the presence of K + ATP, in agreement with the difference in incorporation of N-ethylmaleimide. The spectra suggest that the SH group protected by ATP in the presence of K⁺ is buried in the protein. 7. The results suggest that at least four different conformations of the (Na⁺ + K⁺)-ATPase can be sensed with N-ethylmaleimide: (i) a Na⁺ form of the enzyme with ATP bound to a high-affinity site (E₁-Na-ATP); (ii) a Na⁺ form without ATP bound (E₁-Na); (iii) a K⁺ form without ATP bound (E₂-K); and (iv) an enzyme form with ATP bound to a low-affinity site in the presence of K⁺, probably and E₁-K-ATP form.     

Synapsin Condensates Recruit alpha-Synuclein

Neurotransmission relies on the tight spatial and temporal regulation of the synaptic vesicle (SV) cycle. Nerve terminals contain hundreds of SVs that form tight clusters. These clusters represent a distinct liquid phase in which one component of the phase are SVs and the other synapsin 1, a highly abundant synaptic protein. Another major family of disordered proteins at the presynapse includes synucleins, most notably α-synuclein. The precise physiological role of α-synuclein in synaptic physiology remains elusive, albeit its role has been implicated in nearly all steps of the SV cycle. To determine the effect of α-synuclein on the synapsin phase, we employ the reconstitution approach using natively purified SVs from rat brains and the heterologous cell system to generate synapsin condensates. We demonstrate that synapsin condensates recruit α-synuclein, and while enriched into these synapsin condensates, α-synuclein still maintains its high mobility. The presence of SVs enhances the rate of synapsin/α-synuclein condensation, suggesting that SVs act as catalyzers for the formation of synapsin condensates. Notably, at physiological salt and protein concentrations, α-synuclein alone is not able to cluster isolated SVs. Excess of α-synuclein disrupts the kinetics of synapsin/SV condensate formation, indicating that the molar ratio between synapsin and α-synuclein is important in assembling the functional condensates of SVs. Understanding the molecular mechanism of α-synuclein interactions at the nerve terminals is crucial for clarifying the pathogenesis of synucleinopathies, where α-synuclein, synaptic proteins and lipid organelles all accumulate as insoluble intracellular inclusions.