Capability of intensity discrimination in multiple receptor model of insect taste

A simple model in which one CNS taste neuron integrates inputsfrom multiple peripheral receptors is introduced in order toinvestigate the mechanism of acute intensity taste discriminationin flies. Information theory is applied to evaluate the acuteability of discrimination provided by the model. The presentanalysis is carried out under two statistical conditions concerningthe uncertainty of receptor response. Based on experimentaldata obtained by Smith et al. (1983), we estimate the mutualinformation entropy of the model. The numerical results obtainedhere indicate that the uncertainty observed in a single receptorresponse is dramatically reduced by the central integration.Furthermore, each of the eleven stimulus intensity levels experimentallyapplied by Smith et al., can be discriminated completely byintegrating the responses of the realistic number of receptors(33–212). Such a great improvement of the differentialsensitivity in the model resolves the discrepancy between thelow differential sensitivity of single sugar receptors (Smithet al., 1983) and the high sensitivity obtained in the feedingbehavior (Dethier and Rhoades, 1954; Dethier and Bowdan, 1984)of the blowfly.     

Yolk Phosphoprotein Metabolism during Early Development of the Fish, Oryzias latipes

Changes in yolk phosphoproteins of Oryzias latipes embryos during early development were examined by electrophoresis. Four phosphoproteins were identified in the yolk of blastulae by polyacrylamide gel electrophoresis. Two of them were high molecular weight phosphoproteins containing 0.7% (w/w) phosphorus and with similar amino acid compositions to that of vitellogenin. The other two were low molecular weight phosphoproteins, characterized by high contents of phosphorus [12.2% (w/w)] and serine (44.8 mole%) and low contents of aromatic amino acid residues. From these characteristics, together with their behaviors on DEAE-cellulose chromatography and electrophoresis and low stainability with dyes, the latter two were concluded to be phosvitins. These phosvitins were isolated and partially characterized.
The yolk phosphoproteins, especially the phosvitins, were degraded, their amounts in embryos decreased throughout early development. Studies on the mechanism of endogenous phosphoprotein degradation strongly suggested the participation of some protease(s) that was precipitated on centrifugation of the egg homogenate at 14,000 × g for 10 min.     

Spectrophotometric determination of inorganic phosphate in the presence of thiol compounds

A spectrophotometric method for inorganic phosphate determination in the presence of thiol compounds is described. Thiol compounds, which interfere with the measurement of inorganic phosphate by a modification of the method of Gomori, are removed by carboxymethylation by iodoacetate prior to the formation and reduction of phosphomolybdate complex. A linear standard curve is obtained by this method, and the method is suitable for the assay of a phosphate-releasing enzyme when the measurement must be performed in the presence of thiol compounds.     

A Catechin‐rich Beverage Improves Obesity and Blood Glucose Control in Patients With Type 2 Diabetes

We investigated the effects of continuous ingestion of a catechin‐rich beverage in patients with type 2 diabetes who were not receiving insulin (Ins) therapy in a double‐blind controlled study. The participants ingested green tea containing either 582.8 mg of catechins (catechin group; n = 23) or 96.3 mg of catechins (control group; n = 20) per day for 12 weeks. At week 12, the decrease in waist circumference was significantly greater in the catechin group than in the control group. Adiponectin, which is negatively correlated with visceral adiposity, increased significantly only in the catechin group. Although the increase in Ins at week 12 was significantly greater in the catechin group than in the control group, no apparent difference was noted between the two groups in glucose and hemoglobin A_1c. In patients treated with insulinotropic agents, the increase in Ins at week 12 was significantly greater in the catechin group than in the control group. This significant increase in Ins levels was observed only in the catechin group. In the catechin group receiving other treatments, Ins levels remained unchanged. In addition, in patients treated with insulinotropic agents, the decrease in hemoglobin A_1c at week 12 was significantly greater in the catechin group than in the control group. These results suggest that a catechin‐rich beverage might have several therapeutic uses: in the prevention of obesity; in the recovery of Ins‐secretory ability; and, as a way to maintain low hemoglobin A_1c levels in type 2 diabetic patients who do not yet require Ins therapy.     

Racemization in the Coupling Reaction with the Several Methods beside the Activated Ester Methods

The degree of racemization in the coupling reaction, Pro-Val + Pro, with the several other methods than the activated ester methods was measured and the results were compared with that in the coupling reaction, Leu-Phe + Val, as well as in the previous paper.¹⁾ In the azide and the mixed anhydride methods, no or almost no racemization was detected, whereas in the other tested methods of peptide synthesis (Pachornik-, DCCD- and phosphazo-methods) the significantly large racemization was observed. It can be attributed to the strong nucleo- philic N-atom in the penultimate amino acids (Pro) and the steric hindrance of C-terminal amino acid (Val), which are favourable to the formation of the oxazolone ring.

This assumption was further systematically confirmed in the synthesis of the other several tripeptides with the DCCD method. The separation of the diastereoisomers (LLL and LDL) of the resulting tripeptides by gas chromatography with a packed column was also here reported.