Specific isoprenyl group linked to transducin gamma-subunit is a determinant of its unique signaling properties among G-proteins

Among 11 subtypes of heterotrimeric G-protein gamma-subunit, gamma1 (rod), gamma8 (cone) and gamma11 are modified with farnesyl while the others are modified with geranylgeranyl at the C-terminus. To understand the role of specific isoprenylation (farnesylation) of retinal transducin, we examined how and to what extent the type of isoprenyl group affects transducin-beta gamma (beta1 gamma1) functions such as interactions with membranes, Galpha/receptor, and effectors. To this end, the C-terminal farnesylation signal sequence (CVIS) of gamma1 was replaced by a geranylgeranylation signal (CVIL), and the resultant mutant (S74L) or wild-type (WT) gamma1 was coexpressed with beta1 in the baculovirus-Tn5 insect cell system. Both gamma1WT and gamma1S74L expressed as a beta gamma complex were mixtures modified with farnesyl and geranylgeranyl groups. The ratio of farnesyl to geranylgeranyl in preparations of beta1 gamma1WT and beta1 gamma1S74L purified from the Tn5 cell membrane fraction was about 1:2 and 1:6, respectively. These two forms of recombinant beta1 gamma1 and retinal beta1 gamma1 were different in their abilities to associate with rod outer segment membranes with the following rank order: beta1 gamma1S74L > beta1 gamma1WT > retinal beta1 gamma1. Functionally, beta1 gamma1S74L was the most potent to promote pertussis toxin-catalyzed ADP ribosylation of transducin-alpha (Talpha), to stimulate metarhodopsin II-catalyzed GTPgammaS-binding reaction to Talpha and to modulate adenylyl cyclase and phospholipase C activities. All of the beta1 gamma1 functions absolutely required the isoprenylation of the gamma-subunit. As for the interaction with Goalpha and adenylyl cyclase, predominantly geranylgeranylated beta1 gamma1S74L was less effective than geranylgeranylated beta1 gamma2 purified from bovine brain. These results demonstrate that the properties of Gbeta gamma are strongly affected by the type of functionally indispensable isoprenylation in addition to the amino acid sequence of Ggamma. The relative contribution of the two factors depends on proteins with which Gbeta gamma interacts.     

Broadbanding of corrugated conical horns by means of the ring-loaded corrugated waveguide structure

Broadbanding of corrugated conical horns is investigated with the ring-loaded corrugated circular waveguide (RCWG) structure devised by the authors. The useful frequency bandwidth in which the corrugated horn is effective for the improvement of antenna properties is limited by the frequency characteristics of the horn-aperture field and input VSWR of the horn. By the precise analysis of the RCWG, the maximum frequency range in which the desirable field is obtained is much wider than that in the conventional corrugated circular waveguide, and is achieved almost independent of ring thickness, when ring width is about 20 percent of slot depth. The characteristic impedance of the RCWG is nearly equal to that of the homogeneous circular waveguide when ring thickness becomes large. Therefore, a good transformer between the RCWG and the homogeneous circular waveguide is achieved by increasing ring thickness from the RCWG toward the homogeneous waveguide. From the above investigations, it is found that in the ring-loaded corrugated horn, the useful bandwidth is 1.35 times broader than that in the conventional corrugated horn. The theoretical results are verified by the experimental results.     

Cutoff frequencies of vector wave modes in cladded inhomogeneous optical fibre

Asymptotic vector wave formulas for calculating the cutoff frequencies in optical fibres with graded-index core and uniform cladding are derived. Numerical examples are given in comparison with the scalar wave solutions, in order to show that the mode degeneracy present in the regime of scalar wave approximations is removed and the cutoff values in degenerate states split slightly.     

Graft copolymerization of glass fiber and its application

Modified glass fibers, containing unsaturated hydrocarbon surface groups, were prepared by a hydrothermal treatment, with allylglycidylether in excess as reagent. Graft polymerization of the treated glass fiber with styrene and methylmethacrylate was carried out in sealed tubes, under nitrogen, using benzoyl peroxide (BPO) and cumene hydroperoxide (CHPO) as initiators. When BPO was used as the initiator, the grafting efficiency was extremely low, but the graft copolymerization behavior was similar to that of usual organic polymers. With CHPO, both grafting ratio and grafting efficiency were very high. Various properties of composite materials containing grafted glass cloth were studied. Flexural strength, flexural modulus, and interlaminar shear strength increased proportionally to the increase of the grafting ratio; the same values were decreased only in a small extent after the boiling test.     

Ultrastructural studies in epidermolysis bullosa hereditaria. III. Recessive dystrophic types with dermolytic blistering (Hallopeau-Siemens types and inverse type)

In this paper the authors describe and analyse results that they obtained by infection of the guinea pig organism carried out by subcutaneous or intratracheal application with five mycobacterial strains, namely Myco bovis BCG-Praha, Myco the H37Ra, Myco Kansasii, Myco fortuitum and Myco smegmatis. At predetermined time intervals following subcutaneously or intratracheally performed infection (on 7th, 16th, 28th and 56th day after infection) transplantation of a Deals' guinea pig sarcoma cell suspension was carried out in guinea pigs by the intraltracheal route. As it appears from the results gained the applied mycobacteria exhibit a partial inhibition of growth od Deals' guinea pig sarcoma cells of different character. From among the utilized strains the Myco bovis BCP-Praha and the Myco tbc H37Ra exhibited the highest, Myco fortuitum and Myco smegmatis the lowest inhibitory activity. Intratracheally performed infections yielded in general better results on the growth inhibition than infections carried out with the same strain but by the subcutaneous route. Furthermore, in the experiments reported on in the present paper the authors could verify their earlier experience, namely that inhibition of growth of sarcoma cells is most pronounced at the time of maximal biological activity (logarithmic phase of multiplication) of the applied mycobacterium.     

Relationship between the structures of S-acyl thiol compounds and their rates of hydrolysis by pancreatic lipase and hepatic carboxylic esterase

About 100 S-fatty acyl thiol compounds designed as substrates for pancreatic lipase [EC 3.1.1.3] were synthesized and tested for susceptibility to hydrolysis by hog pancreatic lipase and hog hepatic carboxylic esterase [EC 3.1.1.1] using 5,5'-dithiobis(2-nitrobenzoic acid) as a chromogenic reagent to determine the hydrolytic rates of their S-acyl bonds. In general, the hydrolytic rates of S-acyl bonds by the lipase were fast with thioglycerol type thiol moieties, slow with dithioethyleneglycol type or monothiol type, and negligible with thiopolyol type. As for the acyl moieties, the hydrolysis of the S-acyl bonds was fast with C3-5 acyl groups, followed by C6-8 acyl groups, and the rate decreased as the acyl chain length deviated from these values or branched. On the other hand, the hydrolysis of S-acyl bonds by the esterase occurred with all types of S-acyl esters except for esters of long S-acyl chains. Of all the compounds tested with the lipase, the rate of hydrolysis of S-acyl bond was maximum with 2,3-dimercaptopropan-1-ol tributyroate [I], high with 3-mercaptopropane-1,2-diol tributyroate [II], but negligible with the analogous compound, 1,3-dimercaptopropan-2-ol tributyroate. Compounds [I] and [II] may be practically useful as substrates for lipase assay in human serum samples pretreated with phenylmethylsulfonyl fluoride, a potent inhibitor against both serum arylesterase [EC 3.1.1.2] and hepatic esterase, which attack [I] and [II].     

Scattering Characteristics of VHF/UHF Television Broadcasting Waves by Overhead Power Transmission Conductors

The paper analyzes the scattering characteristics of VHF/UHF television broadcasting waves which are obliquely incident on finite length multibundle conductors of overhead power transmission lines. Numerical calculations were made for four-bundle conductors currently employed in Japan; the attenuation, directivity, and frequency characteristics were clarified. To verify the theoretical results, 1:40 scale (for VHF) and 1:10 scale for (UHF) model experiments have been carried out. Agreement between the theoretical results and the measurements was reasonably good.     

Polymer film-type channel electron multipliers: Their characteristics and comparison with bulk-type flexible multipliers

Polymer film-type channel electron multipliers (CEMs) were developed and their characteristics investigated in comparison with bulk-type flexible CEM. As film-type CEMs, a paint-coating-type CEM and a solvent-etching-type CEM were fabricated. The paint-coating-type CEM is made by coating a “paint” which is prepared by dissolving in a solvent an electronically conductive polymeric composition having a high secondary electron emission yield. Up to the present study the mean gain of the film-type CEM, in spite of the lower resistivity of the dynode, seems to be slightly more dependent on the count rate than that of the bulk-type CEM made of the same material. However, the convenience of fabricating the dynode film by coating the dynode-forming paint on the internal surface of any shaped tube or a flexible polymer tube would overcome the slight disadvantage mentioned above.