Identification of a retina-specific MEKA protein as a 33 K protein

A photoreceptor-specific MEKA protein was purified from bovine retinal soluble fraction. The purified sample was eluted as a single peak of 74 kDa protein from a Superose column, which was dissolved into three components, MEKA protein (32 kDa), beta-(36 kDa) and gamma-(10 kDa) subunits of transducin on a SDS-PAGE. From several lines of evidence, we concluded that MEKA protein is identical with a 33k phosphoprotein reported by Lee et al (1).

Endothelin localizes in the dorsal horn and acts on the spinal neurones: possible involvement of dihydropyridine-sensitive calcium channels and substance P release

The neural effect of endothelin, a vasoconstrictor peptide from vascular endothelium, was investigated in the in vitro spinal cord preparation of the newborn rat. In addition, an immunohistochemical study of endothelin was performed in the porcine spinal cord. Endothelin produced ventral root depolarization in a dose-dependent manner in the newborn rat spinal cord. Endothelin (5 x 10(-8) M)-induced depolarization was depressed by the dihydropyridine-sensitive Ca2+ channel blocker, nicardipine (10(-7) M), or the substance P antagonist, spantide (5 x 10(-6) M). These results suggest that endothelin may cause substance P release and that dihydropyridine-sensitive Ca2+ channels in the spinal cord may be involved in this process. Furthermore, endothelin-like immunoreactivity was localized in dot- and fibre-like structures and neurones in the dorsal horn of the porcine spinal cord. Therefore, it is suggested that endothelin or endothelin-related peptide(s) have a neuromodulatory function in the spinal cord.

Mechanism of isomerization of rhodopsin studied by use of 11-cis-locked rhodopsin analogues excited with a picosecond laser pulse

Primary photochemical behaviors of cattle rhodopsin analogues (Rh5 and Rh7) having cyclopenta- and cycloheptatrienylidene 11-cis-locked retinals (Ret5 and Ret7, respectively) were studied by excitation with a picosecond laser pulse (wavelength 532 nm; duration 21 ps). Picosecond absorption and fluorescence measurements of Rh5 showed formation of only a long-lived excited singlet state (tau l/e = 85 ps). The excited state of the retinal analogue having a five-membered ring was stabilized in protein (Rh5) more than in solvent (protonated Schiff base of Ret5; PSB5). Excitation of Rh7 produced two ground-state photoproducts, Rh7 (580) and Rh7 (630). According to the analysis of photon density dependency, Rh7 (580) was a single-photon product of Rh7, while Rh7 (630) was the photoproduct of Rh7 (580). Fluorescence emitted from a seven-membered ring system like Rh7 or a protonated Schiff base of Ret7 (PSB7) was weaker than that in a corresponding five-membered ring system, especially in protein (Rh7). The difference in photoreaction between Rh5 and Rh7 may originate from the difference in fixation of the 11-cis form. On the basis of the spectral and kinetic similarities between Rh7 (580) and photorhodopsin, a precursor of bathorhodopsin, it was proposed that both have twisted all-trans chromophores in the way of the isomerization. The protein moiety of rhodopsin which fixes the chromophore at both ends seems to accelerate the rotation of the C11-C12 double bond and to prevent it from going through relaxation processes other than the isomerization. This may be a plausible reason why rhodopsin has a large quantum yield (0.67).

Presence of endothelin-1 in porcine spinal cord: isolation and sequence determination

We investigated the molecular forms of endothelin (ET) related peptides in porcine spinal cord by high performance liquid chromatography coupled with radioimmunoassays using three antisera raised against ET-1 and C-terminal fragments of ET-1 and big ET-1. ET-1 and its oxidized form were isolated as major immunoreactive peptides and sequenced. Furthermore, immunoreactivities like ET-3 and big ET-1(22-39) (contents: less than 8% and less than 1% of ET-1, respectively) were detected based on their chromatographic retention times and characteristics of immunoreactivity to the antisera. Big ET-1 was only scarcely detected. Immunohistochemical study showed the presence of ET-1-like immunoreactivity in motoneurons, dorsal horn neurons and dot- and fiber-like structures in the dorsal horn of lumbar spinal cord. These results indicate that ET-1 is present not only in endothelial cells but also in spinal cord, and that big ET-1 is converted into ET-1 in spinal cord by specific processing between Trp21-Val22. The data also indicate that ET-1 may act as a neuropeptide in the central nervous system.

Beta gamma-subunit of bovine transducin composed of two components with distinctive gamma-subunits

During the process of transduction of a photon signal in vertebrate rod outer segments, transducin, a guanine nucleotide binding protein, mediates between a photobleaching intermediate of rhodopsin and a cGMP-phosphodiesterase. We report here that the beta gamma-subunit of bovine transducin (T beta gamma) characterized so far consists of two components (T beta gamma-1 and T beta gamma-2), which can be separated by anion exchange chromatography under nondenaturing conditions. Both components consisted of two polypeptides of Mr 36,000 (T beta) and about 8,000 (T gamma) in sodium dodecyl sulfate polyacrylamide (13%) gel electrophoresis. On a further analysis by 8 M urea/sodium dodecyl sulfate-polyacrylamide gel electrophoresis, T gamma subunits of T beta gamma-1 and T beta gamma-2 showed Mr values of 8,000 (T gamma-1) and 6,000 (T gamma-2), respectively. Amino acid compositions of both T gamma-1 and T gamma-2 roughly corresponded with that of T gamma previously reported and were quite different from that of gamma-subunit of cGMP-phosphodiesterase. Western blot analysis of freshly isolated rod outer segments by an antiserum raised against a mixture of T beta gamma-1 and T beta gamma-2 revealed the presence of both components in the membranes of a starting material. This observation excludes the possibility that one of the components might be produced artificially in the course of the purification. In the presence of a photobleaching intermediate of either unphosphorylated or phosphorylated rhodopsin, the binding of guanosine 5'-(beta, gamma-imido)triphosphate (GppNHp) to the alpha-subunit of transducin (T alpha) was remarkably enhanced with increasing concentrations of purified T beta gamma-2. On the contrary, T beta gamma-1 retained little ability, if any, to enhance the GppNHp binding to T alpha; the ability of T beta gamma-1 was at least 30 times lower than that of T beta gamma-2. Such a low activity of T beta gamma-1 was attributed to inability for coupling of T alpha with a photobleaching intermediate of rhodopsin. These results indicate that T gamma-2 is essential for the GTP binding of transducin. The role of T gamma-1 in vertebrate photoreceptor cells was discussed.

Chicken red-sensitive cone visual pigment retains a binding domain for transducin

Iodopsin (a red-sensitive cone visual pigment) and rhodopsin (a rod pigment) were isolated from chicken retina. They were separately reconstituted into phosphatidylcholine liposomes and then mixed with rod transducin (T alpha and T beta gamma) purified from bovine retina. Iodopsin enhanced, only when irradiated, the binding of GppNHp to T alpha to a similar extent to irradiated rhodopsin. Furthermore, the binding of GppNHp to T alpha in the presence of a photobleaching intermediate of iodopsin preferably required T beta gamma-2 rather than T beta gamma-1, which is very similar in profile to that in the presence of the intermediate of rhodopsin (J. Biol. Chem., in press). These results indicate that the binding domain for transducin in iodopsin should closely resemble that in rhodopsin.

Monoclonal antibodies to chicken iodopsin

The protein moiety of chicken iodopsin, R-photopsin, was purified from the chicken retina using a sucrose flotation method followed by two steps of column chromatography. Apparent molecular weights of R-photopsin and scotopsin (the protein moiety of chicken rhodopsin), which was partly purified in the process of purification of R-photopsin, were estimated to be 34,000 and 36,000, respectively, by sodium docecylsulfate-polyacrylamide gel electrophoresis. Using the purified R-photopsin as an antigen, four kinds of hybridoma cells which secreted monoclonal antibodies specific for R-photopsin and iodopsin were prepared. The antibodies thus obtained reacted with neither other chicken cone visual pigments nor rhodopsin as analyzed by immunoblots and immunoprecipitation methods. All the monoclonal antibodies stained the majority of the cone outer segments in chicken retina, while an antiserum raised against cattle rhodopsin stained the rod outer segments as well as some cone outer segments in the retina.

Dependency of photon density on primary process of cattle rhodopsin

The primary photochemical reactions of cattle rhodopsin suspended in H2O or D2O were compared between excitation with both a weak and an intense picosecond laser pulse (wavelength, 532 nm; duration, 25 ps) at room temperature. The time-dependent change of absorbance at about 575 nm demonstrated that photohodopsin, a precursor of bathorhodopsin, was produced immediately after the excitation with a weak picosecond laser pulse. It decayed to bathorhodopsin with a time constant of 45 ps which is close to the value reported previously [Shichida et al., (1984) Photobiochem. Photobiophys., 7, 221-228]. No deuterium effect was observed in this process. Excitation with an intense laser pulse induced instantaneous increase of the absorbance at about 575 nm and remained at almost constant level on the picosecond time scale, which was in good agreement with the pioneering work [Busch et al., (1972) Proc. Natl. Acad. Sci., USA, 69, 2802-2806]. No deuterium effect was observed in this photochemical process.

[Role of plasma histamine and neutrophil chemotactic factor in exercise-induced asthma]

The mechanism of exercise-induced asthma (EIA) is still controversial, although the role of chemical mediator is strongly suspected. In the present study, 50 asthmatic patients were observed after exercise on bicycle ergometer during dry air breathing, and changes of plasma histamine and neutrophil chemotactic factor (NCF) were measured and effect of anti-allergic drugs was examined. 31 patients developed postexertional bronchoconstriction and their % reduction of FEV1 after exercise correlated significantly with the degree of airway hyperresponsiveness to inhaled methacholine determined by Astograph. Plasma histamine levels were examined in 20 EIA positive cases and 13 EIA negative cases, but no significant changes were observed between pre- and post-histamine levels in either group. On the other hand, NCF was elevated significantly after exercise in both EIA positive and negative cases, but postexertional NCF levels were significantly higher in EIA positive than in EIA negative cases. The relationship between % increase of NCF and the % reduction of FEV1 after exercise was significant (r = 0.472, p less than 0.05). DSCG and Azelastine protected the development of EIA in 14 out on 19 cases and 7 out of 12 cases, respectively. Pretreatment with DSCG significantly reduced the increase of NCF after exercise. These results indicates that one of the chemical mediator, NCF, may play an important role in producing postexertional bronchoconstriction in asthmatic patients.

Endothelin-1 depolarizes a ventral root potential in the newborn rat spinal cord

The effect of endothelin-1 (ET-1) was investigated in the isolated spinal cord of the newborn rat. Bath-applied ET-1 produced a depolarization of a lumbar ventral root, which was suppressed by nicardipine or a substance P antagonist (spantide). In addition, the slow ventral root depolarization from L4 segment evoked by electrical stimulation of the contralateral sciatic nerve was also suppressed by spantide or nicardipine. However, nicardipine did not affect the ventral root depolarization induced by substance P, itself. These results indicate that the dihydropyridine-sensitive Ca2+ channels are associated with substance P release and that the effect of endothelin is probably mediated by substance P.

9,13-dicis-rhodopsin and its one-photon-one-double-bond isomerization

Incubation of purified 9,13-dicis-retinal with cattle opsin in 2% digitonin at 20 degrees C produced two pigments, one unstable (lambda max 478 nm) and the other stable (lambda max 485 nm) in hydroxylamine. The two pigments exhibited different characteristics. HPLC analysis revealed that the chromophores of these pigments have respectively 9,13-dicis and 9-cis geometries. Under various conditions the amount of 9,13-dicis-rhodopsin formed never exceeded 30% of the total pigments. The addition of 9,13-dicis-retinal to the ROS suspension containing opsin produced 9-cis-rhodopsin in 97% yield. Irradiation of the 9,13-dicis-rhodopsin mainly produced 13-cis-retinal, while 9-cis-rhodopsin produced the all-trans isomer. These results demonstrated that the one-photon-one-double-bond isomerization process took place in 9,13-dicis-rhodopsin.

Detection of cyclic GMP binding protein and ion channel activity in frog rod outer segments

In order to identify the cGMP-sensitive ion channel protein in frog rod outer segments (ROS), we analyzed cGMP binding proteins in the ROS by means of photoaffinity labeling with [3H]cGMP. We found four cGMP binding proteins with molecular weights (Mws) of 250K, 100K, 92K, and 53K. The 250K protein was an integral-membrane protein, which we named cG-Protein, (cG stands for cGMP). The cGMP-binding to cG-Protein was slightly increased by CaCl2. cG-Protein has a carbohydrate moiety. The amount of cG-Protein per single rod outer segment was estimated to be 9.0 x 10(6) molecules. Light-dependent phosphorylation of cG-Protein with [gamma-32P]ATP was observed. The 100K and 92K proteins were peripheral-membrane proteins, corresponding to cGMP phosphodiesterase. The 53K protein was a soluble protein. Incorporation of a membrane protein fraction of frog ROS into a planar lipid bilayer resulted in the appearance of at least three kinds of ion channel activities; two of them were related to cGMP. The possibility that cG-Protein is the cGMP-sensitive ion channel in vivo is discussed.

Substance P antagonist (spantide) suppresses the compound action potentials of the rat sciatic nerve in vitro

We examined the effects of substance P, [D-Arg1, D-Trp7, 9, Leu1 1] substance P (spantide) and lidocaine on the compound action potentials (APcs) of the rat sciatic nerve in vitro. Substance P had no effect but spantide suppressed the APcs of both A- and C-fibers in a dose-dependent manner and this suppression was reversible at 10(-4) M but irreversible at 10(-3) M. Lidocaine also suppressed the APcs reversibly but spantide was more potent than lidocaine. There seemed to be differences in the suppressing mechanism between the two drugs.

Electrostatic interaction between retinylidene chromophore and opsin in rhodopsin studied by fluorinated rhodopsin analogues

Photochemical reactions of fluorinated rhodopsin analogues (F-rhodopsins) prepared from 10- or 12-fluorinated retinals (10- or 12-F-retinals) and cattle opsin were investigated by means of low-temperature spectrophotometry. On irradiation with blue light at liquid nitrogen temperature (-191 degrees C), the F-rhodopsins were converted to their respective batho intermediates. On warming, they decomposed to their respective fluororetinals and cattle opsin through lumi and meta intermediates. There was a difference in photochemical behavior between batho-12-F-rhodopsin and batho-10-F-rhodopsin. Upon irradiation with red light at -191 degrees C, batho-12-F-rhodopsin was converted to a mixture of 12-F-rhodopsin and 9-cis-12-F-rhodopsin like that of the natural bathorhodopsin, whereas batho-10-F-rhodopsin was not converted to 9-cis-10-F-rhodopsin but only to 10-F-rhodopsin. This fact suggests that the fluorine substituent at the C10 position (i.e., 10-fluoro) of the retinylidene chromophore may interact with the protein moiety during the process of isomerization of the chromophore or in the state of the batho intermediate. On irradiation with blue light at -191 degrees C, 9-cis-10-F-rhodopsin was converted to another bathochromic intermediate that was different in absorption spectrum from batho-10-F-rhodopsin. 9-cis-10-F-rhodopsin was practically "photoinsensitive" at liquid helium temperature (-265 degrees C), whereas 10-F-rhodopsin was converted to a photo-steady-state mixture of 10-F-rhodopsin and batho-10-F-rhodopsin. The specific interaction between the fluorine atom at the C10 position of the retinylidene chromophore and the opsin was discussed in terms of electrostatic interactions.

Metabolism of three trichothecene mycotoxins, T-2 toxin, diacetoxyscirpenol and deoxynivalenol, by bovine rumen microorganisms

The three trichothecene mycotoxins T-2 toxin, diacetoxyscirpenol (DAS) and deoxynivalenol (DON) were incubated in vitro for 12, 24 and 48 h with rumen microorganisms obtained from a fistulated dairy cow. Gas chromatographic and gas chromatographic-mass spectrometric analyses of extracts indicated all three toxins were biotransformed to a variety of deepoxy and deacylated products. DON was partially converted to a product identified as deepoxy DON. DAS was rapidly converted to four products including 15-monoacetoxyscirpenol (MAS), scirpentriol and two new compounds identified as 15-acetoxy-3 alpha,4 beta-dihydroxytrichothec-9,12-diene (deepoxy MAS) and 3 alpha,4 beta,15-trihydroxytrichothec-9,12-diene (deepoxy scirpentriol). T-2 toxin was also completely biotransformed to the products HT-2, T-2 triol and two new metabolites identified as 15-acetoxy-3 alpha,4 beta-dihydroxy-8 alpha-(3-methylbutyryloxy) trichothec-9,12-diene (deepoxy HT-2) and 3 alpha,4 beta,15-trihydroxy-8 alpha-(3-methylbutyryloxy)trichothec-9,12-diene (deepoxy T-2 triol).

Reconstruction with insertion of expanded polytetrafluoroethylene (EPTFE) for iliac venous obstruction

Surgical therapy for DVT in the legs, including reconstruction of the blood circulation system and thrombectomy with a Fogarty catheter, is not always satisfactory, as indicated by the variety of opinions both for and against them. However, it is also a fact that postphlebitic syndrome can result from incomplete treatment. Therefore, surgical approaches should by given priority in the acute stage of the disease. In 5 patients who showed either complete obstruction or insufficient removal of thrombi from the proximal region in leg DVT, we performed crossover femoro-femoral bypass using EPTFE (including two wire reinforced grafts) and were able to obtain good long-term patency over periods of 8-18 months.

Excretion of deoxynivalenol and its metabolite in milk, urine, and feces of lactating dairy cows

Corn contaminated with deoxynivalenol was added to the diets of three dairy cows for 5 d and milk, urine, and 3 d following feeding of the diets. Dietary concentrations of deoxynivalenol averaged 66 mg/kg. Following exposure to deoxynivalenol, unconjugated deepoxydeoxynivalenol, a metabolite of deoxynivalenol, was present in milk at concentrations up to 26 ng/ml. Deoxynivalenol was not detected in the milk. Approximately 20% of the deoxynivalenol fed was recovered in the urine and feces in the unconjugated forms as deepoxydeoxynivalenol (96%) and deoxynivalenol (4%). After incubating urine with beta-glucuronidase, the concentration of unconjugated deepoxydeoxynivalenol increased by 7 to 15-fold whereas unconjugated deoxynivalenol increased 1.6 to 3-fold. Detectable concentrations of unconjugated deepoxydeoxynivalenol were found in urine and feces up to 72 h after the last oral exposure. Thus, urine and feces are the diagnostic specimens of choice for the determination of deoxynivalenol exposure in cows. Feeding deoxynivalenol-contaminated diets for 5 d did not alter feed intake or milk production nor were the milk concentrations of calcium, phosphorus, sodium, potassium, magnesium, or nitrogen altered.