Primary standardization and determination of gamma ray emission intensities of Ho-166.

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN-CNEN/SP, in São Paulo, for the primary standardization of 166Ho is described. The activity of 166Ho was determined by the efficiency extrapolation technique applied to a 4πß(PC)-γ coincidence system using a gas flow proportional counter in 4π geometry coupled to a 76 × 76 mm NaI(Tl) crystal. The results for the γ-rays intensities at 80.57 and 1379.45 keV were 0.0651(11) and 0.00904(11), respectively.

[Mitral valve papillary fibroelastoma; report of a case].

A 65-year-old woman was admitted to our hospital with a diagnosis of cerebral infarction. She had incomplete paralysis of the right upper extremity. The echocardiogram showed a soft, mobile mass on the atrial side of the mitral posterior leaflet. Surgical treatment was performed 3 weeks after the episode of cerebral infarction. The mass originated from the P1 portion of the posterior leaflet. It was soft and fragile and was carefully resected along with the endocardium of the leaflet, from which it arose. The leaflet was reconstructed with direct 6-0 proline sutures. There was no mitral insufficiency. The histological diagnosis was a papillary fibroelastoma of the mitral valve. The postoperative course was uneventful, with no neurologic complications.

Determination of k0 and Q0 for 74Se, 113In, 186W and 191Ir targets applying covariance analysis.

In the present work, the determinations of k0 and Q0 for 74Se, 113In, 186W and 191Ir targets were performed. The irradiations were conducted near the core of the IEA-R1 4.5 MW swimming-pool nuclear research reactor of the Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP - Nuclear and Energy Research Institute), in São Paulo, Brazil. The irradiation position was chosen where the neutron spectrum shape parameter α is very close to zero. For this reason, the correction to be applied for the determination of Q0 is very close to one, thus improving the accuracy of the results. For each experiment, two irradiations were carried out in sequence: the first one with bare samples and the second with a cadmium cover around the samples. All partial uncertainties were considered, applying the covariance matrix methodology. The final results were compared with the literature.

Standardization of (55)Fe by tracing method.

This work describes the procedure followed by the Laboratório de Metrologia Nuclear (LMN) for the standardization of (55)Fe by the tracing method. This technique was applied using two radionuclides, which decay by the electron capture process followed by a prompt gamma-ray, namely (51)Cr and (54)Mn, as tracers. The calibration was performed in a 4pibeta-gamma coincidence system. The efficiency was obtained by selecting a gamma-ray window set at the 320keV total absorption peak for (51)Cr and at 834keV for (54)Mn.

Disintegration rate and gamma-ray emission probability per decay measurement of Cu-64.

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN for the standardization of activity of 64Cu is described. The measurement was carried out in a 4π (PC) ß-γ coincidence system. The activity per unit mass of the solution was determined by the extrapolation technique. The events were registered using a Time to Amplitude Converter (TAC) associated with a Multi-channel Analyzer. The gamma-ray emission probability per decay of the 1345.7keV transition of 64Cu determined with a calibrated REGe gamma-ray spectrometer was (0.472 ± 0.010) %, in agreement with the literature.

Frequent development of pancreatic carcinomas in the Rana nigromaculata group.

In 1979, 2 species of pond frogs (Rana nigromaculata and Rana plancyi plancyi) were imported from China, and hybrids were made between these and Japanese, Korean, and Taiwanese pond frogs (R. nigromaculata, Rana plancyi fukienensis and Rana brevipoda) that had been kept for a number of years in the Laboratory for Amphibian Biology of Hiroshima University. From 1982, development of tumors, especially in the peritoneal cavity, was noticed frequently in the hybrids and also later, although rarely, in the Japanese pond frogs. Such tumors had never previously been observed among pond frogs in the laboratory. Histological and immunohistochemical studies identified the i.p. tumors to be pancreatic carcinomas with occasional production of insulin and/or somatostatin. Ultrastructural investigation revealed both endocrine and exocrine secretion granules together with C-type retrovirus particles in the carcinoma cells. Other tumors included a retroperitoneal rhabdomyosarcoma, liver adenomas, and an unclassifiable mesenchymal tumor of the foot pad.

Standardization of (59)Fe by 4π(PC)ß-γ software coincidence system.

The procedure for the standardization of (59)Fe using a 4π(PC)ß-γ software coincidence system is described. The standardization was performed with an experimental setup consisting of a thin window gas-flow proportional counter (PC) in 4π geometry coupled to a NaI(Tl) scintillator and to a HPGe detector. The data acquisition was carried out by means of a Software Coincidence System (SCS). The beta efficiency was changed by using Collodion films and aluminum foils as external absorbers.

Heme-linked proton dissociation of carbon monoxide complexes of myoglobin and peroxidase.

It was found from spectrophotometric titration and proton balance measurement that the pKa value of a heme-linked protonation group of horseradish ferro-peroxidase C (donor:H2O2 oxidoreductase, EC 1.11.1.7) shifted from 7.25 to 8.25 upon combination with CO. The spectrophotometric titration experiment with myoglobin also revealed the presence of a heme-linked protonation group, the pKa value being 5.57 in myoglobin and 5.67 in the CO-myoglobin complex. It was concluded that the distinct shift of the pKa value in the case of peroxidase was attributable to the presence of a hydrogen bond between the sixth ligand and the distal base. The difference in the strength of such hydrogen bonding between peroxidase and myoglobin was discussed.

Time-resolved fluorescence spectroscopy and photolysis of the photoreceptor blepharismin.

Blepharismin is the photoreceptor for the photophobic response in the ciliate Blepharisma japonicum (Scevoli, P., Bisi, F., Colombetti, G., Ghetti, F., Lenci, F., and Passarelli, V. (1987) J. Photochem. Photobiol.: B. Biol. 1, 75-84; Lenci, F., Ghetti, F., Gioffre, D., Heelis, P.F., Thomas, B., Phillips, G.O., and Song, P.-S. (1989) J. Photochem. Photobiol.: B. Biol. 3, 449-453). Blepharismin was solubilized from the red cells with 2% n-octylglucopyranoside. A crude pigment-protein preparation was then successively subjected to Bio-Gel A1.5 filtration, FPLC/hydroxyapatite and FPLC/DEAE ion-exchange chromatography. At least two spectrally distinct forms of blepharismin, with the respective absorbance maxima at 597 +/- 1 and 601 +/- 1 nm, were resolved. The steady state fluorescence emission maxima were at 602.5 and 617.5 nm, respectively. The fluorescence decay curves for these pigments were non-exponential. The major component possesses relatively short fluorescence lifetime (200-500 ps) for the former, according to a global analysis. This analysis suggests that the excited state of the shorter wavelength-absorbing form of blepharismin undergoes primary photoprocess faster than that of the free parental chromophore hypericin. Photolysis of blepharismin in solution yielded a irreversible product, accompanied by a 10-12 nm bathochromic shift of the absorbance maximum. However, the mechanistic nature of the time-resolved fluorescence and the photochemistry of blepharismin remains to be elucidated.

Initial spectroscopic characterization of the ciliate photoreceptor stentorin.

Stentorin serves as the primary photosensor in the single cell ciliate, Stentor coeruleus, for its photophobic and phototactic response to light of visible wavelengths. We separated two subunits, stentorin-2A and -2B, from the previous stentorin complex ('stentorin-2') of greater than half a million molecular mass isolated from the photoreceptor organelle (pigment granule). Stentorin-2B bears the chromophore covalently linked to an approx. 50 kDa apoprotein, as determined by SDS-urea-PAGE. Partial amino acid sequences were obtained from this 50 kDa subunit. Its visible and CD spectra were found to be similar to those of stentorin-2. The steady-state and time-resolved fluorescence spectra of stentorin-2B, in H2O and D2O buffers, were also similar to those of stentorin-2. This suggests that the 50 kDa subunit retains the spectral integrity and primary photoreactivity of the stentorin-complex. The picosecond time-resolved fluorescence study revealed that the short picosecond emission component (tau F approximately equal to 8-10 ps) was the predominant emitting species in stentorin-2B and -2, followed by longer decaying species. No deuterium solvent effect was seen in this fast-decaying species. The possible mechanism for the primary photoreaction appears to involve electron transfer coupled with proton transfer.

Fluorescence properties of chlorophyll d-dominating prokaryotic alga, acaryochloris marina: studies using time-resolved fluorescence spectroscopy on intact cells

Antenna components and the primary electron donor of the photosystem (PS) II in the Chlorophyll (Chl) d-dominating prokaryote, Acaryochloris marina, were studied using time-resolved fluorescence spectroscopy in the ps time range. By selective excitation of Chl a or Chl d, differences in fluorescence properties were clearly resolved. At physiological temperature, energy transfer was confirmed by a red shift of emission maximum among PS II antenna components, and the equilibrium of energy distribution among Chl a and Chl d was established within 30 ps. A fluorescence component that can be assigned to delayed fluorescence (DF) was observed at 10 ns after the excitation; however, it was not necessarily resolved by the decay kinetics. At -196 degrees C, a red shift of emission maximum was reproduced but the equilibrium of energy distribution was not detected. DF was resolved in the wavelength region corresponding to Chl a by spectra and by decay kinetics. The lifetime of the DF was estimated to be approx. 15 ns, and the peaks were located at 681 and 695 nm, significantly shorter wavelengths than those of Chl d. These findings strongly suggest that an origin of DF is Chl a, and Chl a is most probably the primary electron donor in the PS II reaction center (RC). These results indicate that the constitution of PS II RC in this alga is essentially identical to that of other oxygenic photosynthetic organisms.

Structure and function of the photoreceptor stentorins in Stentor coeruleus. II. Primary photoprocess and picosecond time-resolved fluorescence.

Stentorin serves as the photoreceptor for the photophobic and negative phototactic responses in Stentor coeruleus. Two forms of the stentorin have been isolated and purified. The strongly fluorescent form, stentorin I at pH 7.8, exhibited nearly exponential fluorescence decay monitored at 620 nm, having two comparable lifetime decay components of 2.53 ns (47%) and 5.95 ns (53%). Stentorin I showed no significant time-resolved fluorescence emission spectra in the picosecond-nanosecond time scales. The weakly fluorescent form, stentorin II, exhibited an ultrafast fluorescence decay component (10 ps) at an emission wavelength of 630 nm and pH 7.8. The amplitudes of the multi-component fluorescence in stentorin II were found to be emission wavelength-dependent. Furthermore, the fluorescence emission spectrum was time-resolvable in the picosecond time scales. Effects of pH and pD on the fluorescence decay kinetics and time-resolved spectra of stentorins I and II have also been investigated. Results are suggestive of proton dissociation as a primary photoprocess from the excited state of stentorin II.

Estrogen prevents oxidative stress-induced endothelial cell apoptosis in rats.

BACKGROUND: Estrogen replacement attenuates the increased risk of cardiovascular disease in postmenopausal women. Recent studies using an in vitro culture system have shown that estrogen inhibits endothelial cell (EC) apoptosis. The in vivo relevance of this finding, however, is not defined. To do so, we have developed a rat vascular injury model in which EC apoptosis induced by hydrogen peroxide plays a role. METHODS AND RESULTS: Intracarotid arterial administration of 0.01 mmol/L hydrogen peroxide for 5 minutes evoked EC apoptosis after 6 to 24 hours, determined by nuclear staining with Hoechst 33342, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, and electron microscopy. Apoptosis was associated with EC loss and was followed by EC regeneration at 72 hours and neointima formation at 1 to 2 weeks. Estradiol replacement in ovariectomized female Wistar rats decreased the rate of apoptotic ECs by approximately 50%, assayed by nuclear morphology of en face specimens, resulting in increased remaining ECs and decreased neointima formation. Progesterone did not influence the effects of estradiol on EC apoptosis. CONCLUSIONS: These results provide new insight into the cardioprotective action of estrogen as well as a paradigm of the response-to-injury hypothesis.

Characteristics of an ovariectomized osteopenic rat model.

Although osteoporosis induced by ovariectomy (Ovx) in the rat has been widely used as a model for postmenopausal osteoporosis in humans, the findings of different investigators are not always consistent. This might be mainly due to differences in the age of the animals at Ovx, time after Ovx, and the variables measured. Therefore, in the present study, Ovx was performed at 4, 10, or 52 weeks and bone changes were observed in rats for 6 months. The effects of Ovx on body weight, femoral length, and femoral volume were marked in rats operated on at the age of 4 weeks, slight in rats operated on at the age of 52 weeks, and intermediate in rats operated on at the age of 10 weeks. A reduction in the ratio of cortical thickness to bone width at the midshaft of the femur was observed only in rats ovariectomized at 52 weeks of age. The specific gravity of the femur and the density of the metaphysis of the femur decreased after Ovx in all rats. The ratio of ash weight to dry weight of the femur, a measure of the normal calcification of bone, was unchanged shortly after Ovx but gradually decreased in all rats.

Free radical mechanisms in enzyme reactions.

Free radicals are formed in prosthetic groups or amino acid residues of certain enzymes. These free radicals are closely related to the activation process in enzyme catalysis, but their formation does not always result in the formation of substrate free radicals as a product of the enzyme reaction. The role of free radicals in enzyme catalysis is discussed.

Energy transfer processes in Rhodopseudomonas palustris grown under low-light conditions. Heterogeneous composition of LH 2 complexes and parallel energy flow pathways.

Excitation energy flow in the purple photosynthetic bacterium Rhodopseudomonas palustris grown under a low-light intensity was studied by time-resolved fluorescence spectroscopy in the ps time range. This bacterium synthesized the B824 component under this light condition. Time-resolved spectra at 20 degrees C indicated the sequential energy flow in the order of B803, B856, B882 and B900, long wavelength antenna. An emission from B803 was not observed. A remarkable feature was the emission from B824 throughout the measuring time. After the excitation pulse of 100 ps, the spectra did not change any further, indicating the establishment of an equilibrium among components. Based on the energy distribution after equilibrium, parallel energy transfer pathways to LH 1 were suggested; one including B824 integrated in the B803-824-856 complex, and the other, from the B803-856 complex to B882. The latter was the dominant energy flow pathway in this bacterium.

Presence and significance of minor antenna components in the energy transfer sequence of the green photosynthetic bacterium Chloroflexus aurantiacus.

Antenna components in the energy transfer processes of a green photosynthetic bacterium Chloroflexus aurantiacus were spectrally investigated by time-resolved fluorescence spectroscopy at -196 degrees C on intact cells. Besides major antenna components so far reported, three minor components were resolved; those were Bchl c located at 785 nm, the baseplate Bchl a at 819 nm and Bchl a in the B808-866 complex at 910 nm. The last component was assigned to a longer wavelength antenna closely associated with a reaction center. An additional Bchl c fluorescence component was kinetically suggested to be present, which can be an energy donor to a major Bchl c. Presence of these minor components was signified in terms of (1) increase in the spectral overlap integral and (2) adjustment of the direction of dipole moments in the energy transfer sequence of intact cells.

Oxygen exchange between the Fe(IV) = O heme and bulk water for the A2 isozyme of horseradish peroxidase.

Resonance Raman spectra were observed for compound II of horseradish peroxidase A2, and the Fe(IV) = O stretching Raman line was identified at 775 cm-1. This Raman line shifted to 741 cm-1 upon a change of solvent from H2(16)O to H2(18)O, indicating occurrence of the oxygen exchange between the Fe(IV) = O heme and bulk water. The oxygen exchange took place only at the acidic side of the heme-linked ionization with pKa = 6.9.

Resonance Raman characterization of hog thyroid peroxidase. An SERRS study.

Resonance Raman (RR) spectra of hog thyroid peroxidase (TPO) were observed for the first time and compared with those of lactoperoxidase (LPO) and horseradish peroxidase (HRP). Since TPO purified by monoclonal antibody-assisted immunoaffinity chromatography was strongly fluorescent, the surface enhancement technique using Ag colloid adsorption was used for the oxidized form, but ordinary RR spectra could be obtained for the reduced form. The RR spectra of TPO were distinct from those of HRP in both the oxidized and reduced states and indicated the presence of six-coordinated iron-protoporphyrin.

Energy migration in allophycocyanin-B trimer with a linker polypeptide: analysis by the principal multi-component spectral estimation (PMSE) method.

Energy migration processes in allophycocyanin-B trimer with a linker polypeptide were analyzed using the principal multi-component spectral estimation (PMSE) method, which does not require assumption of component number, decay function, or the spectral band shape. We determined the number of spectral components showing independent kinetic behavior by the eigen-value of an auto-correlation matrix, and further the spectra of the components and their rise and decay curves. Two decay components were resolved at 20 degrees C: one corresponded to the decay of one type of beta-84 chromophore, and the other to the decay from the thermally equilibrated state between another type of beta-84 chromophore and the alpha-allophycocyanin B chromophore. An additional slow decay process was resolved at -196 degrees C. We also compared the component spectra obtained using the PMSE method with the decay-associated spectra obtained using the global analysis.