Immobilization of collared peccaries (Tayassu tajacu) and feral hogs (Sus scrofa) with Telazol and xylazine

Quantitative [125I]protein G-based immunohistochemistry was used to map the distribution of beta1 thyroid hormone receptor (TRbeta1) in normal and thyroidectomized adult rat brain, using a previously characterized polyclonal antibody. The distribution of TRbeta1-like immunoreactivity in normal brain was largely but not perfectly concordant with previous accounts of TRbeta1 mRNA distribution in rat brain. Thyroidectomy resulted in increased immunolabeling in most brain regions (mean increase: 14%, range: -4% to +25%), with statistically significant effects being observed in 9 of the 36 brain regions examined. Brain regions showing the most pronounced effects included the habenular nucleus (+22%), the oriens layer of the hippocampal CA3 region (+24%), and the lateral geniculate nucleus of the thalamus (+23%). These results demonstrate that the TRbeta1 protein in brain is capable of plastic changes in response to adult-onset alterations in TH levels. The observed pattern of brain regional receptor changes following thyroidectomy may provide clues for functional effects of thyroid function alterations in adults.     

Structural mapping of the catalytic mechanism for a mammalian phosphoinositide-specific phospholipase C

The crystal structures of various ternary complexes of phosphoinositide-specific phospholipase C-delta 1 from rat with calcium and inositol phosphates have been determined at 2.30-2.95 A resolution. The inositol phosphates used in this study mimic the binding of substrates and the reaction intermediate and include D-myo-inositol-1,4,5-trisphosphate, D-myo-inositol-2,4, 5-trisphosphate. D-myo-inositol-4,5-bisphosphate, and D,1-myo-inositol-2-methylene-1,2-cycli?monophosphonate. The complexes exhibit an almost invariant mode of binding in the active site, each fitting edge-on into the active site and interacting with both the enzyme and the catalytic calcium at the bottom of the active site. Most of the active site residues do not undergo conformational changes upon binding either calcium or inositol phosphates. The structures are consistent with bidentate liganding of the catalytic calcium to the inositol phosphate intermediate and transition state. The complexes suggest explanations for substrate preference, pH optima, and ratio of cyclic to acyclic reaction products. A reaction mechanism is derived that supports general acid/base catalysis in a sequential mechanism involving a cyclic phosphate intermediate and rules out a parallel mechanism where acyclic and cyclic products are simultaneously generated.     

Role of P-450 arachidonic acid epoxygenase in the response of cerebral blood flow to glutamate in rats

BACKGROUND AND PURPOSE: Glutamate, a major excitatory neurotransmitter in the brain, has been implicated in the hyperemic response to increases in the activity of neurons, but the mechanism of glutamate-induced dilation of cerebral blood vessels is unknown. Glutamate has been shown to enhance the release of arachidonic acid (AA) in brain tissue and cultured astrocytes. We have previously shown that astrocytes metabolize AA to vasodilator products, epoxyeicostrienoic acids (EETs), and express a P-450 AA epoxygenase, P-450 2C11. We tested the hypothesis that glutamate-induced dilation of cerebral arterioles is mediated in part by changes in the formation and release of EETs by perivascular astrocytes. METHODS: Primary astrocyte cultures were prepared from 3-day-old rat pups. The cells were labeled with [14C]AA, and the effect of glutamate on the formation of EETs from [14C]AA by cultured astrocytes was studied. The expression of P-450 2C11 protein in the microsomal fractions of cultured astrocytes was assessed by Western blot. In vivo cerebral blood flow measurements were made in adult rats by laser-Doppler flowmetry after administration of glutamate into the subdural space of the rat before and after treatment with miconazole. RESULTS: Glutamate treatment (100 mumol/L for 30 minutes) induced a threefold increase in the formation of EETs from [14C]AA by cultured astrocytes, and the increase was inhibited by miconazole (20 mumol/L), an inhibitor of P-450 AA epoxygenase. Treatment with glutamate (100 mumol/L) for 12 hours increased the expression of P-450 2C11 protein in the microsomal fraction of cultured astrocytes. The response of laser-Doppler cerebral blood flow to administration of glutamate (500 mumol/L) into the subdural space of the rat was significantly attenuated after treatment with miconazole (20 mumol/L for 30 minutes). CONCLUSIONS: These findings suggest a role for a P-450 AA epoxygenase in astrocytes in the coupling between the metabolic activity of neurons and regional blood flow in the brain.     

Observation of rhombic facets on platinum wire after heating in air using scanning tunnelling microscopy

Evidence is provided for the formation of surface faceting due to heating in air at 1160 K. For the first time diamond-shaped facets with angles of 60 and 120° have been observed on the surface of a sample of ultrapure platinum wire in air using scanning tunnelling microscopy. The maximum extension of the facets is about 1000 Å.     

All optical multiple-quantum-well waveguide switch

By increasing the input light intensity to a GaAs/GaAlAs multiple-quantum-well waveguide, an induced phase shift of up to ? radians has been detected. Partial switching of light between two such coupled waveguides by variation of the input light intensity has been observed for the first time.     

Radiotherapy after chemotherapy for metastatic seminoma--a diminishing role. MRC Testicular Tumour Working Party

In a retrospective study, data from 302 patients with metastatic testicular seminoma treated with chemotherapy between 1978 and 1990 in 10 European centres were analysed to evaluate the role, if any, of postchemotherapy treatment with irradiation. The primary endpoint of this study was the progression-free survival rate after chemotherapy with or without additional radiotherapy. This was related to the type of primary chemotherapy, sites and sizes of pre- and postchemotherapy masses, the extent of surgical resection after chemotherapy and the use of radiotherapy. 174 patients had residual disease at the end of chemotherapy. The most important prognostic factors for progression were the presence of any visceral metastases or raised LDH prechemotherapy, and the presence of residual disease at visceral sites after chemotherapy. Approximately half the patients with residual masses underwent postchemotherapy radiotherapy, with selection based predominantly on institutional practice. In patients receiving platinum-based chemotherapy, no significant difference was detected in progression-free survival whether or not radiotherapy was employed. Patients receiving BEP (bleomycin, etoposide and cisplatin) had a progression-free survival rate of 88% (95% CI, 80-96%) uninfluenced by postchemotherapy radiotherapy. In patients with residual masses confined to the abdomen after platinum-based chemotherapy, the absolute benefit to radiotherapy was estimated to be 2.3%. The potential benefit of postchemotherapy radiotherapy is minimal, and so it is concluded that the use of adjuvant radiotherapy to residual masses after platinum-based chemotherapy for metastatic seminoma is unnecessary.     

Side-chains in native and random coil protein conformations. Analysis of NMR coupling constants and chi1 torsion angle preferences

The behaviour of amino acid side-chains in proteins in solution has been characterised by analysing NMR 3JHalphaH beta coupling constants and crystallographic chi1 torsion angles. Side-chains both in the core of native folded proteins and in situations where there is an absence of close packing including the random coil state have been considered. An analysis of experimental 3JHalphaH beta coupling constant data for ten proteins shows that in the core of native proteins a very close similarity is observed between the chi1 conformations adopted in solution and in crystals. There is clear evidence, however, for significant motional averaging about the chi1 torsion angles in solution. Using a model of a Gaussian distribution about the average torsion angles the extent of these fluctuations has been quantified; the standard deviation for the motion is 26 degrees, the fluctuations about chi1 in the protein core being similar in size to those found for main-chain phi torsion angles in solution. From the distribution of chi1 torsion angles in a data base of protein crystal structures, torsion angle populations and coupling constants have been predicted for a random coil polypeptide. Significant variations in the chi1 distributions for different amino acids give differences in the predicted coupling constants; for 3JHalphaH beta, for example, values of 5.1 and 5.7 Hz are predicted for serine compared with 4.9 and 9.9 Hz for leucine. Experimental data for short unstructured peptides show an excellent agreement with the predictions, indicating that the overall chi1 distributions in protein crystals reflect the local preferences of the amino acids. Predictions from the protein data base therefore provide an important framework for interpreting experimental data for non-native protein conformations and for residues on the surface of folded proteins.     

Autoprocessing and peptide substrates for human herpesvirus 6 proteinase

Autoprocessing of the precursor form of human herpesvirus 6 (HHV-6) proteinase at two sites (termed M and R) is required to generate the mature enzyme. Kinetic constants were determined for the hydrolysis of a series of synthetic peptide substrates by mature HHV-6 proteinase, purified to homogeneity. Truncation or replacement of individual residues in peptides mimicking the R-site sequence, indicated that the minimum length for effective hydrolysis by the viral enzyme was P4-P3-P2-Ala*Ser-P2'-P3'-P4' and revealed the importance of the P1 Ala and P4 Tyr residues. Consequently, relevant (P1 or P4) mutations were introduced into the precursor form of the proteinase and the ability of these altered proteins to autoprocess was examined. Introduction of Val in place of the P1 Ala at the M-site essentially abrogated cleavage but mature HHV-6 proteinase was still generated by cleavage at the R-site, indicating that processing of the M-site is not a prerequisite for cleavage of the R-site in the precursor. At the R-site, mutation of the P1 Ala, or of the preceding P4 Tyr residue, prevented processing at the R-site in the precursor so that the mature form of HHV-6 proteinase was not generated. The accumulated data suggest a possible new approach to the design of inhibitors for therapeutic intervention in the life cycle of herpesviruses.