Structure of metal site in Cd-substituted His117Gly mutant of azurin with and without addition of imidazole derivatives

The present work uses 111mCd-perturbed angular correlations of gamma-rays (PAC) to investigate the structure of the metal site of the His117Gly mutant of Pseudomonas aeruginosa azurin in aqueous solution and the effect on the structure upon addition of the following exogenous ligands: imidazole, 4-methyl imidazole, 1-methyl imidazole, 2-methyl imidazole and histidine. The nuclear quadrupole interaction of cadmium bound to the mutant without addition of exogenous ligands shows a strong pH dependence with three different nuclear quadrupole interactions consistent with two pKa values at about 7.2 and 8.6 at 2 degrees C. Addition of the imidazole derivatives resulted in a significant change in the PAC spectrum showing that they coordinate. This is in accordance with observations by EPR for the same mutant with copper at the metal site [den Blaauwen, T. & Canters, G. W. (1993) J. Am. Chem. Soc. 115, 1121-1129]. However, whereas EPR and ultraviolet/visual absorption show that the characteristics of the wild-type copper protein are regained by addition of the imidazole derivatives with the exception of the possible bidentates (histidine and histamine), the comparison of the PAC results to model calculations shows that the cadmium ion must be fourfold coordinated in most cases, probably binding an additional water or hydroxide ligand. A fourfold coordination is in contrast to cadmium-substituted wild-type azurin where PAC data inferred a threefold coordination by a Cys and two His residues [Danielsen, E. Bauer, R., Hemmingsen, L., Andersen. M., Bjerrum, M. J., Butz, T., Tr?ger, W., Canters, G. W., Hoitink, C. W. G., Karlsson, G., Hansson, O. & Messerschmidt, A. (1995) J. Biol. Chem. 270, 573-580]     

Mechanistic investigation into the electrolytic formation of iron from iron(III) oxide in molten sodium hydroxide

Iron(III) oxide tablets were electrolytically reduced to iron in molten sodium hydroxide at 530 °C and recovered to produce iron with 2 wt.% oxygen suitable for re-melting. The cell was operated at 1.7 V and an inert nickel anode was used. The thermodynamics and mechanism of the process was also investigated. By controlling the activity of sodium oxide in the melt, the cell could be operated below the decomposition voltage of the electrolyte with the net sequence of events being the ionization of oxygen, its subsequent transport to the anode and discharge leaving behind iron at the cathode. A reduction time of 1 h was achieved for a 1 g oxide tablet (close to the theoretical reduction time predicted by Faraday’s laws) at a current density of 520 mA cm⁻² with iron phase yields of ∼90 wt.%. The energy consumption was 2.8 kWh kg⁻¹.     

An improved system for the control of dissolved oxygen in freshwater aquaria

A system for the removal and control of dissolved oxygen (DO) from freshwater was designed and constructed with aquarium-type fish studies in mind. Degassed water was obtained using a partial vacuum of -14 psi, and DO regulated at an aquarium scale using electronically controlled aeration with timed partial water renewal. The degassing system was capable of producing water with approximately 1.7 mg L(-1) DO within 10 min of operation, and 0.55 mg L(-1) after 2h. The control system was capable of maintaining DO levels of ca 0.8 mg L(-1) over 48 h in the absence of aeration and further capable of precisely controlling DO levels as low as 1.16+/-0.002 mg L(-1) (mean+/-SEM) with aeration over a 48 h period.     

Lumbar lordosis. Effects of sitting and standing

STUDY DESIGN: The effect of sitting versus standing posture on lumbar lordosis was studied retrospectively by radiographic analysis of 109 patients with low back pain. OBJECTIVE: To document changes in segmental and total lumbar lordosis between sitting and standing radiographs. SUMMARY OF BACKGROUND DATA: Preservation of physiologic lumbar lordosis is an important consideration when performing fusion of the lumbar spine. The appropriate degree of lumbar lordosis has not been defined. METHODS: Total and segmental lumbar lordosis from L1 to S1 was assessed by an independent observer using the Cobb angle measurements of the lateral radiographs of the lumbar spine obtained with the patient in the sitting and standing positions. RESULTS: Lumbar lordosis averaged 49 degrees standing and 34 degrees sitting from L1 to S1, 47 degrees standing and 33 degrees sitting from L2 to S1, 31 degrees standing and 22 degrees sitting from L4 to S1, and 18 degrees standing and 15 degrees sitting from L5 to S1. CONCLUSION: Lumbar lordosis while standing was nearly 50% greater on average than sitting lumbar lordosis. The clinical significance of this data may pertain to: 1) the known correlation of increased intradiscal pressure with sitting, which may be caused by this decrease in lordosis; 2) the benefit of a sitting lumbar support that increases lordosis; and 3) the consideration of an appropriate degree of lordosis in fusion of the lumbar spine.     

Factors affecting contrasting results between self-reported and performance-based levels of physical limitation

Molecular electrostatic potential (MEP) maps of certain 3-methoxy flavone derivatives having different anti-picornavirus activities have been studied. Geometries of the molecules were optimised and charge distributions computed using the AM1 molecular orbital method. Hybridization displacement charges (HDC) were combined with the L?wdin charge distributions to compute the MEP maps. Reliability of the method of computing MEP maps was tested by studying certain other molecules for which ab initio MEP results are available. The anti-picornavirus activities of the flavones have been shown to be related with negative MEP values in two regions, one near the 3-methoxy group and another in a diagonally opposite region near the substituent attached to the C7 atom of the molecules.     

Congenital adrenal hyperplasia presenting as massive adrenal incidentalomas in the sixth decade of life: report of two patients with 21-hydroxylase deficiency

Divergent recommendations exist regarding the evaluation of adrenal incidentalomas. Recent data have indicated a prevalence of adrenal tumors of 71% in nonclassical congenital adrenal hyperplasia (CAH) and unmasked heterozygotes. These data expand the differential diagnosis of such incidental tumors and substantially modify the approach to their evaluation. We present two patients, female pseudohermaphrodites with the simple virilizing form of CAH and 21-hydroxylase deficiency, who functioned successfully as married phenotypic males. Both came to medical attention in the sixth decade by virtue of massive adrenal incidentalomas encountered in the evaluation of recurrent urinary tract infections. Each had a 46, XX karyotype, no palpable testes, and markedly elevated baseline levels of 17-hydroxyprogesterone (17-OH Prog) of 6086 ng/dL and 6750 ng/dL. Both responded appropriately to dexamethasone suppression with reduction of 17-OH Prog, androgens and, in the second patient, ACTH to normal or near normal levels. Histologic and autopsy examination of the first patient's tumor and computed tomographic characteristics of the second revealed a benign adenoma and myelolipoma respectively. We extend and confirm previous recommendations that CAH be included in the differential diagnosis of adrenal incidentaloma and that baseline 17-OH Prog. levels be obtained, with ACTH stimulation if necessary, to diagnose the presence of nonclassical CAH.     

Principal axes and surface fitting methods for three-dimensional image registration

We evaluated the effect of the image acquisition parameters on the accuracy of the principal axes and surface-fitting techniques for three-dimensional image registration. Using two types of phantom objects, MR brain image and a mathematically defined ellipsoid, we simulated pairs of scans with known acquisition parameters, including longitudinal coverage, magnitude of mis-registration, number of sections and section thickness. Both methods are sensitive to the systematic deformation of contours. The principal axes method is also sensitive to incomplete scan coverage and to the x-axis and y-axis misangulation. Both methods are insensitive to the number of sections, section thickness and the number of points per section. Surface fitting performed well without user supervision. There is no need for routine inclusion of the scaling factors as search parameters. The results confirm the feasibility of three-dimensional multimodality registration of brain scans with accuracy 1-2 mm, with surface fitting being the method of choice.     

The effects of guided tissue regeneration and fixation technique on osseous wound healing in rabbit zygomatic arch osteotomies

So called lethal midline granuloma is of great clinical and theoretical interest. Recent evidence has shown that most lethal midline granulomas are associated with a T-cell phenotype and they are therefore referred to as nasal T-cell lymphomas (NTCL). Immunohistochemical studies, however, have shown peculiar phenotypic features such as expression of natural killer (NK)-cell-related markers and extensive T-cell antigen loss including absence of expression of alpha beta T-cell receptor (TCR). In this study, we reported genotypic and immunohistochemical features in two cases of lethal midline granuloma. The histopathological diagnosis of the biopsy specimens was polymorphic reticulosis/midline malignant reticulosis. Both cases displayed a CD2+, CD3-, CD3 epsilon+, CD4-, CD8-, CD16-, CD56+ phenotype, suggesting that these tumors may be peripheral T-cell lymphomas with extensive loss of T-cell antigens and expression of NK cell antigen (CD56), or, alternatively, NK cell neoplasias. No TCR beta gene rearrangement was detected in these cases. Monoclonal Epstein-Barr virus (EBV) genome was detected in each specimen by Southern blot hybridization. The tumor cells in one of the two cases expressed latent membrane protein (LMP). These findings support the concept that lethal midline granuloma constitutes a distinct group of lymphomas that, in addition to their peculiar clinical features, exhibits the phenotype of extensive loss of T-cell antigens and expression of the NK cell antigen, as well as harbors the EBV. In view of the LMP-transforming potential, these data suggest that EBV may play a role in the pathogenesis of lethal midline granuloma.