Portal vein arterialization in hepatobiliary surgery and liver transplantation

We reviewed the literature reports and our personal experience on partial portal vein arterialization (PPVA) to prevent and treat acute liver failure (ALF) following major hepatobiliary surgery or another etiology. Experimental studies in rats have assessed the efficacy of PPVA in treatment of ALF induced by extended resections in normal or fatty livers or in toxic carbon-tetrachloride damage. The treated groups showed greater survival and faster recovery of liver function. Among 11 clinical cases reported in the literature, PPVA was performed in four cases to prevent and in seven cases to treat ALF. Eight patients survived, showing rapid recovery of liver function and resolution of the clinical condition. This relatively simple procedure has shown itself able to promote liver regeneration. The PPVA procedure has shown itself to be safe and simple as well as to offer a promising approach to the failing liver.

Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project

We report the generation and analysis of functional data from multiple, diverse experiments performed on a targeted 1% of the human genome as part of the pilot phase of the ENCODE Project. These data have been further integrated and augmented by a number of evolutionary and computational analyses. Together, our results advance the collective knowledge about human genome function in several major areas. First, our studies provide convincing evidence that the genome is pervasively transcribed, such that the majority of its bases can be found in primary transcripts, including non-protein-coding transcripts, and those that extensively overlap one another. Second, systematic examination of transcriptional regulation has yielded new understanding about transcription start sites, including their relationship to specific regulatory sequences and features of chromatin accessibility and histone modification. Third, a more sophisticated view of chromatin structure has emerged, including its inter-relationship with DNA replication and transcriptional regulation. Finally, integration of these new sources of information, in particular with respect to mammalian evolution based on inter- and intra-species sequence comparisons, has yielded new mechanistic and evolutionary insights concerning the functional landscape of the human genome. Together, these studies are defining a path for pursuit of a more comprehensive characterization of human genome function.

Protective Effect of Portal Vein Arterialization in Acute Liver Failure Induced by Hepatectomy in Normal and Fatty Liver Rat

AIM

We sought to determine whether an additional supply of oxygenated blood achieved by partial portal vein arterialization (PPVA) was protective on normal or fatty liver (FL) in rats with acute liver failure (ALF) induced by hepatectomy.

METHODS

Sprague-Dawley rats with normal or FL were segregated either to receive or not to undergo PPVA after hepatectomy. FL was induced by feeding a choline-deficient diet (5 days). PPVA was performed by anactamasing the left renal artery to the splenic vein with a stent following a left nephrectomy and splenectomy; the control rats underwent left nephrectomy and splenectomy only. Liver injury was evaluated by the serum alanine aminotransferase (ALT) level. The animals were sacrificed at 24 hours, 48 hours, and 7 days to collect blood and liver tissue samples for biochemical analysis. The 7-day survival was assessed in separate experimental groups.

RESULTS

PPVA significantly increased Po2 and oxygen saturation in the portal blood compared to non PPVA rats. PPVA significantly improved the 7-day survival compared with controls in both groups: hepatectomy of normal liver (90% vs 30%) and hepatectomy of FL (75% vs 25%). Serum ALT levels were slightly lower in the PPVA groups compared with the non-PPVA groups without a significant difference. Prothrombin activity decreased soon after hepatectomy in the normal and the FL liver groups but recovered rapidly thereafter without differences between the PPVA and non-PPVA treated animals.

CONCLUSION

An additional supply of arterial oxygenated blood through a PPVA promotes rapid resolution of ALF after partial hepatectomy in rats with normal or fatty livers, significantly improving 7-day survivals compared to hepatectomy controls.

Technical aspects of portal vein arterialization for acute liver failure: from rat lab to man

Survival rates of patients with acute liver failure (ALF) without transplantation are poor. However, many of them die awaiting a transplant because of the donor organ shortage. Supporting these patients until an organ becomes available or until their own liver is able to regenerate itself thus avoiding transplantation is a major goal in their multidisciplinary treatment. Animal experimental studies have shown that portal vein arterialization (PVA) enhances the regenerative capacity of hepatocytes by increasing the oxygen supply to the liver after extended hepatectomy or in toxin-induced ALF models. Furthermore, we have reported the application of PVA in patients with ALF. We herein have described the technical aspects of the PVA procedure both in preclinical models and in man.

Double kidney transplantation: initial experience of the Bologna Transplant Center

AIM

Double-kidney transplantation is performed using organs from marginal donors with a histological score not suitable for single kidney transplantation. The aim of the study is to verify the results obtained with double-kidney transplantation in terms of graft and patient survival and complications.

METHODS

Between September 2001 and September 2004, 16 double-kidney transplantations were performed in our center. The kidneys were all perfused with Celsior solution and the mean cold ischemia time was 17.6+/-2.7 hours. In all cases a pre-transplant kidney biopsy was performed to evaluate the damage. Immunosuppression was tacrolimus based for all patients.

RESULTS

Eight patients had good renal postoperative function while the other eight had acute tubular necrosis. Two of the patients who had severe acute tubular necrosis never recovered renal function. There was only one episode of acute rejection, while the incidence of urinary complications was 31.2%; there were two surgical revisions for intestinal perforation. The graft and recipient survival was 78.1% and 100% and 78.1% and 93.7% at 3 and 36 months.

CONCLUSIONS

Double-kidney transplantation is a safe way to face the organ shortage. Moreover the score used in this study is useful to determine whether a kidney should be refused or suitable for single or dual-kidney transplantation. The results of our initial experience are encouraging, but this series is too small in number to consent a conclusive statement.

Genome-scale mapping of DNase I sensitivity in vivo using tiling DNA microarrays

Localized accessibility of critical DNA sequences to the regulatory machinery is a key requirement for regulation of human genes. Here we describe a high-resolution, genome-scale approach for quantifying chromatin accessibility by measuring DNase I sensitivity as a continuous function of genome position using tiling DNA microarrays (DNase-array). We demonstrate this approach across 1% ( approximately 30 Mb) of the human genome, wherein we localized 2,690 classical DNase I hypersensitive sites with high sensitivity and specificity, and also mapped larger-scale patterns of chromatin architecture. DNase I hypersensitive sites exhibit marked aggregation around transcriptional start sites (TSSs), though the majority mark nonpromoter functional elements. We also developed a computational approach for visualizing higher-order features of chromatin structure. This revealed that human chromatin organization is dominated by large (100-500 kb) 'superclusters' of DNase I hypersensitive sites, which encompass both gene-rich and gene-poor regions. DNase-array is a powerful and straightforward approach for systematic exposition of the cis-regulatory architecture of complex genomes.

Activity of trans-2-hexenal against Penicillium expansum in 'Conference' pears

AIMS

To investigate the effects of trans-2-hexenal on blue mould disease, patulin content and fruit quality in 'Conference' pears.

METHODS AND RESULTS

Fruits, wounded and inoculated with Penicillium expansum or non-inoculated, were exposed to trans-2-hexenal vapour treatment (12.5 microl l(-1)) at 20 degrees C. A greater reduction of decay was obtained by treatment application 24 or 48 h after inoculation, in contrast trans-2-hexenal application 2 h after inoculation was ineffective. Fruit storage temperature (-1 degrees C) after treatment did not affect the antifungal activity. Although 2-h exposure to trans-2-hexenal was effective in reducing blue mould, an exposure of at least 8 h was required to reduce fruit patulin content. Treatments did not affect fruit physical-chemical characteristics. After 6 days at 20 degrees C following exposure, trans-2-hexenal residue in treated fruits was less than the natural content of the compound in unripe fruits.

CONCLUSIONS

trans-2-Hexenal treatment is effective in the reduction of blue mould infections and patulin content in Conference pears when applied 24-48 h after pathogen inoculation.

SIGNIFICANCE AND IMPACT OF THE STUDY

trans-2-Hexenal could be a natural alternative to fungicides in the control of P. expansum infections. Further work is needed to study the methods and conditions avoiding the persistence of off-odours and off-flavours in pears after their exposure to trans-2-hexenal vapours.

Successful Treatment of CCL4-Induced Acute Liver Failure With Portal Vein Arterialization in the Rat

INTRODUCTION

Optimization of the conditions for regeneration of the native diseased liver is a major goal in patients with acute liver failure. This study sought to determine whether portal vein arterialization (PVA), which increases the oxygen supply to the liver, was protective in a rat model of liver failure.

METHODS

At 24 hours after CCl(4) intoxication, Sprague-Dawley rats (six per group) were assigned to receive PVA or as controls. We determined blood tests, histology, and 10-day survivals. Hepatocyte regeneration was assessed by the mitotic index and bromodeoxyuridine (BrdU) incorporation.

RESULTS

Serum transaminases were significantly lower in PVA-treated rats than in control animals: liver necrosis resolved rapidly after PVA. The BrdU staining and mitotic index were severalfold higher among PVA-treated than in untreated rats. Survival was 100% among rats with PVA and 40% in untreated animals (P < .01).

CONCLUSIONS

PVA led to resolution of CCl(4)-induced massive liver necrosis in the rat. This effect was probably mediated by activation of rapid and extensive hepatocyte regeneration. PVA might provide a novel, alternative approach to treat acute liver failure.

Portal vein oxygen supply through a liver extracorporeal device to treat acute liver failure in Swine induced by subtotal hepatectomy: preliminary data

AIM

To determine whether the increase of oxygen supply in the portal system by a liver extracorporeal (L.E.O.NARDO) device is effective in treating swine with subtotal hepatectomy leading to acute liver failure (ALF).

METHODS

Eight swine with ALF induced by 85% to 90% liver resection and 5 minutes of ischemia-reperfusion injury were randomly divided into two groups: four animals received L.E.O.NARDO treatment and four swine were not treated (control group). Blood was withdrawn from the iliac artery and reversed in the portal venous system. An extracorporeal device was interposed between the outflow and the inflow in order to monitor the hemodynamic parameters. Each treatment lasted 6 hours. Serum and liver samples were collected in both groups. The survival was assessed at 1 week.

RESULTS

L.E.O.NARDO treatment yielded beneficial effects for subtotal hepatectomy-induced ALF in swine with decreased serum transaminases as compared with the untreated group. International normalized ratio recovered rapidly in the L.E.O.NARDO group, remaining significantly lower than in untreated animals. The 7-day survival of L.E.O.NARDO group swine was significantly higher than that of untreated animals, with a significant difference. Three swine in the L.E.O.NARDO group survived 1 week while none of the swine in the control group were alive at that time.

CONCLUSIONS

Oxygen supply in the portal vein through the L.E.O.NARDO device is easily applicable, efficacious, and safe and may represent a novel approach for ALF in swine induced by subtotal liver resection.

Portal Vein Arterialization for the Treatment of Post Resection Acute Liver Failure in the Rat

INTRODUCTION

Hyperoxygenation of the liver has been suggested to improve its regenerative capacity. Thus, this study sought to determine whether an additional supply of oxygenated blood delivered by portal vein arterialization (PVA) was protective against acute liver failure induced by hepatectomy.

METHODS

Sprague-Dawley rats (six per each group) were divided to either undergo PVA or be untreated after extended hepatectomy. Liver injury was evaluated by the serum alanine aminotransferase (ALT) levels. Hepatocyte regeneration was assessed by calculating the mitotic index and bromodeoxyuridine staining. The 10-day survival was assessed in separate experimental groups.

RESULTS

The pO(2) in portal blood increased significantly following PVA. Serum ALT levels were significantly reduced in arterialized versus nonarterialized rats. PVA promotes liver regeneration. Finally, PVA significantly improved host survival compared to the controls: 90% versus 30%, respectively.

CONCLUSION

These data suggested that an additional supply of arterial oxygenated blood through PVA promoted a rapid regeneration, leading to a faster restoration of liver mass after partial hepatectomy in rats. Thus, PVA may represent a novel tool to optimize hepatocyte regeneration.

Normal neuropsychological development in children with congenital complete heart block who may or may not be exposed to high-dose dexamethasone in utero

BACKGROUND

Antenatal and postnatal treatment with dexamethasone (DEX) may negatively affect the neuropsychological development in children. Maternal anti-Ro/Sjögren's syndrome A (SSA) antibodies may also be associated with learning disabilities in offspring.

OBJECTIVE

To assess neuropsychological development in babies exposed to very high dosages of DEX in utero, whose mothers were anti-Ro/SSA positive.

METHODS

13 children with congenital complete heart block (CHB) (11 exposed and 2 not exposed to DEX) and 3 healthy siblings, all of anti-Ro/SSA-positive women, were evaluated. 11 preschool-aged children (5 boys) were assessed using Griffiths Mental Development Scales. 5 school-aged children (2 boys) were examined using Wechsler Intelligence Scale for Children-Revised to check IQ and reading tests to explore the existence of learning disabilities or dyslexia. None of the children had had major neonatal complications, although those with CHB had to be paced at different intervals from birth.

RESULTS

The children had been exposed in utero to a mean total dose of 186.6 mg DEX. IQ levels were always normal (mean IQ 105.1, standard deviation (SD) 9.5). Only one child had a learning disability, of borderline clinical significance, but this child had never been exposed to DEX.

CONCLUSION

No negative effects were found on the neuropsychological development in this cohort of children, even if they had been exposed to maternal anti-Ro/SSA antibodies and to very high dosages of DEX (much higher than those used to improve fetal lung maturity). These findings might be of interest in view of the large number of infants exposed in the past to repeated antenatal courses of steroids.

Effect of pH on axial ligand coordination of cytochrome c" from Methylophilus methylotrophus and horse heart cytochrome c

The effect of protons on the axial ligand coordination and on structural aspects of the protein moiety of cytochrome c' ' from Methylophilus methylotrophus, an obligate methylotroph, has been investigated down to very low pH (i.e., 0.3). The unusual resistance of this cytochrome to very low pH values has been exploited to carry out this study in comparison with horse heart cytochrome c. The experiments were undertaken at a constant phosphate concentration to minimize the variation of ionic strength with pH. The pH-linked effects have been monitored at 23 degrees C in the oxidized forms of both cytochromes by following the variations in the electronic absorption, circular dichroism and resonance Raman spectra. This approach has enabled the conformational changes of the heme surroundings to be monitored and compared with the concomitant overall structural rearrangements of the molecule. The results indicate that horse heart cytochrome c undergoes a first conformational change at around pH 2.0. This event is possibly related to the cleavage of the Fe-Met80 bond and a likely coordination of a H(2)O molecule as a sixth axial ligand. Conversely, in cytochrome c" from M. methylotrophus, a variation of the axial ligand coordination occurs at a pH that is about 1 unit lower. Further, it appears that a concerted cleavage of both His ligands takes place, suggesting indeed that the different axial ligands present in horse heart cytochrome c (Met/His) and in cytochrome c" from M. methylotrophus (His/His) affect the heme conformational changes.

[Retinopathy of prematurity: incidence and risk factors]

The study analyses the incidence of the retinopathy of prematurity (ROP) and its correlation with the most important risk factors in neonates with gestational age (GE) < or = 32 weeks and/or with birth weight (BW) < or = 1500 g. The cohort of our study is composed by 305 preterms with Mean GE of 29.8 weeks and Mean BW of 1312 g, studied at the Neonatal Intensive Care Unit of the University of Parma during January 1993-December 1999. The incidence of ROP resulted 19.7% in our group and was inversely proportional to the GE and BW. No preterms with GE < or = 32 weeks presented retinopathy, while there has been an incidence of the 65% in the subjects with GE lower than 26 weeks. The most severe grade of ROP was mainly seen in the newborns with the lowest GE (31%), whilst only the 1.5% of the preterms with GE of 30-31 weeks developed ROP of stage 3 or 3+. Similar results were seen when the data were compared with the birth weight. However a direct relation was seen with the duration of the O2 therapy and with the typical pathologies of the prematurity, namely respiratory distress syndrome (RDS) and intraventricular haemorrhages (IVH). Among the other risk factors evaluated, the blood transfusion was the most relevant.

Role of the distal phenylalanine 54 on the structure, stability, and ligand binding of Coprinus cinereus peroxidase

Resonance Raman and electronic absorption spectra obtained at various pH values for the Fe3+ form of distal F54 mutants of Coprinus cinereus peroxidase are reported, together with the Fe2+ form and fluoride and imidazole adducts at pH 6.0, 5.0, and 10.5, respectively. The distal phenylalanine residue has been replaced by the small aliphatic residues glycine and valine and the hydrogen-bonding aromatic residues tyrosine and tryptophan (F54G, -V, -Y, and -W, respectively). These mutations resulted in transitions between ferric high-spin five-coordinate and six-coordinate forms, and caused a decrease of the pKa of the alkaline transition together with a higher tendency for unfolding. The mutations also alter the ability of the proteins to bind fluoride in such a way that those that are six-coordinate at pH 5.0 bind more strongly than both wild-type CIP and F54Y which are five-coordinate at this pH value. The data provide evidence that the architecture of the distal pocket of CIP is altered by the mutations. Direct evidence is provided that the distal phenylalanine plays an important role in controlling the conjugation between the vinyl double bonds and the porphyrin macrocycle, as indicated by the reorientation of the vinyl groups upon mutation of phenylalanine with the small aliphatic side chains of glycine and valine residues. Furthermore, it appears that the presence of the hydrogen-bonding tyrosine or tryptophan in the cavity increases the pKa of the distal histidine for protonation compared with that of wild-type CIP.

Spectroscopic characterization of recombinant pea cytosolic ascorbate peroxidase: similarities and differences with cytochrome c peroxidase

Recombinant pea cytosolic ascorbate peroxidase (APX) has been characterized by resonance Raman (RR) and electronic absorption spectroscopies. The ferric and ferrous forms together with the complexes with fluoride and imidazole have been studied and compared with the corresponding spectra of cytochrome c peroxidase (CCP). Ferric APX at neutral pH is a mixture of 6- and 5-coordinate high-spin and 6-c low-spin hemes, the latter two species being dominant. The results suggest that the low-spin form derives from a water/hydroxo ligand bound to the heme iron and not from a strong internal ligand as observed in CCP at alkaline pH. Two Fe-Im stretching modes are identified, as in CCP, but the RR frequencies confirm a weaker His163-Asp208 hydrogen bond than in CCP, as suggested on the basis of the X-ray structure [Patterson, W. R., and Poulos, T. L. (1995) Biochemistry 34, 4331-4341]. The data show that CCP and APX have markedly different orientations of the vinyl substituents on the heme chromophore resulting from different steric constraints exerted by the protein matrix.

Mutation of the distal arginine in Coprinus cinereus peroxidase--structural implications

Heme peroxidases of prokaryotic, plant and fungal origin share the essential His and Arg catalytic residues of the distal cavity and a proximal His bound to heme iron. Spectroscopic techniques, in contrast to X-ray crystallography, are well suited to detect the precise structure, spin and coordination states of the heme as influenced by its near environment. Resonance Raman and electronic absorption spectra obtained at various pH values for Fe3+ and Fe2+ forms of distal Arg51 mutants of the fungal Coprinus cinereus peroxidase are reported, together with the fluoride adducts at pH 5.0. This basic catalytic residue has been replaced by the aliphatic residue Leu, the polar residues Asn and Gln and the basic residue Lys (Arg51-->Leu, Asn, Gln, and Lys, respectively). These mutations cause changes in the coordination and spin states of the heme iron, and in the v(Fe-Im) stretching frequency. The variations are explained in terms of pH-dependent changes, charge location, size and hydrogen-bonding acceptor/donor properties of the residue at position 51. The present work indicates that the hydrogen-bond capability of the residue in position 51 influences the occupancy of water molecules in the distal cavity and the ability to form stable complexes between anionic ligands and the heme Fe atom.

pH dependence of structural and functional properties of oxidized cytochrome c" from Methylophilus methylotrophus

Cytochrome c" from Methylophilus methylotrophus is an unusual monoheme protein that undergoes a major redox-linked change in the heme arrangement: one of the two axial histidines bound to the iron in the oxidized form is detached upon reduction and a proton is taken up. The kinetics of reduction by sodium dithionite and the spectroscopic properties of the oxidized cytochrome c" have been investigated over the pH range between 1.4 and 10.0. The rate of reduction displays proton-linked transitions of pKa congruent with 5.5 and 2.4, and a spectroscopic transition with a pKa congruent with 2.4 is also observed. The protein displays a complete reversibility after exposure to low pH, and both electronic absorption and resonance Raman spectroscopic properties suggest that the transition at lower pH brings about a drastic change in the heme coordination geometry. Circular dichroism spectra indicate that over the same proton-linked transition, the protein undergoes a marked decrease (approximately 60%) of the alpha-helical content toward a random coil arrangement, which is recovered upon increasing the ionic strength. The structural change at low pH is linked to a concerted two-proton transition, suggesting the detachment and protonation of axial histidine(s). Such kinetic and spectroscopic features along with the remarkable capacity of this protein to recover its native structure after exposure to extremely low pH values makes it a promising model for studying folding processes and stability in heme proteins.

Fluoride binding in hemoproteins: the importance of the distal cavity structure

The electronic absorption and resonance Raman spectra of the fluoride complexes of various peroxidases and selected site-directed mutants have been studied at pH 5.0, and compared to the spectra obtained for the myoglobin-F adduct. It is shown that the electronic absorption maxima depend on the degree of conjugation between the porphyrin macrocycle and the vinyl substituents. Moreover, it is confirmed that the wavelength of the CT1 band is a sensitive probe of axial ligand polarity and of its interaction with the distal protein residues. The results highlight the different mechanism of stabilization of the fluoride ligand exerted by the distal residues in myoglobin and peroxidases. In peroxidases, the Arg is determinant in controlling the ligand binding via a strong hydrogen bond between the positively charged guanidinium group and the anion. Mutation of Arg to Leu decreases the stability of the complex by 900-fold, suggesting that this interaction stabilizes the complex by 4 kcal/mol. The distal His also contributes to the stability of the fluoride complex, presumably by accepting a proton from HF and hydrogen-bonding, through a water molecule, to the anion. Mutation of His to Leu decreases the stability of the fluoride complex by 30-fold, suggesting that this interaction is much weaker than the interaction with the distal Arg. For Mb, the distal His is solely responsible for stabilization of the exogenous ligand.

Particle sizing with a simple differential light-scattering photometer: homogeneous spherical particles

A simple light-scattering photometer has been designed to measure the angular distribution of the intensity of polarized laser light scattered by micrometer and submicrometer samples. The photometer uses an ellipsoidal reflector and simple optical components to collect the He-Ne laser-scattered light and to focus it onto a 512-element photodiode array. Experimental data have been obtained for several monodisperse aqueous solutions of latex spheres of different sizes. The results have been satisfactorily interpreted on the basis of the electromagnetic scattering theory. In particular the Mie formulation has been properly reformulated to take into account the corrections to the scattered intensity determined by the apparatus design making it possible to perform particle sizing.

The study of visual evoked potentials in patients with thyroid-associated ophthalmopathy identifies asymptomatic optic nerve involvement

In the present study we have recorded visual evoked cortical potentials (VECP) in 88 patients affected by autoimmune thyroid disease and thyroid-associated ophthalmopathy (TAO) without clinical signs of optic neuropathy. At the time of ophthalmological examination, 37 of these patients were hyperthyroid, 41 were euthyroid, and 8 were hypothyroid; 2 were not assessed. Twenty-nine normal subjects served as controls. We performed pattern reversal visual stimulation and recorded the amplitude and latency of the cortical electric response at 100 ms (P100 wave). There were no differences in the mean P100 amplitude of TAO patients and normal subjects. The mean P100 latency in patients was 105.6 +/- 0.5 ms, significantly higher than that in normal subjects (102.0 +/- 0.5 ms; P < 0.00003). Latency in euthyroid patients did not differ from that in either hypo- or hyperthyroid patients. The VECP test was positive (latency, > or = 110.0 ms) in 21 (23.8%) TAO patients. In patients with proptosis greater than 21 mm, latency was 106.7 +/- 0.7 ms, significantly higher than that in patients with normal Hertel measurements (104.3 +/- 0.6 ms; P < 0.01). Latency was not increased in patients with acute inflammatory signs compared to those with inactive eye disease and in patients with altered extrinsic motility. In patients with an abnormal visual field study, the mean latency was 110.3 +/- 1.5 ms, significantly higher than that in patients with a normal visual field (104.7 +/- 0.4; by t test, P < 0.000003). In conclusion, we observed a prolongation of the latency of the evoked cortical response in patients with TAO without subjective visual complaints and without optic nerve compression. We believe that the study of VECP in TAO is complementary to the study of the visual field in identifying early optic nerve dysfunction in the absence of decreased visual acuity.

Versatility of heme coordination demonstrated in a fungal peroxidase. Absorption and resonance Raman studies of Coprinus cinereus peroxidase and the Asp245-->Asn mutant at various pH values

The pH dependence of the electronic absorption and resonance Raman (RR) spectra of FeIII and FeII forms of Coprinus cinereus peroxidase (CIP) and its Asp245-->Asn (D245N) mutant has been examined in detail. The spectral data were obtained in the pH range 3.8-12.0. These spectra were used to assess the spin and ligation states of the heme via the porphyrin marker band frequencies and the wavelengths of the absorption maxima, especially that of the band (CT1) due to the charge transfer from the porphyrin to the heme iron via the a' 2u(pi)-->eg (d pi) electronic transition. The RR spectra were obtained by using different excitation wavelengths and polarized light. The data obtained for ferric CIP show that two pH-induced structural transitions exist. At acid pH the Soret and the CT1 absorption maxima occur at 394 and 652 nm, respectively, compared with the values of 403 and 649 nm observed at neutral pH. The electronic data indicate that at acid pH the proximal Fe-Im bond might be weakened or ruptured, and the RR spectra show a new species (5-c HS) different from the normal neutral 5-coordinate high-spin (5-c HS) heme. At pH 12.0, the protein converts to a 6-coordinate low-spin (6-c LS) heme with a hydroxyl ligand coordinated in the sixth position of the heme iron and strongly hydrogen-bonded with the positively charged guanidinium group of the distal Arg51 residue. Replacement of the aspartate carboxylate group of Asp245, which acts as hydrogen-bond acceptor to the proximal His183 ligand of the heme Fe, with a carboxamide group of an asparagine residue has a profound influence on the heme coordination. The RR spectra of the Fe(II) form of this mutant at both neutral and alkaline pH values show a band at 204 cm-1 assigned to the Fe-His stretch associated with a fairly weak or non-hydrogen-bonded imidazole. The ferric form of the mutant shows a great variability in coordination and spin states upon pH titration. Between pH 8.8 and 3.8 the spectra are mainly characteristic of a 6-coordinate high-spin heme, presumably with a water molecule bound on the distal side of the Fe atom. The pKa of the alkaline transition of the mutant is much lower than that of the wild-type protein. At pH 10.0 the D245N mutant is in its final alkaline form, which markedly differs from that of the parent enzyme. The spectral data indicate that the majority of the protein has 5-coordinate high-spin heme (5-c HS), with the Fe-His 183 bond broken and the distal axial coordination site of the heme iron occupied by a hydroxyl group, which is strongly hydrogen-bonded with distal Arg51. Therefore, the Asp245-->Asn mutation on the proximal side results in the breakage of the Fe-His bond at alkaline pH.

Effect of the His175-->Glu mutation on the heme pocket architecture of cytochrome c peroxidase

Resonance Raman (RR) and electronic absorption spectra of the ferric and ferrous forms of the His175Glu mutant of cytochrome c peroxidase are reported. At 296 K, the FeIII form is five-coordinate high spin and the resonance Reman spectra are very similar to those obtained for the wild type enzyme, even though in the mutant the Fe atom is bound to an oxygen atom of the Glu residue. The only difference is that the bands due to the out-of-plane modes are very weak, indicating a less distorted heme plane compared to CCP. The absorption spectrum is similar to that of CCP, as far as the Soret and alpha, beta bands are concerned, but the charge-transfer band due to the a2u(pi)-->eg(d pi) transition is 8 nm blue-shifted relative to that of the wild type enzyme, indicating that a more negative ligand is bound to the heme iron. As the temperature is lowered, the five-coordinate heme converts to a six-coordinate high-spin form. The conversion is readily reversible. A temperature effect on the protein structure is proposed that permits the Fe atom to approach the heme plane and to bind the distal water molecule. The results are discussed in terms of the X-ray structure, which shows a different disposition of the distal water molecules in the Glu175 mutant. The RR spectra also show that the heme is more contracted and distorted at 19 K than at room temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Echographic diagnosis of pretibial myxedema in patients with autoimmune thyroid disease

In the present study we have evaluated the use of pretibial ultrasound for the diagnosis of pretibial myxedema (PTM). We studied 76 patients, 58 with Graves' disease, 13 with Hashimoto's thyroiditis and five with idiopathic hypothyroidism. Thirty-two normal subjects were also studied as controls. Sixty-four patients had associated ophthalmopathy. The ultrasound scanner was equipped with 10- and 13-MHz probes. Punch biopsies were carried out in 11 patients and tissue sections examined on a light microscope. On clinical examination 21 patients (28%) had suspected PTM. By ultrasound, we measured the thickness of dermis and subcutaneous tissue (D1) and that including only deeper dermis (D2) in normal subjects to define the echographic parameters of normal pretibial skin. We then found increased skin thickness in 25 patients (33%), with mean D1 and D2 values significantly higher than those measured in controls (p < 0.00001). The echographic study was positive in 20 patients with ophthalmopathy (31%). Ultrasound showed increased skin thickness in 16 of 21 patients (76%) with clinically suspected PTM. Histopathological findings confirmed the presence of PTM in all the patients who underwent pretibial skin biopsy. We believe that the measurement of pretibial skin thickness by ultrasound may be useful for revealing the presence of PTM.