In vivo imaging of CNS microglial activation/macrophage infiltration with combined [18F]DPA-714-PET and SPIO-MRI in a mouse model of relapsing remitting experimental autoimmune encephalomyelitis.

PURPOSE: To evaluate the feasibility and sensitivity of multimodality PET/CT and MRI imaging for non-invasive characterization of brain microglial/macrophage activation occurring during the acute phase in a mouse model of relapsing remitting multiple sclerosis (RR-MS) using [18F]DPA-714, a selective radioligand for the 18-kDa translocator protein (TSPO), superparamagnetic iron oxide particles (SPIO), and ex vivo immunohistochemistry. METHODS: Experimental autoimmune encephalomyelitis (EAE) was induced in female SJL/J mice by immunization with PLP139-151. Seven symptomatic EAE mice and five controls underwent both PET/CT and MRI studies between 11 and 14 days post-immunization. SPIO was injected i.v. in the same animals immediately after [18F]DPA-714 and MRI acquisition was performed after 24 h. Regional brain volumes were defined according to a mouse brain atlas on co-registered PET and SPIO-MRI images. [18F]DPA-714 standardized uptake value (SUV) ratios (SUVR), with unaffected neocortex as reference, and SPIO fractional volumes (SPIO-Vol) were generated. Both SUVR and SPIO-Vol values were correlated with the clinical score (CS) and among them. Five EAE and four control mice underwent immunohistochemical analysis with the aim of identifying activated microglia/macrophage and TSPO expressions. RESULTS: SUVR and SPIO-Vol values were significantly increased in EAE compared with controls in the hippocampus (p < 0.01; p < 0.02, respectively), thalamus (p < 0.02; p < 0.05, respectively), and cerebellum and brainstem (p < 0.02), while only SPIO-Vol was significantly increased in the caudate/putamen (p < 0.05). Both SUVR and SPIO-Vol values were positively significantly correlated with CS and among them in the same regions. TSPO/Iba1 and F4/80/Prussian blue staining immunohistochemistry suggests that increased activated microglia/macrophages underlay TSPO expression and SPIO uptake in symptomatic EAE mice. CONCLUSIONS: These preliminary results suggest that both activated microglia and infiltrated macrophages are present in vulnerable brain regions during the acute phase of PLP-EAE and contribute to disease severity. Both [18F]DPA-714-PET and SPIO-MRI appear suitable modalities for preclinical study of neuroinflammation in MS mice models.

Imaging of brain TSPO expression in a mouse model of amyotrophic lateral sclerosis with (18)F-DPA-714 and micro-PET/CT.

PURPOSE: To evaluate the feasibility and sensitivity of (18)F-DPA-714 for the study of microglial activation in the brain and spinal cord of transgenic SOD1(G93A) mice using high-resolution PET/CT and to evaluate the Iba1 and TSPO expression with immunohistochemistry. METHODS: Nine symptomatic SOD1(G93A) mice (aged 117 ± 12.7 days, clinical score range 1 - 4) and five WT SOD1 control mice (aged 108 ± 28.5 days) underwent (18)F-DPA-714 PET/CT. SUV ratios were calculated by normalizing the cerebellar (rCRB), brainstem (rBS), motor cortex (rMCX) and cervical spinal cord (rCSC) activities to that of the frontal association cortex. Two WT SOD1 and six symptomatic SOD1(G93A) mice were studied by immunohistochemistry. RESULTS: In the symptomatic SOD1(G93A) mice, rCRB, rBS and rCSC were increased as compared to the values in WT SOD1 mice, with a statistically significantly difference in rBS (2.340 ± 0.784 vs 1.576 ± 0.287, p = 0.014). Immunofluorescence studies showed that TSPO expression was increased in the trigeminal, facial, ambiguus and hypoglossal nuclei, as well as in the spinal cord, of symptomatic SOD1(G93A) mice and was colocalized with increased Iba1 staining. CONCLUSION: Increased (18)F-DPA-714 uptake can be detected with high-resolution PET/CT in the brainstem of transgenic SOD1(G93A) mice, a region known to be a site of degeneration and increased microglial activation in amyotrophic lateral sclerosis, in agreement with increased TSPO expression in the brainstem nuclei shown by immunostaining. Therefore, (18)F-DPA-714 PET/CT might be a suitable tool to evaluate microglial activation in the SOD1(G93A) mouse model.

A randomized controlled double-blind investigation of the effects of vitamin D dietary supplementation in subjects with atopic dermatitis.

BACKGROUND: Subjects with atopic dermatitis (AD) have defects in antimicrobial peptide (AMP) production possibly contributing to an increased risk of infections. In laboratory models, vitamin D can alter innate immunity by increasing AMP production. OBJECTIVE: To determine if AD severity correlates with baseline vitamin D levels, and to test whether supplementation with oral vitamin D alters AMP production in AD skin. METHODS: This was a multi-centre, placebo-controlled, double-blind study in 30 subjects with AD, 30 non-atopic subjects, and 16 subjects with psoriasis. Subjects were randomized to receive either 4000 IU of cholecalciferol or placebo for 21 days. At baseline and day 21, levels of 25-hydroxyvitamin D (25OHD), cathelicidin, HBD-3, IL-13, and Eczema Area and Severity Index (EASI) and Rajka-Langeland scores were obtained. RESULTS: At baseline, 20% of AD subjects had serum 25OHD below 20 ng/mL. Low serum 25OHD correlated with increased Fitzpatrick Skin Type and elevated BMI, but not AD severity. After 21 days of oral cholecalciferol, mean serum 25OHD increased, but there was no significant change in skin cathelicidin, HBD-3, IL-13 or EASI scores. CONCLUSIONS: This study illustrated that darker skin types and elevated BMI are important risk factors for vitamin D deficiency in subjects with AD, and highlighted the possibility that seasonality and locale may be potent contributors to cathelicidin induction through their effect on steady state 25OHD levels. Given the molecular links between vitamin D and immune function, further study of vitamin D supplementation in subjects with AD is warranted.

Classification of prosthetics used in hernia repair based on weight and biomaterial.

PURPOSE: The aim of this study was to classify the polymeric prosthetics used for hernia repair based on biomaterial composition and weight in an effort to clarify to surgeons what kinds of material they are dealing with and to provide a standardized system of categorization. MATERIALS AND METHODS: An intensive research effort was carried out on prosthetics that are commercially available worldwide. We conducted a search of the medical literature and companies' websites to find the weights and thicknesses of commercially available prosthetics. Where these data were lacking, we contacted manufacturers directly in order to render the research more complete. A total of 166 products were considered for classification based on biomaterial properties. Among these, a homogeneous group of 80 polypropylene monofilament knitted or woven prosthetics was selected for classification based on weight. Weights were provided for 70 prosthetics (87%), and both the weight and thickness was provided for 40 prosthetics (50%). RESULTS: Classification based on weight: Ultra-light <35 g/m(2), Light ≥35 < 70 g/m(2), Standard ≥70 < 140 g/m(2), Heavy ≥140 g/m(2). Classification based on biomaterial composition: simple (prosthetics made of one pure biomaterial); composite (prosthetics made of two or more different layers); combined (prosthetics made of two materials knitted or woven together); and biologic. CONCLUSION: Weight and biomaterial classifications were proposed after an extensive analysis of commercially available prosthetics. The need for a common terminology is important to avoid misunderstandings among clinicians and technicians.

Peripheral blood gene expression in alopecia areata reveals molecular pathways distinguishing heritability, disease and severity.

Alopecia areata (AA) is an autoimmune hair loss disorder in which systemic disturbances have been described, but are poorly understood. To evaluate disease mechanisms, we examined gene expression in the blood of defined clinical subgroups (patchy AA persistent type, AAP, n=5; alopecia universalis, AU, n=4) and healthy controls (unaffected relatives, UaR, n=5; unaffected non-relatives, UaNR, n=4) using microarrays. Unsupervised hierarchical clustering separates all four patient and control groups, producing three distinct expression patterns reflective of 'inheritance', 'disease' and 'severity' signatures. Functional classification of differentially expressed genes (DEGs) comparing disease (AAP, AU) vs normal (UaR) groups reveals upregulation in immune response, cytokine signaling, signal transduction, cell cycle, proteolysis and cell adhesion-related genes. Pathway analysis further reveals the activation of several genes related to natural killer-cell cytotoxicity, apoptosis, mitogen activated protein kinase, Wnt signaling and B- and T-cell receptor signaling in AA patients. Finally, 35 genes differentially expressed in AA blood overlap with DEGs previously identified in AA skin lesions. Our results implicate innate and adaptive immune processes while also revealing novel pathways, such as Wnt signaling and apoptosis, relevant to AA pathogenesis. Our data suggest that peripheral blood expression profiles of AA patients likely carry new biomarkers associated with disease susceptibility and expression.

Comparison of polypropylene and polyethylene terephthalate (Dacron) meshes for abdominal wall hernia repair: a chemical and morphological study.

For the first time, by scanning electron microscopy (SEM), polypropylene (PP) excised meshes (ethylene oxide sterilized) for abdominal wall hernia repair have been shown to be greatly damaged physically, independently of the implantation time, while the polyethylene terephthalate (PET), or Dacron, ones (gamma radiation sterilized), did not undergo alterations due to the sterilization process and were not damaged, even after long implantation periods. Fourier-Transform Infrared Spectroscopy (FTIR) study of PP and PET excised meshes, as well as of their extracts with cyclohexane, has shown the presence of species, such as squalene, palmitic and stearic acid, in some cases, cholesterol, transferred from the surrounding tissues to the polymer during the implantation period. In the case of PP meshes, these small organic molecules would reduce physical and mechanical properties of the material. A hypothesis is presented to account for the better behavior (not in the clinical sense) of PET meshes.

Structural alterations of prosthetic meshes in humans.

The use of prosthetic mesh in abdominal wall hernia surgery is a well-accepted practice. What is not settled, however, is the type of prosthesis that best suits the purpose. The narrow choice today means a prosthesis of polyester or polypropylene. These are available in many designs, configuration of weave, thickness of weave and strand, and size of pore. There has been a pervasive feeling that these materials "shrink". To what extent they do has not been accurately defined. This study was designed to measure such "shrinkage". Interestingly, our measurements revealed that prosthetic meshes could "expand" as well as "shrink". The extent to which they do varies between -40% and 58.5%. Whereas it was felt that fibrocyte activity and its eventual scar formation accounted for the "shrinkage" of the mesh, we have discovered that structural alterations in the size of the mesh pores can be affected by distilled water, saline, blood, formalin, bleach, as well as in vivo implantation. Prosthetic meshes are, therefore, not the inert materials they are claimed to be and can expand as well as shrink. We have, unfortunately, not been able to correlate the degree or direction of change to any known parameter.

Gasless laparoscopic-assisted ileostomy or colostomy closure using an abdominal wall-lifting device.

BACKGROUND: Restoration of intestinal continuity in patients with ileostomy after total colectomy or with colostomy after Hartmann's procedure is a major operation. Herein we illustrate the validity of gasless laparoscopically assisted reversal using abdominal wall lifting. METHODS: The operation was performed on 10 patients from February 1997 to May 1999. Seven of them had a left iliac stoma after a Hartmann resection, and three had an ileostomy after total colectomy. RESULTS: The laparoscopic reversal was completed in eight patients; the two others were converted to an open procedure. Three major complications occurred (30%). There were no deaths. The average operation time was 192 min (range, 125-265). Time of discharge from surgery averaged 9.5 days. Mean follow-up of these patients was 12 months and negative. CONCLUSIONS: Laparoscopically assisted ileo- or colorectal anastomosis without pneumoperitoneum and using a laparotenser can be considered for the reversal of patients with ileostomy or colostomy. Even taking the high rate of intraoperative or postoperative complications into consideration, the advantages that make such a laparoscopic approach suitable include reduced trauma related to a second major abdominal operation, reduced postoperative pain, and fewer cutaneous tissues exposed to bacterial contamination. Moreover, the use of a laparotenser makes it possible to operate on elderly patients with cardiovascular diseases. In the absence of pneumoperitoneum, it becomes possible to use traditional instruments, with a consequent reduction in costs.

[Spigelian hernia: an up-to-date]. / Attualità dell'ernia di Spiegel.

Nine cases of Spigelian hernia occurred and surgically treated in the years 1992-1997 are reported. Spigelian hernias were observed in 5 females and 3 males with mean age of 62.1 years (range 49-70). In 5 cases prosthetic repair has been done with preperitoneal mesh and a very good outcome. In a 61 years old obese female spigelian hernia was bilateral. Her left sided hernia needed an emergency operation for strangulation. Hernia has been repaired by simple suture and recurred early. For the diagnosis of Spigelian hernia it is essential to remember it inside the "Spigelian belt". The satisfactory results obtained at present by prosthetic repair are underlined.

Incisional hernia and fascial defect following laparoscopic surgery.

Complications involving the abdominal wall, particularly incisional hernias, were not expected when laparoscopic procedures were first introduced. With the increasing number of laparoscopies in abdominal surgery, more incisional hernias are observed. The authors report 13 cases of umbilical incisional hernia, which occurred late after laparoscopic cholecystectomy, and one case of omental procidentia through a lateral port, which occurred early after laparoscopic hernia repair with the transabdominal preperitoneal technique. There are 4 men and 10 women (mean age, 59.8 years; range, 40-74 years). Between March 1991 and December 1997, a total of 1,287 patients underwent laparoscopic operations at the Surgical Department of the Gradenigo Hospital in Turin, Italy. Incisional hernia incidence is 1%. Risk factors, such as chronic bronchitis or weight increase, which give rise to endoabdominal pressure, are present in some cases. Malnutrition may have a major role in many cases. Calculi larger than 15 mm are also seen frequently. Postlaparoscopy incisional hernia is generally a minor complication--only once did its occurrence cause a strangulated hernia. All precautions, including fascial suturing, must be taken to reduce the 1% incidence of postoperative incisional hernias.

Cross-talk and ammonia channeling between active centers in the unexpected domain arrangement of glutamate synthase.

INTRODUCTION: The complex iron-sulfur flavoprotein glutamate synthase catalyses the reductive synthesis of L-glutamate from 2-oxoglutarate and L-glutamine, a reaction in the plant and bacterial pathway for ammonia assimilation. The enzyme functions through three distinct active centers carrying out L-glutamine hydrolysis, conversion of 2-oxoglutarate into L-glutamate, and electron uptake from an electron donor. RESULTS: The 3.0 A crystal structure of the dimeric 324 kDa core protein of a bacterial glutamate synthase was solved by the MAD method, using the very weak anomalous signal of the two 3Fe-4S clusters present in the asymmetric unit. The 1,472 amino acids of the monomer fold into a four-domain architecture. The two catalytic domains have canonical Ntn-amidotransferase and FMN binding (beta/alpha)8 barrel folds, respectively. The other two domains have an unusual "cut (beta/alpha)8 barrel" topology and an unexpected novel beta-helix structure. Channeling of the ammonia intermediate is brought about by an internal tunnel of 31 A length, which runs from the site of L-glutamine hydrolysis to the site of L-glutamate synthesis. CONCLUSIONS: The outstanding property of glutamate synthase is the ability to coordinate the activity of its various functional sites to avoid wasteful consumption of L-glutamine. The structure reveals two polypeptide segments that connect the catalytic centers and embed the ammonia tunnel, thus being ideally suited to function in interdomain signaling. Depending on the enzyme redox and ligation states, these signal-transducing elements may affect the active site geometry and control ammonia diffusion through a gating mechanism.

Structure of L-aspartate oxidase: implications for the succinate dehydrogenase/fumarate reductase oxidoreductase family.

BACKGROUND: Given the vital role of NAD+ in cell metabolism, the enzymes involved in bacterial de novo NAD+ biosynthesis are possible targets for drug design against pathogenic bacteria. The first reaction in the pathway is catalysed by L-aspartate oxidase (LASPO), a flavoenzyme that converts aspartate to iminoaspartate using either molecular oxygen or fumarate as electron acceptors. LASPO has considerable sequence homology with the flavoprotein subunits of succinate dehydrogenase (SDH) and fumarate reductase (FRD). RESULTS: The crystal structure of the apoform of LASPO from Escherichia coli has been determined to 2.2 A resolution. The enzyme shows a novel fold for an FAD-dependent protein, comprising a three-domain structure: an FAD-binding domain with the dinucleotide-binding fold, a C-terminal three-helical bundle domain, and an alpha + beta capping domain, which is topologically similar to the small subunit of spinach ribulose-1,5-bisphosphate carboxylase/oxygenase. The interface between the FAD-binding and capping domains defines a cleft in which the active site is located. CONCLUSIONS: A number of strictly conserved residues present in all three domains indicate that LASPO, SDH and FRD share the same overall folding topology. Many of these conserved residues are in the FAD-binding site and active centre, suggesting a similar catalytic mechanism. Thus, LASPO, SDH and FRD form a class of functionally and structurally related oxidoreductases that are all able to reduce fumarate and to oxidise a dicarboxylate substrate.

A 30-angstrom-long U-shaped catalytic tunnel in the crystal structure of polyamine oxidase.

BACKGROUND: Polyamines are essential for cell growth and differentiation; compounds interfering with their metabolism are potential anticancer agents. Polyamine oxidase (PAO) plays a central role in polyamine homeostasis. The enzyme utilises an FAD cofactor to catalyse the oxidation of the secondary amino groups of spermine and spermidine. RESULTS: The first crystal structure of a polyamine oxidase has been determined to a resolution of 1.9 Angstroms. PAO from Zea mays contains two domains, which define a remarkable 30 Angstrom long U-shaped catalytic tunnel at their interface. The structure of PAO in complex with the inhibitor MDL72527 reveals the residues forming the catalytic machinery and unusual enzyme-inhibitor CH.O H bonds. A ring of glutamate and aspartate residues surrounding one of the two tunnel openings contributes to the steering of the substrate towards the inside of the tunnel. CONCLUSIONS: PAO specifically oxidizes substrates that have both primary and secondary amino groups. The complex with MDL72527 shows that the primary amino groups are essential for the proper alignment of the substrate with respect to the flavin. Conservation of an N-terminal sequence motif indicates that PAO is member of a novel family of flavoenzymes. Among these, monoamine oxidase displays significant sequence homology with PAO, suggesting a similar overall folding topology.

[The long-term results of mechanical anal sphincteroclasis]. / Risultati a distanza della sfinteroclasia anale meccanica.

BACKGROUND: The long-term results of 36 patients operated of manual dilatation of the anus are presented. Chronic anal fissure or benign anal stricture have been treated by this procedure in the years '80s. METHODS: Patients have been in part clinically examined and the other called up by phone interview. Average follow-up is 78 months. RESULTS: Nobody has been re-operated for the same cause, but 2 patients underwent sphincter sparing operation for rectal cancer. Twenty-five patients (72%) completely recovered, 5 (12.5%) complain sometimes from sudden anal pain and 3 (8%) report minor incontinence problems. CONCLUSIONS: These long-term results do not confirm disastrous conclusions reported by other authors in the literature, even if the incidence of continence disorders is higher than in anal sphincterotomies.

Incisional hernia and fascial defect following laparoscopic surgery.

Complications involving the abdominal wall, particularly incisional hernias, were not expected when laparoscopic procedures were first introduced. With the increasing number of laparoscopies in abdominal surgery, more incisional hernias are observed. The authors report 13 cases of umbilical incisional hernia, which occurred late after laparoscopic cholecystectomy, and one case of omental procidentia through a lateral port, which occurred early after laparoscopic hernia repair with the transabdominal preperitoneal technique. There are 4 men and 10 women (mean age, 59.8 years; range, 40-74 years). Between March 1991 and December 1997, a total of 1,287 patients underwent laparoscopic operations at the Surgical Department of the Gradenigo Hospital in Turin, Italy. Incisional hernia incidence is 1%. Risk factors, such as chronic bronchitis or weight increase, which give rise to endoabdominal pressure, are present in some cases. Malnutrition may have a major role in many cases. Calculi larger than 15 mm are also seen frequently. Postlaparoscopy incisional hernia is generally a minor complication--only once did its occurrence cause a strangulated hernia. All precautions, including fascial suturing, must be taken to reduce the 1% incidence of postoperative incisional hernias.

A novel deamido-NAD+-binding site revealed by the trapped NAD-adenylate intermediate in the NAD+ synthetase structure.

BACKGROUND: Nicotinamide adenine dinucleotide (NAD+) has a central role in life processes. The ubiquitous enzyme NAD+ synthetase catalyzes a key step in NAD+ biosynthesis, transforming deamido-NAD+ into NAD+ by a two-step reaction. NAD+ synthetase belongs to the amidotransferase family and has been recognized as a member of the family of N-type ATP pyrophosphatases. In order to investigate the mechanism of the reaction carried out by NAD+ synthetase we have determined a high-resolution three-dimensional structure of the Bacillus subtilis homodimeric NAD+ synthetase in complex with the trapped reaction intermediate NAD-adenylate. RESULTS: Two NAD-adenylate molecules and two pyrophosphate (PPi) molecules are observed in the 1.3 A resolution structure of the NAD+ synthetase-NAD-adenylate complex. Structural studies on the NAD+ synthetase-NAD-adenylate adduct and on the cation-binding sites reveal a new deamido-NAD+-binding site located at the subunit interface, locate a binuclear magnesium cluster at the ATP-binding site and, identify two monovalent cation sites, one of which may represent an ammonium-binding site. CONCLUSIONS: Our results suggest that two different catalytic strategies have been adopted by NAD+ synthetase in the two different steps of the reaction. During the adenylation step, no protein residues seem to be located properly to directly participate in catalysis, which is likely to be carried out with the fundamental assistance of an electron-withdrawing trimetallic constellation present in the active site. A different behavior is observed for the second step, in which an ammonium ion is the binding species. In this step, Asp173 is a key residue in both deprotonation of the primarily bound ammonium ion, and stabilization of the tetrahedral transition-state intermediate. Moreover, the structural data suggest that product release can take place only after all substrates are bound to the enzyme, and product release is ultimately controlled by the conformation adopted by two mobile loops.

Structure of the mutant E92K of [2Fe-2S] ferredoxin I from Spinacia oleracea at 1.7 A resolution.

Ferredoxin I (Fd I) from Spinacia oleracea is composed of 97 amino-acid residues and a [2Fe-2S] cluster. The crystal structure of the E92K mutant of Fd I was solved by molecular replacement and refined to an R factor of 19.6% for 11755 reflections at 1.7 A resolution. The overall structure and the active centre of spinach Fd is highly conserved with respect to ferredoxins of known structure. The E92K mutation appears to disturb a hydrogen-bond network which stabilizes the loop bearing the [2Fe-2S] cluster. This observation provides a rationale for the reduced electron-transfer efficiency displayed by the E92K mutant. Inspection of the crystal packing reveals that the side chain of Lys92 is engaged in an intermolecular interaction with Asp26 of a symmetry-related molecule. This feature may explain why only the mutant E92K and not wild-type Fd I could be successfully crystallized.

Crystallization and preliminary X-ray analysis of polyamine oxidase from Zea mays L.

Polyamine oxidase catalyses the oxidation of the secondary amino group of spermine, spermidine and their acetyl derivatives. The enzyme plays an important role in the regulation of polyamine intracellular concentration and is a member of the family of flavin-containing amine oxidases. Crystals of maize polyamine oxidase have been grown by the hanging-drop vapour-diffusion technique. The crystals are in hexagonal space group P6122 (or P6522) with cell dimensions a = b = 184.6, c = 280.9 A. A native data set has been collected to 2.7 A resolution at a synchrotron radiation source.

Crystal structures and inhibitor binding in the octameric flavoenzyme vanillyl-alcohol oxidase: the shape of the active-site cavity controls substrate specificity.

BACKGROUND: Lignin degradation leads to the formation of a broad spectrum of aromatic molecules that can be used by various fungal micro-organisms as their sole source of carbon. When grown on phenolic compounds, Penicillium simplicissimum induces the strong impression of a flavin-containing vanillyl-alcohol oxidase (VAO). The enzyme catalyses the oxidation of a vast array of substrates, ranging from aromatic amines to 4-alkyphenols. VAO is a member of a novel class of widely distributed oxidoreductases, which use flavin adenine dinucleotide (FAD) as a cofactor covalently bound to the protein. We have carried out the determination of the structure of VAO in order to shed light on the most interesting features of these novel oxidoreductases, such as the functional significance of covalent flavinylation and the mechanism of catalysis. RESULTS: The crystal structure of VAO has been determined in the native state and in complexes with four inhibitors. The enzyme is an octamer with 42 symmetry; the inhibitors bind in a hydrophobic, elongated cavity on the si side of the flavin molecule. Three residues, Tyr108, Tyr503 and Arg504 form an anion-binding subsite, which stabilises the phenolate form of the substrate. The structure of VAO complexed with the inhibitor 4-(1-heptenyl)phenol shows that the catalytic cavity is completely filled by the inhibitor, explaining why alkylphenols bearing aliphatic substituents longer than seven carbon atoms do not bind to the enzyme. CONCLUSIONS: The shape of the active-site cavity controls substrate specificity by providing a 'size exclusion mechanism'. Inside the cavity, the substrate aromatic ring is positioned at an angle of 18 degrees to the flavin ring. This arrangement is ideally suited for a hydride transfer reaction, which is further facilitated by substrate deprotonation. Burying the substrate beneath the protein surface is a recurrent strategy, common to many flavoenzymes that effect substrate oxidation or reduction via hydride transfer.

[Stoppa's intervention. The complications nd results]. / L'intervento di Stoppa. Complicanze e risultati.

The authors report their experience with the giant prosthetic reinforcement of the visceral sac (Stoppa procedure), developed in the last 6 years operating 126 cases. Postoperative period was regular for two third of the patients, but only in 4 cases we can consider complication severe: 2 cases of preperitoneal haemorrhage with haematoma formation and subsequent recurrence; one sepsis of the preperitoneal space around the prosthesis, cured with drainage and conservative measures without recurrence, and then one peritonitis in a morbid obese individual. There was no mortality. 93.3% of the patients has been clinically controlled after over 6 months (average 27 months; range 6-67 months): 8 recurrences have been observed (3.6% of the hernias operated). 7 required reintervention. Therefore it is possible to affirm that 91% of the operated patients had good results.