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Biomedical subjects

P Hanna

Publications and source records attributed to P Hanna.

At least 19 recordsLinked to original sources
PubMed2001

Crystal structure of the anthrax lethal factor.

Lethal factor (LF) is a protein (relative molecular mass 90,000) that is critical in the pathogenesis of anthrax. It is a highly specific protease that cleaves members of the mitogen-activated protein kinase kinase (MAPKK) family near to their amino termini, leading to the inhibition of one or more signalling pathways. Here we describe the crystal structure of LF and its complex with the N terminus of MAPKK-2. LF comprises four domains: domain I binds the membrane-translocating component of anthrax toxin, the protective antigen (PA); domains II, III and IV together create a long deep groove that holds the 16-residue N-terminal tail of MAPKK-2 before cleavage. Domain II resembles the ADP-ribosylating toxin from Bacillus cereus, but the active site has been mutated and recruited to augment substrate recognition. Domain III is inserted into domain II, and seems to have arisen from a repeated duplication of a structural element of domain II. Domain IV is distantly related to the zinc metalloprotease family, and contains the catalytic centre; it also resembles domain I. The structure thus reveals a protein that has evolved through a process of gene duplication, mutation and fusion, into an enzyme with high and unusual specificity.

Amino Acid Sequence↗
PubMed1999

Patterns of success and failure with laparoscopic Toupet fundoplication.

BACKGROUND: Advocates of the Toupet partial fundoplication claim that the procedure has a lower rate of the side effects of dysphagia and gas bloat than a complete Nissen fundoplication. However, there is increasing recognition that reflux control is not always as good with the Toupet procedure as with the Nissen. Therefore, we set out to evaluate the factors contributing to success and failure in patients who underwent laparoscopic modified Toupet fundoplication (LTF). METHODS: A total of 143 patients undergoing LTF for documented gastroesophageal reflux disease (GERD) were evaluated prospectively in regard to their outcomes over a 4-year period. All patients had preoperative esophagogastroduodenoscopy (EGD) and manometry; 24-h pH testing was used selectively. Esophageal manometry was requested of all patients 6 weeks postoperatively. Clinical follow-up was by office visit or questionnaire every 6 months after surgery; patients with significant problems were investigated further. Failure was defined as the development of recurrent reflux documented by endoscopy, 24-h pH test, or wrap disruption on barium swallow, or severe dysphagia persisting >3 months and requiring surgical revision. RESULTS: At a mean follow-up of 30 months (range, 3-51), 21 of 143 patients failed LTF; two had dysphagia and 19 had recurrent reflux. Failure was associated with preoperative findings of a defective lower esophageal sphincter (LES) (14/21), complicated esophagitis (13/21), and failure to divide short gastric vessels (12/19) (chi-square p < 0.05). Defective esophageal body peristalsis, present in 14 patients, resulted in failure in six cases. Presence of either complicated esophagitis or a defective LES was associated with a 3-year 50% success rate, whereas presence of mild esophagitis and a normal LES was reflected in a 96% 3-year success rate. CONCLUSION: Laparoscopic Toupet fundoplication should be reserved for milder cases of GERD, as assessed by manometry and endoscopy.

Evaluation Studies as Topic↗
PubMed1999

Crystallographic studies of the anthrax lethal toxin

Anthrax lethal toxin comprises two proteins: protective antigen (PA; MW 83 kDa) and lethal factor (LF; MW 87 kDa). We have recently determined the crystal structure of the 735-residue PA in its monomeric and heptameric forms (Petosa et al. 1997). It bears no resemblance to other bacterial toxins of known three-dimensional structure, and defines a new structural class which includes homologous toxins from other Gram-positive bacteria. We have proposed a model of membrane insertion in which the water-soluble heptamer undergoes a substantial pH-induced conformational change involving the creation of a 14-stranded beta-barrel. Recent work by Collier's group (Benson et al. 1998) lends strong support to our model of membrane insertion. 'Lethal factor' is the catalytic component of anthrax lethal toxin. It binds to the surface of the cell-bound PA heptamer and, following endocytosis and acidification of the endosome, translocates to the cytosol. We have made substantial progress towards an atomic resolution crystal structure of LF. Progress towards a structure of the 7:7 translocation complex between the PA heptamer and LF will also be discussed.

Journal Article↗
PubMed1999

Lethal toxin actions and their consequences.

After entry of infectious anthrax spores into the body, host-specific signals induce spore germination, outgrowth of vegetative bacilli and the expression of lethal toxin and other virulence factors. Anthrax lethal toxin (LeTx) is a virulence factor responsible for the major pathologies seen during systemic anthrax infections. Injection of sterile LeTx into test animals mimics the shock and sudden death seen during active bacterial infections. Once large levels of LeTx are produced within the body, destruction of bacteria by administration of antibiotics is usually unsuccessful. The LeTx is believed to be secreted into the bloodstream where it circulates freely throughout the body and binds and enters host cells. Once in the cytoplasm, the lethal factor acts as a zinc-metalloprotease disrupting normal homoeostatic functions. Macrophages are a uniquely sensitive cell type that seem to be vital global mediators of toxin-induced pathologies. Removal of macrophages from mice renders them insensitive to LeTx challenge. Low levels of lethal toxin induce macrophage production, in vitro, of the shock-inducing cytokines TNF and Il-1beta. Higher levels of LeTx cause over-production of reactive oxygen intermediates, bursting of macrophages and release of mediators of shock. We believe that agents capable of blocking key steps of the lethal toxin cascade may prove useful in combating anthrax pathologies.

Animals↗
PubMed1999

Cutaneous mucinosis and mastocytosis in a shar-pei.

A 7-year-old shar-pei was presented because of a recurrent dermatologic condition. Skin biopsies revealed an idiopathic (primary) cutaneous mucinosis that initially responded to corticosteroids. The condition reappeared 2 years later and subsequent biopsies revealed a mast cell tumor in some of the skin sites previously diagnosed with mucinosis.

Animals↗
PubMed1997

Hypoadrenocorticism in young related Nova Scotia duck tolling retrievers.

Five cases of hypoadrenocorticism in young related Nova Scotia duck tolling retrievers are discussed. Two were littermates and the others shared one or more common ancestors. No specific mode of inheritance was determined. Clinical and laboratory findings typical of hypoadrenocorticism were observed. Further documentation will be required to confirm a breed predisposition.

Adrenal Glands↗
PubMed1996

Clinical and manometric results of laparoscopic partial (Toupet) and complete (Rosetti-Nissen) fundoplication.

UNLABELLED: It is unclear whether a partial or complete gastric fundoplication done laparoscopically will offer the best control of reflux with the fewest side effects. Prospective evaluation of laparoscopic Rosetti-Nissen (360) and Toupet (180) fundoplication was performed with assessment of clinical and manometric data. METHODS: Patients with severe gastroesophageal reflux referred for surgical correction underwent preoperative motility and upper endoscopy. A Rosetti-Nissen or Toupet fundoplication was then performed laparoscopically. Short gastrics were not divided. No bougie was used in the Toupet, which was sutured intracorporeally. A 2-cm, loose, floppy wrap about a 50-Fr bougie was performed in the Nissen. Eleven patients underwent Rosetti-Nissen and 11 Toupet fundoplication. Mean ages, duration symptoms, weight, and baseline LES, were not different. Preop esophagitis grades were similar, as were Visick Scores and presence of dysphagia. RESULTS: Visick scores at 6 months were better in the Toupet group than the Rosetti-Nissen (P = 0.07). Persistent Dysphagia in four, Gas-Bloat in two, and Odynophagia in one within the Rosetti-Nissen group accounted for the difference, and were not seen in Toupets. LES pressures differed significantly pre and postop (P < 0.001). The change in LES pressure was significantly different between Toupet and Rosetti-Nissen (chart). Seven patients had postop 24-h pH tests; all had no reflux. Three Rosettis have required revision to Toupet, with resolution of their symptoms. CONCLUSIONS: In patients with severe GERD, laparoscopic Toupet and Rosetti-Nissen control symptoms and esophageal pH similarly. LES pressures are higher postop in the Rosetti-Nissen. Dysphagia and gas-bloat are more prevalent in the Nissen group. Laparoscopic Toupet fundoplication may be superior to Rosetti-Nissen in reducing the frequency of side effects frequently associated with antireflux surgery, yet with equal control of reflux.

Adult↗
PubMed1992

Percutaneous transabdominal hepatic needle biopsies in dogs.

Ninety-six (4/dog) percutaneous transabdominal hepatic needle biopsy specimens were obtained from 24 dogs each weighing 10 to 24 kg. Two biopsies were performed in each dog prior to and 5 days after hepatopathy was experimentally induced. Information pertaining to the difficulty encountered in obtaining hepatic tissue is reported for the first of each pair of biopsies. All specimens were of diagnostic quality for light and electron microscopic evaluation. Adverse consequences (morbidity or mortality) resulting from the biopsy technique were not observed by monitoring of vital signs in the immediate postprocedure period and at 4 weeks. Recovery to an ambulatory state was seen in less than or equal to 30 minutes, except in 1 dog, in which prolonged recovery was attributed to acetylpromazine-induced hypotension.

Acepromazine↗
PubMed1989

Influence of neurophysin residues 1-8 on the optical activity of neurophysin-peptide complexes. Direct evidence that the 1-8 sequence alters the environment of bound peptide.

Circular dichroism was used to compare the environment of peptides bound to native and des 1-8 neurophysin in order to further elucidate the role of the neurophysin 1-8 sequence in peptide-binding. A very large positive ellipticity (approximately 6000 deg cm2 dmol-1), shown earlier to be induced in tyrosine at position 2 of peptides bound to the native protein, was determined by the present study to be paralleled by similar induced changes in tyrosine at peptide position 1. Deletion of the neurophysin 1-8 sequence led to loss of half of the induced optical activity at peptide positions 1 and 2 and changes in binding-induced optical activity in the protein, the latter partially assignable to protein disulfides. In the mononitrated native and des 1-8 proteins, the optical activity of neurophysin Tyr-49, a residue at the peptide-binding site, was reduced by 80% in complexes of the des 1-8 protein relative to those of the native protein. The results suggest a role for neurophysin Arg-8 in modulating the optical activity at the binding site by directly placing a charge proximal to the binding site and/or by altering binding site conformation. The data provide the first unambiguous evidence of a difference in the environment of bound peptide between the native and des 1-8 proteins.

Binding Sites↗
PubMed1986

Familial visceral neuropathy with autosomal dominant transmission.

This report describes a family with a visceral neuropathy without extraintestinal manifestations transmitted over at least four generations in an autosomal dominant manner. Four of 7 living patients underwent extensive evaluation including histology, radiography, gastric emptying and secretory studies, esophageal and jejunal manometry, and measurements of plasma levels of gastrointestinal hormones. The only characteristic radiologic abnormality in 7 patients was dilatation of jejunum and ileum. Gastric emptying studies were normal in 2 patients, whereas 2 others showed accelerated emptying of liquids either alone or in combination with grossly delayed solid emptying. Manometry of the esophagus and proximal small intestine and gastric secretory studies were normal. Histologic studies showed hypertrophy of the smooth muscle, a markedly reduced number of argyrophilic neurons, and degenerative changes of argyrophilic neurons and nerve fibers but without Schwann cell proliferation, intranuclear inclusions, or inflammatory cells. This appears to be a familial visceral neuropathy characterized by distinct involvement of the jejunum and ileum as defined radiographically, histology different from that of two previously described forms of familial visceral neuropathy, autosomal dominant transmission, and no evidence for extraintestinal neurologic manifestations.

Adult↗
PubMed1984

Isolation of preneoplastic rat liver cells by centrifugal elutriation and binding to asialofetuin.

Putative preneoplastic hepatocytes were isolated from male Fischer 344 rats treated with a single dose of diethylnitrosamine, 2-acetylaminofluorene feeding, and partial hepatectomy (Solt-Farber model). The isolation procedure involved, after collagenase dispersion of the liver, separation of the hepatocytes into small- and large-cell fractions by centrifugal elutriation, and subsequent selection of cells deficient in asialoglycoprotein receptor(s) by plating onto asialofetuin (ASF)-coated plates. The number of cell surface binding sites for the asialoglycoprotein receptor was measured with both asialoorosomucoid and ASF as ligands. There was a 50% reduction of binding sites for both ligands in the original cell suspensions obtained from preneoplastic livers. The reduction in receptor binding sites was most pronounced in the large cell fraction (less than or equal to 30% of control value) after separating the original cell suspension by elutriation into small and large cell fractions. Immunohistochemical studies showed a lack of asialoglycoprotein receptor in preneoplastic (i.e., hyperplastic foci) areas. These areas were entirely super-imposable with glucose-6-phosphatase-deficient areas and partially overlapped the gamma-glutamyltranspeptidase-positive areas in serial liver sections. The attachment of preneoplastic hepatocytes to ASF-coated tissue culture dishes was greatly impaired, and the number of gamma-glutamyltranspeptidase-positive cells on the ASF dishes was reduced to less than 7% as compared to 45 to 70% on the collagen-coated plates. Thus, the lack of asialoglycoprotein (asialofetuin) surface receptors and the increased size of the early preneoplastic hepatocytes are characteristics that can be used to separate the preneoplastic cell population from normal liver cells.

2-Acetylaminofluorene↗