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Biomedical subjects

H Pappa

Publications and source records attributed to H Pappa.

11 recordsLinked to original sources
PubMed2005

Mediastinitis from odontogenic infection. A case report.

We report a case of mediastinitis complicating a dental infection in a 40-year-old male. Despite drainage of the localised neck abscess and the administration of systemic antibiotics, his submandibular abscess extended to involve the pericardial and pleural cavities. Drainage procedures and thoracotomies were required to treat the empyema and purulent pericarditis. Computed tomography was used to follow the progression of disease and assess the efficacy of treatment.

Acute Disease↗
PubMed2001

Purification of apolipoprotein H (beta 2-glycoprotein I)-like protein from human follicular fluid.

We purified a glycoprotein of molecular weight 50 kDa that has an N-terminal sequence similar to that of apolipoprotein H indicating that it is identical to or highly homologous to apolipoprotein H. There are indications that apolipoprotein H or its homologue may be involved in the fertilization process. Sperm motion was assessed employing computer-assisted semen analysis. The addition of the purified protein to prepared sperm samples from normospermic men increases significantly the straight line velocity (VSL) and the amplitude of lateral head displacement (ALH) but does not increase the number of progressively motile sperm.

Amino Acid Sequence↗
PubMed2001

Dissolution test for silymarin tablets and capsules.

Silybine (SBN), isosilybine (ISBN), silycristine (SCN), silydianine (SDN), and taxifoline (TXF) are the main active flavonoids commonly found in the dried fruits of Silybum marianum, Gaertner (Compositae). Concentrations of these compounds, except TXF, are usually expressed together as silymarin content. This paper describes a simple dissolution test developed to estimate silymarin (Sl) in pharmaceutical formulations. Five commercial products were tested using this new method (including tablets, sugar tablets, and capsules): two from Argentina, one from Brazil, one from Spain, and one from Italy. Results demonstrated that, provided the dosage form disintegrates, amounts dissolved range from 50 to 90% of the labeled value. Products were analyzed by high performance liquid chromatography (HPLC) and UV spectrophotometry.

Antioxidants↗
PubMed1998

Crystal structure of the C2 domain from protein kinase C-delta.

BACKGROUND: The protein kinase C (PKC) family of lipid-dependent serine/theonine kinases plays a central role in many intracellular eukaryotic signalling events. Members of the novel (delta, epsilon, eta, theta) subclass of PKC isotypes lack the Ca2+ dependence of the conventional PKC isotypes and have an N-terminal C2 domain, originally defined as V0 (variable domain zero). Biochemical data suggest that this domain serves to translocate novel PKC family members to the plasma membrane and may influence binding of PKC activators. RESULTS: The crystal structure of PKC-delta C2 domain indicates an unusual variant of the C2 fold. Structural elements unique to this C2 domain include a helix and a protruding beta hairpin which may contribute basic sequences to a membrane-interaction site. The invariant C2 motif, Pro-X-Trp, where X is any amino acid, forms a short crossover loop, departing radically from its conformation in other C2 structures, and contains a tyrosine phosphorylation site unique to PKC-delta. This loop and two others adopt quite different conformations from the equivalent Ca(2+)-binding loops of phospholipase C-delta and synaptotagmin I, and lack sequences necessary for Ca2+ coordination. CONCLUSIONS: The N-terminal sequence of Ca(2+)-independent novel PKCs defines a divergent example of a C2 structure similar to that of phospholipase C-delta. The Ca(2+)-independent regulation of novel PKCs is explained by major structural and sequence differences resulting in three non-functional Ca(2+)-binding loops. The observed structural variation and position of a tyrosine-phosphorylation site suggest the existence of distinct subclasses of C2-like domains which may have evolved distinct functional roles and mechanisms to interact with lipid membranes.

Amino Acid Sequence↗
PubMed1998

Preliminary X-ray analysis of a C2-like domain from protein kinase C-delta.

C2 domains are intracellular modules of approximately 130 residues that are found in many proteins involved in membrane trafficking and signal transduction. They are known to serve a variety of roles including binding ligands such as calcium, phospholipids and inositol polyphos-phates as well as interacting with larger macromolecules. Although originally identified in the Ca2+-dependent protein kinase C isoforms (PKC), initially no C2 domain was evident within the Ca2+-independent isoenzymes. A recent study identified a divergent C2 domain in several novel, Ca2+-independent PKCs (delta, epsilon, eta and straight theta), located at their N-termini in a region previously referred to as a variable domain zero (Vo) [Ponting & Parker (1996). Protein Sci. 5, 2375-2390]. The functional importance of this domain in the context of the novel PKCs is at present not well understood though it has been implicated in substrate recognition. The expression, crystallization and preliminary crystallographic analysis of recombinant Vo domain (residues 1-123) from PKC-delta is reported here. Crystals were obtained from incomplete factorial screens after removal of the histidine tag used to aid purification. These crystals diffracted to Bragg spacings of approximately 3 A using a rotating-anode source and to 1.9 A using synchrotron radiation. The crystals have cell parameters of a = 60.7, b = 120.9 and c = 40.7 A and systematic absences consistent with the orthorhombic space group P212121. To facilitate structure determination we have prepared, characterized and crystallized selenomethionine-substituted material.

Animals↗
PubMed1997

Human leukocyte antigen system in clozapine-induced agranulocytosis.

Forty-three schizophrenic patients participating in this study were serotyped for human leukocyte antigens (HLA-A, -B, -C, -DR, -DQ antigens). Thirty-six of them were hospitalised in two state mental hospitals and 7 in our general hospital, psychiatric unit. The patients from our unit were typed for HLA before commencing clozapine treatment whereas the patients from state hospitals were typed after commencing treatment. Three out of 43 patients developed agranulocytosis. One had a combination of both 'high-risk' haplotypes (HLA-B16(38,39), DR4, DQ3 and HLA-DR2, DQ1), another had HLA-DR2, DQ1, whereas the last had a totally different haplotype. Between non-agranulocytic patients 1 was found to carry the HLA-B16(38,39), DR4, DQ3 haplotype and 14 (out of 40) had the HLA-DR2, DQ1. Taking into account other factors supposed to be involved (a noxious metabolite, and the presence of a humoral cytotoxic factor) we must admit that despite the finding of a high-risk haplotype in Jewish populations there are other aspects of this question awaiting clarification.

Adult↗
PubMed1997

HLA phenotypes in healthy aged subjects.

One hundred and seventy-one unrelated elderly healthy subjects selected according to the Senieur protocol (57 men and 114 women), aged 75-104 years, and 405 healthy individuals (238 men and 167 women), aged 18-65 years, were typed for HLA-A, HLA-B, and HLA-DR antigens. The purpose of the study was to investigate a possible association between HLA antigens and longevity. In the total group of elderly, an increased frequency of HLA-B16 (11.11 vs. 5.43%) and HLA-DR7 (38.33 vs. 15.67%) and a decreased frequency of HLA-B15 (1.75 vs. 5.18%) and HLA-DR4 (11.66 vs. 24.15%) were observed. The HLA-B15DR4 haplotype was not represented (vs. 2.1%), HLA-A1B8 was found with a low frequency (2.9 vs. 4.4%), and HLA-B8DR3 was very rarely found (1.6 vs. 10.1%), whereas the HLA-B13DR7 haplotype was observed with an increased frequency (6.6 vs. 3.3%). These results are in agreement with other published data and suggest that longevity in humans may be influenced by the genetic background.

Adolescent↗
PubMed1994

Antimicrobial activity of 5,6-dihydrobenzo-[a]-carbazoles.

A new series of 5,6-dihydrobenzo[a]carbazoles was synthesized, some showing good antibacterial activity. The presence of a dialkylamino ethyl chain on the 2-, 3- or 4-O-substituent seems to be critical for such activity.

Anti-Infective Agents↗
PubMed1993

Increased frequency of HLA B17 antigen in girls with Turner syndrome and their fathers.

HLA-A, -B and -DR antigen distribution was studied in 49 girls with Turner Syndrome (TS), in 43 of their parents, as well as in 433 controls. No increased frequency of DR3, DR4 was found in our group. However, an increased frequency of HLA B17 antigen was disclosed (18.3% in TS versus 6.4% in the controls, p < 0.001 and pc < 0.01). Furthermore, the HLA B17 antigen was of paternal origin in 77.7% of the cases. The interpretation of the present findings is quite difficult. Most likely, the findings are related to the chromosomal abnormality rather than to autoimmunity. It is quite possible that genes within the region of class I genes create unfavorable circumstances leading to the loss of the sex chromosome or, alternatively, genes in this region confer protection and prevent miscarriage of the affected fetus.

Fathers↗
PubMedDate not supplied

Crystallization and preliminary crystallographic analysis of cytochrome c553 peroxidase from Nitrosomonas europaea.

The di-heme peroxidase (cytochrome c553 peroxidase) from Nitrosomonas europaea has been crystallized in a form suitable for high-resolution X-ray structure determination. A complete data set was obtained to 2.5A and the data were indexed in space group P2(1) with a = 88.79 A, b = 55.93 A, c = 144.37 A, beta = 103.87 degrees. The self-rotation function indicates one homodimer per asymmetric unit.

Amino Acid Sequence↗