Characterization of the role of N-linked glycosylation on the cell signaling and expression of the human thromboxane A2 receptor alpha and beta isoforms

The alpha and beta isoforms of the thromboxane A2 receptor (TP) mediate the actions of the prostanoid thromboxane A2 and its mimetics in humans. The amino terminal region of the TPs contains two consensus N-linked glycosylation sites at asparagine (N) residues N4 and N16. In this study, we explored the significance of N-linked glycosylation on the signaling and surface expression of the human TP isoforms. Inhibition of N-linked glycosylation reduced selective radioligand ([3H]SQ29,548) binding by either TP in both human erythroleukemia cells and in transfected human embryonic kidney 293 cells. Moreover, site-directed mutagenesis of the putative glycosylation sites of TPalpha revealed that radioligand binding also was reduced greatly for both the single (TPalphaN4-Q4, TPalphaN16-Q16) and double (TPalphaN4,N16-Q4,Q16) mutants, yielding levels of 8% binding relative to the wild-type TPalpha for the double mutants. Reductions in ligand binding were caused by decreased maximal binding and not by changes in affinity (Kd) or in specificity of the receptors for [3H]SQ29,548 or other ligands. Subcellular fractionation confirmed that, in relation to total TP expression, membrane expression was not altered in TPalphaN4-Q4 or TPalphaN16-Q16 but was reduced to levels of 55% of total expression in TPalphaN4,Q4-N16,Q16. Inhibition of glycosylation reduced, but did not abolish, agonist (U46619) mediated intracellular Ca++ mobilization by TPalpha or TPbeta and cAMP production by TPalpha. Thus, N-linked glycosylation of the human TP isoforms is important for ligand binding, efficient second messenger signaling and efficient membrane expression.

Analysis of the physical properties and molecular modeling of Sec13: A WD repeat protein involved in vesicular traffic

WD repeat proteins are a family of proteins that contain a series of highly conserved internal repeat motifs, usually ending with WD (Trp-Asp). The G beta subunit of heterotrimeric guanine nucleotide binding protein is a member of this family, and its crystal structure has been recently solved at high resolution (Wall et al. (1995) Cell 83, 1047-1058; Sondek et al. (1996) Nature 379, 369-374). Based on the coordinates of G beta, we have constructed a model for the structure of Sec13, a 33 kDa WD repeat protein from Saccharomyces cerevesiae essential for vesicular traffic. The model has been tested using a combination of biophysical and biochemical methods. Sec13 was expressed in Escherichia coli as a hexa-His-tagged protein (H6Sec13) and purified to homogeneity. In contrast to some other WD repeat proteins that are unable to fold into monomeric structures when expressed in E. coli, H6Sec13 was soluble and monomeric in the absence of detergent. The far-UV circular dichroism (CD) spectra of H6Sec13 indicated less than 10% alpha-helix consistent with the model which predicts primarily beta-sheets. H6Sec13 shows a cooperative and irreversible thermal denaturation curve consistent with a tightly packed structure. The CD spectrum shows an unusual positive ellipticity at 229 nm that was attributed to interactions of surface tryptophans since the 229 nm maximum could be abolished by modification of 6.3 +/- 0.3 (n = 3) tryptophans (out of 15 total in the molecule) with N-bromosuccinimide. Our model predicts that three sets of tryptophans are clustered near the surface. As predicted by the model, purified H6Sec13 was completely resistant to trypsin digestion. The concordance of the model of Sec13 presented in this paper with the biochemical and biophysical studies suggests that this model can be useful as a guide to further experiments designed to elucidate the function of Sec13 in vesicular traffic.

Mapping genes within a YAC by computer-assisted interpretation of partial restriction digestions

Partial restriction digestion is used to map restriction sites and the location of genes within yeast artificial chromosomes (YACs). Locus-specific probes are hybridised to the partially digested YAC DNA and the fragments to which they hybridise are compared with the pattern of partial digestion products that include each map region. A least squares criterion is presented which allows for error in fragment length determination. This rapidly defines the most likely location of a marker within the restriction map and permits the combination of results from digestions with different restriction enzymes. Approximate confidence intervals may be assigned to gene locations, and tests of goodness-of-fit of the data may be performed. Since the number of erroneously matched fragments increases in proportion to the square of the number of sites, denser maps are not necessarily more informative. Simulations indicate that the optimal number of internal restriction sites given typical experimental error (1% of YAC length) is about five sites; the associated broad support interval (on average one third of YAC length) may be reduced by combining results from different enzyme digestions. Application of a computer implementation of this model to experimental data showed that the model fitted well, and estimates of location were found to be consistent with other evidence.

Anti-phospholipid autoantibodies bind to apoptotic, but not viable, thymocytes in a beta 2-glycoprotein I-dependent manner

Anti-phospholipid autoantibodies (aPL) are associated with a clinical syndrome of hypercoagulability, thrombocytopenia, and fetal loss. Several groups have shown that the in vitro target of many aPL is not a pure phospholipid Ag, but is either a complex between anionic phospholipid and the plasma protein beta2-glycoprotein I (beta 2GPI) or the protein beta 2GPI alone. Anionic phospholipids are normally absent from the extracellular surface of cell membranes but redistribute from the inner to the outer leaflet during apoptosis. We show that aPL bind specifically to apoptotic, but not viable, thymocytes, and that binding is dependent upon the presence of beta 2GPI. Moreover, we show that beta 2GPI binds selectively to the surface of apoptotic thymocytes to generate an epitope for antiphospholipid autoantibodies. These findings suggest that apoptotic cells may be the natural immunogen and/or target for aPL. Moreover, we propose that the interaction of circulating beta 2GPI with redistributed anionic phospholipid may itself generate a novel ligand by which apoptotic cells are recognized directly for phagocytic clearance.

Anti-phospholipid autoantibodies bind to apoptotic, but not viable, thymocytes in a beta 2-glycoprotein I-dependent manner

Anti-phospholipid autoantibodies (aPL) are associated with a clinical syndrome of hypercoagulability, thrombocytopenia, and fetal loss. Several groups have shown that the in vitro target of many aPL is not a pure phospholipid Ag, but is either a complex between anionic phospholipid and the plasma protein beta2-glycoprotein I (beta 2GPI) or the protein beta 2GPI alone. Anionic phospholipids are normally absent from the extracellular surface of cell membranes but redistribute from the inner to the outer leaflet during apoptosis. We show that aPL bind specifically to apoptotic, but not viable, thymocytes, and that binding is dependent upon the presence of beta 2GPI. Moreover, we show that beta 2GPI binds selectively to the surface of apoptotic thymocytes to generate an epitope for antiphospholipid autoantibodies. These findings suggest that apoptotic cells may be the natural immunogen and/or target for aPL. Moreover, we propose that the interaction of circulating beta 2GPI with redistributed anionic phospholipid may itself generate a novel ligand by which apoptotic cells are recognized directly for phagocytic clearance.

Fine mapping of the human pentraxin gene region on chromosome 1q23

The 1q21 to 25 region of human chromosome 1 contains genes which encode proteins with immune- and inflammation-associated functions. These include the pentraxin genes, for C-reactive protein (CRP), serum amyloid P (SAP) protein (APCS),a nd a CRP pseudogene (CRPP1). The region of chromosome 1 containing this cluster is syntenic with distal mouse chromosome 1. We constructed an approximately 1.4 megabase yeast artificial chromosome (YAC) contig with the pentraxin genes at its core. This four-YAC contig includes other genes with immune functions including the FCER1A gene, which encodes the alpha-subunit of the IgE high-affinity Fc receptor and the IFI-16 gene, an interferon-gamma-induced gene. In addition, it contains the histone H3F2 and H4F2 genes and the gene for erythroid alpha-spectrin (SPTA1). The gene order is cen.-SPTA1-H4F2-H3F2-IFI-16-CRP-CRPP1-APCS -FCER1A- tel. The contig thus consists of a cluster of genes whose products either have immunological importance, bind DNA, or both.

Morbillivirus infection in cetaceans of the western Atlantic

We report serologic evidence of morbillivirus infection in eleven of fifteen species of odontocete cetaceans from the western Atlantic since 1986. Blood samples were obtained both from free-ranging and stranded animals. Virus neutralizing titers were higher against porpoise and dolphin morbilliviruses than against peste des petits ruminants virus, phocine distemper virus or canine distemper virus (CDV). Serum from five species, tested in a heterologous immunoprecipitation assay using radiolabelled CDV, precipitated the nucleocapsid (N) protein. Clinical morbillivirus infection may potentially impact already threatened species such as the harbour porpoise and precipitate mass strandings of socially cohesive odontocetes.

Early controlled motion with dynamic splinting versus static splinting for zones III and IV extensor tendon lacerations: a preliminary report

Recent developments in the understanding of tendon healing and the effects of early motion have led to early controlled motion programs (ECM) for lacerated extensor tendons. The purpose of this study was to determine whether there were differences in length of treatment and final results when patients who had been treated with ECM with dynamic splinting were compared with patients who had been treated with traditional static extension splinting (SES) for zone III and zone IV extensor tendon lacerations. A retrospective study of patient charts from June 1984 through January 1990 was conducted. A total of 36 charts were reviewed. Twenty-seven patients met the study criteria: treatment with ECM with dynamic splinting (n = 10) and treatment with traditional SES using a finger-hand splint (n = 17). Data were analyzed for total number of therapy visits (V), total number of weeks of therapy before discharge (W), total active motion achieved (TAM), total passive motion achieved (TPM), and incidence of complications. Significance was established at the p = 0.05 level for all statistical analyses. There were no significant differences between the groups for V (t = 1.76, p = 0.09), W (t = 0.58, p = 0.57), TPM (t = 0.12, p = 0.90), TAM (t = 0.44, p = 0.66), or the incidence of extensor lag (chi 2 = 2.264). The Cohen stat power analysis value was 0.40, revealing that the number of patients was too small for significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapist management of thoracic outlet syndrome

Treatment of the thoracic outlet patient can be a complex and challenging problem for the occupational or physical therapist. The literature supports conservative care as the preferred approach for these patients; therefore, therapy plays an important role in caring for these patients. I question whether TOS is becoming the RDS of the 1990s. Often these "TOS" patients are suffering from additional secondary system complaints including active myofascial trigger points, primary or secondary glenohumeral joint pathologies, cervical pathology, or more distal peripheral neuropathies. A thorough evaluation by the therapist is extremely important in determining TOS and separating compressive TOS from entrapment TOS. It is only after a thorough assessment that a proper treatment approach can be formulated. Treatment should initially address comfort, control, and relief and then progress to the neurovascular component. Finally, strengthening and conditioning, if tolerated, are implemented. Properly educating the patient to achieve behavior modification, exercise compliance, symptom control, and postural correction is requisite to optimal results.

Apoprotein B structure and receptor recognition of triglyceride-rich low density lipoprotein (LDL) is modified in small LDL but not in triglyceride-rich LDL of normal size

We compared the effect of lipid composition and particle size of triglyceride-rich low density lipoprotein (LDL) upon apoprotein B conformation and binding to the LDL receptor. Three groups of triglyceride-rich LDL were studied: (a) LDL isolated from chronic hypertriglyceridemic individuals (HTG-LDL); (b) normal LDL made triglyceride-rich by in vitro incubation with triglyceride emulsion and the neutral lipid transfer protein (R-LDL); and (c) LDL from normolipidemic individuals made acutely hypertriglyceridemic by intravenous infusion of 10% Intralipid (IV-LDL). HTG-LDL was small and dense, whereas R-LDL and IV-LDL had normal size. HTG-LDL, but not R-LDL or IV-LDL, exhibited decreased binding to the LDL receptor on human skin fibroblasts in studies at 4 degrees C and reduced degradation at 37 degrees C. Apoprotein B conformation was assessed by circular dichroism and by analyzing the immunoreactivity of different monoclonal antibodies. HTG-LDL but not R-LDL or IV-LDL showed a change in the CD spectra and a consistent decrease in the immunoreactivity of monoclonal antibody 3F5 (2.5-fold) which recognizes an epitope adjacent to the receptor binding domain of apoprotein B. These findings suggest that in triglyceride-rich LDL, the relative content of neutral lipid in the core of LDL in the absence of changes in the size of the particle does not significantly affect apoprotein B conformation or its affinity for the LDL receptor.

Isolation of St. Louis encephalitis virus from a killer whale

We report the isolation of St. Louis Encephalitis (SLE) virus from a mature male killer whale (Orcinus orca). This represents the first isolation of SLE virus from a marine mammal. The animal presented with reduced appetite, rapidly became lethargic and subsequently died. Virus-induced CPE was observed in a dolphin cell line, SP-1K (ATCC CCL 78), inoculated with brain, kidney, and lung tissues obtained at necropsy. Electron microscopy of infected SP-1K cells revealed the presence of virions having morphology and size resembling members of the Flaviviridae. Final identification as SLE virus was made by neutralization and immunofluorescence staining tests.

Potassium and anaesthesia

Potassium is the principle intracellular ion, and its concentration and gradients greatly influence the electrical activity of excitable membranes. Because anaesthesia is so intimately involved with electrically active cells, potassium concentrations in surgical patients have received considerable attention in diagnostic and therapeutic applications. With the ongoing evolution in the indications for potassium, it is important to review the role of potassium in cellular activity, in storage and regulation, in diseases that alter potassium homeostasis, and in the therapeutic implications of perioperative alterations of potassium concentration. A rational approach to abnormal potassium values and the use of potassium in the operating room is sought, based on a physiological understanding of risks and benefits.

Structure of the N- and O-glycans of the A-chain of human plasma alpha 2HS-glycoprotein as deduced from the chemical compositions of the derivatives prepared by stepwise degradation with exoglycosidases

The structure of the glycans of the A-chain of human plasma alpha 2HS-glycoprotein was established from the chemical compositions of its derivatives prepared by sequential enzymatic degradation of the carbohydrate moiety, from the determination of the kind and amount of the monosaccharides liberated after each step of the enzymatic digestion, and from the distinct specificity of the highly purified exoglycosidases. The exoglycosidases were three sialidases (Vibrio cholerae, fowl plague virus, and Arthrobacter ureafaciens), two beta-galactosidases (Streptococcus pneumoniae and bovine testis), one alpha-N-acetylgalactosaminidase, one beta-N-acetylglucosaminidase, and one alpha-mannosidase. Utilizing sialidases with different cleavage specificities, the number of alpha 2-3- and alpha 2-6-linked sialic acid residues could be separately determined. As to the beta-galactosidases, the enzyme isolated from S. pneumoniae cleaves only beta 1-4-linked galactose residues, whereas the bovine testes enzyme acts on both the beta 1-4- and beta 1-3-linked galactose residues. Jack bean beta-N-acetylglucosaminidase cleaves beta 1-2, beta 1-4, and beta 1-6 GlcNAc with higher activity for the beta 1-2. Jack bean alpha-mannosidase cleaves alpha 1-2, alpha 1-6, and alpha 1-3 Man with greater activity for alpha 1-2 and alpha 1-6. Bovine liver alpha-N-acetylgalactosaminidase cleaves O-linked GalNAc. On the basis of these results, the A-chain of alpha 2 HS-glycoprotein was found to possess two biantennary N-glycans and two O-linked trisaccharides.

Anesthesia for pediatric laparoscopic cholecystectomy

We report the general anesthetic events and clinical concerns encountered with a laparoscopic cholecystectomy in a 19-month-old toddler. Carbon dioxide was insufflated to create a pneumoperitoneum, with resulting intra-abdominal pressures ranging from 5 to 11 mmHg. The end-tidal partial pressure of carbon dioxide (PETCO2) rose as high as 48 mmHg (a 10 mmHg increase from baseline), requiring a 68% increase in minute ventilation to achieve preinsufflation values. Careful monitoring of ventilation, PETCO2, and intra-abdominal pressure are recommended for optimal anesthetic management of the pediatric laparoscopic cholecystectomy patient.

An insight into domain structures and thermal stability of gamma-crystallins

The thermal behavior of gamma II, gamma IIIA, gamma IIIB, and gamma IVA crystallin, from calorimetric and spectral studies, has been analyzed in terms of selective unfolding of domains, interdomain interactions, conformational stability, and the existence of intermediates in the order-disorder transition equilibrium. The major endothermic transition (Tm) observed calorimetrically for all four fractions occurs between 67 and 78 degrees C, with enthalpy change (delta H) from 80 to 150 kcal/mol, values that agree reasonably well with those from spectroscopic measurements. gamma II and gamma IIIB show a second thermal event at T less than Tm whereas gamma IIIA and gamma IVA showed no additional transition. Urea-induced equilibrium unfolding of gamma II at acidic pH, unlike gamma IVA, is biphasic as monitored by CD and fluorescence, indicating the existence of an intermediate. The absence of a cooperative transition in gamma IVA in acidic urea and the appearance of a single endotherm in differential scanning calorimetry at low pH have been attributed to a structured intermediate that melts at low temperature. The difference in the folding/unfolding of gamma II and gamma IVA has been explained by subtle differences in the packing arrangement of their two domains and interactions between them. Thermal aggregation of gamma-crystallins could be prevented either by preincubation with ionic detergents or at low pH or in the presence of chemical denaturant, indicating that the protein surface charge and solvent polarity influence their stability. An increase in the 8-anilino-1-naphthalenesulfonate-bound fluorescence during heat denaturation also suggests that the thermal aggregation is governed by hydrophobic interactions.

Amino acid sequence of human plasma galactoglycoprotein: identity with the extracellular region of CD43 (sialophorin)

The amino acid sequence of galactoglycoprotein purified from human plasma was elucidated to 75% completeness by using chemical degradation of peptides and glycopeptides derived from digests of the protein with seven specific proteases. This sequence represents a polypeptide chain of approximately 220 amino acid residues including a high content of serine, threonine, alanine, and proline with one N-linked and multiple O-linked glycans. Comparison of peptide sequences from the native galactoglycoprotein and the deglycosylated derivative demonstrated the locations of 25 sites of O-glycosylation and three serine sites that are not glycosylated. The homogeneous N terminus was established as serine. C-terminal analysis revealed multiple C-terminal residues, suggesting that galactoglycoprotein molecules are of varying lengths. A search of a protein data base revealed that the galactoglycoprotein polypeptide is identical to the N-terminal (extracellular) polypeptide region of the blood-cell surface molecule CD43 (sialophorin, leukosialin). Further support of the relatedness of these molecules was obtained by immunoprecipitation of 125I-labeled galactoglycoprotein by monoclonal anti-CD43 antibodies. The composition and properties of the molecules together with the known structure of the gene encoding CD43 suggest that galactoprotein is derived by proteolytic cleavage from transmembrane "hexasaccharide CD43," known to be expressed on neutrophils, activated T lymphocytes, and platelets.

Micellar subunit assembly in a three-layer model of oligomeric alpha-crystallin

Differential scanning calorimetry was performed to monitor the heat-induced changes that occur in the structural domain of lens alpha-crystallin. Circular dichroism and fluorescence also were used to resolve the controversial issue of the quaternary structure of alpha-crystallin. Based on the thermal behavior as monitored by these techniques, a model is proposed that can account for all previous data as well as the currently reported thermal data. The proposed model of native alpha-crystallin has a three-layer structure in which the inner layer (core) is a micelle containing 12 subunits arranged in cuboctahedral symmetry. The apolar region is directed inward constituting a hydrophobic core similar to a micelle and adding structural stability. A second layer of six subunits has a similar but not identical structure to the first layer, directing its apolar face toward the hydrophobic core. Thus, these two layers constitute a micelle-like structure with octahedral symmetry. The third layer adds more subunits for a total of not more than 24. Differential scanning calorimetry, circular dichroism, and fluorescence studies indicated that the inner two-layer structure of molecular mass 360 kDa is highly stable and is most likely of the alpha m form. The three-layer structure of the native protein, however, is rather unstable. At 35-45 degrees C the outer layer dissociates from the inner two layers, and at higher temperatures rapidly reassociates to a slightly modified two-layer structure with a stability similar to that of alpha m. The proposed model does not require any specific assembly of the alpha A and alpha B subunits in each layer, but the fluorescence results suggest that the native inner two layers probably contain mostly alpha A.

Expression, secretion, and lipid-binding characterization of the N-terminal 17% of apolipoprotein B

The N-terminal 17% of human apolipoprotein B (apoB-17) was expressed in murine C127 cells following transfection with a bovine papilloma virus-based expression vector. A permanent cell line overexpressing the expected 89-kDa protein was selected and characterized. Pulse-chase experiments showed that the depletion of intracellular apoB-17 follows an apparent first-order kinetics with t1/2 = 51 min. Under conditions of continuous labeling, greater than 60% of the total synthesized apoB-17 was secreted in a soluble form, approximately 98% lipid-poor and approximately 2% lipid-bound. Inclusion of 1.2 mM oleate resulted in 5- and 2.5-fold increases in the amount of labeled apoB-17 in the p less than 1.063 g/ml and 1.063 less than p less than 1.21 g/ml fractions, respectively, which was coordinated with increased secretion of radiolabeled core lipids, triacylglycerols, and cholesteryl esters. Thus under conditions in which lipid pools are enriched a greater fraction of apoB-17 may be secreted on lipoprotein-like particles. The lipid-poor apoB-17 present in p greater than 1.21 g/ml readily associates with exogenously added dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles to form discoidal particles. Discs formed with DMPC/apoB-17, 7:1 (wt/wt), are 239 +/- 43 A in diameter and 61 +/- 4 A thick and contain approximately 2 molecules of apoB-17 and 2250 molecules of DMPC per disc. Based on volume calculations we conclude that apoB-17 forms an annulus about one bilayer high and 10 A thick surrounding the DMPC disc. Circular dichroic spectra of apoB-17 on DMPC discs showed apoB-17 to contain 39% alpha-helix, 36% beta-sheet, 9% beta-turn, and 16% random coil. To be consistent with this model greater than 70% of apoB-17 on DMPC discs must bind to lipid. These data suggest that the N-terminal 17% of apoB-100 can bind lipid and may contribute to some extent to the stabilization of triglyceride-rich lipoproteins.

The effect of the carbohydrate moiety upon the size and conformation of human plasma galactoglycoprotein as judged by electron microscopy and circular dichroism. Structural studies of a glycoprotein after stepwise enzymic carbohydrate removal

Galactoglycoprotein is a unique human plasma protein [76% carbohydrate (23% N-acetylneuraminic acid, 20% galactose, 3% mannose, 1% fucose and 29% N-acetylgalactosamine plus N-acetylglucosamine) and 24% polypeptide, a single polypeptide chain of about 200 amino acid residues that is high in serine and threonine content] [Schmid, Mao, Kimura, Hayashi & Binette (1980) J. Biol. Chem. 255, 3221-3226]. Highly purified exoglycosidases with well-defined specificities were used to prepare five derivatives of galactoglycoprotein in which sequential residues of N-acetylneuraminic acid, galactose, N-acetylglucosamine, a second galactose and N-acetylgalactosamine were removed with 83% of the total carbohydrate cleaved. C.d. shows that native galactoglycoprotein and all derivatives in aqueous buffer are predominantly random coil, suggesting that removal of a large number of electrostatic net charges, as well as the major portion of the carbohydrate moiety, does not alter the secondary structure of the polypeptide chain. Examination of the size and conformation of tungsten-shadowed galactoglycoprotein and asialo and agalacto derivatives by electron microscopy shows the size and conformation of all three preparations to be similar, with only minor differences in particle length and width.

A review of false negative mammography in a symptomatic population

A review of the mammograms of 871 patients with breast cancer from a symptomatic clinic performed at the General Hospital, Birmingham between 1980 and 1988 revealed an overall false negative rate of 8.6%. There has been a steady fall in the number of cancers missed per year from the commencement of review, and this reduction has been more consistent with improvements in radiographic equipment and technique, particularly the introduction of a radiographic grid. In half of the cases the tumour was missed because no radiological abnormality was detectable, even on reviewing the films, and this rate has remained remarkably stable over the study period, emphasizing the importance of a clinical examination in symptomatic women. Comparison of the histological diagnoses revealed similar percentages of ductal carcinomas, 89.6% in the true positive group compared with 85% in the false negative group. Of the false negative carcinomas, 5.5% were medullary tumours compared to 0.8% in the true positive group.

Effect of the carbohydrate moiety on the secondary structure of beta 2-glycoprotein. I. Implications for the biosynthesis and folding of glycoproteins

By use of six highly purified exoglycosidases with well-defined specificity, the oligosaccharide units of human plasma beta 2-glycoprotein I (beta 2I) were modified by sequential enzymatic degradation. The released monosaccharides (NeuAc, Gal, GlcNAc, and Man) were quantified, and the carbohydrate compositions of the resulting glycoprotein (gp) derivatives were determined. The gp was found to be both partially sialylated and galactosylated. These findings which are in agreement with earlier reports suggest that the carbohydrate moiety of beta 2I possesses more bi- than tri-antennas, probably three of the former and two of the latter carbohydrate units. Circular dichroic (CD) spectra of native beta 2I and its derivatives were measured in aqueous buffer and 2-chloroethanol (2-CE). Analysis of these spectra for elements of secondary structure showed beta 2I and most of the derivatives to contain predominantly beta-sheet and beta-turn structures. The lack of alpha-helical structures in aqueous buffer was noted. Removal of a large portion of the carbohydrate moiety did not alter the CD spectra or secondary structure of beta 2I in either aqueous buffer or in 2-CE. However, after enzymatic removal of approximately 96% of the carbohydrate moiety, large significant changes in the spectra and secondary structures were observed. In aqueous buffer a shift in the wavelength minimum occurred, accompanied by an increase in the magnitude of the molar ellipticity and the amount of beta-turn, with a reduction in random coil. One-third of the amino acids which were originally in random coil conformation assumed beta-turns after removal of 96% of the carbohydrate moiety.(ABSTRACT TRUNCATED AT 250 WORDS)

Eimeria caretta sp.nov. (Apicomplexa: Eimeriidae) from the loggerhead sea turtle, Caretta caretta (Testudines)

Eimeria caretta sp.nov. (Apicomplexa: Eimeriidae) is described from the feces of a stranded loggerhead turtle, Caretta caretta (Testudines), rescued from the Atlantic coast near Jensen Beach, Hutchinson Island, Martin County, Florida. Oocysts are subspherical to ellipsoidal, 24.5 × 22.0 (21.4–28.0 × 18.4–24.0) μm, with a smooth, bilayered wall. Micropyle, polar granule, and oocyst residuum are absent. Sporocysts are ovoid, 14.3 × 8.9(12.8–16.0 × 8.2–10.0) μm, and possess a Stieda body but no substieda body. The Stieda body is unusual in that 12–20 long, thin filaments project from its surface. Sporozoites are elongate, each with two refractile bodies. The sporocyst residuum consists only of scattered granules. This coccidian is most similar to Eimeria filamentifera Wacha and Christiansen 1979 from the common snapping turtle, Chelydra serpentina, but differs because it possesses more numerous and elongate filaments associated with the Stieda body and lacks an oocyst residuum.

Calorimetric and spectroscopic investigation of the unfolding of human apolipoprotein B

The unfolding of human apolipoprotein B-100 in its native lipid environment, low density lipoprotein (LDL), and in a soluble, lipid-free complex with sodium deoxycholate (NaDC) has been examined using differential scanning calorimetry (DSC) and near UV circular dichroic (CD) spectroscopy. High resolution DSC shows that LDL undergoes three thermal transitions. The first is reversible and corresponds to the order-disorder transition of the core-located cholesteryl esters (CE) (Tm = 31.1 degrees C, delta H = 0.75 cal/g CE). The second, previously unreported, is reversible with heating up to 65 degrees C (Tm = 57.1 degrees C, delta H = 0.20 cal/g apoB) and coincides with a reversible change in the tertiary structure of apoB as shown by near UV-CD. No alteration in the secondary structure of apoB is observed over this temperature range. The third transition is irreversible (Tm = 73.5 degrees C, delta H = 0.99 cal/g apoB) and coincides with disruption of the LDL particle and denaturation of apoB. The ratio of delta H/delta HvH for the reversible protein-related transition suggests that this is a two-state event that correlates with a change in the overall tertiary structure of the entire apoB molecule. The second protein-related transition is complex and coincides with irreversible denaturation. ApoB solubilized in NaDC undergoes three thermal transitions. The first two are reversible (Tm = 49.7 degrees C, delta H = 1.13 cal/g apoB; Tm = 56.4 degrees C, delta H = 2.55 cal/g apoB, respectively) and coincide with alterations in both secondary and tertiary structure of apoB. The changes in secondary structure reflect an increase in random coil conformation with a concomitant decrease in beta-structure, while the change in tertiary structure suggests that the conformation of the disulfide bonds is altered. The third transition is irreversible (Tm = 66.6 degrees C, delta H = 0.54 cal/g apoB) and coincides with complete denaturation of apoB and disruption of the NaDC micelle. The ratio of delta H/delta HvH for the two reversible transitions indicates that each of these transitions is complex which may suggest that several regions or domains of apoB are involved in each thermal event.

Are multiple examinations of the gall-bladder helpful?

The pattern of use of the oral cholecystogram and ultrasonocholecystography in the investigation of 1014 patients prior to cholecystectomy was analysed. Three hundred and sixty-eight (36.3%) of our patients had both an oral cholecystogram and an ultrasound examination of the gallbladder. In 193 (52.4%) of these the initial investigation was positive: the second test in this group was rarely helpful and sometimes confusing. Overall the predictive value of a positive first study was 98.5%. We conclude that the use of further investigation following an initially positive result is not justified. By these criteria 18.5% of patients had an unnecessary second investigation.

Fatty acid interactions with rat intestinal and liver fatty acid-binding proteins expressed in Escherichia coli. A comparative 13C NMR study

Enterocytes in the small intestinal mucosa contain abundant quantities of two homologous cytosolic proteins known as intestinal and liver fatty acid-binding proteins (I- and L-FABP, respectively). To elucidate structure-function relationships for these proteins, the interactions between 13C-enriched palmitate and oleate and Escherichia coli-expressed rat I- and L-FABP were systematically compared using 13C NMR spectroscopy. NMR spectra of samples containing fatty acids (FA) and I-FABP at different molar ratios (all at pH 7.2 and 37 degrees C) exhibited a single carboxyl resonance corresponding to FA bound to I-FABP (181.4 ppm, peak I) and an additional carboxyl resonance corresponding to unbound FA in a bilayer phase (179.6 ppm). Peak I reached a maximum intensity corresponding to 1 mol of bound FA/mol of I-FABP under all sample conditions examined. NMR spectra for samples containing FA and L-FABP also exhibited a single carboxyl resonance corresponding to FA bound to L-FABP but at a different chemical shift value (182.2 ppm, peak L). Its maximum intensity varied depending on the physical state of the unbound FA (liquid crystalline or crystalline), the FA used (palmitate or oleate), and the sample pH. In the presence of a liquid crystalline (bilayer) phase, up to 1 (oleate) or 2 (palmitate) mol of FA were bound/mol of L-FABP, but in the presence of a crystalline phase (1:1 acid-soap), up to 3 mol of palmitate were bound/mol of L-FABP (all at pH 7.2). Peak I exhibited little or no ionization shift over a wide pH range (pH 3.0-11.0), and its chemical shift was unaffected by the ionization of Lys and His residues. Hence, the carboxylate group of FA bound to I-FABP was solvent inaccessible and most likely involved in an ion-pair electrostatic interaction with the delta-guanidinium moiety of an Arg residue. In contrast, peak L exhibited an ionization shift and an estimated apparent pKa value similar to that obtained for monomeric FA in water, suggesting that the carboxylate groups of FA bound to L-FABP were solvent accessible and located at or near the protein solvent interface. With decreasing pH, FA dissociated from L-FABP but not I-FABP, as monitored by NMR peak intensities. Concurrently, a large decrease in circular dichroism molar ellipticity was observed with L-FABP but not I-FABP. In conclusion, I-FABP and L-FABP are distinct with regards to their FA-binding stoichiometries, binding mechanisms, and sensitivity to pH.(ABSTRACT TRUNCATED AT 400 WORDS)

Secondary structural analysis of retrovirus integrase: characterization by circular dichroism and empirical prediction methods

The retrovirus integrase (IN) protein is essential for integration of viral DNA into host DNA. The secondary structure of the purified IN protein from avian myeloblastosis virus was investigated by both circular dichroism (CD) spectroscopy and five empirical prediction methods. The secondary structures determined from the resolving of CD spectra through a least-squares curve fitting procedure were compared with those predicted from four statistical methods, e.g., the Chou-Fasman, Garnier-Osguthorpe-Robson, Nishikawa-Ooi, and a JOINT scheme which combined all three of these methods, plus a pure a priori one, the Ptitsyn-Finkelstein method. Among all of the methods used, the Nishikawa-Ooi prediction gave the closest match in the composition of secondary structure to the CD result, although the other methods each correctly predicted one or more secondary structural group. Most of the alpha-helix and beta-sheet states predicted by the Ptitsyn-Finkelstein method were in accord with the Nishikawa-Ooi method. Secondary structural predictions by the Nishikawa-Ooi method were extended further to include IN proteins from four phylogenetic distinct retroviruses. The structural relationships between the four most conserved amino acid blocks of these IN proteins were compared using sequence homology and secondary structure predictions.

Interactions of oleic acid with liver fatty acid binding protein: a carbon-13 NMR study

13C NMR spectroscopy was used to probe the structural interactions between carboxyl-13C-enriched oleic acid (18:1) and rat liver fatty acid binding protein (FABP) and the partitioning of 18:1 between FABP and unilamellar phosphatidylcholine (PC) vesicles. Spectra of systems containing 2-8 mol of 18:1/mol of FABP (but no PC) exhibited one carboxyl resonance (182.2 ppm) corresponding to FABP-bound 18:1. At pH values less than 8.0, an additional carboxyl resonance, corresponding to unbound 18:1 in a lamellar phase, was observed. Both resonances exhibited ionization shifts with estimated apparent pKa values of less than 5 (bound 18:1) and greater than 7 (unbound 18:1). The intensity of the resonance corresponding to FABP-bound 18:1 increased with increasing 18:1/FABP mole ratio and at 8/1 mole ratio indicated that at least 2 and 6 mol of 18:1/mol of FABP were FABP-bound at pH 7.4 and 8.6, respectively. NMR spectra of systems containing equal concentrations (w/v) of FABP and PC and from 1 to 4 mol of total fatty acid (FA)/mol of FABP exhibited two 18:1 carboxyl resonances (182.2 and 178.5 ppm, pH 7.4). The downfield resonance corresponded to FABP-bound 18:1 and the upfield resonance to PC vesicle bound 18:1. At 1/1 mole ratio (FA/FABP), the intensities of both resonances were approximately equal, but at 4/1 mole ratio the resonance for PC vesicle bound 18:1 was 3-fold more intense than that for FABP-bound 18:1. The following conclusions are reached: (i) The carboxyl groups of 18:1 bound to liver FABP experience only one type of binding environment (the aqueous milieu adjacent to the protein surface).(ABSTRACT TRUNCATED AT 250 WORDS)

Secondary and tertiary structure of apolipoproteins

The advent of these and other high-powered techniques for the detailed study of apoLP organization will allow us to obtain a high resolution picture of apoLP conformation both in solution and on native lipoprotein particles.

Omphalitis and peritonitis in a young West Indian manatee (Trichechus manatus)

Mortality data for the West Indian manatee (Trichechus manatus) indicates that from 1979 to 1984 16% of the recorded deaths involved young juveniles. Necropsy of a young manatee from the west coast of Florida revealed an active infection of the umbilical area (omphalitis) extending down the umbilical artery and veins. A generalized peritonitis was present. Bacterial cultures revealed Streptococcus faecium, Plesiomonas shigelloides, Pseudomonas putrefaciens and Escherichia coli.

Urogenital sinus calculi in a sand tiger shark (Odontaspis taurus)

Two calculi were found in the urogenital sinus of a 70 kg female sand tiger shark (Odontaspis taurus). The calculi were white in color, rough surfaced, and spherical in shape. Crystallographic examination revealed that they were composed of magnesium ammonium phosphate hexahydrate (80% struvite) and calcium phosphate (15% carbonate apatite). Approximately 5% of the stone matrix consisted of blood and protein and a distinct bacterial nidus was not present microscopically.

Physical properties of apoprotein B in mixed micelles with sodium deoxycholate and in a vesicle with dimyristoyl phosphatidylcholine

Apoprotein B, the major apoprotein of normal human low density lipoprotein (LDL) was solubilized with sodium deoxycholate (NaDC). The protein was recombined with the phospholipid dimyristoyl phosphatidylcholine (DMPC) to produce a complex of DMPC-apoB (4:1 w/w). (Biochemistry. 22: 3170-3178. 1983). Carboxyfluorescein and [3H]dextran entrapment studies show the DMPC-apoB 4:1 (w/w) complex to encapsulate an aqueous volume of 0.17 microliter/mumol of DMPC. From the chemistry and morphology of the complex and the evidence that the complex possesses an encapsulated volume, the most appropriate structural model for this assembly is that of a phospholipid single bilayer vesicle into which apoB is incorporated. Differential scanning calorimetry (DSC) and circular dichroic spectroscopy (CD) were used to investigate the physical properties of apoB in the mixed micellar complex with NaDC and in the vesicular DMPC-apoB complex. CD studies of apoB in NaDC mixed micelles show that apoB exhibits a similar secondary structure as apoB of native LDL over the temperature range 5-30 degrees C. Reversible structural changes occur between 30 and 50 degrees C. However, above 50 degrees C, disruption of the micellar particle and endothermic protein unfolding and denaturation occur with a Tmax of 52 degrees C and an enthalpy of 0.22 cal/g apoB, as shown by DSC. The DMPC-apoB complex exhibits a reversible thermal transition centered at 24 degrees C (delta H = 3.34 Kcal/mol DMPC) which is associated with the order-disorder transition of the hydrocarbon chains of DMPC. An endothermic transition occurs over the range 53-70 degrees C (delta H = 2.09 cal/g apoB) which, as shown by CD and turbidity study, corresponds to protein unfolding-denaturation and particle disruption. CD shows that apoB in the vesicular environment undergoes a series of conformational changes. The major alterations occur over the temperature range of the order-disorder transition of the phospholipid. Between 37-60 degrees C, the conformation is similar to that observed in native LDL.

Reassembly of low-density lipoproteins

The methodologies described here for the selective and sequential reassembly of model LDL particles, although in many instances still in the developmental stages, will undoubtedly provide a basis on which further advances in LDL reassembly will be made. Reassembled LDL complexes of defined lipids and apoB provide well-defined model systems in which to study the molecular interactions and structural organization of LDL, including the lipid-lipid interactions in the particle core, the lipid-lipid and lipid-protein interactions which determine the surface organization and protein conformation, and the interactions between the core and surface components. These reassembled LDL complexes should serve as important models to study the delivery of isotopically labeled lipids with differing physical properties to cells in order to investigate the metabolic complexity of intracellular LDL catabolism and its relationship to positive cholesterol balance and atherogenesis.

Effect of exogenous ACTH on serum corticosterone and cortisol concentrations in the Moluccan cockatoo (Cacatua moluccensis)

The effects of exogenous adrenocorticortrophic hormone (ACTH) on the serum corticosterone and cortisol concentrations were determined in 28 mature Moluccan cockatoos (Cacatua moluccensis), a representative of the psittacine species. Birds were randomly assigned to 4 groups (2 ACTH-treated groups and 2 saline-treated controls). Group I (10 cockatoos [5 males and 5 females] ) was given 15 IU of ACTH after blood samples (base line) were taken at 10:00 AM. Blood samples were taken again at 30 minutes and 2.5 hours after ACTH administration. Group II (10 cockatoos) was given similar treatment, but blood samples were taken at 1 and 4 hours after ACTH was administered. Groups III and IV (each of 4 birds) were given saline solution injections as controls. Blood samples were taken at 30 minutes and 2.5 hours after injection (group III) and at 1 and 4 hours after injection (group IV). All serum samples were analyzed for cortisol and corticosterone. Serum corticosterone concentration increased significantly (P less than 0.01) from base-line levels (26 ng/ml) to 108 ng/ml within 30 minutes after ACTH was administered. The high values were maintained for 3 hours and then decreased to 40 ng/ml at the end of 4 hours. Male birds seemed to respond to the ACTH treatment quickly and maintained increased concentration for a shorter period when compared with the responses seen in female birds. Serum cortisol values remained low throughout the experimental period. These results indicate that serum corticosterone was responsive to ACTH administration, but cortisol was not. In addition, there may be a difference in the responses between male and female members of the species.

Reassembled plasma low density lipoproteins. Phospholipid-cholesterol ester-apoprotein B complexes

Reassembled low density lipoprotein (LDL) complexes have been prepared by the interaction of lipid-free sodium deoxycholate-solubilized apoprotein B (apoB) of native human LDL with preformed, 200 A in diameter, microemulsions of cholesteryl oleate (CO), surface-stabilized by either egg yolk phosphatidylcholine ( EYPC ) or dimyristoyl phosphatidylcholine (DMPC). Gel chromatography of PC/CO/apoB complexes shows co-elution of the complex at 43% PC, 43% CO, and 14% apoB. Negative stain electron microscopy shows the particles to be circular, homogeneous, and approximately 200 A in diameter. PC/CO/apoB complexes exhibit beta-migration on agarose gels and show one high molecular weight protein band on 3.0% sodium dodecyl sulfate-polyacrylamide gels. Differential scanning calorimetry and x-ray scattering show the lipids in the complexes to undergo at least two specific thermal transitions depending on lipid composition, one associated with the core-located cholesterol esters similar to LDL and the protein-free microemulsions and the other from the phospholipid forming the surface monolayer. In addition, particle disruption-protein unfolding/denaturation occur irreversibly at 80-85 degrees C. At 4 degrees C, the secondary structure of apoB on complexes of EYPC /CO/apoB is similar to that of native LDL. For complexes of DMPC/CO/apoB, the secondary structure shows less alpha-helix which correlates with the difference in surface lipid environment. The reassembled complexes of PC/CO/apoB provide a defined system in which the components may be varied systematically in order to study the molecular organization, molecular interactions, and metabolism of LDL.

New horizons: the changing world of television

These are just some of the new opportunities that television is opening up for nonprofits. I should mention that, there are also certain other implications, such as the fracturing of the mass TV audience into more fragmented markets. This means that nonprofit organizations will have to produce more PSA's to reach its audience. There'll also be more competition for available public service time. Finally, as pay TV grows, nonprofit organizations may have to produce special programming for this medium. There's several things we can comfortably predict for the future. One, television will continue to change. And two, the successful nonprofit organizations will be those who seriously explore the new opportunities today.

Solubilization of low-density lipoprotein with sodium deoxycholate and recombination of apoprotein B with dimyristoylphosphatidylcholine

Apoprotein B (apoB) of human plasma low-density lipoprotein (LDL) (d 1.025-1.050 g/mL) has been solubilized with solid sodium deoxycholate (NaDC) above its critical micellar concentration. ApoB is isolated by gel-filtration chromatography as a mixed micellar complex of protein and detergent in high yield in a lipid-free form. A soluble apoB-dimyristoylphosphatidylcholine (DMPC) complex has been prepared by incubation of aqueous solutions of apoB-NaDC and DMPC-NaDC (2/1 w/w) at room temperature with detergent removal by extensive dialysis. A combination of gel chromatographic and density gradient fractionation of DMPC-apoB incubation mixtures demonstrates that a reasonably well-defined complex of DMPC and apoB is formed with a 4:1 w/w lipid:protein ratio. Negative-stain electron microscopy shows these particles to be single-bilayer phospholipid vesicles with a diameter of 210 +/- 20 A into which the apoB is incorporated. Circular dichroic spectra of NaDC-solubilized apoB show apoB to have similar conformation to that seen in the native LDL particle. However, apoB that has been complexed with DMPC exhibits more alpha-helix. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows a single band (apparent Mr 366000) for apoB after solubilization, purification, and interaction with phospholipid. The behavior of apoB during its reassociation with phospholipid and the structural features of the DMPC-apoB particle are similar to those observed in the interaction of solubilized membrane proteins with lipid rather than that of other apo-lipoproteins.