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Biomedical subjects

B F Smith

Publications and source records attributed to B F Smith.

At least 19 recordsLinked to original sources
PubMed1992

Inherited phosphofructokinase deficiency in an American cocker spaniel.

A 3-year-old female American Cocker Spaniel with a chronic hemolytic disorder and hemolytic crises was found to have M-type phosphofructokinase deficiency. This inherited erythroenzymopathy and myopathy is commonly diagnosed in English Springer Spaniels, but the family study of this Cocker Spaniel, although supporting an autosomal recessive mode of inheritance, did not reveal any English Springer Spaniel ancestors. Molecular genetic studies did, however, identify the same mutation in this dog as we previously reported in the English Springer Spaniel breed, suggesting that this mutation originated prior to the separation of these 2 breeds.

Anemia, Hemolytic↗
PubMed1992

Nutritional outcome and pneumonia in critical care patients randomized to gastric versus jejunal tube feedings. The Critical Care Research Team.

OBJECTIVE: To compare nutritional status, gastric colonization, and rates of nosocomial pneumonia in ICU patients randomized to gastric tube feeding vs. patients fed by an endoscopically placed jejunal tube. DESIGN: Randomized, prospective study. SETTING: Medical and surgical ICUs at Boston City Hospital; surgical ICU at University Hospital. PATIENTS: Of the 38 study patients, 19 were randomized to gastric tube feeding and 19 were randomized to an endoscopically placed jejunal tube. The two groups were similar in age, sex, race, underlying disease, and type of surgery. RESULTS: The two patient groups were similar in number of days fed, duration of ICU stay, duration of mechanical ventilation, days of antibiotic therapy, and days with fever. Compared with the gastric group, the jejunal group had more patients with circulatory shock on admission (79% vs. 68.4%), higher admission Acute Physiology Score (24.0 vs. 21.7), and fewer patients with pneumonia at randomization (26.3% vs. 31.6%). The jejunal group received a significantly higher percentage of their daily goal caloric intake (p = .05), and had greater increases in serum prealbumin concentrations (p < .05) than the patients with gastric tube feeding. Although the jejunal tube group had more days of diarrhea (3.3 +/- 6.6 vs. 1.8 +/- 2.9), this difference was not statistically significant. Nosocomial pneumonia was diagnosed clinically in two (10.5%) patients in the gastric tube group and in no patients in the jejunal tube group. CONCLUSIONS: Patients fed by jejunal tube received a significantly higher proportion of their daily goal caloric intake, had a significantly greater increase in serum prealbumin concentrations, and had a lower rate of pneumonia than patients fed by continuous gastric tube feeding.

Adult↗
PubMed1991

Proteins in the fossil bone of the dinosaur, Seismosaurus.

Proteins have been successfully extracted from the fossil vertebra of a 150-million-year-old sauropod dinosaur ("Seismosaurus") recently excavated from the Morrison Formation of New Mexico. HCl and guanidine.HCl extracts of the fossil bone and its sandstone matrix were concentrated, demineralized, and resolved into a number of different protein fractions by reversed-phase high-performance liquid chromatography (HPLC). One of these fractions had the same retention time as collagen. Amino acid analysis (Pico-Tag method) of these fractions confirmed they were proteins. Comparison of the correlation coefficients of the amino acid analyses with that of collagen standards indicated that none of the fractions contained significant amounts of collagen. Similar HPLC profiles were obtained for the HCl extracts of fossil bone and its sandstone matrix suggesting they contained the same proteins. However, different HPLC profiles were obtained when these HCl extracts were dried and reextracted with guanidine.HCl. These different fractions represent proteins unique to the fossil and were not found in the sandstone matrix. These differences were confirmed by amino acid analysis. Such information on fossil bone proteins might provide useful knowledge concerning the evolution of skeletal molecules and the fossilization process. Similar information on the proteins from the geological matrix might provide useful fingerprints for reconstructing ancient environments and for assessing sedimentary rocks for fossil fuel exploration.

Amino Acids↗
PubMed1991

Non-mucin proteins in the matrix of human cholesterol gallstones.

Human cholesterol gallstones contain a pigmented organic matrix that may originate from biliary sludge. The cholesterol gallstone matrix contains mucin, bile pigments, and calcium salts. The goal of this study was to examine whether non-mucin proteins are present in the matrix of cholesterol gallstones. Matrix was prepared from cholesterol gallstones from 18 patients. Proteins were identified by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and by molecular sieve high-performance liquid chromatography (HPLC). Two proteins were present in each gallstone and migrated with or just adjacent to standards of bovine serum albumin on SDS-PAGE. Several additional lower molecular weight proteins were identified, but not in every gallstone. Protein fractions contained visible pigment after chloroform extraction, and pigment co-eluted with proteins on HPLC, suggesting binding of pigments to proteins in the matrix. We conclude that low molecular weight proteins are present in the cholesterol gallstone matrix. The major protein appears to be serum albumin, although definitive identification has not been established. The origin of these matrix proteins and their possible significance in the pathogenesis of cholesterol cholelithiasis is unknown.

Bilirubin↗
PubMed1990

Effect of laser fragmentation of cholesterol and mixed gallstones on in vitro dissolution in methyl tert-butyl ether.

This study examined cholesterol and mixed gallstone dissolution in vitro by methyl-tert-butyl ether (MTBE) after gallstone fragmentation. Three morphologically identical gallstones were obtained from 42 patients. One stone from each patient was fragmented with laser energy at a wavelength of 504 nm delivered to the stone surface with a 320-microns quartz fiber. Intact and fragmented stones from the same patient were incubated without stirring in MTBE and dissolution was expressed as the percent of initial stone weight remaining after 2 hr. Stone composition did not correlate with the amount of laser energy required for stone fragmentation. Fragmented stones dissolved faster than intact stones in MTBE with 13.97% +/- 0.37% vs 31.0% +/- 0.51% respectively (mean +/- SEM) of initial stone weight remaining at 2 hr (P less than 0.0001). Initial stone weight and stone matrix content significantly predicted dissolution of intact (P = 0.0033 and P = 0.0483, respectively) and fragmented stones (P = 0.003 and P = 0.0001, respectively) in MTBE. These data suggest that the gallstone matrix may inhibit stone dissolution even after stone fragmentation.

Cholelithiasis↗
PubMed1990

Addition of N-acetylcysteine to aqueous model bile systems accelerates dissolution of cholesterol gallstones.

The organic matrix of cholesterol gallstones contains a macromolecular complex of mucin and bilirubin that may inhibit stone dissolution by limiting contact of desaturated bile with crystalline cholesterol. The goal of this study was to determine if the mucolytic agent N-acetylcysteine could accelerate gallstone dissolution in vitro. Paired gallstones were dissolved in either pure taurocholate (140 mM) or ursodeoxycholate (100 mM), or in bovine bile supplemented with either taurocholate or ursodeoxycholate to achieve the same respective bile-salt concentrations. N-acetylcysteine was added to 1 stone from each pair at a concentration of 500 mM in pure bile salts and 100 mM in supplemented bile. Gallstones dissolved significantly faster in bovine bile supplemented with taurocholate or ursodeoxycholate than in pure solutions of the respective bile salts (n = 30, p less than 0.001). N-acetylcysteine significantly accelerated gallstone dissolution in pure solutions of bile acids (n = 30, p less than 0.001 for each) and in supplemented bovine biles (n = 30, p less than 0.001). N-acetylcysteine also significantly increased the frequency of complete gallstone dissolution in taurocholate-supplemented (66.6% vs. 40.0%) and ursodeoxycholate-supplemented (76.6% vs. 50.0%) bile. These results indicate that the mucolytic agent N-acetylcysteine significantly accelerates in vitro gallstone dissolution. We speculate that adjuvant therapy with an appropriate mucolytic agent may potentially increase the efficacy of clinical gallstone dissolution.

Acetylcysteine↗
PubMed1990

Isolation and characterization of peptides from the protein core of bovine gallbladder mucin.

Gallbladder mucin may promote cholesterol gallstone formation by accelerating cholesterol monohydrate crystal nucleation in supersaturated bile. In this study, peptides were isolated from the mucin protein core by protease digestion and molecular-sieve high-performance liquid chromatography. Tryptic peptides were purified by anion exchange or reverse-phase high-performance liquid chromatography, and amino acid compositions were determined. Tryptic peptides were (a) nonglycosylated, (b) selectively enriched in serine, glutamic acid plus glutamine, and glycine, and (c) depleted in threonine and proline compared with native gallbladder mucin. Bilirubin derivatized with Woodward's reagent K covalently bound to purified mucin. Tryptic digestion of the mucin-bilirubin complex yielded low-molecular-weight nonglycosylated peptides with covalently bound bilirubin. These data indicate that the mucin protein core contains at least two distinct domains. One domain is rich in threonine and proline and contains the majority of covalently bound carbohydrate. A second domain, possibly internally located, is nonglycosylated, enriched in serine, glutamic acid plus glutamine, and glycine, and binds hydrophobic ligands such as bilirubin and 1-anilino-8-naphthalene sulfonate. Hydrophobic domains on the mucin protein core may contribute to the pathogenesis of cholesterol cholelithiasis.

Amino Acids↗
PubMed1990

Characterization of bovine gallbladder mucin. Amino acid sequences of tryptic peptides from the glycosylated domain of the protein core.

Gallbladder mucin is a densely glycosylated macro-molecule that promotes cholesterol gallstone formation in experimental animals and in humans. Bovine gallbladder mucin structure was studied after chemical deglycosylation by treatment with anhydrous hydrogen fluoride at 23 degrees C for 3 hours. Deglycosylated mucin contained less than 5% of the amino sugar and neutral hexose content of native mucin. Electrophoretic and molecular sieve chromatographic analyses indicated that significant cleavage of the mucin polypeptide core had occurred during deglycosylation. Deglycosylated mucin was separated into three major fractions by reverse-phase chromatography, one of which was enriched with respect to threonine and proline. Tryptic peptides prepared from this fraction were purified by molecular sieve and reverse-phase chromatography, and the amino acid sequences (8-20 residues) of the four principal tryptic peptides were determined. These peptides contained 65%-75% threonine and proline residues and demonstrated 80%-100% sequence similarity. These data provide the first information on the primary structure of gallbladder mucin and suggest that repeating amino acid sequences occur in this protein. Comparison of gallbladder mucin peptide structure with the consensus repeat sequence of human intestinal mucin showed approximately 60% sequence similarity. It was concluded that mammalian gastrointestinal mucins may be derived from a common ancestral gene.

Amino Acid Sequence↗
PubMed1990

Genes transferred by retroviral vectors into normal and mutant myoblasts in primary cultures are expressed in myotubes.

Retroviral vectors were used to transfer genes efficiently into rat and dog myoblasts in primary cultures under conditions which permitted the transduced myoblasts to differentiate into myotubes expressing the transferred genes. The transduced myotubes expressed normal markers of differentiation and were morphologically indistinguishable from uninfected myotubes. Retroviral vector-mediated gene transfer was also used to correct a genetic enzyme deficiency in mutant canine muscle cells.

Animals↗
PubMed1990

Gallbladder mucin as a pronucleating agent for cholesterol monohydrate crystals in bile.

Mucin is a densely glycosylated macromolecule secreted by the gallbladder epithelium as the principal constituent of gallbladder mucus. Hypersecretion of gallbladder mucus occurs in response to a lithogenic diet in experimental animals, and mucus accumulates as a viscous gel within the gallbladder lumen before gallstone formation. In both animals and man, the initial stage of cholesterol gallstone formation, the nucleation of cholesterol monohydrate crystals, occurs within the mucus gel. Inhibition of mucus secretion with aspirin prevents gallstone formation in the cholesterol-fed prairie dog, indicating the importance of mucus in gallstone formation. Mucin contains domains that bind cholesterol and lecithin transported as vesicles in supersaturated bile. Furthermore, mucin accelerates the nucleation of cholesterol crystals in both supersaturated model and native biles. Binding of cholesterol-enriched vesicles to hydrophobic domains on the mucin protein core appears to be critical for the acceleration of cholesterol crystal nucleation by mucin. Further study of the structure and function of gallbladder mucin should help to elucidate the pathogenesis of cholesterol cholelithiasis.

Animals↗
PubMed1989

Subunit interactions and physical properties of bovine gallbladder mucin.

In this study the interaction of gallbladder mucin subunits was examined by gel permeation chromatography, quasielastic laser light scattering, and viscometry. Purified mucin eluted primarily in the void volume of a Sepharose 2B-Cl column, indicating a molecular weight above 2 x 10(6). Disaggregation of the mucin polymer resulted in the elution of glycoprotein in the included volume of the Sepharose 2B-Cl column. Gallbladder mucin had a hydrodynamic radius of 630 A that was independent of mucin concentration below 2 mg/ml. At mucin concentrations above 2 mg/ml, a concentration-dependent increase in both hydrodynamic radius and apparent viscosity of gallbladder mucin was observed. Mucin demonstrated a strong pH dependence in hydrodynamic radius and viscosity with the maximum occurring at approximately pH 5.5. These findings suggest that noncovalent interactions participate in bovine gallbladder mucin subunit associations. Furthermore, changes that occur in the physicochemical environment of the gallbladder during periods of stasis may enhance the viscoelastic properties of mucin and promote the accumulation of biliary sludge in the gallbladder.

Animals↗
PubMed1989

Bovine gallbladder mucin promotes cholesterol crystal nucleation from cholesterol-transporting vesicles in supersaturated model bile.

This study examined the ability of purified gallbladder mucin to accelerate the nucleation of cholesterol monohydrate crystals from the cholesterol-transporting particles in supersaturated model bile. Mixed lipid micelles and cholesterol-phosphatidylcholine vesicles in supersaturated model bile were separated by Sephadex G-200 column chromatography. Mixed lipid micelles prepared by column chromatography had a low cholesterol-phosphatidylcholine ratio (0.30) and did not spontaneously nucleate cholesterol monohydrate crystals. In contrast, vesicles prepared by column chromatography had a cholesterol-phosphatidylcholine ratio of 1.00 and nucleated cholesterol crystals rapidly (P less than 0.001). Nucleation of cholesterol crystals was significantly accelerated in a concentration- and time-dependent manner by purified bovine gallbladder mucin in cholesterol containing vesicles, but not in mixed lipid micelles (P less than 0.001). A rapid filtration binding assay demonstrated significant binding of cholesterol and phosphatidylcholine in vesicles to gallbladder mucin but only minimal binding of cholesterol and phosphatidylcholine in mixed micelles. These data indicate that gallbladder mucin binds cholesterol and phosphatidylcholine in vesicles and accelerates the nucleation of cholesterol monohydrate crystals from these cholesterol-transporting particles in supersaturated model bile.

Animals↗
PubMed1987

Dissolution of cholesterol gallstones in vitro. Gallstone matrix content and diameter, not cholesterol content, predict gallstone dissolution in monooctanoin.

The goal of this study was to identify the structural and compositional features of human gallstones that influence in vitro gallstone dissolution in the cholesterol solvent monooctanoin. Gallstones were obtained from 86 consecutive patients who had at least three morphologically similar stones. One stone from each patient was dissolved in ethanol/ether to determine cholesterol and matrix composition. The remaining two matched stones were dissolved in either monooctanoin plus ethanol (n = 86) or monooctanoin plus 2-mercaptoethanol (n = 86). The thiol reducing agent 2-mercaptoethanol has been previously shown to solubilize the isolated gallstone matrix and to accelerate the dissolution of intact, small cholesterol stones. Stone matrix content and initial diameter had the most significant predictive value for stone dissolution (p less than 0.0001 for each), whereas cholesterol content had no predictive value (p = 0.558). Stones incubated in monooctanoin containing 2-mercaptoethanol dissolved more rapidly than those incubated in monooctanoin plus ethanol (16.7% of initial weight per day vs. 13.8% of initial weight per day, p less than 0.0001). Matrix content correlated significantly with the difference in dissolution rate between stones dissolved in monooctanoin plus ethanol or monooctanoin plus 2-mercaptoethanol (p less than 0.0001). These data indicate that the matrix content of human cholesterol gallstones significantly inhibits in vitro stone dissolution in the cholesterol solvent monooctanoin. This finding may be relevant to the clinical dissolution of gallstones.

Caprylates↗
PubMed1987

Interaction between oxygen radicals and gastric mucin.

The gastrointestinal epithelium is continuously exposed to reactive oxygen metabolites that are generated within the lumen. In spite of this exposure, the healthy epithelium appears unaffected, suggesting efficient mechanisms for protection against these potentially cytotoxic oxidants. The objective of this study is to characterize the interaction between purified gastric mucin and hydroxyl radicals generated from the interaction between ferric iron and ascorbic acid. We found that both native and pronase-treated mucin effectively scavenged hydroxyl radical and that the scavenging properties were not significantly different. The effective concentration of mucin required for a 50% reduction in malondialdehyde production was approximately 10 mg/ml for both native and pronase-treated mucin. In addition, the iron-ascorbic system produced a dramatic decrease (greater than 50%) in the specific viscosity of mucin that was inhibited by catalase, deferoxamine, and mannitol. Superoxide dismutase had no effect. These data suggest that hydroxyl radicals derived from the iron-catalyzed decomposition of hydrogen peroxide are responsible for the depolymerization of native mucin. We propose that mucin may provide protection to the surface epithelium of the gastrointestinal tract by scavenging oxidants produced within the lumen; however, it does so at the expense of its viscoelastic properties.

Animals↗
PubMed1987

Human gallbladder mucin binds biliary lipids and promotes cholesterol crystal nucleation in model bile.

The binding of phosphatidylcholine and cholesterol in model bile to human gallbladder mucin was studied by means of a rapid filtration binding assay and sucrose density gradient ultracentrifugation. Numerous low affinity binding sites for phosphatidylcholine and cholesterol were present on gallbladder mucin. Binding of phosphatidylcholine and cholesterol to mucin increased as a function of cholesterol saturation index. Proteolytic digestion of mucin disaggregated the native mucin polymer and removed hydrophobic domains on the mucin peptide core that bind l-anilino-8-naphthalenesulfonic acid. Proteolytic digestion also resulted in a 91% and 78% decrease, respectively, in the binding of phosphatidylcholine and cholesterol to mucin. The ability of trypsin-treated and native mucin to promote the nucleation of cholesterol monohydrate crystals was compared in a model bile. The incidence of cholesterol monohydrate crystal nucleation with native mucin was significantly greater at 3 days than with trypsin-treated mucin or controls (P less than 0.001). After 3, 6, and 9 days of incubation, samples containing native mucin contained significantly more crystals than controls or trypsin-digested mucin samples (P less than 0.0001 for each). These data indicate that highly purified human gallbladder mucin binds phosphatidylcholine and cholesterol in model bile. Furthermore, this study demonstrates that structural integrity of the native mucin polymer and hydrophobic domains on the peptide core are essential for the nucleation of cholesterol monohydrate crystals by mucin in model bile.

Bile↗
PubMed1986

Differentiated astrocytoma with osteoblastic skeletal metastases in a child.

A 13-year-old boy developed widespread osteoblastic bone metastases, with dissemination throughout the neuraxis, 1 year following treatment of a differentiated (Kernohan and Sayre grade II) astrocytoma of the left parietal cortex. This unusual clinical picture and the possible route of tumour dissemination are discussed.

Adolescent↗