Search PubMed⌕ Search

Biomedical subjects

J E Evans

Publications and source records attributed to J E Evans.

At least 19 recordsLinked to original sources
PubMed1992

A human lysosomal alpha(1----6)-mannosidase active on the branched trimannosyl core of complex glycans.

Normal human fibroblasts and fibroblasts from a patient with alpha-mannosidosis were grown in the presence or absence of 100 microM swainsonine for 7 days. Accumulated oligosaccharides were isolated and analysed by high performance liquid chromatography (HPLC) and methylation analysis. Man alpha 1----3Man beta 1----4GlcNAc and Man alpha 1----2Man alpha 1----3-Man beta 1----4GlcNAc (where Man is D-mannose and GlcNAc is N-acetyl-D-glucosamine) comprised greater than 80% of the total oligosaccharides in untreated mannosidosis cells. However, Man alpha 1----6[Man alpha 1----3]Man beta 1----4GlcNAc was the major Man3GlcNAc isomer present after 7 days of swainsonine treatment. No mannose-containing oligosaccharides were detected in control fibroblasts in the absence of swainsonine but, in its presence, oligosaccharides containing 2-9 mannose residues accumulated. Man alpha 1----6[Man alpha 1----3]-Man alpha 1----6[Man alpha 1----3]Man beta 1----4GlcNAc and Man alpha 1----6-[Man alpha 1----3]Man beta 1----4GlcNAc were the major components (67%). Surprisingly, Man alpha 1----3Man beta 1----4GlcNAc was only observed in swainsonine-treated control cells during the recovery period after removal of swainsonine. These studies suggest the presence of a second lysosomal alpha-mannosidase activity which is unaffected in genetic alpha-mannosidosis, but is inhibited by swainsonine. This enzyme would cleave the alpha(1----6)-linked mannose residue from branched Man3GlcNAc to form Man alpha 1----3Man beta 1----4GlcNAc. To confirm this hypothesis, fractions from alpha-mannosidosis and control fibroblasts that bound to concanavalin A (ConA)-Sepharose and were eluted with 0.5 M alpha-methyl mannoside were incubated at pH 4.0 with Man alpha 1----6[Man alpha 1----3]Man beta 1----4-GlcNAc. As anticipated, Man alpha 1----3Man beta 1----4GlcNAc was the sole product using enzyme from mannosidosis fibroblasts, while the major product from control fibroblasts was Man alpha 1----6Man beta 1----4GlcNAc. This confirmed the presence of a swainsonine-inhibitable alpha(1----6)-mannosidase activity unaffected by the disease. The differing substrate specificities of the alpha(1----6)-mannosidase and the major lysosomal alpha-mannosidase indicate that the alpha(1----6)-mannosidase plays an important role in the generation of the oligosaccharides accumulated in alpha-mannosidosis patients.

Carbohydrate Sequence↗
PubMed1992

Bioavailability studies of drugs with nonlinear pharmacokinetics: I. Tracer dose AUC varies directly with serum concentration.

The authors show that for a drug cleared by one enzyme the area under the serum concentration-time curve from time 0 to infinity (AUC0-INF) of a test dose can be expressed as AUC0-INF = TD x F x (Km + C)/Vmax where TD is test dose size, F is fraction absorbed, C is drug serum concentration at the time of the study, and Km and Vmax are the Michaelis constant and maximum velocity of the enzyme. This equation predicts the AUC0-INF produced by a given tracer dose of drug will vary directly with C in drugs with nonlinear pharmacokinetic properties (i.e., drugs whose value for C approaches or exceeds Km) if C is held constant by administration of tracer and maintenance doses of drug. The AUC0-INF produced by intravenous tracer doses of 150 mg of 13C15N2-sodium phenytoin was determined in 15 subjects at 30 different values of C. AUC0-INF showed a high degree of direct linear correlation with C (AUC0-INF (ug x hr/mL) = 35.4 + 8.1 x C (ug/mL), r = 0.885, P < .0001). Consequences of this observation for relative bioavailability studies of drugs with nonlinear pharmacokinetic properties are discussed.

Adolescent↗
PubMed1991

Perceptions of current and ideal body shape of athletes and nonathletes.

This study was done to examine the relationship between sex and perception of body image among athletes and nonathletes. A total of 211 men and women athletes and nonathletes completed a questionnaire which asked them to identify from a nine-figure body-silhouette scale their current image and the image that they thought was most ideal. t tests showed no significant differences for men based upon athletic participation and that both athletes and nonathletes were satisfied with their body image. However, when comparing current image and ideal image, significant differences were found for women athletes and nonathletes. These data support previous research documenting women's dissatisfaction with their body images and show athletic participation is not associated with this perception.

Adult↗
PubMed1991

Olfactory primary neurons as a route of entry for toxic agents into the CNS.

Reports in the literature suggest that the primary sensory neurons of the olfactory system may provide a direct route of entry for agents into the central nervous system (CNS). To investigate whether cadmium, a heavy metal which is normally excluded from the CNS by the blood-brain barrier, can enter the CNS via the olfactory system, rats were exposed either intranasally (unilaterally) or ip to 109Cd (1 mumol Cd labeled with 1 microCi 109Cd). Rats were allowed to survive 7 days, at which point they were euthanized and the kidneys, livers, right and left forebrains, right and left olfactory bulbs, and right and left olfactory epithelia were removed. Tissues were placed in scintillation vials and radioactivity counted. In rats exposed by intranasal instillation, Cd levels were significantly elevated in the kidney, liver and ipsilateral olfactory bulb and epithelium, but not in the contralateral bulb and epithelium or forebrain areas. With the ip exposure, Cd levels were only elevated in the kidney and liver. In a second study the protocol was repeated (without ip exposure), but the olfactory bulbs and epithelium were washed in EDTA before counting. Cd was still present in the bulbs after washing, suggesting that the metal was internal and not bound to the external membrane. In the final experiment, both time course and dose effect of this phenomenon were explored. Rats were exposed either intransally to 1 mumol Cd labeled with 109Cd (1 microCi) and then sacrificed after 1, 3, 7, or 14 days or were exposed to 0.01, 0.1, or 1.0 mumol Cd labeled with 1 microCi 109Cd and sacrificed after 7 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Lipid composition of lysosomal multilamellar bodies of male mouse urine.

Previous studies from our laboratory have shown that male C57BL/6J mice excrete into the urine multilamellar lysosomal bodies that contain specific neutral glycosphingolipids. These mice excrete approximately 20-30% of their kidney glycolipids each day. The significance and function of this secretion of multilamellar lysosomal organelles is unknown. To characterize these excreted bodies further, we report here their neutral lipid and phospholipid composition. The bodies were collected by differential centrifugation, extracted with chloroform-methanol, and lipids were fractionated into neutral lipids, glycolipids, and phospholipids. The neutral lipids consisted primarily of cholesterol, dolichol, and ubiquinone. The phospholipid fraction consisted primarily of a single molecular species of phosphatidylcholine. This lipid which comprises more than 90% of the total phospholipids was found to contain 16:0 ether and C22:6 n-3 fatty acid as determined by gas-liquid chromatography-mass spectrometry. The glycosphingolipids as reported previously consisted primarily of galabiosylceramides and globotriaosylceramides. This membrane lipid composition is different from any previously reported cellular organelle.

Animals↗
PubMed1990

Cysteine-108 is an acylation site in myelin proteolipid protein.

Myelin proteolipid protein (PLP) contains covalently bound long-chain fatty acids. A large proportion of these acyl moieties are bound in thioester linkages, as demonstrated by alkylation of newly formed SH groups upon deacylation. To identify the Cys residue(s) involved in the thioester linkage(s), reduced and carboxyamidomethylated proteolipid protein was labeled with [14C]iodoacetamide upon deacylation with neutral hydroxylamine. The labeled protein was digested with trypsin or pepsin, and peptides analyzed by RP-HPLC. Identification of the isolated radioactive peptides by amino acid analysis, peptide sequencing and/or fast-atom bombardment-mass spectrometry revealed that Cys108 in the bovine PLP sequence is an acylated site. The sequence surrounding the palmitoylation site in the myelin PLP is strikingly similar to that found in rhodopsin. Furthermore, as in rhodopsin and other members of the G protein-coupled receptor family, this Cys residue is located within a hydrophilic, basic, and possibly cytoplasmic, domain.

Acylation↗
PubMed1990

New pharmacokinetic methods. II: Determination of the presence or absence of product inhibition in drugs with nonlinear pharmacokinetics.

We show that for drugs metabolized by one enzyme the slope of a plot of serum concentration (C) versus 1/clearance (CL) is linear with a value of 1/Vmax in the presence of substrate saturation and may be linear (rarely) or curved (usually) with a slope always greater than 1/Vmax in the presence of substrate saturation and product inhibition (competitive, noncompetitive, or uncompetitive) when the serum concentration of product varies with the serum concentration of substrate. Serum concentration, CL, and Vmax were determined for a group of six subjects receiving phenytoin monotherapy using three approaches. With each approach: 1) a plot C versus 1/CL was linear (r greater than or equal to 0.738, P less than .01); 2) the slope of this regression line did not differ significantly (P greater than .30) from 1/Vmax. We conclude: 1) our method is a simple and useful method for determination of mechanism of a drug's nonlinear pharmacokinetics (substrate saturation versus substrate saturation and product inhibition), 2) phenytoin has nonlinear pharmacokinetics due to substrate saturation only in man.

Humans↗
PubMed1990

New pharmacokinetic methods: I. Estimation of mean serum concentration from trough serum concentration.

An equation is derived to estimate mean steady state serum concentration (Css) from trough steady state serum concentration (Cmin) which can be used for drugs with either linear or nonlinear pharmacokinetic properties. In 15 subjects receiving phenytoin monotherapy, estimated Css did not differ significantly from measured Css, while Cmin differed significantly (P less than .0001) from measured Css and estimated Css. Clearance (CL) and elimination half-life (t1/2) values determined by stable isotope tracer methods or by standard equations and measured Css or estimated Css did not differ significantly, while CL and t1/2 values calculated with standard equations and Cmin differed significantly (P less than .02) from values obtained by any of the other three methods. We conclude: 1) Cmin values and CL and t1/2 values calculated with Cmin values may differ significantly from Css values and CL and t1/2 values calculated with Css; 2) accurate estimates of Css and of CL and t1/2 can be obtained using our procedure to correct a Cmin value to an estimated Css value.

Half-Life↗
PubMed1990

New pharmacokinetic methods. III. Two simple test for "deep pool effect".

If a portion of administered drug is distributed into a "deep" peripheral compartment, the drug's actual elimination half-life during the terminal exponential phase of elimination may be longer than determined by a single dose study or a tracer dose study ("deep pool effect"). Two simple methods of testing for "deep pool effect" applicable to drugs with either linear or nonlinear pharmacokinetic properties are described. The methods are illustrated with stable isotope labeled (13C15N2) tracer dose studies of phenytoin. No significant (P less than .05) "deep pool" effect was detected.

Carbon Radioisotopes↗
PubMed1990

N-acetyl-D-glucosamine is present in cysts and trophozoites of Giardia lamblia and serves as receptor for wheatgerm agglutinin.

Previously, on the basis of lectin binding and glycosidase digestion assays, we have suggested that N-acetyl-D-glucosamine residues (GlcNAc) are major structural components of both trophozoites and in vivo cysts of the intestinal parasite Giardia lamblia. In this report we confirm that GlcNAc is present both in trophozoites and in vitro cysts as assessed by lectin binding and glycosidase digestion assays, galactosyltransferase labeling, immunochemical analysis using antibodies specific for GlcNAc and its beta 1-4 oligomers, and by gas chromatography/mass spectrometry (GC/MS). The results show that wheatgerm agglutinin (WGA) binds specifically to intact trophozoites and in vitro cysts as well as to SDS-PAGE separated proteins. WGA binding to the separated proteins was markedly reduced after their digestion with N-acetyl-beta-D-glucosaminidase, supporting the conclusion that WGA is reacting with terminal beta-linked GlcNAc residues. Labeling of trophozoites and cysts by 3H-exogalactosylation with galactosyltransferase further confirmed the presence of terminal GlcNAc in both surface and intracellular glycoproteins. The presence of GlcNAc is also supported by microfluorometric analysis using antibodies to (GlcNAc)1, (GlcNAc)2, and (GlcNAc)3, which revealed a sugar-inhibitable binding of the antibody to live trophozoites. Finally, the presence of GlcNAc in both cysts and trophozoites was unequivocally confirmed by GC/MS analysis of detergent-extracted membranes and of glycoproteins isolated by affinity chromatography on WGA-agarose. GC/MS analysis also revealed mannose (Man), N-acetyl-D-galactosamine (GalNAc), fucose (Fuc), galactose (Gal), glucose (Glc) and N-acetylneuraminic acid (NANA) to be present in cysts. All these sugars were also present in trophozoites, except for GalNAc. The glycoproteins isolated by WGA affinity chromatography were 5- to 40-fold enriched in GlcNAc, further supporting the conclusion that WGA reacts with GlcNAc in Giardia. In summary, the data presented here provide biological and chemical evidence for GlcNAc in both cysts and trophozoites of G. lamblia and are consistent with previously published results from this and other laboratories.

Acetylglucosamine↗
PubMed1990

Effect of differentiation and cell density on glycosphingolipid class and molecular species composition of mouse neuroblastoma NB2a cells.

The effects of cell density and retinoic acid-induced differentiation on the class and molecular species composition of mouse neuroblastoma NB2a cell glycosphingolipids were examined under conditions where the period of culture was controlled. The total amount of neutral glycosphingolipids per cell decreased both with differentiation and as the cells became confluent. The relative amount of the neutral glycosphingolipid classes was not affected by differentiation, whereas there were small but significant changes in the relative amount of the neutral glycosphingolipid classes as the cells became confluent. The total amount of the gangliosides was unaffected by either differentiation or cell density, but there were significant changes in the ganglioside class composition as a result of both cell density and differentiation, and the effects were additive. The molecular species of all the major neutral glycosphingolipid and ganglioside classes were essentially identical, and were altered only slightly by either differentiation or cell density.

Animals↗
PubMed1989

Characterization of SSEA-1 glycolipids from the brain of a patient with fucosidosis.

Neutral glycolipids from the brain of a patient with Fucosidosis were analyzed and two complex glycolipids containing five and eight sugars were isolated from the cortical grey matter. These two glycolipids reacted with antibodies recognizing the SSEA-1 [Le(x)(X)] carbohydrate determinant. SSEA-1 glycolipids are normally expressed in human embryonic brain but are found in only small amounts in postnatal human brain. The accumulation of the two SSEA-1 glycolipids in Fucosidosis brain thus represents a defect which affects the normal developmentally regulated decrease in postnatal expression of these glycolipids, and may be a contributing factor in the abnormal brain development associated with the disease. Chemical characterization of the two isolated glycolipids by gas chromatographic and mass spectrometric analyses has identified the two glycolipids as lacto-N-fucopentaosylceramide (III) and difucosyl-neolactonorhexaosylceramide.

Brain Chemistry↗
PubMed1989

Characterization of porcine omental lipids.

Porcine omental lipid extracts were fractionated and the major lipid components characterized. Approximately 97% of the chloroform/methanol extract consisted of triglycerides containing primarily 16:0, 18:0, 18:1, and 18:2 fatty acids. Small quantities of free fatty acids, cholesterol, di- and monoglycerides were also detected. The phospholipid fraction, obtained by solvent partition and Unisil column chromatography and characterized by high performance liquid chromatography (HPLC) and HPLC-mass spectrometry, was found to consist primarily of phosphatidylcholine, sphingomyelin, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol. The neutral glycolipids, isolated by solvent partition and Unisil column chromatography and identified by HPTLC and HPLC, were found to consist primarily of di-, tri- and tetraosylceramides. The complex glycolipid fraction, obtained from Folch upper phase solvent partition and characterized by HPTLC and immunoblotting, was found to consist primarily of ganglio-, globo-, and neolacto- neutral glycolipids and ganglio-, globo-, neolacto- and fucosylated gangliosides.

Animals↗
PubMed1989

Bioavailability of ACC-9653 (phenytoin prodrug).

The bioavailability of phenytoin from ACC-9653 versus intravenously administered sodium phenytoin was determined using a crossover design for intravenous and intramuscular administration of ACC-9653 to healthy volunteers. Absolute bioavailability of phenytoin derived from ACC-9653 in each subject was calculated as the ratio of the phenytoin area under the plasma concentration time curve for time 0 to infinity [AUC(0-inf)] after ACC-9653 divided by the phenytoin AUC(0-inf) after intravenous sodium phenytoin. The mean absolute bioavailability of ACC-9653 was 0.992 after intravenous administration and 1.012 after intramuscular administration. These data establish that the bioavailability of ACC-9653 is complete following intravenous or intramuscular administration in single-dose volunteer studies. The absolute bioavailability of phenytoin derived from ACC-9653 in subjects with therapeutic plasma phenytoin concentrations is being studied in patients given simultaneous infusions of stable isotope-labeled tracer doses of ACC-0653 and sodium phenytoin.

Biological Availability↗
PubMed1988

The structures of oligosaccharides excreted by sheep with swainsonine toxicosis.

Eleven oligosaccharides were purified form the urine of sheep with swainsonine toxicosis induced by the feeding of Astragalus lentiginosus. Oligosaccharides were extracted by charcoal adsorption, chromatographed on Bio-Gel P-2, and partially fractionated by preparative-layer chromatography. Separation into individual compounds was completed by semi-preparative high pressure liquid chromatography. Structures were determined by a combination of high pressure liquid chromatography and exo- and endo- glycosidase action, methanolysis followed by gas-liquid chromatography, methylation analysis, and high resolution nuclear magnetic resonance spectroscopy. Two homologous series of oligosaccharides were identified: (a) alpha-D-Manp-(1----6)-beta-D-Manp-(1----4)-D-GlcpNAc, alpha-D-Manp(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp+ ++-(1----4)-D-GlcpNAc, alpha-D-Manp-(1----2)-alpha-D-Manp(1----3)-[alpha-D-Manp+ ++-(1----6)]-beta-D-Manp-(1----4)-D-GlcpNAc, and alpha-D-Manp-(1----2)-alpha-D-Manp-(1----2)-alpha-D-Manp+ ++-(1----3)-[alpha- D-Manp-(1----6)]-beta-D-Manp-(1----4)-D-GlcpNAc (minor series); (b) alpha-D-Manp-(1----6)-beta-D-Manp-(1----4)-beta-D-GlcpNAc- (1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D-Manp -(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, alpha-D-Manp(1----3)-alpha-D-Manp-(1----6)-beta-D-Manp -(1----4)-beta-D-GlcpNAc- (1----4)-D-GlcpNAc, alpha-D-Manp-(1----6)-alpha-D-Manp-(1----6)-beta-D-Manp++ +-(1----4)-beta-D-GlcpNAc - (1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-alpha-D-Manp-(1----6)-[alpha-D-Manp -(1----3)]-beta-D- Manp-(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-alpha-D-Man p-(1----6)-beta-D- Manp-(1----4)-beta-D-GlcpNAc-(1----4)-D-GlcpNAc, and alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-alpha-D-Man p-(1----6)- [alpha-D-Manp-(1----3)]-beta-D-Manp-(1----4)-beta-D-GlcpNAc- (1----4)-D- GlcpNAc (major series).

Alkaloids↗
PubMed1988

A brief neurobehavioral exam useful for early detection of postoperative complications in neurosurgical patients.

This article describes data from 11 patients evaluated before and after neurosurgical intervention for treatment of brain tumor, subdural hematoma and hydrocephalus. The Neurobehavioral Cognitive Status Examination (NCSE) was administered pre- and postoperatively. Improvement was documented by the NCSE in 6 of the 11 patients. In the remaining five patients, there was evidence of deterioration in cognitive functioning. After clinical and diagnostic re-evaluation by the physician, four patients had repeat operations. Follow-up evaluation after the second operation was useful in determining treatable and non-treatable causes of progressive cognitive deterioration. In these patients use of the NCSE may have expedited effective diagnostic evaluation and subsequently improved patient care. Such instruments have clinical utility since they are easily administered, pragmatic, and objectify subtle changes in cognitive functioning which may be early signs of increased intracranial pressure or complications of surgery.

Adult↗