Biomedical subjects

B A Fraser

Publications and source records attributed to B A Fraser.

At least 37 records · Page 2Linked to original sources

PubMed1986

Vasculogenesis and chondrogenesis in the chick wing bud.

Stage 22 to stage 24 chick wing buds were labeled with sulphate-35 to identify chondrogenic areas; these areas were then related to the presence of blood vessels. Blood vessels were found in areas of increased sulphate uptake, indicating that there is no avascular area formed in the limb bud mesenchyme prior to the onset of chondrogenesis, as indicated by increased sulphate-35 uptake. It is, therefore, unlikely that the vasculature plays an initial role in the determination of chondrogenic areas in the wing bud.

Animals↗

PubMed1985

Peptide studies using a fast atom bombardment high field mass spectrometer and data system. 4. Disulfide-containing peptides.

Ten peptides containing one, two or three disulfides were examined to determine their behavior under fast atom bombardment (FAB) mass spectrometric conditions. The mass spectra for the disulfide and the reduced disulfide forms of each peptide were compared. Several factors were examined that contribute to the fast atom bombardment mass spectra of these peptides: components of the FAB matrix such as alkali cations, acids, bases and reducing agents, the intrinsic molecular properties of the intact peptide, and the effect of reducing conditions on sensitivity. The FAB mass spectra of the disulfide-containing peptides examined in this study displayed accurate molecular weight information and fragmentation which indicated the position of the disulfide in the amino acid sequence.

Chemical Phenomena↗

PubMed1984

Synthesis and fast-atom-bombardment-mass spectrometry of N-acetylmuramoyl-L-alanyl-D-isoglutamine (MDP).

N-Acetylmuramoyl-L-alanyl-D-isoglutamine (MDP) was synthesized by a series of condensations of appropriate reagents, followed by hydrogenolysis. Each intermediate step resulted in a stable, crystalline product. D-Isoglutamine 4-benzyl ester was condensed with N-(tert-butoxycarbonyl)-L-alanine N-hydroxysuccinimide ester, to give N-(tert-butoxycarbonyl)-L-alanyl-D-isoglutamine benzyl ester. Condensation of L-alanyl-D-isoglutamine benzyl ester with N-acetyl-1-O-benzyl-4,6-O-benzylidenemuramic acid, followed by hydrogenolysis, gave MDP. The synthetic scheme was shown to be capable of producing gram quantities of highly pure MDP, as well as a few of its analogs. The synthetic MDP was characterized by analytical and biological methods, and it was found that the use of fast-atom-bombardment-mass spectrometry may greatly simplify the characterization process.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1984

The mixed disulfide in the zymogen of streptococcal proteinase. Characterization and implication for its biosynthesis.

The identity of the volatile mercaptide and the metabolic pathway by which it becomes combined with the zymogen of streptococcal proteinase in the mixed disulfide were investigated. Mass spectrometric analysis identified the oxidized form of the volatile mercaptan as methanesulfonic acid. The mass spectrum of a peptide isolated from tryptic and subsequent chymotryptic digests of the zymogen was shown to be consistent with the previously reported amino acid sequence for a chymotryptic peptide with the sequence Val-Gly-Gln-Ala-Ala-Thr-Gly-His-Cys(SCH3)-Val. Studies using [35S] cystine, [methyl-35S]methionine and [methyl-14C]methionine in a cell suspension system revealed that the biosynthesis of the mixed disulfide in the zymogen may involve the formation of protein-S-SH followed by transmethylation rather than result from a direct transfer of an intact methanethiol to the cysteinyl residue of the zymogen. It is proposed that the attachment of the CH3-SH group to the protein-SH to form protein-S-S-CH3 is a process that is intimately related to the mechanism of secretion of the proteinase into the culture fluid by streptococci.

Amino Acid Sequence↗

PubMed1984

ADP-ribosylation of transducin by islet-activation protein. Identification of asparagine as the site of ADP-ribosylation.

Islet-activating protein catalyzes the ADP-ribosylation of transducin, a guanine nucleotide-binding regulatory protein that mediates activation of a retinal cyclic GMP-selective phosphodiesterase. Radiolabel from [adenylate-32P]NAD+ was incorporated specifically into the alpha subunit of purified transducin. Maximal levels of incorporation approximated 0.8 mol of ADP-ribose/mol of transducin. A peptide containing the ADP-ribosyl moiety was purified from a tryptic digest of radiolabeled transducin. This peptide was characterized by chemical and enzymatic procedures and by fast atom bombardment mass spectrometry. The primary structure of this peptide was Glu-Asn-Leu-Lys-Asn(ADP-ribose)-Gly-Leu-Phe. It is probable that the peptide originated from the carboxyl terminus of the alpha subunit and that the ADP-ribosyl moiety is attached by an N-glycosidic linkage to the asparagine residue. Transducin associated with retinal disc membranes is also ADP-ribosylated by cholera toxin. Cholera toxin and islet-activating protein sequentially catalyze the incorporation of 1.9 mol of ADP-ribose/mol of transducin, indicating two distinct sites of ADP-ribosylation within transducin.

Adenosine Diphosphate Ribose↗

PubMed1983

The structure of the repeating oligosaccharide unit of the pneumococcal capsular polysaccharide type 18C.

The structure of the repeating oligosaccharide of the pneumococcal capsular polysaccharide type 18C has been investigated. The repeating oligosaccharide, isolated from an aqueous hydrofluoric acid hydrolyzate of the polysaccharide, was shown, by fast atom bombardment-mass spectrometry, to have a molecular weight of 928, and to contain an O-acetyl group and a glycerol residue. Information about the sequence in the per-O-methylated oligosaccharide was derived from electron-impact mass spectrometry. Supporting data were obtained from methylation analysis, periodate and chromium trioxide oxidations, and enzymic and acid hydrolyses of the oligosaccharide. These studies indicated that the polysaccharide consists of the following pentasaccharide repeating unit. (formula see text)

Oligosaccharides↗

PubMed1983

Peptide studies using a fast atom bombardment high field mass spectrometer and data system. 1--Sample introduction, data acquisition and mass calibration.

Conditions were established for analyzing as little as 5 pmol of an underivatized peptide delivered in a glycerol sample matrix as a thin film onto a gold-plated copper sample stage and then bombarded with xenon fast atoms. Calibration of the fast atom bombardment high field mass spectrometer and data system was achieved using cesium iodide/glycerol as a reference. Calibration at several accelerating potentials permitted a mass range from 393 to 5941 u. Several factors were examined that contribute to the quality of the mass spectrum: components within the glycerol such as other peptides, alkali salts, acid and reducing agents; the nature of the fast atom gas; concentration of the peptide delivered to the sample stage; and the effect of the sample stage and sample matrix on sensitivity.

Angiotensin I↗

PubMed1983

Peptide studies using a fast atom bombardment high field mass spectrometer and data system. 3--Negative ionization: mass calibration, data acquisition and structural characterization.

Under negative ionization conditions, nominal mass calibration of the fast bombardment high field mass spectrometer and data system was accomplished using cesium iodide/glycerol as a reference. Mass calibration at --8 kV accelerating potential extends from m/z 387 to m/z 2170 using xenon fast atoms. Negative xenon FAB mass spectra for human angiotensin I and human gastrin I complement their positive fast atom bombardment spectra. Negative xenon fast atom bombardment spectra of underivatized peptides exhibit molecular proton-abstracted ion envelopes and structurally significant fragment ions. Peptide mixture analysis under negative xenon fast atom bombardment reveals peptide molecular ion envelopes of higher relative intensities than under positive xenon fast atom bombardment.

Angiotensin I↗

PubMed1981

Lipid on capsular polysaccharides of gram-negative bacteria.

Hydrolysis of the meningococcal group A, B, and C, and Escherichia coli K92 polysaccharides by 60% aqueous hydrofluoric acid liberated various 1,2-diacylglycerols. These were extracted with chloroform, trimethylsilylated, and analyzed by gas chromatography-mass spectrometry. Two 1,2-diacylglycerols were the major components isolated. In each polysaccharide, 80 to 90% dipalmitoyl glycerol and 10 to 20% distearoyl glycerol were identified. No monoacylglycerols or mixed diacylglycerols were noted. The presence of the hydrophobic end causes the polysaccharides to aggregate in a micellar form and may be the entity by which the polysaccharide remains attached to the outer membrane of the bacterium giving rise to the structure recognized as a capsule.

Diglycerides↗

PubMed1981

Phospholipid methylation and phospholipase A2 activation in cytotoxicity by human natural killer cells.

The role of phospholipid methylation and phospholipase A2 (phosphatide 2-acylhydrolase, EC 3.1.1.4) in natural killer (NK) function by human peripheral blood mononuclear cells was studied. Pretreatment of effector cells with a methyltransferase inhibitor, 3-deazaadenosine, in the presence of homocysteine thiolactone, reduced cytotoxicity in a dose-dependent fashion. This effect was closely associated with inhibition of methylation of lipids but not of nucleic acids or proteins. The suggestion for a role of phospholipid methylation was supported by the observation that the interaction between NK-susceptible tumor targets and peripheral blood mononuclear cells caused increased phospholipid methylation only when susceptible target cells were used. Phospholipase A2 was also implicated in human NK activity. Inhibitors of the enzyme such as tetracaine, mepacrine, Rosenthal's inhibitor, and corticosteroids impaired NK function. Rosenthal's inhibitor was also shown to exert an inhibitory effect on a purified NK-cell population obtained by the isolation of large granular lymphocytes on Percoll gradients. Peripheral blood mononuclear cells were also directly shown to display phospholipase A2-like activity, as measured by the decrease in radioactive arachidonate from prelabeled phospholipids, specifically phosphatidylcholine, in effector cells. These data suggest that enhanced phospholipid methylation occurs during the recognition function of NK cells. Consequent activation of phospholipase A2 might be involved in the mechanisms leading to lytic events within the target cell.

Adrenal Cortex Hormones↗

PubMed1981

Evaluation of physical therapy service for severely mentally impaired students with cerebral palsy.

The effects of two types of physical therapy service were studied over a five-month period in 19 severely mentally impaired cerebral palsied students aged 3 to 22 years. The students were paired and assigned to either a direct therapy treatment group or a supervised therapy management group. Ten similar students in a comparison group received no physical therapy. The study showed no significant difference in development of mature developmental reflexes, improvement of gross motor skills, or increase of passive joint motion among similar students placed in the direct, supervised, and comparison groups. This pilot study is not intended to decide the issue of physical therapy for these students. It does, however, indicate that objective tests may be used reliably to measure three major areas of sensory motor development. More extensive and longer-term studies are needed to determine the most beneficial form of physical therapy for this double-disability population.

Adolescent↗

PubMed1980

The structures of the cross-reactive types 19 (19F) and 57 (19A) pneumococcal capsular polysaccharides.

The structures for two cross-reactive capsular polysaccharides isolated from Streptococci pneumoniae types 19 and 57 are proposed based on the analytical data obtained from methylation, enzymatic degradation, and periodate oxidation experiments performed on both intact polysaccharides and oligosaccharides isolated from hydrofluoric acid hydrolysates. Both polysaccharides exhibit an identical structure of 4)-beta-2-acetamido-2-deoxymannose-(1 leads to 4)-alpha-D-glucose-(1 leads to 2)-alpha-L-rhamnose-1-phosphate. This trisaccharide is considered the only repeating unit in the type 19 polysaccharide. The type 57 polysaccharide contains this same repeating unit and side chains composed of a beta-D-2-acetamido-2-deoxyglucose-(1 leads to 3)-beta-D-galactose-1-phosphate side chain attached to C-2 of the glucose and an alpha-L-fucose-1-phosphate attached to C-3 of the rhamnose.

Carbohydrate Conformation↗

PubMed1979

Ultimobranchial body cysts in the human foetal thyroid: pathological implications.

In a histological study of 28 human foetal thyroids, ultimobranchial body cysts were found in seven foetuses. Large oval cells were seen adjacent to or within the cysts. There is a morphological resemblance between the cells associated with the ultimobranchial cysts and those of medullary carcinoma of the thyroid gland. This similarity, in humans, substantiates the hypothesis that medullary carcinoma arises from the parafollicular cells, which themselves are known to differentiate from ultimobranchial body tissue.

Cysts↗

PubMed1979

Mass-spectral studies of isomeric D-ribofuranosylribitol disaccharides from the capsular polysaccharides of Haemophilus influenzae type b and Escherichia coli K 100.

Two isomeric-D-ribofuranosylribitols, derived from capsular polysaccharides of Haemophilus influenzae type b and Escherichia coli K 100, were methylated or acetylated, and the products analyzed by gas-liquid chromatography-mass spectrometry. The marked difference in the mass spectra of the methyl ethers of these disaccharides allowed clear distinction between 1- and 2-O-D-ribofuranosylribitol was characteristic for this disaccharide; its isomer, the (1 leads to 2)-linked species, has a base peak at m/e 57. The difference in the base peaks is attributable to fragmentation of the methylated ribitol, as both spectra display common ions characteristic of the methylated D-ribofuranosyl group. For the acetylated disaccharides, the mass spectra displayed common ions characteristic of the acetylated D-ribofuranosyl group. However, no ions similar to those found for the methylated ribitol allowed ready differentiation between the two acetates. Instead, their spectra displayed similar ions, differing somewhat in relative abundance; the M-1 ion, m/e 577, was obtained for both. Comparison of the relative abundance of m/e 139, 259, and 303 in the spectra of the two acetates did allow distinction between them.

Chromatography, Gas↗

PubMed1979

Position of ultimobranchial body cysts in the human fetal thyroid gland.

In a series of 21 human fetal thyroid glands examined histologically in serial sections, seven ultimobranchial body cysts were found. The position of these cysts correlated well with the distribution of calcitonin-containing cells found by previous investigators in the adult thyroid gland. Ultimobranchial body cysts found external to the thyroid lobes may offer a developmental explanation for the paucity of calcitonin found in some adult thyroid glands. The close developmental relationship between the parathyroid gland and the ultimobranchial body could explain the presence of calcitonin found in these glands in some adults.

Animals↗

PubMed1978

The relation of aberrant vasculogenesis to skeletal malformation in the hamster fetus.

Oral administration of teratogenic doses of retinoic acid to pregnant hamsters on day 10 of gestation is associated with dysmorphogenesis of the appendicular skeleton. During the 24 h following retinoic acid treatment, the developing limb bud vasculature was disorganized, with blood vessels encroaching on areas where mesenchymal condensation of the skeletal blastemata normally occurs. Large, branching marginal folds and endothelial cell vesiculations protruded into the blood vessel lumina. It is suggested that the vascular changes observed may affect the concurrent early development of the skeleton and contribute to the skeletal malformation seen in near-term fetuses.

Abnormalities, Drug-Induced↗

PubMed1978

Variable region correlates of group b allotypes: amino acid sequence studies of b9 L chains from homogeneous antibodies.

The amino acid sequence was determined for residues for residues 1 to 88 and residues 110 to 147 for a rabbit light chain (4153-I) with allotype b9 from a homogeneous anti-streptococcal antibody. The amino acid sequence of the L chain from a second antibody (4153-II) was also determined for residues 1 to 49 and 62 to 77. In spite of the large differences in constant region sequence between b4 and b9 L chains, the variable regions of these antibodies are quite similar to those reported for b4 L chains. Both chains bear a b9-specific substitution (glutamic acid) at position 16. The 4153-I chain also has substitutions at positions 70 and 81 that may be exclusive to variable regions of the L chains with the b9 allotype. These allotype-associated VL structural differences offer support to the notion that structural genes for the CL region are either linked to distinct VL gene complexes or that certain V regions are expressed only in concert with certain CL regions.

Amino Acid Sequence↗

PubMed1978

Immunochemistry of streptococcal group C polysaccharide and the nature of its crossreaction with the Forssman glycolipid.

Acid hydrolysis of streptococal Group C polysaccharide yields a disaccharide, 3-O-alpha-N-acetylgalactosaminosyl-N-acetylgalactosamine (3-O-alpha-GalNAc-GalNAc) which expresses Group C antigenic activity. This disaccharide, which exists as a side chain in the intact polysaccharide, can completely inhibit the binding between Group C polysaccharide and most Group C antibodies, indicating that this unit is the immunodominant feature of the intact polysaccharide. The alpha anomeric configuration and N-acetylation are required for the expression of the antigenic activity by the haptenic disaccharide. Also obtained from the acid hydrolysis of the Group C polysaccharide are rhamnose oligosaccharides with structural identity to the Group A-variant polysaccharide and with Group A-variant antigenic activity. It is inferred from these data that the Group A-varient polysaccharide structure is the core unit of the Group C polysaccharide. The nature of the immunologic crossreactivity between the Forssman glycolipid and Group C polysaccharide, which possess identical nonreducing terminal digalactosamine units, was investigated. Rabbit anti-Group C antibodies bound the Forssman glycolipid with approximately the same affinity as 3-O-alpha-GalNAc-GalNAc and were capable of mediating lysis of sheep red blood cells (SRBC). Antibody fractions isolated from anti-sheep hemolysin were likewise able to bind Group C polysaccharide. The heterologous reactions were in most assay systems weaker than reactions with the immunizing antigen.

Amino Sugars↗