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Biomedical subjects

R R Russell

Publications and source records attributed to R R Russell.

At least 91 records · Page 5Linked to original sources
PubMed1990

Nucleotide sequence of the dextran glucosidase (dexB) gene of Streptococcus mutans.

Nucleotide sequencing of DNA in the region of the Streptococcus mutans chromosome adjacent to the previously characterized gtfA gene revealed the presence of two long open reading frames. One of these corresponds to the dexB gene and has been shown to encode an intracellular exodextranase (dextran glucosidase) which has short isomaltosaccharides as preferred substrates. Comparison with other published sequences showed that the dexB gene product shares regions of similarity with enzymes, from a variety of sources, which attack other glucose polymers.

Amino Acid Sequence↗
PubMed1990

Characterization of the product of the gtfS gene of Streptococcus downei, a primer-independent enzyme synthesizing oligo-isomaltosaccharides.

The gtfS gene, coding for a glucosyltransferase which synthesizes water-soluble glucan and previously cloned from Streptococcus downei strain MFe28 (mutans serotype h) into a bacteriophage vector, was subcloned into a plasmid vector. The gtfS gene products expressed in Escherichia coli were compared to the primer-independent, oligo-isomaltosaccharide synthase in Streptococcus sobrinus strain AHT (mutans serotype g) and shown to resemble it closely in molecular mass, isoelectric point, immunological properties, optimum pH and Km values. The glucans produced from sucrose by the gtfS gene products are alpha-1,6-linked linear oligo-isomaltosaccharides without any branching sites. A similar gtfS gene was also detected on chromosomal DNA from S. sobrinus strain AHT.

Blotting, Western↗
PubMed1990

Sequence analysis of the gene for the glucan-binding protein of Streptococcus mutans Ingbritt.

The nucleotide sequence of the gbp gene, which encodes the glucan-binding protein (GBP) of Streptococcus mutans, was determined. The reading frame for gbp was 1,689 bases. A ribosome-binding site and putative promoter preceded the start codon, and potential stem-loop structures were identified downstream from the termination codon. The deduced amino acid sequence of the GBP revealed the presence of a signal peptide of 35 amino acids. The molecular weight of the processed protein was calculated to be 59,039. Two series of repeats spanned three-quarters of the carboxy-terminal end of the protein. The repeats were 32 to 34 and 17 to 20 amino acids in length and shared partial identity within each series. The repeats were found to be homologous to sequences hypothesized to be involved in glucan binding in the GTF-I of S. downei and to sequences within the protein products encoded by gtfB and gtfC of S. mutans. The repeated sequences may represent peptide segments that are important to glucan binding and may be distributed among GBPs from other bacterial inhabitants of plaque or the oral cavity.

Amino Acid Sequence↗
PubMed1990

Analysis of the Streptococcus downei gtfS gene, which specifies a glucosyltransferase that synthesizes soluble glucans.

The complete nucleotide sequence was determined for the Streptococcus downei (previously Streptococcus sobrinus) MFe28 gtfS gene which specifies a glucosyltransferase (GTF-S) producing water-soluble glucan. A single open reading frame which encodes a mature protein with a molecular weight of 147,408 (1,328 amino acids) and a putative signal peptide 36 or 37 amino acids in length was detected. GTF-S shares extensive sequence similarity with GTF-I (gtfI) from S. downei and GTF-I (gtfB) and GTF-SI (gtfC) from Streptococcus mutans. GTF-S contains a highly conserved enzymatic domain and C-terminal repeated sequences which appear to be involved in glucan binding. Comparison of the deduced GTF-S protein sequence with other sequenced GTF genes of mutans streptococci revealed that these C-terminal repeats occurred in all cases, although the patterns of repeated sequences varied with respect to each other and to the glucan-binding protein of S. mutans. GTF-S contains four C-terminal repeat sequences ranging from 49 to 51 amino acids in length and a partial repeat of 13 amino acids. Nuclear magnetic resonance analysis of the glucan produced by GTF-S revealed that the product consisted of more than 90% alpha-1,6-linked glucosyl residues.

Amino Acid Sequence↗
PubMed1989

Genetic and antigenic comparison of Streptococcus mutans fructosyltransferase and glucan-binding protein.

The genes for fructosyltransferase (ftf) and glucan-binding protein (gbp) of Streptococcus mutans strain Ingbritt have been cloned in E. coli using bacteriophage and plasmid vectors. A single ftf gene appears to be responsible for the appearance of several FTF of different electrophoretic mobilities. Despite the fact that both ftf and gbp proteins synthesise fructans from sucrose in S. mutans and shown closely similar electrophoretic mobilities and isoelectric points, the restriction maps of the two genes are distinct, their DNAs do not hybridise and there is no immunological cross-reaction between the two proteins.

Antigens, Bacterial↗
PubMed1989

Antigenic and structural analysis of Treponema denticola.

Polypeptide and Western immunoblot profiles of subcellular fractions of Treponema denticola ATCC 33520 have been determined by SDS-PAGE of Triton X-100-soluble and -insoluble fractions, a lipopolysaccharide-enriched fraction and purified flagella. Major Triton X-100-soluble polypeptides of 72, 68, 54 and 52 kDa were detected. The 54 kDa polypeptide appeared to be a breakdown product of a larger, heat-modifiable polypeptide. Based on the results of SDS-PAGE analysis and immunoblotting of proteinase K digests of T. denticola, a 'rough' lipopolysaccharide appeared to be present. Electron microscopy has been used to monitor the effect of detergent treatment on the morphology of the organism and to examine the detailed structure of the flagella. Treatment with Triton removed the T. denticola outer membrane, resulting in exposure of the flagella. The flagella were shown to have a complex sheath and core structure and polypeptide composition characteristic of that observed for other treponemes. Polypeptides of 38, 35, 32 and 28 kDa were present in purified flagella preparations. Immunoelectron microscopy, iodine-labelling and Western blotting were used to demonstrate the exposure of antigens on the T. denticola surface. Surface iodination located polypeptides of 72, 68 and 54 kDa. Antiserum raised against whole cells of T. denticola recognized these polypeptides and an additional polypeptide of 52 kDa. These data provide a basis for future detailed molecular analysis of the ultrastructure and antigenicity of T. denticola.

Antigens, Bacterial↗
PubMed1989

Sequence analysis of the wall-associated protein precursor of Streptococcus mutans antigen A.

The nucleotide sequence has been determined for the Streptococcus mutans wall-associated protein A (wapA) gene from serotype c strains Ingbritt and GS5. The nucleotide sequence for each wapA gene was virtually identical, although the gene from strain GS5 contained a 24 base pair deletion. A 29 amino acid signal peptide was specified by each wapA gene with a mature protein of 424 amino acids (Mr, 45,276) for strain Ingbritt and 416 amino acids (Mr, 44,846) for strain GS5. In the C-terminal region of the wall-associated protein A, considerable sequence similarity was found with the membrane anchor region of proteins from other Gram-positive organisms such as the group A streptococcal M protein and the group G streptococcal IgG binding protein. Adjacent to the proposed membrane anchor is a highly hydrophilic region which may span the cell wall; both sequence data and experimental evidence indicate the existence of a region immediately outside the wall at which proteolytic cleavage occurs to release antigen A of Mr 29,000 into the culture supernatant. Thus, the wall-associated protein A is a precursor of the 29,000 Mr antigen A.

Amino Acid Sequence↗
PubMed1989

Ptosis and supranuclear downgaze paralysis.

A patient developed the unusual combination of a supranuclear downward gaze paralysis and bilateral ptosis. It was caused by a single midbrain glioma. Other ocular motor functions were intact. The neuropathologic examination showed a tumor growing mainly around the third ventricle and the aqueduct. The findings agree with recent experimental evidence that a network of neural elements involved in eyelid control lies in the supraoculomotor area immediately dorsal to the oculomotor nucleus.

Aged↗
PubMed1988

Dual effect of N-methyl-N-(1-methyl-4-pyrolidino)-2-butyl)acetamide on release of (3H)-acetylcholine from the rat hippocampal slices.

The effect of muscarinic cholinergic drugs on (3H)-acetylcholine [3H)-Ach) release from slices of rat hippocampus was investigated either in the presence of eserine or hemicholinium-3 (HC-3), 10 microM each. BM-5 (N-methyl-N-(1-methyl-4-pyrolidino-2-butyl)acetamide) is a partial muscarinic cholinergic agonist. Like oxotremorine, BM-5 significantly (p less than 0.012) decreased the release of (3H)-Ach in the presence of HC-3. In the presence of eserine, (3H)-Ach release was significantly (p less than 0.001) enhanced both by atropine and BM-5. The decrease or increase in release of (3H)-Ach by BM-5, in the presence of HC-3 or eserine, respectively, may be due to its partial agonist effect on hippocampal muscarinic cholinergic receptors.

Acetylcholine↗
PubMed1988

Streptococcus mutans gtfA gene specifies sucrose phosphorylase.

The ethanol-insoluble product formed from sucrose by purified enzyme encoded by the gtfA gene from Streptococcus mutans, expressed in recombinant Escherichia coli, was analyzed by 13C and 31P nuclear magnetic resonance. The product was identified as alpha-D-glucose-1-phosphate, and it was concluded that the GTF-A enzyme is sucrose phosphorylase (sucrose:orthophosphate alpha-D-glucosyltransferase [EC 2.4.1.7]).

DNA, Bacterial↗
PubMed1988

Sequence analysis of the glucosyltransferase A gene (gtfA) from Streptococcus mutans Ingbritt.

The complete nucleotide sequence of a 2.4-kilobase fragment containing the glucosyltransferase A gene (gtfA) of Streptococcus mutans Ingbritt (serotype c) was determined. The gtfA gene contains 481 codons and specifies a protein of molecular weight 55,665. There is no evidence of a signal peptide in the protein or that the glucosyltransferase A enzyme is secreted. No sequence homologies were observed between the gtfA gene or protein and the gtfI or gtfB gene and its protein.

Amino Acid Sequence↗
PubMed1988

Homology of glucosyltransferase gene and protein sequences from Streptococcus sobrinus and Streptococcus mutans.

The sequences of glucosyltransferase genes from Streptococcus sobrinus (gtfI) and Streptococcus mutans (gftB) were compared and show a high degree of homology. There is a 57.7% homology of nucleotides in the genes and a 56.7% homology of amino acids in the deduced protein sequences. The G + C content for the protein-coding region is 43.6% for S. sobrinus and 41.2% for S. mutans. Internal repeating sequences present in both proteins exhibit some difference in sequence pattern.

Amino Acid Sequence↗
PubMed1987

Reduced response of cerebral blood flow to hypercapnia: restoration by extracranial-intracranial bypass.

Cerebral blood flow, estimated by the xenon clearance technique, has been used to study eight patients before and after extracranial-intracranial (EC-IC) bypass surgery. Response of cerebral blood flow to hypercapnia was also measured to estimate cerebral reactivity, an indicator of cerebral vasodilator reserve capacity. Measurements in all patients were repeated 3 months after surgery. Resting cerebral blood flow was not increased by the operation but cerebral reactivity in the ipsilateral hemisphere was significantly increased in all patients (P = 0.002). Reactivity also increased in the contralateral hemisphere in six of the eight patients (P = 0.065). The response of cerebral blood flow to hypercapnia may prove useful in the selection of symptomatic patients with carotid occlusions or inaccessible stenoses for revascularization by EC-IC bypass.

Aged↗
PubMed1987

Characterization of glucosyltransferase expressed from a Streptococcus sobrinus gene cloned in Escherichia coli.

The gene encoding a glucosyltransferase which synthesized water-insoluble glucan, gtfI, previously cloned from Streptococcus sobrinus strain MFe28 (mutans serotype h) into a bacteriophage lambda vector, was subcloned into the plasmid pBR322. The recombinant plasmid was stable in Escherichia coli and gtfI was efficiently expressed. The GTF-I expressed in E. coli was compared to the corresponding enzymes in S. sobrinus strains MFe28 (serotype h), B13 (serotype d) and 6715 (serotype g) and shown to resemble them closely in molecular mass and isoelectric point. The insoluble glucan produced by GTF-I from recombinant E. coli consisted of 1,3-alpha-D-glycosyl residues (approximately 90%). An internal fragment of the gtfI gene was used as a probe in hybridization experiments to demonstrate the presence of homologous sequences in chromosomal DNA of other streptococci of the mutans group.

Cloning, Molecular↗
PubMed1987

Nucleotide sequence of a glucosyltransferase gene from Streptococcus sobrinus MFe28.

The complete nucleotide sequence was determined for the Streptococcus sobrinus MFe28 gtfI gene, which encodes a glucosyltransferase that produces an insoluble glucan product. A single open reading frame encodes a mature glucosyltransferase protein of 1,559 amino acids (Mr, 172,983) and a signal peptide of 38 amino acids. In the C-terminal one-third of the protein there are six repeating units containing 35 amino acids of partial homology and two repeating units containing 48 amino acids of complete homology. The functional role of these repeating units remains to be determined, although truncated forms of glucosyltransferase containing only the first two repeating units of partial homology maintained glucosyltransferase activity and the ability to bind glucan. Regions of homology with alpha-amylase and glycogen phosphorylase were identified in the glucosyltransferase protein and may represent regions involved in functionally similar domains.

Amino Acid Sequence↗
PubMed1985

Expression of a gene for glucan-binding protein from Streptococcus mutans in Escherichia coli.

The structural gene for a glucan-binding protein (GBP) of Streptococcus mutans has been inserted into a bacteriophage lambda vector and expressed in Escherichia coli K12. Lysates of E. coli infected with the recombinant phage contain an antigenic protein of the same size as S. mutans GBP. The GBP synthesized in E. coli can be affinity-purified on immobilized glucan and antiserum raised against it has been shown to precipitate fructosyltransferase activity from S. mutans.

Antigens, Bacterial↗