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K G Taylor

Publications and source records attributed to K G Taylor.

At least 19 recordsLinked to original sources
PubMed2000

Polycarboxylates inhibit the glucan-binding lectin of Streptococcus sobrinus.

Polycarboxylates, such as carboxymethylcellulose and hyaluronan, were found to be reversible inhibitors of the glucan-binding lectin of Streptococcus sobrinus. When the carboxylate groups were coupled to ethylenediamine, or reduced with carbodiimide-borohydride, inhibitory powers were lost. Similarly, N-deacetylated hyaluronan had poor inhibitory powers, probably due to the introduction of positive charges into the polymer. Other polymers, such as chondroitin sulfates, dextran sulfate, fetuin, heparin were not inhibitors. It appears that inhibition is based on repeating carboxylates, free of influence from ammonium groups. Such polymers have the property of complexing with metals. Earlier studies had concluded that the streptococcal lectin depended on manganese for activity. It is likely the carboxymethylcellulose and hyaluronan perturb essential metal coordination centers in the lectin. Polycarboxylates may have value in oral health care by acting on glucan-dependent microbial adhesion and biofilm formation.

Bacterial Proteins↗
PubMed2000

Conformational studies of sphingolipids by NMR spectroscopy. I. Dihydrosphingomyelin.

The conformational features of dihydrosphingomyelin (DHSM), the major phospholipid of human lens membranes, were investigated by 1H and 31P nuclear magnetic resonance spectroscopy. Several postulates emerge from the observed trends: (a) in partially hydrated samples of DHSM in CDCl3 above 13 mM, at which lipid-lipid interactions prevail, the amide proton is mostly involved in intermolecular H-bonds that link neighboring phospholipids through bridging water molecules. In the absence of water, the NH group is involved in an intramolecular H-bond that restricts the mobility of the phosphate group. (b) In the monomeric form of the lipid molecule, the amide proton of the major conformer is bound intramolecularly with one of the anionic and/or ester oxygens of the phosphate group. A minor conformer may also be present in which the NH proton participates in an intramolecular H-bond linking to the OH group of the sphingoid base. (c) Complete hydration leads to an extension of the head group as water molecules bind to the phosphate and NH groups via H-bonds, thus disrupting the intramolecular H-bonds prevalent at low concentrations.

Carbon Isotopes↗
PubMed2000

Conformational studies of sphingolipids by NMR spectroscopy. II. Sphingomyelin.

Sphingomyelin (SM) is the most prevalent sphingolipid in the majority of mammalian membranes. Proton and 31P nuclear magnetic resonance spectral data were acquired to establish the nature of intra- and intermolecular H-bonds in the monomeric and aggregated forms of SM and to assess possible differences between this lipid and dihydrosphingomyelin (DHSM), which lacks the double bond between carbons 4 and 5 of the sphingoid base. The spectral trends suggest the formation of an intramolecular H-bond between the OH group of the sphingosine moiety and the phosphate ester oxygen of the head group. The narrower linewidth and the downfield shift of the resonance corresponding to OH proton in SM suggest that this H-bond is stronger in SM than in DHSM. The NH group appears to be involved predominantly in intramolecular H-bonding in the monomer. As the concentration of SM increases and the molecules come in closer proximity, these intramolecular bonds are partially disrupted and the NH group becomes involved in lipid-water interactions. The difference between the SM and DHSM appears to be not in the nature of these interactions but rather in the degree to which these intermolecular interactions prevail. As SM molecules cannot come as close together as DHSM molecules can, both the NH and OH moieties remain, on average, more intramolecularly bonded as compared to DHSM.

Animals↗
PubMed1996

Multiple glucan-binding proteins of Streptococcus sobrinus.

Several proteins from culture supernatants of Streptococcus sobrinus were able to bind avidly to Sephadex G-75. The proteins could be partially eluted from the Sephadex by low-molecular-weight alpha-1,6 glucan or fully eluted by 4 M guanidine hydrochloride. Elution profiles were complex, yielding proteins of 16, 45, 58 to 60, 90, 135, and 145 kDa, showing that the wild-type strain possessed multiple glucan-binding proteins. Two mutants of Streptococcus sobrinus incapable of aggregation by high-molecular-weight alpha-1,6 glucan were isolated. One mutant was spontaneous, from a cell suspension to which glucan had been added, whereas the other was induced by ethyl methanesulfonate. Both mutants were devoid of a 60-kDa protein, as shown by gel electrophoresis of culture supernatants and whole cells. Amino acid analysis showed that the 58- to 60-kDa protein and the 90-kDa protein were distinct, although both were N-terminally blocked. Both mutants retained their ability to adhere to glass in the presence of sucrose and to ferment mannitol and sorbitol. Both mutants retained their glucosytransferase activities, as shown by activity gels. Western blots (immunoblots), employing antibody against a glucan-binding protein of Streptococcus mutans, failed to reveal cross-reactivity with S. sobrinus proteins. The results show that even though S. sobrinus produces several proteins capable of binding alpha-1,6 glucans, the 60-kDa protein is probably the lectin needed for glucan-dependent cellular aggregation.

Amino Acids↗
PubMed1996

Neural and glial-mediated effects of growth factors acting via tyrosine kinase receptors on luteinizing hormone-releasing hormone neurons.

It is becoming increasingly evident that the secretory activity of LHRH neurons is regulated not only by transsynaptic inputs but also by trophic molecules of glial and neuronal origin. The present experiments were undertaken to gain insights into the potential cell-cell mechanisms by which basic fibroblast growth factor (bFGF) and transforming growth factor-alpha (TGF alpha), two growth factors produced in the hypothalamus, may affect LHRH neuronal function. Northern blot analysis showed that the LHRH-producing cell line GT1-7 contains the messenger RNA (mRNA) encoding the type 1 fibroblast growth factor receptor (FGFR-1) but not that encoding the epidermal growth factor (EGF) receptors, which mediates the biological actions of both TGF alpha and EGF. Ligand-induced receptor phosphorylation experiments demonstrated that GT1-7 cells possess biologically active FGFR-1s but not EGF receptors. Exposure of the cells to bFGF resulted not only in FGFR-1 tyrosine phosphorylation, but also in tyrosine phosphorylation of phospholipase C gamma, one of the initial enzymes in the intracellular signaling cascade initiated by FGFR activation. GT1-7 cells proliferated in response to this activation. Despite the presence of biologically active receptors, bFGF did not significantly stimulate release of the mature LHRH decapeptide. Instead, bFGF increased the steady-state levels of the mRNA encoding the LHRH precursor processing endoprotease PC2, with a time course comparable to that of phorbol esters, suggesting that, as shown in the companion paper, the actions of the growth factor on LHRH neurons involve facilitation of the initial step in LHRH prohormone processing. The increase in PC2 gene expression was not accompanied by changes in LHRH mRNA levels. Unlike these direct actions of bFGF on GT-1 cells, TGF alpha appears to act indirectly via astroglial intermediacy. Exposure of GT1-7 cells to TGF alpha or EGF failed to affect several parameters of cellular activity including LHRH release, LHRH and PC2 mRNA levels, and cell proliferation. In contrast, astrocyte culture medium conditioned by treatment with TGF alpha led to sustained stimulation of LHRH release with no changes in LHRH gene expression and a transient increase in PC2 mRNA levels. Although no definitive evidence for the presence of FGFR-1 in normal LHRH neurons could be obtained by either double immunohistochemistry or double in situ hybridization procedures, fetal LHRH neurons in primary culture responded to bFGF with neurite outgrowth. Thus, normal LHRH neurons may have an FGFR-1 content too low for detection by regular histochemical procedures, and/or detectable expression of the receptor may be confined to a much earlier developmental stage. The mitogenic effect of bFGF on GT1-7 cells supports this possibility and suggests a role for FGF in the cell proliferation events that precede acquisition of the LHRH neuronal phenotype. It appears that once this phenotype is established, bFGF may promote the differentiation of LHRH neurons. The results also suggest that the secretory capacity of LHRH neurons develops under a dual trophic influence, one on peptide processing exerted directly by bFGF on early neurons, and another on LHRH release, exerted by TGF alpha via the intermediacy of astroglial cells.

Animals↗
PubMed1995

Streptococcal glucan-binding lectins do not recognize methylated alpha-1,6 glucans.

The glucan-binding lectin (GBL) of Streptococcus sobrinus is cell associated, enabling the bacteria to be aggregated by alpha-1,6 glucans. Glucans, such as amylose, pullulan, laminarin and nigeran, have no affinity for the lectin. High molecular weight alpha-1,6 glucans (dextrans) readily aggregate the bacteria, whereas low molecular weight glucans inhibit the aggregation brought about by the high molecular weight species. Methylated glucan T-2000 (an alpha-1,6 glucan with an average molecular weight of 2 x 10(6) Da) aggregated the bacteria very poorly when the extent of methylation (DS, or degree of substitution) was high, and less poorly when the DS was low. Similarly, methylated low molecular weight alpha-1,6 glucan was a poor inhibitor of aggregation induced by the high molecular weight glucan T-2000. Because the methylation occurred primarily on the hydroxyl of C-2, it is suggested that the hydroxyl is needed for formation of the lectin-glucan complex. It appears that the GBL is not only stereospecific in interaction with glucans, but also regio-specific, interacting only with the underivatized alpha-1,6-glucan.

Bacterial Adhesion↗
PubMed1995

Subinhibitory concentrations of antibiotics affect cell surface properties of Streptococcus sobrinus.

Several antibiotics, at subinhibitory concentrations, caused an increase in the ability of Streptococcus sobrinus to bind alpha-1,6-glucans, whereas other antibiotics decreased glucan binding. In every case, glucan binding was inversely proportional to cell surface hydrophobicity. High levels of glucan-binding activity resulted in low levels of hydrophobicity, whereas low levels of glucan binding caused high levels of cellular hydrophobicity. The results show that low concentrations of antibiotics may modulate lectin and hydrophobin adhesins in streptococci.

Alkanes↗
PubMed1994

Fluoride inhibits the glucan-binding lectin of Streptococcus sobrinus.

The glucan-binding lectins of Streptococcus cricetus AHT and Streptococcus sobrinus 6715 were reversibly inhibited by sodium fluoride. Fluoride was superior to chloride, bromide, iodide and thiocyanate in preventing glucan-mediated aggregation of the bacteria. Fluoride was also an effective inhibitor of the sucrose-dependent adhesion of S. sobrinus to glass surfaces. The inhibition of glucan-binding lectin activities may be one of the mechanisms of action of fluoride in preventing dental disease.

Bacterial Adhesion↗
PubMed1994

Separation and characterization of the unknown phospholipid in human lens membranes.

PURPOSE: The major component of human lens membranes was thought to be sphingomyelin until 1991, when a study by phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy revealed the presence of an unknown phospholipid that constituted approximately half the human lens phospholipids. The objective of this work was to isolate this phospholipid and to elucidate its identity. METHODS: The separation of sphingomyelin from the unknown was accomplished using high-performance liquid chromatography (HPLC) and an amino-bound column. Sphingomyelin standard and the membranes from human lenses were chromatographed. Chromatographic fractions were collected and spectrally characterized by proton (1H) NMR and 31P NMR spectroscopy. RESULTS: The chromatographic method did not affect the integrity of the sphingomyelin. Besides the bands corresponding to the unknown components, the chromatogram of the human lens membranes showed three large peaks, the central one with a shoulder, with elution times similar to that for sphingomyelin. The 1H NMR spectra for the fractions collected during the elution of these peaks showed differences. The study by 31P NMR indicated that the first peak contained the unknown phospholipid. The subsequent fractions showed the presence, in different relative levels, of both the unknown and sphingomyelin. By comparison and interpretation of the two-dimensional 1H NMR spectra for sphingomyelin and for the fraction containing the unknown, the unknown phospholipid is proposed to be 4,5 dihydrosphingomyelin, in which the site of unsaturation present in the sphingosine moiety is no longer present. CONCLUSIONS: The ability to separate the unknown from sphingomyelin and the power of 1H NMR spectroscopy allowed the proposition of the identity of the major component of human lens membranes as 4,5-dihydrosphingomyelin. Although the synthetic compound is known to be involved in the formation of extended hydrogen-bonding networks, its biologic and physicochemical properties need further study.

Cell Membrane↗
PubMed1993

Essential amino acids involved in glucan-dependent aggregation of Streptococcus sobrinus.

The active site of the glucan-binding lectin (or agglutinin) (GBL) of Streptococcus sobrinus was probed by specific amino acid modifying reagents. Reagents specific for carboxylates, imidazolium, phenolic, and lysyl residues inactivated the cell bound GBL, whereas agents specific for sulfhydryl, disulfide, and guanidinium groups had no effect on the lectin. A low molecular weight alpha-(1-->6)-glucan provided partial protection against the reagents which inactivated the protein, whereas an alpha-(1-->4)-glucan, incapable of complexing with the lectin, afforded no protection. A reagent specific for tryptophan, 2-hydroxy-5-nitrobenzyl bromide (HNB) did not cause a loss of GBL activity, although N-bromosuccinimide, a reagent capable of oxidizing tryptophan and less selective than HNB, was a very effective inhibitor of the glucan-dependent cellular aggregation. In the latter case, alpha-(1-->6)-glucan did not protect. Hydroxylamine partially restored the loss of lectin activity due to treatment of the cells with N-acetylimidazole (highly specific for tyrosine), glycine methyl ester plus water-soluble carbodiimide (specific for carboxylates), and diethylpyrocarbonate (specific for histidine). Because the soluble form of GBL rapidly loses activity when purified, it was necessary to perform the chemical modification of the amino acid side chains employing the cell-bound form of the lectin. Because specific ligand [alpha-(1-->6)-glucan] protected against the inactivation of the agglutinin by selected reagents and because lectin activity could be restored in some cases, it was possible to identify likely essential amino acid residues needed for glucan binding. The results, taken together, suggest that aspartic (and/or glutamic) acid, histidine, lysine, and tyrosine are critical amino acids responsible for agglutinin activity. Present efforts are directed to the design and synthesis of glucan analogues which may serve as affinity inactivating agents of the lectin. Such glucan derivatives may be of value in studies on the role of the lectin in cariogenesis.

Amino Acids↗
PubMed1993

ACTH-independent Cushing's syndrome in pregnancy with spontaneous resolution after delivery: control of the hypercortisolism with metyrapone.

A 25-year-old primigravid woman presented with Cushing's syndrome at 23 weeks gestation; serum cortisol was 1090 nmol/l at 0900 h, 1230 nmol/l at 2200 h; basal urinary free cortisol excretion was 3680 nmol/24 h, and 8830 nmol/24 h after dexamethasone 8 mg daily for 48 hours; plasma ACTH was < 1.1 pmol/l. CT scan of the adrenal glands showed bilateral adrenal hyperplasia. The hypercortisolism was controlled with metyrapone until elective delivery of the fetus by Caesarean section at 34 weeks gestation because of a decline in growth. No adverse fetal effects of metyrapone treatment were apparent, maternal outcome was uncomplicated and wound healing was unimpaired. Maternal adrenocortical function had returned to normal within 4 weeks of the cessation of pregnancy and biochemical remission has been maintained up to 9 months post-partum. Metyrapone therapy is effective in controlling the hypercortisolism in certain cases of Cushing's syndrome complicating pregnancy.

Adrenocorticotropic Hormone↗
PubMed1993

Acquisition of manganous ions by mutans group streptococci.

The cariogenic bacteria Streptococcus sobrinus and S. cricetus were shown to have an absolute requirement for manganous ion in order to bind glucans or to adhere to glass in the presence of sucrose. The bacteria possessed a reasonably high affinity transport system for 54Mn2+, yielding a Km of about 12 microM. The Vmax for uptake of 54Mn2+ in S. sobrinus was increased when the bacteria were grown in Mn-depleted medium, but the Km remained the same. There was no evidence for two Mn2+ uptake systems, commonly observed for many bacteria. Ions such as Ca2+, Co2+, Co3+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Ni2+, and Zn2+ did not inhibit the uptake of 54Mn2+ by the bacteria, although Cd2+ was a potent inhibitor. Fractionation experiments showed that manganese was distributed in protoplasts (67%) and in the cell wall (33%). Approximately 80% of the 54Mn2+ in S. sobrinus was rapidly exchangeable with nonradioactive Mn2+. Electron spin resonance experiments showed that all of the manganese was bound or restricted in mobility. Proton motive force-dissipating agents increased the acquisition of 54Mn2+ by the streptococci, probably because the wall became more negatively charged when the cell could no longer produce protons.

Bacterial Adhesion↗
PubMed1993

Diagnosis of Pneumocystis carinii infection in HIV-seropositive patients by identification of P carinii in pleural fluid.

Pneumocystis carinii pneumonia (PCP) is the most common pulmonary complication of AIDS and is typically diagnosed by the identification of P carinii organisms in sputum, bronchoalveolar lavage fluid, or tissue obtained with transbronchial biopsy. We describe two HIV-seropositive patients with pleural effusions in whom the diagnosis of P carinii infection was made by examination of pleural fluid. Pleural effusions associated with PCP are very unusual but can provide a source of diagnostic material particularly in those HIV patients who have development of a spontaneous pneumothorax and require chest tube insertion.

AIDS-Related Opportunistic Infections↗
PubMed1992

Chelating agents inhibit activity and prevent expression of streptococcal glucan-binding lectins.

Several of the cariogenic mutans streptococci produce cell wall-associated glucan-binding lectins (GBLs). The lectins bind alpha-1,6-linked glucans and have no affinity for other polysaccharides or anomeric linkages. When citrate or lactate was included in the growth medium, expression of the activities of the GBLs of Streptococcus cricetus and S. sobrinus was prevented. Furthermore, chelating agents, including citrate, lactate, EDTA, and acetylacetone, were able to reversibly inhibit glucan-induced aggregation of GBL+ streptococci. In addition, the chelating agents prevented sucrose-dependent streptococcal adhesion to glass surfaces and dispersed preformed adherent masses of the streptococci. Neither citrate nor other chelating agents modified the activities of glucosyltransferases. Expression of the lectin could only be achieved by the addition of manganous ion to the growth medium. Chloramphenicol and other metabolic inhibitors prevented synthesis of GBL in cells obtained from manganese-deficient medium and shifted to manganous ion-sufficient medium. The GBL may be a manganoprotein, the manganese of which may be perturbed, but not removed, by chelating agents. During synthesis of the GBL, manganous ion may be required in order for the protein to achieve an active conformation. Citrate or other chelating agents may have promise as anticaries agents.

Bacterial Adhesion↗
PubMed1991

Isolation and purification of cell wall polysaccharide of Bacillus anthracis (delta Sterne).

A polysaccharide fraction was isolated form sodium-dodecyl-sulfate (SDS) treated cell walls of Bacillus anthracis (delta Sterne) by hydrofluoric acid (HF) hydrolysis and ethanolic precipitation. The polysaccharide fraction was subsequently purified by several washings with absolute ethanol. Purity of the isolated polysaccharide was tested using the anthrone assay and amino acid analyzer. The molecular mass of the polysaccharide fraction as determined by gel filtration chromatography was about 12000 Da. Preliminary analyses of the polysaccharide was done using thin layer chromatography and amino acid analyzer, and results obtained from these analyses were further confirmed by gas liquid chromatography and 13C-NMR spectroscopy. Results showed that the polysaccharide moiety contained galactose, N-acetylglucosamine, and N-acetylmannosamine in an approximate molar ratio of 3:2:1. This moiety was devoid of muramic acid, alanine, diaminopimelic acid, glutamic acid, and lipid, thus indicating that the isolated polysaccharide was of pure quality.

Acetylglucosamine↗
PubMed1990

Knowledge, attitudes, technical competence, and blood glucose control of Type 1 diabetic patients during and after an education programme.

Thirty-one Type 1 diabetic patients entered a 12-month education programme in which attitudes to diabetes, knowledge of diabetes, and technical competence were assessed using questionnaires and practical tests. A closely matched group of 25 control patients continued to receive routine clinic care. Patients completing the education programme showed improved blood glucose control (HbA1 decreased from 11.8 +/- 0.4% to 10.5 +/- 0.3%, mean +/- SE, p less than 0.01), whereas blood glucose control was not altered in the control group (HbA1 11.8 +/- 0.5% before and 11.6 +/- 0.4% after 12 months). Patients completing the education programme also showed greater knowledge (p less than 0.001), more favourable attitudes (p less than 0.03), and increased competence in technical skills (p less than 0.02) compared with the control group. Six months after completing the programme blood glucose control deteriorated (HbA1 11.0 +/- 0.4%, p less than 0.05), although knowledge, attitudes, and technical competence were unchanged. This might reflect the withdrawal of extrinsic motivation and attention provided during the programme. Thus consideration should be given to development of the patient's intrinsic motivation to prolong the benefits of diabetes education programmes.

Adult↗