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R Pike

Publications and source records attributed to R Pike.

At least 37 records · Page 2Linked to original sources
PubMed1995

The multiple forms of trypsin-like activity present in various strains of Porphyromonas gingivalis are due to the presence of either Arg-gingipain or Lys-gingipain.

Porphyromonas gingivalis contains high concentrations of numerous cysteine proteinases with trypsin-like activity which have been implicated as important virulence factors in adult-onset periodontitis. We have analyzed the subfractions of six P. gingivalis strains for the presence of arginine-X- and lysine-X-specific proteinases (Arg-gingipain [RGP] and Lys-gingipain [KGP]) previously purified from P. gingivalis H66. Western blot (immunoblot) analysis using antibodies produced against RGP and the N-terminal peptides of RGP or the catalytic subunit of KGP indicated that these enzymes are synthesized by the strains studied and exist as multiple molecular mass species. The major forms of RGP were identified as 110-, 95-, 70- to 90-, and 50-kDa proteins, the first two being a complex of the 50-kDa catalytic subunit with hemagglutinins, with or without an added membrane anchorage peptide. The other forms are single-chain enzymes. While the 95- and 50-kDa RGP were found predominantly in culture medium, the 110- and 70- to 90-kDa forms associated with membranous fractions of the bacteria. The predominant form of KGP in all strains was a complex of the 60-kDa catalytic domain with hemagglutinins, and vesicle- and membrane-associated KGP was about 15 kDa larger than the 105-kDa enzyme present in culture media. These data explain the apparent complexity of P. gingivalis proteinases and indicate that in all strains tested there are two identical enzymes, one with arginine-X specificity and the other with lysine-X specificity, which, working in concert, are responsible for the trypsin-like activity associated with this bacterium.

Adhesins, Bacterial↗
PubMed1994

Lysine- and arginine-specific proteinases from Porphyromonas gingivalis. Isolation, characterization, and evidence for the existence of complexes with hemagglutinins.

Porphyromonas gingivalis contains many virulence factors that have been implicated as participants in the progression of periodontal disease. It has been shown to produce proteinases of "trypsin-like" specificity in a number of molecular forms, but previous work in our laboratory resulted in the purification of a major arginine-specific cysteine proteinase, gingipain, which contradicted this supposed specificity. In this study, separate proteinases with arginine and lysine specificity were isolated from a high molecular mass fraction of the P. gingivalis culture fluid. The arginine-specific enzyme was found, by amino acid sequencing studies, to be a high molecular mass form of gingipain, formed by the 50-kDa gingipain noncovalently complexed with 44-kDa binding proteins, subsequently identified as hemagglutinins. The 60-kDa lysine-specific proteinase, referred to as Lys-gingipain, was also found to have one of these hemagglutinins complexed with it in the same manner. Lys-gingipain was found to be a cysteine proteinase with optimal activity and stability at pH 8.0-8.5 and was extensively characterized in terms of its specificity and activation characteristics. The proteinase-hemagglutinin complexes may be important in the uptake of hemin, a vital metabolite for P. gingivalis, via hemagglutination and subsequent hemolysis of erythrocytes.

Adhesins, Bacterial↗
PubMed1994

The role of proteolytic enzymes in the development of pulmonary emphysema and periodontal disease.

Pulmonary emphysema and periodontal disease are each characterized by the uncontrolled proteolysis of connective tissue proteins by proteinases derived from human neutrophils. Although these diseases would not appear to be related in terms of the initial insult to individual tissues, the ultimate result in each disease is the accumulation and degranulation of neutrophils at inflammatory sites, apparently as a result of frustrated phagocytosis and specific activation of these phagocytic cells. This result is easily recognized in the case of emphysema, where there is clear evidence that the primary cause of the disease is the accumulation of foreign materials in the lung (e.g., smoke condensate), followed by the recruitment of neutrophils to the organ and the release of oxidative and hydrolytic enzymes. In periodontitis, however, the problem begins with the accumulation of plaque at the base of the teeth, followed by the growth of opportunistic anaerobic bacteria below the gum line. These parasitic microbes, which are resistant to killing by both monocytes and granulocytes, secrete proteinases that can activate the kallikrein-kinin pathway, degrade clotting factors, and release the potent neutrophil chemotactic factor, C5a, from complement. It is under such conditions that neutrophils are recruited to infected sites within the periodontium. After the neutrophil-recruitment stage, the two diseases become similar in that degranulation of neutrophils occurs during attempted phagocytosis of either cigarette smoke components (emphysema) or bacteria (periodontitis), followed by inactivation of tissue proteinase inhibitors and degradation of connective tissue proteins, the ultimate result being the destruction of the alveolus or gingiva, respectively.

Animals↗
PubMed1994

The first 100 kidney transplants from living related donors at Groote Schuur Hospital.

Improved results with cadaver kidney transplantation and the increase in the number of cadaver organs have caused the continued use of donor kidneys from living relatives to be questioned. In this analysis of our first 100 renal transplants involving a living related donor, the 5-year graft survival rate was 70%. The 5-year graft survival rate for recipients of grafts from HLA-identical donors was 81%, as opposed to the 64% survival rate for grafts from one-haplotype donors. Recipients of grafts from one-haplotype-matched donors who received donor-specific blood transfusions demonstrated better graft survival than those who were not transfused. This analysis demonstrates that the results of living related kidney transplantation are good, and suggests that donor-specific blood transfusions may be beneficial.

Graft Survival↗
PubMed1992

Characterisation of the activity and stability of single-chain cathepsin L and of proteolytically active cathepsin L/cystatin complexes.

The activity of single-chain cathepsin L was found to be markedly dependent on cysteine concentration, while a covalent, proteolytically active cathepsin L/cystatin complex was less cysteine-dependent. Cysteine levels and ionic strength did not affect the stability of either enzyme form and both enzyme forms were found to be stable for significant periods of time at or near physiological pH.

Animals↗
PubMed1989

A high yield method for the isolation of sheep's liver cathepsin L.

A method, giving twice the yield of the previous method, for the isolation of sheep's liver cathepsin L is described. The method uses three phase partitioning (TPP) in t-butanol/water/ammonium sulphate mixtures, followed by two chromatographic steps, at different pH values, in a single column of S-Sepharose.

Animals↗
PubMed1984

The pictorial scale of perceived competence and social acceptance for young children.

A new pictorial scale of perceived competence and social acceptance for young children, a downward extension of the Perceived Competence Scale for Children, is described. There are 2 versions of this instrument, 1 for preschoolers and kindergartners and a second for first and second graders, each tapping 4 domains: cognitive competence, physical competence, peer acceptance, and maternal acceptance. Factor analyses reveal a 2-factor solution. The first factor, general competence, is defined by the cognitive and physical competence subscales. The second factor, social acceptance, comprises the peer and maternal acceptance subscales. The psychometric properties were found to be acceptable. Weak correlations between children's and teachers' judgments are discussed in terms of the young child's tendency to confuse the wish to be competent or accepted with reality. It is urged that this instrument not be viewed as a general self-concept scale but be treated as a measure of 2 separate constructs, perceived competence and social acceptance.

Child↗
PubMed1983

Further analysis of the Crist data on matching performance and the similarity structure of the stimulus set.

We argue that Crist's (1981) analysis of his data on letter matching is incomplete because he did not sufficiently distinguish overall context similarity from the similarity of the other letter present on a trial. That is, the separation of the effects of context similarity and visual similarity is required for a complete analysis. Accordingly, for different trials, modified indices of context similarity are derived and linear regression analyses made to determine the separate effects of context and visual similarity. The results of these analyses show that on different trials, visual similarity is much more predictive of latency than context similarity and that subjects must therefore be making visual similarity judgments, that considerably affect latency variation on these trials. Consequently, we argue that visual similarity judgment may be likewise affecting latency on same trials. However, some simple correlations indicate that context may be more predictive of latency on physically different same trials. We concluded that what can be said about context depends on the type of trial and that the comparative strength of name processing should also be assessed by the method described here.

Discrimination, Psychological↗
PubMed1979

Biosynthesis and characterisation of IgMlambda in a case of chronic lymphocytic leukaemia with intracellular immunoglobulin inclusions.

Lymphocytes from a patient with chronic lymphocytic leukaemia were found to contain crystalline inclusions in the cytoplasm. These crystals were characterised as IgMlambda immunoglobulin. The cells did not have detectable surface immunoglobulin. No paraprotein was detected in the serum and no excess of immunoglobulin was detected in the urine. The cells incorporated radioactive leucine into mu and lambda chains during an 18-hour culture. Studies of labelled lysate immunoglobulin revealed a molar excess of heavy chain over light chain while in contrast free light chain was the only detectable secreted immunoglobulin product during the culture period. These findings are discussed in relation to immunoglobulin synthesis by normal and other neoplastic lymphocyte preparations.

Aged↗
PubMedDate not supplied

Titration and mapping of the active site of cysteine proteinases from Porphyromonas gingivalis (gingipains) using peptidyl chloromethanes.

Porphyromonas gingivalis is one of the major pathogens associated with periodontal disease and releases powerful cysteine proteinases known as the gingipains, which are key virulence factors for this organism. The three forms of gingipains, gingipain R1, gingipain R2 (gingipain Rs) and gingipain K, which cleave specifically after arginine (R) or lysine (K) residues, were characterized in terms of the kinetics of their interaction with a wide range of synthetic peptidyl chloromethane inhibitors and a peptidyl (acyloxy)methane. Chloromethane inhibitors were found to inhibit all the enzymes to varying degree dependent on the peptidyl components of the inhibitor. Thus, inhibitors containing a basic residue at P1 rapidly inactivated the gingipains and some specificity could be seen at the P2 site. The (acyloxy)methane inhibitor, Cbz-Phe-Lys-CH2OCO-2,4,6-Me3-Ph, was very specific in its rapid inhibition of gingipain K over the gingipains R. This inhibitor, together with the peptidyl chloromethanes, D-Phe-Pro-Arg-CH2Cl and D-Phe-Phe-Arg-CH2Cl, which reacted most rapidly with the Arg-specific proteinases, could be used to active site titrate purified forms of the enzymes and enzymes found in crude fractions such as intact P. gingivalis cells, vesicles or membrane fractions. From these titrations it was evident that gingipains R were always in an excess of about 3-fold over gingipain K and that the gingipains as a whole made up 85% of the proteolytic activity associated with the bacterium. The elucidation of the kinetics of inhibition by the range of compounds and the development of the titration method for gingipains will considerably aid in future studies on the proteases elaborated by P. gingivalis.

Adhesins, Bacterial↗