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Biomedical subjects

M A Curtis

Publications and source records attributed to M A Curtis.

At least 109 records · Page 6Linked to original sources
PubMed1988

Detection of high-risk groups and individuals for periodontal diseases. Systemic predisposition and markers of general health.

The evidence for systemic predisposition to periodontal diseases is reviewed in relation to cellular and humoral immunity, drug therapy, diet and nutrition and stress. It is concluded that, apart from defects of polymorphonuclear leukocytes (PMN) and Ehlers-Danlos Syndrome, little firm evidence exists for other diseases, though insulin-dependent diabetes and acquired immune deficiency syndrome (AIDS) may accelerate and/or potentiate the damage of existing disease. The precise rôle of drugs, diet and nutrition and stress remain to be elucidated, but recent advances in these areas offer the prospect of assessing risk using carefully controlled studies.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Detection of high-risk groups and individuals for periodontal diseases. Evidence for the existence of high-risk groups and individuals and approaches to their detection.

It is argued that the periodontal diseases can no longer be regarded as universally prevalent conditions to which all members of the world's population are at equal risk if they fail to practise good oral hygiene. Rather, they should be regarded as a range of different diseases for each of which certain individuals, which together comprise certain minority groups, are at relatively high risk. The epidemiological evidence for the existence of high-risk groups is reviewed, from which it is concluded that world-wide the prevalence of severe destructive periodontitis is of the order of only 7-15% of the adult dentate population. A working classification of the different types of gingivitis and periodontitis is offered, as is a summary of the theoretically possible approaches to the detection of high-risk groups and individuals which are explored in detail in subsequent papers. Successful identification of such individuals will permit scientifically valid, rational and targetted prevention and treatment.

Adult↗
PubMed1988

Detection of high-risk groups and individuals for periodontal diseases. Clinical assessment of the periodontium.

The fundamental concepts of measuring periodontal diseases and the interpretation of such information as an historical record of disease, rather than disease activity, emphasises the need for improved diagnostic and prognostic tests. Criteria for an indicator of disease activity were suggested and an index fulfilling these should allow sites to be categorised as "active", quiescent or healing, and enable one to predict the risk of future disease activity. The ability of current measurements and indices, routinely used during clinical assessments of periodontal diseases, to fulfill the suggested criteria was considered and rejected in all cases. It is concluded that clinical parameters are only capable of identifying disease retrospectively, indicating the need for longitudinal, rather than cross-sectional studies in the search for clinical and laboratory markers of disease activity and susceptibility.

Gingival Crevicular Fluid↗
PubMed1988

The total protein concentration of gingival crevicular fluid. Variation with sampling time and gingival inflammation.

The total protein concentration of gingival crevicular fluid (GCF), sampled repeatedly over a 10-min period with the minimum of physical irritation to the sulcus, was evaluated in a group of 32 healthy adolescents. The mean concentration of the 1st sample was comparable to that of normal tissue fluids and lymph, irrespective of the state of inflammation of the sample site. However, during repeated sampling, the values rose to resemble serum protein levels, except at those sites with no clinically detectable inflammation. Gel electrophoretic analysis confirmed the increasing proportion of serum-derived molecules in the more proteinaceous GCF samples. The results demonstrate the extreme sensitivity of the gingival vasculature to GCF sampling and consequently the need for accurate standardisation of GCF collection protocols. This will apply particularly when compositional data is to be normalised with respect to the total protein content or when the levels of a serum constituent are being examined.

Adolescent↗
PubMed1987

Trace analysis of diazepam in serum using microbore high-performance liquid chromatography and on-line preconcentration.

The feasibility of determining trace analytes in human serum using on-line preconcentration and microbore high-performance liquid chromatography has been demonstrated. The serum is subjected to ultracentrifugation and injected onto a hydrophobic pre-column using water as the mobile phase. This traps the components of interest which are then backflushed onto a microbore analytical column using a stronger mobile phase. The column-switching apparatus was evaluated using highly dilute aqueous paraben solutions and sample enrichment factors as high as 1500 were obtained. The procedure was then applied to diazepam in serum. Recovery was linear and quantitative over the range from at least 4 to 1000 ng/ml. The method was specific against caffeine and the three major metabolites of diazepam: oxazepam, temazepam, and nordiazepam. The effects of varying pre-column dimensions, pre-column loading time, and sample volume were evaluated.

Biotransformation↗
PubMed1987

Proline requirement for glucose utilization by Peptostreptococcus anaerobius ATCC 27337.

Resting cells of Peptostreptococcus anaerobius maintained under anaerobic conditions were unable to metabolize either glucose or alanine. The addition of proline to the appropriate suspension, however, resulted in the immediate utilization of both compounds. Fermentation of alanine by the cells required that stoichiometric concentrations of proline be present in the medium; and during the oxidation of alanine, proline was simultaneously reduced to the ring cleavage product delta-aminovaleric acid. Although proline was required to initiate glucose transport, stoichiometric amounts of the imino acid were not necessary for glucose fermentation. Proline also stimulated the uptake and concomitant phosphorylation of the nonmetabolizable glucose analog 2-deoxy-D-glucose. The proline requirement for glucose transport by P. anaerobius could be replaced by adding ferricyanide or simply by aerating the cell suspension. The initiation of sugar uptake by proline, ferricyanide, and O2 was attributed to the capacity of these compounds to function as electron acceptors, which permitted reoxidation of the (reduced) intracellular nucleotide pool and the formation (from an endogenous reserve) of the high-energy donor(s) required for the vectorial transport and phosphorylation of sugar.

Adenosine Triphosphate↗
PubMed1987

Diplostomiasis (Trematoda: Strigeidae) in Arctic charr (Salvelinus alpinus) from Charr Lake, northern Labrador.

The eyes of 273 Arctic charr (Salvelinus alpinus) taken from Charr Lake, the Ikarut River, and Hebron Fiord in northern Labrador were examined for diplostomula. All anadromous charr taken from the Ikarut river and Hebron Fiord were uninfected. The resident fish from Charr Lake were parasitized with large numbers of diplostomula and intensity of infection increased with age and length. Infections of up to 2,852 diplostomula in one fish are the highest recorded. Such infections did not appear to affect the vision of the charr.

Animals↗
PubMed1986

N5-(1-carboxyethyl)-ornithine, a new amino acid from the intracellular pool of Streptococcus lactis.

Intracellular concentrations of amino acids were determined in cells of Streptococcus lactis 133 during growth in complex, spent, and chemically defined media. Glutamic and aspartic acids represented the major constituents of the amino acid pool. However, organisms grown in spent medium or in defined medium supplemented with ornithine also contained unusually high levels of two additional amino acids. One of these amino acids was ornithine. The second compound exhibited properties of a neutral amino acid by coelution with valine from the amino acid analyzer. The compound did not, however, comigrate with valine or any other standard amino acid by two-dimensional thin-layer chromatography. The unknown amino acid was purified by paper and thin-layer chromatography, and its molecular structure was determined by 1H and 13C nuclear magnetic resonance spectroscopy. This new amino acid was shown to be N5-(1-carboxyethyl)-ornithine. The 14C-labeled compound was formed by cells of S. lactis 133 during growth in spent medium or defined medium containing [14C]ornithine. Formation of the derivative by resting cells required ornithine and the presence of a metabolizable sugar. N5-(1-Carboxyethyl)-ornithine was synthesized chemically from both poly-S-ornithine and (2S)-N2-carbobenzyloxy-ornithine as a 1:1 mixture of two diastereomers. The physical and chemical properties of the amino acid purified from S. lactis 133 were identical to those of one of the synthetic diastereomers. The bis-N-trifluoroacetyl-di-n-butyl esters of the natural and synthetic compounds generated identical gas chromatography-mass spectrometry spectra. A mechanism is suggested for the in vivo synthesis of N5-(1-carboxyethyl)-ornithine, and the possible functions of this new amino acid are discussed.

Gas Chromatography-Mass Spectrometry↗
PubMed1984

The analysis of picomole amounts of L(+)- and D(-)-lactic acid in samples of dental plaque using bacterial luciferase.

L(+)-Lactic acid (5 pmol) and D(-)-lactic acid (20 pmol) were assayed by coupling the generation of NADH with the use of bacterial luciferase. The binding of NADH to L(+)-lactic dehydrogenase made it necessary to denature the protein so that the assay with bacterial luciferase was effective. The coupled luciferase assay of L(+)-lactic acid was 400 times more sensitive than the fluorometric assay. The luciferase coupled assay was used to analyze the L(+)- and D(-)-lactic acid contents of small samples of dental plaque.

Dental Plaque↗
PubMed1983

Biogenesis of methane in primate dental plaque.

Dental plaque samples collected from monkeys (Macaca mulatta) were found to contain a large amount of dissolved methane gas (0.6 nmol CH4/mg wet wt plaque). Enrichment cultures inoculated with dental plaque obtained from Macaca fascicularis produced methane when the medium contained ethanol, methanol, lactate, acetate or a hydrogen + CO2 atmosphere. Methane formation in the enrichments was inhibited by oxidation of the culture medium, autoclaving or the addition of 2-bromoethane sulfonic acid (BES). The methane producing enrichments were observed to contain fluorescent cocci occurring singly and in short chains. It was concluded that methane formation in the monkey dental plaque was the result of the presence of methanogenic bacteria.

Acetates↗
PubMed1983

Application of a competition model to the growth of Streptococcus mutans and Streptococcus sanguis in binary continuous culture.

Streptococcus mutans 6715-15 and Streptococcus sanguis 10558 were grown together in continuous culture with glucose as the limiting carbon source. The relationship of growth rate to substrate concentration was determined for pure cultures of each organism in continuous and batch cultures. A model based on competition for a growth-limiting substrate (glucose) was used to predict the proportions of each organism when grown in binary cultures. The results indicate that interactions other than competition for glucose carbon exist between S. mutans and S. sanguis grown under these conditions.

Bacteriological Techniques↗
PubMed1983

Stickland reactions of dental plaque.

Dental plaque samples from monkeys (Macaca fascicularis) were shown to contain proline reduction activity in coupled Stickland reactions with other amino acids and also with certain end products of bacterial glucose metabolism. The unusually high concentration of bound and free proline in the oral environment may be of importance in both the production of base and in the removal of acid from the tooth surface after dietary carbohydrate ingestion.

Amino Acids↗
PubMed1981

Observations on the occurrence of Diplostomum spathaceum and Schistocephalus sp. in ninespine sticklebacks (Pungitius pungitius) from the Belcher Islands, Northwest Territories, Canada.

All 175 ninespine sticklebacks, Pungitius pungitius (Linné), collected from the Belcher Islands were parasitized by Diplostomum spathaceum (Rudolphi) and 43% by Schistocephalus sp. D. spathaceum metacercariae were mostly confined to a dorso-ventral band encircling the lens of the eye, and were concentrated in the anterio-dorsal sector of this band. The central area of the lens was thus relatively free of diplostomula, probably minimizing interference with the vision of the fish. The frequency distribution of D. spathaceum abundance in P. pungitius was closely approximated by a negative binomial, while that for Schistocephalus was best fitted by a Poisson. None of the fish condition factors examined appeared related to the intensity of the parasitic infections.

Animals↗
PubMed1980

The nonrandom, negative binomial distribution of experimental trichinellosis in rabbits.

The distribution of parasite populations in their hosts has been the subject of a number of mathematical analyses and it has been found that these distributions are generally nonrandom and overdispersed. Data on the recovery of Trichinella spiralis in the laboratory from 371 outbred rabbits were examined. The distribution of their parasite burden was overdispersed and best fit by a negative binomial frequency distribution. The intensity of the infections was almost totally independent of the dose of inoculation, the duration of the infection, and the weight of the animals; the variations within the replicate counts were small and normally distributed about their means. These results indicate that nonrandom overdispersion may be a characteristic of even carefully controlled laboratory infections, and susceptibility factors should be considered seriously in mathematical models of parasites.

Animals↗