Biomedical subjects

D A Lawson

Publications and source records attributed to D A Lawson.

6 recordsLinked to original sources

PubMed1992

Biochemical characterization of Porphyromonas (Bacteroides) gingivalis collagenase.

A protease was purified from Porphyromonas gingivalis 1101, a clinical isolate, by sequential sodium dodecyl sulfate-polyacrylamide gel electrophoresis, substrate diffusion gel electrophoresis, and electroelution. The enzyme cleaved radiolabeled human basement membrane type IV collagen and the synthetic collagen peptide substrate for eukaryotic collagenases. It was inactivated by the thiol protease inhibitor N-ethylmaleimide but not by EDTA or EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] and activated by reducing agents such as beta-mercaptoethanol. The enzyme exists as an active precursor protein of molecular mass 94 kDa and undergoes proteolytic cleavage to 75-, 56-, and 19-kDa forms. Biotin-labeled collagen bound specifically to the 94-kDa form of the protein and to its cleavage products in ligand blots, suggesting a role for this enzyme not only in collagen degradation but also in adhesion to collagenous substrata.

Cell Fractionation↗

PubMed1990

Molecular analysis of periodontal pathogens.

Both Bacteroides gingivalis and Actinobacillus actinomycetemcomitans have been implicated in the destruction of periodontal tissues. To understand better the role putative virulence factors from the two bacterial species may play in an infection, the collagenase gene from Bact. gingivalis and the leucotoxin gene from A. actinomycetemcomitans were cloned. As it is intended to generate strains carrying defined mutations in these genes for in vitro and in vivo experiments, extensive restriction mapping and sequence analyses of these clones are being undertaken. Furthermore a conjugation system for Bact. gingivalis and A. actinomycetemcomitans will be established.

Actinobacillus↗

PubMed1989

Identification of a potential protective microfilarial antigen from Litomosoides carinii (Nematoda, Filarioidea).

The proteins of the filarial parasite Litomosoides carinii that are presented to the host in the course of a natural infection were assessed by surface and intrinsic labelling, microfilarial agglutination assays and ELISA. Surface labelling revealed several proteins present on all parasite stages which were recognised by infected animals. Only one major surface protein of 55 KD was found on microfilariae, while in all other stages (adult males, adult females and infective larvae isolated from pool animals) a range of proteins could be labelled. Immunisation with live microfilariae obtained from blood provoked sera which agglutinated microfilariae in vitro and co-precipitated the 55 KD surface protein. A proportion of animals quantitatively infected with 30 infective larvae (L3) developed antibodies during prepatency that were capable of agglutinating microfilariae, suggesting a common epitope between L3/L4 and microfilariae. Intrinsic labelling of microfilarial proteins was used to identify three additional proteins of 16, 29 and 43 KD which may also be important during infection. The anti-microfilarial antibody titre was quantified by ELISA using microfilarial antigen and sera from various time points during the course of a natural infection.

Agglutination Tests↗

PubMed1988

Observations on the applicability of the Wartenberg pendulum test to healthy, elderly subjects.

Wartenberg developed his pendulum test as a simple but precise test to assist examination of muscle tone in patients with Parkinson's disease. It has recently been reintroduced, and computerised, to evaluate spasticity in young hemiplegics. The results are reported on the highly successful application of this computerised test to large numbers of healthy, elderly subjects. The data have provided normal values for a number of measurements. Analysis of variance has shown that differences between individual subjects account for a major part of the total variabilities seen in all measurements taken. Factors such as position, leg and time trend contribute very little to total variation and, for practical purposes, can be ignored.

Adult↗

PubMed1988

Does the Wartenberg pendulum test differentiate quantitatively between spasticity and rigidity? A study in elderly stroke and Parkinsonian patients.

The results of applying the Wartenberg pendulum test to the assessment of muscle tone in populations of stroke and Parkinsonian patients are described. The test was able to distinguish between increased muscle tone of the spastic or rigid type. The Parkinsonian patients showed a marked reduction of the maximum velocity of the leg swing, with the relaxation index tending to a value of about one. In contrast the affected limb of stroke patients showed a lesser reduction of the velocity of the swing, the relaxation index tending to a value of less than one.

Aged↗

PubMedDate not supplied

Stability of paraspinal tissue compliance in normal subjects.

OBJECTIVE: The following studies were performed in order to evaluate the stability of paraspinal tissue compliance measurements. Tissue compliance is a measure of the consistency or firmness of soft tissue and is determined by a hand-held tissue compliance meter. DESIGN: Descriptive and blinded time course intervention measurements. SETTING: All measurements were performed on subjects placed in the prone position on flat tables in a laboratory setting. PARTICIPANTS: Forty asymptomatic volunteer subjects. INTERVENTION: Tissue compliance measurements of the T6 and L3 paraspinal regions. MAIN OUTCOME MEASURE: Tissue compliance measurements recorded as millimeters of penetration of a metered probe. RESULTS: Data from this study indicate that paraspinal tissue compliance at the T6 and L3 regions does not change significantly over a 10-min interval, is not effected by the testing intervention and the number of abnormal left/right tissue compliance asymmetries is appropriate (5%) for a normal population of subjects. CONCLUSIONS: These findings tend to support the utility of tissue compliance as a possible tool for the evaluation of paraspinal soft tissue.

Chiropractic↗