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Biomedical subjects

J H Clarke

Publications and source records attributed to J H Clarke.

At least 19 recordsLinked to original sources
PubMed1992

Oxidation of a specific methionine in thrombomodulin by activated neutrophil products blocks cofactor activity. A potential rapid mechanism for modulation of coagulation.

Endothelial thrombomodulin (TM) plays a critical role in hemostasis as a cofactor for thrombin-dependent formation of activated protein C, a potent anticoagulant. Chloramine T, H2O2, or hypochlorous acid generated from H2O2 by myeloperoxidase rapidly destroy 75-90% of TM cofactor activity. Activated PMN, the primary in vivo source of biological oxidants, also rapidly inactivate TM. Oxidation of TM by PMN is inhibited by diphenylene iodonium, an inhibitor of NADPH oxidase. Both Met291 and Met388 in the six epidermal growth factor-like repeat domain are oxidized; however, only substitutions of Met388 lead to TM analogues that resist oxidative inactivation. We suggest that in inflamed tissues activated PMN may inactivate TM and demonstrate further evidence of the interaction between the inflammatory process and induction of thrombotic potential.

Adult↗
PubMed1991

Multiple xylanases of Cellulomonas fimi are encoded by distinct genes.

Cellulomonas fimi genomic DNA encoding xylanase activity has been cloned and expressed in Escherichia coli. As judged by DNA hybridization and restriction analysis, twelve xylanase-positive clones carried a minimum of four different xylanase (xyn) genes. The encoded enzymes were devoid of cellulase activity but three of the four bound to Avicel.

Cellulase↗
PubMed1991

Suggestive hypnotherapy for nocturnal bruxism: a pilot study.

Although one can find many case reports of hypnotherapy for bruxism, there is a paucity of scientific research on the subject. This study describes the use of suggestive hypnotherapy and looks at its effectiveness in treating bruxism. Eight subjects who reported bruxism with symptoms such as muscle pain and complaints of bruxing noise from sleep partners were accepted into the study. An objective baseline of the bruxing was established using a portable electromyogram (EMG) detector attached over the masseter muscle during sleep. Hypnotherapy was then employed. Both self-reports and posttreatment EMG recordings were used to evaluate the hypnotherapy. Long-term effects were evaluated by self-reports only. The bruxers showed a significant decrease in EMG activity; they also experienced less facial pain and their partners reported less bruxing noise immediately following treatment and after 4 to 36 months.

Adult↗
PubMed1990

Endoglucanase E, produced at high level in Escherichia coli as a lacZ' fusion protein, is part of the Clostridium thermocellum cellulosome.

The Clostridium thermocellum celE gene was expressed at high level in Escherichia coli TG1 when placed under the transcriptional and translational control of lacZ' in pUC18; in the presence of a multicopy plasmid (pNM52) containing the lacIq gene, expression of full-length and truncated forms of celE was regulated by isopropyl-beta-D-thiogalactopyranoside. Catalytically active endoglucanase E (EGE) produced by E. coli was subject to proteolytic processing. The main protein species produced from full-length and truncated forms of celE was around 40 kDa in size and had an N-terminal amino acid sequence corresponding to that derived for mature EGE from the nucleotide sequence; in addition, larger species of about 75 kDa, presumably corresponding to full-size EGE, were produced by E. coli containing the full-length celE gene. Even after removal of the signal peptide sequence, EGE produced by E. coli was secreted into the periplasm. Up to 157 bp could be deleted from the 5' end of the celE gene without affecting the catalytic activity of EGE produced by E. coli. A polypeptide of Mr 86 kDa, immunoreactive with anti-EGE antiserum, was demonstrated in the high-molecular-weight, cellulose-binding multiprotein aggregate recoverable from C. thermocellum culture supernatant.

Amino Acid Sequence↗
PubMed1989

Some observations on contamination of animal cell cultures by the fungus Aspergillus fumigatus and suggested control measures.

The fungus Aspergillus fumigatus Fres. was found to be a most troublesome contaminant of animal cell cultures (hybridomas). Conditions in a carbon dioxide incubator (37 degrees C; about 100% relative humidity) are very favourable for its growth. Unlike bacteria it spreads by means of passively-released aerial spores and of filaments (mycelium) growing within and between wells of tissue culture vessels. It has the potential to cause mycotic infections and allergic reactions in laboratory workers. Various measures for controlling it in the tissue culture laboratory are briefly discussed, such as use of antifungal antibiotics, fumigation with formaldehyde and heat sterilisation of the incubator.

Amphotericin B↗
PubMed1986

Labeling of functionally sensitive sulfhydryl-containing domains of acetylcholine receptor from Torpedo californica membranes.

N-(1-Pyrene)maleimide, a fluorescent, lipophilic, alkylating agent, was used as a probe for the nicotinic acetylcholine receptor (AChR). Preincubation with N-(1-pyrene)maleimide under nonreducing conditions inhibits agonist-induced cation permeability of AChR-enriched membranes. This inhibition is dependent on the concentration of N-(1-pyrene)maleimide used. This correlation was also exhibited by resonance energy transfer of tryptophan fluorescence to N-(1-pyrene)maleimide and by the labeling stoichiometries. However, agonist-induced desensitization, as based on the time-dependent inhibition of alpha-bungarotoxin binding upon preincubation with the agonist carbamylcholine, was unaffected by N-(1-pyrene)maleimide. Alkylation of the AChR by N-(1-pyrene)maleimide is pH-dependent with an apparent pKa of 7.5 and is unaffected by preincubation with carbamylcholine, alpha-bungarotoxin, tubocurarine, or decamethonium. Preincubation with a 25-fold molar excess of N-ethylmaleimide partially protects against N-(1-pyrene)maleimide, yet simultaneous incubation with an equimolar concentration does not protect. In contrast, simultaneous incubation with equimolar concentrations of phenylmaleimide or naphthylmaleimide inhibited N-(1-pyrene)maleimide alkylation by 52 and 67%, respectively. Each AChR subunit is labeled by N-(1-pyrene)maleimide. Prior alkylation with N-ethylmaleimide does not alter the labeling profile but lowers the amount of labeling of all subunits. Reductive methylation of membranes under conditions which dimethylate all or most protein amino groups does not inhibit alkylation by N-(1-pyrene)maleimide. The above results, as well as amino acid analysis of N-(1-pyrene)maleimide-alkylated receptor, indicate that a homologous class of cysteines, which reside in each subunit within the AChR domain embedded in the membrane, are involved in the reaction with N-(1-pyrene)maleimide.

Alkylation↗
PubMed1986

Dental pathology of prehistoric residents of Oregon.

Dentitions of 208 prehistoric skeletal specimens from five geographic regions of Oregon were studied to describe their dental status. Comparisons were made of the incidence of specific pathologies among regions and between jaws. Maxillary premortem tooth losses were significantly higher than mandibular tooth loss. A relatively high caries incidence occurs in samples from the Willamette Valley and Klamath Basin, where plant foods were used aboriginally to a significant extent. A high frequency of abscesses was recorded in the Klamath Basin and the Lower Columbia River sample, which also showed the highest levels of attrition. Each of the five subsamples shows patterns of dental pathology consistent with former use of natural resources.

Dentition↗
PubMed1986

Counseling principles for more effective patient education.

Patients often fail to progress in preventive dentistry behavior. Greater success will be realized if the dentist uses a counseling approach based on basic theoretical principles of psychological counseling. Humanistic and behavioral counseling theories are adaptable to the dental environment. An approach modeled on the exploration, understanding, and action phases of counseling is practicable for the clinical dentist.

Behavior↗
PubMed1986

Reducing adolescent smoking: a comparison of peer-led, teacher-led, and expert interventions.

To test the effectiveness of a psychosocial strategy of smoking deterence on seventh grade students, the School Health Education Development project implemented peer-led, teacher-led, and expert-led interventions in six Vermont schools. Four additional schools served as control groups. The teacher-led approach reduced the rate of smoking onset and the intention to smoke in the future among highly vulnerable females but not among males. The peer-led approach reduced the behavioral intention to smoke for both sexes but did not affect current smoking behavior. The expert-led approach did not produce favorable effects. Both the peer-led and teacher-led interventions had positive, though not significant, effects on student perception of locus of control. In the control schools, females experienced higher levels of smoking onset than males. Generally, the study points toward further development of a teacher-led approach to smoking deterence based on the theory of adolescent psychosocial development and the principle of continuous reinforcement.

Adolescent↗
PubMed1977

The therapeutic effect of taking a patient's history by computer.

Sixty young women who presented at a general-practice health centre had their medical and social history taken by a computer before having an interview with the doctor. The average length of the automated interview was 90 minutes for the 54 patients who completed the programme, during which an average of 211 questions were answered. The patients found this method acceptable and we think that one of the main reasons for this was that the computer programme was so designed that the patients felt that the doctor was involved throughout.The computer/patient interview also appeared to have therapeutic benefits, and the computer's summary of the history was a sensitive indicator of those topics about which the patient was most concerned. This combination enabled the doctor to communicate more quickly and in greater depth in the time available. In effect, the time which the doctor could spend with the patient was magnified.We suggest that the benefits of this system for taking a history from a patient, of which one is the fact that any language or combination of languages can be used, could be extended to all classes of society.

Computers↗