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Biomedical subjects

L Thomson

Publications and source records attributed to L Thomson.

At least 37 records · Page 2Linked to original sources
PubMed1991

Transformation of a partial nopaline synthase gene into tobacco suppresses the expression of a resident wild-type gene.

A portion of the nopaline synthase gene under the control of the cauliflower mosaic virus 35S promoter was used to transform a tobacco plant that had previously been transformed with a wild-type nopaline synthase (nos) gene. Unexpectedly, in all nine primary transformants tested the wild-type nos expression was virtually completely suppressed. In contrast, plants transformed with the control vector DNA, which differed only in the absence of the partial nos gene, did not show any inhibition of nos expression. Progeny plants were analyzed for the stability of the gene-silencing phenotype. All of the progeny that carried both the wild-type and partial nos genes had no detectable nopaline synthase activity. In addition, wild-type nos mRNA could not be detected in these plants. In most plants in which the wild-type gene was segregated away from the partial nos gene, wild-type levels of activity were detected. Although DNA methylation has been shown to be correlated with a decrease in promoter activity in plants, none of the progeny appeared to carry a methylated nos promoter. The underlying mechanism causing this gene suppression phenomenon is unclear at this time.

Journal Article↗
PubMed1991

Cytochrome c-catalyzed oxidation of organic molecules by hydrogen peroxide.

Cytochrome c catalyzed the oxidation of various electron donors in the presence of hydrogen peroxide (H2O2), including 2-2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 4-aminoantipyrine (4-AP), and luminol. With ferrocytochrome c, oxidation reactions were preceded by a lag phase corresponding to the H2O2-mediated oxidation of cytochrome c to the ferric state; no lag phase was observed with ferricytochrome c. However, brief preincubation of ferricytochrome c with H2O2 increased its catalytic activity prior to progressive inactivation and degradation. Superoxide (O2-) and hydroxyl radical (.OH) were not involved in this catalytic activity, since it was not sensitive to superoxide dismutase (SOD) or mannitol. Free iron released from the heme did not play a role in the oxidative reactions as concluded from the lack of effect of diethylenetriaminepentaacetic acid. Uric acid and tryptophan inhibited the oxidation of ABTS, stimulation of luminol chemiluminescence, and inactivation of cytochrome c. Our results are consistent with an initial activation of cytochrome c by H2O2 to a catalytically more active species in which a high oxidation state of an oxo-heme complex mediates the oxidative reactions. The lack of SOD effect on cytochrome c-catalyzed, H2O2-dependent luminol chemiluminescence supports a mechanism of chemiexcitation whereby a luminol endoperoxide is formed by direct reaction of H2O2 with an oxidized luminol molecule, either luminol radical or luminol diazoquinone.

Ampyrone↗
PubMed1991

Toward a quantitative characterization of patient-therapist communication.

The efficacy of psychotherapy, in its many and varied forms, is one of the most intensely contested issues in clinical practice. Though many theories have been advanced, quantitative evidence in their defense is limited. This contribution is directed to relatively unambitious objectives. Rather than establish yet another qualitative theory of psychotherapeutic practice, we wish to contribute to the construction of research methodologies that can quantitatively characterize the dynamic patterns of patient-therapist communication. It is hoped that a theoretical understanding of psychotherapy might eventually emerge naturally from a growing body of quantitative data.

Communication↗
PubMed1991

Menstrual symptoms in women with pelvic endometriosis.

OBJECTIVE: To investigate menstrual symptoms in relation to pelvic pathology. DESIGN: A prospective questionnaire-based study. SETTING: Aberdeen Royal Infirmary, Scotland. SUBJECTS: 1250 questionnaires were sent out prior to planned admission and 1200 women (96%) brought the completed questionnaires. They comprised 598 women undergoing laparoscopic sterilization, 312 having laparoscopy because of infertility, 156 having laparoscopy because of chronic pelvic pain and 134 women undergoing abdominal hysterectomy for dysfunctional uterine bleeding. MAIN OUTCOME MEASURES: The occurrence of dysmenorrhoea, menorrhagia, menstrual regularity, premenstrual spotting, deep dyspareunia and pelvic pain in women with either endometriosis and post infective pelvic adhesions or a normal pelvis. RESULTS: Menorrhagia, menstrual irregularity and premenstrual spotting occurred with equal frequency in all groups. Deep dyspareunia, pain after intercourse and recurrent pain unrelated to menstruation or coitus was more common in women with endometriosis and those with post infective pelvic adhesions than in those with a normal pelvis. Dysmenorrhoea appears to be more prevalent among women having endometriosis. CONCLUSIONS: Menstrual symptoms, while raising a high index of suspicion for endometriosis, are not entirely reliable as indicators of disease. Dysmenorrhoea is the most common reported symptom in endometriosis sufferers. Diagnostic laparoscopy should be considered before institution of treatment in women complaining of pelvic pain and menstrual symptoms.

Dysmenorrhea↗
PubMed1990

Luminol chemiluminescence using xanthine and hypoxanthine as xanthine oxidase substrates.

Luminol chemiluminescence induced by the xanthine or hypoxanthine-O2-xanthine oxidase system is analyzed and compared. Characteristics of the light emission curves were examined considering the conventional reaction scheme for the oxidation of both substrates in the presence of xanthine oxidase. The ratio of the areas of the rate of superoxide production during substrate oxidation to uric acid. The O2-. to uric acid ratio for each substrate can account for differences in xanthine and hypoxanthine-supported light emission, since uric acid is a strong inhibitor of O2-.-dependent luminol chemiluminescence. These results are consistent with a free radical scavenging role for uric acid. A similar but weaker scavenging effect of xanthine may also contribute to the observed differences in chemiluminescent yields between both substrates.

Animals↗
PubMed1988

PRUFILE: a clinical and laboratory database for the genetics centre.

The growing complexity and volume of workload in a Clinical Genetics Centre can rapidly swamp the available clerical facilities. The multiuser database described gives facilities not only for administrative control and documentation but also for the production of data for clinical and scientific analysis. The close link between clinical and laboratory databases gives great versatility and easy expansion as new tests and disciplines are applied to clinical genetic problems.

Clinical Laboratory Information Systems↗