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Biomedical subjects

D Wilkinson

Publications and source records attributed to D Wilkinson.

At least 253 records · Page 14Linked to original sources
PubMed1992

Mechanisms contributing to ozone-induced bronchial hyperreactivity in guinea-pigs.

The effect of ozone (3 ppm, 15-120 min) on bronchial reactivity in the guinea-pig was studied. Ozone induced marked (6-250-fold) bronchial hyperreactivity (BHR) to a range of inhaled, but not intravenous bronchoconstrictors. The degree of BHR was related to the duration of prior ozone exposure. The glutathione redox status was shifted to a more oxidized state in lung after 120 min ozone treatment, although no changes were found in the energy status of lung tissue, as judged by the concentrations of adenosine phosphates. Ascorbic acid pretreatment prevented BHR induced by 30 min ozone exposure. Neutral endopeptidase inhibitors elicited BHR to both substance P and histamine, but did not further enhance bronchoconstriction to substance P after ozone exposure for 120 min. Neither mepyramine, fentanyl, indomethacin nor a 5-lipoxygenase inhibitor (BW B70C), given prior to ozone exposure prevented the induction of BHR to histamine. Atropine or bilateral vagotomy reduced BHR after a 120-min, but not 30-min exposure to ozone. We conclude that in the guinea-pig, ozone induces non-specific, route-dependent BHR by oxidative injury, reducing airway NEP activity and enhancing the cholinergic and peptidergic component to bronchoconstriction. Neither cyclooxygenase nor 5-lipoxygenase products appear to play a role in ozone-induced BHR in this animal model.

Adenine Nucleotides↗
PubMed1991

A distinct Hox code for the branchial region of the vertebrate head.

The branchial region of the vertebrate head forms through complex interactions involving rhombomeric segments, neural crest and branchial arches. It is though that aspects of their patterning mechanisms are linked and involve Hox-2 genes, whose overlapping and spatially restricted expression domains represent a combinatorial code for generating regional diversity. Vertebrates possess four Hox clusters of Antennapedia class homeobox genes, related to each other by duplication and divergence from a common ancestral complex. In consequence, at equivalent positions in different clusters there are highly related genes known as subfamilies or paralogous groups. As Hox-2 genes cannot fully account for patterning individual rhombomeres, we investigated whether offsets in expression limits of paralogous genes could account for the generation of regional diversity. We report here that, with the exception of the labial subfamily, paralogues show identical expression limits in rhombomeres, cranial ganglia and branchial arches, providing a combinatorial Hox code for the branchial region that seems to be different in organization to that of the trunk.

Alleles↗
PubMed1991

Perinatal mortality--an intervention study.

Perinatal mortality is high in rural hospitals in South Africa. In part this is due to less than optimal care. This study determined the perinatal mortality experienced by a rural hospital and its clinics. Avoidable causes of death are described and various intervention strategies that effectively and rapidly prevented such deaths, reducing perinatal mortality by one-third, are outlined.

Hospitals, Rural↗
PubMed1991

An analysis of synthetic peptide restriction by HLA-DR alleles in T cells from human subjects, naturally sensitized by Streptococcus mutans.

T cells from most human subjects show significant in vitro proliferative responses to a 185-kDa surface Ag from Streptococcus mutans as well as to synthetic peptides derived from the sequence of a Mr 3800 streptococcal Ag. T cells from subjects expressing each of the alleles from DR1 to DR7 responded to synthetic peptides of 17 or 21 amino acid residues. Furthermore, inhibition studies with mAb to HLA class I and class II Ag showed that the DR Ag was a restriction molecule for the proliferative responses. Mouse L cells transfected with DR1, DR2, DR4, DR5, and DR7 were used to confirm the permissive nature of the responses. An analysis of the fine specificity of the responses showed that the minimum peptides capable of stimulating T cells from subjects with different DR types varied by one or two residues. For DR2 and DR3 the shortest peptide was residues 6-15, an additional serine (residue 5) was required for DR1 and DR7 and an aspartic acid (residue 4) for DR4, DR5, and DR6. Successful oral-mucosal bacterial colonisation in humans, by a largely commensal Streptococcus, might be associated with the permissive nature of the HLA-DR restriction of the response to a major streptococcal cell surface peptide. The peptide recognised in association with the HLA-DR molecule may induce an immune response that prevents central entry of the organism from the peripheral mucosal site.

Alleles↗
PubMed1991

Cancer promotion in a mouse-skin model by a 60-Hz magnetic field: II. Tumor development and immune response.

This paper describes preliminary findings on the influence of 60-Hz (2-mT) magnetic fields on tumor promotion and co-promotion in the skins of mice. The effect of magnetic fields on natural killer (NK) cell activity in spleen and blood was also examined. Groups of 32 juvenile female mice were exposed to the magnetic field as described in part I. The dorsal skin of all animals was treated with a subthreshold dose of the carcinogen 7,12-dimethyl-benz(a)anthracene (DMBA). One week after the treatment, two groups were sham exposed (group A) or field exposed at 2 mT (group B) 6 h/day for 21 weeks, to test whether the field would act as a tumor promoter. No tumors developed in these two groups of mice. To test whether the magnetic field would modify tumor development by directly affecting tumor growth or by suppressing immune surveillance, two additional groups of mice were treated weekly with the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA) and then either sham exposed (group C) or field exposed (group D). The time to appearance of tumors was shorter (but not statistically so) in the group exposed to magnetic fields and TPA. Some differences in NK cell activity and spleen size were observed between the sham- and field-exposed groups.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

Allorecognition of HLA-DR and -DQ transfectants by human CD45RA and CD45R0 CD4 T cells: repertoire analysis and activation requirements.

We have investigated the requirements for allogeneic stimulation of human CD4 T cells using HLA class II products expressed on various cellular backgrounds. Human (class II-negative RJ2.2.5 mutant) B cell lines transfected with HLA-DR or -DQ cDNA clones were efficient stimulators for highly purified CD4 T cells. HLA-DR-transfected mouse L cells or IFN-gamma-induced human fibroblasts, although able to function as accessory cells for T cell responses to the mitogen PHA, failed to stimulate strong T cell alloresponses. On the basis of these observations, we have employed class II transfectants to address the following questions: (a) do CD45RA and CD45R0 subpopulations differ in their allogeneic activation requirements, (b) are these subpopulations skewed in their recognition of HLA-DQ vs. HLA-DR in a manner which might support the concept that CD45RA T cells are involved in HLA-DQ-restricted suppressor inducer functions and (c) by using transfectants expressing individual HLA-DR or -DQ heterodimers in combination with limiting dilution analysis, can one for the first time obtain estimates of precursor frequencies for allogeneic cells recognizing each of these class II isotypes? Our results show that CD45RA and CD45R0 T cells respond comparably to optimal numbers of stimulator cells. However, when CD45RA and CD45R0 T cell populations depleted of endogenous accessory cells were cultured with limiting numbers of stimulator cells, CD45R0 cells generally responded more strongly, consistent with the elevated levels of various adhesion molecules known to be expressed by this population. Further, we found a similar representation of responses to HLA-DR and -DQ antigens among populations expressing CD45RA and CD45R0 isoforms. Finally, the precursor frequencies of allogeneic CD4 T cells responding to particular HLA-DR alleles were higher than to -DQ, but only by a factor of about 1.6, indicating that HLA-DQ recognition may occur more frequently than implied from previous antibody blocking studies.

Antibodies, Monoclonal↗
PubMed1991

Comparing subjective and objective assessments of the severity of vibration induced white finger.

The present staging of the disease severity of vibration induced white finger (VWF) is based on the patients' symptoms. Forty patients, with a history of VWF, with disease severity stage III or stage IV, on the Taylor-Pelmear scale, were investigated. Total, reactive hyperaemic blood flow to the hands was measured using an isotope limb blood flow (ILBF) technique. Skin blood flow patterns were assessed using a cold provocation test, followed by thermographic assessment of hand rewarming. Thermographic abnormalities were detected in 39 patients (97%). Decreased post-occlusive, reactive hyperaemic blood flow occurred in 29 patients (73%). There was no difference in skin blood flow patterns or in total hand blood flow between the stage III and stage IV groups. Reduction of postocclusive reactive hyperaemic blood flow may be indicative of occlusive lesions of the digital vessels. We conclude that the classification of the severity of VWF using subjective assessment, needs to be augmented by objective evidence of altered blood flow.

Adult↗
PubMed1991

Radionuclide limb blood flow in peripheral vascular disease: a review of 1100 measurements.

Radionuclide limb blood flow measurements using 99Tcm-labelled human serum albumin and a gamma camera have been performed on normal volunteers and on patients with suspected or confirmed peripheral arterial disease. The normal range of flow was found to be 10.0-22.3 ml per 100 ml tissue per min. Flow in the symptomatic legs of patients with arterial disease varied from 9.0 ml per 100 ml tissue per min in mild claudication to less than 1.0 ml per 100 ml tissue per min in rest pain. The technique has been used as an initial screening procedure, to resolve diagnostic problems, to measure objectively the treatment response and to assess patients with critical ischaemia. The results of 1100 measurements are reported and the clinical utility in routine vascular surgical practice is discussed.

Adult↗
PubMed1991

The effects of a 5-HT2 receptor antagonist (ICI 169,369) on changes in waking EEG, pupillary responses and state of arousal in human volunteers.

1. ICI 169,369 (2-(2-dimethylamino ethylthio)-3-phenyl quinoline) is a potent selective competitive antagonist of the 5-HT2 receptor in animal models. Effects of ICI 169,369 as single oral doses (80 and 120 mg) separated by 1 week, on the power spectrum of waking EEG, dark adapted pupil responses and sedation score, were studied in a double-blind, placebo controlled, randomised cross over within subject comparison, in six healthy male volunteers. 2. Pupillary responses were measured using a portable infrared pupillometer following 15 min dark adaptation, assessing resting vertical pupil diameter (RPD), light constricted diameter (MPD) and recovered final diameter (FPD) at the end of a 3 s measurement cycle. 3. Both doses of ICI 169,369 produced a mean 36% (range 10-54%) decrease in log 10 power of the waking EEG alpha activity with eyes closed (P less than 0.02), and mean 38% (range 2-86%) increase in theta activity at 2 h compared with placebo. 4. Both 80 and 120 mg doses of ICI 169,369 reduced RPD by approximately 30% from a predose value of 6.25 mm (+/- 0.87; 95% CI) and from placebo values 6.41 mm (+/- 1.06) and 7.48 mm (+/- 1.49) at 3 and 5 h after dosing. MPD was reduced by 50% with the 120 mg dose at 5 h after dosing (placebo 5.2 mm; ICI 169,369 2.7 mm; P less than 0.05). FPD was significantly reduced (P less than 0.01) by both doses at 3 h after dosing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗