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Biomedical subjects

G M Jones

Publications and source records attributed to G M Jones.

At least 19 recordsLinked to original sources
PubMed1992

Detection of antigen specific T lymphocytes by determination of intracellular calcium concentration using flow cytometry.

We present a method for the detection of lymphocytes with specific reactivity to antigens on stimulator cells using flow cytometry. Cultured human T lymphocytes were loaded with the intracellular fluorochrome indo-1 and were mixed with stimulator cells. Using flow cytometry we could detect a specific increase in intracellular calcium in the T lymphocytes as well as conjugation between the T cells and the stimulator cells. Examination of antigen-specific CD4+ and CD8+ T cell clones demonstrated that the vast majority of T cells which were conjugated to antigen-bearing stimulator cells manifested a rapid increase in intracellular calcium. In contrast T cells conjugated to stimulator cells which did not bear specific antigen demonstrated no such increase in calcium. A similar finding was observed when examining polyclonal tumor infiltrating lymphocytes obtained from patients with melanoma. Tumor infiltrating lymphocytes with specific antitumor reactivity demonstrated an increase in intracellular calcium when conjugated to autologous tumor but not to allogeneic melanoma. In contrast to the T cell clones, only a small subpopulation of tumor infiltrating lymphocytes manifested this specific signal upon conjugation with autologous tumor. This suggests that tumor infiltrating lymphocyte cultures contain T cells with varying reactivities to tumor or may also imply heterogeneity in the stimulating tumor cell lines. The method allows for the detection of specific T cells on an individual cell basis in real time. The procedure is not lethal to the cell and sorting and subculturing of reactive T cell populations can be readily performed. The method could also be used to sort stimulator cells based on their ability to elicit an increase in intracellular calcium in selected T cells.

CD4 Antigens↗
PubMed1992

Effects of acute subcutaneous nicotine on attention, information processing and short-term memory in Alzheimer's disease.

This single-blind, placebo controlled study reports on the effects of administering three acute doses of nicotine (0.4, 0.6 and 0.8 mg) subcutaneously to a group of Alzheimer's disease (DAT) patients (n = 22), young adult controls (n = 24), and normal aged controls (n = 24). The study extends our previous findings obtained using smaller groups of subjects. Drug effects were examined on three computerised tests: the first measuring rapid visual information processing, sustained visual attention and reaction time (RVIP task); a delayed response matching to location-order task measuring sustained visual attention and visual short-term memory (DRMLO task); and a finger tapping test measuring simple reaction time (FT task). The critical flicker fusion test (CFF) was used as a measure of perception and the WAIS digit span forwards (DS), of auditory short-term memory. Tests were graded in difficulty, titrated to avoid floor and ceiling effects so that meaningful, direct comparisons between groups could be made. Nicotine significantly improved sustained visual attention (in both RVIP and DRMLO tasks), reaction time (in both FT and RVIP tasks), and perception (CFF task--both ascending and descending thresholds). Nicotine administration did not improve auditory and visual short-term memory. There were no consistent, overall patterns of difference in performance between smokers and non-smokers in the control groups, or between males and females in any group. Despite the absence of change in memory functioning, these results demonstrate that DAT patients have significant perceptual and visual attentional deficits which are improved by nicotine administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

In-line skating: physiological responses and comparison with roller skiing.

The use of in-line skates has become popular in recent years for recreational and conditioning purposes. This investigation evaluated the physiological responses of ten subjects during in-line skating on a flat track with three different in-line skating techniques. The double pole technique demonstrated the greatest economy with oxygen uptake requirements that were approximately 12% lower (p less than 0.05) than conventional skating (without poles) or the V1 skate technique. Across the investigated velocity spectrum of 14.6 to 18.0 km.h-1, individuals with an average fitness level of 40 ml.kg-1.min-1 will achieve exercise intensities of 68-90% of maximum oxygen uptake using the conventional skating and V1 skate techniques on flat terrain. These exercise intensities are appropriate for cardiorespiratory training. However, high fit individuals who are attempting to elicit a cardiorespiratory training effect using in-line skates with rolling resistances similar to those tested may need to perform uphill interval work or skate at higher velocities which may be technically difficult and may be unsafe in some training environments. Comparison of the present data with previously published data on roller skiing demonstrates that differences in physiological responses for the two modes of exercise are the result of differences in rolling resistances between the devices. Measurements of rolling resistance and comparison of the oxygen uptake requirements for double polling on both devices allow for the mechanical efficiency to be estimated at approximately 18% for this mode of locomotion.

Analysis of Variance↗
PubMed1992

Use of an enzyme-linked immunosorbent assay to monitor the control of Staphylococcus aureus mastitis.

Conventional culture methods were used to evaluate the ability of an ELISA to identify Staphylococcus aureus IMI. The test was 96% accurate; sensitivity was 90%, and specificity was 97%. The test was used to screen preserved milk samples rapidly in 10 cooperator herds. Prevalence of IMI was greater than 10% in 6 herds at the first test. Average prevalence of cows scoring +2 (suspect) and +3 (positive) was 12.6%. Prevalence declined during the 12-mo study. Incidence of new IMI decreased from 7.9% at 6 mo to 3.6% at 12 mo. Rinsing teat cup liners with a 25-ppm iodophor or 100-ppm chlorine solution reduced the presence of S. aureus on the milking machine liners by 97%. Elevated scores were correlated with increases in lactation number. Milk antibody concentrations changed quadratically with increasing SCC. The SCC increased as milk antibody concentration increased. In 38 dairy herds, bulk tank antibody tests reflected herd prevalence of S. aureus infection. The average prevalence was 15.0% in 87 herds in which all lactating cows were tested.

Animals↗
PubMed1991

A simple method for fixation of mandibular fractures.

A useful but underused technique of mandibular fixation is described. Its main advantages over more traditional techniques are that it is easily and rapidly applied, suitable for both children and adults, and generally well tolerated. The method can be employed where only a few teeth are present and in displaced fractures together with an intraosseous buccal plate wire. It is a method that can be recommended for use in nonmaxillofacial units and in areas where only basic equipment and facilities are available.

Bone Wires↗
PubMed1991

Trends in the aetiology of maxillofacial fractures in the United Kingdom (1977-1987).

A survey was undertaken to assess changes in the aetiology of maxillofacial fractures in the United Kingdom between 1977 and 1987, using data which had been collected in British departments of Oral and Maxillofacial Surgery. Data were available from units serving 17 million people and included details of patients from a broad spread of rural and urban areas. Analysis of data from the 27 maxillofacial units able to supply details from both 1977 and 1987 showed an overall increase of 20% in numbers of patients with maxillofacial fractures, though a trend towards fewer severe injuries was also a feature over the same period. Numbers of patients injured in road accidents had decreased by 34%, numbers of patients injured in assaults had increased by 47% whilst numbers of patients injured in all other ways had increased by 39%.

Accidental Falls↗
PubMed1991

Effects of technique and pole grip on physiological demands of roller skiing on level terrain.

This study evaluated the physiological responses to roller skiing with three different techniques, and compared the physiological responses during roller skiing with a standard pole grip and an innovative "anatomical" pole grip. Data were collected on ten experienced cross-country ski racers while roller skiing with the double pole, V1 skate, and kick double pole techniques on a flat track at mean (+/- SD) velocities of 14.6 +/- 0.2, 16.4 +/- 0.3, and 18.0 +/- 0.4 km.h-1. The kick double pole technique induced the highest (p less than 0.05) oxygen uptakes, heart rates, and ventilations. The double pole technique elicited the lowest (p less than 0.05) oxygen uptakes, and the V1 skate technique elicited the lowest (p less than 0.05) perceived effort and respiratory exchange ratios. Comparison of the two pole grips showed no differences in the physiological responses and perceived effort. While the V1 skate technique is not the most economical roller skiing technique on flat ground, the lower associated perceived effort and respiratory exchange ratios may at least partially account for the general preference of cross-country ski racers to use the V1 skating technique rather than the double pole technique on flat terrain.

Adult↗
PubMed1990

Mapping the fine specificity of a cytolytic T cell response to HIV-1 nef protein.

Epitope mapping of a MHC class I-restricted cytotoxic T cell response to nef, a regulatory protein of HIV, was performed with fresh PBMC from HIV-seropositive donors and target cells pulsed with a panel of overlapping peptides of the nef protein. These nef-specific CTL recognized a synthetic peptide of 10 residues derived from a nonamphipathic, highly conserved region of the nef protein in association with the HLA A3.1 molecule. Using human cell transfectants expressing mutations of the A3 molecule, we demonstrated that the amino acid at position 152 of the A3.1 molecule appears to be critical for detection of this response. Thus, rapid analysis of the epitopes of HIV proteins stimulating CTL responses can be achieved using a combination of fresh donor PBMC and target cells pulsed with synthesized peptides.

Amino Acid Sequence↗
PubMed1979

Visible light-induced DNA crosslinks in cultured mouse and human cells.

Cool-white fluorescent light induces crosslinks in DNA when proliferating cells are exposed at 37 degrees C for 20 h to 4.6 J/m2/s in culture medium supplemented with fetal bovine serum. Using the Kohn alkaline elution technique, we now find that: 1. Increased light intensity increases DNA crosslinks. 2. The crosslinking is medium-mediated. 3. Oxygen enhances the crosslinking. 4. The extent of crosslinking is decreased at high cell density. 5. The crosslinks can be removed by digestion with proteinase K (0.02 to 0.50 mg/ml). 6. Human cell lines including those derived from adult prostate, fetal lung (IMR-90) and mixed fetal tissues are susceptible to light-induced crosslinks. 7. Crosslinkage is not decreased by addition of catalase to the medium and the effective wavelength is probably between 450 nm and 490 nm. From these results we conclude that the mechanism of light-induced crosslinks differs from that of light-induced chromatid breaks and that the major lesion observed is protein-DNA cross-linkage rather than DNA strand breaks.

Animals↗
PubMed1979

Tibialis anterior response to sudden ankle displacements in normal and Parkinsonian subjects.

It is well known that in Parkinsonian subjects with akinesia, reaction times are increased but reflex latencies remain normal. We have attempted to use this knowledge to distinguish between 'reflex' and 'voluntary' components of the electromyographic (EMG) response to ankle displacement. The EMG and torque responses of tibialis anterior (TA) to randomly applied servo-controlled plantar-flexing displacements of the ankle with and without the subject's intentional opposition were examined in 9 Parkinsonian and 9 age-matched normal humans. To obtain a measure of akinesia, the response latency to a visual stimulus was subsequently measured in the same subjects. Three principal findings emerged. (1) The intermediate latency EMG component (PSR) of the response evoked by ankle displacement with the subject instructed to relax was more regularly evoked and of lower threshold in Parkinsonians than in normals. This finding corresponds to the enlarged M2 component in upper limb muscles. However, the facilitation of PSR was not found to be associated with an increase in torque. In fact, the patients did not exhibit more stiffness than normals under our experimental conditions. (2) Mean latency estimate of the PSR was indistinguishable between Parkinsonians and normals. This finding puts the PSR in the nature of a reflex. Indeed, in accordance with reflex behaviour which is proportional to input characteristics, its area increased linearly with increase in the magnitude of displacement velocity. (3) In contrast, the 'late' EMG response (FSR) evoked by opposing sudden ankle displacement exhibited a significantly longer latency in 6 out of 8 Parkinsonians than normals. In the same patients, the EMG response latency to a visual signal was similarly increased. The delay of FSR in akinesia patients thus argued against its being a stereotyped reflex. The result is discussed with reference to the recent finding that preprogrammed responses are delayed in Parkinsonians.

Adult↗
PubMed1979

Soluble cyclic AMP-dependent protein kinases from chick kidney. Effects of dilution and non-protein inhibitors.

Cyclic AMP-dependent protein kinases prepared from crude cytosols of chick kidney, rat kidney and rat liver were found on dilution to exhibit complex kinetics. Dilution of the cytosols appears to increase the state of activation of the enzymes. This effect was due to the presence of inhibitory agents in the cytosol which had a greater inhibitory effect on the cyclic AMP-dependent than on the cyclic AMP-independent enzyme. Two types of inhibitory activity were found by column chromatography, one resistant to trichloroacetic acid precipitation and boiling but affected by trypsin digestion and the other resistant to boiling and trypsin digestion but precipitated by trichloroacetic acid. Inhibitory activity corresponding to the former characteristics has been described previously but the presence of additional soluble inhibitory agents in the cytosol has not been documented. The complete characterisation of this previously undescribed inhibitory activity requires further investigation. The relevance of such cytosolic inhibitory activity to the interpretation of states of activation of protein kinase enzymes is discussed.

Adenosine↗