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Biomedical subjects

J H Gibbs

Publications and source records attributed to J H Gibbs.

At least 37 records · Page 2Linked to original sources
PubMed1983

Effect of anaesthesia and surgery on the pre-S-phase cell cycle kinetics of mitogen-stimulated lymphocytes of previously healthy people.

The influence of general anaesthesia, and of operative surgery, on immune responsiveness was studied in blood obtained from 26 women undergoing laparoscopic sterilization (minor operation group) and in 14 women undergoing abdominal hysterectomy (major operation group). Since immunity depends ultimately on clonal expansion of lymphocytes, the growth potential of peripheral blood lymphocytes was studied in tissue culture by mitogen stimulation. There was no evidence of any change in either the number of responding cells (those that have left the resting G0-phase and responded to mitogen stimulation by entering the G1-phase of the first cycle of growth) or in the rate at which cells grow in volume during the period of study. It was concluded that there was no evidence that anaesthesia, or surgery, impaired this aspect of the immune response in our patients, but the design of the experiments does not allow comment on other aspects of the immune response such as antigen presentation, immunoregulation and effector mechanisms, which are superimposed on the basic clonal expansion mechanisms studied in this investigation. Incidentally, we noted that the standard method for isolation of lymphocytes from peripheral blood frequently yielded highly contaminated preparations: if this fallacy was not appreciated, tests with contaminated lymphocytes could be misinterpreted as showing depression.

Adult↗
PubMed1983

Some tetracycline drugs suppress mitogen-stimulated lymphocyte growth but others do not.

Eight tetracycline drugs were tested for inhibitory effect on phytohaemagglutinin (PHA) stimulated growth (measured by [3H]-TdR uptake) of peripheral blood mononuclear cells: at least 26 normal subjects were tested with each drug. Doxycycline reduced DNA synthesis appreciably at concentrations within and just above the therapeutic range of blood levels: it was the most potent inhibitor, but demeclocycline, methacycline and minocycline had similar, if less potent, effects. Tetracycline, oxytetracycline, chlortetracycline and clomocycline did not inhibit DNA synthesis of 3-day cultures even at concentrations five to ten times greater than the therapeutic blood level. Volume spectroscopy measurements showed that none of the eight tetracycline drugs interfered with the recruitment of cells into G1-phase growth of the first cell cycle after PHA stimulation.

Adult↗
PubMed1983

In vitro effects of doxycycline and tetracycline on mitogen stimulated lymphocyte growth.

Doxycycline and tetracycline were tested for inhibitory effect on PHA stimulated growth (measured by [3H]-TdR uptake) of peripheral blood mononuclear cells from 26 normal subjects. Doxycycline reduced DNA synthesis appreciably at concentrations within and just above the therapeutic range of blood levels: tetracycline did not inhibit DNA synthesis of 3 day cultures even at concentrations five-10 times greater than the therapeutic blood level. Detailed studies on the action of doxycycline by volume spectroscopy and RNA flow cytofluorimetry indicated that this drug did not influence the recruitment of cells into the first G1-phase. Cell counts, DNA flow cytofluorimetry and autoradiography after pulsed exposure to [3H]-TdR showed a reduction in the numbers of growing cells in 2 and 3 day cultures in the presence of doxycycline compared with those containing tetracycline at the same concentration.

Adult↗
PubMed1982

Mechanisms of phytohaemagglutinin (PHA) stimulation of normal human lymphocytes: 'trigger' 'push' or both?

The growth in volume of human peripheral blood lymphocytes after stimulation with various concentrations of PHA was measured with an electronic particle counter. The percentage of growing cells and averaged values describing their growth rates during the elapsed period of culture were estimated by fitting to the observed data the volume distributions derived from a mathematical model. With sub-optimal doses, the percentage of cells stimulated , and their incremental growth rate, increased with increasing dose of PHA, but the time-course of recruitment into the G1-phase was similar with all PHA concentrations studied. The results provide strong support for the 'trigger' hypothesis that there is a distribution of stimulation thresholds within the lymphocyte population: consequently, increasing mitogen concentration will be expected to result in increased numbers of responding cells within the suboptimal concentration range.

Adult↗
PubMed1982

Mitogen stimulation of peripheral blood lymphocytes of duodenal ulcer patients during treatment with cimetidine or ranitidine.

During a double-blind randomised clinical trial of cimetidine and ranitidine in the management of duodenal ulcer, the response of patients' peripheral blood lymphocytes to optimal mitogenic stimulation in vitro has been measured. Treatment with cimetidine, but not ranitidine, was associated with a significant increase in the proportion of peripheral blood lymphocytes responding to this optimal mitogenic stimulation. We conclude that these effects of cimetidine may not be mediated at classical histamine H2-receptors.

Adult↗
PubMed1982

Mitogen-stimulated lymphocyte growth and chronic uraemia.

Lymphocytes were isolated from venous blood by the Böyum method from 36 patients with chronic renal failure: the preparations were more frequently and more heavily contaminated with non-lymphoid cells than the equivalent preparations from normal controls. Volume spectroscopy measurements showed that, in the samples without gross contamination, lymphocytes from uraemic subjects react to mitogen stimulation with normal pre-S-phase cell-cycle kinetics. In other experiments, plasma from uraemic patients was shown to be more potent than serum in inhibiting the growth of mitogen-stimulated lymphocytes from normal subjects, both in the first G1-phase and in replicative growth. Thus humoral suppression appears to be more important than a cellular defect in explaining the depressed responses of uraemic blood to mitogen stimulation.

Cell Cycle↗
PubMed1981

Serum inhibitory factor in lepromatous leprosy: its effect on the pre-S-phase cell-cycle kinetics of mitogen-stimulated normal human lymphocytes.

The sera of ten Egyptian man with long-standing lepromatous leprosy (LL) (mean duration 17.4 years) that had failed to respond to dapsone treatment were shown to inhibit mitogen stimulation responses of normal human lymphocytes. When first tested, the sera partly inhibited the response to phytohaemagglutinin (PHA) and pokeweed mitogen and virtually abolished that to concanavalin A (Con A): after repeated freezing and thawing, the Con A inhibition had disappeared, whereas the PHA response was still partly inhibited. The inhibitory serum factor(s) had similar actions on lymphocytes from each of six normal donors. Although the sera varied in potency, they showed similar dose-response curves when tested against lymphocytes from a single donor. The principal action of the sera was to reduce the number of cells responding to mitogen, without modifying the kinetics of recruitment or rate of volume growth during G1-phase in those cells that were unaffected by the inhibitory substances(s). Study of PHA dose-response curves and of the effect of delayed addition of LL serum suggested that the serum factor(s) act by diminishing the responsiveness of the cells, rather than by reducing the concentrations of free mitogen or by blocking cell membrane mitogen receptors. The serum from one apparently healthy attendant, who had nursed leprosy patients for 30 years but who did not have leprosy or other chronic infective disease, inhibited completely stimulation by all three mitogens in a manner different from that of LL sera. Serum from the other 13 control patients did not modify the response of normal lymphocytes to stimulation by any of the three mitogens studied. It was concluded that the inhibitory factor(s) in the serum of patients with LL were a consequence of the disease and not of the environment in which the patients lived. Microscopy confirmed that the techniques used for recovery of the cultured cells did not introduce bias into the volume spectroscopy measurements.

Adult↗
PubMed1981

The effect of strenuous physical exercise on circulating blood lymphocytes and serum cortisol levels.

Venous blood was removed from healthy subjects immediately before and at intervals after exercise on a bicycle ergometer. Immediately after exercise, the subjects developed a lymphocytosis in which (a) the E-rosette percentage fell by 10% but their absolute number in the circulating blood rose by more than 70%, (b) the percentage of PHA-stimulated cells fell, but their absolute numbers increased considerably and (c) the absolute numbers of Con A- and PWM-responding cells increased. The numbers of lymphocytes in the various subpopulations had returned virtually to the pre-exercise levels 15 minutes after stopping exercise. During the response to exercise, the characteristics of the cells in the various subpopulations did not show any major changes, despite considerable and rapid fluctuations in numbers: it is suggested that exercise discharges intravascularly sequestered cells and that cortisol may be involved in re-sequestration of stress-released cells. It is recommended that, in clinical studies on circulating lymphocyte numbers and populations, the patient should be rested for at least 15 minutes before venesection.

Adolescent↗
PubMed1980

A simple method for determining the extent of cellular contamination in peripheral blood lymphocyte preparations.

A method is described for calculating, from the size distribution of the cells, the extent of cellular contamination of lymphocyte concentrates prepared from venous blood. The precision of this method was checked by direct comparison with differential leucocyte counts obtained by direct microscopy on 29 samples chosen because they showed a wide range of intensity of contamination. By virtue of its technical simplicity, the method has proved useful in a diagnostic service laboratory for checking the purity of lymphocyte preparations either before performing lymphocyte function tests or after a period of 24 h in tissue culture.

Cell Separation↗
PubMed1980

Enzyme reaction rates and the stochastic theory of kinetics.

The kinetics of an elementary reaction step are discussed from the viewpoint of the stochastic theory of chemical kinetics. The general form of the rate constant found in the stochastic approach is described and compared with the expression from transition state theory. Whereas the stochastic theory predicts a rate enhancement in cases which are not adiabatic (in the quantum mechanical sense), transition state theory, which is essentially an adiabatic theory of reaction rates, does not permit inclusion of the effect. This effect can be expected to be of greater importance in cases of catalysis by structures, such as enzymes, containing large numbers of vibrational degrees of freedom (particularly low frequency ones) than in cases lacking such structures. The stochastic theory is more general than the transition state theory, the rate constant expression given by the latter being obtainable from the former when restrictive assumptions, including that of adiabaticity, are made. Interpretations of enzyme catalysis based on the transition state theory must thus be viewed as speculative.

Enzymes↗
PubMed1979

A new method of testing for mitogen-induced lymphocyte stimulation: measurement of the percentage of growing cells and of some aspects of their cell kinetics with an electronic particle counter.

Human lymphocytes were cultured with or without added PHA for periods not exceeding one day so that none of the cells had entered the first mitotic division. The size distribution of the cells was measured with an electronic particle counter and the results were collected in a multichannel analyser. An iterative stochastic model was developed to estimate the proportion of responding cells and their growth characteristics. This mathematical model was based on a few simple assumptions about the pattern of cell growth and was considered to fulfill basic requirements of plausibility and parsimony. The technique described in this paper makes measurement of the absolute percentage of responding cells and their average growth rate in mitogen-induced lymphocyte stimulation tests possible in routine diagnostic laboratories for the first time.

Adult↗
PubMed1979

The effect of culture temperature on the kinetics of human lymphocyte stimulation by phytohaemagglutinin.

The effect of varying the culture temperature on the growth kinetics of human lymphocytes stimulated by phytohaemagglutinin (PHA) has been studied by a new method using a Coulter Channelyzer. Each of three subjects had a distinctive percentage of responding cells (P less than 0.01), greater after 22 hr culture than after 15 hr (P less than 0.05) due to continued recruitment, but these values were unmodified by variation of the culture temperature in the range 35 degrees C--39 degrees C. The incremental growth rate is the major descriptor of cellular growth and, not unexpectedly, each subject has a distinctive value (P less than 0.01) which is greater after culture for 22 hr than after 15 hr (P less than 0.05). We attribute the increase to the effect of recruitment in modifying the mean value of this parameter. These growth rates were similar at 35 degrees C and 37 degrees C (P less than 0.01), but higher at 39 degrees C (P less than 0.01). Lymphocytes cultured at 41 degrees C failed to grow satisfactorily in either the control or PHA-stimulated wells and it was obvious that cells were damaged at this temperature. Our results establish that PHA-stimulated lymphocytes grow more quickly at 39 degrees C than at 37 degrees C in the early stages of the first cell cycle, but that there is no increase in the number of responding cells at the higher temperature. The results suggest that moderate fever might have a beneficial effect on lymphocyte responses to infection.

Cell Division↗