Biomedical subjects
Publications and source records attributed to H G Jones.
A patient with Eisenmenger's syndrome presented for removal of a carotid body tumour. Continuous cervical plexus blockade was successfully used to provide peri-operative and postoperative analgesia. The risks and benefits of regional and general anaesthesia in this high risk patient are discussed.
Most thermal methods for the study of drought responses in plant leaves are based on the calculation of 'stress indices'. This paper proposes and compares three main extensions of these for the direct estimation of absolute values of stomatal conductance to water vapour (gs) using infrared thermography (IRT). All methods use the measured leaf temperature and two environmental variables (air temperature and boundary layer resistance) as input. Additional variables required, depending on the method, are the temperatures of wet and dry reference surfaces, net radiation and relative humidity. The methods were compared using measured gs data from a vineyard in Southern Portugal. The errors in thermal estimates of conductance were of the same order as the measurement errors using a porometer. Observed variability was also compared with theoretical estimates of errors in estimated gs determined on the basis of the errors in the input variables (leaf temperature, boundary layer resistance, net radiation) and the partial derivatives of the energy balance equations used for the gs calculations. The full energy balance approach requires accurate estimates of net radiation absorbed, which may not be readily available in field conditions, so alternatives using reference surfaces are shown to have advantages. A new approach using a dry reference leaf is particularly robust and recommended for those studies where the specific advantages of thermal imagery, including its non-contact nature and its ability to sample large numbers of leaves, are most apparent. Although the results suggest that estimates of the absolute magnitude of gs are somewhat subjective, depending on the skill of the experimenter at selecting evenly exposed leaves, relative treatment differences in conductance are sensitively detected by different experimenters.
The drought-tolerant tree species Ziziphus mauritiana Lamk. and Z. rotundifolia Lamk. were shown to have similar high mucilage concentrations (7-10% dry weight) in their leaves, with large numbers of mucilage-containing cells in the upper epidermis and extracellular mucilage-containing cavities in the leaf veins and stem cortex. The main sugar constituents of the water-soluble mucilage extract were rhamnose, glucose and galactose. During drought-stress in two independent studies, foliar mucilage content was unaffected in both species, but glucose and starch contents declined significantly in crude mucilage extracts from droughted leaves. Enzymatic hydrolysis of the mucilage extract using alpha-amylase and amyloglucosidase released glucose, indicating that a mucilage-associated water-soluble glucan, with alpha-1,4- and alpha-1,6-linkages, may exist which was extracted together with the mucilage. From the current data, it is not possible to localize the glucan to determine whether or not it is associated with mucilage-containing cells. Data from pressure-volume analyses of drought-stressed and control leaves showed that, in line with their similar mucilage contents, the relative leaf capacitance isotherm (change in relative water content per unit change in water potential) was similar in both species. During drought-stress, reduced relative capacitance resulted from osmotic adjustment and decreased wall elasticity. Data suggest that in Ziziphus leaves, intracellular mucilages play no part in buffering leaf water status during progressive drought. In Ziziphus species, growing in environments with erratic rainfall, the primary role of foliar mucilage and glucans, rather than as hydraulic capacitors, may be as sources for the remobilization of solutes for osmotic adjustment, thus enabling more effective water uptake and assimilate redistribution into roots and stems prior to defoliation as the drought-stress intensified.
Plasma replacement for thrombotic thrombocytopenic purpura (TTP) is accomplished with various plasma products. This study sought to determine the incidence of allergic reactions with FFP or CPP as replacement in therapeutic plasma exchange (TPE). Forty-one TTP patients were identified retrospectively who received TPE replacement with either FFP (n=21) or CPP (n=20). Anti-histamine was administered prophylactically following the initial occurrence of an allergic reaction (urticaria, respiratory distress, or anaphylaxis with hypotension). Fifty-one allergic reactions occurred in 65.8% of patients. Urticaria comprised 49 of 51 (96%) of reactions and respiratory distress the remaining 4%. No anaphylaxis occurred. Nineteen urticarial reactions occurred in 50% of CPP recipients compared to 71% of FFP recipients (P=0.28). Anti-histamine breakthrough occurred in 36.3% of patients who experienced a previous allergic reaction with CPP and 37.5% with FFP (P=1.0). The overall risk of allergy per unit of plasma was 1.37% (1.23 % CPP, 1.48% FFP), comparable to estimates in non-TTP recipients. The median number of donor exposures preceding the first allergic reaction was 35 and 32, CPP and FFP, respectively (P=0.63). The mean volume of plasma transfused prior to reaction was 9,883 mL for CPP and 9,348 mL for FFP (P=0.85). Neither product was advantageous in preventing allergic complications. Because of the large volume, the number of donor exposures, and prolonged duration of therapy, allergic reactions to plasma are common (65.8%) in the treatment of TTP.
The physiological basis of drought resistance in Ziziphus rotundifolia Lamk., which is an important, multipurpose fruit tree of the northwest Indian arid zone, was investigated in a greenhouse experiment. Three irrigation regimes were imposed over a 34-day period: an irrigation treatment, a gradual drought stress treatment (50% of water supplied in the irrigation treatment) and a rapid drought stress treatment (no irrigation). Changes in gas exchange, water relations, carbon isotope composition and solute concentrations of leaves, stems and roots were determined. The differential rate of stress development in the two drought treatments did not result in markedly different physiological responses, but merely affected the time at which they were expressed. The initial response to decreasing soil water content was reduced stomatal conductance, effectively maintaining predawn leaf water potential (Psi(leaf)), controlling water loss and increasing intrinsic water-use efficiency, while optimizing carbon gain during drought. Carbon isotope composition (delta13C) of leaf tissue sap provided a more sensitive indicator of changes in short-term water-use efficiency than delta13C of bulk leaf tissue. As drought developed, osmotic potential at full turgor decreased and total solute concentrations increased in leaves, indicating osmotic adjustment. Decreases in leaf starch concentrations and concomitant increases in hexose sugars and sucrose suggested a shift in carbon partitioning in favor of soluble carbohydrates. In severely drought-stressed leaves, high leaf nitrate reductase activities were paralleled by increases in proline concentration, suggesting an osmoprotective role for proline. As water deficit increased, carbon was remobilized from leaves and preferentially redistributed to stems and roots, and leaves were shed, resulting in reduced whole-plant transpiration and enforced dormancy. Thus, Z. rotundifolia showed a range of responses to different drought intensities indicating a high degree of plasticity in response to water deficits.
In situ measurements of alternative respiratory pathway activity are needed to provide insight into the energy efficiency of plant metabolism under various conditions in the field. The only reliable method at present to measure alternative oxidase (AOX) activity is through measurement of changes in delta(18)O(O(2)), which to date has only been used in laboratory environments. We have developed a cuvette system to measure partitioning of electrons to AOX that is suitable for off-line use and for field experiments. Plant samples are enclosed in airtight cuvettes and O(2) consumption is monitored. Gas samples from the cuvette are stored in evacuated gas containers until measurement of delta(18)O(O(2)). We have validated this method using differing plant material to assess AOX activity. Fractionation factors were calculated from delta(18)O(O(2)) measurements, which could be measured with an accuracy and precision to 0.1 per thousand and 0.3 per thousand, respectively. Potential sources of error are discussed and quantified. Our method provides results similar to those obtained with laboratory incubations on-line to a mass spectrometer but greatly increases the potential for adoption of the stable isotope method.
Tumour cell-rich platelet-free preparations were isolated from 21 fresh samples of human intracranial tumours using enzymic digestion, followed by discontinuous density gradient centrifugation on Percoll and (14 preparations) adherence on plastic. Of the disaggregated cells 79.8 to 97.7% (mean 86.2%) were tumour cells, and mean cell viability was 82.6%. All the tumours produced prostaglandin (PG), E2, F2 alpha, 6 oxo F1 alpha and Thromboxane B2 during 16 hours of incubation but the amount varied widely. Highest production of PGE2 and TXB2 per 10(5) cells was by the eight meningiomas in which the prostanoid profile closely resembled that of circulating monocytes.
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A model is presented which enables gas exchange data to be used to partition the intracellular resistance to leaf photosynthesis into carboxylation and transport components. A basic assumption is that the over-all kinetics of the carboxylation reaction fit the Michaelis-Menten equation.The model was tested for cotton (Gossypium hirsutum L., var. Deltapine Smoothleaf), where photorespiration was suppressed by using gas mixtures containing less than 1.5% oxygen. It was concluded that the transport resistance formed the major component of the intracellular resistance for the plants studied. However, in some cases the major intracellular factor limiting photosynthesis, at an ambient CO(2) concentration of 600 ng cm(-3), was the carboxylation system, which was close to saturation.
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