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Biomedical subjects

M Irving

Publications and source records attributed to M Irving.

At least 109 records · Page 6Linked to original sources
PubMed1985

Three years' experience with an intestinal failure unit.

The work of a purpose-built unit for the treatment of intestinal failure is described. In the 3 years following its opening the 4-bed unit treated 83 patients who were admitted for a mean of 35 days. Major indications for admission were difficult cases of Crohn's disease, intestinal fistulae and short bowel syndrome. Since the unit opened the mortality rate in this type of patient has fallen from 42% to 20%. The principal treatment used was total parenteral nutrition (TPN) although 52 of the 83 patients also required major surgery. Repeated experience with the same type of clinical problem has led to more efficient patient management and has reduced the complication rate associated with TPN. The unit has acted as a centre for the management of patients needing Home Parenteral Nutrition and has an active role in training nursing and medical staff in intravenous therapy. A plea is made for the establishment of regional intestinal failure units.

Adolescent↗
PubMed1984

Return to work following ileostomy.

The experiences of 1033 members of the 51 English divisions of the Ileostomy Association of Great Britain and Ireland have been analysed in respect of their return to work after construction of an ileostomy. Although there was a fall in the number of patients returning to work after operation this was often for reasons unrelated to surgery. The majority of those returning to work resumed work with the same employer and usually in the same post. Fifty-nine (5.7 per cent) patients began work for the first time after operation, including 33 (3.2 per cent) who were previously inactive although of working age. Analysis of occupational class shows that, although a number of patients initially resumed work within a lower class, once established in employment successful career advancement was possible. Problems in the gaining or resumption of employment were reported by 56 (5.4 per cent) patients. In 22 (2.1 per cent) patients, almost all approaching or above retirement age, successful surgery resulted in a decision not to return to employment. An ileostomy is no barrier to successful return to work in nearly all occupations, and is accomplished by the majority of patients without major difficulty.

Adolescent↗
PubMed1984

The effect of shortening on energy liberation and high energy phosphate hydrolysis in frog skeletal muscle.

It is generally assumed that the increased rate of energy liberation (as heat and work, h+w) accompanying shortening stems from an increased rate of crossbridge cycling and ATP hydrolysis. Experiments were performed to test two premises of this assumption: first, is the increased rate of heat production accompanying shortening derived from crossbridge activity? This question was answered by measuring the amount of shortening heat produced by a fixed displacement of 0.3 micron/sarcomere in the sarcomere length range of 2.25-3.75 microns. Shortening heat declines linearly with decreasing amounts of thick and thin filament overlap and becomes zero at a sarcomere spacing of ca. 3.70 microns. Secondly, the extent to which the measured consumption of high energy phosphate accounts for the measured tetanic (h+w) production during and after shortening for 300 ms at a velocity of Vmax or 1/ 2Vmax was examined. The results of these experiments showed that within 700 ms of the end of shortening at both velocities, all the (h+w) could be explained by the hydrolysis of ATP. At Vmax all the (h+w) produced by the end of shortening could be explained by the measured ATP hydrolysis. However, at Vmax less than half of the (h+w) produced by the end of shortening could be explained by the measured ATP splitting and there was a high rate of ATP splitting after the end of shortening. These results suggest that while shortening at velocities less than or equal to Vmax the energy liberation is indeed derived from an increased rate of ATP hydrolysis by crossbridges, at Vmax the crossbridge ATPase cycle differs somewhat from that at lower shortening velocities.

Adenosine Diphosphate↗
PubMed1983

The variation in shortening heat with sarcomere length in frog muscle.

Pairs of frog semitendinosus muscles were stimulated tetanically for 2 s at 0 degree C and, after 0.75 s of isometric contraction, were released at constant velocity for 0.16 s. The distance shortened was 0.3 micron per sarcomere. The extra heat (shortening heat) associated with the release was determined by comparison with isometric control tetani. The mean sarcomere length at the start of stimulation was varied between 2.25 and 3.75 microns. At the greater initial lengths there was considerable resting tension and heat was absorbed during releases of unstimulated muscles. This thermoelastic effect was also present during stimulation, so shortening heat values were calculated from the difference between the heat production of the stimulated and unstimulated muscle for releases over the same length range and at the same velocity. Laser diffraction was used to measure mean sarcomere length in the part of the muscle from which heat was recorded. At the greater initial lengths these central sarcomeres slowly elongated by a small amount during nominally isometric tetani. When a release was given during a tetanus the central sarcomere shortening was slightly less than that in a release of the unstimulated muscle with the same change of muscle length. In the period of a tetanus after the release had ended the rate of central sarcomere elongation was greater than that in an isometric tetanus. Shortening heat production had a large early component, during and just after the release, then continued to increase slowly up to the end of the tetanus. It is likely that sarcomere length redistribution along the muscle is responsible for the apparent slow phase, but has little effect on the early component. Shortening heat (determined as the early component) decreased linearly with increasing muscle length in the range studied. The intercept on the length axis was 3.78 +/- 0.08 micron per sarcomere (mean +/- S.E. of mean, n = 7, based on sarcomere length before stimulation). The corresponding intercept for the isometric tension before the release was 3.78 +/- 0.03 micron per sarcomere. The isometric heat rate at this time also decreased with increasing muscle length, but at 3.75 microns per sarcomere was still 50.0 +/- 2.0% of its maximum value. The results suggest that shortening heat, like isometric tension, is produced by the interaction of thick and thin filaments in contracting muscle.

Animals↗
PubMed1982

Accuracy of hospital activity analysis operation codes.

The accuracy of operation codes on hospital activity analysis printouts has been compared with unit and patient records. Inaccurate information is being provided by the hospital activity analysis in a significant number of cases. The same mistake is often repeatedly made, suggesting deficient monitoring procedures. These lapses occurred despite a unit policy of medical staff entering the operation and diagnostic details on the HMRI(IP) sheet and the checking of all entries by a consultant.

Abstracting and Indexing↗
PubMed1982

Failure of delayed hypersensitivity skin testing to predict postoperative sepsis and mortality.

Delayed hypersensitivity skin reactions to a battery of recall antigens, haemoglobin and albumin concentrations, arm-muscle circumference, and percentage of ideal weight were determined before operation in 244 patients undergoing elective major surgery. Depressed skin reactions were found in 70 patients (28%), but this group did not have significantly higher sepsis or mortality rates when compared with patients with normal reactions. Significant associations were found between depressed skin reactions and increasing age, anaemia, hypoalbuminaemia, low arm-muscle circumference, and low weight. Patients with benign and malignant disease had similar distributions of skin reactions. Hypoalbuminaemia was associated with a higher rate of serious postoperative sepsis, and hypoalbuminaemia, low arm-muscle circumference, and low weight were all associated with a higher mortality. These results suggest that the routine use of delayed hypersensitivity skin testing in the preoperative assessment of surgical patients is not justified.

Abdomen↗
PubMed1982

Delayed hypersensitivity skin testing does not influence the management of surgical patients.

Delayed hypersensitivity skin testing was performed at weekly intervals on 95 patients with major surgical illness. Patients with abnormal reactions on initial skin testing had a higher mortality than those who were normal initially (p less than 0.01), but this was not due to a greater rate of major septic complications. Significantly higher rates of sepsis (p less than 0.001) and mortality (p less than 0.001) were found in patients with abnormal reactions at any stage of their illness compared with patients who remained normal throughout. However, careful study of the temporal relationship between skin reactions and clinical events in individual patients suggested that these differences were not of value in clinical practice. Abnormal reactions usually followed obvious complications, such as sepsis or secondary hemorrhage, rather than predicted them. Deterioration of skin reactions from normal to abnormal was observed on 32 occasions in 25 patients but preceded the development of sepsis in only four patients.

Abdomen↗
PubMed1981

The energy liberation of frog skeletal muscle in tetanic contractions containing two periods of shortening.

1. Heat and work production have been measured in pairs of frog sartorius muscles undergoing two periods of rapid isovelocity shortening at 0 degrees C. The first (conditioning) shortening occurred in the sarcomere length range 2.70--2.25 micrometer (as measured in resting muscles) and the second (test) shortening in the range 2.25--2.10 micrometer. The shortening heat associated with the test shortening was obtained as the difference in heat production between pairs of tetani which were identical except for the presence of the test shortening. 2. The shortening heat associated with the test shortening was reduced when it was preceded by the conditioning shortening; with no interval between shortenings its value was 52 +/- 3% (mean +/- S.E. of mean, n = 6) of that without the conditioning shortening. As the interval between shortenings was increased the shortening heat became larger; its recovery was more than half complete with an interval of 0.3 sec. 3. The work produced in the test shortening was also reduced in tetani which contained the conditioning shortening; its dependence on the interval between shortenings was similar to that of the shortening heat.

Animals↗
PubMed1981

The dependence on extent of shortening of the extra energy liberated by rapidly shortening frog skeletal muscle.

1. Pairs of frog sartorius muscles were stimulated for 2 sec at 0 degrees C, after 1 sec of isometric contraction, were released at a constant velocity. The total excess heat (shortening heat) and work associated with the release were determined by comparison with isometric control tetani. 2. Shortening heat and work production were non-linearly related to the distance shortened. There was proportionally more energy liberation for smaller releases. 3. The dependence of shortening heat on muscle length was investigated within the sarcomere length range 2.1--2.6 micrometer (as measured in resting muscle) and was found to be similar to that of isometric tension. 4. A simple model in which heat and work are produced in a two-state cycle can describe these and previous results concerning the energetics of rapidly shortening muscle.

Animals↗
PubMed1981

High-energy phosphate metabolism and energy liberation associated with rapid shortening in frog skeletal muscle.

1. High-energy phosphate metabolism and energy liberated as heat and work were measured in 3 sec tetani of frog sartorius muscles at 0 degrees C.2. Three contraction periods were studied: (a) shortening at near-maximum velocity for 0.3 sec from sarcomere length 2.6 to 1.8 mum, beginning after 2 sec of isometric stimulation, (b) the 0.7 sec isometric period immediately following such rapid shortening, (c) the period from 2 to 3 sec in an isometric tetanus at sarcomere length 1.8 mum.3. There were no significant changes in levels of ATP, ADP or AMP in any contraction period. The observed changes in inorganic phosphate and creatine levels indicated that the only significant reaction occurring was phosphocreatine splitting.4. The mean rate of high-energy phosphate splitting during rapid shortening, 0.48 +/- 0.24 mumole/g.sec (mean +/- s.e. of mean, n = 29; ;g' refers to blotted muscle weight), was not significantly different from that in the 1 sec period in the isometric tetanus, 0.32 +/- 0.11 mumole/g.sec (n = 17). The mean rate in the post-shortening period, 0.71 +/- 0.10 mumole/g.sec (n = 22), was greater than that in the 1 sec period in the isometric tetanus, and this difference is significant (P < 0.02, t test).5. A large quantity of heat plus work was produced during the rapid shortening period, but less than half of this could be accounted for by simultaneous chemical reactions. The unexplained enthalpy production was 6.5 +/- 2.6 mJ/g (mean +/- s.e. of mean). No significant unexplained enthalpy was produced in the 1 sec period in the isometric tetanus.6. In the post-shortening period the observed enthalpy was less, by 6.2 +/- 2.6 mJ/g, than that expected from the simultaneous chemical reactions.7. The results are interpreted in terms of an exothermic shift in the population of cross-bridge states during rapid shortening. It is suggested that a relatively slow subsequent step prevents many of these cross-bridges from completing the cycle and splitting ATP until after the end of shortening.

Adenosine Triphosphate↗