Use of visible spectrophotometry to assess tissue oxygenation in the colostomy stoma.

The aims of this study were to determine the normal range of tissue oxygenation (SO(2)) in the "mature" colostomy stomacolostomy stoma and to investigate whether there were any diurnal variationsdiurnal variations in the SO(2) values. Ten patients with an end colostomy for a minimum duration of three months and using conventional colostomy bags were included in this study. Tissue SO(2) Tissue SO(2) was measured on the stoma using visible wavelength spectroscopy (Whitland RM 200, Whitland Research, Whitland, UK) The measurements were carried out on each patient on three occasions: the first early in the morning (designated "baseline"), a second after 6 h and the third on the next day at 24 h. The results showed that the mean baseline SO(2) in the colostomy stoma was 77.6 +/- 6.8 and there were no differences in the SO(2) measurements between the baseline, 6 h and the 24 h values. There were also no differences in the SO(2) values between the four quadrants of the stomas. In conclusion, visible wavelength spectrophotometry can reliably measure stomal SO(2) in a non-invasive way. No significant diurnal variations in the stomal SO(2) values were detected.

Intraoperative measurement of colonic oxygenation during bowel resection.

Recently lightguide spectrophotometry (LGS) has been investigated for assessing bowel mucosal oxygenation and may prove helpful in the diagnosis of bowel ischaemia. This pilot study explores the use of LGS and laser Doppler flowmetry (LDF) to measure SO2 and perfusion in the bowel during key stages of colon surgery. SO2 and perfusion in the mucosal and serosal layers of the rectum, sigmoid and descending colon were measured in 7 patients by LGS (Whitland Research, UK) and LDF (Moor Instruments, UK) respectively at four stages (baseline, after mobilisation of the sigmoid, after ligation of the inferior mesenteric artery (IMA) and after complete devascularisation of the sigmoid). The sigmoid mucosal SO2 and LDF values were significantly lower than the baseline after the ligation of IMA and devascularisation. Mean (SD) baseline sigmoid mucosal SO2 (73%) decreased to 55% after ligation of IMA and to 39% after complete devascularisation. The sigmoid serosal SO2 did not show any change after ligation of IMA and showed only 7% decrease after devascularisation. There was no difference in baseline SO2 and LDF values in different parts of the bowel but the mean mucosal baseline SO2 (75%) was significantly lower than that in the serosa (87%). In conclusion, mucosal SO2 measurements can accurately diagnose bowel ischaemia but serosal SO2 does not reflect mucosal ischaemia.

On the role of anatomy in learning by the cerebellar cortex.

The properties due to the location of neurons, synapses, and possibly even synaptic channels, in neuron networks are still unknown. Our preliminary results suggest that not only the interconnections but also the relative positions of the different elements in the network are of importance in the learning process in the cerebellar cortex. We have used neural field equations to investigate the mechanisms of learning in the hierarchical neural network. The numerical resolution of these equations reveals two important properties: (i) The hierarchical structure of this network has the expected effect on learning because the flow of information at the neuronal level is controlled by the heterosynaptic effect through the synaptic density-connectivity function, i.e. the action potential field variable is controlled by the synaptic efficacy field variable at different points of the neuron. (ii) The geometry of the system involves different velocities of propagation along different fibers, i.e. different delays between cells, and thus has a stabilizing effect on the dynamics, allowing the Purkinje output to reach a given value. The field model proposed should be useful in the study of the spatial properties of hierarchical biological systems.

Fermentation of the carbohydrate of banana (Paradisiaca sapientum) in the human large intestine.

Fermentation of dietary fiber and resistant starch is one of the major physiological functions of the human large intestine. The major substrate for fermentation is probably starch. This study assessed the effect of bananas--a carbohydrate with a highly resistant starch content--on breath hydrogen and methane production in methane and nonmethane-producing subjects. The results showed that both groups produced significant quantities of hydrogen after a banana meal, compared with a sucrose control test meal, measured as area under the curve (28 +/- 5.6 vs. 8.1 +/- 1.4 10(3) pm/min, p = 0.008 in methane producers and 39 +/- 15.2 vs. 10.5 +/- 4.1 10(3) ppm/min, p = 0.01 in methane nonproducers). The rise in breath hydrogen started a half hour after the banana meal and peaked at 3 1/2 h in methane nonproducers, whereas in methane producers, the rise began after 2 h and peaked at 5 h. Methane production was not significantly stimulated by the test meals. This study shows that bananas stimulate fermentation mainly through the production of hydrogen, with minimal effect on methane production. The possible mechanisms for this process are discussed.

Malabsorption of carbohydrate foods by urban blacks.

Prevalences of non-infective bowel diseases are very low in South African urban blacks compared with the white population. In seeking elucidation, using breath hydrogen measurements in series of black and white subjects, small-bowel transit time was determined, and the malabsorption of maize, wheat, and rice investigated. Median transit times in both ethnic groups were similar. Rice was fully, but wheat incompletely absorbed by both groups. Maize, the staple food of blacks, was incompletely absorbed by them, although completely absorbed by the white subjects. Carbohydrate consumption is high in the black population (60-65% of total energy intake). It is probable that in blacks, despite their now eating a low-fibre diet, an expected increase in large-bowel diseases has been inhibited in part by the protective mechanism of fermentation of malabsorbed maize and wheat.

Glycaemic responses to different carbohydrate foods in healthy and diabetic blacks in Soweto.

Diabetes mellitus is uncommon in rural southern African blacks. With urbanisation and lifestyle changes, incidence rises to that in western populations. To assess associated changes in carbohydrate metabolism, glycaemic responses to glucose, refined maize, refined rice and bread were studied in 8 healthy and 8 non-insulin-dependent diabetic urban blacks. Additionally, in the healthy group serum insulin responses were measured. In the healthy, maize (the staple food of blacks) elicited the highest glucose response (207 mmol/l/min) and bread the lowest (107 mmol/l/min). The glycaemic indices of maize and glucose were similar. Serum insulin responses to maize were significantly lower than that of bread at 90 minutes (maize 66 muU/ml; bread 93 muU/ml; P = 0.02). In diabetics, maize and glucose elicited similar glycaemia (928 mmol/l/min and 921 mmol/l/min respectively). The high glucose response to maize could relate to its processing and physical form. The low insulin secretion could be due to inadequate stimulation by the 'entero-insular' axis. Moreover, variability in glucose insulin responses could stem from ethnic or genetic reasons. In the dietary management of black diabetics, refined maize should be replaced by other cereals.

Limitations of faecal chymotrypsin as a screening test for chronic pancreatitis.

Faecal chymotrypsin was measured in patients with chronic pancreatitis and in healthy black urban and rural control subjects. In the patients, significantly lower values of faecal chymotrypsin were obtained (mean (SD) 2.4 1.79 U/g stool) whereas in urban control subjects, values were within the normal range (mean (SD) 13.2 (11.9)). In rural black control subjects, however, the faecal chymotrypsin value was significantly lower (mean (SD) 7.1 (5.1)) than in urban black control subjects. It is suggested that faecal pH may influence faecal chymotrypsin values. The mean faecal pH in rural black subjects (pH 6.14) was significantly lower than that in urban control subjects (pH 6.77) and in patients with chronic pancreatitis (pH 6.61). Moreover, mean faecal chymotrypsin is high (20.0 U/g stool) at a pH greater than 7. Between pH 6 and 7 the mean value drops to 8.6 U/g stool and below pH 6 mean faecal chymotrypsin is in the abnormal range (4.4 U/g stool). Hence, low values for faecal chymotrypsin may be due to lower faecal pH (less than 6) in healthy control subjects. For diagnostic purposes, the faecal pH value should be determined if a low faecal chymotrypsin value is obtained.