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Biomedical subjects

G C Cook

Publications and source records attributed to G C Cook.

At least 145 records · Page 8Linked to original sources
PubMed1978

Breath hydrogen concentrations after oral lactose and lactulose in tropical malabsorption and adult hypolactasia.

Thirty-six hospital in-patients in London had breath-hydrogen concentrations measured after 50 g lactose were given orally; in 23 or them serial blood glucose concentrations were also estimated. Eight had tropical malabsorption (TM), 14 were Europeans with no detectable disease (normal group) and 14 who also had no detectable disease, were from ethnic groups known to have a very high incidence of genetically determined adult hypolactasia (hl). In 21 of them breath-hydrogen concentrations were also measured after 33.5 g of lactulose were given orally. There was a good inverse correlation between breath-hydrogen production and blood-glucose rise after lactose. Correlations between the first appearance of hydrogen (T) and the area under the hydrogen curve between 0 and 120 min (A) were inversely significant both for lactose and lactulose. Mean T was earlier and mean A greater for lactose compared with lactulose. Correlation between individual values for A after lactase and after lactulose was significant. Indirect measurements of lactase are of no value in either detecting or assessing the severity of TM; that is largely due to the very high incidence of HL in individuals exposed to that disease.

Adult↗
PubMed1977

Effect of systemic bacterial infection on absorption rates of L-histidine and glycylglycine from the human jejunum in vivo.

Jejunal absorption rates of L-histidine (from a 100 mmole/liter solution) and glycylglycine (from a 50 mmole/liter solution) were determined with a souble-lumen tube perfusion system in vivo in 12 Zambian African men; six had acute bacterial pneumonia (infection group) and six had no clinical evidence of a bacterial infection (control group). With this experimental design the mean rate of histidine absorption was significantly higher in the infection compared with the control group, but mean rates for glycine absorption from glycylglycine were not significantly different. During the glycylglycine infusions, the luminal disappearance rate of the intact peptide was significantly greater than the total glycine absorption rate. The correlation between individual histidine and glycylglycine absorption rates was significant. That is probably because after intracellular hydrolysis and efflux to the lumen, some glycylglycine is reabsorbed as free glycine by the amino-acid transfer mechanism, and the rate of that has previously been shown to be increased in subjects with systemic bacterial infections.

Adolescent↗
PubMed1977

Rates and mechanisms of glucose, galactose, and xylose absorption in man in vivo.

Jejunal absorption-rates of glucose, galactose, and xylose were determined consecutively, using a double-lumen tube perfusion technique, in 6 Arab subjects in vivo; perfusion solutions contained 200 mmol/l of each monosaccharide. Mean xylose absorption rate was significantly lower than that for glucose (P less than 0.001) and galactose (P less than 0.001). In order to investigate evidence that glucose and xylose share the same jejunal transfer mechanism, their absorption-rates when given alone and together, at high concentrations, were determined in 6 other Arabs; perfusion solutions contained (1) 200 mmol/l glucose, (2) 100 mmol/l xylose, and (3) 200 mmol/l glucose + 100 mmol/l xylose. Rates of glucose and xylose absorption were not significantly influenced by the other monosaccharide. This study does not therefore confirm existence of a common transfer mechanism. A significant correlation between absorption rate of glucose and weight of xylose excreted after a 25 g oral load (P less than 0.05) was demonstrated.

Adolescent↗
PubMed1977

Effect of systemic infection and raised serum Ig-G concentration on the D-xylose test.

Urinary d-xylose excretion during five hours after a 25 gm. oral load was determined in 47 Zambian African patients; some had systemic infections. Serum albumin, total globulin and gamma-globulin concentrations were determined in all and immunoglobulins Ig-G, Ig-A, Ig-M and Ig-D in 36 of them. An inverse association between weight of xylose excreted and serum gamma-globulin (P less than 0.02) and Ig-G (P less than 0.002) concentrations was significant. Taken together with previous observations, those results indicate reduced xylose absorption in the presence of systemic infection. The mechanism of the association is unknown but seems likely to have a nutritional importance; systemic infections must be eradicated if the nutritional status of rural Africans is to be improved.

Adolescent↗
PubMed1977

Shigellosis.

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Adult↗
PubMed1976

Rapid glucose absorption in Arabs in Saudi Arbia compared with that in Africans in Zambia.

Glucose absorption rates in 14 Arabs in Saudi Arabia were determined by a jejunal perfusion technique and compared with those in 18 Africans in Zambia. None of the subjects had clinical evidence of systemic infection, gastrointestinal disease, malnutrition, or diabetes mellitus. The mean absorption rate was significantly higher in the Arabs. This was associated with a higher incidence of subclinical chronic systemic infection in the Africans. Other factors possibly responsible for the difference, including genetic difference, have, however, not been excluded.

Adolescent↗
PubMed1976

D-xylose absorption and jejunal morphology in African patients with pellagra (niacin tryptophan deficiency).

D-xylose absorption tests and jejunal morphology have been shown to be unaltered in 12 African patients with pellagra when compared with normal values for Zambian Africa adults; that result is contrary to two previous investigations in India and Egypt respectively. A significant inverse association has been shown, however, between D-xylose absorption and serum immunoglobulin IgG and IgA concentrations; that is consistent with previous studies and probably reflects malabsorption of xylose in the presence of systemic infections. It is concluded that pellagra per se does not alter intestinal structure or monosaccharide absorption.

Humans↗
PubMed1976

Impairment of jejunal absorption rate of carnosine by glycylglycine in man in vivo.

Using a double-lumen tube jejunal perfusion system in vivo, the mutual effects of carnosine (beta-alanyl-L-histidine) and glycylglycine on their respective absorption rates have been studied in six Zambian African adults. Data on the effect of the constituent amino-acids of carnosine on glycylglycine absorption rate have similarly been obtained. The solutions infused in each subject contained (A) carnosine (50 mmol l.-1), (B) carnosine (50 mmol l.-1) and glycylglycine (50 mmol l.-1), (C) glycylglycine (50 mmol l.-1), and (D) glycylglycine (50 mmol l.-1), L-histidine (50 mmol l.-1) and beta-alanine (50 mmol l.-1). Glycylglycine produced a significant impairment in the mean rate of histidine absorption from carnosine (P less than 0-01). However, carnosine did not have a significant effect on the mean rate of glycine absorption from glycylglycine. Mean rate of histidine absorption from solution D was significantly higher than that from solution A (P less than 0-01). Mean rate of glycine absorption from glycylglycine was not significantly different during infusion of solutions B, C, and D. The results are consistent with the concept that carnosine on glycylglycine is probably because the affinity of mechanism; the lack of influence of carnosine on glycylglycine is probably because the affinity of carnosine for the dipeptide uptake mechanism is relatively low. A gross difference has been shown between mean absorption rate of histidine from free L-histidine (solution D) (25-8 mmol h-1) and when it is given in the form of carnosine in the presence of another dipeptide (solution B) (8-7 mmol h-1); that emphasizes the complexity of amino acid and peptide interaction during absorption, which must be important in nutrition.

Adolescent↗
PubMed1976

Absorption of xylose, glucose, glycine, and folic (pteroylglutamic) acid in Zambian Africans with anaemia.

Rates of glucose, glycine, and folic (pteroylglutamic) acid absorption were determined for a 30 cm jejunal segment in vivo, with a double-lumen tube perfusion system, in 10 Zambian African women with a mean haemoglobin concentration of 5-1 (3-5-9-2) g/dl. In four the anaemia was megaloblastic (due to folate deficiency) and in six hypochromic. Perfusion solutions contained (1) glucose 200 mmol/1, (2) glycine 100 mmol/1, and (3) folic acid 250 mug/1. D-xylose absorption after a 25 g oral load was determined in them, and also in 18 additional patients (11 had megaloblastic and seven either hypochromic or haemolytic anaemia). Xylose absorption tests were significantly impaired in the patients with megaloblastic compared with hypochromic or haemolytic anaemia (P less than 0-001); those with untreated megaloblastic anaemia had a greater abnormality than those who had started treatment. Mean glucose, glycine, and folic acid absorption rates were similar to those in controls, and the rates in patients with megaloblastic and hypochromic anaemia were not significantly different. Correlation between glucose absorption rate and xylose excretion was, however, significantly (P less than 0-02). If more patients had been studied it seems likely therefore that a significant impairment of glucose absorption rate in the presence of megaloblastic anaemia would also have been demonstrated. In this investigation anaemia per se did not affect glucose, glycine, or folic acid absorption rates or xylose absorption, but xylose absorption was reduced in patients with megaloblastic anaemia. That abnormality was probably related to folate deficiency, and the underlying mechanism seems to be different from that causing impairment of monosaccharide absorption in patients with systemic bacterial infections. Mean glycine and folic acid absorption rates were not altered by megaloblastic anaemia, indicating that folate deficiency does not cause a general depression of absorption.

Adolescent↗
PubMed1975

High intestinal lactase concentrations in adult Arbs in Saudi Arabia.

The maximum rise in blood glucose after 50 g lactose by mouth was determined in 40 adult Arabs. Out of 30 Bedouin, urban Saudi, and Yemeni and 9 of mixed ancestry (usually partly African), 25 (83%) and 2 (22%) respectively showed an increase of over 1-1 mmol/1 (20 mg/100 ml). In common with most northern Europeans and Hamitic people of northern Africa, Arabs in Saudi Arabia usually have high intestinal lactase concentrations in adult life. This persistence of high levels probably originated in the Arabian peninsula. Its selective advantage may have been associated with the fluid and calorie content of camels' milk, which is important for survival in desert nomads.

Adolescent↗