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At least 883 records · Page 49Linked to original sources
PubMed1986

Characteristics of the chicken proximal cecum hexose transport system.

The properties of the sugar transport system present in chicken proximal cecum have been studied and compared to the jejunal transport system. Experiments were carried out in isolated enterocytes from 5- to 7-weak-old birds. Results show that: (1) Cecal cells are capable of high sugar transport rates by a phloridzin-sensitive mechanism. After 60 min incubation, the accumulation ratio (control/phloridzin-incubated cells) for 0.1 mmol/l alpha-methyl-D-glucoside (alpha-MG) was 43 and that of 3-oxy-methyl-D-glucose (3-OMG) was 25. In jejunal cells, ratios were 37 for alpha-MG and 13 for 3-OMG. The differences found in cumulative capacity of 3-OMG between cecal and jejunal cells suggest that the sodium-independent pathway offers a very small contribution to sugar efflux in the steady-state in the former cells. (2) Lowering external Na+ concentration reduces the steady-state alpha-MG accumulation in cecal cells (as in jejunal cells), indicating that the transport system is Na+-dependent. (3) The process depends on the electrochemical Na+ gradient across the cell membrane since both 2,4-dinitrophenol (0.2 mmol/l) and ouabain (0.25 mmol/l) abolish sugar accumulation. (4) Addition of 10 mmol/l) 3-OMG to the incubation medium markedly reduces the uptake of alpha-MG (concentration: 0.1 mmol/l), indicating that the cecal transport system can be inhibited by analogues of the transported substrate. (5) The specific sugar transport process is a saturable function of alpha-MG concentration, the apparent Km being 1.02 mmol/l and Vm 10.7 mmol/mg cell protein X min.(ABSTRACT TRUNCATED AT 250 WORDS)

3-O-Methylglucose↗
PubMed1982

Effect of sodium concentration and plasma sugar concentration on hexose absorption by the rat jejunum in vivo. Further evidence of two transport mechanisms.

The sodium-dependency of both the saturable and non-saturable components of glucose and galactose absorption across the rat jejunum in vivo has been determined. The non-saturable process appears to be unaffected by sodium removal but when Na+ concentrations in the lumenal fluid are progressively reduced from 143 mM to 0 mM the Jmax for active absorption is greatly decreased. In a separate study these two components of glucose transport were further investigated using intravenous sugar infusion to modify the transepithelial sugar concentration gradient. When identical glucose concentrations were present in plasma and intestinal lumen, the reduction in glucose absorption was fully accounted for by the elimination of the non-saturable component from the overall absorptive process. Together, these observations can be interpreted as further evidence for the existence of at least two absorption processes in vivo. The implication for analysing results from experimental studies of intestinal sugar absorption in vivo is discussed.

Absorption↗
PubMed2004

Hexose sugars differentially alter collagen gene expression and synthesis in fibroblasts derived from granulation tissue, hypertrophic scar and keloid.

Clinical observations have suggested that sugar and honey enhance granulation tissue formation and in vitro studies have shown that monosaccharide sugars stimulate mesenchymal and endothelial cells. In this study, the effects of glucose, fructose, galactose and mannose on type I and type III collagen gene expression and synthesis were studied in granulation tissue, hypertrophic scar and keloid fibroblast cultures. Glucose elevated both type I and type III collagen mRNAs in hypertrophic scar fibroblasts. Fructose increased type III collagen mRNA almost sevenfold in granulation tissue fibroblasts. Galactose caused an increase in type I and type III collagen mRNAs in granulation tissue fibroblasts and hypertrophic scar fibroblasts but, in contrast, mannose decreased type I and type III collagen levels in hypertrophic scar and keloid fibroblasts. Analysis of aminoterminal propeptides of type I and type III collagen (PINP and PIIINP) revealed that glucose decreased the amount of PINP in granulation tissue and keloid fibroblasts, whilst fructose decreased the amount in all the fibroblast cell lines studied. Galactose caused a decrease in the synthesis of type I collagen in all cell lines but a decrease was seen in type III collagen only in hypertrophic scar fibroblasts. Mannose decreased the amount of PINP in all cell lines but a decrease in the amount of PIIINP was seen only in granulation tissue fibroblasts. The effect of sugars on the ratio type I/type III collagen was negligible or decreasing with the exception of galactose, which increased the ratio in hypertrophic scar fibroblasts. The results suggest that glucose, fructose and galactose have no significant value in the stimulation of collagen synthesis in vitro. Mannose may have value in the prevention or treatment of abnormal scars.

Cells, Cultured↗