Asynchronous ripening behavior of cactus pear (Opuntia ficus-indica) cultivars with respect to physicochemical and physiological attributes.

Physicochemical and physiological ripening events in cactus pear (Opuntia ficus-indica) fruit of cultivars 'Ntopia' and 'Hercules' were profiled against skin coloration from mature-green (S1) to over-mature (S5). Fructose and glucose accumulation were linear in 'Ntopia' but peaked near S3 in 'Hercules' synchronously to the appearance of sucrose. Betalains increased steadily in 'Ntopia' (103.2mg/l) but peaked before full skin coloration in 'Hercules' (49.7mg/l); whereas phenolic content remained invariable and ascorbate content peaked near S5 in both 'Ntopia' (108.6µg/g) and 'Hercules' (163.1µg/g). Cell wall material diminished with maturity though textural changes with ripening appeared not related to pectin solubilization but to weakening of glycan bonding and loss of neutral sugars. Fruit firmness rather was correlated to seed weight (r=0.89) and seed-to-pulp ratio (r=0.73). Cultivar differences highlighted in the chronology of ripening events are critical for defining optimum harvest maturity and postharvest handling protocols for premium quality cactus pear fruit.

Short-term dietary supplementation with fructose accelerates gastric emptying of a fructose but not a glucose solution.

OBJECTIVE: Short-term dietary glucose supplementation has been shown to accelerate the gastric emptying rate of both glucose and fructose solutions. The aim of this study was to examine gastric emptying rate responses to monosaccharide ingestion following short-term dietary fructose supplementation. METHODS: The gastric emptying rate of a fructose solution containing 36 g of fructose and an equicaloric glucose solution containing 39.6 g glucose monohydrate were measured in 10 healthy non-smoking men with and without prior fructose supplementation (water control) using a randomized crossover design. Gastric emptying rate was assessed for a period of 1 h using the [(13)C]breath test with sample collections at baseline and 10-min intervals following drink ingestion. Additionally, appetite ratings of hunger, fullness, and prospective food consumption were recorded at baseline and every 10 min using visual analog scales. RESULTS: Increased dietary fructose ingestion resulted in significantly accelerated half-emptying time of a fructose solution (mean = 48, SD = 6 versus 58, SD = 14 min control; P = 0.037), whereas the emptying of a glucose solution remained unchanged (mean = 85, SD = 31 versus 78, SD = 27 min control; P = 0.273). Time of maximal emptying rate of fructose was also significantly accelerated following increased dietary fructose intake (mean = 33, SD = 6 versus 38, SD = 9 min control; P = 0.042), while it remained unchanged for glucose (mean = 45, SD = 14 versus 44, SD = 14 min control; P = 0.757). No effects of supplementation were observed for appetite measures. CONCLUSION: Three d of supplementation with 120 g/d of fructose resulted in an acceleration of gastric emptying rate of a fructose solution but not a glucose solution.

Sugar import and phytopathogenicity of Spiroplasma citri: glucose and fructose play distinct roles.

We have shown previously that the glucose PTS (phosphotransferase system) permease enzyme II of Spiroplasma citri is split into two distinct polypeptides, which are encoded by two separate genes, crr and ptsG. A S. citri mutant was obtained by disruption of ptsG through homologous recombination and was proved unable to import glucose. The ptsG mutant (GII3-glc1) was transmitted to periwinkle (Catharanthus roseus) plants through injection to the leaf-hopper vector. In contrast to the previously characterized fructose operon mutant GMT 553, which was found virtually nonpathogenic, the ptsG mutant GII3-glc1 induced severe symptoms similar to those induced by the wild-type strain GII-3. These results, indicating that fructose and glucose utilization were not equally involved in pathogenicity, were consistent with biochemical data showing that, in the presence of both sugars, S. citri used fructose preferentially. Proton nuclear magnetic resonance analyses of carbohydrates in plant extracts revealed the accumulation of soluble sugars, particularly glucose, in plants infected by S. citri GII-3 or GII3-glc1 but not in those infected by GMT 553. From these data, a hypothetical model was proposed to establish the relationship between fructose utilization by the spiroplasmas present in the phloem sieve tubes and glucose accumulation in the leaves of S. citri infected plants.

Fructo-oligosaccharide supplementation: effects on metabolic, endocrine and hematological traits in veal calves.

Fructo-oligosaccharides (FOS) are soluble fibres which exert various effects in the gastrointestinal tract, and induce metabolic and endocrine changes. The effects are favourable in diabetes mellitus, and may be favourable in veal calves, which during late periods of fattening often develop hyperglycemia, glucosuria and insulin resistance, especially during high lactose intake. Based on this we have studied metabolic, endocrine and haematological traits in veal calves (Simmental x Red Holstein) fed FOS (10 g/day; group GrF) or no FOS (group GrC). Whole milk and milk replacer in both groups, on a kg body weight basis, were fed in identical amounts. Experiments, lasting for 3 weeks, started when calves were 10 weeks old and weighed 117 kg. During week 3 lactose was supplemented to enhance post-absorptive glucose loads. Feed intakes were similar in both groups, but weight gain tended to be higher in GrF than GrC. The post-prandial increase of glucose concentrations was significantly smaller, of lactate tended to be smaller, and growth hormone peak frequency tended to be lower, whereas maximal insulin concentrations reached post-prandially were significantly higher in GrF than GrC. Eosinophil granulocytes increased during FOS feeding. In conclusion, FOS had basically similar effects on metabolic and endocrine traits in veal calves as in animals and humans with diabetes mellitus, but changes were small, albeit more prominent after lactose loads.

Calcium and fructose intake in relation to risk of prostate cancer.

Laboratory and clinical data indicate an antitumor effect of 1,25(OH)2 vitamin D (1,25(OH)2D) on prostate cancer. High calcium intake suppresses formation of 1,25(OH)2D from 25(OH)D, thereby decreasing the 1,25(OH)2D level. Ingestion of fructose reduces plasma phosphate transiently, and hypophosphatemia stimulates 1,25(OH)2D production. We thus conducted a prospective study among 47,781 men of the Health Professionals Follow-Up Study free of cancer in 1986 to examine whether calcium and fructose intake influenced risk of prostate cancer. Between 1986 and 1994, 1369 non-stage A1 and 423 advanced (extraprostatic) cases of prostate cancer were diagnosed. Higher consumption of calcium was related to advanced prostate cancer [multivariate relative risk (RR), 2.97; 95% confidence interval (CI), 1.61-5.50 for intakes > or = 2000 mg/day versus < 500 mg/day; P, trend, 0.002] and metastatic prostate cancer (RR, 4.57; CI, 1.88-11.1; P, trend, <0.001). Calcium from food sources and from supplements independently increased risk. High fructose intake was related to a lower risk of advanced prostate cancer (multivariate RR, 0.51; CI, 0.33-0.80, for intakes > 70 versus < or = 40 g/day; P, trend, 0.007). Fruit intake was inversely associated with risk of advanced prostate cancer (RR, 0.63; 95% CI, 0.43-0.93; for > 5 versus < or = 1 serving per day), and this association was accounted for by fructose intake. Non-fruit sources of fructose similarly predicted lower risk of advanced prostate cancer. A moderate positive association between energy-adjusted fat intake and advanced prostate cancer was attenuated and no longer statistically significant when controlled for calcium and fructose. Our findings provide indirect evidence for a protective influence of high 1,25(OH)2D levels on prostate cancer and support increased fruit consumption and avoidance of high calcium intake to reduce the risk of advanced prostate cancer.