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PubMed1990

Kinetics and balance of glucose and galactose appearance in the portal blood after intake of lactose or hydrolysed lactose in conscious pigs.

Five pigs (mean body weight: 66.2 kg) were fitted with portal and arterial catheters and an electromagnetic flow probe around the portal vein. One week after the surgical operation, each animal was successively fed, at 3-day intervals, with two experimental meals containing 392 g dry matter either from hydrolysed or non-hydrolysed lactose together with a protein-mineral-vitamin mixture (200 g). Portal and arterial blood concentrations of glucose, galactose and amino nitrogen were measured together with the portal blood flow rate during a postprandial period of 8 h after the intake of these experimental meals. Amounts of hexoses appearing in the portal blood after hydrolysed-lactose intake were 3- and 2-fold larger within 2 and 8 h, respectively, than after non-hydrolysed-lactose intake. Thus, enzymatic hydrolysis in the intestine is the limiting factor of lactose digestion in unadapted pigs. Whatever the type of lactose ingested, glucose appeared more rapidly and in larger amounts in the portal blood than galactose. After hydrolysed-lactose intake, the amount of glucose appearing in the portal blood exceeded the amount ingested already after 5 h. This means that a fraction of galactose was transformed into glucose during the transport by the enterocyte.

Animals↗
PubMed1980

Freezing point measurement of lactose hydrolysis in acid whey and lactose solutions.

A method for determining lactose hydrolysis by freezing point determinations is described. There is a direct relationship between freezing point and lactose hydrolysis in neutralized acid whey (r = 0.985) and lactose solutions (r = 0.998). In both the acid whey and the lactose solutions that contained 4.6 to 5.0% lactose, the freezing point was depressed approximately 0.050 degrees H for each 1% lactose hydrolyzed.

Cheese↗
PubMed1996

Digestion and tolerance of lactose from yoghurt and different semi-solid fermented dairy products containing Lactobacillus acidophilus and bifidobacteria in lactose maldigesters--is bacterial lactase important?

OBJECTIVE: To compare the digestibility and tolerance of lactose from three semi-solid fermented dairy products with the same amount of lactose but different lactase contents and bacterial cultures in lactase deficient adults. DESIGN: Measurement of breath hydrogen (H2) concentration and of clinical symptoms after consumption of the test meals. SETTING: Metabolic ward for healthy volunteers, INSERM U290, Hôpital St. Lazare, Paris. SUBJECTS: Fifteen lactase-deficient healthy adult volunteers (20-45 y) started the study. One subject became a non-H2-producer during the study; therefore the results of 14 subjects are presented. INTERVENTION: Each subject consumed, on four different days and in random order, after a 12 h fast, three semisolid test meals containing 18 g of lactose, and a 10 g dose of lactulose which allowed calculation of lactose malabsorption. The three meals were: traditional yoghurt, fermented milk (Ofilus) that contained Lactobacillus acidophilus and Bifidobacterium sp., and a similar product 'Bulgofilus' enriched with Lactobacillus bulgaricus to increase the lactase content. RESULTS: Compared with lactulose, the sum of symptoms was significantly lower for Bulgofilus (P = 0.05), and bloating was less severe for Ofilus (P = 0.06). Between the fermented milks, there were no differences. The area under the breath H2 curve was significantly lower for each fermented milk when compared to lactulose (P < 0.0001). The degree of maldigestion of lactose did not differ significantly between the products; it was 21 +/- 3% (range 6-52) for Ofilus, 21 +/- 3% (range 6-44) for Bulgofilus, and 18 +/- 3% (range 3-43) for yoghurt. CONCLUSION: Despite the differences in the lactase and bacterial content, lactose was as well digested and tolerated from the three different semi-sold fermented dairy products. This could be due to a slow gastric emptying of the semi-solid milk.

Adult↗
PubMed1997

The resistance to betalactam antibiotics of lactose-positive and lactose-negative strains of Escherichia coli.

Two groups of Escherichia coli (lactose-positive and lactose-negative strains) were assayed to evaluate the resistance to betalactam antibiotics using disk diffusion technique. 57.66% lactose-positive and 80.82% lactose-negative strains showed the resistance to ampicillin. In lactose-positive E. coli strains 5.00% and in lactose-negative 18.64% strains respectively were resistant to amoxicillin/clavulanic acid.

Amoxicillin-Potassium Clavulanate Combination↗
PubMed1991

Lactose Uptake Driven by Galactose Efflux in Streptococcus thermophilus: Evidence for a Galactose-Lactose Antiporter.

Galactose-nonfermenting (Gal) Streptococcus thermophilus TS2 releases galactose into the extracellular medium when grown in medium containing excess lactose. Starved and de-energized Gal cells, however, could be loaded with galactose to levels approximately equal to the extracellular concentration (0 to 50 mM). When loaded cells were separated from the medium and resuspended in fresh broth containing 5 mM lactose, galactose efflux occurred. De-energized, galactose-loaded cells, resuspended in buffer or medium, accumulated [C]lactose at a greater rate and to significantly higher intracellular concentrations than unloaded cells. Uptake of lactose by loaded cells was inhibited more than that by unloaded cells in the presence of extracellular galactose, indicating that a galactose gradient was involved in the exchange system. When de-energized, galactose-loaded cells were resuspended in carbohydrate-free medium at pH 6.7, a proton motive force (Deltap) of 86 to 90 mV was formed, whereas de-energized, nonloaded cells maintained a Deltap of about 56 mV. However, uptake of lactose by loaded cells occurred when the proton motive force was abolished by the addition of an uncoupler or in the presence of a proton-translocating ATPase inhibitor. These results support the hypothesis that galactose efflux in GalS. thermophilus is electrogenic and that the exchange reaction (lactose uptake and galactose efflux) probably occurs via an antiporter system.

Journal Article↗
PubMed1983

Lactose-poor milk in adult lactose intolerance.

The frequency of lactose intolerance was studied in patients with chronic gastrointestinal disease, mainly peptic ulcer to explore the possibilities of the use of lactose-poor milk. It was found that whole milk caused dyspeptic symptoms in 45% of patients with peptic ulcer; lactose-intolerance was present in 82% of the patients with milk intolerance; lactose poor powdered milk resulted in complete freedom from symptoms. Use of milk with reduced lactose contents is recommended in the diet of adult patients with lactase deficiency.

Adult↗
PubMed1991

[Lactose--a potential dietary fiber. The regulation of its microecologic effect in the intestinal tract. 3. Dietary fiber actions of lactose due to microbial activity].

The activity of the mucosal beta-galactosidase of caecum and colon is low in both germfree and conventional rats. beta-Galactosidase activity occurs also in the chymus of germfree rats. It increases after monoassociation and is higher in conventional than in germfree animals. Lactose entering caecum and colon acts like dietary fibre and is hydrolysed mainly by the intestinal flora. Aerobe lactobacilli and bacteroides predominate in the microflora of rat caecum and colon. A lactose-containing diet increases the total number of germs and stimulates the growth of bifidobacteria. After special diets, rich in lactose and low in protein and phosphate (e.g. human milk and similar formulae), the number of bacteroides and other putrefactive germs decreases. Moreover, a lactose-containing diet alters the metabolic activity of intestinal microorganisms (activity of microbial beta-galactosidase, acidification and lowering of ph in the chymus, production of hydrogen, proteolytic activity.) Lactose as dietary fibre decreases the nitrogen excretion in the urine and increases the N-excretion in the faeces of conventional rats.

Animals↗
PubMed1996

Identification of the epitope for monoclonal antibody 4B1 which uncouples lactose and proton translocation in the lactose permease of Escherichia coli.

Monoclonal antibody 4B1 binds to a conformational epitope on the periplasmic surface of the lactose permease of Escherichia coli, uncoupling lactose and H+ translocation in a manner indicating that it blocks deprotonation [Carrasco, N., Viitanen, P., Herzlinger, D., & Kaback, H. R. (1984) Biochemistry 23, 3681; Herzlinger, D., Viitanen, P., Carrasco, N., & Kaback, H. R. (1984) Biochemistry 23, 3688]. In this paper, 4B1 binding to purified lactose permease is shown to exhibit a KD of about 5 x 10(-10) M by surface plasmon resonance. Furthermore, the combined use of mutants containing 6 contiguous His residues in each periplasmic loop in the permease and Cys-scanning mutagenesis in conjunction with chemical labeling demonstrates that 4B1 binds specifically to the periplasmic loop between helices VII and VIII and that Phe247 and Gly254 are the primary determinants. Remarkably, although 4B1 binding uncouples lactose and H+ translocation, none of the amino acid residues in periplasmic loops, particularly Phe247 or Gly254, play an important role in the transport mechanism. Moreover, binding of avidin to biotinylated Glu255-->Cys in the loop containing the epitope has no effect on transport activity. Therefore, the uncoupling effect of 4B1 involves highly specific interactions which in all likelihood exert a torsional effect on the loop, resulting in a conformational change in helix VII and/or VIII that alters the pKas of residues involved in lactose-coupled H+ translocation.

Amino Acid Sequence↗
PubMed1982

Regulation of lactose permease activity by the phosphoenolpyruvate:sugar phosphotransferase system: evidence for direct binding of the glucose-specific enzyme III to the lactose permease.

Interaction between the glucose-specific enzyme III (enzyme IIIglc) of the phosphoenolpyruvate:sugar phosphotransferase system and the lactose permease was studied with membrane fragments from an Escherichia coli strain that overproduces the lactose permease. Substrates of the permease markedly and specifically stimulated binding of enzyme IIIglc to the membranes. The sugar-stimulated binding of enzyme IIIglc was concluded to the specific to the lactose permease because it (i) was dependent on the amount of the permease, (ii) was promoted only by sugar substrates of the permease, and (iii) was completely eliminated by treatment of the membranes with N-ethylmaleimide in the absence (but not the presence) of thio-beta-D-digalactoside. The pH dependence of binding was similar to that reported for the binding of thio-beta-D-digalactoside to the permease. Phosphoenolpyruvate prevented the binding of enzyme IIIglc to the lactose permease in the presence (but not the absence) of the other phosphate transfer components of the phosphotransferase system. These results support the hypothesis that enzyme IIIglc, in its dephosphorylated form, modulates the activity of the lactose permease by a direct protein-protein interaction.

Allosteric Regulation↗
PubMed2004

Prospective evaluation of lactose malabsorption by lactose hydrogen breath test in individuals infected with Entamoeba histolytica and passing cysts.

The aim of the present prospective study was to detect lactose malabsorption in subjects in northern India infected with Entamoeba histolytica and passing cysts. The study group included forty-one patients with E. histolytica cysts in at least one of three consecutive faecal samples. Lactose malabsorption was detected by a lactose H2 breath test. The results were compared with those of forty controls subjects. Thirty-two of forty-one (78.0 %) subjects passing E. histolytica cysts had lactose malabsorption compared with seventeen of forty (42.5 %) control subjects (P<0.01). In conclusion, the present study shows that lactose malabsorption is significantly more common in individuals infected with E. histolytica and passing cysts compared with control subjects.

Adult↗
PubMed1989

Relative efficiency of yogurt, sweet acidophilus milk, hydrolyzed-lactose milk, and a commercial lactase tablet in alleviating lactose maldigestion.

The relative effectiveness of commercially available plain yogurt (Y), sweet acidophilus milk (SAM), hydrolyzed-lactose milk (HLM), a lactase tablet (LT), and whole milk (WM) was evaluated in 10 lactose-intolerant black subjects. In a 5 x 5 Latin square design, hourly breath hydrogen excretion (BHE) was measured for 5 h after the subjects consumed the above products (18 g lactose in each except HLM, which had 5 g). Mean BHE (ppm) for Y, SAM, LT, HLM, and WM were 12, 37, 29, 18, and 33, respectively. There was a significant (p less than 0.05) positive correlation of 0.808 between the symptoms reported and the mean peak BHE. However, the correlation between the symptoms and diagnosis by history was not significant. Although Y was as effective as HLM in minimizing lactose maldigestion, it was the least accepted by the subjects in sensory evaluations. Results of this study also indicate that microbial endogenous lactase in yogurt is superior to exogenous commercial lactase in alleviating lactose maldigestion.

Adult↗
PubMed1997

Effects of milk viscosity on gastric emptying and lactose intolerance in lactose maldigesters.

The possibility of delaying gastric emptying and improving lactose digestion and tolerance by increasing milk viscosity was studied in 13 lactose maldigesters who ingested three test milks with different viscosities (range: 33-1892 mPa.s) in random order at intervals of 1 wk. Each test portion was 500 mL and provided approximately equal to 1900 kJ and 18 g lactose. The different viscosities were obtained by adding varying proportions of rice starch and maltodextrin to a basic milk formula. A combined [13C]glycine-hydrogen breath test was used to measure gastric emptying and lactose digestion simultaneously. Participants reported their gastrointestinal symptoms by using a four-grade scale. Mean (+/- SEM) gastric-emptying half times were 78 +/- 5.7 min for low-viscosity milk (30 mPa.s), 86 +/- 5.0 min for moderate-viscosity milk (80 mPa.s), and 78 +/- 4.5 min for high-viscosity milk (1.9.10(3) mPa.s). Mean orocecal transit times (180 +/- 24, 163 +/- 23, and 180 +/- 24 min, respectively) were not significantly different. There were no milk-dependent differences in breath-hydrogen excretion or in the severity of gastrointestinal symptoms. The milks were well tolerated; > 50% of the subjects reported nondisturbing symptoms or none. We conclude that gastric emptying, orocecal transit time, and lactose digestion and tolerance were not affected by altering milk viscosity. This may have been due to the high energy content of the test milks, which in itself led to slow gastric emptying.

Adult↗
PubMed1989

The effect of lactose particle size on the extrusion properties of microcrystalline cellulose-lactose mixtures.

Ram extrusion has been used to assess and compare the flow characteristics and quality of wet powder masses formed from mixtures of water with microcrystalline cellulose and two different particle size samples of lactose. The force-displacement profiles can reveal poor flow properties. Steady state flow was achieved for the mixture containing fine lactose which produced an extrudate of uniform moisture content at all extrusion rates except the lowest (5 cm min-1). Increasing the lactose particle size significantly altered the extrusion properties of the formulation with forced flow predominating and high extrusion pressures observed. Formulations showing that type of extrusion are to be avoided as they produce poor quality extrudate which may be unsuitable for spheronization. Flow visualization studies showed that problems associated with such mixtures are caused by failure to maintain a constant angle of convergence during extrusion, which is essential for maintenance of steady state flow. With the mixture made with coarse lactose, the extrudate quality could be improved by extruding at high velocities, information that may be of significance in the development of formulations for large-scale production. Differences between formulations may be expressed quantitatively by plotting the apparent shear stress-shear rate relationship. The curves are modified by the particle size of lactose included in the mixtures. Such curves have implications in predicting the suitability of an extrudate, produced under particular experimental conditions, for spheronization.

Cellulose↗
PubMed1998

Transcriptional regulation and evolution of lactose genes in the galactose-lactose operon of Lactococcus lactis NCDO2054.

The genetics of lactose utilization within the slow-lactose-fermenting Lactococcus lactis strain NCDO2054 was studied with respect to the organization, expression, and evolution of the lac genes. Initially the beta-galactosidase gene (lacZ) was cloned by complementation of an Escherichia coli mutant on a 7-kb HpaI fragment. Nucleotide sequence analysis of the complete fragment revealed part of a gal-lac operon, and the genes were characterized by inactivation and complementation analyses and in vitro enzyme activity measurements. The gene order is galK-galT-lacA-lacZ-galE; the gal genes encode enzymes of the Leloir pathway for galactose metabolism, and lacA encodes a galactoside acetyltransferase. The galT and galE genes of L. lactis LM0230 (a lactose plasmid-cured derivative of the fast-lactose-fermenting L. lactis C2) were highly similar at the nucleotide sequence level to their counterparts in strain NCDO2054 and, furthermore, had the same gene order except for the presence of the intervening lacA-lacZ strain NCDO2054. Analysis of mRNA for the gal and lac genes revealed an unusual transcriptional organization for the operon, with a surprisingly large number of transcriptional units. The regulation of the lac genes was further investigated by using fusions consisting of putative promoter fragments and the promoterless beta-glucuronidase gene (gusA) from E. coli, which identified three lactose-inducible intergenic promoters in the gal-lac operon. The greater similarity of the lacA and lacZ genes to homologs in gram-negative organisms than to those of gram-positive bacteria, in contrast to the homologies of the gal genes, suggests that the genes within the gal operon of L. lactis NCDO2054 have been recently acquired. Thus, the lacA-lacZ genes appear to have engaged the promoters of the gal operon in order to direct and control their expression.

Amino Acid Sequence↗
PubMed2002

[Influence of the lactose free and lactose containing diet on prevalence of gram-negative sepsis and feeding intolerance in very low birth weight infants: double-blind randomized trial].

OBJECTIVE: VLBW infants have a developmental lactase deficiency in the gut. The aim of the study was to evaluate the influence of lactose containing and lactose free diets on prevalence of feeding intolerance and Gram negative sepsis in VLBW infants. METHODS: 80 newborns with mean (+/- SEM) birth weight 1091 +/- 25 g and gestational age 28.5 +/- 0.24 wks were randomized into 2 groups fed during 1st month of life with 1) formula containing lactose (Bebilon Nenatal--BN group; n = 40) or 2) lactose free formula (Pregestimil--PG group; n = 40). The end points of the study were: feeding intolerance episodes, Gram negative sepsis, weight gain and the length of parenteral nutrition. RESULTS: The birthweight (1112 vs 1114 g), gestational age (28.8 vs 28.3 wks), 5th min. Apgar score (5 vs 6 pts), sex (52% vs 55% male), type of delivery (65 vs 58% vaginal delivery) did not differ between the groups. Thirty (75%) newborns of the BN group and 31 (77.5%) newborns of the PG group completed the study (RR = 1.11; 95% CI: 0.54-2.44). The prevalence of Gram negative sepsis were similar in both groups (2/40 vs. 3/40; RR = 0.67; 95% CI: 0.12-3.78). Also a comparable number of children had at least one episode of feeding intolerance (14/40 vs. 12/40; RR = 1.17; 95% CI: 0.69-2.20) The weight gain (11.7 vs 10.9 g/day) and the length of parenteral nutrition did not differ between the groups (16 vs 15 days). CONCLUSION: The inclusion of lactose into feeding formula does not influence feeding tolerance in VLBW infants.

Female↗
PubMed1990

Sensitivity of efflux-driven carrier turnover to external pH in mutants of the Escherichia coli lactose carrier that have tyrosine or phenylalanine substituted for histidine-322. A comparison of lactose and melibiose.

Two Escherichia coli lactose carrier mutants (tyrosine or phenylalanine substituted for histidine 322) were studied under conditions of net efflux or equilibrium exchange. Net lactose efflux by either mutant was 10-20-fold slower than by the parent and was sensitive to extracellular pH (5.6-8.0). The presence of extracellular lactose (equilibrium exchange) failed to accelerate loss of [14C]lactose, indicating that the step(s) rate limiting for exchange were also rate limiting for net lactose efflux. Net melibiose efflux by the Phe-322 mutant was comparable to the normal carrier, while that by the Tyr-322 mutant was 5-fold faster (pH 7.0). Melibiose efflux by either mutant was sensitive to pH (5.6-8.0). Melibiose in the extracellular medium significantly accelerated loss of [3H]melibiose from either mutant, showing that slow exchange is a sugar-specific phenomenon and not an intrinsic property of these mutants. The sugar-specific effect of these mutations could mean that the defect in these mutants is not on the path of the proton, although alternative explanations cannot as yet be eliminated. The modest effect of these mutations on the transport rate indicates that His-322 contributes a far smaller free energy increment to catalyzing of H+/galactoside cotransport than active site histidines contribute to catalyzing peptide bond hydrolysis in serine proteases. We interpret this to mean that in chemical terms the function of these catalytic histidine residues differ considerably.

Disaccharides↗
PubMed1983

[Effects of prolonged consumption of lactose or hydrolyzed lactose in the rat. 5. Intestinal metabolism of glucose and galactose].

Effect of Prolonged Consumption of Lactose or Hydrolyzed Lactose in Rats.--5. Intestinal Metabolism of Glucose and Galactose. The intestinal metabolism of galactose is different according to the form of ingestion. With a lactose diet (L), the galactose is abundant in intestinal contents (Tab. I), since neither the intestinal flora (Tab. II), nor the epithelial tissue (Tab. III) can easily metabolize the galactose. The glucose disappears more rapidly than the galactose (Tab. I). With a hydrolyzed lactose diet (LH), the intestinal contents of two hexoses are identical (Tab. I). In this case, the enzymic activity of epithelium metabolizes an amount of galactose 6 times as big as with the lactose diet (Tab. III).

Animals↗
PubMed1977

Weight-gain inhibition by lactose in Australian Aboriginal children. A controlled trial of normal and lactose hydrolysed milk.

Weight-gain in 35 slightly undernourished Australian Aboriginal infants was studied in hospital (49 admissions) during a blind controlled trial of a pre-hydrolysed low-lactose milk preparation and reconstituted full-cream milk powder. Infants fed the lactose hydrolysed milk gained 70% more weight than those receiving normal milk. Better weight-gains were achieved in those on the lactose hydrolysed milk irrespective of percentage standard weight for age, the presence of diarrhoea on admission to the trial, and stool sugar concentrations. The use of low-lactose milk should be considered in nutritional aid programmes for undernourished children throughout the world.

Animals↗