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PubMed1982

The effect of lactose on the intestinal absorption of calcium and zinc in the rat during maturation.

Lactose facilitates the intestinal absorption of several minerals and trace elements in postweanling rats. There is no information in the literature on the effect of lactose on the process of absorption in suckling rats. Because soy and elemental formulas are nonlactose-containing diets, the role of lactose in facilitating the intestinal absorption of minerals is of considerable nutritional importance. We studied therefore, the effect of water (control), lactose, sucrose, and glucose on the intestinal absorption and tissue uptake of calcium and zinc in the suckling (14-15 day old) and adolescent (42-43 day old) rats. Our results indicate that absorption of calcium and zinc was significantly greater in the suckling than in adolescent rats (P less than 0.01). Lactose enhanced significantly the absorption and tissue uptake of calcium and zinc in the adolescent rats compared to control and other sugars. In the suckling rats lactose had no effect on the intestinal absorption or tissue uptake of calcium and zinc compared to control and other sugars. The possible mechanism(s) responsible for our findings are discussed.

Age Factors↗
PubMed2003

Contribution of plasma galactose and glucose to milk lactose synthesis during galactose ingestion.

We have previously demonstrated that plasma glucose contributed 80% in the fed and 60% in the fasted state to lactose synthesis in humans, and de novo synthesis in the breast contributing to both the glucose and galactose moieties accounted for the remaining 20% and 40%, respectively, of lactose. The present study was conducted to determine, in lactating women, whether oral galactose is directly incorporated from plasma galactose into glucose and galactose in milk lactose or via conversion of galactose to glucose in the liver. Six healthy exclusively breast-feeding women (30 +/- 2 yr) (mean +/- SE) ingested galactose at 22 micromol x kg-1 x min-1 for 9 h after an overnight fast during infusion of [6,6-2H2]glucose and [1-13C]galactose. We observed that 69 +/- 6% of glucose and 54 +/- 4% of galactose in lactose were derived directly from plasma glucose, whereas 7 +/- 2% and 12 +/- 2% of glucose and galactose in lactose, respectively, were derived directly from plasma galactose. De novo synthesis of glucose and galactose via hexoneogenesis accounted for 25 +/- 8% and 35 +/- 6%, respectively. We conclude that during ingestion of galactose the contribution from plasma glucose to glucose and galactose in lactose was similar to that of a short-term fasting, but part of the de novo synthesis of glucose and galactose in the breast was replaced by direct uptake of galactose.

Administration, Oral↗
PubMed2000

Triboelectrification of spray-dried lactose prepared from different feedstock concentrations.

Powder systems may acquire electrostatic charge during various pharmaceutical processing operations and may give rise to difficulties in handling and powder flow, mainly due to adhesion/cohesion effects. We have investigated the electrostatic charging of spray-dried lactose prepared from different feedstock concentrations using a laboratory spray-dryer. Triboelectrification of the spray-dried lactose samples was effected through contact with the stainless steel surface of either a mixing vessel or a cyclone separator. Results from both techniques showed differences in charge accumulation and particle-steel adhesion between the spray-dried lactose samples. As the feedstock concentration used to produce the spray-dried lactose was increased in the range 10-50% w/v, the mean charge on the lactose decreased from -20.8 to -1.3 nC g(-1) and -54.9 to -4.1 nC g(-1) for the mixing vessel and cyclone separator, respectively, with a corresponding decrease in adhesion. In addition, as the feedstock concentration was increased from 10 to 50% w/v, decreases were obtained in surface area values (1.06 to 0.56 m2 g(-1)), pore diameter (198.7 to 83.5 microm) and pore volume (1.09 to 0.75 cm3 g(-1)), and together with differences in crystal form correlated with the charge and adhesion results. The results suggested that the feedstock concentration could have a considerable influence on the charging and adhesional properties of spray-dried lactose. This may have relevance during pharmaceutical processing and manufacturing operations.

Animal Feed↗
PubMed1994

Characterization of the lactose transport system in Citrobacter freundii.

The lactose transport system of Citrobacter freundii was characterized. Both the lactose transport system and beta-galactosidase were induced with either lactose or isopropyl-beta-D-thiogalactopyranoside (IPTG), the latter being the better inducer. The Km values for methyl-beta-D-thiogalactopyranoside (TMG) transport and lactose transport were 0.61 mM and 1.1 mM, respectively, and the Vmax values were 53 nmol/min/mg cell protein and 12 nmol/min/mg cell protein, respectively. Thus, TMG is a better substrate than lactose. Thiogalactopyranoside (TDG) was a very potent competitive inhibitor. Neither Na+ nor Li+ had a significant effect on the TMG transport or the lactose transport. Proton/substrate cotransport (symport) via this system was observed.

Citrobacter freundii↗
PubMed2003

Effect of surface covering of lactose carrier particles on dry powder inhalation properties of salbutamol sulfate.

The effect of the surface covering of lactose carrier particles on the dry powder inhalation properties of salbutamol sulfate was investigated. Lactose carrier surfaces were covered with sucrose tristearate (J-1803F) by a high-speed elliptical-rotor-type powder mixer (Theta-Composer). In the present study, drug/carrier powder mixtures were prepared consisting of micronized salbutamol sulfate and lactose carriers with various particle surface conditions prepared by surface covering. These powder mixtures were aerosolized by a Jethaler), and the in vitro inhalation properties of salbutamol sulfate were evaluated by a twin impinger. Compared with the powder mixed with uncovered lactose carrier, the in vitro inhalation properties of the powder mixture prepared using the surface covering lactose carrier were significantly different, showing that the in vitro inhalation properties of salbutamol sulfate were improved. In vitro inhalation properties increased with the percentage of J-1803F added. Using this surface covering system would thus be valuable for increasing the inhalation properties of dry powder inhalation with lactose carrier particles.

Administration, Inhalation↗
PubMed2004

Influence of storage humidity on the in vitro inhalation properties of salbutamol sulfate dry powder with surface covered lactose carrier.

The influence of storage humidity on the in vitro inhalation properties of salbutamol sulfate dry powder with surface covered lactose carrier was investigated. In the present study, drug/carrier powder mixtures were prepared consisting of micronized salbutamol sulfate and lactose carriers with different particle surface conditions prepared by surface covering. Lactose carrier surfaces were covered with vegetable magnesium stearate (Mg-St-V) by a high-speed elliptical-rotor-type powder mixer (Theta-Composer). These powder mixtures were aerosolized by a Jethaler), and the in vitro inhalation properties of salbutamol sulfate were evaluated by a twin impinger. Compared with the powder mixed with uncovered lactose carrier, the in vitro inhalation properties of the powder mixture prepared using the surface covered lactose carrier were little decreased with increased in relative humidity (RH), showing that the in vitro inhalation properties of salbutamol sulfate were improved at high RH. Using this surface covering technique would thus be valuable for storage humidity of dry powder inhalation (DPI) with lactose carrier particles.

Administration, Inhalation↗
PubMed2004

Effects of surface processing of lactose carrier particles on dry powder inhalation properties of salbutamol sulfate.

The effects of the surface processing of lactose carrier particles on the dry powder inhalation properties of salbutamol sulfate were investigated. Lactose carrier particles were processed using a high-speed elliptical-rotor-type powder mixer (Theta-Composer). In the present study, drug/carrier powder mixtures were prepared, consisting of micronized salbutamol sulfate and coarse lactose carriers with various particle surface conditions prepared by surface processing. These powder mixtures were aerosolized by a Jethaler, and the in vitro inhalation properties of salbutamol sulfate were evaluated with a twin impinger. Compared with those of the powder mixed with unprocessed lactose carriers, the in vitro inhalation properties of the powder mixture prepared using the surface processed lactose carriers were significantly different, showing that the in vitro inhalation properties of salbutamol sulfate were improved. The in vitro inhalation properties increased with the rotor rotation rate. Using this surface processing system would thus be valuable for increasing the inhalation properties of dry powder inhalation with lactose carrier particles.

Administration, Inhalation↗
PubMed2006

Genotyping of the lactase-phlorizin hydrolase -13910 polymorphism by LightCycler PCR and implications for the diagnosis of lactose intolerance.

BACKGROUND: Hypolactasia and lactose intolerance are common conditions worldwide. Hypolactasia seems to be strongly correlated with genotype C/C of the genetic variant C-->T(-13910) upstream of the lactase phlorizin hydrolase (LPH) gene. We developed a rapid genotyping assay for LPH C-->T(-13910) and investigated the relationship of positive lactose breath hydrogen test (LBHT) results suggesting lactose intolerance with LPH C-->T(-13910) genotype. METHODS: Using automated DNA purification on the MagNA Pure LC and real-time PCR on the LightCycler, we examined samples from 220 individuals to estimate genotype frequencies; we then determined LPH C-->T(-13910) genotype in samples from 54 Caucasian patients with a positive LBHT result and symptoms of lactose intolerance. RESULTS: Genotyping of 220 individuals revealed frequencies of 21.4%, 41.8%, and 36.8% for genotypes C/C, C/T, and T/T. Of the patients with positive LBHT results, only 50% had the C/C genotype suggestive of primary adult hypolactasia in our study population. The other patients had various degrees of secondary hypolactasia or symptoms of lactose intolerance. Patients with C/C genotype had a mean (SD) peak H2 increase in the LBHT [108 (58) ppm] that was significantly higher than in patients with the C/T [65 (54) ppm] and T/T [44 (34) ppm] genotypes. CONCLUSIONS: The new real-time PCR assay provides a rapid, labor-saving means for the genotyping of LPH C-->T(-13910). Use of the assay may assist in differentiating patients with primary hypolactasia from those with secondary hypolactasia and lactose intolerance, who may need further clinical examinations to diagnose their underlying primary diseases.

Adolescent↗
PubMed2006

Sugar binding and protein conformational changes in lactose permease.

Lactose permease is an integral membrane protein that uses the cell membrane's proton gradient for import of lactose. Based on extensive biochemical data and a substrate-bound crystal structure, intermediates involved in lactose/H(+) co-transport have been suggested. Yet, the transport mechanism, especially the coupling of protonation states of essential residues and protein conformational changes involved in the transport, is not understood. Here we report molecular-dynamics simulations of membrane-embedded lactose permease in different protonation states, both in the presence and in the absence of lactose. The results analyzed in terms of pore diameter, salt-bridge formation, and substrate motion, strongly implicate Glu(269) as one of the main proton translocation sites, whose protonation state controls several key steps of the transport process. A critical ion pair (Glu(269) and Arg(144)) was found to keep the cytoplasmic entrance open, but via a different mechanism than the currently accepted model. After protonation of Glu(269), the salt bridge between Glu(269) and Arg(144) was found to break, and Arg(144) to move away from Glu(269), establishing a new salt bridge with Glu(126); furthermore, neutralization of Glu(269) and the displacement of Arg(144) and consequently of water molecules from the interdomain region was seen to initiate the closing of the cytoplasmic half channel (2.6-4.0 A reduction in diameter in the cytoplasmic constriction region in 10 ns) by allowing hydrophobic surfaces of the N- and C-domains to fuse. Charged Glu(269) was found to strongly bind the lactose permeant, indicating that proton transfer from water or another residue to Glu(269) is a prerequisite for unbinding of lactose from the binding pocket.

Arginine↗
PubMed1983

Mammary gland lactose, plasma progesterone and lactogenesis in the marsupial Macropus eugenii.

Mammary gland lactose concentrations in pregnant tammar wallabies remained low at 115 +/- 24 (S.E.M.) micrograms/g wet weight of tissue until immediately before parturition, then increased to 1274 +/- 262 micrograms/g after birth. Concentrations in non-pregnant cyclic animals were generally low (143 +/- 36 micrograms/g), but were raised in three animals around the time of oestrus. Removal of the corpus luteum on day 18 of pregnancy or the oestrous cycle caused an increase in lactose concentrations in both lutectomized and sham-operated animals. This occurred despite a significant lowering of peripheral plasma progesterone concentration in only the lutectomized group. Plasma cortisol concentrations were high in some of these animals, but showed no consistent relationships with the raised lactose concentrations. The increased peripartum lactose concentration normally coincides with a sharp fall in peripheral plasma progesterone concentration, but artificial maintenance of high progesterone levels had no effect on the increase of mammary gland lactose at parturition. Mammary gland lactose concentrations in tammar wallabies are therefore a useful indicator of biosynthetic activity and as an index of lactogenesis but the role, if any, of progesterone withdrawal in lactogenesis remains unclear.

Animals↗
PubMed1997

Evaluation of the interrelationships among lactose and protein sources in diets for segregated early-weaned pigs.

We conducted two experiments to evaluate the interactions among lactose and protein sources in diets for segregated early-weaned pigs. In Exp. 1, 360 barrows (initially 5.3 kg and 19 +/- 2 d of age) were fed diets containing crystalline lactose (0, 20, and 40%), spray-dried animal plasma (0 and 7.5%), and soybean meal (0 and 20%) in a 3 x 2 x 2 factorial arrangement. We used a blend of select menhaden fish meal and casein to replace the lysine provided by soybean meal or animal plasma. Diets contained 1.7% total lysine and were fed from d 0 to 14 after weaning. Pigs were fed a common diet from d 14 to 34. From d 0 to 14 after weaning, ADG and ADFI increased with increasing dietary lactose when the diet contained soybean meal but decreased when soybean meal was not in the diet (lactose x soybean meal, P < .05 and .10, respectively). Pigs fed animal plasma had increased (P < .05) ADG and ADFI from d 0 to 14 but decreased (P < .05) ADG from d 14 to 34. In Exp. 2, 324 barrows (initially 3.7 kg and 10 +/- 2 d of age) were fed diets from d 0 to 10 similar to those used in Exp. 1 with the exception that extruded soy protein concentrate replaced the lysine provided by soybean meal or animal plasma. From d 0 to 10 after weaning, increasing lactose improved (linear, P < .05) ADG and ADFI, and pigs fed animal plasma had higher ADFI (P < .05). In conclusion, soybean meal had no negative effect on ADG; however, animal plasma and lactose increased ADG and ADFI for pigs weaned between 10 and 19 d of age.

Aging↗
PubMed1980

Effect of lactose, copper and iron on manganese retention and tissue distribution in rats fed dextrose-casein diets.

The effect of iron, lactose and copper on manganese retention was studied in rats fed two diets. Thirty-six male albino rats (75 to 100 g) were allotted to six groups of six rats each. Three groups received a purified manganese-free dextrose-casein diet, and three groups received the same purified diet with 17% lactose added at the expense of dextrose. One group fed each of the above diets received either a manganese-free mineral mixture, the mineral mixture with 5 ppm supplemental Cu or the same mineral mixture with Fe removed. After 7 days on the diets, each rat was given, by gavage, 10 muCi of 54Mn activity as 54MnCl2 in a sodium acetate buffer. On the third day after dosing, the rats were sacrificed and samples of liver, kidneys, semitendinosus muscle, spleen and tibia were taken for stable and radioactive manganese analysis. Lactose added to the purified diet depressed 54Mn retention in all tissues studied. Lactose addition also decreased specific activities of the livers and kidneys but tended to increase stable manganese values. Copper apparently had little direct effect on 54Mn retention but tended to reduce the effect of lactose on 54Mn retention. Omission of Fe greatly increased 54Mn retention values in all tissues studied with or without added lactose. Fe omission also significantly increased the specific activities and stable Mn values of livers and the specific activity of kidneys. The results indicate that low dietary Fe may be a contributing factor to the increased manganese retention observed in this study and a previous study.

Animals↗
PubMed1980

Effect of lactose supplement on digestion of lucerne hay by sheep. II. Absorption of magnesium and calcium in the stomach.

Lactose (400 g/day) was added to a diet of lucerne hay (700 g/day chopped). The two diets (hay and hay plus lactose) were fed to four adult sheep fitted with rumen cannulas and simple cannulas at the proximal and distal end of the small intestine. The addition of lactose significantly increased apparent absorption of Mg, Ca and P and decreased slightly the apparent absorption of K. With lactose, absorption of Mg before the duodenum was significantly increased (41 vs 19%), and the increased Mg absorption from the stomach was associated with a net secretion of Mg into the small intestine. When hay was fed with lactose, more Ca was absorbed before the duodenum (30%) than when hay was fed alone (2%) and secretion of Ca into the small intestine was increased. Fermentation of lactose in the rumen induced decreases in pH and ammonia, a high lactate concentration and changes in molar proportions of volatile fatty acids. This work shows that readily fermentable carbohydrate increases stomach absorption of Ca and Mg and suggests that this effect is related to changes in fermentation patterns.

Animal Feed↗
PubMedDate not supplied

Role of glutamate-269 in the lactose permease of Escherichia coli.

Glu-269, which is located on the hydrophilic face of putative helix VIII in the lactose permease of Escherichia coli, has been replaced with Asp, Gln or Cys by oligonucleotide-directed, site specific mutagenesis. Cells expressing Asp-269 permease exhibit no lactose accumulation or lactose-induced H+ translocation, but retain some ability to mediate lactose influx down a concentration gradient at high substrate concentrations. Furthermore, right-side-out membrane vesicles containing Asp-269 permease do not catalyse active lactose transport, facilitated lactose efflux or equilibrium exchange. Remarkably, however, Asp-269 permease accumulates beta, D-galactopyranosyl 1-thio-beta,D-galactopyranoside in a partially uncoupled fashion, whereas no transport of methyl-beta,D-thiogalactopyranoside, sucrose or maltose is detectable. Mutant permeases containing neutral replacements (Gln or Cys) or Glu-269 are completely devoid of activity, although the proteins are present in the membrane at concentrations comparable with wild-type or Asp-269 permease. The observations demonstrate that a carboxylate at position 269 is essential for transport activity, and Glu-269 is important for substrate binding and/or recognition.

Amino Acid Sequence↗
PubMed2006

Modeling of lactose crystallization and color changes in model infant foods.

Lactose crystallization and color changes in formulas containing beta-lactoglobulin and gelatinized starch were investigated. Model infant formulas were prepared by colyophilization of 3 components (lactose, beta-lactoglobulin, and gelatinized starch). A mixture design was used to choose the percentage of each mixture component. These formulas were stored for 3 mo at different relative humidities (RH), ranging from approximately 0 to 94.6%, to study the lactose crystallization and color changes. Crystallization kinetics was studied by gravimetric methods, and lactose state (crystalline vs. amorphous) was verified before and after storage by differential scanning calorimetry. Before storage, lyophilized lactose was amorphous, but during storage it crystallized, depending on the RH. The lactose crystallization RH depended on the quantity of beta-lactoglobulin and gelatinized starch, and by increasing these quantities, the crystallization RH increased. For some formulas, the crystallization RH was noted at 3 different RH during storage. The first was noted after 1 d of storage and the second and third were observed later on, showing that crystallization is a time-dependent phenomenon. Nonenzymatic browning was studied in model infant formulas by yellow color changes of samples at 11.3, 43.2, 54.5, and 75.4% RH. In this study, 7 mathematical models were proposed to predict the moisture sorption properties and color changes at different RH, and the models were validated by experimental results.

Adsorption↗
PubMed1975

Effect of cell density on lactose synthesis in bovine mammary cell cultures.

The ability to synthesize lactose was studied in despersed cell cultures of lactating bovine mammary tissue under conditions of varying cell density, time, glucose, and lactose concentrations. The observable rate of lactose synthesis at a given time in an adequate medium is dependent on individual animal, length of time in culture, and density of cells. Rate of loss with time in the ability to synthesize lactose followed first order kinetics (half-time 11 h). Rate of synthesis per cell at a given time was an inverse function of the cell density following a linear relationship expressed by plotting the inverse of the amount accumulated versus the inverse of the cell number. A cell density for such experimental studies of about 2.5 times 10-6 cells per ml was ideal. The medium concentration of lactose and, above a minimum, that of glucose did not affect production of lactose.

Animals↗
PubMed1994

Factors affecting the ability of a high beta-galactosidase yogurt to enhance lactose absorption.

Lactose in yogurt is better absorbed by lactase-deficient subjects than is an equivalent quantity of lactose in milk, presumably because of the microbial activity of the beta-galactosidase present in yogurt. In this study, we describe a process that increases the beta-galactosidase of yogurt 5- to 6-fold and the ability of this high lactase yogurt to enhance lactose absorption in lactase-deficient subjects. These subjects ingested the yogurt meals after a 12-h fast, and lactose malabsorption was determined by measuring breath hydrogen. Breath hydrogen was reduced 39% following ingestion of high lactase yogurt from that after consumption of conventional yogurt, indicating that the high lactase yogurt enhanced lactose absorption. However, the reduction after high lactase yogurt was less than expected, given the 5- to 6-fold increment in beta-galactosidase measured in vitro. In vivo activity of beta-galactosidase requires that the enzyme resist acid denaturation in the stomach. The beta-galactosidase in high lactase yogurt was much less acid resistant than was the beta-galactosidase in conventional yogurt, and the relative inability of high lactase yogurt to enhance lactose absorption was likely due to the destruction of the beta-galactosidase in the stomach.

Absorption↗
PubMed1999

Physical and chemical properties of molecular compounds of lactose.

The physical and chemical properties of the molecular compounds of lactose 5 alpha-/3 beta- and 3 alpha-/2 beta-lactose were studied. The melting point and the heat of combustion were determined. The specific optical rotation of aqueous and organic solutions of these compounds was measured and was in agreement with their stoichiometric formula. Weak differences were observed in the chromatographic mobility of the lactose molecular compounds provided that nonaqueous solvents were used. The analysis by infrared spectroscopy showed that these compounds were due to association of alpha-lactose and beta-lactose crystals by a specific lattice of hydrogen bonding. The latter could be destroyed under controlled water vapor uptake. These physical and chemical properties led us to hypothesize on the means of association of these molecular compounds by comparison with the known structures of the other crystalline lactose forms.

Calorimetry, Differential Scanning↗