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PubMed1988

Characteristics of the early effect of prolactin on lactose biosynthesis in mouse mammary gland explants.

These studies were carried out to characterize the early effect of prolactin (PRL) on lactose biosynthesis in cultured mammary gland explants derived from 12- to 14-day pregnant mice. The rate of lactose biosynthesis was assessed by the rate of radiolabeled glucose incorporation into lactose. For the rapid isolation of lactose, a new method which involves the use of thin-layer chromatography on cellulose-impregnated plastic sheets was employed. The onset of the PRL stimulation of [3H]glucose incorporation into lactose occurred 6-8 hr after exposing the explants to PRL. The response to PRL was essentially all or none with maximum responses occurring with PRL concentrations above 25 ng/ml. The lowest stimulatory concentration of PRL was 10 ng/ml. The action of PRL on lactose biosynthesis requires both ongoing RNA and protein synthesis since puromycin, cyclohexamide, and actinomycin D abolished the PRL effect.

Animals↗
PubMed1991

Decreased Salmonella colonization in turkey poults inoculated with anaerobic cecal microflora and provided dietary lactose.

The effect of intracloacal inoculation with anerobic cultures of cecal microflora and addition of lactose to the feed on Salmonella senftenberg cecal colonization was evaluated in turkey poults. One-day-old poults were divided into four groups and provided 1) no anaerobic cultures, no lactose (control), 2) anaerobic cultures, 3) 5% lactose in the feed, or 4) anaerobic cultures and lactose. All groups were challenged orally with 10(6) S. senftenberg at 3 days of age. Salmonella senftenberg growth in the cecal contents was significantly decreased (P less than .05) at 10 and 30 days of age in both trials and at 20 days of age in Trial 1 in each of the three treatment groups as compared with the controls. On Day 30, the number of poults that were positive for Salmonella cecal culture was significantly decreased (P less than .01) in each of the treatment groups compared with the controls. Protection against Salmonella colonization was similar in the treatment groups inoculated with anaerobic cultures or provided dietary lactose. Combined treatment with anaerobic cultures of cecal microflora and provision of dietary lactose resulted in a level of protection against colonization equal to or higher than did either of the two treatments administered separately.

Animals↗
PubMed2004

Effects of lactose as an inducer on expression of Helicobacter pylori rUreB and rHpaA, and Escherichia coli rLTKA63 and rLTB.

AIM: To demonstrate the effect of lactose as an inducer on expression of the recombinant proteins encoded by Helicobacter pylori ureB and hpaA, and Escherichia coli LTB and LTKA63 genes and to determine the optimal expression parameters. METHODS: By using SDS-PAGE and BIO-RAD gel image analysis system, the outputs of the target recombinant proteins expressed by pET32a-ureB-E.coliBL21, pET32a-hpaA-E.coliBL21, pET32a-LTKA63-E.coliBL21 and pET32a-LTB-E.coliBL21 were measured when using lactose as inducer at different dosages, original bacterial concentrations, various inducing temperatures and times. The results of the target protein expression induced by lactose were compared to those by isopropyl-beta-D-thiogalactoside (IPTG). The proteins were expressed in E.coli. RESULTS: Lactose showed higher efficiency of inducing the expression of rHpaA, rUreB, rLTB and rLTKA63 than IPTG. The expression outputs of the target recombinant proteins induced at 37 degrees were remarkably higher than those at 28 degrees. Other optimal expression parameters for the original bacterial concentrations, dosages of lactose and inducing time were 0.8, 50 g/L and 4 h for rHpaA; 0.8, 100 g/L and 4 h for rLTKA63; 1.2, 100 g/L and 5 h for both rUreB and rLTB, respectively. CONCLUSION: Lactose, a sugar with non-toxicity and low cost, is able to induce the recombinant genes to express the target proteins with higher efficiency than IPTG. The results in this study establish a beneficial foundation for industrial production of H pylori genetic engineering vaccine.

Adhesins, Bacterial↗
PubMed1992

Lactose transport system of Streptococcus thermophilus. The role of histidine residues.

The lactose transport protein (LacS) of Streptococcus thermophilus is a chimeric protein consisting of an amino-terminal carrier domain and a carboxyl-terminal phosphoenolpyruvate:sugar phosphotransferase system (PTS) IIA protein domain. The histidine residues of LacS were changed individually into glutamine or arginine residues. Of the 11 histidine residues present in LacS, only the His-376 substitution in the carrier domain significantly affected sugar transport. The region around His-376 was found to exhibit sequence similarity to the region around His-322 of the lactose transport protein (LacY) of Escherichia coli, which has been implicated in sugar binding and in coupling of sugar and H+ transport. The H376Q mutation resulted in a reduced rate of uptake and altered affinity for lactose (beta-galactoside), melibiose (alpha-galactoside), and the lactose analog methyl-beta-D-thiogalactopyranoside. Similarly, the extent of accumulation of the galactosides by cells expressing LacS(H376Q) was highly reduced in comparison to cells bearing the wild-type protein. Nonequilibrium exchange of lactose and methyl-beta-D-thiogalactopyranoside by the H376Q mutant was approximately 2-fold reduced in comparison to the activity of the wild-type transport protein. The data indicate that His-376 is involved in sugar recognition and is important, but not essential, for the cotransport of protons and galactosides. The carboxyl-terminal domain of LacS contains 2 histidine residues (His-537 and His-552) that are conserved in seven homologous IIA protein(s) (domains) of PTSs. P-enolpyruvate-dependent phosphorylation of wild-type LacS, but not of the mutant H552Q, was demonstrated using purified Enzyme I and HPr, the general energy coupling proteins of the PTS, and inside-out membrane vesicles isolated from E. coli in which the lactose transport gene was expressed. The His-537 and His-552 mutations did not affect transport activity when the corresponding genes were expressed in E. coli.

Amino Acid Sequence↗
PubMed2006

[Relief effect of beta-galactosidase genetically engineered lactococcus lactis on the cell toxicity caused by lactose].

OBJECTIVE: To assess the relief effect of beta-galactosidase genetically engineered Lactococcus lactis on the cell toxicity caused by lactose in vitro. METHODS: An in vitro toxic Caco-2 cell model caused by lactose was established to evaluate the relief effect of beta-galactosidase genetically engineered Lactococcus lactis. Cell morphological parameters and proliferation activity parameter were used. RESULTS: The in vitro toxic Caco-2 cell model caused by lactose was successfully established; the genetically engineered Lactococcus lactis constructed in the authors' laboratory could enable the Caco-2 cell to have normal appearance with the presence of lactose and could improve the proliferation activity with the presence of high concentration of lactose (P < 0.01). CONCLUSION: The beta-galactosidase genetically engineered Lactococcus lactis has significant relief effect on the cell toxicity caused by lactose in vitro, which lays a foundation for food-grade alternation of this bacterium.

Caco-2 Cells↗
PubMed1991

Reversible lactose malabsorption and intolerance in Graves' disease.

Ten patients with untreated Graves' disease underwent tests to determine lactose absorption, liquid gastric emptying, and oral cecal transit time. To determine the influence of thyroid hormone status on lactose absorption, eight of these same patients had repeat studies when rendered euthyroid. Two of these eight patients also underwent studies while transiently hypothyroid. Motility studies were also evaluated in a group of 11 control subjects. Lactose malabsorption occurred in nine patients with Graves' disease. In seven patients who repeated these studies, lactose malabsorption normalized in three, symptoms induced by lactose improved in two and were unchanged in two. However, these latter two patients appeared to have improved symptoms in the transient hypothyroid state. Liquid gastric emptying was significantly faster in untreated patients than controls and treated self-same patients. Transit time was significantly faster in untreated patients than when they were rendered euthyroid. There may be a relationship between altered lactose absorption states and changes in intestinal motility in patients with Graves' disease.

Adult↗
PubMed1977

[Functioning of the lactose operon of E. coli K-12 under the influence of non-specific regulators].

A possible role played by cAMP in the stimulating action of ACTH and hydrocortisone on lactose E. coli K-12 operon was studied. It was shown that ACTH caused no effect in the E. coli WZ-78/F'lac (cya855) and E. coli CA8001 (L1) strains with destroyed positive cAMP control system of the lactose operon function, at the same time producing a stimulating effect on the lactose operon in the strains of wild type, i.e. E coli 200PS/F'lac and E. coli 3000. Hydrocortisone stimulated the lactose operon function both in E. coli 3000 and in the mutant E. coli CA8001 (L1). It was supposed that the accelerating effect of ACTH on the lactose operon was mediated through cAMP; as to hydrocortisone--it stimulated the lactose operon function independently of cAMP.

Adrenocorticotropic Hormone↗
PubMed1991

Dietary treatment of lactose intolerance in infants and children.

During the past several years there have been many reports of alternative dietary therapies for primary and secondary lactose intolerance. We have learned that it is useful to feed through most episodes of mild diarrhea that previously would have been treated with clear liquid diets. Infant formulas, including both soy-protein and hydrolysate formulas with specially designed carbohydrate, protein, and fat components, are available to treat the infant with diarrheal syndromes and secondary lactase deficiency. Also, the diet can be supplemented with lactase. Specialized lactose-reduced products as well as cultured and fermented dairy products may be used in varying degrees for lactose-intolerant children. The ingestion of milk with food and fiber components in the diet has also been shown to improve symptoms of lactose intolerance. This review summarizes the essentials of diagnosis of and dietary therapy for lactose intolerance. Our findings indicate that a number of specialized formulas and products are available for successful dietary management of lactose intolerance in infants and children.

Child↗
PubMedDate not supplied

[Beta-galactosidase activity of strains of Kluyveromyces spp. and production of ethanol from lactose].

We investigated the behavior of yeast of the genus Kluyveromyces (K. fragilis 507, K. lactis 29 and K. lactis 10), which grow on lactose as sole carbon source, since they possess an enzyme system for the utilization of this sugar. We determined the beta-galactosidase activity of these strains, grown in the logarithmic phase in media containing glucose and lactose. On addition of 0 to 12% v/v ethanol to cells treated with toluene, we did not observe inhibition of the enzyme in strain 10 of Kluyveromyces lactis, which showed the greatest activity (704.4 Units). Since there exist the possibility of industrial utilization of concentrated whey (4 times), we performed fermentation tests of the three strains, at 30 C, in media containing initial lactose concentrations of 16.5 and 24.5%. After 48 h the residual lactose concentration was practically zero, and the ethanol concentrations had reached 7.60 and 10.10% v/v. It might be expected that the rate of fermentation of a disaccharide such as lactose would be related to the rate of hydrolysis of the sugar, so that strains having a higher rate of enzymatic hydrolysis should show a higher fermentation rate. However, we did not observe such behavior, as strains of Kluyveromyces having enzymatic activities as different as K. lactis 10 (704.4 U) and K. lactis 29 (189.7 U) did not show any great difference in the production of ethanol from lactose.

Ethanol↗
PubMed1990

Characterization of the double mutant, Val-177/Asn-322, of the lactose permease.

The double mutant, Val-177/Asn-322, was investigated with regard to its ability to transport H+ and galactosides. In downhill lactose transport assays, the wild-type strain had a Km value for lactose uptake of 0.9 mM and a Vmax of 0.65 mumol lactose/min.mg protein while the mutant had a significantly higher Km value of 1.9 mM but a similar Vmax of 0.49 mumol/min.mg protein. In spite of its moderate ability to transport lactose downhill, the Val-177/Asn-322 mutant exhibited the striking property of being completely defective in the uphill accumulation of lactose or methyl-beta-D-thiogalactopyranoside. Direct measurements of H+ transport, however, showed that the mutant's defect in active accumulation is not due to a defect in the ability to transport H+ with lactose or methyl-beta-D-thiogalactopyranoside. The Val-177/Asn-322 mutant strain had a H+:lactose stoichiometry of 0.84 which was similar to that measured in the wild-type strain (0.68). These results are discussed with regard to the role His-322 plays in H+ transport, active accumulation of sugars, and sugar recognition.

Asparagine↗
PubMed1989

Analysis of the structural specificity of the lactose permease toward sugars.

The sugar specificity properties of the lactose permease were investigated. Free galactose was shown to competitively inhibit the lactose permease yielding a Ki value of 7.4 mM. This value was severalfold higher than the observed Km for lactose (1.3 mM). A variety of other monosaccharides also showed significant inhibition of lactose transport. With regard to -OH groups along the galactose ring it appears that the relative importance is OH-3 greater than OH-4 greater than OH-6 greater than OH-2 greater than OH-1. In general, galactosides with alpha-linkages exhibited significantly higher affinities compared with their beta-linked counterparts. An optimal size for the aglycone portion of the galactoside was reached with aglycones containing hexose residues or a benzene ring. The preferred size of the aglycone appears to be hexose, benzene ring greater than methyl group greater than no aglycone much greater than disaccharide greater than trisaccharide. However, neither the specific structure of the aglycone nor its relative hydrophobicity appeared to be important factors in permease recognition. For example, the hydrophobic beta-nitrophenyl-galactosides had lower affinities compared with lactose (a beta-galactoside), whereas the alpha-nitrophenylgalactosides generally had higher affinities compared with melibiose (an alpha-galactoside). In addition, no consistent preference was seen when considering the location of the nitro group on the benzene ring. From this work, a model is presented which depicts the binding of galactosides to the lactose permease.

Binding Sites↗
PubMed1966

Turnover of cholesterol-4-14-C and cholic acid-24-14-C by rabbits fed a diet containing lactose.

Rabbits fed 0.35% of cholesterol in diets containing either 29.35% of lactose or sucrose were studied for 14 weeks. The rabbits fed lactose had higher plasma and liver cholesterol concentrations than those fed sucrose. The half-life of cholesterol was 19.0 days and 35.0 days for rabbits fed sucrose and lactose, respectively. The half-life, pool size, and daily production of deoxycholic acid were 9.7 days, 1.29 g, and 74.1 mg for rabbits fed sucrose; and 14.2 days, 1.40 g, and 49.1 mg, for those fed lactose. Cholesterol was the major neutral sterol in the feces of the rabbits fed lactose, whereas coprostanol (5 Beta-cholestan-3 Beta-ol) dominated the corresponding fraction in those fed sucrose. The fecal steroid composition did not vary between day and night collections. No sterol esters were detected in the feces. Urinary elimination of radioactivity was less than 10% of that injected. The "lactose effect" seems to be due to enhanced retention of steroids, the mechanism of which has not been elucidated.

Animals↗
PubMed1981

Estimation of lactose hydrolysis by freezing point measurements in milk and whey substrates treated with lactases from various microorganisms.

beta-Galactosidase concentrates obtained from several microorganisms were used to hydrolyze skim milk, low fat (2%) milk, sweet whey, acid whey, acid whey permeate, and acid whey concentrate. Among acid substrates, the freezing point depression for each 1% lactose hydrolyzed was the greatest with the lactase from Aspergillus niger (0.0501 degrees H); among neutral substrates, the depression was greater in sweet whey (0.0495 degree H) and lesser in low fat milk (0.0445 degrees H). All data were statistically significant. The average freezing point depression for each 1% lactose hydrolyzed wa s0.0468 degrees H (range 0.0436-0.0501 degrees H). Oligosaccharides formed in the lactose hydrolysis inconsistent freezing point readings of the cryoscope at the low freezing points measured, and protease contamination in some lactases may affect the precision of freezing point determination. Hydration and volume of non-protein components in commercial enzymes, unstable color complex formed by lactose and methylamine solution, and difficulty in the use of methylamine solution might cause variations in determination of lactose by the analytical procedure. These factors can be eliminated or minimized. This method is the simplest and quickest estimation of lactose hydrolysis, and it offers great accuracy and consistency.

Animals↗
PubMed1983

[Possibility of producing lactose-free products for infant and dietetic nutrition].

A study has been made of the conditions for manufacturing a milk-protein concentrate with a low lactose content. In order to hydrolyze lactose, defatted pasteurized milk is supplemented with yeast beta-galactosidase in an amount of 6 Units per g lactose. Milk and lactose are allowed to stand for 6-7 h at 35 degrees C, which provides a 75% hydrolysis of lactose. After thermal treatment and cooling hydrolyzed milk is subjected to lactic fermentation during which the residual amount of lactose and part of galactose are fermented. It is specified that the concentrate manufactured may be used for feeding children with upset carbohydrate metabolism.

Food Technology↗
PubMedDate not supplied

[Lactose content and beta-galactosidase activity in yogurt, cheeses and curdled milk made in Brazil].

We studied yogurts and industrialized curdled milk in three different storage times, as well as homemade and Syrian curdled milk and cheeses. Lactose content (gm%) and beta-galactosidase activity were determined in these products. Lactose content was elevated in yogurts and curdled milk with a lactose reduction of about 22% compared to the lactose of cow milk, with a mean and standard desviation (M +/- SD) of 3.81 +/- 0.47 gm%. In the cheeses lactose content was low, between 1.91 and 0.03 g%. beta-galactosidase activity was present in yogurts and curdled milk, with values between 0.58 and 3.61 U in time I and M +/- SD of 0.15 +/- 0.23 U. A significant decrease of beta-galactasidase activity was observed during the storage time. By analyzing and comparing these findings with the literature, we conclude that the products studied, by their low content of lactose (cheeses and yakult) or by the presence of beta-galactasidase activity (yogurts and curdled milk at time I) probably would be tolerated by most hipolactasic persons.

Brazil↗
PubMed1994

[Abdominal pain in children caused by lactose intolerance. Prospective use of the hydrogen breath test].

OBJECTIVES: We performed the breath hydrogen test in children consulting for abdominal pain in order to determine the minimal quantity of lactose required to prove malabsorption with least patient incomfort and to evaluate the effect of an adapted diet in children with a positive test. METHODS: The breath hydrogen test after lactose intake was performed in 109 children (51 boys, 58 girls, mean age 8.2 + 3.2 years, range 3 to 15) seen for unexplained abdominal pain. All these children had complained of abdominal pain daily for at least 6 months and no other cause could be identified. Children with acute or chronic diarrhoea or constipation were excluded. Nineteen children had been transferred from the surgery unit and 6 had been followed by the psychiatry unit. All these children drank milk regularly. RESULTS: The diagnosis of lactose intolerance was established in 83 children (76.1%) on the basis of a hydrogen peak in the breath after lactose ingestion. One-fourth of the children were of French origin and the others had at least one grandparent who was of Mediterranean or African origin. A lactose-free diet was proposed and led to the disappearance of abdominal pain in 24% and a clear improvement in 32%. CONCLUSION: The breath hydrogen test is a simple non-invasive test which allows a selection of children who could benefit from a lactose-free diet although it cannot be used to predict the effect of diet.

Abdominal Pain↗
PubMed1993

[Relationship between primary lactose malabsorption and consumption of dairy products].

This study was designed to determine the influence of lactose malabsorption on the consumption of dairy products. We studied 157 children and 43 adults. The Breath-hydrogen test was used to define their level of lactose digestion. The prevalence of lactose maldigesters was 12%. We found a large relationship between the consumption of milk and milk products and age. Malabsorbers consumed more fermented dairy products (ripened cheese and yogurt) than did absorbers (p < 0.05). Subjects with normal lactose absorption consumed more milk, butter, cream cheese and global lactose than the maldigesters (p < 0.05). Lactose intolerance, familiar consumption and geographic origins had little influence on an individual's consumption habits.

Adolescent↗
PubMed1993

Dietary management of lactose intolerance--lactase treated milk versus soya milk.

Transient lactose intolerance secondary to infective diarrhoea is common in developing countries, & soya milk formula is commonly prescribed for its management. Lactose predigested milk feeding was done in 70 patients of test group while withdrawing lactose diet & 84.3% had control of motions with absent lactose in stool despite challenge feed, 3 days after withdrawal of lactose diet. 83.3% patients in control group fed soya milk had such improvement but the incidence of feed refusal was 30% in this group as compared to only 2.8% in lactaid group. Vomiting after feed was also found in 10% of babies fed soya milk as compared to none in lactaid group, thus proving superiority of lactaid in management of lactose intolerance diarrhoea.

Female↗