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PubMedDate not supplied

Effect of lactose and Lactobacillus acidophilus on the colonization of Salmonella enteritidis in chicks concurrently infected with Eimeria tenella.

The effect of dietary lactose and Lactobacillus acidophilus on the colonization of Salmonella enteritidis (phage type 4) in newly hatched leghorn chicks concurrently infected with Eimeria tenella was studied. There were six groups of birds in each of two replicate trials: uninfected controls, birds infected with S. enteritidis, birds infected with S. enteritidis and E. tenella, birds infected with S. enteritidis and E. tenella that were fed with dietary lactose (5%), birds infected with S. enteritidis and E. tenella that were provided with L. acidophilus, and birds infected with S. enteritidis and E. tenella that were fed both L. acidophilus and dietary lactose (5%). Chickens were necropsied at 2, 5, and 8 days after S. enteritidis inoculation for bacteriological examination. The cecal population of S. enteritidis was significantly increased by infection with E. tenella. Lactose alone and the combination of lactose and L. acidophilus significantly reduced the population of S. enteritidis in the ceca of birds infected with E. tenella (P < 0.05), but the combination was more effective than lactose alone (P < 0.05). Adding anaerobic culture of L. acidophilus alone did not significantly decrease the population of S. enteritidis in the ceca. No significant reduction of colonization of S. enteritidis in the liver and spleen of birds with coccidiosis was observed.

Animals↗
PubMed1978

[Role of the digestive flora in adaptation to lactose consumption in rats].

Part of the digestive flora in the adaptation to lactose consumption. Lactase activity was determined with adult Wistar rats. Some of which were accustomed to lactose since weaning. For this purpose, the tissue of jejunum, the flora of the ileum, the caecum and the large intestine were examined. When the rats received a high lactose diet, the lactase of the jejunum is more active because of both the intestinal tissue development and a higher production of enzyme by protein unit. But the main source of lactase is the digestive flora of the animal: a lactase flora develops in the ileum, the large intestine and mainly the caecum. The caecum lactase represents about half of the total lactase activity. The flora of the animal which has not consumed lactose since weaning can develop a noticeable lactase activity after 7 hr of incubation in presence of lactose. It is also the caecum flora which shows the greatest capacity of adaptation to lactose.

Animals↗
PubMed1977

Milk and lactose-hydrolyzed milk.

Seven females 18 to 26 years old (mean 23 years) who were lactose malabsorbers as determined by a lactose tolerance test were given two different test meals: 5 ml/kg body weight reconstituted nonfat dry milk and 5 ml/kg body weight reconsituted nonfat dry milk in which 92% of the lactose had been hydrolyzed to glucose and galactose. Lactose malabsorption was determined by the breath H2 test. Tests were done in duplicate for a total of 28 tests. Whether a 3-hr test period of a 5-hr test period was used, the average breath H2 response after the lactose-hydrolyzed nonfat dry milk test meals was significantly lower (P less than 0.002) than the average breath H2 response after the nonfat dry milk test meals. There were significant differences among individual responses (P lless than 0.06 for the 3-hr test period and P less than 0.09 for the 5-hr test period), and no significant differences between duplicate test days.

Adolescent↗
PubMed1987

Milk consumption, symptom response, and lactose digestion in milk intolerance.

The experience of adverse gastrointestinal symptoms (gas, abdominal pain, and diarrhea) after the oral ingestion of 360 mL whole milk was investigated in 25 adults who claimed to be milk intolerant. The level of customary milk consumption by all subjects was low compared with that of 13 control subjects who denied a history of milk intolerance. After drinking the milk, which was accompanied by a hydrogen breath test, most of the subjects experienced some of their accustomed intestinal discomfort and the degree of intolerance was similar for the nine (36%) who proved to be true lactose-maldigester subjects and the 16 (64%) who had flat hydrogen breath responses, ie, who were classified as lactose-digester subjects. There is a subpopulation of lactose-intolerant milk-rejector individuals that absorbs lactose efficiently and responds to other milk-related factor(s) with the same subjective symptoms and dietary conduct as do true lactose-maldigester individuals.

Adult↗
PubMed2005

Evaluation of a new DNA test compared with the lactose hydrogen breath test for the diagnosis of lactase non-persistence.

BACKGROUND AND AIMS: Recent publications have found that the CC genotype of the DNA variant -13910 T/C upstream of the LCT gene is associated with lactase non-persistence. We therefore compared the value of DNA testing for this variant (DNA test) with the lactose hydrogen breath test (H2 test), which is the clinical standard for the diagnosis of lactase non-persistence. PATIENTS AND METHODS: One hundred and twenty-three consecutive patients with suspected lactose malabsorption were tested for the presence of the -13910 T/C variant by polymerase chain reaction-restriction fragment length polymorphism analysis. These patients also underwent the H2 test after ingestion of 50 g lactose. RESULTS: Thirty-seven subjects had a CC genotype of the -13910 T>C polymorphism suggesting lactase non-persistence; 36 (97%) had also a positive H2 test. Eighty-six subjects had either a TC or a TT genotype suggestive of lactase persistence. Seventy-four (86%) of these tested negative on the H2 test, while 12 patients had a positive H2 test. In eight of these 12 patients duodenal biopsies showed no evidence of small bowel disease. One patient carrying a CC genotype had a negative H2 test. In this patient the rise in serum glucose after oral lactose was normal, furthermore H2 non-excretion was also excluded. CONCLUSIONS: An excellent correlation is observed between a CC genotype and a positive H2 test, whereas the correlation between a TC or TT genotype and a negative H2 test result is less strong. Analysis of the -13910 T/C variant can be considered a good test for predicting the presence of lactase non-persistence in a patient population with suspected lactose malabsorption.

Adolescent↗
PubMed1987

Double-blind study on the tolerance of four types of milk in lactose malabsorbers and absorbers.

Eighty Italian adults (53 females, 18-69 years, and 27 males, 18-60 years) underwent double-blind tests involving the intake of increasing amounts (125, 250, 500, 1000 ml/d) of four types of milk with normal or low lactose and/or fat content. The tests were completed satisfactorily by 71 subjects. Forty were lactose malabsorbers (LMs) and 31 were absorbers (LAs), according to a standard oral lactose tolerance test. Each subject reported on a questionnaire whether he/she experienced symptoms during the 24 h after milk intake, and the intensity of the symptoms, adopting a score of 0 to 12, according to an already tested procedure. The aim of the study was to investigate the relationship between lactose malabsorption or absorption and intolerance to milk in Italian adults, relative to lactose and fat contents, dose of milk and individual sensitivity. LMs reported symptoms overall more frequently and with greater intensity than LAs (P less than 0.001). The amount of milk ingested was positively associated with the frequency of symptoms both in LMs and LAs. Contrary to earlier findings, fat seemed to contribute to milk intolerance in LMs rather than to reduce it. According to analysis of variance individual differences accounted for 40 per cent of total variation in symptom frequency.

Adolescent↗
PubMed1976

[Diagnostics of lactose-malabsorption: value of tolerance tests and 14CO2 exhalation test in patients with and without lactase deficiency (author's transl)].

Lactose-tolerance-test (LTT), ethanol-lactose-tolerance-test (ELTT), 14CO2 breath test and 14C-glucose determination were simultaneously performed in 27 healthy subjects, 16 patients with a Billroth II gastrectomy and 6 patients with a malabsorption syndrome. Intestinal mucosal lactase was absent or significant diminished in 5 of the B II cases and in all patients with malabsorption. In the lactase deficient patients a diminished serum glucose rise after ingestion of 50 g lactose was observed in LTT as well as in ELTT. False positive results in LTT could not be prevented by performing the ELTT. Furthermore the ELTT is not suitable for ambulant investigations because of the required high ethanol load of 0.5 g/kg. Most reliable results were obtained by determination of 14C-serum-glucose after oral application of about 15 muCi of 14C lactose. In respect to lactase level neither false positive nor false negative results were observed. For clinical investigations the procedure of isolation and measurement of 14C-glucose is too laborious however. 14CO2-exhalation test cannot be recommended because of many false positive and false negative results. Moreover 14CO2-exhalation seemed to be insensible and predominant depending on factors other than lactose absorption.

Blood Glucose↗
PubMed1997

Binding of monoclonal antibody 4B1 to homologs of the lactose permease of Escherichia coli.

The conformationally sensitive epitope for monoclonal antibody (mAb) 4B1, which uncouples lactose from H+ translocation in the lactose permease of Escherichia coli, is localized in the periplasmic loop between helices VII and VIII (loop VII/VIII) on one face of a short helical segment (Sun J, et al., 1996, Biochemistry 35;990-998). Comparison of sequences in the region corresponding to loop VII/VIII in members of Cluster 5 of the Major Facilitator Superfamily (MFS), which includes five homologous oligosaccharide/H+ symporters, reveals interesting variations. 4B1 binds to the Citrobacter freundii lactose permease or E. coli raffinose permease with resultant inhibition of transport activity. Because E. coli raffinose permease contains a Pro residue at position 254 rather than Gly, it is unlikely that the mAb recognizes the peptide backbone at this position. Consistently, E. coli lactose permease with Pro in place of Gly254 also binds 4B1. In contrast, 4B1 binding is not observed with either Klebsiella pneumoniae lactose permease or E. coli sucrose permease. When the epitope is transferred from E. coli lactose permease (residues 245-259) to the sucrose permease, the modified protein binds 4B1, but the mAb has no significant effect on sucrose transport. The studies provide further evidence that the 4B1 epitope is restricted to loop VII/VIII, and that 4B1 binding induces a highly specific conformational change that uncouples substrate and H+ translocation.

Amino Acid Sequence↗
PubMed1986

Evidence for a protonmotive force related regulatory system in Escherichia coli and its effects on lactose transport.

Strains of Escherichia coli with mutations in the eup (energy-uncoupled phenotype) locus do not grow on nonfermentable carbon sources, have reduced growth yields on limiting glucose, are insensitive to colicins A and K, exhibit resistance to aminoglycoside antibiotics, and are defective in protonmotive force coupled active transport. eup mutations do not result in lowered protonmotive force. Here we show that deenergization of a eup+ strain results in the appearance of a new low KT, low Vmax form of the lactose carrier; in a strain deleted of the eup locus, deenergization does not evoke the low KT, low Vmax form of the lactose carrier. Cells bearing a eup point mutation and exhibiting the Eup- phenotype possess the low KT, low Vmax form of the lactose carrier even when energized. In addition to affecting the kinetic parameters of the lactose carrier, the eup point mutation also reduces the KT and Vmax of the proline carrier. On the basis of these findings, we suggest that the normal eup gene product mediates a novel regulation of lactose carrier function following deenergization. The defect in proline and lactose transport caused by eup point mutations may stem from an altered eup product aberrantly mediating the regulation under energized conditions. Finally, the pleiotropy associated with eup point mutations may be indicative of those protonmotive force driven functions that are subject to eup regulation.

Biological Transport, Active↗
PubMed1972

The effect of hypophysectomy and subsequent replacement therapy with sheep prolactin or bovine growth hormone on the lactose synthetase activity of rabbit mammary gland.

1. The effects of hypophysectomy and replacement therapy with sheep prolactin and bovine growth hormone on the lactose synthetase activity of the mammary glands of lactating rabbits were studied. 2. There was an approximately fourfold decline in the lactose synthetase activity of homogenates calculated on a DNA basis within 6-7 days of hypophysectomy. Prolactin reversed this decline but growth hormone had no effect. 3. Changes in the properties of a particulate fraction isolated from the glands indicated that a decline in the effective concentration of alpha-lactalbumin was one factor contributing to the decreased lactose synthetase activity after hypophysectomy. 4. As the changes in lactose output produced by hypophysectomy and prolactin therapy are much greater than the changes in total lactose synthetase activity it is concluded that the activity of this enzyme is not the main factor controlling lactose output under these conditions.

Animals↗
PubMed2000

Glucose and galactose absorption after ingestion of milk containing hydrolysed lactose in calves with diarrhoea.

Ten calves which had contracted acute diarrhoea caused by rotavirus, coronavirus and Cryptosporidium were used to test the hypothesis that feeding lactose-hydrolysed cow's milk instead of unprocessed cow's milk improves sugar absorption in diarrhoeic calves. The animals were rehydrated with an orally administered solution containing electrolytes and glucose. Thereafter the calves received one test meal of whole fresh cow's milk whose lactose had been hydrolysed by added lactase and one test meal of unprocessed cow's milk at an interval of 24 h in a cross-over design trial. In comparison with unprocessed milk, the intake of milk containing hydrolysed lactose resulted in a slight decrease of mean breath hydrogen concentration (P = 0.18), but also a slight decrease of mean blood galactose concentration (P = 0.14). There was no treatment effect on mean plasma glucose concentration. Peak plasma glucose and blood galactose concentration tended to be delayed after the intake of lactose-hydrolysed milk, which implies that gastric emptying was probably delayed. The results show that feeding milk which contains hydrolysed lactose does not significantly improve lactose utilization in calves that are suffering from benign infectious diarrhoea.

Animals↗
PubMed2000

Phosphorylation state of HPr determines the level of expression and the extent of phosphorylation of the lactose transport protein of Streptococcus thermophilus.

The lactose transport protein (LacS) of Streptococcus thermophilus is composed of a translocator domain and a regulatory domain that is phosphorylated by HPr(His approximately P), the general energy coupling protein of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS). Lactose transport is affected by the phosphorylation state of HPr through changes in the activity of the LacS protein as well as expression of the lacS gene. To address whether or not CcpA-HPr(Ser-P)-mediated catabolite control is involved, the levels of LacS were determined under conditions in which the cellular phosphorylation state of HPr greatly differed. It appears that HPr(Ser-P) is mainly present in the exponential phase of growth, whereas HPr(His approximately P) dominates in the stationary phase. The transition from HPr(Ser-P) to HPr(His approximately P) parallels an increase in LacS level, a drop in lactose and an increase in galactose concentration in the growth medium. Because the K(m)(out) for lactose is higher than that for galactose, the lactose transport capacity decreases as lactose concentration decreases and galactose accumulates in the medium. Our data indicate that S. thermophilus compensates for the diminished transport capacity by synthesizing more LacS and phosphorylating the protein, which results in increased transport activity. The link between transport capacity and lacS expression levels and LacS phosphorylation are discussed.

Bacterial Proteins↗
PubMed1976

Regulation of lactose fermentation in group N streptococci.

Group N streptococci, which have the lactose phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) and phospho-beta-d-galactosidase (beta-Pgal), grew rapidly on lactose and converted more than 90% of the sugar to l-lactate. In contrast, Streptococcus lactis 7962, which does not have a beta-Pgal, grew slowly on lactose and converted only 15% of the sugar to l-lactate. With glucose and galactose, this strain had growth rates and fermentation patterns similar to those of other S. lactis strains, suggesting that the rapid and homolactic fermentation of lactose that is characteristic of group N streptococci is dependent upon a functional PEP-dependent PTS and the presence of beta-Pgal. Seventeen strains of group N streptococci were examined for the activator specificities of pyruvate kinase and lactate dehydrogenase. The properties of each enzyme from all the strains, including S. lactis 7962, were similar. Pyruvate kinase had a broad activator specificity, whereas activation of lactate dehydrogenase was specific for ketohexose diphosphate. All intermediates of lactose metabolism from the hexose phosphates to the triose phosphates activated pyruvate kinase. No activation was obtained with adenosine 5'-monophosphate. K and Mg were required for pyruvate kinase activity but could be replaced by NH(4) and Mn, respectively. Lactate dehydrogenase was activated equally by fructose-1,6-diphosphate and tagatose-1,6-diphosphate, the activation characteristics being pH dependent. The roles of pyruvate kinase and lactate dehydrogenase in the regulation of lactose fermentation by group N streptococci are discussed.

Journal Article↗
PubMed1984

Selection of Galactose-Fermenting Streptococcus thermophilus in Lactose-Limited Chemostat Cultures.

Stock cultures of Streptococcus thermophilus are essentially galactose negative (Gal). Although both galactose 1-phosphate uridyl transferase and uridine-5-diphospho-glucose 4-epimerase are present, suggesting that the genes for the Leloir pathway exist, cells cannot induce high levels of galactokinase. Therefore, galactose is largely excreted when cultures are grown on lactose, and most strains cannot be readily adapted to grow on free galactose. Gal cultures were grown in a chemostat under lactose limitation in which high concentrations of residual galactose were present. Under this selection pressure, Gal organisms eventually took over the culture with all four strains examined. Gal cells had induced galactokinase, and three of the four strains grew on free galactose with doubling times of 40 to 50 min. When Gal organisms were grown on lactose in batch culture, the galactose moiety was only partially utilized while lactose was still present. As lactose was exhausted, and catabolite repression was lifted, the Leloir pathway enzymes (especially galactokinase) were induced and the residual galactose fermented. Neither phospho-beta-galactosidase activity nor the enzymes of the d-tagatose 6-phosphate pathway were detected in S. thermophilus. In contrast to Streptococcus cremoris and Streptococcus lactis, fermentation was homolactic with galactose in batch cultures and with lactose limitation in the chemostat. When mixed Gal-Gal cultures were repeatedly transferred in milk, the Gal cells became the dominant cell type. The Gal phenotype of stock cultures probably reflects their prolonged maintenance in milk.

Journal Article↗
PubMed1983

Cooperative binding of the sugar substrates and allosteric regulatory protein (enzyme IIIGlc of the phosphotransferase system) to the lactose and melibiose permeases in Escherichia coli and Salmonella typhimurium.

An Escherichia coli strain which overproduces the lactose permease was used to investigate the mechanism of allosteric regulation of this permease and those specific for melibiose, glycerol, and maltose by the phosphoenolpyruvate-sugar phosphotransferase system (PTS). Thio-beta-digalactoside, a high affinity substrate of the lactose permease, released the glycerol and maltose permeases from inhibition by methyl-alpha-d-glucoside. Resumption of glycerol uptake occurred immediately upon addition of the galactoside. The effect was not observed in a strain which lacked or contained normal levels of the lactose permease, but growth of wild-type E. coli in the presence of isopropyl-beta-thiogalactoside plus cyclic AMP resulted in enhanced synthesis of the lactose permease so that galactosides relieved inhibition of glycerol uptake. Thiodigalactoside also relieved the inhibition of glycerol uptake caused by the presence of other PTS substrates such as fructose, mannitol, glucose, 2-deoxyglucose, and 5-thioglucose. Inhibition of adenylate cyclase activity by methyl-alpha-glucoside was also relieved by thiodigalactoside in E. coli T52RT provided that the lactose permease protein was induced to high levels. Cooperative binding of sugar and enzyme III(Glc) to the melibiose permease in Salmonella typhimurium was demonstrated, but no cooperativity was noted with the glycerol and maltose permeases. These results are consistent with a mechanism of PTS-mediated regulation of the lactose and melibiose permeases involving a fixed number of allosteric regulatory proteins (enzyme III(Glc)) which may be titrated by the increased number of substrate-activated permease proteins. This work suggests that the cooperativity in the binding of sugar substrate and enzyme III(Glc) to the permease, demonstrated previously in in vitro experiments, has mechanistic significance in vivo. It substantiates the conclusion that PTS-mediated regulation of non-PTS permease activities involves direct allosteric interaction between the permeases and enzyme III(Glc), the postulated regulatory protein of the PTS.

Adenylyl Cyclase Inhibitors↗
PubMed1987

Spontaneous release of temperate phage by relysogenized lactose-positive transductants of Streptococcus lactis C2.

Transduction for lactose-fermenting ability between the lactose-positive lysogen Streptococcus lactis LM0221 and plasmid-cured, prophage-cured, lactose-negative S. lactis LM2301 resulted in the appearance of lactose-positive transductants surrounded by a zone of clearing in the lactose-negative cell lawn. By using plaque assay procedures, the zones were shown to contain bacteriophage particles, and both spontaneous release and UV induction of prophage from these transductants were demonstrated. The DNA hybridization confirmed that LM2301 did not contain the prophage in its chromosome and that the zone-producing transductant KZ1 was relysogenized by the temperate bacteriophage. Further, a 4.35 Kb EcoRI digestion fragment appeared to contain the DNA sequences for integration into the chromosome and may provide a means for stabilizing cloned DNA by effecting chromosomal insertion in LM2301 derivatives. The selection of zone-producing lactose-positive transductants of LM2301 provided a means for detecting strains relysogenized by the temperate phage induced from LM0221.

Bacteriophages↗
PubMed1989

Isolation and characterization of thiodigalactoside-resistant mutants of the lactose permease which possess an enhanced recognition for maltose.

In the current study, lactose permease mutants were isolated which exhibited an enhanced recognition for maltose (an alpha-glucoside) but a diminished recognition for thiodigalactoside, TDG (a beta-galactoside). Maltose/TDGR mutants were obtained from four different parental strains encoding either a wild-type permease (pTE18), a mutant lactose permease which recognizes maltose (pB15) or mutant lactose permeases which recognize maltose but are resistant to inhibition by cellobiose (pTG and pBA). A total of 27 independent mutants were isolated: 12 from pTE18, 10 from pB15, 3 from pTG, and 2 from pBA. DNA sequencing of the 27 mutants revealed that the mutants contain single base pair substitutions within the lac Y gene which result in single amino acid substitutions within the lactose permease. All of the mutants obtained from pTE18, pTG, and pBA involved a change of Tyr-236 to histidine, phenylalanine, or asparagine. From pB15, three different types of mutants were obtained: Tyr-236 to histidine, Ile-303 to phenylalanine, or His-322 to asparagine. When assayed for [14C]maltose transport, the maltose/TDGR mutants were seen to transport maltose significantly faster than the wild type. Furthermore, although TDG was shown to inhibit the uptake of maltose in the four parental strains, all of the mutant strains exhibited a dramatic resistance to TDG inhibition. Most of the maltose/TDGR mutants were also shown to be very defective in the transport of lactose. However, certain mutants (i.e., Asn-322) exhibited moderate lactose transport activity. Finally, it was observed that all of the mutant strains were unable to facilitate the uphill accumulation of beta-methylthiogalactopyranoside. The locations of the amino acid substitutions are discussed with regard to their possible role in sugar recognition.

Arginine↗
PubMed1978

Manifestation and occurrence of selective adult-type lactose malabsorption in Finnish teenagers. A follow-up study.

In 1969--1970, a simple random sample of 129 Finnish school-aged children was examined to study selective adult-type lactose malabsorption (SLM) in this age category. SLM was found in 8 children. All subjects were reexamined 5 years later. SLM was reconfirmed in these 8 persons and found in 3 additional subjects who had normal lactose absorption in the first examination. The prevalence of SLM was 9.3%, being 8.5% in the age category 12--15 years and 9.9% in that 16--20 years. Low rise of blood glucose in the lactose tolerance test of the first examination, very low milk consumption, milk intolerance, and history of gastrointestinal symptoms were found to be of low predictive value as indicators of SLM. It was also concluded that information about dietetic sources of lactose is important to persons with SLM, but categorical exclusion of lactose from the diet is not necessary, at least in the Finnish population.

Adolescent↗