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At least 19 recordsLinked to original sources
PubMed1976

[Azoindoxyl methods for the histochemical investigation of hydrolases. I. Lactase (lactase-beta-glucosidase complex) (author's transl)].

An azoindozyl method for the histochemical demonstration of lactase (lactase-beta-glucosidase complex) is described. The incubation medium consists of 5 mg 5-Br-4-Cl-3-indolyl-beta-D-fucoside (dissolved in 0.5 ml N,N-dimethylformamide) and 0.02 ml hexazotized prosaniline in 10 ml 0.1 M citric acid phosphate buffer, pH 6-6.5. By means of this method lactase can be exactly localized in the brush border of the enterozytes in the jejunum of suckling rats. Compared to the corresponding indigogenic method the azoindoxyl reaction proceeds faster and the reaction product is often precipitated more precisely.

Animals↗
PubMed1975

Suitability of the azocoupling reaction with 1-naphthyl-beta-D-glucoside for the histochemical demonstration of lactase (lactase-beta-glucosidase complex) in human enterobiopsies.

The suitability of the simultaneous azocoupling reaction with 1-naphthyl-beta-D-glucoside and hexazonium-p-rosanilin in the detection of the activity of lactase (or lactase-beta-glucosidase complex) in jejunal biopsies of patients with various forms of the malabsorption syndrome was tested. Results were compared with those obtained with the indigogenic method using 4-Cl-5-Br-3-indolyl-beta-D-fucoside which is the method of choice. Both methods gave identical results as far as the relative intensity of the brush border staining was concerned. The azocoupling method applied in unfixed cold microtome sections can be recommended for the routine diagnostics of the malabsorption syndrome when the indolyl substrate is not available.

Adult↗
PubMed1975

Effects of diets containing dried whey on the lactase activity of the small intestinal mucosa and the contents of the small intestine and cecum of the pig.

Two studies were conducted to establish the effects of dietary lactose supplied from dried whey on the lactase activity in the contents of the small intestine and cecum as well as the mucosa of the small intestine. In the first study, feeding 0, 10, 25, or 40% dried whey for 120 days did not alter the mucosal lactase specific activity (mumoles galactose released/mg protein) in the duodenum, upper jejunum, or lower ileum. In the second study, total lactase activity in the small intestine was estimated from the total activity found in 10-cm segments of each meter of small intestine. Feeding a diet containing 40% whey continuously from weaning at 5 weeks of age or from 12 weeks of age did not alter the total lactase activity of pigs killed at 21 weeks of age. Dietary lactose tended to increase the lactase activity in the contents of the cecum and small intestine, but the increases were not always statistically significant. In the second study, Chester White pigs had approximately threefold greater mucosal lactase activities than that of Hampshires. These two breeds may be suitable models for detailed studies into the relationships between lactase deficiency and lactose intolerance.

Animals↗
PubMed1976

Is lactase the receptor and uncoating enzyme for infantile enteritis (rota) viruses?

Rotaviruses are now regarded as important causes of diarrhoea in man, cattle, pigs, mice, and possibly other animals. Characteristically, disease occurs in newborn and young animals, and infection seems limited to the differentiated gut epithelial cells. The major surface polypeptide of the calf scours rotavirus is glycosylated, and highly purified beta-galactosidase (lactase) interacts with the virus in vitro causing removal of the outer shell of the capsid (uncoating). It is suggested that lactase present in the brush border of the intestinal epithelial cell performs a similar function in vivo by acting as a combined receptor and uncoating enzyme for the rotavirus. This hypothesis is consistent with the observations that rotaviruses seem to infect only gut epithelial cells, and that infant animals, whose lactase concentrations are generally higher than those of adult animals, seem more susceptible to rotavirus infections. Implications of the hypothesis include possible new approaches to laboratory cultivation of rotaviruses, which should be more successful in cells selected for surface lactase activity, and the suggestion that the epidemiology of human rotavirus infections may be influenced by the fact that different ethnic groups have different lactase levels (and hence lactose intolerance) in adulthood.

Acute Disease↗
PubMed1977

Lactase deficiency--a comparative study of diagnostic methods.

The diagnostic value of 1-14C-lactose breath test was compared with the standard lactose tolerance test and lactase assay in jejunal biopsies in 16 control subjects, 14 patients with lactase deficiency (LD) proven by lactase assay and 20 patients with irritable bowel syndrome (IBS). 14CO2 specific activity in the 2-hr breath collection after administration of 1-14C-lactose (5 muCi) provided a satisfactory separation between the control and LD group. Values were 7.0 +/- 2.0% dose administered/mmoles 14CO2 X 10(-3) (mean +/- SD) in the control group versus 2.1 +/- 1.5 in LD (P less than 0.001) versus 4.9 +/- 2.3 in IBS (P less than 0.01). 1-14C-lactose breath test was superior to standard lactose tolerance test in specificity (P less than 0.05) and provided a satisfactory correlation between 14C-lactose absorption and lactase assay (r = 0.77). The prevalence of LD in IBS was 40% by the breath test and 35% by lactase assay, suggesting that lactose malabsorption may play a role in the symptoms in the population of some patients with IBS. It appears that 1-14C-lactose breath test is a sensitive, specific and accurate method for the diagnosis of LD in clinical practice and suitable for large scale epidemiological surveys.

Breath Tests↗
PubMed1979

Relationship between changes in lactase activity and monosaccharide uptake in the small intestine of the rat during development.

The relationship between changes in intestinal lactase activity and monosaccharide uptake was studied in rats of different ages using the technique of intestinal everted sacs. In the postweaning period there is a sharp decrease in the rate of glucose and galactose uptake by the small intestinal mucosa. This change occurs simultaneously with a decrease in lactase activity in the tissue. The kinetic analysis showed a lower Vmax for monosaccharide uptake in the 50-days-old rats as compared with the fifteen-days-old animals, with no change in the apparent Kt. The addition of Tris+ (40 mM) to the incubation media was found to produce a decrease in Vmax for monosaccharide uptake only in the suckling rats but not in the 50-days-old animals; the K1 remained unchanged. Tris+, at the concentration used had previously been shown to completely inhibit lactase activity in homogenates of small intestinal mucosa. These observations lead us to postulate the lactase in the suckling rat might possess a translocating role for sugar, in addition to its hydrolytic function. The decrease in sugar uptake after weaning could be explained by the disappearance of this role.

Age Factors↗
PubMed1979

The biochemical and histochemical demonstration of lactase induction in fetal rat intestine by intra-amniotic injection of lactose.

A single dose of 20 mg beta-D-lactose injected into the amniotic sac of rats on day 17 of pregnancy induced an increase in lactase activity in fetal jejunum. This effect was first noted two days after injection and lasted for at least two additional days. Histoenzymatic investigation indicated that this enzyme was located on the surface of the absorptive cells lining the villi and thus corresponds to the "dietary" form of beta-galactosidase. A much smaller increase, based presumably on progressive increase in fetal size (age) was found in control fetuses which had received glucose or no injections. Peak lactase values in fetuses receiving lactose were substantially higher than peak values in control fetuses. In both lactose-injected and non-injected rats which were allowed to deliver, there was a sharp drop in lactase values coincident with birth.

Amnion↗
PubMed1979

Opposite effects of one and three injections of cortisone or thyroxine on intestinal lactase activity in suckling mice.

A single injection of cortisone or thyroxine to 8-day-old suckling mice initiates a temporary decrease of lactase activity. On the contrary, 3 injections of cortisone or thyroxine provoke a significant increase of lactase activity. It appears that the mechanism which controls the postnatal development of lactase in suckling animals is more complex than expected.

Animal Population Groups↗
PubMed1979

Lactase degradation by human enteric bacteria.

Twelve non-pathogenic bacteria and two yeast strains isolated from the duodenal aspirate or mucosa of five children with diarrhoea were tested for their ability to degrade non-human lactase in vitro. Both yeast strains and eleven of the bacterial strains significantly reduced lactase activity. A similar action on human lactase could be a cause of lactose intolerance.

Bacteria↗
PubMed1979

Development of jejunoileal differences of activity of lactase, sucrase and acid beta-galactosidase in isografts of fetal rat intestine.

Jejunal and ileal segments from preterm rat fetuses were implanted under the kidney capsula of adult rats. Sucrase, lactase and acid beta-galactosidase activities were determined in the isografts at different times after implantation, and in corresponding segments developing in situ. Whereas fetal intestine contains considerable activity of acid beta-galactosidase and lactase, no sucrase activity is detectable. Similarly -- as in situ -- 4 weeks after the implantation the jejunal segment exhibited higher activity of sucrase and lactase than the ileal segment. Acid beta-galactosidase was more active in ileal than in jejunal segments -- both growing in situ as well as isografts. Experiments have thus demonstrated that the expression of the jejunoileal gradient of activity of the 3 enzymes studied does not depend on direct contact with food or gastric, pancreatic and biliary juices. This gives validity to the suggestion that the gradient may already be programmed in fetal intestinal tissue, but other factors active in situ might be responsible for its magnitude.

Animals↗
PubMed1979

Origin and developmental patterns of lactase and other glycosidases in sheep amniotic and allantoic fluid.

Intestinal lactase activity (with its associated cellobiase, 4-methylumbelliferyl-beta-galactosidase and -beta-glucosidase activities) was used as a specific intestinal marker enzyme to study the release of protein and enzymes of intestinal origin in sheep amniotic fluid during gestation. In amniotic fluid, intestinal lactase activity peaked at 66--85 days of gestation and then decreased with gestation. This enzyme activity was very low or absent in allantoic fluid throughout gestation suggesting that there is no important transfer of amniotic fluid lactase towards the allantoic cavity. Maltase and 4-methylumbelliferyl-alpha-glucosidase showed no statistically significant variation with gestation in both amniotic and allantoic fluid whereas alpha-galactosidase and N-acetyl-beta-hexosaminidase which were first higher in allantoic than in amniotic fluid increased in amniotic fluid to reach allantoic fluid levels near term. Such patterns are consistent with the suggestion that the fetal urine is a source of alpha-galactosidase and N-acety-beta-hexosaminidase activities and that sheep urine is first accumulated in the allantoic sac via the urachus up to 86--90 days of gestation and thereafter passes more and more into the amniotic sac.

Allantois↗
PubMed1978

Tolerance to lactose among lactase-deficient American Indians.

To determine the amount of lactose that could be tolerated in a meal, 59 lactase-deficient American Indians, ranging in age from 5 to 62, were given graded doses of lactose. The diagnosis of lactase deficiency had beeen documented previously by showing increased breath hydrogen after an oral lactose load (2 g per kg, maximum 50 g). With this load, 88% of the subjects had symptoms. On 6 consecutive mornings, each subject was given a breakfast that contained graded doses of lactose ranging from 0 to 18 g. The order of the breakfasts was randomized and the contents were double-blinded. Symptoms, which were assessed by a "blinded" observer, were present after 9% of the breakfasts at all dosage levels, including the lactose-free breakfast. Thus, under the conditions of this study, a modest amount of lactose, equivalent to that present in 1 to 1 1/2 glasses of milk, when taken with a meal, is well tolerated by the lactase-deficient American Indian.

Adolescent↗
PubMed1979

[Exhaled hydrogen test in the detection of lactase deficiency].

To determine the validity of breath H2 measurements in detecting lactase deficiency, capillary blood glucose and breath H2 were measured after ingestion of 50 g lactose in 34 patients with abdominal symptoms or diarrhea. 18 patients had biopsy-proven lactase deficiency and 16 normal lactase activity. Blood glucose determination produced 2 false-positive results while breath H2 measurements provided 2 false-negative and 4 false-positive results.

Adult↗
PubMedDate not supplied

Intestinal lactase status of adults in Papua New Guinea.

Fifty hospital patients in Port Moresby (mean age 30 yr) without evidence of malnutrition or gastro-intestinal disease, who came from many parts of Papua New Guinea (P.N.G.), were given 50 g lactose orally after an overnight fast. In 49 blood glucose rise was less than 1.1 mmol 1(-1), indicating hypolactasia. Thirty-three gave a clear history of symptoms, usually diarrhoea, after lactose. Adult hypolactasia approaches 100% in P.N.G. There is no indication that the genetic structure of any part of the population of P,N.G. with regard to lactase has been influenced by genetic drift from peoples with persistence of lactase into adult life (PL).

Adolescent↗
PubMed1979

[Intestinal lactase and milk consumption before and after gastrectomy].

Intestinal lactase assays before and after a Billroth II procedure for chronic duodenal ulcer did not reveal a significant difference. Postoperative lactose intolerance is due to the loss of pyloric function, causing entrance of lactose into the jejunum at a rate exceeding the hydrolytic capacity of the mucosa if the lactase level is low.

Animals↗
PubMed1978

Lactase activity of microorganisms.

Sixty-two strains of yeasts, molds and bacteria were screened for lactase (beta-D-galactosidase) activity. Strains exhibiting the enzyme activity were evaluated for cell yield as well as enzyme units available per litre of the medium, per g cell dry weight and per mg protein of their cell-free extracts. The molds exhibited lowest enzyme activity but highest cell yields, bacteria produced lowest cell yield and maximum enzyme activity. Cultures exhibiting very high activity among yeasts were Saccharomyces fragilis (strain 3217) and among bacteria Streptococcus cremoris (strain H), Lactobacillus bulgaricus (strain RTS and 1373) and Leuconostoc citrovorum (strain 8081).

Bacteria↗
PubMed1977

Regulation of newly evolved enzymes. III Evolution of the ebg repressor during selection for enhanced lactase activity.

The evolution of lactose utilization by lacZ deletion strains of E. coli occurs via mutations in the ebg genes. We show that one kind of mutation in the regulatory gene ebgR results in a repressor which retains the ability to repress synthesis of ebg enzymes, but which permits 4.5-fold more ebg enzyme synthesis during lactose induction than does the wild-type repressor. A comparison between the growth rate of various ebg+ strains on lactose and the amount of ebg enzyme synthesized by these strains shows that the rate of enzyme synthesis permitted by the wild-type repressor is insufficient for growth on lactose as a sole carbon source by a cell with the most active ebg lactase yet isolated. We conclude, therefore, that the evolution of lactose utilization requires both a structural and a regulatory mutation.

Biological Evolution↗
PubMed1976

Intestinal pH and propulsion: an explanation of diarrhoea in lactase deficiency and laxation by lactulose.

Subjects deficient in lactase may experience bloating, cramps and diarrhoea after ingesting milk, due to the unhydrolysed and poorly-absorbed lactose. The diarrhoea may result from an osmotic effect of the lactose itself or its poorly-absorbed acidic products of fermentation (Weijers, van de Kamer & others, 1961; Christopher & Bayless, 1971), possibly together with an alteration of sodium and water absorption due to the lowered colonic pH (Rousseau & Sladen, 1971). Laxation by lactulose (1-4-beta-galactosidofructose) may operate through an analogous mechanism. The drug is a synthetic dissaccharide which, in oral doses of 10-20 g, relieves chronic constipation (Wesselius-de Casparis, Braadbaart & others, 1968). It is neither hydrolysed by intestinal dissaccharidase (Dahlqvist & Gryboski, 1965) nor absorbed in the gut, but it is converted in the colon mainly to lactic and acetic acids by various bacteria including Lactobacillus acidophilus. Apart from the increased osmotic effect, the pH in the proximal colon falls markedly (Bown, Gibson & others, 1974), and larger doses may reduce stool pH. Weijers & others (1961) inferred that the acidic products formed from lactose in the colon stimulate propulsion, and K.S. Liem (Philips-Duphar) suggested to us that lactulose may relieve constipation partly by stimulation of propulsion due to the lowered pH. The experiments described below support this view.

Animals↗