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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bleaching with 35 percent hydrogen peroxide causes enamel surface changes, which result in lower bond strengths of composite resin. Although a previous SEM study showed that home bleaching with 10 percent carbamide peroxide does not cause such surface changes, the results of our study indicate that carbamide peroxide bleaching reduces the shear bond strength of composite to etched enamel. Removal of surface enamel, however, restores bond strengths to normal levels.
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PMID:Bond strength of composite resin to enamel bleached with carbamide peroxide. 188 50

Techniques for the measurement of breath hydrogen excretion have been evaluated in dogs and the breath hydrogen test has been shown to be useful for clinical diagnosis and as a research tool. A simple method was developed for collection of expired air and measurement of breath hydrogen concentrations in cats, which enabled demonstration of carbohydrate malassimilation. Breath hydrogen concentrations were measured in healthy cats after food was withheld and after xylose and lactulose administration. Breath samples were collected by use of an open flow system with the cat confined in an acrylic plastic chamber. Breath hydrogen excretion did not exceed 0.53 ml of hydrogen/h in cats not fed. Breath hydrogen concentrations after the ingestion of xylose, a pentose sugar given orally at 0.75 g/kg of body weight, were not significantly higher from those of cats not fed. After ingestion of 3.35 g of lactulose, a nonabsorbable disaccharide, breath hydrogen excretion increased and breath hydrogen concentrations were significantly higher by 45 minutes (P less than 0.05) and 60 minutes (P less than 0.01) from breath hydrogen concentrations measured in cats not fed and after xylose administration. Administration of lactulose at an increased dosage resulted in further significant (P less than 0.01) increases in breath hydrogen excretion. In this study, mouth-to-cecum transit times were variable. A mean +/- SEM mouth-to-cecum transit time of 86 +/- 6 minutes was calculated from measurement of breath hydrogen excretion after oral administration of 3.35 g of lactulose.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evaluation of carbohydrate malassimilation and intestinal transit time in cats by measurement of breath hydrogen excretion. 189 64

Gingival crevice and periodontal pocket pH, measured directly with glass micro-electrodes, was near neutral at most sites in most individuals (mean pH 6.92 +/- 0.03 SEM, 69 subjects). Periodontal state ranged from healthy to periodontitis but neither clinical evidence of gingivitis at a site nor pocket depth were associated with crevicular pH different from that at healthy sites. This finding contradicts earlier reports that gingivitis is associated with a crevicular pH as alkaline as pH 9.06. Metallic antimony electrodes as used by earlier investigators were found to give pH readings that were too high by as much as 1.5 pH units in the presence of organic reducing agents of the type produced by oral bacteria within gingival crevices. In contrast, glass micro-electrodes respond only to hydrogen ions and thereby provided accurate measurements of pH even in the presence of organic reducing agents. Loss of CO2 to the atmosphere from biological fluids that are bicarbonate buffered resulted in a shift to alkaline pH by as much as 1 pH unit. As a result, only measurements taken within gingival crevices or periodontal pockets can provide accurate measurements of crevice or pocket pH.
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PMID:The pH of gingival crevices and periodontal pockets in children, teenagers and adults. 190 71

Bradykinin produces less dilatation of pial arterioles in stroke-prone spontaneously hypertensive rats than in normotensive Wistar-Kyoto rats. The goals of this study were to determine the mediator of bradykinin-induced dilatation in cerebral arterioles of rats and to determine whether responses to this mediator are altered in hypertensive rats. Diameter of pial arterioles (20-65 microns) was measured using intravital microscopy in 18 normotensive and 17 hypertensive rats. Superfusion of 3 x 10(-7) M bradykinin dilated pial arterioles by 53 +/- 4% (mean +/- SEM) in normotensive rats but only 33 +/- 6% in hypertensive rats (p less than 0.05 versus normotensive rats). Vasodilatation in response to bradykinin was almost completely inhibited by 280 units/ml catalase in both normotensive and hypertensive rats (n = 7 and n = 7, respectively) whereas 150 units/ml superoxide dismutase (n = 6 and n = 5, respectively) and 1 mM deferoxamine (n = 5 and n = 5, respectively) did not attenuate bradykinin-induced vasodilatation. These findings suggest that hydrogen peroxide is the mediator of bradykinin-induced dilatation in cerebral arterioles of rats. We also examined responses of cerebral arterioles to hydrogen peroxide in five normotensive and six hypertensive rats. Dilator responses of cerebral arterioles to 3.2 x 10(-5) M to 1.6 x 10(-4) M hydrogen peroxide did not differ in normotensive and hypertensive rats, which suggests that impaired dilatation of cerebral arterioles in response to bradykinin is not related to altered responsiveness of smooth muscle to an endothelium-derived relaxing factor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanisms of impaired endothelium-dependent cerebral vasodilatation in response to bradykinin in hypertensive rats. 192 61

A simulated digestion technique was used to investigate the characteristics of starch hydrolysis in uncooked, cooked and extrusion-cooked oat products in vitro. The rate and extent of starch hydrolysis were both significantly lower in uncooked rolled oats than in the same material after brief boiling or extrusion cooking. A similar degree of maldigestion in vivo would lead to as much as an estimated 68% of oat starch entering the colon. Breath-hydrogen measurements were used to compare the fermentable carbohydrate content of uncooked and briefly boiled rolled oats in human volunteers and to estimate the relative contributions of soluble dietary fiber and undigested starch to the fermented component. Isolated oat gum (beta-glucan) was readily fermented in vivo and was apparently the main fermentable component of cooked rolled oats. Uncooked rolled oats gave a higher excess hydrogen production than cooked oats, but the results were variable and the differences not statistically significant. In an additional experiment, lactulose was used as a fermentable reference material to calculate the apparent fermentable carbohydrate content of rolled oats and oat gum. Uncooked rolled oats were estimated to contain a statistically significant quantity of undigested starch, amounting at most to 1.01 +/- 0.40 g (mean +/- SEM) of undigested starch per 50 g of fresh weight. We concluded that starch hydrolysis in oats is limited to some extent by the physical state of the food matrix, but this effect may be greatly overestimated by simulated digestion procedures in vitro.
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PMID:Fermentable carbohydrate reaching the colon after ingestion of oats in humans. 200 3

Infusion of 400 microliters air into the left internal carotid artery of five anesthetized rabbits caused transient pial arteriole air embolism, an immediate 41.9 +/- 0.8% dilatation of the embolized vessels, suppression of the cortical somatosensory evoked response to 29.4 +/- 2.7% of baseline, and a progressive decline in ipsilateral cerebral blood flow (measured by hydrogen clearance) to 46 +/- 4.1% of baseline after 2 hours. These values were significantly different from those at baseline and from the responses of 10 control rabbits given equivalent intracarotid saline infusions. Twelve other rabbits were made leukopenic by treatment with 1.5 mg/kg i.v. mechlorethamine 72 hours prior to study. Mean +/- SEM leukocyte count decreased from 6,320 +/- 73/mm3 to 1,890 +/- 66/mm3 without any change in the leukocyte differential or erythrocyte and platelet counts. Intracarotid infusion of saline into seven of the leukopenic rabbits caused no changes. In the other five leukopenic rabbits, infusion of 400 microliters air caused air embolism but did not produce the anticipated declines in cerebral blood flow or the cortical somatosensory evoked response, both of which remained indistinguishable from baseline values and responses in the seven saline-treated leukopenic controls. Similarly, air-embolized arterioles showed nonsignificant dilatation in leukopenic rabbits. Our data suggest that the decreases in both cerebral blood flow and brain function seen after air embolism require the presence of leukocytes.
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PMID:Air embolism of the brain in rabbits pretreated with mechlorethamine. 200 4

A prospective multifactorial study of symptoms and disturbance of gastrointestinal function has been undertaken in 50 patients with non-ulcer dyspepsia. Objective tests including solid meal gastric emptying studies, gastric acid secretion, E-HIDA scintiscan for enterogastric bile reflux, and hydrogen breath studies were carried out in all patients and validated against control data. Gastroscopy and biopsy were carried out in non-ulcer dyspepsia patients only. Non-ulcer dyspepsia patients were categorised on the basis of predominant symptoms as: dysmotility-like dyspepsia (n = 22); essential dyspepsia (n = 14), gastro-oesophageal reflux-like dyspepsia (n = 11); and ulcer-like dyspepsia (n = 3). In the total non-ulcer dyspepsia population, solid meal gastric emptying was delayed (T50 mean (SEM) = 102 (6) minutes (patients) v 64 (6) minutes (controls), (p less than 0.01) and high incidences of gastritis (n = 26) and Helicobacter pyloridis infection (n = 18) were found. An inverse correlation was observed between solid meal gastric emptying and fasting peak acid output (r = -0.4; p less than 0.01). Indeed gastric emptying was particularly prolonged in eight patients (T50 mean (SEM) = 139 (15) minutes) with hypochlorhydria. In the non-ulcer dyspepsia population oral to caecal transit time of a solid meal was delayed (mean SEM = 302 (14) minutes (patients) v 244 (12) minutes (controls) (p less than 0.01]. Seven patients had a dual peak of breath hydrogen suggestive of small bowel bacterial overgrowth. No association was observed between symptoms and any of the objective abnormalities. This multifactorial study has shown that hypomotility, including gastroparesis and delayed small bowel transit, is common in non-ulcer dyspepsia and may be related to other disorders of gastrointestinal function. No relation between symptoms and disorders of function, however, has been shown.
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PMID:Evidence for hypomotility in non-ulcer dyspepsia: a prospective multifactorial study. 201 18

The ability of hypnosis to modulate the orocaecal transit time of 10 g lactulose was tested in six healthy volunteers. Orocaecal transit time was measured by the hydrogen breath test during three periods in random order. During the control period the subjects remained throughout the test in a semirecumbent position without moving. During the hypnotic relaxation period subjects were hypnotised before lactulose ingestion and were instructed to experience relaxation till the orocaecal transit time had elapsed. During the acceleration suggestion period subjects were hypnotised before lactulose ingestion and were repeatedly instructed to imagine the acceleration of lactulose through the intestine until transit time had elapsed. The mean orocaecal transit time was significantly longer during the hypnotic relaxation period (mean (SEM) 133 (8) min) than during the control period (93 (13) min). The mean orocaecal transit time during the acceleration suggestion period was 105 (26) minutes and was not significantly different from the mean transit time during the control period. The individual values during the acceleration suggestion period were scattered. We conclude that lactulose orocaecal transit time is delayed during hypnotic relaxation.
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PMID:Modulation of orocaecal transit time by hypnosis. 202 39

The relative effectiveness of five milk products with various levels of lactose reduction [0%, 50%, 80% (#1), 80% (#2), and 95%] was evaluated in six subjects with lactose malabsorption. Breath hydrogen was measured for 4 h after consumption of 300 mL of each product in a single-blind, randomized design. The mean +/- SEM maximum breath-hydrogen rise (ppm) after the 0%, 50%, 80% (#1), 80% (#2), and 95% lactose-reduced (LR) milks was 31 +/- 6, 7 +/- 3, 5 +/- 3, 5 +/- 2, and 8 +/- 3, respectively. The difference between whole milk and the LR milks was statistically significant (P less than 0.05) but there was no difference between any of the LR milks. Whole milk provoked symptoms in most subjects whereas 95% LR milk produced none. Only one of six subjects reacted to the 50% and 80% LR milks. The results suggest that a 50% level of lactose reduction in milk may be adequate to relieve the signs and symptoms of milk intolerance in the majority of healthy adults with lactose malabsorption.
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PMID:Relative effectiveness of milks with reduced amounts of lactose in alleviating milk intolerance. 205 76

We have investigated lactate intolerance in nine patients with acute hepatorenal failure during 21 machine haemofiltration treatments using a lactate based replacement solution. In all cases hyperlactataemia occurred, the mean arterial lactate increased from 1 +/- 0.2 mmol/l (mean +/- SEM) prior to treatment to 3.2 +/- 0.3 mmol/l at 1 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 2 h (P less than 0.01), 4.2 +/- 0.4 mmol/l at 3 h (P less than 0.01) and 3.9 +/- 0.4 mmol/l (P less than 0.01) post-treatment. There were correlations between the maximum increase in blood lactate and both the change in arterial hydrogen ion concentration (r = 0.71, P = 0.001) and the mean arterial blood pressure prior to starting treatment (r = -0.57, P = 0.007). During eight of the treatments (38%), the arterial hydrogen ion concentration increased. This group showed increased lactate intolerance in association with a lesser pretreatment mean arterial pressure. The administration of exogenous lactate to patients with hepatorenal failure who are at, or near to, the threshold of their own endogenous lactate metabolism can result in an increase in hydrogen ion concentration rather than the expected decrease, and therefore lactate-based dialysate solutions are best avoided.
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PMID:Paradoxical increase in arterial hydrogen ion concentration in patients with hepatorenal failure given lactate-based fluids. 211 25


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