Effects of right ventricular pacing on left ventricular ejection fraction in a pacemaker clinic

The aim of this study was to evaluate whether a change of left ventricular ejection fraction (LVEF) depending on percentage of right ventricular pacing is found in a real-life setting of a pacemaker clinic.

Importance of the sampled milk fraction for the prediction of total quarter somatic cell count

This study investigated the changes in somatic cell counts (SCC) in different fractions of milk, with special emphasis on the foremilk and cisternal milk fractions. Therefore, in Experiment 1, quarter milk samples were defined as strict foremilk (F), cisternal milk (C), first 400 g of alveolar milk (A1), and the remaining alveolar milk (A2). Experiment 2 included 6 foremilk fractions (F1 to F6), consisting of one hand-stripped milk jet each, and the remaining cisternal milk plus the entire alveolar milk (RM). In Experiment 1, changes during milking indicated the importance of the sampled milk fraction for measuring SCC because the decrease in the first 3 fractions (F, C, and A1) was enormous in milk with high total quarter SCC. The decline in SCC from F to C was 50% and was 80% from C to A1. Total quarter SCC presented a value of approximately 20% of SCC in F or 35% of SCC in C. Changes in milk with low or very low SCC were marginal during milking. Fractions F and C showed significant differences in SCC among different total SCC concentrations. These differences disappeared with the alveolar fractions A1 and A2. In Experiment 2, a more detailed investigation of foremilk fractions supported the findings of Experiment 1. A significant decline in the foremilk fractions even of F1 to F6 was observed in high-SCC milk at concentrations >350 x 10(3) cells/mL. Although one of these foremilk fractions presented only 0.1 to 0.2% of the total milk, the SCC was 2- to 3-fold greater than the total quarter milk SCC. Because the trait of interest (SCC) was measured directly by using the DeLaval cell counter (DCC), the quality of measurement was tested. Statistically interesting factors (repeatability, recovery rate, and potential matrix effects of milk) proved that the DCC is a useful tool for identifying the SCC of milk samples, and thus of grading udder health status. Generally, the DCC provides reliable results, but one must consider that SCC even in strict foremilk can differ dramatically from SCC in the total cisternal fraction, and thus also from SCC in the alveolar fraction.

Contribution of mucosal maltase-glucoamylase activities to mouse small intestinal starch alpha-glucogenesis

Digestion of starch requires activities provided by 6 interactive small intestinal enzymes. Two of these are luminal endo-glucosidases named alpha-amylases. Four are exo-glucosidases bound to the luminal surface of enterocytes. These mucosal activities were identified as 4 different maltases. Two maltase activities were associated with sucrase-isomaltase. Two remaining maltases, lacking other identifying activities, were named maltase-glucoamylase. These 4 activities are better described as alpha-glucosidases because they digest all linear starch oligosaccharides to glucose. Because confusion persists about the relative roles of these 6 enzymes, we ablated maltase-glucoamylase gene expression by homologous recombination in Sv/129 mice. We assayed the alpha-glucogenic activities of the jejunal mucosa with and without added recombinant pancreatic alpha-amylase, using a range of food starch substrates. Compared with wild-type mucosa, null mucosa or alpha-amylase alone had little alpha-glucogenic activity. alpha-Amylase amplified wild-type and null mucosal alpha-glucogenesis. alpha-Amylase amplification was most potent against amylose and model resistant starches but was inactive against its final product limit-dextrin and its constituent glucosides. Both sucrase-isomaltase and maltase-glucoamylase were active with limit-dextrin substrate. These mucosal assays were corroborated by a 13C-limit-dextrin breath test. In conclusion, the global effect of maltase-glucoamylase ablation was a slowing of rates of mucosal alpha-glucogenesis. Maltase-glucoamylase determined rates of digestion of starch in normal mice and alpha-amylase served as an amplifier for mucosal starch digestion. Acarbose inhibition was most potent against maltase-glucoamylase activities of the wild-type mouse. The consortium of 6 interactive enzymes appears to be a mechanism for adaptation of alpha-glucogenesis to a wide range of food starches.

Evidence of native starch degradation with human small intestinal maltase-glucoamylase (recombinant)

Action of human small intestinal brush border carbohydrate digesting enzymes is thought to involve only final hydrolysis reactions of oligosaccharides to monosaccharides. In vitro starch digestibility assays use fungal amyloglucosidase to provide this function. In this study, recombinant N-terminal subunit enzyme of human small intestinal maltase-glucoamylase (rhMGAM-N) was used to explore digestion of native starches from different botanical sources. The susceptibilities to enzyme hydrolysis varied among the starches. The rate and extent of hydrolysis of amylomaize-5 and amylomaize-7 into glucose were greater than for other starches. Such was not observed with fungal amyloglucosidase or pancreatic alpha-amylase. The degradation of native starch granules showed a surface furrowed pattern in random, radial, or tree-like arrangements that differed substantially from the erosion patterns of amyloglucosidase or alpha-amylase. The evidence of raw starch granule degradation with rhMGAM-N indicates that pancreatic alpha-amylase hydrolysis is not a requirement for native starch digestion in the human small intestine.

Luminal substrate "brake" on mucosal maltase-glucoamylase activity regulates total rate of starch digestion to glucose

BACKGROUND: Starches are the major source of dietary glucose in weaned children and adults. However, small intestine alpha-glucogenesis by starch digestion is poorly understood due to substrate structural and chemical complexity, as well as the multiplicity of participating enzymes. Our objective was dissection of luminal and mucosal alpha-glucosidase activities participating in digestion of the soluble starch product maltodextrin (MDx). PATIENTS AND METHODS: Immunoprecipitated assays were performed on biopsy specimens and isolated enterocytes with MDx substrate. RESULTS: Mucosal sucrase-isomaltase (SI) and maltase-glucoamylase (MGAM) contributed 85% of total in vitro alpha-glucogenesis. Recombinant human pancreatic alpha-amylase alone contributed <15% of in vitro alpha-glucogenesis; however, alpha-amylase strongly amplified the mucosal alpha-glucogenic activities by preprocessing of starch to short glucose oligomer substrates. At low glucose oligomer concentrations, MGAM was 10 times more active than SI, but at higher concentrations it experienced substrate inhibition whereas SI was not affected. The in vitro results indicated that MGAM activity is inhibited by alpha-amylase digested starch product "brake" and contributes only 20% of mucosal alpha-glucogenic activity. SI contributes most of the alpha-glucogenic activity at higher oligomer substrate concentrations. CONCLUSIONS: MGAM primes and SI activity sustains and constrains prandial alpha-glucogenesis from starch oligomers at approximately 5% of the uninhibited rate. This coupled mucosal mechanism may contribute to highly efficient glucogenesis from low-starch diets and play a role in meeting the high requirement for glucose during children's brain maturation. The brake could play a constraining role on rates of glucose production from higher-starch diets consumed by an older population at risk for degenerative metabolic disorders.

Characterization of the fetuin-binding fraction of Neospora caninum tachyzoites and its potential involvement in host-parasite interactions

Terminal sialic acid residues on surface-associated glycoconjugates mediate host cell interactions of many pathogens. Addition of sialic acid-rich fetuin enhanced, and the presence of the sialidiase inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid reduced, the physical interaction of Neospora caninum tachyzoites and bradyzoites with Vero cell monolayers. Thus, Neospora extracts were subjected to fetuin-agarose affinity chromatography in order to isolate components potentially interacting with sialic acid residues. SDS-PAGE and silver staining of the fetuin binding fraction revealed the presence of a single protein band of approximately 65 kDa, subsequently named NcFBP (Neospora caninum fetuin-binding protein), which was localized at the apical tip of the tachyzoites and was continuously released into the surrounding medium in a temperature-independent manner. NcFBP readily interacted with Vero cells and bound to chondroitin sulfate A and C, and anti-NcFBP antibodies interfered in tachyzoite adhesion to host cell monolayers. In additon, analysis of the fetuin binding fraction by gelatin substrate zymography was performed, and demonstrated the presence of two bands of 96 and 140 kDa exhibiting metalloprotease-activity. The metalloprotease activity readily degraded glycosylated proteins such as fetuin and bovine immunoglobulin G heavy chain, whereas non-glycosylated proteins such as bovine serum albumin and immunoglobulin G light chain were not affected. These findings suggest that the fetuin-binding fraction of Neospora caninum tachyzoites contains components that could be potentially involved in host-parasite interactions.

Prediction of arrhythmic events after myocardial infarction based on signal-averaged electrocardiogram and ejection fraction

Trials on implantable cardioverter-defibrillators (ICD) for patients after acute myocardial infarction (AMI) have highlighted the need for risk assessment of arrhythmic events (AE). The aim of this study was to evaluate risk predictors based on a novel approach of interpreting signal-averaged electrocardiogram (SAECG) and ejection fraction (EF).

Self-reactivity in the dimeric intravenous immunoglobulin fraction

Therapeutic intravenous immunoglobulin (IVIg) preparations contain antibodies reflecting the cumulative antigen experience of the donor population. IVIg contains variable amounts of monomeric and dimeric IgG, but there is little information available on their comparative antibody specificities. We have isolated highly purified fractions of monomeric and dimeric IgG by size-exclusion chromatography. Following treatment of all fractions at pH4, analyses by immunodot and immunocytology on human cell lines showed a preferential recognition of autoantigens in the dimeric IgG fraction. Investigation of the HEp-2 cytoplasmic proteome by 2D-PAGE, Western blot, and subsequent identification of IVIg reactive spots by mass spectrometry (LC-MS/MS) showed that IVIg recognized only a restricted set of the total proteins. Similar experiments showed that more antigens were recognized by the dimeric IgG fraction, especially when the dissociated dimer fraction was used, as compared to its monomeric counterpart. These observations are consistent with idiotype-anti-idiotype masking of auto-specific Abs in the dimeric fraction of IVIg.

Effects of cerebral perfusion pressure and increased fraction of inspired oxygen on brain tissue oxygen, lactate and glucose in patients with severe head injury

OBJECTIVE: The purpose of the study was to measure the effects of increased inspired oxygen on patients suffering severe head injury and consequent influences on the correlations between CPP and brain tissue oxygen (PtiO2) and the effects on brain microdialysate glucose and lactate. METHODS: In a prospective, observational study 20 patients suffering severe head injury (GCS< or =8) were studied between January 2000 and December 2001. Each patient received an intraparenchymal ICP device and an oxygen sensor and, in 17 patients brain microdialysis was performed at the cortical-subcortical junction. A 6 h 100% oxygen challenge (F IO2 1.0) ( Period A) was performed as early as possible in the first 24 hours after injury and compared with a similar 6 hour period following the challenge ( Period B). Statistics were performed using the linear correlation analysis, one sample t-test, as well as the Lorentzian peak correlation analysis. RESULTS: F IO2 was positively correlated with PtiO2 (p < 0.0001) over the whole study period. PtiO2 was significantly higher (p < 0.001) during Period A compared to Period B. CPP was positively correlated with PtiO2 (p < 0.001) during the whole study. PtiO2 peaked at a CPP value of 78 mmHg performing a Lorentzian peak correlation analysis of all patients over the whole study. During Period A the brain microdialysate lactate was significantly lower (p = 0.015) compared with Period B. However the brain microdialysate glucose remained unchanged. CONCLUSION: PtiO2 is significantly positively correlated with F IO2, meaning that PtiO2 can be improved by the simple manipulation of increasing F IO2 and ABGAO2. PtiO2 is positively correlated with CPP, peaking at a CPP value of 78 mmHg. Brain microdialysate lactate can be lowered by increasing PtiO2 values, as observed during the oxygen challenge, whereas microdialysate glucose is unchanged during this procedure. Extension of the oxygen challenge time and measurement of the intermediate energy metabolite pyruvate may clarify the metabolic effects of the intervention. Prospective comparative studies, including analysis of outcome on a larger multicenter basis, are necessary to assess the long term clinical benefits of this procedure.

Luminal starch substrate "brake" on maltase-glucoamylase activity is located within the glucoamylase subunit

The detailed mechanistic aspects for the final starch digestion process leading to effective alpha-glucogenesis by the 2 mucosal alpha-glucosidases, human sucrase-isomaltase complex (SI) and human maltase-glucoamylase (MGAM), are poorly understood. This is due to the structural complexity and vast variety of starches and their intermediate digestion products, the poorly understood enzyme-substrate interactions occurring during the digestive process, and the limited knowledge of the structure-function properties of SI and MGAM. Here we analyzed the basic catalytic properties of the N-terminal subunit of MGAM (ntMGAM) on the hydrolysis of glucan substrates and compared it with those of human native MGAM isolated by immunochemical methods. In relation to native MGAM, ntMGAM displayed slower activity against maltose to maltopentose (G5) series glucose oligomers, as well as maltodextrins and alpha-limit dextrins, and failed to show the strong substrate inhibitory "brake" effect caused by maltotriose, maltotetrose, and G5 on the native enzyme. In addition, the inhibitory constant for acarbose was 2 orders of magnitude higher for ntMGAM than for native MGAM, suggesting lower affinity and/or fewer binding configurations of the active site in the recombinant enzyme. The results strongly suggested that the C-terminal subunit of MGAM has a greater catalytic efficiency due to a higher affinity for glucan substrates and larger number of binding configurations to its active site. Our results show for the first time, to our knowledge, that the C-terminal subunit of MGAM is responsible for the MGAM peptide's "glucoamylase" activity and is the location of the substrate inhibitory brake. In contrast, the membrane-bound ntMGAM subunit contains the poorly inhibitable "maltase" activity of the internally duplicated enzyme.

Mucosal maltase-glucoamylase plays a crucial role in starch digestion and prandial glucose homeostasis of mice

Starch is the major source of food glucose and its digestion requires small intestinal alpha-glucosidic activities provided by the 2 soluble amylases and 4 enzymes bound to the mucosal surface of enterocytes. Two of these mucosal activities are associated with sucrase-isomaltase complex, while another 2 are named maltase-glucoamylase (Mgam) in mice. Because the role of Mgam in alpha-glucogenic digestion of starch is not well understood, the Mgam gene was ablated in mice to determine its role in the digestion of diets with a high content of normal corn starch (CS) and resulting glucose homeostasis. Four days of unrestricted ingestion of CS increased intestinal alpha-glucosidic activities in wild-type (WT) mice but did not affect the activities of Mgam-null mice. The blood glucose responses to CS ingestion did not differ between null and WT mice; however, insulinemic responses elicited in WT mice by CS consumption were undetectable in null mice. Studies of the metabolic route followed by glucose derived from intestinal digestion of (13)C-labeled and amylase-predigested algal starch performed by gastric infusion showed that, in null mice, the capacity for starch digestion and its contribution to blood glucose was reduced by 40% compared with WT mice. The reduced alpha-glucogenesis of null mice was most probably compensated for by increased hepatic gluconeogenesis, maintaining prandial glucose concentration and total flux at levels comparable to those of WT mice. In conclusion, mucosal alpha-glucogenic activity of Mgam plays a crucial role in the regulation of prandial glucose homeostasis.

Assessment of metabolic stability using the rainbow trout (Oncorhynchus mykiss) liver S9 fraction

Standard protocols are given for assessing metabolic stability in rainbow trout using the liver S9 fraction. These protocols describe the isolation of S9 fractions from trout livers, evaluation of metabolic stability using a substrate depletion approach, and expression of the result as in vivo intrinsic clearance. Additional guidance is provided on the care and handling of test animals, design and interpretation of preliminary studies, and development of analytical methods. Although initially developed to predict metabolism impacts on chemical accumulation by fish, these procedures can be used to support a broad range of scientific and risk assessment activities including evaluation of emerging chemical contaminants and improved interpretation of toxicity testing results. These protocols have been designed for rainbow trout and can be adapted to other species as long as species-specific considerations are modified accordingly (e.g., fish maintenance and incubation mixture temperature). Rainbow trout is a cold-water species. Protocols for other species (e.g., carp, a warm-water species) can be developed based on these procedures as long as the specific considerations are taken into account.

Clinical outcomes of patients with low-flow, low-gradient, severe aortic stenosis and either preserved or reduced ejection fraction undergoing transcatheter aortic valve implantation

AIMS Our aim was to evaluate the invasive haemodynamic indices of high-risk symptomatic patients presenting with 'paradoxical' low-flow, low-gradient, severe aortic stenosis (AS) (PLF-LG) and low-flow, low-gradient severe AS (LEF-LG) and to compare clinical outcomes following transcatheter aortic valve implantation (TAVI) among these challenging AS subgroups. METHODS AND RESULTS Of 534 symptomatic patients undergoing TAVI, 385 had a full pre-procedural right and left heart catheterization. A total of 208 patients had high-gradient severe AS [HGAS; mean gradient (MG) ≥40 mmHg], 85 had PLF-LG [MG ≤ 40 mmHg, indexed aortic valve area [iAVA] ≤0.6 cm(2) m(-2), stroke volume index ≤35 mL/m(2), ejection fraction (EF) ≥50%], and 61 had LEF-LG (MG ≤ 40 mmHg, iAVA ≤0.6 cm(2) m(-2), EF ≤40%). Compared with HGAS, PLF-LG and LEF-LG had higher systemic vascular resistances (HGAS: 1912 ± 654 vs. PLF-LG 2006 ± 586 vs. LEF-LG 2216 ± 765 dyne s m(-5), P = 0.007) but lower valvulo-arterial impedances (HGAS: 7.8 ± 2.7 vs. PLF-LG 6.9 ± 1.9 vs. LEF-LG 7.7 ± 2.5 mmHg mL(-1) m(-2), P = 0.027). At 30 days, no differences in cardiac death (6.5 vs. 4.9 vs. 6.6%, P = 0.90) or death (8.4 vs. 6.1 vs. 6.6%, P = 0.88) were observed among HGAS, PLF-LG, and LEF-LG groups, respectively. At 1 year, New York Heart Association functional improvement occurred in most surviving patients (HGAS: 69.2% vs. PLF-LG 71.7% vs. LEF-LG 89.3%, P = 0.09) and no significant differences in overall mortality were observed (17.6 vs. 20.5 vs. 24.5%, P = 0.67). Compared with HGAS, LEF-LG had a higher 1 year cardiac mortality (adjusted hazard ratio 2.45, 95% confidence interval 1.04-5.75, P = 0.04). CONCLUSION TAVI in PLF-LG or LEF-LG patients is associated with overall mortality rates comparable with HGAS patients and all groups profit symptomatically to a similar extent.