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PubMed2000

Homogeneity and diameter of linear lesions induced with multipolar ablation catheters: in vitro and in vivo comparison of pulsed versus continuous radiofrequency energy delivery.

BACKGROUND: For invasive treatment of atrial fibrillation, linear lesions induced with multipolar ablation catheters (MAC) are needed to prevent recurrence. The aim of the study was to compare the efficacy of pulsed versus continuous radiofrequency (RF)-energy delivery using MAC. METHODS: In vitro tests were performed using endomyocardial preparations of fresh pig hearts in a 10-liter-bath of physiologic saline solution (37 degrees C) at constant flow conditions (1.5 l/min). The MAC were placed with a constant pressure of 20 ponds onto the endocardium. The energy (generator: Osypka HAT 200 S) was delivered either pulsed (4 electrodes simultaneously, 5ms duty-cycle) or continuously (each electrode separately). In vivo experiments were performed in 6 anesthetized pigs using fluoroscopic positioning of MAC at 40 different intracardial positions and with similar conditions as in vitro experiments. Lesion volume (LV) was calculated after measuring lesion diameter with a microcaliper. The homogeneity of the lesions (LH) was classified from 1-4; with 1 as highest homogeneity. RESULTS: Pulsed energy delivery produced more homogeneous linear lesions in significantly less time. There was no difference in electrode temperature values (50.2 +/- 0.8 and 51.3 +/- 1.4 degrees C) in vitro and in vivo. In the in vivo experiments, lesion depth and calculated lesion volume were less in both modes of energy delivery but pulsed energy delivery was superior regarding lesion depth and homogeneity. CONCLUSION: With pulsed energy delivery it is possible to create linear lesions of significantly greater homogeneity. Moreover, larger lesions are induced in less time by pulsed energy delivery in vitro and in vivo.

Animals↗
PubMed1967

Amino acid metabolism in various fractions of rat-brain homogenates with special reference to the effect of ethanol.

1. The increase in brain gamma-aminobutyrate, glutamate and aspartate and the decrease in brain glutamine that occur when ethanol is administered to rats in vivo could be reproduced by incubating brain homogenates from rats pretreated with ethanol. 2. For the demonstration of the effects of pretreatment with ethanol on the metabolism of gamma-aminobutyrate and glutamine, the whole homogenate could be replaced by various supernatant preparations, and even by the soluble protein fraction, which was less active, however. The ;postmitochondrial' sediment could likewise mediate the effects of pretreatment with ethanol. 3. When the brain homogenates from control and ethanol-treated rats were allowed to ;age' at 2 degrees for more than 7 days, the metabolic difference at incubation could no longer be demonstrated. The capacities of the homogenate from the control rats had changed to resemble those of ethanol-treated rats. 4. Data are given on the effects of the incubation time and of the concentration of homogenate.

Amino Acids↗
PubMed1967

Studies on glycogen synthesis in pigeon liver homogenates. Incorporation of hexose into glycogen.

Liver homogenates of avian species, but not of mammals, form glycogen from glucose, mannose, fructose and galactose. Incorporation of labelled glucose, fructose and mannose, but not of labelled galactose, into glycogen is diluted isotopically by unlabelled glucose. Except for fructose, glycogen formation from other substrates by pigeon liver homogenates compares favourably with that from the same substrates in pigeon liver slices. Optimum conditions for glycogen synthesis from glucose by pigeon liver homogenate are: medium of incubation, 0.175m-sucrose-45mm-potassium chloride-15mm-glycylglycine buffer, pH7.5; concentration of substrate, 15mm; concentration of tissue, less than 120mg./ml.; temperature of incubation, 37-43 degrees ; atmosphere, oxygen. Uncouplers of oxidative phosphorylation, Ca(2+), EDTA, PP(i), 2-deoxyglucose 6-phosphate and microsomal fraction of rat liver are inhibitory to glycogen synthesis from glucose. Starvation of pigeons for 24 and 48hr. leads to a slight stimulation of glycogen synthesis in their liver homogenates as compared with fed controls. Pigeon liver homogenates can be separated into subcellular fractions that on reconstitution can synthesize glycogen. All the enzymes of the glycogen pathway except soluble high-K(m) glucokinase are present in pigeon liver.

Animals↗
PubMed1971

Glycolytic enzymes in mammalian spermatozoa. Activities and stabilities of hexokinase and phosphofructokinase in various fractions from sperm homogenates.

1. Methods of homogenizing suspensions of washed mammalian spermatozoa were studied. The most useful methods were those using sonication and those using a French press. 2. Hexokinase, phosphofructokinase, glucose phosphate isomerase and adenosine triphosphatase activities in ram, bull and boar spermatozoa were investigated by using these two homogenization methods. Glucose phosphate isomerase, representative of soluble cytoplasmic material, was very readily extracted and remained entirely in the supernatant after centrifugation at 145000g for 60min. In contrast, the other three activities were less easily extracted and were sedimented in various proportions under the described conditions of centrifugation. 3. Attempts to obtain subcellular fractions from sperm homogenates by ;classical' methods failed, owing apparently to the inhomogeneity of subcellular particles in the homogenates. It is concluded that, after removal of sperm heads, the only meaningful fractionation is a separation of spermatozoal material which sediments at 145000g during 60min from that which does not. 4. The stabilities of hexokinase and phosphofructokinase activities in bull, boar and ram sperm homogenates were investigated. Hexokinases showed very little dependence on the various environments tested, whereas the optimum conditions for phosphofructokinase stability were: a minimum of sonication, the presence of phosphate ions and of a thiol-group protectant, and a pH7.5. Activities of hexokinase, phosphofructokinase and glucose phosphate isomerase per sperm cell were compared with published data on rates of fructolysis by spermatozoa; the potential catalytic activities were shown to be considerably in excess of these rates. However, phosphofructokinase may be the rate-limiting enzyme of glycolysis in vivo in bull and ram spermatozoa.

Adenosine Triphosphatases↗
PubMed1981

Oxygen- or organic hydroperoxide-induced chemiluminescence of brain and liver homogenates.

Oxygenation of anaerobically isolated brain and liver homogenates is associated with chemiluminescence and formation of lipid hydroperoxides, the latter determined by the thiobarbituric acid assay. Light emission and formation of malonaldehyde are 20-fold higher in the brain than in liver; chemiluminescence of both decays when accumulation of malonaldehyde ceases. Exogenous organic peroxides, such as t-butyl hydroperoxide, inhibit the light-emission response to oxygenation by brain homogenate, whereas they enhance that of liver homogenate. t-Butyl hydroperoxide-induced photoemission of liver homogenate shows a polyphasic kinetic pattern that is O2-dependent. The spectral analysis of chemiluminescence arising from brain and liver homogenates on oxygenation shows a spectrum with five emission bands at 420-450, 475-485, 510-540, 560-580 and 625-640 nm. These bands are subjected to intensity changes or shifts of the wavelength whenever t-butyl hydroperoxide is present, either inhibiting or stimulating light emission. The blue-band chemiluminescence, around 435 nm, is possibly due to the weak light emission arising from excited carbonyl compounds [Lloyd (1965) J. Chem. Soc. Faraday Trans. 61, 2182-2193; Vassil'ev (1965) Opt. Spectrosc. (USSR) 18, 131-135], whereas the presence of other bands suggests generation of singlet molecular oxygen either in the process triggered on oxygenation (lipid oxygenation) or after supplementation with organic hydroperoxides. We offer several explanations for the spectral analysis presented here.

Animals↗
PubMed1983

Differential substrate oxidation by dissociated brain cells and homogenates during development.

The rates of oxidation of 3-hydroxy[3-14C]butyrate, [3-14C]acetoacetate and [6-14C]glucose were compared by using two different preparations of brain from the same animals (i.e. whole homogenates and dissociated brain cells) at various ages during development. In homogenates the rates of oxidation of 3-hydroxy[3-14C]butyrate and [3-14C]acetoacetate were high in young rats and low in adults, and were significantly higher at most ages during development than those obtained for intact cells. In contrast, rates of [6-14C]glucose oxidation by homogenates and intact cells were essentially the same at early ages; however, the rate by homogenates did not change throughout development, whereas that by intact cells increased severalfold by adulthood. In adult animals the initial glucose concentration affected the rate of glucose oxidation in homogenates, but not in intact cells. These data suggest a role for the intact cell membrane in the regulation of alternative substrate utilization by brain cells and that this process changes during development. However, the data may reflect selective differences in the cellular and subcellular components in these two preparations.

3-Hydroxybutyric Acid↗
PubMed1989

Steroid sulfatase activity in homogenates, microsomes and purified Leydig cells from adult rat testis.

Steroid sulfatase (STS) activity was studied in the Long-Evans rat testis. The rate of dehydroepiandrosterone sulfate (DHA-S) hydrolysis determined in whole testis homogenates was low compared to that of the corresponding microsomal fractions, which was, in contrast, as high as that expressed in homogenates from purified Leydig cells. Such an increment in STS activity between total homogenates and the corresponding microsomes was not observed for the seminiferous tubules. The STS affinity reported for total testicular microsomes (Km = 3.47 +/- 0.54 microM; mean +/- SEM) was of the same magnitude as that previously reported for Leydig cells, but was about 3 times higher than that measured for whole testis homogenate (Km = 10.11 +/- 0.92 microM). In vivo hCG treatment decreased the STS affinity in total testicular microsomes without affecting this kinetic parameter in whole testis homogenate. These data suggest that the steroid sulfatase expressed in total testicular microsomes (activity and regulation by hCG) could be considered as a good index of Leydig cell STS activity.

Animals↗
PubMedDate not supplied

Medium scale production of solid lipid nanoparticles (SLN) by high pressure homogenization.

Solid lipid nanoparticles (SLN) were produced by high pressure homogenization using piston-gap homogenizers. Batch sizes varied between 40 ml and 50 l. Because of the different batch sizes, different homogenizer types were used, but the same functional principles were maintained, and the change from 40 ml to 50 l was not critical. With increasing batch sizes, the product quality in terms of particle size distribution and physical storage stability improved. Medium scale (30 l and 50 l) drug-free and drug-loaded SLN batches could be produced reproducibly and batch-to-batch uniformity was proven: within one batch particle sizes were homogeneous. This study revealed the influence of pressure and temperature for the hot homogenization technique A change of pressure between 300-500 bars induced only minor differences in particle size, but some influence of the heating temperature was found. More important than control of the heating process was the control of the cooling process of the final product. A too rapid cooling deteriorated the product quality: cooling with water of 18 degrees C proved to be the optimum cooling condition.

Drug Compounding↗
PubMed1964

GLUCOSE UTILIZATION BY CHICK EMBRYO HEART HOMOGENATES.

Homogenates of early chick embryos and homogenates of early chick embryonic hearts utilized the phosphogluconate pathway of glucose catabolism to a greater extent, relative to the glycolytic-Krebs cycle pathway, than did homogenates of hearts from older chick embryos or adult chicks. An abrupt drop in the relative participation by the phosphogluconate pathway in embryo heart homogenates occurs at about 5 to 7 days of incubation. Heart homogenates from adult chicks catabolize glucose almost entirely by the glycolytic-Krebs cycle pathway, with negligible participation by the phosphogluconate pathway.

Adenosine Triphosphate↗
PubMed1997

Modelling light distributions of homogeneous versus discrete absorbers in light irradiated turbid media.

Laser treatment of port wine stains has often been modelled assuming that blood is distributed homogeneously over the dermal volume, instead of enclosed within discrete vessels. The purpose of this paper is to analyse the consequences of this assumption. Due to strong light absorption by blood, fluence rate near the centre of the vessel is much lower than at the periphery. Red blood cells near the centre of the vessel therefore absorb less light than those at the periphery. Effectively, when distributed homogeneously over the dermis, fewer red blood cells would produce the same absorption as the actual number of red blood cells distributed in discrete vessels. We quantified this effect by defining a correction factor for the effective absorbing blood volume of a single vessel. For a dermis with multiple vessels, we used this factor to define an effective homogeneous blood concentration. This was used in Monte Carlo computations of the fluence rate in a homogeneous skin model, and compared with fluence rate distributions using discrete blood vessels with equal dermal blood concentration. For realistic values of skin parameters the homogeneous model with corrected blood concentration accurately represents fluence rates in the model with discrete blood vessels. In conclusion, the correction procedure simplifies the calculation of fluence rate distributions in turbid media with discrete absorbers. This will allow future Monte Carlo computations of, for example, colour perception and optimization of vascular damage by laser treatment of port wine stain models with realistic vessel anatomy.

Erythrocytes↗
PubMed1993

Preferential hydrolysis of phosphatidylethanolamine in rat ischemic heart homogenates during in vitro incubation.

Phospholipid-hydrolyzing activities were examined in rat hearts with ischemia induced by occlusion of the left main coronary artery. When homogenates of ischemic heart were incubated in vitro at 37 degrees C, a significant amount of phosphatidylethanolamine (PE) was degraded, whereas the contents of other phospholipids did not change significantly. During the incubation, a stoichiometrical amount of lysoPE was concomitantly formed. The lysoPE formed had mainly saturated fatty acids and its composition resembled that of fatty acids detected at the sn-1 position in the glycerol backbone of heart PE. No appreciable PE degradation was observed in homogenates prepared from nonischemic rat heart. No difference in phospholipase activities was found between ischemic and nonischemic heart homogenates when exogenous radioactive phospholipids were used as substrates. Rabbit anti-rat 14-kDa type II phospholipase A2 antibody suppressed the degradation of PE observed in ischemic heart homogenates. These findings indicate that the type II phospholipase A2 activity may be involved in the breakdown of endogenous PE in ischemic heart homogenates.

Animals↗
PubMed2006

The individual RDH index: a novel vector index for statistical assessment of antihypertensive treatment reduction, duration, and homogeneity.

We propose a new vector index for the statistical assessment of antihypertensive treatment duration and homogeneity from ambulatory blood pressure monitoring. We termed this approach for evaluating and comparing blood pressure coverage offered by antihypertensive drugs over 24 h as the reduction-duration-homogeneity index. The reduction-duration-homogeneity index is a three-component vector index that incorporates information about the reduction, duration, and homogeneity of antihypertensive treatment, as well as their statistical significance. The advantages of the reduction-duration-homogeneity index are demonstrated by several comparative examples.

Adult↗
PubMed2006

Decreased regional homogeneity in schizophrenia: a resting state functional magnetic resonance imaging study.

We used a newly reported regional homogeneity approach to measure the temporal homogeneity of blood oxygen level-dependent signal for exploring the brain activity of schizophrenia in a resting state. The results showed decreased regional homogeneity in schizophrenia, which distributed over the bilateral frontal, temporal, occipital, cerebellar posterior, right parietal and left limbic lobes, similar to the findings reported in previous resting state functional studies. The brain regions that showed decreased regional homogeneity are believed to be involved in the psychopathology and pathophysiology of schizophrenia. Our results indicate that abnormal brain activity of schizophrenia may exist in a resting state and the regional homogeneity may be potentially helpful in understanding the resting state of schizophrenia.

Adult↗
PubMed2004

Homogenization induced by chaotic mixing and diffusion in an oscillatory chemical reaction.

A model for an imperfectly mixed batch reactor with the chlorine dioxide-iodine-malonic acid (CDIMA) reaction, with the mixing being modelled by chaotic advection, is considered. The reactor is assumed to be operating in oscillatory mode and the way in which an initial spatial perturbation becomes homogenized is examined. When the kinetics are such that the only stable homogeneous state is oscillatory then the perturbation is always entrained into these oscillations. The rate at which this occurs is relatively insensitive to the chemical effects, measured by the Damköhler number, and is comparable to the rate of homogenization of a passive contaminant. When both steady and oscillatory states are stable, spatially homogeneous states, two possibilities can occur. For the smaller Damköhler numbers, a localized perturbation at the steady state is homogenized within the background oscillations. For larger Damköhler numbers, regions of both oscillatory and steady behavior can co-exist for relatively long times before the system collapses to having the steady state everywhere. An interpretation of this behavior is provided by the one-dimensional Lagrangian filament model, which is analyzed in detail.

Journal Article↗
PubMed1995

Analysis of cellular response and gamma interferon synthesis in bronchoalveolar lavage fluid and lung homogenate of mice infected with Pneumocystis carinii.

The cellular and cytokine responses in the lungs of mice infected with Pneumocystis carinii were examined on both lung homogenates and bronchoalveolar lavage (BAL) fluids. In the lungs of infected mice, the number of P. carinii cysts rapidly decreased by day 7, then started to increase with a peak on day 14, and thereafter decreased gradually. When the presence of P. carinii was examined at the DNA level by dot blot hybridization, a similar clearance curve was obtained, and the organisms were shown to be completely eliminated on day 28. In the late phase of infection, leukocytes, mainly lymphocytes, increased in number when analyzed on lung homogenates, while no significant increase of inflammatory cells was observed in BAL fluids. An accumulation of both CD4+ and CD8+ T cells and an increase of activated T cells expressing IL-2R alpha were observed in lung homogenates of the infected mice. In addition, a considerable amount of IFN-gamma was detected in lung homogenates, but not in BAL fluids. These data indicate that lung homogenates are more suitable than BAL fluids for the analysis of cellular and cytokine responses in the lungs of mice infected with P. carinii. To define the involvement of IFN-gamma in host defense against P. carinii, the effect of this cytokine on the killing activity of macrophages against P. carinii was examined in vitro. IFN-gamma was found to augment this activity by increasing nitric oxide synthesis of the macrophages. Thus, it is suggested that IFN-gamma plays an important role in the protection of mice from P. carinii infection.

Animals↗
PubMed1988

Control analysis of metabolic networks. 1. Homogeneous functions and the summation theorems for control coefficients.

1. The summation theorem CJ1 + ... + CJn = 1 for flux control coefficients CJi is shown to be equivalent to the assumption that flux J is a homogeneous function of degree 1 of enzyme concentrations E1,..., En, that is to the assumption J (tE1,..., tEn) = tJ (E1,..., En) for any t not equal to 0. Likewise, the summation theorem CXj1 + ... + CXjn = 0 for concentration control coefficients CXj1 is equivalent to homogeneity of degree 0 of steady-state metabolite concentrations Xj, or Xj (tE1,..., tEn) = Xj (E1,..., En). From this equivalence it is obvious that metabolic control analysis applies only to homogeneous systems. 2. The summation theorem for flux control coefficients is shown to be equivalent to that for concentration control coefficients, provided all reaction rates vi are homogeneous functions of enzyme concentrations Ei. 3. The equivalence between homogeneity of flux J and the summation theorem for flux control coefficients is used to analyse branching of fluxes in metabolic pathways in terms of flux control coefficients.

Enzymes↗
PubMed1988

A method for stabilization of monoamine oxidases in homogenates of rat intestine epithelium.

In a homogenate of epithelium isolated from the small intestine of male Wistar rats, the amine oxidase activity with 10(-3)M tyramine was 9200 +/- 200 nmol (g tissue)-1 h-1 of which 91% was due to the A form of monoamine oxidase (MAO) and 9% to the B form. Semicarbazide-sensitive amine oxidase activity was not detected with either 10(-3)M tyramine or 10(-4)M benzylamine as substrate. However, it was detectable in the homogenate of the gut residue where the activity with 10(-4)M benzylamine was 3600 +/- 200 nmol (g tissue)-1 h-1. The MAO activity, in homogenates of epithelium prepared with 0.1 M sodium phosphate pH 7.4, was stable at 4 degrees C for at least 6 h whilst at minus 20 degrees C it decreased by 70% within 24 h. Incorporation of 10% (v/v) glycerol into the homogenization medium stabilized the enzymes. The total activity and proportions due to MAO-A and MAO-B and kinetic constants for tyramine and 5-hydroxytryptamine, did not alter during 5 weeks storage at -20 degrees C. The ability to store tissue homogenates should facilitate studies of intestinal amine oxidases.

Animals↗
PubMed1999

Antiproliferative effects of homogenates derived from five strains of candidate probiotic bacteria.

Unheated and heat-treated homogenates were separately prepared from candidate probiotic bacteria, including Lactobacillus rhamnosus GG, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Streptococcus thermophilus. We compared the phytohemagglutinin-induced proliferation of mononuclear cells in the presence of homogenates and in the presence of a control containing no homogenate by assessing thymidine incorporation in cell cultures. All homogenates suppressed proliferation, whether the enzymatic activity was inactivated or not inactivated by heating. When the proliferation assays were repeated with cytoplasmic and cell wall extracts derived from the homogenate of L. rhamnosus GG, the cytoplasmic extract but not the cell wall extract was suppressive. These findings indicate that candidate probiotic bacteria possess a heat-stable antiproliferative component(s). These bacteria may be used to generate microbiologically nonviable yet immunologically active probiotic food products that are easier to store and have a longer shelf life.

Bifidobacterium↗