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At least 55 records · Page 3Linked to original sources
PubMed1987

The Cushing responses in the systemic and pulmonary circulation: the role of adrenal glands, bronchial circulation and pulmonary innervation.

Systemic hypertension and increased total peripheral vascular resistance are the most consistent observations in the Cushing responses to an increase in intracranial pressure (ICP). In the present study, we evaluated the participation of adrenal glands, bronchial circulation and pulmonary innervation in the systemic and pulmonary hemodynamics following an intracranial hypertension (ICH). In a total of 18 anesthetized, vagotomized and open-chest dogs, total heart bypass was performed to perfuse the systemic and pulmonary circulation with constant flow. The venous outflows were diverted into reservoirs. The preparation allowed us to observe the simultaneous changes in the systemic vascular resistance (SVR) and capacity (SVC) as well as the pulmonary vascular resistance (PVR) and capacity (PVC). ICH was produced by inflation of an epidural balloon to elevate the ICP to a level of 165-175 mmHg for 1.5 min. Our data showed that ICH induced drastic increases in SVR and PVR accompanying decreases in SVC and PVC. Vascular occlusion of the adrenal glands (n = 6) did not affect the hemodynamic changes. Arrest of bronchial circulation (n = 6) or pulmonary denervation (n = 6) also did not affect the changes in systemic circulation (SVR and SVC), but greatly diminished the pulmonary hemodynamic changes (PVR and PVC). The results suggest that the adrenal glands are not involved in the systemic and pulmonary hemodynamic responses to this degree of ICH. The changes in the pulmonary vascular resistance and capacity require the integrity of bronchial blood supply and sympathetic innervation.

Adrenal Glands↗
PubMed2003

A degeneracy study in the circulant and bordered-circulant approach to birdcage and planar coils.

A method for finding closed-form solutions for the normal mode frequencies of systems with circulant (2 pi/n) symmetry was investigated. This method is particularly useful for questions of degeneracy that arise when one considers parallel imaging techniques like SENSE and SMASH in MRI. It is applicable to systems that include birdcage coils as well as planar coils with the appropriate rotational symmetry. A proof is given that complete degeneracy of all normal mode frequencies is impossible when all mutual inductive couplings are included. We tested the method against measurements made on a planar coil array and on an 8-element birdcage coil. The inclusion of the co-rotating end-ring mode changes the fundamental symmetry of the system from circulant to 'bordered circulant.' Closed-form solutions for the normal mode frequencies of a bordered circulant system are also given.

Computer Simulation↗
PubMed1994

Color Doppler imaging of the uteroplacental circulation in the middle trimester: observations on the development of a low-resistance circulation.

We aimed to study the changes in the flow dynamics of the uteroplacental and umbilical circulations in the middle trimester of normal pregnancy, and establish normal ranges for indices of the Doppler flow velocity waveforms (FVWs) from both circulations at 14, 18 and 24 weeks. A longitudinal study was conducted with the use of color Doppler imaging to localize both uterine arteries and umbilical arteries and obtain FVWs from 106 healthy nulliparous women with a singleton pregnancy. Of these, 70 did not have a complicated pregnancy outcome, defined as hypertension, growth retardation, preterm delivery or perinatal death. We measured the resistance index (RI), pulsatility index (PI), systolic/diastolic (S/D) ratio and presence of early diastolic notching in both uterine arteries, and RI, PI and S/D in one umbilical artery. The results showed a fall in all measured indices of blood flow impedance in the uteroplacental and umbilical circulations and a marked reduction in the incidence of the early diastolic notch in the uterine artery FVWs during the mid-trimester. Our conclusion was that color Doppler imaging allows for the accurate localization of both uterine and umbilical arteries. Doppler FVWs then obtained confirm the development of the low-resistance uteroplacental and umbilical circulations in the mid-trimester. Diastolic notching is common at 14 weeks in normal pregnancy but uncommon at 24 weeks.

Journal Article↗
PubMed2000

Leptin gene expression, circulating leptin, and luteinizing hormone pulsatility are acutely responsive to short-term fasting in prepubertal heifers: relationships to circulating insulin and insulin-like growth factor I(1).

In the present study, we tested the hypothesis that short-term fasting would reduce leptin gene expression, circulating leptin, and LH pulsatility in prepubertal heifers in association with a decrease in circulating concentrations of insulin and insulin-like growth factor I (IGF-I). Twelve prepubertal crossbred heifers (mean +/- SD = 315 +/- 5 kg body weight) were assigned randomly to one of two treatments in two replicates: 1) control; normal feed consumption (n = 6) and 2) fasted; 48 h of total feed restriction (n = 6). Blood samples were collected at 15-min intervals for 8 h on Days 0 and 2 of the experiment and twice on Day 1. Subcutaneous fat samples were collected before treatment onset (Day -1) and at the end of the intensive blood sampling on Day 2. Acute feed restriction markedly reduced leptin mRNA in adipose tissue (P < 0.01) and circulating concentrations of leptin (P < 0.05), IGF-I (P < 0.01), and insulin (P = 0.05) as compared with controls on Day 2. Moreover, the treatment x day interaction (P < 0.076) and within-day contrasts (expressed as a percentage of Day 0 values) revealed that the mean frequency of LH pulses in the fasted group was lower (P < 0.06) than in controls on Day 2. Neither mean concentrations of growth hormone (GH) nor GH secretory dynamics were affected by acute feed restriction. Fasting-mediated decreases in leptin gene expression and circulating leptin, in association with reductions in secretion of IGF-I, insulin, and LH, provide a basis for investigating leptin as a hormone signaling energy status to the central reproductive axis in cattle.

Adipose Tissue↗
PubMed1997

Proximal intracranial territory posterior circulation infarcts in the New England Medical Center Posterior Circulation Registry.

We studied 91 patients with proximal intracranial territory posterior circulation ischemia from the New England Medical Center Posterior Circulation Registry to learn their distribution, underlying cardiovascular causes and longterm outcome. All patients had imaging and vascular studies. Six patients had proximal territory TIAs. Among 85 stroke patients, 52% had infarcts limited to the proximal territory, while 48% also had infarcts in other intracranial posterior circulation territories. Eighty-five percent of proximal territory infarcts were posterior inferior cerebellar artery (PICA) territory cerebellar infarcts and 30% were lateral medullary infarcts. One patient had a hemimedullary syndrome. Six patients had PICA territory cerebellar and lateral medullary infarcts. The most common vascular lesion in lateral medullary infarct patients was ipsilateral intracranial vertebral artery (ICVA) disease (38% isolated ICVA disease) and in PICA territory cerebellar infarcts, extracranial vertebral artery (ECVA) disease (29% isolated ECVA disease). Half of all lateral medullary infarcts were due to a hemodynamic mechanism, most often in situ thrombosis of an ICVA occlusive lesion. Half of all PICA territory cerebellar infarcts were due to intra-arterial embolism and one-fifth to cardiac origin embolism. Embolism was a more frequent cause of proximal territory posterior circulation infarcts than intrinsic ICVA disease. The etiological profiles of lateral medullary and PICA cerebellar infarcts were different. Seventeen percent of all patients died during follow-up (41 months) but mortality related to the acute stroke or new strokes was only 6 percent. The outcome was favorable in the surviving patients; 89% had no or only slight disability.

Adult↗
PubMed2003

A degeneracy study in the circulant and bordered-circulant approach to birdcage and planar coils.

A method for finding closed-form solutions for the normal mode frequencies of systems with circulant 2pi/2 symmetry was investigated. This method is particularly good for questions of degeneracy that arise when one considers parallel imaging techniques like SENSE and SMASH in MRI. It is applicable to systems that include birdcage coils as well as planar coils with the appropriate rotational symmetry. A proof is given that complete degeneracy of all normal mode frequencies is impossible when all mutual inductive couplings are included. We tested the method against measurements made on a planar coil array and on an 8-element birdcage coil. The inclusion of the co-rotating end-ring mode changes the fundamental symmetry of the system from circulant to "bordered circulant". Closed-form solutions for the normal mode frequencies of a bordered circulant system are also given.

Computer Simulation↗
PubMed1989

[Retinal circulation in rhegmatogenous retinal detachment demonstrated by videofluorescence angiography and image analysis. I. The condition of retinal circulation before retinal detachment surgery].

The retinal circulation in cases of retinal detachment was studied in eight eyes with rhegmatogenous retinal detachment. Retinal mean circulation times of the detachment areas and the non-detachment areas were measured by a system using videofluorescence angiography and image analysis with dye dilution technique. The mean circulation times were 4.05 +/- 1.13 seconds (mean +/- standard deviation) in the non-detachment areas and 6.59 +/- 2.91 seconds in the detachment areas. The difference between the two areas was statistically significant (p less than 0.03). The results demonstrated that the velocity of retinal circulation is slower in retinal detachment area.

Adult↗
PubMed1977

Effects of pulmonary gas embolism on circulation and respiration in the dog. I. Effects on circulation.

Mongrel dogs weighing 15-25 kg and anesthetized with thiopental-gamma-hydroxybutyric acid were used to investigate the effects of pulmonary gas embolism on pulmonary arterial pressure (Pap), systemic arterial pressure (Pa) and cardiac output (Q). Pulmonary gas embolism was produced either by venous injecton or by venous infusion. The most marked effect of pulmonary gas embolism on circulation was an increase in Pap which returned to the original level after stopping the gas administration. 1. After gas injection Pap rose to a maximum within 30--60 s. The extent of this rise in Pap showed a positive correlation with the volume of the injected gas. The kind of gas (oxygen, helium, neon, nitrogen, air), however, did not influence the extent of the rise in Pap, but did influence the time of return of Pap to the original level. Carbon dioxide showed an exceptional behavior in that it had almost no effect on Pap at all. P a hardly changed with the volume of the gas injections (20--60 ml injected within 1 s); Q was not measured after gas injection (the direct Fick method is not usable in this situation). 2. Gas infusion caused a slow rise of Pap, its steepness and extent depending on the rate of infusion and on the physical properties of the infused gas. When the right ventricle was able to maintain its output, a constant level of Pap was reached after 10--15 min. In this circulatory steady state Pap appeared to be a measure of the degree of embolization. However, this relationship no longer held when the right ventricle failed as evidenced by a fall in Pap, Pa and Q. It may be concluded that pulmonary gas embolism produces a transient partial obstruction in the pulmonary circulation and that the performance of the right ventricle determines the maximum degree of embolization compatible with a sufficient circulation.

Animals↗
PubMed1995

Multivariate autoregressive modelling combined with transcephalic electrical impedance: method to relate neonatal systemic circulation and respiration to cerebral circulation.

We studied the pulsatile component of cerebral circulation with transcephalic electrical impedance (delta Z) in six preterm newborns, three of whom had severe cerebral bleeding, peri-intraventricular haemorrhage (PIVH). The transcephalic electrical impedance delta Z signal, ECG, arterial blood pressure, (aBP) and respirogram were recorded on analogue magnetic tape for 30 min. Artefact-free stationary segments (lasting for 2 min) of the four signals were digitised. A digital multivariate autoregressive (MAR) model was used to study frequency-specific variability in the signals and to quantify interrelations between the variabilities of delta Z, HR, aBP and respiratory signals. MAR modelling describes a system where all the signals simultaneously explain each other. The inherent variability of delta Z was lower and the influences of respiration and aBP on delta Z significantly greater in infants with severe PIVH than in controls. These changes were observed at high frequencies corresponding to respiration and heart rate. This may be interpreted as a marker of pressure passivism in the cerebral circulation following PIVH. We conclude that in preterm babies the application of MAR modelling, together with transcephalic impedance, may be a new, helpful and quantitative method for the study of simultaneous interrelations between variables of cerebral and systemic circulations and respiration.

Cerebral Hemorrhage↗
PubMedDate not supplied

The effect of liver transplantation on circulating levels of estradiol and progesterone in male patients: parallelism with hepatopulmonary syndrome and systemic hyperdynamic circulation improvement.

The correction of hepatopulmonary syndrome (HPS) after liver transplantation (LT) remains controversial. The aims of our study were to: 1) analyze whether LT reverses HPS; 2) note any relationship between HPS and the systemic hemodynamic disturbance; and 3) note changes in circulating sex hormones and the possible association with pulmonary and systemic hemodynamic changes. Systemic hemodynamic parameters, cardiac output and systemic vascular resistance (SVR), sex hormones, and intrapulmonary vasodilatation assessed by contrast transesophageal echocardiography, and gas exchange abnormalities were investigated in 19 patients with advanced cirrhosis prior to and 6 months (176.8+/-30 days) after LT. LT was followed by a marked reduction in cardiac output (6.6+/-1.7 vs 3.5+/-0.5 l/min; p<0.001) and SVR (1039+/-460 vs 1978+/-294 dyn x sec x cm(-5); p<0.005). Before LT, circulating estradiol and progesterone levels were invariably elevated (66+/-22 pg/ml and 1.8+/-1.1 ng/ml, respectively, normal values <31 pg/ml and 0.35 ng/ml, respectively), and dropped after LT (28+/-12 pg/ml p<0.001 and 0.38+/-0.2 ng/ml; p<0.001, respectively). Seventeen of 19 patients had intrapulmonary vasodilatation and increased alveolar-arterial oxygen difference, thereby fulfilling diagnostic criteria for HPS. Patients with HPS presented higher cardiac output (p<0.05), lower SVR (p<0.01), and higher progesterone and estradiol levels than patients without HPS (p<0.05). LT produced normalization of intrapulmonary vasodilatation in all patients. LT normalized hyperdynamic circulation and is a useful therapeutic option in patients with HPS. Normalization of sex hormone levels after LT suggests that they could play a pathogenic role in the development of HPS.

Blood Gas Analysis↗
PubMed2001

Decrease in circulating hematopoietic progenitor cells by trapping in the pulmonary circulation.

BACKGROUND: When stem-cell grafts are infused into the venous circulation and stem/progenitor cells egress from BM, pulmonary capillary beds are the first microcirculation site that they encounter. This provides the potential for circulating progenitor cells to be trapped in the pulmonary circulation. METHODS: We compared the number of progenitor cells [CD34(+) cells, colony-forming unit-granulocyte-macrophage (CFU-GM), CD34(+) CD41(+) cells and CFU-megakaryocyte (CFU-meg)] and their expression of cell-adhesion molecules (CAM) in samples taken simultaneously from radial arteries and central veins of 21 patients following PBSC mobilization. RESULTS: The mean (+/- SD) frequency of progenitor cells in the radial arteries was reduced to 79% +/- 25% for CD34(+) cells, 73% +/- 27% for CFU-GM, 77% +/- 25% for CD34(+) CD41(+) cells and 70% +/- 29% for CFU-meg of the number in the central veins. This suggests that some progenitor cells might be trapped in the lung. No association between progenitor-cell expression of CAM and pulmonary trapping was observed. DISCUSSION: Our data demonstrate pulmonary trapping of PBSC during mobilization, suggesting a potential inhibitory effect on PBSC harvest and medullary trafficking following graft infusion. However, the impact associated with pulmonary PBSC trapping may be negligible in the clinical setting if sufficient cells are infused.

Antigens, CD34↗
PubMed1989

[Changes in circulating blood volume in patients with ischemic heart disease during and after surgery with extracorporeal circulation].

Twelve men scheduled for elective coronary bypass graft surgery were investigated. Blood volume was measured using as a tracer iodine contained in Uropolin and endogenous iron. Concentration of this markers was measured by proton induced x-ray emission PIXE) method. Arterial blood was sampled before operation, every ten minutes during extracorporeal circulation and every hour during the day of operation. Simultaneously all of the outcome and income fluids were noted so it was possible to calculate changes in blood volume related to water moving from intravascular into extravascular space or inversely. It was found that patients suffered from coronary disease had lower circulating blood volume than the normal population. During extracorporeal circulation and the first hours after operation changes in blood volume ranges +/- 20% and this was caused by continuous water exchange between intravascular and extravascular spaces. The degree and direction of the changes were not related to time and type of infused fluids used in the pump prime as well. Most of the patients had the blood volume higher after operation than before, but that did not influence blood pressure and central venous pressure significantly.

Adult↗
PubMed1993

Schistosoma mansoni circulating anodic antigen but not circulating cathodic antigen interacts with complement component C1q.

Adult schistosome parasites, living in the blood vessels of their mammalian hosts, protect themselves against immune damage in a variety of ways. In addition to the tegument, the intestinal epithelium of the blood-feeding worms is permanently exposed to both the innate and the acquired immune system. In this study, we investigated whether the Schistosoma gut-associated antigens CAA and CCA (circulating anodic antigen and circulating cathodic antigen, respectively), which are excreted in relatively large quantities into the host's circulation, might play a role in evading complement attack. Of several complement components tested, only purified C1q showed significant binding to CAA, a negatively charged highly glycosylated glycoprotein. CCA, also highly glycosylated, but neutral or slightly positively charged, did not bind to C1q. CAA bound only to the collagen-like stalks of C1q and not to the globular heads. No detectable interaction of CAA with precursor human C1 was found and CAA did not induce activation of C1 in whole human serum as assessed by consumption of hemolytic C4 activity. Also CAA could not induce activation of precursor C1 in vitro. These results suggest that CAA behaves like a receptor for C1q, and might be involved in protecting the vulnerable schistosome gut against complement-mediated attack.

Animals↗
PubMed1997

Estrogen replacement in ovariectomized rats results in physiologically significant levels of circulating progesterone, and co-administration of progesterone markedly reduces the circulating estrogen.

Estrogen and progesterone replacement in ovariectomized rats in an often-used experimental system for determination of the specific effects of these hormones. In this study, two different delivery systems and two different dosage levels of estrogen, progesterone or a combination of the two have been used. Estrogen and progesterone in the circulation have been measured in response to each treatment. It is reported that estrogen treatment (237.2 +/- 49.2 pg/mL) results in physiologically significant levels of circulating progesterone (11.1 +/- 1.3 ng/mL). Also, co-administration of progesterone (23.7 +/- 2.0 ng/mL) with estrogen decreases the level of estrogen over that seen with estrogen alone (96.7 +/- 19.2 pg/mL with progesterone vs 237.2 +/- 49.2 pg/mL without progesterone). Thus, contrary to expectations, estrogen replacement therapy is not specific to estrogen and some of the antagonistic effects of progesterone are the result of a decrease in circulating estrogen, and not a specific effect on a target tissue. Whereas the mechanism of these effects has not been determined, obvious artifactitous phenomena have been excluded as being their cause. These results could have a major impact on the interpretation of past and future experiments of this kind.

Animals↗
PubMed1987

Ultrastructural localization of the circulating anodic antigen and the circulating cathodic antigen in the liver of mice infected with Schistosoma mansoni: a sequential study.

The present study describes the ultrastructural localization of two important circulating schistosome antigens--the circulating anodic antigen (CAA) and the circulating cathodic antigen (CCA)--in livers of mice at various time intervals after infection with Schistosoma mansoni. For the demonstration of these antigens at the electron microscope level use was made of a direct, double immunogold labeling procedure, in which CAA-specific monoclonal antibodies, labeled with 5-nm gold particles, and CCA-specific monoclonal antibodies, labeled with 15-nm gold particles, were used. Both antigens were localized in granules and in inclusion bodies of Kupffer cells and granuloma macrophages and it was found that in these compartments the degree of 5- and 15-nm gold labeling increased with the duration of the infection. Sometimes gold particles were also encountered on the cell surface and in endocytotic vesicles of these cells, in endothelial cells, and in the space of Disse. From these data it was concluded that in the liver CAA and CCA were primarily accumulated in granules and inclusion bodies of Kupffer cells and granuloma macrophages. It is discussed whether at these locations both antigens are degraded by lysosomal enzymes and whether these antigens are complexed with antibodies.

Animals↗
PubMed2005

Circulation and horizontal fluxes in the northern Adriatic Sea in the period June 1999-July 2002. Part I: geostrophic circulation and current measurement.

The dramatic increase in the occurrence of massive mucilage events in the northern Adriatic (NA) since their recent conspicuous reappearance in the late 1980s prompted a study of circulation and horizontal fluxes. Three transects with equidistant stations (10 km) were thus monitored monthly between June 1999 and July 2002. The geostrophic method was used to compute currents across the three transects from the CTD data, and dynamic heights provided a picture of the horizontal surface circulation. Currentmeter data records were used to adjust the reference surface and to validate the results for the southernmost and deeper (up to 70 m) transect (Senigallia-Susak Island). Geostrophic currents allowed estimation of monthly water fluxes across the transect. Different circulation regimes in the NA were observed, which may have affected mucilage events. When mucilage was absent (1999) or reduced (2001) in the western sector, the Western Adriatic Current (WAC, carrying water out of the NA) was found to be active, whilst the WAC was very weak or reversed when massive mucilage events occurred (2000 and 2002). Opposite behaviour has been observed for the Istrian Coastal Counter-Current (ICCC, retaining freshwater water in the NA) which was more intense during or after massive mucilage events and did not appear when mucilage was absent. Both WAC weakening and ICCC strengthening indicate a longer residence time of riverine waters in the NA, which favours mucilage development. Conclusively, WAC and ICCC result as key elements in controlling massive mucilage phenomena in the NA.

Climate↗
PubMed1998

Circulating adrenomedullin in cirrhosis: relationship to hyperdynamic circulation.

BACKGROUND/AIMS: Peripheral arterial vasodilation may be the key factor in the sodium and water retention of cirrhosis. The mechanism responsible for this vasodilation remains to be fully elucidated. Adrenomedullin is a novel peptide, highly expressed in cardiovascular tissues, with potent and long-lasting vasodilating activity. METHODS: The possible implication of adrenomedullin in the hemodynamic changes of cirrhosis has been investigated. We measured the plasma concentration of adrenomedullin in 20 cirrhotic patients and 11 healthy subjects. In addition, systemic, portal and renal hemodynamics, hormonal factors and renal function parameters were evaluated in the same patients. RESULTS: Circulating adrenomedullin was significantly higher in the group of patients with cirrhosis (72.1; 46-100 vs 21.6; 11-34 fmol/dl, respectively; p<0.02) and was directly correlated with the Pugh score (r: 0.6; p: 0.01), inversely correlated with the creatinine clearance (r: -0.6; p<0.01) and tended to inversely correlate with systemic vascular resistance index (r: -0.46; p: 0.07). There were no portal-peripheral differences in adrenomedullin levels. Transjugular intrahepatic portosystemic shunt insertion did not induce changes in the peripheral concentration of adrenomedullin, but baseline values of this hormone predicted the degree of hyperdynamic circulation after TIPS. CONCLUSIONS: Circulating adrenomedullin is increased in cirrhosis. These levels increase with the severity of the disease, especially in patients with hepatorenal syndrome. This peptide may contribute to vasodilation of cirrhosis.

Adrenomedullin↗
PubMed2005

Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine.

BACKGROUND: Basal metabolic rate (BMR) is the largest component of daily energy demand in Western societies. Previous studies indicated that BMR is highly variable, but the cause of this variation is disputed. All studies agree that variation in fat-free mass (FFM) plays a major role, but effects of fat mass (FM), age, sex, and the hormones leptin, triiodothyrionine (T3), and thyroxine (T4) remain uncertain. OBJECTIVE: We partitioned the variance in BMR into within- and between-subject effects and explored the roles of FFM, FM, bone mineral content, sex, age, and circulating concentrations of plasma leptin, T3, and T4. DESIGN: This was a cross-sectional study of 150 white adults from northeast Scotland, United Kingdom. RESULTS: Only 2% of the observed variability in BMR was attributable to within-subject effects, of which 0.5% was analytic error. Of the remaining variance, which reflected between-subject effects, 63% was explained by FFM, 6% by FM, and 2% by age. The effects of sex and bone mineral content were not significant (P > 0.05). Twenty-six percent of the variance remained unexplained. This variation was not associated with concentrations of circulating leptin or T3. T4 was not significant in women but explained 25% of the residual variance in men. CONCLUSIONS: Our data confirm that both FFM and FM are significant contributors to BMR. When the effect of FM on BMR is removed, any association with leptin concentrations disappears, which suggests that previous links between circulating leptin concentrations and BMR occurred only because of inadequate control for the effects of FM.

Absorptiometry, Photon↗