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M Muzi

Publications and source records attributed to M Muzi.

At least 55 records · Page 3Linked to original sources
PubMed1992

Clonidine reduces sympathetic activity but maintains baroreflex responses in normotensive humans.

Clonidine, an alpha 2-adrenergic agonist, has been shown to modify the hemodynamic responses to surgery. To examine further the mechanism underlying this action, we evaluated the neurocirculatory effects of oral clonidine and the ability of clonidine to alter the hemodynamic and sympathetic responses to a noxious stimulus (cold pressor test) and to baroreceptor perturbations in nine healthy men (ages 20-29 yr). Heart rate (ECG), blood pressure (radial artery catheter), central venous pressure (jugular vein), and cardiac output (impedance cardiography) were monitored before and after oral clonidine (0.3 mg) or placebo. Plasma norepinephrine was measured with high-performance liquid chromatography. Sympathetic nerve activity (SNA) to skeletal muscle blood vessels was recorded from a Tungsten needle positioned within the peroneal nerve. Baroreceptor testing was carried out by intravenous bolus injections of nitroprusside (100 micrograms) followed 60 s later by intravenous phenylephrine (150 micrograms). The slope of the linear relationship between the change in R-R interval versus the change in mean pressure (cardiac baroslope) or change in SNA versus change in diastolic pressure (sympathetic baroslope) was determined at baseline and 75 min after clonidine or placebo. In addition, peak responses to the cold pressor test (60-s hand immersion in ice water) were determined at the same intervals. Clonidine progressively decreased blood pressure and muscle SNA over the 75-min session. Clonidine subtly reduced the sympathoexcitation produced by the cold pressor test but did not alter the gain of the baroreceptor reflex regulating cardiac interval or peripheral SNA; baroslope relationships were simply shifted leftward (to operate at lower pressures).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Scintigraphic assessment of "effort" axillary-subclavian vein thrombosis.

"Effort" axillary-subclavian vein thrombosis (Paget-Schroetter syndrome) is an uncommon deep venous thrombosis due to repetitive activity of the upper limb. Clinical suspicion is usually confirmed by contrast venography. This report describes a case where the diagnosis was made by radionuclide venography (Tc-99m DTPA). The examination was carried out in the acute phase and clearly demonstrated the presence and the site of the obstruction as well as the collateral vessels. Despite a complete clinical recovery, obtained by medical therapy, further examinations performed in the follow-up period showed persistence of the thrombotic obstruction and a rich development of collateral vessels. In the authors' opinion, radionuclide venography is worth considering as a first-choice procedure when an axillary-subclavian vein thrombosis is suspected, and contrast venography should be performed only when surgical treatment is indicated.

Adult↗
PubMed1992

ANP-mediated volume depletion attenuates renal responses in humans.

Brief low-dose infusions of atrial natriuretic peptide (ANP) that emulate physiological plasma concentrations in humans have little if any effect on renal excretory function. This study explored the possibility that ANP-mediated reductions in cardiac filling pressures (through ANP's rapid effect on capillary dynamics) could attenuate its purported renal effects. Protocol A consisted of 16 healthy subjects (ages 19-27 yr old) who underwent three consecutive 45-min experimental sequences: 1) placebo, 2) ANP (10 ng.kg-1 x min-1), and 3) ANP alone (n = 8) or ANP with simultaneous lower body positive pressure (LBPP, n = 8). Electrocardiogram and direct measures of arterial and central venous pressures were continuously monitored. Blood was sampled at the end of each 45-min sequence before subjects stood to void. Compared with control (placebo), ANP produced a hemoconcentration and increased plasma norepinephrine, but did not change heart rate, blood pressure, plasma levels of renin, aldosterone, or vasopressin, or renal excretion of volume or sodium. In subjects receiving LBPP to maintain central venous pressure during the last 45 min of ANP infusion, norepinephrine did not increase and urine volume and sodium excretion increased (P < 0.05). In a second study (protocol B), five healthy subjects received a placebo infusion for 45 min followed by two consecutive 45-min infusions of ANP (10 ng.kg-1 x min-1). Central venous pressure was maintained (LBPP) at placebo baseline throughout the two ANP infusion periods. Urine volume and sodium excretion rates increased progressively and significantly during both ANP infusion periods (P < 0.05) without significant changes in creatinine clearance, blood pressure, or heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Venodilation contributes to propofol-mediated hypotension in humans.

The present investigation explored the possibility that the commonly observed hypotension that occurs during induction of anesthesia with propofol might be related to its ability to produce venodilation. Thirty-six ASA I and II patients who received no premedication were studied. The first 20 patients were divided into two equal groups. Hemodynamic measurements consisted of heart rate, arterial blood pressure, and forearm venous compliance by occlusive plethysmography. Baseline measurements were made in awake patients while resting in a supine position. Repeat measurements were made during steady-state infusions of propofol (2.5 mg/kg bolus injection, followed by a continuous infusion at 200 micrograms.kg-1.min-1) or thiopental (4 mg/kg bolus injection, followed by continuous infusion at 200 micrograms.kg-1.min-1), 10 min after tracheal intubation while patients were artificially ventilated. Both anesthetics resulted in a significant (P less than 0.05) and similar tachycardia; however, propofol produced significant decreases in systolic (-30 +/- 9 mm Hg) and diastolic (-11 +/- 4 mm Hg) arterial blood pressure. Forearm venous compliance was significantly increased during propofol administration but unchanged in patients receiving thiopental. In four additional patients receiving smaller consecutive infusions of propofol (50 and 100 micrograms.kg-1.min-1), significant subtle increases in forearm compliance were also recorded. These increases were not observed in four patients who received placebo infusions. Thus, one mechanism promoting hypotension during propofol anesthesia in humans seems to be related to its direct effects on venous smooth muscle tone and presumably venous return.

Adult↗
PubMed1991

Aztreonam biliary excretion in bile duct ligated jaundiced rats.

An experimental study was undertaken to assess aztreonam biliary concentrations in bile duct ligated jaundiced rats. The study proved that aztreonam biliary concentrations are sufficient to inhibit Gram-negative bacteria within the first and the second hour after antibiotic administration. The experimental model suggests that clinical conditions such as lithiasis or neoplasms of the biliary tree should not totally inhibit the antibiotic excretion.

Animals↗
PubMed1990

Deoxyglucose lumped constant estimated in a transplanted rat astrocytic glioma by the hexose utilization index.

The lumped constant (LC) for calculating the regional glucose (glc) metabolic rate by the deoxyglucose (DG) method was estimated in a transplanted rat glioma and normal rat brain. First, the hexose utilization index (HUI) was measured at 1.5, 3.0, and 4.5 min in right hemisphere glioma implants and uninvolved contralateral hemisphere following bolus intravenous injections of [3H]DG and [14C]glucose. At these times, the glioma HUI values were 0.639, 0.732, and 0.712, respectively, and the coordinate left hemisphere values were 0.432, 0.449, and 0.418. Second, the volumes of distribution of DG and glucose were determined to be 0.436 and 0.235 in glioma implants and 0.402 and 0.237 in left hemisphere, respectively. Third, following simultaneous intracarotid injections of [3H]DG and [14C]glucose, the ratio K1/K1 was 1.1 in glioma grafts and 1.3 in left hemisphere. With these values for HUI, volume of distribution, and K1 ratio, the LC in this rat glioma was estimated to be 2.1 times higher than the left hemisphere LC (p less than 0.02). These results suggest that measurement of brain tumor CMRglc using a normal brain LC may significantly overestimate the true tumor CMRglc.

Animals↗
PubMed1989

Impedance-derived cardiac indices in supine and upright exercise.

Impedance cardiography was used to determine the classical systolic time intervals (STI's) (i.e., pre-ejection period (PEP), left ventricular ejection time (LVET) and the quotient PEP/LVET), in young, healthy, male subjects during supine and seated exercise. With increasing exercise, there was a tendency toward decreases in PEP, LVET, and PEP/LVET. In the seated position, there was an increase in transthoracic Zo incident to the caudal migration of thoracic blood--a result of the postural change. With seated exercise, there were--in contrast to supine exercise-greater decreases in PEP/LVET and greater increases in the Heather index. Similarly, there was a tendency toward increases in dZ/dtmin and the Rapid Ejection Index. We suggest that these differences are related to increased myocardial contractility resulting from the postural augmentation of cardio-sympathetic activity, added to that of exercise per se. This study, as well as previous ones, indicates that impedance cardiography is reliable, effective, and more practicable than the arteriographic method for monitoring STI's. We also believe that certain impedance-derived indices (i.e., transthoracic Zo, dZ/dtmin and the Heather Index) have considerable potential value for physiologic and clinical investigation.

Adult↗
PubMed1989

Deoxyglucose kinetics in a rat brain tumor.

Accurate quantitation of local glucose metabolic rates (LMRglc) of abnormal tissues such as brain tumors with the 2-deoxyglucose (DG) method requires knowledge of the tissue rate constants and lumped constant. The deoxyglucose rate constants were measured in an experimental intracerebral glioma in 24 awake rats with a dual tracer [(3H)-DG and (14C)-DG] method. Tissue time points were obtained at 2, 5, 10, 18, 30, 60, 90, and 180 min after injection by decapitation and liquid scintillation counting. Blood samples were obtained at 1 min intervals initially and at longer intervals later. The rate constants were estimated with parameter estimation. LMRglc was calculated from the rate constants, assuming a lumped constant of 0.5. K1 for normal cerebrum was found to be 0.258 ml/g/min, and k2-k4 were 0.406, 0.075, and 0.0103 min-1; LMRglc = 65.1 mumol/100 g/min. The corresponding values for the glioma were 0.108, 0.126, 0.040, and 0.0019 with LMRglc = 41.7. The considerably lower k4 in the glioma was reflected in persistent higher activity in the glioma at longer times. Thus, tissue activity alone cannot be used to assess relative glucose metabolic rates in abnormal tissues such as gliomas, particularly at late times after injection.

Animals↗
PubMed1989

Determination of the deoxyglucose and glucose phosphorylation ratio and the lumped constant in rat brain and a transplantable rat glioma.

Mitochondrially bound hexokinase (ATP-D-hexose-6-phosphotransferase; EC 2.7.1.1) was dissociatively extracted from normal rat brains and intracerebral and subcutaneous implants of the 36B-10 glioma. At least 70% of the total hexokinase enzyme activity in normal and glioma tissue was associated with the mitochondrial fraction. Purification of the crude tissue extracts by ion-exchange and affinity chromatography followed by analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a successive purification of the enzyme to homogeneity with a molecular size of 98 kilodaltons. Enzyme kinetics with glucose or 2-deoxyglucose (2-DG) as the substrate were measured spectrophotometrically by coupling the appropriate reactions to either NADPH or NAD+ formation. The Km of hexokinase with glucose as the substrate in the intracerebral glioma (0.138 mM) and subcutaneous glioma (0.183 mM) tissues was 2.1-2.7-fold higher than that observed in normal brain tissue (0.067 mM) (p less than 0.001). No significant differences were observed in the Km for hexokinase with 2-DG as the substrate in the glioma and normal brain tissue. The phosphorylation ratio for normal brain was 0.320 and was increased in the intracerebral glioma to 0.694 and in the subcutaneous glioma to 0.519. The ratios of deoxyglucose and glucose volumes of distribution in normal brain and intracerebral glioma tissues were 1.70 and 1.85, respectively. The lumped constants calculated directly from the phosphorylation ratios and the volumes of distribution of deoxyglucose and glucose were 0.517 in normal brain and 1.168 in intracerebral glioma. Our results indicate the lumped constant is increased 2.26-fold in intracerebral glioma compared with normal brain.

Animals↗
PubMed1989

Urinary sodium levels related to jaundice duration in the assessment of postoperative risk of hepatorenal syndrome in elderly patients undergoing surgery for biliary obstruction.

The early diagnosis of hepatorenal syndrome (HRS) is based chiefly on biochemical alterations and in particular, the relationship between urinary sodium levels and duration of jaundice seems to offer the most reliable prognostic index. Urinary sodium levels were determined in 32 elderly patients, who underwent surgery for benign or malignant biliary obstruction, without, major organ resection; in this group 4 patients died of HRS (12.5 per cent). The diagnostic accuracy of the method reached 97 per cent.

Aged↗
PubMed1988

Blood flow changes following 137Cs irradiation in a rat glioma model.

Blood flow changes in response to 20 Gy 137Cs whole brain irradiation were measured with quantitative autoradiography of [14C]iodoantipyrine (IAP) in intracerebral grafts of the 36B-10 rat glioma, the brain around tumor (BAT), the contralateral corpus callosum, and the contralateral cerebral cortex. Irradiations were delivered on Day 14 post-transplantation, and measurements of flow (F) were performed with IAP on Day 15 or Day 16. Mean values of F were determined in individual tumors and in treatment groups. In 15- and 16-day-old unirradiated control tumors, the group mean F was 0.31 ml.g-1.min-1. In both 15- and 16-day-old tumor groups irradiated on Day 14 (Day 1 and 2 postirradiation tumors) the mean F for each day's group was 0.52 ml.g-1.min-1, 68% higher than the control (P less than 0.01). Flow in the BAT and the contralateral corpus callosum similarly was increased at these times (P less than 0.01). Flow in the contralateral cerebral cortex was 1.1, 1.5, and 1.3 ml.g-1.min-1 in the control, 1 day postirradiated, and 2 day postirradiated groups, respectively, but these increases were not significantly different from the control. These data indicate that flow increases in the intracerebral gliomas as well as in normal brain regions during the 2 days following 20 Gy irradiation. Changes such as these following radiotherapy may have important effects on the bioavailability of chemotherapeutic drugs.

Animals↗
PubMed1987

Blood flow in an experimental rat brain tumor by tissue equilibration and indicator fractionation.

The tissue equilibration technique (Kety) was compared with the indicator fractionation technique for the measurement of blood flow to normal brain and an experimental brain tumor in the rat. The tumor was a cloned astrocytic glioma implanted in the cerebral hemisphere of F-344 rats. I-125 Iodoantipyrine, using a rising infusion for one minute, was used for the tissue equilibration technique. C-14 butanol, injected as a bolus 8 seconds before sacrifice, was used for the indicator fractionation technique. Samples were assayed using liquid scintillation counting and the iodoantipyrine results were regressed against the butanol results. For normal tissue R = 0.832, SEE = 0.115 ml/g/min, and Slope = 0.626. For tumor R = 0.796, SEE = 0.070 ml/g/min, and Slope = 0.441. The iodoantipyrine tissue/blood partition coefficient for normal hemisphere (gray and white matter) was 0.861 +/-0.037 (SD) and for tumor was 0.876 +/-0.042. The indicator fractionation technique with C-14 butanol underestimated blood flow in a consistent manner, probably because of incomplete extraction, early washout of activity from tissue and from evaporation of butanol during processing. Our experiments revealed no differences between tumor and normal brain tissue that might invalidate the comparison of iodoantipyrine blood flow results in brain tumors and surrounding normal brain.

1-Butanol↗
PubMed1987

Regional blood-to-tissue transport in an irradiated rat glioma model.

To assess vascular permeability in intracerebral grafts of the 36B-10, F-344 rat glioma following 20 Gy 137Cs whole brain irradiation, the blood-to-tissue transport constant, K, of [14C]-alpha-aminoisobutyric acid (AIB) was measured with quantitative autoradiography. Mean, 90th percentile, and 95th percentile values of K were determined in individual tumors and in treatment groups. In 15-day-old unirradiated control tumors, mean, 90th percentile, and 95th percentile values of K were, respectively, 11.3, 18.4, and 20.8 ml kg-1 min-1. In 15-day-old tumors irradiated on Day 14 (Day 1 postirradiation tumors) the K values were 5.9, 9.4, and 10.4, all of which were significantly less than the respective control values (P less than 0.01). In 16-day-old tumors irradiated on Day 14 (Day 2 postirradiation tumors), the K values were 10.8, 15.0, and 16.0, respectively, none of which was significantly different from control tumors. Mean K values for Day 2 vs Day 1 postirradiation tumors (10.8 vs 5.9) yielded P less than 0.05, but the 90th percentile and 95th percentile values for Day 2 vs Day 1 yielded 0.05 less than P less than 0.10. Separate experiments measured AIB and 86RbCl uptake in 36B-10 cells in vitro 1 and 2 days following 20 Gy irradiation to assess whether this radiation dose reduced the capacity of tumor cells to trap AIB or Rb+. Irradiation did not reduce the accumulation of either tracer, but rather was associated with an increased accumulation of AIB. Therefore, the AIB transport data suggest that vascular permeability and/or surface area decreases significantly in the day following 20 Gy irradiation and that this decrease reverses by the second day following irradiation.

Aminoisobutyric Acids↗
PubMed1985

Determination of cardiac output using ensemble-averaged impedance cardiograms.

Although impedance cardiography provides safe and reliable noninvasive estimates of stroke volume in humans, its usefulness is limited by the necessity for subjects to be apneic and motionless. In an effort to circumvent this restriction we studied the validity of ensemble-averaging of impedance data in exercising normal subjects and in intensive-care patients. The correlation coefficient (r value) between 128 ensemble-averaged and standard hand-digitized determinations of stroke volume index from the same records taken during rest and exercise in six normal male subjects was +0.97 (P less than 0.001). The r value for ensemble-averaged stroke volume indices during free breathing and breath hold in the same subjects was +0.92 (P less than 0.001), suggesting that breath hold did not significantly affect the stroke volume estimation. In 14 freely breathing hospital intensive-care patients the r value between simultaneous thermodilution cardiac output readings and ensemble-averaged impedance determinations was +0.87 (P less than 0.01). The results indicate that ensemble-averaging of transthoracic impedance data provides waveforms from which reliable estimates of cardiac output can be made during normal respiration in healthy human subjects at rest and exercise and in critically ill patients.

Adult↗
PubMedDate not supplied

Correlation of Tc-99m-red blood cell phleboscintigraphy with clinical severity of chronic venous disease.

Equilibrium red blood cell phleboscintigraphy of the lower limbs for the diagnostic management of chronic venous disease has been proposed. The aim of this study was to verify the correlation of the phleboscintigraphic assessment of chronic venous disease with the clinical grading of the severity of the disease, since other diagnostic modalities have been recently demonstrated a poor and only partial correlation. Equilibrium Tc-99m-red blood cell phleboscintigraphy was performed in 27 patients with chronic venous disease. Scintigraphic images of 52 limbs were classified according to a four-class qualitative grading of the severity of the venous disease, and a quantitative scintigraphic index (saphena /femoral ratio) was assigned to each limb. The scintigraphic qualitative grading showed a highly significant correlation with the clinical grading (Rs=0.82, p<0.01), a good interobserver and intraobserver agreement (86.5% and 92.3%, respectively) and more than 90% sensitivity and specificity to identify the categories "minimal or no chronic venous disease" or "more significant disease" (assessed according to the Bayes theorem). Sensitivity and specificity results for the quantitative assessment were not as good. Phleboscintigraphy correlates well with the clinical grading of the severity of chronic venous disease of the lower limbs and may have potential as a valuable diagnostic tool for the noninvasive assessment of chronic venous disease.

Chronic Disease↗
PubMedDate not supplied

[Assessment of the therapeutic effectiveness of alcohol administration in hepatocarcinoma: comparison of spiral computerized tomography and Doppler color ultrasonography].

PURPOSE: To investigate the comparative adequacy of spiral CT and color-Doppler US versus biopsy in assessing the efficacy of percutaneous ethanol injection (PEI) in hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Fifteen patients with 30 known HCCs, 2-5 cm in diameter, underwent PEI. Arterial phase spiral CT and color-Doppler US were performed before treatment in all patients. Treatment efficacy was established on the basis of color-Doppler, spiral CT and percutaneous biopsy findings; biopsy was the gold standard. RESULTS: After PEI, 22 of 30 lesions which were negative for malignant cells at biopsy were completely necrotic at spiral CT and avascular at color-Doppler US. In the extant 8 lesions, which exhibited residual tumor tissue at biopsy, spiral CT detected early enhancement of the viable tumor portion in all cases. Color-Doppler US showed residual tumor vascularization in 4 of 8 lesions. CONCLUSIONS: Our results demonstrate that spiral CT, performed in the arterial phase, can improve the depiction of residual viable tumor tissue in HCCs treated with PEI, overcoming color-Doppler limitations.

Aged↗