Biomedical subjects

V Rizzo

Publications and source records attributed to V Rizzo.

At least 37 records · Page 2Linked to original sources

PubMed1999

[Hypersplenism: current status and perspectives].

The hypersplenism is a syndrome characterized by cytopenia (involving one or several cellular lines of peripheral blood), increased or normal medullar cellularity, elevated turnover of the involved cellular line. Several studies have emphasized the important role of the spleen as an immunocompetent organ, with a microcirculation and typical functional characteristics. The authors attempt to assess relations between the hypersplenism and splenomegaly, as well as indications, risks and complications of splenectomy in pathological conditions. Finally, the alternative procedures to splenectomy are described.

Administration, Cutaneous↗

PubMed1998

In situ flow activates endothelial nitric oxide synthase in luminal caveolae of endothelium with rapid caveolin dissociation and calmodulin association.

Acute changes in pressure or shear stress induce the rapid release of nitric oxide (NO) from the vascular endothelium resulting in vasodilation. Endothelial nitric oxide synthase (eNOS) regulates this flow-induced NO secretion. The subcellular location of flow-induced eNOS activity in the endothelium in vivo as well as the mechanisms by which hemodynamic forces regulate eNOS activity are unknown. The luminal cell surface of the endothelium, which is directly exposed to circulating blood stressors, has been examined for eNOS expression and functional activity. Immunoelectron microscopy of rat lung tissue shows eNOS labeling on the endothelial cell surface primarily within caveolae. Subcellular fractionation to purify luminal endothelial cell plasma membranes and their caveolae directly from rat lungs reveals that eNOS is not only concentrated but also enzymatically active in caveolae. Increasing vascular flow and pressure in situ rapidly activates caveolar eNOS with apparent eNOS dissociation from caveolin and association with calmodulin. Hemodynamic forces resulting from increased flow appear to transmit through caveolae to release eNOS from its inhibitory association with caveolin, apparently to allow more complete activation by calmodulin and other possible effectors. These data demonstrate a physiological relevant mechanotransduction event directly in caveolae at the luminal endothelial cell surface. Caveolae may serve as flow-sensing organelles with the necessary molecular machinery to transduce rapidly, mechanical stimuli and thereby regulate eNOS activity.

Animals↗

PubMed1998

Rapid mechanotransduction in situ at the luminal cell surface of vascular endothelium and its caveolae.

The vascular endothelium is uniquely positioned between the blood and tissue compartments to receive directly the fluid forces generated by the blood flowing through the vasculature. These forces invoke specific responses within endothelial cells and serve to modulate their intrinsic structure and function. The mechanisms by which hemodynamic forces are detected and converted by endothelia into a sequence of biological and even pathological responses are presently unknown. By purifying and subfractionating the luminal endothelial cell plasma membrane from tissue, we show, for the first time, that not only does mechanotransduction occur at the endothelial cell surface directly exposed to vascular flow in vivo but also increased flow in situ induces rapid tyrosine phosphorylation of luminal endothelial cell surface proteins located primarily in the plasmalemmal invaginations called caveolae. Increased flow induces the translocation of signaling molecules primarily to caveolae, ultimately activating the Ras-Raf-mitogen-activated protein kinase pathway. This signaling appears to require intact caveolae. Filipin-induced disassembly of caveolae inhibits both proximal signaling events at the cell surface and downstream activation of the mitogen-activated protein kinase pathway. With the molecular machinery required for mediating rapid flow-induced responses as seen in endothelium, caveolae may be flow-sensing organelles converting mechanical stimuli into chemical signals transmitted into the cell.

Animals↗

PubMed1998

Study of factors affecting the determination of total plasma 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD)-thiol derivatives by liquid chromatography.

A detailed investigation of the factors affecting the determination of total plasma 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD)-thiol derivatives (i.e. cysteine, homocysteine and cysteinylglycine) is described. Essentially, this assay entails extracting specific thiols by plasma disulphide bond reduction, protein precipitation, sulphydryl compound derivatization with the thiol-specific fluorogenic reagent ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-F), and subsequent separation with isocratic reversed-phase high-performance liquid chromatography. By improving the reliability of several analytical parameters (composition of the mobile phase, pretreatment of the sample using different reducing and protein precipitation agents, and optimization of the derivatization of thiols with SBD-F), a number of critical issues can be identified and solved.

Adult↗

PubMed1998

Nitrite/nitrate balance during photoinduced cerebral ischemia in the rat determined by high-performance liquid chromatography with UV and electrochemical detection.

A specific and simple method for the direct simultaneous detection of extracellular nitrite (NO2-) and nitrate (NO3-) has been developed, using high-performance liquid chromatography separation with UV and electrochemical detection in series. These stable endproducts of nitric oxide (NO.) were determined in dialysis perfusate obtained through in vivo brain microdialysis during and after experimental photoinduced cerebral ischemia in rats. The chromatographic conditions were optimized with a reversed-phase column (250 x 46 mm) using 10 mM n-octylamine pH 6.0 as a mobile phase. Absorbance was measured at 220 nm for NO3- detection; electrochemical detection was performed at +0.7 V for NO2- evaluation. This assay system holds the advantages of in vivo consecutive measurements, high precision, good reproducibility, technical simplicity, fast response (about 7 min), and wide availability.

Animals↗

PubMed1998

Experience with antegrade bihemispheric cerebral perfusion in aortic arch operations.

BACKGROUND: Various techniques have been used for cerebral protection in aortic arch operations. Antegrade cerebral perfusion has lost its popularity to hypothermic circulatory arrest to overcome the so-called cluttered operative field. Hypothermic circulatory arrest has its own problems of coagulopathy, time constraints, and prolongation of cardiopulmonary bypass time. METHODS: Since June 1986 we have used antegrade bihemispheric cerebral perfusion with moderate hypothermia in 20 patients with aortic arch disease. Twelve patients had aneurysm, 7 had dissection, and 1 had traumatic tear. Five patients had had previous sternotomy for ascending aortic replacement. In addition to arch reconstruction, 7 patients had aortic valve replacement or repair, 2 patients had Bentall procedure, and 3 had selective innominate reconstruction. The mean cerebral perfusion time was 51+/-29 minutes. In 7 patients the cerebral perfusion time was between 60 and 120 minutes. RESULTS: There was no in-hospital or 30-day mortality. The blood product requirements were significantly less with moderate hypothermia. One patient suffered cerebrovascular accident (5%). None of the 7 patients with cerebral perfusion times of 60 to 120 minutes had any neurologic deficits. These results are superior to those reported for hypothermic circulatory arrest with or without retrograde cerebral perfusion. CONCLUSIONS: Antegrade bihemispheric cerebral perfusion is an optimal adjunct for cerebral protection during aortic arch operations.

Adolescent↗

PubMed1998

Hyperinsulinaemia, regional adipose tissue distribution and left ventricular mass in normotensive, elderly, obese subjects.

Obesity is a metabolic condition, related to abnormalities of the glyco-insulinaemic metabolism, and plays a substantial role in the development of cardiovascular disease. The aim of this study was to establish a correlation among left ventricular mass, evaluated echocardiographically according to Penn Convention criteria, blood pressure, evaluated by ambulatory blood pressure monitoring, anthropometric indices for evaluation of body mass index and waist to hip ratio circumference, regional adipose tissue distribution, evaluated by ultrasound measurements of visceral adipose tissue, and insulin resistance, evaluated by hyperinsulinaemia by oral glucose tolerance test. We selected two groups of elderly male subjects well matched for age (68.5 +/- 6.4 years): 29 obese and 20 lean, with a body mass index, respectively, of 34.6 +/- 2.9 and 23.4 +/- 2.3. Statistical analysis was carried out by Student's t-test and linear regression analysis. In spite of the fact that statistical analysis showed a higher, though not statistically significant, systolic and diastolic mean blood pressure in the lean subjects, we found an increased left ventricular mass in obese subjects (P < 0.0001). The area under the insulin curve was higher in obese than in lean subjects (P < 0.0001) while the area under the glucose curve was not significantly different in the two groups. Furthermore, linear regression analysis showed that in obese subjects left ventricular mass was strictly correlated with visceral adipose tissue (r = 0.607; P < 0.0001) and hyperinsulinaemia (r = 0.615; P < 0.0001). In conclusion, our data suggest that centripetal adipose tissue distribution and hyperinsulinaemia, independent of blood pressure values, are closely correlated with left ventricular mass.

Adipose Tissue↗

PubMed1997

Microvessels of the chick chorioallantoic membrane uniformly restrict albumin extravasation during angiogenesis and endothelial cytodifferentiation.

The present study served to evaluate extravasation of albumin across the microvascular endothelium of the chick chorioallantoic membrane (CAM) during the establishment of endothelial barrier functions (days 4.5 to 6.0), during a rapid phase of normigenesis (day 10), and after initiation of endothelial cytodifferentiation (day 14). CAM preparations in shell-less cultures were evaluated by intravital fluorescence confocal microscopy and videodensitometry after microinjections of chicken serum albumin (CSA) conjugated to Fluorescein isothiocyanate (FITC) (1% in Avian Ringers). At each observed temporal stage, FITC-CSA extravasation from the CAM pre-capillaries, capillaries, and post-capillaries was uniformly negligible. Since the endothelial glycocalyx imparts a net negative luminal charge, impedance of CSA transport by mutual charge repulsion was also evaluated. Accordingly, CAM microvessels were pre-infused with protamine sulfate (100 microliters/ml) to neutralize the negative charge. However, interstitial accumulation of FITC-CSA remained negligible. Thus, the presence of tight junctional clefts and paucity of plasmalemmal vesicles during CAM normigenesis probably serve as the principal morphologic correlates to the observed albumin restriction. Further, the normigenic CAM endothelium presents a more restrictive barrier to macromolecules than that of most angiogenic endothelia.

Allantois↗

PubMed1997

Biological variation in protein C, protein S and antithrombin concentrations in plasma of healthy subjects.

The analytical, intra- and inter-individual components of biological variation were estimated for protein C, protein S and antithrombin over a period of 6 weeks in a cohort of 17 apparently healthy subjects. Expressed as percentage activity (protein C and antithrombin) as a percentage concentration in normal human plasma (protein S), the mean values for men and women show no significant differences (p > 0.05) for any of the analytes studied. Calculated analytical goals (CV, %) for precision required for optimal patient care are: protein C, 2.9; protein S, 2.9 and antithrombin 2.7. A single numerical index, called "index of fiduciality", was also calculated to demonstrate that the analytical performance of our method was satisfactory. The generally applicable differences (% activity or % concentration) required for two results to be significantly different (p < or = 0.05) were calculated as: protein C, 17; protein S, 16 and antithrombin, 16. The usefulness of critical differences as guidelines for the interpretation of changes in serial results was investigated using an "index of heterogeneity" of intra-individual variation. The marked degree of individuality demonstrated for all the quantities indicates that, if conventional population-based ranges are used uncritically, major changes in analyte concentration may not be correctly identified for some patients, because observed values continue to lie within the reference range. The utility of conventional population-based reference intervals was determined by calculating a single numerical index, called "index of individuality". For protein C, protein S and antithrombin we found that five of a patient's specimens are required to achieve a 95% chance that the mean is within +/- 5% of the true value.

Adult↗

PubMed1996

Reference values of neuroactive amino acids in the cerebrospinal fluid by high-performance liquid chromatography with electrochemical and fluorescence detection.

Sampling and HPLC analysis procedures for CSF amino acid determinations were evaluated. In order to increase sensitivity, a precolumn derivatization of amino acids by o-phthalaldehyde-mercaptoethanol reagent was used. By using fluorimetric and electrochemical detection in series, positive peak identification can be obtained in a single chromatographic run. It is recommended to analyze freshly collected CSF. Amino acids are stable for short periods over a wide range of temperature, but storage at -80 degrees C is recommended. The CSF samples for the calculation of the reference values were taken from 40 healthy subjects, hospitalized for lumbar disk herniation, placed on the same diet and kept drug-free for at least 1 week. The mean values (mumol/l) and the ranges (in parentheses) were: 0.27 (0.09-0.63), 0.62 (0.18-1.15), 5.32 (3.05-11.50), 6.16 (2.90-13.30), 0.16 (0.03-0.22) for aspartic acid, glutamic acid, glycine, taurine and gamma-aminobutyric acid respectively.

Adult↗

PubMed1996

Capillary sprouts restrict macromolecular extravasation during normal angiogenesis in the chick chorioallantoic membrane.

During angiogenesis in the chorioallantoic membrane (CAM) of the chick, capillary proliferation occurs primarily by intussusceptive growth. Previously, we reported that such growth in the CAM proceeded without substantial macromolecular extravasation. Neovascularization involving capillary sprout formation, on the other hand, has been associated with a concomitant loss of endothelial selectivity. Thus, the present study tested the hypothesis that endothelial selectivity during angiogenesis is dependent on the mode of microvascular growth. Capillary sprout formation occurs in peripheral regions of the CAM, in addition to the more centrally located areas of intussuceptive growth. In this study, angiogenic endothelial permselectivities were evaluated in these respective areas of CAM microvascular growth by intravital fluorescent microscopy of a graded series of FITC-dextrans. In both cases, the angiogenic endothelia restricted extravasation of macromolecules > or = 20 kDa. Furthermore, capillary sprout endothelia, like the intussusceptive CAM endothelia, remained tightly sealed at the junctional clefts. Thus, angiogenic endothelial permselectivity in the CAM is not dependent on the mode of microvascular growth. Whether distinct cellular mechanisms are operable in capillary endothelial sprouts of the CAM, relative to those of other proliferating sprout endothelia, remains to be tested.

Allantois↗

PubMed1996

Mast cell activation accelerates the normal rate of angiogenesis in the chick chorioallantoic membrane.

Using shell-less cultures of chick embryos, the effect of mast cell degranulation on normal rates of angiogenesis in the chorioallantoic membrane (CAM) was recorded from Day 6 to Day 9. Based on the centripetal ordering method with capillaries as the initial point of reference, the first two orders of pre- and postcapillary microvessels were evaluated. After infusion of compound 48/80 into the allantoic cavity, the normal proliferation rate of order-1 pre- and postcapillaries was markedly increased. Increases of second-order vessel numerical densities (number/cm2) were less than those of the order-1 vessels. Thus, length densities (mean length x numerical density) were increased for the order-1 vessels only. During the accelerated rate of CAM angiogenesis, endothelial restriction of FITC-dextran 150 remained uniformly high. Hence, secreted mast cell products likely worked synergistically with endogenous CAM angiogenic factors between Days 6 and 9, without increasing rates of macromolecular extravasation. However, histamine injection into the allantoic cavity at Day 10, in conjunction with calcium supplementation of the shell-less cultures at Day 9, elevated the rate of FITC-dextran 150 extravasation. Whether differentiation of this transendothelial pathway is required for enhancement of CAM angiogenesis after Day 10 remains uncertain.

Animals↗

PubMed1996

HPLC methods for the determination of bound and free doxorubicin, and of bound and free galactosamine, in methacrylamide polymer-drug conjugates.

Quantitative acid hydrolysis followed by HPLC separation has been established as an analytical procedure for the determination of polymer-bound doxorubicin (an anti-cancer drug) and D-galactosamine (a liver-targetting moiety) in the polymer-drug conjugates FCE 28068 and FCE 28069. Optimal conditions of hydrolysis were determined in both cases: 1 N HCl, 50 degrees C, 1.5 h for doxorubicin, and 6 N HCl, 60 degrees C, 5 h for galactosamine. Appropriate HPLC quantitation of galactosamine required pre-treatment with sodium borohydride and pre-column derivatization with o-phthalalaldehyde and beta-mercaptoethanol. Independent determination of free doxorubicin and glactosamine in untreated polymer samples was also achieved with the same HPLC method up to detection limits of 0.01% and 0.02% respectively. The methods were validated for linearity, precision and repeatability. Validation for accuracy before and after acid hydrolysis was achieved by testing hydrolysis on model compounds and by assessing recovery in polymer solutions spiked with free doxorubicin or galactosamine.

Acrylamides↗

PubMed1996

Concentrations of L-dopa in plasma and plasma ultrafiltrates.

A sensitive and specific procedure is described for the determination of therapeutically relevant concentrations of L-dopa in plasma and plasma ultrafiltrates (free fraction) by high performance liquid chromatography with electrochemical detection. In plasma samples from healthy adult subjects (n = 15) spiked with L-dopa (500 micrograms l-1) the free fraction averaged 76 +/- = 8% (range 61-84%). Free fraction values increased by 38% with increasing plasma concentrations of L-dopa from 100-5000 micrograms 1-1. L-dopa free fraction was not affect by the presence of 3-O-methyl-dopa at concentrations up to 10,000 micrograms l-1.

Adult↗

PubMed1996

Ambulatory blood pressure and echocardiographic left ventricular dimensions in elderly hypertensive subjects.

In a consecutive series of 62 hypertensive elderly subjects, the authors studied the relation of blood pressure circadian variations with echocardiographic parameters of left ventricular (LV) hypertrophy. All the subjects were submitted to an ambulatory blood pressure monitoring (ABPM) and to B- and M-mode echocardiography. In the elderly hypertensive group, LV mass index (LVMI) was more strongly related to twenty-four-hour, daytime and nighttime systolic ambulatory blood pressure (r = 0.52, r = 0.37, r = 0.51) than diastolic ambulatory blood pressures were (r = 0.32, r = 0.18, r = 0.33). Casual systolic and diastolic blood pressure (CBP) was found more weakly related to LVMI than ambulatory blood pressures were (r = 0.35, r = 0.26). Elderly hypertensive subjects were divided into two subgroups in relation to the presence (group 1) or absence (group 2) of blood pressure nocturnal decline. No differences were found between these two subgroups in regard to: casual blood pressure values, ambulatory blood pressures in the diurnal period, sex, body surface area, height, weight, and age. LVMIs were computed in all three groups and showed the following results: 89.32 +/- 19.76 in elderly normotensives, 91.21 +/- 31.32 in group 1, and 99.80 +/- 18.21 in group 2. Echocardiographic parameters of LV dimensions and LVMIs were different in group 1 and 2. An inverse correlation, statistically significant, was observed between LVMIs and the nocturnal blood pressure reduction (systolic: r = -0.36, P < 0.05; diastolic: r = -0.29, P < 0.05). These results suggest an association between a smaller LV mass and nocturnal blood pressure decline in elderly hypertensive patients.

Aged↗

PubMed1996

Degranulation of mast cells in the chick chorioallantoic membrane does not increase macromolecular extravasation during normal angiogenesis.

OBJECTIVE: To test the hypothesis that stimulation of mast cell degranulation during normal angiogenesis in the chick chorioallantoic membrane (CAM) serves to acutely activate macromolecular transendonelial pathways. METHODS: Using shell-less cultures of 6-day-old chick embryos, efflux of fluorescein isothiocyanate (FITC)-dextran 150 from CAM microvessels was evaluated, after applications of compound 48/80 or exogenous histamine, by computer-assisted videodensitometric analyses. Real-time confocal imaging enabled optical differentiation of first-order pre- and postcapillaries from the capillary networks. Cytologic ultrastructure of the microvascular units was also evaluated. RESULTS: Although endogenous histamine was measurable and its concentration was increased after application of compound 48/80, segmental endothelia of the CAM microvascular units consistently restricted extravasation of FITC-dextran 150. Furthermore, intravascular injections of histamine also failed to induce interendothelial gap formation or macromolecular flux across the segmental CAM endothelia. CONCLUSIONS: These results are consistent with the interpretation that histamine-activated transendothelial pathways are inactive in the CAM at day 6. Whether such inactivity serves to retard facilitation of CAM angiogenesis by activated mast cells remains to be tested.

Allantois↗

PubMed1996

White-coat hypertension and cardiac organ damage in elderly subjects.

PURPOSE: The aim of this study was comparing the cardiac mass in elderly normotensive subjects and elderly white-coat hypertensive patients by examining in perspective, in consecutive patients, office blood pressure (BP), ambulatory BP, and echocardiographically determined left ventricular mass. PATIENTS AND METHODS: We studied 42 elderly patients attending a hypertension unit: of these, 22 (mean age 68.7 +/- 3.2 years) had persistent > 90 mm Hg office diastolic blood pressure (DBP), > 140 mm Hg systolic blood pressure (SBP) and < 142/90 mm Hg daytime ambulatory BP (white-coat positives); the remaining 20 (mean age 67.4 +/- 2.2 years) had < 90 mm Hg office DBP, < 140 mm Hg SBP and < 142/90 mm Hg daytime ambulatory BP (normotensives). White coat-patients (n = 22) were selected from a series of 75 consecutive newly diagnosed and never treated patients with mild hypertension (casual DBP constantly between 90 mm Hg and 105 mm Hg). RESULTS: Neither left ventricular mass index (89.9 +/- 23.1 vs 91.8 +/-25.4 P = NS and +/- 25.4 P = NS) and left ventricular mass/height, (115.4 +/- 17.1 vs 119.6 +/- 18.3 P = NS), nor relative wall thickness (0.31 +/- 0.44 vs 0.33 +/- 0.05 P = NS) were significantly higher in white-coat hypertensives as against normotensives. Neither did we find a relevant difference between left atrial diameters in the above considered groups (3.28 +/- 0.41 vs 3.32 +/- 0.37). In fact 81.8% of white-coat hypertensives had left ventricular normal geometry; whilst 13.6% only had concentric remodeling. Age and sex were associated with left ventricular mass index, left ventricular mass/height and relative wall thickness. Multiple regression analysis revealed that it is ambulatory, not office BP that carries independent information about relative wall thickness and left ventricular mass indices. CONCLUSIONS: Since elderly white-coat hypertensive subjects did not display a greater cardiac involvement than age-matched normotensives, they should be treated as such.

Aged↗

PubMed1995

Aminoacid recovery via microdialysis and photoinduced focal cerebral ischemia in brain cortex of rats.

A photochemical method using the Rose Bengal dye as thrombogenic agent was employed to induce focal cerebral ischemia in frontoparietal cortex of rats. A transcerebral microdialysis probe was used to collect samples from ischemic cortical area. An increase in glutamate (6-fold) and in taurine (4-fold) within the first hour occurred. Neuropathological investigations demonstrate a reproducible damaged area surrounded by a thin peripheral area showing neuronal apoptotic phenomena. The method represents a reproducible model of focal cerebral ischemia with neuropathological aspects superimposable to those characteristic of thrombogenic stroke in man. This method could also be relevant in the study of neurotransmitters during the evolution of ischemia. Furthermore, the presence of apoptotic phenomena in the perilesional halo confirms an ischemic penumbra suggesting the significance of preclinical pharmacological trials.

Amino Acids↗