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Biomedical subjects

A De Santis

Publications and source records attributed to A De Santis.

At least 55 records · Page 3Linked to original sources
PubMed1995

Glutathione suppresses spontaneous activity in the frog spinal cord.

Spontaneous electrical activity in the isolated hemisected frog spinal cord increased in the presence of the SH reductant dithiothreitol (DTT) was reversibly suppressed by the oxidant 5-5'-dithio-bis-(2 nitrobenzoic acid) (DTNB) and was irreversibly suppressed by the sulphydryl modifying agents N-ethyl-maleimide (NEM) and monobromotrimethylammonio bimane. Glutathione (GSH), an important natural low molecular weight thiol, reversibly suppressed spontaneous activity. Cords pretreated with glutathione and successively exposed to NEM or bimane maintained their normal electrical activity. This indicates that GSH had interacted with the exposed sulphydryls and prevented their reaction with NEM or bimane. Incubation with bimane resulted in fluorescence-labelled neurones in the dorsal and ventral horns, whereas samples pretreated with NEM or with GSH were not labelled. Neurones appeared again fluorescent in cords preincubated with GSH and sequentially exposed to NEM or bimane. Both electrophysiological and histochemical methods indicate that exposed membrane sulphydryls are involved in the genesis and/or modulation of spontaneous electrical potentials.

Animals↗
PubMed1995

The natural history of gallstones: the GREPCO experience. The GREPCO Group.

During the cross-sectional studies (February 1981 to July 1984) performed by the Group for Epidemiology and Prevention of Cholelithiasis (GREPCO) in Rome, Italy, 161 subjects were identified as having gallstones. Ten subjects did not participate in the prospective follow-up. At entry, 33 of the 151 remaining subjects were symptomatic, and 118 were asymptomatic. Data on incidence of biliary colics, complications, cholecystectomy, and death were collected at least every 2 years. In the initially asymptomatic group, the cumulative probability (% +/- SE) of developing biliary colic was 11.9 +/- 3.0 at 2 years, 16.5 +/- 3.5 at 4 years, and 25.8 +/- 4.6 at 10 years. None of the variables considered as possible modifiers of the natural history were found to be associated with an increased risk of developing biliary colic. The cumulative probability (% +/- SE) of developing complications after 10 years was 3.0 +/- 1.8 in the initially asymptomatic group and 6.5 +/- 4.4 in the symptomatic group (P = NS). Incidence of cholecystectomy was higher in the initially symptomatic than in the asymptomatic group (log-rank test = 2.27; P = .02). Fifteen (53.6%) of the 28 operated in the initially asymptomatic group were submitted to cholecystectomy, although specific symptoms did not occur. Twelve (10.2%) and 2 (6.1%) of the initially asymptomatic and symptomatic subjects died during the follow-up. One patient in the former group died at age 64 of a histologically proven adenocarcinoma of the gallbladder. In conclusion, this study demonstrates that the natural history of gallstones is less benign than is generally considered.

Adult↗
PubMed1995

Elevated levels of soluble E-selectin in patients with IDDM and NIDDM: relation to metabolic control.

The adhesion of leucocytes to the endothelium, an early step in atherogenesis, is mediated by cell adhesion molecules. In this study we evaluated the concentration of soluble adhesion molecules in patients with insulin-dependent (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) and studied its relation to glycaemic control. Soluble adhesion molecules E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1) were measured in 31 diabetic patients (18 with IDDM and 13 with NIDDM), 20 hyperlipoproteinaemic patients (10 with type IIa and 10 with type IIb) and 20 healthy subjects. Increased E-selectin concentrations were found in the patients with IDDM and NIDDM and in the hyperlipoproteinaemic patients when compared to the control subjects (p < 0.01 for all the groups). ICAM-1 was found to be elevated only in the patients with NIDDM (p < 0.01). No significant differences in VCAM-1 concentration were found in the different groups of subjects. The concentration of plasma E-selectin was positively correlated with the glycated haemoglobin (r = 0.54, p < 0.01) in patients with IDDM and NIDDM. In the same patients E-selectin was not related to the concentrations of plasma lipids in spite of the fact that it was found to be elevated in hyperlipoproteinaemic subjects. The results though preliminary suggest that in diabetic patients the concentration of soluble adhesion molecules and especially of E-selectin may be related to metabolic control.

Adult↗
PubMed1995

Increased susceptibility of LDL to in vitro oxidation in patients on maintenance hemodialysis: effects of fish oil and vitamin E administration.

Oxidized low-density lipoproteins (LDL) play an important role in the pathogenesis of atherosclerosis. An increased sensitivity of red blood cell membranes to lipid peroxidation has been previously demonstrated in patients with chronic renal failure, suggesting that the antioxidant defence of lipoproteins might be impaired. Fish oil supplementation has been proposed in dialysis patients, but it is still unclear if the positive effects of fish oil depend only on its polyunsaturated fatty acid content or on other factors, such as the usually added antioxidants. Moreover, the increased concentration of highly peroxidable n-3 polyunsaturated fatty acids induced by fish oil in LDL particles could favour LDL oxidation and possibly the development of atherosclerosis. The present study was designed to evaluate the susceptibility of LDL to in vitro oxidation (lag phase) and the rate of lipid peroxidation (propagation phase) by fluorescence development during copper exposure in 14 hemodialysis patients. A further aim was to compare the effects on lipid metabolism and LDL oxidation of fish oil supplementation (20 ml containing vitamin E 20 IU as antioxidant) for 30 days and of vitamin E administration (50 IU) for another 30 days. The length of the lag phase and vitamin E concentration were significantly reduced (p < 0.01) in hemodialysis patients and increased significantly (p < 0.01) after administration of both fish oil and vitamin E. Fish oil supplementation also reduced plasma lipids significantly (p < 0.01) and increased the propagation phase (p < 0.01). Our results demonstrate that the susceptibility of LDL to oxidation is enhanced in hemodialysis patients, suggesting a possible relationship between excessive LDL peroxidation and accelerated atherosclerosis. The increased susceptibility of LDL to in vitro oxidation can be explained, at least partially, by a reduced LDL vitamin E concentration. Since fish oil increased the lag phase to the same extent as vitamin E supplementation, the positive effect of fish oil could be partly explained by its antioxidant content.

Arteriosclerosis↗
PubMed1994

Ion-sensitive microelectrode system with short response time.

The measurement of changes in ion activity (e.g., pH) in neurons requires fine tip-sized double-barreled microelectrodes: one channel being equipped with an ion-selective liquid membrane, the other used for measurement of the membrane potential. The limited bandwidth and the differing transfer functions for electrical and ionic signals necessitate frequency response linearization networks to ensure that the output signal of the electrode is a faithful image of the input signal. We have developed a linearization network to ensure a rapid response time for ion-sensitive microelectrodes. To test the response characteristic we have developed a test system that allows the pH at the electrode tip to be changed within 1 ms. Application of these techniques to electrodes of 1 micron tip diameter results in a 90% response time to a pH step of approximately 60 ms and of approximately 2 ms with electrodes with 20 micron tip.

Electrophysiology↗
PubMed1994

Effect of plasma on the degradation of hydroperoxides of unesterified linoleic acid and copper-peroxidized LDL.

The determination of lipid hydroperoxides in plasma and lipoproteins recently reached a clinical relevance in disorders such as atherosclerosis, where oxidative reactions have been suggested to play a fundamental pathogenetic role. The peroxide content of lipoproteins is usually measured after ultracentrifugation and extraction. During this procedure, some peroxides might decompose causing a too low recovery. To screen this possibility, the disappearance, in the presence of human plasma, of hydroperoxides of linoleic acid and Cu-oxidized low density lipoprotein (LDL) have been investigated, using both a iodometric titration and an enzymatic assay. While only in the presence of GSH plasma decomposes linoleic acid hydroperoxides quite rapidly, peroxides in Cu-oxidized LDL were stable both in presence as well as in absence of GSH. This indicated that lipid hydroperoxides are stable in plasma and that peroxides of Cu-oxidized LDL are not substrate for the glutathione-dependent peroxidase activity in plasma. The relevant decrease of the iodometric titre of LDL peroxides observed in the presence of elevated amounts of plasma was shown to be artifactual, since some compounds extracted from plasma do react with iodine generated by peroxides. Whole plasma itself, indeed, has been shown to reduce back to I- appreciable amount of free iodine.

Copper↗
PubMed1994

Effect of a medium dose of ursodeoxycholic acid with or without taurine supplementation on the nutritional status of patients with cystic fibrosis: a randomized, placebo-controlled, crossover trial.

Ursodeoxycholic acid administration has been reported to improve cholestasis and inflammatory activity in primary biliary cirrhosis and, in an uncontrolled study, also in young adults with cystic fibrosis (CF) and chronic cholestasis. As an improvement in nutritional status was also observed in these young adult patients, we investigated whether the administration of a medium dose of ursodeoxycholic acid ameliorates the nutritional status of malnourished young adult CF patients with chronic liver disease. The study included 51 patients (27 male patients and 24 female patients; age range, 8-32 years; median, 14) with body mass percentiles < 90%. Patients were randomly assigned to receive either ursodeoxycholic acid (10-12 mg/kg/day) alone or with taurine (18-22 mg/kg/day). Patients were followed in a crossover fashion within each group; 6 months of treatment was randomly alternated with 6 months of placebo. Nine patients dropped out before concluding the study. Liver function tests, nutritional status, and coefficients of fat absorption were determined at entry and after each 6 months of placebo or treatment. Nutritional status and fat absorption were not significantly modified by either treatment. Liver function tests improved after ursodeoxycholic acid administration only in patients with concomitant chronic liver disease. Our findings indicate that 6 months of therapy with a medium dose of ursodeoxycholic acid, either alone or with taurine, does not improve the nutritional status of young malnourished CF patients. Higher doses given for longer periods might be worth investigating.

Absorption↗
PubMed1994

Increased susceptibility of LDL to in vitro oxidation in patients with insulin-dependent and non-insulin-dependent diabetes mellitus.

The susceptibility of LDL to copper-catalyzed oxidation was evaluated in 24 patients with insulin-dependent and 16 patients with non-insulin-dependent diabetes mellitus, 14 abdominal and 14 gluteal-femoral obese women, 22 familial hypertriglyceridemic and 28 control subjects. Differences in the LDL susceptibilities were studied by measuring the changes of fluorescence intensity and expressed as lag-phase. The lag-phase was significantly shorter in patients with insulin-dependent, non-insulin-dependent diabetes mellitus, abdominal obesity and familial hypertriglyceridemic patients than in gluteal-femoral obese subjects and controls (p < 0.01). The shortest lag-phase was found in familial hypertriglyceridemic patients while intermediate values were found in insulin-dependent, non-insulin-dependent and abdominal obese patients who had only a slight increase in triglyceride values. Similarly the lowest value of the LDL cholesterol to protein ratio, as expression of LDL particle size, was found in familial hypertriglyceridemic patients (p < 0.01), while the patients with insulin-dependent, non-insulin-dependent diabetes mellitus and abdominal obesity had intermediate values. The ratio was found to be directly correlated with the length of the lag-phase (r = 0.87, p < 0.001). In spite of similar triglyceride and cholesterol to protein ratio values, however, the length of the lag-phase was significantly shorter in patients with insulin-dependent diabetes mellitus than in those with abdominal obesity. So it is concluded that the different susceptibility to oxidation found in the different groups of patients is only partially explained by plasma triglyceride values.

Adult↗
PubMed1994

[The determination of polyamines in tumors of the maxillofacial area].

Putrescine, spermidine and spermine are polyamines deriving from ornithine. These are vital molecules for cell duplication processes; in fact, enzyme inhibitors responsible for synthesis are able to block cell multiplication. It is interesting to observe that there is an increased concentration of the polyamines and enzymes responsible for synthesis in solid tumours in man and in biological fluids in subjects carrying tumours. The authors assayed the polyamine concentration in tumour tissue taken from 10 cases of parotid carcinoma, noting a considerable increase in their levels compared to healthy control tissues. The hypothesis of being able to use the level of polyamines present in biological fluids in order to make an early diagnosis of tumours has now been definitively abandoned, both due to the scarce specificity and sensitivity of the available methods and due to the fact that increased polyamine concentrations were also found in physiological conditions and in the presence of non-tumour diseases; however, it is now being examined whether it would be possible to use polyamine levels to assess the degree of biochemical tumour malignancy or to evaluate the response to surgical or pharmacological treatment in patients with malignant tumours.

Carcinoma↗
PubMed1993

Determination of lipid hydroperoxides in native low-density lipoprotein by a chemiluminescent flow-injection assay.

Lipid hydroperoxides have been implicated in the pathogenesis of atherosclerosis. This work was therefore set up to obtain a fast and specific chemiluminescent assay for measuring hydroperoxides in native low-density lipoprotein (LDL). The apparatus was a complete HPLC system including two pumps, an autosampler, a computer and a chemiluminescent detector with a T-mixing coil in the place of the column. Samples were injected from the autosampler and mixed with luminescent reagent (3 microM luminol and 1 microM microperoxidase in 0.1 M carbonate buffer (pH 10)) in the T-piece. To generate a calibration curve, linoleic acid hydroperoxide was obtained by incubating soybean lipoxygenase with linoleic acid. The calculated conjugated diene concentration was in good agreement with the nominal linoleic acid hydroperoxide concentration. The chemiluminescence was linear with the amount of linoleic acid hydroperoxide injected and the detection limit was about 3 pmol linoleic acid hydroperoxide. The chemiluminescence induced by copper-oxidized LDL was linear with concentration; the detection limit, when compared with linoleic acid hydroperoxide, was similar. The reproducibility of the linoleic acid hydroperoxide and of oxidized LDL hydroperoxide was examined in single pools. The coefficient of variation on the triplicates of each pool was about 3%. The titre of the linoleic acid hydroperoxide and oxidized LDL peroxides was quite stable for at least 10 days when stored under argon at 4 degrees C in the presence of EDTA. The mean value of the LDL hydroperoxides in 16 control subjects was 145.20 +/- 98.81 pmol/mg LDL protein. In conclusion, the microperoxidase-luminol-dependent chemiluminescence flow-injection assay is a rapid, sensitive and selective method for measuring lipid hydroperoxides in native LDL.

Chromatography, High Pressure Liquid↗
PubMed1993

Steady-state kinetics of ubiquinol-cytochrome c reductase in Saccharomyces cerevisiae mitochondria: effects of fluidity changes obtained by different growth temperatures.

We have investigated the steady-state kinetics of ubiquinol-cytochrome c reductase using either ubiquinol-1 or -2 as the donor substrate in mitochondria from Saccharomyces cerevisiae either grown at 36 degrees C or brought from 36 to 10 degrees C at the end of the exponential phase ("thermal shock"). The fatty acid composition of the mitochondrial lipids varied under the two conditions, with an increase of the unsaturation degree in the thermally shocked cells. The fluorescence polarization of the membrane probe diphenylhexatriene incorporated into mitochondria was decreased in a wide temperature range in the thermally shocked cells, in accordance with the fatty acid changes. Also the motion and order parameters of two fatty acid spin labels revealed significant changes in the thermally shocked cells, interpreted as an increase of membrane fluidity brought about by the thermal shock. This increase agrees with the finding that the diffusion coefficient of the ubiquinone homolog Q3 in the membrane, investigated by collisional fluorescence quenching of the membrane probe 12-(9-anthroyl) stearic acid, was consistently increased in the mitochondria from the thermally shocked cells. In spite of the physical changes of the membrane and the increase in the diffusion coefficients of the ubiquinone homolog, the steady-state kinetics of ubiquinol cytochrome c reductase showed no change to be interpreted in terms of a diffusion-limited component. An increase of Vmax of the enzyme in the thermally shocked cells was the result of an increased content of the bc1 complex; both the Km for ubiquinols and the turnover number were almost identical under the two growth conditions, so that the kcat/Km ratio, which approaches the second-order rate constant of substrate interaction with the enzyme active site, was unmodified. This is a demonstration that the ubiquinol cytochrome c reductase activity in S. cerevisiae mitochondria is not diffusion-controlled in the interaction of the donor substrate with the enzymatic protein.

Cytochromes↗
PubMed1993

Predisposition to LDL oxidation in patients with and without angiographically established coronary artery disease.

Oxidative modification of low density lipoprotein (LDL) may play an important role in the mechanism of atherosclerotic damage to blood vessels. In the present study the LDL isolated from the plasmas of 73 coronary artery disease (CAD) patients, 28 valvular heart disease (VHD) patients, 59 subjects affected by type IIa hyperlipoproteinemia and 71 controls was oxidatively modified by incubation with copper ions. In 15 CAD and 15 Type IIa patients and 15 controls the LDL chemical composition and polyunsaturated fatty acid (PUFA) content were also measured. Differences in the LDL susceptibilities to lipid peroxidation were studied by measuring the changes of fluorescence intensity. The lag phase in the CAD patients was found to be significantly lower than in the VHD and controls (P < 0.001). The lag phase in the type IIa patients was significantly higher than in the CAD patients (P < 0.01), and significantly lower than the VHD and controls (P < 0.01). The LDL isolated from the type IIa patients had an increase in the relative content of free and esterified cholesterol (P < 0.05), while the CAD patients had a decrease in the relative content of free cholesterol (P < 0.05), and an increase in the relative content of protein (P < 0.05). The lowest value of the LDL cholesterol to protein ratio and LDL size, was found in the CAD patients (P < 0.05). When expressed in micrograms/mg LDL cholesterol, the concentration of the LDL PUFAs was significantly higher in the CAD group than in the others (P < 0.05). The LDL alpha-tocopherol concentration was quite similar in the different groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

High-density lipoprotein cholesterol concentrations and postheparin hepatic and lipoprotein lipases in obesity: relationships with plasma insulin levels.

The concentration of high-density lipoprotein (HDL) cholesterol in patients with severe obesity is generally subnormal. The exact mechanism linking obesity with reduced levels of HDL cholesterol remains unclear. In this study we evaluated the postheparin plasma lipolytic enzymes lipoprotein lipoprotein lipase (LPL) and hepatic lipase (HL) in a group of 24 obese women compared with controls and analyzed the interrelationships between insulin, postheparin lipolytic enzymes and HDL subfractions. Total HDL cholesterol was significantly lower in the obese subjects than in the controls, and the difference was mainly due to HDL2 cholesterol concentrations. Mean fasting glucose, insulin and the summated means of glucose (sigma glucose) after the oral glucose tolerance test (OGTT) were not significantly different in the two groups. The summated means of insulin (sigma IRI) after the OGTT were significantly higher in the obese women than in the controls. LPL, HL and the HL-to-LPL ratio were significantly higher in the obese women than in the controls. HL and LPL correlated positively with sigma glucose, sigma IRI and body mass index (BMI) and negatively with plasma triglycerides. Partial correlation analysis demonstrated that, when exposed to similar sigma IRI values, HL and LPL were no longer correlated with sigma glucose, plasma triglycerides and BMI. HDL2 cholesterol levels were negatively correlated with HL, posthepatic plasma lipolytic activity, sigma glucose, plasma triglycerides and BMI. HDL2 cholesterol concentrations were directly correlated with LPL. Partial correlation analysis showed that when exposed to similar HL and LPL values, HDL2 cholesterol values were no longer correlated with sigma glucose, sigma IRI, plasma triglycerides and BMI. Therefore, our results demonstrate that the low HDL2 cholesterol levels found in obese women may be related to the high levels of HL and to the high HL-to-LPL ratio which in turn could be determined by the peripheral insulin resistance.

Adult↗
PubMed1992

Prevalence of hepatitis C virus antibodies and hepatitis C virus-RNA in an urban population.

Several studies had been carried out on anti-hepatitis C virus (HCV) prevalence in populations with blood exposure risks and in blood donors. New tests are now available which allow the investigation to extend to other parameters such as antibody type and HCV-RNA. In this study the prevalence of anti-HCV c100-3 and the associated epidemiological, clinical, and virological markers were evaluated in subjects from an urban population located in central Italy. In positive cases the time persistence of HCV-RNA and anti-HCV antibody pattern was studied. For this purpose, sera from 1,484 randomly sampled individuals, aged 30-69 years, collected in 1985 and stored at -80 degrees C were retrospectively tested. The prevalence was 0.87% (i.e., 13 anti-HCV c100-3 positive cases). A significant association was observed with raised alanine transaminase (ALT) levels (P less than 0.001). Paired serum samples from 11 out of the 13 subjects collected in 1985 and 1991 were tested by nested polymerase chain reaction (PCR) using primers from the 5' non-coding region and by 4-RIBA. Concordant RIBA patterns between 1985 and 1991 were observed in the majority of positive paired sera (7/9) as well as for HCV-RNA (6/9). HCV-RNA was present in sera simultaneously positive to both types of antibody or to anti-c100-3 or anti-c22 alone. A wide spectrum of viral and antibody patterns in anti-HCV c100-3 positive sera was observed in this urban population and persisted for at least 6 years.

Adult↗
PubMed1992

Risk factors for late posttraumatic epilepsy.

The usually accepted risk factors for late post-traumatic seizures (LPTS) are those identified years ago by Jennet: early post-traumatic seizure (EPTS), depressed fracture, intracranial haematoma. Prolonged unconsciousness (PTA greater than 24 hrs) is another factor usually added. More recently, personal experience of the Authors and the data of the literature, compel us to question the validity of known risk factors based on clinical data. Authors believe that the identification of patients at risk for LPTS depends mainly on the precise definition of trauma severity and on CT or surgically documented lesions of brain substance. Three groups of patients, characterized by the presence of one or more of the accepted risk factors of LPTS, have been studied. In our experience, while in adults the presence of documented cortico-subcortical lesions represents the main risk factor of LPTS, in children the appearance of EPTS per se increases the risk of LPTS, irrespective of the presence of documented brain lesions. Alteration of consciousness without a focal lesion, even if prolonged and severe, is not a risk factor for LPTS.

Adolescent↗
PubMed1992

Primary traumatic benign midbrain haematoma in hyperextension injuries of the head.

Primary traumatic brain stem injury occurring in isolation is not universally recognized as a distinct pathological entity which may follow a head injury. We describe two patients with clinical and radiological evidence of primary posttraumatic midbrain haemorrhage occurring in isolation associated with good recoveries. It is suggested that paramedian midbrain syndromes associated with midbrain haemorrhages should be recognized as a distinct, although unusual, complication of hyperextension injury to the head which may have a benign course.

Adult↗
PubMed1992

Bidirectional transmission in the cerebrobuccal connective of Aplysia during feeding.

The neuronal activity of the cerebrobuccal connective (CBC) of Aplysia was recorded, using 2 implanted electrodes, under three conditions; 1) in the absence of feeding behaviour, 2) during appetitive feeding behaviour and 3) during consummatory feeding behaviour. Cross-correlation analysis of the recordings was then performed to subdivide spikes on the basis of their direction and speed of propagation. This revealed differences in the neuronal activity during the 3 conditions. There was little activity in the CBC when animals were not feeding. During appetitive and consummatory feeding behaviour the activity in the CBC increased. Units travelling in each direction were present, but with differential activity during the 2 behavioural patterns.

Animals↗