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Biomedical subjects

G L Viviani

Publications and source records attributed to G L Viviani.

At least 19 recordsLinked to original sources
PubMed2006

Homocysteine, reactive oxygen species and nitric oxide in type 2 diabetes mellitus.

INTRODUCTION: Type 2 diabetes mellitus shows a characteristic altered platelet function that can be due to several mechanisms such as oxidative stress. Hyperhomocysteinemia, considered as a risk factor for various arterial thrombosis, may have a role in generating oxidative damage, even if the pathogenic mechanisms are still not clear. In this report we aimed to determine the role of plasma homocysteine in inducing oxidative stress in type 2 diabetes mellitus. MATERIALS AND METHODS: The study was performed on a group of 34 males with type 2 diabetes and 36 healthy subjects matched for sex and age. Patients and healthy subjects were undergone to laboratory evaluation for plasma homocysteine levels and other metabolic parameters. In both groups of subjects platelet reactive oxygen species, nitric oxide and guanosine 3',5' cyclic monophosphate levels were measured. Moreover the reduced glutathione content in platelets of patients and of healthy subjects was assayed. RESULTS: Plasma homocysteine levels were significantly increased in patients compared with healthy subjects. The basal level of reactive oxygen species was significantly higher in patients than in controls. In addition platelets of patients stimulated with thrombin produced more reactive oxygen species than healthy subjects ones. The nitric oxide, guanosine 3',5' cyclic monophosphate and reduced glutathione content were decreased in platelets of patients. CONCLUSIONS: As homocysteine stimulates oxidative stress and inhibits nitric oxide formation, hyperhomocysteinemia measured in type 2 diabetic patients, promoting platelet hyperactivity, could have a role in the atherogenic effects described in type 2 diabetes.

Aged↗
PubMed1999

Reduced glucose effectiveness as a feature of glucose intolerance: evidence in elderly type-2 diabetic subjects.

One of the factors determining glucose tolerance is glucose disappearance independent from the dynamic insulin (glucose effectiveness); the debate on its role in the development of Type-2 diabetes is still open. The aim of the present study was to evaluate insulin delivery, insulin sensitivity (SI), and glucose effectiveness (SG) in a group of elderly Type-2 diabetic patients (D, 4/6 F/M, age 67 +/- 2 years, 64 +/- 2 kg, BMI 23.8 +/- 0.5 kg/m2), compared to young controls (C, 4/6 F/M, 25 +/- 2 years, 72 +/- 4 kg, 23.7 +/- 1.1 kg/m2) and elderly controls (E, 2/4 F/M, 73 +/- 3 years, 63 +/- 4 kg, 23.1 +/- 0.5 kg/m2). We performed oral (OGTT) and intravenous (FSIGT) glucose tolerance tests. The OGTT showed that C and E were normotolerant, while D had a markedly reduced glucose tolerance. This was also confirmed in the FSIGT where the glucose tolerance index (KG) was 0.6 +/- 0.1% min-1 in D vs 1.8 +/- 0.2 in C and 1.5 +/- 0.2 in E (p < 0.0002). Total insulin area of D and the overall insulin delivery were not different from those of the control groups. The early phase area was instead significantly reduced (0.19 +/- 0.02 mU min/mL vs 0.61 +/- 0.06 of C and 0.46 +/- 0.06 of E, p < 0.001) given the reduction in the dynamic first-phase insulin delivery (0.86 +/- 0.17 min(microU/mL)/(mg/dL) vs 3.95 +/- 0.61 in C (p < 0.005) and 2.61 +/- 0.66 (p < 0.001) in E). SI of D was 3.4 +/- 0.4 10(-4) min-1/(microU/mL), not different from that of C (4.7 +/- 0.6) and E (3.5 +/- 0.2). This study showed a marked difference between SG of D and that of both control groups [0.010 +/- 0.001 min-1 vs 0.026 +/- 0.004 (p < 0.001) of C and 0.020 +/- 0.003 (p < 0.002) of E], mostly due to the zero-insulin component GEZI which was 0.006 +/- 0.001 in D vs 0.021 +/- 0.004 in C and 0.016 +/- 0.003 in E (p < 0.003). In the elderly groups, when taken together, SG exhibited a positive correlation with the area under insulin concentration during the early phase and with KG (r = 0.69, p = 0.0032 and r = 0.90, p = 0.0001, respectively), demonstrating the importance of the first-phase insulin delivery in modulating glucose effectiveness and glucose tolerance.

Adult↗
PubMed1996

Water distribution in insulin-dependent diabetes mellitus in various states of metabolic control.

Alterations in water compartments have been described in insulin-dependent diabetes mellitus (IDDM). Both insulin and lack of natriuretic counteracting response lead to water expansion, while hyperglycemica-induced osmotic diuresis leads to water depletion. Both total body water and water distribution in the extra-intracellular space, as well as their relationships to metabolic control, were investigated in 15 controls (30.1 +/- 1.4 years) and in 26 IDDM patients (31.3 +/- 1.6, diabetes duration 11.3 +/- 1.4 years) who were neither hypertensive nor proteinuric. The amounts of total body water (TBW) and extracellular water (ECW) were predicted by impedance measurements at 100 KHz and at 1 KHz. The amount of intracellular water (ICW) was computed as the difference between the two. Water distribution was estimated by measuring the ratio between low- and high-frequency impedance and by computing the ratio between ECW and ICW. The IDDM patients were divided into four groups on the basis of reference HbA(lc) mean and SD: A < or = mean + 2 SD < B < or = mean + 4 SD < C < or = mean +6SD < D. The groups were comparable with sodium intake, insulin dosage, fasting glycemia and laboratory hydration markers. As compared to controls, impedance values at 1, 5, 10, 50 and 100KHz were significantly lower in diabetic patients and the difference within group D increased as the frequency increased: -3.9% at 1 KHz, -10.1% at 100 KHz. As compared to controls, groups A, B and C showed higher TBW, ECW and ICW while water distribution was normal, and group D showed higher TBW and ICW but normal ECW and a different water distribution. In all IDDM patients, HbA(lc) correlated with ECW (r = -0.49) and distribution ratios (r = 0.42, impedance; r = 0.40, ECW/ICW ratio). These observations suggest that good or moderate long-term control IDDM patients have proportionately normal distributions of ECW and ICW excess. However, water excess in poor control IDDM patients was only found in the ICW space.

Adult↗
PubMed1995

An instrument for real-time spectral estimation of heart rate variability signals.

A Digital Signal Processor (DSP)-based instrument is proposed for estimating and displaying the Heart Rate Variability (HRV) spectrum in real-time. It consists of an intelligent module which is properly interfaced to an IBM PC and whose operations are independent from the computer's other tasks. In this way, the simultaneous recording of the ECG sequence, needed for the more complete off-line analysis, can be performed by the same host. The employed hybrid spectral estimator (in which a classical FFT analysis follows the autoregressive extrapolation of data) appears to be the most apt for the present fixed point arithmetics implementation. The reliability of the instrument and its accuracy are checked both with suitable test signals and by comparison with the results obtained through off-line analysis of the same ECG tracks. The instrument is presently used for cardiovascular investigations, in particular for quickly picking patients with cardiac autonomic neuropathy (CAN) out of a population of diabetic subjects.

Adult↗
PubMed1993

Impairment of central motor conduction in diabetic patients.

In 70 patients with diabetes mellitus (DM) we recorded the motor evoked potentials (MEPs) following magnetic stimulation of the motor cortex and spinal roots. Central motor conduction time (CMCT) was determined as the difference between MEP latencies after cortical and spinal stimulation. The mean CMCTs for the biceps, thenar and tibialis anterior muscles were prolonged in the DM group, as compared to normal controls, and 21 patients exceeded the CMCT upper confidence limit for at least one muscle. CMCT changes and peripheral conduction velocity abnormalities occurred independently and were related to different clinical parameters. We conclude that a subclinical impairment of central motor conduction is present in 30% of DM patients, independently from the occurrence of a diabetic peripheral neuropathy and possibly reflecting different pathophysiological mechanisms.

Adult↗
PubMed1992

Isolation of pig pancreatic islets by a new method with hydraulic shaking: preliminary report.

The limited availability of human pancreas represents a serious problem in islet transplantation. In the past few years many efforts have been made to isolate pancreatic islets from large mammals in order to achieve valid and reproducible isolation methods. For several reasons swine may be considered an ideal source of islet tissue because of the similarity between human and porcine insulin and because of the easy availability of pig pancreata. Some papers have been published recently on this topic with good results. However, some problems, such as islet dissociation into single cells after collagenase digestion, are not completely solved. In this article, an automated method involving a hydraulic shaking system is described for islet isolation from the pig pancreas, developed in our laboratory and derived from Ricordi's model.

Animals↗
PubMed1992

Comparison of the effects of carvedilol and nifedipine in patients with essential hypertension and non-insulin-dependent diabetes mellitus.

The safety and tolerability of carvedilol, a new antihypertensive agent with the combined pharmacological activities of beta-blockade and vasodilation, and of nifedipine were investigated in patients with essential hypertension and non-insulin-dependent (type II) diabetes mellitus. Twenty patients were openly randomized to receive 25 mg carvedilol once daily (five men and five women; mean age, 63 years) or 10 mg nifedipine t.i.d. (three men and seven women; mean age, 64 years) for a period of 4 weeks. Baseline mean sitting blood pressures were 168/98 and 169/95 mm Hg in the carvedilol and nifedipine groups, respectively. Baseline mean areas under the curve (AUC) of the intravenous glucose tolerance test (IVGTT) for the carvedilol and nifedipine groups were 6,136 +/- 1,195 and 6,287 +/- 1,228 mg/dl/min, respectively. Demographic and efficacy variables were not statistically different between treatment groups. After 4 weeks of therapy, mean sitting blood pressure was significantly (p less than 0.02) reduced to 144/91 mm Hg in the carvedilol group and to 149/87 mm Hg in the nifedipine group. Week 4 IVGTT AUC values of 5,735 +/- 1,464 mg/dl/min in the carvedilol group and 5,988 +/- 993 mg/dl/min in the nifedipine group, representing mean reductions of 6.14% and 3.17%, respectively, were not statistically different from baseline. Both treatments were well tolerated. No patient experienced adverse events in the carvedilol treatment group, whereas two patients in the nifedipine group reported episodes of headache (one patient) and palpitations (one patient); each episode was mild in severity and considered to be related to study medication.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1986

[Left ventricular diastolic function in type I diabetes. A longitudinal echocardiographic study].

The present study was performed to assess the extent of left ventricular diastolic abnormalities and their possible progression with time in patients with type I (insulin dependent) diabetes. Two echocardiographic examinations were performed at an interval of 5 years in 18 study patients. Left ventricular diastolic function was assessed by computer digitized analysis of the M-mode echocardiographic tracings. During the study period all patients remained in satisfactory metabolic control and without retinopathy. Twelve normal subjects, matched for age and sex, were used as control group. Peak rate of left ventricular posterior wall excursion and the peak rate of increase in left ventricular internal dimensions were significantly reduced in patients with diabetes (14.12 +/- 2.5; 16.48 +/- 3.9 cm/sec) compared with controls (17.25 +/- 2.8; 20.41 +/- 3.6 cm/sec) (p less than .005; p less than .01). In addition time to peak rate of increase in left ventricular internal dimensions, isovolumic relaxation index and isovolumic relaxation time were significantly prolonged in patients with diabetes (63.66 +/- 16.5; 23.9 +/- 9; 72.7 +/- 14 msec) compared to controls (46.83 +/- 9.8; 13.4 +/- 4; 61.1 +/- 12 msec) (p less than .005; p less than .001; p less than .05). In the study patients, no relation was found between the extent of diastolic abnormalities and age, duration of the disease and insulin dosage. The extent of left ventricular diastolic dysfunction did not show significant changes during follow-up. Our results indicate that diastolic abnormalities are common in patients with type I diabetes and are not related to the duration of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes Mellitus, Type 1↗
PubMed1984

Effect of nicotinic acid associated with retinol and tocopherols on plasma lipids in hyperlipoproteinaemic patients.

Twelve hypercholesterolaemic patients, with or without hypertriglyceridaemia, were treated sequentially with 600 mg nicotinic acid alone per day and 300 mg nicotinic acid plus 60,000 U retinol and 140 mg tocopherols per day, each treatment being given for 30 days in random order sequence. Plasma concentrations of lipid fractions were determined before the start of the study and at the end of each treatment period. Both treatments resulted in a significant decrease in total cholesterol and LDL-cholesterol; HDL-cholesterol showed a small but significant increase and plasma triglycerides presented a variable behaviour pattern of change. The difference between the hypolipidaemic effects of nicotinic acid alone and the lower dose given with Vitamins A and E was small but the combination seemed to be more effective. No side-effects were reported with either treatment.

Cholesterol, HDL↗