Biomedical subjects

A V Greco

Publications and source records attributed to A V Greco.

At least 91 records · Page 5Linked to original sources

PubMed1995

Sterol carrier protein-2 is involved in cholesterol transfer from the endoplasmic reticulum to the plasma membrane in human fibroblasts.

The cellular mechanism of cholesterol transport from the endoplasmic reticulum to the plasma membrane is currently unknown. To assess the possibility that sterol carrier protein-2 (SCP-2) is involved in this transport, we studied the time course of newly synthesized cholesterol incorporation in the plasma membrane of normal and SCP-2-deficient (Zellweger syndrome) human fibroblasts. Cholesterol transfer was rapid, cytoskeleton-independent, and Golgi-independent in normal cells, but it was slower, cytoskeleton-dependent, and Golgi-dependent in SCP-2-deficient cells. After SCP-2 antisense oligonucleotides treatment of normal fibroblasts, the rapid transport was reduced by 81% with a simultaneous increase of the slower one. These results suggest that in normal fibroblasts the major fraction of newly synthesized cholesterol is transported to the plasma membrane by a SCP-2-dependent mechanism. In contrast, in SCP-2-deficient cells, newly synthesized cholesterol leaves the endoplasmic reticulum by a cytoskeleton/Golgi-dependent mechanism.

Base Sequence↗

PubMed1995

Free fatty acid analysis in ascitic fluid improves diagnosis in malignant abdominal tumors.

The fasting concentration of free fatty acids (FFA) in the ascitic fluid was determined in 14 patients with malignant ascites and in 19 patients with liver cirrhosis. In malignant ascites FFA levels were increased more than three times when compared with the levels in cirrhotic ascites (5.241 +/- 0.493 vs. 1.558 +/- 0.170 mumol/ml; P < 0.0001). Palmitic acid was the most representative saturated FFA (which together accounted for 2.499 +/- 0.323 vs. 0.833 +/- 0.064 mumol/ml; P < 0.0001), while unsaturated FFA (2.741 +/- 0.298 vs. 0.725 +/- 0.111 mumol/ml; P < 0.001) were represented, in decreasing order, by oleic, linoleic and arachidonic acids. The ratio of unsaturated to saturated FFA was higher in neoplastic patients (1.35 +/- 0.29 vs. 0.826 +/- 0.065 P < 0.05). Albumin concentration in ascitic fluid of neoplastic patients was 22.44 +/- 1.35 g/l, while that of cirrhotic patients was 8.19 +/- 0.32 g/l, P < 0.0001. A close relationship (R2 = 95.14%) between albumin concentration in ascitic fluid and levels of total FFA was found. These data support the hypothesis that the elevation of FFA in ascitic fluid allows discrimination between malignant and non-malignant ascites.

Adult↗

PubMed1995

Effects of dexfenfluramine on free fatty acid turnover and oxidation in obese patients with type 2 diabetes mellitus.

To test the potential effects of dexfenfluramine (dF) on enhancing free fatty acid (FFA) turnover and oxidation rates, 11 obese female non-insulin-dependent diabetes mellitus (NIDDM) outpatients (age, 52.5 +/- 1.5 years; weight, 81.3 +/- 3.2 kg; height, 158 +/- 3.04 cm; body mass index, 32.4 +/- 0.7 kg/m2) received a primed-constant infusion of 1-14C-palmitate. The waist to hip ratio (WHR) was 0.91 +/- 0.04. Fat body mass and lean body mass, assessed by dual-energy x-ray densitometry, were 32.0 +/- 1.5 and 49.30 +/- 2.67 kg, respectively. All patients had an average hemoglobin A1 of 6.3% +/- 0.3% in the month preceding the study and had not received oral hypoglycemic agents. Gas exchange was measured both basally and during a ventilated-hood system, indirect-calorimetry session. The protocol was a randomized, placebo-controlled, single-blind design. Subjects received dF 30 mg acutely (n = 6) or a placebo (n = 5). A dose of dF 15 mg twice daily or placebo was then administered over 15 days (chronic). To obtain serum peak level of the drug, dF was administered 2 hours before starting palmitate infusion. A free diet was allowed throughout the study, and the group treated with dF lost approximately 0.5 kg body weight. Acute and chronic dF administration resulted in a significant increase in FFA oxidation, expressed as a percentage of the dose of radiocarbon (respectively, 11.47% +/- 0.46% v 9.50% +/- 0.46% [P < .01] and 12.06% +/- 0.71% v 9.88% +/- 0.62% [P < .01]). FFA turnover rate was higher after both acute and chronic dF administration (respectively, 10.71 +/- 2.18 v 7.79 +/- 1.48 mumol/kg/min [P < .05] and 11.92 +/- 2.74 v 8.43 +/- 1.86 mumol/kg/min [P < .05]). Serum FFA concentration during both acute and chronic dF administration increased, but not significantly. Mean serum glucose level decreased after acute dF from 114.3 +/- 8.6 to 86.5 +/- 5.1 mg/dL (P < .001) and after chronic dF from 120.3 +/- 7.3 to 89.8 +/- 5.8 mg/dL (P < .001). Serum insulin was not affected by dF administration. In conclusion, oral acute and chronic dF administration increase FFA turnover and oxidation rates in NIDDM obese patients. This may play an important role in weight reduction. In addition, dF shows a weight-independent effect on glucose metabolism, reducing serum glucose levels without acting on insulin secretion.

Diabetes Mellitus, Type 2↗

PubMed1995

Effect of intensive treatment on diabetic nephropathy in patients with type I diabetes.

We evaluated the long-term effect of an intensive treatment of diabetic nephropathy (anti-hypertensive drugs, low protein diet, multiple insulin injections to achieve a good metabolic control) on glomerular filtration rate (GFR) and albumin excretion rate (AER). Fourteen type I diabetic patients (mean age 45 +/- 9.5 years, mean duration of diabetes 23.5 +/- 7.3 years, 8 males/6 females) with glomerular filtration rate < 70 ml/min-1/1.73 m2 and albumin excretion rate > 30 micrograms/min were treated intensively for 36 months. This intensive treatment consisted of multiple insulin injections, antihypertensive therapy with ACE inhibitors and a low-protein diet (0.8 g/kg body wt/day.) Renal function was evaluated as GFR and AER. HbA1c mean value decreased significantly from 8.7 +/- 0.8% to 6.5 +/- 0.5% (P < 0.0002). GFR rose from 58 +/- 12 ml/min-1/1.73 m2 to 84 +/- 11 ml/min-1/1.73 m2 (P < 0.0008). AER decreased from 208 micrograms/min (range: 73 to 500) to 63.8 micrograms/min (range 15 to 180; P < 0.05). Systolic and diastolic blood pressure decreased respectively from 144 +/- 26 mm Hg to 120 +/- 15 mm Hg and from 89 +/- 9 mm Hg to 75 +/- 8 mm Hg (P < 0.01). We obtained a rise of GFR and a reduction of proteinuria after three years of this treatment. We suggest that this intensive treatment in all patients with early stage diabetic nephropathy may be effective in slowing the progression to renal failure.

Adult↗

PubMed1995

Daily energy metabolism in patients with type 1 diabetes mellitus.

OBJECTIVE: We evaluated the daily energy balance and main substrate utilization in Type 1 insulin dependent diabetic patients and healthy volunteers. METHODS: Ten patients with Type 1 diabetes mellitus and eight healthy volunteers were studied. Diabetic patients were well controlled under intensive insulin treatment (0.6 UI/kg body weight, HbA1c = 5.5 +/- 0.7%). During the 30 hours each subject spent in the respiration chamber VO2, VCO2, respiratory quotient, daily energy intake, 24-hour, day-time, night-time and basal energy expenditure as well as energy expenditure during exercise (at 40% maximal exercise capacity), main substrate oxidation (carbohydrates, lipids and proteins) and overall diet-induced thermogenesis, were measured. The results were corrected for 24-hour urinary nitrogen loss. RESULTS: Diet-induced thermogenesis, expressed as percent of energy intake, was found to be significantly lower in diabetic patients than in control subjects (6.69 +/- 1.29% vs 11.8 +/- 4.71% of energy intake, p < 0.05). A negative correlation was found between diet-induced thermogenesis and daily average glycemia for diabetic patients (r = -0.65, p < 0.01). Energy expenditure during exercise, calculated in terms of net work efficiency, was not different between the two groups. CONCLUSIONS: In conclusion, since diet-induced thermogenesis is highly correlated with the theoretical cost of glucose storage and since no difference was found in carbohydrate oxidation, glucose storage in diabetic patients is probably reduced when hyperglycemia occurs. Diabetic patients in good metabolic control are able to perform mild exercise with a work efficiency very similar to that of control subjects.

Adult↗

PubMed1995

Biliary aminopeptidase-N and the cholesterol crystallisation defect in cholelithiasis.

Several biliary proteins have cholesterol crystallisation promoting activity. One of these glycoproteins is aminopeptidase-N, a canalicular ectoenzyme. This study attempted to localise aminopeptidase-N along the biliary tree, to assess its concentration in a series of 98 patients subjected to abdominal surgery, 40 of them without gall stones, and to correlate its concentration with cholesterol crystal formation time of gall bladder bile. Aminopeptidase-N was isolated from purified native biliary vesicles. A specific polyclonal rabbit anti-aminopeptidase-N antibody was prepared for quantitative immunoblotting and for immunolocalisation. Tissue was obtained from liver biopsy specimens and from gall bladders removed at surgery because of gall stone disease. Aminopeptidase-N was immunolocalised to the apical membranes of hepatocytes and to the apical pole of ductular and gall bladder mucosal cells. The nucleation time of gall bladder bile was mean (SD) 4 (3) days in the gall stone group, compared with 21 (18) days in the control group (p < 0.001). Total absolute biliary protein and aminopeptidase-N concentrations were similar in both the control and gall stone patients. There was a reciprocal significant correlation, however, between the nucleation time and the relative aminopeptidase-N concentration (r = -0.35, p < 0.01) only in the gall stone group of patients. This study shows that this apical transmembrane ectoenzyme with cholesterol crystallisation promoting activity is present along the biliary tree and the hepatocyte. These findings support the concept that high concentrations or qualitative changes of biliary aminopeptidase-N contribute to cholesterol gall stone formation.

Adult↗

PubMed1994

Presence and further development of retinal dysfunction after 3-year follow up in IDDM patients without angiographically documented vasculopathy.

Abnormalities in neuroretinal function may play a role in the development of diabetic retinopathy. The natural course of diabetic retinal dysfunction in a group of subjects with insulin-dependent diabetes mellitus and with no apparent microvascular alterations in the retina was followed-up with fluorescein angiography and a sensitive electrophysiological technique, i.e., steady-state focal electroretinogram at the macula, for 3 years. Before the beginning and throughout our study, strict glycaemic control was maintained by three or four daily insulin injections under careful monitoring. Analysis of macular electroretinogram provided information from different neural layers. At the first examination, functional activities of postreceptoral neurons were significantly decreased with respect to those of age-matched control subjects. Diabetic patients showed a functional loss of both ganglion cell (0.53 +/- 0.09 vs 0.42 +/- 0.11 microV; t = 5; p = 0.0001) and preganglion cell (0.51 +/- 0.13 vs 0.42 +/- 0.14 microV; t = 2.8; p = 0.007) layers. Diabetes did not alter photoreceptor activity. After 3 years, dysfunction was significantly greater in the preganglion cell layer (0.28 +/- 0.11 microV; t = 6.3; p = 0.0001). Although in some patients further impairment of ganglion cell function was shown, no significant difference was found in 3 years. Photoreceptor function remained unaltered. No vascular abnormalities in the retina were noted after 3 years in this group of patients. Metabolic control was not correlated to functional changes. Our findings suggest that the middle retinal layer is the most sensitive physiological locus of progressive diabetes-induced dysfunction in the absence of angiographically documented abnormalities.

Adolescent↗

PubMed1994

Early selective neuroretinal disorder in prepubertal type 1 (insulin-dependent) diabetic children without microvascular abnormalities.

The duration of diabetes before puberty is not considered relevant to the future development of complications. To evaluate the effects of diabetes on the neural retina, we analysed macular function by steady-state focal electroretinography in 20 prepubescent diabetic children without vascular retinopathy and in 39 sex- and age-matched normal children. The mean (+/- SD) response related to retinal cellular elements between the photoreceptors and ganglion cells was significantly lower in diabetic children than in the control group (0.38 +/- 0.12 vs. 0.51 +/- 0.13 microV; unpaired t-test = 3; P = 0.005). Similarly, ganglion cell function showed a significant impairment in diabetic children with respect to the control group (0.4 +/- 0.13 vs. 0.53 +/- 0.09 microV; unpaired t-test = 5.4; P = 0.0001), whereas the photoreceptors appeared unaffected. Metabolic control and disease duration were not correlated with functional deficits. Our results suggest that before puberty, early diabetes may have a selective effect on the neural retina prior to the appearance of microvascular changes. A focal electroretinogram could identify diabetic children with neurosensory disorders who may have a higher risk of developing microvascular retinopathy.

Age of Onset↗

PubMed1994

PC-based differential model fitting as a support for clinical research.

A PC-based minimisation software written in C-language is described, which solves numerically both simple non-linear regression problems and problems expressed as systems of (unsolved) initial-value ordinary or partial differential equations. The software uses second-order iterated Runge-Kutta algorithm to approximate numerically the solution curves. It uses a quasi-Newton algorithm to minimize either sums of squares (weighted or unweighted) or NONMEM loss functions. Inverse Hessian approximation to the parameter dispersion and Monte Carlo generation of artificial samples are offered to test the robustness of the parameter values obtained. A real test problem is described, involving the hydrolysation of plasma Medium Chain Triglycerides to Free Fatty Acids and the uptake of these from plasma. Two competing models were evaluated, one involving linear terms for each transfer and one involving carrier-mediated, rate-limited hydrolysis and tissue absorption steps. The simpler linear model was found to be more robust and eventually used to describe the experimental data.

Algorithms↗

PubMed1994

Protective role of biliary cholesterol and phospholipid lamellae against bile acid-induced cell damage.

BACKGROUND/AIMS: Bile salts (BS) are cytotoxic agents, but cell damage is not observed in the hepatobiliary system. We hypothesized that biliary lipid vesicles (unilamellae and multilamellae) could have a protective role against BS-induced cytotoxicity. METHODS: Biliary lipid lamellar secretion was induced by feeding rats with 0.5% diosgenin. Cytoprotection was assessed in bile duct-obstructed rats and by incubating human erythrocytes with sodium taurocholate. RESULTS: Biliary cholesterol concentration increased > 300% in diosgenin-fed rats; electron microscopic examination showed a great abundance of lipid lamellar vesicles in bile and within the canaliculi. After bile duct obstruction, serum hepatic enzyme activities were significantly lower in diosgenin-fed rats. Histologically severe and confluent hepatocellular necrosis was only observed in control rats. Biliary lamellar lipid material significantly reduced the BS-induced hemolytic effect in vitro in a concentration-dependent manner. This protective effect correlated to a progressive decrease in the intermicellar BS concentration. Phosphatidylcholine or cholesterol, alone or as lamellar structures, also showed cytoprotective effect in vitro but always less than native biliary lamellae. CONCLUSIONS: These results support the concept that native biliary cholesterol phospholipid lamellae represent an important cytoprotective factor for hepatocytes and biliary epithelial cells against BS-induced damage.

Animals↗

PubMed1994

Glucose-induced thermogenesis in postobese women who have undergone biliopancreatic diversion.

We evaluated the metabolic response to a standard (75-g) oral-glucose-tolerance test (OGTT) in eight post-obese women (PO) who underwent biliopancreatic diversion and in eight healthy control women (C). All subjects had been weight-stable for > or = 2 y. Blood samples for glucose, insulin, C-peptide, and nonesterified free fatty acids were taken at baseline and during 180 min after the glucose load. Plasma glucose and insulin concentrations at baseline and during the OGTT were similar in the two groups, suggesting the absence of an insulin-resistant state in the PO. Continuous indirect calorimetry was performed throughout the test. Glucose-induced thermogenesis (GIT) was higher in PO than in C (8.6 +/- 2.6 vs 4.3 +/- 1.9%; P < 0.01). These data indicate that GIT and insulin-glucose metabolism are not impaired in postobese patients when a near ideal body weight is reached and maintained after weight loss; this suggests that thermogenic deficiencies and hyperinsulinemia-insulin resistance are alterations secondary to obesity.

Adult↗

PubMed1993

Serum bile acid concentrations in mild liver cirrhosis.

Fasting serum conjugated bile salt concentrations were measured in a group of 20 patients with moderate post-hepatitis cirrhosis. Twenty healthy volunteers were used as controls. The individual conjugated bile acids were analyzed by a specific and sensitive method which couples reversed-phase high-performance liquid chromatography with mass spectrometry. Significantly elevated levels of the total and individual conjugated bile acids were found in cirrhotic patients. The predominant serum bile acids were conjugates of chenodeoxycholic acid. The conjugates of lithocholic acid were also increased; in subjects with normal liver function, on the contrary, they were found only in traces.

Adult↗

PubMed1993

Cholesterol crystallization-promoting activity of aminopeptidase-N isolated from the vesicular carrier of biliary lipids.

Different hydrophobic glycoproteins are associated to native biliary vesicles, which are the major carrier of biliary cholesterol. Some of these proteins promote cholesterol crystallization, a key step in cholesterol gallstone formation. This study was specifically conducted to identify the 130 kDa biliary vesicle-associated glycoprotein and to determine its in vitro effect on the cholesterol crystal formation time. The 130 kDa vesicular glycoprotein was identified as aminopeptidase-N by amino acid sequencing and specific enzymatic assay. Polyclonal antibodies raised against aminopeptidase-N allowed us to determine its concentration in human hepatic bile, which varied from 17.3 to 57.6 micrograms/ml. Aminopeptidase-N showed a concentration-dependent cholesterol crystallization activity when it was added to supersaturated model bile at a concentration range usually found in native bile. Because of this promoting effect on in vitro cholesterol crystal formation, we suggest that biliary aminopeptidase-N may play a critical role in the pathogenesis of cholesterol gallstone disease.

Amino Acid Sequence↗

PubMed1993

Sebacic acid binding to human plasma albumin.

Sebacic (decanedioic) acid is a dicarboxylic acid proposed recently as an alternative energy substrate in total parenteral nutrition. In this paper, binding of sebacic acid to defatted human plasma albumin, also in the presence of decanoic acid, was studied by means of equilibrium dialysis. In addition, the binding of sebacic acid in human serum was investigated. Binding to defatted albumin was analysed by a model with two independent classes of sites with different affinity constants. The fitting procedure took into account some of the measurement errors that are likely to affect the equilibrium dialysis technique. We found for sebacic acid one binding site with affinity constant 3.69 x 10(4) M-1 and four to five sites with affinity constant 7.14 x 10(2) M-1. Association constants for decanoic acid are 3-4-fold larger than those of sebacic acid. Data of binding of sebacic acid in human serum suggested that only three to five of the low affinity sites are available for binding. When disodium sebacate is administered i.v. for total parenteral nutrition, a substantial fraction of sebacic anions is likely to be bound in serum.

Binding Sites↗

PubMed1993

A rapid GLC method for the direct analysis of plasma medium chain fatty acids.

A new, rapid, gas-liquid-chromatographic (GLC) method for the direct determination of plasma medium-chain fatty acids (MCFA) (from C8 to C12) which does not require derivatization procedures is described. Analysis of underivatized MCFA by GLC showed a detection limit ranging from 0.50 to 0.217 microgram depending on chain length: the longer the chain, the higher the detection limit. Compared with the HPLC and GLC methods currently described in the literature, this GLC procedure appears to be easy, adequately sensitive, accurate and well reproducible for those MCFA, like n-octanoic and n-decanoic acids, present in plasma after p.o. or i.v. MCT administration and it requires a short time (about 30 min) for complete processing.

Adult↗

PubMed1993

Evidence of plasma CoQ10-lowering effect by HMG-CoA reductase inhibitors: a double-blind, placebo-controlled study.

Inhibitors of HMG-CoA reductase are new safe and effective cholesterol-lowering agents. Elevation of alanine-amino transferase (ALT) and aspartate-amino transferase (AST) has been described in a few cases and a myopathy with elevation of creatinine kinase (CK) has been reported rarely. The inhibition of HMG-CoA reductase affects also the biosynthesis of ubiquinone (CoQ10). We studied two groups of five healthy volunteers treated with 20 mg/day of pravastatin (Squibb, Italy) or simvastatin (MSD) for a month. Then we treated 30 hypercholesterolemic patients in a double-blind controlled study with pravastatin, simvastatin (20 mg/day), or placebo for 3 months. At the beginning, and 3 months thereafter we measured plasma total cholesterol, CoQ10, ALT, AST, CK, and other parameters (urea, creatinine, uric acid, total bilirubin, gamma GT, total protein). Significant changes in the healthy volunteer group were detected for total cholesterol and CoQ10 levels, which underwent about a 40% reduction after the treatment. The same extent of reduction, compared with placebo was measured in hypercholesterolemic patients treated with pravastatin or simvastatin. Our data show that the treatment with HMG-CoA reductase inhibitors lowers both total cholesterol and CoQ10 plasma levels in normal volunteers and in hypercholesterolemic patients. CoQ10 is essential for the production of energy and also has antioxidative properties. A diminution of CoQ10 availability may be the cause of membrane alteration with consequent cellular damage.

Adult↗

PubMed1993

Urinary kallikrein excretion in type 1 (insulin-dependent) diabetes mellitus.

Kidney haemodynamics appear to change after the early phases of diabetic nephropathy: increases in glomerular filtration rate and in renal plasma flow have been widely reported, while kidney size is increased. As the renal kallikrein-kinin system has been demonstrated to regulate kidney blood circulation, we have evaluated the excretion of urinary kallikrein in 87 Type 1 (insulin-dependent) diabetic patients with and without hyperfiltration. Urinary kallikrein excretion was measured in 24-h urine collections. The esterolytic activity was determined by fluorimetric assay. The excretion of urinary kallikreins was significantly higher in hyperfiltering patients (472 +/- 125 esterase units/24 h) than in normofiltering (168 +/- 77 esterase units/24 h) and control subjects (151 +/- 39 esterase units/24 h), p < 0.001. Furthermore, we observed a positive correlation between urinary kallikrein excretion and glomerular filtration rate (r = 0.785). These data suggest that variations of kallikrein and kinin concentrations may play a role in the alteration of renal haemodynamics in Type 1 diabetes. It is possible that the kinin-kallikrein system, the renin-angiotensin system and the prostaglandins may interact to determine the haemodynamic alterations which are present in the diabetic disease.

Adult↗

PubMed1993

Hydra: a C-language environment for real-time DOS multitasking at the bedside.

Patient monitoring at the bedside is an inherently parallel job, best handled by multiple individual tasks running concurrently. Cost and diffusion considerations strongly favor the use of PC's at the bedside, but their most widespread operating system, DOS, is not built for multitasking. Hence, a software platform in C language has been prepared, allowing the intermediate programmer to easily write independent modules which will then run simultaneously without conflicts. Such a platform aims at allowing effortless sharing of data among concurrently running processes, while providing strong insulation between tasks, enough to allow multiple copies of any one task to run simultaneously unknown to each other. A cooperative, memory sharing multitasking paradigm has been chosen, which offers fine granularity of timeslicing and low execution overhead at the price of some loss in generality of design. Speed, data exchange capability and number of stackable windows are greater than with commercial packages like Windows or LabWindows. Dynamical reprioritization of tasks is built in, allowing the computerized monitor to focus its attention and resources on urgent tasks.

Algorithms↗