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Biomedical subjects

C Sirtori

Publications and source records attributed to C Sirtori.

At least 19 recordsLinked to original sources
PubMed1997

High-Power Infrared (8-Micrometer Wavelength) Superlattice Lasers

A quantum-cascade long-wavelength infrared laser based on superlattice active regions has been demonstrated. In this source, electrons injected by tunneling emit photons corresponding to the energy gap (minigap) between two superlattice conduction bands (minibands). A distinctive design feature is the high oscillator strength of the optical transition. Pulsed operation at a wavelength of about 8 micrometers with peak powers ranging from approximately 0.80 watt at 80 kelvin to 0.2 watt at 200 kelvin has been demonstrated in a superlattice with 1-nanometer-thick AlInAs barriers and 4.3-nanometer-thick GaInAs quantum wells grown by molecular beam epitaxy. These results demonstrate the potential of strongly coupled superlattices as infrared laser materials for high-power sources in which the wavelength can be tailored by design.

Journal Article↗
PubMed1997

Efficacy and safety of atorvastatin compared to pravastatin in patients with hypercholesterolemia.

Plasma cholesterol and other lipoproteins play a significant role in the development of atherosclerosis and subsequent coronary heart disease (CHD). This 1 year study was designed to confirm the efficacy and safety of atorvastatin (Lipitor) compared to pravastatin, a marketed agent for low density lipoprotein cholesterol (LDL-C) reduction in hypercholesterolemic patients. Patients were recruited at 26 centers in six European countries. After a 6 week placebo baseline phase, patients were randomized to receive atorvastatin 10 mg or pravastatin 20 mg daily. The dose could be doubled at week 16, if LDL-C levels remained > or = 3.4 mmol/l (135 mg/dl). Atorvastatin significantly lowered LDL-C from baseline by 35% compared with 23% for pravastatin (P < 0.05). A total of 72% of atorvastatin patients attained the LDL-C target level of < 3.4 mmol/l, compared to 26% of pravastatin patients. Atorvastatin also significantly reduced TC, TG and apo B (P < 0.05). Safety was assessed by recording adverse events and measuring clinical laboratory parameters. The adverse event profile was similar for both treatment groups and neither treatment caused clinically relevant laboratory abnormalities. Atorvastatin 10 and 20 mg once daily is superior to pravastatin 20 and 40 mg once daily in treating patients with hypercholesterolemia.

Anticholesteremic Agents↗
PubMed1997

Expression of neuronal kinesin heavy chain is developmentally regulated in the central nervous system of the rat.

The kinesin family of motor proteins comprises at least two isoforms of conventional kinesin encoded by different genes: ubiquitous kinesin, expressed in all cells and tissues, and neuronal kinesin, expressed exclusively in neuronal cells. In the present study, we have analyzed the expression of the two kinesin isoforms by immunochemistry at different stages of development of the rat CNS. We have found that the level of expression of neuronal kinesin is five to eight times higher in developing than in adult rat brains, whereas that of ubiquitous kinesin is only approximately 2.5 times higher in maturing versus adult brains. Moreover, we have studied the distribution of neuronal kinesin by light microscopic immunocytochemistry in the rat brain at different postnatal ages and have found this protein not only to be more highly expressed in juvenile than in adult rat brains but also to show a different pattern of distribution. In particular, tracts of axonal fibers were clearly stained at early postnatal stages of development but were markedly unlabeled in adult rat brains. Our results indicate that the expression of at least one isoform of conventional neuron-specific kinesin is up-regulated in the developing rat CNS and suggest that this protein might play an important role in microtubule-based transport during the maturation of neuronal cells in vivo.

Aging↗
PubMed1997

Effect of pivagabine on stress-induced gastric ulcer formation in rats.

In this study the efficacy of pivagabine (4-[(2,2-dimethyl-1-oxopropyl)amino]butanoic acid, CAS 69542-93-4, Tonerg) in preventing experimental stress ulcer in animals was evaluated. Twenty Wistar rats were randomly subdivided into 2 groups; one group received pivagabine (200 mg/kg orally) and the other tap water. The rats were immobilized in a cold room (2-4 degrees C) for 2 h, and the number and extension of gastric ulcerative and hemorrhagic lesions were evaluated. Pivagabine determined a significant reduction in the number of animals with gastric lesions (5 vs. 10, p < 0.05), in the linear extension of ulcers (2.0 +/- 0.8 vs. 7.2 +/- 1.7 mm, percent protection 72.2, p < 0.05) and in the linear extension of hemorrhages (2.6 +/- 1.0 vs. 10.3 +/- 1.6 mm, percent protection 74.8, p < 0.01). The protective effect of pivagabine on experimental stress-induced ulcers is likely to be mediated by the inhibition of corticotropin releasing factor release from hypothalamus, as also suggested by behavioral studies.

Animals↗
PubMed1996

Differential expression of ubiquitous and neuronal kinesin heavy chains during differentiation of human neuroblastoma and PC12 cells.

Kinesin is a microtubule-based motor protein involved in intracellular organelle transport. Neurons are characterized by the presence of at least two isoforms of conventional kinesin: ubiquitous kinesin, expressed in all cells and tissues, and neuronal kinesin, whose pattern of expression is confined to neuronal cells. In order to investigate whether the two kinesin motors, which are encoded by different genes, may play distinct biological roles in neurons, we studied their expression during neuronal differentiation. Human neuroblastoma SH-SY5Y and IMR32 cells and rat phaeochromocytoma PC12 cells were used as an in vitro system for neuronal differentiation and were induced to differentiate in the presence of retinoic acid, a combination of dibutyryl cAMP and 5-bromodeoxyuridine, and nerve growth factor respectively. The expression level of each kinesin isoform was evaluated by quantitative immunoblot before and after pharmacological treatment. We found that in all cell types the expression level of neuronal kinesin, but not of ubiquitous kinesin, is stimulated during differentiation. In particular, SH-SY5Y cells show a 4.5-fold, IMR32 cells a 3-fold and PC12 cells a 7-fold increase in the level of expression of neuronal kinesin. By Northern blot analysis we found that the selective increase in the expression of neuronal kinesin is paralleled by an increase in its mRNA, indicating that there is a transcriptional control of the expression of this kinesin isoform during differentiation of neuroblastoma and PC12 cells. Our results suggest that these cells represent an adequate model to study the function of conventional kinesin and its isoforms.

Animals↗
PubMed1988

Selective and semiselective low-density lipoprotein apheresis in familial hypercholesterolemia.

Seven patients with familial hypercholesterolemia were treated fortnightly for 3 months by selective low-density lipoprotein apheresis with dextran-sulfate cellulose column (DSC). Subsequently, 4 of them were treated with semiselective double filtration. No cholesterol-lowering drugs were given. Plasma processed ranged from 39 to 58 ml/kg body weight/procedure. Fractional removals from plasma filtrate at the secondary treatment (adsorption or fractionation) for total cholesterol, high-density lipoprotein cholesterol, and albumin, respectively, were 0.84, 0.06, and 0.03 with DSC and 0.74, 0.47 and 0.35 with double filtration. Postapheresis reductions of total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol were 57, 15, and 59% with DSC and 47,35, and 48% with double filtration. Both methods are suitable for clinical use, but with a 15-day treatment schedule, lowering circulating lipid fraction levels are maintained with DSC.

Adolescent↗
PubMed1986

Effects of fatty acid esters of cheno- and ursodeoxycholic acids on gallstone formation in hamsters.

Fatty acid esters (at the 7 position) of chenodeoxycholic (CDCA) and ursodeoxycholic (UDCA) acids have been tested for their effects on formation and dissolution of gallstones in hamsters. The free bile acids were fed at a level of 0.2% of the diet and esters were fed at equimolar levels. The earlier finding that CDCA does not affect gallstone formation in hamsters fed the Dam and Christensen diet were confirmed. The acetic, butyric and lauric acid esters of CDCA had a very slight inhibitory effect on lithogenesis but CDCA 7 oleate and linoleate completely inhibited gallstone formation. UDCA and its 7 oleate inhibited both formation and progression of gallstones. The observed effects are probably a function of the form of the bile acid and not of the esterifying acid. The observation that ethyl oleate has a slight litholytic effect suggests that the acid moiety of the ester may exert a slight influence.

Animals↗
PubMed1985

Control of human and animal platelet aggregation by a new prostacyclin analog.

The in vitro effects of ZK 36 374, a new chemically stable prostacyclin (PGI2) analog, on platelet aggregation were studied and compared to those of PGI2. Significantly lower concentrations of ZK 36 374, versus prostacyclin, were required to inhibit collagen and epinephrine-induced aggregation in human platelet-rich plasma. In contrast, in rat and rabbit platelet rich plasma, PGI2 was more effective than ZK 36 374 in inhibiting the aggregation elicited by ADP and collagen. It is concluded that ZK 36 374 is a potent antiaggregatory compound and may be useful in the prevention of cardiovascular disorders.

Adenosine Diphosphate↗
PubMed1983

[Cooking meat in microwave ovens does not cause formation of mutagenic substances].

UNLABELLED: During the cooking process of meat, mutagenic and/or carcinogenic substances can be formed that can induce tumours of the gastro-intestinal tract or of other organs in the rat. The formation of these substances is proportionate to the cooking time, the cooking surface and the quantity of fats contained in meat. A comparison is made between beef cooked on a grid where the temperature reaches 200 degrees C, and cooked in a microwave oven (Cuocorapido Candy 500 CL, frequency 2450 Mhz) where the temperature does not exceed 100 degrees C. Mutagenic substances were extracted by the Commoner technique and mutagenic activity was assayed with the Ames test. RESULTS: no mutagenic activity was demonstrated in the extracts of meat cooked in microwave ovens, while mutagenic activity was clearly demonstrated in the extracts of meat cooked on a grid.

Animals↗