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Biomedical subjects

G Abbiati

Publications and source records attributed to G Abbiati.

At least 19 recordsLinked to original sources
PubMed2001

Asymmetric synthesis of 2-amino-3-hydroxynorbornene-2-carboxylic acid derivatives.

The enantioselective synthesis of 2-amino-3-hydroxynorbornene-2-carboxylic acid derivatives (5) was studied using the Diels-Alder reaction between cyclopentadiene and different dienophiles, i.e., alkyl 5-oxo-2-phenyloxazol-4-methylenecarbonates (1) or 2-benzoylamino-3-alkoxycarbonyloxy-acrylates (12), operating with different Lewis acids and both with thermal and with ultrasound conditions. The enantioselective synthesis of the exo/endo compounds 5c,d and 5'c,d was achieved starting from the chiral menthyl acrylates 12b,c using Mg(ClO(4))(2) as the catalyst and ultrasound. The cycloadducts were obtained in very good yield, in mild conditions, in short time, and in good diastereomeric excess (exo, 80%; endo, 87%). Finally, the use of alkylidene-oxazolones or acrylates and EtAlCl(2) or Mg(ClO(4))(2) as the catalyst allowed control of the cycloaddition reaction in favor of the exo or endo products.

Journal Article↗
PubMed2001

Absorption of calcium administered alone or in fixed combination with vitamin D to healthy volunteers.

Calcium supplementation is widely used in deficiency status and as an adjuvant in the treatment of osteoporosis. As usual with endogenous substances, the calcium absorption, distribution and elimination processes are strictly controlled by homeostatic equilibria. Free calcium ion is the most representative active fraction of the circulating ion. Ion excretion is controlled by a saturable tubular reabsorption process which leads to a renal threshold. Cumulative urinary excretion of calcium is the end-point of absorption, distribution and elimination processes, and is thus a good indicator of bioavailability. In order to increase the oral bioavailability of calcium, the ion is administered in association with vitamin D, which is known to enhance intestinal calcium absorption. The aim of this study was to evaluate the absorption of calcium administered alone and in fixed combination with cholecalciferol (vitamin D3, CAS 67-97-0). In accordance with the study protocol, calcium carbonate (CAS 471-34-1; 1500 mg = 600 mg as calcium ion) was administered as such (reference) and associated with cholecalciferol (400 IU) (test) for four days (2 doses/day) to 18 healthy male volunteers in a sequential pattern, namely reference followed by test. Urinary excretion of total calcium, and serum concentration of free and total calcium, 25-OH-vitamin D3 and parathyroid hormone were carefully analysed the day before (baseline) and on the 4th day of dosing, with validated methods. The effect of cholecalciferol in promoting calcium absorption was clearly observed from urinary excretion of total calcium, which with the test treatment showed a 16.6% increase in excretion (p = 0.025) compared with the reference treatment. The mean excretion values on the 4th day, expressed in mg, were 238.85 and 204.83 with test and reference respectively. Moreover, the results demonstrated an increased serum concentration of both free and total calcium after dosing with test and reference by comparison with the baseline situation. The area under the serum concentration-time curve of total calcium increased from day -1 to day 4 from 550.98 to 575.90 mg l-1 h with test and from 543.03 to 568.16 mg l-1 h with reference. Similarly, ionised calcium increased on day 4 with both the treatments. Parathyroid hormone showed the expected typical decreasing behaviour after dosing with the test and reference drugs. The results of this study suggest that calcium carbonate is absorbed through the intestine when administered either alone or in association with cholecalciferol. Cholecalciferol, however, showed the typical expected activity in promoting calcium absorption, which was evident from the cumulative urinary excretion of the ion. To the authors' knowledge, this study is the first published paper demonstrating the absorption and pharmacodynamic effect of short-term administration of vitamin D associated with calcium at the doses recommended for supplementation in a fixed-combination pharmaceutical product.

Adolescent↗
PubMed1999

A new prosthesis for the metacarpophalangeal joint. Study of materials and biomechanics.

This report discusses the Daphne prosthesis for the metacarpophalangeal joint on the basis of the mechanical, chemical and biological performance of the materials employed. The Daphne prosthesis is a mobile device. The main body is made of a new generation polymethylmetacrylate, while the hinge is made of AISI 316 L stainless steel. Biocompatibility tests were performed on the materials employed. Systemic toxicity, cytotoxicity and contact tests have given favourable results. Mechanical engineering tests have been used to investigate the performances and reliability of the selected materials. The polymethylmetacrylate used in Daphne behaves in a ductile fashion. No mechanical failures were encountered in fatigue tests after 10 million cycles.

Animals↗
PubMed1999

Natural surfactant supplementation in ARDS in paediatric age.

OBJECTIVE: To evaluate the effects of natural surfactant supplementation in infants, children and adolescents affected by ARDS from different origins in order to reduce lung barotrauma due to artificial ventilation, improve gas exchange, reduce oxygen toxicity and survival. MATERIALS AND METHODS: Two groups, the first consisting of 22 children, 7 days-24 months, and the second of 8 oncohaematologic patients, 2-16 years, affected by ARDS from sepsis, inhalation syndrome and interstitial pneumonia, candidates for ECMO, were treated intratracheally with 50 mg/kg of natural surfactant. Before treatment all patients had been mechanically ventilated using PEEP levels > or = 8 cm H2O and FiO2 > or = 0.6, for at least 24 hours without any improvement in gas exchange. RESULTS: From 15 mins after surfactant administration a progressive improvement in PaO2 was noted which peaked at 3 hours. In two cases in the first group a worsening in PaO2 occurred starting from 12-18 hours, which needed additional doses. All patients in the second group needed additional doses after 12 h. No significant PaCO2 variations were noted until 24 hours. In all cases the chest X-ray improved at 4 hours and clearing was obtained starting from 24 hours in those cases where an additional dose had not been necessary. Computed Tomography confirmed the improvement in lung pathology. All the children in the first group survived except one HIV-positive child. The oncohaematologic children showed an improvement in PaO2 after each administration of surfactant even though they later died due to their initial disease, except one child. COMMENT: Surfactant efficacy in this study appears to depend on the severity of lung pathology and to be strictly connected with early treatment.

Adolescent↗
PubMed1998

Urinary markers of bone turnover in healthy children and adolescents: age-related changes and effect of puberty.

During growth, bones change their dimensions rapidly with the changes involving both formation and resorption processes. Small cross-linked peptides coming from type I collagen molecules are excreted in urine when bone is resorbed. To date, conflicting results have been presented concerning the age- and puberty-related changes of urinary markers. The purpose of the present study was to verify the effect of age, gender, and puberty on the urinary excretion of type I collagen degradation products in healthy children and adolescents. Timed spot urines from 176 children (4-20 years old) and 50 young adults were analyzed. The concentrations of N-telopeptides of type I collagen (NTx), pyridinolines (Pyr), and deoxypyridinolines (Dpyr) were measured, and the results were normalized to creatinine. Age-related changes in cross-links excretion were observed. The levels decreased with age, and a peak of excretion was shown at the beginning of adolescence. Prepubertal levels of all the markers were four- to five-fold higher than in adults, and they decreased towards adult levels in late puberty. Girls had significantly higher levels of all biochemical markers than boys at pubertal stage 2. We also observed a remarkable effect of puberty on the levels of bone degradation products that was independent of age and gender. Our results indicate that bone resorption is high in children relative to that in adults, and that urinary levels of NTx, Pyr, and Dpyr change as a function of age, gender, and puberty.

Adolescent↗
PubMed1997

Serum levels of pyridinium crosslinks in postmenopausal women and in Paget's disease of bone.

The purpose of this study was to measure pyridinium crosslinks in serum by high performance liquid chromatography (HPLC) and to correlate levels with urinary excretion in patients with different osteometabolic conditions. Blood and spot urine samples were collected between 9 and 11 A.M. in 92 early postmenopausal, untreated women (age 52.3 +/- 2.6 years, months since menopause 20.4 +/- 9.6), 17 patients with active Paget's disease (10 males, aged 65. 1 +/- 12.6) and 24 healthy premenopausal women (aged 28.4 +/- 4.2). Urinary excretion of the total fraction (free + peptide bound) of pyridinolines (Pyr, Dpyr) was measured by HPLC. Before HPLC analysis, serum samples were submitted to a clean-up procedure by ultrafiltration. In 42 postmenopausal women, bone loss was calculated from two bone mass measurements (L2-L4, DXA), performed at study entry and after 12 months. Statistical analysis was performed by Student's t test for independent samples and linear regression analysis. In pagetic patients' serum levels of Pyr and Dpyr were more than threefold increased over the mean observed in healthy controls and were closely correlated with total alkaline phosphatase levels (Pyr: r = 0.73; Dpyr: r = 0.72, P < 0.0005). Compared with controls, postmenopausal women had significantly increased levels of both urinary and serum Pyr and Dpyr (P < 0.003). In pagetic patients and postmenopausal women, crosslinks serum levels were correlated with their urinary excretion with r values ranging from 0.46 to 0.84. In postmenopausal women, only serum Dpyr correlated with the rate of bone loss (r = -0.36, P = 0.02). The data suggest that serum levels of pyridinium cross-links are correlated with urinary excretion in patients with different osteometabolic conditions. The determination of serum levels prevents limitations related to urinary specimen collection and may be a more practical method for routine application, avoiding corrections for urinary creatinine which could be misleading.

Absorptiometry, Photon↗
PubMed1995

The treatment of chronic flexion contractures of the proximal interphalangeal joint.

A method of treatment of chronic flexion contractures of the PIP joint is presented, with the results obtained in 19 patients treated between 1989 and 1992 after a follow-up of from 6 to 53 months. The flexion contractures, with an extension deficit which ranged between 70 and 90 degrees, had been present for a period of between 2 months and 24 years. Our treatment program involves the surgical release of the unreducible PIP joint followed by the use of static and/or dynamic splints. Surgery is performed using a midlateral approach; the accessory collateral ligament and the flexor sheath are incised and, after the volar plate and check-rein ligaments have been excised, forced hyperextension is applied. The main collateral ligaments are carefully spared and freed from the condyle if there are any remaining adhesions. In our 19 patients, complete extension of the finger was achieved in 11 cases (57.9%); in the remaining 8 cases (42.1%) the residual extension deficit ranges from 10 to 15 degrees. In our experience this combined surgical and rehabilitative approach had led to consistently good results with minimal complications.

Adolescent↗
PubMed1995

Urinary and synovial pyridinium crosslink concentrations in patients with rheumatoid arthritis and osteoarthritis.

OBJECTIVES: To assess urinary and synovial concentrations of hydroxypyridinium crosslinks of collagen in patients with rheumatoid arthritis (RA) and osteoarthritis (OA) and to evaluate whether a combined measurement in the two compartments could give additional information about the origin of these compounds in joint diseases. METHODS: Concentrations of hydroxypyridinoline (HP) and lysylpyridinoline (LP) were measured by high pressure liquid chromatography in urinary and synovial samples collected from 20 patients with RA and 20 patients with knee OA. Full laboratory and clinical assessments were performed. RESULTS: Urinary concentrations of both HP and LP were significantly greater in RA than in OA. Urinary HP in RA correlated with the number of swollen joints corrected for Lansbury index and with erythrocyte sedimentation rate and C reactive protein. In synovial fluid from both groups, only relatively small amounts of HP were measured, while bone type I collagen specific LP was below the limit of detection in all samples. In RA patients, but not in OA patients, there was a strong correlation between urinary and synovial concentrations of HP (r = 0.75). CONCLUSIONS: The results underline the relationship between urinary HP and disease extent and activity in RA. The findings in synovial fluid support the hypothesis of an extraskeletal origin of HP in chronic joint diseases in which cartilage and synovial turnover may be increased.

Amino Acids↗
PubMed1994

Determination of pyridinium crosslinks in plasma and serum by high-performance liquid chromatography.

A chromatographic method for the determination of pyridinoline (Pyr) and deoxypyridinoline (Dpyr) in serum and plasma is described. The analytical procedure involved plasma or serum purification by ultrafiltration (20,000 relative molecular mass cut-off) under centrifugation at 2500 g for 4 h, as an innovative step. Analysis was done by isocratic high-performance liquid chromatography with fluorescence detection. The linearity of the method was tested from 0.6 to 15 pmol/ml and 0.12 to 3 pmol/ml for Pyr and Dpyr, respectively. The detection limit was 60 fmol/ml for both crosslinks. Except for Dpyr in plasma (coefficient of variation 19.9%), intra-assay variation was always below 10% in serum and plasma. The method has been applied to the quantification of crosslinks in serum and plasma of healthy volunteers and also in mouse and rat plasma. Serum proved to be the most suitable biological fluid for the systemic measurement of these compounds in humans and under the experimental conditions used, contained an average of 3.62 +/- 0.65 and 0.7 +/- 0.18 pmol/ml Pyr and Dpyr, respectively.

Adult↗
PubMed1994

Determination of plasma choline by high-performance liquid chromatography with a postcolumn enzyme reactor and electrochemical detection.

A method for the determination of choline in human plasma is described, involving rapid purification of plasma samples and analysis by high-performance liquid chromatography using an on-column enzyme reactor with electrochemical detection. The linearity of the method was tested at choline levels from 3.5 to 28.6 microM in plasma. The recovery was 86% and was independent of the analyte concentration. The inter-assay precision (as coefficient of variation) and accuracy (as the deviation of the concentration found from the theoretical value) were always below 12% in the whole concentration range. The method was applied to the determination of plasma choline levels in eight healthy volunteers after intramuscular administration of L-alpha-glycerophosphorylcholine (1 g) or a placebo. Mean plasma choline levels in the placebo group ranged from 10.6 to 12.0 microM. After drug administration, the plasma choline level reached 35.1 microM in 30 min, then decreased gradually. Plasma choline levels became comparable in the treated and placebo groups 6-8 h after administration.

Adult↗
PubMed1994

Effect of salmon calcitonin on deoxypyridinoline (Dpyr) urinary excretion in healthy volunteers.

To evaluate the influence of synthetic salmon calcitonin (SMC) on bone resorption we investigated the modifications in urinary cross-links excretion [pyridinoline (Pyr) and deoxypyridinoline (Dpyr)] induced by a single dose of the drug. The study was carried out in 16 healthy volunteers given a single dose of either 50 IU SMC I.M. or placebo, according to a double-blind, cross-over design. Urine was collected every 24 hours during the 72 hours after each treatment and Pyr and Dpyr were measured by an automated HPLC method. Pyr showed no significant difference after the two treatments, whereas in the first 24-hour urine collection Dpyr (nmol/24 hours +/- SD) was considerably lower after SMC than after placebo (118.9 +/- 26.0 against 147.2 +/- 45.0, P < 0.05). The amount of saved Dpyr was 19.2%. The selective effect of SMC on Dpyr excretion was more evident comparing the Pyr/Dpyr ratios for placebo and SMC during the first day of the study (4.1 +/- 0.6 against 4.8 +/- 0.7, respectively, P < 0.01). Using Eyre's formula (10 nmol Dpyr = 0.17 g bone) and assuming that no Dpyr is metabolized, the mean daily amount of bone resorbed was calculated (2.5 g for placebo and 2.0 g for SMC). The difference is the index of the bone-saving effect of SMC (0.48 g/day, or 19.2%). In conclusion, assuming that in healthy volunteers bone turnover is balanced with equal rates of formation and resorption, a dose of 50 IU I.M. of SMC reduces resorption, with a bone gain in the first 24 hours calculated as 9.4 mg/IU.

Adult↗
PubMed1994

Comparison of the acute biological action of injectable salmon calcitonin and an injectable and oral calcitonin analogue.

In most countries, calcitonin is available in the form of injections, and less frequently as an intranasal spray. An oral route of administration should improve compliance. In a preliminary feasibility study, we have compared the acute biological action of injectable salmon calcitonin (50 IU), with the injectable calcitonin analogue ASC 710 (0.2 mg) and oral ASC 710 (20 mg) in 6 patients suffering from active Paget's disease of bone. The intensity and duration of the biological response were not significantly different in the 3 modes of therapy. In conclusion, the oral calcitonin analogue ASC 710 possesses an antiresorbing activity in Paget's disease comparable to that of an injection of salmon calcitonin which demonstrates that it can cross the intestinal barrier.

Administration, Intranasal↗
PubMed1993

Monitoring of free and total urinary pyridinoline and deoxypyridinoline in healthy volunteers: sample relationships between 24-h and fasting early morning urine concentrations.

Twelve healthy adults, six men and six women, with no history of bone or joint disease, were studied. They provided 24-h urine samples once weekly, five times, and a 24-h collection including the first sample of the early morning urine (FU). The urinary concentrations of free and total pyridinoline (HP) and deoxypyridinoline (LP), measured during the experimental period, showed no remarkable changes and gave good statistical correlations, particularly LP. Thus, in order to simplify and shorten the analytical procedure and the collection of biological samples, the only measurement of free fraction of HP and LP excreted in FU sample urine could be justified for both diagnostic and epidemiological purposes.

Adult↗
PubMed1992

Determination of picotamide in human plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the determination of picotamide in human plasma and urine is described. After addition of an internal standard (bamifylline), the plasma and urine samples were subjected to liquid-liquid extraction and clean-up procedures. The final extracts were evaporated to dryness and the resulting residues were reconstituted in 100 microliters of methanol-water (50:50, v/v) and chromatographed on a LiChrosorb RP-SELECT B reversed-phase column coupled to an ultraviolet detector monitored at 230 nm. Chromatographic analysis takes about 10 min per sample. The assay was linear over a wide range and has a limit of detection of 0.005 and 0.1 micrograms/ml in plasma and urine, respectively. It was selective for picotamide, accurate and robust and thus suitable for routine assays after therapeutic doses of picotamide.

Chromatography, High Pressure Liquid↗
PubMed1992

A comparative study of free plasma choline levels following intramuscular administration of L-alpha-glycerylphosphorylcholine and citicoline in normal volunteers.

L-alpha-glycerylphosphorylcholine (alpha-GPC) is a recently developed cognitive enhancer whose mode of action is considered to involve the release of free choline, which is then utilized for acetylcholine and phosphatidylcholine biosynthesis in the brain. The purpose of this study was to evaluate the profile of free plasma choline levels following a single i.m. dose of alpha-GPC in 12 normal volunteers. Citicoline (CTC), which also acts as a choline precursor, was included for comparison purposes. Each subject was studied on three randomized occasions, (i) in a control day in the absence of drug administration (to evaluate the plasma level profile of endogenous choline), (ii) after i.m. alpha-GPC (1,000 mg) and (iii) after i.m. CTC (1,000 mg) respectively, with a wash-out period of at least 1-week between sessions. Blood samples for plasma choline HPLC determinations were collected at regular intervals over a 6 h period. In the control session, plasma choline levels remained stable during the sampling period. The administration of alpha-GPC was associated with a rapid rise in plasma choline, peak levels being usually observed at the first (0.25 h) or second (0.5 h) sampling time after the injection. Thereafter, the concentration of choline declined gradually and returned to near baseline values at the end of the observation period. After the administration of CTC, plasma choline levels showed a similar time course but were considerably lower than those observed after the administration of alpha-GPC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

High-performance liquid chromatographic assay of L-alpha-glycerophosphorylcholine using a two-step enzymic conversion.

A high-performance liquid chromatographic method using an enzymic reactor for determination of L-alpha-glycerophosphorylcholine in pharmaceutical forms is described. The procedure includes incubation of L-alpha-glycerophosphorylcholine with glycerophosphorylcholine phosphodiesterase (EC 3.1.4.2), giving choline and glycerophosphate, and subsequent chromatography of choline with a post-column enzymic reactor and electrochemical detection. The results obtained show a close linearity of the whole assay from 2 to 150 nmol/ml L-alpha-glycerophosphorylcholine, the sensitivity being 2 pmol per 20 microliters of injected sample. The precision of the method in the analysis of L-alpha-glycerophosphorylcholine in pharmaceutical forms, ampoules and capsules, was 1.34 and 1.21%, respectively.

Chromatography, High Pressure Liquid↗