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Biomedical subjects

A Donati

Publications and source records attributed to A Donati.

At least 37 records · Page 2Linked to original sources
PubMed2001

The protection of rat liver autophagic proteolysis from the age-related decline co-varies with the duration of anti-ageing food restriction.

Restricting caloric intake (CR) well below that of ad libitum (AL) fed animals retards and/or delays many characteristics of ageing and the occurrence and progression of age-associated diseases, efficacy depending on duration. The hypothesis that the anti-ageing effect of CR might involve stimulation of the cell-repair mechanism autophagy was tested. The effects of ageing and duration of anti-ageing CR on liver autophagic proteolysis (AP) were explored in male AL Sprague-Dawley rats aged 2-, 6-, 12- and 24-months; and 24-month-old rats on a CR diet initiated at 2-, 6- and 12-month of age or initiated at age 2-months and interrupted at age 18 months. The age-related changes in the regulation of AP were studied by monitoring the rate of valine release in the incubation medium from isolated liver cells by an HPLC procedure. Results show that the maximum attainable rate and the regulation of AP decline with increasing age; that changes are prevented by anti-ageing CR initiated at young age, that the protective effects of CR change with the duration of diet. It is concluded that the data are compatible with the hypothesis that AP and improved membrane maintenance might be involved in the antiageing mechanism of CR.

Adenine↗
PubMed2001

Effects of ageing and increased haemolysis on the levels of dolichol in rat spleen.

Dolichol is a long-chain polyisoprenoid. No enzyme pathway for dolichol degradation was discovered. Dolichol accumulates in human and rodent tissues during ageing. Red blood cells contain a larger amount of dolichol and red blood cell life span is shorter in older rats. The effects of age and of the load of dolichol from red blood cell degradation on the ageing-associated accumulation of dolichol in spleen were studied in 2, 6, 12, 18 and 24 month-old male Sprague Dawley rats fed ad libitum (AL) or on an anti-ageing dietary regimen (EOD). Tissue dolichol was extracted and assayed by HPLC [J. Gerontol. 53A (1998) B87]. Levels of dolichol increased in spleen, liver, kidney and muscle in parallel fashion from the age of 2 to 12 months. Unexpectedly, spleen dolichol decreased in older rats whereas liver, kidney and muscle dolichol increased significantly. The effects of haemolysis on spleen dolichol were tested by the administration of phenylhydrazine. Results show that haemolysis does not increase, but rather decreases the levels of dolichol in erythroclastic organs. It is concluded that the levels of spleen dolichol may decrease in the absence of any known enzymatic degradative pathway if the spleen and its resident phagocytes are forced to cope with a higher number of red blood cells to be cleared. Free-radical mediated decomposition of dolichol by phagocytic cells during erythrophagocytosis might be involved in the process.

Aging↗
PubMed2001

Age-related changes in the regulation of autophagic proteolysis in rat isolated hepatocytes.

During intervals between meals, autophagy is a major source of nutrients and may remove damaged organelles and membranes. Age-related changes in the regulation of autophagic proteolysis were studied by monitoring the rate of valine release from liver cells of 2-, 6-, 12-, 18-, and 24-month-old male Sprague-Dawley rats fed ad libitum, and incubated in vitro with added amino acids and 10(-7) M of insulin or glucagon. The maximum rate of proteolysis and its maximum inhibition by amino acids were reached at 6 months and declined thereafter. In contrast, the rate of protein degradation in the presence of high concentrations of amino acids was not affected by aging. The inhibitor effect of insulin was additive to that of amino acids and was not altered significantly by age. The conclusion is that altered regulation of autophagic proteolysis decreases susceptibility of older cells to lysosomal degradation, and it may lead to the accumulation of altered organelles and membranes.

Aging↗
PubMed2001

Age-related changes in the autophagic proteolysis of rat isolated liver cells: effects of antiaging dietary restrictions.

Autophagy is a process that sequesters and degrades organelles and macromolecular constituents of cytoplasm for cellular restructuring and repair and as a source of nutrients for metabolic use in early starvation. The effects of two antiaging dietary regimens (initiated in rats at the age of 2 months), namely, 40% dietary restriction (DR) and every-other-day ad-libitum feeding, that exhibited different effects on metabolism and similar effects on longevity on the age-related changes in the regulation of autophagic proteolysis were studied by monitoring the rate of valine release in the incubation medium from isolated liver cells of male albino Sprague-Dawley rats aged 2, 6, 12, 18, 24, and 27 months. (The liver cells were incubated in vitro with added amino acids and 10(-7) M insulin or glucagon.) Age-matched male albino Sprague-Dawley rats fed ad libitum served as a control. Results show that in ad-libitum-fed rats, after a transient increase by age 6 months, autophagic proteolysis and regulation by amino acid exhibit a dramatic age-related decline, and that the age-related changes are prevented by dietary antiaging intervention. A comparison shows that the protective effects of DR and every-other-day ad-libitum feeding are partially different in 24-month-old rats (but the beneficial effects of the two diets on regulation of autophagic proteolysis are always similar). With regard to endocrine regulation, results confirm that the liver cell response to glucagon (but not to insulin) declines with increasing age, and they show that antiaging DRs significantly improve the effects of glucagon (and have no effect on the response to insulin). The interactions of age by diet, glucagon (and in older rats, insulin), and amino acids are significant. It is concluded that DR significantly improves the susceptibility of liver cells to lysosomal degradation, and it prevents decline with increasing age. It is suggested that improved liver autophagy and lysosomal degradation might be part of the antiaging mechanisms of DR.

Aging↗
PubMed2000

Effects of taurine and some structurally related analogues on the central mechanism of thermoregulation: a structure-activity relationship study.

There is large body of evidences on the role of taurine in the central mechanisms of thermoregulation in mammals, but it is not clear, whether the hypothermic effect of taurine depends on its interaction with GABA receptors or with a specific receptor. In order to answer this question, we have performed a structure-activity relationship study by using both in vitro and in vivo preparations. MicroM amounts of taurine or each of 20 analogues were injected intracerebroventricularly in conscious, restrained rabbits while rectal temperature was recorded. Receptor-binding studies, with synaptic membrane preparations from rabbit brain were used to determine the affinities of these compounds for GABA(A) and GABA(B) receptors. Furthermore, the interaction with presynaptic GABA and taurine uptake systems was studied using crude synaptosomal preparations from rabbit brain. Among the compounds tested, (+/-)-cis-2-aminocyclohexanesulfonic acid, induced hypothermia, but did not interact with GABA(A) and GABA(B) receptors neither did it affect GABA and taurine uptake, thus suggesting that its effect on body temperature is not mediated by the central GABAergic system. Interestingly, the trans-isomer was devoid of effects either in vivo or in vitro. In order to explain (+/-)-cis-2-aminocyclohexanesulfonic acid-induced hypothermia, a stereoscopic model was produced showing its possible interactions with a putative taurine brain receptor.

Animals↗
PubMed1999

Novel potent and selective central 5-HT3 receptor ligands provided with different intrinsic efficacy. 2. Molecular basis of the intrinsic efficacy of arylpiperazine derivatives at the central 5-HT3 receptors.

Novel 5-HT3 receptor ligands were designed and synthesized with the aim of obtaining deeper insight into the molecular basis of the intrinsic efficacy of arylpiperazines interacting with the central 5-HT3 receptor. The newly synthesized compounds and some previously published compounds belonging to the same class of heteroarylpiperazines were tested for their potential ability to displace [3H]granisetron from rat cortical membranes. These 5-HT3 receptor binding studies revealed subnanomolar affinity in several of the compounds under study. The most active ligands were quipazine derivatives bearing a phenyl group in the 4-position and various oxygenated alkyl side chains in the 3-position of the quinoline nucleus. Qualitative and theoretical quantitative structure-affinity relationship studies were carried out, and the interaction model for the 5-HT3 ligands related to quipazine with their receptor, proposed in part 1 of the present work, was updated to incorporate the latest data. The potential 5-HT3 agonist/antagonist activity of 12 selected compounds was assessed in vitro on the 5-HT3 receptor-dependent [14C]guanidinium uptake in NG 108-15 cells. Their intrinsic efficacy ranged from the 5-HT3 full agonist properties of compounds 7a and 8h, i to those of partial agonists 10a,d and antagonists 8b,d,e, and 9c, d,h,i. The comparison between these functional data and those relative to the previously described compounds suggested that in this class of 5-HT3 ligands the intrinsic efficacy is modulated in a rather subtle manner by the steric features of the heteroaryl moiety.

Animals↗
PubMed1999

Structural effect of complete [Rp]-phosphorothioate and phosphorodithioate substitutions in the DNA strand of a model antisense inhibitor-target RNA complex.

Chemically modified DNA oligonucleotides have been crucial to the success of antisense therapeutics. Although such modifications are ubiquitous in the clinic, high-resolution structural studies of pharmaceutically relevant derivatives have been limited to only a few molecules. We have completed a high-resolution NMR structural study of three DNA.RNA hybrids with the sequence d(CCTATAATCC). r(GGAUUAUAGG). All hybrids contain an unmodified RNA strand, whereas the DNA strand of each hybrid contains one of three different sugar-phosphate backbone linkages at each nucleotide: (1) phosphate, (2) [Rp]-phosphorothioate, or (3) phosphorodithioate. The UV and NMR melting profiles revealed that the normal hybrid is more stable than the [Rp]-phosphorothioate, which in turn is more stable than the phosphorodithioate. Homonuclear two-dimensional nuclear Overhauser effect spectroscopy and double quantum-filtered correlation spectroscopy afforded nearly complete non-labile proton assignments. The three molecules show nearly equivalent chemical shifts, with the exception of H3' protons, which are shifted downfield in a manner that appears correlated with the degree of sulfur substitution at phosphate. All three hybrids exhibit unusually broad linewidths for deoxyribose protons H2' and H2".Distance restraints were calculated from NOE cross-peak intensities via a complete relaxation matrix approach using the program RANDMARDI. Detailed comparison of interproton distances from each hybrid indicates that the three molecules share a common structure, with neither strand in canonical A or B form. Correlation of R factors, calculated using the program CORMA with DNA H2'-base and H3'-base distances, revealed a relative increase in the population of B-type sugar conformations for deoxyriboses in the A+T-rich center of the hybrid sequence. It is widely known that the activity of enzymes which act upon DNA.RNA hybrid substrates (e.g. ribonuclease H) is impacted when the hybrids contain phosphorothioate or phosphorodithioate substitutions. The structural similarity of the three hybrids examined here suggests that factors other than global structure may mediate the activity of these enzymes.

Base Sequence↗
PubMed1999

The age-related accumulation of protein carbonyl in rat liver correlates with the age-related decline in liver proteolytic activities.

Increases of protein carbonyl in animal tissues have been associated with the aging process. So far, the accumulation of oxidized proteins, highly susceptible to proteolysis, has been attributed to age-related changes in proteasomal alkaline proteases. Carbonyl in protein was monitored in six different tissues of male Sprague-Dawley rats fed ad libitum up to the age of 27 months, and of 24 and 27-month-old rats subjected to anti-aging diet restriction (every-other-day feeding ad libitum). Alkaline protease activities and liver lysosomal proteolysis were studied. The levels of protein carbonyl were significantly different in different tissues, and quite stable throughout life; accumulation was restricted to liver tissue very late in life, between ages 24 and 27 months; was fully prevented by diet restriction; was not accompanied by any diet-restriction-sensitive decline of alkaline protease activity; and was accompanied by a dramatic age-related decline in lysosomal proteolysis that was partially prevented by anti-aging diet restriction. No correlation was found between levels of alkaline protease activity and levels of protein carbonyl in the different tissues from younger animals. It is concluded that the process of autophagy, a well-known mechanism for cell maintenance, may deserve more interest in aging studies.

Aging↗
PubMed1998

Small structural ensembles for a 17-nucleotide mimic of the tRNA T psi C-loop via fitting dipolar relaxation rates with the quadratic programming algorithm.

Solution structures are typically average structures determined with the help of nmr-derived distance and torsion angle information. However, when a biomolecule populates significantly different conformations, the average structure might be prone to artifacts, and other refinement strategies are necessary. For example, when experimental restraints are used in molecular dynamics simulations in a time-averaged fashion (MDtar), the experimental structural information does no longer need to be satisfied at each step of the simulation; instead, the whole trajectory must agree with the restraints. However, the resulting structural ensembles are large and not unique and it is not trivial to extract the essential dynamic features for a system. Here we demonstrate that large MDtar ensembles can be simplified substantially by reducing the number of members to just a few on the basis of adjusting the individual probabilities of the members with the PDQPRO program [N. B. Ulyanov et al. Biophysical Journal (1995), Vol. 68, p. 13]. This algorithm finds the global minimum for a search function that represents the best match of a given ensemble with the experimental dipolar interproton relaxation rates. We have applied this strategy to a 17-residue RNA hairpin, whose loop exhibited considerable flexibility evident from nmr data. This 17mer is a mimic of the T psi C-loop of tRNA, where nucleotide 54 is usually a ribosylthymidine. The methylation of U54, which is completely buried in transfer ribonucleic acid, is administered by tRNA (m5 U54)-methyltransferase (RUMT). Since the 17mer is a good substrate for RUMT, we previously concluded that the flexibility of the 17mer's loop is a key to how RUMT gains access to the methylation site [L. J. Yao et al. Journal of Biomolecular NMR (1996) Vol. 9. p. 229]. Application of the PDQPRO algorithm to the previously acquired MDtar trajectories allowed us to reduce the number of conformations from several hundred to one major and five or six minor conformations with individual populations from approximately 5% to approximately 50% without any deterioration in the match with the experimental data. The major conformation exhibits a continuation of A-form helicity through part of the loop, involving C60 and U59. In this and most other conformations the methylation site in U54 is no longer buried.

Algorithms↗
PubMed1998

Predictive value of interleukin 6 (IL-6), interleukin 8 (IL-8) and gastric intramucosal pH (pH-i) in major abdominal surgery.

OBJECTIVE: To study plasma concentrations of interleukin 6 (IL-6) and interleukin 8 (IL-8) in patients with splanchnic hypoxia, as documented by gastric intramucosal measurements (pH-i), during major abdominal surgery and the relationship between IL-6 and IL-8 concentrations and postoperative complications as well as clinical outcome. DESIGN: A prospective study. PATIENTS: Twelve patients scheduled for major abdominal surgery with no evidence of coexisting infectious disease. RESULTS: Six out of seven samples from patients with postoperative complications showed intraoperative pH-i levels lower than 7.32 and IL-6 levels higher than 300 pg/ml. Seven out of nine samples from patients without complications showed pH-i levels higher than 7.32 and IL-6 levels lower than 300 pg/ml. The difference in the pattern of distribution was statistically significant (p < 0.01). Only two out of seven samples of patients with postoperative complications showed intraoperative pH-i levels lower than 7.32 and IL-8 levels higher than 60 pg/ml. It was not possible to identify a clear distribution pattern of data points for IL-6 and IL-8 during the postoperative period. CONCLUSIONS: Intraoperative splanchnic ischemia, as documented by gastric intramucosal pH-i, is directly correlated to the increase of IL-6 plasma levels and to the incidence of postoperative complications, while IL-8 levels showed no correlation with surgical complications.

Adult↗
PubMed1998

[The role of lymphadenectomy in colorectal neoplasms].

BACKGROUND: The role of lymphadenectomy in the treatment of large bowel cancer is still controversial, not only because it is deemed to be a basic element for a correct postoperative staging, but also because it brings about, according to some authors, an enhancement of survival and of "disease free survival" rates. The difficulty to collect case histories with homogeneous data and the impossibility to identify preoperatively with certainty the lymph nodes involved, makes it difficult to codify the most suitable surgical treatment, even if it is agreed at present, to extend lymph nodes dissection at least as far as Level II nodes. As a matter of fact, despite of slight enhancement of 5-year survival rate (6-8%), a significant increase in morbility occurs, as reported in the literature, particularly in terms of urological and neurological lesions. However, a few authors, perform systematically Level III dessection, reporting a 20% increase in survival. METHODS: Our study, has been carried out on 84 patients affected by large bowel neoplasm and admitted to the Institute of Surgical Pathology I of "Vittorio Emanuele" Hospital of Catania between 1990-1995. RESULTS: This study showed an involvement of Level I lymph nodes in 77% of patients and of Level II in 33%, while Level III nodes were affected only in 4.7% of cases. CONCLUSIONS: On the basis of these data and of those reported in the literature, the conclusion is drawn that the most suitable and responsible attitude is, at present, to perform invariably Level I and Level II dissection, reserving the lymphadenectomy of Level III only to selected cases or when an involvement is documented pre and intraoperatively.

Adult↗
PubMed1998

[Mathematical model for the predictive value of a test in critically ill patients studies according to APACHE II score and pathology at admission].

OBJECTIVE: To find a predictive model for mortality at four different days from the admission for critically ill patients. DESIGN: Retrospective study on two consecutive series of critically ill patients admitted in ICU. SUBJECTS: 1254 critically ill patients, subdivided into two series of 813 (561 survivors and 252 non survivors) and 441 patients (291 survivors and 150 non survivors), respectively. INTERVENTIONS: None. MEASUREMENTS: All patients had APACHE II calculated within the first 24 hours from the admission in ICU and, if the patient was still in ICU, also at the 5th, 10th and 15th day from the admission. Casistics was subdivided into two unequal series, ratio 2:1, with a random selection made on each of the 6 considered years. On the 1st series, in 1st, 5th, 10th and 15th day, for mathematical predictive models were made, using stepwise logistic regression (BMDP, Los Angeles). In the 1st day the following independent variables were utilized: APACHE II score, the specific diagnosis at admission, fitted following Knaus' diagnostic criteria, united in 6 principal categories, while for the other 3 days the variation % of APACE II score as regards the previous day. RESULTS: For each of the considered day four mathematical models have been made. These models have been validated in both series in calibration from the Hosmer-Lemeshow Goodness-of-fit test and in discrimination from the ROC curves. For each day Y (Prob.% to die) = eLogit/1 + eLogit, where Logit = beta 0 (constant) + beta 1*APACHE II + beta 2*Variat.%APACE II (difference between actual APACHE II - APACHE II of the previous day/actual APACHE II) + beta k, (coefficient pertinent to pathology). CONCLUSIONS: The mathematical model, as other models do, stratifies enough the casistics according to the risk of death. Waiting for further studies to make more precise prognostic mathematical models, this one and others can help the clinical assessment in single patient evaluation.

APACHE↗
PubMed1996

Modeling interpretation of microbe metabolism detected by nuclear magnetic resonance.

A new modeling approach is discussed for the analysis of microbial dynamics. It is based on structurally nonlinear compartmental models and on the dynamics of the substrate and product. Experimental data were acquired by NMR spectroscopy which is a noninvasive technique. This combined approach was tested with the fermentation of glucose to ethanol by Saccharomyces cerevisiae. The model was fitted with the experimental data to obtain the values of the parameters of the model. Similar processes can be analyzed and compared using this approach.

Ethanol↗
PubMed1996

Molecular structure and dynamics of some potent 5-HT3 receptor antagonists. Insight into the interaction with the receptor.

The molecular structure and the dynamic behaviour of some potent 5-HT3 antagonists structurally related to quipazine have been investigated by NMR spectroscopy and by computational methods in order to gain insight into the structure-activity relationships at a molecular level. The role of the different dynamic behaviour of these compounds in the binding to 5-HT3 receptors is discussed. A model of ligand-receptor interaction has been developed on the basis of molecular orbital calculations and on the reference ligands quipazine, ondansetron and LY278584. The interaction model proposed herein rationalizes the observed agonist-antagonist shift between quipazine and investigated compounds with the assumption of different but overlapping binding domains for antagonists and agonists at the 5-HT3 receptor.

Affinity Labels↗
PubMed1996

[Intima flap of the external carotid and postoperative stroke in a patient surgically treated with thromboendarterectomy of the internal carotid].

Retrograde thrombosis of the carotid bifurcation rising from an intimal flap of the external carotid artery represent a rare complication of carotid surgery. We present the case of a patient who had undergone carotid thromboendarterectomy (TEA) whose postoperative course was complicated by the appearance of left hemiplegia and coscience disorders. The timely diagnosis of acute carotid thrombosis and the immediate reoperation prevented neurological deficits becoming settled. An attentive intraoperative evaluation of carotid bifurcation showed only the presence of an intimal flap of the external carotid artery from which a big occluding thrombus, involving the bifurcation, rose. The internal and common carotid arteries showed a successful result of the TEA and a good retrograde flow through the internal carotid artery. The authors underline the existence of this perioperative complication and the need for a timely recognition and treatment to avoid serious neurologic consequences.

Carotid Artery Thrombosis↗
PubMed1995

[Predictivity associated with oxygen-transporting hemodynamic parameters: relation between the cardiac index and oxygen extraction].

OBJECTIVE: To verify the predictivity of a diagram with the cardiac index (CI) on the y-axis and the oxygen extraction (O2ER) on the x-axis and to verify if the haemodynamic therapy could change the outcome. DESIGN: A retrospective study on a consecutive series of patients. SETTING: University Intensive Care Unit of Ancona. SUBJECTS: 65 critically ill patients, subdivided in survivors (38) and non survivors (27). INTERVENTIONS: All the patients have been monitored with a Swan-Ganz catheter. MEASUREMENTS: CI and O2ER at the admission (T0), at 12 (T1), 24 (T2) and 48 hours (T3) from T0. The diagram CI/02ER has been subdivided in 9 parts on the basis of the normal values of CI (> or = 2,5 and < or = 3,5 1/min/m2) and of O2ER (< or = 24 and > or = 28%). RESULTS: At T2 most of survivors (73.7%) is on the most favourable part of the diagram, with the CI and the O2ER normal or increased, while only 21.4% of non survivors is in this part. On the contrary only 26.3% of survivors versus 78.6% of non survivors are in the less favourable part of the diagram. The chi 2-test shows a good significantly (p = 0.003) in the different distribution on the diagram between survivors and non survivors. A 2 x 2 table has been made. We found: sensibility 78.6% specificity 73.7% and total correct 75.4%. In any other time it has been found a significant different distribution on the diagram between survivors and non survivors. CONCLUSIONS: This diagram can be useful to predict the short term outcome in non septic patients, because at 24 hours give a correct prediction of the outcome in 3 patients on 4, with a good prediction either of the good outcome or of the exitus.

Body Surface Area↗