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Biomedical subjects

L Rossini

Publications and source records attributed to L Rossini.

At least 37 records · Page 2Linked to original sources
PubMed1991

Electrophysiological effects of a pumiliotoxin-B-like alkaloid derived from the skin of the Australian frog Pseudophryne coriacea.

Skin extracts of the Australian frog Pseudophryne coriacea (PsC) potentiate and prolong the bioelectric activity of various excitable tissues. When studied by electrophysiological means in a preparation of mouse diaphragm, PsC skin extracts did not affect the spontaneous acetylcholine (ACh) release. However, the indirect stimulation of the preparation in the presence of PsC skin extracts gave rise to a different profile of rhythmic activity showing afterpotentials and variable oscillatory activity. The action potential and the total sodium current recorded in the muscle fibre with the loose patch clamp method were not modified significantly by the alkaloid. Concentrations of PsC skin extract that did not cause repetitive activity, seemed to reduce slightly the quantal content of the evoked release of ACh. The resting potential of muscle fibres was not modified even by the highest PsC skin extract concentrations. These results suggest that the facilitation effects of PsC skin extracts could be due to intracellular mechanisms probably related to the control of the cytosolic calcium concentrations or to an increased excitability of the presynaptic biomembranes.

Acetylcholine↗
PubMed1991

[Persistence of the control of the fluctuations of heart rate in the anesthetized and pithed adult rat. Effect of enteraminergic drugs].

Spontaneous fluctuations in heart rate were analyzed by spectral analysis in the ether anesthetized and pithed adult rat. In order to investigate the changes in the spectral pattern of the fluctuations, the selective 5HT-2 and -3 isoreceptor blockers ritanserin and BRL 43694A were used. In both the experimental conditions, ritanserin blockade led to dose-dependent increased fluctuations in HR low and high frequencies. In both the anesthetized and pithed rats, the low frequency range HR fluctuations were drastically reduced by BRL 43694A.

Anesthesia↗
PubMed1991

[Power spectra of the inter-cycle heart fluctuations in Xenopus laevis (L.), conscious or pithed, exposed to temperature changes and pharmacological treatments].

Spectral analysis of spontaneous heart rate fluctuations, a powerful noninvasive tool for quantifying autonomic nervous system activity, was assessed in Xenopus Laevis, intact or spinalized, at different temperatures and by use of pharmacological tools. As expected, increasing the body temperature resulted in a positive chronotropic effect, both in the conscious and the spinalized preparations. Characteristic modifications of the spontaneous heart rate fluctuations were detected in both the experimental conditions. Different receptor drugs, which selectively interfere with the variously superimposed vegetative sections of the nervous control, had been proved to be effective in the new assay.

Adrenergic beta-Agonists↗
PubMed1991

[Pharmacology of atriopeptin in the adult rat: power spectra of the fluctuations in heart rate].

The persistence of the cardiac beat-to-beat control is studied in the anesthetized and the pithed adult rat by means of spectral analysis. The data show that atriopeptin affects the amplitude of the heart rate low frequency fluctuations, significantly increasing the spectral patterns both in the anesthetized and the pithed rat. The atriopeptin enhancement of the low frequency range in heart rate fluctuations provides further insight into the hypothesis that beat to beat variability in hemodynamic parameters reflects a compensatory response in the short term cardiovascular control.

Anesthesia↗
PubMed1991

[Liposarcoma of the retroperitoneum. A case report].

The authors describe a case of retroperitoneal liposarcoma developing between the leaflets of the transverse mesocolon. They briefly summarise the classification and the symptomatology of retroperitoneal tumours and discuss the way of presentation of their case comparing it with literature data.

Aged↗
PubMed1990

Sodium-activated potassium current in mouse diaphragm.

The mouse diaphragm muscle fiber was studied using the loose patch clamp technique. The voltage gated sodium currents were evoked by step pulses from a holding potential of about - 70 mV. Following the activation of the sodium current, a very large and fast outward current was evoked. The sensitivity of this current to 4-aminopyridine and tetraethylammonium indicates the potassium ion as the possible carrier for the channel. Furthermore, the sensitivity to tetrodotoxin and extracellular sodium demonstrated the sodium dependence of this current.

Action Potentials↗
PubMed1990

Focus on toxicological aspects of pesticide chemical interaction in drinking water contamination.

Toxicological aspects related to chemical and microbial degradation of pesticides in water and to products deriving from the interaction with xenobiotics found in water are reviewed. Other aspects considered are those related to compounds formed in potabilization processes and to water contamination by pesticide synthesis by-products or intermediates. These problems refer to scarcely investigated issues which are nevertheless very interesting because of their impact on human health.

Pesticide Residues↗
PubMed1989

Changes in lipoprotein binding and uptake by hepatocytes during rat liver regeneration.

The binding and uptake of cholesterol enriched lipoproteins by isolated hepatocytes was decreased at 16 hours after partial hepatectomy, with a tendency to return to control values as the regeneration proceeds. The number of lipoprotein binding sites of total cellular membranes remained similar to control at 16 and 24 hours. The plasma lipoprotein pattern, determined by electrophoretic analysis, showed a lower per cent of very low density lipoproteins (VLDL) and a higher per cent of low density lipoproteins (LDL) at 16 and 24 hours post-partial hepatectomy. At these times, plasma lecithin: cholesterol acyltransferase (LCAT) activity was decreased. It is intriguing to suggest that the regenerating liver could regulate the blood lipoprotein pattern and the uptake of lipoproteins by modulating the surface expression of the receptors.

Animals↗
PubMed1989

Characterization of the rabbit aorta endothelium-dependent cholinergic receptor by agonist equipotent molar doses.

The endothelium-dependent acetylcholine, metacholine, carbachol, betanechol, and furtrethonium relaxation values have been measured in vitro for the rabbit aorta, in presence of a high concentration of hexamethonium. The produced EPMR values complete the values that were obtained in a previous experiment under analogous conditions for rat bladder, ileum, iris, stomach, and trachea preparations. The complete set was analyzed by new statistical techniques of data analysis and display, which are both simpler and more precise than the statistical modeling techniques used by us in the past. This has led to new results concerning the clustering of drugs and of receptors, as well as to a characterization of the endothelium receptor.

Animals↗
PubMed1989

Comparative dose study of a theophylline sustained-release tablet formulation after repeated administrations.

Two different doses of a sustained-release tablet formulation of theophylline were administered to two groups of patients affected by chronic obstructive pulmonary disease. Pharmacokinetic parameters were determined after a single administration of the drug. In this experiment, the theophylline plasma levels were determined 1, 2, 4, 8, 12 and 24 h after the drug administration. In another experiment, the patients received the drug "once-daily", in the morning, for nine consecutive days. Plasma theophylline levels were monitored 24 h after the first administration and twice daily on days 3, 6 and 9. Patients receiving 700 mg/day showed theophylline levels ranging from 8.49 +/- 1.04 micrograms/ml to 20.99 +/- 2.09 micrograms/ml. In this group theophylline concentrations were found to be greater than 10 micrograms/ml also 24 h after the tablets' administration. These data show that in case of single daily theophylline administration an high dosage is necessary to maintain the drug concentration within the range of therapeutic levels.

Aged↗
PubMed1986

Determination of doxorubicin and doxorubicin-3-ol in rat heart.

The discovery of a delayed form of DXR-induced cardiotoxicity raises the question whether the presence of the drug or of metabolites in myocardial cells is necessary for the development of cardiotoxicity. The present investigations deal with a new method for the determination of DXR and of its main metabolite, DXR-3-ol, in cardiac cells. Rat hearts "ex-vivo", isolated 24 h after i.v. administration of 6 mg/kg DXR and 20 micro C of DXR-14C, were perfused with ice-cold Tyrode solution, which releases anthracyclines from extracellular spaces. After homogenization DXR and DXR-3-ol were extracted from the cell at room temperature. The separation was carried out by HPLC; the recovery was about 95%, measured by the extracted radioactivity compared with that of the pellet residue.

Animals↗
PubMed1986

Pyrethroid metabolism: studies on cis- and trans-phenothrins, and related epoxide intermediates.

Two synthetic pyrethroids, cis- and trans-phenothrins, undergo an environmental degradation which involves extensive photooxidation on their acidic residue, which contains a double bond. It has been shown that the metabolism of these compounds occurs via epoxidation of the isobutenyl side-chain also with hepatic microsomal preparations. The results did not indicate any formation of epoxide intermediates on the isobutenyl side-chain. Further evidence that metabolism of cis- and trans-phenothrins does not occur via an epoxide intermediate is furnished by the fact that in vitro activity of hepatic microsomal epoxide hydrolase remained unaffected. These findings may be related to the unfavorable steric hindrance of the tri-substituted double bond on the acidic moiety of these pyrethroids.

Animals↗
PubMed1986

Stereochemical considerations on the inhibition of hepatic epoxide hydrolase by some pesticides and their epoxides.

The present studies identify the steric factors involved in the hydration of epoxide intermediates of some pesticides by hepatic epoxide hydrolase. Investigations were carried out regarding the formation of reactive epoxide intermediates and their different interactions with the hepatic epoxide hydrolase. Some pesticides and their parent epoxides were selected on the basis of the steric hindrance on the oxirane ring. The results indicate that the inhibition of this enzyme depends on the steric hindrance produced by substituents on the oxirane ring of these pesticides. Mono- and di-substituted oxiranes are good substrates of the epoxide hydrolase and non-competitive inhibitors of the hydration of styrene oxide, while tri-substituted epoxides are virtually inactive on inhibiting the hepatic epoxide hydrolase activity.

Animals↗