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Biomedical subjects

G Demartini

Publications and source records attributed to G Demartini.

30 records · Page 2Linked to original sources
PubMed1991

The diffusion of clarithromycin and roxithromycin into nasal mucosa, tonsil and lung in humans.

The diffusion of clarithromycin and roxithromycin into respiratory tract tissues was studied in 174 adult patients undergoing surgery. Patients received clarithromycin 250 mg orally (500 mg in the case of lung tissue), or roxithromycin 150 mg orally, both given every 12 h, for three days with the last dose administered at different times before surgery. Clarithromycin reached peak tissue levels 4 h after administration and achieved mean peak concentrations of 8.32 mg/kg +/- 2.57 in nasal mucosa, 6.47 mg/kg +/- 2.8 in tonsil, and 17.47 mg/kg +/- 3.29 in lung tissue. Roxithromycin reached peak tissue levels between 4 and 6 h after administration, achieving mean peak concentrations of 1.78 mg/kg +/- 0.73 in nasal mucosa, 2.2 mg/kg +/- 1.21 in tonsil, and 2.14 mg/kg +/- 0.87 in lung tissue. Clarithromycin and roxithromycin demonstrated contrasting pharmacokinetic behaviour. Roxithromycin was characterized by high concentrations in serum and low concentrations in tissues. Clarithromycin on the other hand, is characterized by therapeutic serum concentrations and high tissue concentrations.

Administration, Oral↗
PubMed1990

Alpha-1 adrenoceptor involvement in the control of melatonin secretion in the golden hamster.

The nocturnal peak in pineal and serum melatonin content was reduced following administration of the selective alpha-1 adrenoceptor antagonist prazosin in a dose of 0.25 mg/kg. The effect was pronounced one hour post treatment during the late dark phase of the daily photocycle. These data confirm the reported findings that the hamster pineal sensitivity to adrenergic challenge is confined to the second part of the dark phase and indicate that postsynaptically located alpha-1 adrenoceptors are also involved in the physiological control of melatonin synthesis and/or release in that species.

Animals↗
PubMed1990

Failure of prazosin to mimic the effects of melatonin under in vivo and in vitro conditions.

The gonads of male hamsters exposed to short photoperiod (LD, 10:14) or treated with melatonin in the late afternoon under long photoperiod (LD, 14:10) had undergone complete regression by the end of the treatments (8 weeks). Animals treated for the same period of time with prazosin (a putative melatonin analogue) under the same conditions failed to show a difference in their gonadal status as compared to the long photoperiod controls. Prazosin was unable to prevent melatonin-induced gonadal atrophy when injected either in the morning or 30 min before melatonin. Moreover, prazosin was without any effect on (and unable to prevent the melatonin-stimulated) progesterone production by rat adrenals under in vitro conditions. These data demonstrate that prazosin, which reportedly inhibits 2-[125I]iodomelatonin binding in the hamster brain in an affinity-related manner, does not possess properties of a biological melatonin analogue under conditions of two different model systems in two species.

Adrenal Glands↗
PubMedDate not supplied

In vitro comparative dynamics of modified-release clarithromycin and of azithromycin.

Antibacterial kinetics of modified-release clarithromycin (CLA) and azithromycin (AZI) against respiratory tract pathogens were compared in relation to their pharmacokinetic profile. The study was carried out in three strains of Streptococcus pneumoniae, group A beta-hemolytic Streptococcus pyogenes, Moraxella catarrhalis and Haemophilus influenzae, respectively, exposed to concentration gradients of CLA and AZI simulating human serum pharmacokinetics after administration of 500 mg p.o. in a single dose. Bactericidal kinetics were assessed by counting the number of survivors before each change in concentration over a period of 36 h. The minimal inhibitory concentrations (MICs) of CLA and AZI were evaluated at time 0 and after 36 h of exposure to antibiotics in the surviving organisms. The results showed that CLA and AZI, in the experimental conditions adopted, had different antibacterial kinetics. Moreover, the addition of the 14-OH metabolite of CLA at the same concentrations reached in human serum exerted a bactericidal effect against two strains of H. influenzae resistant to CLA and AZI. An increase in MICs was observed against S. pyogenes and H. influenzae, with higher values for AZI.

Anti-Bacterial Agents↗
PubMedDate not supplied

Melatonin involvement in immunity and cancer.

The most studied endocrine product of the pineal gland, melatonin, has been reported to be involved in the feedback between neuroendocrine and immune functions and to exert oncostatic action, at least in certain experimental conditions. Melatonin seems to be an integral part of the immune system, by exerting direct and/or indirect stimulatory effects on both cellular and humoral immunity. Likewise, an antitumor activity of melatonin has been shown in several experimental models in vivo and in vitro. The means by which melatonin exerts its effects on immunity and neoplastic growth have not been elucidated. The different putative mechanisms of action of melatonin investigated so far are here briefly discussed.

Adjuvants, Immunologic↗
PubMedDate not supplied

A new model examining intracellular and extracellular activity of amoxicillin, azithromycin, and clarithromycin in infected cells.

An in vitro infection model was created using a suspension of macrophages, polymorphonuclear leukocytes, lymphocytes, fibroblasts, and human serum to which pathogen and antibiotic were added. Separate intracellular and extracellular antibiotic concentrations and activity against Staphylococcus aureus and Legionella pneumophila were assessed for three antimicrobial agents: amoxicillin, azithromycin and clarithromycin. Amoxicillin was found almost exclusively in extracellular fluid, where it was active; intracellularly, it was ineffective. Azithromycin, in contrast, was primarily concentrated and active intracellularly, with little activity in extracellular fluid. Clarithromycin was present in both compartments and possessed significant activity both intracellularly and extracellularly.

Amoxicillin↗
PubMedDate not supplied

Effect of antibiotics on Bordetella pertussis adhering activity: hypothesis regarding mechanism of action.

Microbial adherence to epithelial cell surfaces has been implicated as the first step in the initiation of several infectious diseases. The ability of antibiotics to affect the properties of bacterial adherence to cell surfaces may be a criterion in selecting antibiotics for therapy. This study was performed in order to investigate the activity of amoxicillin, chloramphenicol, and clarithromycin in modifying the adhering activity of Bordetella pertussis to human epithelial cells. The actions of antibiotics, alone or combined with aprotinin, were compared with that of trypsin, aprotinin and trypsin+aprotinin, to investigate the chemical nature of the ligand where antibiotics could act. The adhering activity was evaluated on human epithelial cells, collected from the oral mucosa, challenged with B. pertussis A2963 previously incubated in the presence of the tested substances for 1 h at 37 degrees C in a shaker incubator. After staining, the percentage of mucosal cells with more than 50 adhering bacteria was evaluated. Under the described experimental conditions, trypsin significantly reduced the adherence of B. pertussis. Aprotinin had no effect but was able to counteract the inhibitory action of trypsin. Both clarithromycin and chloramphenicol markedly reduced adhering activity and their actions were not counteracted by aprotinin. Amoxicillin was without effect. It was hypothesized that chloramphenicol and clarithromycin, exerting their antimicrobial action by inhibiting bacterial protein synthesis, affected bacterial adhesion through an unknown mechanism without proteolytic effect.

Amoxicillin↗
PubMedDate not supplied

Concentrations of ceftibuten in bronchial secretions.

Ceftibuten is a broad-spectrum oral cephalosporin exhibiting antimicrobial activity against a wide range of gram-negative and some gram-positive pathogens. Pharmacokinetic studies have shown that the molecule has an oral bioavailability higher than 90% of the administered dose (reaching peak serum concentrations of 5-19 mg/l after a single dose of 200 and 400 mg). Moreover, ceftibuten has been shown to be useful in the treatment of acute lower respiratory tract infections. This study was performed to determine the distribution of ceftibuten in bronchial secretions from patients affected by the exacerbation of chronic bronchitis. Patients were treated with a single 400-mg oral dose of ceftibuten. Blood and bronchial-secretion samples were obtained just before, and at 0.5, 1, 2, 4, 8, 12, 16 and 24 h after dosing. Cells were separated from bronchial secretions by centrifugation. Ceftibuten in duplicate samples of both serum and bronchial secretion was quantified by HPLC. Ceftibuten reached peak levels 2 and 4 h after oral administration in serum and in bronchial secretions, respectively (18.12 +/- 2.13 and 9.19 +/- 3.1 mg/l, respectively). Falling curves after the peaks showed a monoexponential decay. The absorption was very rapid both in serum and bronchial secretions, but elimination was slower in bronchial secretions than in serum.

Administration, Oral↗
PubMedDate not supplied

Bactericidal kinetics of an in vitro infection model of once-daily ceftriaxone plus amikacin against gram-positive and gram-negative bacteria.

The in vitro efficacy of ceftriaxone plus amikacin combination against gram-positive and gram-negative bacteria, clinically isolated from patients affected by pneumonia in intensive care units, was compared to that of the 2 drugs used alone. The study was performed using a dynamic model in which the human kinetics of the drugs after intramuscular administration was simulated. The antibacterial activity was tested by determining the bacterial cell count (CFU/ml). Killing curves came out from plotting the log CFU/ml versus time. In the same way, ceftriaxone and amikacin concentrations were assayed by HPLC and fluorescence polarization immunoassay, respectively. The results show that ceftriaxone plus amikacin combination exert a high killing activity against all tested strains. The two antibiotics alone initially have a good killing activity but this is followed by bacterial regrowth for all tested isolates. This data supports the results of several clinical studies which have shown a good therapeutic efficacy of ceftriaxone plus amikacin combination in the treatment of severe infections caused by organisms intermediately sensitive to these drugs.

Amikacin↗
PubMedDate not supplied

[Non-visual effects of light mediated via the optical route: review of the literature and implications for occupational medicine].

Artificial light which now plays an essential role in industrialized society differs from natural light both in intensity which is usually lower, and in spectrum, which is usually smaller. It is now a well-known fact that the human body is able to use luminous stimulation for aims other than sight; the pineal gland, though no longer directly sensitive to light as in lower animals, is nevertheless the fulcrum of a complex neuro-endocrine system which makes an interaction between light and the human body possible by means of the production of a number of substances of which melatonin is the most widely investigated. Melatonin is secreted at a circadian rhythm characterized by high nocturnal seric levels and low diurnal levels. This secretion appears to be correlated not only with the intensity of the light but also with its spectrum and time exposure. Even though the function of melatonin is still not fully understood, it seems possible to assign a mainly modulatory role to the pineal gland and melatonin. On the basis of studies performed on the pituitary-gonadal and/or hypothalamic axis and the reproductive system in animals, melatonin would appear to affect some endocrine functions (i.e., puberty) in man, too. Changes in melatonin secretion have been found in psychiatric illness, especially in cyclical affective disorders. Melatonin seems to be involved in stress-associated mechanisms, probably with an agonistic role, and also in carcinogenesis, where it seems to play a role in the growth of several tumors. Melatonin also affects both tumoral and cellular immune responses. Lastly, melatonin may be able to reduce the symptoms of the Jet Lag Syndrome. The consequences that prolonged and marked reduction in daylight exposure for occupational reasons could have on operators, especially young people, therefore constitute an interesting subject for occupational health; environmental photometry at the work-place, if adequately performed, could make a useful contribution to the development of this field of research.

Adolescent↗