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Biomedical subjects

M Berti

Publications and source records attributed to M Berti.

At least 91 records · Page 5Linked to original sources
PubMed1990

Synthesis and biological activity of some derivatives of rifamycin P.

A series of derivatives of rifamycin P, an antibiotic produced by fermentation of a mutant strain of Nocardia mediterranea or by chemical modification of rifamycin S, have been prepared. The structures of these compounds were determined by 1H NMR, IR, UV, and LC/MS. Their in vitro and in vivo antibacterial activities in comparison with rifampicin and two other rifamycins under investigation were evaluated. The derivatives were more active than rifamycin P against Mycobacterium avium complex and other slowly and rapidly growing nontuberculous mycobacteria which frequently cause systemic infection in patients with AIDS. 2'-(Diethylamino)rifamycin P (P/DEA) appears suitable for further investigation.

Animals↗
PubMed1990

Synthesis and biological activity of some amide derivatives of the lantibiotic actagardine.

A series of basic carboxamides of actagardine (1), a lantibiotic possessing good antistreptococcal activity, were synthetized. Some physico-chemical characteristics, in particular charge and lipophilicity, that influence water solubility were determined. The in vitro and in vivo activity was evaluated. The monocarboxamides were generally more active than actagardine against selected Gram-positive bacteria. The 3,3-dimethylamino-1-propylamide hydrochloride (4) showed good water solubility, bactericidal action and favourable antibacterial activity and it appears to be a suitable drug for further investigation.

Amides↗
PubMed1990

N15-alkyl and N15,N15-dialkyl derivatives of teicoplanin antibiotics.

The synthesis and the biological properties of a series of N15-alkyl and N15,N15-dialkyl derivatives of teicoplanin A2, its pseudoaglycones and aglycone are described. The alkylation of the terminal amino group did not affect the ability of these teicoplanin derivatives to bind with Ac2-L-Lys-D-Ala-D-Ala, a synthetic model of the antibiotic's target peptide in bacterial cell walls, but influenced their in vitro and in vivo antimicrobial activities to a different extent, depending on the structure and length of the alkyl chains and the type and number of sugars present.

Alkylation↗
PubMed1990

Antibiotic SB22484: a novel complex of the aurodox group. I. Taxonomy of the producing organism, isolation of the antibiotics and chemical and biological characterization.

Antibiotic SB22484 is a novel member of the aurodox type antibiotic group produced in submerged-fermentation cultures of Streptomyces sp. NRRL 15496. The antibiotic complex is composed of two pairs of isomers with MW's of 752 and 766. The individual isomers, which were separated by preparative HPLC, equilibrate to a mixture of the isomer pair when left in aqueous solution. In vitro, SB22484 antibiotics strongly inhibited neisseriae and were also active against Streptococci, Ureaplasma urealyticum and Haemophilus influenzae.

Animals↗
PubMed1990

Carboxyhydrazides of the aglycone of teicoplanin. Synthesis and antibacterial activity.

The condensation of the terminal carboxyl group of the deglucoteicoplanin (TD) with various substituted hydrazines produced hydrazide derivatives having different physico-chemical properties. This chemical modification of the carboxyl function does not affect the ability of teicoplanin antibiotics to interfere in bacterial cell-wall synthesis. The antibacterial activity of deglucoteicoplanin hydrazides (V) were found to depend mostly on their ionic character. All the hydrazides were slightly more active than TD on Escherichia coli. Those possessing an additional basic group were more in vitro active than TD against Gram-negative microorganisms. In Experimental Streptococcus pyogenes septicemia in the mouse, basic hydrazides were more active than other derivatives when administered subcutaneously although they are as potent as TD.

Animals↗
PubMed1990

[The right ventricle and pulmonary circulation in hypertensive patients].

Elevated blood pressure and vascular resistance in patients with systemic hypertension are paralleled by a proportional rise in pressure and resistance in the lesser circulation. It was hypothesized that increased systemic reaction to adrenergic stimulation is shared by the pulmonary vessels. Thus normotensive subjects and patients with primary hypertension were investigated during mental arithmetic and the cold pressor test. Both groups responded to both stimuli; during arithmetic pressure reaction was mediated through an increase of cardiac output, and during the cold pressor test through a predominant rise in systemic vascular resistance. The pressure changes were emphasized in the hypertensive population. Pressure in the pulmonary artery in normotensive subjects was not affected by cold and was slightly raised (systolic) during arithmetic. In hypertensive patients, on the other hand, systolic and diastolic pressures were consistently augmented by both tests, and pulmonary arteriolar resistance rose by 42% and 29% of control during the cold pressor test and arithmetic, respectively. Changes in resistance reflected neurally-mediated vasoconstriction but not variations in the passive relationship between pressure and flow, since during arithmetic, for a similar rise in flow the driving pressure across the lungs was steady in normotensive subjects and rose significantly in hypertensive patients. In these same patients pressure was augmented by cold test in the absence of substantial changes in flow. At baseline and during tests pulmonary wedge pressure, pleural pressure, arterial blood gases, and pH were similar in the two populations. The intravenous infusion of similar scalar doses of norepinephrine (the same mediator released during cold test) was not effective on the pulmonary vessels of normotensives and caused an obvious vasoconstriction in hypertensives.(ABSTRACT TRUNCATED AT 250 WORDS)

Catecholamines↗
PubMed1989

Synthesis and biological evaluation of de(acetylglucosaminyl)didehydrodeoxy derivatives of teicoplanin antibodies.

A series of 34-de(acetylglucosaminyl)-34-deoxy derivatives of 34,35- and 35,52-didehydro teicoplanin antibiotics have been synthesized from teicoplanin and its N-acetylglucosamine containing pseudoaglycons under basic conditions. The structures of these compounds have been determined by 1H NMR, UV, and FAB-MS. 35,52-Unsaturated derivatives maintained in vitro and in vivo antimicrobial activity to a different extent as well as the ability for binding to Ac2-L-Lys-D-Ala-D-Ala, a bacterial cell-wall model for the site of action of glycopeptide antibiotics. In contrast, 34,35-unsaturated compounds were markedly less active and possessed a negligible affinity for the synthetic tripeptide.

Acetylglucosamine↗
PubMed1989

Synthesis and biological properties of N63-carboxamides of teicoplanin antibiotics. Structure-activity relationships.

The condensation of the carboxyl function of teicoplanin A2 (CTA) and its acidic hydrolysis pseudoaglycons (TB, TC) and aglycon (TD) with amines carrying various functional groups and chains produced amide derivatives with different isoelectric points and lipophilicities. Amide formation did not affect the ability of these compounds to bind to Ac2-L-Lys-D-Ala-D-Ala, a model for the natural peptide binding site in bacterial cell walls. The antimicrobial activities of teicoplanin amides were found to depend mostly on their ionic and lipophilic character and on the type and number of sugars present. Positively charged amides were generally more in vitro active than the respective unmodified antibiotics against Gram-positive organisms. In particular, most basic amides of CTA were markedly more active than teicoplanin against coagulase-negative staphylococci. A few amides of TC and most of those of TD also showed a certain activity against Gram-negative bacteria. In experimental Streptococcus pyogenes septicemia in the mouse, some basic amides were more active than the parent teicoplanins when administered subcutaneously. Some of those of CTA were also slightly more effective than teicoplanin by oral route.

Amides↗
PubMed1989

Enhancement of the pulmonary vasoconstriction reaction to alveolar hypoxia in systemic high blood pressure.

1. In systemic hypertension the pulmonary vessels show an excessive tone at rest and hyper-react to adrenoceptor stimulation. Alterations in Ca2+ handling by the vascular smooth muscle cells seem to underlie these disorders. Alveolar hypoxia also constricts pulmonary arteries, increasing the intracellular Ca2+ availability for smooth muscle contraction. This suggests the hypothesis that hypoxic pulmonary vasoconstriction depends on similar biochemical disorders, and that the response to the hypoxic stimulus may be emphasized in high blood pressure. 2. In 21 hypertensive and 10 normotensive men, pulmonary arterial pressure and arteriolar resistance have been evaluated during air respiration and after 15 min of breathing 17, 15 and 12% oxygen in nitrogen. Curves relating changes in pulmonary arterial pressure and arteriolar resistance to the oxygen content of inspired gas had a similar configuration in the two populations, but in hypertension were steeper and significantly shifted to the left of those in normotension, reflecting a lower threshold and an enhanced vasoconstrictor reactivity. 3. This pattern was not related to differences in severity of the hypoxic stimulus, degree of hypocapnia and respiratory alkalosis induced by hypoxia, and plasma catecholamines. 4. The association of high blood pressure with enhanced pulmonary vasoreactivity to alveolar hypoxia could have clinical implications in patients who are chronically hypoxic and have systemic hypertension.

Adult↗
PubMed1989

Enhanced hypoxic pulmonary vasoconstriction in hypertension.

In this study, we tested the hypothesis that hypoxic pulmonary vasoconstriction may be enhanced in systemic hypertension. The hypothesis took origin from the following two considerations: alveolar hypoxia constricts the pulmonary vessels by enhancing the Ca2+ penetration across sarcolemma of the smooth muscle cells and systemic high blood pressure is associated with an elevation of tone and reactivity of the lung vessels, which seems to depend on an excessive cytosol free Ca2+ concentration due to alterations in sodium handling and in the Na+-Ca2+ exchange system. These considerations suggest the possibility that the disorders in the biochemistry of smooth muscle contraction in hypertension facilitate the rise of cytosol Ca2+ concentration during alveolar hypoxia, thus resulting in a potentiation of the vasoconstrictor properties of this stimulus. In 43 hypertensive and 17 normotensive men, pulmonary arteriolar resistance has been evaluated during air respiration and after 15 minutes of breathing 17%, 15%, and 12% oxygen in nitrogen. Curves relating changes in pulmonary arteriolar resistance to oxygen breathing contents had similar configuration in the two populations but in hypertension were steeper and significantly shifted to the left, reflecting a lower threshold and an enhanced reactivity. This pattern was not related to differences in severity of the hypoxic stimulus, plasma catecholamine concentration, or hypocapnia and respiratory alkalosis induced by hypoxia and probably was not mediated through alpha-receptor activation. Calcium channel blockade with nifedipine was able to almost abolish both the normotensive and the hypertensive pulmonary vasoconstriction reaction. These findings support the hypothesis that hypoxic pulmonary vasoconstriction may be enhanced in systemic hypertension.

Adrenergic alpha-Antagonists↗
PubMed1989

Dechloro teicoplanin antibiotics.

Mono- and didechlorinated derivatives of the antibiotic teicoplanin, its pseudoaglycones and aglycone, and of one amide and ester of deglucoteicoplanin were prepared under selective reductive conditions. The selectivity and rate of dehalogenation were studied and compared to those of vancomycin and deglucovancomycin. The influence of the chlorine substituents on the mechanism of action and antibacterial activity of teicoplanin antibiotics was also investigated.

Animals↗
PubMed1989

Synthesis and biological activity of N63-carboxypeptides of teicoplanin and teicoplanin aglycone.

A series of peptide derivatives of teicoplanin A2 (CTA) and deglucoteicoplanin (TD) was prepared by condensation of the 63-carboxyl function with the alpha-amino group of selected amino acids and their derivatives. The modification of the ionic character of CTA and TD influenced their in vitro and in vivo antimicrobial properties to a different extent, depending on the structure of the amino acidic moiety at C-63. A certain effect on binding strength to Ac2-L-Lys-D-Ala-D-Ala, a synthetic model of the antibiotic's target peptide, was also observed.

Animals↗
PubMed1989

A42867, a novel glycopeptide antibiotic.

A42867 is a new glycopeptide antibiotic of the ristocetin-vancomycin class active against aerobic and anaerobic Gram-positive bacteria. A42867 is produced by a strain of Nocardia nov. sp. ATCC 53492. A42867 was isolated during a screening program aimed at the discovery of new members of this glycopeptide class of antibiotics, by affinity chromatography based on an acyl-D-alanyl-D-alanine probe. The structure of A42867 was elucidated by fast atom bombardment MS, high field 2D 1H NMR spectroscopy, and HPLC analysis of the hydrolyzed carbohydrates. A42867 differs from vancomycin in the sugar portion and in the presence of only one chlorine atom in the peptide core. Its biological activity on Gram-positive aerobic and anaerobic bacteria is similar to that of other antibiotics of this group.

Aminoglycosides↗
PubMed1988

Combined hemodynamic overload of the left and right ventricles as a possible cause of interventricular septum preponderance in high blood pressure.

We tested whether overload of the two ventricles may be associated with a preponderance of interventricular septum in patients with high blood pressure. The rationale is that the septum is shared by the greater and lesser circulation and that in hypertension the latter shows the same qualitative hemodynamic alterations as the former. Among 65 hypertensive patients, 40 (group 1) showed (echo) posterior wall thickness within the mean +/- 1 SD of 62 normal subjects, and 25 (group 2) had a posterior wall thickness exceeding the mean + 1 SD of the normal population. Both groups were subdivided into subgroups A and B, which included patients whose ventricular septum was similar to (within the mean + 1 SD) and thicker than (exceeding the mean + 1 SD) the posterior wall thickness in the corresponding group, respectively. Resting differences in systemic and pulmonary pressure and vascular resistance among subgroups 1A, 1B, and 2A were not significant; however, in subgroup 2B these variables exceeded those in the other subgroups to a significant extent. During cold pressor testing (CPT) the levels reached and the changes in pressure and resistance from baseline values in both circuits were much greater in subgroups B than in subgroups A. The baseline plasma norepinephrine value showed a trend toward an increase from subgroup 1A to 1B and from subgroup 2A and 2B; during CPT norepinephrine invariably changed and in subgroups B it rose significantly more than in subgroups A. It was not determined whether this caused the hemodynamic overload in subgroups B.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

A40926 aglycone and pseudoaglycones: preparation and biological activity.

A40926 antibiotics are new glycopeptides which are much more active than other members of this class against Neisseria gonorrhoeae. Their activity against Gram-positive bacteria, including coagulase-negative Staphylococci, is similar to that of other glycopeptides. An A40926 preparation containing factors A and B ("A40926 A + B complex") was hydrolyzed to the aglycone and to the mannosyl and N-acylaminoglucuronyl aglycones. The mannosyl aglycone and the aglycone were less active than A40926 A + B complex against Streptococci and Gram-positive anaerobes and lost the anti-gonorrheal activity. In contrast, the N-acylaminoglucuronyl aglycones were as active as the parent complex against these Gram-positive bacteria and were moderately active against N. gonorrhoeae. The aglycone and, even more so, the N-acylaminoglucuronyl aglycones, had better activity than the parent complex against coagulase-negative Staphylococci. In experimental septicemia in the mouse, A40926 A + B complex and its derivatives had activity proportional to their MIC for the test organism.

Animals↗
PubMed1987

A40926, a new glycopeptide antibiotic with anti-Neisseria activity.

In the course of a search for glycopeptide antibiotics having novel biological properties, we isolated A40926. Produced by an actinomycete of the genus Actinomadura, A40926 is a complex of four main factors which contain a fatty acid as part of a glycolipid attached to the peptide backbone. Its activity was, in most respects, similar to that of other glycopeptides, such as vancomycin and teicoplanin. However, in addition to inhibiting gram-positive bacteria, A40926 was very active against Neisseria gonorrhoeae. A40926 was rapidly bactericidal for N. gonorrhoeae clinical isolates at concentrations equal to or slightly higher than the MIC. In mice, levels in serum were higher and more prolonged than those of an equivalent subcutaneous dose of teicoplanin. These properties suggest that A40926 may have potential in the therapy of gonorrhea.

Anti-Bacterial Agents↗