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Biomedical subjects

A Ripamonti

Publications and source records attributed to A Ripamonti.

At least 37 records · Page 2Linked to original sources
PubMed1985

Metabolic pathways of the anti-hypertensive agent, N-(2,5-dimethyl-1H-pyrrol-1-yl)-6-(4-morpholinyl)-3-pyridazinamine hydrochloride. II: Studies in the dog.

The metabolic fate of a new anti-hypertensive, 1-pyrrolyl-pyridazinamine, was studied in male Beagle dogs given both p.o. and i.v. doses of the 14C-labelled drug (1 mg/kg). The compound given as a single i.v. injection disappeared from the central compartment with a half-life of about 0.9 h. Plasma levels of total 14C were represented mostly by metabolites. Eight urinary metabolites designated as metabolites I, II and XI-XVI were purified and their structures assigned by means of u.v., i.r., n.m.r. and mass spectrometry. Quantitatively the primary metabolic attack involved the morpholine moiety of the molecule which undergoes oxidative opening. A minor pathway afforded the cleavage of the pyrrole followed by chemical rearrangements to form six-membered sidnone-like products or a triazole derivative. The major (XIII) and three minor metabolites were studied for their antihypertensive activity in rats and were shown to be inactive.

Administration, Oral↗
PubMed1984

Thermal behavior of bone and synthetic hydroxyapatites submitted to magnesium interaction in aqueous medium.

The thermal behavior of the products obtained from magnesium interaction with powdered femoral bone and carbonate containing synthetic hydroxyapatite under conditions of pH fluctuation in aqueous medium has been investigated. The products, heat treated at different temperatures from 100 to 1300 degrees C, have been characterized by infrared spectroscopy and X-ray diffraction technique. The results show that the interaction with magnesium ion destabilizes the apatitic structure and favours its thermal conversion into beta-tricalcium phosphate (beta-TCP). The replacement of magnesium with calcium in the beta-TCP crystal lattice hinders its subsequent thermal conversion into the alpha form. The influence of magnesium on the thermal stability is much more evident for carbonate-containing synthetic hydroxyapatite than for bone apatite.

Animals↗
PubMed1984

Metabolic pathways of the contragestational agent, 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4-triazole (DL 111-IT), in the rat.

The metabolic pathways of the non-hormonal anti-fertility agent 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4-triazole (DL 111-IT) were studied in rats given the 14C-labelled compound intramuscularly. The diaryltriazole, once absorbed, was metabolized rapidly by three phase I reactions: (a) hydroxylation at the C-4 of the methoxyphenyl ring, (b) hydroxylation at the alpha-C of the ethyl chain, and (c) demethylation of the methoxyl function. Seven free metabolites and three conjugates have been isolated and characterized by u.v., i.r., n.m.r. and mass spectroscopy. The products of the first step of metabolism of the diaryltriazole were tested for their pregnancy-terminating activity in the rat. They were only 5-9% as effective as the parent compound, indicating that the unchanged drug is the active molecule.

Abortifacient Agents↗
PubMed1984

Structure identification of rifampicin N-oxide.

1H- and 13C-N.M.R. spectra, in addition to previous physicochemical data, confirm the structure of rifampicin N-oxide and indicate that the oxygen atom is bonded to the piperazine N--CH3 group.

Chemical Phenomena↗
PubMed1983

X-ray diffraction analysis of transversal osteonic lamellae.

When isolated osteon samples are submitted to wide-angle X-ray diffraction, it is not possible to detect any preferential orientation of the hydroxyapatite crystallites of the lamellae with transversally arranged fiber bundles. So a complete and exhaustive X-ray diffraction analysis of an osteon needs adequately prepared osteonic subunits. For the present investigation, 2 types of samples were prepared from longitudinal and alternate osteons: osteonic radial sections and isolated straightened transversal lamellae. An X-ray diffraction microcamera has been used with a rotating anode X-ray generator. In accordance with the data provided by the polarizing microscope, the orientation of crystallites runs parallel to the osteon axis in longitudinally structured osteons, whereas in alternate osteons the orientation changes by about 90 degrees in successive lamellae. Neither crystallites associated with the collagen fibrils that run alongside the osteocyte canaliculi nor those associated with the fibrils that run transversally in longitudinally structured osteons are revealed by X-ray diffraction, because there are so few of them.

Crystallization↗
PubMed1983

Disposition and metabolism of a new steroidal anti-inflammatory agent, deflazacort, in cynomolgus monkeys.

The kinetics and metabolic fate of 2'-14C-deflazacort, a new steroidal antiinflammatory agent, were studied in the cynomolgus monkey after both p.o. and i.v. administration (5 mg/kg). There is no unchanged deflazacort in the plasma or urine after either p.o. or i.v. treatment. As judged from the plasma AUC and urinary elimination values, the oral availability of both total 14C and metabolites seems to be lowered because of a route-dependent first-pass. Both radioactivity and the main metabolite (21-desacetyl deflazacort) are eliminated from the plasma with half-lives of 2--3-5 h. The i.v. administered 14C is eliminated mainly in the urine (52--55% of dose), but biliary excretion is also quantitatively important. Six metabolites were isolated from urine and identified by physico-chemical analysis. Among them desacetylated deflazacort and its 6 beta-hydroxy derivative were shown to be the major radioactive products in plasma and urine, respectively. Minor metabolites were: 21-desacetyl, 6 alpha-hydroxy deflazacort; 21-desacetyl, 5 alpha, 1-eno, deflazacort; 21-desacetyl, 20 beta hydroxy deflazacort; and 21-desacetyl, 11-keto deflazacort.

Animals↗
PubMed1982

Species differences in the disposition and metabolism of 1-methyl-3-(3-pyridyl)-5-(2-hydroxy-methylphenyl)-1H-1,2,4-triazole, a potential sedative-hypnotic compound.

1. Disposition and metabolism of 1-methyl-3-(3-pyridyl)-5-(2-hydroxy-methylphenyl)-1H-1,2,4-triazole, a new sedative-hypnotic, were studied in rats (i.v. and p.o.), cats (i.v.) and human volunteers (p.o.) with 14C-labelled drug. 2. In rat and man, the compound is well absorbed, extensively metabolized, and excreted mostly through the kidney; it has short plasma half-lives, 0.6 h in rat, 0.9 h in man, and 1.9 h in cat. 3. In rat and man metabolism involves N-oxidation of the pyridine ring (Metabolite I), and in cat oxidation of the hydroxymethyl group (Metabolite II). Four other conjugated metabolites (III-VI) isolated from rat urine and bile, and from urine of cats and man, have been characterized. 4. The unchanged compound, but not its metabolites, crosses the blood-brain barrier in rat and cat. 5. The species differences in the disposition and metabolism of the compound are consistent with previous pharmacological data indicating a greater and more prolonged effect in cat.

Adult↗
PubMed1981

Effect of homogeneous magnetic fields on responses to toxic stimulation in Spirostomum ambiguum.

Effects of DC magnetic fields, up to 125,000 G, on the survival of the ciliated protozoan Spirostomum ambiguum exposed to the toxic substance 2,2'-dipyridyldisulfide are reported. The magentic field diminishes the ability of the organism to survive the drug, and lengthens the extension phase of the contraction cycle. It is proposed that the magnetic field alters the regulation of intracellular (Ca2+) transients.

2,2'-Dipyridyl↗
PubMed1981

Influence of metabolism on the activity of a new anti-fertility agent, 2-(3-ethoxyphenyl)-5,6-dihydro-s-triazolo [5,1-a]isoquinoline (DL 204-IT), in the rat and the hamster.

The activity of a new non-hormonal anti-fertility agent, 2-(3-ethoxyphenyl)-5,6-dihydro-s-triazolo[5,1-a]isoquinoline (DL 204-IT), effective in terminating pregnancy after i.m. or s.c. treatment, was tested after single and multiple oral doses given to rats and hamsters. Although the compound was absorbed well from the gastrointestinal tract and the plasma levels of the radioactivity administered were rather high and sustained, the oral activity was by two orders of magnitude lower than the parenteral one. The plasma profile of the metabolites found after both p.o. and i.m. administration indicates that the compound is rapidly metabolized. Seven metabolites (I-VII) were isolated from the urine of pregnant rats and fully characterized by MS, IR and NMR spectroscopy. They are 2-(3-hydroxyphenyl)-5,6-dihydro-s-triazolo[5,1-a]isoquinoline (I); 2-(3,4-dihydroxyphenyl)-5,6-dihydro-s-triazolo[5,1-1]isoquinoline (II); 2-(3-hydroxyphenyl)-5,6-dihydro-6 beta-hydroxy-s-triazolo[5,1-a]isoquinoline (III); metabolite I-sulphate ester (IV); metabolite III-3-sulphate ester (V); metabolite I-beta-D-glucuronide (VI) and metabolite II-3-beta-D-glucuronide (VII). Metabolite I was shown to be from 1/10 (rat) to 1/30 (hamster) as active as the parent compound, while metabolites II and III were completely inactive. The very low oral activity of DL 204-IT seems to be due mainly to its rapid biotransformation.

Administration, Oral↗
PubMed1979

X-ray diffraction study of bovine lens capsule collagen.

The wide angle X-ray diffraction pattern of air-dried lens capsule collagen under tension is the same as the tendon collagen diffraction pattern with regard to the main reflections, and indicates that lens capsule collagen has the characteristic three-stranded helical structure with an axial repeat of 0.29 nm as tendon collagen. The low angle X-ray diffraction pattern shows several weak diffraction maxima corresponding to the meridional reflections of capsule collagen which show orders of 63.0 nm periodicity. This is an evidence of quarter staggered molecular assembly typical of tendon collagen even if less ordered. The results are consistent with the existence in lens capsule collagen of clearly defined molecular units, which can be oriented by stress and are packed in a poor-ordered fibrillar assembly.

Animals↗
PubMed1978

X-ray diffraction and electron microscope study of osteons during calcification.

To obtain information on the changes in the inorganic bone fraction during calcification, low- and wide-angle X-ray diffraction techniques and electron microscopy have been applied to single osteon samples. The samples were cylindrically shaped and their axes corresponded to the axes of the Haversian canals. The selection was made according to the degree of calcification and the orientation of collagen bundles and inorganic particles. Osteons at both the initial and final stages of calcification were chosen. Arrangements of fiber bundles and inorganic particles in successive lamellae characteristic of three types of osteon were selected, that is, longitudinally structured osteons, transversely structured osteons, and alternately structured osteons. The results indicate that in osteonic lamellar bone there are two types of inorganic particles: (1) granules arranged in linear or needle-shapred entities with maximum width 40-45 A, which are regularly distributed at the level of the main band of the collagen fibrils where their maximum length reaches the length of the main band itself; that is , about 400 A; and (2) very long crystallites, with a diameter of 40-45 A, which grow with their crystallographic c-axis parallel to the collagen fibrils and cover much more than a major collagen period.

Adolescent↗
PubMed1978

Structural organization of collagen fibrils in media aortic wall.

Small-angle X-ray diffraction patterns of bovine, human and porcine media aortic wall show meridional reflections corresponding to a periodicity which suggest a molecular packing typical of tendon collagen. However the meridional intensity distribution of stretched air dried aortic samples appears different from that of air-dried tendon, probably because of the presence of a large amount of type III collagen with the environment, which are specific for aortic tissue. The stretched wet aortic samples show a marked decrease in intensity, revealing an extensive disorder in the axially-projected structure of the fibrils. When a loading system simulating the effect of blood pressure is applied to a ring of aorta, no evidence of orientation of collagen is seen by X-ray diffraction, as would be expected if collagen fibrils had an isotropic distribution inside the aorta media. Scanning electroni microscopy supports the existence of a network of collagen fibrils surrounding elastic lamellae.

Adult↗
PubMed1977

X-ray diffraction and scanning electron microscopy of bovine media aortic wall.

Scanning electron microscopy and high angle X-ray diffraction were used to define the relationship between collagen and elastin of bovine aortic wall. The diffraction pattern shows on one hand that the broad rings at 4.5 A and 9 A, due to elastin, do not orient on stretching and on the other hand, that the collagen rings at 11 A and 2.9 A start to orient at low elongations. These data together with scanning electron microscopy suggest a tight structural relationship between collagen and elastin that should influence the mechanics of deformation at all degrees of elongation.

Animals↗