Biomedical subjects

L Gabriel

Publications and source records attributed to L Gabriel.

At least 19 recordsLinked to original sources

PubMed2001

Cytoskeleton-interacting activity of geiparvarin, diethylstilbestrol and conjugates.

Geiparvarin, a natural compound isolated from the leaves of Geijera parviflora, inhibits the growth of various tumor cell lines with a mode of action which may be attributed to its anti-microtubular activity. Our previous findings indicated that geiparvarin is able to inhibit the in vitro polymerization of tubulin and to derange the microtubular network in fibroblasts more effectively in the presence of paclitaxel. To further explore its biological activity here we have studied the effects exerted on the other components of the cytoskeleton by geiparvarin and two derivatives obtained by conjugating the 3(2H)-furanone ring of geiparvarin with diethylstilbestrol (DES). Firstly, observations by electron microscopy confirmed anti-microtubular properties, a near-total absence of microtubules is detected when tubulin is incubated with drugs in the presence of paclitaxel, whereas microtubule formation is not inhibited by drugs when assembly is induced by guanosine 5'-triphosphate (GTP). Immunofluorescence assays demonstrated that geiparvarin and DES act in a vinblastine-like fashion, causing a marked depletion of intermediate filaments while the network of microfilaments is not affected. Both the conjugates alter the 'stress fibers' organization of actin and disrupt the vimentin pattern; generally they derange cytoskeleton more markedly than the parent compounds. The cell growth inhibiting effects of geiparvarin and derivatives are dose-dependent; they vary according to the cell line used, when compounds were administered either alone or simultaneously with paclitaxel. Unlike other anti-microtubule agents, they do not exhibit cell-cycle compartment specificity and do not influence thymidine uptake in the cell.

3T3 Cells↗

PubMed2001

Antimicrotubular and cytotoxic activity of geiparvarin analogues, alone and in combination with paclitaxel.

Geiparvarin is an antiproliferative compound isolated from the leaves of Geijera parviflora, and may represent a new drug which targets tubulin. To better explore the potential use of this agent, we investigated the antimicrotubular and cytotoxic effects of new synthetic aromatic derivatives of geiparvarin. These drugs inhibited polymerization of microtubular protein, particularly when the assembly was induced by paclitaxel. The microtubular network organization of fibroblasts was altered more effectively by some drugs. Normal microtubule architecture completely disappeared when the cells were treated simultaneously with drugs and paclitaxel: microtubules depolymerized or were reorganized into bundles, in a similar but more disarrayed fashion than that observed after treatment with paclitaxel alone. Cytotoxicity studies showed a dose-dependent effect, whereas combined administration of drugs and paclitaxel increased cytotoxicity, more effectively in paclitaxel versus derivatives administration alone.

3T3 Cells↗

PubMed2001

Vancomycin levels in human aqueous humour after intravenous and subconjunctival administration.

The purpose of the present study was to evaluate the level of vancomycin in human aqueous humour after intravenous (i.v.) and subconjunctival administration. One hundred patients scheduled to undergo cataract extraction participated in the study. Fifty-three of them received 20 mg vancomycin subconjunctivally and 47 received two doses of vancomycin i.v. (1 g b.i.d.). Specimens of aqueous humour from the first group were collected 1, 2, 2.5, 3, 3.5, 5, 6, 7, and 8 h after the subconjunctival injection. In the second group, specimens of blood and aqueous humour were collected 1, 2, 4, 6, 8, 10, and 12 h after the end of infusion of the second dose of the antibiotic. The levels of vancomycin were determined by fluorescent polarization immunoassay. In the first group peak levels of 24.82+/-3.55 microg/ml were achieved in aqueous humour at 5 h, whereas in the second group peak levels of 1.42+/-0.47 microg/ml were detected at 6 h. The latter levels, although higher than the MICs of most of the Gram-positive pathogens causing eye infections, are inadequate for the treatment of infections in vivo. These results support the need for subconjunctival instead of i.v. administration of vancomycin in order to achieve therapeutic levels of the drug in human aqueous humour or for prophylactic use whenever indicated.

Administration, Topical↗

PubMed2000

Cellular uptake and cytotoxicity of solid lipid nanospheres (SLN) incorporating doxorubicin or paclitaxel.

Solid Lipid Nanospheres (SLN) are colloidal therapeutic systems proposed for several administration routes and obtained by dispersing warm microemulsions in cold water. SLN as carriers of doxorubicin and paclitaxel have been previously studied. In this study, the cellular uptake of SLN and the cytotoxicity of doxorubicin and paclitaxel incorporated into SLN were investigated on two cell-lines, human promyelocytic leukemia (HL60) and human breast carcinoma (MCF-7). Cellular uptake of SLN was determined by incorporating 6-coumarin as fluorescent marker. The cellular uptake of fluorescent SLN was clearly evidenced by fluorescence microscopy. The cytotoxicity of doxorubicin incorporated in SLN was higher compared to the conventional doxorubicin solution, even at the lower concentrations. Paclitaxel in SLN was about 100-fold more effective than free paclitaxel on MCF-7 cells, while on HL60 cells a lower sensitivity was achieved with paclitaxel in SLN. Unloaded SLN had no cytotoxic effect on HL60 and MCF-7 cells.

Antibiotics, Antineoplastic↗

PubMed1997

Geiparvarin and derivatives in combination with taxol: effect on microtubular organization in 3T3 fibroblasts.

Geiparvarin, a natural product that exhibits antiproliferative activity, inhibits the growth of various tumour cell lines with a mechanism of action so far unknown. Our preliminary findings showed that geiparvarin and some derivatives obtained from its conjugation with diethylstilboestrol and meso-hexestrol significantly inhibit taxol-induced in vitro polymerization of both tubulin and microtubular protein. In this study we investigated the effect of geiparvarin and of the oestrogen-combined derivatives on the cellular microtubular network of fibroblasts. Geiparvarin altered the microtubular organization of fibroblasts and strengthened the derangement of the microtubular pattern in cells exposed simultaneously to taxol. However, the microtubular network remained quite well organized in fibroblasts exposed to geiparvarin and preincubated with taxol, which in this case prevented the deranging effect of the former. The antimicrotubular activity of the oestrogen-combined derivatives was more similar to that of geiparvarin than to that of the oestrogens, and often this activity was stronger than that of each reference drug alone; the cytotoxic activity examined in the same experimental conditions generally confirmed the microscopic analysis.

3T3 Cells↗

PubMed1996

An electron-capture dienophile derivatization agent for increasing sensitivity: determination of a vitamin D analog (Ro 24-2090) in plasma samples with liquid chromatography/mass spectrometry.

A practical analytical method has been developed for the determination of an analog of vitamin D3 (Ro 24-2090) in plasma samples. The method employs liquid-liquid extraction, precolumn derivatization, HPLC separation using an automated column-switching system, and particle-beam negative ionization MS determination. An electron-capture derivatization reagent, 4-pentafluorobenzyl-1,2,4-triazoline-3,5-dione, is utilized to attain high sensitivity through a unique ionization mechanism. The method achieved a lower limit of quantitation of 25 pg (63 fmol) of Ro 24-2090 in plasma aliquots ranging from 0.125 to 1.0 ml. Method validation data were obtained for the quantitation of Ro 24-2090 in plasma from humans and seven animal species. Intraassay precision [mean percent relative standard deviation (%RSD)] ranged from 1.49 to 7.12% among the various species. Interassay precision (mean %RSD) ranged from 4.28 to 17.5%. Mean overall recovery ranged from 71 to 89%. The method has been successfully used to analyze plasma samples from several pharmacokinetic studies. The potential use of this method for determination of vitamin D2, vitamin D3, 1 alpha, 25-dihydroxyvitamin D3, and other drugs containing a diene structural moiety is discussed.

Animals↗

PubMed1996

Metabolic profiles of minimally absorbed orlistat in obese/overweight volunteers.

To determine the metabolic profile of minimally absorbed orlistat in obese/overweight patients, an open-label, single-dose study was performed in eight obese/overweight volunteers between 23 and 68 years of age. Each subject received a single oral dose of 360 mg orlistat containing approximately 400 muCi of 14C-labeled orlistat. Serial blood samples were collected at specified times over 10 hours after administration of orlistat for determination of total radioactivity, unchanged orlistat, and major metabolites in the plasma. Urine samples were collected over 24 hours and analyzed to evaluate the urinary recovery of total radioactivity and the profile of orlistat metabolites in the urine. In addition, all fecal samples were collected and analyzed for total radioactivity. Urinary and fecal recovery of the administered dose of total radioactivity were 1.13 +/- 0.50% (24-hour data only) and 96.4 +/- 18.1% (n = 7), respectively. Maximum observed concentration (Cmax) and time to Cmax (tmax) values of plasma total radioactivity were 150 +/- 51 ng.eq/mL and 6.8 +/- 1.5 hrs, respectively. All these parameters obtained in obese/ overweight subjects were similar to those reported previously in healthy subjects. On the basis of the area under the concentration-time curve from 0 to 10 hours (AUC0-10), two major metabolites comprise a total of approximately 42% of the total radioactivity in plasma. The primary metabolite (M1) has a short half-life (approximately 2 hours), whereas the secondary metabolite (M3) disappeared at a slower rate. No strikingly apparent difference in the urinary metabolic profile was observed between two gender groups. It is concluded that the disposition of orlistat appears to be similar between normal and obese/overweight subjects. Of the minimal fraction of the dose that was absorbed systemically, the presence of two major metabolites accounts for approximately 42%.

Absorption↗

PubMed1996

Interaction of geiparvarin and related compounds with purified microtubular protein.

Geiparvarin is an antiproliferative compound whose mechanism of action has not yet been identified. We have investigated the biochemical action on purified microtubular protein, as well as on tubulin, of geiparvarin and of some derivatives resulting from its conjugation with two synthetic oestrogens, diethylstilboestrol and meso-hexoestrol, in comparison with the antimicrotubular action of the reference oestrogens. Geiparvarin and derivatives did not inhibit colchicine binding to tubulin nor did they significantly influence GTP-induced polymerization. On the contrary, they effectively counteracted the stimulating effect of taxol on microtubule formation, both in the presence and in the absence of microtubule-associated proteins. A competitive inhibition mechanism at the taxol binding site of tubulin may thus be proposed to explain the antimicrotubular action of geiparvarin.

Animals↗

PubMed1995

Antimicrotubular effect of calvatic acid and of some related compounds.

A structure-activity relationship has been established between calvatic acid and some related synthetic compounds, and their ability to inhibit GTP-induced microtubular protein polymerization in vitro. These compounds were effective in a dose- and a time-dependent manner. The most active drug was the p-chloro substituted compound, which showed its inhibitory activity without any preincubation period, which the others needed. Since if cysteine was present, polymerization was no longer affected, an involvement of titratable -SH groups of tubulin could be suggested. In contrast, taxol-induced polymerization was only slightly inhibited by these compounds, and colchicine-binding activity was not generally impaired.

Animals↗

PubMed1995

Fibrous dysplasia: a case report.

Fibrous dysplasia is a benign fibro-osseous disorder that often affects both the maxilla and mandible. The dentist, therefore, is often the first person to identify and diagnose the disease. This article focuses on the pathology, diagnosis, clinical course, and treatment of this complex problem. A case report demonstrates the multidisciplinary approach to the management of this disease entity.

Adolescent↗

PubMed1993

Declining incidence of Haemophilus influenzae type b disease since introduction of vaccination.

OBJECTIVE: To determine the incidence of invasive Haemophilus influenzae type b disease in children living in Minnesota and Dallas County, Texas, before and since introduction of plain polysaccharide vaccine in 1985, and conjugate vaccine in 1988. Initially, use of these vaccines was limited to infants 18 months of age and older. DESIGN: Identification of culture-proven cases of H influenzae type b disease was through systems of active, laboratory-based surveillance. The mean incidence of disease (cases observed/100,000 child-years) for 1983 and 1984 served as a baseline for comparison with subsequent years through 1991. PARTICIPANTS: Children less than 5 years of age in Minnesota and Dallas County, Texas. Overall, there were 2557 confirmed age-eligible cases of invasive H influenzae type b disease from 1983 through 1991. RESULTS: Between the 1983-1984 baseline and 1991, the incidence of H influenzae type b disease decreased 85% in Minnesota and 92% in Dallas. Notably, declines in incidence were observed in children in the age group being vaccinated as well as in infants younger than 18 months of age prior to introduction of vaccination. CONCLUSION: In two widely separated areas of the United States, a profound decrease in the incidence of H influenzae type b disease has occurred. The data suggest that vaccination may be protecting against disease, as well as decreasing the spread of infection to unvaccinated infants.

Bacterial Capsules↗

PubMed1993

Comparative pharmacokinetics of ciprofloxacin, ofloxacin and pefloxacin in human aqueous humour.

Eighty-five patients undergoing cataract surgery were given for prophylaxis of intraocular infection two intravenous doses each of 200 mg, 300 mg or 400 mg ciprofloxacin (35 patients), 400 mg or 800 mg pefloxacin (30 patients), or 400 mg ofloxacin (20 patients). Ciprofloxacin levels in aqueous humour ranged from 0.02 to 0.50 microgram/ml, pefloxacin levels from 1.04 to 7.80 micrograms/ml, and ofloxacin levels from 0.44 to 2.27 micrograms/ml with ratios of aqueous humour to serum levels ranging from 3.8% to 25%, 21% to 48.1% and 44% to 88.4%, respectively. It is concluded that the quinolones studied might be suitable for surgical prophylaxis or treatment of anterior chamber infections due to Enterobacteriaceae, while ciprofloxacin at high doses is preferable for Pseudomonas aeruginosa infections.

Adult↗

PubMed1993

Cytoskeletal modifications induced by 4-hydroxynonenal.

The antiproliferative action of 4-hydroxynonenal (HNE) could be related to an interaction with cytoskeletal structures. In this paper the effects exerted by HNE on microtubules and on microfilaments are examined by immunofluorescence. HNE alters cell morphology causing both the depolymerization of the microtubular structures and the dissolution of the stress-fibres. Taxol protects microtubules, preventing the depolymerizing effect of the aldehyde. The action of HNE could be attributed to its affinity for sulphydryl groups, which are essential in maintaining tubulin and actin both in the polymerized form.

3T3 Cells↗

PubMed1992

Aldehyde-induced modifications of the microtubular system in 3T3 fibroblasts.

The molecular structure of aldehydes is closely related to their antimicrotubular effect. Morphological modifications of the microtubular system in living cells after incubation with certain aldehydes are consistent with biochemical alterations detected in previous research. The microtubular arrangement was visualized by an immunofluorescence technique with antitubulin antibodies, while the content of tubulin in the cells was evaluated by a colchicine binding assay. 2-Nonenal behaved similarly to 4-hydroxynonenal, a lipid peroxidation product, disorganizing microtubular network in 3T3 fibroblasts and decreasing the amounts of tubulin able to bind labelled colchicine. Nonanal did not significantly impair the tubulin characteristics in the cells, despite the fact that it has been shown to be active on the purified microtubular system; benzaldehyde was ineffective. This would appear to explain the mechanisms of interaction of aliphatic aldehydes which might be suitable for use as antimicrotubular drugs.

3T3 Cells↗

PubMed1991

Effects of some aldehydes on brain microtubular protein.

4-Hydroxynonenal is one of the main breakdown products of lipid peroxidation. It has an antiproliferative effect, which may partly be the consequence of an interaction with cytoskeletal structures. Its effects on microtubular protein are compared with those of homologous aldehydes with the same number of carbon atoms, and with that of benzaldehyde. Unlike the other aliphatic aldehydes, this latter aldehyde does not impair microtubular functions at every concentration in the range. Nonanal has the greatest effect on tubulin polymerization, whereas it only slightly impairs colchicine binding activity. 2-Nonenal and 4-hydroxynonenal have less inhibiting effect on tubulin polymerization; their effect on colchicine binding activity is dose-dependent. The targets of 4-hydroxynonenal on tubulin are -SH groups; the action mechanism of other aldehydes has not yet been identified.

Aldehydes↗

PubMed1991

Interaction of C-9 aldehydes with microtubular protein in vitro and in cultured cells in the presence of taxol.

Some aldehydes have previously been shown to alter the microtubular system in a concentration-dependent manner. This paper examines the effects of taxol on the impairment of in vitro functionality of microtubular protein and of cytoplasmic microtubules by C-9 aliphatic aldehydes. Taxol-induced polymerization was inhibited by aldehydes in a similar way to GTP-induced polymerization, even though to a different degree. The addition of taxol restored the ability of aldehyde-impaired tubulin to polymerize, but only in the presence of nonanal. Colchicine binding activity in the presence of taxol was slightly modified by aldehydes at 20 degrees C, while it increased at 37 degrees C, compared to controls. Immunofluorescence showed a low disruption of microtubules in fibroblasts incubated with aldehydes and pretreated with taxol, probably as a consequence of its stabilizing activity. Anyway, aldehydes studied behaved differently, indicating a structure-activity relationship.

3T3 Cells↗

PubMed1990

4-Hydroxynonenal interacts with tubulin by reacting with its functional -SH groups.

4-Hydroxynonenal, which is one of the most important products of lipid peroxidation, alters microtubular organization and structure in 3T3 fibroblasts. Changes in cell shape and the disappearance of microtubules are observed by immunofluorescence after incubation with the aldehyde, and the colchicine binding activity of tubulin from 3T3 cells is modified. Moreover, the aldehyde determines a decrease in the ability of purified tubulin to polymerize and to bind colchicine. These effects may be related to the interaction of the aldehyde with functional -SH groups of tubulin which are necessary for protein integrity and functions. Indeed, the addition of cysteine protects against the damaging effects of the aldehyde.

Aldehydes↗

PubMed1990

The fine structural localization of endogenous and exogenous peroxidase activity in human bone marrow mast cells under pathological conditions.

We have examined the ultrastructural characteristics of peroxidase activity in human bone marrow mast cells. These studies were performed in three patients with systemic mast cell disease, and in another six patients showing bone marrow mast cell hyperplasia. Endogenous peroxidase activity was localized in the perinuclear cisternae and strands of endoplasmic reticulum, but never in the granules. We have also demonstrated the "in vivo" existence of exogenous peroxidase activity in two of the three cases of systemic mast cell disease. The peroxidase internalization involved its binding to the plasma membrane, followed by its incorporation into the cell by a general endocytic process comprising the uptake of dispersed peroxidase-positive material mainly by phagocytosis of granular structures containing peroxidase. The exogenous peroxidase appeared in non-membrane bound granules, vacuoles or aggregates, but we have never seen the enzyme linked to the mast cell granules.

Adult↗