PubMed Health⌕ Search

Biomedical subjects

M Nesi

Publications and source records attributed to M Nesi.

12 recordsLinked to original sources
PubMed2002

Solid-supported reagents for multi-step organic synthesis: preparation and application.

Since the early days of combinatorial chemistry solid-phase organic synthesis has been the method of choice for the production of large libraries. Solution-phase synthesis is again gaining importance especially for the synthesis of parallel arrays of smaller, focussed libraries containing single compounds with high degrees of purity. In the field of solution-phase library generation, the use of solid-supported reagents, catalysts and scavengers is emerging as a leading strategy, combining the advantages of both solid-phase organic synthesis (e.g. allowing the employment of an excess of reagent without the need for additional purification steps) and solution-phase chemistry (e.g. the ease of monitoring the progress of the reactions by applying LC-MS, TLC or standard NMR techniques). An account of some of the most recent advances in this area of research will be presented.

Combinatorial Chemistry Techniques↗
PubMed1998

PNU 157706, a novel dual type I and II 5alpha-reductase inhibitor.

PNU 157706 is a novel dual inhibitor of 5alpha-reductase (5alpha-R), the enzyme responsible for the conversion of testosterone (T) to 5alpha-dihydrotestosterone (DHT). Tested on a crude preparation of human or rat prostatic 5alpha-R, PNU 157706 caused enzyme inhibition with IC50 values of 20 and 34 nM, respectively, compared to the values of 32 and 58 nM shown by finasteride. Furthermore, PNU 157706 was highly potent in inhibiting human recombinant 5alpha-R type I and II isozymes, showing IC50 values of 3.9 and 1.8 nM and, therefore, it was several folds more potent than finasteride (IC50 values of 313 and 11.3 nM), particularly on the type I isozyme. PNU 157706 was shown to have no binding affinity for the rat prostate androgen receptor (RBA 0.009% that of DHT). In adult male rats, a single oral dose of 10 mg/kg of PNU 157706 caused a marked and longer lasting reduction of prostatic DHT than did finasteride (at 24 h inhibition by 89 and 47%, respectively). In prepubertal, T- or DHT-implanted castrated rats, PNU 157706, given orally for 7 days at the dose of 10 mg/kg/day, markedly reduced ventral prostate weight in T- but not in DHT-implanted animals, thus showing to be devoid of any anti-androgen activity. In adult rats treated orally for 28 days, PNU 157706 resulted markedly more potent (16-fold) than finasteride in reducing prostate weight, the ED50 values being 0.12 and 1.9 mg/kg/day, respectively. These results indicate that PNU 157706 is a promising, potent inhibitor of both type II and I human 5alpha-R with a very marked antiprostatic effect in the rat.

5-alpha Reductase Inhibitors↗
PubMed1996

FCE 28260, a new 5 alpha-reductase inhibitor: in vitro and in vivo effects.

FCE 28260 is a novel inhibitor of 5 alpha-reductase (5 alpha R), the enzyme responsible for the conversion of testosterone (T) to 5 alpha-dihydrotestosterone (DHT). The compound caused inhibition of rat and human prostatic enzymes, with IC50 values of 15 and 16 nM, respectively, compared to the values of 30 and 52 nM shown by finasteride. Furthermore, FCE 28260 was highly potent in inhibiting human recombinant 5 alpha R type 2 and 1 isozymes, showing IC50 values of 3.3 and 36 nM, and therefore it was more potent than finasteride (IC50 values of 8.5 and 470 nM) on both isozymes. In prepubertal, T-implanted castrated rats, FCE 28260, given orally for 7 days, reduced ventral prostate growth with an ED50 of 0.8 mg/kg, i.e. five times lower than that shown by finasteride. No anti-androgenic activity in DHT-implanted castrated rats was found up to 10 mg/kg/day. In adult male rats, FCE 28260 reduced prostatic DHT concentrations 6 h after oral dosing with a potency similar to that of finasteride (65% reduction at 1 mg/kg) but was found to be markedly more potent than the reference compound at 24 h (74% reduction in prostate DHT at 10 mg/kg, compared to 26% reduction induced by finasteride). These results indicate that FCE 28260 represents a marked improvement over finasteride.

5-alpha Reductase Inhibitors↗
PubMed1994

Preparative isoelectric focusing in multicompartment electrolyzers: novel, hydrolytically stable and hydrophilic isoelectric membranes.

Preparative isoelectric focusing in multicompartment electrolyzers is based on the production of isoelectric membranes of precise isoelectric point, able to buffer at their pI value and to titrate proteins tangent to or crossing the membranes. Up to the present, such membranes have been based on polyacrylamide chemistry; acrylamide, however, is neither stable in acidic nor basic environments. We describe here novel membranes, produced with a unique monomer, N-acryloylaminoethoxyethanol (AAEE). Poly(AAEE) membranes are extremely stable to alkaline hydrolysis (500 times more stable than polyacrylamide) and even more hydrophilic than the latter matrix. This allows production of highly reproducible membranes (these do not change their pI with time, since no acrylic acid is produced by hydrolysis upon storage) which do not adsorb proteins by hydrophobic interaction.

Acrylic Resins↗
PubMed1994

Towards new formulations for polyacrylamide matrices: N-acryloylaminoethoxyethanol, a novel monomer combining high hydrophilicity with extreme hydrolytic stability.

Matrices for electrokinetic separations, based on a unique class of mono- and disubstituted (on the amido nitrogen) acrylamides such as e.g., N-acryloylaminoethoxyethanol (AAEE) and acrylamido-N,N-diethoxyethanol, offer the following advantages: (i) strong resistance to alkaline hydrolysis (most zone separations occurring at basic pH values), (ii) high hydrophilicity and (iii) greater porosity, due to the higher molecular weight of the monomers. When compared with conventional poly(acrylamide), a poly(AAEE) matrix, when subjected to mild alkaline hydrolysis (0.1 N NaOH, 70 degrees C) appears to be 500 times more stable. Such stability is also confirmed under strong alkaline hydrolysis (1 N NaOH, 100 degrees C) as well as under mild and strong acidic hydrolysis. Mildly hydrolyzed poly(AAEE) matrices still perform extremely well in both conventional isoelectric focusing and immobilized pH gradients, techniques which are quite sensitive to traces of acrylate in the polymer coil. Conversely, mildly hydrolyzed poly(acrylamide) matrices, when used in isoelectric focusing, generate pH gradients between pH 4 and 5, having an inflection point (pH 4.6) equivalent to the pK value of acrylic acid. This novel class of monomers shows great promise for future applications in all electrokinetic methodologies.

Acrylamides↗
PubMed1994

Capillary zone electrophoresis of DNA fragments in a novel polymer network: poly(N-acryloylaminoethoxyethanol).

Migration of DNA fragments in the 51 to 21226 bp size range has been investigated by capillary zone electrophoresis in entangled solutions of linear poly(N-acryloylaminoethoxyethanol) from 8 to 16%. Plots of log mobility vs. log size (in base pairs, bp) clearly evidence three different migration regimes: according to Ogston (i.e. as spherical globules) up to 200 bp, reptation without stretching up to 3-4000 bp and reptation with partial stretching for larger fragments. Guidelines on the % polymer to be used for optimum resolution can be obtained from plots of peak spacing (in seconds per base pair) vs. % of polymer in solution and from standard plots of peak resolution vs. % polymer. An optimum linear poly(N-acryloylaminoethoxyethanol) concentration, allowing for good resolution of most fragments, from small to large, is found in the range 10% to 12% polymer (as opposed to conventional polyacrylamide, where a sharp maximum is obtained at 6% polymer). It is hypothesized that in situ polymerization allows for formation of a large distribution of polymer sizes, thus facilitating simultaneous separation of short and long DNA fragments based on the principle that shorter polyacrylamide chains will sieve shorter DNA fragments and vice versa. Due to the fact that the novel monomer is 500 times more resistant to hydrolysis and more hydrophilic than acrylamide, its polymeric solutions allow repeated sample injections (> 35) with minimal absolute standard deviations (of the order of +/- 3%). No carry-over nor sample precipitation at the injection port is experienced with the new matrix composed of poly(N-acryloylaminoethoxyethanol).

Acrylic Resins↗
PubMed1994

Capillary electrophoresis of polymerase chain reaction-amplified products in polymer networks: the case of Kennedy's disease.

In Kennedy disease (an X-linked motoneuronal disorder associated with an increase in the number of (CAG)n triplet repeats in the first exon of the Androgen receptor gene; about twice as many as in normal conditions), polymerase chain reaction-amplified genic products exhibit two DNA fragments in the heterozygous female carriers, one with a range between 468 and 495 bp in the normal polymorphic population and a fragment corresponding to the pathological state that reaches 573 bp. These fragments are easily separated by gel-slab electrophoresis and detected by intercalating dye staining (ethidium bromide). As an alternative procedure, capillary zone electrophoresis in polymer networks, consisting of 8% polyacryloylaminoethoxyethanol at 0% cross-linker, offers a simple procedure for separation and on-line detection via UV absorbance at 254 nm, thus avoiding additional staining steps. The capillary column can be repeatedly used for up to 80-100 times and the electropherogram is stored on a magnetic support. Easy comparison among different runs is obtained by aligning all tracings to an internal standard of a 650 bp fragment added as a marker.

Acrylic Resins↗
PubMed1994

Novel aromatase and 5 alpha-reductase inhibitors.

Inhibitors of aromatase and 5 alpha-reductase may be of use for the therapy of postmenopausal breast cancer and benign prostatic hyperplasia, respectively. FCE 27993 is a novel steroidal irreversible aromatase inhibitor structurally related to exemestane (FCE 24304). The compound was found to be a very potent competitive inhibitor of human placental aromatase, with a Ki of 7.2 nM (4.3 nM for exemestane). In preincubation studies with placental aromatase FCE 27993, like exemestane, was found to cause time-dependent inhibition with a higher rate of inactivation (t1/2 4.5 vs 15.1 min) and a similar Ki(inact) (56 vs 66 nM). The compound was found to have a very low binding affinity to the androgen receptor (RBA 0.09% of dihydrotestosterone) and, in contrast to exemestane, no androgenic activity up to 100 mg/kg/day s.c. in immature castrated rats. Among a series of novel 4-azasteroids with fluoro-substituted-17 beta-amidic side chains, three compounds, namely FCE 28260, FCE 28175 and FCE 27837, were identified as potent in vitro and in vivo inhibitors of prostatic 5 alpha-reductase. Their IC50 values were found to be 16, 38 and 51 nM for the inhibition of the human enzyme, and 15, 20 and 60 nM for the inhibition of the rat enzyme, respectively. When given orally for 7 days in castrated and testosterone (Silastic implants) supplemented rats, the new compounds were very effective in reducing prostate growth. At a dose of 0.3 mg/kg/day inhibitions of 42, 36 and 41% were caused by FCE 28260, FCE 28175 and FCE 27837, respectively.

5-alpha Reductase Inhibitors↗
PubMed1993

Determination of total vitamin C in fruits by capillary zone electrophoresis.

A simple capillary zone electrophoretic (CZE) method is described for the rapid determination of ascorbic acid and dehydroascorbic acid, the physiologically active forms of vitamin C, in fruits. The electrophoretic run was accomplished in 9 min on a coated capillary column using 20 mM phosphate buffer (pH 7.0). Total ascorbic acid was determined by first reducing the dehydroascorbic acid to ascorbic acid by treatment with DL-homocysteine. This reaction was complete in 15 min and total ascorbic acid determination was performed immediately. The data obtained by CZE were in good agreement with HPLC data.

Ascorbic Acid↗
PubMed1992

17 beta-acylurea derivatives of 4-azasteroids as inhibitors of testosterone 5 alpha-reductase.

A series of 17 beta-acylurea-4-aza-5 alpha-androstan-3-one derivatives has been assayed in vitro as inhibitors of testosterone 5 alpha-reductase, using the particulate fraction of human hyperplastic prostate and rat prostate as enzyme sources. The most active derivatives were 1-[4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carbonyl]- 1,3-dicyclohexylurea (compound 1) and 1-[4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carbonyl]- 1,3-diisopropylurea (compound 3) which demonstrated IC50 values of 41 and 55 nM for the human enzyme and of 83 and 53 nM for the rat enzyme, respectively. Neither compound showed any relevant binding affinity to the rat prostate androgen receptor (IC50 of approximately 100 and 84 microM). When given orally in immature castrated rats together with subcutaneous testosterone propionate (TP) for 7 consecutive days, compound 3 (laboratory code FCE 26073), at 3 mg/kg/day, significantly decreased the ventral prostate growth promoting effect of TP by 40-50%, whereas compound 1 was ineffective up to the dose of 10 mg/kg/day.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMedDate not supplied

Capillary electrophoresis of macromolecules in 'syrupy' solutions: facts and misfacts.

'Syrupy' solutions of liquid linear polyacrylamide (> or = 10%T, 0%C) appear to be excellent for fractionation of oligonucleotides and, potentially, for DNA sequencing. For such analyses, the silica wall must be coated by covalently bound strings of polyacrylamide; otherwise, the electroosmotic flow will slowly pump out the viscous electrolyte solution. Due to the enormous viscosity (100 Pa s for an 8% T solution) the polymer strings must be prepared in situ, by filling the capillary with the appropriate monomer solution. The reaction, however, cannot be driven to better than 80-85% conversion: in 10%T, the concentration of unreacted monomers will thus be 200-300 mM. This will give a substantial background absorbance (even at 254 nm) and leave a huge amount of potentially harmful reacting species in the background electrolyte. A chemical scavenging method is proposed here: after polymerization, a 100 mM solution of cysteine is driven in from the cathode and allowed to react for up to 10 h. At the end of the reaction period, the excess cysteine and its acrylamido adduct are driven out electrophoretically and the column is reconstituted with its normal background electrolyte. Columns thus preconditioned have been found to perform extremely well and to last as long as the inner coating (and the linear polymer filling) will last. No 'carry over' from run to run was experienced.

Acrylic Resins↗