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Biomedical subjects

T Järvinen

Publications and source records attributed to T Järvinen.

At least 19 recordsLinked to original sources
PubMed2006

In vitro evaluation of the effect of cyclodextrin complexation on pulmonary deposition of a peptide, cyclosporin A.

The effect of hydroxypropyl-alpha-cyclodextrin (HP-alpha-CD) complexation on in vitro pulmonary deposition of a cyclic peptide cyclosporin A (CsA) was studied. In addition, the effect of storage (32 days, 40 degrees C, 75% RH) on CsA/HP-alpha-CD complexes was studied. The complexation of CsA with CDs was evaluated by a phase-solubility method. Solid CsA/HP-alpha-CD complexes were prepared by freeze drying. Three inhalation formulations were prepared: CsA/lactose reference formulation (LF) (drug:carrier 1:364, w/w), CsA/HP-alpha-CD complex formulation (CDF) (drug:CD 1:269, w/w) and CsA/HP-alpha-CD complex/lactose formulation (CDLF) (complex:carrier 100:114, w/w). The inhalation studies were performed in vitro using Andersen Sampler (Ph. Eur.) and Taifun multi-dose dry powder inhalers (DPIs). Before the storage, the respirable fraction value (RF%) of CsA was 19.8+/-0.7%, 33.0+/-7.0% and 34.6+/-1.1% (mean+/-S.D., n=4 x 20) with LF, CDF and CDLF, respectively. When exposed to moisture (storage in a permeable polystyrene tube), the RF% values of CsA from formulations containing CsA/HP-alpha-CD complexes were lower than before the storage. However, when stored in the Taifun DPI, the RF% value of CsA from any of the formulations did not decrease. In conclusion, an acceptable RF% value of a peptide CsA from freeze-dried, simply micronized CsA/HP-alpha-CD complex powder was achieved before and after storage in the DPI.

Administration, Inhalation↗
PubMed2005

Targeting the cannabinoid CB2 receptor: mutations, modeling and development of CB2 selective ligands.

Since the discovery of the cannabinoid CB2 receptor in 1993, there has been a growing interest to clarify the importance of this G-protein coupled receptor (GPCR) for human physiology, and to investigate it as a possible target for current and future drug development. Several mutation studies have examined the receptor activation and structure of the receptor binding cavity. Additionally, 3D models for the CB2 receptor have been constructed to aid in perceiving important ligand-receptor interactions. In recent years, many research groups have succeeded in synthesizing new CB2 selective ligands. This review focuses on (i) important features for ligand recognition and/or receptor activation at CB2, derived from mutation and modeling studies, and (ii) recent advances in the field of CB2 selective ligands.

Animals↗
PubMed2004

Chemical and enzymatic stability evaluation of lipoamino acid esters of idebenone.

Lipophilic conjugates of idebenone (IDE) with short-chain alkylamino acids were previously synthesized and evaluated in vitro for their antioxidant properties. In this study, their susceptibility to chemical and enzymatic hydrolysis was evaluated. Results indicated that these derivatives release the parent drug quantitatively via enzymatic hydrolysis by serum and liver esterases, with a cleavage rate related to the length of the alkyl side chain. Consequently, the present lipoamino acid conjugates of IDE are prodrugs and their in vivo effects are mediated through the parent compound released in the body.

Amino Acids↗
PubMed2002

[Pathophysiology of overuse tendon injury].

Overuse tendon injury is one of the most common injuries in sports. The etiology as well as the pathophysiological mechanisms leading to tendinopathy are of crucial medical importance. At the moment intrinsic and extrinsic factors are assumed as mechanisms of overuse tendon injury. Except for the acute, extrinsic trauma, the chronic overuse tendon injury is a multifactorial process. There are many other factors, such as local hypoxia, less of nutrition, impaired metabolism and local inflammatory that may also contribute to the development of tissue damage. The exact interaction of these factors cannot be explained entirely at the moment. Further studies will be necessary in order to get more information.

Achilles Tendon↗
PubMed2002

Reliability of the tissue microarray based FISH for evaluation of the HER-2 oncogene in breast carcinoma.

AIMS: Tumour tissue microarray allows the analysis of hundreds of tumour samples simultaneously on a single microscope slide. However, the extremely small tissue samples taken from the original tissue may not always be representative of the entire tumour. METHODS: The reliability of this new technology was investigated by analysing HER-2 oncogene amplification by fluorescence in situ hybridisation (FISH) from representative slides of the whole tumour and small tissue core biopsies from 29 invasive breast tumours. RESULTS: The tissue microarray method had high accuracy; in only one of 29 cases (3.4%; 95% confidence interval, 0% to 10%) were the results discordant with whole tumour analysis. CONCLUSION: Tumour microarray is a highly reliable method for analysing HER-2 oncogene amplification by FISH in human breast tumours.

Biomarkers↗
PubMed2001

Complexation with tolbutamide modifies the physicochemical and tableting properties of hydroxypropyl-beta-cyclodextrin.

The physicochemical and tableting properties of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and its tolbutamide (TBM) complex were studied. The kinetics of TBM/HP-beta-CD inclusion complex formation in solution were determined by the phase solubility method. Solid complexes were prepared by freeze-drying and spray-drying. Water sorption-desorption behaviour of the materials were studied and compacts were made using a compaction simulator. TBM and HP-beta-CD formed 1:1 inclusion complexes in aqueous solution with an apparent stability constant of 63 M(-1). HP-beta-CDs and TBM/HP-beta-CD complexes were amorphous whereas the freeze-dried and spray-dried TBMs were polymorphic forms II and I, respectively. Sorption-desorption studies showed that HP-beta-CDs were deliquescent at high relative humidities. TBM/HP-beta-CD complexes had slightly lower water contents at low relative humidities than the physical mixtures. However, at high humidities their water sorption and desorption behaviours were similar to those of corresponding physical mixtures, indicating a glass transition of the complexed materials. TBM/HP-beta-CD complexes demonstrated a worse compactability than similarly prepared HP-beta-CDs or physical mixtures. Also particle properties that resulted from these preparation methods affected the compactability of the materials. In conclusion, the physicochemical and tableting properties of HP-beta-CD were modified by complexation it with TBM.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2001

Effects of calcium and lipophilicity on transport of clodronate and its esters through Caco-2 cells.

Clodronate, like other bisphosphonates, is poorly absorbed from the gastrointestinal tract, mainly due to its high hydrophilicity and ability to form complexes with divalent cations in the gastrointestinal tract. One strategy for improving oral absorption of these types of molecules is to develop more lipophilic derivatives. The importance of lipophilicity and calcium chelation in the absorption of clodronate was evaluated by studying the penetration of clodronate and its mono-, di-, and triphenyl esters through human intestinal Caco-2 cells. The transport rates of [(14)C]-clodronate and its mono-, di-, and triphenyl esters were quantified by calculating their apparent permeability coefficients (P(app)) both in normal (1.3 mM) calcium concentration and in 'minimum-calcium model'. The transport rate of 1 mM clodronate was very low (0.25 x 10(-7) cm/s), while the removal of calcium from the apical side increased this transport rate 6-fold. The transport rate of clodronate was increased with increasing dose. Mono- and diphenyl esters did not significantly enhance the transport of clodronate. Triphenyl ester, however, increased the transport rate 17-fold compared with parent clodronate. Removal of calcium did not affect the transport rates of di- or triphenyl esters, which indicated that the esterification of hydroxyl groups of clodronate decreased calcium complex formation. These results indicate that clodronate is transported paracellularly through Caco-2 cells and that calcium decreases strongly its absorption. They further suggest that at least three phosphate hydroxyl groups need to be substituted until the permeation route is changed from paracellular to transcellular.

Analgesics, Non-Narcotic↗
PubMed2001

Effects of topical anandamide-transport inhibitors, AM404 and olvanil, on intraocular pressure in normotensive rabbits.

PURPOSE: To evaluate the effects of topically applied anandamide transport inhibitors, AM404 and olvanil, on the intraocular pressure (IOP) of normotensive rabbits. To determine if the ocular hypotension induced by topical anandamide (AEA) can be potentiated by co-administered AM404. METHODS: Test compounds, in either hydroxypropyl-beta-cyclodextrin (HP-beta-CD) or propylene glycol, were administered unilaterally onto rabbit eyes. To determine if AM404 affects the IOP-profile of AEA, AM404 was administered ocularly 15 minutes before topical AEA. Phenylmethylsulfonyl fluoride (PMSF) (24 mg/kg, s.c.) was given 30 min before AEA to prevent its catabolism. IOPs of the treated and untreated eyes were measured. The cannabinoid agonist activities of AM404 and olvanil were studied by using [35S]GTPyS autoradiography. RESULTS: Topical AM404 (62.5 micirog), in HP-beta-CD vehicle, decreased IOP significantly in treated eyes. AM404 (62.5 microg) induced a significant IOP increase without subsequent decrease when given in propylene glycol vehicle. Olvanil (312.5 microg) caused a significant IOP reduction without provoking an initial hypertensive phase. These compounds did not significantly affect the IOP of untreated eyes. Co-administered AM404 (125 microg in HP-beta-CD) had no significant effect on the IOP profile of AEA (62.5 microg). CONCLUSIONS: Ocular administration of AM404 or olvanil decreased IOP in rabbits, although AM404 can provoke an initial ocular hypertension and did not potentiate the IOP responses induced by exogenous AEA.

Administration, Topical↗
PubMed2001

Despite substantial degradation, 2-arachidonoylglycerol is a potent full efficacy agonist mediating CB(1) receptor-dependent G-protein activation in rat cerebellar membranes.

1. Two endocannabinoids, arachidonoyl ethanolamide (AEA) and 2-arachidonoylglycerol (2-AG) bind and activate G-protein-coupled cannabinoid receptors, but limited data exist on their relative ability to activate G-proteins. 2. Here we assess agonist potency and efficacy of various cannabinoids, including 2-AG, HU-310 (2-arachidonoyl glyceryl ether, a third putative endocannabinoid), HU-313 (another ether analogue of 2-AG), AEA, R-methanandamide (an enzymatically stable analogue of AEA), and CP-55,940 at rat brain CB(1) receptors using agonist-stimulated [(35)S]-GTPgammaS binding to cerebellar membranes and whole brain sections. Degradation of endocannabinoids under experimental conditions was monitored by HPLC. 3. To enhance efficacy differences, agonist dose-response curves were generated using increasing GDP concentrations. At 10(-6) M GDP, all compounds, except HU-313, produced full agonists responses approximately 2.5 fold over basal. The superior efficacy of 2-AG over all other compounds became evident by increasing GDP (10(-5) and 10(-4) M). 4. In membrane incubations, 2-AG was degraded by 85% whereas AEA and HU-310 were stable. Pretreatment of membranes with phenylmethylsulphonyl fluoride inhibited 2-AG degradation, resulting in 2 fold increase in agonist potency. Such pretreatment had no effect on AEA potency. 5. Responses in brain sections were otherwise consistent with membrane binding data, but 2-AG evoked only a weak signal in brain sections, apparently due to more extensive degradation. 6. These data establish that even under conditions of substantial degradation, 2-AG is a full efficacy agonist, clearly more potent than AEA, in mediating CB(1) receptor-dependent G-protein activity in native membranes.

Animals↗
PubMed2001

Synthesis and in-vitro/in-vivo evaluation of orally administered entacapone prodrugs.

Entacapone is a new inhibitor of catechol-O-methyltransferase (COMT) that is used as an adjunct to L-dopa therapy in the treatment of Parkinson's disease. The bioavailability of orally administered entacapone is, however, relatively low (29-46%). In this study we have prepared more lipophilic acyl and acyloxyacyl esters, an acyloxy alkyl ether and an alkyloxycarbonyl ester of entacapone, and we have evaluated them as potential prodrugs to enhance the oral bioavailability of entacapone. All the derivatives fulfilled prodrug criteria and released entacapone in human serum in-vitro. The oral bioavailability of monopivaloyl (1a) and dipivaloyl (1b) esters of entacapone were investigated further in rats. The lipophilicity of 1b was high (log Papp 4.0 at pH 7.4) but its oral bioavailability was low (F = 0.6%), most probably due to its low aqueous solubility. The monopivaloyl ester of entacapone (1a) had a higher lipophilicity (log Papp 0.80) than entacapone (log Papp 0.18) at pH 7.4 while maintaining an aqueous solubility equal to entacapone. However, oral bioavailability was not increased when compared with the parent drug entacapone (F = 7.0% and 10.4%, respectively).

Administration, Oral↗
PubMed2000

Synthesis of a water-soluble prodrug of entacapone.

Entacapone was reacted with phosphorous oxychloride in dry pyridine to yield a phosphate ester. The phosphate promoiety increased aqueous solubility of the parent drug by more than 1700- and 20-fold at pH 1.2 and 7.4, respectively. The phosphate ester provides adequate stability (t(1/2) = 2227 h; pH 7.4) towards chemical hydrolysis, and allowed for release of the parent drug via enzymatic hydrolysis in liver homogenate.

Catechol O-Methyltransferase Inhibitors↗
PubMed2000

Cross-cultural music cognition: cognitive methodology applied to North Sami yoiks.

This article is a study of melodic expectancy in North Sami yoiks, a style of music quite distinct from Western tonal music. Three different approaches were taken. The first approach was a statistical style analysis of tones in a representative corpus of 18 yoiks. The analysis determined the relative frequencies of tone onsets and two- and three-tone transitions. It also identified style characteristics, such as pentatonic orientation, the presence of two reference pitches, the frequency of large consonant intervals, and a relatively large set of possible melodic continuations. The second approach was a behavioral experiment in which listeners made judgments about melodic continuations. Three groups of listeners participated. One group was from the Sami culture, the second group consisted of Finnish music students who had learned some yoiks, and the third group consisted of Western musicians unfamiliar with yoiks. Expertise was associated with stronger veridical expectations (for the correct next tone) than schematic expectations (based on general style characteristics). Familiarity with the particular yoiks was found to compensate for lack of experience with the musical culture. The third approach simulated melodic expectancy with neural network models of the self-organizing map (SOM) type (Kohonen, T. (1997). Self-organizing maps (2nd ed.). Berlin: Springer). One model was trained on the excerpts of yoiks used in the behavioral experiment including the correct continuation tone, while another was trained with a set of Finnish folk songs and Lutheran hymns. The convergence of the three approaches showed that both listeners and the SOM model are influenced by the statistical distributions of tones and tone sequences. The listeners and SOM models also provided evidence supporting a core set of psychological principles underlying melody formation whose relative weights appear to differ across musical styles.

Adult↗
PubMed2000

Synthesis and in vitro evaluation of novel morpholinyl- and methylpiperazinylacyloxyalkyl prodrugs of 2-(6-methoxy-2-naphthyl)propionic acid (Naproxen) for topical drug delivery.

Various novel morpholinyl- (3a,b) and methylpiperazinylacyloxyalkyl (3c-f) esters of 2-(6-methoxy-2-naphthyl)propionic acid were synthesized and evaluated in vitro for topical drug delivery as potential prodrugs of naproxen (1). Compounds 3a-f were prepared by coupling the corresponding naproxen hydroxyalkyl ester with the morpholinyl- or (4-methyl-1-piperazinyl)acyl acid in the presence of dicyclohexylcarbodiimide (DCC) and 4-(dimethylamino)pyridine (DMAP) and quantitatively hydrolyzed (t(1/2) = 1-26 min) to naproxen in human serum. Compounds 3c-f showed higher aqueous solubility and similar lipophilicity, determined by their octanol-buffer partition coefficients (log P(app)), at pH 5.0 when compared to naproxen. At pH 7.4 they were significantly more lipophilic than naproxen. The best prodrug 3c led to a 4- and 1.5-fold enhancement of skin permeation when compared to naproxen at pH 7.4 and 5.0, respectively. The present study indicates using a methylpiperazinyl group yields prodrugs that are partially un-ionized under neutral and slightly acidic conditions, and thus, a desirable combination is achieved in terms of aqueous solubility and lipophilicity. Moreover, the resulting combination of biphasic solubility and fast enzymatic hydrolysis of the methylpiperazinylacyloxyalkyl derivatives gave improved topical delivery of naproxen.

Administration, Topical↗
PubMed2000

Piperazinylalkyl prodrugs of naproxen improve in vitro skin permeation.

Novel morpholinyl (4a) and piperazinylalkyl (4b-e) esters were synthesized and evaluated in vitro for their properties as bioreversible topically administered dermal prodrugs of naproxen. These ionizable prodrugs exhibited various aqueous solubilities and lipophilicities, depending on the pH of medium. As indicated by octanol-buffer partition coefficients (logP(app)) at pH 7.4, all of the prodrugs were significantly more lipophilic (logP(app)=0.7-3.9) than naproxen (logP(app)=0.3). Furthermore, the most aqueous of the soluble prodrugs (4b-d) were only 2-3-fold less soluble in an aqueous buffer of pH 7.4 ( approximately 30-50 mM) than was naproxen ( approximately 100 mM). At a pH of 5.0, prodrugs showed a generally higher aqueous solubility and similar logP(app) values, compared to naproxen. The chemical and enzymatic hydrolysis of prodrugs at 37 degrees C was investigated in aqueous buffer solutions (pH 5.0 and 7.4) and in 80% human serum (pH 7.4), respectively. The prodrugs showed moderate chemical stability (t(1/2)=15-150 days at pH 5.0), and they were hydrolyzed enzymatically to naproxen, with half-lives ranging from 0.4 to 77 min. In permeation studies using post-mortem human skin in vitro, the flux of naproxen was 6.5 and 1.6 nmol/cm(2). h in a saturated aqueous buffer vehicle of pH 7.4 and 5.0, respectively. Among the prodrugs, two piperazinyl derivatives (4c and 4d) resulted in a 9- and 4-fold enhancement of permeation, respectively, when compared to naproxen itself at pH 7.4. 4c also resulted in a significantly (4-fold) better permeation than naproxen at pH 5.0. In conclusion, piperazinyl esters improved skin permeation of naproxen and are promising prodrugs of naproxen for topical drug delivery.

Administration, Cutaneous↗
PubMed2000

Bisphosphonate prodrugs: synthesis and in vitro evaluation of alkyl and acyloxymethyl esters of etidronic acid as bioreversible prodrugs of etidronate.

The synthesis and preliminary evaluation of novel alkyl and acyloxymethyl esters of etidronic acid as etidronate prodrugs is reported. Tetramethyl ester of etidronic acid was found be isomerized at pH 7.4 and P-C-P bridge was rearranged to P-C-O-P. This unwanted process was prevented via acylation of the bridging carbon's alcohol group. Acylation showed to be stable if one or more phosphonic OH- groups were substituted. However, when none of the phosphonic OH- groups were substituted, the acylation was chemically hydrolysed and the parent drug was released. This finding was successfully applied in the design of tetrapivaloyloxymethyl ester of acetylated etidronic acid which released etidronic acid via enzymatic (first step) and chemical (second step) hydrolysis in liver homogenate. However, the corresponding tri-substituted pivaloyloxymethyl ester having adequate water-solubility and lipophilicity (logP(app) 0.6 at pH 7.4), is probably the most potential prodrug candidate reported to enhance the oral bioavailability of etidronate.

Animals↗
PubMed2000

Relation between myofibers and connective tissue during muscle injury repair.

The connective tissue framework in skeletal muscle combines the contractile myofibers into a functional unit, in which the contraction of myofibers is transformed into movement via myotendinous junctions (MTJs) at their ends, where myofibers attach to tendons/fascia. The cytoskeletal contractile myofilament apparatus adheres through subsarcolemmal and transmembrane molecules to the surrounding extracellular matrix, with integrin and dystrophin associated chains of molecules being the two main adhesion complexes. In shearing type of muscle injury both myofibers and the connective tissue framework are ruptured and thereby the functional tendon-muscle-tendon units are disrupted. The stumps of the ruptured myofibers are separated and at the same time joined by a connective tissue scar, through which the ends of regenerating myofibers try to pierce, but as the scar becomes more compact the ends attach to the scar by new mini-MTJs. During the early phase ruptured myofibers try to compensate for the lost MTJ attachment by reinforcing their integrin mediated lateral adhesion, which returns to normal low level after formation of the mini-MTJs and at which time complementary increase of dystrophin and associated molecules on lateral sarcolemma takes place. The stumps appear to remain separated by and attached to the interposed scar for many months, possibly for ever, i.e. the original tendon-muscle-tendon units may have become permanently divided into two consecutive units. Remarkably, axon sprouts are able to penetrate through the interposed scar to form new neuromuscular junctions on those abjunctional stumps which were denervated by the rupture.

Athletic Injuries↗
PubMed1999

Bisphosphonate prodrugs: synthesis and in vitro evaluation of novel acyloxyalkyl esters of clodronic acid.

Novel tetra-, tri-, and P,P'-dipivaloyloxymethyl esters of clodronic acid were synthesized, and their properties as possible prodrugs of clodronate were evaluated in vitro. All pivaloyloxymethyl esters were significantly more lipophilic (log P(app) ranged from -2.1 to 7. 4) than clodronate (log P(app) < or = -5.4), which suggests that it may be possible to change the intestinal absorption mechanism of clodronate from a paracellular to a transcellular pathway by a prodrug approach. Pivaloyloxymethyl esters degraded rapidly in 10% rabbit liver homogenate, and half-lives of tri- and P,P'-diesters were 1.1 and 14 min, respectively. The intermediate degradation products were further degraded, and clodronic acid was released in quantitative amounts. In human serum, the stability of pivaloyloxymethyl esters was comparable to their stability in phosphate buffer (pH 7.4), which suggests that their degradation in human serum is mostly due to the chemical hydrolysis. Benzoyloxypropyl esters of clodronic acid were also synthesized, but they did not release clodronic acid due to the enzymatic and chemical stability of the formed 3-hydroxypropyl phosphonate esters and are, therefore, not prodrugs.

Animals↗