Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 11 de 11
Filter
Add more filters










Publication year range
1.
J Neurophysiol ; 131(2): 304-310, 2024 Feb 01.
Article in English | MEDLINE | ID: mdl-38116612

ABSTRACT

Motor performance is monitored continuously by specialized brain circuits and used adaptively to modify behavior on a moment-to-moment basis and over longer time periods. During vocal behaviors, such as singing in songbirds, internal evaluation of motor performance relies on sensory input from the auditory and vocal-respiratory systems. Sensory input from the auditory system to the motor system, often referred to as auditory feedback, has been well studied in singing zebra finches (Taeniopygia guttata), but little is known about how and where nonauditory sensory feedback is evaluated. Here we show that brief perturbations in air sac pressure cause short-latency neural responses in the higher-order song control nucleus HVC (used as proper name), an area necessary for song learning and song production. Air sacs were briefly pressurized through a cannula in anesthetized or sedated adult male zebra finches, and neural responses were recorded in both nucleus parambigualis (PAm), a brainstem inspiratory center, and HVC, a cortical premotor nucleus. These findings show that song control nuclei in the avian song system are sensitive to perturbations directly targeted to vocal-respiratory, or viscerosensory, afferents and support a role for multimodal sensory feedback integration in modifying and controlling vocal control circuits.NEW & NOTEWORTHY This study presents the first evidence of sensory input from the vocal-respiratory periphery directly activating neurons in a motor circuit for vocal production in songbirds. It was previously thought that this circuit relies exclusively on sensory input from the auditory system, but we provide groundbreaking evidence for nonauditory sensory input reaching the higher-order premotor nucleus HVC, expanding our understanding of what sensory feedback may be available for vocal control.


Subject(s)
Finches , Animals , Male , Finches/physiology , Learning/physiology , Brain Stem , Feedback, Sensory , Vocalization, Animal/physiology
2.
J Biomater Sci Polym Ed ; 20(1): 49-69, 2009.
Article in English | MEDLINE | ID: mdl-19105900

ABSTRACT

In this work, different modifications of photo-cross-linked poly(propylene fumarate)/poly(N-vinyl pyrrolidone) (PPF/PNVP) matrices were studied for their effect on the release kinetics of two ophthalmic drugs. The hydrophilicity of solid PPF/PNVP matrices loaded with acetazolamide (AZ) or timolol maleate (TM) was increased by adding various amounts of poly(ethylene glycol) (PEG) or by increasing the amount of N-vinyl pyrrolidone (NVP) in the polymer mixture prior to cross-linking. The in vitro release studies that utilized high-performance liquid chromatography for quantification revealed highly accelerated drug release from the matrices with increasing contents of the hydrophilic modifier. AZ was released from matrices containing 5% PEG in 56 days, which equals approximately 25% of the release period found for the unmodified matrices. A comparable acceleration in drug release was found for TM-loaded samples modified with 5% PEG. These studies further revealed that 1% PEG is sufficient to shorten the TM release duration by one-third. A significant acceleration in drug release was also found for the samples that were fabricated from a PPF-NVP mixture with increased NVP content. Matrix water content and erosion were assessed gravimetrically. Micro-computed tomography was used to image structural changes of the release systems and shed light on the drug-release mechanism. This study showed that hydrophilic matrix modifications of PPF/PNVP matrices accelerate the drug release of two ophthalmic drugs and represent a suitable tool to adjust drug-release rates from PPF-based matrices for different therapeutic needs.


Subject(s)
Drug Carriers/chemistry , Drug Delivery Systems , Fumarates/chemistry , Ophthalmic Solutions/chemistry , Polymers/chemistry , Polypropylenes/chemistry , Acetazolamide/chemistry , Acetazolamide/metabolism , Antihypertensive Agents/chemistry , Antihypertensive Agents/metabolism , Diuretics/chemistry , Diuretics/metabolism , Drug Administration Routes , Eye/chemistry , Eye/metabolism , Fumarates/chemical synthesis , Molecular Structure , Ophthalmic Solutions/metabolism , Polyethylene Glycols/chemistry , Polypropylenes/chemical synthesis , Timolol/chemistry , Timolol/metabolism
3.
J Biomed Mater Res A ; 88(4): 976-89, 2009 Mar 15.
Article in English | MEDLINE | ID: mdl-18384171

ABSTRACT

The function of a photocrosslinked poly(propylene fumarate) (PPF)/poly(N-vinyl pyrrolidone) (PVP) matrix for the sustained release of three ophthalmic model drugs, acetazolamide (AZ), dichlorphenamide (DP), and timolol maleate (TM), was investigated. The drugs differ in molecular weight and degree of dissociation in aqueous environments; both are parameters that significantly influence drug diffusivity. AZ, DP, and TM-loaded cylindrical rods (10 mm length, 0.6 mm diameter) were fabricated by photoinduced cross-copolymerization of PPF and N-vinyl pyrrolidone (NVP) in molds. The released amounts of AZ, DP, TM, and NVP were determined by high-performance liquid chromatography (HPLC). The effects of drug properties and loading on the release kinetics were investigated. The in vitro release of AZ, DP, and TM was well sustained from the polymer matrices over a period of approximately 210, 270, and 250 days, respectively. The release kinetics correlated with the HPLC retention profiles of the different drugs. Following a small initial burst release (<10%), a dual modality release controlled by diffusion and bulk erosion was found for all drugs. Drug release rates of up to 4 microg/day were reached. Matrix drug loading generally affected the extent of the burst release, release kinetics, as well as the matrix water content and matrix degradation that were determined gravimetrically. Microcomputed tomography was used to image structural and dimensional changes of the devices. A preliminary rabbit implantation study revealed promising ocular biocompatibility of drug-free PPF/PVP matrices. All results indicate the potential of photocrosslinked PPF-based matrices as polymeric carriers for long-term ophthalmic drug delivery.


Subject(s)
Biocompatible Materials/chemistry , Drug Carriers/chemistry , Drug Delivery Systems , Eye/metabolism , Fumarates/metabolism , Polypropylenes/metabolism , Acetazolamide/administration & dosage , Acetazolamide/chemistry , Animals , Antihypertensive Agents/administration & dosage , Antihypertensive Agents/chemistry , Carbonic Anhydrase Inhibitors/administration & dosage , Carbonic Anhydrase Inhibitors/chemistry , Chromatography, High Pressure Liquid , Dichlorphenamide/administration & dosage , Dichlorphenamide/chemistry , Diuretics/administration & dosage , Diuretics/chemistry , Eye/anatomy & histology , Fumarates/chemistry , Implants, Experimental , Molecular Structure , Polypropylenes/chemistry , Rabbits , Timolol/administration & dosage , Timolol/chemistry
4.
J Biomed Mater Res A ; 83(3): 656-66, 2007 Dec 01.
Article in English | MEDLINE | ID: mdl-17514745

ABSTRACT

This study sought to develop an injectable formulation for long-term ocular delivery of fluocinolone acetonide (FA) by dissolving the anti-inflammatory drug and the biodegradable polymer poly(propylene fumarate) (PPF) in the biocompatible, water-miscible, organic solvent N-methyl-2-pyrrolidone (NMP). Upon injection of the solution into an aqueous environment, a FA-loaded PPF matrix is precipitated in situ through the diffusion/extraction of NMP into surrounding aqueous fluids. Fabrication of the matrices and in vitro release studies were performed in phosphate buffered saline at 37 degrees C. Drug loadings up to 5% were achieved. High performance liquid chromatography was employed to determine the released amount of FA. The effects of drug loading, PPF content of the injectable formulation, and additional photo-crosslinking of the matrix surface were investigated. Overall, FA release was sustained in vitro over up to 400 days. After an initial burst release of 22 to 68% of initial FA loading, controlled drug release driven by diffusion and bulk erosion was observed. Drug release rates in a therapeutic range were demonstrated. Release kinetics were found to be dependent on drug loading, formulation PPF content, and extent of surface crosslinking. The results suggest that injectable, in situ formed PPF matrices are promising candidates for the formulation of long-term, controlled delivery devices for intraocular drug delivery.


Subject(s)
Eye , Fluocinolone Acetonide/analogs & derivatives , Fumarates/chemistry , Glucocorticoids/chemistry , Polypropylenes/chemistry , Delayed-Action Preparations/chemistry , Fluocinolone Acetonide/chemistry , Kinetics , Pyrrolidinones/chemistry
5.
J Control Release ; 114(2): 251-60, 2006 Aug 28.
Article in English | MEDLINE | ID: mdl-16872709

ABSTRACT

Intraocular drug delivery systems made from biodegradable polymers hold great potential to effectively treat chronic diseases of the posterior segment of the eye. This study is based on the hypothesis that crosslinked poly(propylene fumarate) (PPF)-based matrices are suitable long-term delivery devices for the sustained release of the anti-inflammatory drug fluocinolone acetonide (FA) due to their hydrophobicity and network density. FA-loaded rods of 10 mm length and 0.6 mm diameter were fabricated by photo-crosslinking PPF with N-vinyl pyrrolidone (NVP). The released amounts of FA and NVP were determined by HPLC analysis. The effects of drug loading and the ratio of PPF to NVP on the release kinetics were investigated using a 2(3-1) factorial design. Overall, FA release was sustained in vitro over almost 400 days by all tested formulations. Low burst release was followed by a dual modality release controlled by diffusion and bulk erosion with release rates up to 1.7 microg/day. The extent of the burst effect and the release kinetics were controlled by the drug loading and the matrix composition. Matrix water content and degradation were determined gravimetrically. Micro-computed tomography was used to image structural and dimensional changes of the devices. The results show that photo-crosslinked PPF-based matrices are promising long-term delivery devices for intraocular drug delivery.


Subject(s)
Fluocinolone Acetonide/administration & dosage , Fluocinolone Acetonide/pharmacokinetics , Glucocorticoids/administration & dosage , Glucocorticoids/pharmacokinetics , Chemistry, Pharmaceutical , Chromatography, High Pressure Liquid , Cross-Linking Reagents , Delayed-Action Preparations , Drug Delivery Systems , Drug Implants , Fumarates , Polymers , Polypropylenes , Povidone
6.
Biomaterials ; 22(24): 3257-60, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11700797

ABSTRACT

The adsorption of lysozyme and human serum albumin (HSA) onto hydrogel contact lenses was investigated as a function of lens surface charge. Anionic, cationic and non-ionic contact lenses were deposited using single protein solutions of identical pH and osmolarity. Protein deposition was analyzed using matrix assisted laser desorption ionization mass spectrometry (MALDI-ToF MS) and compared to a direct UV protein analysis method, the bicinchoninic acid (BCA) assay. The results showed remarkable consistency between the two techniques. By inference of results from analyses of sample solutions, lysozyme, a positively charged protein at physiological pH, was only detected on the anionic surface charged contact lenses, presumably a result of electrostatic interactions. Neither the cationic nor the non-ionic lenses deposited lysozyme, possibly due to charge repulsion. HSA, a negatively charged protein at physiological pH, was detected on the cationic lenses, again as a result of electrostatic interactions. The fact that HSA was not observed on either the anionic or non-ionic charged species further demonstrates the effect of charge repulsion.


Subject(s)
Biocompatible Materials/adverse effects , Biocompatible Materials/chemistry , Contact Lenses, Hydrophilic/adverse effects , Proteins/metabolism , Adsorption , Humans , Hydrogels/adverse effects , Hydrogels/chemistry , Hydrogen-Ion Concentration , In Vitro Techniques , Materials Testing , Muramidase/metabolism , Quinolines , Serum Albumin/metabolism , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Static Electricity , Surface Properties
7.
Support Care Cancer ; 8(4): 314-22, 2000 Jul.
Article in English | MEDLINE | ID: mdl-10923773

ABSTRACT

A sizeable percentage of patients receiving conventional medical treatment also use unconventional medicine (UM). Surveys indicate that the prevalence of and motivation for the pursuit of the different approaches of UM is subject to individual, geographical, cultural and disease-related factors. We were interested in the concurrent use of and attitudes towards UM in patients who underwent conventional medical treatment in our oncologically orientated department of internal medicine in a regionally dominant teaching hospital. A representative sample (n = 131) of all inpatients and outpatients receiving treatment in the department or in its oncological/haematological outpatient clinic were asked to participate in a cross-sectional interview study on the use of unconventional therapies. In all, 128 patients (97.7%) agreed to participate in the study, and 65% of these patients were suffering from malignancies. Use of unconventional treatment was reported by 24% of all patients for their current medical problem, and 16% of the remaining patients had been thinking of adjunctive use. The use of UM was significantly higher among oncological patients (32%), and among oncological outpatients in particular (50%), than among patients with acute or chronic non-malignant diseases. Female patients predominated among the users of UM (71%). UM mainly took the form of various pharmacological and dietary approaches. Patients availing themselves of UM most frequently identified physicians (41%) as the source of treatment recommendation. Only 18% of the users of UM relied on these methods as a chance of cure. Use of UM was not generally motivated by dissatisfaction with conventional medical care. Only half the users informed their hospital physician of their adjunctive use of UM. Nearly 2 out of 3 of the users contended that UM had contributed to a mild or distinct improvement in their physical or psychological wellbeing. The use of UM in modern health care systems represents a widespread and intricate phenomenon, which cannot be understood by focusing exclusively on the objective assessment of clinical efficacy. Use of UM may be related more to a disease's unfavourable attribution than to its medically expected outcome. Coherence with individual illness paradigms and perceived efficacy are apparently important factors in patients' use of UM. These subjective aspects need to be recognised in caring patient-doctor communication.


Subject(s)
Attitude , Complementary Therapies , Neoplasms/therapy , Adaptation, Psychological , Adolescent , Adult , Aged , Complementary Therapies/statistics & numerical data , Cross-Sectional Studies , Female , Hematology , Humans , Internal Medicine , Male , Medical Oncology , Middle Aged , Neoplasms/psychology
8.
J Biomed Mater Res ; 32(1): 45-54, 1996 Sep.
Article in English | MEDLINE | ID: mdl-8864872

ABSTRACT

The surface chemistry and topography of cast-molded Etafilcon-A and doubled-sided lathed Etafilcon-A soft contact lenses were determined to be significantly different. The variations in surface chemical and morphologic structure between the two lenses were the result of contact lens manufacturing methods. The surface of the cast-molded Etafilcon-A had a consistently less rough surface compared to the doubled sided lathed Etafilcon-A as determined by atomic force microscopy. The surface of the doubled sided lathed Etafilcon-A contained primarily silicone and wax contamination in addition to minute amounts of HEMA. The cast-molded Etafilcon-A had an elemental and chemical content which was consistent with the polymer stoichiometry. Contact angle wettability profiles revealed inherent wettability differences between the two lenses types. The cast-molded Etafilcon-A had an inherently greater water wettability, polarity, and critical surface tension. This means that these two lenses cannot be compared as similar or identical lens materials in terms of surface composition. The manufacturing method used to produce a soft contact lens directly determines the surface elemental and chemical structure as well as the morphology of the finished lens material. These results suggest possible differences in the clinical comfort, spoilage, and lubricity felt during patient wear.


Subject(s)
Biocompatible Materials , Contact Lenses , Polymers , Humans
9.
Theriogenology ; 35(5): 1001-17, 1991 May.
Article in English | MEDLINE | ID: mdl-16726967

ABSTRACT

A direct radioimmunoassay for estrogen conjugates (EC) was applied to paired blood and urine samples collected from 20 mares and compared against estrone (E(1)) and estradiol-17beta (E(2)) to monitor changes in estrogen production during ovulatory cycles and early pregnancy. Blood samples were taken daily from five mares through two consecutive ovulations and from six mares at 6-h intervals starting 48 hours prior to ovulation and continuing after ovulation had occurred. Blood samples were also collected daily or three times per week from conception until Day 60 of pregnancy in nine pregnant mares. The mean urinary EC, plasma EC and plasma E(2) dynamics were parallel in nonpregnant mares, with a 3-fold increase in mean urinary EC concentrations from baseline to the ovulatory peak, a 1.8-fold increase in mean plasma EC concentrations and a 1.4-fold increase in mean plasma E(2) concentrations. In early pregnancy, a two-fold increase in mean plasma E(1) and EC concentrations occurred in concert with a five-fold rise in mean urinary EC concentrations, whereas plasma E(2) did not change. Following hydrolysis and chromatographic separation, E(1) and E(2) were identified as the hydrolytic products in the urine of nonpregnant and pregnant mares; however, an unidentified estrogen was the major hydrolytic product in nonpregnant mares and pregnant mares prior to Day 38 of pregnancy. The increased resolution of the EC profiles compared with the profiles of other estrogen components indicates that the determination of EC in urine or plasma provides a useful alternative method for monitoring reproductive events in mares.

10.
J Anim Sci ; 69(4): 1733-40, 1991 Apr.
Article in English | MEDLINE | ID: mdl-2071528

ABSTRACT

Trials were conducted to evaluate effects of a fermentation extract of Aspergillus oryzae (AO) on milk production and composition, diet digestibility, and rectal temperature changes in lactating dairy cows. Treatments were incorporated as a top dressing at the morning feeding and consisted of control (90 g/d of ground sorghum) or AO (3 g of culture + 87 g of ground sorghum daily). Twenty-four mid-lactation Holstein cows were paired for production in Lactation Trial 1 (LT-1). In Lactation Trial 2 (LT-2), 46 cows (20 primiparous and 26 multiparous) in early lactation were used. Trials lasted 12 wk. In LT-1, AO supplementation increased milk yields only at 2 (P less than .05) and 8 wk (P less than .10) of treatment. Rectal temperatures were lower (P less than .05) for cows fed AO for 4 of 10 readings made during summer. Supplementation of AO culture in LT-2 (early lactation cows) increased milk production and feed efficiency (P less than .05). Inner ear temperatures tended to be lower (P less than .11) for cows fed AO. Digestion trials, conducted at the end of lactation trials, used Cr2O3 as an indigestible marker. In Digestion Trial 1, digestibilities were not significantly (P greater than .10) affected by AO supplementation. However, in Digestion Trial 2, AO increased (P less than .05) digestibilities of DM, OM, CP, NDF, and ADF. Length and number of meals were not affected (P greater than .10) by feeding AO. In summary, milk yields, efficiency of milk production, and nutrient digestibilities were higher for early lactation cows fed a high-concentrate diet supplemented with 3 g of AO/d. Mid-lactation cows fed a lower-energy diet were less responsive to AO than early lactation cows, though similar trends were shown.


Subject(s)
Aspergillus oryzae/metabolism , Body Temperature , Cattle/microbiology , Eating , Lactation , Analysis of Variance , Animals , Cattle/metabolism , Cattle/physiology , Female , Fermentation , Milk/chemistry , Milk/metabolism , Weight Gain
SELECTION OF CITATIONS
SEARCH DETAIL
...