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Biomedical subjects

M A Camacho

Publications and source records attributed to M A Camacho.

17 recordsLinked to original sources
PubMed2004

Effect of age of feed restriction and microelement supplementation to control ascites on production and carcass characteristics of broilers.

Three experiments were conducted, from January until September 2001, to estimate the optimized age to apply feed restriction to control mortality from ascites, with no negative effects on production and carcass characteristics of broilers. For each experiment, 1,200 1-d-old mixed Ross x Peterson chicks were reared in floor pens (50 chicks in each) and fed commercial feed. Feed restriction was applied for 8 h/d for 14 d at 21 or 28 d of age in experiment 1, 14 or 21 d in experiment 2, and 7 or 14 d in experiment 3. In experiments 2 and 3, a microelement supplement (without or with) was tested; the control groups received feed ad libitum and no supplement. Body weight gain, feed conversion, total mortality, and mortality from ascites, leg problems, and carcass characteristics were considered at the end of each experiment. The data were analyzed as a completely randomized design, or as a 2 x 2 factorial to estimate main and interaction effects (experiments 2 and 3). Additional analyses, including the control, were done; means comparisons were by orthogonal contrasts. The production and carcass characteristics of the restricted groups were lower than the control but were not statistically different in experiments 2 and 3, although the optimized age for feed restriction was at 7 d. Total mortality and mortality from ascites decreased by restriction, but leg problems increased without supplement. The results indicated that quantitative feed restriction and microelement supplementation at 7 d of age reduced mortality from ascites and leg problems and permitted compensatory growth sufficient to equal the production characteristics of the control group at 49 d of age. However, it is necessary to determine the specific microelements to be supplemented and to estimate the effects of season and genetic line.

Animal Feed↗
PubMed2004

Statistical method for evaluation of dissolution stability in the formulation development of solid dosage forms: tablets of amonafide.

A statistical method for the evaluation of the dissolution stability results and for selecting the most stable formulation within a solid dosage form development is discussed. Three types of tablets of an antineoplastic drug, amonafide, stored at a relative humidities (RH), 45% and 75%, were used. The drug release from tablets was tested before and after storage. The experimental data were statistically fitted to empirical model equations. Furthermore, the best mathematical fit was the statistical comparison of the residuals. From the selected model equation, time-dependent dissolution (Q45 and DE45) and dissolved quantity-dependent parameters (t70, t100 and MDT) were calculated. A useful parameter to present and evaluate the results obtained in comparative stability studies was defined: the Modification Factor (MF). It allowed the selection of the most stable formulation in the easiest and fastest way: the most stable formulation should present the smallest modification of the studied characteristics, in other words, the smallest MF value. In this way, tablets II (manufactured by wet granulation and with Emcompress as main excipient) showed the greater dissolution stability of the three types of tablets studied. Amonafide tablets must be packaged in impermeable containers, since the environmental relative humidity strongly modifies their dissolution characteristics.

Adenine↗
PubMed2001

Statistical evaluation for stability studies under stress storage conditions.

During the pharmaceutical development of a new drug, it is necessary to select as soon as possible the formulation with the best stability characteristics. The current International Commission for Harmonisation (ICH) regulations regarding stability testing requirements for a Registration Application provide the stress testing conditions with the aim of assessing the effect of severe conditions on the drug product. In practice, the well-known Arrhenius theory is still used to make a rapid stability prediction, to estimate a drug product shelf life during early stages of its pharmaceutical development. In this work, both the planning of a stress stability study to obtain a correct stability prediction from a temperature extrapolation and the suitable data treatment to discern the reliability of the stability results are discussed. The study was focused on the early formulation step of a very stable drug, Mitonafide (antineoplastic agent), formulated in a parenteral solution and in tablets. It was observed, for the solid system, that the extrapolated results using Arrhenius theory might be statistically good, but far from the real situation if the stability study is not designed in a correct way. The statistical data treatment and the stress-stability test proposed in this work are suitable to make a reliable stability prediction of different formulations with the same drug, within its pharmaceutical development.

Antineoplastic Agents↗
PubMed2001

Procedure to evaluate the stability during processing and storage of a medicated premix and medicated farm feed: erythromycin thiocyanate.

In this paper, a stability study of a medicated premix and medicated farm feed containing erythromycin thiocyanate was planned. No drug degradation was detected during the medicated farm feed processing. In the medicated premix stability study, significant drug degradation was detected only at 40 degrees C and 75% relative humidity. Because after 2 years of storage at 25 degrees C and 60% relative humidity no degradation of erythromycin thiocyanate was detected, this period of time is proposed as the premix shelf life. In the medicated farm feed stability study, drug degradation was detected under accelerated conditions, but it was not detected under long-term storage conditions for 3 months. Therefore, the proposed shelf life of the medicated farm feed is 3 months, as this is time enough to be consumed. The planned stability study-storage conditions, testing frequency, and proposed data evaluation-allowed an easy and reliable evaluation of veterinary medicine stability.

Animal Feed↗
PubMed2000

Stability study of a sulfadimidine-containing medicated premix and its mixture with farm feed.

The objective of this paper was to study the stability of a medicated premix and a medicated farm feed containing sulfadimidine as the active ingredient. The medicated premix is supplied as powdered form and administered orally after mixing with animal feed. The sulfadimidine analytical method described in United States Pharmacopoeia 23 cannot be used to carry out the stability study because of its lack of specificity for different degradation products. Therefore, a high-performance liquid chromatography method was developed to assay sulfadimidine. This method was optimized and validated for the stability study. According to International Committee Harmonization (ICH) guidelines, the samples were stored under long-term testing and accelerated conditions for the stability study of the premix and the medicated farm feed. Sulfadimidine degradation was not detected in either form under any of the conditions studied.

Animal Feed↗
PubMed2000

Thyroid peroxidase activity is inhibited by amino acids.

Normal in vitro thyroid peroxidase (TPO) iodide oxidation activity was completely inhibited by a hydrolyzed TPO preparation (0.15 mg/ml) or hydrolyzed bovine serum albumin (BSA, 0.2 mg/ml). A pancreatic hydrolysate of casein (trypticase peptone, 0.1 mg/ml) and some amino acids (cysteine, tryptophan and methionine, 50 microM each) also inhibited the TPO iodide oxidation reaction completely, whereas casamino acids (0.1 mg/ml), and tyrosine, phenylalanine and histidine (50 microM each) inhibited the TPO reaction by 54% or less. A pancreatic digest of gelatin (0.1 mg/ml) or any other amino acid (50 microM) tested did not significantly decrease TPO activity. The amino acids that impair iodide oxidation also inhibit the TPO albumin iodination activity. The inhibitory amino acids contain side chains with either sulfur atoms (cysteine and methionine) or aromatic rings (tyrosine, tryptophan, histidine and phenylalanine). Among the amino acids tested, only cysteine affected the TPO guaiacol oxidation reaction, producing a transient inhibition at 25 or 50 microM. The iodide oxidation inhibitory activity of cysteine, methionine and tryptophan was reversed by increasing iodide concentrations from 12 to 18 mM, while no such effect was observed when the cofactor (H2O2) concentration was increased. The inhibitory substances might interfere with the enzyme activity by competing with its normal substrates for their binding sites, binding to the free substrates or reducing their oxidized form.

Amino Acids↗
PubMed1999

Microbiological bioassay of erythromycin thiocyanate: optimisation and validation.

The validation of an analytical method for the quantitative determination of erythromycin thiocyanate formulated in an antibiotic preparation for veterinary use was carried out. This method is based on the microbiological method described in the European Pharmacopoeia to analyze erythromycin thiocyanate as a raw material. This erythromycin thiocyanate preparation is presented as a powder for oral administration after mixing with feed. For that reason, it was planned to validate the method for the quantitative determination of erythromycin thiocyanate incorporated both in the medicated premix and the mixture with feed. The microbiological method followed a linear model and was not proportional. The number of replicates needed to obtain a valid result was less than four in all cases. The small difference in concentration, expressed in natural logarithm detected by the method, was 0.1.

Administration, Oral↗
PubMed1998

Experimental dermatophyte infection abated by povidone-iodine: assessment by computerized-assisted corneofungimetry.

The effect of antiseptics upon fungal growth inside human stratum corneum is poorly documented. Therefore the present study was undertaken to assess the anti-dermatophyte activity of a diluted povidone-iodine wash solution using the corneofungimetry bioassay. When compared to a non-medicated cleansing product, regular applications of the antimicrobial for two weeks significantly abated the fungal invasiveness inside human stratum corneum. The present findings are most likely relevant for the clinical practice.

Antifungal Agents↗
PubMed1998

High performance liquid chromatographic method for the determination of lobenzarit disodium in a sustained release tablet formulation.

A rapid and simple high performance liquid chromatographic method is described and validated for the determination of lobenzarit disodium (CAS 64808-48-6) in a sustained release tablet formulation. The calibration graph was linear over the range 20-105 micrograms/ml. The sensitivity (discriminator capacity) was 2.079 micrograms/ml. The coefficient of variations for repeatability and reproducibility were less than 1.60% and 1.30%, respectively. The accuracy of the method did not depend on lobenzarit concentration in tablets. The mean recovery was found to be 100.62%. The method was selective, even when degradation products were present.

Antirheumatic Agents↗
PubMed1997

Electrophysiological evidence for the nomenclature of the pudendal nerve and sacral plexus in the male rat.

Surgical microscopy and electrophysiological techniques were used to standardize the nomenclature for the pudendal nerve and sacral plexus according to their somatic axonal composition in the male rat. We conclude that the pudendal nerve is the segment running from the L6-S1 trunk to the sacral plexus, carrying efferent fibers to the coccygeus, internal obturator, ventral and dorsal bulbospongiosus, ischiocavernosus, external anal sphincter, and external urethral sphincter muscles, and afferent fibers from the penis, prepuce, scrotum, and ventral-proximal tail. The sacral plexus is the complex formed by the bridge-like structure connecting the pudendal nerve with the lumbosacral trunk, and two nerve branches emerging from it, one innervating the proximal half of the scrotal skin, and the other innervating the muscles at the base of the penis known as the motor branch. These branches are only considered as a part of the sacral plexus because they integrate axons from both the lumbosacral trunk and pudendal nerve. The gross anatomy of the pudendal nerve and sacral plexus has a main organization that was observed in 70% of cases, whereas the remaining 30% occurred in two variants. This nomenclature is appropriate to describe the pudendal nerve and sacral plexus in studies that involve them being lesioned or electrophysiologically analysed. A main additional finding was that two large afferent branches innervate the scrotum, one the proximal half and the other the distal half. As mentioned above, the proximal branch belongs to the sacral plexus, whereas the distal branch belongs to the pudendal nerve because all its axons travel to the cord via this nerve. Since stimulation or even manipulation of the scrotal branches resulted in the secretion of semen containing spermatozoa, it is suggested that scrotal afferents are involved in some way in the ejaculatory process, a topic that deserves further research.

Animals↗
PubMed1995

MRI segmentation: methods and applications.

The current literature on MRI segmentation methods is reviewed. Particular emphasis is placed on the relative merits of single image versus multispectral segmentation, and supervised versus unsupervised segmentation methods. Image pre-processing and registration are discussed, as well as methods of validation. The application of MRI segmentation for tumor volume measurements during the course of therapy is presented here as an example, illustrating problems associated with inter- and intra-observer variations inherent to supervised methods.

Head↗
PubMed1995

A three-dimensional finite element model of human transthoracic defibrillation: paddle placement and size.

A detailed 3-D finite element model of the conductive anatomy of the human thorax has been constructed to quantitatively assess the current density distribution produced in the heart and thorax during transthoracic defibrillation. The model is based on a series of cross-sectional CT scans and incorporates isotropic conductivities for eight tissues and an approximation of the anisotropic conductivity of skeletal muscle. Current density distributions were determined and compared for four paddle pairs and two paddle sizes. Our results show that the myocardial current density distributions resulting from a defibrillation shock were fairly uniform for the paddle pairs and sizes examined in this study. Specific details of the spatial distribution of the current density magnitudes in the heart were found to depend on paddle placement and size. When the minimum current necessary to defibrillate was delivered, the maximum myocardial current density produced with any of the paddle sizes and positions examined was less than four times the minimum current density necessary to render a myocyte in a fibrillating heart inexcitable, and less than 40% of the damage threshold. These results suggest that common clinically used defibrillation paddle positions have a safety margin as large as 2.5 for current and approximately 6 for energy.

Adult↗
PubMed1994

Qualitative and quantitative determination of two new antitumor agents from 1-8 naphthalimides in tablets. Validation of a high performance liquid chromatography method.

A high performance liquid chromatography (HPLC) method for the qualitative and quantitative determination of amonafide (CAS 69408-81-7) and mitonafide (CAS 54824-17-8), two new antineoplastic molecules, in finished pharmaceutical dosage forms (tablets) is developed and validated. The results submitted in this work suggest that HPLC method is linear (range 0.54 microgram to 2.70 micrograms for amonafide, and 1.40 micrograms to 5.25 micrograms for mitonafide), sensitive (discriminator capacity 0.1098 microgram for amonafide and 0.1324 microgram for mitonafide), precise (coefficient of variation < or = 2.39% within run, < or = 1.18% between run for tablets with amonafide, and < or = 1.38% within run and < or = 0.96% between run for tablets with mitonafide), accurate (mean recovery 97.55, 98.85, 98.905% for the three different kinds of tablets with amonafide, and 100.73, 101.54% for the two types of tablets with mitonafide) and selective, even when degradation products are present. The volume of extractor liquid must be specially taken into account with regard to the accuracy of the method, because drug extraction can be influenced by the nature of the excipients.

Adenine↗
PubMed1994

Photolability evaluation of the new cytostatic drug mitonafide.

A qualitative and quantitative study on the stability of the new cytostatic drug mitonafide (N-[2-(dimethyl-amino) ethyl]-3-nitronaphthalimide, CAS 54824-17-8) against UVA, UVC and visible radiations was carried out. Initially a test with controlled lighting on samples from mitonafide solution is carried out. This test include the determination of the protector effect of different kinds of glasses (clear and amber glass). The results achieved are verified by means of a test in normal lighting conditions (direct sun light, normal laboratory lighting and darkness). High mitonafide photodecomposition, deeper against UVA radiation, requires conservation of raw material in darkness. Similarly UV sterilizing radiations must be avoided in sterile rooms during manufacture. The use of amber glass ampoules is not enough to protect parenteral solutions from radiations. Direct sunlight must be avoided in the manufacture, control tests and administration in perfusion of pharmaceutical dosage forms, although artificial light can be used during short periods of time.

Antineoplastic Agents↗
PubMed1992

High pressure liquid chromatographic determination of the new non-steroidal anti-inflammatory agent butibufen.

High performance liquid chromatography (HPLC) method for the determination and validation of a new non-steroidal anti-inflammatory agent, butibufen (CAS 55837-18-8), microencapsulated butibufen and its pharmaceutical forms--tablets, sachets (microencapsulated butibufen with excipients), microemulsion and cream--is described. Acetonitrile proved to be the best solvent for the extraction of butibufen from its pharmaceutical forms. The results submitted in this paper suggest that the HPLC method for the quantitative determination of butibufen is linear, accurate, precise and sensitive.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMedDate not supplied

Tensile properties of relaxed excised skin exhibiting striae distensae.

Tensile properties of skin determine some important physical attributes of skin. They may be conveniently assessed using recent technologies. The aim of the study was to compare ex vivo the tensile properties of normal looking skin and striae distensae. The Cutometer was used with 2 and 4 mm diameter probes. Skin distensibility values were dependent on the suction force and area of the skin tested. Conversely, tensile ratios yielding elasticity parameters were not affected by the same variables. Although tensile properties of excised normal skin resembled those previously reported in vivo, striae distensae showed markedly different properties in vivo and ex vivo. The ex vivo and in vivo evaluations of the tensile properties and functions of skin are complementary particularly when the connective tissue is abnormal.

Adult↗