Search PubMed⌕ Search

Biomedical subjects

A Hashem

Publications and source records attributed to A Hashem.

At least 19 recordsLinked to original sources
PubMed1996

Heroin dependence effects on some major and trace elements.

In this study, 56 (14 control and 42 addicts) adult human subjects of both sexes of different periods of heroin dependence were subjected to the measurement of whole blood, serum, and red blood cell levels of some trace elements (zinc, manganese, iron copper, and bromine), as well as some major elements (phosphorus, sulfur, calcium, potassium, and chlorine). This was done by the energy-dispersive X-ray fluorescence (EDXRF) technique, in which copper and bromine showed a significant rise in whole blood (male) (22 and 32%, respectively), while zinc, iron, manganese, calcium, sulfur phosphorus, potassium, and chlorine showed a significant drop (49, 8, 25, 34, 21, 51, 61, and 72%, respectively) in proportion to the period of heroin intake (6 yr) and in comparison with the control group. No significant sexual variation has been reported.

Adolescent↗
PubMed1996

[The concentration changes of different phenylbutazone formulations in horse plasma].

In a study in the horse, the disposition, the pharmacokinetic parameters and the absorption rates of 3 formulations of phenylbutazone (injection solution, powder and paste suspension) have been determined. After i.v. injection, the half-life time of phenylbutazone has been determined to be 6.6-6.7 h. After oral administration, the absorption of phenylbutazone was found to be faster after administration via stomach tube than after direct application into the mouth. The absorption rat constant of the paste suspension was found to be higher than that of the powder (1.797-2.304 h-1 vs. 0.656-1.197 h-1). The maximal plasma concentrations were attained within 0.5-3 hours with all formulations and were dose-dependent. The elimination of phenylbutazone was not dependent on the dose and formulation applied. The bioavailability of the studied powder and paste formulation was calculated to be 55.1-96.7%. Generally, the bioavailability was higher following administration of the drug via stomach tube. In some horses, the disposition pattern was atypical and delayed absorption was found. This may be due to adsorption of phenylbutazone on the food with subsequent release in the large intestine. The minimal therapeutic level of 5 micrograms/ml was attained 0.2-0.8 hours after administration of the drug and lasted 8.2-22 hours depending on the dose applied. The paste suspension of phenylbutazone may provide a good therapeutic tool for horses, which normally refuse to take powder supplemented food. At the end the authors report on their good clinical results in using Butasan-Paste with 30 ill horses.

Absorption↗
PubMed1996

[The tissue cage in dogs--a pharmacologic model for the representation of plasma and tissue kinetics].

Determination of pharmacokinetic data from plasma often is not sufficient in order to predict or to explain the clinical efficacy of drugs, e.g., in non steroidal antiinflammatory drugs (NSAID) with short elimination half lives in plasma a discrepancy appears between elimination half life and clinical effect. We have studied the tissue kinetics of a drug having a long elimination half life (naproxen) in comparison with phenylbutazone and flunixin, having a short elimination half life in dogs after oral application. Tissue fluid was obtained by using so called "tissue cages" implanted laterally in the neck. An inflammatory response was produced by injecting 1-2 ml of 2% carrageenan into the chamber. The drug concentrations were determined throughout the experiments both in plasma and tissue fluid. Naproxen concentrations (elimination half life of about 72 h in dogs) achieved equilibrium between tissue fluid and plasma concentration. In the case of phenylbutazone, concentration in tissue fluid declined with a definitely longer half life than in plasma and exceeded plasma concentrations after some hours. Flunixin concentrations in plasma and exudate attained equilibrium after 2-5 h. Of clinical importance is the finding that after this time flunixin accumulated in inflammatory exudate and the concentration in exudate exceeded that in plasma two to ten times, then declined with an almost identical half-life. The number of leukocytes in exudate as a measure of inflammation was reduced during 2 days after phenylbutazone, 3-4 days after flunixin and 5-7 days after naproxen. This allows therapy with a lower dosage than calculated on the basis of plasma concentrations in the case of phenylbutazone and flunixin, possibly also with other NSAIDs having a short plasma half life.

Animals↗
PubMed1995

Some mechanistic observation on water-deteriorated dental composite resins.

Four different types of dental composite resins were subjected to the water sorption environment in both dyed and undyed distilled water for 1 and 5 weeks at 37 degrees C. Weight changes due to the water sorption, effects of water sorption on mechanical properties, and fractographic observations were conducted. It was found that (i) the water sorption was diffusion-controlled, (ii) both break stress and modulus of elasticity reduced by increasing the amount of absorbed water, and (iii) fractographic observations showed that fracture pattern of the wet/dry/wet lamellar structure was not straight line, rather S-shaped pattern, suggesting that (a) mechanical properties (particularly, the modulus of elasticity) of the wet portion were not same as those in the dry portion, and (b) there could be an internal residual stress developed at/in the interfacial zone between the dry and wet portion. By one-layer removal from the wet/dry/wet lamellar structure composites, the residual stress was calculated from measuring the radius of the curvature. It was found that for all water-sorbed composite materials, tensile residual stresses were developed, which were from 30 to 40% of the break stresses for TPH, Charisma, and Durafil VS, and was 78% of the break stress for Z100 material.

Composite Resins↗
PubMed1994

Technique to restore unfavorably inclined implants.

Unfavorable inclination of implants is a common problem that may compromise esthetics, phonetics, and function of the implant-supported fixed prosthesis. Several methods have been reported to compensate for malaligned implants; however, most techniques are complicated and expensive. A technique that combines a custom abutment from a hexed UCLA-type plastic burn-out pattern and a manually threaded setscrew hole is a relatively inexpensive and uncomplicated approach to eliminate problems caused by unfavorable implant inclination. This article describes the procedures for fabrication of an implant-supported fixed prosthesis with the use of this technique.

Dental Abutments↗
PubMed1994

Experimental development of a chitosan-bonded beta-tricalcium phosphate bone filling paste.

Bone filling substances are needed to meet several requirements including nontoxicity, setting time, changes in pH values, and amount of dissolved elements as well as mechanical properties. In this study, the bone-generating composites were prepared by employing the in vivo absorbable beta-tricalcium phosphate as a parent matrix kneaded with CaO, MgO, and ZnO as bone mineral additives with different compositions. The setting time, pH values, compressive strength were investigated as a function of the amount of these bone mineral additives. It was found that the setting time was shortened by increasing CaO, MgO, and ZnO contents. Increasing ZnO contents resulted in the pH value lower, while the pH values increased by increasing CaO and MgO contents. Increasing ZnO contents caused the compressive strength stronger, on the other hand, the compressive strength was weakened by increasing MgO contents. Furthermore, calcium appears to be selectively released from the hardened composite sample.

Analysis of Variance↗
PubMed1994

Fractal dimension analysis of mandibular bones: toward a morphological compatibility of implants.

In addition to biological and mechanical compatibilities for promising implant materials, a morphological compatibility is proposed by the authors. It has been reported by many investigators that implant surface with appropriate roughness and pore size exhibit better bone ingrowth activities. However, these parameters cannot characterize the complexity of surface textures. In the present study, dentulous and edentulous mandibular alveolar bones were utilized. Four segments from each mandible were subjected to the Fractal Dimension (DF) analysis. It was found that the dentulous mandible showed the DF of 1.81 +/- 0.03 while the edentulous mandible exhibited DF of 1.55 +/- 0.07, indicating that the former has more complex surface texture. It was also found that there could be a linear relationship between the surface roughness and the fractal dimension.

Alveolar Process↗
PubMed1993

Disposition, bioavailability and clinical efficacy of orally administered acepromazine in the horse.

The pharmacokinetics and pharmacological efficacy of orally (p.o.) administered acepromazine were studied and compared with the intravenous (i.v.) route of administration in a cross-over study using six horses. The oral kinetics of acepromazine can be described by a two-compartment open model with first-order absorption. The drug was rapidly absorbed after p.o. administration with a half-life of 0.84 h, tmax of 0.4 h and Cmax of 59 ng/ml. The elimination was slower after p.o. administration (half-life 6.04 h) than after i.v. injection (half-life 2.6 h). The bioavailability of the orally administered drug formulation was 55.1%. After p.o. administration of 0.5 mg/kg acepromazine, the parameters of the sedative effect were similar to those obtained after i.v. injection of 0.1 mg/kg. The effect of the drug on blood cell count and haemoglobin content was similar after both p.o. administration and injection, while the effects on the parameters of penile prolapse and on the mean arterial blood pressure were less pronounced after p.o. administration than after injection. After p.o. administration, no significant effects on haematocrit-level as well as on the heart and respiratory rates were observed, while these parameters were significantly affected after injection. It is concluded that the high initial plasma level of the drug after i.v. injection may play a role in producing adverse effects of acepromazine.

Absorption↗
PubMed1993

Fractal dimension analysis of aluminum oxide particle for sandblasting dental use.

Aluminum oxide particles are commonly used as a sandblasting media, particularly in dentistry, for multiple purposes including divesting the casting investment materials and increasing effective surface area for enhancing the mechanical retention strengths of succeedingly applied fired porcelain or luting cements. Usually fine aluminum oxide particles are recycled within the sandblasting machine. Ceramics such as aluminum oxides are brittle, therefore, some portions of recycling aluminum oxide particles might be brittle fractured. If fractured sandblasting particles are involved in the recycling media, it might result in irregularity metallic materials surface as well as the recycling sandblasting media itself be contaminated. Hence, it is necessary from both clinical and practical reasons to monitor the particle conditions in terms of size/shape and effectiveness of sandblasting, so that sandblasting dental prostheses can be fabricated in optimum and acceptable conditions. In the present study, the effect of recycling aluminum oxide particles on the surface texture of metallic materials was evaluated by Fractal Dimension Analysis (FDA). Every week the alumina powder was sampled and analyzed for weight fraction and contaminants. Surface texture of sandblasted standard samples was also characterized by FDA. Results indicate very little change in particle size, while the fractal dimension increased. Fractal dimension analysis showed that the aluminum oxide particle as a sandblasting media should be replaced after 30 or 40 min of total accumulated operation time.

Air Pressure↗
PubMed1993

Titanium-porcelain system. Part I: Oxidation kinetics of nitrided pure titanium, simulated to porcelain firing process.

The bonding strength of porcelains to metals depends on the oxide layer between the porcelain and the metal. Oxidation of a metal surface increases the bonding strength, whereas excessive oxidation decreases it. Titanium and its alloys are gaining acceptance for dental use since they exhibit excellent biocompatibility, corrosion resistance, low specific gravity, good mechanical properties, and low cost. However, titanium suffers from its violent reactivity with oxygen at high temperatures that yields an excessive thick layer of TiO2, and this presents difficulties with porcelain bonding. The present study deals with the oxidation kinetics of titanium simulated to porcelain firing and evaluating surface nitridation of titanium as a process of controlling the oxidation behavior of titanium. Nitrided samples with the Arc Ion Plating PVD process and un-nitrided control commercially pure titanium (CPT, Grade 1) were subjected to oxidation simulating firing of Procera porcelain with 550 degrees, 700 degrees, and 800 degrees C firing temperatures for 10 min in both 1 and 0.1 atmospheric air. Weight difference before and after oxidation was calculated and the parabolic rate constant, Kp (mg2/cm4/s), was plotted against inverse absolute temperature. Surface layers of the samples were subjected to x-ray and electron diffraction techniques for phase identifications. Results revealed that both nitrided and un-nitrided samples obey a parabolic rate law with activation energy of 50 kcal/mol. In addition this study shows that nitrided CPT had a Kp about 5 times lower than the un-nitrided CPT and hence the former needs about 2.24 times longer oxidation time to show the same degree of oxidation. Phase identification resulted in confirming the presence of TiO2 as the oxide film in both groups but with 1-2 microns thickness for the un-nitrided CPT and 0.3-0.5 micron thickness for the nitrided samples. Therefore it can be concluded that nitridation of titanium surface can be effective in controlling the surface oxide thickness that might ensure satisfactory bonding with porcelain.

Crystallography↗
PubMed1992

[The pharmacokinetics and bioavailability of acepromazine in the plasma of dogs].

Acepromazine is extensively used in veterinary practice. In dogs, it is used mainly as a preanaesthetic and sedative agent, without the knowledge of pharmacokinetic data in this species. We studied the disposition both after oral and intravenous administration. It was shown, that the sedative effect after an oral dose of 1.3-1.5 mg/kg lasted for about 4 hours. The elimination was slower after oral administration (half-life 15.9 h) than after i. v. injection (half-life 7.1 h). The bioavailability of the orally administered drug formulation averaged 20%. The calculation of the pharmacokinetic parameters was performed computer-aided, using conventional compartmental analysis and non-compartmental statistical moment analysis and the results were compared.

Acepromazine↗
PubMed1991

Importance of histamine for seizure susceptibility.

The influence of drugs affecting the turnover of histamine in brain and histamine antagonists on pentetrazole seizure threshold in mice was studied. A rise in histamine brain concentration as well as treatment with central acting H1-, but not H2- and H3-antagonists led to an increase of the convulsive threshold. It is therefore concluded that histamine has a certain anticonvulsant effect which is mediated through H1-receptors.

Animals↗
PubMed1990

Apomorphine-induced emesis in the dog--routes of administration, efficacy and synergism by naloxone.

Apomorphine proved to be more effective as an emetic in dogs after s.c. administration than after i.m. injection with doses of 0.04 and 0.1 mg/kg. This effect is explained by an anti-emetic effect mediated by mu-receptors in the vomiting centre in the brain, which, in contrast to the chemoreceptor trigger zone, is within the blood-brain barrier. A certain delay between the stimulation of D2-receptors in the chemoreceptor trigger zone (causing emesis) and mu-receptors in the vomiting centre (producing anti-emesis) therefore results, leading to a self-limiting emesis. Blockade of the mu-receptors by naloxone increased and prolonged the effect of apomorphine. A relatively narrow range of apomorphine concentrations on s.c. administration is then effective to stimulate the chemoreceptor trigger zone, but can hardly inhibit the vomiting centre, and must therefore be considered the most suitable route for administration of apomorphine.

Animals↗
PubMed1990

Pharmacokinetics, anticonvulsant efficacy and adverse effects of the beta-carboline abecarnil, a novel ligand for benzodiazepine receptors, after acute and chronic administration in dogs.

Abecarnil (ZK 112119; isopropyl-6-benzyloxy-4-methoxymethyl-beta-carboline-3-carboxylate), a novel beta-carboline with high affinity for central benzodiazepine (BZ) receptors, has been shown recently to be a potent anxiolytic and anticonvulsant in animal models whereas lacking ataxia-producing effects, a profile typical for a partial agonist at BZ receptors. In the present study abecarnil was tested in dogs after acute and chronic administration. Pharmacokinetic studies showed that abecarnil was eliminated rapidly after i.v. or p.o. administration, but elimination was delayed substantially after s.c. injection. After i.v. injection, the drug penetrated rapidly into the cerebrospinal fluid, but maximum concentrations reached in cerebrospinal fluid were only 6 to 8% of those in plasma. Anticonvulsant potency of abecarnil in dogs was studied by means of seizures induced by i.v. infusion of pentylenetetrazol. After i.v. administration of single doses, abecarnil was about half as potent as diazepam, dose-dependently increasing the pentylenetetrazol threshold by doses of 0.1-1 mg/kg. In contrast to diazepam, most dogs injected with abecarnil at anticonvulsant doses showed no ataxia. During chronic s.c. administration of abecarnil for 6 weeks, the anticonvulsant efficacy of the drug increased markedly during the first week(s) of treatment, possibly indicating drug accumulation in the brain. During the subsequent weeks of treatment, there was a slight reduction in anticonvulsant potency. No withdrawal symptoms were observed after cessation of the 6-week administration period. Furthermore, injection of the BZ antagonist Ro 15-1788 (flumazenil), 1 mg/kg i.v., after 5 weeks of treatment did not precipitate withdrawal symptoms except slight tremor in two of seven dogs studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗