Design of High-Frequency Carbon Nanotube-Carbon Nanotorus Oscillators for Energy Harvesting: A Molecular Dynamics Study

The objective of this study is to examine the feasibility of using carbon-based nanostructures as nano-oscillators for future nanoelectromechanical applications such as energy harvesting devices and vibration sensing. The proposed nano-oscillator is comprised of a carbon nanotube (CNT) oscillating through a fixed carbon nanotorus molecule. For the first time in the literature, molecular dynamics (MD) simulations in conjunction with the Tersoff-Brenner (TB) and 6-12 Lennard-Jones (LJ) potential functions are adopted to determine the molecular interactions of the introduced nanodevice. To simulate the oscillatory behavior, two different schemes, namely, rigid and flexible, are considered. A detailed parametric study is performed to investigate the effects of rigidity, flexibility, and size of nanostructures as well as initial velocity on the force distribution and time histories of displacement and velocity of the core. Numerical results reveal that unlike the rigid oscillators, the flexible oscillators damp out within a few cycles. It is shown that the escape velocity of the flexible scheme is ∼6 times greater than that of the rigid scheme. The operating frequency and the generated power of rigid and flexible schemes under different system parameters are also calculated and compared. It is demonstrated that with increasing the ratio of nanotube-to-nanotorus diameter, the operating frequencies of both schemes decrease, while the generated powers do not behave monotonically. For a determined system parameter, it is observed that the flexible scheme provides higher operating frequencies compared to the rigid one. Moreover, considering that the initial velocity of the system is identical to the escape velocity, the generated power of the flexible scheme is calculated to be ∼14 times greater than that of the rigid scheme.

The Modified Hospital Elder Life Program (HELP) in geriatric hospitalized patients in internal wards: A double-blind randomized control trial

Background

Hospital Elder Life Program (HELP) provides protocols based on factors for reducing delirium. Due to the lack of geriatric wards and aged care teams in Iran, it seems that some of the original HELP interventions need to be modified through a trial study. Hence, this study was conducted to determine whether the Iranian modified HELP could reduce delirium in geriatric hospitalized patients.

Methods

This double-blind randomized controlled trial was designed and conducted in a hospital at Kashan University of Medical Sciences in Iran. A total of 195 hospitalized patients aged ≥70 years, were 84 in the Intervention Group (IG) and 111 in the Control Group (CG). After assessing delirium risk factors, participants in the IG group received interventions based on the cognitive, vision/hearing, sleep, mobility, feeding, and hydration protocols by nursing students and the CG group received routine care.

Delirium incidence was assessed by the Confusion Assessment Method. Delirium incidence, cognitive and functional abilities, frailty, fall, and length of stay were outcomes.

Results

The mean age of the patients was 78.53(Standard Deviation = 5.87) years. Delirium incidence was higher in the CG comparing to IG (14.71% vs 3.66%).Significant reduction observed in risk incidence of delirium because of interventions [Odds Ratio:0.124, Confidence Interval: 0.03–0.48].

Conclusion

The modified HELP effectively reduced delirium rates in geriatric hospitalized patients.

Trial registration

This study was registered at the Iranian Registry of Clinical Trials IRCT20180910040995N1.

Computational study on subfamilies of piperidine derivatives: QSAR modelling, model external verification, the inter-subset similarity determination, and structure-based drug designing

A new subset of furan-pyrazole piperidine derivatives was used for QSAR model development. These compounds exhibit good Akt1 inhibitory activity; moreover, antiproliferative activities in vitro against OVCAR-8 (Human ovarian carcinoma cells) and HCT116 (human colon cancer cells), were confirmed for them. Based on the relevant three-dimensional (3D) and 2D autocorrelation descriptors, selected by genetic algorithm (GA), multiple linear regression (MLR) was established on half maximal-inhibitory concentration (IC₅₀), in Akt1 and cancer cell lines independently. Robustness, stability, and predictive ability of the models were evaluated using external and internal validation (r²: 0.742-0.832, Q²_LOO: 0.684-0.796, RMSE: 0.247-0.299, F: 32.283-57.578, and r²_y-random: 0.049-0.080). Furthermore, in the new strategy, each of the evaluated models was generalized to two other subfamilies of piperidines to simultaneously compare the activities and structural similarity of these three subsets. Probably, structural similarity can be more considered as a criterion of similarity in the mechanism of action. Also, external verification of suggested predictive models was performed by another subset. Finally, by focusing on M64 as the most potent in vivo antitumor compound, 15 new derivatives were designed and six potent candidates were proposed for further investigation.

Protective effect of pomegranate flower extract against gentamicin-induced renal toxicity in male rats

Introduction: Gentamicin (GM) as an antibiotic is used in clinic. However, its administration is limited by side effects such as nephrotoxicity. Herbal extracts could be used in therapeutic approaches.

Objectives: The present study was planned to investigate whether pomegranate flower extract (PFE) could ameliorate GM-induced renal toxicity in male rats.

Materials and Methods: Twenty eight male Wistar rats were divided into 5 groups. Groups 1 and 2 respectively received PFE 25 and 50 mg/kg for 9 days. Groups 3, 4 and 5 received saline, PFE 25 mg/kg, and PFE 50 mg/kg for 9 days, respectively, and GM (100 mg/kg/day) was administered from day 3 on. Blood samples were obtained, and after sacrificing the animals, the kidneys were removed for histopathology investigations.

Results: GM alone increased the serum levels of creatinine (Cr) and blood urea nitrogen (BUN), and tissue damage and kidney weight (P < 0.05). However, administration of low dose of PFE accompanied with GM decreased these markers significantly (P < 0.05). Low dose of PFE also ameliorated weight loss induced by GM (P < 0.05).

Conclusion: It is concluded that PFE 25 mg/kg is the effective dose to ameliorate nephrotoxicity induced by GM.

Optimizing culture media for in vitro proliferation and rooting of Tetra (Prunus empyrean 3) rootstock

The enormous demand for new rootstock genotypes in Prunus spp. makes us to use micropropagation as an unavoidable propagation method. Therefore, the study on micropropagation of a new semi-dwarf vegetative rootstock namely Tetra (Prunus empyrean 3) was carried out to develop an optimized protocol. Culture establishment using nodal segments was enhanced using WPM (woody plant medium) medium lacking growth regulators. From various shoot multiplication treatments, the highest number of shoots per explant (30.4) was found on ME (Media created specifically) medium supplemented with 0.8 mg l^-1 BAP and 0.05 mg l^-1 IBA. 100% in vitro rooting was achieved on ½ strength MS medium with 0.5 mg l^-1 IBA, 1.6 mg l^-1 thiamine and 150 mg l^-1 iron sequestrene.

PVDF/Carbonnanotubes/Nanoclay Composites for Piezoelectric Applications

Poly(vinylidene) fluoride (PVDF) nanocomposite samples were prepared by incorporation of carbon nanotubes (CNT) and nanoclay into PVDF using a twin screw extruder. Carbon nanotube was added to improve electrical conductivity and nanoclay was included to enhance β crystal formation for piezoelectric property. X-ray diffraction (XRD) results showed that partial melt intercalation of PVDF in clay was achieved. The XRD results also revealed that CNT and nanocaly addition increased β phase crystal amount in PVDF. FTIR spectroscopy measurements confirmed the XRD results and showed that the effect of nanoclay on β phase crystal formation of PVDF was more prominent than CNT. It was found that shear rate applied during crystallization would improve β phase crystal formation but only for the neat PVDF. Electrical conductivity results showed that addition of CNT improved conductivity as a percolation of 2 wt.% was observed. It was found that dispersion of CNT into PVDF matrix is very crucial for obtaining a higher conductivity. The results showed that clay incorporation into CNT nanocomposite improved electrical conductivity. The TEM micrographs showed bundles of CNT were adhered to clay particles. That was considered an indication of affinity between CNT and organically modified clay. The results of compounding of CNT and nanoclay with PVDF in batch mixer also revealed improvement in electrical conductivity when clay was added into PVDF/CNT composite in melt state. The conductivity improved with mixing time for both systems: PVDF/CNT and PVDF/CNT/nanocaly.

Structure, Mechanical and Barrier Properties of Uniaxially Stretched Multilayer Nylon/Clay Nanocomposite Films

Multilayer films consisting of a core layer of nylon 6 (PA6) sandwiched between two linear low density polyethylene (LLDPE) layers by using a tie layer were produced using a semi industrial cast film extrusion line. The core layer of the films was produced from neat PA6 and PA6/clay nanocomposite resins. The films were consequently uniaxially stretched in machine direction. The effect of stretching on crystalline structure, orientation as well as mechanical and barrier properties of the samples were investigated. Orientation of the films for both layers: polyethylene and nylon was assessed using FTIR (Fourier Transform Infrared Spectroscopy) and it was found that clay inclusion hindered orientation of the core nylon layer. Interaction of nylon molecules with clay influences the crystalline structure for nylon/clay nanocomposite film during the stretching as it hindered crystal transformation of γ to α phase. The effect of clay interaction on phase structure was also observed in DSC (Dynamic Scanning Calorimetry) results. Stretching improved barrier to oxygen for the samples. Oxygen transmission rate was reduced about 62.5% for the films having a nylon core and 50% for those with nylon/clay core when stretched to a draw ratio of 1.5 and remained nearly constant for higher draw ratios up to 3. Haze of the films was reduced with stretching; however the effect was more effective for the sample with neat nylon in the core layer when compared to the nylon/clay core one. Finally, it was observed that puncture resistance of the samples was improved significantly with stretching.

Preferred Position and Orientation of Anticancer Drug Cisplatin During Encapsulation Into Single-Walled Carbon Nanotubes

Cisplatin is one of the most widely prescribed chemotherapy drugs to treat different types of cancers. However, this anticancer drug has a number of side effects such as kidney and nerve damages, anaphylactic reactions, hearing loss, nausea, and vomiting that strongly restrict its function. In the present study, single-walled carbon nanotubes (SWCNTs) are used as protective drug carriers which can decrease these severe side effects to some extent. Using the hybrid discrete-continuum model in conjunction with Lennard-Jones potential, new semi-analytical expressions in terms of single integrals are given to evaluate van der Waals (vdW) potential energy and interaction force between an offset cisplatin and a SWCNT. In addition, molecular dynamics (MD) simulations are conducted to validate the results of such a hybrid approach. The preferred location and orientation of cisplatin while entering SWCNTs are determined. It is shown that the equilibrium condition of the drug may be affected by the radius of nanotube, the orientation of cisplatin, and the distance between the central molecule of the drug (Pt) and the left end of nanotube. Furthermore, the influence of equilibrium condition on the distributions of vdW interactions is investigated.

Mechanics of Ellipsoidal Carbon Onions Inside Multiwalled Carbon Nanotubes

On the basis of the continuum approximation along with Lennard–Jones potential function, new semi-analytical expressions are presented to evaluate the van der Waals interactions between an ellipsoidal fullerene and a semi-infinite single-walled carbon nanotube. Using direct method, these expressions are also extended to model ellipsoidal carbon onions inside multiwalled carbon nanotubes. In addition, acceptance and suction energies which are two noticeable issues for medical applications such as drug delivery are determined. Neglecting the frictional effects and by imposing some simplifying assumptions on the van der Waals interaction force, a simple formula is given to evaluate the oscillation frequency of ellipsoidal carbon onions inside multiwalled carbon nanotubes. Also, the effects of the number of tube shells and ellipsoidal carbon onion shells on the oscillatory behavior are examined. It is shown that there exists an optimal value for the number of tube shells beyond which the oscillation frequency remains unchanged.

On the Oscillation Frequency of Ellipsoidal Fullerene–Carbon Nanotube Oscillators

There are many new nanomechanical devices created based on carbon nanostructures among which gigahertz oscillators have generated considerable interest to many researchers. In the present paper, the oscillatory behavior of ellipsoidal fullerenes inside single-walled carbon nanotubes is studied comprehensively. Utilizing the continuum approximation along with Lennard–Jones potential, new semi-analytical expressions are presented to evaluate the potential energy and van der Waals interaction force of such systems. Neglecting the frictional effects, the equation of motion is directly solved on the basis of the actual force distribution between the interacting molecules. In addition, a semi-analytical expression is given to determine the oscillation frequency into which the influence of initial conditions is incorporated. Based on the newly derived expression, a thorough study on the various aspects of operating frequencies under different system variables such as geometrical parameters and initial conditions is conducted. Based on the present study, some new aspects of such nano-oscillators have been disclosed.

Comparison of physicomechanical properties of films prepared from organic solutions and aqueous dispersion of Eudragit RL

BACKGROUND AND THE PURPOSE OF THE STUDY

Mechanical properties of films prepared from aqueous dispersion and organic solutions of Eudragit RL were assessed and the effects of plasticizer type, concentration and curing were examined.

METHODS

Films were prepared from aqueous dispersion and solutions of Eudragit RL (isopropy alcohol-water 9:1) containing 0, 10 or 20% (based on polymer weight) of PEG 400 or Triethyl Citrate (TEC) as plasticizer using casting method. Samples of films were stored in oven at 60°C for 24 hrs (Cured). The stress-strain curve was obtained for each film using material testing machine and tensile strength, elastic modulus, %elongation and work of failure were calculated.

RESULTS AND MAJOR CONCLUSION

The films with no plasticizer showed different mechanical properties depending on the vehicle used. Addition of 10% or 20% of plasticizer decreased the tensile strength and elastic modulus and increased %elongation and work of failure for all films. The effect of PEG 400 on mechanical properties of Eudragit RL films was more pronounced. The differences in mechanical properties of the films due to vehicle decreased with addition of plasticizer and increase in its concentration. Curing process weakened the mechanical properties of the films with no plasticizer and for films with 10% plasticizer no considerable difference in mechanical properties was observed before and after curing. For those with 20% plasticizer only films prepared from aqueous dispersion showed remarkable difference in mechanical properties before and after curing. Results of this study suggest that the mechanical properties of the Eudragit RL films were affected by the vehicle, type of plasticizer and its concentration in the coating liquid.

The effect of pectin on swelling and permeability characteristics of free films containing Eudragit RL and/or RS as a coating formulation aimed for colonic drug delivery

BACKGROUND AND THE PURPOSE OF THE STUDY

The potential of pectin as a bacterially degradable polysaccharide for colon drug delivery has been demonstrated. Due to the high solubility and swelling properties of pectin in aqueous media, it is frequently used in combination with water insoluble polymers for targeting drugs to the colon. The aim of this study was to evaluate free films containing pectin as a bacterially-degradable polysaccharide in combination with Eudragit RL (ERL) and/or RS (ERS) as a coating formulation for colonic drug delivery.

METHODS

Isolated free films comprising 20% pectin and 80% ERL or ERS and their combination in 1:1 ratio were prepared by casting method. Then, free films were evaluated by water vapor transmission (WVT), swelling and permeability experiments for theophylline and indomethacin in different media.

RESULTS

Formulations containing ERL exhibited higher WVT, swelling and permeability compared with formulations containing ERS. The permeability of theophylline through free films composed of pectin and eudragit polymers in simulated colonic media was not significantly different from those obtained in other media. However indomethacin free films containing pectin and ERL showed higher permeation in simulated colonic fluid (SCF) compared to the other media.

MAJOR CONCLUSION

Formulation containing pectin and ERL may be suitable as a coating formulation for colon targeted delivery of drugs of low solubility such as indomethacin.

Identification of frequency and distribution of the nine most frequent mutations among patients with 21-hydroxylase deficiency in Turkey

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders mainly due to defects in the steroid 21-hydroxylase (CYP21A2) gene.

METHODS

To determine the mutational spectrum in the Turkish population, the CYP21A2 active gene was analyzed in 100 unrelated patients with the classical form of 21-hydroxylase deficiency using PCR and RFLP.

RESULTS

Mutations were detected in 78 patients: 64 patients were homozygous for one mutation, seven patients were compound heterozygous with different mutations on each chromosome, two patients were homozygous for two different mutations, five patients were heterozygous, and 22 patients harbored none of the tested mutations. The most frequent mutation was IVS2-13A/C (28.5%), followed by large gene deletion (17%), Q318X (11.5%), I172N (4%), V281L (3.5%), R356W (3.5%), 8-bp (3%), complex alleles (2%), P30L (1%) and E6 cluster (1%).

CONCLUSION

The distribution of mutation frequencies in our study was slightly different from those previously reported in Turkey and in other parts of the world.

Thermal treating as a tool to produce plastic pellets based on Eudragit RS PO and RL PO aimed for tableting

A 3(2) full-factorial design was used for preparation of pellets using extrusion-spheronization technique. Independent variables were %ibuprofen (40, 60, 80) and %Eudragit RS PO/RL PO (0, 50, 100). In all formulations 3% w/w PVP K30 and 10% Avicel PH101 were also used. The pellets were cured in oven at 60 degrees C for 24h. The evaluated responses were crushing strength or yield point, elastic modulus and mean dissolution time (MDT) of pellets. The cured pellets were also compressed at 15kN compaction force and then observed under scanning electron microscope. It was shown that the cured pellets containing 40% or 60% drug exhibited a plastic deformation without any fracture under mechanical tests. The curing process resulted in significant decrease in the elastic modulus of the pellets. The SEM of the compressed pellets were also confirmed the plastic behavior of these pellets. The transition of pellet behavior from brittle to plastic upon curing was due to shift of Eudragit structure from glassy to rubbery state which was supported by DSC studies. However pellets with 80% drug showed brittle properties even after curing due to presence of less amount of Eudragit in their structure. Increasing the ratio of Eudragit RS in the pellets decreased the yield point and elastic modulus of cured pellets containing 40% or 60% drug, indicating more plastic behavior of these pellets. This was attributed to lower Tg of Eudragit RS than Eudragit RL. The curing process also retarded drug release from pellets and increased MDT. Increasing the ratio of Eudragit RS in the pellets increased MDT in cured pellets containing 40% or 60% drug but had no effect in pellets with 80% drug. Overall the results of this study revealed that thermal treating is a proper tool to produce plastic ibuprofen pellets based on Eudragit RS PO and Eudragit RL PO.

Combination of time-dependent and pH-dependent polymethacrylates as a single coating formulation for colonic delivery of indomethacin pellets

The objective of this study was to evaluate the combination of pH-dependent and time-dependent polymers as a single coating for design of colon delivery system of indomethacin pellets. Eudragit S100 and Eudragit L100 were used as pH-dependent polymers and Eudragit RS was used as a time-dependent polymer. A statistical full factorial design was used in order to optimize formulations. Factors studied in design were percent of Eudragit RS in combination with Eudragit S and L and coating level. Dissolution studies of pellets in the media with different pH (1.2, 6.5, 6.8 and 7.2) showed that drug release in colon could be controlled by addition of Eudragit RS to the pH-dependent polymers. The lag time prior to drug release was highly affected by coating level. With combination of two factors, i.e. the percent of Eudragit RS and coating level, the optimum formulation was found to be the one containing 20% Eudragit RS, 64% Eudragit S and 16% Eudragit L, and a coating level of 10%. This formulation was reproduced and tested in continuous condition of dissolution, and also separately at pH 7.5. The results of in vitro experiments indicate that the proposed combined time-dependent and pH-dependent polymethacrylate polymer coating may provide a colonic delivery system for indomethacin.

Permeability and swelling studies on free films containing inulin in combination with different polymethacrylates aimed for colonic drug delivery

The aim of this study was to assess some permeability and swelling characteristics of free films prepared by combination of inulin as a bacterially degradable system and time- or pH-dependent polymers as a coating formulation for colonic drug delivery. Different free films were prepared by casting and solvent evaporation method. Formulations containing inulin with Eudragit RS, Eudragit RL, Eudragit RS-Eudragit RL, Eudragit FS and Eudragit RS-Eudragit S with different ratios of inulin were prepared. After preparation, free films were evaluated by water vapor transmission test, swelling experiment and permeability to indomethacin and theophylline in different media. Formulations containing Eudragit FS had high resistance to water vapor permeation; but were unable to protect premature swelling and drug release in simulated small intestine media. Also, combination of Eudragit RS and Eudragit S had no suitable characteristics for colon delivery. However, Eudragit RS and Eudragit RL in combination with inulin made free films which had more swelling and permeation of drug in the colonic medium rather than the other media. It was shown that formulations containing sustained release polymethacrylates in combination with inulin have more potential as a coating system for specific colon delivery compared with pH-dependent polymers.

Statistical optimization of indomethacin pellets coated with pH-dependent methacrylic polymers for possible colonic drug delivery

The objective of this study was to evaluate the effect of two factors (ratio of Eudragit S100 and Eudragit L100 and the coating level) on indomethacin release from pellets in order to optimize coating formulations for colonic delivery. Coating formulations were designed based on the full factorial design. Two independent variables were the ratio of Eudragit S100:Eudragit L100 (1:4, 1:1 and 1:0) and the level of coating (10%, 15% and 20%, w/w), respectively. The evaluated responses were lag time prior to drug release at pH 6.8 (the time required for drug release up to 2%) and percent of drug release at pH 6.8 in 5h. Polymers were coated onto the pellets containing 20% (w/w) indomethacin, using a fluidized bed coating apparatus. Dissolution test was carried out in media with different pH (1.2, 6.5, 6.8 and 7.2). The dissolution data revealed that the level of coating and the ratio of polymers are very important to achieve optimum formulation. Using responses and resulted statistical equations, optimum formulation consisted of Eudragit S100:L100 in 4:1 ratio and the level of coating (20%) was predicted. Practical results showed that the pellets prepared according to above formulation released no indomethacin at pH 1.2 (simulating stomach pH) and pH 6.5 (simulating proximal part of small intestine pH); drug release was slowly at pH 6.8 (simulating lower part of small intestine pH), but it was fast at pH 7.2 (simulating terminal ileum pH). The results of this study revealed that factorial design is a suitable tool for optimization of coating formulations to achieve colon delivery. It was shown that coating formulation consisted of Eudragit S100:Eudragit L100 in 4:1 ratio at 20% coating level has potential for colonic delivery of indomethacin loaded pellets. The optimized formulation produced dissolution profiles that were close to predicted values.

Preparation and characterization of ibuprofen pellets based on Eudragit RS PO and RL PO or their combination

The aim of this study was to assess the application of Eudragit RL PO and RS PO and their combination for production of ibuprofen pellets by extrusion-spheronization. The pellets were prepared based on full factorial design. Independent variables were % ibuprofen (40, 60, 80), the ratio of Eudragit RS to Eudragit RL (1:0, 1:1, 0:1) and % PVP (1, 3, 5). The evaluated responses were mean dissolution time (MDT), crushing strength and elastic modulus of pellets. Surface characteristics, sphericity and aspect ratio of pellets were also evaluated. Linear regression and response surface modeling was used for analyzing results. It was shown that the amount of water required to prepare a proper wet mass was affected by composition of formulations. The required amount of water decreased with increasing drug load and percent of PVP. It was also shown that formulations containing Eudragit RL need more water. Increasing percent of PVP slightly decreased MDT and elastic modulus but had negligible effect on crushing strength. Increasing the percent of ibuprofen up to 60% decreased MDT but beyond that increased MDT. Increasing the percent of ibuprofen also decreased elastic modulus of pellets. Eudragit RL PO compare with Eudragit RS PO resulted in pellets with high crushing strength; however, Eudragit type did not have a significant effect on elastic modulus.

Tableting of Eudragit RS and propranolol hydrochloride solid dispersion: effect of particle size, compaction force, and plasticizer addition on drug release

The application of a solid dispersion (SD) system of propranolol HCl and Eudragit RS was evaluated in the preparation of prolonged release tablets. The effects of SD size fraction, compaction force, and inclusion of plasticizers [namely diethylphtalate (DEP) and triethylcitrate (TEC)] on crushing strengths of matrices and release profile of drug were also investigated. The results showed that when compressed as a tablet, the SD system was more efficient in prolonging drug release than physical mixture. This effect was due to formation of much harder tablets of the SD system (crushing strength 8.5 kg) compared with those of physical mixtures (crushing strength 2.7 kg). All matrices of the SD system showed release rate patterns that were best described by the Higuchi equation. It was also shown that the rate of drug release decreased from 19.8% to 9.13% min(-1/2) as the SD size fraction decreased from 300-350 to 125-250 microm. However, further reduction of size fraction did not significantly affect tablet crushing strength and drug release rate. Increase in compaction force from 5 to 30 kN increased the crushing strength of matrices from 2.9 to 13.6 kg. However, the rate of drug release remained nearly unchanged beyond compaction pressure of 10 kN, indicating that crushing strength of matrices in the range of 8.5-13.6 kg did not affect drug release rate. The addition of 5% or 10% of either plasticizer (DEP or TEC) led to an increase in crushing strength of matrices and more retardation of drug release. This effect was more pronounced for higher concentrations of plasticizers. This effect was probably due to more plastic deformation of matrices under the compaction force, which helped matrices to retain their shape throughout the dissolution test.

Increasing the aqueous solubility of acetaminophen in the presence of polyvinylpyrrolidone and investigation of the mechanisms involved

It was shown that the aqueous solubility of acetaminophen in the presence of polyvinylpyrrolidone (PVP) increased. The solubility at 25 degrees C increased from 14.3 m mL(-1) in the absence of PVP, to 19.7 mg m(-1) in the presence of 4% w/v PVP, and to 26.7mg mL(-1) in the presence of 8% w/v PVP. Dialysis studies indicated that there is a potential of binding between PVP and acetaminophen in their aqueous solutions. Dialysis studies also revealed that the nature of interaction between PVP and acetaminophen is physical and reversible, and there was no strong binding between PVP and acetaminophen in their solutions. Infrared spectroscopy of acetaminophen/PVP solid dispersion indicated that the mechanism of interaction between PVP and acetaminophen is via hydrogen bonding. Therefore, the increase in solubility of acetaminophen in the presence of PVP is probably attributed to its ability to form a water-soluble complex with PVP.

Crystal habit modifications of ibuprofen and their physicomechanical characteristics

Ibuprofen was crystallized from methanol, ethanol, isopropanol, and hexane at similar conditions. Marked differences in crystal habit of the samples obtained from these solvents were observed. The samples crystallized from methanol and ethanol had a polyhedral crystal habit, while those from hexane were needlelike. Those from isopropanol were elongated crystals. X-ray powder diffraction (XPD) and diferential scanning calorimetry (DSC) studies confirmed that these samples were structurally similar, therefore, polymorphic modifications were ruled out. The results showed that crystal habit modification had a great influence on the mechanical properties (compressibility, flow rate, and bulk density) of ibuprofen crystals. Samples obtained from methanol and ethanol exhibited the highest bulk density and the best flow rate, while those from hexane showed the lowest bulk density and the worst flow rate. The samples obtained from ethanol exhibited the best compression force/hardness profiles, and those obtained from hexane produced the softest tablets.

Study of drug release from pellets coated with Surelease containing hydroxypropylmethylcellulose

The release of metoclopramide hydrochloride (a very water soluble cationic drug) and diclofenac sodium (a sparingly soluble anionic drug) from pellets coated with Surelease containing hydroxypropylmethylcellulose (HPMC) at different coating loads was investigated. The release rates of either drug at each coating composition decreased as the coating load increased. Inclusion of HPMC E15 increased the release rates of both drugs compared to pellets coated only with Surelease. This was thought to be due to the leakage of the soluble part of the film (HPMC E15) during dissolution, which left pores for drug release. The Surelease:HPMC E15 ratio had a major role in the release rates of drugs. Addition of HPMC E15 into Surelease did not change the release mechanism for metoclopramide hydrochloride (the mean value of n approximately 0.57) from that of Surelease alone, and diffusion remained the main mechanism controlling the release. However, the release exponent (approximately 1.28) increased for diclofenac sodium on addition of HPMC E15, indicating a dissolution-controlled mechanism. Despite its lower water solubility, diclofenac sodium was released slightly faster than metoclopramide hydrochloride from pellets coated with Surelease containing HPMC E15 at equivalent coating loads.

Dyspareunia: an unusual presentation of leiomyoma of the bladder

Leiomyoma is a rare, benign tumor of the bladder. It frequently has an unusual presentation and its treatment options remain controversial. We describe a case of a leiomyoma of the bladder in a young female whose chief complaint was dyspareunia, and we review the management options.

Comparative study of drug release from pellets coated with HPMC or Surelease

The release of metoclopramide hydrochloride (very water soluble cationic drug) and diclofenac sodium (sparingly soluble anionic drug) from pellets coated with hydroxypropylmethylcellulose (HPMC; water-soluble polymer) or ethylcellulose aqueous dispersion (Surelease; water-insoluble polymer) at different coating loads was investigated. The release rates of either drug decreased as the coating load of HPMC increased, but overall, the release was fast, and the majority of both drugs released in about 1 hr, even at the highest coating load. The drug release mechanism for either drug was not affected by the coating load of HPMC or by the type of drug used, and it was found to be mainly diffusion controlled. Diclofenac sodium released slightly more slowly than metoclopramide hydrochloride from HPMC-coated pellets. This was attributed to the lower water solubility of the former drug. The release rate of either drug decreased greatly as the coating load of Surelease increased. The release of both drugs was sustained over 12 hr as the coating load of Surelease increased, and only about 70% of either drug was released after this period at the highest coating load (20%). The mechanism of release of metoclopramide hydrochloride was independent of coating load, and it was predominantly diffusion controlled. However, the mechanism of diclofenac sodium release was dependent on the coating load of Surelease. At low coating loads, diffusion of drug was facilitated due to the presence of more pores at the surface of the coated pellets; therefore, the rate of dissolution of the drug particles was the rate-limiting step. However, at high coating loads, drug release was mainly diffusion controlled. Despite its lower water solubility, diclofenac sodium released slightly faster than metoclopramide hydrochloride from Surelease-coated pellets at equivalent coating loads.

Effect of cryptorchidism on testicular histology in a naturally cryptorchid animal model

PURPOSE

To determine the effect of naturally occurring cryptorchidism on testicular histology in both the cryptorchid and normally descended testis from birth to adulthood using the LE/ORL rat model.

MATERIALS AND METHODS

Testicular histology was assessed using established morphometric measures in bilaterally descended (BD), unilaterally descended (UD), bilaterally cryptorchid (BC) and unilaterally cryptorchid (UC) testis at days 15, 22, 30, 45 and 60 of age. Testicular mass was also measured at these times.

RESULTS

Changes in testicular histology in the BC and UC testes were not noted on or prior to day 30 of age. Significant changes were noted by day 45 of age and continued into adulthood at day 60 of age. There were no histological abnormalities noted in the UD and BD groups.

CONCLUSIONS

Since histological changes seen in this animal model occur after the time of testicular descent (day 28 of age), we hypothesize that these changes are due to an abnormal anatomical position of the testis as opposed to an inherent testicular defect in the LE/ORL rat. This hypothesis is supported by the fact that no histological differences were noted between the scrotal testes of unilaterally cryptorchid animals and bilaterally descended control animals.

Prevention of seminiferous tubular atrophy in a naturally cryptorchid rat model by early surgical intervention

In an attempt to determine whether the seminiferous tubular atrophy of the cryptorchid testis is preventable by early surgical correction of the cryptorchid state, aberrantly developed gubernacula destined to result in a cryptorchid testis in the Long-Evans cryptorchid (LE/ORL) rat were surgically reimplanted to the bottom of the scrotum on day 10 to 12 of age. Testis descent was monitored and the changes in testicular histology and in the volumes of the seminiferous tubules and Leydig cells were examined at day 60. As expected, normal testis descent occurred on or about day 25. Compared to untreated undescended testes at day 60, relative seminiferous tubular volumes (volume: % +/- SEM) were significantly increased by early surgical reimplantation of the gubemacula (89 +/- 1 vs. 66 +/- 3; P < 0.01). Absolute seminiferous tubular volumes (microliter +/- SEM) were also significantly increased by early surgical intervention when compared to undescended nontreated testes (893 +/- 27 vs. 170 +/- 12; P < 0.01). The testes of the surgically corrected cryptorchid animals were similar in all respects to those found in the descended testes of the sham-operated controls. Relative Leydig cell volume (% +/- SEM) was increased in the untreated cryptorchid testes compared to the surgically corrected testes (5.2 +/- 0.6 vs. 1.2 +/- 1.0; P < 0.05). Relative Leydig cell volumes in the surgically corrected testes were not significantly different from those found in the sham-operated descended controls. A modest but significant (P < 0.05) increase in absolute Leydig cell volume was also noted in the cryptorchid testes when compared both to normal controls or surgically corrected cryptorchid testes. From these observations, we conclude that early gubernaculopexy reverses the histologic changes normally seen in the cryptorchid rat testis to a relatively normal histologic architecture. These data provide experimental evidence to support the value of orchiopexy in the treatment of cryptorchidism.

Androgens are not major down-regulators of androgen receptor levels during growth of the immature rat penis

This study was undertaken to investigate the prevalent hypothesis that androgens are responsible for the organ-specific down-regulation of penile androgen receptors (ARs) and decline of penile growth in the rat during sexual maturation. Sexually immature male rats (21 days old) were castrated and treated for 3 days ("short-term"), with high doses of: (a) testosterone and the alpha-reductase inhibitor finasteride (T/F); (b) dihydrotestosterone (DHT); or (c) finasteride alone (F). Intact and castrate controls received vehicle only. PolyA + RNA was analysed by Northern blot hybridization and ARs were estimated in the penis and ventral prostates by (3-H)R-1881 binding in the cytosol. Short-term castration, with or without F, increased penile AR mRNA, whereas high doses of T/F and DHT reduced it considerably. Although penile cytosol AR concentration in the control castrates, with or without F, paralleled the AR mRNA rise, treatment with androgens left cytosol AR content per organ and AR concentration above those of the intact rat penis despite the drop in AR mRNA. A "long-term" treatment (10 days) on 19-day-old rats with either medium or high doses of T/F and DHT also failed to down-regulate penile cytosol ARs below the intact controls. Western blot analysis of penile cytosol AR levels confirmed these results. Block of pituitary FSH and LH release by a GnRH antagonist in castrates receiving T/F or DHT at high doses did not modify the response. In the case of intact rats, high doses of T/F or DHT actually increased penile cytosol AR content. No difference was observed between T/F and DHT effects. In contrast to what occurs during sexual maturation, the prostate ARs and growth rate responded to all treatments in a similar way to what was observed in the penis. Our results suggest that increases in serum T or DHT are not major factors in the physiological down-regulation of ARs and androgen-dependent growth in the rat corpora cavernosa.

Hybridization of a complementary ribooligonucleotide to the transcription start site of the lacUV-5-Escherichia coli RNA polymerase open complex. Potential for gene-specific inactivation reagents

An ribooligonucleotide, UGGAA, complementary to the template strand of the lacUV-5 promoter can hybridize to the transcription "bubble" of the open complex formed by Escherichia coli RNA polymerase. Its site-specific binding, measured by gel retardation, enzyme inhibition, and chemical nuclease footprinting, is dependent on catalysis by RNA polymerase and the sequence of the hybridizing ribooligonucleotide. When UGGAA is linked to the chemical nuclease 1,10-phenanthroline copper, site-specific scission of the template strand of the transcriptionally active gene is observed. The formation of single-stranded DNA at transcription start sites by RNA polymerases provides a target for antigene strategies.