Matrix Granules Research Articles

Dermal toxicity: effect of jet propellant-8 fuel exposure on the biophysical, macroscopic and microscopic properties of porcine skin

The effect of jet propellant-8 (JP-8) fuel exposure on the biophysical, macroscopic and microscopic changes in vitro in porcine skin has been investigated. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the biophysical changes in stratum corneum (SC) lipid and protein. FTIR results showed that the treatment of the SC with JP-8 to increasing exposure time caused correspondingly greater percent decrease in the peak heights and areas under the absorbance curve of methylene and amide absorbances, suggesting greater loss of lipid and protein from SC layers. In vitro transepidermal water loss (TEWL) studies allowed an investigation into the macroscopic barrier properties of the skin. TEWL results were in consonance with that of FTIR. There was a significant increase ( P<0.05) in TEWL through 8 and 24 h JP-8 exposed skin in comparison to the control. Light microscopy provided direct, corroborative, visual evidences of epidermal and dermal alterations. Epidermal swelling, dermal matrix granulation, mast cell granules, shortened collagen fibers were observed in the skin exposed with JP-8. Thus, it is concluded that JP-8 exposure causes appreciable biophysical and histological changes along with increased TEWL values in vitro in pig skin which may lead to skin irritation and dermal toxicity in vivo.

Toxoplasma gondii ADP-ribosylation Factor 1 Mediates Enhanced Release of Constitutively Secreted Dense Granule Proteins

Toxoplasma gondii dense granules are morphologically similar to dense matrix granules in specialized secretory cells, yet are secreted in a constitutive, calcium-independent fashion. We previously demonstrated that secretion of dense granule proteins in permeabilized parasites was augmented by the non-hydrolyzable GTP analogue guanosine 5'-3-O-(thio)triphosphate (GTPgammaS) (Chaturvedi, S., Qi, H., Coleman, D. L., Hanson, P., Rodriguez, A., and Joiner, K. A. (1998) J. Biol. Chem. 274, 2424-2431). As now demonstrated by pharmacological and electron microscopic approaches, GTPgammaS enhanced release of dense granule proteins in the permeabilized cell system. To investigate the role of ADP-ribosylation factor 1 (ARF1) in this process, a cDNA encoding T. gondii ARF1 (TgARF1) was isolated. Endogenous and transgenic TgARF1 localized to the Golgi of T. gondii, but not to dense granules. An epitope-tagged mutant of TgARF1 predicted to be impaired in GTP hydrolysis (Q71L) partially dispersed the Golgi signal, with localization to scattered vesicles, whereas a mutant impaired in nucleotide binding (T31N) was cytosolic in location. Both mutants caused partial dispersion of a Golgi/trans-Golgi network marker. TgARF1 mutants inhibited delivery of the secretory reporter, Escherichia coli alkaline phosphatase, to dense granules, precluding an in vivo assessment of the role of TgARF1 in release of intact dense granules. To circumvent this limitation, recombinant TgARF1 was purified using two separate approaches, and used in the permeabilized cell assay. TgARF1 protein purified on a Cibacron G3 column and able to bind GTP stimulated dense granule secretion in the permeabilized cell secretion assay. These results are the first to show that ARF1 can augment release of constitutively secreted vesicles at the target membrane.

Effects of Storage on Viability and Efficacy of Granular Formulations of the Microbial Herbicides Alternaria alternata and Trematophoma lignicola

Alternaria alternata Pesta (gluten matrix) granules stored at 12% relative humidity were still viable and infective, giving total control of Amaranthus retroflexus after 24 months storage. Viability of the propagule in the granule was an important factor of the evaluation test and not just the viability of the granule. The concentration of inoculum in the granule was important, with 10 5 to 10 6 conidia g -1 being the ideal, since lower concentrations may not be able to out-compete the soil micro-flora. Even with soil application, the effect of local humidity was still important. Trematophoma lignicola was also formulated as microbial herbicide granules but the conidia were severely damaged in the production process.

FINE STRUCTURAL MODIFICATIONS OF LIVER, PANCREAS AND BROWN ADIPOSE TISSUE MITOCHONDRIA FROM HIBERNATING, AROUSING AND EUTHERMIC DORMICE

An ultrastructural and morphometric study was performed on mitochondria of euthermic, hibernating and arousing hazel dormice (Muscardinus avellanarius), in order to investigate possible modifications during the seasonal cycle. Hepatocytes, pancreatic acinar cells and brown adipocytes were considered. Our results demonstrated that: (1) the general morphology of mitochondria of all cell types shows slight modifications during the seasonal cycle; (2) mitochondrial size and inner membrane length significantly increase from euthermia to hibernation and decrease upon arousal in all cell types; (3) mitochondrial matrix granules drastically increase in number during hibernation and decrease upon arousal in hepatocytes and pancreatic acinar cells, whereas they do not change in brown adipocytes. These structural modifications are probably related to the changes in cellular energy needs during the euthermia–hibernation–arousal cycle.

Controlled release of a herbicide from matrix granules based on solvent-fractionated organosolv lignins.

An organosolv (Alcell) lignin was fractionated with both sequential solvent-extraction and solvent-mixture precipitation using various organic solvent systems. The resulting fractionated lignins were used to prepare matrix granules with bromacil as a model compound using a melt process. The release rates of bromacil in vitro from the granular matrix system were influenced by both the lignin used as carrier and the solution fractionation. The variations in release rates were related to the high proportion of low-molecular-weight fraction and its associated water-soluble lignin in the fractionated lignins. Fickian diffusion was a predominant factor in controlling the release of bromacil from the matrix granules based on the low-molecular-weight fraction (L(fr1)). For the matrix granules based on the other fractionated lignins, the release of bromacil was of super-case II transport. The fine structure of the matrix granules before and after release was also studied. An unique release pattern of bromacil was observed for the matrix granules based on the low-molecular-weight fraction (L(fr1)), showing a fast release followed by zero-order release, which was a result of remarkable changes in the structure of the matrix granules during the course of release.

Organic acids as excipients in matrix granules for colon-specific drug delivery

Interest exists in developing site-specific systems for release of a drug in the lower part of the small intestine or in the colon. The aim of this study was to investigate whether drug release rates from enteric matrix granules could be influenced by using organic acids as excipients. Ibuprofen was used as a model drug and Eudragit™ S and Aqoat™ AS-HF as enteric polymers. The dissolution rates of the drug were investigated at different levels of pH (5.8, 6.8 and 7.4). Drug absorption was studied in bioavailability tests in healthy volunteers. In vitro/in vivo correlation was also investigated. It was concluded that although inclusion of an organic acid in a formulation retarded in vitro release of the model drug, no corresponding effect was evident in in vivo studies. Bioavailability tests are therefore important early on during development of new dosage forms or formulations. Although no correlation between in vitro and in vivo results was generally evident correlation could be demonstrated for individual formulations following mathematical transformation of data.

Extrusion–Spheronization Manufacture of Gelucire® Matrix Beads

Theophylline extended-release spheres were prepared by extrusion–spheronization of matrix granulations previously obtained by incorporation of the drug in melted Gelucire 50/02 or Gelucire 55/18. Hydrophobic Gelucire 50/02 behaved as an inert matrix and released theophylline very slowly compared with hydrodispersible Gelucire 55/18, which acted as a hydrophilic matrix. Extrusion–spheronization was more easily accomplished with Gelucire 50/02. The use of ethanol as a wetting fluid increased the rate of drug release noticeably with Gelucire 50/02 and less so with Gelucire 55/18. The use of castor oil, in conjunction with ethanol to slow down the solvent evaporation, improved extrusion and spheronization. Castor oil decreased the drug release rate with Gelucire 50/02 and increased it with Gelucire 55/18. These phenomena were explained by the different solubilities of theophylline, Gelucire 50/02, and Gelucire 55/18 in ethanol and castor oil. When microcrystalline cellulose (Avicel® CL 611) was used in the granulation matrix, extrusion was improved. The best formulation was obtained with Gelucire 55/18 and Avicel CL 611 and was wetted by a mixture of ethanol and castor oil. Regardless of the formulation, the mechanism of theophylline release appeared to be via Fickian diffusion.

In Vivo Performance of Wax Matrix Granules Prepared by a Twin-Screw Compounding Extruder

The in vivo performance of wax matrix granules (WMGs) prepared by a twin-screw compounding extruder was evaluated in fasted beagle dogs. In vitro dissolution behavior of the model drug, diclofenac sodium (DS), from WMGs was strongly influenced by pH in a dissolution medium due to its solubility (DS is soluble in pH 6.8 and insoluble in pH 1.2 and 4.0) and was independent of paddle rotation rate (50, 100, and 200 rpm) of the dissolution apparatus. Pharmacokinetics parameters such as mean residence time (MRT) showed a sustained action of WMGs in beagle dogs; however, the transit time of WMGs in the small intestine is found to control total drug absorption. Furthermore, the values of the area under the curve (AUC) of the plasma concentration–time curve and the maximum concentration Cmax significantly decreased with decreases in hydroxypropylcellulose (HPC) content in WMGs. Good correlation between one in vitro dissolution parameter (mean dissolution time, MDT) and two in vivo parameters (AUC12 and MRT) suggested that it would be possible to design WMGs with a desired in vivo performance by controlling HPC content.

Constitutive Calcium-independent Release of Toxoplasma gondii Dense Granules Occurs through the NSF/SNAP/SNARE/Rab Machinery

The signals and the molecular machinery mediating release of dense matrix granules from pathogenic protozoan parasites are unknown. We compared the secretion of the endogenous dense granule marker GRA3 in Toxoplasma gondii with the release of a stably transfected foreign reporter, beta-lactamase, that localizes to parasite dense granules. Both proteins were released constitutively in a calcium-independent fashion, as shown using both intact and streptolysin O-permeabilized parasites. N-Ethylmaleimide and recombinant bovine Rab-guanine dissociation inhibitor inhibited beta-lactamase secretion in permeabilized parasites, whereas recombinant hamster N-ethylmaleimide-sensitive fusion protein and bovine alpha-SNAP augmented release. Guanosine 5'-3-O-(thio)triphosphate, but not cAMP, augmented secretion in the presence but not in the absence of ATP. The T. gondii NSF/SNAP/SNARE/Rab machinery participates in dense granule release using parasite protein components that can interact functionally with their mammalian homologues.

Phenomenological theory of the giant magnetoresistance of ferromagnet-nonmagnetic metal granular media

A phenomenological model is developed for the giant magnetoresistance of granular media comprising ferromagnetic granules in a nonmagnetic metal matrix. Both volume and surface spin-dependent scattering by the ferromagnetic granules are taken into account. The internal electric fields are inhomogeneous because of the different conductivities of the granules and the matrix. The dependence of the effective conductivity of the medium on the average magnetization is calculated and used to explain the giant magnetoresistance effect. The magnetoresistance is plotted as a function of the volume concentration of ferromagnetic granules and the granule radius. Experiments on Co-Cu and Co-Ag granular films are discussed.

Establishment and Characterization of a Nontumorigenic Cell Line Derived from a Human Hepatocellular Adenoma Expressing Hepatocyte-Specific Markers

In the present study the establishment and characterization of a nontumorigenic liver epithelial cell line (HACL-1) derived from a human hepatocellular adenoma is described. The HACL-1 cells have a finite life span (i.e., they proliferate for a period of 2 months and then senesce), show cell–cell contact inhibition, do not grow in soft agar, are not tumorigenic when injected in nude mice, and possess a normal diploid karyotype. The cultured cells resemble hepatocytes, but exhibit some features of dedifferentiation. At the ultrastructural level the cells are endowed with round or oval nuclei, abundant cytoplasmic organelles, and varying amounts of glycogen. The rough endoplasmic reticulum is disorganized, while peroxisomes and matrix granules within mitochondria are lacking. HACL-1 cells are cytokeratin 18-positive as well as (transiently) albumin- and α-fetoprotein-positive, but do not express cytokeratin 19. Furthermore, no mutations were observed in exons 5–8 of the tumor suppressor genep53.Taken together these results show that HACL-1 cells are nontumorigenic proliferating liver epithelial cells, which might prove to be of great value in future studies on diverse aspects of human liver cell biology and carcinogenesis.

The Fine Structure of the Scopula‐Stalk Region of Vorticella convallaria

ABSTRACT. We examined by SEM and TEM the stalk‐scopular junction, the stalk, and stalk formation in Vorticella convallaria Linnaeus, 1767. The stalk sheath is anchored to the walls of the scopular lip and to the scopular cilia by thin fibrils. Experimental extraction of these fibrils weakens this junction enough to separate the stalk from the cell body. Telotrochs escape from the stalk by means of violent contractions of the cell body, accelerated beating of the trochal band cilia, and twisting of the cell body against the stalk. The edges of the scopular lip spread over the scopular cilia after escape and, in some cases, fuse to enclose the entire, aboral scopular surface in a cupola‐like structure. The sessile cells contain fewer and smaller scopular granules than telotrochs. The presence of disintegrating scopular granules in the stalk matrix of some sessile cells suggests that they contain material which is secreted over a period of time to form the stalk. Eruptive formation of the initial adhesive pad and quick elongation of the distal part of the stalk suggests a rapid exocytosis of the larger, more numerous granules of the telotroch. The stalk sheath is formed of fibrils making up complete and incomplete compartments peripherally arranged along the major stalk axis.

Dissolution Mechanism of Diclofenac Sodium from Wax Matrix Granules

Dissolution behavior of diclofenac sodium (DS) from wax matrix granules (WMGs) prepared using a twin-screw compounding extruder is closely related to swelling ability and solubility of the rate-controlling agent employed. A swellable and soluble (hydroxypropyl)-cellulose (HPC-SL) generates both an expansion of pores inside WMGs and a structural change observed as cracking on the surface of WMGs. These changes are confirmed by mercury porosimetry. Release of DS was increased with an increase in the amount of HPC-SL in WMGs, but only 35% of DS was released from WMGs containing 73% (w/w) NaCl at the 24h point of the dissolution. Further, no cracking was observed on the surface of NaCl-containing WMGs. A linear relationship between mean dissolution time (MDT) of DS for WMGs containing different types of HPC (HPC-SL, -M, and -H) and swelling abilities suggests that release of DS could be directly controlled by swelling of HPCs. In addition to this result, an application of the exponential model (Mt/M∞=ktn) introduced by Ritger and Peppas (J. Controlled Release1987, 5, 23–36) to DS release indicates that case II release plays a critical role in HPC-SL-containing WMGs and Fickian release is predominant in NaCl-containing WMGs since the values of n of WMGs containing 73% (w/w) NaCl and 40% (w/w) HPC-SL are 0.41 and 0.71, respectively. These results suggest that proper selection of rate-controlling agents based on their physicochemical properties (such as swelling ability and solubility) is important in designing WMGs with desired dissolution profiles.

Controlled-release of diclofenac sodium from wax matrix granule

A twin-screw compounding extruder was used to prepare wax matrix granules (WMG) consisting of carnauba wax, diclofenac sodium (DS) as a model drug, and rate-controlling agents such as hydroxypropylcellulose (HPC-SL), methacylic acid copolymer L (Eudragit L-100), and sodium chloride (NaCl). In this preparation, a wax matrix with high mechanical strength was obtained even at temperatures lower than the wax melting point. Dissolution behaviors of DS from WMG were strongly influenced by granule formulation, in which an increase in the content of HPC-SL or Eudragit L-100 brought a significant increase in the dissolution rate. The extent of this enhancing effect in HPC-SL was identical in two different dissolution mediums (pH 6.8 buffer solution and water), but in Eudragit L-100 was more significant in pH 6.8 buffer solution than in water. Only a small increase in the dissolution rate was observed in NaCl-containing WMG. These different behaviors were attributed to the physicochemical properties (i.e. swelling and solubility) of the rate-controlling agent in the dissolution medium. Further, mechanical strengths of the wetted WMG after dissolution studies were > 70 g/mm 2 suggesting that burst release of DS in the gastrointestinal tract would be avoided.

In vitro evaluation of a pH-sensitive hydrogel for control of GI drug delivery from silicone-based matrices

The release of drugs having very different aqueous solubilities and partitioning properties, such as salicylamide (SAM), nicotinamide (NAM), clonidine·HCl (CHC) and prednisolone (PDN), from 1 mm thick silicone discs containing, in dispersion, around 35 wt% medicated granules of a pH-sensitive hydrogel, is studied in vitro. The hydrogel is a poly(acrylic acid) (PAA):poly(ethylene oxide) interpenetrating polymer network (IPN). The matrices are eluted with simulated GI fluids, i.e., with a medium of pH 1.2 for 2 h, followed by a medium of pH 6.8 for 2 h, followed by a medium of pH 7.4 for 5 h. The release rate pattern is always bimodal and is determined by the pH-dependent swelling of the IPN granules in matrix. In simulated gastric fluid (SGF) the IPN swelling degree is low and the release is limited to an initial burst, followed by a rapid decline. In simulated intestinal fluid (SIF), PAA in the IPN becomes ionized, the IPN swelling degree increases and the release rate rises to a second maximum. The drug fraction released is always preponderant in SIF compared to SGF. The matrix swelling and drug release rates are influenced by the granule size. With a loading dose of 5 wt% in IPN granules in the 355–425 μm size range, SAM, NAM and PDN show the same release rates in SIF. Differences arise when the load is raised to 20 wt% and/or the granule size range is reduced to 105–250 μm. CHC shows an ionic interaction with PAA in the IPN, which limits the release rate in SIF. The release of drugs not ionically interacting with PAA is virtually uninfluenced by ample variations in osmolality, ionic strength and buffer molarity of dissolution medium.

Predictive value of electrogustometry in the preoperative diagnosis of severity of middle ear pathology

The chorda tympani nerve (CTN) is frequently damaged in various inflammatory middle ear disorders. To determine the validity of electrogustometry in the diagnosis of preoperative severity of a middle ear lesion of the posteosuperior portion of the mesotympanum, the threshold determined by electrogustometry was examined preoperatively and was correlated with the intraoperative findings. One hundred and six ears of 97 patients with various middle ear diseases were examined. The patients ranged in age from 5 to 70 years (average, 39.4) : 55 of them were male and 42 were female. In 80 of them the appearance of the tympanic membrane on the opposite side was normal. The disorders were classified as follows: A : Non-inflammatory diseases including middle ear anomalies, posttraumatic perforation of the tympanic membranes and congenital cholesteatoma without infection (n = 10) ; B : chronic otitis media without cholesteatoma (n = 14) ; C : pars flaccida retraction type cholesteatoma (n = 34) ; D : pars tensa retraction type cholesteatoma and adhesive otitis media (n = 15) ; E : surgically treated ears (n = 33). The average threshold +/- S.D.(dB) of each group according to the above classification was as follows : A : -1.0 +/- 4.4, B : -1.5 +/- 6.2; C : 7.4 +/- 13.7; D : 9.6 +/- 18.2; E : 20.9 +/- 16.8. The rates of abnormal threshold of electrogustometry (more than 8dB) of A, B, C, D and E were 0%, 7.1%, 44.1%, 46.7% and 72.7%, respectively. The intraoperative findings around the CTN were retrospectively classified according to the following 5 groups : I : No pathological tissue was attached to the CTN (n = 44); II : the Granulation tissue or matrix of the cholesteatoma was attached to the CTN (n = 19) ; III : the CTN was surrounded by granulation or a matrix of cholesteatoma (n = 3) ; IV : The CTN was not identifiable due to the severe pathological condition of the middle ear cavity, in either surgically treated or untreated ears (n = 16), V : Surgically treated ears in which the CTN was identifiable (n = 24). The average threshold +/- S.D.(dB) for I, II, III, IV and V were 1.9 +/- 9.6, 2.0 +/- 11.7, 16.0 +/- 20.3, 32.0 +/- 7.4, 16.0 +/- 17.0, respectively. The rates of abnormal threshold of electrogustometry (more than 8dB) of I, II, III, IV and V were 27.3%, 31.6%, 66.7%, 100% and 62.5%, respectively. In both the above classification by the disorders and that by the intraoperative findings around the CTN, differences in the average thresholds between the surgically treated sides and the opposite sides with normally appearing tympanic membranes showed a tendency similar to that of the thresholds of the treated sides. In the present study, the threshold of electrogustometry was correlated with the disease and the intraoperative findings during middle ear surgery, and it was higher in adhesive otitis media and cholesteatoma of the pars tensa type. Electrogustometry is a useful preoperative examination to predict the condition of the posterosuperior portion of the mesotympanum.

Biodegradable blends and composites of polycaprolactone and starch derivatives

High-molecular-weight (40 000 and 80 000 g mol −1) polycaprolactone (PCL) has been blended with high-amylose corn starch (HA-CS, 70% amylose) and waxy corn starch granules, as well as with the non-granular starch acetate derivatives. The properties of films of these blends were evaluated using differential scanning calorimetry, dynamic mechanical thermal analysis and Instron tensile testing, and compared with similar blend films made with poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV, 11.6% HV content). All of the PCL blends and the PHBV blends with granular starch were found to be mechanically compatible but phase-separated. The PHBV/starch acetate blends were also phase-separated, but were too brittle for mechanical testing. The PCL/HA-CS blends were the strongest, with ≈15% lower tensile strength and a 50% higher modulus than PCL, up to 25 wt% HA-CS. Optical microscopy showed that the small size of the HA-CS granules (10 μm) and good dispersion of the granules in the PCL matrix were the reasons for the good mechanical properties compared with the other blends. Crosslinking was found to improve the thermal properties of the blends.

Treatment of articular defects with meniscal allografts in a rabbit knee model

Deep-frozen allogeneic meniscal grafts for the treatment of articular cartilage defects were performed experimentally. Osteochondral defects 3 mm in diameter were created bilaterally on the medial femoral condyles of 50 Japanese white rabbits. A meniscus was then grafted into the defect in the left knee, and the right knee was left untreated. At various periods from 2 to 24 weeks postoperatively, the rabbits were killed and macroscopic and histologic examinations were performed. Two weeks after operation, the grafted meniscus was bonded to the floor of the defect. After 12 weeks, chondrocytes producing matrix granules was shown by electron microscopy. After 24 weeks, a congruous articular surface was formed. With time, cellular elements infiltrated into the graft from the surrounding tissues, and gradually increased in penetration. Weight bearing in the early stage after operation did not degrade the grafted menisci, and no changes were shown in the opposing cartilage of the tibia. Deep-frozen allogeneic menisci may be useful as a biological implant to repair articular cartilage defects in this model.

Evaluation of a silicone based matrix containing a crosslinked polyethylene glycol as a controlled drug delivery system for potential oral application

A silicone based matrix containing dispersed medicated granules of a crosslinked polyethylene glycol with high swelling capacity is evaluated for its potential to release in vitro substantial fractions of drugs of different solubilities within 6 hours at controlled rates. Papaverine- HCl, clonidine- HCl and salicylamide are the model drugs. With a matrix shape of a 0.1-cm thick disc, a weight fraction of granules in matrix of around 35% and an appropriate granule size, dose fractions of around 80% are released with √t-type kinetics. The particular drug type and the drug content in granules, within the range of 5–20%, are without influence on the pattern and rate of fractional release. The release pattern depends on the pH of the elution medium, but the pH effects can be offset by properly controlling the granule size. Thus, the above features of release are obtained with normal saline as the elution medium, using granules of 354–425 μm, or with a medium whose pH is gradually increased from 1.2 to 7.4 to simulate the conditions of the GI tract, using granules of 105–250 μm. Drug release is initially controlled by the rate of increase of the number and size of interconnections among granules in course of swelling. Drug diffusion in the interconnected hydrogel gradually takes control of release.

Studies of magnetic interactions between Gd granules in copper matrix

Ultrafine Gd particles in the Cu metallic material have been obtained by rapid annealing of sputtered metastable GdxCu1−x alloys. The particle shape and size were measured by a transmission electron microscopy. The evolution of crystal structure with annealing temperature has been investigated by x-ray diffraction and electron diffraction. It has been found that the Gd granules have formed following annealing above 300 °C and the granular size increases with rising annealing temperature. The magnetic data show that the as-sputtered metastable Gd0.1Cu0.9 and Gd0.2Cu0.8 alloys obey a Curie–Weiss law at high temperature with a negative value of θ. After annealing, the θ value varies with annealing temperature according to an oscillatory function. The evolution of the magnetic properties and microstructure during annealing are described in detail.