Immunotherapeutic potential of antibodies produced in plants

Plants are capable of synthesizing and assembling virtually every kind of antibody molecule, ranging from the smallest antigen-binding domains and fragments, to full-length, and even multimeric, antibodies. A number of plant hosts can be used, and because this is a versatile expression system that can be scaled-up to agricultural proportions, a cheap and plentiful supply of antibodies could be made available. Immunotherapy is one of the many potential uses for bulk quantities of antibody. In particular, passive immunotherapy of mucosal surfaces may be possible, because functional secretory antibodies can be engineered in plants.

Plant antibodies for immunotherapy

The original report of Hiatt (1989) initiated a wave of excitement at the realization that a complex mammalian protein such as immunoglobulin could be assembled within a plant cell. The general reaction was one of amazement, but interest in exploiting the possibilities arising from the discovery, for example to make antibodies of therapeutic value, has taken a considerable time to develop. In the meantime, other recombinant expression systems and traditional cell culture techniques have advanced and overcome some of their problems, particularly those associated with yields. Plants, however, still offer unique advantages, especially in their ability to match the protein assembly capabilities of mammalian cells (as demonstrated by the assembly of SIgA molecules), as well as to provide antibodies in bulk at low cost. In addition, the area of "immunization" of plants holds great promise and will surely be a field of enormous growth for the future.

The modulatory effect of tetrandrine on the CD23, CD25 and HLA-DR expression and cytokine production in different groups of asthmatic patients

The therapeutic effect and mechanism of action of tetrandrine on asthma are not defined. Recently, it has been proposed that mononuclear cell (MNC) infiltration in the airway plays a role in the pathogenesis of asthma. In this study, we evaluated the effect of tetrandrine on the cell receptor expression and cytokine production of MNC from two groups (young atopic and old non-atopic) of stable asthmatic patients. MNC separated from peripheral blood of both asthmatic patients and normal individual were cultured in serum free RPMI-1640, with or without phytohemagglutinin (5 micrograms/ml) and tetrandrine (2 micrograms/ml). After culture, MNCs were harvested and stained with monoclonal antibodies for HLA-DR, CD23, CD25 and CD3. MNC supernatants were collected for the measurement of IL-2, IL-4 and interferon-gamma (IFN-gamma). The results show that tetrandrine may inhibit (1) MNC proliferation, (2) the production of IL-2, IL-4 and IFN-gamma, and (3) the expression of HLA-DR, CD23 and CD25 on CD3 positive T cells. They were inhibited to a similar extent in both groups of asthmatic patients. These results suggest that tetrandrine might have some therapeutic role in relation to the suppression of lymphocyte function in asthmatics.

Modification of alveolar macrophage function with bis-basic ethers of fluorene and fluoren-9-substituted derivatives

Bis-basic ethers of fluorene and fluoren-9-substituted derivatives such as tilorone have been reported to inhibit silica-induced fibrosis in rats. The potential antifibrotic potency of 2,7-bis(diethylamino)ethoxy fluorene (F-9-H,H), fluorenone (F-9-one), fluorenoxime (F-9-oxime), and fluorenol (F-9-ol) was F-9-oxime > F-9-one approximately F-9-H,H >> F-9-ol. Since the release of reactive oxygen species and growth factors from alveolar macrophages (AM) in response to silica exposure has been linked to the development of pulmonary fibrosis, the present study was carried out to determine the inhibitory effects of these compounds on rat AM activity in vitro. The following parameters were monitored: (1) cellular viability; (2) zymosan-induced respiratory burst activity (superoxide and hydrogen peroxide release, chemiluminescence, and oxygen consumption) of AM; (3) drug binding to AM; and (4) lipopolysaccharide (LPS)-stimulated interleukin-1 (IL-1) release from AM. The bis-basic ethers, at 40 microM, did not affect cell viability when incubated with AM for 30 min, but significantly inhibited zymosan-induced macrophage respiratory burst activity. The inhibitory effect of these agents was F-9-oxime > F-9-one approximately F-9-H,H >> F-9-ol. Binding of these drugs to AM was time and dose dependent, and exhibited the following binding affinity: F-9-oxime > F-9-one > F-9-H,H > F-9-ol. F-9-oxime was shown to inhibit LPS-stimulated IL-1 release by AM in a dose-dependent manner. This inhibition of IL-1 release by AM cannot be explained as a decrease in viability. In addition, these drugs were also shown to impair human fibroblast proliferation in response to serum stimuli without impairing cell viability. These results indicate a positive correlation between drug binding to AM or other cell types and their inhibitory effects on cellular activities including oxygen consumption, superoxide release, hydrogen peroxide secretion, chemiluminescence, IL-1 release, and proliferation. The ability of these bis-basic ethers to modify AM and fibroblast functions in vitro suggests that further investigation of their reported antifibrotic potency in vivo is warranted.

Generation and assembly of secretory antibodies in plants

Four transgenic Nicotiana tabacum plants were generated that expressed a murine monoclonal antibody kappa chain, a hybrid immunoglobulin A-G heavy chain, a murine joining chain, and a rabbit secretory component, respectively. Successive sexual crosses between these plants and filial recombinants resulted in plants that expressed all four protein chains simultaneously. These chains were assembled into a functional, high molecular weight secretory immunoglobulin that recognized the native streptococcal antigen I/II cell surface adhesion molecule. In plants, single cells are able to assemble secretory antibodies, whereas two different cell types are required in mammals. Transgenic plants may be suitable for large-scale production of recombinant secretory immunoglobulin A for passive mucosal immunotherapy. Plant cells also possess the requisite mechanisms for assembly and expression of other complex recombinant protein molecules.

Targeted gene delivery to alveolar macrophages via Fc receptor-mediated endocytosis

Alveolar macrophage (AM) plays important roles in lung homeostasis and pathogenesis of diseases. The study of macrophage gene function and regulation as well as its potential therapeutic intervention will require the development of vectors capable of safe and efficient transfer of DNA to the AM. In the present study, we report a new transfection system that utilizes Fc receptor-mediated endocytosis as a means to target DNA to the AM. This system employs molecular conjugates consisting of a cognate moiety, in this case IgG which recognizes the AM Fc receptor, covalently-linked to a DNA-binding moiety, such as a cationic polyamine. A Complex was formed between immunoglobulin G-polylysine conjugate (IgG-pL) and plasmid DNA carrying the LacZ reporter gene (pSV beta). The conjugate-DNA complex was added directly to the AMs in culture and incubated for 24 h, after which LacZ gene expression was analyzed for beta-galactosidase activity by microfluorometry using a fluorogenic beta-galactosidase substrate, 5-dodecanoylaminofluorescein di-beta-D-galactopyranoside (C12FDG). The AMs treated with the IgG-pL/DNA complex exhibited galactosidase activity significantly augmented over background levels. Effective gene transfer was shown to require both the DNA-binding moiety and cognate moiety for the cell surface receptor. Specific internalization of the complex by the Fc receptor pathway was verified by competitive inhibition using excess IgG. Under this condition, LacZ gene expression was inhibited, suggesting complex internalization through the Fc mediated endocytosis pathway. The requirement of Fc receptors for complex internalization was further demonstrated using cells that lack Fc receptors, e.g., alveolar epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluoromicroscopic studies of bleomycin-induced intracellular oxidation in alveolar macrophages and its inhibition by taurine

The mechanism of bleomycin-induced pulmonary fibrosis is not yet clear. Recent studies have shown that alveolar macrophages (AM) can be stimulated by bleomycin in vitro releasing inflammatory cytokines, suggesting that the interaction of bleomycin with AM is an important step in the drug-induced fibrotic process. Bleomycin is known to bind DNA and generate oxygen radicals through complexation with Fe2+ and oxygen. To provide more insight into the cellular oxidative property of bleomycin, we have developed a fluoromicroscopic method using 2',7'-dichlorofluorescin diacetate (DCFHDA) as an oxidative fluorescence probe to study the bleomycin-induced intracellular oxidation in rat AM and the inhibition of the oxidation by taurine, a compound known to inhibit the bleomycin-induced fibrosis. Bleomycin at 5 to 20 micrograms/ml has a moderate stimulatory effect (1.87- to 2.66-fold) on the secretion of superoxide anion. A high concentration of bleomycin (20 micrograms/ml), however, inhibits cell response to zymosan-induced secretion of superoxide anion. At 4 micrograms/ml, bleomycin has no effect on cell membrane integrity or morphology but results in a significant increase in intracellular oxidation. This oxidative process is Fe(2+)-dependent and is accompanied by an increase in intracellular calcium (35 nM). Both the intracellular oxidation and calcium rise induced by internalized bleomycin are inhibited by pretreatment of cells with varying concentrations of taurine (25, 125, and 187.5 microM). The inhibitory effect on intracellular oxidation was found to be 36, 57, and 60%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Receptor-mediated peptide delivery in pulmonary epithelial monolayers

The present study investigated the feasibility of utilizing receptor-mediated endocytosis as a means to enhance peptide delivery to the pulmonary epithelium. The strategy employs a molecular conjugate consisting of a cognate moiety, transferrin (TF), covalently-linked to a model polypeptide, horseradish peroxidase (HRP), via a reversible disulfide linkage. A cultured alveolar epithelial monolayer system was used to simulate the conditions of the pulmonary epithelium and to allow accurate quantitation of intra- and transcellular peroxidase transport. The alveolar cells were isolated from rat lungs by enzymatic digestion and grown on microporous tissue culture-treated polycarbonate filters. A significant increase in the uptake of HRP by the cell monolayer was observed upon its conjugation with TF. The effect was found to be concentration-dependent, being more pronounced at low concentrations, i.e., 3.9- and 1.2-fold increase over unconjugated HRP controls at the concentration levels of 0.05 and 1.50 U/ml respectively. Effective peroxidase uptake was shown to require the TF cognate moiety for the cell surface receptor. Specific internalization of the conjugate by the TF endocytic pathway was verified by competition for the TF receptor. Conjugate internalization was not followed by a proportional increase in transcytosis, i.e., at 0.05 U/ml conjugate level, a 1.7-fold increase in transcytosis was observed as compared to 3.9-fold for endocytosis. Effective enhancement of transcytosis was achieved by treating the monolayers with brefeldin A (BFA), a compound known to affect intracellular transport of TF receptor complexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel delivery of antioxidant enzyme catalase to alveolar macrophages by Fc receptor-mediated endocytosis

Excessive production of reactive oxygen species by alveolar macrophages (AMs) in response to inhaled toxic substances is a major cause of oxidative lung injury. Therapeutic approaches designed to protect the lungs from oxidative injury by administering native antioxidant enzymes such as catalase and superoxide dismutase have been suggested. However, problems associated with poor penetration of these enzymes to the intracellular target sites have limited their effective use. The present study reports a drug targeting method based on receptor-mediated endocytosis of the antioxidant enzyme catalase to the AMs. This method employs molecular conjugate consisting of a cognate moiety, in this case IgG which recognizes the macrophage Fc receptor, covalently linked to the enzyme catalase via the reversible disulfide linkage. The uptake efficiency of the enzyme conjugate and its protection against oxidative injury were evaluated microfluorometrically using the intracellular oxidative probe dichlorodihydrofluorescein BSA: anti BSA antibody complex (DCHF-IC), and the cell viability indicator propidium iodide. The DCHF-IC-stimulated macrophages exhibited a dose- and time-dependent increase in intracellular fluorescence with a half maximal response dose of approximately 120 micrograms/ml. Free catalase (50-500 U/ml) failed to inhibit the DCHF-IC-induced oxidative burst and had only a marginal protective effect on AM injury. In contrast, the catalase-IgG conjugate (50-500 U/ml) strongly inhibited both the DCHF-IC-induced oxidation and injury in a dose-dependent manner. Effective inhibition was shown to require both the antioxidant catalase moiety ant the cognate moiety for the cell surface receptor. Specific internalization of the conjugate through the Fc receptor was also investigated by competitive inhibition using free IgG.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar permeability enhancement by oleic acid and related fatty acids: evidence for a calcium-dependent mechanism

Pulmonary exposure to oleic acid (OA) is associated with permeability alterations and cellular damage; however, the exact relationship between these two effects has not been clearly established. Using cultured alveolar epithelial monolayers, we demonstrated that OA and some other fatty acids (< or = 50 microM) can induce permeability changes without detectable cellular damage. At higher concentrations, however, OA caused severe membrane damage and leakage to solute flux. The permeability enhancing effect of OA was observed with both the paracellular marker 3H-mannitol and the lipophilic transcellular indicator 14C-progesterone. While the effect of OA on transcellular permeability may be attributed to its known effect on membrane fluidity, the paracellular promoting effect of OA and its mechanism are not well established. We postulated that OA may increase paracellular permeability through a Ca(2+)-dependent tight junction mechanism. Using dual-excitation fluorescence microscopy, we demonstrated that OA can increase intracellular calcium, [Ca2+]i, in a dose-dependent manner. This effect was transient at low OA concentrations (< or = 50 microM) but became more pronounced and sustained at higher concentrations. Free hydroxyl and unsaturated groups were required for this activation since esterified OA (oleic methyl ester) and stearic acid (a saturated fatty acid with equal chain length) had much reduced effects on both the [Ca2+]i and the permeability alterations. Degree of unsaturation was unimportant since linolenic acid (18:3), linoleic acid (18:2), and OA (18:1) had similar and comparable effects on the two parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of bactericidal/permeability-increasing protein in human body fluids by sandwich ELISA

A sensitive sandwich ELISA has been developed to measure levels of native bactericidal/permeability-increasing protein (BPI) as well as two recombinant forms of BPI (rBPI and rBPI23) in human body fluids. The linear range for the rBPI and rBPI23 standard curves were 100-6000 pg/ml and 25-800 pg/ml respectively. Recovery of different concentrations of rBPI spiked into pooled human plasma samples averaged 83% and ranged from 65% at 300 ng/ml to 97% at 3 ng/ml. Recovery of rBPI23 averaged 56% and ranged from 30% at 0.5 ng/ml to 90% at 50,000 ng/ml. Because LBP is present in normal human plasma and shares sequence homology with BPI, the effects of rLBP on the BPI ELISA were also evaluated. Under standard assay conditions, rLBP caused minimal interference with BPI detection. At 100 micrograms/ml, rLBP generated a signal equivalent to 3 ng/ml of rBPI and 0.6 ng/ml of rBPI23. Matched serum and plasma samples were collected from 20 healthy adults to measure endogenous levels of BPI. The range of BPI concentrations was < 0.2-2.1 ng/ml in plasma and 4.9-72.1 ng/ml in serum. Western blot analysis indicated that the BPI ELISA immunoreactivity in plasma and serum correlated with the presence of a protein doublet (M(r) approximately 60,000), which comigrated with native BPI extracted from human neutrophils. These data demonstrate that low levels of holo-BPI are present in plasma, and suggest that additional quantities of BPI were released from neutrophils during the process of coagulation.

Assembly of monoclonal antibodies with IgG1 and IgA heavy chain domains in transgenic tobacco plants

The genes encoding the heavy and light chains of a murine monoclonal antibody (mAb Guy's 13) have been cloned and expressed in Nicotiana tabacum. Transgenic plants have been regenerated that secrete full-length Guy's 13 antibody. By manipulation of the heavy chain gene sequence, constant region domains from an immunoglobulin alpha heavy chain have been introduced, and plants secreting Guy's 13 mAb with chimeric gamma/alpha heavy chains have also been produced. For each plant antibody, light and heavy chains have been detected by Western blot analysis and the fidelity of assembly confirmed by demonstrating that the antibody is fully functional, by antigen binding studies. Furthermore, the plant antibodies retained the ability to aggregate streptococci, which confirms that the bivalent antigen-binding capacity of the full length antibodies is intact. The results demonstrate that IgA as well as IgG class antibodies can be assembled correctly in tobacco plants and suggest that transgenic plants may be suitable for high-level expression of more complex genetically engineered immunoglobulin molecules. Since mAb Guy's 13 prevents streptococcal colonization in humans, transgenic plant technology may have therapeutic applications.

Transport and hydrolysis of enkephalins in cultured alveolar epithelial monolayers

An in vitro cultured monolayer system of alveolar epithelial cells was used as a model to investigate transport and hydrolysis of two enkephalin peptides, Met-enkephalin (TGGPM) and [D-Ala2]Met-enkephalinamide (TAGPM), in pulmonary epithelium. Isolated alveolar type II cells formed continuous monolayers when grown on microporous tissue culture-treated polycarbonate filters in serum-free, hormonally defined medium. Transport and hydrolysis studies of enkephalins in the monolayer system obtained after 6 days in culture, using fluorescence reversed-phase HPLC, indicate a reduced but significant degradation of enkephalins in the alveolar epithelium compared to most other epithelia previously reported. Aminopeptidases and dipeptidyl carboxypeptidase represent two major hydrolytic enzymes for TGGPM, as indicated by the formation of the degradative products Tyr and Tyr-Gly-Gly, while dipeptidyl peptidase, which is responsible for the formation of Tyr-Gly, contributes much less. The enkephalinase inhibitor thiorphan failed to prevent the hydrolysis of TGGPM whereas the enkephalin analog TAGPM was relatively resistant to enzymatic cleavage. The rate of enkephalin transport across the alveolar epithelium was directly proportional to drug concentration and occurred irrespective of transport direction, suggesting passive diffusion as the major mechanism for transepithelial transport. Agents that affect paracellular transport pathways, e.g., EGTA and the calcium ionophore A-23187, greatly promoted the transport rate. The ionophore at high doses, in addition to promoting tight junction permeability, also caused cellular damage associated with a sustained rise in intracellular calcium levels, as indicated by nuclear propidium iodide fluorescence. The cultured monolayer of alveolar epithelium may be used to study pulmonary drug absorption, degradation, and toxicity.

Regulation of tight junction permeability by calcium mediators and cell cytoskeleton in rabbit tracheal epithelium

The present study investigates the mechanisms controlling tight junction permeability of the tracheal epithelium, with an emphasis on the regulatory role of intra- and extracellular calcium as well as the cell cytoskeleton. The tracheas were isolated from rabbits and their junctional permeability barrier was investigated in vitro by means of transepithelial electrical resistance measurements and flux measurements of the radiolabeled paracellular tracer, 14C-mannitol. The effects of intra- and extracellular calcium were studied using the calcium ionophore A 23187 and EGTA, and that of the cytoskeleton was investigated using cytochalasin B. Intracellular calcium of the tracheal epithelium was monitored microfluorometrically using the specific calcium indicator, Fura-2 AM (acetoxymethyl ester). The results indicate that the tight junction permeability of the trachea was significantly increased upon treatment with all three of the test compounds, as evidenced by a substantial decrease in transepithelial electrical resistance and an increase in transepithelial flux of 14C-mannitol. The effects of EGTA and cytochalasin B on the tight junction permeability are fully reversible upon removal of the compounds from the bathing media. On the other hand, tissues treated with the calcium ionophore demonstrate a partial or no recovery in membrane permeability, depending on the intracellular calcium levels. Moderate and transient increases in intracellular calcium caused a partial reversibility of the membrane resistance, while high and sustained intracellular calcium levels induce a complete irreversibility of the membrane resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of hydroxyl free radical-induced cellular injury and calcium overloading in alveolar macrophages

Excessive production of reactive oxygen radicals by alveolar macrophages is proposed to play an important role in oxidative lung injury. A major product oxygen radical formation is the highly reactive hydroxyl radical (.OH) generated via a biologic Fenton reaction. In addition to its known ability to induce lipid peroxidation, recent studies have suggested that the .OH may exert its cytotoxic effect through the alteration of [Ca2+]i homeostasis. To test this potential mechanism as well as to investigate the relationship between .OH and Ca2+ overloading in cytotoxic injury, isolated rat alveolar macrophages were exposed to externally generated radical system, H2O2 (0.01 to 1 mM) and Fe2+ (1 mM) and their [Ca2+]i levels and cell injury were monitored using quantitative fluorescence microscopy with the aid of the specific Ca2+ indicator, Fura-2, and membrane integrity indicator, propidium iodide. Electron spin resonance measurements using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) confirmed the production of the .OH radical by this system. Upon the addition of the radicals, the macrophages displayed a rapid initial rise in [Ca2+]i which was followed by a slower but more pronounced [Ca2+]i elevation that reached a level 3 to 5 times higher than the basal level. This process preceded cell death as evident by nuclear propidium iodide fluorescence. Depletion of extracellular Ca2+ inhibited both the [Ca2+]i response and cell injury. Preincubation of the cells with the Ca2+ channel blocker verapamil or .OH radical scavenger mannitol similarly inhibited the [Ca2+]i rise and loss of viability. Firefly luciferase assay of cellular ATP content demonstrated that the alterations in [Ca2+]i following .OH treatment preceded the depletion of ATP.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in alveolar type II cell metabolism induced by tetrandrine and other alkaloids

Tetrandrine (TT) and other bisbenzylisoquinoline alkaloids have been used in China as a treatment for fibrotic lung diseases. Because of their potential use as pulmonary therapeutic agents, we studied the effects of some of these compounds on energy metabolism in isolated rat alveolar type II cells, i.e., cells which play a critical role in maintaining normal lung function. Incubation of type II cells with most of the alkaloids produces a reduction in cellular ATP content. However, there is no effect of the alkaloids on cellular oxygen consumption. All of the alkaloids which produce reductions in cell ATP levels cause increases in internal calcium levels of type II cells. Incubation of the cells with the calcium ionophore, 4-bromo A-23187, leads to increased amounts of intracellular calcium and reductions in ATP levels, but has no effect on oxygen consumption. Exposure of isolated lung mitochondria to calcium produces a concentration-dependent reduction in ATP synthesis with no effect on mitochondrial oxygen consumption. Direct exposure of mitochondria to TT has no effect on ATP synthesis. These results are consistent with the notion that the alkaloids produce an increase in type II cell internal calcium levels which, in turn, leads to reduced rates of mitochondrial ATP synthesis.

Altered calcium homeostasis and cell injury in silica-exposed alveolar macrophages

There is evidence to suggest that cell injury induced in alveolar macrophages (AM) following phagocytic activation by silica particles may be mediated through changes in intracellular free calcium [Ca2+]i. However, the mechanism of silica-induced cytotoxicity relative to [Ca2+]i overloading is not yet clear. To provide a better insight into this mechanism, isolated rat AMs were exposed to varying concentrations of crystalline silica (particle size < 5 microns in diameter) and the fluctuation in their [Ca2+]i and cell integrity were quantitatively monitored with the fluorescent calcium probe, Fura-2 AM, and the membrane integrity indicator, propidium iodide (PI). Results from this study indicate that silica can rapidly increase [Ca2+]i in a dose-dependent manner with a characteristic transient calcium rise at low doses (< 0.1 mg/ml) and an elevated and sustained rise at high doses (> 0.1 mg/ml). Depletion of extracellular calcium [Ca2+]o markedly inhibited the [Ca2+]i rise (approximately 90%), suggesting that Ca2+ influx from extracellular source is a major mechanism for silica-induced [Ca2+]i rise. When used at low doses but sufficient to cause a transient [Ca2+]i rise, silica did not cause significant increase in cellular PI uptake during the time of study, suggesting the preservation of membrane integrity of AMs under these conditions. At high doses of silica, however, a marked increase in PI nuclear fluorescence was observed. Depletion of [Ca2+]o greatly inhibited cellular PI uptake, induced by 0.1 mg/ml or higher doses of silica. This suggests that Ca2+ influx, as a result of silica activation, is associated with cell injury. Indeed, our results further demonstrated that the low dose effect of silica on Ca2+ influx is inhibited by the Ca2+ channel blocker nifedipine. At high doses of silica (> 0.1 mg/ml), cell injury was not prevented by nifedipine or extracellular Ca2+ depletion, suggesting that other cytotoxic mechanisms, i.e., nonspecific membrane damage due to lipid peroxidation, are also responsible for the silica-induced cell injury. Silica had no significant effect on cellular ATP content during the time course of the study, indicating that the observed silica-induced [Ca2+]i rise was not due to the impairment of Ca(2+)-ATPase pumps, which restricts Ca2+ efflux. Pretreatment of the cells with cytochalasin B to block phagocytosis failed to prevent the effect of silica on [Ca2+]i rise. Taken together, these results suggest that the elevation of [Ca2+]i caused by silica is due mainly to Ca2+ influx through plasma membrane Ca2+ channels and nonspecific membrane damage (at high doses).(ABSTRACT TRUNCATED AT 400 WORDS)

Strategies for the treatment of pneumoconiosis

Regulatory control of dust in the workplace has greatly reduced the development of pneumoconiosis, yet the prevention of silicosis and coal workers' pneumoconiosis has not been accomplished. Cases of pneumoconiosis continue to occur, and there is no proven way to affect the natural history of these progressive inflammatory and fibrotic processes. Although pneumoconiosis and silicosis are considered untreatable in Western countries, in China an aggressive search has been underway for therapeutic agents and clinical procedures to treat these diseases. The important aspects are reviewed for the tried therapies, including corticosteroids, aluminum citrate complex, PVNO, tetrandrine, xinin, and whole lung lavage.

Characterization and applications of antibodies produced in plants

Of the variety of compounds expressed in transgenic plants, antibodies offer probably the widest range of applications. The antibodies appear to possess all of the functional characteristics of antibody derived from hybridoma cells, although further study will be required to determine the effect of the difference in heavy chain glycosylation. More work will also be directed toward the assembly, accumulation, stability and secretion of plant antibodies. The effect of the signal sequence on the expression and assembly of antibodies has been shown and further methods of optimizing transgenic protein accumulation in plants almost certainly exist. Plant antibody technology is still in its infancy. However, it offers enormous potential in "mix-and-match" antibody engineering, and the construction of multimeric immunoglobulin complexes may be feasible relatively easily, for the first time. Furthermore, as there is an enduring interest in using antibodies for therapeutic purposes, agricultural production and distribution offers a means of obtaining large quantities of antibodies at a relatively low cost.

Inhibitory action of tetrandrine on macrophage production of interleukin-1 (IL-1)-like activity and thymocyte proliferation

Tetrandrine is a bisbenzylisoquinoline alkaloid which has been shown to exhibit antifibrotic activity against silicosis. Tetrandrine is characterized by its strong binding to alveolar macrophages and inhibition of particle-induced respiratory burst activity in these phagocytes. In contrast, tubocurine and tubocurarine are structurally similar to tetrandrine but exhibit little effect on fibrosis or activation of alveolar macrophages. The objective of the present study was to test the effect of tetrandrine on macrophage production of monokines in response to occupational dusts, and to determine tetrandrine's effect on monokine-medicated cell growth using a mouse thymocyte proliferation assay and lipopolysaccharide (LPS) as a positive control. Stimulation of alveolar macrophages by respirable silica dust resulted in a release of monokines which caused a fourfold increase in thymocyte proliferation. Coal dust, on the other hand, had no effect on macrophage production of this cytokine. Tetrandrine was found to exhibit a dose-dependent inhibition of monokine release from both silica and LPS-stimulated alveolar macrophages. In experiments where thymocytes were directly treated with tetrandrine, a dose-dependent inhibition of thymocyte proliferation was noted with both interleukin-1-(IL-1) specific and nonspecific mitogenic (concanavalin A) actions. In contrast to the inhibitory potency of tetrandrine, tubocurarine was found to have no effect on either the production of monokines by LPS-stimulated alveolar macrophages or IL-1-mediated thymocyte proliferation. These results provide a correlation between the antifibrotic effect of tetrandrine and inhibition of macrophage activation.

The transport barrier of epithelia: a comparative study on membrane permeability and charge selectivity in the rabbit

The transport barrier of the epithelial presents one of the major problems limiting the effective use of these tissues as alternate delivery routes for macromolecules such as peptides and proteins. In the present study, two membrane transport properties, namely, the permeability and permselectivity of the shunt pathway, were investigated and compared in various tissues including the nasal, tracheal, bronchial, buccal, rectal, vaginal, corneal, epidermal, duodenal, jejunal, ileal, and colonic epithelia. Membrane permeability was evaluated using a combined method based on electrical conductance and flux measurements of a hydrophilic fluorescent probe, 6-carboxy fluorescein (CF). Membrane permselectivity or the charge discriminating ability of the membrane was evaluated by KCl diffusion potential measurements. The results indicate that all epithelia under investigation possess a relatively high degree of permeation barrier and are highly selective for the absorption of positively charged solutes. Shunt path permeability was found to vary greatly among tissues from different epithelia, whereas membrane charge selectivity was relatively constant in these tissues. A good correlation was observed between membrane electrical conductance and steady-state flux of CF, indicating a paracellular transport of the compound. The rank order of the intrinsic membrane permeability was as follows: intestinal approximately nasal greater than or equal to bronchial greater than or equal to tracheal greater than vaginal greater than or equal to rectal greater than corneal greater than buccal greater than skin. Membrane permselectivity, expressed as the ratio of transport number (positive over negative), ranges from 1.78 for the buccal to 1.33 for the rectal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibody engineering in plants

Techniques for plant transformation have been developed to such an extent that a number of foreign genes are currently being introduced into transgenic plants. Tobacco plants that produce monoclonal antibodies are of interest, because in addition to synthesis of two gene products (i.e. the heavy and light chains), the two polypeptides need to be assembled correctly, in order to result in a functional antibody. The studies on a catalytic antibody suggest that this is the case, and that the antibody functions identically to the native murine-derived antibody. The only difference observed was in the glycosylation of the heavy chain. Further transgenic plants are being generated to produce monoclonal antibodies that may be used therapeutically (and are therefore required in large quantities), or to provide disease resistance in plants. In addition, the ability of plants to assemble antibody complexes is being investigated further, to study the possibility of generating secretory IgA, which consists of heavy and light chains as well as two additional polypeptide units.

A mechanism of passive immunization with monoclonal antibodies to a 185,000 M(r) streptococcal antigen

The cell surface streptococcal antigen (SA) I/II of 185,000 M(r) is an immunodominant molecule that expresses one or more adhesion determinants. A series of 14 monoclonal antibodies (MAb) to defined parts of SA I/II were generated and some of these were used in passive immunization of macaques. Topical administration of selected MAb to the teeth of macaques prevented colonization of endogenous or implanted exogenous Streptococcus mutans for a period of 1 year. Significant reduction of both smooth surface and fissure caries was found in macaques who had MAb (Guy's 1) applied to their teeth, as compared with saline-treated animals. A series of in vivo passive immunization experiments was then carried out in 57 human subjects. Topical application of MAb to SA I/II prevented colonization of both artificially implanted exogenous strains of S. mutans, as well as natural recolonization by indigenous S. mutans. The properties of the protective MAb were then investigated and the epitope specificity within the SA I/II molecule was found to be essential but not the isotype specificity of the immunoglobulin (Ig). The requirement for complement activating and the phagocyte binding sites of the Fc fragment of MAb was not essential, as the F(ab')2 fragment of the MAb was as protective as the intact IgG, but the Fab fragment failed to prevent recolonization of S. mutans. Prevention of recolonization was specifically restricted to S. mutans, as the proportion of other organisms, such as S. sanguis, failed to show a significant change. The surprising feature of these experiments was that protection of re-colonization of S. mutans lasted up to 2 years, although MAb was applied for only 3 weeks and functional MAb was detected on the teeth only 3 days following application of the MAb. The long-term protection could therefore not be accounted for by a persistence of MAb on the teeth, but may be due to a shift in the microbial balance in which other bacteria occupy the ecological niche vacated by S. mutans, resulting in colonization resistance to S. mutans. Gene cloning and sequencing the SA from S. mutans, S. sobrinus and S. sanguis identified a conserved region (residues 955-1213) which on Southern hybridization and partial DNA sequence analysis was also found in 19 alpha-haemolytic oral streptococci. The results suggest that the SA molecule may constitute a family of adhesins in oral alpha haemolytic streptococci.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding of bisbenzylisoquinoline alkaloids to phosphatidylcholine vesicles and alveolar macrophages: relationship between binding affinity and antifibrogenic potential of these drugs

A group of bisbenzylisoquinoline alkaloids has been shown to exhibit various degrees of effectiveness in preventing silica-induced fibrosis in animal models. The objective of the present study was to characterize the binding of several of these alkaloids to phosphatidylcholine vesicles and rat alveolar macrophages using fluorometric and equilibrium dialysis methods, respectively. The lipid binding affinity of these alkaloids was found to depend upon several structural factors including hydrophobic substitutions, chiral configurations, and double oxygen bridge-restricted confirmation of the benzylisoquinoline moieties. Tetrandrine, which is a highly effective agent in preventing fibrosis, showed strong binding to both lipid vesicles and alveolar macrophages. In contrast, certain analogues of tetrandrine such as curine and tubocurine, which have little or no effect on silicosis, exhibited only weak binding to lipid vesicles and almost no binding to cells. The moderate binding affinity of fangchinoline to vesicles and cells corresponded to a moderate effectiveness of the compound as an antifibrogenic agent. Methoxyadiantifoline, an alkaloid of unknown antifibrogenic potential, also exhibited high binding affinities for lipid and cells. In conclusion, the results of these studies indicate that alveolar macrophages exhibit large binding capacities for certain members of this class of bisbenzylisoquinoline alkaloids. A positive correlation was observed between binding affinity to alveolar macrophages and the reported antifibrotic potency of these compounds. These data also suggest that the ability of these drugs to interact with alveolar macrophages may be a key step in inhibition of the progression of silica-induced pulmonary disease.

Sequence and structural analysis of surface protein antigen I/II (SpaA) of Streptococcus sobrinus

Streptococcal antigen I/II or the surface protein antigen A (SpaA) of Streptococcus sobrinus is an adhesin which mediates binding of the organism to tooth surfaces. The complete sequence of the gene which encodes SpaA has been determined. The gene consists of 4,584 bp and encodes a protein of 1,528 amino acid residues. The deduced amino acid sequence shows extensive homology with those of the cell surface adhesins from Streptococcus mutans serotypes c and f and from Streptococcus sanguis. Structural analysis of the N-terminal region (residues 50 to 550), which is rich in alanine and includes four tandem repeats of an 82-residue sequence, suggests that it adopts an alpha-helical coiled-coil conformation. Cell surface hydrophobicity may be associated with this region. The C-terminal region is more conserved and includes two tandem repeats of a 39-residue proline-rich sequence. A further proline-rich sequence in this region is predicted to span the cell wall. Although a hydrophobic sequence is present in the C-terminal region, it appears to be too short to span the cell membrane. Anchoring of SpaA in the cell membrane may therefore require some form of posttranslational modification or association with another membrane protein.

Conservation of the gene encoding streptococcal antigen I/II in oral streptococci

The spaP gene of Streptococcus mutans serotype c encodes a major cell surface protein, streptococcal antigen (SA) I/II, with an Mr of 185,000, that is thought to be involved in bacterial adhesion to teeth. Proteins with significant amino acid sequence homology to SA I/II have also been found in S. sobrinus and S. sanguis. The objectives of this study were to investigate the conservation of the spaP gene in the mutans groups of streptococci and to determine whether homologous genes were present in other species of alpha-hemolytic streptococci. DNA extracted from representative strains of 19 streptococcal species was examined by Southern hybridization and partial DNA sequence analysis. A series of five overlapping DNA probes from the spaP gene were amplified by the polymerase chain reaction and used in the Southern hybridizations. The entire gene was found to be well conserved in all strains of S. mutans serotypes c, e, and f investigated. A probe from the 3' region of the gene, which encodes residues 857 to 1207 of the SA I/II protein, hybridized with DNA from a number of mutans streptococci, as well as with DNA from nonmutans alpha-hemolytic streptococci. Conservation within this region was further demonstrated by sequencing gene fragments of two strains of S. intermedius and S. oralis. The results show that some regions of the spaP gene are highly conserved not only in the mutans group of streptococci but also in other nonmutans alpha-hemolytic streptococci. This suggests that a family of cell surface proteins which, by analogy with the 185,000-Mr SA I/II of S. mutans, could be involved in bacterial adhesion might exist.

Restriction fragment length polymorphisms and sequence variation within the spaP gene of Streptococcus mutans serotype c isolates

A restriction fragment length polymorphism study was undertaken to determine the extent and location of heterogeneity within spaP encoding the Mr 185,000 cell surface protein P1 (antigen I/II) of Streptococcus mutans serotype c isolates. The gene was found to be highly conserved except for a central variable (V) region predicted to encode less than 150 amino acids. Sequence analysis identified two V-region variants. These differences were independent of the geographic source of the isolates. Southern analysis using synthetic oligonucleotide probes indicated that nonretention of P1 (I/II) by some isolates is not due to a deletion of the 3'-terminal DNA necessary to encode an intact carboxy terminus.

Effects of bisbenzylisoquinoline alkaloids on alveolar macrophages: correlation between binding affinity, inhibitory potency, and antifibrotic potential

The Chinese have conducted extensive studies concerning the medicinal properties of plant products. In this investigation the ability of three bisbenzylisoquinoline alkaloids to inhibit particle-induced activation of alveolar macrophages was evaluated and this inhibitory potential was correlated with the ability of those drugs to bind to membrane components. Tetrandrine, i.e., an herbal medicine used as an antifibrotic agent in China, was a potent inhibitor of particle-stimulated oxygen consumption, superoxide release, and hydrogen peroxide secretion by alveolar macrophages. Tetrandrine also exhibited substantial binding affinity for membrane lipids and alveolar macrophages. In contrast, tubocurine, an analogue with little antifibrotic potential, exhibited low binding affinity and had little effect on macrophage activation. Methoxyadiantifoline, an alkaloid of unknown antifibrotic potential, exhibited inhibitory and binding properties similar to those of tetrandrine. The data indicate that a strong relationship exists between the antifibrotic potential of these alkaloids and their ability to bind to alveolar macrophages and inhibit particle-induced activation of these phagocytes. These drugs should serve as useful probes to evaluate the role of alveolar macrophages in pulmonary fibrosis.

Cosolvency of dimethyl isosorbide for steroid solubility

Dimethyl isosorbide (DMI), which is currently under investigation for its potential use as a pharmaceutical vehicle and drug permeation enhancer, is a water-miscible liquid with relatively low viscosity. The solubilization behavior of DMI as a cosolvent for nonpolar drugs was characterized via dielectric constant measurements of binary solvent systems containing DMI and either water, propylene glycol (PG), or polyethylene glycol (PEG). Evidence from the dielectric constant profiles and NMR studies suggest that DMI undergoes complexation with water and PG, but not with PEG, through hydrogen bonding interactions. The solvent complexation exhibited a major effect on the solubilities of prednisone, dexamethasone, and prednisolone in the mixed solvent systems. Maximum solubility of each drug was found to occur near a DMI/water or DMI/PG concentration ratio of 1:2. In the DMI-PEG mixed system, while there is no apparent interaction between DMI and PEG molecules, the solubility of prednisone was found to increase with decreasing dielectric constant.

Prevention of colonization of Streptococcus mutans by topical application of monoclonal antibodies in human subjects

Topical application of Streptococcus mutans-specific MAbs was examined as a means of preventing colonization in the mouth. The MAbs recognize the cell surface antigen (SA I/II) of Strep. mutans and also bind to the intact bacterial cell. In experiments with implantation of an exogenous Strep. mutans strain, specific MAb significantly reduced the levels of implantation when compared with that in controls given a non-specific MAb. In a second investigation, the effect of MAb on recolonization by indigenous Strep. mutans was studied in subjects after treatment with a topical antibacterial mouthwash (chlorhexidine), which had decreased Strep. mutans to undetectable levels. In control subjects, the indigenous Strep. mutans started to recolonize within days, but those receiving MAb remained free of Strep. mutans for up to 2 yr. By using different Strep. mutans-specific MAbs, it was found that the serotype and epitope specificities of the IgG MAb were essential, but that the IgG sub-class may not be important. No clinical side-effects were detected in any of the subjects receiving MAb and there was no evidence of serum, salivary or gingival fluid antibody responses against the antibody. Local passive immunization with MAbs is a safe method for preventing colonization of Strep. mutans in the mouth.

Specificity of monoclonal antibodies in local passive immunization against Streptococcus mutans

Local oral passive immunization in human subjects with a monoclonal antibody (MoAb) raised against the 185-kD antigen I/II from S. mutans significantly reduced or prevented oral colonization of an exogenous strain of the organism. In subjects sham-immunized with either saline or an unrelated MoAb, however, significantly greater proportions of S. mutans persisted for a longer duration than in those immunized with the specific anti-streptococcal MoAb. Recolonization of indigenous S. mutans after this organism was reduced to undetectable levels by an antimicrobial agent has also been completely prevented with specific MoAb. Indeed, S. mutans was not detected for a period of over 1 year, as compared with recolonization within 10-82 days in the control subjects. The specificity of MoAb in preventing colonization of the streptococci was studied with four MoAb. This revealed that: (1) the sub-class of antibody is not an essential factor, as both MoAb Guy's 1 and 13 prevented colonization, although Guy's 1 is an IgG2a and Guy's 13 is an IgG1 class of antibody; (2) serotype specificity is important, as MoAb Guy's 9, which only recognizes S. sobrinus (serotypes d and g), does not prevent colonisation by S. mutans (serotype c); (3) neither protein nor carbohydrate nature of the putative adhesin was a determining factor, because MoAb Guy's 1 recognizes a carbohydrate and Guy's 13 a protein determinant and both MoAb prevented adherence of S. mutans; and (4) epitope specificity appears to be the most important factor in preventing adherence of S. mutans, as MoAb Guy's 11 and 13 share the same serotype specificity and both recognize a protein determinant, yet only Guy's 13 prevents colonisation. The long duration of protection from re-colonization by indigenous S. mutans, lasting about 1 year after application of the specific MoAb was stopped, cannot be accounted for by functional MoAb remaining on the teeth. We suggest that initially the MoAb prevents colonization by S. mutans and that the ecological niche vacated by this streptococcus is filled by other organisms from the oral flora, thereby discouraging re-colonization by S. mutans.

[Double-cup replacement in the treatment of tuberculosis of the hip. Long-term follow-up studies]

24 tuberculous hip joints were treated by radical debridement and double-cup replacement in one single stage. They healed up primarily and remained well up to the time of follow-up, a period of 5 years and 7 months on average, except one which recurred 1 month after operation and persisted until removal of the implants. Slipping of head cup occurred in 4 cases in 10 to 12 months post-operatively. The slipped cups were removed or received, showing fibrous drinking of the head stump. Factors influencing and the time taking place of slipping of head cup along with it management were discussed and described. It is shown that radical debridement and double-cup replacement could serve to cure the tuberculosis and preserve the function of the hip joint.

[Observations on the effect of omental transplantation to the traumatized spinal cord]

Experiments with 2 groups of different animals were carried out to observe the effect of wrapping the traumatized spinal cord with transplanted omentum. In the first group, the spinal cords of 20 rabbits were uniformly impacted with a force of 11.2g x 10cm = 112gcf, and the cord specimens prepared in different times after injury were examined under light and electron microscopes. In the second group, the spinal cords of 14 cats were equally struck with a force of 25g x 20cm = 500 gcf, and the animals were checked for motor function and somatosensory evoked potential (SEP) of their hind limbs. The results found in the rabbits in the first group showed that the transplanted omentum was adherent to the cords within 24 hours, and there were vascular communications between them after 72 hours, as shown by the presence of dye in the cord vessels, which had been injected into the omental vessels. The histologic destructions appeared in these cords were obviously less severe than those in the control ones. Motor functions and SEP, demonstrated in the animals in the second group, were favorable in the cords of cats with omental transplantation (P less than 0.05). According to the findings in these experiments, we tend to believe that omental transplantation to the traumatized cord is of some benefit.

Chromatographic studies of mitomycin C degradation in albumin microspheres

Serum albumins and polylactic acid (PLA) have been used as bioerodable polymers in the preparation of drug-containing microspheres for parenteral drug delivery. The albumin microsphere may be prepared via either chemical cross-linking or heat denaturation of the protein. Heat-denatured albumin microspheres containing mitomycin C (MMC) have been used in pre-clinical and clinical investigations. Due to the high reactivity of MMC as a bifunctional alkylating agent, a study on the stability of MMC in the albumin and PLA microspheres has been carried out using a high-performance liquid chromatographic (HPLC) method. Human serum albumin (HSA) microspheres were prepared using an emulsion method via either heat denaturation at 120 or 170 degrees C or the use of 0.5 M biacetyl as a cross-linking agent. The PLA microspheres were prepared by an emulsion method at 55 degrees C. HPLC analysis of the HSA microspheres showed that about 37% of MMC was converted to 2,7-diaminomitosene derivatives in microspheres prepared by heat denaturation at 120 degrees C. The degradation increased to 82% when the microspheres were prepared with a denaturation temperature of 170 degrees C. The use of biacetyl as a cross-linking agent in the preparation of HSA microspheres resulted in a complete degradation of the incorporated MMC. Biacetyl was found to interact with MMC leading to the formation of 7-aminomitosene derivatives. In contrast to the albumin system, MMC may be incorporated into PLA microspheres without degradation.

Synthesis and secretion of mucous glycoprotein by the gill of Mytilus edulis. I. Histochemical and chromatographic analysis of [14C]glucosamine bioincorporation

The ability of the isolated gill epithelium of Mytilus edulis to incorporate [14C]glucosamine as a precursor in the biosynthesis and secretion of mucous glycoproteins was investigated. Localization of mucous cells in the gill filament was achieved using histochemical staining techniques. Mucus cells containing neutral and acidic mucins were found in the lateral region, whereas mucus cells containing primarily neutral or sulfated mucins were found in the abfrontal region. Autoradiographic results showed that in both regions, the mucous cells were rich in content of the incorporated radiolabel. The secreted glycoproteins containing the incorporated radiolabel were analyzed by column chromatography using Bio-Gel P-2 and P-6. Two populations of the glycoproteins differing in molecular size were isolated. Upon alkaline reductive borohydride cleavage of the O-glycosidic linkages of the high molecular weight protein, about 70% of the radiolabel and 85% of the carbohydrate content were removed from the protein. The alkaline borohydride cleavage resulted in the formation of at least six oligosaccharide chains of various lengths of sugar units. Gas chromatographic analysis of the carbohydrate composition shows that the glycoproteins contain N-acetylglucosamine, N-acetylgalactosamine, and galactose, fucose, and mannose as the neutral monosaccharides. The above results indicate that the isolated gill epithelium of M. edulis is capable of incorporating [14C]glucosamine in the synthesis of secretable mucin-type glycoproteins.

A method for the preparation of polylactic acid microcapsules of controlled particle size and drug loading

A solvent partition technique for the microencapsulation of hydrocortisone-polylactic acid has been developed for the preparation of microcapsules of controlled particle size distribution and drug loading. The method involves continuous injection of a drug-polymer solution with a syringe infusion pump into flowing mineral oil where microcapsules are formed as the solvent of the drug-polymer is partitioned into the mineral oil. Using preselected syringe needle size and mechanical control of the mineral oil flow rate at the needle tip, microcapsules of consistent particle sizes and desired drug loadings were prepared. Microcapsules of different internal structures were also prepared by varying the solvent system for the drug-polymer preparation. Dissolution studies showed that at the same drug loading, the rate of the percentage drug release increased with decreasing particle size, and that at similar particle size distributions, the rate increased with increasing drug loading. These results indicate that both the particle size distribution, and the drug loading must be controlled in a microencapsulation process to produce microcapsules of controlled drug release rate.

Association of chlorphentermine with phospholipids in rat alveolar lavage materials, alveolar macrophages and type II cells

Administration of chlorphentermine to rats leads to an increase in the phospholipid content of pulmonary surfactant materials and alveolar macrophages. It is known that this drug binds to pure phospholipids and prevents their degradation by phospholipases. Therefore, experiments were carried out to determine if chlorphentermine binds to surfactant phospholipids in vitro and to measure the in vivo association of drug with phospholipids in alveolar lavage materials from rats injected with [14C]chlorphentermine. The presence of chlorphentermine in alveolar macrophages, type II cells and other small pneumocytes (a population of lung cells which does not include alveolar macrophages or type II cells) from treated animals was also assessed. Binding of the drug to surfactant phospholipids, as measured with the fluorescent probe, 1-anilino-8-naphthalene sulfonate, occurs in vitro and does not differ in various subfractions of alveolar lavage materials isolated by differential centrifugation. Following daily administration of chlorphentermine to rats for 3 days, the drug appears to be associated with surfactant phospholipids such that the molar ratio is 1:100 (chlorphentermine/phospholipid). Chlorphentermine is also associated with alveolar macrophages (molar ratio, 1:18) and type II cells (molar ratio, 1:33). Not much drug is associated with the population of other lung cells (molar ratio, 1:333). In alveolar macrophages, approx. 70% of the drug seems to be bound to phospholipid and/or sequestered in subcellular organelles. However, only 20% of the chlorphentermine is bound and/or sequestered in type II cells. The results of these experiments suggest that following chlorphentermine administration, the drug is associated with phospholipids in acellular pulmonary lavage materials, alveolar macrophages and type II cells. This drug-phospholipid interaction may impair phospholipid degradation and lead to a phospholipidosis in surfactant materials and alveolar macrophages.

Effect of surface active agents on drug release from polylactic acid-hydrocortisone microcapsules

Polylactic acid microcapsules containing randomly distributed hydrocortisone particles were prepared. The rate of release of hydrocortisone from the microcapsules in pH 7.4 phosphate buffer was found to be largely increased by the presence of polysorbate 80, cetylpyridinium chloride, or aerosol OT in the dissolution medium. The surfactant effect was attributed to the ability of the surface active agent to improve solvent penetration into the microcapsules by lowering the surface tension at the solid-liquid interface. The effect of the cationic surfactant, cetylpyridinium chloride on the rate of drug release is similar in magnitude to that of the nonionic surfactant, polysorbate 80. In these systems, the rate of drug release from the microcapsules was found to be linearly related to the surface tension of the dissolution medium in the range of 40-60 dyn/cm (x 10(-3) N/m). In the same surface tension range, the effect of aerosol OT on rate increase was found to be much less than those of the cationic and nonionic surfactants. This suggests that the anionic surfactant is not well adsorbed at the interface due to the negative charge characteristics of the surface of the polylactic acid microcapsules. However, at nearly the critical micelle concentration of aerosol OT, where the corresponding surface tension is much lower than those of the cationic and nonionic surfactants, the microcapsules exhibited the highest rate of drug release.

Use of monoclonal antibodies in local passive immunization to prevent colonization of human teeth by Streptococcus mutans

Local passive immunization with monoclonal antibodies (MAbs) raised against streptococcal antigen (SA) I/II protects monkeys against colonization of teeth by Streptococcus mutans and the subsequent development of dental caries. In this study we extended the preclinical experiments to human subjects. In the first study of eight healthy subjects, four had anti-SA I/II MAb (immunoglobulin G2a [IgG2a]) and four had saline applied to their teeth on three occasions. A streptomycin-resistant S. mutans strain (Guy K2 strain, serotype c) was then implanted onto the teeth, and the organism was cultured sequentially from dental plaque and saliva up to 100 days after the first treatment with MAb. Decreased colonization by S. mutans was found in the dental plaque collected from smooth surfaces and fissures and in saliva of subjects whose teeth were treated with the MAb, as compared with the saline-treated control subjects. The experiment was then repeated on seven new subjects, and the effect of anti-SA I/II MAb was compared with that of an unrelated MAb to Campylobacter jejuni. The results again showed a consistently lower level of colonization of teeth in the anti-SA I/II MAb-treated subjects as compared with those sham immunized with the unrelated MAb. There was little difference in serum IgG, IgM, or IgA, gingival fluid IgG, or salivary IgA anti-SA I/II antibodies between the immunized and sham-immunized subjects, before and after the investigation. No side effects were observed, and the gingival and plaque indices remained unchanged. A sensitive radioimmunoassay failed to detect changes in anti-MAb (IgG2a) antibodies in any of the three fluids examined. We suggest that local passive immunization by means of MAb might be an alternative approach in the prevention of colonization of teeth by S. mutans and the development of dental caries.

A source of error in the chromatographic study of 35S-sulfate labeled mucous glycoproteins secreted by the gill epithelium of Mytilus edulis

HPLC combined with [35S]-sulfate/[3H]-glucosamine radiolabeling were employed to study the synthesis and secretion of mucous glycoproteins. The secreted radiolabeled glycoproteins were separated from the medium by precipitation with a mixture of trichloroacetic-phosphotungstic acids (TCA/PTA). The redissolved glycoproteins were chromatographed on an anion exchange protein column at varying pH of the mobile phase and fractions were collected for liquid scintillation counting. Varying the pH of the mobile phase from pH 3 to 7 resulted in a decrease of glycoprotein bound [35S] from 69.5 to 0.5% of the total recovered [35S]-sulfate with the remainder recovered as free [35S]-sulfate. The [3H]-labeled glycoprotein recovered under the uV peaks at this pH range was 99.5%. When high performance size exclusion chromatography was performed the change in mobile phase pH did not affect the 100% recovery of either [35S]-or [3H]-labels under the uV peaks. No free [35S]-sulfate was obtained when [35S]-labeled glycoproteins were separated from the medium using dialysis. These data suggest that the standard method of TCA/PTA precipitation of [35S]-labeled glycoproteins may cleave the [35S]-sulfate ester linkages to the oligosaccharide chains. The [35S]-sulfate may then rebind to the macromolecule by a relatively strong noncovalent bond. This may prove critical in anion exchange protein HPLC studies.

Kinetics of drug release from polylactic acid-hydrocortisone microcapsules

Polylactic acid microcapsules of similar particle size distribution containing various drug loadings of hydrocortisone were prepared. The microcapsules, which contained randomly dispensed drug particles, showed a dissolution pattern which consists of a fast first-stage and a slow second-stage drug release. Our studies showed that the kinetics of drug release from the microcapsules can be adequately described by a spherical matrix model based on a flux mechanism involving the diffusion of dissolved drug at the penetrating front of the dissolution medium. Drug loading played an important role in the control of drug release rate. An empirical relationship between drug loading and drug diffusibility through the polymeric matrix was developed and showed that the rate of drug release increased exponentially with the increase in drug loading. The microcapsules were further shown to exhibit increased rate of drug release in dissolution medium containing either cetylpyridium chloride or aerosol OT. The effect of the surfactants was attributed to surface tension lowering and improved wetting of the microcapsule particles.

Preparation and in vitro evaluation of polylactic acid-mitomycin C microcapsules

An emulsion method was developed for the incorporation of water-soluble mitomycin C into polylactic acid biodegradable microcapsules. With an average particle size of about 95 microns, microcapsules with a desired loading of from 3.65 to 13.80 per cent were prepared. These microcapsules, which contained both crystalline and finely dispersed drug particles, showed a dose-dependent drug release pattern with microcapsules of higher drug loading having a faster release rate than those of lower drug loading. Effective sterilization of the microcapsules for parenteral use was achieved by 60Co gamma-ray irradiation, which did not affect the microcapsule structure, release rate or drug stability. Mitomycin C showed dose-dependent antiproliferative activity against the growth of the K562 human erythroleukaemia cells. The microencapsulated dosage form of mitomycin C was found to enhance the drug's activity through sustained drug release. In experiments where drug concentrations in the cell medium were reduced according to the drug's biological half-life, the microcapsule systems showed a distinct advantage over the non-capsulated dose for the kinetic inhibition of K562 cell growth.

Fluorescence studies of the binding of amphiphilic amines with phospholipids

The binding characteristics of several amine drugs with dispersed phospholipids (phosphatidylcholine, phosphatidylserine, and phosphatidylglycerol) have been studied using the fluorometric method and 1-anilino-8-naphthalene sulfonate and 1,6 diphenyl-1,3,5-hexatriene as fluorescence probes. The results show that amphiphilic amines, such as chlorphentermine, interact with phospholipids via both ionic and hydrophobic forces. The ionic interaction, which occurs between the protonated amine group of the drug and the phosphate oxygen of the lipid, changes the amphiphilic characteristics of the lipid by reducing the number of negative charges on the lipid vesicles, and inhibits the Ca2+-dependent lipid hydrolysis by blocking the Ca2+ binding sites on the lipid vesicles. The hydrophobic interaction, which involves the nonpolar moieties of the drug and the lipid, is of primary importance to the overall drug-lipid binding stability. Drugs without a strong hydrophobic moiety, such as dopamine, do not interact with phospholipids.

Chromatographic analysis of griseofulvin and metabolites in biological fluids

A simple and accurate assay for the determination of griseofulvin and its metabolites in biological fluids using high-performance liquid chromatography is described. Using a reversed phase column and a mobile phase solvent of 45% acetonitrile in 0.1 M acetic acid, baseline separation of griseofulvin and several analogues was obtained. The described method allows one to quantitatively determine griseofulvin, 6-demethylgriseofulvin, and griseofulvic acid, a newly identified metabolite in man, in urine and plasma samples. Treatment of plasma samples prior to the analysis is simply made by deproteinizing the samples with an equal volume of acetonitrile. For urine samples, the procedure involves diethyl ether extraction with subsequent evaporation to dryness and reconstitution with the mobile phase solvent.

High-performance liquid chromatographic studies of reaction of hydralazine with biogenic aldehydes and ketones

To understand hydrazone formation in hydralazine metabolism, the reaction of hydralazine with various biogenic aldehydes and ketones (acetone, pyruvic acid, acetoacetic acid, formaldehyde, and acetaldehyde) in pH 7.4 buffer was studied for potential alterations in hydralazine pharmacokinetics secondary to alcoholism and diabetes. The corresponding hydrazones were isolated, and their structures were characterized. High-performance liquid chromatography was used to monitor the reactions. An aqueous solvent reversed-phase liquid chromatographic system was used to separate hydralazine and its derivatives. Reaction of hydralazine with formaldehyde or acetaldehyde produced the corresponding hydrazones. Formation of an s-triazolo ring system yielded the known s-triazolo[3,4-alpha]phthalazine and 3-methyl-s-triazolo[3,4-alpha]phthalazine metabolites, which also were isolated and characterized and suggested nonenzymatic metabolism.

Kinetic studies of hydralazine reaction with acetaldehyde

In vitro kinetic studies of the reaction of hydralazine with acetaldehyde at physiological concentrations and pH were conducted. This reaction, which leads to the formation of 3-methyl-S-triazolo[3,4-a]phthalazine, may occur in the plasma and may represent an alternative pathway for hydralazine metabolism. The reaction of hydralazine with acetaldehyde followed second-order kinetics with an activation energy of 16.9 kcal/mole. At 37 degrees, the half-life of the reaction for a colution containing 2.3 microgram of acetaldehyde/ml and 1 microgram of hydralazine/ml was 4.5 hr. The rate increased with increasing acetaldehyde concentrations.