Guillian-Barré syndrome in high tetraplegia following acute respiratory illness

STUDY DESIGN

A case report of a Guillain-Barré syndrome (GBS) variant presenting in a patient with a high cervical spinal cord injury (SCI).

OBJECTIVES

To illustrate a clinical presentation of GBS in an individual with chronic SCI.

SETTING

Vancouver General Hospital, Vancouver, BC, Canada.

METHODS/RESULTS

A 31-year-old man with chronic C2 AIS B (American Spinal Injury Association Impairment Scale) SCI and diaphragmatic pacing presented with respiratory failure with sepsis. His sepsis resolved with antibiotic therapy, but he continued to have autonomic instability and was unable to be weaned off his ventilator. Concurrently he developed flaccidity and facial diplegia. Investigations including nerve conduction studies and cerebrospinal fluid analysis prompted a diagnosis of acute motor-sensory axonal neuropathy, a variant of Guillian-Barré syndrome. Owing to ongoing autonomic instability, he was treated with intravenous immunoglobulin. His autonomic dysfunction resolved and he regained some facial muscle function, but 6 months post injury he remained dysphagic and required 24-h ventilator support.

CONCLUSION

Careful neurological reassessment prompted the diagnosis of acute polyradiculoneuropathy following respiratory sepsis as the root cause of diaphragmatic pacer failure and autonomic instability.

Reversal of HIV drug resistance and novel strategies to curb HIV infection: the viral infectivity factor Vif as a target and tool of therapy

Due to the high genetic variability of human immunodeficiency virus (HIV), treatment of AIDS (acquired immunodeficiency syndrome) patients with inhibitors of reverse trancriptase (RT) and drugs blocking the viral protease regularly results in the accumulation of drug resistant HIV variants and treatment failure. The sensitivity of clinically derived resistant HIV-1 strains to nucleotide RT inhibitors could be restored, however, in several laboratories by pharmacological depletion of the appropriate endogenous deoxynucleotide triphosphate (dNTP), and such a manipulation (induction of dCTP pool imbalance during reverse transcription in the presence of a non-nucleoside RT inhibitor) altered the mutation spectrum of the HIV-1 genome, resulting in a lower level of HIV resistance to certain drugs. The cytoplasmic single-stranded DNA cytidine deaminases APOBEC3G and APOBEC3F block HIV replication by introducing premature stop codons into the viral genome. We suggest that the resulting crippled, defective HIV (dHIV) variants could interfere with replication of "wild type" viruses and curbe disese progression in long term non-progressor individuals. Vif, an accessory protein encoded by HIV, counteracts APOBEC3G/F action. We speculate that small molecule inhibitors of Vif could permit lethal or sublethal mutagenesis of HIV genomes. We suggest that an artificial dHIV construct carrying a mutated vif gene (coding for a Vif protein unable to block APOBEC3G/F) could have a therapeutic effect as well in HIV infected individuals and AIDS patients.

[Ala12]MCD peptide: a lead peptide to inhibitors of immunoglobulin E binding to mast cell receptors1

An effort was made to discover mast cell degranulating (MCD) peptide analogs that bind with high affinity to mast cell receptors without triggering secretion of histamine or other mediators of the allergic reaction initiated by immunoglobulin E (IgE) after mast cell activation. Such compounds could serve as inhibitors of IgE binding to mast cell receptors. An alanine scan of MCD peptide reported previously showed that the analog [Ala12]MCD was 120-fold less potent in histamine-releasing activity and fivefold more potent in binding affinity to mast cell receptors than the parent MCD peptide. Because this analog showed marginal intrinsic activity and good binding affinity it was subsequently tested in the present study as an IgE inhibitor. In contrast to MCD peptide, [Ala12]MCD showed a 50% inhibition of IgE binding to the Fc epsilon RI alpha mast cell receptor by using rat basophilic leukemia (RBL-2H3) mast cells and fluorescence polarization. Furthermore, in a beta-hexosaminidase secretory assay, the peptide also showed a 50% inhibition of the secretion of this enzyme caused by IgE. An attempt was made to relate structural changes and biologic differences between the [Ala12]MCD analog and the parent MCD peptide. The present results show that [Ala12]MCD may provide a base for designing agents to prevent IgE/Fc epsilon RI alpha interactions and, consequently, allergic conditions.

Relative deficiency in CpG dinucleotides is a widespread but not unique feature of Gammaherpesvirinae genomes

Since methylcytosine is relatively unstable, a deficiency of CpG dinucleotides and accumulation of mutations that manifest as TpG (and its complement CpA) is a diagnostic feature of higher eukaryotic DNA sequences subjected to methylation by DNA (cytosine-5) methyltransferases. Latent viral genomes may also be affected by DNA methylation in their host cells. We calculated, therefore, frequencies of dinucleotides in 20 completely sequenced herpesvirus genomes. We found a relative deficiency of CpG dinucleotides and a surplus of TpG + CpA dinucleotides in all lymphotropic gammaherpesvirus genomes except for two strains of rhesus rhadinovirus. DNAs of two strains of human herpesvirus 7, a betaherpesvirus targeting helper T cells, and equine herpesvirus 4, an alphaherpesvirus residing in the lymphoreticular system, also had a moderate CpG deficiency and TpG + CpA surplus. In contrast, most members of Alpha-, and Betaherpesvirinae subfamilies contained a relative surplus of CpG dinucleotides in their DNAs. Our data are consistent with the idea that methylated latent genomes are involved, after reactivation and productive replication, in the natural transmission cycle of most members of Gammaherpesvirinae and certain lymphotropic members of Alpha- and Betaherpesvirinae.

Electromyography of respiratory muscles in amyotrophic lateral sclerosis

We reviewed the records of 52 amyotrophic lateral sclerosis (ALS) patients examined between 1995 and 2000 who had needle electromyography (EMG) of their respiratory muscles, including the diaphragm, at or near the time of their diagnosis. With respiratory function testing, patients with abnormal diaphragmatic EMG at diagnosis (Group 1, n=23) had significantly lower forced vital capacity (FVC), lower daytime arterial PO(2) and higher PCO(2) measurements (p<0.05) than patients with normal diaphragmatic EMG (Group 2, n=29). Twenty-eight percent of the patients without symptoms or signs of respiratory insufficiency at the time they were examined had an abnormal diaphragm EMG. Mean survival of Groups 1 and 2 were similar. However, sub-analysis of patients within each group, comparing those treated with non-invasive positive pressure ventilation (NIPPV) with those not treated, showed that treated patients in Group 1 (abnormal diaphragm EMG) survived significantly longer (p<0.05) than untreated patients. They also started NIPPV earlier than treated patients in Group 2. We conclude that respiratory muscle EMG was simply and safely performed on ALS patients at or around the time of diagnosis. The procedure can detect sub-clinical respiratory muscle dysfunction. The technique used for EMG of the respiratory muscles, its pitfalls and contraindications are also reviewed.

Conformational space comparison of GnRH and lGnRH-III using molecular dynamics, cluster analysis and Monte Carlo thermodynamic integration

The conformational space available to GnRH and lGnRH-III was compared using 5.2 ns constant temperature and pressure molecular dynamics simulations with explicit TIP3P solvation and the AMBER v. 5.0 force field. Cluster analysis of both trajectories resulted in two groups of conformations. Results of free energy calculations, in agreement with previous experimental data, indicate that a conformation with a turn from residues 5 through 8 is preferred for GnRH in an aqueous environment. By contrast, a conformation with a helix from residues 2 through 7 with a bend from residues 6 through 10 is preferred for lGnRH-III in an aqueous environment. The side chains of His2 and Trp3 in lGnRH-III occupy different regions of phase space and participate in weakly polar interactions different from those in GnRH. The unique conformational properties of lGnRH-III may account for its specific anti cancer activity.

Transdermal formulations of deprenyl: guinea pig and pig models

The efficacy of many drugs relies on their presence at the site of action over a period of time. The retardation or programmed release capability of the conventional dosage forms like oral and parenteral are limited and toxic and undesired side-effects may occur after their applications. These problems may be solved using transdermal delivery systems. Transdermal systems are aimed for local, or systemic action. In the letter case controlling the rate of delivery or modulating the distribution in the organism. The selection of an adequate biological method of evaluating a new transdermal formulation is a critical point of the development. The in vitro methods can help in the characterization of the different formulas, but without an in vivo disposition study they cannot give relevant information about the expectable therapeutic behavior. We adapted and improved an in vivo test system for the evaluation of new transdermal particulate systems (patches) and liposomes containing deprenyl selegiline as active ingredient. The in vivo evaluation system consists of two steps: 1. Full biodisposition study on guinea pig, using isotope labeled selegiline. 2. Biodisposition studies on domestic pigs including dose, area, surface dependence and comparative bioavailability with traditional dosage forms and application moods. Specific examples of these studies and experimental technology are presented.

Calculating the local solvent chemical potential in crystal hydrates

Determining solvation patterns in biological systems is crucial in investigating the functional role water may play in structural stabilization and molecular recognition. Determining whether a particular position would be occupied by a solvent molecule requires the local thermodynamics to be known. In this work we introduce a simple and inexpensive approach based on grand canonical molecular simulations to determine the occupancy factors of the cavities. The method is applied to the test case of the sodium salt of hyaluronic acid. The results agree very well with experimental results and demonstrate the success of the method.

Genetic subtypes of HIV type 1 in Hungary

We examined the diversity of HIV-1 subtypes in 11 adults from Hungary, using the heteroduplex mobility assay (HMA) and DNA sequencing. HMA results showed that HIV-1 gp120 sequences from 10 patients were of subtype B, whereas 1 patient, infected in Africa, carried a subtype C strain. DNA sequencing confirmed the HMA results and revealed a high intrasubtype diversity in the C2V3 region of env in different clade B isolates, which suggests multiple introduction of subtype B to Hungary. This study shows that subtype B is the predominant HIV-1 clade in Hungary.

Motor system abnormalities in heterozygous relatives of a D90A homozygous CuZn-SOD ALS patient of finnish extraction

Presently, 64 mutations in the gene encoding the enzyme CuZn-superoxide dismutase have been found in a small fraction of amyotrophic lateral sclerosis patients worldwide. All but one of these mutations show autosomal dominant inheritance. In Scandinavia, the D90A mutation is inherited as an autosomal recessive trait and patients have an easily recognizable characteristic phenotype with little variation among patients, even amongst different families. Importantly, all D90A heterozygous relatives of Scandinavian D90A homozygous patients have been reported as clinically unaffected. We have investigated a Canadian family of Finnish extraction in which the D90A homozygous proband developed ALS with the characteristic phenotype. Remarkably, two D90A heterozygous relatives show slight symptoms and signs of motor system involvement, suggesting that the final phenotype of an individual with a CuZn-superoxide dismutase mutation is shaped by the combination of the particular CuZn-SOD mutation, other polymorphic modifying genes elsewhere in the genome, stochastics and possible environmental factors.

Influence of lamotrigine on progression of early Huntington disease: a randomized clinical trial

OBJECTIVE

To assess the efficacy of lamotrigine, a novel antiepileptic drug that inhibits glutamate release, to retard disease progression in Huntington disease (HD).

BACKGROUND

Excitatory amino acids may cause selective neuronal death in HD, and lamotrigine may inhibit glutamate release in vivo.

METHODS

A double-blinded, placebo-controlled study was conducted of 64 patients with motor signs of less than 5 years' duration who were randomly assigned to either placebo or lamotrigine and assessed at 0 (baseline), 12, 24, and 30 months. The primary response variable was total functional capacity (TFC) score. Secondary response variables included the quantified neurological examination and a set of cognitive and motor tests. Repeated fluorodeoxyglucose measurements of regional cerebral metabolism using PET also were included.

RESULTS

Fifty-five patients (28 on lamotrigine, 27 on placebo) completed the study. Neither the primary response variable nor any of the secondary response variables differed significantly between the treatment groups. Both the lamotrigine and the placebo group deteriorated significantly on the TFC, in the lamotrigine group by 1.89 and the placebo group by 2.11 points. No effect of CAG size on the rate of deterioration could be detected.

CONCLUSIONS

There was no clear evidence that lamotrigine retarded the progression of early Huntington disease over a period of 30 months. However, more patients on lamotrigine reported symptomatic improvement (53.6 versus 14.8%; p = 0.006), and a trend toward decreased chorea was evident in the treated group (p = 0.08). The study also identified various indices of disease progression, including motor tests and PET studies, that were sensitive to deterioration over time.

[Headspace solid phase micro-extraction method optimization for residual solvent analysis]

A systematic headspace SPME method optimization is described for the residual solvent analysis using a polidimethyl-siloxane/divinylbenzene (PDMS/DVB) fiber. The first step was the chromatographic system optimization in which a narrow bore capillary column with a thick film (1 micron) of stationary phase, low starting column temperature (30 degrees C) and a narrow bore injector liner (2 mm I.D.) were used. It was found that for the investigated components a desorption temperature of minimum 150 degrees C should be used. The second step was the extraction optimization. The optimum equilibration time for all components was 30 min. It was found that the sample headspace volume has an important effect on method sensitivity and precision. At low headspace volumes (less than 1/3 of vial volume) sensitivity improves but at the same time precision worsen. The optimum headspace volume was found to be 4.6 ml. The total organic content does also have an important effect on method sensitivity and precision. At low organic content sensitivity increases but precision drops significantly. Over 1% organic content in the sample the system becomes unstable due to stationary phase swelling by the organic components. The optimum range for total organic content was found to be between 0.1% and 1%. The added NaCl quantity does increase the extraction yield. The optimum salt quantity to be added was 2 g NaCl in 5 ml sample. The last step was the desorption optimization. The influence of injector temperature and injection depth on desorption were investigated and it was found that it does not have an important effect on desorption yield. The optimum desorption temperature was 220 degrees C and the optimum injection depth was 2 cm into the injector. Among the investigated fibers the best detection limits and chromatographic behavior were given by the PDMS/DVB fiber. The measured detection limits were between 10 and 100 pg/ml and the RSD data were between 1-3%.

Computer simulation studies of the fully solvated wild-type and mutated GnRH in extended and beta-turn conformations

The conformational preference of the gonadotropin-releasing hormone (GnRH) and its Lys-8 mutant, studied earlier with a continuum model, was revisited using an explicit solvent model and thermodynamic integration to calculate the solvents contribution to the conformation-dependence of its free energy. In addition, the Proximity Criterion was used to further analyze the effects of conformational changes.

Topical anaesthesia of intact skin: liposome-encapsulated tetracaine vs EMLA

In this randomized, double-blind study, we have compared the ability of 5% liposome-encapsulated tetracaine (amethocaine) (LET) vs 5% eutectic mixture of local anaesthetics (EMLA) to produce local anaesthesia of intact skin in 40 healthy volunteers. Volunteers had both preparations applied to their forearms under an occlusive dressing for 1 h. Superficial anaesthesia was measured by a total of nine 1-mm pinpricks on each arm. Deeper anaesthesia was assessed by single insertion of a sterile 22-gauge needle to a depth of 3 mm and pain was reported on a visual analogue scale (VAS). If the volunteer perceived greater than four of the 1-mm pinpricks, the 3-mm insertion was not performed. Results showed that the number of pinpricks perceived was significantly less (P < 0.01) for LET (median 1.0; range 0-9) vs EMLA (1.5; 0-9). In volunteers who had deeper anaesthesia assessed, there was no significant difference (P = 0.065) in VAS scores for LET (mean 1.5 (SD 1.4); n = 34) vs EMLA (2.4 (2.1); n = 28). Overall anaesthetic effect, as ranked by all of the subjects, was significantly better for LET compared with EMLA (P = 0.024). We have demonstrated that when applied in equal volumes, 5% LET produced better superficial local anaesthesia than EMLA.

Chameleon sequences in the PDB

The Brookhaven Protein Data Bank has been searched for sequences that can be found both in helix and sheet conformation. The longest such sequences consist of seven residues.

Evidence for a long-lasting single administration contraceptive vaccine in wild grey seals

A single-administration birth control vaccine based on liposome delivery of porcine zona pellucida antigens reduced pup production in grey seals (Halichoerus grypus) by about 90%. Anti-porcine zona pellucida titers of individual seals with two or more recaptures were variable but without a diminishing trend during the 5 year post-immunization period. Seals that produced at least one or more pups during the 2-5 year post-immunization period when the vaccine is fully effective, had an average anti-porcine zona pellucida titer of 5% of the reference serum. In contrast, the subset of seals that did not reproduce but were recaptured during the breeding season had an average titer of 31% of the reference serum. As measured by antibody titers and pup production, there were no differences in efficacy of the vaccine in 14-, 20- and 21-year-old female grey seals.

Temporal trends in antibody production in captive grey, harp and hooded seals to a single administration immunocontraceptive vaccine

The temporal production of antibody to a single-administration immunocontraceptive vaccine, known to be immunocontraceptive in free-ranging female grey seals (Halichoerus grypus), was studied in captive grey seals, harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata). The vaccine is based on liposome delivery of porcine zona pellucida antigens. When measured by antigen capture, the response of hooded and harp seals to the vaccine was similar to the response of grey seals. Determination of antibody production by ELISA with protein A, ELISA with rabbit anti-seal immunoglobulin sera and SDS-PAGE after affinity chromatography confirmed the similarity in response to the vaccine by grey and harp seals, but suggested lower titers in hooded seals. The vaccine produced titers in captive, juvenile grey and harp seals known to be immunocontraceptive in wild, adult grey seals.

Comparative topical anaesthesia of EMLA and liposome-encapsulated tetracaine

BACKGROUND

The eutectic mixture of local anaesthetics (EMLA) provides effective topical anaesthesia after a minimum of 60 to 90 min application. Since liposome-encapsulated tetracaine (LET) can provide rapid dermal penetration, the goal of this study was to compare the local anaesthetic effects of EMLA and LET in human volunteers after 60 min application.

METHODS

After obtaining institutional approval and informed consent, healthy volunteers were recruited in a double blind, crossover, randomized trial. The study creams (0.5 ml EMLA and 0.5 ml LET 5%) were applied randomly to opposite arms for 60 min. The discomfort of i.v. catheterization was assessed using a visual analogue pain score (VAS). Cutaneous side effects of the creams were recorded.

RESULTS

Sixty-one subjects were studied. Twenty-one were excluded because of technical difficulties. Forty subjects completed the study and were included in the data analysis. The mean ( +/- SD) VAS was lower for LET than for EMLA (10.9 +/- 9.0 mm vs 22.7 +/- 17.1 mm, P < 0.001). Erythema secondary to vasodilatation occurred more frequent in the LET group than in the EMLA group (33 vs 3, P < 0.001). One subject with a history of atopy developed a rash at the LET application site.

CONCLUSION

Liposome-encapsulated tetracaine can provide a more effective topical anaesthesia than EMLA for intravenous catheterization after 60 min application. Clinical evaluations are necessary to determine the efficacy and safety of LET in providing topical anaesthesia for various invasive percutaneous procedures in other patient populations.

The sensitivity of conformational free energies of the alanine dipeptide to atomic site charges

Different atomic point charge sets are obtained for the alpha R and C7,eq conformations of the alanine dipeptide by fitting the charges of each conformation to the respective ab initio electrostatic potential surfaces both individually and simultaneously, in both the united atom and the all-atom representations. Using these charge sets, the sensitivity of the relative conformational aqueous free energies to the atomic site charges is investigated. For this particular system, we find that the solute-water contributions to the conformational free energy differences have a rather weak dependence on site charges; the calculated intramolecular contributions, however, show a rather strong dependence on the atomic site charges. It is suggested that the calculated results for the alanine dipeptide using a single, simultaneously fit set of charges for both conformations are in better agreement with experiments than the calculations carried out with charges determined individually for each conformation.

Grand canonical ensemble Monte Carlo simulation of the dCpG/proflavine crystal hydrate

The grand canonical ensemble Monte Carlo molecular simulation method is used to investigate hydration patterns in the crystal hydrate structure of the dCpG/proflavine intercalated complex. The objective of this study is to show by example that the recently advocated grand canonical ensemble simulation is a computationally efficient method for determining the positions of the hydrating water molecules in protein and nucleic acid structures. A detailed molecular simulation convergence analysis and an analogous comparison of the theoretical results with experiments clearly show that the grand ensemble simulations can be far more advantageous than the comparable canonical ensemble simulations.

Superficial siderosis--a cause of audiovestibular failure

Bilateral vestibular end organ failure in adult life is a rare condition with some specific known causes, such as relapsing polychondritis, autoimmune inner ear disease, Lues venerium, and an acute effect of gentamicin. This case report draws attention to a rare condition that is potentially recognizable early in its development. The patient has superficial siderosis, which is iron deposits over the cerebrum, resulting in progressive neurologic failure involving all of the systems. Early in its course before other symptoms appear, there is development of progressive hearing loss and vestibular failure. This case report and literature review are given, including a potential for attempts at therapy if the disorder is recognized early.

Pharmacokinetics of inhaled liposome-encapsulated fentanyl

BACKGROUND

Pulmonary administration of fentanyl solution can provide satisfactory but brief postoperative pain relief. Liposomes are microscopic phospholipid vesicles that can entrap drug molecules. Liposomal delivery of fentanyl has the potential to control the uptake of fentanyl by the lungs and thus provide sustained drug release. To demonstrate that inhalation of a mixture of free and liposome-encapsulated fentanyl can provide a rapid increase and sustained plasma fentanyl concentrations (CfenS), this study determined the pharmacokinetic profiles after the inhalation of free and liposome-encapsulated fentanyl in healthy volunteers.

METHODS

After obtaining institutional approval and informed consent, ten healthy volunteers (five men, five women) were studied. Each subject received 200 micrograms intravenous fentanyl and inhaled 2,000 micrograms of free (50%) and liposome-encapsulated fentanyl (50%) on separate occasions. Frequent venous blood samples were collected, and CfenS were determined by radioimmunoassay. The pharmacokinetics and absorption characteristics of the inhaled mixture of free and liposome-encapsulated fentanyl were determined using moment analysis and least-squares numeric deconvolution.

RESULTS

The mean (+/- SD) volume of distribution at steady-state and clearance of fentanyl after the intravenous administration were comparable to previous studies: 435 +/- 1821 and 0.584 +/- 0.209 l.min-1, respectively. The mean (+/- SD) peak Cfen was significantly greater for the intravenous administration compared to the aerosol mixture of free and liposome-encapsulated fentanyl (4.67 +/- 1.87 vs. 1.15 +/- 0.36 ng.ml-1). However, CfenS at 8 and 24 h after aerosol administration were greater compared to intravenous (0.25 +/- 0.14 and 0.12 +/- 0.16 ng.ml-1 for aerosol versus 0.16 +/- 0.10 and 0.05 +/- 0.06 ng.ml-1 for intravenous). The peak absorption rate, time to peak absorption, and bioavailability after inhalation were 7.02 (+/- 2.34) micrograms.min, -1(16) (+/- 8.0) min, and 0.12 (+/- 0.11), respectively.

CONCLUSIONS

The data suggest that this analgesic method offers a simple and noninvasive route of administration with a rapid increase of Cfen and a prolonged therapeutic fentanyl concentration. Future studies are required to determine the optimal liposome composition that would produce a sustained stable Cfen within analgesic therapeutic concentrations.

A role for amplified protein kinase C activity in the pathogenesis of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a human neurodegenerative disorder of unknown origin that is characterized by progressive degeneration of corticospinal tracts and anterior horn cells in the brainstem and spinal cord. Previous studies have indicated that motoneuron degeneration associated with ALS may be triggered by mechanisms leading to increased intracellular Ca2+. In the present report, Ca(2+)-activated phospholipid-dependent protein kinase C (PKC) was evaluated in cervical spinal cords from ALS patients and control subjects. In patients who died with ALS, PKC histone H1 phosphotransferase activity was significantly increased by 330% in cytosolic- and 118% in particulate-derived extracts compared with controls. This increase in PKC phosphotransferase activity appeared to be partially due to an increase in the amount of PKC protein present in ALS spinal cord tissue. PKC histone H1 phosphotransferase activities of cytosolic- and particulate-derived extracts from motor and visual cortex of ALS patients and controls were not statistically different, nor were there differences in PKC histone H1 phosphotransferase activity in platelets and leukocytes. The specific nature of PKC alterations in affected regions of the CNS supports a role for PKC in the events leading to motoneuron death in sporadic ALS.

Absorption of liposome-encapsulated tetracaine versus nonliposome-encapsulated tetracaine from open wounds in rabbits

The plasma tetracaine concentration versus time profiles for liposome-encapsulated tetracaine (LET) versus nonliposome-encapsulated tetracaine (NLET) were determined after topical application to open wounds in six rabbits (three in LET and three in NLET). H3-tetracaine preparations of LET or NLET were applied randomly to uniform dermal lacerations in anesthetized rabbits. Plasma tetracaine concentrations (ng/mL) of arterial blood samples obtained were measured at predetermined intervals (0.25, 0.5, 1.0, 2.0, and 24 hours) by isotope tracer assay. Results (mean +/- standard deviation) showed the peak plasma tetracaine concentration (Cmax) and the time to Cmax were 40.8 +/- 5.1 ng/mL and 40.1 +/- 7.3 minutes for LET, and 117.8 +/- 9.7 ng/mL and 49.1 +/- 50.2 minutes for NLET. Plasma tetracaine concentrations at all samples times were significantly lower for LET versus NLET. Liposome encapsulation of topically applied tetracaine significantly decreases both the peak and overall plasma tetracaine concentrations compared with the nonencapsulated form. The data suggest that liposome encapsulation of topically applied local anesthetics such as a solution of tetracaine, adrenaline, and cocaine, might reduce the potential systemic toxicity caused by rapid absorption of these compounds.

Liposomes as carriers for topical and transdermal delivery

The delivery of active agents to the skin by liposome carriers is an interdisciplinary topic of great interest today. Data accumulated over the last decade strongly point to important advantages of these drug delivery systems. A symposium devoted to classic and new approaches in the use of liposomal systems was organized and chaired by M. Mezei and E. Touitou as a part of the Jerusalem Conference on Pharmaceutical Sciences and Clinical Pharmacology, held on May 24-30, 1992, in Jerusalem, Israel. The presentations focused on liposomes as tools in the mechanistic study of absorption promoters (T. Nagai), drug liposomal delivery in the skin strata and structures (N. Weiner), interaction of liposomes and niosomes with the human skin (H.E. Junginger), and design and characterization of caffeine liposomal systems for use in hyperproliferative diseases (E. Touitou). Mezei reviewed biodisposition and clinical studies on liposomal dosage forms containing various drugs.

A heuristic procedure for the detection of locally similar substructures of two equivalent structures

A heuristic procedure is presented for the detection of locally similar substructures in two equivalent molecules, using elementary graph theoretical concepts. The capabilities of the procedure are demonstrated on the comparison of the calmodulin backbone in the X-ray structure and in a structure obtained from molecular dynamics.

Liposomal drug delivery to the eye and lungs: a preliminary electron microscopy study

Colloidal gold was used as an electron-dense marker for multilamellar vesicles to study the mechanism of liposome drug delivery to the eye and lung. A gold labelled multilamellar vesicle could be seen in the conjunctiva but there was no evidence of vesicles adsorbed to the epithelial surface of cornea or conjunctiva. In the lung, a free gold particle was isolated in type 1 epithelial cells and many vesicular structures were observed in the alveolar spaces which were not gold labelled. Experiments performed so far indicate that adsorption and not endocytosis was the major mechanism of uptake of drug or marker for multilamellar vesicles except for conjunctiva.

Intracellular delivery of drugs by liposomes containing P0 glycoprotein from peripheral nerve myelin into human M21 melanoma cells

The effect of P0 protein (a cell adhesion molecule from avian peripheral nerve myelin) on the rate of interaction of liposomes with human M21 melanoma cells was investigated. Liposome uptake by the cells was quantitated using radioactive lipids and liposome-entrapped drugs under various conditions. Liposomes containing P0 protein and [14C]dipalmitoylphosphatidylcholine:cholesterol (10:1 molar ratio) had an interaction rate with M21 cells three times higher than control vesicles of the same lipid composition but without the protein after incubation at 37 or 4 degrees C. The presence of P0 protein could be detected on the surface of melanoma cells by immunofluorescence after incubation. Binding to the cell surface and endocytosis of P0 liposomes was suggested from the sensitivity of cell-associated proteoliposomes to trypsin, metabolic inhibitors, and low temperature. Liposomal encapsulation highly increased the association of model compounds [( 3H]methotrexate and [3H]inulin) with cells. The proteoliposomes appeared to be leaky in the incubation medium, which led to the delivery of a lower amount of drug into cells than could be expected from their initial drug content. The results suggest that the attachment of liposomes to the cell surface can increase their drug delivery potential, because the binding triggers endocytic processes or a juxtapositional temporary permeability increase of liposome and cellular membrane that can lead to the uptake of drug from liposomes.

Inhibition of human renal cancer by monoclonal antibody targeted methotrexate-containing liposomes in an ascites tumor model

The monoclonal antibody DAL K29 against a human renal cell carcinoma associated cell surface antigen was covalently linked to small unilamellar lipid vesicles (SUV) containing the antifolate, methotrexate (MTX), with full retention of antibody activity. In an ascites tumor model developed after intraperitoneal inoculation of 5 x 10(6) cells of the human kidney cancer line Caki-1 per pristane primed nude mouse, the DAL K29 linked MTX-containing SUV was a more potent tumor inhibitor (P less than 0.0005) than the drug or MAB alone, MTX-containing SUV, a mixture of DAL K29 and MTX-containing SUV or MTX-containing SUV linked to an isotype matched nontumor specific IgG.

Dermal drug delivery by liposome encapsulation: clinical and electron microscopic studies

The fate of liposomes and the encapsulated drug was studied after topical application on the skin. Lidocaine applied on the forearm of human volunteers produced greater local anaesthetic effect in the liposomal form than in the cream form (p less than or equal to 0.001 after 1 h application). Autoradiography demonstrated higher concentration (p less than or equal to 0.01) of 14C-lidocaine in the epidermis and dermis of guinea pigs treated with liposome-encapsulated lidocaine as opposed to lidocaine in Dermabase cream. Electron microscopic observations, using colloidal iron as an electrodense marker, indicated that intact liposomes penetrated into the skin and deposited in the dermis where they acted as a slow release depot system. On the basis of results in the human volunteers and animals, a hypothetical model for liposome-skin interaction is proposed.

Computational analysis of the effects of site-specific phosphate alkylation in the DNA oligomer (d-[GGAATTCC])2

Alkylation of the sugar-phosphate backbone of DNA can result upon exposure to several potent carcinogens, inducing DNA misfunction. In order to assess the structural and energetic changes in DNA helices induced by such alkylation, we have performed AMBER-based analyses on phosphotriester containing analogues of (d-[GGAATTCC])2. Fourteen analogues of the nonalkylated oligomer were examined, each bearing a single alkylation of known stereochemistry. Results indicate that although there is minimal effect on the aromatic bases, the presence of a phosphotriester disturbs the sugar-phosphate backbone in complex ways. For most analogues, total minimum energies are lower for the Sp-alkylations than for the Rp-alkylations which point directly into the major groove of the helix; however, different energetic contributions follow different, or no, trends in dependence on alkylation site and/or stereochemistry. Where data is available, experimental nmr results agree with the calculations reported here.