ICTV Virus Taxonomy Profile: Nodaviridae.

The family Nodaviridae includes two genera, Alphanodavirus and Betanodavirus. The family name derives from the Japanese village of Nodamura where Nodamura virus was first isolated from Culex tritaeniorhynchus mosquitoes. Virions are non-enveloped and spherical in shape with icosahedral symmetry (T=3) and diameters ranging from 25 to 33 nm. The genome consists of two molecules of single-stranded positive-sense RNA: RNA1 and RNA2. The virion capsid consists of 180 protein subunits arranged on a T=3 surface lattice. Alphanodaviruses infect insects, whereas betanodaviruses are pathogens of fish. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Nodaviridae, which is available at www.ictv.global/report/nodaviridae.

ICTV virus taxonomy profile: Sarthroviridae.

The family Sarthroviridae includes a single genus, Macronovirus, which in turn includes a single species, Macrobrachium satellite virus 1. Members of this species, named extra small virus, are satellite viruses of Macrobrachium rosenbergii nodavirus, an unclassified virus related to members of the family Nodaviridae. Both viruses have isometric, spherical virions, infect giant freshwater prawns and together cause white tail disease, which is responsible for mass mortalities and severe economic losses in hatcheries and farms. Infection is caused by both vertical and horizontal transmission of virus. Aquatic insects act as a carrier to transmit the disease in prawns. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Sarthroviridae, which is available at www.ictv.global/report/sarthroviridae.

Endogenous grouper and barramundi Mx proteins facilitated the clearance of betanodavirus RNA-dependent RNA polymerase.

This study confirmed that the infection of nervous necrosis virus (NNV), belonging to the betanodavirus, can induce the expression of endogenous Mx in grouper fin-3 (GF-3), grouper brain (cGB), and barramundi brain (cBB) cells, but not in grouper fin-1 (GF-1) cells. In a co-sedimentation assay, RdRp appeared in the mitochondrial pellet of GF-1 cells without endogenous Mx expression. However, in GF-3, cGB, and cBB cells, RdRp was detected in the nuclear pellet accompanied by endogenous Mx. By immunostaining, RdRp was found to colocalize with not only endogenous Mx but also lysosomes and monodansylcadaverine (MDC)-labeled autophagic vacuoles. In GF-1 cells, the RdRp level continuously increased during 24-72 h post infection (hpi). When endogenous Mx expressed during 24-72 hpi in virus-infected GF-3, cGB, and cBB cells, the RdRp level peaked at 24 hpi but decreased at 48-72 hpi. The degradation of RdRp could be suppressed by treatment with 3-methyladenine (3MA), NH4Cl, and Mx-specific siRNA respectively. After poly I:C transfection, the endogenous Mx level peaked at 3 days post transfection (dpt) and then spontaneously decreased at 5-7 dpt. The poly I:C-indued Mx also colocalized with MDC-labeled autophagic vacuoles at 3 dpt, and its degradation could be inhibited by 3MA or NH4Cl treatments. Therefore, the anti-NNV mechanism of endogenous grouper and barramundi Mx is suggested to sequester RdRp for degradation through autophagy and lysosomes.

Effects of pelvic floor muscle exercise on faecal incontinence in rectal cancer patients after stoma closure.

The purpose of this study was to examine the effects of pelvic floor muscle exercise (PFME) on the faecal incontinence (FI) of rectal cancer patients following stoma closure. Participants were randomly distributed into an exercise group (n = 27) and non-exercise group (n = 26). An experimental design and longitudinal approach were implemented for data collection. Baseline data were collected at 1 day before discharge, and then PFME was taught before the patients were discharged from the hospital. We collected data and followed up with the patients at their pre-discharge visit and at 1, 2, 3, 6 and 9 months after discharge. The Cleveland Clinic Faecal Incontinence (CCI) score was used to measure patient outcome. PFME proved to effectively decrease the degree of FI in stoma closure recipients. The FI score of the exercise group significantly decreased from 8.37 to 2.27 after PFME compared with that of the non-exercise group (from 8.54 to 2.58). The generalised estimation equation tests showed that both group and time were significantly different. The tests also indicated that although PFME appeared to hasten the decline of incontinence, this effect was no longer detectable at 9 months; thus, it may be an effective intervention for FI when implemented up to half a year after discharge.

Topical anesthetic EMLA for postoperative wound pain in stereotactic gamma knife radiosurgery: a perspective, randomized, placebo-controlled study.

BACKGROUND: Patients who undergo stereotactic gamma knife radiosurgery (GKRS) need a rigid frame fixation for the stereotactic procedures. Many patients suffered from postoperative wound pain after frame removal. The present study investigated whether an additional application of a topical anesthetic prior to frame removal could reduce this discomfort. PATIENTS AND METHODS: 60 patients who underwent GKRS were enrolled in this study. Of these 60 patients, 30 were treated with a topical application of EMLA, a eutectic mixture of 2.5% lidocaine and 2.5% prilocaine; the remaining 30 were treated with a placebo. The nurses explained the definition of the visual analogue scale (VAS, scored from 0 to 10), and the patients evaluated their pain at 7 time points during the GKRS procedure by using the VAS. After each of these evaluations, the patients' vital signs (blood pressure, heart rate, and respiratory rate) were measured. RESULTS: There was no significant difference in the patients' age, gender, duration of frame fixation, and types of the lesions between the EMLA and placebo groups. The EMLA group reported significantly lower pain scores 20 and 60 min after frame removal than the placebo group (p=0.001 and p<0.001, respectively). Additionally, patients in the placebo group had significantly higher blood pressure readings compared with baseline data, during and after frame removal, thus indicating that postoperative wound pain caused them more discomfort after frame removal. CONCLUSION: EMLA when applied 60 min before frame removal has an anesthetic effect of reducing the postoperative wound pain in patients who undergo GKRS.

Cloning and analysis of antiviral activity of a barramundi (Lates calcarifer) Mx gene.

We obtained a full-length cDNA clone for the Mx gene of barramundi (Lates calcarifer), using RACE (rapid amplification of cDNA ends) polymerase chain reaction (PCR) amplification of RNA extracted from a barramundi brain cell line cBB. The Mx cDNA of 2.2kb contains an open reading frame (ORF) of 1875 nucleotides encoding a protein of 624 amino acids. The predicted barramundi Mx protein is 71.4 kDa and contains a tripartite guanosinetriphosphate (GTP)-binding motif at the amino terminal and a leucine zipper at the carboxyl terminal, characteristic of all known Mx proteins. Poly I:C-transfection induced the expression of Mx gene in cBB cells, and the induction level at 28 degrees C was higher than that at 20 degrees C. Moreover, Mx gene expression was also induced by viral infection, including fish nodavirus, birnavirus, and iridovirus. Among these, nodavirus was a stronger inducer than the other two viruses. Using an antiviral activity assay, we revealed that poly I:C-transfected cBB cells had antiviral activity against fish nodavirus and birnavirus, but not iridovirus. Furthermore, the replication of nodavirus and birnavirus could be restored after the expression of Mx gene was down-regulated by siRNA. Therefore, these results indicated that the expression of barramundi Mx gene was able to inhibit the proliferation of fish nodavirus and birnavirus.

Persistence of betanodavirus in Barramundi brain (BB) cell line involves the induction of Interferon response.

The BB cell line derived from the brain tissue of a barramundi (Lates calcarifer) that survived nervous necrosis virus (NNV) infection is persistently infected with NNV. To elucidate whether interferon (IFN) plays a role in the mechanism of NNV-persistent infection in BB cell line, a virus-negative control cell line was obtained by treating BB cells with NNV-specific rabbit antiserum for 5 subcultures. After the treatment, NNV titer or RNA or capsid protein was no longer detected in the cured BB (cBB) cells. Expression of Mx gene, encoding a type I IFN-inducible antiviral protein, was found in BB cells and cBB cells following NNV infection, but not in NNV-free cBB cells. Moreover, expression of Mx gene and antiviral activity against NNV were induced in cBB cells by the treatment with MAb-neutralized BB cell supernatant. Furthermore, NNV persistent infection was induced again in cBB cell culture if multiplicity of infection (MOI) was low (< or = 1). These experimental results indicated that IFN-like cytokines existed in the culture supernatant of BB cells, and IFN-induced response played an important role in protecting the majority of cells from virus lytic infection and regulating NNV persistence in the BB cell line.

Persistent infection of betanodavirus in a novel cell line derived from the brain tissue of barramundi Lates calcarifer.

In order to obtain an in vitro system for studying the mechanism of persistent infection of fish nodavirus, a novel cell line (BB) was established from the brain tissue of a barramundi, Lates calcarifer, which had survived viral nervous necrosis disease. The cell line has been subcultured > 100 times. The persistence of fish nodavirus designated as barramundi brain nervous necrosis virus (BBNNV) in the BB cells was demonstrated by: (1) the detection of the infectious virus in the culture supernatants, (2) the detection of NNV nucleic acids extracted from the BB cells, (3) the positive result of immunochemical staining using an NNV-specific monoclonal antibody and (4) their resistance to infection by another fish nodavirus grouper NNV (GNNV). No temperature-sensitive mutants were detected in the culture supernatant of the BB cells. Neither truncated genome (RNA1 or RNA2) nor smaller coat protein was found in the purified BBNNV particles, suggesting that defective interfering particles were unlikely to be important in the NNV-persistent infection in the BB cells. The result of the neutralization test indicated that the 5 antigenic determinants, recognized by GNNV-specific neutralizing antibodies, also existed on the coat protein of BBNNV. The BB cell line is the first cell line reported to be persistently infected with NNV, and would be a useful model for understanding the mechanisms of NNV-persistent infection in vitro and in vivo.

Production of monoclonal antibodies against grouper nervous necrosis virus (GNNV) and development of an antigen capture ELISA.

Five (2 IgG, 3 IgM) monoclonal antibodies (MAbs) against the G9508KS strain of grouper nervous necrosis virus (GNNV) were produced and characterized. All 5 MAbs showed positive signals in the retina of GNNV-infected grouper larvae and in the cytoplasm of GNNV-infected GF-1 cells using immunohistochemistry staining. Two MAbs reacted with the denatured capsid protein derived from GNNV-infected GF-1 cells in Western blot analysis, but did not react with the GNNV recombinant capsid protein expressed by E. coli in an indirect immnunosorbent assay (ELISA). All 5 MAbs were able to neutralize GNNV, tiger puffer NNV (TPNNV) and barfin flounder NNV (BFNNV), while only 2 of the MAbs neutralized striped jack NNV (SJNNV). A capture ELISA system based on the use of MAbs for capture and a rabbit polyclonal antibody for detection was developed. When absorbance values higher than 0.5 were judged to be positive, the sensitivity of the capture ELISA system was 2.5 ng per well of purified GNNV protein or 6.5 x 10(4) TCID50 per well of GNNV supernatant from culture cells. This capture ELISA system could become a more specific and sensitive tool for NNV diagnosis in the field and in routine laboratories.

Genetic and antigenic analysis of betanodaviruses isolated from aquatic organisms in Taiwan.

Viral nervous necrosis (VNN) is a worldwide disease among marine fishes. In Taiwan, NNN disease was first identified in 2 species of hatchery-reared grouper, Epinephelus fuscogutatus and E. akaaya in 1994. Since then, increasing mortalities have occurred among groupers Epinephelus spp., and also among European eels Anguilla anguilla L., yellow-wax pompano Trachinotus falcatus, firespot snapper Lutaanus erythropterus B., barramundi Lates calcarifer, cobias Rachycentron canadum, humpback groupers Cromileptes altivelis and Chinese catfish Parasilurus asotus. In the present study, samples were collected from affected fishes and processed for reverse transcriptase (RT) PCR amplification and virus isolation in cell culture. Infected cells (GF-1 cell line) exhibited cytopathic-effect characteristics of grouper nervous necrosis virus (GNNV). A RT-PCR product of approximately 830 bp was amplified from the brain homogenate of tested samples and sequenced. The nucleotide and deduced amino acid sequences of the amplified RT-PCR products from all isolates were strongly homologous (> 97 %) with the corresponding region of the published sequence of red-spotted grouper nervous necrosis virus (RGNVV). Therefore, all Taiwan NNV (nervous necrosis virus) isolates studied in this report belong to the RGNNV genotype. We used 5 neutralizing monoclonal antibodies (MAbs) against GNNV to analyze the antigenic relationship of Taiwan NNV isolates and striped jack nervous necrosis virus (SJNNV). The results of neutralization tests revealed that all Taiwan NNV isolates were closely related, but antigenically different from SJNNV in 3 neutralizing epitopes. To our knowledge, this is the first description of NNV infection in European eels, yellow-wax pompano, firespot snapper, cobia and Chinese catfish, and the first reported instance of natural NNV infection in freshwater fishes causing high mortality.

Interference of the life cycle of fish nodavirus with fish retrovirus.

Interference of the life cycle of grouper nervous necrosis virus (GNNV), a member of the Nodaviridae, genus Betanodavirus, by snakehead retrovirus (SnRV) has been studied in vitro. SGF-1, a new fish cell line that is persistently infected with SnRV, was induced by inoculating SnRV into the grouper fin cell line GF-1. Culture supernatants and cell pellets from both GNNV-infected SGF-1 and GF-1 cells were collected and employed for virus productivity analysis. The yields of GNNV RNA and capsid protein in GNNV-infected SGF-1 cells were similar to those in GNNV-infected GF-1 cells. However, when GF-1 cells were used for titration, the titre of the culture supernatant from GNNV-infected SGF-1 cells was much higher than that from GNNV-infected GF-1 cells. The titration result suggested that SnRV enhanced the infection or cytopathic effect (CPE) of GNNV during GNNV and SnRV coinfection of the GF-1 cell titration system, although SnRV cannot induce any CPE in GF-1 cells alone, nor can it increase the yield of GNNV after GNNV superinfection of SGF-1 cells. Moreover, GNNV cDNA was detected in both the pellet and the supernatant from GNNV-infected SGF-1 cells. This result indicated that SnRV reverse-transcribed the GNNV single-stranded genomic RNA into cDNA during GNNV superinfection of SGF-1 cells and created a new cDNA stage in the life cycle of the fish nodavirus.

Transdermal delivery of ketoprofen using microemulsions.

A transdermal preparation containing ketoprofen was developed using O/W microemulsion system. Of the oils tested, oleic acid was chosen as the oil phase of the microemulsion, as it showed a good solubilizing capacity and excellent skin permeation rate of the drug. Pseudoternary phase diagrams were constructed to obtain the concentration range of oil, surfactant and cosurfactant for microemulsion formation, and the effect of these additives on skin permeation of ketoprofen was evaluated with excised rat skins. The optimum formulation of the microemulsion consisted of 3% ketoprofen, 6% oleic acid, 30% Labrasol/Cremophor RH 40 (1:1) and water. Terpenes were added to the microemulsion at the level of 5% and their effect on the skin permeation of ketoprofen from the microemulsion was evaluated. Of the four terpenes used, only limonene resulted in a powerful enhancing activity (3-fold increase over control).

Effects of adhesives and permeation enhancers on the skin permeation of captopril.

To formulate a transdermal drug delivery system of captopril, monolithic adhesive matrix type patches containing 20% captopril, different pressure-sensitive adhesives, and various permeation enhancers were prepared using a labcoater. The effects of the adhesives and permeation enhancers on skin permeation of captopril from the prepared patches were evaluated using Franz diffusion cells fitted with excised rat skins. The permeation rate of the drug through the excised skin was dependent on the type of polyacrylate copolymers studied. Fatty alcohols resulted in a pronounced enhancing effect on the skin permeation of captopril, while dimethyl sulfoxide, N-methyl-2-pyrrolidone, oleic acid, Transcutol, and polysorbate 20 showed no significant enhancing effect. The permeation-enhancing effect of the fatty alcohols reached the maximum at the level of 100%. Based on these results, a captopril patch may be developed with further optimization.

Enhancing effect of polyoxyethylene alkyl ethers on the skin permeation of ibuprofen.

The influence of polyethoxylated non-ionic surfactants on the transport of ibuprofen across rat skin was investigated. The skin permeation of ibuprofen from a series of 17 polyoxyethylene (POE) alkyl ethers containing 5% ibuprofen was determined using Franz diffusion cells fitted with excised rat skins. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were performed for the physicochemical characterization of ibuprofen-surfactant interaction. In vitro transdermal flux through excised rat skin was found in the decreasing order of POE(5)cetyl/oleyl ether (110.24 microg/cm(2)/h)>POE(2)lauryl ether (99.91 microg/cm(2)/h)>POE(2)oleyl ether (67.46 microg/cm(2)/h)>POE(10)stearyl ether (66.19 microg/cm(2)/h). POE(2)oleyl ether showed the longest lag time (2.47 h). The enhancers containing the EO chain length of 2-5, HLB value of 7-9 and an alkyl chain length of C16-C18 were effective promoters of ibuprofen flux. FT-IR and DSC studies to probe the nature of the interaction between the ibuprofen and surfactant indicated that the hydrogen bonding state of ibuprofen was changed from the dimeric form to the carbonyl-hydroxyl (C=O-HO) hydrogen bond form in the presence of excess POE alkyl ether. These results indicated that this new system may be used in developing a transdermal formulation with improved skin permeation of ibuprofen.

Preparation and in vitro evaluation of self-microemulsifying drug delivery systems containing idebenone.

A new self-microemulsifying drug delivery system (SMEDDS) was developed to increase the dissolution rate, solubility, and, ultimately, bioavailability of a poorly water soluble drug, idebenone. Pseudoternary phase diagrams were used to evaluate the self-microemulsification existence area, and the release rate of idebenone was investigated. The mixtures consisting of Labrafac hydro or Labrafil 2609 (HLB values > 4) with the surfactant (Labrasol containing 80% Transcutol) and cosurfactant (Plurol oleique WL 1173) were found to be optimum formulations. Using the SMEDDS formulations of 5% to 20% of Labrafac hydro or Labrafil 2609 in combination with the surfactant/cosurfactant mixing ratio of 3, the microemulsion existence field was wider compared to the other SMEDDS formulations due to high affinity for the continuous phase. The in vitro dissolution rate of idebenone from SMEDDS was more than twofold faster compared with that of tablets. The developed SMEDDS formulation can be used as a possible alternative to traditional oral formulations of idebenone to improve its bioavailability.

Temperature effect on nervous necrosis virus infection in grouper cell line and in grouper larvae.

This preliminary study elucidates the in vitro and in vivo effects of temperature on grouper nervous necrosis virus (GNNV) infection. A novel continuous cell line derived from the fin tissue of a grouper (Epinephelus coioides, Hamilton), named as GF-1 cell line, was used. Cytopathic effect was observed in GNNV-infected GF-1 cells incubated at 24-32 degrees C after viral adsorption, but not at 20 degrees C or 37 degrees C even though the viral adsorption temperature was 28 degrees C. Viral protein could be detected in the pellets of GNNV-infected GF-1 cells cultured at 20-32 degrees C, but not at 37 degrees C. In a challenge test, GNNV-challenged larvae which were maintained at a constant 28 degrees C began to die 1 day post challenge (p.c.) with a death rate of 80%. Mortality reached 100% by 50 h p.c., while the mortality of negative control fish was only 5%. The cumulative mortality of GNNV-challenged larvae at ambient temperature, i.e. 28 degrees C at noon and 24 degrees C at midnight, was 10% 1 day p.c., and increased to 100% by 80 h p.c. Based on the results, we concluded that temperature plays an important role in GNNV infection and pathogenicity.

High-performance liquid chromatography with a column-switching system and capillary electrophoresis for the determination of ibuprofen in plasma.

Quantitative aspects of high-performance liquid chromatography with a column-switching system (CSS-HPLC) and capillary electrophoresis (CE) were investigated for the determination of ibuprofen in plasma. For CSS-HPLC, 100 microl of plasma was directly injected onto the column system for the three separation steps: (1) deproteinization and fractionation of plasma samples with a polymer-coated mixed-function phase column, (2) concentration with an intermediate column and (3) final separation with a main column. For CE, a mixture of 50 microl of plasma and 1 ml of acetonitrile was centrifuged and the supernatant was introduced onto the capillary (66 cmX50 microm I.D.; 62 cm to detector) at 20 degrees C. Run buffer was 250 mM sodium borate buffer (pH 8.5) and applied electric field was 379 V cm(-1). Linear dynamic ranges were 0.1-250 microg ml(-1) in CSS-HPLC and 1-1000 microg ml(-1) in CE. Intra-day and inter-day coefficients of variation were less than 5.6% and 6.5% for CSS-HPLC, 6.3% and 6.5% for CE, respectively. The limits of detection (S/N=3) for CSS-HPLC and CE were 25 ng ml(-1) and 300 ng ml(-1), respectively. CSS-HPLC was superior in simplicity and sensitivity, while CE was better in efficiency, rapidity, and cost.

Effect of protease inhibitors on degradation of recombinant human epidermal growth factor in skin tissue.

Recombinant human epidermal growth factor (rhEGF), a polypeptide of 53 amino acid residues, is subject to degradation by numerous enzymes, especially proteases, when it is applied on the skin for the treatment of open wound. Amastatin, aprotinin, bestatin, EDTA, EGTA, gabexate, gentamicin, leupeptin, and TPCK were investigated for the possible protease inhibitors, which may use to protect rhEGF from degradation by the enzymes in the skin. Skin homogenates containing protease inhibitors and rhEGF were incubated at 37 degrees C for 30 minutes. After the reaction was stopped with trifluoroacetic acid, the amount of rhEGF remaining in the sample was determined with an HPLC method. The percentages of rhEGF degraded, at the skin/PBS ratio of 0.25, in the mouse, rat, and human skin homogenate were 85%, 70%, and 46%, respectively. The degree of degradation of rhEGF in the cytosolic fraction was higher than that in the membrane fraction and these enzyme reactions were completed in 30 minutes. Bestatin, EGTA, and TPCK showed significant inhibitory effects on the degradation of rhEGF in the two fractions (p<0.05), while the other protease inhibitors had no significant inhibitory effects or, even resulted in deleterious effects. Therefore, the formulation containing one or several inhibitors among these effective inhibitors would be a promising topical preparation of rhEGF for the treatment of open wound.

[Acute encephalopathy associated with centrilobular necrosis of liver mimicking Reye's syndrome--report of two cases].

Recent experience suggests that a diagnosis of Reye's syndrome based on clinical and biochemical grounds alone may be unreliable. Two patients are presented here, whose clinical manifestation suggested Reye's syndrome. The biochemistry data were also compatible with Reye's syndrome except that the levels of serum AST and ALT were significantly higher with normal serum ammonia level. Blood amino acid and urinary organic acid assay all showed negative findings. Histological findings of the liver showed marked centrilobular necrosis rather than fatty metamorphosis. The muscle biopsies did not show lipid accumulation in the muscle fibers as well. The findings in our patients suggested that a confirmatory diagnosis of Reye's syndrome requires a characteristic pathological findings of the liver in order to differentiate Reye's syndrome from Reye-like syndrome, especially acute encephalopathy associated with centrilobular necrosis of the liver.

Central nervous system targeting of 2',3'-dideoxyinosine via adenosine deaminase-activated 6-halo-dideoxypurine prodrugs.

AIDS dementia complex is a neurologic disorder, characterized by increasingly severe cognitive, behavioral, and motor impairment, which is associated with human immunodeficiency virus (HIV) infection in the central nervous system (CNS). Many of the dideoxynucleosides effective systemically in the treatment of HIV infections, such as 2',3'-dideoxyinosine (ddI), exhibit limited penetration into the CNS and limited or variable effectiveness in reversing the symptoms of AIDS dementia. Thus, approaches for increasing the CNS uptake of ddI and other dideoxynucleosides are needed. The CNS uptake of a series of 6-halo-2',3'-dideoxypurine ribofuranosides (6-halo-ddPs) previously shown to be active against HIV because of their conversion to ddI through the action of adenosine deaminase was examined in rats. In vitro studies in rat blood and brain tissue homogenate suggested a favorable selectivity for bioconversion in brain tissue, but with bioconversion half-lives varying widely within the series. In vivo infusions of 6-chloro-ddP (6-Cl-ddP), 6-bromo-ddP (6-Br-ddP), and 6-iodo-ddP (6-I-ddP) resulted in significant increases (20- to 34-fold) in the ddI concentration ratios in brain parenchyma/plasma when compared with those after an infusion of ddI alone. Absolute concentrations of ddI in brain parenchyma were increased 10- and 4-fold, respectively, following 30-min infusions of 6-Cl-ddP or 6-Br-ddP, but were 2.4-fold lower after an infusion of 6-I-ddP relative to that after a control infusion of ddI. Detailed studies of the plasma pharmacokinetics, CNS uptake kinetics, and bioconversion of 6-Cl-ddP were conducted to compare in vivo transport and bioconversion parameters with those predicted from in vitro measurements and to rationalize the efficiency of CNS delivery of ddI from 6-Cl-ddP. The results show that increased lipophilicity alone does not ensure that a given prodrug will deliver higher levels of a parent compound to the CNS. Both the selectivity and absolute rate of bioconversion in the brain are important factors.