Metabolites of caspofungin acetate, a potent antifungal agent, in human plasma and urine

Caspofungin acetate (MK-0991) is a semisynthetic pneumocandin derivative being developed as a parenteral antifungal agent with broad-spectrum activity against systemic infections such as those caused by Candida and Aspergillus species. Following a 1-h i.v. infusion of 70 mg of [(3)H]MK-0991 to healthy subjects, excretion of drug-related material was very slow, such that 41 and 35% of the dosed radioactivity was recovered in urine and feces, respectively, over 27 days. Plasma and urine samples collected around 24 h postdose contained predominantly unchanged MK-0991, together with trace amounts of a peptide hydrolysis product, M0, a linear peptide. However, at later sampling times, M0 proved to be the major circulating component, whereas corresponding urine specimens contained mainly the hydrolytic metabolites M1 and M2, together with M0 and unchanged MK-0991, whose cumulative urinary excretion over the first 16 days postdose represented 13, 71, 1, and 9%, respectively, of the urinary radioactivity. The major metabolite, M2, was highly polar and extremely unstable under acidic conditions when it was converted to a less polar product identified as N-acetyl-4(S)-hydroxy-4-(4-hydroxyphenyl)-L-threonine gamma-lactone. Derivatization of M2 in aqueous media led to its identification as the corresponding gamma-hydroxy acid, N-acetyl-4(S)-hydroxy-4-(4-hydroxyphenyl)-L-threonine. Metabolite M1, which was extremely polar, eluting from HPLC column just after the void volume, was identified by chemical derivatization as des-acetyl-M2. Thus, the major urinary and plasma metabolites of MK-0991 resulted from peptide hydrolysis and/or N-acetylation.

Binding of cell type-specific nuclear proteins to the 5'-flanking region of maize C4 phosphoenolpyruvate carboxylase gene confers its differential transcription in mesophyll cells

C4-type phosphenolpyruvate carboxylase (C4PEPC) acts as a primary carbon assimilatory enzyme in the C4 photosynthetic pathway. The maize C4PEPC gene (C4Ppc1) is specifically expressed in mesophyll cells (MC) of light-grown leaves, but the molecular mechanism responsible for its cell type-specific expression has not been characterized. In this study, we introduced a chimeric maize C4Ppc1 5'-flanking region/beta-glucuronidase (GUS) gene into maize plants by Agrobacterium-mediated transformation. Activity assay and histochemical staining showed that GUS is almost exclusively localized in leaf MC of transgenic maize plants. This observation suggests that the introduced 5' region of maize C4Ppc1 contains the necessary cis element(s) for its specific expression in MC. Next, we investigated whether the 5' region of the maize gene interacts with nuclear proteins in a cell type-specific manner. By gel shift assays with nuclear extracts prepared from MC or bundle sheath cells (BSC), cell type-specific DNA-protein interactions were detected: nuclear factors PEP(Ib) and PEP(Ic) are specific to MC whereas PEP(Ia) and PEP(IIa) are specific to BSC. Light alters the binding activity of these factors. These interactions were not detected in the assay with nuclear extract prepared from root, or competed out by oligonucleotides corresponding to the binding sites for the maize nuclear protein, PEP-I, which is known to bind specifically to the promoter region of C4Ppc1. The results suggest that novel cell type-specific positive and negative nuclear factors bind to the maize C4Ppc1 5'-flanking region and regulate its differential transcription in MC in a light-dependent manner.

A peptide-doxorubicin 'prodrug' activated by prostate-specific antigen selectively kills prostate tumor cells positive for prostate-specific antigen in vivo

We covalently linked doxorubicin with a peptide that is hydrolyzable by prostate-specific antigen. In the presence of prostate tumor cells secreting prostate-specific antigen, the peptide moiety of this conjugate, L-377,202, was hydrolyzed, resulting in the release of leucine-doxorubicin and doxorubicin, which are both very cytotoxic to cancer cells. However, L-377,202 was much less cytotoxic than conventional doxorubicin to cells in culture that do not secrete prostate-specific antigen. L-377,202 was approximately 15 times more effective than was conventional doxorubicin at inhibiting the growth of human prostate cancer tumors in nude mice when both drugs were used at their maximally tolerated doses. Nude mice inoculated with human prostate tumor cells secreting prostate-specific antigen showed considerable reductions in tumor burden with minimal total body weight loss when treated with L-377, 202. This improvement in therapeutic index correlated with the selective localization of leucine-doxorubicin and free doxorubicin in tissues secreting prostate-specific antigen after exposure to L-377,202.

Tamoxifen-induced enhancement of calcium signaling in glioma and MCF-7 breast cancer cells

The antiestrogen tamoxifen is commonly used to treat breast cancer, but it also has therapeutic activity in several other types of cancer. Many of these tumors, including malignant gliomas, are estrogen receptor negative. Nonetheless, high concentrations of tamoxifen can directly reduce cell proliferation in some of these tumors and induce apoptosis. In this study, the role of tamoxifen in calcium signaling and calcium-induced cell death was studied in both malignant glioma cell lines and MCF-7 breast cancer cells. Tamoxifen potently increased the spatial expansion of calcium waves by 30-150% while significantly enhancing and prolonging agonist-induced calcium elevations. Furthermore, tamoxifen pretreatment accelerated calcium ionophore-induced death by more than 20 min, suggesting that tamoxifen lowered cellular resistance to calcium loads. In contrast to its potentiating of calcium signaling in tumors, tamoxifen had no significant effect on calcium signaling in cultures of primary astrocytes from either human or rat brain. This study demonstrates the existence of calcium signaling in breast cancer and glioma cells and identifies tamoxifen as a potential modulator of tumor-associated calcium signaling.

Histopathologic analysis of sentinel lymph nodes in breast carcinoma

BACKGROUND

Intraoperative lymphatic mapping and identification of the first draining lymph node (the sentinel lymph node) may allow some patients with breast cancer to avoid the morbidity of formal axillary clearance. The aim of this study was to determine the accuracy of sentinel lymph node (SLN) biopsy in predicting axillary nodal involvement.

METHODS

From August, 1998 until July, 1999, 41 patients with clinically node-negative breast cancer underwent SLN biopsy that was immediately followed by axillary lymph node dissection. If the SLN section was found free of metastasis by routine hematoxylin and eosin staining (H&E), then an additional four sections of the SLN were cut and examined for the presence of tumor cells by H&E staining (three sections) and by cytokeratin immunohistochemical staining (IHC) (one section). If the SLN had metastatic cells and the other remaining nonsentinel axillary lymph nodes were free of metastases by routine H&E staining, then an additional three sections of the nonsentinel axillary lymph nodes were cut and examined for the presence of tumor cells by H&E staining.

RESULTS

The 41 patients had a mean of 2.2 sentinel (range, 1-7) and 14.6 nonsentinel (range, 5-32) lymph nodes excised per patient. Routine H&E staining identified 13 patients (31.7%) with SLN metastases and 28 patients (68.3%) with tumor-free SLNs. Applying IHC and the additional three sections stained with H&E to these tumor-free SLNs showed one additional patient with sentinel node metastasis. The conversion rate from being a sentinel node-negative patient to a sentinel node-positive patient was 3.6% (1/28). Overall, SLN metastases were detected in 14 (34.1%) of the 41 patients. The SLNs were negative in 27 patients (65.9%), two of whom had at least one positive nonsentinel lymph node each (7.4% "skip" metastasis). Biopsy of SLNs was 92.6% accurate in predicting the absence of nonsentinel nodal metastasis (p=0.001).

CONCLUSIONS

Our results suggest that formal axillary lymph node dissection may need only be performed in SLN-positive patients. Nonetheless, further experience and refinement are needed to perfect this technique.

Norcantharidin-induced post-G(2)/M apoptosis is dependent on wild-type p53 gene

Norcantharidin (NCTD), a synthetic analogue of phosphatase type 2A inhibitors, cantharidin, was shown to have limited effects in treating human and animal tumors. The tumor cell killing mechanisms by norcantharidin, however, remain unclear. In this report, we wished to investigate the mechanisms of norcantharidin-mediated cytotoxicity. Effort was made to investigate whether norcantharidin exerted its cytotoxicity through a p53-dependent or -independent mechanism. RT-2 (wtp53) and U251 (mutant p53) glioblastoma cell lines were exposed to norcantharidin at different dosages. Time-course fluorescent-activated cell sorting (FACS) analysis showed that high doses of norcantharidin arrested the cells at the G(2)/M phase and subsequent post-G(2)/M apoptosis in RT-2 cell line. In comparison, the U251 cell line was found resistant to norcantharidin-induced cytotoxicity. Restoring wild-type p53 gene function in the U251 cell line after adenoviral infections induced tumor cell cytotoxicity after exposure to norcantharidin. These results showed that norcantharidin kills tumor cells efficiently corresponding to their endogenous p53 gene status. The results also showed the feasibility of using adenoviral p53 gene therapy to enhance chemosensitivity of tumor cells to norcantharidin.

Identification of MK-944a: a second clinical candidate from the hydroxylaminepentanamide isostere series of HIV protease inhibitors

Recent results from human clinical trials have established the critical role of HIV protease inhibitors in the treatment of acquired immune-deficiency syndrome (AIDS). However, the emergence of viral resistance, demanding treatment protocols, and adverse side effects have exposed the urgent need for a second generation of HIV protease inhibitors. The continued exploration of our hydroxylaminepentanamide (HAPA) transition-state isostere series of HIV protease inhibitors, which initially resulted in the identification of Crixivan (indinavir sulfate, MK-639, L-735,524), has now yielded MK-944a (L-756,423). This compound is potent, is selective, and competitively inhibits HIV-1 PR with a K(i) value of 0.049 nM. It stops the spread of the HIV(IIIb)-infected MT4 lymphoid cells at 25.0-50.0 nM, even in the presence of alpha(1) acid glycoprotein, human serum albumin, normal human serum, or fetal bovine serum. MK-944a has a longer half-life in several animal models (rats, dogs, and monkeys) than indinavir sulfate and is currently in advanced human clinical trials.

Cytochrome P450 3A4-mediated interaction of diclofenac and quinidine

The metabolism of diclofenac to its 5-hydroxylated derivative in humans is catalyzed by cytochrome P450 (CYP)3A4. We report herein that in vitro this biotransformation pathway is stimulated by quinidine. When diclofenac was incubated with human liver microsomes in the presence of quinidine, the formation of 5-hydroxydiclofenac increased approximately 6-fold relative to controls. Similar phenomena were observed with diastereoisomers of quinidine, including quinine and the threo epimers, which produced an enhancement in the formation of 5-hydroxydiclofenac in the order of 6- to 9-fold. This stimulation of diclofenac metabolism was diminished when human liver microsomes were pretreated with a monoclonal inhibitory antibody against CYP3A4. In contrast, neither cytochrome b(5) nor CYP oxidoreductase appeared to mediate the stimulation of diclofenac metabolism by quinidine, suggesting that the effect of quinidine is mediated through CYP3A4 protein. Further kinetic analyses indicated that V(max) values for the conversion of diclofenac to its 5-hydroxy derivative increased 4.5-fold from 13.2 to 57.6 nmol/min/nmol of CYP with little change in K(m) (71-56 microM) over a quinidine concentration range of 0 to 30 microM. Conversely, the metabolism of quinidine was not affected by the presence of diclofenac; the K(m) value estimated for the formation of 3-hydroxyquinidine was approximately 1.5 microM, similar to the quinidine concentration required to produce 50% of the maximum stimulatory effect on diclofenac metabolism. It appears that the enhancement of diclofenac metabolism does not interfere with quinidine's access to the ferriheme-oxygen complex, implicating the presence of both compounds in the active site of CYP3A4 at the same time. Finally, a approximately 4-fold increase in 5-hydroxydiclofenac formation was observed in human hepatocyte suspensions containing diclofenac and quinidine, demonstrating that this type of drug-drug interaction occurs in intact cells.

Evidence for the packaging of multiple copies of Tf1 mRNA into particles and the trans priming of reverse transcription

Long terminal repeat (LTR)-containing retrotransposons and retroviruses are close relatives that possess similar mechanisms of reverse transcription. The particles of retroviruses package two copies of viral mRNA that both function as templates for the reverse transcription of the element. We studied the LTR-retrotransposon Tf1 of Schizosaccharomyces pombe to test whether multiple copies of transposon mRNA participate in the production of cDNA. Using the unique self-priming property of Tf1, we obtained evidence that multiple copies of Tf1 mRNA were packaged into virus-like particles. By coexpressing two distinct versions of Tf1, we found that the bulk of reverse transcription that was initiated on one mRNA template was subsequently transferred to others. In addition, the first 11 nucleotides of one mRNA were able to prime, in trans, the reverse transcription of another mRNA.

Combinatorial diversification of indinavir: in vivo mixture dosing of an HIV protease inhibitor library

An efficient combination solution-phase/solid-phase route enabling the diversification of the P1', P2', and P3 subsites of indinavir has been established. The synthetic sequence can facilitate the rapid generation of HIV protease inhibitors possessing more favorable pharmacokinetic properties as well as enhanced potencies. Multiple compound dosing in vivo may also accelerate the identification of potential drug candidates.

Factors influencing functional independence outcome in stroke patients after rehabilitation

The purpose of this study was to identify predictive variables relevant to functional independence outcomes for stroke patients following rehabilitation therapy. We prospectively studied 150 stroke patients consecutively admitted to the inpatient rehabilitation department of a university hospital from January 1 to December 31, 1997. Functional ability was assessed with the Functional Independence Measure (FIM) instrument on admission, on discharge of inpatient rehabilitation program, and at the 6 months follow-up visit after discharge. Severity of stroke was determined by using the Canadian Neurological Scale (CNS) on admission. In addition, major medical and sociodemographic factors were documented during hospitalization as independent variables. Of the 142 subjects surveyed, 23 (16.2%) stroke patients achieved functional independence at home when re-visited. Univariate test and multiple logistic regression analyses indicated that the significant factors affecting functional independence included age of onset, occupation, prior heart problems, the presence of medical complications, bilateral hemiplegia, and the functional ability (FIM score) and the severity of stroke (CNS score) on admission. The results of this study suggest that the admission CNS and FIM scores are useful in the prediction of functional independence outcome for stroke survivors following rehabilitation therapy.

Antenatal diagnosis of congenital hepatoblastoma in utero

A fetus with a huge hepatic tumor was detected by sonography at 36 weeks of gestation. The mass appeared as a single, solid and polylobular tumor located in the right lobe of the liver. Foci of hemorrhage, necrosis and some tiny calcifications were seen. The adjacent right kidney appeared normal but was displaced. The right adrenal gland was not visualized. Three-dimensional power Doppler sonography further depicted the corresponding vascular anatomy of the tumor, including its vascularization pattern and blood supply. The tumor was situated to the right of the umbilical vein and portal sinus, possibly deriving its blood supply from the portal circulation. The fundamental findings suggested the diagnosis of hepatoblastoma by exclusion of other possibilities. The baby was delivered by Cesarean section at 36 weeks' gestation, due to signs of fetal distress. Unfortunately, hypotension, tachycardia, and tachypnea developed shortly after birth. Surgical intervention was performed, but intractable bleeding occurred intra-operatively. The infant died at 6 days of age. Autopsy confirmed the diagnosis of hepatoblastoma. We believe this is the first reported case of the antenatal diagnosis of congenital hepatoblastoma.

Efficiency and effectiveness of stroke rehabilitation after first stroke

PURPOSE

To investigate predictive variables of rehabilitation efficiency and achievement of rehabilitation potential following stroke rehabilitation.

METHODS

We prospectively studied 110 first-stroke patients consecutively admitted to the inpatient rehabilitation department of our university hospital from 1 January to 31 December 1997. Functional recovery was measured as improvement in the ability to perform the Functional Independence Measure (FIM) instrument. Major medical (side of paralysis, stroke etiology, risk factors, Brunnstrom motor recovery stage, etc.), rehabilitative (initial FIM subscore, interval from stroke onset to rehabilitation commencement, rehabilitation stay, etc.), and demographic (age, years of education, occupation, marital and living status, care-giver, etc.) variables were examined.

RESULTS

The mean FIM score was 57.7 +/- 24.5 at admission and 77.3 +/- 26.3 at discharge. The mean rehabilitation efficiency (0.7 +/- 0.7) and effectiveness (30.6 +/- 24.0%) of stroke rehabilitation were determined. Rehabilitation efficiency and rehabilitation effectiveness were significantly predicted by length of stay and arm motor recovery stage, and by age and arm motor recovery stage, respectively. The variance explained only 21% of the rehabilitation efficiency and 24% of the achievement of rehabilitation potential.

CONCLUSIONS

The results of this study suggest that the large proportion of the unexplained variance in rehabilitation efficiency and effectiveness is due to nonmedical factors influencing the selection of patients for rehabilitation.

Comparison of imidazole- and 2-methyl imidazole-containing farnesyl-protein transferase inhibitors: interaction with and metabolism by rat hepatic cytochrome P450s

Methylation at the 2-position of the imidazole ring of IBN (I), a 1, 5-substituted imidazole-containing compound, was carried out to minimize its inhibition of rat cytochrome P450 (CYP)3A activity. The resulting analog 2-MIBN (II) exhibited an inhibitory potency 70-fold weaker (K(i) = 25 microM) than that of I (K(i) = 0.3 microM) toward CYP3A, the major rat liver microsomal P450 isoform(s) for the metabolism of I and II by rat liver microsomes in the presence of NADPH. The structural modification did not switch the major metabolic pathways for I and II, but significantly decreased the affinity of II to the metabolizing enzyme(s) as reflected by the difference in their K(i) values for CYP3A. Enzyme kinetic studies also demonstrated that I had a lower apparent K(m) (0.3 microM) than than II (18 microM), but an apparent V(max) 14 times lower than II. This finding indicates that methylation at the imidazole ring reduced the affinity of the compound to CYP3A, but increased the catalytic capacity, turning I as a substrate of low K(m) value but low capacity into a compound of high K(m) but high capacity for the metabolism. Our results suggest the significance of substrate concentration in comparing the metabolic stability of compounds with different kinetic parameters. Although higher intrinsic clearance is implied for I when the substrate concentration is below or close to its K(m) value, higher metabolic rate was constantly seen with II over micromolar range. The different kinetic parameters of I and II may also explain the observation that no significant difference in pharmacokinetic behavior was seen after an i.v. administration of I and II to the rat.

ETS gene Er81 controls the formation of functional connections between group Ia sensory afferents and motor neurons

The connections formed between sensory and motor neurons (MNs) play a critical role in the control of motor behavior. During development, the axons of proprioceptive sensory neurons project into the spinal cord and form both direct and indirect connections with MNs. Two ETS transcription factors, ER81 and PEA3, are expressed by developing proprioceptive neurons and MNs, raising the possibility that these genes are involved in the formation of sensory-motor connections. Er81 mutant mice exhibit a severe motor discoordination, yet the specification of MNs and induction of muscle spindles occurs normally. The motor defect in Er81 mutants results from a failure of group Ia proprioceptive afferents to form a discrete termination zone in the ventral spinal cord. As a consequence there is a dramatic reduction in the formation of direct connections between proprioceptive afferents and MNs. ER81 therefore controls a late step in the establishment of functional sensory-motor circuitry in the developing spinal cord.

Inhibition of mechanotransducer currents in crayfish sensory neuron by CGS 9343B, a calmodulin antagonist

The effects of CGS 9343B (zaldaride maleate), a calmodulin antagonist, on mechanosensitive channels were examined in crayfish slowly adapting sensory neurons using the two-electrode voltage clamp technique. In addition to its inhibition of voltage-gated Na(+) and K(+) currents, CGS 9343B (<30 microM) blocked reversibly the receptor current in a dose-dependent and voltage-dependent manner with a dissociation constant (K(d)) of 26.8 microM. The time course of the block was 265 s. Within the extension range of 3-30%, the reduction in receptor current was stimulus-independent and the gating mechanisms were not affected. Extracellular Ca(2+) was not necessary for its blocking effects. No changes in passive muscle tension were observed in the presence of 20 microM CGS 9343B. These results suggest that CGS 9343B, as a calmodulin antagonist, can also block mechanosensitive channels, possibly by being incorporated into the lipid membrane and/or interacting with the channel protein.

Recurrent hyperfunctioning parathyroid gland demonstrated on radionuclide imaging and an intraoperative gamma probe

Radionuclide imaging with Tc-99m MIBI is the preferred mode of parathyroid localization in current practice. It also successfully identifies hyperfunctioning autotransplanted parathyroid tissue. The authors report a case with recurrent hyperparathyroidism after total parathyroidectomy and autotransplantation in the forearm. Double-phase Tc-99m MIBI imaging successfully localized the hyperfunctioning parathyroid tissue, which was missed by magnetic resonance imaging and ultrasonography. In addition, the parathyroid tissue was localized using an intraoperative probe at subsequent surgery.

The evolution of C4 plants: acquisition of cis-regulatory sequences in the promoter of C4-type pyruvate, orthophosphate dikinase gene

In a previous study, we identified the C4-like pyruvate, orthophosphate dikinase gene (Pdk) in the C3 plant rice, with a similar structure to the C4-type Pdk in the C4 plant maize. In order to elucidate the differences between C4-type and C4-like Pdk genes in C4 and C3 plants, we have produced chimeric constructs with the beta-glucuronidase (GUS) reporter gene under the control of the Pdk promoters. In transgenic rice, both rice and maize promoters directed GUS expression in photosynthetic organs in a light-dependent manner. However, the maize promoter exhibited a much higher transcriptional activity than the rice promoter did. These results indicate that the rice C4-like Pdk gene resembles the maize C4-type Pdk gene in terms of regulation of expression. We also tested the activity of the rice promoter in transgenic maize. GUS activity was seen in both photosynthetic and non-photosynthetic organs. Thus, the rice promoter does not confer a strict organ-specific gene expression, as the maize promoter does. Moreover, the rice promoter directed GUS expression not only in mesophyll cells but also in bundle sheath cells, whereas the maize promoter directed expression only in mesophyll cells. Taken together, the results obtained from both transgenic maize and rice demonstrate that the rice and maize promoters differ not only quantitatively, but also qualitatively, in terms of their cell- and organ-specificity. Experiments with swapped promoters using the rice and maize promoters further demonstrated that a limited sequence region from -330 to -76 of the maize promoter confers light-regulated, high-level expression to the rice promoter in maize mesophyll protoplasts. We conclude the gain of cis-acting elements conferring high-level expression and mesophyll cell specificity was necessary for establishment of a C4-type Pdk gene during the course of evolution from C3 to C4 plants.

ATP-mediated glia signaling

Glia calcium signaling has recently been identified as a potent modulator of synaptic transmission. We show here that the spatial expansion of calcium waves is mediated by ATP and subsequent activation of purinergic receptors. Ectopic expression of gap junction proteins, connexins (Cxs), leads to an increase in both ATP release and the radius of calcium wave propagation. Cx expression was also associated with a phenotypic transformation, and cortical neurons extended longer neurites when co-cultured with Cx-expressing than with Cx-deficient cells. Purinergic receptor activation mediated both these effects, because treatment with receptor antagonists restored the glia phenotype and slowed neurite outgrowth. These results identify a key role of ATP in both short-term calcium signaling events and in long-term differentiation regulated by glia.

Cloning of two new cry genes from Bacillus thuringiensis subsp. wuhanensis strain

With PCR products as probes, we have cloned two new cry-type genes from Bacillus thuringiensis subsp. wuhanensis. The deduced amino acid sequence of the first clone is 77.3% identical to Cry1Ga1. The deduced protein sequence of the second clone is 69.8-78.7% identical to that of Cry1B group. The nomenclature assignment of these two clones is, therefore, named Cry1Gb1 and Cry1Bd1, respectively. The Cry1Bd1 is toxic to Plutella xylostella larvae, and the Cry1Gb1 is toxic to Pieris rapae larvae.

Stability of a melittin pore in a lipid bilayer: a molecular dynamics study

We have investigated the configuration and the stability of a single membrane pore bound by four melittin molecules and embedded in a fully hydrated bilayer lipid membrane. We used molecular dynamics simulations up to 5.8 ns. It is found that the initial tetrameric configuration decays with increasing time into a stable trimer and one monomer. This continuous transformation is accompanied by a lateral expansion of the aqueous pore exhibiting a final size comparable to experimental findings. The expansion-induced formation of an interface between the pore-lining acyl chains of the lipids and the pore water ("hydrophobic pore") is transformed into an energetically more favorable toroidal pore structure where some lipid heads are translocated from the rim to the central part of the interface ("hydrophilic pore"). The expansion of the pore is supported by the electrostatic repulsion among the alpha-helices. It is hypothesized that pore growth, and hence cell lysis, is induced by a melittin-mediated line tension of the pore.

Route-dependent nonlinear pharmacokinetics of a novel HIV protease inhibitor: involvement of enzyme inactivation

L-754,394, a furanopyridine derivative, is an experimental HIV protease inhibitor. Previous studies from this laboratory have demonstrated that L-754,394 is cleared very rapidly in animals, and that this drug is a potent mechanism-based inactivator (suicide inhibitor) for CYP3A4 in human liver microsomes. Because L-754,394 is a high-clearance drug and an enzyme inactivator, it is expected that this drug will be subject to significant first-pass metabolism, and that the degree of enzyme inactivation will be dependent not only on the dose, but also on the route of administration. The purpose of this study is to examine the effects of dose and route of administration on the kinetics of L-754,394 using rats and dogs as animal models. In both rats and dogs, L-754,394 exhibited marked dose-dependent pharmacokinetics after i.v. and oral administration. Irrespective of i.v. or oral administration, the area under the plasma concentration-time curve from zero to infinity increased with dose in a greater than proportional manner. However, the magnitude of area under the plasma concentration-time curve from zero to infinity increase was much greater after oral dosing than after i.v. administration, indicating route-dependent pharmacokinetics. Data from in vitro and in vivo studies suggested that the dose- and route-dependent pharmacokinetics were due mainly to the inactivation (destruction) of the enzymes responsible for its own metabolism.

Biotrickling filtration of nitric oxide

A biotrickling filter with blast-furnace slag packings (sizes = 20-40 mm and specific surface area = 120 m2/m3) was utilized to treat NO in an air stream. The operational stability, as well as the effects of gas empty-bed retention time (EBRT) and nutrient addition on the removal ability of NO, were tested. Approximately six weeks were required for the development of a biofilm for NO degradation, and a two-week organic carbon deficiency resulted in the detachment of biofilms from the packing surfaces. A steady removal rate of 80% was attained at specified influent NO concentrations of 892 to 1237 ppm and an EBRT of 118 sec. The effluent NO concentration diminished exponentially with enlarging EBRT, with influent NO concentrations of 203-898 ppm, and EBRTs of 25 to 118 sec. Nutrient addition is essential for efficient removal of the influent NO. Mass ratios of C: P: N = 7: 1: 30 and NaHCO3: NO-N = 6.3 could be used for practical applications.