Experimental study of intraoperative local chemotherapy with fibrin glue containing nitrosourea for malignant gliomas

BACKGROUND

Local control of the tumor bed after removal of a tumor is one of the most important points in the treatment of malignant gliomas. This study was designed to examine whether fibrin glue is useful as a vehicle for sustained release of intraoperative local chemotherapy with nitrosourea (ACNU).

METHODS

The growth-inhibiting activity of ACNU on C6 glioma cells and ACNU released into 5-mL supernatant saline from fibrin glue containing 5 mg/mL (10 mg) of ACNU was measured in vitro. C6 tumor inoculated in rat brains was covered with fibrin glue containing either 2 mg/mL or 5 mg/mL of ACNU for 5 days, and the histologic changes were examined.

RESULTS

ACNU inhibited the growth of C6 glioma cells in a dose-dependent manner, and the drug concentration required for 50% inhibition of cell growth (IC50) was about 4 micrograms/mL with 1 hour of treatment. Although about 50% of all ACNU included in the fibrin glue was released in the first hour, an effective concentration over the value of IC50 was sustained even after 12 hours. A histologic examination showed tumor cells damaged within a depth of about 2-3 mm from the tumor surface covered with fibrin glue containing ACNU.

CONCLUSIONS

Fibrin glue may be useful as a vehicle for sustained-release chemotherapy, and intraoperative local chemotherapy with fibrin glue containing anticancer agents such as nitrosourea may be helpful in the local control of malignant gliomas.

Effect of liver intoxication by carbon tetrachloride on hepatic local disposition of oxacillin using moment characteristics as index

The effect of liver intoxication by carbon tetrachloride (CCl4) on the hepatic local disposition using oxacillin as a test drug and bovine serum albumin (BSA) as a reference substance was evaluated by single-pass bolus input method in the isolated perfused rat liver. Oxacillin and BSA were introduced into the liver from the portal vein, and the outflow concentration-time profiles of oxacillin and BSA from the rat liver into the hepatic vein were kinetically assessed by moment analysis. Liver damage was monitored by plasma SGOT, plasma SGPT, and bile flow rate. Hepatic recovery ratio FH of oxacillin increased from 50% to 80%, with an increase in liver intoxication by CCl4; whereas FH of BSA was naturally 100%. Mean transit time tH of oxacillin increased from 6 to 12 sec, with an increase in liver intoxication; whereas tH of BSA increased from 7 to 10 sec. The relative variance sigma 2/tH2 of oxacillin increased from 0.2 to 0.7, with an increase in liver intoxication; whereas sigma 2/tH2 of BSA took the value of approximately 0.4, independent of liver damage. In the relationship between the dispersion model and moments, it was shown that the blood space VB increased from 15 to 20%, the index for distribution (1 + k') of oxacillin from 1.0 to 1.5, the efficiency number RN of oxacillin decreased from 0.7 to 0.3 with the increase in liver damage, and the extent of eddy mixing was predicted to be unaffected by liver damage. The intensive increases in tH and sigma 2/tH2 of oxacillin with the liver intoxication by CCl4 were explained by increases in the extent of distribution and nonequilibrium distribution, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of organic modifier concentrations on electrokinetic migrations in micellar electrokinetic chromatography

The effect of low concentrations of organic modifiers on the electroosmotic mobility, mueo, and electrophoretic mobility of the micelle, muep, mc, in micellar electrokinetic chromatography (MEKC) with sodium dodecyl sulfate (SDS) solutions was investigated. The results showed that mueo was mainly influenced by the viscosity of the running solution. A linear relationship between mueo and the concentration of the organic modifier was found in MEKC. A newly defined parameter, the mobility ratio, Rm, mc, which is the ratio of the electrophoretic mobility of the micelle to the electroosmotic mobility, and which characterizes the surface charge density of the micelle in MEKC system with organic modifiers, was introduced. A linear relationship between Rm, mc and the organic modifier concentration was observed. The parameter Rm, mc was found to be useful to investigate the changes in the micellar phase with the addition of organic modifier. The measured muep, mc values showed different and interesting characteristics among different organic modifiers.

Simultaneous bilateral hypertensive intracerebral hemorrhages--two case reports

A 65-year-old male and an 80-year-old female presented with unusual simultaneous bilateral hypertensive intracerebral hemorrhages in the putamina and thalami, respectively. The hematomas were demonstrated by computed tomography performed within a few hours of onset. The patients underwent conservative therapy. The male patient died 4 days after the onset and the female finally became vegetative. The majority of patients with bilateral intracerebral hemorrhages generally have a poor outcome due to the development of severe disturbed consciousness, tetraparesis, and pseudobulbar palsy, even if the hematomas are not so large. The indication of surgery for this type of hemorrhage may be confined to patients with small hematomas who can be expected to have a good functional outcome after removal of the larger hematoma.

The relation between an esophageal cancer and associated cancers in adjacent organs

BACKGROUND

The relation between esophageal cancers and head and neck tumors was studied in order to improve the treatment results in patients with multiple cancers.

METHODS

We reviewed the records of 3,375 patients with an indexed squamous cell carcinoma of the head and neck treated at our institution between 1960 and 1994; and 81 patients were found to have an associated esophageal carcinoma. Similarly, the records of 434 patients with an indexed esophageal cancer were reviewed; and 54 patients had cancers in other organs or in the residual esophagus. A total of 135 esophageal cancers with 154 synchronous or metachronous cancers were entered into the analysis.

RESULTS

The risk of developing esophageal cancer was ten times higher in male patients with head and neck cancer than in female patients. Synchronous or metachronous esophageal cancer associated with head and neck cancer was most frequently seen with pharyngeal cancer (28/360 = 7.8%), followed by in the oral cavity (47/2148 = 2.2%).

CONCLUSIONS

Better knowledge of the relation between an esophageal cancer and a head and neck cancer may lead to the early detection of subsequent small, potentially curable neoplasms sited in either the esophagus or the head and neck region.

Gualamycin, a novel acaricide produced by Streptomyces sp. NK11687. II. Structural elucidation

A novel acaricide, gualamycin was isolated from the culture broth of Streptomyces sp. NK11687. The structure of gualamycin was determined to be (2R,3S,4S)-2-O-[4-O-(2-amino-2-deoxy-beta-D-gulopyranosyl)-alpha-D - galactopyranosyl]-2,3,4-trihydroxy-4-[(2S,3S,4S,5S)-3,4-dihydroxy-5-hydr oxy - methylpyrrolidin-2-yl] butanoic acid by FAB-MS, 1H and 13C NMR, COSY, HMQC, HMBC, IR, X-ray crystallographic analyses and synthetic studies.

Development of the blood-retinal barrier in vitro: formation of tight junctions as revealed by occludin and ZO-1 correlates with the barrier function of chick retinal pigment epithelial cells

To elucidate the molecular mechanisms of the blood-retinal barrier (BRB), we examined chick retinal tissues histochemically using antibodies against tight junction proteins such as ZO-1, 7H6 antigen, and occludin. Retinal pigment epithelial (RPE) cells in situ in chickens and late chick embryos expressed all of the tight junctional proteins examined, showing that tight junctions seal the cell borders of chick RPE cells in vivo. On the other hand, RPE cells isolated from late chick embryos and transferred in vitro did not express occludin, ZO-1 and 7H6 antigen. The effects of differentiation-inducing agents, such as retinoic acid, dexamethasone and dimethyl sulfoxide (DMSO) were tested. Only DMSO induced an increase in transepithelial electrical resistance (TER) in a time-dependent manner. Under supplementation with DMSO, immunofluorescently demonstrable occludin and ZO-1 were induced progressively at cell borders in parallel with the increase in TER that occurred with decreases in inulin and dextran permeability. Electron microscopically tight junction-like junctional apparatus were induced in RPE cells. These results indicated that tight junctions of RPE cells play an important role in the formation of the BRB.

Gualamycin, a novel acaricide produced by Streptomyces sp. NK11687. I. Taxonomy, production, isolation, and preliminary characterization

A novel acaricide, gualamycin, was isolated from the culture broth of Streptomyces sp. NK11687. It was purified from the filtrate by column chromatographies. Gualamycin showed 100% acaricidal activity at 250 micrograms/ml against sensitive and resistant mites to Dicofol.

Effect of temperature in perfusate on local hepatic disposition of BOF-4272, a new xanthine oxidase inhibitor

The effect of temperature on the local hepatic disposition of BOF-4272 [(+/-)-8-(3-methoxy-4-phenylsulfinyl-phenyl)pyrazolo[1,5-a]-1,3,5- triazine-4-olate], a new drug used to treat hyperuricemia, was investigated by means of a perfusion experiment following the pulse input into the portal vein of rat, in which the temperature of the perfusate was changed from 37 degrees C down to 4 degrees C. The same perfusion experiment was also attempted using bovine serum albumin (BSA) as a reference substance to compare with the hepatic disposition of BOF-4272. The elution time profiles of BOF-4272 and BSA from the liver into the hepatic vein were evaluated by moment analysis. The recovery ratio (FH) and the mean transit time (tH) of BOF-4272 were 22.8 +/- 3.3% and 0.111 +/- 0.008 min at 37 degrees C, respectively. Both FH and tH significantly increased with the decrease in the temperature of the perfusate, 3 times and 2 times greater at 4 degrees C than at 37 degrees C, respectively. The FH and tH of BSA were 98.3 +/- 4.5% and 0.129 +/- 0.013 min at 37 degrees C, respectively. These parameters of BSA were independent of temperature, while those of BOF-4272 showed a definite dependency on temperature. A new estimation method for the elimination rate constant (kc) and the partition ratio (k') in the dispersion model was developed by rearranging the theoretical equations of FH and tH. The index for the elimination (ke) of BOF-4272 decreased with the decrease in temperature, while the index for the distribution (k') increased with the decrease in temperature. This result shows that the metabolism (or the biliary excretion) decreased and the distribution increased with a decrease in temperature, indicating that the hepatic metabolizing pathway which is presumably temperature-dependent is blocked, and the blocked portion of BOF-4272 thus returns back to the perfusate at the low temperature.

Lewis Y antigen expression in hepatocellular carcinoma. An immunohistochemical study

BACKGROUND

The altered expression of the Lewis blood group-related antigens during malignant transformation can be used clinically as a tumor marker or as a prognostic indicator. The Lewis Y (LeY) antigen, which is one of the Type 2 human blood group-related antigens, also is thought to behave as an oncodevelopmental cancer-associated antigen. In this study, the authors examined the association between human LeY antigen expression and the clinicopathologic features of HCC, including its proliferative activity.

METHODS

Forty-six histologically confirmed cases of HCC were studied retrospectively. Liver biopsy specimens from the main tumor of each case were obtained under ultrasonic guidance before treatment was initiated. The formalin fixed, paraffin embedded serial sections were immunostained using a modification of the avidin-biotin-peroxidase complex method, with a primary monoclonal antibody (MoAb) directed against the LeY antigen (BM-1/JIMRO). The relationship between LeY antigen expression and the HCC's proliferative activity was analyzed similarly by immunohistochemical methods using a primary MoAb directed against the Ki-67 antigen (MIB 1). In addition, to clarify the relationship between LeY antigen expression and the histologic heterogeneity within HCC, seven cases of surgically resected HCC also were immunostained.

RESULTS

The LeY antigen was detected on the membrane and in the cytoplasm of the cancer cells. Of the 46 HCC cases, 20 (43.5%) expressed the LeY antigen in the tumor cells. There was no correlation between LeY antigen expression and the maximum tumor dimension or the Stage. However, the incidence of LeY antigen-positive cases in poorly differentiated HCCs was found to be significantly higher than that in well or moderately differentiated HCCs (P < 0.01). In resected HCC cases, LeY antigen expression within HCC nodules was frequently greater in the less differentiated tumor than in adjacent differentiated tumor. Moreover, the incidence of LeY antigen expression in alpha-fetoprotein (AFP)-positive (AFP > or = 200 ng/ml) HCC cases was significantly higher than that in AFP-negative (AFP < 200 ng/ml) HCC cases (P < 0.05). Furthermore, the mean value of the Ki-67 labeling index in LeY antigen-positive HCC cases (25.2 +/- 11.3%) was significantly higher than that in LeY antigen-negative HCC cases (9.4 +/- 4.1%) (P < 0.001).

CONCLUSIONS

These results suggest that LeY antigen expression correlated closely to the dedifferentiation and proliferative activity of HCC.

Determination of the new fluoroquinolone balofloxacin and its metabolites in biological fluids by high performance liquid chromatography

A sensitive high performance liquid chromatographic method for the determination in biological fluids of 1-cyclopropyl-6-fluoro-1,4- dihydro-8-methoxy-7-(3-methylaminopiperidin-1-yl)-4-oxoquinoline-3 -carboxylic acid dihydrate (CAS 127294-70-6, balofloxacin, Q-35), a new fluoroquinolone, as well as its metabolites, has been developed. Balofloxacin and its metabolite, N-desmethyl balofloxacin, were separated and determined by reversed-phase column with fluorescence detection. Balofloxacin glucuronide was determined as balofloxacin after alkali hydrolysis. This method exhibited good precision and accuracy. Furthermore, it is a simple method and requires only a small amount of samples, and therefore should be useful for pharmacokinetic studies in animals and humans.

Transesophageal echocardiography combined with magnetic resonance imaging for detecting venous anomalies in dextrocardia. A case report

A fifty-six-year-old woman was admitted to Osaka Rosai hospital because of dyspnea, chills, and fatigue. The patient was diagnosed by transthoracic echocardiography as having congestive heart failure due to severe biatrioventricular valve regurgitation, and cardiac surgery was proposed. Preoperative transesophageal echocardiography (TEE) revealed a dilatation of the coronary sinus (CS), a right-sided hemiazygos vein (R-AZ), and another great vessel lying between the CS and the R-AZ. Magnetic resonance imaging (MRI) was also performed, and this showed a persistent right superior vena cava (PRSVC) entering the left atrium via the dilatated CS. However, the site of connection between the R-AZ and the PRSVC could not be detected by MRI because of inadequate slice acquisition. Each method has its limitations, particularly with regard to visualizing the extracardiac vascular system. Therefore, the authors demonstrated that the combination of TEE and MRI might be more useful than each alone, and the combination is as a valuable method as digital subtraction angiography for the diagnosis of extracardiac venous anomalies.

Pharmacokinetics of the new fluoroquinolone balofloxacin in mice, rats, and dogs

The pharmacokinetics of 1-cyclopropyl-6-fluoro-1, 4-dihydro-8-methoxy-7-(3-methylaminopiperidin-1-yl)-4-oxoquinoline -3-carboxylic acid dihydrate (CAS 127294-70-6, balofloxacin, Q-35), a new fluoroquinolone, were studied in mice, rats and dogs by high performance liquid chromatography. The mean oral bioavailabilities of balofloxacin calculated from the area under the curve after oral and intravenous administration in mice, rats and dogs were 19.03, 87.50 and 87.73%, respectively, indicating that balofloxacin was almost completely absorbed in rats and dogs but not in mice after single oral administration. The mean elimination half-lives in plasma after intravenous administration in mice, rats and dogs were 0.92, 1.33 and 6.38 h, respectively. Mean cumulative urinary excretion percentages of unchanged balofloxacin within 24 h of oral administration of balofloxacin at the dose of 20 mg/kg in mice, rats and dogs were 4.91, 21.77 and 22.49% of the dose, respectively. A small portion of the metabolite was excreted into urine as balofloxacin glucuronide and N-desmethyl balofloxacin in these species. After oral administration of balofloxacin at the dose of 100 mg/kg to rats, absorption was prolonged compared with that after administration at the doses of 5 and 20 mg/kg. Plasma concentration-time profiles and pharmacokinetic parameters of balofloxacin in male rats were similar to those in female rats, indicating no sex-related differences. Once daily 21-day multiple administrations had not affect on these pharmacokinetic profiles of balofloxacin in rats.

Evaluation of intestinal absorption into the portal system in enterohepatic circulation by measuring the difference in portal-venous blood concentrations of diclofenac

PURPOSE

We evaluated the first-pass effects in vivo by the intestine and liver during enterophepatic circulation (EHC) by simultaneously measuring the portal and venous plasma concentrations of the rat.

METHODS

The venous and upper portal blood vessels were cannulated through the jugular and the pyloric veins, respectively, to obtain simultaneously blood samples from both sites. After diclofenac was injected as a bolus through the jugular vein, the concentrations of diclofenac in the portal and jugular veins were measured at time intervals. The absorption rate from the intestinal tract into the portal system was determined using the portal-venous difference in plasma concentrations of diclofenac, considering 40% partitioning of diclofenac into erythrocytes.

RESULTS

After one hour, the plasma concentration in the portal vein was always higher than that in the jugular vein in awakening rats with intact EHC (portal-venous blood concentration difference). No portal-venous difference was observed in awakening rats with bile-duct cannulation. Therefore, it was concluded that this portal-venous concentration difference was not due to the hepatic clearance but to diclofenac reabsorption from the intestinal tract.

CONCLUSIONS

Approximately 40% of the dose of diclofenac was reabsorbed over 8 hours from the intestinal tract into the portal system. By comparing the reabsorbed amounts in the portal system and in the systemic circulation, the hepatic extraction ratio in vivo (FH) of diclofenac was estimated to be 63%.

Intracisternal administration of interleukin-1 beta attenuates naloxone-precipitated withdrawal in morphine-dependent mice

The effect of central administration of interleukin-1 beta on naloxone-precipitated withdrawal in morphine-dependent mice was studied. The degree of physical dependence on morphine was estimated by counting the number of jumps precipitated by naloxone, one of the typical withdrawal signs. Intracisternal (i.c.) administration of interleukin-1 beta (0.01-1 ng/5 microliters per mouse) to morphine-dependent mice 30 min prior to the injection of naloxone (10 mg/kg i.p.) decreased the number of jumps in a dose-dependent manner. The effect of interleukin-1 beta (1 ng) was significantly antagonized when it was co-administered with interleukin-1 receptor antagonist (1 microgram/mouse). These results suggest that centrally administered interleukin-1 beta could attenuate naloxone-precipitated withdrawal in morphine-dependent mice via interleukin-1 receptors in the brain. Co-administration of alpha-melanocyte-stimulating hormone (300 ng/mouse) or alpha-helical corticotropin-releasing factor (CRF)-(9-41), a CRF receptor antagonist (300 ng/mouse), with interleukin-1 beta also antagonized the inhibitory effect of interleukin-1 beta (1 ng). Moreover, i.c. administration of CRF (200 ng/mouse) significantly decreased the number of jumps.

Factors influencing nifedipine-induced gingival overgrowth in rats

Factors such as age, the dose of nifedipine administered in the diet, serum drug level, duration of drug administration, and sex which may influence nifedipine-induced gingival overgrowth were examined in a rat model using 20-, 50-, and 90-days-old male and female rats. Oral administration of nifedipine (50 to 250 mg/kg diet) increased the serum level of the drug in a dose-dependent manner in both males and females. However, a higher serum level was required in females than males to attain the same degree of gingival overgrowth. The minimum dietary concentrations of the drug required to elicit gingival overgrowth in males and females were 150 and 100 mg/kg, respectively, which gave respective minimum serum levels of 800 and 1100 ng/ml. The degree of overgrowth depended on the serum concentration of the drug after it had reached the required minimum in male and female animals. Administration of nifedipine (250 mg/kg diet) for 20 days was enough to induce maximal overgrowth, but this induction occurred only in rats that started to receive the drug when they were 20 days old, not in those that started at 50 and 90 days of age for the same administration period of 55 days, and the overgrowth regressed and the gingiva were normal 40 days after ceasing drug administration. These results suggest that gingival overgrowth occurred in accordance with the drug concentration in the diet, as well as that in the serum, and was more likely to occur in males and younger individuals.

The sulphated carbohydrate-protein linkage region isolated from chondroitin 4-sulphate chains of inter-alpha-trypsin inhibitor in human plasma

Inter-alpha-trypsin inhibitor (ITI) in human plasma has a unique structural architecture composed of three polypeptide chains (H1, H2 and L chains), which are linked to each other through a chondroitin 4-sulphate chain. The structure of the carbohydrate-protein linkage region of the chondroitin 4-sulphate chain attached to the L chain was investigated. The peptide-chondroitin sulphate fraction was isolated by anion-exchange chromatography after exhaustive digestion with lysyl endopeptidase and then V8 protease. The chondroitin 4-sulphate chain was released from the peptides by beta-elimination using NaB3H4 and then digested with chondroitinase ABC. These treatments resulted in a single 3H-labelled hexasaccharide alditol fraction derived from the linkage region which had been associated with the L chain. Chemical and enzymatic analyses as well as fast-atom bombardment-mass spectrometry (FAB-MS) analysis revealed that the 3H-labelled hexasaccharide alditol had the following structure: delta HexA-alpha 1-3GalNAc(4-sulphate)beta 1-4GlcA beta 1-3Gal(4-sulphate)beta 1-3Gal beta 1-4Xyl-ol (where delta HexA is 4-deoxy-alpha-L-threo-hex-4-enepyranosyluronic acid and Xyl-ol is xylitol). The structure contained the novel 4-sulphated Gal residue, which was previously demonstrated in a linkage hexasaccharide isolated from chondroitin 4-sulphate of rat chondrosarcoma (Sugahara et al., J. Biol. Chem., 263, 10168-10174, 1988) and of whale cartilage (Sugahara et al., Eur. J. Biochem., 202, 805-811, 1991). The above disulphated hexasaccharide alditol was the only component detected in the linkage region fraction of the chondroitin 4-sulphate chain of ITI, which implies some biological significance of this novel structure.

DAMGO, a mu-opioid receptor selective ligand, distinguishes between mu-and kappa-opioid receptors at a different region from that for the distinction between mu- and delta-opioid receptors

The structural basis of opioid receptors (OPRs) for the subtype-selective binding of DAMGO, a mu-opioid receptor selective ligand, was investigated using chimeric mu/kappa-OPRs. Replacement of the region from the middle of the fifth transmembrane domain to the C-terminal of mu-OPR with the corresponding region of mu-OPR remarkably decreased the binding affinity to DAMGO, while the reciprocal chimera revealed the high affinity to DAMGO. These results indicate that DAMGO distinguishes between mu- and mu-OPRs at the region around the third extracellular loop, different from the case of the distinction between mu-and delta-OPRs in which the region around the first extracellular loop is important. Furthermore, displacement studies revealed that the region around the third extracellular loop is involved in the discrimination between mu- and kappa-OPRs not only by peptidic mu- selective ligands but also by non-peptidic ligands, such as morphine and naloxone.

An additional limb can be induced from the flank of the chick embryo by FGF4

To elucidate what initiates formation of the limb, we have attempted to induce an additional limb from the flank of the chick embryo by infecting retrovirus or implanting cells. We report here that an additional limb can be formed from the flank when we implant fibroblast growth factor 4 (Fgf4)-expressing cells into the lateral plate mesoderm at the pre-limb bud stage. In a newly formed limb bud, expressions of both Sonic hedgehog and chick Fgf4, which are authentic morphogenetic signals from the zone of polarizing activity and the apical ectodermal ridge, respectively, are induced by the implanted cells. Thus, it is concluded that the competence for limb development is present along the flank of the chick embryo and that FGF4 applied ectopically at the pre-limb bud stage can alter the developmental fate of flank cells to become limb cells. The present experimental system will contribute to a further elucidation on how the limb is formed.

High-performance frontal analysis for the study of protein binding of troglitazone (CS-045) in albumin solution and in human plasma

An on-line frontal analysis HPLC system was developed for the determination of the unbound concentration of troglitazone (CS-045), a new oral antidiabetic agent, in human serum albumin (HSA) solution and in human plasma. This system consists of a high-performance frontal analysis (HPFA) column, an extraction column, and an analytical column, which are connected via two switching valves. After the direct injection of the sample solution into the HPFA column, the drug was eluted as a zonal peak with a plateau region. The unbound drug concentration was determined as the drug concentration in the plateau. As low as 0.3 nM unbound CS-045 was determined with good reproducibility. It was found that CS-045 strongly binds with HSA, and the bound fraction in the 550 microM HSA solution was 99.93%, which was very close to that in human plasma (99.89%). The bound fractions were constant within the total drug concentration range of 1-10 microM in the HSA solution and 250 nM-10 microM in human plasma.

Two distinct functions of the carboxyl-terminal tail domain of NF-M upon neurofilament assembly: cross-bridge formation and longitudinal elongation of filaments

Neurofilaments are the major cytoskeletal elements in the axon that take highly ordered structures composed of parallel arrays of 10-nm filaments linked to each other with frequent cross-bridges, and they are believed to maintain a highly polarized neuronal cell shape. Here we report the function of rat NF-M in this characteristic neurofilament assembly. Transfection experiments were done in an insect Sf9 cell line lacking endogenous intermediate filaments. NF-L and NF-M coassemble to form bundles of 10-nm filaments packed in a parallel manner with frequent cross-bridges resembling the neurofilament domains in the axon when expressed together in Sf9 cells. Considering the fact that the expression of either NF-L or NF-M alone in these cells results in neither formation of any ordered network of 10-nm filaments nor cross-bridge structures, NF-M plays a crucial role in this parallel filament assembly. In the case of NF-H the carboxyl-tail domain has been shown to constitute the cross-bridge structures. The similarity in molecular architecture between NF-M and NF-H suggests that the carboxyl-terminal tail domain of NF-M also constitutes cross-bridges. To examine this and to further investigate the function of the carboxyl-terminal tail domain of NF-M, we made various deletion mutants that lacked part of their tail domains, and we expressed these with NF-L. From this deletion mutant analysis, we conclude that the carboxyl-terminal tail domain of NF-M has two distinct functions. First, it is the structural component of cross-bridges, and these cross-bridges serve to control the spacing between core filaments. Second, the portion of the carboxyl-terminal tail domain of NF-M that is directly involved in cross-bridge formation affects the core filament assembly by helping them to elongate longitudinally so that they become straight.

New hepatocellular diffusion model for analysis of hepatobiliary transport processes of drugs

A new hepatocellular diffusion model was developed to kinetically evaluate the hepatobiliary transport processes of drugs in the perfusion system, based on the physiological structure of the liver. Since the equations describing the hepatocellular diffusion phenomena were derived as image forms in the Laplace domain, the fast inverse Laplace transform (FILT) was adopted to manipulate the image equations. Cefixime and cefpiramide were selected as model drugs. The concentrations in the perfusate and the excreted amounts into the bile were simultaneously measured at appropriate intervals after the rapid administration of each drug into the portal vein. The hepatocellular diffusion model was fitted to the biliary excretion profiles from rat livers, by means of a nonlinear least squares program, MULTI(FILT). According to this model, the hepatobiliary transport process of drug is kinetically separated into three steps, that is, the diffusion into and through the hepatocytes, the transfer from the hepatocytes into the bile canaliculi, and the movement through the bile canaliculi to the outlet of bile duct. These steps are characterized by the diffusion rate constant through hepatocytes (kdif), the permeability rate constant into the bile canaliculi (kbmc) and the transit time through the bile canaliculi to the outlet of bile duct (tcan), respectively. It was demonstrated that kdif of cefixime (0.023 min-1) was significantly smaller than that of cefpiramide (0.044 min-1), while the differences in kbmc and tcan were not obvious between cefixime and cefpiramide. kbmc and tcan of both drugs were about 1.2 min-1 and about 1.0 min, respectively. These parameters were correlated to the excretion ratio into the bile (Fbile) and the mean transit time from the sinusoid through the hepatocytes to the outlet of bile duct (tbile).