Increased plasma drug concentration and decreased additional insulin secretion following oral administration of glimepiride in Spontaneously Diabetic Torii rats

We aimed to evaluate the pharmacokinetics and pharmacological effects of glimepiride in the Spontaneously Diabetic Torii (SDT) rat, which is a non-obese model of type 2 diabetes. After oral administration of glimepiride (10 mg/kg), the maximum plasma concentrations and the area under the curve from 0 to 6 h of glimepiride in SDT rats were significantly higher than those in age-matched Sprague-Dawley rats. Whereas, additional insulin secretion following glimepiride treatment was markedly reduced in SDT rats. Thus, the SDT rat can be regarded as a model that reflects type 2 diabetes with reduced insulin secretory capacity. Our findings suggested that glimepiride could be ineffective in sever type 2 diabetic patients.

The relationship between the glenoid track and the range of shoulder motion: A cadaver study

INTRODUCTION

The concept of the glenoid track has been proposed to evaluate the risk of dislocation. The glenoid track width was demonstrated to be 84% of the glenoid width in cadaveric shoulders and 83% in live shoulders.

HYPOTHESIS

The glenoid track width seems to be affected by the range of motion.

PURPOSE

The purpose of this study was to determine the relationship between the glenoid track and the range of shoulder motion.

METHODS

Ten fresh-frozen cadaveric shoulders were used. The specimen was fixed to a shoulder-positioning device. The anterior rim of the glenoid was marked on the humeral head using a Kirschner wire with the arm in 60° of abduction. This marking was repeated with the arm in (1) horizontal flexion/extension and (2) internal/external rotations (0° to max). The distances from the Kirschner wire markings to the footprint of the rotator cuff tendon were measured.

RESULTS

The greater the angle of the horizontal extension or external rotation, the smaller the glenoid track width, whereas the greater the angle of the horizontal flexion or internal rotation, the greater the glenoid track width. There was a negative relationship between them. The horizontal flexion/extension motion was demonstrated to affect the glenoid track width more than the internal/external rotation motion.

CONCLUSION

The glenoid track width decreased with the increase of horizontal extension. We should consider the range of horizontal extension angle when applying the glenoid track concept in clinical practice.

TYPE OF STUDY

Laboratory study.

Development of a novel algorithm for detecting glucocorticoid-induced diabetes mellitus using a medical information database

WHAT IS KNOWN AND OBJECTIVE

Glucocorticoid-induced diabetes mellitus (GIDM) increases the risk of diabetes mellitus (DM)-related complications but is generally difficult to detect in clinical settings. The criteria for diagnosing GIDM have not been established. Recently, medical information databases (MIDs) have been used in post-marketing surveillance (PMS) studies. We conducted a pharmacoepidemiological study to develop an algorithm for detecting GIDM using MID.

METHODS

We selected 1214 inpatients who were newly prescribed with a typical glucocorticoid, prednisolone, during hospitalization from 2008 to 2014 from an MID of Hamamatsu University Hospital in Japan. GIDM was screened based on fasting blood glucose (FBG) and haemoglobin A1c (HbA1c) levels according to the current Japan Diabetes Society (JDS) DM criteria, and its predictability was evaluated by an expert's review of medical records. We investigated further candidate screening factors using receiver operating characteristics analysis.

RESULTS

Sixty-three inpatients were identified by the JDS DM criteria. Of these, 33 patients were definitely diagnosed as having GIDM by expert's review (positive predictive value = 52·4%). To develop a highly predictive algorithm, we compared the characteristics of inpatients diagnosed with definite GIDM and those diagnosed as non-GIDM. The maximum levels of HbA1c in patients with GIDM were significantly higher than those of patients with non-GIDM (66·9 mmol/mol vs. 58·7 mmol/mol, P < 0·001). The patients with GIDM had significantly higher relative increase in maximum level of HbA1c (RIM-HbA1c) than those with non-GIDM (0·3 vs. 0·03, P < 0·001). However, we did not observe a significant difference in those of fasting blood glucose (FBG) levels. We applied the RIM-HbA1c as a second screening factor to improve the detection of GIDM. It showed that a 13% increase in RIM-HbA1c separated patients with from patients without GIDM.

WHAT IS NEW AND CONCLUSIONS

Patients with GIDM had significantly higher RIM-HbA1c than patients with non-GIDM. There was a 13% increase in RIM-HbA1c in patients with GIDM compared to the others. Our detection algorithm for GIDM using an MID achieved high sensitivity and specificity, and was superior to one based only on the current JDS DM criteria. Our results suggest that monitoring changes in HbA1c levels is important for detecting GIDM and adds to current diagnostic criteria for type 2 DM.

Mitochondrial swelling and incipient outer membrane rupture in preapoptotic and apoptotic cells

Outer mitochondrial membrane (OMM) rupture was first noted in isolated mitochondria in which the inner mitochondrial membrane (IMM) had lost its selective permeability. This phenomenon referred to as mitochondrial permeability transition (MPT) refers to a permeabilized inner membrane that originates a large swelling in the mitochondrial matrix, which distends the outer membrane until it ruptures. Here, we have expanded previous electron microscopic observations that in apoptotic cells, OMM rupture is not caused by a membrane stretching promoted by a markedly swollen matrix. It is shown that the widths of the ruptured regions of the OMM vary from 6 to 250 nm. Independent of the perforation size, herniation of the mitochondrial matrix appeared to have resulted in pushing the IMM through the perforation. A large, long focal herniation of the mitochondrial matrix, covered with the IMM, was associated with a rupture of the OMM that was as small as 6 nm. Contextually, the collapse of the selective permeability of the IMM may precede or follow the release of the mitochondrial proteins of the intermembrane space into the cytoplasm. When the MPT is a late event, exit of the intermembrane space proteins to the cytoplasm is unimpeded and occurs through channels that transverse the outer membrane, because so far, the inner membrane is impermeable. No channel within the outer membrane can expose to the cytoplasm a permeable inner membrane, because it would serve as a conduit for local herniation of the mitochondrial matrix. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.

Cyclosporine alters correlation between free and total mycophenolic acid in kidney transplant recipients in the initial phase

WHAT IS KNOWN AND OBJECTIVE

The factors affecting the pharmacokinetics of free mycophenolic acid (MPA) and its phenolic glucuronide (MPAG) are still unclear. The aim of this study was to evaluate the influence of cyclosporine on the pharmacokinetics of free MPA and MPAG.

METHODS

Seventy-seven kidney transplant recipients (23 were in an initial phase and 54 in a stable phase; 41 were treated with cyclosporine and 36 with tacrolimus) were enrolled. Free and total MPA and MPAG were determined using HPLC. The correlations between free and total predose concentrations (C(0) ) of MPA or MPAG were evaluated separately in patients receiving calcineurin inhibitor medications.

RESULTS AND DISCUSSION

Serum concentration of albumin was lower in the initial phase than in the stable phase. A higher ratio of free MPAG C(0) to free MPA C(0) was observed in cyclosporine-treated than tacrolimus-treated kidney transplant recipients. Free MPA C(0) correlated weakly with total MPA C(0) in kidney transplant recipients treated with cyclosporine in the initial phase (ρ= 0·53, P = 0·06).

WHAT IS NEW AND CONCLUSION

Cyclosporine increased the ratio of free MPAG C(0) to free MPA C(0) and varied the free fraction of MPA in the hypoalbuminaemic kidney transplant recipients in the initial phase.

Prescription trends for treatment of paediatric gastroenteritis at a Japanese hospital between 1997 and 2007

OBJECTIVE

We aimed to investigate recent trends in prescriptions for the treatment of paediatric gastroenteritis in Japan over a 10-year period (1997-2007).

METHODS

In this retrospective cohort study, we collected data for 2295 prescriptions for 1241 putative cases of paediatric gastroenteritis, which were treated between 1997 and 2007 at Hamamatsu University Hospital, Hamamatsu, Japan.

RESULTS

The most frequently prescribed drugs were probiotics (n = 621), followed by anti-emetics (n = 474). In most years between 1997 and 2007, more cases were treated with probiotics than with any other drug type (30.6-63.3% of cases), with the percentage increasing between 2005 and 2007. In contrast, the frequencies of anti-emetic and antipyretic prescriptions remained fairly stable, and prescriptions for antibiotics decreased slightly over the study period. Anti-emetics were commonly used in this hospital.

CONCLUSION

Although experimental evidence upon which to base recommendations is lacking, Japanese evidence-based guidelines are critical for improving the quality of treatment of paediatric gastroenteritis.

Relationship between the pharyngeal airway space and craniofacial morphology, taking into account head posture

This study assessed the relationship between craniofacial characteristics and the size of the pharyngeal airway space (PAS), taking into account head posture. Sixty dental students 25-30 years of age (30 men and 30 women) were examined by lateral cephalometry. The data were corrected with the use of appropriate regression equations for the PAS. The PAS significantly correlated with hyoid position, maxillary and mandibular size, maxillary and mandibular prognathism, and mandibular inclination. A large, anteriorly positioned mandible was associated with a large PAS-TP (the most proximal distance between the posterior pharyngeal wall and the tongue base). Uvula length and PNS-Ba (the distance between the most posterior point of the hard palate and the most inferior point of the anterior foramen magnum) correlated with PAS-UP (the most proximal distance between the posterior pharyngeal wall and uvula). Our results suggest that the anteroposterior dimension of the PAS is substantially affected by the size of the enclosure surrounding the PAS, including the maxilla, mandible and soft palate.

Computed tomographic analysis of the position and course of the mandibular canal: relevance to the sagittal split ramus osteotomy

The aim of this study was to investigate the position and course of the mandibular canal through the mandibular ramus using computed tomographic (CT) imaging and to relate the findings to performing sagittal split ramus osteotomies. The mandibles of 35 patients with skeletal Class III prognathism with symmetry (12 males and 23 females) were observed on transaxial computed tomograms acquired with a slice thickness of 2 mm. The position and course of the mandibular canal from the mandibular foramen to the mandibular body at the level of the second molar were measured at four specific locations in the same plane. Among the 70 rami examined, lack of a bone marrow space on the buccal side, including a fusion type anatomy with no buccal side cortical bone of the mandibular canal, were observed at the CT location between the mandibular foramen and mandibular angle. Our results suggest that special care must be taken when sagittal splitting is performed, and the safest location for the buccal corticotomy is anterior to the mandibular angle.

Thermodynamic stability of base pairs between 2-hydroxyadenine and incoming nucleotides as a determinant of nucleotide incorporation specificity during replication

We investigated the thermodynamic stability of double-stranded DNAs with an oxidative DNA lesion, 2-hydroxyadenine (2-OH-Ade), in two different sequence contexts (5'-GA*C-3' and 5'-TA*A-3', A* represents 2-OH-Ade). When an A*-N pair (N, any nucleotide base) was located in the center of a duplex, the thermodynamic stabilities of the duplexes were similar for all the natural bases except A (N = T, C and G). On the other hand, for the duplexes with the A*-N pair at the end, which mimic the nucleotide incorporation step, the stabilities of the duplexes were dependent on their sequence. The order of stability is T > G > C >> A in the 5'-GA*C-3' sequences and T > A > C > G in the 5'-TA*A-3' sequences. Because T/G/C and T/A are nucleotides incorporated opposite to 2-OH-Ade in the 5'-GA*C-3' and 5'-TA*A-3' sequences, respectively, these results agree with the tendency of mutagenic misincorporation of the nucleotides opposite to 2-OH-Ade in vitro. Thus, the thermodynamic stability of the A*-N base pair may be an important factor for the mutation spectra of 2-OH-Ade.

Age difference in simultaneous permeation and metabolism of ethyl nicotinate in rat skin

The age-dependent characteristics of transdermal permeation of ethyl nicotinate (EN) and its metabolism to nicotinic acid (NA) were examined in rats at the ages of a fetus at 21 d, 3, 10, 50, 270 and 360 d. Skin transport in vitro was investigated using mounted skin in side-by-side diffusion chambers, and flux of EN and NA was determined. With developing and aging in rats, EN flux from EN-saturated solution declined gradually, however, NA flux increased drastically at 10 and 50 d. To elucidate the mechanism of this age-dependent escalation of NA flux, a hydrolysis study was performed using skin homogenate, and the Michaelis-Menten parameters (Vmax and Km) of EN were evaluated. Vmax and Vmax/Km ratio showed the same tendency with NA flux/total (EN+NA) flux ratio, suggesting that skin esterases in rats are developed gradually after birth, then increase markedly and become steady in the adult period. On the other hand, the affinity parameter, Km, was almost the same among all ages. Moreover, metabolic saturation of esterase during the transdermal process occurred in all ages, and maximal NA flux and EN concentration in the donor compartment for the maximal NA flux were also affected by age. These findings indicated that the discrepancy in transdermal profiles of EN among the ages tested was dominantly due to the difference in the development of esterase in the growth process.

In vitro selection of aptamers that act with Zn2+

An in vitro selection was carried out with Zn2+ to isolate novel RNA molecules, zinc-dependent aptamers, that bind to HIV-1 Tat protein. RNAs bound to Tat were collected by using a nitrocellulose filter from a library of random RNAs and regenerated to the next generation of the RNA library by subsequent reverse transcription, polymerase chain reaction, and transcription. Sequences of the selected RNAs were determined after 6 and 12 rounds of the selection. The control clones after normal selection procedure with Mg2+ had a consensus UUG that resembled essential sequences of TAR or Arg aptamers. On the other hand, many unique sequences were revealed from a library selected with Zn2+ and the RNA with most abundant sequence (clone 31) bound to Tat tightly only when Zn2+ existed. The secondary structure of clone 31 RNA was predicted by using a computational prediction with our thermodynamic parameters and enzymatic scission of the RNA. Several model RNAs were prepared and the binding property of these RNAs to Tat were investigated. As a result, all the model RNAs did not reproduce the binding property of clone 31. Therefore, the Tat aptamer that acts with Zn2+ should require a relatively longer region of the sequence which is able to offer tertiary cooperation of several motifs for the binding.

Inhibitory effect of azole antifungal agents on the glucuronidation of lorazepam using rabbit liver microsomes in vitro

Azole antifungal agents (azoles) have inhibitory effects on the cytochrome P450. However, the effect of azoles on conjugative metabolism has not been given much attention. Lorazepam (LZP), a benzodiazepine sedative agent, is known to be metabolized by uridine 5'-diphosphate (UDP)-glucuronyltransferase. Herein we report investigation of the effect of azoles on the enzyme-kinetics of glucuronidation of lorazepam using rabbit liver microsomes in vitro. The Km and Vmax for LZP glucuronidation were determined to be 0.26+/-0.08 mM and 1.25+/-0.21 nmol/min/mg protein, respectively, when evaluated in the presence of a detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) (0.8 mg/mg protein). Azoles fluconazole, miconazole, and ketoconazole competitively inhibited the glucuronidation of LZP, with Ki values of 7.17+/-4.78 mM, 0.17+/-0.08 mM, and 0.092+/-0.026 mM, respectively. These results are comparable to the previously reported Ki values of azoles with zidovudine (AZT) glucuronidation (1.4, 0.18, and 0.08 mM for fluconazole, miconazole, and ketoconazole, respectively) [Sampol et al., Br. J. Clin. Pharmacol., 40, 83-86, 1995]. Therefore, in order to avoid possible side effects of LZP, the concomitant administration of LZP and azoles should be carefully evaluated.

In vivo and in vitro toxicodynamic analyses of new quinolone-and nonsteroidal anti-inflammatory drug-induced effects on the central nervous system

We investigated the correlation between an in vivo isobologram based on the concentrations of new quinolones (NQs) in brain tissue and the administration of nonsteroidal anti-inflammatory drugs (NSAIDs) for the occurrence of convulsions in mice and an in vitro isobologram based on the concentrations of both drugs for changes in the gamma-aminobutyric acid (GABA)-induced current response in Xenopus oocytes injected with mRNA from mouse brains in the presence of NQs and/or NSAIDs. After the administration of enoxacin (ENX) in the presence or absence of felbinac (FLB), ketoprofen (KTP), or flurbiprofen (FRP), a synergistic effect was observed in the isobologram based on the threshold concentration in brain tissue between mice with convulsions and those without convulsions. The three NSAIDs did not affect the pharmacokinetic behavior of ENX in the brain. However, the ENX-induced inhibition of the GABA response in the GABAA receptor expressed in Xenopus oocytes was enhanced in the presence of the three NSAIDs. The inhibition ratio profiles of the GABA responses for both drugs were analyzed with a newly developed toxicodynamic model. The inhibitory profiles for ENX in the presence of NSAIDs followed the order KTP (1.2 microM) > FRP (0. 3 microM) > FLB (0.2 microM). These were 50- to 280-fold smaller than those observed in the absence of NSAIDs. The inhibition ratio (0.01 to 0.02) of the GABAA receptor in the presence of both drugs was well-fitted to the isobologram based on threshold concentrations of both drugs in brain tissue between mice with convulsions and those without convulsions, despite the presence of NSAIDs. In mice with convulsions, the inhibitory profiles of the threshold concentrations of both drugs in brain tissue of mice with convulsions and those without convulsions can be predicted quantitatively by using in vitro GABA response data and toxicodynamic model.

Development and histologic characteristics of synovitis induced by trauma in the rat temporomandibular joint

Histopathological changes caused by trauma to the rat temporomandibular joint synovium were examined by light microscopy. The trauma was induced by forced hypermobility of the condyle. Pathological changes of the synovium were found primarily in the anterior pouch of the upper joint compartment. The main findings included surface cell proliferation, increased capillary hyperemia, fibrin deposits on the surfaces of inflamed synovial membranes, and fibrinous adhesion between closely opposed synovial membranes. A gradual change from fibrinous adhesion to fibrous adhesion was also seen.

Histologic study of synovitis induced by trauma to the rat temporomandibular joint

OBJECTIVE

The purpose of this study was to establish and histologically examine the time course of synovitis induced by trauma to the rat temporomandibular joint.

STUDY DESIGN

Synovitis of the temporomandibular joints of 8-week-old male Wister rats was induced by forced condylar hypermobility, which was administered 10 times successively once a day for 10 days. Pathologic changes were observed microscopically at 2 and 5 days and 2, 4, 6, 8, 10, and 20 weeks after treatment.

RESULTS

Histologic findings from the 5th day to the 6th week after treatment were characterized by multiple layers of synovial cells, an increase of dilated vasculature, fibrin deposits, and synovial adhesion. These findings were in good agreement with those reported for the human temporomandibular joint. The pathologic changes decreased with advancing time, and synovitis was not observed at 20 weeks after treatment.

CONCLUSION

The present procedure for inducing synovitis of the temporomandibular joint in rats will be useful in understanding the pathogenesis of synovitis in human temporomandibular joints.

Relationship between disc displacement and morphologic features of skeletal Class III malocclusion

The present study assessed the relationship between disc displacement and facial morphologic features in 48 patients with skeletal Class III malocclusion. Clinical examination, standardized lateral oblique temporomandibular joint radiographs, and cephalographs were used to investigate this relationship. Disc displacement was evaluated by the presence of joint sounds (clicking and crepitation) or restricted condylar translation at maximal mouth opening. Thirty-two patients with signs of disc displacement were compared with 16 patients without signs of disc displacement. Results showed that patients with signs of disc displacement had a significantly larger gonial angle and/or SN-MP of the mandible. Thus, morphologic features of patients with skeletal Class III malocclusion may represent a risk factor for the development of disc displacement.

Evolution of a phosphorothioate RNA library during in vitro selection

We carried out an in vitro selection of aptamers from an RNA library with phosphorothioate linkages instead of normal phosphodiesters. This "thio-RNA" library had smaller dissociation rate constant (kd) to a target protein than a natural RNA library. On the basis of the results, an improved selection procedure to obtain ideal nucleic acid drugs will be discussed.

Three-dimensional structure of a glycosphingolipid having a novel carbohydrate linkage, Galbeta1-4(Fucalpha1-3)Glcbeta1-3Galbeta, determined by theoretical calculations

The novel glycosphingolipid, SEGLx (Galbeta1-4(Fucalpha1-3)Glcbeta1-3GalbetaCer), which was identified by us (Kawakami Y, et al. (1993) J Biochem 114: 677-83), shows a characteristic spectrum on 1H-NMR analysis, in which the anomeric proton resonances of a reducing end galactose and a glucose are split. To elucidate the structural characteristics of SEGLx, we determined its three-dimensional (3D) structure by means of computer simulation, involving such techniques as molecular mechanics (MM2), the semiempirical molecular orbital method (AM1), molecular dynamics (Amber), and computer 3D modelling. With the hypothesis that all OH group(s) of a ceramide participate in intramolecular hydrogen bonds, two kinds of stable conformers, horizontal and right-angled ones, were formed, depending on the ceramide species. The present findings suggest that the chemical species of both the long chain base and fatty acid moieties, mainly the occurrence of OH group(s), affect the chemical shifts of the anomeric proton resonances not only of the reducing terminal galactose but also the penultimate glucose through the formation of intramolecular hydrogen bonds. Computer simulation through theoretical calculation and 3D modelling was shown to be the best means of confirming the results obtained by experimental analysis.

Neurotoxic study of H2 antagonists using Xenopus oocytes injected with mouse-brain mRNA

To clarify the dominant mechanism for the convulsant activity of H2 antagonists, the effects of an H2 antagonist, cimetidine, on membrane currents induced by various agonists were investigated. In Xenopus oocytes injected with mouse-brain mRNA, acetylcholine (ACh), serotonin (5-HT), gamma-aminobutyric acid (GABA), glycine (Gly), glutamic acid (Glu), kainic acid (KA), quisqualic acid (QA) and N-methyl-D-aspartic acid (NMDA)-induced current responses were recorded under a voltage-clamp condition. Cimetidine inhibited GABA-induced currents in a concentration-dependent manner; however, the current responses induced by the other agonists were not modified. The IC50 of various H2 antagonists, famotidine, nizatidine, cimetidine and ranitidine, for GABA (10 microM)-induced current response were 66, 260, 450 and 980 microM, respectively. However, these values of cimetidine and ranitidine were 40-400 times higher than the reported brain and cerebrospinal fluid (CSF) concentration of H2 antagonists at the occurrence of a clonic convulsion in vivo. In conclusion, we observed an inhibitory effect of H2 antagonists on the GABA response; however, this inhibition of GABA-mediated neurotransmission may not be the dominant mechanism for H2 antagonist-induced clonic convulsion in vivo.

Analysis of the cleavage reaction of a trans-acting human hepatitis delta virus ribozyme

The cleavage reaction catalyzed by the trans -acting genomic ribozyme of human hepatitis delta virus (HDV) was analyzed with a 13mer substrate (R13) and thio-substituted [SR13(Rp) and SR13(Sp)] substrates under single-turnover conditions. The cleavage of RNA by the trans -acting HDV ribozyme proceeded as a first order reaction. The logarithm of the rate of cleavage (kclv) increased linearly (with a slope of approximately 1) between pH 4.0 and 6.0, an indication that a single deprotonation reaction occurred. This result suggests that kclv reflects the rate of the chemical cleavage step, at least around pH 5. The amount of active complex with the SR13(Sp) substrate was almost as large as with R13 (60-80%), whereas the amount of the corresponding active complex formed with the SR13(Rp) substrate was, at most, 20% of this value (with 0.5-100 mM Mg2+ions) at pH 5.0. Nonetheless, the value of kclv for all substrates was almost the same (0.4-0.5 min-1). Neither a 'thio effect' nor a 'Mn2+rescue effect' were observed. These results suggest that Mg2+ions do not interact with pro-R oxygen directly but are essential to the formation of the active complex of the ribozyme and its substrate.

Effect of acute renal failure on neurotoxicity of enoxacin in rats

We investigated the effect of acute renal failure on the neurotoxicity of enoxacin (ENX) in rats. Experimental acute renal failure was produced by bilateral ureteral ligation. ENX was intravenously infused to ureter ligated (UL) and control rats, and its concentration in plasma, brain and cerebrospinal fluid (CSF) was compared. Plasma concentration of ENX increased rapidly in UL rats as compared with control rats. Brain/plasma concentration ratio (Kp)-time profile of ENX was similar in UL and control rats. Brain concentration of ENX at the occurrence of convulsion did not depend on the infusion rate, suggesting that in the brain tissue it equilibrates rapidly with the site of action for clonic convulsion. Brain concentration of ENX in UL rats at the occurrence of clonic convulsion was lower than that in control rats. A similar tendency was also observed with CSF concentration. In conclusion, the potentiation of neurotoxicity of ENX with acute renal failure may be caused by not only decreased capability for renal elimination of ENX but also increased sensitivity to convulsant activity of ENX in the central nervous system.

Inhibitory effect of new quinolones on GABA(A) receptor-mediated response and its potentiation with felbinac in Xenopus oocytes injected with mouse-brain mRNA: correlation with convulsive potency in vivo

Convulsions induced by the interaction of new quinolone antimicrobial agents (NQs) and nonsteroidal anti-inflammatory drugs (NSAIDs) were previously reported, and blockade of GABA(A) receptor by NQs and its potentiation with NSAIDs were considered as one of its possible mechanisms. However, useful methodology for prediction of convulsive potencies of NQs with or without NSAIDs in vivo based on in vitro screening was not established. Therefore, we applied the Xenopus oocytes translation system of exogenous messenger RNA (mRNA) to examine the mechanism of convulsion induced by interaction of NQs and NSAIDs, and the relationship between convulsive potencies in vivo and inhibitory effect on GABA-induced current response in vitro was investigated. This system also has alternative possibility for the in vivo toxicological studies sacrificing innumerous animals. Glutamic acid, kainic acid, quisqualic acid, NMDA, and serotonin-induced currents were not modified by ENX of NQs and/or FLB of NSAIDs, while glycine- and ACh-induced currents were slightly inhibited. GABA (10 microM)-induced current was inhibited by norfloxacin (NFLX), ciprofloxacin, ENX, and ofloxacin (OFLX) with IC50 of 17, 33, 58, and 280 microM, respectively. IC50 of NQs decreased to 1/3 (OFLX)-1/165 (NFLX) in the presence of 10 microM FLB, while FLB did not modulate the GABA response in the absence of NQs. CSF concentration of ENX at the time of convulsion in clinical situation approximated the IC50 of ENX for the GABA response. The increase of incidence for NQs-induced convulsion by concomitant NSAIDs in vivo could also be explained by the potentiation of inhibitory effects of NQs with FLB in the normal range of CSF concentration of these drugs. We also examined convulsive potency (threshold dose for convulsion) in CNS by intracerebral infusion of NQs to mice with or without FLB pretreatment, and significant correlations between the convulsive potencies and IC50 of NQs for the GABA response were observed. These findings suggested that the blockade of GABA-ersic neurotransmission in CNS is a dominant mechanism of convulsion induced by NQs and that the convulsant-adverse reaction of NQs in vivo may be predicted from the inhibitory effect on the GABA(A) receptor in vitro using the Xenopus oocytes translation system of exogenous mRNA.

Constructing an efficient trans-acting genomic HDV ribozyme

We have engineered a genomic HDV ribozyme to construct several trans-acting ribozymes for use in trans to cleave target RNAs. Among the 10 different combinations attempted, only HDV88-Trans had cleavage activity on the 13-nucleotide substrate, R13, in vitro. To improve the cleavage efficiency, at least in vitro, of the HDV88-Trans ribozyme (kclv = 0.022 min(-1)), we have constructed several variants that differ in forming stem II (length) in the pseudoknot secondary structure model. When cleavage rate constants were analyzed and compared among variants of HDV88-Trans, HDV88-Trans-4 yielded kclv = 1.7 min(-1). HDV88-Trans-4 thus represents the highest active genomic HDV ribozyme that functions in trans thus far constructed, and has activity under physiological conditions (pH 7.1 at 37 degrees C with 1 mM of MgCl2).

[Capsaicin-induced corneal epithelial changes in rats]

To elucidate the mechanisms by which corneal sensory denervation causes corneal epithelial disorders, we investigated corneal epithelial changes in rats injected with capsaicin, which is known to desensitize the primary sensory neurons. Neonatal rats were injected with capsaicin (100 mg/kg) or only the vehicle as a control on the 2nd day after birth. Corneas were excised after 7-28 days and subjected to gold chloride staining. 3H-thymidine autoradiography, or immunohistochemistry using anti-substance P (SP) antibody. The results indicated poor attachment of corneal epithelium, decreased corneal nerve ending density, decreased 3H-thymidine uptake by epithelial cells, and decreased expression of SP in the epithelial layer in rats injected with capsaicin compared with the control rats. This suggests that decreased proliferation of corneal epithelial cells associated with decreased SP as well as poor attachment of the epithelium is one of the causes of neuroparalytic keratopathy.

Lack of potentiation with felbinac patch on the convulsive toxicity of enoxacin in rats

We investigated the possible potentiation of the convulsive toxicity of enoxacin (ENX) by the concomitant topical application of a felbinac (FLB) patch in rats. A felbinac patch (Seltouch; 0.5%, 3 cm x 4 cm) was attached on the back of rats where their hair has been removed. ENX was infused from the left jugular vein at 8 h after the application of FLB patch under an unanesthetized and unstrained condition. Blood, CSF and brain samples were collected at the occurrence of convulsion, and ENX concentrations of each part were determined. As a result, no significant potentiation by FLB patch was found in the onset time of convulsion or in the ENX concentration of each part. Moreover, based on the assumption that there are no inter-species differences in ENX concentration in the brain at the occurrence of a convulsion (Cbr), the predicted plasma ENX concentration required to elicit convulsions in humans, which was estimated from the Cbr and Kp value of ENX in the brain of rats, was 20 times higher than the therapeutic plasma level.

Neurotoxic convulsions induced by theophylline and its metabolites in mice

To evaluate the risk of neurotoxicity induced by theophylline and its main metabolites, 1-methylxanthine (1-MX), 3-methylxanthine (3-MX), 1,3-dimethyluric acid (1,3-DMUA) and 1-methyluric acid (1-MUA), we compared their convulsive potency to central nervous system (CNS) after intracerebral administration to mice. All compounds studied induced clonic convulsion in a dose-dependent manner, and the ED50 values for convulsion were 490, 546, 1107, 360 and 620 nmol/kg for theophylline, 1-MX, 3-MX, 1,3-DMUA and 1-MUA, respectively. These compounds were also administered intravenously to mice by constant rate infusion until the onset of convulsion. Clonic convulsion was induced by i.v. infusion of theophylline, 1-MX and 3-MX, while convulsion was not observed during 1,3-DMUA or 1-MUA infusion for 60 min. This finding may be due to the poor blood-brain barrier permeability of both 1-MUA and 1,3-DMUA as compared with theophylline, 1-MX and 3-MX. However, it may be also necessary to consider the possibility of 1,3-DMUA-induced-neurotoxicity judging from its intrinsic convulsive potency.

Selection in vitro of trans-acting genomic human hepatitis delta virus (HDV) ribozymes

In an effort to identify the functional structure as well as new active variants of the trans-acting genomic ribozyme of human hepatitis delta virus (HDV), we applied an in vitro selection procedure. A total of 14 rounds of selection and amplification was repeated and various mutant ribozymes in G10 and G14 pools analyzed. Active ribozymes which were isolated in the present study (from G10 and G14) all possessed conserved bases (that were identified earlier) in the cis-acting molecule. A dominant clone G10-68 variant was accumulated in generation 14. Interestingly, when base substitutions were analyzed in G10-68 variant, we found that this variant appears to be close to antigenome-like HDV ribozyme molecule. Further investigations of G10-68 confirmed that each mutated base was the most appropriate nucleotide at every position of the HDV ribozyme.

Neurotoxic convulsions induced by histamine H2 receptor antagonists in mice

Convulsive potency was evaluated to investigate the mechanism of neurotoxic convulsion induced by histamine H2 receptor antagonists (H2 blockers). Four H2 blockers, cimetidine (721-1236 nmol), ranitidine (477-954 nmol), famotidine (7.4-44 nmol), and nizatidine (226-603 nmol) were administered intracerebrally (i.c.) to mice. Dose dependency of clonic and/or tonic convulsion was observed, and the ED50 values of convulsive occurrence for cimetidine, ranitidine, famotidine, and nizatidine were 997, 662, 23.4, and 404 nmol, respectively. Intraperitoneal pretreatment of muscimol, aminooxy acetic acid, diazepam, (+/-)2-amino-7-phosphonoheptanoic acid (APH), or (+)MK801 suppressed the tonic convulsion after i.c. administration of ranitidine, but had no effect on clonic convulsion. Furthermore, the convulsive threshold concentration in the brain determined by constant rate infusion of ranitidine was not affected by the pretreatment of muscimol, diazepam, APH, and MK801. Ed50 values for convulsive occurrence after i.c. administration of four H2 blockers correlated well with the EC50 values for gastric acid secretion inhibition. The convulsive threshold concentrations of cimetidine and ranitidine in the brain were 11 and 2.5 microM, respectively, which were similar to the dissociation constants determined from the inhibition of gastric acid output in mice. From these results, tonic convulsion induced by H2 blockers can be suppressed by GABAergic or glutamatergic anticonvulsants, while clonic convulsion induced by H2 blockers may be associated with the blockade of H2 receptor in the brain and not be directly associated with the GABA and glutamate-mediated neurotransmission.

Effect of renal failure on neurotoxicity of ranitidine in rats

We investigated the effect of acute renal failure on the neurotoxicity of ranitidine in rats. Experimental acute renal failure was produced by bilateral ureteral ligation. Ranitidine was infused into the ureter ligated (UL) and control rats at the rate of 3.25 mg/min through the jugular vein until the onset of clonic convulsion. In UL rats, the onset time of convulsion was shorter and ranitidine concentrations in plasma and cerebrospinal fluid (CSF) were lower than those of control rats. However, the ranitidine concentration in the brain at the onset of convulsion was not different between the UL and control rats. From these findings, we concluded that acute renal failure is one of the risk factors for ranitidine neurotoxicity, and the increased sensitivity to the drug on the central nervous system may contribute to the increased toxicity of ranitidine in renal failure.

Effect of acute renal failure on neurotoxicity of cimetidine in rats

PURPOSE

We investigated the effect of acute renal failure on the neurotoxicity of cimetidine in rats.

METHODS

Experimental acute renal failure was produced by bilateral ureteral ligation. Cimetidine was intravenously infused to ureter ligated (UL) and control rats, and cimetidine concentration in plasma, brain and cerebrospinal fluid (CSF) were compared.

RESULTS

The cimetidine concentration in plasma was rapidly increased in UL rats as compared to control rats. The cimetidine concentration in CSF at the onset of convulsion did not depend on the infusion rate, suggesting that cimetidine in CSF equilibrates rapidly with the site of action for clonic convulsion. The cimetidine concentration in CSF of UL rats at the onset of clonic convulsion was lower than those of control rats.

CONCLUSIONS

Increased sensitivity to the drug on the central nervous system may contribute to increased toxicity of cimetidine with renal failure.

The position of the mandibular condyle at maximal mouth opening in normal subjects

PURPOSE

To investigate the position of the mandibular condyle at maximal mouth opening in individuals 19 to 30 years of age with no functional disorders of the masticatory system.

PATIENTS AND METHODS

Measurements were made in 153 subjects (99 men, 54 women), and 41 men and 44 women had transcranial radiographs taken of their right and left temporomandibular joints in the closed and maximal opening positions.

RESULTS

In all subjects the condyle moved forward beyond the summit of the articular eminence, and in more than half the subjects the condyle was located inferior to the eminence at maximal opening.

CONCLUSION

The correlation between maximal opening and anterior shift of the condyle from the summit of the eminence was significant, but the correlation with vertical shift of the condyle was not significant. The correlation between the form of the glenoid fossa (length and depth) and anterior or vertical shift of the condyle from the summit of the eminence also was not significant.

Effect of renal or hepatic dysfunction on neurotoxic convulsion induced by ranitidine in mice

We investigated the effect of acute renal and hepatic dysfunction on the neurotoxicity of ranitidine, a histamine H2 receptor antagonist. Experimental acute hepatic and renal dysfunction in mice were produced by i.p. injection of uranyl nitrate (UN) and carbon tetrachloride (CT), respectively. Ranitidine was then constantly infused into the tail vein until the onset of clonic convulsion. When compared to control mice, UN treated mice had a significantly shorter onset time to clonic convulsion, lower total dose and higher plasma concentration at initiation of clonic convulsion. In contrast, the convulsive threshold concentration in the brain of UN treated mice was not significantly different from that of control mice. In CT treated mice, all pharmacokinetic and pharmacodynamic data described above were not significantly different from those of the control mice. No significant difference in the brain/plasma concentration ratio was observed between both disease models and the corresponding control mice. Finally, the effect of UN and CT treatment on the convulsive potency after intracerebral (i.c.) administration of ranitidine was investigated in mice. Potentiation of the intrinsic neurotoxic sensitivity to ranitidine could not be demonstrated for mice with renal or hepatic dysfunction. From these findings, we conclude that renal dysfunction is a risk factor for ranitidine neurotoxicity, and this increased risk results from increase in the drug concentration in plasma and brain as a result of impaired renal excretion. No apparent effect of acute hepatic dysfunction was observed on both the pharmacokinetic and pharmacodynamic behavior of the drug.

The effect of food on the interaction of ofloxacin with sucralfate in healthy volunteers

We have studied the effect of food on the interaction of ofloxacin with sucralfate. Six healthy men took a single oral dose of ofloxacin (200 mg) on 4 occasions: alone after overnight fasting or after breakfast (non-fasting), and with sucralfate fasting or non-fasting. There were no significant differences in the plasma concentration-time profiles of ofloxacin after ofloxacin alone between fasting and non-fasting conditions. On the other hand, the peak plasma concentration and AUC of ofloxacin after co-administration with sucralfate while fasting fell by 70 and 61% compared with ofloxacin alone; the changes non-fasting were 39 and 31% respectively. The interaction of ofloxacin with sucralfate was markedly reduced by food, but still could not be disregarded.