Relation between plasma and saliva concentrations of enoxacin, ciprofloxacin, and theophylline

To assess the reliability of predicting plasma concentrations of enoxacin, ciprofloxacin, and theophylline from drug concentrations in saliva, six healthy volunteers received single oral doses of enoxacin, ciprofloxacin, and theophylline administered in combination on each of four separate study days, with different, doses separated by at least 5 days. Drug concentrations were determined by a newly developed high-performance liquid chromatography (HPLC) assay, which could measure simultaneously all three drugs in plasma or saliva. Saliva data from the postabsorptive phase after drug administration were used to minimize the effects of variation in absorption. There were good correlations between saliva and plasma concentrations of enoxacin, ciprofloxacin, and theophylline (r = 0.91, 0.88, and 0.98, respectively). The mean (+/-SD) saliva-to-plasma (S/P) ratio for theophylline was 0.63 +/- 0.06 with a coefficient of variation (CV) of 7.9 +/- 2.7%. In contrast, the S/P ratios and CV values for enoxacin and ciprofloxacin were 0.72 +/- 0.21 and 28.9 +/- 11.1%, and 0.58 +/- 0.15 and 25.3 +/- 6.7%, respectively. Because of the large inter- and intraindividual variability, saliva concentrations of enoxacin and ciprofloxacin are not reliable for predicting plasma concentrations. However, saliva may be used reliably for predicting plasma concentrations of theophylline.

[Microsurgical anatomical study of the wall of the cavernous sinus]

OBJECTIVE

To observe the microanatomical structures of the wall of cavernous sinus (CS) in order to provide anatomical basis for direct microsurgical operation to the CS.

METHODS

48 aides of the CS of adult cadavers were dissected in detail under operative microscope.

RESULTS

The CS was a narrow and long irregular hexahedron in shape. The supperior wall, the posterior wall and the superficial dural layer of the lateral wall of the CS were formed by internal layer of the cerebral dura. The deep layer of the interal wall was formed by the sheaths of nerves II, IV, V1, V2 with a reticular membrane between these sheaths. There was a superficial compartment between the superficial layer and deep layer of the lateral wall in 31.25% of the specimens. The inferior wall of the CS was intracranial periosteum. The medial wall was formed by stretched fibres from the tentorium of hypophysis. The anterior aspect was formed by the sphenoid sinus and the superior orbital fissure. Direct microsurgical approaches to the CS via the medial trangles of the superior wall and Parkinson tranales of the lateral wall were most important.

CONCLUSION

A microanatomical structure of the wall of the CS is provided for direct microsurgical operation to the CS, and the direct microsurgical approaches are discussed.

Subunit composition is a major determinant in high affinity binding of a Ca2+ channel blocker

Skeletal muscle L-type channels are the pharmacological receptors for Ca2+ channel antagonists, including dihydropyridines (DHPs). High affinity DHP binding to these channels in skeletal muscle membranes has been reported to be independent of Ca2+ addition and to become dependent on Ca2+ after solubilization. The channel is a multimeric complex composed of alpha 1, beta, gamma, and alpha 2 delta, of which alpha 1 is the pore-forming and DHP-binding component. In this study we coexpressed non-alpha 1 components with alpha 1 in L and COS cells and investigated their roles in the regulation of high affinity DHP binding by Mg2+ and Ca2+. No DHP binding to membranes of cells expressing alpha 1 beta alone was detected in the absence of Ca2+ or Mg2+. Addition of Mg2+ revealed the presence of (+)-PN200-110 (DHP) binding sites with a Kd of 1 nM. This affinity was 4-fold lower than that of skeletal muscle membrane binding sites (Kd = 0.25 nM). Addition of Ca2+ increased the affinity for DHP in membranes from alpha 1 beta-expressing cells to that seen in skeletal muscle membranes (Kd = 0.2-0.3 nM; EC50 of 0.2 microM). Ca2+ did not affect DHP binding to skeletal muscle membranes. Coexpression of all of the subunits completely recapitulated the high affinity DHP binding seen with skeletal muscle membranes in the absence of Ca2+ and Mg2+ (Kd = 0.15 nM). This affinity was unaffected by addition of Ca2+ or Mg2+. Coexpression of alpha 1 beta with either alpha 2 delta or gamma alone resulted in DHP binding intermediate between levels seen with alpha 1 beta and alpha 1 beta alpha 2 delta gamma. Thus, this study demonstrates that alpha 2 delta and gamma are essential for full reconstitution of the DHP binding characteristics of the skeletal muscle L-type Ca2+ channel/DHP receptor.

Protein phosphatases independently regulate vesicle movement and microtubule subpopulations in hepatocytes

To investigate the regulation of microtubule (MT)-based vesicle transport and the interphase MT array in hepatocytes, we have used okadaic acid (OKA) and microcystin (MCYST), two toxins that inhibit serine-threonine protein phosphatases (PP) 1 and 2A, to alter cellular phosphorylation. Video-enhanced differential interference contrast microscopy analysis revealed that both toxins inhibited the frequency, velocity, and run length of MT-dependent vesicle movements dose dependently between 50 and 500 nM. At our maximum dose of 500 nM, both toxins significantly decreased PP2A activity (OKA to 45 +/- 12% and MCYST to 57 +/- 2%), whereas PP1 was inhibited only by MCYST. Because no additional effects on vesicle movements were caused by MCYST over the changes caused by OKA, these data implicate PP2A in the regulation of MT-dependent vesicle movement. To understand whether the changes in parameters of vesicle movements were due to changes in the MT array, the effects of these toxins on MT distribution were examined by immunofluorescence microscopy. Although lower doses of OKA produced no effects, treatment with 500 nM OKA altered MT organization and also caused fragmentation and loss of acetylated (stable) MTs. In contrast, MCYST concentrations up to 500 nM elicited no changes in MT organization in general or in the acetylated (stable) array. From these findings we conclude that inhibition of MT-dependent vesicle movement by the PP inhibitors, MCYST and OKA, in hepatocytes cannot result from changes or disruption in the MT array. Because OKA (an inhibitor of PP2A only in our system) at high doses caused loss of stable MTs, whereas MCYST (an inhibitor of both PP1 and PP2A) did not, we conclude that the control of the preservation of the stable MT array in hepatocytes is complex. Stable MTs require active PP2A for maintenance, but the disruption of the array through inhibition of PP2A can be prevented if PP1 is also inhibited, suggesting that the relative degree of phosphorylation of multiple cellular components is the determinant of MT stability.

Histopathology of enzootic ataxia in Sika deer (Cervus nippon Temminck)

Thirteen Sika deer (Cervus nippon Temminck) showing ataxia on a stock farm in the north eastern district of China were examined histopathologically. The principal pathological changes were spongy vacuolation and myelin deficiency in the white matter of the spinal cord and brain stem, fibrosis and rupture of the elastic lamina of the spinal arterioles, and mesothelial hyperplasia in the spinal arachnoid. Other findings included defective formation of the elastic laminae of the aorta, and the blood vessels in the kidney and lung, hemosiderosis in the spleen and liver, and lymphocyte depletion in the systemic lymph nodes. Copper concentrations were low in the serum and liver. In the white matter of the spinal cord and brain stem, demyelination appeared to coexist with dysmyelination and secondary myelin breakdown. It was inferred that decreased activity of copper containing enzyme induced various lesions. The possible role of copper deficiency in the pathogenesis of the ataxic conditions is discussed.

Effective gating charges per channel in voltage-dependent K+ and Ca2+ channels

In voltage-dependent ion channels, the gating of the channels is determined by the movement of the voltage sensor. This movement reflects the rearrangement of the protein in response to a voltage stimulus, and it can be thought of as a net displacement of elementary charges (e0) through the membrane (z: effective number of elementary charges). In this paper, we measured z in Shaker IR (inactivation removed) K+ channels, neuronal alpha 1E and alpha 1A, and cardiac alpha 1C Ca2+ channels using two methods: (a) limiting slope analysis of the conductance-voltage relationship and (b) variance analysis, to evaluate the number of active channels in a patch, combined with the measurement of charge movement in the same patch. We found that in Shaker IR K+ channels the two methods agreed with a z congruent to 13. This suggests that all the channels that gate can open and that all the measured charge is coupled to pore opening in a strictly sequential kinetic model. For all Ca2+ channels the limiting slope method gave consistent results regardless of the presence or type of beta subunit tested (z = 8.6). However, as seen with alpha 1E, the variance analysis gave different results depending on the beta subunit used. alpha 1E and alpha 1E beta 1a gave higher z values (z = 14.77 and z = 15.13 respectively) than alpha 1E beta 2a (z = 9.50, which is similar to the limiting slope results). Both the beta 1a and beta 2a subunits, coexpressed with alpha 1E Ca2+ channels facilitated channel opening by shifting the activation curve to more negative potentials, but only the beta 2a subunit increased the maximum open probability. The higher z using variance analysis in alpha 1E and alpha 1E beta 1a can be explained by a set of charges not coupled to pore opening. This set of charges moves in transitions leading to nulls thus not contributing to the ionic current fluctuations but eliciting gating currents. Coexpression of the beta 2a subunit would minimize the fraction of nulls leading to the correct estimation of the number of channels and z.

Prevention of disability and rehabilitation--results from a collaborative project in China

Eight different geographical districts in China varying in urban and rural characteristics from 6 provinces and 2 municipalities were selected as pilot areas of the project. The interventions included early detection and treatment of neuritis, self-care training, adapted footwear, surgery, comprehensive treatment of complicated ulcers, and prostheses. Main changes in eye, hand and foot impairments between baseline assessment and assessment at 2 years have been presented in this paper.

A monoclonal IgG anticardiolipin antibody from a patient with the antiphospholipid syndrome is thrombogenic in mice

Antiphospholipid antibodies, including anticardiolipin antibodies (ACA), are strongly associated with recurrent thrombosis in patients with the antiphospholipid syndrome (APS). To date, reports about the binding specificities of ACA and their role(s) in causing and/or sustaining thrombosis in APS are conflicting and controversial. The plasmas of patients with APS, usually containing a mixture of autoantibodies, vary in binding specificity for different phospholipids/cofactors and vary in in vitro lupus anticoagulant activity. Although in vivo assays that allow assessment of the pathogenic procoagulant activity of patient autoantibodies have recently been developed, the complex nature of the mixed species prevented determination of the particular species responsible for in vivo thrombosis. We have generated two human IgG monoclonal ACA from an APS patient with recurrent thrombosis. Both bound to cardiolipin in the presence of 10% bovine serum, but not in its absence, and both were reactive against phosphatidic acid, but were nonreactive against purified human beta-2 glycoprotein 1, DNA, heparan sulfate, or four other test antigens. Both monoclonal autoantibodies lacked lupus anticoagulant activity and did not inhibit prothrombinase activity. Remarkably, one of the monoclonal antibodies has thrombogenic properties when tested in an in vivo mouse model. This finding provides the first direct evidence that a particular antiphospholipid antibody specificity may contribute to in vivo thrombosis.

A hyperphosphorylated form of the large subunit of RNA polymerase II is associated with splicing complexes and the nuclear matrix

A hyperphosphorylated form of the largest subunit of RNA polymerase II (pol IIo) is associated with the pre-mRNA splicing process. Pol IIo was detected in association with a subset of small nuclear ribonucleoprotein particle and Ser-Arg protein splicing factors and also with pre-mRNA splicing complexes assembled in vitro. A subpopulation of pol IIo was localized to nuclear "speckle" domains enriched in splicing factors, indicating that it may also be associated with RNA processing in vivo. Moreover, pol IIo was retained in a similar pattern following in situ extraction of cells and was quantitatively recovered in the nuclear matrix fraction. The results implicate nuclear matrix-associated hyperphosphorylated pol IIo as a possible link in the coordination of transcription and splicing processes.

Molecular basis of the human dihydropyrimidine dehydrogenase deficiency and 5-fluorouracil toxicity

Dihydropyrimidine dehydrogenase (DPD) deficiency constitutes an inborn error in pyrimidine metabolism associated with thymine-uraciluria in pediatric patients and an increased risk of toxicity in cancer patients receiving 5-fluorouracil (5-FU) treatment. The molecular basis for DPD deficiency in a British family having a cancer patient that exhibited grade IV toxicity 10 d after 5-FU treatment was analyzed. A 165-bp deletion spanning a complete exon of the DPYD gene was found in some members of the pedigree having low DPD catalytic activity. Direct sequencing of lymphocyte DNA from these subjects revealed the presence of a G to A point mutation at the 5'-splicing site consensus sequence (GT to AT) that leads to skipping of the entire exon preceding the mutation during pre-RNA transcription and processing. A PCR-based diagnostic method was developed to determine that the mutation is found in Caucasian and Asian populations. This mutation was also detected in a Dutch patient with thymine-uraciluria and completely lacking DPD activity. A genotyping test for the G to A splicing point mutation could be useful in predicting cancer patients prone to toxicity upon administration of potentially toxic 5-FU and for genetic screening of heterozygous carriers and homozygous deficient subjects.

Turnover of the cystic fibrosis transmembrane conductance regulator (CFTR): slow degradation of wild-type and delta F508 CFTR in surface membrane preparations of immortalized airway epithelial cells

The protein product of the cystic fibrosis (CF) gene, termed the cystic fibrosis transmembrane conductance regulator (CFTR), is known to function as an apical chloride channel at the surface of airway epithelial cells. It has been proposed that CFTR has additional intracellular functions and that there is altered processing of mutant forms. In examining these functions we found a stable form of CFTR with slow turnover in surface membrane preparations from CF and non-CF immortalized airway epithelial cell lines. The methods used to study the turnover of CFTR were pulse/chase experiments utilizing saturation labeling of [35S] Met with chase periods of 5-24 h in the presence of 8 mM Met and cell fractionation techniques. Preparations of morphologically identifiable surface membranes were compared to total cell membrane preparations containing intracellular membranes. Surface membrane CFTR had lower turnover defined by pulse/chase ratios than that of the total cell membrane preparations. Moreover, mutant CFTR was stable in the surface membrane fraction with little degradation even after a 24 h chase, whereas wild-type CFTR had a higher pulse/chase ratio at 24 h. In the presence of 50 microM castanospermine, which is an inhibitor of processing alpha-glucosidases, a more rapid turnover of mutant CFTR was found in the total cell membrane preparation, whereas wild-type CFTR had a lower response. The results are compatible with a pool of CFTR in or near the surface membranes which has an altered turnover in CF and a glycosylation-dependent alteration in the processing of mutant CFTR.

Pathogenesis of caudal dysgenesis/sirenomelia induced by ochratoxin A in chick embryos

Caudal dysgenesis/sirenomelia is a malformation complex for which the pathogenesis is controversial. This report describes the particular vulnerability of specific caudal structures to Ochratoxin A (OA), a fungal toxin, as the basis for caudal dysgenesis in an avian model. The experimental procedure involved injection of 1 microgram of OA into the air sac of eggs that had been incubated for 48 hours prior to treatment (i.e., embryos that had reached Hamburger and Hamilton stage 9-10 (6-10 somite pairs) [Hamburger and Hamilton (1951) Dev. Dyn. 195:231-272] by the time of treatment). Six to twelve hours following OA injection, excessive cell death, as shown by vital staining and routine histology, was evident in selected cell populations, including cells of the caudal-most mesoderm (the mesoderm that apparently forms the external genitalia and median infraumbilical region), the tail bud, and the neural tube caudal to the wing buds (corresponding to the level of the presomitic mesoderm). The notochord was not severely affected, although there were degenerative changes in the presomitic mesoderm. Except for positional abnormalities, development of the lateral plate mesoderm from which the leg buds are derived appeared relatively normal in most of the treated embryos. Six days post-treatment, varying degrees of caudal dysgenesis, presenting in severely affected specimens as sirenomelia, were observed in approximately 30% of the surviving treated embryos. The potential basis for the differential vulnerability of the affected cell populations and, therefore, the cellular basis for the genesis of caudal dysgenesis/sirenomelia in this model are discussed.

Concentrations of proteoglycan fragments in relation to maturation, sex and time of day: physiologic variations in knee joint fluid of rabbits

We analyzed the concentrations of proteoglycan fragments in knee joint fluid in 142 rabbits to investigate the effect of physiologic variations--i.e., maturation, sex and time of day. The concentrations of proteoglycan fragments differed significantly between young, adolescent and adult animals and showed an inverse correlation to the stage of maturation of the rabbit. Adolescent male rabbits had higher concentrations than age-matched females. Morning and evening samples had similar concentrations. No relation was found between the proteoglycan fragment concentrations in joint fluid and the cartilage mass. The proteoglycan fragment concentrations in knee joint fluid apparently reflect the metabolic status of growing articular cartilage. There are considerable physiologic variations associated with maturation and sex, and these need to be taken into account when using the proteoglycan fragment concentration as a marker for joint diseases.

Increase of the expression of midecamycin 4"-hydroxyl propionyltransferase gene (mpt) by a promoter-like fragment from the midecamycin producing strain

The promoter region of the midecamycin 4"-hydroxyl propionyltransferase gene (mpt) gene was reconstructed by PCR, and ligated with a fragment from the midecamycin producing strain (Streptomyces mycarofaciens var. 68) which contained fairly strong promoter activity (PLF). Recombinant plasmids pCHFPE2 (promoter region of mpt was reconstructed by combining the PLF in the upstream of its own promoter) and pCHFPE3 (the promoter of mpt was replaced by PLF) were obtained. The extent of expression of mpt was measured according to the amount of propionylspiramycin bioconverted from exogenous spiramycin by transformants of S. lividans TK24 containing pCHFPE2 and pCHFPE3. The results showed that the PLF could increase the expression of mpt in S. lividans TK24 up to 89.02% and 58.53%, respectively, and also enhance the expression in the industrial spiramycin producing strain S. spiramyceticus to a great extent.

The nuclear matrix: a structural milieu for genomic function

While significant progress has been made in elucidating molecular properties of specific genes and their regulation, our understanding of how the whole genome is coordinated has lagged behind. To understand how the genome functions as a coordinated whole, we must understand how the nucleus is put together and functions as a whole. An important step in that direction occurred with the isolation and characterization of the nuclear matrix. Aside from the plethora of functional properties associated with these isolated nuclear structures, they have enabled the first direct examination and molecular cloning of specific nuclear matrix proteins. The isolated nuclear matrix can be used for providing an in vitro model for understanding nuclear matrix organization in whole cells. Recent development of high-resolution and three-dimensional approaches for visualizing domains of genomic organization and function in situ has provided corroborative evidence for the nuclear matrix as the site of organization for replication, transcription, and post-transcriptional processing. As more is learned about these in situ functional sites, appropriate experiments could be designed to test molecular mechanisms with the in vitro nuclear matrix systems. This is illustrated in this chapter by the studies of nuclear matrix-associated DNA replication which have evolved from biochemical studies of in vitro nuclear matrix systems toward three-dimensional computer image analysis of replication sites for individual genes.

Increase in Ca2+ channel expression by deletions at the amino terminus of the cardiac alpha 1C subunit

The alpha 1 subunit of the cardiac L-type Ca2+ channel (alpha 1C) is one of the many alternatively spliced products of a single gene that is expressed in a number of excitable tissues. Sequence comparison indicates that the amino terminus is a site of significant structural diversity. To explore the role of the amino terminus of alpha 1C in expression and function of Ca2+ channels, we constructed a series of deletion mutants of the rabbit cardiac alpha 1C subunit and expressed them in Xenopus oocytes. Deletions of up to 120 amino acids from the amino terminus increased both ionic and gating currents by 5- to 8-fold. Ca2+ currents induced by these mutants had voltage-dependent activation, inactivation, modulation by beta subunits, and single channel conductance similar to the wild type cardiac alpha 1C (wt alpha 1C). Thus, deletion of a major portion of the amino terminus of alpha 1C did not alter the three dimensional conformation essential for channel function, but enhanced the expression of Ca2+ channels in Xenopus oocytes. A deletion mutant lacking the first 171 amino acids did not yield any measurable current.

The postnatal development of the insertions of the medial collateral ligament in the rat knee

Bone soft tissue remodelling at the femoral and tibial insertions of the medial collateral ligament (MCL) of the rat knee was monitored at regular intervals from birth to 120 days of age in 40 Sprague Dawley rats. At birth the femoral insertion originated from the perichondrium of the epiphysis. By day 8 the perichondrium within the insertion had turned into fibrocartilage. Secondary ossification of the femoral epiphysis had progressed in the region near to the insertion site by day 15. The epiphyseal cartilage was entirely replaced by bone by day 40 except for the fibrocartilage within the insertion. After that stage, no qualitative change in zonal insertion characteristics was observed, but only increase in size and decrease in cellularity. At birth, the tibial ligament inserted onto the thin cortical bone of the metaphysis via periosteum. At day 8, osteoclasts started to resorb the thin cortical bone at the ligament insertion, thus forming a metaphyseal depression between days 10 and 20. From days 20 to 120, the insertion remained qualitatively unchanged, showing three zones, the ligament, periosteum, and metaphyseal trabecular bone. The deep periosteal layer showed osteoclastic activity in the proximal part and osteoblastic activity in the distal part. The migration-mechanism of the ligament insertion during growth seems to be caused by this growth-related osteoclastic resorption of the proximal metaphyseal bone and by simultaneous osteogenic activity, which successively cements the distal part of the ligament to bone. The persistence of the periosteal layer and the metaphyseal depression for up to 120 days may be regarded as a sign of continuing growth in this animal model. This is the first investigation showing that the formation of the metaphyseal depression is a purely postnatal event, and suggests that this process might be initiated by the change in mode of growth and joint biomechanics after birth, enabling ligament development and migration in a growing and increasingly loaded weight-bearing joint. The mainly resorptive process, which takes place during development of the tibial MCL insertion, may account for the tensile failure of this ligament that commonly occurs at this site during growth. The pronounced morphological differences between the chondral femoral and the periosteal tibial attachment of the adult MCL are apparently caused by the different postnatal development processes at epiphyses and metaphyses.

Reconstitution of the skeletal muscle dihydropyridine receptor. Functional interaction among alpha 1, beta, gamma and alpha 2 delta subunits

The L-type voltage-dependent Ca2+ channel purified from skeletal muscle by virtue of its dihydropyridine (DHP) binding activity, is composed of alpha 1, alpha 2 delta, beta and gamma subunits. The alpha 1 subunit has the ability to function alone as a Ca2+ channel and a receptor for DHP and other Ca2+ channel antagonists. In this study, the non-alpha 1 components coexpressed with alpha 1 in COS cells were investigated for their effects on DHP binding and suppression of an anomalous allosteric regulation of the phenylalkylamine (-)D600 in complexes lacking one or more subunits. (-)D600 increased DHP binding to membranes of COS cells expressing alpha 1 beta while it did not affect DHP binding to skeletal muscle membranes. Coexpression of gamma or alpha 2 delta with alpha 1 beta partially suppressed this effect. Coexpression of all the subunits completely eliminated the stimulatory effect of (-)D600, while at the same time increasing the affinity of the complex for DHP to that stabilized in partial complexes by the phenylalkylamine. These results demonstrate that all of the components that co-purify are required for the formation of a functional DHP receptor having the properties of the native skeletal muscle DHP receptor.

Essential Ca(2+)-binding motif for Ca(2+)-sensitive inactivation of L-type Ca2+ channels

Intracellular calcium (Ca2+) inhibits the opening of L-type (alpha 1C) Ca2+ channels, providing physiological control of Ca2+ entry into a wide variety of cells. A structural determinant of this Ca(2+)-sensitive inactivation was revealed by chimeric Ca2+ channels derived from parental alpha 1C and alpha 1E channels, the latter of which is a neuronal channel lacking Ca2+ inactivation. A consensus Ca(2+)-binding motif (an EF hand), located on the alpha 1C subunit, was required for Ca2+ inactivation. Donation of the alpha 1C EF-hand region to the alpha 1E channel conferred the Ca(2+)-inactivating phenotype. These results strongly suggest that Ca2+ binding to the alpha 1C subunit initiates Ca2+ inactivation.

Relative potency of mexiletine, lidocaine, and tocainide as inhibitors of rat liver CYP1A1 activity

Mexiletine and tocainide are lidocaine congeners that share similar chemical structures. Clinical studies suggest that the in vivo inhibitory effect of mexiletine on the CYP1A family of isoforms is substantially greater than that of tocainide. We investigated the inhibitory property of mexiletine, lidocaine, and tocainide on the in vitro activity of the cytochrome P4501A1 (CYP1A1) isozyme in the rat. Hepatic microsomes were prepared from rat livers induced with 3-methylcholanthrene. The rate of ethoxyresorufin-O-dealkylation (EROD) was used as an index of CYP1A1 activity. Vmax and KM of the reactions were determined from Lineweaver-Burk plots. The Ki values for the inhibitors were derived from Dixon plots. Results showed that mexiletine is a competitive inhibitor, lidocaine is a mixed inhibitor, and tocainide is a noncompetitive inhibitor of EROD. The Ki values for mexiletine and tocainide were 0.30 +/- 0.02 mM and 12.4 +/- 0.7 mM, respectively. Two Ki values for lidocaine were determined. They were 0.65 +/- 0.07 mM and 4.1 +/- 1.3 mM, respectively. The relative inhibitory potency of these agents on rat CYP1A1 activity is mexiletine > lidocaine > tocainide. This difference in potency, which is most likely attributable to the change in the chemical composition in the aliphatic chain among the compounds, suggests that these compounds may be useful probes for studying the mechanism of the interaction with the active site of CYP1A1.

Molecular determinants of cardiac Ca2+ channel pharmacology. Subunit requirement for the high affinity and allosteric regulation of dihydropyridine binding

Cardiac L-type Ca2+ channels are multisubunit complexes composed of alpha 1C, alpha 2 delta, and beta 2 subunits. We tested the roles of these subunits in forming a functional complex by characterizing the effects of subunit composition on dihydropyridine binding, its allosteric regulation, and the ability of dihydropyridines to inhibit channel activity. Transfection of COS.M6 cells with cardiac alpha 1C-a (alpha 1) led to the appearance of dihydropyridine ([3H]PN200-110) binding which was increased by coexpression of cardiac beta 2a (beta), alpha 2 delta a (alpha 2), and the skeletal muscle gamma. Maximum binding was achieved when cells expressed alpha 1, beta, and alpha 2. Cells transfected with alpha 1 and beta had a binding affinity that was 5-10-fold lower than that observed in cardiac membranes. Coexpression of alpha 2 normalized this affinity. (-)-D600 and diltiazem both partially inhibited PN200-100 binding to cardiac microsomes, but stimulated binding in cells transfected with alpha 1 and beta. Again, coexpression of alpha 2 normalized this allosteric regulation. Therefore coexpression of alpha 1 beta and alpha 2 completely reconstituted high affinity dihydropyridine binding and its allosteric regulation as observed in cardiac membranes. Skeletal muscle gamma was not required for this reconstitution. Expression in Xenopus oocytes demonstrated that coexpression of alpha 2 with alpha 1 beta increased the potency and maximum extent of block of Ca2+ channel currents by nisoldipine, a dihydropyridine Ca2+ channel antagonist. Our results demonstrate that alpha 2 subunits are essential components of the cardiac L-type Ca2+ channel and predict a minimum subunit composition of alpha 1C beta 2 alpha 2 delta for this channel.

Alpha-1 subunits of voltage gated Ca2+ channels in the mesencephalon x neuroblastoma hybrid cell line MES23.5

The identity of alpha 1 subunits from voltage operated Ca2+ channels was determined in the rat/mouse mesencephalon x N18TG2 hybridoma cell line MES23.5, by sequence analysis of reverse transcription-polymerase chain reaction products and antagonist binding. Sequences were derived from the L-(alpha 1D), Q-(alpha 1A) and omega-conotoxin GVIA sensitive N-type (alpha 1B) Ca2+ channel alpha 1 subunits. The amplified fragments, which are homologous to the region between domain III and IV of known alpha 1 subunits, reveal splice variation in the L- and Q-type alpha 1 subunit of MES23.5 cells. The transcripts of alpha 1 subunits in these cells were quantified by RNAase protection assay. The data show the existence of different Ca2+ channel types in a single cell line and may reflect multiple functions of voltage operated Ca2+ channels during growth, differentiation and transmitter release.

Corticospinal motor neurons in the adult rat: degeneration after intracortical axotomy and protection by ciliary neurotrophic factor (CNTF)

Little is known about the neurotrophic factors that may regulate maintenance, growth, and/or repair of corticospinal motor neurons (CSMN) in the developing or the adult mammal. We have developed an adult rat in vivo model of CSMN injury involving (i) bilateral prelabeling of CSMN with a cervical spinal cord injection of cholera toxin B subunit (CTB), (ii) unilateral axotomy close to the cell bodies by an intracortical lesion between cell layer V and the corpus callosum, and (iii) implantation of a continuous infusion device in the cortical parenchyma near the lesion. Two weeks later, coronal sections of the cortex are immunostained for CTB, and CTB-stained neurons are counted over defined section areas and compared to those on the contralateral (nonlesioned, noninfused) side. CTB-stainable neurons were 30-40% of the control side when the lesion was about 200 microns from the deeper face of the cell layer, and survival increased with increasing lesion depths. The model can be used to assess protective effects of potential CSMN trophic factors. The low survival achieved with the more superficial lesions (200 and 300 microns) was markedly improved by continuous infusion of ciliary neurotrophic factor at 0.1 to 1.0 microgram/day.

Simultaneous determination of theophylline, enoxacin and ciprofloxacin in human plasma and saliva by high-performance liquid chromatography

A simple reversed-phase high-performance liquid chromatographic method has been developed for the simultaneous determination of theophylline, ciprofloxacin and enoxacin in plasma and saliva. The biological fluid samples were extracted with methylene chloride-isopropyl alcohol prior to isocratic chromatography on a Waters C18 mu Bondapak column. Ultraviolet detection was carried out at 268 nm. The assay is linear for ciprofloxacin and enoxacin (0.05-10 micrograms/ml), and theophylline (0.1-20 micrograms/ml). The assay can be used to investigate the interaction of these two fluoroquinolones with theophylline.

Use of alpha-N,N-bis[carboxymethyl]lysine-modified peroxidase in immunoassays

Horseradish peroxidase was activated by periodate oxidation of the carbohydrate moiety and then modified by the covalent attachment of alpha-N,N-bis[carboxyethyl]lysine (CM-Lys) by reductive alkylation using sodium cyanoborohydride. The resultant CM-Lys peroxidase was charged with nickel ions and then used as a specific labeling reagent for histidine-tagged recombinant proteins. This labeling method was effective for proteins that are soluble or insoluble in the absence of chaotropic agents. The labeled proteins were very effective in direct sandwich enzyme-linked immunosorbent assay for detecting antibodies against the protein in sera as demonstrated by assays for antibodies to such diverse viral proteins as hepatitis B surface and core proteins, hepatitis C core and helicase protein (NS3), and retroviral core proteins.

[Dumbbell like neurinoma at upper cervical vertebra: report of 48 cases]

48 dumbbell like neurinoma at upper cervical vertebra were totally removed operatively and confirmed pathologically. Intermittent pain at neck and occiput limitation of neck movement, and numbness or pain at one or both side limbs were the most common symptoms. In the early stage, the disease was difficalt to recognize. If X-ray film of the cervical vertebra at bioblique position showed an enlarged intervertebral foramen, the diagnosis of neurinoma should be highly considered. MRI could make a definite diagnosis. Vertebral artery angiography is of great value. We also introduced experience in how to protect vertebral artery and respiratory function during operation.

Onset of expression of the alpha subunit of Ca2+/calmodulin-dependent protein kinase II and a novel related protein in the developing retina

Calcium-calmodulin-dependent protein kinase II is an abundant protein in the nervous system and has been associated with many aspects of neuronal function, including events related to synaptic transmission. The purpose of this study is to correlate the onset of expression of this kinase with a specific developmental event in retinal morphogenesis using a monoclonal antibody to the 50-kDa alpha-subunit. Microscopy showed the antigen to be associated with the plexiform layers of the retina. Western blots demonstrated that the onset of expression of the alpha-subunit coincided in time with the initial formation of the plexiform layers. However, the onset of expression of the 50-kDa alpha-subunit was preceded by the earlier embryonic appearance of a related 82.5-kDa antigen that was recognized by the antibody. The amount of this latter protein declined as the amount of the alpha-subunit increased in retinal homogenates. Although this related 82.5 kDa protein disappeared from blots of retinal homogenates after embryonic d 14, it could be detected in concentrated supernatant fractions isolated from the retinae of hatched chicks. Microscopy showed that a subset of retinal cells and their processes contained this antigen in early embryonic chicks. Finally, the 50 kDa alpha-subunit of kinase II and the 82.5 kDa novel antigen were shown to be separable by differential centrifugation.

Characterization of the independent and combined effects of two inhibitors on oxidative drug metabolism in rat liver microsomes

To evaluate how two inhibitors influence oxidative drug metabolism, this study investigated the inhibitory effects of mexiletine with cimetidine and mexiletine with lidocaine, both individually and in combination, on the oxidative metabolism of two probe substrates, aminopyrine and aniline in rat liver microsomes. Mexiletine was a competitive inhibitor of aminopyrine N-demethylation, whereas cimetidine was a mixed type of inhibitor (Ki = 2.00 +/- 0.04 and 0.20 +/- 0.02 mM, respectively). For aniline hydroxylation, mexiletine exhibited a mixed type of inhibition, whereas lidocaine was a noncompetitive inhibitor (Ki = 0.60 +/- 0.07 and 8.50 +/- 0.12 mM, respectively). The combined inhibition of either mexiletine with cimetidine or mexiletine with lidocaine on aminopyrine and aniline metabolism was close to the fully additive effects of the individual compounds when their individual concentrations were below a 2-fold Ki concentration, regardless of the apparent kinetic inhibition type. The combined inhibition was less than fully additive when the individual concentrations were twice the Ki or above. These results demonstrate that, when two inhibitors of oxidative drug metabolism are combined, both the Ki values and the concentrations of inhibitors play important roles in determining the extent of additive inhibition of enzyme activity.

Enzymatic characterisation of recombinant murine inducible nitric oxide synthase

A complementary DNA (cDNA) encoding murine inducible nitric oxide synthase was cloned from activated J774 macrophages. Expression of this cDNA in a baculovirus-insect cell system allowed comparison of the recombinant enzyme with the native homologue. Western blot analysis of activated J774 and baculovirus-infected insect cell cytosols demonstrated reactivity against a protein of 135 kDa. Kinetic studies on the recombinant and native enzymes revealed an absolute requirement for L-arginine and NADPH in order to achieve full activity. In addition, both enzymes were found to have similar maximum velocities and Km values for these two substrates. The nitric oxide synthase antagonists N-guanidino monomethyl L-arginine and N-iminoethyl L-ornithine inhibited both enzymes at a similar rate. Furthermore, comparable concentrations of inhibitor were required to achieve half maximal enzyme inhibition. These results indicate that recombinant inducible NO synthase appears to be pharmacologically indistinguishable from the native enzyme.

Dual activation of the cardiac Ca2+ channel alpha 1C-subunit and its modulation by the beta-subunit

Ca2+ channels are heteromultimeric proteins in which the alpha 1-subunit forms the voltage-dependent Ca(2+)-selective ionic channel. We reported recently that coexpression of the beta-subunit with the cardiac alpha 1-subunit (alpha 1C) facilitates channel opening without affecting either the amplitude or the time course of the gating currents (13). Here we present evidence for the existence of two modes of channel opening. Xenopus oocytes expressing the alpha 1C-subunit alone display two modes of activation as indicated by the double-exponential time course of macroscopic ionic currents and the two open-time distributions of single channels. Coexpression of the beta-subunit potentiates Ca2+ currents by a relative increase of the fast-activating component, an acceleration of the slow component, and a larger proportion of long openings. We propose that multiple modes of gating are encoded in the alpha 1-subunit and that the beta-subunit increases Ca2+ channel opening by favoring a willing mode of gating in which the final transitions leading to channel opening are facilitated. In addition, we show that the carboxy terminus of alpha 1C also modulates the channel-gating behavior.

Voltage-dependent inactivation in a cardiac-skeletal chimeric calcium channel

The loci for inactivation in calcium channel proteins are unknown. Mechanisms for inactivation may be distributed across Ca2+ channel subunits and appear to be complex, multiple and interacting. We took advantage of the properties of chimeras, constructed between cardiac (H4) and skeletal muscle (Sk4) calcium channel alpha 1 subunits to study the molecular mechanism of inactivation in L-type calcium channels. Sk1H3, a chimeric construct of these two L-type calcium channels, was expressed in Xenopus oocytes in the absence of auxiliary subunits. Sk1H3 incorporated repeat I from skeletal muscle alpha 1 and repeats II, III, IV from heart alpha 1 subunit. Sk1H3 inactivated faster (tau = 300 ms) and more fully than the wild-type H4 with Ba2+ ions as the charge carrier. Thus, inactivation of Sk1H3 was 90% complete after a 5-s conditioning pulse at +20 mV while inactivation of H4 was only 37% complete. Sk1H3 inactivation also developed at more negative potentials with E0.5 = -15 mV as compared to E0.5 = -5 mV for H4. In the presence of external calcium ions, the extent of inactivation significantly increased from 37 to 83% for H4 while inactivation of Sk1H3 was only slightly increased. Inactivation with Ba2+ as the charge carrier was confirmed at the single- channel level where averaged single-channel ensembles showed a similar rate of inactivation. Collectively, these observations demonstrate that Sk1H3 inactivation appears to have a prominent voltage-dependent component. Whether Sk1H3 inactivation involves interactions within repeat I alone or interactions between repeat I and site(s) located in the three other repeats of the alpha 1 subunit has yet to be determined.

Probing the structure of influenza B hemagglutinin using site-directed mutagenesis

The crystal structure of the hemagglutinin (HA) of influenza virus A/Aichi/68 (H3N2) from the X-31 reassortant virus was reported in 1981, but as yet there are no X-ray diffraction structures for hemagglutinins of other types or even subtypes of influenza virus. We have used site-directed mutagenesis to probe the structure of the hemagglutinin of influenza B/Hong Kong/8/73. We investigated a region in the globular head domain that is helical in the influenza A HA structure, targeting sidechains that in the H3 HA point toward solvent (Thr196) or into the receptor-binding pocket (Gln197). None of the mutations affected hemagglutination activity, but mutations T196P or Q1971 eliminated binding of a monoclonal antibody. The data suggest that this region of the influenza B HA forms a surface structure different from the alpha-helix of the influenza A HA structure and that it accounts for much of the antigenic activity of influenza B HA.

Viral dynamics in human immunodeficiency virus type 1 infection

The dynamics of HIV-1 replication in vivo are largely unknown yet they are critical to our understanding of disease pathogenesis. Experimental drugs that are potent inhibitors of viral replication can be used to show that the composite lifespan of plasma virus and virus-producing cells is remarkably short (half-life approximately 2 days). Almost complete replacement of wild-type virus in plasma by drug-resistant variants occurs after fourteen days, indicating that HIV-1 viraemia is sustained primarily by a dynamic process involving continuous rounds of de novo virus infection and replication and rapid cell turnover.

The amino terminus of a calcium channel beta subunit sets rates of channel inactivation independently of the subunit's effect on activation

There is molecular diversity in both alpha 1 and beta subunits of voltage-gated Ca2+ channels. Coupling between voltage sensing and pore opening of the C-type alpha 1 (alpha 1c) is improved by the type 2 beta subunit (beta 2), and E-type alpha 1 beta complexes inactivate at different rates depending on the nature of beta. We compared the effects of type 1 and 2 beta subunits on activation of the human E-type alpha 1 (alpha 1E) with the effects they have on inactivation, as seen in Xenopus oocytes. The beta subtypes stimulated activation in similar fashion but affected inactivation differently, and even in opposing directions. beta subunits have a common central core but differ in their N- and C-termini and in a central region. N-terminal chimeras between beta 1 and beta 2 subunits that have opposing effects on inactivation resulted in the reciprocal transfer of their effects. We conclude that regulation of activation and inactivation of alpha 1 by beta are separable events and that the N-terminus of beta is one of the structural determinants important in setting the rate and voltage at which an alpha 1 inactivates.

Ca(2+)-dependent inactivation of a cloned cardiac Ca2+ channel alpha 1 subunit (alpha 1C) expressed in Xenopus oocytes

The alpha 1 subunit of cardiac Ca2+ channel, expressed alone or coexpressed with the corresponding beta subunit in Xenopus laevis oocytes, elicits rapidly inactivating Ca2+ currents. The inactivation has the following properties: 1) It is practically absent in external Ba2+; 2) it increases with Ca2+ current amplitudes; 3) it is faster at more negative potentials for comparable Ca2+ current amplitudes; 4) it is independent of channel density; and 5) it does not require the beta subunit. These findings indicate that the Ca2+ binding site responsible for inactivation is encoded in the alpha 1 subunit and suggest that it is located near the inner channel mouth but outside the membrane electric field.

T-type and N-type calcium channels of Xenopus oocytes: evidence for specific interactions with beta subunits

We used amplifying effects of calcium channel beta subunits to identify endogenous calcium channels in Xenopus oocytes. Expression of rat brain beta 4 increased macroscopic endogenous current magnitude with a small effect on kinetics. In contrast, expression of rat brain/cardiac beta 2 produced a much larger increase in current magnitude and dramatically slowed current decay. Low concentrations of omega-conotoxin GVIA irreversibly blocked currents in both uninjected and beta 2-injected oocytes. Single channel recordings revealed both T- and N-type calcium channels with conductances of 9 and 18 pS, respectively, in uninjected oocytes and in oocytes expressing either beta subunit. Expression of either beta subunit slowed average current decay of T-type single channels. Slowing of T-type current decay by expression of beta 2 was due to reopening of the channels. N-type single channel average current decay showed little change with expression of beta 4, whereas expression of beta 2 slowed average current decay.

Regulation of the cloned L-type cardiac calcium channel by cyclic-AMP-dependent protein kinase

Hormones can regulate cardiac L-type Ca2+ channels via cAMP-dependent protein kinase (PKA) phosphorylation. However, regulation of the cloned L-type Ca2+ channel has been difficult to demonstrate conclusively. We stably transfected a human embryonic kidney (HEK-293) cell with the cardiac alpha 1 and beta 2 subunits, then examined PKA modulation of the Ca2+ current. Although forskolin did not increase basal Ca2+ current, the PKA inhibitors, H-89 and Rp-cAMPS, could inhibit basal current. We reversed H-89 inhibition with either forskolin or okadaic acid. We conclude that the channel was phosphorylated under basal conditions, and that inhibition of PKA allowed dephosphorylation. These studies demonstrate that reversible PKA regulation of cloned Ca2+ channels can be studied in HEK-293 cells.