Conformational analysis of elcatonin in solution

The conformational characteristics of elcatonin, an analogue of eel calcitonin having a disulfide bond Cys1-Cys7 replaced by an ethylene linkage between residues 1 and 7, have been analyzed in aqueous trifluoroethanol solutions. Circular dichroic spectra of elcatonin and eel calcitonin itself reveal the presence of alpha-helices at trifluoroethanol concentrations above 15%. The spectral changes caused by the trifluoroethanol content of the solutions are interesting. An isosbetic point is detected for eel calcitonin indicating that a conformational transition occurs between two states, namely alpha-helical and random coil states. On the other hand, the CD curves of elcatonin at less than 15% trifluoroethanol deviate from the isosbetic point while those at higher concentration are similar to those of eCT. This can probably be attributed to the third element of the ordered structure of elcatonin which is formed in 15% trifluoroethanol. The solution conformation of elcatonin in a mixture of 60% water and 40% trifluoroethanol has been determined by the combined use of 1H-NMR spectroscopy and distance geometry calculations. The conformation is characterized by an amphiphilic alpha-helix between Thr6 and Thr21, which extends into the constrained cyclic portion of the molecule to Thr6. The third structural element of elcatonin found in the CD analysis is detected by some turn structures in the region between residue 1 and Ser5 in the calculated structure.

[Glaucoma with Axenfeld-Rieger syndrome in three generations. Aqueous humor dynamics]

A 21-year-old woman was diagnosed as having glaucoma associated with Axenfeld-Rieger syndrome. Her family was examined and 3 additional patients with Axenfeld-Rieger syndrome were found in three generations. All of them had glaucoma with various types of onset. Aqueous humor dynamics were studied in 5 eyes of 3 patients using fluorophotometry. The basic secretion of aqueous humor in 5 eyes was 4.18 +/- 1.13 microliter/min. Averaged uveoscleral outflow in 3 eyes with low transtrabecular outflow facility was 61% of total aqueous outflow. It appeared that uveoscleral outflow was increased to compensate for the impaired transtrabecular outflow route.

In vivo rodent erythrocyte micronucleus assay

The following summary represents a consensus of the working group except where noted. The items discussed are listed in the order in which they appear in the OECD guideline (474) for easy reference. Introduction, purpose, scope, relevance, application and limits of test. The analysis of immature erythrocytes in either bone marrow or peripheral blood is equally acceptable for those species in which the spleen does not remove micronucleated erythrocytes. In the mouse, mature erythrocytes are also an acceptable cell population for micronucleus analysis when the exposure duration exceeds 4 weeks. Test substances. Organic solvents such as DMSO are not recommended. Freshly prepared solutions or suspensions should be used unless stability data demonstrate the acceptability of storage. Vegetable oils are acceptable as solvents or vehicles. Suspension of the test chemicals is acceptable for p.o. or i.p. administration but not for i.v. injection. The use of any unusual solvent should be justified. Selection of species. Any commonly used laboratory rodent species is acceptable. There is no strain preference. Number and sex. The size of experiment (i.e., number of cells per animal, number of animals per group) should be finalized based on statistical considerations. Although a consensus was not achieved, operationally it was agreed that 2000 cells per animal and four animals per group was a minimum requirement. In general, the available database suggests that the use of one gender is adequate for screening. However, if there is evidence indicating a significant difference in the toxicity between male and female, then both sexes should be used. Treatment schedule. No unique treatment schedule can be recommended. Results from extended dose regimens are acceptable as long as positive. For negative studies, toxicity should be demonstrated or the limit dose should be used, and dosing continued until sampling. Dose levels. At least three dose levels separated by a factor between 2 and square root of 10 should be used. The highest dose tested should be the maximum tolerated dose based on mortality, bone marrow cell toxicity, or clinical symptoms of toxicity. The limit dose is 2 g/kg/day for treatment periods of 14 days or less and 1 g/kg/day for treatment periods greater than 14 days. A single dose level (the limit dose) is acceptable if there is no evidence of toxicity. Controls. Concurrent solvent (vehicle) controls should be included at all sampling times. A pretreatment sample, however, may also be acceptable only in the short treatment period peripheral blood studies. A concurrent positive control group should be included for each experiment.(ABSTRACT TRUNCATED AT 400 WORDS)

Circulatory collapse and sudden death in respirator-dependent amyotrophic lateral sclerosis

Circulatory collapse and sudden death was defined retrospectively as one of the major critical problems among 23 respirator-dependent patients with amyotrophic lateral sclerosis (ALS). Six cases died from sudden cardiac arrest or anoxic encephalopathy following the circulatory collapse. In five among the six cases, sudden death or cardiac arrest occurred during sleep at night. Eight cases had had episodes of marked fluctuation of blood pressure before death, including paroxysmal elevation of blood pressure and heart rate, and successive sudden pressure fall without compensatory tachycardia. The spells of hypotension often occurred during sleep. In addition, the prospective study of diurnal variation of blood pressure, heart rate, plasma norepinephrine and plasma renin activity in nine respirator-dependent ALS patients showed continuous tachycardia and more remarkable nocturnal decrease of blood pressure compared with the control subjects. Plasma norepinephrine levels were constantly higher in the ALS patients particularly in a daytime. These indicate the continuous sympathetic hyperactivity in ALS. We discuss the cause of the circulatory collapse and sudden death in the respirator-dependent ALS patients in terms of the autonomic dysregulatory mechanism or the sympathetic hyperactivity.

Re-examination of arousing and de-arousing effects of cigarette smoking

An attempt was made to replicate arousing and de-arousing effects of cigarette smoking originally reported by Golding and Mangan. Changes in electrodermal activity, heart rate, and magnitude in the EEG alpha (7.5-11.5 Hz) and beta (13.5-20 Hz) bands were measured under conditions of both mild sensory isolation as well as stress induced by loud white-noise. Under both conditions, real smoking as well as sham smoking an unlit cigarette increased beta activity and the skin potential response. In contrast, only real smoking produced a significant increase in heart rate, decrease in alpha activity, and increase in skin potential. De-arousing effects reported by Golding and Mangan for white-noise stress were not replicated.

Isolation of micronuclei from mouse blood and fluorescence in situ hybridization with a mouse centromeric DNA probe

Spontaneously existing and chemically induced micronuclei were isolated from mouse blood. 50 microliters of cardiac blood was diluted with PBS and centrifuged. After this, the cell pellet was subjected to hypotonic treatment, fixed with acetic acid-methanol (1:3), and the lysate was filtrated through a 2-microns polycarbonate nucleopore membrane. Isolated micronuclei were air-dried on a glass slide and subjected to fluorescence in situ hybridization (FISH) using a mouse centromeric gamma satellite probe. Approximately half of the micronuclei isolated from vehicle control mice showed centromere signal(s). In these preliminary studies, the proportion of centromere-positive micronuclei was increased by treatment with spindle poisons (colchicine and vinblastine sulfate), decreased only slightly by 1-beta-D-arabinofuranosylcytosine, and was generally unaffected by mitomycin C.

De novo design and creation of a stable artificial protein

Protein de novo design has been performed, as an exercise of the inverse folding problem. A beta/alpha-barrel protein was designed and synthesized using the Escherichia coli expression system for the structural characterization. A tertiary model with a two-fold symmetry was built, based upon the geometrical parameters extracted from X-ray crystal structures of several beta/alpha-barrel proteins. Amino acid frequencies at each position on the alpha- and beta-structures were investigated, and an amino acid sequence with 201 residues was designed. The associated gene was chemically synthesized and the fusion protein with human growth hormone was expressed in Escherichia coli. The purified protein after being cleaved and refolded was found to be stable and globular with the large amount of secondary structures. However, it has similar characteristics to the molten globules of natural proteins, with loose packing of side-chains. The approach for the tight packing is discussed.

[Polygraphical sleep study on typical absence: relationship between the effect of sodium valproate and nigrostriatal function]

In order to clarify the mechanism of the effect of sodium valproate (VPA) on absence seizures, we performed sleep polygraph recordings in 10 patients with typical absence. VPA was effective in six cases (group A), partially effective in two (group B), and ineffective in two (group C). In 5 of 9 cases, the tonic sleep components were abnormal. In 4 cases, the percentage of slow wave sleep increased before administration of VPA, and did not change remarkably by its administration. In group A and B, twitch movements (TM), one of the phasic sleep components detected in the mentalis muscle on surface EMG, decreased or were unchanged after administration of VPA, especially during the REM period. In contrast, TM increased in group C. We speculate that the changes of TM (especially in the REM periods) after administration of VPA are well related to its effectiveness. Since TMs are thought to be controlled by the nigrostriatal dopaminergic pathway, the different response of basal ganglia to VPA among cases with absence epilepsy would have some relation to the different effectiveness of VPA in controlling seizures.

[Detection of right-to-left shunt flow in atrial septal defect using transesophageal color and pulsed Doppler echocardiography]

The clinical significance of right-to-left (R-L) shunt flow dynamics in atrial septal defects (ASD) were investigated using transesophageal color and pulsed Doppler echocardiography in 30 patients with ASD of the ostium secundum type, including 20 with systolic pulmonary artery pressures (sPA) less than 40 mmHg, 4 with sPA of 40 to 60 mmHg, 3 with sPA of 90 mmHg or greater, 2 with pulmonic stenosis and 1 with Ebstein's anomaly. R-L shunting was detected by a shunt flow signal across the defect during a cardiac cycle. The timing of the R-L shunt was compared with various parameters obtained by echocardiography or cardiac catheterization. R-L shunt flow at the onset of ventricular contraction or closing phase of the tricuspid valve was detected in five patients with isolated ASD associated with increased mean right atrial pressure, but no severe pulmonary hypertension. R-L shunt flow during systole was detected in five of 26 patients with isolated ASD and tricuspid regurgitation and in one patient with Ebstein's anomaly. The tricuspid regurgitation signals in three of the five patients were directed toward the defect, while the other two had massive tricuspid regurgitation. R-L shunt flow during mid-diastole was detected in three patients without pulmonary hypertension. Massive left-to-right shunt flows occurred during the phase from end-systole to early diastole. R-L shunt flow during atrial systole was detected in three patients with severe pulmonary hypertension and two with pulmonic stenosis. The severe pulmonary hypertension patients, in particular, showed the aliasing signal as a high speed shunt flow, and in two of these, R-L shunt flow continued from atrial systole to early ventricular systole, and was also observed in early diastole. R-L shunt flow was detected in ASD patients with and without pulmonary hypertension, and was influenced by right atrial pressure at the phase of tricuspid valve closing, volume or direction of tricuspid regurgitation, rebound flow due to massive left-to-right shunt flow, grade of right ventricular distensibility or pulmonary hypertension, and other cardiac complications.

A null mutation in the human CNTF gene is not causally related to neurological diseases

We report a null mutation in the human ciliary neurotrophic factor gene (CNTF). The mutated allele shows a G to A transition producing a new splice acceptor site and the resulting mRNA species codes for an aberrant protein. Analysis of tissue samples and transfection of CNTF minigenes into cultured cells demonstrates that the mutated allele expresses only the mutated mRNA species. In 391 Japanese people tested, 61.9% were normal homozygotes, 35.8% heterozygotes and 2.3% mutant homozygotes. The distribution of the three genotypes is similar in healthy and neurological disease subjects, indicating that human CNTF deficiency is not causally related to neurological diseases.

Comparison of absorption-enhancing effect between sodium caprate and disodium ethylenediaminetetraacetate in Caco-2 cells

The effects of sodium caprate (C10) and disodium ethylenediaminetetraacetate (EDTA) on the epithelial permeability of polyethylene glycol 4000 (PEG4000) were examined in Caco-2 cell monolayers on the polycarbonate membrane (filter) of a Transwell cluster dish. Under serosal Ca(2+)-free conditions irrespective of the presence or absence of mucosal Ca2+, the permeability of PEG4000 was remarkably enhanced, even in the absence of enhancer. For control experimental conditions with a permeation enhancer in Caco-2 cells, Ca2+ was added to both the mucosal and serosal sides. Under the control conditions, EDTA increased the permeability of PEG4000 to 14 times the control and C10 by 3.5 times. Mucosal Ca(2+)-free conditions further increased the EDTA-enhancing effect, to 29 times the control value. In contrast to the EDTA effect, however, the C10 effect was unchanged in the absence of mucosal Ca2+. These results suggest that the EDTA effect is induced by chelation with Ca2+ but that C10 has some other action in addition to chelation.

Pressure promotes DNA synthesis in rat cultured vascular smooth muscle cells

High blood pressure is one of the major risk factors for atherosclerosis. In this study, we examined the effects of pressure on cell proliferation and DNA synthesis in cultured rat vascular smooth muscle cells. Pressure without shear stress and stretch promotes cell proliferation and DNA synthesis in a pressure-dependent manner. Pressure-induced DNA synthesis was inhibited significantly by the phospholipase C (PLC) inhibitor 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate, the protein kinase C inhibitor H-7, 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine, staurosporine, and the tyrosine kinase inhibitor ([3,4,5-trihydroxyphenyl]methylene)propanedinitrile. To clarify whether activation of PLC and calcium mobilization are involved in pressure-induced DNA synthesis, production of 1,4,5-inositol trisphosphate (IP3) and intracellular Ca2+ was measured. Pure pressure increased IP3 and intracellular Ca2+ in a pressure-dependent manner. The increases in both IP3 and intracellular Ca2+ were inhibited significantly by 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate. This study demonstrates a novel cellular mechanism whereby pressure regulates DNA synthesis in vascular smooth muscle cells, possibly via activation of PLC and protein kinase C.

[Sevoflurane anesthesia for a patient with facioscapulohumeral muscle dystrophy]

We gave anesthesia to a patient with facioscapulohumeral muscle distrophy (FSHMD). Patient was an 18 year old male, having no peculiar complaint and without family history nor past history relating to FSHMD. The restriction of right arm lifting was pointed out in medical examination. Diagnosis of FSHMD was made by muscle biopsy. The thoraco-scapula fixation was scheduled. Four hours prior to the induction, dantrolene 50 mg was administered per os. Before the induction, to estimate the effect of neuromuscular blockade, we applied Datex Relaxograph to the upper and lower extremities. Anesthesia was induced with thiamylal 200 mg and vecuronium 4 mg, and maintained with sevoflurane and nitrous oxide monitoring ETCO2. The time for the onset of muscular relaxation after the administration of vecuronium was quite different between upper and lower extremities (200 sec. and 407 sec.). Neostigmine and atropine for the reversal of neuromuscular blockade was administered evaluating the extent of neuromuscular relaxation obtained from Datex Relaxograph. We concluded that Relaxograph is essential as a monitor of muscular relaxation, especially in the case of neuromuscular disease.

New sublines of Chinese hamster CHL stably expressing human NAT1 or NAT2 N-acetyltransferases or Salmonella typhimurium O-acetyltransferase: comparison of the sensitivities to nitroarenes and aromatic amines using the in vitro micronucleus test

New sublines of Chinese hamster CHL cells stably expressing human NAT1 or NAT2 N-acetyltransferases or O-acetyltransferase of Salmonella typhimurium were established, and their sensitivities to carcinogenic nitroarenes and aromatic amines were compared using the in vitro micronucleus test. The subline expressing human NAT2 N-acetyltransferase exhibited the highest sensitivity to the clastogenicities of 1,8-dinitropyrene and 2-nitrofluorene. These results raise the possibility that human NAT2 N-acetyltransferase is involved in the metabolic activation of 1,8-dinitro-pyrene and 2-nitrofluorene. Since human NAT2 N-acetyltransferase exhibits a marked genetic polymorphism, the polymorphic status of human N-acetyltransferase could be a genetic predisposing factor to cancers caused by the nitroarenes. In contrast, the subline expressing O-acetyltransferase of S. typhimurium exhibited the highest sensitivity to the clastogenicity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) when the microsomes prepared from rat liver were present. This suggests that O-acetyltransferase of S. typhimurium has a higher ability to activate IQ than do the human acetyltransferases. Acetyltransferase enzymes of human enteric bacteria might contribute to the metabolic activation of IQ. The sublines could provide a new tool for investigation of the mechanism of metabolic activation and for assessment of cancer risk of nitroarenes and aromatic amines to humans.

Enhancement of mRNA synthesis from Marek's disease virus genome in the lymphoblastoid cell line, MDCC-MSB1, by 5-azacytidine

Marek's disease virus (MDV) DNA in latently infected lymphoblastoid cell lines is considerably methylated. A treatment of the MDV-derived lymphoblastoid cell line, MDCC-MSB1 (MSB1), with 5-azacytidine (5-AzC) resulted in a hypomethylation of MDV DNA and an increase in mRNA from certain portions of the MDV DNA. These results suggest methylation of MDV DNA as being one of the factors associated with a repression of transcription of MDV DNA in the lymphoblastoid cell line, MSB1.

Flow-cytometric analysis of in vivo induction of differentiation of WEHI-3B myelomonocytic leukemia cells by recombinant granulocyte colony-stimulating factor

An animal leukemia model was developed to investigate in vivo induction of differentiation of myeloid leukemia cells. An aneuploid cell line (C15) was isolated from mouse myelomonocytic leukemia WEHI-3B D+ cells. The C15 cells contained twice as much DNA as the parental cells but retained the morphology of myelomonocytic cells and the ability to differentiate into macrophage-like cells in response to all-trans retinoic acid (ATRA) in vitro. When the C15 cells were inoculated into the peritoneal cavity of syngeneic Balb/c mice (10(6) cells/mouse), the mice died of leukemia within 19 days. The DNA content and differentiation antigen (Mac-1) of the cells in the peritoneal cavity were determined by dual-parameter flow cytometry. On day 12 after inoculation, the C15 cells were distinguishable from normal host cells in the peritoneal cavity by their different DNA content. The administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF) (10 micrograms/day) to mice bearing C15 cells induced the leukemia cells to express Mac-1 antigen and to change morphologically into mature granulocytic cells. Because the C15 cells were not responsive to G-CSF in suspension culture in vitro, this result suggests that the cytokine's actions on the cells in vivo and in vitro are different. This experimental model for analyzing in vivo differentiation of leukemia cells will be useful for studying the therapeutic effects of potential differentiation-inducing agents.

Fimbria-specific immune response in various inbred mice inoculated with Porphyromonas gingivalis 381

We studied the genetic control of Porphyromonas gingivalis fimbriae response. Inbred mice with different H-2 haplotypes and/or different genetic backgrounds were inoculated with viable P. gingivalis 381 cells and tested for fimbria-specific T cell responses in vivo (delayed-type hypersensitivity). H-2d mice showed a strong footpad response, whereas H-2b mice showed a weak response to fimbriae from P. gingivalis. Similar evidence of genetic control was obtained with an enzyme-linked immunosorbent assay for the detection of IgG antibody in inbred mice (BALB/c, C3H/HeN and C57BL/6). Several immunoglobulin G (IgG) subclass responses were associated with H-2 in these B10 congenic mice. However, quantification of IgG antibody to fimbriae was not controlled by H-2 in B10 congenic mice. The results indicate that, in mice, the responsiveness to fimbriae of P. gingivalis can be controlled by several genes, including the H-2 complex. C3H/HeN mice were inoculated with the fimbriae intravenously, and the expression of surface antigens on spleen T cells was measured in a fluorescent antibody cell sorter. Stimulation by fimbriae resulted in a changed expression of surface antigens on T cells. Thus, the fimbriae can induce T cell activation.

Both antisense and sense RNAs against the nucleocapsid protein gene inhibit the multiplication of mouse hepatitis virus

DBT cells and several transfected cell lines which express antisense or sense RNA against the nucleocapsid protein gene of mouse hepatitis virus (MHV) were examined for the yields of MHV. The transfected cells showed 95 and 99% reduction of virus yield at 9 and 12 hr postinfection (p.i.) as compared with untransfected DBT cells. A remarkable decrease in MHV-specific RNA synthesis was observed in both transfected cell lines at 3.5 hr p.i. The result suggested that both antisense and sense RNAs inhibited viral replication at the initial stage of infection.

Age-related changes in nerve growth factor receptor immunoreactive neurons in the magnocellular basal forebrain system in rat brain--an immunocytochemical and morphometric study

Morphometrical changes with aging in nerve growth factor receptor (NGFR) immunoreactive neurons in the basal forebrain were studied in juvenile and aged rat brains by means of NGFR immunohistochemistry. The nucleus basalis of Meynert (NBM) had cell loss and atrophy of NGFR immunoreactive neurons, and the horizontal nucleus of diagonal band of Broca (HNDB) showed only atrophy of these neurons. The medial septal nucleus and vertical nucleus of diagonal band of Broca had no significant change. Neuropil NGFR immunostaining was reduced in its intensity in the aged rats. As nerve growth factor is synthesized in the target areas and retrogradely transported to the nerve cell body within the basal forebrain and NGFR immunoreactive neurons are largely cholinergic ones, degeneration of NGFR-positive neurons in the basal forebrain may be related to a decreased cholinergic activity. The degeneration of the dendrites of NGFR-immunoreactive neurons were reported to be extensively found in the basal forebrain nuclei, in contrast, degeneration of the cell body of NGFR-immunoreactive neurons was confined to those in the NBM and HNDB in the present study. These findings suggest that atrophic changes in the dendrites precede those in the cell bodies of NGFR-immunoreactive neurons.

Transport of low and high molecular peptides across rabbit Peyer's patches

The permeability of peptides across rabbit jejunal epithelium (JE) and Peyer's patches (PP) was compared. Kyotorphin (L-tyrosyl-L-arginine) was almost completely hydrolyzed during its membrane transport in both PP and JE, but [D-Arg2]Kyotorphin (L-tyrosyl-D-arginine) was less hydrolyzed in PP than in JE. Since the permeability of intact [D-Arg2]Kyotorphin was almost equal in PP and JE, no superiority of PP to JE was found for dipeptide transport. More intact fluorescein isothiocyanate (FITC)-labeled bovine serum albumin (FITC-BSA) and concanavalin A (FITC-Con A) were transported in PP than in JE. At both absorption sites, the transport of the intact FITC-Con A was superior to that of the intact FITC-BSA. Colchicine significantly reduced the total transport of the intact and degradation forms of both peptides and the reduction ratio was greater in PP than in JE. Accordingly, it was suggested that PP can be used as prominent absorption sites for polypeptides since they have lower peptidase activity and higher endocytosis activity than JE.

Radiation hypersensitivity of LEC strain rats controlled by a single autosomal recessive gene

LEC strain rats (LEC rats), which are known to develop hereditarily spontaneous fulminant hepatitis 4-5 months after birth, were highly sensitive to whole-body X-irradiation when compared to WKAH strain rats. The radiosensitivity of F1 hybrids of LEC and WKAH rats was similar to that of WKAH rats and significantly lower than that of LEC rats. Segregation data of backcross hybrids (F1 x LEC and LEC x F1) suggested that the hypersensitivity of LEC rats to whole-body irradiation is controlled by a single autosomal recessive gene. The radiosensitivity of fibroblasts from LEC rats was higher than that of fibroblasts from WKAH rats. The repair process of DNA double-strand breaks in LEC cells was slower than that in WKAH cells. LEC rats could provide a useful animal model to assist in understanding the mechanism of radiation-induced DNA damage and repair.

The role of S-mephenytoin 4'-hydroxylase in imipramine metabolism by human liver microsomes: a two-enzyme kinetic analysis of N-demethylation and 2-hydroxylation

1. The metabolism of imipramine (N-demethylation and 2-hydroxylation) was studied in relation to the activity of S-mephenytoin 4'-hydroxylase in human liver microsomes. 2. Eadie-Hofstee plots for the formation of despiramine and 2-hydroxyimipramine were biphasic, suggesting that at least two enzymes are involved in both the N-demethylation and 2-hydroxylation of imipramine by human liver microsomes. 3. The respective mean (+/- s.d.) kinetic parameters for the N-demethylation and 2-hydroxylation of imipramine derived from a two-enzyme kinetic analysis were: Km1 = 1.1 +/- 0.4 and 1.6 +/- 0.6 microM, Vmax1 = 0.11 +/- 0.03 and 0.15 +/- 0.07 nmol mg-1 min-1, and Vmax1/Km1 = 0.10 +/- 0.02 and 0.09 +/- 0.04 ml mg-1 min-1; Km2 = 214 +/- 84 and 257 +/- 148 microM, Vmax2 = 2.22 +/- 0.69 and 0.53 +/- 0.15 nmol mg-1 min-1, and Vmax2/Km2 = 0.011 +/- 0.001 and 0.003 +/- 0.002 ml mg-1 min-1. 4. With regard to imipramine N-demethylation and 2-hydroxylation at 2 microM (representing high-affinity reactions) and at 400 microM (representing low-affinity reactions), only N-demethylation at 2 microM showed a close correlation with the 4'-hydroxylation of S-mephenytoin (rs = 0.952, P < 0.01; n = 10 livers). 5. Concentrations up to 250 microM S-mephenytoin inhibited the N-demethylation of imipramine (2 microM), but no further inhibition was observed using concentrations from 250 to 750 microM. 6. Imipramine inhibited S-mephenytoin 4'-hydroxylation competitively with a Ki value of 12.5 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of a de novo designed protein

A series of 204 amino acid proteins intended to form TIM (triose phosphate isomerase) barrel structures were designed de novo. Each protein was synthesized by expression of the synthetic gene as a fusion protein with a portion of human growth hormone in an Escherichia coli host. After BrCN treatment, the protein was purified to homogeneity. The refolded proteins are globular and exist as monomers. One of the designed proteins is stable toward guanidine hydrochloride (GuHCl) denaturation, with a midpoint of 2.6 M determined from CD and tryptophan fluorescence measurements. The GuHCl denaturation is well described by a 2-state model. The NMR spectra, the thermal denaturation curves, and the 1-anilino-8-naphthalene sulfonic acid binding imply that the stability of the protein arises mainly from hydrophobic interactions, which are probably of a nonspecific nature. The protein has a similar shape to that of rabbit triosephosphate isomerase, as determined by electron microscopy.