Pharmacological studies on the novel antiallergic agent HSR-609: its effects on behavior in mice and electroencephalograms in rabbits

We studied the central nervous system (CNS) effects of HSR-609 (3-[4-(8-fluoro-5,11-dihydrobenz[b]oxepino[4,3-b]pyridin-11- ylidene) piperidino]propionic acid dihydrate), a novel amphoteric antiallergic agent having antihistaminic activity. Its effects on the behavior of mice and the electroencephalograms (EEG) of unanesthetized and unrestrained rabbits after oral administration were compared with those of typical antiallergic agents and the non-amphoteric basic compound PY-608 (8-fluoro-5,11-dihydro-11-(1-methyl-4-piperidylidene)benz [b]oxepino[4,3-b]pyridine), which has chemical structure similar to that of HSR-609. HSR-609 (3-300 mg/kg) had no effect on general behavior, spontaneous locomotor activity, hexobarbital-induced sleeping time and reserpine-induced hypothermia in mice. HSR-609 (10-100 mg/kg) and terfenadine (100 mg/kg) had no effect on spontaneous EEG, sleep-wakefulness cycles and EEG power spectra in rabbits. On the other hand, cyproheptadine (3-30 mg/kg), ketotifen (30-100 mg/kg) and PY-608 (0.3-100 mg/kg) caused increases and/or decreases of spontaneous locomotor activity, prolongation of hexobarbital-induced sleeping time and antagonistic effects on reserpine-induced hypothermia in mice. These agents (30 mg/kg) increased slow wave sleep and enhanced EEG power spectra at low frequency bands such as delta and theta in rabbits. These findings suggest that HSR-609 has no inhibitory effect on the CNS due to its amphoteric chemical structure.

Gabor-based Coding and Facial Similarity Perception

Little is known about how facial representation in the face-selective areas of inferotemporal cortex is built up from the output of earlier visual areas such as primary visual cortex (area V1). We report work on a model of perceived facial similarity based on topographically ordered aggregates of localised, oriented, and spatial-frequency-selective receptive fields characteristic of V1 cells. The receptive fields are approximated with a set of Gabor filters. This Gabor-based code allows representation of the fine differences in texture and configuration needed for facial discrimination processes. Lyons and Morikawa (1996 Investigative Ophthalmology and Visual Science37 910), showed that Gabor-based similarity is a good predictor of facial similarity for comparisons of fairly similar faces but not sufficient to model experience-dependent effects such as the ‘other race effect’.

Here we report results of a study on the effects of image negation on facial similarity perception. Negation of image gray levels interferes with face recognition (Bruce and Lanton, 1994 Perception23 803 – 822) while preserving 2-D facial-shape information. The Gabor similarity measure models non-endstopped complex cells of V1 and is not affected by image negation. One group of subjects judged similarity among a set of normal gray-scale facial images while another group judged similarity between negative images of the same stimuli. Agreement between the model and human subjects did not decrease with image negation. Moreover, human similarity ratings between negative faces were strongly correlated with those between positives. These results support Gabor-based similarity as a model for facial similarity perception.

Peripheral Advantage in Texture Segmentation: The Role of Spatial and Temporal Factors

Previous studies (eg Kehrer, 1989 Spatial Vision4 45 – 62; Gurnsey et al, 1996 Journal of Experimental Psychology: Human Perception and Performance22 738 – 757) have shown that performance peaks several degrees from fixation in texture segmentation tasks, and performance falls as the target texture moves closer to the fovea or further into the periphery. There are two theories for this phenomenon: (1) neural processing speed in the fovea is slower than in the periphery (Kehrer 1989), and (2) the spatial frequency band of the texture is too low (ie too coarse) for the foveal receptive fields (Gurnsey et al 1996). However, the use of backward masking in previous studies made it impossible to decide between the two factors. The purpose of the present study was to isolate them.

In experiment 1 a new stimulus configuration with backward masking was used, and previous reports were replicated. In experiment 2, the same texture was presented for 110 ms without a mask, but with added random-dot noise. Without limitations on processing time, the mid-peripheral advantage disappeared, which indicated that the previous findings were due to slower neural processing in the fovea. In experiment 3, a new type of texture was devised consisting of pairs of vertical lines with a horizontal offset. The offset was reversed for the target. Performance for unmasked 110 ms presentation was worst near the fovea and improved monotonically up to 12 deg. This peripheral advantage was spatial, not temporal, because it arose from larger receptive field sizes in periphery. When these results are taken together, the present study demonstrates that there are two independent causes for the mid-peripheral advantage in texture segregation.

Studies on the novel antiallergic agent HSR-609: its penetration into the central nervous system in mice and guinea pigs and its selectivity for the histamine H1-receptor

We studied the pharmacological characteristics of HSR-609 (3-[4-(8-fluoro-5,11-dihydrobenz[b]oxepino[4,3-b]pyridin-11- ylidene)- piperidino]propionic acid dihydrate), a novel amphoteric antiallergic agent, on the central nervous system (CNS). Its selectivity for the histamine H1-receptor and its ability to penetrate into the CNS were compared with those of typical antiallergic agents and the nonamphoteric basic compound PY-608 (8-fluoro-5,11-dihydro-11-(1-methyl-4-piperidylidene)benz[b]oxe pino- [4,3-b]pyridine), which has a chemical structure similar to that of HSR-609. In the in vitro study, HSR-609 had a high affinity for H1-receptors in the guinea pig cerebral cortex in comparison to affinities for muscarinic and serotonin 5-HT2-receptors in the rat cerebral cortex, while the selectivity of PY-608 for the H1-receptor was low. The inhibitory effects of these antiallergic agents on histamine-induced increase of vascular permeability in mice (ED50) were compared with the displacement of [3H]mepyramine binding to H1-receptors in mouse brain ex vivo (ID50). The ID50/ED50 ratio of HSR-609 was much larger than those of cyproheptadine, ketotifen and PY-608 and larger than those of terfenadine and cetirizine. HSR-609 was found to display selective displacement of the [3H]mepyramine binding to H1-receptors for lung vs cerebral cortex as found with terfenadine in guinea pigs ex vivo. These findings suggest that HSR-609 has high selectivity for the H1-receptor and poor ability to penetrate into the CNS in mice and guinea pigs due to its amphoteric chemical structure.

Strain-gauge force transducer method for evaluating urethral motility in conscious dogs

A new method has been developed that is suitable for physiological studies of urethral motility in the conscious state with a strain-gauge force transducer (force transducer). In anesthetized dogs, the contractile or relaxing responses of the urethral smooth muscle in the direction of the circular layers measured with the force transducer, elicited by either phenylephrine or isoproterenol, were significantly correlated to the increase or decrease in the intra-urethral pressure (r = 0.998 and 0.780, respectively). In conscious dogs, the fluctuation in the urethral tone was observed to be less than in the intra-urethral pressure, and a dose-dependent response to phenylephrine (1-30 micrograms./kg. i.v.) and isoproterenol (0.1-3 micrograms./kg. i.v.) was clearly recognized. Moreover, this conscious model provided a fairly reproducible pattern with the urethral contraction or relaxation related to the filling or voiding phase of the cystometrogram, which was abolished by anesthetization. These results indicate that the present force transducer method makes it possible to evaluate the further physiological characteristics of urethral motility in conscious dogs.

DNA-repair enzymes

Recent crystallographic studies of DNA-repair enzymes have provided the structural basis for the recognition of damaged DNA. The results imply that flipping out of the base is a common and crucial event in DNA repair. Two classes of repair enzymes that recognize distinct types of damage may exist. DNA-repair enzymes that share similar folds and DNA binding motifs have been proposed to belong to a superfamily.

Circular dichroism analysis of the interaction between the alpha and beta subunits in a killer toxin produced by a halotolerant yeast, Pichia farinosa

SMK toxin is a killer toxin produced by a halotolerant yeast, Pichia farinosa. It is a heterodimer consisting of alpha (63 aa) and beta (77 aa) subunits, between which no disulfide bond exists. The two subunits interact tightly with each other below pH 5. However, the subunits dissociate under neutral conditions, resulting in the aggregation of the alpha subunit and the concomitant loss of killer activity. CD spectral measurements showed that the secondary structure of the SMK toxin changes drastically in the pH range 5.1-5.5 and that after the dissociation of the subunits, the soluble beta subunit alone cannot take any secondary structure. It was also shown that the concentration of NaCl does not affect the secondary structure of the SMK toxin.

The novel acidophilic structure of the killer toxin from halotolerant yeast demonstrates remarkable folding similarity with a fungal killer toxin

BACKGROUND

Several strains of yeasts and fungi produce proteinous substances, termed killer toxins, which kill sensitive strains. The SMK toxin, secreted by the halotolerant yeast Pichia farinosa KK1 strain, uniquely exhibits its maximum killer activity under conditions of acidic pH and high salt concentration. The toxin is composed of two distinct subunits, alpha and beta, which tightly interact with each other under acidic conditions. However, they are easily dissociated under neutral conditions and lose the killer activity. The three-dimensional structure of the SMK toxin will provide a better understanding of the mechanism of toxicity of this protein and the cause of its unique pH-dependent stability.

RESULTS

Two crystal structures of the SMK toxin have been determined at 1.8 A resolution in different ionic strength conditions. The two subunits, alpha and beta, are jointly folded into an ellipsoidal, single domain structure belonging to the alpha/beta-sandwich family. The folding topology of the SMK toxin is essentially the same as that of the fungal killer toxin, KP4. This shared topology contains two left-handed split betaalphabeta motifs, which are rare in the other proteins. Many acidic residues are clustered at the bottom of the SMK toxin molecule. Some of the carboxyl sidechains interact with each other through hydrogen bonds. The ionic strength difference induces no evident structural change of the SMK toxin except that, in the high ionic strength crystal, a number of sulfate ions are electrostatically bound near the basic residues which are also locally distributed at the bottom of the toxin molecule.

CONCLUSIONS

The two killer toxins, SMK and KP4, share a unique folding topology which contains a rare structural motif. This observation may suggest that these toxins are evolutionally and/or functionally related. The pH-dependent stability of the SMK toxin is a result of the intensive interactions between the carboxyl groups. This finding is important for protein engineering, for instance, towards stabilization of the toxin molecule in a broader pH range. The present crystallographic study revealed that the structure of the SMK toxin itself is hardly affected by the ionic strength, implying that a high salt concentration affects the sensitivity of the cell against the toxin.

Strength recovery in fractured sheep tibia treated with a plate or an internal fixator: an experimental study with a two-year follow-up

OBJECTIVES

Comparison of fracture healing with two different implants: a conventional Dynamic Compression Plate (DCP) and a new internal Point Contact Fixator (PC-Fix).

DESIGN

Randomized, prospective study in experimental animals. Observation times: 12, 24, 48 and 96 weeks, with six sheep per group.

SETTING

Following surgery, animals were kept with unrestricted weight-bearing in individual stalls for 12 weeks, thereafter in groups.

ANIMALS

56 adult Swiss mountain sheep.

INTERVENTION

A standardized oblique fracture of the sheep tibia was reduced and compressed by a lag screw and "neutralized" with one of the implants.

MAIN OUTCOME MEASUREMENTS

Standard radiographs were used for callus size measurements. After sacrifice the implant was removed and both the treated bone and the contralateral bone were tested for static strength in bending with the plate side under tension. Broken bones were processed for histological evaluation.

RESULTS

In the DCP group all six bones failed through the original fracture at 12 weeks. At 24 and 48 weeks two out of six, at 96 weeks one out of six bones failed through the original fracture, others through one of the screw holes. In the PC-Fix group there were no failures through the original fracture with a single exception at 96 weeks. The strength values in the PC-Fix groups of 12 and 96 weeks were significantly higher then in the corresponding DCP groups.

CONCLUSIONS

Healing of simple diaphysial fractures treated by PC-Fix was superior to that achieved by conventional plating. The histological evaluation suggested that the observed differences can be accounted for by the absence of implant-related cortical necrosis and by the circumferentially uninterrupted (if smaller) callus in the PC-Fix group.

Crystallization and preliminary X-ray diffraction studies of a novel killer toxin from a halotolerant yeast Pichia farinosa

A killer toxin from a halotolerant yeast, Pichia farinosa strain KK1, was crystallized at high- and low-salt concentrations. Crystals from the high-salt solution belonged to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell dimensions of a = b = 81.10, c = 118.46 A. The low-salt solution provided crystals that belonged to the same space group, with nearly same cell dimensions. Preliminary diffraction studies showed that the intensity distributions are significantly different between the two crystals. Both types of crystals contained either two or three molecules per asymmetric unit. They diffracted X-rays beyond 2.0 A resolution and were stable to X-ray irradiation.

Precluding uracil from DNA

Two enzymes, dUTP pyrophosphatase and uracil-DNA glycosylase, prevent the misincorporation of uracil into the genome in distinct manners. The atomic structures of these proteins complexed with substrate analogs reveal the structural basis for uracil recognition and suggest a novel mechanism of DNA repair.

Structure of a replication-terminator protein complexed with DNA

The crystal structure of the Escherichia coli replication-terminator protein (Tus) bound to terminus-site (Ter) DNA has been determined at 2.7 A resolution. The Tus protein folds into a previously undescribed architecture divided into two domains by a central basic cleft. This cleft accommodates locally deformed B-form Ter DNA and makes extensive contacts with the major groove, mainly through two interdomain beta-strands. The unusual structural features of this complex may explain how the replication fork is halted in only one direction.

Proposal for new catalytic roles for two invariant residues in Escherichia coli ribonuclease HI

Three mutants of Escherichia coli ribonuclease HI, in which an invariant acidic residue Asp134 was replaced, were crystallized, and their three-dimensional structures were determined by X-ray crystallography. The D134A mutant is completely inactive, whereas the other two mutants, D134H and D134N, retain 59 and 90% activities relative to the wild-type, respectively. The overall structures of these three mutant proteins are identical with that of the wild-type enzyme, except for local conformational changes of the flexible loops. The ribonuclease H family has a common active site, which is composed of four invariant acidic residues (Asp10, Glu48, Asp70 and Asp134 in E.coli ribonuclease HI), and their relative positions in the mutants, even including the side-chain atoms, are almost the same as those in the wild-type. The positions of the delta-polar atoms at residue 134 in the wild-type, as well as D134H and D134N, coincide well with each other. They are located near the imidazole side chain of His124, which is assumed to participate in the catalytic reaction, in addition to the four invariant acidic residues. Combined with the pH profiles of the enzymatic activities of the two other mutants, H124A and H124A/D134N, the crystallographic results allow us to propose a new catalytic mechanism of ribonuclease H, which includes the roles for Asp134 and His124.

The 1.8-A X-ray structure of the Escherichia coli PotD protein complexed with spermidine and the mechanism of polyamine binding

The PotD protein from Escherichia coli is one of the components of the polyamine transport system present in the periplasm. This component specifically binds either spermidine or putrescine. The crystal structure of the E. coli PotD protein complexed with spermidine was solved at 1.8 A resolution and revealed the detailed substrate-binding mechanism. The structure provided the detailed conformation of the bound spermidine. Furthermore, a water molecule was clearly identified in the binding site lying between the amino-terminal domain and carboxyl-terminal domain. Through this water molecule, the bound spermidine molecule forms two hydrogen bonds with Thr 35 and Ser 211. Another periplasmic component of polyamine transport, the PotF protein, exhibits 35% sequence identity with the PotD protein, and it binds only putrescine, not spermidine. To understand these different substrate specificities, model building of the PotF protein was performed on the basis of the PotD crystal structure. The hypothetical structure suggests that the side chain of Lys 349 in PotF inhibits spermidine binding because of the repulsive forces between its positive charge and spermidine. On the other hand, putrescine could be accommodated into the binding site without any steric hindrance because its molecular size is much smaller than that of spermidine, and the positively charged amino group is relatively distant from Lys 349.

Immunomodulatory effect of recombinant human superoxide dismutase (SOD) on human B lymphocyte function in vitro

Recent investigations demonstrate that B lymphocytes possess an oxygen-generating system which is similar to the phagocytic NADPH-oxidase system. Reduction of nitroblue tetrazolium by stimulated tonsillar B cells is inhibited by superoxide dismutase (SOD). However, the biological significance of the superoxide-generating property of B cells remains to be explored. In this study, we examined the immunomodulatory effect of a recombinant human SOD (rh-SOD) on the activation of human B lymphocytes in vitro. A supplement of rh-SOD in the B cell culture increased the proliferation of unstimulated B cells in the presence of SAC, but not of SAC-preactivated B cells in the presence of cytokines such as IL-2 or IL-4. In addition, rh-SOD enhanced the immunoglobulin generation by B cells at the terminal stage of differentiation. Inactivation of the enzymatic activity of SOD by treatment with anti-SOD antibody abrogated the enhancing effects. These data suggest that the superoxide-generating system in B cells may be involved in the cellular activation process.

Constitutive expression of granulocyte-colony stimulating factor receptor on a human B-lymphoblastoid cell line

The present study demonstrated that a human B-cell line derived from non-Hodgkin's lymphoma. HCF-MLpN. constitutively expressed G-CSF receptor on the cell surface. G-CSF binding to the cell surface was shown by immunofluorescence staining using biotinylated G-CSF preparation and analysed by flow cytometry. Specific binding of G-CSF to the cells was shown by pretreatment with unlabelled G-CSF. In the radioreceptor assay and Scatchard plot analysis using radiolabelled ligand, MLpN cells revealed a single species of binding site with an equilibrium dissociation constant of 167 (153-182) pM and a maximal binding site per cell of 1076 (1044-1116). The G-CSF receptor mRNA transcript was exhibited in the RNA from MLpN cells by reverse transcriptase polymerase chain reaction procedure. [3H]thymidine incorporation and trypan blue exclusion showed that the G-CSF receptor was capable of transducing the growth signal to HCF-MLpN cells. A small fraction of fresh B blasts from six patients with B-cell lymphoma and leukaemia displayed G-CSF binding by two-colour immunofluorescence staining. In contrast, a panel of seven B-cell lines was negative for the binding to biotinylated G-CSF preparation. These results suggest that the phenotype of G-CSF binding may be lost during the culture. The expression of G-CSF receptor in HCF-MLpN cells appeared to be exceptional.

Potent inhibition of spontaneous rhythmic contraction by a novel beta 2-adrenoceptor agonist, HSR-81, in pregnant rat uterus

We examined the effect of HSR-81 ((-)-(R)-alpha-[(tert-butylamino)methyl]-2-chloro-4-hydroxybenzyl alcohol L-tartrate), a newly developed, potent and selective beta 2-adrenoceptor agonist, as well as ritodrine and isoproterenol, on the spontaneous rhythmic contraction in uteri isolated from late pregnant, middle pregnant and non-pregnant (dioestrous and oestrous) rats. The three agonists inhibited the spontaneous rhythmic contraction at all the stages in a concentration-dependent manner. The pD2 value for HSR-81 was greater in late pregnancy than in dioestrus and oestrus. In the uterine preparations of late pregnancy and dioestrus, ICI-118,551 (1-(7-methylindan-4-yloxy)-3-isopropyl-aminobutan-2-ol , a selective beta 2-adrenoceptor antagonist) and atenolol (a selective beta 1-adrenoceptor antagonist) produced a parallel rightward shift of the concentration-response curves for HSR-81. The pKB values for ICI-118,551 and atenolol suggest that the inhibitory effect of HSR-81 was mediated through beta 2-adrenoceptors in the two stages. In the membranes prepared from rat uteri in late pregnancy and dioestrus, the equilibrium dissociation constant for [125I]iodocyanopindolol binding was not significantly different between the two stages. The three beta-adrenoceptor agonists and the two antagonists competed for the specific [125I]iodocyanopindolol binding and the pKi values were not significantly different between the two stages. However, the maximum number of binding sites was significantly greater in late pregnancy than in dioestrus. The configuration of the competition curves and the pKi values for the two antagonists confirmed the fact that these membranes contain predominantly beta 2-adrenoceptor subtype. These results indicate that the potent inhibition of the spontaneous rhythmic contraction by HSR-81 in the pregnant uterus may be due to the increased number of beta 2-adrenoceptors.

Gastroprokinetic effect of a new benzamide derivative itopride and its action mechanisms in conscious dogs

The novel benzamide derivative itopride was assayed for its effect on gastrointestinal motility in conscious dogs when it was administered intraduodenally (i.d.). Gastrointestinal motility was measured by means of chronically implanted force transducers, and itopride at a dose of 10 mg/kg, i.d. or more increased the gastric contractile force during the digestive state. Intraduodenal cisapride, domperidone and metoclopramide also stimulated gastric motility, and their threshold doses were 1, 3 and 1 mg/kg, respectively. Dopamine infusion (1 mg/kg/hr, i.v.) caused the postprandial gastric motility to disappear, but it was immediately restored by itopride at a dose of 3 mg/kg, i.d. With itopride at 1 and 3 mg/kg, i.d., acetylcholine (0.05 mg/kg/min)-induced contractions were greatly enhanced. In addition to its gastric stimulation, itopride at doses of 10-100 mg/kg, p.o. inhibited apomorphine (0.1 mg/kg, s.c.)-induced vomiting in dogs. In conclusion, intraduodenal itopride stimulates gastric motility through both anti-dopaminergic and anti-acetylcholinesterase actions. Its gastroprokinetic threshold dose was as large as 3-10 times those of cisapride, domperidone and metoclopramide. These findings suggest that itopride is an orally active gastroprokinetic with a moderate anti-emetic action.

Modulatory effect of antibiotics on cytokine production by human monocytes in vitro

Some antimicrobial agents have been reported to modify the host immune and inflammatory responses both in vivo and in vitro. Fosfomycin (FOM) and clarithromycin (CAM) have immunomodulatory activity on human lymphocyte function. In the present study, we examined the effects of FOM and CAM on cytokine synthesis by lipopolysaccharide (LPS)-stimulated human monocytes in comparison with that of dexamethasone in vitro. The three drugs demonstrated positive or negative effects on the synthesis of various cytokines by LPS-primed monocytes. They suppressed the synthesis of tumor necrosis factor alpha, interleukin 1 alpha (IL-1 alpha), IL-1 beta, the IL-1 receptor antagonist, and granulocyte-macrophage colony-stimulating factor in a concentration-dependent manner at concentrations between 1.6 and 40 micrograms/ml. On the contrary, the drugs showed different actions on the synthesis of IL-6 and IL-10. Namely, FOM enhanced both IL-6 and IL-10 synthesis, CAM enhanced only IL-10 synthesis, but dexamethasone deeply suppressed the synthesis of both cytokines. These data indicate that antibacterial agents may modify acute-phase inflammatory responses through their effects on cytokine synthesis by monocytes.