Crystal structure of eucaryotic E3, lipoamide dehydrogenase from yeast

The crystal structure of eucaryotic lipoamide dehydrogenase from yeast has been determined by an X-ray analysis at 2.7 (partially at 2.4) A resolution. The enzyme has two identical subunits related by a pseudo twofold symmetry. The tertiary structure is similar to those of other procaryotic enzymes. The active site, consisting of FAD, Cys44, and Cys49 from one subunit and His457' from the other subunit, is highly conserved. This enzyme is directly bound to the core protein E2 of the 2-oxoglutarate dehydrogenase complex, whereas it is bound to the pyruvate dehydrogenase complex through a protein X. The calculated electrostatic potential suggests two characteristic regions for binding with these two proteins.

Morphological analysis of cat masseteric motoneurons after intracellular staining with horseradish peroxidase

Intracellular injection of horseradish peroxidase (HRP) into 58 masseteric motoneurons identified by antidromic activation was performed in cats under pentobarbital anesthesia. Monosynaptic EPSPs were evoked by masseteric nerve stimuli in 52 cells, and were absent in the remaining six cells. The antidromic nature of the evoked spikes was confirmed by IS-SD separation observed at high frequency (50 Hz) stimulation. Motoneurons with monosynaptic excitation from masseter afferents showed IPSPs following stimulation of lingual and inferior alveolar nerves. Motoneurons which did not show monosynaptic excitation from masseter afferents showed no IPSPs from the above nerves. There were no differences in cell size or the number of stem dendrites between motoneurons with and without monosynaptic EPSPs. No recurrent collaterals were observed in any motor axons. Motoneurons with monosynaptic EPSPs were located at all rostrocaudal levels throughout the trigeminal motor nucleus, whereas motoneurons without such EPSPs were encountered only at the middle level. Dendrites of motoneurons with monosynaptic EPSPs did not extend into the medial portion of the nucleus where motoneurons innervating the anterior belly of the digastric muscle were located. In contrast, motoneurons without monosynaptic EPSPs had dendrite branches extending well into the medial part. The results show that there are two subpopulations of masseteric motoneurons that differ in peripheral inputs as well as dendritic morphology.

Induction of growth arrest and cell death by overexpression of the cyclin-Cdk inhibitor p21 in hamster BHK21 cells

p21cip1/waf1/sdi1 is a universal cyclin-Cdk kinase inhibitor that has two functional domains; one binds and inhibits cyclin-Cdk activity and the other binds PCNA and thereby inhibits elongation by DNA polymerase. When transiently expressed in hamster BHK21 cells we found that human p21 was able to cause cell cycle arrest in G1 phase; this arrest was counteracted by coexpression of E2F-1 or SV40 large T antigen. To study the effect of p21 overexpression in vivo, BHK21 cell clones inducibly expressing human p21 (Tet-p21) driven by the tetracycline (Tet)-repressible promoter were established. The maximum induced p21 levels in the absence of Tet were estimated to be ten times that of endogenous hamster p21. As p21 levels rose following removal of Tet, p21-associated histone H1 kinase activity was increased and concomitantly cell growth and DNA synthesis were reduced. Tet-p21 BHK21 cells became arrested in G1 phase and lost colony forming ability irreversibly 2-4 days after removal of Tet. The induction of cyclin E- and cyclin A-associated kinase activities was diminished when G0-synchronized Tet-p21 BHK21 cells were serum stimulated in the absence of Tet. Increased binding of p21 to PCNA and cyclin D1-Cdk4 was detected in induced cells. Overexpression of p21 led to cell death in BHK21 cells at 39.5 degrees C within 4 days.

Mapping of interneurons that contribute to food aversive conditioning in the slug brain

To determine the distribution of neurons that contribute to memory formation induced by odor-taste associative conditioning in the slug's brain, we examined neuronal activity of the central nervous system of the slug Limax marginatus using a fluorescent activity marker [Lucifer yellow (LY)]. When LY was injected into the body cavity just after the conditioning, many of the procerebral (PC) interneurons were labeled. The PC lobe was considered to play important roles in the olfaction of the slug, because the olfactory afferent fibers from both the inferior and the superior tentacular noses innervate it. Such strong dye-uptake activity of PC interneurons was not observed when LY was injected just after unpaired control treatment. Thus, it was suggested that enhancement of dye-uptake activity upon conditioning was caused by the association of a conditioning stimulus (CS) with an unconditioned stimulus (UCS). The distribution patterns of PC interneurons that were labeled by LY after conditioning showed a characteristic feature: They usually formed a belt-shaped cluster parallel to the dorsoventral axis. This feature of the distribution was maintained when different odors were used as a CS. Furthermore, the number of the clusters reflected the number of CS odors but not the number of conditioning sessions. From these observations, we considered that enhancement of the neural activity involving dye uptake in each belt-shaped cluster contributed to formation of each odor memory.

Behavioral modulation induced by food odor aversive conditioning and its influence on the olfactory responses of an oscillatory brain network in the slug Limax marginatus

We compared behaviorally and physiologically the olfactory responses of slugs (Limax marginatus) that had been subjected to aversive, appetitive, or unpaired training with food odors (carrot or cucumber). In the aversive training, the slugs were exposed to the food odor as a conditioned stimulus (CS), and then quinidine sulfate solution as an unconditioned stimulus (UCS) was immediately applied to the lip of the slugs. This training caused a decrease in preference level for the CS. The unpaired training, in which the CS and the UCS were presented to the slugs with a 5-min interval, induced no change in the preference level for the CS. In the appetitive training, the slugs were allowed to eat the CS odor source without UCS application. When we used nonstarved slugs, it was found that the preference level for the CS increased upon the appetitive training. These results indicate that each training changed the preference for the odors in a characteristic manner. In the physiological experiments, we used brain-inferior tentacular nose preparations isolated from slugs and investigated the olfactory responses of the oscillations in the local field potential (LFP) of the procerebral (PC) lobe. We found that odor presentation induced various types of changes in the LFP oscillation frequency, although the rate of occurrence of the frequency modulation differed between odors used in the aversive and the unpaired training (aversive-conditioned and unpaired odors). The aversive-conditioned odors induced a decrease in the oscillatory frequency. Unpaired odors did not change it. Moreover, odors used in the appetitive training (appetitive-conditioned odors) induced an increase in the frequency. Thus, it was considered that those modulations of PC lobe oscillatory activity were independent of odor and reflected learned preference for odors.

Soft X-ray beamline specialized for actinides and radioactive materials equipped with a variably polarizing undulator

This report presents the design of an undulator beamline at SPring-8 to be used for soft X-ray spectroscopy focused on radioactive materials. Photoemission spectroscopy experiments are carried out in a radioisotope (RI)-controlled area where actinide compounds as well as unsealed radioactive materials are usable. Intrusion of the radioactive materials into the electron storage ring or to the outside of the evacuated beamline components can be avoided by a specially devised RI protection/inspection mechanism. The combination of a variably polarizing undulator and a varied-line-spacing plane-grating monochromator provides linearly or circularly polarized soft X-rays with a high resolving power in the energy range 0.28-1.5 keV. The beamline will become operational in December 1997.

Optical recording analysis of olfactory response of the procerebral lobe in the slug brain

We studied the oscillatory properties and the olfactory responses of the procerebral (PC) lobe of the cerebral ganglion in the terrestrial mollusc Limax marginatus. The PC lobe, a central olfactory organ in Limax, is a highly interconnected network of local interneurons that receives olfactory inputs from the inferior and superior tentacular noses. We used an optical recording technique with a voltage-sensitive dye to record the activity of the PC lobe from either the posterior or the dorsal surface. The recordings revealed that almost all PC interneurons showed spontaneous oscillatory activities that had been entrained with each other. Upon presentation to the nose of odors to which the slugs had been aversively conditioned, the basal level of the oscillation changed biphasically. In the early phase of the response, depolarization in the basal level of the oscillation occurred in one or more belt-shaped regions parallel to the dorsoventral axis. In the late phase of the response, hyperpolarization of basal potential level of the PC lobe oscillations occurred in a wider area. Such spatial and temporal modulation was not observed when the unpaired control odors were presented to the preparation, whereas the same preparations responded to the aversively conditioned stimuli. Thus, it was considered that the spatial and temporal response in the basal level of oscillation was specific to the aversively conditioned odors. Furthermore, the spatial pattern of the depolarization modulation in the early phase was repeatable in multiple trials performed using the same odor, although different odors produced different spatial patterns of the modulation. From these results, we conclude that in the PC lobe learned odors are represented as spatial and temporal activity patterns of oscillators that constitute a coherent network.

RagA is a functional homologue of S. cerevisiae Gtr1p involved in the Ran/Gsp1-GTPase pathway

Human RagA and RagB is reported to be 52% identical to a putative GTPase of Saccharomyces cerevisiae, Gtr1p. According to the reported nucleotide sequence, we amplified human RagA and RagBs cDNAs from the human B cell cDNA library with PCR. Both cDNAs rescued a cold sensitivity of S. cerevisiae, gtr1-11. Furthermore, we introduced into the cloned human RagA cDNA, the mutation ‘T21L’ corresponding to the gtr1-11 mutation which has been reported to suppress not only all of rcc1-, temperature-sensitive mutants of Ran/Gsp1p GTPase GDP/GTP-exchanging factor, but also rna1-1, a temperature-sensitive mutant of Ran/Gsp1p GTPase-activating protein. The resulting RagAgtr1-11 cDNA partially, but significantly, suppressed both rcc1- and rna1-1 mutations. These results indicated that RagA and RagBs are functional homologues of S. cervisiae Gtr1p. Interestingly, while wild-type human RagA and RagBs were localized within the cytoplasm, similar to S. cerevisiae Gtr1p, the mutated human RagAgtr1-11 corresponding to a dominant negative form of RagA was distributed in discrete speckles in the nucleus, being localized side by side with SC-35, a non-snRNP of the splicing complex. In contrast, a dominant positive form of RagA, Q66L was localized in the cytoplasm. Thus, RagA was suggested to shuttle between the cytoplasm and the nucleus, depending on the bound nucleotide state.

Crystal structure of 3-isopropylmalate dehydrogenase from the moderate facultative thermophile, Bacillus coagulans: two strategies for thermostabilization of protein structures

The crystal structure of 3-isopropylmalate dehydrogenase from the moderate facultative thermophile Bacillus coagulans (BcIPMDH) has been determined by the X-ray method. BcIPMDH is a dimeric enzyme composed of two identical subunits, each of which takes an open alpha/beta structure with 11 alpha-helices and 14 beta-strands. The polypeptide is folded into two domains. The first domain is composed of residues 1-101 and 257-356, and the second domain, of residues 102-256. The latter domains of the two subunits are associated with one another by a dyad axis to make the dimer, locally forming a beta-sheet and a four-helix bundle. As compared with the structure of the enzyme from the extreme thermophile Thermus thermophilus (TtIPMDH), a new short beta-sheet (residues 329-330 and 340-341) absent in TtIPMDH is formed by the insertion of 5 residues in BcIPMDH. In terms of determinants for thermostabilization, both consistent and inconsistent changes were found between the two enzymes. The regions including inconsistent changes are formed by different usages of the determinants for stabilizing the loops at different levels. Those in BcIPMDH contain some structural redundancies in length of amino acid sequence and flexibility of residues, which seem to be unnecessary for the enzymatic reaction. Such redundancies are also found in the primary structure of the enzyme of the mesophile Bacillus subtilis, but these parts are more stabilized in BcIPMDH by hydrogen bonds and salt bridges. On the other hand, TtIPMDH is stabilized by reducing such redundant parts. This contrast suggests that different strategies may be preferred for thermostabilization, depending on temperature.

Prediction of effect of interferon on chronic hepatitis C

Clinical, pathological, and virological analysis including hypervariable region-1 of hepatitis C virus (HCV) was performed to predict the effect of interferon (IFN) on 41 patients with chronic hepatitis type C. The low virus load, low frequency of the mutation in the hypervariable region-1 as the change of amino acid and high level of serum aminotransferase make one estimate the good effect of IFN on patients with HCV. Mutation in the hypervariable region-1 of HCV measured by fast assay fluorescence single-stranded conformational polymorphism was more frequent in nonresponders to IFN than responders. The most frequently mutated position was amino acid number 406. This indicates that the specific mutation site might affect the response of IFN.

Reactivation-dependent changes in memory states in the terrestrial slug Limax flavus

The change in memory state in the terrestrial slug Limax flavus was studied using cooling-induced retrograde amnesia. Slugs were first conditioned to avoid carrot odor and then a second conditioning procedure was applied 1, 3, 6, or 7 days after the first conditioning trial. Cooling the slugs to approximately 1 degrees C on day 7 immediately after the presentation of the odor used in the conditioning resulted in retrograde amnesia in the slugs that were subject to a second conditioning on day 6 or 7, but not in slugs that were subject to a second conditioning on day 1 or 3. Next, second-order conditioning was used as the second conditioning procedure to distinguish the memory acquired in the first conditioning from that acquired in the second conditioning and similar results were obtained. These results suggest that the reactivation of memory altered the memory state from a cooling-insensitive state to a cooling-sensitive one. A possible model for memory states is discussed.

Effect of lecithinized-superoxide dismutase on the interstitial pneumonia model induced by bleomycin in mice

Superoxide anion (O2-) acts as an exacerbation factor in interstitial pneumonia. Lecithinized-superoxide dismutase (PC-SOD), which is synthesized with a lecithin derivative bound covalently to recombinant human Cu,Zn-SOD, has a longer half-life in plasma and higher affinity to cell membranes than unmodified SOD. The effect of PC-SOD was evaluated using the bleomycin-induced interstitial pneumonia mouse model. Treatment with PC-SOD at 10 mg/kg significantly reduced the hydroxyproline content and fibrosis score. Namely, PC-SOD suppressed the progression of pulmonary fibrosis on the bleomycin-induced interstitial pneumonia mouse model. PC-SOD may be a potential drug for interstitial pneumonia therapy.

FMRF amide-like-immunoreactive primary sensory neurons in the olfactory system of the terrestrial mollusc, Limax marginatus

The distribution of FMRF amide-like immunoreactivity was investigated in the olfactory organs in the tentacle tip of the terrestrial slug, Limax marginatus. Approximately 0.7% of the neurons in the lobules of the tentacle ganglia demonstrated FMRF amide-like immunoreactivity. Most of the FMRF amide-like-immunoreactive somata lay at superficial positions within the lobules, and dendritic processes extended to the outer surface of the sensory epithelium, whereas the axons traveled toward the cerebral ganglion through the ventral part of the tentacle nerve. From their morphological features, FMRF amide-like-immunoreactive cells were considered to be primary sensory neurons.

Determination of the amount of native structural bacteriorhodopsin in purple membrane Langmuir-Blodgett films by a spectroscopic surface denaturation quantifying technique

Purple membrane (PM) shows denaturation when spread over an air/water interface. We established a technique, which we call the spectroscopic surface denaturation quantifying (SSDQ) technique, that uses infrared linear dichroism to determine the amount of native structural bacteriorhodopsin (BR) in PM Langmuir-Blodgett (LB) films. Using the SSDQ technique we found that the conformational change after surface denaturation of BR was the same as that caused by ethanol treatment. By extrapolating the data of the amount of non-denatured BR molecules in PM LB films vs. the area of a single BR molecule on an air/water interface, we also found that the surface area of a single non-denatured BR molecule was 11.5 nm2, which is consistent with that determined by high-resolution electron cryo-microscopy and electron diffraction (EMD). These results demonstrate that the SSDQ technique is effective in quantifying the amount of native structural BR in PM LB films. The SSDQ technique is also applicable to other types of protein consisting of alpha-helical conformation.

Effect of lecithinized-superoxide dismutase on the rat colitis model induced by dextran sulfate sodium

Lecithinized-superoxide dismutase (PC-SOD), which is synthesized with a lecithin derivative bound covalently to recombinant human Cu,Zn-SOD, has a longer half-life in blood and higher cell affinity than unmodified SOD. The effects of PC-SOD were evaluated using the rat ulcerative colitis model induced by 3% dextran sulfate sodium. Intravenous injection of rats with 0.5 or 1 mg/kg of PC-SOD suppressed the progression of bloody stools, the formation of erosion, and the infiltration of the colon with inflammatory cells. Furthermore, it also reduced the increase of leukocytes in blood. Thus, PC-SOD may have therapeutic potential in the treatment of ulcerative colitis.

Further classification of dysmotility-like dyspepsia by interdigestive gastroduodenal manometry and plasma motilin level

OBJECTIVE

To investigate interdigestive gastroduodenal motility with an infused catheter and measure plasma motilin levels in eight normal individuals and 18 patients with dysmotility-like dyspepsia.

METHODS AND RESULTS

All normal individuals had normal gastroduodenal interdigestive migrating complexes. Patients with dysmotility-like dyspepsia were classified into three subgroups on the basis of gastric antral motility: 1) seven patients with normal interdigestive migrating complexes, 2) five patients without interdigestive migrating complexes and with gastric phase II predominant over phase I, and 3) six patients without interdigestive migrating complexes and with phase I predominance. The maximum and mean plasma motilin levels were significantly different in normal individuals from those in subgroup 3 (Kruskal-Wallis test, p < 0.05).

CONCLUSIONS

Dysmotility-like dyspepsia appears to be a heterogeneous condition. Abnormal motilin secretion may cause dysmotility in subgroup 3, but dyspepsia in subgroup 1 and the absence of interdigestive migrating complexes in subgroup 2 could not be explained only on this basis.

Crystallization of eukaryotic E3, lipoamide dehydrogenase, from yeast, for exhibiting X-ray diffraction beyond 2.5 A resolution, and preliminary structure analysis

Lipoamide dehydrogenase, which is a common component of alpha-keto acid dehydrogenase complexes, has been highly purified from yeast (Saccharomyces cerevisiae) to reveal its structure at higher resolution. New crystals obtained by a desalting method exhibited diffraction beyond 2.5 A resolution. The cell dimensions are a = 97.1, b = 158.7, and c = 67.9 A, and the space group is P2(1)2(1)2(1). There is a dimeric enzyme in the asymmetric unit. The crystal structure was solved by means of the molecular-replacement technique and refined in a preliminary manner.

Chemonucleolytic effects of chondroitinase ABC on normal rabbit intervertebral discs. Course of action up to 10 days postinjection and minimum effective dose

STUDY DESIGN

This study demonstrated the chemonucleolytic effects of chondroitinase ABC and its histologic and biochemical background.

OBJECTIVES

To determine the course of chondroitinase ABC action on normal rabbit discs, and to find its minimum effective dosage.

SUMMARY OF BACKGROUND DATA

No previous study has assessed the chemonucleolytic action of chondroitinase ABC in a time- and dose-dependent manner. This study also investigated the biochemical causes of radiologic and histologic changes in the discs.

METHODS

Rabbits were injected with 4 U of pharmaceutical-grade chondroitinase ABC intradiscally. They were radiologically and histologically observed, and biochemical analyses of the discs were conducted on days 1, 3, 5, 7, and 10 postinjection in the time course study. Different doses of chondroitinase ABC were injected, and radiologic observations and water content of the discs were measured in the dose-finding study.

RESULTS

The time course study revealed that the chondroitin sulfate content of discs significantly decreased from day 1 postinjection until the end of the experimental period. The weight and water content of the nucleus pulposus decreased on day 3, and disc space narrowing was observed from the day after injection. The dose-finding study showed that a dose of 0.0002 U/disc still induced disc space narrowing and a decrease in water content.

CONCLUSIONS

Chondroitinase ABC is estimated to have a chemonucleolytic effect at least by day 3 postinjection at a dose level of 0.0002 U/disc or higher in rabbits.