Permeation of redox species through a cell membrane of a single, living algal protoplast studied by microamperometry

Permeation of several redox species through a cell membrane of a single algal protoplast (radius 100 microns) was investigated by amperometry with a Pt microdisk electrode (disk radius, 6.5 microns) located near the membrane. The redox current observed at the microelectrode decreased as the microelectrode approached the cell membrane since the membrane acted as a barrier for diffusion of redox species from bulk to the microelectrode. Permeability coefficient (Pm) of the protoplast membrane was determined by the quantitative analysis of the variation of the redox current with microelectrode-membrane distance using digital simulation. The Pm values for Fe(CN)6(4-), Fe(CN)6(3-), Co(phen)3(2+), ferrocenyl methanol(FMA) and p-hydroquinone(QH2) were < or = 1.0 x 10(-4), < or = 1.0 x 10(-4), 1.0 x 10(-3), 5.0 x 10(-3) and 2.0 x 10(-2) cm/s, respectively. Using these Pm values, the concentration changes inside a model cell and chloroplast were theoretically calculated.

Lidocaine increases the ventricular fibrillation threshold during bupivacaine-induced cardiotoxicity in pigs

Ventricular fibrillation (VF) is a cause of death in bupivacaine-induced cardiovascular toxicity. We have examined the therapeutic effects of lidocaine on the threshold for bupivacaine-induced VF in in situ beating swine hearts. Twenty-four animals were allocated to one of three groups: 0.25% bupivacaine, 1% lidocaine or 0.25% bupivacaine with 1% lidocaine were infused into the left anterior descending coronary artery in increasing doses of 0, 1, 2, 4, 8 and 16 ml h-1 for 15 min, respectively. ECG and haemodynamic variables were monitored continuously during infusion. Regional myocardial function in the area supplied by the left anterior descending coronary artery was assessed using the sonomicrometry technique. VF did not occur in the lidocaine group. VF developed at higher infusion rates in animals given bupivacaine with lidocaine (in one animal at an infusion rate of 8 ml h-1 and in seven at 16 ml h-1) compared with animals given bupivacaine alone (in one at an infusion rate of 4 and in seven at 8 ml h-1). Although regional myocardial function decreased with increases in the infusion rate in each group, the depressant effects of the bupivacaine solution (medial inhibitory infusion rate of systolic shortening: IR50 = 2.43 (0.43) ml h-1) were significantly greater than those of the lidocaine solution (IR50 = 5.83 (0.87) ml h-1), but did not differ from those of the bupivacaine with lidocaine solution (IR50 = 3.54 (0.56) ml h-1). This study indicates that a combination of lidocaine and bupivacaine increased the threshold for bupivacaine-induced VF without further depressing myocardial contractility.

[Super selective bronchial artery embolization using metallic coils in the management of hemoptysis]

Hemoptysis is one of the most important clinical problems of cardiopulmonary disease with high mortality rate. Its management is routinely performed with Bronchial Artery Embolization (BAE). However, it was reported that BAE had some disadvantages such as spinal injury and recurrent bleeding. In order to prevent spinal injury, we tried the super selective bronchial artery embolization (ss-BAE). This technique is especially available in the occlusion of the bronchial artery forming the common trunk with the spinal artery. Besides, BAE, considered to be only a palliative treatment, might cause recanalization due to reabsorption of the occlusive agent. So we used metallic coils to prevent this drawback. The ss-BAE with metallic coils was performed in 2 cases who had refractory hemoptysis against conservative therapy. Hemoptysis disappeared in both cases. The ss-BAE with metallic coils was shown to be safer and more effective than ordinary BAE.

[Evaluation of intrapulmonary nodules by thoracoscopic ultrasonography]

We evaluated the usefulness of thoracoscopic ultrasonography for diagnosing intrapulmonary nodules. We studied 7 patients undergoing thoracoscopic operations. Three had benign lung tumors, one had metastatic lung tumors from a renal cell cancer, and three had primary lung cancers. During thoracoscopy three benign tumors were seen as masses protruding from the visceral pleura in to the pleural space, and two primary lung cancers were seen as pleural indentations. However, the presence of one metastatic lung tumor and one primary lung cancer could not be confirmed by thoracoscopy because of the lack of pleural changes. Furthermore, intrapulmonary spread of malignant tumors in four cases could not be seen by thoracoscopy. All tumors were seen clearly and their characteristics were identified by thoracoscopic ultrasonography. Partial lung resection during thoracoscopy was successful in all patients. We found thoracoscopic ultrasonography to be useful for confirming the presence of peripheral solid nodules, and for deciding where to make incisions for partial lung resection.

CBP as a transcriptional coactivator of c-Myb

CBP (CREB-binding protein) is a transcriptional coactivator of CREB (cAMP response element-binding) protein, which is directly phosphorylated by PKA (cAMP-dependent protein kinase A). CBP interacts with the activated phosphorylated form of CREB but not with the nonphosphorylated form. We report here that CBP is also a coactivator of the c-myb proto-oncogene product (c-Myb), which is a sequence-specific transcriptional activator. CBP directly binds to the region containing the transcriptional activation domain of c-Myb in a phosphorylation-independent manner in vitro. The domain of CBP that touches c-Myb is also required for binding to CREB. A c-Myb/CBP complex in vivo was demonstrated by a yeast two-hybrid assay. CBP stimulates the c-Myb-dependent transcriptional activation. Conversely, the expression of antisense RNA of CBP represses c-Myb-induced transcriptional activation. In addition, adenovirus EIA, which binds to CBP, inhibits c-Myb-induced transcriptional activation. Our data thus identify CBP as a coactivator of c-Myb. These results suggest that CBP functions as a coactivator for more transcriptional activators than were thought previously.

Decreased coronary blood flow is not responsible for myocardial dysfunction during bupivacaine-induced cardiotoxicity

BACKGROUND

Although previous studies have shown that bupivacaine produces a dose-dependent vasoconstriction, the possible effects of decreased coronary blood flow on myocardial dysfunction during bupivacaine-induced cardiotoxicity have not been investigated.

METHODS

We carried out the present study using the in situ beating hearts of six beagles. An autoperfusion circuit was established from the left carotid artery to the anterior descending coronary artery (LAD). Its blood flow (QLAD) was measured with an electromagnetic flow meter, and myocardial oxygen consumption was calculated using Fick's principle. Regional myocardial function (systolic shortening: %SS, post-systolic shortening: %PSS) of the LAD-supplied region was evaluated by the sonomicrometric technique. While saline or bupivacaine (10 micrograms/ml) was continuously infused into the LAD in a crossover design, the effects of a vehicle (baseline), acetylcholine (1 and 3 micrograms/min), nitroglycerin (10 micrograms/min) and adenosine (10 micrograms/min), on coronary haemodynamics and regional myocardial function were evaluated.

RESULTS

Bupivacaine caused a decrease in QLAD and regional myocardial dysfunction (a decrease in %SS and an increase in %PSS) at the baseline. While acetylcholine and adenosine increased QLAD with intracoronary bupivacaine-infusion, regional myocardial dysfunction was not reversed. There was a positive correlation between regional myocardial oxygen consumption and %SS in the whole study.

CONCLUSIONS

The results of this study indicate that the decrease in QLAD during bupivacaine-induced myocardial toxicity is not responsible for regional myocardial dysfunction, and, moreover, that it parallels a decrease in myocardial oxygen demand.

Increase of solubility of foreign proteins in Escherichia coli by coproduction of the bacterial thioredoxin

Eukaryotic proteins are frequently produced in Escherichia coli as insoluble aggregates. This is one of the barriers to studies of macromolecular structure. We have examined the effect of coproduction of the E. coli thioredoxin (Trx) or E. coli chaperones GroESL on the solubility of various foreign proteins. The solubilities of all eight vertebrate proteins examined including transcription factors and kinases were increased dramatically by coproduction of Trx. Overproduction of E. coli chaperones GroESL increased the solubilities of four out of eight proteins examined. Although the tyrosine kinase Lck that was produced as an insoluble form and solubilized by urea treatment had a very low autophosphorylating activity, Lck produced in soluble form by coproduction of Trx had an efficient activity. These results suggest that the proteins produced in soluble form by coproduction of Trx have the native protein conformation. The mechanism by which coproduction of Trx increases the solubility of the foreign proteins is discussed.

Differences in metabolic and morphological reactions after radiation therapy: proton NMR spectroscopy and imaging of patients with intracranial tumors

PURPOSE

The purpose of the present study was to detect tumor cell viability, the diagnosis of which is the most important point in clinical therapy for malignant tumors. The advent of localized proton spectroscopy has made this detection possible. The spectral peak intensities were found to be very different depending on tumor tissue pathology.

METHODS

The tumor cell reaction after radiation therapy was examined with proton localized spectroscopy in addition to enhanced MR imaging using a 1.5 Tesla MR system (Philips, Gyroscan S15-HP). Plain MR images (short spin echo) were used for localization pilot images, and after the MRS study, contrast enhanced MRI was carried out. Studies were performed pre-radiation, mid-radiation, and post-radiation if possible.

MATERIALS

Sixteen patients (total 27 examinations) with intracranial tumors and three normal volunteers underwent proton NMR localized spectroscopy. The brain tumors were diagnosed before the MR study, and nine patients had metastatic brain tumors, such as adenocarcinoma, squamous cell carcinoma, and small cell carcinoma, and seven other patients were diagnosed with glioma-type tumors.

RESULTS

The reaction patterns of proton NMR spectroscopy of brain tumors after radiation therapy were very different and depended on tumor histology.

CONCLUSION

Proton NMR spectroscopy is an excellent means of determining tumor cell viability.

c-Myb repression of c-erbB-2 transcription by direct binding to the c-erbB-2 promoter

The c-myb proto-oncogene product (c-Myb) is a transcriptional activator that can bind to the specific DNA sequences. Although c-Myb also represses an artificial promoter containing the Myb binding sites, natural target genes transcriptionally repressed by c-Myb have not been identified. We have found that the human c-erbB-2 promoter activity is repressed by c-Myb or B-Myb in a chloramphenicol acetyltransferase co-transfection assay. Domain analyses of c-Myb suggested that Myb represses the c-erbB-2 promoter activity by competing with positive regulators of the c-erbB-2 promoter. In in vitro transcription assays, Myb proteins containing only the DNA binding domain could repress c-erbB-2 promoter activity. Two Myb binding sites in the c-erbB-2 promoter were critical for transcriptional repression by c-Myb. One of the two Myb binding sites overlaps the TATA box, and DNase I footprint analyses indicated that c-Myb can compete with TFIID. These results suggest that Myb-induced trans-repression of the c-erbB-2 promoter partly involves competition between Myb and TFIID.

[Prediction of postoperative visual acuity in retinal detachment with macular involvement]

We used laser interferometry (LI) and a potential acuity meter (PAM) to predict visual acuity after surgery for patients with rhegmatogenous retinal detachment with macular involvement. Thirty one eyes of 31 patients with retinal detachment were treated with scleral buckling procedures. Postoperative visual acuity was correlated with preoperative measurements of the LI and PAM, preoperative visual acuity by Landort's ring, and the estimated duration of macular detachment. The correlation between the duration of macular detachment and the postoperative visual acuity was not good (r = 0.55, p < 0.01). Although the preoperative visual acuity showed a relatively good correlation with postoperative visual acuity (r = 0.62, p < 0.01), the results of the LI and PAM provided a better correlation (LI; r = 0.73, PAM; r = 0.71). Our results suggest that the LI and PAM are useful to predict the visual acuity after retinal reattachment in patients with preoperative macular detachment.

c-Myb-induced trans-activation mediated by heat shock elements without sequence-specific DNA binding of c-Myb

The c-myb proto-oncogene product (c-Myb) can transactivate the human hsp70 promoter in a transient cotransfection assay. The present studies have demonstrated that the heat shock element (HSE) in the hsp70 promoter mediates trans-activation by c-Myb. Mutagenesis of the DNA sequence in HSE indicated that the NGAAN motif is necessary for not only the heat shock response but also the c-Myb-induced trans-activation. The HSE in the hsp70 promoter does not contain a c-Myb-binding site, implying that the sequence-specific DNA binding of c-Myb is not required for the HSE-dependent trans-activation by c-Myb. We had demonstrated that a disruption of the leucine zipper motif in the central portion of the c-Myb molecule increased the degree of c-Myb-induced trans-activation of the promoter containing c-Myb-binding sites, suggesting that a putative inhibitor binds to c-Myb through this leucine zipper (Kanie-Ishii, C., MacMillan, E. M., Nomura, T., Sarai, A., Ramsay, R. G., Aimoto, S., Ishii, S., and Gonda, T. J. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 3088-3092). However, disruption of the leucine zipper in c-Myb abolished the HSE-dependent trans-activation by c-Myb, whereas deletion of the transcriptional activation domain containing acidic amino acids in c-Myb did not abolish the HSE-dependent trans-activation by c-Myb. These results suggest that c-HSEs by interacting with unidentified trans-acting factor(s) but not by a direct binding to the promoter through its DNA-binding domain.

Fast-neutron radiotherapy of nonsmall cell-carcinoma of the lung

To determine the efficacy of fast neutron (FN) for the treatment of non-small cell lung cancer, 112 patients with histologically proven adenocarcinoma or squamous cell carcinoma at a limited stage were studied to evaluate local control and survival, after treatment with either FNs or photons alone. The local control rate of adenocarcinoma in FN-treated patients attained 50%, which was significantly higher than that (<10%) of squamous cell carcinoma in FN-treated patients or that of both histological types of carcinoma in patients treated with photons alone. In accordance with this, the 5-year survival rate for the FN-treated patients with adenocarcinoma was significantly higher than that for FN-treated patients with squamous cell carcinoma or that for photon-treated patients with both histological types of disease. The present study clearly suggests the usefulness of FN in the treatment of adenocarcinoma of the lung, though it was a non-randomized trial.

Recognition of specific DNA sequences by the c-myb protooncogene product: role of three repeat units in the DNA-binding domain

The DNA-binding domain of c-Myb consists of three homologous tandem repeats of 52 amino acids. The structure of the third (C-terminal) repeat obtained by NMR analysis has a conformation related to the helix-turn-helix motif. To identify the role of each repeat in the sequence recognition of DNA, we analyzed specific interactions between c-Myb and DNA by measuring binding affinities for systematic mutants of Myb-binding DNA sites and various truncated c-Myb mutants. We found that specific interactions are localized unevenly in the AACTGAC region in the consensus binding site of c-Myb: The first adenine, third cytosine, and fifth guanine are involved in very specific interactions, in which any base substitutions reduce the binding affinity by > 500-fold. On the other hand, the interaction at the second adenine is less specific, with the affinity reduction in the range of 6- to 15-fold. The seventh cytosine involves a rather peculiar interaction, in which only guanine substitution abolishes the specific binding. The binding analyses, together with the chemical protection analyses, showed that the c-Myb fragment containing the second and third repeats covers the AACTGAC region from the major groove of DNA in such an orientation that the third repeat covers the core AAC sequence. These results suggest that the third repeat recognizes the core AAC sequence very specifically, whereas the second repeat recognizes the GAC sequence in a more redundant manner. The first (N-terminal) repeat, which covers the major groove of DNA only partially, is not significant in the sequence recognition, but it contributes to increase the stability of the Myb-DNA complex. The presence of an N-terminal acidic region upstream of the first repeat, which is important for the activation of c-myb protooncogene, was found to reduce the binding affinity by interfering with the first repeat in binding to DNA.

Thermal stability of the DNA-binding domain of the Myb oncoprotein

The DNA-binding domain of the c-myb protooncogene product consists of three homologous tandem repeats of 51-52 amino acids (denoted as R1, R2, and R3 from the N-terminal side). In order to analyze conformational and thermodynamic characteristics of the homologous repeats, we have examined the DNA-binding domain by circular dichroism (CD) and differential scanning calorimetry (DSC). The CD spectra for the three individual repeats are significantly different in the fine profiles, indicating subtle differences in their conformations. The melting analyses for the fragments show that the thermal stability of each fragment is different from one another, with the following order of stability: R1(Tm = 61 degrees C) approximately greater than R3(57 degrees C) >> R2(43 degrees C), where R2 is much less stable than the other repeats. The denaturing process for the whole DNA-binding domain, measured by DSC, is characterized by a very broad transition ranging from 30 to 80 degrees C. The denaturation curve can be fit well by a three-state transition with one intermediate state. The transition temperature for the native-to-intermediate transition coincides with the melting temperature of R2, indicating that the intermediate state corresponds to the unfolding of unstable R2. The CD spectrum of the whole domain is almost identical to the sum of the individual spectra. Thus, these results suggest that the individual repeats in the whole DNA-binding domain behave independently in terms of conformation and stability. The addition of DNA to the DNA-binding fragment drastically changed the melting profile, in which the broad transition curve was replaced by a sharp peak at 58 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of simulation models for protein folding in a thermal annealing process--I: A simulation of BPTI folding by the pearl necklace model

A model system is proposed to simulate the folding processes of proteins during thermal annealing. This system consists of four subsystems: (i) the pearl necklace model with isotropic inter-residue interactions; (ii) the extended pearl necklace model with anisotropic interaction potentials; (iii) molten globule phase dynamics; and (iv) final generation of the three-dimensional structure of a given protein. In this paper results obtained with the pearl necklace model are reported. This model consists of spherical elements and virtual bonds of 3.8 A in length and is intended to simulate dynamical processes at relatively high temperature where entropic terms play a dominant role. Inter-residue interactions are composed of spherical soft repulsive potentials and hydrophobic interactions inherent to respective residues. A simulation of folding processes of BPTI starting from the fully extended conformation indicated that intermediates, even at early stages of folding, are not randomly coiled but assume organized structures that resemble, to some extent, the native conformation.

[Evaluation of treatment of acute myocardial infarction before admission to a coronary care unit]

A fact-finding survey was conducted to ascertain the treatment of 298 patients with acute myocardial infarction (AMI) who were referred to our coronary care unit (CCU) from other medical facilities between May 1978 and December 1987. The controls consisted of 169 patients with AMI who were admitted directly to our CCU during the same period. The mean time from onset of AMI to admission to our CCU was 21.7 +/- 67.9 hours (mean +/- SD) for patients from other medical facilities, and it took longer than that of the controls (11.7 +/- 34.9 hours). However, the mortality was 19.8%, being lower than that of the controls (26.0%). By the Killip's classification, there was no significant differences between both patient groups who belonged to Killip groups I, II and IV, but the mortality of cases in Killip group III was 3.7%, which was lower than that of the controls (7.15%). Among the 298 cases, 169 (56.7%) had received some kind of emergency treatment, and their mortality was 29.9%. However, the mortality of the remaining 129 cases (43.3%) who had received no emergency treatment was only 17.1%. The reason for this contradictory result is attributed to the fact that the former group included relatively severe cases. The number of patients receiving emergency treatment has gradually increased recently; however, the overall results achieved were not satisfactory even with appropriate therapy. Since April 1984, conferences with local practitioners have been held concerning emergency treatment for ischemic heart disease. This resulted in better understanding of CCU among the practitioners, less time delay until admission, and increased frequency and higher quality of emergency treatment. However, the mortality in the CCU did not decline, probably because of the relatively high rate of severe cases. To reduce mortality of AMI, a communication network should be established between practitioners and the CCU.

Optical rotary connector

As optical fiber usage widens, a new kind of optical fiber connector becomes necessary. This connector would be connecting two optical fiber bundles with different speeds around an axis without interruption. It is difficult to make such a connector, especially one with a hollow axis used for mechanical power transmissions. Using an optical fiber bundle for an image inversion and a differential gear system, we have developed an optical rotary connector with a hollow axis that can be used for a multichannel connection.

Effects of amino acid imbalance on polysome profiles and 14C-labeled amino acid incorporation into tissue proteins in rats

Feeding of rats on a low casein diet supplemented with a small amount of methionine caused an enlargement of liver size and an accumulation of lipids in the liver. Experiments were conducted to examine the effects induced by the amino acid-imbalanced diet on the metabolism of dietary amino acids with special reference to protein synthesis. Protein and DNA contents of the liver per 100 g body weight with rats fed on the imbalanced diet were apparently higher than those of rats fed on the basal diet. Ingestion of the imbalanced diet clearly stimulated hepatic ribosome aggregation but not skeletal muscle ribosome aggregation. Incorporation of [14C]leucine into liver protein was markedly increased in the group consisting of rats fed on the imbalanced diet (imbalanced group) and that into skeletal muscle was similar to the result with the group receiving the basal diet (basal group). Relative content of [14C]leucine in plasma albumin was higher in rats of the imbalanced group, whereas that in plasma of very low-density lipoprotein was reduced. These results indicate that the unbalanced inter-organ or intra-organ utilizations of dietary amino acids for protein synthesis were produced by the condition of the amino acid imbalance. Such metabolic effects of the amino acid imbalance may result in the enlargement of liver size and the accumulation of lipids in the liver.