Biomedical subjects

H Sakamoto

Publications and source records attributed to H Sakamoto.

At least 289 records · Page 16Linked to original sources

PubMed1998

[Indications for external ventricular drainage after clipping of ruptured aneurysms in the acute stage].

The indication for external ventricular drainage after clipping of ruptured aneurysms in the acute stage is evaluated. Since 1990, 234 patients who presented with subarachnoid hemorrhage (SAH) and underwent aneurysmal clipping in the acute stage were evaluated retrospectively. Patients with ventricular dilatation had intraoperative placement of a ventriculostomy to obtain intraoperative brain relaxation, but the ventricular catheter was removed at the end of the surgery. All these patients were managed postoperatively in a similar fashion with no ventricular drainage, avoidance of dehydration complemented by a course of sodium ozagrel and nicardipine or fasudil hydrochloride. Acute hydrocephalus was defined as clinically and radiographically demonstrated ventricular dilatation that developed within 2 weeks of the onset of SAH and that required ventricular drainage. Three surgical approaches were employed; pterional approach (PA) for the aneurysms of the anterior circulation and upper basilar artery in 207 patients, interhemispheric approach (IHA) for the aneurysms of the pericallosal artery in 11 patients and lateral suboccipital approach (LSA) for the aneurysms of the vertebral arteries in 16 patients. No significant differences were found among these three approach groups in Fisher CT classification and the Hunt & Kosnik gradings. Four patients developed acute hydrocephalus within two weeks of surgery: three patients were operated on via LSA and one through IHA. Compared to the IHA or LSA, PA was superior for reestablishing cerebrospinal fluid circulation, because it is possible to remove more subarachnoid clot in the basal cisterns than to do so in the other two approaches. Opening of the lamina terminalis and the Liliequist membrane are also possible using PA. In conclusion, PA can prevent development of acute hydrocephalus, whereas postoperative ventricular drainage may be necessary in patients operated upon via IHA or LSA.

Acute Disease↗

PubMed1998

[An experience with St. Jude medical prosthetic 19A-HP which resulted in restricted opening at an early stage after operation].

St. Jude medical hemodynamic plus series is positively used for aortic valve replacement (AVR) of small orifice because it can increase the orifice area by 26% compared with conventional prosthetic valves of the same size. We performed AVR with SJM 19A-HP on a patient having aortic stenosis with regurgitation using horizontal mattress suturing technique. The aortic orifice size was 18.9 mm at the preoperative measurement. The course after the operation was uneventful until 9 days after the operation when cinefluoroscopy revealed symmetrical restriction of opening of valve leaflets. We are now monitoring the clinical course at the patient has not developed any symptoms though the LV-Ao pressures gradient is 60 mmHg by Doppler echocardiography. As the restriction of valve leaflet opening was symmetrical, it is not likely that an excess of the ligature or remnant caused the restriction; structural problems of St. Jude medical prosthesis appear to be a more reasonable explanation. Since the orifice ring of this prosthesis is not reinforced, longitudinal forces applied to the hinge may alter the shape of the ring, thus restricting the movement of valve leaflets. In the present case, forced insertion of 19A-HP instead of more desirable 17-HP is considered to have caused longitudinal forces acting on the hinge.

Aged↗

PubMed1998

[Mitral valve tissue characterization using acoustic microscopy].

Mitral valve hardness in the rough and clear zones was evaluated by measuring the propagation velocity (m/sec) of ultrasound through the valve, based on the hypothesis that harder tissues will have larger ultrasonic velocity values passing through the tissue. Mitral valve specimens were obtained from 16 normal subjects (age, 15-72 years) at autopsy. An acoustic microscope, operating at 450 MHz, was used to measure the ultrasonic velocity through the three layers of the valve: the atrialis; the spongiosa; and the fibrosa. Furthermore, the mean ultrasonic velocity through the three layers was measured. These measurements were conducted in the rough and clear zones of the valve. In the rough zone, the ultrasonic velocities were 1,634 +/- 71 in the atrialis, 1,574 +/- 37 in the spongiosa, and 1,726 +/- 97 m/sec in the fibrosa. In the clear zone, the ultrasonic velocities were 1,691 +/- 117 in the atrialis, 1,575 +/- 44 in the spongiosa, and 1,909 +/- 131 m/sec in the fibrosa. There were significant differences between velocities in the three layers in both the rough and clear zones. Furthermore, the mean ultrasonic velocity in the three layers in the clear zone (1,887 +/- 138 m/sec) was higher than that in the rough zone (1,642 +/- 53 m/sec; p < 0.001). These findings show that fibrosa, which is rich in collagen fibers, is harder than atrialis, which is rich in elastic fibers, and the spongiosa, which is poor in connective tissues, is the softest. The higher mean ultrasonic velocity in the clear zone than in the rough zone indicates that the clear zone is harder than the rough zone, although the clear zone is thinner than the rough zone.

Adolescent↗

PubMed1998

Semiquantitative bacteriology of closed odontogenic abscesses.

Pus samples from twenty-three dentoalveolar abscesses were collected by needle aspiration and examined by direct inoculation technique using 6 different aerobic and anaerobic agar plates. For aerobic culture, sheep blood agar and chocolate agar (Kyokuto Pharmaceutical Co., Tokyo, Japan) were used. For anaerobic culture, four different media, 1) brucella HK agar with hemolyzed rabbit blood and defibrillated sheep blood, 2) paramomycin-vancomycin brucella HK agar with hemolyzed rabbit blood, 3) phenylethyl alcohol brucella HK agar with hemolyzed rabbit blood, 4) bacteroides bile esculin agar (Kyokuto Pharmaceutical Co., Tokyo, Japan) were prepared in an anaerobic jar prior to inoculation. The aerobic agar plates were incubated for 24 h at 37 degrees C, and the anaerobic plates at least 48 h at 37 degrees C in anaerobic jars. From 23 closed odontogenic abscess samples, a total of 112 bacterial strains were isolated; 81 strains (72.3%) were strict anaerobes, and 31 strains (27.7%) were aerobes. The mean number of bacterial strains per positive sample was 4.86. Oral Streptococci, Prevotella, Fusobacterium, Peptostreptococcus and Veillonella were common isolates. The combination of Oral Streptococci and Prevotella was found in 11 patients (47.8%), and that of Prevotella and Peptostreptococcus in 12 patients (52.2%). The present study demonstrated that closed odontogenic abscesses are polymicrobial infections by aerobes and anaerobes. Application of a direct inoculation technique for bacterial culture made it possible to isolate more anaerobes than our commonly used technique using transport medium and to delineate the semiquantitative bacteriology of closed odontogenic abscess.

Acute Disease↗

PubMed1998

[Management of elderly patients with incidentally discovered unruptured aneurysms].

Long-term natural history of unruptured cerebral aneurysms is not found frequently. Hence, the indications for surgery on unruptured asymptomatic cerebral aneurysms are still unclear. The benefit of treatment ultimately depends on the relative risk of subsequent aneurysm rupture in untreated patients versus the risk involved in surgery. Clinical features of fourteen elderly patients aged over 70 years with incidentally discovered unruptured aneurysms were analyzed. Two were male and 12 were female, with ages ranging from 70 to 82 years (mean: 74.5 years). Aneurysms were located in the anterior circulation in 13 patients and in the posterior circulation in 1 patient. One patient had multiple aneurysms, that is, bilateral middle cerebral aneurysms. The size of all these aneurysms was less than 10 mm. The indication for surgery was determined case by case. General information about the natural history of incidentally discovered aneurysms was given to the patients and their relatives. Informed consent was based on the fact that subarachnoid hemorrhage was associated with a poor prognosis, while excellent operative results were common in patients with unruptured aneurysms. Five patients agreed to surgical treatment. Four of them, their ages being 70, 70, 72 and 72 years old, with aneurysms located on the middle cerebral arteries, underwent neck clipping of their aneurysms with no operative morbidity or mortality. However, the remaining one patient was not recommended for surgery in spite of her consent to having it, because of her high age (82 years) and the location of her aneurysm (intracavernous internal carotid artery). Consequently, 10 patients who didn't receive surgery were followed-up at periods ranging from 3 months to 7 years. Two patients developed rupture of the aneurysms, either proven (one patient) or presumed (one patient). The former patient made an uneventful recovery after surgery, but the latter died. None of the remaining eight patients have experienced rupture of the aneurysms. It is our clinical impression, however, that they harbor an unruptured aneurysm with at least mild trepidation. With the rapid aging of the population, withholding aneurysm surgery merely because a patient is elderly may not necessarily be the most appropriate decision. Our conclusions are as follows: (1) Elderly patients in their early seventies are apt to agree to having surgical treatment for their unruptured aneurysms. (2) The cases reported herein show that asymptomatic middle cerebral artery aneurysms were able to be clipped very safely. (3) Most patients have experienced a decrease in quality of life from knowing they are living with an unruptured aneurysm.

Age Factors↗

PubMed1998

The somatostatin analog, octreotide, inhibits in vitro outgrowth of smooth muscle cells from canine coronary and carotid atherosclerotic plaque tissues.

Restenosis is caused by excessive neointima formation resulting from smooth muscle cell (SMC) proliferation and migration from the arterial media into the subendothelial space, stimulated by growth factors. A long-acting somatostatin analog, octreotide, activates protein tyrosine phosphatases and can inhibit the stimulatory effects of growth factors. In this study, we evaluated the effect of octreotide on SMC outgrowth from in vitro explants of both coronary and carotid arterial tissues in a canine endothelium-injury model. After 6 days of culture, SMC grew out of 33.3% and 58.3% of the explants from the injured canine carotid and coronary arterial tissues, respectively. In contrast, SMC outgrowth was not observed from any of the explants from normal canine carotid arterial tissue. Octreotide completely inhibited SMC outgrowth from injured canine carotid arterial tissue at a concentration of 10(-6) M. This agent also inhibited SMC outgrowth from injured canine coronary arterial tissue by 57% and 71% of the control value at concentrations of 10(-8) M and 10(-6) M, respectively. We conclude that our explant cell-culture model may prove to be valuable for assessing the effect of agents designed to reduce intimal proliferation, and that the use of the somatostatin analog octreotide in clinical settings may modify the high incidence of restenosis after coronary interventions by reducing SMC proliferation.

Animals↗

PubMed1998

[Cancer-associated gene abnormalities and chemosensitivity].

One of the most important clinical issues in cancer chemotherapy is the presence of intrinsic resistance or the appearance of acquired resistance against chemotherapy. As for intrinsic resistance, we had to perform direct chemo-sensitivity testing, or had to rely on the knowledge empirically acquired from randomized clinical trials. However, molecular or genetic markers associated with chemo-sensitivity have been reported recently. For example, inactivation of p53 or GML gene has been reported to be associated with chemo-resistance. Overexpression of topo-isomerase I has been reported to be associated with chemo-sensitivity to Topo I inhibitor. Overexpression of Thymidine Phosphorylase has been found to be associated with chemo-sensitivity to prodrug of 5-FU. By checking the status of such chemo-sensitivity markers prior to chemotherapy, it would be possible to predict the chemotherapeutic effect and even the necessity of the chemotherapy in the near future. In this article, we review the chemo-sensitivity markers reported so far, and methodology contributing to the discovery of new chemo-sensitivity markers. As a clinical study, 11 cases of ovarian cancer with high sensitivity to cisplatin-based chemotherapy and 29 cases of ovarian cancer with chemoresistance were analyzed by Comparative Genomic Hybridization (CGH). Copy number decrease in Xp, and copy number increase in 19q were observed in 13, 12 out of 29 resistant cases (45, 41%) and zero, 1 out of 11 sensitive cases (0, 9%), suggesting that -Xp and +19q were likely to be a genetic event associated with intrinsic drug-resistance (p = 0.006, 0.05, respectively). This effort should contribute to the discovery of new chemo-sensitivity and resistance markers.

Antineoplastic Agents↗

PubMed1998

Expression of MUC1 and MUC2 mucins in gastric carcinomas: its relationship with the prognosis of the patients.

Our previous immunohistochemical studies for the expression of MUC1 mucin antigen (which was detected by monoclonal antibody DF3) and MUC2 mucin antigen (which was detected by polyclonal antibody anti-MRP) in pancreatic and intrahepatic bile duct tumors demonstrated that invasive carcinoma with poor outcome showed a pattern of MUC1+ and MUC2- expression, whereas many of the noninvasive tumors with favorable outcome showed a pattern of MUC1- and MUC2+ expression. To clarify the relationship between the expression of these mucin antigens and the biological properties of gastric cancers, the expression of MUC1 and MUC2 mucin antigens was examined immunohistochemically in 136 patients with gastric cancer invading the submucosa or the deeper layer, and the survival of the antigen-positive and antigen-negative patient groups was compared using the Kaplan-Meier method. For MUC1 mucin expression, different glycoforms of MUC1 were examined using four monoclonal antibodies (NCL-MUC-1-CORE, DF3, MY.1E12, and HMFG-1). The patients with MUC1+ mucin antigen staining in the carcinoma showed significantly worse survival than those with MUC1- mucin antigen staining. In contrast, the patients with MUC2+ mucin antigen staining in the carcinoma showed significantly better survival than those with MUC2- mucin antigen staining. In conclusion, MUC1 antigen expression was associated with a poor outcome in patients with gastric cancer, irrespective of its glycosylation status, and MUC1 is thus considered to be a useful prognostic factor for poor outcome in patients. In contrast, MUC2 antigen expression is a prognostic factor associated with a favorable outcome in patients. In addition, combined evaluation of the MUC1 and MUC2 mucin staining is clinically useful to predict outcome in patients with gastric cancer.

Adult↗

PubMed1998

A comparative study of the clinical efficacy of immunotherapy and conventional pharmacological treatment for patients with perennial allergic rhinitis.

This study was designed to compare the clinical outcome of prolonged immunotherapy for perennial allergic rhinitis with that of pharmacological treatment. Patients with perennial allergic rhinitis due to Dermatophagoides farinae (D. farinae) were divided into two groups; a pharmacotherapy group and an immunotherapy group. The pharmacotherapy group was treated with conventional pharmacological treatment using antihistamine tablets and topical steroid sprays and the immunotherapy group was treated with D. farinae extracts for 5 successive years. None of symptom scores at enrollment differed significantly between the groups. At 6 months and 1 year after the start of treatment the rate of decrease in each score was significantly greater in the pharmacotherapy group than in the immunotherapy group. The rate of decrease in sneezing scores, but not in the other scores, at 2 years after the start of treatment was also greater in the pharmacotherapy group than in the immunotherapy group. However, at 3 years the rate of decrease in any of the scores did not differ significantly between groups. The differences between the groups became clear-cut again after 5 years of treatment, when the rate of decrease in all of the scores was significantly greater in the immunotherapy group than in the pharmacotherapy group. Therefore, short-term treatment with pharmacological agents is probably superior to immunotherapy but, in the long-term, immunotherapy is apparently superior to pharmacological treatment with respect to clinical efficacy. In addition, prolonged immunotherapy provided long-term clinical efficacy and might provide a long-standing cure even after discontinuation of the therapy. In a questionnaire interview, approximately half of patients were very satisfied with prolonged immunotherapy and three-quarters were fairly satisfied or more. Additionally, the magnitude of improvement in nasal stuffiness contributed significantly and exclusively to the patient evaluation of immunotherapy. We propose that prolonged immunotherapy is never inferior to anti-allergenic pharmacological treatment and that it is possible to achieve long-term clinical efficacy or long-standing cure even after the discontinuation of immunotherapy, and that patients with perennial allergic rhinitis will be very satisfied with this prolonged therapeutic technique if nasal stuffiness is considerably alleviated.

Adolescent↗

PubMed1998

Suplatast tosilate affects the initial increase in specific IgE and interleukin-4 during immunotherapy for perennial allergic rhinitis.

Suplatast tosilate can inhibit IL-4 production and suppress IgE synthesis in vitro. However, the theory that the agent causes changes in production of IL-4 and IgE in vivo has little experimental support. Immunotherapy could decrease the specific IgE response, but such a favourable effect is only possible with prolonged therapy after an initial increase in specific IgE. The use of suplatast tosilate together with immunotherapy may blunt the initial rise in specific IgE and decrease serum levels of specific IgE more quickly. Eighty-three adult patients with perennial allergic rhinitis due to Dermatophagoides farinae (D. farinae) were treated for 6 months with one of 3 treatments. Seventeen patients were treated with oral administration of 300 mg/day suplatast tosilate alone. Forty-six patients were treated with immunotherapy using standardized D. farinae alone. Twenty patients were treated with immunotherapy together with concurrent oral administration of 300 mg/day suplatast tosilate. Serum samples were collected 3 times from each patient, at enrollment, at 3 months and at 6 months after enrollment. Oral administration of suplatast tosilate for 3 and 6 months significantly decreased serum levels of IL-4 and specific IgE, and the rate of decrease in specific IgE correlated significantly with the rate of decrease in IL-4. The rates of decrease in IL-4 and specific IgE at 3 and 6 months were significantly greater in the patients treated with suplatast tosilate and immunotherapy than in those treated with immunotherapy alone. In conclusion, suplatast tosilate is able significantly to decrease serum levels of IL-4 and specific IgE, and the use of the drug together with immunotherapy can blunt the initial increase in specific IgE during the first 6 months of immunotherapy.

Adult↗

PubMed1998

Positron emission tomographic imaging of pleomorphic adenoma in the parotid gland.

We studied the possible correlation between 2-18F-2-deoxy-D-glucose (FDG) uptake and histopathological findings in mass lesions of the parotid gland. Thirteen pleomorphic adenomas of the parotid gland were evaluated by computed tomography (CT), magnetic resonance imaging (MRI), Gallium scintigraphy, Technetium scintigraphy and FDG-positron emission tomography (PET). Standardized uptake values (SUV) and time-activity curves (TAC) were determined for all mass lesions. Pleomorphic adenomas were histologically classified into the following three types: epithelial, intermediate and mesenchymal, based on their dominant histological components. The numbers of epithelial, intermediate, and mesenchymal types were 5, 2, and 6, respectively. The levels of SUVs were 4.02 +/- 1.91 (range: 1.97-7.07) in the epithelial type, 5.05 +/- 1.12 (range: 4.26-5.58) in the intermediate type and 3.98 +/- 7.74 (range: 1.98-7.74) in the mesenchymal type, respectively. The accumulation of FDG did not differ significantly among the three types. Since the accumulation of FDG was significantly correlated with the tumor size, FDG-PET could reflect tumor growth ability more apparently than the other nuclear or imaging modalities.

Adenoma, Pleomorphic↗

PubMed1998

Monitoring of response to radiotherapy with fluorine-18 deoxyglucose PET of head and neck squamous cell carcinomas.

We examined the usefulness of positron emission tomography (PET) using fluorine-18 deoxyglucose (FDG) in determining the therapeutic effects of irradiation and chemotherapy on head and neck malignant tumors. Twenty-two patients with head and neck lesions who underwent histological examinations were studied. Squamous cell carcinoma was histologically diagnosed in all cases. Sixteen of them underwent radiotherapy with approximately 40 Gy in combination with carboplatin therapy. The remaining 6 patients underwent radiotherapy alone. After these treatments, 11 underwent surgery. For PET study, each patient was injected with intravenous FDG 185-370 MBq. We evaluated the degree of FDG accumulation using scanned images taken 40-55 min after the injection. We measured the standardized uptake value (SUV), a semiquantative evaluation, ROI activity divided by the dosage per weight of each patient. FDG-PET, CT and MRI were performed twice for each patient, before and after treatment. FDG uptake, but not the tumor size in CT or MRI, was significantly reduced in each patient after the treatment. Therefore, our findings have clearly demonstrated that FDG-PET provides for more valuable therapeutic outcomes than conventional imaging such as CT and MRI. FDG-PET should thus provide a new dimension in the management of head and neck malignant tumors.

Carcinoma, Squamous Cell↗

PubMed1998

[Application of ultrafast 3D-CT in cervical spine injury].

The authors investigated the usefulness of the ultrafast three-dimensional computed tomography (UF-3D-CT) in cervical spine injury. At Osaka City General Hospital, between April 1995 and March 1998, the authors examined 38 patients with cervical spine injury using UF-3D-CT. The ultrafast CT reduces scanning time. There were no complications associated with the examination. We examined 12 patients with vertebral body fracture, 11 patients with lamina fracture, 8 cases with subluxation including locking facet, 2 patients with atlanto-axial dislocation and 8 patients without bony abnormality. Results suggested that UF-3D-CT was very useful for helping us to understand the bony deformity and the relationship between the bone and the important vessels. UF-3D-CT is very useful for preoperative evaluation and pathophysiological evaluation in cervical spin injury.

Adolescent↗

PubMed1997

An evaluation of CA125 levels in 291 normal postmenopausal and 20 endometrial adenocarcinoma-bearing women before and after surgery.

Two hundred ninety-one normal postmenopausal women without hormone replacement therapy were studied for their blood levels of CA125. The levels ranged from 0.1 to 31.8 U/ml (mean+/-SEM 5.5+/-0.3 U/ml). Twenty patients with endometrial adenocarcinoma who had preoperative CA125 levels below 50 U/ml were also studied. The levels of CA125 in the latter group ranged from 2.1 to 43.0 U/ml (17.2+/-2.3 U/ml) and the difference of the mean value of the two groups was statistically significant (P < 0.001). The CA125 levels in normal postmenopausal women have a weak negative correlation with their age (CA125 = -0.025 x age + 6.9, P < 0.001), whereas in cancer patients, a positive correlation was seen (CA125 = 0.6 x age + 11.5, P < 0.05). Patients with endometrial cancer showed a decrease in their CA125 levels after a hysterectomy and salpingo-oophorectomy (6.5+/-1.2 U/ml, P < 0.0001). These results confirmed that the normal range of the CA125 of menopausal women is much lower than that of cycling women and each laboratory should establish its own normal range for the population. Also, it was suggested that CA125 levels which apparently fall within the normal range but are high, however, for the respective age, may indicate that an extensive search for an endometrial malignancy is necessary.

Adenocarcinoma↗

PubMed1997

Disruption of the splicing enhancer sequence within exon 27 of the dystrophin gene by a nonsense mutation induces partial skipping of the exon and is responsible for Becker muscular dystrophy.

The mechanism of exon skipping induced by nonsense mutations has not been well elucidated. We now report results of in vitro splicing studies which disclosed that a particular example of exon skipping is due to disruption of a splicing enhancer sequence located within the exon. A nonsense mutation (E1211X) due to a G to T transversion at the 28th nucleotide of exon 27 (G3839T) was identified in the dystrophin gene of a Japanese Becker muscular dystrophy case. Partial skipping of the exon resulted in the production of truncated dystrophin mRNA, although the consensus sequences for splicing at both ends of exon 27 were unaltered. To determine how E1211X induced exon 27 skipping, the splicing enhancer activity of purine-rich region within exon 27 was examined in an in vitro splicing system using chimeric doublesex gene pre-mRNA. The mutant sequence containing G3839T abolished splicing enhancer activity of the wild-type purine-rich sequence for the upstream intron in this chimeric pre-mRNA. An artificial polypurine oligonucleotide mimicking the purine-rich sequence of exon 27 also showed enhancer activity that was suppressed by the introduction of a T nucleotide. Furthermore, the splicing enhancer activity was more markedly inhibited when a nonsense codon was created by the inserted T residue. This is the first evidence that partial skipping of an exon harboring a nonsense mutation is due to disruption of a splicing enhancer sequence.

Adult↗

PubMed1997

Cloning and characterization of novel CIS family genes.

We have reported two JAK-signaling modulators, CIS (cytokine-inducible SH2 protein) and JAB (JAK2 binding protein), which are structurally related. Here we cloned three additional CIS family genes (CIS2, CIS3, and CIS4) on the basis of an expression sequence tag (EST) database search. We also found at least two additional candidates of this gene family in the database. These genes were induced by erythropoietin and granulocyte-macrophage colony stimulating factor in certain hematopoietic cell lines. The SH2 domain and a C-terminal 40 amino acid region, designated the CIS homology domain (CH domain), are highly conserved in this family, while the N-terminal regions of these proteins share little similarity. A yeast two-hybrid assay and in vitro and in vivo binding assays revealed that in addition to JAB, CIS3 bound to the JAK2 tyrosine kinase domain (JH1), although the interaction of CIS3 with the JAK2-JH1 domain was much weaker than that of JAB. Transient expression of JAB and CIS3, but not other CISs, strongly inhibited leukemia inhibitory factor (LIF)-induced STAT3-reporter gene activation in 293 cells. Furthermore, constitutive overexpression of JAB and CIS3 in M1 leukemia cells prevented LIF-induced differentiation and growth arrest. Although the physiological function remains to be investigated, CIS family genes could play a role in the negative regulation of cytokine signaling by interacting with specific targets.

Amino Acid Sequence↗

PubMed1997

Nonideal Mixing in Adsorbed Film and Micelle of Ionic-Nonionic Surfactant Mixtures

The surface tension of aqueous solutions of dodecylammonium chloride-octyl methyl sulfoxide (OMS) and dodecyltrimethylammonium bromide-OMS mixtures was measured as a function of the total molality of surfactants and the composition of OMS. The results were analyzed according to our thermodynamic procedure; the phase diagrams of adsorption and micelle formation and the diagram illustrating the composition relation between the micelle and the adsorbed film at the critical micelle concentration were drawn. The activity coefficient and excess Gibbs energy in the adsorbed film and the micelle were defined and then evaluated from the phase diagrams. They were found to give useful information on the deviation from ideal mixing and intermolecular interaction in the adsorbed film and micelle. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗

PubMed1997

A characteristic arrangement of aromatic amino acid residues in the solution structure of the amino-terminal RNA-binding domain of Drosophila sex-lethal.

The Sex-lethal (Sxl) protein from Drosophila melanogaster has two RNA-binding domains (RBDs). As the amino-terminal RBD (RBD1) of the Sxl protein exhibits low sequence homology to the typical RBDs, particularly at the putative functional residues, it was difficult to unambiguously locate the RNP1 and RNP2 motifs. Therefore, in the present study, we defined the amino and carboxy-terminal borders of the first RNA-binding domain (RBD1) of the Sxl protein by limited tryptic digestion. By replacement of Phe166 by Tyr, we constructed a highly soluble mutant, which exhibits the same RNA-binding properties as those of the wild-type. Using this mutant protein, we performed NMR measurements, and elucidated the secondary and tertiary structures of the Sxl RBD1 in solution. The betaalphabetabetaalphabeta folding pattern is conserved in the solution structure of the Sxl RBD1, as in other reported RBD structures. This allowed us to identify both the RNP1 and RNP2 motifs of the Sxl RBD1 unambiguously. Intriguingly, the RNP2 motif of the Sxl RBD1 has an Ile residue at the second position, which is generally occupied by an aromatic amino acid residue in RBDs and has been suggested to be involved in their RNA binding. Furthermore, the loop region between beta2 and beta3 of the Sxl RBD1 has an exceptional cluster of aromatic amino acid residues, in place of the normal basic amino acid cluster. In contrast, the second RBD of Sxl does not exhibit these characteristic features.

Amino Acid Sequence↗