We cloned and sequenced the leuB gene encoding 3-isopropylmalate dehydrogenase from Escherichia coli K-12 (JM103). Errors (33 residues) were found and corrected in the sequence previously reported for the leuB gene of Thermus thermophilus. The three-dimensional structure of the thermophile enzyme and the amino acid sequence comparison suggested that a part of the high stability of the 7: thermophilus enzyme is conferred by increased hydrophobic interaction at the subunit-subunit interface. Two residues at the interface of the 7: thermophilus enzyme, Leu246 and Va1249, are substituted with less hydrophobic residues, Glu and Met, respectively, in the E. coli enzyme, whereas other residues in this region are highly conserved. The mutated 7: thermophilus enzyme [L246E, V249MlIPMDH had reduced stability to heat. Two residues of the E. coli dehydrogenase, Glu256 and Met259, were replaced with the corresponding residues from the thermophile sequence. The resulted mutant enzyme was more resistant to heat than the wild-type enzyme.Elucidation of the molecular mechanisms of thermostability for enzymes produced by thermophiles are important not only for biophysical understanding of proteins but also for industrial application of enzymes. To answer the question, what kinds of structural uniqueness make the enzymes so stable?, a useful approach is to replace amino acid residues of mesophilic enzyme with the counterparts from thermophiles and to analyze the thermal stability of the mutant enzymes.The genes (leuB) coding for 3-isopropylmalate dehydrogenase (IPMDH) have been cloned and sequenced from a variety of microorganisms such as yeast (Andreadis et al., 1984;Davidow et al., 1987;Hamasawa et al., 1987;Takagi et al., 1987;Sakai and Tani, 1992), Bacilli (Imai et al., 1987;Sekiguchi et al., 1986Sekiguchi et al., , 1987, Salmonella typhimurium (Andreadis and Rosenthal, 1992), a cyanobacterium, Spirulina platensis (Bini et al., 1992) and extreme thermophiles, Thermus thermophilus (Kagawa et al., 1984) and Thermus aquaticus (Kirino and Oshima, 1991 ada et al., 1991) at 0.22 nm resolution. Thus, the enzyme seems to be one of the best candidates for the comparative studies on structure-function and structure-stability relationships.In the present study, the leuB gene from Escherichia coli was cloned and sequenced. During our study, errors were found in the sequence reported previously for the T. thermophilus leuB gene (Kagawa et al., 1984). The whole coding region was carefully sequenced again and 33 nucleotide residues of the gene revised. After revision of the sequence, the deduced amino acid sequence was compared with that of the E. coli enzyme. Two residues in the T thermophilus enzyme, Leu246 and Va1249, which are located at the center of the interface of the two subunits and appeared to play a crucial role in the stabilization of dimeric structure (Imada et al., 1991), are substituted to less hydrophobic residues in the E. coli dehydrogenase. The importance of these two residues in the conformational stability of the enzyme...

Background-Although polypoid lesions ofthe gall bladder are frequently observed in asymptomatic subjects, the natural history of these lesions has never been studied using ultrasonography. Aim-The natural history of polypoid lesions ofthe gall bladder was investigated using ultrasonography. Subjects-Among 4343 patients who presented to the outpatient clinic of Tsuchiura Kyodo General Hospital in 1988, 111 subjects were diagnosed as having polypoid lesions of the gall bladder by ultrasonography. Among these patients, two had gall bladder carcinoma. The remaining 109 subjects (58 female; age: median 54, range 25-89) were enrolled in this study. Methods-The subjects were followed up by ultrasonography once or twice a year until 1994. Results-Four patients received cholecystectomy and two patients died of other causes during the observation period. In one patient, gall bladder carcinoma was found, but its location was different from that of the pre-existing polyp. The size of the lesions did not change in 88.3% of the other 130 patients during this period, even among those in whom the initial size ofthe lesion exceeded 10 mm. There was no apparent correlation between the change in the diameter ofthe polypoid lesions and patients' sex or age. Conclusion-Most polypoid lesions of the gall bladder detected by ultrasonography are benign. (Gut 1996; 39: 860-862) Keywords: gall bladder carcinoma, gall bladder polyp, prognosis, ultrasonography.Ultrasonography has been widely used in clinical medicine, and its usefulness has been reported in the diagnosis of calculous gall bladder disease.' Mass surveys for abdominal disease have recently been performed using ultrasonography, and polypoid lesions of the gall bladder have been one of the most common findings.There are several studies that describe the prevalence of gall bladder polyps.2A6 One epidemiological study in Japan shows that the prevalence of gall bladder polyps was 6.28% in men and 3.5% in women,2 and another showed 5.3%/o in men.3 In Denmark, the prevalence was 4.6% and 4.3% in men and women, respectively,4 and 5.9% and 5.8% in men and women, respectively, in a 70 year old population.5 The prevalence was as low as 1.3% in the United Kingdom.6 However, the only report on the prognosis ofpolypoid lesions of the gall bladder is an old study using cholecystography. Therefore, the natural history of patients with polypoid lesions of the gall bladder was studied in this study. MethodsUltrasonographic examinations were carried out on 4343 patients in the outpatient clinic of the Department of Internal Medicine, Tsuchiura Kyodo Hospital from 1 January to 31 December 1988. Among these patients, 1 1 1 were diagnosed as having polypoid lesions of the gall bladder. Two of them had gall bladder carcinoma. The remaining 109 subjects (58 females; age: median 54, range 25-89) were enrolled in this study. After an overnight fast, ultrasonographic examination was performed by a radiology licensed :echnician using an Aloka Echo Camera SSD-650CL equipped with a 3.5 MHz tran...

No abstract

Purpose. To evaluate the efficacy of setting a preferred retinal locus relocation target (PRT) and performing Macular Integrity Assessment (MAIA) biofeedback training in patients showing insufficient recovery of best corrected visual acuity (BCVA) despite successful closure of an idiopathic macular hole (MH). Methods. Retrospective interventional case series. Nine eyes of 9 consecutive patients with the decimal BCVA of less than 0.6 at more than 3 months after successful MH surgery were included. A PRT was chosen based on MAIA microperimetry and the patients underwent MAIA biofeedback training. BCVA, reading speed, fixation stability, and 63% bivariate contour ellipse area (BCEA) were evaluated before and after the training. Statistical analysis was carried out using paired Student's t-test. Results. PRT was chosen on the nasal side of the closed MH fovea in 8 patients. After the MAIA training, BCVA improved in all patients. The mean logMAR value of BCVA significantly improved from 0.33 to 0.12 (p = 0.007). Reading speed improved in all patients (p = 0.29), fixation stability improved in 5 patients (p = 0.70), and 63% BCEA improved in 7 patients (p = 0.21), although these improvements were not statistically significant. Conclusion. MAIA biofeedback training improved visual acuity in patients with insufficient recovery of BCVA after successful MH surgery.

No abstract