Takeshi Iwasaki

Location and characterization of autonomously replicating sequences from chromosome VI of Saccharomyces cerevisiae.

We have reported the isolation of linking clones of HindIII and EcoRI fragments, altogether spanning a 230-kb continuous stretch of chromosome VI. The presence or absence of autonomously replicating sequence (ARS) activities in all of these fragments has been determined by using ARS searching vectors containing CEN4. Nine ARS fragments were identified, and their positions were mapped on the chromosome. Structures essential for and/or stimulative to ARS activity were determined for the ARS fragments by deletions and mutations. The organization of functional elements composed of core and stimulative sequences was found to be variable. Single core sequences were identified in eight of nine ARSs. The remaining ARS (ARS603) essential element is composed of two core-like sequences. The lengths of 3- and 5-flanking stimulative sequences required for the full activity of ARSs varied from ARS to ARS. Five ARSs required more than 100 bp of the 3-flanking sequence as stimulative sequences, while not more than 79 bp of the 3 sequence was required by the other three ARSs. In addition, five ARSs had stimulative sequences varying from 127 to 312 bp in the 5-flanking region of the core sequence. In general, these stimulative activities were correlated with low local delta Gs of unwinding, suggesting that the low local delta G of an ARS is an important element for determining the efficiency of initiation of replication of ARS plasmids.

Selective destruction of the myenteric plexus: Its relation to Hirschsprung's disease, achalasia of the esophagus and hypertrophic pyloric stenosis

Summary In an attempt to study the role of the myenteric plexus in Hirschsprungs disease, pyloric stenosis and achalasia of esophagus, a selective destructive lesion of the intramural ganglia has been experimentally produced in the respective parts of the gut by perfusion with Tyrodes solution containing 0.002 per cent of mercuric chloride. A nonorganic stenosis accompanied by proximal dilatation and muscular hypertrophy was successfully produced in these three areas. The mechanism of stenosis appears to be a tonic contraction of the smooth muscle. The induced functional stenosis of the lower esophagus and the distal colon of the dog appeared in all respects to be identical physiologically to that seen in achalasia and Hirschsprungs disease in patients. Destruction of the myenteric plexus of the pylorus has produced similar functional stenosis in the pyloric region, but failed to produce the muscular tumor characteristic of the infant with congenital hypertrophic pyloric stenosis. Vagotomy has been carried out in a group of dogs for comparative study. Symptoms which mimic achalasia were produced, but motility studies have revealed it to be a reverse phenomenon, namely, an atonic dilatation of the whole esophagus.

Bulk 4f Electronic States of Ce-Based Heavy Fermion System Probed by High-Resolution Resonance Photoemission

“Bulk-sensitive” Ce 3 d -4 f resonance photoemission (RPES) with an unprecedentedly high resolution has revealed a clear difference of bulk Ce 4 f spectral weights of heavy fermion system CeRu 2 Si 2 and CeRu 2 Ge 2 in the region of the tail of the Kondo peak and its spin-orbit partner. The significant spectral difference in both materials is in strong contrast to the mutually similar “surface-sensitive” 4 d -4 f RPES. The obtained bulk-sensitive spectra are well reproduced by a single impurity model. Consideration of the crystalline electric field splitting is important for estimating a realistic Kondo temperature from the bulk 4 f spectra.

Temperature-dependent change of correlated electronic states in Yb4As3 and Yb4(As1-xSbx)3 probed by high resolution photoemission spectroscopy

Clear changes of the Yb 4f photoemission spectra with temperature are observed in Yb 4 As 3 by high resolution photoemission spectroscopy. The photoemission intensity is very low at the Fermi level and decreases as the temperature is lowered in accord with the narrowing of the 4f spectra. Bulk and surface contributions are deconvoluted in the 4f 13 final state spectra. In comparison with the corresponding results in Yb 4 (As 1- x Sb x ) 3 , the spectral changes of Yb 4 As 3 with temperature are confirmed to be beyond simple thermal broadening effects and related to the charge ordering effects. Although the change from the charge ordering temperature ( T t ) down to about T t /2 is consistent with a theoretical prediction, the change below it is rather unusual and may be ascribed to the incompleteness of the charge ordering effect. Spectral changes with Yb 4 Sb 3 -substitution are qualitatively discussed.

The direct cloning of the yeast genome using the gap-filling method and the complete physical mapping of Saccharomyces cerevisiae chromosome VI.

The ordered clone library of chromosome VI of Saccharomyces cerevisiae has been constructed by Olson et al. [Proc. Natl. Acad. Sci. USA 83 (1986) 7826-7830, and personal communication]. It is composed of four contiguous stretches from the chromosome, each of 40-70 kb. There remained three gaps of unknown length between these four contigs. We applied the gap-repair method to clone these three gap regions directly from the yeast chromosome. All three gap regions, ranging from 7 to 22 kb, were successfully cloned without any structural changes. Together with these gap regions, a precise physical map of EcoRI and HindIII sites was constructed over the 230-kb fragment which covers most of chromosome VI except for two telomeres.

High Resolution 4d-4f Resonance Photoemission Spectroscopy of CePdX (X=As, Sb)

We have studied the electronic structures of ternary Ce compounds CePdX (X=As, Sb) by means of high resolution 4 d -4 f resonance photoemission spectroscopy. In the Ce 4 f spectra, the relative int...

Electronic Structure of Mn Doped Diluted Magnetic Semiconductors

We have measured the Mn 2p core absorption spectra of diluted magnetic semiconductors (DMSs) Hg1-x-yCdxMnyTe. We then performed the Mn 2p-3d resonance photoemission in order to reveal the Mn 3d electronic structures. The Mn 3d spectra have features similar to the Mn 3d spectra of other II-VI group DMSs with higher Mn concentration, which were reported by previous Mn 3p-3d resonance photoemission studies. Slight changes with Cd doping were observed in the Mn 3d photoemission and 2p absorption spectra.