An ice phase of lowest thermal conductivity

On pressurizing at temperatures near 130 K, hexagonal and cubic ices transform implosively at 0.8-1 GPa. The phase produced on transformation has the lowest thermal conductivity among the known crystalline ices and its value decreases on increase in temperature. An ice phase of similar thermal conductivity is produced also when high-density amorphous ice kept at 1 GPa transforms on slow heating when the temperature reaches approximately 155 K. These unusual formation conditions, the density and its distinguished thermal conductivity, all indicate that a distinct crystal phase of ice has been produced.

Arterial and Left Ventricular Pressures Illude Transient Alternans of Contractility during Postextrasystolic Potentiation

We have previously found that the postextrasystolic (PES) potentiation (PESP) of the left ventricular (LV) contractility (Emax) decays typically in transient alternans even in the normally ejecting canine heart. This contradicted the general expectation that arterial pressure (AP) and LV pressure (LVP) usually decay exponentially during PESP. We hypothesized this contradiction to be due to the different cardiodynamic behaviors of AP and LVP from LV Emax during PESP. We tested this hypothesis by measuring AP, LVP, LV volume, Emax, effective arterial elastance (Ea) as an index of afterload, and pulse pressure (PP) during PESP in eight anesthetized open-chest dogs by using the conductance catheter system. We changed Ea by changing the total peripheral resistance (TPR) with methoxamine hydrochloride (iv) and repeated the measurements. Although the Emax alternans patterns during PESP were comparable between the normal and high afterloads, LVP and PP were slightly potentiated and alternated under the normal afterload, whereas LVP and PP were obviously potentiated and alternated under the high afterload. We also simulated the effects of Ea/Emax on the transient alternans of AP and LVP on a computer. Despite the same alternans pattern of Emax, a higher Ea/Emax, which is typical in heart failure, caused a larger PP alternans, whereas a lower Ea/Emax, which is typical in normal hearts, almost eliminated it. These results suggest that a transient alternans of LV contractility during PESP could be overlooked when AP and LVP are monitored in in situ normal hearts.

Hypoplasia of primary and permanent teeth following osteitis and the implications of delayed diagnosis of a neonatal maxillary primary molar

A 2-year-and-6-month-old Japanese girl with delayed eruption of a maxillary right primary canine and disturbance in the development of maxillary right primary molars was examined. The crown of the maxillary right first primary molar was severely decayed and hypoplastic. The periodontal tissues on the maxillary right posterior region were swollen and slight erythrogenic change was observed. Radiographic examination revealed a disturbance in the development of the permanent successor and the primary teeth in the maxillary right quadrant. According to the history, the maxillary right first primary molar had erupted on day seven after birth. It is suggested that the disturbance in development of the permanent successor and the primary teeth was secondary to osteitis caused by infection of the neonatal tooth. Appropriate dental treatment had not been administered for more than two years because the neonatal molar had not been diagnosed.

Electrophoretic karyotyping and gene mapping of seven formae speciales in Fusarium solani

Chromosomal DNAs of 22 strains in 7 formae speciales (f. spp.) of Fusarium solani were compared by pulsed field gel electrophoresis (PFGE) and gene mapping on the chromosomes. Using PFGE, complete separation of the full components of the genome was not attained, due to the limited resolution of large chromosomes, but 5-12 chromosomes with sizes of 0.6-5.7 Mbp were resolvable for every strain. Although each strain had a unique banding profile, similarity in the banding profile was noticed among strains of the same (f. sp.). In gene mapping, the ribosomal RNA gene (rDNA) and putative pathogenesis-related genes encoding kievitone hydratase (khs), pisatin demethylase (pda) and pectate-degrading enzyme (pelA) were located on the chromosomes separated by PFGE. rDNA was always detected on the stacked large bands of 5.2-5.7 Mbp. The khs gene was detected on a chromosome of 2.8-5.4 Mbp in all f. sp. phaseoli strains and one strain of f. sp. pisi. The pda gene was detected on a chromosome of 1.4-5.6 Mbp in f. sp. pisi and pelA was localized on a chromosome of 2.3-2.9 Mbp in f. spp. pisi, xanthoxyli, batatas and mori. The results of PFGE and Southern blot hybridization supported the idea that each f. sp. of F. solani (or mating population of the teleomorph Nectria haematococca) has a distinctive genomic organization, as previously inferred from molecular phylogenetic analyses.

Magnetic resonance imaging findings in schizophrenia and atypical psychoses

The differences among MRI findings were studied in schizophrenic psychoses. The schizophrenics and atypical psychotics had significant reductions in bilateral hippocampal volumes compared to controls, but the two patient groups did not differ from each other. As for ventricle volume, the schizophrenics showed significantly larger temporal horns and third ventricle than normal controls, whereas atypical psychotics did not. Moreover, the left temporal horn in the schizophrenics was significantly larger than that seen in the atypical psychotics. By cluster analysis, schizophrenics and atypical psychotics were found to have a tendency to be distributed in different groups. These results might be considered to support the classification of schizophrenic psychoses into schizophrenia and atypical psychoses.

Sponge homologs of vertebrate protein tyrosine kinases and frequent domain shufflings in the early evolution of animals before the parazoan-eumetazoan split

The protein tyrosine kinases (PTKs) diverged specifically in animal lineages by gene duplications and domain shufflings to form a large protein family comprising diverse subfamilies with distinct domain organizations and functions. On the basis of a phylogenetic tree inferred from a comparison of the shared kinase domains, we previously showed that gene duplications that gave rise to diverse subfamilies predate the divergence of parazoans and eumetazoans. There is, however, still a possibility that, although the kinase domain duplications are ancient events, the domain shufflings that gave rise to different subfamilies with distinct domain organization are more recent event than the kinase domain duplications. To clarify this problem, we have determined the complete sequences of 15 sponge PTKs and have compared the domain organizations of these sponge PTKs and those of eumetazoans. For each of ten sponge PTKs out of 15 analyzed here, a possible eumetazoan (human and Drosophila) ortholog has been identified. The sponge and eumetazoan orthologs are virtually identical in domain organization and belong to the same subfamily in the PTK family tree for each of ten orthologous pairs, except for one subfamily in which a considerable deletions and/or insertions of domains are observed. This result suggests that most, if not all, of the domain shufflings, together with gene duplications, are very old, going back to dates before the parazoan-eumetazoan split, the earliest divergence among extant animal phyla.

Frank-Starling mechanism retains recirculation fraction of myocardial Ca(2+) in the beating heart

Myocardial Ca(2+) handling in excitation-contraction coupling is the second primary determinant of energy or O(2) demand in a working heart. The intracellular and extracellular routes remove myocardial Ca(2+) that was released into the sarcoplasma with different Ca(2+): ATP stoichiometries. The intracellular route is twice as economical as the extracellular route. Therefore the fraction of total Ca(2+) removed via the sarcoplasmic reticulum, i.e., the recirculation fraction of intracellular Ca(2+) (RF), determines the economy of myocardial Ca(2+) handling. RF has conventionally been estimated as the exponential decay rate of postextrasystolic potentiation (PESP). However, we have found that PESP usually decays in alternans, but not exponentially in the canine left ventricle beating above 100 beats/min. We have succeeded in estimating RF from the exponential decay component of an alternans PESP. We previously found that the Frank-Starling mechanism or varied ventricular preload did not affect the economy of myocardial Ca(2+) handling. Then, to account for this important finding, we hypothesized that the Frank-Starling mechanism would not affect RF at a constant heart rate. We tested this hypothesis and found its supportive evidence in 11 canine left ventricles. We conclude that RF at a constant heart rate would remain constant, independent of the Frank-Starling mechanism.

Concurrent molecular recognition of the amino acid and tRNA by a ribozyme

We have recently reported an in vitro-evolved precursor tRNA (pre-tRNA) that is able to catalyze aminoacylation on its own 3'-hydroxyl group. This catalytic pre-tRNA is susceptible to RNase P RNA, generating the 5'-leader ribozyme and mature tRNA. The 5'-leader ribozyme is also capable of aminoacylating the tRNA in trans, thus acting as an aminoacyl-tRNA synthetase-like ribozyme (ARS-like ribozyme). Here we report its structural characterization that reveals the essential catalytic core. The ribozyme consists of three stem-loops connected by two junction regions. The chemical probing analyses show that a U-rich region (U59-U62 in J2a/3 and U67-U68 in L3) of the ribozyme is responsible for the recognition of the phenylalanine substrate. Moreover, a GGU-motif (G70-U72) of the ribozyme, adjacent to the U-rich region, forms base pairs with the tRNA 3' terminus. Our demonstration shows that simple RNA motifs can recognize both the amino acid and tRNA simultaneously, thus aminoacylating the 3' terminus of tRNA in trans.

A single metal ion plays structural and chemical roles in an aminoacyl-transferase ribozyme

Catalytically active RNA molecules rely on metal ions for structural and/or catalytic functions. Our in vitro selected aminoacyl-transferase ribozyme is no exception, as it employs a single fully hydrated Mg2+ ion for catalysis [Suga, H., et al. (1998) Biochemistry 37, 10118-10125]. Here we report the essential catalytic residues of the ribozyme and their spatial arrangement in the relation to the metal binding site. Evidence obtained using a combination of Pb2+ and Tb3+ hydrolytic cleavage assays on wild type and mutant ribozymes revealed a cooperative metal binding site that consists of the tandem G:U wobble pairs in P1 and consecutive G:U and U:A pairs in P3. The formation of this concerted Mg2+ binding site positions the P1 and P3 helices in a parallel manner, placing the L3 tetraloop in close proximity to the internal guide sequence (IGS, substrate binding site), which is adjacent to P1. Certain monovalent metal ions inhibit catalysis at low concentrations but support catalysis at high concentrations. These analyses imply that the Mg2+ ion plays both structural and chemical roles and that it brings about the significant rate acceleration in aminoacyl-transfer in concert with the L3-IGS long-range interaction.

Essential roles of innersphere metal ions for the formation of the glutamine binding site in a bifunctional ribozyme

Numerous studies on naturally occurring ribozymes have shown that the functional roles of metal ions in promoting RNA catalysis are diverse. Earlier studies performed on the in vitro selected aminoacyl-transferase ribozyme (ATRib) have revealed that a fully hydrated Mg2+ ion plays an essential role in catalysis [Suga, H., Cowan, J. A., and Szostak, J. W. (1998) Biochemistry 28, 10118-10125]. More recently, we have evolved this ATRib into a bifunctional ribozyme, called AD02 [Lee, N., et al. (2000) Nat. Struct. Biol. 7, 28-33]. This new ribozyme consists of two catalytic domains, the original ATRib domain and a new glutamine-recognition (QR) domain, and exhibits a function of charging glutamine to tRNA. Here we elucidate crucial roles of metal ions involved in the QR domain, that are distinct from those in the ATRib domain. The metal ions in the QR domain require innersphere coordinations, and both Mg2+ and Ca2+ can support catalysis. Extensive Tb3+-Mg2+ and Tb3+-Co(NH3)6(3+) competition cleavage experiments have shown that the QR domain has high and low affinity metal binding sites, which are involved in the Mg2+-dependent structural alteration to form the glutamine binding site [Lee, N., and Suga, H. (2001) RNA 7, 1043-1051]. Kinetic studies in the presence of divalent and monovalent ions have suggested that the essential role of the metal ions in the QR domain is most likely structural.

Characterization of a New Subgroup of Rhizoctonia solani Anastomosis Group 1 (AG-1-ID), Causal Agent of a Necrotic Leaf Spot on Coffee

ABSTRACT A new foliar disease on coffee leaves was observed in Mindanao, Philippines, in 1996. The symptoms appeared as large circular or irregularly shaped necrotic areas with small circular necrotic spots (1 mm or less in diameter) usually found around the periphery of the large necrotic areas. Rhizoctonia solani was consistently isolated from these diseased coffee leaves. Isolates obtained were multinucleate (3 to 12 nuclei per hyphal cell), had an optimum temperature for hyphal growth at 25 degrees C, prototrophic for thiamine, and anastomosed with tester isolates belonging to R. solani anastomosis group 1 (AG-1). Mature cultures on potato dextrose agar (PDA) were light to dark brown. Sclerotia, light brown to brown, were formed on the surface of PDA and covered the whole mature colony culture. Individual sclerotia often aggregated into large clumps (3 to 8 mm in diameter) and their color was brown to dark brown. In pathogenicity tests, isolates from coffee caused necrotic symptoms on coffee leaves, whereas isolates of AG-1-IA (not isolated from coffee), 1-IB, and 1-IC did not. The results of analyses of restriction fragment length polymorphism of ribosomal DNA internal transcribed spacer, random amplified polymorphism DNA, and fatty acid profiles showed that R. solani isolates from coffee are a population of AG-1 different from AG-1-IA, 1-IB, and 1-IC. These results suggest that R. solani isolates from coffee represent a new subgroup distinct from AG-1-IA, 1-IB, and 1-IC. A new subgroup ID (AG-1-ID) is proposed.

Divergence pattern of animal gene families and relationship with the Cambrian explosion

There are many gene families that are specific to multicellular animals. These have either diverged from ancestral genes that are shared with fungi and/or plants or evolved from an ancestral gene unique to animals. The evolution of gene families involved in cell-cell communication and developmental control has been studied to establish whether the number of member genes increased dramatically immediately prior to or in concert with the Cambrian explosion. A molecular phylogeny-based analysis of several animal-specific gene families has revealed that gene diversification by duplication occurred during two active periods interrupted by a long intervening quiescent period. Intriguingly, the Cambrian explosion is situated in the silent period, indicating that there is no direct link between the first burst of gene diversification and the Cambrian explosion itself. The importance of gene recruitment as a possible molecular mechanism for morphological diversity, and its possible role for the Cambrian explosion, are discussed.

Preparation of new nitrogen-bridged heterocycles. 51. Syntheses and structures of compounds having two indolizine nuclei in a molecule

New compounds having two indolizine nuclei in a molecule were prepared in low to moderate yields from the reactions of potassium 2-indolizinethiolates with 1,omega-dihalides such as 1,2-diiodoethane, 1,3-dibromopropane, 1,4-dibromobutane, alpha,alpha'-dichloro-o-xylene, and alpha,alpha'-dichloro-p-xylene. Most of the products had the conformation in which the two indolizine rings in the molecule are as remote as possible, but only 1,2-bis[[(2-indolizinyl)thio]methyl]benzene derivatives, prepared from potassium 2-indolizinethiolates and alpha,alpha'-dichloro-o-xylene, showed a weak attractive interaction between the two indolizine nuclei in the X-ray analysis and the nuclear Overhauser and exchange spectroscopy (NOESY) spectrum.

Rat cardiac contractile dysfunction induced by Ca2+ overload: possible link to the proteolysis of alpha-fodrin

The aim of the present study was to examine the mechanisms of Ca2+ overload-induced contractile dysfunction in rat hearts independent of ischemia and acidosis. Experiments were performed on 30 excised cross-circulated rat heart preparations. After hearts were exposed to high Ca2+, there was a contractile failure associated with a parallel downward shift of the linear relation between myocardial O(2) consumption per beat and systolic pressure-volume area (index of a total mechanical energy per beat) in left ventricles from all seven hearts that underwent the protocol. This result suggested a decrease in O(2) consumption for total Ca2+ handling in excitation-contraction coupling. In the hearts that underwent the high Ca2+ protocol and had contractile failure, we found marked proteolysis of a cytoskeleton protein, alpha-fodrin, whereas other proteins were unaffected. A calpain inhibitor suppressed the contractile failure by high Ca2+, the decrease in O(2) consumption for total Ca2+ handling, and membrane alpha-fodrin degradation. We conclude that the exposure to high Ca2+ may induce contractile dysfunction possibly by suppressing total Ca2+ handling in excitation-contraction coupling and degradation of membrane alpha-fodrin via activation of calpain.

A minihelix-loop RNA acts as a trans-aminoacylation catalyst

We previously reported a bifunctional ribozyme that catalyzes self-aminoacylation and subsequent acyl-transfer to a tRNA. The ribozyme selectively recognizes a biotinyl-glutamine substrate, and charges the tRNA molecule in trans. Structurally, there are two catalytic domains, referred to as glutamine-recognition (QR) and acyl-transferase (ATRib). We report here the essential catalytic core of the QR domain as determined by extensive biochemical probing, mutation, and structural minimization. The minimal core of the QR domain is a 29-nt helix-loop RNA, which is also able to glutaminylate ATRib in trans. Its amino acid binding site is embedded in an 11-nt cluster that is adjacent to the loop that interacts with the ATRib domain. Our study shows that a minihelix-loop RNA can act as a trans-aminoacylation catalyst, which lends support for the critical role of minihelix-loops in the early evolution of the aminoacylation system.

Diverse roles of metal ions in acyl-transferase ribozymes

The dependence on metal ions for catalysis is one of the hallmark characteristics of ribozymes. Yet despite this universal reliance, the functional role of divalent ions in promoting RNA catalysis is manifold. In this study we elucidate some different roles metal ions play as catalytic cofactors, by comparing two functionally co-evolved acyl-transferase ribozymes. Earlier studies performed on the in vitro selected acyl-transferase ribozyme, E18 [Suga, H., Cowan, J. A., and Szostak, J. W. (1998) Biochemistry 28, 10118-10125], revealed the requirement of a fully hydrated (outer-sphere) Mg2+ ion for catalytic activity. Interestingly, one class of acyl-transferase ribozymes isolated from the same RNA pool as E18 displays a unique metal dependency and is believed to be interacting with inner-sphere coordinated Mg2+ ions. New results show that one of these inner-sphere coordinating ribozymes, HS01, assumes a cloverleaf secondary structure closely resembling E18, yet apparently facilitates a distinct catalytic mechanism. Furthermore, the nature of the RNA-metal interaction(s) in HS01 seems to be dictating a unique reaction mechanism that exhibits a titratable moiety at a near-neutral pK(a). In light of the critical role metal ions play in biochemistry and the proper function of RNAs, these results compare two distinct manners by which metals serve to promote the catalysis of the same reaction.

New calculation of internal Ca(2+) recirculation fraction from alternans decay of postextrasystolic potentiation

In our previous studies, we calculated the internal Ca(2+) recirculation fraction (RF) after obtaining the beat decay constant (tau(e)) of the monoexponential component in the postextrasystolic potentiation (PESP) of the alternans decay by curve fitting. However, this method sometimes suffers from the sensitive variation of tau(e) with small noises in the measured contractilities of the 5th and 6th postextrasystolic (PES) beats in the tail of the exponential component. We now succeeded in preventing this problem by a new method to calculate RF without obtaining tau(e). The equation for the calculation in the new method expresses an alternans decay of PESP as a recurrence formula of PESP. It can calculate RF directly from the contractilities of the 1st through the 4th PES beats without any fitting procedure. To evaluate the reliability of the new method, we calculated RF from the alternans decay of PESP of the left ventricle (LV) of the canine excised cross-circulated heart preparation by both the original fitting and the new method. Although there was no significant difference in the mean value of the obtained RF between these two methods, the variance of RF was smaller with the new method than with the original method. Thus the new method proved useful and more reliable than the original fitting method.

Cardiovascular beneficial effects of electroacupuncture at Neiguan (PC-6) acupoint in anesthetized open-chest dog

Neiguan (PC-6) is a traditional acupoint in the bilateral forearms, overlying the median nerve trunk. Neiguan electroacupuncture (EA) has been believed to affect cardiovascular function and used in traditional Chinese medicine to improve or treat a wide range of health conditions and diseases, including angina pectoris, myocardial infarction, hypertension, and hypotension. However, few physiological studies have assessed the beneficial effects of Neiguan EA on the cardiovascular function. In the present study, we investigated its effects on the cardiovascular function in normal open-chest dogs under pentobarbital and fentanyl anesthesia. We also obtained left ventricular (LV) pressure-volume (P-V) data with a micromanometer catheter and a volumetric conductance catheter. Mean arterial pressure, end-diastolic volume, heart rate, stroke volume, cardiac output, and end-systolic pressure gradually decreased by 5 to 10% over 1.5 h without Neiguan EA. Neiguan EA at 40 Hz, however, increased these cardiovascular variables by 10 to 15%, especially end-systolic elastance (Ees) by 40% (p<0.05) over 15 to 60 min. After Neiguan EA was stopped at 1 h, these facilitated cardiovascular variables decreased below the pre-EA level. This beneficial effect of electroacupuncture may contribute to the effectiveness of the acupuncture in Chinese medicine.