Phylogeography of the leaf beetle Chrysolina virgata in wetlands of Japan inferred from the distribution of mitochondrial haplotypes

The genetic differentiation among populations of the leaf beetle Chrysolina virgata living in wetlands of Japan was studied based on the sequence data of the mitochondrial cytochrome oxidase subunit I gene region (750 bp). Two distinct lineages of mitochondrial haplotypes were found: one (clade A) consisted of 26 haplotypes distributed over the distribution range of C. virgata between north‐east Honshu and Kyushu, whereas the other (clade B) was monotypic and confined to a small region in north‐east Honshu where it coexisted with clade A. Nested clade analysis for these haplotypes suggested that range expansion and following differentiation due to isolation by distance might have resulted in the present distribution pattern of the haplotypes in clade A. We discuss the evolutionary process leading to the occurrence of two distinct haplotype clades in Japan in terms of repeated colonization from the continent and range expansion and contraction during climatic changes.     

Nucleotide sequence and presumed secondary structure of the 28S rRNA of pea aphid implication for diversification of insect rRNA

Determination of the entire nucleotide sequence of the aphid 28S ribosomal RNA gene (28S rDNA) revealed that it is 4,147 by in length with a G + C content of 60.3%. Based on the nucleotide sequence, we constructed a presumed secondary-structure model of the aphid 28S rRNA which indicated that the aphid 28S rRNA is characterized by the length and high G + C content of its variable regions. The G + C content of the aphid's variable regions was much higher than that of the entire sequence of the 28S rRNA, which formed a striking contrast to those ofDrosophila with the G + C content much lower than the entire 28S molecule. In this respect, the aphid 28S rRNA somewhat resembled those of vertebrates. This is the third report of a complete large-subunit rRNA sequence from an arthropod, and the first 28S rRNA sequence for a nondipterous insect. Correspondence to: H. Ishikawa     

Evolution of the therian face through complete loss of the premaxilla

The anatomical framework of the jawbones is highly conserved among most of the Osteichthyes, including the tetrapods. However, our recent study suggested that the premaxilla, the rostralmost upper jaw bone, was rearranged during the evolution of therian mammals, being replaced by the septomaxilla at least in the lateral part. In the present study, to understand more about the process of evolution from the ancestral upper jaw to the therian face, we re-examined the development of the therian premaxilla (incisive bone). By comparing mouse, bat, goat, and cattle fetuses, we confirmed that the therian premaxilla has dual developmental origins, the lateral body and the palatine process. This dual development is widely conserved among the therian mammals. Cell-lineage-tracing experiments using Dlx1-CreER^T2 mice revealed that the palatine process arises in the ventral part of the premandibular domain, where the nasopalatine nerve distributes, whereas the lateral body develops from the maxillary prominence in the domain of the maxillary nerve. Through comparative analysis using various tetrapods, we concluded that the palatine process should not be considered part of the ancestral premaxilla. It rather corresponds to the anterior region of the vomerine bone of nonmammalian tetrapods. Thus, the present findings indicate that the true premaxilla was completely lost during the evolution of the therian mammals, resulting in the establishment of the unique therian face as an evolutionary novelty. Reconsideration of the homological framework of the cranial skeleton based on the topographical relationships of the ossification center during embryonic development is warranted.     

Purification and Characterization of Rice Embryo BAPAase (Benzoyl-L-arginine p-nitroanilide Hydrolase)

Benzoyl-L-arginine p-nitroanilide hydrolase (BAPAase), whichhas both endopeptidase and carboxypeptidase activity towardthe Arg-X or Lys-X bond of small peptides [Shibata and Doi (1984)Plant & Cell Physiol. 25: 1421], was purified from riceembryos by ammonium sulfate and polymin fractionations and byion exchange, gel exclusion and hydrophobic chromatographies.The purified enzyme was homogeneous when analyzed by polyacrylamidegel electrophoresis. It was unstable in the absence of surface-activereagents such as Triton X-100. Maximum activity for benzoyl-Largininep-nitroanilide (L-BAPA) or carboxypeptidase activity towardbutoxycarbonyl-Gly-Lys-Leu was obtained at pH 9.0. L-BAPA athigh concentrations inhibited the enzyme's activity. Di-isopropylphosphofluoridate, N-tosyl-L-lysine chloromethyl ketone, leupeptinand antipain, which are specific inhibitors of trypsin, inhibitedBAPAase activity, but soybean and rice bran trypsin inhibitorhad no effect on it. Sulfhydryl reagents strongly inhibitedthe BAPAase activity. (Received May 26, 1984; Accepted August 29, 1984)     

Role of carbonic anhydrase in photosynthetic CO2 fixation in Chlorella

Chlorella vulgaris 11h cells grown in air enriched with 4% CO₂(high-CO² cells) had carbonic anhydrase (CA) activity whichwas 20 to 90 times lower than that of algal cells grown in ordinaryair (containing 0.04% CO₂, low-CO₂ cells). The CO₂ concentrationduring growth did not affect either ribulose 1,5-bisphosphate(RuBP) carboxylase activity or its Km for CO₂. When high-CO₂ cells were transferred to low CO₂ conditions,CA activity increased without a lag period, and this increasewas accompanied by an increase in the rate of photosynthetic¹⁴CO₂ fixation under ¹⁴CO₂-limiting conditions. On the otherhand, CA activity as well as the rate of photosynthetic ¹⁴CO₂fixation at low ¹⁴CO₂ concentrations decreased when low-CO₂cells were transferred to high CO₂ conditions. Diamox, an inhibitor of CA, at 0.1 mM did not affect photosynthesisof low-CO₂ cells at high CO₂ concentration (0.5%). Diamox inhibitedphotosynthesis only under low CO₂ concentrations, and the lowerthe CO₂ concentration, the greater was the inhibition. Consequently,the CO₂ concentration at which the rate of photosynthesis attainedone-half its maximum rate (Km) greatly increased in the presenceof this inhibitor. When CO₂ concentration was higher than 1%, the photosyntheticrate in low-CO₂ cells decreased, while that in high-CO₂ cellsincreased. Fractionation of the low-CO₂ cells in non-aqueous medium bydensity showed that CA was fractionated in a manner similarto the distribution of chlorophyll and RuBP carboxylase. These observations indicate that CA enhances photosynthesisunder CO₂-limiting conditions, but inhibits it at CO₂ concentrationshigher than a certain level. The mechanism underlying the aboveregulatory functions of CA is discussed. ¹This work was reported at the International Symposium on PhotosyntheticCO₂-Assimilation and Photorespiration, Sofia, August, 1977 (18).Requests for reprints should be addressed to S. Miyachi, RadioisotopeCentre, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan. (Received December 11, 1978; )     

Identification of asymptomatic Entamoeba histolytica infection by a serological screening test: A cross-sectional study of an HIV-negative men who have sex with men cohort in Japan

BackgroundAmebiasis, caused by Entamoeba histolytica, is spreading in developing countries and in many developed countries as a sexually transmitted infection. Here, we evaluated the efficacy of serological screening to identify asymptomatic E. histolytica infection as a potential epidemiological control measure to limit its spread.Methodology/Principal findingsThis cross-sectional study was carried out between January and March 2021 in an HIV-negative men who have sex with men (MSM) cohort at the National Center for Global Health and Medicine. Serological screening was performed using a commercially available ELISA kit. For seropositive individuals, we performed stool polymerase chain reaction (PCR) to determine current E. histolytica infection. We performed E. histolytica serological screening of 312 participants. None had a history of E. histolytica infection prior to the study. The overall E. histolytica seropositivity was 6.7% (21/312), which was similar to that found by the rapid plasma reagin test (17/312). We identified current infection in 8 of 20 seropositive participants (40.0%) by stool PCR.Conclusions/SignificanceOur serological screening approach constitutes a potentially practical epidemiological strategy. Active epidemiological surveys, in combination with an effective screening strategy for asymptomatically infected individuals, should be applied to help reduce sexually transmitted E. histolytica infections.