Are you M Takahashi?

Claim your profile

Publications (19)25.59 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Nuclear magnetic resonance (NMR) technology was applied to study the glucose metabolism in Tribolium confusum (Coleoptera). 13C signals of D-(1-13C)glucose eaten by beetles were clearly detected in such metabolites of the glucose metabolism as glycogen, trehalose, triacylglycerol, alanine and proline by 13C-NMR. After glucose feeding the 31P-NMR spectra of T. confusum showed the signal intensity increases in arginine-phosphate, sugar-phosphate and uridine diphosphoglucose. The results demonstrated the potential of NMR analysis for the study of glucose metabolism in T. confusum.
    Entomologia Experimentalis et Applicata 04/2011; 66(3):269 - 274. DOI:10.1111/j.1570-7458.1993.tb00718.x · 1.71 Impact Factor
  • The Veterinary record 05/2004; 154(15):471-2. DOI:10.1136/vr.154.15.471 · 1.63 Impact Factor
  • Parasitology International 08/1998; 47:331-331. DOI:10.1016/S1383-5769(98)80974-4 · 2.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In colonies of Leptotrombidium fletcheri mites infected with Orientia tsutsugamushi (Ot), the agent of scrub typhus, males rarely appear. In the present study, the development of a high ratio of males was observed after introduction of minocycline (MC). A high dose of MC was injected subcutaneously into a mouse, and by feeding unfed larvae from an infected mite colony on this mouse, the Ot in the mites were successfully killed. Of a total of 130 unfed larvae attached to the mouse, 29 developed into females; of these, 9 laid an average of 112.4 eggs/female. Unfed larvae in the succeeding generations were attached to untreated mice. All adults in the P and F1 generation were females, and males started to appear at the F2 generation. The ratio of males to females was 332:7, 108:13, 263:61 and 71:9 at the F2, F3, F4 and F5 generations, respectively. These data suggest that Ot in the ovary or gonad may suppress the development of males.
    European Journal of Epidemiology 02/1997; 13(1):79-86. DOI:10.1023/A:1007341721795 · 5.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Engorged larvae of Leptotrombidium akamushi (Brumpt), a vector of scrub typhus, were reared in small plastic containers placed on the ground and fed fresh eggs of the collembolan Sinella curviseta Brook. Engorged larvae obtained in October developed into deutonymphs through protonymphs approximately 1 mo before winter and became dormant in the cold winter season (approximately 3 mo). Most deutonymphs developed into tritonymphs in April and adults in May. Females began laying eggs in mid-June and the numbers of unfed larvae showed a peak in August. The mites reared from July rapidly developed into adults by August, and laid eggs in September. Larvae were most abundant in October, and adults became dormant in the winter. The same adults laid eggs from early May to late June and, upon hatching, the larval population peaked in early July of the 2nd summer. Most larvae died before the 2nd winter. Eggs hatched approximately 3 wk after oviposition and longevity of unfed larvae was 2 mo. Because of this very short incubation period, L. akamushi larvae occur in the summer, whereas L. pallidum Nagayo, Miyagawa, Mitamura & Tamiya, and L. scutellare Nagayo, Miyagawa, Mitamura, Tamiya & Tenjin occur in the autumn, although 3 species lay eggs from May to August.
    Journal of Medical Entomology 12/1995; 32(6):843-6. DOI:10.1093/jmedent/32.6.843 · 1.82 Impact Factor
  • H Urakami, M Takahashi, M Murata, A Tamura
    [Show abstract] [Hide abstract]
    ABSTRACT: Leptotrombidium pallidum naturally infected with Rickettsia tsutsugamushi was reared and bred in our laboratory for several generations by brother and sister mating. The larvae and adults at the 8th and 9th generations were sectioned and observed by electron microscopy for analysis for the distribution of rickettsiae in the mites. The distribution densities of rickettsiae were markedly different among organs in each mite, but rickettsiae were seen in all the organs and tissues. Rickettsiae were distributed in the highest density in the salivary gland of larvae, and in the salivary gland, excretory bladder, epidermal layer, ovary and testis of adult mites. Only a few rickettsiae were recognized in the muscle of both larvae and adults. On the other hand, we found, in the infected family line used, a significant number of mites in which no rickettsiae were found by electron microscopy. The grouping of rickettsia-positive and -negative mites according to the parent family revealed that the efficiency of vertical transmission of rickettsia was different from one parent family to another. Thus, it became clear that a significant number of rickettsia-negative mites are produced in an infected family line.
    Japanese journal of medical science & biology 07/1994; 47(3):127-39. DOI:10.7883/yoken1952.47.127
  • [Show abstract] [Hide abstract]
    ABSTRACT: Proton nuclear magnetic resonance (1H NMR) spectroscopy was used to characterize the oxidized products in the serum lipoprotein lipids (LPL) of rabbits infected with Schistosoma japonicum. The loss of bis-allylic and allylic methylenes proton peaks (2.7 and 2.0 p.p.m.) of unsaturated systems of the LPL and the appearance of the signals of the conjugated diene systems of hydroperoxide (5.43-6.45 p.p.m.) and epidioxide (2.45 p.p.m.) of the fatty chains of the serum demonstrated the lipids degradation associated with the Schistosoma infection.
    International Journal for Parasitology 06/1994; 24(3):417-9. DOI:10.1016/0020-7519(94)90092-2 · 3.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Larvae of Leptotrombidium pallidum (Nagayo, Miyagawa, Mitamura & Tamiya) from uninfected laboratory colonies were fed on mice infected with Rickettsia tsutsugamushi (Hayashi) Ogata. Infection of the chiggers with R. tsutsugamushi was determined by passage of chigger exudates into ddY mice. The passage method was modified so that an inoculum was considered to be positive when R. tsutsugamushi or anti-R. tsutsugamushi antibody, or both, were detected in mice up to the third blind passage. R. tsutsugamushi was detected in six of 18 larvae (33.3%) and in all developmental stages. In adults, five of 18 males and 10 of 46 females were infected with R. tsutsugamushi. In L. fuji (Kuwata, Berge & Philip), R. tsutsugamushi was not found in 57 engorged larvae fed on rickettsemic mice but was found in a very low percentage of deutonymphs and adults. Female L. pallidum from larvae fed on infected mice were paired individually, and F1 larvae were collected. Although eight females were found to be positive for R. tsutsugamushi, the rickettsia was not detected in 12 pools (249 larvae) of F1 larvae from these infected females. We concluded that uninfected mites became infected by feeding on rickettsemic mice at comparatively high rates depending on the species and transmitted this infection transstadially to succeeding life stages, but not vertically to larvae in the following F1 generation.
    Journal of Medical Entomology 03/1994; 31(2):212-6. DOI:10.1093/jmedent/31.2.212 · 1.82 Impact Factor
  • H Urakami, M Takahashi, E Hori, A Tamura
    [Show abstract] [Hide abstract]
    ABSTRACT: Rickettsia tsutsugamushi in Leptotromibidium pallidum was observed by electron microscopy and rickettsiae were found in the various tissues and organs of both larvae and adults. Budding of rickettsiae, a manner of release from the host cells, was observed only in the rudiments of the reproductive organs in larvae. Oogonia and maturing oocytes in adult females and eggs after oviposition contained the microorganisms. In adult males, rickettsiae were also found in the spermatogonia, spermatocytes, and spermatids in the early stage of spermatogenesis, but were eliminated from these cells during maturation. Only the maturing spermatids, but not the eliminated rickettsiae, migrated to another rickettsia-free area of the testis, resulting in the separation of spermatids from rickettsiae and in the production of rickettsia-free spermatophores. Based on these observations, the mechanism of vertical transmission of the rickettsiae to the progeny occurs only in the female parents. Most rickettsiae in the somatic cells of larvae and adults were coccoid, but some rickettsiae in the ovary and the testis of adult mites showed bacillary forms and were enveloped by a membrane of unknown origin.
    The American journal of tropical medicine and hygiene 03/1994; 50(2):219-28. · 2.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Engorged larvae of Leptotrombidium pallidum Nagayo, Miyagawa, Mitamura & Tamiya, the vector mite of scrub typhus in Japan, were reared by feeding them with fresh eggs of the collembolan Sinella curviseta Brook while confined in small plastic containers under natural conditions in a copse. The larvae were collected from wild rodents (Apodemus speciosus) in autumn 1985 and spring 1986. Adults were kept alive for 2 yr or longer. The larvae obtained in autumn became dormant in the cold winter season, and growth recommenced in the spring. Thus, the development of mites collected in April became synchronized with that of larvae obtained in the autumn. Most larvae developed into protonymphs in May, deutonymphs in June, tritonymphs in July, and adults in August. The females laid eggs in two consecutive summers. Some larvae collected in autumn were kept in a refrigerator until the following summer. They developed into deutonymphs, tritonymphs, or adults and then became dormant in the winter. Development restarted the next spring and all became adult by summer, when the females laid eggs. Under experimental conditions, all larvae are hatched in the autumn, unlike the natural situation in which two peaks of larval occurrence on wild rodents are observed in autumn and spring.
    Journal of Medical Entomology 04/1993; 30(2):320-5. DOI:10.1093/jmedent/30.2.320 · 1.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the epidemiological surveys on scrub typhus at Chichibu City near Tokyo, an area, 350 m by 35 m, in the Hitsujiyama Park was found to be heavily infested with Rickettsia tsutsugamushi (Rt). Distribution of trombiculid mites and their infection rates in this area were studied using sentinel animals, 48 Microtus montebelli and 10 ddY mice. The surveys were conducted 6 times in the autumn in 1985 and 1986. At the first 2 surveys, 16 animals were placed at random, and 4 restricted areas were identified as highly populated with trombiculid mites. For the detailed survey, each of 4 areas was divided into 2 m x 2 m quadrats to settle a sentinel animal to each. A total of mites collected by all sentinel animals was 331 Leptotrombidium pallidum, 175 L. fuji and 16 Gahrliepia saduski. Almost all mites were collected by M. montebelli, except only 1 L. fuji in 10 mice. From a M. montebelli in a quadrat, 157 L. pallidum were recovered, whereas the number/vole was 0 to 24 in the others. L. fuji was also highly aggregated at 2 sites. Rt was detected from individual mites by avidin-biotin immunofluorescence or isolated by the mouse passage from individual or pooled mites. Only Karp strain of Rt was detected or isolated from L. pallidum at a ratio of 31/286 (10.8%). No Rt was found from L. fuji or G. saduski. The infection rate in L. pallidum was especially high in 3 voles at ratios of 6/11, 2/5 and 3/5, respectively. Out of 14 sentinel M. montebelli with infected L. pallidum, 12 (85.7%) were infected with Rt. It was concluded that L. pallidum was distributed in aggregated clusters to form the mite islands and was infected heavily at the specific sites to make the infective spots.
    The Japanese journal of experimental medicine 01/1991; 60(6):325-35.
  • The Japanese journal of experimental medicine 09/1990; 60(4):241-5.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Transmission of Rickettsia tsutsugamushi (Rt) from a rodent to trombiculid mites was studied. Wild rodents, Apodemus speciosus, were subcutaneously inoculated with Karp strain of Rt, and larval trombiculid mites were released on the ear lobes for feeding, 10 and 20 days after infection. Isolation of Rt was performed from individual mites or pools of 2 to 7 mites by the mouse passage method. From Apodemus 10 days after Rt infection, possibly at the time of high rickettsiaemia, the infection rates among mites were 4/44 (9.1%) or higher in Leptotrombidium fuji, 1/20 (5%) in L. pallidum and 0/41 in L. deliense. From Apodemus 20 days after infection, no mite was infected in 50 L. fuji or 7 L. pallidum possibly due to reduced rickettsiaemia. Transmission of Rt from rodent to mite was proven to occur at low probability on appropriate conditions but not by the incidental chance.
    The Japanese journal of experimental medicine 09/1990; 60(4):203-8.
  • [Show abstract] [Hide abstract]
    ABSTRACT: In an attempt to study nitrogen metabolism in a parasite, we applied 15N-nuclear magnetic resonance (NMR) technology with a stable isotope, a 15N-labeled compound, for the study of the transamination system in A. cantonensis eggs, and demonstrated that 15N-aspartic acid can serve as an amino group donor for both the 2-oxoglutaric-glutamic acid and the pyruvic acid-alanine transamination systems in the eggs.
    International Journal for Parasitology 03/1990; 20(1):131-2. DOI:10.1016/0020-7519(90)90186-Q · 3.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 13C-nuclear magnetic resonance (NMR) spectroscopy was used to identify metabolites excreted by Angiostrongylus cantonensis eggs which had been maintained aerobically in the presence of D-[13C6] glucose. Using 13C-NMR we proved that lactate, acetate and alanine originated from glucose present in the medium via glycolysis. Aminooxyacetate, an inhibitor of alanine transferase, inhibited simultaneously alanine production and the ability to take up glutamate, aspartate and valine from the medium. In addition, we demonstrated that these amino acids can serve as amino group donors of the pyruvate to alanine transamination system in the eggs.
    Physiological chemistry and physics and medical NMR 02/1989; 21(2):165-70.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Engorged larvae of Leptotrombidium pallidum were collected from a wild rodent, Apodemus speciosus, and reared in a plastic container fed with fresh eggs of colembolla, Sinella curviseta, under moist conditions at 25 degrees C. Fully developed adults were separated into individual containers and a proven male was paired with a suspected female. Of the pairings, 38 produced larvae and 4 infected colonies were established. Females in these colonies were shown to be infected with Karp type of Rickettsia tsutsugamushi (Rt) by the method of isolating Rt from individual mites using mouse passage. Males were negative for Rt. Vertical transmission of Rt was monitored in each infected colony. The female of parent generation (P) produced F1 and F2 generations. At F1 generation, 11 males and 12 females maintained until production of eggs and all adults were positive for Rt by detection from individual mites. By sibmating of F1 adults, 11 males and 14 females developed at F2 generation and all males and females were proven to be positive for Rt. From 4 pairs of infected males and infected females at F1 generation, 2, 5, 21 and 35 larvae were collected as samples, respectively, and all larvae were positive for Rt by individual detection. Spermatophores from infected males at F2 generation were examined for Rt and none of 29 spermatophores were positive for Rt. From these results, the transmission rate of Rt from P to F1 and from F1 to F2 was 100% through eggs from infected females but not through spermatophores from infected males.
    The Japanese journal of experimental medicine 11/1988; 58(5):213-8.
  • Physiological chemistry and physics and medical NMR 02/1988; 20(4):269-71.
  • [Show abstract] [Hide abstract]
    ABSTRACT: 1H- and 13C-nuclear magnetic resonance (NMR) spectroscopy was used to study aerobic glucose metabolism in eggs of Angiostrongylus cantonensis in an NCTC-109 medium supplemented with fetal calf serum. Without any pretreatment of the spent medium, we were able to identify and quantitate, by NMR, the end-products of glucose metabolism in eggs after cultivation for 2, 4, and 8 days. We demonstrated that A. cantonensis eggs took up glucose rapidly; among the major end products were found lactic acid, acetic acid and alanine. The eggs are parasitic in a sense that the energy metabolism in them is dependent mainly upon the energy source present in outer medium.
    Japanese journal of medical science & biology 03/1987; 40(1):27-33. DOI:10.7883/yoken1952.40.27