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Biomedical subjects

M Aikawa

Publications and source records attributed to M Aikawa.

At least 73 records · Page 4Linked to original sources
PubMed1998

Isolation of merozoite rhoptries, identification of novel rhoptry-associated proteins from Plasmodium yoelii, P. chabaudi, P. berghei, and conserved interspecies reactivity of organelles and proteins with P. falciparum rhoptry-specific antibodies.

Rhoptries were isolated from merozoites of P. yoelii (17 XL), P. chabaudi adami and P. berghei (K-173), using sucrose gradient density centrifugation. Mouse antisera was prepared against the organelles and characterized. Antibodies specific for a known P. yoelii rhoptry protein were used to identify gradient fractions containing rhoptries and electron microscopy was used to confirm rhoptry enrichment and organelle morphology. Western blotting analysis of the gradients with organelle-specific antisera from each species, revealed several major cross-reactive interspecies protein bands of approximately 235, 210, 180, 160/170, 140, and 96-110 kDa, predominantly in densities of 1.12 and 1.15 g/ml. The parasite origin of the proteins was verified by immunoprecipitation, and reactive epitopes localized to the rhoptries by IEM. By Western blotting antisera specific for P. falciparum rhoptries reacted with protein bands of approximately 96-110 kDa in schizont extracts, and gradient fractions of density 1.12 and 1.15 g/ml from all three rodent malaria species, as well as with the rhoptries in P. yoelii, P. chabaudi, and P. berghei merozoites by IEM. We conclude that the three rodent malaria species and P. falciparum share conserved interspecies epitopes.

Animals↗
PubMed1998

Plasmodium yoelii: identification of rhoptry proteins using monoclonal antibodies.

Thirteen monoclonal antibodies, obtained after immunization of mice with Plasmodium yoelii schizonts, were selected using immunofluorescence assay: they all presented typical fluorescence patterns of rhoptries. This antigen localization was confirmed by immunoelectron microscopy. The molecular weights of the recognized antigens are 68, 80, 105, 130 and 140 kDa as determined by immunoprecipitation and immunoblot under reducing and nonreducing conditions. These values are very similar to these of the low and high molecular weight complex components of Plasmodium falciparum. Furthermore, these antigens are soluble like P. falciparum rhoptry proteins. Interestingly, our monoclonal antibodies also reacted with two other Plasmodium species (Plasmodium berghei NKK173 strain and P. yoelii nigeriensis 798 VK strain), giving sometimes more complex labeling with apical, membranous, nuclear, or/and cytoplasmic localizations. Finally, none of the monoclonal antibodies stained the rhoptries of P. falciparum FCCE-1/Niger strain.

Animals↗
PubMed1998

The prime role of plasma membrane cholesterol in the pathogenesis of immune evasion and clinical manifestations of falciparum malaria.

The pathogenesis of falciparum malaria, with its immune evasion, mechanism of immune suppression and immunological inertia, the cause of its preferential incidence in children and pregnant mothers, and the pathological basis of clinical manifestations, are discussed from biochemical, biophysical and immunological perspectives. Sequestration and recrudescence are highlighted as the evolved means by which malaria parasites survive. These discussions are based on a novel hypothesis that changes in the lipid matrix fluidity of plasma membrane, through alterations of cholesterol and phospholipid content and variation in body temperature, significantly affect the membrane functions of cells. The pathogenesis of aggressive behavior in cerebral malaria is postulated to be different from that of coma, and complicated pregnancy in malaria is also discussed as a multifactorial condition wherein hypocholesterolemia, resulting from increased membrane biogenesis of multiplying parasites, is the common underlying factor.

Aggression↗
PubMed1998

The pivotal role of carbonic anhydrase in malaria infection.

Carbon dioxide (CO2) is essential for the growth of intraerythrocytic malaria parasites to synthesize pyrimidine through CO2 fixation and to regulate intracellular pH. CO2 transport across the plasma membrane of erythrocytes is facilitated by carbonic anhydrase (CA). With the use of electron microscopy and CA-specific Hansson's stain, CA is found also in all the intraerythrocytic stages of Plasmodium falciparum. When CA inhibitors, including acetazolamide, potassium iodide, and sodium deoxycholate, were added to continuous culture of P. falciparum, they, particularly sodium deoxycholate, produced a marked reduction in parasitemia. These results explain the biochemical basis of some of the clinical conditions associated with malaria and strongly suggest that CA inhibitors have potential as a new class of antimalarials.

Animals↗
PubMed1998

Effect of probucol on smooth muscle cell proliferation and dedifferentiation after vascular injury in rabbits: possible role of PDGF.

We previously reported a clinical study in which probucol reduced the restenosis rate. The mechanism of this effect is unclear. Restenosis is characterized by neointimal hyperplasia caused by proliferation of smooth muscle cells (SMCs), which increases the expression of Platelet-derived growth factor (PDGF)-A and SMemb. SMemb, a non-muscle-type myosin heavy chain most predominantly expressed in embryonic smooth muscle, can be used as a good molecular marker for dedifferentiated SMC. The aim of this study was to analyze the effect of probucol on neointimal proliferation and the level of expression of PDGF-A and SMemb after balloon injury in rabbits. Probucol was given orally 1.3 g/d from 2 weeks prior to carotid balloon injury to the time of killing (2 or 4 weeks after balloon injury). Intimal area was determined histologically using a computerized morphometry program. For quantification of SMC proliferation, alpha-actin-positive cells and proliferating cell nuclear antigen (PCNA)-labeled cells were counted. The expression of PDGF-A and SMemb mRNA was analyzed by the RNase protection assay. SMemb expression was also examined by immunohistochemistry. Probucol remarkably decreased intimal area by 70% and the number of SMC and PCNA-labeled cells in the intima. The expression of PDGF-A mRNA was significantly increased after balloon injury in untreated rabbits, whereas it was markedly suppressed with probucol treatment. The expression of SMemb was significantly increased in injured arteries at mRNA and protein levels. However, probucol did not suppress SMemb expression. Probucol is effective in preventing SMC proliferation, which is possibly due to a decrease in the expression of PDGF.

Angioplasty, Balloon↗
PubMed1998

Efficacy of MK-991 (L-743,872), a semisynthetic pneumocandin, in murine models of Pneumocystis carinii.

In addition to its potent efficacy in animal models against Candida sp., Aspergillus fumigatus, and Histoplasma capsulatum, the clinical candidate pneumocandin MK-991 (formerly L-743,872) was also extremely potent against Pneumocystis carinii in models of immune-compromised animals. MK-991 was approximately 14 times more potent than the original natural product lead, pneumocandin B0. The 90% effective dose (ED90) of MK-991 for cyst clearance in the rat model for pneumocystis was 0.011 mg/kg of body weight when delivered parenterally for 4 days twice a day (b.i.d.). In a mouse model, under the same experimental parameters, the ED90 was 0.02 mg/kg. MK-991 was also effective orally, with an ED90 for cyst clearance of 2.2 mg/kg against acute infection in rats (b.i.d. for 4 days). Complete prevention of P. carinii development was achieved in immunocompromised mice at a daily oral dose of 2.25 mg/kg. As reported previously for other pneumocandins and echinocandins, MK-991 selectively prevented the development of P. carinii cysts. When used as a prophylactic agent, neither stage of the organism appeared in the lungs of animals. In response to an acute infection, cysts were eliminated rapidly, while trophozoite forms persisted. Despite good efficacy as an oral agent in murine models, the low oral absorption of this class may limit the use of MK-991 to parenteral therapy.

Administration, Oral↗
PubMed1998

Diagnosis of kala-azar by nested PCR based on amplification of the Leishmania mini-exon gene.

To diagnose visceral leishmaniasis (kala-azar), we have developed a nested PCR method based on amplification of the mini-exon gene, which is unique and tandomly repeated in the Leishmania genome. Nested PCR was sufficiently sensitive for the detection of DNA in an amount equivalent to a single Leishmania parasite or less. We examined the usefulness of this PCR method using bone marrow aspirates and buffy coat cells collected from kala-azar patients who had or had not received chemotherapy in northwest China. We obtained PCR positivity for all of the parasitologically positive bone marrow samples from the patients. Some ambiguities with the primary PCR results were eliminated by the subsequent nested PCR. The buffy coat samples from 7 of 12 patients with splenomegaly were positive by the nested PCR, although only 2 of them were positive for parasites by culture. However, buffy coat samples from nine children, whose splenomegaly has been reduced and clinically cured by antimony treatment, were all negative. Thus, this nested PCR method represents a new tool for the diagnosis of kala-azar with patient blood samples instead of bone marrow or spleen aspirates obtained by more invasive procedures.

Adolescent↗
PubMed1998

Assessment of vasoactive agents and vascular aging by the second derivative of photoplethysmogram waveform.

To evaluate the clinical application of the second derivative of the fingertip photoplethysmogram waveform, we performed drug administration studies (study 1) and epidemiological studies (study 2). In study 1, ascending aortic pressure was recorded simultaneously with the fingertip photoplethysmogram and its second derivative in 39 patients with a mean+/-SD age of 54+/-11 years. The augmentation index was defined as the ratio of the height of the late systolic peak to that of the early systolic peak in the pulse. The second derivative consists of an a, b, c, and d wave in systole and an e wave in diastole. Ascending aortic pressure increased after injection of 2.5 microg angiotensin from 126/74 to 160/91 mm Hg and decreased after 0.3 mg sublingual nitroglycerin to 111/73 mm Hg. The d/a, the ratio of the height of the d wave to that of the a wave, decreased after angiotensin from -0.40+/-0.13 to -0.62+/-0.19 and increased after nitroglycerin to -0.25+/-0.12 (P<0.001 and P<0.001, respectively). The negative d/a increased with increases in plethysmographic and ascending aortic augmentation indices (r=0.79, P<0.001, and r=0.80, P<0.001, respectively). The negative d/a reflects the late systolic pressure augmentation in the ascending aorta and may be useful for noninvasive evaluation of the effects of vasoactive agents. In study 2, the second derivative of the plethysmogram waveform was measured in a total of 600 subjects (50 men and 50 women in each decade from the 3rd to the 8th) in our health assessment center. The b/a ratio increased with age, and c/a, d/a, and e/a ratios decreased with age. Thus, the second derivative aging index was defined as b-c-d-e/a. The second derivative wave aging index (y) increased with age (x) (r=0.80, P<0.001, y=0.023x-1.515). The second derivative aging index was higher in 126 subjects with any history of diabetes mellitus, hypertension, hypercholesterolemia, and ischemic heart disease than in age-matched subjects without such a history (-0.06+/-0.36 versus -0.22+/-0.41, P<0.01). Women had a higher aging index than men (P<0.01). The b-c-d-e/a ratio may be useful for evaluation of vascular aging and for screening of arteriosclerotic disease.

Aged↗
PubMed1998

New insights into plaque stabilisation by lipid lowering.

Thrombosis on the substrate of a disrupted plaque causes most acute coronary events. The physical integrity of the plaque thus governs the most important clinical manifestations of atherosclerosis. Of particular importance is the extracellular matrix of the fibrous capsule overlying the thrombogenic core of the atheroma. Stable atheroma generally have thick fibrous caps, and smaller lipid cores than lesions that have ruptured. Accumulating evidence supports a key role for inflammation as another critical determinant of the stability of human atherosclerotic plaques. Plaques that rupture usually have more abundant leucocytic infiltrates than those considered stable. Inflammatory mediators such as cytokines can influence several biological processes that regulate the stability of the plaque's fibrous cap, and thus its resistance to rupture. For example, interferon-gamma produced by activated T lymphocytes within atheroma inhibits the production of interstitial forms of collagen by human vascular smooth muscle cells. Inflammatory cytokines such as interleukin-1, tumour necrosis factor (TNF) and CD-40 ligand (a cell surface homologue of TNFalpha) can also elicit the expression by macrophages and smooth muscle cells of proteolytic enzymes that can weaken the extracellular matrix. We have hypothesised that lipid lowering reduces stimuli for the inflammatory response within the complex atherosclerotic lesion. Recent studies in rabbits with experimentally produced atherosclerosis have indeed shown that lipid lowering can (i) reduce macrophage numbers, (ii) decrease expression of the collagenolytic enzyme MMP-1, and (iii) reinforce the plaque's fibrous skeleton by increasing the content of interstitial collagen. By reducing local inflammation, lipid lowering can thus stabilise the plaque's fibrous cap, rendering the atheroma less prone to rupture and to precipitate thrombotic complications. These observations provide a mechanistic basis for understanding the marked reduction in acute coronary events and cerebrovascular accidents observed in patients treated with agents that reduce plasma lipids.

Animals↗
PubMed1998

Pentoxifylline as an ancillary treatment for severe falciparum malaria in Thailand.

Pentoxifylline, an inhibitor of tumor necrosis factor, has been evaluated as an antimalarial agent in combination with artesunate in 45 patients with severe falciparum malaria. Patients were admitted to the intensive care unit at the Hospital for Tropical Diseases in Bangkok, Thailand, and randomly assigned to treatment for 72 hr with a combination of intravenously administered artesunate and 1) placebo, 2) low-dose pentoxifylline (0.83 mg/kg/hr), or 3) high-dose pentoxifylline (1.67 mg/kg/hr). All 45 patients had one or more manifestations of severe malaria such as cerebral malaria (n = 18), renal failure requiring hemodialysis (n = 9), azotemia (n = 8), jaundice (n = 25), or hyperparasitemia (n = 30). The overall severity was comparable in the three groups. Clinical outcome was assessed with respect to the parasite clearance time and the fever clearance time in all patients. In addition, a number of subsidiary outcome variables were examined in specific subgroups, including the recovery time from coma for patients with cerebral malaria, the duration of intubation in patients with respiratory distress, the number of hemodialysis treatments needed for patients with acute renal failure, and the number of units of blood administered to patients requiring transfusion. Concentrations of tumor necrosis factor were reduced in all three groups at 48 hr after treatment. No significant differences among the three treatment groups were found for any of the outcome variables examined. We conclude that the addition of pentoxifylline to artesunate therapy for severe malaria produced no evident clinical benefit.

Adolescent↗
PubMed1998

[A case report of use of horseshoe kidney as renal transplant from live donor].

This is a report on a surgery performed in February, 1995 describing the donation of a living donor's horseshoe kidney used for renal transplantation. The recipient was a 31 years-old male on hemodialysis since 1994. The donor was the healthy 55 years-old father of the recipient who had an uncomplicated horseshoe kidney. The isthmus was perfused by an accessory artery. Via transperitoneal approach, the horseshoe kidney was mobilized for in situ perfusion. A microwave coagulator was used to divide the isthmus, and the cut surfaces were closed by mattress sutures and fibrin glue. The left kidney was transplanted into the recipient's right iliacfossa. While his post-transplant course was complicated by urinary leakage, the graft remained free of rejection until and beyond the 6 months post transplant period when he was discharged at s-Cr 1.7 mg/dl. The donor's convalescence was uneventful. During the 20 months post-transplant period both the donor and recipient are doing well.

Adult↗
PubMed1998

Tenascin takes part in the progress of pathological severity in cerebral falciparum infection.

We examined plasma level of circulating form of tenascin (TC) in falciparum malaria patients, cerebral malaria and non cerebral malaria, and compared them to uninfected healthy persons. Plasma level of TC examined were significantly higher in malaria patients than in control persons (p< 0.01). The results also show that among malaria patients, TC level was higher in the cerebral malaria patients compare to non cerebral malaria patients (p<0.10). Kinetics of TC level in plasma were related to kinetics of TNF-alpha level. Moreover, patients with higher level of TC showed higher level of parasitized erythrocytes binding ratio. Immunohistochemical study showed that TC was found in the cerebral microvessels of postmortem cerebral tissues from nine cerebral malaria cases. These results provide evidence that plasma level of TC correlates with the severity in cerebral malaria patients.

Brain↗
PubMed1998

Leishmania mini-exon genes for molecular epidemiology of leishmaniasis in China and Ecuador.

The mini-exon gene is unique and is tandemly repeated in the Leishmania genome. The transcribed region is highly conserved, but the non-transcribed spacer region is distinct in length and in sequence among different Leishmania species. The usefulness of PCR amplification of the Leishmania mini-exon gene was examined for molecular epidemiology of visceral and cutaneous leishmaniasis. We previously described a PCR method for amplification of the mini-exon gene and obtained positive amplification in bone marrow aspirates of patients with visceral leishmaniasis in China. In this study, we have cloned and sequenced two PCR products from the patients. The sequences of two products revealed 100% identity and showed more similarity to the mini-exon gene of L. donovani Indian strain than those of L. donovani complex in Africa and South America. We also applied this PCR method to the diagnosis of cutaneous leishmaniasis. We obtained positive PCR amplification in skin biopsy materials taken from patients with cutaneous leishmaniasis in Ecuador. Since this PCR amplification is simple and requires only a pair of primers to detect all Leishmania species distributed in Ecuador, the method may be a useful tool for the detection of parasites, not only from patients, but also from sandflies and reservoir animals in this area of endemicity.

Animals↗
PubMed1998

Serological evaluation of malaria patients in Thailand: antibody response against electrophoresed antigenic polypeptides of Plasmodium falciparum.

It was reported that a 47kDa antigenic polypeptide of Plasmodium falciparum had been strongly presented by the sera from 1) imported Japanese malaria patients with severe symptoms and 2) symptomatic and parasitemic inhabitants in endemic areas in the Sudan, Malaysia and the Philippines. In the present study, we observed the reactivity of the sera from falciparum malaria patients who had been hospitalized in the Bangkok Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, and compared the antibody response against the 47kDa antigenic polypeptide according to the severity of the patients. It was observed that antibodies to this molecule were more commonly shared in sera from severer patients, although the IFAT titers against the whole P. falciparum parasite antigen were lower in the group, which suggested that this antibody against the 47kDa molecule was playing a specific role at a severe stage of the infection. Determination of the immunological features of the antigenic molecules of parasites by this type of sero-epidemiological study will provide a new assay system for evaluation of immune status of individuals in different severity and suggest a way of vaccine development.

Adolescent↗
PubMed1997

Isolation of the embryonic form of smooth muscle myosin heavy chain (SMemb/NMHC-B) gene and characterization of its 5'-flanking region.

To examine the molecular mechanisms that regulate the expression of the SMemb/NMHC-B gene, a nonmuscle myosin heavy chain isoform predominantly expressed in fetal aorta, we have isolated and characterized the 5'-flanking region of the rabbit SMemb/NMHC-B gene. Transient transfection experiments demonstrated that 105 base pairs of 5'-flanking sequence was necessary to direct high level transcription in C2/2 cells, vascular smooth muscle cells derived from rabbit aorta. An essential cis-regulatory element was localized between -100 and -91 base pairs from the transcription start site based on the results that replacement mutagenesis within this region significantly reduced promoter activity. Sequence of this region is completely conserved between mouse and rabbit and fits no known DNA binding consensus. Gel mobility shift assays revealed that a specific DNA-protein complex was formed at this site with nuclear extracts from C2/2 cells, which can be competed by H-2Kb CCAAT box but not by Hsp70 CCAAT box or other CCAAT-containing sequences. We conclude that expression of the SMemb/NMHC-B gene is regulated through an interaction between a sequence element located at -100 and a distinct member of CCAAT-binding proteins.

3T3 Cells↗
PubMed1997

Redifferentiation of smooth muscle cells after coronary angioplasty determined via myosin heavy chain expression.

BACKGROUND: The pathophysiology of phenotypic modulation of smooth muscle cells (SMCs) involved in restenosis after angioplasty is not well understood. Smooth muscle myosin heavy chain (SM MHC) isoforms (SM1 and SM2) are specific markers for SMC differentiation. In particular, SM2 is useful as a marker of mature SMCs. SMemb is a nonmuscle myosin heavy chain (NM MHC) whose expression is upregulated in immature or activated SMC. METHODS AND RESULTS: To determine SMC phenotypes in neointimal tissues after percutaneous transluminal coronary angioplasty (PTCA), we performed immunohistochemistry on human coronary arteries with antibodies against alpha-SM actin, SM1, SM2, and SMemb. Tissues were obtained from six autopsied patients and from atherectomy specimens from 16 patients who had undergone PTCA. Medial SMCs were positive for alpha-actin, SM1, and SM2. Expression of SM1 and SM2 in the neointima varied with the time after intervention, whereas alpha-actin was constitutively expressed in all cases studied. Neointimal cells at 16 and 20 days after PTCA contained alpha-actin but little or no SM1 or SM2, indicating that these cells modulated their phenotype to the immature state. Neointimal SMCs recovered SM MHC expression, first SM1 and then SM2, by 6 months after PTCA. Increased expression of SMemb was found in the neointima but without apparent relationship to the time after PTCA. CONCLUSIONS: Neointimal SMCs show features of an undifferentiated state, indicated by altered expression of SM MHC, and undergo redifferentiation in a time-dependent manner. The expression of SM MHC isoforms provides insight into the biology of healing after angioplasty and furnishes useful tools for the understanding of the roles of differentiation and phenotypic modulation of SMCs in human vascular lesions.

Aged↗