Biomedical subjects

M Horiuchi

Publications and source records attributed to M Horiuchi.

At least 91 records · Page 5Linked to original sources

PubMed1999

Mutational analysis of human immunodeficiency virus type 1 vif gene.

Mutations were introduced into scattered regions of the HIV-1 vif gene. The twelve in-frame mutants generated were evaluated for the replication potentials in cells by transfection and infection experiments. All the mutants produced a normal level of progeny virions upon transfection, indicating the absence of the late function of HIV-1 Vif protein. The infectivity of virions obtained was monitored in H9 cells, which are non-permissive for HIV-1 without the Vif function. Most of the mutations in various parts of the vif gene, including those in the three conserved regions among HIV/SIV, abrogated the infectivity of the virus. In contrast, the cysteine residue at position 133, which was reported to be critical for viral infectivity, was found not to be essential. In addition, the C-terminal eight amino acid residues (185-192) in the Vif protein could be deleted with no effects on viral growth potential.

Gene Products, vif↗

PubMed1999

Renin-angiotensin system and fibronectin gene expression in Dahl Iwai salt-sensitive and salt-resistant rats.

OBJECTIVE: The tissue renin-angiotensin system and extracellular matrix are involved in the cardiovascular hypertrophy and remodeling induced by hypertension. In this study, we examined the gene expression of the tissue renin-angiotensin system and fibronectin in inbred Dahl Iwai salt-sensitive and salt-resistant rats. MATERIALS AND METHODS: Eight pairs of 6-week-old male Dahl Iwai salt-sensitive and salt-resistant rats were fed either a low- or high-salt diet (0.3% or 8% NaCl, respectively) for 4 weeks. Activities of the circulating renin-angiotensin system were measured by radioimmunoassay and the gene expression of tissue angiotensinogen, the angiotensin II type 1 receptor (AT1) and fibronectin were analyzed by Northern blot analysis. RESULTS: Salt loading significantly increased blood pressure and produced cardiovascular hypertrophy and nephrosclerosis in the salt-sensitive rats. Activities of the circulating renin-angiotensin system were lower in salt-sensitive rats than in salt-resistant rats fed the low-salt diet, and salt loading lowered these activities in salt-resistant rats but not in salt-sensitive rats. In salt-resistant rats, salt loading increased renal, cardiac and aortic angiotensinogen, AT1 and fibronectin messenger (m)RNA expression except for aortic fibronectin mRNA expression. In contrast, in the salt-sensitive rats, salt loading stimulated the expression of cardiac fibronectin and aortic angiotensinogen, AT1 and fibronectin mRNAs. Furthermore, the cardiac and aortic fibronectin mRNA levels in salt-sensitive rats were higher than those in salt-resistant rats when both strains were fed the high-salt diet. CONCLUSIONS: These results demonstrate that the expression of tissue angiotensinogen, AT1 and fibronectin mRNAs is regulated differently in Dahl Iwai salt-sensitive and salt-resistant rats, and indicate that salt-mediated hypertension activates the cardiac fibronectin gene independently of the tissue renin-angiotensin system and stimulates the aortic fibronectin gene with activation of the tissue renin-angiotensin system.

Angiotensin I↗

PubMed1999

Possible involvement of IL-12 expression by Epstein-Barr virus in Sjögren syndrome.

AIM: To determine the correlation between interleukin 12 (IL-12) expression and Epstein-Barr virus (EBV) in Sjögren syndrome. METHODS: Indirect immunohistochemical technique, enzyme linked immunosorbent assay (ELISA), and immunoblot analysis were used to investigate IL-12 expression by EBV activation, using 13 surgical specimens and four B cell lines. RESULTS: Marked expression of IL-12 was found in the epithelial cells and the infiltrating B cells of salivary gland tissues from patients with Sjögren syndrome (six of 10 cases), but not in those from normal individuals (none of three cases). A striking topographic correlation between IL-12 and EBV was found. In addition, levels of IL-12 production by B cell lines were clearly enhanced by EBV activation in vitro. CONCLUSIONS: IL-12 expression closely reflects the intracellular event of EBV activation in Sjögren syndrome, and may contribute to the T helper cell type 1 (Th1) cytokine overexpression seen in this disease.

Adult↗

PubMed1999

Interferon regulatory factors regulate interleukin-1beta-converting enzyme expression and apoptosis in vascular smooth muscle cells.

-Apoptosis has been reported to play a pivotal role in vascular remodeling. However, cellular mechanisms of apoptosis in vascular smooth muscle cells (VSMCs) have not been well defined. In this study, we focused on interleukin-1beta-converting enzyme (ICE), a key protease in the induction of apoptosis in lymphocytes and fibroblasts. We observed an increase in ICE mRNA expression in rat aortic VSMCs after serum depletion, with a peak at 12 hours and then a gradual decline. This was associated with DNA fragmentation, a hallmark of apoptosis and morphological changes of apoptosis. Treatment of these VSMCs with the ICE inhibitor N-(N-acetyl-tyrosinyl-valinyl-alaninyl)-3-amino-4-oxob utanoic acid (YVAD-CHO) attenuated DNA fragmentation. The increased ICE mRNA expression was preceded by an increase in the mRNA expression of interferon regulatory factor (IRF)-1, peaking at 6 hours after serum removal, and a rapid but transient decrease in IRF-2 mRNA expression, reaching a nadir at 3 hours after serum depletion. To demonstrate that these reciprocal changes in IRF-1 and IRF-2 regulated ICE expression and induced apoptosis, we transfected antisense oligonucleotides for IRF-1 and IRF-2 into VSMCs and examined ICE mRNA expression and apoptotic changes. IRF-1 antisense pretreatment attenuated the increase in ICE expression and reduced apoptotic changes, whereas IRF-2 antisense treatment increased ICE mRNA expression and enhanced apoptotic changes. Taken together, our results suggest that serum growth factor depletion in VSMCs upregulates IRF-1 and downregulates IRF-2, thereby increasing ICE expression and inducing apoptosis.

Animals↗

PubMed1999

Recent progress in angiotensin II type 2 receptor research in the cardiovascular system.

Angiotensin II (Ang II) plays an important role in regulating cardiovascular hemodynamics and structure. Multiple lines of evidence have suggested the existence of Ang II receptor subtypes, and at least 2 distinct receptor subtypes have been defined on the basis of their differential pharmacological and biochemical properties and designated as type 1 (AT1) and type 2 (AT2) receptors. To date, most of the known effects of Ang II in adult tissues are attributable to the AT1 receptor. Recent cloning of the AT2 receptor contributes to reveal its physiological functions, but many functions of the AT2 receptor are still an enigma. AT1 and AT2 receptors belong to the 7-transmembrane, G protein-coupled receptor family. However, accumulating evidence demonstrates that the function and signaling mechanisms of these receptor subtypes are quite different, and these receptors may exert opposite effects in terms of cell growth and blood pressure regulation. We will review the role of the AT2 receptor in the cardiovascular system and the molecular and cellular mechanisms of AT2 receptor action.

Adult↗

PubMed1999

AT2 receptor and vascular smooth muscle cell differentiation in vascular development.

The angiotensin II type 2 (AT2) receptor is transiently expressed at late gestation in the fetal vasculature, but its expression rapidly declines after birth. We have previously demonstrated that the expression of this receptor mediates decline in vascular DNA synthesis that occurs at this stage of vascular development. To examine further the role of the AT2 receptor in vasculogenesis, we have focused on the effect of the AT2 receptor on vascular smooth muscle cell (VSMC) differentiation. In this study, we examined the time-dependent expression of differentiation markers for VSMCs in the aorta of wild-type and AT2 receptor-null mice. alpha-Smooth muscle actin was expressed at the early stage of differentiation and exhibited unchanged expression before and after the peak of AT2 receptor expression, which was observed at embryonic day 20, neonatal day 1, and thereafter. No difference in alpha-smooth muscle actin expression was observed between the wild-type and AT2 receptor-null mice. In contrast, the mRNA levels for calponin, expressed in the late stage of VSMC differentiation, were significantly higher in the wild-type mouse aorta as compared with the AT2 receptor-null mice, which correlates with expression of the AT2 receptor. Moreover, the protein levels of calponin and high-molecular-weight caldesmon (h-caldesmon) showed lower expression in the aorta of AT2 receptor knockout mice at 2 and 4 weeks after birth. Taken together, our results suggest that the AT2 receptor promotes vascular differentiation and contributes to vasculogenesis.

Aging↗

PubMed1999

Expression of the AT2 receptor developmentally programs extracellular signal-regulated kinase activity and influences fetal vascular growth.

Angiotensin II type 2 (AT2) receptor is abundantly expressed in vascular smooth muscle cells (VSMC) of the fetal vasculature during late gestation (embryonic day 15-20), during which the blood vessels undergo remodeling. To examine directly the influence of AT2 receptor expression in the developmental biology of VSMC, we studied cultures of VSMC from fetal and postnatal wild-type (Agtr2(+)) and AT2 receptor null (Agtr2(-)) mice. Consistent with in vivo data, AT2 receptor binding in cultured Agtr2(+) VSMC increased by age, peaking at embryonic day 20, and decreased dramatically after birth. Angiotensin II-induced growth in Agtr2(+) VSMC (embryonic day 20) was increased by the AT2 receptor blocker PD123319, indicating that the AT2 receptors are functional and exert an antigrowth effect in Agtr2(+) VSMC. Growth of VSMC in response to serum decreased age dependently and was higher in Agtr2(-) than in Agtr2(+), inversely correlating with AT2 receptor expression. However, serum-induced growth in Agtr2(+) and Agtr2(-) VSMC and the exaggerated Agtr2(-) VSMC growth was maintained even in the presence of PD123319 or losartan, an AT1 receptor blocker. Moreover, Agtr2(-) VSMC showed greater growth responses to platelet-derived growth factor and basic fibroblast growth factor, indicating that Agtr2(-) cells exhibit a generalized exaggerated growth phenotype. We studied the mechanism responsible for this phenotype and observed that extracellular signal-regulated kinase (ERK) activity was higher in Agtr2(-) VSMC at baseline and also in response to serum. ERK kinase inhibitor PD98059 inhibited both growth and ERK phosphorylation dose-dependently, while the regression lines between growth and ERK phosphorylation were identical in Agtr2(+) and Agtr2(-) VSMC, suggesting that increased ERK activity in Agtr2(-) VSMC is pivotal in the growth enhancement. Furthermore, the difference in ERK phosphorylation between Agtr2(+) and Agtr2(-) was abolished by vanadate but not by okadaic acid, implicating tyrosine phosphatase in the difference in ERK activity. These results suggest that the AT2 receptor expression during the fetal vasculogenesis influences the growth phenotype of VSMC via the modulation of ERK cascade.

Angiotensin II↗

PubMed1999

Analysis of functional domains of angiotensin II type 2 receptor involved in apoptosis.

We previously demonstrated that the intracellular third loop (i3 loop) of angiotensin II type 2 receptor (AT2) plays a key role in mediating the biological functions of this receptor. To determine which residues are important for AT2 signaling, mutated receptors with serial deletions within the i3 loop were stably expressed in PC12 cells. Deletion of residues 240-244 within the intermediate portion of the i3 loop resulted in a complete loss of AT2-mediated apoptosis, inhibition of extracellular signal-regulated kinases (ERK), and SHP-1 activation. In contrast to well characterized heptahelical receptors, the AT2 functions were not affected by deletions of the amino- or carboxyl-terminal portions of the i3 loop. Alanine substitutions further demonstrated that lysine 240, asparagine 242, and serine 243 are key residues for AT2-induced apoptosis, ERK inhibition, and SHP-1 activation. To examine whether a functional link exists between activation of SHP-1 and apoptosis, we used a catalytically inactive SHP-1 mutant and demonstrated that preventing SHP-1 activation strongly attenuates AT2-induced ERK inhibition and apoptosis. Our data demonstrate that the intermediate portion of the i3 loop is important for AT2 function and that SHP-1 is a proximal effector of the AT2 receptor that is implicated in the inhibition of ERKs and in the apoptotic effect of this receptor.

Alanine↗

PubMed1999

Tissue-specific changes of type 1 angiotensin II receptor and angiotensin-converting enzyme mRNA in angiotensinogen gene-knockout mice.

This study examined whether type 1 angiotensin II receptor (AT1) and angiotensin-converting enzyme (ACE) mRNAs are regulated during dietary salt loading in angiotensinogen gene-knockout (Atg-/-) mice which are genetically deficient in endogenous production of angiotensin II. Wild-type (Atg+/+) and Atg-/- mice were fed a normal-salt (0.3% NaCl) or a high-salt (4% NaCl) diet for 2 weeks. The mRNA levels were measured by Northern blot analysis. In Atg+/+ mice, concentrations of plasma angiotensin peptides were decreased by salt loading, whereas the treatment increased the brainstem, cardiac, pulmonary, renal cortex, gastric and intestinal AT1 mRNA levels. Salt loading also enhanced renal cortex ACE mRNA levels in Atg+/+ mice. Although plasma angiotensin peptides and urinary aldosterone excretion were not detected in Atg-/- mice, salt loading increased blood pressure in Atg-/- mice. In Atg-/- mice, pulmonary, renal cortex, gastric and intestinal AT1, and renal cortex and intestinal ACE mRNA levels were higher than those in Atg+/+ mice. However, salt loading upregulated AT1 mRNA expression only in the liver of Atg-/- mice, and the treatment did not affect ACE mRNA levels in Atg-/- mice. Furthermore, although the levels of ACE enzymatic activity showed the same trend with the ACE mRNA levels in the lung, renal cortex and intestine of both Atg-/- and Atg+/+ mice, the results of radioligand binding assay showed that cardiac expression of AT1 protein was regulated differently from AT1 mRNA expression both in Atg-/- and Atg+/+ mice. Thus, expression of AT1 and ACE is regulated by salt loading in a tissue-specific manner that appears to be mediated, at least partly, by a mechanism other than changes in the circulating or tissue levels of angiotensin peptides.

Angiotensin II↗

PubMed1999

Kinetics of excess CO2 output during and after intensive exercise.

In order to clarify the kinetics of excess CO2 output during and after intensive exercise, six male subjects were each instructed to perform 40-, 60- and 80-s cycle ergometer exercises (282 +/- 9 W, 90 rpm). Ventilation and gas exchange parameters were recorded breath-by-breath, and lactate concentration (La) was repeatedly measured with blood samples from a finger tip. The increase in La from the resting value to peak value and the duration of exercise showed a significant linear relationship (r = 0.91, p<0.01) passing through zero, indicating that lactic acid was produced at a constant rate in working muscles from the beginning of exercise. However, in contrast to this increase in La, excess V.CO2, defined as the difference between V.CO2 and V.O2, showed a temporary negative value after the start of exercise. Subsequently, excess V.CO2 became positive, reaching a peak at 60 s post-exercise, and then decreased down to zero at about 9 min after the end of the 80-s exercise. End-tidal CO2 rose above the pre-exercise level during exercise and at about 3 min post-exercise, and thereafter remained below the pre-exercise level. Excess CO2, calculated by the sum of excess V. CO2 from the start of exercise to the 10th min after the end of exercise, was significantly COrrelated with the increase in La from resting to 10 min post-exercise (r = 0.88, p<0.01). These results suggest that although excessive CO2 output (excess CO2) in response to intensive exercise is related to the increase in lactic acid, the time course of excessive CO2 output (excess V.CO2) is delayed, relative to the production of lactic acid, and is affected by hyperventilation.

Adult↗

PubMed1999

Role of the sympathetic nervous system and insulin in enhancing glucose uptake in peripheral tissues after intrahypothalamic injection of leptin in rats.

Our previous study demonstrated that microinjection of leptin into the ventromedial hypothalamus (VMH) dramatically increased glucose uptake in the heart, brown adipose tissue (BAT), and skeletal muscles, but not in white adipose tissue (WAT) in conscious unrestrained rats, as assessed in vivo by the 2-[3H]deoxyglucose method. Here we examined the role of the sympathetic nervous system and insulin in enhanced glucose uptake by tissues after hypothalamic leptin injection. Pretreatment with guanethidine significantly suppressed the increased glucose uptake by the tissues in response to leptin injected into the VMH, whereas bilateral adrenal demedullation had no significant effect. Treatment with propranolol but not phenoxybenzamine also decreased significantly enhanced glucose uptake by the tissues. We further examined the interaction of the effects of hypothalamic leptin and insulin administered peripherally by clamping the glucose concentrations at a constant level. When leptin was injected into the VMH and a maximal dose of insulin was administered intravenously, the rates of glucose uptake by the heart, BAT, and skeletal muscles, but not by WAT, markedly increased beyond the values reached by insulin stimulation alone. Surgical sympathetic denervation of BAT abolished the enhancement of glucose uptake in this tissue, decreasing to the level stimulated by insulin alone. These results appear to indicate that leptin in the hypothalamus enhances glucose uptake in certain peripheral tissues through mediation of a beta-adrenergic mechanism for the sympathetic nerves innervating the tissues and that central leptin and peripheral insulin have a synergistic role in augmenting tissue glucose uptake.

Adipose Tissue↗

PubMed1999

Alpha1-adrenergic stimulation induced hypertrophy in protein kinase C down-regulated cultured cardiac myocytes.

To examine whether protein kinase C (PKC) activation is essential for the induction of cardiac myocyte hypertrophy caused by alpha1-adrenergic stimulation, we investigated the hypertrophic effect of phenylephrine in PKC down-regulated and non-treated cultured cardiac myocytes obtained from neonatal Sprague-Dawley rat ventricles. The treatment with 10 nmol/L 12-tetra decanoylphorbol-13-acetate (TPA) for more than 2 hours decreased PKC activity by approximately 80% without marked hypertrophy. Phenylephrine increased [14C] phenylalanine (Phe) incorporation in both TPA non-treated and treated cells, 1.54- and 1.71-fold as large as control, respectively. The cell surface area also enlarged in both groups, 1.67- and 1.74-fold, respectively. Thus, phenylephrine induced the similar grade hypertrophy in cultured cardiac myocytes even when PKC was down-regulated. These results suggest that conventional PKC activation may not be essential for mediating myocyte hypertrophy by alpha1-adrenergic stimulation.

Adrenergic alpha-Agonists↗

PubMed1999

Characterization of antibodies raised against bovine-PrP-peptides.

To analyze the antigenicity of peptides derived from bovine prion protein (PrP) cDNA, we immunized rabbits with four synthetic peptides and compared the immunoreactivity of antibodies to PrPs from various species by immunoblotting and immunohistochemistry. Two of the antibodies reacted strongly with all PrPs. The other antibodies, raised against overlapping peptides close to two glycosylation sites, did not recognize PrPSc-mouse but did recognize PrPSc-sheep which contains two sugar residues and PrPCJD with or without a sugar residue. Our results suggest that these antibodies may have species-specificity for both glycosylation status and amino acid sequences of the protein. In conclusion, we identified two regions in bovine-PrP which appear suitable for raising antibodies that detect various kinds of PrPs, and one region (Ab103-121) which appears suitable for raising antibodies that detect several species of PrPs. These antibodies may be useful for diagnosing prion diseases and for researching their pathogenesis.

Amino Acid Sequence↗

PubMed1999

Effect of intermittent liver ischemia on outcome in patients with hepatocellular carcinoma on liver cirrhosis.

The influence on postoperative liver function of intermittent normothermic hepatic ischemia in cirrhotic patients was studied retrospectively. The mean total ischemia time was 88 (range 30-140) minutes in the hemi-hepatic occlusion group, and 68 (range 10-187) minutes in the total occlusion group. There were no operative deaths due to hepatic failure. Postoperative liver function improved within 1 week of the operation. There was no significant difference in the incidence of postoperative complications between the groups. Thus normothermic hepatic ischemia is tolerated for up to 180 minutes in the cirrhotic liver when an intermittent technique (15 minutes clamped and 5 minutes unclamped) is used.

Carcinoma, Hepatocellular↗

PubMed1999

[Late phase II clinical study of RP56976 (docetaxel) in patients with advanced/recurrent head and neck cancer].

A late phase II clinical study of RP56976 (docetaxel), a new anticancer agent for advanced/recurrent head and neck cancer, was conducted in 29 institutions all over Japan as a multi-institutional cooperative study. Docetaxel was administered by 1 to 2-hour intravenous infusion at a dose of 60 mg/m2 every 3 to 4 weeks. Of 63 patients eligible in this study, 59 were judged as complete cases. Complete response (CR) was observed in 1 patient, partial response (PR) in 13, no change (NC) in 25, and progressive disease (PD) in 20, for an overall response rate of 22.2% (14/63, 95% CI: 12.7-34.5%) in eligible cases, and 23.7% (14/59, 95% CI: 13.6-36.6%) in complete cases. Previously treated patients showed a 17.9% (10/56) response rate, whereas treatment--naive patients showed a 57.1% (4/7) response rate. Among 46 patients who received prior chemotherapy, one CR and 7 PR were observed with a 17.4% response rate. Major hematological toxicities were leucopenia in 95.1% (> or = grade 3, 59.7%) and neutropenia in 90.3% (> or = grade 3, 79.0%). Other severe toxicities (> or = grade 3) included anorexia in 9.7% (6 cases), diarrhea in 3.2% (2 cases), dyspnea in 3.2% (2 cases), and fatigue in 3.2% (2 cases). One patient had a grade 3 interstitial pneumonia; however, symptoms were resolved by the administration of corticosteroids. During this study, one patient died due to multiple organ failure (MOF) caused by disseminated intravascular coagulation (DIC), and this case was reported as a therapy-related death. Based on these results, docetaxel is an active agent for treatment of head and neck cancer.

Adenocarcinoma↗

PubMed1998

Inhibition of protease-resistant prion protein formation by porphyrins and phthalocyanines.

A central aspect of pathogenesis in the transmissible spongiform encephalopathies or prion diseases is the conversion of normal protease-sensitive prion protein (PrP-sen) to the abnormal protease-resistant form, PrP-res. Here we identify porphyrins and phthalocyanines as inhibitors of PrP-res accumulation. The most potent of these tetrapyrroles had IC50 values of 0.5-1 microM in scrapie-infected mouse neuroblastoma (ScNB) cell cultures. Inhibition was observed without effects on protein biosynthesis in general or PrP-sen biosynthesis in particular. Tetrapyrroles also inhibited PrP-res formation in a cell-free reaction composed predominantly of hamster PrP-res and PrP-sen. Inhibitors were found among phthalocyanines, deuteroporphyrins IX, and meso-substituted porphines; examples included compounds containing anionic, neutral protic, and cationic peripheral substituents and various metals. We conclude that certain tetrapyrroles specifically inhibit the conversion of PrP-sen to PrP-res without apparent cytotoxic effects. The inhibition observed in the cell-free conversion reaction suggests that the mechanism involved direct interactions of the tetrapyrrole with PrP-res and/or PrP-sen. These findings introduce a new class of inhibitors of PrP-res formation that represents a potential source of therapeutic agents for transmissible spongiform encephalopathies.

Cell-Free System↗

PubMed1998

Mechanism of angiotensin II-mediated regulation of fibronectin gene in rat vascular smooth muscle cells.

This study was performed to investigate a mechanism of angiotensin II (Ang II)-mediated activation of the fibronectin (FN) gene in rat vascular smooth muscle cells. Actinomycin D and CV11974 completely inhibited Ang II-mediated increase in FN mRNA levels. Inhibitors of protein kinase C (PKC), protein-tyrosine kinase (PTK), phosphatidylinositol-specific phospholipase C, Ras, phosphatidylinositol 3-kinase, p70 S6 kinase, and Ca2+/calmodulin kinase also decreased Ang II-induced activation of FN mRNA. In contrast, cycloheximide; PD123319; or inhibitors of Gi, protein kinase A, or mitogen-activated protein kinase kinase did not affect the induction. FN promoter contained a putative AP-1 binding site (rFN/AP-1; -463 to -437), and the results of a transient transfection and electrophoretic mobility shift assay showed that Ang II enhanced rFN/AP-1 activity. CV11974 and inhibitors of PKC or PTK suppressed Ang II-mediated increases in rFN/AP-1 activity, although neither PD123319 nor a protein kinase A inhibitor affected the induction. Furthermore, mutation of rFN/AP-1 that disrupted nuclear binding suppressed Ang II-induced transcription in the native FN promoter (-1908 to +136) context. Thus, Ang II activates transcription of the FN gene through the Ang II type 1 receptor in vascular smooth muscle cells, at least in part, via the activation of AP-1 by a signaling mechanism dependent on PKC and PTK.

Angiotensin II↗

PubMed1998

Differences in the evolutionary pattern of feline panleukopenia virus and canine parvovirus.

Canine parvovirus (CPV) suddenly appeared in the late 1970s after which it showed continuous antigenic changes. Virological and molecular genetic analyses mainly focused on feline panleukopenia virus (FPLV) were conducted in this study because FPLV is the suspected ancestor of CPV; the way in which FPLV evolves may help to explain the emergence of CPV. Analysis of escape mutants against FPLV-specific monoclonal antibody showed that viruses possessing CPV-like properties were not easily detected in FPLV virus stocks. Phylogenetic analysis revealed that the nonstructural protein 1 (NS1) and capsid protein 2 (VP2) genes of FPLV changed with time. A similar tendency, however, was not observed in the FPLV VP2 proteins. In contrast, the topology of the phylogenetic tree of VP2 proteins of CPV basically concurred with that of the VP2 genes. Analysis of the ratio of nonsynonymous and synonymous substitutions revealed that synonymous substitutions exceeded nonsynonymous substitutions in both the NS1 and VP2 genes of FPLV, even when the analysis focused on specific regions in the VP2 gene that are known to be located on the capsid surface. Comparison of the CPV VP2 genes revealed that nonsynonymous substitution was found to dominate over synonymous substitution in one specific region in the VP2 gene. These results suggested that FPLV has changed mainly by random genetic drift. In contrast, after the appearance of CPV, changes in the CPV VP2 gene appear to be partly selected by certain positive selection forces. CPV and FPLV are known to be closely related viruses genetically and biologically, but the evolutionary mechanisms of the two viruses appeared to be different.

Amino Acid Substitution↗