Biomedical subjects

N Sako

Publications and source records attributed to N Sako.

At least 19 recordsLinked to original sources

PubMed1995

A single amino acid substitution at N-terminal region of coat protein of turnip mosaic virus alters antigenicity and aphid transmissibility.

The antigenic activity of the N-terminal region of coat protein of turnip mosaic virus (TuMV) aphid transmissible strain 1 and non-transmissible strain 31 was examined by using a panel of monoclonal antibodies (MAbs) raised against the two virus strains as well as antisera raised against several synthetic peptides from the N-terminal region of the protein. The reactivity of these antibodies was tested in ELISA and in a biosensor system (BIAcore Pharmacia) using virus particles, dissociated coat protein and synthetic peptides as antigens. Substitution of a single amino acid at position 8 in the coat protein of TuMV strain 1 abolished any cross-reactivity between MAbs to strain 1 and the substituted peptide (strain 31) in ELISA although some cross-reactivity was apparent in BIAcore inhibition experiments. In reciprocal tests with MAbs to strain 31 no cross-reactivity with the heterologous peptide was detected in either type of assay. The amino acid residue present at position 8 appears to play a critical role in the binding capacity of MAbs specific for the N-terminal region of TuMV. Antiserum to a synthetic peptide corresponding to residues 1-14 of the protein of TuMV strain 1 was found to react strongly with dissociated coat protein and intact virus particles and was able to inhibit the aphid transmission of the virus. Antiserum to the corresponding peptide of strain 31 did not have this capacity.

Amino Acid Sequence↗

PubMed1995

Enhanced gustatory neural responses to sugars in the diabetic db/db mouse.

Sweet taste sensitivity in a genetic model of diabetes, the db/db mouse, in which a single major gene defect leads to the expression of diabetes and obesity, was studied by examining chorda tympani nerve responses to various taste stimuli, including sugars. The chorda tympani responses to four sugars, sucrose, fructose, glucose, and maltose, in adult db/db mice showed greater relative magnitudes and lower thresholds than those in adult lean mice, but responses to other basic taste stimuli, such as NaCl, HCl, and quinine HCl, were not different in the two groups. Behavioral experiments using a two-bottle preference test demonstrated that taste preference scores for the four sugars at suprathreshold concentrations, except 1.0 M, were higher in db/db than in control mice. Infant mice of 7-9 days of age possessing the genotype db/db also exhibited greater neural responses and lower thresholds for sugars than infant control mice, whereas streptozotocin-induced adult diabetic mice possessing the genotype +/+ did not exhibit larger sugar responses. These findings suggest that the enhanced sugar sensitivities observed in db/db mice are probably determined by a single major gene, db. The db gene may act on a common factor(s) involved in the stimulus-secretion coupling in the pancreatic B cell and the taste cell of db/db mice.

Aging↗

PubMed1994

Neural substrates for conditioned taste aversion in the rat.

Conditioned taste aversions (CTAs) are well known to be robust and long-lasting instances of learning induced by a single CS (taste)-US (malaise) pairing. CTA can be taken as a general model to search for neural mechanisms of learning and memory. In spite of extensive research on CTAs using a variety of approaches during the last three decades, the neural mechanisms of taste aversion learning still remain unsolved. In this article we propose a model of neural substrates of CTAs on the basis of our recent studies incorporating previous findings by other workers. Our studies mainly included experiments using ibotenic acid injections into various parts of the rat brain as a lesion technique, and c-fos immunohistochemistry in naive and CTA trained rats. CTAs were established by pairing the ingestion of saccharin (CS) with an ip injection of LiCl (US). Behavioral studies have shown that the parabrachial nucleus (PBN), medial thalamus, and basolateral nucleus of the amygdala are essential for both acquisition and retention of CTAs. C-fos studies suggested that association between gustatory CS and visceral US takes place in the PBN. The gustatory cortex (GC) may modify the strength of this association depending on the nature of the CS, viz., novel or familiar. The amygdala is indispensable for the expressions of CTAs. Tastes with hedonic values are stored in the GC in a long-term manner.

Animals↗

PubMed1994

Nucleotide sequences and expression in Escherichia coli of the coat protein genes from two strains of melon necrotic spot virus.

The nucleotide sequences of coat protein (CP) genes of two Japanese strains of melon necrotic spot virus (MNSV-NH and MNSV-S) were determined. The size of the CP genes of both strains was 1170 nucleotides. Comparisons of the deduced amino acid sequences among MNSV strains showed more than 95% homology, and those among other carmoviruses showed 31-34% homology. cDNAs of MNSV CP genes were cloned into an Escherichia coli expression fusion vector and MNSV-NH and MNSV-S CPs were successfully produced. Furthermore, synthetic oligonucleotide primers were used for differentiating MNSV strains by reverse transcription-polymerase chain reaction method.

Amino Acid Sequence↗

PubMed1994

Differences in taste responses to Polycose and common sugars in the rat as revealed by behavioral and electrophysiological studies.

Behavioral and electrophysiological experiments were performed to examine the suggestion that rats have two types of carbohydrate taste receptors, one for polysaccharides (e.g., Polycose) and one for common sugars (e.g., sucrose). Qualitative difference between the tastes of Polycose and sugars including sucrose, maltose, glucose, and fructose was surveyed by means of a conditioned taste aversion paradigm in which the number of licks for 20 s to each taste stimulus was measured. Aversive conditioning to Polycose did not generalize to sugars, while aversive conditioning to sucrose generalized to other sugars, but not to Polycose. In the electrophysiological study, taste responses of the whole chorda tympani were recorded. A proteolytic enzyme, pronase E, suppressed nerve responses to both Polycose and sugars to less than 50%. A novel anti-sweet peptide, gurmarin, strongly suppressed responses to sugars, but had essentially no effect on Polycose responses. On the other hand, KHCO3 enhanced responses to sugars to about 300%, but had little effect on Polycose responses. These results have confirmed the notion that rats can differentiate the tastes between Polycose and common sugars and that rats have two types of carbohydrate receptors.

Animals↗

PubMed1994

Some critical factors involved in formation of conditioned taste aversion to sodium chloride in rats.

Some factors concerning acquisition and retention of conditioned taste aversions (CTAs) were behaviorally examined in the rat. In the CTA paradigm, aqueous solution of 0.1 M NaCl was used as the conditioned stimulus (CS) and an intraperitoneal (i.p.) injection of 0.15 M LiCl was employed as the unconditioned stimulus (US). In experiment 1, CTAs to 0.1 M NaCl were examined in both forward (CS-US) and backward (US-CS) conditioning paradigms. Reliable CTAs were produced in the US-CS conditioning paradigm when the US-CS interval was less than 10 min, as well as in the CS-US conditioning paradigm. In experiment 2, strong CTAs to 0.1 M NaCl were established when water-deprived rats made at least 500 continuous licks, corresponding to 2.5 ml intake and 2 min of drinking time. In experiment 3, effects of gustatory deafferentation on CTA formation were studied. Only the chorda tympani played an important role in acquisition and retention of CTAs to NaCl solutions. These results indicate that strong CTAs can be acquired to 0.1 M NaCl, if its taste information which is conveyed via the chorda tympani during the 500 continuous licks is followed by LiCl-induced sickness.

Animals↗

PubMed1993

c-Fos expression in the parabrachial nucleus after ingestion of sodium chloride in the rat.

The distribution of evoked expression of the proto-oncogene c-Fos was immunohistochemically examined in the parabrachial nucleus (PBN) of the rat after free ingestion of NaCl and some other taste solutions. C-Fos-like immunoreactive neurones (c-Fos neurones) were densely observed in the external lateral subnucleus (els), central lateral subnucleus (cls), and the central part of the medial subnucleus (ms). The finding that the number of c-Fos neurones decreased dramatically in the ms after treatment of the tongue with amiloride or after dissection of the chorda tympani suggests that the taste information of NaCl projects mainly to the ms. The functional significance of the els and cls is discussed, and it is suggested that the els is a recipient zone for general visceral inputs and the cls is concerned with palatability of the liquids ingested. The present study has proved that c-Fos immunoreactivity is a useful anatomical marker for activated neurones in the PBN during ingestive behaviour.

Amiloride↗

PubMed1993

Characterization of epitopes recognized by monoclonal antibodies to aphid transmissible and non-transmissible strains of turnip mosaic virus.

Fourteen monoclonal antibodies (MAbs) were prepared against two strains of turnip mosaic virus (TuMV) differing in aphid transmissibility. Serological specificity of fourteen MAbs against the two strains was tested by indirect ELISA. Three MAbs were able to distinguish aphid transmissible TuMV strain 1 from non-aphid transmissible strain 31 while four MAbs reacted only with strain 31. No cross-reactivity between the two strains was found using these specific MAbs. Based upon the ability of Mab to inhibit the reaction of other MAbs, antibody competition test indicated that fourteen MAbs recognized six different epitopes on the virus particle; MAbs specific to strain 1 recognized two epitopes while MAbs specific to strain 31 also recognized two epitopes. The remaining two epitopes are common. Since the six amino acid differences between the coat proteins of the two strains were found at the N-terminal regions, MAbs specific to strain 1 or 31 bound to the different epitopes on the N-terminal regions in coat proteins of the two strains.

Amino Acid Sequence↗

PubMed1993

Nucleotide sequences of the helper component-proteinase genes of aphid transmissible and non-transmissible isolates of turnip mosaic virus.

We have compared nucleotide sequences of the helper component-proteinase (HC-Pro) coding region of aphid transmissible (isolate 1) and non-transmissible (isolate 31) isolates of turnip mosaic virus (TuMV). HC-Pro coding regions of both TuMV isolates 1 and 31 were 1,374 nucleotide long. The nucleotide sequence homology between these isolates was 93.5%, with 89 nucleotides substitution. The nucleotides of HC-Pro regions of two isolates of TuMV genomes encoded 458 amino acids of M(r) 51,746 (isolate 1) and M(r) 51,764 (isolate 31). The deduced amino acid sequence homology between these isolates was 98.7% with six different amino acids. These amino acids appeared to regulate the activity of HC-Pro needed for aphid transmissibility of TuMV.

Amino Acid Sequence↗

PubMed1992

C-fos expression in the rat brain after intraperitoneal injection of lithium chloride.

The distribution of evoked expression of the proto-oncogene c-fos was immunohistochemically examined in the rat brain after intraperitoneal injection of isotonic LiCl, which is commonly used to induce internal malaise in the conditioned taste aversion paradigm. C-fos-like immunoreactive neurones (c-fos neurones) were most densely observed in the central amygdaloid nucleus, external lateral subnucleus of the parabrachial nucleus (PBN), posteromedial and commissural parts of the nucleus of the tractus solitarius (NTS) and area postrema (AP). Experiments including vagotomy, intravenous injection of LiCl and lesions of the area postrema suggest that NTS neurones are activated via both sides of the vagus nerves, while AP neurones, humorally as well as neurally via the vagal nerve with a right side predominance. The activated NTS and AP neurones project mainly to the external lateral subnucleus of the PBN and lightly to the central lateral subnucleus of the PBN. These results are discussed in terms of the role of LiCl in the formation of conditioned taste aversion.

Animals↗

PubMed1990

Production of avian antibodies to three potyviruses in coturnix quail.

Avian antibodies against three potyviruses were produced in a small bird, coturnix quail (Coturnix coturnix japonica Temminck et Schlegel), with 15-60 micrograms of purified virus preparations. Intramuscular injections of immunogen with Freund's incomplete or complete adjuvant into the birds did not result in higher titer of antibody compared to that of control birds given intravenous injections. Quail egg yolk antibody was as useful as hen antibody for indirect-ELISA and allowed virus to be detected in purified preparation (10-50 ng/ml) and in crude extracts (10(-6)-10(-7) dilution). The advantages of using quail to produce avian antibodies are discussed.

Animals↗

PubMed1989

Strain differences in amiloride inhibition of NaCl responses in mice, Mus musculus.

The effects of lingual treatment with amiloride, an inhibitor of salt taste responses in several mammalian species, on NaCl responses of the chorda tympani nerve were compared between four inbred strains of mouse (BALB/cCrSlc, DBA/2CrSlc, C57BL/6CrSlc and C3H/HeSlc). In C57BL and C3H mice amiloride significantly suppressed responses of the chorda tympani nerve to NaCl at a concentration 0.1 M or more whereas in BALB and DBA mice the drug did not significantly affect the responses to NaCl at any concentration, suggesting a lack of the amiloride-sensitive receptor component for NaCl in the latter two strains. A two-bottle preference test demonstrated that all strains of mouse usually showed no preference for NaCl at any concentration and avoided NaCl at 0.3 M or more, although some differences were observed in that C57BL and C3H mice showed aversive responses to 0.1 and 0.15 M NaCl, whereas BALB and DBA mice were indifferent to these solutions. The results suggest that there exist prominent differences between mouse strains in the amiloride-sensitive component of their salt receptor systems. However, in mice the taste information derived from the amiloride-sensitive receptor component probably has no remarkable effect on behavioral responses to NaCl except for a possible contribution to decreasing aversion thresholds for NaCl by increasing overall taste information about NaCl.

Amiloride↗

PubMed1989

Effects of isoproterenol treatment on gustatory neural responses in three inbred strains of mice.

1. Treatment of a beta-agonist, isoproterenol, for 5 days reduced chorda tympani responses to sucrose by about 40% of the control without affecting responses to other taste stimuli, such as NaCl, HCl and quinine HCl, in balb CrSlc mice whereas such reduction of sucrose responses was not observed in C57BL/6-CrSlc and C3H/HeSlc mice, although in the latter two strains long-lasting off-responses to quinine HCl appeared after the treatment. 2. In BALB mice, the magnitude of reduction of sucrose responses by isoproterenol increased with prolonging the treatment from 1 to 5 days, although it reached almost its maximum level by the 3 days treatment. 3. BALB mice with the removal of the submandibular glands showed slightly greater control responses of the chorda tympani nerve to sucrose than BALB mice with the sham-operation or the removal of the sublingual glands, and showed no significant reduction of sucrose responses by isoproterenol treatment. 4. These results suggest that isoproterenol probably did not act directly on sweetener receptors of taste cell membranes but affect them through the submandibular salivary system.

Animals↗

PubMed1989