Biomedical subjects

J Kato

Publications and source records attributed to J Kato.

At least 19 recordsLinked to original sources

PubMed1992

Purification and characterization of DNA topoisomerase IV in Escherichia coli.

The subunits of topoisomerase IV (topo IV), the ParC and ParE proteins in Escherichia coli, were purified to near homogeneity from the respective overproducers. They revealed type II topoisomerase activity only when they were combined with each other. In the presence of Mg2+ and ATP, topo IV was capable of relaxing a negatively or positively supercoiled plasmid DNA or converting the knotted P4 phage DNA, whether nicked or ligated, to a simple ring. However, supercoiling activity was not detected. The topoisomerase activity was not detectable when the purified ParC and ParE proteins were combined with the purified GyrB and GyrA proteins, respectively. This is consistent with the result that neither a parC nor a parE mutation was compensated by transformation with a plasmid carrying either the gyrA or the gyrB gene. Simultaneous introduction of both the gyrA and gyrB plasmids corrected the phenotypic defect of parC and parE mutants. The results suggest that DNA gyrase can substitute for topo IV at least in some part of the function for chromosome partitioning. Antisera were prepared against the purified ParC, ParE, GyrA, and GyrB proteins and used to investigate cellular localization of these gene products. ParC protein was found to be specifically associated with inner membranes only in the presence of DNA. This result suggests that one of the functions of topo IV might be to anchor chromosomes on membranes as previously proposed for eukaryotic topoisomerase II.

Bacterial Proteins↗

PubMed1992

Human guanylin: cDNA isolation, structure, and activity.

Guanylin is a mammalian peptide homologue of heat-stable enterotoxins that acts on intestinal guanylate cyclase to elicit an increase in cyclic GMP. We have isolated a cDNA encoding an apparent precursor of guanylin from a human intestinal cDNA library. The mRNA is expressed at high levels in human ileum and colon. Human guanylin stimulated increases in T84 cell cyclic GMP levels, displaced 125I-labelled heat-stable enterotoxin (STa) binding to this cell line, and stimulated increases in short-circuit current (Isc) of isolated rat proximal colonic mucosa. This peptide may play a role in regulating fluid and electrolyte absorption in human intestines.

Amino Acid Sequence↗

PubMed1992

Regional distribution of copper, zinc and iron in the brain in Long-Evans Cinnamon (LEC) rats with a new mutation causing hereditary hepatitis.

In Long-Evans Cinnamon (LEC) rats of three different ages (7, 13 and 32 weeks old) concentrations of Cu, Zn and Fe were measured in 8 regions of the brain. The LEC groups aged 7 and 13 weeks showed low concentrations of Cu in all regions compared to Long-Evans Agouti (LEA) rats. In 32-week-old LEC rats, however, Cu concentrations increased in 7 regions, in particular, significantly so in the striatum, hypothalamus, cerebellum, midbrain and cortex. Changes of Zn concentration were not found in any region. The Fe concentration increased in cortex and olfactory lobes. The three LEC groups showed a very high concentration of hepatic Cu and a low concentration of serum Cu compared to LEA rats. In LEC rats aged 32 weeks, however, hepatic Cu decreased and serum Cu increased compared to the other two LEC groups. These results suggest that the increase of the cerebral Cu concentration is closely related to the inherently abnormal Cu metabolism and then to the changes of Cu metabolism from about 13 weeks after birth.

Animals↗

PubMed1992

Rat guanylin cDNA: characterization of the precursor of an endogenous activator of intestinal guanylate cyclase.

Guanylin is a recently discovered endogenous activator of intestinal guanylate cyclase that was purified from intestinal tissue. Clones have been isolated which demonstrate that the guanylin peptide is contained within a 115 amino acid apparent preprohormone encoded by a 600 base messenger RNA in rat jejunum. The messenger RNA is found predominantly in intestinal tissues, showing a striking gradient of expression ranging from undetectable in esophagus and stomach to abundant in colon. Guanylin may serve a paracrine function to regulate intestinal guanylate cyclase activity, cyclic GMP levels, and thereby, fluid and electrolyte absorption. We hypothesize that the heat stable enterotoxins mimic the endogenously produced guanylin to cause diarrhea.

Amino Acid Sequence↗

PubMed1992

Growth-stimulatory monoclonal antibodies against human insulin-like growth factor I receptor.

Monoclonal antibodies (mAbs) against purified human placental insulin-like growth factor I (IGF-I) receptors were prepared and characterized. Three IgG mAbs were specific for the human IGF-I receptor and displayed negligible crossreactivity with the human insulin receptor. They stimulated 125I-labeled IGF-I (125I-IGF-I) or 125I-IGF-II binding to purified human placental IGF-I receptors and to IGF-I receptors expressed in NIH 3T3 cells in contrast to the well-studied mAb alpha IR-3, which inhibits 125I-IGF-I or 125I-IGF-II binding to both forms of IGF-I receptors. The mAbs introduced in this study stimulated DNA synthesis in NIH 3T3 cells expressing human IGF-I receptors approximately 1.5-fold above the basal level and the IGF-I- or IGF-II-stimulated level. In contrast, alpha IR-3 inhibited both basal and IGF-I or IGF-II-stimulated DNA synthesis by approximately 30%. Inhibition of IGF-II-stimulated DNA synthesis by alpha IR-3 was as potent as its inhibition of IGF-I-stimulated DNA synthesis, although IGF-II binding to the IGF-I receptors was not inhibited by IGF-II as potently as was IGF-I. With the purified IGF-I receptors, both inhibitory and stimulatory mAbs were shown to activate autophosphorylation of the IGF-I receptor beta subunit and to induce microaggregation of the receptors. These results suggest that conformational changes resulting from receptor dimerization in the presence of either type of mAb may affect the signal-transducing function of the IGF-I receptor differently. These additional mAbs and alpha IR-3 immunoprecipitated nearly 90% of IGF-I binding activity from Triton X-100-solubilized human placental membranes, indicating that IGF-I receptor reactive with these mAbs is the major form of the IGF-I receptor in human placenta.

3T3 Cells↗

PubMed1992

The effects of morphine administered into the vertebral artery on the somatosympathetic A- and C-reflexes in anesthetized cats.

The effects of morphine (0.2-200 micrograms/kg) administered into the brain stem via a vertebral artery on the somatosympathetic A- and C-reflexes evoked in a cardiac sympathetic nerve by electrical stimulation of somatic myelinated (A) and unmyelinated (C) afferent nerve fibers in anesthetized cats were examined. The intravertebral arterial administration of 20-200 micrograms/kg morphine depressed dose-dependently both the somatosympathetic A- and C-reflexes. Following the administration of 200 micrograms/kg morphine, the amplitudes of the sympathetic A- and C-reflexes were depressed to 71 +/- 8% and 80 +/- 8% of the control magnitude, respectively. Injection of 2-200 micrograms/kg morphine caused hypotension in a dose-dependent manner. It is concluded that morphine administered in the brain stem via the vertebral artery produced a nonselective and slight depression of both the somatosympathetic A- and C-reflexes by acting at the level of brain stem.

Anesthesia↗

PubMed1992

Suppression of atrial natriuretic peptide (ANP) receptor recovery from homologous down-regulation by 8-bromo-cGMP in endothelial cells.

In a previous study we reported that cyclic GMP (cGMP) selectively down-regulates the atrial natriuretic peptide clearance receptor (C-ANP receptor) in the cultured bovine pulmonary artery endothelial (CPAE) cell line. Our efforts in the current study are directed towards determining the effects of cGMP on C-ANP receptor recycling and de novo synthesis following homologous down-regulation by atriopeptin III (APIII, rat ANP 103-126). [125I]APIII binding to CPAE cells was decreased to 45.3 +/- 1.0% of control following the pretreatment with 100 nM APIII for 24 h. After the removal of APIII, the decreased [125I]APIII binding gradually recovered up to 68.8 +/- 1.8% of control for 24 h: a 'long-term recovery'. When CPAE cells were pretreated with 1 nM APIII for 30 min, [125I]APIII binding was also decreased to 62.6 +/- 2.6% of control. Following the removal of APIII, the decrease in [125I]APIII binding quickly recovered to 87.7 +/- 2.7% of control for 1 h: a 'short-term recovery'. 8-bromo-cGMP suppressed the long-term recovery of ANP receptor in a dose-dependent manner, while it had no effect on the short-term recovery. Both actinomycin D (1 ng/ml) and cycloheximide (10 ng/ml) significantly (P less than 0.01) suppressed the long-term recovery, but failed to affect the short-term recovery, whereas, the short-term recovery was significantly (P less than 0.01) inhibited by either 10 mM NH4Cl or 0.2 mM chloroquine which inhibits the recycling of internalized ANP receptor. These findings suggest that new ANP receptor synthesis is necessary for long-term but not for short-term recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1992

Guanylin: an endogenous activator of intestinal guanylate cyclase.

Intestinal guanylate cyclase mediates the action of the heat-stable enterotoxin to cause a decrease in intestinal fluid absorption and to increase chloride secretion, ultimately causing diarrhea. An endogenous ligand that acts on this guanylate cyclase has not previously been found. To search for a potential endogenous ligand, we utilized T84 cells, a human colon carcinoma-derived cell line, in culture as a bioassay. This cell line selectively responds to the toxin in a very sensitive manner with an increase in intracellular cyclic GMP. In the present study, we describe the purification and structure of a peptide from rat jejunum that activates this enzyme. This peptide, which we have termed guanylin, is composed of 15 amino acids and has the following amino acid sequence, PNTCEICAYAACTGC, as determined by automated Edman degradation sequence analysis and electrospray mass spectrometry. Analysis of the amino acid sequence of this peptide reveals a high degree of homology with heat-stable enterotoxins. Solid-phase synthesis of this peptide confirmed that it stimulates increases in T84 cyclic GMP levels. Guanylin required oxidation for expression of bioactivity and subsequent reduction of the oxidized peptide eliminated the effect on cyclic GMP, indicating a requirement for cysteine disulfide bond formation. Synthetic guanylin also displaces heat-stable enterotoxin binding to cultured T84 cells. Based on these data, we propose that guanylin is an activator of intestinal guanylate cyclase and that it stimulates this enzyme through the same receptor binding region as the heat-stable enterotoxins.

Amino Acid Sequence↗

PubMed1992

Inhibition of endothelial cell clearance of atrial natriuretic peptide by cyclic GMP treatment.

In a previous study, we reported that cyclic GMP (cGMP) selectively down-regulates the clearance receptor (C-receptor) for atrial natriuretic peptide (ANP) in the cultured bovine pulmonary artery endothelial (CPAE) cell line. The present study was undertaken in order to examine the effect of cGMP on the internalization of the ANP-receptor complex in CPAE cells. Maximum binding of [125I]APIII to the cells significantly decreased following the treatment with 1 mM 8-bromo-cGMP for 48 or 72 h. Scatchard analysis of the binding assay data from the treated cells showed a decrease in Bmax (616 to 411 fmol/mg protein) without a significant change in Kd. Removal of cell surface-bound APIII by acetic acid revealed that not only the surface binding, but also the internalization of APIII significantly decreased in 8-bromo-cGMP-treated cells, indicating a decrease in receptor-mediated uptake of ANP into the cells. These results suggest that cGMP regulates the clearance of ANP by vascular endothelial cells.

Analysis of Variance↗

PubMed1992

Antitumor activity of basic fibroblast growth factor-saporin mitotoxin in vitro and in vivo.

Many cancer cell lines express basic fibroblast growth factor (FGF) receptors, making them potential targets for the delivery of FGF-based cytotoxic compounds. To this end, we have investigated the antitumor activity of a novel mitotoxin, Fibroblast Growth Factor-saporin (FGF-SAP), a conjugate of FGF and the ribosome-inactivating protein, saporin. In vitro, FGF-SAP is cytotoxic for human melanoma, teratocarcinoma, and neuroblastoma cells expressing FGF-receptors. Mice treated with FGF-SAP i.v., on a variety of schedules, showed dramatic tumor growth inhibition with minimal toxicity. Thus, FGF-SAP appears to be a well-tolerated and potent antitumor agent. The potential of FGF-targeted cytotoxicity is discussed.

Animals↗

PubMed1992

Distribution of cells containing progesterone receptor mRNA in the female rat di- and telencephalon: an in situ hybridization study.

In an attempt to examine regional synthesis of the progesterone receptor (PR) in the brain, the distribution of mRNA encoding PR was investigated in the female adult rat di- and telencephalon by in situ hybridization using T7 RNA polymerase transcripts of a 320 base pair rat PR cDNA clone. The rat PR cDNA had been partially cloned and sequenced by using the reverse transcription-polymerase chain reaction (RT-PCR) method. The primer set corresponds to a part of the progesterone binding domain of human PR cDNA. Large numbers of strong labeling were observed in the arcuate nucleus, medial preoptic nucleus, and ventrolateral part of the ventromedial nucleus which are relative to sexual behavior. Moderate labeling was found in layers II and IV of the isocortex, in the pyramidal layer of the CA1 and CA3 fields of the hippocampal formation, in the cortical nucleus of the amygdala, in the nucleus of the diagonal band, and in the anterior periventricular nucleus. Weak labeling was found in many other regions. These results were largely in agreement with the distribution of PR previously reported by ligand binding assay and autoradiographic studies. This present in situ hybridization study may provide a useful tool for the analysis of the regional regulation of PR synthesis in the rat brain.

Animals↗

PubMed1992

Expression of estrogen receptor in the rat brain: detection of its mRNA using reverse transcription-polymerase chain reaction.

Reverse transcription-polymerase chain reaction (RT-PCR)-Southern blotting was employed for biochemical detection and measurement of the estrogen receptor messenger ribonucleic acid (ERmRNA) in various parts of the Wistar strain female rat brain. Total RNA extracted from the tissues was subjected to RT-PCR using the primer set which flanked the part(287bp) of the estrogen binding domain-corresponding region of the rat ERcDNA. It was confirmed that the RT-PCR product corresponded to the part of the ERcDNA by direct nucleotide sequencing of the product. Moreover, the level of ERmRNA could be determined by Southern blotting which was highly sensitive and produced quantitative results. The RT-PCR product of about 290 bp, corresponding in length to the distance between two primers, was generated from RNA of all the tissues examined. The levels of the product were as follows; anterior hypophysis greater than hypothalamus and preoptic area, amygdala much greater than cerebral cortex, cerebellum. These results indicate that ERmRNA is widely distributed in the whole brain, implying some physiological action of estrogen on target and 'non-target' brain regions.

Animals↗

PubMed1992

Expression of progesterone receptor in the neonatal rat brain cortex: detection of its mRNA using reverse transcription-polymerase chain reaction.

Our previous reports have revealed the postnatal developmental pattern of progesterone receptor (PR) in the rat cerebral cortex, but little is known about PRmRNA changes in the tissue so far. In the present study, we have attempted to detect and quantify PRmRNA in the tissue by the use of the reverse transcription-polymerase chain reaction (RT-PCR)-dot blot analysis. Cerebral cortical tissues were dissected from female Wistar rats at 2 and 8 days of age. Total RNA extracted from the tissues was reverse transcribed, followed by PCR. The PCR primer set, whose sequence was derived from the human clone, flanked the part (320 bp) of the human PRcDNA which corresponded to the progesterone binding domain. The 320 bp of the RT-PCR product was generated from rat uterine RNA. The amino acid sequence deduced from the nucleotide sequence of the product had a 95.5% identity with the corresponding region in human PR, confirming that the product had originated from the rat PRmRNA. Moreover, a highly sensitive and quantitative assay for rat PRmRNA had been developed by the use of RT-PCR-dot blotting. The PRmRNA was detectable in the cerebral cortex of both 2- and 8-day-old rats by the assay. Furthermore, the level of cortical PRmRNA of the 8-day-old rats were greater than the 2-day-old rats. These results indicate that the RT-PCR assay is useful for detection and quantification of PRmRNA in the neonatal rat cerebral cortex, and that increment of the cortical PRmRNA in the 8-day-old rat is associated with a drastic change of the level of the cortical PR around day 10.

Aging↗

PubMed1992

Basic fibroblast growth factor production and growth factor receptors as potential targets for melanoma therapy.

A number of growth factors can stimulate the proliferation of human malignant melanoma cell lines. We investigated the effects of exogenous growth factors including basic fibroblast growth factor (bFGF), epidermal growth factor, transforming growth factor-alpha, insulin, insulin-like growth factor-I (IGF-I), acidic fibroblast growth factor, platelet-derived growth factor, transforming growth factor-beta and nerve growth factor on six human metastatic melanoma cell lines. The mitogenic activity of each growth factor was tested using the [3H]thymidine incorporation assay. There was a variable response of the different cell lines to most growth factors. All of the melanoma cell lines tested responded to IGF-I. Furthermore, the effects of growth factors were additive, a combination of bFGF and IGF-I having the greatest effect on three melanoma cell lines tested. The quantitative radioimmunoassay for bFGF and [125I]bFGF binding assay revealed that all of these melanoma cell lines produced bFGF and expressed high affinity receptors for bFGF. A 20-mer antisense oligodeoxynucleotide against the AUG initiation site of the bFGF coding region inhibited the proliferation of Mel-Tang by 40% (p less than 0.0001) and that of SK-MEL-5 by 20% (p less than 0.005), suggesting that these cell lines are at least under partial autocrine control of proliferation by bFGF. The presence of bFGF receptors on a high percentage of melanoma cell lines makes these a potential target for melanoma therapy.

Base Sequence↗

PubMed1992

Phosphate taxis in Pseudomonas aeruginosa.

Pseudomonas aeruginosa was shown to be attracted to phosphate. The chemotactic response was induced by phosphate starvation. The specificity of chemoreceptors for phosphate was high so that no other tested phosphorus compounds elicited a chemotactic response as strong as that elicited by phosphate. Competition experiments showed that the chemoreceptors for phosphate appeared to be different from those for the common amino acids. Mutants constitutive for alkaline phosphatase showed the chemotactic response to phosphate regardless of whether the cells were starved for phosphate.

Alkaline Phosphatase↗

PubMed1992

Difference in effect of atrial natriuretic peptide on cGMP in aortic and coronary smooth muscle cells.

Blood vessels show a heterogeneous response to the atrial natriuretic peptide (ANP). In our experiments thoracic aorta from the guinea pig relaxed in response to atriopeptin III (AP; rat ANP-103-126) and to sodium nitroprusside (SNP). In contrast, in perfused guinea pig hearts, AP III produced no change in coronary flow, while SNP increased flow. In smooth muscle cells cultured from the coronary system (CASM) and from the thoracic aorta (TASM), we compared receptor binding and the effects on guanosine 3',5'-cyclic monophosphate (cGMP) production of AP III. AP III bound specifically with equal affinity and with equivalent numbers of binding sites in both cell types. AP III produced a dose-dependent increase in cGMP in TASM (50% effective concentration approximately 3 nM) with a maximum 11-fold increase over basal at 1 microM AP III. In contrast, in CASM, AP III failed to increase cGMP. Nitroprusside increased cGMP in both cell types. Autoradiograms of 125I-labeled AP III linked to cell membranes showed bands at 70 kDa (ANP-C receptor) in both cell types. A second band at 140 kDa (ANP-B receptor) was only seen in TASM. These results suggest that smooth muscle cells of coronary resistance vessels of the guinea pig do not express the particulate guanylyl cyclase that is activated by ANP.

Animals↗

PubMed1992

Distribution of calcitonin gene-related peptide and substance P-immunoreactive nerve fibers and their correlation in the periodontal ligament of the mouse incisor.

The distribution of calcitonin gene-related peptide (CGRP)- and substance P (SP)-immunoreactive (IR) nerve fibers and their correlation in the periodontal ligament of mouse incisors were examined by indirect immunofluorescence. Both CGRP-IR and SP-IR thin nerve fibers were abundant in the apical and middle third of the periodontal ligament. In the lingual portion of the incisal periodontal ligament, these nerve fibers were localized in the alveolar half of the periodontal ligament and were observed as free nerve endings. No CGRP-IR and SP-IR specialized nerve endings, such as Ruffini-like corpuscles, were observed. In the labial periodontal ligament, CGRP-IR and SP-IR nerve fibers ran along the incisal axis. The distribution of CGRP-IR nerve fibers was very similar to that of SP-IR nerve fibers.

Animals↗

PubMed1992

[Monotherapy with extracorporeal shock wave lithotripsy for renal and ureteral stones].

We performed extracorporeal shock wave lithotripsy (ESWL) as a monotherapy using the Medstone STS lithotripter on 288 patients with renal and ureteral stones between June, 1989 and June, 1991. We compared our results with previous reports on ESWL as used in combination therapy. Our cases consisted of 121 patients with renal stones and 167 patients with ureteral stones. A total of 437 sessions of lithotripsy were performed on 288 patients, for an average of 1.52 sessions of lithotripsy per patient. The percentage of stones measuring less than 4.0 mm in diameter that were fragmented was 94.3% for renal stones and 87.6% for ureteral stones. The stone-free rates 3 months after ESWL were 60.3% and 90.4%, respectively. Our results of the monotherapy with ESWL did not differ from those reported on ESWL as used in combination therapy, in terms of the rate of stone destruction and stone-free rates. We studied the other reports carefully and determined that ESWL monotherapy could have been performed in most those cases. We concluded that ESWL monotherapy is an excellent therapeutic method in the light of fewer complications and side effects compared with those from combination therapy, and the fact that the rate of recurrence for renal and ureteral stones is high makes ESWL monotherapy very useful because the procedure can be repeated.

Adolescent↗