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Biomedical subjects

A Kato

Publications and source records attributed to A Kato.

At least 613 records · Page 34Linked to original sources
PubMed1985

Sexual Interaction in Heterothallic Strains of Closterium peracerosum-strigosum-littorale: Partial Characterization of a Male-Specific Sexual Pheromone, Protoplast-Releasing Substance.

A sexual pheromone, named the protoplast releasing substance (PRS), was formed by mating type minus cells. PRS activates mating type plus cells and results in the release and fusion of protoplasts within distended conjugation-papilla in paired cells and in the release and disruption of protoplasts in unpaired mating type plus cells. In an agar barrier system, the activation of mating type plus cells was markedly inhibited by treatment with pronase (5-10 micrograms per milliliter), proteinase (100 micrograms per milliliter), and alpha-mannosidase (10 micrograms per milliliter). Trypsin (10-100 micrograms per milliliter) had no effect on the activation in the agar barrier system. The results suggest that PRS is a glycoprotein with pronase-sensitive and trypsin-insensitive structure.

Journal Article↗
PubMed1985

Protein and RNA Synthesizing Activities during Sexual Process of Heterothallic Closterium.

Protein and RNA synthesizing activities increased markedly during the mating process and decreased during the maturation stage of zygotes in heterothallic strains of Closterium peracerosum-strigosum-littoale, KAS-4-29 (mating-type minus) and KAS -4-30 (mating-type plus) and a homothallic Closterium acerosum. Different proteins were synthesized at the different stages of the mating process, suggesting that a sequential expression and repression of mating genes occur for the mating-specific protein synthesis during the sexual reproduction.

Journal Article↗
PubMed1985

Usefulness of intraoperative cortical blood flow measurement by heat clearance method for monitoring cerebral ischaemia during therapeutic carotid ligation.

Changes of regional cortical blood flow (rCBF) was monitored by the heat clearance method during the operation of cervical carotid ligation combined with superficial temporal artery and middle cerebral artery anastomosis for the treatment of inaccessible aneurysms of the internal carotid artery in eight patients. There were three types of rCBF responses upon closure of the internal carotid artery, with or without bypass blood flow. Based on the responses, the internal carotid artery was ligated abruptly or occluded gradually. The usefulness of the method for monitoring cerebral ischaemia for therapeutic carotid ligation is discussed.

Body Temperature↗
PubMed1985

Urinary excretion characteristics of a polymeric prodrug of mitomycin C, mitomycin C-dextran conjugate.

Urinary excretion characteristics of a polymeric prodrug of mitomycin C (MMC), mitomycin C-dextran conjugate (MMC-D), following intravenous administration was studied in rats. Three types of MMC-D, conjugates with dextrans of molecular weights of 10000, 70000 and 500000, were tested and urine concentration of MMC, dextran and spacer were determined by three analytical methods, i.e., bioassay, anthrone method and radioactivity counting. MMC was assayed separately as a free form and conjugated form based on antimicrobiological activity. MMC administered as a free form was excreted rapidly into urine but only a small amount of MMC was excreted following the administration of MMC-D. The excreted amount of MMC in a conjugated form varied with the size of carrier dextran while similar sustained excretion was observed regardless of the carrier size. The excretion of carrier dextran determined by anthrone method was confined as the molecular weight was increased. The effect of molecular weight was also observed in the case of spacer-introduced dextran (dextran-C6 spacer) and original dextran. Compared with neutral dextran, cationic MMC-D and anionic dextran-C6 spacer exhibited diminished excretion, indicating the effect of charge on urinary excretion. The urinary recovery of radioactivity was almost in accordance with that of carrier dextran. However, the urinary recovery of MMC based on biological activity was considerably lower than that of carrier dextran. It was suggested that MMC-D underwent inactivation to a great extent before releasing active MMC in the body. The effect of physicochemical properties such as molecular weight and electric charge on the urinary excretion of the polymeric prodrug was thus elucidated.

Animals↗
PubMed1985

Liposome-type artificial red blood cells stabilized with carboxymethyl chitin.

Liposome-type artificial red blood cells (ARBC) stabilized with carboxymethyl chitin (CM chitin) containing human hemolysate were prepared by a two-step emulsification technique, Oxygen binding abilities of the ARBC and human hemolysate were measured by the use of a Clark-type oxygen electrode. Both of theARBC and human hemolysate exhibited a striking similarity in oxygenation behavior, indicating that the oxygen binding ability of the former is almost identical with that of the latter. Disintegration tests on the ARBC using the enzymes (lysozyme, chitinase and phospholipase C), that can digest the components of the ARBC membrane, suggested that the membrane has a structure in which the phospholipid layer is covered by a mesh of CM chitin molecules. The acute toxicity of the ARBC to male mice (BALB/c) was examined and the LD 50 value of the ARBC for 2 ml of intravenous injection was evaluated to be 13.8 ml/kg by means of the Litchfield-Wilcoxon method.

Animals↗
PubMed1985

Circulatory disturbance of the spinal cord with epidural neoplasm in rats.

An experimental model of spinal epidural neoplasm was produced in rats by injecting Walker 256 carcinoma cell suspension anterior to the T12-13 vertebral body. With this model, spinal cord blood flow (SCBF) and its response to CO2 inhalation were estimated by the carbon-14-antipyrine autoradiography and the hydrogen clearance methods. In the early stages after tumor implantation, weakness, axonal swelling, and edema of the white matter were observed, while both SCBF and its response to CO2 inhalation remained normal. In the next stage, the tumor invaded the spinal canal and compressed the spinal cord epidurally. The edema of the white matter progressed, while the gray matter was morphologically intact. The SCBF and its response to CO2 inhalation were altered at both the compression area and caudally in the spinal cord. Changes in response to CO2 inhalation appeared earlier than the SCBF decrease. In the last stage, the SCBF decreased rapidly to the critical level, producing irreversible nervous tissue damage. Microangiographic studies revealed extensive obliteration of the spinal epidural venous plexus and patency of the larger nutritional vessels. From the data obtained, the progressive vascular pathophysiology related to spinal epidural neoplasm is as follows: 1) the vertebral venous plexus is compressed and obliterated in the early stages of the disease, and vasogenic edema appears in the spinal cord; 2) as the tumor grows, mechanical compression of the spinal cord is added and the circulatory disturbance increases; and 3) in the last stage, SCBF decreases rapidly to a critical flow level, and the loss of cord function becomes irreversible.

Angiography↗
PubMed1985

Development of virus-accelerated thymic lymphoma in AKR mice.

The progression of prelymphoma cells (PLC) in the bone marrow to lymphoma cells (LC) in the thymus in the presence of the lymphomagenic retrovirus SL3-3c was studied in a model system of virus-accelerated thymic lymphoma in AKR/J mice. On the average, a single LC appears in the thymus 30 days after the neonatal ip inoculation of SL3-3c virus; 50 days later, thymic lymphoma is clinically detectable. PLC in the bone marrow and oncogenic virus in the thymus are continuously present during this period before lymphoma develops. Biologically active oncogenic virus in the thymus increases as the animal nears the time of lymphoma development. Intrathymic inoculation, but not ip inoculation, of SL3-3c virus results in accelerated thymic lymphoma in 4- to 6-week-old AKR mice. PLC defined as a population of bone marrow-derived thymocyte progenitor cells susceptible to malignant transformation by oncogenic retrovirus after homing to thymus were further studied and characterized. PLC, like normal bone marrow thymocyte progenitors, were found to be radiosensitive and glucocorticoid resistant. Thymocytes of 21- to 28-day-old AKR mice, neonatally inoculated with SL3-3c virus, were studied for PLC. They could not be detected. It is concluded that lymphoma development is the final outcome of a series of events in which bone marrow-derived thymocyte progenitors are transformed after entering the thymus by virus in the thymic environment.

Animals↗
PubMed1985

[Cerebral blood flow, cerebral oxygen metabolism, cerebral glucose metabolism, and tissue pH in human acute cerebral infarction using positron emission tomography].

It is necessary for treatment and deciding prognosis to make clear about changes of cerebral blood flow and metabolism in acute cerebral infarction. This preliminary PET study was designed to investigate physiological and biochemical changes in acute cerebral infarction by positron emission tomography (PET). PET studies were performed in six patients with acute cerebral infarction within 48 hours after onset of stroke using continuous inhalation of C15O2 for cerebral blood flow (CBF), 15O2 for cerebral metabolic rate for oxygen (CMRO2), 11CO for cerebral blood volume, the intravenous injection of 11C-dimethyloxazolidinedione for tissue pH and the intravenous injection of 18F-fluorodeoxyglucose for cerebral metabolic rate for glucose (CMRGlu). Metabolic coupling index (MCI) image was made from CBF image and CMRGlu image to investigate relation between CBF and CMRGlu. Also oxygen glucose index (OGI) image was made from CMRO2 image and CMRGlu image to investigate relation between CMRO2 and CMRGlu. Preliminary results demonstrate that reduction of CBF, CMRO2, and CMRGlu in the affected cortex except for reperfusion case. Increase of OER was recognized four of six cases. Patterns of MCI and OGI in the cortex which CMRO2 value is less than 65 mumol/100 g/min were different from those in the cortex which CMRO2 value is more than 65. MCI of the affected cortex (CMRO2 less than 65) decreased relative to that of the cortex (CMRO2 greater than or equal to 65). OGI of the affected cortex (CMRO2 less than 65) significantly decreased in comparison with that of the cortex (CMRO2 greater than or equal to 65).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Sequence analysis of Vicia faba repeated DNA, the FokI repeat element.

A type of highly repeated DNA sequences present in the genome of Vicia faba was detected by digestion its nuclear DNA with FokI endonuclease and fractionating the digests on polyacrylamide gels. Four fragments of 59, 108, 177 and 246 bp of the FokI repeated sequences were collected from the gels and their primary structures were determined by the method of Maxam and Gilbert. These repeated DNA sequences were shown to be a multiple tandem array of a 59 bp sequence element. And its nucleotide sequence was almost completely conserved among all the sequence members of each the size class and also among these classes. This sequence element consists of a duplet of an about the duplet has an incomplete dyad symmetrical structure.

Base Sequence↗
PubMed1984

Improved purification and enzymatic properties of three forms of reverse transcriptase from avian myeloblastosis virus.

The purification procedure for quantitative recovery of the three molecular forms, alpha, alpha beta and beta 2 of avian reverse transcriptase (Ueno, A., Ishihama, A. and Toyoshima, K. (1982) J. Biochem. 91, 311-322) was improved with respect to removal of nucleases. The three enzyme forms were prepared from avian myeloblastosis virus by CsCl centrifugation and poly(G)-agarose column chromatography. The alpha- and alpha beta-forms of the enzyme were further purified to near homogeneity by column chromatography on heparin agarose and DNA cellulose, respectively. The three enzyme forms thus purified were equally active in influenza virus RNA-directed synthesis of single-strand cDNA. By contrast, the alpha-form enzyme was more active in the single-strand cDNA-directed synthesis of double-strand DNA than the other two enzyme forms.

Avian Leukosis Virus↗
PubMed1984

Evaluation of [18F]-4-fluoroantipyrine as a new blood flow tracer for multiradionuclide autoradiography.

This article reports the evaluation of [18F]-4- fluoroantipyrine (FAP) as a quantitative blood flow tracer by comparing blood flow measured with [18F]FAP to that determined simultaneously with [14C]-4-iodoantipyrine (IAP), a standard blood flow tracer, by means of double-tracer autoradiography. The single-pass extraction value (m), which indicates diffusibility of a tracer, was determined according to the procedure described by Crone . The diffusibility of FAP was essentially the same as that of IAP. The brain-blood partition coefficient for FAP was found to be similar to that for IAP, 0.89 +/- 0.01. Values of local cerebral blood flow obtained with FAP agree with those determined with IAP. From these results, we concluded that FAP is indeed as good a blood flow tracer as IAP. Since 18F is a positron-emitting radionuclide, it might be a useful tracer for blood flow measurement by positron emission tomography.

Animals↗