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Biomedical subjects

Y Akamatsu

Publications and source records attributed to Y Akamatsu.

At least 127 records · Page 7Linked to original sources
PubMed1980

Evidence for phase separation in the membrane of an osmotically stabilized fatty acid auxotroph of E. coli and its biological significance.

1. An unsaturated fatty acid auxotroph of Escherichia coli accumulated a high content of saturated fatty acids in its membrane when it was cultured under osmotically stabilized conditions. The physicochemical properties of the phospholipid extracts and of the membrane fraction from the cells were investigated by means of proton magnetic resonance, infrared spectroscopy and differential scanning calorimetry. 2. Physicochemical studies indicate that the phospholipid bilayers in the membranes exhibit at least two phase transitions, a minor one at approx. 19 degrees C and a major one at approx. 43 degrees C. Between the two temperatures, gel and liquid crystalline domains co-exist. Moreover, even in the gel state, phospholipids seem to segregated into domains containing different proportions of unsaturated fatty acids. 3. The Arrhenius plot of beta-galactoside transport rates is biphasic. The inflection point is at 22 degrees C. This means that the appearance of the fluid region in the bilayer at approx. 19 degrees C is important in the activation of membrane transport.

Biological Transport↗
PubMed1980

Behavior of vesicular stomatitis virus glycoprotein in mouse LM cells with modified membrane-phospholipids.

LM cells in which the membrane phospholipids had been modified with choline analogues were infected with vesicular stomatitis virus. The choline analogues tested were choline, N,N'-dimethylethanolamine, N-monomethylethanolamine and ethanolamine. These modifications per se did not affect the syntheses of individual viral proteins. The viral glycoprotein was detected in the plasma membranes of all the modified cells by pronase digestion in pulse-chase experiments, but the amount of glycoprotein susceptible to proteolysis varied, decreasing in these modified cells in the following order: N,N'-dimethylethanolamine- greater than choline- greater than N-monomethylethanolamine- greater than ethanolamine-treated cells. After a 4-h chase, glycoprotein was mainly distributed in the plasma membranes of cells modified with N,N'-dimethylethanolamine, whereas it was found in both the microsomes and plasma membranes of cells modified with other analogues. Fairly large amounts of glycoprotein were also found in the soluble fraction of ethanolamine-treated cells, but not in that of choline- or N,N'-dimethylethanolamine-treated cells. More precise experiments on the behaviour of glycoprotein with a short period of chase strongly suggested that migration of glycoprotein from the microsomes to the plasma membranes was fastest in cells modified with N,N'-dimethylethanolamine and slowest in cells modified with ethanolamine. Membrane lipid modifications also resulted in release of different numbers of progeny virions from the cells, release of virions from the cells decreasing in the following order: N,N'-dimethylethanolamine- greater than choline- greather N-monomethylethanolamine- greater than ethanolamine-treated cells. These results indicate that modification of membrane phospholipids influences not only the insertion of glycoprotein into the microsomes and its migration to the plasma membranes, but also the production of progeny virions.

Animals↗
PubMed1980

Increase of radiation damage to potassium-ion permeability in E. coli cells with decrease in membrane fluidity.

Membrane lipids of an auxotroph of E. coli requiring unsaturated fatty acid were manipulated by supplementing the growth medium with unsaturated fatty acids of different chain lengths and/or configurations, and the radiation damage to K+-permeability of the resulting modified cells was investigated in relation with factors influencing membrane fluidity, such as temperature and procaine. Radiation had greater effects on membranes supplemented with unsaturated fatty acids of the trans configuration with a longer chain than on those of the cis configuration with a shorter chain. Radiation damage also increased with decrease in temperature. Furthermore, procaine-treated membranes showed increased resistance to radiation. All these results indicate that the damage was affected by the physical character of membrane lipids and that it was greater in membranes with decreased fluidity.

Biological Transport↗
PubMed1979

A case report of the immunodysplasia syndrome and heavy chain disease associated with subacute bacterial endocarditis.

A 36-year-old man was admitted to Saitama Medical School Hospital, because of a remittent fever which had continued for approximately 6 months, hepatosplenomegaly and lymphadenopathy. He had direct Coombs' test positive auto-immune hemolytic anemia associted with subacute bacterial endocarditis (SBE). The lymphnode demonstrated focal diffuse proliferation of immunoblasts and arborizing vessels with a few small germinal centers, which resembled histological features of the immunoblastic lymphadenopathy. The immunochemical analysis revealed the presence of free IgG Fc fragments in serum. From the above results the patient was diagnosed as immunodysplasia syndrome (IDS) and heavy chain disease (HCD) associated with SBE. It was suggested that the chronic antigenic stimulation due to SBE might have some role in the mechanism of the development of the IDS and HCD in our patient.

Adult↗
PubMed1978

Identification of vasopressor phospholipid in crude soybean lecithin.

The vasopressor phospholipid in crude soybean lecithin was isolated by column chromatography on Sephadex LH-20. It represented 0.1% of crude soybean lecithin. The isolated phospholipid was identified to be lysophosphatidic acid by gas chromatography-mass spectrometry analysis of TMS-deacylated product and acetolysis product. Nuclear magnetic resonance analysis favored the 1-monoacyl isomer over the 2-isomer. By enzymic determination with L-3-glycerophosphate dehydrogenase, the isolated phospholipid was identified as 1-monoacyl-L-3-glycerophosphate. Gas chromatographic examination revealed that it was composed of a large percentage of unsaturated fatty acids, especially linoleic acid. The activity of isolated lysophosphatidic acid was slightly less than that of synthetic 1-linoleoyl-L-3-glycerophosphate.

Animals↗
PubMed1978

Involvement of membrane lipids in radiation damage to potassium ion permeability of Escherichia coli.

Radiation damage to K+ permeability of an unsaturated fatty acid auxotroph of E. coli grown with oleate or linolenate was investigated at different temperatures. A remarkable effect of radiation was observed at 0 degrees C with cells that had been grown with linolenate at 42 degrees C. This indicates that, besides protein, membrane lipids at least are involved in the radiation damage. The damage also seems to be affected by the fluidity of membrane lipids.

Cell Membrane Permeability↗
PubMed1977

Phase transitions of phospholipid bilayers from an unsaturated fatty acid auxotroph of Escherichia coli.

Total phospholipids were extracted from cells of temperature sensitive unsaturated fatty acid auxotrophs of Escherichia coli (K-12 UFAts) grown at 28degrees C (PL28), and at 42degrees C in the presence of 2% KCl as an osmotic stabilizer (PL42 (KCl)). From the analysis of fatty acids, it was shown that the content of unsaturated fatty acids of PL42 (KCl) is only 9% of the total fatty acids, while that of PL28 is 54%. The thermal phase transitions of the bilayers prepared from the phospholipid fractions were studied by proton magnetic resonance. The line widths of the methylene signals and the sums of the methylene and methyl signal intensities were plotted against reciprocal values of absolute temperature 1/T or temperature itself. From the plots phase transitions were detected at about 19degrees C for PL28 and at 43degrees C for PL42 (KCl). In spite of its complex composition of fatty acids a highly cooperative transition was observed in the case of PL42 (KCl). It was also suggested that the phospholipids bilayers in the biomembranes of this strain at the growth temperature (42 degrees C) are in the state where the gel and liquid crystalline phases coexist.

Cell Membrane↗
PubMed1976

Casein and 3-methylcholanthrene carcinogenesis in inbred C57BL/6Os female mice.

Groups of inbred C57BL/6Os female mice were subjected to one of the following -reatments: 1) subamyloidogenic administration of sodium caseinate (C group); 2) four intragastric intubations of 0.25 mg 3-methylcholanthrene (MCA) (MCA group); 3) a sodium caseinate injection followed by MCA (C-MCA group); or 4) MCA followed by a soidum caseinate injection (MCA-C group). During their life-spans, mice of the C group developed a significantly high incidence of neoplasms, especially histiocytic lymphomas, No myelogenous leukemia was observed in the C group, but it was seen in the MCA, C-MCA, and MCA-C groups. The occurrence rate of other neoplasms was significantly high in the C, MCA, and MCA-C groups, but it was not significantly high in the C-MCA group compared with the untreated group. Results suggested that sodium caseinate treatment shifts target organs in MCA carcinogenesis. In all treated groups, amyloidosis of a secondary type was observed at a significantly high rate in the following order of severity by treatment group: MCA, MCA-C, C-MCA, and C groups, MCA was obviously amyloidogenic with or without sodium caseinate adjuvant treatment; although the sodium caseinate treatment was subamyloidogenic, it elicited neoplasms, including neoplasms of lymphoreticular tissue.

Amyloidosis↗
PubMed1976

Staining of keratin and keratohyalin with the reactive dye levafix red violet E-2BL.

Demonstration of keratin in Zenker-fixed skin and in tissues stored in formalin can be difficult because such material is unsuitable for histochemical studies. A reactive dye, Levafix red violet E-2BL, proved useful for demonstration of keratohyalin and some types of keratin. Formalin-, Zenker- and methacarn-fixed sections were pretreated with alkaline alcohol, stained one hour at 60 C in an aqueous solution containing 0.25% Levafix red violet E-2BL plus 0.25% NaCl, rinsed in buffer solution pH 9, dehydrated and mounted. Keratohyalin granules and stratum corneum were colored red violet; hair and tonofibrils remained unstained. In sections prestained with Mayer's acid hemalum, keratohyalin was dark blue. Sulfonated monoazo dyes without reactive groups colored no tissue structures under the conditions of this technic; apparently, Levafix red violet E-2BL is bound via its reactive group. Polarization microscopic studies suggest binding of Levafix red violet E-2BL by an amorphous matrix of keratin. Correlations with chemical data indicate that the staining patterns parallel the distribution of proteins formed in the stratum granulosum.

Azo Compounds↗
PubMed1975

Neoplasms in strains of splenectomized mice after a single 7,12-dimethylbenz[alpha]anthracene treatment.

The effects of splenectomy on carcinogenesis by a single 10-mg dose of 7,12-dimethylbenz[alpha]anthracene (DMBA) given in olive oil by gavage was tested on BTOs, C57BL/60s, C3H/HeOs, and BALB/cOs mice. The splenectomy, performed a week before the DMBA was given, did not affect physical status or the incidence of acute toxic death of animals. DMBA-treated animals developed neoplasms at a significantly higher rate than did untreated mice. Splenectomy did not influence the overall incidence of neoplasms. Observed tumors in DMBA-treated groups were those of skin, forestomach, colon, liver, lung, adrenal, ovary, breast, hematopoietic-lymphoreticular system, and vascular system, depending on the strain. Types of DMBA-treated neoplasms were affected by prior splenectomy, depending on the strain: Splenectomy inhibited lung adenomas in BALB/cOs females and hepatomas in C57BL/60s females; splenectomy enhanced skin neoplasms in C57BL/60s and squamous cell carcinoma of the forestomach in BTOs males. The most significant change was in the incidence of the group of lymphomas. Myelogenous leukemia was increased in DMBA-treated groups of all strains, but splenectomy inhibited the development of this type of lymphoma.

9,10-Dimethyl-1,2-benzanthracene↗