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T Ohsumi

Publications and source records attributed to T Ohsumi.

27 records · Page 2Linked to original sources
PubMed1993

Anti-(p34 protein) antibodies inhibit ribosome binding to and protein translocation across the rough microsomal membrane.

The p34 protein is a non-glycosylated, integral membrane protein characteristic of rough microsomes and is believed to play a role in the ribosome-membrane association. Here, antibodies directed against p34 were examined as to their inhibitory effect on ribosome binding to and protein translocation across the microsomal membrane. Preincubation of the stripped (ribosome-depleted) membrane with anti-p34 immunoglobulins (IgGs) or their Fab fragments led to more than 80% inhibition of the binding of ribosomes and their large (60S) subunit to the membrane. The inhibition was dependent on the amount of antibodies used, but comparable amounts of IgGs and Fab fragments from nonimmune serum had less effect. The p34 antibodies were also inhibitory for cotranslational translocation of secretory proteins, i.e. placental lactogen and serum albumin, across the membrane. These results suggest that p34 is involved in the binding of ribosomes to the microsomal membrane and that it is in close proximity to the protein translocation site in the microsomal membrane.

Animals↗
PubMed1992

Isolation and some properties of a 34-kDa-membrane protein that may be responsible for ribosome binding in rat liver rough microsomes.

We have isolated, by hydroxyapatite chromatography with a non ionic detergent and a high salt concentration, a non-glycosylated, membrane protein with a relative molecular weight of 34 kDa that had previously been found to be a major constituent of the membrane protein fraction showing ribosome-binding activity derived from rat liver rough microsomes (RM). The isolated 34 kDa protein (p34), when incorporated into a liposome model membrane, exhibited significant binding activity toward ribosomes, its binding properties being similar to those observed with intact RM. Immunochemical analyses using antibodies directed against p34 suggested that it is a membrane-embedded RM surface protein, which is specifically localized in ribosome-attached organelles and widely distributed among mammalian tissues. These results would constitute evidence that p34 is a likely candidate for an RM ribosome-binding protein.

Animals↗
PubMed1992

Long-term effects of ozone and nitrogen dioxide on the metabolism and population of alveolar macrophages.

To investigate how alveolar macrophages adapt themselves to oxidative pollutants in the long term, rats were exposed to a strong oxidant, ozone (O3), or a weak oxidant, nitrogen dioxide (NO2), for a maximum duration of 12 wk. After exposures, alveolar macrophages were collected by pulmonary lavage. Throughout 11 wk of exposure to 0.2 ppm O3, the specific activities of glucose-6-phosphate dehydrogenase (G6PDH) and glutathione peroxidase of the peroxidative metabolic pathway and pyruvate kinase and hexokinase of the glycolytic pathway were 40-70% elevated over the controls in alveolar macrophages. The population of alveolar macrophages was consistently 60% higher than the controls. The small-sized macrophages, immature macrophages, preferentially increased. To the contrary, the thymidine incorporation per cell was always 20-30% lower than in the controls, although the total incorporation remained unchanged. No infiltration of polymorphonuclear leukocytes occurred. By 12 wk of exposures to 1.2 and 4.0 ppm NO2, the population of alveolar macrophages increased 30% over the control. Among the enzymes examined, however, only the G6PDH activity increased 10% for 4.0 ppm NO2. No increase in the enzyme activities occurred for 1.2 ppm NO2. Based on these results, alveolar macrophages adapt themselves to the long-term exposure of O3 or NO2 by recruiting immature macrophages through an apparent influx of monocytes. During the exposure to O3, the peroxidative metabolic and glycolytic pathways are enhanced persistently in alveolar macrophages, whereas both pathways were not enhanced by the exposures to NO2.

Adenosine Triphosphate↗
PubMed1991

Identification of a membrane protein responsible for ribosome binding in rough microsomal membranes.

A membrane protein fraction was obtained from rat liver rough microsomes by affinity chromatography on a concanavalin A-Sepharose column and then a chelating-Sepharose column. This protein fraction comprised about 2% of the total membrane proteins of rough microsomes and the ribosome-binding activity of ribosome-stripped rough microsomes was predominantly found in this protein fraction, as determined with a liposome assay system. To identify the essential components responsible for the ribosome binding, two approaches were employed. Trypsin treatment of liposomes reconstituted with this protein fraction resulted in the loss of the ribosome-binding activity in parallel with the loss of a dominant band, estimated Mr 34,000, in SDS-polyacrylamide gels. Next, the direct interaction between the binding sites on the membrane of reconstituted liposomes and 60S ribosomal subunits was investigated by photocrosslinking using sulfosuccinimidyl 2-(m-azido-o-nitrobenzamido)-ethyl-1,3'-dithiopropionate (SAND). The photocrosslinked complex was formed between 60S ribosomal subunits pretreated with SAND and binding-site proteins on the membrane of the liposomes. Then, after the liposomes were solubilized, the complex was isolated by sucrose gradient centrifugation of the binding mixture. The crosslinked proteins were released from 60S ribosomal subunits by cleavage of of crosslinks with beta-ME and analyzed by SDS-polyacrylamide gel electrophoresis and 125I-autoradiography. The 34-kDa protein (p34) was the predominant component that crosslinked to the 60S ribosomal subunits and was found in proportion to the amount of 60S ribosomal subunits added to the system. The p34 was distinguishable by immunoblot analysis from urate oxidase, which is the 34-kDa protein of peroxisomal cores contaminating rough microsomes. These results suggest that the present p34 is a likely candidate molecule for the ribosome-binding activity of rough microsomes.

Animals↗
PubMed1986

Activation and increment of alveolar macrophages induced by nitrogen dioxide.

Male Wistar rats were exposed to 4 ppm nitrogen dioxide (NO2) for 10 d, and at intervals alveolar macrophages were collected by pulmonary lavage. A metabolic enhancement of alveolar macrophages was observed on d 4 of exposure. The specific activities of glucose-6-phosphate dehydrogenase and glutathione peroxidase of the peroxidative metabolic pathway increased to 1.29-fold (p less than 0.001) and 1.17-fold (p less than 0.05) those of the control values, respectively. The specific activities of succinate-cytochrome c reductase of the mitochondrial respiratory system and pyruvate kinase of the glycolytic pathway also increased to 1.17-fold (p less than 0.01) and 1.20-fold (p less than 0.01) those of the control values, respectively. In addition, the incorporation of [3H]leucine and [14C]thymidine into alveolar macrophages were elevated to 1.77-fold (p less than 0.001) and 1.84-fold (p less than 0.01) those of the control values, respectively. The activities of all enzymes tested decreased to control levels by d 10. The number of alveolar macrophages collected from exposed animals increased to 1.24-fold (p less than 0.01) that of the control value on d 7 and was maintained at a significantly higher level until d 10. Alveolar macrophages were heterogeneous in size (7-21 micron in diameter), and most of them were distributed between 11 and 17 micron in diameter. Exposures to 4 ppm NO2 increased significantly the cells of 9-13 micron in diameter on the seventh day. These results show that exposures to 4 ppm NO2 cause a metabolic enhancement and subsequent increase in alveolar macrophages.

Animals↗
PubMed1986

[Effect of glutaraldehyde on cultured cells--restraining effect on multiplication of L cells].

Glutaraldehyde (GA) was tested for its cytotoxic effect on L cell tissue culture system in comparison with formaldehyde (FA). In the first study, the replanted cells were grown to monolayers on the flattened bases of the culture tubes, and then exposed to the drug. In the second study, the drug was added to the cell suspension just put in the culture tubes. In either case, the cells were kept in contact with the drug at 37 degrees C for 24, 48 or 72 hr, after which time the monolayers were removed and the viable cells in each of the tubes were counted up. The change in the number of viable cells was examined in the various concentrations of the drugs and time intervals of cell-drug contact. Both GA and FA showed relatively slight toxic effect when each concentration was 1 microgram/ml. The cells exposed to 1, 10 micrograms/ml of GA or 1 microgram/ml of FA were able to increase in number, though markedly restrained from their multiplication if compared with the control. GA and FA seriously diminished the viable cells at a concentration of 100 micrograms/ml and 10 micrograms/ml, respectively, and they were so toxic that complete cell death was immediately caused even when the concentration of each drug was at 1000 micrograms/ml. Just replanted cells showed less tolerance to the drug effects than the cells of established monolayers; suppression of cell growth was noted with the concentration of 0.8 microgram/ml and above of either GA or FA, and complete cell death was caused by 58 micrograms/ml of GA and 7.0 micrograms/ml of FA.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehydes↗
PubMed1977

Statistical study on malignant melanoma in Japan (1970-1976).

The authors reported in 1972 a statistical study based on 501 cases of malignant melanoma. As continouous study this review was carried out on 456 cases of melanoma which were reported during six years between 1970 and 1976. These two studies showed quite similar results as follows: (1) Yearly incidnece of malignant melanoma indicated a definite upward trend and the average number of patients was 71.1 per year. (2) Distribution by age showed one peak in the seventh decade. (3) Sex ratio was 1.1: 1. (4) The number of cases per total population in Japan showed great increase in over fifth decades and two peaks in the 7th and 8th decades. (5) Average age of the onset of all melanoma was 51.6 years old, while, that of brain and spinal cord melanoma was 25.4 years old. In the skin melanoma with preexisting pigmented skin lesions, the median age of the onset of primary melanoma on the foot was 38.7 years old and that of originated melanoma except foot was 65.9 years old. (6) Incidence of the melanoma was high in the sole considering the number of melanocytes per unit skin area.

Adolescent↗