Scientia Sinica最新文献

It has been demonstrated that a cytochrome b-containing ferritin is present in Azotobacter vinelandii. After DEAE cellulose chromatography and purification fractional precipitation by 50% of the saturated ammonium sulfate of the extract prepared from A. vinelandii cells, a hexagonal crystalline preparation is obtained. The protein contains 4--6% of nonheme iron. The protein molecule is made up of an electron dense iron core with a diameter of 70A and a protein shell with a diameter of 120A. The Fe core can be removed from the shell by the treatment with chelating and reducing agents. Electron micrographs and absorption spectra reveal that the protein shells are very similar before and after the removal of the core. The electrophoretic mobility and immunological properties of the Fe-free protein against the antibody of ferritin are very similar to those of the protein before the removal of the iron. From the above characteristics, it can be inferred that the protein belongs to ferritin. The protein part contains protoheme as prosthetic group and so it belongs to cytochrome b. Hence, the protein prepared from A. vinelandii is a kind of cytochrome b-containing ferritins. The possible role of the ferritin in biological nitrogen fixation is discussed in this paper.

The molecular structures of both native and false hairs as well as the tendon of the female cadaver buried about 2,100 years ago, which was excavated from the Han Tomb, No. 1 at Mawangdui near Changsha, Human Province, China, have been studied with X-ray fiber diffraction. It has been shown that the conformations of alpha-keratin and collagen and the basic longitudinal period of these fibrous protein molecular chains have been preserved in those specimens respectively, but the aggregations of fibrous molecules have somewhat changed. Some exploration was made on the origin where came the cubic mercury sulphide inside the cadaver's hair.

Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April. The Finless porpoises are usually seen in groups of five or six individuals. The blow of Lipotes lasts 0.2-0.6 sec and that of Neophocaena 0.2-0.5 sec. In Lipotes, a short dive would take 10-20 sec and a long dive up to 1-2 min (average value being 31 sec). In Neophocaena a long dive would reach a maximum of 65 sec with an average of 17.5 sec. Lipotes has a pair of functional eyes. The selective secondary atrophy of a number of eye muscles and nerves and the position of the eyes in the head correspond with the physical conditions of the environments, so that the field of vision is directed forwards and upwards. When pursued by motor boat, both species react with a long dive and a change of direction under water. With the Baiji this would occasionally cause fatal injuries by the propeller of the ship. Such a case seems much less often with Neophocaena. The population of Lipotes is at present very small. In the stretch of the river (between Nanjing and Taiyangzhou) under exploration, we found scarcely more than one dolphin per 4 km. The cause for its scarcity is mostly due to accidents or wounds caused by propellers.

The effects of reserpine on the blood pressure, heart rate, higher nervous activity and plasma catecholamine level during the development of neuropsychogenic hypertension induced by overstrain of the central nervous system have been studied in dogs. Overstrain (intensified tension) of the higher nervous activities was induced by a schedule or irregularly arranged strengthening of the conditional stimuli with electric stimuli on the skin. After completion of three stimulative periods, 4 of the 5 untreated control and 2 of the 5 reserpine-treated dogs were found to have developed hypertension. The blood pressure measured in Chamber A (the room for blood pressure measurement) was much lower than that measured in Chamber B, i.e. in the experimental environment. The results showed that reserpine may have some inhibitory influence on the development of this model of neuropsychogenic hypertension, yet it could not prevent its development completely.

The audiometric zero level of air conduction for 100 healthy youths was determined over a frequency range from 20 Hz to 10 KHz in 1971-1973 under the laboratory conditions. The results obtained have been further verified recently on a selected group of 12 persons. This paper also presents the transfer experiments from the original earphone TDH-39(MX-41/AR) to six other types of earphones. The deviation of our data thus obtained from the recommendation by ISO is discussed.

Neoplastic transformation of primary fibroblast culture derived from esophagus tissue of a 52-year old male esophageal cancer patient was induced by chemical carcinogen (N-methyl-N'-nitro-N-nitrosoguanidine, MNNG) treatment. The transformed cells showed the biological and morphological properties characteristic of malignant cells, such as loss of contact inhibition, unlimited growth in vitro, aneuploidy, agglutinability by concanavalin A, formation of microvilli on the cell surface, growth on solid agar medium and tumor (fibrosarcoma) formation after heterotransplantation into immunosuppressed newborn mice.

The proton transport across biological membrane, accompanied by energy transformation, is closely related with many basic processes involved in the maintenance of life. Active researches are carried out in this field, but so far we have not known a complete calculation. This paper presents a model of an open and closed photon-controlled ion pore with a quantitative analysis of the irreversible process of the proton transport across the purple membrane. Upon absorbing photon by the purple membrane, the deprotonation of the Schiff base causes the ion pore to open, but it will close when it returns to bR570. A set of nonlinear differential equations describing this model is given. The stability of the equations is discussed. The results of the numerical calculation for steady state are found in good agreement with the experimental data of Bakker.

Poly A attached RNAs were isolated from carp ovarian and mature eggs. Both were equally potent in cell-free translating wheat germ system. The products were analyzed with rabbit antiserum against carp albumin and polyacrylamide gel electrophoresis. The results revealed the presence of carp albumin, a liver specific protein.