Studies on the metabolism of a sulfur-oxidizing bacterium VII. Oxidation of sulfite by a cell-free extract of Thiobacillus thiooxidans

Properties of the cell-free extract, prepared from a strainof Thiobacillus thiooxidans by sonic disruption followed byfractionation with centrifugatiori, were investigated with referenceto its sulfite-oxidizing activity. Without the addition of cofactors the particulate fraction(F-P)catalyzed oxidation of sulfite with oxygen or bacterial cytochromec-552 obtained from Pseudomonas stutzeri as electron acceptor.TMPD reduced by ascorbic acid was also oxidized by F-P. Thesoluble fraction(F-S) showed no activity in oxidizing sulfiteand TMPD, but stimulated TMPD oxidation by F-P. Oxygen uptake with either sulfite or TMPD as substrate was inhibitedby KCN, NaN₃, CO and c-phenanthroline. CO-Inhibition was reversedby light. Reduction of cytochrome c-552 by sulfite was insensitiveto these agents. Antimycin A markedly inhibited sulfite oxidation with eitheroxygen or cytochrome c-552 as electron acceptor, but was withouteffect on TMPD oxidation. DDC and SAO, both strong inhibitors of sulfur oxidation, didnot affect sulfite and TMPD oxidations. Cytochromes of the a, b and c types were contained in F-P. Thesecytochromes were rapidly reduced when F-P was incubated withsulfite. Cytochrome(s) of the c type was present in F-S, too. ¹VI.=References (3) ²Partly supported by a grant from the Ministry of Education ³Present address: Sanyo Women's College, Hatsukaichi, Hiroshima738, Japan ⁴Present address: Department of Biochemistry, Hiroshima UniversitySchool of Dentistry, Hiroshima 734, Japan (Received May 15, 1970; )     

Nitrogen assimilation by a Citrus tree

Primary assimilation of ¹⁵N-ammonium or ¹⁵N-nitrate by excised leaves of satsuma mandarin (Citrus unshiu Markovitch) was examined under light and dark conditions. Under both conditions both types of nitrogen were most markedly incorporated into glutamine-amide nitrogen in the primary step of the assimilation, and into proline in the later steps. Incorporation of ammonium or nitrate into amino acids was more active in the light than in the dark, although the stimulating effect of light on the incorporation was relatively small in both cases.     

Action Spectra for Step-Up Photophobic Response in Blepharisma

ABSTRACT The cells of Blepharisma which possess red pigment (blepharismin) show step-up photophobic response (temporal ciliary reversal induced by a sudden increase in light intensity). Bleaching of the cells by cold shock raised a threshold light intensity for the response, Oxidation of red pigment that produced blue pigment did not raise the threshold for the response. The action spectrum for the step-up photophobic response of the cells which possess normal red pigment had peaks at about 580, 540 and 490 nm, a value which coincided with peaks of an absorption spectrum of the red pigment. The absorption spectrum of oxidized pigment (blue pigment) shifted 20 nm toward infrared light. The action spectrum for the response of the cells which possess blue pigment also shifted 20 nm toward infrared light. Results suggest that red pigment might be involved in the step-up photophobic response. Key words. Blepharismin, ciliary reversal, photoreceptors, photoresponse.     

Influence of Temperature on Glucose Metabolism of Round Spermatids of Rats

Glucose utilization by spermatids was found to be 17.37±0.37 nmoles/hr/10⁶ cells at 34°C and 28.94±1.12nmoles/hr/10⁶ cells at 40°C. A good parallelism was observed between the increased rate of glucose utilization and lactate production at 40°C. There was no significant change in the levels of glycolytic intermediates in the cells, except for marked accumulations of fructose-1, 6-diphosphate, dihydroxyacetone phosphate and glyceraldehyde-3-phosphate in the presence of glucose (1 mM). Glucose oxidation in the citrate cycle by spermatids was higher at 40°C than at 34°C, but was never greater than 2% of the overall rate of glucose utilization. In addition, glucose did not prevent decrease of ATP at either 34 or 40°C. The effects of temperature on the activities of 11 glycolytic enzymes were examined. The activities of aldolase and phosphoglyceromutase were similar between 30 and 34°C, but increased markedly at 40°C. The higher temperature increased the V_max values, without affecting the Kms. The activities of other glycolytic enzymes were similar at the different temperatures. These findings indicate that the increased overall rate of glucose utilization in glycolysis at higher temperature is due to increased Vmax values of aldolase and phosphoglyceromutase.     

Stimulation of Unfertilized Eggs of the Echiuroid, Urechis unicinctus by Polyamines

Unfertilized eggs of the echiuroid, Urechis unicinctus , were activated by polyamines, such as putrescine, spermidine and spermine at concentrations above 10 μM. Fertilization membrane elevated and germinal vesicle disappeared in unfertilized eggs kept for several min in sea water containing these polyamines. Following the addition of these polyamines, a decrease of pH value in the egg suspension, occurred in a similar manner as observed following fertilization. Several sec after the addition of polyamines to the egg suspension, the respiratoy rate increased very slightly and the sensitivity of the respiration to 2, 4-dinitrophenol, which was lower in unfertilized eggs than in fertilized eggs, became as high as in fertilized ones. Irregular cleavage occurred in the eggs stimulated by polyamines. The incorporation of [³H]-deoxyadenosine into DNA was initiated by adding polyamines in the unfertilized eggs preloaded with the isotope. The rate of [³H]-leucine incorporation into protein in the preloaded unfertilized eggs was also enhanced by polyamines, in almost the same manner as observed following fertilization.     

Properties of Invertases in Sugar Storage Tissues of Citrus Fruit and Changes in Their Activities during Maturation

Both acid and alkaline invertases were present in immature juice sacs of satsuma mandarin (Citrus‘Unshu Marcovitch”) fruit, in which sugar content was low. Maturing and mature juice sacs, in which sugar content increased steadily with time, were characterized by the presence of alkaline invertase and the absence of acid invertase. When the immature juice sacs were homogenized with 0.2 M sodium phosphate-citrate buffer (pH 8.0), almost all of the acid invertase activity was found in the solubilized fraction, whereas almost all of the alkaline invertase activity was present in the insoluble fraction. The distribution of alkaline invertase between the solubilized and insoluble fractions changed with the development of fruit. The acid invertase had a molecular weight of 69,000, optimum pH of 4.8–5.3, and K_m value for sucrose of 7.3 mM. The alkaline invertase had a molecular weight of 200,000, pH optimum of 7.2–7.7, and K_m value of 35.7 mM. The hydrolysing activities of both enzymes for raffinose were considerably less than those for sucrose. The alkaline invertase had lower activity for raffinose than the acid invertase.     

ON THE DE NOVO FORMATION OF THE CENTRIOLE IN THE ACTIVATED SEA URCHIN EGG

Eggs of Pseudocentrotus depressus were activated artificially by Loeb's "double treatment method". 50 min after activation, a number of asters were produced in the eggs. It was confirmed by electron microscopy that centrioles with a typical fine structure were present in artificially induced asters.
An unfertilized egg of Hemicentrotus pulcherrimus was divided into 2 halves, nucleated and non-nucleated, by centrifugation on a sucrose bed. Each half was activated by the same method as mentioned above. Several asters were produced in both halves after a certain period of incubation. The presence of bodies considered to be centrioles were demonstrated in the asters in both nucleated and non-nucleated halves.
The results add probability to the view that the centrioles are produced de novo in artificially activated eggs and fragments.     

Comparative Study on the Ability of Various Teratocarcinomas to Form Chimeric Mouse Embryos

Various embryonal carcinoma cells of different origins were compared as to the ability to form chimeric blastocysts by means of aggregating with normal 8-cell stage mouse embryos. The teratocarcinoma lines examined were OTT6050 and five newly established ones including a spontaneous testicular teratocarcinoma STT-2. The present results have revealed that distinct differences existed in the ability of colonizing blastocysts among teratocarcinomas and also among embryonal carcinoma cell lines.
Since STT-2 stem cells were found to be incorporated into blastocysts most efficiently, further development of the blastocysts were examined in utero. It was found that STT-2 stem cells could be incorporated into the fetuses up to the 7-to 28-somite stages. This is the first case to demonstrate that testicular teratocarcinoma cells with the male germ cell origin have the developmental potency to participate into mouse embryogenesis.     

FURTHER STUDY RE-EXAMINING WHETHER LARVAL EPIDERMIS CAN OMIT THE SECRETION OF A PUPAL CUTICLE, USING THE SILKWORM, BOMBYX MORI

When larval tissue is exposed to a hormonal milieu lacking juvenile hormone, adult characters appear directly, omitting the pupal stage, in some insects but not in others, including Bombyx mori. An attempt was made to induce omission of pupal characters in this species by varying the stage of the larval epidermis to be tested. Pieces of larval integument taken from fourth- and fifth-instar larvae of various stages were transplanted to developing adults. Although the number of cuticle layers and the types of cuticle produced differed depending on the age of the donors, none of the pieces omitted secreting the pupal cuticle. It is concluded that the larval epidermis cannot omit secreting pupal cuticle, and that a transition of tissue competence may play an important part in the sequential appearance of larval, pupal, and adult characters.     

Changes of Chromosome Length and Constitutive Heterochromatin in Association with Cell Division during Early Development of Cynops pyrrhogaster embryo

The length of chromosomes in the presumptive ectoderms of Cynops embryos was measured at nine successive cell divisions from the 6th (cleavage stage) to the 14th (gastrula stage). Up to the 10th cell division (cleavage stage) the chromosome length remained constant. At the 11th cell division the chromosomes began to shorten and continued to shorten at every cell division up to the 14th cell division. The degree of shortening and the mode of variation in length corresponded to the respective developmental stages of cleavage, blastula and gastrula. During those periods when chromosomes became shortened, some fine C-bands of the paracentromeric region found in earlier stages fused together. The chromatin of interphase nuclei also showed considerable changes during chromosome shortening. Besides the size reduction of interphase nuclei, the number of C-band granules in an interphase nucleus decreased in parallel with chromosome shortening and fusion of C-bands in mitotic chromosome.