Photochemical reaction of 9-cis-retro-γ-rhodopsin at low temperatures

9-cis-Retro-γ;rhodopsin (λ_max = 420 nm) was prepared from 9-cis-retro-γ-retinal and cattle opsin. After cooling to liquid nitrogen temperature (77 K), the pigment was irradiated with light at 380 nm. The spectrum shifted to the longer wavelengths, owing to formation of a batho product. This fact indicates that the conjugated double bond system from C-5 to C-8 of the chromophoric retinal in rhodopsin was not necessary for formation of bathorhodopsin. Reirradiation of the batho product with light at wavelengths longer than 520 nm yielded a mixture composed of presumably 9- or 11-cis forms of retro-γ-rhodopsin. These three isomers are interconvertible by light at liquid nitrogen temperature. Thus the retro-γ-rhodopsin system is similar in photochemical reaction at 77 K to cattle rhodopsin system. Each system has its own batho product. Based on these results, it was infered that the formation of bathorhodopsin is due to photoisomerization of the chromophoric retinal of rhodopsin and is not due to translocation of a proton on the ring or on the side chain from C-6 to C-8 of the chromophoric retinal to the Schiff-base nitrogen.     

Synthetic ColE1 plasmids carrying genes for penicillin-binding proteins in Escherichia coli

Clarke and Carbon's collection of 2000 Escherichia coli strains which harbor ColE1 plasmids carrying small random segments of the E. coli chromosome was screened for the correction of mutational defects in penicillin-binding proteins (PBPs): ponA (PBP-1a), ponB (PBP-1b), dacB (PBP-4), and pfv (PBP-5). We found plasmids carrying chromosomal segments containing ponA⁺-aroB⁺ (pLC29-47), ponB⁺-tonA⁺ (pLC4-43, pLC4-44, and pLC19-19), and argG⁺-dacB⁺ (pLC10-46 and pLC18-38). Characters of these plasmids were analyzed. Two other plasmids (pLC26-6 and pLC4-14) previously found to correct ftsI mutation (Y. Nishimura, Y. Takeda, A. Nishimura, H. Suzuki, M. Inouye, and Y. Hirota (1977)Plasmid1, 67–77) were also investigated further. Restriction maps of chromosomal DNAs carried by pLC29-47, pLC4-44, pLC19-19, pLC18-38, pLC26-6, and pLC4-14 were constructed. The regions of ponB-tonA on pLC4-44 and pLC19-19, and of leuA-ftsI-murE and F on pLC26-6 were located on the restriction maps. Although both pLC26-6 and pLC4-14 corrected a thermosensitive mutation, ftsI, which causes a defect in cell division due to abnormal PBP-3, only pLC26-6 led to restoration of PBP-3 production by an ftsI mutant, while pLC4-14 did not. Restriction and heteroduplex analyses of pLC26-6 and pLC4-14 have shown the absence of nucleotide sequence homology between them. The plasmids, pLC29-47 carrying ponA⁺ and pLC4-43, pLC4-44, and pLC19-19 carrying ponB⁺ led the host cell to overproduce the respective PBP.     

Relationships between nucleic acid,nitrogen, and growth rate of tobacco cells in suspension culture

Summary Changes in the amount of nucleic acid and nitrogen, and the relationships between these amounts and the growth rate of tobacco cells (Nicotiana tabacum L. cv. Bright Yellow-2) at different initial nitrogen concentrations in the medium, were examined in batch cultures. During culture in basal medium, the amount of intracellular nucleic acid expressed per unit of dry biomass was 36.3 mg RNA g^–1 cell and 8.1 mg DNA g^–1 cell at the beginning of batch culture. These values increased 2.5 fold for RNA and 1.5 fold for DNA during the exponential growth phase and then gradually decreased with the decline in the growth rate. Similar changes were also observed in the medium containing less nitrogen. The specific growth rate, (day^–1), of the culture corresponded to the magnitude of the intracellular RNA content (mg RNA g^–1 cell), and the linear relationship, RNA=38+23 was obtained. In addition, there were remarkable positive correlations between the total and protein nitrogen, and during the cultures. The mononucleotide composition of total RNA (AMP+UMP)/(GMP+CMP) which was suggested to be a convenient index of metabolic activity was nearly constant (0.78 to 0.80) during tobacco cell culture in the basal medium.     

Detection of the changes in protein distribution of rat plasma induced by carbon tetrachloride administration by means of two-dimensional electrophoresis

The changes in rat plasma protein distribution after carbon tetrachloride administration were examined using two-dimensional electrophoresis, utilizing isoelectric focusing in polyacrylamide gel in the first dimension and pore gradient polyacrylamide gel electrophoresis in the second dimension. Drastic changes in amount of protein were observed at more than 20 spot positions including those of transferrin, Gc-globulin and low-density lipoprotein. The time course of the changes was examined, and the most drastic changes were observed at 2 days after carbon tetrachloride administration.     

Synthesis of desmosterol and epidesmosterol from hyodeoxycholic acid

A new synthesis of desmosterol was described using hyodeoxycholic acid (3,6-dihydroxy-5β-cholanic acid) as a starting material. Epidesmosterol (3-hydroxycholesta-5,24-diene) was also synthesized for the first time from the same starting material.     

Acyl-Coenzyme A synthetase and fatty acid oxidation in rat liver peroxisomes.

Rat liver peroxisomes oxidized palmitate in the presence of ATP, CoA and NAD+, and the rate of palmitate oxidation exceeded that of palmitoyl-CoA oxidation. Acyl-CoA synthetase [acid: CoA ligase (AMP-forming); EC 6.2.1.3] was found in peroxisomes. The substrate specificity of the peroxisomal synthetase towards fatty acids with various carbon chain lengths was similar to that of the microsomal enzyme. The peroxisomal synthetase activity toward palmitate (40--100 nmol/min per mg protein) was higher than the rate of palmitate oxidation by the peroxisomal system (0.7--1.7 nmol/min per mg protein). The data show that peroxisomes activate long chain fatty acids and oxidize their acyl-CoA derivatives.     

Animalizing Effect of A23187 on Sea Urchin Embryos

Pulse treatment of sea urchin embryos with 3 μM A23187 for 2 hr starting at a stage in initial 10 hr period of development at 20°C, followed by a culture in normal sea water up to the pluteus corresponding stage (45 hr after fertilization), yielded many large exogastrulae with thin embryo walls. The pulse treatment starting at a time between 10 and 13 hr after fertilization yielded considerable number of large prisms and gastrulae having thin embryo walls. Probably, the pulse treatment exerts stimulating effects on ectodermal cell determination in whole span of pre-hatching period to produce animalized embryos. On the other hand, pulse treatment with A23187 in pre-hatching period exerts stage-specific effects on gut formation. Embryos, thus treated for 2 hr starting at stages between 3 and 5 hr after fertilization, produced quite small exoguts but those treated at stages between 7 and 8 hr formed well developed and long exoguts. In embryos treated at the other stages than above, guts or exoguts were almost the same in their size to those in normal ones. These effects of A23187 on morphogenesis were canceled by procaine, tetracaine and ruthenium red. Probably, artificial Ca²⁺signal induced by A23187 alters the determination of cell fates, programmed in pre-hatching period.     

Respiration and Motility in Starfish Spermatozoa at Various Times in the Breeding Season

In the spermatozoa of Asterias amurensis , patterns of changes in the respiratory rate and motility following dilution of dry sperm in sea water varied among batches and were classified into three types. The type I spermatozoa were immotile and exhibited quite low respiratory rate. Ethylenediamine tetraacetic acid made the type I spermatozoa motile and elevated their respiratory rate. The type II spermatozoa were also immotile and the respiratory rate remained quite low for about 5 min after the dilution. Thereafter, they spontaneously became motile and the respiratory rate increased. The type III spermatozoa became motile upon their dilution and exhibited high respiratory rate. Differences in the motility and respiratory rate of spermatozoa among batches probably result from degree of their maturation. In moving spermatozoa, the ADP and AMP levels increased at the expense of ATP. 2,4-Dinitrophenol elevated the respiratory rate only in immotile spermatozoa, which showed a high ATP level and quite low ADP level, but did not made them motile. Oligomycin inhibited the respiration of both motile and immotile spermatozoa. Probably, the respiratory rate is made low by a shortage of ADP in immotile spermatozoa and is enhanced by ADP production due to the initiation of their movement.     

Cell-division inhibitor produced by a killer strain of cellular slime mold Polysphondylium pallidum

The killer strain CK-8 of cellular slime mold Polysphondylium pallidum produces a cell-division inhibitor, in addition to a killer factor. This inhibitor represses cell division of many strains and species of cellular slime molds, except CK-8 itself and its complementary mating-type strain. It is sensitive to both heat and trypsin, and capable of binding to Con A. Its apparent molecular mass is more than 100 kDa. Repression of cell division by this inhibitor is reversed by trypsin treatment of the cells.     

Chloride movement across the basolateral membrane of proximal tubule cells

Summary Electrophysiologic and tracer experiments have shown that Cl^– entersNecturus proximal tubule cells from the tubule lumen by a process coupled to the flow of Na⁺, and that Cl^– entry is electrically silent. The mechanism of Cl^– exit from the cell across the basolateral membrane has not been directly studied. To evaluate the importance of the movement of Cl^– ions across the basolateral membrane, the relative conductance of Cl^– to K⁺ was determined by a new method. Single-barrel ion-selective microelectrodes were used to measure intracellular Cl^– and K⁺ as a function of basolateral membrane PD as it varied normally from tubule to tubule. Basolateral membrane Cl^– conductance was about 10% of K⁺ conductance by this method. A second approach was to voltage clamp the basolateral PD to 20 mV above and below the spontaneous PD, while sensing intracellular Cl^– activity with the second barrel of a double-barrel microelectrode. An axial wire electrode in the tubule lumen was used to pass current across the tubular wall and thereby vary the basolateral membrane PD. Cell Cl^– activity was virtually unaffected by the PD changes. We conclude that Cl^– leavesNecturus proximal tubule cells by a neutral mechanism, possibly coupled to the efflux of Na⁺ or K⁺.