Lithium-induced decrease of brain inositol and increase of brain inositol-1-phosphate is transient

The effects of a single does of LiCl (2.5 or 10 mEq/kg) on brain inositol and inositol-1-phosphate (Ins1P), intermediates of brain phosphoinositude (PI) turnover, were determinated in male Han: Wistar rats. There was a remarkable, 36–58 fold elevation of brain Li⁺ as the single does of LiCl was increased 4-fold. Moreover, the accumulation of brain lithium was slow during repeated administration of LiCl. Brain lithium did not correlate with changes in brain PI turnover either after a single or repeated doses. Thus, after a single does of LiCl the increases in brain Ins1P were much less than the decreases in brain inositol. Also, brain inositol was significantly decreased only with the high dose of LiCl whereas brain Ins1P accumulation was more prominent with the lower dose. Moreover, repeated daily doses of LiCl only transiently increased brain Ins1P at 1 and 7 d whereas inositol remained at control levels throughout the 14 d observation period. Lithium probably caused the transient decrease in brain inositol by inhibiting several enzymes, in addition to the inhibition of myo-inositol mono-phosphates, in the PI cycle. Moreover, a slow dampening down of PI turnover by lithium, possible via an inhibitory action on G-protein-coupling, may also explain the present findings.     

表面活性剂和Ca~(++)对大麦根质膜透性的作用

阳离子型表面活性剂(CTMA)以低于CMC的浓度、非离子型表面活性剂(Triton-X-100)以高于CMC的浓度引起大麦离体根K~+及可溶性糖的外流,并有浓度效应。5℃时表面活性剂引起溶质外流,CTMA预处理10 min后,Ca~(++)无抑制作用。Ca~(++)与 Triton-X-100同时处理大麦根促进溶质外流。Mg~(++)、Mn~(++)对CTMA及Triton-X-100引起溶质外流的效应与Ca~(++)的相类似,但不如Ca~(++)有效。     

Molecular cloning of a human gene that regulates chromosome condensation and is essential for cell proliferation.

The tsBN2 cell line, a temperature-sensitive (ts) mutant of baby hamster kidney cell line BHK21/13, seems to possess a mutation in the gene that controls initiation of chromosome condensation. At the nonpermissive temperature (39.5 degrees C), the chromatin of tsBN2 cells is prematurely condensed, and the cells die. Using tsBN2 cells as a recipient of DNA-mediated gene transfer, we investigated a human gene that is responsible for regulation of chromosome condensation and cell proliferation. We found that the human gene complementing the tsBN2 mutation resides in the area of the 40- to 50-kilobase HindIII fragment, derived from HeLa cells. Based on this finding, we initiated cloning of a human gene complementing the tsBN2 mutation. From lambda and cosmid libraries carrying partial digests of DNA from the secondary transformants, the 41.8-kilobase HindIII fragment containing the human DNA was isolated. The cloned human DNA was conserved in ts+ transformants through primary and secondary transfections. Two cosmid clones convert the ts- phenotype of tsBN2 cells to ts+ with more than 100 times a higher efficiency, compared with cases of transfection with total human DNA. Thus, the cloned DNA fragments contain an active human gene that complements the tsBN2 mutation.     

The effect of bisulfite modification on the template activity of DNA for DNA polymerase I

Cytosine residues of poly(C) and heat-denatured calf thymus DNA were transformed into 5,6-dihydrouracil-6-sulfonate (U(SO⁻₃)) residues by treatment with bisulfite. The poly(U(SO⁻₃)₂, C₃) and poly(U(SO⁻₃)₉, C₁) prepared did not form inter-base binding with either poly(A) or poly(I) as judged by the absence of hypochromicity in ultraviolet absorbance. U(SO⁻₃) residues in the DNA inactivated it to serve as template for E.coli DNA polymerase I, while the template activity was restored by conversion of the U(SO⁻₃) residues into U.     

Effect of Oxygen on Heme and Porphyrin Accumulation from δ-Aminolevulinic Acid by Suspensions of Anaerobically Grown Staphylococcus epidermidis

The effect of various conditions on the accumulation of porphyrins and heme by resting suspensions of anaerobically grown cells of Staphylococcus epidermidis was examined. Anaerobically grown cells contain 10 to 15% of the amount of protoheme found in cells grown aerobically. Resting suspensions of anaerobically grown cells, when incubated aerobically in buffer with delta-aminolevulinic acid and glucose for 60 min, exhibited a fourfold increase in protoheme content. At high levels of delta-aminolevulinic acid, there was also a significant accumulation of porphyrins with the solubility and chromatographic properties of coproporphyrin and uroporphyrin. Protoporphyrin was not accumulated. When oxygen was excluded from the incubation mixture, accumulation of protoheme was prevented, but accumulation of coproporphyrin and total porphyrin was enhanced. Nitrate served as an electon acceptor as indicated by its reduction to nitrite; however, nitrate did not substitute for oxygen in causing the accumulation of protoheme. These results suggested that oxygen is required for one of the late steps of heme synthesis in S. epidermidis, possibly for the conversion of coproporphyrinogen to protoporphyrin. The inability of nitrate to substitute for oxygen suggests a role for molecular oxygen as a substrate rather than as an electron acceptor for heme synthesis.     

ENZYMES OF PHOSPHOINOSITIDE METABOLISM DURING RAT BRAIN DEVELOPMENT

—The activities of four enzymes concerned with inositol lipid metabolism have been determined in homogenates of rat brains of different ages. The enzymes are CDP-diglyceride inositol phosphatidate transferase, phosphatidylinositol kinase, diphosphoinositide kinase and triphosphoinositide phosphomonoesterase. The activities of all the enzymes increased with age. Phosphatidylinositol kinase activity rose most sharply well before myelination, reaching a maximum at about 6 days of age. Diphosphoinositide kinase and triphosphoinositide phosphomonoesterase activities increased most rapidly during myelination. The increase in CDP-diglyceride inositol phosphatidate transferase showed no definite association with any period of development. It is concluded that triphosphoinositide metabolism is associated with myelin or a closely related structure.     

PUC衍生质粒的一个低拷贝数突变型

本文报道大肠杆菌的ColE1类似质粒的一个低拷贝数突变型。从载体质粒pUC4衍生的重组质粒pPGVT3在大肠杆菌宿主DF2145中是不稳定的,以pPGVT3转化DF2145时在4o℃培养得不到转化子。用诱发点突变的羟胺体外处理pPGVF3质粒DNA,得到一个稳定性提高了的突变质粒pPGVT3HA,突变的位置被确定在质粒的pUC部分,突变降低了pUC及其衍生质粒的拷贝数。文中对质粒的稳定性与拷贝数的关系作了讨论。