芽殖酵母PHO85基因对细胞周期调控的影响

本文通过同源重组方法,构建了一系列单倍体缺失株:pho85△单缺失株YPH600、pho85△cln1△双缺失株YPH610、cln1△cln2△双缺失株YPH640和半乳糖诱导存活的pho85△chn1△cln2△(GAL1-10PHO85)三缺失株YPH630。比较不同缺失株的生长速度可以看出,PHO85单基因缺失比CLN1、CLN2双基因缺失对细胞生长速度的影响大。在去诱导的不同时间,取细胞进行光学显微镜形态学分析及DNA含量的流式细胞计量分析(FACS)。结果表明YPH630三缺失株的单倍体酵母细胞休止在G1期。     

ROLE OF FETAL AND INFANT GROWTH IN PROGRAMMING METABOLISM IN LATER LIFE

Fetal growth and development is dependent upon the nutritional, hormonal and metabolic environment provided by the mother. Any disturbance in this environment can modify early fetal development with possible long-term outcomes as demonstrated by extensive work on ‘programming’. Growth restriction resulting from a deficit in tissue/organ cell number (as measured by tissue DNA content) is irrecoverable. However, when the cell size (or cell protein content) is reduced, the effects on growth may not be permanent. Recent epidemiological studies using archival records of anthropometric measurements related to early growth in humans have shown strong statistical associations between these indices of early development and diseases in later life. It has been hypothesised that the processes explaining these associations involve adaptive changes in fetal organ development in response to maternal and fetal malnutrition. These adaptations may permanently alter adult metabolism in a way which is beneficial to survival under continued conditions of malnutrition but detrimental when nutrition is abundant. This hypothesis is being tested in a rat model which involves studying the growth and metabolism in the offspring of rat dams fed a low-protein diet during pregnancy and/or lactation. Using this rat model, it has been demonstrated that there is:

• (i) Permanent growth retardation in offspring nursed by dams fed a low-protein diet.
• (ii) Permanent and selective changes in organ growth. Essential organs like the brain and lungs are relatively protected from reduction in growth at the expense of visceral organs such as the liver, pancreas, muscle and spleen.
• (iii) Programming of liver metabolism as reflected by permanent changes in activities of key hepatic enzymes of glycolysis and gluconeogenesis (glucokinase and phosphoenolpyruvate carboxykinase) in a direction which would potentially bias the liver towards a ‘starved’ setting. We have speculated that these changes could be a result of altered periportal and perivenous regions of the liver which may also affect other aspects of hepatic function.
• (iv) Deterioration in glucose tolerance with age.
• (v) An increase in the life span of offspring exposed to maternal protein restriction only during the lactation period, and a decrease in life span when exposed to maternal protein restriction only during gestation.

These studies show that hepatic metabolism and even longevity can be programmed by events during early life.     

ROLE OF MALATE TRANSPORT IN REGULATING METABOLISM IN MITOCHONDRIA ISOLATED FROM RABBIT BRAIN

Abstract— Partly purified chromaffin granules were incubated in vitro with Ca²⁺ (with trace amounts of ⁴⁵Ca²⁺) in concentrations ranging from 4 μm to 1 mm. After incubation the granules were washed with media containing EDTA and then subjected to density gradient centrifugation (1.3 to 2.0 m-sucrose solutions) in order to characterize the particles which had taken up ⁴⁵Ca²⁺. By using marker enzymes and various inhibitors of Ca²⁺ uptake into such cell particles as mitochondria it was established that under the conditions of the experiments chromaffin granules took up Ca²⁺ from the incubation medium. To characterize this uptake a simplified density gradient procedure was tested and found to be suitable. The uptake of Ca²⁺ into chromaffin granules was strongly dependent on temperature. It was not activated by ATP. The uptake was linear up to 10 min. At high calcium concentrations (above 200 μm) the rate of uptake levelled off. The uptake at 37°C was 1 nmol Ca²⁺/mg protein/min at a Ca²⁺ concentration of 500 μm. Mg²⁺ had no influence on Ca²⁺ uptake, whereas Sr²⁺ (1 mm) inhibited it. The methods established in this study should prove useful for a further characterization of this Ca²⁺ uptake into chromaffin granules which is likely to represent a useful model for the Ca²⁺ uptake occurring in the intact gland.     

ROLE OF NUCLEIC ACID AND PROTEIN METABOLISM IN THE INITIATION OF GROWTH AT GERMINATION

When dry decotyledonized embryos of Raphanus are supplied withwater, a brief period of water absorption (phase A) is followedby a period of no fresh weight increase (phase B) which lastsfor 8 hr at 30°. In this period, embryos become ready toadvance into the period of fresh weight increase (phase C). When embryos were exposed to various concentrations of thiouracilor actinomycin D solution from 0 hr of water supply, increasesin fresh weight and in RNA content measured at 13 hr were inhibitedin parallel with each other. Chloramphenicol and puromycin inhibitedthe fresh weight increase without affecting the RNA increase.When embryos were exposed to thiouracil or puromycin for 2,4 and 6 hr, beginning at 0 hr of water supply, the start ofphase C delayed 2, 4 and 6 hr, respectively. When these drugswere given after phase B had progressed at least for 2 hr, thedelay of the start of phase C was shorter than the period ofthe drug treatment. If given at the end of phase B, thiouraciland actinomycin D inhibited the incorporation of ¹⁴C-uracilbut not the fresh weight increase, while chloramphenicol andpuromycin inhibited the latter without inhibiting the former. During phase B, protein content per dry weight of embryo didnot increase, but the rate of ¹⁴C-leucine incorporation increasedremarkably to reach the level in phase C. Incorporation of labeledleucine was inhibited if embryos were subjected to thiouracilor actinomycin D action during phase B, but not if the drugswere given when phase B had been completed. Puromycin and chloramphenicolinhibited the incorporation whenever they were given. The increase in respiratory activity during phase B was inhibitedrelatively little by the above mentioned four drugs. In conclusion syntheses of RNA and protein seem to be essentialfor the progress of phases B and C, protein synthesis havinga more direct effect. (Received September 17, 1965; )     

THE ROLE OF GABA METABOLISM IN THE CONVULSANT AND ANTICONVULSANT ACTIONS OF AMINOOXYACETIC ACID

Abstract— At high dosage levels AOAA acted as a convulsant agent in mice and rats but in lower amounts it was an effective anticonvulsant agent against INH-induced seizures, by tripling the time to the onset of the convulsions. AOAA elevated brain GABA levels as a result of a preferential inhibition of the GABA-T enzyme system but, contrary to previous reports, the activity of the GAD enzyme system was also inhibited, even by relatively low dosage levels of AOAA. The state of excitability of the brain following the administration of AOAA was related, within the limits of the present study, to changes in GAD activity and GABA levels, but additional data are required before the relationship can be properly evaluated.     

光合能量代谢对C_3植物光呼吸的调节作用

C_3植物光呼吸与光合作用关系受光合能量代谢状况的调节。在外界无CO_2和照光条件下,贮藏性光合产物经某种转化途径能“回迁”光合与光呼吸碳循环并显著地受到光合能量代谢的影响。在无CO_2或低CO_2浓度、高光强条件下,此碳素“回迁”过程对协调光合能量代谢与光合碳素代谢平衡,可能起重要作用。     

BIOCHEMICAL CHANGES IN YEAST DURING SPORULATION. II. ACETATE METABOLISM

Acetate metabolism was studied with Saccharomyces cerevisiae diploid strain G2-2 in sporulating culture, asporogenic diploid strains 3c × a and 3c × 3a, and respiratory deficient haploid strain 3c (asporogenic). Acetate in a sporulating medium was utilized by sporogenic and asporogenic diploid yeasts linearly with time. Activities of aconitase, NADP-linked isocitrate dehydrogenase, and succinate dehydrogenase initially increased in the cell-free homogenate of either strain. Activity of glucose-6-phosphate dehydrogenase decreased. Isocitrate lyase activity increased remarkably in the sporogenic strain but not in the asporogenic strain. The rate of production of ¹⁴CO₂ from ¹⁴C-1-acetate was accelerated more than from ¹⁴C-2-acetate in intact cells of the sporogenic strain during sporulating culture. Fractionation of radioactive cell substances showed remarkable lipid synthesis. Accumulation and reutilization of cold acid-soluble precursor substances occurred during sporogenesis. The role of glyoxylate and tricarboxylate cycle enzymes in sporulation is discussed.     

A MODULATING ROLE OF PITUITARY-ADRENAL AXIS IN CEREBRAL METABOLISM OF ADENOSINE 3'',5''-MONOPHOSPHATE

Abstract— The effect of adrenalectomy or hypophysectomy on the metabolism of adenosine 3',5'-monophosphate (cyclic AMP) in the cerebral cortex of male Wistar rats was investigated.
The bilateral removal of adrenal glands reduced significantly the activity of cerebral adenylate cyclase [EC 4.6.1.1]. whereas that of cyclic 3'.5'-nucleotide phosphodiesterase [EC 3.1.4.17] remained unchanged. The formation of cyclic AMP measured in cerebral cortical slices from adrenalectomized or hypophysectomized rats was also diminished. Decreases in the activity of adenylate cyclase and formation of cyclic AMP following adrenalectomy were antagonized by in vivo administration of dexamethasone or aldosterone, while those observed in hypophysectomized rats were restored by ACTH or dexamethasone. It is suggested that the pituitary adrenal axis has a modulating role in the metabolism of cerebral cyclic AMP, possibly by changing adenylate cyclase activity.     

ROLE OF SULFUR IN THE CELL DIVISION OF CHLORELLA, WITH SPECIAL REFERENCE TO THE SULFUR COMPOUNDS APPEARING DURING THE PROCESS OF CELL DIVISION II.

1. Chlorella cells, which had been grown synchronously undersulfur-deficient conditions and thus rendered unable to performcell division, were made capable of nuclear and cellular divisionby being supplied with ³⁵S-labeled sulfate and nitrate underphotosynthesizing conditions, and the fate of sulfur duringthese recovery processes was followed. 2. When the S-starved cells were provided with sulfate aloneunder photosynthesizing conditions, cells grew appreciably inmass performing nuclear division but remaining incapable ofcellular division. During these processes most of the ³⁵S wasfound to be incorporated into the protein fraction of algalcells. 3. When the cells which had been stalemated at the above-mentionedstage were supplied with nitrate, they grew further in massand eventually performed cellular division. During this periodthe ³⁵S was found to be distributed not only in the proteinfraction, but also in an appreciable amount in the cold andhot acid-soluble fractions. 4. By paper-electrophoretic experiments it was found that thenature of the sulfur substances appearing in the hot acid-solublefraction changed strikingly during the process of cellular division.Zone electrophoresis and an anion-exchange chromatography ofthese substance isolated from the cells at the completion ofcellular division, disclosed that they were most probably deoxypentosepolynucleotides containing sulfur in some form yet unidentified. 5. It was demonstrated that there exist some antagonistic relationsbetween the protein synthesis and the formation of these sulfur-containingdeoxypentose polynucleotides, and that the former predominatesunder photosynthesizing conditions while the latter outweighsunder nonphotosynthesizing conditions. (Received August 9, 1960; )     

ROLE OF SULFUR IN THE CELL DIVISION OF CHLORELLA, WITH SPECIAL REFERENCE TO THE SULFUR COMPOUNDS APPEARING DURING THE PROCESS OF CELL DIVISION. I.

1. The role of sulfur in the cell division of Chlorella was studiedby following the fate of the sulfur supplied to the sulfur-deficientcells using ³⁵S as a tracer.
2. The sulfur-deficient cells whichwere unable to perform celldivision were made capable of divisionby the provision of ³⁶S-labeledsulfate under non-photosynthesizingconditions. Soon after theprovision of sulfate the labeledsulfur went rapidly into thecold perchloric acid (PCA)-solublefraction of algal cells,almost entirely in the form of sulfateand/or some other inorganicsulfur substance (s). With the lapseof time, more or less remarkablechanges occurred in the patternof ³⁵S-distribution in differentfractions of cell material.It was noticed that, at the onsetof cell division, a sulfur-containingpeptide-nucleotide compound(s)(SPN), which has been reportedearlier, appeared in a largequantity in the cold PCA-solublefraction, and that its quantitydecreased gradually during thesubsequent process of cell division,suggesting that the compoundwas transformed into some othersubstance (s), presumably withits nucleotide moiety going intonucleic acids and the peptidemoiety going into some essentialproteins.
3. Another noteworthyphenomenon observed during the process ofcell division wasthe incorporation of ³⁶S in a group of hotPCA-soluble substances.These sulfur substances were revealedto be sulfur-containingnucleotidic compounds, which might possiblybe some essentialcomponents of, or substances in close relationto, deoxypentosenucleic acid (DNA).

(Received March 1, 1960; )