Gamma-ray irradiation as a pretreatment for the enzymatic hydrolysis of cellulose

Summary The susceptibility of cellulose to enzymatic hydrolysis can be significantly affected through pretreatment by means of gamma-ray radiation. Experiments were carried out to investigate the effects of this radiation on enzymatic hydrolysis and on the two major structural features of cellulose that most influence hydrolysis, namely, specific surface area and crystallinity.D. H. Beardmore is currently with Phillips Petroleum Company, Bartlesville, OK 74004, U.S.A.     

Highly inducible cell lines derived from mice genetically transmitting the Moloney murine leukemia virus genome.

Permanent, non-virus-producing cell lines have been established from a mouse embryo carrying an endogenous, genetically transmitted Moloney murine leukemia virus (M-MuLV) genome. These cells carry the M-MuLV genome, as demonstrated by hybridization of cellular DNA to M-MuLV complementary DNA, but do not express it at the levels of virus production, accumulation of intracellular viral p30, or M-MuLV-specific RNA. Treatment with bromodeoxyuridine (50 microgram/ml for 24 h) resulted in induction of XC-positive NB-tropic virus, although only a small fraction of the cells released virus (less than 0.1% after 48 h). Immunofluorescent staining and flow microfluorometry indicated that a wave of p30 accumulation occurs in the induced cells, with a maximum at 24 to 48 h after the addition of bromodeoxyuridine. Furthermore, most, if not all, cells were induced to produce p30 protein. Similar kinetics were found for the accumulation of M-MuLV-specific RNA in the cytoplasm of induced cells. This rapid induction of virus expression in a majority of cells was dependent on the presence of the M-MuLV genome and probably represents primarily the expression of this endogenous virus since induction was not observed in cells similarly derived from a sibling embryo lacking the M-MuLV genome.     

Response of white adipocyte of mouse and rabbit to catecholamines and ACTH

Summary Hormone stimulated lipolysis of mouse and rabbit adipocytes as measured by both free fatty acid and glycerol release, is proportionally elevated with increase in the adipocyte cAMP level up to 1 nmole/g. The correlation coefficients are 0.94 and 0.97 for FFA/cAMP and glycerol/cAMP respectively. Increments in cAMP greater than 1 nmole/g show no correlation with increase in lipolysis. The release of lipolytic products, glycerol and free fatty acids, from white adipocytes in response to ACTH, epinephrine or morepinephrine was measured using radiochemical assays in short term incubation systems, with cAMP levels measured at the same time and from the same cell sample. Under the conditions studied, epinephrine is a more effective lipolytic hormone than ACTH in mouse adipocyte, and ACTH is more effective than epinephrine in rabbit adipocyte. The effect of catecholamines on the rabbit adipocyte is not modified by phentolamine (10 μM), but it is potentiated by 1-methyl-3-isobutyl xanthine (0.1 mM). The results suggest that cAMP mediates the action of these lipolytic hormones in white adipocytes of mouse and rabbit.     

Low-multiplicity infection of Moloney murine leukemia virus in mouse cells: effect on number of viral DNA copies and virus production in producer cells.

Mouse cells infected with Moloney murine leukemia virus (M-MuLV) were prepared by two methods, and the number of M-MuLV-specific DNA copies in the infected cells was measured. The number of M-MuLV-specific DNA copies detected varied from one to eight per infected cell in different cell lines. Cells in which multiple rounds of viral infection occurred during establishment had on the average more viral DNA copies than cells in which infection at low multiplicity was performed, followed by cloning of the cells. However, even in cells derived by the low multiplicity of infection method, most cell lines carried more than one copy of M-MuLV-specific DNA. Virus production per cell was also measured, and no strict correlation was observed between the number of M-MuLV DNA copies present and the amount of virus produced.     

Polyamine metabolism in McCoy cells: III. Comparative studies of the metabolic fate of exogenous putrescine in human fibroblasts and McCoy cultures

The fate of exogenously added 14C-putrescine following incubation for 24 hours with McCoy and human skin fibroblast cultures was examined. The nature of the polyamine derivatives found were quite different indicative of a difference in the cellular metabolism of polyamines. Exogenously added putrescine (PUT) was metabolized by both McCoy and human skin fibroblast cultures to form spermidine (SPD), spermine (SPM), gamma-aminobutyric acid (GABA) and some unidentified compounds. Within the experimental period of observation, human cultured fibroblasts metabolized PUT more efficiently than McCoy cells and converted more than 50% of it into SPD, SPM, GABA and unknown compounds. Monoacetyl putrescine (MAP) was formed by human skin fibroblasts. It was mainly identified in the culture medium. No MAP was detectable either intracellularly or extracellularly in McCoy cultures. The percentage of 14C-radioactivity found as PUT in the culture medium was greater in McCoy cells (86.0%) than in human fibroblasts (53.9%). The reverse was true for the percentage distribution of 14C-radioactivity as PUT inside the cells. No low Mr conjugates of SPD or SPM were found in the medium or intracellularly with either culture type. Some low Mr putrescine conjugates were found in the culture media; these were identified by the liberation of PUT upon acid hydrolysis.     

Kinetic studies of enzymatic hydrolysis of insoluble cellulose: analysis of the initial rates

A study was conducted on the kinetics of enzymatic hydrolysis of pure insoluble cellulose using unpurified culture filtrate Trichoderma reesei, with the emphasis on the initial reaction period. The initial hydrolysis rate and extent of enzyme (soluble protein)adsorption, either apparent or initial, were evaluated under various experimental conditions. It has been found that the various mass-transfer steps do not control the overall hydrolysis rate and that the hydrolysis rate is mainly controlled by the surface reaction step promoted by the adsorbed enzyme. It has also been found that the initial hydrolysis rate strongly depends on the initial extent of soluble protein adsorption and the effectiveness of the adsorbed soluble protein to promote the hydrolysis. The initial extent of soluble protein adsorption, in turn, is related to the initial cellulose concentration, enzyme concentration, and specific surface area of cellulose, whereas the effectiveness of the initially adsorbed soluble protein to promote the derived to interrelate these parameters without resorting to the Michaelis-Menten kinetics. The present result appear to imply that the role of enzyme-substrate complex formation should not be ignored in deriving a mechanistic kinetic model for enzymatic hydrolysis of cellulose.     

龙牙百合3个地方品种的形态特征及核型分析

采用经典测量和染色体常规压片法,对龙牙百合（Lilium brownii var.viridulum Baker）3个地方品种的形态特征及核型进行研究。植株形态分析结果显示：‘江西’龙牙的株高、开花口径、种球重量和周长、中外层鳞片重量和长度以及鳞片扦插产生小鳞茎数等指标均显著大于‘大叶’龙牙和‘平头’龙牙;‘大叶’龙牙的叶片最长,均值为14.54 cm。花粉、叶表皮气孔及鳞片淀粉粒的微形态特征分析结果显示：‘江西’龙牙的花粉粒径最大,均值达111.76 μm;‘平头’龙牙的叶表皮气孔最长,气孔密度也最大（约47.6个/mm²）;‘大叶’龙牙的淀粉粒径最大,均值为47.61 μm;‘江西’龙牙的淀粉粒大小分布更集中,差异性小。染色体核型分析结果显示：龙牙百合3个品种的染色体数目均为2n=2x=24,为二倍体,其中‘江西’龙牙核型公式为2n=2x=24=2m（2SAT）+6sm（2SAT）+12st（4SAT）+4t;‘平头’龙牙核型公式为2n=2x=24=4m+8sm+10st（4SAT）+2t;‘大叶’龙牙核型公式为2n=2x=24=2m（2SAT）+6sm+14st（4SAT）+2t,三者核型均为3B型。     

甘蔗节间伸长过程赤霉素生物合成关键基因的表达及相关植物激素动态变化

以甘蔗(Saccharum officinarum)优良品种桂糖42号(GT42)为研究材料, 分别于未伸长期(9-10叶龄以前) (Ls1)、伸长初期(12-13叶龄) (Ls2)和伸长盛期(15-16叶龄) (Ls3)取甘蔗第2片真叶(自顶部起)对应的节间组织, 测定其赤霉素(GA)、生长素(IAA)、油菜素甾醇(BR)、细胞分裂素(CTK)、乙烯(ETH)和脱落酸(ABA)的含量, 并通过实时荧光定量PCR (qRT-PCR)分析赤霉素合成途径关键基因GA₂₀氧化酶基因(GA20-Oxidase1)、赤霉素受体基因(GID1)和DELLA蛋白编码基因(GAI)的差异表达。结果表明, 在甘蔗伸长期间, GA和IAA含量呈现上升趋势, CTK和ABA含量呈下降趋势, ETH含量先上升后下降, BR含量则变化不明显; GA20-Oxidase1和GID1的表达呈上升趋势, 而GAI的表达则呈下降趋势, 这与相关植物激素的变化基本一致。综上, 甘蔗节间伸长过程主要与GA和IAA相关, 其次为CTK和ABA, 而ETH受到IAA的调控影响节间伸长; 植物激素间通过相互作用调控GA20-Oxidase1、GID1和GAI的表达, 影响GA含量和GA的信号转导过程, 进而影响甘蔗节间的伸长。该研究揭示了甘蔗节间伸长过程中赤霉素生物合成途径和信号转导关键基因的差异表达及植物激素含量的动态变化规律。