Preparation and properties of insolubilized restriction endonucleases.

Type II restriction endonucleases Bam HI and Eco RI were covalently coupled to Sepharose. These insolubilized enzymes generated fragment patterns for several viral DNAs identical to those produced by the respective free enzymes. Conditions for optimal activity were similar for both bound and unbound forms of the enzymes. Insolubilization improved thermal stability of Bam HI and Eco RI. The bound enzyme can be recovered from reaction mixtures and reused several times. Upon storage at 4 degrees C, coupled endonucleases remained stable for several months.     

Alpha-D-Mannosidase. Preparation and properties of free and insolubilized enzyme.

Alpha-D-Mannosidase (alpha-D-mannoside mannohydrolase, EC 3.2.1.24) has been purified to homogeneity as demonstrated by polyacrylamide gel electrophoresis and ultracentrifugation. The molecular weight of the enzyme is approx. 200000; the protein appears to contain 4 subunits, with molecular weights of 66000 and 44000. The enzyme was immobilized on Sepharose and the properties of the coupled and free enzyme were compared. Both were stable up to 70 degrees C with rapid loss of activity between 75-80 degrees C; both retained 25-30% activity in 6 M urea and 65% of the original activity could be restored in the coupled preparation by removal of the urea. The pH maximum of each form was approximately the same, with the maximum of the immobilized enzyme shifted slightly to a lower pH. The coupled alpha-D-mannosidase presented in this report offers the possibility of digesting high molecular weight substrates, such as glycoproteins, with the advantages of (1) recovering large quantities of digested substrate; (2) recovery of the active glycosidase; and (3) digestion at high temperatures and under conditions that denature many proteins.     

Factors affecting the yield and properties of bacterial cellulose

Acetobacter xylinum E₂₅ has been applied in our studies in order to find optimal culture conditions for effective bacterial cellulose (BC) production. The strain displays significantly higher stability in BC production under stationary culture conditions. In contrast, intensive agitation and aeration appear to drastically reduce cellulose synthesis since such conditions induced formation of spontaneous cellulose nonproducing mutants (Cel−), which dominated in the culture. Mutation frequency strictly depends on the medium composition in agitated cultures. Enrichment of the standard SH and Yamanaka media with 1% ethanol significantly enhanced BC production in stationary cultures. Horizontal fermentors equipped with rotating discs or rollers were successfully applied in order to improve culture conditions. Relatively slow rotation velocity (4 rpm) and large surface area enabling effective cell attachment are optimal parameters for cellulose production. Physical properties of BC samples synthesized either in stationary cultures or in a horizontal fermentor revealed that cellulose from stationary cultures demonstrated a much higher value of Young's modulus, but a much lower value of water-holding capacity. Journal of Industrial Microbiology & Biotechnology (2002) 29, 189–195 doi:10.1038/sj.jim.7000303 Received 01 March 2002/ Accepted in revised form 18 July 2002     

Factors affecting the incidence of hypertension.

The incidence of hypertension was determined among 10,173 patients of general practices in southwestern Ontario studied from 1978 to 1982. For both sexes the incidence of hypertension rose with increasing age. The incidence was higher among men than among women until age 50, after which it was similar for the two sexes. Obesity was positively associated with incidence for both sexes. In men this association diminished significantly with increasing age. The similar trend in women fell just short of statistical significance. In men but not women heavy alcohol consumption was positively related to the incidence of hypertension. However, the broad definition of this variable may have obscured a relation in women. Among men the effect of obesity on the incidence of hypertension was less for heavy drinkers than for light drinkers. Smoking was not related to the incidence of hypertension in either sex.     

Factors affecting the viability and properties of microorganisms in different preservation methods

The review of literature devoted to the influence of the different methods of longterm preservation on the survival, physiological and biochemical properties of microorganisms: at low and ultralow temperatures, freeze-drying, drying, storage under the mineral oil etc. is given. The microorganisms viability depends on their nature, age and density of population, storage and recovery conditions of cells. Some features of the industrial microorganisms storage have been marked. The different hypotheses concerning the mechanism of preservation, injury and reactivation of microorganisms under the action of external factors during their storage are being discussed.     

恶梦的影响因素研究

恶梦是与睡眠相关的常见心理现象.目前,恶梦的概念仍具有争议,但恶梦与心理健康的关系,已经引起了研究者广泛关注.恶梦的病因学研究表明,恶梦与遗传及生理因素有关;恶梦具有人格倾向性,应激与创伤因素是其产生的主要原因,与分裂症等精神疾病高度相关;恶梦与睡眠呼吸相关因素关系不是很明确;恶梦与多巴胺受体激动剂等药物显著相关,恶梦产生的其他因素研究尚待发现.然而这些因素与恶梦的因果关系并不确定,各因素之间的关系及作用机制有待进一步研究.未来的研究可以改进研究方法,扩大研究对象,进行纵向研究等.     

Factors affecting flow karyotype resolution.

BACKGROUND: One of the major factors which influences the chromosome purity achievable particularly during high speed sorting is the analytical resolution of individual chromosome peaks in the flow karyotype, as well as the amount of debris and fragmented chromosomes. We have investigated the factors involved in the preparation of chromosome suspensions that influence karyotype resolution. METHODS: Chromosomes were isolated from various human and animal cell types using a series of polyamine buffer isolation protocols modified with respect to pH, salt concentration, and chromosome staining time. Each preparation was analyzed on a MoFlo sorter (DAKO) configured for high speed sorting and the resolution of the flow karyotypes compared. RESULTS: High resolution flow cytometric data was obtained with chromosomes optimally isolated using hypotonic solution buffered at pH 8.0 and polyamine isolation buffer (with NaCl excluded) between pH 7.50 and 8.0. Extending staining time to more than 8 h with chromosome suspensions isolated from cell lines subjected to sufficient metaphase arrest times gave the best result with the lowest percentage of debris generated, tighter chromosome peaks with overall lower coefficients of variation, and a 1- to 5-fold increase in the yield of isolated chromosomes. CONCLUSIONS: Optimization of buffer pH and the length of staining improved karyotype resolution particularly for larger chromosomes and reduced the presence of chromosome fragments (debris). However, the most interesting and surprising finding was that the exclusion of NaCl in PAB buffer improved the yield and resolution of larger chromosomes.     

Factors affecting mushroom Pleurotus spp.

Pleurotus genus is one of most extensively studied white-rot fungi due to its exceptional ligninolytic properties. It is an edible mushroom and it also has several biological effects, as it contains important bioactive molecules. In basidiomycete fungi, lignocellulolytic enzymes are affected by many typical fermentation factors, such as medium composition, ratio of carbon to nitrogen, pH, temperature, air composition, etc. The survival and multiplication of mushrooms is related to a number of factors, which may act separately or have interactive effects among them. Out that understanding challenges in handling Pleurotus species mushroom requires a fundamental understanding of their physical, chemical, biological and enzymatic properties. This review presents a practical checklist of available intrinsic and extrinsic factors, providing useful synthetic information that may help different users. An in-depth understanding of the technical features is needed for an appropriate and efficient production of Pleurotus spp.     

Factors affecting the isopenicillin N synthetase reaction.

1. Isopenicillin N synthetase (IPNS) from Cephalosporium acremonium, which requires Fe2+ and O2 for activity, was highly purified for studies of factors affecting its conversion of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (LLD-ACV) into isopenicillin N (IPN). EDTA was used to quench the reaction by removal of Fe2+. 2. IPNS was inactivated during the course of the conversion of LLD-ACV into IPN, although it was relatively stable in the absence of LLD-ACV under otherwise similar conditions. In the presence of GSH and ascorbate each IPNS molecule carried out about 200 catalytic events before inactivation, but the turnover number was decreased 5-fold in the absence of ascorbate. 3. After trace metal ions had been removed from IPNS and other components of the reaction mixture by Chelex-100 resin, only about 10 microM-Fe2+ was required for maximum stimulation. Several other transition-metal ions were inhibitors of the enzyme. 4. Both dithiothreitol (DTT) and GSH stimulated IPNS activity, but GSH, unlike DTT, was not rapidly oxidized in the presence of O2 and Fe2+. 5. IPNS was rapidly inhibited by the thiol-blocking reagents N-ethylmaleimide and 2,2'- and 4,4'-dipyridyl disulphide, but not by 5,5'-dithiobis-(2-nitrobenzoic acid) in the same concentration. Inhibition by 2,2'-dipyridyl disulphide could be reversed by DTT.     

Preparation and properties of cloning inhibitory factor. II. Factors affecting its production and assay

Cloning Inhibition Factor (CIF), an activity present in PHA or antigen stimulated lymphocyte culture supernatants, inhibited the cloning of HeLa cells when diluted 1:9 in HeLa culture medium. CIF was not detectable at 8 hr, was maximal at 24–48 hr, and declined with longer periods of lymphocyte culture. CIF production increased with lymphocyte concentration up to 1–2 × 10⁶ lymphs/ml but plateaued at higher concentrations. At lower lymphocyte concentrations, more CIF activity was present when lymphocytes were cultured in 5% rather than 12% serum. PPD elicited similar CIF activity from either highly purified or unpurified lymphocytes. CIF activity was independent of HeLa medium serum concentration. It remained stable for 3–6 months at ?20 °C, but was inactivated by heating at 56 °C for 30 min. At a 1:9 dilution CIF was not cytocidal but produced cytopathic changes. CIF shares many properties with, and may be identical to, Proliferation Inhibitory Factor.     

Factors affecting the encapsulation of drugs within liposomes.

The reported efficiencies of drug encapsulation into liposomes range from less than 0.1% to more than 10% per micromole phospholipid, depending on the nature of the drug and of the liposome employed. We have sought to investigate some of the factors which control the efficiency of drug encapsulation. We have found that most polar drugs are sequestered within the internal aqueous compartment of the liposomes, while nonpolar drugs can bind to the liposome membrane in addition to being sequestered, thus accounting for their higher efficiencies of encapsulation. The encapsulation of nonpolar drugs, but not of polar drugs, is very sensitive to the physical characteristics of the liposome membrane; in particular, a fluid membrane favors the efficient encapsulation of nonpolar compounds. The drug cytosine arabinoside is anomalous in that this highly polar compound seems to interact with the liposome membrane at physiological conditions of pH and ionic strength, thus allowing it to be encapsulated with high efficiency.     

Factors affecting quality of informed consent.

OBJECTIVE--To examine the factors influencing quality of informed consent. DESIGN--Prospective study comprising interviews with patients and patients'' completing standard questionnaires. SETTING--Academic surgical unit of large teaching hospital. PATIENTS--265 patients undergoing intrathoracic, intraperitoneal, and vascular surgical procedures. Of these patients, 192 have been followed up for six months. MAIN OUTCOME MEASURES--Patients'' recall of information at various points in the study; this score was compared by age, provision of written information, cognitive function, intelligence quotient (IQ), mood state and personality traits, and health locus of control. RESULTS--The patients were best informed immediately after signing the consent form and from then on recall of information deteriorated. A total of 172/250 (69%) patients admitted to not reading the consent form before signing it. Old age adversely affected recall of information at all assessment points. Impaired cognitive function reduced information recall only during the stay in hospital. Patients with above average IQs handled information better than those with a lower IQ except immediately after the signing of consent forms. Patients with an internal locus of health control (that is, those who believed their health to be in their own control) were better informed than those with an external locus of health control. Operation information cards improved recall only on the day of discharge. CONCLUSION--Elderly patients and patients with below average IQ, impaired cognitive functions, and an external locus of control have poor information recall. Written information may be more useful if given before admission to hospital.     

Factors affecting the palmitoyl-coenzyme A desaturase of Saccharomyces cerevisiae.

The activity and stability of the palmitoyl-coenzyme A (CoA) desaturase complex of Saccharomyces cerevisiae was influenced by several factors. Cells, grown nonaerobically and then incubated with glucose, either in air or under N2, showed a marked increase in desaturase activity. Cycloheximide, added during such incubations, prevented the increase in activity, suggesting de novo synthesis. The stability of the desaturase from cells grown nonaerobically was affected by subsequent treatment of the cells; enzyme from freshly harvested cells, or from cells that were then shaken under nitrogen, readily lost activity upon washing or during density gradient analysis, whereas aerated cells, in the presence or absence of glucose, yielded stable enzyme preparations. The loss of activity in nonaerobic preparations could be reversed by adding soluble supernatant from these homogenates and could be prevented by growing the cells in the presence of palmitoleic acid and ergosterol, but not with several other lipids tested.