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71.
Summary The effects of phosphate on -amylase fermentation byBacillus amyloliquefaciens were investigated. It was observed through batch culture that optimal phosphate level which maximizes -amylase biosynthesis exists. High concentration of phosphate level promotes maltose uptake and growth of the microorganism, while high maltose uptake rate in the microorganism at the same time represses the enzyme biosynthesis presumably due to catabolite repression inside the microorganism. In continuous cultivation, a steady state of -amylase biosynthesis was obtained by maintaining phosphate level at a certain level. In fed-batch culture, by intermittant feeding of phosphate as well as maltose, higher activity of -amylase in the broth was obtained compared to the result from single nutrient feeding. 相似文献
72.
Summary In enzymatic synthesis of cephalexin (CEX) from 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) and D--phenylglycine methyl ester (PGM) using an acylase fromXanthomonas citri, it was found that the synthetic activity and conversion yield were enhanced markedly by depressing the water activity (a
w
) of reaction system. This enhancement was probably resulted from the change of thermodynamic equilibrium and maximized at a range ofa
w
from 0.96 to 0.97. 相似文献
73.
Heat generation in laser irradiated tissue 总被引:1,自引:0,他引:1
A J Welch J A Pearce K R Diller G Yoon W F Cheong 《Journal of biomechanical engineering》1989,111(1):62-68
Many medical applications involving lasers rely upon the generation of heat within the tissue for the desired therapeutic effect. Determination of the absorbed light energy in tissue is difficult in many cases. Although UV wavelengths of the excimer laser and 10.6 microns wavelength of the CO2 laser are absorbed within the first 20 microns of soft tissue, visible and near infrared wavelengths are scattered as well as absorbed. Typically, multiple scattering is a significant factor in the distribution of light in tissue and the resulting heat source term. An improved model is presented for estimating heat generation due to the absorption of a collimated (axisymmetric) laser beam and scattered light at each point r and z in tissue. Heat generated within tissue is a function of the laser power, the shape and size of the incident beam and the optical properties of the tissue at the irradiation wavelength. Key to the calculation of heat source strength is accurate estimation of the light distribution. Methods for experimentally determining the optical parameters of tissue are discussed in the context of the improved model. 相似文献
74.
The constitution and properties of phosphorylated and unphosphorylated C-terminal fragments of progastrin from dog and ferret antrum 总被引:1,自引:0,他引:1
Antibodies to the extreme C-terminal tryptic (nona-) peptide fragment of porcine progastrin have been used in radioimmunoassay to identify progastrin fragments in dog, ferret and pig antral mucosa extracts and to monitor their purification. In addition to previously characterised phosphorylated and unphosphorylated C-terminal tryptic peptides of porcine progastrin a minor form corresponding to the C-terminal octapeptide (i.e. des-Ser C-terminal nonapeptide) was isolated and characterised. The latter form together with phosphorylated and unphosphorylated forms of the nonapeptides were also isolated and chemically characterised from dog antrum, and the unphosphorylated nonapeptide was characterised from ferret antrum. The primary amino acid sequences of the dog, ferret and pig nonapeptides were identical. In ferret the unphosphorylated nonapeptide predominated, and in dog the phosphorylated form predominated; in pig both forms of the nonapeptide were well represented. Intact progastrin was identified in gel filtration eluates of extracts of all 3 species, but occurred only in relatively low concentrations. The nonapeptides did not stimulate acid secretion in the conscious gastric fistula rat and they did not modify the acid response to G17. Phosphorylation of progastrin-derived peptides is evidently well conserved across a range of species even though there appear to be differences in the relative proportions of phosphorylated and unphosphorylated forms. 相似文献
75.
Dual translational initiation sites control function of the lambda S gene. 总被引:17,自引:3,他引:14
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Lysis gene S of phage lambda has a 107 codon reading frame beginning with the codons Met1-Lys2-Met3. Genetic data have suggested that translational initiation occurs at both Met1 and Met3, generating two polypeptides, S107 and S105 respectively. We have proposed a model in which the proper scheduling of lysis depends on the partition of translational initiations between the two start codons. Here, using in vitro methods, we show that two stem-loop structures, one immediately upstream of the reading frame and a second approximately 10 codons within the gene, control the partitioning event. Utilizing primer-extension inhibition or 'toeprinting', we show that the two S start codons are served by two adjacent Shine-Dalgarno sequences. Moreover, the timing of lysis supported by the wild-type and a number of mutant alleles in vivo can be correlated with the ratio of ternary complex formation over Met1 and Met3 in vitro. Thus the regulation of the S gene is unique in that the products of two adjacent in-frame initiation events have opposing function. 相似文献
76.
Electroantennogram responses of the Mediterranean fruit fly, Ceratitis capitata to identified volatile constituents from calling males 总被引:1,自引:0,他引:1
Eric B. Jang Douglas M. Light Robert A. Flath Janice T. Nagata Thomas R. Mon 《Entomologia Experimentalis et Applicata》1989,50(1):7-19
Fifty-six compounds from the odor of calling, sexually mature, laboratory reared males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) were isolated by headspace trapping on Tenax columns and identified using GC/MS techniques (69 total compounds were detected). Electroantennogram responses (EAGs) to 54 of the 56 identified compounds as well as 5 analogs were tested on both sexes. Significant differences between the sexes in their responsiveness were found in 9 of the 54 identified compounds tested. There was no correlation between the amplitude of the EAG response and the relative abundance of compound identified from headspace analysis. Of the five major identified components, three elicited relatively small EAG responses, while two elicited large EAGs compared to the hexan-1-ol standard. The relative ranking of EAG responses were: methyl and ethyl hexenoates and hexanoates > C4–C6 esters and/or acetates > ethyl and methyl octenoates > monoterpenes > sesquiterpenes > C2–C5 acetates, alcohols and ketones. Behavioral bioassays on each of the five major identified components as well as a blend of six of the compounds showed some degree of attractancy to virgin females which in some cases approached the response to a pheromonal standard (male odors absorbed onto filter paper). These results are discussed in relationship to the insect's antennal sensitivity to putative pheromone components and/or allomonal components and to other reported C. capitata pheromone studies.
Résumé Cinquante-six composés de l'odeur de mâles de C. capitata Weidemann, élevés en laboratoire, sexuellement mûrs et en appel, ont été isolés par piégeage sur colonnes tenax et identifiés par la technique GC/MS (69 composés avaient été détectés en tout). Les électroantennogrammes (EAGs) ont été examinés chez les deux sexes pour 54 des 56 composés identifiés et 5 de leurs analogues. Des différences significatives entre les sexes ont été observées pour 9 des 54 composés identifiés. Il n'y avait pas de corrélation entre l'ampleur de l'EAG et l'abondance relative du composé lors de son isolement. Pour les 5 principaux composés identifiés, 3 ont induit des EAGs relativement faibles, tandis que 2 étaient importants, par comparaison avec l'Hexane-1-ol utilisé comme témoin. Le classement relatif des EAG a été: hexénoates et hexanoates d'éthyl et de méthyl C4–C6 esters et/ou acétates octénoates d'éthyl ou de méthyl monoterpènes sesquiterpènes C2–C5 acétates, alcools et kétones. Les expériences de comportement avec chacun des 5 composés principaux identifiés, comme avec des mélanges de 6 composés ont mis en évidence une attraction des femelles vierges qui dans quelques cas avoisine la réponse à la phéromone témoin (odeur du mâle absorbée sur papier filtre). Ces résultats sont discutés en fonction de la sensibilité de l'antenne d'insexte aux composés supposés de la phéromone et aux composés allomonaux, et en fonction des autres études connues sur les phéromones de C. capitata.相似文献
77.
A cdc2-3w weel-50 double mutant of fission yeast displays a temperature-sensitive lethal phenotype that is associated with gross abnormalities of chromosome segregation and has been termed mitotic catastrophe. In order to identify new genetic elements that might interact with the cdc2 protein kinase in the regulation of mitosis, we have isolated revertants of the lethal double mutant. The suppressor mutations define six mcs genes (mcs: mitotic catastrophe suppressor) that are not allelic to any of the following mitotic control genes: cdc2, wee 1, cdc13, cdc25, suc1 or nim1. Each mcs mutation is recessive with respect to wild-type in its ability to suppress mitotic catastrophe. None confer a lethal phenotype as a single mutant but few of the mutants are expected to be nulls. A diverse range of genetic interactions between the mcs mutants and other mitotic regulators were uncovered, including the following examples. First, mcs2 cdc2w or mcs6 cdc2w double mutants display a cell cycle defect dependent on the specific wee allele of cdc2. Second, both mcs1 cdc25-22 or mcs4 cdc25-22 double mutants are nonconditionally lethal, even at a temperature normally permissive for cdc25-22. Finally, the characteristic suppression of the cdc25 phenotype by a loss-of-function wee1 mutation is reversed in a mcs3 mutant background. The mcs genes define new mitotic elements that might be activators or substrates of the cdc2 protein kinase. 相似文献
78.
A lethally malformed neonate with mosaic tetrasomy 12p is presented. This is the third reported case of mosaic tetrasomy 12p to have died in the neonatal period. These three babies have shown a consistent phenotype characterized by dysmorphic facies and large diaphragmatic hernia. Mosaic tetrasomy 12p is usually not detectable from lymphocyte investigation, indicating that chromosome studies from cultured fibroblasts should be undertaken in neonates with multiple malformations which include a diaphragmatic defect. 相似文献
79.
A J Ping A E Reeve D J Law M R Young M Boehnke A P Feinberg 《American journal of human genetics》1989,44(5):720-723
Beckwith-Wiedemann syndrome (BWS), characterized by multiorgan developmental abnormalities and predisposition to cancer, usually occurs sporadically, but small apparently dominant pedigrees have been described. Since rare patients show varying karyotypic abnormalities on the short arm of chromosome 11, it has been suggested that BWS may be related to the Wilms tumor gene on 11p13 or, alternatively, to growth factor genes on 11p15. We performed genetic linkage analysis on two BWS kindreds, using RFLPs for loci on 11p. BWS was linked to the insulin gene (11p15.5), with an overall maximum lod score of 3.60 (recombination fraction = .00). Linkage to D11S16 (11p13) could be excluded for recombination fractions less than or equal to .03. These results suggest that BWS defines a tumor-predisposition gene on 11p15. 相似文献
80.
Differential susceptibility of type III erythrocytes of paroxysmal nocturnal hemoglobinuria to lysis mediated by complement and perforin 总被引:1,自引:0,他引:1
S Jiang P M Persechini W F Rosse B Perussia J D Young 《Biochemical and biophysical research communications》1989,162(1):316-325
Previous reports have suggested that a 65 kDa membrane protein, termed homologous restriction factor (HRF), in addition to protecting erythrocytes (E) against lysis by homologous complement (C), may also be involved in protecting cytolytic lymphocytes against lysis mediated by a pore-forming protein (PFP/perforin), one of their own lytic mediators. Here, we used HRF-deficient type III E of patients with paroxysmal nocturnal hemoglobinuria (PNH) to study their susceptibility to lysis mediated by homologous C and perforin, and compared it with lysis of HRF-bearing control or PNH type I E. We show that type III E of PNH patients are indeed more susceptible to lysis mediated by homologous C than control or type I E, but they are as susceptible to perforin-mediated lysis as type I E. In addition, all human E (type I or III) tested here are equally susceptible to lysis mediated by either human (homologous) or murine (heterologous) perforin. By immunoblot analysis, we confirm that type III E, in contrast to type I E, were deficient in the 65 kDa HRF. These results support the notion that homologous species restriction is seen in the C- but not in the lymphocyte perforin-system and argue against an active participation of HRF in protecting cells from perforin-mediated lysis. 相似文献