Observation of a topological phase in a noncyclic case by use of a half-sturn optical fiber

We describe direct observation of a geometrical phase in a noncyclic case as the rotation of the plane of polarization of a linearly polarized beam of light. The beam travels down uniformly wound half-turn single-mode optical fibers with various pitch angles.

[[A study on sex ratio variation in Korea]]

"The purpose of this study is to find out the trend of sex ratio variation in [the Republic of] Korea. The data...were derived from the government publications including the Population and Housing Census Reports covering the period of 1960-1985 and the Korea Urbanic Year Book, 1985. The major findings of the study are summarized as follows: The average sex ratio in all age groups is 100.17-101.44 from 1960 through 1980. Sex ratio imbalance was most severe in 1960 due to the Korean War." Sex ratios are compared among urban and rural areas and for industrialized and agricultural areas. (SUMMARY IN ENG)

MR demonstration of cryptic vascular malformation producing a palatal myoclonus--a case report

A 47-year-old man had suffered oscillopsia associated with palatal myoclonus for 10 years. High-field magnetic resonance imaging (MRI) revealed a cryptic vascular malformation within the "Guillain-Mollaret triangle" which was thought to be the responsible lesion.

A case of Stewart-Treves syndrome

Several months after left radical mastectomy without irradiation therapy for breast cancer, a 74-year-old woman developed severe edema on the homolateral arm extending to the axilla. Ten years later, purplish to brownish blotch and nodules accompanied with heating sensation and pain appeared and increased in size gradually on the left forearm. The patient was treated by irradiation therapy under the clinical and histopathologic diagnosis of Stewart-Treves syndrome and almost all of the skin lesions and symptoms disappeared after irradiation of 6450 rads.

A mathematical model for lambda dv plasmid replication: analysis of copy number mutants

A mathematical model based on the molecular control mechanisms for lambda dv plasmid replication in a single Escherichia coli cell has been applied to simulate replication of mutant lambda dv plasmids. Model simulations of changes in repressor level and copy number resulting from mutations in the promoter-operator PROR region are consistent with experimental data. Calculated effects on lambda dv plasmid copy number of oligomer formation and of alternations in termination efficiency at tR1 also agree with experiment. The model has been employed to simulate the influence of cro mutants and of cro and tR1 double mutants on copy number and stable maintenance of lambda dv plasmid copy number. The genetic structure included in formulation of the replicon model provides a framework for relating changes in specific genetic loci on the plasmid with resulting alterations in host-plasmid system function.

A mathematical model for lambda dv plasmid replication: analysis of wild-type plasmid

A mathematical model for lambda dv plasmid replication in a growing single cell of Escherichia coli has been formulated and solved numerically. Quantitative description of the molecular control mechanism for initiation of lambda dv replication presumes regulatory functions of repressor and initiator proteins and transcriptional activation of the origin region. Random selection of a single plasmid for activation and replication is assumed, as is regular plasmid segregation to daughter cells. The model is capable of simulating the periodic changes in each regulatory element and the plasmid copy number during the cell cycle. The calculated average copy number, repressor concentration, and timing of plasmid replication agree well with experimental data. The simulated lambda dv plasmid replication rate is controlled primarily by transcription frequency. Initiation of plasmid replication is not related to variations in the levels of repressor or initiator proteins during the cell cycle. Simulation studies of perturbations in plasmid and repressor segregation indicate that replication regulation of the lambda dv plasmid compensates to readjust copy number to normal values in a few generations. Implications of these studies relative to the molecular mechanisms of replication control are discussed.

Kinetics of product formation and plasmid segregation in recombinant microbial populations

Experimental and mathematical analysis of productivity of cultures containing recombinant plasmids is based in this work on the following paradigm: molecular controls leads to single cell kinetics leads to cell population dynamics leads to reactor productivity. Mathematical models have been developed for replication control of the lambda dv plasmid and for efficiency of the lac promoter-operator based on the molecular control mechanisms of these systems in Escherichia coli. A special and important attribute of these models is their ability to describe quantitatively a wide range of genetic effects as well as environmental influences on molecular control function. Equations describing plasmid maintenance and distribution in growing cell cultures have been determined based on the population-balance equations applicable to a segregated culture model. The washout dilution rate for continuous cultivation of plasmid-containing Saccharomyces cerevisiae in selective medium is given in terms of single-cell division-cycle parameters and plasmid copy number for one single-cell model of plasmid replication and segregation. A new experimental method based on flow cytometry for rapid characterization of heterogeneity of single-cell accumulation of a plasmid gene product is also described. Generalization of these methods and of the overall strategy should provide a useful framework for synthesis of biological and engineering principles and methods to optimize organisms and processes based on recombinant DNA technology.

Cytosolic factors that alter the metabolism of N,N-dimethyl-4-aminoazobenzene by rat liver microsomes

N,N-Dimethyl-4-aminoazobenzene (DAB), an azo dye carcinogen, is N-demethylated and 4'-hydroxylated by rat liver microsomes. Addition of hepatic cytosol to the microsomal system stimulated both pathways. This occurred in the presence of added NADPH or an NADPH-generating system. Cytosol was effective only when present prior to addition of substrate; no stimulation was seen when added after the reaction had begun. This suggested a direct effect on the microsomes rather than a chemical interaction with one or more metabolic intermediates of DAB. The degree of stimulation was somewhat different when using microsomes from phenobarbital- or beta-naphthoflavone-treated animals, implying a selectivity of the cytosolic effect for various isozymes of cytochrome P-450. Some loss of stimulatory activity occurred with dialysis. Activity was restored by adding back glutathione (GSH) which can stimulate DAB metabolism even in the absence of cytosol. DAB metabolism is also stimulated by EDTA. Although both EDTA and cytosol inhibit lipid peroxidation, cytosol stimulated DAB metabolism even in the presence of EDTA. Therefore, suppression of lipid peroxidation does not explain satisfactorily the cytosolic effect. Separation of cytosolic proteins by gel filtration revealed a factor which inhibits N-demethylation but not 4'-hydroxylation of DAB. Heating at 100 degrees partially inactivated the stimulatory activity. However, inhibitory activity was less susceptible to heat inactivation than was stimulatory activity. These results indicate that, in the whole cell, microsomal metabolism of xenobiotics is regulated to an appreciable extent by macromolecular cytosolic substances.

Enzymatic biosynthesis of cephalexin

The reaction kinetics of the enzymatic synthesis of cephalexin from 7-aminodeacetoxy cephalosporanic acid and phenylglycine methylester was studied using the synthesizing enzyme obtained from Xanthomonas citri. The activation energy, Km values for 7-aminodeacetoxy cephalosporanic acid and phenylglycine methylester, and Ki value for phenylglycine methylester were determined as 8.63 kcal/mol, 3.7mM, 14.5mM, and 70mM, respectively. The enzyme was found to be constitutive and susceptible to deactivation.