Nonlinear-optical response in polythiophene films using four-wave mixing techniques

We report measurement of X(3) in polythiophene and a homologous series of polycondensed thiophene-based polymers above and below the absorption edge using the folded-boxcar four-wave mixing technique. Above gap the nonlinear coefficient X(3) was found to be one of the largest and fastest in a polymer.

Quinacrine decreases the slow inward current and force in guinea pig ventricular tissue

In guinea pig isolated ventricular myocytes, quinacrine (40 microM) decreases the action potential amplitude and duration, and markedly decreases the slow inward current (Isi). A lower quinacrine concentration (20 microM) has similar but smaller effects. In guinea pig papillary muscles, quinacrine decreases contractile force reversibly. Thus, in myocardial fibers the decrease in Isi by quinacrine appears to predominate over the inhibition of Na-Ca exchange found in membrane vesicles.

Template supercoiling during ATP-dependent DNA helix tracking: studies with simian virus 40 large tumor antigen

Incubation of topologically relaxed plasmid DNA with simian virus 40 (SV40) large tumor antigen (T antigen), ATP, and eubacterial DNA topoisomerase I resulted in the formation of highly positively supercoiled DNA. Eukaryotic DNA topoisomerase I could not substitute for eubacterial DNA topoisomerase 1 in this reaction. Furthermore, the addition of eukaryotic topoisomerase I to a preincubated reaction mixture containing both T antigen and eubacterial topoisomerase I caused rapid relaxation of the positively supercoiled DNA. These results suggest that SV40 T antigen can introduce topoisomerase-relaxable supercoils into DNA in a reaction coupled to ATP hydrolysis. We interpret the observed T antigen supercoiling reaction in terms of a recently proposed twin-supercoiled-domain model that describes the mechanics of DNA helix-tracking processes. According to this model positive and negative supercoils are generated ahead of and behind the moving SV40 T antigen, respectively. The preferential relaxation of negative supercoils by eubacterial DNA topoisomerase I explains the accumulation of positive supercoils in the DNA template. The supercoiling assay using DNA conformation-specific eubacterial DNA topoisomerase I may be of general use for the detection of ATP-dependent DNA helix-tracking proteins.

Identification of a developmentally regulated gene for a 140-kDa secretory protein in salivary glands of Chironomus tentans larvae

Secretory proteins are synthesized in salivary glands of the insect, Chironomus tentans, and assemble in vivo into silk-like threads which aquatic larvae use to construct tubes for filter feeding and pupation. Thus far, all known secretory protein genes contain repetitious protein-coding sequences and are located in cytological structures known as Balbiani rings, giant puffs found on polytene secretory cell chromosomes. In this paper we describe the identification of another secretory protein gene which is comprised of repeated sequences; however, this gene is not located in a Balbiani ring. Two partial cDNA clones from a 3.6-kilobase pair poly(A)+ RNA were sequenced and found to contain two open reading frames for protein synthesis. Antibodies were raised against synthetic oligopeptides whose sequences were derived from these two open reading frames. An immunoaffinity-purified antibody for one of these peptides bound specifically to a 140-kDa secretory protein (sp140). The cDNA sequences contain tandem repeats of 42 base pairs which encode a repeat of 14 amino acids with a composition and oligopeptide sequence similar to other secretory proteins. The C. tentans genome contains about 70 copies of this 42-base pair repeat organized as a contiguous block of 3 kilobase pairs or less. The sp140 gene was mapped by in situ hybridization to polytene chromosome band I-17-B. Developmental studies of protein accumulation, steady-state levels of mRNA, and relative transcription rate suggested that the sp140 gene is developmentally regulated so that maximal expression is achieved during the prepupal stages of the fourth larval instar. Based upon these results we proposed that sp140 gene belongs to a prepupal class of secretory protein genes. While the sp140 gene shares structural and expression characteristics with other secretory protein genes, its unique chromosomal location shows that this multigene family is not restricted to Balbiani rings.

Self-phase modulation in multimode optical fibers produced by moderately high-powered picosecond pulses

The spectral distributions of 8-psec ultrashort laser pulses propagating through multimode glass fibers were measured and compared with those of single-mode fibers at comparable intensities. In multimode optical fibers the spectral broadening arising from self-phase modulation was found to be asymmetric to the Stokes side owing to modal dispersion.

Discussion of the optics of a new 3-D imaging system

The geometric optics of a new 3-D imaging system, which has several innovative features, is discussed. The principles governing the primary design of the system are considered in some detail, and the calculation method employed in achieving the basic design parameters is presented. The aberration of the system is then investigated in detail using primary aberration theory, and the limitations imposed on a light beam passing through the arrangement is discussed quantitatively.

Three-dimensional imaging systems: a new development

An optical system which produces 3-D images exhibiting continuous parallax with no flipping or cardboarding is described. Both integral and lenticular images can be recorded on photographic film without recourse to a specialized environment. Standard photographic processing and enlarging techniques are used to obtain hard copy. Measurements on commercially available retrodirective screens and a new retroscreen arrangement show that the new screen developed gives significant advantages. A retrodirective and a transmission version of the system have been constructed.

Identification of a downstream sequence and binding protein that regulate adenovirus major late promoter transcription in vitro

Gel electrophoresis mobility shift and DNase I footprint assays detect a cellular nuclear protein in extracts made from uninfected human cells which binds to a downstream promoter sequence (DPS) in the human adenovirus 2 major late promoter. By DNase I footprint and mutation analyses, we have determined that this new regulatory element extends from positions +146 to +165 (relative to the cap site at position +1). We show by UV cross-linking that a 40-kDa polypeptide specifically binds to this region. Mutations within the DPS which decrease protein binding by 80-90% also cause a 2.5-3-fold decrease in in vitro major late promoter transcription efficiency. Alteration of the template in the 5'-flanking region of the DPS does not affect nuclear protein binding or transcription efficiency. Interestingly, a T----G transversion at position +160 which increases protein binding also impairs promoter activity.

Caffeine, mental stress, and risk for hypertension: a cross-cultural replication

Separate and combined effects of caffeine and mental arithmetic stress on systolic blood pressure (SBP) and heart rate (HR) were assessed in a double-blind, placebo-controlled study. Thirty-six Chinese nationals, half with and half without a family history of hypertension, received either 0, 125, or 250 mg of caffeine in three separate experimental sessions, each preceded by a 12-hour abstention from caffeine consumption. Caffeine and mental stress elevated SBP, but caffeine did not potentiate the SBP response to mental stress. Caffeine did not affect HR. A positive family history of hypertension was associated with larger SBP elevations to the higher dose of caffeine. Family history of hypertension was associated with larger blood pressure elevations during mental stress, but only under conditions of high-level stimulation provided by the initial exposure to the stress. These results support previous findings of greater cardiovascular reactivity to laboratory stress in individuals at high risk for hypertension.

Prebiotic synthesis of imidazole-4-acetaldehyde and histidine

The prebiotic synthesis of imidazole-4-acetaldehyde and imidazole-4-glycol from erythrose and formamidine has been demonstrated as well as the prebiotic synthesis of imidazole-4-ethanol and imidazole-4-glycol from erythrose, formaldehyde and ammonia. The products were identified by TLC, HPLC, and LC-MS by comparison with authentic samples. The maximum yields of imidazole-4-acetaldehyde, imidazole-4-ethanol, and imidazole-4-glycol obtained in these reactions are 1.6, 5.4, 6.8% respectively, based on the erythrose. Imidazole-4-acetaldehyde would have been converted to histidine on the primitive earth by a Strecker synthesis, and several prebiotic reactions would convert imidazole-4-glycol and imidazole-4-ethanol to imidazole-4-acetaldehyde.

Roles of DNA topoisomerases in simian virus 40 DNA replication in vitro

We examined the roles of DNA topoisomerases in the replication of simian virus 40 (SV40) DNA in a cell-free system composed of an extract from HeLa cells supplemented with purified SV40 tumor antigen. When the activities of both topoisomerase I (EC 5.99.1.2) and topoisomerase II (EC 5.99.1.3) in the extract were blocked with specific inhibitors or antibodies, DNA synthesis was decreased by a factor of 15-20. Addition of purified HeLa DNA topoisomerase II to extracts immunologically depleted of both topoisomerases completely restored replication, and the replication products consisted largely of monomeric daughter molecules. Addition of purified HeLa DNA topoisomerase I to depleted extracts restored DNA synthesis, but the primary products were multiply intertwined, catenated daughter molecules. We conclude that DNA topoisomerases have at least two roles in the replication of SV40 DNA. Either topoisomerase I or topoisomerase II is sufficient to provide the unlinking activity necessary for fork propagation during SV40 DNA replication. However, topoisomerase II is uniquely required for the segregation of newly synthesized daughter molecules.

Research note: sleep problems of normal Chinese adolescents

Eight hundred and forty-six Chinese adolescents were surveyed concerning sleep behaviours including insomnia, nightmares, somniloquism, somnambulism, bruxism, and enuresis. Bruxism was reported most frequently (22%) followed by somniloquism (17%) and insomnia (14.9%). Subjects were compared by sex, age, and rearing by parents or parent surrogates. Cross cultural comparisons and the possible significance of findings are discussed.

[Fetal liver cell transfusion in chemotherapy of malignant tumors and blood diseases]

From Feb. to Dec. 1985, 15 patients were treated with fetal liver cell transfusion (FLT). They were 10 cases with malignant tumors treated by chemotherapy (tumor group) and 5 with blood diseases (blood group). Under strict aseptic technique, 3 1/2-6 month old fetus was selected for preparing suspension of the fetal liver cells on the superclean table. The speed of FLT should be increased gradually from slow to rapid. There are 1.8 X 10(8)-4 X 10(12) fetal liver cells in a fetus of more than 5 months old, in which most are CFU-C. In the tumor group, after FLT, white blood cell, platelet and hemoglobin increased by 700-3,900/mm3, 5,000-116,000/mm3 and 0.5-2.0 gm/mm3 respectively. But in the blood group, they increased by 800-1,300/mm3, 14,000-84,000/mm3 and 0.4-11.0 gm/mm3. In most of the cases, these hematological indexes reached up to the highest in 2 weeks after FLT. It suggests that FLT can improve the peripheral blood picture obviously and stimulate bone marrow. Experiment confirms that there are considerable hematopoietic stem cells in the fetal liver, by which the functions of hematopoiesis and immunity are able to recover. It is more marked in the tumor group than in the blood group. FLT provides a favourable condition for high dose chemotherapy.