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At least 37 records · Page 2Linked to original sources
PubMed1976

Analaysis of photoenzymatic repair of UV lesions in DNA by single light flashes. XI. Light-induced activation of the yeast photoreactivating enzyme.

Photoreactivating enzyme (PRE) from yeast (as semi-crude extract, or in highly purified form) shows increased activity if it is illuminated with near UV or short wavelength visible light prior to its use for photoenzymatic repair of UV-induced pyrimidine dimers in transforming DNA in vitro. This effect results from an alternation in PRE molecules changing those with low activity in the light-dependent step of the reaction to a higher activity. Light-induced activation of PRE preparations is slowly lost by dark storage for several hours to 1 day (faster at 23 degrees C than at 5 degrees C), but can be recovered repeatedly by renewed preillumination. The action spectrum for these preillumination effects generally resembles that for the photoenzymatic repair reaction itself, having its maximum in the same 355-385 nm region as the latter, but light of somewhat longer wavelengths (546 nm) is still effective. Preilluminated PRE is also more stable to thermal inactivation (65 degrees C) than untreated enzyme.

DNA Repair↗
PubMed1976

Light-induced glutamate transport in Halobacterium halobium envelope vesicles. II. Evidence that the driving force is a light-dependent sodium gradient.

Illumination of cell envelope vesicles from H. halobium causes the development of protonmotive force and energizes the uphill transport of glutamate. Although the uncoupler, p-trifluoromethoxycarbonyl cyanide phenylhydrazone (FCCP), and the membrane-permeant cation, triphenylmethylphosphonium (TPMP+), are inhibitory to the effect of light, the time course and kinetics of the production of the energized state for transport, and its rate of decay after illumination, are inconsistent with the idea that glutamate accumulation is driven directly by the protonmotive force. Similarities between the light-induced transport and the Na+-gradient-induced transport of glutamate in these vesicles suggest that the energized state for the amino acid uptake in both cases consists of a transmembrane Na+ gradient (Na+out/Na+in greater than 1). Rapid efflux of 22Na from the envelope vesicles is induced by illumination. FCCP and TPMP+ inhibit the light-induced efflux of Na+ but accelerate the post-illumination relaxation of the Na+ gradient created, suggesting electrogenic antiport of Na+ with another cation, or electrogenic symport with an anion. The light-induced protonmotive force in the H. halobium cell envelope vesicles is thus coupled to Na+ efflux and thereby indirectly to glutamate uptake as well.

Biological Transport, Active↗
PubMed1977

[Serotonin binding activity of light and heavy synaptosomes from different animal brain structures following light deprivation].

The extent of interaction between serotonin (ST) with light and heavy synaptosomes from different brain regions of normal and dark-reared rabbits was studied by the author's technique, using gel filtration. The activity of this interaction in the heavy synaptosomes of the visual cortex and the colliculi superiores of the control rabbits was the same and significantly higher than that in the motor cortex. The light synaptosomes of all the investigated regions were similar by the extent of this process activity. In dark-reared rabbits the activity of ST binding by heavy synaptosomes in the visual cortex and the colliculi superiores decreased by 74--81 per cent only. A fall in the ST binding by light synaptosomes in all the regions was the same (approximately 73 per cent as compared to the control). The results obtained are discussed in the light of a possible mediator or modulator role of ST in the visual system structures.

Animals↗
PubMed1978

Light effects in yeast: inhibition by visible light of growth and transport in Saccharomyces cerevisiae grown at low temperatures.

Growth rate, sugar transport, and amino acid transport of yeast cells grown at 12 degrees C were inhibited by cool-white fluorescent light. At light intensities below 1,250 lx, growth and membrane transport were only slightly inhibited. Above 1,250 lx, there was increasing inhibition of both processes. Transport of histidine was completely inhibited after 3 to 5 days in cultures grown at 12 degrees C under 3,500-lx illumination. Cells grown at 20 degrees C were not inhibited by light intensities that caused complete loss of viability and membrane transport activity in cells grown at 12 degrees C.

Amino Acids↗
PubMed1979

A simple light-level recording device to monitor lighting in animal quarters.

The performance of lighting timers in animal rooms was tested with a portable light-level recorder. The instrument monitored the light and dark phases under various degrees of illumination. This inexpensive method of electronic surveillance ensured the validity of experiments dependent on photoperiodicity.

Animals↗
PubMed1975

Periodic acid-Schiff-light green stain to detect glomerular protein deposits by routine light microscopy.

A simple, easily reproducible periodic acid-Schiff-light green stain (PAS-LG) for the detection of glomerular protein deposits by routine light microscopy is described. The deposits are selectively stained a deep blue and contrast sharply with the staining of adjacent glomerular structures. Correlation with immunofluorescent and electron microscopy has shown that it is possible with this stain to categorize accurately a large variety of glomerular lesions by light microscopy alone.

Antigen-Antibody Complex↗
PubMed1976

[RNA concentration in neuron-neuroglia systems of the retina and visual zones of the cerebral cortex during light deprivation and light stimulation].

A two-wave-length cytophotometry of the gallocyanin-chromium alum-stained preparations showed that in adult rats kept for 30 days in complete darkness there was a decrease in the RNA content in the perineuronal neuroglia of the retinal ganglion cell layer only, with no changes in the corresponding neurons. No changes were found in the neurons and in the perineuronal glia of the layer II---III of the visual cerebral cortex. After the end of light deprivation a 2-hour stimulation with a constant or flickering light did not influence the RNA content in the neurons of both regions of the visual analyzer studied, whereas in control rats this stimulation induced a marked increase in the RNA content in these neurons. Qualitative changes in the metabolism of the cellular RNA in the nervous system of adult animals under the effect of light deprivation are emphasized. Differences in the biochemical peculiarities of various neuron-neuroglia systems, depending on their localization in the visual analyzer, are discussed.

Animals↗
PubMed1978

[Pupil and light sense perimetry with light and dark adaptation (author's transl)].

In comparison to light sense perimetry the use of pupillomotoric thresholds determination in the central region of the retina at various visual field illumination (10 asb, 0,1 asb, 0,001 asb, 45 degrees Meridian, 27' testpoint) has yielded the following results: 1. The maximum of the pupillomotoric sensitivity profile lies independant of the state of adaptation in the fovea. 2. Irrespective of adaptation state the course of the pupillographic profile curves are congruent. 3. Sensoric determinations show a slow flattening of the curves to the periphery whereas comparatively pupillographic determination yields a steep course (difference in areal summation). 4. In total the pupillomotoric sensitivity increases only about 10 db during the change of adaptation from light to dark. --As the phasic pupillo-light-reflex is elicited by rods and cones the differences between the sensoric and pupillomotoric threshold determinations must arise from intraretinal neuronal processes and not from the receptor reactions.

Adult↗
PubMed1978

Induction of persistent estrus by constant light: effects of neonatal constant light and Harderian gland function.

The effect of constant light on the age at onset of persistent estrus was compared in rats exposed to constant light since birth (LL-0) and those exposed beginning at 70 days of age (LL-70). Persistent estrus occurred about 27 days later in the LL-0 rats than in the LL-70 rats. Exposure to LL for just the 1st 15 days of life (LL-0-15) and then subsequent exposure to LL at 71 days also delayed the induction of persistent estrus. Neonatal injection of a Harderian gland (HG) homogenate to LL-0-15 rats reduced the age of vaginal opening and 1st estrus and reduced the delayed onset of persistent estrus caused by the neonatal LL. Harderianectomy of LL-0 or hematoporphyrin injections in LL-0-15 rats had no effect on the onset of LL-induced persistent estrus.

Animals↗
PubMed1978

Light and lighting in the dental office.

For any task, the eye can respond effectively if there is enough light, if that light is properly distributed, if the appropriate color correction is provided, and if visual contrasts are balanced. Dental offices differ in the types of work performed, the number of people engaged in various tasks, and the types of patients treated. Each office and each room can be planned according to the guidelines herein suggested as long as a rational analysis is applied to the result desired and the tasks being accomplished. The authors suggest that all concerned with office design, the architect, the contractors, and even other illuminating engineers be asked to read this article before integrating their efforts, for the dental office presents some variations not frequently encountered by these people. The need for conservation of our energy sources mandates wise use of all our energy expenditures. There is another resource conservation need that is sometimes overlooked--the effective use of talented people such as the dentist and his staff. The employment of adequate illumination design heeds both demands while giving a rewarding pleasantness and enjoyment of the work environment.

Age Factors↗
PubMed1978

Covalent immunoglobulin assembly in vitro: reactivity of light chain covalent dimers (L2) and blocked light chain monomers.

Covalent light chain dimers (L2) and cysteine-blocked L chain monomers readily react with partially reduced heavy (H) chains. A rapid disappearance of these blocked L chain species is followed by the appearance of covalent intermediates-HL, H2, and H2L-leading to fully assembled H2L2. The mechanism of initial disulfide bond formation between heavy and light chains is disulfide interchange.

Bence Jones Protein↗
PubMed1979

Amino acid sequences of antibody light chain variable regions of pedigreed rabbits: kappa light chain K49-501 (allotype b4 anti-streptococcal group A-variant polysaccharide antibody).

The amino acid sequence of positions 1--150 of a light chain, isolated from another monoclonal rabbit anti-streptococcal group A-variant polysaccharide antibody, was determined. The analysis was performed with 2 mumol of polypeptide chain, using a grossly modified Beckman 890B sequenator. This sequence stretch accounts for the whole variable region and a considerable part of the constant region at a total length of 218 amino acids. This allotype b4 light chain was isolated from a non-precipitating, end-group-specific antibody with a KD = 1.3 X 10(-5)M. This brings the present number of totally known rabbit VL sequences of antigen elicited antibodies to 21. A comparison of these 21 sequences reveals a building plan of ribbit VL homologous to that of human and murine VL regions. The observed variability does follow a pattern of linked amino acid substitutions, indicating that this information must be contained in the germ-line of the rabbit in the form of multiple VL region genes. This conclusion, however, does not rule out the occasional variant being due to somatic rearrangement. Finally, this comparison reveals that the joining peptide between positions 96--110 is also a separate entity in rabbit VL region sequences.

Amino Acid Sequence↗
PubMed1978

Oligoclonal immunoglobulins, light chain ratios and free light chains in cerebrospinal fluid and serum from patients affected with various neurological diseases.

Several immunological parameters, of which the most important are the kappa-lambda ratios, the presence of free light chains and the double ring formation for kappa-chains in single radial immunodiffusion, were investigated in the cerebrospinal fluid and serum of patients affected with different neurological diseases. Parallels were run either with multiple sclerosis or subacute sclerosing panencephalitis. There seems to be a correlation between the frequency of the presence of free light chains and the degree of severity of the immunological process.

Humans↗
PubMed1978

Kinetics of interaction of heavy and light chains in immunoglobulins. Use of a sulfhydryl-specific light chain fluorescent probe.

The fluorescent probe N-(iodoacetylaminoethyl)-8-naphthylamine-1-sulfonic acid (1,8-I-AEDANS) reacts stoichiometrically with the COOH-terminal cysteine residue of a human immunoglobulin light (L) chain. The absorption and fluorescence spectral properties of the L-AEDANS product and the environmental sensitivity of the fluorescence suggest the utility of L-AEDANS in the study of the subtle conformational changes accompanying interactions between light chain and other proteins or ligands. Its applicability to the problem of immunoglobulin assembly is illustrated by the association of L-AEDANS with heavy chain dimers, which results in an enhancement of fluorescence. The data indicate that L-AEDANS binds to kinetically equivalent, noninteracting sites with an apparent second order rate constant of 6 X 10(6) liters mol(-1) s(-1) at 20 degrees, pH 7.5.

Dansyl Compounds↗
PubMed1978

Detection of serum cardiac myosin light chains in acute experimental myocardial infarction: radioimmunoassay of cardiac myosin light chains.

To develop a more specific plasma test for myocardial infarction, antibodies specific for cardiac myosin light chains (CM-LC) were elicited that showed less than 3% cross-reactivity with skeletal muscle light chains. These antibodies were used to develop a radioimmunoassay for CM-LC that had a sensitivity of 20 ng (+/- 4 SD; P less than 0.001). Normal dog plasma showed no measurable concentrations of CM-LC (n = 6). Plasma samples from 10 dogs with experimental myocardial infarction produced by persistent left anterior descending coronary artery (LAD) occlusion were obtained at 0, 2, 4, 6, 24, 48 and 72 hours. CM-LC were first detectable in all 10 animals 6 hours after occlusion (97.98 +/- 14 ng/ml [mean +/- SEM]; P less than 0.001). Maximal CM-LC levels were usually obtained between 24 and 48 hours. Sham-operated open chest dogs (0--48 hours, n = 3) showed no measurable CM-LC in the plasma samples. Another group of 10 dogs were subjected to 5 hours of LAD occlusion, followed by reperfusion. In four dogs, CM-LC were detectable as early as 1 hour after reperfusion (81.88 +/- 37.75 ng/ml serum). Sera from all 10 dogs showed elevated levels of CM-LC (199.75 +/- 24.0 ng/ml) by 24 hours. Peak CM-LC concentrations were obtained in five dogs at 24 hours (247.0 +/- 35.28 ng/ml) and in another dog at 120 hours (245 ng/ml). Histochemical infarct size was determined to be 0.5--10% of the left ventricular mass at seven days by triphenyltetrazolium chloride staining. The specificity and sensitivity of this radioimmunoassay for detection of CM-LC, unique proteins to the heart, may be valuable in the diagnosis of myocardial infarction.

Acute Disease↗
PubMed1978

[Intensive transillumination and spot-lighting with a new fiber optic light source (author's transl)].

An equipment for intensive transillumination is described which is able to provide approximate 8 fould higher angular emittance and 2.5 fould higher flux compared with customary used tools. The diameter of the fiber optic is about 1 mm and the angle of emittance of 30 or 60 degrees can be chosen. Even the experimental use of fiber optic with smaller diameter for intravitreal illumination has shown higher light intensity compared with other available light sources.

Fiber Optic Technology↗
PubMed1976

The flexibility of low molecular weight double-stranded DNA as a function of length. I. Light scattering measurements and the estimation of persistence lengths from light scattering, sedimentation and viscosity.

In the preceding paper are described the isolation and physical characterization of seven narrowly disperse fractions of calf thymus DNA in the molecular weight range 0.3 to 1.3 X 10(6) daltons. Herein, we have determined by light scattering the molecular weights and root mean square radii of these fractions in a solvent comprising 0.2 M NaCl, 2 mM EDTA, 2mM Na-PO4,pH7. Measurements were made in a modified Wippler-Scheibling photometer to a 20 degree lower limit of scattering angle on solutions rendered virtually dust-free by procedures described. The optical anisotropies of the DNA fractions were measured permitting the experimental molecular weights and root mean square radii to be corrected to their true values. From these values, with appropriate polydispersity corrections, we calculate a Kratky-Porod persistence length, a, of 54.0 +/- 5.6 nm which is invariant over the molecular range examined. From the sedimentation coefficients (preceding paper) and the theory of Yamakawa and Fujii, we calculate a to be 66 nm, a value found to apply equally well to several DNA samples of various origins whose sedimentation rates are known in themolecular weight range from about 4 X 10(4) to 10(8) daltons. Similarly, from the intrinsic viscosities and the theory of Yamakawa and Fujii, we calculate a to be 59 nm, which again adequately applies to a number of DNA samples whose viscosities have been measured by other workers in the molecular wieght range 3 X 10(5) to 10(8) daltons. The Flory-Mandelkern paramerter, beta, was found to vary with molecular weight in the manner predicted by the theory of Yamakawa and Fujii. The average value of a from the three sets of measurements is 60 +/- 6nm, which we believe applies to double-stranded DNA molecules, independent of chain length, over the whole range of molecular weights from which reliable data exist.

Animals↗