Visual pigment fluorescence

The fluorescence of cattle rod outer segments (dried) and of rhodopsin in solution lies in the range of 575 to 600 millimicrons with a quantum efficiency of 0.005 if excitation is in the visible band near 500 millimicrons. The emission is abolished by bleaching at -196 degrees C but can be reversibly regenerated by irradiation with light of longer wavelength (600 millimicrons). This behavior reflects the known interconversion of rhodopsin to prelumirhodopsin at this temperature.     

Photoreception in a barnacle: electrophysiology of the shadow reflex pathway in Balanus cariosus

The photoreceptors in the median ocellus of the rock barnacle depolarize when illuminated. This depolarization spreads passively to the axon terminals in the supraesophageal ganglion. A small number of cells in the supraesophageal ganglion hyperpolarize when the median ocellus is illuminated and depolarize when it is shadowed. Nerve impulses are superimposed on the slow depolarization of the ganglion cells. Impulse activity in response to shadowing the median ocellus is recorded in a few fibers of the circumesophageal connectives. Picrotoxin blocks this shadow-induced activity. A model of the shadow reflex pathway is presented.     

Ultraviolet irradiation of DNA in vitro and in vivo produces a 3d thymine-derived product

A new thymine-derived product was separated from DNA irradiated with utlraviolet light in vitro and in vivo. This compound was mistaken to be thymine homodiner (T=T) by other workers because it is chromatographically indistinguishable from T=T in most eluents. It has absorbancy maximums at 312, 312, and 300 millimicrons in neutral, pH 2, and pH 11 aqueous solutions, respectively. When it is irradiated in aqueous solution with wavelengths of 360 and 313 millimicrons its spectrum reverts to one similar to that of thymine. Therefore, at least three thymine-derived products can be detected in ultraviolet irradiated DNA, namely the homodimer, a material with absorbancy maximum at 312 millimicrons, and a "minor" product suggested by others to be a dimer of cytosine and thymine. In cells, the latter two are formed in aboult equal amounts. While these three products were shown to exist in the acid hydrolyzates of ultraviolet irradiated DNA, a material with absorbancy maximum at about 310 millimicrons was demonstrated to form in ultraviolet irradiated DNA without further treatment. The magnitude of this spectral increase varied directly with the incrcase in the adenine-thymine contents in the DNA as shlown by differential transmittance spectra of the irradiated Micrococcus lysodeikticus, calf thymus, Bacillus cereus, and Hemophilus influenzae DNA.     

5-Ethyldeoxyuridine, a thymidine analog: photochemical transformation

Irradiation at 254 millimicrons transforms 5-ethyldeoxyuridine to deoxyuridine by way of photohydration of the 5,6 bond and elimination of ethanol. At wavelengths to the red side of 265 millimicrons, photodimerization is the principal reaction, with a pronounced oxygen effect. The results are related to the photochemistry of thymidine and of bacteriophages containing incorporated 5-ethyluracil in place of thymine.     

Quantum yield of oxygen evolution and the emerson enhancement effect in deuterated chlorella

The maximum quantum yield of oxygen evolution in deuterated chlorella is found to be 0.075, while normal chlorella showed, in parallel experiments, a value of 0.10. Deuterated Chlorella vulgaris showed a decline in the quantum yield of oxygen evolution ("red drop") beginning at 680 millimicrons and a clear Emerson enhancement effect qualitatively similar to that obtained in normal chlorella cells. However, the ratio of quantumn yield at 680 to that at 710 millimicrons was about 1.5 times higher in normal than in deuterated chlorella cells. Action spectra of the Emerson enhancement effect in deuterated chlorella also are qualitatively similar to those of normal cells.     

Absorption and Metabolism of Iron

In the article "Absorption and metabolism of iron" [Science 123, 87 (20 Jan. 1955)], the wavelength of maximum absorption of the iron-siderophilin complex was incorrectly given as 520 millimicrons. On page 89, the first sentence in the second paragraph under the heading "Iron transport" should read "The Fe+++-B(1)-globulin complex has a characteristic salmon-pink color with a maximum light absorption at 460 millimicrons...."     

Virus-like particles in normal and tumorous tissues of Drosophila

A new virus-like particle has been found in Drosophila. Thus far it has been detected only in electron micrographs of certain cells capable of division, such as those in larval imaginal disks, cell lines derived from imaginal disks, cells from a genetically controlled brain tumor, and adult gut cells. It appears to be slightly elliptical in shape, about 37 millimicrons by 45 millimicrons, and occurs in both the nucleus and cytoplasm. From the evidence it is suggested that the particle is a new virus.     

Meteorites: optical activity in organic matter

A low- amplitude, positive, Cotton effect, centered at about 340 millimicrons, has been observed in organic extracts of samples from ordinary (noncarbonaceous) chondrites. Ancillary evidence renders it likely that this optical activity derived from contamination by biologic materials on Earth.     

温室粉虱成虫体形特征的扫描电镜观察

运用扫描电子显微镜对温室粉虱雌雄成虫的体形结构特征进行了观察.结果表明,雌雄成虫具有1对单眼和1对复眼,分别位于头部两侧,复眼呈哑铃型,单个复眼约有110个单眼组成;刺吸式口器具3个口针,下唇特化为喙,喙的尾端1/3处耳状膨大;线状触角共7节;翅前缘具有乳头状缘齿,缘齿上簇生鬃毛;跳跃足前跗节的2个侧爪之间具有1个发达的爪间突.产卵器具3个产卵瓣,阳茎长推状;肛门下面的舌状突在雌雄之间存在明显差异.超徽结构特征丰富了温室粉虱及其外类群的生物学和分类学资料.     

Nucleic acid guanine: reaction with the carcinogen N-acetoxy-2-acetylaminofluorene

Reaction of N-acetoxy-2-acetylaminofluorene with DNA or RNA at pH 7 causes marked increase in absorption at 280 to 320 millimicrons and marked decrease in guanine content. Reaction with guanosine-8-(14)C yields a radioactive fluorescent derivative. The data suggest that metabolic esters of N-hydroxy-2-acetylaminofluorene may be intermediates in the binding of this proximate carcinogen to nucleic acids in vivo.     

Viral hemorrhagic encephalopathy of rats

A virus has been isolated and serially passed in suckling rats; it causes an acute fatal paralysis associated with hemorrhage and necrosis in the brain and spinal cord. The agent is relatively resistant to heat and ether, is about 20 millimicrons in diameter, and is antigenically closely related to rat virus. Its isolation resulted from the study of occasional cases of paralysis in adult rats after administration of cyclophosphamide.     

Virus-like particles in the spiral ganglion of the guinea pig cochlea

Double-walled spherical particles 100 millimicrons in diameter were accidentally discovered in the cytoplasm of spiral ganglion neurons of apparently healthy guinea pigs with normal startle responses. These particles in some ways resemble viruses of the herpes group and may represent a latent form of neuronal infection.     

Tubular structures associated with turnip yellow mosaic virus in vivo

Plants infected with a necrotic strain of turnip yellow mosaic virus contain tubes averaging about 80 millimicrons in diameter and attaining 3 microns in length. The main constituent of these tubes is a protein that is related chemically and immunologically to the protein of the virus. The tubes are composed of hexagonally packed hexagonal subunits resembling the hexamer protein subunits of the virus particles and are probably helical in construction.     

Studies of chlorophyll-lipid-water systems

Preliminary studies of the electronic absorption spectra of chlorophyll molecules in aqueous glycolipid and phospholipid dispersions are reported. The spectra show a shift for the red peak of chlorophyll of some 10 millimicrons to longer wavelength compared with the spectrum of chlorophyll in ether. Photochemical studies were carried out with cytochrome c incorporated into the aqueous layers separating the lipid bilayers.     

THE USE OF "TAGGED" DERIVATIVES IN THE FLUORIMETRIC ASSAY OF VITAMINS

In a study of the Konig reaction, it was found that nicotinic acid, on reacting with CNBr and certain substituted aromatic amines, yields glutaconic dialdehyde derivatives which fluoresce with a greenish-yellow light in visible violet light of about 440 millimicrons wave-length. A procedure was described which is applicable to 0.1 to 6 micrograms in 5 cc of solution or extract. It is suggested that the principle of preparing fluorescing "tagged" derivatives be applied to other vitamins of the B-complex.     

"C"-type viral particles in plasma of cats with feline leukemia

Linear sucrose-density gradient was used to detect and isolate typical "C"-type viral particles in plasma of cats with spontaneous and experimentally induced leukemia. The density of the agent is similar to known murine leukemia virus (1.15 to 1.17 grams per cubic centimeter). In the electron microscope the virus showed typical "C"-type particle morphology with various maturation stages. The maximum diameter of the mature viral particles in plasma was 115 millimicrons, a diameter slightly larger than budding particles observed in tissue. Leukemia was transmitted with cellular and cell-free inoculum after a 5-week period of latency.     

Atmospheric burnup of a plutonium-238 generator

The stratospheric inventory of the plutonium-238 resulting from the disintegration of a nuclear auxiliary power generator (SNAP-9A) in early 1966 accounts for essentially all the plutonium present in the original generator that reentered the atmosphere. Consequently, the pyrophoric (238)Pu must have completely burned up during reentry and ablated into small particles. The arithmetic mean of the distribution of the (238)Pu particle size was estimated to be 10 millimicrons, which confirms this conclusion.     

端黑萤头部形态的扫描电镜观察

利用扫描电镜观察了端黑萤(Luciola praeusta Kiesenwetter)成虫及幼虫头部的形态,结果表明:端黑萤成虫复眼发达,但口器退化,仅由上唇、1对上颚、1对下颚须及下唇组成;幼虫有1对不发达的侧单眼,1对发达的、左右对称的3节触角,其口器非常发达.具有1对锋利的、中空的镰刀状上颚,1对下颚须,1对下唇须和1对内颚叶.端黑萤幼虫口器的典型特征为上颚近1/2处向内侧弯曲成1个齿状突起.     

Oceili: a celestial compass in the desert ant cataglyphis

In addition to multifaceted lateral compound eyes, most insects possess three frontal eyes called ocelli. Each ocellus has a single lens, as does the vertebrate eye. The ocelli of some flying insects, locusts and dragonflies, have been shown to function as horizon detectors involved in the visual stabilization of course. In a walking insect, the desert ant Cataglyphis, it is now shown that the ocelli can read compass information from the blue sky. When the ant's compound eyes are occluded and both sun and landmarks are obscured, the ocelli, using the pattern of polarized light in the sky as a compass cue, help in guiding the ant back home.     

A hyperpolarizing component of the receptor potential in the median ocellus of Limulus

There are two classes of photoreceptor cells in the median ocellus of Limulus. One class of cells respond to long wavelength (visible) stimuli with a depolarizing receptor potential and to near ultraviolet light with a biphasic, initially hyperpolarizing, receptor potential. The other class of receptors respond with a depolarization to near ultraviolet and with a biphasic response to visible light. In the latter type of cell, visible light can counteract the depolarization elicited by near ultraviolet light. The evidence suggests that there are two photopigments in each cell and that both are involved in the generation of receptor potential.